Abstract: A polymerization process is carried out in at least two zones, wherein in one zone polymerization is effected in the presence of a liquid phase which is at least one liquid olefine monomer and in a subsequent zone polymerization is effected by contacting the solid polymer with a gaseous olefine monomer, the product from the first zone being subjected to a concentration stage to remove some of the liquid olefine monomer before the concentrated polymer mixture is passed to the subsequent zone for polymerization with the gaseous olefine monomer. The monomer in each case may be the same, for example liquid propylene in one zone and gaseous propylene in a subsequent zone. The concentration stage may be effected using a hydrocyclone.

Abstract: A quench bath for cooling an axially moving tubular form comprises an axially compressible jacket with a liquid-retaining annular seal assembly engageable with the tubular form, inlet and discharge means for cooling liquid, and means to releasably support the jacket in an extended configuration.The bath is suitable for cooling tubular extrudates in the production of oriented tubular film.

Abstract: A polymerization process is carried out in at least two zones, wherein in one zone polymerization is effected in the presence of a liquid phase which is at least one liquid olefine monomer and in a subsequent zone polymerization is effected by contacting the solid polymer with a gaseous olefine monomer, the product from the first zone being subjected to a concentration stage to remove some of the liquid olefine monomer before the concentrated polymer mixture is passed to the subsequent zone for polymerization with the gaseous olefine monomer. The monomer in each case may be the same, for example liquid propylene in one zone and gaseous propylene in a subsequent zone. The concentration stage may be effected using a hydrocyclone.

Abstract: Cooling a tubular extrudate for conversion to tubular film by passing the extrudate through a bath of cooling liquid so that the external surface of the extrudate contacts in sequence countercurrent streams of cooling liquid in a quiescent zone, a restricted throttle zone and a spiral flow zone.

Abstract: an improved method of cooling an extruded tube of plastics material such as a substantially crystalline polymer of propylene, is disclosed in which the extruded tube is fed, in the direction of extrusion, in heat-transfer relationship with an adjacent cooling surface, such as an internal mandrel extending axially within the extruded tube, while maintaining this cooling surface at a temperature below the melting point of the plastics material. Interposed between and in contact with the tube and the cooling surface is a continuous sheath of a heat transfer liquid having a dynamic viscosity at 20.degree. C. of from 2 to 20,000 centipoise. Preferably the heat transfer liquid has a boiling point below that of the die during extrusion of the tube. An aqueous dispersion or solution of a viscosity modifier, such as a cellulosic resin, is used and supplied to the sheath at a rate of from 0.02 to 0.5 liters/minute/centimeter width of tube surface. The thus cooled tube is subsequently withdrawn from the cooling surface.