EP1723280A1

EP1723280A1 - Method for permanently dyeing cellulose-based textiles; textiles and clothes obtained thereby

Info

Publication number: EP1723280A1
Application number: EP05734830A
Authority: EP
Inventors: Giuseppe Picerno; Roberto Pacini; Enrico Tomassini
Original assignee: Leineweber & Co Kg GmbH; Lanificio Europa SNC Di Piero E Luigi Guarducc I E Donatello Lombardi; Tintoria Rifinizione Tessuti-Trt SpA
Current assignee: Leineweber & Co Kg GmbH; Lanificio Europa SNC Di Piero E Luigi Guarducc I E Donatello Lombardi; Tintoria Rifinizione Tessuti-Trt SpA
Priority date: 2005-03-04
Filing date: 2005-03-04
Publication date: 2006-11-22
Anticipated expiration: 2025-03-04
Also published as: DK1723280T3; DE602005010670D1; EP1723280B1; ATE412798T1; WO2006092815A1

Abstract

The present invention relates to a method for permanently dyeing cellulose-based textiles, to dyed textiles obtained with said method and to items of clothing manufactured with said textiles.

Description

METHOD FOR PERMANENTLY DYEING CELLULOSE-BASED TEXTILES; TEXTILES AND CLOTHES OBTAINED THEREBY

The present invention relates to a method for permanently dyeing cellulose-based textiles, to dyed tex- s tiles obtained with said method and to items of clothing manufactured with said textiles.

In the textile field several dyeing methods for dyeing fiber in the form of fibers, yarn, fabric or garment are known. io Said methods differ from one another depending on the type of fiber (natural, artificial or synthetic fiber) and on the form thereof (fiber, yarn, fabric or garment) . More to the point, every dyeing method uses given

15 classes of dyes, operating conditions and dyeing devices .

In the case of a cellulose-based fiber, direct dyes and reactive dyes are used most frequently. Reactive dyes are particularly preferred for dyeing

20 cellulose piece-shaped fabrics.

Reactive dyes are known to be substances that bind to textile cellulose fibers by forming covalent bonds with said fibers. A reactive dye comprises: at least one chromophore

25 group (giving color) , at least one reactive group (or leaving group) and a bridge group placed between said chromophore group and said leaving group. Preferably, depending on the number of reactive groups pro molecule, reactive dyes are divided into monofunc-

30 tional and bifunctional groups.

Among reactive leaving groups the following can be mentioned by way of example: halides (Cl, Br), sulfonamides, phthalazines, pyrimidines. Among chromophore groups the following can be mentioned

35 by way of example: groups with a system of conjugated double bonds such as azoic groups, azomethinic groups, quinone groups, ethylene groups.

Among bridge groups the following can be mentioned by way of example: alkylene radicals of variable length (methylene, ethylene and higher radicals) , interrupted if necessary by nitrogen atoms (secondary or tertiary atoms), oxygen, sulfur, or by groups such as amido groups, carbamyl groups, carbamoyl groups, ureic groups and the like. Depending on the reactivity of the leaving group or groups, reactive dyes are further divided into: dyes to be applied at low temperature (30-40⁰C), at medium temperature (50-60⁰C) and at high temperature (80-90⁰C) . The ability of said dyes to bind in a stable manner with the reactive functions of cellulose fibers gives the dyeing a higher color solidity than the one that could be obtained for instance with direct dyes (indeed, the latter bind to the textile fibers by means of weak electrostatic interactions, such as for instance hydrogen bridge bonds, van der Waals forces and so on) . "Color solidity" commonly refers to the resistance of the color of a textile to degradation, i.e. to loss of color due to various factors such as for instance light, humidity, heat, washing. In particular, color degradation due to textile washing (or in ^'case items of clothing and/or fabrics produced with said textile are washed) is determined by comparing the color of the unwashed textile with the color of the same textile after washing (or after a series of repeated washing operations), referring to the gray scale for color variation as provided by international norm ISO 105 A02 (and by corresponding Italian norm UNI EN 20105 A02Λ96) . Said gray scale is made up of 10 pairs of gray plates, a plate of each pair being characterized by a decreas- ing gray intensity.

As a consequence, within the single pairs intensity and contrast difference varies: to every intensity difference correspond different values of color degradation, which are classified according to a scale going from 5 to 1 (also comprising intermediate values). Degree 5 corresponds to two identical gray plates, i.e. with no color difference; said degree means therefore an inexistent degradation to washing (or to the number of washing operations that have been carried out).

Degree 1 corresponds to the maximum degree of color contrast between the two gray plates; said degree means therefore a very high degradation to washing, i.e. the maximum degradation as possible. After washing a sample (or after washing it for a number of times as provided by the test) , said washed sample is compared with the unwashed original sample and the color contrast between said two samples is compared with the contrast of gray tones between the pairs of plates of the gray scale.

Thus, color variation as a consequence of the washing operation/s can be given an objective value. Unfortunately, if reactive dyes are applied in a traditional manner by means of dyeing machines, techniques and methods commonly used in the field, they cannot react with all reactive functions present on cellulose fibers .

Conversely, even if used in a high excess, reactive dyes can react only with a given number of said reac- tive functions, due to an incomplete penetration of said dye into textile fibers.

As a consequence, reactive dyes cannot meet in a satisfactory way the more and more urgent consumers' need for dyed items of clothing whose color does not de- grade, i.e. does not fade in a short time, in particu- - A -

lar as a consequence of repeated domestic washing operations in a washing machine, though following care instructions .

Above all involved by this phenomenon are those items of clothing such as for instance trousers, skirts, shirts, jackets, coats, overcoats, which due to their use are more subject to get dirty and, therefore, have to be washed more frequently than other items of clothing. This drawback is known to involve especially darker colors (for instance black, blue, brown, green, red, in all their tones).

As a matter of fact, in said colors every variation (either in terms of degradation or in terms of alterna- tion in the homogeneity of said color) is more evident and immediate with respect to lighter colors. Among dark colors, black, blue, brown and green are known to be the most delicate from this point of view, in particular black. As a consequence, there is a strong need for textiles, preferably dyed in dark colors, with a suitable long- term resistance, especially to the bleaching action of washing operations. In particular, there is a strong need for cellulose- based textiles, preferably cotton-based textiles, dyed in black, in blue, in brown, in green, in a permanent manner, so as to enable the production of items of clothing (such as trousers, shirts, jackets, coats, overcoats) that can resist a large number of domestic washing operations in a washing machine, keeping their original color both from a qualitative and from a quantitative point of view.

No method for manufacturing permanently dyed textiles, i.e. meeting the urgent need for dyed textiles resist- ing repeated washing operations over time, is known to- day.

In particular, no method for manufacturing cotton-based textiles dyed permanently in dark colors is known. Among dyeing techniques most frequently used in indus- trial dyeing the following can be mentioned by way of example:

- pad batch dyeing: the fabric, after getting through a tub containing the dyeing mixture, is rolled up on itself and kept moving (practically it turns on itself) for the time necessary so that it reacts with the dye itself. The fabric is then washed and dried;

- pad steam dyeing: the fabric, after getting through a tub containing the dyeing mixture, gets into a steam chamber in which it remains for the time necessary so that it reacts with the dye; the fabric is then washed continuously (practically by means of a series of washing tubs arranged one after the other) ;

- jigger dyeing: the fabric is rolled up alternatively on two parallel cylinders, getting through the dyeing bath;

- flow dyeing: the fabric is sewn together on its head and tail and it turns inside the dyeing bath by means of a series of cylinders, being free to roll up on itself. Cotton textile dyeing (cotton and/or cotton mixture) with reactive dyes is generally undertaken in "open width" mode (meaning that the textile is dyed keeping it spread in all its width) , preferably with pad batch and pad steam techniques. A disadvantage of the two techniques referred to above consists in that none of said two methods can ensure a high dye penetration into textile fibers, even though process operating parameters are changed. As a consequence, the number of chemical bonds forming between dye and fiber cannot be large and, therefore, a long-term color resistance to repeated domestic washing operations in a washing machine cannot be achieved. Flow dyeing enables a high dye penetration into the fibers, since said method keeps the continuously moving fabric in contact with the dyeing bath and therefore exalts the dynamic component of the dyeing process (which component is almost unused in the methods described above) . On the other hand, this method is however characterized by huge problems concerning textile appearance after dyeing (for instance abrasions and possibly an imperfect homogeneity in color distribution) .

Moreover, the productive performance of flow dyeing machines is very low. Known techniques cannot ensure a deep and homogeneous penetration of reactive dyes into the fibers of cotton- based fabrics. As a consequence, they do not enable the formation of a large number of covalent dye-fiber bonds and do not therefore allow to dye textiles permanently, preferably with dark colors.

There is therefore a strong need for a cellulose-based textile, preferably a cotton-based textile, with a higher color solidity than known dyed textiles. In particular, color degradation to washing should be lower than known dyed textiles.

Thus, there is also a strong need for a suitable dyeing method enabling to manufacture textiles (and therefore items of clothing) with properties of color solidity and non-degradability as referred to above. In particular, there is a strong need for a dyeing process for manufacturing textiles (and therefore items of clothing)', in particular cotton-based textiles, permanently dyed in dark colors. To the purposes of the present invention, "permanently dyed" refers to textiles or items of clothing and/or fabrics with properties of color solidity and non- degradability as referred to above, in particular textiles resisting to a large number of domestic washing operations keeping their original color. The same meaning should be given to "dye or color in a permanent manner".

In particular, to the purposes of the present invention, a permanently dyed textile refers to a cellulose- based textile having a color degradation after repeated washing operations not below degree 3 of the gray scale for color variation, according to international norm ISO 105 A02, or to the corresponding Italian norm UNI EN 20105 A02/' 96. The number of said repeated washing operations is not below 5.

An aim of the present invention is to provide a cellulose-based textile with properties of color solidity and non-degradability as referred to above. Another aim of the present invention is to provide an industrial method for permanently dyeing cellulose- based textiles, thus enabling to manufacture dyed items of clothing and/or fabrics with properties of color solidity and non-degradability as referred to above. This and other aims, as will be evident from the fol- lowing detailed description, have been achieved by the Applicant, who has manufactured a cellulose-based textile with improved properties of color solidity and non-degradability with respect to known technique. An object of the present invention is a textile com- prising cellulose fibers in which said fibers are chemically modified so as to give said textile a permanent color as disclosed in the appended independent claim. Another object of the present invention is a method for permanently dyeing cellulose-based textiles, as dis- closed in the appended independent claim. A further object of the present invention is the use of said textile for manufacturing an item of clothing and/or a fabric dyed in a permanent manner, as dis- closed in the appended independent claim.

A still further object of the present invention is said item of clothing and/or fabric dyed in a permanent manner, whose characteristics are disclosed in the appended independent claim. Preferred embodiments of the present invention are disclosed in the appended dependent claims.

The dyeing method according to the present invention modifies the original textile in a stable manner and gives it a structural variation so as to alter its chemical and physical properties.

In practice, before the dyeing process, the cellulose- based textile comprises fibers characterized by free hydroxyl functions giving said textile certain properties . With the dyeing method according to the present invention, said fibers are modified in a stable manner by means of a chemical reaction between the free hydroxyl functions of said fibers and the reactive groups of the dye/s used, thus forming covalent ether-type bonds. Chemical modification is obtained after a "substitution" of hydrogen atoms of hydroxyl functions on the fibers .

Thus, said fibers are almost completely covered with the molecules of the dye/s. As a consequence, at the end of the process, the fibers that were originally present in the textile will have an outer surface containing a large number of chromo- phore groups bonded in a stable manner to said fibers. Said "exhaustive" cover of cellulose fibers is surpris- ingly obtained thanks to a new use of known reactive dyes in the dyeing method according to the present invention.

Said reactive dyes are used not as such, but in a first stage of the dyeing step they are used as direct dyes, thus enabling them to penetrate deeply and completely into the textile.

Only afterwards, in a second stage of the dyeing step, said dyes are used as reactive dyes, thus enabling them to react with the fiber. In practice, advantageously, the first stage of the dyeing process is carried out at the same temperature as or preferably at a higher temperature than the one used in the following second stage of said process, and bath pH is characterized by approximately neutral val- ues.

At the end of said first stage of the dyeing process, bath pH is brought to basic values higher than those of the first stage, thus allowing textile fibers to react with the dye absorbed by said textile. In a preferred embodiment, the dyeing method according to the present invention includes at least one dyeing step carried out in a dyeing bath comprising at least one reactive dye. Said reactive dye is a medium or high temperature dye; preferably a medium temperature dye. Preferably, said dyeing step is carried out with a bath ratio, expressed as kilos of textile per liters of bath water, of 1:2 to 1:5, preferably of 1:2 to 1:3. Preferably, said at least one reactive dye is present in an amount of 5 to 20% by weight of dye per liter of bath, referring to the dye in powder form; preferably of 5 to 15%.

In a preferred embodiment, said dyeing method includes the following stages: a) impregnating said textile in said dyeing bath at a bath temperature of about 40 to 110⁰C and about a neu- tral pH; b) chemically reacting OH groups, which are present on the fibers of the impregnated textile, with said at least one reactive dye at the same temperature as or at 5 a lower temperature than stage a) , after bringing bath pH to higher values than in stage a) .

Preferably, stage a) is carried out at a bath temperature of 70 to 110⁰C; preferably of 85 to 105⁰C. Preferably, stage a) is carried out at a bath pH of 6 io to 8.

Preferably, stage b) is carried out at a bath temperature of 80 to 110⁰C; preferably of 90 to 95°C. In a particularly preferred embodiment, stage b) is carried out at a bath temperature of 50 to 75°C; pref-

I₅ erably of 60 to 7O⁰C.

Preferably, stage b) is carried out at a bath pH of 10 to 12; preferably of 10.5 to 11.

In a preferred embodiment, said pH value is reached by adding anhydrous sodium carbonate in an amount of 5 g/1

20 of bath, and the necessary amount of NaOH at 30% by weight .

The chemical reaction of stage b) lasts at least 60 min; preferably more than 60 min. In a preferred embodiment of the invention, each of the

2S stages a) and b) is carried out by keeping the textile in movement in the dyeing bath, so as to create a deep contact between the fibers of said textile and said at least one reactive dye of the bath, thus enabling on one hand maximum dye penetration into the cellulose fi-

30 bers of the textile, and on the other hand allowing the dye to chemically react to an exhaustive extent with all free OH groups that are present on said fibers. Preferably, said at least one reactive dye is a medium or high temperature dye; more preferably a medium tem-

3S perature dye. In a particularly preferred embodiment, the permanent dyeing method according to the present invention includes the following steps:

- impregnating the textile in a dyeing bath comprising at least one medium temperature reactive dye, at a bath temperature of 70 to 110⁰C; preferably of 85 to 105⁰C; and about a neutral pH;

- letting the bath cool at a temperature of 50 to 75°C; preferably of 60 to 70°C; - alkalinizing the bath at a pH value of 10 to 12, preferably of 10.5 to 11;

- keeping the textile in movement inside the bath for at least 60 min.

Preferably, the method according to the present inven- tion further includes the following stage: a' ) adding at the end of stage a) at least one inorganic salt, such as anhydrous sodium sulfate, in an amount of 50 to 80 g/1 of bath; preferably of 40 to 70 g/1. Preferably, the method according to the present invention further comprises the following operations: before the dyeing step: pre-treating the textile with an imbibing and impregnating aqueous solution; after the dyeing step: rinsing the textile until excess dye is removed, then washing said textile with soap until every residual substance originating from previous treatments is completely removed.

The method according to the present invention is preferably implemented by using a jigger dyeing machine. In this case said dyeing machine is operated in typical flow dyeing conditions, thus privileging the dynamic component of the dyeing process. Thus, dye penetration into the textile and the contact of said dye with cellulose fibers are favored. In a particularly preferred embodiment, dyes that are used are those to be applied at medium temperature, belonging to the class of bifunctional dyes, i.e. with two reactive leaving groups for each molecule of dye (such as, only by way of example, Levafix dyes). To the purposes of the present invention, particularly preferred have proved those dyes that, individually or in a suitable mixture, give the textile a dark color. In a preferred embodiment, said dyes and/or mixtures thereof are chosen among those giving the textile a dark color such as for instance: black, blue, brown, green, red. Preferably black, blue, brown; more preferably black.

The type and amount of the single dye or dyes is suitably identified and chosen by the dyer depending on the textile to be dyed.

To such purpose, the dyer will consider on the basis of his professional knowledge: the type of color and tone to be obtained; textile weave (i.e. of the way in which weft yarns weave warp yarns); its surface mass (i.e. the weight of a square meter of textile) ; its dye absorption capacity.

By way of example, in a preferred embodiment, the dyeing method according to the present invention is implemented as follows, including the following steps: A) a pre-impregnating step, in which the textile is contacted with a suitable impregnating aqueous solution, until it is homogeneously impregnated;

B) a dyeing step, as previously described;

C) a rinsing step, in which the excess of un-reacted dye is removed from the dyed textile;

D) a soaping step, in which said dyed textile is washed until every residual substance originating from previous treatments is completely removed.

The jigger dyeing machine, preferably used for imple- menting the process according to the present invention, basically comprises two parallel rotary cylinders placed over a tub designed to contain the various baths to be used during the dyeing process.

Preferably the textile, after being rolled up on a cyl- inder (machine loading) , is shifted several times in different manners from one cylinder to the other getting through the dyeing bath, thus getting deeply impregnated and reacting with the dye. The operating modes of the machine can vary, also to a considerable extent, for each working cycle and are decided by the dyer depending above all on machine load (i.e. on the amount of textile, preferably measured in meters and/or kilos, to be loaded onto the cylinder for every working cycle) ; said load is directly related to the type of textile used, in particular to its surface mass, i.e. to the weight of a square meter of textile. Depending on said parameter the following further operating parameters are defined:

- bath ratio, corresponding to the number of liters of water used per kilo of textile to be dyed;

- number of runs, or number or rolling-up cycles between one cylinder and the other, to be carried out in the various process steps; said number depends on the type of textile to be dyed, in particular on its sur- face mass, on its hydrophilic properties, on its capacity of absorbing chemical products and dyes;

- textile rolling-up speed between the two cylinders of the machine.

At every working cycle the machine, if working at full load, is loaded with 500 to 1,600 m of textile, preferably with 800 to 1,200 m, depending on the type of textile to be treated.

Said textile has a surface mass of 180 to 600 g/m²; preferably of 200 to 500 g/m²; more preferably of 230 to 400 g/m². In the pre-impregnating step A) the textile is preferably contacted with an impregnating aqueous solution comprising;

- at least one imbiber; - at least one dispersing agent;

- at least one sequestrant.

Water in said impregnating aqueous solution is in such an amount that bath ratio (kilos of textile/liters of water) varies from 1:2 to 1:5, preferably from 1:2 to 1:3.

Preferably, water hardness varies from 0 to 3°F, corresponding to an amount of CaCC>₃ of 0 to 3 ppm. Moreover, in said aqueous solution:

- the imbiber is present in an amount of 2 to 6 g/1, preferably of 4 g/1;

- the disperser is present in an amount of 0.5 to 4 g/1, preferably of 2 g/1;

- the sequestrant is present in an amount of 0.5 to 3 g/1, preferably of 1.3 g/1. Said imbibing, dispersing and sequestering agents are suitably chosen among those that are known and can commonly be found on the market to the described purpose. Preferably, agents with a higher purity degree are preferred (by mere way of non-limiting example, in a pre- ferred embodiment the following compounds were used: as imbiber the product known as Erkantol^®; as disperser the product known as Levegal ; as sequestrant the product known as Plexene ) .

The impregnating step is preferably carried out in hot conditions, at a temperature of 35 to 65⁰C, preferably of 45 to 60⁰C; more preferably of about 50⁰C. The number of runs performed during said step is of 1 to 6; preferably of 1 to 4; more preferably of 1 to 3. The speed at which the textile is rolled up between the two cylinders of the jigger machine is of 70 to 200 m/min; preferably of 90 to 160 m/min; more preferably of 110 to 140 m/min.

During the dyeing step B) , a series of sequential stages is preferably carried out, comprising: 5 -a) adding the reactive dye or dyes to the solution as in step A) so as to obtain a dyeing bath; -b) turning the impregnated textile in said dyeing bath so as to obtain a homogenous dye distribution in the textile; o -c) heating the dyeing bath and turning the textile in it;

-d) adding to the bath an effective amount of at least one inorganic salt and turning the textile in it; -e) letting the bath cool and turning the textile in s it;

-f) alkalinizing the bath and turning the textile in it until the dye has reacted completely with textile fibers .

Stages a) to f) can be performed as a continuous se- 0 quence with the textile always moving, or preferably separately one from the other, so as to prevent as much as possible problems related to selvedge center (i.e. problems of non-uniformity of dye on the whole textile width) and to head-tail (i.e. problems of non- 5 uniformity of dye on the whole textile length) , the .textile being still and completely rolled up on one of the two cylinders or moving depending on the working step.

In a particularly preferred embodiment, between an op- 0 erating stage and the other one the textile is rolled up on one of the two cylinders of the machine, and reagent addition as well as bath temperature regulation take place with still textile (preferably, the textile oscillating on itself at low speed) . S Preferably, in the various stages the textile is turned in the bath at least until its temperature is balanced with the temperature of said bath.

In stage f) the textile is turned in said basic bath for at least 60 min, preferably even longer, so as to ensure that the dye has completely reacted with the cellulose fibers of the textile.

The number of runs for every single stage b) to f) varies much, independently for every stage, depending on the dye and on the amount and type of textile undergo- ing dyeing. Said number is basically decided by the skilled technician for every specific case, taking into account the operating parameters mentioned above. By way of example, for every single stage said number can vary from 1 to 10. It preferably varies from 1 to 8; still more preferably from 2 to 6; from 2 to 5; from 3 to 4.

The speed at which the textile is rolled up between the two cylinders of the machine is the same as was described for previous operations. During the rinsing step C) , after the dyeing bath has been loaded from the machine tub, the dyed textile is washed with cold water several times.

A rinsing cycle with water is preferably alternated to a rinsing cycle with acidulous water so as to neutral- ize the textile.

Preferably, said rinsing step includes the following stages :

-g) filling up the machine tub with cold water, turning the dyed textile in it and unloading dirty water; -h) filling up the tub with cold water, adding acetic acid 80% by weight in such an amount that the pH of the solution is of 5.5 to 6.0, and turning the textile in it until it reaches bath pH, then unloading the aqueous solution; -i) filling up the tub with cold water, turning the dyed textile in it and unloading water.

If necessary, said series of stages g) to i) can be repeated more than once depending on dye persistency in the rinsing bath. The number of runs per single rinse is of 2 to 5, preferably of 2 to 4.

The speed at which the textile is rolled up between the two cylinders of the machine is the same as was described for previous operations. During the soaping step D) , the textile undergoes a given number of treatments with soaped water, which number varies depending on the textile and dye, until soaping water is almost colorless. Every type of soap known in the field and present on the market to this purpose can be used (by mere way of example, in a preferred embodiment of the invention the soap known on the market as Levapon TGH is used) . Preferably, soap is added to washing water in an amount of 0.5 to 4 g/1; preferably of 1.5 to 3 g/1; more pref- erably of 2 g/1.

Washing is preferably carried out at a bath temperature of 85 to 100⁰C; preferably of 90 to 100⁰C; more preferably of 95⁰C. The number of runs for every single washing and rinsing operation is of 1 to 3, preferably of 1 to 2.

The speed at which the textile is rolled up between the two cylinders of the machine is the same as was described for previous operations. At the end of said soaping step, the textile is rinsed with cold water and sent to following operations.

Indeed, the textile is unloaded, dried and sent to current steps involving control and physical treatment for giving it the desired dimensional stability to washing. Said steps generally vary depending on the textile and comprise for instance: - controls with a mirror on the uniformity of final appearance;

- thermofixation in a chamber at high temperature (160- 180⁰C) ; - pre-shrinkage in a steam chamber, so that the textile shrinks and therefore gets stable.

The method according to the present invention is preferably used for dyeing cotton-based textile (meaning by "cotton-based textiles": 100% cotton, cotton mixture textile with natural and/or artificial cellulose fibers and/or other artificial fibers commonly used in the tailoring field) . Said textiles can also be elasticized by adding a suitable amount of elastic fiber. In a particularly preferred embodiment, said textile is an orthogonal textile (i.e. with weft and warp).

The textile according to the present invention is a permanently dyed textile, having a chemically modified cellulose base as previously described, with a color degradation after repeated washing operations not below degree 3 of the gray scale for color variation. Preferably, said color degradation is between degree 4 to the maximum value, i.e. degree 5, of said gray scale. In a particularly preferred embodiment, said color degradation corresponds to degree 4/5 of said gray scale. The number of repeated washing operations undergone by the textile according to the present invention is not below 5. Preferably, it is of 10 to 50; more preferably of 15 to 25. The textile according to the present invention is pref- erably dyed in a permanent manner with a dark color; said color is preferably black, blue, brown, green; more preferably black.

In a particularly preferred embodiment, said textile is made up of 98% cotton and of 2% elastam. For instance, elasticized cotton textiles in black, blue, brown and green color that do not fade after repeated domestic --washing operations in a washing machine have been obtained; moreover, color tones have proved particularly deep and dark. As a consequence, consumers have the impression that the item of clothing (shirt or trousers) does not get old because of the wear and tear due to washing operations and therefore said item seems to be always new. The Applicant has carried out a series of comparison tests between black trousers manufactured with a textile dyed with the method according to the present invention and between similar black trousers manufactured with the same textile dyed with the following dyeing techniques as are known in the field. The following tests using reactive, medium temperature dyes have been carried out: i) pad batch dyeing trying to modify in various way manufacturing parameters; ii) jigger dyeing according to traditional methods; iii) flow dyeing; iv) jigger dyeing modified with the method according to the present invention.

The obtained results, described below, have confirmed that: - pad batch [i] and traditional jigger [ii] dyeing does not enable to achieve the aim of color permanence, neither using reactive dyes;

- flow dyeing [iii] , though a dynamic process, has allowed to obtain a non-uniformly dyed textile. Moreover, even if results had been better, there would still be the problem of too low productivity, which on average does not go beyond about 500 m per bath working at full load;

- with jigger dyeing modified according to the present invention [iv] the desired aim (color permanence, pro- ductivity and acceptable costs) has been achieved. Moreover, particularly dark and deep color tones have also been advantageously obtained (in particular in black) . Comparative tests have all been carried out on the same textile: elasticized cotton made up of 98% cotton, 2% elastam; surface mass 240 g/m² (Nicla) , dyed in black. The textile has been dyed using a black dye known as Carbone Remazol RGB. Evaluations tests have been carried out by washing repeatedly, 15 times in a washing machine, the trousers turned inside out according to norm ISO 6330/00, cycle 8A, at 3O⁰C, dried by hanging; said washing tests have been performed according to the label containing care instructions.

The comparative examination of the differences between the new (unwashed) item and the item that has been washed 15 times, in traditional pad batch dyeing [i] and jigger dyeing modified according to the present in- vention [iv] , show that:

- the trousers dyed with modified jigger technique [iv] look basically unchanged after 15 repeated washing operations; only some slight abrasions on pockets and seams are present, these being the areas of highest friction between the trousers and the drum of the washing machine. The corresponding color degradation is therefore between degree 4/5 and degree 5, referring to the gray scale for color variation according to norm ISO 105 A02; - conversely, the trousers dyed with traditional pad batch technique [i] look after the washing operations extremely older since in the central areas color has become gray with a color degradation corresponding to degree 2 or even less than 2, referring to the gray scale for color variation according to norm ISO 105 A02. Pockets and seams look basically white. The number of repeated washing operations performed on trousers dyed according to the present invention has been increased up to 50 washing operations. Tests have been carried out after 25 and after 50 washing operations .

Test results have confirmed that color degradation is not below degree 3 of the gray scale as referred to above . Beyond what has been said before about color permanence, the black color obtained with the jigger method [iv] modified according to the present invention has proved far deeper and more intense. Also the trousers manufactured with textiles dyed with techniques [ii] and [iii] have shown the same reaction to washing - if not worse - as the trousers manufactured with a textile dyed with technique [i] . The above remarks thus confirm that:

- the textile dyed with the method according to the present invention is characterized by a basically deeper color rich in reflections with respect to the one obtained with known dyeing techniques; said characteristic is particularly important as far as the outer appearance (look) of the item is concerned; - with the method according to the present invention, dyeing carried out in dynamic conditions results in a better penetration of the reactive dye into the textile (and therefore into the fibers); this involves a larger number of dye molecules bonded to the textile with a covalent bond and therefore a higher resistance of color to washing operations;

- the dyeing method according to the present invention ensures the advantages of open width dyeing (uniform textile appearance) combined with a strong color pene- tration into the textile (typical of flow dyeing) . The method according to the present invention enables to manufacture cellulose-based textiles, preferably cotton-based textiles, dyed in a permanent manner and provided with a higher richness and depth of reflec- tions, especially as far as dark colors are concerned. The present invention therefore relates to said dyeing method and to permanently dyed textiles obtained with said method, and to the use of said textiles for manufacturing permanently dyed items of clothing and/or fabrics.

Moreover, the present invention also relates to items of clothing and to fabrics manufactured with said textiles . In a particularly preferred embodiment, the present in- vention relates to shirts made of cotton or cotton mixture, permanently dyed in black, blue, brown or green. In another particularly preferred embodiment, the present invention relates to trousers made of cotton or cotton mixture, elasticized if necessary, permanently dyed in black, blue, brown or green.

In another particularly preferred embodiment, the present invention relates to jackets, coats, overcoats made of cotton or cotton mixture, permanently dyed in black, blue, brown or green. In another particularly preferred embodiment, the present invention relates to skirts made of cotton or cotton mixture, permanently dyed in black, blue, brown or green.

Claims

1. A textile comprising cellulose fibers, in which said fibers are chemically modified by means of a chemical reaction between OH groups of said fibers and at least one reactive dye, so as to give said textile a permanent color with a color degradation after repeated washing operations not below degree 3 of the gray scale for color variation.

2. The textile according to claim 1, in which said color degradation is between degree 4 to the maximum value, degree 5, of said gray scale.

3. The textile according to claim 1, in which said color degradation corresponds to degree 4/5 of said gray scale.

4. The textile according to one or more of the preceding claims, in which the number of said washing operations is not below 5; preferably, it is of 10 to 50; more preferably of 15 to 25.

5. The textile according to one or more of the preceding claims, in which said textile is dyed in a dark color; preferably said color is black, blue, brown, green; more preferably black.

6. A method for manufacturing the textile according to one or more of the preceding claims, in which said method comprises at least one dyeing step performed in a dyeing bath comprising at least one reactive dye.

7. The method according to claim 6, in which bath ratio, expressed as kilos of textile/liters of bath wa- ter, is of 1:2 to 1:5; preferably of 1:2 to 1:3.

8. The method according to claim 6, in which said at least one reactive dye is present in an amount of 5 to 20% by weight of dye per liter of bath, referring to the dye in powder form, preferably of 10 to 15%.

9. The method according to one or more claims 6 to 8, characterized in that said dyeing step comprises the following stages: a) impregnating said textile in said dyeing bath at a bath temperature of about 40 to HO⁰C and about a neu-

5 tral pH; b) reacting chemically OH groups, which are present on the fibers of the impregnated textile, with said at least one reactive dye at the same temperature as or at a lower temperature than stage a) , after bringing bath

I₀ pH to higher values than in stage a) .

10. The method according to claim 9, in which stage a) is performed at a bath temperature of 70 to HO⁰C; preferably of 85 to 105°C.

11. The method according to claim 9, in which stage a) is is performed at a bath pH of about 6 to 8.

12. The method according to claim 9, in which stage b) is performed at a bath temperature of 80 to 110⁰C; preferably of 90 to 95°C.

13. The method according to claim 9, in which stage b) 20 is performed at a bath temperature of 50 to 75°C; preferably of 60 to 7O⁰C.

14. The method according to claim 9, in which stage b) is performed at a bath pH of 10 to 12; preferably of 10.5 to 11.

2₅ 15. The method according to claim 14, in which said pH value is reached by adding anhydrous calcium carbonate in an amount of 5 g/1 of bath, and of the necessary amount of NaOH at 30% by weight.

16. The method according to one or more claims 9 to 30 15, in which the chemical reaction as in step b) lasts at least 60 min.

17. The method according to claim 9, in which each of the stages a) and b) is performed by keeping the textile in movement inside the dyeing bath, so as to cres ate a deep contact between the fibers of said textile and said at least one reactive dye of the bath.

18, The method according to claim 9, in which said at least one reactive dye is a medium or high temperature dye; preferably a medium temperature dye.

19. The method according to claim 18, comprising the following steps:

- impregnating the textile in a dyeing bath comprising at least one medium temperature reactive dye, at a bath temperature of 70 to 110⁰C; preferably of 85 to 105⁰C, and about a neutral pH;

- letting the bath cool at a temperature of 50 to 75⁰C; preferably of 60 to 70⁰C;

- alkalinizing the bath at a pH value of 10 to 12, preferably of 10.5 to 11; - keeping the textile in movement inside the bath for at least 60 min.

20. The method according to one or more claims 9 to

19, further comprising the following stage: a' ) adding at the end of stage a) at least one inor- ganic salt, such as anhydrous sodium sulfate, in an amount of 50 to 80 g/1 of bath; preferably of 40 to 70 g/1.

21. The method according to one or more claims 6 to

20, further comprising the following steps: before the dyeing step: pre-treating the textile with an imbibing and impregnating aqueous solution; after the dyeing step: rinsing the textile until excess dye is removed, then washing said textile with soap until every residual substance originating from previous treatments is completely removed.

22. The method according to one or more claims 6 to

21, in which said method is implemented by using a jigger dyeing machine.

23. Use of a textile according to one or more claims 1 to 5, for manufacturing items of clothing and/or fab- ric, dyed in a permanent manner, with a color degradation after repeated washing operations not below degree 3 of the gray scale for color variation.

24. The use according to claim 23, in which said color degradation is of degree 4 to degree 5 of said gray^¬ scale; preferably it corresponds to degree 4/5.

25. The use according to one or more claims 23 to 24, in which the number of said washing operations is not below 5; preferably it is of 15 to 50; more preferably of 15 to 25.

26. The use according to one or more claims 23 to 25, in which said items of clothing and/or fabrics are dyed in black, blue, brown, green, preferably in black.

27. A permanently dyed item of clothing, which can be obtained with a textile according to any of the claims

1 to 5.

28. The item of clothing according to claim 27, said item being a pair of trousers, a skirt, a shirt, a jacket, a coat, an overcoat.

29. The pair of trousers according to claim 28, dyed in black.

30. The pair of trousers according to claim 29, made of elasticized cotton.