Green single-sided adhesive tape for lithium battery and preparation method of green single-sided adhesive tape

Abstract

The invention relates to a green single-sided adhesive tape for a lithium battery and a preparation method of the green single-sided adhesive tape, and belongs to the technical field of adhesives and lithium battery materials. The green single-sided adhesive tape for the lithium battery sequentially comprises a hot-melt pressure-sensitive adhesive layer, a PET (Polyethylene Terephthalate) base material layer and a release coating from top to bottom, comprising the following components in parts by weight: 15-30 parts of a hydrogenated styrene block copolymer, 5-10 parts of a maleic anhydride modified polyolefin copolymer, 20-40 parts of hydrogenated rosin resin, 10-20 parts of hydrogenated petroleum resin with a high softening point, 0.1-1 part of an antioxidant and 0.1-1.0 part of a curing agent. According to the invention, high-strength bonding is realized by adopting the electrolyte-resistant synthetic rubber type glue, and the long-term stability of the lithium battery adhesive tape is remarkably improved through cooperation of the green PET base material and the pigment-free pressure-sensitive adhesive layer.

Description

Technical Field

[0001] This invention relates to a green single-sided adhesive tape for lithium batteries and its preparation method, belonging to the technical field of adhesives and lithium battery materials. Background Technology

[0002] Lithium-ion batteries are rechargeable batteries that are widely used in portable electronic devices such as mobile phones and laptops, as well as electric vehicles, due to their advantages such as high operating voltage, small size, light weight, high energy, no memory effect, low self-discharge, long cycle life, and high capacity per unit density.

[0003] Internal protection mechanisms such as winding termination and bottom insulation fixation in lithium battery cells typically employ single-sided termination tape. These tapes are mostly made of transparent PET substrate coated with acrylic pressure-sensitive adhesive containing green pigment. Acrylic adhesives offer advantages such as moderate adhesion at room temperature, good adhesion, and low cost. However, existing termination adhesives suffer from weakened adhesion after immersion in electrolyte, reducing the lithium battery's drop resistance. Furthermore, the pigments added to the adhesive system pose a risk of leaching with prolonged immersion. Chinese invention patent application CN202211273053.1 uses a PI substrate coated with an electrolyte-resistant rubber-based adhesive, offering advantages such as puncture resistance and high-temperature resistance. This can be used for electrode tab bonding protection in lithium batteries; however, the PI substrate in this patented solution is expensive and has not been widely adopted. Summary of the Invention

[0004] The present invention provides a green single-sided adhesive tape for lithium batteries and a method for preparing the same, in order to solve the technical problems existing in the prior art as described above.

[0005] The technical solution provided by this invention is as follows: One objective of this invention is to provide a green single-sided adhesive tape for lithium batteries, comprising, from top to bottom, a hot-melt pressure-sensitive adhesive layer, a PET substrate layer, and a release coating. The hot-melt pressure-sensitive adhesive layer comprises, by weight, the following components: 15-30 parts of hydrogenated styrene block copolymer, 5-10 parts of maleic anhydride-modified polyolefin copolymer, 20-40 parts of hydrogenated rosin resin, 10-20 parts of high softening point hydrogenated petroleum resin, 0.1-1 parts of antioxidant, and 0.1-1.0 parts of crosslinking agent.

[0006] Based on the above technical solution, the present invention can be further improved as follows: Furthermore, the PET substrate layer is a green biaxially oriented PET substrate; the release coating is a non-silicone release coating.

[0007] Furthermore, the thickness of the hot melt pressure-sensitive adhesive layer is 2~10μm, and the thickness of the PET substrate layer is 6~12μm. Furthermore, the hydrogenated styrene block copolymer is one or two of hydrogenated styrene-polyisoprene-styrene block copolymer (SEPS) and hydrogenated styrene-polybutadiene-styrene block copolymer (SEBS), and the styrene content of the hydrogenated styrene block copolymer is 10~30wt%. Furthermore, the maleic anhydride-modified polyolefin copolymer is one or more of maleic anhydride-modified polyethylene (PP-g-MAH), maleic anhydride-modified polypropylene (PE-g-MAH), and maleic anhydride-modified ethylene and octene copolymer (POE-g-MAH).

[0008] Furthermore, the modification grafting rate of the maleic anhydride-modified polyolefin copolymer is 0.5~3.0%.

[0009] Furthermore, the hydrogenated rosin resin is an ultra-light-colored hydrogenated rosin resin, and the softening point of the hydrogenated rosin resin is 90~120℃.

[0010] Furthermore, the high softening point hydrogenated petroleum resin is a fully hydrogenated or semi-hydrogenated C9 petroleum resin, and the softening point of the high softening point hydrogenated petroleum resin is >130℃.

[0011] The second objective of this invention is to provide a method for preparing the green single-sided adhesive tape for lithium batteries as described above, comprising the following steps: (1) Weigh the raw materials of the hot melt pressure-sensitive adhesive layer according to the weight parts, dissolve them with solvent, and prepare a hot melt pressure-sensitive adhesive solution with a solid content of 20~30wt% and a viscosity of 500~3000mPas; (2) Add the adhesive solution prepared in step (1) into the transfer coating machine, and place the single-sided release film in the first unwinding unit of the transfer coating machine. Apply the adhesive solution to the release surface of the single-sided release film and dry it in the drying tunnel to obtain hot melt pressure sensitive adhesive. (3) Place the non-silicone release PET substrate into the second unwinding unit at the tail of the transfer coating machine with the non-silicone release coating side facing up. The corona machine performs corona treatment on one side and the hot melt pressure-sensitive adhesive dried in step (2) is laminated onto the surface of the PET substrate through the composite roller. The semi-finished product is then obtained by winding. (4) Place the semi-finished product in the curing workshop, cure it at 40~60℃ for 48 hours, take it out, rewind and peel off the single-sided release film, and roll it into green single-sided tape.

[0012] Furthermore, in step (2), the temperature of the drying tunnel is 80~110℃ and the time is 3~5min; in step (3), the temperature of the composite roller is 80~100℃ and the composite pressure is 0.5~0.6MPa.

[0013] The technical solution provided by this invention has the following advantages compared with the prior art: 1. This invention uses an electrolyte-resistant synthetic rubber adhesive to achieve high-strength bonding, and by combining a green PET substrate with a pigment-free pressure-sensitive adhesive layer, it significantly improves the long-term stability of the lithium battery tape.

[0014] 2. The adhesive of this invention maintains excellent bonding strength after being applied at room temperature and then soaked in electrolyte, effectively resisting electrolyte corrosion and ensuring the firmness of the bonding interface during long-term battery cycling. The pressure-sensitive adhesive layer eliminates the addition of pigments and combines with a highly stable green PET substrate, fundamentally avoiding the problem of tape discoloration caused by pigment precipitation and maintaining the consistency of battery appearance. Through material optimization, the tape maintains stable performance during long-term charge-discharge cycles, which helps to extend the overall service life and reliability of lithium batteries. Detailed Implementation

[0015] The principles and features of the present invention are described below with reference to examples. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0016] Example 1 A method for preparing green single-sided adhesive tape for lithium batteries includes the following steps: (1) In a 100L glass reactor equipped with an oil bath heating device, a condenser and a stirring device, add 75kg of solvent (toluene: methyl ethyl ketone w / w=90:10), turn on the oil bath heating circulation device, set the oil bath temperature to 70℃, and gradually add 7.5kg of hydrogenated styrene block copolymer (Karton FG1657 SEBS produced by Kerteng Polymer, styrene content 13wt%), 2.5kg of maleic anhydride modified polyolefin copolymer (Fine-Blend® CMG9801 produced by Shanghai Jiayirong), 10kg of hydrogenated rosin resin (PINECRYSTAL KE-311 produced by Arakawa Chemical, softening point 96℃), 5kg of high softening point hydrogenated petroleum resin (ARKON P-140 fully hydrogenated C9 petroleum resin produced by Arakawa Chemical, softening point 140℃), and 0.1kg of antioxidant (IRGANOX B215 produced by BASF); stir for 2 hours to obtain a pressure-sensitive adhesive composition; (2) Cool the pressure-sensitive adhesive composition to room temperature, and add 0.1 kg of curing agent (polyfunctional isocyanate, Desmodur L75 curing agent produced by Bayer) while stirring to obtain a hot melt pressure-sensitive adhesive solution with a solid content of 25%; (3) Add the adhesive solution to the transfer coating machine, and place the single-sided release film in the first unwinding unit of the transfer coating machine. Apply the adhesive solution to the release surface of the single-sided release film, and dry it through the drying tunnel to obtain hot melt pressure-sensitive adhesive. The temperature of the drying tunnel is set to 80~110℃, and the drying time is 3~5 min, with a dry adhesive thickness of 4μm. (4) Place the non-silicone release green biaxially oriented PET substrate (purchased green biaxially oriented PET substrate with a thickness of 12μm, and then coated with a non-silicone release coating) into the second unwinding unit of the transfer coating machine with the non-silicone release coating side facing up. The corona machine coronasizes one side and uses a composite roller to composite the hot melt pressure-sensitive adhesive onto the surface of the PET substrate. The temperature of the composite roller is 80~100℃ and the composite pressure is 0.5~0.6MPa. The semi-finished product with a thickness of 16μm is obtained by winding.

[0017] (5) Place the semi-finished product in the curing workshop, cure it at 40~60℃ for 48 hours, take it out, rewind and peel off the single-sided release film, roll it into green single-sided tape for lithium batteries, and cut it according to the user's width to obtain the finished product.

[0018] Example 2 The thickness of the green biaxially oriented PET substrate film was replaced with 8 μm, and everything else was the same as in Example 1.

[0019] Example 3 The thickness of the green biaxially oriented PET substrate film was replaced with 6 μm, and everything else was the same as in Example 1.

[0020] Example 4 The thickness of the dry adhesive coating was 2 μm, and everything else was the same as in Example 1.

[0021] Example 5 The thickness of the dry adhesive coating was 10 μm, and everything else was the same as in Example 1.

[0022] Comparative Example 1 The green biaxially oriented PET substrate film was replaced with a transparent PET substrate film; The pressure-sensitive adhesive composition was replaced with a polyacrylate pressure-sensitive adhesive composition: 100 kg of acrylate polymer pressure-sensitive adhesive (BLJ-1717G, 40% solids content, produced by Yantai Baolijia) was added, along with 1.5 kg of curing agent (CAT-78, produced by Yantai Baolijia) and 0.5 kg of green color paste (Green Color Paste 943, produced by Huizhou Yikai Packaging Materials). The mixture was stirred until homogeneous to obtain the polyacrylate pressure-sensitive adhesive composition. The dry adhesive coating thickness was 4 μm, and the total tape thickness was 16 μm.

[0023] Comparative Example 2 The green biaxially oriented PET substrate film was replaced with a transparent PET substrate film, and 0.5 kg of green pigment (green pigment 943 produced by Huizhou Yikai Packaging Materials) was added to the pressure-sensitive adhesive composition. Everything else was the same as in Example 1.

[0024] The performance of the single-sided adhesive tapes obtained in Examples 1-5 and Comparative Examples 1-2 was tested: 1) Peel strength test: in accordance with national standard GB / T 2792-2014; 2) Electrolyte peel strength test: A 12μm thick aluminum foil was bonded with single-sided adhesive tape, left to stand for 30 minutes, and then immersed in lithium battery electrolyte (electrolyte temperature 85℃) for 6 hours. The electrolyte mass ratio was as follows: EC:PC:DEC:EP=30:10:30:30, and the mass ratio of 1M LiPF6 lithium salt was calculated as 12.5%. After cooling to room temperature, the peel strength test was carried out according to the national standard GB / T 2792-2014. The evaluation standard requires a peel strength of 0.1N / mm or higher. 3) Electrolyte immersion color test: Immerse in electrolyte (temperature 80~90℃) for more than 6 hours, with the mass ratio of single-sided tape to electrolyte being 1:20~100. Observe the color change of the electrolyte. The evaluation criteria are: no suspended or precipitated matter, no turbidity, and a light yellow color. 4) Charge and discharge aging test: The single-sided tape is made into a secondary lithium battery and subjected to 500cycle, 1000cycle and 1500cycle charge and discharge aging tests. Then the battery is disassembled and the tape is observed to see if it loses its stickiness, fades or changes color.

[0025] Table 1. Performance test results of single-sided adhesive tapes obtained in Examples 1-5 and Comparative Examples 1-2

[0026] As can be seen from the results shown in Table 1, the green single-sided tape provided by the present invention has good adhesion performance to lithium battery electrodes, is resistant to electrolyte corrosion, reduces pigment precipitation, and solves the problem of tape discoloration after long-term charge-discharge cycles of lithium batteries, thus demonstrating its feasibility for commercial industrial use.

[0027] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A green single-sided adhesive tape for lithium batteries, comprising, from top to bottom, a hot-melt pressure-sensitive adhesive layer, a PET substrate layer, and a release coating, characterized in that, The hot melt pressure-sensitive adhesive layer comprises, by weight, the following components: 15-30 parts of hydrogenated styrene block copolymer, 5-10 parts of maleic anhydride modified polyolefin copolymer, 20-40 parts of hydrogenated rosin resin, 10-20 parts of high softening point hydrogenated petroleum resin, 0.1-1 parts of antioxidant, and 0.1-1.0 parts of curing agent.

2. The green single-sided adhesive tape for lithium batteries according to claim 1, characterized in that, The PET substrate layer is a green biaxially oriented PET substrate; the release coating is a non-silicone release coating.

3. The green single-sided adhesive tape for lithium batteries according to claim 1, characterized in that, The thickness of the hot melt pressure-sensitive adhesive layer is 2~10μm, and the thickness of the PET substrate layer is 6~12μm.

4. The green single-sided adhesive tape for lithium batteries according to claim 1, characterized in that, The hydrogenated styrene block copolymer is one or both of hydrogenated styrene-polyisoprene-styrene block copolymer and hydrogenated styrene-polybutadiene-styrene block copolymer, and the styrene content of the hydrogenated styrene block copolymer is 10~30wt%.

5. The green single-sided adhesive tape for lithium batteries according to claim 1, characterized in that, The maleic anhydride-modified polyolefin copolymer is one or more of maleic anhydride-modified polyethylene, maleic anhydride-modified polypropylene, and maleic anhydride-modified ethylene-octene copolymer.

6. The green single-sided adhesive tape for lithium batteries according to claim 1, characterized in that, The maleic anhydride-modified polyolefin copolymer has a modification grafting rate of 0.5-3.0%.

7. The green single-sided adhesive tape for lithium batteries according to claim 1, characterized in that, The hydrogenated rosin resin is an ultra-light-colored hydrogenated rosin resin, and the softening point of the hydrogenated rosin resin is 90~120℃.

8. The green single-sided adhesive tape for lithium batteries according to claim 1, characterized in that, The high softening point hydrogenated petroleum resin is a fully hydrogenated or semi-hydrogenated C9 petroleum resin, and the softening point of the high softening point hydrogenated petroleum resin is >130℃.

9. A method for preparing a green single-sided adhesive tape for lithium batteries as described in any one of claims 1 to 8, characterized in that, Includes the following steps: (1) Weigh the raw materials of the hot melt pressure-sensitive adhesive layer according to the weight parts, dissolve them with solvent, and prepare a hot melt pressure-sensitive adhesive aqueous solution with a solid content of 20~30wt% and a viscosity of 500~3000mPas; (2) Add the adhesive solution prepared in step (1) into the transfer coating machine, and place the single-sided release film in the first unwinding unit of the transfer coating machine. Apply the adhesive solution to the release surface of the single-sided release film and dry it in the drying tunnel to obtain hot melt pressure sensitive adhesive. (3) Place the non-silicone release PET substrate into the second unwinding unit of the transfer coating machine with the non-silicone release coating side facing up. The corona machine performs corona treatment on one side and the hot melt pressure-sensitive adhesive obtained in step (2) is laminated onto the surface of the PET substrate through the composite roller. The semi-finished product is then rolled up. (4) Place the semi-finished product in the curing workshop, cure it at 40~60℃ for 48 hours, take it out, rewind and peel off the single-sided release film, and roll it into green single-sided tape.

10. The preparation method according to claim 9, characterized in that, In step (2), the temperature of the drying tunnel is 80~110℃ and the time is 3~5min; in step (3), the temperature of the composite roller is 80~100℃ and the composite pressure is 0.5~0.6MPa.

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