Halogen-free flame-retardant epoxy resin pouring sealant as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of pouring sealants, and provides a halogen-free flame-retardant epoxy resin pouring sealant as well as a preparation method and application thereof. The composite material is prepared from the following raw materials in parts by mass: 12.6-15.6 parts of bisphenol F epoxy resin, 12.5-14.5 parts of polyfunctional epoxy resin, 6-8 parts of a 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 an anhydride curing agent and 1-3 parts of a Lewis acid curing accelerator. The halogen-free flame-retardant epoxy resin pouring sealant disclosed by the invention has the characteristics of good thermal conductivity, low heat release and high compressive strength, the storage period of the pouring sealant is long, the storage temperature of the pouring sealant is high, and the pouring sealant does not need to be pre-cured at normal temperature in advance before being cured, so that the stability and the reliability of the pouring sealant are greatly improved.

Description

Technical Field

[0001] The 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 the inserts in the honeycomb sandwich structure of aviation interior parts, the method of co-curing the potting adhesive and the honeycomb base plate is generally used to make the inserts stick firmly. The potting glue currently used in the aviation field is a single-component adhesive, which is prone to explosion when curing, especially when curing at high temperature. Therefore, it needs to be placed at room temperature for a period of time before use to allow the resin to pre-cure for a period of time to release part of the reaction heat in advance, and then cure the product. This can avoid concentrated heat release during the curing process and explosion. However, this potting glue has the problems of short storage period (3 months) and low storage temperature (-30℃), which can easily cause product scrapping, affect on-site manufacturing efficiency and cause huge waste.

[0003] Therefore, there is an urgent need to provide a potting adhesive with a long storage period, high storage temperature and no need for 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 adhesive and a preparation method and application thereof, so as to solve the problems that the existing aviation potting adhesive has a short storage period, a low storage temperature and needs to be pre-cured at room temperature before the product is cured.

[0005] In order to achieve the above object, the present invention adopts the following technical solution: The present invention provides a halogen-free flame-retardant epoxy resin potting adhesive, comprising the following components in 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.

[0006] 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.

[0007] Preferably, the phosphorus-nitrogen flame retardant includes one or more of ammonium polyphosphate, melamine, melamine cyanurate, melamine polyphosphate, dimelamine pyrophosphate, and piperazine pyrophosphate.

[0008] 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.

[0009] Preferably, the acid anhydride curing agent includes one or more of methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, and trialkyltetrahydrophthalic anhydride.

[0010] Preferably, the Lewis acid curing accelerator includes one or more of boron trichloride dimethyloctylamine complex, boron trichloride trimethylamine complex, and boron trifluoride benzylamine complex.

[0011] The present invention also provides a preparation method of the above halogen-free flame-retardant epoxy resin potting adhesive, which includes the following steps: 1) Mix bisphenol F-type epoxy resin, multi-functional epoxy resin, phosphazene-based flame retardant, aluminum hydroxide, glass powder, fumed silica, and modified asphalt-based carbon fiber powder to obtain a mixture; 2) Mix the mixture with an acid anhydride curing agent and a Lewis acid curing accelerator to obtain a halogen-free flame-retardant epoxy resin potting adhesive.

[0012] Preferably, the mixing time in step 1) is 60 - 70 minutes.

[0013] Preferably, the mixing time in step 2) is 30 - 40 minutes, and the mixing vacuum degree ≥ 0.09 Mpa.

[0014] The present invention also provides an application of the halogen-free flame-retardant epoxy resin potting adhesive prepared by the above preparation method of the halogen-free flame-retardant epoxy resin potting adhesive in the installation of aviation interior inserts.

[0015] Through the above technical solutions, compared with the prior art, the beneficial effects of the present invention are as follows: The present invention uses an acid 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 low temperature. At the same time, by regulating the reaction rate to disperse the exothermic peak value, the concentrated heat release can be reduced. And by adding modified asphalt-based carbon fiber powder, a three-dimensional heat conduction network structure can be formed in the resin, improving the thermal conductivity of the resin, and effectively conducting the heat released during the curing process of the potting adhesive, thereby solving the problem of explosive polymerization of the potting adhesive during the curing process, especially during high-temperature curing.

[0016] The halogen-free flame-retardant epoxy resin potting adhesive described in the present invention has the characteristics of good thermal conductivity, low heat release, and high compressive strength. Moreover, the potting adhesive has a long storage period (6 months) and a high storage temperature (-18°C). In addition, the potting adhesive has low heat release during curing and good thermal conductivity, and is not prone to explosive polymerization during the curing process. Therefore, the halogen-free flame-retardant epoxy resin potting adhesive described in the present invention does not need to be pre-cured at room temperature in advance before product curing, which greatly improves the stability and reliability of the potting adhesive. At the same time, when using this potting adhesive to install aviation interior inserts, the production efficiency of aviation interior parts can be greatly improved. Detailed implementation mode

[0017] The present invention provides a halogen-free flame-retardant epoxy resin potting adhesive, which comprises the following components in parts by mass: 12.6 - 15.6 parts of bisphenol F epoxy resin, 12.5 - 14.5 parts of multi-functional epoxy resin, 6 - 8 parts of phosphorus-nitrogen-based 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, 1 - 3 parts of Lewis acid curing accelerator.

[0018] In the present invention, the bisphenol F epoxy resin is preferably 13.5 - 15.0 parts, more preferably 14.0 - 14.8 parts, and most preferably 14.2 parts; the multi-functional epoxy resin is preferably 12.5 - 14.0 parts, more preferably 13.0 - 13.5 parts, and most preferably 13.2 parts; the phosphorus-nitrogen-based flame retardant is preferably 6.5 - 7.5 parts, more preferably 7 parts; the aluminum hydroxide is preferably 5.5 - 6.8 parts, more preferably 5.8 - 6.2 parts, and most preferably 6 parts; the glass powder is preferably 7.2 - 8.8 parts, more preferably 7.5 - 8.2 parts, and most preferably 8 parts; the fumed silica is preferably 1.2 - 2.8 parts, more preferably 1.5 - 2.5 parts, and most preferably 2 parts; the modified asphalt-based carbon fiber powder is preferably 10.2 - 11.8 parts, more preferably 10.5 - 11.3 parts, and most preferably 11 parts; the acid anhydride curing agent is preferably 37.0 - 40.5 parts, more preferably 38.0 - 39.5 parts, and most preferably 38.9 parts; the Lewis acid curing accelerator is preferably 1.2 - 2.8 parts, more preferably 1.5 - 2.2 parts, and most preferably 2 parts.

[0019] In the present invention, the specification of the aluminum hydroxide is preferably 2000 - 4000 mesh, more preferably 2500 - 3500 mesh, and even more preferably 2800 - 3000 mesh; the specification of the glass powder is preferably 2000 - 4000 mesh, more preferably 2500 - 3500 mesh, and even more preferably 2800 - 3000 mesh; the specification of the fumed silica is preferably 20 - 40 nm, more preferably 25 - 35 nm, and even more preferably 28 - 30 nm.

[0020] In the present invention, the bisphenol F epoxy resin can reduce the viscosity; the polyfunctional epoxy resin can increase the glass transition temperature.

[0021] In the present invention, the polyfunctional epoxy resin includes one or more of 4-(2,3-epoxypropoxy)-N,N-bis(2,3-epoxypropyl)aniline, N,N,N,N,-tetraglycidyl-4,4-diaminodiphenylmethane, and diglycidyl 4,5-epoxytetrahydrophthalate.

[0022] In the present invention, the phosphorus-nitrogen based flame retardant includes one or more of ammonium polyphosphate, melamine, melamine cyanurate, melamine polyphosphate, di-melamine pyrophosphate, and piperazine pyrophosphate, and is preferably ammonium polyphosphate.

[0023] In the present invention, the modified asphalt-based carbon fiber powder is an asphalt-based carbon fiber powder modified by a silane coupling agent; the silane coupling agent includes one or more of vinyltriethoxysilane, vinyltrimethoxysilane, and vinyltris(β-methoxyethoxy)silane; by adding the asphalt-based carbon fiber powder modified by the silane coupling agent, the thermal conductivity coefficient of the resin can be increased, and the heat released during the curing process of the potting adhesive can be effectively conducted out.

[0024] 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, carrying out a modification reaction, and sequentially performing drying, pulverizing, and sieving after the modification reaction is completed to obtain the modified asphalt-based carbon fiber powder.

[0025] In the present invention, the mass ratio of the silane coupling agent to the asphalt-based carbon fiber powder is preferably 1:20 - 50, more preferably 1:25 - 45, and even more preferably 1:30 - 40.

[0026] In the present invention, the temperature of the modification reaction is preferably 60-70 °C, more preferably 62-68 °C, and still more preferably 65 °C; the time of the modification reaction is preferably 1-2 h, more preferably 1.2-1.8 h, and still more preferably 1.5 h; the temperature of the drying is preferably 110-130 °C, more preferably 115-125 °C, and still more preferably 120 °C; the time of the drying is preferably 1.5-2.5 h, more preferably 1.8-2.2 h, and still more preferably 2 h; the mesh number of the sieving is preferably 200-400 meshes, more preferably 230-360 meshes, and still more preferably 260-320 meshes.

[0027] In the present invention, before adding the pitch-based carbon fiber powder, a pretreatment operation of the pitch-based carbon fiber powder is further included. The pretreatment operation of the pitch-based carbon fiber powder is preferably: drying the pitch-based carbon fiber powder under vacuum to obtain the pretreated pitch-based carbon fiber powder; the temperature of the drying is preferably 60-80 °C, more preferably 65-75 °C, and still more preferably 70 °C; the time of the drying is preferably 1.5-2.5 h, more preferably 1.8-2.2 h, and still more preferably 2 h; the purpose of the drying is to remove the adsorbed water on the surface of the pitch-based carbon fiber powder.

[0028] In the present invention, the acid anhydride curing agent includes one or more of methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, and trialkyltetrahydrophthalic anhydride, and is preferably methyltetrahydrophthalic anhydride.

[0029] 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, and is preferably boron trichloride dimethyloctylamine complex; wherein, the combination of the acid anhydride curing agent and the Lewis acid curing accelerator can reduce the total heat release during curing and the concentrated heat release.

[0030] The present invention also provides a preparation method of the above-mentioned halogen-free flame-retardant epoxy resin potting adhesive, which includes the following steps: 1) Mix bisphenol F type epoxy resin, multi-functional group epoxy resin, phosphorus-nitrogen based flame retardant, aluminum hydroxide, glass powder, fumed silica, and modified pitch-based carbon fiber powder to obtain a mixture; 2) Mix the mixture with an acid anhydride curing agent and a Lewis acid curing accelerator to obtain a halogen-free flame-retardant epoxy resin potting adhesive.

[0031] In the present invention, the mixing time in step 1) is 60-70 minutes, preferably 62-68 minutes, and more preferably 65 minutes.

[0032] In the present invention, the mixing time in step 2) is 30 to 40 minutes, preferably 32 to 38 minutes, more preferably 35 minutes; the degree of vacuum for mixing is ≥0.09 Mpa, preferably 0.095 to 0.1 Mpa.

[0033] The present invention also provides an application of a halogen-free flame-retardant epoxy resin potting adhesive prepared by the above-mentioned preparation method of the halogen-free flame-retardant epoxy resin potting adhesive in the installation of aviation interior inserts.

[0034] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the protection scope of the present invention. Among them, the silane coupling agent-modified asphalt-based carbon fiber powder is obtained by modifying conventional fibers with a silane coupling agent.

[0035] Example 1

[0036] 1) First, dry the asphalt-based carbon fiber powder under vacuum at 60 °C for 2.5 h to obtain the pretreated asphalt-based carbon fiber powder; then mix vinyltrimethoxysilane with the pretreated asphalt-based carbon fiber powder and carry out a modification reaction at 60 °C for 2 h. Among them, the mass ratio of vinyltrimethoxysilane to asphalt-based carbon fiber powder is 1:20. After the modification reaction is completed, dry it at 110 °C for 2.5 h, and then pulverize and screen it through a 200-mesh sieve to obtain vinyltrimethoxysilane-modified asphalt-based carbon fiber powder for standby; then add 15.6 parts of bisphenol F-type epoxy resin, 14.5 parts of N,N,N,N,-tetraglycidyl-4,4-diaminodiphenylmethane, 8 parts of ammonium polyphosphate flame retardant, 7 parts of aluminum hydroxide (2000 mesh), 8 parts of glass powder (2000 mesh), 1 part of fumed silica (20 nm), and 12 parts of vinyltrimethoxysilane-modified asphalt-based carbon fiber powder into a closed stirring container and mix for 65 minutes to obtain a mixture; 2) Add 40.9 parts of methyltetrahydrophthalic anhydride and 1 part of boron trichloride dimethyloctylamine complex to the mixture, turn on the vacuum pump and control the vacuum degree at 0.092 Mpa, and carry out degassing and stirring for 35 minutes to obtain a halogen-free flame-retardant epoxy resin potting adhesive.

[0037] After testing, the performance parameters of the halogen-free flame-retardant epoxy resin potting adhesive obtained in Example 1 are shown in Table 1.

[0038] Table 1 Performance parameters of the halogen-free flame-retardant epoxy resin potting adhesive

[0039] As can be seen from Table 1, the halogen-free flame-retardant epoxy resin potting adhesive described in the present invention has the characteristics of low density, high thermal conductivity, high compressive strength, high high-temperature compressive strength, long freeze storage period, low curing exotherm, and not being prone to explosive polymerization during the curing process of the product.

[0040] Application Example 1 The halogen-free flame-retardant epoxy resin potting adhesive prepared in Example 1 was potted in a 30-mm-thick honeycomb panel, and then the autoclave curing process was used. The temperature was raised to 180 °C at a rate of 2 °C per minute and cured for 4 hours, and then the temperature was lowered to 60 °C at a rate of 2 °C per minute to obtain the potted honeycomb panel.

[0041] In this application example, the halogen-free flame-retardant epoxy resin potting adhesive prepared in Example 1 of the present invention did not undergo explosive polymerization during the curing process of the 30-mm-thick honeycomb panel. That is, the potting adhesive provided by the present invention solves the problems that the existing potting adhesives are prone to explosive polymerization during product curing and need to be pre-cured at room temperature in advance before product curing.

[0042] Example 2

[0043] 1) First, the pitch-based carbon fiber powder was dried under vacuum at 70 °C for 2 h to obtain the pretreated pitch-based carbon fiber powder; then vinyltriethoxysilane was mixed with the pretreated pitch-based carbon fiber powder, and a modification reaction was carried out at a temperature of 65 °C for 1.5 h. Among them, the mass ratio of vinyltriethoxysilane to pitch-based carbon fiber powder was 1:30. After the modification reaction was completed, it was dried at a temperature of 120 °C for 2 h, and then pulverized and sieved through a 250-mesh sieve to obtain the vinyltriethoxysilane-modified pitch-based carbon fiber powder for standby; then 13.5 parts of bisphenol F-type epoxy resin, 12.5 parts of 4-(2,3-epoxypropoxy)-N,N-bis(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), 1.5 parts of fumed silica (30 nm), and 10 parts of vinyltriethoxysilane-modified pitch-based carbon fiber powder were added to a closed stirring container and mixed for 62 minutes to obtain a mixture; 2) 37.0 parts of methylhexahydrophthalic anhydride and 1.5 parts of boron trichloride trimethylamine complex were added to the mixture, the vacuum pump was turned on and the vacuum degree was controlled at 0.095 Mpa, and degassing and stirring were carried out for 33 minutes to obtain the halogen-free flame-retardant epoxy resin potting adhesive.

[0044] Example 3

[0045] 1) First, dry the pitch-based carbon fiber powder under vacuum conditions at 80 °C for 1.5 h to obtain the pretreated pitch-based carbon fiber powder; then mix vinyltris(β-methoxyethoxy)silane with the pretreated pitch-based carbon fiber powder and carry out a modification reaction at a temperature of 70 °C for 1 h. Among them, the mass ratio of vinyltris(β-methoxyethoxy)silane to the pitch-based carbon fiber powder is 1:50. After the modification reaction is completed, dry it at a temperature of 130 °C for 2 h, then pulverize it and pass through a 400-mesh sieve to obtain the pitch-based carbon fiber powder modified with vinyltris(β-methoxyethoxy)silane for standby; then add 14.2 parts of bisphenol F-type epoxy resin, 13.2 parts of diglycidyl 4,5-epoxytetrahydrophthalate, 7 parts of melamine cyanurate flame retardant, 6 parts of aluminum hydroxide (4000 mesh), 8 parts of glass powder (4000 mesh), 2.5 parts of fumed silica (40 nm), and 11 parts of the pitch-based carbon fiber powder modified with vinyltris(β-methoxyethoxy)silane into a closed stirring container and mix for 70 minutes to obtain a mixture; 2) Add 38.9 parts of methyl nadic anhydride and 2 parts of boron trifluoride benzylamine complex to the mixture, turn on the vacuum pump and control the vacuum degree at 0.098 Mpa, and carry out degassing and stirring for 40 minutes to obtain a halogen-free flame-retardant epoxy resin potting adhesive.

[0046] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A halogen-free flame-retardant epoxy resin potting adhesive, characterized in that: The composition includes the following components in parts by weight: 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.

2. The halogen-free flame-retardant epoxy resin potting adhesive 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 adhesive 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. A halogen-free flame-retardant epoxy resin potting adhesive according to any one of claims 1 to 3, characterized in that: The modified asphalt-based carbon fiber powder is an asphalt-based carbon fiber powder modified by a silane coupling agent; The silane coupling agent includes one or more of vinyl triethoxy silane, vinyl trimethoxy silane, and vinyl tri(β-methoxyethoxy) silane.

5. The halogen-free flame-retardant epoxy resin potting adhesive according to claim 4, characterized in that: The acid anhydride curing agent includes one or more of methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, and trialkyl tetrahydrophthalic anhydride.

6. The halogen-free flame-retardant epoxy resin potting adhesive according to claim 5, characterized in that: The Lewis acid curing accelerator includes one or more of boron trichloride dimethyloctylamine complex, boron trichloride trimethylamine complex, and boron trifluoride benzylamine complex.

7. The method for preparing a halogen-free flame-retardant epoxy resin potting adhesive according to any one of claims 1 to 6, 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 adhesive.

8. The method for preparing a halogen-free flame-retardant epoxy resin potting adhesive according to claim 7, characterized in that: The mixing time in step 1) is 60 to 70 minutes.

9. The method for preparing a halogen-free flame-retardant epoxy resin potting adhesive according to claim 8, characterized in that: The mixing time in step 2) is 30 to 40 minutes, and the mixing vacuum degree is ≥ 0.09 MPa.

10. Use of the halogen-free flame retardant epoxy resin potting adhesive as claimed in any one of claims 1 to 6 or the halogen-free flame retardant epoxy resin potting adhesive prepared by the preparation method of the halogen-free flame retardant epoxy resin potting adhesive as claimed in any one of claims 7 to 9 in the installation of aviation interior trim inserts.

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