High-temperature and high-humidity resistant epoxy magnetic circuit adhesive and preparation method thereof

Abstract

The application provides a high-temperature and high-humidity resistant epoxy magnetic circuit adhesive and a preparation method thereof. The adhesive comprises the following raw materials: bisphenol type epoxy resin, tetra-functional silicon-based epoxy resin with a structure as shown in formula I, toughening agent, mercaptan curing agent, latent curing accelerator, filler, tackifier and thixotropic agent. The tetra-functional silicon-based epoxy resin with a structure as shown in formula I is used to replace part of the bisphenol type epoxy resin, which can improve the crosslinking density of the magnetic circuit adhesive and the heat resistance, and reduce the hydrophilicity of the magnetic circuit adhesive, so that the magnetic circuit adhesive is not easy to soften in a high-temperature and high-humidity environment, and the durability is improved. The inventors find that the tetra-functional silicon-based epoxy resin with a structure as shown in formula I and the polysulfide rubber toughening agent have a synergistic effect of improving the anti-shock and anti-falling performance of the magnetic circuit adhesive.

Description

Technical Field

[0001] This invention belongs to the field of epoxy adhesive technology, specifically relating to a high-temperature and high-humidity resistant epoxy magnetic circuit adhesive and its preparation method. Background Technology

[0002] Epoxy adhesives are widely used and play a significant role in electroacoustic devices, such as the cone center, spider center, and magnetic circuit. Because the magnetic circuit requires bonding to materials with surfaces that are different from those in other parts, such as galvanized or nickel-plated passivated steel and magnets (main magnet, upper clamp) (main magnet, T-iron) (secondary magnet, T-iron), the bonding performance of the epoxy adhesive is crucial.

[0003] For example, 3M's DP100 is a transparent, high-performance, fast-curing epoxy magnetic circuit adhesive that reaches operational strength in 15-20 minutes and has good peel and shear strength.

[0004] For example, patent CN114933879B discloses an epoxy adhesive for shock-resistant and drop-resistant miniature loudspeakers, its preparation method, and its application. The epoxy adhesive includes the following raw materials: bisphenol F type epoxy resin, polythiol curing agent, latent curing accelerator, stabilizer, thermally conductive filler, and thixotropic agent. The polythiol curing agent is produced by first polymerizing acrylate monomers and unsaturated disulfide compounds to generate oligomers containing disulfide bonds. The disulfide bonds are broken under the action of a reducing agent to generate thiol groups. This curing agent has a longer and more flexible molecular chain than conventional curing agents. It not only provides a highly efficient toughening effect for epoxy adhesives, but also improves adhesion to nickel-plated, zinc-plated, and other parts due to the coordination effect of sulfur (S) with metals, thus improving the shock-resistant and drop-resistant performance of the adhesive.

[0005] While the epoxy magnetic circuit adhesive disclosed in the above technology exhibits good bonding properties, the epoxy resin softens under high temperature and humidity conditions, leading to a sharp decrease in adhesive strength and ultimately bond failure. Therefore, it is necessary to develop an epoxy magnetic circuit adhesive that is resistant to high temperature and humidity. Summary of the Invention

[0006] To solve the above-mentioned technical problems, the present invention provides a high-temperature and high-humidity resistant epoxy magnetic circuit adhesive and its preparation method. The magnetic circuit adhesive contains a tetrafunctional silicone-based epoxy resin with the structure shown in Formula I. Replacing part of the bisphenol type epoxy resin with it can improve the crosslinking density and heat resistance of the magnetic circuit adhesive, and reduce the hydrophilicity of the magnetic circuit adhesive, making the magnetic circuit adhesive less prone to softening in high-temperature and high-humidity environments and improving its durability.

[0007] A high-temperature and high-humidity resistant epoxy magnetic circuit adhesive comprises the following raw materials: bisphenol type epoxy resin, tetrafunctional silicone-based epoxy resin with the structure shown in Formula I, toughening agent, thiol curing agent, latent curing accelerator, filler, tackifier, and thixotropic agent.

[0008]

[0009] In Formula I, R1-R4 are independently selected from - and O; R5-R8 are independently selected from C3H6OCH2, C2H4COOCH2, and C 2n H 4n n is an integer from 1 to 4.

[0010] Further, it includes the following raw materials in parts by weight: 40-50 parts bisphenol type epoxy resin, 7-10 parts tetrafunctional silicone-based epoxy resin with the structure shown in Formula I, 1-3 parts toughening agent, 18-20 parts thiol curing agent, 2-3 parts latent curing accelerator, 20-30 parts filler, 1-2 parts tackifier, and 0.5-2 parts thixotropic agent.

[0011] The tetrafunctional silicone-based epoxy resin with the structure shown in Formula I is prepared by a method comprising the following steps:

[0012] Under an inert atmosphere, hydrogen-containing silane, organic solvent, catalyst, and unsaturated epoxy compound are added to a reaction vessel and mixed evenly. The mixture is heated and kept at a constant temperature for reaction. After the reaction is completed, impurities are removed by vacuum distillation to obtain a tetrafunctional silicone-based epoxy resin with the structure shown in Formula I.

[0013] The temperature is increased to 80-100℃, the reaction time is 3-5 hours, the catalyst is a 1-2.5 wt% isopropanol solution of chloroplatinic acid hydrate (H₂PtCl₆·6H₂O), the chloroplatinic acid hydrate is 0.01-0.02 wt% of the total mass of a hydrogen-containing silane and an unsaturated epoxide, the hydrogen-containing silane having four Si-H bonds, specifically selected from one or two of tetra(dimethylsilyl)silane and tetra(dimethylsiloxane). The unsaturated epoxy compound is selected from one or more combinations of glycidyl acrylate, 1,2-epoxy-5-hexene, 1,2-epoxy-9-decene, 3,4-epoxy-1-butene, and allyl glycidyl ether; the molar ratio of the hydrogen-containing silane to the unsaturated epoxy compound is 1:4.0-4.5, preferably 1:4.18-4.23; and the organic solvent is selected from one or more combinations of benzene, toluene, and xylene.

[0014] The bisphenol type epoxy resin has an epoxy value of 0.44-0.53 and is selected from one or a combination of two of bisphenol A type epoxy resin and bisphenol F type epoxy resin.

[0015] The toughening agent is selected from one or a combination of two of polysulfide rubber, urethane prepolymer, polyurethane epoxy resin, and linear phenolic epoxy resin.

[0016] Preferably, the toughening agent is polysulfide rubber, selected from one or a combination of two of Akzo LP-3, Akzo LP-33, and Akzo LP-8. The inventors have found that when the toughening agent is polysulfide rubber, the shock resistance and drop resistance of the magnetic circuit adhesive are significantly improved. They speculate that this is because the tetrafunctional silicone-based epoxy resin, as shown in Formula I, not only increases the crosslinking degree of the magnetic circuit adhesive, but also helps to increase the crosslinking degree of the polysulfide rubber, thereby enhancing the structural stability of the polysulfide rubber and further improving the toughening effect.

[0017] The active hydrogen equivalent of the thiol curing agent is 200-300 g / eq, including but not limited to one or a combination of two of Toray QE-340M from Japan and Gabriel GPM-800 from the United States.

[0018] The latent curing accelerator is an imidazole adduct, selected from one or a combination of two or more of Ajinomoto Fine Chemicals PN-23, Ajinomoto Fine Chemicals PN-23J, Ajinomoto Fine Chemicals PN-31J, and Ajinomoto Fine Chemicals PN-40.

[0019] The filler is silica powder with an average particle size of 250-600 mesh.

[0020] The tackifier is an epoxy silane coupling agent selected from one or a combination of two or more of 3-(2,3-epoxypropoxypropyl)trimethoxysilane, 3-(2,3-epoxypropoxypropyl)triethoxysilane, 3-(2,3-epoxypropoxypropyl)methyldiethoxysilane, 3-(2,3-epoxypropoxypropyl)methyldiethoxysilane, 2-(3,4-epoxyhexane)ethyltrimethoxysilane, and 2-(3,4-epoxyhexane)ethyltriethoxysilane.

[0021] The thixotropic agent is fumed silica, such as Evonik's AEROSILR974.

[0022] This invention also provides a method for preparing the above-mentioned high-temperature and high-humidity resistant epoxy magnetic circuit adhesive, comprising the following steps:

[0023] Bisphenol type epoxy resin and tetrafunctional silicone-based epoxy resin with the structure shown in Formula I are added to a kettle, heated and stirred until uniform. Toughening agent, thiol curing agent and filler are added and mixed evenly. Then, latent curing accelerator, tackifier and thixotropic agent are added and mixed until uniform. Vacuum degassing is performed to obtain the above-mentioned high temperature and high humidity resistant epoxy magnetic circuit adhesive.

[0024] The temperature is raised to 40-60℃, and the vacuum degassing is carried out by stirring for 0.5-2 hours under a vacuum of 0.1-0.2MPa.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] The magnetic circuit adhesive of this invention contains a tetrafunctional silicone-based epoxy resin with the structure shown in Formula I. Replacing part of the bisphenol type epoxy resin with it can improve the crosslinking density and heat resistance of the magnetic circuit adhesive, and reduce the hydrophilicity of the magnetic circuit adhesive, making it less prone to softening in high temperature and high humidity environments and improving its durability.

[0027] The inventors discovered that the tetrafunctional silicone-based epoxy resin shown in Formula I and the polysulfide rubber toughening agent have a synergistic effect in improving the shock resistance and drop resistance of the magnetic circuit adhesive. Detailed Implementation

[0028] The present invention will be further described below with reference to specific embodiments, but is not limited to the contents of the specification. Unless otherwise specified, all "parts" mentioned in the embodiments of the present invention are parts by weight. All reagents used are commercially available in the art.

[0029] The silica powder was purchased from Kramar, with an average particle size of 500 mesh.

[0030] The tetrafunctional silicone-based epoxy resin shown in Formula I was prepared.

[0031] Preparation Example 1

[0032] Under a nitrogen atmosphere, 1 mol of tetra(dimethylsiloxane)silane, 1.2 L of toluene, 6 g of 2 wt% isopropanol solution of chloroplatinic acid hydrate (H2PtCl6·6H2O), and 4.23 mol of allyl glycidyl ether were added to a reactor and mixed thoroughly. The mixture was heated to 90 °C and kept at that temperature for 4 h. After the reaction was completed, impurities were removed by vacuum distillation to obtain a tetrafunctional silicone-based epoxy resin with the structure shown in the following formula.

[0033]

[0034] Preparation Example 2

[0035] The rest is the same as in Preparation Example 1, except that tetra(dimethylsilyl)silane is replaced with an equimolar amount of tetra(dimethylsiloxane)silane.

[0036] Preparation Example 3

[0037] The rest is the same as in Preparation Example 1, except that an equimolar amount of 1,2-epoxy-5-hexene is used instead of allyl glycidyl ether.

[0038] Preparation Example 4

[0039] The rest is the same as in Preparation Example 1, except that the amount of allyl glycidyl ether used is 4.18 mol.

[0040] Preparation of epoxy magnetic circuit adhesive

[0041] Example 1

[0042] 40 parts of bisphenol A type epoxy resin E44 and 10 parts of tetrafunctional silicone-based epoxy resin from Preparation Example 1 were added to a reactor and heated to 60°C and stirred until homogeneous. Then, 3 parts of toughening agent Akzo LP-3, 18 parts of thiol curing agent Toray QE-340M, and 3 parts of filler silica powder were added and mixed until homogeneous. Next, 3 parts of latent curing accelerator Ajinomoto Fine Chemicals PN-23, 2 parts of tackifier 3-(2,3-epoxypropoxypropyl)trimethoxysilane, and 2 parts of thixotropic agent Evonik AEROSIL R974 were added and mixed until homogeneous. The mixture was stirred for 2 hours under a vacuum of 0.1 MPa to remove bubbles, thus obtaining the above-mentioned high-temperature and high-humidity resistant epoxy magnetic circuit adhesive.

[0043] Examples 2-4

[0044] The rest is the same as in Example 1, except that the tetrafunctional silicone-based epoxy resin used is the same as that prepared in Examples 2-4.

[0045] Example 5

[0046] The rest is the same as in Example 1, except that the amount of tetrafunctional silicone-based epoxy resin used in Example 1 is 7 parts.

[0047] Example 6

[0048] The rest is the same as in Example 1, except that Akzo LP-3 is replaced with an equal amount of linear phenolic epoxy resin Arkema NC-547.

[0049] Example 7

[0050] 50 parts of bisphenol A type epoxy resin E44 and 7 parts of tetrafunctional silicone-based epoxy resin from Preparation Example 1 were added to a reactor and heated to 60°C and stirred until homogeneous. Then, 3 parts of toughening agent Akzo LP-3, 20 parts of thiol curing agent Toray QE-340M, and 3 parts of filler silica powder were added and mixed until homogeneous. Next, 3 parts of latent curing accelerator Ajinomoto Fine Chemicals PN-23, 2 parts of tackifier 3-(2,3-epoxypropoxypropyl)trimethoxysilane, and 2 parts of thixotropic agent Evonik AEROSIL R974 were added and mixed until homogeneous. The mixture was stirred for 2 hours under a vacuum of 0.1 MPa to remove bubbles, thus obtaining the above-mentioned high-temperature and high-humidity resistant epoxy magnetic circuit adhesive.

[0051] Comparative Example 1

[0052] The rest is the same as in Example 1, except that the tetrafunctional silicone-based epoxy resin of Preparation Example 1 is not added, and the amount of bisphenol A type epoxy resin E44 is 50 parts.

[0053] Application examples

[0054] The epoxy magnetic circuit adhesives prepared in the above examples and comparative examples were applied to the bonding samples at an application rate of 30 g / m2. The bonding samples included one galvanized stainless steel plate with dimensions of 15×10×2 mm, two long galvanized magnets with dimensions of 12×1×1.5 mm, and two short galvanized magnets with dimensions of 4×1×1.5 mm. The long side of the four galvanized magnets was 1.5 mm away from the corresponding edge of the steel plate. The samples were heated and cured at 120°C for 30 seconds.

[0055] The epoxy magnetic circuit adhesives prepared in the above examples and comparative examples were subjected to the following performance tests:

[0056] Shear strength: The shear strength of the specimens before and after heating and humidifying aging was tested according to the standard ASTM D1002, and the strength retention rate after aging was calculated. The test temperature was 25℃, the substrate was galvanized steel sheet, and the heating and humidifying aging conditions were 85℃ / 85%RH / 120h.

[0057] Viscosity: GB / T 2794-2013 Determination of viscosity of adhesives - single-cylinder rotational viscometer method, No. 52 rotor, 5 r / min.

[0058] Seismic and drop resistance performance tests: The test was conducted in accordance with the drop test method of standard GB / T 2423.8-1995. The drop height was 1000mm, and the drop was free. Visual inspection was performed. The drop frequency was 10 times per minute. The number of drops when the first magnet fell off was recorded.

[0059] The above performance tests are simplified and the project numbers are uniformly recorded as examples or comparative examples.

[0060] Table 1

[0061]

[0062]

[0063] As can be seen from Table 1, the magnetic circuit adhesive of the present invention does not soften easily under high temperature and high humidity conditions and has good durability.

[0064] The drop test results show that the tetrafunctional silicone-based epoxy resin and the polysulfide rubber toughening agent synergistically improve the shock resistance and drop resistance of the magnetic circuit adhesive. Viscosity tests indicate that the tetrafunctional silicone-based epoxy resin reduces viscosity, while the polysulfide rubber toughening agent increases viscosity. The relative amounts of both must be maintained within a certain range; otherwise, significant viscosity fluctuations will occur, which is detrimental to dispensing.

[0065] The above detailed description is a specific description of one of the feasible embodiments of the present invention. This embodiment is not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the present invention should be included within the scope of the technical solution of the present invention.

Claims

1. A high-temperature and high-humidity resistant epoxy magnetic circuit adhesive, characterized in that, The raw materials include: bisphenol type epoxy resin, tetrafunctional silicone-based epoxy resin with the structure shown in Formula I, toughening agent, thiol curing agent, latent curing accelerator, filler, tackifier, and thixotropic agent; (I) In Formula I, R1-R4 are O; R5-R8 are independently selected from C3H6OCH2, C2H4COOCH2, and C 2n H 4n n is an integer from 1 to 4.

2. The high-temperature and high-humidity resistant epoxy magnetic circuit adhesive according to claim 1, characterized in that, The raw materials include the following parts by weight: 40-50 parts bisphenol type epoxy resin, 7-10 parts tetrafunctional silicone-based epoxy resin with the structure shown in Formula I, 1-3 parts toughening agent, 18-20 parts thiol curing agent, 2-3 parts latent curing accelerator, 20-30 parts filler, 1-2 parts tackifier, and 0.5-2 parts thixotropic agent.

3. The high-temperature and high-humidity resistant epoxy magnetic circuit adhesive according to claim 1, characterized in that, The tetrafunctional silicone-based epoxy resin with the structure shown in Formula I is prepared by a method comprising the following steps: Under an inert atmosphere, hydrogen-containing silane, organic solvent, catalyst, and unsaturated epoxy compound are added to a reaction vessel and mixed evenly. The mixture is heated and kept at a constant temperature for reaction. After the reaction is completed, impurities are removed by vacuum distillation to obtain a tetrafunctional silicone-based epoxy resin with the structure shown in Formula I.

4. The high-temperature and high-humidity resistant epoxy magnetic circuit adhesive according to claim 3, characterized in that, The four Si-H bonds of the hydrogen-containing silane are specifically selected from one or a combination of two of tetra(dimethylsilyl)silane and tetra(dimethylsiloxane); the unsaturated epoxy compound is selected from one or a combination of two or more of glycidyl acrylate, 1,2-epoxy-5-hexene, 1,2-epoxy-9-decene, 3,4-epoxy-1-butene, and allyl glycidyl ether.

5. The high-temperature and high-humidity resistant epoxy magnetic circuit adhesive according to claim 3, characterized in that, The molar ratio of the hydrogen-containing silane to the unsaturated epoxy compound is 1:4.0-4.

5.

6. The high-temperature and high-humidity resistant epoxy magnetic circuit adhesive according to claim 5, characterized in that, The molar ratio of the hydrogen-containing silane to the unsaturated epoxy compound is 1:4.18-4.

23.

7. The high-temperature and high-humidity resistant epoxy magnetic circuit adhesive according to claim 3, characterized in that, The temperature is raised to 80-100℃, the reaction time is 3-5h, the catalyst is an isopropanol solution of 1-2.5wt% chloroplatinic acid hydrate, the chloroplatinic acid hydrate is 0.01-0.02wt% of the mass of hydrogen-containing silane and unsaturated epoxy compound, and the organic solvent is selected from one or a combination of two or more of benzene, toluene, and xylene.

8. The high-temperature and high-humidity resistant epoxy magnetic circuit adhesive according to claim 1, characterized in that, The toughening agent is selected from one or a combination of two of polysulfide rubber, urethane prepolymer, polyurethane epoxy resin, and linear phenolic epoxy resin.

9. The high-temperature and high-humidity resistant epoxy magnetic circuit adhesive according to claim 8, characterized in that, The toughening agent is polysulfide rubber, selected from one or a combination of two of Akzo LP-3, Akzo LP-33, and Akzo LP-8.

10. The high-temperature and high-humidity resistant epoxy magnetic circuit adhesive according to claim 1, characterized in that, The active hydrogen equivalent of the thiol curing agent is 200-300 g / eq, and is selected from one or a combination of two of Toray QE-340M (Japan) and Gabriel GPM-800 (USA); the epoxy value of the bisphenol type epoxy resin is 0.44-0.53, and is selected from one or a combination of two of bisphenol A type epoxy resin and bisphenol F type epoxy resin.

11. The method for preparing the high-temperature and high-humidity resistant epoxy magnetic circuit adhesive according to any one of claims 1-10, characterized in that, Includes the following steps: Bisphenol type epoxy resin and tetrafunctional silicone-based epoxy resin with the structure shown in Formula I are added to a kettle, heated and stirred until uniform. Toughening agent, thiol curing agent and filler are added and mixed evenly. Then, latent curing accelerator, tackifier and thixotropic agent are added and mixed until uniform. Vacuum degassing is performed to obtain the above-mentioned high temperature and high humidity resistant epoxy magnetic circuit adhesive.

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