A dyeing method developed for dyeing cationic dyeable polyester fabrics with basic (cationic) dyestuffs

Abstract

The invention relates to a new dyeing method developed in the textile industry for dyeing cationic dyeable polyester (CDPET) fabrics with basic (cationic) dyes. The invention relates particularly to a continuous dyeing method that involves fixation in a thermosol oven to enable dyes to diffuse into the fibers, for dyeing cationic dyeable polyester (CDPET) fabrics with basic (cationic) dyes.

Description

[0001] A DYEING METHOD DEVELOPED FOR DYEING CATIONIC DYEABLE POLYESTER FABRICS WITH BASIC (CATIONIC) DYESTUFFS

[0002] Field of the Invention

[0003] The invention relates to a new dyeing method developed in the textile industry for dyeing cationic dyeable polyester (CDPET) fabrics with basic (cationic) dyes.

[0004] The invention relates particularly to a continuous dyeing method that involves fixation in a thermosol oven to enable dyes to diffuse into the fibers, for dyeing cationic dyeable polyester (CDPET) fabrics with basic (cationic) dyes.

[0005] State of the Art

[0006] Polyester fibers have a wide range of uses thanks to their superior properties against other natural and synthetic (man-made) fibers. The production and use of polyester fiber has increased year by year and has now become the most produced and consumed fiber in the world. Polyester fiber production constitutes more than half of the world’s fiber production. Although polyester fibers become the primary fiber in textile production due to their superior and appropriate strength properties and versatility in use, they are hydrophobic fibers. The very low water absorption of the fibers constitutes both an advantage and a disadvantage in terms of the usage of these fibers.

[0007] The most important problem of polyester fibers is that they are very difficult to dye due to their hydrophobic properties. Studies on fiber internal structures and dyestuff classes available in the market have shown that polyester fibers can be dyed with disperse dyes. Disperse dyes are dyestuffs developed primarily to dye cellulose acetate fibers at the end of the 1920s, and their most important feature is their nonionic structure. It has been understood that this nonionic structure has a very high affinity in the amorphous regions of man-made (synthetic) fibers and it has been understood that polyester fibers can be dyed with disperse dyes according to the experiences obtained from cellulose acetate fibers. However, the fact that the glass transition temperatures of polyester fibers are in the range of 75-800 and the dyeing t emperatures of 1300 has shown that it is not possible to dye polyester fibers with disperse dyes under atmospheric conditions. In this context, the thermosol method has been developed for dyeing polyester fibers with disperse dyes. This method is a continuous dyeing process in which the dyeing solution comprising the disperse dye is impregnated into the polyester fabric, which is passed openly through a padder, then a drying is performed to remove excess water, and after this drying, fixation is performed in the thermosol oven at very high temperatures for diffusion of the disperse dye molecules on the fiber into the fiber. However, this method has disadvantages such as the requirement to dye very large amounts of fabric batches in order to work efficiently.

[0008] Another method developed for dyeing polyester fibers is the Carrier dyeing process. Carrier is synthesized as an auxiliary chemical for dyeing; and yarns and fabrics made of polyester fibers can be dyed in open-air machines with disperse dyes. There are two basic theories about how the Carrier chemical behaves under dyeing conditions. According to one theory, Carrier chemicals interact with disperse dyes to provide dyeing, while according to the other theory, Carrier chemicals act as plasticizers in the dyeing solution, reducing the glass transition temperatures of polyester fibers and making the internal structure of the fiber accessible at boiling temperatures so that disperse dyes can diffuse into the fiber. Although both theories have alternate subtheories, generally, the second theory is accepted. According to this, Carrier chemicals allow the internal structures of polyester fibers to accessible at boiling temperatures. However, this method has some unfavorable properties such as the fact that the produced Carrier chemicals are generally harmful compounds to human health and nature, and the problems encountered in dyed fabrics.

[0009] In the art, there are also "jet dyeing machines" operating under high pressure and closed to atmospheric conditions for dyeing polyester fibers with disperse dyes. Jet dyeing machines are dyeing kiers that can be heated up to 1400 and are resistant to approximately 4 atm pressure. In these kiers, fabrics (or yarns) made of polyester fibers may be dyed at 1300. Dyeing on these machin es, which work according to the exhaust method and the batch dyeing principle, has been the main application for coloring polyester products since the 1960s.

[0010] After the 1960s, it was possible to produce new fibers in which the properties of existing man-made (regenerated and synthetic, artificial) fibers could be combined with successful engineering studies in fiber production technology. One of these fibers, cationic dyeable polyester fibers (CDPET; Cationic Dyeable PET), both have the superior properties of polyester fibers and can be dyed with cationic (basic) dyes other than disperse dyes. In the production of CDPET fibers, anionic polymers, which are also used in the production of acrylic fibers, are added to the polyester polymer, and as a result, the fiber contains two polymers within its structure. While polyester (polyethylene terephthalate, (PET)), which is one of these polymers, provides its strength properties, the other anionic polymer (copolymer) added forms end groups (dyeing sites) in which cationic (basic) dyes can make electrostatic bonds under dyeing conditions. In this dyeing stage, the polymer that binds with the dye molecules is not polyester, but rather the anionic polymer present as a copolymer. The amount of anionic copolymer added to the polyester polymer is adjusted according to the desired properties of the produced CDPET fibers. The purpose of producing CDPET fibers is to obtain fibers that can be an alternative to polyester fibers but can be dyed with much darker and more vivid colors. In addition, the use of CDPET and normal PET fibers together provides some visual properties that cannot be obtained especially when these fibers are used alone. With this type of blend, fabrics with a melange effect, which are highly popular among consumers, are produced and have a great demand in the market.

[0011] CDPET fibers are negatively charged both in surface and internal structure under dyeing conditions and can make very strong ionic bonds with the positively charged cationic (basic) dye molecules in the dyeing medium. This negative charge is the property of the anionic copolymer, which is used in combination with the polyester polymer and has acidic properties. In addition, the advantage of cationic (basic) dyes is that they are the dyes that give the brightest and vivid colors among all available dyestuff classes.

[0012] In the art, yarns and fabrics made of CDPET fibers are dyed with cationic (basic) dyes, whether they are blended or not with PET fibers, primarily in jet dyeing machines (kiers) according to the exhaust method and batch dyeing principle. In this batch dyeing principle, the production amount is in relation with the capacity of the dyeing machine. Among the dyeing that need to be made consecutively in batches with high quantity, there is a difference in dye purchase, called lot / batch difference, and as a result, color differences occur.

[0013] Cationic (basic) dyeable polyester (CDPET) fibers, yarns, and fabrics produced from these fibers have historically been dyed primarily using basic (cationic) dyes. Since cationic (basic) dyeable polyester (CDPET) fibers are synthetic fibers, although it is possible to dye them with disperse dyes, the targeted dark and bright dyeing results cannot be obtained. Disperse dyes are nonionic dyes and basic dyes are cationic dyes. Other dyes used in the dyeing of textile fibers are anionic, and anionic dyestuffs have no affinity for cationic (basic) dyeable polyester (CDPET) fibers due to the ionic structure difference.

[0014] Yarns and fabrics made of cationic (basic) dyeable polyester (CDPET) fibers can be dyed to very dark and bright colors with basic (cationic) dyes. According to the exhaust method, dyeing is carried out intermittently in dyeing kiers which are closed to the atmosphere. However, under dyeing conditions, since the internal structure and surface of the cationic (basic) dyeable polyester (CDPET) fibers are negatively charged and the basic dye molecules are positively charged, a very high electrostatic attraction force occurs between the fibers and the dye molecules. Due to this attraction force, the dyeing rate increases very much and even dyeing becomes very difficult to be achieved. Therefore, it is necessary to slow down the dyeing rate under dyeing conditions in the dyeing of cationic (basic) dyeable polyester (CDPET) products with basic (cationic) dyes according to the exhaust method. In this context, temperature control, retarder chemical addition or temperature / retarder combinations are used to slow down the dyeing rate. Under the dyeing conditions, the dyeing temperature is raised very slowly, dyeings are performed at boiling temperature and under monitored acidic pH conditions. The dyeing processes carried out according to the exhaust method are carried out in certain material weights and batches depending on the capacity of the dyeing machine (kier) used. However, as a result of the dyeing made independently of each other in these batches, errors called lot / batch difference or batch dyeing differences occur and it is not possible to obtain the same color in each separate batch. According to the exhaust method, dyeing large amounts of fabric in successive batches in this way always causes problems in obtaining the same color.

[0015] When cationic (basic) dyeable polyester (CDPET) fabrics are dyed in batch processes according to the exhaust method, they must be in the form of fabric rope in closed atmospheric jet dyeing machines, and as a result, under dyeing conditions, traces called crack marks and light colored marks where the dyes have not fully penetrated are obtained. For this reason, dyeing cationic (basic) dyeable polyester (CDPET) products in fabric form and in dyeing machines according to the exhaust method is not a commonly used process under practical industrial conditions and dyeing in yarn form are preferred. These problems encountered in dyeing according to the exhaust method result in the use of CDPET fibers as a blend with normal PET fibers always.

[0016] As a result of the research conducted in the literature, the application numbered EP3992339A1 was found. The said application relates to fabric dyed after being shaped into a fabric and dyeing method. The said method comprise dyeing a fabric comprising meta-type wholly aromatic polyamide fiber, para-type wholly aromatic polyamide fiber, and polyester fiber with a dyeing solution containing cationic dyestuff; and dyeing a fabric comprising polyester fiber with a dye solution comprising disperse dyestuff. However, the document does not specifically mention the process of dyeing cationic dyeable polyester (CDPET) fabrics directly with basic dyestuffs.

[0017] As a result due to the above-mentioned drawbacks and the insufficiency of the current solutions regarding the subject matter, a development is required to be made in the relevant technical field.

[0018] Objective of the Invention

[0019] The objective of the invention is to solve said disadvantages by being inspired from the current conditions.

[0020] The main objective of the invention is to develop a method that allows for the use of basic (cationic) dyes in continuous dyeing processes, rather than batch processes with the exhaust method, which causes dyeing defects in the dyeing of cationic dyeable polyester (CDPET) fabrics in the current technique.

[0021] The objective of the invention is to provide a method for dyeing cationic dyeable polyester (CDPET) fabrics with basic (cationic) dyes without the need for processes such as temperature control or the addition of retarder chemicals.

[0022] Another objective of the invention is to provide dye immersion solution content that allows the basic (cationic) dyes to diffuse into the fiber by keeping the fabrics wet during the fixation period.

[0023] Another objective of the invention is to provide fixation directly in the thermosol oven after the dye impregnation applied to the cationic dyeable polyester fabric without the intermediate drying step used in the conventional thermosol application^ In order to achieve said objectives, the invention is a method developed for dyeing cationic dyeable polyester (CDPET) fabrics with basic (cationic) dyes, comprising the following process steps; i. Preparation of the dyeing solution comprising basic (cationic) dyestuff, Carrier, urea, thickener, water, weak acid buffer and migration inhibitor, ii. Passing the cationic dyeable polyester (CDPET) fabric in an impregnation trough (padder) containing the dyeing solution, iii. Squeezing the fabric with the squeezing rollers at the exit of the impregnation trough (padder), iv. Fixation of the dye by passing the fabric through a thermosol oven, v. Washing dyed fabric and then drying.

[0024] The structural and characteristic features and all the advantages of the invention will be understood more clearly thanks to the detailed description given below, and therefore the evaluation should be made by taking this detailed description into consideration.

[0025] Detailed Description of the Invention

[0026] In this detailed description, the method and the preferred embodiments of the invention are described only for a better understanding of the subject.

[0027] The invention relates to a method developed for the dyeing of Cationic dyeable polyester (CDPET) fabrics with basic (cationic) dyes. The said method comprises the following process steps; i. Preparation of the dyeing solution comprising basic (cationic) dyestuff, carrier, urea, thickener, water, weak acid buffer (pH5) and migration inhibitor, ii. Passing the cationic dyeable polyester (CDPET) fabric in an impregnation trough (padder) containing the dyeing solution, iii. Squeezing the fabric with the squeezing rollers at the end of the impregnation trough (padder), iv. Performing the dye fixation of the fabric by having it passed through a thermosol oven, v. Washing the dyed fabric and then drying. Table 1. Dyeing solution composition

[0028] In a preferred embodiment of the method of the invention, in the process step i), a dyeing solution comprising basic dyestuff in the range of 1-8% by weight, carrier in the range of 15-30% by weight, urea in the range of 10-60% by weight, thickener in the range of 1 -60% by weight, water and weak acid buffer in the range of 10-68% by weight and migration inhibitor in the range of 5-25% by weight is prepared. Here, the weak acid buffer is added to bring solution to pH5.

[0029] In a preferred embodiment of the method of the invention, in the process step ii), the cationic dyeable polyester (CDPET) is passed through an impregnation (dyeing) trough (padder) containing fabric dyeing solution in the temperature range of 22-450 for 1 -6 seconds.

[0030] In a preferred embodiment of the method of the invention, in the process step iv), the fabric is passed through the thermosol oven in the range of 120-2200 for 30 to 480 seconds.

[0031] In a preferred embodiment of the method of the invention; In the process step v), the dyed fabric is washed by cold washing, warm washing and final rinse processes, respectively. Said cold washing is carried out with water for 20-30 minutes in the range of 20-400. Said warm washing is carried out for 20 -30 minutes in a solution containing anionic and nonionic surfactants in the range of 50-65'C. Said final rinse is carried out with water at room temperature.

[0032] Basic (cationic) dyestuff: An organic-synthetic dye molecule that colors cationic (basic) dyeable polyester (CDPET). It has a cationic molecular structure and is a colored cation that dissolves in the aqueous environment.

[0033] The method of the invention can be used for dyeing woven or knitted Cationic dyeable polyester (CDPET) fabric.

[0034] Thickener: A water retaining chemical additive that increases the consistency of the dye liquor, thereby enhancing its retention on the fabric after immersion. Here, natural or regenerated thickeners can be used. An example of these is carboxymethylcellulose (CMC). Additionally, though not limited to these, alginate and guar ether can also be used.

[0035] Carrier in the dyeing solution is an organic-synthetic chemical substance used to help to open the internal structures of polyester fibers under high thermosolling temperature. Here, as carrier, though not limited to these, chlorophenoxyethanol, diphenyl, ortho- and para-hydroxydiphenyl, monochloro-ortho-hydroxydiphenyl, and N-alkylphthalimide can be used.

[0036] Urea (CH4N2O) in the dyeing solution is used due to its water retention properties.

[0037] Migration inhibitor in the dyeing solution: it is used to prevent the displacement of the dye liquor on the fabric under high temperature conditions and the migration (transfer) of the solution from wet areas to dry areas.

[0038] Water is liquid that dissolves soluble dyestuff and other chemicals, allowing the fabric to absorb the solution in the impregnation trough (padder).

[0039] The weak acid buffer is added in small amounts to the solution for pH5. Here, as a weak acid buffer, though not limited to these, acetic acid or formic acid and sodium acetate can be used. The amount of additive is within the total amount of water. Impregnation Trough (Padder): It is a vessel (vat) in which there is a dyeing solution and on which the CDPET fabric is passed through the dyeing solution. There are squeezing rollers on it and the impregnated fabric is passed through the squeezing rollers and the " Amount of Liquor Pick-Up (% Pick-Up)” (amount of dyeing solution taken into the fabric) is adjusted. A gentle squeeze should be applied so that the received flotte is as high as possible. Care is taken to ensure maximum uptake of the solution (dyeing liquor). The dyeing solution is at room temperature. The pressure of the squeezing rollers is selected between 0.25 to 5.5 bar (3.5 to 80 psi). The pick-up ratio (%PU) of the dyeing solution obtained after immersion and squeezing should be as high as possible.

[0040] Thermosol Oven: It is the drying machine through which the dye impregnated CDPET fabric passes. It operates in an open-air environment and based on convective heat transfer principles. It has the capability to heat up to 220tC. It should be able to provide homogeneous heating in the range of 120-2200 for 30-480 seconds. Basic dye fixation is performed into CDPET fibers through convective heat transfer, and the hot drying air should be directed perpendicularly to the front and back surfaces of the fabric through the hot air transmission channels inside the machine. Preferably, the thermosol oven is a stenter.

[0041] In a preferred embodiment of the method of the invention, the following processes should be followed:

[0042] 1. Step:, a dyeing solution comprising basic dyestuff in the range of 1-8% by weight, carrier in the range of 15-30% by weight, urea in the range of 10-60% by weight, thickener in the range of 1 -60% by weight, water and weak acid buffer in the range of 10-68% by weight and migration inhibitor in the range of 5-25% by weight is prepared.

[0043] 2. Step: Passing the cationic (basic) dyeable polyester (CDPET) fabric in an impregnation trough (padder) containing the dyeing solution in a range of 22-450 for 1 -6 seconds,

[0044] 3. Step: The fabric is squeezed with the squeezing rollers at the exit of the impregnation trough (padder), with pressures ranging from 0.25 to 5.5 bar (3.5 to 80 Psi)- 4. Step: The fabric being passed through a thermosol oven at temperatures ranging from 120-220'C for a duration of 30 to 480 seconds to perform the fixation of the dye,

[0045] 5. Step: involves cold washing the dyed fabric at 20-400 for 20-30 minutes, followed by warm washing in a solution containing anionic and nonionic surfactants at 50-650 for 20-30 minutes, and doing the final rinse processes at room temperature and drying it afterwards. The drying temperature should not exceed 700, and the drying process should be concluded without excessive drying.

[0046] The difference of the method of the invention from the present art is that the water retention on the fabric is maintained with the use of thickener, migration inhibitor and urea, and the thermosolling process step is performed directly with dry heat while the fabric is still wet without intermediate drying. In order to open the internal structures of the fibers more easily, a carrier chemical was used.

[0047] An experimental study with the method of the invention was carried out as follows:

[0048] Parameters:

[0049] Thermosolling temperatures: 1800 and 1900

[0050] Dyeing concentration: 2 gram / Liter

[0051] Dyeing liquor: 15% migration inhibitor ; 5% thickener ; 20% carrier ; 20% urea, acid buffer pH5, water filling it to 2 liters, dyeing liquor %pick-up ~ %80; acid buffer pH5

[0052] Thermosoling time: 300 seconds

[0053] The color nuance of the basic dye: Blue

[0054] The standard CDPET (Cationic Dyeable Polyethylene Terephthalate) test fabric cut in 25x25 sizes was impregnated with the prepared dyeing solution, the fabric was passed through the squeezing rollers with its taken dyeing liquor (%Pick-up) being maximum and was preferably placed between the stenter pins of the thermosol oven. The fixation was carried out in a closed environment in hot air presence for the specified duration. During this fixation, the internal structures of the fibers are opened and the basic (cationic) dye in the solution impregnated on the fabric diffuses into the fibers and binds to the anionic groups of the copolymer in the internal structure with an ionic bond.

[0055] With the addition of migration inhibitor, thickener and urea into the dyeing solution, it was ensured that the water remained in the fabric during the thermosolling period and thus the water-soluble state of basic (cationic) dyes was maintained.

[0056] In the experimental study, the color coordinate values obtained from the dyeing performed for two different thermosolling temperatures are given. (Table 2) The experimental study demonstrates that the method according to the invention operates successfully. Table 2. Experimental study data

Claims

CLAIMS1. The invention is a method developed to dyeing cationic dyeable polyester (CDPET) fabrics with basic (cationic) dyes, characterized by comprising; the following process steps; i. Preparation of the dyeing solution comprising basic (cationic) dyestuff, carrier, urea, thickener, water, weak acid buffer and migration inhibitor, ii. Passing the cationic dyeable polyester (CDPET) fabric in an impregnation trough (padder) containing the dyeing solution, iii. Squeezing the fabric with squeezing rollers at the exit of the impregnation trough (padder), iv. Performing the dye fixation of the fabric by having it passed through a thermosol oven, v. Washing the dyed fabric and then drying.

2. The method according to claim 1 , characterized in that; in the process step i), a dyeing solution comprising 1 -8% basic dyestuff by weight, 15-30% carrier by weight, 10-60% urea by weight, 1 -60% thickener by weight, 5-25% migration inhibitor by weight, 10-68% water and weak acid buffer by weight is prepared.

3. The method according to claim 1 , characterized in that; in the process step ii), passing the cationic dyeable polyester (CDPET) fabric through an impregnation trough (padder) containing the dyeing solution for 1 -6 seconds.

4. The method according to claim 1 or 3, characterized in that; in the process step ii), the temperature of the dyeing solution in the impregnation trough (padder) being in the range of 22-450.

5. The method according to claim 1 , characterized in that; in the process step iv), the fabric being passed through the thermosol oven in the range of 120-2200 for 30 to 480 seconds.

6. The method according to claim 1 , characterized in that; in the process step v), the dyed fabric being washed with cold washing, warm washing, and final rinse processes respectively.

7. The method according to claim 6, characterized in that; the said cold washing is carried out with water for 20-30 minutes in the range of 20-40'C.

8. The method according to claim 6, characterized in that; the said warm washing is carried out in a solution containing anionic and nonionic surfactants for 20-30 minutes in the range of 50-65'C.

9. The method according to claim 6, characterized in that; the said final rinse is carried out with water at room temperature.

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