US1940768A - Bleaching fur skins - Google Patents

Description

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FIPBSO CANON OF TEXTILES & FiBERS,

9 GR 1QS00Q768 Patented Dec. 26, 1933 sears BLEACHING FUR SKINS William E. Popkin, Brooklyn, N. Y.

No Drawing.

Application June 12, 1930 Serial No. 460,795

8 Claims.

This invention relates to the bleaching of animal fur skins preparatory to dyeing the same, and has for its object to provide a new and improved method resulting in an improved product.

The known methods of bleaching fur skins either injure the hair fibres or discolor the skins. When fur skins are treated directly with a strong oxidizing bleaching solution, the action is so drastic that the air and leather of the skins are tendered. When the skins are first treated with metal salts existing in two valences according to United States Patent 1,573,200, prior to bleaching, there is furthermore a concomitant dyeing effect, which leaves the hair and leather tinted with insoluble characteristic colored compounds, the color depending on the nature of the metal salt used. For instance, when ferrous sulfate is used, the entire fur including hair and leather are tinted a light brown characteristic iron oxide color. When cuprous salts are used, a greenish color is produced, and when manganous salts are used a purple tint is imparted to the fur skin. Furthermore, when metal salts are used they leave the hair and leather impregnated with an undesirable deposit, as for instance, oxidized iron, which imparts an undesirable tint to the fur, weakens the leather and hair fibres, interferes with the subsequent dyeing treatment and is generally known to result in dyed furs of greatly inferior quality.

It is an object of the present invention to avoid the deleterious tendering action of direct bleaching, and also to obviate the use of materials which will remain as such or produce reaction products that will remain in or upon the fur skins after the completion of the bleaching operation, the presence of which is objectionable, and in this way to produce bleached fur skins, which have the color, texture, strength and lustre of unbleached light fur skins.

According to my invention, the fur skins after being killed in any known or preferred manner, as by being treated with a dilute weak alkali, {i is impregnated with what I term a cyclic oxidizing catalyst and then the impregnated fur is img mersed in a bleaching solution, whereupon the oxygen that is liberated from the bleach is immediately taken up by the catalyst which is contained in and adheres to the fur skin. The bleaching effect starts promptly and its rate is controlled by the chemical liberation of oxygen from the oxidizing solution. In this way, the skins, which were originally dark colored, are bleached to a light fiesh color unimpaired as to structural strength, lustre and texture.

The bleached skins obtained by this process may now be dyed to any light, or other desired color in accordance with the procedures used for dyeing natural white or light colored skins.

The following is a specific example of one mode of applying the method of the present invention; it being understood however that the following description is given merely by way of illustration and that the process is not limited to the specific details of the following illustrative example. Brown or black Australian rabbit skins are killed in a dilute solution of sodium carbonate. The skins are then rinsed and hydro-extracted. They are then immersed in a solution of sodium tetraborate (borax) or an equivalent cyclic ox: i in catal t and a low d. 9 re Overnight- While the strength of the borax solution ors'olution of an equivalent catalyst may vary within considerable limits, I prefer to use an aqueous solution of a strength of about 0.5 to about 10.0 per cent sodium tetraborate. To this may be added a more or less quantity of salts of tartaric acid. After soaking for 8 to 12 hours the fur skins are rinsed and the excess of borax removed. The immersion in the borax solution has impregnated the leather and hair of the fur skin with the cyclic oxidizing catalyst. The skins are then immersed in a solution of nygrggenperoxr ide or equivalent oxidizifiblEzhing agent; the quantity of free oxygen in this solution being regulated by controlling the hydrogen ion concentration. The cyclic oxidizing catalyst jigging;- diately takes up"tlie"6xygn liberat''d" from the bleaching solution and forms unstable intermediate compounds which draw the bleach onto and into the material comprising the fur skin. In this way the dark colored skins are quickly and smoothly bleached to a light flesh color. The bleaching operation is conducted at room temperature until the skins have become sufficiently decolorized. These light colored skins are then rinsed and can, if desired, be dyed in accordance with any of the well known or desirable processes employed for dyeing furs or the like.

It may be here stated especially in connection with the foregoing specific example of applying the method of the present invention, that the preliminary killing operation may be omitted or combined with the impregnating treatment. It may also be stated that salts or other chemical compounds of a character compatible with the oxygen carrier may be added to that solution prior to the treatment with the bleaching or oxidizing agent.

Examples of cyclic oxidizing catalysts are acetone-bisulfite, borax, ethyl-alcohol, glucose, urea,

and formaldehyde. Such compounds under the mild conditions used and in the presence of hydrogen peroxides temporarily form intermediate substances containing more oxygen which is obtained from the oxidizing bleaching solution. They give up their absorbed or combined oxygen slowly to the fur skin or equivalent and are found in their original state at the conclusion of the bleaching action, as distinguished from the ferrous sulfate or other metallic equivalents, of other methods of bleaching, which become 0xidized permanently to a higher state of oxidation. The catalysts of the present invention suffer no final oxidation.

Furthermore the catalysts are colorless compounds which are soluble in water and are capable of readily absorbing oxygen from aqueous solutions at room temperature. In this process these compounds exert no chemical or tendering action either on the leather or hair of the fur skin at any stage of the bleaching process and they leave it unimpaired as to original strength of leather and lustre of the hair.

The skins remain submerged in the solution of cyclic oxidizing catalyst for several hours until the fibres and leather are thoroughly impregnated. The excess of catalysts solution is then removed by suitable means and the fur skins are then immersed in an oxidizing bleaching solution. The bleach may consist of hydrogen peroxide, perborates, or persulfates of any suitable strength, the quantity of free oxygen present being regulated by governing the hydrogen ion concentration of the solution. The oxygen that is liberated from the bleach is immediately taken up by the catalyst which is contained in and adheres to the fur skin. The bleaching effect starts promptly and its rate is controlled by the chemical liberation of oxygen from the oxidizing solution. In this way, I convert skins which were originally dark colored into skins possessing a light flesh color, being unimpaired as to structural strength, lustre and texture.

In my illustrative example the borax functions as an oxygen carrier, 1. e. cyclic oxidizing catalyst, becoming temporarily oxidized to sodium perborate as an intermediate product. The intermediate compound being unstable in aqueous solutions gives up its added oxygen in a gradual manner to the fur skins that are being bleached. When acetone or its addition compounds are used as cyclic oxidizing catalysts, acetone peroxides are formed as unstable intermediate compounds; and when ethyl alcohol is used as the catalyst, ethyl-hydrogen peroxide or diethyl peroxide are formed as the unstable oxidizing agents.

In prior practice, when metallic salts, a ferrous salt for example, is used as an impregnating agent, the metal salt takes up the oxygen with drastic avidity until it becomes oxidized to a ferric compound. Then it no longer possess the power to take up oxygen; further bleaching of the fur skins depends then on the direct action of the bleaching or oxidizing agent on the hair of the skin.

The bleached fur skins obtained as a result of the illustrative example consequently differ from fur skins which are treated with metal salts such as ferrous sulfate. In my process the catalysts and the bleaching agents and the products of reaction are all completely soluble in aqueous solutions. The bleached fur skins obtained after washing, therefore, resemble a natural light col ored fur skin in appearance and strength and lustre of hair. When ferrous salts or its equivalents are used in conjunction with an alkaline peroxide of hydrogen solution in the bleaching process, there is deposited into and onto the hair and leather of the fur skin a gelatinous precipitate of ferric hydroxide or equivalent metal hydroxide. Such precipitates are insoluble in water and give the fur skins a characteristic coloration depending on the metal salt that has been used. This precipitate furthermore causes a swelling on the inside of the hair and leather fibres thus weakening them structurally.

The advantages and superiorities of my process are numerous and of great practical importance, and may be summarized as follows: The process makes possible the bleaching of dark colored fur skins to a light or flesh color possessing the strength of leather and lustre of hair of the original skin, and also enables the obtaining of such bleached skins free from metal discoloration and free of the injurious tendering activities induced by the presence of metal salts particularly those in a higher state of oxidation. Furthermore, my process permits an economical utilization of the bleaching and oxidizing agent because the catalyst acts as an accumulator for the available oxygen and gradually releases it as the decolorizing process progresses. By my process the oxidizing or decolorizing activity is so controlled by the cyclic oxidizing catalyst that the accumulated oxygen is very gradually delivered to the hair of the fur skin, thus avoiding the tendering and injurious action which characterizes the use of metallic reducing agents.

What is claimed is:

1. The herein described method of bleaching animal fur skins, which comprises impregnating fur skins with a colorless soluble cyclic oxidizing catalyst, and subjecting the impregnated fur skins to an oxidizing bleaching action.

2. The herein described method of bleaching animal fur skins, which comprises impregnating fur skins with a colorless water soluble cyclic oxidizing catalyst, and subjecting the impregnated fur skins to an oxidizing bleaching action.

3. The herein described method of bleaching animal fur skins, which comprises impregnating fur skins with a cyclic oxidizing catalyst, and subjecting the impregnated fur skins to an oxidizing bleaching action.

4. The herein described method of bleaching animal fur skins, which comprises impregnating fur skins with a colorless water soluble cyclic oxidizing catalyst, and subjecting the impregnated skins to an oxidizing bleaching and decolorizing action without the formation of insoluble reaction products.

5. The herein described method of bleaching animal fur skins, which comprises impregnating the furs with cyclic oxidizing catalyst, and then immersing the impregnated furs in an oxidizing bleaching solution and permitting the oxygen of the bleaching solution to combine with or be absorbed by the catalyst and then given off slowly from the catalyst to the fur skins.

6. The herein described method of bleaching fur skins, which comprises impregnating the furs with a water soluble cyclic oxidizing catalyst, and then immersing the impregnated fur skins in an oxidizing bleaching solution and permitting the oxygen of the bleaching solution to combine with or be absorbed by the catalyst and then given off slowly from the catalyst to the fur skins.

'7. The herein described method of bleaching fur skins, which comprises immersing fur skins in a solution of a cyclic oxidizing catalyst until the TREATMENT & CHEMICAL MODE HEHG & DYEING; FLUiU CANON OF TEXTILES & FiBERS,

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solution of water soluble cyclic oxidizing catalyst until the hair and the leather are impregnated with the catalyst, removing the excess catalyst solution from the fur skins, and then immersing the impregnated fur skins in an aqueous oxidizing bleaching solution containing free oxygen and permitting the oxygen of the solution to combine with or be absorbed by the catalyst and then given ofl slowly from the catalyst to the fur skins.

WILLIAM E. POPKIN.