Studies in dyeing. I. Effect of crystal modification of disperse dyes on their dyeing behavior

Abstract

SynopsisThree commercial disperse dyes and a laboratory-synthesized disperse azo dye were converted to different crystal forms. These were characterized by melting point, x-ray diffractograms, and their dyeing behavior on polyester fibers. The different crystal modifications of the same dye were shown to dye polyester fibers (but not polyamide fibers) a t different rates and to different fiber saturation values. An attempt has been made to explain these differences based on a thermodynamic approach. An attempt is made to apply the concept of crystal modification of disperse dyes to same of the earlier studies done on dyeing and printing of disperse dyes on polyester and secondary cellulose acetate substrates reported in the literature.

Dyeing with mineral colour

“…Following are the related chemical reactions (Shenai, 1993 , 1975). Use of NaOH alone forms colloidal metal hydroxides which are difficult to oxidise; if soda ash is also present, metal hydroxide and carbonate are formed which makes conversion into oxides much easier.…”

“…Chrome yellow, chrome red, chrome orange, chrome green, manganese brown, prussian blue, iron oxide etc are the other examples (Shenai, 1993;Allen, 1971). Chrome colours are derivatives of lead chromate (PbCrO 4 ) and so are invariably poisonous.…”

Dyeing machineries

“…A perforated stainless steel cylindrical container surrounds a central perforated hollow cylindrical tube and the container fits on a conical seating at the base of the tube (Shenai, 1993). The central tube receives the dye liquor and circulates it in an in-out mode for dyeing.…”

“…A winch consists of a trough containing the dye liquor across and over which is fitted a circular or elliptical roller known as driving reel (Shenai, 1993). Fabric is stitched in the shape of endless ropes of equal length; a few such ropes are passed over the driving reel and as the later rotates, it carries forward the ropes.…”

Dyeing of Grafted Polyester Fiber Part I. Effect of Polyvinylacetate Graft on Dyeing Characteristics

“…Investigations have been carried out in this field in relation to the particle size of the dye dispersion [ 19,23,31 ]; crystallographic forms of the dye [ 1,27,28]; solubility of dye in water [2,8]; polarity of the dye molecules [26]; and chemical constitution of the dye molecules [10,25,30]; size and shape of dye molecules [11,12,14]; concentration of dye in the dyebath [20]; nature and concentration of dispersing agent [3,6]; dyeing temperature [4,13,24]; nature of the fiber, crystallinity, and orientation of fiber matrix [7,9,17,21,22,32]; all these indicate that many factors influence dyeing of disperse dyes on synthetic fibers.…”