Patent Publication Number: US-2010125958-A1

Title: Method for yarn- dyeing microfibers

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part application of prior U.S. patent application Ser. No. 11/659,208, filed Mar. 13, 2007, the disclosure of which is incorporated herein by reference in its entirety. The parent application is the National stage of PCT/KR05/02530, filed Aug. 3, 2005, the disclosure of which is incorporated herein by reference in its entirety. The parent application claims priority to Korean Application No. 10-2004-0061287, filed Aug. 4, 2004, and Korean Application No. 10-2005-0059298, filed Jul. 1, 2005, the disclosures of which are incorporated herein by reference in their entireties. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a method for yarn-dyeing weight-reduced microfibers. More specifically, the present invention relates to a method for yarn-dyeing weight-reduced split-type microfibers made of a composite of polyester and polyamide. 
     2. Description of the Related Art 
     A microfiber refers to a fiber which measures not higher than one denier, which has a three-dimensional structure and includes microspaces formed during splitting, thus exhibiting excellent moisture-absorption, washing properties, texture and warmth retention. Cloths made of microfibers, including dish towels, dust-clothes, towels, gowns and the like, are highly valued due to excellent washing properties, rapid drying properties, and good antimicrobial activity and durability. However, in the case of fabrics such as knitted wear or fashion socks, which will have a more effective value by the use of microfibers, products utilizing microfibers have not been developed yet. This is the reason that foreign materials present in weight-reduced microfibers in the process of microfiber dyeing cannot be removed. 
     Fabric dyeing is divided into piece dyeing wherein dyeing is performed after the yarn has been constructed into fabric, and yarn-dyeing wherein dyeing is performed before the yarn is weaved. Piece dyeing has been conventionally used in microfiber dyeing. Since microfibers exhibit considerably high migration properties, they are suitable for dyeing with various colors and are thus usable to prepare only woven or knitted fabrics rendering only one color. For example, in the case where socks knitted with microfibers and rubber threads (spandex) are weight-reduced at high temperatures and are then dyed, the spandex melts and the socks thus cannot exert their intended functions. Accordingly, in order to prepare microfiber woven or knitted fabrics with various colors or to dye fabrics with various materials and designs, yarn-dyeing is required. 
     Conventional yarn-dyeing methods were attempted only by methods for weight-reduction and dyeing microfibers at the same time and thus fail to obtain the desired effects and are not commercially feasible. This is the reason that the simultaneous conduction of weight reduction and dyeing makes the splitting of microfibers difficult and causes foreign matter generated during the weight reduction process to interfere with the infiltration of dyes into fibers, causing deterioration in absorption and dye fastness. 
     These problems of the conventional microfiber yarn-dyeing can be solved by adopting a method for washing with water and dyeing, after weight-reduction. In the prior art, the method of dyeing after weight reduction was not attempted, because an appropriate water-washing method, to remove foreign materials present in microfibers, required before dyeing and after weight reduction, or appropriate processing conditions in weight-reduction and dyeing had yet to be understood. 
     Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a method for dyeing microfibers, comprising weight-reducing the microfibers, followed by washing with water, wherein yarn-dyed microfibers with high absorbance rate and dye fastness can be obtained, and the yarn-dyed microfibers are used as the material of woven or knitted fabrics to allow the production of various products woven with yarns of various colors while having the advantages of microfibers. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a schematic enlarged view illustrating split microfibers made of a composite of polyester and polyamide. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In accordance with the present invention, the above and other objects can be accomplished by the provision of a method for yarn-dyeing split microfibers made of a composite of polyester and polyamide, the method including: winding microfibers on a plurality of cones provided with outlet openings and inserting the microfiber-wound cones into a plurality of rods provided with discharge holes arranged in a lower part in a cheese dyeing machine, to load the microfibers in the cheese dyeing machine; adding an alkali agent to the microfibers in the cheese dyeing machine at a constant temperature of 100 to 130° C. for 30 to 60 minutes to induce a reduction of 6 to 15% in weight of the microfibers; spraying high-pressure water of 70 to 80° C. from inside of the hollow rods through the discharge holes into the cheese dyeing machine, in a state wherein weight-reduced microfiber yarns wound on the cone are mounted on the rod, to allow the high-pressure water to pass through the microfibers through the discharge holes provided on the cone, and cause the water to remove foreign materials, while being discharged to the outside, and at the same time, showering the microfibers through a plurality of nozzles provided on a top cover of the cheese dyeing machine, to wash the microfibers with water; scouring the microfibers with a scouring agent and treating the microfibers with acid to a pH of 4-5; and adding a dispersing agent, a leveling agent, an antistatic agent and a softening agent to the microfibers at 100 to 130° C. for 30 to 60 minutes and dyeing the microfibers under a predetermined pressure. 
     The water may contain small amounts of calcium (Ca) and magnesium (Mg), and may be free of iron (Fe). 
     The cheese dyeing machine may have a cylindrical shape and is provided on the top thereof with a cover and on an inner bottom thereof with the plurality of hollow rods, wherein an inside of the hollow of each rod is connected to a high-pressure water-supply pipe and the water-supply pipe is connected to each of the nozzles provided on the cover. 
     The microfibers may be twisted to 100 to 1,000 tpm, to prevent the yarn from being untwisted during pressurization by the high-pressure water. 
     Hereinafter, the present invention will be described with reference to the annexed drawing in more detail. 
     As shown in  FIG. 1 , microfibers, the target of dyeing in the present invention, are split-type microfibers made of a composite of polyester  1  and nylon  2  (hereinafter, referred to as “microfibers”). The microfibers consist of 70% polyester and 30% polyamide and the composition thereof may be slightly varied depending on yarn manufacturers. 
     The steps for weight-reducing, washing with water and dyeing microfibers are carried out in a state wherein microfibers are wound on a plurality of hollow cones provided with outlet openings and the cones is mounted on a plurality of hollow rods provided with discharge holes provided in a cheese dyeing machine. 
     Preferably, prior to winding, the microfibers are subjected to a twisting process so that their twist level is 100 to 1,000 tpm (twists per meter). The twisting process enables life span of woven fabrics to be lengthened and secures desired dyeing results, as can be confirmed through experimentation. In the case where microfibers are dyed without being subjected to twisting, a number of points in yarns remain white (are not dyed) due to high-pressure upon injecting of water at the pressure, thus making it difficult to handle. 
     In the process of mounting wherein the cones provided with outlet openings, on which the microfibers are wound, are inserted into the rods provided with discharge holes in a lower part of a cheese dyeing machine, the cheese dyeing machine has a cylindrical shape and is provided on the top thereof with a cover and on an inner bottom thereof with the plurality of hollow rods. The inside of the hollow of the rod is connected to a high-pressure water-supply pipe. A plurality of nozzles are provided in the cover to spray water into the cheese dyeing machine Each nozzle is connected to the high-pressure water-supply pipe. The rod has a closed upper end, allowing water to be sprayed through the discharge holes of the rod into the cheese dyeing machine, when the water is sprayed into the hollow of the rod through the high-pressure water-supply pipe connected to a lower end of the rod. 
     The weight-reduction is carried out at 100 to 130° C. for 30 to 60 minutes in a state wherein the cone, on which the microfibers are wound, is mounted on the rod of the cheese dyeing machine. The term “weight-reduction” as used herein refers to alkali weight-reduction which is commonly used to improve texture of polyester clothes using sodium hydroxide (NaOH) as a reagent. As a result of the weight-reduction, polyester is hydrolyzed to produce disodium terephthalate (hereinafter, referred to as “DST”) and ethylene glycol as water-soluble by-products, and polyamide is split to form spaces therebetween. 
     The weight-reduction rate is proportional to the concentration of sodium hydroxide (NaOH) and treatment temperature. In particular, the weight-reduction rate greatly depends on treatment temperature. Accordingly, the treatment temperature should be maintained at a uniform temperature of 100 to 130° C. The weight-reduction rate is preferably 6 to 15%. When the weight-reduction rate is higher than the range defined above, fluff occurs and plucking will occur due to friction with other fabrics, resulting from a napping phenomenon. When the weight-reduction rate is lower than the above range, absorption and rapid-drying properties are degraded and checking of the weight-reduction rate is required for the weight-reduction. 
     After the weight-reduction, water-washing is performed to remove hydrolysis by-products produced during the weight-reduction. The water-washing process is carried out in a state where the cone, on which weight-reduced split-type microfibers are wound, is inserted into the rod in the cheese dyeing machine. In the water washing process, high-pressure water sprayed through discharge holes provided on the rod in the cheese dyeing machine passes through microfibers wound on the cone through the outlet openings of the cone, is discharged together with hydrolysis by-products to the outside and is sprayed through the plurality of nozzles from the cover arranged on the top of the cheese dyeing machine to perform showering. 
     More specifically, high-pressure water supplied through the water supply pipe connected to the inside of the hollow is discharged through the discharge holes of the rod into the cheese dyeing machine. When the discharged water passes through microfibers wound on the cone through the outlet openings of the cone inserted into the rod and is discharged to the outside, hydrolysis by-products left in the microfibers after weight-reduction are discharged to the outside together with the high-pressure water. At the same time, by showering water above the cone in the cheese dyeing machine through water nozzles provided in the cover arranged on the top of the cheese dyeing machine, the hydrolysis by-products derived from microfibers wound on the cone are washed off and flow below the cheese dyeing machine and are then discharged to the outside together with the water through the discharge holes provided in a lower part of the cheese dyeing machine. 
     In addition, the water-washing process should be carried out using warm water of 70 to 80° C., rather than cool water. The water used for the water-washing process should contain small amounts of calcium (Ca) and magnesium (Mg) and be free of iron (Fe). This is necessary because the presence of iron (Fe) ions causes dye staining or color variation. In the water washing process, care is required so that the yarn is not elongated, and failure caused by insufficient water washing should be solved by physical methods. 
     After the water-washing, a scouring agent is added to remove impurities and sodium triphosphate is used to remove DST, if necessary. In addition, alkali is treated with an acid. The alkali is preferably treated with an acidic agent (RC cleaning, available from Hansol Chemical Co., Ltd., Korea) to adjust the yarn to a pH of 4.5. This is because when the yarn is maintained at high pH without treatment with acid, dyeing does not proceed well. It is preferred that cationic agents not be used if possible. This is because when the cationic agents bind to anionic dispersing or leveling agents or other oligomers, they will form insoluble salts, thus causing spots. 
     After completion of the scouring and water-washing processes, water is removed, and dyeing is performed as soon as possible. In the dyeing process, high-pressure dispersion dyes are used and close attention is required. As the dye, dye for polyester or a composite of polyester and polyamide is used. Examples of this dye include Dianix Flavine XF, Dianix red, and CBN XF, which are available from Dystar Co., Ltd. The dyeing can be performed with various colors ranging from light colors to dark colors. 
     The dyeing is carried out at a temperature of 100 to 130° C. under high pressure for 30 to 60 minutes, in which dye is added while confirming an increase in temperature. Upon addition of the dye, a dispersing agent, a leveling agent, a fiber softener and an antibacterial agent are added together with the dye. Furthermore, chloroxylenol having an excellent effect on the removal of viruses is preferably added together with the dye. 
     The dyeing may be performed either by a one-step process or by a two-step process wherein the polyamide is dyed after dyeing the polyester. The one-step process has disadvantages in that three times more dye is consumed than during the two-step process, and dyeing defects may occur. Nevertheless, the one-step process may be considered because the two-step process is time-consuming and complicated. The two-step process is carried out by dyeing the polyester with a disperse dye at 130° C. and then dyeing the polyamide with a dye for polyamide at 100° C. As the dye for polyamide, a disperse dye or an acidic dye may be used. 
     After completion of the dyeing process, the dyed yarn is washed with water to remove molten polyester and foreign materials, followed by drying. The dyed and dried yarn is used to weave or knit the desired fabrics. 
     Alternatively, after completion of the dyeing process, the dyed microfibers may be used to constitute a part or all of fancy yams with design effects. That is, the above dyed microfibers may be used alone or in combination with other yams to make fancy yams. Alternatively, after microfibers before dyeing are used to make fancy yarn, the fancy yarn may be dyed. Examples of the fancy yarn are as follows. 
     Chenille yarn is a kind of yarn for the decoration of the edge of embroideries and is used as weft to make chenille fabrics. The chenille yams are arranged at intervals of a few warps and woven using yams to be plied as wefts. The woven material is cut in the warp direction and twisted, thus obtaining thick fluffy yams. 
     Slub yarn is a yarn obtained by making continuous soft knots on untwisted yarn using twisted yarn. The slub yarn is not uniform in thickness and has knots at a number of points. 
     Nep yarn is a single yarn which has small fluffs irregularly placed at a number of points and comprises knot-like shapes intermittently protruding from the surface thereof. 
     Loop yarn, also called “boucle yarn”, is a fancy twisted yarn having loops at a number of points, and is frequently used in knitted wear or woolen fabrics. 
     Feather yarn is made by knitting warp and weft in various specifications with a needle to make clothes and cutting the clothes with a knife. 
     Methods for producing the above-described fancy yams are well known to those skilled in the art and a detailed explanation thereof is thus omitted. 
     Hereinafter, an example will be provided for a further understanding of the invention. The following example is for illustrative purposes only and is not intended to limit the scope of the present invention. 
     EXAMPLE 
     Split-type microfibers made of a composite of 70% polyester and 30% polyamide were twisted such that their twist level was adjusted to 250 tpm. A plurality of cones, on which the twisted microfibers have been wound, were mounted on rods in a cheese dyeing machine, and sodium hydroxide was added at a constant temperature of 130° C. for 30 minutes to induce a reduction of 7% in the microfiber weight. Iron (Fe)-free water was injected onto the weight-reduced microfibers through the discharge holes provided on the rod to allow high-pressure water to pass through the microfibers wound on the cones and then to be discharged to the outside. Then, iron (Fe)-free water was injected onto the weight-reduced microfibers through nozzles provided with a top cover of the cheese dyeing machine to remove foreign materials and thereby to remove polyester molten in a water-pressure spray manner. Then, the yarn was scoured by the addition of sodium hydroxide, and treated with acid (RC cleaning available from Hansol Chemical Co., Ltd.) to adjust the pH of the yarn to 4.5. Then, a black dye (Dianix black available from Dystar Co., Ltd.), DC-505 (available from Shin Kwang Oil Chemical Co., Ltd, Korea) as a dispersing agent, Anol-25B (available from Shin Kwang Oil Chemical Co., Ltd, Korea) as an antistatic agent, and 3M (available from Shin Kwang Oil Chemical Co., Ltd, Korea) as a softening agent were added at 130° C. for 30 minutes to dye the yarn. Then, the dyed yarn was removed from the dyeing machine, dried and wound on the bobbin of the dyeing machine. Then, the dyed yarn was woven together with spandex in a sock weaving machine to produce socks. The produced socks were measured for washing fastness, drying rate and absorption rate. For comparison, general black cotton socks were also measured for washing fastness, drying rate and absorption rate. The results thus obtained are shown in Table 1 for washing fastness, Table 2 for drying rate, and Table 3 for absorption rate. 
                                 TABLE 1                       Microfiber               socks   Cotton socks                                                    Washing   Color change   4-5   4-5                                 fastness   Color Staining   Cotton   —   4-5               Nylon   4   4-5               Wool   4-5   —                    
Color fastness was tested according to KS K 0430-2001, A-1, 40±2° C.; unit: grade
 
                                 TABLE 2                       Microfiber socks   Cotton socks                                                        Drying rate   27.49   18.29                        
Drying rate tested according to KS K 0815-2001 6. 28. 1B, “evaporation free water amount”; unit: g/202.5 cm 2    
                                 TABLE 3                       Microfiber socks   Cotton socks                                                    Absorbance rate   Wale direction   8   0           Course direction   7   0                    
Absorption rate tested according to KS K 0815-2001 6. 27. 1B; unit: mm
 
     As apparent from the fore-going, in accordance with the method for yarn-dyeing microfibers of the present invention, split-type microfibers made of a composite of polyester and polyamide can be obtained, which feel soft to the touch and are dyed with the desired colors due to weight reduction. The use of the dyed microfibers allows production of woven fabrics with various colors. Fabrics woven or knitted with the dyed microfibers are high-level products and provide various colors and functionalities, thus enabling various products to be produced and creating high added value. 
     Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.