US2256808A - Process of dyeing with vat dyes - Google Patents

Description

Patented Sept. 1941 PROCESS OF DYEING WITH VAT DYES ,Jean G. Kern, East Aurora, N. Y., assignor to National Aniline & Chemical Company, Inc., New York, N. Y., a corporation of New York No Drawing. Application November 28, 1938,

Serial No. 242,744

11 Claims.

This invention relates to the art of dyeing and particularly to the art of dyeing cellulosic textile fibers, such as cotton or regenerated cellulose fibers in the form 01 yarns or piece goods, with vat dyes.

As is well known, the vat dyes are insoluble in water in the unreduced form, but upon reduction with a reducing agent, such as sodium hydrosulfite, they are converted to leuco forms which are soluble to a certain extent in alkaline solutions. In dyeing with these dyes, the procedures used involve either first forming an alkaline solution or suspension of a leuco vat dye, contacting the material to be dyed with the solution or sus-v pension, and then oxidizing the dye in the fabric,

or applying the unreduced vat dye to the material, subsequently passing the impregnated material through an alkaline solution containing a reducing agent whereby the dye in the material is converted to the leuco form and penetrates the material, and then oxidizing the dye.

At the present time, piece goods are generally dyed with vat dyes in any one of three methods involving the use of the above procedures. In the first two methods, a jigger and a padding machine are used, respectively. They are similar in that a non-acid solution or suspension of a leuco vat dye is employed, the piece goods being brought into contact with the solution or suspension so as to impregnate the material with the relatively soluble leuco vat dye. The dyeing is then completed by oxidizing the leuco dye in the goods, as by passing .the goods through an oxidizing bath, and finishing in the usual manner. In thethird method for dyeing piece goods with vat dyes, the goods are padded with a padding liquor containing an unreduced vat dye, water, and a thickener, and are then passed through an alkaline bath of hydrosulfite wherein the unreduced dye is converted tothe leuco form in the presence of the goods. The dyeing of the piece goods 7 is completed in a manner, in general, simil r to that employed in dyeing piece goods in a re uced solution. Raw stock and spun cotton are generally dyed in dyeing machines in which these ma-- terials are brought into contact with a non-acid solution or suspension of a leuco vat dye- Dyeing of yarns is accomplished in a similar manner except that the solution or suspension of the leuco vat dye is passed through the yarns disposed on perforated beams or the like.

The reduced bath which is required in most of the above-described processes is ordinarily made by passing a water mix of the vat dyestuff inch) to form an aqueous paste, diluting the paste' somewhat with water, and addingit to a dye bath containing a corresponding amount of alkali and a reducing agent such as sodium hydrosulfite. The dyeing is carried out by first raising the temperature of the dye bath to a suitable point according to the particular dyestuiT used and, when complete reduction of the dyestufi is effected, starting the dyeing operation. It is important in order to secure satisfactory results that during the dyeing operation the dye be kept in as complete solution or dispersion as possible. Although the theoretical considerations uponwhich the process of dyeing with vat dyes is based are not clearly understood, it is known that results, which are evidenced by the brilliancy', penetratiomiastness, and yield in the process, are'better as the I leuco vat dyes are more finely divided and more nearly in true solution,

In order to obtain a solution or fine dispersion of the leucoyat dyes in the dye bath, it is important first that the dyestuff as added to the dye bath be very finely divided. To this end the dyestufi, prior to being introduced into the dye bath, is converted to a finely-divided form and is ordinarily employed in the form of a paste prepared as described above by screening-a mixture of the dyestuff and water. Pastes of this type may contain, in addition, dispersing agents and/or other suitable ingredients. The dyestufi may also be supplied in the form of a powder containing the finely-divided vat dyestufl. and materials which assist in making the powder readily dispersible in water. Even with the use of the dyestuff pastes and powders at present in commercial use, some color value is often lost because the fiber does not absorb all of the dye present in the bath. This is due to the fact that part of the dye is not' in a suitable adsorbable form. The unused'and therefore wasted dvestui! in many cases adheres loosely to the surface of the fibers and is washed ofi. readily during the soaping operation which follows the dyeing. Also, in many cases the production of even dyelngs has been prevented because of the excessive afiinity of the reduced dyestufl for the fiber, some portions of the fiber being dyed more readily than other portions.

It'is an object of the invention to provide a process for dyeing with vat dyes which is characterized by producing dyeings of excellent penetration, brilliancy, and levelness.

Another object of the invention is to provide a through a fine screen (e. g.,.200 mesh per square process of dyeing with vat dyes in which the vat dyes are substantially completely exhausted from the dye bath, and excellent yields are obtained.

Another object of the invention is to provide a valuable process of dyeing with vat dyes with which satisfactory results ordinarily are not obtained when using commercial processes.

A further object of the invention is to provide dyeing liquors containing vat dyes, which liquors may be employed in the production of valuable dyeings.

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

The present invention is based upon the discovery that certain hydroxylated aliphatic polyamines, which are identified more fully hereinafter, possess a combination of properties which make them valuable additions to dye baths for the dyeing of textile fibers, particularly natural and artificial cellulosic fibers, with vat dyes. Thus, it has been found that by mixin one or more of these hydroxylated aliphatic polyamines with a finely-divided vat dye and water and then introducing the resulting mixture into an aqueous solution containing corresponding amounts of alkali and a reducing agent such as sodium hydrosulfite, a dye bath consisting of a true solution of the leuco vat dye is obtained which produces excellent results when used in dyeing textile fibers. Similarly, it has been found that the hydroxylated aliphatic polyamines can be incorporated with advantage in a padding liquor containing an unreduced vat dye. In this case,

- they assist in producing an effective dispersion of the insoluble dye in the padding liquor and increase the solubility of the leuco vat dye formed when the material impregnated with the padding liquor is passed through the jigger containing the alkaline solution of the reducing agent. The latter effect may also be obtained by adding the polyamines to the alkaline reducing solution in the jigger.

The hydroxylated aliphatic polyamines which are adapted for use in the process and compositions of the present invention are aliphatic amino compounds containing a plurality of amino groups and at least one hydroxyl group. The central aliphatic radical of the polyamines may be a chain or cyclic alkyl radical. The amino groups of these polyamines may be unsubstituted or may contain alkyl radicals or aralkyl radicals as substituents. As employed in this specification and claims the term alkyl radicals" denotes and includes chain and cyclic alkyl radicals. The hydroxyl group or groups of the compounds may be in the central aliphatic radical thereof or may be in an N-alkyl radical or radicals. Where the central aliphatic radical is free from hydroxyl groups at least one and preferably two or more of the substituents of the amino groups are hydroxyalkyl radicals containingla maximum of three hydroxyl groups.

Thus the polyamines which may be used in the vat dye compositions may be represented by the following general formula:

wherein R. represents an alkyl radical (which radical may be an open chain or cyclic alkyl radical and may be unsubstituted or may contain substituents which do not alter the essential characteristics of the compound, such as, for example, hydroxyl, alkoxy, and aralkyloxy groups, etc.) X1, X2, X1, and X4 each represents hydrogen, an alkyl'radical, an aralkyl radical. a hydroxyalkyl radical containing a maximum of three hydroxyl groups, or a. part of a cyclic radical including R, and at least one and preferably two or more of the substituents represented by X1, X2, X3, and X4 being a hydroxyalkyl radical of this class when the radical represented by R. is free from hydroxyl groups; and n represents a small whole number. It will be understood that the aralkyl substituents of the amino groups of the compounds may themselves contain substituents, especially hydroxyl groups in the alkyl groups thereof. Where the alkyl group of an aralkyl radical is two carbon atoms in length or longer and contains hydroxyl groups, it is regarded as a hydroxyalkyl radical for the purposes of this invention.

1,2-di-(2-ethanol-amino-) ethane HOCHzCHzNH-CHaCHz-NHCHzCI-HOH 1,2-bis- (di-2' -ethan ol-amino) ethane (HOCHzCHz) eNCH2CH2-N(CH2CH2OH) 2 1 ,2-di- 2 ,3 -propan-diol-amino-) ethane on I on di- (N-butyl-N-ethanolamino-) ethane C(Hl CAH NCHzCH:N

HOCHaCH: CHzCHzOH 1,3-di-(2'-ethano1amino-)-2-propano1 HOCHzCHzNH-CHzCHOHCHz-NHCH2CH2OH 1,3-bis- (di-2'-ethanolamino-) -2-propanol tri- (mono-methyl-amino-methy1-) ethanol CHINHCH;

cnmncm-o 011,011

OHaNHCH: tri (di-methyl-amino-methyl-) ethanol (one aNCH:

( a)2NCH2-C CHzOH (CH3) 2N CH2 l-para-hydroxy-benzyl-amino 2 di -(hydroxyethy1amino-) ethane HOOCHzNH-CHzCHz-N(CH1CHzOH)z 1,2-di- (4'-cyclohexanol-amino-) ethane 1,2-di-(N hydroxycyclohexyl N ethylamino-) ethane 1100,1110 oinl'oon N-CHzCHz-N H5O: CzHt l-para hydroxybenzylamino- 2 hydroxyethyl amino-ethane HoOonmn-cmom-rmombmon 1,2-di (N cyclohexyl-N-hydroxy-ethylamino-) 1 ethane CaHu CoHu '\NCH:CH2' noomon; 011,011,011 N,'N' diethanol diethylenediamine, otherwise known as 1.4-diethanolpiperazine CH:OH2 nocnzcnm NCHzCIhOEi CHa-C a N,N di (propandiol 2,3)-diethylenediamine, I

otherwise known as l.4-di(propandiol-2,3)- piperazine The lower carbon chain compounds of the above type have low melting points, and are viscous liquids at ordinary temperatures; the viscosity of the compounds increasing with increase methods; for example, they may be obtained by the action of alkylene oxides upon: an aliphatic diar'nine as disclosed by Knorr, Ber. vol. 35, page 4471, or by condensation of monoor dialkylolamines with the poly halohydrins of poly alcohols.

where the process involves the use of a non-acid solution of a leuco vat dye, one or more of the hydroxylated aliphatic polyamines above described can be added as such to the dye bath, the dyestuff being'separately added. However, it is usually preferred to mix the polyamines with a vat dyestufi paste comprising essentially a relatively finely-divided unreduced vat dye and water. The resulting mixture is then diluted somewhat with water to. form a suspension which is passed through a screen of the type referred to above. A highly dispersed suspension of the unreduced vat dye is obtained as a result of this treatment and the suspension is added to the dye bath containing the alkali and the reducing agent; The temperature of the dye bath is then brought to the appropriate dyeing temperature required at the beginning of the dyeing operation. By prothe dyeing of piece goods in a jigger or padding device or it may be used for the dyeing of raw stock, spun cotton, or yarn in the machines which ordinarily. takes about 45 minutes, the

material is rinsed and treated with an oxidizing agent such as sodium bichromate or sodium perborate, rinsed, thoroughly soaped, again rinsed,

allowed to dry, and finished according to the usual methods.

In dyeing textile fibers in accordance with the present invention using the pad and jig process, one or more of the above-described hydroxylated aliphatic polyamines can be used in the padding liquor or in the development bath, or both. It is usually preferable to use the polyamines in the padding liquor and in this case the unreduced vat dyestuff is mixed with one or more of the hydroxylated aliphatic polyamines and to the resulting mixture water, a gum, and an oil, such as bleaching oil, are added to form a padding liquor having a desired concentration of the ingredients. The material to be dyed is then padded with the padding liquor, dried, and later developed on a jigger in a solution containing The process of the present invention can be 0 the alkali and reducing agent in the'manner above described. Additional dyestufi may of course be added in the jigger if necessary.

Instead of preparing ,a mixture for incorporation withthe other ingredients of a vat or padding liquor as described above, there may be employed for the preparation of these dyeing solutions or suspensions a vat dyestuif paste prepared as described in my application Serial No. 242,742, filed of even date herewith, and containing one or a mixture of the hydroxylated aliphatic polyamines. Further, in place 'of the vat dyestufi pastes referred to above, there may be used vat dye powder c'ompositio'ns' as described in my United States Patents Nos. 2,067,926 and 2,074,150, in which case the dyestuff powders are first impasted with water and the resulting vat dye pastes are then used in thesame manner as the pastes of finely-divided vat dye and wa-- ter referred to above.

Although it will be understood that the invention is not limited to any theoretical explanation, Y it appears that the advantages resulting from the use of the hydroxylated aliphatic polyaminesin the present process are at least partly due to the fact that the polyamines are capable of forming amine salts with leuco vat dyes which salts are relatively soluble in alkaline solutions as compared with the alkali salts of the leuco vat dyes. Thus, as above pointed out, while in the normal vat a portion at least of the leuco vat dye is in the form of a suspension rather than a true solution, by adding a proportion of a hydroxylated aliphatic polyamine of the above class to the vat, the portion of the leuco vat dye in dispersed form is rendered substantially completely soluble. This result is probably in part due to the fact that the above hydroxylated aliphatic polyamines are relatively strongly basic, this property making them capable of forming amine salts with the leuco vat dyes. In this way, the hydroxylated aliphatic polyamines are distinguished from the alkylolmonoamines which have been suggested for use in vat dyeing processes, the beneficial effect of the alkylolmonoamines being evidenced only in the cases of certain dyes of the indanthrene series. The increase in the solubility of leuco vat dyes by use of the hydroxylated aliphatic polyamines also appears to be due to the fact that these amines are relatively soluble in water and the combination of a leuco vat dye and a hydroxylated aliphatic polyamine consists substantially of a leuco vat dye containing a water-solubilizing group.

Whatever the explanation, it has been found that the use of the hydroxylated aliphatic polyamine involves several important advantages.

- Thus,'the exhaust of vat dye baths containing the rate of absorption of the dyes by the fiber,

thereby equalizing the depth of dyeing and giving deeply penetrated and level results. The penetration is apparently due to the wetting and penetrating power of the polyamines for the fabric. This action is especially important when dyeing with highly chlorinated blues of the indanthrene type, such as Carbanthrene Blue BCS (Color Index No. 1114).

Due to the excellent penetration and fixation of the dyestuif on the material, on soaping the material in a boiling soap solution, the dyestufi remains on the fiber which thus retains the full color value of the penetrated dyestufi'. An important application of the process of the present invention is in the dyeing of shirting material using the indanthrene blues. In this case, it is of utmost importance to obtain shades which do not change in cast on repeated washings'with soap. By using the present process in dyeing shirting material with the various indanthrene blues, vivid and red-cast shades are obtained at the end of the dyeing process, which shades are stable and do not change on repeated soapings. Examples of indanthrene blues are the following: Carbanthrene Blue GCD (C I. No. 1113) and Carbanthrene Blue BCS (C. I. No. 1114) As pointed out above, the hydroxylated aliphatic polyamines employed in the present process are preferably incorporated in the dyeing compositions by mixing them with the dyestufl paste prior'to adding the paste to the dye bath. This is of advantage since the polyamines assist in insuring a well-dispersed condition of the dyestufi, thus expediting the screening operation which ordinarily precedes the incorporation of the dyestufi paste into the dye bath. This property of the polyamines is particularly valuable when the pad and jig dyeing process is used since substantially speck-free suspensions may be obtained which are adapted to be uniformly applied to a material. The present process is especially well adapted for the tinting and dyeing of spun goods in a reduced bath in a continuous manner. Because of the solubilizing power of the hydroxylated aliphatic polyamines, the leuco vat dyes are substantially completely soluble and penetrate rapidly into the fibers when applied by means of a three-roller padding machine.

In order that the invention may be more fully understood, reference should be had to the following examples which illustrate typical processes coming within the scope of the invention. It will be understood, of course, that these examples are given for illustrative purposes merely and are not intended as limitations of the invention.

Example 1.-An 8 /2 per cent shade of Carbanthrene Blue GCD (C. I. No. 1113) on 150 pounds of mercerized cotton piece goods is obtained in the following manner. of Carbanthrene Blue GCD paste are mixed with 6 pounds of 1,2-di-(2-ethanol-amino-)ethane. To the resulting mixture 1 gallon of cold water is added and the suspension thus formed is passed through a fine screen. A speck-free paste is obtained which is added to ajigger dye bath containing 10 pounds of caustic soda, 15 pounds of sodium hydrosulfite (concentrated10 pounds being added immediately and the remaining 5 pounds after one passage), and 100 gallons of water. The temperature is raised to 110 F. and after complete reduction the dyeing is started at this temperature. The temperature is then allowed to rise to 125 F; over a period of 30 minutes and the dyeing operation is carried on at this temperature for about 15 minutes. The goods are then given one wash, four passages in an aqueous solution containing 2 /2 pounds of sodium perborate per 100 gallons at a temperature of 120 F., two cold washes, and five passages in a boiling soap solution containing 3 pounds of soap per 100 gallons. The goods are thereafter rinsed and washed in the open, dried, and finished in the usual manner.

Exampie 2.In this example an 8 /2 per cent shade of Carbanthrene Blue GCD is obtained on 150 pounds of mercerized cotton piece goods using a vat dyestufi paste prepared by mixing 400 parts by weight of a press cake of Carbanthrene Blue GCD (containing 70 per cent water and 30 per cent solids as dry vat dye) with a smooth paste composed of l00 parts of water and 500 parts of 1,2-di-(2-ethanol-amino-)ethane. 12.75 pounds of this vat dye color paste are screened and introduced into a bath consisting of 100 gallons bulk and containing 10 pounds of caustic soda (dry) and 15 pounds of sodium hydrosulfite. The dyeing process in this bath is carried out as described in Example 1.

Example 3.This example offers an illustration of the application of the present invention to the dyeing of the piece goods by the pad and mixing 5 pounds of this vat dyestuffpaste, 11V;

gallons of water, 8 ounces of gum tragacanth,

12.75 pounds I and pounds of bleaching oil, the whole making up 12 /2 gallons bulk. This padding liquor is then used for padding cotton shirting cloth, the pressure of the pad roller being so regulated as to leave 60 per cent of moisture in the padded cloth. The padded material is then dried and developed in a jigger containing a developing bath prepared in .the same manner as the dye bath of Example 2 prior to the addition of the vat dyestufl paste of that example, an additional quantity of the above vat dyestufi past being added to the solution in the jigger so as to produce an 8 /2 per cent dyeing. The oxidation and finishing of the. material are carried out in the I usual manner.

GCD, 11 gallons ofwater, 8 ounces of gum tragacanth, and 5 pounds of bleaching oil to make up a total of 12 gallons bulk. The development bath is th same as that described in Example 3 except that a' quantity of 2-hydroxy- 1,3-di(hydroxyethylamino)propane equal to the amount of the dyestufi is added. The dyeing is carried out in the same manner as in Example 3. In place of the Carbanthrene Blue GCD of this example, there may be employed an equal amount of Carbanthrene Dark Blue DR (C. I. No. 1099) or Carbanthrene Violet 2R (C. I. No. 1104).

Example 5.This is an example of the application of the invention in the dyeing of yarns in packages so as to produce a 5 per cent shade of Carbanthrene Dark Blu DR. The percentages referred to below are based upon the weight of yarn to be dyed. The dyeing liquor is made up by mixing 5 per cent of the ordinary vat color paste of the above dye, 2 per cent of caustic soda (dry), 3 per cent of sodium hydrosulfite, and 3 per cent of1,2-bis-(di-2-ethanol-amino) ethane with enough water'to insure proper circulation, the amount of water'depending upon the size and model of the machine used. The conditions of dyeing are the same as are usually employed in dyeing yarns in packages with vat dyes. After dyeing, th yarn is rinsed, oxidized with approximately 2 per cent of sodium perborate, rinsed, soaped, rinsed, and dried.

If desired, this example may be varied by using a vat dyestufi paste already containing a hydroxylated aliphatic polyamine in place of the vat dyestuiI paste used above. In this case the addition of a hydroxylated aliphatic polyamine as such to the dye bath may be dispensed with. The Carbanthrene Dark Blue DR of the above example may be replaced with other vat dyes; e. g., excellent results may be obtained using Carbanthrene Violet 2R.

As previously indicated, the foregoing examples are merely illustrative of a few of the ways in which the present invention may be practiced. Hence, the procedures herein described may be varied widely within the scope of the invention. Thus, in place of the hydroxylated aliphatic polyamines used in the processes described in the examples, there may be employed one or a mixture of the hydroxylated aliphatic polyamines of the above class; e. g., there may be employed any one or a mixture of those specifically mentioned above. While the results obtained in particular cases willvary depending upon the specific polyamine used, in using any of the above class, the advantages'herein pointed out can be obtained. With respect to the amount of hydroxylated aliphatic polyamine required to produce these advantages, .it will be recognized that this will be dependent upon the dyestuff employed, the material to be dyed, and the specific dyeing procedure used. In this connection it is to be noted that the aliphatic polyamines not only act to increase the solubility of leuco vat dyes, but also appear to act upon textile fibers to increase their ability to absorb the dyes. In general, there should be employed an amount of hydroxylated aliphatic polyamine about equal to. the amount of dystufi employed and ordinarily the amount of hydroxylated aliphatic polyamine should not be reduced below about one-half part by weight for each part by weight .of the dyestufl. Although an excess of a polyamine ordinarily does not have a critical eifect upon the operativeness of the process, the use of an excess is undesirable for economic reasons.

The process of the invention, in general, may be employed with advantage for dyeing with any vat dyestufi. Among suitable vat dyestufls may be mentioned the following:

- Color Index No. Carbanthrene Yellow G paste 1118 Carbanthrene Golden Orange 2RT paste 1097 Carbanthrene Golden Orange G double paste 1096 Carbanthrene Blue Green FFB double paste 1173 Carbanthrene Violet 2R paste 1104 Carbanthrene Dark Blue DR paste 1099 Carbanthrene Flavine GC double powder 1095 Carbanthrene Red Violet'ZRNX paste 1161 Carbanthrene Brilliant Green supra 1101 Brilliant Indigo 4G 1189 wherein R represents an alkyl radical; X1, X2, X3, and X4 each represents a member selected from the group consisting of hydrogen, alkyl radicals, an ethylene radical formed by X1 and X3 together when R is an ethylene radical and n is 1, aralkyl radicals, and hydroxyalkyl radicals containing a maximum of three hydroxyl groups, at least one of the substituents represented by X1, X2, X1, and X4 being a hydroxyalkyl radical of said class when the radical represented by R. is free from hydroxyl groups; and n represents a whole number not greater than 2. I

2. The process of dyeing textile fibers with vat dyes which comprises contacting the fibers with a bathcomprising a non-acid solution of a leuco vat dye and a hydroxylated aliphatic diamine containing at least one N-hydroxyalkyl group,

said diamine being free from hydroxalkyl groups containing more than three hydroxyl groups and free from N-substituents other than alkyl groups, aralkyl groups and their hydroxy derivatives.

" 3. In the dyeing of textile fibers with vat dyes by the pad and jig process in which the fibers are impregnated with a padding liquor comprising a suspension of an unreduced vat dye and are then passed through a developing bath comprising an alkaline reducing solution, the improvement which comprises incorporating in the padding liquor a hydroxylated aliphatic diamine containing at least one N-hydroxyalkyl group, said diamine being free from hydroxyalkyl groups containing more than three hydroxyl groups and free from N-substituents other than alkyl groups, aralkyl groups and their hydroxy derivatives.

4. In the dyeing of textile fibers with vat dyes by the pad and jig process in which the fibers are impregnated with a padding liquor comprising a suspension of an unreduced vat dye and are then passed through a developing bath comprising an alkaline reducing solution, the improvement which comprises incorporating in the developing bath a hydroxylated aliphatic diamine containing at least one N-hydroxyalkyl group, said diamine being free from hydroxyalkyl groups containing more than three hydroxyl groups and free from N-substituents other than alkyl groups, aralkyl groups and their hydroxy derivatives.

5. In the dyeing of textile fibers with vat dyes from a dye bath, the improvement which comprises carrying out the dyeing with the aid of a hydroxyalkylated alkylene diamine containingat least one N-hydroxyalkyl group, said diamine being free from hydroxyalkyl groups containing more than three hydroxyl groups and from N- substituents other than alkyl groups, aralkyl groups and their hydroxy derivatives.

6. A vat dye bath comprising an alkaline aqueous solution of a leuco vat dye and a hydroxylated aliphatic polyamine of the following general formula:

wherein R represents an alkyl radical; X1, X2, 11;,

and X4 each represents a member selected from said class when the radical represented by R is free from hydroxyl groups; and n represents a whole number not greater than 2.

7. A padding liquor for dyeing with vat dyes comprising an aqueous suspension of an unreduced vat dye, a thickener, and a hydroxylated aliphatic polyamine of the following general wherein R represents an alkyl radical; X1, X2,

. n is 1, aralkyl radicals, and hydroxy-alkyl radicals containing a maximum of three hydroxyl groups, at least one of the substituents represented by X1, 1%, X3, and X4 being a hydroxyalkyl radical of said class when the radical represented by R is free from hydroxyl groups; and n represents a whole number not greater than 2.

8. A developing bath for developing unreduced vat dyes on piece goods comprising an aqueous solution containing caustic soda, sodium hydro sulfite, and a hydroxylated aliphatic polyamine of the following general formula:

wherein R represents an alkyl radical; X1, X2,

IQ, and X4 each represents a member selected from the group consisting of hydrogen; alkyl radicals, an ethylene radical formed by X1 and X2 together when R is an ethylene radical and n is 1, aralkyl radicals, and hydroxyalkyl radicals containing a maximum of three hydroxyl groups, at least one of the substituents represented by X1, X2, X3, and X4 being a hydroxyalkyl radical of said class when the radical represented by R is free from hydroxyl groups; and 11. represents a whole number not greater than 2.

9. In the dyeing of textile fibers with vat dyes from a dye bath, the improvement which comprises carrying out the dyeing with the aid of 2- hydroxy- L ,,3-di (hydroxyethylamino) propane.

10. In the dyeing of textile fibers with vat dyes from a dye bath, the improvement which comprises carrying out the dyeing with the aid of 1,4- di (propandio1-2,3) -piperazine.

11. In the dyeing of textile fibers with vat dyes from a dye bath, the improvement which comprises carrying out the dyeing with the aid of 1,2-di(4 cyclohexanol-amino-) ethane.

JEAN G. KERN.