JPH03213561A - Bleaching of textile with oxygen - Google Patents

Abstract

PURPOSE: To reduce the amount of hydrogen peroxide needed for bleaching by allowing the knitted or woven fabric to be treated to pass through the hydrogen peroxide aqueous solution and the oxygen-containing head space alternately. CONSTITUTION: The fabric to be bleached 1 is passed through the usual caustic alkali aqueous solution vessel 2, the squeezing rollers 7 and into the air-tightly sealed bleaching vessel 8, and through a series of the rollers 13 and 14 alternately. The fabric 1 passes through alternately an aqueous hydrogen peroxide solution of a desired concentration 9 and the oxygen-containing gas space 10 and more efficient bleaching with hydrogen peroxide can be effectively attained.

Description

DETAILED DESCRIPTION OF THE INVENTION The objects of the invention are achieved by using an oxygen bleaching operation in conjunction with hydrogen peroxide bleaching to considerably reduce the cost of the overall bleaching operation. Not only does the invention allow for a significant reduction in the amount of hydrogen peroxide used, but the processing equipment required is also smaller compared to that used in conventional hydrogen peroxide processes.

That is, the advantage of a single bleaching container in the practice of the invention,
Eliminates the J-box, bleach tank and heater tube of conventional implementations. Additionally, the residence times used in the practice of the invention are typically much shorter than those required for conventional hydrogen peroxide fabric bleaching.

As used herein, the term "oxygen fabric bleaching" is used to describe a process in which the fabric to be bleached is passed alternately through a hydrogen peroxide and oxygen-containing head space in accordance with the practice of the invention. Oxygen is much cheaper than hydrogen peroxide, so the savings in hydrogen peroxide consumption achieved in the practice of the invention make the oxygen fabric bleaching approach more economical to operate than traditional hydrogen peroxide approaches. I think that is acceptable.

Referring to the figure, the fabric to be bleached, designated in its entirety by the numeral 1, is passed through a suitable roller 3.4.5 into and out of a caustic solution containing container 2, and the fabric is removed from the liquid contained in the container. 3. Perform the desired immersion into the caustic solution through below level 6. Cloth 1 is
This treatment is carried out with caustic alkali and passed through a series of squeeze rolls 7 for partial drying. It will be understood that such a chemical sequence is generally the same as conventional hydrogen peroxide processing. The fabric 1 exiting the squeezing roller 7 in carrying out the oxygen fabric bleaching process of the invention is transferred from the squeezing roller to a conventional process bleaching tank, heater tube,
Rather than passing through a J-tube sequence, it is passed through an essentially airtight bleaching vessel 8. The bleaching vessel 8 contains an aqueous hydrogen peroxide solution 9 of the desired concentration and an oxygen-containing gas space 10, the numeral 11 representing the gas-liquid interface between the oxygen-containing gas space in the vessel 8 and the hydrogen peroxide solution.

The fabric 1 to be treated enters the container 8 through a pair of essentially gas-tight rollers 12 or a slit or some other suitable essentially gas-tight opening in the bleaching container 8. The fabric 1 passes in the container 8 over a series of rollers 13 and 14 alternately. The rollers 13 position the fabric 1 to pass through the oxygen-containing head space 10 in the container 8 . The roller 14 sinks the cloth 1 below the gas-liquid interface so that it passes through the hydrogen peroxide aqueous solution 9 in the container 8. Thus, by alternately arranging the rollers 13 and 14, the fabric 1 is passed alternately through the aqueous hydrogen peroxide solution and the oxygen-containing head space 10. This alternating passage of the fabric through separate sections of the bleach vessel 8 constitutes the oxygen fabric bleaching process of the invention.

In an embodiment illustrating the invention, the fabric 1 exiting the bleach container 8 is passed through an essentially gas-tight roller 15 or other essentially gas-tight opening into a suitable rinsing and drying zone 16 before storage. It is shown passing through collection rollers 17 and then being distributed, processed and used. It will be appreciated that such processing after the fabric 1 has been treated in the bleach vessel 8 is essentially that of conventional hydrogen peroxide processing.

Those skilled in the art will appreciate that various changes and modifications in the details of the method and apparatus for oxygen fabric bleaching as described herein may be made without departing from the scope of the invention as claimed. I think you will agree that you will get 5. That is, although the figures show three rollers 13 positioned in the oxygen-containing head space 10 and two rollers 14 positioned within the aqueous hydrogen peroxide solution 9, the number of such rollers used in any particular application may vary depending on the container. 8 and the number of times the fabric 1 is immersed in the hydrogen peroxide solution or alternatively passed through the hydrogen peroxide solution and oxygen-containing headspace sequence for the desired bleaching level for a given textile material. Become. The fabric should, for all purposes of the invention, be treated at least once after being immersed in the peroxide solution. In a preferred embodiment, the fabric is passed through an oxygen-containing atmosphere at least once before and after such immersion in the hydrogen peroxide solution. The illustrated embodiment includes fabric 1 first passing through an oxygen-containing headspace 10 and then passing through a hydrogen peroxide bleaching solution 9;
Although shown passing through the oxygen-containing headspace 10 and exiting the container 8, once the fabric to be bleached has undergone the desired number of alternating contacts with the aqueous hydrogen peroxide solution and with the oxygen-containing headspace for a given application. , any 6 I think it is accepted that other population and emission arrangements are possible.

The rollers 14 are shown completely immersed in the aqueous hydrogen peroxide solution 9 and the rollers 13 are positioned completely within the gas space 10 to achieve the desired alternation of the fabric being bleached. It will be appreciated that they may be positioned in any convenient manner. That is,
The roller 14 need not be completely submerged below the gas-liquid interface 11 so long as the desired passage of the fabric into the hydrogen peroxide solution 9 is achieved. In this regard, it is noted that it is typical in the practice of the invention to have very low liquid levels, and in preferred embodiments of the invention, the gas-liquid interface 11 is typically up to about the top of the roller 14. Should. However, it should be understood that it is not necessary to use the roller-box arrangement described above. It is within the scope of the invention to pass the fabric to be treated alternately between hydrogen peroxide and oxygen gas spaces at least once, preferably twice or more, using any suitable equipment, and such Passage depends on the desired residence time and other factors related to the given application.

The operating conditions used in the practice of the invention may vary depending on the particular textile fabric being processed, the degree of bleaching desired, and various other requirements regarding the overall technical and economic demands of the particular bleaching operation. That is, it is desirable to save hydrogen peroxide solution, reduce capital costs, and shorten residence time obtained in carrying out the invention, and it is highly desirable to carry out the invention as a more economical alternative to conventional hydrogen peroxide bleaching. There are several cases where this can be important. However, in other applications, even if each of the various potential improvement areas, i.e. hydrogen peroxide savings, capital cost reduction and/or residence time reduction, is achieved in each such area for a given bleaching operation, Even if the available advantages are not utilized to the maximum, the alternating sequence of the invention can be used to achieve desirable overall bleaching results that are more favorable than those obtained by conventional processing.

It will be appreciated that the fabrics processed in the practice of the invention include any textile material that can be effectively bleached by conventional hydrogen peroxide bleaching approaches. Approximately 90% of all cotton fabrics are currently bleached using hydrogen peroxide. Other bleaching agents that are sometimes used for specific bleaching applications include sodium chlorite, sodium hypochlorite, and peracetic acid. The advantage of using hydrogen peroxide over other known bleaching agents is that hydrogen peroxide does not react with proteins in the fabric fibers. Although the invention is described and claimed in terms of reducing the amount of hydrogen peroxide used for bleaching purposes, satisfactory bleaching action also includes:
There are applications in which the textile fabric to be treated may be brought into contact with pure oxygen or oxygen-enriched air after first being immersed in caustic or otherwise moistened, without any immersion of the fabric in hydrogen peroxide. There are also several things to note. Also, practicing the invention in various embodiments involving contacting the fabric with an oxygen-containing atmosphere is acceptable with respect to various textile materials that cannot be satisfactorily bleached by conventional hydrogen peroxide bleaching processes. It should also be recognized that 9 levels of bleaching action can be achieved.

As described with respect to the exemplary embodiments, treating the cotton with a bleach solution, typically an aqueous solution, involves dispensing the fabric into a caustic holding container where the fabric is bleached in caustic solution for pre-desizing purposes. , typically 4% NaOH at about 70°C.

It will be appreciated that when bleaching specific textile materials, it may not be necessary to employ such a caustic sizing step prior to the actual bleaching step.

The residence time of the fabric in the bleaching container of the invention depends on the degree of bleaching desired, the fabric being bleached, the hydrogen peroxide concentration used, the liquid level of hydrogen peroxide, and/or the amount of fabric being treated in the bleaching container in each alternating sequence. Depending on the ratio of the residence time in the hydrogen peroxide solution to the residence time in the oxygen-containing headspace in the general pass through the wafer, the range will range from about 30 to about 90 minutes. The invention can thus achieve significant reductions in residence time in certain applications compared to conventional peroxide-based processes. In some experimental embodiments of the invention, about 60
Although we observed an arbitrary fabric residence time of 10 minutes, due to a combination of factors and the unique geometry of the equipment used in actual commercial applications, the residence time and other operational factors, such as the hydrogen peroxide concentration used, the operating temperature It will be understood that changes and optimizations may be made.

The concentration of hydrogen peroxide used in the practice of the invention can be at levels used for conventional hydrogen peroxide bleaching, typically about 1.5% by weight or higher, but preferably at a predetermined level. significantly lower depending on overall factors related to usage.

That is, in the oxygen fabric bleaching method and apparatus of the invention,
An aqueous hydrogen peroxide solution having a hydrogen peroxide concentration as low as about 0.1% by weight or less can be used. Concentrations below 1.5%, down to about 0.1%, are usually preferred.

It was previously noted that hydrogen peroxide decomposes rapidly at the high temperatures necessary to adequately bleach textiles, i.e., the 90-99 DEG C. levels used in conventional hydrogen peroxide bleaching techniques. There are several embodiments of the oxygen bleaching method of the invention in which lower temperatures may be used depending on other factors involved. That is, both the hydrogen peroxide and the oxygen-containing gas used in the bleaching vessel are heated to a temperature of about 70°C to about 100°C, preferably about 70°C.
C. to about 90.degree. C., although temperatures outside this range may also be used for specific applications. For example, to minimize decomposition of the hydrogen peroxide, the hydrogen peroxide solution may be cooled and kept at a lower temperature, e.g., below 70°C to -lower ambient temperature levels, to reduce the bleaching action of the process. Heating the oxygen-containing gas space to promote 70° to 100°C
It is possible to make it within the range of . Such an implementation is particularly useful in larger scale bleaching operations where conventional heat exchangers, cooling coils, etc. can be used in conjunction with the bleach vessel to maintain such different temperature levels in separate sections of the vessel. I think it will be understood that this is both desirable and desirable. Thus, the intersection of inventions 2. The mutual hydrogen peroxide-oxygen process provides the opportunity for further processing advantages by using lower hydrogen peroxide operating temperatures than are necessarily used in conventional hydrogen peroxide bleaching operations. I hope you understand.

It is within the scope of the invention to use any convenient form of oxygen in the oxygen-containing headspace within the bleach vessel. That is, although essentially pure oxygen can be used and is usually preferred, air or another suitable oxygen-containing gas may be used. For example, at least about 35% oxygen, such as can be produced with a dialysis membrane, is desirable in certain applications.

When using air rather than high-purity oxygen, air-tight rollers or other forms of air-tight openings are not necessary at the inlet and outlet ends of the bleach container, but may be used to prevent unwanted vapor emissions from the container. I think good things should be recognized.

The invention is further illustrated herein by specific examples thereof.

Such examples are included for illustrative purposes only and should not be considered as limiting the scope of the invention as claimed.

Example 2 In a series of laboratory tests, cotton fabrics were rinsed by hand and lowered between a hydrogen peroxide solution and an oxygen gas space in a bleach container. The aqueous hydrogen peroxide solution contained hydrogen peroxide at the desired concentration, sodium silicate was used as a conventional stabilizer at a concentration of 1.2% by weight, and the balance was distilled water. Operating temperature 190″F (8
8°C) was used throughout. Bleached fabrics were analyzed using a modified spectrophotometer to measure reflectivity. Reflectivity determines the brightness, ness of the fabric. The test demonstrated that the hydrogen peroxide concentration required to achieve satisfactory commercial bleaching results was determined by using the inventive alternating process with an oxygen-containing gas, i.e., an air space.
．． It was shown that it can be reduced from the 5% level to 0.5%. Also, for this embodiment of the invention where each fabric sample is rinsed by hand and the fabric is lowered twice into the hydrogen peroxide solution after the initial soaking, the residence time of the fabric in the bleach container is at least 1 hour. I conducted a test to determine this. Also,
It should be noted that hydrogen peroxide 4 tends to decompose somewhat easily at the high temperatures of the test, which, as expected, are still lower than the temperatures required for conventional hydrogen peroxide bleaching.

Therefore, the hydrogen peroxide had to be constantly replaced to maintain its bleaching activity.

Experiments in the Takumi laboratory were conducted as in Example 1 above, but sodium sulfite was added to the hydrogen peroxide solution at various concentrations. Sodium sulfite is known to increase the oxidation potential of oxygen. In a series of comparative tests, the concentration of sodium sulfite was varied from 0% to 2% by weight of the total solution. Adding sodium sulfite to the bleach solution
At the 2% level, it was observed that the whiteness of the fabric was improved by as much as 33%. Thus, sodium sulfite, when used in the inventive oxygen fabric bleaching method and apparatus, serves to significantly increase the inventive bleaching performance.

It has been found that adding 1-lium sulfite to the aqueous bleaching solution also helps reduce the overall consumption of 5 sodium hydroxide during the bleaching operation.

It will be appreciated that, in a preferred embodiment of the invention, it is desirable to incorporate sodium to lithium sulfite into the hydrogen peroxide solution as a useful oxidation enhancer. For this purpose, such sulfites should be about 0.0% based on the weight of the total hydrogen peroxide solution.
．． Amounts ranging from 1 to about 4% by weight, preferably from about 1 to about 3% by weight may be used, although amounts outside this range may also be used.

Thus, as an alternative to using sodium sulfite as an oxidation enhancer, it is within the scope of the invention to add sulfur dioxide to the oxygen-containing atmosphere of the invention. For such purposes, sulfur dioxide may be present in an amount of about 0.1 to about 4% by volume, preferably about 1 to about 3% by volume, based on the total volume of the oxygen-containing headspace or other oxygen-containing atmosphere used in the practice of the invention. It is convenient to use amounts within % by volume. It will be appreciated that amounts outside this range may also be used and combinations of sulfite and sodium dioxide or other oxidation enhancing additives may be used.

6 Further testing determined that improvements in the invention could achieve acceptable bleaching action to the point of not only significantly reducing the use of hydrogen peroxide, but eliminating it entirely. . That is, a cotton fabric is immersed in caustic as in a typical conventional procedure and then exposed to a pure oxygen atmosphere, i.e., 99.9'' oxygen at about 89°C.
Contacted for an hour. This caustic alkali-oxygen-containing atmosphere treatment resulted in whitening to an extent of 23% of the degree of whitening at the complete bleaching level. In contrast, when such bleaching is carried out without hydrogen peroxide by immersing the fabric in caustic alkaline in an airy, oxygen-containing atmosphere for 1 hour at about 89°C, the bleaching effect is approximately The result was less than 2%. From this, without immersing it in hydrogen peroxide,
Such treatments, which involve immersion in caustic alkali and exposure to an oxygen-containing atmosphere, range from air separation using dialysis membranes to
Preferably, an oxygen-poor (about 35%) oxygen-containing atmosphere is used, up to the point of using a pure or substantially pure oxygen atmosphere. Levels are typically lower than those achievable with the hydrogen peroxide-oxygen atmosphere sequence of the invention depending on the operating conditions used, such that the achievable bleach levels meet the requirements of the specific bleaching operation. I think it is accepted that it can be appropriate to do so.

The use of an oxygen-containing gas space in the bleaching container and passing the fabric alternately through the gas space with an aqueous hydrogen peroxide solution increases the effectiveness of the bleaching action and thus significantly reduces the amount of hydrogen peroxide used. It is recognized that the following can be achieved. This effect can be achieved by adding small amounts of sodium sulfite to the hydrogen peroxide solution, by adding SO□ to the oxygen-containing headspace, or by some other method that can increase the oxidation potential of oxygen. It can be seen from the second example above that improvements can be made by using additives. As a result of the practice of the invention, the amount of hydrogen peroxide consumed for a given bleaching operation can be minimized in optimized embodiments of the invention. Typically, the inventive oxygen fabric bleaching method will reduce the amount of hydrogen peroxide used and consumed in actual commercial applications by at least 25%, and typically by more than 50%. Even high purity oxygen for use in the practice of the invention is much cheaper compared to the additional amount of hydrogen peroxide required in conventional hydrogen peroxide bleaching, making the invention less expensive than conventional processes. It is clear that the operating costs are low.Apart from the additional advantages of potentially reducing residence times and reducing capital expense requirements, the invention makes it suitable for further significant advances in the field. Another way of expressing this is that it is possible to reduce the amount of hydrogen peroxide required for bleaching operations.The considerable costs associated with bleaching operations are associated with the step of removing the used aqueous hydrogen peroxide solution. Such used liquids pose further problems in that, after removal, they must be either disposed of as waste or recovered for reuse. Environmental problems are encountered and must be overcome when disposing of aqueous liquids containing bleach. If such aqueous liquids are to be recovered for reuse, elaborate systems must be used. The present invention provides a further significant advance in the development of the textile bleaching field by appreciably reducing the amount of hydrogen peroxide required for use in aqueous solutions.

3. The accompanying figures are schematic representations of apparatus used in practicing embodiments of the present invention.

2... Caustic alkaline solution storage container 8...Bleach container 9...Hydrogen peroxide aqueous solution 10...Oxygen-containing gas space 16... Rinse and dry area

Claims (1)

[Claims] 1. A method for bleaching textiles with hydrogen peroxide, which comprises soaking the textile fabric to be treated in a hydrogen peroxide solution and then contacting it with an oxygen-containing atmosphere to achieve a predetermined bleaching level. A method that can reduce the amount of hydrogen peroxide required. 2. The hydrogen peroxide solution has a hydrogen peroxide concentration of 0.1 to 1.
2. A method according to claim 1, comprising an aqueous solution having 5% by weight. 3. The method according to claim 1, wherein the peroxide solution and the oxygen-containing atmosphere are heated to 70° to 100°C. 4. The method according to claim 3, wherein the peroxide solution and the oxygen-containing atmosphere are heated to 70° to 90°C. 5. The method of claim 1, comprising heating the oxygen-containing atmosphere to 70° to 100°C and maintaining the hydrogen peroxide solution at a temperature of lower ambient temperature to 70°C. 6. The method of claim 5, wherein the hydrogen peroxide solution is maintained at about ambient temperature. 7. The method of claim 1, wherein said oxygen-containing atmosphere comprises essentially pure oxygen. 8. The method of claim 1, wherein the oxygen-containing atmosphere comprises air. 9. The oxygen-containing atmosphere contains at least 35% by volume of oxygen.
The method of claim 1 comprising: 10. The method according to claim 1, wherein the fabric to be treated is immersed in a caustic solution and then treated with a hydrogen peroxide solution and an oxygen-containing atmosphere. 11. The method according to claim 1, wherein the residence time for treating the fabric with a hydrogen peroxide solution and an oxygen-containing atmosphere is 30 to 60 minutes. 12. The method according to claim 2, wherein the peroxide solution and the oxygen-containing atmosphere are heated to 70° to 100°C. 13. The method according to claim 2, wherein the peroxide solution and the oxygen-containing atmosphere are heated to 70° to 90°C. 14. Heating the oxygen-containing atmosphere to 70° to 100°C
3. A method according to claim 2, comprising: heating the hydrogen peroxide solution and maintaining the hydrogen peroxide solution at a temperature between ambient temperature and 70<0>C. 15. The method of claim 14, wherein the hydrogen peroxide solution is maintained at about ambient temperature. 16. The method of claim 12, wherein said oxygen-containing atmosphere comprises essentially pure oxygen. 17. The method of claim 12, wherein the oxygen-containing atmosphere comprises air. 18. The method of claim 12, wherein the oxygen-containing atmosphere contains at least 35% by volume oxygen. 19. The method of claim 14, wherein said oxygen-containing atmosphere comprises essentially pure oxygen. 20. The method of claim 14, wherein the oxygen-containing atmosphere comprises air. 21. The method of claim 14, wherein said oxygen-containing atmosphere contains at least 35% by volume oxygen. 22. The method of claim 1, wherein the textile fabric comprises a cotton fabric. 23. The textile fabric to be treated is soaked in hydrogen peroxide solution for at least 2 hours.
2. The method of claim 1, wherein the fabric is immersed in an aqueous hydrogen peroxide solution and is subsequently exposed to an oxygen-containing atmosphere. 24. The peroxide solution has a hydrogen peroxide concentration of 0.1 to 1.5
24. The method of claim 23, wherein the oxygen-containing atmosphere is heated to 70 DEG to 100 DEG C. and the total residence time of the treatment is 30 to 90 minutes. 25. The method of claim 24, wherein the peroxide solution is heated to 70° to 100°C. 26. The hydrogen peroxide solution is heated to a lower ambient temperature ~70°C.
25. The method of claim 24, comprising maintaining at a temperature of . 27. The method of claim 24, wherein the oxygen-containing atmosphere includes oxygen. 28. The method of claim 26, wherein said oxygen-containing atmosphere comprises oxygen. 29. The method of claim 1, comprising adding sodium sulfite to the hydrogen peroxide solution to increase the oxygen oxidation potential in the bleaching process. 30. The method of claim 29, wherein the hydrogen peroxide solution is an aqueous solution and the sodium sulfite concentration is 0.1 to 4% by weight of the total solution. 31. The method of claim 1 comprising adding sulfur dioxide to the oxygen-containing atmosphere to increase the oxidation potential of oxygen in the bleaching process. 32. The method of claim 31, wherein sulfur dioxide is used in an amount ranging from 0.1 to 4% by volume, based on the total volume of the oxygen-containing atmosphere. 33. The hydrogen peroxide solution has a hydrogen peroxide concentration of 0.1 to 1
．． 5% by weight and heating said oxygen-containing atmosphere to 70° to 100°C.
The method described in item 0. 34. The oxygen-containing atmosphere contains essentially pure oxygen at 70%
34. The method according to claim 33, wherein the method is heated to between 90°C and 90°C. 35. The hydrogen peroxide solution has a hydrogen peroxide concentration of 0.1 to 1
．． 5% by weight and heating said oxygen-containing atmosphere to 70° to 100°C.
The method described in Section 2. 36, the oxygen-containing atmosphere contains essentially pure oxygen at 70
36. The method according to claim 35, wherein the method is heated to a temperature of 90°C to 90°C. 37. successively passing the strip of textile fabric to be treated through a bleaching vessel containing a hydrogen peroxide solution and an overhead oxygen-containing gas space, immersing the fabric in the hydrogen peroxide solution;
A method that allows for at least one immersion followed by passage through an overhead oxygen-containing gas space before removal from the bleaching vessel, thereby reducing the amount of hydrogen peroxide required to achieve a desired level of bleaching. 38. The hydrogen peroxide solution has a hydrogen peroxide concentration of 0.1 to 1
．． Claim 31 comprising an aqueous solution having 5% by weight
The method described in section. 39. The method of claim 37, wherein the peroxide solution and the oxygen-containing atmosphere are heated to 70° to 100°C. 40. Passing said strip of fabric to be treated through an overhead oxygen-containing gas space of said bleaching vessel and then immersing it in a hydrogen peroxide solution and withdrawing therefrom at least once into a gas space before leaving the bleaching vessel. 37th
The method described in section. 41. The strip of fabric is immersed in a hydrogen peroxide solution at least twice alternately and removed from the bleaching container after being drawn from the solution into an oxygen-containing gas space.
The method described in item 0. 42. The hydrogen peroxide solution has a hydrogen peroxide concentration of 0.1 to 1
．． Claim 41 comprising an aqueous solution having 5% by weight
The method described in section. 43. The method of claim 42, wherein the peroxide solution and the oxygen-containing atmosphere are heated to 70° to 100°C. 44. The residence time of the fabric to be treated in the bleaching container is 30 to 90 minutes.
43. The method of claim 42, wherein the method is: 45. The method of claim 37, wherein the peroxide solution and the oxygen-containing atmosphere are heated to 70° to 90°C. 46. Heating the oxygen-containing atmosphere to 70° to 100°C
and bring the hydrogen peroxide solution to a lower ambient temperature ~70°C.
38. The method of claim 37, comprising maintaining at a temperature of . 47. The hydrogen peroxide solution has a hydrogen peroxide concentration of 0.1 to 1
．． 47. The method of claim 46, comprising an aqueous solution having a peroxide concentration of 5% by weight and maintaining said peroxide solution at about ambient temperature. 48. The method of claim 37, comprising adding sodium sulfite to the hydrogen peroxide solution to increase the oxygen oxidation potential in the bleaching process. 49. The method of claim 42, comprising adding sodium sulfite to the aqueous hydrogen peroxide solution. 50, sodium sulfite concentration is 1 to 4% by weight of the solution
50. The method according to claim 49. 51. The method of claim 37, comprising adding sulfur dioxide to the oxygen-containing atmosphere to increase the oxidation potential of oxygen in the bleaching process. 52. The method of claim 51, wherein sulfur dioxide is used in an amount ranging from 0.1 to 4% by volume, based on the total volume of the oxygen-containing atmosphere. 53. The method of claim 42, wherein said oxygen-containing space comprises essentially pure oxygen. 54. The method of claim 42, wherein the oxygen-containing space comprises air. 55. The oxygen-containing space contains at least 35% by volume of oxygen.
43. The method of claim 42 comprising: 56. The method of claim 37, wherein the strip of fabric is introduced into the bleach container through an essentially airtight opening. 57. The method of claim 37, comprising passing the strip of fabric through a caustic solution and partially drying the fabric before passing it through the bleaching vessel. 58. Claim 3 comprising rinsing and drying said strip of fabric after removing it from said bleach container.
The method described in Section 7.