US1912345A - Process for bleaching tanner's wool - Google Patents

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Patented May 30, 1933 UNITED STATES PATENT OFFICE PARKER HAYWOOD DEL PLAINE, OF BRISTOL, PENNSYLVANIA, ASSIGNOR TO ROHM & HAAS COMPANY, OF PHILADELPHIA, PENNSYLVANIA PROCESS FOR BLEACHING TANNERS WOOL No Drawing. Application filed December 24, 1930. Serial No. 504,641.

This application is a continuation in part of Serial No. 413,428 filed December 11th, 1929, now abandoned.

When sheep pelts are intended for use as 5, furs, they are usually tanned with vegetable tannins of various descriptions, and afterwards the wool is shorn to the right length. The short wool fibres, so removed, are badly stained red or brown by the vegetable tanning material, and it has been, heretofore, dlfficult to remove this stain sufliciently to allow its use in light colored shoddy mixtures. The bleaching of this so-called tanners wool could neither be accomplished by the use of 15 oxidizing or reducing substances. Oxidizing compounds deepen the color and fix the tannins more firmly in the wool, while reducing compounds reduce the depth of the stain but the original color soonreappears thru oxidation in the air. It was logical,

therefore, to try to extract as much as possible of the tannins from the wool preliminary to any bleaching eltort. On the other hand, such products as alkalis that would be able to combine with the tannin were not recommended, because it was assumed that the action of alkali on the wool would be detrimental to it. The only alkali which seemed to be available, was ammonia, which is not strong enough an alkali to extract the tannins from the wool in an economical way.

I have found, in contradiction to the reigning opinion, that a very good extraction can be obtained with caustic alkalis, if care be taken to operate at low temperatures and with the proper buffering agents. Even a small amount of caustic alone will not harm the wool if tried under the right conditions, chiefly because the tannates of the alkali act as a buffer. When the tannin has been extracted by cold buffered caustic alkalis in this fashion, there still remains a strong staining of the wool due to the effect of the so-called non-tans on the wool. I found, then, that this residual stain is easily and permanently removed by well-known reducing agents such as the hydrosulphites and sulphoxylates.

To illustrate my way of operating, the following examples are given without, however, any intention on my part to limit myself to the exact conditions, as percentages, temperature, time composition of the buffering material or caustic alkali.

Ewample #1.25 grams of so-called tanners wool, which was reddish brown, were treated with 1 liter of water, containing 2.16 grams of caustic soda, for 4 hours at room temperature. The wool was then Washed, extracted and acidified with one liter of acetic acid; then washed again. The wool was then bleached with a solution of one liter of water, containing 1.5 grams of a sulfoxylate reducing (stripping) agent called Protolin S (registered trade-mark) and gram of glacial acetic acid, at the boil for one-half hour. After that the wool was washed and extracted. The sodium tannate formed on the extraction of the tannin from the wool acted as the buffering agent for the remaining caustic soda and the process was carried out without harm to the wool. Practically all. the stain was removed and the product was of a light cream color, which did not reoxidize to a deeper shade on prolonged standing, even after the addition of ammonia. Eamon- 9Z6 #2.Was carried out in the same manner with 6 grams of soda ,ash (anhydrous sodium carbonate) added to the caustic soda with the same results.

Example #5.WVas carriedput in the same way, using 20 grams of borax in addition to 2 grams of caustic potash with excellent results.

Example #4.In this case 10 grams of disodium phosphate were added as the buffer salt and the tanners wool treated for eight hours with the same good results.

Ewample #5.In this case 10 grams of trisodium phosphate were used for four hours without caustic soda. The trisodium phosphate acts in a manner very similar to the mixtures of alkalies in Example 4. This also gave good and lasting results.

The results of all of these treatments were uniformly good and neither harshened nor weakened the wool. On the other hand, experiments carried on with other alkalis, such as the hydroxides of the earth alkali group, gave a very inferior extraction of the tan nm.

It is understood that in the following claims the phase room temperature is to be taken to mean the temperature of a room in which such a process would ordinarily be carried out; substantially between the limits of 6095 F.

I claim,

1. The process of bleachingtanners wool which comprises extracting the vegetable tannins by subjecting it at room temperature to the action of solutions of the hydroxides of the alkali metals bufiiered by alkali metal salts or polyvalent acids, then removing the residual stain with a reducing agent.

2. The process of bleaching tanners wool which comprises extracting the vegetable tannins by subjecting the wool at room temperature to the action of solutions of hydroxides of the alkali metals in the presence of borax as a bulfer, then removing the residual stain with a reducing agent.

3. A process as described in claim 2 in which disodium phosphate is the buffering salt.

4. A process as described in claim 2 in which trisodium phosphate is the buflering salt.

5. The process of bleaching tanners wool which comprises extracting the vegetable tannins by subjecting the W001 at room temperature to the action of a solution of caustic soda in the presence of borax as a butler, then removing the residual stain with a reducing agent.

6. A process as described in claim 5 in which disodium phosphate is the bufl'ering salt.

7. A process as described in claim 5 in which trisodium phosphate is the buffering salt.

In testimony whereof I aflix my signature.

PARKER HAYWOOD DEL PLAINE.