Patent ID: 6527997
Filing Date: 2003-03-04
Classification: C08B,C09K,D01F,Y10T

Abstract:
A process for spinning a liquid-crystal solution of cellulose formate to obtain a cellulose formate fiber having the following properties:a) filaments of the fiber exhibit a banded structure under an optical polarizing microscope, wherein such structure is characteristic of a liquidâ€”crystal origin, and b) the fiber satisfies the following relationships: DS&gE;2; Ar&gE;8; Te<45; Mi>500; Er>10, wherein DS is the degree of substitution of the cellulose with formate groups in the fiber (in %), Ar is the elongation at break (in %) of the fiber, Te is the tenacity of the fiber (in cN/tex), Mi is the initial modulus of the fiber (in cN/tex) and Er is the energy of the fiber at break (in J/g), â€ƒthe process comprising: (i) extruding a solution of cellulose formate in phosphoric acid, said solution being optically anisotropic at ambient temperature and at rest, through a spinneret at a temperature (Tf), whereby the solution is optically anisotropic if at rest, (ii) stretching the extruded solution through a non-coagulating layer, (iii) coagulating the stretched solution in water at a temperature (Tc) greater than 5Â° C. to form a fiber, wherein the tensile stress (&sgr;c) to which the fiber is subjected after coagulation is less than 5 cN/tex, and (iv) washing the fiber.