US1908481A - Method of bleaching fibers - Google Patents

Description

Patented May 9, 1933 UNITED STATES search Re PATENT OFFICE HANS KAUFFMANN, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR T0 BUFFALO ELECTED-CHEMICAL CO. INC., 0F BUFFALO, NEW YORK METHOD OF BLEACHING- FIBERS No Drawing. Application filed December 10, 1931, Serial No. 580,219, and in- Germany October 4, 1930.

The present invention relates to a process of bleaching fibers and more particularly to the bleaching of fibers of vegetable origin such as cotton.

The present invention provides a process for bleaching goods in which the goods are saturated with an acid hypochlorite solution, thereafter laid down, washed and subsequently treated with a hot alkaline hydrogen peroxide solution. This process possesses numerous advantages over the older processes since the goods treated in this manner have a lower cost in preliminary treatment, due to the small quantities of bleaching agents required, since the goods treated do not have the same tendency to decompose hydrogen peroxide solutions which untreated goods possess or which is possessed by goods subjected to other preliminary treatments. They can therefore, either be bleached with smaller quantities of hydrogen peroxide of a given strength, or conversely the use of proportionately stronger solutions of hydrogen peroxide is permitted, which can be used again. In addition, solutions of hydrogen peroxide of higher alkalinities may be used.

Further, goods treated in the manner as outlined herein apparently do not lose in strength or in weight, even over long and extensive periods of contact with certain of the bleaching materials. It has been found that colored stripes, designs, etc., which are woven in the goods do not have their colors affected appreciably by this process, due to the short duration of the treating time and therefore the limited time of contact of the colored portions with the bleaching agents. Pre-treatment of the goods with chlorine efiects a material saving in handling since the necessity of desizing and boiling is eliminated.

In proceeding in accordance with the present invention unbleached goods are treated initially with chlorine and subsequently with hydrogen peroxide. The treatment with chlorine may be effected in either of two ways: first, the goods may be wet out and thereafter placed in an atmosphere in contact with chlorine gas or, the goods may be passed through water into which a stream of chlorine is being introduced.

It is to be noted, that in either method of treatment with chlorine, contacts of chlorine with the goods should be of short duration, on the order of a few seconds to several minutes or more. In either case, after treatment with chlorine in the presence of moisture, for a time which is suflicient to produce a preliminary effect therein, the goods are washed out and then subjected to the final hydrogen peroxide bleaching process.

It is believed that the elfectiveness of the chlorine is due to the presence of hydrochloric and hypochlorous acids in equilibrium in the water solution, and that due to the presence of these chemicals, the preparation of the goods, as above described, takes place without damage thereto. The preliminary treatment of the goods therefore, is effected by hypochlorous acid in the presence of an excess of hydrogen ions.

Solutions of hydrochloric and hypochlorous acids may also be prepared in other ways than the method described, as for instance, by acidifying and diluting ordinary commercial alkaline hypochlorite solutions, as for instance sodium hypochlorite or by dissolving and acidifying ordinary chloride of lime or bleaching powder. In any case, wherever hydrochloric and hypochlorous acids are produced in solutions, this solution has the specific effect of preparing goods in a condition quite suitable for bleaching with hydrogen peroxide, since such goods, after treatment and subsequent water washing exert a substantially slight decomposing action on hydrogen peroxide.

After subjecting the goods to the preliminary tr-eatment with chlorine and water mixtures, the goods are subsequently washed with water and thereafter treated with a hydrogen peroxide solution. This treatment may be eflected in apparatus currently in use, as for instance by piling the goods upon a kier where the goods come in contact with the hot alkaline hydrogen peroxide solution which is caused to circulate in contact with the goods for a period of from two to six hours or until the goods are properly bleached.

Hydrogen peroxide solutions may be made up of one gram of caustic soda, eight grams of silicate of soda, two grams of 100% hydrogen peroxide, per liter of water. It has also been found that the concentration of hydrogen peroxide as well as the concentration of the alkaline materials may be substantially increased above the quantity mentioned above, and the time of contact of the solution with the goods materially decreased in order to obtain the same bleaching effect. Thus, it has been found that a liter of water to which has been added four grams of caustic soda, fourteen grams of silicate of soda and 3.3 grams of 100% hydrogen peroxide would give an excellent bleach in from fifteen to thirty minutes when circulated in contact with the goods, at a temperature close to the boiling point of the solution. The results desired in the various bleaching processes will indicate the alkalinity and concentration of hydrogen peroxide best suited. as at higher temperatures and higher concentrations slightly larger consumptions of hydrogen peroxide are encountered, while with lower concentrations smaller consumptions of hydrogen peroxide may be expected but the time of contact to produce a certain bleach will, of course, be of greater duration.

After treatment with the circulating hot alkaline hydrogen peroxide, the goods are washed and rinsed and are found to be in an excellent white condition, perfectly bleached and with fibers which are undamaged, and which possess substantially their original strength and almost their original weight. The white obtained is permanent.

It has been found that when using five parts of bleaching solution to one part of goods and good bleaching results are obtained, the hydrogen peroxide loss is about ten percent. Satisfactory bleaching results may be obtained by this process with a loss of 0.1 to 0.2% of 100% hydrogen peroxide, based on the weight of the goods while bleaching processes .in use heretofore in which hydrogen peroxide has been used, consumed 0.5 to of 100% hydrogen peroxide per unit of goods.

It is to be noted that various steps of the present process are adapted for use in an equipment currently installed and lends itself suitably for performance in a continuous system, in contra-distinction to a batch process.

hile it is very desirable to use hydrogen peroxide of definite strength, as for instance 100 volume hydrogen peroxide, it is to be understood that this reagent may be introduced into the alkaline peroxide solution by the use of other chemical. compounds. Thus, the solution for the final bleach may be prepared from perborate of soda, peroxide of soda, peroxide of barium or zinc, or other chemicals containing active oxygen which upon treatment with aqueous solutions produces hydrogen peroxide.

What is claimed is:

1. A process for bleaching cotton fibers and products produced therefrom, which comprises treating the goods with chlorine water for a short period of time and thereafter treating the fibers with an alkaline solution of hydrogen peroxide.

2. A process for bleaching cotton fibers and products produced therefrom which comprises treating the goods with chlorine of water for a short period of time and thereafter treating the fibers with an alkaline solution of hydrogen peroxide at an elevated temperature.

3. A process for bleaching cotton fibers and products produced therefrom which comprises treatin the fibers with chlorine water for a short period of time, and subsequently treating the fibers with an alkaline solution of hydrogen peroxide which contains at least one gram of caustic soda per liter and gyro grams of 100% hydrogen peroxide per HANS KAUFFMANN.