One-step dyeing process for polyester / natural fiber blend fabrics

Abstract

The present invention provides a method and a novel process for dyeing polyester / natural fiber blends in an all-in-one step dyeing process, which is enabled by pre-treatment of the fabric with one or more synthetic cationic agents. The all-in-one dyeing can then be carried out at lower temperatures and neutral pH using a combination of disperse and reactive dyes.

Description

[Technical field]

[0001] The present disclosure relates to an improved process for dyeing fabrics containing polyester fibers and natural fibers (e.g., cotton-based), where dyeing is performed in a single step. [Background technology]

[0002] Textile dyeing is the process of applying pigments or dyes to textile materials such as fabrics, yarns and fibers. Desirably, the dyeing process is efficient and rapid, providing dyed textiles with the desired degree of coloration and resistance to dye fading and color loss (color fastness). Furthermore, the dyeing process and materials used therein preferably do not adversely affect aspects of the textile, such as its flexibility, durability and tactile properties such as softness, smoothness, stiffness. Depending on the material of the textile (e.g., natural, synthetic or mixtures thereof) and the coloration desired, various dye types are used.

[0003] Polyester blends with natural fibers, especially polyester / cotton blends, are important in the textile industry, with polyester / cotton blends accounting for about 60% of the production of all types of blends in the textile industry. Such blends typically require the use of both disperse and reactive dyes due to the nature of the different fibers in the blend.

[0004] Conventional exhaust dyeing processes for blends with disperse / reactive dyes are of two types: 1.) the two-bath process, where the two fibers in the blend are dyed separately with different dyes in two separate dye baths, and 2.) the one-bath, two-step process, where the dyes are mixed in a single bath, but the dyeing process is divided into separate steps for each fiber.

[0005] In the two-bath process, the polyester part is first dyed with disperse dyes in the first bath, and then the bath is drained. The fabric is then subjected to a reduction wash treatment and washed with a reducing agent to remove the unfixed disperse dyes from the fabric surface. Then, in the next bath, the cotton part is dyed with reactive dyes together with salt and soda. The second bath is then drained, and then the hydrolyzed reactive dyes are removed by washing and soaping. These two baths are therefore independent of each other. The two-bath process is similar to that of pure polyester and pure cotton dyeing.

[0006] In the one-bath, two-step process, the disperse and reactive dyes are added together to the dye bath first. This process uses a single bath to dye both the polyester and cotton portions of the blended fabric, but in two separate steps. In the first step, the polyester fibers are dyed using a relatively high temperature and low pH. In the second step, the reactive dyes are fixed to the natural fibers using a relatively low temperature and high pH. Thus, there is a shift from the high temperature and low pH from step one to the low temperature and high pH required in the second step. This change is necessary to facilitate proper disperse dyeing on the polyester at high temperature but lower pH, followed by a reduction in temperature for the second step. Typically, an alkali is added to facilitate fixation of the reactive dyes on the cotton portion.

[0007] Traditional two-bath dyeing processes require long dyeing times that can be up to 9-10 hours, of which about 2 hours are spent on washing and soaping. The longer dyeing cycles also increase production costs. Also, the chemicals used in the reduction washing process that follows the polyester dyeing step have a negative impact on the environment.

[0008] The one-bath, two-step dyeing process can be completed in less time, but it has other challenges. Because both reactive and disperse dyes are present in one bath at the same time, each dye must be able to withstand the different dyeing conditions of the other. Reactive dyes must withstand higher temperatures of acidic baths, and disperse dyes must be stable to alkaline and high electrolyte conditions. In addition, it is essential to select disperse and reactive dyes that do not react with each other or cross-dye.

[0009] Therefore, improved methods for dyeing fabrics or textiles containing polyester / natural fiber blends are desirable. Summary of the Invention

[0010] The present invention provides a method and a novel process for dyeing polyester / natural fiber blends in an all-in-one step dyeing process. This all-in-one step dyeing process is made possible by pre-treatment of the fabric using one or more synthetic cationic agents. The all-in-one dyeing can then be carried out at lower temperatures and neutral pH using a combination of disperse and reactive dyes. The process generally involves first immersing the cationic fabric in a water bath containing reactive and disperse dyes, the water bath having a pH of 6-7, at a temperature ranging from 80-100°C for a period of time ranging from 30 to 60 minutes. The dyed fabric is then washed with water at a temperature ranging from 30-40°C for at least 20 minutes, and then further washed with water at a temperature ranging from 50-70°C for at least 10 minutes. After this step, the fabric is washed with an aqueous solution containing 0.5-2 grams of soap per liter, 1-3 grams of 50% hydrogen peroxide per liter, and 1-3 grams of sodium hydroxide per liter at a temperature ranging from 70-90°C for at least 10 minutes. The fabric is then washed in water at a temperature in the range of 50-70°C for at least 10 minutes and then finally washed in an acidic aqueous solution at a temperature in the range of 30-40°C for at least 10 minutes. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The embodiments of the present invention described below are not intended to be exhaustive or to limit the present invention to the precise forms disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art can appreciate and understand the principles and practices of the present invention.

[0012] All publications and patents mentioned herein are incorporated herein by reference to the full extent permitted under the relevant laws. Publications and patents disclosed herein are provided solely for their disclosure. Nothing herein should be construed as an admission that the inventors are not entitled to antedate any publications and / or patents, including any publications and / or patents cited herein.

[0013] The term "about" used preceding any numerical value in this disclosure or the appended claims allows for some slight imprecision in the numerical value stated, which may be understood in the art or may result from the measurement method (e.g., chemical or physical measurements, etc.) used to obtain such numerical value, and any numerical value in this disclosure or the appended claims not preceded by the term "about" may be similarly understood.

[0014] Methods and compositions of the present disclosure described as "comprising" or "including" may include the recited steps and compounds, respectively, and may optionally include other steps and components. When a method or composition of the present disclosure is described as "consisting of", the method or composition has the recited steps or compounds, but does not include steps or compounds that are not recited. The term "consisting essentially of" generally refers to a composition that includes the recited compounds, and may include other unrecited compounds, but in insubstantial amounts. For example, such a composition may include one or more other unrecited components, but not in amounts greater than about 1% (by weight), greater than about 0.5% (by weight), or greater than about 0.1% (by weight) of the total composition. In a composition "consisting of" recited components, there are no measurable amounts of other components other than the recited components, or a method "consisting of" a particular step does not include steps other than those recited.

[0015] For purposes of the present invention, "textile" should be understood to include yarn, fabric, and articles made from the fabric or yarn, such as garments or linens.

[0016] This disclosure describes a new method for dyeing fabrics containing polyester and natural fibers, and especially cotton fibers. The method is suitable for use with fabrics that have first been subjected to a cationization treatment generally known in the art. A preferred method of such treatment was recently disclosed in patent applications WO 2021 / 158538 and WO 2021 / 158540. These cationization processes can be carried out in a relatively short period of time, and the process produces low levels of waste and uses minimal energy. The methods and systems taught in these references treat the textile in an aqueous solution (which may also be referred to as a "padding" solution) that contains an alkali metal hydroxide and a cationizing agent (e.g., a mono- or di-quaternized nitrogen compound capable of generating one or two epoxide groups, respectively, in the presence of an alkali metal hydroxide, or a halogenated compound capable of generating two epoxide groups in the presence of an alkali metal hydroxide). Preferred cationizing agents include aqueous solutions of quaternary ammonium, such as those commercially available under the trade name ECOFAST™ from Dow.

[0017] In some embodiments, the padding process can be performed quickly, for example, in a time period of 1 minute or less, and at a temperature such as ambient temperature, which does not require heating of the aqueous solution. In some embodiments, after padding, excess solution is removed from the textile, and then the textile is introduced into a heating device to cause the reaction of the cationizing agent with the textile. The heat treatment is also performed somewhat quickly and at a defined temperature range. In particular, the textile is heated at a temperature of less than 90°C to 110°C for a period of time ranging from 1 minute to 10 minutes. In some embodiments, more specific temperature and time ranges may be used.

[0018] Advantageously, good cationization is achieved without the need for long padding and reaction times (such as periods of time) characteristic of cold batch padding processes. Instead, the treatment temperatures and times of the present disclosure have been found to provide good cationization of textiles while minimizing loss of reagents due to hydrolysis.

[0019] Cationization renders the textile in an excellent state for association with the dye, and the dyeing process can thus provide good coloration of the textile.

[0020] The steps of the methods of the present invention can be carried out using continuous processes, semi-continuous processes, batch processes, or combinations thereof, as would be generally understood by one of ordinary skill in the art.

[0021] One option for processing textiles is to use a continuous process. A continuous process is a flow product method used to manufacture, process or produce an article without stopping the process flow. In a continuous process, the article being processed or manufactured is moving. In continuous processing of textiles, the textile is often in the form of a sheet that is moved through two or more processing areas (e.g., "processing zones"), and the sheet is subjected to different chemical, mechanical and / or physical processes in each processing area while being moved. The movement of the textile in a continuous process can be facilitated by system devices such as a textile conveyor having rollers that contact and facilitate the movement of the textile in the continuous process. A continuous process can be implemented in the system of the present disclosure described herein.

[0022] In an embodiment, two or more steps of the method of the present disclosure may be described as a continuous process. For example, in the steps of padding a textile in a solution of a base and a cationizing agent, mechanically removing a portion of the solution from the padded textile, and then heat treating the textile, the textile may be moved continuously through a treatment zone, which provides a predetermined treatment of the textile during the movement. Other steps in the process of dyeing (e.g., washing, neutralizing, and / or optional dyeing) may also be described as continuous, or optionally discontinuous.

[0023] A semi-continuous process may include one in which a flow product operation (continuous) is stopped and then restarted after a period of time. In some embodiments, two or more steps of the method of the present disclosure may be described as a semi-continuous process. For example, depending on the desired processing conditions, the movement of the textile may be stopped in the processing zone for a period of time and then resumed to move the textile from the processing zone. The method of the present disclosure may use a semi-continuous process, where the movement of the textile is stopped in the heat treatment device for a period of time and at a temperature as described herein suitable for reaction of the cationizing agent with the textile, and then the movement of the textile is resumed after that period to move the textile from the heat treatment device. The semi-continuous process may be performed in the system of the present disclosure described herein.

[0024] Optionally, in an embodiment, one or more steps in the method of the present disclosure may be performed in a batch process. For example, before the processing steps of the present disclosure or after the processing steps of the present disclosure, the textile may be modified to be configured for use in a batch process rather than a continuous process. The modification may be performed by cutting the textile and then providing the textile portion to be used in one or more batch processing steps. In a batch process, the system may include equipment configured such that the textile is not automatically transferred from one device to another that is otherwise associated with the continuous process equipment. For example, in a system that includes equipment for batch processing steps, a system feature such as a conveyor device that would otherwise transfer the textile from one device to another in a continuous process may not be present in at least some of the equipment of the system used for batch processing.

[0025] In an embodiment of the present disclosure, a cationized textile is provided and then processed according to the steps described herein. The term "textile" refers to a flexible material that includes a network of fibers and is intended to encompass all forms of textile-based articles, including woven textiles, knitted textiles, and nonwoven textiles. The textile can be in the form of a sheet (fabric) or fine strands (yarn). The textile can be formed by techniques known in the art, including one or more processes of weaving, knitting, crocheting, felting, or braiding strands of fiber-containing material together. An exemplary textile substrate can be provided in the form of a textile roll, which provides a continuous sheet of textile that can have a width of more than 1 meter and a length of up to 100 meters or more.

[0026] The textiles to be cationized for use in the present invention include natural fibers or derivatives thereof. The natural fibers of the textiles can be obtained from plants such as cotton, hemp, ramie, flax, jute, kapok, coir, bamboo, etc. Plant raw fibers can be spun to produce long strands, which can be included in the textile by weaving (interweaving threads), knitting (interweaving spun yarns), etc., as is known in the art of weaving. In nonwoven fabrics, the plant-based fibers are not converted into threads or yarns, but rather are directly intermingled with each other or with other fibers to produce the nonwoven fabric.

[0027] The natural fibers in the textile material may include natural polymers such as naturally occurring polysaccharides such as cellulose or cellulosic materials or chitin, or combinations thereof, or derivatives thereof. The cellulose or cellulosic materials, which may include modified cellulose, as well as chitin and their derivatives, have chemicals that allow them to react with cationizing agents. Cellulose consists of repeating glucopyranose subunits that exhibit three hydroxyl groups on each subunit. Chitosan consists of repeating glycosamine subunits that exhibit two hydroxyl groups and one amine group on each subunit. The hydroxyl groups of these polysaccharides are reactive with hydroxide-activated cationizing agents.

[0028] Cellulosic materials also include rayon (viscose) produced from wood pulp, and lyocell, which is a form of rayon (e.g., Tencel™).Textile substrates treated according to the present disclosure may also include cellulose derivatives such as cellulose acetate, or imidazolidinone-modified cellulose.

[0029] Blends of natural fibers are also contemplated for use in the present invention, including blends such as wool / cotton blends, silk / cotton blends, and angora / cotton blends.

[0030] Textiles that may be cationized for use in the present invention may also include polyester fibers.

[0031] Cationic textiles for use in the present invention preferably have at least about 5% (by weight) of natural fibers such as cotton, or derivatives thereof, and more preferably about 25% (by weight) or more, about 35% (by weight) or more, or about 40% (by weight) or more of natural fibers (e.g., cellulose), or derivatives thereof. Exemplary blends include weight ratios of natural fibers (or derivatives thereof, e.g., cellulose) to polyester fibers ranging from about 5:95 to about 95:5, 25:75 to about 25:75, or 40:60 to about 60:40.

[0032] Woven textiles can also be described in terms of textile weight (weight / area), which is often expressed in ounces per square yard or grams per square meter. Textile weight can be influenced by the type(s) of fiber in the textile and their characteristics, the type of weave of the textile, and the finish of the textile. Exemplary textile weights are typically about 50 g / m 2 ~about 450g / m 2 , or about 100 g / m 2 ~about 500g / m 2 , or further 400 g / m 2 The range is.

[0033] In an embodiment, the process of the present disclosure utilizes bleached cationized textiles as generally known in the art. Bleached textiles may have natural colors, odors, and impurities otherwise present when the textile fibers are in their raw (natural) form removed from the textile. Oxidative bleaching is typically performed using oxidative bleaching agents such as hydrogen peroxide, sodium hypochlorite, sodium chlorite, sulfuric acid, or combinations thereof. Sodium hydrosulfite is often used in reductive bleaching of textiles.

[0034] Once the cationic textile is obtained, the dyeing process is as follows: a. Immersing the cationized fabric in a water bath containing a reactive dye and a disperse dye at a temperature in the range of 80°C to 100°C and having a pH of 6 to 7 for 30 to 60 minutes; b. Washing the dyed fabric with water at a temperature of 30°C to 40°C for at least 20 minutes; c. washing the dyed fabric obtained from step b. with water having a temperature ranging from 50 to 70°C for at least 10 minutes; d. washing the dyed fabric obtained from step c. with an aqueous solution containing 0.5-2 grams per liter of soap, 1-3 grams per liter of 50% hydrogen peroxide, and 1-3 grams per liter of sodium hydroxide at a temperature ranging from 70°C to 90°C for at least 10 minutes; e. washing the dyed fabric obtained from step d. with water having a temperature ranging from 50°C to 70°C for at least 10 minutes; and f. washing the dyed fabric obtained from step e. with an acidic aqueous solution (e.g., pH in the range of 4 to 6) at a temperature in the range of 30°C to 40°C for at least 10 minutes.

[0035] In the first step, the cationic fabric is immersed in a water bath containing reactive and disperse dyes, the reactive dyes can be any known in the art or combination of such dyes. The "reactive", or anionic dyes, can contain one or more anionic groups, such as sulfonate or carboxylate groups. For example, the anionic dyes can contain one or more sodium sulfonate (-SO3Na) groups. The one or more anionic groups can be present in the dye molecule, which can absorb light within the visible spectrum and have at least one chromophore / color-carrying group with a conjugated system. Commonly used anionic dyes include those based on azo chemistry, anthraquinone chemistry, and triphenylmethane chemistry. Azo dyes are chemically characterized by the group RN=N-R', where R and R' generally contain aryl groups with various chemical substituents attached to the aryl group. Other anionic dyes include those with nitro chemistry, azine chemistry, and quinoline chemistry. Acid dyes are a type of anionic dye that may contain acid groups such as carboxylic acid, sulfonic acid, or phosphoric acid groups. Anionic dyes that may be used in the methods of the present disclosure are described in various references such as Aspland, JR, (1997) Textile Dyeing and Coloration, American Association of Textile Chemists and Colorists, AATCC, Knutson, L. (1986) Synthetic Dyes for Natural Fiber, Interweave Press; Revised edition. Examples include dyes named "Reactive", "Direct" and "Acid" preceded or followed by the color name and numbers and / or letters, such as "Reactive Blue 19", "Direct Blue 71", "Acid Blue 62", "Reactive Red ME4BL", etc.

[0036] In some embodiments, the concentration of the reactive dye in the dye solution ranges from about 0.001 g / L to about 5.0 g / L, from about 0.01 to about 2 g / L, with more concentrated dye solutions providing a more intense dye color to the textile.

[0037] The disperse dyes used in the first step can also be any known in the art, or mixtures thereof. Disperse dyes are a category of synthetic dyes typically used on polyester and related hydrophobic fibers. Disperse dyes are polar molecules that typically contain anthraquinone or azo groups. Disperse dyes are non-ionic in nature and partially soluble in water. In some embodiments, the concentration of the reactive dye in the dye solution ranges from about 0.001 g / L to about 5.0 g / L, more preferably from about 0.01 to about 2 g / L, with more concentrated dye solutions providing more intense dye color to the textile.

[0038] The water bath containing the reactive and disperse dyes should be kept at a temperature of 70° C. to 100° C., more preferably at least 80° C. or even 90° C. during the dyeing step. It is also preferred that the water bath is kept at a neutral pH, for example in the range of 6 to 8, more preferably 6 to 7 or even 6.5 to 7.

[0039] The staining step can be carried out for a desired period of time, for example, in the range of about 30 minutes to about 60 minutes, more preferably in the range of 35 minutes to 55 minutes or 40 minutes to 50 minutes.

[0040] After the dyeing step, the dyed textile is subjected to a first washing step in which the textile is washed in water at a temperature of 20-50°C, preferably 25°C-35°C, or even 30°C-40°C for at least 15 minutes, more preferably at least 20 minutes, or even 30 minutes.

[0041] After the first washing step, the dyed textile is subjected to a second washing step in which the textile is washed with water at a temperature ranging from 45° C. to 75° C., preferably from 50° C. to 70° C., or even from 55° C. to 65° C. This second washing step is carried out for at least 5 minutes, preferably for at least 10 minutes, or even for 20 minutes.

[0042] After the second washing step, the dyed fabric is subjected to a soap wash in which the fabric is washed with an aqueous solution containing 0.5-2 grams per liter, preferably 0.8-1.75 grams per liter, or even 1-1.5 grams per liter of one or more soaps. This soap solution also contains 1-3 grams of 50% hydrogen peroxide per liter (i.e., the 50% hydrogen peroxide solution is added approximately to result in 0.5-1.5 grams of hydrogen peroxide per liter of aqueous solution), preferably 1.5-2.5 grams of 50% hydrogen peroxide per liter, or even 1.75-2.25 grams per liter. Finally, this soap solution also contains 1-3 grams of sodium hydroxide per liter, preferably 1.5-2.5 grams of sodium hydroxide per liter, or even 1.75-2.25 grams per liter. The temperature of this soap bath should be in the range of 70° C. to 95° C., more preferably 75° C. to 90° C., or even 80° C. to 85° C. This soaping step is carried out for at least 5 minutes, preferably at least 10 minutes, or even 20 minutes. The soap used in this step can be any soaping agent known in the art, especially belonging to the class of anionic wetting agents, such as sulfonates, carboxylates, sulfates, and phosphates, or combinations thereof.

[0043] After the soap washing step, the dyed textile is subjected to another washing step in which the textile is washed with water at a temperature ranging from 45° C. to 75° C., preferably from 50° C. to 70° C., or even from 55° C. to 65° C. This additional washing step is carried out for at least 5 minutes, preferably at least 10 minutes, or even 20 minutes.

[0044] Finally, the fabric is subjected to washing with an acidic aqueous solution at a temperature ranging from 20°C to 45°C, preferably from 25°C to 40°C, or even from 30°C to 35°C. This acidic washing is carried out for at least 5 minutes, preferably for at least 10 minutes, or even for 20 minutes. The acids used in this washing may be acids typically used in the industry, such as acetic acid and / or phosphoric acid (green acid). The pH of this washing may range from 4 to 6, preferably from 4 to 5, or even from 4.5 to 5.5.

[0045] The above steps are considered the minimum steps for the process, however, it should be understood that additional steps, including additional washes, may be performed as commonly known in the art.

[0046] It will be appreciated that this new dyeing process for textiles made from polyester / cotton (or other natural fiber) blends improves the productivity of the process by reducing the process time to only 4-5 hours and also helps save energy since the dyeing can be carried out at temperatures below 100°C instead of the 130°C typically used for dyeing polyester textiles.

[0047] As is generally known in the art, other materials not mentioned above may be added to one or more of the steps in the above process, however, it may be advantageous to carry out the process in a salt-free and alkali-free manner.Furthermore, it should be understood that the dispersant may be omitted and still obtain good results.

[0048] The process of the present invention is illustrated in the following examples. EXAMPLES

[0049] Pretreatment of polyester / cotton blend fabrics Bleached polyester / cotton fabric (25 gsm) is immersed in an aqueous solution containing 50 grams per liter of a quaternary ammonium salt commercially available from The Dow Chemical Company under the trade name ECOFAST™ Pure and 50 grams per liter of sodium hydroxide. The fabric is passed through the solution through a cold pad batch (CPB) or a padding mangle with 70% squeeze-out (wet pick-up). The fabric is then wrapped on an A-Frame and covered with a polyethene sheet for 12-16 hours at a temperature of about 25°C.

[0050] After this time, the fabric is subjected to a hot wash at 80°C for 10 minutes, followed by a neutralization process at room temperature for 10 minutes using acetic acid (concentration of 1 gram of acetic acid per liter of water). The fabric is passed through two rollers of a padding mangle with 70% squeeze-out (wet pick-up) to squeeze out excess solution from the fabric. The fabric is wrapped on the rollers and covered with a polyethene sheet for 16 hours.

[0051] "All-in-one" dyeing process A dye bath containing 2% (based on the weight of the fabric) reactive dye and 2% disperse dye is prepared and heated to a temperature of 40°C to 50°C. A 5 gram sample of the pretreated polyester / cotton fabric is added to the bath. A combination of commercially available reactive and disperse dyes shown in the combinations in Table 1 are used for these examples. Dyeing is carried out in an Infra Red laboratory dye machine with a L:R (liquor ratio or fabric to water ratio) of 1:20 over a period of 40 minutes. [Table 1]

[0052] After dyeing, the dyed fabric is subjected to a finishing process as described below: a) a room temperature (25°C to 30°C) water wash over a period of 10 minutes; b) hot (60°C) water for 10 minutes; c) a soapy water wash with 1 gram per liter soap solution (ACUSOL™-479N, a commercially available solution containing a copolymer of acrylic acid and maleic anhydride having a molecular weight of about 70,000) at a temperature of 80° C. for 10 minutes; d) a hot (60°C) wash for 10 minutes, and then e) 10 minute room temperature (25° C.-30° C.) water wash with acetic acid added to bring the pH to the range of 5-7.

[0053] Pretreated polyester / cotton fabrics dyed with the new "all-in-one" dyeing process can be compared to similar non-cationized fabrics dyed with conventional dyeing processes, i.e., a two-bath process and a one-bath, two-step process. Dye strength is evaluated using computer color matching software that reports color strength as a percentage (the two-bath process using untreated fabric is established as the 100% baseline). As shown in Table 2, dye strength is increased when polyester / cotton fabrics are pretreated and dyed using the new "all-in-one" dyeing process. [Table 2]

[0054] The ISO method (ISP 105C10:C(2)) is used to evaluate the color fastness of dyed fabrics to washing. In this method, the dyed fabrics are sandwiched between two specific adjacent fabrics, namely a cotton sheet and a polyester sheet. They are then mechanically agitated in an aqueous solution containing 5 grams per liter of soap solution (e.g. ACUSOL™-479N) and 2 grams per liter of sodium carbonate (NaCO3) at a temperature of 60° C. for 30 minutes, followed by rinsing and drying. The color change of the specimens and the staining of the adjacent fabrics are evaluated on a gray scale and reported in Table 3. [Table 3]

[0055] As can be seen from the above experiments, the process of the present invention results in better dyeing performance while using more environmentally friendly conditions and shorter overall time.

Claims

1. 1. A method for dyeing a fabric comprising polyester fibers and natural fibers, comprising the steps of: a) pretreating the fabric with an aqueous solution comprising an alkali metal hydroxide and a cationizing agent comprising either a halogenated compound capable of generating two epoxide groups in the presence of the alkali metal hydroxide, or a mono- or di-quaternized cationizing agent; b. immersing the pretreated fabric in a water bath containing reactive and disperse dyes at a temperature ranging from 80 to 100° C. and having a pH of 6 to 7 for a period of 30 to 60 minutes; c. washing the dyed fabric in [cold] water at a temperature between 30°C and 40°C for at least 20 minutes; d. washing the dyed fabric obtained from step c. with water at a temperature of 50-70°C for at least 10 minutes; e. washing the dyed fabric obtained from step d. with an aqueous solution containing 0.5-2 grams per liter of soap, 1-3 grams per liter of 50% hydrogen peroxide, and 1-3 grams per liter of sodium hydroxide at a temperature ranging from 70° C. to 90° C. for at least 10 minutes; f. washing the dyed fabric obtained from step e. with water at a temperature between 50°C and 70°C for at least 10 minutes; g. washing the dyed fabric obtained from step f. with an aqueous solution having a pH in the range of 4 to 6 and a temperature in the range of 30° C. to 40° C. for at least 10 minutes.

2. 1. A method for dyeing a fabric comprising cationized polyester and natural fibers, comprising: a. immersing the cationized fabric in a water bath containing reactive dyes and disperse dyes at a temperature ranging from 80° C. to 100° C. and having a pH of 6 to 7 for a period of 30 to 60 minutes; b. washing the dyed fabric with water at a temperature of 30°C to 40°C for at least 20 minutes; c. washing the dyed fabric obtained from step b. with water at a temperature ranging from 50 to 70° C. for at least 10 minutes; d. washing the dyed fabric resulting from step c. with an aqueous solution containing 0.5-2 grams per liter of soap, 1-3 grams per liter of 50% hydrogen peroxide, and 1-3 grams per liter of sodium hydroxide at a temperature ranging from 70° C. to 90° C. for at least 10 minutes; e. washing the dyed fabric obtained from step d. with water at a temperature ranging from 50°C to 70°C for at least 10 minutes; f. washing the dyed fabric obtained from step e. with an aqueous solution having a pH in the range of 4 to 6 and a temperature in the range of 30° C. to 40° C. for at least 10 minutes.

3. 3. The method of claim 2, wherein said cationization of said fabric in an aqueous solution is accomplished by contacting said fabric with a solution comprising an alkali metal hydroxide and a cationizing agent comprising either a halogenated compound capable of generating two epoxide groups in the presence of said alkali metal hydroxide, or a mono- or di-quaternized cationizing agent.

4. 3. The method of claim 2, wherein the pH in steps a. and f. is maintained by the use of acetic acid and / or phosphoric acid (green acid).

5. 3. The method of claim 2, wherein the soap used in step d. is an anionic wetting agent.

6. The method of claim 5, wherein the anionic wetting agent is selected from the group consisting of sulfonates, carboxylates, sulfates, phosphates, and mixtures thereof.

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