FR2572430A1 - IMPROVEMENT TO OXIDIZING WHITENING PROCESSES MADE IN ACID. - Google Patents

Abstract

FIBER BLEACHING PROCESS, BY MEANS OF AN ACIDIC SOLUTION OF HYDROGEN PEROXIDE; THE ACID SOLUTION IS ACTIVATED BY MEANS OF A CHLORITE AND A VANADATE, PRESENT SIMULTANEOUSLY IN THE SAID SOLUTION.

Description

I

  The present invention relates to an improvement

  oxidative bleaching processes

  in acidic medium, by the action of hydrogen peroxide.

  It is known that the bleaching efficiency of the dilutions of hydrogen peroxide is not very high in acid medium and generally does not allow the bleaching of a fiber. It is for this reason that hydrogen peroxide or alkaline peroxides are

  generally used in alkaline medium.

  Various compounds have been recommended to increase the stability and the effectiveness of the peroxides in an alkaline medium. The use of silicates, different magnesium complexes or various other salts is

example recommended.

  However, alkaline bleaching is unsuitable for certain fibers, such as synthetic fibers. In addition, other desiderata can rule out the use of an alkaline medium even with fibers, such as cellulosic fibers, which are not altered in such a medium. For example, we may want to preserve the natural fats of fibers of plant or animal origin, fats that would be saponified

in an alkaline medium.

  The plaintiff has therefore considered the problem of the industrial improvement of money laundering

  in an acid medium, by action of hydrogen peroxide.

  Various compounds, such as metal salts,

  such as iron or copper, are likely to increase the rate of decomposition

  Hydrogen peroxide baths in an acid medium. It appears

  However, this type of activation results in the release of oxygen molecules, which is a process with virtually no effect on the bleaching of a fiber.

and therefore can not be retained.

  The use of various other compounds also

  been advocated without, however, ever leading to an effective

  sufficient bleaching capacity to allow genuine

  to perform acid-based bleaching with the aid of

of hydrogen peroxide.

  The Applicant has found experimentally that the introduction of a chlorite and a small amount of a vanadate in an aqueous and acidic dilution of hydrogen peroxide makes it possible to greatly increase the bleaching activity of the acidic oxidizing solution. and to realize industrially bleaching in good

  pH and temperature conditions.

  The use of sodium chlorite alone, without vanadate, in the acid solution of hydrogen peroxide,

  does not sufficiently increase the white activity

  the oxidizing environment. If one can in this case observe an improvement of the whitening effect, this improvement is however manifested only in a moderate way and provided to achieve bleaching at relatively high temperatures of the order of 120 to 130 C. Comparatively, the presence of vanadate makes it possible to record a much greater efficiency of

  whitening power in a temperature range.

  much more acceptable, efficiency being manifested

already from 40 C.

  Moreover, it becomes possible, as observed by the applicant, to carry out, during the same operation, both bleaching and dyeing of the fibers, in particular synthetic fibers, including dyeing.

  is generally carried out in a pH range acidic.

  Various other advantages are also offered, such as the possibility of bleaching dyed woven fabrics in an acid environment, avoiding the risk of alteration of the various colors, or the possibility of producing the same.

  enzymatic desizing during the process of bleaching

  chiment, by eliminating, in an economic way, the gluing products. The subject of the present invention is therefore a process for bleaching fibers, using acid-diluted hydrogen peroxide, which is characterized in that

  hydrogen peroxide is activated by the simul-

  chlorite and an alkaline vanadate in the bath

whitening.

  The range of acidic pH of the bath may be between 3 and 6 and the temperatures between 50 and 130 ° C,

preferably between 60 and 90 C.

  Vanadate may be selected from the family comprising alkali metal vanadates and ammonium vanadate. Preference will be given among chlorites,

to the use of sodium chlorite.

  The necessary quantities of hydrogen peroxide

  gene will depend on the particularities of the process of

  bleaching; these quantities may therefore vary widely

  for example, between 1 and 100 g / 1 of a

  hydrogen peroxide solution at 3 / o.

  The necessary quantities of sodium chlorite shall be between 0.1 and 10 g of chlorite per

  liter of the bath and preferably between 1 and 4 g / l.

  The amounts of vanadate will be between 0.01 and 1 g per liter of bleaching bath and,

  preferably between 0.1 and 0.4 g / l.

  The method of the invention provides significant advantages in the preparation and dyeing

  different fibers. These advantages include:

  to retain: - The possibility of bleaching with hydrogen peroxide all the different fibers which are particularly sensitive to the alkaline environment, as by

example synthetic fibers.

  - The possibility of laundering items

  woven dyed without risk of degradation of various colors.

  - Simultaneous realization of money laundering

and dyeing.

  - The realization of an enzymatic desizing

  during the bleaching process.

  The following examples given for information and not limitation will illustrate more concretely the possibilities offered by the present invention.

EXAMPLE 1

  An ecru cotton fabric is treated by operating comparatively in baths respectively having the following composition: bath a: 4 cm3 / 1 hydrogen peroxide 35% 2 cm3 / 1 acetic acid bath b: 4 cm3 / 1 hydrogen peroxide 35% 2 cm3 / 1 acetic acid 2 g / 1- sodium chlorite bath c: 4 cm3 / 1 hydrogen peroxide 55% 2 cm3 / 1 acetic acid 2 g / 1 sodium chlorite 0.2 g / 1 sodium vanadate bath d: 4 cm / 1 hydrogen peroxide at 35% 2 cm3 / 1 acetic acid

0.2 g / l sodium vanadate.

  In all cases the following conditions are adopted: Bath ratio I to 10 - (between fiber weight and bath volume) Temperature 90 0

Duration 60 minutes.

  After treatment, the various samples are rinsed and dried. It is observed that the sample bleached in the bath c has a much higher level of whiteness than that of the samples from the other baths with further good elimination of the hulls of the fiber. The determination of the degree of whiteness makes it possible to record the following results: Bath a = degree of whiteness of the sample = 71% Bath b = "= 74% Bath c =" il 81%

Bath d = "= 72%.

EXAMPLE 2

  A fabric consisting of cellulosic fibers, some of which has been previously dyed with reactive dyes to form a dyed fabric article, is treated in the respective whitening baths having the following composition: bath a: 3 cm 3 / l hydrogen peroxide at 35% 2 cm3 / l acetic acid bath b: 3 cm3 / l hydrogen peroxide at 35% 2 cm3 / l acetic acid 1.5 g / 1 sodium chlorite 0.2 g / l sodium vanadate bath c: 5 cm 3/1 hydrogen peroxide 35% 3 g / 1 sodium silicate

2 cm3 / l caustic soda at 30%.

  The following operating conditions are adopted: Ratio of bath I to 10 Duration I hour

Temperature 80 C.

  Rinsed after treatment and then dried. The following results are observed for the samples from the various

baths: -

  bath a: poor bleaching of undyed fibers, with no elimination of the shells of the fiber, bath b: very good degree of white. Elimination

  total hulls. We also observe

  that the various colors have not undergone any degradation, a good degree of white bath. Total elimination of the hulls but we observe a clear

color degradation.

EENMPLE:

  A fabric consisting of unbleached cotton fibers and triacetate fibers is treated in the bleaching baths below, with disperse dyes added, to dye the triacetate fiber.

  at the same time as the bleaching of the cellulosic fiber.

  bath a: 2 cm3 / 1 hydrogen peroxide 35% 0.75 g / l sodium chlorite 0.1 g / l sodium vanadate bath a: 0.5 g / l of a disperse dye referenced

in the Color Index under the call-

  Disperse Red 60, 2 cm3 / 1 acetic acid bath b: 0.5 g / l Disperse Red 60

2 cm3 / l acetic acid.

  The following operating conditions are adopted:

Bath ratio I to 10.

  The temperature of the baths is raised to 80 ° C, maintains this temperature for 20 minutes, and then carries

the temperature at 1100C.

  It maintains a temperature of 110 C during

  minutes, cool and rinse the dyed material.

  After dyeing, the sample obtained from the bath has an excellent coloring on the triacetate part with a bleached cotton fiber and very little soiled by the

disperse dye.

  Comparatively, the sample from bath b has a weaker and duller color, the

  cellulosic fiber is not bleached and stands strong-

  dirty by the disperse dye.

EXAMPLE 4

  An unbleached cotton fabric is treated as follows: This fabric is impregnated by padding in a bath having the following composition: cm3 / l hydrogen peroxide g / l sodium chlorite 0.3 g / l sodium vanadate I cm3 acetic acid so as to obtain a pH of 5

  cm3 / l of an enzymatic product, commercially

  under the name of Enzylase C, by the Diamalt Company.

  It is expressed after impregnation so as to maintain 90% of the impregnation bath, rolled up

  then take the roll to a vaporizing chamber

  90 minutes at a temperature of 800C.

  Rinse after treatment and then dry the fabric obtained. We observe after treatment a degree of white

  medium with a good elimination of the hulls of the fiber.

  There is also excellent desizing of the whitened article which thus corresponds to a fabric perfectly prepared for any other dyeing or finishing operation.

Claims (10)

  1. Process for bleaching fibers with an acidic solution of hydrogen peroxide, characterized in that the acidic solution is activated by means of a chlorite and a vanadate, present simultaneously in the acid solution.   2. Method according to claim 1, characterized   rised in that the acid solution has a pH between 3 and 6.   3. Process according to claim 1 or 2, characterized in that the vanadate is chosen from the family comprising alkali metal vanadates and the ammonium vanadate.   4. Method according to one of claims 1 to   3, characterized in that the chlorite is sodium chlorite.   5. Method according to one of claims I   a 4, characterized in that the amount of vanadate is between 0.01 and I g of vanadate per liter of bath oxidant.   6. Process according to claim 5, characterized   rised in that the amount of vanadate is between 0.1 and 0.4 g / l.   7. Method according to one of claims 1   to 6, characterized in that the amount of chlorite is between 0.1 and 10 g / l bath.   8. Process according to claim 7, characterized in that the amount of chlorite is between 1 and 4 g / l.   9. Method according to one of claims 1 to   8, characterized in that the bleaching is carried out at a   temperature between 30 and 1300 C.   10. Process according to claim 9, characterized   rised in that the temperature is between 60 and 9000.