US2231426A - Method of bleaching gray goods - Google Patents

Description

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1 Patented Feb. 11, 1941 UNITED STATES PATENT OFFICE Hans 0. Kaufimann, Eggertsville, N. Y., assignor to Buffalo Electro-Chemical Company, Inc.,

Buffalo, N. Y.

N Drawing.

Application May 10, 1939,

Serial No. 272,915

9 Claims.

The present invention relates to a method for bleaching cellulose, whether natural or regenerated, particularly in the form of fibers and filaments. More particularly it relates to a method for bleaching such fibers and filaments with alkaline solutions containing hydrogen peroxide, or material generating hydrogen peroxide, by first subjecting the cellulose to the alkaline bleaching solution under conditions where a low liquor ratio is maintained, and then subjecting the cellulose to an alkaline bleach where a relatively high liquor ratio is maintained.

Heretofore it has been suggested that cellulose be bleached by dampening the fibers with peroxide bleaching solutions and permitting the fibers to bleach in the dampened condition. Relatively high concentrations of hydrogen peroxide are required to produce goods of excellent white and considerable bleaching agent remains at the termination of the bleaching period. In general, bleaching in the damp condition with this type of solution is eifected at room temperatures or slightly elevated temperatures. Although considerable energy is saved, the peroxide consumption is high.

It has also been proposed to bleach cellulose in order to obtain excellent white by heating the fibers in a considerable body of bleachingsolution. In the cold damp bleach mentioned above, the liquor ratio is about 0.5 to 1.5. In the hot bleach using circulating hydrogen peroxide solutions, the liquor ratio is about 1:4 to 1:8. In or der to obtain full whites from gray goods by this hot treatment, the goods must be treated at least twice with the hot circulating bleaching liquor and in many instances additional treatments are required. Although excellent whites are obtained by the hot procedure, the consumption of energy is relatively high.

The present invention provides a method for bleaching cellulose readily and expeditiously in equipment presently employed. The present invention also provides a method for the production of full whites with a minimum consumption of energy and with a minimum consumption of bleaching ingredient.

In accordance with the procedure of the present invention, gray goods are first treated under conditions of low liquor ratio with an alkaline hydrogen peroxide bleach. The goods are partially bleached by this procedure and the motes and shives partially bleached and loosened. The goods are then rinsed and finished off under conditions of prevailing high liquor ratio by treating the goods at an elevated temperature with a, hot alkaline peroxide bleaching solution. When finished the goods possess a full white, are free of motes and shives, and possess substantially their original tensile strength. Additionally, the

peroxide consumption in the hot bleaching solution is relatively low due to the fact that the goods have been treated in the damp condition yarn, woven or knitted goods,is thoroughly wet out,

or saturated with the desired bleaching solution, and contain about 50 to 150% of solution based on the weight of goods. This step will usually include saturation of the goods with bleaching solution, as, for instance, by immersion therein and elimination of the surplus bleaching solution above that necessary to saturate the same by any well known means, as, for instance, by squeezing or hydroextracting, or by any known device or method, or the goods are saturated by any other convenient method and then permitted to stand in the dampened or saturated condition until the desired bleach is obtained. This desired bleached condition is obtained after a period of a few hours to about 16 hours or more depending upon the kind of bleaching solution used and the kind of goods.

The composition of bath effective for bleaching cellulose fibers with a low liquor ratio contains an alkali in addition to water and hydrogen peroxide, or some material generating hydrogen peroxide. This alkali may include materials acting as stabilizers for the hydrogen peroxide solution and may include, among others, silicate of soda, phosphates, such as sodium pyrophosphate, trisodium phosphate, disodium phosphate, sodium bicarbonate, borax, and the like. It is preferred, however, to use the well-known alkaline substances employed in bleaching operations, namely, caustic soda, soda ash, and the like. The quantity of alkaline material used should be considerably in excess of that thought permissible in circulating solutions and the alkali, calculated as sodium hydroxide, should be between about and 50 g per liter.

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it this are saturated with the bleaching ion- Will, the QXEQES of the solution being expressed or eliminated whereby the goods retained from to to ltil ii oi their original weight, or this quantity of bleaching solution is incorporated in the goods in any other fashion. The dampened goods are then permitted to stand in this saturated condition from about 2 to 16 hours. In order to obtain bleaching in this dampened condition, the goods may be stacked, piled or stored and generally covered in order to prevent evaporation or local changes in the concentration of the bleaching solution and to permit the goods to bleach in the damp condition with a liquor ratio, that is, the ratio of weight of treating solution to weight of goods being treated therewith, of about 0.5 to 1.5.

The temperature of the goods may be maintained at room temperature or at temperatures somewhat above room temperature and in general at temperatures below F. It will be understood where the temperature is high, the time of bleaching will be correspondingly low and also where the concentration of peroxide is high, somewhat shorter times are required to obtain the desired bleaching effect than are required with lower concentration of bleaching ingredient.

After the goods have stood in the damp condition for the desired period of time, they may be rinsed and transferred to kiers for treatment under conditions of high liquor ratio. After transference to a suitable heating vessel or kier, the goods are subjected to the final bleaching operation which includes treatment of the goods at elevated temperatures with a hot alkaline circulating peroxide bleaching solution. The quantity of solution with respect to the quantity of goods is relatively high and the liquor ratio should be maintained at from about 1:4 to 1:8. The alkaline peroxide bleaching solution is circulated over and through the goods in any desired fashion and by the employment of any conventional means and in general the goods will be piled in a conventional type of kier. The time of treatment will be from about one hour to about 10 hours and the temperature of the circulating solution will be above about F. and in general form about F. to F.

The alkaline peroxide bleach suitable for use in the hot treatment contains in one liter approximately 5 cc. silicate and 3.5 cc. IOU-volume hydrogen peroxide. At the end of the hot treatment the goods are removed, rinsed and finished in the usual manner.

As an example of the advantage of the present invention, it may be mentioned that in the bleaching of certain types of colored yarn goods the goods are desized, washed, and then subjected to two or more bleaching operations in which about 1 hydrogen peroxide 100-volume, based on the weight of the goods, is emlitili less in die gen e hall of the total h ii e more than y ween p de found neces- Sary to obtain the desired bleach is incorporated 15 in the solution used for bleaching with a low liquor ratio, the remainder, of course, being ineorporated in the bleaching solution used ior bleaching with a high liquor ratio. In most instances it will be found expedient to incorpo- 20 rate about 25 to 33% of the total peroxide in the first or low liquor ratio treatment and the remainder in the final bleaching step using a high liquor ratio.

In bleaching certain types of goods where two 25 hot hydrogen peroxide bleach baths are normally used (with the high liquor ratio), the present invention makes it possible to use considerably less peroxide by applying only one high liquor ratio treatment and one low liquor ratio 30 treatment. The low liquor ratio treatment may replace the entire desizing operation and thereby also eliminate one boil. In case only one boil is used with the regular operation, the

time of this boil may be considerably shortened 35 by applying a cold low liquor ratio step first. Therefore in the treatment of goods requiring about 3% 100-volume hydrogen peroxide, based on the weight of the goods, the present invention makes possible the obtaining of goods of 40 equal white and quality by employing approximately 2% hydrogen peroxide, based on the weight of the goods, and in addition gives increased kier capacity with some saving in eny.

Another example is the bleaching of heavy goods, for instance, sheeting. Sheets are usually treated first with one alkali pressure boil or a plurality of alkaline open boils, followed by a bleaching treatment. In most cases the gray 50 goods are first subjected to a desizing operation, followed by a thorough wash. In accordance with the present invention the goods may be bleached to the same degree of white and to a better quality by subjecting the gray goods 5 first to a low liquor ratio treatment, such as described, using approximately one third of the total amount of peroxide for bleaching. Thereafter the goods are washed and given a single alkaline open boil treatment, followed by a hydrogen peroxide bleach using two thirds of the total amount, that is to say, the quantity of peroxide in the low liquor ratio treatment is about of lOO-volume hydrogen peroxide, based on the weight of the goods, and in the second approximately 1% lOO-volume hydrogen peroxide, based on the weight of the goods. To bleach this type of sheeting according to the conventional method it would require over 2% of hydrogen peroxide 100-volume.

The present invention therefore includes also a method to eliminate any desizing operation which is usually necessary before the goods are bleached to a full white or in all the cases where goods are later on dyed, printed, or fin- 6- DLEHLII'HWU or Urunu; iLUHJ :ished, whereby residual impurities, espeicially starch, may cause difficulties or unevenness.

Although hydrogen peroxide has been described as the preferred bleaching agent, it will be under stood that materials generating hydrogen peroxide may be employed and to this end alkali metal and alkaline earth metal peroxides are suitable as are the perborates, percarbonates, perphosphates, persilicates, and the like. These materials, including hydrogen peroxide, being designated herein as peroxides.

It will be understood that the term liquor ratio refers to the relation between the weight of treating solution and the weight of goods treated therewith and that a low liquor ratio is one less than about 1.5 while a. high liquor ratio is above about 4. The former is generally used in padding operations and the latter in circulating operations.

I claim:

1. A method for bleaching goods made of unboiled cellulose which comprises treating the goods with an alkaline peroxide solution under conditions of low liquor ratio until a partial bleach is obtained and thereafter With an alkaline peroxide solution under conditions of high liquor ratio until a complete bleach is obtained.

2. A method for bleaching goods made of unboiled cellulose which comprises treating the goods with an alkaline peroxide solution under conditions of low liquor ratio until a partial bleach is obtained and thereafter with an alkaline peroxide solution under conditions of high liquor ratio until a complete bleach is obtained, the alkali concentration calculated as sodium hydroxide being higher in the first than in the second solution.

3. A method for bleaching goods made of unboiled cellulose which comprises treating the goods with an alkaline peroxide solution under conditions of low liquor ratio until a partial bleach is obtained and thereafter with an alkaline peroxide solution under conditions of high liquor ratio until a complete bleach is obtained, the temperature of treatment being lower in the first than in the second peroxide treatment.

4. A method for bleaching goods made of unboiled cellulose which comprises incorporating in the goods from 50% to 150% of an alkaline peroxide bleaching solution based upon the weight of the goods and then permitting the goods to stand and partially bleach, thereafter heating the goods in an alkaline peroxide solution under conditions of high liquor ratio and circulating the solution over and through the goods until a complete. bleach is obtained.

5. A method for bleaching goods made of unboiled cellulose which comprises incorporating in the goods from 50% to 150% of an alkaline peroxide bleaching solution based upon the weight of the goods and then permitting the goods to stand and bleach at a temperature below F., thereafter heating the goods in an alkaline peroxide solution at a temperature above 125 F. under conditions of high liquor ratio and circulating the solution over and through the goods until a complete bleach is obtained.

6. A method for bleaching goods made of unboiled cellulose comprising incorporating in the goods more than 50% and less than of an alkaline peroxide bleaching solution based upon the weight of the goods for partially bleaching the goods, and thereafter treating the goods under conditions of high liquor ratio with a hot circulating alkaline peroxide bleaching solution until a complete bleach is obtained.

'7. A method for bleaching heavy goods, such as sheeting and the like, made of unboiled cellulose comprising incorporating in the goods more than 50% and less than 150% of an alkaline peroxide bleaching solution based upon the weight of the goods for partially bleaching the goods, then washing the goods and subjecting them to an alkaline boil and thereafter heating the goods under conditions of high liquor ratio in a hot circulating alkaline peroxide bleaching solution until a complete bleach is obtained.

8. A method for bleaching heavy goods, such as sheeting and the like, made of unboiled cellulose comprising incorporating in the goods more than 50% and less than 150% of an alkaline peroxide bleaching solution based upon the weight of the goods for partially bleaching the goods, then washing the goods and subjecting them to an alkaline boil and thereafter heating the goods under conditions of high liquor ratio in a hot circulating alkaline peroxide bleaching solution until a complete bleach is obtained, the amount of peroxide employed in. the second bleaching solution being about twice that in the first solution.

9. A method for bleaching heavygoods, such as sheeting and the like, made of unboiled cellulose comprising incorporating in the goods less than 150% of an alkaline peroxide solution containing about of peroxide calculated at 1001 volume hydrogen peroxide for partially bleaching the goods, then Washing the goods and subjecting them to an alkaline boil and thereafter heating the goods under conditions of high liquor ratio in a hot circulating alkaline peroxide bleaching solution containing about 1% of peroxide calculated as 100 volume hydrogen peroxide until a complete bleach is obtained.

HANS O. KAUFFMANN.

Gilli? CERTIFICATE OF CORRECTION.

Patent No. 2,251A26. February 11, 19b1,

N HANS O. KAUFFMANN. g It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows; Page 5 sec- 0nd column, line 14.8, claim 9, for the word at read --as-; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 11th day of March, A. D. 1911;.

a Henry Van Arsdale, (Seal) A m Acting Commissioner of Pr"-ents.

CERTIFICATE OF CORRECTION. Patent No. 2,25l,).|.26. February 11, 19141.

HANS O. KAUFFMAN'N.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correctionas follows: Page 5, second column, line 14.8, claim 9, for the word "at" read -as-; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 11th day of March, A. D. 191

Henry Van Arsdale (Seal) Acting Commissioner of Patents.