Abstract: The invention relates to a rope for the taking along and transferring of paper webs in the manufacture on paper machines of paper and cardboard made from round-braided textile fiber material. In accordance with the invention, raised positions are distributed over the circumference of the rope at regular or irregular distances. The raised positions are generated by design measures such as the selection of a different multiple thread count in the different running directions and/or the use of twisted and laid fiber elements, and/or by the use of fibers with profiled fiber cross-sections and/or textured or crimped fiber yarns and or by the use of fibers with profiled fiber crosssections and/or textured or crimped fiber yarns.

Abstract: 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.

Abstract: There are disclosed flame-retardant, high temperature resistant polyimide fibers of the general formula ##STR1## wherein n is an integer larger than 1, A is a tetravalent aromatic group and R is at least one divalent aromatic group. These polyimide fibers have been heat-treated in the unstretched state and have a maximum shrinkage of 14% when heated to a temperature of 400.degree. C. These polyimide fibers are produced by initially spinning crude fibers from a solution of the appropriate polyimide in an aprotic organic solvent, preferably according to the dry-spinning method, which solution optionally contains additives. The crude fibers obtained are washed with water to remove the solvent. The washed crude fibers are dried to a moisture content of less than 5% by mass, are subjected to a heat treatment at a temperature of between 315.degree. C and 450.degree. C, are cooled and, if desired, are crimped and cut to staple fibers.

Abstract: 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.

Abstract: 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.

Abstract: There are disclosed flame-retardant, high-temperature resistant polyimide foams having the general formula ##STR1## The foams have an elevated thermostability and, determined in a thermogravimetric analysis at a heating rate of 20 degrees per minute, have a maximum weight loss between 550.degree. and 650.degree. C. The overall weight loss up to a heating temperature of 350.degree. C. amounts to less than 3% by mass.

Abstract: In preparing polyimides by heating a solution of intramolecular tetracarboxylic acid dianhydrides and organic diisocyanates in an aprotic organic solvent in the presence of a polymerization accelerator, a catalytic amount of an alkali metal hydroxide is used as the polymerization accelerator. By this process, polyimides having high molecular weights are produced in a simple manner. The polyimides produced exhibit a high-temperature resistance.

Abstract: To produce flame-retardant thermostable new homopolyimides having structural units of the general formula ##STR1## by reacting 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride with an overall equimolar amount of 2,4- and/or 2,6-toluene diisocyanate, the reaction is carried out in the presence of a polymerization accelerator. The new homopolyimides have a glass transition point of at least 320.degree. C. and are processible to moulded articles exhibiting a similarly good structural strength as could hitherto be observed in mixed polyimides only. Furthermore, the new homopolyimides can be spun to fibres.

Abstract: 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.

Abstract: 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.

Abstract: To produce mixed polyimides having structural units of the general formulae ##STR1## wherein n is an integer larger than 1 and R represents a divalent aromatic residue, a solution of an intramolecular tetracarboxylic acid dianhydride mixture including 50 to 99% by mol benzophenone-3,3',4,4'-tetracraboxylic acid dianhydride and 50 to 1% by mol pyromellitic acid dianhydride is heated in a polar aprotic solvent and is admixed with an altogether equimolar amount of 2,4- and/or 2,6-toluenediisocyanate and/or methylenebis(phenylisocyanate). The mixed polyimides according to the invention are readily soluble in organic solvents, are flame-retardant and exhibit a good thermostability.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: Non-flammable, high-temperature resistant polyimide fibers have irregularly lobed or serrated cross-sections, a wool-like smooth hand and high brightness. They are produced by a dry-spinning process which is carried out in a spinning column, wherein a 20 to 40% solution of the polyimide is spun from spinnerets having circular orifices, the orifice numbers ranging from 20 to 800 and the orifice diameters from 100 to 300 .mu.m. An extrusion speed of between 20 and 100 m/min, a take-up speed of between 100 and 800 m/min, an amount of spin gas between 40 and 100 m.sup.3 /h under standard conditions and a spin gas temperature of between 200.degree. and 350.degree. C. are applied. The tows leaving the spinning column, which contain residual solvent from 5 to 25% by weight--based on dry polymer--and have a single filament titer of between 3.

Abstract: A polyacrylonitrile fiber which has flame-retardant properties, is produced by dry spinning, has an acrylonitrile content of at least 85% by weight in the parent polymer and contains as flame retarder 15 to 40% by weight of tris-2,3-dibromopropyl isocyanurate, based on the polymer. The flame-retardant effect can be further increased by a content of up to 10% by weight of one or more synergistic compounds.