A method for the preparation of methyl methacrylate - polymer syrups

摘要

1,138,593. Continuous production of methylmethacrylate monomer/polymer syrups. E. I. DU PONT DE NEMOURS & CO. 13 March, 1967 [14 March, 1966], No. 11741/67. Heading C3P. [Also in Division B1] Syrups of polymethyl methacrylate or copolymers containing more than 60% by weight of methyl methacrylate units, in the corresponding monomer, are prepared in continuous manner by a process which comprises exposing a mixture of a free radical polymerization initiator and the monomer at an elevated temperature to " an environment of constant polymerization conditions " (as defined) to form 40-95% by weight of the final polymer content, exposing the resultant mixture at an elevated temperature to at least one subsequent environment of constant polymerization conditions to form the remainder of the polymer content (which has a higher molecular weight than the previously formed polymer content) and to reduce the amount of residual initiator to a level such that on subsequent cooling the initiator is substantially inactive, and thereafter cooling the reaction product. Suitable comonomers for the methyl methacrylate include acrylonitrile, ethylene, butadiene, vinyl acetate, styrene, 2-methylstyrene and alkyl-(meth)-acrylates, e.g. nbutyl methacrylate or ethylacrylate (see Examples 5 and 6). Initiators specified are azobisisobutyronitrile, benzoyl peroxide, lauryl peroxide and di-t-butyl peroxide. A chain transfer agent may be included in the preparation of the syrups, e.g. glycol di-mercaptoacetate, lauryl mercaptan and n-butyl mercaptan. Storage stability of the syrups is enhanced by addition of a polymerization inhibitor, e.g. quinone, hydroquinone and 2,4-dimethyl-6-tbutyl-phenol. The syrups are useful for casting solid articles such as sheets with conventional curing agents.