EP3122926A1

EP3122926A1 - Method for dyeing and/or bleaching textile materials

Info

Publication number: EP3122926A1
Application number: EP15718615.6A
Authority: EP
Inventors: Roberto Franchetti
Original assignee: Individual
Current assignee: Individual
Priority date: 2014-03-24
Filing date: 2015-03-24
Publication date: 2017-02-01
Also published as: WO2015145341A1

Abstract

Method for dyeing and/or bleaching textile materials (13) and suchlike, in which an autoclave (10) is used, and in which the textile material (13) to be dyed and/or bleached is wound on at least a holed drum (12) disposed inside said autoclave (10), an aqueous solution of dye/dyes, or an aqueous solution of hydrogen peroxide or other reducing substances, and corresponding chemical auxiliaries, or other aqueous solution. The solution is introduced inside the holed drum (12) by introduction means (15, 17, 18, 19). The holed drum (12) is made to rotate at a speed such as to obtain, during the dyeing and/or bleaching, an impregnation by centrifugation so as to leave homogeneously distributed on all the fibers of the textile material (13) only the aqueous solution that is chemically bonded to them.

Description

"METHOD FOR DYEING AND/OR BLEACHING TEXTILE MATERIALS"

FIELD OF THE INVENTION

The present invention concerns a method for dyeing and/or bleaching any type of textile material and suchlike.

By textile material and suchlike, hereafter in the description, we refer for example, but not restrictively, to fabrics, non-woven fabrics, knitwear yarns, warp and weft, tops, tow fabrics or flock with a base of cellulose fibers, animal fibers, artificial or synthetic fibers and corresponding mixes.

BACKGROUND OF THE INVENTION

In the field of finishing processes for textile material, one of the most important and critical for the final quality of the garment is dyeing, where a dye is applied to the textile material arriving from previous workings.

We shall now give some definitions for a better understanding of the concepts on which the invention is based.

Dye is defined as a colored chemical substance able to fix itself stably to a textile fiber. In the field of textiles in question, the application of a dye is usually made in an aqueous medium.

By the term pick-up we mean the ratio between the weight of the textile material in a perfectly dry state and the weight of the aqueous solution absorbed in it; a pick-up of 30%, for example, means that 100 kg of textile material have absorbed 30 kg of aqueous solution.

By the expression bath ratio (B:R), we mean the ratio between the weight of the textile material, again in a perfectly dry condition, and the volume of the dyebath; for example, in an B:R = 1 :6, for each kg of textile material there are 6 liters of aqueous solution.

To dye means to transfer the dye from the aqueous solution to the fiber, so as to distribute it uniformly and fix it stably, to reproduce the color in its different hues, from which various quality indexes are also required.

The main classes of dyes for dyeing fibers are: acids, chrome acids, pre- metalized, reactive, direct, vat, sulphur, basic, dispersed, pigments and azoic dyes.

To apply dyes to textile fibers two techniques are mainly used: - exhaust dyeing;

- foulard dyeing.

In exhaust dyeing, the dyes, dissolved in water, are made to rise and are fixed to the fibers progressively, with the aid of determinate chemical auxiliaries, by raising the temperature to an established point; subsequently, the temperature is maintained for a determinate time, as a function of the exhaustion of the dye from the dyebath.

Exhaust dyeing is mainly performed on fabrics or knitwear, with known machines, such as those called overflow, jet, torpedo or jigger machines. Exhaust dyeing of yarns wound in reels is generally performed with autoclave machines. Contraindications of exhaust dyeing with said machines are:

- high bath ratio between weight of the textile material and volume of dyebath; for example, inside the same machine, for every kg of textile material there are from 6 to 10 liters of bath;

- high water consumption: in dyeing cotton textile material with reactive dyes, for dyeing and subsequent washing cycles, from 40 to 80 liters of water all in all are required for each kg of dyed textile material;

- high steam consumption;

- high consumption of chemical auxiliaries: in dyeing cotton with reactive dyes, for example in the case of an intense hue, up to 100 g/1 of sodium sulfate are required in the recipe, and up to 30 g/1 of bicarbonate of soda;

- limited dye yield: the reactive dyes used in dyeing cotton combine with the cellulose, reacting with the hydroxyl groups of the cellulose. The reaction of the dye with the cellulose is in competition with the possible reaction with the water hydroxide, to the detriment of the dye yield; indeed, as the bath ratio increases, the percentage of dye that is fixed on the cellulose fiber decreases; in the case of dyeing with B:R = 1 :6, the percentage goes down to about 70%;

- with overflow, jet or jigger machines there is a long duration of the dyeing cycle; in cotton dyeing with reactive dyes, about 4-5 hours are needed, since every piece to be dyed can be longer than 1000 meters and moreover its speed of circulation inside the machine cannot be more than some hundreds of meters per minute. The uniformity of the color is guaranteed by using reactive dyes, or other type, with low to average affinity with regard to the fiber, which, however, have the advantage of having high migration power. To obtain a uniform color over a whole piece, even 1000 meters long, it is therefore indispensable to respect parameters such as:

. the affinity curve of each dye with regard to the fiber;

. the speed at which the dye in the dyebath is exhausted;

. the migratory power of each dye;

. the distribution of the electrolyte in the dyebath;

. the distribution of the alkali in the dyebath;

. the time in which the temperature of the dyebath is gradually raised until the point established by the recipe, then followed by the time said temperature is maintained so as to fix the dyes to the fibers; in the case of dyeing cotton with reactive dyes, about 20 minutes are needed to raise the temperature to the established point, which must then be maintained for about 60 minutes, which time is necessary to exhaust the dye from the dyebath.

Considering the slow replacement of the bath through the textile material, long times and many revs of the piece inside the machine are required, to guarantee a uniform dyeing, which must then be followed by various washing steps, soaping and final rinsing.

There are also problems of uniformity of color and deformations of the textile material, such as creases, pilling and elongation.

The state of the art in dyeing textile materials, with reference to exhaust dyeing, proposes documents GB 854 221, GB 404 044 and FR 2 010 121, which describe methods for dyeing textiles wound around a holed drum; the textiles are dyed thanks to the continuous passage of the dyebath through the textile material wound around the rotating drum.

In GB 854 221, during dyeing, the peripheral speed of the holed drum, with a diameter of 1 meter, is 10 meters per second while in FR 2 010 121, during dyeing, the drum with a diameter of 1.2 meters can reach a speed of rotation of 500 rpm. It is known that centrifugal acceleration is calculated with the formula Ac = W² x R; centrifugal acceleration in (G) expresses how many times the acceleration of a moving body is greater than gravity acceleration (9.81 m/s ).

In FR 2 010 121, the radius R of the drum is 0.6 meters while the revs of the drum are 500 per minute.

If we do the calculations we have:

500 x 6.28 = 3140

3140 : 60 = 52.33

52.33 x 52,33 = 2738.42

2738.42 x 0.6 = 1643.052 (m/s²)

1643.052 : 9.81 = 167.487 G (centrifugal accelerazion)

In GB 854 221, with a drum with a radius of 0.5 meters and a peripheral speed of 10 m/s, the centrifugal acceleration goes down to a very low level equal to about 20 G.

The values of centrifugal acceleration expressed in (G) in the two documents cited above cannot physically guarantee an equal pick-up between the internal and external spirals of the rolled material, and moreover the pick-up value is very high.

The methods described in the above documents guarantee a good circulation of the bath through the textile material, and therefore the dyeing, using only the exhaust dyeing technique and keeping an B:R of about 1 :3, is homogeneous. The various consumptions of dyes, chemical auxiliaries, water and steam are always high, even if they are lower than the values obtained by dyeing with an overflow machine.

In these known methods too, it is absolutely necessary to respect all the parameters listed above, including the time required to raise the temperature of the dyebath to the point established by the recipe, followed by the time needed to fix the dyes to the fibers.

Compared with dyeing performed with an overflow machine, the textile material is not subjected to deformations, but the difficult passage of the bath through the fibers limits the length of each batch, and hence the production of these machines is low, for which reason they are not very widely used. The state of the art also proposes a document in the name of the present Applicant: WO 2008/058689 Al . This describes a method for treating fabrics wound around a holed drum with a liquid ammonia solution + dyes: the drum can be taken to a high rotation speed.

It is known that liquid ammonia penetrates inside cellulose fiber, modifying its structure but without bonding with it. The values of density 0.68, viscosity 0.266, surface tension 34.4 are much lower than those of water, which are respectively 1, 1.002 and 72.8 therefore, it can be almost completely removed uniformly from the textile material by applying centrifugal acceleration values of about 150-200 G, depending on the type and weight of the article.

Steaming methods are also known, performed at atmospheric pressure or in conditions of high pressure, for articles rolled around a holed drum which can be made to rotate upon itself. These methods can be for example decatising a wool fabric, fixing cotton or wool articles, heat fixing fabrics or knitwear consisting of synthetic fibers, stabilizing cotton fabrics, improving the fastness of dyes in articles previously dyed and dried, restoring fabrics treated with resins and others.

In the continuous foulard dyeing method, mainly for cellulose fiber, the "pad steam" system is particularly important: in fact, with this method the parameters present in the exhaust dyeing technique are not respected.

After impregnation of the fabric by means of a foulard, a pick-up of about 80- 90%, with an aqueous solution containing up to 5-6% of reactive, direct or vat dyes, or sulfur dyes or others, together with the corresponding chemical auxiliaries, the fabric then transits for about 1 minute inside a steamer kept at a temperature of 98-100°C, which time and temperature are needed to fix the dyes to the cellulose fibers.

The dyes used have great affinity with fiber, since their molecules are able to fix themselves to the fibers very quickly, despite the presence of the water impregnating the fabric; the migratory power of the dyes is very low and therefore it is difficult to use them with the exhaust dyeing technique.

After the dye has been fixed to the fibers the fabric is washed, soaped and rinsed, for an overall time of about 3 minutes, in a continuous washing plant located downstream of the steamer. Given the high production of the pad steam plant, it is necessary to have long lengths of fabric to dye or bleach.

The disadvantages of this technique are:

. poor penetration of the dye inside the fiber;

. problems of lack of uniformity of the color due to a non-homogeneous humidity rate in the batch of textile material, irregular drying of the textile material before dyeing, the morphology of the textile material, the different density of the warp thread between the center and the selvedges of the fabric so that the pick-up is irregular;

. limited dye yield; about 30% of the dye is not fixed to the fiber;

. dyeing/bleaching of fabrics only;

. high energy consumption;

. poor flexibility of the plant;

. cost of the plant.

Purpose of the present invention is to obtain a method for dyeing and bleaching textile materials that is very quick, characterized by drastic savings in dyes, chemical auxiliaries, water and steam, and more generally that overcomes at least some of the shortcomings described above.

SUMMARY OF THE INVENTION

The present invention is set forth and characterized in the independent claim, while the dependent claims describe other characteristics of the invention or variants to the main inventive idea.

In accordance with the above purpose, the invention achieves an innovative method for dyeing and/or bleaching textile materials, such as fabrics, non-woven fabrics, knitwear, yarns, tops, tow fabrics or flock, with a base of cellulose, animal, artificial or synthetic fibers and corresponding mixes.

In particular, in the method according to the invention the textile products are impregnated with an aqueous solution, put at a determinate temperature, of dyes and corresponding chemical auxiliaries, inside an autoclave.

In the autoclave, substantially in correspondence to its longitudinal axis, there is a holed drum around which the textile products are wound.

In a variant embodiment, a permeable backgray is tightly wound around and externally to the textile material being treated. In the dyeing process with an aqueous solution, the water acts as a solvent with regard to the dyes and the corresponding chemical auxiliaries but also as a transporter agent of the dyes on the textile fibers.

A high B: , in ratio to the weight of the textile, becomes however a source of the following contraindications:

- high percentage of dye which reacts, by hydrolysis, with the water, so that the dye yield is low;

- high consumption of chemical auxiliaries which are always measured on the basis of the quantity of water present;

- high steam consumption;

- high water consumption in the final washing step.

According to the invention, the aqueous solution of dyes, bleaches and corresponding chemical auxiliaries is fed into the holed drum and brought onto the textile material by centrifugation through the holed drum, which is made to rotate at a speed such as to impregnate the textile material by centrifugation so as to leave homogeneously distributed on all the fibers of the material only the aqueous solution that has bonded with the fibers.

Thanks to this, we obtain an extremely fast method for dyeing or bleaching textile material with a minimum quantity of water needed, that is an almost zero water consumption.

The fibers can retain water, or an aqueous solution containing dyes, thanks to: . surface tension of the liquid;

. adhesion to the fibers;

. capillarity inside the fibers;

. water - fiber chemical bond.

Applicant has verified that in the treatment of a textile material wound round a drum and impregnated with an aqueous solution containing dyes, the centrifugal acceleration determined by the rotation speed of the drum set to values of 700 - 900 G, and possibly more, leaves on the textile only the water that has chemically bonded to the fibers; the water is homogeneously distributed, with regular pickup, through all the article rolled around the drum. The water retained by the textile material due to the surface tension of the liquid, adhesion to the fibers or by capillarity, can be totally extracted mechanically by applying the centrifugal acceleration values indicated above.

The water part that has chemically bonded to the textile, on the other hand, is always retained by the fibers, even if a very high centrifugal acceleration is applied, for example even with values of more than 2,000 G. In fact, this can only be extracted by evaporation, for example by administering heat.

The percentage of water that is chemically bonded to the fibers, depending on their type, with water temperature of 20-30°C working at atmospheric pressure, with percentages referred with respect to the dry weight of the textile material, can assume the following values.

. cotton 40%

. linen 40%

. viscose 45-50%»

. 67% cotton - 33% polyester 20%

. wool 25%

The quantity of water that chemically and homogeneously bonds to the various fibers can vary by a few percentage points depending on the provenance of the fiber, the year the cotton was picked, the variation in climate in the case of wool, the fineness of the fiber, the count of the yarns, the type of article or other.

At a temperature of 60°C the above percentages fall by a few percentage points; even in a condition of strong depression the above percentages fall by a few percentage points.

In the step after the homogeneous impregnation, for example with a pick-up of about 40% in the case of cotton, of a whole batch of textile material, the high affinity dyes dissolved in the aqueous solution that has bonded to the fibers are fixed to the fibers by a steaming operation, performed under pressure and at a temperature adjustable between 100°C and 160°C, advantageously between 1 10°C and 140°C.

In an alternative solution, the dyes can also be fixed by heating the textile material and aqueous solution by means of a radiofrequency system.

After the dyes have been fixed to the fibers the invention provides a brief wash, possibly a brief soaping and a final rinsing. The time needed for the entire dyeing cycle, or bleaching cycle, with the method according to the invention used in batch mode is about 10-15 minutes, divided in this way:

. homogeneous impregnation of a whole batch of textile material with pick-up as per the values indicated above; temperature of the aqueous solution containing the dyes of about 20-30°C; impregnation time 3-5 minutes;

. fixing of 95-98% of the dyes to the fibers by means of a steaming cycle, preferably under pressure and at a temperature of for example 1 10 - 120°C for reactive dyes applied to cellulose fiber; steaming time 3-5 minutes;

. final wash after the dyes have been fixed to the fibers; washing time 3-5 minutes.

With the method according to the invention there are a number of advantages, such as:

- very limited B:R, even with respect to the "pad steam" method;

- uniform color;

- total penetration of dyes into the fiber;

- high color fastness;

- high dyeing yield; about 95%-98% of the dye is fixed to the fiber;

- very low consumption of chemical auxiliaries;

- very low consumption of water and steam;

- dyeing or bleaching under different pressure and temperature conditions;

- dyeing with high but also low affinity dyes;

- reduced dyeing and washing times;

- dyeing and bleaching every type of fiber;

- dyeing or bleaching of fabrics, non-woven fabrics, knitwear, yarns, tops, tow fabrics or flock;

- no deformation of the textile.

Using a permeable backgray wound around the rolled textile material prevents possible deformation of the textiles or the knitwear and acts as a container in the case of dyeing or bleaching of tops, tow fabrics or flock.

BRIEF DESCRIPTION OF THE DRAWINGS We will now describe in detail these and other characteristics of the invention, with reference to a particular form of embodiment, given as a non-restrictive example, with the aid of the attached drawing wherein:

-fig. 1 shows a schematic view in longitudinal section of an autoclave in which the method of the invention is shown.

DETAILED DESCRIPTION OF A PREFERENTIAL FORM OF

EMBODIMENT

We will now refer in detail to a form of embodiment of the invention, an example of which is shown in the attached drawing. The example is supplied by way of illustration of the invention and is not intended as a limitation thereof.

As seen in fig. 1 , the method of the invention provides to use an autoclave 10, inside which there is a holed drum 12.

In this case, the holed drum 12 is located substantially in correspondence to the longitudinal axis of the autoclave 10 and can be made to rotate around its own axis.

A textile material 13 is wound around the holed drum 12 with a controlled tension; the textile material 13, as we said, can be a fabric, a non-woven fabric, knitwear, a yarn, tops, tow fabrics or flock, to be dyed or bleached.

The thickness of the textile material 13, wound in overlapping spirals, is adjustable depending on the type of article and the length of the batch; in general this thickness does not exceed 10 centimeters.

According to a variant, not shown, a robust backgray, permeable to air and liquids, made of textile fabric, or carbon fiber, or glass fiber, or steel fiber, or any combination of these or any other material, can be wound around said batch of textile material 13.

The function of the backgray is to contain the textile material 13, wound around the holed drum 12, so as to prevent the deformation of said textile 13 during working.

According to a variant, not shown, after first batch of textile material 13 has been wound, with subsequent winding of a first backgray, a second or various other batches of textile material 13 can then be wound around the first batch, each of which is then wound by a corresponding backgray which is permeable to the passage of water. The winding can be performed outside the machine, and the holed drum 12 can be subsequently inserted inside the autoclave 10, or, in an alternative solution, directly with the holed drum 12 inserted in the autoclave 10.

To guarantee high production, the machine can be equipped with two or more drums; in this way, during the time needed to perform the dyeing or bleaching cycle of a batch of textile material 13 inside the autoclave 10, a second batch of textile product 13 can be prepared outside the machine. At the end of the dyeing cycle, the dyed batch will be discharged from the autoclave 10, to leave place for a new batch of textile material 13, ready to begin a new dyeing cycle.

Once the holed drum 12 is positioned, it is provided to introduce into the autoclave 10 the aqueous solution of dye/dyes and corresponding chemical auxiliaries, previously prepared in a known way.

The aqueous solution can be introduced under a condition of depression, with an adjustable entity guaranteed by a vacuum pump, not shown in the attached drawing, connected to the autoclave 10.

A depression condition inside the autoclave 10 allows to ensure a deep impregnation of the textile material 13 in a short time and to eliminate the oxygen present, which, in the case of some classes of dyes for example vat dyes, is a harmful element in subsequent dyeing cycle.

In the form of embodiment shown in fig. 1, the aqueous solution is fed to the autoclave 10 from a tank 15, inside which it is taken to a predetermined temperature and kept regulated by a heating/cooling circuit 16.

The aqueous solution is made to circulate by means of a circulation pump 17 and a delivery pipe 18, connected to a distribution bar 19, located longitudinally inside the holed drum 12. The latter is made to rotate, at a predetermined peripheral speed, by a motor 14, in order to guarantee the homogeneous distribution of the dyebath, distributed inside the drum 12, along the whole length of the distribution bar 19, and then through all the fibers of textile material 13.

The mechanical structure of the holed drum 12 is suitably sized to support the weight of the textile material 13 rolled around it, and to guarantee a high rotation speed of the drum, in the absence of vibrations or deformations.

The external surface of the holed drum 12 is advantageously covered by some layers of metal netting which has a very fine mesh; the jets of aqueous solution exiting from every hole of the holed drum 12, each of which, for structural reasons, has a determinate diameter, are at high speed and high pressure, caused by the high centrifugal acceleration, and therefore, advantageously, they are homogeneously nebulized before coming into contact with the textile material 13, so as to guarantee it is properly impregnated.

Nebulization is guaranteed by the passage of the jets of aqueous solution through the fine mesh layers of the metal netting.

In a preferred solution, the homogeneous distribution of the dyebath inside the holed drum 12, made to rotate on itself at a high number of revs, is guaranteed by the distribution bar 19 and by a series of lamellar discs, a few centimeters high and positioned at a distance of a few centimeters from each other; the discs are positioned in contact against the internal part and around the whole circumference of the holed drum 12. The function of the dividing lamellar discs is to prevent non-uniform passages of the dyebath between the internal part and the sides of the holed drum 12 and then subsequently through the rolled textile material 13.

The peripheral speed of the drum 12, with the textile material 13 wound on it, is regulated to generate a high centrifugal acceleration, that is, number of G, on the totality of the liquid mass present in all the fibers of the textile material 13, also when the textile material 13 has irregular sizes and weight.

According to an important feature of the present invention, the peripheral speed of the holed drum 12 is chosen so as to generate a centrifugal acceleration (expressed in number of G) above 700 G, so as to leave on the fibers of textile material 13 only the humidity that is chemically bonded with said fibers; the humidity is also homogeneously distributed in percentage (pick-up) through all the thickness of the textile material 13 wound around the holed drum 12, irrespective of its morphology, its humidity rate, regularly or irregularly distributed, its degree of dryness, its density, the counts of the fibers and the sizes of the textile product.

In the case of thick articles, cellulose fibers or animal fibers or synthetic fibers or various mixes, to guarantee homogenous impregnation through all the thickness of the textile material 13 wound around the holed drum 12, the invention provides to generate a centrifugal acceleration of more than 900 G. In bleaching cellulose fibers, or animal origin fibers such as wool, the textile material 13 wound around the holed drum 12 is impregnated with an aqueous solution of hydrogen peroxide or other reducing agent and corresponding chemical auxiliaries.

After passing through the textile material 13 wound around the holed drum 12 through centrifugation, the aqueous solution of dye/s and the corresponding chemical auxiliaries is collected on the bottom of the autoclave 10 and conveyed to the tank 15 by means of a connector pipe 20.

The temperature of the aqueous solution is continuously monitored in the tank 15 by the heating/cooling circuit 16, and is then re-introduced inside the holed drum 12 by means of the circulation pump 17, the delivery pipe 18 and the distribution bar 19; here, due to centrifugal force, it will again pass through the textile material 13.

According to a variant of the invention, not shown, the rolled textile material 13 is impregnated with an aqueous solution containing dyes and the corresponding chemical auxiliaries, which is put on the bottom of the autoclave 10; the whole batch of textile material 13 is impregnated keeping the holed drum 12 in slight rotation for some minutes.

At the end of impregnation, with high pick-up, the holed drum 12 is taken to a high rotation speed so as to generate a centrifugal acceleration adjustable from 700 to 900 G, and possibly more, so as to eliminate the excess bath and to leave on the textile material 13 only the dyed aqueous solution which has chemically bonded with the fibers; for example, in the case of cotton, we have a pick-up of 40% of aqueous solution kept at a temperature of 20-30°C and homogeneously distributed through all the fibers.

According to another variant of the invention, not shown, the aqueous solution containing dyes and the corresponding chemical auxiliaries is made to circulate for a few minutes by means of a bath circulation pump, through the holed drum 12 and subsequently through the spirals of the rolled textile material 13. At the end of impregnation, with high pick-up, the holed drum 12 is taken to a high rotation speed so as to generate a centrifugal acceleration adjustable from 700 to 900 G, and possibly more, so as to eliminate the excess bath and to leave on the textile material 13 only the dyed aqueous solution which has chemically bonded with the fibers; for example, in the case of cotton, we have a pick-up of 40% of aqueous solution kept at a temperature of 20-30°C and homogeneously distributed through all the fibers.

For example, at a rotation speed of 1,000 rpm, with a diameter of the holed drum 12 of 1500 mm and a wound thickness of the textile material of 50 mm, the centrifugal acceleration, average value of the internal and external spirals, is 840 G: this value is enough to leave on the cellulose fibers only the aqueous solution containing the dyes and the corresponding chemical auxiliaries which has chemically bonded with the fibers homogeneously. The peripheral speed of the drum, in this example, is about 79 meters per second.

The length of the batch of cotton with an average weight of 120 g/m², wound thickness of 50 mm around a holed drum 12 with a diameter of 1,500 mm, is about 1,100 meters.

The hourly production of this article, calculating 3 cycles per hour, with 15 minutes for each dyeing + washing cycle, is about 3,000 meters, which is identical to that given by a continuous "pad steam" dyeing plant with a working speed of 50 m/min.

In the case of a textile material consisting of 67% polyester fibers and 33% cotton fibers, the centrifugal acceleration is kept at values of about 700 G, which is enough to guarantee pick-up of about 30%, homogeneously distributed through all the fibers.

If we go down to centrifugal acceleration values of less than 700 G, between internal and external spirals, the pick-up values are different, so that in the subsequent step of fixing the dyes to the fibers, by means of steaming or radiofrequency systems, the different pick-up values would cause different intensities of hue between start and end of a batch.

With this method it is also possible to impregnate yarns wound around suitably sized beams. In this case, not shown in the attached drawing, the distaffs are packed horizontally one adjacent to the other, for example inside holed steel tubes that are subsequently inserted inside the autoclave 10 and can be made to rotate on themselves at a determinate speed. The delivery and distribution of the solution of dyes and the corresponding chemical auxiliaries are made from inside the distaffs. At the end of the homogeneous impregnation of a whole batch of textile material 13, it is only the humidity present in the textile material 13 that is the only aqueous solution remaining chemically bonded with the fibers.

Subsequently, the dyes are fixed to the fibers, using the corresponding chemical auxiliaries, by means of a steaming cycle, saturated water steam or superheated steam.

The steaming cycle can be carried out at atmospheric pressure or, advantageously, at high pressure.

According to this variant, the saturated water steam or superheated water steam is introduced into the autoclave 10 from a steam entry pipe 21, and distributed inside the holed drum 12, kept in rotation, by the distribution bar 19. The steam raises the temperature of the fibers and the aqueous solution containing the dyes to a predetermined value, and keeps it constant for the predetermined time.

The working pressure and temperature inside the autoclave 10 are regulated by the temperature and pressure of the entering steam, by its condensation on the fibers and by the vent valve 23. The steaming time needed to fix the dyes to the fibers is only a few minutes.

After the dyeing cycle, a second or various impregnation cycles can be repeated on the same batch of already dyed textile material 13, always leaving on the fibers only the humidity that chemically bonds; the cycles are followed by the corresponding steaming and are performed one after the other, using the remaining quantity of dyebath still present in the hydraulic circuit of the machine. The first steaming cycle therefore fixes the dye to the fibers but, at the same time, it impoverishes its concentration in the aqueous solution impregnating the textile material 13. A second impregnation, performed with the aqueous solution present in the hydraulic circuit of the machine, or with another solution rich in dyes, substitutes the impoverished solution present on the textile material 13 through centrifugation, still keeping the same pick-up, and is then fixed to the textile material 13 by a new steaming cycle.

In this way, almost all the dye present in the dyebath, that is, the bath absorbed by the fiber and that present in the circuit of the machine, can be fixed to the textile material 13. In this step, as well as the dye already present in the solution, more dye or other chemical auxiliaries, such as for example caustic soda in the case of dyeing cellulose with reactive dyes, can be added if required before the second impregnation.

Alternatively, the second impregnation can be made on the already dyed textile material 13 in combination with the steaming cycle.

Compared with the continuous "pad steam" dyeing method performed on cellulose articles, given the same quantity of dyes, with the method according to the present invention 95-98% of the dyes present are chemically fixed on the fibers: this high dye yield is guaranteed by the limited percentage of water impregnating the fibers, so as to eliminate almost completely the hydrolysis of the dyes, and by the subsequent fixing of the dyes on the fibers by means of steaming, generally carried out at atmospheric pressure and at a temperature of 1 10-120°C, which temperature is maintained for a few minutes.

With the invention it is also possible to dye textiles consisting of a mix of cellulose/synthetic fibers, wool/synthetics, other mixes or again 100% polyester fibers; in these cases the adjustable steaming temperature can also reach 150°C.

According to a variant of the invention, not shown in the drawing, the aqueous solution of dye/s and corresponding chemical auxiliaries absorbed by the textile material 13 is heated together with the fibers by means of a radiofrequency system, with the drum 12 always kept in slight rotation. The aqueous solution and fibers are heated uniformly with the radiofrequency system, external part and internal part of the fibers and irrespective of the morphology, weight, density and sizes of the textile material 13 ; the heating generates steam uniformly inside the textile material 13, which guarantees that the dyes are fixed to the fibers.

Heating with the radiofrequency system is carried out for a determinate time depending on the fibers and the dyes, at atmospheric pressure or at an adjustable pressure higher than atmospheric.

In the case of bleaching with hydrogen peroxide or other oxidizing or reducing agent, present together with the corresponding chemical auxiliaries in the aqueous solution absorbed by the textile material 13, the bleaching of the fibers will always be developed by means of a steaming cycle, or a heating cycle performed with a radiofrequency system. The steaming cycle or radiofrequency cycle can be carried out inside the autoclave 10 or, after the previously impregnated textile material 13 has been discharged from the machine, in another external system set up for the purpose.

At the end of dyeing or bleaching, the chemical auxiliaries and the reduced quantity of dyes not fixed to the fibers of the textile material 13 are preferably removed with hot water washing and possibly with soaping followed by final washing.

The hot water, or hot water with soap, are introduced into the autoclave 10 through the washing water entrance pipe 22, and are then distributed inside the holed drum 12, kept rotating, through the distribution bar 19; they then pass through the textile material 13. After washing, the dirty water is discharged through the discharge exit 24.

The washing time after dyeing is short, and the water consumption is very small, even in the case of cellulose fibers dyed with reactive dyes, since the percentage of hydrolyzed dyes not fixed to the fibers is minimal, thanks to the very limited mass of solution impregnating the textile part and to the B:R ratio which is kept very limited.

After the steaming cycle or treatment with a radiofrequency system, the textile material 13, discharged from the autoclave 10, can alternatively be washed in an external washing plant.

Example.

1, 100 meters of cotton fabric with a weight of 120 g/m , medium hue, were dyed with reactive dyes and subsequently washed.

The values detected were as follows:

"invention" pad steam v: 50 m/min overflow B:R

Cycle time 1 5 min. 20 min. 4 hours

Dye yield 98% 70 % 70%

Consumption of H₂0/kg ; textile 3 1 10 1 50 1

Consumption of auxiliaries very low low very high

Steam consumption very low very high very high

Machine management very easy difficult difficult

Other advantages of the method according to the present invention are as follows: . dyeing/bleaching of elasticized fabrics.

. dyeing/bleaching of knitwear.

. dyeing/bleaching of very delicate articles.

. dyeing/bleaching of non woven fabrics.

. dyeing/bleaching of yarns.

. dyeing/bleaching of tops.

. dyeing/bleaching of flock.

. dyeing/bleaching of tow.

It is clear that modifications and/or additions of parts may be made to the method for dyeing and/or bleaching textile material as described heretofore, without departing from the field and scope of the present invention.

It is also clear that, although the present invention has been described with reference to some specific examples, a person of skill in the art shall certainly be able to achieve many other equivalent forms of method for dyeing and/or bleaching textile material, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.

Claims

1. Method for dyeing and/or bleaching textile materials (13) consisting of a plurality of fibers, in which an autoclave (10) is used, inside which is disposed at least one holed drum (12) on which the textile material (13) is wound, an aqueous solution of dye/dyes, in the case of dyeing, or an aqueous solution of hydrogen peroxide or other reducing substance, in the case of bleaching, and corresponding chemical auxiliaries being introduced inside said holed drum (12), characterized in that it provides that said textile material (13) is impregnated by centrifugation with said aqueous solution of dye or bleaching substances, said holed drum (12) being made to rotate at a speed such as to generate a centrifugal acceleration higher than a value of 700 G so as to leave homogeneously distributed on said textile material (13) only the aqueous solution that is chemically bonded with said fibers.

2. Method as in claim 1, characterized in that said homogeneous distribution of the aqueous solution that has chemically bonded to the textile fibers is obtained by keeping uniform the ratio between the weight of the textile material in a perfectly dried state and the weight of the aqueous solution absorbed therein, that is to say, the pick-up.

3. Method as in claim 2, characterized in that the pick-up values, with the temperature of the solution maintained at 20-30°C in atmospheric pressure conditions, after the impregnation of the textile material (13) by means of centrifugation are, with respect to the dry weight of the textile material (13), about 40% in the case of cotton or linen, about 45-50% in the case of an artificial fiber such as viscose, about 20% in the case of a textile material consisting of a 67/33 mix of polyester fibers/cotton and about 25% in the case of animal fibers.

4. Method as in any claim hereinbefore, characterized in that after the impregnation step a steam treatment step is provided to fix the dyes chemically to the textile material (13) or to allow the bleaching action on said textile material (13).

5. Method as in any claim hereinbefore, characterized in that said steam treatment step is performed with saturated water steam, or super-heated water steam, with adjustable pressure and temperature, introduced into the autoclave (10) by a steam inlet pipe (21) and distributed inside the holed drum (12), kept in rotation.

6. Method as in any claim hereinbefore, characterized in that the same batch of textile material (13), wound around the holed drum (12), is dyed with one or more impregnation cycles followed by the corresponding steam treatment, performed one after the other.

7. Method as in any claim hereinbefore, characterized in that, in the step where the dyes are fixed to the textile fibers, or where said textile fibers are bleached, it provides to heat the textile material (13) with a radiofrequency system.

8. Method as in any claim hereinbefore, characterized in that, after the dyeing or bleaching, it provides to perform a washing step by passing water or water with a corresponding detergent, by centrifugation, through all the fibers of said textile material (13).

9. Method as in any claim hereinbefore, characterized in that the entire dyeing cycle, consisting of impregnation, steaming and washing, of a batch of cellulose fibers is performed in an overall time of about 10-15 minutes.

10. Method as in any claim hereinbefore, characterized in that the textile material (13) to be dyed or bleached is a warp and weft, or a non- woven fabric, or knitwear, or yarns, or tops, or tow fabrics or even loose fiber.

1 1. Method as in any claim hereinbefore, characterized in that it provides that the inside of the autoclave (10) is kept in a condition of atmospheric pressure, at an adjustable pressure lower than atmospheric pressure or at an adjustable pressure higher than atmospheric pressure.

12. Method as in any claim hereinbefore, characterized in that at least one backgray, permeable to air and water and made of textile fiber, or carbon fiber, or glass fiber, or steel fiber, or any combination of these, is wound during use tightly around said textile material (13).

13. Apparatus for dyeing and/or bleaching textile materials (13) consisting of a plurality of cellulose fibers, comprising an autoclave (10), inside which there is at least one holed drum (12) on which the textile material (13) is wound, said holed drum (12) being associated to introduction means for the introduction of an aqueous solution of dye/dyes in the case of dyeing, or an aqueous solution of hydrogen peroxide or other reducing substance in the case of bleaching, and corresponding chemical auxiliaries, characterized in that said holed drum (12) is associated with means configured to make it rotate at a speed such as to generate a centrifugal acceleration higher than a value of 700 G so as to leave homogeneously distributed on said textile material (13) only the aqueous solution that has chemically bonded with said fibers.

14. Apparatus as in claim 13, characterized in that it comprises at least one backgray, permeable to air and to water and made of textile fiber, or carbon fiber, or glass fiber, or steel fiber, or any combination of these, which is wound during use tightly around said textile material (13).

15. Apparatus as in claim 13 or 14, characterized in that said holed drum (12) has an external surface covered by layers of metal netting with a very fine mesh, with the function of nebulizing the jets of aqueous solution exiting from every hole of said holed drum (12) in order to guarantee a regular impregnation of said fibers with the aqueous solution.

16. Apparatus as in any of the claims from 13 to 15, characterized in that it comprises a plurality of lamellar discs positioned, at a distance of a few centimeters from each other, in contact against the internal part and around the whole circumference of the holed drum (12), having the function of preventing non-uniform passages of the dyebath between the internal part and the sides of the holed drum (12) and then subsequently through the rolled textile material (13).