Decoloring method of polyester cloth

Abstract

The decolorizing method of the polyester cloth comprises the following steps that the polyester cloth is placed in an extraction device, the extraction device contains a decolorizing agent, and the decolorizing agent comprises a methoxy alcohol solvent and ion exchange resin; the temperature of the extraction device is set to be 100-120 DEG C, and the polyester cloth is subjected to a decolorizing reaction in the decolorizing agent. The decolorizing method of the polyester cloth disclosed by the invention can improve the decolorizing efficiency and achieve a good decolorizing effect.

Description

Technical Field

[0001] The present disclosure relates to a method for treating cloth, and more particularly to a method for decolorizing polyester cloth. Background Art

[0002] For dyed and recycled fabric, dyes are impurities. Conventional methods typically use solvent extraction to remove dyes, but solvent selection presents numerous challenges. For example, using supercritical carbon dioxide as a solvent requires processing under high pressure, and the carbon dioxide cannot be recycled. Furthermore, supercritical equipment is expensive, making it cost-effective. For another example, using acids as solvents can cause fabric degradation, affecting the regranulation properties of the recycled fabric. For another example, using activated carbon adsorption to remove dyes can easily cause the activated carbon to become lodged in the fabric's crevices, resulting in a grayish appearance and poor appearance. Therefore, achieving efficient decolorization of fabric while ensuring both solvent and fabric recyclability is a topic of active research for those skilled in the art. Summary of the Invention

[0003] The present disclosure provides a method for decolorizing polyester cloth, which can improve decolorization efficiency and achieve good decolorization effect.

[0004] According to one or more embodiments of the present disclosure, a method for decolorizing polyester fabric includes the following steps: placing the polyester into an extraction device, wherein the extraction device contains a decolorizing agent, wherein the decolorizing agent includes a methoxy alcohol solvent and an ion exchange resin; and setting the temperature of the extraction device to 100° C. to 120° C. to allow the polyester fabric to undergo a decolorization reaction in the decolorizing agent.

[0005] In one or more embodiments of the present disclosure, the content of the methoxy alcohol solvent is 73 parts by weight to 78 parts by weight, and the content of the ion exchange resin is 3 parts by weight to 8 parts by weight.

[0006] In one or more embodiments of the present disclosure, the methoxy alcohol solvent includes 3-methoxy-1-butanol, 3-methoxy-methyl-1-butanol, 3-methoxy-1-propanol, 1-methoxy-2-propanol, or a combination thereof.

[0007] In one or more embodiments of the present disclosure, the Hildebrand solubility parameter (δ) of the methoxy alcohol solvent is 20.2 MPa. 1 / 2 to 21.2MPa 1 / 2 .

[0008] In one or more embodiments of the present disclosure, the boiling point of the methoxy alcohol solvent is 170°C to 190°C.

[0009] In one or more embodiments of the present disclosure, the ion exchange resin is a nuclear grade ion exchange resin.

[0010] In one or more embodiments of the present disclosure, the decolorization reaction includes the following steps: the methoxy alcohol solvent in the decolorizer dissolves the disperse dye in the polyester cloth.

[0011] In one or more embodiments of the present disclosure, the decolorization reaction further comprises the following step: the ion exchange resin in the decolorizer decomposes the dissolved disperse dye.

[0012] In one or more embodiments of the present disclosure, the ion exchange resin decomposes the dissolved disperse dye to generate gas.

[0013] In one or more embodiments of the present disclosure, the method for decolorizing polyester cloth further includes the following steps: after the decolorization reaction, placing the activated carbon material in an extraction device; performing a filtration step to filter out the activated carbon material and recover the decolorizer; and placing the recovered decolorizer in the extraction device to repeat the next decolorization reaction.

[0014] According to the above-mentioned embodiment of the present disclosure, since the decolorization method for polyester cloth can decompose the dissolved dye while the decolorization reaction is being carried out, the decolorizer that has originally reached dye saturation can be restored to an unsaturated state. Therefore, it can not only improve the decolorization efficiency and achieve a good decolorization effect, but also avoid the need for continuous replacement of new solvents, thereby saving costs and improving environmental friendliness. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] To make the above and other objects, features, advantages and embodiments of the present disclosure more apparent and understandable, the accompanying drawings are described as follows:

[0016] Figure 1 A method for decolorizing polyester cloth according to one or more embodiments of the present disclosure is disclosed.

[0017]

Explanation of symbols

[0018] S10~S20: Steps DETAILED DESCRIPTION

[0019] The following drawings illustrate various embodiments of the present disclosure. For clarity, many practical details will be included in the following description. However, it should be understood that these practical details should not be construed as limiting the present disclosure. In other words, in some embodiments of the present disclosure, these practical details are not essential and therefore should not be construed as limiting the present disclosure. Furthermore, to simplify the drawings, some commonly used structures and components are depicted in simplified schematic form. Furthermore, for ease of viewing, the dimensions of the components in the drawings are not drawn to scale.

[0020] In this document, the structure of a polymer or group is sometimes represented using a skeleton formula. This representation may omit carbon atoms, hydrogen atoms, and carbon-hydrogen bonds. However, if an atom or atomic group is explicitly depicted in a structural formula, the depicted atom or atomic group shall prevail.

[0021] This disclosure provides a method for decolorizing polyester fabric. The method decomposes the dissolved dye during the decolorization reaction, restoring the previously saturated decolorizer to an unsaturated state, thereby improving decolorization efficiency and effectiveness. The polyester fabric disclosed herein may be, for example, recycled, dyed fabric.

[0022] See also Figure 1 This method for decolorizing polyester fabric according to one or more embodiments of the present disclosure includes steps S10 to S20. In step S10, the polyester is placed in an extraction device containing a decolorizing agent. In step S20, the temperature of the extraction device is set to a temperature that allows the decolorizing agent to react, causing the polyester fabric to undergo a decolorizing reaction in the decolorizing agent. The following description details these steps.

[0023] In step S10, polyester is arranged in an extraction device. In detail, the polyester cloth can be a cloth interwoven with a plurality of polyester fibers. In some embodiments, the material of the polyester cloth can be, for example, polyethylene terephthalate, polybutylene terephthalate, or a combination thereof. The extraction device is filled with a decolorizing agent, and the decolorizing agent includes a methoxy alcohol solvent and an ion exchange resin. Through the mutual matching of the methoxy alcohol solvent and the ion exchange resin, the decolorizing agent can first open the gaps between the polyester fibers (swelling), then dissolve the dye in the gaps, and continue to decompose the dissolved dye to ensure that the decolorizing agent can maintain an unsaturated state and continue to dissolve the dye in the polyester cloth, thereby improving the decolorizing efficiency and decolorizing effect.

[0024] In detail, the methoxy alcohol solvent in the discolorant can dissolve the disperse dyes in the polyester cloth. Compared to the generally commonly used benzene solvents (for example, xylene) and ether alcohol solvents, methoxy alcohol solvents not only have low toxicity, but also have low odor and biodegradability, which can provide environmental friendliness. In addition, because methoxy alcohol solvents have high solubility in water, it is conducive to waste liquid treatment. In addition, because methoxy alcohol solvents have a high flash point, it can improve operational safety. It is worth noting that polyester cloth has hydrophobicity, and dye has hydrophilicity, and because methoxy alcohol solvents belong to amphiphilic solvents, it has hydrophilicity and lipophilicity simultaneously, so methoxy alcohol solvents can first be infiltrated into the polyester cloth by its hydrophobicity so that the gap between the polyester fibers is opened, and then the dye is taken out from the gap by its hydrophilicity, so that the dye is thoroughly dissolved out from the polyester cloth effectively.

[0025] In some embodiments, the methoxy alcohol solvent may include 3-methoxy-1-butanol, 3-methoxy-methyl-1-butanol, 3-methoxy-1-propanol, or 1-methoxy-2-propanol, or a combination thereof. The methoxy alcohol solvents listed above not only have good amphiphilic properties, but also have low steric hindrance due to their molecular structures, and thus can facilitate entry into the gaps in the polyester fabric and remove the dye. In a preferred embodiment, the methoxy alcohol solvent may be 3-methoxy-1-butanol or 3-methoxy-methyl-1-butanol to achieve better results.

[0026] On the other hand, since the ion exchange resin disclosed herein requires high temperatures to decompose the dye dissolved from the polyester fabric, restoring the previously saturated decolorant to an unsaturated state, the decolorization reaction disclosed herein must be carried out at high temperatures. To address this, the methoxy alcohol solvent disclosed herein has a high boiling point, so even at high temperatures, the methoxy alcohol solvent does not become a gas and can still perform its decolorization function. In some embodiments, the boiling point of the methoxy alcohol solvent can be between 170°C and 190°C (e.g., 175°C, 180°C, or 185°C). From another perspective, the high boiling point of the methoxy alcohol solvent allows decolorization to be performed at relatively high temperatures, improving decolorization efficiency. It is worth noting that ether alcohol solvents are often used for decolorization in conventional techniques in this field. However, due to their strong odor, ether alcohol solvents with low boiling points must be selected to facilitate subsequent removal from the fabric (e.g., by heating). Because the ion exchange resin disclosed herein requires high temperatures to decompose the dye dissolved in the polyester fabric, if ether-alcohol solvents with low boiling points are used for decolorization, they will be converted into gas and lost at high temperatures, thus failing to achieve a satisfactory decolorization effect. Based on this, the present invention uses a methoxy alcohol solvent that is resistant to high temperatures (relatively high boiling points) for the decolorization reaction. This not only achieves a good decolorization effect, but also ensures that the polyester fabric does not retain any residual odor after decolorization.

[0027] As mentioned above, methoxy alcohol solvents are amphiphilic solvents with good amphiphilic properties, which can be reflected by the polarity of the methoxy alcohol solvents. In detail, in addition to selecting the methoxy alcohol solvents listed above, methoxy alcohol solvents can also be selected according to polarity. In some embodiments, methoxy alcohol solvents with polarity of 4 to 7 (for example, 4.7, 6.3 or 5.4) can be selected to achieve better decolorization effect. On the other hand, in addition to selecting the methoxy alcohol solvents listed above, methoxy alcohol solvents can also be selected according to the Hildebrand solubility parameter (δ). In detail, the so-called Hildebrand solubility parameter is a predicted value of the degree of interaction between materials defined by the regular solution theory (regular solution theory) imported by Hildebrand, which can reflect the state of mutual miscibility (also known as infinite miscibility) between materials. In some embodiments, the Brand solubility parameter can be selected to be 20.2MPa 1 / 2 to 21.2MPa 1 / 2 Methoxy alcohol solvent (e.g. 20.2 MPa 1 / 2 , 20.4MPa 1 / 2 or 21.2MPa 1 / 2 ), so that the methoxy alcohol solvent and the dye can have a better mutual solubility effect, thereby quickly removing the disperse dye from the polyester fibers.

[0028] On the other hand, the ion exchange resin in the decolorizing agent can decompose the dissolved disperse dye. In detail, the ion exchange resin disclosed herein can decompose the dye dissolved by the methoxy alcohol solvent at high temperature. The decomposed dye becomes gas and leaves the reaction tank, causing the concentration of the dye in the methoxy alcohol solvent to decrease. In this way, the methoxy alcohol solvent that has already reached dye saturation is restored to an unsaturated state to accelerate the dissolution rate of the dye from the polyester cloth, thereby improving the decolorization efficiency and decolorization effect, and there is no need to continuously replace new solvents to completely dissolve the dye in the polyester cloth. For example, the ion exchange resin can decompose and reorganize the dye to form carbon dioxide, methane, ammonia, nitrogen, hydrogen or other organic gases. The following method (1) is a schematic diagram of dye decomposition, and the dotted line represents the decomposition position.

[0029]

[0030] In some embodiments, the ion exchange resin may be a nuclear-grade ion exchange resin. In detail, the nuclear-grade ion exchange resin can dissociate into anions and cations at the same time, and the anions and cations can break the molecular structure of the dye and generate gas. Compared with ion exchange resins that only have anions or cations, the nuclear-grade ion exchange resin can dissociate into anions and cations at the same time, so it can break more types of functional groups in the dye molecules, and therefore can more efficiently decompose the dye, thereby improving the decolorization efficiency. In addition, since the nuclear-grade ion exchange resin is a strong acid and strong base type ion exchange resin, it can dissociate into strong acid radicals and strong base radicals (H+, OH-), which helps to break the molecular structure of the dye. Specifically, the nuclear-grade ion exchange resin may be, for example, Purolite Ultra Clean TM UCW3700 (brand and model).

[0031] In general, by making the discoloring agent contain methoxy alcohol solvent and ion exchange resin, the discoloring agent can decompose the dissolved dye while carrying out decolorization reaction, thereby improving decolorization efficiency and decolorization effect. In some embodiments, the content of methoxy alcohol solvent is 73 weight parts to 78 weight parts, and the content of ion exchange resin is 3 weight parts to 8 weight parts. By making the ratio of methoxy alcohol solvent and ion exchange resin fall in the above range, the recovery rate of decolorization efficiency and methoxy alcohol solvent can be taken into account. In detail, if the ratio of ion exchange resin is too low (less than 3 weight parts), methoxy alcohol solvent is easier to reach dye saturation, and the degree of improvement of decolorization efficiency is limited; If the ratio of ion exchange resin is too high (greater than 8 weight parts), ion exchange resin also can decompose methoxy alcohol solvent simultaneously, resulting in a low recovery rate of methoxy alcohol solvent.

[0032] In step S20, the temperature of the extraction device is set to 100°C to 120°C (for example, 110°C), so that the polyester cloth undergoes a decolorization reaction in the decolorizer. As mentioned above, at high temperatures (100°C to 120°C), the methoxy alcohol solvent in the decolorizer dissolves the disperse dyes in the polyester cloth, and the ion exchange resin in the decolorizer decomposes the dissolved disperse dyes. In this way, not only can the decolorization efficiency be improved, but there is no need to constantly replace new solvents, saving costs and improving environmental friendliness. In some embodiments, the decolorization reaction time can be 4.5 to 14 hours. In some embodiments, the decolorization reaction is started at normal pressure (about 760 mmHg), and gradually has an increasing pressure as the gas is generated, and the increase in pressure also contributes to the improvement of the decolorization efficiency.

[0033] After the decolorization reaction, a decolorized polyester fabric is obtained. In some embodiments, the structure of the decolorized polyester fabric remains intact, indicating that the decolorizing agent used in the present disclosure does not destroy the structure of the polyester fabric but merely dissolves the dye from the fabric. In some embodiments, the intrinsic viscosity of the decolorized polyester fabric can be between 0.550 dL / g and 0.617 dL / g, meeting the standards for regranulation.

[0034] On the other hand, after the decolorization reaction, the extraction device still contains decolorizing agent. In some embodiments, the decolorizing agent can be further recovered after the decolorization reaction. Specifically, the polyester cloth decolorization method may further include steps S30 and S40. In step S30, an activated carbon material is placed in the extraction device to adsorb the dye and dye residue in the decolorizing agent. In some embodiments, the weight percentage concentration of the activated carbon material in the decolorizing agent is 0.5% to 10% to ensure complete adsorption of the dye. In step S40, a filtration step is performed to remove the activated carbon material and recover the decolorizing agent. In some embodiments, the decolorizing agent recovery rate can be 75.2% to 84.7% ([volume of recovered decolorizing agent / volume of recovered agent before reaction] × 100%). As mentioned above, the ratio of methoxy alcohol solvent to ion exchange resin can affect the decolorizing agent recovery rate. After the decolorizing agent is recovered, the recovered decolorizing agent can be placed in the extraction device to repeat the next decolorization reaction. This saves costs and improves environmental friendliness. It's worth noting that conventional techniques in this field often use activated carbon materials to absorb dyes from fabrics for decolorization. However, this method can easily cause the activated carbon material to become lodged in the fabric's crevices, resulting in a light gray color and poor appearance. In the present disclosure, the activated carbon material is added after the polyester fabric is removed and is not required during the decolorization reaction. This prevents the activated carbon material from becoming lodged in the polyester fabric, improving the fabric's appearance while maintaining its structural integrity and, consequently, its intrinsic viscosity, making it suitable for spinning and pelletizing.

[0035] The following will describe the features and effects of the present disclosure in more detail with reference to various comparative examples and examples. It should be understood that the materials used, their contents and ratios, processing details, and processing procedures may be appropriately modified according to common knowledge in the art without exceeding the scope of the present disclosure. Therefore, the present disclosure should not be construed as being limited by the examples described below.

[0036] Table 1 lists the decolorizing agent formulations, decolorizing method details, and color properties after decolorization for each comparative example and each example. The decolorization method used in each example is the same as described in steps S10-S40 above, with the decolorization reaction performed at 120°C and the polyester fabric being made of polyethylene terephthalate (PET). The decolorization method used in each comparative example is identical to that used in each example, differing only in the decolorizing agent formulation used.

[0037] Table 1

[0038]

[0039]

[0040] [Note 1]

[0041] A: 3-methoxy-methyl-1-butanol;

[0042] B: 3-methoxy-methyl-1-butanol + nuclear grade ion exchange resin (Purolite Ultra Clean™ UCW3700), wherein the content of 3-methoxy-methyl-1-butanol is 75 parts by weight and the content of the nuclear grade ion exchange resin is 5 parts by weight;

[0043] C: 3-methoxy-1-butanol;

[0044] D: 3-methoxy-methyl-1-butanol + water, the volume ratio of 3-methoxy-methyl-1-butanol to water is 9:1.

[0045] [Note 2]

[0046] K / S value: K is the colorant absorption coefficient, S is the colorant scattering coefficient.

[0047] [Note 3]

[0048] Decolorization rate (%) = [(K / S value before decolorization - K / S value after decolorization) / K / S value before decolorization] × 100%.

[0049] The results in Table 1 show that when 3-methoxy-methyl-1-butanol is combined with a nuclear-grade ion exchange resin as a decolorizing agent (Example B), the decolorization rate reaches over 98.34%. The decolorization time (reaction time) is significantly reduced compared to the comparative examples (A, C, and D), demonstrating a significant improvement in reaction efficiency. Furthermore, when 3-methoxy-methyl-1-butanol is combined with a nuclear-grade ion exchange resin as a decolorizing agent, the decolorized polyester fabric exhibits color difference and whiteness close to that of undyed polyester fabric, demonstrating the high reusability of the recycled polyester fabric.

[0050] In summary, the polyester fabric decolorization method disclosed herein decomposes the dissolved dye during the decolorization reaction, restoring the previously dye-saturated decolorizer to an unsaturated state. This not only improves decolorization efficiency and effectiveness, but also eliminates the need for constant solvent replacement, thereby saving costs and improving environmental friendliness. Furthermore, the decolorizer disclosed herein can be recycled and reused with a high recovery rate, thus achieving a circular economy. Furthermore, the recycled polyester fabric maintains its original structural integrity, resulting in a suitable intrinsic viscosity suitable for spinning and pelletizing.

[0051] Although the present disclosure has been disclosed above in terms of implementation methods, this is not intended to limit the present disclosure. Anyone skilled in the art may make various changes and modifications without departing from the spirit and scope of the present disclosure. Therefore, the scope of protection of the present disclosure shall be determined by the appended claims.

Claims

1. A method for decolorizing polyester cloth, characterized in that: include: Placing a polyester in an extraction device, wherein the extraction device contains a decolorizing agent, and the decolorizing agent includes a methoxy alcohol solvent and an ion exchange resin; The temperature of the extraction device is set to 100° C. to 120° C., so that the polyester cloth undergoes a decolorization reaction in the decolorizing agent.

2. The method for decolorizing polyester cloth according to claim 1, characterized in that: The content of the methoxy alcohol solvent is 73 parts by weight to 78 parts by weight, and the content of the ion exchange resin is 3 parts by weight to 8 parts by weight.

3. The method for decolorizing polyester cloth according to claim 1, wherein: The methoxy alcohol solvent includes 3-methoxy-1-butanol, 3-methoxy-methyl-1-butanol, 3-methoxy-1-propanol, 1-methoxy-2-propanol or a combination thereof.

4. The method for decolorizing polyester cloth according to claim 1, wherein: The Hildebrand solubility parameter of the methoxy alcohol solvent is 20.2 MPa 1 / 2 Up to 21.2MPa 1 / 2 .

5. The method for decolorizing polyester cloth according to claim 1, wherein: The methoxy alcohol solvent has a boiling point of 170°C to 190°C.

6. The method for decolorizing polyester cloth according to claim 1, wherein: The ion exchange resin is a nuclear grade ion exchange resin.

7. The method for decolorizing polyester cloth according to claim 1, wherein: The decolorization reaction includes: The methoxy alcohol solvent in the decolorizing agent dissolves a disperse dye in the polyester cloth.

8. The method for decolorizing polyester cloth according to claim 7, characterized in that: The decolorization reaction also includes: The ion exchange resin in the decolorizing agent decomposes the dissolved disperse dye.

9. The method for decolorizing polyester cloth according to claim 8, characterized in that: The ion exchange resin decomposes the dissolved disperse dye to generate gas.

10. The method for decolorizing polyester cloth according to claim 1, wherein: Also includes: After the decolorization reaction is performed, an activated carbon material is placed in the extraction device; Performing a filtering step to filter out the activated carbon material and recover the decolorizing agent; and The recovered decolorizing agent is placed in the extraction device to repeat the decolorizing reaction for the next time.

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