Water-soluble polyimide precursor, aqueous polyimide precursor solution, polyimide, impregnated material with polyimide binder, and laminate

Abstract

A water-soluble polyimide precursor, which can be suitably applied for aromatic polyimides and exhibits a low reduction in heat resistance and mechanical properties, an aqueous solution of the polyimide precursor and a polyimide obtained from the precursor. A heat-resistant fiber impregnated material and an impregnated sheet-like material are prepared by using the precursor and a laminate is prepared by employing the precursor.

What we claim is:  
     
         1 . A water-soluble polyimide precursor which gives a polyimide with a thermal decomposition temperature of 500° C. or higher and a breaking elongation of 15% or greater when shaped into a film.  
     
     
         2 . A water-soluble polyimide precursor according to  claim 1 , wherein the polyimide is amorphous based on X-ray analysis and has a glass transition temperature of 190-350° C.  
     
     
         3 . A polyimide precursor solution prepared by dissolving a water-soluble polyimide precursor according to  claim 1  in water.  
     
     
         4 . A polyimide obtained by imidation of a water-soluble polyimide precursor according to  claim 1 .  
     
     
         5 . A polyimide according to  claim 4 , wherein the polyimide has a heat sealing property.  
     
     
         6 . A polyimide according to  claim 4 , which is used as a binder for a woven fabric or nonwoven fabric made of organic or inorganic fibers.  
     
     
         7 . A powdered water-soluble polyimide precursor which is obtained by separation from the mixture resulting from reaction between a polyimide precursor comprising a tetracarboxylic acid component and an aromatic diamine component with 1,2-dimethylimidazole and/or 1-methyl-2-ethylimidazole at 0.7 molar equivalents or more with respect to the carboxyl groups of said polyimide precursor.  
     
     
         8 . A water-soluble polyimide precursor according to  claim 7 , wherein the polyimide is amorphous based on X-ray analysis.  
     
     
         9 . A water-soluble polyimide precursor according to  claim 7 , wherein the tetracarboxylic acid component contains at least 50% of a 2,3,3′,4′-biphenyltetracarboxylic acid component.  
     
     
         10 . A polyimide precursor solution prepared by dissolving a water-soluble polyimide precursor, according to  claim 7 , in water.  
     
     
         11 . A polyimide obtained by imidation of a water-soluble polyimide precursor according to  claim 7 .  
     
     
         12 . A polyimide according to  claim 11 , wherein the polyimide has a heat sealing property.  
     
     
         13 . A polyimide according to  claim 11 , which is used as a binder for a woven fabric or nonwoven fabric made of organic or inorganic fibers.  
     
     
         14 . A polyimide obtained by heat imidation of a water-soluble polyimide precursor, which exhibits heat resistance equivalent to that of a polyimide obtained by heat imidation of a non-water-soluble polyimide precursor obtained by reaction of the same tetracarboxylic acid and aromatic diamine components that give said water-soluble polyimide precursor, at the same composition.  
     
     
         15 . A heat-resistant fiber impregnated material which retains at least 70% of its tensile strength even when left in an environment at 200° C. for one hour and which is obtained by using a polyimide obtained from a water-soluble polyimide precursor as the binder resin for heat-resistant fibers.  
     
     
         16 . A heat-resistant fiber impregnated material according to  claim 15 , wherein the polyimide is amorphous based on X-ray analysis.  
     
     
         17 . A heat-resistant fiber impregnated material, according to  claim 15 , wherein the polyimide is obtained with at least 50% of a 2,3,3′,4′-biphenyltetracarboxylic acid component as the tetracarboxylic acid component.  
     
     
         18 . A heat-resistant fiber impregnated material wherein a polyimide obtained from a water-soluble polyimide precursor containing 1,2-dimethylimidazole and/or 1-methyl-2-ethylimidazole is used as the binder resin for heat-resistant fibers.  
     
     
         19 . A heat-resistant fiber impregnated material according to  claim 18 , wherein the polyimide is amorphous, based on X-ray analysis.  
     
     
         20 . A heat-resistant fiber impregnated material according to  claim 18 , wherein the polyimide is obtained with at least 50% of a 2,3,3′,4′-biphenyltetracarboxylic acid component as the tetracarboxylic acid component.  
     
     
         21 . An impregnated sheet-like material prepared by further impregnating an impregnated material according to  claim 18  with a heat-bonding polyimide.  
     
     
         22 . An impregnated sheet-like material according to  claim 21 , wherein the heat-bonding polyimide is a polyimide with an imide unit represented by the following formula:  
       
         
           
           
               
               
           
         
       
       wherein Ar 1  is an aromatic tetracarboxylic dianhydride residue, comprising 3,3′,4,4′-biphenyltetracarboxylic dianhydride residue and 2,3,3′,4′-biphenyltetracarboxylic dianhydride residue in a molar ratio of 0:100-90:10, and Ar 2  is an aromatic diamine residue comprising 1,3-bis(4-aminophenoxy)benzene or 1,3-bis(3-aminophenoxy)benzene and p-phenylenediamine and/or diaminodiphenylether in a molar ratio of 10:90-100:0.  
     
     
         23 . An impregnated sheet-like material obtained by further impregnating a heat-bonding polyimide into a heat-resistant fiber impregnated material prepared by using, as a binder for heat-resistant fibers, a polyimide obtained from a water-soluble polyimide precursor which gives a polyimide with a thermal decomposition temperature of 500° C. or higher and a breaking elongation of 15% or greater when shaped into a film.  
     
     
         24 . A laminate prepared by bonding a conductive metal layer onto an impregnated sheet-like material according to  claim 21 .  
     
     
         25 . A laminate according to  claim 24 , wherein the metal layer is a copper foil.  
     
     
         26 . A laminate prepared by bonding a conductive metal layer onto an impregnated sheet-like material according to  claim 23 .  
     
     
         27 . A laminate according to  claim 26 , wherein the metal layer is a copper foil.