Patent GB-351417-A (GB)
Title: Improvements in or relating to materials made of or containing organic esters of cellulose
IPC: D01F2/28
Filed: 1930-03-24
Abstract: The process for the saponification of materials made of a containing cellulose acetate or other organic esters of cellulose as described in the parent Specification and in Specification 318,468, [Class 2 (ii), Cellulose &c.], is carried out in the case of filaments, threads, yarns, ribbons, &c., by applying the saponifying agent to the travelling materials and immediately drying the same under the application of heat.  The saponifying agent is conveniently applied continuously with the production of the threads &c., for example, as they leave a dry or wet spinning apparatus or as they emerge from an after-treatment bath; or the saponifying agent may be applied as the materials are being wound from one package to another, or during a washing operation in which case it may precede and be combined with a sizing operation.  The saponification may also be combined with operations designed to produce particular effects such as modification of the lustre, the production of metallic effects, the dyeing of the material, or the imparting of a fugitive colouration for identification purposes.  It is convenient to treat a number of yarns simultaneously.  The dyeing properties of the materials depend on the depth and extent of the saponification; thus, if saponification is complete, the materials acquire an affinity for cotton dyes, but if not complete, materials may be obtained which have an affinity for both cotton dyes and cellulose ester dyes, for example, the dispersed insoluble colours.  For the purpose of obtaining cross-dyed effects such fibres may be mixed with completely saponified fibres or with fibres saponified to a less extent.  As another alternative, completely saponified fibres may be mixed with unsaponified fibres; and generally any of the saponified fibres, whether the saponification be complete, partial or superficial, may be mixed with other fibres of artificial, animal or vegetable origin. The saponification process may be applied to mixed yarns. When a number of threads are treated together, the process may be arranged so that differential saponification occurs, for example, by arranging that certain threads are caused to follow a different path or are treated with a stronger saponifying agent or for a longer time, other threads being saponified to a less extent or not at all. Differential effects may also be produced along the length of certain threads.  The saponified threads &c. wet out more quickly, are less liable to crease, and have an improved safe-ironing point.  The saponifying agent is preferably employed as a solution, which may be applied in a bath through which the materials pass, or by means of a wick, roller, &c., or as a spray; but a paste may be used, in which case it may be applied by a roller.  The solution or paste may be applied uniformly to the threads or at selected points along their length, in order to obtain differential effects, as in Specification 332,263, [Class 2 (ii), Cellulose &c.].  Materials capable of producing coloured or other effects may be incorporated in the solution or paste.  In order to secure uniform saponification it is preferred to employ a solution or paste containing a low concentration of alkali, for example, of 1-5 per cent of caustic soda.  The saponification is preferably carried out at temperatures below 85 DEG  C., and the materials after the application of the saponifying agent are quickly dried without washing, preferably at 65-85 DEG  C., by passage round heated cans or rollers, or over a hot plate, or through a heated atmosphere.  After drying, the materials are washed either with water or, if cross-dyeing effects are subsequently to be produced, with dilute hydrochloric acid; washing may be effected by passage through a bath or by padding rolls.  The materials may be dyed prior to or during saponification, in the latter case by incorporating dyes having an affinity for cotton in the saponifying medium.  Specification 330,950, [Class 2 (ii), Cellulose &c.], is referred to.