CN110573560A - Porous sintered sheet and method for producing same - Google Patents

Porous sintered sheet and method for producing same Download PDF

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Publication number
CN110573560A
CN110573560A CN201880028798.7A CN201880028798A CN110573560A CN 110573560 A CN110573560 A CN 110573560A CN 201880028798 A CN201880028798 A CN 201880028798A CN 110573560 A CN110573560 A CN 110573560A
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Prior art keywords
porous sintered
sintered sheet
sheet
porosity
resin
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CN110573560B (en
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出口隆宏
田中贤哉
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Saibaole Industrial Co ltd
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Asahi Kasei Corp
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
    • B01L3/00—Containers or dishes for laboratory use, e.g. laboratory glassware; Droppers
    • B01L3/50—Containers for the purpose of retaining a material to be analysed, e.g. test tubes
    • B01L3/502—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures
    • B01L3/5023—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures with a sample being transported to, and subsequently stored in an absorbent for analysis
    • 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
    • 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
    • C08J9/24—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof by surface fusion and bonding of particles to form voids, e.g. sintering
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
    • B01L2300/00—Additional constructional details
    • B01L2300/12—Specific details about materials

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  • Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Polymers & Plastics (AREA)
  • Materials Engineering (AREA)
  • Medicinal Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Organic Chemistry (AREA)
  • Analytical Chemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • Hematology (AREA)
  • Clinical Laboratory Science (AREA)
  • Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
  • Molding Of Porous Articles (AREA)

Abstract

A porous sintered sheet containing a resin and having continuous pores, wherein the minimum value of the cross-sectional porosity of the porous sintered sheet is 10% or more, and the position where the minimum value of the cross-sectional porosity is present is within 20% of the depth in the thickness direction from one surface of the sintered sheet.

Description

Porous sintered sheet and method for producing same
Technical Field
The present invention relates to a porous sintered sheet and a method for producing the same.
Background
As one means for fixing or conveying a film-like, plate-like or film-like material such as a glass plate for liquid crystal or a printed circuit board for laminated ceramic capacitor, there is a method of performing suction fixing or suction conveying by a suction table under reduced pressure suction. In this suction table, a resin porous body having air permeability as a suction cushion is attached to the suction surface in order to prevent scratches and contact marks from being generated on the member to be sucked. In such a porous resin body, a sintered molded article obtained by sintering and molding a polyethylene powder may be used from the viewpoint of rigidity, cushioning properties, and the like.
In recent years, the size and performance of liquid crystal and multilayer ceramic capacitors have been rapidly increased, and the thickness of glass plates and ceramic green sheets as raw materials thereof has been reduced. Thus creating the need to perform very precise adsorptive immobilization or adsorptive transport. Therefore, excellent surface smoothness, strength and rigidity are required as an adsorption buffer material to be attached to an adsorption table under reduced pressure adsorption.
As a porous sintered sheet having a dense structure and excellent surface smoothness, a sheet having high air permeability in the thickness direction, a small surface aperture ratio, and a small surface roughness as a whole has been proposed (for example, see patent document 1).
Further, as a porous composite having excellent filtration accuracy, high rigidity, and excellent handleability, a porous composite in which a resin porous body having continuous pores formed therein and a microporous membrane are substantially integrated has been proposed (for example, see patent document 2).
Further, a molding method of a porous body capable of forming continuous pores by stacking a raw material resin on an endless belt and then heating is disclosed (for example, see patent document 3).
Documents of the prior art
Patent document
Patent document 1: japanese patent laid-open No. 2001-28390
Patent document 2: japanese patent laid-open publication No. 2000-177040
Patent document 3: japanese laid-open patent publication No. 3-143821
Disclosure of Invention
Problems to be solved by the invention
However, in patent document 1, in order to improve the surface smoothness of the sheet, a PET sheet or the like having high surface smoothness is brought into contact with a surface in contact with the member to be sucked, and heat treatment is performed in a state where a pressure of a certain level or more is applied. When strong compression is performed to improve surface smoothness, the porosity in the entire thickness direction is reduced. Therefore, a problem arises in that the thickness of the sheet must be reduced in order to obtain high air permeability. In this case, the following problems arise: in order to reinforce the thinned sheet, it is necessary to laminate another sheet having high air permeability on the side opposite to the surface in contact with the member to be adsorbed.
In addition, in patent document 2, in order to obtain a sheet excellent in filtration accuracy, it is necessary to produce two types of sheets, i.e., a thin sheet having a small porosity and poor permeability and a thick sheet having a large porosity and excellent permeability, and then to bond the two types of sheets. Further, when hot pressing is performed to bond the divided sheets, there is a problem that porosity is reduced or holes in the bonded surface are crushed.
Patent document 3 does not disclose or suggest structural control of the continuous pores in the thickness direction.
In view of the above-described problems of the prior art, it is therefore an object of the present invention to provide a porous sintered sheet which has excellent gas or liquid permeability, high mechanical strength, and low pressure loss, and thus has excellent long-term durability, despite having a small porosity in the vicinity of at least one surface (for example, the surface and/or the surface opposite to the surface), and a method for producing the same.
Means for solving the problems
The present inventors have conducted extensive studies to solve the above problems, and as a result, have found that the above object can be achieved when the minimum value of the porosity of a porous sintered sheet containing a resin and having continuous pores is set to a specific value or more and the position where the minimum value of the porosity is present is set within a specific range in the thickness direction from one surface of the sintered sheet, thereby completing the present invention.
Namely, the present invention is as follows.
(1)
A porous sintered sheet containing a resin and having continuous pores, wherein,
The porous sintered sheet has a minimum value of cross-sectional porosity of 10% or more, and the position where the minimum value of cross-sectional porosity is present is within 20% of the depth in the thickness direction from one surface of the sintered sheet.
(2)
The porous sintered sheet according to (1), wherein a difference between an average porosity of the entire porous sintered sheet and a minimum value of a cross-sectional porosity of the porous sintered sheet is 10% or more and 50% or less.
(3)
The porous sintered sheet according to (1) or (2), wherein the product of the air permeability of the porous sintered sheet and the thickness of the porous sintered sheet is 0.2cm3More than/cm/second.
(4)
The porous sintered sheet according to any one of (1) to (3), wherein the average porosity of the entire porous sintered sheet is 20% or more and 80% or less.
(5)
The porous sintered sheet according to any one of (1) to (4), wherein, in a depth in the thickness direction from the one surface, there is no depth position deeper than a depth position at which an average porosity of the entire porous sintered sheet is reached and having a cross-sectional porosity greater than the average porosity by 20% or more.
(6)
The porous sintered sheet according to any one of (1) to (5), wherein 1m is added2The above porous sintered sheet was divided into 100cm2Each block obtained as follows satisfies the following condition a:
(Condition A)
X≤Y×0.2
X: the difference between the depth position at which the minimum value of the cross-sectional porosity exists and the depth position at which the maximum value of the cross-sectional porosity exists
Y: thickness of the blocks.
(7)
the porous sintered sheet according to any one of (1) to (6), wherein the thickness of the porous sintered sheet is 0.05mm or more and 5.0mm or less.
(8)
A method for producing the porous sintered sheet in a sheet form according to any one of (1) to (7), wherein a resin is supplied onto an endless conveyor belt and molded into a sheet-like molded body, and then the molded body is heated and pressed.
(9)
The method for producing a porous sintered sheet according to item (8), wherein the molded body is heated, and then the heated molded body is compressed by a pressing means within a temperature range of ± 30 ℃ from the melting point of the resin.
(10)
The method for producing a porous sintered sheet according to item (9), wherein a compression ratio of the porous sintered sheet by the compression means is 0.5% or more and 2% or less.
(11)
An adsorption-fixation conveying sheet comprising the porous sintered sheet according to any one of (1) to (7).
(12)
A support sheet for a rapid detection kit by immunochromatography, comprising the porous sintered sheet according to any one of (1) to (7).
Effects of the invention
According to the present invention, a porous sintered sheet having a compact structure with a small porosity in the vicinity of at least one surface (for example, the surface and/or the surface opposite to the surface), excellent gas or liquid permeability, large mechanical strength, and a small pressure loss, and thus excellent long-term durability, and a method for producing the same can be provided. The porous sintered sheet of the present invention has a small porosity in the vicinity of at least one surface and excellent permeability, and therefore, when used as a sheet, it is not necessary to bond the sheet to another sheet having high permeability in order to improve the permeability.
Drawings
FIG. 1 is a view showing the X-ray CT measurement of a porous sintered sheet of example 1.
FIG. 2 is a view showing the X-ray CT measurement of the porous sintered sheet of comparative example 1.
Detailed Description
Hereinafter, specific embodiments of the present invention (hereinafter, referred to as "the present embodiment") will be described in detail. The present invention is not limited to the following embodiments, and various modifications can be made within the scope of the present invention.
[ porous sintered sheet ]
the porous sintered sheet of the present embodiment is a porous sintered sheet containing a resin and having continuous pores, and has a minimum value of cross-sectional porosity of 10% or more, and the position where the minimum value of cross-sectional porosity is present is within 20% of the depth in the thickness direction from one surface (for example, the surface or the surface opposite to the surface) of the sintered sheet. Accordingly, the porous sintered sheet of the present embodiment is excellent in gas or liquid permeability, high in mechanical strength, and low in pressure loss, and thus excellent in long-term durability.
The resin constituting the porous sintered sheet (for example, porous sheet) may be any of a thermoplastic resin and a thermosetting resin. As the thermoplastic resin, there may be mentioned: polyolefin-based resins, polyester-based resins, polyarylates, liquid crystal polyesters, polyvinyl chloride, polyvinyl alcohol, polystyrene, acrylonitrile-butadiene-styrene copolymer resins, acrylonitrile-styrene copolymer resins, polymethyl methacrylate, polyamide-based resins, polyacetal, polycarbonate, fluorine-containing resins, polyether ether ketone, polyether sulfone, polyphenylene sulfide, and the like. Examples of the thermosetting resin include: phenol resin, urea resin, melamine resin, allyl resin, epoxy resin, and the like. These resins may be used alone in 1 kind, or may be used in combination in 2 or more kinds.
Among them, a thermoplastic resin is preferable from the viewpoint of excellent shaping properties and secondary processability. Among thermoplastic resins, polyolefin-based resins such as polyethylene and polypropylene are preferred from the viewpoint of low cost, chemical resistance and processability, and excellent low moisture absorption and low water absorption of raw materials. As the polyolefin-based resin, there may be mentioned: ethylene homopolymers or ethylene copolymers of ethylene and 1 or more α -olefin monomers such as propylene, 1-butene, 1-hexene, 1-octene, etc.; ethylene copolymers of ethylene with monomers other than α -olefins, such as vinyl acetate, acrylic acid, methacrylic acid, acrylic acid esters, and methacrylic acid esters; propylene homopolymers and propylene copolymers of propylene and 1 or more α -olefin monomers such as ethylene and 1-butene.
Among polyolefin resin particles, polyethylene particles are most preferable from the viewpoint of being inexpensive, easy to sinter-mold, excellent in processability and chemical resistance after molding, and low in hygroscopicity and water absorption of the raw material itself.
The density of the resin (e.g., thermoplastic resin, particularly polyethylene) is preferably 890kg/m3～970kg/m3. The passing density is 890kg/m3As described above, the porous sintered sheet (for example, porous sheet) tends to have sufficient rigidity. From the same viewpoint, the density is more preferably 920kg/m3Above, more preferably 930kg/m3Above, particularly preferably 940kg/m3The above. Further, the pass density was 970kg/m3Hereinafter, the ease of handling tends to be more excellent. From the same viewpoint, the density is more preferably 960kg/m3The following.
The density of the resin can be adjusted as follows: the amount of each copolymer component of different types, the molecular weight, or the mixture of 2 or more copolymer components of the same type but different densities. For example, in the case where the resin is polyethylene, the density of the polyethylene can be adjusted as follows: 2 or more polyethylenes having different molecular weights or mixed densities by adjusting the amount of other monomers (for example, alpha-olefin monomers) to be copolymerized with ethylene. The density of the polyethylene may be determined in accordance with JIS K7112: 1999, measurement was carried out by the density gradient tube method (23 ℃).
In addition, the viscosity-average molecular weight of the resin (for example, a thermoplastic resin, particularly polyethylene) is preferably 1000 to 1000 ten thousand, more preferably 1 ten thousand or more, and further preferably 10 ten thousand or more, from the viewpoint that the flow of the resin, which is a factor inhibiting the formation of voids at the time of sintering molding, is small and the fusion property of adjacent resin particles is excellent.
The viscosity-average molecular weight (Mv) of the resin particles (for example, thermoplastic resin particles, particularly polyethylene particles) can be controlled by appropriately adjusting polymerization conditions and the like. Specifically, the viscosity average molecular weight can be adjusted as follows: hydrogen is allowed to exist in the polymerization system, or the polymerization temperature is changed.
The viscosity average molecular weight can be determined by the following method, for example. First, a resin (for example, polyethylene) is dissolved in decalin (decalin) to prepare a plurality of solutions having different concentrations. The solutions were placed in a thermostatic bath at 135 ℃ and the reduced viscosities (. eta.) were determined using a Cannon-Fensk viscometerspand/C). Deriving the concentration (C) and the reduced viscosity (. eta.) of the polymerspLinear equation of/C) to determine the intrinsic viscosity ([ eta ] when extrapolated to a concentration of 0]). The intrinsic viscosity ([ eta ] can be determined from]) The viscosity average molecular weight (Mv) was determined.
Mv＝5.34×104×[η]1.49
The porous sintered sheet (for example, porous sheet) may be a raw material mixture of the same type of resins (for example, polyethylene) having different resin densities and/or viscosity-average molecular weights as raw materials, or may be a raw material mixture of different types of resins.
These resins (e.g., polyolefin-based resins) can be hydrophilized by: copolymerized with a monomer having a hydrophilic group, or graft-copolymerized with a monomer having a hydrophilic group, or added with a surfactant. For hydrophilization, a resin hydrophilized in the form of powder may be molded into a porous body to obtain a hydrophilic porous sintered sheet, or a sintered body previously molded into a porous sintered body may be hydrophilized by a known method. The term "hydrophilization" as used herein refers to, for example, a state in which when about 50 ml of water droplets are dropped onto a molded article, the water droplets are absorbed into the molded article within 30 seconds.
[ method for producing porous sintered sheet ]
As a method for producing the porous sintered sheet of the present embodiment, a known method is used. As a known method, for example, a sintering molding method or the like is mainly used, and in addition to this, for example, the following methods may be used: the porous sintered sheet having continuous pores is formed by molding a molded body with a resin melted together with an extractable component and then extracting the extractable component. As a specific example of the sintering method, a porous sintered sheet having continuous pores can be formed by filling a mold with a raw material (for example, a powdery resin), putting the raw material into a heating furnace maintained at a temperature of not less than the melting point, sintering the raw material, and then cooling the sintered product.
The method for producing the porous sintered body in a sheet form is not particularly limited, and a sintering molding method using a die, an extrusion molding method, a method of molding the porous sintered body molded by the above molding method into a sheet form by slicing or scraping, or the like can be suitably used.
In particular, from the viewpoint of excellent continuous productivity and flexibility in thickness, it is preferable to produce a sheet-like porous sintered body by supplying (depositing) a resin as a raw material onto an endless conveyor, molding (shaping) the resin into a sheet shape, and then heating the sheet.
In the present specification, the term "continuous pores" means that pores are continuous from one surface of the molded article to the other surface. The air holes may be straight or curved. The size of the pores may be changed between the surface layer and the inside or between one surface layer and another surface layer, for example.
The porous sintered sheet obtained by the above-described various molding methods may be further compressed by a pressing unit. More specifically, the porous sintered sheet may be pressed and compressed by sandwiching the porous sintered sheet between pressing plates, or may be pressed and compressed by a pressing roller, a pressing device of an endless belt, or the like. The temperature at the time of compression under pressure is preferably within a temperature range of the melting point. + -. 30 ℃. When the temperature is lower than the melting point by more than 30 ℃, the resin particles are already solidified, and the effect of compression may not be obtained, whereas when the temperature is higher than the melting point by more than 30 ℃, the porous sintered sheet may adhere to the compression plate or the pressure roller, and the pores on the other surface (for example, the surface) may be crushed. The compression ratio when the porous sintered sheet is subjected to compression is preferably 0.5% or more and 2% or less, and more preferably 0.7% or more and 1% or less, with respect to the thickness before compression. When the compressibility is less than 0.5%, the powder dropping property and wear resistance of the surface are poor, and when the compressibility is 2% or less, the porous sintered sheet of the present embodiment tends to have even more excellent permeability (for example, air permeability). The compressibility referred to herein means a ratio obtained by dividing a value obtained by subtracting the final thickness from the original thickness by the original thickness.
When the porous sintered sheet is obtained by sintering molding, the raw material resin is preferably used in a powdery form. In this case, in order to obtain sufficient permeability (for example, air permeability) and sufficient mechanical strength and appropriate rigidity in the porous sintered sheet, the average particle diameter of the raw material resin is preferably 10 to 300 μm, more preferably 20 to 250 μm, further preferably 30 to 200 μm, and particularly preferably 50 to 180 μm. The average particle diameter of the raw material resin is a median diameter that is a particle diameter when the cumulative weight reaches 50%, and can be measured using methanol as a dispersion medium using a laser diffraction particle size distribution measuring apparatus ("SALD-2100" manufactured by Shimadzu corporation).
"cross-sectional porosity" refers to the porosity of a cross section parallel to the surface of the porous sintered sheet. The cross-sectional porosity can be measured using an X-ray CT apparatus. This can be determined as follows: a cross-sectional image is gradually obtained from one surface of the porous sintered sheet in the thickness direction, and the image of the pores of each layer is binarized. By this method, the distribution of the cross-sectional porosity in the thickness direction of the porous sintered sheet can be obtained.
The average porosity is an average value of the cross-sectional porosities of all the layers, and the thickness of the porous sintered sheet is a distance from a first measurement point at which the porosity is 100% or less (in a state of not being in contact with the porous sintered sheet) in the X-ray CT measurement to a last measurement point at which the porosity is more than 100% on the opposite side.
The position where the minimum value of the cross-sectional porosity of the porous sintered sheet in the present embodiment is present is within 20%, preferably within 18%, more preferably within 16% of the depth in the thickness direction from one surface of the sintered sheet. In general, porous sintered sheets have the following tendency: the porosity gradually decreases as the depth from one surface increases in the thickness direction, and after reaching a substantially constant porosity at a certain depth, the porosity becomes minimum near the center of the thickness (near 50% of the depth from one surface in the thickness direction). On the other hand, in the porous sintered sheet of the present embodiment, the porosity gradually decreases as the depth from one surface in the thickness direction increases, the porosity becomes minimum within 20% of the depth from one surface in the thickness direction, and the porosity increases as the depth increases, and then the porosity becomes substantially constant. Since the minimum value of the porosity is within 20% of the depth in the thickness direction from one surface, for example, a powdery resin (for example, powder) lacking in the inside of the porous sintered sheet tends not to be easily released to the outside. When the porous sintered sheet of the present embodiment is used as a filter or an adsorption/transport plate, even if objects passing through the pores of the porous sintered sheet are clogged in the pores, the pressure loss can be reduced. Further, the porous sintered sheet has excellent mechanical strength on one surface, and one surface is less likely to be scratched, crushed, or deformed by external pressure. Therefore, the following tendency is exhibited: can maintain permeability (such as air permeability) and filtering ability for a long time, and is not easy to generate debris.
In general, in a die method in which a raw material powder is charged into a die and is charged into a heating furnace maintained at a temperature equal to or higher than the melting point and sintered, the raw material resin (for example, powdery resin) expands during heating, but is compressed due to the presence of the die. In the die method, the porous sintered sheet is gradually cooled by air cooling after heating, but in this case, the porous sintered sheet tends to have a minimum value of porosity from one surface to around 50% of the depth.
On the other hand, the method for producing the porous sintered sheet of the present embodiment having the minimum value of the porosity within 20% of the depth in the thickness direction from the one surface is not particularly limited. The raw resin is preferably accumulated on an endless conveyor belt, then heated and sintered, and then sandwiched in a pressing plate to be pressed. The temperature during heat sintering is adjusted to 180 to 230 ℃ and the temperature during compression is set to ± 30 ℃ with respect to the melting point of the resin, so that the minimum value of the porosity can be adjusted to be within 20% of the depth in the thickness direction from one surface of the porous sintered sheet.
In the porous sintered sheet of the present embodiment, the minimum value of the cross-sectional porosity is, for example, 10% or more and 40% or less, preferably 12% or more and 38% or less, and more preferably 15% or more and 36% or less. Sufficient permeability (for example, air permeability and water permeability) can be provided by setting the minimum value of the cross-sectional porosity to 10% or more. On the other hand, when the minimum value of the cross-sectional porosity is 40% or less, a porous sintered sheet having excellent mechanical strength and excellent filtration accuracy can be obtained.
The average porosity of the entire porous sintered sheet of the present embodiment is preferably 20% or more and 80% or less, more preferably 25% or more and 75% or less, and still more preferably 30% or more and 70% or less. When the average porosity is 20% or more, the porous sintered sheet of the present embodiment tends to have the following: the required space in the porous sintered sheet through which gas or liquid passes or is retained can be further secured, and the mechanical strength and durability are further excellent. On the other hand, when the average porosity is 80% or less, the porous sintered sheet of the present embodiment tends to have further excellent mechanical strength. The average porosity can be controlled by adjusting the average particle size of the resin particles, the calcination temperature, calcination time, compression temperature, compression pressure, compression time, and the like in the production of the molded article, as a method for adjusting the average porosity to 20% or more and 80% or less. The "average porosity" as used herein means an average value of cross-sectional porosities of all layers measured by X-ray CT.
The porous sintered sheet of the present embodiment is characterized by obtaining a porous sintered sheet having a pore structure different in the depth direction without performing bonding or the like. For example, when sheets of different structures are bonded with an adhesive or the like, the porosity of the adhesive layer is very different, and there are positions where the porosity is much lower than the average porosity of the entire structure in the depth direction.
In the porous sintered sheet of the present embodiment, it is preferable that no depth position is present in the depth in the thickness direction from one surface, which depth position is deeper than a depth position at which the average porosity of the entire porous sintered sheet is reached, and which depth position has a cross-sectional porosity greater than the average porosity by 20% or more. Thus, a porous sintered sheet having a dense structure in the surface layer portion can be obtained without interposing a pressure-sensitive adhesive layer that causes peeling.
In the porous sintered sheet of the present embodiment, 1m is preferably used2The above porous sintered sheet was divided into 100cm2Each block obtained as follows satisfies the following condition a:
(Condition A)
X≤Y×0.2
X: the difference between the depth position at which the minimum value of the cross-sectional porosity exists and the depth position at which the maximum value of the cross-sectional porosity exists
Y: thickness of the blocks.
By satisfying the condition a, the porous sintered sheet becomes a more uniform sheet, and the problems such as the difference in permeability of liquid or gas depending on the position, the inability to uniformly suck, and the inability to filter are further reduced. From the same viewpoint, X is more preferably Y × 0.1 or less, and further preferably Y × 0.05 or less.
The difference between the average porosity of the entire porous sintered sheet and the minimum value of the cross-sectional porosity of the porous sintered sheet in the present embodiment is, for example, 10% or more and 50% or less, preferably 12% or more and 40% or less, and more preferably 15% or more and 30% or less. When the difference between the average porosity and the minimum value of the cross-sectional porosity is 10% or more, a porous sintered sheet having excellent mechanical strength and excellent filtration accuracy can be obtained. On the other hand, when the difference between the average porosity and the minimum value of the cross-sectional porosity is 50% or less, the permeability of gas or liquid is excellent, and the pressure loss tends to be small.
The method of adjusting the difference between the average porosity and the minimum value of the cross-sectional porosity to 10% or more can be performed by the same method as the method of making the minimum value of the porosity within 20% of the depth in the thickness direction from one surface of the porous sintered sheet exist.
The product of air permeability and thickness of the porous sintered sheet in the present embodiment is 0.2cm3At least one/cm/sec, preferably 0.3cm3At least one unit of a material having a specific thickness of 0.3 cm/sec3A/cm/s to 1.0cm3/cm/sec), more preferably 0.4cm3More than/cm/second. The product of air permeability and thickness is 0.2cm3The porous sintered sheet of the present embodiment tends to have further excellent permeability (for example, air permeability and water permeability), further excellent mechanical strength, and further excellent durability. The air permeability may be measured by using an air permeability measuring apparatus ("FX 3360 PORTAIR" manufactured by TEXTEST corporation) in a measurement range of 20cm2and the differential pressure was measured at 125 Pa.
The thickness of the porous sintered sheet of the present embodiment is preferably 0.05mm or more and 5mm or less, more preferably 0.1mm to 3mm, and further preferably 0.2mm to 2 mm. When the thickness is within the above range, the porous sintered sheet of the present embodiment tends to be further excellent in self-supporting property and handling property, further excellent in permeability (for example, air permeability and water permeability), and further excellent in filtration accuracy.
The surface roughness (Ra) of the porous sintered sheet of the present embodiment is preferably 0.1 μm or more and 20 μm or less, more preferably 0.1 μm or more and 10 μm or less, and further preferably 0.1 μm or more and 5 μm or less. When the surface roughness is within the above range, when the porous sintered sheet of the present embodiment is used as an adsorption buffer material, scratches or contact marks can be further prevented from being generated on the member to be adsorbed. The method of adjusting the surface roughness (Ra) of the porous sintered sheet to be within the above range is not particularly limited, and includes: a method of producing a porous sintered sheet by a stacking method, a method of press-molding the obtained porous sintered sheet, a method of cutting the obtained porous sintered sheet, and the like. Further, since the minimum value of the cross-sectional porosity is present within 20% of the depth in the thickness direction from the surface of the porous sintered sheet, the surface tends to have a dense structure and to have a small surface roughness. The surface roughness (Ra) can be measured by a stylus surface roughness meter ("HANDYSURF E-35B" manufactured by Tokyo Kogyo K.K.) using a tip diameter R: 5 μm, speed: 0.6 mm/sec, measurement length: 12.5mm, sample value λ c: 2.5mm, number of measurements: the measurement was performed under the condition that n is 5.
[ use ]
The porous sintered sheet of the present embodiment has excellent gas permeability, and, for example, has a dense structure in the vicinity of the surface, and thus has small surface roughness, and therefore can be suitably used as an adsorption buffer. As one of means for fixing or conveying a film-like, plate-like or film-like material such as a sheet for adsorption/fixation/conveyance, a sheet for a support of a rapid test kit by immunochromatography, a glass plate for liquid crystal, or a sheet for laminated ceramic capacitor, there is a method of adsorption/fixation or adsorption/conveyance using an adsorption stage under reduced pressure adsorption, and the adsorption buffer material is a material attached to an adsorption surface of the adsorption stage.
The thin film may be a ceramic green sheet. The ceramic green sheet is generally obtained by: a ceramic coating material containing ceramic powder, a binder (acrylic resin, butyral resin, etc.), a plasticizer (phthalate, glycol, adipic acid, phosphate, etc.), and an organic solvent (toluene, MEK, acetone, etc.) is prepared, and the ceramic coating material is applied to a carrier sheet by a doctor blade method or the like, and then heated and dried.
Further, the filter material has a dense structure in the vicinity of one surface, but has high air permeability as a whole, and thus can be used as a filter material having high filtration efficiency.
Examples
Next, this embodiment will be described more specifically by way of examples and comparative examples, but the present embodiment is not limited to the following examples as long as the gist thereof is not exceeded.
The physical properties of each material were measured as follows.
(1) Cross sectional porosity
An X-ray CT apparatus (microfocus X-ray CT system HPC instexios SMX-225 CT: Shimadzu corporation) was used, the X-ray conditions were 160 kV/40. mu.A and no metal filter, and the imaging conditions were: the three-dimensional structure of the porous sintered sheet was obtained with an exposure time equivalent to 0.33 seconds, an image size of 1024 pixels × 1024 pixels, a spatial resolution of 5 μm/pixel, at 1200 sheets/360 ° rotation. A sectional image was obtained from one surface of the porous sheet in the thickness direction step by step, and the porosity of each layer was binarized by the Otsu method of the image, and the sectional porosity was obtained. This method can obtain the distribution of the porosity in the thickness direction of the porous sintered sheet (for example, fig. 1), and the average of the cross-sectional porosities of all layers is the average porosity of the entire porous sintered sheet.
(2) Surface roughness (Ra)
For the measurement of the surface roughness (Ra), a stylus type surface roughness meter ("hand yurf E-35B" manufactured by tokyo co., ltd) was used, and the diameter at the tip R: 5 μm, speed: 0.6 mm/sec, measurement length: 12.5mm, sample value λ c: the measurement was carried out under the condition of 2.5 mm. The measurement positions were measured for 1 position of the center of the surface of the object to be measured, and for 1 position of the center of the surface divided by 4 times so that the surface has the same shape, and for a total of 5 positions.
(3) Degree of air permeability
For the measurement of air permeability, an air permeability measuring apparatus ("FX 3360 PORTAIR" manufactured by TEXTEST) was used, and the measurement range was 20cm2The differential pressure was measured at 125 Pa.
(4) Thickness of
The thickness of the porous sintered sheet is measured by taking the distance from the first measurement point of the X-ray CT measurement where the porosity is 100% or less to the last measurement point of the X-ray CT measurement before more than 100%.
(5) Evaluation of powder dropping Property
In the evaluation of the powder dropping property of the porous polyolefin sintered sheet, 1 porous polyolefin sintered sheet having a size of 200mm × 200mm was Vibrated for 2 minutes by a vibrator ("woven playback vp-15D" manufactured by sheng steel electric motors) on a paper having a color opposite to the color of the raw material particles of the porous polyolefin sintered sheet, and then the presence or absence of the raw material particles on the paper having the opposite color was visually confirmed, and the evaluation was performed based on the following criteria.
O: the raw material powder hardly falls off.
X: the raw material powder falls off in large quantities.
(6) Evaluation of pressure loss
The pressure loss was measured by measuring the filtration rate and the silica content in the filtrate when the silica dispersion was suction-filtered using a porous sintered sheet as a filter. A porous sintered sheet was cut to match the size of the stent using a glass Filter stent (Filter holder) KG-47 (manufactured by tokyo glass instruments), attached to the stent, and clamped with a clip. 1L of the silica dispersion Snowtex MP-4540M (manufactured by Nissan chemical industries, Ltd.) was poured into the reactor under reduced pressure of 40kPa by an aspirator, and the time taken for water to pass was measured. Next, the content of silica in the filtrate was determined by measuring the dry weight, and evaluated based on the following criteria.
Very good: passing in less than 20 seconds.
O: the time for passing is 20 seconds or more and less than 40 seconds.
X: passing over for more than 40 seconds. Or even if passing for less than 40 seconds, the silica content reaches 50% or more of the content before filtration.
(7) Evaluation of scratch resistance on surface of porous sintered sheet
The surface of the porous sintered sheet was subjected to reciprocal friction 50 times using #0000 steel wool with a load of 100g, and the generation of shavings was observed and evaluated based on the following criteria.
O: the amount of the shavings generated is small, and the major diameter of the shavings is 1mm or less.
X: the amount of shavings generated was large, and shavings having a major diameter of 1mm or more were present.
[ example 1]
0.3 part by weight of polyoxyethylene sorbitan monolaurate was added to 100 parts by weight of an ultrahigh-molecular-weight polyethylene having a viscosity average molecular weight (Mv) of 40 ten thousand, an average particle diameter of 95 μm, a bulk density of 0.53g/cc and a melting point of 136 ℃ and mixed by a mixer. The ultrahigh molecular weight polyethylene composition was charged into a hopper and supplied. The supplied resin was deposited on a metal endless belt rotating at a moving speed of 10 cm/min so that the thickness thereof became 0.505 mm. Subsequently, it was passed through a heating zone set at 200 ℃ for 10 minutes. The resin temperature at the outlet of the heating zone was 190 ℃. After passing through the heating zone, the sheet was peeled off from the endless belt after 15 seconds, air-cooled from both sides, and wound on a roll to obtain a porous sintered sheet blank. Subsequently, the porous sintered sheet blank was cut into an appropriate size, and pressed under pressure at 140 ℃ for 90 seconds and 1MPa with a template thickness of 0.500mm, to obtain a porous sintered sheet having a thickness of 0.501 mm. The properties of the porous sintered sheet are shown in table 1. In addition, the distribution of the cross-sectional porosity is shown in fig. 1.
further, 100 sheets obtained by cutting the obtained sheet into 10cm square pieces were prepared, and the positions in the depth direction showing the respective minimum porosities were measured, and as a result, the maximum value was 0.075mm and the minimum value was 0.055mm, and the difference was 4% of the entire thickness, which was a uniform sheet as a whole.
[ example 2]
A porous sintered sheet having a thickness of 0.120mm was obtained in the same manner as in example 1, except that the supplied resin was deposited on a metal endless belt rotating at a moving speed of 9 cm/min so as to have a thickness of 0.121mm, and the resin was press-pressed with a template thickness of 0.120 mm. The properties of the porous sintered sheet are shown in table 1.
[ example 3]
A porous sintered sheet having a thickness of 0.501mm was obtained in the same manner as in example 1, except that an ultrahigh-molecular-weight polyethylene having a viscosity average molecular weight (Mv) of 100 ten thousand, an average particle diameter of 50 μm, a bulk density of 0.50g/cc and a melting point of 136 ℃ was used. The properties of the porous sintered sheet are shown in table 1.
[ example 4]
A porous sintered sheet having a thickness of 0.500mm was obtained in the same manner as in example 1, except that an ultrahigh-molecular-weight polyethylene having a viscosity average molecular weight (Mv) of 300 ten thousand, an average particle diameter of 50 μm, a bulk density of 0.33g/cc and a melting point of 136 ℃ was used. The properties of the porous sintered sheet are shown in table 1.
[ example 5]
A porous sintered sheet having a thickness of 0.100mm was obtained in the same manner as in example 1, except that an ultrahigh-molecular-weight polyethylene having a viscosity average molecular weight (Mv) of 500 ten thousand, an average particle diameter of 80 μm, a bulk density of 0.49g/cc and a melting point of 136 ℃ was used and the porous sintered sheet was deposited so that the thickness became 0.101 mm. The properties of the porous sintered sheet are shown in table 1.
comparative example 1
Using the resin used in example 1, in an aluminum mold with a gap adjusted to 0.510mm, the resin was filled while applying vibration for 30 seconds by a vibrator, the mold temperature was heated to 180 ℃, and after cooling, the mold was released, thereby obtaining a porous sintered sheet with a thickness of 0.506 mm. The properties of the porous sintered sheet are shown in table 1. Fig. 2 shows the distribution of the cross-sectional porosity.
Comparative example 2
The resin used in example 5 was filled into a net-like cylindrical mold (inner diameter 250mm, height 500mm), and the resin was filled while applying vibration for 30 seconds by a vibrator. The resultant was placed in a pressure-resistant container, steam (160 ℃ C., 8 atm) was introduced, and the resultant was sintered by heating for 10 hours, and then, it was left to stand at 25 ℃ C. and cooled. The obtained cylindrical porous sintered block was cut to obtain a porous sintered sheet having a thickness of 0.101 mm. The properties of the porous sintered sheet are shown in table 1.
Comparative example 3
A porous sintered sheet having a thickness of 0.120mm was obtained in the same manner as in example 1, except that the resin used in example 1 was stacked on a metal endless belt so that the thickness became 0.140mm and press-pressed with a template thickness of 0.120 mm. The properties of the porous sintered sheet are shown in table 1.
Comparative example 4
A porous sintered sheet was obtained in the same manner as in example 1, except that the resin used in example 1 was used, and the press pressing temperature was adjusted to 180 ℃. The properties of the porous sintered sheet are shown in table 1.
Comparative example 5
The porous body obtained in comparative example 1 was pressed under pressure at 95 ℃ for 90 seconds and 1MPa with a template thickness of 0.500mm to obtain a porous sintered sheet having a thickness of 0.503 mm. The properties of the porous sintered sheet are shown in table 1.
Comparative example 6
A porous sintered sheet having a thickness of 0.505mm was obtained in the same manner as in example 1, except that the resin used in example 1 was used and press-pressed with a template thickness of 0.505 mm. The properties of the porous sintered sheet are shown in table 1.
Comparative example 7
A porous sintered sheet having a thickness of 0.505mm was obtained in the same manner as in example 1, except that the resin used in example 1 was not subjected to press molding. The properties of the porous sintered sheet are shown in table 1.
Comparative example 8
The porous sintered sheet obtained in comparative example 3 was bonded to the porous sintered sheet obtained in comparative example 4 with a spray adhesive (3M spray 55) so that the thickness of the adhesive layer became 0.001mm, and a laminated porous sheet having an average porosity of 30% and a thickness of 0.621mm was obtained. The depth to which the average porosity of the laminated porous sheet was reached was 8% of the entire thickness from the sheet side where comparative example 3 was laminated (depth 0.05mm), and the porosity was 69.3% at a position 20% of the entire thickness at a deeper position (depth 0.125 mm). When the pressure loss of the laminated porous sheet was evaluated, the adhesive layer peeled off and the evaluation could not be performed.
Industrial applicability
The porous sintered sheet of the present invention has industrial applicability as a filter, an adsorption buffer material, an adsorption fixing and transporting material, a gas diffusion tube, a liquid-sensitive material, a holding material, a support material, and the like in the electronic field, the medical field, and the like.
The present application is based on the japanese patent application published on 5/9/2017 (japanese application 2017-093107), the content of which is incorporated herein by reference.

Claims (12)

1. A porous sintered sheet containing a resin and having continuous pores, wherein,
The porous sintered sheet has a minimum value of cross-sectional porosity of 10% or more, and the position where the minimum value of cross-sectional porosity is present is within 20% of the depth in the thickness direction from one surface of the sintered sheet.
2. The porous sintered sheet according to claim 1, wherein a difference between an average porosity of the entire porous sintered sheet and a minimum value of a cross-sectional porosity of the porous sintered sheet is 10% or more and 50% or less.
3. The porous sintered sheet of claim 1 or 2, wherein the product of the air permeability of the porous sintered sheet and the thickness of the porous sintered sheet is 0.2cm3More than/cm/second.
4. The porous sintered sheet according to any one of claims 1 to 3, wherein the average porosity of the entire porous sintered sheet is 20% or more and 80% or less.
5. The porous sintered sheet according to any one of claims 1 to 4, wherein, in a depth in a thickness direction from the one surface, there is no depth position deeper than a depth position at which an average porosity of the entire porous sintered sheet is reached and having a cross-sectional porosity greater than the average porosity by 20% or more.
6. The porous sintered sheet as claimed in any one of claims 1 to 5, wherein the porous sintered sheet is obtained by mixing 1m2The above porous sintered sheet was divided into 100cm2Each block obtained as follows satisfies the following condition a:
(Condition A)
X≤Y×0.2
X: the difference between the depth position at which the minimum value of the cross-sectional porosity exists and the depth position at which the maximum value of the cross-sectional porosity exists
Y: thickness of the blocks.
7. The porous sintered sheet as claimed in any one of claims 1 to 6, wherein the thickness of the porous sintered sheet is 0.05mm or more and 5.0mm or less.
8. A method for producing the porous sintered sheet in a sheet form according to any one of claims 1 to 7, wherein a resin is supplied onto an endless conveyor belt and molded into a sheet-form molded body, and then the molded body is heated and pressed.
9. The method for producing a porous sintered sheet according to claim 8, wherein the molded body is heated and then compressed by a pressing means at a temperature within a range of ± 30 ℃ from the melting point of the resin.
10. The method for producing a porous sintered sheet according to claim 9, wherein a compression ratio of the compression by the pressing means is 0.5% or more and 2% or less.
11. An adsorption-fixing-transporting sheet comprising the porous sintered sheet according to any one of claims 1 to 7.
12. A sheet for a support of a rapid test kit by immunochromatography, comprising the porous sintered sheet according to any one of claims 1 to 7.
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