US2318133A - Process of dyeing with vat dyes - Google Patents

Description

Patented May 4, 1943 2,318,133 I I i PROCESS or? DYEING wrrn va'rnvns 7 William M. Wentz, Carneys Point, N. J;, assignor to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application Deccmber'31, 1940, Serial N0. 372,578

11 Claims. (01. 8-34) This invention relates to a process of dyeing with vat dyes and more particularly to an improved process for applying vat dyes to fabrics duced in such solution with reducingagents, such as with sodium -hydrosulfla, to the leuco known method of vat dyeing where even mediumly strong shades were required; I

Modified derivatives of the vat fcolors have been produced with the hope of finding a method of applying the vat colors to the alkali sensitive fibers by methods that would not require strong alkalies. As illustrative of f this type arethe dyes known in the trade as Indigosols which are leuco sulphuric acid esters of certain vat colors which are dyed from an aqueous solution and developed by means of diluteacids and suitable oxidizing agents which are not as harmful to wool, silk and cellulose acetate as are the strong alkalies. These colors, however, are very.

form, which as the alkali metal salt is-quit 15 expensive t manufacture and e difficult t v "'yappirto-fibers in even mediumly strong shades soluble in relatively strong alkali solutions but is much less soluble in solutions of low alkalinity. The process of dissolving vat colors in alkaline hydrosulfite solutions is usually referred to as vatting.

While certain of the vat colors when in the form of the alkali'metal salts of the leuco are soluble in sodium carbonate solutions in sulficient amount to permit dyeing fibers'from such a solution in weak shades, the class as a whole and particularly those of the anthraquinone series are not sufficiently soluble in such alkaline solution to permit, the preparation of comv mercially satisfactory dyeings therefrom.

Because it is necessary to use the vat dyes in a caustic alkali solutions their use has been limited almost exclusively to the dyeing of cotton or other cellulose fibers, for silk, wooland cellulose acetate are deleteriously affected by caustic alkali solutions of the strength normally used in vat dyeing.

With the development of the newer fibers such as cellulose rayons, cellulose acetate, nylon, etc., great advances have been made in fabric design by mixing these fibers with wool, silk and cotton. For instance, viscose rayon in filament or staple form, cellulose acetate, wool, silk or nylon may be woven as effect threads with cotton or with each other or they may be mixed in staple form to give threads from which many novel and vale uable fabrics may be produced, and many such fabrics are on the market today.

The advance of these new fabrics, however, has been retarded somewhat because of the difiiculties encountered in dyeing them in fast shades for the fast colors of the vat dye class could not be commercially applied to the alkali sensitive fibers or to goods containing such fibers by the usual methods of dyeing, or by any previously because of theirflirhithd solubilityin. "water and their lack of substantivity for mostfibers,

known as the continuous piece goods dyeing.

process wherein the fabric ispassedthrough the padder, developing bath, oxidizing bath} soaper, etc., in a continuous piece.- Such con-s tinuous dyeing processes introduce difiiculties that arenot experienced in the ordinary "batch dyeingprocesses, although in certain cases the continuous process permits the application of vat dyestuffs to fabrics that could not ordinarily be dyed with vat dyes by the batch process. Because of the speed with which the fiber passes through the caustic alkali solution certain fabrics containing caustic alkali sensitive fibers such as wool and cellulose acetate could be dyed with out harmfully affecting such sensitive fibers; where the temperature and time of treatment. were held at a minimum. Such process, however, can be used only for dyeing in verylight shades, because the restricted conditions do not permit sufficient absorption of the dyeto give by passing the material, after being padded with norrna lIy takes p1ace inthe alkalinity of the re-reduction bath. Q Hebden, U. S. 1,148,966, describes a process for dyeing with rat colors by the batch process in which the color is forced on the goods by progressively diminishing the solvent capacity of the bath fontheileuco compound during the dyeing operation. .It-is also alleged that this method can beemployed in the dyeing of animal fibers with vat dyes, although the process has never been commercially successful for such fibers. This process, however, can not be applied to con-- tinuous. piece goods dyeing processes. a

In the continuous piece goods dyeing of cotton fabrics by a process such as described, for instance, in the-Tlce patent above mentioned, the

re-reduction bath isoriginally charged with the same color that is used in the padding bath, caustic soda and sodium hydrosulflte but in reduced concentrations. However, the chemical reaction which normally occurs, due to the reduction of theyatdye and to exposure of the hydrosulflte on the goods and in the open vat 'as'it comes in contact with air, forms sodium bisulflte and sodium bisulfate which react with the caustic soda in the re-reduction bath to form sodium sulfite and sulfate. These salts exert a salting'out action in the dye bath, tending to change the strength of dyeing as the goods passes there-through as the ccncentrati OHSISmOIB m: y escribed by Hebden. Because the caustic soda in the re-reducing bath is used up due to the oxidation of the-hydrosulfite it was found that the re-reduction bath finally became acid causin precipitation of the dye from the solution unless additional caustic is added. In the continuous piece goods dyeing of cotton by the Tice process, theloose improperly fixed color,

' together with some of the color that is actually fixed but which can be stripped off with alkaline sodium hydrosulilte' is capable of being dissolved in the re-reduction bath and bleeds off until an other chemicals necessary forthe dyeing operation.

It is a further object of the invention to provide a commercial method for dyeing animal fibers or mixed goods containing animal fibers and/or hydrolyzable cellulose esters or ethers with vat dyestuffs without harmful effect to such alkali sensitive fibers.

I have found that in continuous processes for dyeing piece goods with vat colors uniform dyeings can be obtained with a minimum consumption of color and other chemicals by padding the goods with the usual caustic alkaline solution of the reduced color and then subjecting the goods while the color is still in a substantially reduced state to a development with an alkaline hydrosulfite or similar reducing agent solution in which the alkalinity is maintained sufficiently high to retain the color in solution at all times,

but which hasapH value materially less than that of a caustic alkaline hydrosulfite solution,

and which can be maintained at predetermined ing the piece goods which have been padded with the usual caustic alkaline hydrosulfite solution of a vat dye or dyes into a developing bath comprising an alkali metal carbonate, an alkali metal equilibrium is reached where the amount of Since the aifinity of these vat colors for fabrics varies with the alkalinity of the dye bath any change in the alkalinity in the re-reduction bath shifts the equilibrium to cause a greater or less amount of dye to be absorbed by the fiber or to go into solution in the dye bath. As long as there are fluctuations in the alkalinity of the re-reduction bath material variations in the resulting dyeings are noted. It was therefore found necessaryto continually add caustic soda to the re-reduction bath to maintain as near as possible uniform conditions but 'due to the chemical reactions as above pointed out it was found to be necessary to add considerable quantitles of caustic soda to maintain the original dyeing conditions and that due to the rapid accumulation of the salts in the bath some means had to be devised for preventing their accumulation. 'I'his'was done by the addition of water with continuous draining oil of part of the solution. Any water drained oil also carries some valuable dye which must be continually replaced either by addition or by bleeding from the goods being dyed. This process, because of theuse of hydrosulfite and a small amount of the color employed in the original vat. the color is fixed in the fiber and uniform shades are obtained as long as the development solution is maintained with sodium carbonate to give sodium bicarbonate and'sodium sulfate. The accumulation of the undesirable salts in the solution is therefore at a very much reduced rate as compared with the process in which caustic soda is employed as the alkali in the developing bath. The sodium bicarbonate formed in the reaction reacts with the sodium hydroxide being brought in on the fiber from the original pad liquor to form more sodium carbonate inthe developing bath.

This obviates the addiudn or further alkali as long as undue oxidation of the hydrosulfite is not experienced such as when there is too long a contact with air or Whenworking with pile fabrics or other very loosely woven fabrics which carry larger quantities of adsorbed air into the development bath, or when the run is of such a length that the sodium carbonate reserve falls below the ascertained limits for any particular set of conditions. When dyeing such goods larger amounts of caustic are usually employed in the adding liquor, although if desired, additional x 33 the, eq'uilibriun l between the amount of coin caustic b developliientjpath bonate are forined due to the 'abs'oi ption of one: 1

terial quantities .of carbonqdioxldei fom the air 5 by the caustic soda solution in: the padding liquor both on the goods and in. the vat. This sodium carbonate is detrimental'wh'ere'.Caustic soda alka- -i nity is desired but is ,a necessary and desired 311; tojperrnit the us of thesewaker alliali'es in the developingba't h Whileoiiie fthe colors particularlfir of th indi'goic l olasa in the "luc'o' f or n are readily soluble s luupn s navlng s 151-1 0; as low as}; 8, others} partioularlymosebr jthe' 'anthraquinone floss usually require gin-alkali'n hydrosulfite solution oiia pHotmpr-aboiiej Tneem'lre range o'f'- vat C0 are when aoblled tothe cloth from the or'dinary caustic alkaline sodium carbonate alkallnexhydrosulfite solution (provided no undue oxidation has oqourred) to permitcomplete developuient" t olor for: the fiber when it is treated in such a solution; In

51 1 1 01 theig'olor orithe f-a-brio as the padded'material- Ieai es' th'e padding "solutiom sodium 1 oanbonate hydrosulfite is f sumciently strong to rereduce the? "oxidized" color; and 'oa'use fixation.

However: Withi a few I of the anthraquinone vat e ga ore, suol'l' as the. 110'rilia'ted' indanthrone, earejs'h be'take" tobre'i'ent undue oxidation he fiber in t e inte'rva1"oftiine 'betweenthe jpa and development' operation because ot 1 the jdii fiioultfekpriehoed inbrereducing :such

b016 5; With iiat' colols, nii'ld alkalies having; a pH? l wer {mgn-*-10 may be employed; :iThe limits of alkalinity-Witliin Which"a particulari "color is sumciently soluble can be readily-determined 70 by a simple experimentationl' As long as the color is slightly soluble in I thedeyelopment baththe alkalinityfjof that solution mayfbe maintained at any predetermined"pointgabovethat at which-the color is 'precipltateuj while ig-above stated, s

lower-l alkalinity employed :;in:-:;the:; deyelopn ent quickly'es'tabllshem becauseof: the small amq t;

in'tsolution' when noaustic, soda sis usedtzgthlisi 50 hydrosulfite vat are sufiiciently soluble in athe mel g'o *orthe beudeo'materiarandithat-goinfg; on 'ffoni' the-development liath changes with l in the alkaliiilty} when onceithe-sequiez abllshed-and' that 1 set of? oonditions;

' the depth or shade of 'thel res ultw f rrespeotlve of whether tstin' this sollitibfiis advisable; partidularly until bi 'oper running "condition's 'arei'establishedz 'hieh neriodio fcheck's are made tordetectI any trend awayiron'l' *the starting .jcondi'tionsz; vWhere sodium carbonate is employedtauxiliary; teklsotfeaustio l soda;- sodium carbonateiand; sol diunifi bloarbon'ate arei made r-liesi tdiltr;:availablaln;v case unfIoi-eseen: conditions:'zarise-rwhicmcauae-za; variation in thefalkalinityrbeyond:theji'toleranoes allowable Whermropei-arunning; conditions are; established origlnallylawithi manyifahrios: only; minor arid sometimesnq'additionsneedgbe; made;

to the development bath fonrrunsot'lseveral thou:

bathythe equllibrium wlth regardit the color is of color in solution;as' compared'wlthgthegaino ing a materl'al savlnggpartlcularly in .;short cloth: where -:the 300.10! or: c019 emp oyed, 3 i?" sin el msp l s n d ed t o ta daa t ee il rmm thi me n min ster al 19 lbiin he u ua mim h alkali metal hydrosulfite or othe h l and re erab y wi th' dmo'n 9r suitablepenetrating and -fo M mrbl resent such as now employed in ;;the rt, The alkali o a o ss thqvnddin q1iri11 dev j upon the nature of the particular we ooloriin} volved ,in the depthot shade and a the type- '61 a ab icbeing y yed-wf 'srfia u ht it'yl nd :an-excess of them uclng agentare always main.- a e -w ...After.-..-the dyed- 489 1151 a ted s v. veloping bath it is oxidized rinfsed, 'soa'p'ed, rinsed, d ied and yfinishe eh s memo f 1 9. nl yed'for thet veular we. otl t 'VQ1Ved,* By the :oontinuous 'dyeing' p "refermore particularly; ho fbro cess A N th ysoods is a sed; 7 e t v r0 3 'hebad summ n athroughthe degelopment, thMWeIalso .those continuous. piece T Wifli Elli- M nm -n e i t m v able range of anmumty' whioh firaotioe has shown will not cause any shade variationa T0 bef sure;

J that the alkali'nity of tlie 'developmrit 1 m 's maintai 'ed co "tarit; "continualsainolingeand llpeluqe wherein the goods is transferred from one machine to another between thepadding and developingoperations. goods must be batched off the padder and cannot be readily transferred to another machine, such I transfer operation.

I have found that satisfactory results can be obtained if the goods to be batched 0113 is passed throughv a solution containingv approximately 1% of sodium carbonate between the padding and batching operation. It is of course understood that in the padding, developing and in the batching-off steps the goodsis passed through the squeeze or nip rolls usually employedin the dyeing processes whereby the' amount of liquid remaining in the fabric can be controlled.

In the dyeing of cellulose rayons and other fabrics containing alkali sensitivefibers it is often impossible, due to their low tensile strength when wet, to dye 'this type of-goods in the usual continuous piece goods dyeing equipment because of the tension required on the goods.

This tension also stretches the goods and imparts In such cases where the 7 controlpurposes by titration with certain indicators. The following practical methods have been developed fordetermining the alkalinity .in terms of sodium bicarbonate or caustic soda content, and for determining the total alkalinity,

of the developing carbonate. V

0 cc. of the solution from the development solution interms of sodium bath are placed in a small beaker or Erlenmeyer flask and 15 cc. of 10% barium chloride solutionare added- After the addition of phenolphthalein the solution .is titrated with N/10 NaQH if the solution is acid or with 10/N H01 if the solution is alkaline. While the end-point is somewhat obscure it may be readily estimated within 0.5 cc. of the N/10 solutions. The first end-point should be taken for with the presence undesirable effects which cannot be' corrected in V subsequent operations. By using sodium car-.

bonate or otherweak alkali inthe development bath such'gohdscan be dyed by padding in the in cases where the dye employed is extremely sen-- sitive to air oxidation. It is therefore to be understood that the use of mild alkalies in the developing bath according to this invention is not limited to continuous dyeing processes.

Where sodium carbonate is employed the amount may vary within wide limits for its alkalinity is such that alkali sensitive fibers are not detrimentally affected by it. A sufficient quantity should be used to maintain the color in the developing bath in solution and a reserve to prevent the solution from becoming too low in alkalinity before the proper adjustments can be made. From 0.5 to 2.5 ounces per gallon will usually be found to be suflicient for-proper operation;

The amount of alkali metal hydrosulfite in the developing bath should be sufficient to keep the color in the reduced state. A substantial excess of hydrosulfite is desirable. Limits of from 0.15 to 0.5 ounce per gallon are adequate for proper operation and control.

While in determining what mild alkalies may be employed in the developing bath and the concentrations in which they may be used the pH values maybe determined by the usual colormetric or electrometric methods inwater solutions, it has been found that the alkalinity of who developing bath which contains oxidizing and reducing agents can best be determined for of the other'salts in the solution the end-point will shift as the solution stands. The entire determination'should therefore be carried out as quickly as possible The amount of sodium bicarbonate or. sodium hydroxide may then be determined by the following formula percent NaliC 03 cc. HClXNX LO 50 -pcrcent NaOli Having determined the amount of either caustic or bicarbonate present in the developing bath byrthe barium chloride titration method as above described the total alkalinity of the bath may be titrated directly with HCl using phenolphthalein as theindicator. By taking into consideration the barium chloride finding the differ ence inithe titrations may be considered as so-v dium carbonate. c r

The necessary sodium hydrosulfite concentration should, of course, be maintained in the development bath. Tne amount of sodium hydrosulfite can readily be determined by titrating a known amount of a standard solutionof sulfonated indigo as follows:

Pipette 5 cc. of standard indigo solution into 'a 250 cc. Erlenmeyer flask, dilute with '75 cc. of water. Titrate as rapidly as possible with the Na2S2O4 solution taken directly from the development bath with a 25 cc. calibrated pipette until 1 drop causes the blue color of the indigo to disappear.

, ,(Zalculation fl ew cc. Nazszol (developing solution) -purcent Nazszoi by volume The sulfonated indigo solution may be prepared as follows: Weigh 3.76 grams of finely allow the solution, to stand for at least one-half hour before using.

EXAMPLE 1 Jean cloth running 2.85 yards to the pound in the form of piece goods is dyed in desirabletan shades suitable for cotton work clothing by the continuous process as follows:

The cloth is impregnated or padded in the open width by passing it through a padding bath held at 120 F. and containing 20 gallons of the vatted color made up as follows:

A penetrating and foam control agent such as the fatty alcohol sulfate Modinal D 0.1

at the rate of about 70 yards per minute. The

goods is then passed through squeeze rolls mounted over the pan or pad box adjusted so that the material carries approximately 60% of its dry weight of the padding solution. The pad liquor taken outby the cloth is constantly replaced by additional pad liquor known as the pad After padding, the cloth is passed at the same speed, with the color still in substantially reduced state, through a development bath where it is treated for three minutes. This development bath consists of two 1700 gallon boxes fitted with rollers to lead the cloth up and down through the boxes in a progressive manner in such a manner that approximately 210 yards of cloth are immersed in the 3400 gallons of solution atany one time. veloping solution comprising 3400 gallons of water containing 1.5 oz. per gallon of sodium carbonate and 0.25 oz. per gallon of sodium hydrosulfite. The temperature is brought to 150 F. and a color solution made up as follows is added:

- Pounds "Ponsol Brown AG double paste 4.68 Ponsol Olive AR-.. 0.05 Ponsol Brown VR. 0.18

are reduced in 20 gallons of water with 2 pounds of sodium hydroxide, and 1% pounds of sodium hydrosulfite. Two-thirds of this color mixture are added to the first 1700 gallons of solution in the first bath and one-thirdis added to the 1700 gallons of solution in the second bath. Seven hundred pounds of salt (NaCl) are added to each 1700 gallons of water. This amount of color closely approximates equilibrium at the start. The solution is then titrated=to determine if These boxes are charged with a de-' I talned. Experience has shown that a tolerance of 1.4 to 1.6 oz. per gallon of sodium carbonate in the development bath is permissible forthis type of cloth. The amount of hydrosulfite present in the development bath should also be checked from time to time and the starting concentra tion of .25 oz. per gallon of sodium hydrosulfite should be maintained. Experience shows that a drop to .18 oz. per gallon of hydrosulfite is permissible on this type of cloth; Approximately 15 pounds ofsodium hydrosulfite must be ,added to the development'per hour tov maintain proper concentration, where the goods is being passed throughthe solutions at the speed mentioned.

Under the above conditions the alkalinity of the development bath stays within the degree of tolerance mentioned without auxiliary feeds of sodium bicarbonate or sodium hydroxide.- However, auxiliary feeds ofthese materials and an auxiliary feed of sodium carbonate should be made conveniently available foruse should the control tests indicate a trend requiring theiruse. After development, the goods is washed with water, oxidized with a solution of sodium dichromate and acetic acid, rinsed, soaped, rinsed, dried and finished in the usual manner.

By this method, a saving of 11.2 pounds of color in the development bath is made for a 20,000 yard run as compared with the amount of color necessary where caustic soda is employed with the same amount of salt in the developing solution,

, or a saving of 70% in color used in the developing'. A further material saving in alkali and other chemicals employed was experienced due to the use of sodiumcarbonate in place of caustic soda, for additional feed of alkali is not required, and because with the lower alkalinity, less 7 color required in the solution for maintaining 1 this color equilibrium, and because the alkalinity of the solution is readily controlled, much more uniform dyeings are obtained than where caustic soda is employed.

While in the mild alkaline developing bath the addition of inert salts such as sodium chloride and sodium sulfate further reduces the amount ,of color required to establish equilibrium in-the same manner as when caustic alkali is used, with any sodium bicarbonate is present in the solution by the barium chloride method above described and any bicarbonate present is converted to sodium carbonate with the necessary amountof caustic soda. This usually requires from .05 to .1 oz. per gallon of caustic soda. After the continuous dyeing has started periodic tests are many colors and certain fabrics the use of large amounts of salt is not advisable. With the weak alkalies however, salt is not necessary for the solubility of the colors is small as compared with their solubility in caustic alkali. Where caustic alkali is .used without salt almost prohibitive amounts of color are required in the developing bath, particularly where the more soluble colors are used and more particularly where small yardages of goods are being dyed, for the dye remaining in the developing bath cannot be recovered. Furthermore, color equilibrium is exceedingly difficult to reach in the caustic alkali developing bath whensalt is not employed. A

While a single developing bathmay be employed, a series of'two or more is ordinarily used with diminishing amounts of color in each bath.

This materially reduces the amount of color required in the development for as more and more i of .the color is fixed on the fiber, less color is required in the developing bath to establish the color equilibrium. Where only a single bath is the developing bath under the conditions orig-1 colors by the continuous dyeing process as dcs'cribed in Example 1. The padder which is equipped'with' a 30 gallon pad box is charged with 30*gallons of the vatted color made up as above described with:

= Ounces per gallon Ponsol Brown VR paste; 0.567 Ponsol Olive GGL paste 0.413 Ponsol Brown AR dbl. paste 0.495 Caustic soda (dry) 1.750 Sodium hydrosulflte 1.500 ModinaP' D 0.10

and is held at a temperature of 120 F. The pad feed is made up as describedin Example 1 with:

Ounces per gallon Ponsol" Brown VR paste 0.63 Ponsol Olive GGL paste 0.59 PonsoP' Brown AR dbl. paste 0.55 Caustic soda (dry) 1.75 Sodium hydrosulfite 1.50 Modlnal D 0.10

Alter paddingthe cloth, it is passed while the color is still substantially in reduced form into a developing bath where it is treated for three -minutes at 145 F. In this case, a developing bath consists of 4 six hundred gallon boxes fitted with rollers to lead the cloth from the top to the bottom of the boxes in such a fashion that 90 yards of cloth are immersed in the 2400 gallons. The boxes are charged with the total of 2400 gallons of water containing sodium carbonate equivalent to 1.25 oz. per gallon and sodium hydrosulfite equivalent to 0.25 oz. per gallon.

"I W f f Ounces Ponsol .Brown VR paste ,7.40 "Ponsol" Olive GGL paste 3.00 Ponsol Brown AR. dbl. paste 6.50

are reduced and dissolved in. 11 gallons of water with Zpounds caustic soda (dry) "and 2 pounds sodiumhydrosulfite at 120? F. Six gallons of this color solution is added to the first box.- Three gallons to the second and one gallon each to the third and fourth boxes. The developing solution is then titrated for sodium bicarbonate and adjusted as in Example 1. The dyeing is run at 30 yards per minute. By periodical determinations the alkalinity of the developing solution is maintained as closely as possible to the starting conditions. Tolerances of from 1.20 to 1.35 oz. per gallon of sodium carbonate, .01 oz. per gallon of caustic soda and .05 oz. per gallon of soduim bicarbonate are permissible.

Under these conditions and with this type of cloth it is not desirable 'to control the alkalinity in the developing bath by increasingthe amount of causticsoda in the pad feed because of the deleterious effect' it may have on the alkaline sensitive fibers in the fabric and since in dyeing: fabrics containing animal fibers by this method there ,is'fa faster neutralization of thealkali in the development bath, auxiliary feeds of caustic soda are usually necessary; After development, the goods is given a running rinse'with water,

skyed to the air to oxidize the color, and then soaped,-rinsed, dried, and'finished. The goods thus dyed is fast to laundering and dry cleaning and tests indicate that there is substantially no deterioration of the alkali sensitive fibers.

EXAMPLE 3 Suiting material comprising spun viscose rayon with an acetate stripeand blend in which the.

I Ounces per gallon Ponsol Blue 3G paste 4.73 Ponsol Violet BNX Supra 0.425 Caustic soda (dry) 1.75 Sodium hydrosulfite 1.50

The auxiliary pad feed of this color comprises:

Ounces per gallon PonsoP Blue 3G paste 5.5 Ponso1" Violet BNX Supra 0.5 Caustic soda (dry) -1 1.75 Sodium hydrosulflte 1.50

which is made up and held at 130 F. The padded goods may bedeveloped in either of two ways:

A. By the continuous process in which the goods passes directly from the padder while the color is still in the substantially reduced state into a developing bath consisting of three eight hundred gallon boxes fitted with rollers which lead the cloth from the top to the bottom of the boxes in a progressive manner and in such a fashion that approximately 120 yards of cloth are immersed in a total of 2400 gallons at a time. The developing boxes are charged with 2400 gallons of water containing 1.25ozs. per gallon of sodium carbonate and 0.25 oz. per gallon sodium hydrosulfite. Seven gallons of color for use in the developing bath was prepared by dissolving in 7 gallons of water:

Ounces per gallon Ponsol Blue 3G paste 22 Ponsol" Violet BNX Supra 2 Caustic soda (dry) 6 Sodium hydrosulfite 6 at a temperature of 130 F. Four gallons of this mixture were added to the first box after the padder, two gallons to the second box and one gallon to the third box. The temperature of the development bath is brought to F. after the usual correction for any sodium bicarbonate present. The run of the goods through the developingbath is started and the sodium carbonate alkalinity is maintained within the tolerance of from 1.20 to 1.35 ozs. per gallon. The caustic soda should not go above .02 oz. per gallon and the bicarbonate should not go above .05 oz. per gallon while the sodium hydrosulfite should be maintained at not less than .18 oz. per gallon. Under the above conditions with this type of cloth it is not desirable to control the alkalinity in the developing bath by increasing the amount of caustic to pad feed and therefore auxiliary feeds of caustic soda, sodium carbonate and sodium bicarbonate are mad conveniently available should the control tests made during the continuous run indieate a trend beyond the tolerance above indica ed.

The goods as it passes from the development bathis rinsed with water, oxidized with sodium perborate, rinsed, soaped, rinsed, dried andfinishedinthe usual manner. I

- B. The development may also be carried out on the reel or dye beck type of apparatus inwhich case the goods as it passes from the padder'is given a wash in a 1% solution of sodium carbonate. Four hundred and eighty'yards of goods at a time are then transferred and loaded on to the in the rope form. The dye beck is previously charged with 1050 gallons'of water containing 1.25 ozs. of sodium carbonate per gallon. The

temperature is brought to 150 F. and the goods is turned in this solution for five minutes. While reel dye machine or dye beck Whereitis-handled the goods is in motion sodium hydrosulfite equivalent to 0.25 oz. per gallon and caustic soda equivalent to .05 oz. per gallon are added. The goods is moved in the solution for 15 minutes after whichit is given a running wash with clear wa ter, oxidized with hydrogen peroxide, rinsed, soaped at 150 F., rinsed, dried and finished in the usual manner. Since the development in this case is carried out as a unit with continued repassage of the goods through the same bath and the hydrosulfite is added after the goods are in motion in the solution color need not be added to this developing bath.

EXAMPLE 4 EXAMPLE 5 Upholstery pile fabric having a cotton back 'andmohair face may be dyed with vat colors by the process asabove described. The vat colors are selected to produce certain styling or color A as above described, was ubjecte balance between the cotton back and mohair face v i and also to produce superlative fastness particularly to light. The following exam-ples are given which illustrate the dyeing of these mixed fiber fabrics and the possibility of color selections for,

such materials. In these examples the fabric is padded with the caustic alkaline solution of the vat color and while the color is still in substantially reduced state it is subjected to development in a bath containing 1.25 ozs. per gallon of sodium carbonate and..25 oz, per gallon of sodium hydrosulfi'te and the ascertained amount of-color to efiect equilibrium for a period of three minutes at 145 F. In all cases the padding liquors are prepared'by dispersing the vat colors inwater, adding'1.75 ozs. per gallon of caustic soda (dry), bringing to the proper vatting temperature and adding 1.5 ozs. per gallon of sodium hydrosulfite.

The concentration of color and the vattingtemperatures are given with the description of the dyeing effects produced.

A. Eight ozs. per gallon Ponsol Red BN double paste, padded at 120 F.,'dyes both the cotton back and mohair pile in red shades brighter in shade than the mohair pile. it I exhibits good light fastness.

F. The mixtureoi 0.5..oziper gallon SuIfanthrene 0 green shade with vat colors giving desirable'con is'made up of:

.After padding, the cloth is batched on ashelli I given two passages through the sodium carbonate sage through the solution. This. development C. Eight ozs. :per gallonf Ponsol Yellow AR, V, padded atf R. dyes, cotton to aboutthe same ;depth-but i'gieener and: brighter than the mohair pile; I It; exhibits. excellent rest,-

ness to lightl w, I D. Two ozs.-per gallon Ponsolifyellowf'Gdouble;. g I paste, padded";"atrg lliil Il.-, -=dyes'thefcotto'n very' much heavierthanthen ohairl' r E. Three ozs. per gallon sulfanthrene .Brown G paste, padded=atl40i-Fgj-dyes the cotton very muchlightershade"thansthemohair.

7 ew standard abrasion test andnodete'r'iorat'ion of the moha r.w s is r i le -v L'Exmrtaca A mixed fiberfor men sxsuit'simade ofcotton, 4 viscose staple rayon and. woolis dyed in astone trasting color effects bypaddln'g the'clothwitn 5 the vat dye padding'solution in' a {manner' d scribed in Example 1 in whichthe padding li'qu v i Ounces per gallon Ponsol Direct Black 33 dbl. paste." Ponsol Green 2BL 0.4 Caustic soda (dry)' "l"."75 Sodium hydrosulfite 1.75

The padding is carried out at a temperature of F. The pad feed was made up as follows:

i 'Ouncespergalloi'i v Ponsol Direct Black 3G dbLpaste 3.0 Ponsol Green 2B1; 0.5,, Caustic soda iig 1,75 Sodium hydrosu1'flte 1175v and immediatelytransferredto a jig..; The ,jig;

is previously charged with 80-gallons of a solution containing 1 ozs. of sodium carbonate main tained ata temperature of F. The cloth is solution by running the; cloth down from the j shell on to the jig] beam and then passing back on to the second jig beam. v; 0.25 oz.- per gallon, of sodium hydrosulfite is then added to the carbonate solution and after titratingfor sodium bicarbonate, alkalinityand total alkalinity it is adjustedso as to contai'nl ,1, ozs. per gallonsodium carbonate and 0.05 oz per gallon of caustic soda.. "Whilethe solution is maintained at 150 the cloth is given apasbath is again titrated and adjusted. The ge I velopment requires from 2 to 4 passages, depend: j

..-Sod

passed directly from'thepadder'into a continuous ing onthe depth or shade, size "of. roll and the ,nun'iber of "yards on the roll, The bath should I be testedfor alkalinity between the passes and indicated adjustments madei. After development the cloth is given twopassages in cold water, two

passages through'an. oxidizing bath then rinsed, soaped yrinsed 'andidried in the usual manner. I Y T A mixed fiber fabric containing 80% spun ,vis-

cose rayon and 2.0% w'ool..i s..dyed.a solid bright blue shade with vat colorsiby the process of Exampledjb y employing for, the padding solution 'V fQuncesper'gallon fBlu MR 4.0

Bons'ol Green 2'13 0.5 caustic sodadry'u's, 1.5 hydrosulfitearm 1.5

yeing'is carriedoutat 140% F. The cloth is reel dyeing'machine" containing; thev development bath of sodium carbonatefsodium. hydrosulfite,

l. and' sufficient amount :of -thercolors to "approxiinmate?! equilibrium v,withw the padded material. Limits of.0'2'oz. per gallon; of caustic soda and. .05

oz. per gallon -of:ssodium(bicarbonate should be maintainedfiiThe sodium" carbonate concentrae, tlon'should beheld at l20 to "l.3 5 ozs. per gallon,

I v andthe sodium hydr'osulfiteshould not fall-below'.18oz'. per-gallon. The reel dyeing machine is so arrangedv thatthecloth ,is stillin the open that have been dyed on cotton, and; on'mixed" fiber fabrics .containing spun rayon and wool without showing any harmful .efiect on the alkali sensitive fibers where the goods were padded at" 130 F. with a vat solution made up as follows:

. Ounces per gallon Ponsol Direct. Black 36 double paste 4.0

I Caustic soda (-dry) 1.80

width-when it .enters the machine, After immersion in the open width thefcloth goes into the rope form in which form ,itremains for the development, oxidationand soaping operations.

librarians-8 I A viscose staple spunrayon fabric is dyed in blue shades fast to light and washing by nip padding with a solution of thevatted color prepared from I Ounces per gallon ."Po'nsolu Blue BF double paste e 2.0

I Ponsol Violet BN supra .25 Ponsol". Olive GGL paste .25 Potassium hydroxide 1.75

Sodium hydrosulfite 1.5

The goods is passed from the padder through a developing bath, as described in Example 1, in

which the required amount" of colors have been added to approximate color equilibrium at the start... The alkalinity of the developing bath is maintained from 1.4 to 1.6 ozs. per gallon of sodiurn'carbonateand from 0.02 to 0.05 oz. per gallon of sodium hydroxide. Due to the nature of this combination of colors, bicarbonate alkalinity in the bath is to be avoided. The hydrosulfite should not be allowed to fall below .18 oz. per gallon." I

Other alkaline salts than sodium carbonate may be employed for the development of these vat colors, provided they are sufficiently alkaline to maintain the reduced vat dye in solution, and, where'the process is-used on alkali sensitive fibers, the alkalinity is not of such a; strength that it injures such materials in the time required for'developrnent. Alkaline solutions of between pHof 8 and pH 12 have been found to be satis-- factory.

The following salts and combination of salts,

which in water solutions have a pH value in the concentrations used as indicated, have been found to be suitable for developing vat dyes of all types Sodium hydrosulfite 1.50

The padded goods were developed for 3 minutes at F..in a developing bath containing 0.25 oz, per gallon of sodium 'hydrosulfite and the following amount of alkaline salt or mixture of salts:

(a) 1.5 oz. per gallon sodium carbonate (pH 11.25) (bi 1.5'oz. per gallon sodium phosphate (NazPOa) H 11.93) ell/fixture of:

' 0.938 oz. per gallon NaaPO4 0.56 oz. per gallon Na2HPO4} (pH 11'44) (d) 2.5 ozs. per gallon potassium carbonate (pH (e) 1.5 ozs. per gallon 42. B. NazSiOa (pH 10.49)

Satisfactory color shade development was obtained in all cases.

The pH measurements for the above solutions were made prior to the addition of the hydrosulsodium hy- PH 11.8)

fite with a hydrogen electrode using a saturated calomelelectrode as a reference electrode. The

hydrogen electrode was checked against a standard'buffer solution of pH 10.00 before and after the measurements'were made. I

While in the above examples, standard commercial vat dyes of the anthraquinone and indigoid types are used, it is to be understood that the invention is not limited to these particular colors but is applicable to all vat dyes, such as those of'the anthraquinone, indigo, thioindigo The invention is of particular importance in the dyeing of those and sulfur vat dye classes.

colors'that must be used in caustic alkali solutions for by the present process these colors can be applied to fabrics containing wool; silk and cellulose acetate rayons;

As illustrated in the above specific examples it is usually necessary in dip padding to have the pad feed somewhat stronger in dye content than the initial padding solution, for, due to the affinity of the color for the cloth there is relatively more color than water retained by the cloth. This causes a partial exhaustion of the.

color in the pad box. -To correct this the pad liquor fedinto the pad box to replace that taken up by the cloth must contain a proper amount of additional color to maintain the starting concentrations; Unless this is done a taper or progressive loss in depth of shade will result when a single "color is used and a taper in both depth and shade will result when a mixture of colors is used which have different rates of exhaust.

It has been" found that complete development of the color in the mild alkaline development bath requires about three minutes or more. The time of development may be decreased but only with a possible sacrifice of fastness and color economy.

It will be obvious that this process for developing vat dyes is not limited to piece goods dyeing. This process makes possible the dyeing of fibers, and particularly the alkali sensitivefibers with vat dyes in any form such asv in skeins, warps, slivers, etc., provided the material can be impregnated, squeezed and passed into the development bath before deterioration of the alkali sensitive fibers takes place.

It is to be understood that the amount of sodium carbonate in the developing bath can vary within wide, limits provided the starting amounts are maintained within relatively narrow limits. From the standpoint of control the starting sodium carbonate concentration. should be set high so that the total alkalinity of the devel oping bath is not subject to wide variations in short periods of time.

I claim:

1. In the process for dyeing textile fibers with vat colors the steps which comprise padding the fibers with a caustic alkali solution of the re-' vat colors the steps which comprise padding the fibers with a caustic alkali solution of the reduced colors and developing the colors on the fibers by subjecting them, while the color is in substantially the reduced form, to a mild alkaline solution of an alkali metal hydrosulfite until development of the color is substantially complete, said developing solution having an alkalinity of from about pH 8 to about pH 12 and maintaining the alkalinity of the solution relativelyconstant at any chosen value within these limits, and after the development of the color is substantiallycomplete oxidizing the reduced dye on the fibers.

3. In the process for dyeing textile fibers with vat colors the steps which comprise padding the fibers with a caustic alkali solution of the reduced colors and developing the colors on the fibers by subjecting them, while the color is in substantially the reduced form to a mild alkaplete, said developing solution having an alkalinity of from about pH 8 to about pH' 12 and maintaining the alkalinity of the solution relatively constant at any chosen value within these limits said developing solution containing at the start a sufficient amount of the colors employed in the padding operation to approximate the amount necessary to establish equilibrium between the amount of color coming oil of the fibers being dyed and the amount going onto the fibers from the developing solution during the developing operation, and after the development of the color is substantially complete oxidizing the reduced dye on the fibers.

4. In the process for dyeing textile fibers with vat colors the steps which comprise padding the fibers with a caustic alkali solution of the reduced colors and developing the colors on" the fibers by subjectlng'them, while the color is in substantially the'reduced state toa mild alkaline fibers by subjecting them, while the color is 'in substantially the reduced state to a mild alkaline solution of an alkali metal hydrosulfite the alkalinity'of which solution is between pH 10.5 and pH 12 while maintaining the alkalinity relatively constant at any chosen value within these limits,

said developing solution containing at the start a sufiicient amount of the colors employedin the padding operation to approximate the amount necessary to establish equilibrium between the amount 01' color coming ofi of the fibers being dyed and the amount going onto the fibers from the developing solution during the developing operation, and after the development of thecolor is substantially complete oxidizing the reduced dye on the fibers.

6. In the dyeing of fibers with vat colors by continuous .dyeing processes wherein the fiber is padded with a caustic alkali solution of the ree duced color, the steps which comprise passing the fibers into a developing bath while the dye is in substantially the reduced state, said developing bath being an alkaline hydrosulfite solution having a pH of from 10.5 to 12 and maintainingthe alkalinity of the developing solution relatively constant at any chosen value within these limits during the developing operation, and after the development of the color is substantially complete oxidizing the reduced dyeon the fibers. i

7. A process of dyeing textiles containing caustic alkalisensitive fibers which comprises padding the textiles with a caustic alkali solution of a reduced vat colorand immediately passing the padded fabric into a development solution of sodium'carbonate and an alkali metal hydrosulfite, maintaining the alkalinity of the solution at a sodium carbonate content of from 0.5 to 2.5

ounces per gallon of solution, sufllcient alkali hydrosulfite being present in the development solution to retain the color in the reduced state at all times, and after the development of the color is substantially complete oxidizing the reduced dye on the fibers.

8. A process of dyeing textilescontaining causat a sodium carbonate content of from 0.5 to2.5 ounces per gallon of solution with sufllcient alkali hydrosulfite in the solution to retain the color in the reduced state at all times, said developing solution containing .at the start a sufllcient amount of the colors employed in the padding operation to approximate the amount necessary to establish equilibrium between the amountot color coming off ofthe fibers being dyed and the amount going onto the fibers from the developing solution during the developing operation, and after the development of the color is substantially complete oxidizing the reduced dye-on the taining a sodium carbonate alkalinity in the solu-e tion within relatively narrow limits during the run. and after the development of the color is substantially complete oxidizing theireduced dye on the fibers. V I g V 1 0. In the process for dyeing textile fibers with wit colors the steps which comprise padding the fibers with'a caustic alkali solution of the -re-- duced colors anddev'eloping the colors on the fibers by subjecting them to a mild alkaline solution of an alkali'rnetal hydrosulfite until development ofthecolor is substantially complete, said developing solution having an alkalinity of from about pH 8 to about pH 12, and after the development of the color is-substantiaily complete oxidizing the reduced dye on the fibers.

411. In the process for dyeing textile fibers with vatcolo'rs the steps which comprise padding'the fibers with a caustic alkali solution of the reduced colors'and developing the colors on the fibersoy subjecting them'to a mild alkaline solution of an alkali metal hydrosulfite until development of the color is substantially complete, saiddevelcping solution having an alkalinity of from about pH 8 to about pH 12 and maintaining the alkalinity of the solution relatively constant at any chosen value within these limits and after the development of the color is substantially complete oxidizing the reduced dye on the fibers.