US3552907A - Industrial process for bleaching liberian fibres by applying chlorinated derivatives of cyanuric acid - Google Patents

Abstract

A RAPID PROCESS OF INDUSTRIAL BLEACHING OF TEXTILE PRODUCTS WITH A BASIS OF LIBERIAN FOBRES SUCH AS LINEN, HEMP, OR JUTE, CONSISTING IN THREE ESSENTIAL STAGES, IN THE COURSE OF WHICH THE UNBLEACHED PRODUCT IS BROUGHT SUCCESSIVELY INTO CONTACT WITH A STRONGLY ALKALINE AQUEOUS BATH, UNDER A STEAM ATMOSPHERE AT 100*C., A BATH CONSTITUTED BY AN AQUEOUS SOLUTION WITH A PH OF 4-5 OF CHLOROCYANURIC DERIVATIVES AT 20-50*C. HAVING AN AVAILABLE CHLORINE CONTENT OF 7 TO 15 G./L., AND AN ALKALINE BATH OF HYDROGEN PEROXIDE, IT BEING POSSIBLE TO PRECEDE THESE THREE TREATMENTS WITH A PRELIMINARY TREATMENT IN A BATH IDENTICAL TO THAT OF THE SECOND TREATMENT; THE PRELIMINARY TREATMENT AND THE SECOND TREATMENT MAY BE CONDUCTED EITHER IN CONTINUOUS OPERATION LIKE THE FIRST AND THIRD TREATMENTS, OR SEMICONTINUOUSLY, BY WINDING.

Description

D LUE-QL United States Patent Int. Cl. D06! 3/06 US. Cl. 8-108 9 Claims ABSTRACT OF THE DISCLOSURE A rapid process of industrial bleaching of textile products with a basis of Liberian fibres such as linen, hemp, or jute, consisting in three essential stages, in the course of which the unbleached product is brought successively into contact with a strongly alkaline aqueous bath, under a steam atmosphere at 100 C., a bath constituted by an aqueous solution with a pH of 4-5 of chlorocyanuric derivatives at 20-50" C. having an available chlorine content of 7 to g./l., and an alkaline bath of hydrogen peroxide, it being possible to precede these three treatments with a preliminary treatment in a bath identical to that of the second treatment; the preliminary treatment and the second treatment may be conducted either in continuous operation like the first and third treatments, or semicontinuously, by winding.

' The large proportion of natural impurities which are associated with Liberian fibres such as linen, hemp and jute, added to the great sensitivity of the latter to reagents usually employed to bleach them requires working with a low concentration of active agents (alkalines, sodium hypochlorite, hydrogen peroxide etc.) thereby requiring complex treatments of long duration. These inescapable factors which are scarcely compatible with the demands of modern industry, particularly as regards labor, expenses of standing idle and costs of productivity, are largely re sponsible for the unpopularity of these textile products at present despite the high qualities ascribed to them.

The use of sodium chlorite in an acid medium enables non-cellulose parts to be broken down with the bleaching of the cellulose parts of the fibers. However, in order to obtain good whiteness, it is practically always necessary to undertake preliminary boiling off in alkaline medium followed by treatment with chlorine or in hydrogen peroxide, the operations being carried out as a continuous operation on threads or fabrics.

Although this technique largely used for bleaching cotton enables the duration of treatment of Liberian fibers to be reduced to about hours, the use of high concentrations of alkali, hydrogen peroxide and even chlorite, proves to be extremely harmful especially as regards the diminution of the degree of polymerization and the resultant loss of mechanical resistance of the linen, hemp or jute products which have been subjected thereto.

The object of the present invention is to provide an industrial rapid bleaching process carried on continuously or semi-continuously, by impregnating in the presence of aqueous solutions containing chlorinated derivatives of cyanuric acid, optionally comprising a preliminary treatment in the presence of these same products combined with alkaline treatments of high concentration in an atmosphere of water vapor and with oxidizing in the presence of hydrogen peroxide, The Liberian products treated in accordance with the process deteriorate very little and display a good whiteness, the technical progress 3,552,907 Patented Jan. 5, 1971 of the invention moreover consisting in the considerably reduced durations of treatment, of some 4060 minutes to fours hours in the case of very heavy fabrics, rich in ligneous materials.

The continuous operation of the process of bleaching by impregnation is carried out in principle in three successive stages:

(1) The textile product of linen, hemp or jute passes loosely at high speed into a washing machine, where it is brought in contact with boiling water containing, if necessary, detergents or Wetting agents. After being wrung out it is impregnated with a solution of caustic soda of 40-60 g./l., possibly in the presence of detergents and wetting agents, then -100% wrung out. It is then admitted into a vaporizer in a steam atmosphere at C., then disposed in the form of folds in a ripening apparatus where it stays for 10 to 20 minutes at 100 C.

(2) Leaving the ripening apparatus, the textile product undergoes washing, and intense rinsing on a washing machine comprising several baths so as to remove the soda and the impurities rendered soluble in the course of ripening, then, without interrupting continuous operation, it passes into a saturation bath containing a solution of chlorinated derivatives of cyanuric acid at 7-15 g./l. of available chlorine, having a pH of between 4 and 5. These solutions are generally made up of a mixture of trichlorocyanuric acid, cyanuric acid, and alkali metal carbonate or bicarbonate, or again, of alkali metal salts of dichlorocyanuric acid in which case it is advisable to add to the bath 4 to 6 g./l. of an acid such as acetic acid. The textile product wrung out at 100-110% is deposited in the form of folds in a second ripening apparatus in which it remains for 10 to 20 minutes at a temperature chosen between atmospheric and 50 C. before passing into a washing machine with two baths containing boiling water, where it is freed of excess available chlorine and dissolved impurities, then wrung out at 90100%.

(3) The wrung out product passes into an alkaline bath of hydrogen peroxide stabilized with sodium silicate, then, after having been wrung out at l00-110%, into a vaporizer where its temperature is raised to 100 C., before being deposited in the form of folds in a third ripening apparatus in which it remains 10 to 20 minutes at 100 C. The final product is then washed to eliminate the last impurities rendered soluble.

By such a technique it is possible, for example, to perform the continuous bleaching in 40 to 60 minutes of a raw linen closely woven fabric of high denier. The quality of whiteness is very good, and the final degree of polymerization is of the order of 2000, whereas more often than not, it is only about 1000 to 1300 if the normal processes are used which take more than 20 hours.

According to another method of working in accordance with the invention by which the whole of the available chorine in the chloro-cyanuric solution may be used, similar results are obtained by substituting the second treatment of the continuous process described above, with a semi-continuous one: the textile product emerging from the first ripening apparatus, after washing and rinsing, 1s impregnated with the solution of chlorinated derivatives of cyanuric acid, then wound round a slowly rotating drum'for 1 to 2 hours. The product is then unwound, wrung out and subjected to washing operations preceding the third continuous treatment.

In the case of unbleached fabrics, in particular, very heavy materials with a high ligneous content, it is particularly advantageous to carry out a preliminary continuous or semi-continuous operation before carrying out the first treatment described above. Such treatment consists in impregnating the textile product in a solution of chlorinated derivatives of cyanuric acid titrating 7 to 15 g./ 1. of available chlorine the pH of which is reduced to between 4 and 5. The fabric is then deposited in the form of folds in a ripening apparatus, or preferably, wound on a drum made to rotate slowly for l to 3 hours before being washed hot, rinsed, wrung out and subjected to the first treatment.

The examples which follow are given by way of illustration with the sole object of better understanding the conditions under which the process of the present invention may best be employed, and the results which may be attained thereby, it being of course understood that they limit the invention neither to the nature of the initial textile product, nor to the particular conditions of treatmen which are described.

EXAMPLE 1 An untreated linen textile fabric is subjected to continuous bleaching according to the present invention at a speed of 70 meters per minute. This fabric has the following characteristics:

Natural impurities soluble in water% Hemi-cellulose1 3 Mean degree of polymerization3,000 The denier200 g. per square meter (1) Continuous alkaline treatment The fabric treated in boiling water, then impregnated in a solution of caustic soda at 50 grams per liter, after having been wrung out at IOU-110%, is subjected to a vaporized steam atmosphere at 100 C., then to ripening in the form of folds in a J-Box for minutes at the same temperature. It is then well washed and rinsed on a washing machine with 6 baths, at the outlet from the J-Box.

(2) Continuous treatment in chlorocyanuric solution The wrung-out fabric is admitted into a saturator containing an aqueous bath heated to 50 C. having the following ingredients maintained constant:

Trichlorocyanuric acid (ATCC)11.l g./ liter of bath Cyanuric acid (AC)3.0 g./liter of bath 8odium bicarbonate (BS)-6.1 g./liter of bath Acetic acid necessary to maintain the pH at 4.5

This solution in which the molecular ratio ATCC/AC/ BS is substantially 2/ 1/3 has a concentration of available chlorine of 10 g./l.

On leaving the saturator, the fabric is wrung out to about 100%, and is then subjected to ripening in a second J-Box at 50 C. for 15 minutes before being washed in boiling water, rinsed and forcibly wrung out.

(3) Continuous treatment in alkaline solution of hydrogen peroxide At the close of the second treatment, the fabric is admitted into a second saturator containing an oxidizing aqueous solution the following composition of which is maintained constant:

Hydrogen peroxide at 130 volumes cm. /liter of bath Sodium silicate at 37 B.24 g./liter of bath Sodium hydroxide6 g./ liter of bath The fabric impregnated by exchange is wrung out at 100 110% at the outlet from the saturator. After passing into a vaporizer at 100 C. it is passed in the form of folds into a third J-Box where it is subjected to ripening for 15 minutes at 100 C. The final washing is effected on a washing machine with 5 baths, the two first of which are fed with boiling water.

After drying, the fabric displays a degree of whiteness of 90.3%, the degree of percent of transmission being effected by means of a photo-colorimeter, related to a standard of whiteness of MgCO The degree of polymerization of the cellular fiber exceeds 1950.

Trichlorocyanuric acid (ATCC)1 1.1 g./l. of bath Cyanuric acid (AC)3.0 g./l. of bath Sodium carbonate (CS)4.0 g./l. of bath Acetic acidquantity necessary for maintaining a pH The molecular ratio ATCC/AC/ CS is: 2/ 1/ 1.5

Dichlorocyanurate of sodium16.5 g./l. of bath Phosphoric acidquantity necessary for keeping a pH Dichlorocyanurate of potassium-18.0 g./l. of bath Formic acidquantity necessary for keeping a pH of 4.5

EXAMPLE 2 A jute fabric is subjected to bleaching by the mixed semi-continnous/continuous processes of the invention, comprising a preliminary chlorocyanuric treatment.

(1) Preliminary semi-continuous treatment in chlorocyanuric solutions.

The unbleached fabric is impregnated by passing through a bath having the same constant molecular ratio ATCC/AC/BS as that of the second treatment of Example 1, the pH being maintained at 4.8 by adding phosphoric acid. The available chlorine content in the solution is 15 g./l., and its composition, kept constant, is the following:

Trichlorocyanuric acid (ATCC)16.7 g./l. of the bath Cyanuric acid (AC)4.5 g./l. of the bath Sodium bicarbonate (BS)9.2 g./l. of the bath Phosphoric acidquantity necessary for maintaining a pH of 4.8

The impregnated product is wrung out to then wound onto a mandrel maintained slowly in rotation for three hours at 20 C.

(2) Continuous alkaline treatment under conditions identical to those in Example 1. (3) Continuous treatment in chlorocyanuric solution.

The impregnation is effected in a bath of identical composition to that of the preliminary treatment bath, the ripening in a J-Box being then effected at 20 C. for 20 minutes.

(4) Continuous treatment in alkaline solution of hydrogen peroxide.

At the end of the chlorocyanuric treatment, the fabric, washed in boiling water, rinsed and forcibly wrung out is admitted into a third saturator containing an aqueous oxidizing solution the following composition of which is maintained constant:

Hydrogen peroxide volumes)50 cmfi/l. of bath Sodium silicate (37 B.)40 cm. /l. of bath Sodium hydroxide--10 g./l. of bath After wringing out, evaporation and maturation under the conditions described for the third treatment of Example 1, the fabric, washed and dried, displays a good whiteness. its dynamic resistance is lowered at most 10% compared with the initial value which proves that the deterioration is very limited.

The total time taken for bleaching is under 4 hours.

EXAMPLE 3 The-untreated linen fabric of Example 1 is subjected to continuous/semi-continuous bleaching, according to one of the variations of the process of this invention.

( 1) The continuous alkaline treatment is effected under the same conditions as those described in Example 1. (2) Semi-continuous treatment in chlorocyanuric solution.

The forcibly wrung out fabric is impregnated by passing it through a bath with an available chlorine content of about 7 g./l;, and of which the composition, kept constant, is as follows:

Trichlorocyanuric acid (ATCC)--8.3 g./l. of the bath Cyanuric Acid (AC)2.2 g./l. of the bath Sodium bicarbonate (BS)4.5 g./l. of the bath Phosphoric acid--quantity necessary for maintaining a pH of 5 Molar ratio ATCC/AC/BS-substantially 2/ 1/3 The impregnated fabric is wrung out at 100-110% then wound onto a drum kept slowly rotating for 3 hours at 20 C.

(3) The continuous treatment in alkaline solution of hydrogen peroxide of the unwound fabric, washed in boiling water, rinsed and forcibly wrung out is carried out under the same conditions as those described in Example 1.

The total time for bleaching is about 3 hours and 35 minutes.

The resultant product, of an average degree of polymerization of 2040, presents an average degree of whiteness of 89.5%, the percentage of transmission being effected in relation to a standard whiteness of MgCO by means of a photo-colorimeter.

SUMMARY The main objects of the invention are:

(1) A continuous industrial process of bleaching textile products having a base of Liberian fibers such as linen, hemp and jute, which, if necessary, may be partly carried out semi-continuously, by means of which textile products of a very good whiteness and hardly deteriorated at all, may be obtained in 40 minutes to 4 hours, according to the nature and the quality of the materials used, characterized by the following points taken singly or in any combination:

(1) The bleaching process comprises three essential stages in the course of which the unbleached product after washing is brought successively in contact with a strongly alkaline bath under "a steam atmosphere at 100 C., a bath formed of an aqueous solution of chlorinated derivatives of cyanuric acid with an available chlorine content of between 7 and g./l., the pH of which is maintained at a value between 4 and 5 at temperatures of to 50 C., and an alkaline bath of hydrogen peroxide at 70100 C. stabilized with sodium silicate, it being possible for these three treatments to be preceded by preliminary treatment in a bath of the same composition as that of the second treatment, when handling initial products with a high proportion of natural impurities, the product being subjected to bleaching being washed and wrung out between each treatment.

(2) The chlorinated derivatives of cyanuric acid constituting the bath of the second treatment, as well as that of the preliminary treatment if necessary, described under (1), are selected amongst trichloro-cyanuric acid mixed with cyanuric acid and alkali metal bicarbonate or carbonate in the molecular ratio 2/ 1/ 3 or 2/ 1/ 1.5 or amongst the alkali metal salts of dichlorocyanuric acid, the pH of the bath being maintained at a value of between 4 and 5 by the addition of a mineral or organic acid.

(3) The operation of bleaching described under (1) and (2) comprises three continuous treatments lasting altogether 40 to 60 minutes, the second being conducted at (4) The operation of bleaching described under (1) and (2) comprises three treatments of which the first and third are conducted continuously and the second semicontinuously, in the course of which the textileproduct of the first treatment, after washing, wringing out, is impregnated in a bath constituted by an aqueous solution of chlorinated derivatives of cyanuric acid, then, after being wrung out at is wound at a temperature of between 20 and 50 -C. for 1 to 3 hours, before being unwound andsubjected to the third continuous treatment, the operation lasting altogether from -1 hour 30 minutes to 3.hours 45 minutes.

(5) The preliminary treatment in a chlorocyanuric medium of the bleaching operation described under (1) and (2) is combined to the three treatments described under (3), and conducted semicontinuously, the total duration of the treatment not exceeding four hours.

(6) The preliminary treatment in chlorocyanuric medium of the bleaching operation described under (1) and (2) is combined to the three treatments described under (4) and conducted in continuous operation the total time of the treatments not exceeding four hours.

(2)'Textile products with a basis of Liberian fibers such as thread, cords or textiles of linen, hemp or jute, obtained by applying the process of industrial bleaching described under (1).

It will be obvious to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to What is described in the specification.

What is claimed is:

1. An industrial process for bleaching textile products having a base of Liberian fibers selected from the group consisting of linen, hemp and jute comprising a first stage in which the unbleached product is washed and then impregnated with a sodium hydroxide solution and steamed at approximately 100 C.; a second stage wherein the product is then brought into contact with an aqueous solution consisting essentially of a bleaching ingredient selected from the group consisting of at least one of trichlorocyanuric acid, dichlorocyanuric acid and their alkali metal salts, said solution having an available chlorine content of between 7 and 15 g./l., the pH of which is maintained between 4 and 5 at temperatures of 2050 C.; and a third stage wherein the product is then brought into contact with an alkaline aqueous solution having a pH higher than 7 of hydrogen peroxide at 70100 C. stabilized with sodium silicate, the product being washed and wrung out between each stage.

2. A process according to claim 1 wherein the unbleached product is treated before said first stage with a bath having the same composition as in the second stage.

3. A process according to claim 1 wherein the bath composition of the second stage is selected from the group consisting of mixtures of trichlorocyanuric acid, cyanuric acid and sodium carbonate or bicarbonate in a molecular ratio of 2:1:1.53; and alkali metal salts of dichlorocyanuric acid, the pH of the bath being maintained between 4-5.

4. A process according to claim 1 wherein the product passes continuously through the three stages, the total process lasting approximately 40-60 minutes.

5. A process according to claim 1 wherein the first and third stages are conducted continuously and the second stage is conducted semi-continuously, the second stage comprising after impregnation in said bath, wringing out the product and then winding onto a drum which is kept slowly rotating for 1 to 3 hours at a temperature of between 2050 C. before unwinding and subjecting the product to the third stage treatment.

6. A process according to claim 2 wherein the preliminary treatment before the first stage is semi-continu- 7. The process according to claim 1 wherein the product passes in continuous operation through the first and third stages and semi-continuously through the second stage, the total processing time not exceeding 4 hours.

8. The process according to claim 2 wherein the preliminary treatment before the first stage is semi-continuous 10 and the remaining stages are continuous, the total processing time not exceeding 4 hours.

9. The process according to claim 2 wherein the preliminary treatment and the three stages of operation are continuous, the total processing time not exceeding 4 hours.

References Cited UNITED STATES PATENTS I 2,202,332 5/1940 Butterworth 8108 3,281,202 10/1966 Helmick et a1 8 108X MAYER WEINBLATT, Primary Examiner