Sulfur Dyes on Cellulosic Fibers

The main applications are piece dyeing, which is important for the dyeing of the CEL component of PES-CEL blended fabrics, yarn dyeing, and dyeing of flock, card, sliver, etc., for blended yams with wool and man-made fibers. 

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RETARDER SD is a leveling agent for vat, sulfur and direct dyes on cellulosic fibers. 

Dyes for cellulose fiber include the direct, sulfur, vat, a2oic, and reactive dyes. R D activities of world dye manufacturers have been focused on the area of reactive dyes, because reactive dyes offer brighter shades and excellent wet-fastness and have been increasingly used for dyeing cotton. 

Few production figures have been available since 1966, when sulfur dyes represented 9.1% of total U.S. dye production and 15.8% of the dyes made for use on cellulosic fibers. World production is estimated at 110,000—120,000 t/yr. This is the highest percentage of any group of dyes. In terms of value, however, the picture is very different because the dyes are relatively inexpensive. 

Sulfur Dyes. These dyes arc synthesized by heating aromatic amines, phenols, or nitro compounds with sulfur or. more usually, alkali polysullides. Sulfur dyes are used for dyeing cellulosic fibers. They are insoluble in water and are reduced to ihe water-soluble leuco form for application to the substrate by using sodium sulfide solulion, The sulfur dye proper is then formed within the fiber pores by atmospheric oxidation. Sulfur dyes constitule an important class of dye lor producing cost-effective tertiary shades, especially black, on cellulosic fibers. 

Uses Calendering extmsion thickener for latex paints and adhesives laminating adhesive hand modifier, finishing agent, abrasion resist, aid for cellulosic and syn. fibers. crockfastness improver (i.e., sulfur dyeings on cotton)... 

Blends of polyester with cotton (qv) or viscose are first dyed with disperse dyes, then with sulfur dyes (see Fibers, polyester Fibers, regenerated CELLULOSics). Disperse and sulfur dyes can also be appHed simultaneously in a pad—dry—thermofix/chemical reduction pad—steam sequence. In this case, the sulfur dyes cannot be used in thein reduced form because of the effect of the sodium sulfide on the disperse dye. Therefore, this method is confined to the solubilized sulfur dyes or sulfur dyes in the dispersed form. 

Sulfur dyes are used mainly for dyeing textile cellulosic materials or blends of cellulosic fibers (qv) with synthetic fibers such as acrylic fibers, polyamides (nylons), and polyesters. They are also used for silk (qv) and paper (qv) in limited quantities for specific applications. Solubilized sulfur dyes are used on certain types of leathers (qv). 

The vinyl fibers, with the exception of vinal and vinyon-vinal matrix fibers, are extremely hydrophobic and difficult to dye, and consequently they can be dyed only through pigmentation of the polymer melt before fiber formation or through dyeing with disperse dyes. Vinal and vinyon-vinal matrix fibers dye readily with dyes used on cellulosics including direct, mordant, reactive, vat, and sulfur dyes. 

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