Synthetic leather

Abstract

To provide a synthetic leather that is excellent in feeling (touch, appearance, color, scent) and has improved peel strength between a skin layer and a base material.SOLUTION: An artificial leather has a base material, an adhesive layer including a first urethane resin, and a skin layer including a second urethane resin and cellulose substance. The first urethane resin is a cured material consisting of a main agent containing polyol composition (A) and a hardener containing isocyanate component (B). The polyol composition (A) includes polyol (a1) as constitutional unit. The polyol (a1) includes polyol (a1-1) with number average molecular weight of 1000 or less. Weight ratio of constitutional unit derived from the polyol (a1-1) with the number average molecular weight of 1000 or less in the constitutional unit derived from the polyol (a1) in the polyol composition (A) is 50 wt.% or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to synthetic leather. [Background technology]

[0002] A known synthetic leather is one in which a substrate and a resin layer are bonded together with an adhesive. For example, Patent Document 1 describes a synthetic leather having a substrate layer, a resin layer provided on the substrate layer, and an outermost layer provided on the resin layer. Patent Document 1 also describes that a polyurethane adhesive can be used to bond the substrate layer and the resin layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6267016 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional synthetic leathers have the problem of insufficient texture (feel, appearance, color, and scent). The inventors have conceived the idea of including a cellulose material such as wood in the resin layer (skin layer) in order to improve the texture (feel, appearance, color, and scent) of synthetic leather.

[0005] However, in synthetic leathers in which the resin layer (skin layer) contains a cellulose material such as wood, conventional adhesives have poor wettability with the resin layer (skin layer) containing the cellulose material, which can result in insufficient adhesion between the resin layer (skin layer) and the substrate.

[0006] The present invention has been made in view of the above-mentioned problems, and aims to provide a synthetic leather that has an excellent texture (feel, appearance, color, and scent) and improved peel strength between the surface layer and the substrate. [Means for solving the problem]

[0007] The present inventors have conducted extensive research to solve the above problems and have arrived at the present invention. Specifically, the present invention relates to synthetic leather comprising a substrate, an adhesive layer containing a first urethane resin, and a skin layer containing a second urethane resin and a cellulose substance, wherein the first urethane resin is a cured product of a main component containing a polyol composition (A) and a curing agent containing an isocyanate component (B), the polyol composition (A) contains polyol (a1) as a structural unit, and the polyol (a1) contains polyol (a1-1) having a number-average molecular weight of 1000 or less, and the weight proportion of the structural units derived from the polyol (a1) in the polyol composition (A) derived from the polyol (a1) having a number-average molecular weight of 1000 or less is 50 wt % or more. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide synthetic leather that has an excellent texture (feel, appearance, color, and scent) and an improved peel strength between the surface layer and the substrate. DETAILED DESCRIPTION OF THE INVENTION

[0009] The synthetic leather of the present invention comprises a substrate, an adhesive layer containing a first urethane resin, and a skin layer containing a second urethane resin and a cellulose material.

[0010] <Base material> The substrate is not particularly limited, and various materials can be used, including woven fabrics, knitted fabrics, nonwoven fabrics, felts, and raised fabrics made from natural fibers (such as wool, cotton, hemp, silk, or cellulose fibers), regenerated fibers (such as cupra, rayon, Polynosic, or Tencel fibers), semi-synthetic fibers (such as acetate, triacetate, or Promix fibers), synthetic fibers (such as nylon, aramid, vinylon, polyester, polyvinyl chloride, acrylic, polyethylene, polypropylene, polyurethane, or polylactic acid fibers), or mixed fibers of two or more of these; resin-treated fabrics in which resins (such as natural rubber, polyurethane, polyacrylic ester, polyester, polyvinyl alcohol, polyolefin, or polybutadiene resins) are attached to the above fibers; paper (such as plain paper, flame-retardant paper, paper cloth, or release paper); and plastic films (such as nylon, aramid, vinylon, polyester, polyvinyl chloride, acrylic, polyethylene, polypropylene, polycarbonate, polyurethane, or polylactic acid plastic films). In view of moisture absorption and release properties, natural fibers and regenerated fibers are preferred, in view of stretchability, knitted fabrics are preferred, and in view of ease of processing of cut surfaces, nonwoven fabrics are preferred.

[0011] <Adhesive layer> The adhesive layer contains a first urethane resin that is a cured product of a base agent containing a polyol composition (A) and a curing agent containing an isocyanate component (B). The adhesive layer may consist of only the first urethane resin.

[0012] <First urethane resin> The first urethane resin is a cured product of a base agent containing a polyol composition (A) and a curing agent containing an isocyanate component (B). The first urethane resin may be a cured product of a two-component polyurethane adhesive composition consisting of a base agent containing a polyol composition (A) and a curing agent containing an isocyanate component (B).

[0013] <Polyol composition (A)> The polyol composition (A) contains a polyol (a1) as a constituent unit.

[0014] For example, the polyol composition (A) may be composed of a hydroxyl-terminated polyurethane prepolymer containing the polyol (a1) as a constituent unit. When the polyol composition (A) is composed of a hydroxyl-terminated polyurethane prepolymer containing the polyol (a1) as a constituent unit, the hydroxyl-terminated polyurethane prepolymer may be a reaction product of the polyol (a1) and the polyisocyanate (b1).

[0015] The polyol (a1) includes a polyol (a1-1) having a number average molecular weight (hereinafter abbreviated as Mn) of 1,000 or less. The polyol (a1) may also include a polyol (a1-2) having a molecular weight of 200 or less. The polyol (a1-2) having a molecular weight of 200 or less is included in the polyol (a1-1) having an Mn of 1,000 or less.

[0016] Mn can be measured by gel permeation chromatography (GPC), for example, under the following conditions. Apparatus: Waters Alliance 2695, Waters Corporation Column: Guardcolumn Super HL (1 column), TSKgel SuperH2000, TSKgel SuperH3000, TSKgel SuperH4000 (all Tosoh Corporation) connected together Sample solution: 0.25% by weight tetrahydrofuran solution Solution injection volume: 10μl Flow rate: 0.6ml / min Measurement temperature: 40℃ Detector: Refractive index detector Reference material: Standard polyethylene glycol

[0017] As the polyol (a1-1) having an Mn of 1000 or less, polyols (a1-2), polyester polyols (a11), polyether polyols (a12), polyether ester polyols (a13), castor oil fatty acid esters (a14), etc. having a molecular weight of 200 or less can be used. The polyol (a1-1) having an Mn of 1000 or less may be one type or a mixture of two or more types.

[0018] Examples of the polyol (a1-2) having a molecular weight of 200 or less include aliphatic diols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, 3-methyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, and 2-methyl-1,3-propanediol; alicyclic diols such as 1,4-cyclohexanediol and 1,4-cyclohexanedimethanol; and tri- or higher functional hydroxyl group-containing compounds such as glycerin, trimethylolpropane, and pentaerythritol.

[0019] The polyester polyol (a11) includes a condensation type polyester polyol (a111), a polylactone polyol (a112) and a polycarbonate polyol (a113).

[0020] Examples of the condensation type polyester polyol (a111) include those obtained by condensing a polyol (a1-2) having a molecular weight of 200 or less with a polycarboxylic acid having 2 to 20 carbon atoms, and its acid anhydride, lower (carbon number 1 to 4) alkyl ester, acid halide, etc.

[0021] Examples of polycarboxylic acids having 2 to 20 carbon atoms, and their acid anhydrides, lower (1 to 4 carbon atoms) alkyl esters and acid halides include aliphatic dicarboxylic acids (succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, octadecanedicarboxylic acid, decylsuccinic acid, fumaric acid, maleic acid, etc.), alicyclic dicarboxylic acids (dimer acid, etc.), aromatic dicarboxylic acids (terephthalic acid, isophthalic acid, phthalic acid, t-butylisophthalic acid, 2,6-naphthalenedicarboxylic acid, 2,5-furandicarboxylic acid, 4,4'-biphenyldicarboxylic acid, etc.), trivalent or higher polycarboxylic acids (trimellitic acid, pyromellitic acid, etc.), anhydrides thereof (succinic anhydride, maleic anhydride, phthalic anhydride, trimellitic anhydride, etc.), acid halides thereof (adipic acid dichloride, etc.), and low-molecular-weight alkyl esters thereof (dimethyl succinate, dimethyl phthalate, etc.). The polycarboxylic acid may be one kind or a mixture of two or more kinds. Among these, aliphatic dicarboxylic acids, alicyclic dicarboxylic acids and aromatic dicarboxylic acids are preferred, and succinic acid, adipic acid, 2,5-furandicarboxylic acid, sebacic acid and dimer acid are more preferred.

[0022] Examples of the polylactone polyol (a112) include those obtained by ring-opening polymerization of lactone monomers having 3 to 12 carbon atoms (such as β-propiolactone, γ-butyrolactone, γ-valerolactone, ε-caprolactone, η-caprylolactone, 11-undecanolactone, and 12-tridecanoid) using polyhydric alcohols having 2 to 20 carbon atoms as an initiator. The lactone monomers may be one type or a mixture of two or more types.

[0023] Examples of the polycarbonate polyol (a113) include polycarbonate polyols produced by condensing one or more polyhydric alcohols having 2 to 20 carbon atoms (preferably aliphatic dihydric alcohols) with a low molecular weight carbonate (such as a dialkyl carbonate in which the alkyl group has 1 to 6 carbon atoms, an alkylene carbonate having an alkylene group of 2 to 6 carbon atoms, or a diaryl carbonate having an aryl group of 6 to 9 carbon atoms) while causing a dealcoholization reaction. The low molecular weight carbonate may be one type or a mixture of two or more types. As the polycarbonate polyol (a113), commercially available products may be used, such as Benebiol NL1030DB (manufactured by Mitsubishi Chemical Corporation).

[0024] The polyether polyol (a12) includes a compound in which an alkylene oxide (hereinafter abbreviated as AO) having 2 to 8 carbon atoms is added to a polyol (a1-2) having a molecular weight of 200 or less. The AO may be one type or a mixture of two or more types. When two or more types are mixed, the AO may be in a block form, a random form, or a mixture thereof.

[0025] Examples of AOs having 2 to 8 carbon atoms include ethylene oxide, 1,2- or 1,3-propylene oxide, 1,2-, 1,3- or 2,3-butylene oxide, tetrahydrofuran, 3-methyltetrahydrofuran, styrene oxide, α-olefin oxide, and epichlorohydrin.

[0026] Examples of the polyether polyol (a12) include ethylene oxide adducts of polyols, propylene oxide adducts of polyols, tetrahydrofuran adducts of polyols, 3-methyltetrahydrofuran adducts of polyols, tetrahydrofuran / ethylene oxide block copolymers of polyols, and tetrahydrofuran / 3-methyltetrahydrofuran random copolymers of polyols. Examples of the polyether polyol (a12) also include polyethylene glycol, polypropylene glycol, polytrimethylene glycol (also called polytrimethylene ether glycol), polytetramethylene glycol (also called polytetramethylene ether glycol), etc.

[0027] The polyether polyol (a12) may be a nitrogen-containing polyether polyol, such as Sannix NP-300 (manufactured by Sanyo Chemical Industries, Ltd.).

[0028] Examples of the polyether ester polyol (a13) include those obtained by condensation polymerization of one or more polyether polyols (a12) with one or more polycarboxylic acids having 2 to 20 carbon atoms, or their acid anhydrides, lower (1 to 4 carbon atoms) alkyl esters, or acid halides.

[0029] Examples of the castor oil fatty acid ester (a14) include castor oil (such as glycerin triester); polyester polyols of castor oil fatty acids (such as ricinoleic acid) and polyhydric alcohols having 2 to 20 carbon atoms (such as mono- or diglycerides of castor oil fatty acids, mono-, di-, or triesters of castor oil fatty acids and trimethylolpropane, and mono- or diesters of castor oil fatty acids and polyoxypropylene glycol); castor oil to which an AO having 2 to 8 carbon atoms has been added; and mixtures of two or more of these.

[0030] In the present invention, of the structural units derived from the polyol (a1) in the polyol composition (A), the weight proportion of structural units derived from the polyol (a1-1) having a number average molecular weight of 1000 or less is 50% by weight or more.

[0031] The weight proportion of structural units derived from polyol (a1-1) having a number average molecular weight of 1,000 or less means a weight proportion including the weight proportion of structural units derived from polyol (a1-2) having a molecular weight of 200 or less, which will be described later.

[0032] When the weight proportion of structural units derived from polyol (a1-1) having a number average molecular weight of 1,000 or less among the structural units derived from polyol (a1) in polyol composition (A) is 50% by weight or more, the peel strength between the surface layer of synthetic leather and the substrate can be improved.

[0033] For example, if the weight proportion of structural units derived from polyol (a1-1) having a number-average molecular weight of 1,000 or less among the structural units derived from polyol (a1) in polyol composition (A) is less than 50% by weight, polyol composition (A) is likely to crystallize (solidify) in the two-component polyurethane adhesive composition that becomes the first urethane resin after curing. As a result, when used to bond a wood-containing surface layer to a substrate, the wettability with the surface layer may be poor, potentially reducing the peel strength between the surface layer and the substrate. The synthetic leather of the present invention can solve these problems and thereby improve the peel strength between the surface layer and the substrate.

[0034] Of the structural units derived from the polyol (a1) in the polyol composition (A), the weight proportion of structural units derived from the polyol (a1-1) having a number average molecular weight of 1,000 or less is preferably 70% by weight or more, and more preferably 100% by weight.

[0035] From the viewpoint of rebound resilience, it is preferable that the polyol (a1-1) having a number average molecular weight of 1000 or less contains a polyether polyol (a12) having a number average molecular weight of 1000 or less, and from the viewpoint of rebound resilience, it is preferable that the polyether polyol (a12) having a number average molecular weight of 1000 or less is polytetramethylene glycol or polytrimethylene glycol.

[0036] Furthermore, from the viewpoint of improving the peel strength when the two-component polyurethane adhesive composition is used as an adhesive layer for synthetic leather, the weight proportion of structural units derived from polyol (a1-2) having a molecular weight of 200 or less among the structural units derived from polyol (a1) in polyol composition (A) is preferably 3 wt % or less, and more preferably 1 wt % or less.

[0037] The polyol composition (A) may not contain any structural units derived from a polyol (a1-2) having a molecular weight of not more than 200. In other words, the weight proportion of structural units derived from a polyol (a1-2) having a molecular weight of not more than 200 among the structural units derived from the polyol (a1) in the polyol composition (A) may be 0% by weight.

[0038] Alternatively, the polyol composition (A) may contain structural units derived from a polyol (a1-2) having a molecular weight of 200 or less, and the weight proportion of structural units derived from the polyol (a1-2) having a molecular weight of 200 or less among the structural units derived from the polyol (a1) in the polyol composition (A) may be 3 wt % or less.

[0039] From the viewpoint of peel strength, the polyol (a1-2) having a molecular weight of 200 or less may be trimethylolpropane. The polyol composition (A) may contain structural units derived from trimethylolpropane as the polyol (a1-2) having a molecular weight of 200 or less, and the weight proportion of trimethylolpropane among the structural units derived from the polyol (a1) in the polyol composition (A) may be 3 wt % or less.

[0040] The polyol (a1) may contain a polyol (a1-3) having an Mn of greater than 1000. Examples of the polyol (a1-3) having an Mn of greater than 1000 include the above-mentioned polyester polyols (a11), polyether polyols (a12), polyether ester polyols (a13) and castor oil fatty acid esters (a14) each having an Mn of greater than 1000.

[0041] Examples of polyisocyanates (b1) include aromatic polyisocyanates (b11) having 8 to 26 carbon atoms, aliphatic polyisocyanates (b12) having 4 to 22 carbon atoms, alicyclic polyisocyanates (b13) having 8 to 18 carbon atoms, araliphatic polyisocyanates (b14) having 10 to 18 carbon atoms, and modified products (b15) of these organic isocyanates. These polyisocyanates have 2 to 3 isocyanate groups. The polyisocyanate (b1) may be one type or a mixture of two or more types. In the case of a mixture of two or more types of polyisocyanates (b1), it is preferable to use a mixture of polyisocyanates from the same family, since the reactivities of aromatic polyisocyanates, araliphatic polyisocyanates, and aliphatic polyisocyanates generally differ greatly.

[0042] Examples of the aromatic polyisocyanate (b11) having 8 to 26 carbon atoms include 1,3- or 1,4-phenylene diisocyanate, 2,4- or 2,6-tolylene diisocyanate (hereinafter, tolylene diisocyanate will be abbreviated as TDI), crude TDI, 4,4'- or 2,4'-diphenylmethane diisocyanate (hereinafter, diphenylmethane diisocyanate will be abbreviated as MDI), crude MDI, 4,4'-diisocyanatobiphenyl, 3,3'-dimethyl-4,4'-diisocyanatobiphenyl, 3,3'-dimethyl-4,4'-diisocyanatodiphenylmethane, 1,5-naphthylene diisocyanate, 4,4',4"-triphenylmethane triisocyanate, and m- or p-isocyanatophenylsulfonyl isocyanate.

[0043] Examples of the aliphatic polyisocyanate (b12) having 4 to 22 carbon atoms include ethylene diisocyanate, tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate, hexamethylene diisocyanate (hereinafter abbreviated as HDI), dodecamethylene diisocyanate, 1,6,11-undecane triisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2,6-diisocyanatomethyl caproate, bis(2-isocyanatoethyl) fumarate, bis(2-isocyanatoethyl) carbonate, and 2-isocyanatoethyl-2,6-diisocyanatohexanoate.

[0044] Examples of the alicyclic polyisocyanate (b13) having 8 to 18 carbon atoms include isophorone diisocyanate (hereinafter abbreviated as IPDI), 4,4'-dicyclohexylmethane diisocyanate (hereinafter abbreviated as hydrogenated MDI), cyclohexylene diisocyanate, methylcyclohexylene diisocyanate, bis(2-isocyanatoethyl)-4-cyclohexene-1,2-dicarboxylate, and 2,5- or 2,6-norbornane diisocyanate.

[0045] Examples of the aralkyl polyisocyanate (b14) having 10 to 18 carbon atoms include m- or p-xylylene diisocyanate and α,α,α',α'-tetramethylxylylene diisocyanate.

[0046] Examples of the modified products (b15) of these organic isocyanates include urethane-modified products, carbodiimide-modified products, allophanate-modified products, urea-modified products, biuret-modified products, uretdione-modified products, uretoimine-modified products, isocyanurate-modified products, and oxazolidone-modified products of the polyisocyanates (b11) to (b14) {modified MDI (urethane-modified MDI, carbodiimide-modified MDI, trihydrocarbyl phosphate-modified MDI, etc.), urethane-modified TDI, biuret-modified products of HDI, isocyanurate-modified products of HDI, isocyanurate-modified products of IPDI, etc.}.

[0047] Among these, from the viewpoint of impact resilience, the polyisocyanate (b1) is preferably an aromatic polyisocyanate, more preferably MDI.

[0048] When the polyol composition (A) is composed of a hydroxyl group-terminated polyurethane prepolymer, the equivalent ratio (NCO / OH) of the isocyanate groups contained in the polyisocyanate (b1) to the hydroxyl groups contained in the polyol (a1) is preferably 0.5 to 0.8, more preferably 0.55 to 0.78, and particularly preferably 0.6 to 0.75, from the viewpoints of transparency and viscosity at 0°C. The number average molecular weight of the hydroxyl group-terminated polyurethane prepolymer is preferably 1,000 to 20,000, more preferably 1,500 to 15,000, and particularly preferably 2,000 to 10,000, from the viewpoint of the strength and adhesive power of the resulting adhesive layer.

[0049] The hydroxyl group-terminated polyurethane prepolymer can be obtained by reacting the polyol (a1) with the polyisocyanate (b1) by a general method. The hydroxyl-terminated polyurethane prepolymer of the present invention can be produced, for example, by reacting polyol (a1) with polyisocyanate (b1) in the presence or absence of a solvent (toluene, xylene, ethyl acetate, butyl acetate, N,N-dimethylformamide, acetone, methyl ethyl ketone, tetrahydrofuran, etc.). The hydroxyl-terminated polyurethane prepolymer can be produced by increasing the ratio of the hydroxyl group equivalents of polyol (a1) to the isocyanate group equivalents of polyisocyanate (b1) (preferably by adjusting the ratio within the above-mentioned range of the equivalent ratio of the isocyanate groups contained in polyisocyanate (b1) to the hydroxyl groups contained in polyol (a1)).

[0050] For the reaction, a known reaction apparatus (such as a mixing tank equipped with a stirrer or a static mixer) can be used. The reaction temperature is preferably 10 to 160°C, more preferably 25 to 120°C, from the viewpoints of reactivity and suppression of thermal degradation, and the gas phase is preferably substituted with nitrogen from the viewpoint of stability.

[0051] The polyol composition (A) may contain components other than the hydroxyl group-terminated polyurethane prepolymer, and the polyol composition (A) may be a mixture of the hydroxyl group-terminated polyurethane prepolymer and unreacted polyol (a1).

[0052] The polyol composition (A) may contain an organic solvent. When the polyol composition (A) contains a hydroxyl group-terminated polyurethane prepolymer, the polyol composition (A) may contain the organic solvent used in producing the hydroxyl group-terminated polyurethane prepolymer.

[0053] Examples of the organic solvent include toluene, xylene, ethyl acetate, butyl acetate, N,N-dimethylformamide, acetone, methyl ethyl ketone, and tetrahydrofuran.

[0054] From the viewpoint of environmental load, the content of the organic solvent in the polyol composition (A) may be 60% by weight or less based on the content of the polyol composition (A).

[0055] The polyol composition (A) may further contain additives such as a tackifier, antioxidant, ultraviolet absorber, plasticizer, filler, pigment, and light stabilizer, as described below, within the range that does not impair the effects of the present invention. When the polyol composition (A) contains a hydroxyl group-terminated polyurethane prepolymer, the polyol composition (A) may also contain additives used in producing the hydroxyl group-terminated polyurethane prepolymer.

[0056] The hydroxyl value of the polyol composition (A) and the hydroxyl-terminated polyurethane prepolymer is preferably 5 to 60 mgKOH / g, more preferably 10 to 50 mgKOH / g, and particularly preferably 15 to 40 mgKOH / g, from the viewpoint of peel strength. The hydroxyl value is the number of milligrams of potassium hydroxide required to neutralize acetic acid bonded to hydroxyl groups when 1 g of a sample is acetylated, and is measured by the method described in "JIS K 1557-1 Plastics - Test methods for polyurethane raw material polyols - Part 1: Determination of hydroxyl value."

[0057] From the viewpoint of handleability, the viscosity of the polyol composition (A) at 25°C is preferably 1,500 to 20,000 mPa·s, more preferably 1,600 to 8,000 mPa·s, and particularly preferably 1,700 to 5,000 mPa·s. The viscosity in the present invention is a value measured in accordance with JIS Z8803:2011, "9 Viscosity measurement method using a single cylindrical rotational viscometer" (for example, measurement is performed using a Brookfield viscometer at 6 rpm, 1 minute after the rotor starts to rotate).

[0058] <Curing agent> The curing agent in the present invention contains an isocyanate component (B).

[0059] Examples of the isocyanate component (B) include the above-mentioned aromatic polyisocyanates (b11) having 8 to 26 carbon atoms, aliphatic polyisocyanates (b12) having 4 to 22 carbon atoms, alicyclic polyisocyanates (b13) having 8 to 18 carbon atoms, araliphatic polyisocyanates (b14) having 10 to 18 carbon atoms, and modified products (b15) of these organic isocyanates.

[0060] Alternatively, the isocyanate component (B) may be an isocyanate group-terminated polyurethane prepolymer, which has an isocyanate group at its terminal.

[0061] The isocyanate group-terminated polyurethane prepolymer may be a reaction product of an active hydrogen component and an organic isocyanate component, or may be a reaction product of the above-mentioned polyol (a1) and the above-mentioned polyisocyanate (b1).

[0062] When the isocyanate component (B) is composed of an isocyanate group-terminated polyurethane prepolymer, the equivalent ratio (NCO / OH) of the isocyanate groups contained in the polyisocyanate (b1) to the hydroxyl groups contained in the polyol (a1) is preferably 1.1 to 50, more preferably 1.5 to 30, and particularly preferably 2 to 10, from the viewpoint of peel strength. The number average molecular weight of the isocyanate group-terminated polyurethane prepolymer is preferably 300 to 10,000, more preferably 400 to 5,000, and particularly preferably 500 to 1,000, from the viewpoint of peel strength. The isocyanate group-terminated polyurethane prepolymer is preferably bifunctional (that is, a compound in which 1 mole of the isocyanate group-terminated polyurethane prepolymer has 2 moles of isocyanate groups). The isocyanate group content of the isocyanate group-terminated polyurethane prepolymer is preferably 1 to 40% by weight, more preferably 5 to 30% by weight, based on the weight of the isocyanate group-terminated polyurethane prepolymer. The isocyanate group content is measured in accordance with JIS K7301-1995, 6.3 Isocyanate group content.

[0063] The isocyanate group-terminated polyurethane prepolymer can be obtained by reacting the polyol (a1) with the polyisocyanate (b1) by a general method. The isocyanate-terminated polyurethane prepolymer of the present invention can be produced, for example, by reacting polyol (a1) with polyisocyanate (b1) in the presence or absence of a solvent (toluene, xylene, ethyl acetate, butyl acetate, N,N-dimethylformamide, acetone, methyl ethyl ketone, tetrahydrofuran, etc.). The isocyanate-terminated polyurethane prepolymer can be produced by reducing the ratio of the hydroxyl group equivalents of polyol (a1) to the isocyanate group equivalents of polyisocyanate (b1) (preferably by adjusting the ratio within the above-mentioned range of the equivalent ratio of the isocyanate groups contained in polyisocyanate (b1) to the hydroxyl groups contained in polyol (a1)).

[0064] <First urethane resin> As described above, the first urethane resin is a cured product of a base agent containing the polyol composition (A) and a curing agent containing the isocyanate component (B). The first urethane resin may be a cured product of a two-component polyurethane adhesive composition consisting of a base agent containing the polyol composition (A) and a curing agent containing the isocyanate component (B).

[0065] In the two-component polyurethane adhesive composition, from the viewpoint of environmental impact, the content of the organic solvent is preferably 60 wt % or less, more preferably 50 wt % or less, and particularly preferably 35 wt % or less, based on the weight of the two-component polyurethane adhesive composition. In the two-component polyurethane adhesive composition, the content of the organic solvent may be 10 wt % or more, or may be 20 wt % or more, based on the weight of the two-component polyurethane adhesive composition.

[0066] The two-component polyurethane adhesive composition may further contain additives such as tackifiers, antioxidants, UV absorbers, plasticizers, fillers, pigments, and light stabilizers, provided that the effects of the present invention are not impaired. The above additives may be added to either the base resin and / or the curing agent, but additives that react with the isocyanate component are preferably added to the base resin. The amount of each additive used below is expressed in weight percent relative to 100% by weight, the total weight of the base resin and curing agent excluding the weight of the additive.

[0067] Examples of tackifiers include terpene resins, terpene phenol resins, phenol resins, aromatic hydrocarbon-modified terpene resins, rosin resins, modified rosin resins, synthetic petroleum resins (aliphatic, aromatic, or alicyclic synthetic petroleum resins, etc.), coumarone-indene resins, xylene resins, styrene-based resins, dicyclopentadiene resins, and hydrogenated products of those having hydrogenatable unsaturated double bonds among these. One tackifier may be used alone, or two or more may be used in combination. Of these, those having an acid value and / or a hydroxyl value are preferred from the viewpoint of adhesive strength, with rosin resin, phenol resin, terpene phenol resin, xylene resin and hydrogenated products thereof being more preferred, and terpene phenol resin and hydrogenated products thereof being particularly preferred.

[0068] The amount of tackifier used is preferably 100% by weight or less, more preferably 1 to 50% by weight, particularly preferably 3 to 40% by weight, particularly preferably 5 to 35% by weight, and most preferably 10 to 30% by weight, based on the total weight of the base agent and curing agent, from the viewpoint of the adhesive strength and heat resistance of the adhesive.

[0069] Examples of antioxidants include hindered phenol compounds (e.g., triethylene glycol bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate], pentaerythrityl tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 2,2-thiodiethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]) and phosphite compounds (e.g., tris(2,4-di-t-butylphenyl)phosphite, 2,2-methylenebis(4,6-di-t-butylphenyl)octylphosphite, bis(2,6-di-t-butylphenyl)pentaerythritol diphosphite, tetrakis(2,4-di-t-butylphenyl)4,4'-biphenylene diphosphonite). These antioxidants may be used alone or in combination. The amount of antioxidant used is preferably 5% by weight or less, more preferably 0.05 to 1% by weight, based on the total weight of the base agent and curing agent, from the viewpoint of antioxidant effect and adhesive strength of the adhesive.

[0070] UV absorbers include salicylic acid derivatives (phenyl salicylate, p-octylphenyl salicylate, p-tert-butylphenyl salicylate, etc.), benzophenone compounds (2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxy-5-sulfobenzophenone, 2-hydroxy-4-methoxy-2'-carboxybenzophenone, , 2-hydroxy-4-methoxy-5-sulfobenzophenone trihydrate, 2-hydroxy-4-n-octoxybenzophenone, 2-hydroxy-4-octadecyloxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 4-dodecyloxy-2-hydroxybenzophenone, 2-hydroxy-4-(2-hydroxy-3-methacryloxy)propoxybenzophenone, bis(2-methoxy-4-hydroxy-5-benzoylphenyl)methane, etc.], benzotriazole compounds {2-(2'-hydroxy- 5'-methyl-phenyl)benzotriazole, 2-(2'-hydroxy-3',5'-di-t-butyl-phenyl)benzotriazole, 2-(2'-hydroxy-3'-t-butyl-5'-methyl-phenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-t-butyl-phenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-4'-n-octoxyphenyl)benzotriazole, 2-(2'-hydroxy-5'-t-butylphenyl)benzotriazole, 2-(2'-hydroxy Examples of the ultraviolet absorber include 2-[2'-hydroxy-3'-(3",4",5",6"-tetrahydrophthalimidomethyl)-5'-methylphenyl]benzotriazole, 2,2-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol], and cyanoacrylate compounds (2-ethylhexyl-2-cyano-3,3'-diphenylacrylate, ethyl-2-cyano-3,3'-diphenylacrylate, and the like). One type of ultraviolet absorber may be used alone, or two or more types may be used in combination.The amount of the ultraviolet absorber used is preferably 5% by weight or less, more preferably 0.1 to 1% by weight, based on the total weight of the base agent and curing agent, from the viewpoint of the ultraviolet absorbing effect and the adhesive strength of the adhesive.

[0071] Plasticizers include hydrocarbons [process oil, liquid polybutadiene, liquid polyisobutylene, liquid polyisoprene, liquid paraffin, chlorinated paraffin, paraffin wax, copolymers of ethylene and α-olefins (carbon number 3-20) (weight ratio 99.9 / 0.1-0.1 / 99.9) oligomers (weight average molecular weight Mw 5,000-100,000), copolymers of propylene and α-olefins (carbon number 4-20) excluding ethylene (weight ratio 99.9 / 0.1-0.1 / 99.9) oligomers (weight average molecular weight Mw 5,000-100,000)]; chlorinated Examples of suitable plasticizers include paraffin; esters (phthalates [diethyl phthalate (DEP), dibutyl phthalate (DBP), di-2-ethylhexyl phthalate (DOP), didecyl phthalate, dilauryl phthalate, distearyl phthalate, diisononyl phthalate, etc.], adipates [di(2-ethylhexyl)adipate (DOA), dioctyl adipate, etc.], and sebacates (dioctyl sebacate, etc.)]; animal and vegetable oils and fats (linoleic acid, linolenic acid, etc.); and hydrogenated versions of those containing hydrogenatable unsaturated double bonds. One type of plasticizer may be used alone, or two or more types may be used in combination. The amount of plasticizer used is preferably 100% by weight or less, more preferably 0.5 to 30% by weight, based on the total weight of the base agent and curing agent, from the viewpoint of the adhesive strength and cohesive strength of the adhesive.

[0072] Examples of fillers include carbonates (magnesium carbonate, calcium carbonate, etc.), sulfates (aluminum sulfate, calcium sulfate, barium sulfate, etc.), sulfites (calcium sulfite, etc.), molybdenum disulfide, silicates (aluminum silicate, calcium silicate, etc.), diatomaceous earth, silica powder, talc, silica, and zeolite. The fillers are preferably fine particles having a volume average particle size of about 0.01 to 5 μm, and one type may be used alone, or two or more types may be used in combination. The amount of filler used is preferably 250% by weight or less, more preferably 0.5 to 100% by weight, based on the total weight of the base agent and curing agent, from the perspective of the cohesive strength of the adhesive.

[0073] Examples of pigments include inorganic pigments (alumina white, graphite, titanium oxide, ultrafine titanium oxide, zinc oxide, black iron oxide, micaceous iron oxide, white lead, white carbon, molybdenum white, carbon black, litharge, lithopone, baryte, cadmium red, cadmium mercury red, red iron oxide, molybdenum red, red lead, yellow lead, cadmium yellow, barium yellow, strontium yellow, titanium yellow, titanium black, chromium oxide green, cobalt oxide, cobalt green, cobalt-chromium green, ultramarine, Prussian blue, cobalt blue, cerulean blue, manganese purple, and cobalt purple), and organic pigments (shellac, insoluble azo pigments, soluble azo pigments, condensed azo pigments, phthalocyanine blue, and dye lake). The pigments are preferably fine particles with a volume average particle size of about 0.01 to 5 μm, and may be used alone or in combination of two or more. The amount of pigment used is preferably 250% by weight or less, more preferably 0.1 to 50% by weight, based on the total weight of the base agent and curing agent, from the viewpoint of the cohesive strength of the adhesive.

[0074] Examples of the light stabilizer include hindered amine light stabilizers, such as Tinuvin PA 144 (manufactured by BASF Japan Ltd.).

[0075] The equivalent ratio (NCO / OH) of isocyanate groups to hydroxyl groups in the two-component polyurethane adhesive composition is preferably 1.0 to 4.0, more preferably 1.2 to 3.5, and particularly preferably 1.5 to 3.0.

[0076] The cured product of the two-component polyurethane adhesive composition can be produced by any known method for producing a cured product of a two-component polyurethane adhesive composition, such as a method of reacting the base agent with the curing agent in the presence or absence of a solvent (toluene, xylene, ethyl acetate, butyl acetate, N,N-dimethylformamide, acetone, methyl ethyl ketone, tetrahydrofuran, etc.). For the reaction, a known reaction apparatus (such as a mixing tank equipped with a stirrer or a static mixer) can be used. The reaction temperature is preferably 10 to 160°C, more preferably 25 to 120°C, from the viewpoints of reactivity and suppression of thermal degradation, and the gas phase is preferably substituted with nitrogen from the viewpoint of stability.

[0077] The base agent and / or hardener may or may not contain a cellulose material. That is, in the synthetic leather of the present invention, the adhesive layer may or may not contain a cellulose material. Cellulose materials that can be contained in the adhesive layer include those described below as cellulose materials contained in the skin layer.

[0078] When the adhesive layer contains a cellulose substance, the cellulose substance may be blended into the base agent or the hardener. When the adhesive layer contains a cellulose substance, the cellulose substance contained in the adhesive layer and the cellulose substance contained in the skin layer may be the same or different.

[0079] <Epidermal layer> The skin layer includes a second urethane resin and a cellulose material. The skin layer may be a dried film obtained by solidifying a resin composition including the second urethane resin and a cellulose material.

[0080] <Second urethane resin> The second urethane resin comprises an active hydrogen component, an organic isocyanate component, and optionally a chain-extending component as constituent units. That is, the second urethane resin comprises an active hydrogen component, an organic isocyanate component, and a chain-extending component as constituent units, or an active hydrogen component and an organic isocyanate component as constituent units.

[0081] The active hydrogen component is not limited as long as it is a compound having an active hydrogen atom, for example, the active hydrogen atom includes the above-mentioned polyol (a1), the active hydrogen compound having an ionic group (a2), and the monoalcohol or monoamine (a3).

[0082] The active hydrogen compound (a2) having an ionic group includes an active hydrogen compound (a21) having an anionic group and an active hydrogen compound (a22) having a cationic group. The compound (a23) having an ionic group may be one type or a mixture of two or more types.

[0083] Examples of the active hydrogen compound (a21) having an anionic group include hydroxycarboxylic acids having 2 to 10 carbon atoms {dialkylolalkanoic acids (2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, 2,2-dimethylolheptanoic acid, and 2,2-dimethyloloctanoic acid), tartaric acid, and amino acids (glycine, alanine, valine, and the like)}; hydroxysulfonic acids having 2 to 16 carbon atoms {3-(2,3-dihydroxypropoxy)-1-propanesulfonic acid, sulfoisophthalic acid di(ethylene glycol) ester, and the like}; hydroxysulfamic acids having 2 to 10 carbon atoms {N,N-bis(2-hydroxyethyl)sulfamic acid, and the like}; and salts thereof neutralized with a base.

[0084] Examples of the base include ammonia, amines having 1 to 6 carbon atoms, and alkali metal hydroxides (sodium hydroxide, potassium hydroxide, lithium hydroxide, etc.). Examples of the amines having 1 to 6 carbon atoms include primary amines (monomethylamine, monoethylamine, monobutylamine, monoethanolamine, etc.); secondary amines (dimethylamine, diethylamine, dibutylamine, diethanolamine, diisopropanolamine, methylpropanolamine, etc.); and tertiary amines (trimethylamine, triethylamine, dimethylethylamine, dimethylmonoethanolamine, triethanolamine, etc.). Of these, from the viewpoints of the drying properties of the resin composition and the water resistance of the dried film, ammonia and amines are preferred, more preferably ammonia, monomethylamine, monoethylamine, dimethylamine, diethylamine, trimethylamine, triethylamine, and dimethylethylamine, and particularly preferably triethylamine.

[0085] Among the active hydrogen compounds (a21) having an anionic group, 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, and salts thereof are preferred from the viewpoint of texture and durability, and ammonium salts or amine salts of 2,2-dimethylolpropionic acid or 2,2-dimethylolbutanoic acid are more preferred.

[0086] Examples of the active hydrogen compound (a22) having a cationic group include tertiary amino alcohols having 1 to 20 carbon atoms {N-alkyldialkanolamines (N-methyldiethanolamine, N-propyldiethanolamine, N-butyldiethanolamine, N-methyldipropanolamine, etc.) and N,N-dialkylmonoalkanolamines (N,N-dimethylethanolamine, etc.)} and salts thereof neutralized with an acid or a quaternizing agent.

[0087] Examples of acids include monocarboxylic acids having 1 to 10 carbon atoms (formic acid, acetic acid, propanoic acid, etc.) and carbonic acid. Examples of quaternizing agents include dimethyl carbonate, dimethyl sulfate, methyl chloride, and benzyl chloride. Of these, from the viewpoint of the drying properties of the resin composition and the water resistance of the dried film, acids are preferred, more preferably monocarboxylic acids having 1 to 10 carbon atoms and carbonic acid, particularly preferably formic acid and carbonic acid, and most preferably carbonic acid.

[0088] Examples of the monoalcohol or monoamine (a3) include monoalcohols having 1 to 20 carbon atoms (e.g., methanol, ethanol, butanol, octanol, decanol, dodecyl alcohol, myristyl alcohol, cetyl alcohol, and stearyl alcohol); and monoamines having 1 to 20 carbon atoms (e.g., mono- or di-alkylamines such as monomethylamine, monoethylamine, monobutylamine, dibutylamine, and monooctylamine; and mono- or di-alkanolamines such as monoethanolamine, diethanolamine, and diisopropanolamine).

[0089] Examples of the organic isocyanate component include the aromatic polyisocyanates (b11) having 8 to 26 carbon atoms, aliphatic polyisocyanates (b12) having 4 to 22 carbon atoms, alicyclic polyisocyanates (b13) having 8 to 18 carbon atoms, aralkyl polyisocyanates (b14) having 10 to 18 carbon atoms, and modified products (b15) of these organic isocyanates. These polyisocyanates have 2 to 3 isocyanate groups. The organic isocyanate component may be one type or a mixture of two or more types. In the case of a mixture of two or more organic isocyanate components, it is preferable to use a mixture of compounds from the same family, since the reactivities of aromatic polyisocyanates, aralkyl polyisocyanates, and aliphatic polyisocyanates generally differ greatly.

[0090] As the organic isocyanate component, MDI, HDI, IPDI and hydrogenated MDI are preferred from the viewpoints of texture and durability.

[0091] The chain extender component includes polyamines having an Mn or molecular weight of 40 or more but less than 500, such as aliphatic polyamines having 2 to 36 carbon atoms {alkylenediamines such as ethylenediamine and hexamethylenediamine; polyalkylenepolyamines having an alkylene group with 2 to 6 carbon atoms and 3 to 7 nitrogen atoms such as diethylenetriamine, dipropylenetriamine, dihexylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, and hexaethyleneheptamine}; alicyclic polyamines having 6 to 20 carbon atoms {1,3- or 1,4-diaminocyclohexane, 4,4'- or 2,4'-dicyclohexylmethanediamine, and isophoronediamine}; aromatic polyamines having 6 to 20 carbon atoms {1,3- or aromatic aliphatic polyamines having 8 to 20 carbon atoms {1,3- or 1,4-xylylenediamine, bis(aminoethyl)benzene, bis(aminopropyl)benzene, bis(aminobutyl)benzene, etc.}; heterocyclic polyamines having 3 to 20 carbon atoms {2,4-diamino-1,3,5-triazine, piperazine, N-(2-aminoethyl)piperazine, etc.}; hydrazine; dibasic acid dihydrazides {adipic acid dihydrazide, etc.}; and aminoalcohols having 2 to 20 carbon atoms {ethanolamine, diethanolamine, 2-amino-2-methylpropanol, triethanolamine, etc.}.

[0092] <Cellulose substances> The surface layer contains a cellulose material. The surface layer may be a dried film obtained by solidifying a resin composition containing a second urethane resin and a cellulose material. The surface layer of the present invention may be obtained by mixing an aqueous dispersion of the second urethane resin or a solvent solution of the second urethane resin with a cellulose material to obtain a resin composition containing the second urethane resin and a cellulose material, and then solidifying the resin composition.

[0093] When the skin layer contains cellulose substances, it is possible to give synthetic leather a warm, natural texture (feel, appearance, color, scent) like wood, thereby improving the texture (feel, appearance, color, scent) of synthetic leather.

[0094] Cellulosic materials include cellulose powder, lignocellulosic materials, and the like.

[0095] The cellulose powder is powdered cellulose. As the cellulose powder, a commercially available cellulose powder may be used, for example, KC Flock W-400Y (manufactured by Nippon Paper Industries Co., Ltd.). The cellulose powder may be derived from plants such as wood.

[0096] Lignocellulose materials include lignocellulose and charcoal prepared from it. Lignocellulose includes wood, bamboo, rice husks, wheat husks, buckwheat husks, rice straw, wheat straw, buckwheat straw, rice bran, soybean dregs, coffee grounds, fruit pomace, skins, or stems, and vegetable pomace, skins, or stems, as well as pulp and waste paper. Charcoal prepared from lignocellulose includes charcoal and bamboo charcoal. Of these, wood, bamboo, charcoal, and bamboo charcoal are preferred from the standpoints of texture and durability. Lignocellulose materials may be used alone or in combination of two or more types.

[0097] From the viewpoints of production costs, texture, and durability, the cellulose material is preferably appropriately dry. The moisture content (wt%) is preferably 0.1-20, more preferably 1-15, and particularly preferably 3-10.

[0098] The moisture content is a value obtained in accordance with JIS A1476:2016 (105°C, mass-based mass moisture content).

[0099] There are no particular restrictions on the bulk density of the cellulose material, but from the viewpoints of production costs, texture and durability, it is preferably about 0.1 to 0.7, and more preferably 0.2 to 0.5.

[0100] The shape of the cellulose material is not particularly limited, but from the viewpoint of texture and durability, amorphous, powdery, and fibrous shapes are preferred, and fine powdery and fibrous shapes are more preferred.

[0101] The volume average particle size (μm) of the cellulose material is preferably 0.1 to 500, more preferably 1 to 300, particularly preferably 10 to 150, and most preferably 20 to 100, from the viewpoint of texture and durability.

[0102] The volume average particle size is determined in accordance with JIS Z8825:2022 "Particle size analysis - Laser diffraction and scattering method," by wet dispersing using water as the dispersion medium, adjusting the concentration so that the laser light transmittance is in the range of 65 to 95%, calculating the volume-based particle size distribution with a relative refractive index of 1.1 (refractive index of dispersoid 1.470 / refractive index of water 1.333), and using the median diameter as the volume average particle size.

[0103] From the viewpoint of texture, wood flour is preferred as the cellulose material. The wood flour is not particularly limited as long as it is powder obtained from any tree (Japanese cypress, cedar, etc.), and may be, for example, Japanese cypress wood flour or Japanese cedar wood flour.

[0104] From the viewpoint of texture, the content of the cellulose material in the weight of the skin layer is preferably 1 to 70% by weight, more preferably 10 to 60% by weight, and particularly preferably 20 to 50% by weight. The content of the cellulose material in the weight of the skin layer can be calculated, for example, by determining the ratio of the weight of the cellulose material added as a raw material for the skin layer to the weight of the entire skin layer.

[0105] The resin composition that becomes the surface layer after solidification may contain a solvent. The solvent may evaporate during solidification of the resin composition. Examples of the solvent include water, ketones (e.g., acetone and methyl ethyl ketone), esters (e.g., butyl acetate, propyl acetate, and ethyl acetate), ethers (e.g., tetrahydrofuran), amides (e.g., N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone), and aromatic hydrocarbons (e.g., toluene). One or more solvents may be used. Among these, from the viewpoints of texture and durability, water, N,N-dimethylformamide, N,N-dimethylacetamide, butyl acetate, propyl acetate, ethyl acetate, methyl ethyl ketone, tetrahydrofuran, and toluene are preferred, with water, N,N-dimethylformamide, and N,N-dimethylacetamide being even more preferred, and water being particularly preferred. When water is contained in the solvent, some or all of the water also functions as a chain-extending component and becomes a constituent of the second urethane resin.

[0106] The resin composition that becomes the skin layer after solidification may contain additives such as dispersants, viscosity modifiers, antifoaming agents, preservatives, weathering stabilizers, fillers, flame retardants, foaming agents, and mold release agents.

[0107] The viscosity (mPa·s, 20°C) of the resin composition that will become the skin layer after solidification is preferably from 1,000 to 500,000, more preferably from 1,300 to 200,000, particularly preferably from 1,600 to 100,000, and most preferably from 2,000 to 50,000, from the viewpoints of coatability, texture, and durability. The viscosity of the resin composition can be adjusted by the type and content of the solvent and viscosity modifier.

[0108] The resin composition can be obtained by uniformly mixing the second urethane resin, the cellulose material, and the solvent. Part or all of the solvent can be used to prepare the second urethane resin. When part of the solvent is used, the remaining solvent can be used during uniform mixing with the cellulose material or during the final viscosity adjustment.

[0109] When the solvent is water, it can be produced by a known method (a method in which an active hydrogen component, an organic isocyanate component, and optionally a chain extender component are reacted in an organic solvent, the resultant mixture is dispersed in water, and then, if necessary, the active hydrogen component and / or the chain extender component are further reacted, and the organic solvent is removed (the so-called acetone method; for example, JP-A Nos. 2013-234214 and 2016-188362)). The resultant mixture may be further diluted with an organic solvent before being dispersed in water.

[0110] When an active hydrogen compound (a2) having an ionic group is used as the active hydrogen component, a base, an acid or a quaternizing agent may be further added after the above reaction to react with the ionic group. A dispersant may be added when dispersing in water. Furthermore, if isocyanate groups remain after dispersion in water, the isocyanate groups can be reacted with an active hydrogen component and / or a chain extender component.

[0111] When the solvent is other than water, the second urethane resin can be prepared by reacting an active hydrogen component, an organic isocyanate component, and, if necessary, a chain extender component in the presence or absence of a solvent {a known method (for example, JP 2005-171228 A)}.

[0112] <Manufacturing method for synthetic leather> The synthetic leather of the present invention can be produced, for example, by the following method. A resin composition that will form the surface layer after solidification is coated onto a support material such as release paper, and the resin composition is solidified by dry coagulation, wet coagulation, heat-sensitive coagulation, or the like to obtain a dry film. A two-component polyurethane adhesive composition that will form the adhesive layer after curing is coated onto the dry film, and the surface coated with the two-component polyurethane adhesive composition is attached to a substrate, after which the two-component polyurethane adhesive composition is cured. The support material such as release paper is then peeled off to produce the synthetic leather of the present invention.

[0113] In the above manufacturing method, instead of applying a two-component polyurethane adhesive composition that will become an adhesive layer after curing to a dried film, the two-component polyurethane adhesive composition that will become an adhesive layer after curing may be applied to a substrate.

[0114] The present disclosure (1) is a synthetic leather comprising a substrate, an adhesive layer containing a first urethane resin, and a skin layer containing a second urethane resin and a cellulose material, wherein the first urethane resin is a cured product of a main component containing a polyol composition (A) and a curing agent containing an isocyanate component (B), the polyol composition (A) contains polyol (a1) as a structural unit, and the polyol (a1) contains polyol (a1-1) having a number average molecular weight of 1000 or less, and the weight proportion of the structural units derived from the polyol (a1) in the polyol composition (A) derived from the polyol (a1) having a number average molecular weight of 1000 or less is 50 wt % or more.

[0115] The present disclosure (2) is the synthetic leather according to the present disclosure (1), in which the weight proportion of structural units derived from polyol (a1-2) having a molecular weight of 200 or less among structural units derived from the polyol (a1) in the polyol composition (A) is 3 wt % or less.

[0116] The present disclosure (3) is the synthetic leather according to the present disclosure (2), in which the polyol (a1-2) having a molecular weight of 200 or less is trimethylolpropane.

[0117] The present disclosure (4) is the synthetic leather according to any one of the present disclosures (1) to (3), wherein the polyol composition (A) comprises a hydroxyl group-terminated polyurethane prepolymer, and the hydroxyl group-terminated polyurethane prepolymer is a reaction product of the polyol (a1) and the polyisocyanate (b1).

[0118] The present disclosure (5) is the synthetic leather according to the present disclosure (4), in which the equivalent ratio (NCO / OH) of the isocyanate groups contained in the polyisocyanate (b1) to the hydroxyl groups contained in the polyol (a1) is 0.5 to 0.8.

[0119] The present disclosure (6) is the synthetic leather according to the present disclosure (4) or (5), in which the polyisocyanate (b1) is an aromatic polyisocyanate.

[0120] The present disclosure (7) is the synthetic leather according to any one of the present disclosures (1) to (6), wherein the polyol (a1-1) having a number average molecular weight of 1,000 or less includes a polyether polyol having a number average molecular weight of 1,000 or less.

[0121] The present disclosure (8) is the synthetic leather according to the present disclosure (7), in which the polyether polyol having a number average molecular weight of 1,000 or less is polytetramethylene glycol or polytrimethylene glycol. [Example]

[0122] In the following, "parts" means parts by weight, and "%" means % by weight.

[0123] [Production of Polyol Composition (A) Comprising Hydroxyl-Terminated Polyurethane Prepolymer] (Production Examples 1 to 7, Comparative Production Example 8) Polyol (a1), polyisocyanate (b1), and each additive shown in Table 1 were added to a four-neck flask equipped with a reflux condenser, a stirrer, and a thermometer in the amounts (parts by weight) shown in Table 1, and the mixture was allowed to react at 70°C for 4 hours to obtain polyol compositions (A-1) to (A-7), and (RA-8) each consisting of a hydroxyl-terminated polyurethane prepolymer.

[0124] [Table 1]

[0125] The raw materials listed in Table 1 are as follows: Polyol (a1-1) having an Mn of 1000 or less Benebiol NL1030DB: Polycarbonate polyol [Mitsubishi Chemical Corporation, number average molecular weight 1000] BioPTMG650: Polytetramethylene glycol [Mitsubishi Chemical Corporation, number average molecular weight 650] BioPTMG1000: Polytetramethylene glycol [Mitsubishi Chemical Corporation, number average molecular weight 1000] ECOTRION H1000: Polytrimethylene glycol [SK Chemicals Co., Ltd., number average molecular weight 1000] Sannix PP-1000: Polypropylene glycol [Sanyo Chemical Industries, Ltd., number average molecular weight 1000] ELA-DR: Refined castor oil [Toyokuni Oil Mills, number average molecular weight 950] Sannix NP-300: Nitrogen-containing polyether polyol [manufactured by Sanyo Chemical Industries, Ltd., number-average molecular weight 300] Polyol (a1-2) having a molecular weight of 200 or less 1,3-Propanediol Trimethylolpropane Polyols (a1-3) having Mn greater than 1000 HS-2P-203S: polyester polyol obtained from 1,3-propanediol and sebacic acid [manufactured by Toyokuni Oil Mills, Ltd., number average molecular weight 2000] BioPTMG2000: Polytetramethylene glycol [Mitsubishi Chemical Corporation, number average molecular weight 2000] Polyisocyanate (b1) Millionate MT: 4,4'-diphenylmethane diisocyanate (MDI) [manufactured by Tosoh Corporation] Cosmonate T80: Tolylene diisocyanate (TDI) [Mitsui Chemicals, Inc.] antioxidants Irganox 245 [BASF Japan Ltd.] UV absorbers Tinuvin 326 [BASF Japan Ltd.] Hindered amine light stabilizers Tinuvin PA 144 [BASF Japan Ltd.]

[0126] For each of the polyol compositions (A-1) to (A-7) and (RA-8), the "weight proportion of structural units derived from polyol (a1-1) having a number average molecular weight of 1,000 or less, among the structural units derived from polyol (a1)," calculated based on the amount of each polyol (a1) added, is shown in Table 1. Similarly, the "weight proportion of structural units derived from polyol (a1-2) having a molecular weight of 200 or less, among the structural units derived from polyol (a1)," calculated based on the amount of each polyol (a1) added, is shown in Table 1. Table 1 also shows the "equivalent ratio (NCO / OH) of the isocyanate groups contained in polyisocyanate (b1) to the hydroxyl groups contained in polyol (a1)," calculated based on the amount and hydroxyl group content of each polyol (a1) added, and the amount and isocyanate group content of each polyisocyanate (b1).

[0127] In the polyol composition (RA-8), the weight proportion of structural units derived from polyol (a1-1) having a number average molecular weight of 1000 or less among structural units derived from polyol (a1) is less than 50% by weight.

[0128] [Hydroxyl value] The hydroxyl value (mgKOH / g) of each of the polyol compositions (A-1) to (A-7) and (RA-8) was measured using the method described in "JIS K 1557-1 Plastics - Test methods for polyurethane raw polyols - Part 1: Determination of hydroxyl value." Table 1 shows this.

[0129] [viscosity] The viscosity (mPa s) at 25°C of each of the polyol compositions (A-1) to (A-7) and (RA-8) was measured in accordance with JIS Z8803:2011, "9 Viscosity measurement method using a single cylindrical rotational viscometer." The results are shown in Table 1.

[0130] [Transparency at 0℃] Each of the polyol compositions (A-1) to (A-7) and (RA-8) was left to stand at 0° C. for 1 day, and then the transparency was evaluated according to the following criteria. The results are shown in Table 1. ⊚: No solid precipitation was observed. ◯: A slight amount of solid precipitation was observed.

[0131] [Production of Isocyanate Component (B) Composed of Isocyanate-Terminated Polyurethane Prepolymer] (Production Example 9) The polyol (a1) and polyisocyanate (b1) shown in Table 2 were added to a four-neck flask equipped with a reflux condenser, a stirrer, and a thermometer in the amounts (parts by weight) shown in Table 2, and the mixture was allowed to react at 70°C for 4 hours to obtain an isocyanate component (B-1) consisting of an isocyanate group-terminated polyurethane prepolymer.

[0132] [Table 2]

[0133] [Production of two-component polyurethane adhesive composition] (Production Examples 10 to 17, Comparative Production Example 18) According to the formulation (parts by weight) shown in Table 3, a base agent containing a polyol composition (A) and a curing agent containing an isocyanate component (B) were mixed to obtain two-component polyurethane adhesive compositions (C-1) to (C-8), and (RC-9) of Production Examples 10 to 17 and Comparative Production Example 18.

[0134] [Table 3]

[0135] The raw materials listed in Table 3 are as follows: Polyol composition (A) Polyol compositions (A-1) to (A-7), and (RA-8) produced in Production Examples 1 to 7 and Comparative Production Example 8 Cellulose materials Cedar wood flour: Cedar wood flour with a volume average particle size of 30 μm [manufactured by Naka Wood Co., Ltd.] (bulk density: 0.3 g / ml, moisture content: 5% by weight) Cypress (hinoki) wood flour: Cypress wood flour with a volume average particle size of 40 μm [manufactured by Naka Wood Co., Ltd.] (bulk specific gravity: 0.3 g / ml, moisture content: 6% by weight) KC Flock W-400Y: Cellulose powder [manufactured by Nippon Paper Industries Co., Ltd.] (volume average particle size: 30 μm, bulk density: 0.4 g / ml, moisture content: 6% by weight) Bamboo powder: Bamboo material [manufactured by Nihon Aim Co., Ltd.] (volume average particle size: 75 μm, bulk density: 0.5 g / ml, moisture content: 7% by weight) pigment NX-501 White [Dainichi Seika Color & Chemicals Mfg. Co., Ltd.] Isocyanate component (B) Isocyanate component (B-1) produced in Production Example 9

[0136] The resulting two-component polyurethane adhesive composition was evaluated for the following items. The evaluation results for each item are shown in Table 3.

[0137] [viscosity] The viscosity (mPa·s) at 25°C of each of the two-component polyurethane adhesive compositions (C-1) to (C-8) and (RC-9) was measured in accordance with JIS Z8803:2011, "9 Viscosity measurement method using a single cylindrical rotational viscometer." The results are shown in Table 3.

[0138] [Pot life] Table 3 shows the time (hrs) required for each of the two-component polyurethane adhesive compositions (C-1) to (C-8) and (RC-9) to reach a viscosity (mPa·s) of 40,000 or more when left at 25°C.

[0139] [Production of aqueous dispersion or solvent solution of polyurethane resin for surface layer] (Manufacturing Example 19) 60.6 parts of HS-2P-203S (a polyester polyol obtained using 1,3-propanediol and sebacic acid) as an active hydrogen component, 6.0 parts of 2,2-dimethylolpropionic acid (manufactured by Perstorp Japan Co., Ltd.), 27.4 parts of hydrogenated MDI as an organic isocyanate component, 41.1 parts of acetone as an organic solvent, and the antioxidants shown in Table 4 were uniformly mixed, and then a urethane reaction was carried out at 80°C for 10 hours with stirring.The mixture was then cooled to approximately 25°C, yielding an acetone solution of a urethane prepolymer for the surface layer.

[0140] Next, 72.0 parts of acetone as an organic solvent, an ultraviolet absorber, a hindered amine light stabilizer shown in Table 4, and 3.6 parts of triethylamine (manufactured by Daicel Corporation) as a base were added to the obtained acetone solution of the urethane prepolymer for the surface layer and mixed uniformly. Then, 120.8 parts of a solvent (ion-exchanged water) was added to the mixture while stirring to prepare an aqueous dispersion of the polyurethane resin for the surface layer.

[0141] After uniformly mixing 1.1 parts of ethylenediamine (manufactured by Tosoh Corporation) as a chain extension component and 20.8 parts of a solvent (ion exchange), this was added to the dispersion and chain extension and termination reactions were carried out at 25°C. Subsequently, the organic solvent was distilled off under reduced pressure (0.01 MPa) at 65°C over 8 hours to obtain an aqueous dispersion (D-1) of polyurethane resin for the surface layer. Table 4 shows the formulation of the aqueous dispersion (D-1) of polyurethane resin for the surface layer.

[0142] (Examples 20-22) Aqueous dispersions (D-2) to (D-4) of polyurethane resin for surface layer were obtained by changing the type and amount of each raw material as shown in Table 4. In Production Examples 20 and 21, monoethanolamine was added as an active hydrogen component together with the chain extending component or instead of the chain extending component.

[0143] [Table 4]

[0144] (Manufacturing Example 23) 25.9 parts of HS-2P-203S (a polyester polyol obtained using 1,3-propanediol and sebacic acid) as an active hydrogen component, 2.6 parts of 1,3-propanediol, 11.8 parts of Millionate MT (4,4'-diphenylmethane diisocyanate (MDI)) as an organic isocyanate component, 32.0 parts of N,N-dimethylformamide as an organic solvent, and an antioxidant shown in Table 5 were mixed uniformly, and then a urethane reaction was carried out at 70°C for 8 hours with stirring. After cooling to approximately 25°C, 64.0 parts of the ultraviolet absorber, hindered amine light stabilizer, and methyl ethyl ketone shown in Table 5 were added and mixed uniformly to obtain a urethane resin solvent solution for the surface layer (D-5). Table 5 shows the formulation of the polyurethane resin solvent solution for the surface layer (D-5).

[0145] (Manufacturing Example 24) The types and amounts of each raw material were changed as shown in Table 5 to obtain a polyurethane resin solvent solution for a surface layer (D-6).

[0146] (Manufacturing Example 25) 98.8 parts of BioPTMG2000 (polytetramethylene glycol) as the active hydrogen component, 24.7 parts of Millionate MT (4,4'-diphenylmethane diisocyanate (MDI)) as the organic isocyanate component, and the antioxidants shown in Table 5 were uniformly mixed, and then a urethane reaction was carried out at 70°C for 4 hours with stirring, and the mixture was cooled to approximately 25°C to obtain a urethane prepolymer for the surface layer.

[0147] Next, 432.7 parts of N,N-dimethylformamide as an organic solvent was added to the obtained urethane prepolymer for the surface layer and mixed uniformly. Then, while stirring, 0.8 parts of ion-exchanged water and 0.3 parts of n-butanol were added to carry out a chain extension reaction and a termination reaction at 70°C for 5 hours. The ultraviolet absorber and hindered amine light stabilizer shown in Table 5 were added and mixed uniformly to obtain a urethane resin solvent solution for the surface layer (D-7). Table 5 shows the formulation of the polyurethane resin solvent solution for the surface layer (D-7).

[0148] (Manufacturing Example 26) The types and amounts of each raw material were changed as shown in Table 5 to obtain a polyurethane resin solvent solution for a surface layer (D-8).

[0149] [Table 5]

[0150] [Production of Resin Composition for Surface Layer] (Manufacturing Example 27) 30.0 parts of the solvent (ion-exchanged water), 2.0 parts of a dispersant (SN Dispersant 5029, manufactured by San Nopco Ltd.) (containing 1.5 parts of ion-exchanged water), 23.8 parts of the polyurethane resin aqueous dispersion (D-1) for a surface layer obtained in Production Example 19 (comprising 9.5 parts of polyurethane resin for a surface layer and 14.3 parts of ion-exchanged water), 15.3 parts of cedar wood flour (the same as that used in Table 3), and 0.01 part of an antifoaming agent (Noptam 777-F, manufactured by San Nopco Ltd.) were uniformly mixed, and then 0.5 parts of a thickener (SN Thickener 665T, manufactured by San Nopco Ltd.) (containing 0.4 parts of ion-exchanged water) was added and mixed uniformly to obtain a resin composition for a surface layer (E-1).

[0151] (Production Examples 28 to 34, Comparative Production Example 35) Resin compositions for surface layers (E-2) to (E-8) and (RE-9) were obtained by changing the type and amount of each raw material as shown in Table 6. No wood flour was added to the resin composition for surface layers (RE-9) of Comparative Production Example 35.

[0152] [Table 6]

[0153] Among the raw materials listed in Table 6, those that have not been used in the previous production examples are explained below. (D) Aqueous dispersion of polyurethane resin for surface layer or solvent solution of polyurethane resin for surface layer D-1: Aqueous dispersion of polyurethane resin obtained in Production Example 19 (composed of 9.5 parts of polyurethane resin and 14.3 parts of water) D-2: Aqueous dispersion of polyurethane resin obtained in Production Example 20 (consisting of 3.5 parts polyurethane resin and 7.0 parts water) D-3: Aqueous dispersion of polyurethane resin obtained in Production Example 21 (consisting of 7.2 parts polyurethane resin and 16.8 parts water) D-4: Aqueous dispersion of polyurethane resin obtained in Production Example 22 (consisting of 21.6 parts of polyurethane resin and 40.0 parts of water) D-5: A solvent solution of the polyurethane resin obtained in Production Example 23 (consisting of 9.0 parts of polyurethane resin and 21.0 parts of solvent) D-6: A solvent solution of the polyurethane resin obtained in Production Example 24 (consisting of 6.7 parts of polyurethane resin and 15.5 parts of solvent) D-7: A solvent solution of the polyurethane resin obtained in Production Example 25 (consisting of 7.1 parts of polyurethane resin and 16.4 parts of solvent) D-8: A solvent solution of the polyurethane resin obtained in Production Example 26 (consisting of 7.4 parts of polyurethane resin and 17.4 parts of solvent) Dispersants SN Dispersant 5029: 25% aqueous solution of polycarboxylic acid ammonium salt [manufactured by San Nopco Co., Ltd.] SN-PW-43: 41% aqueous solution of sodium condensed naphthalene sulfonate [manufactured by San Nopco Co., Ltd.] Naroacty CL-120: Alkylene oxide adduct of higher alcohol [manufactured by Sanyo Chemical Industries, Ltd.] thickener SN Thickener 665T: 30% aqueous solution of urethane-modified polyether [manufactured by San Nopco Co., Ltd.] SN Thickener 618: 12% aqueous solution of modified sodium polyacrylate [manufactured by San Nopco Co., Ltd.] Antifoaming agents Noptum 777-F: Hydrophobic silica-based defoamer [manufactured by San Nopco Ltd.] Dappo SN-348: Solvent-based defoamer [manufactured by San Nopco Co., Ltd.]

[0154] The viscosities of the resin compositions for surface layers (E-1) to (E-8) and (RE-9) were measured in the same manner as in the measurement of the viscosity of the polyol composition (A-1) described above. The results are shown in Table 6.

[0155] [Manufacturing of synthetic leather] Example 1 The resin composition for the surface layer (E-1) was applied onto release paper (DN-TP APZT DE-30, manufactured by Ajinomoto Trading Co., Ltd.) using a slot die so that the dry film thickness was 35 μm, and then dried in a dryer at 100°C for 10 minutes to obtain a dry film that was dry-coagulated.

[0156] The two-component polyurethane adhesive composition (C-1) was applied to the dried film using a bar coater so that the dry film thickness was 100 μm, and then dried for 1 minute at 100° C. Next, a cotton smooth (knitted fabric) was placed on top and pressed with a laminator, and then the film was aged at 40° C. for 2 days, and the release paper was peeled off to obtain synthetic leather (F-1).

[0157] (Examples 2 to 8, Comparative Examples 1 and 2) Synthetic leathers (F-2) to (F-8) and (RF-1) to (RF-2) were obtained by changing the types and dry film thicknesses of the resin composition for the surface layer and the two-component polyurethane adhesive composition, as well as the type of substrate, as shown in Table 7. The "rayon / polyester = 50 / 50 nonwoven fabric" in Table 7 refers to a nonwoven fabric containing 50% by mass of rayon and 50% by mass of polyester.

[0158] [Table 7]

[0159] The resulting synthetic leather was evaluated for the following items. The evaluation results for each item are shown in Table 7.

[0160] [Texture] When the warm, natural texture (feel, appearance, color, and scent) of wood was felt more strongly, it was judged as "◎", when it was felt somewhat, it was judged as "〇", and when it was not felt at all, it was judged as "×".

[0161] [Peel strength] For each of the synthetic leathers (F-1) to (F-8) and (RF-1), the 180° peel strength (unit: N) was measured using a tensile tester on strip-shaped test pieces 30 mm wide and 150 mm long at 23°C and a pulling rate of 300 mm / min in accordance with JIS K6772. The results are shown in Table 7.

[0162] The synthetic leathers of the examples had an excellent feel and sufficient peel strength. On the other hand, the synthetic leather (RF-1) of Comparative Example 1, in which the weight proportion of the structural units derived from polyol (a1-1) among the structural units derived from polyol (a1) in the polyol composition (A) was less than 50% by weight, had low peel strength. Furthermore, the synthetic leather of Comparative Example 2 (RF-2), in which the skin layer did not contain any cellulose material, had a poor feel.

Claims

1. A substrate; an adhesive layer containing a first urethane resin; a skin layer containing a second urethane resin and a cellulose material, the first urethane resin is a cured product of a base resin containing a polyol composition (A) and a curing agent containing an isocyanate component (B), The polyol composition (A) contains a polyol (a1) as a structural unit, the polyol (a1) includes a polyol (a1-1) having a number average molecular weight of 1,000 or less, A synthetic leather in which, among the structural units derived from the polyol (a1) in the polyol composition (A), the weight ratio of structural units derived from the polyol (a1-1) having a number average molecular weight of 1,000 or less is 50% by weight or more.

2. 2. The synthetic leather according to claim 1, wherein, among the structural units derived from the polyol (a1) in the polyol composition (A), the weight proportion of structural units derived from a polyol (a1-2) having a molecular weight of 200 or less is 3% by weight or less.

3. 3. The synthetic leather according to claim 2, wherein the polyol (a1-2) having a molecular weight of 200 or less is trimethylolpropane.

4. The polyol composition (A) comprises a hydroxyl group-terminated polyurethane prepolymer, 3. The synthetic leather according to claim 1, wherein the hydroxyl-terminated polyurethane prepolymer is a reaction product of the polyol (a1) and the polyisocyanate (b1).

5. 5. The synthetic leather according to claim 4, wherein the equivalent ratio (NCO / OH) of the isocyanate groups contained in the polyisocyanate (b1) to the hydroxyl groups contained in the polyol (a1) is 0.5 to 0.

8.

6. The synthetic leather according to claim 4, wherein the polyisocyanate (b1) is an aromatic polyisocyanate.

7. 3. The synthetic leather according to claim 1, wherein the polyol (a1-1) having a number average molecular weight of 1,000 or less includes a polyether polyol having a number average molecular weight of 1,000 or less.

8. 8. The synthetic leather according to claim 7, wherein the polyether polyol having a number average molecular weight of 1,000 or less is polytetramethylene glycol or polytrimethylene glycol.

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