GB1288652A - - Google Patents

Abstract

1288652 Porous aromatic polyamide filaments E I DU PONT DE NEMOURS & CO 8 Sept 1970 [8 Sept 1969] 42980/70 Heading B5B Dyeable porous fibres of aromatic polyamides are characterized in that they have a density of less than 1À3 gm./c.c.; a void volume for pores with pore diameters of 0À12 microns or less of greater than 0À03 c.c./gm., and a void volume for pores with diameters of 0À12 microns or more of less than 0À02 c.c./gm.; said void volumes, pore diameters and density being measured by the Mercury Porosimeter Method (defined and described in the Specification). Preferably the density is between 0À97 and 1À18 gm./c.c. and the void volume 0À05 to 0À18 c.c./gm. for pores of diameter between 0À012 and 0À12 microns. Suitably the aromatic polyamide is derived from reaction of an aromatic diamine with an aromatic dicarboxylic acid and contains phenyl rings, which besides being substituted by one or more non-polyamide forming substituents have two units of formula in meta-relationship attached thereto. Preferably the aromatic polyamide is poly(metaphenylene isophthalamide). A process for the production of the fibres comprises dry spinning a solution, preferably containing between 10% and 30% by weight of the aromatic polyamide, in a solvent, for example DMF, dimethylacetamide, dimethylsulphoxide or N - methyl - 2 - pyrrolidone, containing a solubilizing salt, for example LiCl, LiBr or CaCl 2 ; cooling the freshly spun fibres with an aqueous liquid whereby the fibres become waterswollen; drawing the fibres in one or more stages to a total draw ratio of at least 2À2 in aqueous draw bath solutions which contain 20% to 35% by weight of the spinning solvent and 6% to 11% by weight of the solubilizing salt, said draw bath solutions being heated to between 70‹ C. and the boiling point of the solutions, with the proviso that with total draw ratio greater than 2À75 the baths are heated to at least 90‹ C.; washing the drawn fibres to remove all solvent and salt used above; drying the fibres at a temperature of less than 170‹ C., suitably in air at a temperature in the range 100-170‹ C., whilst they are free from substantial tension, and when the draw baths used in the drawing step above are below 90‹ C. or contain between 20% and 28% by weight of solvent the fibres are additionally treated, whilst free from substantial tension, with saturated steam at a pressure of from 3 to 60 p.s.i.g. for 0À3 sees. to 10 minutes prior to the drying step. Preferably the total draw ratio in the draw baths is at least 2À8 effected in at least two stages in aqueous baths containing from 26% to 32% by weight of the solvent and 6% to 9% by weight of the salt at a temperature between 90‹ and 100‹ C.