Garment Processing-A PROCESS FOR DESIZING AND COLOR FADING GARMENTS
Garment and fabric processing today includes dyeing and desizing. Sizing is important in the fabric weaving process. This size is usually removed in a finishing operation after the fabric is woven. In some fabrics e.g. Denim, this size is left in woven goods to give desirable properties to the denim garment so as to improve the wear properties of the fabrics or garments. However, if the garments or fabrics are further processed, for example, treated with a crosslinking agent and/or decolorized or finished in garment form, it is necessary to first remove the sizing.
The removal of sizing is today performed in most textile plants by one or more of the following methods. The primary method of desizing is enzymatically, for example utilizing amylolytic enzymes. In garment finishing this process is more costly. Mechanical action during garment desizing whereby abrasive drum linings in extractors and/or pumice stones are utilized to improve the garment softness and give the garment special features etc. Alkaline and acidic hydrolysis have also been employed but such techniques also cause chemical attack of the fabric so as to result in a loss of the abrasive strength of the fabric. Oxidative desizing is generally employed using large amounts of sodium hypochlorite in solution. The use of hypochlorite creates environmental problem and further can significantly degrade the fabric. Desizing is required where the fabrics or garments are to undergo further processing such as dyeing, printing, decolorization, treatment with a crosslinker, ozone treatments and the like.
Garment dyeing technology, particularly with denim jeans, to achieve a differential color appearance has focused on treatments in which the dyer starts with a dyed garment and achieves a differential color effect by partial color removal. Removal of color is achieved by use of porous stones soaked in oxidizing agents, such as strong bleach or permanganates, and more recently, by after treatment with cellulose enzymes to remove fiber and thereby also remove some sizing.
The desizing and removal of color of denim garments generally requires two independent operations wherein the sizing is first removed and then the garment is treated chemically or physically to obtain removal of the color. It would be more economical and less time consuming if the two operations could be accomplished simultaneously. Such a procedure would be advantageous in garment treating processes wherein the garment undergoes a color fading procedure such as treatment with a bleaching agent or an oxidizing agent such as ozone, permanganates, sodium hypochlorite and the like.
In the new suggested process, the garments or fabrics are placed in a washer-extractor which is similar'to the type that would have been utilized in a conventional desizing operation utilizing an enzyme. The washer-extractor is then filled with water having an elevated temperature, that is, about 120 to 185°F. The higher the temperature the greater the discoloration. It is understood that at the higher temperatures the reducing agent selected must have a requiste temperature stability. The pH of the bath is adjusted according to the type of reducing agent utilized. The reducing agent is then added to the bath. The bath is normally agitated for about 0.3 to 1.0 hours and then the water is extracted and the garments or fabrics are rinsed with water. The garments or fabrics can then be further processed if desired.
The amount of reducing agent utilized is determined by the type of reducing agent utilized and the effect desired. For example, in a commercial size washer-extractor in which about 180 denim jeans are to be desized, when thiourea dioxide is the reducing agent, about 0.75 lbs is used in a bath containing 260 gal. of water to achieve a light blue effect. While 1.5 lbs gives a pale blue effect. With sodium hydrosulfite as the reducing agent, about 1.75 lbs is utilized to achieve a similar result. It is understood that compounds such as polyvinylpyrolidone can be added to the system to prevent redeposition of the dye removed from the garments during reduction.