Uv and thermal dual-curing adhesive for bonding copper foil and pet and method for preparing the same

Abstract

The application discloses a UV and thermal double-curing adhesive for bonding copper foil and PET, which comprises the following raw materials in parts by weight: flexible double-curing epoxy acrylate 20-30 parts, polyurethane acrylate 30-45 parts, methacrylate diluent 15-25 parts, photoinitiator 2-4 parts, leveling agent 0.1-0.3 parts, and curing agent 10-20 parts. The preparation method of the adhesive is also disclosed. The packaging adhesive prepared by the application has the characteristics of short curing time, bending resistance, low volume shrinkage, high thin-coating bonding strength, high and low temperature cycle resistance, and electrolyte corrosion resistance.

Description

Technical Field

[0001] This invention relates to the field of adhesives, and in particular to a UV and heat-curing dual-curing adhesive for bonding copper foil and PET, and a method for preparing the same. Background Technology

[0002] To meet the demands of improving battery energy density, reducing weight, and lowering costs, existing technologies propose replacing some metal current collectors with lightweight polymer films. Among these, PET (polyethylene terephthalate) is widely used as a substrate for composite current collectors due to its high mechanical strength, low cost, and good film-forming properties. A typical "copper foil-adhesive layer-PET" structure is prepared through hot pressing or coating composite processes, theoretically achieving weight reduction, puncture resistance, and improved battery cycle life. However, under actual operating conditions of new energy batteries, this structure faces several key bottlenecks affecting reliability. For example, UV adhesives require very thick coatings to achieve strong adhesion, leading to increased battery volume. Existing common acrylic adhesives swell, hydrolyze, or corrode at the interface after long-term immersion in carbonate electrolyte systems. This leads to a significant decrease in the peel strength between the copper foil and the PET base film, causing local delamination, interrupting the electron transport path, increasing internal resistance, and posing a danger. Furthermore, the thermal expansion coefficients of PET and copper differ greatly. The repeated stress caused by temperature fluctuations (-20 to 80°C) and electrode volume changes during battery charging and discharging causes microcracks to appear in the interfacial adhesive layer and propagate during cycling, eventually leading to local fracture or complete peeling of the copper layer.

[0003] Therefore, there is an urgent need to provide a novel UV and heat-curing adhesive for bonding copper foil and PET, and its preparation method, to solve the above problems. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a UV and heat dual-curing adhesive for bonding copper foil and PET and its preparation method, which can solve the problems of weak adhesion, poor resistance to electrolyte corrosion, and weakened adhesion after high and low temperature impact of existing adhesives.

[0005] To solve the above-mentioned technical problems, one technical solution adopted by the present invention is: to provide a UV and heat-curing dual-curing adhesive for bonding copper foil and PET, comprising the following components by weight fraction:

[0006] 20-30 parts of flexible dual-cured epoxy acrylate

[0007] 30-45 parts of polyurethane acrylate

[0008] 15-25 parts of methacrylate diluent

[0009] 2-4 parts of photoinitiator

[0010] Leveling agent 0.1-0.3 parts

[0011] 10-20 parts of curing agent

[0012] In a preferred embodiment of the present invention, the preparation method of the flexible dual-cured epoxy acrylate is as follows: PEG200DGE is added to a container, followed by the polymerization inhibitor MEHQ and triphenylphosphine catalyst. The air in the container is replaced with nitrogen, and the temperature is raised to 75-85°C. While stirring, methacrylic acid (MAA) is added dropwise. The temperature is further raised to 90-100°C and maintained at a constant temperature for 4-6 hours, with nitrogen protection throughout the process. When the acid value is ≤5mg KOH / g, heating is stopped, and the flexible dual-cured epoxy acrylate is obtained. The chemical reaction process is as follows:

[0013]

[0014] In a preferred embodiment of the present invention, the polyurethane acrylate is a difunctional polyurethane acrylate. Specifically, commercially available difunctional polyurethane acrylates include, for example, Qianyou 3166, Shuangjian 5400, and Changxing 6148J-75.

[0015] In a preferred embodiment of the present invention, the methacrylate diluent is one or more of dicyclopentane methacrylate (HDCPMA), isobornyl methacrylate (IBOMA), and tricyclodecanedimethyl dimethacrylate (TCDMA).

[0016] In a preferred embodiment of the present invention, the photoinitiator is one or more of photoinitiator ITX, photoinitiator TPO, photoinitiator 819 and photoinitiator 184.

[0017] In a preferred embodiment of the present invention, the leveling agent is a polyether-modified siloxane, and commercially available products can be Digo 450.

[0018] In a preferred embodiment of the present invention, the curing agent is 1,3-cyclohexanedimethylamine, and commercially available products can be G240.

[0019] To solve the above-mentioned technical problems, another technical solution adopted by the present invention is: to provide a method for preparing a UV and heat-curing adhesive for bonding copper foil and PET as described in any of the preceding claims, comprising the following steps:

[0020] Step 1: Add photoinitiator to isobornyl methacrylate, heat in a water bath at 70℃-75℃ to dissolve and stir until clear and transparent, then add flexible dual-curing epoxy acrylate, polyurethane acrylate and leveling agent, and stir at 800-1000r / min to disperse evenly.

[0021] Step 2: Cool the material obtained in Step 1 to 10°C;

[0022] Step 3: Add curing agent to the material obtained in Step 2, stir, maintain the material temperature at 10°C, filter, vacuum degas, and bottle to obtain a UV and heat-curing adhesive for bonding copper foil and PET.

[0023] The beneficial effects of this invention are:

[0024] (1) The adhesive of the present invention significantly improves corrosion resistance and enhances its bonding performance after high and low temperature cycling through flexible dual-curing epoxy acrylate. Specifically, the molecular structure of flexible dual-curing epoxy acrylate has two functional groups, one epoxy group and one acrylate group, which play a linking role in the whole system, organically combining the epoxy component and the UV curing component, so that it can be both UV cured and heat cured, making the colloid a cohesive whole. Furthermore, flexible dual-curing epoxy acrylate has the characteristics of epoxy resin, thus significantly improving its aging resistance. Among the two reactive groups with different curing modes in this resin, the epoxy group has small volume shrinkage and small internal stress during the heat curing reaction, thus resulting in high bonding strength. Also, due to the small volume shrinkage, the stress change caused by temperature is small, thus maintaining high bonding strength under high and low temperature cycling. Therefore, this adhesive has both the reaction speed of UV curing and the bonding strength and aging performance of epoxy system;

[0025] (2) The adhesive of the present invention has a short UV curing and setting time, and the workpiece can be carried out in the next process after setting. The adhesive is also stable in storage and easy to operate.

[0026] (3) The adhesive of the present invention has excellent resistance to electrolyte corrosion;

[0027] (4) The encapsulating adhesive of the present invention has excellent bonding performance, is 100% solid, contains no volatile components, and does not produce toxic or harmful substances during curing, making it green and environmentally friendly. Detailed Implementation

[0028] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, a detailed description of specific embodiments of the present invention is provided. The following content is merely illustrative and explanatory of the concept of the present invention. Various modifications, additions, or similar substitutions made by those skilled in the art to the described specific embodiments, as long as they do not depart from the inventive concept or exceed the scope defined in these claims, should fall within the protection scope of the present invention.

[0029] Unless otherwise specified, all raw materials used in the following examples were commercially available.

[0030] Example 1

[0031] The flexible dual-cured epoxy acrylate used in this embodiment was prepared as follows: 100g of PEG200DGE was added to a four-necked flask, followed by 0.1g of polymerization inhibitor MEHQ and 0.5g of triphenylphosphine catalyst. Nitrogen was bubbled to displace the air in the container, and the temperature was raised to 75-85℃. While stirring, 55.5g of methacrylic acid (MAA) was added dropwise to avoid local overheating. The temperature was further raised to 90-100℃ and maintained at a constant temperature for 4-6 hours, with nitrogen protection throughout the process. When the acid value was ≤5mg KOH / g, heating was stopped, and the material was discharged into a brown bottle to obtain the flexible dual-cured epoxy acrylate.

[0032] In this embodiment, the adhesive is prepared according to the following steps:

[0033] Step 1: Take 25g of isobornyl methacrylate, add 0.5g of photoinitiator ITX and 2.1g of TPO, heat in a 70℃ water bath to dissolve and stir until clear and transparent, then add 20g of flexible dual-curing epoxy acrylate, 35g of polyurethane acrylate 3166 and 0.2g of leveling agent 450, stir and disperse at 1300rpm for 25 minutes until uniformly dispersed.

[0034] Step 2: Cool the material obtained in Step 1 to 10°C;

[0035] Step 3: Add 15g of epoxy curing agent G240 to the material obtained in Step 2, stir at 300rpm for 10 minutes, and keep the material temperature at 10℃. Filter, degas under vacuum, and bottle to obtain a UV and heat-curing adhesive for bonding copper foil and PET.

[0036] Example 2

[0037] The materials and process steps used in this embodiment are the same as those in Embodiment 1, except that the amount of the flexible double-cured epoxy acrylate used is 25g.

[0038] Example 3

[0039] The materials and process steps used in this embodiment are the same as those in Embodiment 1, except that the amount of flexible double-cured epoxy acrylate used is 30g.

[0040] Comparative Example 1

[0041] This comparative example prepared the adhesive using the same method as in Example 1, except that the flexible dual-curing epoxy acrylate was replaced with an equal amount of bisphenol A epoxy acrylate (using Miki 6175-35).

[0042] Comparative Example 2

[0043] This comparative example prepared the adhesive using the same method as in Example 1, except that the flexible dual-curing epoxy acrylate was replaced with an equal amount of aliphatic epoxy acrylate (using Changxing 6140-100).

[0044] Comparative Example 3

[0045] This comparative example uses commercially available UV adhesives as a comparison, whose main resin components are: phenolic epoxy acrylate and polyurethane acrylate.

[0046] Comparative Example 4

[0047] This comparative example uses commercially available UV adhesives as a comparison, whose main resin components are: bisphenol A epoxy acrylate and polyurethane acrylate.

[0048] The encapsulating adhesives of each embodiment and comparative example were subjected to the following performance tests:

[0049] 1. The 500-hour damp heat resistance test method involves bonding copper foil and PET with an adhesive film thickness of 1µm. After curing, the film is cut into 2.5 cm wide strips and placed in an environment with a temperature of 85℃ and a relative humidity of 85% RH for 500 hours. The peel strength at 180° after damp heat aging is compared. The main instruments used for the test are Hongjin Instruments HTK-TH-100DH (constant temperature and humidity chamber) and Zhiqu Instruments ZQ-990LA-2 (universal tensile testing machine).

[0050] 2. Test method for 500h high and low temperature cycling: Copper foil and PET are bonded with adhesive with a film thickness of 1µm. After curing, it is cut into strips 2.5 cm wide and placed in an environment of -25℃ (0.5h) to 70℃ (0.5h) for 500h. The peel strength at 180° after high and low temperature cycling impact aging is compared. The main instruments for testing are Huitai Machinery HT-LC60-502 and Zhiqu Instrument ZQ-990LA-2.

[0051] 3. Test method for electrolyte corrosivity over 72 hours: Copper foil and PET are bonded together with adhesive with a film thickness of 1µm. After curing, the film is cut into strips 2.5 cm wide and immersed in electrolyte. The strips are then placed in a 60℃ oven for 72 hours.

[0052] 4. Shear strength test method: Copper foil and PET were bonded with adhesive with a film thickness of 1µm. After curing, the film was cut into strips 2.5 cm wide and measured at 180°. The main instrument used for the test was the Zhiqu Instrument ZQ-990LA-2.

[0053] Table 1. Comparison of peel strength after aging between the examples and comparative examples

[0054] The test results of Examples 1-3 and Comparative Examples 1-2 show that the flexible dual-curing epoxy acrylate has better weather resistance than pure UV-cured resin. The flexible dual-curing epoxy acrylate makes the adhesive more resistant to electrolyte corrosion. Compared with the comparative examples and existing UV-cured adhesives on the market, the performance advantage is obvious.

[0055] This embodiment is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may use the above content as inspiration to make changes or modifications to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications listed in the above embodiments that do not depart from the technical essence of the claims of the present invention shall still fall within the scope of protection of the claims of the present invention.

Claims

1. A UV and heat-curing dual-curing adhesive for bonding copper foil and PET, characterized in that, By weight fraction, it includes the following components: 20-30 parts of flexible dual-cured epoxy acrylate 30-45 parts of polyurethane acrylate 15-25 parts of methacrylate diluent 2-4 parts of photoinitiator Leveling agent 0.1-0.3 parts 10-20 parts of curing agent.

2. The UV and heat-curing dual-curing adhesive for bonding copper foil and PET according to claim 1, characterized in that, The preparation method of the flexible dual-cured epoxy acrylate is as follows: PEG200DGE is added to a container, followed by the polymerization inhibitor MEHQ and triphenylphosphine catalyst. The air in the container is replaced with nitrogen, and the temperature is raised to 75-85℃. While stirring, methacrylic acid MAA is added dropwise. The temperature is then raised to 90-100℃ and kept constant for 4-6 hours. Nitrogen protection is maintained throughout the process. When the acid value is ≤5mg KOH / g, heating is stopped, and the flexible dual-cured epoxy acrylate is obtained.

3. The UV and heat-curing dual-curing adhesive for bonding copper foil and PET according to claim 1, characterized in that, The polyurethane acrylate is a difunctional polyurethane acrylate.

4. The UV and heat-curing dual-curing adhesive for bonding copper foil and PET according to claim 1, characterized in that, The methacrylate diluent is one or more of dicyclopentane methacrylate (HDCPMA), isobornyl methacrylate (IBOMA), and tricyclodecanedimethyl dimethacrylate (TCDMA).

5. The UV and heat-curing dual-curing adhesive for bonding copper foil and PET according to claim 1, characterized in that, The photoinitiator is one or more of photoinitiator ITX, photoinitiator TPO, photoinitiator 819, and photoinitiator 184.

6. The UV and heat-curing dual-curing adhesive for bonding copper foil and PET according to claim 1, characterized in that, The leveling agent is a polyether-modified siloxane.

7. The UV and heat-curing dual-curing adhesive for bonding copper foil and PET according to claim 1, characterized in that, The curing agent is 1,3-cyclohexanedimethylamine.

8. A method for preparing a UV and heat-curing dual-curing adhesive for bonding copper foil and PET as described in any one of claims 1 to 7, characterized in that, The steps include the following: Step 1: Add photoinitiator to isobornyl methacrylate, heat in a water bath at 70℃-75℃ to dissolve and stir until clear and transparent, then add flexible dual-curing epoxy acrylate, polyurethane acrylate and leveling agent, and stir at 800-1000r / min to disperse evenly. Step 2: Cool the material obtained in Step 1 to 10°C; Step 3: Add curing agent to the material obtained in Step 2, stir, maintain the material temperature at 10°C, filter, vacuum degas, and bottle to obtain a UV and heat-curing adhesive for bonding copper foil and PET.

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