| abstract |
Compositions which are aerobically polymerizable in the presence of a free radical catalyst comprise one or more mono- and/or bisacrylate or methacrylate monomers and 0.05-6% by weight of the monomer(s) of a triarylborane complex of the formula R3B-Am in which R represents an aryl radical of 6-12 carbon atoms and Am represents sodium hydroxide, ammonia, benzene or an amine. The radical R is preferably free from hydroxyl, carboxyl and amino groups but may contain substituents such as halo, alkyl and alkoxy groups. The (meth)acrylate monomer is one which normally polymerizes only with difficulty with a free radical catalyst unless oxygen is almost completely absent; suitable esters are alkyl, allyl and fusel oil (meth)acrylates, the bisesters of glycols and bisphenols, and the bisester condensation products of phenols and glycidyl(meth)acrylate (which may contain additional ethylenic unsaturation). The composition may also include an oxirane-type monomer, e.g. glycidyl acrylate or methacrylate or a diluent monomer such as phenyl acrylate, hydroxyethyl methacrylate or acrylonitrile. A free base may also be included as a co-catalyst component, e.g. dimethyl-p-toluidine, tri-nbutylamine, diethylenetriamine, N-methylpiperidine, N-methylmorpholine, 2,5-dimethylpiperazine or 1,2,4-trimethylpiperazine. Other optional components include solvents, fillers (e.g. silica, alumina or synthetic fluorapatite), pigments, dyes and plasticizers. To effect polymerization a free radical catalyst is added, e.g. benzoyl peroxide, methyl ethyl ketone peroxide, t-butyl hydroperoxide or azobisisobutyronitrile, and the composition is then activated by heating or acidifying, e.g. with an inorganic or organic acid; the latter is preferably a compound which will copolymerize with the (meth)acrylate monomer, e.g. acrylic, methacrylic, maleic or citraconic acid. The compositions may be stored as multi-component kit, each component containing some of the ingredients of the composition in stable form. The compositions are suitable for coating, moulding, potting, embedding or sealing and, particularly, for use as a vehicle in dental filling compositions, as described in Specification 1,113,723. |