Heat-curable epoxy resin composition containing one blocked and one epoxide-terminated polyurethane prepolymer

A heat-curing epoxy resin composition comprising

• at least one epoxy resin A having an average of more than one epoxide group per molecule;
• at least one hardener B for epoxy resins, where this hardener is activated via an elevated temperature;
• at least one end-capped polyurethane prepolymer of the formula (I)
• at least one polyurethane prepolymer of the formula (II) terminated by epoxide groups
• where R1 is a p-valent moiety of a linear or branched polyurethane prepolymer PU1 terminated by isocyanate groups after the removal of the terminal isocyanate groups;
• R3 is an n-valent moiety of a linear or branched polyurethane prepolymer PU1′ terminated by isocyanate groups after the removal of the terminal isocyanate groups;
• R4, independently of the others, is a moiety of an aliphatic, cycloaliphatic, aromatic, or araliphatic epoxide comprising a primary or secondary hydroxy group after the removal of the hydroxide and epoxide groups;
• m=1, 2 or 3, and n and p, independently of each other, are respectively values from 2 to 8;
• and
• R2, independently of the others, is a substituent selected from the group consisting of
• where
• in each case R5, R6, R7 and R8, independently of the others, is an alkyl or cycloalkyl or aralkyl or arylalkyl group,
• or R5 together with R6, or R7 together with R8, forms a portion of 4- to 7-membered ring which is optionally substituted;
• in each case R9, R9′, and R10, independently of the others, is an alkyl or aralkyl or arylalkyl group, or is an alkyloxy or aryloxy or aralkyloxy group;
• R11 is an alkyl group,
• in each case R13 and R14, independently of each other, are an alkylene group having from 2 to 5 carbon atoms and, optionally, having double bonds or substitution, or is a phenylene group, or is a hydrogenated phenylene group;
• in each case R15, R16, and R17, independently of the others, is H, or is an alkyl group, or is an aryl group or an aralkyl group;
• and
• R18 is an aralkyl group or is a mono- or polynuclear substituted or unsubstituted aromatic group which, optionally, has aromatic hydroxy groups.