| 摘要 |
1340962 Polyethylene foam CITIES SERVICE CO 27 May 1971 [25 Aug 1970] 17667/71 Heading C3C [Also in Division B5] A foamed low density polyethylene material is made by withdrawing polyethylene-ethylene solution as a liquid stream from a high pressure, high temperature ethylene polymerization zone, reducing the pressure of the withdrawn polyethylene-ethylene solution to a pressure of from 150 to 1200 psi while maintaining the reduced pressure solution in the liquid state, and expelling (e.g. by extrusion) the reduced pressure polyethylene-ethylene solution into a zone of atmospheric pressure and a temperature below the melting point of said polyethylene, whereby the ethylene vaporizes during the expulsion step forming a foamed polyethylene material having a multiplicity of closed cells. In the Fig. ethylene is polymerized in reactor 12 and a solution of polyethylene in ethylene is fed via 14 to separator 16 where a stream at reduced pressure is fed via 20 and valve 22 to feed hopper 24 having cap 28 and vent 32 (for release of the ethylene) which is connected to extruder 40 and die 46. Polyethylene melt containing ethylene, 58, is forced through 48 into the atmosphere and cooling tank 50 having rollers 52 and 54, and then to draw-off rolls 56. |
