GB1283065A - Aromatic polyamide fibers - Google Patents

Abstract

1283065 Aromatic polyamide fibres E I DU PONT DE NEMOURS & CO 12 June 1969 [12 June 1968] 49395/71 Divided out of 1283064 Heading B5B] A fibre comprises polymer consisting essentially of at least one type of carbocyclic wholly aromatic homo- or copolyamide whose bonds linking each aromatic nucleus are coaxial or parallel and oppositely directed, said fibre being characterized by an orientation angle of less than 45 degrees, preferably less than 35 degrees and desirably less than 25 degrees, and an initial modulus of at least 192 gpd., preferably at least 200 gpd. and especially at least 300 gpd. Such fibres may also be characterized by a sonic velocity of at least 4À0 km./sec., preferably at least 6À0 km./sec. and especially at least 7À0 km./sec., a tenacity of at least 5 gpd., an initial modulus of at least 400 gpd, an elongation, in the as-extruded state, of at least 5%. In such fibres about 77% of the crystallites may be aligned within one half of the orientation angle. Such fibres may be made by spinning an anisotropic dope as disclosed in Specifications 1,283,064 and 1,283,066 and optionally heatsetting the fibres so made. A preferred heattreated fibre so made has a sonic velocity of at least 4.0 km./sec., especially at least 7À0 km/sec., an orientation angle of less than 25 degrees and an initial modulus of at least 400 gpd. The optically anisotropic dope of Specification 1,283,064 comprises (I) a carbocyclic wholly aromatic homo- or co-polyamide wherein at least 90% of the bonds linking each aromatic undens are coaxial or parallel and oppositely extended and (II) a liquid medium comprising at least one of concentrated sulphuric acid, oleum, HF, chloro- or fluoro-sulphonic acid or methane sulphonic acid, the concentration of (I) being above the "critical concentration point" (C.C.P.) at which there is a sharp discontinuity, in the viscosity v. concentration curve. The dope may also include solvation additives, e.g. Na 2 HPO 4 , Na 2 SO 4 or CH 3 COOK with sulphuric acid or oleum, NaF, KF or CH 2 Cl 2 with HF, or LiCl with sulphonic acids, dyes, fillers, delusterants, U-V. stabilizers or antioxidants. The optically anisotropic dope of Specification 1,283,066 comprises a polyamide as in (I), having an inherent viscosity of at least 0À7 as determined in sulphuric acid at 30‹ C., (II) a liquid medium comprising at least one of N,N- dimethylacet-, propion- or butyr-amide; N,N - dimethylmethoxyacetamide; N,N- diethylacetamide; N - methyl pyrrolidone, -piperidone or -caprolactam; N - ethyl pyrrolidone; N - acetyl - pyrrolidine or - piperidine; N,N<SP>1</SP> - dimethyl - ethylene or -propylene urea; N,N,N<SP>1</SP>,N<SP>1</SP>-tetramethyl urea; and hexamethyl phosphoramide and (III) LiCl, CaCl 2 or HCl, the concentration of (I) being above the C.C.P. Component (III) may be formed in situ, e.g. by using Li 2 CO 3 to neutralize HCl formed during polymer preparation. The dope may also contain dyes, fillers, delusterants, U-V-stabilizers and antioxidants. Alternative techniques to "C.C.P." for determining anisotropy are described in both Specifications 1,283,064 and 1,283,066. Other polyamides useful in the making of the fibres of the invention may be made by the reaction of pphenylene diamine or 2-chloro-p-phenylene diamine with polyamide-forming derivatives of terephthalic acid by a low temperature polymerization procedure. Conventional wet- or dry-spinning techniques are used. In wet-spinning, specified coagulants include water, ethylene glycol, glycerol, mixtures of water, methanol and an amide or urea solvent, mixtures of water and alcohols and aqueous salt baths, suitably at from -20‹ to +90‹ C. After wind-up, the fibres may be soaked, on the bobbins, in water or mixtures of water and water-miscible inert organic liquids, e.g. acetone, ethyl alcohol, glycerol, N,N,N<SP>1</SP>,N<SP>1</SP> - tetramethyl urea, or N,N- dimethylacetamide, to remove residual amide liquid and salt or acidic solvents followed by drying. Alternatively, removal of such residues may be effected by continuous treatment of the running fibre, or by washing and soaking skeins, rather than bobbins. Dry-spun yarn may be strengthened by washing with a small amount of water. As indicated above, fibres may possess the specified high tensile properties in the asextruded state, and require only washing and drying, or may require heat-treatment, which is suitably effected by heating the fibre, maintained in a taut state, or drawn in a nitrogen atmosphere at 300-1000‹ C., preferably 500- 600‹ C., for 0À1 sees. to 5 mins., preferably 0À1- 10 sees., or by using hot air ovens, hot liquid baths, or heated pins, plates or slots, using draw ratios up to 1À75, but generally of 1À04 to 1À16.