| 摘要 |
Crystalline polymethyl methacrylate may be prepared by polymerization in the presence of a catalyst formed by mixing (1) a compound of a metal of Group IVa, Va, VIa, VIIa or VIII of the Periodic Table of Mendeleeff with (2) an organometallic compound of an alkali metal, an alkaline earth metal, zinc or aluminium. The catalyst may comprise the reaction product obtained by mixing (1) and (2) above together with a further quantity of the organometallic component, and the reaction mixture may comprise a complexing agent for the organometallic compound, e.g. ethers, esters, ketones, tertiary amines and nitroaromatic compounds. Many suitable metal compounds and organometallic compounds are listed and examples describe the use of (1) vanadium trichloride, vanadium tetrachloride, titanium tetrachloride, molybdenum trichloride, chromium dichloride, chromium trichloride, chromium trioxide, potassium dichromate and ferric chloride, and (2) triisobutyl aluminium, diethyl aluminium chloride, triethyl aluminium and diethyl magnesium. Specified complexing agents are diethyl ether, tetrahydrfuran, triethylamine and ethyl acetate. The polymerization may be effected batchwise or continuously, with incremental or continuous addition of catalyst, in bulk or in an inert organic diluent, e.g. hexane, heptane, cyclohexane, benzene, toluene, xylene, ethyl chloride, methyl chloride, methylene chloride, ethylene chloride, chlorobenzene, diethyl ether, dioxane and tetrahydrofuran. After polymerization the catalyst may be destroyed by adding ethanol or butanol, and the polymer washed with methanol, ethanol, methyl isobutyl ketone, heptane or methanol-hydrochloric acid mixtures. The polymer may be dissolved in boiling toluene, xylene or methylene chloride and reprecipitated with methanol or ethanol. The polymers may be compounded with stabilizers and pigments, may be formed into films and fibres, and may be coated, e.g. on aluminium by solvent casting. |
