Surface treatment agent and leather treated with the same

Abstract

To provide a surface treatment agent that can impart excellent abrasion resistance to leather substrates without impairing their abrasion resistance. [Solution] The solution contains (a) an organic polyisocyanate, (b) a polyol, and (c) a neutralized isocyanate-terminated prepolymer which is a reaction product of a compound having an anionic hydrophilic group and at least two active hydrogens, and (d) an aqueous polyurethane resin which is a chain extension product of a polyamine having two or more amino groups and / or imino groups. A surface treatment agent characterized in that the (b) polyol contains a hydroxyl-terminated polyalkadiene having an unsaturated hydrocarbon structure (b1).

Description

Technical Field

[0001] The present invention relates to a surface treatment agent and leather surface-treated using the same, and more particularly to a surface treatment agent containing an aqueous polyurethane resin and leather surface-treated using the same.

Background Art

[0002] In the manufacturing process of synthetic leather having an epidermal layer made of polyurethane resin, leather made of vinyl chloride-based resin (hereinafter referred to as PVC), etc., in order to improve the abrasion resistance and dulling resistance of the surface of synthetic leather and PVC leather, processing with a surface treatment agent is performed. The resin composition used in conventional surface treatment agents was mainly a solvent-based type containing organic solvents such as dimethylformamide, toluene, and methyl ethyl ketone. However, since these organic solvents have strong flammability and many are highly toxic, there have been problems such as the risk of fire, deterioration of the working environment, and environmental pollution of the atmosphere, water quality, etc. Also, in the production of synthetic leather and PVC leather, although these organic solvents are recovered, there is a problem that it requires a large amount of cost and labor.

[0003] In recent years, not only has environmental regulation become stricter, but due to the residual organic solvents inside synthetic leather and PVC leather obtained using organic solvent-based surface treatment agents, the impact on the human body such as skin disorders has also become a problem. Therefore, the development of aqueous surface treatment agents that contain as little or no organic solvents as possible has been promoted. In particular, in leather materials such as synthetic leather and PVC leather used for automotive interior materials, since the impact of residual organic solvents on the human body is feared, an aqueous surface treatment agent is strongly demanded.

[0004] For example, International Publication No. 2019 / 221088 (Patent Document 1) describes a polyurethane resin containing a polyol component and an isocyanate component, wherein (1) the polyol component contains a polycarbonate diol component, and the isocyanate component contains a linear aliphatic isocyanate component, (2) the polycarbonate diol component has a number average molecular weight of 500 to 3000 and contains a diol-derived structure with 3 to 10 carbon atoms in its structure, and (3) 10 mol% or more of the isocyanate component is a linear aliphatic isocyanate component with 4 to 10 carbon atoms, and a synthetic imitation leather comprising the polyurethane resin and a structure containing the polyurethane resin is described, and in the examples, polycarbonate diols derived from 1,4-butanediol and 1,10-decanediol are used as the polycarbonate diol component. In synthetic imitation leather prepared by coating a substrate with a polyurethane resin prepared using polycarbonate diols derived from 1,4-butanediol and 1,10-decanediol, both abrasion resistance and chemical resistance could be achieved, but abrasion resistance was insufficient.

[0005] Furthermore, International Publication No. 2015 / 107933 (Patent Document 2) describes an aqueous surface treatment agent containing an aqueous polyurethane (A) and a carbodiimide-based crosslinking agent (B) having a 100% modulus in the range of 10 to 20 MPa. In the examples, a 1,6-hexanediol-based polycarbonate diol is used as the aqueous polyurethane (A). When the surface of a leather substrate is treated with an aqueous surface treatment agent containing an aqueous polyurethane prepared using this 1,6-hexanediol-based polycarbonate diol, leather with excellent abrasion resistance is obtained, but there is a problem that the resistance to rubbing decreases. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2019 / 221088 [Patent Document 2] International Publication No. 2015 / 107933 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] This invention has been made in view of the problems of the prior art described above, and aims to provide a surface treatment agent that can impart excellent rubbing resistance to a leather base material without impairing its abrasion resistance, and leather that has excellent rubbing resistance without impairing its abrasion resistance. [Means for solving the problem]

[0008] As a result of diligent research to achieve the above objective, the present inventors have discovered that by treating the surface of a leather substrate with a surface treatment agent containing an aqueous polyurethane resin prepared using a hydroxyl-terminated polyalkadiene having an unsaturated hydrocarbon structure, it is possible to impart excellent abrasion resistance to the leather substrate without impairing its abrasion resistance, thus completing the present invention.

[0009] In other words, the present invention provides the following embodiments. [1] Contains (a) an organic polyisocyanate, (b) a polyol, and (c) a neutralized isocyanate-terminated prepolymer which is a reaction product of a compound having an anionic hydrophilic group and at least two active hydrogens, and (d) an aqueous polyurethane resin which is a chain extension product of a polyamine having two or more amino groups and / or imino groups. A surface treatment agent wherein the (b) polyol contains a hydroxyl-terminated polyalkadiene having an unsaturated hydrocarbon structure (b1). [2] The surface treatment agent according to [1], wherein the content of the structural unit derived from the (b1) unsaturated hydrocarbon structure hydroxyl-terminated polyalkadiene in the aqueous polyurethane resin is 20 to 80% by mass. [3] The surface treatment agent according to [1] or [2], wherein the content of anionic hydrophilic groups in the aqueous polyurethane resin is 0.3 to 4.0% by mass. [4] The surface treatment agent according to any one of [1] to [3], wherein the content of free isocyanate groups in the isocyanate group-terminated prepolymer is 0.2 to 5.0% by mass. [5] Leather comprising a leather base material and a surface treatment layer formed on the base material with a surface treatment agent described in any one of [1] to [4]. [Effects of the Invention]

[0010] According to the present invention, it is possible to obtain leather with excellent rubbing resistance without compromising abrasion resistance. [Modes for carrying out the invention]

[0011] The present invention will be described in detail below with reference to its preferred embodiments.

[0012] First, the aqueous polyurethane resin constituting the surface treatment agent of the present invention will be described. The aqueous polyurethane resin used in the present invention is a self-emulsifying aqueous polyurethane resin in which (a) an organic polyisocyanate, (b) a polyol, and (c) a chain extension of a neutralized isocyanate-terminated prepolymer which is a reaction product of a compound having an anionic hydrophilic group and at least two active hydrogens, and (d) a polyamine having two or more amino groups and / or imino groups, wherein the (b) polyol contains (b1) a hydroxyl-terminated polyalkadiene having an unsaturated hydrocarbon structure. In the self-emulsifying aqueous polyurethane resin, "aqueous" means that after emulsifying and dispersing the self-emulsifying polyurethane resin in water to prepare an emulsion dispersion with a water concentration of 40% by mass, it is possible to maintain a state in which no separation or sedimentation is observed even when this emulsion dispersion is left standing at 20°C for 12 hours.

[0013] (a) Organic polyisocyanates The (a) organic polyisocyanate used in the present invention is not particularly limited, and examples include aromatic, aliphatic, and alicyclic polyisocyanates that have been commonly used in the past. For example, aromatic polyisocyanates include m-phenylenediisocyanate, p-phenylenediisocyanate, 2,4-tolylenediisocyanate, 2,6-tolylenediisocyanate, 4,4'-diphenylmethanediisocyanate, 2,4'-diphenylmethanediisocyanate, 3,3'-dimethyl-4,4'-biphenylenediisocyanate, 3,3'-dichloro-4,4'-biphenylenediisocyanate, 1,5-naphthalenediisocyanate, tolidinediisocyanate, tetramethylenexylylenediisocyanate, xylylenediisocyanate, and the like. Examples of aliphatic polyisocyanates include tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, dodecamethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate. Examples of alicyclic polyisocyanates include isophorone diisocyanate, hydrogenated xylylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 3,3'-dimethyl-4,4'-dicyclohexylmethane diisocyanate, norbornane diisocyanate, and 1,3-bis(isocyanatomethyl)cyclohexane. These organic polyisocyanates may be used individually or in combination of two or more. Among these organic polyisocyanates, isophorone diisocyanate is preferred from the viewpoint of adhesion and resistance to yellowing.

[0014] (b) Polyol The (b) polyol used in the present invention includes (b1) a hydroxyl-terminated polyalkadiene having an unsaturated hydrocarbon structure.

[0015] (b1) Hydroxyl-terminated polyalkadienes having an unsaturated hydrocarbon structure The (b1) hydroxyl-terminated polyalkadienes having an unsaturated hydrocarbon structure used in the present invention (hereinafter also referred to as "(b1) hydroxyl-terminated polyalkadienes") are not particularly limited as long as they are polymers of alkadienes having an unsaturated hydrocarbon structure (e.g., a hydrocarbon group having a double bond) in at least one of the main chain and side chains, and having a hydroxyl group at at least one terminal, for example, polybutadiene diol (e.g., poly(1,2-butadiene)diol, Poly(1,3-butadiene)diols, and copolymer diols of 1,2-butadiene and 1,3-butadiene), polyisoprendiols (poly(2-methyl-1,3-butadiene)diol), polypentadiene diols (e.g., poly(1,2-pentadiene)diol, poly(1,3-pentadiene)diol, poly(1,4-pentadiene)diol, and copolymer diols of two or more pentadienes), polyhexadiene diols (e.g., poly(1, 2-Hexadiene)diols, poly(1,3-Hexadiene)diols, poly(1,4-Hexadiene)diols, poly(1,5-Hexadiene)diols, and copolymer diols of two or more hexadienes), polyheptadiene diols (e.g., poly(1,2-Heptadiene)diols, poly(1,3-Heptadiene)diols, poly(1,4-Heptadiene)diols, poly(1,5-Heptadiene)diols, poly(1,6-Heptadiene)diols, and Examples include homopolymer diols of alkadienes (such as copolymer diols of two or more heptadienes) and copolymer diols of two or more alkadienes; and copolymer diols of alkadienes with other copolymer monomers such as poly(ethylene-co-(1,2- and / or 1,3-butadiene))diol, poly(propylene-co-(1,2- and / or 1,3-butadiene))diol, and poly(styrene-b-(1,2- and / or 1,3-butadiene))diol. Among these hydroxyl-terminated polyalkadienes, polybutadiene diols are preferred from the viewpoint of abrasion resistance.

[0016] When using polybutadiene diol as the (b1) hydroxyl-terminated polyalkadiene, the structure of the repeating unit may be either the cis or trans type which is 1,4-addition type, or the vinyl type which is 1,2-addition type. Also, as the molecular structure, it may be a structure of a single type alone or a structure in which two or more types are mixed. Furthermore, although there is no particular limitation on the content of the 1,4-addition type (the total content of the cis type and the trans type), as the lower limit, 50 mol% or more is preferable, 80 mol% or more is more preferable, and as the upper limit, it may be less than 100 mol% or may be 90 mol% or less.

[0017] Although there is no particular limitation on the weight average molecular weight of the (b1) hydroxyl-terminated polyalkadiene, as the lower limit, it may be 1000 or more, 2000 or more, or 2300 or more, and as the upper limit, it may be 4000 or less or 3000 or less.

[0018] Although there is no particular limitation on the content of the (b1) hydroxyl-terminated polyalkadiene in the aqueous polyurethane resin, as the lower limit, 20% by mass or more is preferable, 25% by mass or more is more preferable, and as the upper limit, 70% by mass or less is preferable, 60% by mass or less is more preferable, and 50% by mass or less is even more preferable. When the content of the (b1) hydroxyl-terminated polyalkadiene in the aqueous polyurethane resin is less than the lower limit, the abrasion resistance of the obtained leather tends to decrease. On the other hand, when it exceeds the upper limit, the scuff resistance of the obtained leather tends to decrease.

[0019] Also, the content of the (b1) hydroxyl-terminated polyalkadiene in the (b) polyol is not particularly limited, but as the lower limit, 20% by mass or more is preferable, 30% by mass or more is more preferable, and as the upper limit, 100% by mass or less may be used, but less than 100% by mass is preferable, 95% by mass or less is more preferable, 60% by mass or less is further preferable, and 55% by mass or less is particularly preferable. When the content of the (b1) hydroxyl-terminated polyalkadiene in the (b) polyol is at least the lower limit, leather having excellent abrasion resistance tends to be easily obtained. On the other hand, when it is at most the upper limit, leather having excellent flex resistance tends to be easily obtained.

[0020] (Other polyols) In the surface treatment agent of the present invention, when the content of the (b1) hydroxyl-terminated polyalkadiene in the (b) polyol is less than 100% by mass, the (b) polyol may contain a polyol other than the (b1) hydroxyl-terminated polyalkadiene (hereinafter also referred to as "other polyol"). Examples of such other polyols include polymer polyols and low molecular weight diols. Examples of polymer polyols include polyether polyols, polyester polyols, polycarbonate polyols, polyolefin polyols, dimer diols, and the like.

[0021] Examples of the polyether polyols include polymers of alkylene oxides such as ethylene oxide, propylene oxide, and butylene oxide. Such polymers may be homopolymers of one type of alkylene oxide or copolymers of two or more types of alkylene oxides, but copolymers are preferred from the viewpoint of self-emulsification. If copolymers are used, they may be random polymers or block polymers. The molecular weight of such polyether polyols is preferably 200 to 6000, and more preferably 400 to 5000. Furthermore, as the polyether polyols, polyether diols obtained by adding one or more types of alkylene oxides to a low molecular weight dihydric alcohol, or polyether diols obtained by ring-opening polymerization reactions of cyclic ether compounds such as tetrahydrofuran, can also be used. Examples of the low molecular weight dihydric alcohols include ethylene glycol, propylene glycol, and butanediol.

[0022] The aforementioned polyester polyols include, for example, diol components such as ethylene glycol, propylene glycol, propanediol, butanediol, pentanediol, 3-methyl-1,5-pentanediol, hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol with a molecular weight of 300 to 1000, dipropylene glycol, tripropylene glycol, bishydroxyethoxybenzene, 1,4-cyclohexanedimethanol, bisphenol A, bisphenol S, hydrogenated bisphenol A, hydroquinone, or alkylene oxide adducts thereof, and dimer acid, succinic acid, and Examples include polyester polyols obtained by dehydration condensation reactions with dicarboxylic acid components such as dipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, maleic anhydride, fumaric acid, 1,3-cyclopentanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, naphthalic acid, biphenyldicarboxylic acid, 1,2-bisphenoxyethane-p,p'-dicarboxylic acid, anhydrides of dicarboxylic acids, or ester-forming derivatives; polyester polyols obtained by ring-opening polymerization reactions of cyclic ester compounds such as ε-caprolactone; and polyester polyols copolymerized from these.

[0023] Examples of the aforementioned polycarbonate-based polyols include polytetramethylene carbonate diol, poly(1,4-cyclohexanedimethylene carbonate) diol, 1,6-hexanediol polycarbonate polyol, 3-methyl-1,5-pentanediol / 1,6-hexanediol polycarbonate polyol, and 1,6-hexanediol / 1,5-pentanediol polycarbonate polyol.

[0024] Examples of the polyolefin polyols include the hydrides of the (b1) hydroxyl-terminated polyalkadienes.

[0025] Examples of the aforementioned dimer ol include diols obtained by reducing polymerized fatty acids. Examples of polymerized fatty acids include unsaturated fatty acids with 18 carbon atoms such as oleic acid and linoleic acid, drying oil fatty acids, semi-drying oil fatty acids, and lower monoalcohol esters of these fatty acids, which are subjected to a Diels-Alder type bimolecular polymerization reaction in the presence or absence of a catalyst. Various types of polymerized fatty acids are commercially available, but a typical example is one consisting of 0-5% by mass of a monocarboxylic acid with 18 carbon atoms, 70-98% by mass of a dimer acid with 36 carbon atoms, and 0-30% by mass of a trimer acid with 54 carbon atoms.

[0026] Examples of the low molecular weight diols include ethylene glycol, propylene glycol, diethylene glycol, butanediol, hexanediol, nonanediol, and neopentyl glycol.

[0027] These other polyols may be used individually or in combination of two or more.

[0028] (c) Compounds having an anionic hydrophilic group and at least two active hydrogens The (c) compound having an anionic hydrophilic group and at least two active hydrogens used in the present invention (hereinafter also referred to as "(c) compound") is a compound having an anionic hydrophilic group such as a carboxyl group, carboxylate group, sulfo group, or sulfonate group and two or more active hydrogen-containing groups such as a hydroxyl group. By copolymerizing this (c) compound having an anionic hydrophilic group and at least two active hydrogens, a self-emulsifying aqueous polyurethane resin can be obtained. Examples of the (c) compound include 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, 2,2-dimethylolbutyric acid, 2,2-dimethylolvaleric acid, dihydroxymaleic acid, and 2,6-dihydroxybenzoic acid.

[0029] Furthermore, the content of the anionic hydrophilic groups in the aqueous polyurethane resin is preferably 0.3 to 4.0% by mass, and more preferably 0.5 to 3.0% by mass, from the viewpoint of emulsification stability, storage stability, and leather tread resistance. If the content of the anionic hydrophilic groups falls below the lower limit, the emulsification stability and storage stability of the aqueous polyurethane resin tend to decrease, and it may not be possible to use the aqueous polyurethane resin stably. On the other hand, if it exceeds the upper limit, the aqueous polyurethane resin tends to become too hard, and the leather tread resistance may decrease.

[0030] (d) Polyamines having two or more amino groups and / or imino groups The (d) polyamines having two or more amino groups and / or imino groups used in the present invention (hereinafter also referred to as "(d) polyamines") act as chain extenders. Examples of such (d) polyamines include diamines such as ethylenediamine, propylenediamine, tetramethylenediamine, hexamethylenediamine, diaminocyclohexylmethane, hydrazine, 2-methylpiperazine, isophoronediamine, norboranediamine, diaminodiphenylmethane, tolylenediamine, xylylenediamine; polyamines such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, iminobispropylamine; diprimeramines and Examples include amidoamines derived from monocarboxylic acids; water-soluble amine derivatives such as monoketimine of diprimer amines; and hydrazine derivatives such as dihydrazide oxalate, dihydrazide malonate, dihydrazide succinate, dihydrazide glutarate, dihydrazide adipic acid, dihydrazide sebacate, dihydrazide maleate, dihydrazide fumarate, dihydrazide itaconic acid, 1,1'-ethylenehydrazine, 1,1'-trimethylenehydrazine, and 1,1'-(1,4-butylene)dihydrazine. These polyamines may be used individually or in combination of two or more. Furthermore, the amount of such (d) polyamine used is preferably an amount containing 0.8 to 1.2 equivalents of amino groups, etc., relative to the free isocyanate groups of the isocyanate-terminated prepolymer described later.

[0031] (Isocyanate-terminated prepolymer) The isocyanate-terminated prepolymer used in the present invention is a reaction product of (a) an organic polyisocyanate, (b) a polyol, and (c) a compound having an anionic hydrophilic group and at least two active hydrogens.

[0032] There are no particular limitations on the method for producing such isocyanate-terminated prepolymers. Examples include the conventionally known one-stage so-called one-shot method and the multi-stage isocyanate polyaddition reaction method. The reaction temperature is preferably 40 to 150°C. In this case, a reaction catalyst such as dibutyltin dilaurate, stanus octoate, dibutyltin di-2-ethylhexoate, triethylamine, triethylenediamine, N-methylmorpholine, or bismastris (2-ethylhexanoate), or a reaction inhibitor such as phosphoric acid, sodium hydrogen phosphate, p-toluenesulfonic acid, adipic acid, or benzoyl chloride may be added as needed.

[0033] Furthermore, an organic solvent that does not react with the isocyanate group may be added during or after the reaction. Examples of such organic solvents include acetone, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, dioxane, dimethylformamide, dimethyl sulfoxide, toluene, xylene, ethyl acetate, butyl acetate, and methylene chloride. Of these organic solvents, methyl ethyl ketone, toluene, and ethyl acetate are particularly preferred. These organic solvents can also be removed by heating and reducing pressure after emulsification, dispersion, and chain extension of the prepolymer.

[0034] In the production of isocyanate-terminated prepolymers, the molar ratio (NCO / OH) of isocyanate groups to hydroxyl groups in the raw material is preferably 2.0 / 1.0 to 1.1 / 1.0, and more preferably 1.7 / 1.0 to 1.25 / 1.0. By adjusting the molar ratio of isocyanate groups to hydroxyl groups in the raw material within the above range, an isocyanate-terminated prepolymer having a desired free isocyanate group content can be obtained. On the other hand, if the molar ratio of isocyanate groups to hydroxyl groups in the raw material falls below the lower limit, the free isocyanate group content tends to decrease too much, while if it exceeds the upper limit, the free isocyanate group content tends to increase too much.

[0035] The content of free isocyanate groups in the isocyanate-terminated prepolymer obtained in this manner is preferably 0.2 to 5.0% by mass, more preferably 0.4 to 4.0% by mass, and even more preferably 0.6 to 3.0% by mass. If the free isocyanate group content falls below the lower limit, the viscosity of the isocyanate-terminated prepolymer during production tends to increase significantly, requiring a large amount of organic solvent, which is disadvantageous in terms of cost and tends to make emulsification and dispersion difficult. On the other hand, if the free isocyanate group content exceeds the upper limit, the balance of water solubility after emulsification and dispersion and after chain extension by (d) polyamine tends to change significantly, which may reduce the storage stability or processing stability of the aqueous polyurethane resin over time. In addition, the rubbing resistance of the leather may decrease.

[0036] Furthermore, the (a) organic polyisocyanate, the (b) polyol, and the (c) compound having an anionic hydrophilic group and at least two active hydrogen atoms all have multiple reaction sites. The isocyanate-terminated prepolymer obtained by reacting such (a) organic polyisocyanate, (b) polyol, and (c) compound having an anionic hydrophilic group and at least two active hydrogen atoms has a complex structure and cannot be directly represented by a general formula (structural formula).

[0037] (Neutralized product of isocyanate-terminated prepolymer) The neutralized isocyanate-terminated prepolymer used in the present invention is obtained by neutralizing the anionic hydrophilic groups in the isocyanate-terminated prepolymer. Such a neutralized isocyanate-terminated prepolymer may be produced by (i) reacting the (a) organic polyisocyanate, the (b) polyol, and the (c) compound having an anionic hydrophilic group and at least two active hydrogens, and then neutralizing the anionic hydrophilic groups in the isocyanate-terminated prepolymer by a known method; or (ii) mixing the (a) organic polyisocyanate, the (b) polyol, and the (c) compound having an anionic hydrophilic group and at least two active hydrogens, then neutralizing the anionic hydrophilic groups in the (c) compound by a known method, and then reacting the neutralized (c) compound, the (a) organic polyisocyanate, and the (b) polyol. Furthermore, the neutralized product of the isocyanate-terminated prepolymer can also be produced by reacting (iii) the (a) organic polyisocyanate, the (b) polyol, and the (c) compound, in which the anionic hydrophilic group is a salt of the anionic hydrophilic group.

[0038] In the production methods described in (i) and (ii) above, there are no particular restrictions on the basic compound used for neutralizing the anionic hydrophilic group (hereinafter also referred to as the "neutralizing basic compound"), and examples include amines such as trimethylamine, triethylamine, tri-n-propylamine, tributylamine, N-methyl-diethanolamine, N,N-dimethylethanolamine, N,N-diethylethanolamine, and triethanolamine; alkali metal hydroxides such as potassium hydroxide and sodium hydroxide; and ammonia. Among these, tertiary amines such as trimethylamine, triethylamine, tri-n-propylamine, and tributylamine are particularly preferred.

[0039] In the neutralization of the anionic hydrophilic group in the manufacturing methods (i) and (ii) described above, the amount of the neutralizing basic compound used is preferably 0.5 to 1.5 equivalents, more preferably 0.6 to 1.4 equivalents, and particularly preferably 0.7 to 1.3 equivalents, relative to the anionic hydrophilic group. If the amount of the neutralizing basic compound used falls below the lower limit, the emulsification and storage stability of the aqueous polyurethane resin tend to decrease. On the other hand, adding an amount of the neutralizing basic compound exceeding the upper limit does not further improve the emulsification and storage stability of the aqueous polyurethane resin, which is economically undesirable.

[0040] (Water-based polyurethane resin) The aqueous polyurethane resin used in the present invention is obtained by extending the chain of the neutralized isocyanate-terminated prepolymer with the (d) polyamine (chain extension product). In extending the chain of the neutralized isocyanate-terminated prepolymer, the neutralized isocyanate-terminated prepolymer is emulsified and dispersed in water, and this emulsified and dispersed neutralized isocyanate-terminated prepolymer is chain-extended with the (d) polyamine. This forms the aqueous polyurethane resin.

[0041] (emulsification dispersion) There are no particular limitations on the method for emulsifying and dispersing the isocyanate-terminated prepolymer neutralized product in water; for example, conventionally known methods using homomixers, homogenizers, dispersers, etc. can be used. The isocyanate-terminated prepolymer neutralized product can be emulsified and dispersed in water at temperatures within the range of 0 to 40°C without the addition of any emulsifier. This suppresses the reaction between the isocyanate group and water. Furthermore, when emulsifying and dispersing the isocyanate-terminated prepolymer neutralized product, reaction inhibitors such as phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, p-toluenesulfonic acid, adipic acid, and benzoyl chloride may be added as needed.

[0042] (Chain elongation) There are no particular limitations on the method for extending the chain of the isocyanate-terminated prepolymer neutralized product, which is emulsified and dispersed in water, using the (d) polyamine. For example, it is preferable to add the (d) polyamine to the emulsified dispersion of the isocyanate-terminated prepolymer neutralized product and react the isocyanate-terminated prepolymer neutralized product with the (d) polyamine to extend the chain, or to add the emulsified dispersion of the isocyanate-terminated prepolymer neutralized product to the (d) polyamine and react the isocyanate-terminated prepolymer neutralized product with the (d) polyamine to extend the chain. The reaction between the isocyanate-terminated prepolymer neutralized product and the (d) polyamine is usually completed at a reaction temperature of 20 to 50°C, within 30 to 120 minutes after mixing the isocyanate-terminated prepolymer neutralized product and the (d) polyamine.

[0043] Such chain elongation may be performed simultaneously with the emulsification and dispersion, after the emulsification and dispersion, or before the emulsification and dispersion. Furthermore, if the obtained aqueous polyurethane resin contains an organic solvent, it is preferable to remove the organic solvent under reduced pressure at a temperature of 30 to 80°C.

[0044] Furthermore, similar to the (a) organic polyisocyanates, the (b) polyols, and the (c) compounds having an anionic hydrophilic group and at least two active hydrogens, the (d) polyamine also has multiple reaction sites. The chain extension product of the neutralized isocyanate-terminated prepolymer (aqueous polyurethane resin) obtained by extending the chain of the neutralized isocyanate-terminated prepolymer using such a (d) polyamine also has a complex structure, similar to the isocyanate-terminated prepolymer, and cannot be directly represented by a general formula (structural formula).

[0045] The aqueous polyurethane resin obtained in this manner is preferably used in an emulsified and dispersed state in water. There are no particular restrictions on the resin concentration, but 20 to 60% by mass is preferred. The resin concentration in such an aqueous emulsified dispersion of aqueous polyurethane resin can be adjusted by adding or removing water.

[0046] [Surface treatment agent] Next, the surface treatment agent of the present invention will be described. The surface treatment agent of the present invention contains the aqueous polyurethane resin. By treating the surface of a leather substrate with such a surface treatment agent, a surface treatment layer is formed on the surface of the leather substrate by the surface treatment agent, thereby adjusting the color, gloss, texture, feel, etc. Furthermore, the leather substrate can be given excellent abrasion resistance without impairing its abrasion resistance.

[0047] In the surface treatment agent of the present invention, in addition to the aqueous polyurethane resin, various additives such as resins other than the aqueous polyurethane resin (acrylic resins, polyester resins, etc.), matting agents, smoothing agents, thickeners, crosslinking agents, surfactants, defoaming agents, leveling agents, viscoelastic modifiers, wetting agents, dispersants, preservatives, film-forming agents, plasticizers, penetrating agents, fragrances, bactericides, acaricides, fungicides, ultraviolet absorbers, antioxidants, antistatic agents, flame retardants, dyes, pigments, etc. may be blended, as long as they do not impair the effects of the present invention.

[0048] (Acrylic resin) Examples of the acrylic resin include homopolymers and copolymers of acrylic monomers. By incorporating the acrylic resin, stain-resistant properties can be imparted to the leather substrate.

[0049] Examples of the acrylic monomers include methyl (meth)acrylate, ethyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, benzyl (meth)acrylate, (meth)acrylic acid, glycidyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, and 2-hydroxypropyl (meth)acrylate, which are derivatives of (meth)acrylic acid. Here, (meth)acrylic acid refers to acrylic acid or methacrylic acid. Furthermore, these acrylic monomers may be used individually or in combination of two or more.

[0050] Examples of copolymer monomers used in the copolymer of the acrylic monomers mentioned above include aromatic vinyl compounds such as styrene, α-methylstyrene, and p-methylstyrene; acrylamides such as acrylamide, diacetone acrylamide, methacrylamide, and maleamide; heterocyclic vinyl compounds such as vinylpyrrolidone; vinyl compounds such as vinyl chloride, acrylonitrile, vinyl ether, vinyl ketone, and vinylamide; α-olefins such as ethylene and propylene; maleic acid, fumaric acid, itaconic acid, and their derivatives. These copolymer monomers may be used individually or in combination of two or more.

[0051] (Matte agent) In the surface treatment agent of the present invention, a matting agent may be added to adjust the gloss and shine of the leather surface. Examples of such matting agents include organic beads, silica particles, talc, aluminum hydroxide, calcium sulfate, calcium silicate, calcium carbonate, magnesium carbonate, barium carbonate, alumina silicate, kaolin, mica, and other similar substances. These matting agents may be used individually or in combination of two or more.

[0052] Examples of the organic beads include urethane beads, acrylic beads, silicone beads, olefin beads, high-density polyethylene, and low-density polyethylene. Examples of the silica particles include dry silica and wet silica, with dry silica being preferred from the viewpoint of high scattering effect and the ability to adjust the gross value with a small amount. The average particle size of the organic beads is preferably 2 to 20 μm, and more preferably 3 to 15 μm.

[0053] The amount of such a matting agent used should be appropriate depending on the desired matte finish (gloss / sheen) of the leather surface, but typically, 1 to 150 parts by mass, more preferably 5 to 120 parts by mass, and even more preferably 7 to 100 parts by mass, per 100 parts by mass of the aqueous polyurethane resin.

[0054] (Smoothing agent) In the surface treatment agent of the present invention, a smoothing agent may be added to improve the smoothness and abrasion resistance of the leather surface. Examples of such smoothing agents include polydimethyl silicone, hydrogen-modified silicone, vinyl-modified silicone, epoxy-modified silicone, amino-modified silicone, carboxyl-modified silicone, halogenated-modified silicone, methacryloxy-modified silicone, mercapto-modified silicone, fluorine-modified silicone, alkyl-modified silicone, phenyl-modified silicone, and polyether-modified silicone. These smoothing agents may be used individually or in combination of two or more. Among these smoothing agents, polydimethyl silicone and epoxy-modified silicone are preferred from the viewpoint of having a significant effect in improving abrasion resistance.

[0055] In the surface treatment agent of the present invention, commercially available smoothing agents can be used. Examples of commercially available polydimethyl silicone emulsions include DOWSIL SM490EX, DOWSIL SM-8706EX, DOWSIL IE-7046T, DOWSIL FBL-3289, DOWSIL Q2-3238 (all manufactured by Dow-Toray Industries, Inc.), KM-752T, KM-862T, KM-9737A, and POLON MF-33 (all manufactured by Shin-Etsu Chemical Co., Ltd.). Examples of commercially available epoxy-modified silicone emulsions include DOWSIL SM-8701 (manufactured by Dow-Toray Industries, Inc.), POLON MF-18T, and X-51-1264 (all manufactured by Shin-Etsu Chemical Co., Ltd.).

[0056] The amount of such smoothing agent (amount of non-volatile content) should be appropriate depending on the smoothness and abrasion resistance of the leather surface, but generally, 1 to 150 parts by mass, more preferably 5 to 120 parts by mass, and even more preferably 7 to 100 parts by mass, per 100 parts by mass of the aqueous polyurethane resin.

[0057] (Thickening agent) In the surface treatment agent of the present invention, a thickening agent may be added to adjust the viscosity to an appropriate level. Examples of such thickening agents include alkali-thickening acrylic resins, association-type thickening agents, and water-soluble organic polymers. These thickening agents may be used individually or in combination of two or more.

[0058] In the surface treatment agent of the present invention, commercially available alkali-thickened acrylic resins can be used. Examples of commercially available alkali-thickened acrylic resins include Nikazol VT-253A (manufactured by Nippon Carbide Industries, Ltd.), Aron A-20P, Aron A-7150, Aron A-7070, Aron B-300, Aron B-300K, Aron B-500 (all manufactured by Toagosei Co., Ltd.), Julimar AC-10LHP, Julimar AC-10SHP, Leozic 835H, Junron PW-110, Junron PW-150 (all manufactured by Toagosei Co., Ltd.). Examples include Primal ASE-60, Primal TT-615, and Primal RM-5 (all manufactured by Rohm & Haas Japan Co., Ltd.), SN Thickener A-818 and SN Thickener A-850 (both manufactured by Sunopco Corporation), Paragum 500 (manufactured by Parachem Southern Co., Ltd.), Leolate 430 (manufactured by Elementis Japan Co., Ltd.), and NeoSticker V-420 (manufactured by Nikka Chemical Co., Ltd.). Such alkali-thickened acrylic resins are usually commercially available as emulsified dispersions of resins, and it is preferable to use them in an emulsified dispersion state.

[0059] Furthermore, in the surface treatment agent of the present invention, commercially available associative thickeners can be used. Examples of commercially available associative thickeners include Adekanol UH-450, Adekanol UH-540, Adekanol UH-752 (all manufactured by Asahi Denka Kogyo Co., Ltd.), SN Thickener 601, SN Thickener 612, SN Thickener 621N, SN Thickener 623N, SN Thickener 660T (all manufactured by Sunopco Co., Ltd.), Leolate 244, Leolate 278, Leolate 300 (all manufactured by Elementis Japan Co., Ltd.), and DK Thickener SCT-275 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.).

[0060] Examples of the aforementioned water-soluble organic polymers include natural water-soluble organic polymers, semi-synthetic water-soluble organic polymers, and synthetic water-soluble organic polymers. Examples of the aforementioned natural water-soluble organic polymers include starches such as potato starch, sweet potato starch, wheat starch, rice starch, tapioca starch, and corn starch; resin polysaccharides such as gum arabic, tragacanth gum, karaya gum, and tororo aoi; seaweed polysaccharides such as sodium alginate, carrageenan, agar (galactan), and funori; microbial fermentation polysaccharides such as xanthan gum, pullulan, curdlan, dextrin, and levan; proteins such as casein, gelatin, arabine, glue, and collagen; and pectin, chitin, and chitosan.

[0061] Examples of the aforementioned semi-synthetic water-soluble organic polymers include cellulose derivatives such as methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, carboxymethylcellulose, and sodium cellulose sulfate; starch derivatives such as dextrin, soluble starch, oxidized starch, carboxymethyl starch, hydroxyethyl starch, hydroxypropyl starch, dialdehyde starch, phosphate starch, and acetyl starch; and propylene glycol alginate.

[0062] Examples of the aforementioned synthetic water-soluble organic polymers include polyvinyl alcohol, polyacrylic acid, polyacrylate salts, polyacrylamide, polyvinylpyrrolidone, polyvinyl alkyl ethers, maleic anhydride copolymers, maleic acid copolymers, maleate copolymers, and the like.

[0063] The amount of such thickener (amount of non-volatile component) should be appropriate depending on the viscosity of the surface treatment agent, but generally, 0.5 to 40 parts by mass, more preferably 1 to 30 parts by mass, and even more preferably 2 to 20 parts by mass, per 100 parts by mass of the aqueous polyurethane resin.

[0064] (Crosslinking agent) In the surface treatment agent of the present invention, a crosslinking agent may be added to improve the water resistance and durability of the leather. Examples of such crosslinking agents include carbodiimide-based crosslinking agents, isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, blocked isocyanate-based crosslinking agents, water-dispersible isocyanate-based crosslinking agents, and melamine-based crosslinking agents. These crosslinking agents may be used individually or in combination of two or more. Furthermore, if the aqueous polyurethane resin contained in the surface treatment agent of the present invention is a self-emulsifying aqueous polyurethane resin having carboxyl groups, among these crosslinking agents, it is particularly preferable to add a carbodiimide-based crosslinking agent from the viewpoint of texture and stability of the processing liquid.

[0065] In the surface treatment agent of the present invention, commercially available crosslinking agents can be used. Examples of commercially available carbodiimide-based crosslinking agents include Carbodilite E-02, Carbodilite SV-02, Carbodilite V02-L2, Carbodilite V-10 (all manufactured by Nisshinbo Chemical Co., Ltd.), and NK Assist CI-02 (manufactured by Nikka Chemical Co., Ltd.).

[0066] From the viewpoint of the abrasion resistance and rubbing resistance of the leather, the amount of such crosslinking agent (amount of non-volatile components) is preferably 1 to 15 parts by mass, and more preferably 2 to 10 parts by mass, per 100 parts by mass of the aqueous polyurethane resin.

[0067] 〔leather〕 Next, the leather of the present invention will be described. The leather of the present invention comprises a leather base material and a surface treatment layer formed on the base material with the surface treatment agent of the present invention. Examples of the leather base material include synthetic leather having a surface layer made of polyurethane resin (PU), PVC leather, polyurethane thermoplastic elastomer (TPU), and other imitation leathers. Examples of leather products using the leather of the present invention include vehicle interior materials, motorcycle seats and grips, sports shoes, clothing, furniture, etc., using synthetic leather, artificial leather, natural leather, or PVC leather.

[0068] There are no particular limitations on the method for forming the surface treatment layer on the leather substrate. For example, the surface treatment layer can be formed by applying the surface treatment agent to the leather substrate and then drying it.

[0069] Methods for applying the surface treatment agent include, for example, applying the surface treatment agent to the leather substrate using various coaters such as a gravure coater, bar coater, comma coater, blade coater, and air knife coater; spraying the surface treatment agent onto the leather substrate; and immersing the leather substrate in the surface treatment agent. However, the direct coating method and the reverse coating method using a gravure coater are more preferred. The amount of surface treatment agent applied is 4 to 40 g / m² after drying. 2 A suitable amount is 6-30 g / m². 2 A quantity that results in this is more preferable.

[0070] There are no particular restrictions on the drying method of the coated surface treatment agent. For example, it is preferable to dry it at a temperature in the range of 40 to 160°C for 30 seconds to 10 minutes, and more preferably at a temperature in the range of 80 to 130°C for 30 seconds to 2 minutes. Furthermore, it is preferable to perform an aging treatment at a temperature in the range of 20 to 100°C for 5 to 72 hours after drying. [Examples]

[0071] The present invention will be described more specifically below based on examples and comparative examples, but the present invention is not limited to the following examples. The free isocyanate group content in the synthesis examples was measured by the following method.

[0072] (Content of free isocyanate groups) 0.3 g of urethane prepolymer was placed in an Erlenmeyer flask, and 10 ml of 0.1 N dibutylamine toluene solution was added to dissolve the urethane prepolymer. Then, a few drops of bromophenol blue solution were added, and the mixture was titrated with 0.1 N methanol hydrochloric acid solution to obtain the following formula: NCO% = (ab) × 0.42 × f / x (In the above formula, a: titration volume of 0.1N hydrochloric acid methanol solution when only 10 ml of 0.1N dibutylamine toluene solution is titrated, b: titration volume of 0.1N hydrochloric acid methanol solution when the solution containing the dissolved urethane prepolymer is titrated, f: factor of 0.1N hydrochloric acid methanol solution, x: amount of urethane prepolymer) The free isocyanate group content (NCO%) was determined by this method.

[0073] Furthermore, the raw materials used in the synthesis example are listed below.

[0074] (a) Organic polyisocyanates H12MDI: Dicyclohexylmethane 4,4'-diisocyanate (Desmodulo W, manufactured by Covestro). IPDI: Isophorone diisocyanate (VESTANAT(R)IPDI manufactured by Evonik Japan Co., Ltd.). 1,5-PDI: 1,5-pentamethylene diisocyanate. HDI: Hexamethylene diisocyanate.

[0075] (b) Polyol (b1) Hydroxyl-terminated polyalkadien POLYVEST HT: Polybutadiene diol manufactured by Evonik Japan Co., Ltd., trade name "POLYVEST HT", weight-average molecular weight 2400. Poly bd R-15HT: Polybutadiene diol manufactured by Idemitsu Petrochemical Co., Ltd., trade name "Poly bd R-15HT", weight-average molecular weight 1200. NISSO-PB G-3000: Polybutadiene diol manufactured by Nippon Soda Co., Ltd., product name "NISSO-PB G-3000", weight-average molecular weight 3500. Poly ip: Polyisoprendiol manufactured by Idemitsu Petrochemical Co., Ltd., trade name "Poly ip", weight-average molecular weight 2500. NISSO-PB G-2000: Polybutadiene diol manufactured by Nippon Soda Co., Ltd., product name "NISSO-PB G-2000", weight-average molecular weight 2100.

[0076] (Other polyols) P-2012: Polyester diol manufactured by Kuraray Co., Ltd., poly(3-methyl-1,5-pentanediol adipate / 3-methyl-1,5-pentanediol isophthalate), product name "Kuraray Polyol P-2012", weight-average molecular weight 2000. T6002: Polycarbonate diol (1,6-hexanediol) manufactured by Asahi Kasei Chemicals Corporation, trade name "Duranol T6002", weight-average molecular weight 2000. T6001: Polycarbonate diol (1,6-hexanediol) manufactured by Asahi Kasei Chemicals Corporation, trade name "Duranol T6001", weight-average molecular weight 1000. T5652: Polycarbonate diol (1,5-pentanediol / 1,6-hexanediol) manufactured by Asahi Kasei Chemicals Corporation, trade name "Duranol T5652", weight-average molecular weight 2000. DC-1100: A polyether-based polyol manufactured by NOF Corporation, polyoxytetramethylene polyoxyethylene glycol, trade name "Unisafe DC-1100", weight-average molecular weight 1000. NL2010DB: Polycarbonate diol (1,4-butanediol / 1,10-decanediol) manufactured by Mitsubishi Chemical Corporation, trade name "Beneviol NL-2010DB", weight-average molecular weight 2000. 1,3-BD: 1,3-butanediol. NISSO-PB GI-3000: Hydrogenated polybutadiene diol manufactured by Nippon Soda Co., Ltd., weight-average molecular weight 4000.

[0077] (c) compound DMPA: Dimethylolpropionic acid.

[0078] (Basic compounds for neutralization) DMEA: N,N-dimethylethanolamine.

[0079] (d) Polyamines HDZ: Hydrazine monohydrate. EDA: Ethylenediamine. DETA: Diethylenetriamine.

[0080] Furthermore, the aqueous polyurethane resins used in the examples and comparative examples were synthesized by the following method.

[0081] (Synthesis Example 1) A four-necked flask equipped with a stirrer, reflux condenser, thermometer, and nitrogen blowing tube contains (b1) polybutadienediol (Evonik Japan Co., Ltd. "POLYVEST") as a hydroxyl-terminated polyalkadiene. (c) 25.0 parts by mass of (HT), number average molecular weight 2400, 47.6 parts by mass of polyester diol (poly(3-methyl-1,5-pentanediol adipate / 3-methyl-1,5-pentanediol isophthalate)) (Kuraray Co., Ltd. "P-2012", weight average molecular weight 2000) as other polyols, 3.0 parts by mass of dimethylolpropionic acid and 28.1 parts by mass of methyl ethyl ketone as compounds were charged and uniformly mixed. Then, 21.3 parts by mass of dicyclohexylmethane 4,4'-diisocyanate and 0.03 parts by mass of bismastris (2-ethylhexanoate) were added as organic polyisocyanates, and the mixture was reacted at 80°C for 240 minutes to obtain a methyl ethyl ketone solution of an isocyanate-terminated urethane prepolymer with a free isocyanate group content of 2.11% by mass relative to the isocyanate-terminated prepolymer.

[0082] To this solution, 1.9 parts by mass of N,N-dimethylethanolamine was added as a neutralizing basic compound and mixed uniformly. Then, 162.2 parts by mass of water was gradually added to emulsify and disperse the mixture. To the resulting emulsified dispersion, 0.7 parts by mass of hydrazine monohydrate and 0.5 parts by mass of diethylenetriamine were added as (d) polyamines, and the mixture was stirred for 90 minutes to obtain a polyurethane dispersion. Next, this polyurethane dispersion was desolvented under reduced pressure at 40°C to obtain a stable aqueous dispersion of polyurethane resin with a resin content of 35.0% by mass, a viscosity of 50 mPa·s, and an average particle size of 0.3 μm.

[0083] Table 1 shows the content of free isocyanate groups in the isocyanate-terminated urethane prepolymer, and the content of structural units derived from (b1) hydroxyl-terminated polyalkadienes in the aqueous polyurethane resin, the proportion of (b1) hydroxyl-terminated polyalkadienes in the (b) polyol, and the content of anionic hydrophilic groups in the aqueous polyurethane resin in the aqueous polyurethane resin in the aqueous dispersion of the obtained aqueous polyurethane resin.

[0084] (Synthesis Examples 2-20 and Comparative Synthesis Examples 1-6) An aqueous dispersion of a polyurethane resin (35.0% by mass of resin) was obtained in the same manner as in Synthesis Example 1, except that the types and amounts of (a) organic polyisocyanate, (b) polyol, (c) compound, neutralizing basic compound, and (d) polyamine shown in Tables 1 to 3 were used. The content of free isocyanate groups in the isocyanate-terminated urethane prepolymer, the content of structural units derived from (b1) hydroxyl-terminated polyalkadiene in the aqueous polyurethane resin, the proportion of (b1) hydroxyl-terminated polyalkadiene in (b) polyol, and the content of anionic hydrophilic groups in the aqueous polyurethane resin are shown in Tables 1 to 3.

[0085] (Examples 1-20 and Comparative Examples 1-6) 286 parts by mass (35% by mass of resin content) of aqueous dispersions of each aqueous polyurethane resin obtained in Synthesis Examples 1-20 and Comparative Synthesis Examples 1-6, and silica particles manufactured by a dry process as a matting agent (Evonik Degussa "ACEMATT TS"). A aqueous surface treatment agent was prepared by uniformly mixing 7 parts by mass of (100), average particle size: 10 μm, 30 parts by mass of urethane beads (Negami Kogyo Co., Ltd. "Art Pearl P-800T", average particle size: 6 μm, Tg=-34℃), 40 parts by mass of a smoothing agent (Shin-Etsu Chemical Co., Ltd. "KM-862T", non-volatile content 60% by mass), 12 parts by mass of an associative thickener (Sunopco Co., Ltd. "SN Thickener 612", non-volatile content 40% by mass), 343 parts by mass of ion-exchanged water, and 12 parts by mass of a water-dispersible carbodiimide-based crosslinking agent (Nisshinbo Chemical Inc. "Carbodilite SV-02", non-volatile content 40% by mass) using a disperser.

[0086] <Preparation of base materials for leather> A coating material for the surface layer, comprising 100 parts by mass of aqueous polyurethane resin (Evaphanol HA-68, manufactured by Nikka Chemical Co., Ltd., 35% by mass of non-volatile content), 10 parts by mass of aqueous pigment (PSM Black C, manufactured by Mikuni Pigment Co., Ltd., 31.5% by mass of non-volatile content), 1 part by mass of water-dispersible carbodiimide crosslinking agent (NK Assist CI-02, manufactured by Nikka Chemical Co., Ltd., 40% by mass of non-volatile content), and 3 parts by mass of association-type thickener (Neo Sticker S, manufactured by Nikka Chemical Co., Ltd.), was applied to release paper (Asahi Release AR-148, manufactured by Asahi Roll Co., Ltd.) to a coating thickness of 100 μm (WET coating amount). Pre-drying was performed at 80°C for 2 minutes using a dryer, and then drying was performed at 120°C for 3 minutes to completely evaporate the moisture and obtain a polyurethane resin film (hereinafter referred to as the "surface layer").

[0087] On this surface layer, a polyurethane adhesive mixture was applied to a thickness of 200 μm (WET application amount), comprising 100 parts by mass of a two-component aqueous polyurethane resin (Evaphanol HO-38, manufactured by Nikka Chemical Co., Ltd., adhesive main component, non-volatile content 35% by mass), 7 parts by mass of an aqueous polyisocyanate curing agent (NK Assist NY-27, manufactured by Nikka Chemical Co., Ltd., non-volatile content 100% by mass), and 5 parts by mass of an associative thickener (Neo Sticker N, manufactured by Nikka Chemical Co., Ltd., non-volatile content 30% by mass).

[0088] Next, the material was dried in a dryer at 90°C for 1 minute, and immediately after drying, a polyester knit was laminated on top as a fiber base material. Then, it was cured at 120°C for 3 minutes, and further aged at 40°C for 72 hours, after which the release paper was peeled off to obtain a fiber laminate (evaluation base material).

[0089] <Leather production> On the surface layer of the obtained fiber laminate, the aqueous surface treatment agent obtained in the example or comparative example was applied using a 100-mesh gravure coater, with a dry coating amount of 10-20 g / m². 2 The leather was coated to achieve the desired surface treatment, and then air-dried at 125°C for 3 minutes to produce an evaluation leather with a surface treatment layer. The abrasion resistance and rubbing resistance of this evaluation leather were evaluated as follows.

[0090] (Abrasion resistance) The obtained evaluation leather was cut to approximately 300 mm in length and 70 mm in width. A 10 mm thick urethane foam (UEI-3, manufactured by Inoac Corporation) was attached to the fibrous base material on the back side using double-sided tape, and the leather was fixed to the flat abrasion table of a flat abrasion tester (PA-2A, manufactured by Daiei Kagaku Seiki Seisakusho) without wrinkles. A 4.5 mm diameter wire was placed in the center of the underside of the urethane foam during fixing. A friction element fitted with JIS L3102 (cotton canvas) No. 6 cotton canvas was set up, and an abrasion test was conducted by sliding the test piece and the friction element back and forth 8000 times parallel to the wire attached to the test piece under the conditions of a pressing load of 19.6 N including the friction element, a stroke of 140 mm, and a speed of approximately 60 reciprocations / minute. The appearance change of the surface treatment layer after the abrasion test was checked, and the abrasion resistance was evaluated according to the following criteria. The results are shown in Tables 1 to 3. <Evaluation Criteria> Grade 5: No change was observed. Grade 4: Slight tears or other damage were observed in the epidermal layer. Grade 3: Tears were observed in a portion of the epidermal layer, but the underlying fiber material was not exposed. Grade 2: Tears or other damage were observed in the epidermal layer, exposing the fibrous base material on the reverse side. Grade 1: Tears or other damage occurred in the surface layer after fewer than 8,000 cycles, exposing the fibrous base material on the reverse side.

[0091] (Rubber resistance) Two test pieces, each approximately 120 mm long and 30 mm wide, were cut from the obtained evaluation leather. These two pieces were stacked so that their longitudinal directions were the same and their surface treatment layers were in contact with each other. They were then mounted on the chucks of a Scott-type flexibility tester (manufactured by Daiei Kagaku Seiki Seisakusho) with a chuck spacing of 30 mm. The chuck spacing was narrowed to adjust the load on the surface treatment layers of the test pieces to 9.8 N. A kneading operation was performed 1000 times under conditions of a stroke of 50 mm and a speed of 120 cycles / minute. The change in the appearance of the test piece surface after the kneading operation was observed, and the kneading resistance was evaluated according to the following criteria. The results are shown in Tables 1 to 3. <Evaluation Criteria> Grade 5: No change was observed. Grade 4: Slight whitening was observed in the husk area. Grade 3: Some whitening was observed in the husk portion, but no cracks or other damage were found. Grade 2: Whitening was observed throughout the entire grain, but no cracks or other damage were found. Grade 1: Whitening was observed throughout the entire fur portion, and cracks were found in the coating.

[0092] [Table 1]

[0093] [Table 2]

[0094] [Table 3]

[0095] As shown in Tables 1 and 2, when the surface of a leather substrate is treated with a surface treatment agent containing an aqueous polyurethane resin synthesized using (b1) a hydroxyl-terminated polyalkadien having an unsaturated hydrocarbon structure as at least a portion of the polyol (Examples 1 to 20), it was found that leather with excellent rubbing resistance can be obtained without impairing abrasion resistance.

[0096] On the other hand, as shown in Table 3, when the surface of a leather substrate was treated with a surface treatment agent containing an aqueous polyurethane resin synthesized without using (b1) a hydroxyl-terminated polyalkadiene having an unsaturated hydrocarbon structure (Comparative Examples 1-6), it was found that the abrasion resistance of the resulting leather was impaired and its resistance to rubbing decreased. [Industrial applicability]

[0097] As described above, the present invention makes it possible to impart excellent rubbing resistance to a leather base material without impairing its abrasion resistance. Therefore, since the leather of the present invention has excellent rubbing resistance without impairing its abrasion resistance, it can be suitably used in various industrial fields such as vehicles, furniture, clothing, bags, shoes, pouches, and general merchandise. Furthermore, by providing a surface treatment layer, it can also be suitably used as a stable and high-quality leather product.

Claims

1. The product contains (a) an organic polyisocyanate, (b) a polyol, and (c) a neutralized isocyanate-terminated prepolymer which is a reaction product of a compound having an anionic hydrophilic group and at least two active hydrogens, and (d) an aqueous polyurethane resin which is a chain extension product of a polyamine having two or more amino groups and / or imino groups. A surface treatment agent characterized in that the (b) polyol contains a hydroxyl-terminated polyalkadiene having an unsaturated hydrocarbon structure (b1).

2. The surface treatment agent according to claim 1, characterized in that the content of structural units derived from hydroxyl-terminated polyalkadienes having the (b1) unsaturated hydrocarbon structure in the aqueous polyurethane resin is 20 to 80% by mass.

3. The surface treatment agent according to claim 1, characterized in that the content of anionic hydrophilic groups in the aqueous polyurethane resin is 0.3 to 4.0% by mass.

4. The surface treatment agent according to claim 1, characterized in that the content of free isocyanate groups in the isocyanate group-terminated prepolymer is 0.2 to 5.0% by mass.

5. Leather comprising a leather base material and a surface treatment layer formed on the base material with a surface treatment agent according to any one of claims 1 to 4.

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