JP7650298B2 - Island-in-the-sea type composite multifilament, ultrafine multifilament, and ultrafine fiber structure - Google Patents

Description

Related Applications

This application claims priority to Patent Application No. 2021-004876, filed in Japan on January 15, 2021, the entire contents of which are incorporated by reference into this application.

The present invention relates to islands-in-the-sea type composite multifilaments having a thermoplastic elastomer resin as an island component, and ultrafine fibers including ultrafine multifilaments obtained from the islands-in-the-sea type composite multifilaments.

Island-in-sea composite multifilaments are made by forming composite multifilaments using a resin that can be dissolved and removed in the sea component, and then removing the sea component to produce ultrafine fibers.

For example, Patent Document 1 (JP 2014-101613 A) describes an ultrafine fiber having an average single fiber diameter of 10 to 2500 nm and a tensile strength of 4.5 cN/dtex or more,
(A) The composite mass ratio (sea:island) of the sea part and the island part of the islands-in-sea type composite fiber is in the range of 40:60 to 20:80.
(B) The melt viscosity ratio (sea/island) of the sea part and the island part of the islands-in-sea type composite fiber is in the range of 0.2 to 1.0.
(C) The islands-in-sea type composite fiber is produced by melting and extruding a sea part and an island part from a spinneret for islands-in-sea type composite fiber, and then taking up the melted parts at a spinning speed of 400 to 2,000 m/min.
(D) The islands-in-the-sea type composite fiber is preheated on a preheat roller, stretched at a draw ratio of 3.0 to 6.0 times, heat-set on a set roller, and wound up.
(E) The islands-in-sea type composite fiber is drawn so that the residual elongation is 5 to 30%.

JP 2014-101613 A

In Patent Document 1, it is possible to form ultrafine polyester fibers with excellent strength, but these fibers cannot exhibit gripping properties because the ultrafine fibers slide against each other. For example, when used as anti-slip materials for innerwear, gloves, etc., the friction and adhesion effects are insufficient.

Therefore, the object of the present invention is to provide an ultra-fine multifilament having excellent gripping properties, an island-in-the-sea type composite multifilament capable of forming the ultra-fine multifilament, and a manufacturing method and fiber structure thereof.

As a result of intensive research conducted by the present inventors to achieve the above object, they discovered that in order to obtain an ultra-fine multifilament with excellent grip, it is effective to use a thermoplastic elastomer resin exhibiting a specific hardness as the island component of an islands-in-the-sea type composite multifilament. However, because thermoplastic elastomer resins are highly elastic, they are difficult to manufacture as island components of islands-in-the-sea type composite multifilaments in the same way as non-elastomer resins, and this became a new problem.

As a result of further research, it was discovered that when a thermoplastic elastomer resin is used as the island component, by reducing the single yarn fineness of the islands-in-sea type composite multifilament while decreasing the number of island components in the islands-in-sea type composite multifilament, an islands-in-sea type composite multifilament having a thermoplastic elastomer resin as an island component can be produced, and by removing the sea component from the multifilament, an ultrafine multifilament of thermoplastic elastomer can be produced. Furthermore, when the thermoplastic elastomer resin has a specific hardness, it is possible to exhibit excellent grip properties that were not previously available, and thus the present invention was completed.

That is, the present invention can be configured in the following manner.
[Aspect 1]
The islands-in-sea type composite multifilament has an island component made of a thermoplastic elastomer resin (A) having a Shore A hardness of 90 or less, a Shore D hardness of 60 or less (preferably 58 or less, more preferably 55 or less, even more preferably 53 or less, and even more preferably 50 or less), and a Rockwell hardness (R scale) of 70 or less (preferably 65 or less, and even more preferably 60 or less), and a sea component made of a water-soluble or easily alkali-soluble thermoplastic resin (B), and an average single island diameter of 8000 nm or less (preferably 6000 nm or less, and more preferably 4000 nm or less).
[Aspect 2]
The islands-in-sea type composite multifilament according to aspect 1, wherein the thermoplastic resin (B) of the sea part is a modified polyvinyl alcohol-based polymer in which units derived from α-olefins and/or vinyl ethers are present in the polyvinyl alcohol-based polymer.
[Aspect 3]
The islands-in-sea type composite multifilament according to Aspect 1 or 2, wherein the number of islands in the islands-in-sea type composite multifilament is 3 to 200 islands (preferably 5 to 100 islands, more preferably 6 to 80 islands, and even more preferably 7 to 60 islands), and the composite mass ratio of the sea component to the island components (sea component:island component) is 20:80 to 70:30 (preferably 25:75 to 70:30, and even more preferably 30:70 to 60:40).
[Aspect 4]
The islands-in-sea type composite multifilament according to any one of Aspects 1 to 3, wherein the thermoplastic elastomer resin (A) is a polyamide-based elastomer resin or a polyester-based elastomer resin.
[Aspect 5]
A fiber structure comprising at least a portion of the islands-in-the-sea type composite multifilament and/or cut fibers thereof according to any one of Aspects 1 to 4.
[Aspect 6]
The ultrafine multifilament comprises a thermoplastic elastomer resin (A) that satisfies any one of a Shore A hardness of 90 or less, a Shore D hardness of 60 or less, and a Rockwell hardness (R scale) of 70 or less, and has a yarn-metal dynamic friction coefficient of 0.30 or more (preferably 0.33 or more, more preferably 0.36 or more).
[Aspect 7]
The ultrafine multifilament according to aspect 6, having a single yarn fineness of 0.005 to 0.5 dtex (preferably 0.010 to 0.4 dtex, more preferably 0.015 to 0.3 dtex).
[Aspect 8]
An ultrafine fiber structure comprising at least a portion of the ultrafine multifilament and/or cut fibers thereof according to aspect 6 or 7.
[Aspect 9]
The microfibrous structure of claim 8, which is a woven or knitted fabric.
[Aspect 10]
A method for producing an ultrafine multifilament, comprising at least a step of dissolving and removing the thermoplastic resin (B) from the islands-in-sea type composite multifilament according to any one of Aspects 1 to 4.
[Aspect 11]
A method for producing an ultrafine fiber structure, comprising at least a step of dissolving and removing the thermoplastic resin (B) from the fiber structure according to aspect 5.

It should be noted that any combination of at least two elements disclosed in the claims and/or the specification and/or the drawings is included in the present invention. In particular, any combination of two or more of the claims described in the claims is included in the present invention.

The islands-in-sea type composite multifilament of the present invention is compositely spun using a thermoplastic elastomer resin having a specific hardness as a resin constituting island parts (hereinafter may be referred to as island component resin) and a resin that can be easily removed by water or alkali as a resin constituting a sea part (hereinafter may be referred to as sea component resin), and therefore it is possible to efficiently form the thermoplastic elastomer resin into ultrafine fibers.
In addition, since the ultrafine multifilaments are made of a thermoplastic elastomer resin, the dynamic friction coefficient is increased, and gripping properties can be improved.

[Sea-island type composite multifilament]
The islands-in-sea type composite multifilament of the present invention is an islands-in-sea type composite multifilament, in which a resin constituting the island parts is a thermoplastic elastomer resin (A) having any one of a Shore A hardness of 90 or less, a Shore D hardness of 60 or less, and a Rockwell hardness (R scale) of 70 or less, and a resin constituting the sea part is a water-soluble or easily alkali-soluble thermoplastic resin (B).

The islands-in-the-sea composite multifilament may have a small average island diameter, and the average island diameter of the islands-in-the-sea composite multifilament may be 8,000 nm or less, preferably 6,000 nm or less, and more preferably 4,000 nm or less. The lower limit of the average island diameter is not particularly limited, but may be, for example, 500 nm or more. Here, the average island diameter is a value measured by the method described in the examples described later.

(Island component resin)
The island component resin is a thermoplastic elastomer resin (A) having a specific hardness. The appropriate measurement standard for the hardness of the thermoplastic elastomer resin (A) varies depending on the hardness. Among Shore A hardness, Shore D hardness, and Rockwell hardness (R scale), (i) when the hardest, it is measured by Rockwell hardness (R scale), (ii) when the Rockwell hardness (R scale) is less than 50, it is measured by Shore D hardness, and (iii) when the Shore D hardness is 40 or less, it can be measured by Shore A hardness.

The hardness of the island component resin may be any one of the following: Shore A hardness 90 or less, Shore D hardness 60 or less, or Rockwell hardness (R scale) 70 or less. For example, even if the Shore D hardness is not 60 or less, it may be sufficient that the Rockwell hardness (R scale) is 70 or less.

The Shore A hardness is a measurement of the indentation hardness using a durometer according to JIS K 7215, and is measured using a type A indenter (frustum-shaped tip, tip diameter 0.79 mm, cone angle 35°). The hardness of the island component resin is Shore A hardness 90 or less from the viewpoint of gripping property when made into an ultra-fine multifilament, and the lower limit is not particularly limited as long as it does not impair the effects of the present invention, but for example, the Shore A hardness may be 20 or more, and is preferably 50 or more.

The Shore D hardness is a measurement of the indentation hardness using a durometer according to JIS K 7215, and is measured using a type D indenter (conical tip, tip diameter 0.1 mm, cone angle 30°). From the viewpoint of gripping properties when made into an ultra-fine multifilament, the hardness of the island component resin is Shore D hardness 60 or less, preferably 58 or less, more preferably 55 or less, even more preferably 53 or less, and even more preferably 50 or less. As long as the effect of the present invention is not hindered, the lower limit of the hardness is not particularly limited, but for example, the Shore D hardness may be 20 or more.

Rockwell hardness (R scale) is a measurement of indentation hardness according to JIS Z 2245, and is measured using a hard ball with a diameter of 12.7 mm as an indenter. From the viewpoint of gripping property when made into an ultra-fine multifilament, the hardness of the island component resin is Rockwell hardness (R scale) 70 or less, preferably 65 or less, and more preferably 60 or less. As long as it does not impair the effects of the present invention, the lower limit of the hardness is not particularly limited, but for example, the Rockwell hardness (R scale) may be 50 or more.

Examples of thermoplastic elastomer resins include polyolefin-based elastomer resins, polyvinyl chloride-based elastomer resins, polyurethane-based elastomer resins, polystyrene-based elastomer resins, polyester-based elastomer resins, and polyamide-based elastomer resins. From the viewpoint of good handling properties, polyamide-based elastomer resins or polyester-based elastomer resins are preferred, and from the viewpoint of washing fastness, polyamide-based elastomer resins are more preferred.

Polyolefin-based elastomer resins are composed of polyethylene or polypropylene as hard segments and SEBS or ethylene/propylene copolymers as soft segments.

Polyvinyl chloride elastomer resins are composed of crystalline polyvinyl chloride as hard segments and amorphous polyvinyl chloride or acrylonitrile as soft segments.

The polyurethane elastomer resin is composed of a hard segment composed of a low molecular weight glycol and a diisocyanate, and a soft segment composed of a high molecular weight diol and a diisocyanate.
Examples of low molecular weight glycols include _C1-10 diols such as ethylene glycol, 1,4-butanediol, and 1,6-hexanediol. Examples of high molecular weight diols include poly(1,4-butylene adipate), poly(1,6-hexane adipate), polycaprolactone, polyethylene glycol, polypropylene glycol, and polyoxytetramethylene glycol. Examples of diisocyanates include tolylene diisocyanate, 4,4-diphenylmethane diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate.

The polystyrene-based elastomer resin is composed of polystyrene as a hard segment and polybutadiene, polyisoprene, hydrogenated polybutadiene, polyethylene, polypropylene, etc. as a soft segment, and examples thereof include SBS (styrene/butadiene/styrene block copolymer), SIS (styrene/isoprene/styrene block copolymer), SEBS (styrene/ethylene/butadiene/styrene block copolymer), SEPS (styrene/ethylene/propylene/styrene block copolymer), etc. As the polystyrene -based elastomer resin, a resin having a predetermined hardness can be selected from those commercially available, for example, "Septon" manufactured by Kuraray Co., Ltd., "Hybler" manufactured by Kuraray Co., Ltd.

Polyester-based elastomer resins are composed of aromatic polyester resin components as hard segments and aliphatic polyether or aliphatic polyester as soft segments. For polyester-based elastomer resins, resins with a specified hardness can be selected from those commercially available, such as "SKYPEL" manufactured by SK Chemical, "Hytrel" manufactured by DuPont Toray Co., Ltd., and "Pelprene" manufactured by Toyobo Co., Ltd.

The polyamide-based elastomer resin may be a polyether block polyamide, a polyester block polyamide, or a polyester ether block polyamide, which is composed of a polyamide-based elastomer resin component as a hard segment and a polyether block or a polyester block as a soft segment.

The polyamide-based elastomer may have, for example, an aliphatic polyamide having 6 to 22 carbon atoms as a hard segment, and preferably an aliphatic polyamide having a prime number of 9 to 20 as a hard segment. Here, the aliphatic polyamide means a polyamide in which the hydrocarbon groups in the repeating units of the following formulas (1) to (3) are saturated aliphatic hydrocarbon groups.

-NH-R1-NH- (1)
-CO-(R2) _m -CO- (2)
-NH-R3-CO- (3)

Here, R1, R2, and R3 are the same or different and are linear or branched aliphatic hydrocarbon groups having 1 to 22 carbon atoms, and m is an integer of 0 or 1.

Specifically, for example, the hard segment may be polyamide 6, polyamide 6/6, polyamide 6/11, polyamide 6/12, polyamide 9, polyamide 11, or polyamide 12, and the soft segment may be polyethylene glycol, polypropylene glycol, or polytetramethylene glycol. The polyamide elastomer resin may be selected from those commercially available as "VESTAMID" and "DAIAMID" manufactured by Daicel-Evonik Ltd., "Pebax" manufactured by ARKEMA, and "UBESTAXPA" manufactured by Ube Industries, Ltd., and has a predetermined hardness.

In addition, from the viewpoint of improving color development, an amino group-containing color development improver may be used in combination. The amino group-containing color development improver has at least an amino group, and is used together with a polyamide-based elastomer resin to impart a predetermined terminal amino group concentration. The amino group-containing color development improver may have a terminal amino group concentration of, for example, 100 to 2000 μeq/g, preferably 125 to 2000 μeq/g, and more preferably 200 to 1000 μeq/g.

The amino group-containing color improver can be combined in an appropriate ratio according to the type of amino group-containing color improver, so long as it does not impair the properties of the polyamide-based elastomer resin. For example, the mass ratio of the polyamide-based elastomer resin to the amino group-containing color improver may be, for example, 99/1 to 70/30 (former/latter), preferably 98/2 to 75/25, and more preferably 95/5 to 80/20, from the standpoint of color development and compatibility.

Examples of the amino group-containing color development improver include polyamide oligomers and amino group-containing compounds such as polyamines (for example, linear aliphatic, alicyclic or aromatic polyamines having 3 to 12 amino groups) from the viewpoint of improving the color development of polyamide fibers without impairing the characteristics of polyamide elastomer resins.

The polyamide oligomer is preferably composed of any of the repeating units represented by formulas (1) to (3) described in the polyamide-based elastomer resin. Examples of the hydrocarbon group having 1 to 22 carbon atoms used in the repeating units represented by formulas (1) to (3) include linear or branched saturated aliphatic hydrocarbon groups having 1 to 22 carbon atoms (preferably 6 to 20, more preferably 9 to 18), linear or branched saturated alicyclic hydrocarbon groups having 6 to 22 carbon atoms (preferably 6 to 20, more preferably 6 to 18), and linear or branched aromatic hydrocarbon groups having 6 to 22 carbon atoms (preferably 6 to 20, more preferably 6 to 18). These hydrocarbon groups may have a substituent within a range that does not impair the effects of the present invention.

Preferred polyamide oligomers include polyamide 6 oligomer, polyamide 4/6 oligomer, polyamide 6/6 oligomer, polyamide 6/10 oligomer, polyamide 6/11 oligomer, polyamide 6/12 oligomer, polyamide 9 oligomer, polyamide 10 oligomer, polyamide 11 oligomer, polyamide 12 oligomer, etc.

From the viewpoint of compatibility with the polyamide-based elastomer resin, it is preferable that the hydrocarbon groups of the repeating units of the polyamide oligomer and the polyamide-based elastomer resin have similar monounsaturation numbers. For example, the number of carbon atoms of the hydrocarbon group of the repeating unit in the polyamide oligomer may be within a range of the monounsaturation number in the repeating unit of the polyamide-based elastomer resin ±3, preferably within a range of the monounsaturation number in the repeating unit of the polyamide-based elastomer resin ±2, and more preferably within a range of the monounsaturation number in the repeating unit of the polyamide-based elastomer resin ±1. When the polyamide-based elastomer resin is a polyamide-based elastomer, it is preferable that the hydrocarbon groups of the repeating units of the polyamide-based elastomer resin component in the hard segment have the above-mentioned relationship.

The number average molecular weight of the polyamide oligomer may be, for example, 500 to 10,000, preferably 500 to 9,000, and more preferably 1,000 to 6,000. Here, the molecular weight of the polyamide oligomer is a value measured by the method described in the examples below.

The island component resin may contain various commonly used additives as necessary. Examples of additives include heat stabilizers, antioxidants, light stabilizers, UV absorbers, antistatic agents, colorants (e.g., color pigments), smoothing agents, plasticizers, antibacterial agents, fungicides, and deodorants. The island component resin may also contain other non-thermoplastic elastomer resins to the extent that the effects of the present invention are not impaired.

From the viewpoint of achieving good fiberization, it is preferable that the melt viscosity of the island component resin at 240°C is 600 to 3000 poise. If the melt viscosity exceeds 3000 poise, high-speed spinnability during fiberization may decrease. If the melt viscosity is less than 600 poise, the yarn may easily break during spinning, resulting in poor productivity and low strength of the obtained fiber. The melt viscosity of the island component resin is more preferably 800 to 2000 poise.

(Sea component resin)
The sea component resin is composed of a water-soluble or easily alkali-soluble thermoplastic resin (B). Examples of the thermoplastic resin (B) include thermoplastic resins that are soluble in water (including hot water) and alkali, and preferably include thermoplastic polyvinyl alcohol resins that are soluble in water and easily soluble polyester resins that are soluble in alkali.

When the thermoplastic polyvinyl alcohol resin is immersed in hot water at 100°C in a bath ratio of 1:30, it may be almost completely dissolved (decomposed) within 60 minutes, preferably within 50 minutes, more preferably within 30 minutes, and particularly preferably within 15 minutes.

The readily soluble polyester resin may, for example, be almost completely dissolved (decomposed) within 60 minutes, preferably within 45 minutes, more preferably within 30 minutes, and particularly preferably within 15 minutes, when immersed in a 2% aqueous sodium hydroxide solution at 100°C in a bath ratio of 1:30.

(Thermoplastic polyvinyl alcohol resin)
The polyvinyl alcohol (hereinafter sometimes referred to as PVA) constituting the thermoplastic polyvinyl alcohol resin mainly contains vinyl alcohol units and may be a homopolymer of vinyl alcohol units or a modified polymer containing, in addition to vinyl alcohol units, copolymerizable units and/or functional groups.

The PVA used in the present invention is obtained by saponifying the vinyl ester unit of a vinyl ester polymer. Examples of vinyl compound monomers for forming the vinyl ester unit include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, and vinyl versatate. Among these, vinyl acetate is preferred from the viewpoint of obtaining PVA.

The PVA used in the present invention may be either a homopolymer or a modified polymer into which copolymerization units have been introduced. From the viewpoints of melt spinnability, water solubility, and fiber properties, however, it is preferable to use modified polyvinyl alcohol into which copolymerization units have been introduced. Examples of types of copolymerization monomers include α-olefins such as ethylene, propylene, 1-butene, isobutene, and 1-hexene; acrylic acid and its salts, acrylic acid esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate, and i-propyl acrylate; methacrylic acid and its salts, methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, and i-propyl methacrylate; acrylamide derivatives such as acrylamide, N-methylacrylamide, and N-ethylacrylamide; methacrylamide; and N-methylmethacrylamide. acrylamide, methacrylamide derivatives such as N-ethyl methacrylamide, vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, hydroxyl group-containing vinyl ethers such as ethylene glycol vinyl ether, 1,3-propanediol vinyl ether, 1,4-butanediol vinyl ether, allyl ethers such as allyl acetate, propyl allyl ether, butyl allyl ether, hexyl allyl ether, monomers having an oxyalkylene group, vinyl trimer vinyl silyls such as butyl silane; hydroxyl group-containing α-olefins such as isopropenyl acetate, 3-buten-1-ol, 4-penten-1-ol, 5-hexen-1-ol, 7-octen-1-ol, 9-decen-1-ol, and 3-methyl-3-buten-1-ol; monomers having a carboxyl group derived from fumaric acid, maleic acid, itaconic acid, maleic anhydride, phthalic anhydride, trimellitic anhydride, or itaconic anhydride; monomers derived from ethylenesulfonic acid, allylsulfonic acid, methallylsulfonic acid, and 2-acrylamido-2-methylpropanesulfonic acid; monomers having a sulfonic acid group derived from vinyloxyethyl trimethyl ammonium chloride, vinyloxybutyl trimethyl ammonium chloride, vinyloxyethyl dimethylamine, vinyloxymethyl diethylamine, N-acrylamidomethyl trimethyl ammonium chloride, N-acrylamidoethyl trimethyl ammonium chloride, N-acrylamidodimethylamine, allyl trimethyl ammonium chloride, methallyl trimethyl ammonium chloride, dimethylallylamine, allylethylamine, and the like.

Among these monomers, in view of ease of availability, preferred are α-olefins such as ethylene, propylene, 1-butene, isobutene, and 1-hexene; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, and n-butyl vinyl ether; hydroxyl group-containing vinyl ethers such as ethylene glycol vinyl ether, 1,3-propanediol vinyl ether, and 1,4-butanediol vinyl ether; allyl ethers such as allyl acetate, propyl allyl ether, butyl allyl ether, and hexyl allyl ether; monomers having an oxyalkylene group; and monomers derived from hydroxyl group-containing α-olefins such as 3-buten-1-ol, 4-penten-1-ol, 5-hexen-1-ol, 7-octen-1-ol, 9-decen-1-ol, and 3-methyl-3-buten-1-ol. Particularly preferred are monomers derived from α-olefins and/or vinyl ethers.

In particular, from the standpoint of copolymerizability, melt spinnability, and water solubility of the fibers, α-olefins having 4 or less carbon atoms, such as ethylene, propylene, 1-butene, and isobutene; and vinyl ethers linked by linear or branched alkylene groups having 4 or less carbon atoms, such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, and n-butyl vinyl ether, are more preferred.

The content of these monomers is usually 20 mol% or less, preferably 15 mol% or less, and more preferably 13 mol% or less . The lower limit of the monomer is not particularly limited, and may be, for example, 0.1 mol% or more, preferably 3 mol% or more, and more preferably 6 mol% or more.

In particular, when the α-olefin is ethylene, it is preferable to use a modified polymer in which 4 to 15 mol %, more preferably 6 to 13 mol %, of ethylene units are introduced, since this improves the fiber properties.

From the viewpoints of spinnability and solubility, the viscosity average degree of polymerization (hereinafter simply referred to as degree of polymerization) of the PVA used in the present invention is preferably 200 to 500, more preferably 230 to 470, and particularly preferably 250 to 450. In particular, by using a PVA having a so-called low degree of polymerization, that is, a degree of polymerization of 500 or less, not only can the dissolution rate of the sea component be increased when the islands-in-sea type composite multifilament is dissolved in an aqueous solution, but also the shrinkage of the islands-in-sea type composite multifilament when it is dissolved can be reduced.

The degree of polymerization (P) of PVA is measured with reference to JIS-K6726. That is, the degree of polymerization (P) is calculated by the following formula from the intrinsic viscosity [η] (dl/g) measured in water at 30° C. after resaponifying and purifying the PVA.
P=([η]×10 ³ /8.29) ^(1/0.62)

From the viewpoint of spinnability and solubility, the PVA used in the present invention preferably has a degree of saponification of 90 to 99.99 mol%, more preferably 93 to 99.98 mol%, further preferably 94 to 99.97 mol%, and particularly preferably 96 to 99.96 mol%.

In particular, the preferred PVA used in the present invention may have a molar fraction of the central hydroxyl group in the three hydroxyl group chains in a triad representation for the vinyl alcohol unit of 70 to 99.9 mol %, more preferably 72 to 99 mol %, even more preferably 74 to 97 mol %, and particularly preferably 76 to 95 mol %.

In the present invention, the central hydroxyl group of the hydroxyl group triad of polyvinyl alcohol refers to the peak (I) reflecting the tacticity of the triad of the hydroxyl group protons measured at 65°C using a 500 MHz proton NMR (JEOL GX-500) device in a d6-DMSO solution of PVA. Peak (I) is represented by the sum of the isotacticity chain (4.54 ppm), heterotacticity chain (4.36 ppm), and syndiotacticity chain (4.13 ppm) of the hydroxyl group triad of PVA, and the peak (II) of the hydroxyl group in all vinyl alcohol units appears in the chemical shift region of 4.05 ppm to 4.70 ppm. Therefore, the molar fraction of the central hydroxyl group of the hydroxyl group triad of the vinyl alcohol unit of the present invention is represented by 100 x (I)/(II).

Furthermore, when the PVA of the present invention is an ethylene-modified PVA, the effect of the present invention is further enhanced by satisfying the following formula:
−1.5×Et+100≧molar fraction≧−Et+85

Here, the molar fraction (unit: mol%) represents the molar fraction of the central hydroxyl group in the triad representation of the hydroxyl group triplet for the vinyl alcohol unit, and Et represents the ethylene content (unit: mol%) contained in the vinyl alcohol polymer.

The melting point (Tm) of the PVA used in the present invention is preferably 160 to 230° C., more preferably 170 to 227° C., further preferably 175 to 224° C., and particularly preferably 180 to 220° C. The melting point of the PVA means the peak top temperature of the endothermic peak showing the melting point of the PVA when the PVA is heated to 250° C. at a heating rate of 10° C./min in nitrogen using a DSC, cooled to room temperature, and then heated again to 250° C. at a heating rate of 10° C./min.

The PVA used in the present invention preferably contains alkali metal ions from the viewpoint of improving solubility, and the content of the alkali metal ions is preferably 0.0003 to 1 part by mass, more preferably 0.0003 to 0.8 parts by mass, even more preferably 0.0005 to 0.6 parts by mass, and particularly preferably 0.0005 to 0.5 parts by mass, calculated as sodium ions per 100 parts by mass of PVA. Examples of alkali metal ions include potassium ions and sodium ions.

In the present invention, the method of incorporating a specific amount of alkali metal ions into PVA is not particularly limited, and examples include a method of adding an alkali metal ion-containing compound after polymerizing PVA, and a method of blending alkali metal ions into PVA by using an alkaline substance containing alkali ions as a saponification catalyst when saponifying a vinyl ester polymer in a solvent, and washing the saponified PVA with a cleaning solution to control the content of alkali metal ions in the PVA, but the latter method is preferred. The content of alkali metal ions can be determined by atomic absorption spectrometry.

In addition, in order to improve the melt fluidity and spinnability of the PVA at high temperatures, the thermoplastic polyvinyl alcohol resin may contain, as necessary, 1 to 30% by mass, preferably 2 to 20% by mass, of a plasticizer such as polyethylene glycol, propylene glycol and its oligomers, butylene glycol and its oligomers, polyglycerin derivatives, glycerin derivatives in which alkylene oxides such as ethylene oxide and propylene oxide are added to glycerin, etc., derivatives in which alkylene oxides such as ethylene oxide and propylene oxide are added to sorbitol, polyhydric alcohols such as pentaerythritol and their derivatives, and PO/EO random copolymers, relative to the PVA.

In particular, in order to prevent thermal decomposition during the fiberization process and to obtain good plasticization and spinnability, it is preferable to incorporate 1 to 30% by mass, preferably 2 to 20% by mass, of a plasticizer such as an alkylene oxide adduct of sorbitol, polyglycerol alkyl monocarboxylate ester, or PO/EO random copolymer, and in particular a compound in which 1 to 30 moles of ethylene oxide are added to sorbitol is preferred.

(Readily soluble polyester resin)
Examples of the easily soluble polyester resin include polar group-containing copolymer polyesters and aliphatic polyesters.

Examples of polar group-containing copolymer polyesters include copolymer polyesters in which dicarboxylic acid units such as terephthalic acid and isophthalic acid, diol units such as ethylene glycol, and ester-forming sulfonic acid metal salt compounds (e.g., 4-sodium sulfoisophthalic acid, 5-potassium sulfoisophthalic acid, 5-sodium sulfoisophthalic acid, 4-sodium sulfoterephthalic acid, 5-potassium sulfoterephthalic acid, 4-sodium sulfophthalic acid, etc.) are copolymerized.

In addition to terephthalic acid and isophthalic acid, examples of dicarboxylic acid units include aromatic dicarboxylic acids such as diphenylsulfonedicarboxylic acid, benzophenonedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, and 3,3'-diphenyldicarboxylic acid; aliphatic dicarboxylic acids such as adipic acid, succinic acid, azelaic acid, sebacic acid, and dodecanedioic acid; and alicyclic dicarboxylic acids such as hexahydroterephthalic acid and 1,3-adamantanedicarboxylic acid.

In addition to ethylene glycol, examples of diol units include aromatic diols such as chlorohydroquinone, 4,4'-dihydroxybiphenyl, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfide, 4,4'-dihydroxybenzophenone, and p-xylene glycol; aliphatic diols such as diethylene glycol, propanediol, butanediol, hexanediol, and neopentyl glycol; and alicyclic diols such as cyclohexanedimethanol.

From the standpoint of water solubility and water resistance, the ester-forming sulfonic acid metal salt compound may be used in an amount of, for example, 1 to 20 mol %, preferably 1 to 12 mol %, and more preferably 1 to 5 mol % of the total dicarboxylic acid components.

Furthermore, polyalkylene glycol (for example, poly C _1-4 alkylene glycol such as polypropylene glycol and polyethylene glycol) may be copolymerized, and the polyalkylene glycol may be contained in an amount of, for example, about 5 to 30 mass %, preferably about 6 to 25 mass %, in the polar group-containing copolymerized polyester.

Examples of aliphatic polyesters include polylactic acid; polyesters of aliphatic diols and aliphatic carboxylic acids, such as poly(ethylene succinate), poly(butylene succinate), and poly(butylene succinate-co-butylene adipate); polyhydroxycarboxylic acids, such as poly(glycolic acid), poly(3-hydroxybutyric acid), poly(3-hydroxyvaleric acid), and poly(6-hydroxycaproic acid); and poly(omega-hydroxyalkanoates), such as poly(ε-caprolactone) and poly(δ-valerolactone). These aliphatic polyesters may be used alone or in combination of two or more. Of these, polylactic acid is preferred, and the polylactic acid may be poly-D-lactic acid, poly-L-lactic acid, or a mixture thereof.

From the viewpoint of achieving good fiberization, it is preferable that the sea component resin has a melt viscosity of 600 to 3000 poise at 240°C. If the melt viscosity exceeds 3000 poise, the high-speed spinnability during fiberization may decrease. If the melt viscosity is less than 600 poise, the yarn may easily break during spinning, resulting in poor productivity, and the strength of the obtained fiber may also be low. The melt viscosity of the sea component resin is more preferably 800 to 2000 poise.

(Manufacturing method of islands-in-the-sea type composite multifilament)
The islands-in-sea type composite multifilament of the present invention can be formed into fibers using a conventionally known composite spinning device. Since the thermoplastic elastomer resin (A) having a specific hardness is used as the island components to make the island components extremely fine, the island components can be made extremely fine by reducing the single fiber fineness of the islands-in-sea type composite multifilament while decreasing the number of island components in the islands-in-sea type composite multifilament, even when a thermoplastic elastomer resin is used as the island components.

The manufacturing method for islands-in-sea composite multifilament includes a melt-kneading process in which the island component resin and the sea component resin are melt-kneaded in separate extruders to obtain a molten resin, a discharge process in which the molten resins are introduced into a composite spinning nozzle and the island component and sea component are discharged in a predetermined composite ratio, and a winding process in which the discharged yarn (or molten raw yarn) is wound up at a predetermined take-up speed (or spinning speed).

In the melt-kneading process, the island component resin and the sea component resin are melted according to their respective melting points. During the melt-kneading, various additives such as color development improvers and plasticizers may also be mixed in as necessary. These additives may be added directly, or a master batch may be formed first and then kneaded with the island component resin and the sea component resin.

In the extrusion process, it is preferable to reduce the number of islands per yarn, for example, 3 to 200 islands per yarn, but in consideration of high-speed spinning properties and yarn-making stability, it is preferable to have 5 to 100 islands, more preferably 6 to 80 islands, and even more preferably 7 to 60 islands. If the number of islands exceeds the above upper limit, due to the high elasticity of the thermoplastic elastomer, the islands may adhere to each other due to the shrinkage of the island components before the island component and sea component resins are combined and cooled and solidified.

The composite ratio of the sea component to the island component, in terms of mass ratio (sea:island), is preferably 20:80 to 70:30, more preferably 25:75 to 70:30, and even more preferably 30:70 to 60:40, taking into consideration high-speed spinnability and grip properties.

It is preferable to directly draw (spin-draw) the discharged yarn without winding it up. For example, the discharged yarn may be directly drawn (after a cooling process if necessary) and then directly wound up as a drawn yarn after being subjected to a direct drawing process.

In the cooling process, the discharged yarn may be cooled in a quenching zone. In the quenching zone, the discharged yarn may be cooled and solidified, for example, by cooling air. In the direct drawing process, drawing may be performed on the cooled and solidified cooled yarn.

In the winding step, the fiber may be taken up at a take-up speed of, for example, 2000 to 4000 m/min. In consideration of the spinning stability, the take-up speed is preferably 2200 to 3800 m/min, and more preferably 2300 to 3700 m/min.
The islands-in-sea type composite multifilament of the present invention uses a thermoplastic elastomer resin as an island component resin, and the thermoplastic elastomer resin is coated with a sea component resin which is a non-thermoplastic elastomer resin. Therefore, the islands-in-sea type composite multifilament obtained after the winding step has good spinnability and good unwinding properties during rewinding.

The single yarn fineness of the islands-in-sea composite multifilament may be, for example, 0.5 to 5 dtex, preferably 0.8 to 4.5 dtex, and more preferably 1 to 4 dtex. Here, the single yarn fineness is a value measured by the method described in the examples described later. If the single yarn fineness exceeds the upper limit value, the cooling and solidification of the fiber will be delayed, and peeling of the island and sea components will occur, which may result in poor fiber properties and handling properties such as releasability.

In islands-in-sea type composite multifilaments, it is possible to reduce the average single island fineness, and the average single island fineness of the islands-in-sea type composite multifilaments may be, for example, 0.005 to 0.5 dtex, preferably 0.010 to 0.4 dtex, and more preferably 0.015 to 0.3 dtex. Here, the average single island fineness is a value measured by the method described in the examples below.

From the viewpoint of processability, the fiber strength of the islands-in-the-sea composite multifilament at room temperature may be, for example, 1.0 cN/dtex or more, and preferably 1.1 cN/dtex or more. There is no particular upper limit to the fiber strength, but since a thermoplastic elastomer resin is used as the island component resin, it may be, for example, 2.5 cN/dtex or less. Here, the fiber strength is a value measured by the method described in the examples below.

The islands-in-the-sea composite multifilament thus produced may be used as a continuous filament or may be cut and processed into staples, etc. It may also be interwoven, interwoven, or mixed with other natural or synthetic fibers.

(Fiber structure including islands-in-the-sea type composite multifilament)
One aspect of the present invention includes a fiber structure at least partially including islands-in-sea type composite multifilament and/or cut fibers thereof. The fiber structure may be a one-dimensional structure such as threads, strings, ropes, etc., made of spun yarn including islands-in-sea type composite multifilament and/or cut fibers thereof, a two-dimensional structure such as a woven or knitted fabric made of spun yarn including islands-in-sea type composite multifilament and/or cut fibers thereof, or a nonwoven fabric made of cut fibers of islands-in-sea type composite multifilament, or a three-dimensional structure using these. The fiber structure may be made of islands-in-sea type composite multifilament only, or may include other fibers such as natural fibers, chemical fibers, and synthetic fibers in addition to the islands-in-sea type composite multifilament.

(Ultrafine multifilaments and ultrafine fiber structures)
In one aspect of the present invention, an ultrafine multifilament may be obtained by a method for producing an ultrafine multifilament, which includes at least a step of dissolving and removing the thermoplastic resin (B) from the above-mentioned islands-in-sea type composite multifilament. Alternatively, an ultrafine fiber structure may be obtained by a method for producing an ultrafine fiber structure, which includes at least a step of dissolving and removing the thermoplastic resin (B) from a fiber structure at least partially including the islands-in-sea type composite multifilament and/or its cut fibers.

The sea component, the thermoplastic resin (B), may be removed by alkali treatment, water treatment, or the like, depending on the type of resin constituting the sea component. In the water treatment, water or an aqueous solution may be used, and in the alkali treatment, an aqueous alkaline solution may be used.

The dissolution and removal process may be carried out, for example, at 50 to 120°C, preferably 80 to 100°C, depending on the type of treatment liquid.

The ultra-fine multifilament comprises a thermoplastic elastomer resin (A) that satisfies any one of Shore A hardness of 90 or less, Shore D hardness of 60 or less, and Rockwell hardness (R scale) of 70 or less, and may have a yarn-metal kinetic friction coefficient of 0.30 or more. The yarn-metal kinetic friction coefficient of the ultra-fine multifilament may preferably be 0.33 or more, and more preferably 0.36 or more. The upper limit of the yarn-metal kinetic friction coefficient is not particularly limited, but may be, for example, 1.0 or less, or 0.50 or less. The yarn-metal kinetic friction coefficient is a value measured by the method described in the examples below.

The single yarn fineness of the ultra-fine multifilament may be, for example, 0.005 to 0.5 dtex, preferably 0.01 to 0.4 dtex, and more preferably 0.015 to 0.3 dtex. Here, the single yarn fineness is a value measured by the method described in the examples below. When the single yarn fineness is small, the coefficient of friction can be increased, and gripping properties can be improved.

The fiber strength of the ultra-fine multifilament at room temperature may be, for example, 1.0 cN/dtex or more, preferably 1.1 cN/dtex or more, and more preferably 1.2 cN/dtex or more. The upper limit of the fiber strength is not particularly limited, but since a thermoplastic elastomer resin is used, it may be, for example, 2.5 cN/dtex or less. Here, the fiber strength is a value measured by the method described in the examples described later.

One aspect of the present invention includes an ultrafine fiber structure that at least partially contains ultrafine multifilaments and/or cut fibers of ultrafine multifilaments. In this specification, ultrafine multifilaments and/or cut fibers of ultrafine multifilaments may be collectively referred to simply as ultrafine fibers. In the ultrafine multifilaments and ultrafine fiber aggregates of the present invention, friction occurs between single fibers due to the ultrafine fibers derived from the ultrafine multifilaments, and therefore good gripping properties can be exhibited due to the frictional force.

For example, the ultrafine fiber structure may be a yarn or woven or knitted fabric of ultrafine multifilaments or cut fibers thereof, or a nonwoven fabric composed of cut fibers of ultrafine multifilaments. The ultrafine fiber structure may be composed only of ultrafine fibers, or may contain other fibers such as natural fibers, chemical fibers, and synthetic fibers in addition to the ultrafine fibers.

The ultrafine fiber structure may be a one-dimensional structure such as threads, strings, ropes, etc., made of ultrafine multifilaments and/or their cut fibers, a two-dimensional structure such as a woven or knitted fabric made of spun yarn containing ultrafine multifilaments and/or their cut fibers, or a nonwoven fabric made of cut ultrafine multifilaments, or a three-dimensional structure using these. The fiber structure may be made of ultrafine multifilaments only, or may contain other fibers such as natural fibers, chemical fibers, and synthetic fibers in addition to the ultrafine multifilaments.

The ultrafine fiber structure may contain ultrafine multifilaments and/or their cut fibers in an amount of, for example, 20 to 100% by mass, preferably 30 to 100% by mass, and more preferably 40 to 100% by mass.

In addition, since the ultrafine multifilament and/or its cut fiber of the present invention have excellent color development, the ultrafine multifilament and/or its cut fiber, as well as the ultrafine fiber structure, may be dyed. The dyeing process can be carried out by a known method depending on the dye used.

Dyeing agents include acid dyes, acid mordant dyes, metal complex acid dyes, disperse dyes, etc. Of these, acid dyes, acid mordant dyes, and metal complex acid dyes are preferred from the standpoint of color development and spinnability.

Acid dyes are dyes that contain sulfonic acid groups, carboxyl groups, hydroxyl groups, etc. as soluble groups, and examples of acid dyes include azo-based, triphenylmethane-based, anthraquinone-based, oxygen anthracene-based, phthalocyanine-based, indigoid-based, nitroso-based, and pyrazolone-based.

Acid mordant dyes are dyes that have the color-developing properties of acid dyes but can mainly form metal complexes (for example, by coordinate bonding with chromium atoms), and examples of acid mordant dyes include azo, triphenylmethane, anthraquinone, oxygen anthracene, phthalocyanine, indigoid, nitroso group, and pyrazolone.

Metal complex acid dyes are broadly classified into 1:1 type dyes, in which one metal atom is bonded to one dye molecule, and 1:2 type dyes, in which two dye molecules are bonded to one metal atom. Examples of metal complex acid dyes include azo, triphenylmethane, anthraquinone, oxygen anthracene, phthalocyanine, indigoid, nitroso group and pyrazolone.

The ultra-fine multifilament of the present invention has excellent color development, particularly excellent color development in dark dyeing such as dark blue, dark brown, and black. The ultra-fine multifilament of the present invention may have an L* value of 70 or less in dark dyeing, preferably 60 or less, more preferably 50 or less, and even more preferably 45 or less. The smaller the L* value, the higher the dark color, and although there is no lower limit, it may be, for example, 10 or more. The L* value is a value measured by the method described in the examples described later.

The ultrafine fiber structure of the present invention also has good washing fastness, and can exhibit, for example, grade 4 or higher in the washing fastness test defined in JIS L 0844.

The present invention will be explained in detail below with reference to examples, but the present invention is not limited thereto in any way.

[hardness]
(Shore A hardness)
In accordance with JIS K 7215, the durometer hardness (Shore A hardness) of the island component resin was measured with a durometer using a type A indenter (frustum-shaped tip, tip diameter 0.79 mm, cone angle 35°).
(Shore D hardness)
In accordance with JIS K 7215, the durometer hardness (Shore D hardness) of the island component resin was measured with a durometer using a type D indenter (conical tip, tip diameter 0.1 mm, cone angle 30°).
(Rockwell hardness (R scale))
The Rockwell hardness (R scale) of the island component resin was measured in accordance with JIS Z 2245 using a hard ball with a diameter of 12.7 mm as an indenter.

[Average single island diameter]
The average island diameter was measured by the following method. A cylindrical knitted fabric was prepared from the islands-in-sea type composite multifilament obtained in the Examples and Comparative Examples, and treated in hot water at 95°C with a bath ratio of 1:30 for 20 minutes to dissolve and remove the sea component, and then dried. Thereafter, the fiber cross section was observed with a scanning electron microscope (JCM-6000Plus, manufactured by JEOL Ltd.), and the diameter of each single yarn was measured for 10 single yarns randomly selected from the fiber cross section photograph, and the average value was calculated.

[Fineness]
The fineness was measured with reference to JIS L 1013 "Testing method for chemical fiber filament yarns." The total fineness is the fineness of the entire multifilament, and the single yarn fineness is the value obtained by dividing the total fineness by the number of filaments.

[Spinnability]
The islands-in-the-sea type composite multifilament was spun at 3000 m/min and evaluated for the occurrence of yarn breakage.
A: No thread breakage for 24 hours or more B: Thread breakage occurs between 3 hours and 24 hours C: Thread breakage occurs between 1 hour and 3 hours D: Thread breakage occurs within 1 hour

[Releaseability]
The islands-in-the-sea type composite multifilament yarn that had been wound after spinning was rewound at 200 m/min. and was evaluated based on the occurrence of yarn breakage and fluff/loops after 300 minutes.
A: No yarn breakage, no fluff or loops B: No yarn breakage, but fluff and loops C: Yarn breakage

[Fiber strength]
According to JIS L 1013, the breaking strength and elongation (initial tensile resistance) was determined under conditions of a test length of 20 cm, an initial load of 0.1 g/d, and a tensile speed of 10 cm/min, and the average value of 5 or more points was used.

[Coefficient of dynamic friction between yarn and metal]
Using the islands-in-sea type composite multifilaments obtained in the Examples and Comparative Examples, the sea part was dissolved and removed, and then the tension (T2) on the exit side of the friction body was measured with a yarn-metal running friction tester using a matte chrome pin with a diameter of 60 mm as the friction body at a running speed of 300 m/min, a contact angle of 180°, and a tension (T1) on the entry side of the friction body of 10 g. The yarn-metal dynamic friction coefficient (f) was calculated from the following well-known formula related to the friction of a belt running on a cylinder.
f=(1/π)×ln(T2/T1)

[L* value]
The ultrafine multifilaments obtained in the examples and comparative examples were made into circular knitted fabrics using a circular knitting machine (18 gauge), and the L* value was measured using a Konica Minolta spectrophotometer "CM-3700A" under the following conditions: regular reflection treatment: SCE, measurement diameter: LAV (25.4 mm), UV conditions: 100% Full, field of view: 2 degrees, main light source: D65 light source.
<Dyeing conditions>
A circular knitted fabric was obtained from the obtained islands-in-sea composite multifilament using a circular knitting machine (18 gauge). The fabric was then treated in hot water at 100°C with a bath ratio of 1:30 for 40 minutes to dissolve and remove the sea component, and a circular knitted fabric formed of ultrafine multifilaments was obtained. In Examples 1 to 7 and Comparative Examples 3 to 5, the circular knitted fabric was dyed with an acid dye, and in Example 8 and Comparative Examples 1 and 2, it was dyed with a disperse dye. The evaluation of the obtained circular knitted fabric is shown in Table 1.
<Acid dyeing method>
(Dyeing conditions)
Dye: Kayanol Milling Black TLB (manufactured by Nippon Kayaku Co., Ltd.) 4% owf
Auxiliary agent: Unigal ASS-10 (manufactured by Meisei Chemical Industry Co., Ltd.) 2.0% owf
Ammonium sulfate (manufactured by Nippon Kayaku Co., Ltd.) 0.5 g/L
Acetic acid 2% owf
Bath ratio: 1/50
Dyeing temperature x time: 90℃ x 40 minutes (soaping)
Laccol PSK (Meisei Chemical Industry Co., Ltd.) 1g/L
Bath ratio: 1/50
Dyeing temperature x time: 70°C x 40 minutes <Dyeing method with disperse dyes>
(Dyeing conditions)
Dye: Kayalon Polyester Black ECXN300
4.0% owf
Auxiliary agent: Disper TL 1.0cc/L
Acetic acid 1.0cc/L
Bath ratio: 1/50
Dyeing temperature x time: 120°C x 40 minutes (reduction cleaning)
Sodium hydroxide: 1.0 g/L
Sodium hydrosulfite: 1.0 g/L
Amylazine D: 1.0 g/L
Bath ratio: 1/50
Reduction cleaning temperature x time: 70°C x 20 minutes

[Washing fastness]
The fibers obtained in the examples and comparative examples were made into circular knitted fabrics using a circular knitting machine (18 gauge), and dyed in the same manner as in the measurement of the L* value. The obtained circular knitted fabrics were measured in accordance with the measurement method of JIS L 0844 B-4.

[Grip evaluation]
A circular knitted fabric was produced from the islands-in-the-sea composite multifilaments obtained in the Examples and Comparative Examples using a circular knitting machine (18 gauge). The circular knitted fabric obtained was immersed in hot water at 90° C. for 30 minutes, and then passed through a tunnel-type setter at 160° C. for 1 minute to obtain a circular knitted fabric formed of ultrafine multifilaments.
The obtained circular knitted fabric was 10 cm wide and 50 cm long, wrapped around the arm three times, and a load of 200 g was applied to the remaining end of the fabric, and the fabric was left to stand for three minutes, after which the feeling of slippage was evaluated. A sensory evaluation was performed by 10 panelists according to the following evaluation criteria.
"No sense of misalignment at all" 2 points "Slight sense of misalignment" 1 point "Sense of misalignment" 0 points

Thereafter, the grip performance was evaluated by calculating the total score given by each panelist.
A: 15 points or more B: 11-14 points C: 7-10 points D: 6 points or less

[Dynamic friction coefficient (fabric)]
The coefficient of friction was measured according to ASTM D 1894 using an Instron 5500R (Instron Corporation, Model 2810-005) friction coefficient tool.
Bioskin (manufactured by Viewlux) was fixed to the test table with double-sided tape, and a circular knitted fabric formed from ultra-fine multifilaments prepared as a test piece in the same manner as in the grip property evaluation was attached to a 200 g moving sled with double-sided tape, and measurements were made at a speed of 100 mm/min and a measurement distance of 150 mm.
One test piece was used per measurement, and the measurement was carried out five times. The dynamic friction coefficient was calculated by rounding off the average value to two decimal places.

[Example 1]
As the island component resin, a polyamide-based elastomer nylon (Ny) 12 elastomer 1 (Vestamid E47-S1 manufactured by Daicel-Evonik Ltd.) was used, while as the sea component resin, an ethylene-modified polyvinyl alcohol copolymer (manufactured by Kuraray Co., Ltd., saponification degree: 98.5 mol%, ethylene content: 8.0 mol%, polymerization degree: 380) was used. The island component and sea component were mixed in a mass ratio of 50/50, and each was melted in a separate extruder, and a yarn having 37 island parts per monofilament was extruded from a composite spinning nozzle.

The yarn discharged from the spinneret was then cooled using a 1.0 m long horizontal blowing type cooling air device, and then continuously introduced into a 1.0 m long, 30 mm inner diameter tube heater (inner wall temperature: 180°C) located 1.3 m from directly below the spinneret and directly stretched in the tube heater. An oil was then applied to the fiber emerging from the tube heater, which was then wound up via a roller at a take-up speed of 3000 m/min to obtain an 84 dtex/24 filament island-in-the-sea composite multifilament.

The resulting islands-in-the-sea composite multifilament was treated in hot water at 100°C with a bath ratio of 1:30 for 40 minutes to dissolve and remove the sea component, yielding an ultrafine multifilament of thermoplastic elastomer resin. The evaluation of the resulting islands-in-the-sea composite multifilament and ultrafine multifilament is shown in Table 1.

[Example 2]
The islands-in-sea type composite multifilament and ultrafine multifilaments of a thermoplastic elastomer resin were obtained by spinning in the same manner as in Example 1, except that the number of island parts per monofilament of the islands-in-sea type composite multifilament was 12. The evaluations of the obtained islands-in-sea type composite multifilament and ultrafine multifilament are shown in Table 1.

[Example 3]
The islands-in-sea type composite multifilament and ultrafine multifilaments of thermoplastic elastomer resin were obtained by spinning in the same manner as in Example 1, except that the number of island parts per monofilament of the islands-in-sea type composite multifilament was 7 and the composite ratio of the island parts to the sea parts was 30/70 by mass. The evaluations of the obtained islands-in-sea type composite multifilament and ultrafine multifilaments are shown in Table 1.

[Example 4]
Spinning was performed in the same manner as in Example 1 to obtain islands-in-sea type composite multifilaments and ultrafine multifilaments of a thermoplastic elastomer resin, except that the number of filaments in the islands-in-sea type composite multifilaments was 72. The evaluations of the obtained islands-in-sea type composite multifilaments and ultrafine multifilaments are shown in Table 1.

[Example 5]
The islands-in-sea type composite multifilament and ultrafine multifilaments of a thermoplastic elastomer resin were obtained by spinning in the same manner as in Example 1, except that the number of island parts per monofilament of the islands-in-sea type composite multifilament was 100. The evaluations of the obtained islands-in-sea type composite multifilament and ultrafine multifilament are shown in Table 1.

[Example 6]
Spinning was performed in the same manner as in Example 1, except that a polyamide-based elastomer Ny12 elastomer 2 (Vestamid E55-S4 manufactured by Daicel-Evonik Ltd.) was used as the island component resin, to obtain islands-in-the-sea type composite multifilament and ultrafine multifilament of thermoplastic elastomer resin. Evaluations of the obtained islands-in-the-sea type composite multifilament and ultrafine multifilament are shown in Table 1.

[Example 7]
(1) Preparation of polyamide 12 oligomer The autoclave was replaced with nitrogen, and 1.000 g of lauryllactam and 38 g of dodecanediamine were added together with a small amount of water and a small amount of phosphoric acid, and the mixture obtained was stirred under heating. The temperature of the reaction system was gradually raised and the pressure was adjusted with nitrogen gas, and the reaction system was kept at 270°C at 17.5 kgf/ ^cm2 (1.7 x ¹⁰⁶ Pa), and the mixture was heated and stirred for about 4 hours. Next, the reaction system was gradually returned to normal pressure, and the water in the system was discharged by decompressing the system for about 1 hour while circulating a very small amount of nitrogen gas. After that, the polyamide 12 oligomer was taken out in a molten state while cooling the system at normal pressure. The obtained polyamide 12 oligomer was further cooled and obtained as a slightly brittle solid. The number average molecular weight of the polyamide 12 oligomer was a low molecular weight of about 5400, and the content of terminal amino groups was 350 μeq/g. This polyamide 12 oligomer was used as an amino group-containing color development improver.
(2) Except for adding the polyamide 12 oligomer obtained above to the island component resin so as to give a weight ratio of 9%, spinning was performed in the same manner as in Example 1 to obtain islands-in-sea type composite multifilaments and ultrafine multifilaments of a thermoplastic elastomer resin. The evaluations of the obtained islands-in-sea type composite multifilaments and ultrafine multifilaments are shown in Table 1.

[Example 8]
Except for using a polyester-based PET elastomer ("Hytrel 4047N" manufactured by DuPont-Toray Co., Ltd.) as the island component resin, spinning was performed in the same manner as in Example 1 to obtain islands-in-the-sea type composite multifilaments and ultrafine multifilaments of a thermoplastic elastomer resin. The evaluations of the obtained islands-in-the-sea type composite multifilaments and ultrafine multifilaments are shown in Table 1.

[Comparative Example 1]
Spinning was performed in the same manner as in Example 1 to obtain islands-in-sea type composite multifilaments and ultrafine multifilaments of thermoplastic elastomer resin, except that general-purpose polyethylene terephthalate (PET) was used as the island component resin and the number of islands per monofilament of the islands-in-sea type composite multifilament was set to 726. Evaluations of the obtained islands-in-sea type composite multifilaments and ultrafine multifilaments are shown in Table 1.

[Comparative Example 2]
Except for using general-purpose polyethylene terephthalate (PET) as the island component resin, spinning was performed in the same manner as in Example 1 to obtain islands-in-the-sea type composite multifilaments and ultrafine multifilaments of a thermoplastic elastomer resin. Evaluations of the obtained islands-in-the-sea type composite multifilaments and ultrafine multifilaments are shown in Table 1.

[Comparative Example 3]
Spinning was performed in the same manner as in Example 1, except that a polyamide-based elastomer Ny12 elastomer 3 (Vestamid E62-S1 manufactured by Daicel-Evonik Ltd.) was used as the island component resin, to obtain islands-in-the-sea type composite multifilament and ultrafine multifilament of thermoplastic elastomer resin. Evaluations of the obtained islands-in-the-sea type composite multifilament and ultrafine multifilament are shown in Table 1.

[Comparative Example 4]
Except for using nylon (Ny) 6 ("1013B" manufactured by Ube Industries, Ltd.) as the island component resin, spinning was performed in the same manner as in Example 1 to obtain islands-in-the-sea type composite multifilaments and ultrafine multifilaments of a thermoplastic elastomer resin. The evaluations of the obtained islands-in-the-sea type composite multifilaments and ultrafine multifilaments are shown in Table 1.

[Comparative Example 5]
Except for using Ny11 elastomer ("Pebax Rnew 70R53" manufactured by ARKEMA Co., Ltd.), which is a polyamide-based elastomer, as the island component resin, spinning was performed in the same manner as in Example 1 to obtain islands-in-the-sea type composite multifilaments and ultrafine multifilaments of a thermoplastic elastomer resin. The evaluations of the obtained islands-in-the-sea type composite multifilaments and ultrafine multifilaments are shown in Table 1.

As shown in Table 1, in Examples 1 to 8, it was possible to obtain islands-in-the-sea type composite multifilaments that could efficiently produce ultrafine multifilaments. Furthermore, when producing the islands-in-the-sea type composite multifilaments of Examples 1 to 8, the spinnability and reelability were good.

In the ultrafine multifilaments of Examples 1 to 8, the polyamide-based elastomer resin used has a specific hardness, a yarn-metal dynamic friction coefficient of 0.30 or more, and good gripping properties. As the single yarn fineness decreases, both the yarn-metal dynamic friction coefficient and the dynamic friction coefficient (fabric) tend to increase.
In addition, the ultrafine multifilaments of Examples 1 to 7 and the ultrafine multifilaments of Comparative Examples 3 and 5 were dyed with the same dyeing agent as the ultrafine multifilaments. When comparing ultrafine multifilaments having the same single yarn fineness, the L* values of the ultrafine multifilaments of Examples 1, 6 and 7 are generally lower than those of Comparative Examples 3 and 5. In particular, Example 7, to which an amino group-containing color development improver was added, showed a particularly low L* value and was excellent in color development.
Furthermore, all of the ultrafine multifilaments of Examples 1 to 8 have good washing fastness, and Examples 1 to 7 made of ultrafine multifilaments of polyamide-based elastomer show particularly good washing fastness.

On the other hand, in Comparative Example 1, the number of islands in the islands-in-sea type composite multifilament was too large, so that the spinnability and releasability were poor, and the obtained ultrafine multifilament had insufficient washing fastness. In addition, compared to Example 3, which had the largest average single island diameter, the gripping property was inferior to all of the Examples, even though the average single island diameter was about 1/10 of that of Example 3.
Comparative Examples 2 and 4 have good spinnability and unwindability, but cannot exhibit gripping properties because the island component resin is a non-elastomer resin. In addition, although the single yarn fineness is the same as that of Example 1, the yarn-metal dynamic friction coefficient and the dynamic friction coefficient (fabric) are significantly smaller than those of Example 1.
In Comparative Examples 3 and 5, the polyamide elastomer resin used as the island component resin does not have a specific hardness, so that the dynamic friction coefficient is lower than that of the ultrafine multifilament of Example 1 having the same single yarn fineness, and the gripping property cannot be sufficiently exhibited.

The islands-in-the-sea composite multifilament of the present invention can efficiently form ultrafine multifilaments of a thermoplastic elastomer, and the obtained ultrafine multifilaments can exhibit good gripping properties as ultrafine fibers, and are therefore useful, for example, in various types of clothing (outerwear, innerwear, uniforms, surgical gowns, hospital gowns, white coats, work clothes, swimsuits, ski wear, aprons, hats, belly warmers, socks, gloves, scarves, etc.), various household items (futons, futon covers, pillow covers, beds, bed covers, blankets, sheets, bath mats, towels, tablecloths, curtains, shower curtains, nets, doorknob covers, diaper covers, slippers, etc.), building materials (carpets, curtains, etc.), industrial materials (nets, filters, ropes, etc.), and agricultural, forestry, and fishery materials (insect and weed control nets, shading covers, fishing nets, etc.).

As described above, a preferred embodiment of the present invention has been described with reference to the drawings. However, a person skilled in the art would easily imagine various changes and modifications within the obvious scope upon reading this specification. Therefore, such changes and modifications are to be interpreted as being within the scope of the invention as defined by the claims.

Claims (9)

the island component is composed of a thermoplastic elastomer resin (A) having any one of a Shore A hardness of 90 or less, a Shore D hardness of 60 or less, and a Rockwell hardness (R scale) of 70 or less, the sea component is composed of a water-soluble or alkali-soluble thermoplastic resin (B), and the average single island diameter is 8000 nm or less,
The islands-in-the-sea type composite multifilament , wherein the thermoplastic elastomer resin (A) is a polyamide-based elastomer resin or a polyester-based elastomer resin . The islands-in-the-sea composite multifilament according to claim 1, wherein the thermoplastic resin (B) of the sea component is a modified polyvinyl alcohol polymer in which units derived from α-olefins and/or vinyl ethers are present in the polyvinyl alcohol polymer. The islands-in-sea composite multifilament according to claim 1 or 2, wherein the number of islands in the islands-in-sea composite multifilament is 3 to 200 islands, and the composite mass ratio of the sea component to the island component (sea component:island component) is 20:80 to 70:30. A fiber structure comprising at least a part of the islands-in-the-sea type composite multifilament and/or cut fibers thereof according to any one of claims 1 to 3 . The thermoplastic elastomer resin (A) has a Shore A hardness of 90 or less, a Shore D hardness of 60 or less, or a Rockwell hardness (R scale) of 70 or less, and has a yarn-metal dynamic friction coefficient of 0.30 or more;
the thermoplastic elastomer resin (A) is a polyamide-based elastomer resin or a polyester-based elastomer resin,
An ultra-fine multifilament having a single yarn fineness of 0.005 to 0.5 dtex . An ultrafine fiber structure comprising at least a portion of the ultrafine multifilament and/or cut fibers thereof according to claim 5 . The microfiber structure according to claim 6 , which is a woven or knitted fabric. A method for producing an ultrafine multifilament, comprising at least a step of dissolving and removing the thermoplastic resin (B) from the islands-in-the-sea type composite multifilament according to any one of claims 1 to 3 . A method for producing an ultrafine fiber structure, comprising at least a step of dissolving and removing the thermoplastic resin (B) from the fiber structure according to claim 4 .