Patent GB-473004-A (GB)
Title: Improvements in or relating to the treatment of cellulose esters and materials comprising the same
IPC: D06M11/38
Filed: 1936-04-03
Abstract: Cellulose ester materials particularly filaments, yarns, fabrics and the like having a basis of an organic ester of cellulose are subjected to the influence of a damp atmosphere to increase their moisture content and are then subjected to saponification treatment. The pre-treatment facilitates the subsequent saponification so that the concentration, temperature, or time of treatment may be reduced. As an alternative or additional pre-treatment, the materials may be subjected to a preliminary saponification to an extent substantially less than that finally required, and subsequently further saponified with a less alkaline substance than that employed in the pre-treatment. The final saponification is carried out while the materials still contain the reaction products of the preliminary saponification. Yarns may be stored prior to saponification in a chamber containing damp air of a relative humidity of 40 to 65 or 85 per cent, or more.  Steam or humidifiers employing atomized water may be used.  Yarns after subjection to the humid atmosphere may pass over a wick or roller dipping into the saponifying agent, and contact with the wick may be continuous or intermittent.  Local saponification of fabrics may be obtained by printing methods. For the preliminary saponification an aqueous or alcoholic solution having a high pH value, e.g. up to 14 may be used.  A 20 per cent solution of caustic soda is suitable.  Caustic potash, ammonium hydroxide, sodium or potassium acetate, amines such as ethanolamines, tetra-methyl- or tetra-ethyl-ammonium hydroxide, may also be used. Winding, knitting, and weaving may be performed between the preliminary and final saponifications.  Preliminary saponification may be uniform or local and is preferably small causing a loss in weight of a few per cent.  The materials may be treated in bobbins, hanks, running warps, yarns, or in fabric form.  Yarns may be saponified slightly and locally during a winding operation and the final saponification may be effected on the fabric so that the original saponification is intensified while the unsaponified portions are not affected.  The agents used in the final saponification are preferably of low alkalinity having, e.g. a pH value of 8--11.  Soaps, sodium acetate solutions, or dilute solutions of stronger agents may be used. Preliminary saponification may be so small as not to affect the dye affinities, or it may be carried out on portions of a fabric to such extent that after the final treatment these portions have no affinity for cellulose ester dyes; other portions may be treated so as to gain affinity for cotton dyes without losing that for cellulose ester dyes.  The treatment is applicable to materials of cellulose acetate, propionate, and butyrate.  Yarns may contain dyes, lakes, fillers, plasticizers, or lubricants. They may be treated alone or with wool, cotton, silk, flax, or other yarns.  Before treatment, the materials may be lubricated with a dispersion of sulphonated naphthene in a mineral oil.  In an example, cellulose acetate yarn is exposed to a humid atmosphere, unwound and passed in contact with a roller moistened with caustic soda solution to effect preliminary saponification, and then treated for 30 minutes with hot soap solution to effect the final saponification.  In another example, a roll of cellulose acetate fabric is placed in a moist atmosphere, then printed in a pattern with a paste containing saponifying agent.  It is then treated with hot soap solution.  In another example, cellulose acetate yarn is periodically brought into contact with a roller supplied with caustic soda solution, and is then treated with hot soap solution for several hours.  The portions of the yarn which do not undergo preliminary saponification are not sufficiently saponified by the soap solution to acquire affinity for cotton dyes, but those portions which are pre-saponified are saponified by the soap solution so as to acquire affinity for cotton dyes and to be resistant to cellulose ester dyes.  The process of stretching continuous cellulose acetate filaments or threads in the presence of steam under pressure and saponifying continuously with this operation, as claimed in Specification 438,584 is excluded.