The present invention concerns methods for removing sulfur from yarn comprising the steps of: a) contacting never-dried polymeric yarn with an aqueous base, the polymer comprising imidazole groups and said polymer comprising sulfur atoms characterized as being in the form of sulfate anions; b) contacting the yarn with an aqueous acid solution of pH 5 or lower; and c) rinsing the yarn.

An intimate blend of staple fibers, and a yarn, fabric, and article of clothing providing surprising arc performance and coloration capability, comprising a mixture of a first staple fiber made from a flame resistant polymer that retains at least 90 percent of its weight when heated to 425 degrees Celsius at a rate of 10 degrees per minute and comprises 0.5 to 20 weight percent discrete homogeneously dispersed carbon particles; and either (a) a second staple fiber from a flame resistant polymer being free of discrete carbon particles and having an L* lightness coordinate of 70 or greater and being capable of accepting a dye or coloration, or (b) a second staple fiber blend being free of discrete carbon particles and comprising at least one second staple fiber from a flame resistant polymer and having an L* lightness coordinate of 70 or greater and being capable of accepting a dye or coloration; the mixture having a total content of 0.5 to 3 weight percent discrete carbon particles.

A composite polymer solution comprising a homogeneous mixture of a first polymer solution comprising a first polymer having a structure derived from the reaction of one or more amine monomers and a plurality of acid monomers, wherein i) the one or more amine monomers includes at least 60 mole percent 5(6)-amino-2-(p-aminophenyl)benzimidazole; and ii) the plurality of acid monomers include those having a structure of
Cl—CO—Ar.sub.1—CO—Cl and Cl—CO—Ar.sub.2—CO—Cl wherein Ar.sub.1 is a para-oriented aromatic group and Ar.sub.2 is a meta-oriented aromatic group, and wherein the plurality of acid monomers has at least 50 mole percent of the monomer containing Ar.sub.2; and a second polymer solution comprising a second polymer having a structure derived from the reaction of metaphenylene diamine and isophthaloyl chloride.

Disclosed is a high-strength copolymerized aramid fiber which includes aramid copolymers containing an aromatic group substituted with a cyano group (—CN), so as to have an intrinsic viscosity (IV) of 6.0 to 8.5, a polydispersity index (PDI) of 1.5 to 2.0, a strength of 23 to 32 g/d, and an elastic modulus of 1,100 to 1,300 g/d. The high-strength copolymerized aramid fiber may be prepared by a method which includes, when para-phenylenediamine, cyano-para-phenylenediamine, and terephthaloyl dichloride are sequentially added to an organic solvent and reacted together to prepare a copolymerized aramid fiber, adding and dispersing a neutralizing agent in the organic solvent before the reaction of the para-phenylenediamine, cyano-para-phenylenediamine and terephthaloyl dichloride, which were dissolved in the organic solvent.

The present invention concerns methods for producing a yarn comprising the steps of: (a) producing a plurality of dope filaments by spinning a polymer solution in sulfuric acid through a multi-hole spinneret, the polymer comprising imidazole groups; (b) coagulating the plurality of dope filaments into an as-spun yarn; (c) contacting the yarn with an aqueous base having a pKa less than or equal to 11; and (d) rinsing the yarn.

A task is to provide a cloth which is advantageous in that the cloth has extremely excellent flame retardancy, and further has excellent washing shrinkage resistance and excellent hand as well as excellent antistatic properties, preferably in that the whole of the cloth can be uniformly dyed, and a fiber product, and the task is achieved by obtaining a cloth using a spun yarn which comprises a meta-type wholly aromatic polyamide fiber, a modacrylic fiber, and a conductive fiber.

The present invention concerns yarn comprising polymer, the polymer comprising imidazole groups, the yarn having a sulfur content of 0.01 to 3.0 percent by weight, based on weight of the yarn, the yarn having a tenacity of 30 cN/dtex (33.3 gpd) or higher.

A wholly aromatic polyamide fiber has a reduced total fineness and a reduced single yarn fineness and is also excellent in quality and reinforcing property. The wholly aromatic polyamide fiber is characterized in that it has a single yarn fineness of 0. 4 dtex to 3. 5 dtex, a total fineness of 5 dtex to 30 dtex, a breaking strength of 15 cN/dtex or more, an initial tensile modulus of 500 cN/dtex to 750 cN/dtex, and the number of fibrils of less than 100/m.

Provided is a semi-aromatic polyamide fiber having excellent spinning stability, heat resistance and chemical resistance. The semi-aromatic polyamide fiber includes a semi-aromatic polyamide resin having a melting point of 290 C. or higher and a plasticizer having a 5% thermal weight reduction temperature of 320 C. or higher, the resin having as a dicarboxylic acid component an aromatic dicarboxylic acid unit and as a diamine component 1,9-nonanediamine unit and 2-methyl-1,8-octanediamine unit in a molar ratio (the former:the latter) of 70:30 to 99:1.

Aramids and nanostructures formed from the aramids are described.