WO2016121788A1 - Low-adhesiveness foam sheet - Google Patents

Low-adhesiveness foam sheet Download PDF

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Publication number
WO2016121788A1
WO2016121788A1 PCT/JP2016/052257 JP2016052257W WO2016121788A1 WO 2016121788 A1 WO2016121788 A1 WO 2016121788A1 JP 2016052257 W JP2016052257 W JP 2016052257W WO 2016121788 A1 WO2016121788 A1 WO 2016121788A1
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WO
WIPO (PCT)
Prior art keywords
foam
weight
sheet according
elastic modulus
foam sheet
Prior art date
Application number
PCT/JP2016/052257
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French (fr)
Japanese (ja)
Inventor
土井浩平
加藤和通
徳山英幸
高橋忠男
Original Assignee
日東電工株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Priority claimed from JP2016012405A external-priority patent/JP6632891B2/en
Application filed by 日東電工株式会社 filed Critical 日東電工株式会社
Priority to KR1020167018984A priority Critical patent/KR101814314B1/en
Priority to CN201680000702.7A priority patent/CN106103557B/en
Publication of WO2016121788A1 publication Critical patent/WO2016121788A1/en

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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
    • C08J9/12—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J7/00—Adhesives in the form of films or foils
    • C09J7/20—Adhesives in the form of films or foils characterised by their carriers

Definitions

  • the present invention relates to a foam sheet excellent in shock absorption even if the thickness is small, and an electric / electronic device using the foam sheet.
  • an image display member fixed to an image display device such as a liquid crystal display, an electroluminescence display, a plasma display, a display member attached to a so-called “mobile phone”, “smart phone”, “portable information terminal”, camera,
  • a foam material is used when an optical member such as a lens is fixed to a predetermined part (for example, a housing).
  • Examples of such a foam material include a low-foam, fine-cell urethane-based foam having a closed cell structure and a product obtained by compression molding a highly foamed urethane, and a polyethylene-based foam having a closed cell and an expansion ratio of about 30 times. It was used.
  • a gasket made of a polyurethane foam having an apparent density of 0.3 to 0.5 g / cm 3 , or an electrical / electric structure made of a foam structure having an average cell diameter of 1 to 500 ⁇ m.
  • a sealing material for electronic devices is used.
  • shock absorbing sheets used to prevent damage to display members, etc.
  • electronic devices such as PCs (personal computers), tablet PCs, PDAs (personal personal digital assistants), and mobile phones become more sophisticated.
  • These members for example, a heat conductive layer
  • the shock-absorbing sheet has adhesiveness, it will be difficult to peel off and correct it when assembled and the yield will be reduced. Is desired.
  • an object of the present invention is to provide a foamed sheet that exhibits excellent shock absorption even when the thickness is very small. Another object of the present invention is to provide a foam sheet that can be corrected in position when other members are laminated in addition to the above characteristics. Another object of the present invention is to provide an electric / electronic device that is less likely to be damaged by an impact at the time of dropping even if it is reduced in size and thickness.
  • the present inventors have found that a foam sheet having a specific apparent density, a specific average cell diameter, a specific shock absorption characteristic, and a low surface tackiness is used again. In addition to excellent releasability, even a thin thickness of 30 to 500 ⁇ m is remarkably excellent in impact absorption. Therefore, when such a foam sheet is laminated with another member, position correction is easy. It has been found that the built-in electric / electronic devices are less likely to be damaged by a shock or the like even when dropped on the ground. The present invention has been completed based on the above findings and further studies.
  • the present invention is a foam sheet composed of a foam having a thickness of 30 to 500 ⁇ m, an apparent density of 0.2 to 0.7 g / cm 3 , and an average cell diameter of 10 to 150 ⁇ m,
  • a value R obtained by dividing the impact absorption rate (%) defined by the following formula by the thickness ( ⁇ m) of the foamed sheet is 28 g in weight of the impactor.
  • the angle is 40 °, it is 0.20 or more, and at least one surface of the foam sheet is a 23 ° C. environment, a SUS304 cylindrical probe having a diameter ⁇ of 5 mm, an indentation speed of 30 mm / min, an indentation load.
  • a foamed sheet having a maximum load value of 100 kN / m 2 or less when pressed at 100 gf and a pressing time of 1 second and peeled at a peeling speed of 30 mm / min.
  • Impact absorption rate (%) ⁇ (F 0 ⁇ F 1 ) / F 0 ⁇ ⁇ 100 (In the above formula, F 0 is the impact force when the impactor collides only with the support plate, and F 1 causes the impactor to collide with the support plate of the structure composed of the support plate and the foam sheet. Is the impact force when
  • the foam has a peak top in a range where a loss tangent (tan ⁇ ), which is a ratio of a storage elastic modulus and a loss elastic modulus at an angular frequency of 1 rad / s in dynamic viscoelasticity measurement, is ⁇ 50 ° C. or higher and 50 ° C. or lower. It is preferable.
  • the loss tangent (tan ⁇ ) preferably has a peak top in the range of ⁇ 40 ° C. to 40 ° C., more preferably has a peak top in the range of ⁇ 30 ° C. to 30 ° C., and ⁇ 20 ° C. It is particularly preferable to have a peak top in the range of 20 ° C. or lower.
  • the maximum value of the loss tangent (tan ⁇ ) in the foam in the range of ⁇ 50 ° C. to 50 ° C. is preferably 0.2 or more.
  • the initial elastic modulus of the foam in a tensile test at a tensile speed of 300 mm / min in an environment of 23 ° C. is preferably 10 N / mm 2 or less. Also, the initial elastic modulus is more preferably 0.1 N / mm 2 or more 10 N / mm 2 or less, and more preferably 0.1 N / mm 2 or more 5N / mm 2 or less.
  • the foam can be formed of at least one resin material selected from the group consisting of acrylic polymer, rubber, urethane polymer, styrene polymer, and ethylene-vinyl acetate copolymer.
  • the foam may contain a crosslinking agent.
  • the foam may contain a filler.
  • the foam may be formed of an emulsion resin composition.
  • the foam may be formed through Step A of mechanically foaming the resin composition.
  • the foam may be further formed through a step B in which a mechanically foamed emulsion resin composition is applied onto a substrate and dried.
  • the pressure-sensitive adhesive layer may be provided on one side or both sides of the foam.
  • the foamed sheet can be used as an impact absorbing sheet for electric / electronic devices.
  • the present invention also provides an electric / electronic device in which the foam sheet is used.
  • This electric / electronic device is an electric / electronic device provided with a display member, wherein the foam sheet is sandwiched between a housing of the electric or electronic device and the display member. Includes electronics.
  • the foamed sheet of the present invention Even if the foamed sheet of the present invention is thin, it has excellent shock absorption, and when other members (for example, a heat conductive layer) are laminated, they are peeled off when they are misaligned and assembled. The position can be corrected. Even if an electric / electronic device using the foamed sheet of the present invention falls on the ground or the like, it is possible to prevent damage to the display or the like due to impact.
  • FIG. 1 It is a schematic block diagram of a pendulum type impact tester (impact test device). It is a figure which shows schematic structure of the holding member of a pendulum type impact tester (impact test apparatus).
  • the foam sheet of the present invention is composed of a foam having a thickness of 30 to 500 ⁇ m, an apparent density of 0.2 to 0.7 g / cm 3 , and an average cell diameter of 10 to 150 ⁇ m.
  • a value R obtained by dividing the impact absorption rate (%) defined by the formula described later by the thickness ( ⁇ m) of the foamed sheet is a weight of impactor of 28 g and a swing-up angle of 40. In the case of °, it is 0.20 or more, and at least one surface of the foamed sheet is a 23 ° C.
  • a SUS304 cylindrical probe having a diameter ⁇ of 5 mm, an indentation speed of 30 mm / min, an indentation load.
  • the maximum load value is 100 kN / m 2 or less when pressed under the condition of 100 gf and pressing time of 1 second and peeled off at a peeling speed of 30 mm / min. Therefore, it is excellent in shock absorption, and when the other members are laminated, the position can be easily corrected even if they are misaligned and assembled.
  • the thickness of the foamed sheet of the present invention is 30 to 500 ⁇ m.
  • the lower limit is preferably 40 ⁇ m, more preferably 50 ⁇ m, and the upper limit is preferably 400 ⁇ m, more preferably 300 ⁇ m, and even more preferably 200 ⁇ m.
  • the thickness of a foamed sheet is 30 micrometers or more, it can contain a bubble uniformly and can exhibit the outstanding impact absorption.
  • the thickness of the foamed sheet is 500 ⁇ m or less, it can easily follow a minute clearance.
  • the foamed sheet of the present invention is excellent in impact absorbency despite being as thin as 30 to 500 ⁇ m.
  • the apparent density of the foam constituting the foam sheet of the present invention is 0.2 to 0.7 g / cm 3 .
  • the lower limit is preferably 0.21 g / cm 3 , more preferably 0.22 g / cm 3
  • the upper limit is preferably 0.6 g / cm 3 , more preferably 0.5 g / cm 3 , still more preferably 0.00. 4 g / cm 3 .
  • the apparent density of the foam is 0.2 g / cm 3 or more, the strength can be maintained, and when it is 0.7 g / cm 3 or less, high impact absorbability is exhibited. Further, when the apparent density of the foam is in the range of 0.2 to 0.4 g / cm 3 , even higher impact absorbability is exhibited.
  • the average cell diameter of the foam is 10 to 150 ⁇ m.
  • the lower limit is preferably 15 ⁇ m, more preferably 20 ⁇ m, and the upper limit is preferably 140 ⁇ m, more preferably 130 ⁇ m, and even more preferably 100 ⁇ m.
  • the maximum cell diameter of the foam is, for example, 40 to 400 ⁇ m, and the lower limit is preferably 60 ⁇ m, more preferably 80 ⁇ m, and the upper limit is preferably 300 ⁇ m, more preferably 220 ⁇ m.
  • the minimum cell diameter of the foam is, for example, 5 to 70 ⁇ m, and the lower limit is preferably 8 ⁇ m, more preferably 10 ⁇ m, and the upper limit is preferably 60 ⁇ m, more preferably 50 ⁇ m.
  • the average cell diameter is determined by observing an image containing about 20 to 40 cells in the cross section of the foam with a scanning electron microscope (SEM), a digital microscope, or the like. In order from the largest cell, the area of the cell is measured at 20 points or more, and an average value of the diameter of the circle is calculated from the area by image analysis.
  • SEM scanning electron microscope
  • the ratio of the average cell diameter ( ⁇ m) to the thickness of the foamed sheet ( ⁇ m) is preferably in the range of 0.2 to 0.9 from the viewpoint of shock absorption.
  • the lower limit of the ratio of the average cell diameter ( ⁇ m) to the thickness of the foamed sheet ( ⁇ m) is preferably 0.25, more preferably 0.3, and the upper limit is preferably 0.85, more preferably 0. .8.
  • the foamed sheet of the present invention has excellent impact absorbability while being thin. That is, in an impact absorption test using a pendulum type impact tester (impactor weight 28 g, swing-up angle 40 °), the impact absorption rate (%) defined by the following formula is the thickness of the foam sheet ( ⁇ m).
  • the impact absorption rate R per unit thickness is obtained by dividing by R, the R is 0.20 or more.
  • R is preferably 0.25 or more, more preferably 0.28 or more.
  • the upper limit value of R is, for example, about 0.5.
  • Impact absorption rate (%) ⁇ (F 0 ⁇ F 1 ) / F 0 ⁇ ⁇ 100 (In the above formula, F 0 is the impact force when the impactor collides only with the support plate, and F 1 causes the impactor to collide with the support plate of the structure composed of the support plate and the foam sheet. Is the impact force when
  • the impact absorption rate varies depending on the thickness of the foamed sheet, etc., but is usually 10 to 70%, and the lower limit is preferably 20%, more preferably 30%, still more preferably 35%.
  • the upper limit is preferably 60%.
  • the impact test apparatus 1 (pendulum tester 1) includes a holding member 3 as a holding means for holding the test piece 2 (foamed sheet 2) with an arbitrary holding force, and the test piece 2
  • An impact load member 4 for applying an impact stress to the test piece
  • a pressure sensor 5 as an impact force detection means for detecting an impact force of the impact load member 4 against the test piece 2 and the like.
  • the holding member 3 that holds the test piece 2 with an arbitrary holding force includes a fixing jig 11 and a holding jig 12 that is slidable so as to sandwich and hold the test piece 2 facing the fixing jig 11. It is configured.
  • the pressing jig 12 is provided with a pressing pressure adjusting means 16.
  • the impact load member 4 for applying an impact force to the test piece 2 held by the holding member 3 is supported so that one end 22 is pivotally supported with respect to the column 20 and an impactor 24 is provided on the other end side. It is composed of a rod 23 (shaft 23) and an arm 21 that lifts and holds the impactor 24 at a predetermined angle.
  • a steel ball is used as the impactor 24, it is possible to lift the impactor 24 integrally by a predetermined angle by providing an electromagnet 25 at one end of the arm.
  • the pressure sensor 5 that detects the impact force acting on the test piece 2 by the impact load member 4 is provided on the opposite side of the surface of the fixing jig 11 that contacts the test piece.
  • the impactor 24 is a steel ball (iron ball).
  • the angle at which the impactor 24 is lifted by the arm 21 is 40 °
  • the weight of the steel ball (iron ball) is 28 g.
  • the test piece 2 is a highly elastic plate material such as a resin plate (acrylic plate, polycarbonate plate, etc.) or a metal plate between the fixing jig 11 and the holding jig 12. It is clamped via the support plate 28 configured.
  • the impact absorbability is an impact force F 0 measured by causing the impactor 24 to collide with the support plate 28 after tightly fixing the fixing jig 11 and the support plate 28 using the impact test apparatus described above.
  • the impact force F 1 measured by causing the impactor 24 to collide with the support plate 28 after inserting the test piece 2 between the fixing jig 11 and the support plate 28 and fixing the test piece 2 tightly is calculated.
  • the Note that the impact test apparatus is the same apparatus as that of Example 1 of JP-A-2006-47277.
  • the peak top of the loss tangent (tan ⁇ ) which is the ratio of the storage elastic modulus and the loss elastic modulus at an angular frequency of 1 rad / s in the dynamic viscoelasticity measurement of the foam, is ⁇ 50 ° C. to 50 ° C.
  • the following range is preferable.
  • the lower limit of the temperature range where the peak tangent of the loss tangent exists is preferably ⁇ 40 ° C., more preferably ⁇ 30 ° C., further preferably ⁇ 20 ° C., and the upper limit is preferably 40 ° C., more preferably 30 ° C. More preferably, it is 20 ° C. In the case of a material having two or more peak tops of loss tangents, it is desirable that at least one of them falls within the above range.
  • the peak temperature is ⁇ 50 ° C. or higher, excellent compression recovery is exhibited.
  • the peak temperature is 50 ° C. or lower, high flexibility is exhibited and excellent shock absorption is exhibited.
  • the peak top strength (maximum value) of loss tangent (tan ⁇ ) in the range of ⁇ 50 ° C. or higher and 50 ° C. or lower is preferably higher from the viewpoint of shock absorption, for example 0.2 or higher, preferably 0.3 or higher.
  • the upper limit value of the peak top intensity (maximum value) is, for example, 2.0.
  • the peak temperature and peak top strength of the loss tangent (tan ⁇ ) greatly contribute to the shock absorption of the foam.
  • the peak top of the loss tangent (tan ⁇ ) which is the ratio of the storage elastic modulus and the loss elastic modulus at an angular frequency of 1 rad / s in the dynamic viscoelasticity measurement of the foam, is in the range of ⁇ 50 ° C. or more and 50 ° C. or less.
  • the loss tangent (tan ⁇ ) peak exists at a location that matches the frequency of impact. That is, the range where the loss tangent (tan ⁇ ) is ⁇ 50 ° C. or more and 50 ° C.
  • the storage elastic modulus is a repulsive force with respect to the impact energy applied to the foam sheet. If the storage elastic modulus is high, the impact is repelled as it is.
  • the loss elastic modulus is a physical property that changes impact energy applied to the foam sheet to heat, and the higher the loss elastic modulus is, the more the impact energy is changed to heat, so the impact is absorbed and the strain is reduced.
  • the foamed sheet of the present invention it is desirable that at least one surface of the foamed sheet has low adhesiveness (tackiness) from the viewpoint of position correction.
  • the adhesiveness can be measured by a known tacking tester using a probe tack method.
  • At least one surface of the foamed sheet is a 23 ° C. environment, and a SUS304 cylindrical probe having a diameter ⁇ of 5 mm is pressed at a speed of 30 mm /
  • the maximum load value is 100 kN / m 2 or less when pressed under the conditions of min, indentation load 100 gf, and press time 1 second, and peeled off at a peeling speed of 30 mm / min.
  • the foam sheet of the present invention has a very low surface tack. Therefore, when laminating other members on the foamed sheet, even if they are misaligned and assembled, they can be easily removed to correct the position.
  • the crosslinking density of the foam is increased, an appropriate amount of filler is added, or the resin material constituting the foam has a high Tg (for example, 50 to 200).
  • ° C) polymer for example, styrene-based polymer, etc. may be blended in an appropriate amount.
  • the initial elastic modulus of the foam is preferably low from the viewpoint of impact absorption.
  • the initial elastic modulus (a value calculated from a slope at the time of 10% strain in a tensile test under a 23 ° C. environment and a tensile speed of 300 mm / min) is preferably 10 N / mm 2 or less, more preferably 5 N / mm 2. It is as follows.
  • the lower limit value of the initial elastic modulus is, for example, 0.1 N / mm 2 .
  • the foam constituting the foam sheet of the present invention is not particularly limited in its composition and cell structure as long as it has the above characteristics.
  • the cell structure may be any of an open cell structure, a closed cell structure, and a semi-continuous semi-closed cell structure. From the viewpoint of impact absorption, an open cell structure and a semi-open semi-closed cell structure are preferable.
  • the foam can be constituted by a resin composition containing a resin material (polymer).
  • the loss which is a ratio of the storage elastic modulus and the loss elastic modulus at an angular frequency of 1 rad / s in the dynamic viscoelasticity measurement of the resin composition in an unfoamed state [resin composition when not foamed (solid matter)]
  • the peak top of tangent (tan ⁇ ) is preferably in the range of ⁇ 50 ° C. to 50 ° C.
  • the lower limit of the temperature range where the peak tangent of the loss tangent exists is preferably ⁇ 40 ° C., more preferably ⁇ 30 ° C., further preferably ⁇ 20 ° C., and the upper limit is preferably 40 ° C., more preferably 30 ° C. More preferably, it is 20 ° C. In the case of a material having two or more peak tops of loss tangents, it is desirable that at least one of them falls within the above range. Loss tangent (tan ⁇ ) peak top strength of the resin composition (solid) in the range of ⁇ 50 ° C. to 50 ° C. (this value is the loss tangent of the foam in the range of ⁇ 50 ° C.
  • the peak top strength of (tan ⁇ ) (corresponding to the value obtained by dividing the apparent density (g / cm 3 ) of the foam) is preferably higher from the viewpoint of impact absorption.
  • the peak top intensity of the loss tangent (tan ⁇ ) in the range of ⁇ 50 ° C. to 50 ° C. of the resin composition (solid material) is preferably 0.9 (g / cm 3 ) ⁇ 1 or more,
  • the upper limit is, for example, about 3 (g / cm 3 ) ⁇ 1 .
  • the initial elastic modulus (23 ° C., tensile speed 300 mm / min) of the unfoamed resin composition (solid material) is desirably lower, preferably 50 N / mm 2 or less, more preferably 30 N / mm 2. It is as follows.
  • the lower limit value of the initial elastic modulus is, for example, 0.3 N / mm 2 .
  • the resin material (polymer) constituting the foam is not particularly limited, and a known or well-known resin material constituting the foam can be used.
  • the resin material include acrylic polymer, rubber, urethane polymer, styrene polymer, and ethylene-vinyl acetate copolymer. Among these, acrylic polymer, rubber, urethane polymer, and styrene polymer are preferable from the viewpoint of impact absorption.
  • One type of resin material (polymer) constituting the foam may be used alone, or two or more types may be used.
  • the amount of the styrene polymer used is, for example, 100 parts by weight of at least one resin material selected from the group consisting of an acrylic polymer, rubber, urethane polymer, and ethylene-vinyl acetate copolymer.
  • the lower limit thereof is preferably 1 part by weight, more preferably 5 parts by weight, and the upper limit thereof is preferably 80 parts by weight, more preferably 50 parts by weight.
  • the peak top of the loss tangent (tan ⁇ ), which is the ratio of the storage elastic modulus and the loss elastic modulus at an angular frequency of 1 rad / s in the dynamic viscoelasticity measurement of the foam, is in the range of ⁇ 50 ° C. to 50 ° C.
  • the Tg of the resin material (polymer) can be used as an index or a guide.
  • the resin material (polymer) constituting the foam has a Tg of ⁇ 50 ° C. or more and less than 50 ° C.
  • the resin material (polymer) can be selected so as to be in the range of 30 ° C.
  • the acrylic polymer is preferably an acrylic polymer formed with a monomer having a homopolymer Tg of ⁇ 10 ° C. or more and a monomer having a homopolymer Tg of less than ⁇ 10 ° C. as essential monomer components.
  • the ratio of the storage elastic modulus and loss elastic modulus at an angular frequency of 1 rad / s in dynamic viscoelasticity measurement is obtained by adjusting the amount ratio of the former monomer and the latter monomer.
  • a foam having a loss tangent (tan ⁇ ) peak top of ⁇ 50 ° C. or more and 50 ° C. or less can be obtained relatively easily.
  • glass transition temperature (Tg) when forming a homopolymer means “glass transition temperature (Tg of homopolymer of the monomer)”.
  • Tg of homopolymer glass transition temperature (Tg of homopolymer of the monomer).
  • the Tg of a homopolymer of a monomer not described in the above document refers to, for example, a value obtained by the following measurement method (see JP 2007-51271 A).
  • this homopolymer solution is cast-coated on a separator and dried to prepare a test sample (sheet-like homopolymer) having a thickness of about 2 mm.
  • This test sample was punched into a disk shape having a diameter of 7.9 mm, sandwiched between parallel plates, and subjected to a shear strain at a frequency of 1 Hz using a viscoelasticity tester (ARES, manufactured by Rheometrics). Viscoelasticity is measured in a shear mode at a heating rate of 150 ° C. and 5 ° C./min, and the peak top temperature of tan ⁇ is defined as Tg of the homopolymer.
  • the Tg of the resin material (polymer) can also be measured by this method.
  • the Tg is, for example, ⁇ 10 ° C. to 250 ° C., preferably 10 to 230 ° C., more preferably 50 to 200 ° C.
  • Examples of the homopolymer having a Tg of ⁇ 10 ° C. or more include, for example, (meth) acrylonitrile; amide group-containing monomers such as (meth) acrylamide and N-hydroxyethyl (meth) acrylamide; (meth) acrylic acid; methacrylic acid (Meth) acrylic acid alkyl esters having homopolymers such as methyl and ethyl methacrylate having a Tg of ⁇ 10 ° C. or higher; (meth) acrylic acid isobornyl; heterocycle-containing vinyl monomers such as N-vinyl-2-pyrrolidone; Examples thereof include hydroxyl group-containing monomers such as ethyl methacrylate.
  • (meth) acrylonitrile (especially acrylonitrile) is particularly preferable.
  • (meth) acrylonitrile (especially acrylonitrile) is used as a monomer having a homopolymer Tg of ⁇ 10 ° C. or higher, the peak top strength of the loss tangent (tan ⁇ ) of the foam is increased because of the strong intermolecular interaction. be able to.
  • the Tg is, for example, ⁇ 70 ° C. or more and less than ⁇ 10 ° C., preferably ⁇ 70 ° C. to ⁇ 12 ° C., more preferably ⁇ 65 ° C. to ⁇ 15 ° C. .
  • Examples of the homopolymer having a Tg of less than ⁇ 10 ° C. include, for example, (meth) acrylic acid alkyl esters having a homopolymer Tg of less than ⁇ 10 ° C., such as ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, etc. Is mentioned. These can be used individually by 1 type or in combination of 2 or more types. Among these, acrylic acid C 2-8 alkyl ester is particularly preferable.
  • the content of the monomer having a Tg of -10 ° C. or more of the homopolymer is, for example, 2 to 30% by weight with respect to all the monomer components forming the acrylic polymer (total amount of monomer components), and the lower limit is preferably 3%. %, More preferably 4% by weight, and the upper limit is preferably 25% by weight, more preferably 20% by weight.
  • the content of the monomer having a Tg of the homopolymer of less than ⁇ 10 ° C. with respect to all the monomer components forming the acrylic polymer (total amount of monomer components) is, for example, 70 to 98% by weight, and the lower limit is preferably The upper limit is preferably 97% by weight, more preferably 96% by weight.
  • the viscosity of the composition decreases when the emulsion resin composition is foamed by applying mechanical shearing or the like. Many bubbles are likely to be taken into the emulsion, and when the emulsion resin composition containing the bubbles is applied onto a substrate and dried in a stationary state, the composition tends to aggregate and the viscosity is increased. The foam rises and the bubbles are retained in the composition and hardly diffused to the outside, so that a foam having excellent foaming characteristics can be obtained.
  • nitrogen atom-containing copolymerizable monomer examples include cyano group-containing monomers such as (meth) acrylonitrile; lactam ring-containing monomers such as N-vinyl-2-pyrrolidone; (meth) acrylamide, N And amide group-containing monomers such as hydroxyethyl (meth) acrylamide, N-methylolacrylamide, N, N-dimethylacrylamide, N, N-diethylacrylamide, and diacetoneacrylamide.
  • cyano group-containing monomers such as acrylonitrile and lactam ring-containing monomers such as N-vinyl-2-pyrrolidone are preferable.
  • a nitrogen atom containing monomer can be used individually by 1 type or in combination of 2 or more types.
  • the content of the structural unit derived from the nitrogen atom-containing monomer is preferably 2 to 2 with respect to all the structural units constituting the acrylic polymer.
  • the lower limit is more preferably 3% by weight, still more preferably 4% by weight, and the upper limit is more preferably 25% by weight, still more preferably 20% by weight.
  • an acrylic acid C 2-18 alkyl ester (particularly acrylic acid C 2 -8 alkyl ester) is preferred.
  • Acrylic acid C 2-18 alkyl ester can be used alone or in combination of two or more.
  • the content of structural units derived from acrylic acid C 2-18 alkyl esters (particularly acrylic acid C 2-8 alkyl esters) is based on the total structural units constituting the acrylic polymer.
  • the lower limit is more preferably 75% by weight, still more preferably 80% by weight, and the upper limit is more preferably 97% by weight, still more preferably 96% by weight. .
  • the rubber may be natural rubber or synthetic rubber.
  • examples of the rubber include nitrile rubber (NBR), methyl methacrylate-butadiene rubber (MBR), styrene-butadiene rubber (SBR), acrylic rubber (ACM, ANM), urethane rubber (AU), and silicone rubber.
  • NBR nitrile rubber
  • MRR methyl methacrylate-butadiene rubber
  • SBR styrene-butadiene rubber
  • ACM acrylic rubber
  • AU urethane rubber
  • silicone rubber silicone rubber.
  • urethane polymer examples include polycarbonate polyurethane, polyester polyurethane, and polyether polyurethane.
  • ethylene-vinyl acetate copolymer a known or well-known ethylene-vinyl acetate copolymer can be used.
  • styrene polymer a known or well-known styrene polymer can be used.
  • the foam constituting the foam sheet may contain a surfactant, a cross-linking agent, a thickener, a rust preventive agent, and other additives as required in addition to the resin material (polymer).
  • an optional surfactant may be included for the purpose of reducing the bubble diameter and stabilizing the foam.
  • the surfactant is not particularly limited, and any of an anionic surfactant, a cationic surfactant, a nonionic surfactant, an amphoteric surfactant, and the like may be used. From the viewpoint of the stability of the foam, an anionic surfactant is preferable, and a fatty acid ammonium surfactant such as ammonium stearate is more preferable.
  • Surfactant may be used individually by 1 type and may be used in combination of 2 or more type. Different surfactants may be used in combination, for example, an anionic surfactant and a nonionic surfactant, or an anionic surfactant and an amphoteric surfactant may be used in combination.
  • the addition amount [solid content (nonvolatile content)] of the surfactant is, for example, 0 to 10 parts by weight with respect to 100 parts by weight of the resin material (polymer) [solid content (nonvolatile content)], and the lower limit is preferably 0.5 part by weight, the upper limit is preferably 8 parts by weight.
  • an arbitrary cross-linking agent may be included.
  • the crosslinking agent is not particularly limited, and any of oil-soluble and water-soluble may be used.
  • examples of the crosslinking agent include epoxy, oxazoline, isocyanate, carbodiimide, melamine, and metal oxide. Among these, an oxazoline-based crosslinking agent is preferable.
  • the addition amount [solid content (nonvolatile content)] of the crosslinking agent is, for example, 0 to 30 parts by weight with respect to 100 parts by weight of the resin material (polymer) [solid content (nonvolatile content)], and the lower limit is preferably 0. 0.01 parts by weight, and the upper limit is preferably 20 parts by weight.
  • the addition amount of the crosslinking agent [solid content (nonvolatile content)] has, for example, a resin material [polymer, particularly a crosslinking point (hydroxyl group, carboxyl group, etc.).
  • Solid content (nonvolatile content)] is preferably 0.5 to 30 parts by weight with respect to 100 parts by weight, and the lower limit thereof is more preferably 1 part by weight, still more preferably 2 parts by weight. More preferably, it is 25 parts by weight, still more preferably 20 parts by weight.
  • an optional thickener may be included.
  • the thickener is not particularly limited, and examples thereof include acrylic acid type, urethane type, and polyvinyl alcohol type. Of these, polyacrylic acid thickeners and urethane thickeners are preferred.
  • the addition amount of the thickener is, for example, 0 to 10 parts by weight with respect to 100 parts by weight of the resin material (polymer) [solid content (nonvolatile content)], and the lower limit is preferably 0.1 parts by weight, the upper limit is preferably 5 parts by weight.
  • an arbitrary rust inhibitor may be included to prevent corrosion of the metal member adjacent to the foam sheet.
  • an azole ring-containing compound is preferable. When an azole ring-containing compound is used, it is possible to achieve both high levels of corrosion prevention for metals and adhesion to adherends.
  • the azole ring-containing compound may be a compound having a 5-membered ring containing one or more nitrogen atoms in the ring.
  • compounds having a ring, a thiazole ring, or an isothiazole ring may be condensed with an aromatic ring such as a benzene ring to form a condensed ring.
  • Examples of the compound having such a condensed ring include a compound having a benzimidazole ring, a benzopyrazole ring, a benzotriazole ring, a benzoxazole ring, a benzoisoxazole ring, a benzothiazole ring, or a benzoisothiazole ring.
  • the azole ring and the condensed ring each may have a substituent.
  • substituents include alkyl groups having 1 to 6 carbon atoms (preferably 1 to 3 carbon atoms) such as methyl group, ethyl group, propyl group, isopropyl group and butyl group; methoxy group, ethoxy group, isopropyloxy
  • benzotriazole compounds include 1,2,3-benzotriazole, methylbenzotriazole, carboxybenzotriazole, carboxymethylbenzotriazole, and 1- [N, N-bis (2-ethylhexyl) aminomethyl] benzotriazole.
  • 1- [N, N-bis (2-ethylhexyl) aminomethyl] methylbenzotriazole, 2,2 ′-[[(methyl-1H-benzotriazol-1-yl) methyl] imino] bisethanol, or these A sodium salt etc. are mentioned.
  • benzothiazole compound examples include 2-mercaptobenzothiazole, 3- (2- (benzothiazolyl) thio) propionic acid, or a sodium salt thereof.
  • the azole ring-containing compound may be used alone or in combination of two or more.
  • the addition amount [solid content (nonvolatile content)] of the rust inhibitor (for example, the azole ring-containing compound) [solid content (nonvolatile content)] is within a range that does not impair the adhesion to the adherend and the original properties of the foam.
  • 0.2 to 5 parts by weight is preferable with respect to 100 parts by weight of the resin material (polymer) [solid content (nonvolatile content)].
  • the lower limit is more preferably 0.3 parts by weight, still more preferably 0.4 parts by weight, and the upper limit is more preferably 3 parts by weight, still more preferably 2 parts by weight.
  • any appropriate other component may be included within the range not impairing the shock absorption.
  • Such other components may contain only 1 type and may contain 2 or more types.
  • the other components include polymer components other than those described above, softeners, antioxidants, anti-aging agents, gelling agents, curing agents, plasticizers, fillers, reinforcing agents, foaming agents (such as baking soda), micro Capsules (thermally expandable microspheres, etc.), flame retardants, light stabilizers, UV absorbers, colorants (pigments, dyes, etc.), pH adjusters, solvents (organic solvents), thermal polymerization initiators, photopolymerization initiators, etc. Is mentioned.
  • the addition amount [solid content (nonvolatile content)] of these components may be in a range that does not impair the adhesion to the adherend and the original properties of the foam.
  • resin material (polymer) solid content (nonvolatile content)
  • a range of 0.2 to 100 parts by weight is preferable with respect to 100 parts by weight.
  • the addition amount [solid content (nonvolatile content)] of the foaming agent is preferably 0.5 to 20 parts by weight with respect to 100 parts by weight of the resin material (polymer) [solid content (nonvolatile content)]. is there.
  • the addition amount [solid content (nonvolatile content)] of the microcapsule (thermally expandable microspheres) is more preferably 0.2 to 100 parts by weight with respect to 100 parts by weight of the resin material (polymer) [solid content (nonvolatile content)]. 10 parts by weight.
  • the filler examples include silica, clay (mica, talc, smectite, etc.), alumina, aluminum hydroxide, alkaline earth metal hydroxide (magnesium hydroxide, etc.), and alkaline earth metal carbide (calcium carbide).
  • Etc. titania, zinc oxide, tin oxide, zeolite, graphite, carbon nanotube, inorganic fiber (carbon fiber, glass fiber, potassium titanate fiber, etc.), organic fiber, metal powder (silver, copper, etc.), wax (polyethylene wax) , Polypropylene wax, etc.).
  • piezoelectric particles titanium oxide, barium titanate, etc.
  • conductive particles conductive titanium oxide, tin oxide, etc.
  • thermally conductive particles boron nitride, etc.
  • organic fillers silicone powder, polyethylene powder) , Polypropylene powder, etc.
  • the amount of the filler added is, for example, 0.3 to 100 parts by weight with respect to 100 parts by weight of the resin material (polymer) [solid content (non-volatile content)].
  • the amount of filler added is preferably 1 to 100 parts by weight, and the lower limit thereof is preferably 5 parts by weight, more preferably 10 parts by weight.
  • the upper limit is preferably 80 parts by weight, more preferably 50 parts by weight.
  • the addition amount is particularly in the range of 0.3 to 10 parts by weight with respect to 100 parts by weight of the resin material (polymer) [solid content (nonvolatile content)]. preferable.
  • the addition amount thereof is particularly preferably in the range of 5 to 40 parts by weight with respect to 100 parts by weight of the resin material (polymer) [solid content (nonvolatile content)].
  • the addition amount thereof is particularly preferably in the range of 5 to 40 parts by weight with respect to 100 parts by weight of the resin material (polymer) [solid content (nonvolatile content)].
  • the amount of generated charges can be adjusted by pressure.
  • the foam sheet of the present invention can be produced by subjecting a resin composition containing a resin material (polymer) constituting the foam to foam molding.
  • foaming method bubble forming method
  • methods usually used for foam molding such as physical methods and chemical methods, can be employed.
  • the physical method is a method in which gas components such as air and nitrogen are dispersed in a polymer solution and bubbles are formed by mechanical mixing (mechanical foam).
  • the chemical method is a method of obtaining a foam by forming cells with a gas generated by thermal decomposition of a foaming agent added to a polymer base. From the viewpoint of environmental problems, a physical method is preferable. Bubbles formed by physical methods are often open cells.
  • a resin composition containing a resin material (polymer) to be subjected to foam molding a resin solution in which a resin material is dissolved in a solvent may be used.
  • an emulsion containing a resin material (emulsion resin composition) ) Is preferably used. That is, it is preferable that the foam which comprises the foam sheet of this invention is a foam of an emulsion resin composition.
  • the solid content concentration of the emulsion is preferably higher from the viewpoint of film formability.
  • the solid content concentration of the emulsion is preferably 30% by weight or more, more preferably 40% by weight or more, and further preferably 50% by weight or more.
  • a method of producing a foam through a step (Step A) in which a resin composition (for example, an emulsion resin composition) is foamed mechanically is preferable. That is, it is preferable that the foam which comprises the foam sheet of this invention is a mechanical foam of a resin composition (for example, emulsion resin composition).
  • the foaming device is not particularly limited, and examples thereof include a high-speed shearing method, a vibration method, and a pressurized gas discharge method. Among these, the high-speed shearing method is preferable from the viewpoint of finer bubble diameter and production of a large capacity.
  • Bubbles when foamed by mechanical stirring are gas (gas) taken into the emulsion.
  • the gas is not particularly limited as long as it is inert to the emulsion, and examples thereof include air, nitrogen, carbon dioxide and the like. Among these, air is preferable from the viewpoint of economy.
  • the foamed sheet of the present invention can be obtained through a step (Step B) in which a resin composition (for example, an emulsion resin composition) foamed by the above method is applied onto a substrate and dried.
  • the substrate is not particularly limited, and examples thereof include a peeled plastic film (such as a peeled polyethylene terephthalate film), a plastic film (such as a polyethylene terephthalate film), and a heat conductive layer (a heat conductive layer described later). It is done.
  • the adhesion between the foam layer and the heat conductive layer can be improved, and the efficiency of the drying process when the foam layer is produced can also be improved.
  • Step B a general method can be adopted as a coating method and a drying method.
  • Step B is a pre-drying step B1 in which the bubble-containing resin composition (eg, emulsion resin composition) applied on the substrate is dried at 50 ° C. or higher and lower than 125 ° C., and then further dried at 125 ° C. or higher and 200 ° C. or lower. It is preferable that this drying process B2 is included.
  • the bubble-containing resin composition eg, emulsion resin composition
  • the temperature in the preliminary drying step B1 is preferably 50 ° C. or higher and 100 ° C. or lower.
  • the time of the preliminary drying step B1 is, for example, 0.5 minutes to 30 minutes, preferably 1 minute to 15 minutes. Moreover, the temperature in this drying process B2 becomes like this.
  • the main drying step B2 is, for example, 0.5 minutes to 30 minutes, preferably 1 minute to 15 minutes.
  • the average cell diameter, maximum cell diameter, and minimum cell diameter of the foam can be adjusted by adjusting the type and amount of the surfactant, and by adjusting the stirring speed and stirring time during mechanical stirring.
  • a foam sheet having a range of 10 to 150 ⁇ m can be obtained.
  • the apparent density of the foam is an apparent density of 0.2 to 0.7 g / cm 3 by adjusting the amount of gas (gas) component taken into the resin composition (for example, emulsion resin composition) during mechanical stirring.
  • gas gas
  • a foam sheet having a density can be obtained.
  • the foamed sheet of the present invention may have a pressure-sensitive adhesive layer (adhesive layer) on one or both sides (particularly, a surface other than the low tack surface) of the foam.
  • a pressure-sensitive adhesive layer adheresive layer
  • the foamed sheet of the present invention may be distributed on the market as a wound body (rolled material) wound in a roll shape.
  • the foamed sheet of the present invention is excellent in impact absorption even if the thickness is small. Therefore, for example, in an electrical / electronic device, various members or parts (for example, optical members) are used for attaching (attaching) a predetermined part (for example, a housing) to a member for electrical / electronic devices, In particular, it is useful as an impact absorbing sheet.
  • an image display member attached to an image display device such as a liquid crystal display, an electroluminescence display, a plasma display (particularly, a small image display).
  • display members such as touch panels attached to mobile communication devices such as so-called “mobile phones”, “smartphones” and “portable information terminals”, cameras and lenses (particularly small cameras and lenses), etc.
  • mobile communication devices such as so-called “mobile phones”, “smartphones” and “portable information terminals”, cameras and lenses (particularly small cameras and lenses), etc.
  • the electrical / electronic device of the present invention uses the foam sheet of the present invention.
  • Such an electric / electronic device is, for example, an electric / electronic device provided with a display member, in which the foamed sheet is sandwiched between a housing of the electric or electronic device and the display member.
  • Electric and electronic equipment having Examples of the electric / electronic devices include mobile communication devices such as so-called “mobile phones”, “smartphones”, and “portable information terminals”.
  • % representing the content means% by weight.
  • all the compounding parts are values in terms of solid content (non-volatile content).
  • Example 1 100 parts by weight of acrylic emulsion solution (solid content 55%, ethyl acrylate-butyl acrylate-acrylonitrile copolymer (weight ratio 45: 48: 7)), fatty acid ammonium surfactant (aqueous dispersion of ammonium stearate, (Solid content 33%) (surfactant A) 2 parts by weight, carboxybetaine type amphoteric surfactant (“Amogen CB-H”, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) (surfactant B) 2 parts by weight, oxazoline-based crosslinking 10 parts by weight of agent (Epocross WS-500, manufactured by Nippon Shokubai Co., Ltd., solid content 39%), 1 part by weight of pigment (carbon black) (NAF-5091, manufactured by Daiichi Seika Kogyo Co., Ltd.), polyacrylic acid thickening agent 0.6 parts by weight of an agent (ethyl acrylate-acrylic acid cop
  • This foamed composition was applied onto a release-treated PET (polyethylene terephthalate) film (thickness: 38 ⁇ m, trade name “MRF # 38” manufactured by Mitsubishi Plastics), 70 ° C. for 4.5 minutes, and 140 ° C. It was dried for 4.5 minutes to obtain an open cell foam (foamed sheet) having a thickness of 130 ⁇ m, an apparent density of 0.28 g / cm 3 , and an initial elastic modulus of 1.15 N / mm 2 .
  • Example 2 100 parts by weight of acrylic emulsion solution (solid content 55%, ethyl acrylate-butyl acrylate-acrylonitrile copolymer (weight ratio 45: 48: 7)), fatty acid ammonium surfactant (aqueous dispersion of ammonium stearate, (Solid content 33%) (surfactant A) 2 parts by weight, carboxybetaine type amphoteric surfactant (“Amogen CB-H”, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) (surfactant B) 2 parts by weight, oxazoline-based crosslinking 4 parts by weight of agent (Epocross WS-500, manufactured by Nippon Shokubai Co., Ltd., solid content 39%), 1 part by weight of pigment (carbon black) (NAF-5091, manufactured by Daiichi Seika Kogyo Co., Ltd.), polyacrylic acid thickening agent Agent (ethyl acrylate-acrylic acid copolymer (acrylic acid
  • This foamed composition was applied onto a release-treated PET (polyethylene terephthalate) film (thickness: 38 ⁇ m, trade name “MRF # 38” manufactured by Mitsubishi Plastics), 70 ° C. for 4.5 minutes, and 140 ° C. It was dried for 4.5 minutes to obtain a foam (foamed sheet) having an open cell structure having a thickness of 130 ⁇ m, an apparent density of 0.30 g / cm 3 , and an initial elastic modulus of 0.82 N / mm 2 .
  • Example 3 100 parts by weight of acrylic emulsion solution (solid content 55%, ethyl acrylate-butyl acrylate-acrylonitrile copolymer (weight ratio 45: 48: 7)), fatty acid ammonium surfactant (aqueous dispersion of ammonium stearate, (Solid content 33%) (surfactant A) 2 parts by weight, carboxybetaine type amphoteric surfactant (“Amogen CB-H”, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) (surfactant B) 2 parts by weight, oxazoline-based crosslinking 4 parts by weight of agent (Epocross WS-500, manufactured by Nippon Shokubai Co., Ltd., solid content 39%), 1 part by weight of pigment (carbon black) (NAF-5091, manufactured by Daiichi Seika Kogyo Co., Ltd.), polyacrylic acid thickening agent Agent (ethyl acrylate-acrylic acid copolymer (acrylic acid
  • This foamed composition was applied onto a release-treated PET (polyethylene terephthalate) film (thickness: 38 ⁇ m, trade name “MRF # 38” manufactured by Mitsubishi Plastics), 70 ° C. for 4.5 minutes, and 140 ° C. It was dried for 4.5 minutes to obtain a foam (foamed sheet) having an open cell structure having a thickness of 130 ⁇ m, an apparent density of 0.34 g / cm 3 , and an initial elastic modulus of 2.37 N / mm 2 .
  • Example 4 Acrylic emulsion solution (solid content 55%, ethyl acrylate-butyl acrylate-acrylonitrile copolymer (weight ratio 45: 48: 7)) 100 parts by weight, styrene emulsion solution (solid content 53%, Boncoat SK-105 -E ", manufactured by DIC) 20 parts by weight, fatty acid ammonium surfactant (aqueous dispersion of ammonium stearate, solid content 33%) (surfactant A) 2 parts by weight, carboxybetaine type amphoteric surfactant ( "Amorgen CB-H" (Daiichi Kogyo Seiyaku Co., Ltd.) (Surfactant B) 2 parts by weight, Oxazoline-based crosslinking agent ("Epocross WS-500" Nippon Shokubai Co., Ltd., solid content 39%) 4 parts by weight, pigment (Carbon black) ("NAF-5091" manufactured by Dainichi Seika Kogyo Co., Ltd.
  • This foamed composition was applied onto a release-treated PET (polyethylene terephthalate) film (thickness: 38 ⁇ m, trade name “MRF # 38” manufactured by Mitsubishi Plastics), 70 ° C. for 4.5 minutes, and 140 ° C. After drying for 4.5 minutes, a foam (foamed sheet) having an open cell structure having a thickness of 130 ⁇ m, an apparent density of 0.29 g / cm 3 , and an initial elastic modulus of 3.64 N / mm 2 was obtained.
  • Example 5 100 parts by weight of acrylic emulsion solution (solid content 55%, ethyl acrylate-butyl acrylate-acrylonitrile copolymer (weight ratio 45: 48: 7)), fatty acid ammonium surfactant (aqueous dispersion of ammonium stearate, (Solid content 33%) (surfactant A) 2 parts by weight, carboxybetaine type amphoteric surfactant (“Amogen CB-H”, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) (surfactant B) 2 parts by weight, oxazoline-based crosslinking 4 parts by weight (“Epocross WS-500” manufactured by Nippon Shokubai Co., Ltd., solid content 39%), 1 part by weight pigment (carbon black) (“NAF-5091” manufactured by Dainichi Seikagaku), silica (average particle size 5 ⁇ m) , BET specific surface area 80 ⁇ 130m 2 / g, an apparent specific gravity of 0.26 ⁇
  • This foamed composition was applied onto a release-treated PET (polyethylene terephthalate) film (thickness: 38 ⁇ m, trade name “MRF # 38” manufactured by Mitsubishi Plastics), 70 ° C. for 4.5 minutes, and 140 ° C. It was dried for 4.5 minutes to obtain a foam (foamed sheet) having an open cell structure having a thickness of 130 ⁇ m, an apparent density of 0.30 g / cm 3 and an initial elastic modulus of 0.53 N / mm 2 .
  • Comparative Example 1 100 parts by weight of acrylic emulsion solution (solid content 55%, ethyl acrylate-butyl acrylate-acrylonitrile copolymer (weight ratio 45: 48: 7)), fatty acid ammonium surfactant (aqueous dispersion of ammonium stearate, (Solid content 33%) (surfactant A) 1.5 parts by weight, carboxybetaine type amphoteric surfactant (“Amogen CB-H”, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) (surfactant B) 1 part by weight, oxazoline -Based crosslinking agent (Epocross WS-500, manufactured by Nippon Shokubai Co., Ltd., solid content 39%) 0.35 parts by weight, polyacrylic acid thickener (ethyl acrylate-acrylic acid copolymer (acrylic acid 20% by weight) , 0.78 parts by weight of solid content 28.7%) and 0.5 parts by weight of benzotriazole rust inhibitor
  • This foamed composition was applied onto a release-treated PET (polyethylene terephthalate) film (thickness: 38 ⁇ m, trade name “MRF # 38” manufactured by Mitsubishi Plastics), 70 ° C. for 4.5 minutes, and 140 ° C. Dried for 4.5 minutes, foamed with an open cell structure having a thickness of 130 ⁇ m, an apparent density of 0.33 g / cm 3 , an initial elastic modulus of 0.32 N / mm 2 , a maximum cell diameter of 110 ⁇ m, a minimum cell diameter of 20 ⁇ m, and an average cell diameter of 45 ⁇ m. A body (foamed sheet) was obtained.
  • Comparative Example 2 A commercially available polyethylene-based foam (“Bora La XLIM WF01”, manufactured by Sekisui Chemical Co., Ltd.) was used as the foam (foamed sheet).
  • the foam had a thickness of 100 ⁇ m, an apparent density of 0.31 g / cm 3 , and an initial elastic modulus of 13.13 N / mm 2 .
  • An average cell diameter ( ⁇ m) was obtained by capturing an enlarged image of the foam cross section with a low vacuum scanning electron microscope (“S-3400N scanning electron microscope” manufactured by Hitachi High-Tech Science Systems) and analyzing the image. The number of analyzed cells is 20. In the same manner, the minimum cell diameter ( ⁇ m) and the maximum cell diameter ( ⁇ m) of the foam were determined.
  • a foam (foamed sheet) is punched with a 100 mm ⁇ 100 mm punching blade mold, and the dimensions of the punched sample are measured. Further, the thickness is measured with a 1/100 dial gauge having a measurement terminal diameter ( ⁇ ) of 20 mm. The volume of the foam was calculated from these values. Next, the weight of the foam is measured with an upper pan balance having a minimum scale of 0.01 g or more. From these values, the apparent density (g / cm 3 ) of the foam was calculated.
  • the initial elastic modulus (N / mm 2 ) calculated from the slope at 10% strain in a tensile test at a tensile speed of 300 mm / min in a 23 ° C. environment was evaluated.
  • the R was 0.20 or more, and excellent shock absorption was exhibited.
  • R was less than 0.20.
  • a tacking tester (“TAC-2”, manufactured by Resca) was used.
  • TAC-2 A tacking tester
  • a SUS304 cylindrical probe having a diameter of 5 mm is pressed from the top of the foam sheet under the conditions of an indentation speed of 30 mm / min, an indentation load of 100 gf, and a press time of 1 second, and peeled off at a delamination speed of 30 mm / min.
  • the maximum load value (kN / m 2 ) was measured.
  • the maximum load value was 100 kN / m 2 or less, and the tackiness was significantly lowered as compared with Comparative Example 1.
  • the foamed sheet of the present invention is used, for example, in electrical / electronic devices when various members or parts (for example, optical members) are attached (attached) to a predetermined part (for example, a housing). It is useful as a member for electronic equipment, particularly as an impact absorbing sheet.

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Abstract

A foam sheet is provided which is extremely thin and exhibits excellent shock absorption. This foam sheet is configured from a foam body which has a thickness of 30-500 µm, an apparent density of 0.2-0.7 g/cm3, and an average cell diameter of 10-150 µm. In shock absorption tests using a pendulum impact tester, the value R obtained by dividing the shock absorption rate (%) defined in the specification, by the thickness (μm) of the foam sheet is 0.20 or greater given an impactor weight of 28g and a swing-up angle of 40°, and it holds of at least one surface of the foam sheet that in a 23°C environment, when pressing a cylindrical probe having a diameter φ of 5 mm and made of SUS 304 against said at least one surface with the conditions of a pressing speed of 30 mm/min, a pressing load of 100 gf, and a pressing time of 1 second, and separating said probe therefrom at a separation speed of 30 mm/min, the maximum load value is less than or equal to 100 kN/m2.

Description

低粘着性発泡シートLow adhesive foam sheet
　本発明は、厚さが小さくても衝撃吸収性に優れた発泡シート、及び該発泡シートが用いられている電気・電子機器に関する。 The present invention relates to a foam sheet excellent in shock absorption even if the thickness is small, and an electric / electronic device using the foam sheet.
　従来、液晶ディスプレイ、エレクトロルミネッセンスディスプレイ、プラズマディスプレイ等の画像表示装置に固定された画像表示部材や、いわゆる「携帯電話」、「スマートフォン」や「携帯情報端末」等に装着された表示部材、カメラ、レンズなどの光学部材を、所定の部位（例えば、筐体等）に固定する際に、発泡材が使用されている。このような発泡材としては、低発泡で且つ独立気泡構造を有する微細セルウレタン系発泡体や高発泡ウレタンを圧縮成形したものの他、独立気泡を有する発泡倍率３０倍程度のポリエチレン系発泡体などが使用されていた。具体的には、例えば、見掛け密度０．３～０．５ｇ／ｃｍ3のポリウレタン系発泡体からなるガスケット（特許文献１参照）や、平均気泡径が１～５００μｍの発泡構造体からなる電気・電子機器用シール材（特許文献２参照）などが使用されている。 Conventionally, an image display member fixed to an image display device such as a liquid crystal display, an electroluminescence display, a plasma display, a display member attached to a so-called “mobile phone”, “smart phone”, “portable information terminal”, camera, A foam material is used when an optical member such as a lens is fixed to a predetermined part (for example, a housing). Examples of such a foam material include a low-foam, fine-cell urethane-based foam having a closed cell structure and a product obtained by compression molding a highly foamed urethane, and a polyethylene-based foam having a closed cell and an expansion ratio of about 30 times. It was used. Specifically, for example, a gasket (see Patent Document 1) made of a polyurethane foam having an apparent density of 0.3 to 0.5 g / cm 3 , or an electrical / electric structure made of a foam structure having an average cell diameter of 1 to 500 μm. A sealing material for electronic devices (see Patent Document 2) is used.
　しかしながら、近年、光学部材（画像表示装置、カメラ、レンズなど）が装着される製品がますます薄型化されていくにつれ、発泡材が使われる部分のクリアランスが著しく減少していく傾向にある。このクリアランス減少に伴い、該発泡部材の厚さを小さくする必要があるが、従来の発泡材では、厚さを小さくすると十分な衝撃吸収性が発揮されない。そのため、例えば、「スマートフォン」等の表示部材付き電気・電子機器を地面等に落とした場合に、衝突する際の衝撃を吸収し、表示部材の破損を防止する発泡シートが求められている。 However, in recent years, as products to which optical members (image display devices, cameras, lenses, etc.) are mounted are becoming thinner and thinner, the clearance of the portion where the foam material is used tends to decrease remarkably. As the clearance decreases, it is necessary to reduce the thickness of the foamed member. However, when the thickness of the conventional foamed material is reduced, sufficient shock absorption is not exhibited. Therefore, for example, when an electric / electronic device with a display member such as “smartphone” is dropped on the ground or the like, there is a demand for a foam sheet that absorbs an impact at the time of collision and prevents the display member from being damaged.
　また、ＰＣ（パーソナルコンピュータ）、タブレットＰＣ、ＰＤＡ（個人用の携帯情報端末）、携帯電話等の電子機器の高機能化に伴い、表示部材等の破損防止のために用いられる衝撃吸収シートにその他の部材（例えば、熱伝導層）を積層させて組み込まれるようになっている。衝撃吸収シート表面に粘着性を有していると、位置ズレして組み付けてしまった際に、剥がして修正することが困難であり、歩留りが低下することから、表面粘着性の低い衝撃吸収シートが要望されている。 In addition to shock absorbing sheets used to prevent damage to display members, etc., as electronic devices such as PCs (personal computers), tablet PCs, PDAs (personal personal digital assistants), and mobile phones become more sophisticated. These members (for example, a heat conductive layer) are stacked and incorporated. If the shock-absorbing sheet has adhesiveness, it will be difficult to peel off and correct it when assembled and the yield will be reduced. Is desired.
特開２００１－１００２１６号公報Japanese Patent Laid-Open No. 2001-100216 特開２００２－３０９１９８号公報JP 2002-309198 A
　従って、本発明の目的は、厚さが非常に小さくても、優れた衝撃吸収性を発揮する発泡シートを提供することにある。
　本発明の他の目的は、上記特性に加え、他部材を積層する際に、位置修正が可能である発泡シートを提供することにある。
　また、本発明の別の目的は、小型化、薄型化されていても、落下時の衝撃により破損しにくい電気・電子機器を提供することにある。 Accordingly, an object of the present invention is to provide a foamed sheet that exhibits excellent shock absorption even when the thickness is very small.
Another object of the present invention is to provide a foam sheet that can be corrected in position when other members are laminated in addition to the above characteristics.
Another object of the present invention is to provide an electric / electronic device that is less likely to be damaged by an impact at the time of dropping even if it is reduced in size and thickness.
　本発明者らは、上記目的を達成するため鋭意検討した結果、特定の見掛け密度、特定の平均セル径、特定の衝撃吸収特性を有し、且つ表面タック性の低い発泡シートによれば、再剥離性に優れるとともに、３０～５００μｍという薄い厚みであっても衝撃吸収性に著しく優れること、そのためこのような発泡シートを他部材と積層する際には位置修正が容易であり、該発泡シートを組み込んだ電気・電子機器では、地面等に落としても衝撃等による表示装置等の破損が生じにくいことを見出した。本発明は上記知見を基づき、さらに検討を加えて完成したものである。 As a result of intensive investigations to achieve the above object, the present inventors have found that a foam sheet having a specific apparent density, a specific average cell diameter, a specific shock absorption characteristic, and a low surface tackiness is used again. In addition to excellent releasability, even a thin thickness of 30 to 500 μm is remarkably excellent in impact absorption. Therefore, when such a foam sheet is laminated with another member, position correction is easy. It has been found that the built-in electric / electronic devices are less likely to be damaged by a shock or the like even when dropped on the ground. The present invention has been completed based on the above findings and further studies.
　すなわち、本発明は、厚さが３０～５００μｍであり、見掛け密度が０．２～０．７ｇ／ｃｍ3、平均セル径が１０～１５０μｍである発泡体で構成されている発泡シートであり、振り子型衝撃試験機を用いた衝撃吸収性試験において、下記式で定義される衝撃吸収率（％）を発泡シートの厚さ（μｍ）で割った値Ｒが、衝撃子の重さ２８ｇ、振り上げ角度４０°の場合に０．２０以上であり、該発泡シートの少なくとも一方の面は、２３℃環境下で、直径φが５ｍｍのＳＵＳ３０４製円柱のプローブを、押し込み速さ３０ｍｍ／ｍｉｎ、押し込み荷重１００ｇｆ、プレス時間１秒の条件で押しつけ、剥離速さ３０ｍｍ／ｍｉｎで引き剥がした際の最大荷重値が１００ｋＮ／ｍ2以下である発泡シートを提供する。
　　衝撃吸収率（％）＝｛（Ｆ0－Ｆ1）／Ｆ0｝×１００
（上記式において、Ｆ0は支持板のみに衝撃子を衝突させた時の衝撃力のことであり、Ｆ1は支持板と発泡シートとからなる構造体の支持板上に衝撃子を衝突させた時の衝撃力のことである） That is, the present invention is a foam sheet composed of a foam having a thickness of 30 to 500 μm, an apparent density of 0.2 to 0.7 g / cm 3 , and an average cell diameter of 10 to 150 μm, In an impact absorption test using a pendulum type impact tester, a value R obtained by dividing the impact absorption rate (%) defined by the following formula by the thickness (μm) of the foamed sheet is 28 g in weight of the impactor. When the angle is 40 °, it is 0.20 or more, and at least one surface of the foam sheet is a 23 ° C. environment, a SUS304 cylindrical probe having a diameter φ of 5 mm, an indentation speed of 30 mm / min, an indentation load. Provided is a foamed sheet having a maximum load value of 100 kN / m 2 or less when pressed at 100 gf and a pressing time of 1 second and peeled at a peeling speed of 30 mm / min.
Impact absorption rate (%) = {(F 0 −F 1 ) / F 0 } × 100
(In the above formula, F 0 is the impact force when the impactor collides only with the support plate, and F 1 causes the impactor to collide with the support plate of the structure composed of the support plate and the foam sheet. Is the impact force when
　前記発泡体は、動的粘弾性測定における角振動数１ｒａｄ／ｓでの貯蔵弾性率と損失弾性率の比率である損失正接（ｔａｎδ）が－５０℃以上５０℃以下の範囲にピークトップを有することが好ましい。また前記損失正接（ｔａｎδ）は、－４０℃以上４０℃以下の範囲にピークトップを有することがより好ましく、－３０℃以上３０℃以下の範囲にピークトップを有することが更に好ましく、－２０℃以上２０℃以下の範囲にピークトップを有することが特に好ましい。 The foam has a peak top in a range where a loss tangent (tan δ), which is a ratio of a storage elastic modulus and a loss elastic modulus at an angular frequency of 1 rad / s in dynamic viscoelasticity measurement, is −50 ° C. or higher and 50 ° C. or lower. It is preferable. The loss tangent (tan δ) preferably has a peak top in the range of −40 ° C. to 40 ° C., more preferably has a peak top in the range of −30 ° C. to 30 ° C., and −20 ° C. It is particularly preferable to have a peak top in the range of 20 ° C. or lower.
　前記発泡体における損失正接（ｔａｎδ）の－５０℃以上５０℃以下の範囲での最大値が、０．２以上であることが好ましい。 The maximum value of the loss tangent (tan δ) in the foam in the range of −50 ° C. to 50 ° C. is preferably 0.2 or more.
　２３℃環境下で引張速度３００ｍｍ／ｍｉｎでの引張試験における発泡体の初期弾性率が１０Ｎ／ｍｍ2以下であることが好ましい。また前記初期弾性率は、０．１Ｎ／ｍｍ2以上１０Ｎ／ｍｍ2以下であることがより好ましく、０．１Ｎ／ｍｍ2以上５Ｎ／ｍｍ2以下であることが更に好ましい。 The initial elastic modulus of the foam in a tensile test at a tensile speed of 300 mm / min in an environment of 23 ° C. is preferably 10 N / mm 2 or less. Also, the initial elastic modulus is more preferably 0.1 N / mm 2 or more 10 N / mm 2 or less, and more preferably 0.1 N / mm 2 or more 5N / mm 2 or less.
　前記発泡体は、アクリル系ポリマー、ゴム、ウレタン系ポリマー、スチレン系ポリマー、及びエチレン－酢酸ビニル共重合体からなる群より選択された少なくとも１種の樹脂材料で形成することができる。 The foam can be formed of at least one resin material selected from the group consisting of acrylic polymer, rubber, urethane polymer, styrene polymer, and ethylene-vinyl acetate copolymer.
　前記発泡体は、架橋剤を含んでいてもよい。 The foam may contain a crosslinking agent.
　前記発泡体は、充填剤を含んでいてもよい。 The foam may contain a filler.
　前記発泡体は、エマルション樹脂組成物により形成されていてもよい。 The foam may be formed of an emulsion resin composition.
　前記発泡体は、樹脂組成物を機械的に発泡させる工程Ａを経て形成されていてもよい。この場合、発泡体は、さらに、機械的に発泡させたエマルション樹脂組成物を基材上に塗工して乾燥する工程Ｂを経て形成されていてもよい。 The foam may be formed through Step A of mechanically foaming the resin composition. In this case, the foam may be further formed through a step B in which a mechanically foamed emulsion resin composition is applied onto a substrate and dried.
　前記発泡体の片面又は両面に粘着剤層を有していてもよい。 The pressure-sensitive adhesive layer may be provided on one side or both sides of the foam.
　前記発泡シートは、電気・電子機器用衝撃吸収シートとして用いることができる。 The foamed sheet can be used as an impact absorbing sheet for electric / electronic devices.
　本発明は、また、前記の発泡シートが用いられている電気・電子機器を提供する。 The present invention also provides an electric / electronic device in which the foam sheet is used.
　この電気・電子機器には、表示部材を備えた電気・電子機器であって、前記の発泡シートが該電気又は電子機器の筐体と前記表示部材との間に挟持された構造を有する電気・電子機器が含まれる。 This electric / electronic device is an electric / electronic device provided with a display member, wherein the foam sheet is sandwiched between a housing of the electric or electronic device and the display member. Includes electronics.
　本発明の発泡シートは、厚さが薄くても、衝撃吸収性に優れるとともに、他部材（例えば、熱伝導層など）を積層する際に、位置ズレして組み付けてしまった際に、剥がして位置修正することができる。本発明の発泡シートを用いた電気・電子機器が地面等に落下しても、衝撃によるディスプレイ等の破損を防止できる。 Even if the foamed sheet of the present invention is thin, it has excellent shock absorption, and when other members (for example, a heat conductive layer) are laminated, they are peeled off when they are misaligned and assembled. The position can be corrected. Even if an electric / electronic device using the foamed sheet of the present invention falls on the ground or the like, it is possible to prevent damage to the display or the like due to impact.
振り子型衝撃試験機（衝撃試験装置）の概略構成図である。It is a schematic block diagram of a pendulum type impact tester (impact test device). 振り子型衝撃試験機（衝撃試験装置）の保持部材の概略構成を示す図である。It is a figure which shows schematic structure of the holding member of a pendulum type impact tester (impact test apparatus).
　本発明の発泡シートは、厚さが３０～５００μｍであり、見掛け密度が０．２～０．７ｇ／ｃｍ3、平均セル径が１０～１５０μｍである発泡体で構成されており、振り子型衝撃試験機を用いた衝撃吸収性試験において、後述の式で定義される衝撃吸収率（％）を発泡シートの厚さ（μｍ）で割った値Ｒが、衝撃子の重さ２８ｇ、振り上げ角度４０°の場合に０．２０以上であり、さらに、該発泡シートの少なくとも一方の面は、２３℃環境下で、直径φが５ｍｍのＳＵＳ３０４製円柱のプローブを、押し込み速さ３０ｍｍ／ｍｉｎ、押し込み荷重１００ｇｆ、プレス時間１秒の条件で押しつけ、剥離速さ３０ｍｍ／ｍｉｎで引き剥がした際の最大荷重値が１００ｋＮ／ｍ2以下である。そのため、衝撃吸収性に優れるとともに、他部材を積層する際に、位置ズレして組み付けても容易に位置修正できる。 The foam sheet of the present invention is composed of a foam having a thickness of 30 to 500 μm, an apparent density of 0.2 to 0.7 g / cm 3 , and an average cell diameter of 10 to 150 μm. In an impact absorption test using a testing machine, a value R obtained by dividing the impact absorption rate (%) defined by the formula described later by the thickness (μm) of the foamed sheet is a weight of impactor of 28 g and a swing-up angle of 40. In the case of °, it is 0.20 or more, and at least one surface of the foamed sheet is a 23 ° C. environment, a SUS304 cylindrical probe having a diameter φ of 5 mm, an indentation speed of 30 mm / min, an indentation load. The maximum load value is 100 kN / m 2 or less when pressed under the condition of 100 gf and pressing time of 1 second and peeled off at a peeling speed of 30 mm / min. Therefore, it is excellent in shock absorption, and when the other members are laminated, the position can be easily corrected even if they are misaligned and assembled.
　本発明の発泡シートの厚さは、３０～５００μｍである。その下限は、好ましくは４０μｍ、より好ましくは５０μｍであり、上限は、好ましくは４００μｍ、より好ましくは３００μｍ、さらに好ましくは２００μｍである。本発明では、発泡シートの厚さが３０μｍ以上であるため、気泡を均一に含有することができ、優れた衝撃吸収性を発揮できる。また、発泡シートの厚さが５００μｍ以下であるため、微小クリアランスに対しても容易に追従できる。本発明の発泡シートは、厚みが３０～５００μｍという薄さであるにもかかわらず、衝撃吸収性に優れる。 The thickness of the foamed sheet of the present invention is 30 to 500 μm. The lower limit is preferably 40 μm, more preferably 50 μm, and the upper limit is preferably 400 μm, more preferably 300 μm, and even more preferably 200 μm. In this invention, since the thickness of a foamed sheet is 30 micrometers or more, it can contain a bubble uniformly and can exhibit the outstanding impact absorption. Moreover, since the thickness of the foamed sheet is 500 μm or less, it can easily follow a minute clearance. The foamed sheet of the present invention is excellent in impact absorbency despite being as thin as 30 to 500 μm.
　本発明の発泡シートを構成する発泡体の見掛け密度は０．２～０．７ｇ／ｃｍ3である。その下限は、好ましくは０．２１ｇ／ｃｍ3、より好ましくは０．２２ｇ／ｃｍ3、上限は、好ましくは０．６ｇ／ｃｍ3、より好ましくは０．５ｇ／ｃｍ3、さらに好ましくは０．４ｇ／ｃｍ3である。発泡体の見掛け密度が０．２ｇ／ｃｍ3以上であることにより強度を維持でき、０．７ｇ／ｃｍ3以下であることにより高い衝撃吸収性が発揮される。また、発泡体の見掛け密度が０．２～０．４ｇ／ｃｍ3の範囲であることにより、さらにより高い衝撃吸収性が発揮される。 The apparent density of the foam constituting the foam sheet of the present invention is 0.2 to 0.7 g / cm 3 . The lower limit is preferably 0.21 g / cm 3 , more preferably 0.22 g / cm 3 , and the upper limit is preferably 0.6 g / cm 3 , more preferably 0.5 g / cm 3 , still more preferably 0.00. 4 g / cm 3 . When the apparent density of the foam is 0.2 g / cm 3 or more, the strength can be maintained, and when it is 0.7 g / cm 3 or less, high impact absorbability is exhibited. Further, when the apparent density of the foam is in the range of 0.2 to 0.4 g / cm 3 , even higher impact absorbability is exhibited.
　前記発泡体の平均セル径は、１０～１５０μｍである。その下限は、好ましくは１５μｍ、より好ましくは２０μｍであり、上限は、好ましくは１４０μｍ、より好ましくは１３０μｍ、さらに好ましくは１００μｍである。平均セル径が１０μｍ以上であることにより、優れた衝撃吸収性が発揮される。また、平均セル径が１５０μｍ以下であるため、圧縮回復性にも優れる。なお、前記発泡体の最大セル径は、例えば、４０～４００μｍであり、その下限は、好ましくは６０μｍ、より好ましくは８０μｍ、上限は、好ましくは３００μｍ、より好ましくは２２０μｍである。また、前記発泡体の最小セル径は、例えば、５～７０μｍであり、その下限は、好ましくは８μｍ、より好ましくは１０μｍ、上限は、好ましくは６０μｍ、より好ましくは５０μｍである。 The average cell diameter of the foam is 10 to 150 μm. The lower limit is preferably 15 μm, more preferably 20 μm, and the upper limit is preferably 140 μm, more preferably 130 μm, and even more preferably 100 μm. When the average cell diameter is 10 μm or more, excellent impact absorbability is exhibited. Moreover, since the average cell diameter is 150 μm or less, the compression recovery property is also excellent. The maximum cell diameter of the foam is, for example, 40 to 400 μm, and the lower limit is preferably 60 μm, more preferably 80 μm, and the upper limit is preferably 300 μm, more preferably 220 μm. The minimum cell diameter of the foam is, for example, 5 to 70 μm, and the lower limit is preferably 8 μm, more preferably 10 μm, and the upper limit is preferably 60 μm, more preferably 50 μm.
　なお、前記平均セル径は、走査型電子顕微鏡（ＳＥＭ）やデジタルマイクロスコープ等により、前記発泡体の断面のセル数が２０～４０点程度含まれる画像を観察し、該断面画像内のセル径が大きいセルから順に、セルの面積を２０点以上測定し、画像解析により面積から円の直径の平均値を算出して求めることができる。 The average cell diameter is determined by observing an image containing about 20 to 40 cells in the cross section of the foam with a scanning electron microscope (SEM), a digital microscope, or the like. In order from the largest cell, the area of the cell is measured at 20 points or more, and an average value of the diameter of the circle is calculated from the area by image analysis.
　本発明では、衝撃吸収性の観点から、平均セル径（μｍ）と発泡シートの厚さ（μｍ）の比（前者／後者）は、０．２～０．９の範囲にあるのが好ましい。上記平均セル径（μｍ）と発泡シートの厚さ（μｍ）の比の下限は、好ましくは０．２５、より好ましくは０．３であり、上限は、好ましくは０．８５、より好ましくは０．８である。 In the present invention, the ratio of the average cell diameter (μm) to the thickness of the foamed sheet (μm) (the former / the latter) is preferably in the range of 0.2 to 0.9 from the viewpoint of shock absorption. The lower limit of the ratio of the average cell diameter (μm) to the thickness of the foamed sheet (μm) is preferably 0.25, more preferably 0.3, and the upper limit is preferably 0.85, more preferably 0. .8.
　本発明の発泡シートは、薄肉でありながら優れた衝撃吸収性を有する。すなわち、振り子型衝撃試験機を用いた衝撃吸収性試験（衝撃子の重さ２８ｇ、振り上げ角度４０°）において、下記式で定義される衝撃吸収率（％）を発泡シートの厚さ（μｍ）で割り、単位厚さ当たりの衝撃吸収率Ｒを求めたとき、前記Ｒは０．２０以上である。前記Ｒは、好ましくは０．２５以上、さらに好ましくは０．２８以上である。前記Ｒの上限値は、例えば０．５程度である。
　　衝撃吸収率（％）＝｛（Ｆ0－Ｆ1）／Ｆ0｝×１００
（上記式において、Ｆ0は支持板のみに衝撃子を衝突させた時の衝撃力のことであり、Ｆ1は支持板と発泡シートとからなる構造体の支持板上に衝撃子を衝突させた時の衝撃力のことである） The foamed sheet of the present invention has excellent impact absorbability while being thin. That is, in an impact absorption test using a pendulum type impact tester (impactor weight 28 g, swing-up angle 40 °), the impact absorption rate (%) defined by the following formula is the thickness of the foam sheet (μm). When the impact absorption rate R per unit thickness is obtained by dividing by R, the R is 0.20 or more. R is preferably 0.25 or more, more preferably 0.28 or more. The upper limit value of R is, for example, about 0.5.
Impact absorption rate (%) = {(F 0 −F 1 ) / F 0 } × 100
(In the above formula, F 0 is the impact force when the impactor collides only with the support plate, and F 1 causes the impactor to collide with the support plate of the structure composed of the support plate and the foam sheet. Is the impact force when
　なお、前記衝撃吸収率は、発泡シートの厚さ等によっても異なるが、通常、１０～７０％であり、下限は、好ましくは２０％、より好ましくは３０％、さらに好ましくは３５％であり、上限は、好ましくは６０％である。 The impact absorption rate varies depending on the thickness of the foamed sheet, etc., but is usually 10 to 70%, and the lower limit is preferably 20%, more preferably 30%, still more preferably 35%. The upper limit is preferably 60%.
　振り子型衝撃試験機（衝撃試験装置）の概略構成について、図１及び図２により説明する。図１及び図２に示すように、衝撃試験装置１（振り子試験機１）は、試験片２（発泡シート２）を任意の保持力で保持する保持手段としての保持部材３と、試験片２に衝撃応力を負荷する衝撃負荷部材４と、衝撃負荷部材４による試験片２に対する衝撃力を検出する衝撃力検出手段としての圧力センサー５等により構成されている。また、試験片２を任意の保持力で保持する保持部材３は、固定治具１１と、固定治具１１に対向して試験片２を挟み込んで保持できるようスライド可能な押さえ治具１２とで構成されている。さらに、押さえ治具１２には押さえ圧力調整手段１６が設けられている。さらに、保持部材３によって保持された試験片２に衝撃力を負荷する衝撃負荷部材４は、一端２２が支柱２０に対して回動可能に軸支され、他端側に衝撃子２４を有する支持棒２３（シャフト２３）と、衝撃子２４を所定角度に持ち上げて保持するアーム２１とで構成されている。ここで衝撃子２４として鋼球を使用しているので、アームの一端に電磁石２５を設けることによって衝撃子２４を一体に所定角度持ち上げることが可能となっている。さらにまた、衝撃負荷部材４による試験片２に作用する衝撃力を検出する圧力センサー５は、固定治具１１の試験片が接する面の反対面側に設けられている。 A schematic configuration of a pendulum type impact tester (impact test apparatus) will be described with reference to FIGS. As shown in FIGS. 1 and 2, the impact test apparatus 1 (pendulum tester 1) includes a holding member 3 as a holding means for holding the test piece 2 (foamed sheet 2) with an arbitrary holding force, and the test piece 2 An impact load member 4 for applying an impact stress to the test piece, a pressure sensor 5 as an impact force detection means for detecting an impact force of the impact load member 4 against the test piece 2 and the like. The holding member 3 that holds the test piece 2 with an arbitrary holding force includes a fixing jig 11 and a holding jig 12 that is slidable so as to sandwich and hold the test piece 2 facing the fixing jig 11. It is configured. Further, the pressing jig 12 is provided with a pressing pressure adjusting means 16. Further, the impact load member 4 for applying an impact force to the test piece 2 held by the holding member 3 is supported so that one end 22 is pivotally supported with respect to the column 20 and an impactor 24 is provided on the other end side. It is composed of a rod 23 (shaft 23) and an arm 21 that lifts and holds the impactor 24 at a predetermined angle. Here, since a steel ball is used as the impactor 24, it is possible to lift the impactor 24 integrally by a predetermined angle by providing an electromagnet 25 at one end of the arm. Furthermore, the pressure sensor 5 that detects the impact force acting on the test piece 2 by the impact load member 4 is provided on the opposite side of the surface of the fixing jig 11 that contacts the test piece.
　衝撃子２４は、鋼球（鉄球）である。本発明においては、衝撃子２４がアーム２１により持ち上げられる角度（図１中の振り上げ角度ａ）は４０°であり、鋼球（鉄球）の重さは２８ｇである。 The impactor 24 is a steel ball (iron ball). In the present invention, the angle at which the impactor 24 is lifted by the arm 21 (the swing angle a in FIG. 1) is 40 °, and the weight of the steel ball (iron ball) is 28 g.
　図２に示すように、試験片２（発泡シート２）は、固定治具１１と押さえ治具１２間に樹脂性板材（アクリル板、ポリカーボネート板等）や金属製板材等の高弾性な板材で構成される支持板２８を介して挟持される。 As shown in FIG. 2, the test piece 2 (foamed sheet 2) is a highly elastic plate material such as a resin plate (acrylic plate, polycarbonate plate, etc.) or a metal plate between the fixing jig 11 and the holding jig 12. It is clamped via the support plate 28 configured.
　衝撃吸収性は、上記の衝撃試験装置を使用して、固定治具１１と支持板２８とを密着固定させてから衝撃子２４を支持板２８に衝突させることにより測定される衝撃力Ｆ0、及び固定治具１１と支持板２８と間に試験片２を挿入し密着固定させてから衝撃子２４を支持板２８に衝突させることにより測定される衝撃力Ｆ1を求め、前記式により算出される。なお、衝撃試験装置は、特開２００６－４７２７７号公報の実施例１と同様の装置である。 The impact absorbability is an impact force F 0 measured by causing the impactor 24 to collide with the support plate 28 after tightly fixing the fixing jig 11 and the support plate 28 using the impact test apparatus described above. The impact force F 1 measured by causing the impactor 24 to collide with the support plate 28 after inserting the test piece 2 between the fixing jig 11 and the support plate 28 and fixing the test piece 2 tightly is calculated. The Note that the impact test apparatus is the same apparatus as that of Example 1 of JP-A-2006-47277.
　衝撃吸収性は、平均セル径、見掛け密度等を選択することにより調整できる。しかし、発泡シートの厚さが非常に小さい場合には、これらの特性を調整するだけでは衝撃を十分に吸収できない場合がある。発泡シートの厚さが非常に薄い場合には、発泡体中の気泡が衝撃によりすぐに潰れて、気泡による衝撃緩衝機能が消失するからである。このような観点から、前記発泡体の動的粘弾性測定における角振動数１ｒａｄ／ｓでの貯蔵弾性率と損失弾性率の比率である損失正接（ｔａｎδ）のピークトップを－５０℃以上５０℃以下の範囲とすることが好ましい。損失正接（ｔａｎδ）のピークトップを上記範囲とすることで、気泡が潰れた後でも、発泡体の構成材料が衝撃を緩衝する機能を発揮する。 Shock absorption can be adjusted by selecting the average cell diameter, apparent density, and the like. However, when the thickness of the foamed sheet is very small, it may not be possible to sufficiently absorb the impact only by adjusting these characteristics. This is because when the thickness of the foam sheet is very thin, the bubbles in the foam are immediately crushed by the impact and the shock buffering function by the bubbles is lost. From such a viewpoint, the peak top of the loss tangent (tan δ), which is the ratio of the storage elastic modulus and the loss elastic modulus at an angular frequency of 1 rad / s in the dynamic viscoelasticity measurement of the foam, is −50 ° C. to 50 ° C. The following range is preferable. By setting the peak top of the loss tangent (tan δ) in the above range, the constituent material of the foam exhibits a function of buffering the impact even after the bubbles are crushed.
　前記損失正接のピークトップが存在する温度範囲の下限は、好ましくは－４０℃、より好ましくは－３０℃、さらに好ましくは－２０℃であり、上限は、好ましくは４０℃、より好ましくは３０℃、さらに好ましくは２０℃である。損失正接のピークトップを２個以上持つ材料の場合は、そのうちの少なくとも１つが上記範囲に入ることが望ましい。ピーク温度が－５０℃以上であることにより、優れた圧縮回復性が発揮される。また、ピーク温度が５０℃以下であることにより、高い柔軟性を示し、優れた衝撃吸収性が発揮される。 The lower limit of the temperature range where the peak tangent of the loss tangent exists is preferably −40 ° C., more preferably −30 ° C., further preferably −20 ° C., and the upper limit is preferably 40 ° C., more preferably 30 ° C. More preferably, it is 20 ° C. In the case of a material having two or more peak tops of loss tangents, it is desirable that at least one of them falls within the above range. When the peak temperature is −50 ° C. or higher, excellent compression recovery is exhibited. Moreover, when the peak temperature is 50 ° C. or lower, high flexibility is exhibited and excellent shock absorption is exhibited.
　－５０℃以上５０℃以下の範囲における損失正接（ｔａｎδ）のピークトップ強度（最大値）は衝撃吸収性の観点から高い方が好ましく、例えば０．２以上、好ましくは０．３以上である。前記ピークトップ強度（最大値）の上限値は、例えば２．０である。 The peak top strength (maximum value) of loss tangent (tan δ) in the range of −50 ° C. or higher and 50 ° C. or lower is preferably higher from the viewpoint of shock absorption, for example 0.2 or higher, preferably 0.3 or higher. The upper limit value of the peak top intensity (maximum value) is, for example, 2.0.
　このように、前記損失正接（ｔａｎδ）のピーク温度、ピークトップ強度が発泡体の衝撃吸収性に大きく寄与する。発泡体の動的粘弾性測定における角振動数１ｒａｄ／ｓでの貯蔵弾性率と損失弾性率の比率である損失正接（ｔａｎδ）のピークトップが－５０℃以上５０℃以下の範囲に存在すると、発泡シートの衝撃吸収性が高くなる理由は必ずしも明らかではないが、衝撃の周波数に合うところに前記損失正接（ｔａｎδ）のピークが存在していることによるものと推測される。すなわち、前記損失正接（ｔａｎδ）が－５０℃以上５０℃以下の範囲は、粘弾性測定における温度時間換算則より、構造物の落下衝撃に相当する周波数の範囲に換算されるため、－５０℃以上５０℃以下の範囲に前記損失正接（ｔａｎδ）のピーク温度を有する発泡シートほど、衝撃吸収性が高くなると推測される。また、貯蔵弾性率は、発泡シートに加わる衝撃エネルギーに対する反発力であり、貯蔵弾性率が高いと衝撃をそのまま反発する。一方で損失弾性率は、発泡シートに加わる衝撃エネルギーを熱に換える物性であり、損失弾性率が高いほど衝撃エネルギーを熱に換えるため、衝撃を吸収し、ひずみを小さくする。このことから、衝撃を多く熱に換え、且つ反発力が小さい、すなわち貯蔵弾性率と損失弾性率との比率である損失正接（ｔａｎδ）が大きい発泡シートほど、衝撃吸収率が高いと推測される。 Thus, the peak temperature and peak top strength of the loss tangent (tan δ) greatly contribute to the shock absorption of the foam. When the peak top of the loss tangent (tan δ), which is the ratio of the storage elastic modulus and the loss elastic modulus at an angular frequency of 1 rad / s in the dynamic viscoelasticity measurement of the foam, is in the range of −50 ° C. or more and 50 ° C. or less, The reason why the foam sheet has high impact absorbability is not necessarily clear, but it is presumed that the loss tangent (tan δ) peak exists at a location that matches the frequency of impact. That is, the range where the loss tangent (tan δ) is −50 ° C. or more and 50 ° C. or less is converted to the frequency range corresponding to the drop impact of the structure by the temperature-time conversion rule in the viscoelasticity measurement. It is presumed that the shock absorption becomes higher as the foamed sheet has a peak temperature of the loss tangent (tan δ) in the range of 50 ° C. or lower. The storage elastic modulus is a repulsive force with respect to the impact energy applied to the foam sheet. If the storage elastic modulus is high, the impact is repelled as it is. On the other hand, the loss elastic modulus is a physical property that changes impact energy applied to the foam sheet to heat, and the higher the loss elastic modulus is, the more the impact energy is changed to heat, so the impact is absorbed and the strain is reduced. From this, it is surmised that a foam sheet having a larger loss tangent (tan δ), which is a ratio of the storage elastic modulus and the loss elastic modulus, has a higher impact absorption rate by changing the impact to heat and reducing the repulsive force. .
　本発明の発泡シートにおいては、該発泡シートの少なくとも一方の面は、位置修正性の観点から粘着性（タック性）が低い方が望ましい。該粘着性は公知のプローブタック法によるタッキング試験機により測定でき、該発泡シートの少なくとも一方の面は、２３℃環境下で、直径φが５ｍｍのＳＵＳ３０４製円柱のプローブを、押し込み速さ３０ｍｍ／ｍｉｎ、押し込み荷重１００ｇｆ、プレス時間１秒の条件で押しつけ、剥離速さ３０ｍｍ／ｍｉｎで引き剥がした際の最大荷重値が１００ｋＮ／ｍ2以下である。該最大荷重値は、好ましくは、８０ｋＮ／ｍ2以下、より好ましくは６０ｋＮ／ｍ2以下、さらに好ましくは５０ｋＮ／ｍ2以下である。なお、該最大荷重値の下限値は０である。すなわち、本発明の発泡シートは表面のタック性が非常に低い。そのため、他部材を発泡シートに積層する際、位置ズレして組み付けても、容易に剥がして位置修正できる。 In the foamed sheet of the present invention, it is desirable that at least one surface of the foamed sheet has low adhesiveness (tackiness) from the viewpoint of position correction. The adhesiveness can be measured by a known tacking tester using a probe tack method. At least one surface of the foamed sheet is a 23 ° C. environment, and a SUS304 cylindrical probe having a diameter φ of 5 mm is pressed at a speed of 30 mm / The maximum load value is 100 kN / m 2 or less when pressed under the conditions of min, indentation load 100 gf, and press time 1 second, and peeled off at a peeling speed of 30 mm / min. It said maximum load value, preferably, 80 kN / m 2 or less, more preferably 60 kN / m 2, more preferably not more than 50 kN / m 2. The lower limit value of the maximum load value is 0. That is, the foam sheet of the present invention has a very low surface tack. Therefore, when laminating other members on the foamed sheet, even if they are misaligned and assembled, they can be easily removed to correct the position.
　発泡シートの表面のタック性を低下させる手段として、例えば、発泡体の架橋密度を上げたり、充填剤を適宜量添加したり、発泡体を構成する樹脂材料にＴｇが高い（例えば、５０～２００℃）ポリマー（例えば、スチレン系ポリマー等）を適宜量配合することなどが挙げられる。 As a means for reducing the tackiness of the surface of the foamed sheet, for example, the crosslinking density of the foam is increased, an appropriate amount of filler is added, or the resin material constituting the foam has a high Tg (for example, 50 to 200). ° C) polymer (for example, styrene-based polymer, etc.) may be blended in an appropriate amount.
　前記発泡体の初期弾性率は、衝撃吸収性の観点から低い方が望ましい。該初期弾性率（２３℃環境下、引張速度３００ｍｍ／ｍｉｎでの引張試験における１０％歪み時の傾きから算出した値）は、好ましくは１０Ｎ／ｍｍ2以下であり、より好ましくは５Ｎ／ｍｍ2以下である。なお、前記初期弾性率の下限値は、例えば、０．１Ｎ／ｍｍ2である。 The initial elastic modulus of the foam is preferably low from the viewpoint of impact absorption. The initial elastic modulus (a value calculated from a slope at the time of 10% strain in a tensile test under a 23 ° C. environment and a tensile speed of 300 mm / min) is preferably 10 N / mm 2 or less, more preferably 5 N / mm 2. It is as follows. The lower limit value of the initial elastic modulus is, for example, 0.1 N / mm 2 .
　本発明の発泡シートを構成する発泡体としては、前記特性を有していれば、その組成や気泡構造などは特に制限されない。気泡構造としては、連続気泡構造、独立気泡構造、半連続半独立気泡構造のいずれであってもよい。衝撃吸収性の観点からは、連続気泡構造、半連続半独立気泡構造が好ましい。 The foam constituting the foam sheet of the present invention is not particularly limited in its composition and cell structure as long as it has the above characteristics. The cell structure may be any of an open cell structure, a closed cell structure, and a semi-continuous semi-closed cell structure. From the viewpoint of impact absorption, an open cell structure and a semi-open semi-closed cell structure are preferable.
　前記発泡体は、樹脂材料（ポリマー）を含む樹脂組成物により構成することができる。なお、未発泡状態の該樹脂組成物［発泡させない場合の樹脂組成物（固形物）］の動的粘弾性測定における角振動数１ｒａｄ／ｓでの貯蔵弾性率と損失弾性率の比率である損失正接（ｔａｎδ）のピークトップは－５０℃以上５０℃以下の範囲にあるのが好ましい。前記損失正接のピークトップが存在する温度範囲の下限は、好ましくは－４０℃、より好ましくは－３０℃、さらに好ましくは－２０℃であり、上限は、好ましくは４０℃、より好ましくは３０℃、さらに好ましくは２０℃である。損失正接のピークトップを２個以上持つ材料の場合は、そのうちの少なくとも１つが上記範囲に入ることが望ましい。該樹脂組成物（固形物）の－５０℃以上５０℃以下の範囲での損失正接（ｔａｎδ）のピークトップ強度（この値は、前記発泡体における－５０℃以上５０℃以下の範囲における損失正接（ｔａｎδ）のピークトップ強度を発泡体の見掛け密度（ｇ／ｃｍ3）で割った値に相当する）は衝撃吸収性の観点から高い方が好ましい。例えば、前記樹脂組成物（固形物）の－５０℃以上５０℃以下の範囲での損失正接（ｔａｎδ）のピークトップ強度は、好ましくは０．９（ｇ／ｃｍ3）-1以上であり、上限は、例えば、３（ｇ／ｃｍ3）-1程度である。 The foam can be constituted by a resin composition containing a resin material (polymer). In addition, the loss which is a ratio of the storage elastic modulus and the loss elastic modulus at an angular frequency of 1 rad / s in the dynamic viscoelasticity measurement of the resin composition in an unfoamed state [resin composition when not foamed (solid matter)] The peak top of tangent (tan δ) is preferably in the range of −50 ° C. to 50 ° C. The lower limit of the temperature range where the peak tangent of the loss tangent exists is preferably −40 ° C., more preferably −30 ° C., further preferably −20 ° C., and the upper limit is preferably 40 ° C., more preferably 30 ° C. More preferably, it is 20 ° C. In the case of a material having two or more peak tops of loss tangents, it is desirable that at least one of them falls within the above range. Loss tangent (tan δ) peak top strength of the resin composition (solid) in the range of −50 ° C. to 50 ° C. (this value is the loss tangent of the foam in the range of −50 ° C. to 50 ° C.) The peak top strength of (tan δ) (corresponding to the value obtained by dividing the apparent density (g / cm 3 ) of the foam) is preferably higher from the viewpoint of impact absorption. For example, the peak top intensity of the loss tangent (tan δ) in the range of −50 ° C. to 50 ° C. of the resin composition (solid material) is preferably 0.9 (g / cm 3 ) −1 or more, The upper limit is, for example, about 3 (g / cm 3 ) −1 .
　また、未発泡状態の該樹脂組成物（固形物）の初期弾性率（２３℃、引張速度３００ｍｍ／ｍｉｎ）は、低い方が望ましく、好ましくは５０Ｎ／ｍｍ2以下、より好ましくは３０Ｎ／ｍｍ2以下である。なお、前記初期弾性率の下限値は、例えば、０．３Ｎ／ｍｍ2である。 Further, the initial elastic modulus (23 ° C., tensile speed 300 mm / min) of the unfoamed resin composition (solid material) is desirably lower, preferably 50 N / mm 2 or less, more preferably 30 N / mm 2. It is as follows. The lower limit value of the initial elastic modulus is, for example, 0.3 N / mm 2 .
　前記発泡体を構成する樹脂材料（ポリマー）としては、特に限定されず、発泡体を構成する公知乃至周知の樹脂材料を使用できる。該樹脂材料として、例えば、アクリル系ポリマー、ゴム、ウレタン系ポリマー、スチレン系ポリマー、エチレン－酢酸ビニル共重合体などが挙げられる。これらの中でも、衝撃吸収性の観点から、アクリル系ポリマー、ゴム、ウレタン系ポリマー、スチレン系ポリマーが好ましい。発泡体を構成する樹脂材料（ポリマー）は１種単独であってもよく、２種以上であってもよい。 The resin material (polymer) constituting the foam is not particularly limited, and a known or well-known resin material constituting the foam can be used. Examples of the resin material include acrylic polymer, rubber, urethane polymer, styrene polymer, and ethylene-vinyl acetate copolymer. Among these, acrylic polymer, rubber, urethane polymer, and styrene polymer are preferable from the viewpoint of impact absorption. One type of resin material (polymer) constituting the foam may be used alone, or two or more types may be used.
　優れた衝撃吸収性を保持しつつシート表面のタック性を低くして位置修正のしやすい発泡シートを得るという観点からは、アクリル系ポリマー、ゴム、ウレタン系ポリマー及びエチレン－酢酸ビニル共重合体からなる群より選択された少なくとも１種の樹脂材料と、スチレン系ポリマーとを組み合わせて使用するのが好ましい。この場合、スチレン系ポリマーの使用量は、アクリル系ポリマー、ゴム、ウレタン系ポリマー及びエチレン－酢酸ビニル共重合体からなる群より選択された少なくとも１種の樹脂材料１００重量部に対して、例えば、０．１～１００重量部であり、その下限は、好ましくは１重量部、さらに好ましくは５重量部であり、その上限は、好ましくは８０重量部、さらに好ましくは５０重量部である。 From the viewpoint of obtaining a foam sheet that is easy to correct the position by reducing the tackiness of the sheet surface while maintaining excellent shock absorption, from acrylic polymer, rubber, urethane polymer and ethylene-vinyl acetate copolymer It is preferable to use a combination of at least one resin material selected from the group and a styrenic polymer. In this case, the amount of the styrene polymer used is, for example, 100 parts by weight of at least one resin material selected from the group consisting of an acrylic polymer, rubber, urethane polymer, and ethylene-vinyl acetate copolymer. The lower limit thereof is preferably 1 part by weight, more preferably 5 parts by weight, and the upper limit thereof is preferably 80 parts by weight, more preferably 50 parts by weight.
　なお、前記発泡体の動的粘弾性測定における角振動数１ｒａｄ／ｓでの貯蔵弾性率と損失弾性率の比率である損失正接（ｔａｎδ）のピークトップを－５０℃以上５０℃以下の範囲にするためには、前記樹脂材料（ポリマー）のＴｇを指標あるいは目安とすることができる。例えば、前記発泡体を構成する樹脂材料（ポリマー）のＴｇが－５０℃以上５０℃未満（下限は、好ましくは－４０℃、より好ましくは－３０℃、上限は、好ましくは４０℃、より好ましくは３０℃）の範囲となるように樹脂材料（ポリマー）を選択することができる。 The peak top of the loss tangent (tan δ), which is the ratio of the storage elastic modulus and the loss elastic modulus at an angular frequency of 1 rad / s in the dynamic viscoelasticity measurement of the foam, is in the range of −50 ° C. to 50 ° C. For this purpose, the Tg of the resin material (polymer) can be used as an index or a guide. For example, the resin material (polymer) constituting the foam has a Tg of −50 ° C. or more and less than 50 ° C. (lower limit is preferably −40 ° C., more preferably −30 ° C., upper limit is preferably 40 ° C., more preferably The resin material (polymer) can be selected so as to be in the range of 30 ° C.
　前記アクリル系ポリマーとしては、ホモポリマーのＴｇが－１０℃以上のモノマーと、ホモポリマーのＴｇが－１０℃未満のモノマーを必須のモノマー成分として形成されたアクリル系ポリマーが好ましい。このようなアクリル系ポリマーを用い、前者のモノマーと後者のモノマーの量比を調整することにより、動的粘弾性測定における角振動数１ｒａｄ／ｓでの貯蔵弾性率と損失弾性率の比率である損失正接（ｔａｎδ）のピークトップが－５０℃以上５０℃以下の発泡体を比較的容易に得ることができる。 The acrylic polymer is preferably an acrylic polymer formed with a monomer having a homopolymer Tg of −10 ° C. or more and a monomer having a homopolymer Tg of less than −10 ° C. as essential monomer components. Using such an acrylic polymer, the ratio of the storage elastic modulus and loss elastic modulus at an angular frequency of 1 rad / s in dynamic viscoelasticity measurement is obtained by adjusting the amount ratio of the former monomer and the latter monomer. A foam having a loss tangent (tan δ) peak top of −50 ° C. or more and 50 ° C. or less can be obtained relatively easily.
　なお、本発明における「ホモポリマーを形成した際のガラス転移温度（Ｔｇ）」（単に「ホモポリマーのＴｇ」と称する場合がある）とは、「当該モノマーの単独重合体のガラス転移温度（Ｔｇ）」を意味し、具体的には、「Ｐｏｌｙｍｅｒ　Ｈａｎｄｂｏｏｋ」（第３版、Ｊｏｈｎ　Ｗｉｌｅｙ＆Ｓｏｎｓ，Ｉｎｃ、１９８７年）に数値が挙げられている。なお、上記文献に記載されていないモノマーのホモポリマーのＴｇは、例えば、以下の測定方法により得られる値（特開２００７－５１２７１号公報参照）をいう。すなわち、温度計、撹拌機、窒素導入管及び還流冷却管を備えた反応器に、モノマー１００重量部、２，２’－アゾビスイソブチロニトリル０．２重量部及び重合溶媒として酢酸エチル２００重量部を投入し、窒素ガスを導入しながら１時間撹拌する。このようにして重合系内の酸素を除去した後、６３℃に昇温し１０時間反応させる。次いで、室温まで冷却し、固形分濃度３３重量％のホモポリマー溶液を得る。次いで、このホモポリマー溶液をセパレータ上に流延塗布し、乾燥して厚さ約２ｍｍの試験サンプル（シート状のホモポリマー）を作製する。そして、この試験サンプルを直径７．９ｍｍの円盤状に打ち抜き、パラレルプレートで挟み込み、粘弾性試験機（ＡＲＥＳ、レオメトリックス社製）を用いて周波数１Ｈｚの剪断歪を与えながら、温度領域－７０～１５０℃、５℃／分の昇温速度で剪断モードにより粘弾性を測定し、ｔａｎδのピークトップ温度をホモポリマーのＴｇとする。なお、上記樹脂材料（ポリマー）のＴｇもこの方法により測定できる。 In the present invention, “glass transition temperature (Tg) when forming a homopolymer” (sometimes simply referred to as “Tg of homopolymer”) means “glass transition temperature (Tg of homopolymer of the monomer)”. ) ”, Specifically,“ Polymer Handbook ”(3rd edition, John Wiley & Sons, Inc., 1987). The Tg of a homopolymer of a monomer not described in the above document refers to, for example, a value obtained by the following measurement method (see JP 2007-51271 A). That is, in a reactor equipped with a thermometer, a stirrer, a nitrogen introduction tube and a reflux condenser, 100 parts by weight of monomer, 0.2 part by weight of 2,2′-azobisisobutyronitrile, and ethyl acetate 200 as a polymerization solvent. A part by weight is charged and stirred for 1 hour while introducing nitrogen gas. After removing oxygen in the polymerization system in this way, the temperature is raised to 63 ° C. and the reaction is carried out for 10 hours. Next, the mixture is cooled to room temperature to obtain a homopolymer solution having a solid concentration of 33% by weight. Next, this homopolymer solution is cast-coated on a separator and dried to prepare a test sample (sheet-like homopolymer) having a thickness of about 2 mm. This test sample was punched into a disk shape having a diameter of 7.9 mm, sandwiched between parallel plates, and subjected to a shear strain at a frequency of 1 Hz using a viscoelasticity tester (ARES, manufactured by Rheometrics). Viscoelasticity is measured in a shear mode at a heating rate of 150 ° C. and 5 ° C./min, and the peak top temperature of tan δ is defined as Tg of the homopolymer. The Tg of the resin material (polymer) can also be measured by this method.
　ホモポリマーのＴｇが－１０℃以上のモノマーにおいて、該Ｔｇは、例えば、－１０℃～２５０℃、好ましくは１０～２３０℃、さらに好ましくは５０～２００℃である。 In a monomer having a homopolymer Tg of −10 ° C. or higher, the Tg is, for example, −10 ° C. to 250 ° C., preferably 10 to 230 ° C., more preferably 50 to 200 ° C.
　上記のホモポリマーのＴｇが－１０℃以上のモノマーとして、例えば、（メタ）アクリロニトリル；（メタ）アクリルアミド、Ｎ－ヒドロキシエチル（メタ）アクリルアミド等のアミド基含有モノマー；（メタ）アクリル酸；メタクリル酸メチル、メタクリル酸エチル等のホモポリマーのＴｇが－１０℃以上の（メタ）アクリル酸アルキルエステル；（メタ）アクリル酸イソボルニル；Ｎ－ビニル－２－ピロリドン等の複素環含有ビニルモノマー；２－ヒドロキシエチルメタクリレート等のヒドロキシル基含有モノマーなどを例示することができる。これらは１種単独で又は２種以上を組み合わせて使用できる。これらの中でも、特に、（メタ）アクリロニトリル（とりわけ、アクリロニトリル）が好ましい。ホモポリマーのＴｇが－１０℃以上のモノマーとして（メタ）アクリロニトリル（とりわけ、アクリロニトリル）を用いると、分子間相互作用が強いためか、発泡体の前記損失正接（ｔａｎδ）のピークトップ強度を大きくすることができる。 Examples of the homopolymer having a Tg of −10 ° C. or more include, for example, (meth) acrylonitrile; amide group-containing monomers such as (meth) acrylamide and N-hydroxyethyl (meth) acrylamide; (meth) acrylic acid; methacrylic acid (Meth) acrylic acid alkyl esters having homopolymers such as methyl and ethyl methacrylate having a Tg of −10 ° C. or higher; (meth) acrylic acid isobornyl; heterocycle-containing vinyl monomers such as N-vinyl-2-pyrrolidone; Examples thereof include hydroxyl group-containing monomers such as ethyl methacrylate. These can be used individually by 1 type or in combination of 2 or more types. Among these, (meth) acrylonitrile (especially acrylonitrile) is particularly preferable. When (meth) acrylonitrile (especially acrylonitrile) is used as a monomer having a homopolymer Tg of −10 ° C. or higher, the peak top strength of the loss tangent (tan δ) of the foam is increased because of the strong intermolecular interaction. be able to.
　ホモポリマーのＴｇが－１０℃未満のモノマーにおいて、該Ｔｇは、例えば、－７０℃以上－１０℃未満、好ましくは－７０℃～－１２℃、さらに好ましくは－６５℃～－１５℃である。 In a monomer having a Tg of less than −10 ° C., the Tg is, for example, −70 ° C. or more and less than −10 ° C., preferably −70 ° C. to −12 ° C., more preferably −65 ° C. to −15 ° C. .
　上記のホモポリマーのＴｇが－１０℃未満のモノマーとして、例えば、アクリル酸エチル、アクリル酸ブチル、アクリル酸２－エチルヘキシル等のホモポリマーのＴｇが－１０℃未満の（メタ）アクリル酸アルキルエステルなどが挙げられる。これらは１種単独で又は２種以上を組み合わせて使用できる。これらの中でも、特に、アクリル酸Ｃ2-8アルキルエステルが好ましい。 Examples of the homopolymer having a Tg of less than −10 ° C. include, for example, (meth) acrylic acid alkyl esters having a homopolymer Tg of less than −10 ° C., such as ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, etc. Is mentioned. These can be used individually by 1 type or in combination of 2 or more types. Among these, acrylic acid C 2-8 alkyl ester is particularly preferable.
　上記アクリル系ポリマーを形成する全モノマー成分（モノマー成分全量）に対する、ホモポリマーのＴｇが－１０℃以上のモノマーの含有量は、例えば、２～３０重量％であり、下限は、好ましくは３重量％、より好ましくは４重量％であり、上限は、好ましくは２５重量％、より好ましくは２０重量％である。また、上記アクリル系ポリマーを形成する全モノマー成分（モノマー成分全量）に対する、ホモポリマーのＴｇが－１０℃未満のモノマーの含有量は、例えば、７０～９８重量％であり、下限は、好ましくは７５重量％、より好ましくは８０重量％であり、上限は、好ましくは９７重量％、より好ましくは９６重量％である。 The content of the monomer having a Tg of -10 ° C. or more of the homopolymer is, for example, 2 to 30% by weight with respect to all the monomer components forming the acrylic polymer (total amount of monomer components), and the lower limit is preferably 3%. %, More preferably 4% by weight, and the upper limit is preferably 25% by weight, more preferably 20% by weight. In addition, the content of the monomer having a Tg of the homopolymer of less than −10 ° C. with respect to all the monomer components forming the acrylic polymer (total amount of monomer components) is, for example, 70 to 98% by weight, and the lower limit is preferably The upper limit is preferably 97% by weight, more preferably 96% by weight.
　なお、アクリル系ポリマーを形成するモノマー中に窒素原子含有共重合性モノマーが含まれていると、エマルション樹脂組成物を機械的撹拌等によりせん断を加えて発泡させる際は組成物の粘度が低下して多数の気泡がエマルション内に取り込まれやすくなるとともに、その後気泡を含有するエマルション樹脂組成物を基材上に塗布し静置状態で乾燥する際には該組成物が凝集しやすくなって粘度が上昇し、気泡が組成物内に保持され外部に拡散しにくくなるため、発泡特性に優れた発泡体を得ることができる。 If the monomer that forms the acrylic polymer contains a nitrogen atom-containing copolymerizable monomer, the viscosity of the composition decreases when the emulsion resin composition is foamed by applying mechanical shearing or the like. Many bubbles are likely to be taken into the emulsion, and when the emulsion resin composition containing the bubbles is applied onto a substrate and dried in a stationary state, the composition tends to aggregate and the viscosity is increased. The foam rises and the bubbles are retained in the composition and hardly diffused to the outside, so that a foam having excellent foaming characteristics can be obtained.
　前記窒素原子含有共重合性モノマー（窒素原子含有モノマー）としては、例えば、(メタ)アクリロニトリル等のシアノ基含有モノマー；Ｎ－ビニル－２－ピロリドン等のラクタム環含有モノマー；（メタ）アクリルアミド、Ｎ－ヒドロキシエチル（メタ）アクリルアミド、Ｎ－メチロールアクリルアミド、Ｎ，Ｎ－ジメチルアクリルアミド、Ｎ，Ｎ－ジエチルアクリルアミド、ジアセトンアクリルアミド等のアミド基含有モノマーなどが挙げられる。これらの中でも、アクリロニトリル等のシアノ基含有モノマー、Ｎ－ビニル－２－ピロリドン等のラクタム環含有モノマーが好ましい。窒素原子含有モノマーは１種単独で、又は２種以上を組み合わせて用いることができる。 Examples of the nitrogen atom-containing copolymerizable monomer (nitrogen atom-containing monomer) include cyano group-containing monomers such as (meth) acrylonitrile; lactam ring-containing monomers such as N-vinyl-2-pyrrolidone; (meth) acrylamide, N And amide group-containing monomers such as hydroxyethyl (meth) acrylamide, N-methylolacrylamide, N, N-dimethylacrylamide, N, N-diethylacrylamide, and diacetoneacrylamide. Among these, cyano group-containing monomers such as acrylonitrile and lactam ring-containing monomers such as N-vinyl-2-pyrrolidone are preferable. A nitrogen atom containing monomer can be used individually by 1 type or in combination of 2 or more types.
　このような窒素原子含有モノマーに由来する構造単位を有するアクリル系ポリマーにおいて、窒素原子含有モノマーに由来する構造単位の含有量は、アクリル系ポリマーを構成する全構造単位に対して、好ましくは２～３０重量％であり、その下限は、より好ましくは３重量％、さらに好ましくは４重量％であり、その上限は、より好ましくは２５重量％、さらに好ましくは２０重量％である。 In such an acrylic polymer having a structural unit derived from a nitrogen atom-containing monomer, the content of the structural unit derived from the nitrogen atom-containing monomer is preferably 2 to 2 with respect to all the structural units constituting the acrylic polymer. The lower limit is more preferably 3% by weight, still more preferably 4% by weight, and the upper limit is more preferably 25% by weight, still more preferably 20% by weight.
　また、このような窒素原子含有モノマーに由来する構造単位を有するアクリル系ポリマーにおいては、窒素原子含有モノマーに由来する構造単位のほかに、アクリル酸Ｃ2-18アルキルエステル（特に、アクリル酸Ｃ2-8アルキルエステル）に由来する構造単位を含んでいることが好ましい。アクリル酸Ｃ2-18アルキルエステルは１種単独で、又は２種以上を組み合わせて用いることができる。このようなアクリル系ポリマーにおいて、アクリル酸Ｃ2-18アルキルエステル（特に、アクリル酸Ｃ2-8アルキルエステル）に由来する構造単位の含有量は、アクリル系ポリマーを構成する全構造単位に対して、好ましくは７０～９８重量％であり、その下限は、より好ましくは７５重量％、さらに好ましくは８０重量％であり、その上限は、より好ましくは９７重量％、さらに好ましくは９６重量％である。 In addition, in the acrylic polymer having a structural unit derived from such a nitrogen atom-containing monomer, in addition to the structural unit derived from the nitrogen atom-containing monomer, an acrylic acid C 2-18 alkyl ester (particularly acrylic acid C 2 -8 alkyl ester) is preferred. Acrylic acid C 2-18 alkyl ester can be used alone or in combination of two or more. In such an acrylic polymer, the content of structural units derived from acrylic acid C 2-18 alkyl esters (particularly acrylic acid C 2-8 alkyl esters) is based on the total structural units constituting the acrylic polymer. The lower limit is more preferably 75% by weight, still more preferably 80% by weight, and the upper limit is more preferably 97% by weight, still more preferably 96% by weight. .
　前記ゴムとしては、天然ゴム、合成ゴムのいずれであってもよい。前記ゴムとして、例えば、ニトリルゴム（ＮＢＲ）、メチルメタクリレート－ブタジエンゴム（ＭＢＲ）、スチレン－ブタジエンゴム（ＳＢＲ）、アクリルゴム（ＡＣＭ、ＡＮＭ）、ウレタンゴム（ＡＵ）、シリコーンゴムなどが挙げられる。これらの中でも、ニトリルゴム（ＮＢＲ）、メチルメタクリレート－ブタジエンゴム（ＭＢＲ）、シリコーンゴムが好ましい。 The rubber may be natural rubber or synthetic rubber. Examples of the rubber include nitrile rubber (NBR), methyl methacrylate-butadiene rubber (MBR), styrene-butadiene rubber (SBR), acrylic rubber (ACM, ANM), urethane rubber (AU), and silicone rubber. Among these, nitrile rubber (NBR), methyl methacrylate-butadiene rubber (MBR), and silicone rubber are preferable.
　前記ウレタン系ポリマーとしては、例えば、ポリカーボネート系ポリウレタン、ポリエステル系ポリウレタン、ポリエーテル系ポリウレタンなどが挙げられる。 Examples of the urethane polymer include polycarbonate polyurethane, polyester polyurethane, and polyether polyurethane.
　エチレン－酢酸ビニル共重合体としては、公知乃至周知のエチレン－酢酸ビニル共重合体を使用できる。 As the ethylene-vinyl acetate copolymer, a known or well-known ethylene-vinyl acetate copolymer can be used.
　スチレン系ポリマーとしては、公知乃至周知のスチレン系ポリマーを使用できる。 As the styrene polymer, a known or well-known styrene polymer can be used.
　前記発泡シートを構成する発泡体は、樹脂材料（ポリマー）のほか、必要に応じて、界面活性剤、架橋剤、増粘剤、防錆剤、その他の添加物を含んでいてもよい。 The foam constituting the foam sheet may contain a surfactant, a cross-linking agent, a thickener, a rust preventive agent, and other additives as required in addition to the resin material (polymer).
　例えば、気泡径の微細化、起泡した泡の安定性のために、任意の界面活性剤を含んでいてもよい。界面活性剤としては特に制限されず、アニオン系界面活性剤、カチオン系界面活性剤、ノニオン系界面活性剤、両性界面活性剤等のいずれを用いてもよいが、気泡径の微細化、起泡した泡の安定性の観点から、アニオン系界面活性剤が好ましく、特にステアリン酸アンモニウム等の脂肪酸アンモニウム系界面活性剤がより好ましい。界面活性剤は１種単独で用いてもよく、２種以上を組み合わせて用いてもよい。また、異種の界面活性剤を併用してもよく、例えば、アニオン系界面活性剤とノニオン系界面活性剤、アニオン系界面活性剤と両性界面活性剤を併用してもよい。 For example, an optional surfactant may be included for the purpose of reducing the bubble diameter and stabilizing the foam. The surfactant is not particularly limited, and any of an anionic surfactant, a cationic surfactant, a nonionic surfactant, an amphoteric surfactant, and the like may be used. From the viewpoint of the stability of the foam, an anionic surfactant is preferable, and a fatty acid ammonium surfactant such as ammonium stearate is more preferable. Surfactant may be used individually by 1 type and may be used in combination of 2 or more type. Different surfactants may be used in combination, for example, an anionic surfactant and a nonionic surfactant, or an anionic surfactant and an amphoteric surfactant may be used in combination.
　界面活性剤の添加量［固形分（不揮発分）］は、例えば、樹脂材料（ポリマー）［固形分（不揮発分）］１００重量部に対して、０～１０重量部であり、下限は好ましくは０．５重量部、上限は好ましくは８重量部である。 The addition amount [solid content (nonvolatile content)] of the surfactant is, for example, 0 to 10 parts by weight with respect to 100 parts by weight of the resin material (polymer) [solid content (nonvolatile content)], and the lower limit is preferably 0.5 part by weight, the upper limit is preferably 8 parts by weight.
　また、発泡体の強度、耐熱性、耐湿性を向上させるために、任意の架橋剤を含んでいてもよい。架橋剤は特に制限されず、油溶性、水溶性のいずれを用いてもよい。架橋剤として、例えば、エポキシ系、オキサゾリン系、イソシアネート系、カルボジイミド系、メラミン系、金属酸化物系などが挙げられる。中でも、オキサゾリン系架橋剤が好ましい。 Moreover, in order to improve the strength, heat resistance, and moisture resistance of the foam, an arbitrary cross-linking agent may be included. The crosslinking agent is not particularly limited, and any of oil-soluble and water-soluble may be used. Examples of the crosslinking agent include epoxy, oxazoline, isocyanate, carbodiimide, melamine, and metal oxide. Among these, an oxazoline-based crosslinking agent is preferable.
　架橋剤の添加量［固形分（不揮発分）］は、例えば、樹脂材料（ポリマー）［固形分（不揮発分）］１００重量部に対して、０～３０重量部であり、下限は好ましくは０．０１重量部、上限は好ましくは２０重量部である。発泡シートの表面のタック性を低下させるという観点からは、架橋剤の添加量［固形分（不揮発分）］は、例えば、樹脂材料［ポリマー、特に架橋点（ヒドロキシル基、カルボキシル基等）を有するポリマー］［固形分（不揮発分）］１００重量部に対して、０．５～３０重量部が好ましく、その下限は、より好ましくは１重量部、さらに好ましくは２重量部であり、その上限は、より好ましくは２５重量部、さらに好ましくは２０重量部である。 The addition amount [solid content (nonvolatile content)] of the crosslinking agent is, for example, 0 to 30 parts by weight with respect to 100 parts by weight of the resin material (polymer) [solid content (nonvolatile content)], and the lower limit is preferably 0. 0.01 parts by weight, and the upper limit is preferably 20 parts by weight. From the viewpoint of reducing the tackiness of the surface of the foamed sheet, the addition amount of the crosslinking agent [solid content (nonvolatile content)] has, for example, a resin material [polymer, particularly a crosslinking point (hydroxyl group, carboxyl group, etc.). Polymer] [Solid content (nonvolatile content)] is preferably 0.5 to 30 parts by weight with respect to 100 parts by weight, and the lower limit thereof is more preferably 1 part by weight, still more preferably 2 parts by weight. More preferably, it is 25 parts by weight, still more preferably 20 parts by weight.
　さらに、起泡した泡の安定性、成膜性の向上のために、任意の増粘剤を含んでいてもよい。増粘剤としては特に制限されず、アクリル酸系、ウレタン系、ポリビニルアルコール系などが挙げられる。中でも、ポリアクリル酸系増粘剤、ウレタン系増粘剤が好ましい。 Furthermore, in order to improve the stability of the foamed foam and the film forming property, an optional thickener may be included. The thickener is not particularly limited, and examples thereof include acrylic acid type, urethane type, and polyvinyl alcohol type. Of these, polyacrylic acid thickeners and urethane thickeners are preferred.
　増粘剤の添加量［固形分（不揮発分）］は、例えば、樹脂材料（ポリマー）［固形分（不揮発分）］１００重量部に対して、０～１０重量部であり、下限は好ましくは０．１重量部、上限は好ましくは５重量部である。 The addition amount of the thickener [solid content (nonvolatile content)] is, for example, 0 to 10 parts by weight with respect to 100 parts by weight of the resin material (polymer) [solid content (nonvolatile content)], and the lower limit is preferably 0.1 parts by weight, the upper limit is preferably 5 parts by weight.
　また、発泡シートに隣接する金属部材の腐食防止のため、任意の防錆剤を含んでいてもよい。該防錆剤として、アゾール環含有化合物が好ましい。アゾール環含有化合物を用いると、金属に対する腐食防止性と被着体に対する密着性とを高いレベルで両立できる。 Also, an arbitrary rust inhibitor may be included to prevent corrosion of the metal member adjacent to the foam sheet. As the rust inhibitor, an azole ring-containing compound is preferable. When an azole ring-containing compound is used, it is possible to achieve both high levels of corrosion prevention for metals and adhesion to adherends.
　前記アゾール環含有化合物としては、環内に窒素原子を１個以上含む５員環を有する化合物であればよく、例えば、ジアゾール（イミダゾール、ピラゾール）環、トリアゾール環、テトラゾール環、オキサゾール環、イソオキサゾール環、チアゾール環、又はイソチアゾール環を有する化合物などが挙げられる。これらの環はベンゼン環等の芳香環と縮合して縮合環を形成していてもよい。このような縮合環を有する化合物として、例えば、ベンゾイミダゾール環、ベンゾピラゾール環、ベンゾトリアゾール環、ベンゾオキサゾール環、ベンゾイソオキサゾール環、ベンゾチアゾール環、又はベンゾイソチアゾール環を有する化合物などが挙げられる。 The azole ring-containing compound may be a compound having a 5-membered ring containing one or more nitrogen atoms in the ring. For example, a diazole (imidazole, pyrazole) ring, triazole ring, tetrazole ring, oxazole ring, isoxazole And compounds having a ring, a thiazole ring, or an isothiazole ring. These rings may be condensed with an aromatic ring such as a benzene ring to form a condensed ring. Examples of the compound having such a condensed ring include a compound having a benzimidazole ring, a benzopyrazole ring, a benzotriazole ring, a benzoxazole ring, a benzoisoxazole ring, a benzothiazole ring, or a benzoisothiazole ring.
　前記アゾール環、前記縮合環（ベンゾトリアゾール環、ベンゾチアゾール環等）は、それぞれ、置換基を有していてもよい。該置換基としては、例えば、メチル基、エチル基、プロピル基、イソプロピル基、ブチル基等の炭素数１～６（好ましくは炭素数１～３）のアルキル基；メトキシ基、エトキシ基、イソプロピルオキシ基、ブトキシ基等の炭素数１～１２（好ましくは炭素数１～３）のアルコキシ基；フェニル基、トリル基、ナフチル基等の炭素数６～１０のアリール基；アミノ基；メチルアミノ基、ジメチルアミノ基等の（モノ又はジ）Ｃ1-10アルキルアミノ基；アミノメチル基、２－アミノエチル基等のアミノ－Ｃ1-6アルキル基；Ｎ，Ｎ－ジエチルアミノメチル基、Ｎ，Ｎ－ビス（２－エチルヘキシル）アミノメチル基等のモノ又はジ（Ｃ1-10アルキル）アミノ－Ｃ1-6アルキル基；メルカプト基；メトキシカルボニル基、エトキシカルボニル基等の炭素数１～６のアルコキシカルボニル基；カルボキシル基；カルボキシメチル基等のカルボキシ－Ｃ1-6アルキル基；２－カルボキシエチルチオ基等のカルボキシ－Ｃ1-6アルキルチオ基；Ｎ，Ｎ－ビス（ヒドロキシメチル）アミノメチル基等のＮ，Ｎ－ビス（ヒドロキシ－Ｃ1-4アルキル）アミノ－Ｃ1-4アルキル基；スルホ基などが挙げられる。また、前記アゾール環含有化合物は、ナトリウム塩、カリウム塩等の塩を形成していてもよい。 The azole ring and the condensed ring (benzotriazole ring, benzothiazole ring, etc.) each may have a substituent. Examples of the substituent include alkyl groups having 1 to 6 carbon atoms (preferably 1 to 3 carbon atoms) such as methyl group, ethyl group, propyl group, isopropyl group and butyl group; methoxy group, ethoxy group, isopropyloxy An alkoxy group having 1 to 12 carbon atoms (preferably 1 to 3 carbon atoms) such as a butoxy group; an aryl group having 6 to 10 carbon atoms such as a phenyl group, a tolyl group or a naphthyl group; an amino group; a methylamino group; (Mono or di) C 1-10 alkylamino group such as dimethylamino group; amino-C 1-6 alkyl group such as aminomethyl group, 2-aminoethyl group; N, N-diethylaminomethyl group, N, N— bis (2-ethylhexyl) mono or di (C 1-10 alkyl) such as aminomethyl group amino -C 1-6 alkyl group; a mercapto group; a methoxycarbonyl group, the number of carbon atoms such as an ethoxycarbonyl group An alkoxycarbonyl group having 1-6; carboxyl group; carboxyl -C such as 2-carboxyethyl thio group 1-6 alkylthio group; carboxy carboxy -C 1-6 alkyl group such as a methyl group N, N-bis (hydroxymethyl) N, N-bis (hydroxy-C 1-4 alkyl) amino-C 1-4 alkyl group such as aminomethyl group; sulfo group and the like. The azole ring-containing compound may form a salt such as a sodium salt or a potassium salt.
　金属に対する防錆作用の点から、アゾール環がベンゼン環等の芳香環と縮合環を形成している化合物が好ましく、中でも、ベンゾトリアゾール系化合物（ベンゾトリアゾール環を有する化合物）、ベンゾチアゾール系化合物（ベンゾチアゾール環を有する化合物）が特に好ましい。 From the viewpoint of rust prevention action on metals, compounds in which the azole ring forms a condensed ring with an aromatic ring such as a benzene ring are preferred. A compound having a benzothiazole ring is particularly preferred.
　上記ベンゾトリアゾール系化合物としては、例えば、１，２，３－ベンゾトリアゾール、メチルベンゾトリアゾール、カルボキシベンゾトリアゾール、カルボキシメチルベンゾトリアゾール、１－［Ｎ，Ｎ－ビス（２－エチルヘキシル）アミノメチル］ベンゾトリアゾール、１－［Ｎ，Ｎ－ビス（２－エチルヘキシル）アミノメチル］メチルベンゾトリアゾール、２，２′－［［（メチル－１Ｈ－ベンゾトリアゾール－１－イル）メチル］イミノ］ビスエタノール、又はこれらのナトリウム塩などが挙げられる。 Examples of the benzotriazole compounds include 1,2,3-benzotriazole, methylbenzotriazole, carboxybenzotriazole, carboxymethylbenzotriazole, and 1- [N, N-bis (2-ethylhexyl) aminomethyl] benzotriazole. 1- [N, N-bis (2-ethylhexyl) aminomethyl] methylbenzotriazole, 2,2 ′-[[(methyl-1H-benzotriazol-1-yl) methyl] imino] bisethanol, or these A sodium salt etc. are mentioned.
　上記ベンゾチアゾール系化合物としては、例えば、２－メルカプトベンゾチアゾール、３－(２－（ベンゾチアゾリル）チオ）プロピオン酸、又はこれらのナトリウム塩などが挙げられる。 Examples of the benzothiazole compound include 2-mercaptobenzothiazole, 3- (2- (benzothiazolyl) thio) propionic acid, or a sodium salt thereof.
　アゾール環含有化合物は１種単独で用いてもよく、２種以上を組み合わせて用いてもよい。 The azole ring-containing compound may be used alone or in combination of two or more.
　防錆剤（例えば、前記アゾール環含有化合物）［固形分（不揮発分）］の添加量［固形分（不揮発分）］は、被着体に対する密着性や発泡体本来の特性を損なわない範囲であればよく、例えば、樹脂材料（ポリマー）［固形分（不揮発分）］１００重量部に対して、例えば、０．２～５重量部が好ましい。その下限は、より好ましくは０．３重量部、さらに好ましくは０．４重量部であり、その上限は、より好ましくは３重量部、さらに好ましくは２重量部である。 The addition amount [solid content (nonvolatile content)] of the rust inhibitor (for example, the azole ring-containing compound) [solid content (nonvolatile content)] is within a range that does not impair the adhesion to the adherend and the original properties of the foam. For example, 0.2 to 5 parts by weight is preferable with respect to 100 parts by weight of the resin material (polymer) [solid content (nonvolatile content)]. The lower limit is more preferably 0.3 parts by weight, still more preferably 0.4 parts by weight, and the upper limit is more preferably 3 parts by weight, still more preferably 2 parts by weight.
　また、衝撃吸収性を損なわない範囲内で、任意の適切な他の成分を含んでいてもよい。このような他の成分は、１種のみを含んでいてもよいし、２種以上を含んでいてもよい。該他の成分としては、例えば、前記以外のポリマー成分、軟化剤、酸化防止剤、老化防止剤、ゲル化剤、硬化剤、可塑剤、充填剤、補強剤、発泡剤（重曹など）、マイクロカプセル（熱膨張性微小球等）、難燃剤、光安定剤、紫外線吸収剤、着色剤（顔料や染料など）、ｐＨ調整剤、溶剤（有機溶剤）、熱重合開始剤、光重合開始剤などが挙げられる。これらの成分の添加量［固形分（不揮発分）］は、被着体に対する密着性や発泡体本来の特性を損なわない範囲であればよく、例えば、樹脂材料（ポリマー）［固形分（不揮発分）］１００重量部に対して、それぞれ、例えば０．２～１００重量部の範囲が好ましい。 Further, any appropriate other component may be included within the range not impairing the shock absorption. Such other components may contain only 1 type and may contain 2 or more types. Examples of the other components include polymer components other than those described above, softeners, antioxidants, anti-aging agents, gelling agents, curing agents, plasticizers, fillers, reinforcing agents, foaming agents (such as baking soda), micro Capsules (thermally expandable microspheres, etc.), flame retardants, light stabilizers, UV absorbers, colorants (pigments, dyes, etc.), pH adjusters, solvents (organic solvents), thermal polymerization initiators, photopolymerization initiators, etc. Is mentioned. The addition amount [solid content (nonvolatile content)] of these components may be in a range that does not impair the adhesion to the adherend and the original properties of the foam. For example, resin material (polymer) [solid content (nonvolatile content) )] For example, a range of 0.2 to 100 parts by weight is preferable with respect to 100 parts by weight.
　発泡剤（重曹等）の添加量［固形分（不揮発分）］は、樹脂材料（ポリマー）［固形分（不揮発分）］１００重量部に対して、より好ましくは０．５～２０重量部である。マイクロカプセル（熱膨張性微小球等）の添加量［固形分（不揮発分）］は、樹脂材料（ポリマー）［固形分（不揮発分）］１００重量部に対して、より好ましくは０．２～１０重量部である。 The addition amount [solid content (nonvolatile content)] of the foaming agent (e.g. baking soda) is preferably 0.5 to 20 parts by weight with respect to 100 parts by weight of the resin material (polymer) [solid content (nonvolatile content)]. is there. The addition amount [solid content (nonvolatile content)] of the microcapsule (thermally expandable microspheres) is more preferably 0.2 to 100 parts by weight with respect to 100 parts by weight of the resin material (polymer) [solid content (nonvolatile content)]. 10 parts by weight.
　前記充填剤としては、例えば、シリカ、クレー（マイカ、タルク、スメクタイト等）、アルミナ、水酸化アルミニウム、アルカリ土類金属の水酸化物（水酸化マグネシウム等）、アルカリ土類金属の炭化物（炭化カルシウム等）、チタニア、酸化亜鉛、酸化スズ、ゼオライト、グラファイト、カーボンナノチューブ、無機繊維（炭素繊維、ガラス繊維、チタン酸カリウム繊維等）、有機繊維、金属粉（銀、銅等）、ワックス（ポリエチレンワックス、ポリプロピレンワックス等）などが挙げられる。また、充填剤として、圧電粒子（酸化チタン、チタン酸バリウム等）、導電性粒子（導電性酸化チタン、酸化スズ等）、熱伝導性粒子（窒化ホウ素等）、有機フィラー（シリコーンパウダー、ポリエチレンパウダー、ポリプロピレンパウダー等）などを添加することもできる。 Examples of the filler include silica, clay (mica, talc, smectite, etc.), alumina, aluminum hydroxide, alkaline earth metal hydroxide (magnesium hydroxide, etc.), and alkaline earth metal carbide (calcium carbide). Etc.), titania, zinc oxide, tin oxide, zeolite, graphite, carbon nanotube, inorganic fiber (carbon fiber, glass fiber, potassium titanate fiber, etc.), organic fiber, metal powder (silver, copper, etc.), wax (polyethylene wax) , Polypropylene wax, etc.). As fillers, piezoelectric particles (titanium oxide, barium titanate, etc.), conductive particles (conductive titanium oxide, tin oxide, etc.), thermally conductive particles (boron nitride, etc.), organic fillers (silicone powder, polyethylene powder) , Polypropylene powder, etc.) can also be added.
　充填剤の添加量は、樹脂材料（ポリマー）［固形分（不揮発分）］１００重量部に対して、例えば０．３～１００重量部である。発泡シートの表面のタック性を低下させるという観点からは、充填剤の添加量は、好ましくは１～１００重量部であり、その下限は、好ましくは５重量部、さらに好ましくは１０重量部であり、その上限は、好ましくは８０重量部、さらに好ましくは５０重量部である。なお、充填剤として、マイカ等のクレーを用いる場合、その添加量は、樹脂材料（ポリマー）［固形分（不揮発分）］１００重量部に対して、０．３～１０重量部の範囲が特に好ましい。また、充填剤として、圧電粒子を用いる場合、その添加量は、樹脂材料（ポリマー）［固形分（不揮発分）］１００重量部に対して、５～４０重量部の範囲が特に好ましい。さらに、充填剤として、導電性粒子を用いる場合、その添加量は、樹脂材料（ポリマー）［固形分（不揮発分）］１００重量部に対して、５～４０重量部の範囲が特に好ましい。また、充填剤として圧電粒子と導電性粒子とを組み合わせて用いると、圧力により電荷の発生量を調整することができる。この場合、圧電粒子と導電性粒子の比率は、例えば、前者／後者（重量比）＝１０／９０～９０／１０、好ましくは、前者／後者（重量比）＝２０／８０～８０／２０、さらに好ましくは、前者／後者（重量比）＝３０／７０～７０／３０である。 The amount of the filler added is, for example, 0.3 to 100 parts by weight with respect to 100 parts by weight of the resin material (polymer) [solid content (non-volatile content)]. From the viewpoint of reducing the tackiness of the surface of the foam sheet, the amount of filler added is preferably 1 to 100 parts by weight, and the lower limit thereof is preferably 5 parts by weight, more preferably 10 parts by weight. The upper limit is preferably 80 parts by weight, more preferably 50 parts by weight. When clay such as mica is used as the filler, the addition amount is particularly in the range of 0.3 to 10 parts by weight with respect to 100 parts by weight of the resin material (polymer) [solid content (nonvolatile content)]. preferable. In addition, when piezoelectric particles are used as the filler, the addition amount thereof is particularly preferably in the range of 5 to 40 parts by weight with respect to 100 parts by weight of the resin material (polymer) [solid content (nonvolatile content)]. Further, when conductive particles are used as the filler, the addition amount thereof is particularly preferably in the range of 5 to 40 parts by weight with respect to 100 parts by weight of the resin material (polymer) [solid content (nonvolatile content)]. In addition, when piezoelectric particles and conductive particles are used in combination as fillers, the amount of generated charges can be adjusted by pressure. In this case, the ratio of the piezoelectric particles to the conductive particles is, for example, the former / the latter (weight ratio) = 10/90 to 90/10, preferably the former / the latter (weight ratio) = 20/80 to 80/20, More preferably, the former / the latter (weight ratio) = 30/70 to 70/30.
　本発明の発泡シートは、発泡体を構成する樹脂材料（ポリマー）を含む樹脂組成物を発泡成形に付すことにより製造できる。発泡方法（気泡の形成方法）としては、物理的方法、化学的方法等、発泡成形に通常用いられる方法が採用できる。一般的に物理的方法は、空気や窒素などのガス成分をポリマー溶液に分散させて、機械的混合により気泡を形成させるもの（機械発泡体）である。また、化学的方法は、ポリマーベースに添加された発泡剤の熱分解により生じたガスによりセルを形成し、発泡体を得る方法である。環境問題などの観点から、物理的方法が好ましい。物理的方法により形成される気泡は、連続気泡であることが多い。 The foam sheet of the present invention can be produced by subjecting a resin composition containing a resin material (polymer) constituting the foam to foam molding. As the foaming method (bubble forming method), methods usually used for foam molding, such as physical methods and chemical methods, can be employed. In general, the physical method is a method in which gas components such as air and nitrogen are dispersed in a polymer solution and bubbles are formed by mechanical mixing (mechanical foam). The chemical method is a method of obtaining a foam by forming cells with a gas generated by thermal decomposition of a foaming agent added to a polymer base. From the viewpoint of environmental problems, a physical method is preferable. Bubbles formed by physical methods are often open cells.
　発泡成形に付す樹脂材料（ポリマー）を含む樹脂組成物としては、樹脂材料を溶剤に溶解させた樹脂溶液を用いてもよいが、気泡性の観点から、樹脂材料を含むエマルション（エマルション樹脂組成物）を用いるのが好ましい。すなわち、本発明の発泡シートを構成する発泡体は、エマルション樹脂組成物の発泡体であることが好ましい。エマルションとしては、２種以上のエマルションをブレンドして用いてもよい。 As a resin composition containing a resin material (polymer) to be subjected to foam molding, a resin solution in which a resin material is dissolved in a solvent may be used. From the viewpoint of cellularity, an emulsion containing a resin material (emulsion resin composition) ) Is preferably used. That is, it is preferable that the foam which comprises the foam sheet of this invention is a foam of an emulsion resin composition. As an emulsion, you may blend and use 2 or more types of emulsion.
　エマルションの固形分濃度は成膜性の観点から高い方が好ましい。エマルションの固形分濃度は、好ましくは３０重量％以上、より好ましくは４０重量％以上、さらに好ましくは５０重量％以上である。 The solid content concentration of the emulsion is preferably higher from the viewpoint of film formability. The solid content concentration of the emulsion is preferably 30% by weight or more, more preferably 40% by weight or more, and further preferably 50% by weight or more.
　本発明では、樹脂組成物（例えば、エマルション樹脂組成物）を機械的に発泡させて起泡化させる工程（工程Ａ）を経て発泡体を作製する方法が好ましい。すなわち、本発明の発泡シートを構成する発泡体は、樹脂組成物（例えば、エマルション樹脂組成物）の機械発泡体であることが好ましい。起泡装置としては、特に限定されず、例えば、高速せん断方式、振動方式、加圧ガスの吐出方式などの装置が挙げられる。これらの中でも、気泡径の微細化、大容量作製の観点から、高速せん断方式が好ましい。 In the present invention, a method of producing a foam through a step (Step A) in which a resin composition (for example, an emulsion resin composition) is foamed mechanically is preferable. That is, it is preferable that the foam which comprises the foam sheet of this invention is a mechanical foam of a resin composition (for example, emulsion resin composition). The foaming device is not particularly limited, and examples thereof include a high-speed shearing method, a vibration method, and a pressurized gas discharge method. Among these, the high-speed shearing method is preferable from the viewpoint of finer bubble diameter and production of a large capacity.
　機械的撹拌により起泡した際の気泡は、気体（ガス）がエマルション中に取り込まれたものである。ガスとしては、エマルションに対して不活性であれば特に制限されず、空気、窒素、二酸化炭素などが挙げられる。中でも、経済性の観点から、空気が好ましい。 Bubbles when foamed by mechanical stirring are gas (gas) taken into the emulsion. The gas is not particularly limited as long as it is inert to the emulsion, and examples thereof include air, nitrogen, carbon dioxide and the like. Among these, air is preferable from the viewpoint of economy.
　上記方法により起泡化した樹脂組成物（例えば、エマルション樹脂組成物）を基材上に塗工して乾燥する工程（工程Ｂ）を経ることで、本発明の発泡シートを得ることができる。前記基材としては、特に限定されないが、例えば、剥離処理したプラスチックフィルム（剥離処理したポリエチレンテレフタレートフィルム等）、プラスチックフィルム（ポリエチレンテレフタレートフィルム等）、熱伝導層（後述の熱伝導層）などが挙げられる。熱伝導層を基材として塗工した場合には、発泡体層と熱伝導層の密着性を向上でき、また、発泡体層作製時の乾燥工程の効率も向上できる。 The foamed sheet of the present invention can be obtained through a step (Step B) in which a resin composition (for example, an emulsion resin composition) foamed by the above method is applied onto a substrate and dried. The substrate is not particularly limited, and examples thereof include a peeled plastic film (such as a peeled polyethylene terephthalate film), a plastic film (such as a polyethylene terephthalate film), and a heat conductive layer (a heat conductive layer described later). It is done. When coating is performed using the heat conductive layer as a base material, the adhesion between the foam layer and the heat conductive layer can be improved, and the efficiency of the drying process when the foam layer is produced can also be improved.
　前記工程Ｂにおいて、塗工方法、乾燥方法としては、一般的な方法を採用できる。工程Ｂは、基材上に塗布した気泡含有樹脂組成物（例えば、エマルション樹脂組成物）を５０℃以上１２５℃未満で乾燥する予備乾燥工程Ｂ１と、その後さらに１２５℃以上２００℃以下で乾燥する本乾燥工程Ｂ２を含んでいることが好ましい。 In the step B, a general method can be adopted as a coating method and a drying method. Step B is a pre-drying step B1 in which the bubble-containing resin composition (eg, emulsion resin composition) applied on the substrate is dried at 50 ° C. or higher and lower than 125 ° C., and then further dried at 125 ° C. or higher and 200 ° C. or lower. It is preferable that this drying process B2 is included.
　予備乾燥工程Ｂ１と本乾燥工程Ｂ２を設けることにより、急激な温度上昇による気泡の合一化、気泡の破裂を防止できる。特に厚さの小さい発泡シートでは温度の急激な上昇により気泡が合一か、破裂するので、予備乾燥工程Ｂ１を設ける意義は大きい。予備乾燥工程Ｂ１における温度は、好ましくは５０℃以上１００℃以下である。予備乾燥工程Ｂ１の時間は、例えば、０．５分～３０分、好ましくは１分～１５分である。また、本乾燥工程Ｂ２における温度は、好ましくは１３０℃以上１８０℃以下、より好ましくは１３０℃以上１６０℃以下である。本乾燥工程Ｂ２の時間は、例えば、０．５分～３０分、好ましくは１分～１５分である。 By providing the preliminary drying step B1 and the main drying step B2, it is possible to prevent the bubbles from being coalesced and the bubbles to burst due to a rapid temperature rise. In particular, in the foam sheet having a small thickness, bubbles are united or ruptured due to a rapid rise in temperature, and therefore, the provision of the preliminary drying step B1 is significant. The temperature in the preliminary drying step B1 is preferably 50 ° C. or higher and 100 ° C. or lower. The time of the preliminary drying step B1 is, for example, 0.5 minutes to 30 minutes, preferably 1 minute to 15 minutes. Moreover, the temperature in this drying process B2 becomes like this. Preferably they are 130 degreeC or more and 180 degrees C or less, More preferably, they are 130 degreeC or more and 160 degrees C or less. The time of the main drying step B2 is, for example, 0.5 minutes to 30 minutes, preferably 1 minute to 15 minutes.
　発泡体の平均セル径、最大セル径、及び最小セル径は、界面活性剤の種類や量を調整することや、機械的撹拌時の撹拌速度や撹拌時間を調整することで、平均セル径が１０～１５０μｍの範囲である発泡シートを得ることができる。 The average cell diameter, maximum cell diameter, and minimum cell diameter of the foam can be adjusted by adjusting the type and amount of the surfactant, and by adjusting the stirring speed and stirring time during mechanical stirring. A foam sheet having a range of 10 to 150 μm can be obtained.
　発泡体の見掛け密度は、機械的撹拌時の樹脂組成物（例えば、エマルション樹脂組成物）中に取り込む気体（ガス）成分量を調整することで、０．２～０．７ｇ／ｃｍ3の見掛け密度の発泡シートを得ることができる。 The apparent density of the foam is an apparent density of 0.2 to 0.7 g / cm 3 by adjusting the amount of gas (gas) component taken into the resin composition (for example, emulsion resin composition) during mechanical stirring. A foam sheet having a density can be obtained.
　本発明の発泡シートは、発泡体の片面又は両面（特に、低タック面以外の面）に粘着剤層（粘着層）を有していてもよい。粘着剤層を構成する粘着剤としては、特に限定されず、例えば、アクリル系粘着剤、ゴム系粘着剤、シリコーン系粘着剤等のいずれであってもよい。また、粘着剤層を設ける場合は、その表面に、使用時まで粘着剤層を保護する剥離ライナーを積層してもよい。 The foamed sheet of the present invention may have a pressure-sensitive adhesive layer (adhesive layer) on one or both sides (particularly, a surface other than the low tack surface) of the foam. It does not specifically limit as an adhesive which comprises an adhesive layer, For example, any of an acrylic adhesive, a rubber adhesive, a silicone adhesive, etc. may be sufficient. Moreover, when providing an adhesive layer, you may laminate | stack the release liner which protects an adhesive layer until the time of use on the surface.
　本発明の発泡シートは、ロール状に巻回した巻回体（ロール状物）として市場に流通させてもよい。 The foamed sheet of the present invention may be distributed on the market as a wound body (rolled material) wound in a roll shape.
　本発明の発泡シートは、厚さが小さくても衝撃吸収性に優れる。そのため、例えば、電気・電子機器において、各種部材又は部品（例えば、光学部材など）を、所定の部位（例えば、筐体等）に取り付ける（装着する）際に用いられる電気・電子機器用部材、特に、衝撃吸収シートとして有用である。 The foamed sheet of the present invention is excellent in impact absorption even if the thickness is small. Therefore, for example, in an electrical / electronic device, various members or parts (for example, optical members) are used for attaching (attaching) a predetermined part (for example, a housing) to a member for electrical / electronic devices, In particular, it is useful as an impact absorbing sheet.
　本発明の発泡シートを利用して取付（装着）可能な光学部材としては、例えば、液晶ディスプレイ、エレクトロルミネッセンスディスプレイ、プラズマディスプレイ等の画像表示装置に装着される画像表示部材（特に、小型の画像表示部材）や、いわゆる「携帯電話」、「スマートフォン」や「携帯情報端末」等の移動体通信の装置に装着されるタッチパネル等の表示部材、カメラやレンズ（特に、小型のカメラやレンズ）などが挙げられる。 As an optical member that can be attached (attached) using the foam sheet of the present invention, for example, an image display member attached to an image display device such as a liquid crystal display, an electroluminescence display, a plasma display (particularly, a small image display). Members), display members such as touch panels attached to mobile communication devices such as so-called “mobile phones”, “smartphones” and “portable information terminals”, cameras and lenses (particularly small cameras and lenses), etc. Can be mentioned.
　本発明の電気・電子機器は、前記本発明の発泡シートが用いられている。このような電気・電子機器には、例えば、表示部材を備えた電気・電子機器であって、上記の発泡シートが該電気又は電子機器の筐体と前記表示部材との間に挟持された構造を有している電気・電子機器が含まれる。該電気・電子機器として、例えば、いわゆる「携帯電話」、「スマートフォン」、「携帯情報端末」等の移動体通信の装置などが挙げられる。 The electrical / electronic device of the present invention uses the foam sheet of the present invention. Such an electric / electronic device is, for example, an electric / electronic device provided with a display member, in which the foamed sheet is sandwiched between a housing of the electric or electronic device and the display member. Electric and electronic equipment having Examples of the electric / electronic devices include mobile communication devices such as so-called “mobile phones”, “smartphones”, and “portable information terminals”.
　以下に実施例を挙げて本発明をより詳細に説明するが、本発明はこれらの実施例により何ら制限されるものではない。なお、特に言及しない限り、含有量を表す「％」は重量％を意味する。なお、配合部数（重量部）は、全て固形分（不揮発分）換算の値である。 Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, “%” representing the content means% by weight. In addition, all the compounding parts (parts by weight) are values in terms of solid content (non-volatile content).
　実施例１
　アクリルエマルション溶液（固形分量５５％、アクリル酸エチル－アクリル酸ブチル－アクリロニトリル共重合体（重量比４５：４８：７））１００重量部、脂肪酸アンモニウム系界面活性剤（ステアリン酸アンモニウムの水分散液、固形分量３３％）（界面活性剤Ａ）２重量部、カルボキシベタイン型両性界面活性剤（「アモーゲンＣＢ－Ｈ」、第一工業製薬社製）（界面活性剤Ｂ）２重量部、オキサゾリン系架橋剤（「エポクロスＷＳ－５００」日本触媒社製、固形分量３９％）１０重量部、顔料（カーボンブラック）（「ＮＡＦ－５０９１」大日精化工業社製）１重量部、ポリアクリル酸系増粘剤（アクリル酸エチル－アクリル酸共重合体（アクリル酸２０重量％）、固形分量２８．７％）０．６重量部をディスパー（「ロボミックス」プライミクス社製）で撹拌混合して起泡化した。この発泡組成物を、剥離処理をしたＰＥＴ（ポリエチレンテレフタレート）フィルム（厚さ：３８μｍ、商品名「ＭＲＦ♯３８」三菱樹脂社製）上に塗布し、７０℃で４．５分、１４０℃で４．５分乾燥させ、厚さ１３０μｍ、見掛け密度０．２８ｇ／ｃｍ3、初期弾性率１．１５Ｎ／ｍｍ2の連続気泡構造の発泡体（発泡シート）を得た。 Example 1
100 parts by weight of acrylic emulsion solution (solid content 55%, ethyl acrylate-butyl acrylate-acrylonitrile copolymer (weight ratio 45: 48: 7)), fatty acid ammonium surfactant (aqueous dispersion of ammonium stearate, (Solid content 33%) (surfactant A) 2 parts by weight, carboxybetaine type amphoteric surfactant (“Amogen CB-H”, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) (surfactant B) 2 parts by weight, oxazoline-based crosslinking 10 parts by weight of agent (Epocross WS-500, manufactured by Nippon Shokubai Co., Ltd., solid content 39%), 1 part by weight of pigment (carbon black) (NAF-5091, manufactured by Daiichi Seika Kogyo Co., Ltd.), polyacrylic acid thickening agent 0.6 parts by weight of an agent (ethyl acrylate-acrylic acid copolymer (acrylic acid 20% by weight), solid content 28.7%) disperse ("Robomix It was caused blowing and stir-mixed in a PRIMIX Co., Ltd.). This foamed composition was applied onto a release-treated PET (polyethylene terephthalate) film (thickness: 38 μm, trade name “MRF # 38” manufactured by Mitsubishi Plastics), 70 ° C. for 4.5 minutes, and 140 ° C. It was dried for 4.5 minutes to obtain an open cell foam (foamed sheet) having a thickness of 130 μm, an apparent density of 0.28 g / cm 3 , and an initial elastic modulus of 1.15 N / mm 2 .
　実施例２
　アクリルエマルション溶液（固形分量５５％、アクリル酸エチル－アクリル酸ブチル－アクリロニトリル共重合体（重量比４５：４８：７））１００重量部、脂肪酸アンモニウム系界面活性剤（ステアリン酸アンモニウムの水分散液、固形分量３３％）（界面活性剤Ａ）２重量部、カルボキシベタイン型両性界面活性剤（「アモーゲンＣＢ－Ｈ」、第一工業製薬社製）（界面活性剤Ｂ）２重量部、オキサゾリン系架橋剤（「エポクロスＷＳ－５００」日本触媒社製、固形分量３９％）４重量部、顔料（カーボンブラック）（「ＮＡＦ－５０９１」大日精化工業社製）１重量部、ポリアクリル酸系増粘剤（アクリル酸エチル－アクリル酸共重合体（アクリル酸２０重量％）、固形分量２８．７％）０．６重量部、水酸化アルミニウム（「ハイジライトＨ４２」昭和電工社製）４０重量部をディスパー（「ロボミックス」プライミクス社製）で撹拌混合して起泡化した。この発泡組成物を、剥離処理をしたＰＥＴ（ポリエチレンテレフタレート）フィルム（厚さ：３８μｍ、商品名「ＭＲＦ♯３８」三菱樹脂社製）上に塗布し、７０℃で４．５分、１４０℃で４．５分乾燥させ、厚さ１３０μｍ、見掛け密度０．３０ｇ／ｃｍ3、初期弾性率０．８２Ｎ／ｍｍ2の連続気泡構造の発泡体（発泡シート）を得た。 Example 2
100 parts by weight of acrylic emulsion solution (solid content 55%, ethyl acrylate-butyl acrylate-acrylonitrile copolymer (weight ratio 45: 48: 7)), fatty acid ammonium surfactant (aqueous dispersion of ammonium stearate, (Solid content 33%) (surfactant A) 2 parts by weight, carboxybetaine type amphoteric surfactant (“Amogen CB-H”, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) (surfactant B) 2 parts by weight, oxazoline-based crosslinking 4 parts by weight of agent (Epocross WS-500, manufactured by Nippon Shokubai Co., Ltd., solid content 39%), 1 part by weight of pigment (carbon black) (NAF-5091, manufactured by Daiichi Seika Kogyo Co., Ltd.), polyacrylic acid thickening agent Agent (ethyl acrylate-acrylic acid copolymer (acrylic acid 20% by weight), solid content 28.7%) 0.6 parts by weight, aluminum hydroxide ("Heidi" Ito H42 "was caused blowing and stirring and mixing in the Showa Denko Co., Ltd.) 40 parts by weight of the disperser (" Made in ROBOMIX "PRIMIX Co., Ltd.). This foamed composition was applied onto a release-treated PET (polyethylene terephthalate) film (thickness: 38 μm, trade name “MRF # 38” manufactured by Mitsubishi Plastics), 70 ° C. for 4.5 minutes, and 140 ° C. It was dried for 4.5 minutes to obtain a foam (foamed sheet) having an open cell structure having a thickness of 130 μm, an apparent density of 0.30 g / cm 3 , and an initial elastic modulus of 0.82 N / mm 2 .
　実施例３
　アクリルエマルション溶液（固形分量５５％、アクリル酸エチル－アクリル酸ブチル－アクリロニトリル共重合体（重量比４５：４８：７））１００重量部、脂肪酸アンモニウム系界面活性剤（ステアリン酸アンモニウムの水分散液、固形分量３３％）（界面活性剤Ａ）２重量部、カルボキシベタイン型両性界面活性剤（「アモーゲンＣＢ－Ｈ」、第一工業製薬社製）（界面活性剤Ｂ）２重量部、オキサゾリン系架橋剤（「エポクロスＷＳ－５００」日本触媒社製、固形分量３９％）４重量部、顔料（カーボンブラック）（「ＮＡＦ－５０９１」大日精化工業社製）１重量部、ポリアクリル酸系増粘剤（アクリル酸エチル－アクリル酸共重合体（アクリル酸２０重量％）、固形分量２８．７％）０．６重量部、チタン酸カリウム繊維（「ティスモＤ」大塚化学社製）３０重量部をディスパー（「ロボミックス」プライミクス社製）で撹拌混合して起泡化した。この発泡組成物を、剥離処理をしたＰＥＴ（ポリエチレンテレフタレート）フィルム（厚さ：３８μｍ、商品名「ＭＲＦ♯３８」三菱樹脂社製）上に塗布し、７０℃で４．５分、１４０℃で４．５分乾燥させ、厚さ１３０μｍ、見掛け密度０．３４ｇ／ｃｍ3、初期弾性率２．３７Ｎ／ｍｍ2の連続気泡構造の発泡体（発泡シート）を得た。 Example 3
100 parts by weight of acrylic emulsion solution (solid content 55%, ethyl acrylate-butyl acrylate-acrylonitrile copolymer (weight ratio 45: 48: 7)), fatty acid ammonium surfactant (aqueous dispersion of ammonium stearate, (Solid content 33%) (surfactant A) 2 parts by weight, carboxybetaine type amphoteric surfactant (“Amogen CB-H”, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) (surfactant B) 2 parts by weight, oxazoline-based crosslinking 4 parts by weight of agent (Epocross WS-500, manufactured by Nippon Shokubai Co., Ltd., solid content 39%), 1 part by weight of pigment (carbon black) (NAF-5091, manufactured by Daiichi Seika Kogyo Co., Ltd.), polyacrylic acid thickening agent Agent (ethyl acrylate-acrylic acid copolymer (acrylic acid 20% by weight), solid content 28.7%) 0.6 parts by weight, potassium titanate fiber ("Te Mo D "manufactured by Otsuka Chemical Co., Ltd.) was caused foaming by stirring and mixing at 30 parts by weight disper (" manufactured ROBOMIX "PRIMIX Corporation). This foamed composition was applied onto a release-treated PET (polyethylene terephthalate) film (thickness: 38 μm, trade name “MRF # 38” manufactured by Mitsubishi Plastics), 70 ° C. for 4.5 minutes, and 140 ° C. It was dried for 4.5 minutes to obtain a foam (foamed sheet) having an open cell structure having a thickness of 130 μm, an apparent density of 0.34 g / cm 3 , and an initial elastic modulus of 2.37 N / mm 2 .
　実施例４
　アクリルエマルション溶液（固形分量５５％、アクリル酸エチル－アクリル酸ブチル－アクリロニトリル共重合体（重量比４５：４８：７））１００重量部、スチレン系エマルション溶液（固形分量５３％、「ボンコート ＳＫ－１０５－Ｅ」、ＤＩＣ社製）２０重量部、脂肪酸アンモニウム系界面活性剤（ステアリン酸アンモニウムの水分散液、固形分量３３％）（界面活性剤Ａ）２重量部、カルボキシベタイン型両性界面活性剤（「アモーゲンＣＢ－Ｈ」、第一工業製薬社製）（界面活性剤Ｂ）２重量部、オキサゾリン系架橋剤（「エポクロスＷＳ－５００」日本触媒社製、固形分量３９％）４重量部、顔料（カーボンブラック）（「ＮＡＦ－５０９１」大日精化工業社製）１重量部、ポリアクリル酸系増粘剤（アクリル酸エチル－アクリル酸共重合体（アクリル酸２０重量％）、固形分量２８．７％）０．６重量部をディスパー（「ロボミックス」プライミクス社製）で撹拌混合して起泡化した。この発泡組成物を、剥離処理をしたＰＥＴ（ポリエチレンテレフタレート）フィルム（厚さ：３８μｍ、商品名「ＭＲＦ♯３８」三菱樹脂社製）上に塗布し、７０℃で４．５分、１４０℃で４．５分乾燥させ、厚さ１３０μｍ、見掛け密度０．２９ｇ／ｃｍ3、初期弾性率３．６４Ｎ／ｍｍ2の連続気泡構造の発泡体（発泡シート）を得た。 Example 4
Acrylic emulsion solution (solid content 55%, ethyl acrylate-butyl acrylate-acrylonitrile copolymer (weight ratio 45: 48: 7)) 100 parts by weight, styrene emulsion solution (solid content 53%, Boncoat SK-105 -E ", manufactured by DIC) 20 parts by weight, fatty acid ammonium surfactant (aqueous dispersion of ammonium stearate, solid content 33%) (surfactant A) 2 parts by weight, carboxybetaine type amphoteric surfactant ( "Amorgen CB-H" (Daiichi Kogyo Seiyaku Co., Ltd.) (Surfactant B) 2 parts by weight, Oxazoline-based crosslinking agent ("Epocross WS-500" Nippon Shokubai Co., Ltd., solid content 39%) 4 parts by weight, pigment (Carbon black) ("NAF-5091" manufactured by Dainichi Seika Kogyo Co., Ltd.) 1 part by weight, polyacrylic acid thickener (ethyl acrylate-acrylic 0.6 parts by weight of a phosphoric acid copolymer (acrylic acid 20% by weight, solid content 28.7%) was stirred and mixed with a disper (“Robomix” Primix) to make foam. This foamed composition was applied onto a release-treated PET (polyethylene terephthalate) film (thickness: 38 μm, trade name “MRF # 38” manufactured by Mitsubishi Plastics), 70 ° C. for 4.5 minutes, and 140 ° C. After drying for 4.5 minutes, a foam (foamed sheet) having an open cell structure having a thickness of 130 μm, an apparent density of 0.29 g / cm 3 , and an initial elastic modulus of 3.64 N / mm 2 was obtained.
　実施例５
　アクリルエマルション溶液（固形分量５５％、アクリル酸エチル－アクリル酸ブチル－アクリロニトリル共重合体（重量比４５：４８：７））１００重量部、脂肪酸アンモニウム系界面活性剤（ステアリン酸アンモニウムの水分散液、固形分量３３％）（界面活性剤Ａ）２重量部、カルボキシベタイン型両性界面活性剤（「アモーゲンＣＢ－Ｈ」、第一工業製薬社製）（界面活性剤Ｂ）２重量部、オキサゾリン系架橋剤（「エポクロスＷＳ－５００」日本触媒社製、固形分量３９％）４重量部、顔料（カーボンブラック）（「ＮＡＦ－５０９１」大日精化工業社製）１重量部、シリカ（平均粒径５μｍ、ＢＥＴ比表面積８０～１３０ｍ2／ｇ、見掛け比重０．２６～０．３２ｇ／ｃｍ3）２５重量部をディスパー（「ロボミックス」プライミクス社製）で撹拌混合して起泡化した。この発泡組成物を、剥離処理をしたＰＥＴ（ポリエチレンテレフタレート）フィルム（厚さ：３８μｍ、商品名「ＭＲＦ♯３８」三菱樹脂社製）上に塗布し、７０℃で４．５分、１４０℃で４．５分乾燥させ、厚さ１３０μｍ、見掛け密度０．３０ｇ／ｃｍ3、初期弾性率０．５３Ｎ／ｍｍ2の連続気泡構造の発泡体（発泡シート）を得た。 Example 5
100 parts by weight of acrylic emulsion solution (solid content 55%, ethyl acrylate-butyl acrylate-acrylonitrile copolymer (weight ratio 45: 48: 7)), fatty acid ammonium surfactant (aqueous dispersion of ammonium stearate, (Solid content 33%) (surfactant A) 2 parts by weight, carboxybetaine type amphoteric surfactant (“Amogen CB-H”, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) (surfactant B) 2 parts by weight, oxazoline-based crosslinking 4 parts by weight (“Epocross WS-500” manufactured by Nippon Shokubai Co., Ltd., solid content 39%), 1 part by weight pigment (carbon black) (“NAF-5091” manufactured by Dainichi Seikagaku), silica (average particle size 5 μm) , BET specific surface area 80 ~ 130m 2 / g, an apparent specific gravity of 0.26 ~ 0.32g / cm 3) 25 parts by weight of a disper ( "ROBOMIX" Priming It was caused blowing and stirring and mixing vinegar Co., Ltd.). This foamed composition was applied onto a release-treated PET (polyethylene terephthalate) film (thickness: 38 μm, trade name “MRF # 38” manufactured by Mitsubishi Plastics), 70 ° C. for 4.5 minutes, and 140 ° C. It was dried for 4.5 minutes to obtain a foam (foamed sheet) having an open cell structure having a thickness of 130 μm, an apparent density of 0.30 g / cm 3 and an initial elastic modulus of 0.53 N / mm 2 .
　比較例１
　アクリルエマルション溶液（固形分量５５％、アクリル酸エチル－アクリル酸ブチル－アクリロニトリル共重合体（重量比４５：４８：７））１００重量部、脂肪酸アンモニウム系界面活性剤（ステアリン酸アンモニウムの水分散液、固形分量３３％）（界面活性剤Ａ）１．５重量部、カルボキシベタイン型両性界面活性剤（「アモーゲンＣＢ－Ｈ」、第一工業製薬社製）（界面活性剤Ｂ）１重量部、オキサゾリン系架橋剤（「エポクロスＷＳ－５００」日本触媒社製、固形分量３９％）０．３５重量部、ポリアクリル酸系増粘剤（アクリル酸エチル－アクリル酸共重合体（アクリル酸２０重量％）、固形分量２８．７％）０．７８重量部、ベンゾトリアゾール系防錆剤（「ＳＥＥＴＥＣ　ＢＴ－ＮＡ」、シプロ化成社製）０．５重量部をディスパー（「ロボミックス」プライミクス社製）で撹拌混合して起泡化した。この発泡組成物を、剥離処理をしたＰＥＴ（ポリエチレンテレフタレート）フィルム（厚さ：３８μｍ、商品名「ＭＲＦ♯３８」三菱樹脂社製）上に塗布し、７０℃で４．５分、１４０℃で４．５分乾燥させ、厚さ１３０μｍ、見掛け密度０．３３ｇ／ｃｍ3、初期弾性率０．３２Ｎ／ｍｍ2、最大セル径１１０μｍ、最小セル径２０μｍ、平均セル径４５μｍの連続気泡構造の発泡体（発泡シート）を得た。 Comparative Example 1
100 parts by weight of acrylic emulsion solution (solid content 55%, ethyl acrylate-butyl acrylate-acrylonitrile copolymer (weight ratio 45: 48: 7)), fatty acid ammonium surfactant (aqueous dispersion of ammonium stearate, (Solid content 33%) (surfactant A) 1.5 parts by weight, carboxybetaine type amphoteric surfactant (“Amogen CB-H”, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) (surfactant B) 1 part by weight, oxazoline -Based crosslinking agent (Epocross WS-500, manufactured by Nippon Shokubai Co., Ltd., solid content 39%) 0.35 parts by weight, polyacrylic acid thickener (ethyl acrylate-acrylic acid copolymer (acrylic acid 20% by weight) , 0.78 parts by weight of solid content 28.7%) and 0.5 parts by weight of benzotriazole rust inhibitor (“SEETEC BT-NA”, manufactured by Cypro Kasei Co., Ltd.) The mixture was stirred and mixed with a spar (“Robomix” manufactured by Primics) to generate foam. This foamed composition was applied onto a release-treated PET (polyethylene terephthalate) film (thickness: 38 μm, trade name “MRF # 38” manufactured by Mitsubishi Plastics), 70 ° C. for 4.5 minutes, and 140 ° C. Dried for 4.5 minutes, foamed with an open cell structure having a thickness of 130 μm, an apparent density of 0.33 g / cm 3 , an initial elastic modulus of 0.32 N / mm 2 , a maximum cell diameter of 110 μm, a minimum cell diameter of 20 μm, and an average cell diameter of 45 μm. A body (foamed sheet) was obtained.
　比較例２
　市販のポリエチレン系発泡体（「ボラーラＸＬＩＭ　ＷＦ０１」、積水化学工業社製）を発泡体（発泡シート）として用いた。発泡体の厚さは１００μｍ、見掛け密度は０．３１ｇ／ｃｍ3、初期弾性率は１３．１３Ｎ／ｍｍ2であった。 Comparative Example 2
A commercially available polyethylene-based foam (“Bora La XLIM WF01”, manufactured by Sekisui Chemical Co., Ltd.) was used as the foam (foamed sheet). The foam had a thickness of 100 μm, an apparent density of 0.31 g / cm 3 , and an initial elastic modulus of 13.13 N / mm 2 .
　＜評価＞
　実施例及び比較例で得られた発泡体（発泡シート）について、以下の評価を行った。結果を表１に示す。表１において、各実施例、比較例における各成分の部（重量部）は［固形分（不揮発分）換算］である。「Ｅｍ」はエマルションを示す。 <Evaluation>
The following evaluation was performed about the foam (foamed sheet) obtained by the Example and the comparative example. The results are shown in Table 1. In Table 1, the part (part by weight) of each component in each example and comparative example is [in terms of solid content (nonvolatile content)]. “Em” indicates an emulsion.
（平均セル径）
　低真空走査電子顕微鏡（「Ｓ－３４００Ｎ型走査電子顕微鏡」日立ハイテクサイエンスシステムズ社製）により、発泡体断面の拡大画像を取り込み、画像解析することにより平均セル径（μｍ）を求めた。なお解析したセル数は２０個である。同様の方法で、発泡体の最小セル径（μｍ）及び最大セル径（μｍ）を求めた。 (Average cell diameter)
An average cell diameter (μm) was obtained by capturing an enlarged image of the foam cross section with a low vacuum scanning electron microscope (“S-3400N scanning electron microscope” manufactured by Hitachi High-Tech Science Systems) and analyzing the image. The number of analyzed cells is 20. In the same manner, the minimum cell diameter (μm) and the maximum cell diameter (μm) of the foam were determined.
（見掛け密度）
　１００ｍｍ×１００ｍｍの打抜き刃型にて発泡体（発泡シート）を打抜き、打抜いた試料の寸法を測定する。また、測定端子の直径（φ）２０ｍｍである１／１００ダイヤルゲージにて厚さを測定する。これらの値から発泡体の体積を算出した。
　次に、発泡体の重量を最小目盛り０．０１ｇ以上の上皿天秤にて測定する。これらの値より発泡体の見掛け密度（ｇ／ｃｍ3）を算出した。 (Apparent density)
A foam (foamed sheet) is punched with a 100 mm × 100 mm punching blade mold, and the dimensions of the punched sample are measured. Further, the thickness is measured with a 1/100 dial gauge having a measurement terminal diameter (φ) of 20 mm. The volume of the foam was calculated from these values.
Next, the weight of the foam is measured with an upper pan balance having a minimum scale of 0.01 g or more. From these values, the apparent density (g / cm 3 ) of the foam was calculated.
（動的粘弾性）
　粘弾性測定装置（「ＡＲＥＳ２ＫＦＲＴＮ１－ＦＣＯ」ＴＡ　Ｉｎｓｔｒｕｍｅｎｔｓ　Ｊａｐａｎ社製）のフィルム引張り測定モードにて、角振動数１ｒａｄ／ｓで温度分散性試験を行った。その際の貯蔵弾性率Ｅ’と損失弾性率Ｅ’’の比率である損失正接（ｔａｎδ）のピークトップの温度（℃）と強度（最大値）を測定した。
　表１の「ｔａｎδ温度」の欄に、発泡体の損失正接（ｔａｎδ）のピークトップの温度（℃）を記載し、「ｔａｎδ」の欄に、該ピークトップの強度（最大値）を記載し、「ｔａｎδ/見掛け密度」の欄に、前記ピークトップの強度（最大値）を発泡体の見掛け密度で割った値［発泡体を構成する材料自体（気泡を除外する）のｔａｎδのピークトップ強度（最大値）に相当する］を記載した。 (Dynamic viscoelasticity)
A temperature dispersibility test was performed at an angular frequency of 1 rad / s in a film tension measurement mode of a viscoelasticity measurement apparatus (“ARES2KFRTN1-FCO” manufactured by TA Instruments Japan). The peak top temperature (° C.) and strength (maximum value) of loss tangent (tan δ), which is the ratio of storage elastic modulus E ′ and loss elastic modulus E ″ at that time, were measured.
The peak top temperature (° C.) of the loss tangent (tan δ) of the foam is described in the “tan δ temperature” column of Table 1, and the strength (maximum value) of the peak top is described in the “tan δ” column. In the “tan δ / apparent density” column, the value obtained by dividing the peak top strength (maximum value) by the apparent density of the foam [the peak top strength of tan δ of the material constituting the foam itself (excluding bubbles) Corresponds to (maximum value)].
（初期弾性率）
　２３℃環境下で引張速度３００ｍｍ／ｍｉｎでの引張試験における１０％歪み時の傾きから算出した初期弾性率（Ｎ／ｍｍ2）を評価した。 (Initial elastic modulus)
The initial elastic modulus (N / mm 2 ) calculated from the slope at 10% strain in a tensile test at a tensile speed of 300 mm / min in a 23 ° C. environment was evaluated.
（衝撃吸収性試験）
　前記の振り子型衝撃試験機（衝撃試験装置）（図１及び図２参照）を用いて衝撃吸収性試験を行った。実施例及び比較例で得られた発泡シート（サンプルサイズ：２０ｍｍ×２０ｍｍ）について、２８ｇの鉄球を４０°傾けた低衝撃条件にて衝撃試験を行い、衝撃吸収率（％）を求めた。
　次に、該衝撃吸収率（％）を発泡シートの厚さ（μｍ）で割って、単位厚さ当たりの衝撃吸収率Ｒを求めた。 (Shock absorption test)
An impact absorption test was performed using the above-described pendulum impact tester (impact test apparatus) (see FIGS. 1 and 2). The foamed sheets (sample size: 20 mm × 20 mm) obtained in the examples and comparative examples were subjected to an impact test under low impact conditions in which a 28 g iron ball was tilted by 40 °, and the impact absorption rate (%) was obtained.
Next, the impact absorption rate (%) was divided by the thickness (μm) of the foamed sheet to determine the impact absorption rate R per unit thickness.
　表１に示されるように、実施例の発泡シートでは、前記Ｒは０．２０以上で、優れた衝撃吸収性を示した。これに対し、比較例２の発泡シートではＲは０．２０未満であった。 As shown in Table 1, in the foamed sheets of the examples, the R was 0.20 or more, and excellent shock absorption was exhibited. On the other hand, in the foamed sheet of Comparative Example 2, R was less than 0.20.
（プローブタック試験）
　タッキング試験機（「ＴＡＣ－２」、レスカ社製）を用いた。２３℃環境下で、直径φ５ｍｍのＳＵＳ３０４製円柱のプローブを発泡シート上部から、押し込み速さ３０ｍｍ／ｍｉｎ、押し込み荷重１００ｇｆ、プレス時間１秒の条件で押しつけ、剥離速さ３０ｍｍ／ｍｉｎで引き剥がす際の最大荷重値（ｋＮ／ｍ2）を測定した。 (Probe tack test)
A tacking tester (“TAC-2”, manufactured by Resca) was used. In a 23 ° C environment, when a SUS304 cylindrical probe having a diameter of 5 mm is pressed from the top of the foam sheet under the conditions of an indentation speed of 30 mm / min, an indentation load of 100 gf, and a press time of 1 second, and peeled off at a delamination speed of 30 mm / min. The maximum load value (kN / m 2 ) was measured.
　表１に示されるように、実施例の発泡シートでは、最大荷重値は１００ｋＮ／ｍ2以下であり、比較例１に比べ、大幅にタック性が低下した。 As shown in Table 1, in the foamed sheet of the example, the maximum load value was 100 kN / m 2 or less, and the tackiness was significantly lowered as compared with Comparative Example 1.
（再剥離性試験）
　発泡シートを１００ｍｍ×１００ｍｍに切断し、ＳＵＳ３０４ＢＡ板上に貼りつけて測定試料とした。水平に置いた測定試料に１ｋｇローラーを一往復させて圧着した。圧着後、常温（２３℃）下で、１８０℃方向に再度剥がした際の発泡シートの状態を測定した。
　◎：ＳＵＳ３０４ＢＡ板にくっつかない。
　○：ＳＵＳ３０４ＢＡ板にくっつくが、発泡シート形状は変化せずに剥がせる。
　×：ＳＵＳ３０４ＢＡ板にくっつき、剥がした際に発泡シート形状が変化する。 (Removability test)
The foamed sheet was cut into 100 mm × 100 mm and attached on a SUS304BA plate to obtain a measurement sample. A 1 kg roller was reciprocated once on a measurement sample placed horizontally and pressed. After crimping, the state of the foamed sheet when peeled again in the 180 ° C. direction at room temperature (23 ° C.) was measured.
(Double-circle): It does not stick to a SUS304BA board.
○: Although it sticks to the SUS304BA plate, it can be peeled off without changing the shape of the foam sheet.
X: The foamed sheet shape changes when it sticks to the SUS304BA plate and peels off.
　表１に示されるように、実施例の発泡シートでは、ＳＵＳ３０４ＢＡ板から剥がしても、発泡シートは元通りの形状に戻り、再度貼りなおすことができたが、比較例１は、剥がした際に伸びたり、千切れて元通りの形状に戻らず、再度貼りなおすことができなかった。 As shown in Table 1, in the foam sheet of the example, even when peeled from the SUS304BA plate, the foam sheet returned to its original shape and could be re-applied, but Comparative Example 1 It could not be stretched or shredded to return to its original shape and re-applied.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　本発明の発泡シートは、例えば、電気・電子機器において、各種部材又は部品（例えば、光学部材など）を、所定の部位（例えば、筐体等）に取り付ける（装着する）際に用いられる電気・電子機器用部材、特に、衝撃吸収シートとして有用である。 The foamed sheet of the present invention is used, for example, in electrical / electronic devices when various members or parts (for example, optical members) are attached (attached) to a predetermined part (for example, a housing). It is useful as a member for electronic equipment, particularly as an impact absorbing sheet.
　１　　振り子型衝撃試験機（衝撃試験装置）
　２　　試験片（発泡シート）
　３　　保持部材
　４　　衝撃負荷部材
　５　　圧力センサー
　１１　固定治具
　１２　押さえ治具
　１６　圧力調整手段
　２０　支柱
　２１　アーム
　２２　支持棒（シャフト）の一端
　２３　支持棒（シャフト）
　２４　衝撃子
　２５　電磁石
　２８　支持板
　ａ　　振り上げ角度 1 Pendulum type impact tester (impact tester)
2 Test piece (foamed sheet)
DESCRIPTION OF SYMBOLS 3 Holding member 4 Impact load member 5 Pressure sensor 11 Fixing jig 12 Holding jig 16 Pressure adjusting means 20 Support | pillar 21 Arm 22 End of support rod (shaft) 23 Support rod (shaft)
24 Impactor 25 Electromagnet 28 Support plate a Swing angle

Claims (19)

  1. 　厚さが３０～５００μｍであり、見掛け密度が０．２～０．７ｇ／ｃｍ3、平均セル径が１０～１５０μｍである発泡体で構成されている発泡シートであり、振り子型衝撃試験機を用いた衝撃吸収性試験において、下記式で定義される衝撃吸収率（％）を発泡シートの厚さ（μｍ）で割った値Ｒが、衝撃子の重さ２８ｇ、振り上げ角度４０°の場合に０．２０以上であり、該発泡シートの少なくとも一方の面は、２３℃環境下で、直径φが５ｍｍのＳＵＳ３０４製円柱のプローブを、押し込み速さ３０ｍｍ／ｍｉｎ、押し込み荷重１００ｇｆ、プレス時間１秒の条件で押しつけ、剥離速さ３０ｍｍ／ｍｉｎで引き剥がした際の最大荷重値が１００ｋＮ／ｍ2以下である発泡シート。
    　　衝撃吸収率（％）＝｛（Ｆ0－Ｆ1）／Ｆ0｝×１００
    （上記式において、Ｆ0は支持板のみに衝撃子を衝突させた時の衝撃力のことであり、Ｆ1は支持板と発泡シートとからなる構造体の支持板上に衝撃子を衝突させた時の衝撃力のことである）     A foam sheet made of a foam having a thickness of 30 to 500 μm, an apparent density of 0.2 to 0.7 g / cm 3 and an average cell diameter of 10 to 150 μm. In the shock absorption test used, when the value R obtained by dividing the shock absorption rate (%) defined by the following formula by the thickness (μm) of the foam sheet is a weight of impactor of 28 g and a swing angle of 40 °. It is 0.20 or more, and at least one surface of the foamed sheet is a 23 ° C. environment, a SUS304 cylindrical probe having a diameter φ of 5 mm, a pressing speed of 30 mm / min, a pressing load of 100 gf, and a pressing time of 1 second. A foamed sheet having a maximum load value of 100 kN / m 2 or less when pressed under the above conditions and peeled at a peeling speed of 30 mm / min.
    Impact absorption rate (%) = {(F 0 −F 1 ) / F 0 } × 100
    (In the above formula, F 0 is the impact force when the impactor collides only with the support plate, and F 1 causes the impactor to collide with the support plate of the structure composed of the support plate and the foam sheet. Is the impact force when
  2. 　前記発泡体は、動的粘弾性測定における角振動数１ｒａｄ／ｓでの貯蔵弾性率と損失弾性率の比率である損失正接（ｔａｎδ）が－５０℃以上５０℃以下の範囲にピークトップを有する請求項１記載の発泡シート。 The foam has a peak top in a range where a loss tangent (tan δ), which is a ratio of a storage elastic modulus and a loss elastic modulus at an angular frequency of 1 rad / s in dynamic viscoelasticity measurement, is −50 ° C. or higher and 50 ° C. or lower. The foam sheet according to claim 1.
  3. 　前記発泡体は、動的粘弾性測定における角振動数１ｒａｄ／ｓでの貯蔵弾性率と損失弾性率の比率である損失正接（ｔａｎδ）が－４０℃以上４０℃以下の範囲にピークトップを有する請求項２記載の発泡シート。 The foam has a peak top in a range where a loss tangent (tan δ), which is a ratio of a storage elastic modulus and a loss elastic modulus at an angular frequency of 1 rad / s in dynamic viscoelasticity measurement, is −40 ° C. or higher and 40 ° C. or lower. The foam sheet according to claim 2.
  4. 　前記発泡体は、動的粘弾性測定における角振動数１ｒａｄ／ｓでの貯蔵弾性率と損失弾性率の比率である損失正接（ｔａｎδ）が－３０℃以上３０℃以下の範囲にピークトップを有する請求項３記載の発泡シート。 The foam has a peak top in a range where a loss tangent (tan δ), which is a ratio of a storage elastic modulus and a loss elastic modulus at an angular frequency of 1 rad / s in dynamic viscoelasticity measurement, is −30 ° C. or higher and 30 ° C. or lower. The foam sheet according to claim 3.
  5. 　前記発泡体は、動的粘弾性測定における角振動数１ｒａｄ／ｓでの貯蔵弾性率と損失弾性率の比率である損失正接（ｔａｎδ）が－２０℃以上２０℃以下の範囲にピークトップを有する請求項４記載の発泡シート。 The foam has a peak top in a range where a loss tangent (tan δ), which is a ratio of a storage elastic modulus and a loss elastic modulus at an angular frequency of 1 rad / s in dynamic viscoelasticity measurement, is −20 ° C. or higher and 20 ° C. or lower. The foam sheet according to claim 4.
  6. 　前記発泡体における損失正接（ｔａｎδ）の－５０℃以上５０℃以下の範囲での最大値が、０．２以上である請求項１～５の何れか１項に記載の発泡シート。 The foamed sheet according to any one of claims 1 to 5, wherein the maximum loss loss tangent (tan δ) in the range of -50 ° C to 50 ° C is 0.2 or more.
  7. 　２３℃環境下で引張速度３００ｍｍ／ｍｉｎでの引張試験における発泡体の初期弾性率が１０Ｎ／ｍｍ2以下である請求項１～６の何れか１項に記載の発泡シート。 The foam sheet according to any one of claims 1 to 6, wherein the foam has an initial elastic modulus of 10 N / mm 2 or less in a tensile test in a 23 ° C environment at a tensile speed of 300 mm / min.
  8. 　２３℃環境下で引張速度３００ｍｍ／ｍｉｎでの引張試験における発泡体の初期弾性率が０．１Ｎ／ｍｍ2以上１０Ｎ／ｍｍ2以下である請求項７に記載の発泡シート。 The foamed sheet according to claim 7, wherein the initial elastic modulus of the foam in a tensile test at a tensile speed of 300 mm / min in a 23 ° C environment is 0.1 N / mm 2 or more and 10 N / mm 2 or less.
  9. 　２３℃環境下で引張速度３００ｍｍ／ｍｉｎでの引張試験における発泡体の初期弾性率が０．１Ｎ／ｍｍ2以上５Ｎ／ｍｍ2以下である請求項８に記載の発泡シート。 The foamed sheet according to claim 8, wherein an initial elastic modulus of the foam in a tensile test at a tensile speed of 300 mm / min in a 23 ° C environment is 0.1 N / mm 2 or more and 5 N / mm 2 or less.
  10. 　発泡体が、アクリル系ポリマー、ゴム、ウレタン系ポリマー、スチレン系ポリマー、及びエチレン－酢酸ビニル共重合体からなる群より選択された少なくとも１種の樹脂材料で形成されている請求項１～９の何れか１項に記載の発泡シート。 10. The foam according to claim 1, wherein the foam is formed of at least one resin material selected from the group consisting of an acrylic polymer, rubber, urethane polymer, styrene polymer, and ethylene-vinyl acetate copolymer. The foam sheet of any one of Claims 1.
  11. 　前記発泡体が架橋剤を含む請求項１～１０の何れか１項に記載の発泡シート。 The foam sheet according to any one of claims 1 to 10, wherein the foam contains a crosslinking agent.
  12. 　前記発泡体が充填剤を含む請求項１～１１の何れか１項に記載の発泡シート。 The foam sheet according to any one of claims 1 to 11, wherein the foam contains a filler.
  13. 　発泡体がエマルション樹脂組成物により形成される請求項１～１２の何れか１項に記載の発泡シート。 The foam sheet according to any one of claims 1 to 12, wherein the foam is formed of an emulsion resin composition.
  14. 　発泡体が、樹脂組成物を機械的に発泡させる工程Ａを経て形成される請求項１～１３の何れか１項に記載の発泡シート。 The foam sheet according to any one of claims 1 to 13, wherein the foam is formed through a step A of mechanically foaming the resin composition.
  15. 　発泡体が、さらに、機械的に発泡させたエマルション樹脂組成物を基材上に塗工して乾燥する工程Ｂを経て形成される請求項１４に記載の発泡シート。 The foamed sheet according to claim 14, wherein the foam is further formed through a step B in which a mechanically foamed emulsion resin composition is coated on a substrate and dried.
  16. 　発泡体の片面又は両面に粘着剤層を有する請求項１～１５の何れか１項に記載の発泡シート。 The foam sheet according to any one of claims 1 to 15, which has an adhesive layer on one side or both sides of the foam.
  17. 　電気・電子機器用衝撃吸収シートとして用いられる請求項１～１６の何れか１項に記載の発泡シート。 The foam sheet according to any one of claims 1 to 16, which is used as an impact absorbing sheet for electrical and electronic equipment.
  18. 　請求項１～１７の何れか１項に記載の発泡シートが用いられている電気・電子機器。 An electric / electronic device in which the foam sheet according to any one of claims 1 to 17 is used.
  19. 　表示部材を備えた電気・電子機器であって、請求項１～１７の何れか１項に記載の発泡シートが該電気又は電子機器の筐体と前記表示部材との間に挟持された構造を有する請求項１８記載の電気・電子機器。 An electric / electronic device comprising a display member, wherein the foamed sheet according to any one of claims 1 to 17 is sandwiched between a housing of the electric or electronic device and the display member. The electric / electronic device according to claim 18.
PCT/JP2016/052257 2015-01-30 2016-01-27 Low-adhesiveness foam sheet WO2016121788A1 (en)

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