Increasing the yield of cast plastic lenses

In the process of preparing a polymerized lens in a glass mold by preparing a reactant mixture of methyl methacrylate, diethylene glycol bis (allyl carbonate) and an acid selected from the group consisting of acrylic acid and methacrylic acid, which method comprises:

• preparing a monomer mixture of methyl methacrylate and diethylene glycol bis (allyl carbonate) wherein the methyl methacrylate monomer ranges from about 10 to about 50% by weight of the monomer mixture, balance diethylene glycol bis (allyl carbonate);
• adding to said monomer mixture a lubricant and a catalyst of benzoyl peroxide ranging from between about 1 to 1.5% by weight of the monomer mixture;
• exposing said reactant mixture to a thermal treating zone to polymerize said reactant mixture and form a terpolymer therefrom with the improvement comprising adding to said monomer mixture an acid selected from the group consisting of acrylic acid and methacrylic acid, with said acid ranging from between about 1/2 to 5% by weight of said monomer mixutre.