Aqueous urethane resin composition, synthetic leather, and method for producing aqueous urethane resin composition

Abstract

The present invention provides: an aqueous urethane resin composition which contains a urethane resin (A), an aqueous medium (B) and an emulsifying agent (C), and which is characterized in that the urethane resin (A) uses, as essential starting materials, a polyol compound (a1) that contains a nonionic polyol and an aromatic polyisocyanate compound (a2), and that the urea bond concentration in the urethane resin (A) is 100 mmol / kg or less; a synthetic leather which has an adhesive layer that is formed from this aqueous urethane resin composition; and a method for producing this aqueous urethane resin composition. This aqueous urethane resin composition has a long pot life, while exhibiting excellent peel strength and light resistance.

Description

[Technical Field]

[0001] The present invention relates to an aqueous urethane resin composition, a synthetic leather, and a method for producing the aqueous urethane resin composition. [Background technology]

[0002] Because aqueous urethane resin compositions can reduce volatile organic compounds compared to conventional solvent-based urethane resin compositions, in recent years they have been considered for use as environmentally friendly materials in a variety of applications, such as artificial leather, synthetic leather, coating agents, glove coatings and membranes, and adhesives.

[0003] In particular, for use in adhesive layers of synthetic leather, aqueous polyurethane resin-based adhesives containing an aqueous polyurethane resin (PUD) with a softening temperature of 50°C or less and a melt viscosity at 50°C of 60,000 Pa·s or less, and a polyisocyanate compound, are known (see, for example, Patent Document 1). However, two-component adhesives that combine a PUD base with an isocyanate crosslinking agent have the problem that the usable time (pot life) of the blended liquid is short, making it difficult to process stably.

[0004] Therefore, there has been a demand for a material that has a long pot life, excellent peel strength and light resistance. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-108289 Summary of the Invention [Problem to be solved by the invention]

[0006] The problem to be solved by the present invention is to provide an aqueous urethane resin composition having a long pot life and excellent peel strength and light resistance, a synthetic leather having an adhesive layer formed from the aqueous urethane resin composition, and a method for producing the aqueous urethane resin composition. [Means for solving the problem]

[0007] As a result of intensive research to solve the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by using an aqueous urethane resin composition containing a specific urethane resin and an aqueous medium, and have completed the present invention.

[0008] Specifically, the present invention relates to an aqueous urethane resin composition containing a urethane resin (A), an aqueous medium (B), and an emulsifier (C), wherein the urethane resin (A) contains, as essential raw materials, a polyol compound (a1) containing a nonionic polyol and an aromatic polyisocyanate compound (a2), and the urea bond concentration in the urethane resin (A) is 100 mmol / kg or less. [Effects of the Invention]

[0009] The aqueous urethane resin composition of the present invention has a long pot life and excellent peel strength and light resistance, and therefore can be used as a coating agent or adhesive, and is particularly suitable for use in adhesive layers of synthetic leather. DETAILED DESCRIPTION OF THE INVENTION

[0010] The aqueous urethane resin composition of the present invention is characterized by containing a urethane resin (A), an aqueous medium (B), and an emulsifier (C).

[0011] The urethane resin (A) is made from a polyol compound (a1) containing a nonionic polyol and an aromatic polyisocyanate compound (a2) as essential raw materials.

[0012] Examples of the nonionic polyol include compounds having an oxyethylene structure. These nonionic polyols can be used alone or in combination of two or more. Among these, compounds having an oxyethylene structure are preferred because they can provide an aqueous urethane resin composition having a long pot life and excellent peel strength and light resistance.

[0013] Examples of the compound having an oxyethylene structure include polyether polyols having an oxyethylene structure, such as polyethylene glycol, polyoxyethylene polyoxypropylene glycol, polyoxyethylene polyoxytetramethylene glycol, and polyethylene glycol dimethyl ether. These compounds having an oxyethylene structure can be used alone or in combination of two or more. Among these, polyethylene glycol and polyethylene glycol dimethyl ether are preferred because they provide an aqueous urethane resin composition having a long pot life and excellent peel strength and light resistance.

[0014] The number average molecular weight of the nonionic polyol is preferably in the range of 200 to 10,000, more preferably in the range of 300 to 3,000, and even more preferably in the range of 300 to 2,000, since an aqueous urethane resin composition having a long pot life and excellent peel strength and light resistance can be obtained. In the present invention, the number average molecular weight is a value measured by gel permeation column chromatography (GPC).

[0015] The proportion of the nonionic polyol used in the polyol compound (a1) is preferably in the range of 1 to 30% by mass, more preferably 2 to 10% by mass, since an aqueous urethane resin composition having a long pot life and excellent peel strength and light resistance can be obtained.

[0016] Furthermore, as the polyol compound (a1), polyols other than the nonionic polyols (hereinafter abbreviated as "other polyol compounds") can also be used, if necessary.

[0017] Examples of the other polyol compounds include polyether polyols, polyester polyols, polyacrylic polyols, polycarbonate polyols, polybutadiene polyols, etc., other than the nonionic polyols. These other polyol compounds can be used alone or in combination of two or more. Among these, polyether polyols, polyester polyols, and polycarbonate polyols are preferred because they can provide an aqueous urethane resin composition with a long pot life and excellent peel strength and light resistance.

[0018] Examples of the aromatic polyisocyanate compound (a2) include phenylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, naphthalene diisocyanate, polymethylene polyphenyl polyisocyanate, and carbodiimidized diphenylmethane polyisocyanate. These aromatic polyisocyanate compounds can be used alone or in combination of two or more. Among these, toluene diisocyanate is preferred because it can provide an aqueous urethane resin composition with a long pot life and excellent peel strength and light resistance.

[0019] If necessary, polyisocyanate compounds other than the aromatic polyisocyanate compound (a2) (hereinafter abbreviated as "other polyisocyanate compounds") can also be used in combination.

[0020] Examples of the other polyisocyanate compounds include aliphatic polyisocyanates such as hexamethylene diisocyanate, lysine diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, dimer acid diisocyanate, and norbornene diisocyanate; and alicyclic diisocyanates such as norbornane diisocyanate, isophorone diisocyanate, hydrogenated xylylene diisocyanate, and hydrogenated diphenylmethane diisocyanate. These other polyisocyanate compounds can be used alone or in combination of two or more.

[0021] Examples of the emulsifier (C) include nonionic emulsifiers such as polyoxyethylene nonylphenyl ether, polyoxyethylene lauryl ether, polyoxyethylene styrylphenyl ether, polyoxyethylene sorbitol tetraoleate, and polyethylene-polypropylene copolymers; anionic emulsifiers such as fatty acid salts such as sodium oleate, alkyl sulfate ester salts, alkylbenzene sulfonates, alkyl sulfosuccinates, naphthalene sulfonates, polyoxyethylene alkyl sulfates, sodium alkanesulfonates, and sodium alkyldiphenyl ether sulfonates; and cationic emulsifiers such as alkylamine salts, alkyltrimethylammonium salts, and alkyldimethylbenzylammonium salts. These emulsifiers can be used alone or in combination. Among these, anionic emulsifiers are preferred because they provide aqueous urethane resin compositions with long pot life, excellent peel strength, light resistance, and storage stability.

[0022] The amount of the emulsifier (C) used is preferably 10 parts by mass or less, more preferably in the range of 0.5 to 5 parts by mass, per 100 parts by mass of the urethane resin (A), in order to obtain an aqueous urethane resin composition having a long pot life and excellent peel strength, light resistance, and storage stability.

[0023] The urea bond concentration of the urethane resin (A) is 100 mmol / kg or less, and is preferably 50 mmol / kg or less, more preferably 30 mmol / kg or less, and particularly preferably 0 mmol / kg, because an aqueous urethane resin composition having a long pot life and excellent peel strength and light resistance can be obtained.

[0024] The average particle size of the urethane resin (A) is preferably in the range of 0.01 to 1 μm, more preferably in the range of 0.05 to 0.9 μm, since an aqueous urethane resin composition having a long pot life and excellent peel strength and light resistance can be obtained. In the present invention, the method for measuring the average particle size will be described in the Examples below.

[0025] In addition to the polyol compound (a1) and the aromatic polyisocyanate compound (a2), a chain extender having no amino group may be used as the urethane resin (A) if necessary. It is preferable to use a chain extender having a hydroxyl group, since this will result in an aqueous urethane resin composition having a particularly long pot life and excellent peel strength and light resistance.

[0026] Examples of the chain extender having a hydroxyl group include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, hexamethylene glycol, sucrose, methylene glycol, glycerin, sorbitol, bisphenol A, 4,4'-dihydroxydiphenyl, 4,4'-dihydroxydiphenyl ether, and trimethylolpropane. These chain extenders can be used alone or in combination of two or more. Among these, it is preferable to use an aliphatic polyol compound because it is easy to suppress discoloration and can obtain even better light resistance.

[0027] The method for producing the urethane resin (A) is not particularly limited, and any method may be used. For example, the urethane resin (A) may be produced by reacting all of the reaction raw materials containing the polyol compound (a1) and the aromatic polyisocyanate compound (a2) at once, or by reacting the reaction raw materials sequentially. These reactions are preferably carried out at a temperature of 50 to 100°C for 3 to 10 hours.

[0028] The molar ratio of the total number of moles of hydroxyl groups in the polyol (a1) and the chain extender to the number of moles of isocyanate groups in the aromatic polyisocyanate (a2) [(isocyanate groups) / (hydroxyl groups)] is preferably in the range of 0.80 to 0.95, more preferably in the range of 0.85 to 0.94.

[0029] An organic solvent may also be used when producing the urethane resin (A).

[0030] Examples of the organic solvent that can be used include ketone compounds such as acetone and methyl ethyl ketone; ether compounds such as tetrahydrofuran and dioxane; acetate compounds such as ethyl acetate and butyl acetate; nitrile compounds such as acetonitrile; and amide compounds such as dimethylformamide and N-methylpyrrolidone. These organic solvents may be used alone or in combination of two or more. The organic solvent is preferably removed by distillation or the like when obtaining the aqueous urethane resin composition.

[0031] The weight average molecular weight of the urethane resin (A) is preferably in the range of 2,000 to 150,000, more preferably in the range of 4,000 to 100,000, still more preferably in the range of 6,000 to 70,000, and particularly preferably in the range of 8,000 to 50,000, in order to provide a long pot life and excellent peel strength and light resistance. The weight average molecular weight of the urethane resin (A) is a value obtained by measuring in the same manner as the number average molecular weight of the polyol (a1).

[0032] Examples of the aqueous medium (B) include ion-exchanged water, distilled water, etc. These aqueous media can be used alone or in combination of two or more.

[0033] The method for producing the aqueous urethane resin composition of the present invention is not particularly limited, and any method may be used, such as a method of mixing the urethane resin (A) and the aqueous medium (B).

[0034] Examples of methods for mixing the urethane resin (A) and the aqueous medium (B) include methods using a reaction vessel equipped with a stirring blade; a kneader, a continuous kneader, a taper roll, a single-screw extruder, a twin-screw extruder, a triple-screw extruder, a universal mixer, a Plastomill, a Bodeta-type kneader, or the like; a rotary dispersion mixer such as a homomixer, a static mixer, FILMICS, an Ebara Milder, a Clearmix, an Ultra-Turrax, a Cavitron, or a Biomixer; an ultrasonic dispersion device; or a device such as an in-line mixer that has no moving parts and can mix by the flow of the fluid itself.

[0035] The mass ratio of the urethane resin (A) to the aqueous medium (B) [(A) / (B)] is preferably in the range of 50 / 50 to 80 / 20, more preferably in the range of 50 / 50 to 70 / 30, since an aqueous urethane resin composition having a long pot life and excellent peel strength and light resistance can be obtained.

[0036] The aqueous urethane resin composition of the present invention may contain other additives as needed.

[0037] Examples of the other additives include surfactants, thickeners, urethanization catalysts, fillers, pigments, dyes, flame retardants, leveling agents, and antiblocking agents. These additives can be used alone or in combination of two or more. It is preferable that the urethane resin (A) is produced without substantially containing an organic solvent, but an organic solvent may be added as an additive.

[0038] Examples of the surfactant include nonionic surfactants such as polyoxyethylene nonylphenyl ether, polyoxyethylene lauryl ether, polyoxyethylene styrylphenyl ether, polyoxyethylene sorbitol tetraoleate, and polyethylene-polypropylene copolymer; anionic surfactants such as fatty acid salts such as sodium oleate, alkyl sulfate ester salts, alkylbenzene sulfonates, alkyl sulfosuccinates, naphthalene sulfonates, polyoxyethylene alkyl sulfates, sodium alkanesulfonates, and sodium alkyldiphenyl ether sulfonates; and cationic surfactants such as alkylamine salts, alkyltrimethylammonium salts, and alkyldimethylbenzylammonium salts.

[0039] Examples of the thickener include associative and acid thickeners.

[0040] Examples of the urethane catalyst include organotin catalysts and bismuth catalysts.

[0041] Examples of the filler include calcium carbonate and silica.

[0042] Examples of the pigment include carbon black.

[0043] Examples of the dye include azo dyes.

[0044] Examples of the flame retardant include phosphorus-based flame retardants.

[0045] Examples of the leveling agent include silicon-based leveling agents.

[0046] Examples of the anti-blocking agent include acrylic agents and cellulose ester agents.

[0047] The synthetic leather of the present invention has at least a base fabric (i), an adhesive layer (ii), and a skin layer (iii), and examples thereof include the following synthetic leathers (1) to (4).

[0048] Synthetic leather (1): base fabric (i), adhesive layer (ii), skin layer (iii) Synthetic leather (2): Base fabric (i), adhesive layer (ii), intermediate layer, skin layer (iii) Synthetic leather (3): base fabric (i), porous layer, adhesive layer (ii), skin layer (iii) Synthetic leather (4): Base fabric (i), porous layer, adhesive layer (ii), intermediate layer, skin layer (iii)

[0049] Examples of the base fabric (i) include nonwoven fabrics, woven fabrics, knitted fabrics, and the like made from polyester fibers, polyethylene fibers, nylon fibers, acrylic fibers, polyurethane fibers, acetate fibers, rayon fibers, polylactic acid fibers, cotton, hemp, silk, wool, glass fibers, carbon fibers, and blends thereof.

[0050] The adhesive layer (ii) is formed from the aqueous urethane resin composition of the present invention, and the thickness of the adhesive layer (ii) is, for example, in the range of 30 to 60 μm.

[0051] Examples of the material for forming the surface layer (iii) (hereinafter, sometimes referred to as "surface layer-forming resin") include known aqueous urethane resins, solvent-based urethane resins, solventless urethane resins, aqueous acrylic resins, silicone resins, polypropylene resins, polyester resins, etc. These materials can be used alone or in combination of two or more.

[0052] The porous layer may be formed from a solvent-based urethane resin composition by a known wet film-forming method; or from a water-based urethane resin composition made porous by a known method; or the like.

[0053] Examples of materials for forming the intermediate layer include known aqueous urethane resins, solvent-based urethane resins, solventless urethane resins, aqueous acrylic resins, silicone resins, polypropylene resins, polyester resins, etc. These materials can be used alone or in combination of two or more.

[0054] The synthetic leather may be produced by any method without any particular limitation. Examples thereof include a method (1) in which a resin for forming a surface layer is applied to a release-treated substrate, followed by drying and processing to obtain a surface layer (iii), and then the aqueous urethane resin composition of the present invention is applied to the surface layer (iii) and dried to form an adhesive layer (ii), which is then laminated to a base fabric (i), and a method (2) in which a resin for forming a surface layer is applied to a release-treated substrate, followed by drying and processing to obtain a surface layer (iii), and then the aqueous urethane resin composition of the present invention is applied to the surface layer (iii), which is then laminated to a base fabric (i) and dried to form an adhesive layer (ii).

[0055] Examples of methods for applying the resin for forming the surface layer and the aqueous urethane resin composition include methods using an applicator, a roll coater, a spray coater, a T-die coater, a knife coater, a comma coater, and the like.

[0056] After the synthetic leather is produced, it may be aged, for example, at 30 to 100° C. for 1 to 10 days, if necessary. [Example]

[0057] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the examples given below.

[0058] Example 1: Preparation of aqueous urethane resin composition (1) In a four-neck flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen inlet tube, 1,000 parts by mass of polyether polyol ("PTMG1000" manufactured by Mitsubishi Chemical Corporation, number average molecular weight: 1,000, hereinafter abbreviated as "PTMG1000"), 61 parts by mass of methoxypolyethylene glycol ("UNIOX M1000" manufactured by NOF Corporation, number average molecular weight: 1,000, hereinafter abbreviated as "MPEG"), and 163 parts by mass of toluene diisocyanate (hereinafter abbreviated as "TDI") were reacted under a nitrogen stream at 120°C for 3 hours to obtain a urethane resin (1) ([NCO] / [OH] ratio: 0.90). Next, urethane resin (1) heated to 70°C was mixed with 141 parts by mass of a 35% by mass aqueous solution of sodium alkylnaphthalenesulfonate ("Pelex NBL" manufactured by Kao Corporation) and 309 parts by mass of water, and then water was added to finally obtain an aqueous urethane resin composition (1) with a urethane resin content of 50% by mass. The urea bond concentration in this aqueous urethane resin composition (1) was 0 mmol / kg.

[0059] (Example 2: Preparation of aqueous urethane resin composition (2)) In a four-neck flask equipped with a stirrer, reflux condenser, thermometer, and nitrogen inlet, 1,000 parts by weight of "PTMG1000," 61 parts by weight of polyethylene glycol (NOF Corporation's "PEG #600," number average molecular weight: 600, hereinafter abbreviated as "PEG"), and 174 parts by weight of TDI were reacted at 120 °C for 3 hours under a nitrogen stream to obtain urethane resin (2) ([NCO] / [OH] ratio: 0.90). Next, urethane resin (2) heated to 70 °C was mixed with 141 parts by weight of a 35% by weight aqueous solution of sodium alkylnaphthalenesulfonate (Kao Corporation's "Pelex NBL") and 309 parts by weight of water, and then water was added to obtain an aqueous urethane resin composition (2) with a final urethane resin content of 50% by weight. The urea bond concentration in this aqueous urethane resin composition (2) was 0 mmol / kg.

[0060] (Example 3: Preparation of aqueous urethane resin composition (3)) In a four-neck flask equipped with a stirrer, reflux condenser, thermometer, and nitrogen inlet, 1,000 parts by weight of "PTMG1000," 67 parts by weight of "MPEG," 106 parts by weight of 1,4-butanediol (hereinafter abbreviated as "1,4BG"), and 347 parts by weight of TDI were reacted at 120°C for 3 hours under a nitrogen stream to obtain urethane resin (3) ([NCO] / [OH] ratio 0.90). Next, urethane resin (3) heated to 70°C was mixed with 141 parts by weight of a 35% by weight aqueous solution of sodium alkylnaphthalenesulfonate ("Pelex NBL" manufactured by Kao Corporation) and 309 parts by weight of water, and then water was added to obtain an aqueous urethane resin composition (3) with a final urethane resin content of 50% by weight. The urea bond concentration in this aqueous urethane resin composition (3) was 0 mmol / kg.

[0061] (Example 4: Preparation of aqueous urethane resin composition (4)) In a four-neck flask equipped with a stirrer, reflux condenser, thermometer, and nitrogen inlet, 1,000 parts by weight of "PTMG1000," 61 parts by weight of "MPEG," 5 parts by weight of isophorone diamine (hereinafter abbreviated as "IPDA"), and 168 parts by weight of TDI were reacted at 120°C for 3 hours under a nitrogen stream to obtain urethane resin (4) ([NCO] / [OH] ratio 0.90). Next, urethane resin (4) heated to 70°C was mixed with 141 parts by weight of a 35% by weight aqueous solution of sodium alkylnaphthalenesulfonate ("Pelex NBL" manufactured by Kao Corporation) and 309 parts by weight of water, and further water was added to obtain an aqueous urethane resin composition (4) with a final urethane resin content of 50% by weight. The urea bond concentration in this aqueous urethane resin composition (4) was 48 mmol / kg.

[0062] (Example 5: Preparation of aqueous urethane resin composition (5)) In a four-neck flask equipped with a stirrer, reflux condenser, thermometer, and nitrogen inlet, 1,000 parts by weight of polycarbonate polyol (Ube Industries, Ltd., "ETERNACOL PH-200D," number average molecular weight: 2,000), 75 parts by weight of "MPEG," and 84 parts by weight of TDI were reacted at 120°C for 3 hours under nitrogen atmosphere to obtain urethane resin (5) ([NCO] / [OH] ratio: 0.90). Next, urethane resin (5) heated to 70°C was mixed with 132 parts by weight of a 35% by weight aqueous solution of sodium alkylnaphthalenesulfonate (Kao Corporation, "Pelex NBL") and 290 parts by weight of water, and then water was added to obtain an aqueous urethane resin composition (5) with a final urethane resin content of 50% by weight. The urea bond concentration in this aqueous urethane resin composition (5) was 0 mmol / kg.

[0063] (Example 6: Preparation of aqueous urethane resin composition (6)) In a four-neck flask equipped with a stirrer, reflux condenser, thermometer, and nitrogen inlet, 1,000 parts by weight of a polyester polyol (number average molecular weight: 1,000) prepared by reacting 1,4-hexanediol and adipic acid, 61 parts by weight of MPEG, and 163 parts by weight of TDI were reacted at 120°C for 3 hours under a nitrogen stream to obtain urethane resin (6) ([NCO] / [OH] ratio: 0.90). Next, urethane resin (6) heated to 70°C was mixed with 141 parts by weight of a 35% by weight aqueous solution of sodium alkylnaphthalenesulfonate ("Pelex NBL" manufactured by Kao Corporation) and 309 parts by weight of water, followed by the addition of water to obtain an aqueous urethane resin composition (6) with a final urethane resin content of 50% by weight. The urea bond concentration in this aqueous urethane resin composition (6) was 0 mmol / kg.

[0064] (Comparative Example 1: Preparation of aqueous urethane resin composition (R1)) A four-neck flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen inlet tube was charged with 1,000 parts by mass of polypropylene glycol having a hydroxyl value of 56.1 and an average molecular weight of 2,000, 47.2 parts by mass of neopentyl glycol, 9.3 parts by mass of trimethylolpropane, 68.6 parts by mass of MPEG, and 588 parts by mass of methyl ethyl ketone under a nitrogen stream and mixed uniformly. After that, 247 parts by mass of TDI was added, and the mixture was reacted at 70°C for approximately 4 hours to obtain a methyl ethyl ketone solution of an isocyanate-terminated urethane prepolymer ([NCO] / [OH] ratio 1.30). Next, 2450 parts by mass of ion-exchanged water was added to the methyl ethyl ketone solution of the urethane prepolymer obtained by the above method to emulsify it, and an aqueous solution of 12.3 parts by mass of 80% hydrazine hydrate and 20.6 parts by mass of diethanolamine dissolved in 296 parts by mass of water was added to extend the chain, and the methyl ethyl ketone was distilled off under reduced pressure to finally obtain an aqueous urethane resin composition (R1) with a urethane resin content of 50% by mass. The urea bond concentration in this aqueous urethane resin composition (R1) was 578 mmol / kg.

[0065] (Comparative Example 2: Preparation of aqueous urethane resin composition (R2)) A four-neck flask equipped with a stirrer, reflux condenser, thermometer, and nitrogen inlet tube was charged with 1,000 parts by weight of "PTMG1000," 30 parts by weight of 2,2-dimethylolpropionic acid (hereinafter abbreviated as "DMPA"), and 856 parts by weight of methyl ethyl ketone under a nitrogen stream. After uniform mixing, 234 parts by weight of TDI was added, followed by 0.1 parts by weight of dibutyltin dilaurate. The mixture was reacted at 70°C for approximately 4 hours ([NCO] / [OH] ratio 1.30). Next, 22 parts by weight of 1,3-butanediol was added, and the mixture was reacted at 70°C for approximately 1 hour to complete the reaction, yielding a methyl ethyl ketone solution of a urethane prepolymer. Next, 20 parts by weight of N,N-dimethylethanolamine was added to the methyl ethyl ketone solution of the urethane prepolymer obtained by the above method to neutralize the carboxyl groups in the urethane polymer, and then 1928 parts by weight of ion-exchanged water was added, and the methyl ethyl ketone was distilled off under reduced pressure to finally obtain an aqueous urethane resin composition (R2) with a urethane resin content of 40% by weight. The urea bond concentration in this aqueous urethane resin composition (R2) was 0 mmol / kg.

[0066] (Comparative Example 3: Preparation of aqueous urethane resin composition (R3)) Under a nitrogen stream, 1,000 parts by mass of "PTMG2000" and 18 parts by mass of PEG were placed in a four-neck flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen inlet tube, and after uniform mixing, 272 parts by mass of dicyclohexylmethane diisocyanate (hereinafter abbreviated as "HMDI") was added, followed by 0.1 parts by mass of dibutyltin dilaurate, and the mixture was allowed to react at 70°C for approximately 4 hours to obtain an isocyanate-terminated urethane prepolymer ([NCO] / [OH] ratio 1.30). The urethane prepolymer heated to 70°C was mixed with 147 parts by weight of a 35% by weight aqueous solution of sodium alkylnaphthalenesulfonate ("Pelex NBL" manufactured by Kao Corporation) and 875 parts by weight of water, and then an aqueous solution of 39 parts by weight of isophoronediamine (hereinafter abbreviated as "IPDA") and 15 parts by weight of diethanolamine dissolved in 367 parts by weight of water was immediately added to extend the chain, finally yielding an aqueous urethane resin composition (R3) with a urethane resin content of 50% by weight. The urea bond concentration in this aqueous urethane resin composition (R3) was 447 mmol / kg.

[0067] (Comparative Example 4: Preparation of aqueous urethane resin composition (R4)) In a four-neck flask equipped with a stirrer, reflux condenser, thermometer, and nitrogen inlet tube, 1,000 parts by mass of "PTMG1000," 61 parts by mass of MPEG, and 163 parts by mass of TDI were reacted under a nitrogen stream at 120°C for 3 hours to obtain a urethane resin ([NCO] / [OH] ratio 0.90). The urethane resin heated to 70°C was mixed with 309 parts by mass of ion-exchanged water, but emulsification was not achieved, and an aqueous urethane resin composition was not obtained.

[0068] (Comparative Example 5: Preparation of aqueous urethane resin composition (R5)) In a four-neck flask equipped with a stirrer, reflux condenser, thermometer, and nitrogen inlet, 1,000 parts by weight of "PTMG1000," 62 parts by weight of MPEG, 22 parts by weight of IPDA, and 183 parts by weight of TDI were reacted at 120°C for 3 hours under a nitrogen stream to obtain a urethane resin (NCO / OH ratio 0.90). The urethane resin was heated to 70°C and mixed with 141 parts by weight of a 35% by weight aqueous solution of sodium alkylnaphthalenesulfonate ("Pelex NBL" manufactured by Kao Corporation) and 309 parts by weight of water. Further water was added to obtain an aqueous urethane resin composition (R5) with a final urethane resin content of 50% by weight. The urea bond concentration in this aqueous urethane resin composition (R5) was 204 mmol / kg.

[0069] (Example 7: Production of synthetic leather (1)) A mixture consisting of 100 parts by mass of an aqueous urethane resin composition for the surface layer (DIC Corporation's "Hydran WLS-250"), 10 parts by mass of a water-dispersible black pigment (DIC Corporation's "Dylac HS-9530"), and 1 part by mass of an associative thickener (DIC Corporation's "Hydran Assister T10") was applied to a flat release paper (Ajinomoto Co., Inc.'s "DN-TP-155T") so that the film thickness after drying would be 30 μm, and then dried at 70 ° C. for 2 minutes and then at 120 ° C. for 2 minutes. Next, 14 parts by mass of a polyisocyanate-based crosslinking agent (DIC Corporation's Burnock DNW-5500) was added to 100 parts by mass of the aqueous urethane resin composition (1) obtained in Example 1 and stirred for 5 minutes. The mixture was applied to a solid film thickness of 50 μm and dried at 90 ° C. for 3 minutes. After laminating with T / R raised fabric, it was heat treated at 130°C for 10 minutes, and the release paper was peeled off to obtain synthetic leather.

[0070] (Examples 8 to 12: Production of synthetic leathers (2) to (6)) Synthetic leathers (2) to (6) were obtained in the same manner as in Example 7, except that the aqueous urethane resin composition (1) used in Example 7 was replaced with the aqueous urethane resin compositions (2) to (6) obtained in Examples 2 to 6.

[0071] (Comparative Examples 6 to 9: Production of Synthetic Leathers (R1) to (R4)) Synthetic leathers (R1) to (R4) were obtained in the same manner as in Example 7, except that the "aqueous urethane resin composition (1)" used in Example 7 was replaced with the aqueous urethane resin compositions (R1) to (R3) and (R5) obtained in Comparative Examples 1 to 3 and 5.

[0072] [Method for measuring peel strength] A 2.5 cm wide hot melt tape ("BW-2" manufactured by Sun Chemical Industry Co., Ltd.) was placed on the synthetic leather obtained in the Examples and Comparative Examples and heated at 150°C for 3 minutes to adhere it. A sample was cut along the width of the hot melt tape. A portion of this sample was peeled off, and the substrate and hot melt tape were clamped with a zipper. The peel strength was measured using an autograph ("AG-1" manufactured by Shimadzu Corporation) and evaluated according to the following criteria.

[0073] A: The peel strength was 3.5 kgf / 25 mm or more. B: The peel strength was 2.5 kgf / 25 mm or more and less than 3.5 kgf / 25 mm. C: The peel strength was less than 2.5 kgf / 25 mm.

[0074] [Pot life evaluation method] To 100 parts by mass of the aqueous urethane resin compositions obtained in the Examples and Comparative Examples, 10 parts by mass of a polyisocyanate-based crosslinking agent (Burnoc DNW-5500, manufactured by DIC Corporation) was added, and the mixture was left at 40°C for 4 hours. Synthetic leather was then produced in the same manner as in Example 1. A 2.5 cm wide hot melt tape (BW-2, manufactured by Sun Chemical Industry Co., Ltd.) was placed on the synthetic leather and heated at 150°C for 3 minutes to adhere it. A sample was then cut along the width of the hot melt tape. A portion of the sample was peeled off, and the substrate and hot melt tape were clamped together. The peel strength was measured using an autograph (AG-1, manufactured by Shimadzu Corporation) and evaluated according to the following criteria.

[0075] A: The peel strength was 3.5 kgf / 25 mm or more. B: The peel strength was 2.5 kgf / 25 mm or more and less than 3.5 kgf / 25 mm. C: The peel strength was less than 2.5 kgf / 25 mm.

[0076] [Lightfastness evaluation method] The synthetic leathers obtained in the examples and comparative examples were irradiated with light for 100 hours using a fade meter "U48AU" (63°C, humidity 50%) manufactured by Suga Test Instruments Co., Ltd. Thereafter, the synthetic leathers were visually observed and evaluated according to the following criteria.

[0077] A: There was no change in appearance. B: Slight yellowing was observed on the exterior. C: Significant yellowing was observed in appearance.

[0078] JPEG0007750435000001.jpg53170

[0079] In Table 1, "-" in Comparative Example 4 indicates that emulsification was not possible and preparation was not possible.

[0080] Examples 1 to 6 shown in Table 1 are examples in which the aqueous urethane resin composition of the present invention was used. It was confirmed that these aqueous urethane resin compositions had a long pot life and excellent peel strength and light resistance.

[0081] On the other hand, Comparative Example 1 shown in Table 1 is an example of an aqueous urethane resin composition using a urethane resin with a urea bond concentration of more than 100 mmol / kg. It was confirmed that this aqueous urethane resin composition had significantly insufficient light resistance.

[0082] Comparative Example 2 shown in Table 1 is an example of an aqueous urethane resin composition using a urethane resin that does not contain a nonionic polyol as a raw material. It was confirmed that this aqueous urethane resin composition had a significantly insufficient pot life.

[0083] Comparative Example 3 in Table 1 is an example of an aqueous urethane resin composition that does not use an aromatic polyisocyanate compound as a raw material for the urethane resin. It was confirmed that this aqueous urethane resin composition was significantly insufficient in peel strength and pot life.

[0084] Comparative Example 4 shown in Table 1 is an example of an aqueous urethane resin composition that does not use emulsifier (C). It was confirmed that this aqueous urethane resin composition could not be emulsified and could not be prepared.

[0085] Comparative Example 5 shown in Table 1 is an example of an aqueous urethane resin composition using a urethane resin with a urea bond concentration of more than 100 mmol / kg. It was confirmed that this aqueous urethane resin composition had significantly insufficient light resistance.

Claims

1. An aqueous urethane resin composition containing a urethane resin (A), an aqueous medium (B), and an emulsifier (C), the urethane resin (A) contains, as essential raw materials, a polyol compound (a1) containing a nonionic polyol and an aromatic polyisocyanate compound (a2); the amount of the nonionic polyol used is in the range of 2 to [75 / (1000+75)] mass% in the polyol compound (a1), the nonionic polyol is methoxypolyethylene glycol, the polyol compound (a1) further comprises at least one selected from the group consisting of polyether polyols, polyester polyols, and polycarbonate polyols; the aromatic polyisocyanate compound (a2) is toluene diisocyanate, the urea bond concentration in the urethane resin (A) is 0 mmol / kg or more and 100 mmol / kg or less, The aqueous urethane resin composition, wherein the emulsifier (C) is an anionic emulsifier.

2. The aqueous urethane resin composition according to claim 1, wherein the amount of the emulsifier (C) used is 10 parts by mass or less per 100 parts by mass of the urethane resin (A).

3. Synthetic leather comprising at least a base fabric (i), an adhesive layer (ii), and a surface layer (iii) laminated together.

2. A synthetic leather, wherein the adhesive layer (ii) is formed from the aqueous urethane resin composition according to claim 1.

4. 2. The method for producing an aqueous urethane resin composition according to claim 1, wherein the urethane resin (A) is obtained by reacting raw materials containing the polyol compound (a1) and the aromatic polyisocyanate compound (a2) in the absence of a solvent.

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