A coating liquid for an aluminum-plastic composite film, a preparation method thereof, and an aluminum-plastic composite film

Abstract

The application provides a coating liquid for an aluminum-plastic composite film, a preparation method of the coating liquid and the aluminum-plastic composite film, and the preparation raw materials of the coating liquid include 1-5 parts of polytetrafluoroethylene emulsion, 1-10 parts of polyolefin resin, 1-5 parts of epoxy curing agent, 80-100 parts of organic solvent, 0.05-1 part of filling material and 0.05-1 part of stearic acid amide emulsion in terms of weight fraction. The coating liquid is coated on the surface of a nylon layer, and a coating layer is formed after drying. The coating layer has low friction, wear resistance and corrosion resistance, and can improve the punching performance. Therefore, the prepared aluminum-plastic composite film has deep forming performance, wear resistance and corrosion resistance.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum-plastic films for soft-package lithium-ion batteries, and in particular to a coating liquid for an aluminum-plastic composite film, a preparation method thereof, and the aluminum-plastic composite film. Background Art

[0002] Lithium-ion batteries are currently a common secondary battery and have been widely used in the 3C industry. With the development of electric vehicles, higher requirements have been placed on the energy density and other aspects of large lithium-ion batteries. Soft-pack lithium-ion batteries are increasingly favored by the electric vehicle industry, and the requirements for the performance of the outer packaging materials of soft-pack lithium-ion batteries are also becoming increasingly stringent. The battery pack of an electric vehicle is typically composed of multiple battery packs. When the battery pack is used in a vehicle, factors such as road conditions and the driving environment may affect one or more battery packs due to collisions or other factors, causing electrolyte leakage in one or more battery packs. If the outer packaging material of the soft-pack lithium-ion battery is not highly corrosion-resistant or moisture-resistant, an electrolyte leak in a single battery pack can damage the entire battery pack, rendering the electric vehicle unable to operate normally.

[0003] Currently, the outer packaging material used for lithium-ion batteries is aluminum-plastic composite film. Its structure generally consists of a central aluminum foil layer flanked by nylon layers and heat-seal layers. When using aluminum-plastic composite film as the outer packaging for lithium batteries, electrolyte dripping onto the surface of the composite film during injection and extraction often causes corrosion. To address this issue, aluminum-plastic film manufacturers typically laminate a PET film over the outer nylon surface of the film. However, PET film has poor ductility, which severely affects the formability of the film shell, leading to the development of trachoma and pinholes in the film shell.

[0004] Therefore, it is necessary to prepare an aluminum-plastic composite film with surface resistance to electrolyte and good deep drawing performance to solve the defects of the existing technology. Summary of the Invention

[0005] In view of the above problems, the object of the present invention is to provide a coating liquid for aluminum-plastic composite film, which forms a coating on the surface of the nylon film with low friction, wear resistance, corrosion resistance, and can improve the punching performance.

[0006] In order to achieve the above-mentioned object, the present invention provides a coating liquid for aluminum-plastic composite film, wherein the raw materials for preparing the coating liquid include, by weight, 1-5 parts of polytetrafluoroethylene emulsion, 1-10 parts of polyolefin resin, 1-5 parts of epoxy curing agent, 80-100 parts of organic solvent, 0.05-1 part of filler, and 0.05-1 part of stearamide emulsion.

[0007] As an example, the content of the polytetrafluoroethylene emulsion can be, but is not limited to, 1 part, 2 parts, 3 parts, 4 parts, 5 parts; the content of the polyolefin resin can be, but is not limited to, 2 parts, 4 parts, 6 parts, 8 parts, 10 parts; the content of the epoxy curing agent can be, but is not limited to, 1 part, 2 parts, 3 parts, 4 parts, 5 parts; the content of the organic solvent can be, but is not limited to, 80 parts, 85 parts, 90 parts, 95 parts, 100 parts; the content of the filler can be, but is not limited to, 0.05 parts, 0.06 parts, 0.07 parts, 0.08 parts, 0.09 parts, 1.0 parts; the content of the stearic acid amide emulsion can be, but is not limited to, 0.05 parts, 0.06 parts, 0.07 parts, 0.08 parts, 0.09 parts, 1.0 parts.

[0008] It can be understood that the polytetrafluoroethylene emulsion generally contains polytetrafluoroethylene resin, water, and emulsifier. As preferred, the melting point of the polytetrafluoroethylene resin in the polytetrafluoroethylene emulsion of the present application is 200-327℃, and the setting of the melting point in this range can avoid the occurrence of reverse sticking of the coating during the curing process and the storage process due to excessively high ambient temperature. Further, in order to ensure the stability of the coating liquid, the pH of the polytetrafluoroethylene emulsion is set to about 7-8.

[0009] In some embodiments, the organic solvent is selected from at least one of ethyl acetate, butanone, and cyclohexane.

[0010] In some embodiments, the filler is selected from at least one of titanium powder, wollastonite powder, and ore powder. In some embodiments, the filler is wollastonite powder, and the finer the fineness of the wollastonite powder, the stronger the alkalinity and the greater the whiteness, and the better the coating performance. Further, the filler is treated with a silane coupling agent, for example, the wollastonite powder is treated with a silane coupling agent, to improve the electrolyte corrosion resistance, and at the same time, to improve the tensile strength and prevent cracking of the coating.

[0011] It should be understood that stearic acid amide has good slip performance, and the polytetrafluoroethylene emulsion has a low coefficient of friction, and the stearic acid amide emulsion prepared from stearic acid amide is used in combination with the polytetrafluoroethylene emulsion, and under the dual action, the low slip performance of the coating is ensured. In some embodiments, the particle size of the stearic acid amide in the stearic acid amide emulsion is less than 10μm, and as an example, the particle size of the stearic acid amide can be, but is not limited to, 1-10μm, 5-10μm, 1-5μm. When the particle size of the stearic acid amide is too large, the coating liquid is prone to precipitation when prepared, and the coating is prone to floating on the surface after curing. In some embodiments, in order to ensure good flowability of the coating liquid during coating, the viscosity of the stearic acid amide emulsion is 100-200mpa.s. In some other embodiments, in order to ensure the stability of the entire coating liquid, the pH of the stearic acid amide emulsion is controlled to about 7-8.

[0012] Accordingly, the present invention also provides a method for preparing a coating liquid for an aluminum-plastic composite film, comprising the steps of:

[0013] (1) Add part of the organic solvent into the reaction device and heat it, then add the filler and epoxy curing agent and stir evenly;

[0014] (2) adding stearamide emulsion into the reaction apparatus and stirring evenly;

[0015] (3) adding the polyolefin resin to the remaining organic solvent and stirring uniformly, then adding the polytetrafluoroethylene emulsion and stirring uniformly to obtain material A;

[0016] (4) Add material A to the reaction device and stir evenly. After the reaction is completed, a coating liquid is obtained.

[0017] In some embodiments, in step (1), the heating temperature is 40-50°C.

[0018] Accordingly, the present invention also provides an aluminum-plastic composite film comprising an aluminum foil, a nylon layer located on one side of the aluminum foil, and a heat-seal layer located on the other side of the aluminum foil. The nylon layer is provided with a coating on a side facing away from the aluminum foil, the coating being formed using the aforementioned coating solution for aluminum-plastic composite films. It is understood that the coating is formed by applying the aforementioned coating solution to the surface of the nylon layer and drying it. In some embodiments, the drying temperature is 90-120°C. By way of example, the heat-seal layer includes, but is not limited to, a polypropylene film (CPP film).

[0019] Compared with the prior art, the coating liquid for aluminum-plastic composite film provided by the present invention comprises raw materials such as polytetrafluoroethylene emulsion, polyolefin resin, epoxy curing agent, organic solvent, filler, and stearic acid amide emulsion. The raw materials are prepared into a coating liquid, which is then applied to the surface of a nylon layer and dried to form a coating having low friction, wear resistance, corrosion resistance, and improved punching performance. The reason is that in the present invention, the polyolefin resin is used as the coating matrix. The polyolefin resin not only has good electrolyte resistance, but also has good adhesion and flexibility. It reacts with the epoxy bond in the epoxy curing agent to tightly and firmly bind the filler and stearic acid amide in the system, ensuring that the coating has good adhesion. The polytetrafluoroethylene emulsion has a low friction coefficient, and the stearic acid amide has good slippery properties. The stearic acid amide emulsion prepared by using stearic acid amide is compounded with the polytetrafluoroethylene emulsion to ensure the low slippery properties of the coating under the dual effects. Therefore, the coating has high slipperiness, and thus can effectively reduce the friction coefficient of the surface of the aluminum-plastic film, so that the aluminum-plastic film has deeper forming performance, wear resistance and corrosion resistance. DETAILED DESCRIPTION

[0020] The following is a preferred implementation of the embodiment of the present invention. It should be noted that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the embodiment of the present invention. These improvements and modifications are also considered to be within the scope of protection of the embodiment of the present invention.

[0021] Example 1

[0022] A coating liquid for aluminum-plastic composite film, wherein the raw materials for its preparation include, by weight, 3 parts of polytetrafluoroethylene emulsion (Juhua JF-4DCD), 5 parts of polyolefin resin (Toyobo PMA-KE), 3 parts of epoxy curing agent (Toyobo LAE-004), 90 parts of butanone, 0.05 parts of wollastonite powder (Bosheng No. 01), and 1 part of stearamide emulsion (Guangzhou Zhenghao XA-28).

[0023] The coating solution is prepared by using the raw materials, and the steps are as follows:

[0024] (1) Add part of butanone to the reaction apparatus and heat to 45°C, then add wollastonite powder and stir for 30 minutes, then add epoxy curing agent and stir for 20 minutes until the mixture is uniform;

[0025] (2) slowly adding the stearamide emulsion dropwise into the reaction apparatus at a stirring speed of 100 r / min until uniformly dispersed;

[0026] (3) adding the polyolefin resin to the remaining butanone solvent and stirring evenly, then adding the polytetrafluoroethylene emulsion and stirring evenly to obtain material A;

[0027] (4) Material A was gradually added to the reaction apparatus and stirred for 60 min until uniform. After the reaction was completed, the mixture was cooled to room temperature and poured out to obtain a coating solution;

[0028] The preparation of aluminum-plastic composite film includes the following steps:

[0029] (1) applying the coating solution on the surface of the nylon layer, drying at 100°C, and aging at 65°C for 36 hours to form a corrosion-resistant coating on the outer surface of the nylon layer;

[0030] (2) Compounding the nylon layer with one side of the aluminum foil;

[0031] (3) Compounding the polypropylene film with the other side of the aluminum foil to obtain an aluminum-plastic composite film.

[0032] Example 2

[0033] A coating liquid for aluminum-plastic composite film, wherein the raw materials for its preparation include, by weight, 1 part of polytetrafluoroethylene emulsion (Juhua JF-4DCD), 4 parts of polyolefin resin (Toyobo PMA-KE), 3 parts of epoxy curing agent (Toyobo LAE-004), 85 parts of butanone, 0.1 part of wollastonite powder (Bosheng No. 01), and 0.5 part of stearamide emulsion (Guangzhou Zhenghao XA-28).

[0034] The preparation of the coating liquid and the aluminum-plastic composite film is the same as in Example 1 and will not be elaborated here.

[0035] Example 3

[0036] A coating liquid for aluminum-plastic composite film, wherein the raw materials for its preparation include, by weight, 4 parts of polytetrafluoroethylene emulsion (Juhua JF-4DCD), 4 parts of polyolefin resin (Toyobo PMA-KE), 4 parts of epoxy curing agent (Toyobo LAE-004), 95 parts of ethyl acetate, 0.05 parts of wollastonite powder (Bosheng No. 01), and 0.05 parts of stearamide emulsion (Guangzhou Zhenghao XA-28).

[0037] The preparation of the coating liquid and the aluminum-plastic composite film is the same as in Example 1 and will not be elaborated here.

[0038] Example 4

[0039] A coating liquid for aluminum-plastic composite film, wherein the raw materials for its preparation include, by weight, 2 parts of polytetrafluoroethylene emulsion (Juhua JF-4DCD), 6 parts of polyolefin resin (Toyobo PMA-KE), 5 parts of epoxy curing agent (Toyobo LAE-004), 90 parts of butanone, 0.1 parts of titanium powder (PTA121), and 0.5 parts of stearamide emulsion (Guangzhou Zhenghao XA-28).

[0040] The preparation of the coating liquid and the aluminum-plastic composite film is the same as in Example 1 and will not be elaborated here.

[0041] Comparative Example 1

[0042] Comparative Example 1 is basically the same as Example 1, except that stearamide emulsion is not added to the raw materials for preparing the coating solution of Comparative Example 1. The rest is the same as Example 1 and will not be elaborated here.

[0043] Comparative Example 2

[0044] Comparative Example 2 is basically the same as Example 1, except that no filler is added to the raw materials for preparing the coating liquid in Comparative Example 2. The rest is the same as Example 1 and will not be elaborated here.

[0045] Comparative Example 3

[0046] Comparative Example 3 is basically the same as Example 1, except that no polyolefin resin and epoxy curing agent are added to the raw materials for preparing the coating liquid of Comparative Example 3. The rest is the same as Example 1 and will not be elaborated here.

[0047] Comparative Example 4

[0048] Comparative Example 4 is used as a reference, in which the surface of the nylon layer in the aluminum-plastic composite film does not contain a coating.

[0049] The aluminum-plastic composite films obtained in the examples and comparative examples were subjected to electrolyte corrosion resistance, friction, and impact tests, and the results are shown in Table 1. The test methods are as follows:

[0050] Electrolyte corrosion resistance: Take 50-100ppm electrolyte, drop 2-3 drops on the R corner of the membrane shell after punching, and add electrolyte on the four sides of the membrane shell, and record the time when corrosion marks begin to appear.

[0051] Wear test: Cut 65mm*75mm wide strips of aluminum-plastic film to wrap around the sliding block and secure them with tape. A steel block 80mm wide with a surface roughness of 12.5S was fixed to the friction test platform. After the slider was fixed to the sensor hook, multiple movement tests were performed, and the number of slides before scratches began to appear was recorded.

[0052] Static / dynamic friction: Tested in accordance with GB / T 10006-2021. A 200mm x 80mm section of aluminum-plastic film was used as a friction track, and a 63.5mm x 80mm test sample was used. Surface sliding tests were performed on a friction tester to obtain three sets of static and dynamic friction data.

[0053] Cold stamping: Aluminum-plastic film is cut into 15*15mm sheets and punched at different depths on an 18350 core punching machine. The greater the forming depth, the better the forming performance.

[0054] Table 1 Performance test results

[0055]

[0056] As can be known from the data of Table 1, the aluminium plastic composite film that adopts technical scheme of the present invention to obtain has good electrolyte corrosion resistance, wear resistance and friction effect, can further improve the aluminium plastic film formability.Reason is: among the present invention, using polyolefin resin as coating matrix, it is not only excellent in electrolyte resistance, and has good cohesiveness, pliability, with the epoxy bond reaction in the epoxy curing agent, filler, stearic acid amide are tightly firmly in the system, guarantee that coating has good adhesiveness, polytetrafluoroethylene emulsion has lower friction coefficient, stearic acid amide has good smoothness, adopt stearic acid amide to make and the composite use of polytetrafluoroethylene emulsion, under dual action, guaranteed the low smoothness of coating.Therefore, this coating has higher smoothness, thereby can effectively reduce the friction coefficient on the aluminium plastic film surface, make aluminium plastic film have darker formability, corrosion resistance.

[0057] In Comparative Example 1, since no stearamide emulsion was added, the friction of the aluminum-plastic composite film obtained was relatively high.

[0058] In Comparative Example 2, no filler was added, resulting in greater wear. In Example 1, wollastonite was used as the filler, and its unique needle-like structure can enhance the wear resistance of the product when used in this system. Moreover, after treatment with a silane coupling agent, the compatibility of the filler with other interfaces is improved, thereby strengthening its bonding strength.

[0059] In Comparative Example 3, since no polyolefin resin and epoxy curing agent were added, the surface coating of the aluminum-plastic composite film directly fell off and had poor adhesion.

[0060] The surface of the nylon layer in the aluminum-plastic composite film of Comparative Example 4 does not contain a coating, and the friction is also relatively high, which is not conducive to deep punching. At the same time, the electrolyte resistance and wear resistance are poor.

[0061] In summary, by compounding raw materials such as polytetrafluoroethylene emulsion, polyolefin resin, epoxy curing agent, organic solvent, filler, stearamide emulsion to prepare a coating liquid, and forming a coating on the surface of the nylon layer, the forming performance, wear resistance and corrosion resistance of the aluminum-plastic film can be greatly improved.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the scope of protection of the present invention. Although the present invention is described in detail with reference to the preferred embodiments, it is not limited to those listed in the embodiments. Those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. An aluminum-plastic composite film comprising an aluminum foil, a nylon layer on one side of the aluminum foil, and a heat-sealing layer on the other side of the aluminum foil, characterized in that: A coating is provided on a side of the nylon layer away from the aluminum foil, and the coating is formed by a coating liquid for aluminum-plastic composite film. The coating liquid for aluminum-plastic composite film is prepared from raw materials, in parts by weight, including 1-5 parts of polytetrafluoroethylene emulsion, 1-10 parts of polyolefin resin, 1-5 parts of epoxy curing agent, 80-100 parts of organic solvent, 0.05-1 part of filler, and 0.05-1 part of stearic acid amide emulsion. The filler is selected from wollastonite powder. The filler is treated with a silane coupling agent. The stearic acid amide particle size in the stearic acid amide emulsion is less than 10 μm, and the viscosity of the stearic acid amide emulsion is 100-200 MPa.s.

2. The aluminum-plastic composite film according to claim 1, characterized in that The melting point of the polytetrafluoroethylene resin in the polytetrafluoroethylene emulsion is 200-327°C.

3. The aluminum-plastic composite film according to claim 1, characterized in that The pH of the polytetrafluoroethylene emulsion is set at 7-8.

4. The aluminum-plastic composite film according to claim 1, characterized in that The organic solvent is selected from at least one of ethyl acetate, butanone and cyclohexane.

5. The aluminum-plastic composite film according to claim 1, characterized in that The method for preparing the coating liquid for aluminum-plastic composite film comprises the steps of: (1) Add part of the organic solvent into the reaction device and heat it, then add the filler and epoxy curing agent and stir evenly; (2) adding stearamide emulsion into the reaction apparatus and stirring evenly; (3) adding the polyolefin resin to the remaining organic solvent and stirring uniformly, then adding the polytetrafluoroethylene emulsion and stirring uniformly to obtain material A; (4) Add material A to the reaction device and stir evenly. After the reaction is completed, a coating liquid is obtained.

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