Preparation method of high-barrier PET packaging material
By preparing PET packaging materials containing crosslinking agents, the problem of insufficient gas barrier performance of PET packaging materials is solved, and efficient gas barrier and ultraviolet absorption of beer and beverages are achieved, thereby improving the overall performance of packaging materials.
Patent Information
- Application Number
- CN202510567520.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-30
- Publication Date
- 2025-07-11
AI Technical Summary
The poor gas barrier performance of existing PET packaging materials in the beer beverage field has caused damage to beer quality and flavor, and plastic packaging has advantages in transportation and storage but needs improvement.
Nitrification reaction is performed by using raw materials such as dimethyl 4,4'-carbonyl dibenzoate and concentrated sulfuric acid to prepare a nitrification polymer monomer, and react with 2-cyanoethyl acetate to form a crosslinking agent, added to the PET molecular chain, forming a conjugated system to enhance gas barrier properties, and improve crosslinking degree through transesterification reaction.
It significantly improves the gas barrier properties and ultraviolet absorption capacity of PET packaging materials, while maintaining good mechanical properties, and is suitable for packaging beer and beverages.
Smart Images
Figure CN120289769A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of packaging materials, and specifically, relates to a preparation method of a high-barrier PET packaging material. Background Art
[0002] Beer and beverages are products widely loved by people. In 2023, the beer production in China reached 37.88 million kiloliters. Among them, about 70% of the beer is packaged in glass bottles. Glass bottle packaging has stable physical properties and strong barrier properties. However, glass bottles are relatively heavy in quality and fragile by themselves, and require higher transportation costs compared to plastic packaging. Plastic packaging not only has the advantages of being light, durable, easy to transport and store, but also is easy to mold. In addition, plastic packaging also has certain advantages in terms of usage experience and appearance design. The main reason restricting the use of plastic packaging in the field of beer and beverages is that beer is sensitive to the concentrations of oxygen and carbon dioxide. Even the PET material with the best gas barrier performance in the existing technology is difficult to meet the requirements of beer and beverage packaging. Poor gas barrier performance may lead to damage to the quality and flavor of beer. In order to retain the quality and flavor of beer while improving the usage experience of consumers, the present invention provides a preparation method of a high-barrier PET packaging material. Summary of the Invention
[0003] The purpose of the present invention is to provide a preparation method of a high-barrier PET packaging material to solve the problems mentioned in the above background art.
[0004] The purpose of the present invention can be achieved by the following technical solutions:
[0005] A preparation method of a high-barrier PET packaging material includes the following steps:
[0006] First step: Mix dimethyl 4,4'-carbonyldibenzoate, concentrated sulfuric acid, and concentrated nitric acid in a three-necked flask, install a condenser and a thermometer, start magnetic stirring, and react at a temperature of 20 - 80°C for 2 - 12 hours. After the reaction is completed, filter off the concentrated sulfuric acid while it is hot. The obtained solid is washed with deionized water and then recrystallized with absolute ethanol to obtain a nitrated polymerization monomer;
[0007] Second step: Add the nitrated polymerization monomer, ethyl cyanoacetate, and a catalyst into a three-necked flask and dissolve them with absolute ethanol. Install a condenser and a thermometer, start magnetic stirring, and then react at a temperature of 60 - 80°C for 1 - 3 hours. After the reaction is completed, cool to room temperature and carry out vacuum filtration. The filter cake is washed with cold absolute ethanol to obtain a crosslinking agent;
[0008] Step 3: Put terephthalic acid, the first batch of ethylene glycol, polymerization catalyst, and trimethyl phosphate into the esterification reactor, continuously introduce nitrogen to exhaust the air in the esterification reactor, and react at a temperature of 220 - 260 °C for 4 - 5 h to polymerize PET oligomers. Then cool to 160 - 170 °C, and put crosslinking agent, transesterification catalyst, and the second batch of ethylene glycol into the esterification reactor, and react at a temperature of 160 - 170 °C for 4 - 6 h for transesterification. Then evacuate the esterification reactor to vacuum and react under low pressure and high temperature conditions for 3 - 5 h to complete polycondensation. After the reaction ends, cool the product to room temperature, pelletize and dry to obtain modified PET;
[0009] Step 4: Put the modified PET into a twin-screw extruder, melt and extrude it, and then obtain a high-barrier PET packaging material through blow molding.
[0010] Further, the mass fraction of the concentrated sulfuric acid is 92 - 98%.
[0011] Further, the mass fraction of the concentrated nitric acid is 60 - 68%.
[0012] Further, the catalyst is an organic amine catalyst, which is one of diethylamine, pyrrolidine, and piperidine.
[0013] Further, the polymerization catalyst is an antimony catalyst, which is one of antimony trioxide, antimony acetate, and antimony glycolate.
[0014] Further, the transesterification catalyst is a titanate catalyst, which is one of tetraisopropyl titanate, tetraethyl titanate, and tetrabutyl titanate.
[0015] Further, in the first step, the dosage ratio of 4,4'-carbonyldibenzoic acid dimethyl ester, concentrated sulfuric acid, and concentrated nitric acid is 6 - 7 g : 12 - 16 mL : 3 - 4 mL.
[0016] Further, in the second step, the dosage ratio of the nitrated polymerization monomer, ethyl cyanoacetate, and the catalyst is 6.9 - 7.8 g : 2.0 - 2.4 g : 0.16 - 0.24 g.
[0017] Further, in the third step, the conditions of low pressure and high temperature are a pressure of 100 - 1000 Pa and a temperature of 270 - 290 °C.
[0018] Further, in the fourth step, the temperature condition for melt extrusion is 280 - 290 °C.
[0019] Further, by mass parts, the usage ratio of the raw materials used in the third step, namely terephthalic acid, the first batch of ethylene glycol, polymerization catalyst, trimethyl phosphate, crosslinking agent, transesterification catalyst, and the second batch of ethylene glycol, is 149-182:56-69:1.1-1.3:0.01-0.016:11.5-14:0.4-0.6:4-10.
[0020] Advantages of the present invention:
[0021] 1) In the present invention, 4,4'-dicarboxylic acid dimethyl ester and concentrated nitric acid are used as raw materials, and concentrated sulfuric acid is used as a dehydrating agent. Through nitration reaction, a nitrated polymerization monomer with a nitro group is obtained. Then, using the nitrated polymerization monomer and ethyl 2-cyanoacetate as raw materials, a crosslinking agent is obtained through Knoevenagel reaction between the active methylene group between the aryl group and the cyano group and the carbonyl group of the nitrated polymerization monomer under the action of an organic amine catalyst. The crosslinking agent of the present invention can significantly enhance the polarity of the PET molecular chain by introducing a strong electron-withdrawing group nitro into the PET molecular chain, thereby weakening the interaction with non-polar gases (O2, CO2), inhibiting the segmental movement between PET molecules, and promoting the polymer to form a more compact segment stacking structure, effectively improving the gas barrier performance of the polymer.
[0022] 2) The crosslinking agent of the present invention contains cyano group, aryl group and acrylate group. A conjugated system can be formed among the three groups, expanding the delocalization range of π electrons in the molecule, and effectively absorbing ultraviolet rays through intramolecular electron transition absorption. The structure of the crosslinking agent does not contain groups that are easily oxidized, and it can still have good stability during high-temperature processing without reducing the mechanical properties of PET.
[0023] 3) The crosslinking agent of the present invention contains three ester groups, which can be combined in the PET molecular chain through transesterification reaction during the transesterification process, reducing the migration rate, effectively increasing the crosslinking degree of the PET molecular chain, reducing the free volume in the polymer and restricting the movement of the PET molecular chain, hindering the diffusion of gas molecules, and further improving the barrier property of the polymer. Description of the drawings
[0024] Figure 1 It is the infrared spectrum test chart of the crosslinking agent of the present invention. Detailed implementation manners
[0025] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.
[0026] Example 1
[0027] A crosslinking agent is prepared by the following steps:
[0028] First step: Mix 6 g of dimethyl 4,4'-carbonyldibenzoate, 12 mL of concentrated sulfuric acid with a mass fraction of 98%, and 3 mL of concentrated nitric acid with a mass fraction of 68% in a three-necked flask. Install a condenser and a thermometer, start magnetic stirring, and react at a temperature of 20 °C for 12 h. After the reaction is completed, filter off the concentrated sulfuric acid while it is hot. The obtained solid is washed with deionized water and then recrystallized with absolute ethanol to obtain a nitrated polymer monomer;
[0029] Second step: Add 6.9 g of the nitrated polymer monomer, 2.0 g of ethyl 2-cyanoacetate, and 0.16 g of piperidine to a three-necked flask and dissolve them in 40 mL of absolute ethanol. Install a condenser and a thermometer, start magnetic stirring, and then react at a temperature of 60 °C for 3 h. After the reaction is completed, cool to room temperature and perform vacuum filtration. The filter cake is washed with cold absolute ethanol to obtain the crosslinking agent.
[0030] Example 2
[0031] A crosslinking agent is prepared by the following steps:
[0032] First step: Mix 6.5 g of dimethyl 4,4'-carbonyldibenzoate, 14 mL of concentrated sulfuric acid with a mass fraction of 95%, and 3.5 mL of concentrated nitric acid with a mass fraction of 64% in a three-necked flask. Install a condenser and a thermometer, start magnetic stirring, and react at a temperature of 50 °C for 4 h. After the reaction is completed, filter off the concentrated sulfuric acid while it is hot. The obtained solid is washed with deionized water and then recrystallized with absolute ethanol to obtain a nitrated polymer monomer;
[0033] Second step: Add 7.5 g of the nitrated polymer monomer, 2.2 g of ethyl 2-cyanoacetate, and 0.2 g of pyrrolidine to a three-necked flask and dissolve them in 50 mL of absolute ethanol. Install a condenser and a thermometer, start magnetic stirring, and then react at a temperature of 70 °C for 2 h. After the reaction is completed, cool to room temperature and perform vacuum filtration. The filter cake is washed with cold absolute ethanol to obtain the crosslinking agent.
[0034] Example 3
[0035] A crosslinking agent is prepared by the following steps:
[0036] First step: Mix 7 g of dimethyl 4,4'-carbonyldibenzoate, 16 mL of concentrated sulfuric acid with a mass fraction of 92%, and 4 mL of concentrated nitric acid with a mass fraction of 60% in a three-necked flask. Install a condenser and a thermometer, start magnetic stirring, and react at a temperature of 80 °C for 2 h. After the reaction is completed, filter off the concentrated sulfuric acid while it is hot. The obtained solid is washed with deionized water and then recrystallized with absolute ethanol to obtain a nitrated polymer monomer;
[0037] Step 2: Add 7.8 g of nitrated polymer monomer, 2.4 g of ethyl 2-cyanoacetate, and 0.24 g of diethylamine into a three-necked flask, dissolve them with 60 mL of absolute ethanol, install a condenser and a thermometer, turn on the magnetic stirrer, and then react at 80 °C for 1 h. After the reaction is completed, cool to room temperature and perform suction filtration under reduced pressure. Wash the filter cake with cold absolute ethanol to obtain the crosslinking agent.
[0038] Experimental Example 1
[0039] The crosslinking agent obtained in Example 1 was characterized by infrared spectroscopy. After pressing with potassium bromide tablets, infrared spectroscopy tests were carried out on a Nicolet 6700 Fourier transform infrared spectrometer produced by Thermo Company in the United States. As Figure 1 shown, there is a C-H absorption peak on the benzene ring at 3100 - 3000 cm -1 ⁻¹, a cyano absorption peak appears at 2219 cm -1 ⁻¹. Affected by double bond conjugation, a C=O double bond absorption peak appears at 1723 cm -1 ⁻¹, a C=C double bond absorption peak appears at 1649 cm⁻¹, and nitro absorption peaks appear at 1512 cm -1 and 1355 cm -1 ⁻¹, indicating that the reaction occurred successfully.
[0040] Example 4
[0041] A preparation method of a high-barrier PET packaging material, comprising the following steps:
[0042] Step 1: By mass, put 149 parts of terephthalic acid, the first batch of 56 parts of ethylene glycol, 1.1 parts of antimony trioxide, and 0.01 part of trimethyl phosphate into an esterification reaction kettle, continuously introduce nitrogen to exhaust the air in the esterification reaction kettle, and react at 220 °C for 5 h to polymerize to obtain a PET oligomer. Then cool to 160 °C, and put 11.5 parts of the crosslinking agent in Example 1, 0.4 part of tetraisopropyl titanate, and the second batch of 4 parts of ethylene glycol into the esterification reaction kettle, and react at 160 °C for 6 h for transesterification. Then evacuate the esterification reaction kettle to vacuum, and react at a pressure of 100 Pa and a temperature of 270 °C for 5 h to complete polycondensation. After the reaction is completed, cool the product to room temperature, pelletize and dry it to obtain modified PET;
[0043] Step 2: Add the modified PET into a twin-screw extruder, melt and extrude it at 280 °C, and then obtain a high-barrier PET packaging material through blow molding.
[0044] Example 5
[0045] A preparation method of a high-barrier PET packaging material, comprising the following steps:
[0046] Step 1: By mass parts, put 166 parts of terephthalic acid, the first batch of 62 parts of ethylene glycol, 1.2 parts of antimony acetate, and 0.013 parts of trimethyl phosphate into the esterification reactor. Continuously introduce nitrogen to exhaust the air in the esterification reactor, and react at 240 °C for 4.5 h to polymerize to obtain PET oligomers. Then cool to 165 °C, and put 12.8 parts of the cross-linking agent in Example 2, 0.5 parts of tetraethyl titanate, and the second batch of 7 parts of ethylene glycol into the esterification reactor. React at 165 °C for 5 h for transesterification. Then evacuate the esterification reactor to vacuum, and react at 550 Pa and 280 °C for 4 h to complete polycondensation. After the reaction is completed, cool the product to room temperature, pelletize and dry it to obtain modified PET;
[0047] Step 2: Add the modified PET into a twin-screw extruder, melt and extrude it at 285 °C, and then obtain a high-barrier PET packaging material through blow molding.
[0048] Example 6
[0049] A preparation method of a high-barrier PET packaging material, comprising the following steps:
[0050] Step 1: By mass parts, put 182 parts of terephthalic acid, the first batch of 69 parts of ethylene glycol, 1.3 parts of ethylene glycol antimony, and 0.016 parts of trimethyl phosphate into the esterification reactor. Continuously introduce nitrogen to exhaust the air in the esterification reactor, and react at 260 °C for 4 h to polymerize to obtain PET oligomers. Then cool to 170 °C, and put 14 parts of the cross-linking agent in Example 3, 0.6 parts of tetrabutyl titanate, and the second batch of 10 parts of ethylene glycol into the esterification reactor. React at 170 °C for 6 h for transesterification. Then evacuate the esterification reactor to vacuum, and react at 1000 Pa and 290 °C for 3 h to complete polycondensation. After the reaction is completed, cool the product to room temperature, pelletize and dry it to obtain modified PET;
[0051] Step 2: Add the modified PET into a twin-screw extruder, melt and extrude it at 290 °C, and then obtain a high-barrier PET packaging material through blow molding.
[0052] Comparative Example 1
[0053] Remove the raw material "cross-linking agent obtained in Example 2" used in Example 5, and keep the other conditions and preparation steps unchanged.
[0054] Comparative Example 2
[0055] This comparative example is a commercially available PET packaging material.
[0056] Experimental Example 2
[0057] The high-barrier PET packaging materials in Examples 4 to 6 and Comparative Example 1 and the commercially available PET packaging material in Comparative Example 2 were respectively subjected to performance tests. Referring to the national standard GB / T 19789-2005 "Test Method for Oxygen Permeability of Plastic Films and Sheets for Packaging Materials - Coulometer Detection Method", the gas barrier properties of each component packaging material were tested, and the absorbance at wavelengths of 280 - 320 nm was tested by an ultraviolet-visible spectrophotometer. The test results are shown in Table 1:
[0058] Table 1
[0059] Project <![CDATA[Oxygen transmission rate cm 3 / (m 2 ·24h·0.1MPa)]]> Absorbance Example 4 11.14 2.14 Example 5 10.93 2.21 Example 6 10.77 2.23 Comparative Example 1 29.14 0.21 Comparative Example 2 28.09 1.16
[0060] As can be seen from Table 1, the gas barrier properties and ultraviolet absorption properties of the high-barrier PET packaging materials in Examples 4 to 6 are superior to those of the commercially available PET packaging material in Comparative Example 2. Combining with Comparative Example 1, it can be shown that adding the cross-linking agent of the present invention can effectively improve the oxygen permeability and ultraviolet absorption properties of the PET packaging material.
[0061] The preparation method of a high-barrier PET packaging material provided by the present invention has been introduced in detail above. Specific examples are used herein to elaborate on the principle and implementation manner of the present invention. The description of the above examples is only used to help understand the method and its core idea of the present invention, including the best mode, and also enables any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combination method. It should be noted that for those of ordinary skill in the art in the technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention. In particular, as long as there is no structural conflict, the various features in the disclosed embodiments of the present invention can be combined with each other in any way, and the exhaustive description of these combinations is omitted in this specification only for the sake of saving space and resources. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.
Claims
1. A preparation method of a high-barrier PET packaging material, characterized in that, It includes the following steps: Preparing a crosslinking agent: 4,4'-dimethyl dicarbonate benzoate is nitrated with concentrated sulfuric acid and concentrated nitric acid to obtain a nitrated polymerization monomer. Then, the nitrated polymerization monomer, ethyl cyanoacetate, and a catalyst are dissolved in absolute ethanol, and the reaction is carried out at a system temperature of 60-80°C to obtain the crosslinking agent; Preparing a high-barrier PET packaging material: Under nitrogen protection, terephthalic acid, the first batch of ethylene glycol, a polymerization catalyst, and trimethyl phosphate are polymerized to obtain a PET oligomer. Then, a crosslinking agent, a transesterification catalyst, and the second batch of ethylene glycol are added to the system. After transesterification, polycondensation, cooling, pelletizing, drying, and melt extrusion, blow molding is carried out to obtain the high-barrier PET packaging material.
2. The preparation method of a high-barrier PET packaging material according to claim 1, characterized in that, In the step of preparing the crosslinking agent, the mass fraction of the concentrated sulfuric acid is 92-98%, and the mass fraction of the concentrated nitric acid is 60-68%.
3. The preparation method of a high-barrier PET packaging material according to claim 1, characterized in that, In the step of preparing the crosslinking agent, the catalyst is an organic amine catalyst, which is one of diethylamine, pyrrolidine, and piperidine.
4. The preparation method of a high-barrier PET packaging material according to claim 1, characterized in that, In the step of preparing the crosslinking agent, the dosage ratio of 4,4'-dimethyl dicarbonate benzoate, concentrated sulfuric acid, and concentrated nitric acid is 6-7 g: 12-16 mL: 3-4 mL.
5. The preparation method of a high-barrier PET packaging material according to claim 1, characterized in that, In the step of preparing the crosslinking agent, the dosage ratio of the nitrated polymerization monomer, ethyl cyanoacetate, and the catalyst is 6.9-7.8 g: 2.0-2.4 g: 0.16-0.24 g.
6. The preparation method of a high-barrier PET packaging material according to claim 1, characterized in that, In the step of preparing the high-barrier PET packaging material, the polymerization catalyst is an antimony catalyst, which is one of antimony trioxide, antimony acetate, and antimony glycolate. The transesterification catalyst is a titanate catalyst, which is one of tetraisopropyl titanate, tetraethyl titanate, and tetrabutyl titanate.
7. The preparation method of a high-barrier PET packaging material according to claim 1, wherein In the step of preparing the high-barrier PET packaging material, the polymerization condition is to react at a temperature of 220-260°C for 4-5 h, and the transesterification condition is to react at a temperature of 160-170°C for 4-6 h.
8. The preparation method of a high-barrier PET packaging material according to claim 1, characterized in that, In the step of preparing the high-barrier PET packaging material, the polycondensation condition is to react at a pressure of 100-1000 Pa and a temperature of 270-290°C for 3-5 h.
9. The preparation method of a high-barrier PET packaging material according to claim 1, characterized in that, In the step of preparing the high-barrier PET packaging material, the temperature condition for melt extrusion is 280-290°C.
10. The preparation method of a high-barrier PET packaging material according to claim 1, characterized in that, By mass fraction, the dosage ratio of the raw materials terephthalic acid, the first batch of ethylene glycol, the polymerization catalyst, trimethyl phosphate, the crosslinking agent, the transesterification catalyst, and the second batch of ethylene glycol used in the step of preparing the high-barrier PET packaging material is 149-182: 56-69: 1.1～1.3：0.01～0.016：11.5～14：0.4～0.6：4～10。