Mitsui Petrochemical Industries, Ltd.

Isaburo Higashi

Kazuo Yagi

Hitoshi Mantoku

Yoshinori Akana

Akinao Hashimoto

Tadao Yatsu

Biaxially oriented films from high molecular weight polyethylene are characterized by a gas permeable structure formed from random-arranged microfibrils. The films have coefficients of static friction and kinetic friction of not more than 1.0. The biaxially oriented films are further characterized by service smoothness as well as tensile (tangent) modulus and tensile strength. The films may be used for lamination, filter, or for packaging for moisture absorbers. The biaxially oriented films may be obtained by extracting a hydrocarbon plasticizer from a sheet formed from the high molecular weight polyethylene and a hydrocarbon plasticizer, stretching the resulting sheet to obtain an oriented film having a specific surface area of at least 70 m.sup.2 /g and a fibril structure, and heating the oriented film under a standard length constraint to reduce the oriented film in specific area by at least 20 m.sup.2 /g.

Biaxially oriented film of high molecular weight polyethylene, process

The biaxially oriented films of high molecular weight polyethylene is formed and its surface modified to provide a hydrophilic property to the resulting film. The film is prepared by melt-kneading the high molecular weight polyethylene with an ordinarily solid hydrocarbon plasticizer and a raw fabric sheet is formed from the resulting molten mixture. After the hydrocarbon plasticizer is extracted the resulting unstretched sheet is stretched under conditions providing a stretched film having a specific surface area of 70 m.sup.2 /g or more and a fibril structure. This stretched film is then heated under standard length constraint conditions to reduce the specific surface area of the stretched film by at least 20 m.sup.2 /g to obtain a biaxially oriented film of high molecular weight polyethylene. The surface of the film is thereafter subjected to surface modification by polymerizing a vinyl monomer having a hydrophilic group on the surface of the film whereby the film surface becomes hydrophilic, as measured by a contact angle of the film surface to a water drop at a level of not more than 90.degree.. The biaxially oriented films are further characterized by their excellent gas permeability, surface smoothness, tensile modulus and tensile strength.

Process for preparing surface-modified biaxially oriented film of high

A film-forming and thermocurable vinyl alcohol-substituted acrylamide copolymer consisting essentially of

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Kuga-gun, Japan

Isaburo Higashi