Single-component high-temperature-resistant epoxy resin adhesive and preparation method thereof

Abstract

The invention provides a single-component high-temperature-resistant epoxy resin adhesive which comprises the following components in parts by weight: 20-30 parts of epoxy resin; 10 to 20 parts of a diluent; 5-10 parts of a toughening agent; 10-20 parts of a curing agent; 4-8 parts of an accelerant; 1-3 parts of a coupling agent; 3-10 parts of fumed silica; 20 to 40 parts of aluminum oxide; 1-3 parts of color paste; the diluent is an active diluent of which the main body structure contains a benzene ring and two ends contain epoxy groups; the toughening agent is bisphenol S type epoxy resin of which the main body structure contains a polysulfone group and two ends contain epoxy groups. According to the single-component high-temperature-resistant epoxy resin adhesive and the preparation method thereof provided by the invention, the problem that an adhesive in the prior art does not well balance curing temperature and storage time and has high attenuation mechanical strength at high temperature can be solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of heat-curable epoxy resin compositions, and particularly relates to a single-component high-temperature-resistant epoxy resin adhesive and a preparation method thereof. BACKGROUND

[0002] Epoxy resin has excellent electrical insulation, excellent mechanical properties, low curing shrinkage and good bonding performance, and is widely used in adhesives, electronic packaging materials and coating materials. In recent years, in order to improve the bonding efficiency during the use of electronic appliances and adapt to the large amount of heat generated during the high-speed operation of electronic appliances, the development of single-component high-temperature-resistant epoxy resin adhesives has important significance.

[0003] There are many problems in the single-component high-temperature-resistant epoxy resin adhesives on the market: first, common single-component adhesives mostly add dicyandiamide as a curing agent, mainly in the selection of accelerators, which do not balance the storage period and the curing temperature. The storage time is long, but the curing temperature may reach 170 DEG C for 2 hours; the storage time is short at low curing temperature. Second, the mechanical properties are insufficient under high temperature conditions, which cannot meet the specific application requirements. For example: the stirring paddle of a high-speed running vacuum pump generates a large amount of heat, sometimes even reaching 200-300 DEG C. At this time, the bonding performance of the general single-component epoxy resin adhesive will decrease, and the shear strength may decrease from 30 MPa at room temperature to 2 MPa, with a shear strength attenuation of 93%, which cannot meet the application requirements. In summary, it is of great significance to develop a single-component high-temperature-resistant epoxy resin adhesive with high bonding efficiency, long storage period, suitable curing temperature and low mechanical strength attenuation at high temperature. SUMMARY

[0004] The application solves the problems in the prior art, and provides a single-component high-temperature-resistant epoxy resin adhesive and a preparation method thereof, so as to balance the curing temperature and the storage time and the high mechanical strength attenuation at high temperature of the adhesive in the prior art.

[0005] The technical scheme adopted by the application to achieve the above-mentioned purposes is as follows: A single-component high-temperature-resistant epoxy resin adhesive comprises the following components in parts by weight: Epoxy resin 20-30 parts; Diluent 10-20 parts; Toughening agent 5-10 parts; Curing agent 10-20 parts; Accelerator 4-8 parts; Coupling agent 1-3 parts; Fumed silica 3-10 parts; Aluminum oxide 20-40 parts; Color paste 1-3 parts; The structural formula of the epoxy resin is as follows: ; The diluent is an active diluent containing a benzene ring in the main structure and epoxy groups at both ends;

[0006] The toughening agent is a bisphenol S type epoxy resin containing a polysulfone group in the main structure and epoxy groups at both ends.

[0007] Further, the epoxy value of the epoxy resin is 185 g / mol, and the viscosity is 50000 Cp.

[0008] Further, the active diluent is a bis-epoxy group active diluent, and its structure is as follows: .

[0009] Further, the structural formula of the bisphenol S type epoxy resin is as follows: .

[0010] Further, the curing agent is dicyandiamide.

[0011] Further, the accelerator is an imidazole type accelerator, and its structural formula is as follows: .

[0012] Further, the coupling agent is a coupling agent containing an epoxy group at one end and a methoxy group at the other end in the main structure.

[0013] Further, the coupling agent is KH-560 silane coupling agent.

[0014] Further, the aluminum oxide is spherical aluminum oxide with a particle size of 20 nm.

[0015] The application also provides a preparation method of the above-mentioned one-component high-temperature resistant epoxy resin adhesive, comprising the following steps: (1) According to the weight ratio, the epoxy resin, diluent, toughening agent, curing agent, accelerator, coupling agent, fumed silica, aluminum oxide and color paste are added in turn, and the fillers are uniformly dispersed by preliminary stirring; (2) Then the mixture after preliminary stirring in the above step is placed in a high-speed dispersion machine and stirred, vacuumized, and stirred at 400-800 r / min for 1-10 min. The vacuum degree is maintained at-101 KPa or below during the stirring process. After the stirring is completed, the adhesive is obtained; (3) Then the adhesive is placed under a three-roll mill for dispersion, so that the curing agent is uniformly dispersed in the adhesive; (4) Finally, the glue material is uniformly stirred in a high-speed mixer under vacuum, and finally a uniformly dispersed adhesive curing product is obtained, which is a single-component high-temperature-resistant epoxy resin adhesive.

[0016] Compared with the prior art, the above technical scheme provided by the present application has the following beneficial effects: (1) In the present application, by optimizing the structure of the adhesive, adding epoxy resin, curing agent and accelerator with specific structure, the selected phenolic epoxy resin has excellent thermal stability, electrical insulation performance and high glass transition temperature; the active diluent has epoxy groups at both ends, which can reduce the viscosity and increase the crosslinking density. The active diluent is a multi-epoxy diluent, which has small viscosity and good dilution effect, and will not damage the performance of the epoxy curing product, but will enhance the crosslinking density. And it contains a benzene ring, which can enhance the rigidity of the curing product to a certain extent, improve the glass transition temperature and improve the heat resistance of the curing product. The toughening agent is a bisphenol S type epoxy resin, which contains a polysulfone group in its main structure and contains epoxy resin at both ends. It is a liquid with high viscosity at room temperature, and has a large molecular weight. On the one hand, it can participate in the overall crosslinking and curing, and on the other hand, the long molecular chain can form effective entanglement in the polymer. It helps to improve the toughness of the adhesive curing product, improve the impact strength, improve the heat shock resistance, relieve the internal stress generated during material curing, and thus improve the adhesion to the metal substrate. After the above components are reasonably matched, a high crosslinking density adhesive is formed, which forms a three-dimensional network structure after the epoxy resin is cured, and the fumed silica is attached to the epoxy resin molecular chain, limiting the movement of the molecular chain at high temperature; the filler aluminum oxide is dispersed in the adhesive, which forms effective heat conduction at high heat, dissipates heat, and reduces the heat propagation to the inside of the glue.

[0017] (2) The single-component epoxy resin adhesive formula of the present application is simple, and the raw materials are easy to obtain, without the need for separate design and synthesis, and has the characteristics of wide repeated operation, high bonding efficiency, long storage period, suitable curing temperature and low mechanical strength at high temperature. The common problems of single-component epoxy resin adhesives on the market are solved.

[0018] (3) The preparation method of the single-component high-temperature-resistant epoxy resin adhesive of the present application is simple, and the materials are uniformly dispersed during the preparation process. The equipment used is a common high-speed disperser and a three-roll mill. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The mechanism diagram of the single-component high-temperature-resistant epoxy resin adhesive provided by the present application and the metal substrate. DETAILED DESCRIPTION

[0020] The application will be further described in connection with specific examples. The scope of the application is not limited to the following examples. The high-temperature-resistant epoxy resin adhesive provided in the examples has good adhesion to metal substrates and maintains high mechanical properties at high temperatures, and is widely used in environments that generate high heat during use of motors, electrical appliances, and the like.

[0021] The preparation method of the high-temperature-resistant epoxy resin adhesive provided in the example is as follows: first, the following components are weighed: The phenolic epoxy resin has a structure as follows: The phenolic epoxy resin has an epoxy value of 185 g / mol and a viscosity of 50,000 Cp. The high viscosity and high epoxy content result in a higher crosslinking density during the reaction. The rigid benzene ring in the molecular chain limits the slippage of the molecular chain during thermal motion at high temperatures, thereby improving the thermal stability. In addition, the methyl group in the benzene ring side chain imparts flexibility. Compared with general phenolic epoxy resins without methyl groups, the phenolic epoxy resin maintains rigidity while having a certain flexibility. For high-temperature-resistant adhesives, excessive rigidity and hardness can easily cause brittle fracture when subjected to impact and displacement changes. Therefore, when designing the molecular structure, a structure with a flexible group in the benzene ring side chain is selected to achieve a good combination of rigidity and flexibility. The phenolic epoxy resin is mainly added because it has excellent thermal stability, electrical insulation performance, and a high glass transition temperature.

[0022] The diluent is 15 parts. The diluent is an active diluent with epoxy groups at both ends, which reduces the viscosity and increases the crosslinking density. The active diluent is a multi-epoxy diluent with small viscosity and good dilution effect, and does not damage the performance of the epoxy cured product, but enhances the crosslinking density. In addition, it contains benzene rings that can enhance the rigidity of the cured product to some extent, increase the glass transition temperature, and improve the heat resistance of the cured product. Therefore, a bis-epoxy group active diluent with an epoxy equivalent of 0.0143 mol / 100 g is selected. The structure is as follows: 。

[0023] The toughening agent is 6 parts. The toughening agent is a bisphenol S type epoxy resin containing a polysulfone group in the main structure and epoxy groups at both ends. The structure is as follows: .

[0024] The above-mentioned bisphenol S type epoxy resin is a liquid with high viscosity at room temperature, and has a large molecular weight. On the one hand, it can participate in the overall cross-linking and curing, and on the other hand, the long molecular chain can form effective entanglement in the polymer. This helps to improve the toughness of the cured adhesive, increase the impact strength, improve the heat shock resistance, relieve the internal stress generated during the curing of the material, and thus improve the adhesion to the metal substrate.

[0025] The curing agent 15 parts is selected from dicyandiamide, which is a white crystalline powder that can exist stably when dried. It has low activity at room temperature and does not react with epoxy resin. Under heating conditions, it can cure and cross-link.

[0026] The accelerator 5 parts is an imidazole accelerator, and its structural formula is: The pyrrole nitrogen atom at position 1 and the pyridine nitrogen atom at position 3 of the above imidazole ring have high activity and are active sites for promoting the ring-opening reaction of epoxy resin. The above structure contains a methyl group, which can increase the steric hindrance of the structure, reduce the activity, and balance the storage stability and reaction catalytic activity.

[0027] The coupling agent 2 parts is KH-560. Since the coupling agent KH-560 contains an epoxy group at one end, it can participate in the curing and cross-linking reaction. The other end contains a methoxy group, which can form a Si-O bond with the hydroxyl group on the surface of the substrate after hydrolysis. The silicon-oxygen bond has high bond energy and strong coupling with the substrate. The coupling agent KH-550 contains an amine group at one end. In theory, it can also cure and cross-link with the epoxy group. In this embodiment, KH-550 is not selected mainly because of its storage stability. Since the adhesive in this application is a single-component heat-curing adhesive, the active amine group at the end of KH-550 can slowly cure with the epoxy group at room temperature. The remaining common coupling agents KH-570, KH-580, and KH-590 do not participate in the reaction and cannot play the role of "bridging" bridge.

[0028] The fumed silica 5 parts is selected from Wanjing A380. The fumed silica is a hydrophilic fumed silica with a specific surface area of 380 m 2 / g. The amount added is 2-3 parts, mainly to adjust the rheological property of the adhesive. If the viscosity of the adhesive is too small, it cannot form effective contact; if the viscosity is too large, it is not conducive to construction and operation. Adding a small amount of fumed silica can enhance the rheological property of the adhesive, and the surface of the fumed silica has a large number of hydroxyl groups, which can form hydrogen bonds with the cured product of the epoxy resin, thereby playing a certain reinforcing role.

[0029] The color paste 3 parts is selected from black color paste.

[0030] Thermal conductive filler aluminum trioxide 25 parts, the aluminum trioxide is spherical aluminum trioxide, particle size is 20 nm. Selecting smaller particle size of aluminum trioxide, small particle size can form effective dispersion, reduce the slip between molecular chains. Spherical aluminum trioxide can form effective heat conduction under high heat, dissipate heat, reduce heat propagation to the inside of the rubber.

[0031] After the above raw materials are weighed, the following steps are taken to prepare: (1) each raw material is added to the container in turn, and is initially stirred to make the filler uniform; (2) the mixture is then placed in a high-speed dispersion machine and stirred, vacuum is extracted, and low-speed stirring is performed at 600 r / min for 3 min, the vacuum degree is maintained at-101 KPa during the process to prevent the filler from being cured due to heat generated during high-speed stirring. The first stirring is mainly to disperse the powder in the rubber to avoid scattering when passing through the three rollers directly; (3) the rubber is then placed under a three-roller machine for dispersion, mainly to uniformly disperse the curing agent dicyandiamide in the adhesive; (4) finally, the adhesive curing product is uniformly stirred in a high-speed stirrer and vacuum is extracted, and the uniformly dispersed adhesive curing product is obtained.

[0032] In this embodiment, the preparation method of the high-temperature-resistant epoxy resin adhesive is consistent with that in Example 1, and the difference lies in that each raw material is weighed according to the following components: phenolic epoxy resin 35 parts, diluent 10 parts, toughening agent 6 parts, curing agent 17 parts, accelerator 5 parts, coupling agent 2 parts, fumed silica 5 parts, and color paste 3 parts.

[0033] In this embodiment, the preparation method of the high-temperature-resistant epoxy resin adhesive is consistent with that in Example 1, and the difference lies in that each raw material is weighed according to the following components: phenolic epoxy resin 25 parts, diluent 20 parts, toughening agent 6 parts, curing agent 12.5 parts, accelerator 5 parts, coupling agent 2 parts, fumed silica 5 parts, and color paste 3 parts.

[0034] Examples 2 and 3 mainly aim to emphasize a reasonable portion and range of the amount of the main epoxy resin, and the amount of the resin is adjusted by the control variable method to finally obtain an optimized ratio.

[0035] In this comparative example, each component is weighed according to the following raw materials: the difference compared with Example 1 is that the phenolic epoxy resin is replaced by E-51 epoxy resin. The components of each raw material are as follows: E-51 epoxy resin 30 parts; diluent 15 parts; toughening agent 6 parts; curing agent 15 parts; accelerator 5 parts; coupling agent 2 parts; fumed silica 5 parts; color paste 3 parts; thermal conductive filler aluminum trioxide 25 parts. The preparation steps are the same as in Example 1.

[0036] Comparative Example 2 In this comparative example, each component was weighed according to the following raw materials: the difference compared with Example 1 is that the thermal conductive filler aluminum oxide is replaced by ordinary silica powder. Each raw material component is as follows: Phenolic epoxy resin 30 parts; diluent 15 parts; toughening agent 6 parts; curing agent 15 parts; accelerator 5 parts; coupling agent 2 parts; fumed silica 5 parts; color paste 3 parts; ordinary silica powder 25 parts. The preparation steps are the same as Example 1.

[0037] Comparative Example 3 In this comparative example, each component was weighed according to the following raw materials: the difference compared with Example 1 is that the imidazole accelerator is replaced by an ordinary accelerator. Each raw material component is as follows: Phenolic epoxy resin 30 parts; diluent 15 parts; toughening agent 6 parts; curing agent 15 parts; ordinary accelerator 5 parts; coupling agent 2 parts; fumed silica 5 parts; color paste 3 parts; thermal conductive filler aluminum oxide 25 parts. The preparation steps are the same as Example 1.

[0038] Performance tests were carried out on Example 1 and Comparative Examples 1-3 and commercially available products 1-2, wherein commercially available product 1: Loctite HY4070, commercially available product 2: Sanjin 2273G. Test indicators include hardness, storage time, room temperature shear strength and 200°C shear strength.

[0039] Hardness: durometer, Shore D.

[0040] Storage time: aging test chamber.

[0041] Shear strength: tensile testing machine.

[0042] The test was tested according to GB / T 21196.2 standard. After testing, the test results are shown in the following table: Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Commercial Product 1 Commercial Product 2 Hardness (Shore D) 85 87 81 80 82 83 83 84 Storage Time (Time Corresponding to Double Viscosity) One year One year One year One year One year Half a year 0.75 years Half a year Shear Strength / MPa 34 33 29 30 31 32 26 28 Shear Strength at 200°C / MPa 8 7.2 5 3 3.5 3.2 3 4

[0043] By analyzing the data in the above table, it can be seen from the comparison of Examples 1, 2 and 3 that the reasonable range of the relative content of phenolic epoxy resin. By comparing Example 1 and Comparative Example 1, it can be found that the introduction of phenolic epoxy resin strengthens the overall crosslinking density, and the phenolic resin has a high Tg, so its shear strength at high temperature is much higher than that of Comparative Example 1; by comparing Example 1 and Comparative Example 2, it can be known that spherical aluminum oxide as a filler can form effective dispersion due to its small particle size, reducing the sliding between molecular chains. Spherical aluminum oxide can form effective heat conduction under high heat, dissipating heat and reducing heat propagation to the inside of the compound. By comparing Example 1 and Comparative Example 3, it can be known that different types of imidazole have an effect on storage time; by comparing Example 1 with commercially available products 1 and 2, it can be shown that the formula has a great advantage compared with products on the market.

[0044] Figure 1 ​The mechanism diagram of the single-component high-temperature resistant epoxy resin adhesive provided for example 1 and the metal substrate, Figure 1 The middle dotted arrow represents heat transfer, the rectangular plate represents 304 stainless steel or other metal substrate, the circular small ball represents fumed silica, and the circular large ball represents the heat-conducting filler. The curved line represents the network structure that has been cured. Mechanism interpretation: the single-component high-temperature resistant epoxy resin adhesive is mainly cured by heating, and the epoxy resin and the dicyandiamide curing agent. The main reason for its high-temperature resistance is that the rigid epoxy resin forms a three-dimensional network structure with high cross-linking density after curing, and is filled with high-temperature resistant fillers of different particle sizes, which limits the movement of molecular chains at high temperatures and protects the structure from being destroyed.

Claims

1. A single component high temperature resistant epoxy resin adhesive, characterized by: By weight parts, including the following components: Epoxy resin 20-30 parts; Diluent 10-20 parts; Toughening agent 5-10 parts; Curing agent 10-20 parts; Promoter 4-8 parts; Coupling agent 1-3 parts; Fumed silica 3-10 parts; Aluminum oxide 20-40 parts; Color paste 1-3 parts; The structural formula of the epoxy resin is as follows: ； The diluent is an active diluent containing a benzene ring in the main structure and containing epoxy groups at both ends; The toughening agent is a bisphenol S type epoxy resin containing a polysulfone group in the main structure and containing epoxy groups at both ends.

2. The single component high temperature resistant epoxy resin adhesive according to claim 1, characterized in that: The epoxy value of the epoxy resin is 185 g / mol, and the viscosity is 50000 Cp.

3. The single component high temperature resistant epoxy resin adhesive as claimed in claim 1, wherein: The active diluent is a bis-epoxy active diluent, and its structure is as follows: 。 4. The single component high temperature resistant epoxy resin adhesive as claimed in claim 1, wherein: The structural formula of the bisphenol S type epoxy resin is as follows: 。 5. The single component high temperature resistant epoxy resin adhesive as claimed in claim 1, wherein: The curing agent is dicyandiamide.

6. The single component high temperature resistant epoxy resin adhesive as claimed in claim 1, wherein: The promoter is an imidazole type promoter, and its structural formula is as follows: 。 7. The single component high temperature resistant epoxy resin adhesive as claimed in claim 1, wherein: The coupling agent is a coupling agent containing an epoxy group at one end and a methoxy group at the other end in the main structure.

8. The single component high temperature resistant epoxy resin adhesive according to claim 7, characterized in that: The coupling agent is KH-560 silane coupling agent.

9. The single component high temperature resistant epoxy resin adhesive as claimed in claim 1, wherein: The aluminum oxide is spherical aluminum oxide with a particle size of 20 nm.

10. The process for the preparation of the single-component high temperature resistant epoxy resin adhesive according to any one of claims 1 to 9, characterized in that Including the following steps: (1) According to the weight ratio, the epoxy resin, diluent, toughening agent, curing agent, promoter, coupling agent, fumed silica, aluminum oxide and color paste are added in turn, and the fillers are uniformly dispersed by preliminary stirring; (2) Then the mixture after preliminary stirring in the above step is placed in a high-speed dispersion machine and stirred, vacuumized, and stirred at 400-800 r / min for 1-10 min. The vacuum degree is maintained at-101 KPa or below during stirring. After stirring, the adhesive is obtained; (3) Then the adhesive is placed under a three-roll mill for dispersion, so that the curing agent is uniformly dispersed in the adhesive; (4) Finally, the adhesive is uniformly stirred in a high-speed stirrer and vacuumized, and the uniformly dispersed adhesive curing product is obtained, which is a single-component high-temperature resistant epoxy resin adhesive.

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