Preparation method and application of high-temperature-resistant hot-melt bismaleimide resin

Abstract

The invention relates to the technical field of high polymer materials, and particularly discloses a preparation method and application of high-temperature-resistant hot-melt bismaleimide resin. The resin system comprises a bismaleimide monomer, an allyl compound and a special norbornene reactive diluent. The diluent is prepared from norbornene dianhydride and aromatic diamine through a condensation reaction, and the diluent is crushed into micron-sized powder. In the preparation process, the diluent powder is mixed with bismaleimide resin and other components, and the resin meets the hot melting method prepreg preparation technological process. During heating and curing, the diluent powder is molten, so that the melt viscosity of a resin system is remarkably reduced, and the process operability is improved; then, an active end group in the diluent is copolymerized with bismaleimide resin to form a compact cross-linked network, so that small molecule volatile matters are eliminated, and the glass-transition temperature and the thermal decomposition temperature of a cured product are remarkably improved. The method is simple in process and suitable for manufacturing high-performance composite materials in the aerospace field.

Description

Technical Field

[0001] This invention belongs to the field of high-performance thermosetting resin technology, and relates to a preparation method and application of a high-temperature resistant hot-melt bismaleimide resin. It is a high-temperature resistant bismaleimide resin suitable for hot-melt processes, along with its preparation method and application. Background Technology

[0002] Bismaleimide resins are widely used in the aerospace field due to their excellent heat resistance, mechanical properties, and electrical insulation properties. However, traditional bismaleimide resins have disadvantages such as high melting point, high melt viscosity, and narrow processing window, which severely limit their application in advanced composite material molding processes such as hot melt molding and resin transfer molding.

[0003] To improve its processability, reactive diluents are often added. However, common diluents (such as styrene and vinyltoluene) often have problems such as low boiling point, high volatility, porosity during curing, or significant decrease in the heat resistance of the cured product due to the introduction of flexible segments. CN119391185B provides a method for synthesizing hot-melt bismaleimide resin, using a mixture of toluene and diallyl phthalate as a reactive diluent. Although this effectively improves the hot-melt processability of the resin, the introduction of the diluent reduces the temperature resistance of the resin. CN105295048B modifies bismaleimide resin with diallyl compounds as toughening agents, effectively improving the processability and toughness of the resin, but the temperature resistance of the bismaleimide resin is somewhat reduced.

[0004] Therefore, developing a modification method that can effectively reduce resin melt viscosity and improve processability, while maintaining or even improving the resin's heat resistance after curing, has become a pressing technical problem to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing bismaleimide resins, such as high melt viscosity, poor processability, and decreased heat resistance due to the addition of diluents, by providing a method for preparing and using a high-temperature hot-melt bismaleimide resin with excellent processability and higher temperature resistance after curing.

[0006] The core of this invention lies in the design and synthesis of a novel norbornene-based reactive diluent. This diluent has a rigid molecular structure and is a solid powder that can be dry-mixed with resin components at room temperature. During heating, it first melts, reducing viscosity; more importantly, the norbornene groups at the molecular ends and the internal imide rings possess high reactivity and thermal stability, enabling it to copolymerize with the bismaleimide-allyl system to form a denser and more rigid cross-linked network structure. This "first viscosity reduction, then reinforcement" characteristic achieves a synergistic improvement in processability and heat resistance.

[0007] The objective of this invention is achieved through the following technical solution: <First Aspect> This invention relates to a high-temperature resistant hot-melt bismaleimide resin, comprising the following components by weight: 100-150 parts of bismaleimide monomer 50-90 parts of allyl compound, 5-30 parts of norborneol-based reactive diluent; The norbornene-based reactive diluent is an oligomer containing a norbornene ring and an imide structure, generated by the reaction of norbornene olefinic anhydride with p-phenylenediamine or m-phenylenediamine.

[0008] As one embodiment, the norborneol-based active diluent is prepared by reacting norborneol olefinic anhydride with m-phenylenediamine or p-phenylenediamine in a molar ratio of 2.5:1 to 1.0:1.

[0009] As one embodiment, the norbornene-based reactive diluent is a powder with a particle size D50 of 0.1~40μm.

[0010] As one embodiment, the allyl compound is at least one of diallyl bisphenol A, allyl phenol-oxygen resin, diallyl diphenyl ether, and bisphenol A type diallyl ether.

[0011] As one embodiment, the bismaleimide monomer is one or a combination of several of the following: diphenylmethane-type bismaleimide monomer, 4,4'-diaminodiphenyl sulfone bismaleimide monomer, and 4,4'-diaminodiphenyl ether bismaleimide monomer.

[0012] <Second aspect> The present invention also relates to a method for preparing the bismaleimide resin, the method comprising: mixing and stirring bismaleimide monomer and allyl compound at 100-140°C for 20-50 min, and then cooling to 60-100°C; and mechanically mixing with norborneol alkenyl reactive diluent powder at 60-100°C for 30-90 min to obtain bismaleimide resin.

[0013] As one implementation, the mechanical mixing method employs a vertical kneader.

[0014] As one embodiment, the norbornene-based reactive diluent powder is prepared by a method comprising the following steps: S1. Under nitrogen protection, dissolve m-phenylenediamine or other aromatic diamines in N-methylpyrrolidone (NMP) and stir at room temperature until completely dissolved; S2. Add norborneol enediic anhydride in batches, controlling the reaction temperature below 40℃; S3. After the addition of materials is completed, the temperature is raised to 120-140℃ and the reaction is carried out for 3-5 hours to obtain an amic acid prepolymer solution. S4. Perform chemical imidization reaction: Cool the system to 70-90℃, add acetic anhydride as a dehydrating agent, add a catalyst, and stir the reaction for 2-4 hours. S5. After the reaction is complete, pour the reaction solution into a large amount of deionized water to precipitate. Take the precipitate, wash and dry it, and then crush it to obtain diluent powder.

[0015] As one implementation, the pulverization is performed using mechanical grinding or air jet milling.

[0016] As one embodiment, the catalyst may be selected from one or a mixture of several of triethylamine, pyridine, N,N-dimethylaniline, and β-picolinate, preferably triethylamine. In a preferred embodiment, the catalyst is a mixture of triethylamine and 4-dimethylaminopyridine, whose synergistic effect can further improve the imidization efficiency.

[0017] As one implementation scheme, the mass ratio of m-phenylenediamine or p-phenylenediamine to norbornene olefinic anhydride is 5–8:4.

[0018] As one implementation scheme, the amount of acetic anhydride added is 0.1 to 0.3 times the mass of norbornene.

[0019] As one implementation method, the amount of triethylamine added is: 0.15 to 0.35 ml of triethylamine per gram of norbornene.

[0020] <Third aspect> The present invention also relates to the application of the aforementioned bismaleimide resin in the preparation of prepregs by the hot-melt method.

[0021] As one implementation scheme, the curing process used in preparing bismaleimide prepregs via the hot-melt method involves: melt impregnation at 120–180°C, pre-curing at 180–220°C, and finally post-curing at 220–250°C. In some implementation examples, melt impregnation is performed at 120–180°C for 1–3 hours, followed by pre-curing at 180–220°C for 2–4 hours, and finally post-curing at 220–250°C for 5–7 hours.

[0022] As one implementation, the prepreg is used to prepare an aircraft air intake.

[0023] Compared with the prior art, the present invention has the following beneficial effects: 1) Significantly improved processability: The diluent is added in powder form and mixed evenly with the resin components. It melts during the hot melt process, which greatly reduces the melt viscosity of the system and improves the resin's wettability to the fiber. It is particularly suitable for the thermal preparation of high-quality prepregs.

[0024] 2) Effective guarantee of heat resistance: The diluent participates in the final curing reaction, and its rigid norbornene structure and imide ring are introduced into the three-dimensional cross-linking network, which improves the cross-linking density and chain segment rigidity, thereby increasing the glass transition temperature (Tg) and thermal decomposition temperature (Td) of the cured product.

[0025] 3) No small molecule volatilization: The diluent is reactive, and no small molecule volatilization is generated during the curing process, which avoids the formation of pores in the composite material and improves the quality of the product.

[0026] 4) Simple process and easy to implement: The entire preparation process does not require complex equipment, the conditions are mild, and it is suitable for large-scale production. Detailed Implementation

[0027] The present invention will be described in detail below with reference to embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several adjustments and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention. Unless otherwise specified, percentage content and percentage concentration in the present invention refer to mass percentage content and mass percentage concentration. Unless otherwise specified, the raw materials are all obtainable from commercially available sources.

[0028] Example 1 This embodiment relates to a high-temperature resistant hot-melt bismaleimide resin and its preparation.

[0029] Step 1: Under nitrogen protection, 6.2 g of m-phenylenediamine was dissolved in 150 mL of N-methylpyrrolidone and stirred at room temperature until completely dissolved. 4.0 g of norborneol adienoic anhydride was added in batches, and the reaction temperature was controlled below 40 °C. After the addition was complete, the temperature was raised to 120 °C and the reaction was carried out for 4.5 hours to obtain an ammonium acid prepolymer solution. Then the system was cooled to 90 °C, 0.8 g of acetic anhydride was added as a dehydrating agent, and 1 mL of triethylamine was added. The mixture was stirred and reacted for 4 hours. After the reaction was completed, the reaction solution was poured into a large amount of deionized water to precipitate. The precipitate was collected, washed, dried, and then air-jet pulverized to obtain a diluent powder with a particle size of 1 μm.

[0030] Step 2: In a three-necked flask equipped with a mechanical stirrer, thermometer, and nitrogen inlet / outlet, add 100 parts of diphenylmethane-type bismaleimide monomer and 80 parts of diallyl bisphenol A, heat to 120°C, stir for 30 min, then cool to 100°C, add 5 parts of diluent powder, stir for 20 min, then transfer to a vertical kneader, knead and disperse at 90°C for 30 min, cool down, and obtain high-temperature resistant hot-melt bismaleimide resin.

[0031] Example 2 By replacing the intermediate phenylenediamine in step 1 of the example with p-phenylenediamine, and then following the same subsequent steps, a high-temperature resistant hot-melt bismaleimide resin was obtained.

[0032] Example 3 By changing the powder particle size from 1 μm to 20 μm in step 1 of the example, and following the same subsequent steps, a high-temperature resistant hot-melt bismaleimide resin was obtained.

[0033] Example 4 In step 2 of the example, 100 parts of diphenylmethane-type bismaleimide monomer were replaced with 50 parts of diphenylmethane-type bismaleimide monomer and 50 parts of 4,4'-diaminodiphenyl sulfone bismaleimide monomer, while the other implementation steps remained the same, to obtain a high-temperature resistant hot-melt bismaleimide resin.

[0034] Example 5 In step 2 of the example, diallyl bisphenol A was replaced with bisphenol A type diallyl ether, and the subsequent implementation steps were the same to obtain a high-temperature resistant hot-melt bismaleimide resin.

[0035] Example 6 The number of diphenylmethane-type bismaleimide monomers in step 2 of the example was changed to 80 parts, and the subsequent implementation steps were the same to obtain a high-temperature resistant hot-melt bismaleimide resin.

[0036] Example 7 The kneading and dispersion time in step 2 of the embodiment was changed to 90 min, and the subsequent implementation steps were the same to obtain a high-temperature resistant hot-melt bismaleimide resin.

[0037] Comparative Example 1 In a three-necked flask equipped with a mechanical stirrer, thermometer, and nitrogen inlet / outlet, 100 parts of diphenylmethane-type bismaleimide monomer and 80 parts of diallyl bisphenol A were added. The temperature was raised to 120°C and stirred for 30 minutes. Then, 5 parts of polyethersulfone resin were added and stirred for 20 minutes. The mixture was then transferred to a vertical kneader and kneaded and dispersed at 90°C for 30 minutes. After cooling, high-temperature resistant hot-melt bismaleimide resin was obtained.

[0038] Comparative Example 2 Step 1: Under nitrogen protection, 6.2 g of m-phenylenediamine was dissolved in 150 mL of N-methylpyrrolidone and stirred at room temperature until completely dissolved. 4.0 g of norborneol olefinic anhydride was added in batches, and the reaction temperature was controlled below 40 °C. After the addition was complete, the temperature was raised to 120 °C and the reaction was carried out for 4.5 hours to obtain an ammonium acid prepolymer solution. The system was then cooled to 90 °C, 0.8 g of acetic anhydride was added as a dehydrating agent, and 1 mL of triethylamine was added. The mixture was stirred and reacted for 4 hours. After the reaction was completed, the reaction solution was poured into a large amount of deionized water to precipitate. The precipitate was collected, washed, dried, and pulverized to obtain a diluent powder with a particle size of 1 μm.

[0039] Step 2: In a three-necked flask equipped with a mechanical stirrer, thermometer and nitrogen inlet / outlet, add 100 parts of diphenylmethane type bismaleimide monomer, 80 parts of diallyl bisphenol A and 5 parts of diluent powder, heat to 120°C, stir for 30 minutes, cool down to obtain high temperature resistant hot melt bismaleimide resin.

[0040] Comparative Example 3 In Example 1, the intermediate phenylenediamine in step 1 was replaced with BAPP, and the subsequent steps were the same to obtain bismaleimide resin.

[0041] Comparative Example 4 The diluent powder in Example 5 was replaced with an active diluent (toluene and diallyl phthalate in a ratio of 1:1.2), and the subsequent steps were the same to obtain bismaleimide resin.

[0042] The bismaleimide resin of the above scheme was cured at 180℃ for 2h + 220℃ for 3h + 250℃ for 6h to prepare a resin curing product and the glass transition temperature of the resin was tested. The resin was then combined with carbon fiber by hot melt method to prepare a hot melt prepreg. After curing, the glass transition temperature and thermal decomposition temperature of the composite material were tested, and the results are shown in Table 1.

[0043] Table 1 Properties of Bismaleimide Resins and Their Composites

[0044] In summary, the resin system provided by this invention comprises a bismaleimide monomer, an allyl compound, and a specially formulated norbornene-based reactive diluent. This diluent is prepared by a condensation reaction of norbornene olefinic anhydride and an aromatic diamine, and then pulverized into micron-sized powder. During the preparation process, this diluent powder is mixed with other components such as bismaleimide resin, and the resin meets the requirements of the hot-melt prepreg preparation process. During heating and curing, the diluent powder melts, significantly reducing the melt viscosity of the resin system and improving process operability. Subsequently, the active end groups in the diluent copolymerize with the bismaleimide resin to form a dense cross-linked network, which not only eliminates small-molecule volatiles but also significantly increases the glass transition temperature and thermal decomposition temperature of the cured product. This invention has a simple process and is suitable for the manufacture of high-performance composite materials in the aerospace field.

[0045] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A high-temperature resistant bismaleimide resin produced by hot-melt process, characterized in that, By mass parts, it includes the following components: 100-150 parts of bismaleimide monomer 50-90 parts of allyl compound, 5-30 parts of norborneol-based reactive diluent; The norbornene-based reactive diluent is an oligomer containing a norbornene ring and an imide structure, generated by the reaction of norbornene olefinic anhydride with m-phenylenediamine or p-phenylenediamine.

2. The bismaleimide resin according to claim 1, characterized in that, The norborneol-based active diluent is prepared by reacting norborneol olefinic anhydride with m-phenylenediamine or p-phenylenediamine in a molar ratio of 2.5:1 to 1.0:

1.

3. The bismaleimide resin according to claim 1 or 2, characterized in that, The norborneol-based reactive diluent is a powder with a particle size D50 of 0.1~40μm.

4. The bismaleimide resin according to claim 1, characterized in that, The allyl compound is at least one of diallyl bisphenol A, allyl phenolic resin, diallyl diphenyl ether, and bisphenol A type diallyl ether; And / or, the bismaleimide monomer is one or a combination of several of the following: diphenylmethane-type bismaleimide monomer, 4,4'-diaminodiphenyl sulfone bismaleimide monomer, and 4,4'-diaminodiphenyl ether bismaleimide monomer.

5. A method for preparing bismaleimide resin as described in any one of claims 1 to 4, characterized in that, The method includes: mixing and stirring bismaleimide monomer and allyl compound at 100-140℃ for 20-50 min; then cooling to 60-100℃ and mechanically mixing with norborneol alkenyl reactive diluent powder at 60-100℃ for 30-90 min to obtain bismaleimide resin.

6. The method for preparing bismaleimide resin according to claim 5, characterized in that, The mechanical mixing method employs a vertical kneader.

7. The method for preparing bismaleimide resin according to claim 5, characterized in that, The norborneol-based active diluent powder is prepared by a method comprising the following steps: S1. Under nitrogen protection, dissolve m-phenylenediamine or p-phenylenediamine in N-methylpyrrolidone and stir at 20-30 °C until completely dissolved; S2. Add norborneol enediic anhydride in batches, controlling the reaction temperature below 40℃; S3. After the addition of materials is completed, the temperature is raised to 120-140℃ and the reaction is carried out for 3-5 hours to obtain an amic acid prepolymer solution. S4. Perform chemical imidization reaction: Cool the system to 70-90℃, add acetic anhydride as a dehydrating agent, add a catalyst, and stir the reaction for 2-4 hours. S5. After the reaction is complete, pour the reaction solution into a large amount of deionized water to precipitate. Take the precipitate, wash and dry it, and then crush it to obtain diluent powder.

8. The method for preparing bismaleimide resin according to claim 7, characterized in that, The catalyst is selected from one or a mixture of several of triethylamine, pyridine, N,N-dimethylaniline, and β-picolin; And / or, the mass ratio of m-phenylenediamine or p-phenylenediamine to norbornene anhydride is 5–8:4; And / or, the amount of acetic anhydride added is 0.1 to 0.3 times the mass of norbornenic anhydride; And / or, the amount of triethylamine added is: 0.15 to 0.35 ml of triethylamine per gram of norbornenic anhydride; And / or, the pulverization is performed using mechanical grinding or air jet milling.

9. The use of the bismaleimide resin as described in any one of claims 1 to 4 in the preparation of prepregs by the hot-melt method.

10. The application according to claim 9, characterized in that, The curing process used in preparing prepregs by hot-melt method with bismaleimide resin is as follows: melt impregnation at 120~180℃, pre-curing at 180~220℃, and post-curing at 220~250℃. And / or, the prepreg is used to prepare aircraft air intakes.

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