US1958483A - Method of stripping - Google Patents

Description

Patented-May 15, 1934 UNITED STATES PATENT OFFICE METHOD OF STRIPPING No Drawing.

Application November 21, 1930,

Serial No. 497,336

6 Claims.

This invention relates to a method of stripping the color of dyed textile material, and relates more particularly to the stripping of textile materials made of cellulose acetate or other organic derivatives of cellulose.

- An object of my invention is to strip the color of dyed textile materials in an expeditious manner. A further object of my invention is to remove the color in whole or in part of dyed textile 10 materials containing organic derivatives of cellulose. Other objects of this invention will appear from the following detailed description.

It is often desirable to strip or remove the color or dyed fabrics in order to render them capable of being dyed in a different color or shade. Thus if errors have been made in the dyeing of fabrics, hosiery and the like so that an undesired color is imparted thereto or the dyeing is streaky, the usual practice is to remove the color and then dye the materials to the desired shade. However the stripping of textile materials containing cellulose acetate or other organic derivatives of cellulose which have been dyed with dispersed dyestufls has heretofore not been commercially successful when the ordinary methods of stripping are employed.

I have found that textile materials containing cellulose acetate which have been dyed with dispersed dyestuffs may be stripped to the extent required in commercial operation if the same are first treated with a reducing agent, preferably in the presence of an acid, and then treated with an oxidizing agent, also preferably in the presence of an acid.

In accordance with my invention, I strip a dyed textile material by first treating the same with a reducing agent and then treating it with an oxidizing agent.

The textile materials to be stripped in accordance with this invention may be yarns, woven or knitted fabrics, or articles of apparel such as hose, dresses, underwear and the like. While this invention may be used for the stripping of textile materials containing any kind of fibre, it is of particular importance in the stripping of textile materials containing filaments of organic derivatives of cellulose such as organic esters of cellulose and cellulose ethers. Examples of such organic esters of cellulose are cellulose acetate,

cellulose formate, cellulose propionate and cellulose butyrate, while examples of cellulose ethers are ethyl cellulose, methyl cellulose and benzyl cellulose. The textile material may be a mixed material containing yarns or filaments of the organic derivative of cellulose and other textile fibres such as cotton, wool, silk or reconstituted cellulose.

The textile material to be stripped may have been previously dyed with any dyestulf, but this invention is of particular importance in connection with the stripping of organic derivative of cellulose material which has been dyed with dispersed dyes, that is water insoluble dyes that are applied in finely dispersed or colloidal suspensions, since these dyestuffs are quite fast. Examples 05 of such dispersed dyes are amino-azo-benzene derivatives, benzene-azo-naphthyl amine derivatives, naphthalene-azo-aniline derivatives or amino-azo-naphthalene derivatives, as more particularly described in the U. S. patent to Ellis 1,618,- 413 of February 22, 1927; nitro derivatives of diaryl amines as described in the U. S. patent to Ellis 1,618,415 of February 22, 1927; vat dyestufl's of the anthraquinone series in unreduced state as described in the patent to Ellis 1,641,965 of 7 Sept. 13, 1927; unsulfonated stilbene compounds as described in patent to Ellis 1,694,414 of December 11, 1928, etc.

To effect the stripping, the textile material is first treated with a reducing agent which may be an aqueous solution of zinc sulfoxylate-formaldehyde or sodium sulfoxylate-formaldehyde, preferably in the presence of an acid and at elevated temperatures of say 160 to 190 F.

After treatment with the reducing agent, with 86 or without previous washing, the material is then treated with an oxidizing agent such as an aqueous solution of sodium hypochlorite, potassium hypochlorite or calcium hypochlorite, pref erably in the presence of an acid and preferably 9 at ordinary temperatures.

The stripping process may be conducted so that all of the color is stripped from the textile materials or only partially stripped so that the shade remaining does not interfere with the color to be imparted to the textile material by subsequent dyeing.

In order further to illustrate my invention, but without being limited thereto, the following specific example is given.

Example 100 parts by weight of hosiery made of cellulose acetate yarn which have been dyed with a dispersed dyestufl is entered in a machine containallowed to run for 30 minutes at 180 F. The

machine is then drained and refilled with water to rinse the goods thoroughly so as to remove all traces of the zinc sulfoxylate-formaldehyde and the machine is then drained. There is then added to the machine a solution of the hypochlorite of sodium or calcium of 1 Tw. and 5 parts by weight of acetic acid (56% strength) and the goods are allowed to remain in this bath at room temperatures for 30 minutes.

The machine is then drained and refilled with water and the goods well rinsed. Thereupon the machine is drained and refilled with water and one part by weight of sodium bi-sulfite, as antichlor, is added to the bath and the goods treated for 10 minutes at ordinary temperature. The machine is then drained and refilled with plain water and the goods rinsed.

It is to be understood that the foregoing description is given merely by way of illustration and thatanany variations may be made therein, without departing from the spirit of my invention.

Having described my invention, what I desire to secure by Letters Patent is: I

1. Method of removing color from a dyed textile material containing yarns of organic derivatives of cellulose comprising treating the textile material with a reducing agent comprising a sulfoxylate and then treating the material with an oxidizing agent comprising a hypochlorite.

2. Method of removing color from a dyed textile material containing cellulose acetate comprising treating the textile material with a reducing agent comprising a sulfoxylate and then treating the material with an oxidizing agent comprising a hypochlorite.

3. Method of removing color from a textile material comprising yarns of cellulose acetate which have been dyed with a dispersed dyestuflf comprising treating the textile material with a reducing agent comprising a sulfoxylate in the presence of an acid and then treating with an oxidizing agent comprising a hypochlorite in the presence of an acid.

4. Method of removing color from a textile material comprising yarns of cellulose acetate which have been dyed with a dispersed dyestufl comprising treating the textile material with zinc sulfoxylate-formaldehyde in the presence of an acid and then treating with an oxidizing agent comprising a hypochlorite in the presence of an acid.

5. Method of removing color from a textile material comprising yarns of cellulose acetate which have been dyed with a dispersed dyestuff comprising treating the textile material with zinc sulfoxylate-formaldehyde in the presence of an acid and then treating with a hypochlorite in the presence of an acid.

6. Method of removing color from a textile material comprising yarns of cellulose acetate which have been dyed with a dispersed dyestuff comprising treating the textile material with zinc sulfoxylate-formaldehyde in the presence of an acid at a temperature of 160 to 190 F., rinsing the material, treating with a solution of a hypochlorite in the presence of acid at room temperatures, washing the material, and then treating with an anti-chlor.

KENNETH CLARKE LOUGHLIN.

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