GB455021A - Improvements in textile yarns and processes for producing them - Google Patents

Abstract

Yarns formed from crimped filaments or fibres are treated in such a way as to render the crimp in some filaments or fibres out of phase with that in other filaments or fibres and a synthetic resin is formed in the filaments or fibres, to increase the permanence of the crimp, before or after the treatment. The resin may be formed by interaction of suitable reagents in the materials or by carrying out the last stages of the condensation reaction in the material. Preferably, the impregnation is effected before crimping especially when the reagents are applied from an aqueous solution or emulsion. If one of the reagents is gaseous, e.g. formaldehyde, it may be applied after crimping. Suitable resins are of the phenolaldehyde, phenol - ketone - aldehyde, ketonealdehyde, or urea- or thiourea-aldehyde type or aliphatic or aromatic amines or amides generally may be condensed with formaldehyde or other aldehyde. Polyvinyl compounds may also be employed. The reagents or intermediate products may be applied from solutions in water, organic solvents or mixtures thereof. Organic solvents used with products which they can swell assist penetration. Excess of the reagents should be removed under heavy pressure. The crimp may be imparted by crimping rollers which may be heated or steam may be applied to the materials passing through the rollers. Or the yarn may be twisted preferably highly and then untwisted, the condensation preferably being effected between the application and the removal of the twist although the twist may be temporarily set by steam or hot water before untwisting and the resin formed after untwisting. In yarns having little or no twist, the crimp may subsequently be broken up by insertion of twist. With ordinarily or highly twisted yarns the crimp may be broken up by the insertion of reverse twist past the neutral point of no twist. Another process for breaking up the crimp is to convert the yarn to a staple fibre yarn while retaining its continuity, e.g. as described in Specifications 424,683, 424,752, 424,830, 424,879, 453,432, 453,433, and 453,434, [all in Group IX], and if it originally had a low degree of twist, twisting also aids the breaking up process. A drawing operation is sufficient to break up the crimp in the case of a staple fibre yarn. Again in the case of a substantially twistless yarn a blast of air applied to the running yarn breaks up the crimp. The resin formation may be carried out before or after the operation to break up the crimp. In an example, a solution is prepared containing 40 parts by weight of urea and 80 parts of 40 per cent formaldehyde. It is made alkaline, brought to the boil and 5 parts of magnesium chloride added. The solution is cooled and poured into 240 parts of water containing 15 parts of magnesium chloride. A viscose yarn is soaked in this solution for 5 minutes, squeezed and dried at 50 DEG C., and twisted, e.g. 50--60 turns per inch. It is then heated for 5 minutes at 140 DEG C. The yarn is then untwisted and a reverse twist of about 5 turns per inch inserted. A very woolly yarn is produced. In another example, a viscose yarn is crimped by the process and apparatus described in Specifications 424,880 and 442,073, [both in Group IX]. It is then padded with a 5 per cent solution of the substance sold under the Registered Trade Mark "Brilliant Avirol" in 20 per cent formaldehyde with or without a little concentrated hydrochloric acid. The yarn is squeezed, dried, heated for 5 minutes at 140 DEG C., and converted directly into a staple fibre yarn. In a third example, a cellulose acetate yarn saponified to a loss in weight of 5--25 per cent is treated by the process of the preceding examples, a swelling in aqueous acetone (46,5 per cent acetone by volume) being interposed before the impregnation with the reagents for the synthetic resin. Specification 378,054 also is referred to.