How recycled polyester fabric is made

Abstract

To provide a method for manufacturing a recycled polyester fabric having excellent performances in both a yield and hue.SOLUTION: A method for manufacturing a recycled polyester fabric executes a preliminary depolymerization step on a stock solution colored fabric, executes a posttreatment step on a preliminary depolymerization body, and obtains a recycled polyester fabric. The stock solution colored fabric contains a pigment and a polyethylene terephthalate resin, and a first particle size of the pigment is less than 1 micron. The preliminary depolymerization step includes: executing a first depolymerization process on the stock solution colored fabric, and forming an oligomer; and adding the oligomer to active carbon, executing a mixing process and a filtration process, separating the oligomer and the active carbon, and obtaining a preliminary depolymerization body. A second particle size of the active carbon is larger than the first particle size of the pigment. The posttreatment step includes a second depolymerization step, a monomer purification process, a polymerization process or a combination thereof.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing recycled polyester fabric. [Background technology]

[0002] Current polyester fabric recovery technologies often use pretreatment processes such as solvent extraction to remove dyes from the gaps between the fibers of the fabric to achieve effective recovery. However, these treatment methods cannot effectively separate the smaller particle size pigments dispersed in the resin of dope-dyed polyester fabric (e.g., due to the difficulty of filtration and the tendency of the pigments to adhere during the subsequent crystallization process), resulting in low yields. Summary of the Invention [Problem to be solved by the invention]

[0003] Smaller particle size pigments dispersed in the resin of dyed polyester fabrics cannot be effectively separated (e.g., they are difficult to filter and tend to adhere during the subsequent crystallization process), resulting in low yields. [Means for solving the problem]

[0004] The present invention provides a method for producing recycled polyester fabric that has excellent performance in both yield and color.

[0005] The method for producing a recycled polyester fabric of the present invention includes the following: providing a solution-colored fabric; subjecting the solution-colored fabric to a pre-depolymerization step; and subjecting the pre-depolymerized fabric to a post-treatment step to obtain a recycled polyester fabric. The solution-colored fabric includes a pigment and a polyethylene terephthalate resin, and the pigment has a first particle size of less than 1 micron. The pre-depolymerization step includes subjecting the solution-colored fabric to a first depolymerization process to form an oligomer; adding the oligomer to activated carbon; performing a mixing process and a filtration process to separate the oligomer from the activated carbon to obtain a pre-depolymerized fabric. The activated carbon has a second particle size larger than the first particle size of the pigment. The post-treatment step includes a second depolymerization process, a monomer purification process, a polymerization process, or a combination thereof.

[0006] In one embodiment of the present invention, the second particle size of the activated carbon is between more than 1 micron and less than or equal to 100 microns.

[0007] In one embodiment of the present invention, the weight ratio of pigment in the above-mentioned liquid-dyed material is between 1 wt% and 10 wt%.

[0008] In one embodiment of the present invention, the weight ratio of said activated carbon to oligomer is between 0.005 and 0.3.

[0009] In one embodiment of the present invention, the temperature at which the above-mentioned mixing process is carried out is between 110°C and 190°C.

[0010] In one embodiment of the present invention, the duration of the above-mentioned mixing process is between 5 minutes and 90 minutes.

[0011] In one embodiment of the present invention, the first depolymerization process described above includes using ethylene glycol and a catalyst.

[0012] In one embodiment of the present invention, the weight ratio of the catalyst to the liquid dye material is between 0.001 and 0.1.

[0013] In one embodiment of the present invention, the temperature at which the first depolymerization process is carried out is between 180°C and 220°C.

[0014] In one embodiment of the present invention, the duration of the first depolymerization process is between 5 minutes and 120 minutes. [Effects of the Invention]

[0015] Based on the above, the present invention introduces a pre-depolymerization step to generate weak agglomerates and strong aggregates between large particle size activated carbon and small particle size pigment, thereby effectively separating the pigment and resin through a filtration process, improving the efficiency of post-treatment steps, and further achieving excellent performance in both yield and color.

[0016] In order to make the above-mentioned features and advantages of the present invention clearer and easier to understand, the following embodiments are shown and described in detail with reference to the accompanying drawings. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a partial flow diagram of a method for producing recycled polyester fabric according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] In the following detailed description, for purposes of explanation and not limitation, exemplary embodiments disclosing specific details are set forth in order to provide a thorough understanding of various principles of the present invention. However, it will be apparent to one skilled in the art having the benefit of this disclosure that the present invention may be practiced in other embodiments that depart from the specific details disclosed herein. Moreover, descriptions of well-known devices, methods, and materials may be omitted so as not to obscure various principles of the present invention.

[0019] DETAILED DESCRIPTION OF THE INVENTION The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

[0020] Unless otherwise defined, all technical terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0021] The term "between," as used herein to define a range of values, is intended to include the endpoints and any ranges between those endpoints. For example, a size range between a first value and a second value means that the size range can include the first value, the second value, and any values ​​between the first value and the second value.

[0022] FIG. 1 is a partial flow schematic diagram of a method for producing recycled polyester fabric according to one embodiment of the present invention.

[0023] 1, the method for producing a recycled polyester fabric in this embodiment includes at least the following steps: First, as shown in step S110, a solution-dyed fabric is provided, where the solution-dyed fabric includes a pigment and a polyethylene terephthalate (PET) resin, and the first particle size of the pigment is less than 1 micrometer.

[0024] In some embodiments, the first particle size of the pigment is an average particle size, which may be 0.003 microns or greater, and the pigment includes, but is not limited to, carbon black or the like.

[0025] In some embodiments, the weight ratio of the pigment in the solution-dyed fabric is 1 wt% to 10 wt%, and the weight ratio of the resin in the solution-dyed fabric is 89 wt% to 99 wt%. If the pigment and resin cannot be effectively separated within these ratio ranges, it will have a negative impact on the efficiency of subsequent depolymerization and even affect the yield. Therefore, adopting the method for producing recycled polyester fabric of this embodiment within these ratio ranges will provide more benefits, but the present invention is not limited thereto.

[0026] In some embodiments, the liquid-dyed material is composed of a pigment and a polyethylene terephthalate resin, i.e., the sum of the weight percentage of the pigment in the liquid-dyed material and the weight percentage of the resin in the liquid-dyed material is 100 wt %, but the present invention is not limited thereto.

[0027] It should be noted that this embodiment does not limit the specific type of solution-dyed fabric, and any solution-dyed fabric that requires recycling and is produced by dispersing a suitable pigment in a suitable polyester resin and spinning the resulting material falls within the scope of protection of the present invention.

[0028] Next, as shown in step S120, the liquid-dyed material is subjected to a pre-depolymerization step. In this embodiment, the pre-depolymerization step can be performed by steps S121, S122, and S123. More specifically, as shown in step S121, the liquid-dyed material is subjected to a first depolymerization process to form oligomers. Then, as shown in step S122, the oligomers are added to activated carbon, and a mixing process is performed. Here, the second particle size of the activated carbon is larger than the first particle size of the pigment. Finally, as shown in step S123, a filtration process is performed to separate the oligomers from the activated carbon to obtain a pre-depolymerized product.

[0029] Therefore, in this embodiment, the pre-depolymerization step is introduced to cause weak and strong flocculation between the large particle size activated carbon and the small particle size pigment, which allows the pigment and resin to be effectively separated through the filtration process, improving the efficiency of the post-treatment step and further achieving excellent performance in both yield and color.

[0030] Furthermore, after using the aforementioned methods to weakly and strongly agglomerate nanoscale pigments (less than 1 micron), the particle size can be increased to 1 micron or greater. This allows the pigment to be separated using appropriate filtration methods, improving the efficiency of subsequent treatment processes (such as the second depolymerization process and crystal refinement process) and improving yield and color. Furthermore, since the activated carbon can be further used as a fuel for recovering thermal energy after the filtration process, using activated carbon to separate the pigment in the pre-depolymerization step also offers the advantages of easy waste disposal and low carbon dioxide emissions.

[0031] After performing the filtration process, as shown in step S130, the pre-depolymerization can be subjected to a post-treatment process to obtain a recycled polyester fabric, as shown in step S130, where the post-treatment process includes a second depolymerization process, a monomer purification process, a polymerization process, or a combination thereof.

[0032] Specific details of the various steps above are described in turn below.

[0033] <First depolymerization process>

[0034] In some embodiments, the temperature at which the first depolymerization process is carried out is between 180°C and 220°C, and may be between 190°C and 210°C to achieve favorable depolymerization efficiency and color.

[0035] In some embodiments, the duration of the first depolymerization process can be between 5 minutes and 120 minutes, such as between 10 minutes and 90 minutes.

[0036] In some embodiments, the first depolymerization process includes using ethylene glycol (EG) and a catalyst, where the catalyst includes an organometallic, such as zinc acetate, organotitanium, organoantimony, organoaluminum, an ionic liquid, or a combination thereof.

[0037] In some embodiments, the weight ratio of ethylene glycol to solution-colored material (ethylene glycol / solution-colored material) as fed in the first depolymerization process can be between 2 and 10, such as between 3 and 8.

[0038] In some embodiments, the weight ratio of catalyst to stock coloring material (catalyst / stock coloring material) as fed in the first depolymerization process can be between 0.001 and 0.1, for example, 0.005 and 0.05.

[0039] In some embodiments, the first depolymerization process further includes carrying out a heating process and / or a stirring process in a suitable manner, wherein the heating process is carried out at a temperature ranging from 190°C to 210°C and the stirring process is carried out for a time ranging from 10 minutes to 90 minutes, but the present invention is not limited thereto.

[0040] <Mixing process>

[0041] In some embodiments, the second particle size of the activated carbon in the mixing process is greater than 1 micron and less than or equal to 100 microns, for example, 2 microns to 75 microns, or 43 microns to 63 microns, thereby ensuring a larger size of the pigment to be separated and improving separation performance, but the present invention is not limited thereto.

[0042] In some embodiments, the temperature at which the mixing process is carried out can be between 110°C and 190°C, for example, between 120°C and 180°C.

[0043] In some embodiments, the duration of the mixing process can be between 5 minutes and 90 minutes, such as between 10 minutes and 60 minutes.

[0044] In some embodiments, the weight ratio of activated carbon to oligomer is between 0.005 and 0.3, e.g., between 0.005 and 0.15, or between 0.01 and 0.1, or between 0.025 and 0.3, or between 0.05 and 0.2.

[0045] In some embodiments, the weight ratio of activated carbon in the oligomer is between 0.5 wt % and 15 wt %, although the invention is not limited thereto.

[0046] In some embodiments, the mixing process is carried out through a stirring process, and the time is between 10 minutes and 60 minutes, but the present invention is not limited thereto, and any mixing of the oligomer and the activated carbon falls within the scope of protection of the present invention.

[0047] In some embodiments, when a heating process is used in the first depolymerization process, a cooling process can be carried out in an appropriate manner before carrying out the mixing process. Here, the cooling process is, for example, cooling the temperature from 120° C. to 180° C., but the present invention is not limited thereto. When a heating process is not used in the first depolymerization process, a separate cooling process does not need to be carried out.

[0048] <Filtration process>

[0049] In some embodiments, the pre-depolymerization with activated carbon is passed through a suitable filter to separate impurities such as pigments, where the filter pore size can be less than 1 micron, for example, less than 0.5 microns.

[0050] <Second depolymerization process>

[0051] In some embodiments, the temperature at which the second depolymerization process is carried out can be between 180°C and 220°C, such as between 190°C and 210°C.

[0052] In some embodiments, the duration of the second depolymerization process may be between 120 minutes and 480 minutes, or between 150 minutes and 360 minutes.

[0053] In some embodiments, the second depolymerization process includes using a catalyst, the catalyst including an organometallic, such as zinc acetate, organotitanium, organoantimony, organoaluminum, an ionic liquid, or a combination thereof.

[0054] In some embodiments, the weight ratio of catalyst to pre-depolymerized material (catalyst / pre-depolymerized material) as fed in the second depolymerization process can be between 0.0009 and 0.099, e.g., between 0.0048 and 0.048, where 1 part of dough can be depolymerized to about 1.1 parts of oligomers.

[0055] In some embodiments, the second depolymerization process further comprises carrying out a heating process and / or a stirring process in a suitable manner, wherein the heating process is carried out at a temperature ranging from 190° C. to 210° C. and the stirring process is carried out for a time ranging from 150 minutes to 360 minutes, but the invention is not limited thereto.

[0056] In some embodiments, the second depolymerization process further includes using ethylene glycol, wherein the weight ratio of ethylene glycol to pre-depolymerized polymer (ethylene glycol / pre-depolymerized polymer) when fed is between 0 and 10 (ethylene glycol can be added optionally, i.e., ethylene glycol can be omitted depending on actual design requirements), for example, between 3 and 8.

[0057] After the second depolymerization process, a bis(2-hydroxyethyl) terephthalate (BHET) monomer (hereinafter referred to as a crude BHET product) can be obtained. The crude BHET product may contain oligomers, but the present invention is not limited thereto.

[0058] <Monomer purification process>

[0059] The steps of the purification process of the crude BHET product may include cooling crystallization (e.g., in an ethylene glycol phase), separating oligomers (e.g., in an aqueous phase), adsorbing impurities (e.g., in an aqueous phase) using an adsorbent material (e.g., activated carbon), again performing cooling crystallization (e.g., in an aqueous phase), and / or drying, and may include operations known to those skilled in the art, but the present invention is not limited thereto.

[0060] In some embodiments, in the second depolymerization process, to improve the adsorption efficiency of the adsorbent material (e.g., activated carbon) for impurities (e.g., organic dyes), the specific surface area of ​​the adsorbent material (e.g., activated carbon) is greater than or equal to 400 m 2 / g to 4,000m 2 / g, and 2 / g to 2,000m 2 / g, but the present invention is not limited thereto.

[0061] The pH value of the adsorbent material (such as activated carbon) is preferably between 4 and 7, more preferably between 5 and 6.5, and the micropore volume is preferably between 0.20 ml / g and 2.00 ml / g, more preferably between 0.80 ml / g and 1.50 ml / g, although the present invention is not limited thereto.

[0062] <Polymerization process>

[0063] The BHET in the monomer purification process is polymerized. In one embodiment, the polymerization method is, for example, maintaining a pressure of 0.2 torr to 30 torr and a temperature of 240°C to 280°C for 20 to 120 minutes to polymerize into a recycled polyester (PET) fabric. In another embodiment, the polymerization method is maintaining a pressure of 360 torr and a temperature of 260°C for 30 minutes to carry out a first stage polymerization, and then maintaining a pressure of 0.5 torr and a temperature of 280°C for 30 minutes to carry out a second stage polymerization to obtain a recycled polyester (PET) fabric.

[0064] The effects of the present invention will be specifically explained below using examples and comparative examples, but the scope of the present invention is not limited to these examples.

[0065] The recycled polyester fabrics produced in each of the examples and comparative examples were evaluated by the following methods.

[0066] Yield: (weight of recycled polyester fabric / weight of polyester in solution-dyed fabric) x 100%.

[0067] Hue: We adopted the color space defined by the International Commission on Illumination (CIE) Lab. The Lab color space is a color-opposite space, with dimension L representing lightness (called the whiteness of a color) and a and b representing the color-opposite dimensions, and is a CIE XYZ color space coordinate based on nonlinear compression.

[0068] Examples 1 to 6 were produced by the following method.

[0069] In response to step S110, the liquid-dyed fabrics shown in Table 1 were provided.

[0070] Corresponding to step S121, the undiluted colored material was placed in a 1-liter three-neck glass flask, and ethylene glycol and a catalyst shown in Table 1 were added. The heating and stirring processes were carried out at the temperatures and times shown in Table 1 to form oligomers.

[0071] Corresponding to step S122, the oligomer was cooled to the temperature shown in Table 1, activated carbon was added, and a mixing process was carried out at the temperature and for the time shown in Table 1.

[0072] Corresponding to step S123, a filtration process was carried out using a 1 micron filter to separate the pigment and the activated carbon, and a filtered liquid (pre-depolymerized) was obtained.

[0073] Corresponding to the second depolymerization process in step S130, the liquid after preliminary depolymerization filtration was added to the catalyst shown in Table 1, and a heating reaction (crude BHET product) was carried out at the temperature and time shown therein.

[0074] Corresponding to step S130 of the monomer purification process, the BHET crude product was cooled from 195°C to 10°C to promote crystallization of the BHET crude product to form a solid so that it could be separated from the liquid (e.g., ethylene glycol) and filtered. Next, 210 grams of the resulting BHET filter cake was added to a three-neck glass flask, and water and activated carbon shown in Table 1 were added. The mixture was then heated to 90°C and stirred for 30 minutes. After filtering through a 5-micron filter, the filtrate was cooled from 90°C to 5°C, and operations such as crystallization, filtration, and drying of BHET were carried out to obtain BHET monomer.

[0075] Corresponding to the polymerization process of step S130, the BHET monomer was polymerized (first-stage polymerization was carried out at a pressure of 360 Torr and a temperature of 260°C for 30 minutes, and then second-stage polymerization was carried out at a pressure of 0.5 Torr and a temperature of 280°C for 30 minutes to obtain recycled polyester fabrics), thereby obtaining recycled polyester fabrics of Examples 1 to 6 with the colors and yields shown in Table 1.

[0076] [Table 1]

[0077] Comparative Examples 1 to 6 were produced by the following method.

[0078] First, a stock coloring material shown in Table 2 was prepared. A depolymerization process (similar to the second depolymerization process, but omitting the first depolymerization process) was performed. The stock coloring material was added to a 1-liter three-neck glass flask, and ethylene glycol and a catalyst shown in Table 2 were added. The heating and stirring processes were carried out at the temperature and time shown in Table 2 to form a crude BHET product. The crude BHET product was then cooled from 195°C to 10°C to promote crystallization of the BHET crude product and form a solid so that it could be separated from the liquid (e.g., ethylene glycol) and filtered. Next, 210 grams of the resulting BHET filter cake (containing 102 grams of ethylene glycol) was added to a three-neck glass flask, and water and activated carbon shown in Table 2 were added. The mixture was then heated to 90°C and stirred for 30 minutes. After filtering through a 5-micron filter, the filtrate was cooled from 90°C to 5°C, followed by crystallization, filtration, and drying to obtain BHET monomer. Finally, the BHET monomer was polymerized (first-stage polymerization was carried out at a pressure of 360 Torr and a temperature of 260°C for 30 minutes, and then second-stage polymerization was carried out at a pressure of 0.5 Torr and a temperature of 280°C for 30 minutes to obtain recycled polyester fabrics), to obtain recycled polyester fabrics of Comparative Examples 1 to 6 with the colors and yields shown in Table 2.

[0079] [Table 2]

[0080] The results in Tables 1 and 2 lead to the following conclusions: The recycled polyester fabric of the example has a yield of over 65%, and its L / a / b is 60.0% or more / ±2.0 / ±4.0, which gives it advantages such as excellent hue. In contrast, the recycled polyester fabric of the comparative example has a relatively low yield and an L / a / b of 48.4% / 1.1 / 4.4, which gives it disadvantages such as poor hue, because the solution-dyed fabric is unable to effectively remove the pigment before depolymerization (such as removing nanoscale fine pigments through a pre-depolymerization step, as in the example).

[0081] In summary, the present invention introduces a pre-depolymerization step to cause weak agglomeration and strong agglomeration between large particle size activated carbon and small particle size pigment, thereby enabling effective separation of the pigment and resin through a filtration process, improving the efficiency of post-treatment steps, and achieving excellent performance in both yield and color.

[0082] Although the present invention has been disclosed through the above embodiments, they are not intended to limit the present invention, and a person skilled in the art can make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the scope of the attached patent application. [Industrial Applicability]

[0083] The method for producing a recycled polyester fabric of the present invention can be applied to the field of recycled polyester fabrics. [Explanation of symbols]

[0084] S110, S120, S121, S122, S123, S130: Step

Claims

1. providing a solution-dyed substrate, the solution-dyed substrate comprising a pigment and a polyethylene terephthalate resin, and the pigment having a first particle size of less than 1 micron; The solution-colored fabric is subjected to a pre-depolymerization step, the pre-depolymerization step comprising: subjecting the solution-colored substrate to a first depolymerization process to form oligomers; adding the oligomer to activated carbon and performing a mixing process, wherein a second particle size of the activated carbon is larger than the first particle size of the pigment; performing a filtration process to separate the oligomers from the activated carbon to obtain a pre-depolymerized product; said performing comprising: performing a post-treatment step on the pre-depolymerization to obtain a recycled polyester fabric, wherein the post-treatment step includes a second depolymerization process, a monomer purification process, a polymerization process, or a combination thereof; Including, A method for producing recycled polyester fabric, wherein the monomer purification process includes adding another activated carbon.

2. the second particle size of the activated carbon is between greater than 1 micron and less than or equal to 100 microns; A method for producing the recycled polyester fabric according to claim 1.

3. The weight ratio of the pigment in the concentrate coloring material is between 1 wt% and 10 wt%; A method for producing the recycled polyester fabric according to claim 1.

4. the weight ratio of the activated carbon to the oligomer is between 0.005 and 0.3; A method for producing the recycled polyester fabric according to claim 1.

5. The temperature at which the mixing process is carried out is between 110°C and 190°C. A method for producing the recycled polyester fabric according to claim 1.

6. The duration of the mixing process is between 5 and 90 minutes. A method for producing the recycled polyester fabric according to claim 1.

7. the first depolymerization process includes using ethylene glycol and a catalyst; A method for producing the recycled polyester fabric according to claim 1.

8. The weight ratio of the catalyst to the liquid dye is between 0.001 and 0.1; The method for producing the recycled polyester fabric according to claim 7.

9. The temperature at which the first depolymerization process is carried out is between 180°C and 220°C. A method for producing the recycled polyester fabric according to claim 1.

10. The duration of the first depolymerization process is between 5 minutes and 120 minutes. A method for producing the recycled polyester fabric according to claim 1.

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