US2130416A - Dyeing - Google Patents

Description

Patented Sept. 20, 1938 PATENT OFFICE DYEING Arthur J. Buchanan, Charlotte, N. 0., assignor, by mesne assignments, to Southern Dyestufl? Corporation, Charlotte, N. 0., a corporation of North Carolina .No Drawing. Application June 19, 1936, Serial No. 86,078

2 Claims.

This invention relates to improvements in the art of dyeing with sulphur or sulphurized dyestuiis, andmore particularly to the production of concentrated solutions of such dyestufls, and it includes an improved method. of making such solutions and the concentrated liquid sulphurized dyestuffs resulting therefrom.

The sulphur or sulphurized dyestufis are generally speaking insoluble or sparingly soluble in water, but they are soluble in solutions of sodium sulphide. In order to use these colors for dyeing purposes it is necessary that they be made soluble and reduced. It is also important that these colors, after being dissolved and reduced; remain in solution in the reduced state until the dyeing operation is complete.

The usual procedure in applying sulphur dyestufis to the fiber is to dissolve and reduce the dyestuif with the aid of sodium sulphide and an alkali such as sodium carbonate (soda ash). Other or additional reducing and solubilizing agents are sometimes used, either alone or With sodium sulphide. The dissolved and reduced dyestuifs are subsequently diluted and the cotton or other fabric or fiber immersed in the liquor, with subsequent exposure to the air, etc. In dyeing cotton, for example, the cotton is commonly immersed in the dye liquor at a temperature near the boiling pointfor a suitable period of time, e. g., around one hour, followed by exposure to the air, etcl The preparation of dye liquors by dissolving and reducing the sulphurized dyestuffs with sodium sulphide, or with sodium sulphide and alkali, has certain well known and commonly recognized objections. The solutions are strongly alkaline and have the disadvantage of removing the natural waxes and fats from v getable and animal fibers and tend to leave the dyed material depleted in these constituents and with a harsh texture, unlike the softness of. texture of the original undyed material. Sodium sulphide, when used as a reducing and dissolving agent for the sulphur colors, also has the objection that it is readily oxidized by the air, thus tending to lose its value for keeping the dyestuff in a state of reduction and in solution. Sodium sulphide crystallizes from strong solutions and is consequently dlfiicult to filter in high concentrations.

In an attempt to overcome the objections to the use'oi sodium sulphide in preparing reduced solutions of sulphur dyes, it has been proposed to reduce the high alkalinity of the dye solution,

for example, by the use of sodium bisulphite,

sodium hydrosulphite, glucose, salts of ammonia,

etc.; in which case the sulphur dyestufi is first dissolved and reduced in a highly alkaline solution of sodium sulphide and the alkalinity of the solution is subsequently reduced in an attempt to prevent or minimize injury to the fibers and other objectionable effects of strongly alkaline dye liquors.

The present invention is based upon the discovery that improved results can be obtained by the use of sodium disulphide (NazSz) instead of the ordinary sodium sulphide NazS), as the dissolving and reducing agent for sulphurized dyestuffs.

The sodium disulphide has a greater reduction capacity or potential for a given unit of weight of strength than does the ordinary sodium sulphide, due evidently to the greater amount of combined low valent sulphur which the sodium disulphide contains. Because of this it is possible to use less of the sodium disulphide, with resulting beneficial results in that there is less alkali present during the dyeing and, consequently, less saponification of the natural oils and waxes in the cotton; consequently the cotton is left in better condition, more nearly approximating natural, untreated cotton. It is possible also to produce shades which are brighter and fuller.

The use of sodium disulphide as a reducing agent has the added advantage or additional beneficial property that it is more stable toward oxidation than sodium sulphide; that is, it oxidizes more slowly and this makes it a more desirable reducing agent for use in concentrated liquid dyestufi solutions which are marketed in that form.

Because of the advantageous properties which sodium disulphide possesses as a dissolving and reducing agent for sulphurized dyestuffs, highly concentrated dye solutions can be obtained by it use, which concentrated solutions, because of their desirable properties, can advantageously be marketed in that form.

The use of solutions of sodium disulphide for dissolving and reducing the sulphurized dyestufls gives directly a solution of the reduced dye which is less caustic and more stable toward oxidation than when sodium sulphide is used. The dyestuffs are readily kept in solution in a sodium disulphide solution and can be handled in a concentrated form. Such dye solutions in general produce brighter and fuller shades, leaving the dyed material less harsh, and are less alkaline and of a lower pH value than solutions in sodium sulphide.

The new dye liquors or solutions can readily be used for dyeing vegetable fibers and fabrics and various artificial fibers, and also for printing with the sulphur colors.

The method of application of the new dyestuif solutions is similar to that with sodium sulphide solutionsbut with the use of materially lower temperatures; since it has been found that the dyeing temperature can be reduced to around 150 F. with beneficial results, whereas it is customary to dye with sodium sulphide dye solutions at around 200 F. This use of a lower temperature involves not only a saving in time and cost of steam for heating but leaves the dyed cotton in a better condition.

I have also found that sodium disulphide can advantageously be employed in combination with sodium hydrosulphide, for example, using the sodium disulphide and sodium hydrosulphide in about equal proportions.

I have also found that a very small quantity of caustic soda may be used with the sodium di-- sulphide in which case the solution consists mainly of sodium disulphide with a small amount of sodium sulphide.

I have also found that a very small quantity of caustic soda can be used along with the combination of disulphide and hydrosulphide; in which case the resulting composite solution contains sodium sulphide, sodium hydrosulphide and sodium disulphide in varying proportions; but the resulting solution has a lower pH value than a sodium sulphide solution and gives beneficial results, such as those above mentioned.

In making the new dye solutions, and in carrying out the new dissolving and reduction process, the sodium disulphide is advantageously used in a solution of about 30% strength. Such a solution has a similar reduction capacity to that of a solution of sodium'hydrosulphide of about the same strength and considerably greater reduction capacity as compared with a sodium sulphide solution of similar strength.

Highly concentrated solutions of sulphur colors can be prepared with relative ease by dissolving and-reducing them in a solution of the sodium disulphide, and such highly concentrated solutions can be readily filtered, stored, transported and used. Solutions of similar high concentration can similarlybe obtained by the use of admixed sodium disulphide and sodium hydrosulphide without or with the addition of a very small amount of caustic soda. When the sodium disulphide and sodium hydrosulphide are used together with a small amount of caustic soda, the composite solution contains sodium sulphide, sodium hydrosulphide and sodium disulphide in varying proportions, e. g., with' the quantities of each that may be present in the composite solution varying from a minimum of around 10% up to a maximum of around In applying the sodium disulphide solution of the sulphurized dyestufi, the highly concentrated solution can be handled much the same as sodium sulphide solutions of the dyestuffs, but with added advantages, such as the use of lower temperatures and other advantages above mentioned. The concentrated solution-can, for example, be diluted and the fiber or fabric dyed therein and the dyestuif exhausted by the addition of sodium chloride, sodium sulphate, ammonium sulphate, sodium hydrosulphite, sodium bisulphite, etc.

The sulphur dyestufls-are commonly marketed in the form of powders, usually admixed or diluted with more or less salt. Additional salt can be added to aid in the dyeing operation and in exhausting the dye bath. It is common to add a small amount of soda ash or caustic soda to the dye bath; and such alkalies in small amount can be added in the practice of the present process, although excellent results have been obtained without such addition.

A particularly valuable application of the invention results from the use of the moist presscake which is produced in the manufacture of sulphur dyes, and without the drying of the dyes to produce a dry powder. Such moist dyestufl press-cakes are readily dissolved and reduced in a strong solution of sodium disulphite, and the resulting solutions are particularly advantageous for use in the dyeing of textile fibers and fabrics. The use of the fresh moist press-cake and its reduction and dissolving in the sodium disulphide solution eliminates or minimizes the changes which take place on drying of the press-cake to form dry dye powders. Solutions of the sulphurized dyes can be more readily and advantageously prepared by using the moist presscake than by using the dried dyestuffs which are produced by the drying of the press-cake and which are generally less soluble and. less readily dissolved and reduced.

The new disulphide solutions of the sulphur dyes are readily prepared without the use of neutralizing agents such as have heretofore been added to sodium sulphide solutions to reduce their alkalinity. The new dye solutions can thus be prepared free or relatively free from sulphites or bisulphites or other added neutralizing agents. The solutions are initially prepared by dissolving and reducing the sulphur dyes in the disulphide solution so that the solutions are initially of much lower alkalinity and pH value than sodium sulphide solutions, and with other advantages, such as those above mentioned.

The invention will be further illustrated by the following specific examples, but it will be understood that the invention is not limited thereto, since different sulphur or sulphurized dyestuffs can be employed, and somewhat varying amounts and strengths of solutions of sodium disulphide. The following examples are typical:

Example 1.- pounds of commercial sulphur black in the form of a dry powder having common salt admixed therewith for standardization are dissolved in from 100 to 200 pounds of a 30% solution of sodium disulphide at a temperature of about 80 C., and with accompanying reduction of the dyestuflf. At this temperature and concentration the solution can be readily filtered, decanted, etc., to remove insoluble, objectionable matter and a strong, stable solution of the dyestufl thus obtained suitable for storage and transportation or ready for use, by dilution, etc., in making a dye bath for dyeing textile fibers or fabrics. On cooling of the solution to ordinary temperatures the dyestufl remains in solution, and is ready for use, after dilution, etc.

Example 2.-100 pounds of commercial sulphur blue in the form of a dry powder having salt admixedtherewith for standardization are dissolved in from 100 to 200 pounds of a 30% solution or sodium disulphide and the process is otherwise carried out in a manner similar to that described in Example 1.

Example 3.--A sulphurized dyestufl, such as sulphur black or, sulphur blue, sulphur brown, etc., is used in the form of a moist press-cake containing e. 3. around 45% of water; and 100 75 pounds of this press-cake is dissolved in from 100 to 200 pounds of a 30% solution of sodium disulphide. The dissolving and reduction take place more readily in this case than with the dry sulphurized dye powder, and somewhat improved dye solutions are thus obtained without the necessity of isolating and drying the sulphur dye and subsequent handling of dry dye powders with their well known objections due to dusting, and the irritating or toxic effect of the dust, etc.

The following examples illustrate the production of concentrated solutions of sulphurlzed dyestufi's with a composite solution 01' sodium disulphide and sodium hydrosulphite either without or with the addition of a small amount of caustic soda, in which case the composite solutions contain sodium disulphide, sodium sulphide and sodium hydrosulphide.

Example 4.--100 pounds of commercial sulphur black in the form of a dry powder having commonsalt admixed therewith for standardization are dissolved in from 100 to 200 pounds of a composite solution of sodium hydrosulphide and sodium disulphide containing approximately equal amounts of the hydrosulphide and disulphide in amount suflicient to give a solution of about 30% strength and at a temperature of about 80 C.-, with accompanying reduction of the dyestuff. At this temperature and concentration the solution can be readily filtered, decanted, etc., to remove insoluble, objectionable matter and a strong, stable solution of the dyestufl thus obtained suitable for storage and transportation or ready for use, by dilution, etc., in making a dye bath for dyeing textile fibers or fabrics. On cooling of the solution to ordinary temperatures the dyestuii remains in solution, and is ready foruse, after dilution, etc.

Example 5.A sulphurlzed dyestuii', such as sulphur black or sulphur blue, etc., is used in the form of a moist press-cake containing e. g., around of water; and 100 pounds ot'this press-cake is dissolved, in from 100 to 200 pounds of a 30% solution, containing approximately equal proportions of sodium hydrosulphide, sodium sulphide and sodium disulphide. The dissolving and reduction take place more readily in this case than with the dry sulphurlzed dye powder, and somewhat improved dye solutions are thus obtained without the necessity oi isolatabove examples are typical and may be used:

without or with additional substances, by dilution, etc., in making dye liquors or dye baths for dyeing and printing textile fibers and fabric-a Where the sodium disulphide is used in admixture with sodium hydrosulphide, the proportions of disulphide and hydrosulphide can be varied, as above indicated. Similarly, where a .small amount of caustic soda is used in addition to the sodium disulphide and sodium hydrosuiphide, the resulting composite solution of sodium sulphide, sodium disulphide and sodium hydrosulphide may also vary in its proportions, as previously pointed out.

It' is one 01 the advantages oi the new composite dye liquor, as well as an advantage of the dye liquor made with sodium disulphide alone, that lower temperatures can be used in the dyeing process than with the sodium sulphide solutions commonly used.

The new composite dyestuif solutions, produced by reducing the sulphurized dyestuffs with the sodium disulphide'red'ucing agent, or with the composite reducing agent containing sodium disulphide, are advantageously marketed commercially as concentrated, reduced dyestuiI solutions ready for the dyer to use.

Various sulphur dyestuifs and various shades of sulphurlzed dyestuffs can be used in making the new dyestufi solutions; for example, such sulphurlzed dyestuilfs and such shades of sulphurized dyestuifs as black, blue, tan, yellow, green, etc., sulphurized dyes.

It will be evident that the above examples can be varied, e. g., in the particular sulphurlzed dyestuil employed and in the particular composition of the reducing solution, particularly where a composite reducing solution is used.

I claim:

1.. Liquid sulphur dye being a concentrated, fliterable solution of sulphurlzed dyestufi dissolved and reduced in a-concentrated composite solution of sodium sulphide, sodium disulphide and sodium hydrosulphide, in which the sodium sulphide, sodium disulphide and sodium hydrosulphide are present in approximately equal amounts, said dye solution containing approximately from 18% to of the sulphurized dyestuii', and being characterized by improved stability toward oxidation and by relatively low pH value. v

2. Liquid sulphur dye, being a concentrated, filterable solution of suiphurized dyeatufl' dissolved and reduced in a concentrated composite solution of sodium disulphide and sodium hydrosulphide, in which the sodium disulphide, and sodium hydrosulphide are present in approximately equal amounts, said dye solution containing approximately from 18% to 50% of the sulphurlzed dy'estufi, and being characterized by improved stability toward oxidation and by relatively low pH value.

. ARTHUR. J. BUCHANAN.