Lenzing Aktiengesellschaft

Manfred Schobesberger

Klaus Weinrotter

Josef Baumgartinger

Erich Wanek

Rupert Stadlbauer

Haio Harms

Robert Vodiunig

Norbert Rossak

Herbert Sollradl

Heimo Bieringer

A process for producing high-temperature resistant and flame-retardant shaped articles of polyimide polymers of the general formula ##STR1## wherein A represents a four-valent group and R represents a divalent aromatic group, by heating a manipulatable sheet-like structure to a temperature in the glass transition range of between 280.degree. C. and 360.degree. and pressing it at pressures ranging between 10 bar and 500 bar. The polyimide shaped bodies obtained have densities of at least 1.30 g/cm.sup.3. Preferably, they may be completed as sheets having uniform thicknesses of between 0.1 and 6 mm.

Process for producing flame retardant high temperature resistant shaped

Surfaces are coated by flame spraying onto the surfaces a powder mixture including a high-temperature resistant plastic and a metal, the high-temperature resistant plastic being a polyimide having a glass transition point of above 250.degree. C. and containing low-molecular emittable components in an amount of at least 1.0% by weight, preferably of between 1.0 and 10% by weight.

Method of coating surfaces with a plastic and metal mixture

For the continuous automated production of powders that are well suited for hot pressing, i.e. those consisting essentially of spherical or cubic particles, of high-temperature resistant polymers without damage to the polymer structure in the course of the production process, a concentrated solution of the polymer in an aprotic polar solvent is continuously expressed into a twisting cone of hot aqueous precipitant. In doing so, short irregular wormy formations form, which are united to a fleece-like web, washed with aqueous solvents and finally with water, dried and comminuted. The plant provided for carrying out the process requires comparatively little space, since it does not include treatment tanks for extraction and drying.

Apparatus for producing high-temperature resistant polymers in powder

For the continuous automated production of powders that are well suited for hot pressing--i.e. those consisting essentially of spherical or cubic particles, of high-temperature resistant polymers without damage to the polymer structure in the course of the production process, a concentrated solution of the polymer in an aprotic polar solvent is continuously expressed into a twisting cone of hot aqueous precipitant. In doing so, short irregular wormy formations form, which are united to a fleece-like web, washed with aqueous solvents and finally with water, dried and comminuted. The plant provided for carrying out the process requires comparatively little space, since it does not include treatment tanks for extraction and drying.

Process for producing high-temperature resistant polymers in powder form

In a process of producing a high-temperature resistant film or a polyimide polymer, a solution of the polymer in an organic solvent is caused to flow out through a slots spinneret of a film forming arrangement and to coagulate in an aqueous precipitation bath containing the organic solvent. The film made up of coagulated liquid is stripped, the organic solvent is removed and the film is dried. In order to attain sufficient strength properties without subsequent orientation and, thus, achieve a better dimensional stability at elevated temperatures, the liquid film formed in the slot spinneret is allowed to fall directly freely into the aqueous precipitation bath through a short air gap. The film formed is drawn off the precipitation bath and is subjected to a subsequent thermal treatment to achieve a transparent homogeneous film. The organic solvent is then removed by treatment with an aqueous extraction agent, and the film is finally dried.

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Seewalchen, Austria

Manfred Schobesberger