Heat insulation sheet and method of producing the same

Abstract

A heat insulation sheet includes, as a substrate, a silica aerogel with low heat conductivity and high mechanical strength In a hydrophobization reaction of a hydrogel, a silane coupling agent having a reactive organic functional group is used to conduct hydrophobization, and, after volatilization of a solvent in a drying step, the temperature is elevated to 100° C. or higher that is a reaction-starting temperature, thereby reacting and bonding the reactive functional group and a fiber to each other. This allows prevention of detachment or loss of fine particles of silica xerogel from the unwoven fabric fiber.

What is claimed is: 
     
         1 . A heat insulation sheet, comprising:
 a silica xerogel; and   a fabric, wherein   the silica xerogel and the fabric are chemically cross-linked to one another through a silane coupling agent having a reactive organic functional group.   
     
     
         2 . The heat insulation sheet according to  claim 1 , wherein a plurality of silica xerogels are chemically cross-linked to one another through the silane coupling agent. 
     
     
         3 . The heat insulation sheet according to  claim 1 , wherein the silane coupling agent is a compound represented by Y n Si(OR) 4-n . 
     
     
         4 . The heat insulation sheet according to  claim 1 , wherein the silane coupling agent is any one or more of Y n Si(OR) 4-n , R 3 SiO(SiR 2 O) n SiR 3 , R 3 SiCl, and R 1   n Si(OR 2 ) 4-n . 
     
     
         5 . The heat insulation sheet according to  claim 3 , wherein Y is any one or more of a glycidoxypropyl group, a 3,4-epoxycyclohexylethyl group, a styryl group, an acrylate group, a methyl methacrylate group, a vinyl group and a derivative thereof, a thiol propyl group, and an aminopropyl group. 
     
     
         6 . The heat insulation sheet according to  claim 3 , wherein R is any of a methyl group, an ethyl group and a propyl group. 
     
     
         7 . A method of producing a heat insulation sheet, comprising:
 providing as a material a high molar ratio silicate aqueous solution having a particle size of 1 to 10 nm, which is a medium size between water glass and colloidal silica, and adding an acid to the high molar ratio silicate aqueous solution to prepare a sol; or   providing a water glass as a material, removing sodium from the water glass by ion exchange, and then, adding a base thereto to prepare a sol solution;   impregnating a fabric with the sol solution;   conducting a polymerization reaction based on dehydration condensation at 50° C. to 100° C. to obtain a hydrogel;   hydrophobizing a surface of the hydrogel with a silane coupling agent having a reactive organic functional group, the silane coupling agent represented by Y n Si(OR) 4-n ;   drying the hydrophobized hydrogel; and   heating the dried hydrogel to 100° C. or higher to cause Y, which is the reactive organic functional group, to undergo a ring opening polymerization, thereby allowing a silica xerogel and the fabric to bind to each other, wherein,   in the silane coupling agent represented by Y n Si(OR) 4-n , Y, which corresponds to the reactive organic functional group, is any of a glycidoxypropyl group, a 3,4-epoxycyclohexylethyl group, a styryl group, an acrylate group, a methyl methacrylate group, a vinyl group and a derivative thereof, a thiol propyl group, and an aminopropyl group,   R is any of a methyl group, an ethyl group and a propyl group, and   n is 1 to 3.   
     
     
         8 . The method of producing a heat insulation sheet according to  claim 7 , wherein Y, which corresponds to the reactive organic functional group, is a glycidoxypropyl group. 
     
     
         9 . The method of producing a heat insulation sheet according to  claim 7 , wherein any one of 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropylmethyltrimethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane is used for Y n Si(OR) 4-n  in the hydrophobizing step.