Polyester manufacturing method

Abstract

A method for producing polyester is provided. [Solution] A method for producing polyester is provided, comprising providing a recovered material, ethylene glycol, and a catalyst. The recovered material includes polyethylene terephthalate. A depolymerization step is carried out using the recovered material, ethylene glycol, and catalyst to obtain a crude bishydroxyethyl terephthalate product. A purification step is carried out using the crude bishydroxyethyl terephthalate product to obtain a bishydroxyethyl terephthalate monomer. A phosphorus-containing monomer is provided. An esterification step and a polymerization step are carried out using the bishydroxyethyl terephthalate monomer and the phosphorus-containing monomer.

Description

Technical Field

[0001] The present invention relates to a method for producing flame-retardant polyester.

Background Art

[0002] In products such as 3C transmission cables, it is common to use fabrics spun and woven from materials such as flame-retardant polyester. However, products manufactured by conventional polyester production methods have many problems, which reduces the competitiveness of those products. Therefore, how to improve the polyester production method has become a major issue.

Summary of the Invention

Problems to be Solved by the Invention

[0003] In products such as 3C transmission cables, it is common to use fabrics spun and woven from materials such as flame-retardant polyester. However, products manufactured by conventional polyester production methods have many problems, which reduces the competitiveness of those products.

Means for Solving the Problems

[0004] The present invention provides a method for producing polyester with excellent product competitiveness.

[0005] The method for producing polyester of the present invention includes providing recycled materials, ethylene glycol, and a catalyst. The recycled materials include polyethylene terephthalate. A depolymerization step is performed using the recycled materials, ethylene glycol, and the catalyst to obtain a crude bis-hydroxyethyl terephthalate product. A purification step is performed using the crude bis-hydroxyethyl terephthalate product to obtain a bis-hydroxyethyl terephthalate monomer. A phosphorus-containing monomer is provided. An esterification step and a polymerization step are performed using the bis-hydroxyethyl terephthalate monomer and the phosphorus-containing monomer.

[0006] In one embodiment of the present invention, the phosphorus-containing monomer is any of the following: [ka]

[0007] In one embodiment of the present invention, the operating temperature of the depolymerization step is 180 to 220°C, the operating temperature of the purification step is 10 to 120°C, the operating temperature of the esterification step is 170 to 230°C, and the operating temperature of the polymerization step is 240 to 280°C.

[0008] In one embodiment of the present invention, the operation time for the depolymerization step is 2 to 6 hours, the operation time for the purification step is 0.5 to 8 hours, the operation time for the esterification step is 0.2 to 3 hours, and the operation time for the polymerization step is 1 to 5 hours.

[0009] In one embodiment of the present invention, the weight ratio of ethylene glycol to recovered material used in the depolymerization step is 2 to 8.

[0010] In one embodiment of the present invention, the molar ratio of the bishydroxyethyl terephthalate monomer to the phosphorus-containing monomer used is 10 to 60.

[0011] In one embodiment of the present invention, the catalyst includes an organometallic element, an ionic liquid, or a combination thereof.

[0012] In one embodiment of the present invention, the organometallic comprises zinc acetate, cobalt acetate, tetrabutyl titanate, titanium citrate, triethoxyantimony(III)ethoxide, tri-n-octylaluminum, or a combination thereof, and the ionic liquid comprises 1-butyl-3-methylimidazolium hexafluorophosphate (BMI-PF6), 1-butyl-3-methylimidazolium tetrafluoroborate (BMI-BF4), or a combination thereof.

[0013] In one embodiment of the present invention, the purification step includes an impurity adsorption process. The impurity adsorption process uses activated carbon, polystyrene, activated clay, or a combination thereof as the adsorption material.

[0014] In one embodiment of the present invention, the purification step further includes a crystallization process, a filtration process, and a drying process, the crystallization process, the filtration process, and the drying process are performed sequentially after the impurity adsorption process. [Effects of the Invention]

[0015] Based on the above, the present invention can simultaneously improve problems such as poor processability, poor flame resistance, long thermal history and carbon dioxide emissions, poor color, and negative environmental impact that occur in conventional physical mixing and chemical modification methods, by depolymerizing and purifying the recovered material into bishydroxyethyl terephthalate monomer, and then performing further steps such as esterification and polymerization using a phosphorus-containing monomer. In this way, high-quality flame-retardant polyester with superior product competitiveness can be produced.

[0016] To make the above-mentioned features and advantages of the present invention clearer and easier to understand, embodiments are described below and explained in detail with reference to the accompanying drawings. [Brief explanation of the drawing]

[0017] [Figure 1] It is a schematic diagram of part of the flow of a method for producing polyester according to an embodiment of the present invention. **Embodiments for Carrying Out the Invention**

[0018] In the following detailed description, for purposes of illustration and not limitation, exemplary embodiments are set forth in order to provide a thorough understanding of the various principles of the present invention. However, it will be apparent to those 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. Further, descriptions of well-known devices, methods, and materials may be omitted so as not to obscure the various principles of the present invention.

[0019] The present invention will be described in more detail below with reference to the drawings of the present embodiment. However, the present invention can be embodied in various forms and should not be limited to the embodiments described herein.

[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.

[0021] As used herein, the term "between" used to define a numerical range is intended to cover a range equal to the specified end values and the range between the specified end values. For example, if a size range is between a first value and a second value, it indicates that the size range includes the first value, the second value, and any value between the first value and the second value.

[0022] FIG. 1 is a schematic diagram of part of the flow of a method for producing polyester according to an embodiment of the present invention. Referring to FIG. 1, the method for producing polyester of the present embodiment includes at least the following steps.

[0023] First, a recycled material, ethylene glycol, and a catalyst are provided. The recycled material includes polyethylene terephthalate (PET). Then, as shown in step S110, a depolymerization step is performed using the recycled material, ethylene glycol, and the catalyst to obtain a crude bis-2-hydroxylethyl terephthalate (BHET) product. Here, the crude product includes BHET dimer, BHET trimer, BHET oligomer, or the like.

[0024] Next, as shown in step S120, a purification step is performed using the crude bis-2-hydroxylethyl terephthalate product to obtain a bis-2-hydroxylethyl terephthalate monomer. In this step, the hue L of the bis-2-hydroxylethyl terephthalate monomer may be greater than 90%, a may be between ±1, and b may be between ±2, but the present invention is not limited thereto.

[0025] Then, a phosphorus-containing monomer is provided, and as shown in step S130, an esterification step and a polymerization step are performed using the bis-2-hydroxylethyl terephthalate monomer and the phosphorus-containing monomer. The hue L of the flame-retardant polyester formed in this step may be greater than 80%, a may be between ±2, and b may be between ±4. The average yarn breakage rate of the subsequent product is less than 3 times per day, the spinning yield is greater than 90%, and the flame resistance can reach the M1 level. Therefore, in this embodiment, after depolymerizing and purifying the recycled material into a bis-2-hydroxylethyl terephthalate monomer, further steps such as esterification and polymerization are performed using the phosphorus-containing monomer, thereby simultaneously improving problems such as poor processability, poor flame resistance, long heat history and carbon dioxide emissions, poor hue, and negative impact on the environment that occur in conventional physical mixing and chemical modification methods. In this way, a high-quality flame-retardant polyester with excellent product competitiveness can be produced.

[0026] Furthermore, flame-retardant polyesters formed by conventional physical mixing methods are formed by extruding using an extruder, cooling, and granulating, which leads to problems such as easy yarn breakage and poor processability in the subsequent spinning process. At the same time, they suffer from poor mixing uniformity and reduced flame retardancy. On the other hand, conventional chemical modification methods use terephthalic acid (PTA), ethylene glycol, and phosphorus-containing monomers to directly perform esterification copolymerization to form flame-retardant polyesters. However, this process involves prolonged high temperatures, often resulting in problems such as long thermal history and poor coloration, and it is prone to carbon dioxide emissions and waste generation during the manufacturing process, thus failing to meet environmental protection needs. For this reason, the manufacturing method of this embodiment does not employ the physical mechanism of extrusion molding, nor the chemical mechanism of raw materials such as terephthalic acid. Therefore, the copolymer structure formed by the manufacturing method of this embodiment can solve the problems that arise from these conventional mechanisms, but the present invention is not limited to this.

[0027] The following describes the specific operations of each of the above steps in an illustrative manner, but these descriptions are not intended to limit the present invention.

[0028] <Depolymerization process>

[0029] In some embodiments, to obtain a more favorable improvement effect by performing the depolymerization process under preferred operating conditions, for example, the operating temperature of the depolymerization process may be 180 to 220°C and / or the operating time of the depolymerization process may be 2 to 6 hours, and under more preferred operating conditions, the operating temperature may be 190 to 210°C and / or the operating time may be 2 to 5 hours, but the present invention is not limited thereto.

[0030] In some embodiments, the weight ratio of ethylene glycol to recovered material used in the depolymerization step is preferably 2 to 8, and preferably 3 to 6, but the present invention is not limited thereto. Here, the weight ratio of ethylene glycol to recovered material used is obtained by dividing the weight of ethylene glycol used by the weight of recovered material used, that is, the weight of ethylene glycol used is greater than the weight of recovered material used.

[0031] In some embodiments, the source of the recovered material may be recycled film, recycled PET bottles, recycled fibers, or similar materials.

[0032] In some embodiments, the catalyst includes organometallic, ionic liquid, or a combination thereof. For example, organometallics include zinc acetate, cobalt acetate, tetrabutyl titanate, titanium citrate, triethoxyantimony, tri-n-octylaluminum, or a combination thereof, and ionic liquids include 1-butyl-3-methylimidazole hexafluorophosphate, 1-butyl-3-methylimidazole tetrafluoroborate, or a combination thereof, but the present invention is not limited thereto.

[0033] <Purification process>

[0034] In some embodiments, the process may be carried out under preferred operating conditions to obtain a more favorable improvement effect. For example, the operating temperature of the purification process may be 10 to 120°C, and / or the operating time of the purification process may be 0.5 to 8 hours, but the present invention is not limited thereto.

[0035] In some embodiments, the purification step includes an impurity adsorption process, which uses activated carbon, polystyrene, activated clay, or a combination thereof as the adsorption material.

[0036] In some embodiments, the purification process further includes a crystallization process, a filtration process, and a drying process, which are performed sequentially after the impurity adsorption process. For example, the temperature of the crystallization process can be reduced to 10-45°C, preferably 20-35°C, but the present invention is not limited thereto.

[0037] <Esterification process>

[0038] In some embodiments, to obtain a more favorable improvement effect by performing the esterification step under preferred operating conditions, for example, the operating temperature of the esterification step may be 170 to 230°C and / or the operating time of the esterification step may be 0.2 to 3 hours, and under more preferred operating conditions, the operating temperature of the esterification step may be 180 to 220°C and / or the operating time of the esterification step may be 0.5 to 2 hours, but the present invention is not limited thereto.

[0039] In some embodiments, the esterification pressure can also be controlled to 1-3 bar, but the present invention is not limited thereto.

[0040] In some embodiments, the molar ratio of bishydroxyethyl terephthalate monomer to phosphorus-containing monomer is 10 to 60, for example, 10 to 30, or for example, 15 to 20, but the present invention is not limited thereto. Here, the molar ratio of bishydroxyethyl terephthalate monomer to phosphorus-containing monomer is obtained by dividing the number of moles of bishydroxyethyl terephthalate monomer used by the number of moles of phosphorus-containing monomer used; that is, the number of moles of bishydroxyethyl terephthalate monomer used is greater than the number of moles of phosphorus-containing monomer used.

[0041] In some embodiments, the phosphorus-containing monomer is any of the following to have a more favorable reactivity, but the present invention is not limited thereto. [ka]

[0042] In some embodiments, the esterification step may optionally include an additional catalyst. The catalyst may be, for example, antimony glycol or a similar substance, but the present invention is not limited thereto.

[0043] <Polymerization process>

[0044] In some embodiments, to obtain a more favorable improvement effect by performing the process under preferred operating conditions, for example, the operating temperature of the polymerization process may be 240 to 280°C and / or the operating time of the polymerization process may be 1 to 5 hours. Under more preferred operating conditions, the operating temperature of the polymerization process may be 250 to 270°C and / or the operating time of the polymerization process may be 2 to 4 hours, but the present invention is not limited thereto.

[0045] In some embodiments, the polymerization pressure can also be controlled to 0.2 to 2 Torr, preferably 0.5 to 1.5 Torr, but the present invention is not limited thereto.

[0046] The effects of the present invention will be explained below with reference to examples and comparative examples, but the scope of the present invention is not limited to these examples.

[0047] The flame-retardant polyesters produced in each example and comparative example were evaluated according to the following method.

[0048] Intrinsic viscosity (IV): Reduced viscosity when the concentration of a polymer solution approaches zero.

[0049] Phosphorus content: The molecular weight of total phosphorus / molecular weight of flame retardant polyester in the flame retardant polyester structure was calculated using analysis and quantification with LC (liquid chromatography) equipment.

[0050] Hue: The color space defined by the CIE Lab (International Commission on Illumination) is adopted. The color space (Lab color space) is a color-opposite space, where dimension L represents lightness (also known as the whiteness of the color), a and b represent the opposite dimensions of the color, and are CIE XYZ color space coordinates based on nonlinear compression.

[0051] Yield: Weight of acceptable product after spinning / Weight of polyester.

[0052] Flame resistance: Meets NF P 92-507 standard.

[0053] The polyesters in Examples 1-6 were manufactured by the following method.

[0054] In accordance with step S110, a depolymerization process was carried out using 1000 kg of PET bottle flakes (recovered polyethylene terephthalate material), 4000 kg of ethylene glycol, and 8 kg of zinc acetate (catalyst) to obtain the crude bishydroxyethyl terephthalate product. Furthermore, a depolymerization process was carried out in a reaction vessel using PET bottle flakes, ethylene glycol, and zinc acetate under operating conditions of 195°C and 4 hours.

[0055] Corresponding to step S120, the obtained crude bishydroxyethyl terephthalate product was used in a purification process to obtain bishydroxyethyl terephthalate monomer. Furthermore, the purification process included an impurity adsorption process, a crystallization process, a filtration process, and a drying process. First, an impurity adsorption process was carried out, where the temperature was lowered from 195°C to 120°C, 80 kg of activated carbon (adsorbent material) was added and stirred for 30 minutes, and then 2000 kg of ethylene glycol was removed by distillation. After that, the activated carbon and impurities were filtered off using a 0.1 μm filter bag. After the impurity adsorption process, a crystallization process was carried out, where the filtrate was first lowered from 120°C to 80°C, then 4000 kg of water was added and stirred for 30 minutes, and then the temperature was further lowered from 80°C to 10°C to crystallize the bishydroxyethyl terephthalate. Further filtration and drying processes were carried out, and the mixture was filtered using a 5 μm filter to obtain a wet-basis bishydroxyethyl terephthalate solid filter cake. Furthermore, the moisture-based bishydroxyethyl terephthalate solid filter cake was dried at 80°C and 200 Torr for 2 hours to obtain 1200 kg of bishydroxyethyl terephthalate monomer (hue: L was 94.5%, a was 0.4, b was 1.7).

[0056] Corresponding to step S130, 1200 kg of the obtained bishydroxyethyl terephthalate monomer and 45 kg of the phosphorus-containing monomers (compounds 1-5) from Table 1 were used to carry out esterification and polymerization steps to obtain 890 kg of flame-retardant polyesters for Examples 1-6. Furthermore, 9 kg of bishydroxyethyl terephthalate monomer, phosphorus-containing monomer, and catalyst (antimony glycol) were placed in a three-necked glass flask and carried out the esterification step under operating conditions of 195°C, 760 Torr, and 1 hour. After the esterification step, the polymerization step was carried out under operating conditions of 260°C, 0.6 Torr, and 2.5 hours. In Table 1, the trade name of compound 1 is Phosgard PF100 (registered trademark), the trade name of compound 2 is Ukanol ES (registered trademark), the trade name of compound 3 is Exolit PE100 (registered trademark), the trade name of compound 4 is ring-opening Exolit PE100 (registered trademark), and the trade name of compound 5 is DOPO-Itaconic acid. [ka]

[0057] [Table 1]

[0058] Table 2 shows the properties and spinning evaluation of polyester in Examples 1-6.

[0059] [Table 2]

[0060] The polyesters in Comparative Examples 1-6 were manufactured by the following method.

[0061] <Comparative Example 1>

[0062] 890 kg of virgin polyethylene terephthalate resin (IV: 0.83 dl / g, L: 83.4%, a: 0.3, b: 0.8) and 4.6 kg of the flame retardant DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide, CAS No: 35948-25-5) were injected into a twin-screw extruder at an extrusion temperature of 260°C. The molten resin was then filtered through a 60 μm mesh, followed by a cooling and granulation process to obtain the polyester of Comparative Example 1.

[0063] <Comparative Example 2>

[0064] The only difference between Comparative Example 2 and Comparative Example 1 was that the flame retardant in Comparative Example 1 was changed to DPPE (1,2-bis(diphenylphosphino)ethane, CAS No: 1663-45-2) and the weight used was 57.3 kg, resulting in the polyester of Comparative Example 2.

[0065] <Comparative Example 3>

[0066] 865 kg of terephthalic acid (PTA), 338 kg of ethylene glycol, 51.3 kg of flame retardant (compound 1, Phosgard PF100®), and 9 kg of catalyst (antimony glycol) were placed in a reaction vessel. An esterification reaction was carried out under operating conditions of 260°C, 2.8 Torr, and 1.5 hours. Simultaneously, the water produced by esterification was removed by distillation to obtain an oligomer of bishydroxyethyl terephthalate. Next, a polymerization reaction was carried out under operating conditions of 260°C, 0.6 Torr, and 2.5 hours. Simultaneously, the ethylene glycol produced by polymerization was removed by distillation to obtain 934 kg of polyester of Comparative Example 3.

[0067] <Comparative Example 4>

[0068] The only difference between Comparative Example 4 and Comparative Example 3 was that the flame retardant in Comparative Example 2 was changed to Compound 2 (Ukanol ES®) and the weight used was 96.4 kg, resulting in 928 kg of polyester for Comparative Example 4.

[0069] <Comparative Example 5>

[0070] The only difference between Comparative Example 5 and Comparative Example 1 was that the virgin polyethylene terephthalate resin in Comparative Example 1 was recycled PET bottles (IV: 0.81 dl / g, L: 71.3%, a: 0.2, b: 0.6), and the weight of the flame retardant used was 48.4 kg, resulting in the polyester of Comparative Example 5.

[0071] <Comparative Example 6>

[0072] The only difference between Comparative Example 6 and Comparative Example 5 was that the flame retardant in Comparative Example 5 was changed to DPPE (CAS No: 1663-45-2), the weight used was 51.7 kg, and recycled PET bottles were used (IV: 0.81 dl / g, L: 70.1%, a: 0.3, b: 0.8), resulting in the polyester of Comparative Example 6.

[0073] Table 3 shows the properties and spinning evaluation of the polyesters in Comparative Examples 1 to 6.

[0074] [Table 3]

[0075] From the results in Tables 2 and 3, the following conclusions can be drawn. Examples 1-6 have advantages such as excellent spinnability, excellent flame resistance, low carbon process, and excellent color, whereas Comparative Examples 1-2 and 5-6 use a physical mixing mechanism, and therefore their uniformity is not as good as that of chemical mixing. Comparative Examples 3-4 use a chemical modification mechanism, and therefore the thermal history temperature in the process is high. In particular, the esterification temperature and polymerization temperature both reach 260°C and the reaction is carried out for more than 2.5 hours. As a result, the flame-retardant polyesters of Comparative Examples 1-6 all have problems such as poor quality, spinnability, and color.

[0076] In summary, the present invention, by depolymerizing and purifying the recovered material into bishydroxyethyl terephthalate monomer, and then performing further steps such as esterification and polymerization using a phosphorus-containing monomer, can simultaneously improve the problems of poor processability, poor flame resistance, long thermal history and carbon dioxide emissions, poor color, and negative environmental impact that occur in conventional physical mixing and chemical modification methods. In this way, high-quality flame-retardant polyester with superior product competitiveness can be produced.

[0077] Although the present invention has been disclosed through embodiments described above, these are not intended to limit the invention, and any person with ordinary skill in the relevant art may make several modifications and alterations without departing from the spirit and scope of the invention. The scope of protection of the present invention shall be determined by the scope of the appended patent application. [Industrial applicability]

[0078] The method for manufacturing flame-retardant polyester can be applied to the field of flame-retardant polyester. [Explanation of Symbols]

[0079] S110, S120, S130: Process

Claims

1. To provide a recovered material containing polyethylene terephthalate, ethylene glycol, and a catalyst, The recovered material, the ethylene glycol, and the catalyst are used to carry out a depolymerization step to obtain a crude bishydroxyethyl terephthalate product. The crude bishydroxyethyl terephthalate product is used in a purification step to obtain bishydroxyethyl terephthalate monomer, To provide phosphorus-containing monomers, The esterification step and polymerization step are carried out using the bishydroxyethyl terephthalate monomer and the phosphorus-containing monomer. A method for manufacturing polyester, including

2. The method for producing polyester according to claim 1, wherein the phosphorus-containing monomer is any of the following. 【Chemistry 1】

3. The method for producing polyester according to claim 1, wherein the operating temperature of the depolymerization step is 180 to 220°C, the operating temperature of the purification step is 10 to 120°C, the operating temperature of the esterification step is 170 to 230°C, and the operating temperature of the polymerization step is 240 to 280°C.

4. The method for producing polyester according to claim 1, wherein the operation time for the depolymerization step is 2 to 6 hours, the operation time for the purification step is 0.5 to 8 hours, the operation time for the esterification step is 0.2 to 3 hours, and the operation time for the polymerization step is 1 to 5 hours.

5. The method for producing polyester according to claim 1, wherein in the depolymerization step, the weight ratio of ethylene glycol to the recovered material used is 2 to 8.

6. The method for producing polyester according to claim 1, wherein the molar ratio of the bishydroxyethyl terephthalate monomer to the phosphorus-containing monomer used is 10 to 60.

7. The catalyst includes organometallic, ionic liquid, or a combination thereof. A method for producing polyester according to claim 1.

8. The method for producing a polyester according to claim 7, wherein the organometallic comprises zinc acetate, cobalt acetate, tetrabutyl titanate, titanium citrate, triethoxyantimony, tri-n-octylaluminum, or a combination thereof, and the ionic liquid comprises 1-butyl-3-methylimidazole hexafluorophosphate, 1-butyl-3-methylimidazole tetrafluoroborate, or a combination thereof.

9. The method for producing polyester according to claim 1, wherein the purification step includes an impurity adsorption step, and the impurity adsorption step uses activated carbon, polystyrene, activated clay, or a combination thereof as the adsorption material.

10. The method for producing polyester according to claim 9, wherein the purification step further comprises a crystallization process, a filtration process, and a drying process, the crystallization process, the filtration process, and the drying process being performed sequentially after the impurity adsorption process.

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