Abstract: The process, which makes it possible to reduce the adhesive nature of a partially crystalline copolymer (E) of ethylene and at least one alpha-olefin with a density of between 0.865 and 0.900 approximately, and to increase its resistance to crushing, consists in mixing closely said ethylene copolymer with at least one non-atactic propylene polymer (P) with a fluidity index (measured according to the ASTM D 1238 standard, condition L) between 35 and 200 dg/min. approximately, in a proportion of between 22 to 50 parts by weight approximately for 100 parts by weight of ethylene copolymer.

Abstract: Polyolefin rubber which is an ethylene/propylene and/or 1-butene copolymer, which has a melt index of 0.3 to 15 dg/min and a relative density of 0.860 to 0.885, comprising 74-91 mol % of units derived from ethylene and 9-26 mol % of units derived from propylene and/or from 1-butene, characterised by a crystalline melting point J of 100.degree. to 125.degree. C. The process for obtaining this rubber consists in copolymerising, at a temperature of 150.degree.-300.degree. C. and at a pressure of 400-2000 bars, a gas stream containing 15-42% by vol. of ethylene and 58-85% by vol. of propylene and/or 1-butene, in the presence of a Ziegler-type catalyst system comprising at least one compound of a transition metal of groups IVB, VB, VIB and VIII of the Periodic Classification, and at least one organoaluminium compound and, if appropriate, in the presence of at least one chain transfer agent.

Abstract: Process and device for cooling a tubular sleeve produced by hot extrusion-blowing of a thermoplastic material through an annular die. In the process, a stream of primary air is flowed under pressure substantially parallel to and spaced from the tubular sleeve and reaches the tubular sleeve at a second stage. The stream of primary air induces a stream of secondary air which flows substantially parallel and proximate to the tubular sleeve at a first stage and whose flow is substantially laminar over most of its path. The device includes a first cylindrical sleeve member that, in combination with the tubular sleeve, defines a secondary air flow space. A second cyclindrical sleeve member and the first sleeve member define a primary air flow space therebetween. A cylindrical ring disposed proximate to the annular die directs air into the secondary air flow space. A source of pressurized air is in flow communication with the primary air flow space.