A method for preparing a low-polarity polyfunctional acrylate resin

Abstract

This invention discloses a method for preparing a low-polarity polyfunctional acrylate resin. A hydroxyl-terminated polybutadiene liquid rubber with a molecular weight of 2000-4500 is selected, and the low-polarity polyfunctional acrylate resin is synthesized through a three-step method. The main characteristic of this low-polarity polyfunctional acrylate resin is that each end of the molecular chain contains a highly reactive double bond, and multiple active double bonds are introduced into the side chains. The low-polarity polyfunctional acrylate resin of this invention can be cured by free radical initiation. The cured product has an adjustable modulus and low polarity, thus exhibiting excellent resistance to polar chemicals.

Description

Technical Field

[0001] A method for preparing a low-polarity polyfunctional acrylate resin relates to a flexible polymer liquid polybutadiene rubber modified acrylate resin, belonging to the field of adhesive application technology. Background Technology

[0002] In recent years, with the rapid development of the new energy vehicle industry and the power storage industry, lithium-ion battery technology has also been rapidly iterating and updating. Lithium-ion batteries have many advantages such as high energy density and long cycle life. Besides the external casing, the main internal structure of a lithium battery includes the positive electrode, negative electrode, separator, and polar chemicals. Pressure-sensitive adhesive tape is often used in the bonding of the insulating parts of the positive and negative electrode tabs and the fixing of the cell termination parts during lithium battery assembly. This pressure-sensitive tape needs to have resistance to polar chemicals. Currently, traditional pressure-sensitive tapes are mostly made of low molecular weight polymers, which exhibit significant adhesion attenuation and even delamination during long-term contact and immersion in polar chemicals. The low-polarity polyfunctional acrylate resin with excellent resistance to polar chemicals prepared in this invention can be applied to pressure-sensitive tapes, overcoming the disadvantage of significant adhesion attenuation during long-term contact and immersion in polar chemicals, and has relatively broad market application prospects. Summary of the Invention

[0003] This invention discloses a method for preparing a low-polarity polyfunctional acrylate resin. The invention uses hydroxyl-terminated polybutadiene liquid rubber with a molecular weight of 2000-4500 and synthesizes a low-polarity polyfunctional acrylate resin through a three-step method. The main characteristic of this acrylate resin is that each end of the molecular chain contains a highly reactive double bond, and multiple active double bonds are introduced into the side chains. The acrylate resin of this invention can be cured by free radical initiation, and the cured product has an adjustable modulus and low polarity, thus exhibiting excellent resistance to polar chemicals.

[0004] The general structural formula of low-polarity polyfunctional acrylate resins is shown below:

[0005] Where n1 = 15 - 20; R1 structural formula:

[0006] R2 represents one of the following: hexamethylene diisocyanate, toluene diisocyanate, and isophorone diisocyanate whose molecular structures do not contain the isocyanate portion; n2 = 1, 2, 3; When n2=1, R3 represents

[0007] When n2=2, R3 represents ; When n2=3, R3 represents ; The specific synthesis steps are as follows: Step 1: Hydroxyl-terminated polybutadiene liquid rubber and a thiol compound undergo a Michael addition reaction under alkaline amine catalysis. An appropriate amount of initiator is added, the reaction temperature is 40-60℃, and the reaction time is 6-8 hours. Thiol groups are introduced into the side chains. Preferably, the molar ratio of hydroxyl-terminated polybutadiene liquid rubber to the thiol compound is 1:(4-8), the initiator dosage is 1%-3% of the total system weight, and the alkaline amine catalyst dosage is 0.5%-5% of the total system weight. Step 2: Add the product from Step 1 to diisocyanate and react with -OH and -SH functional groups to introduce -NCO groups. The reaction temperature is 70-80℃ and the reaction time is 2-4h. The isocyanate is one of hexamethylene diisocyanate, toluene diisocyanate, and isophorone diisocyanate.

[0008] When n2=1, the preferred molar ratio of the first step product to isocyanate is 1:(6~10). When n2=2, the preferred molar ratio of the first step product to isocyanate is 1:(10~18). When n2=3, the preferred molar ratio of the first step product to isocyanate is 1:(14~26). Step 3: Add the reaction product from step 2 to hydroxyethyl acrylate and react for 3-4 hours at a temperature of 70-80°C to obtain the low-polarity polyfunctional acrylate resin of this invention.

[0009] When n2=1, the preferred molar ratio of the second step product to hydroxyethyl acrylate is 1:(6~10). When n2=2, the preferred molar ratio of the second step product to hydroxyethyl acrylate is 1:(10~18). When n2=3, the preferred molar ratio of the second step product to hydroxyethyl acrylate is 1:(14~26). Furthermore, the basic amine catalyst is one or a combination of triethylamine, tripropylamine, and tributylamine; The initiator is further selected from one or more of azobisisobutyronitrile, benzoyl peroxide, and cumene hydroperoxide; Furthermore, the selected difunctional thiols, trifunctional thiols, and tetrafunctional thiols introduce sulfhydryl functional groups with different branched structures into the side chains of terminal hydroxyl polybutadiene. The sulfhydryl functional groups with different branched structures are converted into double bond functional groups through the isocyanate reaction route, and finally a low polarity polyfunctional acrylate resin is generated. Alkaline gel catalysts and initiators improve the reaction efficiency of double bonds and sulfhydryl groups in the first step of the reaction, thereby reducing the reaction temperature and shortening the reaction time. The beneficial effects of this invention are that the low-polarity polyfunctional acrylate resin can be cured by free radical initiation, and the cured product has adjustable modulus and low polarity. This invention forms a higher crosslinking density during the free radical initiation polymerization process, thereby effectively improving the resistance to polar chemicals. Detailed Implementation

[0010] The principles and features of the present invention are described below. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0011] Example 1 (when n2=1) 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 down to 50℃, add 4.15g of triethylamine and 8g of azobisisobutyronitrile, and continue the reaction for 7 hours. Step 2: Raise the temperature of the product from step 1 to 75°C, add 120g of hexamethylene diisocyanate, and react for 3 hours. Step 3: Add 82g of hydroxyethyl acrylate to the isocyanate-capped product from step 2, and continue the reaction at 75°C for 3.5h to obtain the final reaction product.

[0012] Example 2 (when n2=2) 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 continue the reaction for 7 hours. Step 2: Raise the temperature of the product from step 1 to 75℃, add 227g of toluene diisocyanate, and react for 3 hours. Step 3: Add 152g of hydroxyethyl acrylate to the product of the second step reaction, and continue the reaction at 75℃ for 3.5h to obtain the final reaction product.

[0013] Example 3 (when n2=3) 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 continue the reaction for 7 hours. Step 2: Raise the temperature of the product from step 1 to 75°C, add 350g of isophorone diisocyanate, and react for 3 hours. Step 3: Add 183g of hydroxyethyl acrylate to the isocyanate-capped product from step 2, and continue the reaction at 75°C for 3.5h to obtain the final reaction product.

[0014] The effects of the photocurable adhesives prepared from the high molecular weight methacrylate resins described in Examples 1-3 of the present invention and the ordinary methacrylate resin of Comparative Example 1 on the performance parameters of the photocured products were verified by the following formulation experiments.

[0015] The acrylate resin of the present invention 86 copies Ordinary acrylic resin 86 copies Isoborneol acrylate 10 copies Isoborneol acrylate 10 copies Benzoin diethyl ether (651 initiator) 2 copies Benzoin diethyl ether (651 initiator) 2 copies 1-Hydroxycyclohexylphenyl ketone (184 initiator) 2 copies 1-Hydroxycyclohexylphenyl ketone (184 initiator) 2 copies

[0016] Formulation Example 1 Step 1: Add 86 parts of acrylate resin, 10 parts of isoborneol acrylate, 2 parts of 651 initiator, and 2 parts of 184 initiator of Example 1 of this invention to the mixing vessel, and stir for 30 minutes under light-protected conditions.

[0017] Step 2: Vacuum stir for 30 minutes, vacuum degree < -0.09Mpa, discharge under light-proof conditions, and seal and store in a light-proof environment.

[0018] Formulation Example 2 Step 1: Add 86 parts of acrylate resin, 10 parts of isoborneol acrylate, 2 parts of 651 initiator, and 2 parts of 184 initiator of Example 2 of this invention to the mixing vessel, and stir for 30 minutes under light-protected conditions.

[0019] Step 2: Vacuum stir for 30 minutes, vacuum degree < -0.09Mpa, discharge under light-proof conditions, and seal and store in a light-proof environment.

[0020] Formulation Example 3 Step 1: Add 86 parts of acrylate resin, 10 parts of isoborneol acrylate, 2 parts of 651 initiator, and 2 parts of 184 initiator of Example 3 of the present invention to the mixing vessel, and stir for 30 minutes under light-protected conditions.

[0021] Step 2: Vacuum stir for 30 minutes, vacuum degree < -0.09Mpa, discharge under light-proof conditions, and seal and store in a light-proof environment.

[0022] Formula Comparison 1 Step 1: Add 86 parts of ordinary acrylate resin, 10 parts of isoborneol acrylate, 2 parts of 651 initiator, and 2 parts of 184 initiator to the mixing tank, and stir for 30 minutes under light-protected conditions.

[0023] Step 2: Vacuum stir for 30 minutes, vacuum degree < -0.09Mpa, discharge under light-protected conditions, and store in a sealed, light-protected container.

[0024] Test Experiment 1: Modulus Test Equipment used: TA DMA-Q800 (USA) Test Experiment 2: Weight Gain Test for Absorption Rate of Polar Chemicals A 365nm wavelength LED light source was used to fully cure the sample, which was then thoroughly immersed in polar chemicals and tested at 25℃ and 50% humidity. Sample dimensions: length * width * thickness = 20 * 20 * 1 (mm);

[0025] Note: Dimethyl carbonate is selected as the polar chemical.

[0026] After soaking in polar chemicals for 168 hours, no dissolution was observed on the surface of the formulations in Examples 1-3. After soaking in polar chemicals for 168 hours, the solidified material in Formulation Comparative Example 1 had mostly dissolved and the surface was sticky and stringy, making it no longer suitable for the test method of weight gain from absorption of polar chemicals. As can be seen from Table 1, the low-polarity polyfunctional acrylate resin synthesized in this invention has excellent resistance to polar chemicals. After photocuring, it has different moduli, with room temperature moduli ranging from 800 MPa to 4000 MPa, which is adjustable. Furthermore, the cured product has good resistance to polar chemicals.

[0027] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of 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 method for preparing a low-polarity polyfunctional acrylate resin, characterized in that, The general structural formula of the low-polarity polyfunctional acrylate resin is shown below: ； Where n1 = 15 - 20; R1 structural formula: ; R2 represents one of the following: hexamethylene diisocyanate, toluene diisocyanate, and isophorone diisocyanate whose molecular structures do not contain the isocyanate portion; n2=1，2，3； When n2=1, R3 represents ; When n2=2, R3 represents ; When n2=3, R3 represents .

2. The method for preparing a low-polarity polyfunctional acrylate resin according to claim 1, characterized in that, The synthesis steps are as follows: Step 1: Hydroxyl-terminated polybutadiene liquid rubber and thiol compounds undergo a Michael addition reaction under alkaline amine catalysis, with the addition of an appropriate amount of initiator, reaction temperature 40-60℃, reaction time 6-8h; thiol groups are introduced into the side chain; Step 2: Add the product from Step 1 to diisocyanate, react at 70-80℃ for 2-4 hours; the isocyanate is one of hexamethylene diisocyanate, toluene diisocyanate, and isophorone diisocyanate. Step 3: Add the reaction product from step 2 to hydroxyethyl acrylate and react for 3-4 hours at a temperature of 70-80℃ to obtain a low-polarity polyfunctional acrylate resin.

3. The method for preparing a low-polarity polyfunctional acrylate resin according to claim 2, characterized in that, The alkaline amine catalyst is one or a combination of triethylamine, tripropylamine, and tributylamine.

4. The method for preparing a low-polarity polyfunctional acrylate resin according to claim 2, characterized in that, The initiator is one or a combination of azobisisobutyronitrile, benzoyl peroxide, and cumene hydroperoxide.

5. The method for preparing a low-polarity polyfunctional acrylate resin according to claim 2, characterized in that, The thiol compound is one of the following: a difunctional thiol compound, a trifunctional thiol compound, or a tetrafunctional thiol compound.

6. The method for preparing a low-polarity polyfunctional acrylate resin according to claim 2, characterized in that, In the first step, the molar ratio of hydroxyl-terminated polybutadiene liquid rubber to thiol compound is 1:(4-8).

7. The method for preparing a low-polarity polyfunctional acrylate resin according to claim 2, characterized in that, In the first step, the amount of initiator used is 1% to 3% of the total weight fraction of the system.

8. The method for preparing a low-polarity polyfunctional acrylate resin according to claim 2, characterized in that, In the first step, the amount of alkaline amine catalyst used is 0.5% to 5% of the total weight of the system.

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