Alkali-resistant PETG (polyethylene terephthalate glycol) thermal shrinkage film for battery label and preparation method thereof

Abstract

The invention relates to the field of PETG heat shrink films, and provides an alkali-resistant PETG heat shrink film for battery labels and a preparation method thereof, the PETG heat shrink film comprises the following raw materials by weight: 90-110 parts of PETG, 5-15 parts of a composite alkali-resistant filler, 1-4 parts of an antistatic agent, 0.5-2 parts of an antioxidant, and 0.3-2 parts of a lubricant; wherein the composite alkali-resistant filler is a mixture of modified mica and modified calcined kaolin. The PETG thermal shrinkage film provided by the invention has the characteristics of high thermal shrinkage rate, high strength, good chemical stability and excellent alkali resistance.

Description

Technical Field

[0001] The present invention relates to the field of PETG heat shrinkable films, and particularly to an alkali-resistant PETG heat shrinkable film for battery labels and a preparation method thereof. Background Art

[0002] The battery-specific label film refers to a label film with a high starting shrinkage temperature and a significantly reduced shrinkage force after shrink packaging, which can improve the surface flatness and anti-corrosion performance of the packaging. Initially, PVC was used for battery label films, but PVC production can be harmful to the environment and human health. With the progress of technology and the continuous improvement of people's living standards, PETG heat shrinkable films have been gradually applied to the field of battery label films due to their advantages such as non-toxicity, odorlessness, high strength, and high heat shrinkage rate.

[0003] Although PETG heat shrinkable films have many excellent properties mentioned above that enable them to be applied to battery labels, since battery labels may come into contact with alkaline substances, the battery label film also needs to have excellent alkali resistance, while the alkali resistance of PETG heat shrinkable films themselves remains to be improved.

[0004] Patent CN 103483785 B discloses a PETG heat shrinkable film and a preparation method thereof, which are mainly made of the following raw materials: PETG pellets, additives, lubricants, antistatic agents, and anti-sticking agents. This PETG heat shrinkable film not only has good shrinkage performance but also improved transparency and tensile strength, and is an environmentally friendly heat shrinkable film. Moreover, this application discloses that this PETG heat shrinkable film can be applied not only to food and personal care product packaging, medical and health equipment, food, etc., but also to electronic device packaging. Therefore, it is not excluded that it may be applied to battery labels. However, this application does not consider the problem that the PETG heat shrinkable film may be corroded by alkaline substances when applied to battery labels and does not improve its alkali resistance, resulting in certain application limitations.

[0005] Therefore, there is an urgent need in the market for an alkali-resistant PETG heat shrinkable film for battery labels that not only has basic properties such as high heat shrinkage rate, high strength, and good chemical stability but also has high alkali resistance. Summary of the Invention

[0006] Aiming at the problems existing in the prior art, the present invention uses PETG as the main component of the heat shrinkable film and synthesizes an alkali-resistant PETG heat shrinkable film for battery labels by adding a composite alkali-resistant filler composed of modified mica and modified calcined kaolin, an antistatic agent, an antioxidant, and a lubricant. In addition to having basic properties such as high heat shrinkage rate, high strength, and good chemical stability, it also has the characteristic of high alkali resistance.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] On the one hand, the present invention provides an alkali-resistant PETG heat-shrinkable film for battery labels. By weight, the PETG heat-shrinkable film comprises the following raw materials: 90-110 parts of PETG, 5-15 parts of a composite alkali-resistant filler, 1-4 parts of an antistatic agent, 0.5-2 parts of an antioxidant, and 0.3-2 parts of a lubricant; wherein, the composite alkali-resistant filler is a mixture of modified mica and modified calcined kaolin.

[0009] The present invention places no special restrictions on the source of the PETG, which can be obtained by purchasing commercially or by self-synthesis.

[0010] In some embodiments of the present invention, the mass ratio of modified mica to modified calcined kaolin in the composite alkali-resistant filler is 1:(0.6-1).

[0011] Preferably, the mass ratio of modified mica to modified calcined kaolin in the composite alkali-resistant filler is 1:0.8.

[0012] In some embodiments of the present invention, the preparation method of the modified mica comprises the following steps:

[0013] (1) Add azobisisobutyronitrile and dodecyl mercaptan to N,N-dimethylformamide, stir to obtain a mixed solution for standby. Add sodium p-styrenesulfonate, isoamyl acrylate, and vinyltris(2-methoxyethoxy)silane to N,N-dimethylformamide, introduce an inert gas, heat to 50-60 °C, stir, add the mixed solution, heat to 65-75 °C, stir for 1-2 h, filter, cool to room temperature, dry to obtain an intermediate product for standby;

[0014] (2) Mix mica, the intermediate product of step (1), and deionized water, grind, filter, Soxhlet extract, dry, and grind to obtain modified mica.

[0015] In some embodiments of the present invention, in step (1), the molar ratio of sodium p-styrenesulfonate, isoamyl acrylate, and vinyltris(2-methoxyethoxy)silane is 1:(7.5-8.5):(1.5-2.5).

[0016] Preferably, in step (1), the molar ratio of sodium p-styrenesulfonate, isoamyl acrylate, and vinyltris(2-methoxyethoxy)silane is 1:8:2.

[0017] In some embodiments of the present invention, in step (2), the mass ratio of mica to the intermediate product is 1:(0.05-0.2).

[0018] Preferably, in step (2), the mass ratio of mica to the intermediate product is 1:0.1.

[0019] In some embodiments of the present invention, the method for preparing the modified calcined kaolin comprises the following steps:

[0020] 1) Grind the calcined kaolin to obtain a powder for standby;

[0021] 2) Take the powder from step 1), add sodium dodecylbenzenesulfonate and silane coupling agent KH570, stir, filter, and dry to obtain the modified calcined kaolin.

[0022] Among them, in step 2), the mass ratio of the powder, sodium dodecylbenzenesulfonate and silane coupling agent KH570 is 1:(0.1 - 0.4):(0.05 - 0.2).

[0023] Preferably, in step 2), the mass ratio of the powder, sodium dodecylbenzenesulfonate and silane coupling agent KH570 is 1:0.2:0.1.

[0024] In some embodiments of the present invention, in step 1), the average particle size of the powder is 1 - 5 μm.

[0025] Preferably, in step 1), the average particle size of the powder is 3 μm.

[0026] The chemical composition of mica is mainly composed of elements such as silicon, aluminum, magnesium, and potassium. It is a layered silicate mineral. Due to its high chemical stability, it is not easy to react with alkaline substances and has good alkali resistance. However, the layered structure of mica makes there be strong van der Waals forces between its structures, making it easy to agglomerate during the dispersion process, resulting in difficulty in being uniformly dispersed in the PETG matrix.

[0027] The applicant used sodium p-styrenesulfonate, isoamyl acrylate, and vinyltris(2-methoxyethoxy)silane as raw materials to synthesize a terpolymer (intermediate product) through free radical polymerization, and used this terpolymer as an interfacial modification modifier to modify mica, so that the dispersibility of mica was improved well, and thus the alkali resistance of the PETG heat shrinkable film could be effectively improved. It is speculated that the reasons are as follows: First, the applicant selected mica with a specific particle size as the matrix, which has good high-temperature resistance and insulation; second, the hydroxyl groups generated after hydrolysis of the siloxane branches introduced by vinyltris(2-methoxyethoxy)silane in the intermediate product form weak hydrogen bonds with the active groups such as hydroxyl groups and amino groups on the mica surface. Under the temperature effect generated by frosting, the weak hydrogen bonds are further transformed into strong covalent bonds, enabling the intermediate product to be anchored on the mica surface, increasing the degree of organification of the mica powder surface, and thus improving the compatibility between mica and the PETG matrix; furthermore, the longer molecular chain segments in the intermediate product can form a steric hindrance and steric effect on the mica surface, effectively preventing the agglomeration phenomenon between mica powder particles.

[0028] In addition, the applicant grinds the calcined kaolin to an average particle size of 1 - 5 μm, making it have excellent dispersibility and chemical stability. Further, the applicant uses sodium dodecylbenzenesulfonate and silane coupling agent KH570 to modify it jointly, improving its dispersibility. Then, the modified calcined kaolin and modified mica are compounded in a specific mass ratio to obtain a composite alkali-resistant filler, which can play a role in synergistic alkali resistance.

[0029] In some embodiments of the present invention, the antistatic agent is fatty alcohol polyoxyethylene ether phosphate.

[0030] In some embodiments of the present invention, the antioxidant is any one of antioxidant 1010, antioxidant 1076, and antioxidant 168.

[0031] In some embodiments of the present invention, the lubricant is at least one of erucamide, zinc stearate, and ethylene bisstearamide.

[0032] On the other hand, the present invention also provides a preparation method of the alkali-resistant PETG heat-shrinkable film for battery labels described in the above technical solution, including the following steps:

[0033] S1. PETG, the composite alkali-resistant filler, the antistatic agent, the antioxidant, and the lubricant are dried at 60 - 80 °C for 4 - 6 h and then added to a reaction vessel, stirred, heated to 290 - 310 °C, stirred at 80 - 90 Pa for 2 - 3 h, extruded, pelletized, and dried to obtain polyester chips for standby;

[0034] S2. The polyester chips in step S1 are melt-extruded at 280 - 290 °C, cast into a film by a die head, the cast film is wound, biaxially stretched at 100 - 110 °C, cooled and shaped, the thickness is controlled to be 30 - 45 μm, and then wound up to obtain the alkali-resistant PETG heat-shrinkable film for battery labels.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) The present invention uses PETG as the main component of the heat-shrinkable film, and synthesizes an alkali-resistant PETG heat-shrinkable film for battery labels by adding a composite alkali-resistant filler composed of modified mica and modified calcined kaolin, an antistatic agent, an antioxidant, and a lubricant. Through the synergistic effect among the components, it has the characteristics of high heat shrinkage rate, high strength, good chemical stability, and excellent alkali resistance, and can be widely used in the field of PETG heat-shrinkable films, having good commercial application value.

[0037] (2) The present invention uses sodium p-styrenesulfonate, isopentyl acrylate, and vinyltris(2-methoxyethoxy)silane as raw materials to synthesize a terpolymer (intermediate product) through free radical polymerization. The mica is modified with this terpolymer as an interfacial modifier to obtain modified mica with good dispersibility. Finally, the modified mica and modified calcined kaolin are compounded at a specific mass ratio to obtain a composite alkali-resistant filler, which can play a role in synergistic alkali resistance. Specific embodiments

[0038] The present invention will be described below in conjunction with specific implementation examples. It should be noted that the following examples are examples of the present invention and are only used to illustrate the present invention, rather than to limit the present invention. Other combinations and various improvements within the concept of the present invention can be made without departing from the main idea or scope of the present invention.

[0039] In the following examples and comparative examples, except for PETG and the composite alkali-resistant filler, the compound monomers and related reagents used can all be purchased from the market. Among them, PETG is synthesized by our company; the antistatic agent is fatty alcohol polyoxyethylene ether phosphate AEO-3P, purchased from Jinan Jiayang Chemical Co., Ltd.

[0040] Preparation Example 1

[0041] The synthesis method of PETG includes the following steps:

[0042] Heat 0.3 mol of CHDM until it melts, and then add it together with 0.4 mol of PTA, 0.7 mol of EG, and 0.05 g of Sb2O3 into the reaction kettle. Replace the air with nitrogen three times, heat up to 230 °C, introduce nitrogen until the pressure is 100 KPa, stir for 3 h, heat up to 260 °C, stir at 4 KPa for 1 h, reduce the pressure to 100 Pa, stir for 1 h, discharge the material, draw, and pelletize to obtain PETG.

[0043] Preparation Example 2

[0044] The synthesis method of modified mica A includes the following steps:

[0045] (1) Add 0.3 g of azobisisobutyronitrile and 0.15 g of dodecyl mercaptan to 10 ml of N,N-dimethylformamide, stir to obtain a mixed solution for standby. Add 0.1 mol of sodium p-styrenesulfonate, 0.8 mol of isopentyl acrylate, and 0.2 mol of vinyltris(2-methoxyethoxy)silane to 400 ml of N,N-dimethylformamide, introduce nitrogen, heat up to 55 °C, stir for 10 min, add the mixed solution, heat up to 70 °C, stir for 1.5 h, filter, cool to room temperature, and dry at 60 °C for 8 h to obtain the intermediate product for standby;

[0046] (2) Mix 20 g of mica, 2 g of the intermediate product from step (1), and 60 ml of deionized water, grind for 40 min, filter, perform Soxhlet extraction with 95 wt% ethanol aqueous solution at 60 °C for 12 h, dry at 60 °C for 8 h, and grind for 5 min to obtain modified mica A.

[0047] Preparation Example 3

[0048] Modified mica B, the specific implementation method is the same as that of modified mica A, the difference is: in step (1), replace the molar amount of isopentyl acrylate with 0.73 mol.

[0049] Preparation Example 4

[0050] Modified mica C, the specific implementation method is the same as that of modified mica A, the difference is: in step (1), replace the molar amount of vinyltris(2-methoxyethoxy)silane with 0.13 mol.

[0051] Preparation Example 5

[0052] Modified mica D, the specific implementation method is the same as that of modified mica A, the difference is: in step (2), replace the mass of the intermediate product with 0.8 g.

[0053] Preparation Example 6

[0054] The synthesis method of modified calcined kaolin A includes the following steps:

[0055] 1) Grind the calcined kaolin until the average particle size is 3 μm to obtain a powder for standby;

[0056] 2) Take 10 g of the powder from step 1), add 2 g of sodium dodecylbenzenesulfonate and 1 g of silane coupling agent KH570, stir for 2 h, filter, and dry at 60 °C for 12 h to obtain modified calcined kaolin A.

[0057] Preparation Example 7

[0058] Modified calcined kaolin B, the specific implementation method is the same as that of modified calcined kaolin A, the difference is: in step (1), replace the mass of sodium dodecylbenzenesulfonate with 0.7 g.

[0059] Example 1

[0060] An alkali-resistant PETG heat-shrinkable film for battery labels, by weight, the PETG heat-shrinkable film comprises the following raw materials: 100 parts of PETG, 10 parts of composite alkali-resistant filler, 2.5 parts of fatty alcohol polyoxyethylene ether phosphate AEO-3P, 1.25 parts of antioxidant 1010, 1.5 parts of erucamide; wherein, the composite alkali-resistant filler is a mixture of modified mica A and modified calcined kaolin A, and the mass ratio is 1:0.8.

[0061] In this embodiment, the preparation method of the alkali-resistant PETG heat-shrinkable film for battery labels comprises the following steps:

[0062] S1. Add PETG, composite alkali-resistant filler, fatty alcohol polyoxyethylene ether phosphate AEO-3P, antioxidant 1010 and erucamide into a reaction vessel after drying at 70°C for 5 h, stir for 20 min, heat up to 300°C, stir at 70 Pa for 2.5 h, extrude, pelletize, and dry at 60°C for 12 h to obtain polyester chips for standby;

[0063] S2. Melt and extrude the polyester chips obtained in step S1 at 285°C, cast films through a die head, wind the cast films, conduct biaxial stretching at 105°C, cool and shape, control the thickness to be 40 μm, and wind up to obtain the alkali-resistant PETG heat-shrinkable film for battery labels.

[0064] Example 2

[0065] An alkali-resistant PETG heat-shrinkable film for battery labels, by weight, the PETG heat-shrinkable film comprises the following raw materials: 90 parts of PETG, 5 parts of composite alkali-resistant filler, 1 part of fatty alcohol polyoxyethylene ether phosphate AEO-3P, 0.5 part of antioxidant 1076, 0.3 part of zinc stearate; wherein, the composite alkali-resistant filler is a mixture of modified mica A and modified calcined kaolin A, and the mass ratio is 1:0.6.

[0066] In this embodiment, the preparation method of the alkali-resistant PETG heat-shrinkable film for battery labels comprises the following steps:

[0067] S1. Add PETG, composite alkali-resistant filler, fatty alcohol polyoxyethylene ether phosphate AEO-3P, antioxidant 1076 and zinc stearate into a reaction vessel after drying at 60°C for 6 h, stir for 20 min, heat up to 290°C, stir at 80 Pa for 3 h, extrude, pelletize, and dry at 60°C for 12 h to obtain polyester chips for standby;

[0068] S2. Melt and extrude the polyester chips obtained in step S1 at 280°C, cast films through a die head, wind the cast films, conduct biaxial stretching at 100°C, cool and shape, control the thickness to be 40 μm, and wind up to obtain the alkali-resistant PETG heat-shrinkable film for battery labels.

[0069] Example 3

[0070] An alkali-resistant PETG heat-shrinkable film for battery labels, by weight, the PETG heat-shrinkable film comprises the following raw materials: 110 parts of PETG, 15 parts of a composite alkali-resistant filler, 4 parts of fatty alcohol polyoxyethylene ether phosphate AEO-3P, 2 parts of antioxidant 168, and 2 parts of ethylene bis-stearamide; wherein, the composite alkali-resistant filler is a mixture of modified mica A and modified calcined kaolin A, with a mass ratio of 1:1.

[0071] The preparation method of the alkali-resistant PETG heat-shrinkable film for battery labels in this embodiment comprises the following steps:

[0072] S1. Add PETG, the composite alkali-resistant filler, fatty alcohol polyoxyethylene ether phosphate AEO-3P, antioxidant 168, and ethylene bis-stearamide into a reaction vessel after drying at 80°C for 4 h, stir for 20 min, heat up to 310°C, stir at 90 Pa for 2 h, extrude, pelletize, and dry to obtain polyester chips for standby;

[0073] S2. Melt and extrude the polyester chips from step S1 at 290°C, cast the film with a die head, wind the cast film, perform biaxial stretching at 110°C, cool and shape it, control the thickness to be 40 μm, and wind it up to obtain the alkali-resistant PETG heat-shrinkable film for battery labels.

[0074] Example 4

[0075] This embodiment provides an alkali-resistant PETG heat-shrinkable film for battery labels and its preparation method. The specific implementation manner is the same as that of Embodiment 1, except that the mass ratio of modified mica A and modified calcined kaolin A in the composite alkali-resistant filler is 1:0.3.

[0076] Example 5

[0077] This embodiment provides an alkali-resistant PETG heat-shrinkable film for battery labels and its preparation method. The specific implementation manner is the same as that of Embodiment 1, except that the mass ratio of modified mica A and modified calcined kaolin A in the composite alkali-resistant filler is 1:1.3.

[0078] Example 6

[0079] This embodiment provides an alkali-resistant PETG heat-shrinkable film for battery labels and its preparation method. The specific implementation manner is the same as that of Embodiment 1, except that modified mica B is used to replace modified mica A in equal amount.

[0080] Example 7

[0081] This embodiment provides an alkali-resistant PETG heat-shrinkable film for battery labels and a preparation method thereof. The specific implementation manner is the same as that of Embodiment 1, except that modified mica C is used to replace modified mica A in equal amounts.

[0082] Example 8

[0083] This embodiment provides an alkali-resistant PETG heat-shrinkable film for battery labels and a preparation method thereof. The specific implementation manner is the same as that of Embodiment 1, except that modified mica D is used to replace modified mica A in equal amounts.

[0084] Example 9

[0085] This embodiment provides an alkali-resistant PETG heat-shrinkable film for battery labels and a preparation method thereof. The specific implementation manner is the same as that of Embodiment 1, except that calcined kaolin B is used to replace modified calcined kaolin A in equal amounts.

[0086] Comparative Example 1

[0087] This comparative example provides an alkali-resistant PETG heat-shrinkable film for battery labels and a preparation method thereof. The specific implementation manner is the same as that of Embodiment 1, except that mica is used to replace modified mica A in equal amounts.

[0088] Comparative Example 2

[0089] This comparative example provides an alkali-resistant PETG heat-shrinkable film for battery labels and a preparation method thereof. The specific implementation manner is the same as that of Embodiment 1, except that modified mica A is used to replace the composite alkali-resistant filler in equal amounts.

[0090] Comparative Example 3

[0091] This comparative example provides an alkali-resistant PETG heat-shrinkable film for battery labels and a preparation method thereof. The specific implementation manner is the same as that of Embodiment 1, except that calcined kaolin is used to replace modified calcined kaolin A in equal amounts.

[0092] The average particle size of the calcined kaolin is 3 μm.

[0093] Comparative Example 4

[0094] This comparative example provides an alkali-resistant PETG heat-shrinkable film for battery labels and a preparation method thereof. The specific implementation manner is the same as that of Embodiment 1, except that modified calcined kaolin A is used to replace the composite alkali-resistant filler in equal amounts.

[0095] Performance test

[0096] The alkali resistance of the PETG heat-shrinkable films of the above-mentioned Embodiments 1-9 and Comparative Examples 1-4 was tested, and the test results are shown in Table 1.

[0097] The PETG heat-shrinkable films of Examples 1-9 and Comparative Examples 1-4 were placed in an oven at 50 °C, taken out and weighed after 24 h, denoted as m a , and then placed in a 40 wt% NaOH solution, maintained at a temperature of 70 °C for 16 h. After taking out, the surface was rinsed with deionized water, and then the surface moisture was blotted with filter paper, dried at 50 °C and weighed, denoted as m b ,

[0098] Calculate the weight loss rate before and after alkali corrosion. The weight loss rate = (m a -m b ) / m a ×100%. The smaller the weight loss rate, the better the alkali resistance. Refer to the standard GBT11547-2008.

[0099] Table 1

[0100] Group Weight Loss Rate (%) Example 1 8.05 Example 2 8.10 Example 3 8.07 Example 4 9.25 Example 5 9.30 Example 6 10.45 Example 7 10.37 Example 8 10.56 Example 9 10.25 Comparative Example 1 11.37 Comparative Example 2 11.40 Comparative Example 3 10.75 Comparative Example 4 12.25

[0101] As can be seen from the data in Table 1, the PETG heat-shrinkable films for battery labels in Examples 1-3 of the present invention as a whole have a smaller weight loss rate, that is, they have good alkali resistance. Among them, in Examples 4-5, the mass ratio of modified mica A and modified calcined kaolin in the composite alkali-resistant filler was changed, weakening their synergistic effect, and thus resulting in a decrease in the alkali resistance of the PETG heat-shrinkable film; in Examples 6-8, the proportion of key components in the synthesis process of modified mica was changed, resulting in poor improvement of the dispersibility of mica, and thus resulting in poor improvement of the alkali resistance of the modified mica for the PETG heat-shrinkable film; in Example 9, the modification ratio of sodium dodecylbenzenesulfonate to calcined kaolin was changed, reducing the combined modification effect of sodium dodecylbenzenesulfonate and silane coupling agent KH570 on the dispersibility of calcined kaolin, and thus resulting in a certain degree of decrease in the alkali resistance of the PETG heat-shrinkable film; in Comparative Examples 1-4, mica was used to replace modified mica A in equal amounts, modified mica A was used to replace the composite alkali-resistant filler in equal amounts, and calcined kaolin was used to replace modified calcined kaolin A in equal amounts and modified calcined kaolin was used to replace the composite alkali-resistant filler in equal amounts, all resulting in poor alkali resistance performance of the PETG heat-shrinkable film.

[0102] The above embodiments are only used to illustrate the technical concept and characteristics of the present invention. The purpose is to enable those who are familiar with this technology to understand the content of the present invention and implement it, and it cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims

1. An alkali-resistant PETG heat-shrinkable film for battery labels, characterized in that, By weight parts, the PETG heat shrinkable film comprises the following raw materials: 90 - 110 parts of PETG, 5 - 15 parts of composite alkali - resistant filler, 1 - 4 parts of antistatic agent, 0.5 - 2 parts of antioxidant, 0.3 - 2 parts of lubricant; wherein, the composite alkali - resistant filler is a mixture of modified mica and modified calcined kaolin.

2. The alkali-resistant PETG heat-shrinkable film for battery labels according to claim 1, characterized in that, In the composite alkali - resistant filler, the mass ratio of modified mica to modified calcined kaolin is 1:(0.6 - 1).

3. The alkali-resistant PETG heat-shrinkable film for battery labels according to claim 1, characterized in that, The preparation method of the modified mica comprises the following steps: (1) Add azobisisobutyronitrile and dodecyl mercaptan into N,N - dimethylformamide, stir to obtain a mixed solution for standby. Add sodium p - styrenesulfonate, isoamyl acrylate and vinyltris(2 - methoxyethoxy)silane into N,N - dimethylformamide, introduce an inert gas, heat up to 50 - 60 °C, stir, add the mixed solution, heat up to 65 - 75 °C, stir for 1 - 2 h, filter, cool to room temperature, dry to obtain an intermediate product for standby; (2) Mix mica, the intermediate product of step (1) and deionized water, grind, filter, Soxhlet extract, dry, grind to obtain modified mica.

4. The alkali-resistant PETG heat-shrinkable film for battery labels according to claim 3, characterized in that In step (1), the molar ratio of sodium p - styrenesulfonate, isoamyl acrylate and vinyltris(2 - methoxyethoxy)silane is 1:(7.5 - 8.5):(1.5 - 2.5).

5. The alkali-resistant PETG heat-shrinkable film for battery labels according to claim 3, wherein In step (2), the mass ratio of mica to the intermediate product is 1:(0.05 - 0.2).

6. The alkali-resistant PETG heat-shrinkable film for battery labels according to claim 1, wherein The preparation method of the modified calcined kaolin comprises the following steps: 1) Grind the calcined kaolin to obtain a powder for standby; 2) Take the powder of step 1), add sodium dodecylbenzenesulfonate and silane coupling agent KH570, stir, filter, dry to obtain modified calcined kaolin.

7. The alkali-resistant PETG heat-shrinkable film for battery labels according to claim 6, wherein In step 1), the average particle size of the powder is 1 - 5 μm.

8. The alkali-resistant PETG heat-shrinkable film for battery labels according to claim 1, characterized in that, The antistatic agent is fatty alcohol polyoxyethylene ether phosphate.

9. The alkali-resistant PETG heat-shrinkable film for battery labels according to claim 1, wherein The antioxidant is any one of antioxidant 1010, antioxidant 1076, antioxidant 168.

10. A method for preparing an alkali-resistant PETG heat-shrinkable film for battery labels according to any one of claims 1-9, characterized in that, Comprises the following steps: S1. Dry PETG, composite alkali - resistant filler, antistatic agent, antioxidant and lubricant at 60 - 80 °C for 4 - 6 h, then add them into a reaction vessel, stir, heat up to 290 - 310 °C, stir at 80 - 90 Pa for 2 - 3 h, extrude, pelletize, dry to obtain polyester chips for standby; S2. Melt - extrude the polyester chips of step S1 at 280 - 290 °C, cast films through a die head, wind the cast films, perform biaxial stretching at 100 - 110 °C, cool and shape, control the thickness to be 30 - 45 μm, wind up to obtain the alkali - resistant PETG heat shrinkable film for battery labels.