Methacrylate-based adhesive compositions

An adhesive composition for multi-part adhesive systems is curable via radical polymerisation and comprises a (meth)acrylate monomer, 1-7 wt.% urethane (meth)acrylate oligomer, 0.5-6 wt.% organoclay, a trivalent organophosphorus compound, and wax as an anti-tack agent for forming a film on the surface of the composition. Typically, the composition comprises ≥40 wt.% (meth)acrylate monomer, 0.05-2 wt.% organophosphorus compound, and 0.5-4 wt.% anti-tack agent. The (meth)acrylate monomer is preferably methyl methacrylate. The organoclay may be benzalkonium sepiolite, benzalkonium montmorillonite, or stearalkonium bentonite and the wax may be paraffin wax. The organophosphorus compound is normally a phosphine or phosphite, e.g. triphenyl phosphine, trioctyl phosphine, triphenyl phosphite, tetraphenyl dipropyleneglycol diphosphite, poly(dipropyleneglycol)phenyl phosphite, C12-15 alkyl bisphenol A phosphite, tris(tridecyl) phosphite, or 3,9-bis(octadecyloxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane. In another aspect, a multi-part adhesive system comprises the adhesive composition, a radical initiator, and polymerisation promoter, wherein the initiator and promoter and optionally the adhesive composition are contained in different parts.