Multi-material mixed PET (Polyethylene Terephthalate) composition for injection molding and application

Abstract

The invention relates to the field of beverage packaging materials, in particular to a PET composition for multi-material mixed injection molding and application. The multi-material mixed PET composition for injection molding is prepared from the following raw material components in parts by weight: 70 to 80 parts of PET, 20 to 30 parts of PEF and 0.1 to 0.3 part of antioxidant, the preparation method of the multi-material mixed PET composition for injection molding comprises the following steps: carrying out melt blending on the raw materials, cooling and granulating to obtain the multi-material mixed PET composition for injection molding, the temperature range of the melt blending is 250 to 280 DEG C. The PET and the PEF are adopted as main raw materials, the gas barrier performance of the material is improved due to the structural characteristics of a furan ring in the PEF, ester exchange reaction is carried out in the melt blending process to form a copolymer, the compatibility between the PET and the PEF is effectively enhanced, the microstructure of the material is optimized, and the gas barrier performance of the material is further improved.

Description

Technical Field

[0001] The present application relates to the field of beverage packaging materials, and specifically to a PET composition for multi-material mixed injection molding and its application. Background Art

[0002] Compared to traditional aluminum cans or glass bottles, polyester (PET) bottles are used to manufacture various liquid food packaging containers due to their excellent overall performance and high cost-effectiveness. However, they also suffer from poor gas barrier properties (especially oxygen barrier properties). Currently, resin-based packaging materials for beverages such as juices, sauces, alcoholic beverages, and chocolate milk have become a common trend. However, many of these beverages are oxygen-sensitive. Even a small amount of oxygen penetrating the packaging container can alter the taste and aroma of the beverage. This places higher demands on the gas barrier properties of PET bottles used in food packaging, especially oxygen barrier properties. Summary of the Invention

[0003] In order to solve the problem of PET bottles being limited as packaging materials for oxygen-sensitive beverages, the present application provides a multi-material mixed injection molding PET composition. The multi-material mixed injection molding PET composition uses PET and PEF as the main raw materials, utilizes the structural characteristics of the furan ring in PEF to improve the gas barrier performance of the material, and undergoes an ester exchange reaction during the melt blending process to form a copolymer, effectively enhancing the compatibility between the two and optimizing the microstructure of the material, further improving the gas barrier performance of the material.

[0004] In a first aspect, the present application provides a PET composition for multi-material mixed injection molding, which adopts the following technical solution: a PET composition for multi-material mixed injection molding, the raw materials of which include the following components in parts by weight: PET 70-80 parts, PEF 20-30 parts, antioxidant 0.1-0.3 parts; The preparation method of a PET composition for multi-material mixed injection molding comprises the following steps: The raw materials are melt-blended and granulated after cooling to obtain a multi-material mixed injection molding PET composition; the temperature range of the melt-blending is 250-280°C.

[0005] By adopting the above technical solution, a multi-material hybrid PET composition for injection molding uses PET (polyethylene terephthalate) and PEF (polyethylene 2,5-furandicarboxylate) as its main components. PEF, an emerging polyester material, has a unique asymmetry and polarity due to the furan ring in its molecular structure. This structural feature increases chain rigidity, restricts the rotation and mobility of chain segments, and effectively hinders the diffusion of small molecules (such as gas molecules).

[0006] Although PET and PEF belong to the same polyester family, they differ in terms of crystallinity, chain segment flexibility, and surface energy. These differences can easily lead to the formation of phase-separated structures during simple physical blending, affecting the overall performance of the material. However, under melt blending conditions, PET and PEF can undergo an ester exchange reaction. This reaction results in the formation of PET / PEF copolymers in some PET and PEF. These copolymers act as a bridge at the molecular level, tightly connecting PET and PEF. This connection not only enhances the compatibility between the two but also optimizes the material's microstructure and reduces the occurrence of phase separation. More importantly, due to the presence of furan rings in PEF, these copolymers inherit PEF's high gas barrier properties. The asymmetry and polarity of the furan rings make the chain segments more rigid, further restricting the diffusion paths of gas molecules, thereby improving the gas barrier properties of PET compositions for multi-material mixed injection molding.

[0007] The present invention uses PET and PEF as the main raw materials. The structural characteristics of the furan ring in PEF improve the gas barrier performance of the material, and an ester exchange reaction occurs during the melt blending process to form a copolymer, which effectively enhances the compatibility between the two and optimizes the microstructure of the material, further improving the gas barrier performance of the material.

[0008] Preferably, the PET is 75 parts and the PEF is 25 parts.

[0009] Preferably, the raw materials further include the following components in parts by weight: 1-3 parts of an auxiliary agent; the auxiliary agent includes at least one of tetrabutyl titanate and zinc acetate.

[0010] By adopting the above technical solution, tetrabutyl titanate acts as a Lewis acid catalyst to coordinate with the carbonyl oxygen groups of PET and PEF polyesters during the melt blending process, reducing the activation energy of transesterification and accelerating intersegmental transesterification, achieving the formation of PET–PEF copolymer segments, reducing large-scale phase separation, and improving the compatibility of the two phases. Furthermore, the rigidity of the furan rings in the PEF segments (compared to the benzene rings in PET) restricts molecular chain motion, while the polycondensation reaction catalyzed by tetrabutyl titanate increases molecular weight. The two synergistically reduce gas permeability. Zinc acetate, acting as a weaker Lewis acid, complexes with the terminal hydroxyl groups in the early stages of transesterification, regulating the transesterification rate and inhibiting the formation of low-molecular-weight fragments, thereby optimizing the molecular weight distribution. The synergistic catalysis of tetrabutyl titanate and zinc acetate strikes a balance between enhancing compatibility and controlling molecular weight distribution, jointly reducing permeation channels within the material and significantly improving gas barrier properties.

[0011] This application introduces tetrabutyl titanate and zinc acetate as a composite catalyst during the melt blending process. Through a synergistic catalytic transesterification reaction (tetrabutyl titanate leads the chain segment recombination, while zinc acetate regulates the reaction kinetics), it promotes the formation of a localized copolymer segment structure between PET and PEF. This structure, combined with the rigidity of the PEF furan ring and the molecular weight-enhancing effect, significantly reduces gas permeability, systematically optimizing the gas barrier properties of PET compositions for multi-material hybrid injection molding.

[0012] Preferably, the auxiliary agent is tetrabutyl titanate.

[0013] Preferably, the auxiliary agents are tetrabutyl titanate and zinc acetate.

[0014] By employing this technical solution, tetrabutyl titanate catalyzes the transesterification reaction between PET and PEF molecular chains, promoting the formation of localized copolymer segments and enhancing the compatibility between the two phases. Zinc acetate, by complexing with terminal hydroxyl groups, regulates the transesterification rate, inhibiting premature chain breakage and optimizing molecular weight distribution. The synergistic effect of these two factors results in denser segment packing of the PET composite for multi-material hybrid injection molding. This, combined with the rigid furan ring's restriction of segment motion, significantly improves the material's gas barrier properties.

[0015] Preferably, the mass ratio of tetrabutyl titanate to zinc acetate is 3:1.5-2.5.

[0016] By adopting the above technical solution, when the proportion of zinc acetate is too low, its function of regulating the reaction rate is weakened, and the ester exchange reaction proceeds excessively, resulting in intensified disordered reorganization of the molecular chains and increased gas permeability; when the proportion of zinc acetate is too high, the catalytic activity of tetrabutyl titanate is inhibited, the reactivity of the PET and PEF molecular chains is limited, the material density is deteriorated, and the gas barrier performance of the material is also reduced.

[0017] Preferably, the PET, antioxidant and auxiliary agent are first mixed and then melt-blended with PEF.

[0018] By adopting the above technical solution, when PET, antioxidants and additives are preliminarily mixed, the antioxidants and additives can be promoted to be evenly dispersed in the entire PET system, thereby improving the overall gas barrier performance of the material.

[0019] Preferably, the temperature range of the melt blending includes the temperature range of the feeding section, the temperature range of the melting section, the temperature range of the reaction section, the temperature range of the exhaust section, and the temperature range of the discharging section; the temperature range of the reaction section is 270-280°C.

[0020] By adopting the above technical solution, the reaction zone temperature is set at 270-280°C, ensuring that the PET is fully melted and well dispersed with the PEF, achieving interfacial migration and an effective transesterification reaction. If the temperature is too low, the raw materials may not fully melt, resulting in the presence of unmelted particles, which will affect the uniformity and performance of the material. At higher temperatures, the transesterification reaction may be too intense, and the furan ring structure may thermally degrade and yellow, which will in turn reduce the gas barrier properties of the material.

[0021] The second aspect of the present application relates to the use of the above-mentioned PET composition for multi-material mixed injection molding in packaging materials.

[0022] In summary, this application has the following beneficial effects: 1. Since this application uses PET and PEF as the main raw materials, the structural characteristics of the furan ring in PEF improve the gas barrier performance of the material, and an ester exchange reaction occurs during the melt blending process to form a copolymer, which effectively enhances the compatibility between the two and optimizes the microstructure of the material, further improving the gas barrier performance of the material; 2. The present application incorporates tetrabutyl titanate and zinc acetate as additives during the melt blending process. This facilitates segment exchange and finely controls the degree of transesterification, contributing to the formation of a more optimized copolymer segment structure. This structural optimization further enhances the gas barrier properties of the PET composition for multi-material mixed injection molding. DETAILED DESCRIPTION

[0023] The present application is further described in detail below with reference to the following examples and comparative examples.

[0024] Example 1 A method for preparing a PET composition for multi-material mixed injection molding comprises the following steps: 750g of PET, 250g of PEF, and 2g of antioxidant were melt-blended and pelletized after cooling to obtain a multi-material mixed injection molding PET composition; the melt-blending temperature range was 250-280°C. The melt-blending temperature range included a feed section temperature range of 255°C (250-260°C), a melting section temperature range of 265°C (260-270°C), a reaction section temperature range of 275°C (270-280°C), a degassing section temperature range of 265°C (260-270°C), and a discharge section temperature range of 255°C (250-260°C).

[0025] A PET bottle is injection-molded from the above-mentioned multi-material mixed injection molding PET composition, and the volume of each PET bottle is 1L.

[0026] Example 2-3 In Example 2-3, based on the preparation method of Example 1, the content of each component of the raw material of the multi-material mixed injection molding PET composition was adjusted. The specific adjustments are shown in Table 1.

[0027] Comparative Example 1-2 Comparative Example 1: Based on the preparation method of Example 1, 750 g of PET and 250 g of PEF were replaced with 1000 g of PET.

[0028] Comparative Example 2: 750 g of PET, 250 g of PEF, and 2 g of antioxidant were stirred and mixed, and then directly injection-molded to obtain PET bottles, each of which had a volume of 1 L.

[0029] Performance testing Oxygen transmission rate and carbon dioxide transmission rate Oxygen transmission rate (OTR) is measured using GB / T 31354-2014 "Oxygen permeability test method for packages and containers - Coulometric method" and is expressed in cm. 3 / (bottle·d·0.21atm).

[0030] The general requirement for beer bottles is oxygen permeability ≤ 0.05cm 3 / (bottle·d·0.21atm).

[0031] The carbon dioxide transmission rate is tested according to GB / T 45318-2025 "Polyethylene terephthalate (PET) beer bottles", and the carbon dioxide loss rate after 6 months (24 weeks) of storage is used as the carbon dioxide transmission rate.

[0032] According to the above detection method, the PET bottles of Examples 1-3 and Comparative Examples 1-2 were tested, and the results are shown in Table 1 below: Table 1 Component ratio and performance test table of PET bottles of Examples 1-3 and Comparative Examples 1-2 (unit: g) project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 PET / g 750 700 800 1000 / PEF / g 250 300 200 / / Antioxidant / g 2 3 1 2 / Oxygen transmission rate 0.024 0.031 0.040 0.094 0.077 Carbon dioxide permeability / % 9.15 9.37 9.51 25.70 20.35 As shown in Table 1, comparing Examples 1-3 with Comparative Examples 1-2, the addition of some PEF to PET improves the material's gas barrier properties. This is likely due to the unique asymmetry and polarity imparted by the furan rings in the PEF molecular structure. This structural feature increases chain rigidity, restricts chain segment rotation and mobility, and thus effectively hinders the diffusion of small molecules (such as gas molecules).

[0033] In addition, PET and PEF differ in crystallinity, segment flexibility, and surface energy. These differences can easily lead to the formation of phase separation structures during simple physical blending, affecting the overall performance of the material. Therefore, it is necessary to undergo an ester exchange reaction between PET and PEF under melt blending conditions. This reaction results in the formation of PET / PEF copolymers in some PET and PEF. These copolymers act as a bridge at the molecular level, tightly connecting PET and PEF together. This connection not only enhances the compatibility between the two, but also optimizes the microstructure of the material and reduces the occurrence of phase separation. Compared with simple physical blending, melt blending is more conducive to PEF exerting its gas barrier properties in the material.

[0034] In addition, comprehensive comparison shows that Example 1 has the best performance among Examples 1-3, and Example 1 is preferred.

[0035] Examples 4-7 Example 4 Based on the preparation method of Example 1, 20 g of tetrabutyl titanate was melt-blended with PET, PEF and an antioxidant.

[0036] Example 5-6 Based on the preparation method of Example 4, the amount of tetrabutyl titanate added was adjusted. The specific adjustment is shown in Table 2. Example 7 Based on the preparation method of Example 1, 20 g of zinc acetate was melt-blended with PET, PEF and an antioxidant.

[0037] The PET bottles of Examples 4-7 were subjected to the above performance tests, and the test results are shown in Table 2.

[0038] Table 2 Amount of additives added and performance test data of Example 1 and Examples 4-7 project Example 1 Example 4 Example 5 Example 6 Example 7 Tetrabutyl titanate / g / 20 10 30 / Zinc acetate / g / / / / 20 Oxygen transmission rate 0.024 0.019 0.022 0.020 0.020 Carbon dioxide permeability / % 9.15 8.04 8.53 8.27 8.16 As shown in Table 2, a comparison of Example 1 with Examples 4-7 shows that the addition of tetrabutyl titanate and zinc acetate to the multi-material mixed injection molding PET composition further enhances the material's gas barrier properties. This is likely due to tetrabutyl titanate acting as a Lewis acid catalyst during the melt blending process, coordinating with the carbonyl oxygen groups of PET and PEF, thereby reducing the transesterification activation energy and accelerating intersegmental transesterification, enabling the formation of PET-PEF copolymer segments, reducing large-scale phase separation, and improving the compatibility of the two phases.

[0039] Zinc acetate acts as a weak Lewis acid, complexing with the terminal hydroxyl groups in the early stages of transesterification, regulating the transesterification rate and inhibiting the formation of low molecular weight fragments, thereby optimizing the molecular weight distribution. In comparison, tetrabutyl titanate has a better promoting effect on zinc acetate, and Example 4 is preferred.

[0040] Examples 8-11 Example 8 Based on the preparation method of Example 4, 20 g of tetrabutyl titanate was replaced with 20 g of an auxiliary agent mixture. The auxiliary agent mixture was composed of tetrabutyl titanate and zinc acetate, and the mass ratio of tetrabutyl titanate to zinc acetate was 3:2.

[0041] In Examples 9-10, based on the preparation method of Example 8, the mass ratio of tetrabutyl titanate and zinc acetate was adjusted. The specific adjustment is shown in Table 3.

[0042] Example 11 Based on the preparation method of Example 4, 750 g of PET, 2 g of antioxidant and 20 g of tetrabutyl titanate were first stirred and mixed, and then melt-blended with 250 g of PEF.

[0043] The PET bottles of Examples 8-11 were subjected to the above performance tests, and the test results are shown in Table 3.

[0044] Table 3 Mass ratio of tetrabutyl titanate and zinc acetate and performance test data of Example 4 and Examples 8-11 project Example 4 Example 8 Example 9 Example 10 Example 11 Mass ratio / 3:2 3:1.5 3:2.5 / Oxygen transmission rate 0.019 0.016 0.017 0.017 0.018 Carbon dioxide permeability / % 8.04 6.95 7.29 7.20 7.91 As shown in Table 3, a comparison of Example 4 with Examples 8-11 shows that tetrabutyl titanate catalyzes the transesterification reaction between PET and PEF molecular chains, promoting the formation of localized copolymer segments and enhancing biphasic compatibility. Zinc acetate, by complexing with terminal hydroxyl groups, regulates the transesterification rate, inhibiting premature chain breakage and optimizing molecular weight distribution. The synergistic effect of these two factors results in denser segment packing in the PET composite for multi-material hybrid injection molding. This, combined with the rigid furan ring's restriction of segment motion, significantly improves the material's gas barrier properties.

[0045] When the proportion of zinc acetate is too low, its function of regulating the reaction rate is weakened, and the ester exchange reaction proceeds excessively, resulting in intensified disordered reorganization of the molecular chains and increased gas permeability; when the proportion of zinc acetate is too high, the catalytic activity of tetrabutyl titanate is inhibited, the reactivity of the PET and PEF molecular chains is limited, the material density is deteriorated, and the gas barrier performance of the material is also reduced.

[0046] In addition, when PET, antioxidant and tetrabutyl titanate are preliminarily mixed, the antioxidant and tetrabutyl titanate can be promoted to be uniformly dispersed in the entire PET system, thereby improving the overall gas barrier performance of the material.

[0047] Examples 12-13 In Examples 12-13, based on the preparation method of Example 1, the temperature of the reaction section was adjusted. The specific adjustments are shown in Table 4.

[0048] The PET bottles of Examples 12-13 were subjected to the above performance tests, and the test results are shown in Table 4.

[0049] Table 4 Reaction section temperature and performance test data of Example 1 and Example 12-13 project Example 1 Example 12 Example 13 Reaction temperature / ℃ 275 270 280 Oxygen transmission rate 0.024 0.032 0.026 Carbon dioxide permeability / % 9.15 9.63 9.21 As shown in Table 4, a comparison between Example 1 and Examples 12-13 reveals that as the reaction zone temperature increases, the oxygen and carbon dioxide permeabilities of the PET bottles gradually increase and then decrease. This is likely because as the reaction zone temperature increases, the raw materials fully melt and the transesterification reaction gradually proceeds, thereby improving the material's gas barrier properties. However, when the temperature exceeds a certain range, the transesterification reaction becomes overly intense, tending to produce more random copolymers, which in turn reduces the material's gas barrier properties.

[0050] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A PET composition for multi-material mixed injection molding, characterized in that: The raw materials include the following components in parts by weight: PET 70-80 parts, PEF 20-30 parts, antioxidant 0.1-0.3 parts; The preparation method of a PET composition for multi-material mixed injection molding comprises the following steps: The raw materials are melt-blended and granulated after cooling to obtain a multi-material mixed injection molding PET composition; the temperature range of the melt-blending is 250-280°C.

2. The multi-material mixed injection molding PET composition according to claim 1, characterized in that: The PET is 75 parts and the PEF is 25 parts.

3. The multi-material mixed injection molding PET composition according to claim 1, characterized in that: The raw materials further include the following components in parts by weight: 1-3 parts of an auxiliary agent; the auxiliary agent includes at least one of tetrabutyl titanate and zinc acetate.

4. The multi-material mixed injection molding PET composition according to claim 3, characterized in that: The auxiliary agent is tetrabutyl titanate.

5. The multi-material mixed injection molding PET composition according to claim 3, characterized in that: The auxiliary agents are tetrabutyl titanate and zinc acetate.

6. The multi-material mixed injection molding PET composition according to claim 5, characterized in that: The mass ratio of tetrabutyl titanate to zinc acetate is 3:1.5-2.

5.

7. The multi-material mixed injection molding PET composition according to claim 3, characterized in that: The PET, antioxidant and auxiliary agent are first mixed and then melt-blended with PEF.

8. The multi-material mixed injection molding PET composition according to claim 1, characterized in that: The temperature range of the melt blending includes the temperature range of the feeding section, the temperature range of the melting section, the temperature range of the reaction section, the temperature range of the exhaust section, and the temperature range of the discharging section; the temperature range of the reaction section is 270-280°C.

9. An application of a PET composition for multi-material mixed injection molding, characterized in that: Use of the multi-material mixed injection molding PET composition according to any one of claims 1 to 8 in packaging materials.