US2211126A - Vat dye composition - Google Patents

Description

Patented Aug. 13, 1940 UNITED v STATES PATENT OFFICE 2,211,126 VAT DYE coMPosrnoN Jean G. Kern, Buffalo, Y2, assignor to National Aniline & Chemical Company, Inc. New York, N. Y., a corporation of New York No Drawing.

solutions or dispersions for coloring textile;nia-- terials and the like. The vat dye past'es' or p w;

ders are particularly valuable for preparation of printing pastes and paifdin'gbaths. The invention also includes processes for making the vat dye compositions.

In the art of dyeing with vat dyes, two general methods are ordinarily employed. In accordance with one method, a vat comprising an alkalinesolution of a reduced vat dye isprepared and the fibrous material to be dyed is worked in this solution whereby the fiber takes up the reduced compound of the dye. The material is then subjected to oxidation and other finishing treatments to convert the vat dye from the reduced to the unreduced form and further complete the fixing of the dye and finishing of the material. In accordance with the other method the dye is applied to the material to be dyed while in the unreduced form; it is then subjected to a reducing treatment whereby the dye 'is converted to the soluble form in the presence of the fiber and is then taken up by the fiber. It is then subjected to oxidation and/or other finishing treatments to fix the dye on the fiber, remove undesired residual material, and complete the finishing of the material.

In dyeing with vat dyes by the latter method, one of two procedures is usually followed, depending upon'whether the material is to be dyed a solid color or with a pattern in one or more colors. If the material is to be dyed a solid color, the pigment padding (pad and jig) ,process is ordinarily employed, andif the material is to be dyed with a pattern, the printing process is generally utilized. 1

In the pigment padding process, the unreduced vat dye in finely-divided form is suspended in a suitable suspension medium, usually water containing added materials such as thickeners and alkaline substances. The material to be dyed is passed through thissuspension, the fiber mechanically picks up the particles of insoluble dye, and the material is subsequently worked in a reducing bath whereby the dye is'reducedto the the dye to the insoluble form, fix it on the fiber,

and further complete the finishing of themate- 55 rial..

- paste.

soluble-form and is absorbed and/or adsorbed by the fiber. The material is finally subjected to.

Application January 28, 1939, Serial No. 253,347

The printing process of dyeing a textile fabric generally involves applying a so-called printing paste to the fabric in the form of a design (e. g., by means of a screen, a stencil, or an engraved 'roll), and then subjecting the printed fabric to 5 further treatment to fix the dye. In general, vat

dye printing pastes, in addition to the unreduced vat dye, contain substances which in themselves do notreduce the vat dye under the conditions of Y the printing operation but which in subsequent 10 operations react with the dye to convert it to the soluble form (such assodium formaldehydesulfoxylate and potassium carbonate), other substances or assistants which promote the reduction of the dye and/or absorption of the reduced 15 compound by the fiber, and suitable gums or thickeners. The fixing treatment usually comprises subjecting the printed fabric to a so-called' steaming or ageing treatment to induce reduction of the vat dye by the action of the re- 20 ducing agent present on the fabric, and cause the reduced dye to be taken up by the fiber. The fabric is then subjected to oxidizing, washing, and other finishing treatments.

In dyeing with the vat dyes, particularly by the pigment padding or printing processes, the success of the operation is in a large measure dependent upon the uniformity with which the vat dye (e. g., the unreduced vat dye) is applied to the fabric. The vat dyes in unreduced form, as is well known, are insoluble in water and are not readilywetted by water. In preparing a padding bath or printing paste it isimportant that the vat dye be in finely-divided form, that it be uniformly distributed throughout the bath or paste, and in condition such that it may be taken up'by the fiber. Further, it is important that the vat dye be capable of rapid and substantially complete reduction to the reduced form. The vat dyes, especially those which are intended for use in the pigment padding and printing processes, are generally marketed in the form of so-called dye pastes or color pastes, and dye powders. A dye paste of this kind is usually an aqueous mixture or suspension of finely-divided -vat dye, whichge'nerally makes up 10 to 20 per cent or the Th'paste usually contains a small amount of a dispersing agent such as Leukanol (a'condensation' product of formaldehyde and a T naphthalenesulfonic acid) and the remainder is main! from ordinary vat dye pastes.

poly-glycols, etc. These vat dye pastes are ordinarily produced by stirring the dispersing and other agents with the filter cake of the dye resulting from filtration of a precipitate of the dye obtained in its manufacture, or by precipitation in the finely-divided form from a vat of sulfuric acid or other solution.

As noted above, vat dyes for use in the preparation of padding baths and printing pastes may be supplied in the form of vat dye powders. In the case of the powders, it is important that the vat dyes contained therein not only have the properties pointed out above in connection with the vat dye pastes, but also that the powders be rapidly converted to uniform suspensions of the vat dye. Especially successful vat dye powders are described in my United States Patents Nos. 2,067,926 and 2,145,193. These vat dye powders are prepared by incorporating with the usual vat dyepaste (e. g., one containing a small amount of a dispersing agent) a soluble salt of an acid alkyl ester of an oxygen-containing polybasic inorganic acid (e. g., a soluble salt of a sulfuric acid ester of a lower aliphatic alcohol) and preferably also an added substance such as, for example, dextrine, sugar, gum arabic, and the like, and then drying and grinding the resulting composition.

It is the principal object of the present invention to provide vat dye compositions which are productive of excellent dyeings and printings when employed in the usual ways. Anotherobject of the invention is to provide vat dye pastes and powders which are adapted for use in the eflicient preparation of padding baths and printing pastes containing uniformly distributed therethrough the finely-divided particles of the vat dyes. Another object of the invention is to provide vat dye pastes and powders .which when used in the preparation of padding baths and printing pastes are productive of compositions characterized by the marked eiiiciency with which the dye is initially taken up by the fiber andthe increased brilliancy and strength of the resulting dyeings and printings as compared with the dyeings and printings obtained by the use of padding baths and printing pastes prepared A further object of the invention is to provide vat dye pastes which remain fluid on standing and which may be easily and quickly mixed with the ingredients making up the conventional padding baths and printing pastes to form homogeneous com-. positions containing the vat dyes in well-dispersed condition.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

It has been found in accordance with the present invention that the properties of vat dye compositions containing a vatdye in the unreduced or other form can be improved by incorporating in them a soluble organic ester of an organic polycarboxylic acid (e. g., an allphatic or aromatic polycarboxylic acid) and an organic hydroxy compound free from aliphatic radicals containing a total of more than 12 allphatic carbon atoms per aliphatic radical and from aliphatic radicals containing more than 8 aliphatic carbon atoms in a straight carbon chain, which ester contains in the acyl radical thereof an unesterified carboxyl group as the sole solubilizing group. In speaking of soluble esters herein it is meant esters that are soluble in water and/or in alkaline solutions. It has been found that esters of this class, particularly the esters of aliphatic carboxylic acids, possess a combination of properties which make them valuable for use in compositions containing vat dyes, and especially in vat dye compositions in paste or powder form intended for use in the preparation of padding baths or printing pastes.

In preparing a vat dye paste in accordance with the present invention, a vat dye, usually in the form of a press cake (a mixture of a vat dye in finely-divided form with water as obtained in the course of manufacture of the dye) is mixed with an ester of the above class and also preferably with a dispersing agent (for example, Leukanol or sulflte waste liquor). The resulting mixture is then diluted with water to the desired dye-strength; or if the paste is to be a so-callednon-drying paste, that is to say, one in which the water is replaced in whole or part by a water miscible high-boiling alcohol such as iso-butyl alcohol, glycerine, glycol, poly-glycerines, poly-glycols, and alkyl ethers of these compounds, the requisite amount of such alcohol is added to the mixture and water is removed therefrom by evaporation until the paste has the desired dye strength. The compositions prepared in this way comprise fluid pastes consisting of dispersions of the finely-divided vat dye. The compositions are relatively stable and do not settle on standing over a relatively long period of time. Furthermore, as compared with many available vat dye pastes, they are in a fluid or free-running state. Thus they are adapted to be efllciently 'and quickly incorporated with the other ingredients of padding baths and printing pastes to prepare such baths and pastes in a form such that the resulting compositions may be efficiently employed in dyeing and printing.

When preparing the vat dye compositions of the present invention in the form of vat dye powders, the paste prepared as described above, but usually with little or no high-boiling watermiscible alcohol therein, may be concentrated and/or dried as by means of a vacuum or atmospheric rotary drum drier by spray drying or by means of the addition to the paste of an anhydrous hydrate-forming inorganic salt. It is preferable, however, when preparing the. powders to add to the paste before drying a substance such as sugar, dextrine, gum or starch, or derivations of alginic acids and/or other suitable additions. In preparing the dry products employing a mechanical drier, the dry product scraped from the drier is in the form of flakes,

scales, or grains, and may be used as such, but i may also be ground to produce a finely-divided powder.

The esters employed in the vat dye compositions of the present invention are such as are derivable from aromatic polycarboxylic acids,

The said esters may be derivatives of aliphatic mono-hydric or poly-hydric alcohols, or of mono-, or poly-hydric hydro-aromatic alcohols, cycloaliphatic alcohols, heterocyclic alcohols, aralkyl alcohols, mixed aliphatic-hydro-aromatic alcohols, or of monoand poly-hydric alcohol'ethers. As examples of such alcohols there may be mentioned ethyl, propyl, allyl', butyl, amyl, hexyl, heptyl, octyl, and the like alcohols; cyclohexanol, methyl cyclohexanol, cyclopentanol, tetrahydrofurfuryl, alcohol, benzyl' alcohol, phenyl ethyl alcohol, phenyl methyl carbinol, the various terpene alcohols, ethylene, propylene, di-ethylene and tri-ethylene glycols, and the like; and the methyl and ethyl ethers of ethylene, diethylene or other glycols. As typical alcohols there may be also mentioned the following alcohols which are obtainable as vby-products in the production of methanol by the catalytic hydrogenation of mixturesof carbon monoxide and carbon dioxide: 4-methyl-1-pentanol; 2-methyll-pentanol; 2,4-dimethyl-l-pentanol; 3-methyl- Z-pentanol; 2,4 dimethyl 3 pentanol (di-isopropyl-carbinol) 2-methyl 3 pentanol; 4- methyl-l-hexanol 2,4-dimethyl-1-hexanol; 2,5- dimethyl-3-hexanol; Z-ethyl-butanol; and others of like character.

The above parent alcohols may be primary or secondary but all of them are characterized by containing no aliphatic radicals containing more than 8 aliphatic-carbon atoms in a straight carbon chain. The esters derived from alcohols wherein the direct chain between the esterified alcohol function and the nearest branching point in the ester group (alcohol residue) is not long-' er than 4 or at most 6 carbon atoms, are particularly valuable for use in the vat dye compositions.

Where in the appended claims an ester of an alcohol and an aromatic or aliphatic carboxylic acid is referred to it will be understood that an ester derivable from an alcohol selected from any of the above described classes and an aromatic or aliphatic carboxylic acid is intended, unless otherwise indicated.

It will be understood that the alcohols from which the esters are derivable may contain substituents which do not alter the essential physical or chemical characteristics of the esters. As indicated above, polyhydric alcohols may be employed and in this case either one or both of the hydroxyl groups may be esterified with the carboxylic' acid group of the acid employed. When only one of the hydroxyl groups is esterified, one or more free hydroxyl groups remain, which are not objectionable and in some cases appear to have an advantageous effect-upon the properties of the esters. The amino group may also be mentioned as an example of a substituent which may be present in the alcohol residue of the esters, valuable esters adapted for use in the vat dye compositions being derivable from amino alcohols. Also, the alcohols may contain alkylamino substituents.

Although any of the above described esters may be used with advantage in theyat dyecompositions of the present invention, .it will be understood that these esters will vary in'degree in their possession of the valuable properties characteristic of the class. It has been found that the best results are obtained with esters of the above class which display high solubility in aqueous so,- lutions and/or alkaline printing pastes; Accordingly, the preferred esters are those which are derived from loweraliphatic alcohols (is, containing 2 to 6 carbon atoms), cycloalkyl alcohols, and aromatic alcohols. It has been found that esters which are derivatives of isobutyl alcohol are of markedly high value. For similar reasons the esters that are derivatives of aliphatic polycarboxylic acids, particularly those that contain from 3 to 6 carbon atoms, are preferred for use in the compositions of the invention.

In view of the foregoing disclosure, it will be readily apparent that a large number of esters are available for use in the compositions of the invention. The following esters (described in the form of the free acids) are given as examples of typical esters of theclass hereinabove disclosed: isobutyl acid .phthalate, isobutyl acid succinate, p-carboxyl-isobutyl cinnamate, mono-n-amyl adipate, mono-isobutyl pyrotartrate, and monoisopropyl glutarate. It has been .found that of the above esters, isobutyl acid succinate, particularly in the form of the sodium salt, produces especially valuable results when incorporated in vat dye compositions.

The esters are preferably employed in the form of their neutral soluble salts. The alkali metal salts, or the salts obtained by neutralizing the acid esters with organic derivatives of ammonia, are especially important. As examples of suitable organic derivatives of ammonia, the following are mentioned: the alkylolamines (e. g.,

"mono-db, or triethanolamine); the alkylol diamines, (e. g., 1,2-di-(2'-ethanolamino) ethane and 1,3-di-(2'-ethanolamino) -2-propanol) the quaternary alkylolamines, the diquaternary alkylolamines (e. g., tetra-hydroxy-ethylamine ammonium hydroxide. hexa hydroxy ethyl ethylene diammonium hydroxide); and the quaternary aralkyl-alkyl ammonium hydroxides or the aralkyl-hydroxyalkyl-ammonium hydroxides (e. g., tri-methyl-benzyl ammonium hydroxide, tri- (hydroxy-ethyl) -benzylammonium hydroxide, etc.).

The valuable effects resulting from the inclusion of the above described esters in vat'dye-coinpositions in accordance with the present invention are noticed both in vat dye pastes and powders from which dyeing compositions (baths and printing pastes) are prepared and also in the dyeings and printings obtained with the ultimate compositions.

The value of vat dye compositions is primarily dependent upon the excellence of the dyeings and printings obtained therefrom. The physical form of vat dye pastes and powders prior to their use bined or commingled with the vat dye particles,

as to form therewith a composition resembling a solid dispersed suspension. The particles of the vat dyes, therefore, are prevented from combining to form larger particles which. would be difilcult to disperse'in a padding bath or printing paste.

When the vat dye pastes and powders are incorporated with the other usual ingredients of vats, padding baths, or printing pastes, several advantageous results are obtained. First, as predyeing or printing textiles.

viously noted, the compositions may be mixed readily with such ingredients to form homogeneous dyeing compositions. Further, it appears that the esters act to increase the solubility of leuco vat dyes and increase the strength and brilliancy of the dyeings and printings obtained. This is because, while leuco vat dyes are regarded as being soluble in alkaline solutions, and because of this solubility may be taken up by the fiber to be dyed, they are not freely soluble and their increased solubility caused by the esters accelerates the rate of their absorption or adsorption by the fiber.

The vat dye compositions of the present invention are particularly valuable as compared with ordinary vat dye compositions when they are applied to synthetic fibers composed of regenerated cellulose, or to unbleached natural fibers, such as cotton and raw silk. It is known that these latter fibers do not, as a rule, readily absorb the reduced vat dyes because of their coating of natural waxes which act as resist agents.

As before stated, the soluble esters of this invention may be used per se or in admixture with other substances ordinarily used in the art of These substances may, be in the nature of the alkyl partial inorganic esters specifically disclosed in my patents above referred to, other substances used in dyeing and printing, such as the alkylolamines, polyhydric alcohols, and ethers, e. g., the ethers of diethylene glycol, glucosic compounds, dextrines, gums, starches, etc., or compounds in the nature of printing catalysts, such as heavy metal compoundsor the heavy metal salts of alkyl partial esters, such as isobutyl-nickel-sulfate, or the heavy metal salts of the soluble carboxylic esters of the present invention, themselves.

Inasmuch as the quality and dispersibility of the resulting dye composition are dependent to a considerable extent upon the original degree of dispersion of. the dye in the suspension or in the dry form, the vat dye is preferably treated in the highly dispersed form. A suitable dispersing agent is preferably incorporated into the disprsion or suspension so as to aid in preventing precipitation and agglutination of the dye particles during storage or during the drying and to increase the fluidity and render easier the incorporation of the soluble salts of the carboxylic acid esters.

Among the dispersing agents which may be employed for this purpose there may be mentioned, for example, the sulfonic acids of benzene, hydroxybenzenes, naphthalene, hydroxynaphthalenes, their nuclear alkyl, nuclear aralkyl, and hydrogenated derivatives, as well as aldehyde condensation products thereof (as for example, 2,6-napthalene-disulionic acid, 1,7-naphthalene- -disulfonic acid, 2,8-naphthalene-disulfonic acid,

isopropyl-naphthalene-sulfonic acids. dibutylnaphthalene-sulfonic acids, amylnaphthalenesulfonic acids, butyl-benzyl-naphthalene-sulfonic acids, cyclo-hexylnaphthalene-sulfonic acids, methylene-d1(p-naphthalene-suli'onic acid, methylene-di (di-isopropyl-naphthalene-sulfonic acid) in the form of the free acids or salts (e. g.,.alkali metal salts), etc.; sulfite cellulose waste liquors and their mildly oxidized products and evaporated residues; sulfonated resins; abietene, abietine and abietane sulfonic acids; soaps; sulfonated higher fatty acids, fats and oils; and the like, as well as mixtures of two or more of such substances.

Further, additional substances having diluent,

anti-foaming, assisting, wetting, catalytic, enolyzing, or other suitable action in the subsequent use of the compositions may also be incorporated into the compositions of the present invention, preferably while the latter are in the form of aqueous suspensions or in the form of non-drying pastes containing high boiling alcohols or alcohol ethers.

In preparing the vat dye pastes and powders in accordance with a preferred manner of proceeding, the mixture of vat dye in aqueous or high boiling solvent dispersion is agitated with the appropriate amount of the carboxylic acid ester salt together with the other substances, if added, until a homogeneous paste is formed, or the mixture of the aqueous suspension of the dispersed vat dye and a carboxylic acid ester salt together with the other substances, if added, is evaporated with agitation until a thick paste is formed, with or without the aid of vacuum and preferably at a temperature not exceeding 100 C. The resulting paste constitutes a valuable vat dye paste. If desired, it may be brought to substantial dryness to form a dry vat dye composition. Thus, the paste may be evaporated to dryness on an atmospheric or vacuum rotary drum drier, and the dry product scraped off in the form of flakes, scales, or grains which may be used as such, or the paste, with or without preliminary evaporation, may be admixed with a suitable hydrateforming'soluble salt in an anhydrous condition, such as anhydrous trisodium phosphate, and the admixture stirred to produce a dry product. If desired, the dry product may be disintegrated in any suitable manner into a powder.

Mixtures of the carboxylic acid ester salts or mixtures of them with 'alkyl inorganic ester salts, disclosed in .my patents referred to above may also be employed in accordance with the present invention. Further, the esters used in the com positions of the invention may be used together with or in place of the esters disclosed in my applications Serial Nos. 253,345 and 253,346, filed of even date herewith.

The amount of the soluble carboxylic acid esters employed in the preparation of the compositions of the present invention may be varied over a considerable range, depending in part upon the concentration of vat dye in the composition, the use to which the composition is to be put, and whether or not other diluents and other materials having a catalytic, assisting, wetting, enolyzing, dispersing. or other action, are included in the composition.

The invention may be employed in connection with vat dyes of all types including those derived from anthraquinone, indophenols, various indigoid, thioindigoid and indirubin compounds, etc.; as for example, indanthrones, pyranthrones, fiavanthrones, dibenzanthrones, isodibenzanthrones, perylene vquinones, anthranthrones, dibenzpyrene quinones, anthrimido-carbazoles, naphthacridones, indigo, thioindigo, indirubin, etc., including derivatives thereof, such as their halogen, nitro, sulfur and/or alkoxy derivatives.

It should be noted that while the vat dyes in the compositions of the invention are preferably in the unreduced form, they may also be in the reduced or leuco form. For example, leuco ester salts of vat dyes and leuco compounds of vat dyes prepared by careful acidification of an alkaline v'at, or by other methods, may be used, if desired.

, Although it is generally preferable and desirable, in order to take full advantage of their properties, to employ the esters in vat dye pastes or powders which are used in the preparation of padding baths or printing pastes, the esters may also be mixed with the other ingredients used in padding baths or printing pastes at the time these compositions are prepared. In proceeding in this way, the dye may be introduced into the mixture in the form of a press cake or an ordinary dye or other form of paste, the ester or esters being added at any desired or suitable point in the preparation of the compositions.

In the foregoing description, the use of the vat dye compositions in the dyeing and/or printing of textile materials has been stressed since this is the most important application of the compositions. The compositions, however, especially when in the form of powders, may be used in the preparation of dispersions of vat-dyes for use in the pigment form in the dyeing of paper, the tinting of fibers and other materials, and the like. The ready dispersibility of the compositions makes them especially valuable for such purposes.

The invention will be further described in connection with the following specific examples (in which the parts are by weight), which are given to illustrate the invention. It will be realized, however, that the invention is not limited thereto but that changes may be made in the materials treated and their proportions, manipulative steps, and other conditions without departing from the scope of the appended patent claims.

Example 1.400 parts of indigo paste (con-- taining 20% of pure indigo as shown by indigotine titration and resulting from the precipitation of indigo from an alkaline solution of indoxyl by aeration) are stirred with two parts of Leukanol until a thin fluid paste is obtained.

13 parts of cane sugar and parts of normalbutyl sodium succinate are then added, the mixture is stirred until solution of the mono-butyl succinate is complete, and the resulting mixture is evaporated with stirring until a thick paste is formed. The thick paste is then placed in drying pans and evaporated to dryness. The dry product is ground and screened.

There is thus obtained an indigo powder containing 80 per cent of indigo which, when added Instead of the normal-butyl sodium succinate,

an equal amount of isopropyl sodium succinate. or amyl sodium pyrotartrate may be used.

Example 2.To 100 parts of the chlorinated indanthrone vat dye known as National Carbanthrene Blue BCS (Color Index #1114) in the form of an aqueous suspension or commercial paste containing 18 per cent of total dye solids, there are added, with stirring, 2 parts of Leukanol (or 6 parts of a 30 per cent solution of Leukanol), 50 parts of cane sugar, and 25 parts/of dextrine. The suspension is stirred until homogeneous, and then 5 parts of sodium isobutyl phthalate are added and the mixture is stirred until solution of the monoalkyl phthalate is complete. The resulting mass, either as such. or after evaporation, may be used as a paste; or it may be evaporated to dryness, ground and screened, as in Example 1, to produce a powder that is readily dispersed when added to water. The product, either in the form of paste or powder, gives uniform dyeings of high tinctorial value when employed to dye fabrics in accordance with standard practice, and especially by the pad and jig method. Instead of the sodium isobutyl phthalate, any one of the soluble carboxylic acid esters herein disclosed may be used.

Example 3.-100 parts of the thioindigoid vat dye known as National Vat Orange R (Color Index #1217) in the form of an aqueous paste containing about 11 per cent of dye solids, are mixed with 2 parts of Leukanol and 87 parts of sodium p-carboxy-isopropyl cinnamate until solution of the latter is complete. The resulting suspension is evaporated to dryness, ground and screened. Instead of the sodium p-carboxy-isopropyl cinnamate, equivalent amounts of the. neutral sodium salt of the mono-n-amyl ester of adipic acid may be employed. 100 parts of a Vat Orange R powder are thus.obtained which, when employed in the preparation of. a printing paste (for example, by mixing 150 parts of the powder with 200 parts of British gum, 140 parts of potassium carbonate, 80 parts of sodium formaldehyde sulfoxylate, 50 parts of glycerine, and 380 parts of water) and. utilized in the printing of rayon materials in accordance with the usual proneutral soluble carboxylic acid ester salt results in a much greater brilliancy of shade and more complete penetration of the material, so that in many' instances there are no back sides and the fastness to crocking is much enhanced.

Example 4.-To 100 parts of National Carbanthrene Blue GCD Double Paste (Color Index #1113) containing 16.5 per cent of dye solids and 1 per cent of Leukanol, there are added-50 parts of sodium isopropyl glutarate and 32.5 parts of urea, and the mixture is stirred until the latter are dissolved. The resulting suspension is evaporated to dryness, ground and screened. A very readily dispersible vat powder is obtained which is suitable for printing as well as dyeing.

In place of sodium isopropyl glutarate, any one or a mixture of the neutral sodium salts of monoalkyl carboxylic esters hereinbefore mentioned can be used.

As before stated, the esters described above can be employed in' compositions containing any vat dye. which may be present in the compositions of the invention:

The following are examples of vat dyes I claim:

1. A vat dye composition comprising a vat dye compound and a soluble organic ester of an organic poiycarboxylic acid, said ester containing at least one unesterified carboxyl group inthe acyl radical and being free from other solubilizing groups, said ester being free from aliphatic radicals containing a totalof more than 12 aliphatic carbon atoms and from aliphatic radicals con- I taining more than 8 aliphatic carbon atoms in a as the-sole solubilizing group, said ester being free from aliphatic radicals containing a total of more than 12 aliphatic carbon atoms and from aliphatic radicals containing more than 8 aliphatic carbon atoms in a straight carbon chain.

3. A vat dye composition comprising a vat dye compound and a soluble salt of an organic ester of an aliphatic polycarboxylic acid containing not more than 8 carbon atoms, said ester containing an unesterified carboxyl group in the acyl radical as the sole solubilizing group, said ester being free from aliphatic radicals containing a total of more than 12 aliphatic carbon atoms and from aliphatic radicals containing more than 8 aliphatic carbon atoms in a straight carbon chain.

4. A vat dye composition comprising a vat dye compound and a soluble alkali metal salt of an ester of an aliphatic alcohol and an aliphatic polycarboxylic acid containing not more than 8 carbon atoms, said ester containing an unesterifled carboxyl group in the acyl radical as the sole solubilizing group, said ester being free from aliphatic radicals containing a total of more than 12 aliphatic carbon atoms and from aliphatic radicals containing more than 8 aliphatic carbon atoms in a straight carbon chain.

5. A vat dye composition comprising a vat dye compound and a-soluble alkali metal salt of a mono-ester of an unsubstituted aliphatic dicarboxylic acid containing 3 to 6 carbon atoms with an aliphatic alcohol containing 2 to 6 carbon atoms.

6. A vat dye composition comprising a vat dye compound and a soluble alkali metal salt of a mono-ester of an aromatic dicarboxylic acid of the benzene series and an aliphatic alcohol containing 2 to 6 carbon atoms.

7. A vat dye composition comprising a vat dye compound and a soluble alkali metal salt of a butyl ester of an organic polycarboxylic acid, said ester containing an unesterified carboxyl group in the acyl radical as the sole solubilizing ro 8. A vat dye composition comprising a vat dye compound and a soluble alkali metal salt of an organic mono-ester of succinic acid, said ester being free from aliphatic radicals containing a total. of more than 12 aliphatic carbon atoms and from aliphatic radicals containing more than 8 aliphatic carbon atoms in a straight carbon chain.

9. A vat dye composition comprising a vet dye compound and a soluble alkali metal salt of a mono-ester of succinic acid and an aliphatic'alcohol containing 2 to 6 carbon atoms.

10. A vat'dye composition comprising a vat dye compound and sodium isobutyl phthalate.

11. A vat dye composition comprising a vat dye compound and sodium isobutyl succinate.

12. A vat dye paste adapted for use in the preparation of printing pastes and padding baths comprising an unreduced vat dye, a dispersing agent, and a soluble organic ester of an organic polycarboxylic acid, said ester containing at least one unesterifled carboxyl group in the acyl radical and being free from other solubilizing groups, said ester being free from aliphatic radicals containing a total of more than 12 aliphatic carbon atoms and from aliphatic radicals containing more than 8 aliphatic carbon atoms in a straight carbon chain.

13. A vat dye paste adapted for use in the preparation of printing pastes and padding baths comprising an unreduced vat dye, a dispersing agent, and a soluble salt of an organic ester of an allphatic polycarboxylic acid containing not more than 8 carbon atoms, said ester containing an unesterifled carboxyl group in the acyl radical as the sole solubilizing group, said ester being free from aliphatic radicals containing a total of more than 12 aliphatic carbon atoms and from aliphatic radicals containing more than 8 allphatic carbon atoms in a straight carbon chain.

14. A vat dye paste adapted for use in the preparation of printing pastes and padding baths comprising an unreduced vat dye, a dispersing agent,-

and a soluble alkali metal salt of an aliphatic alcohol and an aliphatic polycarboxylic acid containing not more than 8 carbon atoms, said ester.

containing an unesterified carboxyl group in the acyl radical as the sole solubilizing group, said ester being free from aliphatic radicals containing a total of more than 12 aliphatic carbon atoms and from aliphatic radicals containing more than 8 aliphatic carbon atoms in a straight carbon chain.

15. A vat dye paste adapted for use in the preparation of printing pastes and padding baths comprising an unreduced vat dye, a,dispersing agent, and a soluble alkali metal salt of a mono-ester of an unsubstituted aliphatic dicarboxylic acid containing 3 to 6 carbon atoms with an aliphatic alcohol containing 2 to 6 carbon atoms.

16. A vat dye paste adapted for use in the preparation of printing pastes and padding baths comprising an unreduced vat dye, a dispersing agent, and a soluble alkali metal salt of a butyl ester of an organic polycarboxylic acid, said ester containing an unesterified carboxyl group in the acyl.

radical as the sole solubilizing group.

17. A vat dye paste adaptedfor use in the preparation of printing pastes and padding baths comprising an unreduced vat dye, a dispersing agent, and a soluble alkali metal salt of a mono-ester of succinic acid and an aliphatic alcohol containing 2 to 6 carbon atoms.

18. A vat dye paste adapted for use in the preparation of printing pastes and padding baths comprising an unreduced vat dye,.a dispersing agent, and sodium isobutyl phthalate.

19. A vat dye paste adapted for use in the preparation of printing pastes and padding baths comprising an unreduced vat dye, a dispersing agent, and sodium isobutyl succinate.

JEAN G. KERN.