Process of foaming and extruding polyethylene using 1, 2-dichlorotetrafluoroethane as the foaming agent

Expanded polyolefine polymers and copolymers are obtained by using as volatile expanding agent 1,2-dichlorotetrafluoroethane. The polymers may be blended with acrylo-nitrile-butadiene rubbers, polychloroprene, polyisoprene, ethylene-vinyl acetate copolymers, or halogenated polyolefines.ALSO:A cellular polymer body is prepared by heating a normally solid polymer obtained by polymerising one or more aliphatic p mono-olefines alone or in admixture with vinyl acetate, styrene, methyl methacrylate, tetrafluoroethylene or acrylonitrile, at heat-plastifying temperatures between 90 DEG and 200 DEG C. in admixture with from 0,05 to 0,702 gram molecular preportion of 1, 2-dichlorotetrafluoroethane per 100 grams of the polymer, under pressure to form a flowable gel, and the gel is extruded into a zone of lower pressure wherein the extruded material expands with resultant formation of the cellular polymer body. Specified olefines are ethylene, propylene, butene-1, pentene-1, 3-methylbutene-1,4-methyl-pentene-1,4-methyl hexene or 5-methylhexene-1. The aliphatic olefine polymers can be modified by blending with polymeric materials such as acrylonitrile-butadiene rubbers, poly (2-chloro-butadiene-1, 3), polyisoprene, or ethylene-vinyl acetate copolymers. Halogenated aliphatic olefin polymers may be employed. Finely divided solid materials such as calcium silicate, zinc stearate and magnesium stearate may be incorporated with the polymer or gel prior to expanding, preferably in amounts from 0,1 to 2% by weight of the polymer, to aid in controlling the size of the cells. According to an example solid granules of polyethylene with 1,5% by weight zinc stearate were fed at a rate corresponding to 30 lbs/hr. into an extruder comprising a four foot long barrel having a 2 1/2 inch diam. screw equipped with a mixing head and a sealing plate positioned midway of the screw. The heat-plastified polyethylene was forwarded under pressure of the screw around the sealing plate into the second section wherein it was mixed with 1, 2-dichlorotetrafluoroethane fed in at a rate of 7,5 lbs./hr. The resulting mixture was brought to a temperature between 98 DEG and 102 DEG C. and then forced through a discharge orifice of 1/8 by 1/2 inch cross-section into the atmosphere. The product was a cellular body of about 1 by 2 inches cross-section and was composed of substantially uniform fine cells of approximately 0,7 mm. diameter.