artificial leather

Abstract

To provide an artificial leather excellent in color development and light resistance in an artificial leather including an entangled fiber body composed of an ultrafine fiber, and a polymer elastomer as constituents.SOLUTION: An artificial leather includes: an entangled fiber body composed of an ultrafine fiber; and a polymer elastomer as constituents, where a movable amorphous amount of the ultrafine fiber is 17% or more and 40% or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to artificial leather with excellent color development and lightfastness. [Background technology]

[0002] Artificial leather that mimics natural leather, primarily composed of fibrous entanglements made of ultrafine fibers and polymeric elastic materials, possesses superior characteristics compared to natural leather, such as high durability and uniform quality. For this reason, it is used in a wide range of applications, including automotive interior materials, consumer electronics, and clothing. In particular, when artificial leather is used in automotive interior materials, excellent mechanical properties, as well as superior texture, surface quality, and high lightfastness are required.

[0003] The texture and surface quality of artificial leather tend to improve as the fiber density of the entangled fiber structure increases, and as the ultrafine fibers constituting the entangled fiber structure grip the polymer elastic material, resulting in more adhesive areas between the ultrafine fibers and the polymer elastic material. Therefore, it is generally desirable for the entangled fiber structure to be a highly entangled and dense sheet, and for the artificial leather to have an increased number of adhesive areas between the ultrafine fibers and the polymer elastic material, thereby providing a flexible texture and excellent surface quality.

[0004] Furthermore, regarding the control of the properties of artificial leather, artificial leather with excellent abrasion resistance has been proposed by controlling the fiber structure of the ultrafine fibers that make up the artificial leather (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2014-231650 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] In the technology disclosed in Patent Document 1, by increasing the degree of crystallinity of the ultrafine fibers constituting the artificial leather and reducing the amount of movable amorphous material, it is possible to obtain ultrafine fibers with high rigidity. This makes it possible to promote entanglement because the entangled fiber mass is less likely to be crushed in the thickness direction during the fiber entanglement process in needle punching, and it is also possible to produce artificial leather with high abrasion resistance.

[0007] However, in the fiber structure disclosed in Patent Document 1, the rigidity of the ultrafine fibers is high, resulting in strong constraints on the molecular chains, which tends to make it difficult for the dye to penetrate the ultrafine fibers during the dyeing process. Although strong constraints on the molecular chains make it difficult for the dye to degrade due to molecular chain severance, this also makes it difficult for the dye to penetrate the ultrafine fibers, resulting in the problem of not being able to obtain good color development.

[0008] Therefore, the present invention has been made in view of the above circumstances, and its object is to provide an artificial leather having excellent color development and lightfastness, comprising a fiber entanglement body composed of ultrafine fibers and a polymeric elastic body as constituent elements. [Means for solving the problem]

[0009] As a result of repeated studies by the inventors in order to achieve the above objectives, they found that by controlling the amount of movable amorphous material of the ultrafine fibers constituting the artificial leather within a specific range, the molecular chains of the ultrafine fibers have appropriate flexibility and restraint. Therefore, when the artificial leather made of the ultrafine fibers is dyed, the dye easily penetrates into the ultrafine fibers, and dye degradation due to molecular chain severance is reduced. As a result, it is possible to obtain artificial leather with excellent color development and lightfastness, as well as an elegant surface quality.

[0010] This invention was completed based on these findings, and according to this invention, the following inventions are provided.

[0011] In other words, the artificial leather of the present invention is an artificial leather comprising a fiber entanglement body composed of ultrafine fibers and a polymer elastic body as constituent elements, The thermoplastic resin constituting the ultrafine fibers is polyethylene terephthalate. The ratio of the weight-average molecular weight Mw of the thermoplastic resin constituting the ultrafine fibers to the number-average molecular weight Mn (Mw / Mn) is 1.1 or more and 2.5 or less, and further, The mobile amorphous amount of the ultra-fine fiber is 20% not less than and less than 40%.

[0012] According to a preferred embodiment of the artificial leather of the present invention, the crystallinity of the ultra-fine fiber is 20% or more and 40% or less.

[0014] According to a preferred embodiment of the artificial leather of the present invention, the mass ratio of the polymer elastomer in the artificial leather is 15% by mass or more and 50% by mass or less.

[0015] The method for manufacturing artificial leather in the present invention is A method for manufacturing the aforementioned artificial leather, a step of manufacturing a fiber complex mainly composed of a sea-island composite fiber in which the sea component is a thermoplastic resin having a melt flow rate of 1.0 g / 10 min or more and 90.0 g / 10 min or less, and the island component is a thermoplastic resin having an intrinsic viscosity of 0.7 or more and 1.2 or less, a step of removing the sea component from the fiber complex to develop ultra-fine fibers having an average single fiber diameter of 0.1 μm or more and 10.0 μm or less, a step of imparting a polymer elastomer and , including fruit , The aforementioned island component is polyethylene terephthalate, In the process of manufacturing the aforementioned fiber entanglement composite, the sea-island type composite fiber is stretched to a stretch ratio of 2.1 times or more and 4.0 times or less. .

Advantages of the Invention

[0016] According to the artificial leather of the present invention, a dye can easily enter during dyeing, and dye deterioration can be suppressed. As a result, an artificial leather excellent in color development and light resistance and having an elegant surface quality can be obtained. The artificial leather of the present invention can be widely used from furniture, chairs, and automotive interior materials to clothing applications. However, as described above, since it is excellent in color development and light resistance and has an elegant surface quality, it can be particularly preferably used for automotive interior materials.

Embodiments for Carrying Out the Invention

[0017] The artificial leather of the present invention is an artificial leather comprising a fiber entanglement composed of ultrafine fibers and a polymer elastic material as constituent elements, The thermoplastic resin constituting the ultrafine fibers is polyethylene terephthalate, and the ratio of the weight-average molecular weight Mw of the thermoplastic resin constituting the ultrafine fibers to the number-average molecular weight Mn (Mw / Mn) is 1.1 or more and 2.5 or less, further, The movable amorphous amount of the aforementioned ultrafine fibers 20% The percentage is less than 40%. The components will be described in detail below, but the present invention is not limited to the scope described below, unless it exceeds the gist of the invention.

[0018] [Fiber entanglement] The artificial leather of the present invention includes a fibrous entanglement composed of ultrafine fibers as a constituent element. The ultrafine fibers are made of a thermoplastic resin, and examples of thermoplastic resins include polyester, polyamide, polyolefin, acrylic, and polyphenylene sulfide. Examples of polyester include polyethylene terephthalate, polybutylene terephthalate, butyltrimethylene terephthalate, and polylactic acid. Examples of polyamide include polyamide 6, polyamide 66, polyamide 610, and polyamide 12. Examples of polyolefin include polyethylene and polypropylene. Among these, polyester is preferably used from the viewpoint of strength, dimensional stability, and heat resistance.

[0019] In the present invention, examples of dicarboxylic acids and / or ester-forming derivatives used in polyesters include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyl-4,4'-dicarboxylic acid and its ester-forming derivatives. The ester-forming derivatives referred to in the present invention are lower alkyl esters, acid anhydrides, acyl chlorides, etc., of these dicarboxylic acids, and specifically methyl esters, ethyl esters, hydroxyethyl esters, etc., are preferably used. A more preferred embodiment of the dicarboxylic acid and / or ester-forming derivative used in the present invention is terephthalic acid and / or its dimethyl ester.

[0020] In the present invention, examples of diols used in polyesters include ethylene glycol, 1,3-propanediol, 1,4-butanediol, and cyclohexanedimethanol, with ethylene glycol being the most preferred choice.

[0021] The thermoplastic resin used in the aforementioned ultrafine fibers may contain, depending on the purpose, inorganic particles such as titanium dioxide particles, lubricants, pigments, heat stabilizers, ultraviolet absorbers, conductive agents, heat storage agents, antibacterial agents, etc., to the extent that they do not hinder the objectives of the present invention.

[0022] Furthermore, it is preferable that the ratio of the weight-average molecular weight Mw of the thermoplastic resin constituting the ultrafine fibers to the number-average molecular weight Mn (Mw / Mn) is 1.1 or more and 2.5 or less. More preferably, it is 1.2 or more and 2.3 or less. By setting the molecular weight distribution within the above range, it is possible to obtain artificial leather having ultrafine fibers with the fiber structure described below, in addition to achieving excellent spinnability and stability during manufacturing.

[0023] The ultrafine fibers of the present invention have a movable amorphous content of 17% or more and less than 40%. By setting the movable amorphous content of the ultrafine fibers to 17% or more, more preferably 20% or more, and even more preferably 25% or more, the molecular chains have appropriate flexibility, resulting in artificial leather with good color development. On the other hand, by setting the movable amorphous content of the ultrafine fibers to less than 40%, dye degradation due to molecular chain severance can be suppressed, resulting in artificial leather with excellent lightfastness.

[0024] The movable amorphous content of the ultrafine fibers can be set to the above range by, for example, adjusting the intrinsic viscosity and Mw / Mn of the thermoplastic resin, the spinning rate, the draw ratio, etc.

[0025] In this invention, the movable amorphous content of the ultrafine fiber is calculated from the change in specific heat (ΔCp) before and after the glass transition on the temperature-thermal flux reversible curve, obtained by the temperature-modulated DSC method (TMDSC). Here, ΔCp is calculated using the specific heat gap before and after the glass transition, which is calculated by extrapolating a tangent to the temperature-thermal flux reversible curve before and after the glass transition, and is calculated by the following equation 1. Here, ΔCp 0 This is the difference in specific heat around the Tg of a thermoplastic resin in a perfectly amorphous state. If the thermoplastic resin is polyethylene terephthalate, this value is 0.4052 J / (g·℃). Movable amorphous amount (%)=(ΔCp / ΔCp 0 ) × 100 ···(1) Further details of the temperature-modulated DSC method described above can be found in, for example, the following [Reference 1]. [Reference 1]: B. Wunderlich, Thermal Analysis of Polymeric Materials, Springer (2005) Furthermore, for measuring the movable amorphous content of ultrafine fibers, a thermal analyzer such as the "Q1000" manufactured by TA Instruments can be used.

[0026] The ultrafine fibers of the present invention preferably have a crystallinity of 20% to 40%. By setting the crystallinity of the ultrafine fibers to preferably 20% or more, and more preferably 25% or more, the entangled fiber mass becomes less likely to be crushed in the thickness direction during the fiber entanglement process in needle punching, thereby promoting entanglement. On the other hand, by setting the crystallinity of the ultrafine fibers to preferably 40% or less, and more preferably 35% or less, an artificial leather with a good texture can be obtained.

[0027] The degree of crystallinity of the ultrafine fibers can be set to the above range by, for example, adjusting the intrinsic viscosity of the thermoplastic resin, the spinning rate and draw ratio, and the drying temperature.

[0028] In this invention, the degree of crystallinity of the ultrafine fiber is calculated by the DSC method, determining the difference between the heat of fusion and the heat of cold crystallization (ΔHm - ΔHc), and then calculated using the following equation 2. Here, ΔHm 0This represents the heat of fusion of a thermoplastic resin in a perfectly amorphous state. If the thermoplastic resin is polyethylene terephthalate, this value is 140.10 J / g. Details of the measurement method are described in [Reference 1] mentioned above. Crystallinity (%)=(ΔHm-ΔHc) / ΔHm 0 ×100 ···(2) Furthermore, to measure the degree of crystallinity of ultrafine fibers, for example, a thermal analyzer such as the "Q1000" manufactured by TA Instruments can be used.

[0029] In the present invention, the average single fiber diameter of the ultrafine fibers is preferably 0.1 μm or more and 10.0 μm or less. By setting the average single fiber diameter of the ultrafine fibers to preferably 0.1 μm or more, more preferably 0.2 μm or more, and even more preferably 0.5 μm or more, excellent effects are obtained in terms of color development after dyeing, lightfastness, friction fastness, and stability during spinning. On the other hand, by setting the average single fiber diameter of the ultrafine fibers to preferably 10.0 μm or less, more preferably 7.0 μm or less, and even more preferably 5.0 μm or less, an artificial leather with a dense, soft touch and excellent surface quality can be obtained.

[0030] The average single fiber diameter of ultrafine fibers shall be calculated using the following method. (1) Take a scanning electron microscope (SEM) image of the cross-section of the artificial leather and randomly select 10 ultrafine fibers that are circular or nearly circular in shape. (2) Measure the diameter of the single fibers and calculate the arithmetic mean of 10 fibers, then round to the second decimal place. (However, if an ultrafine fiber with an irregular cross-section is used, the diameter of the single fiber shall be determined by first measuring the cross-sectional area of ​​the single fiber and then calculating the diameter when the cross-section is considered to be circular.) Furthermore, while a round cross-section is preferable for the cross-sectional shape of the ultrafine fibers from the viewpoint of ease of processing and operation, other irregular cross-sectional shapes such as elliptical, flat, triangular, sector-shaped, cross-shaped, hollow, Y-shaped, T-shaped, and U-shaped can also be adopted.

[0031] The artificial leather of the present invention is in the form of a fiber complex composed of the above-mentioned ultrafine fibers, and when the surface is raised by the method described later, a uniform and beautiful appearance and texture can be obtained.

[0032] As the form of the fiber complex, after forming a laminated fiber web using short fibers with a card or a cross lapper, a short fiber complex obtained by subjecting it to needle punching or water jet punching, a long fiber complex obtained from the spunbond method, the melt blow method, etc., and a complex obtained by the papermaking method are available. When the base material of the fiber layer constituting the artificial leather is a long fiber complex, it is preferable because an artificial leather excellent in strength can be obtained. On the other hand, when using a short fiber complex, compared with the case of a long fiber complex or a complex obtained by a papermaking method, more fibers can be oriented in the thickness direction of the artificial leather, and a high density can be imparted to the surface of the artificial leather when raised. Furthermore, since a product with good thickness uniformity and the like can be obtained, it is preferably used.

[0033] When using a short fiber complex, the fiber length of the ultrafine fiber is preferably 25 mm or more and 90 mm or less. By making the fiber length of the ultrafine fiber preferably 25 mm or more, more preferably 35 mm or more, and even more preferably 40 mm or more, an artificial leather excellent in abrasion resistance can be obtained. Also, by making the fiber length of the ultrafine fiber preferably 90 mm or less, more preferably 80 mm or less, and even more preferably 70 mm or less, an artificial leather having good surface quality and texture can be obtained.

[0034] The basis weight of the fiber complex constituting the artificial leather according to the present invention is measured by "6.2 Mass per unit area (ISO method)" of JIS L1913:2010 "General test methods for nonwovens", and is 50 g / m 2 or more and 800 g / m 2 or less. By making the basis weight of the fiber complex preferably 50 g / m 2 or more, more preferably 80 g / m 2 or more, an artificial leather with a substantial feeling and excellent texture can be obtained. Also, by making the basis weight of the fiber complex preferably 800 g / m 2More preferably, 700g / m² 2 By doing the following, it is possible to create a flexible artificial leather with excellent moldability.

[0035] [Polymer elastic material] The polymeric elastic material constituting the artificial leather of this invention refers to a polymer compound that has rubber elasticity at room temperature. The binder effect of the polymeric elastic material not only prevents ultrafine fibers from falling out of the artificial leather, but also makes it possible to provide appropriate cushioning.

[0036] Examples of polymeric elastic materials include polyurethane, polyurea, polyacrylic acid, ethylene vinyl acetate, acrylonitrile butadiene, styrene butadiene, polyvinyl alcohol, and polyethylene glycol. From the viewpoint of durability and compressive properties, polyurethane is preferably used. Furthermore, the polymeric elastic material may contain multiple polymeric elastic materials.

[0037] In the present invention, when polyurethane is used as the polymeric elastic material, either an organic solvent-based polyurethane used in a dissolved state in an organic solvent or a water-dispersible polyurethane used in a dispersed state in water can be used.

[0038] When using organic solvent-based polyurethane, its weight-average molecular weight is preferably 50,000 or more and 500,000 or less. By setting the weight-average molecular weight to preferably 50,000 or more, more preferably 100,000 or more, and even more preferably 150,000 or more, the strength of the artificial leather can be maintained and the shedding of composite fibers can be prevented. Furthermore, by setting the weight-average molecular weight to preferably 500,000 or less, more preferably 400,000 or less, even more preferably 300,000 or less, and particularly preferably 250,000 or less, the increase in viscosity of the polyurethane solution can be suppressed, making it easier to impregnate the fiber entanglement.

[0039] When using water-dispersible polyurethane, its number-average molecular weight is preferably between 20,000 and 500,000. By setting the number-average molecular weight to preferably 20,000 or more, and more preferably 30,000 or more, the strength of the polyurethane can be increased. Furthermore, by setting the number-average molecular weight to preferably 500,000 or less, and more preferably 300,000 or less, the viscosity stability of the polyurethane solution can be improved, thereby enhancing workability.

[0040] As the polyurethane described above, polyurethane obtained by the reaction of a polymer diol, an organic diisocyanate, and a chain extender is preferably used.

[0041] When polyurethane is used as the polymeric elastic material, polymer diols such as polycarbonate-based diols, polyester-based diols, polyether-based diols, silicone-based diols, and fluorine-based diols can be used, and copolymers combining these can also be used. Among these, polycarbonate-based diols and polyether-based diols are preferred from the viewpoint of hydrolysis resistance.

[0042] The aforementioned polycarbonate diols can be produced, for example, by a transesterification reaction between alkylene glycol and a carbonate ester, or by a reaction between phosgene or chlorformate ester and alkylene glycol.

[0043] Examples of alkylene glycols include linear alkylene glycols such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, and 1,10-decanediol; branched alkylene glycols such as neopentyl glycol, 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, and 2-methyl-1,8-octanediol; alicyclic diols such as 1,4-cyclohexanediol; aromatic diols such as bisphenol A; glycerin; trimethylolpropane; and pentaerythritol. In the present invention, either polycarbonate diols obtained from individual alkylene glycols or copolymerized polycarbonate diols obtained from two or more alkylene glycols can be used.

[0044] Examples of the aforementioned polyester diols include polyester diols obtained by condensing various low molecular weight polyols with polybasic acids.

[0045] Examples of low molecular weight polyols include one or more selected from ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,2-dimethyl-1,3-propanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,8-octanediol, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, cyclohexane-1,4-diol, and cyclohexane-1,4-dimethanol. Adducts obtained by adding various alkylene oxides to bisphenol A can also be used.

[0046] Examples of polybasic acids include one or more selected from succinic acid, maleic acid, adipic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid, and hexahydroisophthalic acid.

[0047] Examples of the aforementioned polyether-based diols include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and copolymer diols combining these.

[0048] In this invention, the number-average molecular weight of the polymer diol used is preferably 500 or more and 5000 or less. By setting the number-average molecular weight to preferably 500 or more, and more preferably 1500 or more, hardening of the artificial leather can be prevented. Furthermore, by setting the number-average molecular weight to preferably 5000 or less, more preferably 4000 or less, and even more preferably 3000 or less, the strength as a polyurethane can be maintained.

[0049] When polyurethane is used as the polymeric elastic material, examples of organic diisocyanates include aliphatic diisocyanates such as hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, and xylylene diisocyanate, as well as aromatic diisocyanates such as diphenylmethane diisocyanate and tolylene diisocyanate. These can also be used in combination. In particular, when durability and heat resistance are important, aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate are preferred, and when light resistance is important, aliphatic diisocyanates such as hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and isophorone diisocyanate are preferred.

[0050] Examples of chain extenders when polyurethane is used as the polymeric elastic material include water, low molecular weight diols such as ethylene glycol, propylene glycol, 1,3-butylene glycol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, and neopentyl glycol, alicyclic diols such as 1,4-bis(hydroxymethyl)cyclohexane, aromatic diols such as 1,4-bis(hydroxyethyl)benzene, aliphatic diamines such as ethylenediamine, alicyclic diamines such as isophoronediamine, aromatic diamines such as 4,4-diaminodiphenylmethane, aromatic aliphatic diamines such as xylenediamine, alkanolamines such as ethanolamine, hydrazine, and dihydrazides such as adipic acid dihydrazide. These can also be used in combination. Among these, more preferred chain extenders are water, low molecular weight diols, and aromatic diamines, and even more preferred are water, ethylene glycol, 1,4-butanediol, 4,4'-diaminodiphenylmethane, and mixtures of two or more of these.

[0051] In the present invention, when using water-dispersible polyurethane, it is preferable to use an internal emulsifier to disperse the polyurethane in water. Examples of internal emulsifiers include cationic internal emulsifiers such as quaternary amine salts, anionic internal emulsifiers such as sulfonates and carboxylates, and nonionic internal emulsifiers such as polyethylene glycol. Furthermore, combinations of cationic and nonionic internal emulsifiers, and combinations of anionic and nonionic internal emulsifiers can be used. Among these, nonionic internal emulsifiers are preferred because they have superior light resistance compared to cationic internal emulsifiers and do not cause adverse effects from neutralizing agents compared to anionic internal emulsifiers.

[0052] The polymer elastomer used in the present invention may be used in combination with a crosslinking agent to improve water resistance, abrasion resistance, hydrolysis resistance, etc. The crosslinking agent may be an external crosslinking agent added as a third component to the polymer elastomer, or an internal crosslinking agent may be used to introduce reaction sites that form a crosslinked structure into the molecular structure of the polymer elastomer in advance. From the viewpoint of forming crosslinking sites more uniformly within the molecular structure of the polymer elastomer and reducing the decrease in flexibility, it is preferable to use an internal crosslinking agent.

[0053] As the crosslinking agent, compounds having isocyanate groups, oxazoline groups, carbodiimide groups, epoxy groups, melamine resins, and silanol groups can be used.

[0054] Furthermore, polymeric elastic materials may contain various additives depending on the purpose, such as pigments like carbon black, flame retardants such as phosphorus-based, halogen-based, and inorganic types, antioxidants such as phenol-based, sulfur-based, and phosphorus-based types, ultraviolet absorbers such as benzotriazole-based, benzophenone-based, salicylate-based, cyanoacrylate-based, and oxalic acid anilide-based types, light stabilizers such as hindered amine-based and benzoate-based types, hydrolysis-resistant stabilizers such as polycarbodiimide, plasticizers, antistatic agents, surfactants, coagulation modifiers, and dyes.

[0055] Generally, the content of polymeric elastic material in artificial leather can be adjusted as appropriate, taking into account the type of polymeric elastic material used, the manufacturing method of the polymeric elastic material, and the texture and physical properties. However, in the present invention, it is preferable that the content of polymeric elastic material be 15% by mass or more and 50% by mass or less relative to the mass of the artificial leather. By setting the content of polymeric elastic material to 15% by mass or more, more preferably 20% by mass or more, the bonding between fibers by the polymeric elastic material can be strengthened, and the abrasion resistance of the artificial leather can be improved. On the other hand, by setting the content of polymeric elastic material to 50% by mass or less, more preferably 45% by mass or less, the artificial leather can be made more flexible.

[0056] [Artificial leather] In the artificial leather of the present invention, it is preferable to have a nap on the surface. The nap may be present only on the surface of the artificial leather, or it may be present on both sides. When the surface has a nap, from the viewpoint of design effect, it is preferable that the nap has a length and directional flexibility such that when the nap is traced with a finger, the direction of the nap changes, leaving a mark, so-called finger marks.

[0057] More specifically, the pile length on the surface is preferably 100 μm or more and 500 μm or less. By setting the pile length to preferably 100 μm or more, and more preferably 150 μm or more, a sense of volume and design effect can be obtained. Furthermore, by setting the pile length to preferably 500 μm or less, and more preferably 450 μm or less, an artificial leather with excellent abrasion resistance can be obtained, and the deterioration of surface quality due to entanglement of ultrafine fibers can be suppressed.

[0058] In this invention, the pile length of the artificial leather is calculated by the following method. (1) Using a lint brush or the like, raise the nap of the artificial leather and prepare a 1 mm thick thin section in the cross-sectional direction of a surface perpendicular to the longitudinal direction of the artificial leather. (2) Take SEM images of the cross-section of the artificial leather and measure the height of the pile (layer consisting only of ultrafine fibers) at 10 points at 200 μm intervals in the width direction of the cross-section. (3) Calculate the arithmetic mean of the heights of the 10 points of the raised pile that were measured.

[0059] The artificial leather of the present invention has a basis weight of 100 g / m² as measured by JIS L1913:2010 "General Nonwoven Fabric Testing Methods" 6.2 "Mass per unit area (ISO method)". 2 More than 500g / m 2 The following is preferable: The weight of the artificial leather is preferably 100 g / m². 2 Above, a comfortable 150g / m 2 By doing so, sufficient morphological and dimensional stability can be easily obtained in the artificial leather. Furthermore, the basis weight of the artificial leather is preferably 500 g / m². 2 More preferably, 400 g / m² 2By doing the following, sufficient flexibility and texture can be obtained.

[0060] The artificial leather of the present invention preferably has a thickness of 0.2 mm or more and 1.2 mm or less, as measured by "6.1 Thickness (ISO method)" "6.1.1 Method A" of "General Nonwoven Fabric Testing Methods" in JIS L1913:2010. By making the thickness of the artificial leather preferably 0.2 mm or more, more preferably 0.3 mm or more, and even more preferably 0.4 mm or more, it not only becomes easy to process during manufacturing but also has a substantial feel and excellent texture. Furthermore, by making the thickness of the artificial leather preferably 1.2 mm or less, more preferably 1.1 mm or less, and even more preferably 1.0 mm or less, it is possible to make a flexible artificial leather with excellent moldability.

[0061] Furthermore, in the abrasion resistance test measured by "8.19 Abrasion Resistance and Friction Discoloration Resistance" "8.19.5 Method E (Martindale Method)" of "Test Methods for Woven and Knitted Fabrics" of the present invention, it is preferable that the mass loss of the artificial leather after abrasion 20,000 times with a pressing load of 12.0 kPa is 10 mg or less, more preferably 8 mg or less, and even more preferably 6 mg or less. A mass loss of 10 mg or less prevents contamination due to shedding of lint during actual use.

[0062] Furthermore, it is preferable that the artificial leather of the present invention has a friction fastness of grade 4 or higher, as measured by "9.1 Type I friction tester (clock meter) method" of JIS L0849:2013 "Test method for color fastness to friction" and a lightfastness of grade 4 or higher, as measured by "7.2 Exposure method a) First exposure method" of JIS L0843:2006 "Test method for color fastness to xenon arc light". Having a friction fastness and lightfastness of grade 4 or higher prevents color fading and staining of clothing, etc., during actual use.

[0063] [Manufacturing method for artificial leather] The present invention provides a method for manufacturing artificial leather, comprising the steps of: producing a fiber entanglement mainly composed of sea-island type composite fibers, wherein the sea component is a thermoplastic resin having a melt flow rate (hereinafter sometimes abbreviated as MFR) of 1.0 g / 10 min to 90.0 g / 10 min, and the island component is a thermoplastic resin having an intrinsic viscosity of 0.7 to 1.2; removing the sea component from the fiber entanglement to produce ultrafine fibers having an average single fiber diameter of 0.1 μm to 10.0 μm; and imparting a polymeric elastic material. Details are described below.

[0064] <Formation of fiber entanglement> In the method for manufacturing artificial leather according to the present invention, a preferred embodiment includes a step of manufacturing a fiber entanglement composite mainly composed of sea-island type composite fibers.

[0065] Sea-island composite fibers can be produced using a polymer interconnected array, which is spun by interconnecting two components, a sea component and an island component, using a spinning nozzle for sea-island composite fibers. Other methods include a mixed spinning method, which involves mixing the two components, the sea component and the island component, before spinning. However, from the viewpoint of obtaining ultrafine fibers with uniform single fiber fineness, sea-island composite fibers produced using a polymer interconnected array are preferred.

[0066] The ratio of sea components to island components in sea-island composite fibers is preferably 20% to 90% by mass ratio of island components to sea-island composite fibers. By setting the mass ratio of island components to preferably 20% or more, and more preferably 30% or more, the removal rate of sea components can be reduced, thereby improving productivity. Furthermore, by setting the mass ratio of island components to preferably 90% or less, and more preferably 85% or less, the merging of island components can be prevented, and a decrease in surface quality can be suppressed.

[0067] The thermoplastic resin used as the marine component of sea-island type composite fibers can be polyethylene, polypropylene, polystyrene, copolymerized polyester obtained by copolymerizing sodium sulfisophthalic acid or polyethylene glycol, and polylactic acid, but from the viewpoint of spinnability and ease of elution, polystyrene and copolymerized polyester are preferably used.

[0068] When using copolymerized polyester, copolymerized polyester obtained by copolymerizing sodium 5-sulfoisophthalate in an amount of 3 mol% to 15 mol% is preferred. By copolymerizing the sodium 5-sulfoisophthalate component in an amount of 3 mol% or more, sufficient alkali elution properties can be obtained. Furthermore, when the copolymerized amount of sodium 5-sulfoisophthalate component is 15 mol% or less, the thickening of the polyester is suppressed, resulting in the effect of reducing the likelihood of yarn breakage during composite fiber spinning. More preferably, the range is 5 mol% to 13 mol%.

[0069] In the sea-island type composite fiber according to the present invention, the sea component is preferably a thermoplastic resin with a melt flow rate (MFR) of 1.0 g / 10 min or more and 90.0 g / 10 min or less. By setting the MFR of the sea component to preferably 1.0 g / 10 min or more, more preferably 5.0 g / 10 min or more, even more preferably 10.0 g / 10 min or more, or preferably 90.0 g / 10 min or less, and more preferably 80.0 g / 10 min or less, it is possible to achieve excellent spinnability and cross-section formation during spinning, and by combining it with the island component described below, it is possible to easily obtain ultrafine fibers having the characteristic fiber structure of the present invention.

[0070] The thermoplastic resins used as island components in sea-island composite fibers include polyester, polyamide, polyolefin, acrylic, and polyphenylene sulfide, as mentioned above as thermoplastic resins constituting the ultrafine fibers. Examples of polyester include polyethylene terephthalate, polybutylene terephthalate, butyltrimethylene terephthalate, and polylactic acid. Examples of polyamide include polyamide 6, polyamide 66, polyamide 610, and polyamide 12. Examples of polyolefin include polyethylene and polypropylene. Among these, polyester is preferred from the viewpoint of strength, dimensional stability, and heat resistance.

[0071] In the sea-island type composite fiber according to the present invention, the island component is preferably a thermoplastic resin having an intrinsic viscosity of 0.7 or more and 1.2 or less. By setting the intrinsic viscosity of the island component to preferably 0.7 or more, preferably 1.2 or less, preferably 1.1 or less, and more preferably 1.0 or less, excellent spinnability and stability are achieved during spinning. Furthermore, by combining it with the sea component described above, it is possible to obtain an ultrafine fiber having the characteristic fiber structure of the present invention.

[0072] Furthermore, the sea and island components constituting the sea-island composite fiber may contain inorganic particles such as titanium dioxide particles, lubricants, pigments, heat stabilizers, ultraviolet absorbers, conductive agents, heat storage agents, antibacterial agents, etc., to the extent that they do not hinder the objectives of the present invention, depending on the purpose.

[0073] In the method for manufacturing artificial leather of the present invention, when using sea-island type composite fibers, it is preferable that the strength of the island components is 2.5 cN / dtex or higher. By making the strength of the island components preferably 2.5 cN / dtex or higher, more preferably 2.8 cN / dtex or higher, and even more preferably 3.0 cN / dtex or higher, the abrasion resistance of the artificial leather can be improved.

[0074] In the present invention, the strength of the island component of the sea-island type composite fiber is calculated by the following method. (1) Bundle together 10 pieces of sea-island type composite fiber, each 20 cm long. (2) After dissolving and removing marine components from the sample in (1), the sample is air-dried. (3) The test is performed 10 times under the conditions of grip length 5 cm, tensile speed 5 cm / min, and load 2 N, as specified in "8.5 Tensile strength and elongation" of "8.5 Standard time test" in JIS L1013:2010 "Test method for chemical fiber filament yarn". (4) The arithmetic mean (cN / dtex) of the test results obtained in (3) is rounded to two decimal places and the resulting value is taken as the strength of the island components constituting the sea-island composite fiber.

[0075] Furthermore, the sea-island type composite fiber can be stretched using known methods, but the stretching ratio is preferably 2.1 times or more and 4.0 times or less. By setting the stretching ratio to preferably 2.1 times or more, more preferably 2.3 times or more, and even more preferably 2.5 times or more, a sea-island type composite fiber with sufficient strength can be obtained. In addition, by setting the stretching ratio to preferably 4.0 times or less, more preferably 3.8 times or less, and even more preferably 3.5 times or less, it is possible to obtain an ultrafine fiber having the fiber structure that is characteristic of the present invention, as well as providing excellent stability during stretching.

[0076] Furthermore, it is also preferable to perform a drying treatment after the stretching of the sea-island type composite fiber. The drying temperature is preferably 50°C to 100°C. By preferably setting the drying temperature to 50°C or higher, efficient drying of the sea-island type composite fiber becomes possible. Also, by preferably setting the drying temperature to 100°C or lower, changes in the fiber structure due to the drying treatment can be suppressed.

[0077] The fibrous entanglement that constitutes the artificial leather of the present invention can be obtained by opening the spun sea-island type composite fibers, forming a fiber web using a cross wrapper or the like, and then entangling the fiber web. As a method for entangling the fiber web to obtain the fibrous entanglement, needle punching or water jet punching can be used.

[0078] As mentioned above, both short fiber entanglements and long fiber entanglements can be used as the entanglement structure. However, with short fiber entanglements, there are more fibers oriented in the thickness direction of the artificial leather compared to long fiber entanglements, resulting in a denser surface texture when the artificial leather is napped.

[0079] When forming a short fiber entanglement, the obtained sea-island type composite fiber is preferably crimped and cut to a predetermined length to obtain raw fibers, which are then opened, laminated, and entangled to obtain the short fiber entanglement. Known methods can be used for the crimping and cutting processes.

[0080] In the needle used in the needle punching process described above, the number of needle barbs (notches) is preferably between 1 and 9. Having one or more needle barbs allows for efficient fiber entanglement. Furthermore, having 9 or fewer needle barbs helps to minimize fiber damage.

[0081] The number of sea-island composite fibers caught in the barb is determined by the shape of the barb and the diameter of the sea-island composite fibers. Therefore, the barb shape of the needle used in the needle punching process is preferably one in which the kick-up is 0 μm to 50 μm, the undercut angle is 0° to 40°, the throat depth is 40 μm to 80 μm, and the throat length is 0.5 mm to 1.0 mm.

[0082] The number of punches is 1000 per cm. 2 Over 8000 strands / cm 2 The following is preferable: The number of punches is preferably 1000 per cm. 2 By doing so, a dense fiber entanglement can be obtained. Furthermore, the number of punches is preferably 8000 per cm. 2 By doing the following, deterioration of processability, fiber damage, and reduction in strength can be prevented.

[0083] Furthermore, when performing water jet punching, it is preferable to carry out the water in a columnar flow state. Specifically, it is preferable to eject water from a nozzle with a diameter of 0.05 mm or more and 1.0 mm or less at a pressure of 2 MPa or more and 60 MPa or less.

[0084] The apparent density of the fiber entanglement body, consisting of sea-island type composite fibers after needle punching or water jet punching, is 0.15 g / cm³. 3 More than 0.45g / cm 3 Preferably, the apparent density is 0.15 g / cm³. 3 By doing so, the artificial leather can obtain sufficient shape and dimensional stability. Furthermore, the apparent density is preferably 0.45 g / cm³. 3By doing the following, it is possible to maintain sufficient space for imparting the polymeric elastic material.

[0085] In order to improve the density of the fibers, it is also preferable to subject the aforementioned fiber entanglement to a heat shrinkage treatment using hot water or steam.

[0086] Next, the aforementioned fiber entanglement can be impregnated with an aqueous solution of a water-soluble resin and dried to impregnate it with the water-soluble resin. By impregnating the fiber entanglement with the water-soluble resin, the fibers are fixed and dimensional stability is improved.

[0087] <Emergence of ultrafine fibers> Furthermore, the method for producing artificial leather according to the present invention preferably includes a step of removing marine components from the aforementioned fiber entanglement to produce ultrafine fibers having an average single fiber diameter of 0.1 μm or more and 10.0 μm or less.

[0088] The process of generating ultrafine fibers can be carried out by immersing a fiber entanglement composed of sea-island type composite fibers in a solvent to dissolve and remove the marine components of the sea-island type composite fibers.

[0089] For dissolving and removing marine components, organic solvents such as toluene or trichloroethylene can be used if the marine components are polyethylene, polypropylene, or polystyrene. If the marine components are copolymerized polyester or polylactic acid, an alkaline aqueous solution such as sodium hydroxide can be used. If the marine components are water-soluble thermoplastic polyvinyl alcohol-based resins, hot water can be used.

[0090] <Improving the elasticity of polymeric materials> Furthermore, the method for manufacturing artificial leather of the present invention preferably includes a step of impregnating a fiber entanglement made of sea-island type composite fibers or a fiber entanglement made of ultrafine fibers from which the sea component of sea-island type composite fibers has been dissolved and removed with a polymer elastic solution and solidifying it to impregnate the polymer elastic.

[0091] Methods for fixing polymeric elastic materials to fiber entanglements include a wet coagulation method, in which a solution of the polymeric elastic material is impregnated into the fiber entanglement, and then fixed by immersion in a coagulation bath, and a dry coagulation method, in which the material is fixed by drying. These methods can be appropriately selected depending on the type of polymeric elastic material to be applied.

[0092] When imparting polyurethane as a polymeric elastic material, N,N'-dimethylformamide and dimethyl sulfoxide are preferred solvents. Alternatively, a water-dispersible polyurethane solution, in which polyurethane is dispersed as an emulsion in water, may be used.

[0093] <Other processes> The sheet material obtained after the above process may be used as artificial leather as is, but from the viewpoint of improving manufacturing efficiency, it is also preferable to cut it in half in the thickness direction to make two sheet materials and use those as artificial leather.

[0094] Furthermore, artificial leather can be produced by applying a napping treatment to the surface of a sheet-like material to which the aforementioned polymeric elastic material is applied, or to a sheet-like material to which a halved polymeric elastic material is applied. The napping treatment can be applied by grinding using sandpaper or a roll sander. The napping treatment can be applied to only one side of the sheet-like material or to both sides.

[0095] When performing the aforementioned napping treatment, a lubricant such as a silicone emulsion can be applied to the surface of the sheet material before the napping treatment. In addition, applying an antistatic agent before the napping treatment makes it less likely for grinding dust generated from the sheet material during grinding to accumulate on the sandpaper.

[0096] Furthermore, it is preferable to dye the aforementioned sheet-like material to produce artificial leather. For this dyeing process, for example, immersion dyeing using a jigger dyeing machine or a liquid flow dyeing machine, thermosol dyeing using a continuous dyeing machine, or printing on the napped surface using roller printing, screen printing, inkjet printing, sublimation printing, and vacuum sublimation printing are all possible. Among these, using a liquid flow dyeing machine is preferable because it provides a flexible texture and is superior in terms of quality and finish. Additionally, various resin finishing processes can be applied after dyeing as needed.

[0097] In addition, the aforementioned sheet-like material can be made into artificial leather by applying a design to its surface according to the desired configuration. For example, post-processing treatments such as perforation, embossing, laser processing, pin sonic processing, and printing can be applied.

[0098] The artificial leather of the present invention, obtained by the manufacturing method exemplified above, has excellent color development and lightfastness, as well as an elegant surface quality, and can therefore be used in a wide range of applications, from furniture, chairs, and automotive interior materials to clothing. [Examples]

[0099] Next, the artificial leather of the present invention will be described in more detail using examples, but the present invention is not limited to these examples. First, the evaluation method and measurement conditions used in the examples will be described. However, unless otherwise specified, the measurements of each physical property were performed based on the method described above. Furthermore, from this point forward, any references to "Example 6" or "Example 8," including those within Table 1, should be interpreted as "Reference Example 6" or "Reference Example 8."

[0100] [Measurement method and processing method for evaluation] A. Movable amorphous and crystallinity of ultrafine fibers The movable amorphous and crystallinity of the ultrafine fibers were analyzed using a TA Instruments Q1000 thermal analyzer, and the data was processed using TA Instruments Universal Analysis 2000.

[0101] B. Molecular weight distribution: The molecular weight distribution of the thermoplastic polymer constituting the ultrafine fibers was calculated using the HLC-8220 gel permeation chromatography system manufactured by Tosoh Corporation.

[0102] C. Average single fiber diameter of ultrafine fibers: In measuring the average single fiber diameter of ultrafine fibers, the ultrafine fibers were observed using a digital microscope "VHX-D510" manufactured by Keyence Corporation, and the average single fiber diameter was calculated.

[0103] D. Friction fastness of artificial leather: The degree of contamination of the sample after measurement is graded using the contamination gray scale specified in JIS L0805:2005 "Contamination Gray Scale", and grade 4 or higher (L * a * b * Color difference ΔE due to color system * ab A score of 4.5 ± 0.3 or less was considered a passing grade.

[0104] E. Lightfastness of artificial leather: The degree of discoloration of the irradiated sample is graded using the gray scale for discoloration specified in JIS L0804:2004 "Gray Scale for Discoloration", and grades 4 and above (L * a * b * Color difference ΔE due to color system * ab A score of 1.7 ± 0.3 or less was considered acceptable.

[0105] F. Color development of artificial leather: Twenty healthy adult men and women (10 each) served as evaluators, visually distinguishing the following evaluations. The most frequent evaluation was designated as the color development of the artificial leather. In the event of a tie in evaluations, the higher evaluation was designated as the color development of the artificial leather. In this invention, a good level is "A or B". A: Excellent color development. • B: Good color development. • C: Poor color development. • D: Has very poor color development.

[0106] G. Surface quality of artificial leather: Twenty healthy adult men and women (10 each) served as evaluators, and the artificial leather was evaluated by sensory assessment as follows. The most frequent rating was used as the surface quality rating for the artificial leather. In the event of a tie in ratings, the higher rating was used as the surface quality rating for that artificial leather. In this invention, a good level is "A or B". A: The surface quality is very good. B: Good surface quality • C: Poor surface quality • D: Very poor surface quality.

[0107] [Example 1] First, sea-island composite fibers were melt-spun under the following conditions. • Island component: Polyethylene terephthalate with an intrinsic viscosity (IV value) of 0.73 (indicated as "PET" in Tables 1 and 2) • Marine component: Polystyrene with an MFR (measured using the test method specified in ISO 1133:1997) of 65 g / 10 min (indicated as "PS" in Tables 1 and 2) • Nozzle: Sea island type composite nozzle with 16 islands / hole Spinning temperature: 285℃ • Mass ratio of island areas to coastal areas: 55 / 45 • Discharge rate: 1.9g / (min / hole) Spinning speed: 1100 m / min Next, the obtained sea-island composite fibers were stretched to 3.4 times their original length, crimped using a press-type crimping machine, dried at 60°C, and then cut to a length of 51 mm to obtain raw sea-island composite fibers with a single fiber fineness of 6.1 dtex. The average single fiber diameter of the ultrafine fibers obtained from these sea-island composite fibers was 4.4 μm.

[0108] Using the raw cotton obtained as described above, a laminated web was formed through carding and cross-wrapping processes. The resulting web was sized at 2500 strands / cm².2 The needle-punched material has a weight of 540g / m². 2 Then, a fiber entanglement composite with a thickness of 2.4 mm was obtained.

[0109] The fibrous entanglement obtained as described above was subjected to shrinkage treatment with hot water at 96°C. Subsequently, an aqueous solution of polyvinyl alcohol (hereinafter sometimes abbreviated as PVA) with a concentration of 12% by mass and a degree of saponification of 88% was impregnated into the fibrous entanglement that had been shrunk with hot water. Furthermore, this was squeezed with a roll and dried for 10 minutes with hot air at a temperature of 120°C while migrating the PVA, thereby obtaining a PVA-coated sheet in which the mass of PVA relative to the mass of the sheet substrate was 25% by mass. The PVA-coated sheet thus obtained was immersed in trichloroethylene and subjected to mangle extraction and compression 10 times. This dissolved and removed the marine components and compressed the PVA-coated sheet, obtaining a PVA-coated sheet in which ultrafine fiber bundles coated with PVA were intertwined.

[0110] The PVA-coated sheet obtained as described above was immersed in a polyurethane dimethylformamide (DMF) solution, which was prepared to have a solid content concentration of 13% polyurethane as the main component. The desaturated PVA-coated sheet immersed in the polyurethane DMF solution was then squeezed with a roller. Next, this sheet was immersed in a 30% by mass DMF aqueous solution to solidify the polyurethane. Afterward, the PVA and DMF were removed with hot water, and the sheet was dried with hot air at 110°C for 10 minutes. This resulted in a polyurethane-coated sheet with a thickness of 1.8 mm and a polyurethane mass of 30% by mass relative to the mass of the artificial leather.

[0111] The polyurethane-coated sheets obtained through the above processes were cut in half so that each half had half the thickness. The surface of the cut surfaces was sanded to a thickness of 0.3 mm using 180-grit endless sandpaper to create a napped surface, resulting in a 0.6 mm thick napped sheet.

[0112] The pile sheet obtained as described above was dyed in a liquid jet dyeing machine at 120°C, and then dried in a dryer to obtain artificial leather with an average single fiber diameter of 4.4 μm, a movable amorphous content of 35%, and a crystallinity of 30%. The obtained artificial leather had excellent abrasion resistance, lightfastness, and color development, as well as an elegant surface quality. The results are shown in Table 1.

[0113] [Example 2] Artificial leather was obtained in the same manner as in Example 1, except that the MFR of the marine component was set to 10 g / 10 min. The movable amorphous content of the ultrafine fibers in the obtained artificial leather was 38%, and the degree of crystallinity was 25%. The artificial leather exhibited excellent abrasion resistance, lightfastness, and color development, as well as a beautiful surface quality. The results are shown in Table 1.

[0114] [Example 3] Artificial leather was obtained in the same manner as in Example 1, except that the intrinsic viscosity of the island component was set to 1.10. The movable amorphous content of the ultrafine fibers in the obtained artificial leather was 21%, and the degree of crystallinity was 35%. The artificial leather exhibited excellent abrasion resistance, lightfastness, and color development, as well as a beautiful surface quality. The results are shown in Table 1.

[0115] [Example 4] Artificial leather was obtained in the same manner as in Example 1, except that the MFR of the sea component was set to 10 g / 10 min and the intrinsic viscosity of the island component was set to 1.10. The movable amorphous content of the ultrafine fibers in the obtained artificial leather was 32%, and the degree of crystallinity was 28%. The artificial leather exhibited excellent abrasion resistance, lightfastness, and color development, as well as a beautiful surface quality. The results are shown in Table 1.

[0116] [Example 5] Artificial leather was obtained in the same manner as in Example 1, except that the discharge rate was 1.2 g / (min·Hole) and the stretching ratio was 2.1 times. The movable amorphous content of the ultrafine fibers in the obtained artificial leather was 39%, and the degree of crystallinity was 17%. Compared to the artificial leather of Example 1, this artificial leather was slightly inferior in abrasion resistance and surface quality, but it was superior in lightfastness and color development. The results are shown in Table 1.

[0117] [Example 6] Artificial leather was obtained in the same manner as in Example 1, except that the Mw / Mn ratio of the island component was set to 2.6. The movable amorphous content of the ultrafine fibers in the obtained artificial leather was 30%, and the degree of crystallinity was 25%. Compared to the artificial leather of Example 1, this artificial leather had slightly inferior abrasion resistance and color development, but it had excellent lightfastness and an elegant surface quality. The results are shown in Table 1.

[0118] [Example 7] Artificial leather was obtained in the same manner as in Example 1, except that the mass ratio of polymeric elastic material to artificial leather was set to 55%. The obtained artificial leather had slightly inferior surface quality compared to the artificial leather of Example 1, but it had superior abrasion resistance, lightfastness, and color development. The results are shown in Table 1.

[0119] [Example 8] Sea-island type composite fibers were melt-spun under the following conditions. • Island component polymer: Same as in Example 1 • Marine component polymer: Copolymerized PET obtained by copolymerizing 8 mol% sodium 5-sulfoisophthalate with an MFR of 80 g / 10 min (indicated as copolymerized PET in Table 1). • Nozzle: Sea island type composite nozzle with 16 islands / hole Spinning temperature: 285℃ • Mass ratio of island areas to coastal areas: 80 / 20 • Discharge rate: 1.6g / (min / hole) Spinning speed: 1100 m / min Next, the obtained sea-island composite fibers were stretched to 3.8 times their original length, crimped using a press-type crimping machine, and then cut to a length of 51 mm to obtain raw sea-island composite fibers with a single fiber fineness of 4.4 dtex. The average single fiber diameter of the ultrafine fibers obtained from these sea-island composite fibers was 4.4 μm.

[0120] Using the raw cotton obtained as described above, a laminated web was formed through carding and cross-wrapping processes. The resulting web had a density of 3500 strands / cm². 2 The needle punching process is performed with this number of punches, resulting in a basis weight of 700g / m². 2 Then, a fiber entanglement composite with a thickness of 3.0 mm was obtained.

[0121] The fibrous composite obtained as described above was subjected to shrinkage treatment with hot water at 98°C. Then, 20% by mass of sodium sulfate was added as a heat-sensitive coagulant to 100% by mass of polyurethane solids, and 3% by mass of a carbodiimide-based crosslinking agent was added. The composite was then impregnated with a water-dispersible polyurethane solution prepared by adding water to adjust the overall solid content to 12%, and dried with hot air at 160°C for 20 minutes to obtain a polyurethane-coated sheet with a thickness of 2.1 mm.

[0122] The polyurethane-coated sheet obtained as described above was immersed in an 8 g / L sodium hydroxide aqueous solution heated to 95°C for 5 minutes to remove the marine components of the sea-island type composite fiber. Afterward, it was washed in water for 30 minutes and dried in a 160°C dryer for 30 minutes to obtain a sheet (polyurethane-coated sheet) made of ultrafine fibers.

[0123] The polyurethane-coated sheets obtained through the above processes were cut in half so that each half had half the thickness, and then sanded with 180-grit endless sandpaper to create a napped surface, resulting in a napped sheet with a thickness of 0.75 mm.

[0124] The pile sheet obtained as described above was dyed in a liquid jet dyeing machine at 120°C, and then dried in a dryer to obtain artificial leather with an average single fiber diameter of 4.4 μm, a movable amorphous content of 17%, and a crystallinity of 34%. The obtained artificial leather had excellent abrasion resistance, lightfastness, and color development, as well as an elegant surface quality. The results are shown in Table 1.

[0125] [Example 9] Artificial leather was obtained in the same manner as in Example 8, except that the MFR of the marine component was set to 50 g / 10 min. The movable amorphous content of the ultrafine fibers in the obtained artificial leather was 25%, and the degree of crystallinity was 33%. The artificial leather exhibited excellent abrasion resistance, lightfastness, and color development, as well as a beautiful surface quality. The results are shown in Table 1.

[0126] [Comparative Example 1] Artificial leather was obtained in the same manner as in Example 1, except that the MFR of the marine component was set to 100 g / 10 min. The movable amorphous content of the ultrafine fibers in the obtained artificial leather was 15%, and the degree of crystallinity was 32%. The artificial leather had excellent abrasion resistance, lightfastness, and a beautiful surface quality, but poor color development, and was inferior to Example 1. The results are shown in Table 2.

[0127] [Comparative Example 2] Artificial leather was obtained in the same manner as in Example 1, except that the intrinsic viscosity of the island component was set to 0.60. The amount of movable amorphous material of the ultrafine fibers in the obtained artificial leather was 50%, and the degree of crystallinity was 17%. Although the artificial leather had excellent color development and a beautiful surface quality, it had poor abrasion resistance and light resistance, and was inferior to Example 1. The results are shown in Table 2.

[0128] [Comparative Example 3] Artificial leather was obtained in the same manner as in Example 1, except that the intrinsic viscosity of the island component was set to 1.30. The movable amorphous content of the ultrafine fibers in the obtained artificial leather was 14%, and the degree of crystallinity was 35%. The artificial leather had excellent abrasion resistance, lightfastness, and a beautiful surface quality, but it had poor color development and was inferior to Example 1. The results are shown in Table 2.

[0129] [Table 1]

[0130] [Table 2]

[0131] As shown in Tables 1 and 2, the artificial leathers of Examples 1 to 9 have a suitable degree of flexibility and restraint in their molecular chains because the amount of movable amorphous material of the ultrafine fibers constituting the artificial leather is controlled within a specific range. As a result, when the artificial leather made of these ultrafine fibers is dyed, the dye easily penetrates the ultrafine fibers, and dye degradation due to molecular chain severance is reduced. Consequently, the resulting artificial leather has excellent color development and lightfastness, as well as an elegant surface quality.

[0132] On the other hand, as shown in Comparative Examples 1 and 3, when the amount of movable amorphous material in the ultrafine fibers constituting the artificial leather is reduced, the rigidity of the ultrafine fibers is high, resulting in strong constraints on the molecular chains. This makes it difficult for the dye to penetrate the ultrafine fibers during the dyeing process, and consequently, the resulting artificial leather has poor color development.

[0133] Furthermore, as shown in Comparative Example 2, when the amount of movable amorphous material in the ultrafine fibers constituting the artificial leather is increased, the molecular chain constraint force of the ultrafine fibers weakens, making dye degradation due to molecular chain severance more likely, resulting in artificial leather with poor lightfastness.

Claims

1. An artificial leather comprising a fiber entanglement body composed of ultrafine fibers and a polymeric elastic material as constituent elements, The thermoplastic resin constituting the ultrafine fibers is polyethylene terephthalate. The ratio of the weight-average molecular weight Mw of the thermoplastic resin constituting the ultrafine fibers to the number-average molecular weight Mn (Mw / Mn) is 1.1 or more and 2.5 or less, and further, The movable amorphous content of the aforementioned ultrafine fibers is 20% or more and less than 40%. Artificial leather.

2. The artificial leather according to claim 1, wherein the degree of crystallinity of the ultrafine fibers is 20% or more and 40% or less.

3. The artificial leather according to claim 1 or 2, wherein the mass ratio of the polymeric elastic material to the artificial leather is 15% by mass or more and 50% by mass or less.

4. A method for manufacturing artificial leather according to any one of Claims 1 to 3, A process for producing a fiber entanglement composite mainly composed of sea-island type composite fibers, wherein the sea component is a thermoplastic resin with a melt flow rate of 1.0 g / 10 min or more and 90.0 g / 10 min or less, and the island component is a thermoplastic resin with an intrinsic viscosity of 0.7 or more and 1.2 or less; A step of removing marine components from the aforementioned fiber entanglement to produce ultrafine fibers having an average single fiber diameter of 0.1 μm or more and 10.0 μm or less, A step of imparting a polymeric elastic material, Includes, The aforementioned island component is polyethylene terephthalate, In the process of manufacturing the aforementioned fiber entanglement composite, the sea-island type composite fiber is stretched to a stretch ratio of 2.1 times or more and 4.0 times or less. A method for manufacturing artificial leather.

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