US2020437A - Process for bleaching vegetable fibers - Google Patents

Description

table fibers which are regularly bleached in the 7 course of manufacture, in disclosing my improved process I shall describe it as when utilized for the 1 bleaching of cotton material.

PatentedNov. 12, 1935 UNITED STATES PATENT bll Hun: v

OFFICE PROCESS FOR BLEACHING VEGETABLE FIBERS Irwin J. Smith, Albany, N. Y.

No Drawing. Application March 15, 1928, Serial No. 262,051

17 Claims. (Cl. 82)

This invention relates to processes for bleaching vegetable fibers and fibers obtained from a cellulose base, as for instance cotton, fiax in the form of cellulose, and/or mixtures thereof.

The object of this invention is to provide an efficient, economical, and more simple process than those now generally used; one which will require a minimum of skill, time, labor, and equipment.

As cotton forms a major part of those vege- It is, however, to be understood that the same process is applicable to the other named fibers and to artificial silks of those varieties which consist wholly or essentially n l of regenerated cellulose (as distinguished from lulose acetate), gnaterialsznadeirmna ture of such fibers, or of such artificial silks and one or more of such fibers, without material change.

The present generally used process for bleaching cotton material is the so-called hypochlorite process, the first step in which is to boil out the material in a kier under pressure and containing an alkaline liquor. It is next thoroughly washed, and thereafter submitted to the action of a solution of hypochlorite; again washed, then subjected to an acid bath or sour in order to decompose any residual hypochlorite which may be retained by the fiber. Heat treatment with alkali peroxide is sometimes used instead of the acid or sour treatment. thorough washing completes the process. The time required for the carrying out of this usual process varies from seven to twenty four hours.

Another method of bleaching which is used to some extent is known as the peroxide bleach, and consists in treating the material with an alkaline solution of hydrogen peroxide at various temperatures, and thereafter giving the material a thorough washing, which completes the process. This method requires but from three to ten hours to complete the bleaching of cotton materials, the time depending on the temperature and alkalinity of the bath; but is objectionable on account of its high cost of chemical, as compared with that of the first described, or hypochlorite method.

It is impossible to obtain the same degree of whiteness by the peroxide method as economically as by the hypochlorite method on account of the difference in the usual market value of the chemicals necessarily used in the carrying out of the two processes; but I have discovered a method After the sour bath another whereby it is possible to secure some of the ad vantages of the peroxide bleach, such as the saving in the loss of weight or shrinkage, and the retention of tensile strength and softness; and to eliminate some of the disadvantages of the hypochlorite bleach, especially the initial boiling out in a kier or in an open alkaline bath, and which is an absolutely necessary step in the carrying out of the hypochlorite process if a clear whit e is to be produced and the cotton seeds, motes and shives are to be completely removed.

My improved process for bleaching cotton and other vegetable fibers, etc. as before enumerated, is as follows:

The material to be bleached is first wet out in any suitable manner, then subjected to the action of a hypochlorite solution (preferably made from sodium hypochlorite though calcium hypochlorite 1 may be used) at a strength of from 1 to 5 Twaddell, and at a temperature of from 50 to 120 F., 20 for a periodof from twenty minutes to an hour or a more. The degree of concentration, the temperature of the solution, and the length of time depend on the grade of fiber being treated. The length of time is to be sufficient for an appreciable bleaching action to take place, but not long enough for the solution to impair or injure the material being processed. The exact degree 01' concentration, the temperature of the solution, and the duration of the operation depend entirely upon the grade of cotton or other material being processed, and the amount of foreign matter which may be present therein.

At this point in my process the material is partially bleached, but cotton seeds, motes and shives, if any were present have not been completely removed.

The bath is now dumped (and the material rinsed if necessary to remove surplus hypochlorite solution), and a solution of some suitable antichlor (or chlorine-neutralizing agent) such as ammonium hydroxide, or an acid such as sulfuric or hydrochloric or sodium bisulfite, or s u l f 1,r dioxide, is added to the bath.

11 ng of the hypochlorite 4,5 solution and the rinsing of the material may both be omitted, the solution containing the antichlor being introduced, at the proper time, directly into the hypochlorite solution (which at this stage Will have lost most of its strength) In such cases 50 the entire operation may be completed in a single bath or operation.

An alkaline oxidizing solution is next added to the bath and the temperature thereof preferably fill-fist to, and held at or about the boiling point until the material has reached the desired degree of whiteness, and the cotton seeds, motes and shives are completely removed. This operation will generally require from forty-five to ninety minutes, but may sometimes take longer, the time depending on the condition of the material being processed and the temperature of the solution. Bleaching and cleaning action will take place if the temperature of the bath be lower than that preferred, but the action will be correspondingly slower.

When the desired degree of whiteness has been obtained, the bath is drained and the material Washed in the usual manner.

As the bleaching action of hydrogen peroxide is much greater in an alkaline bath, in the carrying out of my improved process I prefer to make use of an alkaline oxidizing solution made by dissolving from 1% to 4% (based on weight of materials) of sodium peroxide in water, whereby a solution of caustic alkali and hydrogen peroxide is formed. As just stated, this percentage is based on the weight of the goods, and if based on the contemplation of the sodium peroxide in water, about one-third to three grams of sodium peroxide per liter would be used. This solution being strongly alkaline and at the same time oxidizing, the completion of the bleaching action takes place in much less time than by other methods; and the time required for dissolving and removing the cotton seeds, motes and shives which may be present in the material being processed is reduced to a minimum.

In my process the quantity of alkaline oxidizing solution, and the time necessary to complete the bleaching is considerably reduced because of the fact that a partial bleach was obtained in the initial hypochlorite treatment.

Although I now prefer to use sodium peroxide to produce the alkaline oxidizing solution, satisfactory results may be obtained by using any persalt, or sodium perborate, sodium persulfate, or hydrogen peroxide to which a suitable agent has been added to make the solution alkaline.

Hydrogen peroxide being its own neutralizing agent, if it be used to produce the alkaline oxidizing solution, the use of any of the above enumerated neutralizing agents in the carrying out of this improved process may be omitted except when it is desirable for economic reasons to pre serve the hydrogen peroxide entirely for the bleaching operation.

By means of the improved process above described I am able to attain a degree of whiteness equal to that which may be obtained by either of the before described usual processes; at a lower chemical cost than by the usual peroxide method; and at a lower cost in time, labor, and equipment than by the usual hypochlorite method.

In the improved process which I have developed a number of variables are necessarily present, and in describing it I have given these a range which I now believe to be ample to cover any condition which is likely to be met with in commercial practice. I do not, however, wish to limit myself to the limits of variation above set forth, as further may be advisable, all of which would be within the ambit of the appended claims.

I claim:

1. The process of bleaching cotton and flax, and materials composed thereof, consisting of subjecting the unboiled material to the action of a hypochlorite solution, until a partial bleach is obtained and the seeds, motes and shives partly removed, then dumping the bath, then introducobtained, and the seeds, motes and shives partly 10 removed, then dumping the bath and rinsing the material, then introducing a fresh bath contain- 1 ing an antichlor, adding thereto an alk aline peroxide solution, and finally boiling the material therein until the required degree of white- 5 ness is obtained, and the seeds, motes and shives completely removed.

3. The process of bleaching cotton and flax, and materials composed thereof, consisting of subjecting the unboiled material to the action of 0 a bath containing a hypochlorite solution, until a partial bleach is obtained, and the seeds, motes and shives partly removed, dumping the bath and thereafter introducing an alkali n e peroxide solution, and finally boiling the material therein until the required degree of whiteness is obtained, and the seeds, motes and shives completely removed.

4. The process of bleaching cotton and flax, and materials composed thereof, consisting in subjecting the unboiled material to the action of a bath containing a hypochlorite solution, until a partial bleach is obtained and the seeds, motes and shives partly removed, dumping the bath and rinsing the material, and thereafter in a fresh bath introducing an antichlor alkaline oxidizing agent of a group consisting of peifialtsl and finally boiling the material therein until the required degree of whiteness is obtained, and the seeds, motes and shives completely removed.

5. A process of bleaching textile material consisting essentially of cellulose, which comprises subjecting the unboiled material to the action of a hypochlorite solution until it is partially bleached, then subjecting such treated material 45 to the action of a per salt alkaline oxidizing bleaching agent.

6. A process of bleaching textile material consisting essentially of cellulose, comprising first subjecting the Wetted material, without pre- 5 liminary boiling in alkali solution, to the action of a bath containing a hypochlorite solution, and thereafter to one containing an antichlor per salt alkalinepxidizing solution.

7. A process for bleaching textile material consisting essentially of cellulose, which comprises subjecting the unboiled material to the action of a bath containing a hypochlorite soluton until a partial bleach is obtained, then dumping the bath and rinsing the material, then introducing an antichlor solution and later subjecting the so treated material to action of an alkaline oxidizing agent of a group consisting of per salts-k,

8. The process of bleachihg--textile material consisting essentially of cellulose which comprises first submitting the unboiled material to the action of a bath containing a 1 to 5 (Twaddell) solution of sodium hypochlorite, and afterwards subjecting such material to action of a bath containing a 'per salt alkaline oxidizing bleaching agent.

9. A process of bleaching textile material consisting essentially of cellulose which comprises first submitting the wetted raw material to the action of a bath containing a hypochlorite solu- 75 some summon cl Uri-Jr; rum) \EA 'it'FF iT t Fri-PE LZZAL ltiqDti-L T v C (l t-H ll (ii- T xt-51 3 required degree of whiteness is obtained, and the seeds, motes and shives completely removed.

13. A process of bleaching textile material consisting essentially of cellulose, consisting in subjecting the unboiled material to the action of a 5 bath containing a hypochlorite solution, until a partial bleach is obtained and the seeds, motes and shives partly removed, dumping the bath, rinsing the work, and thereafter subjecting said subjecting the material to the action of a bath material to an antichlor and to an alkaline oxidiz- 10 containing a hypochlorite solution until a partial ing solution of a group consisting of per salts, and bleach is obtained, then adding to the bath an finally boiling the material therein until the antichlor and thereafter adding thereto a 1% to required degree of whiteness is obtained and the 4% solution of sodium peroxide dissolved in seeds, motes and shives completely removed.

water. 14. A process of bleaching cotton and materials l5 11. A process for bleaching textile material conproduced therefrom, consisting of subjecting the sisting essentially of cellulose which comprises first unboiled cotton to the action of a hypochlorite submitting the unboiled material to the action of solution, and thereafter to an alkaline oxidizing a bath containing a 1 to 5 (Twaddell) hyposolution of a group consisting of per salts.

chlorite solution for a period of from 20 to '75 15. Aprocess of bleaching cotton and materials 20 minutes until a partial bleach is obtained and produced therefrom, consisting of subjecting the the seeds, motes and shives partly removed, then unboiled cotton to the action of a hyp j adding to the bath an alkaline oxidizing agent solution, and thereafter to an antichlor alkaline of a group consisting of per salts, and finally boiloxidizing agent of a group Consistlng of p fismg the material therein until the required degree A process of bleachlegpmon mammals 25 of whiteness is obtained and the seeds, motes and prod1 1ced therefrom conslsFmg E i hives completely removed unbo led cotton to the act on 0 a hypoc on e s solution, an antichlor solution, and thei eafter to A proces for bleachmg textfle i i an alkaline oxidizing solution of a group consisting sisting essentially of cellulose, consistmg in subof per sarw 30 jecting the unboiled material to the action of a bath containing a hypochlorite solution, until a partial bleach is obtained and the seeds, motes and shives partly removed, dumping the bath and thereafter introducing an antichlor alkaline oxidizing solution of a group consisting of per salts, and finally boiling the material therein until the 17. A process of bleaching cotton and materials produced therefrom, consisting in subjecting the unboiled material to the action of a hypochlorite solution, rinsing the material, and then subjecting the material to the action of an alkaline oxidizing solution of a group consisting of per salts,

IRWIN J. SMITH.