US2373881A - Rayon bleaching and scouring treatment - Google Patents

Description

Patented Apr. 17, 1945 UNITED STATES PATENT OFFICE RAYON BLEACHING AND SCOURING TREATMENT No Drawing.

Application April 27, 1940,

Serial No. 332,012

8 Claims.

This invention relates to an improved process for the treatment of fabrics of vegetable origin whereby scouring,.desizing and bleaching operations may be effected simultaneously. The process of the invention is of particular advantage in the treatment of unfinished fabrics of a rayon, or containing a large proportion of rayon fibers, such as spun or filament rayon.

Greige cloth and similar newly woven fabrics have a very limited use. For most purposes, they must be subjected to further treatment to place them in salable form because, first, the natural color bodies occurring in the vegetable fibers detract from the appearance of the fabric, second, they contain varying amounts of motes (i. e., nonfibrous particles such as cottonseed fragments) that adhere to the fibers throughout the spinning and weaving processes, and third, the presence of natural waxes and pectins and of sizings, principally starchy (which are applied to the warp threads during weaving) makes the fabric waterrepellent and thus tends to interfere with bleaching or dyeing. Removal of these various impurities from the fabrics so as to render them white and absorbent frequently involves a long and extensive series of treatments, and in general the more delicate and finer fabrics (which will not withstand the action of strong hot alkalies) require the longer and more complex treatments. Thus, certain cloths, including cotton and rayon mixtures used extensively in corset cloth and draperies, spun rayon and spun rayon mixtures, yarn dyed fabrics such as marquisette with colored dots and shirting with colored stripes, velveteen, tafieta and corduroy, are usually subjected to a mild, long and complex treatment in such equipment as Rodney-Hunt kettles, becks, jigs and the like. Such complex treatments are exemplified by that in a Rodney-Hunt kettle which, for a heavy cloth, involves the following series of operations: desizing, usually by malting; a hot water wash to remove malt and such starch as has been solubilized; scouring. usually with soap and weak alkali; a second water wash; bleaching, usually with sodium hypochlorite; a third water wash; an anti-chlor wash, a fourth water wash.

In the process of the present invention the above-enumerated series of operations is simplified and shortened to the end that substantial savings in time, labor, equipment and reagents are realized. Furthermore, the results attained with respect to desizing, scouring and bleaching are not only attained concurrently but are superior to those achieved by the more complicated methods of the art. By the use of the process of this invention a whiter cloth which is more absorbent, has a softer hand and lower starch content, and which has suffered less deterioration than in heretofore customary practice is obtained.

In accordance with this invention impurities and substances whose presence is undesirable, such as natural color bodies and sizings, may be satisfactorily and simultaneously removed from unfinished rayon fabrics by subjecting the fabric to the action of an alkaline aqueous solution having dissolved therein hydrogen peroxide and a synthetic organic detergent salt which is watersoluble, free of fatty acid salt or ester substituents, active in the presence of the alkali and resistant to decomposition and oxidation by the hydrogen peroxide present. Such an operation, which simultaneously desizes, scours and bleaches, may be carried out in any suitable apparatus, such as for example a Rodney-Hunt kettle.

The alkalinity required by the process of the invention may be produced by any suitable alkali or alkaline buffer substance capable of producing and maintaining a moderate hydroxyl ion concentration in the treating solution. Best results are obtained in solutions in which the pH value is not greater than about 11 to 12. One particularly effective and cheap reagent suitable for this purpose is sodium silicate. A concentration of sodium silicate approximating 5 grams per liter produces a treating solution having a pH of 9.4, and a concentration of silicate approximating 10 grams per liter produces a treating solution having a pH of 10.9. Silicate concentrations of this order of magnitude are appropriate for the process of the invention, the exact quantity used being dependent on the type of material treated and amount of impurities present.

The concentration of hydrogen peroxide will also be governed by the properties of the unfinished fabric being treated and. the difficulty of producing the desired whiteness in that particular fabric. In general we have found that satisfactory results are obtained by using quantities of volume H202 solution appropriate to give aqueous solutions containing between about 1 gram per liter and 6 grams per liter of 100 volume peroxide. The peroxide solution known as 100 volume peroxide is a readily available commercial product in the form of an aqueous solution and averages about 27.4% H202 by weight. The stated range of 1 to 6 grams per liter is therefore equivalent to a range of about 0.275 to about 1.654 grams per liter pure H202.

The ynthetic detergent to be employed must exert its detergent action and be active in the presence of the alkali concentrations in the treating solutions and must be resistant to decomposition and oxidation by the hydrogen peroxide. The detergents which we prefer are sulfated or sulfonated high molecular weight organic compounds which are water soluble salts free of fatty acid salt or ester substituents which in warm or hot alkaline solutions would undergo hydrolysis with the consequent production of ordinary alkali metal soaps. As examples of such high molecularweight organic sulfates and sulfonates may be mentioned sodium lauryl sulfate, sodium oleyl sulfate, sodium stearyl sulfate, sodium lauryl sulfonate, sodium decyl benzene sulfonate, sodium dodecyl benzene sulfonate, or salt of other sulfonated alkylated benzene, sodium hexadecyl sulfonate or mixtures of this and similar sulfonated aliphatic hydrocarbons, and sodium-2 methyl pentane-4 sulfate. It is to be understood that compounds other than those just mentioned, or mixtures thereof, are suitable provided they are higher organic sulfates or sulfonates free of fatty acid salt or ester substituents, and provided they have the other above-described properties. We have found that sodium lauryl sulfate and sodium oleyl sulfate give particularly good results. It will be understood that by the expression free of fatty acid salt or ester substituents used herein 1 in identifying our detergent, we intend to indicate that the detergent contains no free or combined carboxyl group. The concentration of the detergent is not particularly critical except that enough should be employed to emulsify the impurities present in the textile. Hence the proportion will depend upon the particular detergent, the amount of impurities to be removed and the speed with which removal is to be accomplished. In most cases concentrations approximating /2 gram per liter to 1 gram per liter will be satisfactory.

Most effective operation of the present process is attained at relatively high solution temperature, 80 C. being a particularly advantageous temperature at which to treat most fabrics. Any elevated temperature, substantially above room temperature and below the boiling point of the solution, may be used.

The time of treatment will vary according to the fabric being treated, the quantity of impurities present and the difficulty of their removal. In general we have found that a reaction time ranging from one to two hours is satisfactory to produce the desired results, although in some instances a period of /2 hour will be found sufficient.

The process of the invention will be illustrated by the following examples of small scale operation. The only important difference between such operation and large scale commercial runs which we have noted is that the large scale operations sometimes require treating solutions having a slightly higher H202 concentration. In each of the following illustrative examples /8 yard of cloth was placed in a pint jar with 125 c. c. of treating solution. These jar were agitated while immersed in water maintained at a temperature approximating 80 C.

Example I Spun rayon was treated in an aqueous solution containing 4.33 g. p. l. 100 volume H202, g. p. 1. sodium silicate which caused the solution to have a pH value approximating 9.4, and /2 g. p. 1. sodium lauryl sulfate. The treatment was continued for /2 hour at the end of which time the cloth had attained a brightness value of 74.4 as measured on a G. E. refiectometer, had a good absorbency and soft hand, and had been partially freed of its original high starch content. In a similar run employing the same reagents and conditions except for the substitution of 1 g. p. l. of soap for the synthetic organic detergent, the brightness attained was 72.6, the absorbency was poor, and the starch removal was negligible.

Example II Rayon taffeta was treated in an aqueous solution containing 1.08 g. p. 1. volume H202, 10 g. p. 1. sodium silicate which caused the solution to have a pH value approximating 10.9, and /2 g. p. 1. sodium lauryl sulfate. The treatment was continued for 2 hours at the end of which time the cloth had a brightness value of 75.6, good absorbency and soft hand, and a very low starch content.

Tensile strength measurements made on other samples of cloth treated in the manner and under the conditions described in these examples indicate that the cloth is not materially weakened as a result of such a treatment, either with respect to the warp strength or the filler strength.

We claim:

1. In the treatment of rayon containing colo-r bodies and starchy substances, the improvement which comprises simultaneously scouring and bleaching the rayon by subjecting it in a single immersion treatment to the action of an alkaline aqueous solution having dissolved therein hydrogen peroxide in a concentration within the range of about 0.275 to about 1.65 grams per liter and a synthetic organic water-soluble detergent salt having no free nor combined carboxyl group, which detergent salt is active in the presence of the alkali and is resistant to decomposition and oxidation by the hydrogen peroxide.

2. In the treatment of rayon containing color bodies and starchy substances, the improvement which comprises simultaneously scouring and bleaching the rayon by subjecting it in a single immersion treatment to the action of an alkaline aqueous solution maintained at an elevated. temperature and having dissolved therein hydrogen peroxide in a concentration within the range of about 0.275 to about 1.65 grams per liter and a synthetic organic water-soluble detergent salt having no free nor combined carboxyl group, which detergentsalt is active in the presence of the alkali and is resistant to decomposition and oxidation by the hydrogen peroxide.

3. In the treatment of rayon containing color bodies and starchy substances, the improvement which comprises simultaneously scouring and bleaching the rayon by subjecting it in a single immersion treatment to the action of an alkaline aqueous solution having dissolved therein hydrogen peroxide in a concentration within the range of about 0.275 to about 1.65 grams per liter and a synthetic organic Water-soluble detergent salt having no free nor combined carboxyl group, which detergent salt is active in the presence of the alkali and is resistant to decomposition and oxidation by the hydrogen peroxide, said detergent being selected from the group of high molecular weight organic compounds consisting of aliphatic alcohol sulfates, aliphatic sulfonates and alkylated aromatic sulfonates.

4. In the treatment of rayon containing color 9% ill timers $1 H359.

bodies and starchy substances, the improvement which comprises simultaneously scouring and bleaching the rayon by subjecting it in a single immersion treatment to the action of an alkaline aqueous solution having a pH maintained within the range of 9' to 12 by means of sodium silicate and having dissolved therein hydrogen peroxide in a concentration within the range of about 0.275 to about 1.65 grams per liter and a synthetic organic water-soluble detergent salt having no free nor combined carboxyl group, which detergent salt is active in the presence of the alkali and is resistant to decomposition and oxidation by the hydrogen peroxide.

5. In the treatment of rayon containing color bodies and starchy substances, the improvement which comprises simultaneously scouring and bleaching the rayon by subjecting it in a single immersion treatment to the action of an alkaline aqueous solution having dissolved therein hydrogen peroxide in a concentration within the range of about 0.275 to about 1.65 grams per liter and sodium lauryl sulfate.

6. In the treatment of rayon containing color bodies and starchy substances, the improvement which comprises simultaneously scouring and bleaching the rayon by subjecting it in a single immersion treatment to the action of an alkaline aqueous solution having dissolved therein hydro- Qibiiltiii I? soon gen peroxide in a concentration Within the range of about 0.275 to about 1.65 grams per liter and sodium lauryl sulfate in a concentration approximating /2 gram per liter.

7. In the treatment of rayon containing color bodies and starchy substances, the improvement which comprises simultaneously scouring and bleaching the rayon by subjecting it in a single immersion treatment to the action of an alkaline aqueous solution having a pH maintained within the range of 9 to 12 by means of sodium silicate and having dissolved therein hydrogen peroxide in a concentration Within the range of about 0.275 to about 1.65 grams per liter, and sodium lauryl sulfate in a concentration approximating /2 gram per liter.

8. In the treatment of rayon containing color bodies and starchy substances, the improvement which comprises simultaneously scouring and bleaching the rayon by subjecting it in a single immersion treatment to the action of an alkaline aqueous solution having dissolved therein hydrogen peroxide in a concentration within the range of about 0.275 to about 1.65 grams per liter and sodium oleyl sulfate.

ARCHIE LOUIS DUBEAU. JAMES DOUGLAS MACMAHON. GEORGE PAUL VINCENT.