Korea Institute of Science and Technology

Korea Advanced Institute of Science and Technology

Byung G Min

Tae W Son

Chul J Lee

Han S Yoon

Jae W Cho

Byung C Kim

Wha Seop Lee

Han-Sik Yoon

A highly-oriented acrylic staple fiber prepared by simple extrusion of a PAN/H.sub.2 O melt in a gel crystalline state without spinning is provided. The acrylic fibers according to the present invention are characterized by the following properties: a degree of orientation between 80 and 97% observed by an X-ray diffraction; a length distribution ranging from 5 to 500 mm and a thickness distribution ranging from 5 to 500 .mu.m, a length to thickness ratio ranging from 100 to 100,000 determined by a scanning electromicroscope; a tensile strength of 10 to 70 kg/mm.sup.2 ; an initial tensile modulus of 300 to 1,500 kg/mm.sup.2 ; an elongation of 5 to 20%; and a specific surface area of 1 to 50 m.sup.2 /g.

Unspun acrylic staple fibers

Pulp-like short fibers prepared from liquid crystal polyesters capable of forming an anisotropic melt phase at a temperature of 200.degree. C. to 400.degree. C. and having a molecular weight of 2,000 to 100,000 are provided. These fibers consist of microfibrils and have the following highly-oriented fiber characteristics and properties:

Pulp-like short fibers from liquid crystal polyesters

A non-spun fiber of acrylic polymers, characterized by a pulp-like short fiber form of a thickness distribution of 0.1 to 100 .mu.m and a length distribution of 0.1 to 100 mm, and by irregular cross-sections in a plane taken perpendicular to the fiber axis and needle point-like ends similar to those of natural wood pulp fibers. The acrylic fiber of the present invention is made of an acrylonitrile homopolymer or copolymer consisting of a least 70% acrylonitrile (by weight) and at most 30% copolymerizable monomers (by weight) and having a viscosity average molecular weight between 10,000 to 600,000. The acrylic fiber according to the invention is further featured by the following physical properties: a degree of orientation of more than 80% based on X-ray diffraction pattern data, a tensile strength of 3 to 10 g/denier and an initial modulus of 30 to 100 g/denier, and absolutely no cylindrically-shaped filament trunks.

Non-spun, short, acrylic polymer, fibers

A new, pulp-like, acrylic short fiber having excellent heat- and chemical-resistance is provided. The fiber has a thickness distribution of 0.1 .mu.m to 50 .mu.m, a length distribution of 1 mm to 20 mm, and a thermal transition temperature (Tg) of above 200.degree. C. The fiber is produced by heating a mixture of polyacrylonitrile and water of about 5% to 100% by weight to temperatures above hydration-melting temperature under seal to an amorphous melt; cooling the resulting amorphous melt to temperatures between the melting and the solidifying temperatures of the melt to form a supercooled melt; extruding the resulting supercooled melt to give extrudates; heat-stabilizing the resulting extrudates at temperatures between 180.degree. C. and 300.degree. C. for 1 minute to 4 hours after drying and drawing; and cutting and beating the resulting heat-stabilized extrudates into an appropriate size.

Heat- and chemical-resistant acrylic short fibers without spinning

A process for the production of pulp-like short fibers having a highly-oriented fibril structure without spinning is provided. This process comprises heating a mixture of water and an acrylonitrile homopolymer or copolymer to a temperature above the melting temperature of the mixture under enclosed conditions to form an amorphous melt; cooling the resulting amorphous melt to a temperature below the melting temperature to obtain a supercooled melt phase; extruding the resulting supercooled melt phase through a slit die at a temperature between the melting and the solidifying temperatures of the melt phase into an external atmosphere to give extrudates; and subjecting the resulting extrudates to drawing and heat treatment followed by beating mechanically.

Process for the production of acrylic short fibers without spinning

Novel wholly aromatic polyamides and copolyamides of the formula: ##STR1## are provided. The aromatic polyamides and copolyamides are prepared by condensation polymerizing an aromatic diamine selected from 3,5-diaminobenzophenone and a mixture of 3,5-diaminobenzophenone and m-phenylenediamine with an aromatic dibasic acid chloride in a chemical equivalent amount. The polymers of the invention can be easily dissolved in an organic solvent to give a molding solution suitable for use in the film casting. The film resulted from the polyamides of the invention has excellent physiochemical properties such as durability, chemical resistance, flexibility, compactness, tenacity, transparency and electric insulation.

Wholly aromatic polyamides and copolyamides, and process therefor

New wholly aromatic polyamides are provided. This polymers are prepared by a mixture of N,N'-bis(4-aminophenyl)-isophthalamide and p-phenylenediamine in a tertiary amide solvent containing an alkali metal salt such as LiCl and a tertiary amine as an acid acceptor. The polymers are easily dry-jet spun to form a fiber and cast to form a film. The fiber and film so obtained have ultrahigh tenacity, elasticity and elongation.

Wholly aromatic polyamide from N,N'-bis (4-amino phenyl)-isophthalamide

Ultrahigh tenacity, ultrahigh modulus fibers are provided. The fibers are prepared by dissolving a mixture of poly(phenyleneterephthalamide) polymer with an inherent viscosity of at least 5 and a regularly ordered aromatic-aliphatic copolymer with an inherent viscosity of at least 2 in concentrated sulfuric acid to form a spinning solution, which solution is subsequently subject to extrusion by a known per se dry-jet spinning process.

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Seoul, South Korea

Byung G Min