Organic silicon modified phthalonitrile resin as well as preparation method and application thereof

Abstract

The invention relates to organic silicon modified phthalonitrile resin and a preparation method and application thereof.The organic silicon modified phthalonitrile resin is synthesized through a two-step method, the obtained product has certain fluidity in a room temperature environment due to the existence of silicon-oxygen bonds, and the silicon-oxygen bonds have high bond energy so that the silicon-oxygen bonds can not be easily decomposed in a high-temperature environment; meanwhile, high machinability and high temperature resistance are achieved, the synthesis process is simple, and universality is achieved. The resin can be used for easily preparing a composite material prepreg, and is compatible with various composite material forming methods, so that the application prospect of the resin in the field of composite materials is greatly expanded.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of phthalonitrile resin-based composites, and particularly relates to an organic silicon modified phthalonitrile resin and a preparation method and application thereof. BACKGROUND

[0002] Phthalonitrile resin is a new type of high-performance thermosetting resin, which has excellent high-temperature resistance, corrosion resistance and high-temperature strength retention rate. The composites prepared therefrom have gradually been applied to various aircraft. The most typical and most widely used ones are bisphenol A type phthalonitrile and biphenyl type phthalonitrile, which have excellent high-temperature resistance, ensuring the normal operation of aircraft in extreme environments. However, the conventional phthalonitrile has a high melting point, resulting in poor processing performance.

[0003] The organic silicon resin monomer is usually in a liquid state at room temperature, because the bond length and bond angle of the silicon-oxygen bond are larger than those of the carbon chain, the molecular chain is more relaxed, the intermolecular force is weak, the steric hindrance of the methyl side group prevents the molecules from being closely arranged, and the molecular chain is highly flexible and easy to move at room temperature. In addition, the silicon-oxygen bond has higher bond energy than the carbon-carbon bond, and is more stable at high temperature. Therefore, synthesizing a new type of phthalonitrile resin based on an organic silicon skeleton can ensure that the obtained resin has excellent processing performance while having high high-temperature resistance. SUMMARY

[0004] In order to overcome the processing difficulty problem caused by the high melting point of the conventional phthalonitrile resin, the application adopts an organic silicon skeleton, modifies the phthalonitrile group thereon, so as to realize an organic silicon modified phthalonitrile resin in a liquid state at room temperature, which greatly improves the processing performance of the composite material in a room temperature environment without sacrificing the heat resistance of the resin after curing.

[0005] To achieve the above purpose, the technical scheme adopted by the application is as follows:

[0006] An organic silicon modified phthalonitrile resin, the molecular structure of the composite material is:

[0007]

[0008] wherein R is a fatty chain structure and / or an aromatic ring structure, and X is a curable group. The purpose of the curable group is to realize the molding ability of the resin at low temperature and prevent the generation of defects in the curing process due to the thermal expansion of organic silicon.

[0009] Further, the curable group is one of an epoxy group, an acrylate group, an isocyanate group or a double bond. The organic silicon skeleton should have a reactive group; the reactive group is a silicon hydrogen group or a silicon ethylene group.

[0010] Further, the grafting rate of the phthalonitrile structure on the silicone is 20%~80%.

[0011] A preparation method of the above-mentioned silicone-modified phthalonitrile resin, wherein the method is as follows:

[0012] Step one: hydrogen-containing silicone oil is weighed by mass, and the molar amount of silicon hydrogen contained in the hydrogen-containing silicone oil is calculated according to the hydrogen content, and then the hydrogen-containing silicone oil is dissolved in ethyl acetate, and equal molar amount of allyl phenol monomer and 60~80 ppm of platinum catalyst mixture are added dropwise according to the calculation result, and the reaction is carried out at 65~75℃ for 3~5h, and then the ethyl acetate is removed by reduced pressure distillation, and the obtained product is a silicone oil containing phenolic hydroxyl groups in the side chain;

[0013] Step two: the molar amount of the phenolic hydroxyl groups contained in the above-mentioned silicone oil is calculated, and then the silicone oil is dissolved in NMP, and equal molar amount of 4-nitrophthalonitrile and potassium carbonate is added, and then the mixture is stirred at 80℃ for 10~20h, and then the mixture is poured into deionized water, and hydrochloric acid is added dropwise to make the pH of the system 3, and then ethyl acetate is added to extract the product, and then the upper clear liquid is taken after the separation of the layers, and then the ethyl acetate is removed by reduced pressure distillation, and the obtained product is a silicone-modified phthalonitrile resin containing phthalonitrile groups in the side chain.

[0014] Further, in step one, the hydrogen content of the hydrogen-containing silicone oil is 0.4~1.6.

[0015] Further, in step two, the molar amount of potassium carbonate is 1.2~3.

[0016] The application of the silicone-modified phthalonitrile resin prepared by the above-mentioned preparation method, wherein the application is as follows:

[0017] Step one: ethyl acetate is used to dilute the silicone-modified phthalonitrile resin to obtain a resin system with suitable viscosity at room temperature, and then 3wt%~5wt% of phthalonitrile curing agent based on the mass of the resin is added and mixed uniformly, and then the resin is applied to a carbon fiber cloth with a suitable size, and then the ethyl acetate is volatilized to obtain a prepreg of the silicone-modified phthalonitrile resin.

[0018] Step two: the prepreg is cut into a shape matching the size of the mold, and then the prepreg is stacked in the mold by layer-by-layer stacking, and then a traditional hot pressing process is adopted to form the composite material, and the composite material forming process is as follows: 180℃ for 2h, 220℃ for 4h, and 260℃ for 4h, and then the mold is demolded after the process is completed, and then a silicone-modified phthalonitrile composite material is obtained.

[0019] Further, in step one, the phthalonitrile curing agent is an amine curing agent.

[0020] Further, in step one, the amine curing agent is one of DDM, DDS, and h256.

[0021] The organic silicon modified phthalonitrile resin provided by the present application can ensure certain fluidity at room temperature, greatly improves the processing performance, and does not reduce the heat resistance compared with the traditional phthalonitrile resin due to the high bond energy of the silicon-oxygen bond. Meanwhile, various composite material forming methods can be adopted, greatly expanding the application prospect in the field of composite materials. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a physical diagram of the organic silicon modified phthalonitrile resin in the embodiment 2 and the embodiment 3 of the present application;

[0023] Figure 2 is an infrared spectrum diagram of the organic silicon modified phthalonitrile resin in the embodiment 2 of the present application. DETAILED DESCRIPTION

[0024] The present application will be described in detail below with examples, and the description in this part is only exemplary and explanatory, and should not have any limiting effect on the protection scope of the present application. The drawings described are used to provide further understanding of the present application, and form a part of the present application. The schematic embodiments of the present application and the description thereof are used to explain the present application, and do not constitute improper limitation on the present application. It should be noted that the experimental methods used in the examples are conventional methods, and the materials, reagents and the like used in the examples can be obtained from commercial channels if not specifically stated.

[0025] The organic silicon modified phthalonitrile resin of the present application is obtained by a two-step method. The product obtained has certain fluidity at room temperature due to the presence of the silicon-oxygen bond, and the silicon-oxygen bond has high bond energy to ensure that it is not easy to decompose at high temperature, and at the same time realizes high processability and high temperature resistance. The synthesis process is simple and has universality. The resin can be used to easily prepare composite material prepreg, and is compatible with various composite material forming methods, greatly expanding the application prospect in the field of composite materials.

[0026] Example 1

[0027] 10 g of hydrogen-containing silicone oil with a hydrogen content of 0.4 is dissolved in 20 mL of ethyl acetate, transferred to a three-necked flask, heated to 70℃, and refluxed under nitrogen for 10 minutes. Then 0.04 mol of allyl phenol and 60 ppm of platinum catalyst are slowly added dropwise, and the reaction is continued for 3 h after the dropwise addition is completed. Then, vacuum distillation is carried out to obtain a silicone oil product containing phenolic hydroxyl groups in the side chain.

[0028] Take 10 g of the above phenolic hydroxyl silicone oil, dissolve it in NMP, then add 0.02 mol of 4-nitrophthalonitrile and 0.03 mol of anhydrous potassium carbonate, and react at 80°C for 10 h. After the system cools to room temperature, pour it into excess saturated brine, and add hydrochloric acid dropwise to control the pH of the system to 6. Then add a certain amount of ethyl acetate to extract the product, collect the upper clear liquid, and add a certain amount of anhydrous calcium chloride to remove the residual water. Distill under reduced pressure to obtain a silicone-modified phthalonitrile resin.

[0029] Take a certain amount of silicone-modified phthalonitrile resin, dissolve it in a DDM solution of ethyl acetate, and ensure that the curing agent is 3 wt% of the resin mass. Stir well, apply it to carbon fibers, and then place it in a vacuum oven to remove excess solvent to obtain a phthalonitrile / carbon fiber prepreg.

[0030] Cut the prepreg into a shape matching the size of the mold, and neatly stack 10 layers, then transfer to a hot press. The curing process is: 180°C for 2 h, 220°C for 4 h, and 260°C for 4 h. After cooling and demolding, a silicone-modified phthalonitrile laminate with a glue content of 40% is obtained.

[0031] The laminate has high mechanical properties and high temperature strength retention rate. The room temperature bending strength is 571.8 MPa, the bending strength at 300°C is 310.4 MPa, and the strength retention rate is 54.3%.

[0032] Example 2

[0033] Dissolve 10 g of hydrogen-containing silicone oil with a hydrogen content of 0.8 in 20 mL of ethyl acetate, transfer to a three-necked flask, heat to 70°C, and reflux for 10 minutes under nitrogen. Then slowly add 0.08 mol of allyl phenol and 60 ppm of platinum catalyst dropwise. After the addition is complete, continue to react for 3 h, then perform vacuum distillation to obtain a silicone oil product with phenolic hydroxyl groups in the side chain.

[0034] Take 10 g of the above phenolic hydroxyl silicone oil, dissolve it in DMSO, then add 0.04 mol of 4-nitrophthalonitrile and 0.06 mol of anhydrous potassium carbonate, and react at 80°C for 15 h. After the system cools to room temperature, pour it into excess saturated brine, and add hydrochloric acid dropwise to control the pH of the system to 6. Then add a certain amount of ethyl acetate to extract the product, collect the upper clear liquid, and add a certain amount of anhydrous calcium chloride to remove the residual water. Distill under reduced pressure to obtain a silicone-modified phthalonitrile resin. The actual picture is shown in Figure 1 , and the infrared spectrum is shown in Figure 2 .

[0035] A certain amount of silicone-modified phthalonitrile resin was weighed, and a DDM solution in ethyl acetate was dissolved therein to ensure that the curing agent was 3 wt% of the mass of the resin. After being uniformly stirred, it was applied to carbon fibers, and then placed in a vacuum oven to remove excess solvent, thereby obtaining a phthalonitrile / carbon fiber prepreg.

[0036] The prepreg was cut into a shape matching the size of the mold, and neatly stacked in 10 layers, and then transferred to a hot press, and the curing process was: 180°C for 2h, 220°C for 4h, 260°C for 4h, and then cooled and demolded to obtain a silicone-modified phthalonitrile laminate with a glue content of 40%.

[0037] The laminate has high mechanical properties and high-temperature strength retention rate, with a room temperature bending strength of 583.4 MPa, a bending strength at 300°C of 350.6 MPa, and a strength retention rate of 60.1%.

[0038] Example 3

[0039] 10 g of hydrogen-containing silicone oil with a hydrogen content of 1.2 was dissolved in 20 mL of ethyl acetate, transferred to a three-necked flask, heated to 70°C, and refluxed under a nitrogen atmosphere for 10 minutes. Then 0.12 mol of allyl phenol and 80 ppm of platinum catalyst were slowly added dropwise, and after the addition was completed, the reaction was continued for 5h. Then, vacuum distillation was performed to obtain a silicone oil product containing phenolic hydroxyl groups in the side chain.

[0040] 10 g of the above phenolic hydroxyl silicone oil was dissolved in NMP, and then 0.06 mol of 4-nitrophthalonitrile and 0.12 mol of anhydrous potassium carbonate were added. The reaction was carried out at 80°C under reflux conditions for 20h. After the system cooled to room temperature, it was poured into excess saturated brine, and hydrochloric acid was added dropwise to control the pH of the system to 6. Then a certain amount of ethyl acetate was added to extract the product. A certain amount of anhydrous calcium chloride was added to remove the residual water, and vacuum distillation was performed to obtain a silicone-modified phthalonitrile resin. The actual picture is shown in Figure 1

[0041] A certain amount of silicone-modified phthalonitrile resin was weighed, and a DDM solution in ethyl acetate was dissolved therein to ensure that the curing agent was 3 wt% of the mass of the resin. After being uniformly stirred, it was applied to carbon fibers, and then placed in a vacuum oven to remove excess solvent, thereby obtaining a phthalonitrile / carbon fiber prepreg.

[0042] The prepreg was cut into a shape matching the size of the mold, and neatly stacked in 10 layers, and then transferred to a hot press, and the curing process was: 180°C for 2h, 220°C for 4h, 260°C for 4h, and then cooled and demolded to obtain a silicone-modified phthalonitrile laminate with a glue content of 40%.​

[0043] The laminated plate has high mechanical properties and high temperature strength retention rate, the room temperature bending strength is 623.2 MPa, the bending strength at 300 DEG C is 417.8 MPa, and the strength retention rate is 67.0%.

[0044] The above is only an embodiment of the present application, and does not limit the patent scope of the present application, and any equivalent structure or equivalent process transformation made by using the content of the present application specification, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A silicone-modified phthalonitrile resin, characterized in that: The molecular structure of the composite material is: Wherein, R is a fatty chain structure and / or an aromatic ring structure, and X is a curable group.

2. The resin according to claim 1, wherein: The curable group is one of an epoxy group, an acrylate group, an isocyanate group or a double bond.

3. The resin according to claim 1, wherein: The grafting rate of phthalonitrile structure on silicone is 20%~80%.

4. A method for preparing the organosilicon-modified phthalonitrile resin according to any one of claims 1 to 3, characterized in that: The method is: Step 1: Weigh 1 part of hydrogenated silicone oil by mass, calculate the molar amount of silicon hydrogen in the hydrogenated silicone oil based on its hydrogen content, dissolve it in ethyl acetate, and add dropwise an equal molar amount of allylphenol monomer and 60-80 ppm of platinum catalyst mixture according to the calculated result. After reacting at 65-75°C for 3-5 hours, remove the ethyl acetate by vacuum distillation to obtain a silicone oil with phenolic hydroxyl groups on the side chain; Step 2: Calculate the molar amount of phenolic hydroxyl groups in the silicone oil and dissolve it in NMP. Add equimolar amounts of 4-nitrophthalonitrile and potassium carbonate, and stir at 80°C for 10 to 20 hours. Then pour the mixture into deionized water, and add hydrochloric acid dropwise to adjust the pH of the system to 3. Then add ethyl acetate to extract the product, let it stand and separate the layers. Take the supernatant and remove the ethyl acetate by vacuum distillation. The resulting product is a silicone-modified phthalonitrile resin containing phthalonitrile groups in the side chains.

5. The method for preparing the organosilicon-modified phthalonitrile resin according to claim 4, wherein: In step 1, the hydrogen content of the hydrogen-containing silicone oil is 0.4~1.

6.

6. The method for preparing the organosilicon-modified phthalonitrile resin according to claim 4, wherein: In step 2, the molar ratio of potassium carbonate is 1.2~3.

7. Use of an organosilicon-modified phthalonitrile resin prepared by the preparation method according to any one of claims 4 to 6, characterized in that: The applications are: Step 1: Dilute the organosilicon-modified phthalonitrile resin with ethyl acetate to obtain a resin system with suitable viscosity at room temperature, then add 3wt% to 5wt% of phthalonitrile curing agent by weight of the resin, mix thoroughly, and then apply it to a carbon fiber cloth of appropriate size. After the ethyl acetate is fully volatilized, a prepreg of the organosilicon-modified phthalonitrile resin is obtained; Step 2: Cut the prepreg into a shape that matches the mold size and stack it in the mold layer by layer. Use the traditional hot pressing process to form the composite material. The composite material molding process is: 180℃ 2h, 220℃ 4h, 260℃ 4h. After the process is completed, demolding is carried out to obtain the silicone-modified phthalonitrile composite material.

8. The use of the organosilicon-modified phthalonitrile resin according to claim 7, wherein: In step 1, the phthalonitrile curing agent is an amine curing agent.

9. The use of the organosilicon-modified phthalonitrile resin according to claim 8, wherein: In step 1, the amine curing agent is one of DDM, DDS, and h256.

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