Modified chloroprene rubber adhesive for mica tape and preparation method of modified chloroprene rubber adhesive

Abstract

The invention belongs to the technical field of adhesives, and provides a modified chloroprene rubber adhesive for a mica tape and a preparation method of the modified chloroprene rubber adhesive in order to solve the practical application problems of poor thermal conductivity, high brittleness, poor impact resistance and the like of the existing adhesive for the mica tape. The adhesive for the mica tape is prepared by modifying neoprene latex with unsaturated carboxylic acid metal salt, taking the modified neoprene latex as a main component of the adhesive for the mica tape, and taking epoxy resin, a dispersing agent, an emulsifying agent, distilled water and the like as auxiliary components in proportion. The unsaturated carboxylic acid metal salt is metal salt of carboxylate ions of acrylic acid, methacrylic acid, maleic acid and the like. And the anionic emulsifier prepared from the neoprene latex is sodium dodecyl diphenyl ether disulfonate. The initiator is an azo initiator. The obtained modified chloroprene rubber adhesive is environment-friendly, low in toxicity, small in smell and stable in performance. The main component in the latex adhesive is modified neoprene latex, so that the mica paper has good insulating property, and the mechanical property and heat-conducting property of the mica paper can be effectively enhanced.

Description

Technical Field

[0001] This invention belongs to the field of adhesive technology, specifically relating to a modified chloroprene adhesive for mica tape and its preparation method. Background Technology

[0002] Mica tape is a composite material made of reinforcing materials (such as fiberglass cloth, polyester film, etc.), mica paper and adhesive. The adhesive plays an important role in bonding the mica paper and reinforcing materials in mica tape. Although the adhesive accounts for a small proportion in mica tape, the performance of the adhesive greatly affects the mechanical properties, electrical properties and heat resistance of mica tape (Wang Wen, Xia Yu. Current status and trend of application of low-adhesion mica tape in high voltage motors [J]. Insulating Materials, 2014, 47(1):6-11).

[0003] In existing technologies, most adhesives for mica tapes are based on modified ordinary epoxy resins or ordinary linear polyester resins. These adhesives have insufficient bonding strength and poor compatibility, resulting in mica tapes with low mica basis weight, easy powder shedding, low breakdown voltage, and high dielectric loss. This leads to high heat generation and poor aging resistance in motors. Furthermore, 70%–80% of the adhesives used in the impregnation process are organic solvents such as toluene and acetone, which are released into the atmosphere during the pressing process, causing significant waste of raw materials and environmental pollution. (Research Progress on Mica-Based Composite Insulation Materials, Zhang Xiaowei et al., Materials Reports, 2015-05-25).

[0004] Epoxy resin, as an adhesive for main insulating materials, has poor thermal conductivity. Therefore, the most mainstream approach is to improve the thermal conductivity of epoxy resin, thereby improving the overall thermal conductivity of mica tape insulation (Pan Yanming, Fu Qiang. Research progress and application prospects of high thermal conductivity insulating materials for large generators [J]. Insulating Materials, 2017, 000(008):46-52. ) (Dong Fumin, Huang Zuhong, Zhou Jian. Current status and development trend of high thermal conductivity main insulating materials at home and abroad [J]. Electrical Technology, 2009, 01(No.105): 11-14.). However, pure epoxy resin cured products have a three-dimensional network structure, and the high crosslinking density will lead to high internal stress. Therefore, epoxy resin cured products are brittle and have poor impact resistance, which limits their practical application (a preparation method of adhesive for mica tape, CN201911317189.6).

[0005] Chloroprene latex is mainly composed of macromolecules with a 1,4-trans structure. Its structure is uniform, the molecular arrangement is close-knit, and a highly polar chlorine atom is present on the molecular chain, resulting in strong crystallinity and excellent tensile strength in its adhesive film. Waterborne chloroprene adhesives offer advantages such as high safety, low risk of fire, low odor, minimal environmental pollution, easy adjustment of viscosity and concentration, good operability, good adhesion, and the absence of stringing problems common in solvent-based adhesives. (Research Progress on Performance Improvement of Waterborne Chloroprene Rubber Adhesives, Peng Jun et al., Chemistry and Adhesion, 2018-1-15).

[0006] Unsaturated carboxylic acid metal salts contain unsaturated double bonds and ionic bonds. This compound is often used as a reactive reinforcing agent and is widely used in the reinforcement of hydrogenated nitrile butadiene rubber. Unsaturated zinc carboxylic acid salts can effectively improve the heat and oxygen aging resistance of hydrogenated nitrile butadiene rubber (Influence of unsaturated zinc carboxylic acid salts on the mechanical and heat and oxygen aging resistance of hydrogenated nitrile butadiene rubber, Huang Xiuxu et al., Elastomers, 225.10.25, 35(5):7-13). The mechanism of zinc dimethacrylate (ZDMA) reinforcing elastomers involves the combined effects of physical adsorption and chemical grafting of polyZDMA nanoparticles and rubber molecular chains, as well as the ionic cluster structure formed by electrostatic attraction. (LI XS, LI HQ, LAI XJ, et al. A new strategy for improving high-temperature mechanical properties of HNBR / ZDMA composites through polymerization of ZDMA promoted by zinc methylmercaptobenzimidazole[J]. Journal of Applied Polymer Science, 2023, 140(47):e54714).

[0007] Patent application number 202111044970.8 discloses a chloroprene latex adhesive for mica tape, composed of the following raw materials in parts by weight: 100 parts chloroprene latex, 4-30 parts resin, 0.1-2 parts dispersant, 0.25-1 part emulsifier, and 40-80 parts distilled water. It indicates that chloroprene latex can be applied to the chloroprene latex adhesive for mica tape. This adhesive can impart certain insulation properties to mica paper and enhance its elasticity and impact resistance; however, these properties do not meet the design requirements. Summary of the Invention

[0008] This invention provides a modified chloroprene adhesive for mica tape and its preparation method. The chloroprene latex is modified with an unsaturated carboxylic acid metal salt. The metal ions in the modified chloroprene latex can form ionic cross-linking bonds, and the presence of C-C bonds improves the latex's heat resistance. Using the modified chloroprene latex as the main component of the mica tape adhesive, and epoxy resin as an auxiliary component, it can more effectively improve the mechanical properties, insulation properties, and thermal conductivity of the mica tape.

[0009] The present invention is achieved by the following technical solution: a modified chloroprene adhesive for mica tape, wherein the modified chloroprene adhesive for mica tape is prepared from the following raw materials in the following weight ratio: 70-100 parts of modified chloroprene latex, 4-30 parts of resin, 0.1-2 parts of dispersant, 0.25-1 parts of emulsifier, and 40-80 parts of distilled water; Wherein: the modified chloroprene latex is made from the following raw materials in the following weight ratio: 100 parts chloroprene latex, 10-40 parts unsaturated carboxylic acid metal salt, 0.2-3 parts emulsifier, 0.02-0.2 parts initiator, 4-6 parts methyl methacrylate, 0.02 parts 2,6-di-tert-butyl-p-cresol, and 60-90 parts distilled water; The preparation method is as follows: 10-40 parts of unsaturated carboxylic acid metal salt are dissolved in 60-90 parts of distilled water to obtain a solution. The solution is stirred at 30-50℃ for 15-20 min. Then, the above solution and 0.2-3 parts of emulsifier are added to 100 parts of chloroprene latex. The solution is stirred at room temperature for 10-20 min. The temperature is raised to 60-90℃ and stirred at 100-150 r / min. At the same time, 0.02-0.2 parts of initiator and 4-6 parts of methyl methacrylate are added uniformly within 60-100 min to react. After stirring for 3.5-4 h, 0.02 parts of 2,6-di-tert-butyl-p-cresol are added to stop the reaction, and the modified chloroprene latex is obtained. The resin is one or more of bisphenol A type epoxy resin, phenolic type epoxy resin, and alicyclic epoxy resin mixed in any proportion; The dispersant is one or a mixture of two of polyvinyl alcohol and polyethylene glycol in any proportion; The emulsifier is one or more of nonionic emulsifiers and anionic emulsifiers mixed in any proportion.

[0010] The unsaturated carboxylic acid metal salt is a metal salt of the carboxylic acid ion of acrylic acid, methacrylic acid, or maleic acid.

[0011] The emulsifier is sodium dodecyl diphenyl ether disulfonate.

[0012] The initiator is an azo initiator.

[0013] During the latex curing process, the carboxyl groups containing active hydrogen in the latex cause the epoxy resin to open its ring, and at room temperature, it cures and crosslinks to form a stable network structure, thereby improving the cohesiveness and adhesion of the latex.

[0014] The specific steps for preparing the modified chloroprene adhesive for the mica tape are as follows: (1) Preparation of modified chloroprene latex: Unsaturated carboxylic acid metal salt is added to distilled water and stirred at 30-50℃ for 15-20 min to obtain a solution with a mass fraction of 10%-40%; the obtained solution is added to 100 parts of chloroprene latex in equal proportion, and 0.2-3 parts of sodium dodecyl diphenyl ether disulfonate emulsifier is added at the same time, and stirred at room temperature for 10-20 min; then the above chloroprene latex is heated to 60-90℃ and stirred at a rate of 100-150 r / min, and 4-6 parts of methyl methacrylate and 0.02-0.2 parts of initiator are added uniformly within 60-100 min, and after stirring for 3.5-4 h, 0.02 parts of 2,6-di-tert-butyl-p-cresol are added to end the reaction to obtain modified chloroprene latex; (2) Add the dispersant to distilled water and stir at 320-360 r / min at 40℃ for 20-35 min to obtain a dispersant aqueous solution with a mass fraction of 0.25%-1%; (3) Add the dispersant aqueous solution to the modified chloroprene latex and stir at 320-360 r / min for 12-17 min at room temperature to obtain a mixed emulsion; (4) Add the emulsifier to the remaining distilled water and stir at 600-800 r / min for 25-35 min at room temperature to obtain an emulsifier aqueous solution; (5) Add the emulsifier aqueous solution and resin to the mixed emulsion prepared in step (3), and stir at 320-360 r / min for 20-30 min at room temperature to obtain the modified chloroprene latex adhesive for mica tape.

[0015] This invention uses unsaturated carboxylic acid metal salts to modify chloroprene latex as the main component of the adhesive for mica tape. Through the formation of ionic crosslinking bonds by metal ions, the crosslinking density of the modified chloroprene latex is effectively increased, and the distribution of crosslinking bonds is more uniform, resulting in better elasticity of the mica tape. Simultaneously, the unsaturated carboxylic acid metal salts can form matrix-metal ionic bonds, which can improve the adhesion between mica and glass fiber.

[0016] Compared with existing technologies that do not use modified chloroprene rubber, the advantages of this invention are as follows: This invention uses a modified chloroprene adhesive that is free of organic solvents. The resulting modified chloroprene adhesive is environmentally friendly, low in toxicity, has little odor, and is easy to apply. The main component of this latex adhesive is modified chloroprene latex, which not only gives mica paper good insulation properties but also effectively improves and enhances the mechanical and thermal conductivity of the mica paper. Attached Figure Description

[0017] Figure 1 This is the test data for dielectric loss factor. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains, and all materials publicly cited herein and cited by them are incorporated herein by reference.

[0020] Equivalent technologies of the specific embodiments described herein that are apparent to those skilled in the art through routine experimentation are included in this application.

[0021] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the instruments and equipment used in the following examples are all standard laboratory instruments and equipment; unless otherwise specified, the experimental materials used in the following examples were all purchased from regular biochemical reagent stores.

[0022] Example 1: A chloroprene adhesive for mica tape, made from the following raw materials in the indicated weight ratios: 100 parts modified chloroprene latex, 9 parts resin C12, 0.04 parts PVA-203, 0.07 parts PVA-403, and 80 parts distilled water; The modified chloroprene latex is composed of the following raw materials in parts by weight: 15 parts magnesium methacrylate, 85 parts distilled water, 100 parts chloroprene latex, 0.6 parts emulsifier, and 4 parts methyl methacrylate.

[0023] The specific preparation method is as follows: (1) Magnesium methacrylate was added to distilled water and stirred at 40°C for 15 min. The resulting solution was added to 100 parts of chloroprene latex, and 1.2 parts of sodium dodecyl diphenyl ether disulfonate emulsifier was added at the same time. The mixture was stirred at room temperature for 10-20 min. Then the chloroprene latex was heated to 75°C and stirred at a rate of 150 r / min. At the same time, 4 parts of methyl methacrylate and 0.08 parts of initiator were added at a uniform rate within 100 min. After stirring for 3.5-4 h, 0.02 parts of 2,6-di-tert-butyl-p-cresol were added to stop the reaction, and the modified chloroprene latex was obtained.

[0024] (2) Mix 100 parts of modified chloroprene latex, 9 parts of resin C12, 0.04 parts of PVA-203, 0.07 parts of PVA-403, and 80 parts of distilled water evenly to prepare an adhesive for mica tape.

[0025] Example 2: A chloroprene adhesive for mica tape, composed of the following raw materials in parts by weight: 100 parts of modified chloroprene latex from Example 1, 6 parts of resin C12, 0.07 parts of PVA-203, 0.04 parts of PVA-403, and 70 parts of distilled water, mixed evenly to obtain the adhesive for mica tape.

[0026] Example 3: A chloroprene adhesive for mica tape, made from the following raw materials in the indicated weight ratios: 100 parts modified chloroprene latex, 13 parts bisphenol A epoxy resin, 0.05 parts PVA-203, 0.05 parts PEG-200, 0.05 parts OP-13, and 75 parts distilled water; The modified chloroprene latex is composed of the following raw materials in parts by weight: 20 parts zinc monomethacrylate, 80 parts distilled water, 100 parts chloroprene latex, 1 part emulsifier, and 4.5 parts methyl methacrylate.

[0027] The specific preparation method is as follows: (1) Zinc monomethacrylate was added to distilled water and stirred at 50°C for 15 min. The resulting solution was added to 100 parts of chloroprene latex, and 1 part of sodium dodecyl diphenyl ether disulfonate emulsifier was added at the same time. The mixture was stirred at room temperature for 10-20 min. Then the chloroprene latex was heated to 90°C and stirred at a rate of 150 r / min. At the same time, 4.5 parts of methyl methacrylate and 0.12 parts of initiator were added at a uniform rate over 100 min. After stirring for 3.5-4 h, 0.02 parts of 2,6-di-tert-butyl-p-cresol were added to stop the reaction, and the modified chloroprene latex was obtained.

[0028] (2) Mix 100 parts of modified chloroprene latex, 13 parts of bisphenol A epoxy resin, 0.05 parts of PVA-203, 0.05 parts of PEG-200, 0.05 parts of OP-13 and 75 parts of distilled water evenly to prepare an adhesive for mica tape.

[0029] Example 4: A chloroprene adhesive for mica tape, characterized in that it is composed of the following raw materials in parts by weight: 100 parts of modified chloroprene latex from Example 3, 7 parts of bisphenol A epoxy resin, 0.03 parts of PVA-203, 0.06 parts of TW-80, 0.05 parts of OP-10, and 78 parts of distilled water, which are mixed evenly to obtain the adhesive for mica tape.

[0030] Example 5: A chloroprene adhesive for mica tape, characterized in that it is composed of the following raw materials in parts by weight: 100 parts modified chloroprene latex, 7 parts bisphenol A epoxy resin, 0.02 parts PVA-203, 0.02 parts PEG-200, 0.05 parts OP-10, and 75 parts distilled water; The modified chloroprene latex has the following raw material composition in parts by weight: 30 parts zinc dimethacrylate, 70 parts distilled water, 100 parts chloroprene latex, 1.3 parts emulsifier, and 4.2 parts methyl methacrylate.

[0031] The specific preparation method is as follows: (1) Add 30 parts of zinc dimethacrylate to distilled water and stir at 65°C for 20 min. Add the resulting solution to 100 parts of chloroprene latex and 1.3 parts of sodium dodecyl diphenyl ether disulfonate emulsifier, and stir at room temperature for 10-20 min. Then heat the above chloroprene latex to 90°C and stir at a rate of 150 r / min. At the same time, add 4.2 parts of methyl methacrylate and 0.06 parts of initiator at a constant rate over 100 min. After stirring for 3.5-4 h, add 0.02 parts of 2,6-di-tert-butyl-p-cresol to stop the reaction and obtain modified chloroprene latex.

[0032] (2) Mix 100 parts of modified chloroprene latex, 7 parts of bisphenol A epoxy resin, 0.02 parts of PVA-203, 0.02 parts of PEG-200, 0.05 parts of OP-10 and 75 parts of distilled water evenly to prepare an adhesive for mica tape.

[0033] Example 6: A chloroprene adhesive for mica tape, characterized in that it is composed of the following raw materials in parts by weight: 100 parts of modified chloroprene latex from Example 5, 7 parts of bisphenol A epoxy resin, 0.03 parts of PVA-203, 0.06 parts of TW-80, 0.05 parts of OP-10, and 78 parts of distilled water, which are mixed evenly to obtain the adhesive for mica tape.

[0034] Comparative example: Neoprene adhesive for mica tape (refer to patent application number: 202111044970.8, Example 1).

[0035] The modified chloroprene adhesive for mica tape prepared in Examples 1-6 of this invention, along with a control example, were used to test the thermal conductivity of mica tape. The samples were prepared according to Appendix of GB / T 5019.13 and tested according to GB / T 29313. The test results are shown in Table 1.

[0036] Table 1: Comparison of Thermal Conductivity As shown in Table 1, the thermal conductivity of Examples 1-6 is higher than that of the control example, and also higher than the requirement of ≥0.3 W / (mk) for thermal conductivity in GB / T 5019.13. The modified chloroprene adhesive prepared by this invention has better thermal conductivity.

[0037] The dielectric loss factor of embodiments 1-6 and the comparative example of the present invention was tested in mica tape according to GB / T 34665—2017 "Method for Measurement of Dielectric Loss Factor of Motor Coil and Winding Insulation". The test results are as follows: Figure 1 As shown.

[0038] from Figure 1 It can be seen that the increase in dielectric loss factor in Examples 2-5 is smaller than that in the control example, indicating that the overall insulation structure of Examples 2-5 is better than that in the control example. This suggests that the adhesive in Examples 2-5 generates less heat during mica tape operation and has little impact on the normal operation of the components. The larger increases in dielectric loss factor in Examples 1 and 6 may be because the adhesive and resin in the mica tape cannot form a homogeneous phase. Under increased voltage, discharge occurs in the interfacial air gap, causing an increase in dielectric loss factor.

[0039] The modified neoprene adhesive for mica tape prepared in Examples 1-6 of this invention and the adhesive for mica tape in the control example were used for testing on mica tape. The flexural strength test method was performed according to GB / T 9341-2008. The volume resistivity test method was performed according to Chapter 25 of GB / T 5019.2-2023. The test results are shown in Table 2.

[0040] Table 2: Performance Characterization Comparison Table As shown in Table 2, the adhesive prepared in this invention exhibits higher flexural strength than the control example when used in mica tape, indicating better flexural strength. Furthermore, the volume resistivity is significantly increased, demonstrating a more effective improvement in the material's insulation performance. This indicates that the modified chloroprene adhesive of this invention can more effectively enhance the mechanical and insulating properties of mica tape.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A modified chloroprene adhesive for mica tape, wherein the modified chloroprene adhesive for mica tape is prepared from the following raw materials in the indicated weight ratios: 70-100 parts modified chloroprene latex, 4-30 parts resin, 0.1-2 parts dispersant, 0.25-1 part emulsifier, and 40-80 parts distilled water; in: The modified chloroprene latex is made from the following raw materials in the following weight ratio: 100 parts chloroprene latex, 10-40 parts unsaturated carboxylic acid metal salt, 0.2-3 parts emulsifier, 0.02-0.2 parts initiator, 4-6 parts methyl methacrylate, and 60-90 parts distilled water; The preparation method is as follows: 10-40 parts of unsaturated carboxylic acid metal salt are dissolved in 60-90 parts of distilled water to obtain a solution, and the solution is stirred at 30-50℃ for 15-20 min. Then, the above solution and 0.2-3 parts of emulsifier are added to 100 parts of chloroprene latex, stirred at room temperature for 10-20 min, heated to 60-90℃, stirred at 100-150 r / min, and at the same time, 0.02-0.2 parts of initiator and 4-6 parts of methyl methacrylate are added uniformly within 60-100 min to react and obtain modified chloroprene latex. The resin is one or more of bisphenol A type epoxy resin, phenolic type epoxy resin, and alicyclic epoxy resin mixed in any proportion; The dispersant is one or a mixture of two of polyvinyl alcohol and polyethylene glycol in any proportion; The emulsifier is one or more of nonionic emulsifiers and anionic emulsifiers mixed in any proportion.

2. The modified neoprene adhesive for mica tape according to claim 1, characterized in that: The unsaturated carboxylic acid metal salt is a metal salt of the carboxylic acid ion of acrylic acid, methacrylic acid, or maleic acid.

3. The modified chloroprene adhesive for mica tape according to claim 1, characterized in that: The emulsifier is sodium dodecyl diphenyl ether disulfonate.

4. The modified neoprene adhesive for mica tape according to claim 1, characterized in that: The initiator is an azo initiator.

5. A method for preparing the modified chloroprene adhesive for mica tape according to any one of claims 1-4, characterized in that: The specific steps are as follows: (1) Preparation of modified chloroprene latex: Unsaturated carboxylic acid metal salt is added to distilled water and stirred at 30-50℃ for 15-20 min to obtain a solution with a mass fraction of 10%-40%; the obtained solution is added to 100 parts of chloroprene latex in equal proportion, and 0.2-3 parts of sodium dodecyl diphenyl ether disulfonate emulsifier is added at the same time, and stirred at room temperature for 10-20 min; then the above chloroprene latex is heated to 60-90℃ and stirred at a rate of 100-150 r / min, and 4-6 parts of methyl methacrylate and 0.02-0.2 parts of initiator are added uniformly within 60-100 min, and after stirring for 3.5-4 h, 0.02 parts of 2,6-di-tert-butyl-p-cresol are added to end the reaction to obtain modified chloroprene latex; (2) Add the dispersant to distilled water and stir at 320-360 r / min at 40℃ for 20-35 min to obtain a dispersant aqueous solution with a mass fraction of 0.25%-1%; (3) Add the dispersant aqueous solution to the modified chloroprene latex and stir at 320-360 r / min for 12-17 min at room temperature to obtain a mixed emulsion; (4) Add the emulsifier to the remaining distilled water and stir at 600-800 r / min for 25-35 min at room temperature to obtain an emulsifier aqueous solution; (5) Add the emulsifier aqueous solution and resin to the mixed emulsion prepared in step (3), and stir at 320-360 r / min for 20-30 min at room temperature to obtain the modified chloroprene latex adhesive for mica tape.

Images