Stamicarbon B.v.

Dsm N.v.

Lambert H Van Unen

Pieter J Lemstra

Pieter B Pluyter

Antoon Dorrestijn

Paul Smith

Hendrikus J Rutten

Cornelis W Bastiaansen

Henricus E Meijer

Willibrordus M Pontenagel

The invention relates to microporous films of ultrahigh molecular weight polyethylene and to a process for the preparation thereof by forming a solution of UHMWPE in an evaporable solvent into a film and evaporating the solvent from the film at a temperature below the dissolution temperature, the shrinking tendency occurring in the film being prevented in at least one direction in the plane of the film.

Process for making microporous films of ultrahigh molecular weight

Process of making microporous films of UHMWPE

A process is disclosed for producting thin stretched films having a thickness between 0.1 and 20 .mu.m from polyolefins of ultrahigh molecular weight by dissolving the polyolefin in a solvent, shaping the solution at a temperature above the solution temperature of the polyolefin to a tape, cooling the tape to a temperature below the solution temperature to obtain gelation and stretching the gelled tape. In this process the gelled tape is initially subjected to a preliminary orientation in one direction, under solvent removal, and is then stretched in a direction essentially perpendicular to the direction of preliminary orientation, at elevated temperature, followed by final stretching to obtain the finished thin films. This process makes possible the production of films which are free from pores, that is to say transparent and which posses high Young's moduli, high tensile strengths and favorable values for elongation at break.

Process for the production of thin stretched films from polyolefin of

High strength and modulus articles, such as filaments, fibers, tapes, films, tubes, bars or profiles, are prepared by irradiating a solid, particular, lamellar, disentangled polyethylene with a Mw&gt;4.times.10.sup.5, transforming this polyethylene above the melt temperature into an article, cooling said article to below the melting point and stretching it in several steps at rising temperature but below the melting point of the article. Advantages are i.a. the lower costs compared with the known processes, such as solid state extrusion or thermoreversible gelation.

Process for producing polyethylene articles having a high tensile

A continuous process is described wherein suspensions of high molecular weight polymers are readily transformed into solutions thereof for extrusion, to make gel filaments, tapes, tubes and films, by use of an extruder having alternate mixing and transporting sections and operating at mechanical shear rates of from 30 to 2,000 sec..sup.-1, and with relatively short residence times therein.

Process for the continuous preparation of homogeneous solutions of high

New rigid polyvinyl chloride foam having a density of less than 200 kg/m.sup.3 and having a uniform, fine-celled cell-structure consisting of a rigid vinyl chloride homopolymer containing per 100 parts by weight of polyvinyl chloride 0.1-15 parts by weight of a homo- or copolymer of an alkyl methacrylate having an alkylgroup of 1-10 carbon atoms having a viscosity of the solution .eta..sub.0.1 of between 1.times.10.sup.-6 and 4.times.10.sup.-6 m.sup.2 /s measured at 293 K in 1,2 dichloro ethylene and a method for the preparation of such a new rigid polyvinyl chloride foam.

Rigid polyvinyl chloride foam

New rigid polyvinyl chloride foam having a density of between 10 and 50 kg/m.sup.3 and having a uniform, fine-celled cell-structure consisting of a rigid vinyl chloride homopolymer containing per 100 parts by weight of polyvinyl chloride 0.1-15 parts by weight of a homo- or copolymer of an alkyl methacrylate having an alkyl group of 1-10 carbon atoms and a method for the preparation of such a rigid polyvinyl chloride foam.

Method for the preparation of rigid polyvinyl chloride foams with a density of below 200 kg/m.sup.3, in which method rigid polyvinyl chloride which is provided with a melt-flow improver is foamed with a physical blowing agent via an extruder, in which method in a first step, rigid polyvinyl chloride, together with and preferably mixed with 0.1-15 parts by weight per 100 parts by weight of polyvinyl chloride of a melt-flow improver is fed to an extruder and extruded therewith to form a granulate, this granulate is subsequently impregnated, in a second step, with a physical blowing agent and finally, in a third step, the impregnated granulate is fed, to a foaming extruder in which the granulate is extruded while it passes through a temperature profile in which process the rigid polyvinyl is foamed.

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Heerlen, Netherlands

Lambert H Van Unen