Silane coupling agent containing phthalonitrile group as well as preparation method and application of silane coupling agent

Abstract

The invention relates to a silane coupling agent containing a phthalonitrile group as well as a preparation method and application thereof, and the silane coupling agent containing the phthalonitrile group is synthesized by an organic silicon monomer with a hydrolyzable group and phthalonitrile containing a phenolic hydroxyl group under the action of three catalysts at high yield. According to the invention, the synthesis of the silane coupling agent containing the phthalonitrile group is realized for the first time, the synthesis process is simple and has universality, and the silane coupling agent is utilized to modify the surfaces of fibers and inorganic particles to enable the surfaces to have the phthalonitrile group, so that the connection of organic-inorganic interfaces is realized; therefore, the interface bonding strength between a resin matrix and a reinforcing material is greatly improved, and the application prospect of the phthalonitrile resin in the fields of composite materials, coatings and the like is greatly expanded.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of phthalonitrile-based composite material preparation, and particularly relates to a silane coupling agent containing a phthalonitrile group as well as a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of China's aerospace industry, higher requirements are put forward for the carrying capacity, lightweight and extreme space environment resistance of spacecraft. As a high-performance thermosetting resin material, phthalonitrile resin has good dimensional and strength stability at high temperature, and the characteristics of flame retardant, low toxicity and smokeless. The phthalonitrile-based fiber reinforced composite material prepared therefrom applied to spacecraft can make it have the performance of lightweight and extreme environment resistance, and has become a key material for the sustainable development of China's aerospace industry.

[0003] Although phthalonitrile resin has many advantages, the existing composite material has insufficient resin-fiber interfacial bonding strength, which leads to the macroscopic performance of the prepared composite material being reduced in strength. As a classic means of interface modification, silane coupling agent bridges the fiber and resin through covalent bond with its bifunctional structure (Y-Si-(OR)3), and has the advantages of high chemical bonding strength, strong process compatibility (impregnation / spraying) and low cost. Since the curing mode of phthalonitrile resin is cyan ring formation, the common silane coupling agent on the market cannot form chemical bonding with it. If the phthalonitrile group is introduced into the silane coupling agent, this problem can be effectively solved. SUMMARY

[0004] In order to overcome the defect that the traditional silane coupling agent cannot form chemical bonding with the phthalonitrile matrix, the application provides a silane coupling agent containing a phthalonitrile group as well as a preparation method and application thereof.

[0005] To achieve the above-mentioned purpose, the technical solutions adopted by the application are as follows: A silane coupling agent containing a phthalonitrile group, characterized in that the molecular structure of the silane coupling agent is: wherein X is a hydrolyzable group, R is a fatty chain or an aromatic ring structure, and n ranges from 1 to 3.

[0006] Further, the hydrolyzable group is one of methoxy, ethoxy and silicon chloride.

[0007] Further, the silane coupling agent is prepared from the following components in terms of the amount of substance: 1-5 parts of an organic silicon monomer containing a hydrolyzable group, 1-5 parts of a phthalonitrile monomer containing a phenolic hydroxyl group, 2-10 parts of an alkali catalyst, 0.1-1 parts of a phase transfer catalyst and 0.5-3 parts of a halide salt catalyst. Further, the hydrolysable group-containing organic silicon monomer is one of (3-chloropropyl)triethoxysilane and (3-chloropropyl)trimethoxysilane; Further, the phenolic hydroxyl-containing phthalonitrile monomer is one of 4-hydroxyphthalonitrile, 4-[(3-hydroxyphenyl)oxy]benzene-1,2-dinitrile, 3-hydroxyphthalonitrile and 4-(4-hydroxyphenoxy)phthalonitrile. Further, the base catalyst can promote the conversion of phenolic hydroxyl into phenoxide anion and then promote nucleophilic substitution on the one hand, and can act as an acid-binding agent to neutralize the acid that may be generated to promote the reaction to continue on the other hand, and can be one or more of triethylamine, pyridine and potassium carbonate. Further, the phase transfer catalyst can increase the solubility of the base in the solvent, thereby promoting the reaction, and can be one or more of 18-crown-6, tetrabutylammonium bromide and polyethylene glycol. Further, the halide salt catalyst is potassium iodide, which can realize Finkelstein reaction to promote the nucleophilic substitution reaction as a better leaving group.

[0008] A preparation method of the above-mentioned silane coupling agent containing a phthalonitrile group, the method being: adding raw materials to a polar aprotic solvent which is pre-dehydrated, and performing a Williamson etherification reaction of hydroxyl group substituting chlorine atom at 70-90 DEG C for 12-36 h under a nitrogen atmosphere; after the reaction is completed, the reaction system is cooled to room temperature, then filtration is performed to remove solid precipitates, the obtained filtrate is subjected to vacuum distillation to remove the solvent and unreacted raw materials, and finally residual solids are removed by centrifugation, and the obtained upper liquid is the silane coupling agent containing a phthalonitrile group.

[0009] An application of the above-mentioned silane coupling agent containing a phthalonitrile group, the application being: immersing a hydroxyl group-containing fiber into a system with a dimethyl sulfoxide:water volume ratio of 5-10:1, then adding the silane coupling agent with a concentration of 1-5 wt% of the liquid, then adding ammonia water to control the pH of the system to 9, and hydrolysis condensation is performed at 60 DEG C for 3-6 h, then the system is placed into an oven at 100-120 DEG C to further promote the reaction to be completed, and a fiber containing a phthalonitrile group on the surface is obtained.

[0010] The silane coupling agent containing a phthalonitrile group provided by the present application can bridge a phthalonitrile group on the surface of inorganic materials, thereby greatly improving the interfacial bonding strength between a phthalonitrile resin matrix and inorganic materials, which greatly expands the application prospect of phthalonitrile resin materials in the fields of composite materials and coating. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1is the nuclear magnetic hydrogen spectrum of the silane coupling agent containing phthalonitrile group in Example 1 of the present application; Figure 2 is the nuclear magnetic carbon spectrum of the silane coupling agent containing phthalonitrile group in Example 1 of the present application; Figure 3 is the infrared spectrum of the silane coupling agent containing phthalonitrile group in Example 2 of the present application; Figure 4 is the SEM image of the fiber surface modification of the silane coupling agent containing phthalonitrile group in Example 3 of the present application. DETAILED DESCRIPTION

[0012] 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 illustrative embodiments of the present application and their descriptions are used to explain the present application, and do not constitute undue limitations on the present application. It should be noted that the experimental methods used in the examples are conventional methods, and the materials, reagents, etc. used in the examples can be obtained from commercial channels if not specifically stated.

[0013] The synthesis of the silane coupling agent containing phthalonitrile group is realized for the first time in the present application, and the synthesis process is simple and universal. The surface of the fiber and inorganic particles is modified by using the silane coupling agent, so that the surface is provided with the phthalonitrile group, thereby realizing the connection of the organic-inorganic interface, greatly improving the interfacial bonding strength between the resin matrix and the reinforcing material, and greatly expanding the application prospect of the phthalonitrile resin in the fields of composite materials, coatings, etc.

[0014] Example 1 0.12 mol of (3-chloropropyl)triethoxysilane, 0.1 mol of 4-hydroxyphthalonitrile, 0.3 mol of potassium carbonate, 0.01 mol of 18-crown-6 ether, and 0.05 mol of potassium iodide were added into a three-necked flask, followed by adding 150 mL of anhydrous DMF, and stirring vigorously while maintaining the system inert by nitrogen blowing. Then the system was heated to 70°C, and reacted for 12 h. After the reaction was completed, the system was cooled to room temperature, and the residual solid was removed by suction filtration. Then the filtrate was distilled under reduced pressure to remove the solvent and residual reactants. Then the unreacted raw materials were further removed by centrifugation to obtain the pure silane coupling agent containing phthalonitrile group. The nuclear magnetic structure characterization is shown in FIGS. 1 and 2. Figure 1

[0015] The molecular structure of the obtained silane coupling agent is as follows: ​The prepared silane coupling agent was dissolved in a mixed solution of dimethyl sulfoxide and water to a concentration of 5 wt%, then the carbon fiber bundle containing hydroxyl groups on the surface was placed in the system, heated to 60°C for 5h, then the carbon fiber bundle was taken out and placed in an oven at 110°C to ensure that the condensation was sufficient and the residual solvent and moisture were removed, obtaining a carbon fiber bundle containing phthalonitrile groups on the surface.

[0016] The phthalonitrile composite sample was pressed with a carbon fiber bundle, the interlaminar shear strength of the unmodified composite was 60.3 MPa, and the interlaminar shear strength of the modified composite was 81.2 MPa, with an improvement rate of 34.6%.

[0017] Example 2 0.12 mol of (3-chloropropyl)triethoxysilane, 0.1 mol of 4-hydroxyphthalonitrile, 0.3 mol of triethylamine, 0.02 mol of tetrabutylammonium bromide, and 0.05 mol of potassium iodide were added to a three-necked flask, then 150 mL of anhydrous acetonitrile was added, and the system was stirred vigorously while being maintained inert by nitrogen gas. After refluxing, the temperature was raised to 70°C, and the reaction was carried out for 24 h. After the reaction was completed, the system was cooled to room temperature, and the residual solids were removed by suction filtration. Then the filtrate was distilled under reduced pressure to remove the solvent and residual reactants. Finally, the unreacted raw materials were further removed by centrifugation to obtain a pure silane coupling agent containing phthalonitrile groups. Its infrared structure characterization chart is shown in Figure 3 .

[0018] The molecular structure of the obtained silane coupling agent is: The prepared silane coupling agent was dissolved in a mixed solution of dimethyl sulfoxide and water to a concentration of 3 wt%, then the carbon fiber bundle containing hydroxyl groups on the surface was placed in the system, heated to 60°C for 3h, then the carbon fiber bundle was taken out and placed in an oven at 110°C to ensure that the condensation was sufficient and the residual solvent and moisture were removed, obtaining a carbon fiber bundle containing phthalonitrile groups on the surface.

[0019] The phthalonitrile composite sample was pressed with a carbon fiber bundle, the interlaminar shear strength of the unmodified composite was 60.3 MPa, and the interlaminar shear strength of the modified composite was 77.3 MPa, with an improvement rate of 28.2%.

[0020] Example 3 Into a three-necked flask, 0.12 mol (3-chloropropyl)trimethoxysilane, 0.1 mol 4-[(3-hydroxyphenyl)oxy]benzene-1,2-dicarbonitrile, 0.3 mol pyridine, 0.02 mol 18-crown-6, 0.05 mol potassium iodide were added, followed by adding 150 mL anhydrous DMF, and stirring vigorously while maintaining the system inert by nitrogen blowing, and then refluxing, and then warming to 70°C, and then reacting for 12 h; after the reaction, the system was cooled to room temperature, the residual solid was removed by suction filtration, and then the filtrate was distilled under reduced pressure to remove the solvent and residual reaction materials, and then the unreacted materials were further removed by centrifugation, to obtain the pure silane coupling agent containing phthalonitrile groups.

[0021] The molecular structure of the obtained silane coupling agent is as follows: The prepared silane coupling agent was dissolved in a mixed solution of dimethyl sulfoxide and water to a concentration of 3 wt%, and then the hydroxyl-containing carbon fiber bundle was placed in the system, and warmed to 60°C for 3 h, and then the carbon fiber bundle was taken out and placed in an oven at 110°C to ensure that the condensation was complete and the residual solvent and moisture were removed, to obtain the carbon fiber bundle containing phthalonitrile groups on the surface. The SEM micro-morphology diagram thereof is shown in Figure 4 .

[0022] The phthalonitrile composite sample was pressed using the carbon fiber bundle, the interlaminar shear strength of the unmodified composite was 60.3 MPa, and the interlaminar shear strength of the modified composite was 75.2 MPa, with an improvement rate of 24.7%.

[0023] The above only describes the embodiments of the present application, and does not limit the patent scope of the present application, and any equivalent structure or equivalent process transformation using the content of the present application specification, or direct or indirect application in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A silane coupling agent containing an o-phthalonitrile group, characterized by: The molecular structure of the silane coupling agent is: X is a hydrolysable group, R is a fatty chain or an aromatic ring structure, and n ranges from 1 to 3.

2. The silane coupling agent according to claim 1, wherein: The hydrolysable group is one of methoxy, ethoxy, and silicon chloride.

3. The silane coupling agent as described in claim 1, characterized in that: The silane coupling agent is prepared from the following components by mass: 1 to 5 parts of an organic silicon monomer containing a hydrolysable group, 1 to 5 parts of a phthalonitrile monomer containing a phenolic hydroxyl group, 2 to 10 parts of an alkali catalyst, 0.1 to 1 part of a phase transfer catalyst, and 0.5 to 3 parts of a halide salt catalyst.

4. The silane coupling agent according to claim 3, wherein: The organic silicon monomer containing a hydrolysable group is one of (3-chloropropyl)triethoxysilane and (3-chloropropyl)trimethoxysilane.

5. The silane coupling agent according to claim 3, wherein: The phthalonitrile monomer containing a phenolic hydroxyl group is one of 4-hydroxyphthalonitrile, 4-[(3-hydroxyphenyl)oxy]benzene-1,2-dinitrile, 3-hydroxyphthalonitrile, and 4-(4-hydroxyphenoxy)phthalonitrile.

6. The silane coupling agent according to claim 3, wherein: The alkali catalyst is one or more of triethylamine, pyridine, and potassium carbonate.

7. The silane coupling agent according to claim 3, wherein: The phase transfer catalyst is one or more of 18-crown-6, tetrabutylammonium bromide, and polyethylene glycol.

8. The silane coupling agent according to claim 3, wherein: The halide salt catalyst is potassium iodide.

9. A process for the preparation of silane coupling agents containing phthalonitrile groups according to any one of claims 1 to 8, characterized in that: The method is: adding raw materials to a polar aprotic solvent that has been previously dehydrated, reacting at 70 to 90°C under a nitrogen atmosphere for 12 to 36 hours; after the reaction is complete, cooling the reaction system to room temperature, then filtering to remove solid precipitates, distilling the obtained filtrate under reduced pressure to remove the solvent and unreacted raw materials, and finally removing residual solids by centrifugation, and the obtained upper liquid is the silane coupling agent containing a phthalonitrile group.

10. Use of a silane coupling agent containing a phthalonitrile group according to any one of claims 1 to 9, characterized in that: The application is: immersing a hydroxyl-containing surface fiber in a system with a dimethyl sulfoxide:water volume ratio of 5 to 10:1, then adding a silane coupling agent at a concentration of 1 to 5 wt% of the liquid, then adding ammonia to control the pH of the system to 9, hydrolyzing and condensing at 60°C for 3 to 6 hours, then placing it in an oven at 100 to 120°C to further promote the completion of the reaction, and obtaining a fiber containing a phthalonitrile group on the surface.

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