Activator for epoxy resin compositions

Abstract

Activators for heat-curing epoxy resin compositions, as well as use thereof in heat-curing epoxy resin compositions. These activators are distinguished by a good activation effect as well as good storage stability.

1 . An activator C for epoxy resin compositions, which has formula (I) or is a reaction product between a compound of formula (Ia) and an isocyanate or epoxide 
       
         
           
           
               
               
           
         
         wherein n stands for 1 or 2 or 3 or 4; 
         R 1  stands for an n-valent, optionally hetero atom-containing aliphatic, cycloaliphatic, or aromatic organic radical, or else R 1  stands for a radical of formula (II) 
       
       
         
           
           
               
               
           
         
         wherein 
         i and j and k each stand for a number from 0 to 10, provided that the sum of i and j is at least 2, 
         X stands for O or S or NR 7 , 
         Y stands for OR 7  or SR 7  or N(R 7 )(R 7′ ) or for a substituent of formula (III), 
       
       
         
           
           
               
               
           
         
         wherein R 2′  and R 3′  each independently stand for either H or OH or halogen or NH 2  or NHR 7  or N(R 7 ) 2  or for an alkoxy, alkyl, aryl, alkylaryl, or arylalkyl group, 
         or wherein R 2′  together with R 3′  form an optionally substituted aliphatic or aromatic ring; 
         R 7  and R 7′  each independently stand for H or for an alkyl, cycloalkyl, aralkyl, or aryl group with 1 to 8 carbon atoms, 
         R 2  and R 3  each independently stand for H or OH or a halogen or NH 2  or NHR 7  or N(R 7 ) 2  or for an alkoxy, alkyl, aryl, alkylaryl, or arylalkyl group, 
         or R 2  and R 3  together form a substituted or unsubstituted aliphatic or aromatic ring; 
         R 4  and R 5  each independently stand either for H or OH, 
         or R 4  and R 5  together form an optionally a substituted or unsubstituted aliphatic or aromatic ring; 
         providing that at least one of the radicals R 2 , R 3 , R 4 , and R 5  is different from H and that if the radicals R 2′  and/or R 3′  are present, at least three of the radicals R 2 , R 2′ , R 3 , and R 3′  are different from H. 
       
     
     
         2 . The activator as in  claim 1 , wherein the activator C has formula (I-1) or (I-2) 
       
         
           
           
               
               
           
         
         wherein g stands for 0 or 1 or 2 or 3 and h stands for 0 or 1 or 2. 
       
     
     
         3 . The activator as in  claim 2 , wherein R 2  and R 2′  stand for OH and R 3  and/or R 3′  stand for OH, Cl, CH 3 , or OCH 3 . 
     
     
         4 . The activator as in  claim 1 , wherein the activator C is a reaction product between a compound of formula (Ia) and an isocyanate, and has at least one structural element of formula (Ia-1). 
       
         
           
           
               
               
           
         
       
     
     
         5 . The activator as in  claim 4 , wherein the isocyanate is selected from the group consisting of phenyl isocyanate, tolyl isocyanate, hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), methylene diphenyl diisocyanate (MDI), and toluene diisocyanate (TDI). 
     
     
         6 . The activator as in  claim 1 , wherein the activator C is a reaction product between a compound of formula (Ia) and an epoxide, and has at least one structural element of formula (Ia-2) or (Ia-2′): 
       
         
           
           
               
               
           
         
       
     
     
         7 . The activator as in  claim 1 , wherein the activator C does not have any primary or secondary amino groups. 
     
     
         8 . A heat-curing epoxy resin composition consisting of
 a) at least one epoxy resin A with more than one epoxy group per molecule on the average;   b) at least one curing agent B for epoxy resins, which is activated by elevated temperature, and   c) least one activator C as in  claim 1 .   
     
     
         9 . The heat-curing epoxy resin composition as in  claim 8 , wherein the epoxy resin composition additionally contains at least one toughener D. 
     
     
         10 . The heat-curing epoxy resin composition as in  claim 9 , wherein the toughener D is selected from the group consisting of blocked polyurethane polymers, liquid rubbers, epoxy resin-modified liquid rubbers, and core/shell polymers. 
     
     
         11 . The heat-curing epoxy resin composition as in  claim 10 , wherein the toughener D is a liquid rubber which is an acrylonitrile/butadiene copolymer, which is terminated by carboxyl groups or (meth)acrylate groups or epoxy groups, or is a derivative thereof. 
     
     
         12 . The heat-curing epoxy resin composition as  claim 9 , wherein the toughener D is a blocked polyurethane polymer of formula (IV): 
       
         
           
           
               
               
           
         
         wherein 
         Y 1  stands for a linear or branched polyurethane polymer PU1 terminated by m+m′ isocyanate groups, after removal of all terminal isocyanate groups; 
         Y 2  each independently stand for a blocking group which is cleaved at a temperature above 100° C.; 
         Y 3  each independently stand for a group of formula (IV′) 
       
       
         
           
           
               
               
           
         
         wherein R14 stands for an aliphatic, cycloaliphatic, aromatic, or araliphatic epoxy radical containing a primary or secondary hydroxyl group, after removal of the hydroxy and epoxy groups; 
         p=1, 2, or 3, and 
         m and m′ each stand for numbers between 0 and 8, provided that m+m′ stands for a number from 2 to 8. 
       
     
     
         13 . The heat-curing epoxy resin composition as in  claim 12 , wherein Y 2  stands for a radical selected from the group consisting of 
       
         
           
           
               
               
           
         
         wherein 
         R 15 , R 16 , R 17  and R 18  each independently stand for an alkyl or cycloalkyl or aryl or aralkyl or arylalkyl group 
         or R 15  together with R 16 , or R 17  together with R 18 , form part of a 4- to 7-membered ring, which is optionally substituted; 
         R 19 , R 19′ , and R 20  each independently stand for an alkyl or aralkyl or aryl or arylalkyl group or for an alkyloxy or aryloxy or aralkyloxy group; 
         R 21  stands for an alkyl group, 
         R 22 , R 23  and R 24  each independently stand for an alkylene group with 2 to 5 C atoms, which optionally has double bonds or is optionally substituted, or for a phenylene group or for a hydrogenated phenylene group; 
         R 25 , R 26 , and R 27  each independently stand for H or for an alkyl group or for an aryl group or an aralkyl group; and 
         R 28  stands for an aralkyl group or for a mononuclear or polynuclear substituted or unsubstituted aromatic group, which optionally has aromatic hydroxyl groups. 
       
     
     
         14 . The heat-curing epoxy resin composition as in  claim 12 , wherein m is different from 0. 
     
     
         15 . A method for bonding heat-stable substrates, comprising:
 i) applying the heat-curing epoxy resin composition  claim 8  to the surface of a heat-stable substrate S1;   ii) bringing the applied heat-curing epoxy resin composition into contact with the surface of another heat-stable substrate S2;   iii) heating the composition to a temperature of 100° C.-220° C.;   wherein the substrate S2 consists of material which is the same as or different from the substrate S1.   
     
     
         16 . A heat-curing one-component bodyshell adhesive in vehicle assembly comprising the heat curing epoxy resin composition of  claim 8 . 
     
     
         17 . A bonded article, which has been obtained by the method as in  claim 15 . 
     
     
         18 . A stiffening material comprising the heat curing epoxy resin of  claim 8 . 
     
     
         19 . A foamable, heat-curing composition for reinforcement in cavities of structural components and reinforcement elements comprising the heat curing epoxy resin of  claim 8 .