Phosphorus-containing compounds useful for making halogen-free, ignition-resistant polymers

Abstract

Phosphorus-containing compounds useful for flame retardant epoxy resins are disclosed. The flame retardant epoxy resins may be used to make electrical laminates. This invention is particularly useful in end use applications in which a low bromine or low halogen content is required or desired.

1 - 7 . (canceled) 
     
     
         8 . A homogeneous solution, comprising:
 dicyandiamide; and   a phenolic hardener having the general formula:   
       
         
           
           
               
               
           
         
         where R′ and R″ may be the same or different and each represents R- or RO-radicals, with R being an alkyl or aromatic radical; R′″ is hydrogen, an alkyl or aromatic radical, —CH 2 P(O)R′R″, or —CH 2 OR; n is a whole number within the range from 0 to 100, 
         wherein said dicyandiamide is not dissolved in a solvent selected from the group consisting of dimethylformamide, N-methylpyrodinone, dimethylsulfoxide, and combinations thereof 
         and wherein the homogeneous solution does not contain an epoxy resin. 
       
     
     
         9 . The solution of  claim 8  further comprising a solvent comprising at least one of an alcohol, a ketone, and a glycol ether. 
     
     
         10 . The solution of  claim 9 , wherein the alcohol comprises a butanol. 
     
     
         11 . The solution of  claim 9 , wherein the ketone comprises methyl ethyl ketone. 
     
     
         12 . The solution of  claim 9 , wherein the glycol ether comprises propylene glycol methyl ether. 
     
     
         13 . The solution of  claim 8 , further comprising an imidazole catalyst. 
     
     
         14 . The solution of  claim 8 , further comprising at least one additional hardener selected from the group consisting of a phenol novolac, a bisphenol A novolac, and a cresol novolac. 
     
     
         15 . The solution of  claim 9 , wherein the solution comprises:
 1 to 60 weight percent of the phenolic hardener;   1 to 20 weight percent of the dicyandiamide; and   5 to 30 weight percent of the solvent;   wherein the weight percentages given are based on the combined weight of the phenolic hardener, the dicyandiamide, and the solvent.   
     
     
         16 . A curable composition, comprising the solution of  claim 8  and an epoxy resin. 
     
     
         17 . The curable composition of  claim 16 , wherein the composition comprises:
 30 to 99 weight percent of the epoxy resin,   0.01 to 5 weight percent of the dicyandiamide;   1 to 40 weight percent of the phenolic hardener; and   0 to 30 weight percent of a solvent comprising at least one of an alcohol, a ketone, and a glycol ether;   wherein the weight percentages given are based on the combined weight of the phenolic hardener, the dicyandiamide, the epoxy resin, and the solvent.   
     
     
         18 . The curable composition of  claim 16 , wherein the epoxy resin comprises an epoxy terminated polyoxazolidone-containing compound. 
     
     
         19 . The curable composition of  claim 18 , wherein the epoxy terminated polyoxazolidone-containing compound comprises a reaction product of a polyepoxide compound and a polyisocyanate compound. 
     
     
         20 . A process for forming a dicyandiamide hardener composition, comprising:
 admixing dicyandiamide and a phenolic hardener having the general formula:   
       
         
           
           
               
               
           
         
         where R′ and R″ may be the same or different and each represents R- or RO-radicals, with R being an alkyl or aromatic radical; R′″ is hydrogen, an alkyl or aromatic radical, —CH 2 P(O)R′R″, or —CH 2 OR; n is a whole number within the range from 0 to 100 wherein said dicyandiamide hardener does not contain a solvent selected from the group consisting of dimethylformamide, N-methylpyrodinone, dimethylsulfoxide and combinations thereof and wherein the hardener does not contain an epoxy resin. 
       
     
     
         21 . The process of  claim 20 , further comprising admixing a solvent comprising at least one of an alcohol, a ketone, and a glycol ether with at least one of the dicyandiamide and the phenolic hardener. 
     
     
         22 . The process of  claim 20 , further comprising
 admixing an epoxy resin with the hardener composition to form a curable composition.   
     
     
         23 . The process of  claim 22 , further comprising curing the curable composition to form a thermoset resin.