A method of producing articles of thermosetting plastics material

摘要

1,092,749. Moulding lenses &c. PITTSBURGH PLATE GLASS CO. Nov. 30, 1965 [Dec. 1, 1964], No. 50664/65. Heading B5A. In a method of producing thermosetting resinous articles, e.g. lens, a mould is produced from a master pattern of the article by casting a thermo- , plastic resinous material about the pattern removing the pattern and introducing a thermosetting resinous material into the mould, heating the filled mould to cure the thermosetting material and separating the cured article from the mould. A glass lens 20 may comprise the master pattern which is placed on a ring holder 25 located within a mounting ring 22. Polyethylene is poured into the ring and forms the male section of the mould; the female mould part is similarly produced after inverting the lens and mounting ring, and placing the lens on a support which locates it centrally of the ring. The female mould part (31), Fig. 12, not shown, is located in a ring (40), and its cavity supplied with thermosetting resinous moulding material, e.g. allyl diglycol carbonate to which a catalyst has been added. The male mould part 30 is then placed in position and the assembly subjected to a curing cycle. The mould may be melted down and re-used. The material of the mould and article are so matched that the mould material is relatively rigid during initial curing and becomes progressively softer so that surface stress on the article is obviated and the mould follows the curvature of the shrinking article.