US2304435A - Treatment of dyed textile fabric - Google Patents

Description

Patented D.s,1'942 TREATMENT OF DYED TEXTILE FABRIC Thomas E. Bell, Philadelphia, Pa., assignor to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application September 25, 19' Serial No. 412,337

9 Claims.

This invention relates to improvements in the treatment of partially dyed cotton textile fabrics. More especially, it relates to the stripping of marked-oif dye stains, particularly marked-01f naphthol dye stains, from cotton textile fabrics which have been bleached with alkaline solutions of bleaching agents. In this improved process for stripping marked-off dye stains from these textile fabrics, I employ certain novel oxidizing agents, the organic peracids and persalts.

In the dyeing of cotton textiles, for example with naphthol type dyestuiis, the cloth to be dyed is impregnated with the dyebase, a stabilized diazo compound. This dyebase is then developed with a phenolic compound, for example, betanaphthol. As-a result, there areprobably at least four types of compounds present: fully developed dyestuir; partially developed dyestufi; and unchanged dyebase and unchanged developer. Unchanged dyebase and developer may readily be washed from the cloth and create no dimculty in the later processing of the cloth. Fully developed dyestufis are reasonably resistant to the action of alkaline oxidizing agents, and mixtures of alkali and oxidizing agents. They therefore cause no difficulty in the subsequent steps wherein the cotton goods are bleached with alkaline solutions of oxidizing agent. "However, the remaining product, the partially developed dyestuff, is less resistant to the action of alkaline solutions of oxidizing bleaching agents.

In certain bleaching processes wherein alkaline solutions of oxidizing bleaching agents are employed for bleaching cotton textiles containing areas or patterns dyed with naphthol dyestuffs, theconditions under which the cloth is handled are conducive to marking-oil of the partially developed dyestuffs into the white areas of the fabric. Fully developed dyestuffs are apparently not harmed by this treatment, and the pattern of the dyestuff is not harmed. In order to strip or remove this marked-off dyestuff, the stripping should take place in a substantially neutral solution when an oxidizing agent is employed, since dye-stripping treatments involving the'use of alkaline solutions may result in additional marking-off of the partially developed naphthol dyestuffs.

In the past it has been customary to strip such marked-01f naphthol dye stains with alkaline solutions of hypochlorites. However, this method for removing marked-oft color has not generally given very good results because the high alka-.

7 linlty of the hypochlorite solutions under some 55 circumstances might result in additional marking-ofi of the dye. Moreover, the presence of the hypochlorite may result in damage to the textile fabric. Treatment with hypochlorites also requires subsequently subjecting the fabric to the action of an anti-chlor", as well as to several additional washings. For these reasons the hypochlorites, while valuable in stripping marked-0E color, have not been considered in the industry to be entirely satisfactory for this purpose.

Unfortunately other common oxidizing agents, such as hydrogen peroxide or alkali metal peroxides, are not efiective in removing marked-01f dye stains. This is true regardless of the pH of the solution of hydrogen peroxide or other inorgan c peroxide applied to the fabric.

i have now found that the organic peracids and persalts are particularly suitable for stripping marked-off naphthol dye stains from bleached cotton textiles. Accordingly, it is the primary object of this invention to develop an improved method wherein these oxidizing agents may cidciently be utilized for the removal or" marked-off dye stains from partially bleached textile fabrics. In view of the possibility of additional marking off occurring if the stripping agent is applied in solutions which are too highly alkaline, it is a further object of this invention to develop a method wherein solutions of organic peracids or persalts which are approximately neutral in reaction are utilized for this purpose. These and still further objects of my invention will become apparent from the ensuing disclosure of certain preferred embodiments thereof.

The oxidizing agents which are utilized for removing marked-off dyes from cotton fabrics include the organic peracids and persalts. These peracids or persalts may be utilized either as a single percompoound, or, if desired, mixtures thereof may be utilized. The treatment may also be applied in one or more stages it necessary, utilizing one or a plurality of these oxidizing agents.

The oxidizing agents utilized may be classified generically as the organic peracids and products secured by the neutralization, either partial or complete, of these peracids with alkaline agents such as caustic soda, caustic potash, soda ash, sodium bicarbonate, trisodium phosphate, ammonium hydroxide, lime, etc. These will include the monoperacids, diperacids, and triperacids, etc., but because of the ready availability of the chemical compounds from which they can be partial or complete, of the peracid solutions with an alkali, I prefer to utilize the alkali metal salts, the ammonium, or the alkaline earth metal salts such as the calcium salts.

Monoperacids constitute a class of acids which ane chemically characterized by the presence of the perhydroxyl grouping -'OOH as part of the molecule. These peracids may be regarded as derived from other acids by replacing 'the hydroxyl group containing the ionizable hydrogen atom of said acids by the perhydroxyl group OOH. Thus, monopersuccinic acid, one of the acids with which I have had substantial success in the elimination of dye stains from cotton textile fabrics, may be regarded as derived from succinic acid,

cmcoon CHzCOOH Y by the replacement of a hydroxyl group containample, the methods of Bayer and Villiger are described in the Berichte 34, page 762 1901) Other methods for preparing these compounds are those of DAns and his collaborators described in Z. anorg. Chem. 73, page 325 (1912) and in Berichte der Deutschen Chemischen Gesellschaft, vol. 4 5, page 1845 (1912). These methods generally involve reacting an acid and a concentrated solution of a peroxide such as concentrated hydrogen .peroxide.

The percompo'unds and the persalts may also be prepared by reacting an acid anhydride with a dilute or concentrated solution of a peroxide such I as hydrogen peroxide, or by reacting an acid anhydride with an alkaline solution of a peroxide.

In the copending patent application of Reichert;

istics of the solution of the peroxygen compound,

before addition of the acid anhydride, as regards its alkalinity or acidity, are carefully controlled. This method, which utilizes relatively dilute solutions of peroxides or peroxygen compounds, is one that I prefer to use, although any method known to the art for producing the peracids or the salts of the peracids'in solution may be .utilized.

.Any organic peracid or its salt may be utilized as oxidizing agents in my improved process for stripping marked-off dye stains from cotton fabrics. These peracids may be monoperacids or higher peracids such as diperacids. Among monoperacidsJor example, the following classes of acids may be regarded as starting materials for Preparing the peracids by replacement .of the hydroxyl group containing the ionizable hydrogen atom by the perhydroxyl group OOH: carboxylic organic acids; hydroxy organic acids; and saturated or unsaturated acids, whether those acids be aliphatic or aromatic. Organic acids not characterized by the presence of-a .carboxyl group, such as sulfonic acids, either aliphatic or aromatic, may also be mentioned. Acids derived fromheterocyclic compounds, such as furoic acid, are included.

Among aliphatic acids from which peracids or their salts may be prepared for utilization in my process of bleaching may be mentioned monobasic acids, such as acetic acid, and dibasic acids, such as succinic acid. The monoperacids, for example, suitable for use in my process, may be regarded as derived from these aliphatic acids by replacement of the hydroxyl group thereof by th perhydroxyl group. Among hydroxy acids suitable for use in preparing. peracids which may be utilized in accordance with my process are acids such as glycolic acid, and unsaturated aliphatic dibasic acids such as maleic acid.

For preparing oxidizing agents suitable for use in my process for removing marked-01f dyes, by replacement of 'the hydroxyl group'of an acid containing the ionizable hydrogen atom by a perhydroxyl group, there may be mentioned aromatic acids such as benzoic acid, which yields monoperbenzoic acid, a valuable oxidizing agent. Among other aromatic acids may be mentioned monoperphthalic acid, readily derived from phthalic anhydride. Alicyclic organic acids, such as cyclohexane carboxylic acid, may also be utilized to prepare peracids and persalts which may be efiectively utilized in my process.

Among sulfonic acids from which peracids and their salts capable of utilization in my process may be prepared are acids such as benzene sulfonic acid. Among'heterocyclic acids, nicotinic and quinolinic acids form suitable starting materials for preparing peracids suitable for use in treating cotton goods to strip ofi dye stains.

Among the various organic peracids I prefer to use monopersuccinic acid or its salts, monoperphthalic acid or its salts, and peracetic acid or its salts. In view of the relative inexpensiveness and ready availability of acetic anhydride, from which peracetic acid is prepared, peracetic acid and salts of this acid may be regarded as my pre-- ferred agent.

However, perpropionic acid, perbutyric acid, perc'rotonic acid, monopermaleic acid, monoperglutaric acid, perbenzoic acid, diperterephthalic acid, monoperadipic acid, perglycolic acid (bydroxymonoperacetic acid) and the salts of these acids are among the organic peracids and their salts which may be utilized in accordance with my process in the treatment of dyed cotton goods.

The stripping of marked-0E naphthol dye stains may be carried out by either a steeping or a saturation method. In the steeping method, the dyed cotton cloth to be treated is allowed to soak in an amount of peracid or persalt solution which is several times the weight of they dry material, this soaking continuing for the duration of the treatment. In the saturation method the cloth is thoroughly wet out in the peracid or persalt solution and excess'solution over. that necessary to moisten the goods uniformly removed by suitable means. The cloth is then stored in the moistened condition for the duration of the treatment. When practicing the saturation method, it is preferred to saturate the cloth at room temperature. The temperature is then raised to the stripping temperature and Ordinarily it is preferred to utilize solutions of organic peracids or persalts which have pH values not appreciably in excess of 8.0. The pH of the solution is readily adjusted by the addition of alkali or acid, as needed, in order to secure one of approximately 8.0. However, this pH is not unduly critical and it may be varied somewhat over fairly wide limits of acidity a and alkalinity. For some industrial purposes it may be desirable to strip the marked-off naphthol dye stains from the textile fabrics with solutions of lower pH values, such as pHs of 6.0 to 7.0. In general, however, in the use of peracid or persalt solutions for stripping marked-off naphthol dye stains, a pH value in excess of 9.0 is of no particular advantage as the stain strip ping activity of the peracids or persalts decreases rapidly at pH values above 9.0. The ability of the peracid or persalt to remove naphthol dye stains is greatest in the pH range 7.0 to 9.0 and decreases only slightly as the pH decreases. For my purpose, however, I prefer to employ the organic peracid and persalt solutions for stripping naphthol dye stains from cotton fabrics at a pH of approximately 8.0, in this way avoiding the danger of marking off additional dyestuffand thus securing additional staining by the employment of solutions which are too alkaline.

The condition of the marked-off naphthol dye stain and the procedure elected for carrying out thefstripping will generally control conditions of time, stripping temperature, and the concentrations of stripping agent utilized in the process. Organic peracid or persalt solutions of any concentration may be employed, but I prefer to utilize a concentration ranging from 0.25 volume to 1.0 volume, depending upon the intensity of the marked-off dye stain to be removed. The volume concentration of a solution of a percompound is a usual manner of expressing its concentration, and is defined as the number of volumes of oxygen gas, measured at 0 C. and 760 I mm. of mercury pressure, which willbe released upon complete decomposition of the percompound from one volume of the solution maintained at 20 C.

Ordinarily it is preferred to utilize elevated temperatures in the process as the use of such temperatures greatly reduces the time required satisfactory stain removal has been secured in. the temperature range 50 F. to 210 F. If tem,.

peratures above 120 F. are mair'itained,'together with concentrations of t he organic peracidor persalt solution ranging from 0.25 volume to 1.0

volume, the stripping operation will generally be completed in a very short period of time, for example, aperiod ranging from one-half to one hour.

As an example of my improved method for stripping marked-off naphthol dye stains from cotton textile fabrics, the following may be given:

Example Cloth batches stained with marked-off paph-.

thol dye stains were immersed in various solutions of peracetic acid of concentration ranging from 0.125 volume to 1.0 volume, these solutions all having a pH of approximately 8.0. Temperatures ranging from F. to 160 F. were maintained. In all cases the stains were stripped from the fabric at the end of three hours and, in most cases, especially where temperatures of F. or higher were maintained, stain removal was complete in one hour or less.

In place of peracetic acid or salts of this per;- acid as utilized in the above-described illustra tive example, other organic peracids or persalt may be employed as stripping agents. However, monopersuccinic acid, monoperphthalic acid, and peracetic acid, and their salts are preferred as stain stripping agents because of the commerical availability and low cost of the substances'from which solutions of these agents may be prepared. But perpropionic, perbutyric, percrotonic, monopermaleic, monoperglutaric, perbenzoic, diperterephthalic, and perfuroic acids, and their salts will, in general, give satisfactory results in the removal of marked-off naphthol dyes.

It may be remarked that in no case wherein peracids or their salts have been utilized for removing marked-off naphthol dye stains from cotton goods, or from goods consisting largely or predominantly of cotton, has there been observed any objectionable degradation or weakening in appears in the textile treating bath, i. e., whether the compound is present in the formof the peracid or in the form of a salt of a peracid, depends largely on the pH of the solution and on the alkaline agents added to neutralize or partially neutralize the peracid (if in fact any such alkaline agents are added) it is apparent that there is no essential difference in my process regardless of whether the peracid or its salt is present. Accordingly, I employ the term peracid as including both the acid itself and salts of the acid, such as the various metal peracetates, perphthalates, perbenzoates, etc.

Wherever I refer in the claims to fcottonf cotton goods, or cotton textiles, I mean to include within the scope of 'that term both fabrics consisting substantially entirely of cotton, as well as those consisting largely or. predominantly of cotton but containing, in addition, non-cotton fibres. Y

It will be apparent that many changes may be made in my process as herein described which will nevertheless fall within the scope of the invention. Accordingly, it is my intention that the invention is not to be restricted to the various de-.

tails, conditions, amounts and procedures given as typical and illustrative of preferred embodiments, except insofar as necessitated by the prior art and appended claims.

I claim:

1- The mf in ad of treating dyed cotton textile fabrics inorder .to remove marked-off naphthol dye stains therefrom which comprises contacting said fabric with an aqueous solution of an organic peracid.

2. The method of treating dyed cotton textile fabrics in order to remove marked-01f naphthol dye stains therefrom which comprises subjecting said textile fabric to the action of an aqueous solution of an organic peracid having a pH falling within the range 6.0 to 9.0.

3. The method of treating dyed cotton textile fabrics in order to remove marked-off naphthol dye stains therefrom which comprises subjecting said textile fabric to the action of an aqueous solution of an organic peracid having a pH of approximately 8.0.

4. The method of treating dyed cotton textile fabrics in order to remove marked-off naphthol dye stains therefrom which comprises subjecting said textile fabric to the action of an aqueous solution of an organic peracid at a temperature in excess of 120 F.

5. The method of treating dyed cotton textile fabrics in order to remove marked-off naphthol dye stains therefrom which comprises subjecting said textile fabric to the action of an aqueous solution ofan organic peracid having a volume concentration ranging from 0.125 volume to 1.0

volume." I

6. The method of treating dyed cotton textile fabrics in order to remove marked-off naphthol dye stains therefrom which comprises subjecting said textile fabric to the action of an aqueous solution of, an organic peracid at a temperature in excess of 120 F., said solution having a peracid concentration ranging from 0.25 volume to 1.0 volume.

7. The method of treating dyed cotton textile fabrics in order to remove marked-01f naphthol dye stainstherefrom which comprises subjecting said, textile fabric. to the action of. an aqueous solution of peraoetic acid.

8. The method of treating dyed cotton textile fabrics in order to remove marked-off naphthol dye stains therefrom which comprises subjecting said textile fabric to the action of an aqueous solution of monoperphthalic acid.

9. The method of treating dyed cotton textile fabrics in order to remove marked-off naphthol dye stains therefrom which comprises subjecting said textile fabric to the action of an aqueous solution of monopersuccinic acid.

THOMAS E. BELL.