Halogen-free flame-retardant epoxy resin potting adhesive, preparation method thereof, and application thereof

Abstract

The present invention belongs to the technical field of potting compounds, and provides a halogen-free flame-retardant epoxy resin potting compound, a preparation method thereof, and an application thereof. The potting compound is prepared from the following raw materials in parts by mass: 12.6 to 15.6 parts of bisphenol F epoxy resin, 12.5 to 14.5 parts of multifunctional epoxy resin, 6 to 8 parts of phosphorus-nitrogen flame retardant, 5 to 7 parts of aluminum hydroxide, 7 to 9 parts of glass powder, 1 to 3 parts of fumed silica, 10 to 12 parts of modified asphalt-based carbon fiber powder, 36.9 to 40.9 parts of anhydride curing agent, and 1 to 3 parts of a Lewis acid curing accelerator. The halogen-free flame-retardant epoxy resin potting compound of the present invention has the characteristics of good thermal conductivity, low heat release, and high compressive strength. In addition, the potting compound has a long storage period and a high storage temperature. It does not need to be pre-cured at room temperature before the product is cured, which greatly improves the stability and reliability of the potting compound.

Description

Technical Field

[0001] The present invention relates to the technical field of potting adhesives, and in particular to a halogen-free flame-retardant epoxy resin potting adhesive and a preparation method and application thereof. Background Art

[0002] When installing inserts in the honeycomb sandwich structure of aviation interior components, a potting adhesive is typically co-cured with the honeycomb base sheet to ensure a secure bond. The potting adhesive currently used in the aviation field is a single-component adhesive that is prone to implosion during curing, especially at high temperatures. Therefore, it needs to be left at room temperature for a period of time before use to allow the resin to pre-cure and dissipate some of the reaction heat before curing. This prevents implosion caused by concentrated heat release during the curing process. However, this potting adhesive suffers from a short storage period (three months) and low storage temperature (-30°C), which can easily lead to product scrapping, affecting on-site manufacturing efficiency and causing significant waste.

[0003] Therefore, there is an urgent need to provide a potting compound that has a long storage period, high storage temperature, and does not require pre-curing at room temperature before the product is cured. Summary of the Invention

[0004] In view of this, the present invention provides a halogen-free flame-retardant epoxy resin potting compound and its preparation method and application, in order to solve the problems of the existing aviation potting compound having a short storage period, low storage temperature and the need for pre-curing at room temperature before the product is cured.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention provides a halogen-free flame-retardant epoxy resin potting compound, comprising the following components in parts by mass:

[0007] 12.6-15.6 parts of bisphenol F epoxy resin, 12.5-14.5 parts of multifunctional epoxy resin, 6-8 parts of phosphorus-nitrogen flame retardant, 5-7 parts of aluminum hydroxide, 7-9 parts of glass powder, 1-3 parts of fumed silica, 10-12 parts of modified asphalt-based carbon fiber powder, 36.9-40.9 parts of acid anhydride curing agent, and 1-3 parts of Lewis acid curing accelerator.

[0008] Preferably, the multifunctional epoxy resin includes one or more of 4-(2,3-epoxypropoxy)-N,N-di(2,3-epoxypropyl)aniline, N,N,N,N,-tetraepoxypropyl-4,4-diaminodiphenylmethane, and 4,5-epoxytetrahydrophthalic acid diglycidyl ester.

[0009] Preferably, the phosphorus-nitrogen flame retardant includes one or more of ammonium polyphosphate, melamine, melamine cyanurate, melamine polyphosphate, dimelamine pyrophosphate, and piperazine pyrophosphate.

[0010] Preferably, the modified asphalt-based carbon fiber powder is asphalt-based carbon fiber powder modified with a silane coupling agent; the silane coupling agent includes one or more of vinyltriethoxysilane, vinyltrimethoxysilane, and vinyltri(β-methoxyethoxy)silane.

[0011] Preferably, the acid anhydride curing agent includes one or more of methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, and trialkylated tetrahydrophthalic anhydride.

[0012] Preferably, the Lewis acid curing accelerator includes one or more of boron trichloride dimethyloctylamine complex, boron trichloride trimethylamine complex, and boron trifluoride benzylamine complex.

[0013] The present invention also provides a method for preparing the above-mentioned halogen-free flame-retardant epoxy resin potting adhesive, comprising the following steps:

[0014] 1) mixing bisphenol F epoxy resin, multifunctional epoxy resin, phosphorus-nitrogen flame retardant, aluminum hydroxide, glass powder, fumed silica, and modified asphalt-based carbon fiber powder to obtain a mixture;

[0015] 2) The mixture is mixed with an anhydride curing agent and a Lewis acid curing accelerator to obtain a halogen-free flame retardant epoxy resin potting compound.

[0016] Preferably, the mixing time in step 1) is 60 to 70 minutes.

[0017] Preferably, the mixing time in step 2) is 30 to 40 minutes, and the mixing vacuum degree is ≥0.09 MPa.

[0018] The present invention also provides a use of the halogen-free flame retardant epoxy resin potting adhesive prepared by the preparation method of the halogen-free flame retardant epoxy resin potting adhesive in the installation of aviation interior trim inserts.

[0019] It can be seen from the above technical solution that compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention utilizes an anhydride curing agent in combination with a Lewis acid curing accelerator, which can reduce the reaction activation energy so that the curing reaction can be started at a low temperature. At the same time, by regulating the reaction rate to disperse the exothermic peak, the concentrated heat release can be reduced. In addition, by adding modified asphalt-based carbon fiber powder, a three-dimensional heat-conducting network structure can be formed in the resin, thereby improving the thermal conductivity of the resin and effectively conducting away the heat released by the potting compound during the curing process, thereby solving the problem of implosion of the potting compound during the curing process, especially during high-temperature curing.

[0021] The halogen-free flame-retardant epoxy resin potting compound described in this invention features excellent thermal conductivity, low heat release, and high compressive strength. It also has a long shelf life (6 months) and a high storage temperature (-18°C). Furthermore, the potting compound exhibits low curing heat release and good thermal conductivity, making it less susceptible to implosion during the curing process. Therefore, the halogen-free flame-retardant epoxy resin potting compound described in this invention eliminates the need for room-temperature pre-curing before product curing, significantly improving the potting compound's stability and reliability. Furthermore, using this potting compound to install aircraft interior inserts can significantly increase the production efficiency of aircraft interior components. DETAILED DESCRIPTION

[0022] The present invention provides a halogen-free flame-retardant epoxy resin potting compound, comprising the following components in parts by mass:

[0023] 12.6-15.6 parts of bisphenol F epoxy resin, 12.5-14.5 parts of multifunctional epoxy resin, 6-8 parts of phosphorus-nitrogen flame retardant, 5-7 parts of aluminum hydroxide, 7-9 parts of glass powder, 1-3 parts of fumed silica, 10-12 parts of modified asphalt-based carbon fiber powder, 36.9-40.9 parts of acid anhydride curing agent, and 1-3 parts of Lewis acid curing accelerator.

[0024] In the present invention, the bisphenol F epoxy resin is preferably 13.5 to 15.0 parts, more preferably 14.0 to 14.8 parts, more preferably 14.2 parts; the multifunctional epoxy resin is preferably 12.5 to 14.0 parts, more preferably 13.0 to 13.5 parts, more preferably 13.2 parts; the phosphorus nitrogen flame retardant is preferably 6.5 to 7.5 parts, more preferably 7 parts; the aluminum hydroxide is preferably 5.5 to 6.8 parts, more preferably 5.8 to 6.2 parts, more preferably 6 parts; the glass powder is preferably 7.2 to 8.8 parts, more preferably 7 .5~8.2 parts, more preferably 8 parts; the fumed silica is preferably 1.2~2.8 parts, more preferably 1.5~2.5 parts, more preferably 2 parts; the modified asphalt-based carbon fiber powder is preferably 10.2~11.8 parts, more preferably 10.5~11.3 parts, more preferably 11 parts; the acid anhydride curing agent is preferably 37.0~40.5 parts, more preferably 38.0~39.5 parts, more preferably 38.9 parts; the Lewis acid curing accelerator is preferably 1.2~2.8 parts, more preferably 1.5~2.2 parts, more preferably 2 parts.

[0025] In the present invention, the specification of the aluminum hydroxide is preferably 2000~4000 mesh, more preferably 2500~3500 mesh, more preferably 2800~3000 mesh; the specification of the glass powder is preferably 2000~4000 mesh, more preferably 2500~3500 mesh, more preferably 2800~3000 mesh; the specification of the fumed silica is preferably 20~40 nm, more preferably 25~35 nm, more preferably 28~30 nm.

[0026] In the present invention, the bisphenol F epoxy resin can reduce viscosity; and the multifunctional epoxy resin can increase glass transition temperature.

[0027] In the present invention, the multifunctional epoxy resin includes one or more of 4-(2,3-epoxypropoxy)-N,N-di(2,3-epoxypropyl)aniline, N,N,N,N,-tetraepoxypropyl-4,4-diaminodiphenylmethane, and 4,5-epoxytetrahydrophthalic acid diglycidyl ester.

[0028] In the present invention, the phosphorus-nitrogen flame retardant includes one or more of ammonium polyphosphate, melamine, melamine cyanurate, melamine polyphosphate, dimelamine pyrophosphate, and piperazine pyrophosphate, preferably ammonium polyphosphate.

[0029] In the present invention, the modified asphalt-based carbon fiber powder is an asphalt-based carbon fiber powder modified with a silane coupling agent; the silane coupling agent includes one or more of vinyltriethoxysilane, vinyltrimethoxysilane, and vinyltri(β-methoxyethoxy)silane; by adding the asphalt-based carbon fiber powder modified with a silane coupling agent, the thermal conductivity of the resin can be improved, and the heat released by the potting compound during the curing process can be effectively conducted away.

[0030] In the present invention, the preparation method of the silane coupling agent modified asphalt-based carbon fiber powder is a conventional method for modifying fibers with a silane coupling agent. The specific preparation method is preferably: mixing the silane coupling agent with the asphalt-based carbon fiber powder, conducting a modification reaction, and after the modification reaction is completed, drying, crushing and sieving are performed in sequence to obtain modified asphalt-based carbon fiber powder.

[0031] In the present invention, the mass ratio of the silane coupling agent to the pitch-based carbon fiber powder is preferably 1:20-50, more preferably 1:25-45, and even more preferably 1:30-40.

[0032] In the present invention, the temperature of the modification reaction is preferably 60-70°C, more preferably 62-68°C, and more preferably 65°C; the time of the modification reaction is preferably 1-2 h, more preferably 1.2-1.8 h, and more preferably 1.5 h; the drying temperature is preferably 110-130°C, more preferably 115-125°C, and more preferably 120°C; the drying time is preferably 1.5-2.5 h, more preferably 1.8-2.2 h, and more preferably 2 h; the mesh size of the sieving is preferably 200-400 mesh, more preferably 230-360 mesh, and more preferably 260-320 mesh.

[0033] In the present invention, before adding the asphalt-based carbon fiber powder, a pretreatment operation of the asphalt-based carbon fiber powder is also included. The pretreatment operation of the asphalt-based carbon fiber powder is preferably: drying the asphalt-based carbon fiber powder under vacuum to obtain pretreated asphalt-based carbon fiber powder; the drying temperature is preferably 60~80°C, more preferably 65~75°C, and more preferably 70°C; the drying time is preferably 1.5~2.5 h, more preferably 1.8~2.2 h, and more preferably 2 h; the purpose of the drying is to remove water adsorbed on the surface of the asphalt-based carbon fiber powder.

[0034] In the present invention, the acid anhydride curing agent includes one or more of methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, and trialkyl tetrahydrophthalic anhydride, preferably methyltetrahydrophthalic anhydride.

[0035] In the present invention, the Lewis acid curing accelerator includes one or more of boron trichloride dimethyloctylamine complex, boron trichloride trimethylamine complex, and boron trifluoride benzylamine complex, preferably boron trichloride dimethyloctylamine complex; wherein, the use of anhydride curing agent in combination with the Lewis acid curing accelerator can reduce the total amount of curing heat release and concentrated heat release.

[0036] The present invention also provides a method for preparing the above-mentioned halogen-free flame-retardant epoxy resin potting adhesive, comprising the following steps:

[0037] 1) mixing bisphenol F epoxy resin, multifunctional epoxy resin, phosphorus-nitrogen flame retardant, aluminum hydroxide, glass powder, fumed silica, and modified asphalt-based carbon fiber powder to obtain a mixture;

[0038] 2) The mixture is mixed with an anhydride curing agent and a Lewis acid curing accelerator to obtain a halogen-free flame retardant epoxy resin potting compound.

[0039] In the present invention, the mixing time in step 1) is 60 to 70 minutes, preferably 62 to 68 minutes, and more preferably 65 minutes.

[0040] In the present invention, the mixing time in step 2) is 30 to 40 minutes, preferably 32 to 38 minutes, and more preferably 35 minutes; the mixing vacuum degree is ≥ 0.09 MPa, preferably 0.095 to 0.1 MPa.

[0041] The present invention also provides a use of the halogen-free flame retardant epoxy resin potting adhesive prepared by the preparation method of the halogen-free flame retardant epoxy resin potting adhesive in the installation of aviation interior trim inserts.

[0042] The technical solutions provided by the present invention are described in detail below with reference to the following examples, but they should not be construed as limiting the scope of protection of the present invention. Silane coupling agent-modified asphalt-based carbon fiber powder is obtained by conventional silane coupling agent-modified fiber methods.

[0043] Example 1

[0044] 1) First, the asphalt-based carbon fiber powder was dried under vacuum at 60 ° C for 2.5 h to obtain pretreated asphalt-based carbon fiber powder; then, vinyl trimethoxysilane was mixed with the pretreated asphalt-based carbon fiber powder and subjected to modification reaction at 60 ° C for 2 h, wherein the mass ratio of vinyl trimethoxysilane to asphalt-based carbon fiber powder was ‌1:20. After the modification reaction was completed, the powder was dried at 110 ° C for 2.5 h, and then pulverized and passed through a 200 mesh sieve to obtain vinyl trimethoxysilane-modified asphalt-based carbon fiber powder for later use; then, 15.6 parts of bisphenol F epoxy resin, 14.5 parts of N,N,N,N,-tetraepoxypropyl-4,4-diaminodiphenylmethane, 8 parts of ammonium polyphosphate flame retardant, 7 parts of aluminum hydroxide (2000 mesh), 8 parts of glass powder (2000 mesh), and fumed silica (20 nm) 1 part and 12 parts of asphalt-based carbon fiber powder modified with vinyltrimethoxysilane were added into a closed stirring container and mixed for 65 minutes to obtain a mixture;

[0045] 2) Add 40.9 parts of methyltetrahydrophthalic anhydride and 1 part of boron trichloride dimethyloctylamine complex to the mixture, start the vacuum pump and control the vacuum degree at 0.092 MPa, degas and stir for 35 minutes to obtain a halogen-free flame retardant epoxy resin potting compound.

[0046] After testing, the performance parameters of the halogen-free flame retardant epoxy resin potting compound obtained in this Example 1 are shown in Table 1.

[0047] Table 1 Performance parameters of halogen-free flame retardant epoxy resin potting adhesive

[0048]

[0049] As can be seen from Table 1, the halogen-free flame-retardant epoxy resin potting adhesive of the present invention has the characteristics of low density, high thermal conductivity, high compressive strength, high high-temperature compressive strength, long frozen storage period, low curing heat release, and is not easy to explode during the curing process of the product.

[0050] Application Example 1

[0051] The halogen-free flame-retardant epoxy resin potting adhesive prepared in Example 1 was potted in a 30 mm thick honeycomb panel. The panel was then cured in an autoclave by heating the panel to 180° C. at a heating rate of 2° C. per minute for 4 hours and then cooling the panel to 60° C. at a cooling rate of 2° C. per minute to obtain a potted honeycomb panel.

[0052] In this application example, the halogen-free flame-retardant epoxy resin potting adhesive prepared in Example 1 of the present invention did not undergo implosion during the curing process of a 30 mm thick honeycomb panel. That is, the potting adhesive provided by the present invention solves the problem that existing potting adhesives are prone to implosion during product curing and require pre-curing at room temperature before product curing.

[0053] Example 2

[0054] 1) First, the asphalt-based carbon fiber powder was dried under vacuum at 70 ° C for 2 h to obtain pretreated asphalt-based carbon fiber powder; then, vinyl triethoxysilane was mixed with the pretreated asphalt-based carbon fiber powder and subjected to modification reaction at 65 ° C for 1.5 h, wherein the mass ratio of vinyl triethoxysilane to asphalt-based carbon fiber powder was ‌1:30. After the modification reaction was completed, the powder was dried at 120 ° C for 2 h, then crushed and passed through a 250 mesh sieve to obtain vinyl triethoxysilane-modified asphalt-based carbon fiber powder for later use; then, 13.5 parts of bisphenol F epoxy resin, 12.5 parts of 4-(2,3-epoxypropyloxy)-N,N-di(2,3-epoxypropyl)aniline, 6 parts of melamine flame retardant, 5.5 parts of aluminum hydroxide (3000 mesh), 7 parts of glass powder (3000 mesh), and fumed silica (30 nm) 1.5 parts and 10 parts of asphalt-based carbon fiber powder modified with vinyltriethoxysilane were added into a closed stirring container and mixed for 62 minutes to obtain a mixture;

[0055] 2) Add 37.0 parts of methylhexahydrophthalic anhydride and 1.5 parts of boron trichloride trimethylamine complex to the mixture, start the vacuum pump and control the vacuum degree at 0.095 MPa, degas and stir for 33 minutes to obtain a halogen-free flame retardant epoxy resin potting compound.

[0056] Example 3

[0057] 1) First, the asphalt-based carbon fiber powder was dried under vacuum at 80 ° C for 1.5 h to obtain pretreated asphalt-based carbon fiber powder; then, vinyl tris (β-methoxyethoxy) silane was mixed with the pretreated asphalt-based carbon fiber powder and subjected to modification reaction at 70 ° C for 1 h, wherein the mass ratio of vinyl tris (β-methoxyethoxy) silane to asphalt-based carbon fiber powder was ‌1:50. After the modification reaction was completed, the powder was dried at 130 ° C for 2 h, and then pulverized and passed through a 400 mesh sieve to obtain vinyl tris (β-methoxyethoxy) silane-modified asphalt-based carbon fiber powder for later use; then, 14.2 parts of bisphenol F epoxy resin, 13.2 parts of 4,5-epoxytetrahydrophthalic acid diglycidyl ester, 7 parts of melamine cyanurate flame retardant, 6 parts of aluminum hydroxide (4000 mesh), 8 parts of glass powder (4000 mesh), and fumed silica (40 nm) and 11 parts of asphalt-based carbon fiber powder modified with vinyl tris(β-methoxyethoxy)silane were added into a closed stirring container and mixed for 70 minutes to obtain a mixture;

[0058] 2) Add 38.9 parts of methyl nadic anhydride and 2 parts of boron trifluoride benzylamine complex to the mixture, start the vacuum pump and control the vacuum degree at 0.098 MPa, degas and stir for 40 minutes to obtain a halogen-free flame retardant epoxy resin potting compound.

[0059] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A halogen-free flame retardant epoxy resin potting compound, characterized in that: The composition includes the following parts by mass: 12.6-15.6 parts of bisphenol F epoxy resin, 12.5-14.5 parts of multifunctional epoxy resin, 6-8 parts of phosphorus-nitrogen flame retardant, 5-7 parts of aluminum hydroxide, 7-9 parts of glass powder, 1-3 parts of fumed silica, 10-12 parts of modified asphalt-based carbon fiber powder, 36.9-40.9 parts of acid anhydride curing agent, and 1-3 parts of Lewis acid curing accelerator; The modified asphalt-based carbon fiber powder is asphalt-based carbon fiber powder modified with a silane coupling agent; The silane coupling agent includes one or more of vinyltriethoxysilane, vinyltrimethoxysilane, and vinyltri(β-methoxyethoxy)silane; The acid anhydride curing agent includes one or more of methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, and trialkyl tetrahydrophthalic anhydride; The Lewis acid curing accelerator includes one or more of boron trichloride dimethyloctylamine complex, boron trichloride trimethylamine complex, and boron trifluoride benzylamine complex.

2. The halogen-free flame-retardant epoxy resin potting compound according to claim 1, characterized in that: The multifunctional epoxy resin includes one or more of 4-(2,3-epoxypropoxy)-N,N-di(2,3-epoxypropyl)aniline, N,N,N,N,-tetraepoxypropyl-4,4-diaminodiphenylmethane, and 4,5-epoxytetrahydrophthalic acid diglycidyl ester.

3. The halogen-free flame-retardant epoxy resin potting compound according to claim 1, characterized in that: The phosphorus-nitrogen flame retardant includes one or more of ammonium polyphosphate, melamine, melamine cyanurate, melamine polyphosphate, dimelamine pyrophosphate, and piperazine pyrophosphate.

4. The method for preparing a halogen-free flame-retardant epoxy resin potting compound according to any one of claims 1 to 3, characterized in that: The steps include: 1) mixing bisphenol F epoxy resin, multifunctional epoxy resin, phosphorus-nitrogen flame retardant, aluminum hydroxide, glass powder, fumed silica, and modified asphalt-based carbon fiber powder to obtain a mixture; 2) The mixture is mixed with an anhydride curing agent and a Lewis acid curing accelerator to obtain a halogen-free flame retardant epoxy resin potting compound.

5. The method for preparing a halogen-free flame-retardant epoxy resin potting compound according to claim 4, characterized in that: The mixing time in step 1) is 60 to 70 minutes.

6. The method for preparing a halogen-free flame-retardant epoxy resin potting compound according to claim 5, characterized in that: The mixing time in step 2) is 30 to 40 minutes, and the mixing vacuum degree is ≥ 0.09 MPa.

7. Use of the halogen-free flame retardant epoxy resin potting compound according to any one of claims 1 to 3 or the halogen-free flame retardant epoxy resin potting compound prepared by the preparation method of the halogen-free flame retardant epoxy resin potting compound according to any one of claims 4 to 6 in the installation of aviation interior trim inserts.

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