| 摘要 |
Polymer-in-monomer syrups, wherein the said monomer is methyl methacrylate alone or with a copolymerizable a , b -ethylenically unsaturated compound, wherein the polymer is a methyl methacrylate homopolymer or a copolymer of methylmethacrylate and a copolymerizable a , b -ethylenically unsaturated compound, has an inherent viscosity in the range 0,25 to 1 and is dissolved in said monomer, and wherein the syrup has a bulk viscosity in the range 0,5 to 50 poises and contains less than 20 p.p.m. of a polymerization initiator, may be prepared by heating the monomer in the presence of a chain transfer agent, stopping the polymerization by cooling when the reaction mixture has a bulk viscosity of 0,5 to 50 poises and the polymer an inherent viscosity of 0,25 to 1, and by using a polymerization initiator in sufficiently small amount that the final syrup contains less than 20 p.p.m. of the initiator. Specified copolymerizable compounds are vinyl acetate, styrene, alkyl acrylates and other alkyl methacrylates. Specified chain transfer agents are thiophenol and lauryl mercaptan. The initiator may be benzoyl peroxide, diethyl peroxide, diisobutyl peroxide, a , a 1-azodiisobutyronitrile or a , a 1-azobis-(methylisobutyrate). Cooling is preferably effected by adding as quenching liquid a cold solution of an inhibitor, e.g. hydroquinone, catechol or pyrocatechol, in monomer. The syrups may also contain cross-linking agents, e.g. ethylene dimethacrylate, propylene dimethacrylate, polyethylene glycol dimethacrylate, divinyl benzene, triallyl cyanurate and diallyl phthalate, and inert additives, e.g. glass fibres, powdered metals, pigments, natural and synthetic fibres and may be used in laminating, moulding and potting. U.S.A. Specification 2,471,959 is referred to. |
