Method and apparatus for processing textile products

Abstract

The present invention aims to provide a method for processing textile products that enables efficient decolorization of textile products using a supercritical fluid. [Solution] The method for processing textile products involves decolorizing a textile product made of a dyed fiber material using a supercritical carbon dioxide fluid to which a cosolvent or adsorbent has been added. By adding a cosolvent or adsorbent with a value close to the solubility parameter of the dye at a ratio of 2% of obv or more relative to the bath volume, the decolorization process can be performed efficiently.

Description

[Technical Field]

[0001] This invention relates to a method and apparatus for decolorizing dyed textile products and processing them into recycled textile products, etc. [Background technology]

[0002] In recent years, the transition to a sustainable society has been advocated in many fields, and particular scrutiny has been placed on mass consumption and the resulting mass waste. Regarding fashion-related textile products, it has been reported that approximately 60% of new products are discarded without being purchased, leading to discussions about reuse and recycling of textile waste.

[0003] When recycling textile products, it is difficult to easily separate the dyes from dyed textiles, limiting reuse to products of the same color. Therefore, to promote the reuse of textile waste, it is necessary to develop efficient decolorization processes for textile products.

[0004] As methods for decolorizing textile products, solvent-based treatments using organic solvents and aqueous treatments using solutions in which surfactants and reducing agents are added to water have been proposed. For example, Patent Document 1 describes a method for decolorizing polyester textile products dyed with alkaline dispersible dyes, using a decolorization treatment solution containing an alkaline agent, a reducing agent, and a nonionic surfactant, and decolorizing at a temperature of 130°C to less than 140°C. Patent Document 2 describes a method for recycling dyes from dyed textiles, in which dyed textiles are added to a bath containing an ionic liquid solution, thereby stripping the dye from the textiles and dispersing it in the solution. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2023-63248 [Patent Document 2] Special Publication No. 2024-510719 [Overview of the project] [Problems that the invention aims to solve]

[0006] In the decolorization techniques described above, solvent-based treatments can achieve nearly 100% decolorization, but the organic solvent used in the treatment is discarded along with the treatment solution, resulting in a significant environmental burden and the use of large amounts of energy. Similarly, aqueous treatments have low decolorization efficiency and require long processing times, and like solvent-based treatments, they present challenges in terms of the disposal of the treatment solution and the use of large amounts of energy.

[0007] On the other hand, in dyeing technology, dyeing treatment using supercritical fluids has been proposed. This method allows for the recovery and reuse of the supercritical fluid after dyeing, and also allows for the separation and recovery of excess dye, thus offering advantages such as a low environmental impact and low energy consumption.

[0008] Therefore, the present invention aims to provide a method and apparatus for processing textile products that can efficiently decolorize textile products using a supercritical fluid. [Means for solving the problem]

[0009] The present invention relates to a method for processing textile products, in which a textile product made of a dyed fiber material is decolorized using a supercritical carbon dioxide fluid to which a co-solvent or adsorbent is added. Furthermore, the amount of the co-solvent or adsorbent added is 2% of obv or more relative to the bath volume. Furthermore, the textile product is made of polyester fibers, and the dye is a disperse dye. Furthermore, the solubility parameter of the co-solvent or adsorbent is close to the solubility parameter of the dye.

[0010] The processing apparatus for fiber products according to the present invention is a processing apparatus for fiber products that decolorizes fiber products made of fiber materials dyed with dyes, and includes a processing unit that houses a co-solvent or an adsorbent together with the fiber products, a supply unit that supplies carbon dioxide into the processing unit, and a control unit that controls the temperature and pressure of the carbon dioxide filled in the processing unit to set the carbon dioxide in the processing unit to a predetermined temperature and a predetermined pressure and perform a decolorization treatment in a supercritical fluid state, and a recovery unit that separates and recovers carbon dioxide, dyes, and co-solvent or adsorbent from the treatment liquid generated by the decolorization treatment.

Advantages of the Invention

[0011] In the present invention, by performing a decolorization treatment using a supercritical carbon dioxide fluid added with a co-solvent or an adsorbent, the surface of the dyed fiber material is swollen with the supercritical carbon dioxide fluid and the dye is dissolved together with the co-solvent, or the dissolved dye is adsorbed by the adsorbent, making it possible to efficiently perform the decolorization treatment. When a co-solvent is added, the swelling state of the fiber material is promoted, and the efficiency of the treatment can be enhanced.

[0012] In addition, for the treatment liquid from which the dye has been extracted, carbon dioxide used as the solvent, the extracted dye, and the co-solvent or adsorbent can be separated and recovered for reuse, making it possible to reduce the environmental load.

[0013] Furthermore, the decolorized fiber products can be reused by being dyed using a supercritical fluid as recycled fiber products or by recycling them into raw materials through depolymerization, realizing a circular and sustainable industrial structure.

Brief Description of the Drawings

[0014] [Figure 1] It is a schematic configuration diagram related to a processing apparatus for fiber products. [Figure 2] It is a list of co-solvents or adsorbents used in the decolorization treatment in the examples. [Figure 3] It is a table showing the treatment results of Example 1. [Figure 4]This table shows the processing results for Example 2. [Figure 5] This table shows the processing results of Example 3. [Figure 6] This graph shows the processing results of Example 3. [Figure 7] This table shows the processing results of Example 4. [Modes for carrying out the invention]

[0015] The present invention will be described in detail below. The method for processing textile products according to the present invention involves decolorizing a textile product made of a textile material dyed with a dye using a supercritical carbon dioxide fluid to which a cosolvent or adsorbent has been added.

[0016] Decolorization treatments using supercritical carbon dioxide fluid as a medium include methods such as the solvent trap method, the solid trap method, and the homogeneous method.

[0017] The solvent trap method decolorizes textile products by dissolving the dye in a supercritical carbon dioxide fluid and trapping the dye in a solvent phase containing a co-solvent that accumulates at the bottom of the decolorization container. The solvent trap method is effective when using a co-solvent that has a boiling point higher than the treatment temperature and does not completely dissolve in the supercritical carbon dioxide fluid.

[0018] The solid trap method involves placing a treated material, such as cotton cloth pre-treated with a co-solvent or adsorbent, into a decolorization container along with the textile product. In the case of a co-solvent, supercritical carbon dioxide fluid dissolves the co-solvent and adsorbs onto the dye in the textile product, trapping the dye in the treated material and thus performing the decolorization. In the case of an adsorbent, supercritical carbon dioxide fluid dissolves the dye from the textile product, and the dissolved dye is trapped by the adsorbent, thus performing the decolorization. The solid trap method is effective when using a co-solvent with a boiling point below the treatment temperature and a solid adsorbent.

[0019] In the homogeneous method, the co-solvent completely dissolves in the supercritical carbon dioxide fluid, creating a homogeneous state within the decolorization container. The dye from the textile product then dissolves in this supercritical carbon dioxide fluid containing the dissolved co-solvent, thus performing the decolorization process.

[0020] These methods can be appropriately selected and implemented depending on the characteristics of the dyed textile product and the characteristics of the co-solvent or adsorbent.

[0021] In the decolorization treatment of textile products using supercritical carbon dioxide fluid, the affinity between the dye and the added cosolvent or adsorbent is important, and this affinity can be determined by the solubility parameter (SP value) of both.

[0022] The SP value is defined as the square root of the cohesive energy density in regular solution theory (unit: J / cm²). 3 ) 1 / 2 It is determined from the heat of vaporization, surface tension, and solubility of the substance. It is known that the solubility between two components increases as the difference in SP values ​​decreases.

[0023] Therefore, by selecting a co-solvent or adsorbent with an SP value close to that of the dye, decolorization can be efficiently performed using a co-solvent or adsorbent that has affinity for the dye. Specifically, as will be described later, the SP value of the dye is 20 (J / cm²). 3 ) 1 / 2 ~30 (J / cm) 3 ) 1 / 2 In such cases, decolorization can be performed efficiently by selecting a co-solvent or adsorbent with SP values ​​within a similar range.

[0024] The decolorization treatment can be evaluated using the K / S value, which is the surface color density index of textile products. The K / S value is defined by the following formula, where R is the surface reflectance. K / S = (1 - R) 2 / 2R Then, the cumulative value of the K / S values ​​at 10 nm intervals in the wavelength range of light from 360 nm to 740 nm is taken as the K / S total value, and the decolorization rate is calculated using the following formula with respect to the K / S total value. Decolorization rate (%)=100-(T-T1) / (T2-T1)×100 Here, T is the total K / S value of the textile product after decolorization, T1 is the total K / S value of the textile product before dyeing, and T2 is the total K / S value of the textile product before decolorization. The decolorization rate increases as the dye is removed from the textile product and the surface color becomes lighter, and it is practically preferable that the decolorization rate is 70% or more after a single decolorization treatment.

[0025] When using bleached textile products as recycled textile products, a bleaching rate of 90% or higher is preferable. In some cases, the bleaching rate can be increased by repeating the bleaching process multiple times. As described later, the textile processing method according to the present invention allows for the separation, recovery, and reuse of carbon dioxide and additives, thus minimizing the environmental impact even when the bleaching process is repeated, and enabling efficient processing.

[0026] Furthermore, textile products after decolorization can be evaluated by the residual color rate, which indicates how much color remains. The residual color rate is calculated using the following formula, with T being the total K / S value of the textile product after decolorization and T2 being the total K / S value of the textile product before decolorization. Residual color rate (%)=(T / T2)×100 When using bleached textile products as recycled textile products, it is preferable that the residual color rate is 10% or less. If the residual color rate is greater than 10%, the residual color is likely to have an impact when the recycled textile products are re-dyed, which will limit the uses of the recycled products.

[0027] Examples of textile products to be processed include those made using dyeable materials such as woven or knitted fabrics, nonwoven fabrics, fiber bundles, and yarns. Examples of textile materials include synthetic fibers such as polyester fibers, nylon fibers, acrylic fibers, and polypropylene fibers, and natural fibers such as cotton fibers, hemp fibers, silk fibers, and wool fibers. In particular, it is suitable for decolorizing textile products made of polyester fibers, which are commonly manufactured as dyed textile products.

[0028] The dyes used to color the textile products are dyes that are soluble in supercritical carbon dioxide fluid, and specifically include disperse dyes, oil-soluble dyes, and vat dyes. Disperse dyes are preferred for the decolorization treatment. There are no particular restrictions on the type of disperse dye; either azo-based or quinone-based dyes are acceptable. The fact that a textile product is dyed with a disperse dye can be confirmed, for example, by boiling the textile product in a hydrophobic organic solvent.

[0029] The supercritical carbon dioxide fluid used in the decolorization process can be produced by known methods. For example, by heating and pressurizing liquefied carbon dioxide in a decolorization container to a state exceeding the critical point (31°C, 7.4 MPa), it transitions from a subcritical to a supercritical state, generating a supercritical fluid in the decolorization container. The decolorization process can be carried out by placing dyed textile products and a co-solvent or adsorbent in the decolorization container beforehand.

[0030] Examples of cosolvents used in the decolorization process include ethylene glycol monobutyl ether, tetrahydrofuran, 1-methylnaphthalene, 2-methylnaphthalene, n-methylpyrrolidone, phenoxyethanol, benzyl alcohol, N,N-dimethylformamide, dimethyl sulfoxide, ethylene glycol, glycerin, water, hexane, acetone, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 2-methyl-2-butanol, 3-methyl-2-butanol, 2,2-dimethyl-1-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, 2-propanol, ethanol, methanol, and ethyl acetate.

[0031] Furthermore, solid adsorbents are preferred as adsorbents used in the decolorization process. Examples include thermoplastic polyurethane, thermoplastic polyester, thermoplastic styrene block copolymer, thermoplastic carbonate, acrylonitrile-styrene-butadiene copolymer, acrylonitrile-styrene-acrylate copolymer, polytetrafluoroethylene, and polyvinylidene fluoride.

[0032] Furthermore, when performing decolorization, it is preferable to add the co-solvent or adsorbent in such a way that its ratio (%obv) to the bath volume of the decolorization container (described later) is 2%obv or more. If the amount added is less than 2%obv, the decolorization process will be insufficient, and uneven coloring is likely to occur.

[0033] Figure 1 is a schematic diagram of a textile processing apparatus. The processing apparatus 1 comprises a decolorization container 10 that contains the textile product and the co-solvent or adsorbent to be added, and a liquefied carbon dioxide cylinder 11 that supplies carbon dioxide into the decolorization container 10.

[0034] In the supply pipeline from the liquefied carbon dioxide cylinder 11 to the decolorization container 10, the liquefied carbon dioxide cylinder 11 is connected to the supply pump 13 via a valve 12, and the supply pump 13 is connected to the decolorization container 10 via a valve 14 and a safety valve 15. A pressure gauge 16 is connected to the pipeline connecting the supply pump 13 and the decolorization container 10.

[0035] The decolorization container 10 is installed inside the oven 17, and a temperature sensor (not shown) for detecting the internal temperature is attached to the decolorization container 10. Inside the decolorization container 10, a metal mesh for placing the textile product is placed in the middle section, and an agitation mechanism is attached to the bottom. The supercritical carbon dioxide fluid is introduced into the decolorization container 10 and agitated by the agitation mechanism to circulate inside, ensuring that it is evenly distributed throughout the textile product.

[0036] The processing apparatus 1 includes a control unit (not shown) that detects the temperature and pressure of the carbon dioxide filled in the decolorization container 10 using a pressure gauge 16 and a temperature sensor, and controls the supply of the supply pump 13 and the heating of the oven 17. The control unit sets the carbon dioxide in the decolorization container 10 to a predetermined temperature and pressure to generate a supercritical carbon dioxide fluid state and performs the decolorization process.

[0037] A discharge container 18 is connected to the discharge pipeline of the decolorization container 10 via a discharge valve 19. By opening the discharge valve 19, the treatment liquid generated by the decolorization process is discharged into the discharge container 18. A first recovery unit 20 is connected to the discharge container 18 for vaporizing and recovering carbon dioxide, and a second recovery unit 21 is connected to the first recovery unit 20 for separating and recovering the dye and the added co-solvent or adsorbent, respectively.

[0038] The carbon dioxide gas recovered in the first recovery unit 20 can be liquefied and reused. In the second recovery unit 21, if a co-solvent is present, it can be easily separated and recovered by utilizing the difference in boiling points between it and the dye, and if an adsorbent is present, the adsorbed dye can be dissolved in a solvent such as acetone and then separated and recovered. Since the recovered dye and co-solvent or adsorbent can be reused, a circular system can be constructed that minimizes waste to the outside.

[0039] The amount of supercritical carbon dioxide fluid and the amount of co-solvent or adsorbent added to the decolorization container 10 is preferably set to a ratio (bath ratio) of 500 or more to the amount of textile product being introduced. If the bath ratio is less than 500, the amount of dye dissolved by the processing medium will be limited, resulting in insufficient decolorization.

[0040] In addition, the treatment temperature during the decolorization treatment is preferably set at 120°C or higher. When it is lower than 120°C, the decolorization treatment will be insufficient. When the boiling point of the added co-solvent is 120°C or lower, the decolorization treatment can be carried out by the solid trap method. When the boiling point of the co-solvent is 120°C or higher, the decolorization treatment can be carried out by the solvent trap method or the uniform method.

Examples

[0041] Next, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

[0042] <Regarding the evaluation of the decolorization treatment> For the samples, a spectrophotometer (manufactured by Konica Minolta Japan Inc.; CM-2600d) was used to measure the L*a*b* values and the spectral reflectance at every 10 nm within the measurement range of 360 nm to 740 nm, and the average value of four measurements was calculated.

[0043] Using the calculated average values, the K / S value was calculated by the above-described calculation formula. The K / S values at every 10 nm were integrated to obtain the total K / S value. As described above, the decolorization rate was calculated based on the total K / S values of the sample before dyeing, before decolorization, and after decolorization for evaluation.

[0044] <Regarding the samples and dyes used> For the samples, a fabric made of polyethylene terephthalate (PET) (manufactured by Shikisen Co., Ltd., SP value 21.7 (J / cm 3 ) 1 / 2 ) was used. As the dyes, red dye DR60 (C.I.Disperse Red 60; manufactured by Sumitomo Chemical Co., Ltd., SP value 22.7 (J / cm 3 ) 1 / 2 , blue dye DB301 (C.I.Disperse Blue 301; manufactured by Kowa Chemical Co., Ltd., SP value 22.8 (J / cm 3 ) 1 / 2 and yellow dye SY93 (C.I.Solvent Yellow 93; manufactured by Kowa Chemical Co., Ltd., SP value 20.5 (J / cm 3 ) 1 / 2 were used.

[0045] For the samples, a supercritical fluid staining apparatus (manufactured by Hisaka Works, Ltd.) was used to pre-add dye to the fabric so that the dyeing concentration was 2% owf. The dyeing process was then carried out at a temperature of 120°C, a pressure of 25.0 MPa, and a processing time of 1 hour to obtain samples dyed to the desired color.

[0046] <Regarding the co-solvent and adsorbent to be added> The co-solvents or adsorbents used for the decolorization process were those listed in Figure 2.

[0047] <About the processing equipment> The processing apparatus described in Figure 1 was used, along with a windowed supercritical cell manufactured by JASCO Corporation, which was combined with a high-pressure vessel and pump. The heater of the windowed supercritical cell was heated to a set temperature, and once the temperature inside the cell was constant at 120°C, a glass container containing the sample and the co-solvent or adsorbent was placed inside the cell. Subsequently, carbon dioxide was injected into the cell to set the pressure inside the cell to 25.0 MPa.

[0048] [Example 1] Samples stained with the red dye DR60 were decolorized by adding benzyl alcohol (BA), a type of cosolvent. The bath ratio of the processing apparatus was set to 1:500. The amount of BA added was varied to 0.5% obv, 1.0% obv, 2.0% obv, 3.0% obv, and 4.0% obv. The decolorization treatment was performed at a temperature of 120°C and a pressure of 25.0 MPa for 3 hours.

[0049] Figure 3 shows the treatment results. As shown in the graph in Figure 3, the decolorization rate was 90% or higher when the amount of cosolvent added was 2.0% obv or more, and the decolorization rate increased gradually as the amount of added cosolvent increased beyond 2.0% obv. This increase in the decolorization rate is thought to be because increasing the amount of cosolvent increases the amount of dye that can be dissolved in the cosolvent, and it was confirmed that the amount of added cosolvent affects the decolorization rate.

[0050] [Example 2] Using samples stained with the red dye DR60, decolorization was performed in the same manner as in Example 1 by adding the cosolvent shown in Figure 2. The amount of cosolvent added was set to 2.0% obv.

[0051] Figure 4 shows the treatment results. The SP value of the red dye DR60 is 22.7 (J / cm²). 3 ) 1 / 2 ) is an SP value close to 20 (J / cm 3 ) 1 / 2 ~30 (J / cm) 3 ) 1 / 2 With the cosolvent, the decolorization rate was over 70%, confirming that efficient decolorization was performed. Furthermore, in the decolorization treatment using only supercritical carbon dioxide without the addition of a cosolvent, the decolorization rate was 41.01%, confirming that the decolorization rate was significantly improved by the addition of a cosolvent.

[0052] Also, a high decolorization rate is achieved with an SP value of 20 (J / cm²). 3 ) 1 / 2 ~30 (J / cm) 3 ) 1 / 2 When using the co-solvent, the residual color rate was low, and it was confirmed that the product could be processed into a recycled textile product with a residual color rate of 10% or less through efficient decolorization.

[0053] [Example 3] Samples stained with red dye DR60, blue dye DB301, and color dye SY93 were used, and a portion of the cosolvent shown in Figure 2 was added to perform decolorization treatment in the same manner as in Example 1. The amount of cosolvent added was set to 2.0% obv.

[0054] Figure 5 shows the processing results, and Figure 6 shows the processing results in a graph. The processing results for the blue dye DB301 and the yellow dye SY93 are similar to those for the red dye DR60, and are within a range close to the SP value of each dye, at 20 (J / cm²). 3 ) 1 / 2 ~30 (J / cm) 3 ) 1 / 2In cosolvents with SP values ​​included in the formula, the decolorization rate is 70% or higher. Therefore, by selecting a cosolvent associated with the SP value, which indicates affinity to the dye, the decolorization process can be performed efficiently.

[0055] [Example 4] Using samples stained with the red dye DR60, a decolorization treatment was performed in the same manner as in Example 1 by adding the adsorbent shown in Figure 2. The amount of adsorbent added was set to 2.0% obv.

[0056] Figure 7 shows the treatment results. The SP value of the red dye DR60 is 22.7 (J / cm²). 3 ) 1 / 2 ) is an SP value close to 20 (J / cm 3 ) 1 / 2 ~30 (J / cm) 3 ) 1 / 2 With the adsorbents, the decolorization rate was 70% or higher, and with some adsorbents, it was achieved to over 90%. Therefore, it was confirmed that efficient decolorization can be performed by adding adsorbents.

[0057] Furthermore, in the decolorization treatment of the adsorbent, when examining the change in decolorization rate with respect to treatment time, it was found that the decolorization rate was 70% or more after a treatment time of 30 minutes, confirming that efficient decolorization treatment is possible in a short time. [Industrial applicability]

[0058] This invention is widely applicable to dyed textile products such as clothing, can be implemented with minimal environmental impact, and is expected to make a significant contribution to building a sustainable industrial structure for the future. [Explanation of Symbols]

[0059] 1... Processing equipment, 10... Decolorization container, 11... Liquefied carbon dioxide cylinder, 12... Valve, 13... Supply pump, 14... Valve, 15... Safety valve, 16... Pressure gauge, 17... Oven, 18... Discharge container, 19... Discharge valve, 20... First recovery section, 21... Second recovery section

Claims

1. A method for processing textile products, comprising decolorizing textile products made from dyed fiber materials using a supercritical carbon dioxide fluid with a cosolvent or adsorbent added.

2. The method for processing textile products according to claim 1, wherein the amount of the co-solvent or adsorbent added is 2% of the bath volume or more.

3. The method for processing a textile product according to claim 1 or 2, wherein the textile product is made of polyester fibers and the dye is a disperse dye.

4. The method for processing a textile product according to claim 1 or 2, wherein the solubility parameter of the cosolvent or the adsorbent is close to the solubility parameter of the dye.

5. A textile processing apparatus for decolorizing textile products made of fibrous material dyed with dyes, comprising: a processing unit that contains the textile products together with a co-solvent or adsorbent; a supply unit that supplies carbon dioxide into the processing unit; a control unit that controls the temperature and pressure of the carbon dioxide filled in the processing unit to set the carbon dioxide in the processing unit to a predetermined temperature and pressure and performs decolorization in a supercritical fluid state; and a recovery unit that separates and recovers carbon dioxide, dye, and co-solvent or adsorbent from the processing liquid produced by the decolorization process.

6. The processing apparatus for textile products according to claim 5, wherein the processing unit is set such that the ratio of the amount of processing liquid to the amount of the textile product is 500 or more.

7. A recycled textile product which is a dyed textile product that has been decolorized, and in which the residual color rate of the fiber surface plasticized with supercritical carbon dioxide fluid is 10% or less.

8. The aforementioned textile product is a recycled textile product according to claim 7, comprising polyester fibers.

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