Regenerated PET (Polyethylene Terephthalate) material as well as preparation method and application thereof

Abstract

The invention discloses a regenerated PET (Polyethylene Terephthalate) material as well as a preparation method and application thereof. The preparation method of the regenerated PET material comprises the following steps that regenerated PET slices are subjected to stage heating pre-crystallization treatment, a compound main catalyst is combined for reactive extrusion, then solid-phase tackifying is conducted, and the prepared regenerated PET material has high intrinsic viscosity, low yellowness and high tensile strength; the intrinsic viscosity of the prepared regenerated PET material is not lower than 0.66 dL / g, the yellowness change value is not higher than 3.5, and the tensile strength is not lower than 50 MPa.

Description

Technical Field

[0001] This invention belongs to the field of polymer material recycling and modification technology, specifically relating to a recycled PET material, its preparation method, and its application. Background Technology

[0002] Polyethylene terephthalate (PET resin) is a widely used plastic with good rigidity and abrasion resistance, producing parts with a glossy surface and high transparency. However, recycled PET resin has a lower intrinsic viscosity after recycling, resulting in severely insufficient inherent mechanical properties, heat resistance, and processing performance, which collectively limits the high-value application of recycled PET. It cannot meet the requirements of processes such as blow molding and foaming, and is difficult to use in environments with standards for strength or heat resistance, leading to its often downgraded use.

[0003] In existing technologies, solid-phase thickening is often used to increase the intrinsic viscosity of recycled PET materials. However, due to the slow thickening rate, which requires a long time and high energy consumption, and the increased yellowing of recycled PET materials, it cannot be used to manufacture water bottles and beverage bottles that require high transparency and appearance, as well as outdoor building materials and automotive exterior parts that require excellent weather resistance and durability. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing recycled PET materials that cannot simultaneously possess high viscosity, low yellowness, and high mechanical properties, and to provide a recycled PET material.

[0005] Another object of the present invention is to provide a method for preparing the recycled PET material.

[0006] Another object of the present invention is to provide applications of the recycled PET material.

[0007] To achieve the above objectives, the present invention employs the following technical solution:

[0008] A recycled PET material, wherein the recycled PET material is made from recycled PET chips, and the intrinsic viscosity of the recycled PET material is not less than 0.66 dL / g, the yellowness value change is not higher than 3.5, and the tensile strength is not less than 50 MPa.

[0009] The intrinsic viscosity of the recycled PET material described in this invention is not less than 0.66 dL / g, for example, but not limited to, not less than 0.66 dL / g, 0.68 dL / g, 0.7 dL / g, 0.72 dL / g, 0.75 dL / g, 0.78 dL / g, 0.8 dL / g, 0.82 dL / g, 0.85 dL / g, 0.88 dL / g, or 0.9 dL / g, etc., as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the specific values ​​included in the range are not exhaustively listed in this invention.

[0010] Preferably, the intrinsic viscosity of the recycled PET material is 0.7~0.85 dL / g.

[0011] Specifically, the test standard for the intrinsic viscosity of the recycled PET material is GB / T 1632.5-2008.

[0012] The yellowness value variation of the recycled PET material described in this invention is no higher than 3.5, for example, but not limited to, no higher than 3.5, 3.4, 3.3, 3.2, 3.1, 3, 2.9, 2.8, 2.7, 2.6, 2.5, 2.4, 2.3, 2.2, 2.1, 2, 1.9, or 1.8, etc., as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the specific values ​​included in the range are not exhaustively listed in this invention.

[0013] Preferably, the yellowness value of the recycled PET material varies from 2 to 3.4.

[0014] Specifically, the yellowness of the recycled PET material is tested according to standard GB / T 39822-2021.

[0015] It should be noted that the change in yellowness value of the recycled PET material in this invention = yellowness of the recycled PET material - yellowness of the recycled PET slices.

[0016] The tensile strength of the recycled PET material described in this invention is not less than 50 MPa, for example, but not limited to, not less than 50 MPa, 50.5 MPa, 51 MPa, 51.5 MPa, 52 MPa, 52.5 MPa, 53 MPa, 53.5 MPa, 54 MPa, 54.5 MPa, 55 MPa, 55.5 MPa, 56 MPa, 56.5 MPa, 57 MPa, 57.5 MPa, 58 MPa, 58.5 MPa, 59 MPa. The specific values ​​within the ranges of Pa, 59.5 MPa, 60 MPa, 60.5 MPa, 61 MPa, 61.5 MPa, 62 MPa, 62.5 MPa, 63 MPa, 63.5 MPa, 64 MPa, 64.5 MPa, 65 MPa, 65.5 MPa, 66 MPa, 66.5 MPa, or 67 MPa, as well as specific values ​​between the above-mentioned values, are not exhaustively listed in this invention due to space limitations and for the sake of brevity.

[0017] Preferably, the tensile strength of the recycled PET material is 51~66 MPa.

[0018] Specifically, the tensile strength of the recycled PET material is tested according to standard GB / T 1040.2025.

[0019] This invention also provides a method for preparing the above-mentioned recycled PET material, comprising the following steps: S1. Precrystallize recycled PET chips by heating to obtain a precrystallized product; S2. The pre-crystallized product from step S1 is mixed with the main catalyst, chain extender and co-catalyst, and the reaction is extruded to obtain pre-adhesive particles; S3. The pre-adhesive particles from step S2 are subjected to solid-phase adhesion and post-treatment to obtain recycled PET material; The main catalyst includes titanate compounds and nano-silica.

[0020] The inventors discovered through research that by using a staged heating pre-crystallization process, combined with a compound main catalyst reaction extrusion followed by solid-phase thickening, the resulting recycled PET material has high intrinsic viscosity, low yellowness, and high tensile strength.

[0021] In the preparation method of this invention, the low-temperature stage of phased heating and pre-crystallization can achieve stable formation and preliminary drying of recycled PET chip nuclei, avoiding agglomeration; the high-temperature stage achieves rapid improvement in crystallinity and deep drying, creating a uniform, stable, and dry reaction environment for subsequent thickening. Combined with an efficient catalytic chain extension system, it achieves rapid and precise repair of molecular chains. At the same time, the side reactions are minimized through mild process conditions and stabilizers. The resulting recycled PET material has high viscosity, low yellowness, and good tensile strength.

[0022] Preferably, the recycled PET chips contain ≥98wt% PET, such as, but not limited to, 98.1wt%, 98.2wt%, 98.3wt%, 98.4wt%, 98.5wt%, 98.6wt%, 98.7wt%, 98.8wt%, 98.9wt%, 99wt%, 99.1wt%, 99.2wt%, 99.3wt%, 99.4wt%, 99.5wt%, 99.6wt%, 99.7wt%, 99.8wt%, 99.9wt%, or 100wt%, all of which satisfy the requirements of this invention.

[0023] Specifically, the recycled PET chips are obtained by crushing, extruding, and pelletizing PET bottle products.

[0024] Preferably, the pre-crystallization stage in step S1 is as follows: the recycled PET chips are dried at 85~105℃ for 2~3 hours, and then crystallized at 125~175℃ for 1.5~2 hours.

[0025] Preferably, the main catalyst in step S2 is 0.15~0.3 wt% of the pre-crystallized product in step S1.

[0026] Preferably, the mass ratio of titanate compound to nano-silica in the main catalyst is (3~6):1.

[0027] Preferably, the titanium-based catalyst comprises one or more of tetrabutyl titanate, tetraethyl titanate, tetraisopropyl titanate, or tetran-n-propyl titanate.

[0028] Preferably, the average particle size of the nano-silica is ≤100nm.

[0029] More preferably, the average particle size of the nano-silica is 20~100nm.

[0030] Preferably, the co-catalyst in step S2 is 0.08~0.15 wt% of the pre-crystallized product of the recycled PET resin in step S1.

[0031] Preferably, the co-catalyst comprises phosphate ester and montmorillonite.

[0032] More preferably, the mass ratio of phosphate ester to montmorillonite in the co-catalyst is 1:(1.5~2.5).

[0033] Specifically, the phosphate ester may be triphenyl phosphate and / or pentaerythritol phosphate.

[0034] Preferably, the phosphate ester is triphenyl phosphate.

[0035] Preferably, the chain extender in step S2 is 0.08~0.5 wt% of the pre-crystallized product in step S1.

[0036] Preferably, the chain extender in step S2 includes one or more of isocyanate compounds, epoxy compounds, or oxazoline compounds.

[0037] Specifically, the isocyanate compounds include one or more of hexamethylene diisocyanate, hexamethylene diisocyanate isocyanurate trimer, 4,4-diisocyanate dicyclohexylmethane, or tetramethylphenyldiisocyanate.

[0038] Specifically, the epoxy compounds include bisphenol A type epoxy resin, Jia Yi Rong SG-20, ADR 4370S or ADR 4468.

[0039] Specifically, the oxazoline compounds include 2,2'-bis(2-oxazoline) and / or 1,3-bis(4,5-dihydrooxazol-2-yl)benzene.

[0040] Preferably, step S2 further includes 0.08 to 0.12 wt% of an antioxidant in the pre-crystallized product of step S1.

[0041] The antioxidants described in this invention can be commonly used antioxidants, such as, but not limited to, hindered phenolic antioxidants and / or phosphite antioxidants.

[0042] Specifically, the hindered phenolic antioxidants are N,N'-hexamethylene bis(3,5-di-tert-butyl-4-hydroxyphenylpropionamide) (Irganox 1098), pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (Irganox 1010), 1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)-1,3,5-triazine-2,4,6-(1H,3H,5H)-trione (antioxidant 1790), 1,6-hexanediol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (Irganox 259), and octadecyl β-(4-hydroxy-3,5-di-tert-butylphenyl)propionate (Irganox 1098). 1076) or one or more of 3,9-bis{2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)acrylic acid]-1,1-dimethyl}-2,4,8,10-tetraoxaspirocycloundecane (ADK AO-80).

[0043] The phosphite antioxidant is one or more of tris(2,4-di-tert-butylphenyl) phosphite (antioxidant 168), bis(2,6-di-tert-butyl-4-tolyl) pentaerythritol phosphite (PEP-36), or 627A.

[0044] Preferably, the reactive extrusion in step S2 is as follows: preheating in the feeding section, melting and mixing activation in the melting section, high-speed shearing in the mixing section, and stable extrusion in the die head section.

[0045] Specifically, the preheating temperature of the feeding section is 165~175℃. Preheating the mixture prevents clumping and uneven dispersion.

[0046] Specifically, the melting and mixing activation temperature of the molten section is 245~255℃. This allows the pre-crystallized product to completely melt while simultaneously undergoing preliminary mixing and activation with the main catalyst and chain extender.

[0047] Specifically, the high-speed shearing temperature in the mixing section is 230~250℃. The titanate compound and chain extender in the main catalyst react synergistically, avoiding excessive cross-linking of the chain extender due to high temperature, and initially improving viscosity.

[0048] Specifically, the stable extrusion temperature of the die head section is 248~255℃, and the die head pressure is 11~14MPa.

[0049] Preferably, the solid phase thickening process in step S3 is performed using a rotary drum solid phase thickening furnace.

[0050] Preferably, the solid-phase thickening temperature in step S3 is 190~200℃.

[0051] Preferably, the vacuum degree of the solid-phase thickening in step S3 is ≤30 Pa. This accelerates the removal of small molecules generated in the reaction and avoids the small molecules inhibiting the synergistic effect between the titanate compound and the chain extender.

[0052] Preferably, the solid-phase thickening time in step S3 is 1~3 hours.

[0053] Preferably, the rotary drum solid phase thickening furnace rotates at 8-12 rpm, and the tilt angle of the rotary drum vacuum solid phase thickening furnace is 15°.

[0054] Preferably, the post-treatment in step S3 involves holding the product at 100-110°C for 0.5-1.5 hours, followed by cooling to room temperature at a rate of 5-8°C / hour. This step reduces the internal stress of the molecular chains after chain extension, preventing cracking during subsequent processing.

[0055] This invention also protects the use of the above-mentioned recycled PET material in the manufacture of packaging products, textile fiber products or engineering plastic products.

[0056] A plastic product made from the aforementioned recycled PET material, such as polyester fiber, everyday bottles, folder covers, plastic trays, etc.

[0057] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a method for preparing and applying recycled PET material. By pre-crystallizing recycled PET chips through staged heating and then reacting and extruding them with a compound main catalyst, the resulting recycled PET material has high intrinsic viscosity, low yellowness, and good tensile strength. Detailed Implementation

[0058] The present invention will be further described in detail below with reference to specific embodiments. These embodiments are only used to explain the present invention and are not intended to limit the scope of the present invention. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods; the materials and reagents used are commercially available unless otherwise specified.

[0059] 1. Raw materials used in each embodiment and comparative example: Recycled PET chips: Recycled PET chips 1: RPET UCM-0413 GN64 (LSK), intrinsic viscosity of 0.52 dL / g, tensile strength of 44.5 MPa (tested according to GB / T 1040.2025 standard), purchased from Lisaike Environmental Materials Technology Co., Ltd. Recycled PET chips 2: RPET UCM-0412 PW71(SWE), intrinsic viscosity of 0.46 dL / g, tensile strength of 46.0 MPa (tested according to GB / T 1040.2025 standard), purchased from Jiangsu Saiweier New Material Technology Co., Ltd. 3. Recycled PET Chips: PET BG80 (purchased from Sinopec Yizheng Chemical Fiber Co., Ltd.) granules were placed in a dehumidifying dryer and treated in dry air at 160℃±5℃ for more than 4 hours to control the moisture content below 50ppm. Subsequently, the dried granules were fed into the injection molding machine barrel and injected into a preform mold at 80℃±10℃ under a melt temperature of 285℃±5℃ and an injection pressure of 75±10 bar. After pressure holding and cooling, preforms of the specified weight were obtained. Next, the cooled preforms were transferred to a blow molding machine oven and uniformly heated to the optimal stretching state above the glass transition temperature (preform wall temperature approximately 105~115℃) using a far-infrared heater set at 100℃±10℃. Then, the hot preforms were quickly transferred to the blow molding mold and subjected to longitudinal mechanical stretching using a stretching rod at a speed of 0.8~1.2 m / s, while simultaneously introducing 25±5... The bar uses high-pressure clean air to radially inflate the PET bottle, causing it to be stretched and formed bidirectionally within the mold cavity at 10-15°C. Finally, after holding the pressure and cooling for 2-4 seconds, the mold is opened and the PET bottle is demolded to obtain the product. The PET bottle products were balanced indoors for one week, then crushed by a crusher and screened with a 16mm sieve to obtain fragments smaller than 16mm. These fragments were then melt-extruded at 265℃ by an extruder, filtered into strips, and water-cooled and pelletized to obtain recycled PET chips 3 with a tensile strength of 57.6MPa (tested according to GB / T 1040.2025 standard).

[0060] Main catalyst: Main catalyst 1: a compound of tetrabutyl titanate (Titanium(IV) butoxide, purchased from Innochem) and silicon dioxide (Silicon dioxide-50 nm, purchased from Innochem) in a mass ratio of 4:1; Main catalyst 2: a mixture of tetraethyl titanate (Titanium(IV) butoxide, purchased from Innochem) and silicon dioxide (Silicon dioxide-50 nm, purchased from Innochem) in a mass ratio of 5:1; Main catalyst 3: Tetrabutyl titanate (Titanium(IV) butoxide, purchased from Innochem); Co-catalyst: Co-catalyst 1: a mixture of triphenyl phosphate and montmorillonite in a mass ratio of 1:2, purchased from Innochem; Co-catalyst 2: a mixture of pentaerythritol phosphate and montmorillonite in a mass ratio of 1:2, purchased from Innochem; Chain extender: Chain extender 1: Epoxy compound, ADR4370, purchased from BASF; Chain extender 2: Oxazoline compound, 2,2'-bis(2-oxazoline), purchased from Aladdin; Antioxidants: A compound of antioxidant 1010 and antioxidant 168 in a mass ratio of 2:1, both of which are commercially available; It should be noted that the parallel experiments in the examples and comparative examples all used raw materials from the same source.

[0061] 2. The recycled PET materials for each embodiment and comparative example were prepared according to the formulations in Tables 1-2 and the following preparation methods: S1. The recycled PET chips are dried at 90℃ for 2.5h and then crystallized at 130℃ for 1.8h to obtain the pre-crystallized product; S2. The pre-crystallized product from step S1 is mixed with the main catalyst, chain extender, co-catalyst, and antioxidant, and then reacted and extruded. The resulting powder is then granulated after being washed with water to obtain pre-adhesive particles. The reaction extrusion process is as follows: S21. The feeding section is preheated to 170℃; S22. The activation temperature for the melting and mixing of the molten section is 250℃; S23. The high-speed shearing temperature in the mixing section is 240℃; S24. The stable extrusion temperature of the die head section is 250℃, and the die head pressure is 12MPa; S3. The pre-adhesive particles from step S2 are loaded into a rotary drum vacuum solid-phase adhesion enhancement furnace for solid-phase adhesion enhancement. The solid-phase adhesion enhancement temperature is 190℃, the vacuum degree is ≤25Pa, the solid-phase adhesion enhancement time is 2.5h, the rotation speed of the rotary drum vacuum solid-phase adhesion enhancement furnace is 10rpm, and the tilt angle of the rotary drum vacuum solid-phase adhesion enhancement furnace is 15°. Then, it is kept at 105℃ for 1h, and then cooled to room temperature at 6℃ / h to obtain recycled PET material.

[0062] The only difference between Comparative Example 1 and Example 1 is that the pre-crystallization in step S1 was directly crystallized at 90°C for 4.3 hours.

[0063] The only difference between Comparative Example 2 and Example 1 is that the pre-crystallization in step S1 was directly crystallized at 130°C for 4.3 hours.

[0064] 3. Performance Testing: (1) Intrinsic viscosity test: The recycled PET materials prepared in each example and comparative example were used as solvents in the standard GB / T1632.5-2008, with a mixture of phenol and tetrachloroethane (mixed thoroughly at a mass ratio of 50:50) to prepare sample solutions with a concentration of 0.005 g / ml. The time for the pure solvent and PET solution to flow through the capillary was measured using an Ubbelohde viscometer in a constant temperature water bath at 25℃. (2) Yellowness value change test: The recycled PET materials prepared in each example and comparative example were injection molded into standard color plates of 55mm×80mm×2mm and tested according to standard GB / T 39822-2021, and recorded as yellowness values; the recycled PET chips of the corresponding raw materials used in each example and comparative example were injection molded into standard color plates of 55mm×80mm×2mm and tested according to standard GB / T39822-2021, and recorded as initial yellowness values. The yellowness value change was calculated by yellowness value change = yellowness value - initial yellowness value (where the initial yellowness value of recycled PET chip 1 is 5.8; the initial yellowness value of recycled PET chip 2 is 5.6; and the initial yellowness value of recycled PET chip 3 is 4.5). (3) Tensile strength test: The recycled PET materials prepared in each example and comparative example were injection molded into 1A type standard dumbbell strips. The dimensions of the strips were: total length ≥ 150 mm, gauge length 50 mm, parallel section width 10 mm, and thickness 4 mm. The test was carried out in accordance with GB / T1040.2025 standard.

[0065] Examples 1-8 and Comparative Examples 1-5 Table 1. Amount (parts by weight) and properties of each component in the recycled PET materials of Examples 1-8

[0066] Table 2. Amounts (parts by weight) and properties of each component in each comparative example of recycled PET material

[0067] As can be seen from Table 1, the recycled PET material of the present invention has high intrinsic viscosity, low yellowness and good tensile strength. Specifically, the intrinsic viscosity of the recycled PET material is not less than 0.66 dL / g, the yellowness value change is not higher than 3.5, and the tensile strength is not less than 50 MPa.

[0068] As can be seen from Comparative Examples 1 and 2, if the pre-crystallization does not use staged heating, resulting in insufficient crystallization and drying, severe hydrolysis and degradation will occur during subsequent melting, leading to molecular chain breakage and a sharp drop in viscosity and mechanical properties. The high temperature throughout the process causes residual moisture inside to cause degradation. Since the outer layer has been crystallized and hardened, the degradation is more concentrated inside. The long-term high-temperature treatment itself will cause severe thermo-oxidative degradation. The resulting recycled PET material cannot have both low yellowness and high intrinsic viscosity and tensile strength. Moreover, the energy consumption of high temperature throughout the process in Comparative Example 2 is significantly increased.

[0069] As can be seen from Comparative Example 3, without the use of a compounded main catalyst, the intrinsic viscosity of the resulting recycled PET material is lower, and its yellowness is significantly higher than that of the example. This may be because pure titanate compounds are rapidly deactivated by hydrolysis and are unevenly dispersed in the high-viscosity melt, resulting in local over-catalysis and low overall efficiency. On the one hand, the trace amounts of water that are difficult to completely remove from recycled PET will cause some of the catalyst to hydrolyze and generate inactive titanium dioxide precipitates, resulting in insufficient chain extension reaction and limited improvement in intrinsic viscosity. On the other hand, unevenly dispersed catalyst microclusters will trigger violent local reactions, forming branching, cross-linking, and even gel points. At the same time, rapid exothermic reactions induce severe thermo-oxidative degradation, ultimately resulting in severe yellowing of the product, a widening of the molecular weight distribution, a decrease in mechanical properties, and a narrowing of the processing window, leading to a decrease in production stability.

[0070] As can be seen from Comparative Example 4, the yellowness of the recycled PET material obtained without the addition of a co-catalyst is higher than that of the Example.

[0071] As can be seen from Comparative Example 5, although increasing the amount of a single main catalyst can improve the intrinsic viscosity of recycled PET material, the yellowness increases significantly and the tensile strength is lower than that of the example.

[0072] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing recycled PET material, characterized in that, Includes the following steps: S1. Precrystallize recycled PET chips by heating to obtain a precrystallized product; S2. The pre-crystallized product from step S1 is mixed with the main catalyst, chain extender and co-catalyst, and the reaction is extruded to obtain pre-adhesive particles; S3. The pre-adhesive particles from step S2 are subjected to solid-phase adhesion and post-treatment to obtain recycled PET material; The main catalyst comprises a composite of titanate compound and nano-silica.

2. The preparation method according to claim 1, characterized in that, The pre-crystallization stage described in step S1 is as follows: the recycled PET resin of the slices is dried at 85~105℃ for 2~3h, and then crystallized at 125~175℃ for 1.5~2h.

3. The preparation method according to claim 1, characterized in that, The main catalyst described in step S2 satisfies at least one of the following two conditions: (a) The main catalyst is 0.15~0.3 wt% of the pre-crystallized product of step S1; (b) The mass ratio of titanate compound to nano-silica in the main catalyst is (3~6):

1.

4. The preparation method according to claim 1, characterized in that, Satisfy at least one of the following two conditions: (a) The co-catalyst in step S2 is 0.08 to 0.15 wt% of the pre-crystallized product in step S1; the co-catalyst includes phosphate ester and montmorillonite; preferably, the mass ratio of phosphate ester to montmorillonite in the co-catalyst is 1:1.5 to 1:2.5; (b) The chain extender in step S2 is 0.08 to 0.5 wt% of the pre-crystallized product in step S1; the chain extender includes one or more of isocyanate compounds, epoxy compounds or oxazoline compounds.

5. The preparation method according to claim 1, characterized in that, Step S2 also includes 0.08 to 0.12 wt% of an antioxidant in the pre-crystallized product of step S1.

6. The preparation method according to claim 1, characterized in that, The reactive extrusion described in step S2 is as follows: preheating in the feeding section, melting and mixing activation in the melting section, high-speed shearing in the mixing section, and stable extrusion in the die head section; Preferably, the preheating temperature of the feeding section is 165~175℃; The temperature for the melting and mixing activation of the molten section is 245~255℃; The high-speed shearing temperature in the mixing section is 230~250℃; The stable extrusion temperature of the die head section is 248~255℃, and the die head pressure is 11~14MPa.

7. A recycled PET material, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 6.

8. The recycled PET material according to claim 7, characterized in that, The intrinsic viscosity of the recycled PET material is not less than 0.66 dL / g, and the tensile strength is not less than 50 MPa; preferably, the intrinsic viscosity of the recycled PET material is 0.7~0.85 dL / g, and the tensile strength is 51~66 MPa.

9. The use of the recycled PET material of claim 7 or 8 in the manufacture of packaging products, textile fibers or engineering plastic articles.

10. A plastic product, characterized in that, It is prepared using the recycled PET material described in claim 7 or 8.

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