Modified high-barrier PET (Polyethylene Terephthalate) copolyester as well as preparation method and application thereof

Abstract

The invention discloses modified high-barrier PET copolyester as well as a preparation method and application thereof, and belongs to the field of high polymer materials. The modified high-barrier PET copolyester comprises the following components in parts by weight: 100 parts of terephthalic acid; 37 to 40 parts of ethylene glycol; 16 to 22 parts of 1, 4 cyclohexanedimethanol; 0.8 to 2.5 parts of hydroxyl-terminated polybutadiene; 0.15 to 0.5 part of polyethylene glycol modified nano montmorillonite; 0.03 to 0.06 part of a catalyst; and 0.04 to 0.08 part of a stabilizing agent. The rigidity of a polyester main chain is optimized by a third single CHDM, and a multi-scale synergistic oxygen blocking effect is realized by combining with a unique mechanism that HTPB and oxygen react to generate a high-density oxide layer in situ and assisting with a physical blocking synergistic effect of O-MMT; meanwhile, an oxidation catalyst system with low migration risk is adopted, the oxygen barrier property is remarkably improved under the condition that the process is simplified finally, the balance of transparency and mechanical property of the material is kept, and an efficient solution is provided for the food-grade high-barrier packaging material.

Description

Technical Field

[0001] The present invention belongs to the field of polymer materials, and in particular relates to a modified high-barrier PET copolyester, a preparation method and an application thereof. Background Art

[0002] Polyethylene terephthalate (PET), a key thermoplastic polyester material, is widely used in food and pharmaceutical packaging, as well as electronic device packaging, thanks to its lightweight, transparency, mechanical strength, and ease of processing. However, conventional PET materials suffer from insufficient gas barrier properties (especially oxygen barrier properties), which can lead to oxidation and deterioration of packaged contents, shortening shelf life. This deficiency is particularly prominent in high-end packaging and high-humidity environments, becoming a key technical bottleneck restricting its further adoption.

[0003] However, existing barrier modification technologies often rely on a single approach, resulting in limited performance improvements or an imbalance in overall performance. For example, excessive addition of nanofillers can significantly reduce the material's transparency and mechanical strength, while the introduction of comonomers can lead to reduced esterification efficiency. Therefore, there is an urgent need to develop a PET modification technology that combines high barrier properties with process suitability and safety, achieving performance breakthroughs through the synergistic effects of multiple components while avoiding the constraints of complex processes and high costs. Summary of the Invention

[0004] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a modified high-barrier PET copolyester, a preparation method and an application thereof, which solve the problems in the prior art.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A modified PET copolyester comprises the following raw materials in parts by weight:

[0007]

[0008]

[0009] Furthermore, the preparation process of the polyethylene glycol-modified nano-montmorillonite is as follows: the nano-montmorillonite modified by cationic intercalation is mixed with polyethylene glycol, added into a mixed solution of water and ethanol to form a suspension, reacted under ultrasound assistance, and then washed, dried, and ball-milled to obtain the suspension.

[0010] Furthermore, the mass ratio of the nano-montmorillonite to the polyethylene glycol is 1:(0.5-2).

[0011] Furthermore, the catalyst is one or more combinations of antimony-based catalysts, titanium-based catalysts and germanium-based catalysts.

[0012] Furthermore, the antimony-based catalyst is ethylene glycol antimony.

[0013] Furthermore, the stabilizer is one of phosphoric acid, trimethyl phosphate, triethyl phosphate and triphenyl phosphate.

[0014] The preparation method of the above-mentioned modified PET copolyester comprises the following steps:

[0015] The polyethylene glycol-modified nano-montmorillonite is uniformly dispersed in the ethylene glycol solution to obtain an O-MMT dispersion;

[0016] Terephthalic acid, ethylene glycol, 1-4 cyclohexanedimethanol, terminal hydroxy polybutadiene, a catalyst and a stabilizer are respectively added to an esterification reactor for beating. After beating, an O-MMT dispersion is added to the reactor. After esterification and polycondensation reactions, the modified PET copolyester is obtained by cooling and granulation.

[0017] Furthermore, the O-MMT dispersion is prepared by gradually adding the polyethylene glycol-modified nano-montmorillonite to the ethylene glycol solution at a stirring speed of 600 rpm; after the polyethylene glycol-modified nano-montmorillonite is added, stirring is continued at a speed of 1200 rpm for 20 minutes.

[0018] Furthermore, the temperature of the esterification reaction is 230-250° C. and the pressure is 0.2-0.3 MPa; the temperature of the polycondensation reaction is 275-285° C. and the vacuum degree is less than 70 Pa.

[0019] The modified PET copolyester is used as a raw material in the preparation of packaging materials.

[0020] Beneficial effects of the present invention:

[0021] 1. The present invention uses the third monomer 1,4-cyclohexanedimethanol (CHDM) to optimize the rigidity of the polyester main chain, reduce the free volume of the molecular chain, and shorten the oxygen permeation path. It also combines the unique mechanism of in-situ generation of a high-density oxide layer by the reaction of hydroxyl-terminated polybutadiene (HTPB) with oxygen, supplemented by the physical barrier synergy of polyethylene glycol-modified nano-montmorillonite (O-MMT) (extending the gas diffusion path through nanosheets) to achieve a multi-scale synergistic oxygen barrier effect. At the same time, it adopts an oxidation catalyst system with low migration risk, ultimately achieving a significant improvement in oxygen barrier performance under simplified process conditions, while maintaining a balance between material transparency and mechanical properties, providing an efficient solution for food-grade high-barrier packaging materials.

[0022] 2. The present invention abandons the high cost defects of traditional blending technology (such as the high cost of PEN raw materials) and complex surface modification processes (such as silane coupling treatment of nanofillers), and adopts a one-step in-situ polymerization to achieve efficient and uniform dispersion of CHDM, HTPB and O-MMT. The process has good process repeatability, reduced energy consumption, and significantly lower raw material costs than the PEN / PET blend system. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0024] Figure 1 This is a physical picture of the PET polyester chip in Comparative Example 1;

[0025] Figure 2 This is a physical picture of the modified PET copolyester in Example 3. DETAILED DESCRIPTION

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0027] A modified high-barrier PET copolyester comprising the following raw materials in parts by weight:

[0028]

[0029] The preparation process of the polyethylene glycol-modified nano-montmorillonite is as follows: nano-montmorillonite (MMT) modified by cationic intercalation is mixed with polyethylene glycol in a mass ratio of 1:(0.5-2), added to a mixed solution of water and ethanol to form a suspension, reacted for 3-5 hours under ultrasound assistance, washed, vacuum-dried at 60°C for 12 hours, and ball-milled to obtain O-MMT powder with uniform particle size.

[0030] The cationic intercalation modification process of nano-montmorillonite is as follows: the nano-montmorillonite is uniformly dispersed in a mixed solution of water and ethanol, and a quaternary ammonium salt intercalation modifier (such as hexadecyltrimethylammonium bromide and octadecyltrimethylammonium chloride) is reacted continuously for 6 hours at 60-80°C and pH 5. After centrifugal washing and drying, the cationic intercalation modified nano-montmorillonite is obtained.

[0031] The catalyst is one or more combinations of antimony-based catalysts, titanium-based catalysts and germanium-based catalysts.

[0032] The stabilizer is one of phosphoric acid, trimethyl phosphate, triethyl phosphate and triphenyl phosphate.

[0033] The preparation steps of the modified high-barrier PET copolyester include:

[0034] S1, uniformly dispersing O-MMT in ethylene glycol solution to prepare a stable O-MMT dispersion;

[0035] S2, adding terephthalic acid, ethylene glycol, 1-4 cyclohexanedimethanol, terminal hydroxy polybutadiene, a catalyst and a stabilizer into an esterification reactor for beating respectively, adding the prepared O-MMT dispersion into the reactor after beating, and cooling and granulating to obtain modified PET copolyester after esterification and polycondensation reaction.

[0036] In S1, the O-MMT dispersion is prepared by gradually adding O-MMT powder to ethylene glycol using a high-speed stirring disperser at 600 rpm. After complete addition, stirring is continued at 1200 rpm for 20 minutes to obtain a stable O-MMT dispersion. It should be noted that the weight percentage of ethylene glycol in the present invention includes the ethylene glycol used to disperse the O-MMT.

[0037] In S2, the temperature of the esterification reaction is 230-250°C, and the pressure of the esterification reaction is 0.2-0.3 MPa; the temperature of the polycondensation reaction is 275-285°C, and the vacuum degree is <70 Pa.

[0038] The technical solution of the present invention is illustrated below through the following examples and comparative examples; wherein, in the examples and comparative examples. Moreover, in Examples 1-6, the preparation process of O-MMT is as follows: 500g of water and ethanol are prepared in a mass ratio of 2:8, 25g of PEG-8000 is evenly dispersed in the mixed solution, and then 25g of cationic intercalation modified nano-montmorillonite is added to the above solution and evenly dispersed; the reaction is continued at 80°C with ultrasound assistance for 4 hours, after centrifugation and washing, vacuum drying is carried out at 60°C for 12 hours, and O-MMT powder with uniform particle size is obtained by ball milling.

[0039] Example 1

[0040] S1, 9.6 g of O-MMT was uniformly dispersed in 200 g of ethylene glycol solution to prepare a stable O-MMT dispersion;

[0041] S2, 6.4kg terephthalic acid, 2.34kg ethylene glycol, 1.03kg 1-4 cyclohexanedimethanol, 51.2g terminal hydroxy polybutadiene, 1.92g catalyst ethylene glycol antimony and 2.56g stabilizer trimethyl phosphate are added into a 20L polymerization reaction device for beating. After beating, the O-MMT dispersion prepared in S1 is added into the reaction device, and through esterification (temperature: 243°C, pressure 0.28MPa) and polycondensation reaction (temperature: 275°C, vacuum degree 70Pa), when the stirring motor power reaches the predetermined target, the melt is cooled and granulated to obtain modified PET copolyester.

[0042] The specific process of the esterification reaction is as follows: the esterification temperature is controlled at 243°C, the reaction pressure is 0.28 MPa, and the esterification water output reaches 95% of the theoretical water output, and the esterification reaction is completed;

[0043] The specific process of the polycondensation reaction is as follows: after the esterification reaction is completed, after 20 minutes at normal pressure, low vacuum is turned on for pre-polycondensation, the vacuum degree is -0.1MPa, the reaction temperature is 275℃, and after 35 minutes of low vacuum, the intermediate polycondensation begins, the vacuum degree is 70Pa, and the polycondensation is completed when the motor power reaches more than 250W.

[0044] Example 2

[0045] S1, uniformly dispersing 32g of O-MMT in 700g of ethylene glycol solution to prepare a stable O-MMT dispersion;

[0046] S2, 6.4kg terephthalic acid, 1.69kg ethylene glycol, 1.37kg 1-4 cyclohexanedimethanol, 102g terminal hydroxy polybutadiene, 2.2g catalyst ethylene glycol antimony and 3.84g stabilizer trimethyl phosphate are added into a 20L polymerization reaction device for beating. After beating, the O-MMT dispersion prepared in S1 is added into the reaction device, and through esterification (temperature: 240°C, pressure 0.3MPa) and polycondensation reaction (temperature: 275°C, vacuum degree <570Pa), when the stirring motor power reaches the predetermined target, the melt is cooled and granulated to obtain modified PET copolyester.

[0047] Example 3

[0048] S1, uniformly dispersing 15.3 g of O-MMT in 300 g of ethylene glycol solution to prepare a stable O-MMT dispersion;

[0049] S2, 6.4kg terephthalic acid, 2.15kg ethylene glycol, 1.23kg 1-4 cyclohexanedimethanol, 81.4g terminal hydroxyl polybutadiene, 2.5g catalyst ethylene glycol antimony and 3.84g stabilizer trimethyl phosphate were added to a 20L polymerization reaction device for beating. After beating, the O-MMT dispersion prepared in S1 was added to the reaction device, and esterification (temperature: 245℃, pressure 0.3MPa) and polycondensation reaction (temperature: 278℃, vacuum degree 70Pa) were carried out. When the stirring motor power reached the predetermined target, the melt was cooled and granulated to obtain modified PET copolyester (see the actual picture). Figure 2 shown).

[0050] Example 4

[0051] S1, uniformly dispersing 20g of O-MMT in 500g of ethylene glycol solution to prepare a stable O-MMT dispersion;

[0052] S2, 6.4kg terephthalic acid, 2.04kg ethylene glycol, 1.03kg 1-4 cyclohexanedimethanol, 102g terminal hydroxy polybutadiene, 2.2g catalyst ethylene glycol antimony and 3.84g stabilizer trimethyl phosphate are added into a 20L polymerization reaction device for beating. After beating, the O-MMT dispersion prepared in S1 is added into the reaction device, and through esterification (temperature: 248°C, pressure 0.3MPa) and polycondensation reaction (temperature: 280°C, vacuum degree 70Pa), when the stirring motor power reaches the predetermined target, the melt is cooled and granulated to obtain modified PET copolyester.

[0053] Example 5

[0054] S1, uniformly dispersing 20g of O-MMT in 500g of ethylene glycol solution to prepare a stable O-MMT dispersion;

[0055] S2, 6.4kg terephthalic acid, 2.04kg ethylene glycol, 1.03kg 1-4 cyclohexanedimethanol, 160g terminal hydroxy polybutadiene, 3.84g catalyst ethylene glycol antimony and 5.12g stabilizer trimethyl phosphate are added into a 20L polymerization reaction device for beating. After beating, the O-MMT dispersion prepared in S1 is added into the reaction device, and through esterification (temperature: 245°C, pressure 0.25MPa) and polycondensation reaction (temperature: 275°C, vacuum degree 70Pa), when the stirring motor power reaches the predetermined target, the melt is cooled and granulated to obtain modified PET copolyester.

[0056] Example 6

[0057] S1, uniformly dispersing 32g of O-MMT in 700g of ethylene glycol solution to prepare a stable O-MMT dispersion;

[0058] S2, 6.4kg terephthalic acid, 1.69kg ethylene glycol, 1.37kg 1-4 cyclohexanedimethanol, 155g terminal hydroxy polybutadiene, 2g catalyst ethylene glycol antimony and 3.2g stabilizer trimethyl phosphate are added into a 20L polymerization reaction device for beating. After beating, the O-MMT dispersion prepared in S1 is added into the reaction device, and through esterification (temperature: 250°C, pressure 0.3MPa) and polycondensation reaction (temperature: 280°C, vacuum degree 70Pa), when the stirring motor power reaches the predetermined target, the melt is cooled and granulated to obtain modified PET copolyester.

[0059] Comparative Example 1

[0060] A 20L polymerization reaction device was used to add 6.4kg of terephthalic acid, 3.0kg of ethylene glycol, 2.2g of antimony ethylene glycol catalyst, and 3.84g of trimethyl phosphate stabilizer. Through esterification (temperature: 245℃, pressure 0.3MPa) and polycondensation reaction (temperature: 278℃, vacuum degree 70Pa), when the stirring motor power reached the predetermined target, the melt was cooled and granulated to obtain PET polyester chips (theoretical yield 7.42kg), as shown in the actual picture. Figure 1 shown.

[0061] Comparative Example 2

[0062] A 20L polymerization reaction device was used, 6.4kg of terephthalic acid, 2.45kg of ethylene glycol, 1.23kg of 1-4 cyclohexanedimethanol, 2.5g of catalyst ethylene glycol antimony and 3.2g of stabilizer trimethyl phosphate were added, and esterification (temperature: 247°C, pressure 0.3MPa) and polycondensation reaction (temperature: 278°C, vacuum 70Pa) were carried out. When the stirring motor power reached the predetermined target, the melt was cooled and granulated to obtain PET copolyester.

[0063] Performance Testing

[0064] The copolyester prepared in the above proportions and examples was extruded through a twin-screw extruder and then biaxially stretched to form a film. The oxygen transmission rate of the film was tested according to the pressure difference method in accordance with the national standard. The experimental results are shown in Table 1 below:

[0065] Table 1 Performance test results of polyester in comparative examples and examples

[0066]

[0067] As can be seen from the data in Table 1, compared with Comparative Example 1, the oxygen permeability coefficient of Comparative Example 2 decreased after copolymerization modification with 1-4-cyclohexanedimethanol, indicating that 1-4-cyclohexanedimethanol can improve the barrier properties of the copolyester; further addition of hydroxyl-terminated polybutadiene (HTPB) and OMMT, the oxygen permeability coefficients of the modified copolyesters in Examples 1-6 were further decreased compared with Comparative Example 1, among which, in Example 3, the oxygen permeability coefficient of the modified PET copolyester decreased by 93.8% compared with Comparative Example 1, and the oxygen barrier performance was doubled, indicating that hydroxyl-terminated polybutadiene (HTPB) and OMMT can further improve the barrier properties of PET polyester. In summary, the modified PET copolyester prepared by the present invention has good oxygen barrier properties.

[0068] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0069] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the invention as claimed.

Claims

1. A modified PET copolyester, characterized in that: Including the following raw materials by weight:

2. A modified PET copolyester according to claim 1, characterized in that, The preparation process of the polyethylene glycol-modified nano-montmorillonite is as follows: the nano-montmorillonite modified by cationic intercalation is mixed with polyethylene glycol, added into a mixed solution of water and ethanol to form a suspension, reacted under ultrasound assistance, and washed, dried, and ball-milled to obtain the suspension.

3. A modified PET copolyester according to claim 2, characterized in that, The mass ratio of the nano-montmorillonite to the polyethylene glycol is 1:(0.5-2).

4. A modified PET copolyester according to claim 1, characterized in that, The catalyst is one or more combinations of antimony-based catalysts, titanium-based catalysts and germanium-based catalysts.

5. A modified PET copolyester according to claim 4, characterized in that, The antimony-based catalyst is ethylene glycol antimony.

6. A modified PET copolyester according to claim 1, characterized in that, The stabilizer is one of phosphoric acid, trimethyl phosphate, triethyl phosphate and triphenyl phosphate.

7. A method for preparing a modified PET copolyester according to any one of claims 1 to 6, characterized in that: The following steps are involved: The polyethylene glycol-modified nano-montmorillonite is uniformly dispersed in the ethylene glycol solution to obtain an O-MMT dispersion; Terephthalic acid, ethylene glycol, 1-4 cyclohexanedimethanol, terminal hydroxy polybutadiene, a catalyst and a stabilizer are respectively added to an esterification reactor for beating. After beating, an O-MMT dispersion is added to the reactor. After esterification and polycondensation reactions, the modified PET copolyester is obtained by cooling and granulation.

8. The method for preparing a modified PET copolyester according to claim 7, wherein: The O-MMT dispersion was prepared by gradually adding the polyethylene glycol-modified nano-montmorillonite to the ethylene glycol solution at a stirring speed of 600 rpm; and after the polyethylene glycol-modified nano-montmorillonite was added, stirring was continued at a speed of 1200 rpm for 20 minutes.

9. The method for preparing a modified PET copolyester according to claim 7, wherein: The temperature of the esterification reaction is 230-250° C. and the pressure is 0.2-0.3 MPa; the temperature of the polycondensation reaction is 275-285° C. and the vacuum degree is less than 70 Pa.

10. Use of the modified PET copolyester according to any one of claims 1 to 6 as a raw material in the preparation of packaging materials.

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