Semicarbazones as accelerators for curing epoxy resins

Abstract

The present invention describes the use in epoxy resin compositions of semicarbazones of the general formula (I) having the meanings stated for the residues R 1 , R 2 , R 3 and R 4 . These semicarbazones exhibit elevated latency in epoxy resin compositions and are thus outstandingly suitable as latent curing accelerators for single-component epoxy resin compositions.

1 . A method for curing epoxy resin compositions comprising:
 mixing a heat-activatable curing agent with an epoxy resin composition to form a mixture; and,   adding at least one semicarbazone to the mixture, wherein the at least one semicarbazone is of the general formula (I)   
       
         
           
           
               
               
           
         
         wherein 
         R 1 =branched or linear alkyl residue, cycloalkyl residue, aryl residue or alkylaryl residue, 
         R 2 ═H, branched or linear alkyl residue, cycloalkyl residue, aryl residue or alkylaryl residue, and 
         R 3 , R 4 =simultaneously or mutually independently H, branched or linear alkyl residue, cycloalkyl residue, alkylaryl residue, aryl residue, heteroaryl residue or CN;
 or 
 
         R 1 =branched or linear alkyl residue, cycloalkyl residue, aryl residue or alkylaryl residue, and 
         R 2 ═H, branched or linear alkyl residue, cycloalkyl residue, aryl residue or alkylaryl residue, 
         R 3  and R 4 =alkylene with —(CH 2 ) n — and 2≦n≦11. 
       
     
     
         2 . The method of  claim 1 , wherein the heat-activatable curing agent is selected from the group of amines, amides, guanidines, biguanides, carboxylic anhydrides or polyphenols. 
     
     
         3 . The method of  claim 1 , wherein the heat-activatable curing agent is dicyandiamide. 
     
     
         4 . The method of  claim 1 , wherein the at least one semicarbazone or mixtures of semicarbazones are used in a quantity of 0.1 to 15 wt. % relative to the epoxy resin composition. 
     
     
         5 . The method of  claim 2 , wherein the at least one semicarbazone or mixtures of semicarbazones are used in a quantity of 0.1 to 15 wt. % relative to the epoxy resin composition. 
     
     
         6 . The method of  claim 3 , wherein the at least one semicarbazone or mixtures of semicarbazones are used in a quantity of 0.1 to 15 wt. % relative to the epoxy resin composition. 
     
     
         7 . The method of  claim 1 , wherein the at least one semicarbazone or mixtures of semicarbazones are used in a ratio of 0.1 to 15 parts, relative to 100 parts of the epoxy resin composition. 
     
     
         8 . The method of  claim 2 , wherein the at least one semicarbazone or mixtures of semicarbazones are used in a ratio of 0.1 to 15 parts, relative to 100 parts of the epoxy resin composition. 
     
     
         9 . The method of  claim 3 , wherein the at least one semicarbazone or mixtures of semicarbazones are used in a ratio of 0.1 to 15 parts, relative to 100 parts of the epoxy resin composition. 
     
     
         10 . The method of  claim 1 , further comprising supplying energy to the mixture. 
     
     
         11 . The method of  claim 10 , wherein the energy is supplied in form of heat. 
     
     
         12 . An epoxy resin composition comprising:
 a) an epoxy resin with at least one reactive epoxy group;   b) at least one heat-activatable curing agent; and,   c) a curing accelerator comprising at least one semicarbazone of the general formula (I),   
       
         
           
           
               
               
           
         
         wherein 
         R 1 =branched or linear alkyl residue, cycloalkyl residue, aryl residue or alkylaryl residue, 
         R 2 ═H, branched or linear alkyl residue, cycloalkyl residue, aryl residue or alkylaryl residue, and 
         R 3 , R 4 =simultaneously or mutually independently H, branched or linear alkyl residue, cycloalkyl residue, alkylaryl residue, aryl residue, heteroaryl residue or CN; 
         or 
         R 1 =branched or linear alkyl residue, cycloalkyl residue, aryl residue or alkylaryl residue, 
         R 2 ═H, branched or linear alkyl residue, cycloalkyl residue, aryl residue or alkylaryl residue, and 
         R 3  and R 4 =alkylene with —(CH 2 ) n — and 2≦n≦11. 
       
     
     
         13 . The epoxy resin composition of  claim 12 , wherein
 R 1 =methyl, ethyl, benzyl or phenyl,   R 2 ═H, methyl, ethyl, benzyl or phenyl, and   R 3 , R 4 =simultaneously or mutually independently H, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, benzyl or phenyl,   or   R 1 =methyl, ethyl, benzyl or phenyl,   R 2 ═H, methyl, ethyl, benzyl or phenyl, and   R 3  and R 4 =alkylene with —(CH 2 ) n — and 2≦n≦6   
     
     
         14 . The epoxy resin composition of  claim 12 , wherein the epoxy resin is selected from the group of glycidyl polyethers of 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), the bromine-substituted derivative (tetrabromobisphenol A) thereof, glycidyl polyethers of 2,2-bis(4-hydroxyphenyl)methane (bisphenol F) and glycidyl polyethers of novolak resins together with aniline or substituted anilines, preferably p-aminophenol or 4,4′-diaminodiphenylmethane. 
     
     
         15 . The epoxy resin composition of  claim 13 , wherein the epoxy resin is selected from the group of glycidyl polyethers of 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), the bromine-substituted derivative (tetrabromobisphenol A) thereof, glycidyl polyethers of 2,2-bis(4-hydroxyphenyl)methane (bisphenol F) and glycidyl polyethers of novolak resins together with aniline or substituted anilines, preferably p-aminophenol or 4,4′-diaminodiphenylmethane. 
     
     
         16 . The epoxy resin composition of  claim 12 , wherein the at least one heat-activatable curing agent comprises biguanides, preferably ortho-tolylbiguanide (OTB), methylenedianiline (MDA, DDM), para-aminocyclohexylmethane (PACM), 3,3′- or 4,4′-diaminodiphenyl sulfone (DDS), polyetheramines, dicyandiamide (DCD), dihydrazides of adipic or sebacic acid, anhydrides of pyromellitic, trimellitic or phthalic acid, phenol novolaks or cresol novolaks, or mixtures thereof. 
     
     
         17 . The epoxy resin composition of  claim 13 , wherein the at least one heat-activatable curing agent comprises biguanides, preferably ortho-tolylbiguanide (OTB), methylenedianiline (MDA, DDM), para-aminocyclohexylmethane (PACM), 3,3′- or 4,4′-diaminodiphenyl sulfone (DDS), polyetheramines, dicyandiamide (DCD), dihydrazides of adipic or sebacic acid, anhydrides of pyromellitic, trimellitic or phthalic acid, phenol novolaks or cresol novolaks, or mixtures thereof. 
     
     
         18 . The epoxy resin composition of  claim 14 , wherein the at least one heat-activatable curing agent comprises biguanides, preferably ortho-tolylbiguanide (OTB), methylenedianiline (MDA, DDM), para-aminocyclohexylmethane (PACM), 3,3′- or 4,4′-diaminodiphenyl sulfone (DDS), polyetheramines, dicyandiamide (DCD), dihydrazides of adipic or sebacic acid, anhydrides of pyromellitic, trimellitic or phthalic acid, phenol novolaks or cresol novolaks, or mixtures thereof. 
     
     
         19 . The epoxy resin composition of  claim 15 , wherein the at least one heat-activatable curing agent comprises biguanides, preferably ortho-tolylbiguanide (OTB), methylenedianiline (MDA, DDM), para-aminocyclohexylmethane (PACM), 3,3′- or 4,4′-diaminodiphenyl sulfone (DDS), polyetheramines, dicyandiamide (DCD), dihydrazides of adipic or sebacic acid, anhydrides of pyromellitic, trimellitic or phthalic acid, phenol novolaks or cresol novolaks, or mixtures thereof.