Functional gradient type three-layer co-injection PCR (Polymerase Chain Reaction) composite packaging bottle and preparation method thereof

Abstract

The invention relates to the technical field of PCR, in particular to a functional gradient type three-layer co-injection PCR composite packaging bottle and a preparation method thereof.The functional gradient type three-layer co-injection PCR composite packaging bottle comprises an inner layer, a middle layer and an outer layer which are sequentially arranged from inside to outside, the inner layer is made of food-grade high-purity PET, and the thickness of the inner layer is 0.08-0.18 mm; the middle layer is made of food-grade toughened modified PCR-PET, and the thickness of the middle layer is 0.22-0.42 mm; the outer layer is made of a high-barrier PCR composite material, the thickness is 0.12-0.27 mm, the oxygen transmission rate is as low as 0.022 cm / (m.24h. Atm), the CO2 retention rate is as high as 97.8% (30 days), and the shelf life of beverages, cosmetics and the like is greatly prolonged. According to the invention, the impact strength reaches 4.5 J, the high light transmittance of 87.2% is maintained, the perfect balance of strength and transparency is realized, and the deformation rate at the high temperature of 60 DEG C is only 0.25%.

Description

Technical Field

[0001] The invention relates to the field of PCR technology, and in particular to a functional gradient three-layer co-injection PCR composite packaging bottle and a preparation method thereof. Background Art

[0002] With the increasing awareness of environmental protection and the popularization of the concept of circular economy, the application of recycled polyethylene terephthalate (PET) materials in the packaging field is becoming more and more extensive. However, recycled PET (PCR-PET) faces many challenges in terms of performance, such as decreased mechanical properties, insufficient gas barrier properties, and poor thermal stability, which greatly limits its application in high-end packaging.

[0003] In the prior art, single-layer structures or simple multi-layer structures are usually used to prepare PCR-PET packaging bottles, but these methods are difficult to simultaneously meet the requirements of food safety, mechanical properties, barrier properties, etc. For example, although single-layer PCR-PET bottles are easy to prepare, their gas barrier properties and mechanical properties are poor; and although simple multi-layer structures have improved in some aspects, the interlayer bonding strength is insufficient and it is impossible to achieve an optimized combination of the functions of each layer.

[0004] In addition, the existing PCR-PET modification methods often make it difficult to improve one property while maintaining other properties. For example, toughening modification may reduce transparency, and increasing crystallinity may reduce processing performance. This contradiction of "one gain and the other loss" seriously restricts the application of PCR-PET in the field of high-performance packaging.

[0005] Therefore, there is an urgent need to develop a new type of PCR composite packaging bottle that can fully utilize recycled materials, meet the various performance requirements of high-end packaging, and at the same time ensure food safety and good processing performance. Summary of the invention

[0006] The present invention aims to solve the above technical problems and achieve comprehensive improvement and optimized combination of the performance of PCR-PET packaging bottles through innovative three-layer functional gradient structure design, precise material modification and advanced preparation technology.

[0007] The object of the present invention is to provide a functional gradient three-layer co-injection PCR composite packaging bottle, comprising an inner layer, a middle layer and an outer layer arranged in sequence from the inside to the outside, wherein: The inner layer is made of food-grade high-purity PET with a thickness of 0.08-0.18 mm; The middle layer is made of food-grade toughened modified PCR-PET with a thickness of 0.22-0.42 mm; The outer layer is made of a high-barrier PCR composite material and has a thickness of 0.12-0.27 mm.

[0008] Specifically, the food-grade high-purity PET of the inner layer has an intrinsic viscosity of 0.82-0.87 dL / g, an acetaldehyde content of ≤1 ppm, a melting point of 250-255°C, and a crystallinity of 35-40%.

[0009] Specifically, the food-grade toughened modified PCR-PET of the middle layer is made of the following components in parts by weight: Food grade PCR-PET: 100 copies; Food grade ethylene-methyl acrylate-glycerol acrylate terpolymer E-MA-GMA: 3-10 parts; Food grade epoxidized polyethylene E-GMA: 1-5 parts.

[0010] Specifically, the high barrier PCR composite material of the outer layer is made of the following components in parts by weight: Solid phase polycondensation food grade PCR-PET: 100 copies; Food grade silicon dioxide (SiO2) nanoparticles: 0.3-1.5 parts; Food grade vitamin E (α-tocopherol): 0.05-0.2 parts.

[0011] The method for preparing the functional gradient three-layer co-injection PCR composite packaging bottle comprises the following steps: (1) Preparation of middle-layer food-grade toughened modified PCR-PET; (2) preparing an outer layer high barrier PCR composite material; (3) Three-layer co-injection molding; (4) Post-processing.

[0012] Specifically, the step (1) comprises: First, food-grade PCR-PET was vacuum dried at 85-105°C for 18-26 hours, and the water content was controlled below 20 ppm; E-MA-GMA and E-GMA were vacuum dried at 55-65°C for 5-9 hours; Secondly, a food-grade twin-screw extruder with an L / D ratio of 52:1 was used for melt extrusion reaction, and the temperature distribution from the feed zone to the die head was 225°C, 245°C, 265°C, 278°C, 278°C, 272°C, and 262°C, the screw speed was 200-300rpm, and the vacuum degree was -0.088 to -0.098 MPa; Then, the dried food-grade PCR-PET was added through the main feed port, E-MA-GMA was added through the first side feed port at L / D=0.3, and E-GMA was added through the second side feed port at L / D=0.6; Finally, food-grade water-cooled pulling is carried out, the water temperature is controlled at 16-21°C, pelletized to 2.5-4.5 mm, and vacuum dried at 88°C for 12-16 hours.

[0013] Specifically, the step (2) comprises: First, a food-grade PCR-PET flake material is placed in a food-grade solid phase polycondensation reactor, heated to 195-215°C at a rate of 1.8°C / min under a nitrogen atmosphere, maintained for 18-30 hours, then cooled to room temperature at a rate of 0.8°C / min, evacuated to -0.098 MPa, maintained for 7-11 hours, and the intrinsic viscosity is increased by 0.18-0.28 dL / g; Secondly, the food-grade PCR-PET after solid phase polycondensation is dry-mixed with SiO2 nanoparticles and vitamin E in a food-grade high-speed mixer at a mixing condition of 3800-5800 rpm for 7-13 minutes; Again, a food-grade twin-screw extruder with an L / D ratio of 44:1 was used for melt extrusion compounding, and the temperature distribution from the feed zone to the die head was 248°C, 268°C, 278°C, 288°C, 288°C, 278°C, and 268°C, the screw speed was 240-340rpm, and the vacuum degree was -0.088 to -0.098 MPa; Finally, food-grade water-cooled pulling is carried out, the water temperature is controlled at 19-23°C, pelletized to 2.5-4.5 mm, and vacuum dried at 108°C for 18-30 hours.

[0014] Specifically, the step (3) uses a food-grade three-layer co-injection blow molding device, wherein: The barrel temperatures of the inner layer, middle layer, and outer layer are 278-288°C, 268-278°C, and 288-298°C, respectively; The mold temperature is 20-30°C; The injection pressures of the inner layer, middle layer, and outer layer are 88-108 MPa, 78-98 MPa, and 98-118 MPa, respectively; The injection speeds of the inner layer, middle layer, and outer layer are 68-88 mm / s, 58-78 mm / s, and 78-98 mm / s, respectively; The holding time is 3.8-5.8 s; Cooling time is 13-19 seconds; Blowing pressure is 3.8-4.8 MPa; The blowing time is 4.5-6.5 s.

[0015] Specifically, the step (4) comprises: First, heat setting is performed at a temperature of 88-108°C, a time of 13-23 s, and a pressure of 0.48-0.68 MPa; Secondly, supercritical CO2 surface treatment is carried out at a pressure of 15-25 MPa, a temperature of 40-60°C, and a treatment time of 20-40 s; Finally, the inner coating of the bottle was carried out by plasma enhanced chemical vapor deposition (PECVD) method to deposit food grade silicon dioxide (SiO2) nanocoating with a coating thickness of 20-100 nm, a temperature of 50-70 °C, a pressure of 5-20 Pa, and a time of 25-45 s.

[0016] The functional gradient three-layer co-injection PCR composite packaging bottle prepared by the preparation method.

[0017] Specifically, the present invention achieves a technical breakthrough in the following ways: First, a three-layer functional gradient structure is used to give full play to the advantages of each layer of materials. The inner layer uses food-grade high-purity PET to ensure food safety; the middle layer uses toughened modified PCR-PET to provide the main mechanical support; the outer layer uses high-crystallinity PCR composite material to provide gas barrier and protection functions. This gradient structure design achieves an optimized combination of performance and synergistic effects.

[0018] Secondly, the comprehensive performance of PCR-PET is improved through precise material modification. The middle layer is toughened and modified with E-MA-GMA and E-GMA, which improves the toughness of PCR-PET at the molecular level. The glycerol groups in E-MA-GMA form hydrogen bonds with the hydroxyl and carboxyl groups on the PCR-PET molecular chain, enhancing the intermolecular forces. At the same time, the introduced methyl acrylate groups improve the flexibility of the material. E-GMA increases the molecular weight and melt strength through the reaction of epoxy groups with the end groups of PCR-PET. This double modification not only significantly improves the impact resistance of the material, but also maintains good transparency.

[0019] Again, the outer layer uses solid phase polycondensation technology to increase the intrinsic viscosity of PCR-PET, and adds SiO2 nanoparticles and vitamin E for functionalization. During the solid phase polycondensation process, the PCR-PET molecular chain undergoes a polycondensation reaction in the solid state, which effectively increases the molecular weight and crystallinity, thereby improving the thermal stability and gas barrier properties of the material. SiO2 nanoparticles form a tortuous gas diffusion path in the PCR-PET matrix, significantly improving the barrier properties. Vitamin E, as a natural antioxidant, not only improves the antioxidant properties of the material, but also provides additional protection for the beverage.

[0020] Finally, through innovative preparation processes, such as precise melt flow control, differentiated temperature control strategies and post-processing processes, the performance of each layer of materials is fully utilized and the interlayer bonding strength is maximized. In particular, the use of supercritical CO2 surface treatment and SiO2 nano-coating technology further improves the overall performance of the bottle.

[0021] The beneficial effects of the present invention include but are not limited to: 1. Excellent gas barrier performance: oxygen permeability is as low as 0.022 cm³ / (m²·24h·atm), CO2 retention rate is as high as 97.8% (30 days), which greatly extends the shelf life of beverages, cosmetics, etc.

[0022] 2. Excellent mechanical properties: The impact strength reaches 4.5 J, while maintaining a high light transmittance of 87.2%, achieving a perfect balance between strength and transparency.

[0023] 3. Excellent thermal stability: The deformation rate at a high temperature of 60°C is only 0.25%, which significantly expands the application range of PCR-PET.

[0024] 4. Excellent food safety: The acetaldehyde migration amount is as low as 0.6 mg / kg, which is far below the national standard limit, ensuring the quality and safety of the beverage.

[0025] 5. Environmentally friendly: The extensive use of PCR-PET realizes the efficient recycling of resources and conforms to the concept of sustainable development.

[0026] 6. Excellent processing performance: Through precise process control, good processing performance and production efficiency are achieved.

[0027] In summary, the present invention successfully solves many technical problems in the application of PCR-PET in the field of high-performance packaging through innovative structural design, material modification and process optimization, opens up a new path for the high-value utilization of PCR-PET, and has important theoretical significance and application value. DETAILED DESCRIPTION

[0028] The present invention discloses a functional gradient three-layer co-injection PCR composite packaging bottle, a) inner layer: food grade high-purity PET, trade name: Crystar 3934 (produced by Indorama Ventures), intrinsic viscosity: 0.82-0.87 dL / g, acetaldehyde content: ≤1 ppm, melting point: 250-255°C, crystallinity: 35-40%, formula (weight parts): high-purity PET: 100, thickness: 0.08-0.18 mm; b) middle layer: food grade toughened modified PCR-PET, toughening agent: food grade ethylene-methyl acrylate-glyceryl acrylate terpolymer (E-MA-GMA), trade name: Elvaloy PTW (produced by DuPont); compatibilizer: food grade epoxidized polyethylene (E-GMA), trade name: Lotader AX8900 (produced by Arkema), Formula (weight parts): food grade PCR-PET: 100; E-MA-GMA: 3-10; E-GMA: 1-5; thickness: 0.22-0.42 mm; c) Outer layer: high barrier PCR composite material; substrate: solid phase polycondensation food grade PCR-PET; barrier enhancer: food grade silicon dioxide (SiO2) nanoparticles; trade name: AEROSIL 200 F (produced by Evonik Industries); antioxidant: food grade vitamin E (α-tocopherol), trade name: Covi-ox T-70 (produced by BASF), formula (weight parts): solid phase polycondensation food grade PCR-PET: 100; SiO2 nanoparticles: 0.3-1.5; vitamin E: 0.05-0.2; thickness: 0.12-0.27 mm; The preparation method of solid phase polycondensation food grade PCR-PET comprises the following steps: 1. Raw material preparation: Choose appropriate PCR-PET flakes or granules.

[0029] 2. Pretreatment: Vacuum dry the PCR-PET at 80-100°C for 12-24 hours and control the water content below 50 ppm.

[0030] 3. Solid phase polycondensation: a) The dried PCR-PET is placed in a solid phase polycondensation reactor.

[0031] b) Under nitrogen atmosphere, increase the temperature to 180-220°C at a rate of 1.5-2.5°C / min.

[0032] c) Maintain at this temperature for 18-36 hours.

[0033] d) Cool down to room temperature at a rate of 0.8-1.2°C / min.

[0034] e) Evacuate to above -0.09 MPa and maintain for 4-8 hours.

[0035] 4. Post-processing: Cooling, pelletizing, etc. of the PCR-PET after solid phase polycondensation.

[0036] 5. Performance testing: measure intrinsic viscosity, crystallinity and other indicators to ensure that the intrinsic viscosity is increased by 0.1-0.3 dL / g. This process requires parameter optimization based on the specific PCR-PET raw materials and target performance. Solid phase polycondensation can effectively increase the molecular weight and crystallinity of PCR-PET, thereby improving its thermal stability and mechanical properties, and providing better raw materials for subsequent processing.

[0037] The compatibility mechanism and beneficial effects of the formula of the present invention are derived from the complex synergistic effects among the components, which can be explained in depth from the molecular, atomic and electronic levels: 1. Middle layer toughening modification mechanism: The interaction between E-MA-GMA and PCR-PET involves multiple mechanisms. First, the glycerol groups (-CH2-CH(OH)-CH2-OH) in E-MA-GMA form a hydrogen bond network with the hydroxyl (-OH) and carboxyl (-COOH) groups on the PCR-PET molecular chain. This hydrogen bonding not only strengthens the intermolecular forces, but also forms physical cross-linking points on a microscopic scale, improving the toughness of the material.

[0038] From the perspective of molecular orbital theory, the lone pair of electrons in the glycerol group partially overlaps with the antibonding orbital (σ*) on the PET molecular chain, forming a weak interaction. Although the strength of this interaction is not as strong as that of a covalent bond, the number is large and has a significant impact on the overall performance of the material.

[0039] The methacrylate group (-COO-CH3) in E-MA-GMA increases the freedom of the molecular chain through its flexible side chain structure, thereby improving the flexibility of the material. This flexibility enhancement effect can be explained from the free volume theory: the presence of the methacrylate group increases the free volume between molecules, making it easier for the molecular chain to undergo conformational changes under the action of external forces, thereby absorbing more energy.

[0040] At the same time, the epoxy groups of E-GMA react with the end groups (mainly hydroxyl and carboxyl) of PCR-PET to form a ring-opening reaction. This reaction increases the molecular weight from the perspective of chemical bonds and forms macromolecules with branched structures. The branched structure increases the probability of molecular chain entanglement, thereby improving the melt strength and impact resistance of the material.

[0041] 2. Mechanism of high barrier properties of the outer layer: During the solid phase polycondensation process, PCR-PET molecules undergo polycondensation reactions in the solid state. The uniqueness of this process is that it avoids thermal degradation in the molten state, and at the same time, due to the restricted molecular motion, it is conducive to the formation of crystalline regions with higher orientation. From a thermodynamic point of view, this highly ordered structure reduces the entropy of the system and improves the thermal stability and gas barrier properties of the material.

[0042] The dispersion of SiO2 nanoparticles in the PCR-PET matrix involves complex interfacial interactions. The silanol (-Si-OH) on the SiO2 surface forms hydrogen bonds with polar groups (such as ester groups) on the PET molecular chain. This interaction not only facilitates the uniform dispersion of the nanoparticles, but also creates a large number of interfacial regions. The presence of these interfacial regions significantly increases the diffusion path length of gas molecules, thereby improving the gas barrier properties of the material.

[0043] From the perspective of quantum mechanics, the presence of SiO2 nanoparticles changes the local electron cloud density distribution. This inhomogeneity in electron cloud density sets up an additional energy barrier for the diffusion of gas molecules, further enhancing the barrier effect.

[0044] As an antioxidant, the mechanism of action of vitamin E (α-tocopherol) involves free radical capture. The phenolic hydroxyl group in the vitamin E molecule is prone to lose hydrogen atoms to form relatively stable free radicals, which can combine with active free radicals in the material to block the propagation of the oxidation chain reaction. From the perspective of molecular orbital theory, the conjugated system of vitamin E enables the formed free radicals to be stabilized through the resonance effect, improving its ability to capture other free radicals.

[0045] 3. Interlayer interface optimization mechanism: The core of precise melt flow control and differentiated temperature control strategy lies in regulating the motion state of molecular chains. Under appropriate temperature and shear conditions, molecular chains of different layers can fully diffuse and entangle at the interface. From the perspective of polymer physics, this entanglement can be understood as the formation of "molecular hooks", which greatly enhances the bonding strength between layers.

[0046] 4. Post-treatment synergistic effect: Supercritical CO2 treatment utilizes the unique properties of CO2 in a supercritical state. Supercritical CO2 has a liquid-like density and a gas-like diffusion coefficient, and can quickly penetrate into the polymer matrix. It can not only dissolve and carry away residual low molecular weight substances, but also slightly expand the polymer matrix during the treatment process to increase the free volume. After treatment, these tiny free volumes may be partially retained, forming nano-scale pores, which is beneficial to improve the toughness of the material.

[0047] The deposition process of SiO2 nanocoating involves complex surface chemical reactions. Under the assistance of plasma, SiO2 precursor molecules (such as TEOS) are excited and decomposed to form highly active Si-O groups. These groups react and polymerize rapidly on the surface of the bottle to form a dense network structure. From an atomic level, this network structure fills the microscopic defects on the surface and significantly improves the gas barrier properties.

[0048] In summary, the components and process steps of the formulation of the present invention achieve synergy at multiple scales. From the entanglement of molecular chains, the interaction of functional groups, to the interface effect of nanoparticles, and then to the regulation of electron cloud density, a multi-level, multi-scale synergistic system is formed. This complex synergistic mechanism not only achieves the overall optimization of material performance, but also produces some unexpected synergistic effects, such as the simultaneous improvement of transparency and impact resistance, and the consideration of barrier properties and recyclability. The realization of these effects breaks through the performance limitations of traditional PCR-PET and provides new ideas and directions for the development of high-performance, environmentally friendly packaging materials. Example

[0049] This embodiment provides a functional gradient three-layer co-injection PCR composite packaging bottle and a preparation method thereof. The packaging bottle is provided with an inner layer, a middle layer and an outer layer in sequence from the inside to the outside.

[0050] The inner layer is made of food-grade high-purity PET, which has an intrinsic viscosity of 0.82 dL / g, an acetaldehyde content of 1 ppm, a melting point of 250°C, a crystallinity of 35%, and a thickness of 0.08 mm. Preferably, using high-purity PET as the inner layer material can effectively ensure food safety and minimize interaction with the beverage, thereby maintaining the original flavor of the beverage.

[0051] The middle layer is made of food-grade toughened modified PCR-PET with a thickness of 0.22 mm. Its component formula is as follows (by weight): Food grade PCR-PET: 100 copies Food grade ethylene-methyl acrylate-glyceryl acrylate terpolymer (E-MA-GMA): 3 parts Food grade epoxidized polyethylene (E-GMA): 1 part In the embodiments of the present invention, E-MA-GMA as a toughening agent can significantly improve the impact strength and ductility of PCR-PET, while E-GMA as a compatibilizer can improve the interface bonding between the components, thereby improving the mechanical properties of the overall material.

[0052] The outer layer is made of high barrier PCR composite material with a thickness of 0.12 mm. Its component formula is as follows (by weight): Solid phase polycondensation food grade PCR-PET: 100 copies Food grade silicon dioxide (SiO2) nanoparticles: 0.3 parts Food grade vitamin E (α-tocopherol): 0.05 parts Preferably, SiO2 nanoparticles can significantly improve the gas barrier properties of the material, while vitamin E, as a natural antioxidant, can not only improve the antioxidant properties of the material but also prevent the oxidation of nutrients in the beverage.

[0053] The preparation method of the functional gradient three-layer co-injection PCR composite packaging bottle comprises the following steps: (1) Preparation of middle-layer food-grade toughened modified PCR-PET First, food-grade PCR-PET was vacuum dried at 85 °C for 18 h, and the moisture content was controlled below 20 ppm; E-MA-GMA and E-GMA were vacuum dried at 55 °C for 5 h.

[0054] Secondly, a food-grade twin-screw extruder with an L / D ratio of 52: 1 was used for melt extrusion reaction. The temperature distribution from the feed zone to the die head was 225°C, 245°C, 265°C, 278°C, 278°C, 272°C, and 262°C, the screw speed was 200 rpm, and the vacuum degree was -0.088 MPa.

[0055] Then, the dried food-grade PCR-PET was added through the main feed port, E-MA-GMA was added through the first side feed port at L / D=0.3, and E-GMA was added through the second side feed port at L / D=0.6.

[0056] Finally, food-grade water-cooled pulling was performed, the water temperature was controlled at 16 °C, pelletized to 2.5 mm, and vacuum dried at 88 °C for 12 h.

[0057] (2) Preparation of outer layer high barrier PCR composite material First, the food-grade PCR-PET flakes were placed in a food-grade solid phase polycondensation reactor, heated to 195°C at a rate of 1.8°C / min under a nitrogen atmosphere, maintained for 18 hours, then cooled to room temperature at a rate of 0.8°C / min, evacuated to -0.098 MPa, and maintained for 7 hours, thereby increasing the intrinsic viscosity by 0.18 dL / g.

[0058] Secondly, the food-grade PCR-PET after solid phase polycondensation was dry-mixed with SiO2 nanoparticles and vitamin E in a food-grade high-speed mixer at 3800 rpm for 7 minutes.

[0059] Again, a food-grade twin-screw extruder with an L / D ratio of 44: 1 was used for melt extrusion compounding. The temperature distribution from the feed zone to the die head was 248°C, 268°C, 278°C, 288°C, 288°C, 278°C, and 268°C, the screw speed was 240 rpm, and the vacuum degree was -0.088 MPa.

[0060] Finally, food-grade water-cooled pulling was performed, the water temperature was controlled at 19 °C, pelletized to 2.5 mm, and vacuum dried at 108 °C for 18 h.

[0061] (3) Three-layer co-injection molding The food-grade three-layer co-injection blow molding equipment was used for molding. The barrel temperatures of the inner layer, middle layer, and outer layer were 278°C, 268°C, and 288°C, respectively; the mold temperature was 20°C; the injection pressures of the inner layer, middle layer, and outer layer were 88 MPa, 78 MPa, and 98 MPa, respectively; the injection speeds of the inner layer, middle layer, and outer layer were 68 mm / s, 58 mm / s, and 78 mm / s, respectively; the holding time was 3.8 s; the cooling time was 13 s; the blowing pressure was 3.8 MPa; and the blowing time was 4.5 s.

[0062] (4) Post-processing First, heat setting was performed at a temperature of 88 °C, a time of 13 s, and a pressure of 0.48 MPa.

[0063] Secondly, supercritical CO2 surface treatment is performed at a pressure of 15 MPa, a temperature of 40°C, and a treatment time of 20 s. Preferably, supercritical CO2 treatment can effectively remove residual monomers and low molecular weight substances on the surface of the bottle, thereby improving the food safety of the bottle.

[0064] Finally, the inner coating of the bottle is treated by plasma enhanced chemical vapor deposition (PECVD) method to deposit food grade silicon dioxide (SiO2) nano coating with a coating thickness of 20 nm, a temperature of 50°C, a pressure of 5 Pa, and a time of 25 s. In the embodiment of the present invention, the SiO2 nano coating can further improve the gas barrier properties of the bottle and extend the shelf life of the beverage. Example

[0065] This embodiment provides another functional gradient three-layer co-injection PCR composite packaging bottle and its preparation method. The structure of the packaging bottle is the same as that of Example 1, but the components and preparation parameters of each layer are different.

[0066] The inner layer is made of food-grade high-purity PET with an intrinsic viscosity of 0.85 dL / g, an acetaldehyde content of 0.5 ppm, a melting point of 253°C, a crystallinity of 38%, and a thickness of 0.13 mm.

[0067] The middle layer is made of food-grade toughened modified PCR-PET with a thickness of 0.32 mm. Its component formula is as follows (by weight): Food grade PCR-PET: 100 copies Food grade ethylene-methyl acrylate-glyceryl acrylate terpolymer (E-MA-GMA): 7 parts Food grade epoxidized polyethylene (E-GMA): 3 parts The outer layer is made of high barrier PCR composite material with a thickness of 0.20 mm. Its component formula is as follows (by weight): Solid phase polycondensation food grade PCR-PET: 100 copies Food grade silicon dioxide (SiO2) nanoparticles: 0.9 parts Food grade vitamin E (α-tocopherol): 0.13 parts The preparation method of the functional gradient three-layer co-injection PCR composite packaging bottle comprises the following steps: (1) Preparation of middle-layer food-grade toughened modified PCR-PET First, food-grade PCR-PET was vacuum dried at 95 °C for 22 h, and the moisture content was controlled below 15 ppm; E-MA-GMA and E-GMA were vacuum dried at 60 °C for 7 h.

[0068] Secondly, a food-grade twin-screw extruder with an L / D ratio of 52: 1 was used for melt extrusion reaction. The temperature distribution from the feed zone to the die head was 235°C, 255°C, 270°C, 280°C, 280°C, 275°C, and 265°C, the screw speed was 250 rpm, and the vacuum degree was -0.093 MPa.

[0069] Then, the dried food-grade PCR-PET was added through the main feed port, E-MA-GMA was added through the first side feed port at L / D=0.3, and E-GMA was added through the second side feed port at L / D=0.6.

[0070] Finally, food-grade water-cooled pulling was performed, the water temperature was controlled at 18.5 °C, pelletized to 3.5 mm, and vacuum dried at 90 °C for 14 h.

[0071] (2) Preparation of outer layer high barrier PCR composite material Firstly, the food-grade PCR-PET flakes were placed in a food-grade solid phase polycondensation reactor, heated to 205°C at a rate of 1.9°C / min under a nitrogen atmosphere, maintained for 24 hours, then cooled to room temperature at a rate of 0.9°C / min, evacuated to -0.095 MPa, and maintained for 9 hours, thereby increasing the intrinsic viscosity by 0.23 dL / g.

[0072] Secondly, the food-grade PCR-PET after solid phase polycondensation was dry-mixed with SiO2 nanoparticles and vitamin E in a food-grade high-speed mixer at 4800 rpm for 10 minutes.

[0073] Again, a food-grade twin-screw extruder with an L / D ratio of 44: 1 was used for melt extrusion compounding. The temperature distribution from the feed zone to the die head was 258°C, 273°C, 283°C, 290°C, 290°C, 283°C, and 273°C, the screw speed was 290 rpm, and the vacuum degree was -0.093 MPa.

[0074] Finally, food-grade water-cooled pulling was performed, the water temperature was controlled at 21 °C, pelletized to 3.5 mm, and vacuum dried at 110 °C for 24 h.

[0075] (3) Three-layer co-injection molding The food-grade three-layer co-injection blow molding equipment was used for molding. Among them, the barrel temperatures of the inner layer, middle layer, and outer layer were 283°C, 273°C, and 293°C respectively; the mold temperature was 25°C; the injection pressures of the inner layer, middle layer, and outer layer were 98 MPa, 88 MPa, and 108 MPa respectively; the injection speeds of the inner layer, middle layer, and outer layer were 78 mm / s, 68 mm / s, and 88 mm / s respectively; the holding time was 4.8 s; the cooling time was 16 s; the blowing pressure was 4.3 MPa; and the blowing time was 5.5 s.

[0076] (4) Post-processing First, heat setting was performed at 98 °C, time 18 s, and pressure 0.58 MPa.

[0077] Secondly, supercritical CO2 surface treatment was carried out with a pressure of 20 MPa, a temperature of 50 °C, and a treatment time of 30 s.

[0078] Finally, the inner coating of the bottle was carried out by plasma enhanced chemical vapor deposition (PECVD) method to deposit food grade silicon dioxide (SiO2) nanocoating with a coating thickness of 60 nm at a temperature of 60 °C, a pressure of 13 Pa, and a time of 35 s. Example

[0079] This embodiment provides a third functional gradient three-layer co-injection PCR composite packaging bottle and its preparation method. The structure of the packaging bottle is the same as the previous two embodiments, but the components and preparation parameters of each layer are further adjusted.

[0080] The inner layer is made of food-grade high-purity PET with an intrinsic viscosity of 0.87 dL / g, an acetaldehyde content of 0.3 ppm, a melting point of 255°C, a crystallinity of 40%, and a thickness of 0.18 mm.

[0081] The middle layer is made of food-grade toughened modified PCR-PET with a thickness of 0.42 mm. Its component formula is as follows (by weight): Food grade PCR-PET: 100 copies Food grade ethylene-methyl acrylate-glyceryl acrylate terpolymer (E-MA-GMA): 10 parts Food grade epoxidized polyethylene (E-GMA): 5 parts The outer layer is made of high barrier PCR composite material with a thickness of 0.27 mm. Its component formula is as follows (by weight): Solid phase polycondensation food grade PCR-PET: 100 copies Food grade silicon dioxide (SiO2) nanoparticles: 1.5 parts Food grade vitamin E (α-tocopherol): 0.2 parts The preparation method of the functional gradient three-layer co-injection PCR composite packaging bottle comprises the following steps: (1) Preparation of middle-layer food-grade toughened modified PCR-PET First, food-grade PCR-PET was vacuum dried at 105 °C for 26 h, and the moisture content was controlled below 10 ppm; E-MA-GMA and E-GMA were vacuum dried at 65 °C for 9 h.

[0082] Secondly, a food-grade twin-screw extruder with an L / D ratio of 52: 1 was used for melt extrusion reaction. The temperature distribution from the feed zone to the die head was 240°C, 260°C, 275°C, 282°C, 282°C, 277°C, and 267°C, the screw speed was 300 rpm, and the vacuum degree was -0.098 MPa.

[0083] Then, the dried food-grade PCR-PET was added through the main feed port, E-MA-GMA was added through the first side feed port at L / D=0.3, and E-GMA was added through the second side feed port at L / D=0.6.

[0084] Finally, food-grade water-cooled pulling was performed, the water temperature was controlled at 21 °C, pelletized to 4.5 mm, and vacuum dried at 92 °C for 16 h.

[0085] (2) Preparation of outer layer high barrier PCR composite material Firstly, the food-grade PCR-PET flakes were placed in a food-grade solid phase polycondensation reactor, heated to 215°C at a rate of 2.0°C / min under a nitrogen atmosphere, maintained for 30 hours, then cooled to room temperature at a rate of 1.0°C / min, evacuated to -0.098 MPa, and maintained for 11 hours, thereby increasing the intrinsic viscosity by 0.28 dL / g.

[0086] Secondly, the food-grade PCR-PET after solid phase polycondensation was dry-mixed with SiO2 nanoparticles and vitamin E in a food-grade high-speed mixer at 5800 rpm for 13 minutes.

[0087] Again, a food-grade twin-screw extruder with an L / D ratio of 44: 1 was used for melt extrusion compounding. The temperature distribution from the feed zone to the die head was 268°C, 278°C, 288°C, 292°C, 292°C, 288°C, 278°C, the screw speed was 340 rpm, and the vacuum degree was -0.098 MPa.

[0088] Finally, food-grade water-cooled pulling was performed, the water temperature was controlled at 23 °C, pelletized to 4.5 mm, and vacuum dried at 112 °C for 30 h.

[0089] (3) Three-layer co-injection molding The food-grade three-layer co-injection blow molding equipment was used for molding. Among them, the barrel temperatures of the inner layer, middle layer, and outer layer were 288°C, 278°C, and 298°C respectively; the mold temperature was 30°C; the injection pressures of the inner layer, middle layer, and outer layer were 108 MPa, 98 MPa, and 118 MPa respectively; the injection speeds of the inner layer, middle layer, and outer layer were 88 mm / s, 78 mm / s, and 98 mm / s respectively; the holding time was 5.8 s; the cooling time was 19 s; the blowing pressure was 4.8 MPa; and the blowing time was 6.5 s.

[0090] (4) Post-processing First, heat setting was performed at a temperature of 108 °C, a time of 23 s, and a pressure of 0.68 MPa.

[0091] Secondly, supercritical CO2 surface treatment was carried out with a pressure of 25 MPa, a temperature of 60 °C, and a treatment time of 40 s.

[0092] Finally, the inner coating of the bottle was carried out by plasma enhanced chemical vapor deposition (PECVD) method to deposit food grade silicon dioxide (SiO2) nanocoating with a coating thickness of 100 nm at a temperature of 70 °C, a pressure of 20 Pa, and a time of 45 s. Example

[0093] This embodiment provides a fourth functional gradient three-layer co-injection PCR composite packaging bottle and its preparation method. The structure of this packaging bottle is the same as the previous three embodiments, but the components and preparation parameters of each layer are further optimized.

[0094] The inner layer is made of food-grade high-purity PET with an intrinsic viscosity of 0.84 dL / g, an acetaldehyde content of 0.7 ppm, a melting point of 252°C, a crystallinity of 37%, and a thickness of 0.11 mm.

[0095] The middle layer is made of food-grade toughened modified PCR-PET with a thickness of 0.27 mm. Its component formula is as follows (by weight): Food grade PCR-PET: 100 copies Food grade ethylene-methyl acrylate-glyceryl acrylate terpolymer (E-MA-GMA): 5 parts Food grade epoxidized polyethylene (E-GMA): 2 parts The outer layer is made of high barrier PCR composite material with a thickness of 0.16 mm. Its component formula is as follows (by weight): Solid phase polycondensation food grade PCR-PET: 100 copies Food grade silicon dioxide (SiO2) nanoparticles: 0.6 parts Food grade vitamin E (α-tocopherol): 0.09 parts The preparation method of the functional gradient three-layer co-injection PCR composite packaging bottle comprises the following steps: (1) Preparation of middle-layer food-grade toughened modified PCR-PET First, food-grade PCR-PET was vacuum dried at 90 °C for 20 h, and the moisture content was controlled below 18 ppm; E-MA-GMA and E-GMA were vacuum dried at 58 °C for 6 h.

[0096] Secondly, a food-grade twin-screw extruder with an L / D ratio of 52: 1 was used for melt extrusion reaction. The temperature distribution from the feed zone to the die head was 230°C, 250°C, 268°C, 279°C, 279°C, 274°C, and 264°C, the screw speed was 225 rpm, and the vacuum degree was -0.091 MPa.

[0097] Then, the dried food-grade PCR-PET was added through the main feed port, E-MA-GMA was added through the first side feed port at L / D=0.3, and E-GMA was added through the second side feed port at L / D=0.6.

[0098] Finally, food-grade water-cooled pulling was performed, the water temperature was controlled at 17.5 °C, pelletized to 3.0 mm, and vacuum dried at 89 °C for 13 h.

[0099] (2) Preparation of outer layer high barrier PCR composite material Firstly, the food-grade PCR-PET flakes were placed in a food-grade solid phase polycondensation reactor, heated to 200°C at a rate of 1.85°C / min under a nitrogen atmosphere, maintained for 21 hours, then cooled to room temperature at a rate of 0.85°C / min, evacuated to -0.096 MPa, and maintained for 8 hours, thereby increasing the intrinsic viscosity by 0.21 dL / g.

[0100] Secondly, the food-grade PCR-PET after solid phase polycondensation was dry-mixed with SiO2 nanoparticles and vitamin E in a food-grade high-speed mixer at 4300 rpm for 9 minutes.

[0101] Again, a food-grade twin-screw extruder with an L / D ratio of 44: 1 was used for melt extrusion compounding. The temperature distribution from the feed zone to the die head was 253°C, 271°C, 281°C, 289°C, 289°C, 281°C, and 271°C, the screw speed was 265 rpm, and the vacuum degree was -0.091 MPa.

[0102] Finally, food-grade water-cooled pulling was performed, the water temperature was controlled at 20 °C, pelletized to 3.0 mm, and vacuum dried at 109 °C for 21 h.

[0103] (3) Three-layer co-injection molding The food-grade three-layer co-injection blow molding equipment was used for molding. Among them, the barrel temperatures of the inner layer, middle layer, and outer layer were 281°C, 271°C, and 291°C respectively; the mold temperature was 23°C; the injection pressures of the inner layer, middle layer, and outer layer were 93 MPa, 83 MPa, and 103 MPa respectively; the injection speeds of the inner layer, middle layer, and outer layer were 73 mm / s, 63 mm / s, and 83 mm / s respectively; the holding time was 4.3 s; the cooling time was 15 s; the blowing pressure was 4.1 MPa; and the blowing time was 5.0 s.

[0104] (4) Post-processing First, heat setting was performed at a temperature of 93 °C, a time of 16 s, and a pressure of 0.53 MPa.

[0105] Secondly, supercritical CO2 surface treatment was carried out with a pressure of 18 MPa, a temperature of 45 °C, and a treatment time of 25 s.

[0106] Finally, the inner coating of the bottle was carried out by plasma enhanced chemical vapor deposition (PECVD) method to deposit food grade silicon dioxide (SiO2) nanocoating with a coating thickness of 40 nm at a temperature of 55 °C, a pressure of 9 Pa, and a time of 30 s.

[0107] Through the above four embodiments, the various parameters and process conditions of the functional gradient three-layer co-injection PCR composite packaging bottle and its preparation method of the present invention are fully covered. These embodiments not only demonstrate the feasibility and flexibility of the present invention, but also reflect the impact of different process parameters on the performance of the final product. Preferably, by adjusting the component ratio and preparation process of each layer of material, the most suitable packaging bottle structure and performance can be customized according to the characteristics and shelf life requirements of different beverages.

[0108] Comparative Example 1: Single-layer PCR-PET packaging bottle This comparative example is intended to verify the superiority of the three-layer functional gradient structure. The packaging bottle is made of only a single layer of PCR-PET with a thickness of 0.40 mm, which is the same as the total thickness of the three-layer structure in Example 1.

[0109] The preparation method comprises the following steps: (1) Preparation of PCR-PET First, PCR-PET was vacuum dried at 90°C for 20 hours, and the water content was controlled below 30 ppm. Secondly, melt extrusion was performed using a single screw extruder with an L / D ratio of 40:1. The temperature distribution from the feed zone to the die head was 260°C, 270°C, 280°C, 280°C, 270°C, the screw speed was 180 rpm, and the vacuum degree was -0.085 MPa. Finally, water-cooled traction was performed, the water temperature was controlled at 18°C, pelletized to 3.0 mm, and vacuum dried at 90°C for 12 hours.

[0110] (2) Injection blow molding Standard injection blow molding equipment was used for molding. The barrel temperature was 275°C, the mold temperature was 20°C, the injection pressure was 90MPa, the injection speed was 70 mm / s, the holding time was 4.0 s, the cooling time was 14 s, the blowing pressure was 4.0 MPa, and the blowing time was 5.0 s.

[0111] (3) Post-processing Heat setting was performed at 90°C for 15 s and a pressure of 0.5 MPa.

[0112] By comparing with Example 1, it can be found that the gas barrier property, mechanical properties and food safety of the single-layer PCR-PET packaging bottle are not as good as those of the three-layer functional gradient structure, which verifies the necessity and superiority of the multi-layer structure of the present invention.

[0113] Comparative Example 2: PCR composite packaging bottle with three-layer structure but without toughening modification The comparative example is intended to verify the importance of toughening and modifying the middle layer. The packaging bottle adopts the same three-layer structure as Example 2, but the middle layer is not toughened and modified.

[0114] The components and preparation methods of the inner layer and the outer layer are the same as those in Example 2. The preparation method of the middle layer is as follows: (1) Preparation of middle layer PCR-PET First, PCR-PET was vacuum dried at 95°C for 22 hours, and the water content was controlled below 15 ppm. Secondly, melt extrusion was performed using a twin-screw extruder with an L / D ratio of 52:1. The temperature distribution from the feed zone to the die head was 235°C, 255°C, 270°C, 280°C, 280°C, 275°C, and 265°C, the screw speed was 250 rpm, and the vacuum degree was -0.093 MPa. Finally, water-cooled traction was performed, the water temperature was controlled at 18.5°C, pelletized to 3.5 mm, and vacuum dried at 90°C for 14 hours.

[0115] The three-layer co-injection molding and post-processing steps are the same as in Example 2.

[0116] By comparing with Example 2, it can be found that the PCR composite packaging bottle without toughening modification is significantly inferior in impact resistance and ductility. This verifies the necessity of using E-MA-GMA and E-GMA for toughening modification in the present invention, and highlights the synergistic effect of these components in improving the overall mechanical properties of the bottle.

[0117] Comparative Example 3: Bottle with three-layer structure but no high-barrier PCR composite material on the outer layer This comparative example is intended to verify the importance of the high barrier PCR composite material of the outer layer. The packaging bottle adopts the same three-layer structure as Example 3, but only ordinary PCR-PET is used for the outer layer without adding SiO2 nanoparticles and vitamin E.

[0118] The components and preparation methods of the inner layer and the middle layer are the same as those in Example 3. The preparation method of the outer layer is as follows: (1) Preparation of outer layer PCR-PET First, PCR-PET was vacuum dried at 105°C for 26 hours, and the water content was controlled below 10 ppm. Secondly, melt extrusion was performed using a twin-screw extruder with an L / D ratio of 44:1. The temperature distribution from the feed zone to the die head was 268°C, 278°C, 288°C, 292°C, 292°C, 288°C, and 278°C, the screw speed was 340 rpm, and the vacuum degree was -0.098 MPa. Finally, water-cooled traction was performed, the water temperature was controlled at 23°C, pelletized to 4.5 mm, and vacuum dried at 112°C for 30 hours.

[0119] The three-layer co-injection molding and post-processing steps are the same as in Example 3.

[0120] By comparing with Example 3, it can be found that the packaging bottle without high-barrier PCR composite material is significantly inferior in gas barrier property and antioxidant performance. This verifies the necessity of using SiO2 nanoparticles and vitamin E in the present invention, and highlights the synergistic effect of these components in improving the barrier property of the bottle and extending the shelf life of the beverage.

[0121] Comparative Example 4: PCR composite packaging bottle with three-layer structure but no post-treatment This comparative example is intended to verify the importance of post-processing technology. The packaging bottle adopts the same three-layer structure and preparation method as Example 4, but no heat setting, supercritical CO2 surface treatment and bottle inner coating treatment are performed.

[0122] The three-layer co-injection molding steps are the same as those in Example 4, but the post-processing step is omitted.

[0123] By comparing with Example 4, it can be found that the PCR composite packaging bottle without post-treatment is inferior to the packaging bottle after comprehensive post-treatment in terms of dimensional stability, surface performance and gas barrier properties. This verifies the necessity of using heat setting, supercritical CO2 surface treatment and SiO2 nano-coating in the present invention, and highlights the synergistic effect of these processes in optimizing the comprehensive performance of the bottle.

[0124] Comparative Example 5: Three-layer structure but the inner layer uses ordinary PET packaging bottle This comparative example is intended to verify the importance of using food-grade high-purity PET in the inner layer. The packaging bottle adopts the same three-layer structure as Example 1, but ordinary PET is used in the inner layer instead of food-grade high-purity PET.

[0125] The components and preparation methods of the middle layer and the outer layer are the same as those in Example 1. The preparation method of the inner layer is as follows: (1) Preparation of inner layer ordinary PET Commercial common PET (intrinsic viscosity 0.75 dL / g, acetaldehyde content 5 ppm, melting point 245°C, crystallinity 30%) was used for drying and melt extrusion. The drying condition was vacuum drying at 80°C for 16 hours. The melt extrusion conditions were the same as those in Example 1.

[0126] The three-layer co-injection molding and post-processing steps are the same as in Example 1.

[0127] By comparing with Example 1, it can be found that the packaging bottle using ordinary PET as the inner layer is inferior in terms of food safety and taste retention. This verifies the necessity of using food-grade high-purity PET as the inner layer in the present invention, and highlights the important role of high-purity PET in minimizing the interaction with beverages.

[0128] Comparative Example 6: PCR composite packaging bottle with three-layer structure but insufficient solid phase polycondensation time This comparative example is intended to verify the importance of sufficient solid phase polycondensation of the outer PCR-PET layer. The packaging bottle adopts the same three-layer structure as Example 2, but the solid phase polycondensation time of the outer PCR-PET layer is halved.

[0129] The components and preparation methods of the inner layer and the middle layer are the same as those in Example 2. The preparation method of the outer layer is as follows: (1) Preparation of outer layer high barrier PCR composite material First, the food-grade PCR-PET flake material was placed in a food-grade solid phase polycondensation reactor, heated to 205°C at a rate of 1.9°C / min under a nitrogen atmosphere, maintained for 12 hours (rather than 24 hours in Example 2), then cooled to room temperature at a rate of 0.9°C / min, evacuated to -0.095 MPa, maintained for 4.5 hours, and the intrinsic viscosity increased by about 0.11 dL / g. The subsequent steps were the same as in Example 2.

[0130] The three-layer co-injection molding and post-processing steps are the same as in Example 2.

[0131] By comparison with Example 2, it can be found that the PCR composite packaging bottle with insufficient solid phase polycondensation time is inferior in mechanical strength and gas barrier properties. This verifies the necessity of sufficient solid phase polycondensation of the outer layer PCR-PET in the present invention, and highlights the key role of this process in improving material performance.

[0132] Through these six comparative examples, the various innovations and advantages of the present invention are fully verified. These comparative examples cover multiple aspects such as formula components, structural design and preparation process, clearly demonstrate the synergistic mechanism of various technical features of the present invention, and provide strong support for the creativity of the present invention.

[0133] In order to comprehensively evaluate the performance of the functional gradient three-layer co-injection PCR composite packaging bottle of the present invention, the following test experiments were designed: 1. Oxygen transmission rate test Experimental purpose: To evaluate the gas barrier properties of the bottle; Experimental method: Adopt ASTM D3985 standard and use Ox-Tran 2 / 21 oxygen transmission rate tester; Experimental conditions: temperature 23°C, relative humidity 50%, test time 48 hours; 2. Carbon dioxide retention rate test Experimental purpose: To simulate the CO2 loss during the storage of carbonated beverages; Experimental method: The bottles were filled with carbonated water of standard concentration, sealed and stored at 38°C for 30 days, and the CO2 content was measured regularly; Experimental equipment: Anton Paar DMA 4500 M density meter; 3. Impact resistance test Experimental purpose: To evaluate the impact resistance of the bottle Test method: Adopt ASTM D2463 standard, use drop weight impact tester Experimental conditions: drop weight 1.8 kg, drop height 0.5 m, test temperature 23°C 4. Thermal stability test Experimental purpose: To evaluate the dimensional stability of the bottle under high temperature environment; Experimental method: Fill the bottle with 60°C hot water, seal it and leave it for 4 hours, then measure the deformation of the bottle; Experimental equipment: digital caliper; 5. Chemical resistance test Purpose of the experiment: To evaluate the tolerance of bottles to common beverage additives Experimental method: Soak the bottles in 1% citric acid solution, 1% acetic acid solution and 1% sodium hydroxide solution for 24 hours, and measure the weight change and appearance change. Experimental equipment: precision electronic balance, optical microscope 6. Light transmittance test Experimental purpose: To evaluate the transparency of the bottle; Experimental method: Adopt ASTM D1003 standard and use spectrophotometer; Experimental conditions: Test wavelength 380-780 nm; 7. Acetaldehyde migration test Experimental purpose: To evaluate the impact of bottle on food safety; Experimental method: GB 31604.8-2016 standard was adopted, using headspace gas chromatography; Experimental conditions: The simulated liquid was 3% acetic acid solution, immersed at 70°C for 2 hours; The test results are shown in the following table Table 1. Performance test results of functional gradient three-layer co-injection PCR composite packaging bottles

[0134] According to the test results in Table 1, the following conclusions can be drawn: 1. Gas barrier performance: Examples 1-4 all exhibit excellent oxygen barrier properties and CO2 retention rates, with Example 3 having the best effect. This is mainly due to the synergistic effect of the three-layer functional gradient structure and the outer layer high-barrier PCR composite material. In contrast, the gas barrier properties of Comparative Example 1 (single-layer structure) and Comparative Example 3 (no high-barrier material in the outer layer) are significantly inferior.

[0135] 2. Mechanical properties: The impact strength of Examples 1-4 is significantly higher than that of the comparative examples, especially Example 3. This demonstrates the importance of the toughened PCR-PET in the middle layer and the advantages of the three-layer structure in stress dispersion. The impact resistance of Comparative Example 2 (without toughening modification) is significantly poor, which verifies the necessity of the toughening agent.

[0136] 3. Thermal stability: Examples 1-4 showed excellent thermal stability, and the deformation rate was much lower than that of the comparative example. This is due to the fact that the solid phase polycondensation process improved the crystallinity and thermal stability of PCR-PET. The thermal stability of comparative example 6 (insufficient solid phase polycondensation time) was poor, indicating that a sufficient solid phase polycondensation process is crucial to improving thermal stability.

[0137] 4. Chemical resistance: Examples 1-4 show good chemical resistance with minimal weight change. This is mainly due to the synergistic protection of the three-layer structure and the chemical stability of the outer high barrier material. The chemical resistance of Comparative Example 1 (single-layer structure) is significantly inferior.

[0138] 5. Light transmittance: Although the light transmittance of Examples 1-4 is slightly lower than that of Comparative Example 1 (single-layer structure), it is still maintained at a very high level, meeting the transparency requirements of the packaging. This shows that the present invention successfully maintains good appearance quality while improving performance.

[0139] 6. Food safety: The acetaldehyde migration of Examples 1-4 is significantly lower than that of the comparative examples, especially comparative examples 1 and 5 (the inner layer uses ordinary PET). This verifies the importance of using food-grade high-purity PET as the inner layer, and the advantages of the three-layer structure in blocking the migration of harmful substances.

[0140] Comprehensive analysis shows that Example 3 exhibits the best comprehensive performance and can be regarded as the best embodiment of the present invention.

[0141] The present invention also has the following unexpected technical effects: 1. Ultra-low oxygen permeability: The oxygen permeability of Example 3 is only 0.022 cm³ / (m²·24h·atm), which is much better than the conventional level in the industry. This excellent gas barrier performance is the result of the synergistic effect of the three-layer functional gradient structure, the outer layer high barrier PCR composite material and the SiO2 nano-coating. The SiO2 nanoparticles form a tortuous diffusion path in the PCR-PET matrix, and the SiO2 nano-coating on the surface further blocks the microscopic pores, forming a nearly perfect barrier layer.

[0142] 2. Balance between excellent impact resistance and high transparency: Generally, improving the impact resistance of polymers will lead to a decrease in transparency. However, the present invention achieves a perfect balance between high impact resistance (4.5 J) and high light transmittance (87.2%) by precisely controlling the phase structure of the toughened modified PCR-PET in the middle layer. This is due to the formation of a nano-scale dispersed phase in the PCR-PET matrix by the toughening agent E-MA-GMA, which effectively improves toughness without significantly affecting light transmittance.

[0143] 3. Extremely low acetaldehyde migration: The acetaldehyde migration of Example 3 is only 0.6 mg / kg, which is far below the national standard limit (6 mg / kg). This ultra-low migration not only ensures food safety, but also greatly improves the shelf life and taste retention of beverages. This effect is due to the low acetaldehyde content of the inner layer of high-purity PET and the effective barrier of the three-layer structure to the diffusion of acetaldehyde.

[0144] 4. Excellent CO2 retention rate: The 30-day CO2 retention rate of 97.8% means that the packaging bottle of the present invention can extend the shelf life of carbonated beverages by at least 50%. This performance breakthrough provides a new packaging solution for the carbonated beverage industry, which is expected to significantly reduce the quality loss of carbonated beverages during storage and transportation.

[0145] 5. Breakthrough in heat resistance and recyclability: Generally, improving the heat resistance of PET bottles will reduce their recyclability. However, the present invention improves thermal stability while maintaining good recyclability through solid phase polycondensation technology and precise control of crystallinity. The low deformation rate of 0.25% allows the packaging bottle of the present invention to be used in hot filling processes, expanding the potential of PCR-PET in high-temperature applications.

[0146] These unexpected technical effects fully demonstrate the breakthroughs of the present invention in material design, structural optimization and process innovation, and open up new possibilities for the application of PCR-PET in the field of high-performance packaging.

[0147] The above description is only an embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A functional gradient three-layer co-injection PCR composite packaging bottle, characterized in that: It includes an inner layer, a middle layer and an outer layer arranged in sequence from the inside to the outside, wherein: The inner layer is made of food-grade high-purity PET with a thickness of 0.08-0.18 mm; The middle layer is made of food-grade toughened modified PCR-PET with a thickness of 0.22-0.42 mm; The outer layer is made of a high-barrier PCR composite material and has a thickness of 0.12-0.27 mm.

2. The functional gradient three-layer co-injection PCR composite packaging bottle according to claim 1, characterized in that: The food-grade high-purity PET of the inner layer has an intrinsic viscosity of 0.82-0.87 dL / g, an acetaldehyde content of ≤1 ppm, a melting point of 250-255°C, and a crystallinity of 35-40%.

3. The functional gradient three-layer co-injection PCR composite packaging bottle according to claim 1, characterized in that: The food-grade toughened modified PCR-PET of the middle layer is made of the following components in parts by weight: Food grade PCR-PET: 100 copies; Food grade ethylene-methyl acrylate-glycerol acrylate terpolymer E-MA-GMA: 3-10 parts; Food grade epoxidized polyethylene E-GMA: 1-5 parts.

4. The functional gradient three-layer co-injection PCR composite packaging bottle according to claim 1, characterized in that: The high barrier PCR composite material of the outer layer is made of the following components in parts by weight: Solid phase polycondensation food grade PCR-PET: 100 copies; Food grade silica nanoparticles: 0.3-1.5 parts; Food grade vitamin E: 0.05-0.2 parts.

5. A method for preparing a functional gradient three-layer co-injection PCR composite packaging bottle according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) Preparation of middle-layer food-grade toughened modified PCR-PET; (2) preparing an outer layer high barrier PCR composite material; (3) Three-layer co-injection molding; (4) Post-processing.

6. The preparation method according to claim 5, characterized in that: The step (1) comprises: First, food-grade PCR-PET was vacuum dried at 85-105°C for 18-26 hours, and the water content was controlled below 20 ppm; E-MA-GMA and E-GMA were vacuum dried at 55-65°C for 5-9 hours; Secondly, a food-grade twin-screw extruder with an L / D ratio of 52:1 was used for melt extrusion reaction, and the temperature distribution from the feed zone to the die head was 225°C, 245°C, 265°C, 278°C, 278°C, 272°C, and 262°C, the screw speed was 200-300 rpm, and the vacuum degree was -0.088 to -0.098 MPa; Then, the dried food-grade PCR-PET was added through the main feed port, E-MA-GMA was added through the first side feed port at L / D=0.3, and E-GMA was added through the second side feed port at L / D=0.6; Finally, food-grade water-cooled pulling is carried out, the water temperature is controlled at 16-21°C, pelletized to 2.5-4.5 mm, and vacuum dried at 88°C for 12-16 hours.

7. The preparation method according to claim 5, characterized in that: The step (2) comprises: First, a food-grade PCR-PET flake material is placed in a food-grade solid phase polycondensation reactor, heated to 195-215°C at a rate of 1.8°C / min under a nitrogen atmosphere, maintained for 18-30 hours, then cooled to room temperature at a rate of 0.8°C / min, evacuated to -0.098 MPa, maintained for 7-11 hours, and the intrinsic viscosity is increased by 0.18-0.28 dL / g; Secondly, the food-grade PCR-PET after solid phase polycondensation is dry-mixed with SiO2 nanoparticles and vitamin E in a food-grade high-speed mixer at a mixing condition of 3800-5800 rpm for 7-13 minutes; Again, a food-grade twin-screw extruder with an L / D ratio of 44:1 was used for melt extrusion compounding, and the temperature distribution from the feed zone to the die head was 248°C, 268°C, 278°C, 288°C, 288°C, 278°C, and 268°C, the screw speed was 240-340 rpm, and the vacuum degree was -0.088 to -0.098 MPa; Finally, food-grade water-cooled pulling is carried out, the water temperature is controlled at 19-23°C, pelletized to 2.5-4.5 mm, and vacuum dried at 108°C for 18-30 hours.

8. The preparation method according to claim 5, characterized in that: The step (3) uses a food-grade three-layer co-injection blow molding device, wherein: The barrel temperatures of the inner layer, middle layer, and outer layer are 278-288°C, 268-278°C, and 288-298°C, respectively; The mold temperature is 20-30°C; The injection pressures of the inner layer, middle layer, and outer layer are 88-108 MPa, 78-98 MPa, and 98-118 MPa, respectively; The injection speeds of the inner layer, middle layer, and outer layer are 68-88 mm / s, 58-78 mm / s, and 78-98 mm / s, respectively; The holding time is 3.8-5.8 s; Cooling time is 13-19 seconds; Blowing pressure is 3.8-4.8 MPa; The blowing time is 4.5-6.5 s.

9. The preparation method according to claim 5, characterized in that: The step (4) comprises: First, heat setting is performed at a temperature of 88-108°C, a time of 13-23 s, and a pressure of 0.48-0.68 MPa; Secondly, supercritical CO2 surface treatment is carried out at a pressure of 15-25 MPa, a temperature of 40-60°C, and a treatment time of 20-40s; Finally, the bottle inner coating treatment was carried out, and a food-grade silica nanocoating was deposited by plasma enhanced chemical vapor deposition method with a coating thickness of 20-100 nm, a temperature of 50-70°C, a pressure of 5-20 Pa, and a time of 25-45 s.

10. A functional gradient three-layer co-injection PCR composite packaging bottle prepared according to the preparation method according to any one of claims 5 to 9.

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