US3775047A - Oxidizing sulfur dyes on cellulose with sodium iodate or potassium iodate - Google Patents

Abstract

Method for oxidizing sulfur dyes on natural or regenerated cellulose textile fibers comprising contacting said fibers having thereon at least one sulfur dye in reduced form with an aqueous, acid, oxidizing solution comprising water, acetic acid and XIO3, wherein X is Na or K.

Description

United States Patent 1191 Weston Nov. 27, 1973 OXIDIZING SULFUR DYES ON CELLULOSE WITH SODIUM IODATE OR POTASSIUM IODATE [75] Inventor: Charles Douglas Weston, Charlotte,

[73] Assignee: Martin Marietta Corporation, New

York, N.Y.

[22] Filed:' July 6, 1971 21 App]. No.: 160,174

[52] US. Cl. 8/37, 8/21 A, 8/21 B,

8/2] C, 8/82, 8/1 Q [51] Int. Cl.... C09!) 49/00, C09b 49/10, D06p 1/30 [58] Field of Search 8/37, 82, 1 Q

{56] References Cited UNITED STATES PATENTS 2,484,300 10/1949 Mayhew ..8/37X 4 1933 Dreyfus et al. 8/64 12/1941 Fryer et al. 8/l08 OTHER PUBLICATIONS Knecht et al., Principles & Practice of Textile Printing, 1952, pp. 589590 Primary Examiner-George F. Lesmes Assistant Examiner-Patricia C. lves Attorney-John A. Crowley, Jr. et al.

[5 7] ABSTRACT 1 Claim, No Drawings OXIDIZING SULFUR DYES N CELLULOSE WITH SODIUM IODATE 0R POTASSIUM IODATE The present invention relates to a method for oxidizing sulfur dyes on natural or regenerated cellulose textile fibers.

Generally speaking, the method of the present invention may be described as in the method for oxidizing sulfur dyes on natural or regenerated cellulose textile fibers comprising the step of contacting natural or regenerated cellulose textile fibers having thereon at least one sulfur dye in reduced (leuco) form with an aqueous, acid oxidizing solution comprising water, acetic acid and an oxidant, whereby the dye is oxidized and fixed on the fibers, the improvement characterized in that said oxidant is sodium iodate or potassium iodate.

By far the most popular prior art method for oxidizing sulfur dyes on textiles is with the use of aqueous sodium bichromate and acetic acid oxidizing agent, commonly called the chrome and acid method.

However, the chrome and acid method has a number of disadvantages, including the following. With many sulfur dyes on cotton or regenerated cellulose, chrome and acid produces dyeings having a harsh hand or fee], which causes excessive wearing of needles and fiber fracture during sewing and necessitates use of lubricants during yarn and raw stock dyeing to soften the harshness. Natural and regenerated cellulose textile fibers dyed with sulfur dyes, wherein chrome and acid are used, are not easily rewettable, which necessitates use of wetting agents in subsequent wet finishing operations. Residual chrome and acid is not easily washed away from dyeings, and it is customary to soap the fibers at the boil during such washing. Chrome does not permit the best clarity of shade with many sulfur dyes, probably because of the formation of a metal complex between the chrome and those sulfur dyes. That latter property also causes some such dyeings to have less stability to shade change following washings, as the metal complex is gradually washed away leaving a clearer dyeing. Finally, and most important, use of chrome and acid causes stream pollution problems, as bichromate is reportedly toxic, and stream pollution control authorities in some areas are now beginning to demand changes from past practices of bichromate disposal.

Aqueous hydrogen peroxide is another commercially used prior art oxidant for oxidizing sulfur dyes on natural and regenerated cellulose textile fibers.

The major disadvantages associated with peroxide oxidation of sulfur dyes follow. The wash fastness of the resulting dyeings is considerably less than when chrome and acid is employed. Not all sulfur dyes, particularly those made by sulfurizing 4-hydroxydiphenylamine, can be fully oxidized to stable shades with peroxide. Concentration of hydrogen peroxide in the oxidizing bath is both critical to the fastness properties of the resulting dyeing and troublesome to control. Hydrogen peroxide does not spontaneously oxidize most sulfur dyes to their fully developed shade, and the time lag between application of the aqueous hydrogen peroxide and oxidation (fixation) of the dye causes loss of dye from the fibers, particularly in jig dyeing.

A few textile finishing plants in the United States have recently adopted aqueous potassium ferricyanide as the oxidizing agent for sulfur dyes. The primary difficulties with potassium ferricyanide are a slight time lag between application and dye oxidation, leading to some dye loss from the fiber.

The method of the present invention overcomes some of the above prior art disadvantages and provides additional advantages, all of which will be discussed later herein.

The following is a more detailed description of the method of the present invention.

Textile fibers used in the method of the present invention may be in any desired form, such as knitted or woven fabric, yarn, ball warps, non-woven fabric or raw stock.

According to the method of the present invention, an aqueous, acid, oxidizing solution comprising water, acetic acid, and XIQ, wherein X is Na or K, is contacted with natural or regenerated cellulose textile fibers having thereon at least one sulfur dye in its reduced (leuco) form, and the reduced sulfur dye is oxidized by the iodate ions, while on the fibers, to the oxidized form of the sulfur dye. Thus, the dye is fixed (insolubilized) upon the fibers, and a dyeing results.

As used herein, the term sulfur dyes is defined as those dyes which may be applied in a reduced (leuco) state to cotton fibers from solutions containing sodium sulfide, or sodium hydrosulfide, or sodium polysulfide, and which dyes have affinity for cotton, and which dyes may be subsequently oxidized on the fibers, and which dyes contain divalent sulfur in the form of thiol or alkali metal thiolate when in their reduced state.

The present process may be used in dyeing or printing textile fibers. The sulfur dye may be applied to the fibers in any desired manner, such as by jig, pad, beck, printing roller or yarn package dyeing machine. The sulfur dye may be first applied to the fibers in reduced or oxidized form, but in the latter case the oxidized dye must be converted to its reduced form prior to contact with the oxidizing solution.

If desired, the fibers may be optionally batched for a period of time, steamed or dried to facilitate penetration of the dye into the fibers, or to assist in reducing the dye. They also may be rinsed with water to remove excess reducing agent.

The fibers having thereon sulfur dye in reduced form are then contacted with the oxidizing solution to oxidize and fix the dye on the fibers, such as by immersing the fibers in the oxidizing solution.

The oxidizing reaction is spontaneous, and almost no time elapses between contact of the fibers having reduced sulfur dye thereon with the oxidizing solution and development of the full shade of the dyeing (oxidation).

The aqueous, acid, oxidizing solution comprises water, acetic acid, and X10 wherein X is Na or K. If desired, the oxidizing solution may also contain a fiber wetting agent, e. g. a non-ionic or anionic surface active agent.

The quantity of X10 wherein X is as above defined, which will be used in the aqueous, acid, oxidizing solution depends primarily upon the amount of dye used. Enough of the XIO will be used to oxidize the quantity of leuco form dye on the fibers. For most purposes, an aqueous, acid oxidizing solution comprising 0.75-7.5 gms. XIO /liter of water, wherein X is Na or K, will be suitable for use in the present method. It is suggested that the oxidizing solution be adjusted to about pH 34.5 with acetic acid.

The oxidizing solution may be at about -l80F., and preferably about l40F., when it contacts the fibers having reduced dye thereon.

Following oxidation of the sulfur dye, the fibers may be washed and dried in conventional manner.

In some instances, polyacrylic and polyamide textile fibers may be dyed by the above method, depending upon the particular sulfur dye selected. Blends of natural or regenerated cellulose textile fibers with polyacrylic, polyamide or synthetic linear polyester textile fibers may be used in the present method, in which case the natural and regenerated cellulose will be dyed, the polyacrylic and polyamide dyed by some sulfur dyes and not by others, and the polyester substantially unaffected by the process.

The method of the present invention has a number of advantages, some of which follow.

The waste aqueous sodium, potassium and iodate ions, and iodine molecules, resulting from the present system are non-toxic in the quantities involved, and a substantial improvement over the objectionable bichromate resulting from the chrome and acid method. Hence, stream pollution problems will be improved.

Dyeings without a harsh hand and which are easily rewettable without the aid of a rewetting agent, result from the method of the present invention, which are improvements over the chrome and acid method.

Residual iodate ions, iodine molecules, and acid are washed off fibers more easily than the chrome and acid residue.

Many dyeings which have been prepared by the present method have better clarity of shade than those in which chrome and acid is employed, particularly sulfur blue dyeings.

The degree of wash fastness of natural and regenerated cellulose dyeings made from sulfur dyes depends upon the particular sulfur dye and the oxidizing agent employed. The wash fastness of dyeings prepared by the present process varies from acceptable to very good. Generally speaking, the wash fastness (staining and color loss) of dyeings made by the process of the present invention is superior to those resulting from hydrogen peroxide oxidation, and in some instances equal to and in other instances slightly inferior to dyeings made by the chrome and acid method. However, dyeings prepared by the present method are more stable against shade change on washing than dyeings made with peroxide or chrome and acid.

Light fastness of dyeings prepared by the present process appears equal to light fastness of dyeings made by the chrome and acid method.

All sulfur dyes can be oxidized to stable shades by the present process, including those sulfur dyes made by sulfurizing 4-hydroxydiphenylamine, in contrast to the hydrogen peroxide oxidation method.

I have titrated aqueous N/2O Na S reducing agent against aqueous N/2O chrome and acid and against aqueous N/20 NaIO and acid, and measured the oxidation potentials at various levels during the titration. The oxidation potential of the chrome and acid gradually diminishes in a substantially straight line relationship as Na s is added to the chrome and acid. Surprisingly, the oxidation potential of the aqueous NalO increases slightly as the first Na S is added, then is maintained at a fairly constant and high level while most of the Na S is added, and finally diminishes greatly and rapidly, but only after consuming substantially more Na s than did the chrome and acid. The practical effects of this surprising phenomenon are that during continuous processing the use of iodate insures a high oxidation potential and a uniform developed shade throughout the continuous process, without precise control of iodate concentration, whereas the maintenance of a uniform oxidation potential and shade with chrome and acid is difficult.

The following are illustrative examples of the present invention in which all parts are by weight unless otherwise specified. References in the examples to C. 1. names and numbers for sulfur dyes are to COLOUR INDEX, Second Edition, Supplement 1963, published by The Society of Dyers and Colourists, Yorkshire, England.

Example 1 A dye solution consisting of 4 02. C. I. Leuco Sulphur Black 1, C. I. No. 53185, per gallon of water is padded at 150F. onto woven cotton shirting weighing 4 oz./sq. yd. The fabric is squeezed to permit percent wetpick-up based on fabric weight; steamed at 230F. for 1 minute; passed through four wash boxes containing water at ambient temperature and equipped with exit nip rolls; immersed in an oxidizing solution at F. consisting of 2.0 gms. NalO and 2.5 ml. glacial acetic acid/liter of water for 30 seconds; rinsed well with water and dried.

An excellent black dyeing results.

Example 2 A Gaston County yarn dyeing machine is loaded with cotton yarn. The yarn is boiled ofi in conventional manner with 1 percent acetic acid and 2 percent sulfonate wetting agent by running 30 minutes at 200F.; the bath is dumped and the machine is recharged with 1 percent sodium sulfide; the machine is run 10 minutes at 120F., whereafter there is added to the machine and to the above solution 15 percent of a 200 gm./liter aqueous solution of pre-reduced C. I. Leuco Sulphur Yellow 4, C. I. No. 53160, in 4 parts over 20 minutes at 120F. The temperature is then raised to F. at which time 40 percent sodium chloride is added in 4 parts over 20 minutes. The machine is run an additional 30 minutes at 160F. Without dropping the bath, overflow washes using water at 90F. are given with circulation through the yarn package in the outside-in direction until the overflow is clear. The pump direction is then reversed and washing continued with an inside-out direction until the overflow is clear. The drain is then closed and a circulating wash at 120F. is given for 10 minutes. The bath is dropped, the machine refilled with water at 120F. to which is added 0.75 gms./liter K10 and 1.0 gm./liter glacial acetic acid which is run for 10 minutes at 120F. This bath is then dumped, the yarn washed with water and the water dumped, and the machine refilled with water at 180F. to which is added a 0.5 percent tetrasodium pyrophosphate and 1 percent synthetic detergent which is run for 10 minutes at 180F. The bath is dropped and the yarn is given a running water rinse until clear.

All the percentages given above in this example are based on the weight of the cotton fiber being dyed. The ratio of solution to fiber is 10:1 by weight. All of the chemicals given above are added to water to form aqueous solutions prior to adding to the machine.

An excellent yellow dyeing results on the yarn.

Example 3 This example is the same as Example 1 above, except Example 4 This example is the same as Example 1 above, except that the dye solution consists of 2.4 oz. C. l. Leuco Sulphur Blue 13, C. I. No. 53450, per gallon of water; except that the amount of NaIO is reduced to 0.75 gmsJliter; and except that the oxidation bath is at 50F.

An excellent blue dyeing results.

Example This example is the same as Example 1 above, except that woven regenerated cellulose fabric weighing 3 oz./sq. yd. is substituted for the cotton fabric of Example 1; and except that the dye solution consists of 4.8

oz. C. I. Leuco Sulphur Green 3, C. l. 535 70, per gallon of water.

An excellent green dyeing results.

Example 6 This example is the same as Example 1 above, except that the dye solution consists of 0.8 02. C. l. Leuco Sulphur Blue 7, C. I. No. 53440, per gallon of water.

An excellent blue dyeing results.

What is claimed is:

1. In the method for oxidizing sulfur dyes on natural or regenerated cellulose textile fibers comprising the step of contacting natural or regenerated cellulose textile fibers having thereon at least one sulfur dye in reduced form with an aqueous, acid oxidizing solution comprising water, acetic acid and an oxidant, the improvement wherein said oxidant is sodium iodate or potassium iodate.