Preparation of polymethacrylate molding material with high heat deflection temperature and high stability against thermal degradation

PURPOSE: To prepare, on a commercial scale and at a low cost, a polymethacrylate molding material which has high heat deflection temp. and high stability against thermal degradation by conducting a reaction at a specific monomer concn. CONSTITUTION: Polymn. is carried out so that at least 70 wt.% of the molding material is prepd. at a methacrylate monomer concn. of more than 5 mol per liter. The polymn. temp. is 30 to 120°C. The amt. of the polynm. initiator is 0.05 wt.%, and the content of the mol.wt. modifier is 0.1 to 2 wt.%. The polymn. is carried out in a non-continuous manner. The monomer remaining unreacted is separated by vacuum degassing and fed to a new reaction. At the time of completion of the polyrmm., the polymn. initiator is added in an amt. of 10 -4 to 1 wt.% to the reaction mixture. In the molding material, a monomer mixture having a methyl methacrylate content exceeding 75 wt.%, pref. 98 to 100 wt.% is used, and the presence of a methacrylic ester contg. a 2-8C alkyl group being present in the ester group or other monomer is acceptable. COPYRIGHT: (C)1995,JPO