Preparation system of anti-UV hydrolysis-resistant PET functional master batch

Abstract

The utility model discloses a preparation system of an anti-UV (ultraviolet) hydrolysis-resistant PET (polyethylene terephthalate) functional master batch, which comprises a stainless steel esterification tank and a stainless steel polycondensation tank, and an outlet of the stainless steel esterification tank is connected with an inlet of the stainless steel polycondensation tank through a pipeline; wherein the upper part of the stainless steel esterification tank is connected with a first vacuum pump, and a first condenser is arranged in a pipeline through which the first vacuum pump is connected with the stainless steel esterification tank; a first heat-conducting oil jacket is arranged on the outer side of a tank body of the stainless steel esterification tank; a second vacuum pump is connected above the stainless steel polycondensation tank; a second condenser is arranged in a pipeline for connecting the second vacuum pump with the stainless steel polycondensation tank; a second heat-conducting oil jacket is arranged on the outer side of the tank body of the stainless steel polycondensation tank. The preparation system of the PET functional master batch with the anti-UV and hydrolysis-resistant functions fills the blank of lack of a special system for continuously preparing the PET functional master batch with the anti-UV and hydrolysis-resistant functions in the prior art, and can be used for continuously producing and preparing the PET functional master batch with the anti-UV and hydrolysis-resistant functions in batches and obtaining the PET functional master batch with the anti-UV and hydrolysis-resistant functions.

Description

TECHNICAL FIELD

[0001] The utility model relates to a kind of preparation systems of anti-UV hydrolysis-resistant PET functional masterbatch. BACKGROUND

[0002] Anti-UV hydrolysis-resistant PET functional masterbatch plays an increasingly important role in modern industry, in addition to the fields of electronics, photovoltaics and high-performance packaging, such masterbatch is also widely used in automotive interiors, outdoor billboards, medical devices and other fields, providing durable protection and aesthetics. Such masterbatch combines the excellent properties of PET materials and key properties such as UV resistance and hydrolysis resistance, providing durable protection for various application scenarios. For example, in some application scenarios in the packaging field that require UV resistance, all UVA ultraviolet rays below 400 nm need to be shielded to ensure that the substances inside the packaging are not affected by long-term ultraviolet radiation, such as discoloration and aging. In the field of electronics or photovoltaics, some need to remain stable in high-temperature and high-humidity environments and are not prone to hydrolysis reactions, thereby extending the service life of the product.

[0003] In the prior art, the anti-UV hydrolysis resistance is generally improved by adding hydrolysis-resistant agents and UV absorbers to PET. Common hydrolysis-resistant agents include carbodiimides, oxazolines, etc., and UV absorbers include o-hydroxybenzophenone, benzotriazole, etc. However, there are compatibility and dispersion problems of hydrolysis-resistant agents and UV absorbers in actual application. For example, by using nanodispersion technology to disperse hydrolysis-resistant agents and UV absorbers in the PET matrix, it is necessary to avoid the problem of agglomeration caused by mutual interference between the two. In addition, it is also difficult to uniformly disperse nanomaterials inside the matrix, especially in the manufacturing process of PET film and other products, the stretching of the film may change the molecular arrangement, causing the nanometer particles of the hydrolysis-resistant agent and the UV absorber originally dispersed in the matrix to change with the stretching position, which may cause the nanometer particles to re-agglomerate or unevenly distribute.

[0004] Common solutions to compatibility and dispersion include surface modification of nanometer particles to increase their affinity with the PET matrix, thereby improving dispersion and compatibility. Advanced blending techniques such as melt blending, solution blending, etc. are also used to ensure uniform dispersion of hydrolysis-resistant agents and UV absorbers in the PET matrix. However, these solutions are highly dependent on process and equipment, production costs are high, and it is difficult to adjust the production process for different products.

[0005] Therefore, how to improve the anti-UV and hydrolysis resistance of PET products has become a problem to be solved in the field of polymer material preparation technology. The utility model is just aimed at this problem, and provides a PET functional masterbatch with excellent anti-UV and hydrolysis resistance and a preparation system thereof, so as to fill the gap of the existing technology that lacks a special system for continuously preparing anti-UV and hydrolysis resistant PET functional masterbatch. SUMMARY

[0006] The technical problem to be solved by the utility model is to provide a preparation system of anti-UV and hydrolysis resistant PET functional masterbatch, so as to reduce or avoid the problems mentioned above.

[0007] To solve the above technical problems, the utility model provides a preparation system of anti-UV and hydrolysis resistant PET functional masterbatch, which comprises a stainless steel esterification tank and a stainless steel polycondensation tank, the outlet of the stainless steel esterification tank is connected to the inlet of the stainless steel polycondensation tank through a pipeline;Wherein, the upper portion of the stainless steel esterification tank is connected with a first vacuum pump, and a first condenser is arranged in the pipeline connecting the stainless steel esterification tank and the first vacuum pump;The outer side of the tank body of the stainless steel esterification tank is provided with a first heat conducting oil jacket;The upper portion of the stainless steel polycondensation tank is connected with a second vacuum pump, and a second condenser is arranged in the pipeline connecting the stainless steel polycondensation tank and the second vacuum pump;The outer side of the tank body of the stainless steel polycondensation tank is provided with a second heat conducting oil jacket.

[0008] Preferably, the first mechanical stirring device is arranged in the stainless steel esterification tank.

[0009] Preferably, the second mechanical stirring device is arranged in the stainless steel polycondensation tank.

[0010] Preferably, the outlet of the stainless steel polycondensation tank is connected to the inlet of the double-screw extruder through a pipeline.

[0011] Preferably, the outlet of the double-screw extruder is connected to the pelletizer, and a water cooling system is arranged between the pelletizer and the double-screw extruder.

[0012] Preferably, the diameter of the particles formed by the pelletizer is 4-8mm.

[0013] The preparation system of the PET functional masterbatch with UV resistance and hydrolysis resistance function fills the blank of the prior art that lacks a special system for continuously preparing the PET functional masterbatch with UV resistance and hydrolysis resistance, and can continuously produce and prepare the PET functional masterbatch with UV resistance and hydrolysis resistance. In the functional masterbatch prepared by the preparation system, isophorone diester and 2,4-dihydroxybenzoic acid and other UV absorbing groups are introduced, so that the UV resistance is enhanced, and neopentyl glycol and trimethylolpropane are introduced to enhance the hydrolysis resistance of the molecular chain. In addition, the uniform distribution of the light stabilizer and the ultraviolet absorber in the molecular structure is improved by using Beta molecular sieve, zinc metaborate and other additives, and the uneven UV absorption performance and hydrolysis resistance caused by the change of molecular arrangement in the stretching process of the film is effectively avoided. The synergistic effect of each component in the formula of the functional masterbatch of the utility model enhances the ultraviolet resistance, strength and hydrolysis resistance of the film, so as to meet the application requirements of PET products in the fields of packaging, electronics, photovoltaics, automobiles, medical devices and the like. BRIEF DESCRIPTION OF DRAWINGS

[0014] The following drawings are only intended to illustrate and explain the present application, and do not limit the scope of the utility model.

[0015] Figure 1 The structure of the preparation system of the PET functional masterbatch with UV resistance and hydrolysis resistance is shown according to one embodiment of the utility model. DETAILED DESCRIPTION

[0016] In order to have a clearer understanding of the technical features, objects and effects of the utility model, the specific embodiments of the utility model will be described in detail.

[0017] In view of the problems existing in the UV resistance and hydrolysis resistance of PET products, the utility model carries out functional modification on polyethylene terephthalate (PET) to prepare a special functional masterbatch suitable for PET products. Through the utility model and its preparation method, the UV resistance and hydrolysis resistance of PET products can be significantly improved, and the mechanical strength, thermal stability and the like of the material can be improved, so as to meet the application requirements of PET products in the fields of packaging, electronics, building and the like.

[0018] Specifically, the utility model provides a kind of PET functional masterbatch with UV resistance and hydrolysis resistance, which can be used as raw material for preparing PET product, for example, as the total raw material for preparing PET product, or as part of the raw material for preparing PET product, by combining with other raw materials to prepare the required PET product.

[0019] In one specific embodiment, the anti-UV hydrolysis-resistant PET functional masterbatch of the utility model is prepared from the following raw materials by weight: terephthalic acid (PTA): 95-105 parts by weight; ethylene glycol (EG): 60-70 parts by weight; isophorone diester (IPDE): 20-30 parts by weight; 2,4-dihydroxybenzoic acid (2,4-DHBA): 10-18 parts by weight; titanium tetrachloride (TiCl4): 0.05-0.10 parts by weight; antimony acetate (Sb2O3): 0.04-0.08 parts by weight; phosphoric acid (H3PO4): 0.03-0.06 parts by weight; 2,6-di-tert-butyl-p-cresol (BHT): 0.03-0.08 parts by weight; zinc metaborate: 0.01-0.03 parts by weight; diethylene glycol (DEG): 3-7 parts by weight; neopentyl glycol (NPG): 8-12 parts by weight; Beta molecular sieve: 8-12 parts by weight; trimethylolpropane (TMP): 3-6 parts by weight.

[0020] PTA serves as the main diacid component of the polyester, providing a stable structure for the backbone. EG provides the dihydric alcohol required for the reaction, adjusting the flexibility and viscosity of the polyester molecules. IPDE improves mechanical properties and thermal stability by introducing rigid groups, while also assisting in improving UV resistance. 2,4-DHBA serves as a UV absorption component, participating in copolymerization of the polyester chain through its hydroxyl and carboxyl groups. Neopentyl glycol (NPG) replaces part of the ethylene glycol, providing a more stable alcohol component and significantly improving the hydrolysis resistance of the polyester chain. Trimethylolpropane (TMP) is introduced as a crosslinking monomer, improving the spatial stability of the molecular chain and enhancing hydrolysis resistance. TiCl4 serves as a catalyst for the esterification stage, promoting rapid esterification. Sb2O3 serves as a polymerization catalyst, used to increase the polymerization rate and molecular weight. H3PO4 is used to stabilize the polyester chain structure and inhibit side reactions. BHT is used to inhibit oxidative degradation of the material at high temperatures. Zinc metaborate is used to improve the thermal stability of the film during high-temperature stretching. DEG serves as an auxiliary solvent, helping to adjust the viscosity of the reaction and prevent premature precipitation of the polymer. Xylene is used to improve mixing at the beginning of the reaction and help evaporate the byproduct water. Beta molecular sieve is a type of nanoscale molecular sieve with a 12-membered ring cross-channel structure, used to ensure efficient dehydration of the esterification reaction. Its unique cage-free three-dimensional pore structure facilitates the diffusion of reactant and product molecules, while also having a shape-selective catalytic effect.

[0021] The raw material of the utility model relates to complex chemical reaction process, mainly includes the ester group of IPDE and the carboxyl of PTA reaction, generates polyester chain;The esterification reaction of the hydroxyl in NPG and the carboxyl in terephthalic acid (PTA) or 2,4-dihydroxybenzoic acid (2,4-DHBA) occurs, and the monoester or diester is formed;The esterification reaction of the 3 hydroxyls of TMP and the carboxyl of PTA or 2,4-DHBA occurs, and the monoester, diester and triester are gradually generated.Secondly, the esterification reaction of the carboxyl of DHBA and the hydroxyl of EG occurs, and the esterification monomer is generated, which provides the precursor for the subsequent polymerization reaction.Thirdly, the ester group of IPDE and the carboxyl of DHBA react to form a copolymer.Finally, all the intermediates are mixed and polymerized with EG to form the high molecular chain of PET.

[0022] Wherein, since IPDE has two ester groups, it can esterify with PTA and EG.Moreover, when the ester groups of IPDE can esterify with the carboxyl in PTA and the hydroxyl in EG, long-chain polyester is formed.The introduction of IPDE can bring rigidity of molecular chain and certain ultraviolet absorption capacity.DHBA is an aromatic compound containing phenolic hydroxyl group.In the reaction, its carboxyl can esterify with EG and PTA, and its phenolic hydroxyl group can copolymerize with IPDE through esterification reaction.Meanwhile, the presence of phenolic hydroxyl group provides a functional group for ultraviolet absorption.

[0023] Further, the anti-UV and hydrolysis-resistant PET functional masterbatch can be prepared by the following method.

[0024] Specifically, the method comprises the following steps: firstly, terephthalic acid, ethylene glycol, 2,4-dihydroxybenzoic acid, diethylene glycol and neopentyl glycol are weighed and added into a stainless steel esterification tank in sequence, the added materials are stirred uniformly by a mechanical stirring device in the stainless steel esterification tank, and then the temperature is raised to 150 DEG C;Then, titanium tetrachloride is added as a catalyst, nitrogen is introduced under normal pressure to discharge air from the esterification tank, the pressure is gradually reduced to 0.5 Mpa, and the esterification reaction is carried out under nitrogen protection for 6-8 hours, and the reaction temperature is controlled to 190-220 DEG C;During the esterification reaction, the by-product water generated in the esterification reaction is evaporated and then condensed and discharged by a condenser connected to the top of the stainless steel esterification tank.

[0025] When the esterification reaction time is left for 60 minutes, trimethylolpropane is added into the stainless steel esterification tank and stirred uniformly by the mechanical stirring device in the stainless steel esterification tank, so as to prevent uneven TMP reaction and affect the viscosity of the system.

[0026] When the esterification reaction time is left for 30 minutes, Beta molecular sieve is added into the stainless steel esterification tank, and the outflow of water from the condenser is obviously reduced or even stopped, so that the esterification reaction is determined to be completed; the temperature in the esterification tank is reduced to 220 DEG C; under the protection of nitrogen, phosphoric acid is added according to the formula proportion; the mechanical stirring device in the stainless steel esterification tank is stirred for 5-10 minutes, so that the phosphoric acid is uniformly distributed.

[0027] The temperature in the esterification tank is gradually increased to 230 DEG C-250 DEG C, the pressure in the tank is adjusted to 500-1000 Pa, under the stirring of the mechanical stirring device, antimony acetate is added as a polycondensation catalyst according to the formula proportion, and isophorone diester is added; under the protection of nitrogen, the pressure is 500-1000 Pa, and the pre-polycondensation reaction is continuously carried out in the esterification tank for 3-5 hours.

[0028] When the pre-polycondensation reaction time is up, the pre-polycondensation product is transferred from the stainless steel esterification tank to the stainless steel polycondensation tank, and 2,6-di-tert-butyl-p-cresol and zinc metaborate are added into the stainless steel polycondensation tank; the polycondensation tank is connected with a vacuum system, so that the pressure in the polycondensation tank is reduced to 10-50 Pa; then the temperature is gradually increased to 280 DEG C-290 DEG C, and the polycondensation reaction is carried out for 2-3 hours; the mechanical stirring device in the stainless steel polycondensation tank is continuously stirred, the molecular weight of the polymer is detected to be 35,000-45,000 g / mol, and the polycondensation reaction is determined to be completed. Because TMP introduces a branching point, the viscosity of the system increases during the polycondensation reaction, so the temperature needs to be gradually increased, and stirring needs to be maintained to prevent local gelation. In addition, in the polycondensation reaction, the ester bonds formed by NPG participate in further polycondensation, and ethylene glycol or water is released, so the by-product generated in the polycondensation reaction needs to be evaporated and condensed and discharged through the condenser connected to the top of the polycondensation tank.

[0029] The polyester melt is introduced into the double-screw extruder from the polycondensation tank, extrusion cooling is formed into a long strip, the long strip is rapidly cooled through the water cooling system, and the long strip is cut into particles by using a pelletizer to form particles with a diameter of 4-8 mm.

[0030] Corresponding to the preparation method, the utility model also proposes a system specially used for preparing the anti-UV and hydrolysis-resistant PET functional master batch, as shown in Figure 1 .

[0031] As described above, the preparation system of the anti-UV and hydrolysis-resistant PET functional master batch, including the stainless steel esterification tank 100 and the stainless steel polycondensation tank 200, the outlet of the stainless steel esterification tank 100 is connected with the inlet of the stainless steel polycondensation tank 200 through a pipeline, and is used for transferring the pre-polycondensation product from the stainless steel esterification tank 100 to the stainless steel polycondensation tank 200.

[0032] The first vacuum pump 101 is connected to the upper portion of the stainless steel esterification tank 100, and a first condenser 102 is arranged in the pipeline connected to the first vacuum pump 101.

[0033] In order to control the reaction temperature in the esterification tank, in one embodiment, a first heat conducting oil jacket 103 is arranged outside the tank body of the stainless steel esterification tank 100.

[0034] Further, a first mechanical stirring device 104 can be arranged in the stainless steel esterification tank 100, and a second mechanical stirring device 204 can be arranged in the stainless steel polycondensation tank 200.

[0035] Further, the outlet of the stainless steel polycondensation tank 200 is connected to the inlet of the double screw extruder 300 through a pipeline, so as to guide the polyester melt from the polycondensation tank 200 into the double screw extruder 300.

[0036] Further, the outlet of the double screw extruder 300 is connected to the pelletizer 500, and a water cooling system 400 is arranged between the double screw extruder 300 and the pelletizer 500.

[0037] Further, the diameter of the particles formed by the pelletizer 500 is 4-8mm.

[0038] The preparation system of the anti-UV and hydrolysis resistant PET functional masterbatch fills the blank of the prior art, and can continuously produce and obtain the anti-UV and hydrolysis resistant PET functional masterbatch.

[0039] The performance of the PET film prepared by the PET functional masterbatch of the utility model will be described in detail below through specific embodiments 1-6.

[0040] In order to facilitate the description, each raw material of the PET functional masterbatch is represented in alphabetical order.

[0041] A: terephthalic acid (PTA); B: ethylene glycol (EG); C: isophorone diester (IPDE); D: 2,4-dihydroxybenzoic acid (2,4-DHBA); E: titanium tetrachloride (TiCl4); F: antimony acetate (Sb2O3); G: phosphoric acid (H3PO4); H: 2,6-di-tert-butyl-p-cresol (BHT); I: zinc metaborate; J: diethylene glycol (DEG); K: neopentyl glycol (NPG); L: Beta molecular sieve; M: trimethylolpropane (TMP).

[0042] The following table lists the weight parts of each component of the PET functional masterbatch for Examples 1-6.

[0043] Embodiments 1 2 3 4 5 6 A 95 105 95 100 100 100 B 65 75 70 75 65 70 C 25 35 30 25 35 30 D 15 25 20 25 20 15 E 0.05 0.1 0.07 0.08 0.06 0.07 F 0.04 0.08 0.06 0.08 0.05 0.06 G 0.03 0.06 0.05 0.06 0.04 0.05 H 0.03 0.08 0.06 0.07 0.05 0.06 I 0.01 0.03 0.02 0.03 0.02 0.03 J 3 7 5 6 4 5 K 8 9 10 10 3 12 L 8 12 10 11 9 10 M 3 4 4 5 5 6

[0044] The following table lists the performance parameters of the PET films prepared using the PET functional masterbatch of Examples 1-6.

[0045]

[0046]

[0047] The performance parameters are analyzed as follows: (1) UV resistance. 2,4-dihydroxybenzoic acid (2,4-DHBA) and isophorone diester (IPDE) provide high-efficiency UV absorption capability, with absorption peaks covering the UV-A and UV-B ranges. Beta molecular sieve further reduces UV transmittance by adsorbing part of the ultraviolet radiation through pore distribution. (2) Strength performance. The optimization of the PTA and EG ratio provides a balance between the rigidity and flexibility of the main chain. The rigid structure of isophorone diester (IPDE) significantly improves the tensile strength. In the range of 3-8 μm, the strength performance is better. (3) Thermal stability. The synergistic effect of phosphoric acid and BHT inhibits high-temperature degradation, improving the thermal stability of the film. The isophorone group further enhances the mechanical properties at high temperatures. (4) Hydrolysis resistance. The introduction of neopentyl glycol (NPG) and trimethylolpropane (TMP) enhances the cross-linking degree of the molecular chain and the hydrolysis resistance, ensuring stability in a humid and hot environment.

[0048] Summary: Examples 1-6 demonstrate the potential for optimizing UV resistance and hydrolysis resistance by fine-tuning the raw material ratio and changing the film thickness, while ensuring a balance of strength and thermal stability.

[0049] To make performance comparison, the utility model discloses the design of comparative example 1-6, and the design idea of comparative example is: omitting some key components (for example IPDE, 2, 4-DHBA, Beta molecular sieve etc.), test UV absorption or hydrolysis resistance parameter;Or replace some components (such as using traditional plasticizing agent to replace IPDE, using conventional antioxidant to replace BHT), test mechanical performance or thermal stability parameter;Or keep basic component (PTA and EG) to ensure copolymerization, test the performance drop of the absence of functional component.

[0050] The scheme measures used therein are shown in the following table.

[0051]

[0052]

[0053] The following table is the performance parameter of comparative example 1-6 PET film, and the reason of performance drop is listed in the processing mode of corresponding comparative example.

[0054]

[0055] In the above table, the processing mode of each comparative example is as follows: comparative example 1 omits IPDE and 2, 4-DHBA relative to example 1;Comparative example 2 uses phthalate to replace IPDE relative to example 2;Comparative example 3 omits Beta molecular sieve and Sb2O3 relative to example 3;Comparative example 4 replaces TMP with silane coupling agent relative to example 4;Comparative example 5 omits NPG and EMP relative to example 5;Comparative example 6 omits H3PO4 relative to example 6. In addition to the above differences, the remaining components and weight parts of each comparative example and its corresponding example remain unchanged.

[0056] Through performance comparison of comparative example 1-6 and example 1-6, it can be found that the UV transmittance of the film of comparative example increases significantly, the main reason is the absence or replacement of IPDE and 2, 4-DHBA, and the omission of Beta molecular sieve. In the example, IPDE provides excellent UV absorption capacity, 2, 4-DHBA enhances UV resistance, and Beta molecular sieve further improves the overall barrier property. In addition, the strength of comparative example decreases, especially when IPDE is omitted or replaced with flexible plasticizer, the mechanical property decreases due to insufficient molecular chain rigidity. Moreover, the hydrolysis resistance of comparative example is lower than that of example, mainly due to the omission of NPG and EMP or the use of substitutes. H3PO4 and BHT stabilize the molecular chain in high temperature environment in the example. And the hydrolysis resistance of comparative example decreases significantly, because Beta molecular sieve and zinc metaborate are omitted. The two components significantly enhance the barrier property in the example through physical filling and interface adsorption.

[0057] By comparing the above comparative examples and examples, the following conclusions can be drawn: the functional components (such as IPDE, 2, 4-DHBA, Beta molecular sieve, NPG and EMP, etc.) in the examples have significant contribution to the UV resistance, strength and hydrolysis resistance. The performance parameters of the comparative example films all decrease significantly after the key components are omitted or replaced, which proves the necessity and superiority of the optimized formula and unique design of the example combination.

[0058] In summary, the PET functional masterbatch of the present application significantly overcomes the defects of limited UV resistance and hydrolysis resistance of PET products by optimizing the molecular structure and functional component combination. By introducing UV absorbing groups such as isophorone diester (IPDE) and 2, 4-dihydroxybenzoic acid (2, 4-DHBA), the molecular chain's ability to absorb UV light is enhanced, and the film's aging resistance is improved. In addition, the use of Beta molecular sieve, zinc metaborate and other additives improves the uniform distribution of light stabilizers and UV absorbers in the molecular structure, effectively avoiding the uneven UV absorption performance of the film during the stretching process due to the change of molecular arrangement. The synergistic effect of components such as NPG and EMP in the formula not only improves the film's UV resistance, strength and hydrolysis resistance, but also ensures the uniformity of the film's performance, providing an innovative material solution for the preparation of high-performance PET products.

[0059] The above description is only a specific embodiment of the present application, and is not intended to limit the scope of the present application. Any equivalent changes, modifications and combinations made by those skilled in the art without departing from the concept and principles of the present application shall fall within the scope of the present application.

Claims

1. A system for preparing an anti-UV hydrolysis-resistant PET functional masterbatch, characterized in that, The preparation system comprises a stainless steel esterification tank (100) and a stainless steel polycondensation tank (200), the outlet of the stainless steel esterification tank (100) is connected to the inlet of the stainless steel polycondensation tank (200) through a pipeline; wherein the upper portion of the stainless steel esterification tank (100) is connected to a first vacuum pump (101), a first condenser (102) is arranged in the pipeline connected to the stainless steel esterification tank (100); a first heat conducting oil jacket (103) is arranged outside the tank body of the stainless steel esterification tank (100); the upper portion of the stainless steel polycondensation tank (200) is connected to a second vacuum pump (201), a second condenser (202) is arranged in the pipeline connected to the stainless steel polycondensation tank (200); a second heat conducting oil jacket (203) is arranged outside the tank body of the stainless steel polycondensation tank (200).

2. The preparation system of claim 1, wherein, The stainless steel esterification tank (100) is provided with a first mechanical stirring device (104).

3. The preparation system of claim 1, wherein, The stainless steel polycondensation tank (200) is provided with a second mechanical stirring device (204).

4. The preparation system of claim 1, wherein, The outlet of the stainless steel polycondensation tank (200) is connected to the inlet of a double screw extruder (300) through a pipeline.

5. The preparation system of claim 4, wherein, The outlet of the double screw extruder (300) is connected to a granulator (500), and a water cooling system (400) is arranged between the double screw extruder (300) and the granulator (500).

6. The preparation system of claim 4, wherein, The diameter of the particles formed by the granulator (500) is 4-8 mm.

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