Urethane resin composition, leather-like sheet, and method for producing the leather-like sheet

Abstract

Provided is an aqueous urethane resin composition with which a fiber base can be impregnated, which is capable of thermal coagulation, which does not detach from the fiber base due to water or heat in the step of coloring the impregnated base, and which is capable of forming a coating film having resistance to discoloration which may occur with time and an excellent feeling, that is, flexibility and resilience. The aqueous urethane resin composition includes a urethane resin a nonionic emulsifier, and an aqueous medium, the urethane resin being produced by reacting a polyol including a polyol including a carboxyl group with an aromatic polyisocyanate and a chain extender, the content of urea linkage in the urethane resin being 0.3 mol/kg or less. Also provided is a leather-like sheet produced by impregnating a fiber base with the aqueous urethane resin composition and subsequently performing thermal coagulation of the urethane resin composition.

The invention claimed is: 
     
       1. A leather-like sheet produced by impregnating a fiber base with an aqueous urethane resin composition and subsequently performing thermal coagulation of the aqueous urethane resin composition, the aqueous urethane resin composition including a urethane resin (A), a nonionic emulsifier (B), an aqueous medium (C), and a coagulant (D), the urethane resin (A) being produced by reacting a polyol (a1) including a polyol (a1-1) including a carboxyl group with an aromatic polyisocyanate (a2) and a chain extender (a3), the content of urea linkage in the urethane resin (A) being 0.3 mol/kg or less, wherein
 an amount of the polyol (a1-1) is 0.05% to 10% by mass, 
 an amount of the chain extender (a3) used is 1% to 10% by mass of a total amount of the polyol (a1), the aromatic polyisocyanate (a2), and the chain extender (a3), 
 the aromatic polyisocyanate (a2) is a diphenylmethane diisocyanate, and 
 an amount of the coagulant (D) is 0.1% to 20% by mass relative to 100 parts by mass of the urethane resin (A). 
 
     
     
       2. The leather-like sheet according to  claim 1 , wherein the content of aromatic ring in the urethane resin (A) is 0.3 to 5 mol/kg. 
     
     
       3. The leather-like sheet according to  claim 1 , wherein the polyol (a1) includes at least one polyol selected from the group consisting of a polyether polyol, a polyester polyol, and a polycarbonate polyol. 
     
     
       4. The leather-like sheet according to  claim 1 , wherein the polyol (a1-1) including a carboxyl group is 2,2′-dimethylolpropionic acid, 2,2′-dimethylolbutanoic acid, or 2,2′-dimethylolbutyric acid. 
     
     
       5. The leather-like sheet according to  claim 1 , wherein the chain extender (a3) is ethylene glycol or 1,4-butanediol. 
     
     
       6. The leather-like sheet according to  claim 1 , wherein the nonionic emulsifier (B) includes an oxyethylene group, the average number of moles of the oxyethylene group included in the nonionic emulsifier (B) being 1 to 50. 
     
     
       7. The leather-like sheet according to  claim 1 , wherein the amount of the nonionic emulsifier (B) used is 0.1 to 30 parts by mass relative to 100 parts by mass of the urethane resin (A). 
     
     
       8. The leather-like sheet according to  claim 1 , wherein the amount of the polyol (a1-1) including a carboxyl group is 0.05% to 10% by mass of the amount of the polyol (a1).