A kind of preparation method of modified bismaleimide resin

Abstract

The invention discloses a method for preparing a nitrogen-containing propargyl compound modified bismaleimide resin. The modified bismaleimide resin is obtained by prepolymerization of two components A and B in a molten state, wherein component A is a bismaleimide monomer 4,4'-bismaleimidodiphenylmethane, and component B is a N,N,N',N'-tetrapropargyl aromatic diamine compound, and the prepolymerized modified resin is prepared by electron beam radiation curing or thermal curing process to prepare a resin cured product. The modified bismaleimide resin prepared by the present invention has good soluble and fusible processing performance, and the heat resistance and flame retardancy of its cured product are better than those of traditional modified bismaleimide resins. Electron beam radiation curing bismaleimide resin has the advantages of low energy consumption and fast curing speed, and its application potential is large.

Description

Technical Field

[0001] The invention belongs to the field of high-performance thermosetting resins, and in particular relates to a method for preparing a modified bismaleimide resin with excellent heat resistance and flame retardancy, and a process for electron beam irradiation curing and heat curing the modified bismaleimide resin. Background Art

[0002] Bismaleimide (BMI) resin is a type of high-performance thermosetting resin derived from the polyimide (PI) resin system. It is a bifunctional compound with maleimide (MI) as the active end group. It has excellent properties such as high temperature resistance, radiation resistance, moisture and heat resistance, high modulus, low moisture absorption rate and small thermal expansion coefficient. Therefore, bismaleimide resin can be used as a high-performance composite material matrix, wear-resistant material, high-temperature resistant insulation material and high-temperature structural adhesive, etc., and is widely used in aerospace, electronic and electrical industries. Traditional bismaleimide resin is prepared by blending bismaleimide monomer and diallyl bisphenol A. The maleimide group easily reacts with the allyl group. After the two components are prepolymerized at a certain temperature for a period of time, a homogeneous solution can be formed, and it has a wide low-viscosity processing window. The cured resin has good heat resistance and mechanical properties. In the 1980s, Giby-Geigy pioneered a new method for modifying bismaleimide with allyl compounds and launched the XU292 modified bismaleimide resin system. Subsequently, the QY8911 series and "CYCOM5250" series were launched in the market.

[0003] In order to meet the application requirements of high-performance maleimide resin, research on environmentally friendly halogen-free, phosphorus-free intrinsic flame-retardant bismaleimide resin has been carried out. Dithiophenyl allyl ether and BDM were prepolymerized at 140℃ and then cured at 150℃ / 2h+180℃ / 2h+200℃ / 2h+220℃ / 2h+240℃ / 4h to prepare a product with a T g The temperature of the bio-based resveratrol allyl ether copolymer modified BDM is cured at 150℃ / 2h+180℃ / 2h+200℃ / 2h+220℃ / 2h+240℃ / 4h. The T g and T d5They are 388°C and 415°C respectively, and the limiting oxygen index is 37.7% (V-0 grade) (PolymDegrad Stab, 2021, 193: 109717.). Allyl eugenol ether was grafted onto polysiloxane and prepolymerized with BDM at 140°C for 30 min and then cured at 150°C / 2h+180°C / 2h+200°C / 2h+220°C / 2h+240°C / 4h. The limiting oxygen index of the resin was 34.6% (UL-94V-0), and the peak heat release rate (PHRR), total heat release (THR) and total smoke production (TSP) decreased by 58.6%, 33.1% and 41.9%, respectively (EurPolym J, 2022, 180:111594.) After allyl etherification, 3,4-dihydroxybenzaldehyde reacted with diaminophenylmethane (DDM) to form a Schiff base. After copolymerization with BDM, the resin was cured at 150°C / 2h+180°C / 2h+200°C / 2h+230°C / 8h. g It can reach 343.5°C, and the limiting oxygen index is 36.4% (PolymAdvTechnol, 2022, 33: 1642-1654.).

[0004] Compared with allyl compounds modifying bismaleimide resins, there are relatively few studies on using alkynyl-terminated compounds to modify bismaleimide resins. Similar to allyl compounds, propargyl compounds can also undergo addition reactions with maleimide groups, and no small molecules are released during the curing process. The difference is that since alkynyl compounds have a higher degree of unsaturation and the hydrogen atoms connected to the alkynyl groups are more active, the unsaturated bonds and active hydrogen make the cross-linked structure of the resin more complex, in which cyclization reactions between multiple end groups may occur, and some propargyl compounds can also undergo self-cyclization. Such cross-linked structures are often beneficial to improving the thermal stability and mechanical properties of bismaleimide resins. The activity of the alkynyl group makes it easier to react with the bismaleimide monomer than the allyl group, which can not only reduce the activation energy of the resin curing reaction, but also help improve the processing performance and thermal properties of the resin. The invention patent (200710043883) discloses a diphenylmethane bismaleimide (BDM) resin modified with isophthalic dipropargyl ether. After curing at 180℃ / 4h+220℃ / 2h+260℃ / 4h, the resin has a 5% thermal weight loss temperature (T d5 ) reached 438°C. Liu Feng et al. (J Appl Polym Sci, 2006, 102: 3610-3615.) synthesized bisphenol A dipropargyl ether for modifying BDM resin. After curing at 170°C / 4h+200°C / 4h+250°C / 6h, the resin T d5 The glass transition temperature (T g) is 358℃. Bisphenol A dipropargyl ether and polyformaldehyde were condensed to prepare propargyl ether phenolic resin. After the blended modified BDM was cured at 170℃ / 4h+200℃ / 4h+250℃ / 6h, its T g The T of PET was 399℃ (J Appl Polym Sci, 2006, 102: 4207-4212.). Zhou et al. (Polymer, 2016, 102: 301-307.) synthesized a tripropargyl ether triazine compound PET, which was prepolymerized with BDM and cured at 180℃ / 2h+240℃ / 4h+290℃ / 2h. d5 Up to 481℃, T g The temperature of bismaleimide resin modified by acetylene compounds has great research potential, but the high temperature and long time curing conditions bring about the disadvantages of high energy consumption and high investment.

[0005] Electron beam curing is a process that uses a high-energy electron beam generated by an electron accelerator as a radiation source to induce a reactive resin system to quickly transform into a solid. Compared with traditional thermal curing processes, electron beam curing, as a non-heating and pressurizing curing method, has the advantages of energy saving, rapid curing, simple tooling, good process flexibility and process matching, and no volatile release. Zhang Zuoguang's research group carried out research on electron beam curing of epoxy resin in China earlier. The cationic photoinitiator diphenyliodonium hexafluorophosphate was added to bisphenol A epoxy resin as a radiation-sensitive initiator to achieve electron beam curing of epoxy resin (Journal of Polymer Science, 2003, (5): 699-703.). The glass transition temperature of epoxy resin cured under the total dose of 150 kGy of electron beam irradiation is 215°C, the tensile strength of the resin casting can reach 52.7 MPa, the tensile elastic modulus is 2.79 GPa, and the elongation at break is 2.18% (Thermosetting Resins, 2007, 22 (6): 29-32.). For bismaleimide resin, due to the electron deficiency of the double bond in the structure, it is difficult for the electron beam to cure pure bismaleimide. Only the resin system with the addition of active diluent can be cured by electron beam induction, and the increase of diluent content and radiation dose is conducive to the complete reaction of bismaleimide. Li Min et al. (Journal of Composite Materials, 2001, 18 (2): 54-56.) The silicon-containing acrylate synthesized from tetraethyl orthosilicate and hydroxyethyl acrylate can be used as an active diluent to crosslink with maleimide by electron radiation, and the cured product has a higher hardness. Li et al. (J Appl Polym Sci, 2004, 94: 2407-2416.) added active diluent N-vinyl pyrrolidone (NVP) to a bismaleimide resin system composed of BDM, 1,3-bismaleimidotoluene and diallyl bisphenol A for electron beam irradiation curing, and studied the correlation between irradiation dose, NVP dosage and curing reaction degree and the temperature rise of the resin system during irradiation, but there is no report on the performance of irradiation cured bismaleimide resin system. Zhang Lijun et al. (Journal of Wuhan University of Technology, 2014, 36 (3): 33-37.) used active diluent styrene and bismaleimide to ultrasonically blend and then irradiate with electron beam to initiate copolymerization. The T of styrene-bismaleimide copolymer was 0.0447 W·m-1.34 ... d5 The addition of reactive diluent can realize the electron beam irradiation curing of bismaleimide resin, but it will cause the decrease of thermal / mechanical properties of bismaleimide resin.

[0006] Acetylene can be irradiated with radiation to react. Zhu Changjin et al. (Journal of Radiation Research and Radiation Processing, 2012, 30(6):339-342.) used polyarylacetylene resin (PAA) to 60After Co is prepolymerized, the thermal stability of the resin obtained by thermal curing is higher than that of PAA directly thermally cured. The alkynyl group of the propargyl compound is rich in electrons. Adding it to the bismaleimide resin can greatly reduce the activation energy required for the resin curing reaction, and the initial product of the reaction can continue to participate in the subsequent curing reaction. Therefore, the bismaleimide resin modified by the propargyl compound is suitable for electron beam radiation curing process. Tripropargyl ether compound modified bismaleimide resin can obtain a heat-resistant resin system. There are no research reports on the copolymerization of tetrapropargyl ether modified bismaleimide resin system, and there are no related work reports on the electron beam radiation curing and resin system performance of tetrapropargyl ether modified bismaleimide resin.

[0007] In view of this, the present invention is proposed. Summary of the invention

[0008] The purpose of the present invention is to prepare a modified bismaleimide resin that can be cured by an electron beam irradiation process, and the resin has better performance than traditional bismaleimide, and the performance of the resin cured by electron beam irradiation is not inferior to the performance of the resin cured by heat. In the present invention, a nitrogen-containing propargyl compound N,N,N',N'-tetrapropargyl aromatic diamine is added as a modifier to a bismaleimide monomer 4,4'-bismaleimidodiphenylmethane (BDM), and a modified bismaleimide resin is obtained by melt prepolymerization, and then a resin cured product can be obtained by electron beam irradiation curing or heat curing. The modified bismaleimide resin cured products obtained under the two curing processes have similar properties, and a new modification method for bismaleimide resin is proposed, which is simple, energy-saving, environmentally friendly, and highly efficient.

[0009] The technical solution adopted by the present invention is:

[0010] A method for preparing a modified bismaleimide resin, the method comprising the following steps:

[0011] (1) 4,4'-bismaleimidodiphenylmethane (component A) and N,N,N',N'-tetrapropargyl-p,p'-diaminodiphenylmethane (component B) are mixed in a certain proportion, the molar ratio of the two components is (1.0-2.0):1.0, and the corresponding mass ratio is (50.6-67.2):(49.4-32.8). Preferably, the molar ratio of components A to B is 2.0:1.0, and the corresponding mass ratio is 67.2:32.8.

[0012] (2) The mixture of components A and B is heated to a certain temperature and stirred at a low speed for a period of time to complete the melt prepolymerization process of the resin. The temperature of the melt copolymerization is 120°C to 150°C, and the reaction time is 30min to 120min. Preferably, the temperature of the melt copolymerization is 130°C, and the reaction time is 60min.

[0013] (3) The prepolymer resin is cured by electron beam radiation in air by scanning multiple times with a fixed dose of electron beam, during which the curing degree of the resin is estimated by differential scanning calorimetry (DSC). The radiation dose of each electron beam radiation curing is 20 kGy, and the total radiation dose is 300 kGy to 800 kGy.

[0014] (4) The modified bismaleimide prepolymer is melted at 60-100°C and poured into a mold or an aluminum box. The staged temperature rise curing program of the prepolymer resin thermal curing is determined by DSC, which is used for the thermal curing process of the prepolymer resin.

[0015] The structure of component A in (1) is:

[0016]

[0017] The structure of component B in (1) is:

[0018]

[0019] The B component is synthesized by reacting an aromatic diamine with 3-halogenated-1-propyne (propargyl halide) by phase transfer catalysis, that is, referring to the literature (J Appl Polym Sci, 2007, 104: 1038-1042., US Pat 4, 885, 403 (1989).) to add an aromatic diamine, an organic solvent and a phase transfer catalyst to an alkaline aqueous solution, add propargyl halide and react at 60-70°C for a certain time, separate the obtained oil phase and wash it with water, remove the solvent and post-treat the product (distillation or recrystallization) to obtain a tetrapropargyl-substituted aromatic diamine. The aromatic diamines in the B component structure are: 1,3-diaminobenzene, 1,4-diaminobenzene, 4,4'-benzidine, 4,4'-diaminodiphenyl ether (ODA), 4,4'-diaminodiphenyl sulfide (DDS) and 4,4'-diaminodiphenylmethane (DDM). 4,4'-diaminodiphenylmethane (DDM) is preferred. Referring to the literature (J Appl Polym Sci, 2007, 104: 1038-1042), MDA, water, potassium carbonate and dichloroethane are added to a reaction flask, and then tetrabutylammonium bromide is added. Propargyl bromide is added dropwise at 70°C under stirring. After the addition, the mixture is reacted for a certain period of time, and then the oil layer is separated by cooling. The crude product is washed with water to remove dichloroethane to obtain a crude product, which is recrystallized from petroleum ether to obtain white crystals - N,N,N',N'-tetrapropargyl-p,p'-diaminodiphenylmethane (TPDDM) with a yield of 85% and a melting point of 55.0°C (measured by SGW X-4 micro melting point instrument of Shanghai Instrument and Electrical Physical Optics Co., Ltd., with a heating rate of 5°C / min).

[0020] In step (2), the heating temperature of the mixture of components A and B is 120° C. to 150° C. Preferably, the heating temperature is 130° C.

[0021] The stirring time of the mixture in step (2) is 60 min to 120 min. Preferably, the stirring time is 60 min.

[0022] The prepolymer prepared in step (2) can be melted at 60°C to 100°C and then poured into a mold or an aluminum box.

[0023] The electron beam emission source in step (3) is an electron gun with an energy of 10 MeV. The radiation curing is performed by multiple staged scanning irradiation, and the atmosphere is air.

[0024] Preferably, the fixed dose of a single electron beam irradiation in the electron beam irradiation curing process in step (3) is 20 kGy.

[0025] Preferably, the total dose of electron beam curing of the resin in the electron beam curing process in step (3) is 720 kGy.

[0026] The heating and curing process described in step (4) is carried out in an oven or a tube furnace in an air atmosphere.

[0027] The present invention provides a preparation method of a modified bismaleimide resin and an electron beam irradiation curing and curing process thereof, and the invention has the following beneficial effects:

[0028] 1. The raw materials used in the present invention can be obtained by a simple method, among which 4,4'-bismaleimidodiphenylmethane (BDM) is a representative raw material for commercial bismaleimide resin, and the modified BDM N,N,N',N'-tetrapropargyl-p,p'-diaminodiphenylmethane (TPDDM) is synthesized by the laboratory with reference to literature. The preparation process of the modified bismaleimide resin only involves the mixing and heating and stirring process of the raw materials BDM and TPDDM, and the preparation method is convenient. The obtained resin is a dark red transparent liquid with a wide low-viscosity processing window, and can also be dissolved in common organic solvents such as acetone, tetrahydrofuran, and dichloromethane, which can meet the molding processes of resin-based composite materials such as molding, prepreg molding, and resin transfer molding.

[0029] 2. Different from the traditional bismaleimide resin modified by allyl compound, the present invention adopts bismaleimide modified by propargyl compound, the activation energy required for the curing reaction is greatly reduced, the heat released during the curing reaction is greatly increased, and the curing reaction can occur by transferring less energy to the resin during the curing process, and the heat generated during the curing process promotes the curing process of the resin.

[0030] 3. Compared with the traditional thermal curing process, the electron beam curing process has the advantages of simple operation, energy saving and environmental protection, and high curing efficiency. In the present invention, when a certain dose of electron beam is irradiated to the modified bismaleimide resin, it will first trigger a free radical reaction in the resin system, and the heat released by the reaction will further promote the resin to undergo a curing process similar to thermal curing. The curing degree of the resin cured by electron beam irradiation can reach more than 80%, and it has similar properties to thermal curing resins. The preparation of this modified bismaleimide resin and its electron beam irradiation curing process provide a feasible, green, environmentally friendly, fast and efficient technical route for the preparation of bismaleimide resin materials.

[0031] 4. In the present invention, N,N,N',N'-tetrapropynyl-p,p'-diaminodiphenylmethane is added to bismaleimide BDM as an active modifier, which can greatly reduce the melting point of the resin from more than 150°C to 60-100°C, greatly improving the processing performance of the bismaleimide resin. Multiple propargyl groups can form a polycyclic structure similar to a benzene ring through a cyclization reaction, thereby improving the heat resistance of the resin. Its glass transition temperature can reach more than 380°C after being tested by a dynamic thermodynamic analyzer (DMA). The cured product of the modified BDM resin still has a bending strength of more than 90% when placed in an air environment at 300°C for 30 minutes.

[0032] 5. The TPDDM modified BDM resin of the present invention contains a large amount of nitrogen, which will produce ammonia, nitrogen oxides and other non-combustible gases during the combustion process, playing a certain role in isolating oxygen. Therefore, the modified bismaleimide resin of the present invention has better flame retardant properties than traditional bismaleimide resin, and the heat release during the combustion process is also lower. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a physical appearance diagram of the active modifier N,N,N',N'-tetrapropynyl-p,p'-diaminodiphenylmethane (TPDDM) used in the present invention;

[0034] Figure 2 is the DSC curve of the modified bismaleimide resin prepared in Example 1 of the present invention in nitrogen;

[0035] Figure 3 is the infrared spectrum of the cured product obtained by electron beam irradiation curing and thermal curing of the modified bismaleimide resin prepared in Example 1 of the present invention;

[0036] Figure 4 is a thermogravimetric analysis (TGA) curve in air of a cured product obtained by electron beam irradiation curing and thermal curing of the modified bismaleimide resin prepared in Example 1 of the present invention;

[0037] Figure 5 DMA curve of the cured product obtained by electron beam irradiation curing and thermal curing of the modified bismaleimide resin prepared in Example 1 of the present invention in nitrogen; DETAILED DESCRIPTION

[0038] In order to more clearly and completely illustrate the technical solution and advantages of the present invention, the technical solution of the present invention is described in detail below through embodiments. The described embodiments are only part of the embodiments of the present invention and are only used for illustration, but not for limiting the scope of the present invention.

[0039] The diphenylmethane bismaleimide (BDM) used in the examples of the present invention was purchased from Hubei Honghu Shuangma New Material Technology Co., Ltd., and N,N,N',N'-tetrapropynyl-p,p'-diaminodiphenylmethane (TPDDM) was synthesized by the laboratory with reference to literature.

[0040] The electron beam irradiation curing of the modified bismaleimide resin in the present invention is carried out by electron beam irradiation on an accelerator irradiation device (DZ-10 / 20) of Shanghai Gaoying Technology Co., Ltd. The power of the electron gun is 20-25kW and the energy is 10MeV.

[0041] The staged temperature rise program of the thermal curing of the modified bismaleimide resin in the present invention is determined based on the exothermic curve obtained by differential scanning calorimeter of the modified bismaleimide resin after prepolymerization, and the specific curing process is related to the proportion of raw materials in the resin.

[0042] In the following embodiments:

[0043] The curing reaction temperature of the modified bismaleimide resin was tested by DSC on a DSC 214Polyma instrument from NETZSCH, with a heating rate of 10°C / min and a nitrogen flow rate of 50 mL / min.

[0044] The structure of the cured product of the modified bismaleimide resin was characterized using a Nicoleti S10 infrared chromatograph from Thermo Fisher, USA.

[0045] The thermal stability of the cured product of the modified bismaleimide resin was tested by TGA on a TGA-DSC 1 of Mettler-Toledo with a heating rate of 10°C / min and a nitrogen flow rate of 60 mL / min.

[0046] The glass transition temperature of the cured product of the modified bismaleimide resin was tested by DMA using a DMA-1 of Mettler-Toledo with a frequency of 1 Hz and a heating rate of 5°C / min.

[0047] The impact performance test of the modified bismaleimide resin after curing was carried out in accordance with the standard ISO 180-Determination of impact strength of plastics, and was carried out on a 9050 impact tester of CEAST Company, Italy.

[0048] The bending performance test of the modified bismaleimide resin after curing was carried out in accordance with the standard GB / T2567-2021-Resin casting performance test method, and was tested using Shenzhen Sansi CMT5504 electronic universal testing machine. The 300°C bending performance test was carried out on the CCSS-44100 electronic universal testing machine of Changchun Institute of Mechanical Science Co., Ltd. The test was carried out after the resin casting was placed at 300°C for 10 minutes.

[0049] The limiting oxygen index (LOI) of the modified bismaleimide resin after curing was tested by a 5801 digital oxygen index instrument produced by Suzhou Yangyi Walch Company in accordance with GB / T 2406.2-2009.

[0050] The combustion performance of the cured modified bismaleimide resin was tested on the MCC-3 micro-combustion calorimeter produced by Deatak, USA.

[0051] Example 1

[0052] Weigh 67.17 g of 4,4'-bismaleimidodiphenylmethane and 32.83 g of N,N,N',N'-tetrapropynyl-p,p'-diaminodiphenylmethane and add them into a 250 mL four-necked round-bottom flask respectively. The flask is equipped with a mechanical stirrer, a condenser and a thermometer. Heat to 130°C and start stirring. The stirring speed is 180 rpm and the stirring time is 60 min to obtain a dark red homogeneous liquid, which is the modified bismaleimide resin.

[0053] The resin was poured into an aluminum box coated with a release agent while hot, placed in a vacuum oven, heated to 130°C, and vacuum degassed at a pressure of -0.1 MPa for 60 minutes.

[0054] The aluminum box containing the modified bismaleimide resin prepolymer is placed on a conveyor disk for electron beam irradiation curing, and the electron beam emitted by the electron gun is perpendicular to the irradiated resin surface. The dose of a single electron beam irradiation is set to 20kGy, and the irradiation dose is accumulated at 20kGy / time, and the total irradiation dose of the modified bismaleimide resin curing is 720kGy. After the irradiation is completed, the cured modified bismaleimide resin is naturally cooled to room temperature, and the cured resin is taken out from the aluminum box, and the surface is polished to a smooth surface using an MPZ-1 metallographic polishing machine (Shanghai Minxin Testing Instrument Co., Ltd., the speed is 350rpm), and the size meets the requirements of the relevant test standard specimens.

[0055] The test results of mechanical properties, thermal stability and combustion performance of the modified bismaleimide resin cured product obtained in Example 1 are shown in Table 1.

[0056] Example 1 Comparison

[0057] Weigh 67.17 g of 4,4'-bismaleimidodiphenylmethane and 32.83 g of N,N,N',N'-tetrapropynyl-p,p'-diaminodiphenylmethane and add them into a 250 mL four-necked round-bottom flask respectively. The flask is equipped with a mechanical stirrer, a condenser and a thermometer. Heat to 130°C and start stirring. The stirring speed is 180 rpm and the stirring time is 60 min to obtain a dark red homogeneous liquid, which is the modified bismaleimide resin.

[0058] The resin was poured into a mold coated with a release agent while hot, placed in a vacuum oven, heated to 130°C, and vacuum degassed at a pressure of -0.1 MPa for 60 minutes.

[0059] After the resin was vacuum degassed, the curing exothermic enthalpy of the resin was measured by differential scanning calorimetry and the step-wise temperature rise thermal curing program of the modified bismaleimide resin was determined. Figure 2 ) The curing reaction temperature determines the curing process of the modified bismaleimide resin as: 150℃ / 2h+180℃ / 2h+220℃ / 2h+260℃ / 4h.

[0060] The resin in the mold is heated and cured in an oven at 150℃ / 2h+180℃ / 2h+220℃ / 2h+260℃ / 4h, and then naturally cooled to room temperature in the oven. After the solidified material is demolded, the surface is polished with an MPZ-1 metallographic polishing machine until it is smooth and flat, and the size meets the requirements of relevant test standard specimens.

[0061] Example 1 Comparison of the infrared analysis results of the obtained modified bismaleimide resin cured product and the infrared analysis results of the electron beam irradiation cured product (see Appendix Figure 3 ) It can be seen that the structures of the modified bismaleimide resin cured by the two curing processes are basically the same. The test results of the mechanical properties, thermal stability and combustion performance of the thermally cured modified bismaleimide resin are shown in Table 1. The modified bismaleimide resin cured product still has a flexural strength of more than 90% when placed in an air environment at 300°C for 30 minutes.

[0062] Example 2

[0063] Weigh 58.88 g of 4,4'-bismaleimidodiphenylmethane and 41.12 g of N,N,N',N'-tetrapropynyl-p,p'-diaminodiphenylmethane and add them into a 250 mL four-necked round-bottom flask respectively. The flask is equipped with a mechanical stirrer, a condenser and a thermometer. The temperature is raised to 130°C and stirring is started. The stirring speed is 180 rpm and the stirring time is 60 min to obtain a dark red homogeneous liquid, which is the modified bismaleimide resin.

[0064] The resin was poured into an aluminum box and a mold coated with a release agent while hot, placed in a vacuum oven, heated to 130°C, and vacuum degassed at a pressure of -0.1 MPa for 60 minutes.

[0065] The aluminum box containing the modified bismaleimide resin prepolymer is placed on a conveyor disk for electron beam irradiation curing, and the electron beam emitted by the electron gun is perpendicular to the irradiated resin surface. The dose of a single electron beam irradiation is set to 20kGy, and the irradiation dose is accumulated at 20kGy / time, and the total irradiation dose of the modified bismaleimide resin curing is 720kGy. After the irradiation is completed, the cured modified bismaleimide resin is naturally cooled to room temperature, and the cured resin is taken out from the aluminum box, and the surface is polished to a smooth surface using an MPZ-1 metallographic polishing machine (Shanghai Minxin Testing Instrument Co., Ltd., the speed is 350rpm), and the size meets the requirements of the relevant test standard specimens.

[0066] The test results of mechanical properties, thermal stability and combustion performance of the modified bismaleimide resin cured product obtained in Example 2 are shown in Table 1.

[0067] Example 2 Comparison

[0068] Weigh 58.88 g of 4,4'-bismaleimidodiphenylmethane and 41.12 g of N,N,N',N'-tetrapropynyl-p,p'-diaminodiphenylmethane and add them into a 250 mL four-necked round-bottom flask respectively. The flask is equipped with a mechanical stirrer, a condenser and a thermometer. The temperature is raised to 130°C and stirring is started. The stirring speed is 180 rpm and the stirring time is 60 min to obtain a dark red homogeneous liquid, which is the modified bismaleimide resin.

[0069] The resin was poured into an aluminum box and a mold coated with a release agent while hot, placed in a vacuum oven, heated to 130°C, and vacuum degassed at a pressure of -0.1 MPa for 60 minutes.

[0070] After the resin was vacuum degassed, the staged temperature-raising curing program of the modified bismaleimide resin was determined by differential scanning calorimetry. The curing reaction temperature in the measured DSC curve determined that the curing process of the modified bismaleimide resin was: 150°C / 2h+180°C / 2h+220°C / 2h+260°C / 4h.

[0071] The resin in the mold was heated and cured in an oven at 150°C / 2h+180°C / 2h+220°C / 2h+260°C / 4h, and then naturally cooled to room temperature in the oven. After the solidified material was demolded, the surface was polished to a smooth surface using an MPZ-1 metallographic polishing machine (Shanghai Minxin Testing Instrument Co., Ltd., with a rotation speed of 350rpm).

[0072] Example 2 Comparison of the mechanical properties, thermal stability and combustion performance of the modified bismaleimide resin cured product is shown in Table 1.

[0073] Example 3

[0074] Weigh 50.56 g of 4,4'-bismaleimidodiphenylmethane and 49.44 g of N,N,N',N'-tetrapropynyl-p,p'-diaminodiphenylmethane respectively and add them into a 250 mL four-necked round-bottom flask equipped with a mechanical stirrer, a condenser and a thermometer. Raise the temperature to 130°C and start stirring at a stirring speed of 180 rpm for 60 min to obtain a dark red homogeneous liquid, which is the modified bismaleimide resin.

[0075] The resin was poured into an aluminum box and a mold coated with a release agent while hot, placed in a vacuum oven, heated to 130°C, and vacuum degassed at a pressure of -0.1 MPa for 60 minutes.

[0076] The aluminum box containing the modified bismaleimide resin prepolymer is placed on a conveyor disk for electron beam irradiation curing, and the electron beam emitted by the electron gun is perpendicular to the irradiated resin surface. The dose of a single electron beam irradiation is set to 20kGy, and the irradiation dose is accumulated at 20kGy / time, and the total irradiation dose of the modified bismaleimide resin curing is 720kGy. After the irradiation is completed, the cured modified bismaleimide resin is naturally cooled to room temperature, and the cured resin is taken out from the aluminum box, and the surface is polished to a smooth surface using an MPZ-1 metallographic polishing machine (Shanghai Minxin Testing Instrument Co., Ltd., the speed is 350rpm), and the size meets the requirements of the relevant test standard specimens.

[0077] The test results of mechanical properties, thermal stability and combustion performance of the modified bismaleimide resin cured product obtained in Example 3 are shown in Table 1.

[0078] Example 3 Comparison

[0079] Weigh 50.56 g of 4,4'-bismaleimidodiphenylmethane and 49.44 g of N,N,N',N'-tetrapropynyl-p,p'-diaminodiphenylmethane respectively and add them into a 250 mL four-necked round-bottom flask equipped with a mechanical stirrer, a condenser and a thermometer. Raise the temperature to 130°C and start stirring at a stirring speed of 180 rpm for 60 min to obtain a dark red homogeneous liquid, which is the modified bismaleimide resin.

[0080] The resin was poured into an aluminum box and a mold coated with a release agent while hot, placed in a vacuum oven, heated to 130°C, and vacuum degassed at a pressure of -0.1 MPa for 60 minutes.

[0081] After the resin was vacuum degassed, the staged temperature-raising curing program of the modified bismaleimide resin was determined by differential scanning calorimetry. The curing reaction temperature in the measured DSC curve determined that the curing process of the modified bismaleimide resin was: 150°C / 2h+180°C / 2h+220°C / 2h+260°C / 4h.

[0082] The resin in the mold was heated and cured in an oven at 150°C / 2h+180°C / 2h+220°C / 2h+260°C / 4h, and then naturally cooled to room temperature in the oven. After the solidified material was demolded, the surface was polished to a smooth surface using an MPZ-1 metallographic polishing machine (Shanghai Minxin Testing Instrument Co., Ltd., with a rotation speed of 350rpm).

[0083] Example 3 Comparison of the mechanical properties, thermal stability and combustion performance of the modified bismaleimide resin cured product is shown in Table 1.

[0084] Table 1 Performance test results of modified bismaleimide resin cured products of Examples 1-3 and their comparisons.

[0085]

[0086]

[0087] From the data in Table 1, it can be seen that the cured resin obtained by the two curing processes of thermal curing and electron beam irradiation curing of the modified bismaleimide resin in the above embodiment has similar thermal properties and mechanical properties, among which some properties of the electron beam irradiation cured resin are even better than the corresponding properties of the thermal curing resin. It shows that the tetrapropargyl substituted aromatic diamine modified bismaleimide resin prepared by the present invention can be efficiently cured by electron beam irradiation, and the performance of the resin cured by electron beam irradiation is not inferior to that of the thermal curing resin. The bismaleimide BDM resin modified by the tetrapropargyl substituted analytical diamine TPDDM copolymer of the present invention has good flame retardancy after thermal curing, and the limiting oxygen index can reach more than 27%.

[0088] One application of the modified bismaleimide resin is: the modified bismaleimide resin is dissolved in acetone to obtain a resin solution, fibers are impregnated with the resin solution to obtain a prepreg, the prepreg is placed in a vacuum bag and pressurized by vacuuming, and the prepreg in the vacuum bag can be cured by an electron beam irradiation process to obtain a resin-based composite material.

[0089] The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with the present invention can make some changes or modify the technical contents suggested above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the solution of the present invention.

Claims

1. A method for preparing a modified bismaleimide resin, characterized in that: The preparation method comprises the following steps: (1) Component A 4,4'-bismaleimidodiphenylmethane and component B N,N,N',N'-tetrapropargyl-p,p'-diaminodiphenylmethane are mixed in proportion, and the molar ratio of component A:component B is (1.0-2.0):1.0; (2) heating the mixture of component A and component B to a certain temperature and stirring for a period of time to complete the melt prepolymerization process of the resin, the melt prepolymerization temperature is 120° C. to 150° C., and the reaction time is 30 min to 120 min to obtain a bismaleimide resin prepolymer; (3) Pour the bismaleimide resin prepolymer into an aluminum box coated with a release agent while it is still hot, place it in a vacuum oven, heat it to 130° C., and vacuum degas for 60 min at a pressure of −0.1 MPa; (4) completing electron beam radiation curing of the prepolymer resin by scanning irradiation with a fixed dose of electron beam in air for multiple times in stages, during which the curing degree of the resin is estimated by differential scanning calorimetry (DSC), the radiation dose of each electron beam radiation curing is 20 kGy, and the total radiation dose is 300 kGy to 800 kGy, to obtain a modified bismaleimide resin; Wherein, the structure of the B component is: The B component is 4,4'-diaminodiphenylmethane substituted with tetrapropargyl groups.

2. The method for preparing the modified bismaleimide resin according to claim 1, wherein Said In step (1), the molar ratio of component A to component B is 2.0:1.0.

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