Method for manufacturing thermoplastic polyester elastomers

Abstract

The present invention provides a method for producing thermoplastic polyester elastomers that can effectively recycle recovered polyester and reduce recycling costs. [Solution] This method includes the steps of: providing a recovered polyester containing polyethylene terephthalate; performing a first depolymerization step which includes mixing the recovered polyester with a polyethylene terephthalate oligomer and performing extrusion depolymerization to obtain at least a polyethylene terephthalate polymer; and performing a polymerization step which includes adding a long-chain polyalkyl glycol and performing a polymerization reaction to obtain at least a thermoplastic polyester elastomer.

Description

Technical Field

[0001] The present invention relates to a method for producing a thermoplastic polyester elastomer, and particularly to a method for producing a thermoplastic polyester elastomer including extrusion depolymerization.

Background Art

[0002] Polyester products are widely used in daily life, so a large amount of polyester waste is generated. Currently, the method used for recycling polyester waste is usually a method of performing extrusion and alcoholysis using a large amount of diol. However, since diol is likely to vaporize at high temperatures, it poses a danger in the recycling process and is difficult to control the reaction. Therefore, how to effectively recycle and / or process polyester waste has become a current research topic.

Summary of the Invention

Problems to be Solved by the Invention

[0003] The present invention provides a method for producing a thermoplastic polyester elastomer that can effectively recycle recovered polyester and reduce the recycling cost.

Means for Solving the Problems

[0004] The present invention provides a method for producing a thermoplastic polyester elastomer, comprising the steps of: providing a recovered polyester containing polyethylene terephthalate (PET); performing a first depolymerization step, which includes mixing the recovered polyester with a polyethylene terephthalate oligomer and performing extrusion depolymerization to obtain at least a polyethylene terephthalate polymer; and performing a polymerization step, which includes adding a long-chain polyalkyl glycol and carrying out a polymerization reaction to obtain at least a thermoplastic polyester elastomer (TPEE).

[0005] In one embodiment of the present invention, the polyethylene terephthalate oligomer described above includes bis(2-hydroxyethyl) terephthalate (BHET), polyethylene terephthalate dimer, polyethylene terephthalate trimer, mono(2-hydroxyethyl) terephthalic acid (MHET), or a combination thereof.

[0006] In one embodiment of the present invention, the long-chain polyalkyl glycol described above includes polyethylene glycol (PEG), polytetramethylene ether glycol (PTMEGG), or a combination thereof.

[0007] In one embodiment of the present invention, the amount of the long-chain polyalkyl glycol added in the polymerization step described above accounts for 20% to 60% by weight of the total weight of the reactants of the polymerization reaction.

[0008] In one embodiment of the present invention, the above-described manufacturing method further includes a step of performing a second depolymerization step, which involves mixing the polyethylene terephthalate polymer with a depolymerization solution to perform chemical depolymerization to obtain at least a bis(2-hydroxyethyl) terephthalate monomer.

[0009] In one embodiment of the present invention, the above-described production method further comprises a step of performing a transesterification step, which includes mixing a bis(2-hydroxyethyl) terephthalate monomer with an aliphatic diol to carry out a transesterification reaction to obtain a product. The product includes bis-hydroxypropyl terephthalate (BHPT), bis-hydroxybutyl terephthalate (BHBT), or a combination thereof.

[0010] In one embodiment of the present invention, the aliphatic diol described above includes diols having 3 to 10 carbon atoms.

[0011] In one embodiment of the present invention, the polymerization step described above includes mixing the product with a long-chain polyalkyl glycol to carry out a polymerization reaction to obtain at least a thermoplastic polyester elastomer.

[0012] In one embodiment of the present invention, the polymerization step described above includes mixing a polyethylene terephthalate polymer with a long-chain polyalkyl glycol to carry out a polymerization reaction to obtain at least a thermoplastic polyester elastomer.

[0013] In one embodiment of the present invention, the first depolymerization step, the second depolymerization step, and / or polymerization step described above further include the addition of a catalyst. [Effects of the Invention]

[0014] As described above, the method for producing a thermoplastic polyester elastomer of the present invention includes mixing recovered polyester and polyethylene terephthalate oligomer, followed by a depolymerization step and a polymerization reaction step to produce a thermoplastic polyester elastomer, wherein the depolymerization step is performed by extrusion depolymerization. This allows for the effective recycling of discarded polyester and reduces the cost of polyester recycling, thereby reducing the environmental burden and achieving the effects of environmental protection and a circular economy.

[0015] To make the above-mentioned features and advantages of the present invention easier to understand, they will be described in detail below with reference to examples. [Brief explanation of the drawing]

[0016] [Figure 1] This is a schematic flowchart of a method for producing a thermoplastic polyester elastomer according to one embodiment of the present invention. [Modes for carrying out the invention]

[0017] The following are embodiments illustrating the content of the present invention in detail. The details of the implementation provided in the embodiments are for illustrative purposes only and do not limit the scope of protection of the present invention. A person with ordinary skill in the art to which the present invention pertains may modify or change these details of implementation as necessary for the actual embodiments. Furthermore, descriptions of well-known apparatus, methods, and materials may be omitted so as not to obscure the description of the various principles of the present invention.

[0018] Ranges can be expressed herein as from "about" one particular value to "about" another particular value, or can be expressed directly as to one particular value and / or another particular value. When expressing the above ranges, another embodiment includes from and / or to such one particular value. Similarly, when using the antecedent "about" to express a value as an approximation, it is understood that such particular value forms another embodiment. Further, it is understood that the endpoints of each range are clearly related to or independent of the other endpoints.

[0019] As used herein, non-limiting terms (e.g., can, may, for example, or other similar terms) may be non-essential or may be optional implementations, incorporations, additions, or existences.

[0020] 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. Further to be understood is that terms (defined in commonly used dictionaries) should be interpreted to have a meaning consistent with the meaning in the relevant technical context, and should not be interpreted in an idealized or overly formal sense unless clearly so defined herein.

[0021] FIG. 1 is a schematic flowchart of a method for manufacturing a thermoplastic polyester elastomer according to one embodiment of the present invention. As shown in FIG. 1, the process of the method for manufacturing a thermoplastic polyester elastomer can include the following steps.

[0022] Step S100: Provide recycled polyester.

[0023] Step S105: Provide polyethylene terephthalate (PET) oligomer.

[0024] Step S110: First depolymerization step: Perform extrusion depolymerization.

[0025] Step S120: Second depolymerization step: Add a depolymerization solution to perform chemical depolymerization.

[0026] Step S130: Transesterification step: Add an aliphatic diol to perform a transesterification reaction.

[0027] Step S140: Polymerization step: Add a long-chain polyalkyl glycol to perform a polymerization reaction to obtain at least a thermoplastic polyester elastomer.

[0028] Specifically, the steps of the method for producing a thermoplastic polyester elastomer can include, in order, a first depolymerization step, a second depolymerization step, a transesterification step, and a polymerization step. In another embodiment, the steps of the method for producing a thermoplastic polyester elastomer can include, in order, only the first depolymerization step and the polymerization step. Hereinafter, each step will be described in detail.

[0029] [Provide recycled polyester]

[0030] The recycled polyester includes polyethylene terephthalate (PET). For example, the source of the recycled polyester can include textile products, packaging materials (e.g., PET bottle flakes), or other suitable polyethylene terephthalate products. The recycled polyester may further contain dyes or other impurities.

[0031] In some embodiments, the recovered polyester may be pretreated (i.e., treated before subsequent processing; essentially still recycled). Pretreatment may include, for example, removal of objects on the recycled material (e.g., clips, fasteners, ornaments, zippers, labels, and / or other obviously non-polyester materials), initial cleaning of the recycled material (e.g., washing away dirt, removing impurities, etc.), and other appropriate procedures such as decolorization. For example, decolorization can be achieved by immersing the recovered polyester in an extraction solvent by an extraction method to extract impurities. However, the present invention is not limited thereto, and it is sufficient that impurities can be removed from the recovered polyester. In some embodiments, the extraction solvent may be at least one selected from the group consisting of toluene, xylene, acetic acid, propylene glycol methyl ether, and ethylene glycol.

[0032] In this text, the term "polyester" includes polymers generally known as polyester, but specifically refers to aromatic polyesters, and in this context specifically refers to polyesters derived from purified terephthalic acid (PTA) and ethylene glycol (EG) (i.e., polyethylene terephthalate (PET)). Furthermore, the polyesters used herein may further include, for example, polypropylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, or combinations thereof.

[0033] [First depolymerization step]

[0034] The first depolymerization step includes mixing the recovered polyester and polyethylene terephthalate oligomer and performing extrusion depolymerization to obtain at least a polyethylene terephthalate (PET) polymer. For example, recovered polyester or recycled polyester can be fed into an extruder and extruded, and depolymerization of the polyester therein can be carried out by a reactive extrusion method.

[0035] The extruder may include a screw extruder, for example, a commercially available single-screw extruder (SSE), a twin-screw extruder (TSE), or other suitable extruder, but the present invention is not limited thereto. The structure and / or operation of the commercially available screw extruders described above are similar to those well known to those ordinary skill in the art, and therefore a detailed description is omitted here.

[0036] By supplying polyethylene terephthalate oligomers to the extruder, the polyester depolymerization rate and / or quality in the extruder can be improved. In this embodiment, the polyethylene terephthalate oligomer may include bis(2-hydroxyethyl) terephthalate, polyethylene terephthalate dimer, polyethylene terephthalate trimer, mono(2-hydroxyethyl) terephthalate, a combination thereof, or other suitable polyethylene terephthalate oligomers, preferably comprising bis(2-hydroxyethyl) terephthalate or polyethylene terephthalate dimer. In the first depolymerization step, the amount of polyethylene terephthalate oligomer added may account for about 5% to about 20% by weight of the total weight of the extruded depolymerization reaction product, preferably about 10% to about 15% by weight.

[0037] In this embodiment, compared to supplying ethylene glycol (EG) to the extruder, supplying polyethylene terephthalate oligomer to the extruder makes it safer and / or simplifies the remanufacturing process and / or the corresponding equipment. For example, compared to supplying ethylene glycol (EG), supplying polyethylene terephthalate oligomer to the extruder eliminates the need to provide additional back pressure or reduce the back pressure of the extruder.

[0038] In the first depolymerization step, a catalyst may be added. For example, the recovered polyester, polyethylene terephthalate oligomer, and catalyst can be mixed before extrusion depolymerization. By supplying the catalyst to the extruder, the polyester depolymerization rate in the extruder can be improved. There are no particular restrictions on the catalyst, and an appropriate catalyst can be selected as needed. For example, the catalyst may include a chelate-type titanium catalyst, organozinc (e.g., zinc acetate), organocobalt (e.g., cobalt acetate), organotitanium (e.g., alkoxytitanate salt), organotimon (e.g., antimony acetate), organoaluminum (e.g., organoaluminum acids such as aluminum formate, aluminum acetate, and aluminum propionate), or other suitable catalysts. The catalyst may be used alone or in combination of multiple types. In this embodiment, the catalyst is preferably organotitanium or organocobalt. When the depolymerization reaction is carried out in an environment containing the catalyst, the reaction rate can be improved. In the first depolymerization step, the amount of catalyst added can account for about 0.2% to about 8% by weight of the total weight of the extrusion depolymerization reaction product, preferably about 0.5% to about 5% by weight.

[0039] In one embodiment, the extruder may be fitted with at least one feeder (e.g., a side feeder). The feeder may be a loss-in-weight feeder equipped with a loss-in-weight weighing device. The aforementioned feeders are also common commercially available devices and / or optional accessories. That is, each of the aforementioned components (e.g., recovered polyester, polyethylene terephthalate oligomer, and / or catalyst) may be mixed before feeding, or they may be fed into the extruder by different feeders and mixed within the extruder. The mixture in the extruder can essentially undergo the corresponding homogeneous reaction, which may reduce the corresponding mass transfer bottleneck.

[0040] The extruder may further have a heating region. This allows the polyester-containing mixture inside the extruder to be extruded and heated after the recovered polyester is supplied to the extruder, thereby depolymerizing by a thermal extrusion reaction before being extruded. The heating temperature of the heating region may be about 200°C to about 280°C, and more preferably about 220°C to about 260°C.

[0041] For example, the extrusion depolymerization time for polyester carried out by the reaction extrusion method may be about 1 minute to about 10 minutes, more preferably about 2 minutes to about 5 minutes. The extrusion depolymerization time for polyester carried out by the heated reaction extrusion method may be about 1 minute to about 10 minutes, more preferably about 2 minutes to about 5 minutes. Here, the heating temperature may be about 200°C to about 280°C, more preferably about 220°C to about 260°C. If the aforementioned depolymerization time is too short (e.g., less than 1 minute) and / or the heating temperature is too low (e.g., less than 200°C), the depolymerization efficiency may decrease, potentially reducing the efficiency of subsequent processing. If the aforementioned depolymerization time is too long (e.g., more than 10 minutes) and / or the heating temperature is too high (e.g., more than 280°C), the proportion of other by-products or impurities may become too high, potentially reducing the efficiency of subsequent processing.

[0042] In this embodiment, the first depolymerization step can depolymerize most of the polyester during recycling into a polyethylene terephthalate polymer, which may further include oligomers. For example, the polyethylene terephthalate polymer may be a polymerization of about 2 to 5 ethylene terephthalate monomers. The number of monomers corresponding to the polyethylene terephthalate polymer can be estimated by an appropriate method (e.g., by estimation from molecular weight).

[0043] [Second depolymerization step]

[0044] The second depolymerization step is performed after the first depolymerization step. The second depolymerization step may include mixing the polyethylene terephthalate polymer with the depolymerization solution and performing chemical depolymerization to obtain at least bis(2-hydroxyethyl) terephthalate (BHET) monomer. For example, the polyethylene terephthalate polymer obtained in the first depolymerization step and the depolymerization solution can be placed in a depolymerization tank to perform chemical depolymerization.

[0045] There are no special restrictions on the depolymerization solution, and an appropriate solution can be selected as needed. The depolymerization solution can essentially achieve further depolymerization by again cleaving the chains of the polyethylene terephthalate polymer. For example, shorter molecular chain polyester compositions (e.g., polyethylene terephthalate oligomers) and ester monomers composed of one dicarboxylic acid unit and two glycol units (e.g., bis(2-hydroxyethyl) terephthalate (BHET) monomers) may be obtained. The average molecular weight of the mixture after chemical depolymerization is essentially smaller than the average molecular weight of the mixture obtained in the first depolymerization step (mostly polyethylene terephthalate polymer).

[0046] For example, the depolymerization solution may contain alcohols, such as methanol, ethanol, ethylene glycol (EG), diethylene glycol, combinations thereof, or other suitable alcohols, preferably ethylene glycol. Ethylene glycol is a preferred depolymerization solution because it is considered to be the reaction monomer that produces virgin PET chips. In the second depolymerization step, the amount of depolymerization solution added may account for about 30% to about 80% by weight of the total weight of the reactants in the chemical depolymerization reaction, preferably about 40% to about 70% by weight. If the amount of ethylene glycol added is too small (e.g., less than 30% by weight), the depolymerization efficiency may decrease, potentially reducing the efficiency of subsequent processing. If the amount of ethylene glycol added is too large (e.g., more than 80% by weight), the depolymerization efficiency may improve, but at the same time, excess diethylene glycol may be produced, potentially affecting the quality of the product.

[0047] The second depolymerization step may further include the addition of a catalyst. For example, chemical depolymerization can be carried out after mixing polyethylene terephthalate polymer, depolymerization solution, and catalyst. There are no particular restrictions on the catalyst, and an appropriate catalyst can be selected as needed. The catalyst added in the second depolymerization step may be the same as or different from the catalyst added in the first depolymerization step. In the second depolymerization step, the amount of catalyst added may account for about 0.3% to about 8% by weight of the total weight of the reactants in the chemical depolymerization reaction, preferably about 1% to about 5% by weight.

[0048] When carrying out a chemical depolymerization reaction, the heating step can be performed appropriately. Generally, heating can accelerate the progress of a chemical reaction. For example, after adding the polyethylene terephthalate polymer and ethylene glycol obtained in the first depolymerization step to the depolymerization vessel, the alcohol decomposition reaction can be carried out at a temperature of about 190°C to about 260°C for about 1 to 6 hours, preferably at a temperature of about 205°C to about 245°C for about 3 to 5 hours. If the aforementioned depolymerization time is too short (e.g., less than 1 hour) and / or the heating temperature is too low (e.g., less than 190°C), the depolymerization efficiency may decrease, and the subsequent transesterification efficiency may decrease. If the depolymerization time is too long (e.g., more than 6 hours) and / or the heating temperature is too high (e.g., more than 260°C), a large portion of the polyethylene terephthalate polymer will be depolymerized to bis(2-hydroxyethyl) terephthalate (BHET) monomer. While this can slightly improve the depolymerization ratio of the substance to be depolymerized, it will also require more time and cost (e.g., thermal energy), potentially increasing the overall cost.

[0049] [Transesterification step]

[0050] The transesterification step may include mixing a bis(2-hydroxyethyl) terephthalate (BHET) monomer with an aliphatic diol and carrying out a transesterification reaction to obtain a product. The product may include bis(3-hydroxypropyl) terephthalate (BHPT), bis(4-hydroxybutyl) terephthalate (BHBT), or a combination thereof.

[0051] The aliphatic diol may include diols having 3 to 10 carbon atoms, preferably diols having 3 to 5 carbon atoms, and more preferably 1,2-propanediol, 1,3-propanediol, or 1,4-butanediol. For example, the aliphatic diol may include 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, or other suitable aliphatic diols. In the transesterification step, the molar ratio of bis(2-hydroxyethyl) terephthalate (BHET) monomer to aliphatic diol may be 1:1 to 1:5, preferably 1:2 to 1:4.

[0052] For example, the reaction time for the transesterification reaction may be about 1 to 6 hours, preferably about 3 to 5 hours. The reaction temperature may be about 210°C to 260°C, preferably about 220°C to 250°C. The reaction pressure is atmospheric pressure to about 3.5 kg / cm². 2 It may be, preferably about 1.0 kg / cm³ 2 ~Approx. 3.0kg / cm 2 That is the case.

[0053] The esterification rate in the transesterification reaction may be approximately 90% to approximately 99.5%, and preferably approximately 95% to approximately 99.5%.

[0054] [Polymerization step]

[0055] The polymerization step includes adding a long-chain polyalkyl glycol to carry out a polymerization reaction to obtain at least a thermoplastic polyester elastomer. The thermoplastic polyester elastomer may include a soft segment and a hard segment, the soft segment mainly consisting of a long-chain polyalkyl glycol, and the hard segment mainly consisting of polybutylene terephthalate (PBT) obtained by the condensation polymerization of bis(4-hydroxybutyl) terephthalate (BHBT). In other embodiments, the hard segment of the thermoplastic polyester elastomer mainly consists of polytrimethylene terephthalate (PTT) obtained by the condensation polymerization of bis(3-hydroxypropyl) terephthalate (BHPT).

[0056] In this embodiment, the long-chain polyalkyl glycol may include polyethylene glycol, polytetramethylene ether glycol, a combination thereof, or other suitable polyethylene terephthalate oligomers, preferably polyethylene glycol or polytetramethylene ether glycol. In the polymerization step, the amount of long-chain polyalkyl glycol added may account for about 20% to about 60% by weight of the total weight of the reactants in the polymerization reaction, preferably about 25% to about 55% by weight.

[0057] In one embodiment, if the steps of the method for producing a thermoplastic polyester elastomer include, in order, a first depolymerization step, a second depolymerization step, a transesterification step, and a polymerization step (hereinafter referred to as the first production method for simplicity of explanation), the polymerization step may include mixing the product obtained in the transesterification step with a long-chain polyalkyl glycol to carry out a polymerization reaction to obtain at least a thermoplastic polyester elastomer. If the sum of the proportion of soft segments and hard segments in the thermoplastic polyester elastomer is taken as 100%, the proportion of soft segments in the resulting thermoplastic polyester elastomer may be about 20% to about 60%, preferably about 25% to about 55%. In this embodiment, the amount of polyethylene terephthalate oligomer added can account for about 5% to about 20% by weight of the total weight of the extrusion depolymerization reactants in the first depolymerization step, preferably about 10% to about 15% by weight.

[0058] In another embodiment, if the steps of the method for producing a thermoplastic polyester elastomer include, in order, a first depolymerization step and a polymerization step (hereinafter referred to as the second production method for simplicity of explanation), the polymerization step may include mixing the polyethylene terephthalate polymer obtained in the first depolymerization step with a long-chain polyalkyl glycol to carry out a polymerization reaction to obtain at least a thermoplastic polyester elastomer. If the sum of the proportion of soft segments and hard segments in the thermoplastic polyester elastomer is taken as 100%, the proportion of soft segments in the resulting thermoplastic polyester elastomer may be about 0% to about 20%, preferably about 5% to about 15%. In this embodiment, the amount of polyethylene terephthalate oligomer added can account for about 3% to about 15% by weight of the total weight of the extrusion depolymerization reactants in the first depolymerization step, preferably about 5% to about 10% by weight.

[0059] The polymerization step may further include the addition of a catalyst. For example, the transesterification reaction may be carried out after mixing the product obtained in the transesterification step, the long-chain polyalkyl glycol, and the catalyst, or after mixing the polyethylene terephthalate polymer obtained in the first depolymerization step, the long-chain polyalkyl glycol, and the catalyst. There are no particular restrictions on the catalyst, and an appropriate catalyst can be selected as needed. The catalyst added in the polymerization step may be the same as or different from the catalyst added in the first depolymerization step and / or the second depolymerization step. In the polymerization step, the amount of catalyst added (e.g., the amount of titanium added) can account for about 25 ppm to about 150 ppm of the total weight of the reactants in the polymerization reaction, preferably about 50 ppm to about 100 ppm.

[0060] In the polymerization step, the addition of antioxidants may be included. There are no particular restrictions on the antioxidants, and an appropriate antioxidant can be selected as needed. For example, the antioxidant may include tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid]pentaerythritol, tris(2,4-di-tert-butylphenyl)phosphite, octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid, or other suitable antioxidants. The antioxidant may be used alone or in combination of several types. When the polymerization reaction is carried out in an environment containing antioxidants, degradation due to oxidation of the resulting thermoplastic polyester elastomer can be avoided. In the polymerization step, the amount of antioxidant added may account for about 500 ppm to about 1500 ppm of the total weight of the reactants in the polymerization reaction, preferably about 750 ppm to about 1250 ppm.

[0061] The polymerization step described above is also referred to as the main polymerization reaction. In other embodiments, a prepolymerization reaction may be carried out before the main polymerization reaction. For example, the reaction time for the main polymerization reaction may be about 1 hour to about 3 hours, preferably about 1 hour to about 2 hours. The reaction temperature may be about 200°C to about 300°C, preferably about 240°C to about 280°C. The reaction pressure may be about 0 torr to about 10 torr, preferably about 0 torr to about 0.5 torr. This allows the thermoplastic polyester elastomer to reach the target intrinsic viscosity (IV), for example, about 0.6 dL / g to about 2.0 dL / g. The prepolymerization reaction may include heating the reactants to 200°C to 300°C and reducing the pressure to atmospheric pressure to 20 torr within 1 hour.

[0062] Subsequently, a single-screw or twin-screw granulator can be used to granulate the thermoplastic polyester elastomer obtained in the polymerization step, forming thermoplastic polyester elastomer pellets that facilitate subsequent applications.

[0063] In this embodiment, the thermoplastic polyester elastomer produced by the manufacturing method can have excellent hue quality. Hue quality can be expressed in terms of L, a, and b values ​​in the CIE Lab color space, which is commonly used in the industry. The L value represents luminance, the a value represents the green-red value, and the b value represents the blue-yellow value. For example, the L value of the thermoplastic polyester elastomer may be greater than 65, preferably greater than 70. The b value may be less than 12, preferably less than 10.

[0064] Examples of methods for producing thermoplastic polyester elastomers

[0065] Examples 1 to 3 and Comparative Example 1 of the method for producing thermoplastic polyester elastomer are described below.

[0066] Example 1

[0067] 180g of recycled PET bottle flakes and 26.5g of bis(2-hydroxyethyl) terephthalate (BHET) were fed into an extruder and extruded to perform the first depolymerization step. In the first depolymerization step, the heating temperature for the polyester extrusion depolymerization, which was performed by a heated reaction extrusion method, was approximately 245°C, and the depolymerization time was approximately 2.5 minutes.

[0068] Next, 95.7 g of ethylene glycol (EG) and 0.4 g of catalyst AQ5000 (product name, purchased from Praktic) were added to the product obtained after the first depolymerization step, and chemical depolymerization was carried out. In the second depolymerization step, an alcohol decomposition reaction was carried out at a temperature of approximately 210°C for approximately 191 minutes.

[0069] Subsequently, 337 g of 1,4-butanediol (1,4-BDO) was added to the product obtained after the alcohol decomposition reaction, and a transesterification reaction was carried out. The reaction time for the transesterification reaction was approximately 217 minutes, the reaction temperature was approximately 240°C, and the reaction pressure was atmospheric pressure.

[0070] Next, the product obtained after the transesterification reaction was transferred to a polymerization tank. 70.655 g of PTMEG1000 (product name FAS PTMG; molecular weight: 1000; purchased from Taira Plastics Asahi Elastic Fiber Co., Ltd.), 70.655 g of PTMEG2000 (product name FAS PTMG; molecular weight: 2000; purchased from Taira Plastics Asahi Elastic Fiber Co., Ltd.), 94.2 g of PTMEG3000 (product name FAS PTMG; molecular weight: 3000; purchased from Taira Plastics Asahi Elastic Fiber Co., Ltd.), 0.45 g of antioxidant I-1010 (product name Irganox® 1010; purchased from BASF), 0.113 g of sodium acetate (as an auxiliary catalyst) (purchased from Kawasaki Chemical Industries, Ltd. Headquarters (Air Water Performance Chemical)), and 0.45 g of catalyst AQ5000 (product name, purchased from Praktic) (as a polymerization catalyst) were added to the polymerization tank and mixed with the product obtained after the transesterification reaction.

[0071] Subsequently, the mixture was heated in a reaction vessel at 275°C, and a preliminary polymerization reaction was carried out for 60 minutes while gradually reducing the reaction pressure from atmospheric pressure to 20 Tor over 1 hour. Next, a main polymerization reaction was carried out for 35 minutes at a reaction temperature of 255°C and a reaction pressure of less than 1.5 Tor to produce the thermoplastic polyester elastomer of Example 1.

[0072] Example 2

[0073] Example 2 is similar to the manufacturing method of Example 1, but differs in that 0.2 g of zinc acetate (as a catalyst) was added in the first depolymerization step, the reaction time of the alcohol decomposition reaction in the second depolymerization step was changed to approximately 176 minutes, the reaction time of the transesterification reaction in the transesterification step was changed to approximately 230 minutes, and the reaction time of the main polymerization reaction in the polymerization step was changed to approximately 21 minutes.

[0074] Example 3

[0075] Example 3 is similar to the manufacturing method of Example 1, but differs in that, in the first depolymerization step, the amount of recycled PET bottle flakes used was changed to 160g, the amount of bis(2-hydroxyethyl) phthalate (BHET) used was changed to 53.0g, and the heating temperature for polyester extrusion depolymerization was changed to approximately 240°C; in the second depolymerization step, the amount of ethylene glycol (EG) used was changed to 85.1g, and the reaction time for the alcohol decomposition reaction was changed to approximately 193 minutes; in the transesterification step, the reaction time for the transesterification reaction was changed to approximately 227 minutes; and in the polymerization step, the reaction time for the main polymerization reaction was changed to approximately 41 minutes.

[0076] Comparative Example 1

[0077] Comparative Example 1 is similar to the manufacturing method of Example 1, but differs in that, in the first depolymerization step, the amount of recycled PET bottle flakes used was changed to 200g, bis(2-hydroxyethyl) phthalate (BHET) was not added, and the heating temperature for polyester extrusion depolymerization was changed to approximately 250°C; in the second depolymerization step, the reaction time for the alcohol decomposition reaction was changed to approximately 225 minutes; in the transesterification step, the reaction time for the transesterification reaction was changed to approximately 215 minutes; and in the polymerization step, the reaction time for the main polymerization reaction was changed to approximately 21 minutes.

[0078] The thermoplastic polyester elastomers produced in each example were evaluated using the following evaluation method, and the results are shown in Table 1.

[0079] [Table 1]

[0080] <Evaluation Method>

[0081] Intrinsic viscosity: The viscosity of thermoplastic polyester elastomers was measured based on ASTM D4603.

[0082] Hue Quality: The hue quality (L value, a value, b value) of thermoplastic polyester elastomers was measured according to ASTM E1164.

[0083] <Evaluation Results>

[0084] As can be seen from Table 1, the thermoplastic polyester elastomers produced in Examples 1 to 3, which involve a first depolymerization step in the manufacturing method that includes mixing recovered polyester and polyethylene terephthalate oligomer and performing extrusion depolymerization, have good viscosity and color requirements. In contrast, the thermoplastic polyester elastomer produced in Comparative Example 1, which does not include polyethylene terephthalate oligomer in the first depolymerization step in the manufacturing method, has poor color quality.

[0085] As described above, the present invention provides a method for producing thermoplastic polyester elastomers, which involves a depolymerization step and a polymerization step in which recovered polyester and polyethylene terephthalate oligomer are mixed and extruded to produce a thermoplastic polyester elastomer. This allows for the effective recycling and reuse of discarded polyester, thereby reducing environmental impact and achieving the goals of environmental protection and a circular economy. Furthermore, when the method for producing thermoplastic polyester elastomers includes a depolymerization step and a transesterification step in which chemical depolymerization is carried out, the range of soft segments in the produced thermoplastic polyester elastomer can be broadened, thereby expanding its applicability.

[0086] Although the present invention has been disclosed by the above embodiments, these do not limit the invention. A person with ordinary skill in the art may make some modifications and improvements without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention shall be defined by the claims described below. [Industrial applicability]

[0087] The method for producing thermoplastic polyester elastomers of the present invention can be applied to the recycling and / or treatment of polyester waste, enabling the effective recycling of discarded polyester and reducing the cost of polyester recycling. This reduces the environmental burden and achieves the effects of environmental protection and a circular economy. [Explanation of symbols]

[0088] S100, S105, S110, S120, S130, S140 Step

Claims

1. To provide recycled polyester containing polyethylene terephthalate, The first depolymerization step involves mixing the recovered polyester and polyethylene terephthalate oligomer and performing extrusion depolymerization to obtain at least a polyethylene terephthalate polymer. The polymerization step involves adding a long-chain polyalkyl glycol and carrying out a polymerization reaction to obtain at least a thermoplastic polyester elastomer, A method for producing a thermoplastic polyester elastomer containing [a specific component].

2. The method for producing a thermoplastic polyester elastomer according to claim 1, wherein the polyethylene terephthalate oligomer includes bis(2-hydroxyethyl) terephthalate, polyethylene terephthalate dimer, polyethylene terephthalate trimer, mono(2-hydroxyethyl) terephthalate, or a combination thereof.

3. A method for producing a thermoplastic polyester elastomer according to claim 1, wherein the long-chain polyalkyl glycol comprises polyethylene glycol, polytetramethylene ether glycol, or a combination thereof.

4. The method for producing a thermoplastic polyester elastomer according to claim 1, wherein the amount of the long-chain polyalkyl glycol added in the polymerization step is 20% to 60% by weight of the total weight of the reactants in the polymerization reaction.

5. The process further includes performing a second depolymerization step, The method for producing a thermoplastic polyester elastomer according to claim 1, comprising the second depolymerization step of mixing the polyethylene terephthalate polymer with a depolymerization solution to perform chemical depolymerization to obtain at least a bis(2-hydroxyethyl) terephthalate monomer.

6. Further including performing a transesterification step, The transesterification step includes mixing the bis(2-hydroxyethyl) terephthalate monomer with an aliphatic diol to carry out a transesterification reaction and obtain a product. A method for producing a thermoplastic polyester elastomer according to claim 5, wherein the product comprises bis(3-hydroxypropyl) terephthalate, bis(4-hydroxybutyl) terephthalate, or a combination thereof.

7. The method for producing a thermoplastic polyester elastomer according to claim 6, wherein the aliphatic diol comprises a diol having 3 to 10 carbon atoms.

8. The method for producing a thermoplastic polyester elastomer according to claim 6, wherein the polymerization step comprises mixing the product with the long-chain polyalkyl glycol to carry out the polymerization reaction to obtain at least the thermoplastic polyester elastomer.

9. A method for producing a thermoplastic polyester elastomer according to claim 1, wherein the polymerization step comprises mixing the polyethylene terephthalate polymer and the long-chain polyalkyl glycol to carry out a polymerization reaction to obtain at least the thermoplastic polyester elastomer.

10. A method for producing a thermoplastic polyester elastomer according to any one of claims 1 to 9, further comprising adding a catalyst in the first depolymerization step, the second depolymerization step, and / or the polymerization step.

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