Setting of wool

Interest in the reaction between wool and sulfite stems from the bleaching of wool by sulfur stoving or by the application of bisulfite solutions, the use of sulfite solutions as antichlors after treatment to make wool unshrinkable and, more recently, the use of sulfite solutions for the setting of wool fabrics. Early work established that the reaction of sulfite with wool followed a similar pathway (I) to that found earlier by Clarke (1932) for cystine. 

Setting of wool and hair by either steam or hot alkaline solutions is a very old technique [54]. Steam is also very effective for producing a permanent set. Alkali and steam are known to cleave the disulfide bond in keratins [55-57] and alkaline treatments are reputed to be the most effective hair-straightening compositions because they provide the most permanent set (see the section on hair straightening in this chapter). The reaction with hydroxide is summarized by Equation E. Because sulfenic acids are generally unstable species [58], they have been suggested as intermediates that can react with the nucleophilic side chains in the keratin macromolecules [56]. 

Water or steam treatments are used in the flat pressing and setting of wool fabrics. Resistance to wrinkling [262,263] in wool fabrics can be increased by exposing them to a humid atmosphere. The higher the temperature, the shorter the exposure needed. 

Visual and Manual Tests. Synthetic fibers are generally mixed with other fibers to achieve a balance of properties. Acryhc staple may be blended with wool, cotton, polyester, rayon, and other synthetic fibers. Therefore, as a preliminary step, the yam or fabric must be separated into its constituent fibers. This immediately estabUshes whether the fiber is a continuous filament or staple product. Staple length, brightness, and breaking strength wet and dry are all usehil tests that can be done in a cursory examination. A more critical identification can be made by a set of simple manual procedures based on burning, staining, solubiUty, density deterrnination, and microscopical examination. 

Finishing of Wool. Wool (qv) competes for markets where warmth, wrinkle recovery, and abiUty to set in creases are important. Wool problems relate to shrinkage, particularly to its tendency to felt. This is caused by scaly stmcture, which tends toward fiber entanglement when wet and subjected to mechanical action. In order to compensate for this tendency, wool needs to be set and also made shrinkproof if it is to be laundered. 

Although designed to color the fiber, dyeing operations also impart large amounts of permanent set to wool. 

To produce easy care wool—polyester blend garments, heat setting of the polyester component will impart set stability to repeated machine washing. A minimum of 20—30% polyester is needed for adequate stability. A fabric shrink-resist treatment such with Synthappret BAP may be necessary to give the required shrink-resistance for easy cate performance. If the polyester content is increased, particularly above 50%, and a suitable fabric constmction is used, heat setting alone will give easy care performance. 

Permanent Red 2B, Calcium Salt, pigment for plastics, 7 366t Permanent set, of fibers, 11 184 Permanent setting, in wool processing, 26 387-388... 

Wet milling, asbestos minerals, 3 308 Wet permanent setting in wool processing, 26 388 Wet phosphoric acid, economic aspects of, 18 860... 

Originally the amounts of dichromate used in the traditional afterchrome process varied between about 25 and 50% of the total amount of chrome dyes present, with the lower and upper limits set at 0.25% and 2.5% of the mass of wool. These quantities were well in excess... 

The versatility of this system is reflected in its suitability for blends of wool with other fibres [89]. The ideal conditions for the dyeing of wool/acrylic blends are at pH 4-5 and Albegal SET inhibits the risk of co-precipitation between Lanaset anionic dyes and basic dyes. Lanaset dyes are quite stable when dyeing polyester/wool at pH 4-5 and 115-120°C using Irgasol HTW (Ciba) as wool protectant. These dyes are also suitable for dyeing wool in its blends with silk, nylon or cellulosic fibres. 

---