Lenzing Aktiengesellschaft

Robert Vodiunig

Klaus Weinrotter

Manfred Schobesberger

Gerhard Reiter

Norbert Rossak

The present disclosure describes flame-retardant, high-temperature resistant polyimide fibers, nonwovens made from said fibers, as well as the fibers and molded articles obtained after a heat treatment. A composite of such fibers is heated to a temperature in the glass transition range of the fiber, i.e. between 280.degree. and 350.degree. C. This heat treatment develops a contraction force of 0.3 to 1.1 cN in the fibers which results in a fiber shrinkage of between 20 and 60% and the formation of cohesive bonds. The fibers of the invention enable the manufacture of molded articles that are particularly strong, have a high temperature resistance and flame-retardant properties, while having a relatively low density.

Flame retardant high-temperature-resistant polyimide fibers and molded

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

A high-temperature resistant stacking support is composed of a, preferably self-supporting, core which at least partially is surrounded by a high-temperature resistant fiber composite made of polyimide fibers of the general formula ##STR1## wherein n is an integer larger than 1 and A represents a four-valent aromatic group. The stacking support can be produced by shrinking a polyimide fiber nonwoven consisting of polyimide fibers of the general formula (I) onto the core under heat exposure. These stacking supports are particularly useful for stacking heated aluminum sections.

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Leoben, Austria

Robert Vodiunig