A yellowing-resistant flame-retardant epoxy resin electronic potting adhesive and a preparation method thereof

Abstract

The present application relates to the technical field of epoxy adhesive, especially to the field of IPC C09J163, more particularly to a yellowing-resistant flame-retardant epoxy resin electronic potting adhesive and a preparation method thereof. The components include: component A and component B, the component A includes: 80-130 parts of epoxy resin, 10-20 parts of active diluent, 10-20 parts of filler, 5-10 parts of toughening agent, and 5-15 parts of flame retardant; the component B includes: 50-80 parts of curing agent and 5-15 parts of accelerator. 3. The epoxy resin includes bisphenol A epoxy resin, bisphenol F epoxy resin and alicyclic epoxy resin, and when the weight ratio of the bisphenol A epoxy resin, the bisphenol F epoxy resin and the alicyclic epoxy resin is 1:(1-2):(5-8), the hardness and yellowing resistance of the prepared potting adhesive can be improved.

Description

Technical Field

[0001] This invention relates to the field of epoxy adhesive technology, particularly to the field of IPC C09J163, and more specifically, to a yellowing-resistant, flame-retardant epoxy resin electronic potting compound and its preparation method. Background Technology

[0002] Potting compounds are a cutting-edge technology in the field of electronic assembly, effectively protecting electronic components under extremely challenging environmental conditions, improving mechanical strength, and providing excellent electrical insulation. Electronic potting compounds are widely used in numerous industries, various consumer electronics products, and industries such as automotive, aerospace, and others that frequently involve electronic assembly. Currently, the main types are epoxy resin potting compounds, silicone potting compounds, and polyurethane potting compounds. Silicone potting compounds are expensive and have poor scratch resistance. Polyurethane potting compounds have poor high-temperature resistance and are prone to foaming, while their aging resistance and UV resistance are also insufficient. Epoxy resin potting compounds, on the other hand, have excellent high-temperature resistance and electrical insulation properties, a simple production process, high stability before and after curing, and a high product yield, leading to their widespread application. However, currently, epoxy electronic potting compounds tend to yellow under high heat conditions, resulting in a deterioration in electrical, thermal, and protective properties.

[0003] CN105907346A discloses an epoxy electronic potting compound and its preparation method, which is prepared by mixing E-51 bisphenol A epoxy resin, epoxy diluent, epoxy toughening agent, curing agent, filler, and additives. The epoxy electronic potting compound of this invention uses bisphenol A type epoxy resin as the main resin, and the types and amounts of accelerators and fillers are screened to select an optimal formulation. The resulting epoxy potting compound has good thermal conductivity and flame retardancy, low internal stress, and all performance characteristics are superior to similar foreign potting compounds, making it suitable for potting high-power electronic components. However, this invention uses a large amount of aromatic epoxy resin bisphenol A structure, which is easily oxidized to produce carbonyl groups, forming yellowing groups, which to some extent reduces the yellowing resistance of the epoxy electronic potting compound. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the present invention provides a yellowing-resistant and flame-retardant epoxy resin electronic potting compound and its preparation method. By using different types of epoxy resins and adjusting the ratio between components, the potting compound obtained not only has excellent mechanical properties, but also good yellowing resistance and flame retardant properties.

[0005] To achieve the objectives of this invention, the first aspect of this invention provides a yellowing-resistant, flame-retardant epoxy resin electronic potting compound, comprising, by weight, a component A and a component B. Component A comprises: 80-130 parts epoxy resin, 10-20 parts reactive diluent, 10-20 parts filler, 5-10 parts toughening agent, and 5-15 parts flame retardant; component B comprises: 50-80 parts curing agent and 5-15 parts accelerator.

[0006] The applicant has discovered that epoxy resins include bisphenol A epoxy resin, bisphenol F epoxy resin, and alicyclic epoxy resin. When the weight ratio of bisphenol A epoxy resin, bisphenol F epoxy resin, and alicyclic epoxy resin is 1:(1-2):(5-8), the hardness and yellowing resistance of the prepared potting compound can be improved. The large steric hindrance of the ether groups and benzene rings in bisphenol A epoxy resin brings higher mechanical properties and insulation properties. However, bisphenol A epoxy resin has a high viscosity, which affects the dispersion performance of the system. Bisphenol F epoxy resin has a significant dilution effect on bisphenol A type epoxy resin. When the amount of bisphenol F is too large, it will lead to the viscosity of the mixed resin system being too low, which will greatly reduce the workability. When the amount is too small, it is difficult to achieve the effect of reducing viscosity. Bisphenol F epoxy resin and bisphenol A epoxy resin both contain a large number of benzene ring structures, which are easily oxidized to produce carbonyl groups, forming yellowing groups and reducing the resistance to yellowing. Alicyclic epoxy resins do not contain benzene rings in their molecular structure, so they have good weather resistance and UV resistance. At the same time, since the epoxy groups of alicyclic epoxy resins are directly attached to the alicyclic rings, they can form a tight and rigid molecular structure. After curing, they form an interpenetrating network structure with bisphenol F epoxy resin and bisphenol A epoxy resin, which further reduces the spacing between crosslinking points, reduces the amount of oxygen penetration, and effectively improves the flame retardant properties of the potting compound.

[0007] Preferably, the epoxy resin includes bisphenol A epoxy resin, bisphenol F epoxy resin, and alicyclic epoxy resin, wherein the weight ratio of the bisphenol A epoxy resin, bisphenol F epoxy resin, and alicyclic epoxy resin is 1:(1-2):(5-8).

[0008] More preferably, the epoxy resin includes bisphenol A epoxy resin, bisphenol F epoxy resin, and alicyclic epoxy resin, wherein the weight ratio of the bisphenol A epoxy resin, bisphenol F epoxy resin, and alicyclic epoxy resin is 1:1.5:7.

[0009] Preferably, the bisphenol A epoxy resin has an epoxy value between 0.2 and 0.6.

[0010] Preferably, the bisphenol A epoxy resins include E51, E44, E42, and E20, where the numbers represent epoxy values.

[0011] More preferably, the bisphenol A epoxy resin includes E51, purchased from Hebei Zhuozheng Rubber & Plastic Products Co., Ltd.

[0012] Preferably, the bisphenol F epoxy resin includes F51, NPEF-170, EPALLOY 8220, and EPALLOY 8230.

[0013] More preferably, the bisphenol F epoxy resin includes F51 (purchased from Jinan Baijin Chemical Technology Co., Ltd.).

[0014] Preferably, the alicyclic epoxy resin includes at least one of 4,5-epoxytetrahydrophthalic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, and hydrogenated bisphenol A epoxy resin.

[0015] More preferably, the alicyclic epoxy resin comprises 4,5-epoxytetrahydrophthalic acid diglycidyl ester, purchased from Hubei Chengfeng Chemical Co., Ltd.

[0016] The active diluent includes one of butyl glycidyl ether, ethylene glycol diglycidyl ether, and phenyl glycidyl ether.

[0017] Preferably, the active diluent comprises butyl glycidyl ether (CAS: 2426-08-6).

[0018] Preferably, the weight ratio of the epoxy resin, reactive diluent, and filler is 1:(0.1-0.2):(0.1-0.2).

[0019] More preferably, the weight ratio of the epoxy resin, reactive diluent, and filler is 1:0.15:0.18.

[0020] The filler includes modified inorganic powder materials.

[0021] Preferably, the modified inorganic powder material has a mesh size of 800-2000 mesh.

[0022] Preferably, the modified inorganic powder material includes at least one of silicon dioxide, aluminum hydroxide, aluminum oxide, magnesium hydroxide, and wollastonite.

[0023] More preferably, the modified inorganic powder material includes silicon dioxide with a mesh size of 2000, purchased from Foshan Shunde Jinchun Silicon Materials Co., Ltd.

[0024] The modified inorganic powder material is modified with a coupling agent.

[0025] Preferably, the coupling agent includes KH550, KH560, and KH570.

[0026] More preferably, the coupling agent includes KH550.

[0027] Preferably, the modification method includes: adding 2-4 parts of coupling agent to 96-98 parts of solvent, stirring at 70-90℃ for 4-6 hours, and filtering to obtain the product.

[0028] More preferably, the modification method includes: adding 4 parts of coupling agent to 98 parts of solvent, stirring at 90°C for 5 hours, and filtering to obtain the modified inorganic powder material.

[0029] The toughening agent includes one of polyester and polyether.

[0030] Preferably, the toughening agent comprises a polyester, wherein the polyester comprises dibutyl phthalate (CAS: 84-74-2).

[0031] The applicant discovered that flame retardants including aluminum hydroxide and DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) can improve flame retardant efficiency and reduce the amount of small molecule flame retardants added. Due to the presence of highly active P-H bond structures in the molecule, DOPO can react with epoxy groups. On the one hand, during combustion, a large number of non-flammable gases such as CO2, NH3, N2 and H2O are generated to dilute the active free radicals, thereby reducing the reaction rate. On the other hand, it absorbs heat and lowers the matrix temperature to achieve the flame retardant effect. On the other hand, DOPO groups decompose during the combustion of the polymer matrix to produce phosphoric acid and polymetaphosphoric acid, removing moisture from the matrix and promoting char formation to create a heat-insulating char layer that is difficult to pyrolyze. At the same time, the decomposition product, polymetaphosphoric acid glass, covers the epoxy resin surface, preventing oxygen and heat from being transferred to the interior of the matrix. However, DOPO has low dispersion performance in epoxy resin systems. The addition of aluminum hydroxide can effectively improve the dispersibility of DOPO, possibly because aluminum hydroxide has higher polarity and better compatibility with polymeric epoxy resin materials. DOPO can be dispersed between aluminum hydroxide, which can reduce the porosity of the material surface, thereby reducing the oxygen permeability inside the resin during combustion.

[0032] Further research revealed that when the weight ratio of aluminum hydroxide to DOPO is 1:(0.2-0.5), the yellowing resistance of the potting compound can be improved. This may be because aluminum hydroxide has high thermal conductivity, and at a specific ratio, DOPO can absorb the heat inside the system, achieving internal photothermal balance, thereby reducing photothermal yellowing.

[0033] Preferably, the flame retardant comprises aluminum hydroxide and DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide), wherein the weight ratio of aluminum hydroxide to DOPO is 1:(0.2-0.5).

[0034] More preferably, the flame retardant comprises aluminum hydroxide and DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide), wherein the weight ratio of aluminum hydroxide to DOPO is 1:0.3.

[0035] Preferably, the aluminum hydroxide is purchased from Hebei Qingjiang New Material Technology Co., Ltd.

[0036] Preferably, the DOPO is purchased from Weifang Dakang Chemical Co., Ltd.

[0037] The curing agent includes one of the following: aromatic amine curing agent, acid anhydride curing agent, polyamide curing agent, and aliphatic polyamine curing agent.

[0038] Preferably, the curing agent includes an anhydride curing agent, which includes methyltetrahydrophthalic anhydride and methylhexahydrophthalic anhydride, wherein the weight ratio of methyltetrahydrophthalic anhydride to methylhexahydrophthalic anhydride is 1:(0.3-0.6).

[0039] More preferably, the curing agent includes an anhydride curing agent, which includes methyltetrahydrophthalic anhydride (CAS: 11070-44-3) and methylhexahydrophthalic anhydride (CAS: 25550-51-0), and the weight ratio of methyltetrahydrophthalic anhydride to methylhexahydrophthalic anhydride is 1:0.5.

[0040] The accelerator includes one of tertiary amine accelerators, substituted urea accelerators, and phenolic accelerators.

[0041] Preferably, the accelerator includes a tertiary amine accelerator, which includes at least one of 2,4,6-tris(dimethylaminomethyl)phenol, benzyldimethylamine, triethylamine, and triethanolamine.

[0042] More preferably, the accelerator includes a tertiary amine accelerator, which includes 2,4,6-tris(dimethylaminomethyl)phenol and triethylamine, wherein the weight ratio of 2,4,6-tris(dimethylaminomethyl)phenol to triethylamine is 1:(0.3-0.8).

[0043] Preferably, the accelerator comprises 2,4,6-tris(dimethylaminomethyl)phenol (CAS: 90-72-2) and triethylamine (CAS: 121-44-8), wherein the weight ratio of 2,4,6-tris(dimethylaminomethyl)phenol to triethylamine is 1:0.5.

[0044] A second aspect of this invention provides a method for preparing a yellowing-resistant, flame-retardant epoxy resin electronic potting compound, comprising the following steps:

[0045] S1, Epoxy resin, reactive diluent, filler, toughening agent and flame retardant are mixed evenly to form component A;

[0046] S2, mix the curing agent and accelerator evenly to form component B;

[0047] S3: Mix components A and B and heat to cure.

[0048] Preferably, the weight ratio of component A to component B is 1:(0.1-0.3).

[0049] More preferably, the weight ratio of component A to component B is 1:0.25.

[0050] The heating and curing temperature is 50-75℃, and the heating and curing time is 1-3 hours.

[0051] Preferably, the heating and curing temperature is 60°C, and the heating and curing time is 2 hours.

[0052] Beneficial effects:

[0053] 1. When flame retardants include aluminum hydroxide and DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide), the flame retardant efficiency can be improved and the amount of small molecule flame retardants added can be reduced.

[0054] 2. When the weight ratio of aluminum hydroxide to DOPO is 1:(0.2-0.5), the yellowing resistance of the potting compound can be improved.

[0055] 3. The epoxy resin includes bisphenol A epoxy resin, bisphenol F epoxy resin, and alicyclic epoxy resin, wherein the weight ratio of the bisphenol A epoxy resin, bisphenol F epoxy resin, and alicyclic epoxy resin is 1:(1-2):(5-8).

[0056] This can improve the hardness and yellowing resistance of the prepared potting compound. Detailed Implementation

[0057] Example 1

[0058] A yellowing-resistant and flame-retardant epoxy resin electronic potting compound, by weight, comprises: component A and component B. Component A comprises: 100 parts epoxy resin, 15 parts reactive diluent, 18 parts filler, 7 parts toughening agent, and 10 parts flame retardant. Component B comprises: 70 parts curing agent and 12 parts accelerator.

[0059] The epoxy resin includes bisphenol A epoxy resin, bisphenol F epoxy resin, and alicyclic epoxy resin, wherein the weight ratio of bisphenol A epoxy resin, bisphenol F epoxy resin, and alicyclic epoxy resin is 1:1.5:7.

[0060] The bisphenol A epoxy resin includes E51, which was purchased from Hebei Zhuozheng Rubber & Plastic Products Co., Ltd.

[0061] The bisphenol F epoxy resin includes F51 (purchased from Jinan Baijin Chemical Technology Co., Ltd.).

[0062] The alicyclic epoxy resin includes 4,5-epoxytetrahydrophthalic acid diglycidyl ester, purchased from Hubei Chengfeng Chemical Co., Ltd.

[0063] The active diluent includes butyl glycidyl ether (CAS: 2426-08-6).

[0064] The filler includes modified inorganic powder materials.

[0065] The modified inorganic powder material includes silicon dioxide with a mesh size of 2000, purchased from Foshan Shunde Jinchun Silicon Materials Co., Ltd.

[0066] The modified inorganic powder material is modified by a coupling agent, including KH550.

[0067] The modification method includes: adding 4 parts of coupling agent to 98 parts of solvent, stirring at 90°C for 5 hours, and filtering to obtain the modified inorganic powder material.

[0068] The toughening agent comprises polyester, which includes dibutyl phthalate (CAS: 84-74-2).

[0069] The flame retardant comprises aluminum hydroxide and DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide), wherein the weight ratio of aluminum hydroxide to DOPO is 1:0.3.

[0070] The aluminum hydroxide was purchased from Hebei Qingjiang New Material Technology Co., Ltd.

[0071] The DOPO was purchased from Weifang Dakang Chemical Co., Ltd.

[0072] The curing agent includes anhydride curing agents, including methyltetrahydrophthalic anhydride (CAS: 11070-44-3) and methylhexahydrophthalic anhydride (CAS: 25550-51-0), with a weight ratio of methyltetrahydrophthalic anhydride to methylhexahydrophthalic anhydride of 1:0.5.

[0073] The accelerator includes 2,4,6-tris(dimethylaminomethyl)phenol (CAS: 90-72-2) and triethylamine (CAS: 121-44-8), wherein the weight ratio of 2,4,6-tris(dimethylaminomethyl)phenol to triethylamine is 1:0.5.

[0074] A method for preparing a yellowing-resistant, flame-retardant epoxy resin electronic potting compound includes the following steps:

[0075] S1. Stir epoxy resin, reactive diluent, filler, toughening agent and flame retardant at 500 rpm until homogeneous to prepare component A.

[0076] S2, mix the curing agent and accelerator evenly at 500 rpm to prepare component B;

[0077] S3: Mix components A and B at 500 rpm and heat to cure.

[0078] The weight ratio of component A to component B is 1:0.25.

[0079] The heating and curing temperature is 60°C, and the heating and curing time is 2 hours.

[0080] Example 2

[0081] The specific implementation method is the same as in Example 1; the difference is that the weight ratio of epoxy resin, reactive diluent and filler in Example 2 is 1:0.17:0.16.

[0082] Example 3

[0083] The specific implementation method is the same as in Example 1; the difference is that the flame retardant in Example 3 includes aluminum hydroxide and DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide), and the weight ratio of aluminum hydroxide to DOPO is 1:0.4.

[0084] Comparative Example 1

[0085] The specific implementation method is the same as in Example 1; the difference is that the flame retardant in Comparative Example 1 includes aluminum hydroxide.

[0086] Comparative Example 2

[0087] The specific implementation method is the same as in Example 1; the difference is that the flame retardant in Comparative Example 2 includes aluminum hydroxide and DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide), and the weight ratio of aluminum hydroxide to DOPO is 1:2.

[0088] Comparative Example 3

[0089] The specific implementation method is the same as in Example 1; the difference is that the weight ratio of bisphenol A epoxy resin, bisphenol F epoxy resin, and alicyclic epoxy resin in Comparative Example 3 is 1:1:1.

[0090] Performance testing methods

[0091] The potting compounds obtained in Examples 1-3 and Comparative Examples 1-3 were subjected to performance tests, and the test data are listed in Table 1.

[0092] 1. Flame retardant rating: UL-94 (thickness: 1.5mm)

[0093] 2. Yellowing resistance: After the electronic potting compound is fully cured, the product is placed in a 180°C environment with light for 3 days to check for yellowing.

[0094] 3. Shore hardness: GB / T 531-1999.

[0095] 4. Breakdown voltage: GB / T7752, 500V / min.

[0096] Performance test data

[0097] Table 1

[0098]

[0099]

Claims

1. A yellowing-resistant flame-retardant epoxy resin electronic potting adhesive, characterized in that, The components include: A component and B component by weight parts, the A component includes: epoxy resin 80-130 parts, active diluent 10-20 parts, filler 10-20 parts, toughening agent 5-10 parts, flame retardant 5-15 parts; the B component includes: curing agent 50-80 parts, accelerator 5-15 parts; The epoxy resin includes bisphenol A epoxy resin, bisphenol F epoxy resin, alicyclic epoxy resin, the weight ratio of the bisphenol A epoxy resin, bisphenol F epoxy resin, alicyclic epoxy resin is 1:1.5:7; The flame retardant includes aluminum hydroxide, DOPO, the weight ratio of the aluminum hydroxide, DOPO is 1:0.3; The active diluent includes butyl glycidyl ether.

2. The yellowing-resistant flame-retardant epoxy resin electronic potting adhesive according to claim 1, characterized in that, The weight ratio of the epoxy resin, active diluent, filler is 1:(0.1-0.2):(0.1-0.2). 3.The yellowing-resistant flame-retardant epoxy resin electronic potting adhesive according to claim 1 or 2, characterized in that, The filler includes modified inorganic powder material, the modified inorganic powder material mesh is 800-2000 mesh.

4. The yellowing-resistant flame-retardant epoxy resin electronic potting adhesive according to claim 3, characterized in that, The modified inorganic powder material is modified by coupling agent.

5. The yellowing-resistant flame-retardant epoxy resin electronic potting adhesive according to claim 1, characterized in that, The curing agent includes one of aromatic amine curing agent, acid anhydride curing agent, polyamide curing agent, aliphatic polyamine curing agent.

6. A process for the preparation of the flame retardant, yellowing resistant, epoxy resin based electronic potting compound according to any one of claims 1 to 5, characterized in that, It includes the following steps: S1, the epoxy resin, active diluent, filler, toughening agent, flame retardant are stirred uniformly, and A component is prepared; S2, the curing agent and the accelerator are mixed uniformly, and B component is prepared; S3, A component and B component are mixed, and heated and cured.

7. The preparation method of the yellowing-resistant flame-retardant epoxy resin electronic pouring sealant according to claim 6, characterized in that, The weight ratio of the A component and B component is 1:(0.1-0.3).

8. The preparation method of the yellowing-resistant flame-retardant epoxy resin electronic pouring sealant according to claim 7, characterized in that, The temperature of the heating and curing is 50-75 DEG C, and the time of the heating and curing is 1-3 h.

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