Highly transparent high-barrier polyester article and method for producing the same

Abstract

The application discloses a kind of high transparent high barrier polyester products and preparation method thereof.The method is under molten state to polyester, polyester blend or polyester composite material is applied dynamic force field, through the periodic loading-unloading process provided by dynamic force field, induce the rearrangement of polymer molecular chain, enhance the interaction between polymer molecular chain, regulate the free volume of polyester material, increase the diffusion resistance of gas molecule in material interior, reduce the gas permeation coefficient of material, so as to significantly improve its gas barrier property, finally, using different geometric size mold cooling forming film, sheet, bar, pipe or profile etc..Through accurate control to polymer microstructure and macroscopic performance, the application realizes one-step preparation of high transparent high barrier polyester product, with obvious advantages such as simple production method, controllable process, low cost, without any additive and post-treatment process etc..

Description

Technical Field

[0001] This invention belongs to the technical field of high-performance polyester materials and polymer material processing and molding methods, specifically relating to a high-transparency, high-barrier polyester product and its preparation method. Technical Background

[0002] The green and efficient preparation of high-performance polymer materials aligns with national development strategies and is a key aspect of achieving the dual-carbon strategy goals. Polyethylene terephthalate (PET), as an engineering plastic, possesses excellent mechanical properties, solvent resistance, high transparency, and good hygiene and safety, making it widely used in packaging, electronics, automotive parts, and machinery. However, PET's relatively weak gas barrier properties severely restrict its promotion and application in high-end fields. Therefore, improving the barrier properties of PET has become a critical issue that urgently needs to be addressed. To date, methods such as chemical modification, physical blending, induced crystallization, and surface modification have been widely used to improve the barrier properties of materials. However, existing methods suffer from drawbacks such as high preparation costs, severe environmental pollution, poor transparency, and low efficiency, significantly limiting the preparation of high-barrier polymer materials.

[0003] A molding process in which all physical parameters remain unchanged over time is called a steady-state molding process. However, by introducing controllable periodic perturbations into the molding process, the physical quantities change over time, transforming steady-state molding into a dynamic molding process. Introducing a dynamic force field into the processing can more effectively control the molecular chain conformation, crystal structure, crystallinity, and free volume of polymers, allowing for effective intervention and control over the final properties of the material during molding. Precise control of the microstructure and macroscopic properties of polymer materials through dynamic force fields not only simplifies the process and facilitates continuous production, but also allows for greater development of their inherent potential, achieving self-enhancing performance without any additives. This is considered an economical, efficient, and green molding process for preparing high-performance polymer materials.

[0004] Chinese patent application for a three-layer co-extruded high-transparency, high-barrier BOPET film discloses a PET base film layer in the middle, with a barrier layer on each of the top and bottom surfaces of the PET base film layer, and a coating material layer on the side of the barrier layer opposite to the PET base film layer. This method can improve the barrier performance to a certain extent, but it has shortcomings such as complex processes, formulations and equipment, and limited product variety. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention aims to provide a high-transparency, high-barrier polyester product and its preparation method, addressing the problems of high preparation cost, severe environmental pollution, low transparency, and low preparation efficiency in existing technologies. This invention significantly improves gas barrier performance by controlling the free volume of the polymer, increasing the diffusion resistance of gas molecules within the material, and constructing a gas barrier. This method is simple, requires no additives or post-processing, and can achieve one-step preparation of high-barrier, high-transparency products.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] (1) A certain amount of polyester, polyester blend or polyester composite material is placed in a molding die and melted to obtain a polymer melt;

[0008] (2) Apply a dynamic force field to the polymer melt prepared in step (1) and cool it to obtain a high-transparency and high-barrier polyester product. Each cycle of the dynamic pressure field includes a loading zone and an unloading zone. In the loading zone, the pressure applied to the material increases linearly from 0 MPa to a maximum pressure of 2.5-100 MPa at a rate of 10 MPa / s-400 MPa / s, and is maintained at the maximum pressure for 0-5s. Then, it decreases linearly to 0 MPa at a rate of 10 MPa / s-400 MPa / s. In the unloading zone, the pressure applied to the material is constant at 0 MPa and is maintained for 0.05-5s.

[0009] Further, the polyester in step (1) includes one or more of PET (polyethylene terephthalate), PBT (polybutylene terephthalate), PEN (polyethylene terephthalate), and PLA (polylactic acid).

[0010] Preferably, the number-average molecular weight of the PET is 20,000-50,000 g / mol, the number-average molecular weight of the PBT is 10,000-50,000 g / mol, the number-average molecular weight of the PEN is 10,000-60,000 g / mol, and the number-average molecular weight of the PLA is 50,000-200,000 g / mol.

[0011] Further, the polyester blend in step (1) includes one or more of PET / PEN, PET / PBT, and PEN / PBT.

[0012] Further, the polyester composite material in step (1) includes one or more of PET / silica, PBT / silica, PEN / silica, PLA / silica, PET / carbon nanotubes, PBT / carbon nanotubes, PEN / carbon nanotubes, PLA / carbon nanotubes, PET / boron nitride, PBT / boron nitride, PEN / boron nitride, and PLA / boron nitride.

[0013] Further, in step (1), the mass ratio of PET to other polyesters besides PET in the polyester blend is (99-1):1.

[0014] Further, the polyester composite material in step (1) is composed of nanofillers and polyester materials, and the mass ratio of nanofillers to polyester materials is (99:1)-(70:30).

[0015] Furthermore, the polyester, polyester blend or polyester composite material described in step (1) needs to be dried at 50-150°C before melting.

[0016] Furthermore, the polyester, polyester blend or polyester composite material described in step (1) needs to be dried at 80°C before melting.

[0017] Further, the polyester blend or polyester composite material in step (1) is achieved by a melt blending device, which is a twin-screw extruder, a Brabender internal mixer, a single-shaft eccentric rotor internal mixer or a dual-shaft eccentric rotor internal mixer. The melt blending temperature is 20-50°C higher than the melting temperature or viscous flow temperature, and the blending time is 0.1-10 min.

[0018] Further, the molding die in step (1) includes a die with a cavity of film, sheet, rod, tube or profile, and the cavity thickness is 0.1-3mm.

[0019] Furthermore, in step (2), the load-unload loop is repeated 10-500 times.

[0020] Furthermore, the dynamic force field described in step (2) is a dynamic pressure field.

[0021] Furthermore, in step (2), the loading period of the dynamic pressure field is 0.55s.

[0022] Furthermore, the cooling method described in step (2) is water cooling or oil cooling.

[0023] Furthermore, the cooling rate in step (2) is greater than 50°C / s; the present invention rapidly and uniformly cools the polymer melt after applying a dynamic force field, fully preserving the structural changes caused by the dynamic force field and suppressing the formation of crystal structure, thereby obtaining a highly transparent and high-barrier material.

[0024] Furthermore, the cooling rate in step (2) is 100°C / s.

[0025] The present invention also provides a high-transparency, high-barrier polyester product prepared by the aforementioned preparation method.

[0026] This invention discloses a method for preparing highly transparent and high-barrier polyester products. The method involves melting polyester, polyester blends, or polyester composites at a specific temperature, followed by applying a dynamic force field while the material is molten. Through a periodic loading-unloading process provided by the dynamic force field, the polymer molecular chains are induced to rearrange, enhancing the interactions between them, regulating the material's free volume, increasing the diffusion resistance of gas molecules within the material, and reducing the gas permeability coefficient. This significantly improves the material's gas barrier properties. Finally, the material is cooled and molded into films, sheets, rods, tubes, or profiles using molds of different geometric dimensions. By precisely controlling the polymer's microstructure and macroscopic properties, this invention achieves a one-step preparation of highly transparent and high-barrier polyester products, offering significant advantages such as simple production methods, controllable processes, low cost, and the elimination of any additives or post-processing steps.

[0027] The present invention has the following beneficial effects:

[0028] 1. Compared with existing related technologies, the present invention realizes a one-step preparation of high transparency and high barrier polyester material products, which can meet a wider range of application needs.

[0029] 2. This invention achieves barrier properties of self-reinforced polymer materials in a one-step process, with low equipment cost, simple process, and isotropic internal structure of the product.

[0030] 3. During the processing, the internal structure of the material is controlled by a dynamic force field, without any additives or post-processing, and there are no pollutant emissions. Attached Figure Description

[0031] Figure 1 This diagram illustrates the evolution of the internal microstructure of PET under steady-state and dynamic force fields.

[0032] Figure 2 This is a graph showing the change of pressure over time under a dynamic force field.

[0033] Figure 3 This is a graph showing the change of pressure over time under a steady-state force field. Detailed Implementation

[0034] The purpose of the present invention will be further described in detail below through specific embodiments. The embodiments cannot be repeated one by one here, but the implementation of the present invention is not limited to the following embodiments.

[0035] The polyesters, polyester blends or polyester composites used in the following implementations were all dried before melting.

[0036] Example 1:

[0037] This embodiment describes a method for preparing highly transparent and high-barrier PET, including the following steps:

[0038] (1) Place 30g of PET granules into a mold cavity with a thickness of 0.5mm and melt it at 270℃ for 10min to obtain PET melt;

[0039] (2) At 270℃, the motion program of the molding die is adjusted by setting process parameters to control the motion of the PET melt obtained in step (1), so that it produces the following... Figure 2 The dynamic pressure field was applied at a linear rate of 60 MPa / s to the maximum pressure (15 MPa), and then held for 0 s. The pressure was then linearly reduced to 0 MPa at a rate of 60 MPa / s. The holding times in the unloading zone were 0.70 s, 1.20 s, 1.63 s, and 2.10 s, respectively. The number of cycles (loading-unloading) was 120. The samples were then water-cooled to room temperature at a rate of 100 °C / s. The resulting high-transparency, high-barrier PET sheet samples were named CPP1, CPP2, CPP3, and CPP4, respectively.

[0040] Comparative Example 1

[0041] (1) Place 30g of PET granules into a mold cavity with a thickness of 0.5mm and melt it at 270℃ for 10min to obtain PET melt;

[0042] (2) At 270℃, the motion program of the molding die is adjusted by setting process parameters to control the motion of the PET melt obtained in step (1), so that it produces the following... Figure 3 A steady-state pressure field with a pressure of 15 MPa was established and maintained at this pressure for 180 s. Then, the sample was water-cooled to room temperature at a rate of 100 ℃ / s to obtain a PET sheet sample, which was used as a control group and named CPM.

[0043] Comparative Example 2

[0044] Step (2) except that the unloading time is set to 15s, the preparation method of Comparative Example 2 is the same as that of Example 1, and the PET sheet prepared is named CPP15.

[0045] Comparative Example 3

[0046] Step (2) except that the cooling rate is set to 30℃ / s, the preparation method of Comparative Example 3 is the same as that of CPP3 in Example 1, and the PET sheet prepared is named CPP30.

[0047] Table 1 shows the changes in oxygen barrier properties of CPP1, CPP2, CPP3, and CPP4 prepared in Example 1, CPM prepared in Comparative Example 1, CPP15 prepared in Comparative Example 2, and CPP30 prepared in Comparative Example 3 under different processing conditions. Compared with the control group CPM prepared under steady-state pressure in Comparative Example 1 and CPP15 prepared in Comparative Example 2, the oxygen permeability coefficients of the experimental groups CPP1, CPP2, CPP3, and CPP4 prepared in Example 1 were significantly reduced. The oxygen permeability coefficient of CPP3 was only 12% of that of the control group CPM, showing a significantly improved barrier performance. This indicates that the unloading zone duration of 0.05-5s in this invention can significantly improve the barrier performance of polyester products. If the unloading zone duration is too long (>5s), the barrier performance of the prepared polyester products will be greatly reduced. The PET sheet sample of Comparative Example 3 was opaque, indicating that the present invention requires rapid cooling (greater than 50℃ / s) after the dynamic force field is applied in order to obtain transparent products.

[0048] Table 1. Changes in oxygen permeability coefficients of PET sheets, Comparative Example 1 (CPM), and Comparative Example 2 (CPP15) under a dynamic force field in Example 1.

[0049]

[0050] Table 2 shows the changes in free volume of CPP3 prepared in Example 1 and CPM prepared in Comparative Example 1 under different processing external fields. Table 2 shows that the dynamic force field can regulate the free volume of the material; the free volume of the experimental group CPP3 prepared in Example 1 is lower than that of the control group CPM. Combining the results of Tables 1 and 2, it can be concluded that effectively regulating the free volume of PET through a dynamic force field is a key factor in preparing high-barrier polyester products.

[0051] Table 2 shows the changes in the free volume of PET sheet CPP3 and Comparative Example 1 CPM under a dynamic force field in Example 1.

[0052]

[0053] Example 2:

[0054] Step (2) except for linearly increasing the pressure to the maximum pressure of 10 MPa by 10 MPa / s and linearly decreasing the pressure to 0 MPa by 10 MPa / s, the preparation method of Example 2 is the same as that of Example 1. The PET sheets prepared are named CPP1, CPP2, CPP3 and CPP4 respectively.

[0055] Comparative Example 4

[0056] Step (2) except that the pressure is set to 10 MPa, the preparation method of Comparative Example 4 is the same as that of Comparative Example 1, and the resulting sheet is named CPM as the control group.

[0057] Table 3. Changes in oxygen permeability coefficient of PET sheets under dynamic force field in Example 2 and Comparative Example 4 (CPM)

[0058]

[0059] Example 3:

[0060] Step (2) except that the pressure is linearly increased to a maximum of 100 MPa by 400 MPa / s and linearly decreased to 0 MPa by 400 MPa / s, the preparation method of Example 3 is the same as that of Example 1. The PET sheets prepared are named CPP1, CPP2, CPP3 and CPP4 respectively.

[0061] Comparative Example 5

[0062] Step (2) except that the pressure is set to 100 MPa, the preparation method of Comparative Example 5 is the same as that of Comparative Example 1, and the resulting sheet is used as the control group and named CPM.

[0063] Table 4 shows the changes in oxygen permeability coefficient of PET sheets under dynamic force field in Example 3 and Comparative Example 5 (CPM).

[0064]

[0065] Example 4:

[0066] Step (2) except that the number of cycles (load-unload) is set to 60 times, the preparation method of Example 4 is the same as that of Example 1, and the PET sheets prepared are named CPP1, CPP2, CPP3 and CPP4 respectively.

[0067] Comparative Example 6

[0068] The preparation method of Comparative Example 6 was the same as that of Comparative Example 1, and the resulting sheet was used as a control group and named CPM.

[0069] Table 5. Changes in oxygen permeability coefficient of PET sheets under dynamic force field in Example 4 and Comparative Example 6 (CPM)

[0070]

[0071] Example 5:

[0072] Step (2) except that the number of cycles (load-unload) is set to 500, the preparation method of Example 5 is the same as that of Example 1, and the PET sheets prepared are named CPP1, CPP2, CPP3 and CPP4 respectively.

[0073] Comparative Example 7

[0074] The preparation method of Comparative Example 7 was the same as that of Comparative Example 1, and the resulting sheet was used as a control group and named CPM.

[0075] Table 6. Changes in oxygen permeability coefficient of PET sheets under dynamic force field in Example 5 and Comparative Example 7 (CPM)

[0076]

[0077] Example 6:

[0078] Step (1) Except for placing 10g of PET granules into a mold cavity with a thickness of 0.1mm, the preparation method of Example 6 is the same as that of Example 1. The PET sheets prepared are named CPP1, CPP2, CPP3 and CPP4 respectively.

[0079] Comparative Example 8

[0080] Step (1) Except for placing 10g of PET granules into a mold cavity with a thickness of 0.1mm, the preparation method of Comparative Example 8 is the same as that of Comparative Example 1, and the resulting sheet is used as a control group and named CPM.

[0081] Table 7. Changes in oxygen permeability coefficient of PET sheets under dynamic force field in Example 6 and Comparative Example 8 (CPM)

[0082]

[0083] Example 7:

[0084] Step (1) Except for placing 150g of PET granules into a mold cavity with a thickness of 3mm, the preparation method of Example 7 is the same as that of Example 1. The PET sheets prepared are named CPP1, CPP2, CPP3 and CPP4 respectively.

[0085] Comparative Example 9

[0086] Step (1) Except for placing 150g of PET granules into a mold cavity with a thickness of 3mm, the preparation method of Comparative Example 9 is the same as that of Comparative Example 1, and the resulting sheet is used as a control group and named CPM.

[0087] Table 8. Changes in oxygen permeability coefficient of PET sheets under dynamic force field in Example 7 and Comparative Example 9 (CPM)

[0088]

[0089] Tables 7 and 8 reflect the effect of dynamic processing on the oxygen barrier properties of PET under different sample thicknesses. As shown in Tables 7 and 8, when the sample thickness is 0.1 mm and 3 mm, the effect of the dynamic force field on the oxygen barrier properties of PET is the same as that when the sample thickness is 0.5 mm; the oxygen permeability coefficient increases with the unloading zone duration (T). off The increase in ) shows a trend of first decreasing and then increasing.

[0090] Example 8:

[0091] This embodiment describes a method for preparing high-barrier, high-transparency PET, comprising the following steps:

[0092] (1) Place 30g of PET granules with molecular weights of 20500, 24600 and 50800 into a mold cavity with a thickness of 0.5mm and melt it at 270℃ for 10min to obtain PET melt.

[0093] (2) Under the condition of 270℃, the motion program of the molding motor template of the PET melt obtained in step (1) is controlled by setting the process parameters. The maximum pressure (15MPa) is loaded linearly at 60MPa / s and held for 0s. The pressure is then linearly reduced to 0MPa at 60MPa / s. The unloading zone is held for 1.63s. The number of cycles (loading-unloading) is 120. The PET sheet is water-cooled to room temperature at a rate of 100℃ / s to obtain high transparency and high barrier PET sheets, which are named PET20500, PET24600 and PET50800 respectively.

[0094] Comparative Example 10

[0095] (1) Place 30g of PET granules with molecular weights of 20500, 24600 and 50800 into a mold cavity with a thickness of 0.5mm and melt it at 270℃ for 10min to obtain PET melt.

[0096] (2) At 270℃, the motion program of the molding die is adjusted by setting process parameters to control the motion of the PET melt obtained in step (1), so that it produces the following... Figure 3 A steady-state pressure field with a pressure of 15 MPa was established and maintained at this pressure for 180 s. Then, the sample was water-cooled to room temperature at a rate of 100 ℃ / s to obtain a PET sheet sample, which was used as a control group and named CPM.

[0097] Table 9 shows the changes in oxygen permeability coefficient of PET sheets with different molecular weights prepared under a dynamic force field in Example 8. As can be seen from Table 9, the dynamic force field significantly improves the oxygen barrier performance of all three PET sheets with different molecular weights. This result indicates that the improvement in barrier performance by the dynamic force field is applicable to PET materials with various molecular weights.

[0098] Table 9. Variation of normalized oxygen permeability coefficient of PET sheets with different molecular weights under dynamic force field in Example 8.

[0099]

[0100] Example 9:

[0101] This embodiment describes a method for preparing high-barrier, high-transparency PET / PEN, comprising the following steps:

[0102] (1) PET and PEN are mixed in a mass ratio of 90 / 10. The mixed material is added to an internal mixer and mixed for 8 minutes at 270°C and 45 rpm to obtain a blend. 60 g of the blend is placed in a mold cavity with a thickness of 0.5 mm and melted at 270°C for 10 minutes to obtain a PET / PEN blend melt.

[0103] (2) At 270℃, the PET / PEN blend melt obtained in step (1) is subjected to process parameter settings to regulate the motion program of the molding die, so as to produce the following... Figure 2 The dynamic pressure field was applied at a linear rate of 60 MPa / s to the maximum pressure (15 MPa), and then held for 0 s. The pressure was then linearly decreased to 0 MPa at a rate of 60 MPa / s. The holding times in the unloading zone were 0.70 s, 1.20 s, 1.63 s, and 2.10 s, respectively. The number of cycles (loading-unloading) was 120. The samples were then water-cooled to room temperature at a rate of 100 °C / s. The resulting high-transparency, high-barrier PET / PEN sheet samples were named CPP1, CPP2, CPP3, and CPP4, respectively.

[0104] Comparative Example 11

[0105] (1) PET and PEN are mixed in a mass ratio of 90 / 10. The mixed material is added to an internal mixer and blended for 8 minutes at 270°C and 45 rpm to obtain a blend. 30 g of the blend is placed in a mold cavity with a thickness of 0.5 mm and melted at 270°C for 10 minutes to obtain a PET / PEN blend melt.

[0106] (2) At 270℃, the PET / PEN blend melt obtained in step (1) is subjected to process parameter settings to regulate the motion program of the molding die, so as to produce the following... Figure 3 A steady-state pressure field with a pressure of 15 MPa was applied and maintained at this pressure for 180 s. The sample was then water-cooled to room temperature at a rate of 100 ℃ / s to obtain a PET / PEN sheet sample, which was used as a control group and named CPM.

[0107] Table 10 shows the changes in oxygen permeability coefficient of PET / PEN sheets (CPP1, CPP2, CPP3, and CPP4) prepared under a dynamic force field in Example 9. As can be seen from Table 10, the oxygen permeability coefficient of the PET / PEN sheets under the dynamic force field is significantly lower than that of the control group (CPM), indicating that the oxygen barrier performance of the PET / PEN sheets prepared under the dynamic force field is significantly improved.

[0108] Table 10. Changes in oxygen permeability coefficient of PET / PEN sheets and Comparative Example 11 CPM under dynamic force field in Example 9.

[0109]

[0110] Example 10:

[0111] Step (1) Except for mixing PET and PEN at a mass ratio of 99 / 1, the preparation method of Example 10 is the same as that of Example 9. The PET sheets prepared are named CPP1, CPP2, CPP3 and CPP4 respectively.

[0112] Comparative Example Twelve

[0113] Step (1) Except for mixing PET and PEN at a mass ratio of 99 / 1, the preparation method of Comparative Example 12 is the same as that of Comparative Example 11. The resulting sheet is used as the control group and named CPM.

[0114] Table 11. Changes in oxygen permeability coefficient of PET / PEN sheets and Comparative Example 12 CPM under dynamic force field in Example 10.

[0115]

[0116] Example 11:

[0117] Step (1) Except for mixing PET and PEN in a mass ratio of 50 / 50, the preparation method of Example 11 is the same as that of Example 9. The PET sheets prepared are named CPP1, CPP2, CPP3 and CPP4 respectively.

[0118] Comparative Example Thirteen

[0119] Step (1) Except for mixing PET and PEN in a mass ratio of 50 / 50, the preparation method of Comparative Example 13 is the same as that of Comparative Example 11. The resulting sheet is used as the control group and named CPM.

[0120] Table 12. Changes in oxygen permeability coefficient of PET / PEN sheets and Comparative Example 13 (CPM) under dynamic force field in Example 11.

[0121]

[0122] Example 12:

[0123] This embodiment describes a method for preparing high-transparency, high-barrier PET / BN, comprising the following steps:

[0124] (1) 69.3g of PET and 0.7g of BN (boron nitride) were added to an internal mixer at a mass ratio of 99:1. The mixing temperature was 270℃, the mixing time was 10min, and the rotor speed was 45rpm to obtain PET / BN. 30g of the PET / BN obtained from the internal mixer was placed in a mold cavity with a thickness of 0.5mm and melted at 270℃ for 10min to obtain PET / BN melt.

[0125] (2) Under conditions of 270℃, the motion program of the molding die of the PET / BN melt obtained in step (1) is adjusted by setting process parameters to produce the following: Figure 2 The dynamic pressure field was applied at a linear rate of 60 MPa / s to the maximum pressure (15 MPa), and then held for 0 s. The pressure was then linearly reduced to 0 MPa at a rate of 60 MPa / s. The holding times in the unloading zone were 0.70 s, 1.20 s, 1.63 s, and 2.10 s, respectively. The number of loading-unloading cycles was 120. The samples were then water-cooled to room temperature at a rate of 100 °C / s. The resulting high-transparency, high-barrier PET / BN sheet samples were named CPP1, CPP2, CPP3, and CPP4, respectively.

[0126] Comparative Example 14

[0127] (1) 69.3g of PET and 0.7g of BN were added to an internal mixer at a mass ratio of 99:1. The mixing temperature was 270℃, the mixing time was 10min, and the rotor speed was 45rpm to obtain PET / BN. 60g of the PET / BN obtained from the internal mixer was placed in a mold cavity with a thickness of 0.5mm and melted at 270℃ for 10min to obtain PET / BN melt.

[0128] (2) Under conditions of 270℃, the motion program of the molding die of the PET / BN melt obtained in step (1) is adjusted by setting process parameters to produce the following: Figure 3 A steady-state pressure field with a pressure of 15 MPa was applied and maintained at this pressure for 180 s. The sample was then water-cooled to room temperature at a rate of 100 ℃ / s to obtain a PET / BN sheet sample, which was used as a control group and named CPM.

[0129] Table 13. Changes in oxygen permeability coefficient of PET / BN sheets under dynamic force field in Example 12 and Comparative Example 14 (CPM).

[0130]

[0131] Example 13:

[0132] Step (1) except that 67.9g of PET and 2.1g of BN are added to the internal mixer in a mass ratio of 97:3, the preparation method of Example 13 is the same as that of Example 12. The PET / BN sheets prepared are named CPP1, CPP2, CPP3 and CPP4 respectively.

[0133] Comparative Example 15

[0134] Step (1) except that 67.9g of PET and 2.1g of BN are added to the internal mixer in a mass ratio of 97:3, the preparation method of Comparative Example 15 is the same as that of Comparative Example 14. The PET / BN sheet prepared is used as the control group and named CPM.

[0135] Table 14. Changes in oxygen permeability coefficient of PET / BN sheets under dynamic force field in Example 13 and Comparative Example 15 (CPM).

[0136]

[0137] Example 14:

[0138] Step (1) except that 49g of PET and 21g of BN are added to the internal mixer in a mass ratio of 70:30, the preparation method of Example 14 is the same as that of Example 12. The PET / BN sheets prepared are named CPP1, CPP2, CPP3 and CPP4 respectively.

[0139] Comparative Example 16

[0140] Step (1) Except for adding 49g PET and 21g BN to the internal mixer in a mass ratio of 70:30, the preparation method of Comparative Example 16 is the same as that of Comparative Example 14. The PET / BN sheet prepared is used as the control group and named CPM.

[0141] Table 15. Changes in oxygen permeability coefficient of PET / BN sheets under dynamic force field in Example 14 and Comparative Example 16 (CPM)

[0142]

[0143] Table 13-15 shows the changes in oxygen permeability coefficient of PET / BN sheets prepared under a dynamic force field in Examples 12, 13, and 14. As can be seen from Table 13-15, the oxygen permeability coefficient of the PET / BN sheets prepared under the dynamic force field is significantly lower than that of the control group (CPM), indicating that the oxygen barrier performance of the PET / BN sheets prepared under the dynamic force field is significantly improved.

[0144] As described above, the present invention can be well implemented. The above embodiments are only preferred embodiments of the present invention and are not intended to limit the scope of implementation of the present invention; that is, all equivalent changes and modifications made in accordance with the content of the present invention are covered by the scope of protection claimed in the claims of the present invention.

Claims

1. A method for preparing a high-transparency, high-barrier polyester product, characterized in that, Includes the following steps: (1) Melt polyester, polyester blends or polyester composites to obtain a polymer melt; (2) Apply a dynamic force field to the polymer melt prepared in step (1) and then cool it to obtain a high-transparency and high-barrier polyester product. Each cycle of the dynamic force field includes a loading zone and an unloading zone. In the loading zone, the pressure applied to the material increases linearly from 0 MPa to a maximum pressure of 2.5-100 MPa at a rate of 10 MPa / s-400 MPa / s, and is held at the maximum pressure for 0-5 s. Then, it decreases linearly to 0 MPa at a rate of 10 MPa / s-400 MPa / s. In the unloading zone, the pressure applied to the material is constant at 0 MPa and maintained for 0.05–5 s; The loading-unloading cycle of the dynamic force field is 10-500 times. The cooling rate is greater than 50 °C / s; The polyester includes one or more of PET, PBT, PEN, and PLA, wherein the number-average molecular weight of PET is 20,000-50,000 g / mol, the number-average molecular weight of PBT is 10,000-50,000 g / mol, the number-average molecular weight of PEN is 10,000-60,000 g / mol, and the number-average molecular weight of PLA is 50,000-200,000 g / mol. The mass ratio of PET to other polyesters besides PET in the polyester blend is (99:1) to (50:50). The polyester composite material is composed of nanofillers and polyester materials, and the mass ratio of polyester materials to nanofillers is (99:1)-(70:30).

2. The method for preparing a high-transparency, high-barrier polyester product according to claim 1, characterized in that, The polyester in step (1) includes one or more of PET, PBT, PEN, and PLA.

3. The method for preparing a high-transparency, high-barrier polyester product according to claim 1, characterized in that, The polyester blend in step (1) includes one or more of PET / PEN, PET / PBT, and PEN / PBT.

4. The method for preparing a high-transparency, high-barrier polyester product according to claim 1, characterized in that, The polyester composite material in step (1) includes one or more of PET / silica, PBT / silica, PEN / silica, PLA / silica, PET / carbon nanotubes, PBT / carbon nanotubes, PEN / carbon nanotubes, PLA / carbon nanotubes, PET / boron nitride, PBT / boron nitride, PEN / boron nitride, and PLA / boron nitride.

5. The method for preparing a high-transparency, high-barrier polyester product according to claim 1, characterized in that, The polyester, polyester blend or polyester composite material described in step (1) needs to be dried at 50-150 °C before melting.

6. The method for preparing a high-transparency, high-barrier polyester product according to claim 1, characterized in that, The polyester blend or polyester composite material in step (1) is achieved by a melt blending device, which is a twin-screw extruder, a Brabender internal mixer, a single-shaft eccentric rotor internal mixer or a double-shaft eccentric rotor internal mixer. The melt blending temperature is 20-50 ℃ higher than the melting temperature or viscous flow temperature, and the blending time is 0.1-10 min.

7. A highly transparent and highly barrier polyester product prepared by the preparation method according to any one of claims 1-6.

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