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

Abstract

The present invention provides an aqueous urethane resin composition, a synthetic leather having an adhesive layer formed from the aqueous urethane resin composition, and a method for producing the aqueous urethane resin composition, the aqueous urethane resin composition being characterized in that: the aqueous urethane resin composition has a specific surface area, a specific surface area, and a specific surface area; the present invention relates to an aqueous polyurethane resin composition which contains (A) a urethane resin that contains, as essential raw materials, a polyol compound (a1) that contains a nonionic polyol and an aromatic polyisocyanate compound (a2), an aqueous medium (B), and an emulsifier (C), and which has a urea bond concentration of 100 mmol / kg or less. The aqueous urethane resin composition has a long pot life, and has 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 an aqueous urethane resin composition. Background Art

[0002] An aqueous urethane resin composition can reduce volatile organic compounds compared to conventional solvent-based urethane resin compositions. Therefore, in recent years, as an environmental response material, it has been studied for various uses such as artificial leather, synthetic leather, coating agents, glove coatings and glove films, adhesives, and the like.

[0003] Among them, in the use of the adhesive layer of synthetic leather, an aqueous polyurethane resin (PUD)-based adhesive containing an aqueous polyurethane resin having a softening temperature of 50°C or lower and a melt viscosity at 50°C of 60,000 Pa·s or lower and a polyisocyanate compound is known (for example, refer to Patent Document 1). However, a two-component adhesive formed by combining a PUD main agent and an isocyanate crosslinking agent has a problem that it is difficult to process stably because the pot life (working life) of the mixed liquid is short.

[0004] Therefore, there is a demand for a material having a long pot life, excellent peel strength, and light resistance.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2000-108289 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] The problems to be solved by the present invention are to provide an aqueous urethane resin composition having a long pot life, excellent peel strength, and light resistance, a synthetic leather having an adhesive layer formed of the above aqueous urethane resin composition, and a method for producing the above aqueous urethane resin composition.

[0010] Means for Solving the Problems

[0011] The present inventors conducted intensive studies to solve the above problems and found that by using an aqueous urethane resin composition containing a specific urethane resin and an aqueous medium, the above problems can be solved, thus completing the present invention.

[0012] That is, the present invention relates to the following aqueous urethane resin composition, which is characterized by containing a urethane resin (A), an aqueous medium (B), and an emulsifier (C). The above urethane resin (A) uses a polyol compound (a1) containing a nonionic polyol and an aromatic polyisocyanate compound (a2) as essential raw materials, and the concentration of urea bonds in the above urethane resin (A) is 100 mmol / kg or less.

[0013] Advantages of the Invention

[0014] The aqueous urethane resin composition of the present invention has a long pot life, excellent peel strength and light resistance, and can therefore be used as a coating agent or an adhesive, and is particularly suitably used for the adhesive layer of synthetic leather. Detailed Embodiments

[0015] 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).

[0016] Regarding the above urethane resin (A), a polyol compound (a1) containing a nonionic polyol and an aromatic polyisocyanate compound (a2) are used as essential raw materials.

[0017] Examples of the above nonionic polyol include compounds having an oxyethylene structure. These nonionic polyols can be used alone or in combination of two or more. Among these, from the viewpoint of obtaining an aqueous urethane resin composition having a long pot life, excellent peel strength and light resistance, compounds having an oxyethylene structure are preferred.

[0018] Examples of the above compounds having an oxyethylene structure include polyether polyols having an oxyethylene structure such as polyethylene glycol, polyoxyethylene polyoxypropylene glycol, polyoxyethylene polytetramethylene 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, from the viewpoint of obtaining an aqueous urethane resin composition having a long pot life, excellent peel strength and light resistance, polyethylene glycol and polyethylene glycol dimethyl ether are preferred.

[0019] Regarding the number average molecular weight of the above nonionic polyol, from the viewpoint of obtaining an aqueous urethane resin composition having a long pot life, excellent peel strength and light resistance, it is preferably in the range of 200 to 10,000, more preferably in the range of 300 to 3,000, and further preferably in the range of 300 to 2,000. It should be noted that in the present invention, the number average molecular weight represents a value measured by gel permeation column chromatography (GPC) method.

[0020] Regarding the usage ratio of the above nonionic polyol, from the aspect of obtaining an aqueous urethane resin composition with a long pot life, excellent peel strength and light resistance, it is preferably in the range of 1 to 30% by mass, more preferably in the range of 2 to 10% by mass in the above polyol compound (a1).

[0021] In addition, as the above polyol compound (a1), polyols other than the above nonionic polyol (hereinafter simply referred to as "other polyol compounds") can also be used as needed.

[0022] Examples of the above other polyol compounds include polyether polyols, polyester polyols, polyacrylate polyols, polycarbonate polyols, polybutadiene polyols, etc. other than the above nonionic polyol. These other polyol compounds can be used alone or in combination of two or more. In addition, among these, from the aspect of obtaining an aqueous urethane resin composition with a long pot life, excellent peel strength and light resistance, polyether polyols, polyester polyols, and polycarbonate polyols are preferred.

[0023] Examples of the above aromatic polyisocyanate compound (a2) include phthalic diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, naphthalene diisocyanate, polymethylene polyphenyl polyisocyanate, carbodiimide-modified diphenylmethane polyisocyanate, etc. These aromatic polyisocyanate compounds can be used alone or in combination of two or more. In addition, among these, from the aspect of obtaining an aqueous urethane resin composition with a long pot life, excellent peel strength and light resistance, toluene diisocyanate is preferred.

[0024] In addition, as needed, polyisocyanate compounds other than the above aromatic polyisocyanate compound (a2) (hereinafter simply referred to as "other polyisocyanate compounds") can also be used together.

[0025] Examples of the above 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, norbornene diisocyanate; alicyclic diisocyanates such as norbornane diisocyanate, isophorone diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated diphenylmethane diisocyanate, etc. These other polyisocyanate compounds can be used alone or in combination of two or more.

[0026] Examples of the emulsifier (C) include nonionic emulsifiers such as polyoxyethylene nonylphenyl ether, polyoxyethylene lauryl ether, polyoxyethylene styrenylphenyl ether, polyoxyethylene sorbitol tetraoleate, and polyethylene-polypropylene copolymer; fatty acid salts such as sodium oleate, anionic emulsifiers such as alkyl sulfate esters, alkylbenzene sulfonates, alkyl sulfosuccinates, naphthalene sulfonates, polyoxyethylene alkyl sulfates, sodium alkanesulfonates, and sodium alkyl diphenyl ether sulfonates; and cationic emulsifiers such as alkylamine salts, alkyltrimethylammonium salts, and alkyldimethylbenzylammonium salts. These emulsifiers can be used alone or in combination of two or more. Among these, anionic emulsifiers are preferred in terms of obtaining an aqueous urethane resin composition having a long pot life, excellent peel strength, light resistance, and storage stability.

[0027] Regarding the amount of the emulsifier (C) used, in terms of obtaining an aqueous urethane resin composition having a long pot life, excellent peel strength, light resistance, and storage stability, it is preferably 10 parts by mass or less, more preferably in the range of 0.5 to 5 parts by mass, based on 100 parts by mass of the urethane resin (A).

[0028] The urethane bond concentration of the urethane resin (A) is 100 mmol / kg or less, and in terms of obtaining an aqueous urethane resin composition having a long pot life, excellent peel strength, and light resistance, it is preferably 50 mmol / kg or less, more preferably 30 mmol / kg or less, and particularly preferably 0 mmol / kg.

[0029] Regarding the average particle diameter of the urethane resin (A), in terms of obtaining an aqueous urethane resin composition having a long pot life, excellent peel strength, and light resistance, it is preferably in the range of 0.01 to 1 μm, more preferably in the range of 0.05 to 0.9 μm. It should be noted that in the present invention, the method for measuring the average particle diameter is described in the examples below.

[0030] Regarding the urethane resin (A), if necessary, in addition to the above polyol compound (a1) and the above aromatic polyisocyanate compound (a2), a chain extender having no amino group can also be used. In particular, in terms of obtaining an aqueous urethane resin composition having a long pot life, excellent peel strength, and light resistance, a chain extender having a hydroxyl group is preferably used.

[0031] As the chain extender having a hydroxyl group as described above, examples thereof include chain extenders having a hydroxyl group such as 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, trimethylolpropane and the like. These chain extenders can be used alone or in combination of two or more. Among these, from the aspect of being easy to suppress discoloration and obtaining more excellent light resistance, aliphatic polyol compounds are preferably used.

[0032] Regarding the method for producing the above-mentioned urethane resin (A), there is no particular limitation, and any method can be used for production. For example, it can be produced by a method in which all the reaction raw materials containing the above-mentioned polyol compound (a1) and the above-mentioned aromatic polyisocyanate compound (a2) are reacted together, or it can be produced by a method in which the reaction raw materials are reacted successively. Regarding these reactions, a method of carrying out the reaction at a temperature of 50 to 100 °C for 3 to 10 hours is preferably used, for example.

[0033] The molar ratio [(isocyanate group) / (hydroxyl group)] of the total molar number of the hydroxyl groups of the above-mentioned polyol compound (a1) and the hydroxyl groups of the above-mentioned chain extender to the molar number of the isocyanate groups of the above-mentioned aromatic polyisocyanate compound (a2) is preferably in the range of 0.80 to 0.95, more preferably in the range of 0.85 to 0.94.

[0034] In addition, an organic solvent can also be used when producing the above-mentioned urethane resin (A).

[0035] As the above-mentioned organic solvent, for example, 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; amide compounds such as dimethylformamide and N - methylpyrrolidone, etc. can be used. These organic solvents can be used alone or in combination of two or more. It should be noted that the above-mentioned organic solvent is preferably removed by a distillation method or the like when obtaining the aqueous urethane resin composition.

[0036] Regarding the weight average molecular weight of the above-mentioned urethane resin (A), from the aspects of long pot life, excellent peel strength and light resistance, it is preferably in the range of 2,000 to 150,000, more preferably in the range of 4,000 to 100,000, further preferably in the range of 6,000 to 70,000, and particularly preferably in the range of 8,000 to 50,000. It should be noted that the weight average molecular weight of the above-mentioned urethane resin (A) represents a value obtained by measuring in the same manner as the number average molecular weight of the above-mentioned polyol (a1).

[0037] As the above-mentioned aqueous medium (B), for example, ion-exchanged water, distilled water, etc. can be cited. These aqueous media can be used alone or in combination of two or more.

[0038] Regarding the method for producing the aqueous urethane resin composition of the present invention, there is no particular limitation, and any method can be used for production. For example, a method of mixing the above-mentioned urethane resin (A) and the above-mentioned aqueous medium (B) can be cited.

[0039] As a method for mixing the above-mentioned urethane resin (A) and the above-mentioned aqueous medium (B), for example, a method carried out by using the following devices, etc. can be cited, that is, a reaction kettle equipped with a stirring blade; kneaders, continuous kneaders, conical rollers, single-screw extruders, twin-screw extruders, triple-screw extruders, universal mixers, plastic mills, main body type kneaders, etc.; rotary dispersion mixers such as homogenizing mixers, static mixers, Filmix, Ebara Milder, Claire mix, ULTRA-TURRAX, Cavitron, Biomixer, etc.; ultrasonic dispersion devices; devices without moving parts such as in-line mixers that can mix through the flow of the fluid itself.

[0040] Regarding the mass ratio [(A) / (B)] of the above-mentioned urethane resin (A) and the above-mentioned aqueous medium (B), from the aspect of obtaining an aqueous urethane resin composition with a long pot life, excellent peel strength and light resistance, it is preferably in the range of 50 / 50 to 80 / 20, more preferably in the range of 50 / 50 to 70 / 30.

[0041] The aqueous urethane resin composition of the present invention may also contain other additives as needed.

[0042] As the above-mentioned other additives, for example, surfactants, thickeners, urethanization catalysts, fillers, pigments, dyes, flame retardants, leveling agents, anti-blocking agents, etc. can be cited. These additives can be used alone or in combination of two or more. It should be noted that it is preferably substantially free of organic solvents when producing the above-mentioned urethane resin (A), but organic solvents can also be added as additives.

[0043] As the above surfactants, for example, the following can be cited: nonionic surfactants such as polyoxyethylene nonylphenyl ether, polyoxyethylene lauryl ether, polyoxyethylene styrylphenyl ether, polyoxyethylene sorbitol tetraoleate, polyethylene-polypropylene copolymer; fatty acid salts such as sodium oleate, anionic surfactants such as alkyl sulfate esters, alkylbenzene sulfonates, alkyl sulfosuccinates, naphthalene sulfonates, polyoxyethylene alkyl sulfates, sodium alkanesulfonates, sodium alkyl diphenyl ether sulfonates; cationic surfactants such as alkylamine salts, alkyltrimethylammonium salts, alkyldimethylbenzylammonium salts, etc.

[0044] As the above thickeners, for example, associative, acid-based thickeners, etc. can be cited.

[0045] As the above urethanization catalysts, for example, organotin-based, bismuth-based, etc. can be cited.

[0046] As the above fillers, for example, calcium carbonate, silica, etc. can be cited.

[0047] As the above pigments, for example, carbon black, etc. can be cited.

[0048] As the above dyes, for example, azo dyes, etc. can be cited.

[0049] As the above flame retardants, for example, phosphorus-based flame retardants, etc. can be cited.

[0050] As the above leveling agents, for example, silicone-based leveling agents, etc. can be cited.

[0051] As the above anti-blocking agents, for example, acrylic-based, cellulose esters, etc. can be cited.

[0052] Regarding the synthetic leather of the present invention, it has at least a base fabric (i), an adhesive layer (ii), and an epidermal layer (iii), and for example, the following constitutions of synthetic leathers (1) to (4) can be cited.

[0053] Synthetic leather (1): base fabric (i), adhesive layer (ii), epidermal layer (iii)

[0054] Synthetic leather (2): base fabric (i), adhesive layer (ii), intermediate layer, epidermal layer (iii)

[0055] Synthetic leather (3): base fabric (i), porous layer, adhesive layer (ii), epidermal layer (iii)

[0056] Synthetic leather (4): base fabric (i), porous layer, adhesive layer (ii), intermediate layer, epidermal layer (iii)

[0057] As the above-mentioned base fabric (i), for example, non-woven fabrics, woven fabrics, knitted fabrics, etc. made of polyester fiber, polyethylene fiber, nylon fiber, acrylonitrile-based fiber, polyurethane fiber, acetate fiber, rayon fiber, polylactic acid fiber, cotton, hemp, silk, wool, glass fiber, carbon fiber, their blended fibers, etc. can be cited.

[0058] As the above-mentioned adhesive layer (ii), an adhesive layer formed from the aqueous urethane resin composition of the present invention is used, and the thickness of the above-mentioned adhesive layer (ii) can be cited, for example, in the range of 30 to 60 μm.

[0059] As the material for forming the above-mentioned skin layer (iii) (hereinafter sometimes referred to as "resin for forming skin layer"), for example, known aqueous urethane resins, solvent-based urethane resins, solvent-free urethane resins, aqueous acrylic resins, silicone resins, polypropylene resins, polyester resins, etc. can be cited. These materials can be used alone or in combination of two or more.

[0060] As the above-mentioned porous layer, a porous layer formed by a known wet film-forming method for a solvent-based urethane resin composition; a porous layer obtained by making a water-based urethane resin composition porous by a known method, etc. can be used.

[0061] As the material for forming the above-mentioned intermediate layer, for example, known water-based urethane resins, solvent-based urethane resins, solvent-free urethane resins, water-based acrylic resins, silicone resins, polypropylene resins, polyester resins, etc. can be cited. These materials can be used alone or in combination of two or more.

[0062] Regarding the manufacturing method of the above-mentioned synthetic leather, there is no particular limitation, and any method can be used for manufacturing. For example, the following can be cited: a method (1) in which a skin layer (iii) is obtained by a step of coating a resin for forming a skin layer on a demolded substrate and drying, and then an aqueous urethane resin composition of the present invention is coated on the skin layer (iii), dried, and an adhesive layer (ii) is formed and bonded to the base fabric (i); a method (2) in which a skin layer (iii) is obtained by a step of coating a resin for forming a skin layer on a demolded substrate and drying, and then the aqueous urethane resin composition of the present invention is coated on the skin layer (iii), bonded to the base fabric (i), and then dried to form an adhesive layer (ii), etc.

[0063] As a method for coating the above-mentioned resin for forming a skin layer and the above-mentioned aqueous urethane resin composition, for example, methods using a coater, a roll coater, a spray coater, a T-die coater, a knife coater, a comma coater, etc. can be cited.

[0064] After manufacturing the above synthetic leather, if necessary, it can also be aged at 30 to 100 °C for 1 to 10 days, for example.

[0065] [Examples]

[0066] Hereinafter, the present invention will be specifically described by way of examples and comparative examples. It should be noted that the present invention is not limited to the examples listed below.

[0067] (Example 1: Preparation of aqueous urethane resin composition (1))

[0068] In a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen inlet tube, 1,000 parts by mass of polyether polyol (manufactured by Mitsubishi Chemical Corporation, "PTMG1000", number average molecular weight: 1,000, hereinafter simply referred to as "PTMG1000"), 61 parts by mass of methoxypolyethylene glycol (manufactured by NOF Corporation, "UNIOX M1000", number average molecular weight: 1000, hereinafter simply referred to as "MPEG"), and 163 parts by mass of toluene diisocyanate (hereinafter simply referred to as "TDI") were reacted at 120 °C for 3 hours under a nitrogen stream to obtain urethane resin (1) ([NCO] / [OH] ratio: 0.90). Next, the urethane resin (1) heated to 70 °C was mixed with 141 parts by mass of a 35% by mass aqueous solution of sodium alkylnaphthalenesulfonate (manufactured by Kao Corporation, "Pelex NBL") and 309 parts by mass of water, and then further water was added to finally obtain an aqueous urethane resin composition (1) having a urethane resin content of 50% by mass. The concentration of urethane bond groups in this aqueous urethane resin composition (1) was 0 mmol / kg.

[0069] (Example 2: Preparation of aqueous urethane resin composition (2))

[0070] In a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen inlet tube, 1,000 parts by mass of "PTMG1000", 61 parts by mass of polyethylene glycol (manufactured by NOF Corporation, "PEG#600", number average molecular weight: 600, hereinafter simply referred to as "PEG"), and 174 parts by mass 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, the urethane resin (2) heated to 70 °C was mixed with 141 parts by mass of a 35% by mass aqueous solution of sodium alkylnaphthalenesulfonate (manufactured by Kao Corporation, "Pelex NBL") and 309 parts by mass of water, and then further water was added to finally obtain an aqueous urethane resin composition (2) having a urethane resin content of 50% by mass. The concentration of urethane bond groups in this aqueous urethane resin composition (2) was 0 mmol / kg.

[0071] (Example 3: Preparation of Aqueous Urethane Resin Composition (3))

[0072] In a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen inlet tube, 1,000 parts by mass of "PTMG1000", 67 parts by mass of "MPEG", 106 parts by mass of 1,4-butanediol (hereinafter simply referred to as "1,4BG"), and 347 parts by mass 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, the urethane resin (3) 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 further water was added to finally obtain an aqueous urethane resin composition (3) having a urethane resin content of 50% by mass. The concentration of urethane bond groups in this aqueous urethane resin composition (3) was 0 mmol / kg.

[0073] (Example 4: Preparation of Aqueous Urethane Resin Composition (4))

[0074] In a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen inlet tube, 1,000 parts by mass of "PTMG1000", 61 parts by mass of "MPEG", 5 parts by mass of isophorone diamine (hereinafter simply referred to as "IPDA"), and 168 parts by mass 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, the urethane resin (4) 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 further water was added to finally obtain an aqueous urethane resin composition (4) having a urethane resin content of 50% by mass. The concentration of urethane bond groups in this aqueous urethane resin composition (4) was 48 mmol / kg.

[0075] (Example 5: Preparation of Aqueous Urethane Resin Composition (5))

[0076] In a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen inlet tube, 1,000 parts by mass of a polycarbonate polyol ("ETERNACOL PH-200D" manufactured by Ube Industries, Ltd., number average molecular weight: 2,000), 75 parts by mass of "MPEG", and 84 parts by mass of TDI were reacted at 120 °C for 3 hours under a nitrogen stream to obtain a urethane resin (5) ([NCO] / [OH] ratio: 0.90). Next, the urethane resin (5) heated to 70 °C was mixed with 132 parts by mass of a 35% by mass aqueous solution of sodium alkylnaphthalenesulfonate ("Pelex NBL" manufactured by Kao Corporation) and 290 parts by mass of water, and then further water was added to finally obtain an aqueous urethane resin composition (5) having a urethane resin content of 50% by mass. The concentration of urethane bond groups in this aqueous urethane resin composition (5) was 0 mmol / kg.

[0077] (Example 6: Preparation of aqueous urethane resin composition (6))

[0078] In a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen inlet tube, 1,000 parts by mass of a polyester polyol (number average molecular weight: 1,000) obtained by reacting 1,4-hexanediol and adipic acid, 61 parts by mass of "MPEG", and 163 parts by mass of TDI were reacted at 120 °C for 3 hours under a nitrogen stream to obtain a urethane resin (6) ([NCO] / [OH] ratio: 0.90). Next, the urethane resin (6) 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 further water was added to finally obtain an aqueous urethane resin composition (6) having a urethane resin content of 50% by mass. The concentration of urethane bond groups in this aqueous urethane resin composition (6) was 0 mmol / kg.

[0079] (Comparative Example 1: Preparation of aqueous urethane resin composition (R1))

[0080] In a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen inlet tube, 1000 parts by mass of polypropylene glycol with a hydroxyl value of 56.1 and an average molecular weight of 2000, 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 were added under a nitrogen stream and uniformly mixed. Then, 247 parts by mass of TDI was added, and the reaction was carried out at 70 °C for about 4 hours to obtain a methyl ethyl ketone solution of an isocyanate-terminated urethane prepolymer ([NCO] / [OH] ratio was 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 for emulsification. Further, an aqueous solution prepared by dissolving 12.3 parts by mass of 80% hydrazine hydrate and 20.6 parts by mass of diethanolamine in 296 parts by mass of water was added for chain extension. Methyl ethyl ketone was distilled off under reduced pressure, and thus an aqueous urethane resin composition (R1) with a urethane resin content of 50% by mass was finally obtained. The concentration of ureylene bond groups in the aqueous urethane resin composition (R1) was 578 mmol / kg.

[0081] (Comparative Example 2: Preparation of aqueous urethane resin composition (R2))

[0082] In a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen inlet tube, 1000 parts by mass of "PTMG1000", 30 parts by mass of 2,2-dimethylolpropionic acid (hereinafter simply referred to as "DMPA"), and 856 parts by mass of methyl ethyl ketone were added under a nitrogen stream and uniformly mixed. Then, 234 parts by mass of TDI was added. Next, 0.1 part by mass of dibutyltin dilaurate was added, and the reaction was carried out at 70 °C for about 4 hours ([NCO] / [OH] ratio was 1.30). Next, 22 parts by mass of 1,3-butanediol was added, and the reaction was carried out at 70 °C for about 1 hour to end the reaction, obtaining a methyl ethyl ketone solution of a urethane prepolymer. Next, 20 parts by mass 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 above urethane polymer. Then, 1928 parts by mass of ion-exchanged water was added, and methyl ethyl ketone was distilled off under reduced pressure. Thus, an aqueous urethane resin composition (R2) with a urethane resin content of 40% by mass was finally obtained. The concentration of ureylene bond groups in the aqueous urethane resin composition (R2) was 0 mmol / kg.

[0083] (Comparative Example 3: Preparation of aqueous urethane resin composition (R3))

[0084] In a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen inlet tube, 1,000 parts by mass of "PTMG2000" and 18 parts by mass of PEG were added under a nitrogen stream and uniformly mixed. Then, 272 parts by mass of dicyclohexylmethane diisocyanate (hereinafter abbreviated as "HMDI") was added. Next, 0.1 part by mass of dibutyltin dilaurate was added to obtain a urethane prepolymer with an isocyanate end after reacting at 70°C for about 4 hours ([NCO] / [OH] ratio: 1.30). The urethane prepolymer heated to 70°C was mixed with 147 parts by mass of a 35% aqueous solution of sodium alkylnaphthalenesulfonate ("Pelex NBL" manufactured by Kao Corporation) and 875 parts by mass of water. Immediately thereafter, an aqueous solution prepared by dissolving 39 parts by mass of isophorone diamine (hereinafter abbreviated as "IPDA") and 15 parts by mass of diethanolamine in 367 parts by mass of water was added for chain extension, and finally, an aqueous urethane resin composition (R3) with a urethane resin content of 50% by mass was obtained. The concentration of urethane bond groups in this aqueous urethane resin composition (R3) was 447 mmol / kg.

[0085] (Comparative Example 4: Preparation of aqueous urethane resin composition (R4))

[0086] In a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a 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 at 120°C for 3 hours under a nitrogen stream 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 could not be achieved, and an aqueous urethane resin composition could not be obtained.

[0087] (Comparative Example 5: Preparation of aqueous urethane resin composition (R5))

[0088] In a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen inlet tube, 1,000 parts by mass of "PTMG1000", 62 parts by mass of MPEG, 22 parts by mass of IPDA, and 183 parts by mass 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 heated to 70°C was mixed with 141 parts by mass of a 35% aqueous solution of sodium alkylnaphthalenesulfonate ("Pelex NBL" manufactured by Kao Corporation) and 309 parts by mass of water. Then, water was further added, and finally, an aqueous urethane resin composition (R5) with a urethane resin content of 50% by mass was obtained. The concentration of urethane bond groups in this aqueous urethane resin composition (R5) was 204 mmol / kg.

[0089] (Example 7: Manufacture of Synthetic Leather (1))

[0090] A coating liquid containing 100 parts by mass of an aqueous urethane resin composition for the skin layer ("Hydran WLS-250" manufactured by DIC Corporation), 10 parts by mass of a water-dispersible black pigment ("Dyrac HS-9530" manufactured by DIC Corporation), and 1 part by mass of an associative thickener ("Hydran Asister T10" manufactured by DIC Corporation) was applied onto a flat release paper ("DN-TP-155T" manufactured by Ajinomoto Co., Inc.) so that the dried film thickness became 30 μm, dried at 70°C for 2 minutes, and further dried at 120°C for 2 minutes. Next, a coating liquid prepared by adding 14 parts by mass of a polyisocyanate-based crosslinking agent ("Burnock DNW-5500" manufactured by DIC Corporation) to 100 parts by mass of the aqueous urethane resin composition (1) obtained in Example 1 and stirring and mixing for 5 minutes was applied so that the solid component film thickness became 50 μm, and dried at 90°C for 3 minutes. After laminating with a T / R fleece fabric, heat treatment was performed under the conditions of 130°C for 10 minutes, and the release paper was peeled off to obtain synthetic leather.

[0091] (Examples 8 to 12: Manufacture of Synthetic Leathers (2) to (6))

[0092] The "aqueous urethane resin composition (1)" used in Example 7 was changed to the aqueous urethane resin compositions (2) to (6) obtained in Examples 2 to 6, and except for the above, the same operations as in Example 7 were performed to obtain synthetic leathers (2) to (6).

[0093] (Comparative Examples 6 to 9: Manufacture of Synthetic Leathers (R1) to (R4))

[0094] The "aqueous urethane resin composition (1)" used in Example 7 was changed to the aqueous urethane resin compositions (R1) to (R3) and (R5) obtained in Comparative Examples 1 to 3 and 5, and except for the above, the same operations as in Example 7 were performed to obtain synthetic leathers (R1) to (R4).

[0095] [Method for Measuring Peel Strength]

[0096] On the synthetic leather obtained in the examples and comparative examples, a 2.5-cm-wide hot melt tape ("BW-2" manufactured by San Chemical Co., Ltd.) was placed, heated at 150 °C for 3 minutes, and bonded. The specimen was cut along the width of the hot melt tape. A part of the specimen was peeled off, the substrate and the hot melt tape were clamped with a chuck, and the peel strength was measured using an Autograph ("AG-1" manufactured by Shimadzu Corporation), and evaluated according to the following criteria.

[0097] A: The peel strength is 3.5 kgf / 25 mm or more.

[0098] B: The peel strength is 2.5 kgf / 25 mm or more and less than 3.5 kgf / 25 mm.

[0099] C: The peel strength is less than 2.5 kgf / 25 mm.

[0100] [Evaluation method for the applicable period]

[0101] To 100 parts by mass of the aqueous urethane resin composition obtained in the examples and comparative examples, 10 parts by mass of a polyisocyanate-based crosslinking agent ("Burnock DNW-5500" manufactured by DIC Corporation) was added, and after standing at 40 °C for 4 hours, a synthetic leather was produced in the same manner as in Example 1. On this synthetic leather, a 2.5-cm-wide hot melt tape ("BW-2" manufactured by San Chemical Co., Ltd.) was placed, heated at 150 °C for 3 minutes, and bonded. Next, the specimen was cut along the width of the hot melt tape. A part of the specimen was peeled off, the substrate and the hot melt tape were clamped with a chuck, and the peel strength was measured using an Autograph ("AG-1" manufactured by Shimadzu Corporation), and evaluated according to the following criteria.

[0102] A: The peel strength is 3.5 kgf / 25 mm or more.

[0103] B: The peel strength is 2.5 kgf / 25 mm or more and less than 3.5 kgf / 25 mm.

[0104] C: The peel strength is less than 2.5 kgf / 25 mm.

[0105] [Evaluation method for light resistance]

[0106] For the synthetic leather obtained in the examples and comparative examples, light irradiation was performed for 100 hours using a fade meter "U48AU" (63 °C, humidity 50%) manufactured by SUGA Test Instruments Co., Ltd. The synthetic leather was visually observed thereafter and evaluated according to the following criteria.

[0107] A: The appearance has not changed.

[0108] B: A slight yellowing of the appearance was confirmed.

[0109] C: A significant yellowing of the appearance was confirmed.

[0110]

[0111] The "-" in Comparative Example 4 in Table 1 indicates that emulsification was not possible and preparation could not be carried out.

[0112] Examples 1 to 6 described in Table 1 are examples of the aqueous urethane resin composition of the present invention. It was confirmed that these aqueous urethane resin compositions have a long pot life and excellent peel strength and light resistance.

[0113] On the other hand, Comparative Example 1 described in Table 1 is an example of an aqueous urethane resin composition using a urethane resin having a urethane bond concentration exceeding 100 mmol / kg. It was confirmed that the light resistance of this aqueous urethane resin composition was significantly insufficient.

[0114] Comparative Example 2 described in Table 1 is an example of an aqueous urethane resin composition using a urethane resin that does not use a nonionic polyol as a raw material. It was confirmed that the pot life of this aqueous urethane resin composition was significantly insufficient.

[0115] Comparative Example 3 described 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 the peel strength and pot life of this aqueous urethane resin composition were significantly insufficient.

[0116] Comparative Example 4 described in Table 1 is an example of an aqueous urethane resin composition that does not use an emulsifier (C). It was confirmed that this aqueous urethane resin composition could not be emulsified and could not be prepared.

[0117] Comparative Example 5 described in Table 1 is an example of an aqueous urethane resin composition using a urethane resin having a urethane bond concentration exceeding 100 mmol / kg. It was confirmed that the light resistance of this aqueous urethane resin composition was significantly insufficient.

Claims

1. An aqueous urethane resin composition, characterized in that, it contains a urethane resin (A), an aqueous medium (B) and an emulsifier (C), the urethane resin (A) uses a polyol compound (a1) containing a nonionic polyol and an aromatic polyisocyanate compound (a2) as essential raw materials, the concentration of urea bonds in the urethane resin (A) is 100 mmol / kg or less.

2. The aqueous urethane resin composition according to claim 1, wherein, the aromatic polyisocyanate compound (a2) is toluene diisocyanate.

3. The aqueous urethane resin composition according to claim 1 or 2, wherein, the emulsifier (C) contains an anionic emulsifier.

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

5. A synthetic leather, characterized in that, it has at least a base fabric (i), an adhesive layer (ii) and a skin layer (iii) laminated thereon, the adhesive layer (ii) is formed of the aqueous urethane resin composition according to any one of claims 1 to 4.

6. A method for manufacturing an aqueous urethane resin composition, wherein, the aqueous urethane resin composition is the aqueous urethane resin composition according to any one of claims 1 to 5, and the urethane resin (A) is obtained by reacting raw materials containing the polyol compound (a1) and the aromatic polyisocyanate compound (a2) without a solvent.

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