Heat-curing epoxy resin composition containing non-aromatic ureas as accelerator

A method of adhesively bonding heat-stable materials with improved impact peel strength, comprising:

• contacting a first heat-stable material with a heat-curing epoxy resin composition;
• applying a second heat-stable material to said heat-curing epoxy resin composition on said first heat-stable material;
• and
• curing the heat-curing epoxy resin composition at a temperature of from 100 to 220° C. to bond the first and second heat-stable materials together;
• wherein the heat-curing epoxy resin composition comprises:
• 10% to 85% by weight, based on the overall weight of the composition, of (A) at least one epoxy resin having on average more than one epoxide group per molecule;
• 0.1% to 30% by weight, based on the weight of (A), of (B) a dicyandiamide hardener;
• 0.02% to 0.85% by weight, based on the weight of (A), of (C) an accelerant;
• 0.1% to 50% by weight, based on the overall weight of the composition, of (D) at least one toughener;
• 2% to 50% by weight, based on the overall weight of the composition, of (F) at least one filler;
• and
• 0.1%-20% by weight, based on the overall weight of the composition, of (G) at least one reactive diluent which carries one or more epoxy groups per molecule;
• wherein (A) comprises a liquid epoxy resin having the formula (A-II) and optionally a solid epoxy resin of the formula (A-I):
• wherein R′″ and R″″ independently of one another are either H or CH3, and r is from 0 to 1, and
• wherein R′ and R″ independent of one another are either H or CH3, and s is >1.5;
• wherein (C) is selected from compounds of formula (Ia) and compounds of formula (Ib):
• wherein:
• R1 is H or an n′-valent aliphatic, cycloaliphatic or araliphatic radical;
• R2 and R3 either each independently of one another are an alkyl group or aralkyl group;
• or
• together are a divalent aliphatic radical having 3 to 20 C atoms which is part of an optionally substituted heterocyclic ring having 5 to 8 ring atoms;
• R1′ is an n′-valent aliphatic, cycloaliphatic or araliphatic radical;
• R2′ is an alkyl group or aralkyl group;
• R3′ independently at each occurrence is H or an alkyl group or aralkyl group;
• and
• n and n′ are each from 1 to 4;
• wherein (D) comprises a blocked polyurethane polymer and optionally further comprises one or more of liquid rubbers, epoxy-modified liquid rubbers, and core-shell polymers;
• and
• wherein the heat-cured epoxy resin composition provides an impact peel strength between the first and second heat-stable materials that is higher than an impact peel strength of a similar heat-cured epoxy resin composition, which is formulated with components (A), (B), (D), (F), and (G), but not with component (C).