Patent ES-292261-A1 (ES)
Title: Method for producing synthetic composite fibres
IPC: D01F8/08
Filed: 1963-10-07
Abstract: A synthetic multicomponent composite crimped fibre is made by eccentrically arranging in the cross-section of a single fibre two or more phases differing in their degrees of shrinkage, by interposing between two adjacent pure component phases, at least one mixed phase, comprising the said adjacent components, wherein the relative proportion of the said components is such that the shorter the distance from one pure component phase, the more the proportion of that component, the cross-sectional area of the said mixed phase being 35 6% of the total cross-sectional area, and at least 30% by weight of one pure adjacent component being incorporated in the total mixed phase between two adjacent pure component phases. Two kinds of polymers or copolymers may be used as fibreforming components. Specified polymers include acrylonitrile polymers and copolymers containing at least 85% by weight acrylonitrile, and wet-spinning is the preferred method, especially using concentrated nitric acid as spinning solvent, and dilute nitric acid as the coagulating bath. In examples: (1) Component A is polyacrylonitrile. Component B is a copolymer of 91À5% acrylonitrile with 8À0% methyl acrylate and 0À5% methallyl in 68% by weight nitric acid to form spinning solutions A and B. A third spinning solution C is made by mixing solutions A and B at a ratio of 1: 2 by weight and the three solutions are spun through a spinneret as in Fig. 17, the speeds of the gear pumps being adjusted so that the ratio A: C: B becomes 30: 40: 30 by weight. Spinning is effected into a bath of 33% aqueous nitric acid and the coagulated filaments are withdrawn at a draft of 0À70, washed with water and stretched 7 times in hot water, lubricated, dried and cut. Stable crimps are obtained on treatment with steam at 120 C. for 5 minutes. (2) As above, using the spinneret of Fig. 18 (not shown). (3) As in (1), except that B is a 1: 2 by weight mixture of an acrylonitrile homopolymer and a copolymer comprising 91% by weight acrylonitrile, 8À0% by weight methyl acrylate and 1À0% by weight methallyl sulphonic acid, and C is a 1: 1 by weight mixture of solutions A and B. (4) As in (3), but using an A: C: B ratio of 32: 36: 32. (5) As in (3) except that A is a copolymer of 96% acrylonitrile and 4À0% methyl acrylate. B is a copolymer of 92% acrylonitrile, 7À5% methyl acrylate and 0À5% methallyl aulphonic acid. (6) A copolymer of 91À5% acrylonitrile, 8À0% methyl acrylate and 0À5% methallyl sulphonic acid is dissolved in 70% by weight nitric acid to form a 15% by weight solution which is used as solution A. The same solution containing also 0À7% carbon black and 4À0% by weight methyl phthalyl ethyl glycolate is used as solution B and solution C is a 1: 1 by weight mixture of A and B. The three solutions are spun at an A: C: B ratio of 32: 36: 32, as in (4). (7) A and B solutions made as in (5). Solutions C and D are 2: 1 and 1: 2 by weight mixtures of A and B. The four spinning solutions are extruded through one spinneret so that the order of the components in the cross-section of the resulting fibre is A, C, D, B, the bonding ratio being 30: 20: 20: 30 by weight, and other conditions as in Example 1. Fig. 19 (not shown) is a diagram of the orifice portion of a conventional spinneret for making conjugate filaments, incorporated for comparative purposes. Fig. 17 is a crosssectional view of a spinneret suitable for the process of the invention, the cross-section being taken along the line f-f in Fig. 20. Dimension d in Fig. 20 is actually zero, the adjacent plates being shown spaced apart by spaces d simply to show clearly the passages for the flow of liquids A, B and C. Composite fibres so made have a greatly reduced tendency to yarnsplitting. The theory of the method is discussed at length in the Specification.