Urea bond modified bismaleimide resin-based elastomer and synthesis method thereof

Abstract

The invention relates to a urea bond modified bismaleimide resin-based elastomer and a synthesis method thereof, and belongs to the field of elastomer composites.The synthesis method comprises the following steps that S1, raw materials are dehydrated; s2, preparing an isocyanate solution from isocyanate and a solvent, and adding polyether amine into the isocyanate solution; s3, heating and pre-polymerizing the reaction solution to obtain a prepolymer; s4, an amino-terminated chain extender is added for a chain extension reaction; and S5, mixing the diamine compound containing carbamido and bismaleimide for reaction, and cooling to obtain the urea bond modified bismaleimide resin-based elastomer. When the carbamido-containing diamine compound reacts with bismaleimide, the amino group of the carbamido-containing diamine attacks the double bond of the bismaleimide to form a carbamido-containing intermediate, and then the carbamido-containing intermediate is cyclized to generate a stable imide structure. The reaction not only can effectively enhance the mechanical properties such as tensile strength and impact toughness of the resin, but also obviously improves the key properties such as heat resistance, chemical corrosion resistance, water resistance and dimensional stability of the resin.

Description

Technical Field

[0001] The present invention belongs to the technical field of elastomer composites, and particularly relates to a urea bond modified bismaleimide resin-based elastomer and a synthesis method thereof. Background Art

[0002] Due to its excellent heat resistance, chemical resistance, corrosion resistance and electrical insulation properties, bismaleimide resin has been widely used in the aviation field, especially in many key fields such as aviation coatings, composites, electronic systems, interior materials, sealants and thermal insulation materials. With the continuous progress of aviation technology, the demand for high-performance materials is increasing day by day. With its excellent comprehensive properties, bismaleimide resin will surely play an increasingly important role in the aviation industry, especially in improving the reliability of materials, extending the service life and meeting the usage requirements under extreme environments, and has great application potential.

[0003] Although bismaleimide resin shows unique advantages in the aviation field, such as excellent heat resistance, chemical resistance and electrical insulation properties, it still faces some limitations in practical applications. These limitations are mainly manifested in its high brittleness, poor low-temperature performance, large processing difficulty, poor ultraviolet stability and insufficient moisture resistance. With the continuous improvement of the material performance requirements in the aviation industry, these inherent disadvantages may restrict the wide use of bismaleimide resin in certain specific applications. Therefore, in the practical applications in the aviation field, bismaleimide resin often needs to be compounded with other high-performance resins (such as epoxy resin, polyimide resin, etc.), or through modification, formulation optimization and processing technology adjustment to improve its performance defects and further expand its application range.

[0004] The modification of bismaleimide resin can significantly improve its applicability in the aviation field and other high-performance applications, especially in key properties such as heat resistance, mechanical properties, low-temperature performance, weather resistance and chemical resistance. The modified bismaleimide resin can adapt to more complex and demanding working environments and ensure stable performance during long-term use. Therefore, with the continuous increase in the demand for high-performance materials, the modification technology of bismaleimide resin has been widely applied in modern aviation and other industrial fields to meet diverse engineering needs and improve the comprehensive performance of materials.

[0005] At present, the modification methods of bismaleimide resin mainly include copolymerization modification, blending modification, chemical modification, nano modification and crosslinking modification, etc. These methods have effectively improved its mechanical properties, heat resistance and processing performance. However, there are still some problems with the modified bismaleimide resin, such as poor processing performance, high cost, insufficient interfacial compatibility, limited thermal stability under extreme conditions, and unbalanced mechanical properties. These problems need to be solved through further research and technology optimization to promote the application of bismaleimide resin in a wider range of fields. Summary of the Invention

[0006] The object of the present invention is to overcome the disadvantages and deficiencies of the prior art, and to provide a urea bond modified bismaleimide resin-based elastomer and a synthesis method thereof. When the urea bond modified bismaleimide resin-based elastomer is reacted with a diamine compound containing a urea group, the amino group in the diamine compound containing a urea group attacks the double bond of the bismaleimide, and after forming an intermediate containing a urea group, it cyclizes to generate a stable imide structure. This nucleophilic addition reaction can not only effectively enhance the mechanical properties of the bismaleimide resin, but also significantly improve its key properties such as heat resistance, chemical corrosion resistance, water resistance and dimensional stability. In addition, with the introduction of the imide structure having a urea group, the heat distortion temperature of the bismaleimide resin can be increased, so that it still maintains good structural stability under high temperature conditions. The performance of the bismaleimide resin can be finely optimized, and the comprehensive performance of the bismaleimide resin can be further optimized to meet the increasingly strict requirements for material properties in modern industry.

[0007] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0008] The synthesis method of the urea bond modified bismaleimide resin-based elastomer of the present invention comprises the following steps:

[0009] S1: Vacuum dehydrate the raw materials of the urea bond modified bismaleimide resin-based elastomer, and after cooling to room temperature, reserve them for use;

[0010] S2: Weigh the dehydrated raw materials according to the raw material ratio of the urea bond modified bismaleimide resin-based elastomer; mix the isocyanate and the solvent evenly to obtain an isocyanate solution;

[0011] Slowly drop the polyetheramine into the isocyanate solution, and stir to obtain a reaction solution;

[0012] S3: Under an inert atmosphere, carry out a prepolymerization reaction on the reaction solution to obtain an isocyanate prepolymer;

[0013] S4: Add an end amino chain extender to the isocyanate prepolymer, stir to carry out a chain extension reaction, and after curing, obtain a diamine compound containing a urea group;

[0014] S5: Mix the diamine compound containing a urea group and the bismaleimide evenly, and under an inert atmosphere, carry out a nucleophilic addition reaction, cool down, and obtain a urea bond modified bismaleimide resin-based elastomer.

[0015] In the said S1, the raw materials for vacuum dehydration include isocyanate, polyetheramine, end amino chain extender, and solvent.

[0016] In the said S1, the vacuum dehydration process is vacuum dehydration at -0.9 Mpa and 100 - 120 °C for 4 - 6 h.

[0017] In the above-mentioned S1, the isocyanate is preferably an aliphatic isocyanate, and more preferably isophorone diisocyanate.

[0018] In the above-mentioned S1, the solvent is selected from one or more of dimethylformamide, dimethylacetamide, and ethylenediamine, and is preferably dimethylformamide.

[0019] In the above-mentioned S2, the isocyanate is preferably isophorone diisocyanate.

[0020] In the above-mentioned S2, the purpose of slow dropping is to slow down the reaction heat release rate and ensure the full fusion of reactants. The preferred dropping rate is 2 - 3 mL / min.

[0021] Furthermore, in the above-mentioned S2, in terms of molar ratio, isocyanate: polyetheramine: solvent is (1 - 5):(5 - 15):(1 - 2).

[0022] Furthermore, in the above-mentioned S2, the polyetheramine is selected from one or more of polyetheramine D2000, polyetheramine D400, and polyetheramine D230.

[0023] Furthermore, in the above-mentioned S3, the temperature of the prepolymerization reaction is 80 - 120 °C, preferably 85 - 100 °C, and it is heated for 1 - 2 h.

[0024] In the above-mentioned S4, the stirring rate of the chain extension reaction is 500 - 800 rpm, the stirring time is 2 - 10 min, and preferably 5 - 10 min.

[0025] In the above-mentioned S4, the temperature of the chain extension reaction is -10 - 30 °C, preferably -5 - 20 °C.

[0026] In the above-mentioned S4, the terminal amino group chain extender is selected from one or more of p-phenylenediamine, isophorone diamine, and phenylenediamine.

[0027] Furthermore, in terms of molar ratio, isocyanate: terminal amino group chain extender = (1 - 5):(1 - 5); preferably (1 - 5):(1 - 2).

[0028] In the above-mentioned S5, the reaction temperature of the nucleophilic addition reaction is 100 - 180 °C, preferably 120 - 180 °C, and the time is 0.5 - 2 h.

[0029] Furthermore, in the above-mentioned S5, in terms of molar ratio, bismaleimide: urea-containing diamine compound = (1 - 3):(1 - 5).

[0030] The present invention also provides a urea - bond - modified bismaleimide - based elastomer, which is prepared by using the above - mentioned synthesis method of the urea - bond - modified bismaleimide - based elastomer. In terms of structure, the urea - bond - modified bismaleimide - based elastomer modifies bismaleimide by introducing a urea - based cross - linked structure, thereby improving its structural characteristics, transforming from a brittle resin material into a new resin material with elastomer characteristics. Its elongation at break can be increased to 160 - 650%, and it maintains the unique high - temperature stability of bismaleimide resin. In the urea - bond - modified bismaleimide - based elastomer, the introduction of the urea - based cross - linked structure not only enhances the cross - linking degree of bismaleimide resin but also optimizes the molecular structure of bismaleimide resin, enabling it to maintain good mechanical strength and morphological stability under high - temperature and corrosive environments. Specifically, the urea - bond - modified bismaleimide - based elastomer exhibits high tensile strength and elongation at break in terms of mechanical properties, and has more excellent toughness and impact resistance compared with traditional unmodified bismaleimide resin. At the same time, due to the stability of the urea - based cross - linked structure, the elastomer can maintain good strength in a high - temperature environment, is not easily softened or deformed, thus expanding its scope of use in high - temperature industrial applications.

[0031] For the urea - bond - modified bismaleimide - based elastomer of the present invention, its tensile strength is 40 - 75 MPa, its elongation at break is 190 - 690%, and its impact strength is 150 - 300 kJ / m 2 ; and its high - temperature stability is 280 - 350 °C.

[0032] In addition, the urea - bond - modified bismaleimide - based elastomer shows outstanding performance in chemical resistance, can resist a variety of solvents and chemical corrosion, and is particularly suitable for application fields that come into contact with chemical reagents or extreme environments. At the same time, due to the presence of the urea - based cross - linked structure, the dimensional stability of bismaleimide resin is effectively improved, so that the urea - bond - modified bismaleimide - based elastomer will not show significant dimensional changes or shape instability during long - term use, further improving its reliability and service life.

[0033] The beneficial effects of the urea - bond - modified bismaleimide - based elastomer and its synthesis method provided by the present invention are as follows:

[0034] When the urea group-containing diamine compound reacts with bismaleimide, the amino group of the urea group-containing diamine compound mainly attacks the double bond of bismaleimide. After forming an intermediate containing a urea group, it cyclizes to generate a stable imide structure. This cross-linking reaction can not only effectively enhance the mechanical properties of bismaleimide, such as tensile strength and impact toughness, but also significantly improve its key properties such as heat resistance, chemical corrosion resistance, water resistance and dimensional stability. This modification reaction optimizes the three-dimensional network structure of bismaleimide by introducing more cross-linking points between bismaleimide molecules, thereby improving its long-term stability and durability under extreme environmental conditions such as high temperature, strong acid, strong alkali, and humid heat. In addition, the introduction of a new urea group cross-linking structure can adjust the glass transition temperature (Tg) of bismaleimide, increase the heat distortion temperature of bismaleimide, and keep its good structural stability under high temperature conditions. Therefore, the urea bond-modified bismaleimide resin-based elastomer has an important application role and is widely used in the preparation of composite materials, coatings, adhesives and other fields, especially in industrial environments that require high strength, high temperature resistance, corrosion resistance and long-term service. By precisely controlling the reaction conditions and raw material ratios, the fine optimization of the resin properties can be achieved, and the comprehensive properties of the resin can be further optimized to meet the increasingly strict requirements for material properties in modern industry. Detailed implementation mode

[0035] The present invention will be further described in detail below with reference to the embodiments.

[0036] The present invention provides a method for synthesizing a urea bond-modified bismaleimide resin-based elastomer, comprising the following steps:

[0037] S1: The raw materials required for the experiment, including isocyanate, polyetheramine, chain extender with terminal amino group, and solvent, are vacuum dehydrated at -0.9 Mpa and 110 °C for 4-5 h, and then cooled to room temperature for standby;

[0038] S2: According to the ratio, a quantitative amount of isophorone diisocyanate and solvent are weighed at room temperature and added to the same reaction vessel to make isophorone diisocyanate uniformly dispersed in the solvent, obtaining an isophorone diisocyanate solution. Then, under stirring conditions, polyetheramine is added dropwise to the above isophorone diisocyanate solution according to the ratio to obtain a reaction solution.

[0039] S3: Transfer the above reaction solution to a three-necked flask and carry out a prepolymerization reaction at 85 °C under a nitrogen atmosphere. After the reaction is completed, an aliphatic isocyanate prepolymer is obtained. The nitrogen atmosphere during the experiment can avoid the generation of excessive side reactions;

[0040] S4: Add an amino - terminated chain extender to the isocyanate prepolymer for chain - extension reaction. The reaction is carried out with mechanical stirring at a rotation speed of 500 - 800 rpm for 5 - 10 min, then transferred to a mold, and the curing of the diamine compound containing urea groups is completed at low temperature under nitrogen conditions to obtain the diamine compound containing urea groups. During the experiment, the nitrogen condition can avoid the generation of excessive side reactions;

[0041] S5: Add a certain amount of bismaleimide to the obtained diamine compound containing urea groups, and heat it under nitrogen conditions for the synthesis of the urea - bond - modified bismaleimide resin - based elastomer. During the experiment, the nitrogen condition can avoid the generation of excessive side reactions; cool down to obtain the urea - bond - modified bismaleimide resin - based elastomer.

[0042] In S3, control the prepolymerization temperature at 80 - 120 °C, preferably 80 - 100 °C, and heat for 1 - 2 h. In S4, control the curing temperature at 0 - 30 °C. In S5, control the nucleophilic addition temperature at 120 - 180 °C.

[0043] When the diamine compound containing urea groups reacts with bismaleimide, it mainly reacts through its amino group (-NH 2 ) with the double bond of bismaleimide to form an intermediate containing urea groups and then cyclize to generate a stable imide structure. This cross - linking reaction can not only effectively enhance the mechanical properties of the resin, such as tensile strength, impact toughness, etc., but also significantly improve its key properties such as heat resistance, chemical corrosion resistance, water resistance and dimensional stability. This modification reaction optimizes the three - dimensional network structure of the resin by introducing more cross - linking points between resin molecules, thereby improving its long - term stability and durability under extreme environmental conditions such as high temperature, strong acid and alkali, and humid heat. In addition, the introduction of the urea - based cross - linking structure can adjust the glass transition temperature (Tg) of the resin, increase the heat distortion temperature of the resin, and make it still maintain good structural stability under high - temperature conditions. Therefore, the application of the diamine compound containing urea groups in bismaleimide resin has an important modification effect and is widely used in the preparation of composite materials, coatings, adhesives and other fields, especially in industrial environments that require high strength, high temperature resistance, corrosion resistance and long - term service. By precisely controlling the reaction conditions and raw material ratios, the fine optimization of the resin properties can be achieved, and the comprehensive properties of the resin can be further optimized to meet the increasingly strict requirements for material properties in modern industry.

[0044] The molar ratio of isophorone diisocyanate: polyetheramine: isophorone diamine = (1 - 5):(5 - 15):(1 - 2). If the dosage of isophorone diamine is too much, then the amino group (-NH 2)The group will react with the isocyanate (-NCO) group in the ureylene molecular chain to form more crosslinking points. Excessive isophorone diamine may lead to a higher degree of crosslinking, making the ureylene crosslinked structure more compact, further enhancing its mechanical strength, thermal stability and chemical resistance. However, excessive crosslinking may also lead to an increase in the brittleness of the ureylene crosslinked structure, affecting its toughness, and may also cause an increase in the brittleness of the material, resulting in easy fracture of the material when subjected to impact or tension.

[0045] The molar ratio of the bismaleimide to the ureylene-containing diamine compound is (1 - 2):(1 - 5). When the amount of the ureylene-containing diamine compound is excessive, the ureylene crosslinking points in the bismaleimide decrease, reducing the crosslinking density, and thus weakening the mechanical properties and heat resistance of the material. Excessive diamine will react with bismaleimide to form oligomers, resulting in a decrease in the molecular weight of the final product, affecting its mechanical properties and thermal stability. The decrease in molecular weight and crosslinking degree makes it too soft and loses a certain rigidity. The decrease in molecular weight and crosslinking degree will not only affect the mechanical properties of the resin, reducing its performance in some specific applications, but may also cause difficulties in the processing process. When the amount of the ureylene-containing diamine compound is insufficient, the bismaleamide cannot react completely, and the remaining bismaleamide may affect the properties of the product. Incomplete reaction will lead to limited growth of the polymer chain, resulting in a decrease in the toughness of bismaleimide. The flexibility of bismaleimide is crucial for many applications, especially during the process of withstanding external forces or deformation, and flexibility can effectively avoid cracking or splitting of the material. Excessive amount of the ureylene-containing diamine compound may increase the viscosity of the resin, thus affecting its fluidity and uniformity during the processing process (such as casting, coating, etc.), resulting in processing difficulties. When the amount is insufficient, the crosslinking reaction of bismaleimide may be incomplete, affecting its curing process, causing uneven curing of bismaleimide, and resulting in unstable final quality of the material.

[0046] The solvent is selected from one or more of dimethylformamide, dimethylacetamide, and ethylenediamine.

[0047] The end amino chain extender is selected from one or more of p-phenylenediamine, isophorone diamine, and phenylenediamine.

[0048] The polyetheramine is selected from one or more of polyetheramine D2000, polyetheramine D400, and polyetheramine D230.

[0049] Example 1

[0050] A method for synthesizing a urea bond modified bismaleimide resin-based elastomer, comprising the following steps:

[0051] S1: Weigh the polyetheramine D2000, isophorone diisocyanate, and dimethylformamide required for the experiment. After vacuum dehydration at 100 °C for 4 h, cool to room temperature and set aside.

[0052] S2: According to the molar ratio, isophorone diisocyanate: polyetheramine D2000: dimethylformamide = 2:5:1, weigh the dehydrated raw materials; at room temperature, evenly distribute isophorone diisocyanate in dimethylformamide to obtain an isophorone diisocyanate solution. Then add polyetheramine D2000 to the above isophorone diisocyanate solution by slow dropping at a rate of 2 mL / min to obtain a reaction solution.

[0053] S3: Transfer the above reaction solution to a three-necked flask and react at 85 °C for 1 h under a nitrogen atmosphere. After the reaction, an aliphatic isocyanate prepolymer is obtained. The nitrogen atmosphere during the experiment can avoid the formation of excessive side reactions;

[0054] S4: According to the molar ratio, isophorone diisocyanate: isophorone diamine = 2:1, weigh isophorone diamine, add isophorone diamine to the above aliphatic isocyanate prepolymer for reaction. The reaction is carried out with mechanical stirring, under a nitrogen atmosphere, stir at a low temperature of 5 °C, a rotation speed of 500 rpm, and stir for 5 min to obtain a diamine compound containing a urea group. The nitrogen atmosphere during the experiment can avoid the formation of excessive side reactions.

[0055] S5: According to the molar ratio, bismaleimide: diamine compound containing a urea group = 2:3, add bismaleimide to the diamine compound containing a urea group, and heat under a nitrogen atmosphere to synthesize a urea-bond modified bismaleimide resin-based elastomer, maintaining the temperature at 110 °C. The nitrogen atmosphere during the experiment can avoid the formation of excessive side reactions; cool down to obtain a urea-bond modified bismaleimide resin-based elastomer.

[0056] Example 2

[0057] A method for synthesizing a urea-bond modified bismaleimide resin-based elastomer, comprising the following steps:

[0058] S1: Weigh the polyetheramine D230, isophorone diisocyanate, and dimethylacetamide required for the experiment. After vacuum dehydration at 120 °C for 5 h, cool to room temperature and set aside.

[0059] S2: According to the molar ratio, isophorone diisocyanate: polyetheramine D230: dimethylacetamide = 1:5:1, weigh the dehydrated raw materials. At room temperature, evenly distribute isophorone diisocyanate in dimethylacetamide to obtain an isophorone diisocyanate solution. Then add polyetheramine D230 to the above isophorone diisocyanate solution by slow dropping at a rate of 3 mL / min to obtain a reaction solution.

[0060] S3: Transfer the above reaction solution to a three-necked flask and carry out a prepolymerization reaction at 85 °C for 1 h under a nitrogen atmosphere. After the reaction, an aliphatic isocyanate prepolymer is obtained. The nitrogen atmosphere during the experiment can avoid the formation of excessive side reactions;

[0061] S4: According to the molar ratio, isophorone diisocyanate: isophorone diamine = 5:1, weigh isophorone diamine and add it to the above aliphatic isocyanate prepolymer for reaction. The reaction is carried out with mechanical stirring, under a nitrogen atmosphere and at a low temperature of 15 °C, with a rotation speed of 600 rpm, and stir for 7 min to obtain a urea-group-containing diamine compound. The nitrogen atmosphere during the experiment can avoid the formation of excessive side reactions

[0062] S5: According to the molar ratio, bismaleimide: urea-group-containing diamine compound = 2:5, add bismaleimide to the urea-group-containing diamine compound, and carry out the synthesis of urea-bond modified bismaleimide resin-based elastomer by heating under a nitrogen atmosphere, maintaining the temperature at 160 °C. The nitrogen atmosphere during the experiment can avoid the formation of excessive side reactions; cool down to obtain a urea-bond modified bismaleimide resin-based elastomer.

[0063] Example 3

[0064] A method for synthesizing a urea-bond modified bismaleimide resin-based elastomer, comprising the following steps:

[0065] S1: Weigh the polyetheramine D400, isophorone diisocyanate, and ethylenediamine required for the experiment, vacuum dehydrate them at 100-120 °C for 4-6 h, and then cool them to room temperature for standby.

[0066] S2: According to the molar ratio, isophorone diisocyanate: polyetheramine D400: ethylenediamine = 5:10:2, weigh the dehydrated raw materials; at room temperature, evenly distribute isophorone diisocyanate in ethylenediamine to obtain an isophorone diisocyanate solution. Then add polyetheramine D400 to the above isophorone diisocyanate solution by slow dropping to obtain a reaction solution.

[0067] S3: Transfer the above reaction solution to a three-necked flask and carry out a reaction at 85 °C for 1 h under a nitrogen atmosphere. After the reaction, an aliphatic isocyanate prepolymer is obtained. The nitrogen atmosphere during the experiment can avoid the formation of excessive side reactions;

[0068] S4: Weigh isophorone diamine according to the molar ratio of isophorone diisocyanate: isophorone diamine = 2:3, and add isophorone diamine to the above-mentioned aliphatic isocyanate prepolymer for reaction. The reaction is carried out with mechanical stirring, under nitrogen conditions, stirring at a low temperature, with the temperature being 5 - 20 °C, the rotation speed being 500 - 800 rpm, and stirring for 5 - 10 min to obtain a diamine compound containing a urea group. During the experiment, the nitrogen condition can avoid the generation of excessive side reactions.

[0069] S5: According to the molar ratio of bismaleimide: diamine compound containing a urea group = 1.5:2, add bismaleimide to the diamine compound containing a urea group, and heat under nitrogen conditions for the synthesis of a urea bond modified bismaleimide resin-based elastomer, maintaining the temperature at 180 °C. During the experiment, the nitrogen condition can avoid the generation of excessive side reactions; cool down to obtain a urea bond modified bismaleimide resin-based elastomer.

[0070] Example 4

[0071] A synthesis method of a urea bond modified bismaleimide resin-based elastomer, comprising the following steps:

[0072] S1: Weigh the polyetheramine D2000, isophorone diisocyanate, and dimethylformamide required for the experiment, and dehydrate them under vacuum at 100 - 120 °C for 4 - 6 h, then cool to room temperature for standby.

[0073] S2: According to the molar ratio of isophorone diisocyanate: polyetheramine D2000: dimethylformamide = 2:8:1.5, weigh the dehydrated raw materials; at room temperature, evenly distribute isophorone diisocyanate in dimethylformamide to obtain an isophorone diisocyanate solution. Then add a quantitative amount of polyetheramine D2000 to the above-mentioned isophorone diisocyanate solution by slow dropping to obtain a reaction solution.

[0074] S3: Transfer the above reaction solution to a three-necked flask and react at 85 °C for 1 h under nitrogen conditions. After the reaction is completed, an aliphatic isocyanate prepolymer is obtained. During the experiment, the nitrogen condition can avoid the generation of excessive side reactions;

[0075] S4: According to the molar ratio of isophorone diisocyanate: isophorone diamine = 3.5:1, weigh isophorone diamine; add isophorone diamine to the above-mentioned aliphatic isocyanate prepolymer for reaction. The reaction is carried out with mechanical stirring, under nitrogen conditions, stirring at a low temperature, with the temperature being 5 °C, the rotation speed being 500 - 800 rpm, and stirring for 5 - 10 min to obtain a diamine compound containing a urea group. During the experiment, the nitrogen condition can avoid the generation of excessive side reactions.

[0076] S5: According to the molar ratio, bismaleimide: urea-containing diamine compound = 1:3.5, add bismaleimide to the urea-containing diamine compound, and heat under nitrogen conditions to synthesize the urea-bond modified bismaleimide resin-based elastomer. Maintain the temperature at 150 °C. The nitrogen condition during the experiment can avoid the generation of excessive side reactions; cool down to obtain the urea-bond modified bismaleimide resin-based elastomer.

[0077] Example 5

[0078] A method for synthesizing a urea-bond modified bismaleimide resin-based elastomer, comprising the following steps:

[0079] S1: Weigh the polyetheramine D230, isophorone diisocyanate, and dimethylformamide required for the experiment, vacuum dehydrate at 100 - 120 °C for 4 - 6 h, and then cool to room temperature for standby.

[0080] S2: According to the molar ratio, isophorone diisocyanate: polyetheramine D230: dimethylformamide = 3:15:2, weigh the dehydrated raw materials; at room temperature, evenly distribute isophorone diisocyanate in dimethylformamide to obtain an isophorone diisocyanate solution. Then add a quantitative amount of polyetheramine D230 to the above isophorone diisocyanate solution by slow dropping to obtain a reaction solution.

[0081] S3: Transfer the above reaction solution to a three-necked flask, and react at 85 °C for 1 h under nitrogen conditions. After the reaction, an aliphatic isocyanate prepolymer is obtained. The nitrogen condition during the experiment can avoid the generation of excessive side reactions;

[0082] S4: According to the molar ratio, isophorone diisocyanate: isophorone diamine = 5:2, weigh isophorone diamine; add isophorone diamine to the above aliphatic isocyanate prepolymer for reaction. The reaction uses mechanical stirring, stir at low temperature under nitrogen conditions, the temperature is 5 - 20 °C, the rotation speed is 500 - 800 rpm, and stir for 5 - 10 min to obtain a urea-containing diamine compound. The nitrogen condition during the experiment can avoid the generation of excessive side reactions.

[0083] S5: According to the molar ratio, bismaleimide: urea-containing diamine compound = 3:2, add bismaleimide to the urea-containing diamine compound, and heat under nitrogen conditions to synthesize the urea-bond modified bismaleimide resin-based elastomer. Maintain the temperature at 100 °C - 180 °C. The nitrogen condition during the experiment can avoid the generation of excessive side reactions; cool down to obtain the urea-bond modified bismaleimide resin-based elastomer.

[0084] Example 6

[0085] A method for synthesizing a urea-bond modified bismaleimide resin-based elastomer, comprising the following steps:

[0086] S1: Weigh the polyetheramine D400, isophorone diisocyanate, and dimethylformamide required for the experiment. After vacuum dehydration at 100 - 120 °C for 4 - 6 h, cool it to room temperature for standby.

[0087] S2: According to the molar ratio, isophorone diisocyanate : polyetheramine D400 : dimethylformamide = 2 : 10 : 1, weigh the dehydrated raw materials. At room temperature, evenly distribute isophorone diisocyanate in dimethylformamide to obtain an isophorone diisocyanate solution. Then, under the condition of stirring in an ice - water bath, quantitatively add polyetheramine D400 to the above - mentioned isophorone diisocyanate solution by slow dropping to obtain a reaction solution.

[0088] S3: Transfer the above - mentioned reaction solution to a three - necked flask and react at 85 °C for 1 h under a nitrogen atmosphere. After the reaction, an aliphatic isocyanate prepolymer is obtained. The nitrogen atmosphere during the experiment can avoid the generation of too many side reactions.

[0089] S4: According to the molar ratio, isophorone diisocyanate : isophorone diamine = 4 : 1.5, weigh isophorone diamine. Add isophorone diamine to the above - mentioned aliphatic isocyanate prepolymer for reaction. The reaction uses mechanical stirring and stirs at a low temperature of 10 °C and a rotation speed of 500 rpm under a nitrogen atmosphere for 5 min to obtain a urea - containing diamine compound. The nitrogen atmosphere during the experiment can avoid the generation of too many side reactions.

[0090] S5: According to the molar ratio, bismaleimide : urea - containing diamine compound = 2 : 5, add bismaleimide to the urea - containing diamine compound and heat under a nitrogen atmosphere for the synthesis of urea - bond - modified bismaleimide resin - based elastomer, maintaining the temperature at 170 °C. The nitrogen atmosphere during the experiment can avoid the generation of too many side reactions. Cool down to obtain the urea - bond - modified bismaleimide resin - based elastomer.

[0091] Comparative Example 1

[0092] Same as Example 1, except that the solvent used is ethanol. Then, the reaction efficiency and product yield of the prepared urea - bond - modified bismaleimide resin - based elastomer decrease. This is because during the synthesis process, the choice of solvent has an important impact on the progress of the reaction, the final properties of the urea - based cross - linked structure, and the processing process. The solvent not only affects the reaction rate and uniformity but also may affect the final mechanical properties, viscosity, processability, and curing properties of the bismaleimide resin. The choice of solvent has an important impact on aspects such as the reaction process, the structure of the urea - based molecular chain, mechanical properties, and the stability of the final product. Reasonable selection of solvent can optimize the synthesis reaction of the urea - based cross - linked structure, improve the product performance, and enhance the processability.

[0093] Comparative Example 2

[0094] Same as Example 1, except that the polyetheramine is polyetheramine T5000. In this case, the molecular weight is too large, and the urea bond-modified bismaleimide resin-based elastomer prepared will be significantly affected in terms of mechanical properties, processing properties, and degree of hydrogen bonding. This shows that the molecular weight of polyetheramine plays a decisive role in the synthesis of urea bond-modified bismaleimide resin-based elastomers. Low molecular weight polyetheramines are usually suitable for urea bond-modified bismaleimide resin-based elastomers that require high strength, rigidity, and heat resistance, but may lead to a decrease in flexibility. High molecular weight polyetheramines, on the other hand, help to improve the flexibility, elasticity, and impact toughness of urea bond-modified bismaleimide resin-based elastomers and are suitable for applications that require good processability and high ductility. However, choosing a high molecular weight polyetheramine will cause the material to lose its original rigidity. In actual production, choosing the appropriate molecular weight of polyetheramine is a key factor that needs to be weighed according to the performance requirements of the final product.

[0095] Comparative Example 3

[0096] Same as Example 1, except that the end-amino chain extender is selected as ethylenediamine. The tensile strength of the urea bond-modified bismaleimide resin-based elastomer prepared is 35.7 ± 1.2 MPa, and the elongation at break is 120 ± 5%. This shows that the end-amino chain extender plays an important role by reacting with isocyanate to form a urea crosslinked structure. Different amino chain extenders have different effects on the molecular weight, structure, mechanical properties, and other physical properties of the urea crosslinked structure. Smaller diamine chain extenders (such as ethylenediamine) will result in harder and more brittle materials, while larger diamine chain extenders help to improve toughness and ductility. Diamine chain extenders can also significantly enhance the chemical resistance of the urea crosslinked structure and are suitable for applications in corrosive environments.

[0097] Comparative Example 4

[0098] Same as Example 1, except that in S4, by molar ratio, isocyanate: end-amino chain extender = 1:9. The tensile strength of the urea bond-modified bismaleimide resin-based elastomer prepared is 30.4 ± 1.2 MPa, and the elongation at break is 100 ± 5%. This shows that when the amount of end-amino chain extender is too large, the amino (-NH 2 ) group will react with the isocyanate (-NCO) group in the urea molecular chain to form more crosslinking points. Too much end-amino chain extender may lead to a higher degree of crosslinking, making the urea crosslinked structure more compact, further enhancing its mechanical strength, thermal stability, and chemical resistance. However, excessive crosslinking may also increase the brittleness of the urea crosslinked structure, affecting its toughness and causing the material to easily break when subjected to impact or tension.

[0099] Comparative Example 5

[0100] Same as Example 1, except that in S5, by molar ratio, bismaleimide: urea-containing diamine compound = 1:7. Then, the tensile strength of the urea bond-modified bismaleimide resin-based elastomer prepared is 25.22 ± 1.4 MPa, and the elongation at break is 540.74 ± 5%. When the dosage of the urea-containing diamine compound is excessive, the urea crosslinking points in bismaleimide increase, which may lead to overcrosslinking. Overcrosslinking will reduce the mechanical properties, heat resistance and chemical corrosion resistance of bismaleimide. If the dosage of the urea-containing diamine compound is insufficient, the crosslinking density is relatively low, resulting in an incomplete crosslinking structure of bismaleimide, making bismaleimide too hard and losing a certain degree of flexibility. It may even affect the processability of the resin and increase brittleness. Excessive amount of the urea-containing diamine compound may increase the viscosity of the resin, thus affecting its fluidity and uniformity during processing (such as pouring, coating, etc.), resulting in processing difficulties. When the dosage of the urea-containing diamine compound is insufficient, the crosslinking reaction of bismaleimide may be incomplete, affecting its curing process, causing uneven curing of bismaleimide, and resulting in unstable final quality of the material. The addition ratio of bismaleimide and the urea-containing diamine compound will have an important impact on the properties of the resin during synthesis. When the proportion of bismaleimide is relatively high, it helps to improve the hardness, strength, heat resistance, chemical resistance and anti-aging properties of the resin, but may lead to higher brittleness and poorer flexibility. When the proportion of the urea-containing diamine compound is relatively high, it can enhance the flexibility, ductility and processability of the resin, but may reduce the thermal stability, chemical resistance and mechanical strength.

[0101] Test Example 1

[0102] The tensile property test of a urea bond-modified bismaleimide resin-based elastomer material includes the following steps:

[0103] S1: Prepare four samples respectively from a urea bond-modified bismaleimide resin-based elastomer material obtained by the method in Examples 1-6. The tensile specimen is 35 mm long, 2 mm wide in the middle, 1 mm thick, and the gauge length is 10 mm.

[0104] S2: Clamp the prepared specimen between the fixtures of the tensile testing machine to ensure uniform and firm clamping at both ends of the specimen.

[0105] S3: Start the tensile testing machine, and the test is carried out at a strain rate of 50 mm / min. Each sample is tested according to ISO 37-2005. At the same time, record the changes in the tensile force and displacement (elongation) of the specimen.

[0106] S4: After the specimen breaks, record the maximum displacement of the specimen during tensile (usually measured from the initial gauge length) as the elongation at break in the test. And calculate the tensile strength and elongation at break of the specimen.

[0107] Test Example 2

[0108] S1: Take 5 mg of the sample and evenly distribute it on the bottom of the crucible. Place the sample crucible in the sample chamber of the TG instrument.

[0109] S2: During the test, introduce gas (such as ammonia or air) at a rate of 150 mL / min to ensure that the sample is tested in a controlled atmosphere. Control the temperature program and raise the temperature to 105 °C at a certain heating rate (such as 10 - 20 °C and hold for 1 minute), and maintain this temperature for 5 - 10 minutes to remove moisture or other volatile components in the sample.

[0110] S3: Subsequently, continue to raise the temperature from 105 °C at the same heating rate.

[0111] S4: During the entire heating process, continuously record the mass change of the sample using the instrument to generate a mass - temperature curve (TG curve). This curve shows the mass change of the sample at different temperatures, reflecting the thermal stability, decomposition behavior, and composition of the material.

[0112] The test results are as follows in the table

[0113]

[0114] The comparison results test are as follows in the table

[0115]

[0116] Note:

[0117] 1) Tensile strength: Clamp the sample of the urea - bond - modified bismaleimide resin - based elastomer between the fixtures of an electronic tensile testing machine, start the tensile testing machine at a set tensile rate of 50 mm / min, and record the changes in the tensile force and displacement (or elongation) of the specimen. After the specimen breaks, calculate the tensile strength of the specimen based on the maximum tensile force recorded during the test and the initial cross - sectional area of the specimen.

[0118]

[0119] 2) Elongation at break: Clamp the sample of the urea - bond - modified bismaleimide resin - based elastomer between the fixtures of an electronic tensile testing machine, start the tensile testing machine at a set tensile rate of 50 mm / min, and record the changes in the tensile force and displacement (or elongation) of the specimen. After the specimen breaks, record the maximum displacement of the specimen during tensile (usually measured from the initial gauge length) as the elongation at break in the test.

[0120]

[0121] Where: Lf is the gauge length (final length) of the specimen at fracture. LO is the initial gauge length (starting length) of the specimen.

[0122] The present invention is not limited to the above embodiments. If various modifications or variations of the present invention do not depart from the spirit and scope of the present invention, and provided that these modifications and variations are within the scope of the claims of the present invention and equivalent technical scope, the protection scope of the present invention also includes these modifications and variations.

Claims

1. A method for synthesizing a urea bond-modified bismaleimide resin-based elastomer, characterized in that: The synthesis method of the urea bond modified bismaleimide resin-based elastomer comprises the following steps: S1: vacuum dehydrating the raw materials for synthesizing urea bond modified bismaleimide resin-based elastomer; S2: according to the raw material ratio of the urea bond modified bismaleimide resin-based elastomer, weigh the dehydrated raw materials; mix the isocyanate and the solvent evenly to obtain an isocyanate solution; Slowly adding polyetheramine dropwise into the isocyanate solution and stirring to obtain a reaction solution; S3: Under an inert atmosphere, subjecting the reaction solution to a prepolymerization reaction to obtain an isocyanate prepolymer; S4: adding the terminal amino chain extender to the isocyanate prepolymer, stirring to carry out a chain extension reaction, and after curing, obtaining a urea-containing diamine compound; S5: uniformly mixing the urea-containing diamine compound and bismaleimide, carrying out a nucleophilic addition reaction under an inert atmosphere, and cooling to obtain a urea-modified bismaleimide resin-based elastomer.

2. The method for synthesizing the urea bond modified bismaleimide resin-based elastomer according to claim 1, characterized in that: The raw materials for vacuum dehydration include isocyanate, polyetheramine, amino-terminated chain extender and solvent. The raw materials are vacuum dehydrated at 100-120° C. for 4-6 hours and then cooled to room temperature for standby use.

3. The method for synthesizing the urea bond modified bismaleimide resin-based elastomer according to claim 2, characterized in that: The solvent is selected from one or more of dimethylformamide, dimethylacetamide and ethylenediamine.

4. The method for synthesizing the urea bond modified bismaleimide resin-based elastomer according to claim 1, characterized in that: In S2, the molar ratio of isocyanate:polyetheramine:solvent is (1-5):(5-15):(1-2).

5. The method for synthesizing the urea bond modified bismaleimide resin-based elastomer according to claim 1, characterized in that: The polyetheramine is selected from one or more of polyetheramine D2000, polyetheramine D400 and polyetheramine D230.

6. The method for synthesizing the urea bond modified bismaleimide resin-based elastomer according to claim 1, characterized in that: In the above-mentioned S3, the temperature of the prepolymerization reaction is 80-120° C., and the heating time is 1-2 hours.

7. The method for synthesizing the urea bond modified bismaleimide resin-based elastomer according to claim 1, characterized in that: In S4, the amino-terminated chain extender is selected from one or more of p-phenylenediamine, isophoronediamine, and phenylenediamine.

8. The method for synthesizing the urea bond modified bismaleimide resin-based elastomer according to claim 1, characterized in that: In the S4, the stirring rate of the chain extension reaction is 500-800 rpm, the stirring time is 2-10 min, and the temperature of the chain extension reaction is -10-30° C.; in molar ratio, isocyanate: terminal amino chain extender = (1-5): (1-5).

9. The method for synthesizing a urea bond-modified bismaleimide resin-based elastomer according to claim 1, characterized in that: In the above-mentioned S5, the reaction temperature of the nucleophilic addition reaction is 100-180° C., and the reaction time is 0.5-2 h. In terms of molar ratio, bismaleimide: urea-containing diamine compound = (1-3): (1-5).

10. A urea bond modified bismaleimide resin-based elastomer, characterized in that: The urea-modified bismaleimide resin-based elastomer is prepared by the synthesis method of any one of claims 1 to 9; the urea-modified bismaleimide resin-based elastomer has a tensile strength of 40 to 75 MPa, an elongation at break of 190 to 690%, and an impact strength of 150 to 300 kJ / m 2 ; High temperature stability is 280~350℃.

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