A methacrylate structural adhesive with excellent electrolyte resistance and its preparation method

Abstract

This invention relates to the field of adhesive technology, and particularly to a methacrylate structural adhesive with excellent electrolyte resistance and its preparation method. The methacrylate structural adhesive with excellent electrolyte resistance provided by this invention comprises component A and component B; component A, by weight, comprises: 1-15 parts methacrylic acid, 30-50 parts methacrylate monomer, 19-30 parts elastomer toughening agent, 10-20 parts low-polarity polyfunctional acrylate resin, 0.8-2.0 parts reducing agent, and 0.05-0.6 parts stabilizer; component B, by weight, comprises: 30-50 parts plasticizer, 25-45 parts oxidant, 20-40 parts epoxy resin, and 0.1-0.5 parts pigment. In addition to the advantages of conventional acrylate structural adhesives such as fast curing speed and high bonding strength, the methacrylate structural adhesive provided by this invention also exhibits excellent electrolyte resistance in the cured product.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, and in particular to a methacrylate structural adhesive with excellent resistance to electrolytes and its preparation method. Background Technology

[0002] Acrylic structural adhesives offer numerous advantages, including rapid room temperature curing, good toughness, and a wide range of bonding materials, making them widely used in structural component bonding in industries such as electronics and electrical appliances. In recent years, with the rapid development of the new energy vehicle and power storage industries, lithium-ion battery technology has also been rapidly iterating and updating. Lithium-ion batteries boast advantages such as high energy density and long cycle life. Besides the external structural casing, the main internal structures of a lithium battery include the positive electrode, negative electrode, separator, and electrolyte. During lithium battery assembly, pressure-sensitive adhesive tapes are often used for bonding the insulating parts of the positive and negative electrode tabs and fixing the cell termination parts. These pressure-sensitive tapes need to have electrolyte resistance. Currently, traditional pressure-sensitive tapes are mostly made from low molecular weight polymers, which experience significant adhesion weakening and even delamination during long-term contact and immersion in electrolyte.

[0003] Therefore, there is an urgent need to develop a methacrylate structural adhesive with excellent electrolyte resistance to replace the traditional pressure-sensitive tape, in order to overcome the disadvantage of the traditional pressure-sensitive tape having large adhesion attenuation during long-term contact and immersion in electrolyte. Summary of the Invention

[0004] To address the aforementioned technical problems in the prior art, this invention provides a methacrylate structural adhesive with excellent electrolyte resistance and its preparation method.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0006] The first aspect of the present invention is to provide a methacrylate structural adhesive with excellent electrolyte resistance, comprising component A and component B; wherein component A comprises, by weight parts: 1-15 parts methacrylic acid, 30-50 parts methacrylate monomer, 19-30 parts elastomer toughening agent, 10-20 parts low polarity polyfunctional acrylate resin, 0.8-2.0 parts reducing agent, and 0.05-0.6 parts stabilizer; wherein component B comprises, by weight parts: 30-50 parts plasticizer, 25-45 parts oxidant, 20-40 parts epoxy resin, and 0.1-0.5 parts pigment.

[0007] Based on the above technical solution, the present invention can also be improved in the following ways:

[0008] Furthermore, the low-polarity polyfunctional acrylate resin has the structure shown in formula (I):

[0009]

[0010] Where n1 is an integer between 15 and 20, and n2 is 1, 2, or 3;

[0011] R1 has the structure shown in equation (II):

[0012]

[0013] The technical effect of adopting the above-mentioned further technical solution is that the low polarity polyfunctional acrylate resin contains a double bond (C=C) at each end of the molecular chain and introduces multiple double bonds (C=C) into the side chains, which greatly improves the reactivity.

[0014] Furthermore, when n2 = 1, R2 has the structure shown in (III-1):

[0015] -CH2-CH2-CH2-

[0016] (III-1);

[0017] When n2 = 2, R2 has the structure shown in (III-2):

[0018]

[0019]

[0020] When n2 = 3, R2 has the structure shown in (III-3):

[0021]

[0022] The technical effect of adopting the above-mentioned further technical solution is that: when n2 takes different values, that is, when the branch chain of the low polarity polyfunctional acrylate resin contains different numbers of C=C active double bonds, the reactivity can be improved to different degrees; when n2=1, the structure connected to R2 contains 1 C=C structure; when n2=2, the structure connected to R2 contains 2 C=C structures; when n2=3, the structure connected to R2 contains 3 C=C structures.

[0023] Furthermore, the low-polarity polyfunctional acrylate resin is prepared using the following steps:

[0024] S1. An initiator is added to a mixture of hydroxyl-terminated polybutadiene liquid rubber and thiol compounds, and an addition reaction is carried out under the catalysis of basic amine. The reaction temperature is controlled at 40-60℃ and the reaction time is 6-8h to obtain an intermediate product.

[0025] S2. Add ethyl isocyanate acrylate and react with the intermediate product to obtain the low-polarity polyfunctional acrylate resin.

[0026] The technical advantages of the above-mentioned further technical solution are as follows: The low-polarity polyfunctional acrylate resin of the present invention is obtained by a two-step synthesis of hydroxyl-terminated polybutadiene liquid rubber with a molecular weight of 2000-4500. In step S1, the Michael addition reaction introduces mercapto groups into the side chains of the hydroxyl-terminated polybutadiene liquid rubber. In step S2, ethyl isocyanate is added and reacts with the -OH and -SH groups in the intermediate product obtained in S1 to obtain the low-polarity polyfunctional acrylate resin product. The advantage of using ethyl isocyanate is that, compared to traditional polyurethane acrylate synthesis products where each molecular chain contains two polar urethane bonds at both ends, the product synthesized in the present invention contains only one polar urethane bond at each end of the molecular chain. This further reduces the polarity of the product and also further reduces its viscosity, resulting in better processability.

[0027] Furthermore, the basic amine catalyst is one or a combination of triethylamine, tripropylamine, and tributylamine; the initiator is one or a combination of azobisisobutyronitrile, benzoyl peroxide, and cumene hydroperoxide; and the thiol compound is one or a combination of 1,3-propanedithiol, trimethylolpropane tris(3-mercaptopropionate), and pentaerythritol tetrakis(3-mercaptopropionic acid) ester.

[0028] The technical effect of adopting the above-mentioned further technical solution is that by using thiol compounds with different functionalities, after reacting with hydroxyl-terminated polybutadiene liquid rubber, a low polarity polyfunctional acrylate resin with different structures in the side chain can be finally generated.

[0029] Furthermore, the molar ratio of the hydroxyl-terminated polybutadiene liquid rubber to the thiol compound is 1:(4-8), the amount of initiator is 1% to 3% of the weight of the mixture of the hydroxyl-terminated polybutadiene liquid rubber and the thiol compound, and the amount of alkaline amine catalyst is 0.5% to 5% of the weight of the mixture of the hydroxyl-terminated polybutadiene liquid rubber and the thiol compound.

[0030] Furthermore, when n2 = 1, the molar ratio of the intermediate product to ethyl isocyanate acrylate is 1:(6-10); when n2 = 2, the molar ratio of the intermediate product to ethyl isocyanate acrylate is 1:(10-18); and when n2 = 3, the molar ratio of the intermediate product to ethyl isocyanate acrylate is 1:(14-26).

[0031] Furthermore, the methacrylate monomer is one or a mixture of two or more of methyl methacrylate, tetrahydrofuran methacrylate, and 2-phenoxyethyl methacrylate; the elastomer toughening agent is one or a mixture of two or more of ABS, MBS, and SBS; the reducing agent is one or a mixture of two or more of tetramethylthiourea, N,N-dimethyl-p-toluidine, N,N-dihydroxyethyl-p-toluidine, N-methyl-N-hydroxyethyl-p-toluidine, and triphenylphosphine; and the stabilizer is one or a mixture of two or more of thiodiphenylamine, p-hydroxyanisole, p-tert-butylcatechol, and tetrasodium ethylenediaminetetraacetate.

[0032] Furthermore, the plasticizer is alkyl benzyl phthalate; the oxidant is one or any mixture of benzoyl peroxide, lauroyl peroxide, or cumene hydroperoxide; the epoxy resin is at least one of E51 and E44; and the pigment is Prussian blue.

[0033] Furthermore, the volume ratio of component A to component B is 10:1.

[0034] Another aspect of the present invention is to provide a method for preparing the above-mentioned methacrylate structural adhesive with excellent electrolyte resistance, comprising the following steps:

[0035] (1) Preparation of component A: Add methacrylic acid, methacrylate monomer and elastomer toughening agent according to the weight parts, stir at high speed for 1.5h until the material is a uniform and fine paste, then add low polarity polyfunctional acrylate resin, reducing agent and stabilizer in sequence, stir at high speed for 1h, and finally degas for 5min, and discharge the material to obtain component A.

[0036] (2) Preparation of component B: Epoxy resin and plasticizer are added to the reactor and stirred evenly for 0.5h, oxidant is added and stirred at low speed for 1h, pigment is added and stirred at low speed for 1h, and finally vacuum is applied for 5min to remove bubbles. Component B can be obtained by discharging the material.

[0037] (3) Mixing component A with component B yields the methacrylate structural adhesive with excellent electrolyte resistance.

[0038] Furthermore, the high-speed stirring speed is 800 rpm / min, and the low-speed stirring speed is 400 rpm / min.

[0039] Compared with the prior art, the present invention has the following technical effects:

[0040] This invention provides a methacrylate structural adhesive with excellent electrolyte resistance. By adding a self-synthesized low-polarity polyfunctional acrylate resin and other components to its composition, and adjusting the ratio of each component, the synthesized methacrylate structural adhesive not only has the advantages of conventional acrylate structural adhesives such as fast curing speed and high bonding strength, but also has good electrolyte resistance in the cured product. Detailed Implementation

[0041] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Although the description of the present invention is presented in conjunction with preferred embodiments, this does not mean that the features of the invention are limited to these embodiments. On the contrary, the purpose of describing the invention in conjunction with embodiments is to cover other options or modifications that may be derived based on the claims of the present invention. To provide a deep understanding of the invention, many specific details will be included in the following description. The invention may also be implemented without using these details. Furthermore, to avoid confusion or obscuring the focus of the invention, some specific details will be omitted in the description. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0042] Example 1

[0043] The components are as follows:

[0044]

[0045] The specific preparation steps are as follows:

[0046] The preparation process of component A is as follows: First, add 12.6g of methacrylic acid, 46g of methyl methacrylate, and 25g of ABS, and stir at high speed for 1.5h until the material is a uniform and fine paste. Then, add 15g of low polarity polyfunctional acrylate resin, 1.2g of N,N-dimethyl-p-toluidine, and 0.2g of p-tert-butylcatechol in sequence, and stir at 800rpm / min for 1h. Finally, degas under vacuum for 5min to obtain the finished product component A. The preparation process of component B is as follows: Add 21.88g of E44 epoxy resin and 48g of plasticizer alkyl benzyl phthalate to the reactor and stir evenly for 0.5h. Add 30.0g of lauroyl peroxide and stir at low speed for 1h. Then, add 0.12g of Prussian blue and stir at 400rpm / min for 1h. Finally, degas under vacuum for 5min to obtain the finished product component B. Mix component A and component B in a volume ratio of 10:1 to obtain the methacrylic acid structural adhesive.

[0047] The synthesis steps of the low-polarity polyfunctional acrylate resin are as follows (when n2 = 1):

[0048] Step 1: Take 350g of hydroxyl-terminated polybutadiene liquid rubber and 64.8g of 1,3-propanedithiol, heat to 110℃, vacuum for 2.5 hours to remove moisture and other small molecule impurities, cool to 50℃, add 4.15g of triethylamine and 8g of azobisisobutyronitrile, and react for 7 hours.

[0049] Step 2: Add 100g of ethyl isocyanate acrylate to the product from Step 1, and continue the reaction at 75℃ for 3.0h to obtain the final reaction product.

[0050] Example 2

[0051] The components are as follows:

[0052]

[0053] The specific preparation steps are as follows:

[0054] The preparation process of component A is as follows: First, add 13g of methacrylic acid, 48g of tetrahydrofuran methacrylate, and 19g of MBS, and stir at high speed for 1.5h until the material is a uniform and fine paste. Then, add 18g of low polarity polyfunctional acrylate resin, 1.5g of N,N-dihydroxyethyl p-toluidine, and 0.5g of p-hydroxyanisole in sequence, and stir at 800rpm / min for 1h. Finally, degas under vacuum for 5min to obtain the finished product component A. The preparation process of component B is as follows: Add 21.88g of E51 epoxy resin and 45g of plasticizer alkyl benzyl phthalate to the reactor and stir evenly for 0.5h. Add 33.0g of benzoyl peroxide and stir at low speed for 1h. Then, add 0.12g of Prussian blue and stir at 400rpm / min for 1h. Finally, degas under vacuum for 5min to obtain the finished product component B. Mix component A and component B in a volume ratio of 10:1 to obtain the methacrylic acid structural adhesive.

[0055] The synthesis steps of the low-polarity polyfunctional acrylate resin are as follows (when n2 = 2):

[0056] Step 1: Take 370g of hydroxyl-terminated polybutadiene liquid rubber and 270g of trimethylolpropane tris(3-mercaptopropionate), heat to 110℃, vacuum for 2.5 hours to remove moisture and other small molecule impurities, cool to 50℃, add 6.4g of tripropylamine and 9.8g of benzoyl peroxide, and react for 7 hours.

[0057] Step 2: Add 184g of ethyl isocyanate acrylate to the product from Step 1, and continue the reaction at 75°C for 3.0h to obtain the final reaction product.

[0058] Example 3

[0059] The components are as follows:

[0060]

[0061] The specific preparation steps are as follows:

[0062] The preparation process of component A is as follows: First, add 11g of methacrylic acid, 49.6g of 2-phenoxyethyl methacrylate, and 21g of SBS, and stir at high speed for 1.5h until the material is a uniform and fine paste. Then, add 16g of low-polarity polyfunctional acrylate resin, 1.8g of N-methyl-N-hydroxyethyl p-toluidine, and 0.6g of thiodiphenylamine in sequence, and stir at 800rpm / min for 1h. Finally, degas under vacuum for 5min, and the finished product component A can be obtained by discharging. B The preparation process of the components is as follows: 29.88g of E44 epoxy resin and 44g of plasticizer alkyl benzyl phthalate are added to the reaction vessel and stirred evenly for 0.5h. Then, 26.0g of lauroyl peroxide is added and stirred at low speed for 1h. Then, 0.12g of Prussian blue is added and stirred at 400rpm / min for 1h. Finally, vacuum is applied for 5min to remove bubbles, and the finished product B component is obtained. Component A and component B are mixed at a volume ratio of 10:1 to obtain methacrylate structural adhesive.

[0063] The synthesis steps for low-polarity polyfunctional acrylate resin are as follows (when n2 = 3):

[0064] Step 1: Take 360g of hydroxyl-terminated polybutadiene liquid rubber and 330g of pentaerythritol tetrakis(3-mercaptopropionic acid) ester, heat to 110℃, vacuum for 2.5 hours to remove moisture and other small molecule impurities, cool to 50℃, add 8g of tributylamine and 12g of cumene hydroperoxide, and react for 7 hours.

[0065] Step 2: Add 222g of ethyl isocyanate acrylate to the product from Step 1, and continue the reaction at 75℃ for 3.0h to obtain the final reaction product.

[0066] Performance testing

[0067] The following tests were conducted to verify the performance of the methacrylate structural adhesive samples obtained in Examples 1-3 compared to ordinary acrylate structural adhesives.

[0068] Test Experiment 1: Curing Speed ​​Test

[0069] Referring to the test method in GB / T 7128-2008, the time required for room temperature curing strength to be >1 MPa was characterized by shear strength.

[0070] Test material: 3003 aluminum plate / 3003 aluminum plate;

[0071] Dimensions: 100*25*1.5mm.

[0072] Test Experiment 2: Pull-out Force Test

[0073] The determination was performed according to the method specified in GB / T 6329-1996;

[0074] Test materials: PC plastic parts / 316 stainless steel;

[0075] Dimensions: Both PC plastic parts and 316 stainless steel parts are 25*25*2.5mm.

[0076] Test Experiment 3: Modulus Test

[0077] Components A and B were mixed at a volume ratio of 10:1, and the sample was cured for 24 hours.

[0078] Equipment used: DMA-Q800 from TA Instruments, USA.

[0079] Test Experiment 4: Electrolyte Absorption Rate Weight Gain Test

[0080] Components A and B were mixed at a volume ratio of 10:1, the sample was cured for 24 hours, and then fully immersed in polar chemicals and tested at 25°C and 50% humidity.

[0081] Sample size: length * width * thickness = 20 * 20 * 1 (mm).

[0082] The performance test data for the above items are shown in Table 1.

[0083] Table 1. Performance test results of samples from Examples 1-3 and ordinary acrylic structural adhesives.

[0084]

[0085] As can be seen from Table 1, the methacrylate structural adhesive synthesized in this invention has the advantages of fast curing speed and high bonding strength. In addition, the cured product also has good electrolyte resistance and can be used for bonding the insulating parts of the positive and negative electrode tabs and fixing the cell termination parts in the lithium battery assembly process.

[0086] 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 methacrylate structural adhesive with excellent electrolyte resistance, characterized in that, The product comprises component A and component B. Component A, by weight, includes: 1-15 parts methacrylic acid, 30-50 parts methacrylic acid monomer, 19-30 parts elastomer toughening agent, 10-20 parts low-polarity polyfunctional acrylate resin, 0.8-2.0 parts reducing agent, and 0.05-0.6 parts stabilizer. Component B, by weight, includes: 30-50 parts plasticizer, 25-45 parts oxidant, 20-40 parts epoxy resin, and 0.1-0.5 parts pigment. The low-polarity polyfunctional acrylate resin has the structure shown in formula (I): （I）； Where n1 is an integer between 15 and 20, and n2 is 1, 2, or 3; R1 has the structure shown in equation (II): (II); When n2=1, R2 has the structure shown in (III-1): (III-1); When n2=2, R2 has the structure shown in (III-2): (III-2); When n2=3, R2 has the structure shown in (III-3): (III-3).

2. The methacrylate structural adhesive with excellent electrolyte resistance according to claim 1, characterized in that, The low-polarity polyfunctional acrylate resin was prepared using the following steps: S1. An initiator is added to a mixture of hydroxyl-terminated polybutadiene liquid rubber and thiol compounds, and an addition reaction is carried out under the catalysis of basic amine. The reaction temperature is controlled at 40-60℃ and the reaction time is 6-8h to obtain an intermediate product. S2. Add ethyl isocyanate acrylate and react with the intermediate product to obtain the low-polarity polyfunctional acrylate resin.

3. The methacrylate structural adhesive with excellent electrolyte resistance according to claim 2, characterized in that, The molar ratio of the hydroxyl-terminated polybutadiene liquid rubber to the thiol compound is 1:4 to 8, the amount of initiator is 1% to 3% of the weight of the mixture of the hydroxyl-terminated polybutadiene liquid rubber and the thiol compound, and the amount of basic amine catalyst is 0.5% to 5% of the weight of the mixture of the hydroxyl-terminated polybutadiene liquid rubber and the thiol compound.

4. The methacrylate structural adhesive with excellent electrolyte resistance according to claim 2, characterized in that, When n2=1, the molar ratio of the intermediate product to ethyl isocyanate acrylate is 1:6 to 10; when n2=2, the molar ratio of the intermediate product to ethyl isocyanate acrylate is 1:10 to 18; when n2=3, the molar ratio of the intermediate product to ethyl isocyanate acrylate is 1:14 to 26.

5. The methacrylate structural adhesive with excellent electrolyte resistance according to claim 2, characterized in that, The basic amine catalyst is one or a combination of triethylamine, tripropylamine, and tributylamine; the initiator is one or a combination of azobisisobutyronitrile, benzoyl peroxide, and cumene hydroperoxide; and the thiol compound is one of 1,3-propanedithiol, trimethylolpropane tris(3-mercaptopropionate), and pentaerythritol tetrakis(3-mercaptopropionic acid) ester.

6. The methacrylate structural adhesive with excellent electrolyte resistance according to claim 1, characterized in that, The methacrylate monomer is one or a mixture of two or more of methyl methacrylate, tetrahydrofuran methacrylate, and 2-phenoxyethyl methacrylate; the elastomer toughening agent is one or a mixture of two or more of ABS, MBS, and SBS; the reducing agent is one or a mixture of two or more of tetramethylthiourea, N,N-dimethyl-p-toluidine, N,N-dihydroxyethyl-p-toluidine, N-methyl-N-hydroxyethyl-p-toluidine, and triphenylphosphine; and the stabilizer is one or a mixture of two or more of thiodiphenylamine, p-hydroxyanisole, p-tert-butylcatechol, and tetrasodium ethylenediaminetetraacetate.

7. The methacrylate structural adhesive with excellent electrolyte resistance according to claim 1, characterized in that, The plasticizer is alkyl benzyl phthalate; the oxidant is one or any mixture of benzoyl peroxide, lauroyl peroxide, or cumene hydroperoxide; the epoxy resin is at least one of E51 and E44; and the pigment is Prussian blue.

8. A method for preparing a methacrylate structural adhesive with excellent electrolyte resistance as described in any one of claims 1-7, characterized in that, Includes the following steps: (1) Preparation of component A: Add methacrylic acid, methacrylate monomer and elastomer toughening agent according to the weight parts, stir at high speed for 1.5h until the material is a uniform and fine paste, then add low polarity polyfunctional acrylate resin, reducing agent and stabilizer in sequence, stir at high speed for 1h, and finally degas for 5min, and discharge the material to obtain component A. (2) Preparation of component B: Epoxy resin and plasticizer are added to the reactor and stirred evenly for 0.5h, oxidant is added and stirred at low speed for 1h, pigment is added and stirred at low speed for 1h, and finally vacuum is applied for 5min to remove bubbles, and component B is obtained by discharging. (3) Mixing component A with component B yields the methacrylate structural adhesive with excellent electrolyte resistance.

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