Manufacturing method of recycled polyester fabric

Abstract

The invention provides a manufacturing method of a recycled polyester fabric. The manufacturing method comprises the following steps: providing an original fabric; a pre-depolymerization step is performed on the original fabric and a post-treatment step is performed on the pre-depolymerized fabric to obtain a recycled polyester fabric. The original fabric includes a pigment and a polyethylene terephthalate resin, and the first particle size of the pigment is less than 1 micron. The pre-depolymerization step comprises performing a first depolymerization procedure on the original fabric to form an oligomer; adding the oligomer into activated carbon to execute a mixing procedure and a filtering procedure so as to separate the oligomer from the activated carbon and obtain a pre-depolymerized product; the second particle size of the activated carbon is larger than the first particle size of the pigment. The post-treatment step includes a second depolymerization procedure, a monomer purification procedure, a polymerization procedure, or a combination thereof.

Description

Technical Field

[0001] The invention relates to a method for manufacturing recycled polyester fabric. Background Art

[0002] Current polyester fabric recycling technologies often utilize pre-treatment processes such as solvent extraction for decolorization, separating the dye from the interstices between fabric fibers to achieve recycling. However, these methods are ineffective in separating the smaller pigment particles dispersed in the resin within dope-dyed polyester fabrics (e.g., they are difficult to filter or easily adhere to during subsequent crystallization), resulting in low yields. Summary of the Invention

[0003] The present invention provides a method for producing recycled polyester fabric, which has good performance in both yield and color.

[0004] The present invention provides a method for producing recycled polyester fabric, comprising providing an original fabric; performing a pre-depolymerization step on the original fabric; and performing a post-processing step on the pre-depolymer to obtain the recycled polyester fabric. The original fabric comprises a pigment and a polyethylene terephthalate resin, wherein the first particle size of the pigment is less than 1 micron. The pre-depolymerization step comprises performing a first depolymerization step on the original fabric to form oligomers; adding the oligomers to activated carbon, performing a mixing step, and performing a filtration step to separate the oligomers from the activated carbon and obtain the pre-depolymers. The second particle size of the activated carbon is larger than the first particle size of the pigment. The post-processing step comprises a second depolymerization step, a monomer purification step, a polymerization step, or a combination thereof.

[0005] In one embodiment of the present invention, the second particle size of the activated carbon is greater than 1 micron and less than or equal to 100 microns.

[0006] In one embodiment of the present invention, the weight ratio of the pigment in the original fabric is between 1 wt % and 10 wt %.

[0007] In one embodiment of the present invention, the weight ratio of the activated carbon to the oligomer is between 0.005 and 0.3.

[0008] In one embodiment of the present invention, the mixing process is performed at a temperature between 110° C. and 190° C.

[0009] In one embodiment of the present invention, the execution time of the mixing process is between 5 minutes and 90 minutes.

[0010] In one embodiment of the present invention, the first depolymerization process includes using ethylene glycol and a catalyst.

[0011] In one embodiment of the present invention, the weight ratio of the catalyst to the original fabric is between 0.001 and 0.1.

[0012] In one embodiment of the present invention, the first depolymerization process is performed at a temperature between 180°C and 220°C.

[0013] In one embodiment of the present invention, the execution time of the first depolymerization process is between 5 minutes and 120 minutes.

[0014] Based on the above, the present invention introduces a pre-depolymerization step to cause large-particle activated carbon and small-particle pigment to aggregate and agglomerate. This allows for effective separation of the pigment and resin through filtration, increases the efficiency of post-processing steps, and achieves excellent performance in both yield and color.

[0015] In order to make the above features and advantages of the present invention more clearly understood, embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 FIG. 4 is a partial flow diagram of a method for manufacturing recycled polyester fabric according to an embodiment of the present invention. DETAILED DESCRIPTION

[0017] In the following detailed description, for purposes of illustration and not limitation, exemplary embodiments disclosing specific details are described to provide a thorough understanding of the various principles of the present invention. However, it will be apparent to one of ordinary skill in the art, having benefit of this disclosure, that the present invention may be practiced in other embodiments that depart from the specific details disclosed herein. Furthermore, descriptions of well-known devices, methods, and materials may be omitted so as not to obscure the description of the various principles of the present invention.

[0018] The present invention will be more fully described with reference to the drawings of this embodiment. However, the present invention may be embodied in various forms and should not be limited to the embodiments described herein.

[0019] Unless otherwise defined, all 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.

[0020] The term "between" used in this specification to define a numerical range is intended to cover ranges equal to and between the endpoint values. For example, a size range between a first value and a second value means that the size range can cover the first value, the second value, and any value between the first value and the second value.

[0021] Figure 1 FIG. 4 is a partial flow diagram of a method for manufacturing recycled polyester fabric according to an embodiment of the present invention.

[0022] Please refer to Figure 1 The method for manufacturing recycled polyester fabric of this embodiment includes at least the following steps: First, as shown in step S110, providing an original fabric, wherein the original fabric includes a pigment and a polyethylene terephthalate (PET) resin, and the first particle size of the pigment is less than 1 micrometer.

[0023] In some embodiments, the first particle size of the pigment is an average particle size, which may be greater than or equal to 0.003 μm, and the pigment includes carbon black or the like, but the present invention is not limited thereto.

[0024] In some embodiments, the weight ratio of the pigment in the original fabric is between 1 wt% and 10 wt%, while the weight ratio of the resin in the original fabric is between 89 wt% and 99 wt%. Within this ratio range, if the pigment and resin cannot be effectively separated, the subsequent depolymerization efficiency will be adversely affected, thereby affecting the yield. Therefore, within this ratio range, the method for manufacturing recycled polyester fabric of this embodiment can be more advantageous, but the present invention is not limited thereto.

[0025] In some embodiments, the original fabric is composed of pigment and polyethylene terephthalate resin, that is, the sum of the weight ratio of the pigment in the original fabric and the weight ratio of the resin in the original fabric is 100 wt %, but the present invention is not limited thereto.

[0026] It should be noted that this embodiment does not limit the specific type of original fabric. As long as the original fabric is made by dispersing suitable pigments in suitable polyester resins and then spinning them into waste and recycled original fabrics, they all fall within the scope of protection of the present invention.

[0027] Next, as shown in step S120, a pre-depolymerization step is performed on the original fabric. In this embodiment, the pre-depolymerization step can be performed through steps S121, S122, and S123. Specifically, as shown in step S121, the original fabric undergoes a first depolymerization step to form oligomers. Then, as shown in step S122, the oligomers are added to activated carbon and mixed, wherein 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 step is performed to separate the oligomers from the activated carbon and obtain the pre-depolymerized product.

[0028] Accordingly, this embodiment introduces a pre-depolymerization step to aggregate and agglomerate the large-particle activated carbon and the small-particle pigment. This allows for effective separation of the pigment and resin through filtration, increases the efficiency of the post-processing step, and achieves excellent performance in both yield and color.

[0029] Furthermore, by aggregating and agglomerating nano-pigments (less than 1 micron) using the aforementioned method, their particle size can be increased to over 1 micron. This allows for the separation of the pigments using suitable filtration methods. This pigment removal improves the efficiency of post-processing steps (such as the secondary depolymerization step and crystallization purification), thereby increasing yield and color. Furthermore, after the filtration step, the activated carbon can be further used as fuel rods to recover heat. Therefore, using activated carbon to separate pigments in the pre-depolymerization step offers advantages such as easier waste disposal and a lower carbon footprint.

[0030] After the filtration process is performed, the pre-depolymerized product may be subjected to a post-processing process as shown in step S130 to obtain recycled polyester fabric, wherein the post-processing process includes a second depolymerization process, a monomer purification process, a polymerization process, or a combination thereof.

[0031] The following will illustrate the specific details of the different procedures in the above steps in sequence.

[0032] <First Depolymerization Procedure>

[0033] In some embodiments, the first depolymerization process is performed at a temperature between 180° C. and 220° C., for example, between 190° C. and 210° C. to achieve better depolymerization efficiency and color.

[0034] In some embodiments, the first deaggregation process may be performed for a time period ranging from 5 minutes to 120 minutes, for example, from 10 minutes to 90 minutes.

[0035] In some embodiments, the first depolymerization process includes using ethylene glycol (EG) and a catalyst, wherein the catalyst includes an organometallic, and the organometallic is, for example, zinc acetate, organotitanium, organoantimony, organoaluminum, an ionic liquid, or a combination thereof.

[0036] In some embodiments, the weight ratio of ethylene glycol to original fabric (ethylene glycol / original fabric) when feeding the first depolymerization process is between 2 and 10, for example, between 3 and 8.

[0037] In some embodiments, the weight ratio of the catalyst to the original fabric (catalyst / original fabric) when feeding the first depolymerization process is between 0.001 and 0.1, for example, between 0.005 and 0.05.

[0038] In some embodiments, the first depolymerization process further comprises performing a heating process and / or a stirring process by a suitable method, wherein the heating process is performed at a temperature ranging from 190° C. to 210° C., and the stirring process is performed for a time ranging from 10 minutes to 90 minutes, but the present invention is not limited thereto.

[0039] <Mixed Program>

[0040] 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, it can be between 2 microns and 75 microns, or it can be between 43 microns and 63 microns. In this way, the size of the pigment to be separated can be effectively increased and the separation ability can be enhanced, but the present invention is not limited to this.

[0041] In some embodiments, the mixing process is performed at a temperature between 110° C. and 190° C., for example, between 120° C. and 180° C.

[0042] In some embodiments, the mixing process may be performed for a time period ranging from 5 minutes to 90 minutes, for example, from 10 minutes to 60 minutes.

[0043] In some embodiments, the weight ratio of activated carbon to oligomer is between 0.005 and 0.3, such as 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.

[0044] In some embodiments, the weight ratio of activated carbon to the oligomer is between 0.5 wt % and 15 wt %, but the present invention is not limited thereto.

[0045] In some embodiments, the mixing process is performed by a stirring process for a time ranging from 10 minutes to 60 minutes, but the present invention is not limited thereto. As long as the oligomer and the activated carbon are mixed together, it falls within the scope of protection of the present invention.

[0046] In some embodiments, when a heating process is used in the first depolymerization process, a cooling process may be performed in a suitable manner before the mixing process is performed. The cooling process may be, for example, to reduce the temperature to between 120° C. and 180° C. However, the present invention is not limited thereto. When a heating process is not used in the first depolymerization process, the cooling process may not be performed additionally.

[0047] <Filter>

[0048] In some embodiments, the pre-depolymer containing activated carbon is passed through a suitable filter to separate impurities such as pigments, wherein the pore size of the filter is less than or equal to 1 micron, for example, less than 0.5 micron.

[0049] <Second Depolymerization Procedure>

[0050] In some embodiments, the second depolymerization process is performed at a temperature between 180°C and 220°C, for example, between 190°C and 210°C.

[0051] In some embodiments, the second disaggregation process is performed for a time period between 120 minutes and 480 minutes, or, alternatively, between 150 minutes and 360 minutes.

[0052] In some embodiments, the second depolymerization process comprises using a catalyst, wherein the catalyst comprises an organometallic, and the organometallic is, for example, zinc acetate, organotitanium, organoantimony, organoaluminum, an ionic liquid, or a combination thereof.

[0053] In some embodiments, the weight ratio of catalyst to pre-depolymer (catalyst / pre-depolymer) during the second depolymerization step is between 0.0009 and 0.099, for example, between 0.0048 and 0.048. Here, 1 part of fabric can be depolymerized into approximately 1.1 parts of oligomers.

[0054] In some embodiments, the second depolymerization process further comprises performing a heating process and / or a stirring process by a suitable method, wherein the heating process is performed at a temperature ranging from 190° C. to 210° C., and the stirring process is performed for a time ranging from 150 minutes to 360 minutes, but the present invention is not limited thereto.

[0055] In some embodiments, the second depolymerization process further includes the use of ethylene glycol, wherein the weight ratio of ethylene glycol to pre-depolymer (ethylene glycol / pre-depolymer) during feeding is between 0 and 10 (ethylene glycol is optional, i.e., ethylene glycol can be omitted depending on actual design requirements), for example, between 3 and 8.

[0056] Here, after performing the second depolymerization procedure, bis(2-HydroxyEthyl)Terephthalate (BHET) monomer (hereinafter referred to as BHET crude product) can be obtained, wherein the BHET crude product may contain oligomers, but the present invention is not limited thereto.

[0057] <Monomer Purification Procedure>

[0058] The steps of the purification process of the crude BHET product may include: performing crystallization by cooling (for example, in an ethylene glycol phase), separating oligomers (for example, in an aqueous phase), adsorbing impurities by an adsorption material (such as activated carbon) (for example, in an aqueous phase), crystallizing by cooling again (for example, in an aqueous phase), and / or drying, etc., which are known to those skilled in the art, but the present invention is not limited thereto.

[0059] In some embodiments, in order to improve the adsorption efficiency of the adsorption material (such as activated carbon) for impurities (such as organic dyes) in the second depolymerization process, the specific surface area of ​​the adsorption material (such as activated carbon) is preferably between 400m2 / g to 4,000m 2 / g, and preferably between 800m 2 / g to 2,000m 2 / g, but the present invention is not limited thereto.

[0060] In addition, the pH value of the adsorption material (such as activated carbon) is preferably between 4 and 7, and more preferably between 5 and 6.5, and its micropore volume is preferably between 0.20 ml / g and 2.00 ml / g, and more preferably between 0.80 ml / g and 1.50 ml / g, but the present invention is not limited thereto.

[0061] <Aggregation Procedure>

[0062] The BHET obtained in the monomer purification process is polymerized. In one embodiment, the polymerization method is, for example, performed at a pressure of 0.2 torr to 30 torr and a temperature of 240° C. to 280° C. for 20 to 120 minutes to produce recycled polyester (PET) fabric. In another embodiment, the polymerization method is performed at a pressure of 360 torr and a temperature of 260° C. for 30 minutes in the first stage, followed by a second stage polymerization at a pressure of 0.5 torr and a temperature of 280° C. for 30 minutes to produce recycled polyester (PET) fabric.

[0063] The following examples and comparative examples are given to illustrate the effects of the present invention, but the scope of the present invention is not limited to the scope of the examples.

[0064] The recycled polyester fabrics prepared in the Examples and Comparative Examples were evaluated according to the following methods.

[0065] Yield: (weight of recycled polyester fabric / weight of polyester in original fabric) x 100%.

[0066] Hue: Uses the color space defined by the CIE Lab International Commission on Illumination. The Lab color space is a color-opponent space with the dimension L representing lightness (also known as the whiteness of a color), and a and b representing the color-opponent dimensions. It is based on the nonlinearly compressed CIE XYZ color space coordinates.

[0067] Examples 1 to 6 were produced in the following manner.

[0068] Corresponding to step S110 , the original fabric shown in Table 1 is provided.

[0069] Corresponding to step S121 , the original fabric is placed in a 1-liter three-necked glass flask, ethylene glycol and a catalyst shown in Table 1 are poured into it, and a heating process and a stirring process are performed at the temperature and time shown in Table 1 to form oligomers.

[0070] Corresponding to step S122 , the oligomer is cooled to the temperature shown in Table 1 and the activated carbon therein is mixed at the temperature and time shown in Table 1 .

[0071] Corresponding to step S123 , a filtration process is performed using a 1-micron filter to separate the pigment from the activated carbon, and a filtered liquid (pre-depolymerized product) is obtained.

[0072] Corresponding to the second depolymerization process of step S130 , the liquid after the pre-depolymerization is filtered is added to the catalyst shown in Table 1 and a heating reaction is performed at the temperature and time therein (BHET crude product).

[0073] In the monomer purification process corresponding to step S130, the crude BHET product was cooled from 195°C to 10°C to induce crystallization of the BHET into a solid, allowing it to be separated from the liquid (e.g., ethylene glycol) and filtered. Next, 210 g of the resulting BHET filter cake was placed in a three-necked glass flask, and the water and activated carbon listed 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 for BHET crystallization, filtration, and drying to obtain BHET monomer.

[0074] In the polymerization process corresponding to step S130, the BHET monomer was polymerized (a first stage polymerization was performed at a pressure of 360 Torr and a temperature of 260° C. for 30 minutes, followed by a second stage polymerization at a pressure of 0.5 Torr and a temperature of 280° C. for 30 minutes to obtain recycled polyester fabric) to obtain the recycled polyester fabrics of Examples 1 to 6 having the hues and yields shown in Table 1.

[0075] Table 1

[0076]

[0077]

[0078] Comparative Examples 1 to 6 were produced in the following manner.

[0079] First, a raw fabric as shown in Table 2 was provided. Next, a depolymerization process (similar to the second depolymerization process, but without the first depolymerization process) was performed. The raw fabric was placed in a 1-liter three-necked glass flask, and the ethylene glycol and catalyst listed in Table 2 were added. A heating and stirring process was performed at the temperature and time specified in Table 2 to form a crude BHET product. The crude BHET product was then cooled from 195°C to 10°C to induce crystallization of the crude BHET into a solid, which could be separated from the liquid (e.g., ethylene glycol) by filtration. Next, 210 g of the resulting BHET filter cake (containing 102 g of ethylene glycol) was placed in a three-necked glass flask, and water and activated carbon as 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 for BHET crystallization, filtration, and drying to obtain BHET monomer. Finally, the BHET monomer was polymerized (at a pressure of 360 Torr and a temperature of 260° C. for 30 minutes for the first stage polymerization, followed by a pressure of 0.5 Torr and a temperature of 280° C. for 30 minutes for the second stage polymerization to obtain recycled polyester fabric) to obtain the recycled polyester fabrics of Comparative Examples 1 to 6, with the hues and yields shown in Table 2.

[0080] Table 2

[0081]

[0082]

[0083] The results in Tables 1 and 2 indicate that the recycled polyester fabric of the Example has a yield exceeding 65%, and its L / a / b ratio is greater than 60.0% / ±2.0 / ±4.0, thus exhibiting advantages such as good hue. In contrast, the recycled polyester fabric of the Comparative Example has a lower yield, with L / a / b ratios of 48.4% / 1.1 / 4.4, due to the inability to effectively remove pigments from the original fabric prior to depolymerization (e.g., the Example utilizes a pre-depolymerization step to remove nano-sized pigments). Furthermore, the comparative example also exhibits disadvantages such as poor hue.

[0084] In summary, the present invention introduces a pre-depolymerization step to cause large-particle activated carbon and small-particle pigment to aggregate. This allows for effective separation of the pigment and resin through filtration, increases the efficiency of post-processing steps, and achieves excellent performance in both yield and color.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for producing recycled polyester fabric, characterized in that: include: Providing an original fabric, wherein the original fabric comprises a pigment and a polyethylene terephthalate resin, and a first particle size of the pigment is less than 1 micron; Performing a pre-depolymerization step on the original fabric, wherein the pre-depolymerization step comprises: subjecting the original fabric to a first depolymerization process to form oligomers; adding the oligomer to activated carbon and performing a mixing procedure, wherein a second particle size of the activated carbon is larger than the first particle size of the pigment; and performing a filtration process to separate the oligomers from the activated carbon and obtain a pre-depolymerized product; and The pre-depolymerized product is subjected to a post-processing step to obtain the recycled polyester fabric, wherein the post-processing step comprises a second depolymerization procedure, a monomer purification procedure, a polymerization procedure, or a combination thereof.

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

3. The method for producing recycled polyester fabric according to claim 1, wherein: The weight proportion of the pigment in the original fabric is between 1 wt % and 10 wt %.

4. The method for producing recycled polyester fabric according to claim 1, wherein: The weight ratio of the activated carbon to the oligomer is between 0.005 and 0.

3.

5. The method for producing recycled polyester fabric according to claim 1, wherein: The mixing process is performed at a temperature between 110°C and 190°C.

6. The method for producing recycled polyester fabric according to claim 1, wherein: The mixing procedure took between 5 and 90 minutes to perform.

7. The method for producing recycled polyester fabric according to claim 1, wherein: The first depolymerization process includes using ethylene glycol and a catalyst.

8. The method for producing recycled polyester fabric according to claim 7, wherein: The weight ratio of the catalyst to the original fabric is between 0.001 and 0.

1.

9. The method for producing recycled polyester fabric according to claim 1, wherein: The first depolymerization process is performed at a temperature between 180°C and 220°C.

10. The method for producing recycled polyester fabric according to claim 1, wherein: The execution time of the first disaggregation process is between 5 minutes and 120 minutes.

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