Patent GB-1294723-A (GB)
Title: Conjugate fibres
IPC: D01F8/14
Filed: 1970-02-18
Abstract: 1294723 Conjugate fibres ASAHI KASEI KOGYO KK 18 Feb 1970 [28 Feb 1969] 7691/70 Heading B5B Conjugate fibres consist of a polymeric component (hereinafter referred to as PEP) containing 75% or more by weight of repeating structural units of the structure and a polymeric component (hereinafter referred to as PET) containing 75% or more by weight of repeating structural units of the structure in which the shrinkage caused by boiling water treatment of non-heat-treated stretched fibres is less than 8% for the PEP component and in which the PET component shrinks more than the PEP component under crimp-developing conditions, the PET component occupies the inside of the curves in the crimped state and the relationships # n PEP>0À16 and # n PET <# n PEP -0À02, where A n  PEP and A n  PET are the birefringencies of the PEP and PET components respectively, are obeyed. The ethylene glycol in either component may be replaced by another glycol, in particular by diethylene glycol, tetraethylene glycol or hexamethylene glycol, to an extent of up to 25% by weight of the polymer. Similarly the 1,2-diphenoxyethane-4,4<SP>1</SP>-dicarboxylic acid in the PEP and the terephthalic acid in the PET may be replaced by up to 25% by weight of the polymer of a dicarboxylic acid such as hexahydroterephthalic acid, isophthalic acid, diphenyldicarboxylic acid, adipic, sebacic, azelaic, naphthalene dicarboxylic or 2,5-dimethylterephthalic or succinic acids. A hydroxy acid such as #-hydroxyethoxybenzoic acid may be used also, and terephthalic acid may be used in the PEP component and 1,2-diphenoxyethane-4,4<SP>1</SP>-dicarboxylic acid in the PET, all within the limit of 25% by weight of the polymer. In addition to the above, which are copolymerized with the major components, other materials may be blended to up to 25% by weight in the PET and PEP polymers. Thus, polystyrene, polyethylene, nylon 6 and nylon 6,6 may be used in either and polyethylene terephthalate in the PEP component and polyethylene - 1,2 - diphenoxyethane - 4,4<SP>1</SP> - dicarboxylate in the PET component. If α and # are the contents expressed as weight per cent of constituent materials other than the major components in the PEP and PET components respectively and if either α or # exceeds 15% then the relationship is a condition for the formation of good crimps. The PET has preferably a reduced viscosity of from 0À65 to 0À95 and the PEP one of from 0À60 to 1À00 as measured in a 1 : 2 by weight mixture of phenol and tetrachloroethane at 35‹ C. and the PET may be between 30 and 95%, preferably between 40 and 80% of the total fibre. The polymers are melted at a temperature of between 275‹ and 300‹ C. and conjugate spun in known fashion to give the conjugate fibres in a side-by-side, sheath-core or other relationship. The filaments obtained are then stretched in known manner, using a hot plate or hot pin and a heating medium such as steam or hot water. This stretching may be in a one- or two-stage process and is best performed at a temperature above 90‹ C. The stretching ratio used depends on this temperature, and is chosen such that the conditions used produce fibre where the relationships # n PEP > 0À16 and # n  PET < A n  PEP - 0À02 hold. After stretching, the crimp may be developed by heat treatment. These conjugate fibres have a maximum thermal stress of more than 50 mg./d. and consequently a low tendency to crease. The fibres maintain their crimp even when subjected to loads above 3 mg./d.