CN111748911B

CN111748911B - Nonwoven fabric, method for producing the same, fastening tape, wound covering material, and absorbent article

Info

Publication number: CN111748911B
Application number: CN202010224187.9A
Authority: CN
Inventors: 左鹏
Original assignee: JNC Corp; JNC Fibers Corp
Current assignee: JNC Corp; JNC Fibers Corp
Priority date: 2019-03-29
Filing date: 2020-03-26
Publication date: 2023-10-31
Anticipated expiration: 2040-03-26
Also published as: CN111748911A; JP2020165035A; JP7295495B2

Abstract

The invention provides a nonwoven fabric having self-adhesiveness and capable of easily releasing an adhesive state, a method for producing the same, a fastening tape, a wound covering material, and an absorbent article. A method for producing a nonwoven fabric having self-adhesiveness, comprising: a step of forming a web comprising at least one composite fiber selected from the group consisting of an eccentric core-sheath composite fiber and a side-by-side composite fiber; a step of heat-treating the web to curl the composite fibers constituting the web into a coil shape to obtain a nonwoven fabric; and a step of needling at least one surface of the nonwoven fabric.

Description

Nonwoven fabric, method for producing the same, fastening tape, wound covering material, and absorbent article

Technical Field

The present invention relates to a nonwoven fabric having self-adhesiveness (self-adhesiveness). More particularly, the present invention relates to a nonwoven fabric in which nonwoven fabrics are laminated on each other, and the nonwoven fabrics of an upper layer and a lower layer are physically entangled and integrated by only lightly applying force, and the integrated nonwoven fabric can be easily released by physical force, a method for producing the same, a fastening tape, a wound covering material, and an absorbent article.

Background

Nonwoven fabrics are widely used in various fields such as absorbent articles, filters, and packaging materials, because they can be produced in a large scale at low cost and have breathability and stretchability. For example, a fastening material for hook and loop fasteners (nonwoven fabrics) using nonwoven fabrics is used in sanitary products and the like because the characteristics of breathability, stretchability and the like of nonwoven fabrics can be effectively utilized.

As a nonwoven fabric used for such a hook and loop application, patent document 1 discloses a loop material for a hook and loop fastener including a loop layer of a staple fiber nonwoven fabric and a base layer of a staple fiber nonwoven fabric, patent document 2 discloses a loop material for a loop/loop fastener including a composite nonwoven fabric, and patent document 3 discloses a fluffy nonwoven fabric that can be used as a base material (female materials) of a hook and loop fastener.

Patent document 4 discloses a method for producing a fluffed nonwoven fabric, which is characterized by comprising: after a fiber web (web) in which the split type composite fibers are gathered is locally applied with heat and pressure to obtain a fiber fleece (fleece), at least one surface of the fiber fleece is subjected to a needle punching (needle punching) treatment, whereby a part of the split type composite fibers existing in a region outside the thermo-compression bonding portion are projected to the other surface to generate a plurality of fiber round hairs, and the projected split type composite fibers are split by the impact of the needle punching treatment to visualize the split fiber group.

However, the inventions of patent documents 1 to 3 each relate to a circle Mao Goujian (base material) of the fastening tape, and a pin Mao Goujian (male materials) to be engaged with the circle Mao Goujian needs to be separately prepared. The fluffy nonwoven fabric obtained by the method of patent document 4 is used as a wiping cloth having excellent dirt removing performance, and does not have a fastening tape function.

In contrast, if the nonwoven fabric itself has self-adhesiveness, the nonwoven fabrics can be adhered to each other and integrated without using any other member. For example, if such a nonwoven fabric is used as hemostatic gauze, the gauze having a desired thickness can be prepared according to the degree of the flaws by overlapping and lightly pressing the gauze of a desired number of pieces or lightly pressing the gauze after folding the gauze, and adhering the upper layer and the lower layer to each other to integrate the gauze. Further, for example, when such a nonwoven fabric is used as a bandage, it is possible to wrap around an affected area a plurality of times and then attach and fix the overlapped bandages to each other, so that the bandages are not easily detached, and further, it is not necessary to fix the end portions of the bandages by using an adhesive tape or the like, so that the wound can be easily disposed. In addition, if the degree of self-adhesiveness is low and the nonwoven fabric in the bonded state can be released with a small force, it is convenient when the quick release of the bonding or the re-bonding is required.

[ Prior Art literature ]

[ patent literature ]

[ patent document 1] Japanese patent laid-open publication No. 2017-113391

[ patent document 2] Japanese patent application laid-open No. 2010-524573

[ patent document 3] Japanese patent laid-open No. 2002-302861

[ patent document 4] Japanese patent laid-open No. 9-59861

Disclosure of Invention

[ problem to be solved by the invention ]

Accordingly, an object of the present invention is to provide a nonwoven fabric which can be easily bonded by self-adhesion and can be easily released from a bonded state. The present invention also provides a method for producing such a nonwoven fabric at low cost.

[ means of solving the problems ]

The present inventors have made diligent studies to solve the above problems. As a result, it has been found that a web for nonwoven fabric is formed using at least one type of composite fiber selected from the group consisting of eccentric core-sheath type composite fiber and side-by-side type composite fiber, and the composite fiber is curled into a coil shape by heating by an air-passing method (through air method) or the like to form a nonwoven fabric, and thereafter, the nonwoven fabric is subjected to a needling process, whereby the composite fiber constituting the coil-shaped curl is pulled apart, and a plurality of endless curl portions (including spiral) or fluff (pile) curl portions (curl portions having no closed loop structure such as arches or waveforms) or straight or gentle curved fibers are caused to appear, whereby the self-adhesiveness (self-adhesiveness) is generated by physically interweaving these, thereby completing the present invention.

That is, the present invention has the following configuration to solve the above-described problems.

[1] A method for producing a nonwoven fabric having self-adhesiveness, comprising:

a step of forming a web comprising at least one composite fiber selected from the group consisting of an eccentric core-sheath composite fiber and a side-by-side composite fiber;

a step of heat-treating the web to curl the composite fibers constituting the web into a coil shape to obtain a nonwoven fabric; and

and a step of needling at least one surface of the nonwoven fabric.

[2] The method according to [1], wherein the heat treatment is performed by an aeration method.

[3]According to [1]]Or [2]]The method, wherein the needling density in the needling process is 6 times/cm ² About 40 times/cm ² The depth of the needle is 8 mm-26 mm.

[4] A nonwoven fabric produced by the method according to any one of [1] to [3 ].

[5] A fastening tape comprising the nonwoven fabric according to [4 ].

[6] A wound covering material or an absorbent article comprising the fastening tape according to the item [5 ].

[ Effect of the invention ]

The nonwoven fabric of the present invention has a plurality of endless crimp portions, fluff crimp portions, linear or gentle curved fibers, etc. which are formed by unwinding the loop-like crimp portions of the composite fibers constituting the nonwoven fabric, and therefore, these are physically entangled to exhibit self-adhesiveness by overlapping and lightly pressing the two nonwoven fabrics. The nonwoven fabric of the present invention is excellent in breathability and stretchability due to the presence of the crimp portion.

Drawings

Fig. 1 a to 1C are diagrams illustrating a state of being curled, a is a diagram schematically showing a coil-like curled portion 1 in which adjacent annular bodies are closely adhered to each other, and B and C are diagrams schematically showing a continuous annular curled portion 2.

Fig. 2 a and 2B are diagrams illustrating a state of curling, where a is a schematic diagram showing the discontinuous annular curled portion 3 and the fluff curled portion 4, and B is a schematic diagram showing a (length of a straight line connecting two rising portions of the fluff curled portion) and B (length of a straight line drawn perpendicularly from the apex of the fluff curled portion to a) in the fluff curled portion 4.

Fig. 3 is a photomicrograph (magnification 200) of the air-blown nonwoven fabric (through air nonwoven fabric) of example 1 (before needling).

Fig. 4 is a photomicrograph (magnification 200) of the needled nonwoven fabric of example 1.

Fig. 5 is a photomicrograph (magnification 200) of the needled nonwoven fabric of example 2.

Fig. 6 is another photomicrograph (magnification 200) of the needled nonwoven fabric of example 2.

Fig. 7 is a photomicrograph (magnification 200) of the air-blown nonwoven fabric of example 3 (before needling).

Fig. 8 is a photomicrograph (magnification 200) of the needled nonwoven fabric of example 3.

Fig. 9 is another photomicrograph (magnification 200) of the needled nonwoven fabric of example 3.

Fig. 10 a to 10C are photomicrographs of respective curl shapes, where a represents a coil-like curl portion, B represents a curl portion extending while rotating spirally, and a broken line portion of C represents a fluff-like curl and a discontinuous curl portion.

Fig. 11 is a photomicrograph (magnification 20) showing physical interleaving when the surfaces of the nonwoven fabric of the present invention are brought into contact with each other.

Fig. 12 is a photomicrograph (magnification 200) showing physical interleaving when the surfaces of the nonwoven fabric of the present invention are brought into contact with each other.

Fig. 13 is a photomicrograph (magnification 200) showing physical interleaving when the surfaces of the nonwoven fabric of the present invention are brought into contact with each other.

Description of symbols

1: coil-shaped curled portion

2: continuous annular curl

3: discontinuous annular curl

4: a villiated curl.

Detailed Description

The nonwoven fabric of the present invention contains eccentric core-sheath type composite fibers and/or side-by-side type composite fibers. These composite fibers are called latent crimping composite fibers, and when heat treatment is applied, the coil-like three-dimensional crimp is developed due to the difference in heat shrinkage between the two components constituting the composite fibers, and the crimp is remarkable. When such a latent crimping composite fiber is used, a nonwoven fabric having a large volume and a light weight can be obtained by three-dimensional crimping.

The fineness of the composite fiber used in the present invention is preferably 1dtex to 5dtex, more preferably 2dtex to 4dtex. By setting the fineness to the above range, the coil-like curl is easily developed. The cross-sectional shape of the conjugate fiber is not limited to a circular shape, and may be a non-circular shape such as a flat shape.

The composite fiber used in the present invention generally comprises at least two thermoplastic resin components having different melting points. In the case of an eccentric core-sheath type, a resin component having a low melting point (for example, a resin having a melting point of 123 to 134 ℃) is used as the sheath component, and a resin component having a high melting point (for example, a resin having a melting point of 150 to 170 ℃) is used as the core component. In the conjugate fiber used in the present invention, the area ratio of the resin component having a low melting point to the resin component having a high melting point (the area ratio in the cut surface perpendicular to the fiber axis direction) is preferably in the range of 30 to 70/70 to 30, and more preferably in the range of 40 to 60/60 to 40. The conjugate fiber used in the present invention is preferably a split conjugate fiber not as used in patent document 4.

Examples of the thermoplastic resin component include: polyolefin-based (for example, polypropylene, propylene copolymer [ copolymer of propylene and other α -olefin as main component; for example, ethylene-propylene copolymer, propylene-butene-1 copolymer, propylene-hexene-1 copolymer, etc. ], polyethylene, etc.), polyester-based (for example, polyethylene terephthalate), polyamide-based (for example, nylon (nylon) 6, etc.), PHBH (3-hydroxybutyrate-co-3-hydroxycaproate polymer) biodegradable polyesters. Specific combinations of the low-melting point component and the high-melting point component in the composite fiber can be exemplified: ethylene-propylene copolymer (low melting point component) and homo-polypropylene (high melting point component), polyethylene (low melting point component) and polypropylene (high melting point component), and the like.

In the case where the composite fiber is an eccentric core-sheath type, the sheath component is preferably a polyolefin elastomer, and preferably contains 2 to 20 wt% of the elastomer component and 98 to 80 wt% of the olefin component, and exhibits a melt Mass Flow Rate (MFR) of 2 to 45g/10 min. In addition, such polyolefin-based elastomer may be used for the side-by-side type composite fiber.

Examples of the polyolefin elastomer include: ethylene-propylene rubber (ethylene propylene rubber, EPR), ethylene-propylene non-conjugated diene copolymer rubber (ethylene-propylene-diene monomer (EPDM)).

A web containing at least one composite fiber selected from the group consisting of an eccentric core-sheath type composite fiber and a side-by-side type composite fiber is heat-treated with hot air or the like to cause heat shrinkage and heat bonding in the composite fiber, thereby forming a nonwoven fabric. In the nonwoven fabric after the heat treatment, three-dimensional crimp was developed in the composite fiber, and a coil-like crimp was mainly observed in which the endless bodies were closely adhered to each other and connected (see a in fig. 1). The temperature of the heat treatment such as hot air is preferably higher than the melting start temperature of the resin component having a lower melting point among the resin components constituting the composite fiber, and lower than the melting start temperature of the resin component having a higher melting point. For example, the temperature of the heat treatment is preferably 10 ℃ or higher than the melting start temperature of the resin component having a low melting point, and is preferably 20 ℃ or higher than the melting start temperature of the resin component having a high melting point.

The web used for producing the nonwoven fabric may contain, in addition to the composite fibers, fibers other than the fibers having thermal adhesiveness, fibers (hereinafter referred to as "non-thermal adhesiveness fibers") such as natural fibers (wood fibers, etc.), regenerated fibers (rayon, etc.), semisynthetic fibers (acetate, etc.), chemical fibers, synthetic fibers (polyester, acrylic, nylon, vinyl chloride, etc.), and the like. The term "non-heat-bondable fibers" refers to fibers that do not undergo thermal changes (melting or softening) that are involved in heat bonding during heat bonding performed in the manufacture of nonwoven fabrics. When the fibers other than the composite fibers of the present invention (eccentric core-sheath composite fibers/side-by-side composite fibers) are included, the proportion of the composite fibers of the present invention relative to the total weight of the web is not limited as long as the effect of the present invention is not inhibited, and may be, for example, 60 to 100 wt%, preferably 70 to 100 wt%, more preferably 80 to 100 wt%, and particularly preferably 90 to 100 wt%. Particularly, a nonwoven fabric composed of only eccentric core-sheath type composite fibers or side-by-side type composite fibers is preferable.

In the case of webs made by carding machines, the composite fibers preferably have a crimp. For example, it is preferable to impart a saw tooth (zig) shaped mechanical curl with a crimper (crimpe). The number of curls is preferably 5 peaks/2.54cm (peaks/2.54 cm) to 15 peaks/2.54cm, more preferably 5 peaks/2.54cm to 8 peaks/2.54 cm. In addition, the composite fibers applied to the carding machine are preferably staple fibers cut into fibers of preferably 30mm to 126mm, more preferably 38mm to 64 mm.

Alternatively, a plurality of different kinds of webs including eccentric core-sheath type composite fibers and side-by-side type composite fibers may be stacked and then subjected to the heat treatment described below. Alternatively, a web containing the eccentric core-sheath type composite fiber/side-by-side type composite fiber and a web containing a fiber other than the eccentric core-sheath type composite fiber/side-by-side type composite fiber may be overlapped and then subjected to the heat treatment described below.

Preferable examples of the method for heat-treating the web include: a method of heating the whole web by a so-called aeration method (also referred to as an air passage method (air through method)) using a heat treatment apparatus or the like (for example, a hot air circulation type oven, a hot air through type heat treatment machine, or a hot air blowing type heat treatment machine) including a conveyance support for supporting and conveying the web. If the web is pressed by a roller or the like, the coil-like curl is hard to develop, and therefore, a heating method (a method in which thermal compression is not performed) in which mechanical pressure is not applied to the web is preferable.

The conditions of the air-passing method are not particularly limited as long as the conjugate fiber can be heat-shrunk and the coil-like curl is developed. For example, the heat treatment conditions may be set so that, when the surface of the nonwoven fabric is observed by a digital microscope (magnification 200 times), a coil-like curl is observed over the substantial whole of the microscope field of view. The diameter of the coil-shaped curled portion (maximum diameter in the case of not being completely circular) is preferably 20 μm to 90 μm, more preferably 40 μm to 70 μm.

The appropriate heat treatment conditions may be varied depending on the thickness of the composite fiber or web to be used, and may be, for example, 40 seconds to 180 seconds, more preferably 50 seconds to 120 seconds, and particularly preferably 60 seconds to 80 seconds at a temperature of 100 ℃ to 130 ℃, more preferably 105 ℃ to 125 ℃, and particularly preferably 110 ℃ to 120 ℃. The wind speed may be set to 0.2m/sec to 3.0m/sec, more preferably 1.2m/sec to 2.4m/sec.

Regarding the heat shrinkage of the nonwoven fabric due to the heat treatment, when the length between predetermined points measured in the machine direction (machine direction, MD) of the web before the heat treatment is set to the x value and the length between the same points after the heat treatment is measured and set to the y value, the shrinkage obtained by the following formula is preferably 10% to 90%. For example, 30% or more and less than 90%, 50% or more and 85% or less, 70% or more and 83% or less may be used.

[ number 1]

The method comprises the following steps: and (3) needling the non-woven fabric obtained after the heat treatment. The needling is a processing method generally used for the purpose of producing a nonwoven fabric, and may be used for the purpose of mechanically interlacing fibers to produce a nonwoven fabric, or may be used for the purpose of performing a pretreatment (temporary fixation of a web) prior to the thermal bonding method (thermal bond method), only in the case of the needling.

In the above-described conventional method of use, the needling is performed for the purpose of interlacing fibers with each other, but the present invention is characterized in that: the needling is performed for the purpose of unwinding the coiled portion generated by the heat treatment and causing the continuous/discontinuous annular curled portion, the fluffy curled portion, or the like to appear.

The condition of the needling process varies depending on the degree of self-adhesive force of the nonwoven fabric to be expected, the weight per unit area of the nonwoven fabric, or the like, and it is generally preferable to set the needling machine such that the needle density (indicating that the needles are at 1cm ² How many times the nonwoven fabric is buried) becomes preferably 6 times/cm ² About 40 times/cm ² More preferably 10 times/cm ² About 30 times/cm ² In particular 15 times/cm ² 25 times/cm ² Is a range of ways. The number of barbs of each needle may be, for example, preferably 3 to 8, more preferably 4 to 6. The needle depth may be, for example, preferably 8 to 26mm, more preferably 10 to 20 mm.

The needling may be performed not only on one side but also on both sides of the nonwoven fabric.

In the present invention, the coil-shaped curled portion refers to a curled portion in which one fiber is curled in three dimensions while being spirally rotated by heat shrinkage, as shown in a of fig. 1 and a of fig. 10.

In the present invention, since the composite fiber is curled by the heat treatment to develop the coil-shaped curled portion and then needle punching is performed, most of the coil-shaped curled portion generated in the heat treatment is released by the barbs of the needle. Therefore, there are spaces between the annular bodies, and there are continuous annular curled portions (B in fig. 1, C in fig. 1, and B in fig. 10) in which a plurality of annular bodies are adjacent to each other, discontinuous annular curled portions (symbol 3 in fig. 2 a and B in fig. 2, and C in fig. 10), and fluffy curled portions (symbol 4 in fig. 2 a and B in fig. 2, and C in fig. 10).

The continuous annular curled portion of the present invention may be a curled portion in which annular bodies having substantially the same direction of the rotation surface are connected (for example, a spirally curled portion extending linearly in a direction of straight movement with respect to the rotation surface) as shown in fig. 1B, or may be a curled portion in which annular bodies having different directions of the rotation surface are connected as shown in fig. 1C.

In the present invention, the discontinuous annular curl portion refers to a curl portion adjacent to the annular curl which is not formed in an annular shape (symbol 3 in fig. 2 a and 2B), or a curl portion which is not recognized as a continuous shape due to a distance between annular curls.

The continuous/discontinuous annular curl portion has a larger diameter (for example, the coil curl has a diameter of 40 μm to 60 μm, and the annular curl has a diameter of 80 μm to 110 μm) than the diameter of the coil-like curl portion (the maximum diameter in the case of not being completely circular; hereinafter the same).

In the present invention, the fluff-like curled portion refers to a curled portion having no closed loop structure in which a convex portion is observed in a mountain shape, an arch shape, a wave shape, or the like, as indicated by symbol 4 in fig. 2 a and 2B. In the nonwoven fabric of the present invention, when a length of a straight line connecting two raised portions of the fluff curl portion by a straight line is a and a length of a straight line drawn perpendicularly from an apex of the fluff curl portion (a point farthest from the straight line a in a vertical direction) to the straight line a is b, the length of b is preferably 40 μm or more, and more preferably 50 μm or more. Further, it is considered that when the nonwoven fabric of the present invention is overlapped with each other by increasing the value of either one of a and b, the fluff-like curled portions are interwoven with the annular curled portions (including the spiral curled portions) in the nonwoven fabric by the physical force at the time of overlapping, and thus the nonwoven fabric is easily integrated. In other words, it is considered that, in the nonwoven fabric of the present invention, the fluff-like curled portion and the spiral curled portion or other annular curled portion (continuous or discontinuous annular portion) become the male/female portions of the entangled bristles and interweave, thereby causing self-adhesion to occur (see fig. 11, 12 and 13).

As shown in the photomicrographs of fig. 4 to 6, 8 and 9, it is difficult to appropriately specify the structure or characteristics in terms of language, and it is also difficult to analyze the structure or characteristics based on measurement and specify them, and when the nonwoven fabric of the present invention is observed by a microscope, a state in which continuous annular curled portions, discontinuous annular curled portions and fluff curled portions are mixed is confirmed at least on one side thereof. Further, if necessary, a curled portion remaining in a coil-like curled state, or a fiber having a linear or curved shape may be confirmed. Since the loop-like curled portion is pulled apart by needling, in the nonwoven fabric of the present invention, a lot of annular curls having different orientations and diameters of the rotating surfaces from those of the adjacent annular curls are generally observed.

In the present invention, the number of fluff-like curled portions of at least one side of the nonwoven fabric is preferably 4/mm ² The above. More preferably 8/mm ² The number of the above components is particularly preferably 10 per mm ² The above. If the number of the fluff-like curled portions per unit area is 4 or more, it is considered that the fluff-like curled portions interweave with the annular curled portions or the like in the nonwoven fabric and are easily integrated (i.e., self-adhesive property is exhibited) when the nonwoven fabrics are overlapped with each other.

In the present invention, the self-adhesiveness means the following state: the two nonwoven fabrics are overlapped by being pressed lightly by hand or by being applied lightly (for example, by applying only 1 g/cm) ² If the upper layer nonwoven fabric is held and lifted, the lower layer nonwoven fabric is lifted while being adhered to the upper layer nonwoven fabric, and the lower layer nonwoven fabric does not fall even if the upper layer nonwoven fabric is directly held (for example, 1 minute or 10 minutes).

Further, the round-hair/thorn-hair type fastening tape exhibits a strong adhesive force by the engagement of the round-hair members with the thorns Mao Goujian, but the nonwoven fabric of the present invention is loosely bonded by the interlacing of the loop-shaped body with the nap or the like, and therefore, the two nonwoven fabrics can be separated by applying only a small force (for example, a force of 0.02N) and no sound is generated even when the two nonwoven fabrics are separated.

Further, the nonwoven fabric of the present invention generally exhibits self-adhesiveness in any of the back surfaces, the front surfaces, and the combination of the back and front surfaces, and therefore can be used in various applications without being limited by the combination of the adhesive surfaces.

The self-adhesive nonwoven fabric obtained by the present invention preferably has a weight per unit area of 10g/m ² ～200g/m ² More preferably 30g/m ² ～90g/m ² Particularly preferably 40g/m ² ～70g/m ² 。

The nonwoven fabric of the present invention has a loop-like curled portion, a continuous/discontinuous loop-like curled portion, and a fluff-like curled portion, and therefore has moderate stretchability, and also has excellent hand feeling and breathability. Further, since no chemical substance for adhesion is used, no harmful component is contained and skin irritation is small. Further, the adhesive tape can be integrated by physical bonding and has a function of an adhesive tape that is easily peeled off by physical force, and therefore, the adhesive tape can be used as a wound covering material such as a bandage or a gauze (for example, hemostatic gauze) or an adhesive tape for an absorbent article (for example, a disposable diaper), and is convenient because it is not necessary to distinguish a round hair material from a burr material and it is easy to use.

The nonwoven fabric of the present invention can be produced by an air-through method and a needle punching method which are generally used for producing nonwoven fabrics, and therefore can be produced with low labor and low cost without introducing a new machine.

Examples (example)

Hereinafter, the present invention will be described in detail using examples. However, the present invention is not limited to the following examples.

a and b measurement method

The surface of the nonwoven fabric was 3D-photographed at a magnification of 200 times using a digital microscope VHX-6000 (trade name) manufactured by Kenji (KEYENCE). Using the data of the obtained 3D photograph, a, b of the villiated curled portion existing in the range of 1000 μm×1000 μm were measured. The procedure carried out by VHX-6000 was used for the measurement.

Method for measuring elongation recovery rate (elongation recovery rate at 50% elongation) of elastic nonwoven fabric

A nonwoven fabric test piece having a width of 25mm and a length of 200mm was produced by setting the machine direction of the nonwoven fabric as the longitudinal direction. Test pieces were fixed by setting the gap between chucks to 100mm using a tensile tester ott Gu Lafu (autograph) AG-500D (manufactured by shimadzu corporation). After being stretched to 50% at a stretching speed of 200mm/min, the nonwoven fabric was returned at the same speed, and the load applied to the elastic nonwoven fabric was set to 0. Immediately thereafter, the load was again elongated to 50% at the same speed, and the length of the elongation at the time of starting the load application again was set to L mm. The elongation recovery rate was determined according to the following equation.

Elongation recovery at 50% elongation (%) = { (100) ^*1 -L)/100 ^*1 }×100

*1: initial length (mm) of test piece between chucks

Example 1

A propylene copolymer (copolymer of ethylene and propylene; mfr=16 g/10 min) and a homo-polypropylene (mfr=10 g/10 min) were composite-spun in a side-by-side manner to obtain a side-by-side composite fiber having a fineness of 3.3dtex (the area ratio of the propylene copolymer to the homo-polypropylene in a cut plane perpendicular to the fiber axis was about 50 to 50). The composite fiber was subjected to mechanical crimping (zigzag crimping) to obtain a composite fiber having an average crimp number of 8 peaks/2.54 cm. The composite fibers were cut into short fibers of 51mm length, a web was produced by a carding machine, and the obtained web was heated by a hot air circulation type air-through processor (traveling speed of 8.5 m/min, 120 ℃ C., 1 minute, wind speed of 1.2 m/sec) at 120 ℃ C., thereby obtaining an air-through nonwoven fabric having a shrinkage of 80%. Fig. 3 shows a photograph of the surface of the nonwoven fabric obtained by photographing the surface with the digital microscope. The coil-like curled portion which is exhibited by heat shrinkage of the composite fibers constituting the nonwoven fabric was observed over the entire visual field.

Further, the air-blown nonwoven fabric was processed on one side by a needling machine. The needles used were 1.2mm (model 15 x 18 x 40 x 3.5) needles with 6 barbs per 1 needle and a needling density of 20 times/cm ² The working machine was set so that the needle depth was 10 mm. After the needling, the surface (needle insertion surface) of the nonwoven fabric was observed by a microscope (see fig. 4), and as a result, a continuous annular curl portion and a discontinuous annular curl portion, which are generated by collapse of the coil-like curl, were observed, and a fluffy curl portion was also observed. Further, the coil-like curl portion is not continuous in one direction as in the coil-like curl before the needling, but a curl portion considered as a coil-like curl can be confirmed.

The nonwoven fabric obtained in example 1 had a weight per unit area of 60g/m ² 。

The needled nonwoven thus obtained was cut into a sheet of 2.5mm (MD direction). Times.10 mm (CD direction) (area 25mm ² ) After the surfaces (needle insertion surfaces) of the two nonwoven fabrics were superposed on each other and lightly pressed (a force of about 0.9N was applied at maximum), a tensile test was performed at a speed of 200mm/min using Aute Gu Lafu (autograph) AG-500D, manufactured by Shimadzu corporation. The tensile strength in the MD direction was 0.6N. The self-adhesive force of the nonwoven fabrics is highest when the two nonwoven fabrics are overlapped so that the needle insertion surfaces overlap each other, but the two nonwoven fabrics are adhered to each other by lightly pressing the two laminated nonwoven fabrics by hand regardless of whether the needle insertion surfaces (front surfaces) are in contact with the surface (back surfaces) of the base plate (bed plate) or the back surfaces are in contact with each other, and in either case, when the nonwoven fabrics on the upper layer side are lifted up, the nonwoven fabrics on the lower layer side are lifted up in a state of being adhered to the nonwoven fabrics on the upper layer side, and even if 1 minute passes, the nonwoven fabrics on the lower layer do not fall down. In either case, the two integrated nonwoven fabrics can be separated by a small force (0.02N).

The needled nonwoven fabric was subjected to force in the MD direction, and its recovery was measured. The elongation recovery at 50% elongation was 45%.

Further, a and b of villiated curls (22 pieces) in the range of 1000 μm×1000 μm were measured using data of a 3D photograph obtained by a microscope. The results are shown in table 1.

TABLE 1

As apparent from Table 1, it was confirmed whether the fluffy curled portion b > a or the fluffy curled portion b < a was present. In particular, a or b is a curled portion of 100 μm or more.

Example 2

The air-through nonwoven fabric obtained in example 1 was laminated on a nonwoven fabric (20 g/m ² ) On the needle, a needling machine is used to perform needling at a needling density of 20 times/cm ² The laminate was processed with a needle depth of 10 mm. After the processing, the air-permeable nonwoven fabric (needled nonwoven fabric) is separated from the laminate integrated by the needling processing. The shrinkage of the obtained needled nonwoven fabric with respect to the web obtained in the carding process was 65%. In addition, the weight per unit area of the needled nonwoven fabric is 45g/m ² 。

As a result of observation of the surface (needle insertion surface) of the nonwoven fabric by a microscope (see fig. 5 and 6), continuous annular curled portions, discontinuous annular curled portions, fluffy curled portions, and straight or gently curved fibers were observed. In addition, there is also a curl portion identified as a coil-like curl. In a view of 1000 μm×1000 μm, 10 or more villiated curled portions were observed.

As a result of confirming the self-adhesiveness of the nonwoven fabric, even if any one of the front surface, the back surface, and the front and back surfaces is combined as in the needled nonwoven fabric of example 1, the nonwoven fabric is adhered to each other only by stacking and lightly pressing with a hand, and in any case, when the nonwoven fabric on the upper layer side is lifted up, the nonwoven fabric on the lower layer side is lifted up while maintaining the state of being adhered to the nonwoven fabric on the upper layer side, and even after 1 minute, the nonwoven fabric on the lower layer does not fall down. In either case, the two integrated nonwoven fabrics may be separated by a small force (e.g., 0.02N).

The needled nonwoven thus obtained was cut into 2.5mm (MD direction). Times.10 mm (CD direction) (area 25 mm) ² ) After the front surfaces (needle insertion surfaces) or the back surfaces (bottom plate side surfaces) of the two nonwoven fabrics were superposed and lightly pressed, a tensile test was performed at a speed of 200mm/min using an Ott Gu Lafu (autograph) AG-500D, manufactured by Shimadzu corporation. The tensile strength in the MD direction was 0.2N on the needle insertion face and 0.1N on the face on the bottom plate side.

Example 3

The web obtained in example 1 was placed on a web comprising concentric core-sheath type composite fibers of low density polyethylene (melting point 120 ℃) and homo-polypropylene (2.1 dtex, cut length 38mm, and area ratio of low density polyethylene to homo-polypropylene in the cross section of the composite fiber: 50/50), to form a two-layer web. The proportion of the concentric core-sheath type composite fibers in the double-layer web was 33 wt% and the proportion of the side-by-side type composite fibers was 67 wt%. After heat treatment (air speed 1.2m/sec heating time 1 min) of the double-layer web using a 120℃hot air circulation type air ventilation processing machine, needling density 20 times/cm using a needling processing machine ² Processing the needle with the depth of 10mm to obtain the needled non-woven fabric. The shrinkage of the obtained needled nonwoven fabric was 10% relative to the web obtained in the carding process. In addition, the weight per unit area of the needled nonwoven fabric is 35g/m ² 。

Fig. 7 shows a photograph of the air-blown nonwoven fabric (before needling) of example 3, and fig. 8 and 9 show photographs after needling. As shown in fig. 7, the nonwoven fabric of example 3 was obtained by superposing a web containing concentric core-sheath type composite fibers on the web of example 1 (web containing side-by-side type composite fibers) and performing a heat treatment, and therefore, after the heat treatment, side-by-side type composite fibers curled in a coil shape and concentric core-sheath type composite fibers which were hardly curled were observed. When the air-permeable nonwoven fabric is subjected to needling, as shown in fig. 8, continuous/discontinuous annular curled portions, fluff-like curled portions, or straight or gentle curved fibers are observed by the collapse of the coil-like curl, the entanglement with uncrimped fibers, and the like. In a view of 1000 μm×1000 μm, 10 or more villiated curled portions were observed. In fig. 9, a curled portion which is considered to be a coil-like curl is also observed.

Comparative example 1

Polypropylene (mfr=20 g/10min, containing 2 wt% of elastomer, "PM822V" manufactured by san-a roman (sunallimer)), and other polypropylene (mfr=10 g/10min, "MA3H" manufactured by japan polypropylene (Japan Polypropylene)) were used, and the spinning was performed by a composite spinning apparatus at 230 ℃, a neck drawing step at 90 ℃, and further drying at 90 ℃. The obtained tow was cut to obtain a side-by-side type composite fiber having a fiber length of 45mm and a fineness of 2.2 dtex.

The obtained side-by-side type composite fiber was made into a web by a carding machine, the front and back of the web were sandwiched by kraft paper, and heated by an oven at a set temperature of 120℃for 5 minutes to obtain a weight per unit area of 50g/m ² Is a nonwoven fabric of (a) a nonwoven fabric.

Using microscopesThe nonwoven fabric obtained was observed to have a loop-like curled portion at one side, and a fluff-like curled portion was 0/mm ² . In addition, when two nonwoven fabrics are stacked and lightly pressed, no combination of the two nonwoven fabrics is adhered to each other, and if only the upper nonwoven fabric is gripped and lifted, only the upper nonwoven fabric is lifted.

The nonwoven fabric of comparative example 1 may also exhibit self-adhesiveness by being subjected to a needling process.

Example 4

A propylene copolymer (copolymer of ethylene and propylene; mfr=31 g/10 min) was spun in combination with a homo-polypropylene (mfr=5 g/10 min) to obtain a side-by-side type composite fiber having a fineness of 2.6dtex (the area ratio of the propylene copolymer to the homo-polypropylene in a cut plane perpendicular to the fiber axis was about 60 to 40). The composite fiber was subjected to mechanical crimping (zigzag crimping) to obtain a composite fiber having an average crimp number of 5 peaks/2.54 cm. The composite fiber was cut into short fibers of 51mm length, a web was produced by a carding machine, and the obtained web was heated at a wind speed of 0.2m/sec for 3 minutes by a hot air circulation type aeration processor at 120℃to thereby obtain an aeration nonwoven fabric having a shrinkage of 75%. As a result of observation of the surface of the nonwoven fabric using the digital microscope, a coil-like curled portion, which is exhibited by heat shrinkage of the composite fibers constituting the nonwoven fabric, was observed over the entire visual field.

Further, the air-blown nonwoven fabric was processed on one side by a needling machine. The needles used were 1.2mm (model 15 x 18 x 40 x 3.5) needles with 6 barbs per 1 needle and a needling density of 20 times/cm ² The working machine was set so that the needle depth was 10 mm. After the needling, the surface (needle insertion surface) of the nonwoven fabric was observed with a microscope, and as a result, a continuous annular curled portion, a discontinuous annular curled portion, and a coiled curled portion were observed, and a fluffy curled portion was also observed. In the field of view of 1000 μm×1000 μm, 8 villiated curled portions were observed. The weight per unit area of the nonwoven fabric obtained was 55g/m ² 。

Claims

1. A method for producing a nonwoven fabric having self-adhesiveness, comprising:

a step of needlepunching at least one surface of the nonwoven fabric to unwind the composite fiber wound in a coil shape and form a loop-like wound portion, a fluff-like wound portion, or a curved fiber,

wherein the composite fiber comprises at least two thermoplastic resin components having different melting points, and the thermoplastic resin components comprise polyolefin-based, polyester-based and polyamide-based,

the number of the villus curls is 4/mm ² The above-mentioned steps are carried out,

the needling density in the needling process is 6 times/cm ² About 40 times/cm ² The needle depth is 8 mm-26 mm,

the number of barbs of each needle in the needling process is 6-8.

2. The method for producing a nonwoven fabric according to claim 1, wherein the heat treatment is performed by an air ventilation method.

3. A nonwoven fabric produced by the method for producing a nonwoven fabric according to claim 1 or 2.

4. A fastening tape comprising the nonwoven fabric according to claim 3.

5. A wound covering material comprising the fastening tape according to claim 4.

6. An absorbent article comprising the fastening tape according to claim 4.