Anaerobic adhesives compositions

In an anaerobic adhesive composition which contains a plurality of polymerizable unsaturated monomers and a free radical generating polymerization initiator and which will cure at ambient temperature in the absence of oxygen, but will not cure at ambient temperature in the presence of air;

• the improvement which consists essentially of employing as the principal polymerizable monomers a mixture of:
• (a) a polyacrylate terminated ester of 3,4,3',4'-benzophenone tetracarboxylic acid (BTA), and
• (b) an acrylate terminated urethane prepolymer;
• the weight ratio of component (a) to component (b) being from about 1/4 to about 4/1;
• said component (a) having the formula:
• ##STR10## where R.sub.a is an alkyl group containing up to about 18 carbon atoms, or an alkoxy ether moiety having the structure:
• ##STR11## where R.sub.c is an alkyl group containing up to about 18 carbon atoms, R.sub.d is hydrogen or a methyl group, and n is zero or a small integer, and R.sub.b has the structure:
• ##STR12## where R.sub.e is hydrogen or a methyl group and n' is a small integer, said component (b) having the formula:
• ##STR13## where the phenanthrene ring contains up to 3 double bonds, R.sub.1 is an alkylene or arylene divalent radical, and R.sub.2 is a divalent alkylene radical, or a divalent radical having the structure:
• ##STR14## or a divalent radical having the structure:
• ##STR15## R.sub.3 is a hydrogen or a methyl group and R.sub.5 is an alkyl group.