"As mentioned previously, the polymer may also be a copolymer involving a major portion of the methyl methacrylate monomer with such monomers as vinyl acetate, styrene, methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, etc." . . . . .