US2164930A - Process for reducing vat dyestuffs - Google Patents

Description

Patented July 4, 1939 UNITED STATES PATENT OFFICE PROCESS FOR REDUCING VAT DYESTUFFS No Drawing.

8 Claims.

This invention relates to a novel process for reducjng vat dyestuffs, and may be applied to the arts of dyeing, printing, discharging, reserving, stripping or other operations involving the 5 coloring of textile fiber with vat dyestuffs or the removal of such color from the fiber. More particularly, this invention relates to a new assistant for the dyeing of textile fibers particularly those of vegetable origin such as cotton,

10 linen and regenerated cellulose with vat dyes by a process in which in some cases a leuco compound of a vat dye is formed prior to the introduction of the fiber to be dyed and in other cases a leuco compound is formed in the presence of the fiber to be dyed, as, for example, by a printing process or a pad-jig dyeing process. It relates also to processes for the removal of the color in toto from dyed textile fibers, commonly known as stripping and to the production of 20 white or colored pattern effects on textile materials by the process commonly known as colored or white discharging or reserve printing. This invention further comprises novel compositions of matter which are contemplated 2 for use in my improved processes above referred to, and which facilitate the carrying out of my invention.

It is well known that vat dyes are solid substances, insoluble in water, and that in order to render them useful for the dyeing of textile fibers it is necessary to reduce them to the water soluble or so-called leuco form so that they may be taken up by the fiber. The fiber, impregnated with the reduced water soluble dyestufl, is then subjected to an oxidizing or fixing treatment whereby the vat dyestufl is again converted to the insoluble form (the Keto form).

Hitherto, the hydrosulfites and the aldehyde condensation products of hydrosulfites have been used almost exclusively for the conversion of vat dyes to their water soluble forms as well as for the reductive removal of the color from dyed fabrics. The processes of U. S. P. 746,784 of December 15, 1903, of U. S. P. 744,501 of November 17, 1903, and of U. S. P. 808,443 of December 26, 1905, are practically identical with the current processes for dyeing, discharging and printing, respectively, with vat dyestufls. These patents am accumulated experience show that two diflerent agents, sodium hydrosulfite and form- Application November 10, 1937, Serial No. 173,848

aldehyde sulfoxylate, are required for the various processes of dyeing, printing, and discharging. Because of its instability at elevated temperatures sodium hydrosulfite is unsatisfactory for use in the commonly practiced printing procedures. Because of its inactivity under the usual dyeing conditions, sodium formaldehyde sulfoxylate is unsatisfactory for use except for printing. v

The present invention is based on the dis- 10 covery that the product resulting from the oxidation ofthiourea in neutral solution with hydrogen peroxide is eminently useful for the various processes for the application of vat dyestuffs to textile fibers and to the stripping of color by reductive processes from dyed fabric. 'The oxidation product, known as thioureadioxide, imino-amino methane sulfinic acid, or formamidinc-sulfinic acid, was first made and described by Barnett (J. Chem. Soc. 97, 63-65; 1910). It was later observed that an ammoniacal solution of this compound is a powerful reducing agent for certain inorganic substances. (Boeseken, Koninklijke Akad. Wetenschappen, Amsterdam, 39, 717421; Receuil des Travaux Chimique des Pays Bas, 55, 1040-1045; 1936). But that it had the power to reduce organic substances, and in particular to reduce vat dyestufis to the leuco stage without destroying the dye- 3 stuff, has apparently not been known to date.

It must be observed here that the reduction of vat dyestuffs is a delicate operation, since there are many reduction stages possible, but only a particular one is desired. For instance, in the case of anthraquinone itself, the reduction thereof may produce various successive stages of reduction known as hydro-anthraquinone, leuca-anthraquinone, hydroxy-anthrone, hydroxy-anthranol, anthrone, anthranol, etc., all the way down to anthracene or even dihydroanthracene. Some of these compounds are tautomers, while two of the other members mentioned in the above group are probably identical respectively with leuco-anthraquinone and hydro-anthraquinone. The tautomers are nevertheless producible by different methods, and the hydro form cannot be used where the "leuco form is required. 7

It is known that certain reducing agents will 0 lead preferentially to one or another of the above reduction stages, while others will give a mixture of several reduction stages simultaneously. (See Houben, Das'Anthracen und die. Anthrachinone, pages 143-147.) Under certain conditions the reduction may lead further to compounds of the dianthryl and dianthranol types. (Ibid, pages 172-183.)

It is clear from the above, that to be a useful reducing agent for vat dyestufls, a given reagent must not only be capable of carrying the reduction to the desired degree, but must also be selective; that is, it must not produce the other reduction products to any appreciable extent. Considering further other prerequisites of a physical or economic nature, for instance stability at various temperatures of practical operation, solubility in caustic, or cost, it becomes clear why commercial practice has hitherto been confined practically to the single compound sodium hydrosulflte for dyeing and to the limited sulfoxylate group for printing.

I have now discovered that formamidine sulflnic acid has physical and chemical properties such as to adapt it ideally for the commercial reduction of vat dyestuffs. Moreover, I found that its stability over various ranges of temperature is so good that it may be applied with equal success to dyeing and printing; discharging, resisting and stripping. My invention accordingly consists of a process for the reduction of vat dyestuffs to their so-called leuco"-stage, which comprises treating said dyestuffs with the reaction product of thiourea and hydrogen peroxide, in the presence of alkali, following in all other respects the details of procedure employed by the art in conjunction with the standard re ducing agents, namely sodium hydrosulflte, and sodium-formaldehyde-sulfoxylate or other compounds of this class. My invention further comprises novel processes for reducing vat dyestuffs with the above mentioned reaction product, under conditions to which the hitherto standard reducing agents have not been applicable.

My novel processhas the advantage over the processes of the art in being more versatile; in other words, the same reducing agent is applied to all processes wherein the reduction of a vat dye becomes necessary, including the processes of vat dyeing, pigment padding, printing, resisting, discharging and stripping. Another advantage lies in the fact that by virtue of the higher reducing value of formamidine-sulflnic acid not more than V to of it by weight is used as compared with hydrosulflte or sulfoxylate.

Furthermore, its stability in neutral and acid.

solutions permits of the development of novel application methods hitherto impossible with the known reducing agents. For instance, when my novel reducing agent is employed in printing, the subsequent step of ageing with steam may be omitted altogether or may be delayed for a considerable time, even several days, after the application of the printing paste, whereas in the sulfoxylate process immediate ageing is necessary at the penalty of producing inferior prints. My novel reducing agent also possesses greater stability in alkaline solution than sodium hydrosulflte. This fact enables me to produce vats of Greater stability.

The versatility of my novel process is illustrated by the following examples which show the application of formamidine-sulflnic acid as a reducing agent under most varied conditions to various processes of coloring fabric and removing color therefrom.

It is generally known that one method for the application of vat dyes to the dyeing of textile fibers is to apply the dye in unreduced form to the material, convert the dye to the water-soluble, reduced form on the fiber, in which form it is taken up by the fiber, and subsequently to fix the dye, as for example by oxidation, and finish the material by the customary processes. If the material is to be dyed a solid color, the "pad-jig or "pigment-padding process may be employed. If the color is to be applied locally in the form of a pattern or design, a "printing" process is utilized.

The following examples are given to illustrate the practical mode of operation in the various applied arts without, however, limiting my invention to any details of procedure. Parts mentioned are by weight.

I. DYIING BY THE Prommr Panama Marnon Example 1 Cotton cloth, preferably in open form, is passed through a liquor heated to 120 to 140 F. containing in suspension 16 ounces per gallon of a double paste of the dye described in Example 5 of U. 3. Patent No. 1,705,023, and containing further formamidine sulflnic acid in the proportion of 4 ounces per gallon; it is then passed between squeeze rolls to remove surplus liquor and dried, preferably in open form, by any convenient means and temperature, but preferably not above 200' F. The fabric is next immersed for 3 minutes in a bath heated to 180 to 190 F. and containing 1 ounce per gallon of caustic soda. It is then passed between squeeze rolls and then treated for 1 to 3 minutes in a bath heated to 120 to 140 F. containing 54 to 1 ounce per gallon sodium or potassium di-chromate and to 2 ounces per gallon of acetic acid (56 then rinsed thoroughly by passage through water and then treated for 3 minutes in a bath heated to 200 to 212 F. containing to 1 ounce per gallon soap. It is then rinsed and dried. The result is a uniformly dyed cloth of greenish yellow shade, possessing exceptional fastness properties.

The above example illustrates a novel application method made possible by the use of the new reducing agent. Neither sodium hydrosulfite nor 9. formaldehyde sulfoxylate derivative is applicable under these conditions.

Example 2 Cotton cloth, preferably in open form, is passed through a liquor heated to 120t0 140 F. containing in suspension 16 ounces per gallon of a double paste of the dye made according to Example 1 of U. S. Patent No, 1,761,624, and in solution 4 ounces per gallon formamidine sulflnic acid. It is then passed between squeeze rolls and dried, preferably in open forms, by any convenient means and temperature but preferably not above 200 F. The fabric is next immersed for 3 minutes in a bath heated-to 180 to 190 F. and containing 2 to 4 ounces per gallon caustic soda; then passed between squeeze rolls and then treated for 1 to 3 minutes in a bath heated to 120 to 140 F. containing to 1 ounce per gallon sodium or potassium di-chromate and to 2 ounces per gallon of acetic acid (56%), then rinsed thoroughly by passage through water and soap. It is then rinsed and dried. The resultlng cloth is dyed uniformly in a navy blue shade of excellent iastness qualities.

Example 3 Example 4 Cotton cloth, preferably in open form, is passed through a liquor heated to 120 to 140 F. containing in suspension 4 ounces per gallon of a 13% paste of 4,4'-dimethyl-6,6'-dichlor thioindigo and in solution 2 to 4 ounces formamidine sulfinic acid, then passed through squeeze rolls, dried, then immersed for 3 minutes in a bath heated to 180 to 190 F. and containing to 1 ounce per gallon caustic soda; then passed between squeeze rolls and then treated for 1 to 3 minutes in a bath heated to 120 to 140 F. containing V to 1 ounce per gallon sodium or potassium di-chromate and to 2 ounces per gallon of acetic acid (56%), then rinsed thoroughly by passage through water and then treated for 3 minutes in a bath heated to 200 to 212 F. containing to 1 ounce per gallon soap. It is then rinsed and dried.

Exampe 5 Cotton cloth is treated exactly as described in Examples 1 to 4 inclusive and with the dyes therein described, except that after passage through the liquor containing the dye and the formamidine sulfinic acid it is treated in the caustic soda solution Without previous drying.

Example 6 Cotton cloth, preferably in open form, is passed through a liquor heated to 120 to 140 F. containing in suspension 16 ounces per gallon of the dyes mentioned in Examples 1 to 4 inclusive, and in solution 4 ounces per gallon formamidine sulfinic acid, passed through squeeze rolls, dried and then passed through 15 to 30% solution of caustic soda heated to 80 to 140 F. It is then treated in an agar or chamber containing moist steam and heated to a temperature of 160 to 220 F. for 3 to 30 minutes. It is then oxidized and finished as described in Examples 1 to 4.

Example 7 II. DYEING FROM THE REDUCED VAT The use of formamidine sulfinic acid for the application of vat dyes in reduced form is shown by the following examples:

Example 8 4 lbs. of a double paste of 1,5-dibenzoylaminoanthraquinone (Color Index 1132) are reduced in gallons of water with 3 lbs. of caustic soda and 2 to 3 lbs. of formamidine sulfinic acid for 20 minutes at a temperature of 120 F. In the interval, to 80 gallons of cold water is added 4 ounces of caustic soda and 4 ounces of formamidine sulfinic acid. The reduced dye is added to this latter and 50 lbs. of cotton cloth or yarn are entered into it and treated for from 30 to 60 minutes. The cotton is then removed, and after removing excess moisture by any convenient means, it is oxidized at 120 to 140 F. in a bath containing A, to 1 ounce per gallon of sodium or potassium di-chromate and to 2 ounces per gallon acetic acid (56%), then thoroughly rinsed with water and finished by treatment in a boiling soap solution.

Example 9 10 lbs. of a single paste of 6,6-diethoxy-2,2- bis-thionaphthen-indigo (Color Index 1217) are reduced in 100 gallons of water containing 4 to 5 lbs. caustic soda and 2 to 3 lbs. of formamidine sulfinic acid for 20 minutes at 140 F. 50 lbs. of cotton cloth or skeins is treated in this for from 30 to 60 minutes and then oxidized and finished as described in Example 8.

Example 10 30 lbs. of a double paste of nitrated dibenzanthrone (Color Index 1102) is reduced in 50 gallons of water containing 10 lbs. caustic soda and 3 to 6 lbs. of formamidine sulfinic acid for 20 minutes at 140 F. In the interval, 1 lb. of caustic soda and 4 ounces of formamidine sulfinic acid are dissolved in 50 gallons of water. The reduced dye is added to this and 50 lbs. of cotton cloth or skeins are entered and stirred for to 30 minutes. To assist penetration of the dye into the fiber and a more complete exhaustion of the dye bath the temperature is then raised to 160 to 200 F. and treatment continued for 15 to 30 minutes longer. The cotton is removed, oxidized and finished as described in Example 8.

III. DYEING UNDER VARIOUS SPECIAL Connrrrons My novel process is also adapted for vat dyeing in a circulating liquor machine, for instance the Franklin or Chatanooga machine, as is illustrated by Examples 11 to 13 below.

When applying some of the vat dyes in machines as well as in open vessels it is customary to use as assistants, substances such as animal glue, sulfite waste liquor and others, to retard the rate at which the dyes are absorbed and thus aid their uniform absorption and penetration into the fibers. It is also well known that raising the temperature of the dye baths to between 180 and 200 F. toward the end of the operation, after all or the greatest quantity of the dyes has been absorbed, will aid their uniform distribution through the material and their penetration into the fibers. This reduces the tendency of the dye on the material to rub off and stain other materials with which it may come into contact. It will also in many instances beneficially infiuence the resistance of the color to the destructive agencies to which the fibers are subjected during the manufacturing processes and in subsequent use.

Under many of these conditions sodium hydrosulfite is inapplicable because of its insufiicient stability at the higher temperatures. My novel process, however, using formamidine sulfinic acid may be readily carried out under these special conditions.

15 to minutes longer.

Example 11 100 lbs. of loose cotton is placed in a circulating liquor type machine and wet out as is customary, by treating with boiling water containing small quantities of sodium carbonate or other wetting agents. In the interval 5 to 30 lbs. of the paste or powder types of any of the dyes known by the trade name of Ponsol Yellow G (C. I. 1118) Ponsol Golden Orange G (see Color Index Supplement p. 50)

Ponsol Violet RRD (C. I. 1104) Ponsol Dark Blue DR. (C. I. 1099) are reduced in 20 to 50 gallons of water, containing 8 to 10 lbs. of caustic soda and 3 to 6 lbs. of formamidine sulflnic acid by stirring the ingredients together for 20 minutes at 140 F.

After the loose cotton is thoroughly and uniformly wetted, the liquor is drained, the machine is partly filled with water this is heated to F., and 4 to 8 ounces of caustic soda and 4 ounces formamidine sultlnic acid are added.

This liquor is circulated for 5 to 15 minutes, the reduced dye is added, the liquor is circulated with reversal of its flow and the temperature is raised gradually within 45 minutes to 180 to 200 F. and there maintained for 15 to 30 minutes. This liquor is then drained, the stock is rinsed with cold water, oxidized with 1 to 2% of its weight of sodium perborate and again well rinsed in cold water containing 5 to 15 lbs. of common salt (sodium chloride) or small quantities of other substances that aid manufacturing operations,-

and then dried.

Example The procedure is as described in the preceding example, except that the dyes used are those known in the trade as Sulfanthrene Blues G and GR, (Color Index Supplement page 53), and their reduction is efl'ected with 2 to 5 lbs. caustic soda and 1% to 3 lbs. of formamidine sulflnic acid.

Example 13 lbs. of cotton or linen yarn in package form, or in loose form, is dyed in" a circulating liquor type machine by first thoroughly wetting with boiling water, with or without the aid of wetting and penetrating assistants. This liquor is then drained, the machine partly filled with water, this is heated to to F. and circulated for a short time, with or without the addition of dispersing and penetrating assistants. 5 to 30 lbs. of the paste or specially prepared easily dispersible powders, known to the trade as the Grain or S types, of the dyes described in Example 11, are uniformly dispersed in 10 to 30 gallons of cold water, added to the machine andthe liquor circulated for a short time. 8 to 10 lbs. of caustic soda in any convenient strength of solution is added, circulation is continued for 15 to 30'minutes; 3 to 6 lbs. of i'ormamidine sulfinic acid are added and circulation continued for another 15 minutes; the temperature is then raised to to 200 F. and circulation continued for Rinsing, oxidation and finishing follow by the means usually employed for processes of this kind.

While formamidine sulfinic acid is extremely valuable because of its stability at elevated temperatures, it is also useful for the reduction and application of the vat dyes normally applied at temperatures between 80 to 120 F.

IV. Dmno or Woor. Wrrn Inmoo Example 14 Prepare a stock vat as follows:

From the above stock vat a dye bath for wool may be prepared as follows:

. Parts Stock vat 35.0 Ammonia (.880) 1.2 Formamidine sulflnic acid .75 Glue 0.4

make up to 100 parts with water; clip 25 parts of wool for 10 minutes at 120.F.

Squeeze the material, allow to air-oxidize for about 5 to 10 minutes and give a good rinsing, then dry. The dye bath may be used continuously by replenishing the indigo by additions of stock vat and formamidine sulflnic acid after each dip and ammonia and glue after 4 or 5 successive dips. The amounts to be added must be determined by experiment in each particular case.

V. DYEINGIN Gr mmer.

While specific quantities of the dyes are mentioned in the above examples, these quantities may be varied within wide limits depending upon the tinctorial strength of the shade desired. The quantity of the formamidine-sulfinic acid required may also be varied accordingly, and, whereas in the examples cited the temperature and time for the application of the dye together with the formamidine-sulfinic acid as well as the temperature and time for subsequent reduction in the caustic soda solution is described, these also may be varied to advantage between room temperature, 70 to 80 F., and 212 F. and between 1 and 30 minutes, depending upon the material and character of the individual dyes. Whereas in the examples cited oxidation is effected with chrome and acetic acid it can be equally satisfactorily accomplished by exposing the material in air or by treatments for suitable periods of time and temperatures in baths containing .05 to .25 ounce per gallon sodium perborate or hydrogen peroxide or solutions of sodium hypochlorite containing .01 to .05% available chlorine.

When sodium perborate or hydrogen peroxide is used as the oxidation medium the finishing the procedure for the application of the vat dyes is well known and recognized in the art of dyeing and is dependent upon the type of apparatus used, form in which the material is colored and other variables in local conditions.

Rayon, linen, silk and wool, the latter with the aid of protective colloids, alone or in combination, may be dyed with the dyes and under the conditions described in the above examples.

In addition to the dyes specifically described in the above examples, many others have been satisfactorily applied under the conditions described and produced commercially satisfactory results in relation to penetration of the cloth, uniformity of its appearance and resistance to tions at present in practical use. The dyes thus tested include among others:

Ponsol Blue BCS (Color Index 1114) Ponsol Blu GD (Color Index 1113) Caledon Brown R. (Color Index 1151) Caledon Brown G (Color Index 1152) Caledon Red FF (Color Index Supplement p. 30) Caledon Olive (Color Index Supplement p. 30)

Caledon Golden I Orange G (Color Index Supplement p. 30)

VI. Pam-mm or Fannie Formamidine sulflnic acid can be used in the printing of vat colors either by incorporating the formamidine sulflnic acid in the usual printing composition of color, alkali, thickener and hydrotropic and hygroscopic agent, or by including the formamidine sulflnic acid in with the dye as a powder or as a paste, in which case no further addition of formamidine sulflnic acid or other reducing agent need be made to the printing paste. In addition to direct printing, formamidine sulflnic acid can be satisfactorily used (for the production of white or colored discharges" and in resist printing.

The unusual properties of formamidine sulfinic acid which distinguish it from the usual reducing agent used in printing, namely sodium sulfoxylate formaldehyde, are its exceptionally strong and rapid reducing action in the presence of alkali which enables satisfactory prints to be obtained with much less of formamidine sulflnic acid than of sodium sulfoxylate formaldehyde; it also allows satisfactory prints to be made with a shorter than normal aging period (say 3 to 6 minutes against to 10 minutes); and since reducing fumes, such as formaldehyde or sulfur dioxide, are not given off in the aging process, it permits the printing of azoic colors in the same pattern along with vat colors.

Example A printing paste prepared as follows:

Dimethoxy dibenzanthrone, double paste,

(Color Index 1101) 20.0

Formamidinesulflnic acid 5.0 Sodium hydroxide (35%). 5.0 Potassium carbonate 10.0 Glycerin 5.0 Starch-British gum 55.0

This printing paste may be applied to cotton or rayon fabric by such means as the usual roller printing machine, by engraved blocks, by stencil,

or by screen. After the dye paste has been applied This printing paste is applied to cotton or rayon fabric and subjected to the usual operations of Example 16 A printing paste prepared as follows:

. i Parts Tetra bromo indigo paste.(C. I. 1184) 20.0

Formamidine sulflnicacid 5.0

Sodium hydroxide (35%); 5.0

Potassium carbonate 10.0

Glycerin I 5.0 Starch-British gum thickener 55.0

drying, aging, oxidation and soaping as in Ex-' ample 15. A blue print of exceptional brightness, levelness and strength is obtained.

Example 17 A printing paste prepared as follows:

Parts Ciba brown G (C. I. Supplement p. 34) 20.0 Formamidine sulflnlc acid 5.0 Sodium hydroxide (35%) 5.0 Potassium carbonate 5.0 Sodium dibenzyl aniline sulfonic acid....: 2.0 StarchBritish gum thickener 58.0

This paste is applied to the fabric and subjected to the same developing and finishing operations as in Example 15. A bright, strong and lever brown print isobtained.

Example 18 A vat color printing paste 1Q prepared by mixing and milling as in a paint mill, 50 parts by weight of dimethoxy dibenzanthrone, double paste (C. I.

- 1101), 25 parts by weight offormamidine sulflnic acid and 25 parts by weight of water. 20.0 parts of this paste are then incorporated with Parts Potassium hydroxide (50%) 5.0 Potassium carbonate 10.0 Glycerin 5.0 Starch-British gum thickener .60.0

1 This paste is applied to the fabric and subjected to the same developing and finishing operations as in Example 15. A bright, level green print is obtained.

VII. Jomr PRINTING wrrn Var AND Azoro Gomas Example 19 A vat color printing paste may be prepared and printed in the same pattern with an azoic color as follows:

AZOIC COLOR Parts Red azoic composition as described in Ex.

21 of U. S. P. 1,882,561 4.0 Sodium hydroxide 1.5 Water 24.5 Starch-tragacanth thickeners 70.0

The vat and azoic colors may be applied to cotton fabric by one or another of the customary printing devices in a pattern on which the two classes of colors are-adjacent. The fabric is then dried, aged in a vat color ager, such as the Mather-Flatt type, for 5 minutes, then aged in an acid fume ager for 3 minutes; it is then oxidized for 5 minutes in a bath of 1% sodium per borate plus acetic acid at 120 F. then rinsed and soaped in the usual manner. A bright yellow and red design is obtained in which there is no dulling or discharge of the azoic color where it touches the vat color.

/ Example 20 A vat color may be printed in conjunction with an azoic color by a novel modification of the familiar Colloresin printing process, which comprises the addition of the reducing agent to the vat color printing paste. This procedure has heretofore been impossible.

VAT COLOR PRINTING PASTE The vat and azoic colors may be applied by one of the customary printing devices to a pattern on which the two classes of colors are adjacent, dried, aged for 3 minutes in an acid fume ager, air dried, slop-padded in a solution containing 20% potassium carbonate and 5% glycerin, dried and aged 4 minutes in a Mather-Flatt ager, oxidized for seconds in a bath containing acetic acid plus A% sodium bichromate at 120 F., rinsed and soaped in the usual manner.

A bright, level red and green pattern in which there is no dulling or bleeding of the green vat color or dulling or discharge of the red azoic color is obtained.

In a similar manner other combinations of vat dyes and azoic colors may be printed in the same pattern or textile fabric. The azoic colors for this purpose are preferably selected from the class which may be broadly defined as a coloring composition comprising a stabilized diazonium compound, preferably one stabilized by the aid of the salt of a secondary amine, in admixture with an azo-coupling component, preferably one of the type which develop intoa water-insoluble dye, for instance one of the arylides of 2.3-hydroxynaphthoic acid.

VIII. Drscnsaama Example 21 Cotton goods dyed with tetra bromo indigo v paste (C. I. 1184) printed in the usual manner with a past of the following compositions:

' Parts Zinc oxide paste 200 Anthraquinone 30% paste 50 Formamldine-sulfinic acid 150 Dimethyl-benzyl-phenylammonium chloride 100 Caustic soda 76 'Iw 100 British gum thickening 400 Total 1000 After printing, the goods are steamed, passed through silicate of soda, and then soaped in the usual manner, as described forinstance on page 613, The Principles and Practice of Textile Printing, E. Knecht and J. B. Fothergill. (London, 1936.)

Example 22 r Parts 5,5-dichloro-6,6' dimethyl 2,2 bisthionaphthenindigo (C. I. 1212) 20.00 Formamidine sulflnic acid--. 8.0 Sodium hydroxide (35%) "J... 8.0 Potassium carbonate 10.0 Glycerin 5.0 Starch--British gum thickener 49.0

The above printing paste when applied on a fabric dyed with a dischargeable azoic color by one of the usual printing methods followed by the developing and finishing operations as in Example 15 yields a, sharply defined reddish-violet discharge design on the dyed ground.

IX. Rasrs'r Psm'rrNa Rmsnava PRINTING) Example 23 The vat color printing paste as formulated in Example 15 may be locally resisted by preprinting the fabric with a resist design of the following composition:

Parts British gum (40%) Dimethyl-benzyl-phenyl-ammonium chloride 10 Potassium carbonate 12 Zinc oxide-glycerin mixture 10 Formamidine-sulfinic acid -Q 8 A fabric printed with the above resist paste is overprinted without drying with the vat color printing paste as given in Example 15 and developed and finished by the customary operations as in Example 15. A bright white resist" design stands out against a brilliant green setting where the "resist paste has been applied.

, Example 24 The procedure is the same as in Example 23,

.but the resist paste is prepared from the following ingredients:

A bright white resist design is obtained.

X. S'rmrrme Example 25 50 parts of cotton, linen, rayon or mixtures of these, in the form of cloth or yarn, previously colored with vat dyes are treated in 1000 parts of water containing Parts Cetyl-trimethyl-ammonium bromide,

with or without oleic acid (see U. S. I P. 2,003,928 and 2,019,124) 0.25 to 5 Caustic soda-"u; 1.5 to 3 Formamidine-sulfinic acid 1 to 5 The above materials may be added to the bath either before or after entry of the textile material. In either event, the bath is heateed to a temperature of 120 to 140 F, at the beginning of the treatment, and is then gradually raised in temperature to at least 200 F., and preferably 212 F., the treatment being continued with suitable agitation of the material for from 30 to 60 minutes, The source of heat is then removed, and cold water is run in, permitting the excess to flow away through any suitable arrangement, until all of the original liquorhas been displaced. This water is then drained and 1000 parts of a Tw. solution of sodium hypochlo'rite is added, and the material is treated in it at a temperature between 65 and 80 F. for 20 to 30 minutes. This is followed by the usual rinsing in cold water, or treatment in cold solutions of sodium thiosuliate or of other suitable substances to remove the residual hypo-chlorite. This treatment will remove some or all of the color, depending upon the dye or dyes and their quantity that the material originally contained.

Among the vat dyes that are completely or nearly completely removed by this treatment are Anthraflavone 60 (C. I. 1095) Caledon Brown R (C. I. 1151) Pcisol Blue GD (C. I. 1113) Ca1edon Olive (see C. 1. Supplement page 30) 6,6-diethoxy-2,2-bisthionaphthen-indigo (C, I.

XI. DYmNe WITH SULFUR Comes Ewample 26 oxidizing and drying in the usual manner. There is thus produced textile material dyed a fast black shade.

Example 2''! The procedure is thesame as in Example 26 above, except that the dye prepared as in Example 1 of U. S. P. 1,944,250 is used in lieu of the color therein mentioned. There is thus obtained textile material dyed a blue shade of unusual fastness.

XII. DYEING BY Pnsrssmo Rsoocmo Aosrz'r m Sr'ro It is a remarkable feature of my novel process that the reducing agent may be prepared in situ in the process of dyeing. For instance, one may-proceed as follows:

Ewample 28 2 partsof thiourea are dissolved in 100 parts .of water, and to this are added 30 parts of 3% hydrogen peroxide preferably keeping the temperature under 80 F.

To this solution there is then added 1 part of 13% paste of 4,4-dimethyl-6,6-dichlor-thioindigo. Then there are added 2.5 parts of sodium hydroxide. The suspension thus formed is then heated at 180 F. until the reduction of the vat dyestufi is complete. The goods to be dyed are then immersed in this solution, removed after 1 hour, and finished in the customary manner, in-- cluding the steps of oxidation and soaping. The dyeings thus obtained are as good as when the ordinary sodium hydrosulfite bath is employed.

Example 29 v The procedure is the same as in Example 28,

except that Anthraflavone GC is employed as color. The results are very good.

In a similar manner tetrabromo indigo dyestufi paste or other vat dyestuffs may be dyed upon cotton or rayon goods, with slight variations, in some cases, of the temperature, caustic concentration and dyeing time, to suit the best conditions for any particular dyestuff, as is well understood by those skilled in the art. If desired the vat dye may be mixed with the thiourea, or with the aqueous solution thereof, prior to the treatment of the latter with the hydrogen peroxide.

XIII. DYESTUFF CoMPosrnoNs By virtue of the general stability of my preferred reducing agent in this invention, it is possible to compound the same with the dyestuif, either in powder form or in paste form, and to market the resulting composition as a vat dye preparation which is adapted for direct use requiring no additional reagents for its solution except alkali. These dyeing preparations may contain further dyeing or printing assistants, for instance wetting agents, dispersing agents, etc., and may be prepared specially for use in dyeing or for printing, or for both.

The following examples illustrate typical compositions in accordance with this particular feature of my invention.

Example 31 50 parts of an aqueous double paste of tetrabromoindigo are mixed with 50 parts of formamidine-sulfinic acid and milled together until thor oughly uniform.

Theresulting composition is satisfactory for use in the various processes, of printing and dyeing, without further addition of any reducing agent.

Example 32 100 parts of tetrabromoindigo double paste are mixed with 60 parts of a polyhydric alcohol, such as ethylene glycol, and the whole is evaporated to a weight of parts. There is then added 20 parts of formamidine-sulfinic-acid and the mass is intimately mixed by means of a suitable grinder.

The assistant paste so produced is very satisfactory for use in the printing of textileilbers without further addition of reducing agent. Instead of the ethylene glycol there may be used diethylene glycol, glycerine or a mixture of. these materials with liquids such as the ethanolamines.

It will'be understood that the above examples are merely illustrative, and that the details of my process are susceptible of wide variation and modification within the skill of those engaged in i this art.

Thus, the alkalinity of the dyeing bath, printing paste, discharge paste or stripping bath, as the case may be, is generally to be selected in accordance with the practice of the art in regard to the particular dye employed when using hydrosulfites or sulfoxylates. It is well known that the alkaline concentration required for best .resuits varies with the nature of the dye employed. Some dyestuffs will not dissolve completely when reduced unless a strongly alkaline'bath is employed. Dyestuffs of the indanthrene group, for instance, require such a strongly alkaline bath as to prohibit the application of the process to wool fibers (Houben, ibid, page 31). Indigo on the other hand is very easily reducible and can be treated in a mildly alkaline bath, for instance an ammoniaoal bath.

It will be clear from the aforegoing, that the nature of the alkali employed, that is whether sodium-, potassiumor ammonium-hydroxide may likewise vary with the individuality of the dye employed, and will generally conform to the usual practice with such dye when hydrosulfite or sulfoxylate reducing agents are employed,

The nature of the operation, of course, is also determinative of the nature and strength of the alkali required. Thus, in ordinary pigment padding, a bath containing less than 1% of NaOH is often satisfactory. (Cf. Example 1, above.) Where, however, the pigment padding method is employed in conjunction with a steaming operation', a concentrated bath containing as high as 15 to 30% by weight of caustic soda may be employed. (Cf. Example 6.) Likewise, in printing, the alkali employed is generally in the form of a carbonate, for instance potassium or sodium carbonate. Sometimes, this may be used in conjunction with sodium or potassium hydroxide.

In all such details, the general rule which I recommend with my invention, is to follow the preferred practice of the art as if the particular operation concerned were carried out with the hitherto customary reducing agents (i. e. sodium hydrosulfite or the various sulfoxylates).

In other details, for instance temperatures, in-

gredients of the pastes, use [of assistants, retardly, in the claims below, the term vat dyestuif shall be construed as a comprehensive term for all dyes which are water-insoluble and which are generally applicable to the fiber by a process involvingflrsttreatment of the dye with a reducing agent to produce an alkali-soluble reduction product of the dye (the so-called leuco" form), and then re-oxidizing the dye on the iiber to convert it into its original water-insoluble form. The nature of the reducing agent hitherto employable or preferable. for the reduction step, (whether a 'hydro'sulf lte, a sulfoxylate, sodium sulfide, sugar or any other reducing agent) does not enter into the above definition of vat dyestuff, and is not intended to limit the construction thereof in this application.

As regards the novel reducing agent employed by me in this invention, it will be understood that although I refer to it as formamidine-sulfinic acid, I do not intend thereby to limit my invention to any particular structure or any particular form of this compound. A review of the literature concerning this compound shows that its structure is still somewhat in dispute. Some workers called this compound thiourea dioxide,

NH; 0 NH O ll 8 0:8 I l NH: O N H: OH

Formula I Formula II It is possible that both forms are correct, and that the compound spontaneously undergoes tautomeric rearrangement, depending on the medium it is in (whether acid or alkali) or on the temperature.

Furthermore, if the second formula be considered, it is conceivable that it forms a salt when in alkaline solution, for instance the sodium sulfinate when in sodium hydroxide solution. It is further conceivable that. in acid solution it forms salts on the imino group, for instance a hydrochloride.

All the above are finetheoretical points which cannot readily be determined in, practice.

Moreover, as shown above in Examples 28 and 29, instead of using the isolated formamidinesulfinic acid, one may employ in my process materials which when brought together in aqueous solution form said compound in situ, for instance thiourea and hydrogen peroxide. It is to be understood therefore that in the claims below when I speak of formamidine-sulflnic acid, I am referring to the compound which is obtainable by oxidizing thiourea with hydrogen peroxide at.

a relatively low temperature, for instance around 0 to 10 C., and to any compound which is chemically identical therewith regardless of the mode of its synthesis, as well as to any tautomeric form thereof and to any salt thereof which behaves in alkaline solution in the same manner as an alkaline solution of said compound, including further any combination of initial materials which when brought together in aqueous solution produce said compound in situ.

As regards the materials that may be dyed or printed by my novel process, it will be understood that my invention is applicable to any of the materials heretofore employable with vat dyes. These may include cellulosic textile material, for instance cotton, rayon, cellulose acetate, or, in certain instances, animal fiber such as wool. Then again the material may be in the form of textile fiber, for instance fabric or yarn, or it may be in the form of sheets, films or filaments, as for instance in Cellophane.

I claim:

1. In the process of converting a vat dyestufli into its leuco form, the step which comprises reducing the vat dyestuff by the aid of formamidine-sulflnic acid.

2. The process of reducing a vat dyestufi to its leuco form, which comprises treating the same with formamidine-sulfinic acid and alkali.

3. In the processof converting a vat dyestufi 4. The process of coloring textile material which comprises reacting with alkali and formamidine-sulfinic acid upon a vat dyestufi in contact with the textile material, and then subjecting the textile material to an oxidation treatment whereby to reconvert the vat dyestufi into its water-insoluble form.

5. A process for dyeing cellulosic textile material which comprises padding the same with an aqueous suspension of a vat dye containing further formamidine-sulfinic acid, then treating the material in an alkaline aqueous bath whereby to effect reduction of the vat dye on the flber to its leuco form, and subsequently oxidizing the vat dye on the fiber whereby to reconvert the vat dye into its water-insoluble form.

6. A process for dyeing textile material which comprises treating the same in a vat formed by reacting with alkali upon an aqueous mixture of a vat dye and formamidine-sulfinic acid, whereby to impregnate the textile material with the reduced vat dye, and then further treating the textile material so impregnated with an oxidizing bath adapted to reconvert the reduced vat dye to its water-insoluble form.

'7. A, process of printing textile material, which comprises applying thereto locally a printing paste comprising a vat dye, formamidine-sulfinicacid, an alkali and a soluble gum, and then subjecting the printed material successively to steam aging and to oxidation, whereby to develop the color upon the fiber.

8. A vat color preparation comprising, in intimate admixture, a vat dye and formamidine sulfinic acid.

HERBERT A. LUBS.