| 摘要 |
1376430 Seaming non-metallic sheet material PONT-A-MOUSSON SA 20 Aug 1973 [25 Aug 1972] 39269/73 Heading B5K Welded objects of cross-linked plastics material are produced by first producing parts which are not cross-linked from cross-linkable plastics material containing cross-linking agents at a temperature lower than that required for the cross-linking to take place, welding the parts together and effecting cross-linking of the assembly. Preferably, the cross-linkable plastics material is a polyolefin, e.g. high or low density polyethylene or polypropylene, and may contain a filler, e.g. a fibreglass filler. High density polyethylene may contain as cross-linking agent an organic peroxide, e.g. ditert-butyl peroxide, dicumyl peroxide or diperoxide 1,3- ditert-butyl peroxide isopropylbenzene and is extruded at 140-180‹ C. to form parts which are welded at 180-200‹ C. and cross-linked at or above 200‹ C. The parts may be welded with overlapping edges, Fig. 1 (not shown), or with abutting up-turned flanges, Fig. 2. Specified welding methods are (a) passing the parts in front of a stream of hot air and then pressing between rollers; (b) passing the parts between heating pads having a low coefficeint of friction and then pressing between rollers; (c) simultaneous heating and pressing by heating tongs; and (d) treating the parts with ultrasonic sound and passage between rollers. |
