US3150918A - Method of bleaching cotton piece goods - Google Patents

Description

3 150,918 METHOD OF BLEACH ING COTTON PIECE GGGDS Raymond R. Currier, Pittsburgh, Pa, assignor to Pittsburgh Plate Glass Company, Pittsburgh, P3,, a corporation of Pennsylvania No Drawing. il iled Mar. 29, 1962, Ser. No. 183,412 3 Claims. (Cl. 8-111) The present invention relates to the bleaching of cotton goods. More particularly, the present invention relates to the bleaching of cotton piece goods. Still more particularly, the present invention relates to an improvement in the bleaching of cotton hosiery.

The term cotton goods as used herein in the speci fication and claims means fabric composed entirely of cotton as well as unions or mixtures of cotton fibers with other fibers such as rayon, nylon and other synthetic and natural fibers easily blended with cotton fibers. The unions or mixtures above contemplated generally contain at least percent cotton by weight of the cloth. The cotton goods also include cloth comprised of cotton or cotton unions which have been woven and/ or knitted.

In the bleaching of cotton piece goods, such as cotton hosiery, recourse is had to special techniques and equipment to insure adequate treatment of the goods for a desired degree of brightness. The bleaching techniques employed by the prior art on piece goods such as hosiery are in general batch type operations as opposed to the continuous bleaching methods used in treating cloth in open width form. Thus, to achieve a desired degree of bleaching for a specific batch of cotton piece goods or cotton yarn considerable expense is incurred in chemical costs for bleaching solutions. In addition, the bleaching operations as conventionally carried out require considerable time to achieve the desired bleaching effect, thereby adding to the overall cost of the operation.

Thus, for example, in the operation of one of the conventional processes of the prior art, cotton piece goods such as cotton hosiery are scoured, washed, and treated with an aqueous hypochlorite solution in a rotary dyer. After thorough wetting of the goods in the dyer, the bleach solution is heated in the machine to an elevated temperature to insure full bleaching action. After a period of time, usually one-half hour, the goods are washed and treated with hydrogen peroxide as an anti chlor. This treatment also involves heating of the peroxide solution to an elevated temperature. The goods are then treated with water to Wash residual chemicals therefrom and are then ready for further finishing, such as by treatment with solutions containing optical or fluorcscent whiteners.

As can be readily seen. processes of the above type require the heating of treating solutions to elevated temperature and washing steps, both of which are time consuming and costly. A conventional process such as described above requires three hours or more to provide cotton piece goods such as cotton hosiery in a finished condition. in addition, processes of this type are quite costly from the standpoint of the chemical requirements for a given degree of bleaching on any specific type of cotton piece goods.

Piece goods, as employed herein in the specification and claims. refers to goods which are comprised essentially of individual units or articles of cotton cloth which are normally treated in batch type operations. Typical of materials embraced by the term piece goods are socks. stockings and other'forms of hosiery. towels, underwear. shirts. sweaters, blankets, bedspreads and other like cotton material in article or unit form. Also included are cotton yarns contained on spools.

In accordance with the present invention, there has been States Patent 0 provided for the art an improved method of bleaching cotton piece goods, particularly cotton hosiery, which method reduces substantially many of the problems formerly encountered in conducting bleaching operations on these materials. Thus, the time required for a given degree of bleaching on any specific type of cotton piece goods is reduced substantially, usually at least to 200 percent or more. In addition, substantial reductions in chemical costs for a given bleaching operation are readily attained. By substantially reducing the time required for a given bleaching operation, plant productivity is increased to a significant extent. Still further, the process requires no specialized equipment and may be readily adapted to the equipment presently employed to conduct batch bleaching of piece goods in a conventional manner.

Thus, it has been found according to the present invention that in bleaching cotton piece goods, particularly cotton hosiery, excellent bleaching of the material may be readily accomplished by thoroughly saturating the goods in an aqueous alkaline solution of hydrogen peroxide to provide the goods with a solution content of between 250 and 600 percent by weight, basis the weight of the dry goods, and then contacting the goods with steam at elevated temperatures, usually between 210 and 212 F. for a period of at least fifteen minutes.

Bleaching, in accordance with the teachings contained herein, is conducted in equipment that is conventionally employed to bleach cotton piece goods such as hosiery. Typical of machines utilized for this purpose is the Turbo Rotary Dyeing Machine manufactured by the Turbo Machine Co. of Lansdale, Pennsylvania, and shown on page 182 of the Technical Manual of the American Association of Textile Chemists and Colorists, volume XXXV. As can be readily seen in the reference referred to, these machines are constructed of an inner perforated basket, usually cylindrical in shape which is contained in an outer solid shell. The inner shell is rotated by a drive means connected to a suitable motor. The outer shell of the dyer is equipped with an inlet for the introduction of the bleaching fluids and a suitable outlet is provided for emptying fluids from the machine.

Spools of yarn are conventionally bleached by treatment in package dyers. Typical of the package dyers employed for this purpose are the Turbo Package Dyer, manufactured by the Turbo Machine Co. of Lansdale, Pennsylvania, and the Gaston-County Package Dyer manufactured by the Gaston-County Dyeing Machine Co. of Stanley, North Carolina. These machines are shown on pages 182 and 177, respectively, of the Technical Manual of the American Association of Textile Chemists and Colorists. This equipment may be readily employed to conduct the bleaching operation herein contemplated to provide enhanced bleaching of spools of cotton yarn.

Bleaching solutions utilized in the instant process are aqueous alkaline solutions of hydrogen peroxide. The alkalinity of the aqueous peroxide solutions is usually imparted by alkali metal hydroxides such as sodium or potassium hydroxide employed therein though alkaline earth metal hydroxides may also be employed. The quantity of alkali metal or alkaline earth metal employed in any given aqueous peroxide solution is considerably variable. Conveniently, the alkali metal or alkaline earth etal concentration in the aqueous peroxide solutions is such that a pH of between 8 and 13 is provided in the solution. Preferably, the alkali concentration is sufiicient to impart a pH of between 10 and 12 to the aqueous peroxide solutions.

Aqueous alkaline hydrogen peroxide saturating solutions as employed herein conveniently contain less than three (3) percent hydrogen peroxide (anhydrous) by weight of the bleaching solution. Usually the hydrogen peroxide (anhydrous) content of the solution is between 0.1 percent to about two (2) percent by weight. Preferably, baths employing hydrogen peroxide (anhydrous) concentrations of between 0.3 to 0.7 percent by weight basis the weight of the solution are utilized. The aqueous alkaline hydrogen peroxide solutions can be utilized during the saturation phase of the operation at ambient temperatures (70 F.) as well as at elevated temperatures. A temperature range in these solutions of between 85 F. to about 110 F. has been found particularly desirable during the saturation cycle for the bleaching of cotton hosiery. Generally, temperatures which reach or exceed the boiling point of the bleaching solutions are to be avoided.

In addition to the hydrogen peroxide contained in the bleaching solutions herein employed, small quantities of alkali metal silicates are usually present therein. The use of an alkali metal silicate in the aqueous alkaline peroxide bleaching solutions has an enhancing effect on the bleaching solutions. Typical of the silicates contemplated for use herein is sodium silicate having the composition Na O(SiO where x is a value between 2 and 4. Concentrations of between 0.1 and 3 percent by weight of solution of 42 Baum sodium silicate (Na O(SiO are conveniently employed. Preferably an 0.5 percent by weight concentration is employed.

In applying the bleaching solution to the goods to be bleached, considerable care should be maintained to provide adequate saturation of the cloth. Thus, the cloth should contain at least 250 percent by weight bleaching solution therein basis the weight of the dry goods and may contain up to 600 percent solution by weight. Preferably, solution pick-up is regulated so that a pick-up between 300 and 450 percent solution by weight is obtained. Solution pick-up of the goods may be conveniently regulated by regulating the volume of bleaching solution introduced into the treatment vessel. Thus, if a solution weight pick-up of cloth of 300 percent is desired on a 100 pound batch of cotton hosiery, 300 pounds of bleach solution will be required. As a practical matter, an excess of solution over that desired for saturating the dry goods to a given degree is employed since most equipment utilized is capable of containing small quantities of solution in areas not in contact with goods contained in the equipment. This residual liquid capacity can be easily determined for any particular piece of equipment however and this quantity of solution is added to the quantity necessary to give the desired pick-up. Thus, in a rotary dyer of 100 pound capacity where it was desired to provide a 300 percent solution pick-up or 300 pounds of solution, the volume of bleach solution would be calculated by dividing the 300 pounds of solution desired by the weight of the bleach solution in pounds per gallon. This would provide the required volume of bleaching solution in gallons. Rotary dyers of 100 pound capacity usually hold between 12 to 14 gallons of solution which does not enter the inner cloth containing basket. Thus, to the gallons of solution required to supply the desired 300 percent pickup, an additional 12 to 14 gallons of solution are added.

For a more complete understanding of the instant invention, reference is made to the following examples which are illustrative of methods which may be employed in carrying out the novel bleaching process herein disclosed:

Example I A Turbo Rotary Dyer of 100 pound (dry goods) capacity was employed to prepare the bleaching solution. Fifty gallons of water were introduced into the machine through a liquid intake and the water was heated by steam coils located in the bottom of the machine to 90 F. To the water contained in the machine was added 0.8 pound of flake caustic soda (NaOH), 2.5 pounds of 42 Baum sodium silicate (Na O(SiO and 8.3 pounds of 35 percent hydrogen peroxide. The inner basket of the machine was rotated during the addition of chemicals to assist in the dissolving of the chemicals. The rotation of the basket was stopped and to the inner basket was added a batch of gray cotton socks weighing pounds. The inner basket was closed and the outer shell also closed and the basket again rotated for five minutes to thoroughly saturate the socks. This provided a solution pick-up of 300 percent basis the weight of the dry socks. The excess solution was drained from the machine by opening the drain valve in the bottom of the shell encompassingthe basket. Leaving the drain open, live steam was admitted to the machine through a steam inlet at a temperature of 212 F. for a period of twenty minutes. Hot water F. to F.) was then introduced through the liquid inlet and the basket again rotated to thoroughly wash the goods. After washing for five to ten minutes, the rotation of the basket was discontinued, the machine drained, and the socks were bleached to a full white.

Example II Cotton yarn mounted on spools and placed in a package dyer such as a Gaston-County package dyer previously referred to may be bleached in a similar manner within the purview of the instant invention. Thus, in treating cotton yarn, the bleaching solution is admitted to the dyer in quantities suflicient to give the desired solution pick-up on the yarn. The solution, after the yarn has been saturated to the desired degree, is then removed from the dyer and steam is admitted at temperature of usually 210 F. to 212 F. for twenty minutes. After steaming, the yarn is washed with water, preferably hot (160 F. to 180 F.) and the yarn is bleached to a full white.

In utilizing the instant process, recourse to high temperature steaming steps may be had if the equipment is capable of withstanding the corresponding pressures. Some package dyeing machines can withstand sufiicient pressure to permit the steaming operation to be conducted at temperatures up to about 240 F. Generally, where high temperature steaming is contemplated, temperatures of between 220 F. to 230 F. are employed.

Usually in the bleaching of white cotton hosiery and other like materials, optical bleaching agents are employed. These fluorescent brightening agents are conventionally added to the goods after the bleaching and washing steps have been completed. When they are added directly to the bleaching solutions and heated therein during bleaching as has been the practice in the past, they are found quite frequently to be rapidly depleted and the absorption on the cloth is often uneven and unsatisfactory. In the applicants process, these fluorescent brighteners may be added to the bleaching solution with no difficulty and upon completion of the steaming operation the goods are found to contain adequate quantities of brightener thereon and uniformly distributed.

Example III A three liter volume of aqueous solution is prepared containing 4.1 percent H 0 (50 percent), 1.5 percent Na SiO and 0.5 percent NaOH by weight of solution. The solution also contains 0.075 percent Uvitex V.R. (a water soluble optical bleach manufactured by Ciba Co. Inc.). Two cotton socks of 100 percent cotton are immersed in the solution for twenty seconds and then removed. The wetted socks are placed in an autoclave and steamed for forty-five minutes at 212 F., washed and dried. E mple IV bleach contained on the two samples can be detected.

As can be readily seen from the above examples and description, the present process provides considerable reductions in time for bleaching cotton piece goods while still providing adequate bleaching. In addition, considerable savings of chemical costs is accomplished since the bleaching solutions herein employed can be reused due to the fact that little heat is employed directly on the solutions themselves.

Certain references have been made herein to optical bleaches or fluorescent brightening agents. Typical of the substances embraced by these terms are the chemicals listed on page 322 of the Technical Manual of the American Association of Textile Chemists and Colorists, volume XXXV, under the heading Fluorescent Brightening Agents.

While the invention has been described with reference to certain specific embodiments thereof, it is not intended to be so limited except insofar as appears in the accompanying claims. This application is a continuationin-part of US. patent application Serial No. 12,265, filed March 2, 1960, now abandoned.

I claim:

1. A method of batch bleaching cotton piece goods comprising introducing said goods into an aqueous alkaline solution of hydrogen peroxide, said solution containing between 0.2 and 3 percent hydrogen peroxide by weight of solution 0.1 and 3 percent sodium silicate by weight of solution and having a pH of between 8 and 13, wetting said goods with the solution until the solution content of the cloth is between 250 to 600 percent by weight basis the weight of dry cloth, removing the goods from contact with solution and steaming the wet goods at temperature of from 200 F. to 240 F. for at least fifteen minutes.

2. A method of batch bleaching cotton piece goods comprising introducing said goods into an aqueous solution of hydrogen peroxide, said solution containing between 02 and 3 percent hydrogen peroxide by weight and having a pH of between 8 and 13, wetting said goods with solution to provide between 250 to 600 percent solution in the cloth by weight basis the weight of the dry goods, separating the wet goods from the solution, and steaming said Wet goods at temperatures between 200 F. to 240 F. for at least fifteen minutes.

3. A method of bleaching cotton piece goods comprising introducing said goods into an aqueous alkaline hydrogen peroxide solution containing 0.2 to 3 percent hydrogen peroxide by weight, 0.1 to 3 percent sodium silicate by weight, and having a pH of 8 to 13, said solution being maintained at a temperature of between F. to F., wetting said goods with solution to provide between 250 to 600 percent solution in the goods by weight basis the weight of the dry goods, separating the wet goods from the solution and heating said Wet goods by direct contact With steam at temperature of between 200 F. to 240 F. for at least fifteen minutes.

References Cited in the file of this patent UNITED STATES PATENTS 2,029,985 Clark et al. Feb. 4, 1936 2,194,358 Hundt et al Mar. 19, 1940 2,202,478 Bell May 28, 1940 2,220,682 Kauffmann et al. Nov. 5, 1940 2,334,066 Campbell et al. Nov. 9, 1943 2,740,689 Easton et al. Apr. 3, 1956 2,903,430 Butler Sept. 8, 1959

Claims (1)

1. A METHOD OF BATCH BLEACHING COTTOM PIECE GOODS COMPRISING INTRODUCING SAID GOODS INTO AN AQUEOUS ALKALINE SOLUTION OF HYDROGEN PEROXIDE, SAID SOLUTION CONTAINING BETWEEN 0.2 AND 3 PERCENT HYDROGEN PEROXIDE BY WEIGHT OF SOLUTION 0.1 AND 3 PERCENT SODIUM SILICATE BY WEIGHT OF SOLUTION AND HAVING A PH OF BETWEEN 8 AND 13, WETTING SAID GOODS WITH THE SOLUTION UNTIL THE SOLUTION CONTENT OF THE CLOTH IS BETWEEN 250 AND 600 PERCENT BY WEIGHT BASIS THE WEIGHT OF DRY CLOTH, REMOVING THE GOODS FROM CONTACT WITH SOLUTION AND STEAMING THE WET GOODS AT TEMPERATURE OF FROM 200*F. TO 240*F. FOR AT LEAST FIFTEEN MINUTES.