| 摘要 |
1425948 Polymer casting process IMPERIAL CHEMICAL INDUSTRIES Ltd 11 May 1973 [2 June 1972] 25867/72 Heading C3P Thermoplastic polymer sheets are obtained by casting and polymerizing an alkyl methacrylate (containing 1 to 4 carbon atoms in the alkyl group, and optionally mixed with up to 20 wt. per cent of other monomers) in the presence of 0À02-3%, based on the weightof the sheet, of a cross-linking agent, the conditions being such that in the absence of the crosslinking agent a polymer having a reduced viscosity of 1À5-4À0 would be obtained. The product comprises 10-95 wt. per cent of solvent-extractable polymer with a reduced viscosity of not more than 4À0, the remainder being insoluble and cross-linked, and has an elongation-at-break of at least 600%. Preferably the casting composition also contains a pre-formed polymer; it may be prepared by adding the cross-linking agent and fresh initiator to a polymer-in-monomer syrup obtained by a preliminary partial polymerization of the monomer. Chain transfer agents may be-added in one or both of the polymerization stages to control the viscosity of the product. In the examples the monomer is methyl methacrylate and the cross-linking agent is glycol dimethacrylate, triallyl cyanurate, triallyl phosphate, allyl methacrylate or diallyl phthalate. |
