Curing agents for low-emission epoxy resin products

Abstract

Curing agents for epoxy resins, containing at least one adduct of a primary diamine and an aromatic monoepoxide, at least one primary diamine and at least one secondary diamine which is free of primary amino groups and free of hydroxyl groups, are disclosed. The curing agent is of low viscosity and cures, together with epoxy resins, rapidly and without blushing, even under damp, cold conditions, to form films of high hardness and low brittleness. It is particularly well suited for low-emission coatings that cure at room temperature.

1 . A curing agent, suitable for curing epoxy resins, comprising:
 at least one adduct of at least one primary diamine P1, which has two primary amino groups, is free of secondary amino groups and has a molecular weight in the range of 100 to 200 g/mol, and at least one aromatic monoepoxide;   at least one primary diamine P2; and   at least one secondary diamine, which is free of primary amino groups and free of hydroxyl groups, and which is not 1,3-bis(benzylaminomethyl)benzene.   
     
     
         2 . The curing agent according to  claim 1 , wherein the adduct is a reaction product of the at least one primary diamine P1 with the at least one aromatic monoepoxide in a ratio of moles of the at least one primary diamine P1 to moles of the at least one aromatic monoepoxide ranges from 1/0.8 to 1/1.5. 
     
     
         3 . The curing agent according to  claim 2 , wherein the ratio of moles of the at least one primary diamine P1 to moles of the at least one aromatic monoepoxide ranges from 1/1 to 1/1.5. 
     
     
         4 . The curing agent according to  claim 1 , wherein the ratios of the at least one adduct, the at least one primary diamine P2 and the at least one secondary diamine are such that, of the total number of amine hydrogens thereof that are reactive to epoxy groups,
 15 to 75% are from the at least one adduct,   15 to 60% are from the at least one primary diamine P2, and   10 to 40% are from the at least one secondary diamine.   
     
     
         5 . The curing agent according to  claim 4 , wherein the ratios of the at least one adduct, the at least one primary diamine P2 and the at least one secondary diamine are such that, of the total number of amine hydrogens thereof that are reactive to epoxy groups,
 15 to 60% are from the at least one adduct,   25 to 50% are from the at least one primary diamine P2, and   10 to 20% are from the at least one secondary diamine.   
     
     
         6 . The curing agent according to  claim 1 , wherein the monoepoxide is a cresyl glycidyl ether. 
     
     
         7 . The curing agent according to  claim 1 , wherein the primary diamine P1 is selected from the group consisting of 1,6-hexanediamine, 1,5-diamino-2-methylpentane, 2,2,4- and 2,4,4-trimethylhexamethylenediamine, isophoronediamine, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, 2- and 4-methyl-1,3-diaminocyclohexane, 1,3-bis(aminomethyl)benzene, and mixtures thereof. 
     
     
         8 . The curing agent according to  claim 7 , wherein the primary diamine P1 is 1,5-diamino-2-methylpentane. 
     
     
         9 . The curing agent according to  claim 1 , wherein the primary diamine P2 has a molecular weight ranging from 140 to 300 g/mol, and is selected from the group consisting of isophoronediamine, 2,2,4- and 2,4,4-trimethylhexamethylenediamine, 1,3-bis(aminomethyl)-cyclohexane, 1,4-bis(aminomethyl)cyclohexane, bis(4-aminocyclohexyl)methane, bis(4-amino-3-methylcyclohexyl)methane, 4,7-dioxadecane-1,10-diamine, polyoxypropylenediamines and cycloaliphatic ether group-containing diamines from the propoxylation and subsequent amination of 1,4-dimethylolcyclohexane. 
     
     
         10 . The curing agent according to  claim 1 , wherein the secondary diamine is an N,N′-dialkylation product of a primary diamine with a molecular weight in the range of 28 to 300 g/mol. 
     
     
         11 . The curing agent according to  claim 1 , wherein the secondary diamine is an N,N′-dialkylation product of a primary diamine P3, wherein the primary diamine P3 is selected from the group consisting of 1,6-hexanediamine, 1,5-diamino-2-methylpentane, 1,3-bis(aminome-thyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane and 1,3-bis(aminomethyl)benzene. 
     
     
         12 . An epoxy resin composition containing at least one epoxy resin and at least one curing agent according to  claim 1 . 
     
     
         13 . The epoxy resin composition according to  claim 12 , being a two-component composition, consisting of:
 (i) a resin component containing at least one epoxy resin and   (ii) a curing agent component containing the curing agent.   
     
     
         14 . A cured composition obtained by curing a composition according to  claim 13 .