JP2013170340A - Fiber for air-laid nonwoven fabric and air-laid nonwoven fabric using the fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fiber for an air-laid nonwoven fabric capable of producing an air-laid nonwoven fabric having sufficient flexibility, liquid-retaining properties, air permeability, bulkiness, hydrophilic properties and strength as a nonwoven fabric.SOLUTION: The fiber for the air-laid nonwoven fabric comprises an ethylene-vinyl alcohol based copolymer containing 5-70 mol% of ethylene, and has a fiber length of 2-30 mm and a crimp number of 3-30 crimps/inch. The air-laid nonwoven fabric that uses at least 10 wt.% or more of the fiber is also disclosed.

Description

  The present invention relates to a fiber for an air laid nonwoven fabric, and more particularly to a fiber for an air laid nonwoven fabric made of an ethylene-vinyl alcohol copolymer. More preferably, it relates to an airlaid nonwoven fabric for cosmetic products.

The airlaid manufacturing method is one type of dry nonwoven fabric manufacturing method, in which short fibers such as pulp and synthetic fibers are opened in the air and then a web is formed on the wire. Therefore, reduction of drainage load by not using water for sheet production, random fiber orientation, and SAP (high water absorption resin), activated carbon, etc. Since powder and the like can also be intervened in the voids inside the nonwoven fabric at the same time, attention has been focused on features such as the ability to obtain a nonwoven fabric in which various materials are mixed in one step, and in recent years the method of application has been particularly expanded. is there.
In particular, air laid nonwoven fabrics using pulp fibers having water absorption performance and oil absorption performance and relatively low cost are applied to a wide range of products such as wipers, towels and hygiene materials as inexpensive nonwoven fabrics.

As a web bonding method in the airlaid nonwoven fabric manufacturing process, currently, a latex bond method in which an adhesive is sprayed and bonded, a thermal bond method in which a polyolefin-based or polyester-based heat-adhesive fiber is used as a binder fiber, or both are bonded. Is used (see, for example, Patent Documents 1 to 3). However, in the bonding by the latex bond method, the adhesive permeates into the voids of the nonwoven fabric, resulting in problems such as a decrease in liquid retention and flexibility. Also, polyolefin-based and polyester-based thermal adhesiveness Bonding by a thermal bond method using fibers has problems such as a decrease in hydrophilicity, water retention and water absorption of the obtained nonwoven fabric due to the hydrophobicity derived from these materials.
Therefore, an airlaid nonwoven fabric produced by the above-mentioned production method as a nonwoven fabric for cosmetic products is not preferable because the chemical solution does not sufficiently penetrate into the nonwoven fabric and the flexibility is lowered, and the sheet is uncomfortable when touched to the skin.

Japanese Patent Publication No. 2007-154163 Japanese Patent Publication 2001-329432 Japanese Patent Publication No. 2003-89958

  Accordingly, an object of the present invention is to provide a heat-bonding fiber for an airlaid nonwoven fabric without losing the liquid retaining property and flexibility.

  As a result of intensive studies to solve the above problems, the present inventors have used a fiber using an ethylene-vinyl alcohol copolymer having a hydroxyl group in the molecule as a binder fiber, thereby improving hydrophilicity and water retention. It has been found that a maintained airlaid nonwoven can be obtained.

  That is, the present invention is a fiber comprising an ethylene-vinyl alcohol copolymer having an ethylene content of 5 to 70 mol%, wherein the fiber has a fiber length of 2 to 30 mm and a number of crimps of 3 to 30 / inch. It is a fiber for air laid nonwoven fabric characterized by being, The composite fiber comprised with thermoplastic resins (B) preferably other than ethylene-vinyl alcohol copolymer (A) and ethylene-vinyl alcohol type copolymer Wherein the ethylene-vinyl alcohol copolymer (A) is present on the fiber surface, and is a fiber for an airlaid nonwoven fabric, and more preferably contains at least 10% by weight of the fiber. The present invention relates to an airlaid nonwoven fabric.

  According to the present invention, it is possible to provide a heat-adhesive fiber for airlaid without using an adhesive, a polyolefin-based resin that is a hydrophobic thermoplastic resin, or a polyester-based resin as a binder fiber. The air-laid nonwoven fabric obtained by using can obtain an air-laid nonwoven fabric having hydrophilicity, water retention and flexibility.

Hereinafter, the present invention will be described in detail.
The fiber of the present invention can be obtained by a melt spinning method using an ethylene-vinyl alcohol copolymer as a raw material, and may be subjected to stretching treatment, heat treatment, and the like as necessary. Moreover, when obtaining a composite fiber, it can obtain by changing a nozzle | cap | die with a melt spinning method. For example, when obtaining a composite fiber of an ethylene-vinyl alcohol copolymer (A) and a thermoplastic polymer (B), each raw material is melted in a separate extruder, and these melts are combined into a composite spin pack. It is obtained by introducing it into a spinning device having the same, and combining and spinning in a spinning pack.

  The ethylene-vinyl alcohol copolymer fiber in the present invention is a fiber containing a saponification product of a copolymer of ethylene and vinyl acetate as a component, and the amount of ethylene contained in the copolymer is 5 to 70 mol%. Is used. When the ethylene content is less than 5 mol%, melt spinnability deteriorates, which is not preferable. On the other hand, when the ethylene content exceeds 70 mol%, the physical properties such as hydrophilicity and water retention aimed at by the present invention are not preferred. Preferably it is 20-50 mol%.

  The fineness of the fiber of the present invention may be selected according to the purpose and is not particularly limited, but is used in the range of about 0.5 to 100 dtex.

  The fiber length of the fiber of the present invention needs to be in the range of 2 to 30 mm, and preferably in the range of 3 to 10 mm. When the fiber length is less than 2 mm, sufficient strength cannot be obtained as an air laid nonwoven fabric, and the process passability deteriorates, which is not preferable. Moreover, when the fiber length exceeds 30 mm, the fibers are entangled with each other, and problems such as poor air opening and causing unevenness of the nonwoven fabric occur, which is not preferable.

  The fibers of the present invention are preferably crimped from the viewpoint of air opening. By being crimped, a fiber lump in an unopened state can be easily opened by an elastic effect due to crimping upon impact by air or collision with the inner wall surface of the rotating drum. For this reason, the number of crimps needs to be in the range of 3 to 30 pieces / inch, and more preferably in the range of 5 to 20 pieces / inch. When the number of crimps is less than 3 / inch, unopened fibers are likely to be generated and the texture is deteriorated. On the other hand, when the number of crimps exceeds 30 / inch, the air-opening property is deteriorated, and a defect in a bundled shape tends to occur, which is not preferable.

  The dry heat shrinkage rate of the fiber of the present invention at 140 ° C. is preferably in the range of −20 to 20%, and more preferably in the range of −15% to 15%. That the dry heat shrinkage rate at 140 ° C. is negative, that is, indicates elongation due to heat treatment, and if this value is less than −20%, the fiber of the present invention stretches during heat treatment, so the dimensional stability of the nonwoven fabric is reduced. Since it gets worse, it is not preferable. On the other hand, if it exceeds 20%, spot-like shrinkage occurs, which is not preferable because not only the dimensional stability of the nonwoven fabric is deteriorated but also unevenness in appearance occurs. In the present invention, the dry heat shrinkage at 140 ° C. is measured by the method described later.

  Since the melting point of the fiber of the present invention changes depending on the ethylene content, the range is around 120 ° C. to 230 ° C., but when the ethylene content is about 40 mol% or less, the melting point is 170 ° C. or more. Therefore, in order to develop the binder performance, it is necessary to process at a high temperature, so that the nonwoven fabric tends to shrink and deform, and there is a problem that uneven spots etc. occur. It is preferable to carry out a heat treatment and bonding method.

  The fiber of the present invention may be a single fiber or a composite fiber with another thermoplastic polymer. Other thermoplastic polymers include polyolefin resins, polyester resins, polyamide resins, polyvinyl chloride, polyvinylidene chloride, styrene resins, polyvinyl acetate resins, acrylic resins, polylactic acid resins, polycarbonate resins, A thermoplastic polymer such as a thermoplastic elastomer is used, and ethylene-vinyl alcohol copolymers having different degrees of ethylene copolymerization may be used.

  When the fiber of the present invention is a composite fiber with another thermoplastic polymer, the ratio (mass ratio) of the ethylene-vinyl alcohol copolymer (A) and the thermoplastic polymer (B) is the structure (for example, core It can be selected according to the sheath-type structure, and is not particularly limited as long as it has an ethylene-vinyl alcohol copolymer (A) on at least a part of the fiber surface, but the ratio of the ethylene-vinyl alcohol copolymer (A) Is preferably 10% or more. If the ratio of the ethylene-vinyl alcohol copolymer is less than 10%, the thermal adhesiveness is lowered, which is not preferable.

  Examples of the cross-sectional structure of the conjugate fiber of the present invention include a core-sheath type, a sea-island type, a side-by-side type or a multilayer bonding type, a radial bonding type, and a random composite type. Of these cross-sectional structures, from the viewpoint of adhesiveness, it is sufficient that the ethylene-vinyl alcohol copolymer is at least part of the fiber surface, but the entire surface continuously occupies the length direction. A certain core-sheath type structure (that is, a core-sheath type structure in which the sheath part is composed of wet heat adhesive resin) is preferable.

  The cross-sectional shape of the fiber of the present invention may be any shape, and may be a circular or irregular shape. In the case of an irregular cross-section, for example, flat, elliptical, triangular to octagonal, etc., T-shape, H-shape, V-shape, dogbone (I-shape), multi-leaf shape such as 3-8 leaf shape Any shape such as a hollow cross-section thereof may be used.

  The fibers of the present invention further comprise conventional additives such as antibacterial agents, deodorants, flame retardants, heat stabilizers, UV absorbers, light stabilizers, antioxidants, colorants, antistatic agents, and plasticizers. , Lubricants, crystallization rate retarders, and the like, and these additives may be used alone or in combination of two or more. Moreover, these additives may be contained in the fiber and may be carried on the fiber surface.

  The oil component to be imparted to the fiber of the present invention is not particularly limited as long as it is an oil agent that improves the air opening property and suppresses the generation of static electricity. Alkyl phosphate alkali metal salt, alkyl ether type nonion, quaternary A preferred example includes a composition containing components such as an ammonium type cationic activator, an amphoteric activator, and a modified silicone depending on the purpose.

  The water retention rate of the airlaid nonwoven fabric obtained using the fiber of the present invention is desirably 2000% or more. When the water retention rate is less than 2000%, for example, it is not preferable because a water-soluble chemical solution cannot be sufficiently retained and cannot be used for cosmetics.

  The oil retention of the air-laid nonwoven fabric obtained using the fiber of the present invention is desirably 2000% or more. When the oil retention is less than 2000%, for example, a chemical solution such as essential oil cannot be sufficiently retained and cannot be used for cosmetics.

  The air-laid nonwoven fabric obtained using the fiber of the present invention preferably has a dehydration rate of 1000% or more. When the dehydration rate is less than 1000%, for example, when a non-woven fabric containing a water-soluble chemical solution is brought into contact with the skin, it will remain touching the skin forever. For example, when used as a face mask, It is not preferable because the touch is not good.

  Desirably, the air-laid nonwoven fabric obtained by using the fiber of the present invention has a bending resistance of 90 mm or less. When the bending resistance exceeds 90 mm, the nonwoven fabric has a hard feel. For example, when used as a face mask, the nonwoven fabric cannot be deformed along the shape of the face. This is not preferable because problems such as insufficient penetration of the chemical into the skin occur.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these at all.

<Fiber fineness dtex>
Evaluation was made according to JIS L1015 “Testing method for chemical fiber staples (8.5.1)”.
<Fiber length mm>
Evaluation was made according to JIS L1015 “Testing method for chemical fiber staples (8.4.1)”.
<Number of crimped fibers / inch>
The evaluation was made according to JIS L1015 “Testing method for chemical fiber staples (8.12.1)”.

<Dry heat shrinkage% of fiber>
Cut the fiber to about 50 cm and use a drooping device with appropriate performance to tie both ends so that the knot spacing is 35 cm. The weight is measured using a direct balance, an initial load of 50 mg per denier is added, and the yarn length between the knots is measured (L1). Next, the initial load is removed, and heat treatment is performed at 140 ° C. for 15 minutes in a hot air dryer. After allowing to cool, a load of 50 mg per denier is added again and the yarn length between the knots is measured (L2).
The dry heat shrinkage was calculated from the following formula.
Dry heat shrinkage (%) = [(L1-L2) / L1] × 100

<Nonwoven fabric water retention, oil retention%>
Evaluated according to JIS L1913 “General Short Fiber Nonwoven Fabric Test Method (6.9.2)”. As the test solution, ion-exchanged water was used for the water retention rate, and salad oil was used for the oil retention rate.

<Dehydration rate of nonwoven fabric%>
Using a test piece of 5 cm × 5 cm, the weight (a) after being immersed in ion-exchanged water for 20 minutes was measured, and then the weight after being subjected to dehydration treatment at 1000 G for 2 minutes using a centrifugal dehydrator (b ) And the dehydration rate was calculated from the following formula.
Dehydration rate (%) = (ab) / b × 100 (a: weight after immersion treatment, b: weight after dehydration)

<Flexibility of nonwoven fabric mm>
The evaluation was made according to JIS L1913 “General Short Fiber Nonwoven Fabric Test Method (6.9.3) Cantilever Method”.

[Examples 1 to 8]
(1) A thermoplastic polymer made of polyethylene terephthalate (manufactured by Kuraray Co., Ltd., intrinsic viscosity [η] = 0.59) having an ethylene-vinyl alcohol copolymer (A) having an ethylene content shown in Table 1 as a sheath component. Using (B) as a core component, a composite spinning device was used to join a core-sheath mold with a round cross-section die at a composite ratio (A / B) = 50/50 (weight ratio). The spun yarn was cooled and solidified, and then wound on a bobbin via a take-up roller.
(2) Next, this crimped yarn was hot-drawn at a draw ratio of 2 times, and after applying the oil in an oil bath, a mechanical crimping treatment was performed. The mechanical crimping treatment was performed using a crimping device such as a normal stuffer type crimping device. Subsequent to the crimping treatment, the fiber was dried with hot air and then cut to obtain a short fiber made of an ethylene-vinyl alcohol copolymer. Each fiber property is shown in Table 1.

Using short fibers obtained by the above production method, the short fibers were 100% by weight in Examples 1 to 7, 10% by weight of short fibers in Example 8, pulp (Wood Hauser, wood-pulverized pulp) ) An air laid nonwoven fabric having a basis weight of 50 g / m ² was manufactured using a blending drum unit manufactured by Dan-Web forming using 90% by weight. Table 1 shows the physical properties of each nonwoven fabric.

[Comparative Example 1]
The air laid nonwoven fabric was manufactured using the same short fiber as in Example 1 except that the fiber length was 1 mm. However, since the fiber length was too short, the inter-fiber adhesion in the nonwoven fabric was not sufficient, and after heat treatment Since the web breakage occurred in the paper guiding process from the wire to the scissor roll, the air-laid nonwoven fabric could not be collected.

[Comparative Example 2]
An air laid nonwoven fabric was produced using the same short fiber as in Example 1 except that the fiber length was 35 mm. However, since the fiber length was too long, the opening in the forming head was not sufficiently performed, and the slit portion Since no fiber was released from the airlaid fabric, the airlaid nonwoven fabric could not be collected.

[Comparative Example 3]
An airlaid nonwoven fabric was produced using the same short fibers as in Example 1 except that the number of crimps was 2 / inch. However, since the number of crimps was too small, the interfiber entanglement was not sufficient, and the nonwoven fabric. Since the strength of itself decreased and web breakage occurred in the paper introduction process from the wire after heat treatment to the scooping roll, the air-laid nonwoven fabric could not be collected.

[Comparative Example 4]
An airlaid nonwoven fabric was produced using the same short fibers as in Example 1 except that the number of crimps was 35 / inch. However, since the number of crimps was too large, the opening in the forming head was not sufficiently performed. Since no fiber was released from the slit portion, the air-laid nonwoven fabric could not be collected.

[Comparative Example 5]
Except for using an ethylene-vinyl alcohol copolymer having an ethylene content of 4 mol%, melt spinning was performed under the same conditions as in Example 1, but the spinnability was poor, and it was not necessary to collect the desired short fibers. It was.

[Comparative Example 6]
A short fiber having the same fineness, fiber length, and number of crimps as in Example 1 was produced except that an ethylene-vinyl alcohol copolymer having an ethylene content of 75 mol% was used. Airlaid using the short fiber The nonwoven fabric was inferior in water retention because the hydrophilicity of the nonwoven fabric decreased.

[Comparative Example 7]
An airlaid nonwoven fabric was produced in which the weight ratio of the fiber made of the same ethylene-vinyl alcohol copolymer as in Example 1 was 8% by weight and the weight ratio of the pulp was 92% by weight, but ethylene-vinyl functioning as a binder fiber. Since the weight ratio of the fiber made of alcoholic copolymer is small, the strength of the nonwoven fabric itself is reduced, and the web breakage occurs in the paper introduction process from the wire after heat treatment to the take-up roll. I couldn't.

[Comparative Example 8]
An airlaid nonwoven fabric was produced using fibers (1.7 ttex, 3 mm, manufactured by Teijin Fibers Ltd.) having polyethylene (PE) as a sheath component and a thermoplastic polymer made of polyethylene terephthalate (PET) as a core component as binder fibers. However, since the hydrophilic property of the nonwoven fabric was lowered, the water retention rate was inferior. Further, the nonwoven fabric had high bending resistance and a hard texture.

[Comparative Example 9]
Thermoplastic polymer made of polyethylene terephthalate (PET) with non-crystalline polyethylene terephthalate (manufactured by Kuraray Co., Ltd., isophthalic acid 40 mol% copolymerized PET, intrinsic viscosity [η] = 0.59) as a sheath component as binder fiber The air-laid nonwoven fabric was manufactured using a fiber having a core-sheath ratio of 50/50, but the water retention was poor because the hydrophilicity of the nonwoven fabric was lowered. Further, the nonwoven fabric had high bending resistance and a hard texture.

  The fiber for airlaid nonwoven fabric obtained by the present invention can provide a heat adhesive fiber for airlaid without using an adhesive, a polyolefin resin that is a hydrophobic thermoplastic resin, or a PET resin as a binder fiber. Therefore, the air-laid nonwoven fabric obtained by using the fiber can provide an air-laid nonwoven fabric having hydrophilicity, water retention, air permeability, bulkiness and flexibility while having sheet strength. For this reason, the application to the cosmetics field | area which was difficult for the use expansion | deployment with the conventional airlaid nonwoven fabric becomes possible sufficiently.

Claims (3)

  A fiber comprising an ethylene-vinyl alcohol copolymer having an ethylene content of 5 to 70 mol%, wherein the fiber has a fiber length of 2 to 30 mm and a number of crimps of 3 to 30 / inch. An airlaid nonwoven fabric.   A composite fiber composed of an ethylene-vinyl alcohol copolymer (A) and a thermoplastic resin (B) other than an ethylene-vinyl alcohol copolymer, and the ethylene-vinyl alcohol copolymer (A) is a fiber surface. The air-laid nonwoven fabric according to claim 1, wherein the fiber is present in the air-laid nonwoven fabric.   An airlaid nonwoven fabric using at least 10% by weight or more of the fiber according to claim 1 or 2.