| 摘要 |
1,196,036. Moulding expanded polyolefin. BADISCHE ANILIN- & SODA-FABRIK A.G. 10 Nov., 1967 [12 Nov., 1966], No. 51279/67. Heading B5A. [Also in Division C3] Expanded mouldings of olefin polymers are moulded from particles of a closed cell expanded polymer of an olefin, having two or three carbon atoms, which are heated to a surface temperature above the crystallite melting point, and fused together under pressure in a closed mould, whereby the heat supplied is not more than 50% of the heat required to melt the particles of olefin polymers and the particles are compressed by 5 to 70% of their original volume. The particles are heated to surface temperatures preferably of 5% to 25‹ C. above the crystallite melting point, prior to fusion together. Heat is supplied by gaseous heating media, e.g. air or steam or mixtures thereof, or fluid, e.g. water, or water and glycerol. The particles are heated in the mould or in separate equipment before introduction to the mould, e.g. by hot air blowing of the particles into the mould. The mould is preferably perforated or provided with nozzles whereby gases are vented and moulding pressure is preferably applied by relative movement of a pair of opposite mould walls. Alternatively, continuous mouldings may be produced employing four co-operating conveyer belts or a pair of opposed belts with stationary side guides, and the particles are preferably compressed by the belts prior to fusion. A gaseous heating medium is preferably introduced at one side and vented at another side or the base of the mould, or heating probes may be used. The mouldings may be postheated to above the olefin melting point to densify the surface thereof. The mouldings may be produced for upholstery, floats, packaging components, thermal and acoustic insulation, shock absorbing inserts, floating intermediate floorings, decorations, toys, seals, laminates. Mouldings may be cut into films or sheeting by a hot wire. Examples are given of moulding polyethylene particles, a mixture of 80% (by weight) high pressure polyethylene with 20% polyisobutylene, and a mixture of 70% (by weight) polypropylene with 30% polyisobutylene. The olefin polymers, which preferably have an X-ray crystallinity of more than 25% at 25‹ C., may be homopolymers of ethylene or propylene preferably having 2-4% weight fractions soluble in n-heptane, or may comprise copolymers thereof (see Division C3) and should be free from cross-linked molecules. The diameter of the particles is preferably 3-40 mm. and the particle average cell diameter is 0À1 to 0À01 mm. The particles may comprise comminuted expanded extrudate, or a heated mixture of polymer and expanding agents which decompose to gaseous products. The particles may also contain flame proofiing agents, dyes, lubricants, or other polymers, e.g. polyisobutylene, or fillers such as wood fibres or other porous materials or thermoplastics fibres. Reinforcements of fabric or netting of thermoplastics may also be incorporated in the mouldings. The particles may have applied to the surface thereof high-boiling aliphatic, cycloaliphatic or aromatic hydrocarbons, e.g. paraffin oil, xylenes, toluene or benzene, in an amount of 0À1 to 0À5% (volume) whereby improved particle fusion is obtained. |
