US2169881A - Reagent used in simultaneous dyeing and degumming fabrics - Google Patents

Description

Patented Aug. .15, 1939 UNITED STATES PATENT OFFICE REAGENT USED IN SIMULTANEOUS liYEING AND DEGUMMING FABRICS No Drawing. Application January I, 1938,

Serial No; 183,803

1 Claim.

My invention relates to novel reagents intended primarily for use as color stabilizers in baths for v the simultaneous degumming and dyeing of materials made of silk alone or of silk and other yarns.

Silken fabrics are almost exclusively prepared from yarns which contain the sericin and other natural impurities intact about the inner core of fibroin or silky matter. The horny integument is maintained intact about the fibroin as a protection for the latter because the delicate silk fiber is easily abraded by the mechanical agencies employed .in throwing and weaving or knitting the yarn into finished fabrics. The flbroin requires a protective size and, fortunately, nature furnishes such a lacquer in the sericin with which she encloses the fibroin. The size, however, is stiff and brittle and requires plasticization and lubrication in order to fabricate effectively.

The requisite plasticization and lubricity are imparted to the sericin by soaking the raw yarn in solutions which may contain in a dispersed form, various oils of either a saponifiable or min-- eral nature, glycerine, alkalies and soaps or sulphonated oils. Sulphated fatty alcohols, fat acid condensates, pine oil, cresylic acid and other The elimination of the wetting agents and antiseptics are frequently em ployed for special purposes.

The natural impurities present on raw silk and the various ingredients employed to plasticize and lubricate the sericin, mask and obscure the natural brilliance and softness of the flbroin and prevent the silk from acquiring the colors em, ployed in dyeing. Consequently, almost all si$ fabrics are first submitted to an operation designed to remove all extraneous matter from the-fibroinr This operation'is variously known as boil-off, degumming and scouring, the three terms being synonymous and designating the same operation. I

sericin with its attendant impurities is accomplished by the use of a fairly high degree of alkalinity, (pH values between 9.7 and 10.5) potent emulsifying agents,

elevated temperatures (over 95 C.) and a prolonged exposure of the silk to the stripping tions (from one to three hours).

The reagents most generally employed in degumming are red and olive oil soaps frequently augmented in potency by small additions of soda ash, tri-sodium phosphate and other alkaline salts and sulphonated oils, or the so-called boilolf oils which are mixtures of sulphated oils and potash soaps adjusted and buffered with basic solusalgs, penetrants and auxiliaries to a pH of about 10.

Subsequent to degumming the silk is generally dyed, with or without bleaching and converted into the finished articles of commerce.

Most of the heavier types of broad goods survive the degumming, bleaching and dyeing operation without any perceptible fabric deterioration. However, knitted silk merchandise such as silk hosiery does not exhibit the same resistance. Such fabrics are generally of light and fragile construction and care must be exercised in preventing excessive abrasion. This is generally accomplished by dyeing the silk material in a bath containing at the start of the operation most of the sericin on the fabric. As degumming proceeds, the dyestuffs aflix themselves upon the filaments and the dissolved sericin acts as a fiber protectorant.

Technically, two methods of treating light and fragile fabrics are in common commercial use, the so-called split and single bath processes. The former accomplishes the emulsification of the natural or artificially added throwing oils and greases in a preliminary operation with a minimal loss of silk gum or sericin. The actual elimination of the sericin with'a simultaneous dyeing occurs in a subsequent degumming and dyeing liquor. The single bath process aims at elimination of the oil, fats and waxes as well as the removal of sericin and the dyeing of the fabrics in a single boil-oil operation.

The performance of these operations is complicated by virtue of the fact that knit goods, particularly silk hosiery, are rarely composed solely of a single kind of textile fiber. The toes, heels and tops of hosiery are frequently of cotton or rayon and sometimes even of unions of the two, while the seam yarns are invariably made of cotton threads. This necessitates the employment of dyes in the degumming bath which will impart the same tone and color efiect to cotton or rayon as well as to silk. The selection of the. colors suitable for this operation is very limited. Few dyestuffs will dye silk and cellulosic fibers the same shade in the alkaline conditions of the bath. Direct colors which simultaneously dye both cotton and silk do not operate effectively at that basicity, and the equilibrium of the dye on cotton and silk fluctuates material'- ly with slight variations in the pH and temperature of the bath. Milling colors are even more objectionable, so the dyer is limited to the stuffs which have a tinctorial effect only toward the single kind of fiber.) Few as these colors are, yet they are suflicient to produce any hosiery shade demanded by the industry. They dye level at the pH of the dye bath, feed and shade evenly and possess the requisite light and wash fastness.

It is the customary procedure in the textile industry to conduct the degumming and dyeing operation with the use of soap, sulfonated oil builered to a pH of 10.2 and alkaline salts as the stripping agents. Such reagents are not entirely satisfactory but find use by virtue of the fact that no better materials have thus far been developed.

Many of the true silk and cotton colors are easily destroyed by the combined action of the high alkalinity of the bath, the elevated temperature of degumming and the reducing action of the silk sericin and the preparations employed in silk soaking.

Commercial attempts to prevent this color re duction have been only partially successful. Most attempts aim at this accomplishment by lowering the pH of the dye bath or by churning air into the dye liquor. Whatever benefits have accrued through these practices are ascribable to a lowering of the temperature or alkalinity of the dye bath and have resulted in a greatly extended time of degumming and dyeing.

With the foregoing in mind the principal object of my invention is to provide chemical reagents for the degummlng and dyeing operation which "eifect complete color stabilization, facilitate and shorten the degumming and dyeing procedure and decrease the cost thereof.

I have found that the cause of the color change is the sericin content of the bath and that by insolubilizing the serioin which enters solution or by absorbing it by certain other colloids the color reduction can be entirely prevented. I have also found that the protectorant or color stabilizer must possess both protein coagulation and oxidizing properties. As the color stabilizer is to be employed with a degumming solution, its protein coagulation properties should be sufliciently potent to convert solubilized sericin into an insoluble colloidal form but not yet to perceptibly' arrest or prevent the elimination of the sericin from the material being degummed. The stabilizer should preferably be devoid of reducing properties though this characteristic can in part be neutralized by a suitable oxidizing agent.

In stabilizing the dye employed with the degumming agent in coloring silk fabrics the liquor should have amild oxidizing action, preferably no greater than that of hydrogen peroxide.

Among the stabilizers or protectorants usable for the purposes of my invention arez-sodium phosphotun'gstate, sodium phosphomolybdate, mixtures of sodium perborate and aluminum saItscadmium sulfate, potassium permanganate. potassium dichromate and certain peroxides such as magnesium peroxide.

The following examples will serve to illustrate, without limiting, my invention:

aieaoei Example 1 A degumming preparation was prepared as follows:

Per cent Olive 011 se n 75 Sodium tetrapyrophosphate 5 Cadmium sulphate 20 A degumming solution of 1% strength of the above was prepared and V Silk Brown G N Example 2 A degurnming oil of the following composition was prepared:

Per cent Potassium hydroxide 6 Sulionated castor oil 25 Cresylic acid 10 Sodium phosphotungstate 2 Sodium perborate 2% A 1% solution of the above was prepared and one ounce per 1000 pounds of Durol Black B (Color Index 307) was added to the solution. Ten pounds of silk sweaters were added to the solution and degumming and dyeing continued until a color match was secured.

A 1% solution of the above was prepared and per 1000 pounds of the solution five ounces each of Silk'Brown G N (Color Indore-Special) and Silk Brown R (Color Index 234) and seven ounces of Silk Brown L (Color Index-Special) were added. When the solution had reached boiling twenty pounds of raw silk skeins were entered andtwere simultaneously degummed and dyed.

No loss of color resulted.

I claim: A silk degumming and dyeing bath, comprising soap, a boil off oil, a degummlng alkaline salt, a-

direct dye and an oxidizing color stabilizer having protein coagulation properties sufllciently potent to convert solublllzed sericln into insoluble colloidal form but not substantially to prevent elimination of sericin from the material phosphotungstate.