CPET plastic uptake tray and preparation method thereof

Abstract

The invention relates to the technical field of high polymer materials, and particularly discloses a CPET blister tray and a preparation method thereof. The product comprises a CPET special polyester chip, a nucleating agent, a color master batch, a maleic anhydride grafted polyolefin elastomer flexibilizer and a polyfunctional group epoxy polymer chain extender. The preparation method comprises the following steps: carrying out drying pretreatment on the CPET slices, premixing the raw materials step by step, carrying out melt blending extrusion by a twin-screw extruder to obtain a sheet, carrying out infrared heating on the sheet, carrying out plastic molding, cooling, shaping, trimming and punching to obtain the product. The CPET plastic uptake tray can be used for aviation meal boxes, cake baking boxes, egg tart boxes, cake steaming trays, trays for food and medical disinfection, trays for electronic baking varnish and electronic screen thermocuring and the like, has excellent heat resistance, is not prone to deformation at high temperature and is good in toughness and structural stability; in addition, the preparation method is reasonable in step, capable of guaranteeing full action of the raw materials and suitable for industrial production.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of high polymer materials, in particular to a CPET blister tray and a preparation method thereof. BACKGROUND

[0002] The CPET blister tray is a packaging container made of crystalline polyethylene terephthalate (CPET) as the main raw material through a blister forming process. It is widely used in food, medicine and other fields due to its good mechanical properties and forming stability. In the food industry, it can be used for packaging of fresh food, cooked food and other products, which not only protects the food from external pollution, but also adapts to various storage and processing methods such as refrigeration and heating. In the medical field, it can be used for sterile packaging of medical devices and drugs to provide a safe and clean storage environment. However, the conventional packaging materials commonly used in these scenarios, such as PVC and PE, have obvious shortcomings in heat resistance. When facing high-temperature sterilization, microwave heating and other situations, such materials are prone to deformation due to temperature rise, and even cracking, which not only damages the integrity of the packaging and affects the use effect, but also may cause the internal items to be contaminated or damaged due to deformation, and cannot meet the demand for maintaining the shape stability of the packaging material in a high-temperature environment. SUMMARY

[0003] In order to solve the problem that the conventional packaging material in the prior art is prone to deformation in a high-temperature environment and is difficult to maintain shape stability, the application provides a CPET blister tray and a preparation method thereof.

[0004] In a first aspect, the application provides a CPET blister tray, which adopts the following technical solution: A CPET blister tray is composed of the following raw materials in mass percentage: CPET special polyester chips 87-93.8%, nucleating agent 3-5%, color masterbatch 1.4-3%, toughening agent 2-5%, chain extender 0.2-1%; The color masterbatch includes white color masterbatch and black color masterbatch, the tray has a double-layer composite structure composed of a base layer containing white color masterbatch and a surface layer containing black color masterbatch, the toughening agent is maleic anhydride grafted polyolefin elastomer, and the chain extender is a multi-functional epoxy polymer.

[0005] By adopting the above technical solution and using CPET-specific polyester chips as the main raw material, the tray is provided with basic structural support and heat resistance. Nucleating agents promote material crystallization and improve the crystalline structure. Maleic anhydride-grafted polyolefin elastomers act as toughening agents, enhancing the material's toughness. Multifunctional epoxy polymer chain extenders optimize the molecular chain structure and improve the material's overall integrity. White and black masterbatches impart the desired color to the tray without affecting its basic properties. These raw materials are blended in specific proportions, and the interaction of each component synergistically improves the overall performance of the material, thus achieving a harmonious balance in structure, heat resistance, and toughness of the CPET blister tray.

[0006] Preferably, the maleic anhydride-grafted polyolefin elastomer is a maleic anhydride-grafted ethylene-octene copolymer POE-g-MAH or an ethylene-methyl acrylate copolymer EMA, with a grafting rate of 0.8-1.5%.

[0007] By adopting the above technical solutions, both the ethylene-octene copolymer POE-g-MAH and the ethylene-methyl acrylate copolymer EMA are maleic anhydride-grafted modified polyolefin elastomers. POE-g-MAH uses an elastomer formed by copolymerizing ethylene and octene as its main chain, introducing polar groups through maleic anhydride grafting, thus possessing both the flexibility of polyolefins and the reactivity of polar groups. EMA, on the other hand, is a copolymer of ethylene and methyl acrylate grafted with maleic anhydride, retaining good elasticity and processing fluidity. The maleic anhydride groups in these two components can interact with the functional groups on the CPET molecular chain, improving compatibility with CPET and avoiding performance degradation due to poor compatibility. Simultaneously, their inherent elastic characteristics can form flexible regions within the material, absorbing energy and dispersing stress when subjected to external forces. Combined with a reasonable grafting rate, this can help improve the overall toughness and impact resistance of the material without affecting the basic properties of CPET.

[0008] Preferably, the multifunctional epoxy polymer chain extender is a styrene-glycidyl methacrylate copolymer.

[0009] By employing the above technical solution and using styrene-glycidyl methacrylate copolymer as a multifunctional epoxy polymer chain extender, the epoxy groups in its molecules can react with the functional groups at the ends of the CPET molecular chains, extending the molecular chain length and increasing the degree of intermolecular entanglement. This effect strengthens the internal structure of the material and enhances the bonding force between molecular chains. While ensuring the original properties of the material, it works synergistically with toughening agents and other components to optimize the mechanical properties of the material, thereby making the CPET blister tray less prone to breakage under stress and achieving a more stable overall structure.

[0010] Secondly, this application provides a method for preparing a CPET blister tray, which adopts the following technical solution: A method for preparing a CPET blister tray includes the following steps: S1. Raw material pretreatment: Dry CPET special polyester chips at 120-140℃ for 3-5 hours to reduce their moisture content to less than 50ppm; S2. Premixing: The dried CPET chips, nucleating agent, toughening agent, chain extender and color masterbatch are premixed. S3. Melt Blending Extrusion: The premixed material is fed into a twin-screw extruder. The extruder temperature is controlled from zone one to the die head, with the temperature range set at 245-275℃ and the screw speed at 250-350r / min. After melt blending and reactive extrusion, the material is formed into sheets through the die head. S4. Vacuum forming: The obtained sheet is preheated to 185-205℃ in an infrared heating furnace, and then placed in a vacuum forming mold. Positive and negative pressure are used for forming. The positive pressure is 0.4-0.6MPa, the negative pressure is 0.06-0.08MPa, and the holding time is 5-10 seconds. S5. Cooling and shaping: The formed tray is shaped in a cooling and shaping mold; S6. Trimming and punching: The cooled and shaped pallet is trimmed by a precision punching die to obtain the final product.

[0011] By adopting the above technical solutions, raw material pretreatment can effectively remove moisture from CPET special polyester chips, avoiding defects such as bubbles caused by moisture in subsequent processing; the premixing step can make the raw materials initially mixed evenly, laying the foundation for subsequent melt blending; during melt blending extrusion, specific temperature and screw speed can promote the full melting and reaction of raw materials, forming a uniform sheet; in thermoforming, infrared heating and specific forming pressure and holding time can accurately shape the sheet; cooling and setting can fix the tray shape, and trimming and punching can ensure the dimensional accuracy of the product. The synergistic effect of each step ensures the stable production and good performance of CPET thermoforming trays.

[0012] Preferably, in step S2, the premixing is divided into two steps: first, CPET chips are mixed with toughening agent and chain extender at a speed of 300-500 r / min for 3-5 minutes, and then nucleating agent and color masterbatch are added and mixed at a speed of 200-300 r / min for 2-4 minutes.

[0013] By adopting the above technical solution, the first step of mixing CPET chips with toughening agents and chain extenders at a high rotation speed allows the toughening agents and chain extenders to adhere more evenly to the surface of the CPET chips, creating conditions for a full reaction during subsequent melting. The second step of adding nucleating agents and color masterbatches at a lower rotation speed reduces the agglomeration of nucleating agents caused by high-speed stirring and avoids local color differences caused by uneven dispersion of color masterbatches. The combination of these two premixing steps ensures more uniform dispersion of various raw materials, guaranteeing the synergistic effect of each component in subsequent processing.

[0014] Preferably, in step S3, the screw length-to-diameter ratio of the twin-screw extruder is 28:1 to 36:1, and a vacuum extraction port is provided in the middle of the barrel, with the vacuum degree of the vacuum extraction port controlled at -0.04 to -0.06 MPa.

[0015] By adopting the above technical solution, the screw length-to-diameter ratio is controlled between 28:1 and 36:1, providing sufficient melting time and shearing action for the raw materials. This ensures that CPET chips are fully mixed and reacted with other additives, improving the material's plasticizing effect. The vacuum vent in the middle of the barrel, operating at a vacuum level of -0.04 to -0.06 MPa, effectively removes volatiles and residual gases generated during the melting process, preventing the formation of bubbles or pinholes in the sheets. The combination of these two methods helps improve the density and uniformity of the sheets, providing a high-quality substrate for subsequent thermoforming.

[0016] Preferably, in step S3, the thickness of the melt-extruded sheet is 0.4-1.2 mm, and it is immediately calendered and shaped by a three-roll calender after extrusion, wherein the temperature of the upper roll is 80-90℃, the temperature of the middle roll is 70-80℃, and the temperature of the lower roll is 60-70℃.

[0017] By adopting the above technical solution, the thickness of the melt-extruded sheet is controlled between 0.4-1.2mm. The material usage can be adjusted according to actual usage requirements, balancing the structural strength and lightweight of the tray. Immediately after extrusion, the sheet passes through a three-roll calender. Under the temperature gradient of the upper, middle, and lower rollers (80-90℃, 70-80℃, and 60-70℃ respectively), the surface of the sheet can be quickly smoothed, reducing textures and unevenness. At the same time, it promotes the cooling and shaping of the sheet, improving surface smoothness. This process ensures uniform sheet thickness and optimizes surface condition, which is beneficial to the uniform heating and shaping accuracy during subsequent thermoforming.

[0018] Preferably, in step S4, the heating power of the infrared heating furnace is controlled by zones, wherein the power of the preheating zone is 40-50% of the total power, the power of the forming zone is 50-60%, and the heating time of the sheet in each zone is 10-20 seconds.

[0019] By adopting the above technical solution, the infrared heating furnace controls power in zones of 40-50% for the preheating zone and 50-60% for the forming zone, with each zone requiring a heating time of 10-20 seconds, allowing the sheet material to gradually heat up. The preheating zone first preheats the sheet material evenly, avoiding direct high temperatures that could lead to localized overheating; the forming zone then heats the sheet material at a higher power to the appropriate forming temperature, ensuring uniform softening of the sheet material and meeting the requirements of vacuum forming. This zoned heating method reduces deformation or damage to the sheet material caused by uneven heating, ensuring precise shaping during subsequent vacuum forming.

[0020] Preferably, in step S5, the temperature of the cooling and shaping mold is controlled at 25-40℃, and the cooling time is 6-10 seconds.

[0021] By adopting the above technical solution, the temperature of the cooling and shaping mold is controlled at 25-40℃, and a cooling time of 6-10 seconds is set. This allows the heat of the tray to be quickly removed after vacuum forming, causing it to solidify from a softened state into its final shape. This avoids tray deformation or dimensional deviations caused by insufficient cooling. Simultaneously, the appropriate temperature and time prevent surface cracking of the tray due to excessively rapid cooling, ensuring the stability of the tray's shape and the integrity of its structure, providing a qualified semi-finished product for subsequent trimming and punching.

[0022] Preferably, in step S6, the punching gap of the precision punching die is 0.02-0.05mm, and the punching frequency is 20-30 times / minute.

[0023] By adopting the above technical solution, the punching clearance of the precision punching die is controlled within 0.02-0.05mm, ensuring the neatness of the punched edges, reducing burrs and breakage, and improving the dimensional accuracy of the pallet. A punching frequency of 20-30 times / minute ensures both punching quality and production efficiency, avoiding excessive die wear or increased product defects due to excessive frequency. The combination of these two methods results in smooth, dimensionally accurate pallets after trimming, meeting the product's appearance and assembly requirements.

[0024] In summary, this application has the following beneficial effects: 1. Since this application uses CPET special polyester chips as the main raw material, combined with nucleating agent, maleic anhydride grafted polyolefin elastomer toughening agent, multifunctional epoxy polymer chain extender and color masterbatch, and each raw material is combined in a specific ratio, the heat resistance of CPET and the crystallization strengthening effect of nucleating agent work together to make the product less prone to deformation under heat environment and achieve better thermal stability.

[0025] 2. In this application, maleic anhydride-grafted ethylene-octene copolymer is preferred as a toughening agent and the grafting rate is controlled. Styrene-glycidyl methacrylate copolymer is used as a chain extender. The toughening agent after grafting can better combine with the CPET molecular chain, and the chain extender extends the molecular chain. The two work together to enhance the material's ability to resist impact and achieve a better impact resistance effect.

[0026] 3. The method of this application, through steps such as raw material pretreatment, two-step premixing, and melt blending extrusion with specific parameters, reduces the impact of moisture on processing, and the two-step premixing makes the raw materials more uniformly mixed, ensuring the consistency of material properties in subsequent processing and achieving stable product performance. Attached Figure Description

[0027] Figure 1 This is a flowchart of a CPET blister tray preparation method provided in this application. Detailed Implementation

[0028] The present application will be further described in detail below with reference to embodiments and comparative examples.

[0029] Technical concept: Traditional packaging materials used in food, medical, and other fields, such as PVC and PE, are prone to deformation under high temperatures. The core reason lies in the limitations of their material structure and performance. These materials have insufficient molecular chain stability, and when heated, molecular motion intensifies, making it difficult to maintain their original shape. Furthermore, they lack the synergistic effect of components that can enhance heat resistance and stability, resulting in their inability to maintain structural stability in scenarios such as high-temperature sterilization and microwave heating, thus affecting the reliability of the packaging. To address this issue, this technical solution addresses both the raw material formulation and the preparation process. Regarding raw materials, CPET-specific polyester chips are used as the main ingredient, combined with nucleating agents, maleic anhydride-grafted polyolefin elastomer toughening agents, multifunctional epoxy polymer chain extenders, and color masterbatches, all blended in specific proportions. This leverages the synergistic effect of CPET's heat resistance and the crystallization-strengthening effect of the nucleating agents to enhance the material's heat resistance stability. In terms of the preparation process, through raw material pretreatment, step-by-step premixing, precise control of melt blending extrusion, and thermoforming parameters, the solution ensures that each raw material fully functions, ultimately making the CPET thermoforming tray less prone to deformation in high-temperature environments, meeting the requirements for use in high-temperature scenarios.

[0030] Preparation Example 1 The preparation method of ethylene-octene copolymer POE-g-MAH is as follows: 80 parts by weight of ethylene-octene copolymer (POE), 10 parts by weight of maleic anhydride, and 1.5 parts by weight of dicumyl peroxide were added to a high-speed mixer and mixed at 100°C for 10 minutes. The mixture was then fed into a twin-screw extruder, with the extrusion temperature controlled at 160°C and the screw speed at 300 r / min. After a melt grafting reaction, the mixture was extruded and granulated to obtain POE-g-MAH with a grafting rate of 0.8-1.5%. This process involves dicumyl peroxide initiating a grafting reaction between maleic anhydride and the POE molecular chain, thereby introducing polar groups to meet the compatibility requirements between the toughening agent and the CPET molecular chain.

[0031] Preparation Example 2 The preparation method of the styrene-glycidyl methacrylate copolymer chain extender is as follows: Prepare a reaction vessel equipped with a stirrer, thermometer, condenser, and dropping device. Add 60 parts by weight of toluene solvent and heat to 110°C. Simultaneously, thoroughly mix 40 parts by weight of styrene monomer, 60 parts by weight of glycidyl methacrylate monomer, and 1.5 parts by weight of benzoyl peroxide (BPO) initiator to form a homogeneous mixture. Then, slowly and uniformly add this mixture dropwise to the reaction vessel over 3 hours using a constant-pressure dropping funnel. After the addition is complete, maintain the reaction temperature and continue the reaction for 5 hours. After the reaction is complete, cool the reaction system to room temperature, pour the product into a large amount of ethanol to precipitate it, and filter to obtain a solid product. Finally, place the obtained solid in a vacuum drying oven and dry at 60°C for 12 hours to obtain a white powdery styrene-glycidyl methacrylate copolymer, which can be used as a chain extender.

[0032] The raw material information used in this application is as follows: 1. CPET special polyester chips were purchased from Dongguan Jinshixiang Plastic Raw Materials Co., Ltd., item number: 1699; 2. The nucleating agent was purchased from Shanghai Yuanye Biotechnology Co., Ltd., product number: Y11854; 3. The color masterbatch was purchased from Shanghai Juqian New Materials Development Co., Ltd.; 4. Toughening agent - maleic anhydride-grafted ethylene-octene copolymer (POE-g-MAH) was purchased from Haozheng New Material Technology (Dongguan) Co., Ltd., item number: R905; 5. Toughening agent - ethylene-methyl acrylate copolymer (EMA) was purchased from Shanghai Chuangsai Technology Co., Ltd., item number: PR01024.

[0033] Example 1 This application provides a CPET blister tray, composed of the following raw materials by weight percentage: 90% CPET-specific polyester chips, 4% nucleating agent, 1.4% color masterbatch, 4% toughening agent, and 0.6% chain extender. The color masterbatch includes white and black masterbatches. The tray has a double-layer composite structure consisting of a base layer containing white masterbatch and a surface layer containing black masterbatch. The toughening agent is a maleic anhydride-grafted polyolefin elastomer, specifically a maleic anhydride-grafted ethylene-octene copolymer POE-g-MAH with a grafting rate of 1.15%. The chain extender is a multifunctional epoxy polymer, specifically a styrene-glycidyl methacrylate copolymer.

[0034] The above-mentioned method for preparing a CPET blister tray includes the following steps: S1. Raw material pretreatment: Dry CPET special polyester chips at 130℃ for 4 hours to reduce their moisture content to less than 50ppm; S2. Premixing: The dried CPET chips, nucleating agent, toughening agent, chain extender and color masterbatch are premixed. The premixing is divided into two steps. First, the CPET chips are mixed with toughening agent and chain extender at 400 r / min for 4 minutes. Then, the nucleating agent and color masterbatch are added and mixed at 250 r / min for 3 minutes. S3. Melt Blending Extrusion: The premixed material is fed into a twin-screw extruder with a screw length-to-diameter ratio of 32:1. A vacuum extraction port is provided in the middle of the barrel, and the vacuum degree of the vacuum extraction port is controlled at -0.05MPa. The extruder temperature is controlled in zones from zone 1 to the die head, with the temperature range set at 260℃. The screw speed is 300r / min. After melt blending and reactive extrusion, the material is formed into a sheet through the die head. The thickness of the melt-extruded sheet is 0.8mm. Immediately after extrusion, the material is calendered and shaped by a three-roll calender, with the upper roll temperature at 85℃, the middle roll temperature at 75℃, and the lower roll temperature at 65℃. S4. Vacuum forming: The obtained sheet is preheated to 195°C in an infrared heating furnace. The heating power of the infrared heating furnace is controlled by zones, with the preheating zone power being 45% of the total power and the forming zone power being 55%. The heating time of the sheet in each zone is 15 seconds. Then, it is placed in a vacuum forming mold and formed by positive and negative pressure. The positive pressure is 0.5MPa, the negative pressure is 0.07MPa, and the holding time is 7.5 seconds. S5. Cooling and shaping: The formed tray is shaped in the cooling and shaping mold. The temperature of the cooling and shaping mold is controlled at 33℃ and the cooling time is 8 seconds. S6. Trimming and punching: The cooled and shaped pallet is trimmed by a precision punching die. The punching gap of the precision punching die is 0.035mm and the punching frequency is 25 times / minute to obtain the final product.

[0035] Example 2 This application provides a CPET blister tray, composed of the following raw materials by weight percentage: 93.8% CPET-specific polyester chips, 3% nucleating agent, 1% color masterbatch, 2% toughening agent, and 0.2% chain extender. The color masterbatch includes white and black masterbatches. The tray has a double-layer composite structure consisting of a base layer containing white masterbatch and a surface layer containing black masterbatch. The toughening agent is a maleic anhydride-grafted polyolefin elastomer, specifically a maleic anhydride-grafted ethylene-octene copolymer POE-g-MAH with a grafting rate of 0.8%. The chain extender is a multifunctional epoxy polymer, specifically a styrene-glycidyl methacrylate copolymer.

[0036] The above-mentioned method for preparing a CPET blister tray includes the following steps: S1. Raw material pretreatment: Dry CPET special polyester chips at 120℃ for 3 hours to reduce their moisture content to less than 50ppm; S2. Premixing: The dried CPET chips, nucleating agent, toughening agent, chain extender and color masterbatch are premixed. The premixing is divided into two steps. First, the CPET chips are mixed with toughening agent and chain extender at 300 r / min for 3 minutes. Then, the nucleating agent and color masterbatch are added and mixed at 200 r / min for 2 minutes. S3. Melt Blending Extrusion: The premixed material is fed into a twin-screw extruder with a screw length-to-diameter ratio of 28:1. A vacuum extraction port is provided in the middle of the barrel, and the vacuum degree of the vacuum extraction port is controlled at -0.04MPa. The extruder temperature is controlled in zones from zone 1 to the die head, with the temperature range set at 245℃ and the screw speed at 250r / min. After melt blending and reactive extrusion, the material is formed into a sheet through the die head. The thickness of the melt-extruded sheet is 0.4mm. Immediately after extrusion, the material is calendered and shaped by a three-roll calender, with the upper roll temperature at 80℃, the middle roll temperature at 70℃, and the lower roll temperature at 60℃. S4. Vacuum forming: The obtained sheet is preheated to 185°C in an infrared heating furnace. The heating power of the infrared heating furnace is controlled by zones, with the preheating zone power being 40% of the total power and the forming zone power being 50%. The heating time of the sheet in each zone is 10 seconds. Then, it is placed in a vacuum forming mold and formed by positive and negative pressure. The positive pressure is 0.4MPa and the negative pressure is 0.06MPa, with a holding time of 5 seconds. S5. Cooling and shaping: The formed tray is shaped in a cooling and shaping mold. The temperature of the cooling and shaping mold is controlled at 25℃ and the cooling time is 6 seconds. S6. Trimming and punching: The cooled and shaped pallet is trimmed by a precision punching die. The punching gap of the precision punching die is 0.02mm and the punching frequency is 20 times / minute to obtain the final product.

[0037] Example 3 This application provides a CPET blister tray, composed of the following raw materials by weight percentage: 86% CPET-specific polyester chips, 5% nucleating agent, 3% color masterbatch, 5% toughening agent, and 1% chain extender. The color masterbatch includes white and black masterbatches, and the tray has a double-layer composite structure consisting of a base layer containing white masterbatch and a surface layer containing black masterbatch. The toughening agent is a maleic anhydride-grafted polyolefin elastomer, specifically maleic anhydride-grafted ethylene-methyl acrylate copolymer (EMA) with a grafting rate of 1.5%. The chain extender is a multifunctional epoxy polymer, specifically a styrene-glycidyl methacrylate copolymer.

[0038] The above-mentioned method for preparing a CPET blister tray includes the following steps: S1. Raw material pretreatment: Dry CPET special polyester chips at 140℃ for 5 hours to reduce their moisture content to less than 50ppm; S2. Premixing: The dried CPET chips, nucleating agent, toughening agent, chain extender and color masterbatch are premixed. The premixing is divided into two steps. First, the CPET chips are mixed with the toughening agent and chain extender at 500 r / min for 5 minutes. Then, the nucleating agent and color masterbatch are added and mixed at 300 r / min for 4 minutes. S3. Melt Blending Extrusion: The premixed material is fed into a twin-screw extruder with a screw length-to-diameter ratio of 36:1. A vacuum extraction port is provided in the middle of the barrel, and the vacuum degree of the vacuum extraction port is controlled at -0.06MPa. The extruder temperature is controlled in zones from zone 1 to the die head, with the temperature range set at 275℃. The screw speed is 350r / min. After melt blending and reactive extrusion, the material is formed into a sheet through the die head. The thickness of the melt-extruded sheet is 1.2mm. Immediately after extrusion, the material is calendered and shaped by a three-roll calender, with the upper roll temperature at 90℃, the middle roll temperature at 80℃, and the lower roll temperature at 70℃. S4. Vacuum forming: The obtained sheet is preheated to 205°C in an infrared heating furnace. The heating power of the infrared heating furnace is controlled by zones, with the preheating zone power being 50% of the total power and the forming zone power being 60%. The heating time of the sheet in each zone is 20 seconds. Then, it is placed in a vacuum forming mold and formed by positive and negative pressure. The positive pressure is 0.6MPa, the negative pressure is 0.08MPa, and the holding time is 10 seconds. S5. Cooling and shaping: The formed tray is shaped in a cooling and shaping mold. The temperature of the cooling and shaping mold is controlled at 40℃ and the cooling time is 10 seconds. S6. Trimming and punching: The cooled and shaped pallet is trimmed by a precision punching die. The punching gap of the precision punching die is 0.05mm and the punching frequency is 30 times / minute to obtain the final product.

[0039] Comparative Example 1 The only difference from Example 1 is that the CPET-specific polyester chips are replaced with an equal amount of ordinary APET, while the remaining raw material ratios and preparation steps are exactly the same as in Example 1.

[0040] Comparative Example 2 The only difference from Example 1 is that no nucleating agent is added to the raw materials; its mass fraction is made up by CPET special polyester chips. The remaining raw material ratios and preparation steps are exactly the same as in Example 1.

[0041] Comparative Example 3 The only difference from Example 1 is that no chain extender is added to the raw materials; its mass fraction is made up by CPET-specific polyester chips. The remaining raw material ratios and preparation steps are exactly the same as in Example 1.

[0042] Comparative Example 4 The only difference from Example 1 is that the toughening agent POE-g-MAH is replaced with an equal amount of ordinary POE elastomer that is not grafted with maleic anhydride, while the other raw material ratios and preparation steps are exactly the same as in Example 1.

[0043] Comparative Example 5 The only difference from Example 1 is that in step S2, the two-step premixing is omitted, all raw materials are added at once, and mixed at 400 r / min for 7 minutes. The remaining raw material ratios and preparation steps are exactly the same as in Example 1.

[0044] Comparative Example 6 The only difference from Example 1 is that in step S3, the three-roll calendering process is omitted, and the extruded sheet is directly drawn and wound up for thermoforming. The remaining raw material ratios and preparation steps are exactly the same as in Example 1.

[0045] 1. Heat distortion temperature test: CPET blister trays prepared in Examples 1-3 and Comparative Examples 1-6 were used. Samples measuring 120mm × 10mm × 4mm were cut from the flat portion of each tray, with three parallel samples prepared for each group. A heat distortion temperature meter was used, and the test was conducted according to GB / T1634.1-2019 standard. The test load was 1.82MPa, and the heating rate was 12℃ / min. The temperature at which each sample deformed by 0.25mm under the load was recorded. The arithmetic mean of the three parallel samples was taken as the heat distortion temperature of that group of samples. By comparing the heat distortion temperatures of different groups, the dimensional stability advantage of the product under thermal conditions can be reflected.

[0046] 2. Impact Strength Test: From each CPET blister tray in Examples 1-3 and Comparative Examples 1-6, a simply supported beam impact specimen with a length of 80 mm, a width of 10 mm, and a thickness equal to the actual thickness of the tray was cut from a wrinkle-free and bubble-free area. Five parallel specimens were prepared for each group. The notched specimens were required to have a 2 mm deep V-shaped notch machined in the middle of the specimen according to the standard. Using a simply supported beam impact testing machine, the test was conducted according to GB / T1043.1-2008 standard. The impact absorption energy of each specimen was measured, and the impact strength was calculated. The arithmetic mean of the five parallel specimens was taken as the impact strength of the group of samples. This index reflects the toughness advantage of the product when subjected to external impact and, together with the heat distortion temperature, reflects the mechanical property stability of the material. 3. Tensile Strength and Elongation at Break Test: Dumbbell-shaped tensile specimens, 150 mm long, 10 mm wide, and with a thickness equal to the actual thickness of the tray, were cut from the CPET blister trays of Examples 1-3 and Comparative Examples 1-6. Five parallel specimens were prepared for each group. An electronic universal testing machine was used, and the tests were conducted according to GB / T1040.3-2006 standard. The tensile speed was set to 50 mm / min. The maximum load and gauge length elongation at fracture were recorded. The tensile strength and elongation at break were calculated. The arithmetic mean of the five parallel specimens was taken as the test result for that group of samples. Tensile strength reflects the material's resistance to tensile failure, while elongation at break reflects the material's ductility. Both are related to impact strength and together reflect the comprehensive mechanical performance advantages of the product. 4. Transmittance Test: From the CPET blister trays of Examples 1-3 and Comparative Examples 1-6, select flat, impurity-free areas and cut out samples with dimensions of 50mm × 50mm. Prepare three parallel samples for each group. Use a UV-Vis spectrophotometer to test according to GB / T2410-2008 standard. The test wavelength is 550nm, with air as a reference. Measure the transmittance of each sample and take the arithmetic mean of the three parallel samples as the transmittance of the group of samples. This index can reflect the product's appearance transparency advantage and is related to the selection of color masterbatch in the raw materials and calendering steps in the process, indirectly reflecting the influence of the production process on product performance.

[0047] The test data for the key performance tests of Examples 1-3 and Comparative Examples 1-6 are shown in Table 1.

[0048] Table 1: 1. The test standard for heat distortion temperature is GB / T1634.1-2019 "Determination of heat distortion temperature of plastics under load - Part 1: General test method"; 2. The test standard for impact strength is GB / T1043.1-2008 "Determination of impact properties of simply supported plastic beams - Part 1: Non-instrumental impact test"; 3. The test standard for tensile strength is GB / T1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets" (Note: Applicable to specimens cut from sheets); 4. The test standard for elongation at break is GB / T1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets" (Note: This is a different test index under the same standard as tensile strength). 5. The test standard for light transmittance is GB / T2410-2008 "Determination of light transmittance and haze of transparent plastics".

[0049] Combining Examples 1-3 and Comparative Example 1 with the data in Table 1, it can be seen that the choice of raw material type will bring about significant differences in performance. When ordinary APET is used to replace CPET special polyester chips, the changes in heat distortion temperature, impact strength and elongation at break are particularly prominent. This is related to the characteristics of the two raw materials themselves. Different raw materials have different stability after heating and performance under stress, which in turn affects the overall performance of the final product. Based on Examples 1-3 and Comparative Example 2, and referring to the data in Table 1, it can be seen that the addition or absence of a nucleating agent affects product performance. Without the addition of a nucleating agent, heat distortion temperature, impact strength, elongation at break, and light transmittance all showed varying degrees of change. This is because the nucleating agent plays a regulatory role in the raw material system; its presence or absence alters the internal structural state of the material, thus causing differences in various product properties. Based on Examples 1-3 and Comparative Example 3, and referring to the data in Table 1, it can be seen that the presence or absence of chain extenders has a significant impact on the impact strength and elongation at break of the products. Without chain extenders, these two indicators show a larger decrease, while the changes in heat distortion temperature and tensile strength are relatively smaller. This indicates that chain extenders play a certain role in improving the toughness and ductility of the products, and their interaction with other components in the raw material system affects the product's performance under stress and deformation. Combining Examples 1-3 and Comparative Example 4 with the data in Table 1, it can be seen that whether the toughening agent has undergone maleic anhydride grafting treatment affects the product performance. After replacing the maleic anhydride-grafted POE-g-MAH with ordinary POE elastomer, the impact strength and elongation at break decreased significantly. This is because the interaction mode between the grafted toughening agent and other raw materials is different, resulting in differences in its effect on improving product toughness and ductility, thus leading to changes in product performance. Based on Examples 1-3 and Comparative Example 5, and referring to the data in Table 1, it can be seen that different premixing methods have a certain impact on product performance. After canceling the two-step premixing and replacing it with one-step mixing, the impact strength and elongation at break decreased slightly, while other performance indicators did not change much. This is because different premixing methods affect the uniformity of the raw material mixing. Different uniformity of raw material mixing will result in differences in the material structure formed during subsequent processing, thus affecting the product performance. Based on Examples 1-3 and Comparative Example 6, and referring to the data in Table 1, it can be seen that whether or not a three-roll calendering process is used has a significant impact on the light transmittance of the product. After eliminating the three-roll calendering process, the light transmittance decreases significantly, while other performance indicators change less. This is because the three-roll calendering process affects the surface condition of the sheet. Different degrees of smoothness on the sheet surface result in differences in light transmission, thus causing changes in the product's light transmittance.

[0050] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A CPET blister tray characterized by: The raw materials are composed of the following quality percentages: CPET special polyester chips 86-93.8%, nucleating agent 3-5%, color masterbatch 1.4-3%, toughening agent 2-5%, chain extender 0.2-1%; The color masterbatch includes white color masterbatch and black color masterbatch, the tray has a double-layer composite structure composed of a base layer containing white color masterbatch and a surface layer containing black color masterbatch, the toughening agent is a maleic anhydride grafted polyolefin elastomer, and the chain extender is a multi-functional epoxy polymer.

2. The CPET blister tray of claim 1, wherein: The maleic anhydride grafted polyolefin elastomer is a maleic anhydride grafted ethylene-octene copolymer POE-g-MAH or ethylene-methyl acrylate copolymer EMA, with a grafting rate of 0.8-1.5%.

3. The CPET blister tray of claim 1, wherein: The multi-functional epoxy polymer chain extender is a styrene-glycidyl methacrylate copolymer.

4. A method of making a CPET blister tray, characterized in that, A CPET blister tray according to any one of claims 1-4, comprising the following steps: S1, raw material pretreatment: dry the CPET special polyester chips at 120-140℃ for 3-5 hours to reduce the water content to less than 50ppm; S2, premixing: premix the dried CPET chips, nucleating agent, toughening agent, chain extender and color masterbatch; S3, melt blending and extrusion: feed the premixed material into a double-screw extruder, control the temperature from the first zone to the die zone, set the temperature range to 245-275℃, and the screw speed to 250-350r / min, after melt blending and reaction extrusion, form a sheet through the die; S4, blister forming: preheat the obtained sheet to 185-205℃ in an infrared heating furnace, then place it in a blister mold, and form it under positive and negative pressure, with the positive pressure being 0.4-0.6MPa and the negative pressure being 0.06-0.08MPa, and the holding time being 5-10 seconds; S5, cooling and setting: set the formed tray in a cooling and setting mold; S6, trimming and cutting: trim the cooled and set tray through a precision cutting die to obtain the final product.

5. The method of claim 4, wherein: In step S2, the premixing is divided into two steps: first mix the CPET chips with the toughening agent and chain extender at a speed of 300-500r / min for 3-5 minutes, then add the nucleating agent and color masterbatch and mix at a speed of 200-300r / min for 2-4 minutes.

6. The method of claim 4, wherein: In step S3, the screw length-diameter ratio of the double-screw extruder is 28:1 to 36:1, and a vacuum air outlet is provided in the middle of the cylinder, with the vacuum degree controlled at -0.04 to -0.06MPa.

7. The method for preparing a CPET blister tray according to claim 4, characterized in that: In step S3, the thickness of the melt-extruded sheet is 0.4-1.2mm, and immediately after extrusion, pass it through a three-roll calender for calendering and setting, with the upper roll temperature being 80-90℃, the middle roll temperature being 70-80℃, and the lower roll temperature being 60-70℃.

8. The method of claim 4, wherein: In step S4, the heating power of the infrared heating furnace is controlled in zones, with the preheating zone power being 40-50% of the total power and the forming zone power being 50-60%, and the heating time of the sheet in each zone being 10-20 seconds.

9. The method of claim 4, wherein: In step S5, the temperature of the cooling and setting mold is controlled at 25-40℃, and the cooling time is 6-10 seconds.

10. The method of claim 4, wherein: In step S6, the die-cutting gap of the precision die-cutting die is 0.02-0.05 mm, and the die-cutting frequency is 20-30 times per minute.

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