| 摘要 |
1,239,806. Expanded polyethylene and polypropylene. BADISCHE ANILIN- & SODAFABRIK A.G. 11 Dec., 1968 [12 Dec., 1967], No. 58903/68. Heading B5A. [Also in Division C3] Expanded plastics mouldings are made by treating expanded particles of ethylene or propylene polymers with high energy radiation until the surface of the particles are at a temperature above the crystallite melting point of the polymer and compressing the particles to 5-80% of their original bulk volume. The particles preferably have a closed cell structure, the heating is preferably performed by an electron beam and the particles are preferably compressed to 30-65% of their original volume. The polymer may be a homopolymer of ethylene or propylene or a copolymer which contains at least 50 wt. per cent of the olefin and, for example, esters of acrylic or methacrylic acid or vinyl carboxylic acids especially esters of acrylic acid with n-butyl alcohol or tert-butyl alcohol and vinyl acetate. The particle diameter is preferably 3 to 20 mm. |
