US2048991A - Process for bleaching fibrous material - Google Patents

Description

GR. 2O459991 known bleaching a Patented July 28, 1936 UNITED STATES UKQUH Una PATENT OFFICE PROCESS FOR BLEACHING FIBROUS MATERIAL Karl Butz, Chemnitz, and Gustav Deuschle and Giinther Simon, Stuttgart, Germany, assignors to H. Th. Bohme Aktiengesellschaft, Chemnitz, Germany, a corporation of Germany No Drawing. Application June 22, 1933, Serial No. 677,164. In Germany June 29, 1932 9 Claims.

This invention relates to processes for the bleaching of textile material and is particularly applicable to the treatment of vegetable fibers. It is the principal object of the invention to provide a bleaching process which may be simply and quickly carried out, and which is less expensive and which enhances the desirable qualities of. the material to a greater extent than processes heretofore employed.

It has hitherto been generally customary to bleach plant fibers by boiling them in alkali solutions, for instance lime or soda ash, caustic soda, or the like, under pressure at relatively high temperatures. In this step of the process the foreign substances which are present in the fibers, such as waxes, pectin bodies, and albuminous substances, are converted to a soluble form and are decomposed or bleached out by a subsequent bleaching. process with calcium chloride, sodium hypochlor' on other flwell- V This process gives excellent results so far as the appearance of the material is concerned, a beautiful white effect being obtained, but the process requires a great deal of time and is not entirely satisfactory since the fibers lose weight and become hard to the touch.

Processes of an entirely different character have also been employed in which the material to be bleached is treated without employing chlorine compounds, alkaline peroxide solutions being used. Such processes avoid certain defects of the chlorine bleaching but the expense is greater and the bleaching effect is not as satisfactory.

In accordance with the present invention it is found that the advantages of both types of process can be obtained and the defects thereof avoided if the processes are, in a sense, combined. Thus it is a feature of the invention that the material to be bleached is preferably first wetted with a suitable wetting or dispersing agent such as a highl sulphonated oil or the like and is then impr e gmmmorine bleaching solution for a short period of time sufficient only to enable the fibers to completely absorb the solution. The impregnated fibrous material is then subjected to the action of an alkaline oxidizing agent such as a peroxide bath. It is found that in this process the active or available chlorine of the impregnating bath is almost completely consumed in effecting chlorination of the albuminous substances present in the cellular structures of the fibers, the impregnated material introduced into the peroxide bath containing practically no active chlorine even though no effort is made to remove the chlorine, for instance by washing or by an antichlorinating process. It is presumed that by reason of. the relatively brief period during which the chlorine is 5 applied to the material, albumin chloramines are formed which do not act destructively. On the contrary, these chloramines probably exert an activating effect on the peroxide bath and owing to the presence of caustic alkali in the bath are more easily and completely disintegrated and. dissolved out than are the original albuminous substances. Unless this assumption is made it is difficult to explain the manner in which the material, which has been impregnated with chlorine but not bleached, can be thereafter effectively bleached with the use of a relatively small quantity of peroxide and in a short period of time to a surprisingly beautiful full white, the bleached goods exhibiting an ability to absorb which is not 20 attained when peroxide baths are employed in accordance with the teachings of the prior art.

The process may be carried. out in the following manner.

Example I 25 350 kg. of raw woven Egyptian yarn are first soaked in a bath containing about 1.5 kg. of highly sulphonated castor oil in 500 liters of water at a temperature of. 50 C., the yarn being thereafter impregnated with asoda-chlorine bleaching solution of about 4 g. active chlorine per liter, sufficient solution being used to provide about 3 kg. of active chlorine. The solution is applied to the material only for a length of time sufficient to effect complete impregnation of the fibers, and the material is then squeezed out and without intermediate treatment is placed in a bleaching vat which is supplied with a peroxide bleaching bath of the following composition:

Water liters 2000 Water-glass 36 B do 7.5 Caustic soda kg 3 Hydrogen peroxide 40% 1iters '7 45 Example II Water liters 3000 Water-glass 36 B do 3 Caustic soda kg 3 Hydrogen peroxide 40% liters 4 Magnesium salt of sulphonated oleic alcohol kg 0.25

After three hours treatment at 90 to 95 C. the bleaching is complete and the goods are finished as indicated in the preceding example.

Example III 1700 kgs. of heavy Egyptian damask are singed as usual undressed by means of a ferment and. under addition of a wetting agent, rinsed and thereupon impregnated at 30 with a strong alkaline hypochlorite liquor, containing 6-8 grams of active chlorine per liter. Then the goods are soaked, without being rinsed, with a peroxide liquor as follows:

The bleaching liquor consists of Water liters Sodium silicate solution of 36 B do Barium-salt of highly sulphonated oleic alcohol kg 1.7 Sodium peroxidedo 8 Hydrogen peroxide solution 40 liters 16 Within five hours the solution is slowly heated up to 90 by means of steam-pipes and under circulation, and the goods are kept in the liquor during the night. After finishing the bleaching, the peroxide contained in the liquor is not totally spent in most cases. It is advisable to add the missing chemicals to the bleaching liquor for another use.

The bleached goods are washed and thereupon finished as usual. By this method of working the very difficult bleaching of Egyptian tissue is performed without treatment under pressure within two days, while four days at least were necessary before.

It will be observed that in the foregoing examples the material is subjected to a preliminary treatment with a wetting agent in order to facilitate penetration of the fibers by the bleaching agent. Various other types of wetting agents may be employed, the following agents being found satisfactory: dodecylalcohol, sulphuric ester, sulphated oleic acid amide, sulphated ricinoleic acid anilide, sulphated linoleic acid methyl ester.

In general we prefer to use wetting agents derived from fatty materials by sulphation or sulphonation processes such as sulphonic acids and sulphuric acid esters of oils, fats, and higher fatty alcohols, which may be described for convenience as sulphuric derivatives of fatty materials.

With respect to the nature of the chlorine bleaching agent employed, any of the conventional agents containing available chlorine such as are commonly used in the treatment of plant fibers are satisfactory; thus, we may use an alkaline chlorine bath such as a calcium chloride or oxychloride solution or the like, such compounds being referred to for convenience hereinafter as chlorine bleaching solutions.

Among additional compounds containing available chlorine may be mentioned p-toluolsulfochloramide, alkali metal hypochlorites.

It is also understood that the expression alkaline' oxidizing bath is intended to cover any alkaline solution suitable for use with fibrous materials and capable of liberating oxygen. The following compounds may be successfully employed for this purpose in lieu of the hydrogen peroxide and sodium peroxide mentioned in the foregoing examples: sodium perborate, sodium percarbonate, sodium perpyrophosphate and other persalts.

It'is found that the action of the alkaline bath is facilitated by the employment of a stabilizing agent which is added to the oxidizing bath as hereinbefore indicated, earth alkali salts of sulphuric acid esters or sulphonic acids of the higher molecular fatty alcohols, and salts of fatty acid alkyl estersulphuric acid esters being particularly satisfactory. A mixture which comprises the magnesium salt of a high molecular fatty alcohol sulphuric acid ester and the magnesium salt of a true sulphonic acid of a fatty alcohol, is extremely' effective for the purpose. In addition to the striking stability of these salts to alkalies, they exhibit the property, even in the presence of very high alkali concentration and high temperature of the bleaching bath, of efficiently stabilizing the peroxide and at the same time reducing the surface tension of the bleaching bath to a minimum, thus ensuring effective and rapid bleaching of large areas. The mixing of these salts with the bath also maintains the latter in a. clear condition so that precipitates tending to harden the fibrous materials are excluded. B'y proceeding in this manner a. bleaching effect superior to that obtained by earlier methods can be secured without loss of oxygen.

It has heretofore been proposed to combine a chlorine bleaching with a peroxide bleaching, but the prior processes are essentially different in that the fibers have heretofore been exposed for several hours to the action of the chlorine bleaching solution and have been subjected to the action of the peroxide bath only after washing and/or antichlorinating. The present invention is essentially simpler, quicker, and cheaper in operation than such prior combined processes and is entirely different in principle since the chlorine treatment apparently affects only the albuminous substances and does not accomplish bleaching of the fibers.

It will be understood that the present invention is applicable to the bleaching of plant fibers in all stages of preparation, for example in the form of loose material, carded bands, yarn in skeins or on spools, or woven and twisted goods of all kinds.

Having thus described the invention, what is claimed as new and desired to be secured by Let ters Patent is:

1. A process for bleaching textile material of vegetable origin which comprises immersing the material in an alkaline chlorine bleaching solution for a period not appreciably longer than that required for penetration of the fibers of the material, and thereafter soaking the material in a peroxide bath. ifk process for bleaching fibrous material of vegetable origin which comprises the steps of iON OF TEXTELES KEEP ZS,

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MoDlFL treating the material with a wetting agent, impregnating the fibers with an alkaline chlorine bleaching solution for a period not appreciably longer than that required for penetration of the fibers of the material, and immediately thereafter immersing the material in an oxidizing bath.

3. A process for bleaching fibrous material of vegetable origin which comprises the steps of treating the material with a wetting agent including a sulphuric acid derivative"offatty'material, impregnating the fibers with an alkaline chlorine bleaching solution for a period not appreciably longer than that required for penetration of the fibers of the material, and immediately thereafter immersing the material in an oxidizing bath.

4. A process for bleaching fibrous material of vegetable origin which comprises the steps of treating the material with a wetting agent comprising a sulphuric acid ester-oflawfattynacidalkyl ester, impregnating the fibers with an alkaline chlorine bleaching solution for a period not appreciably longer than that required for penetration of the fibers of the material, and immediately thereafter immersing the material in an oxidizing bath.

5. A process for bleaching fibrous material of vegetable origin which comprises the steps of treating the material with a wetting agent comprising sulphonated castor oil,impregnating the fibers with an alkaline chlorine bleaching solu- HUME Milli smug longer than that required for penetration of the fibers of the material, and immediately thereafter immersing the material in a bath including a peroxide and an earth alkali salt of a sulphuric derivative of fatty material. 5

7. A process for bleaching fibrous material of vegetable origin which comprises the steps of treating the material with a I h impregnating the fibers with an alkaline chlorine bleaching solution for a period not appreciably longer than that required for penetration of the fibers of the material, and immediately thereafter immersing the material in a bath including a peroxide and an earth alkali salt of a sulphuric derivative of a high molecular fatty alcohol. 8. A process for bleaching fibrous material of vegetable origin which comprises the steps of treating the material with a wetting agent, impregnating the fibers with an n'ephlorine bleaching solution for a period not appreciably longer than that required for penetration of the fibers of the material, and immediately thereafter immersing the material in a bathincluding a peroxide and an earth alkali salt of a. sulphuric derivative of a fatty acid alkyl ester. 9. A process for bleaching fibrous material of vegetable origin which comprises the steps of treating the material with a wetting agent, impregnating the fibers with an al'kalirie'bhlorine bleaching solution for a period not appreciably longer than that required for penetration of the fibers of the material, and immediately thereafter immersing the material in an oxidizing bath including a peroxide and a mixture of the magnesium salts of a high molecular fatty alcohol GUNTHER SIMON.

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