| 摘要 |
1,178,890. Particulate expanded cross-linked ethylene and propylene polymers. BADISCHE ANILIN- & SODA-FABRIK A.G. 26 May, 1967 [27 May, 1966], No. 24599/67. Headings C3C and C3P. The invention comprises particulate expanded ethylene or propylene polymers having a particle diameter of 3-50 mm., a bulk density of 5-200 gm/l. and a gel-content of 10-85% by weight. Gel-content is defined as the proportion by weight of polymer insoluble in solvents at temperatures above the crystalline melting point. The preferred method of preparation comprises treating particulate expanded polymers of ethylene or propylene, having an X-ray crystallinity at 25‹ C. of greater than 25%, with high energy radiation in a dosage of 5-60 Mrad. Suitable polymers are homopolymers and copolymers of ethylene or propylene and copolymers of ethylene with 5-30% by weight of esters of acrylic acid or methacrylic acid. High energy radiation includes X-rays, electron beams and neutron radiation. In Example 1 a mixture of polyethylene, 2,2 - dimethylpropane and talc is extruded and converted into expanded particles which are then exposed to radiation of 60 Mrad in an electron accelerator, to yield a product having a gel content of 84%. A copolymer of 75% ethylene and 25% tert-butyl acrylate may replace the polyethylene in this example. The expanded particles may be obtained by conventional means e.g. by mixing the polymer with an expanding agent or employing a heat-decomposable agent which liberates a gas. The particles may be cross linked on their surfaces prior to high-energy radiation treatment by spraying with a solution of di-tert-butyl peroxide and cobalt naphthenate. |
