High-thermal-oxidation-resistance modified phthalonitrile resin prepolymer and preparation method thereof

Abstract

The invention discloses a modified phthalonitrile resin prepolymer with high thermal oxidation resistance and a preparation method of the modified phthalonitrile resin prepolymer. Specifically, the invention discloses an o-carborane modified phthalonitrile resin prepolymer, and the main raw material of the o-carborane modified phthalonitrile resin prepolymer is a phthalonitrile resin monomer. The prepared modified phthalonitrile resin prepolymer has improved thermal oxidation resistance, and can be widely applied to the fields of high and new technology industries such as aerospace, high-performance composite materials and the like.

Description

Technical Field

[0001] The present invention belongs to the field of polymer materials. Specifically, the present invention relates to a highly heat-resistant oxidized modified phthalonitrile resin prepolymer and a preparation method thereof. Background Art

[0002] Phthalonitrile resin is a high-performance engineering resin with excellent thermal stability and mechanical properties. However, the thermal-oxidative stability of phthalonitrile resin is still one of its main defects. Its performance will decline significantly at high temperatures. The mass retention rate at 800 °C in air atmosphere of the conventional system is 0%, which greatly limits its applications in the fields of aerospace, automobiles, electronics, etc.

[0003] In view of this, there is an urgent need in the art to develop phthalonitrile resins with more excellent high thermal stability. Summary of the Invention

[0004] One object of the present invention is to provide a highly heat-resistant oxidized modified phthalonitrile resin prepolymer.

[0005] Another object of the present invention is to provide a preparation method of a highly heat-resistant oxidized modified phthalonitrile resin prepolymer.

[0006] Another object of the present invention is to provide a cured product of a highly heat-resistant oxidized modified phthalonitrile resin.

[0007] In the first aspect of the present invention, there is provided a modified phthalonitrile resin prepolymer with high heat and oxidation resistance. The raw materials of the modified phthalonitrile resin prepolymer are phthalonitrile resin monomer and o-carborane. Among them, the o-carborane catalyst has the structure shown below

[0008] In another preferred example, the phthalonitrile resin monomer is selected from the group consisting of: biphenyl-type phthalonitrile resin, benzophenone-type phthalonitrile resin, bisphenol A-type phthalonitrile resin, bisphenol AF-type phthalonitrile resin, bisphenol F-type phthalonitrile resin, bisphenol S-type phthalonitrile resin, or a combination thereof.

[0009] In another preferred example, the phthalonitrile resin monomer has the structure shown below:

[0010]

[0011] R:

[0012]

[0013] In a second aspect of the present invention, there is provided a method for preparing the modified phthalonitrile resin prepolymer described in the first aspect of the present invention, comprising the following steps:

[0014] Under an inert atmosphere, the phthalonitrile resin monomer, the carborane catalyst, and the organic polar solvent are subjected to a prepolymerization reaction at 160°C to 240°C for 1 to 5 hours; a precipitant is poured in, and the product is precipitated, namely the modified phthalonitrile resin prepolymer;

[0015] Wherein, the carborane catalyst has the following structure

[0016] In another preferred example, the phthalonitrile resin monomer is selected from the group consisting of: biphenyl-type phthalonitrile resin, benzophenone-type phthalonitrile resin, bisphenol A-type phthalonitrile resin, bisphenol AF-type phthalonitrile resin, bisphenol F-type phthalonitrile resin, bisphenol S-type phthalonitrile resin, or a combination thereof.

[0017] In another preferred example, the phthalonitrile resin monomer has the following structure:

[0018]

[0019] R:

[0020]

[0021] In another preferred example, the organic polar solvent is selected from the group consisting of: aromatic solvents, amide solvents, or a combination thereof; preferably N,N-dimethylformamide, N-methylpyrrolidone, N,N-dimethylacetamide, diphenyl ether, or a combination thereof; more preferably N-methylpyrrolidone, diphenyl ether.

[0022] In another preferred example, the precipitant is selected from the group consisting of: water, methanol, ethanol, or a combination thereof; preferably water and methanol.

[0023] In another preferred example, the mass ratio of the phthalonitrile resin monomer to the carborane catalyst is 100:(1 to 50), preferably 100:(3 to 30); more preferably 100:(5 to 20).

[0024] In another preferred example, the reaction temperature is 180 to 220°C.

[0025] In another preferred example, the reaction time is 2 to 4 hours.

[0026] In a third aspect of the present invention, there is provided a cured product of the modified phthalonitrile resin prepolymer described in the first aspect of the present invention, and the cured product is obtained by curing the modified phthalonitrile resin prepolymer.

[0027] In another preferred example, the curing refers to temperature gradient curing.

[0028] In another preferred example, the temperature gradient refers to 220 °C / 1 h + 260 °C / 1 h + 300 °C / 3 h.

[0029] In another preferred example, the temperature gradient refers to 220 °C / 1 h + 260 °C / 1 h + 300 °C / 3 h + 350 °C / 3 h.

[0030] In another preferred example, the temperature gradient refers to 220 °C / 1 h + 260 °C / 1 h + 300 °C / 2 h + 350 °C / 4 h + 400 °C / 2 h.

[0031] In another preferred example, the T of the cured product in a nitrogen atmosphere d5 is 543 - 560 °C; the T in an air atmosphere d5 is 543 - 562 °C.

[0032] In another preferred example, the mass retention rate of the cured product at 1000 °C in a nitrogen atmosphere is 75.2 - 81.8%; the mass retention rate in an air atmosphere is 14.7 - 75.6%.

[0033] It should be understood that within the scope of the present invention, the above-mentioned technical features of the present invention and the technical features specifically described below (such as in the examples) can be combined with each other to form new or preferred technical solutions. Due to space limitations, they will not be elaborated one by one here. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is the infrared spectrum of the biphenyl-type phthalonitrile resin prepolymer prepared in Example 1.

[0035] Figure 2 is the GPC spectrum of the biphenyl-type phthalonitrile resin prepolymer prepared in Example 1.

[0036] Figure 3 is the DSC spectrum of the biphenyl-type phthalonitrile resin before and after prepolymerization in Example 1.

[0037] Figure 4 is the structural schematic diagram of o-carborane catalyzing phthalonitrile resin.

[0038] Figure 5 is the TGA curve of the cured product of the biphenyl-type phthalonitrile resin prepared in Example 1.

[0039] Figure 6 is the TGA curve of the cured product of the bisphenol A-type phthalonitrile resin prepared in Example 2.

[0040] Figure 7 TGA curve of the cured product of the bisphenol S-type phthalonitrile resin prepared in Example 3. Detailed implementation manners

[0041] After extensive and in-depth research, the inventors first provided a novel high heat-resistant oxidized modified phthalonitrile resin prepolymer and its preparation method. Compared with the traditional phthalonitrile resin system, based on the boron-nitrogen coordination principle of carborane, the heat resistance and heat-resistant oxidation performance of the phthalonitrile system are greatly improved, the resin processing performance is improved, and it is applicable to various molding processes, soluble in a variety of low-boiling solvents, which is beneficial to the preparation of various high-performance composite materials. Based on this, the inventors completed the present invention.

[0042] Carborane-modified phthalonitrile resin prepolymer

[0043] o-Carborane is a special type of compound. Its special cage structure and elemental composition endow it with strong electrophilicity, high thermal stability and high chemical stability. It is not easy to undergo thermal degradation or cracking, and it is not easy to undergo chemical reactions or degradation. By organically combining with the resin matrix, it can effectively improve the high-temperature resistance and heat-resistant oxidation performance of the resin matrix.

[0044] To solve the problem of the thermal stability of phthalonitrile resin, the present invention introduces a novel catalyst o-carborane to react with phthalonitrile resin to prepare a high heat-resistant oxidized modified phthalonitrile resin prepolymer. Through the catalytic action of the B-H bond of o-carborane and the boron-nitrogen coordination mechanism, the carborane structure is organically combined with the resin matrix through a coordination bond, introducing inorganic components into the resin system, improving the overall heat-resistant oxidation performance of the resin, and the prepolymer has good processing performance, soluble in various low-boiling solvents, and applicable to a variety of molding processes.

[0045] Since o-carborane is prone to sublimation when heated above 150 °C in an air environment, and its catalytic cyanide reaction usually requires a high temperature above 180 °C, this system is difficult to apply to traditional melting processes. To solve this problem, a solution prepolymerization process is designed. By dissolving o-carborane and phthalonitrile resin in an organic solvent together, the sublimation behavior of o-carborane is effectively inhibited. At the same time, by increasing the concentration of the reaction system, the catalytic efficiency is significantly improved, and the preparation of the phthalonitrile resin prepolymer catalyzed by o-carborane at high temperature is successfully realized. This process provides a new solution for the application of o-carborane in high-temperature catalytic systems.

[0046] The modification method of the present invention is applicable to various types of phthalonitrile resin monomers, including but not limited to biphenyl-type phthalonitrile resin, benzophenone-type phthalonitrile resin, bisphenol A-type phthalonitrile resin, bisphenol AF-type phthalonitrile resin, bisphenol F-type phthalonitrile resin, bisphenol S-type phthalonitrile resin, and the structural formulas are as follows:

[0047]

[0048] R:

[0049]

[0050] In the preparation method of the high heat-resistant oxidation modified phthalonitrile resin prepolymer of the present invention, the structural formula of the catalyst used is:

[0051] The present invention uses a novel catalyst, o-carborane, to react with phthalonitrile to prepare a high heat-resistant oxidation modified phthalonitrile resin prepolymer. Specifically, the modification method of the present invention includes the following steps:

[0052] Under the protection of an inert gas, the phthalonitrile resin monomer and o-carborane catalyst are dissolved in an organic polar solvent according to a mass ratio of 100:(1-50), and pre-polymerized at 160°C - 240°C for 1 - 5 h; after the reaction is completed, it is cooled to room temperature, and the reaction solution is added to a precipitant, and the product precipitates to obtain the prepolymer of the high heat-resistant oxidation modified phthalonitrile resin.

[0053] Among them, the inert gas is a common inert gas in the art, including but not limited to: nitrogen, argon, etc.

[0054] Compared with the prior art, the main advantages of the present invention include:

[0055] (1) Using o-carborane to modify phthalonitrile resin greatly improves the heat resistance and oxidation resistance of the phthalonitrile resin system.

[0056] (2) The modified phthalonitrile resin of the present invention is applicable to various molding processes and can be dissolved in a variety of low-boiling solvents, which is beneficial to the preparation of various high-performance composite materials.

[0057] The following combines specific embodiments to further illustrate the present invention. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. The experimental methods without specific conditions noted in the following embodiments are usually carried out according to conventional conditions or according to the conditions recommended by the manufacturer. Unless otherwise specified, percentages and parts are calculated by weight.

[0058] Unless otherwise defined, all professional and scientific terms used herein have the same meaning as those familiar to persons skilled in the art. In addition, any methods and materials similar or equivalent to those described may be applied to the method of the present invention. The preferred methods and materials described herein are for illustrative purposes only.

[0059] Example 1

[0060] Steps for preparing a highly heat-resistant oxidized modified phthalonitrile resin cured product:

[0061] (1) Add 15 g of biphenyl-type phthalonitrile monomer, 3 g of o-carborane, and 10 g of N-methylpyrrolidone to a dry four-necked flask. Under nitrogen protection, heat up to 200 °C and react for 2.5 h under high-speed stirring. After the reaction is completed, cool to room temperature.

[0062] (2) Pour the product solution obtained in step (1) into 200 ml of H2O. A large amount of black precipitate appears. Filter by suction, and wash the filter residue with deionized water and ethanol solution multiple times. Vacuum dry to obtain a black solid, which is the highly heat-resistant oxidized modified phthalonitrile resin prepolymer.

[0063] (3) After grinding the prepolymer in step (2), take a small amount of the powder and place it in a ceramic crucible.

[0064] (4) Cure the sample prepared in step (3) in a muffle furnace by stepwise heating under the conditions of 220 °C / 1 h + 260 °C / 1 h + 300 °C / 3 h. Wait for the muffle furnace to cool to room temperature to obtain the cured product of the highly heat-resistant oxidized modified phthalonitrile resin.

[0065] Example 2

[0066] Steps for preparing a highly heat-resistant oxidized modified phthalonitrile resin cured product:

[0067] (1) Add 15 g of bisphenol A-type phthalonitrile monomer, 1.5 g of o-carborane, and 10 g of N-methylpyrrolidone to a dry four-necked flask. Under nitrogen protection, heat up to 190 °C and react for 3 h under high-speed stirring. After the reaction is completed, cool to room temperature.

[0068] (2) Pour the product solution obtained in step (1) into 200 ml of H2O. A large amount of dark brown precipitate appears. Filter by suction, and wash the filter residue with deionized water and ethanol solution multiple times. Vacuum dry to obtain a black solid, which is the highly heat-resistant oxidized modified phthalonitrile resin prepolymer.

[0069] (3) After grinding the prepolymer in step (2), take a small amount of the powder and place it in a ceramic crucible.

[0070] (4) The sample prepared in step (3) was cured by stepwise heating in a muffle furnace under the conditions of 220 °C / 1 h + 260 °C / 1 h + 300 °C / 3 h + 350 °C / 3 h. After the muffle furnace cooled to room temperature, the cured product of the highly heat-resistant oxidized modified phthalonitrile resin was obtained.

[0071] Example 3

[0072] Preparation steps of the cured product of the highly heat-resistant oxidized modified phthalonitrile resin:

[0073] (1) 15 g of bisphenol S phthalonitrile monomer, 0.45 g of o-carborane, and 10 g of diphenyl ether were added to a dry four-necked flask. Under nitrogen protection, the temperature was raised to 220 °C, and the reaction was carried out for 3 h under high-speed stirring. After the reaction, it was cooled to room temperature.

[0074] (2) The product solution obtained in step (1) was poured into 200 ml of H2O, and a large amount of brown precipitate appeared. It was filtered by suction, and the filter residue was washed repeatedly with deionized water and ethanol solution, and then dried in vacuum to obtain a black solid, which was the prepolymer of the highly heat-resistant oxidized modified phthalonitrile resin.

[0075] (3) After grinding the prepolymer in step (2), a small amount of powder was taken and placed in a ceramic crucible.

[0076] (4) The sample prepared in step (3) was cured by stepwise heating in a muffle furnace under the conditions of 220 °C / 1 h + 260 °C / 1 h + 300 °C / 2 h + 350 °C / 4 h + 400 °C / 2 h. After the muffle furnace cooled to room temperature, the cured product of the highly heat-resistant oxidized modified phthalonitrile resin was obtained.

[0077] Comparative Example 1

[0078] (1) 100 g of bisphenol A phthalonitrile resin was added to a 200 mL beaker. The beaker was placed in an oil bath and heated to 200 °C until the monomer was completely melted, and then it was placed in a 200 °C vacuum oven and evacuated for 30 min.

[0079] (2) 3 g of 4,4'-bis(4-aminophenoxy)diphenyl sulfone (p-BAPS) was added to the resin in step (1). After rapid stirring for 2 min, it was slowly poured into a crucible for curing treatment. The curing regime was 270 °C / 12 h + 300 °C / 3 h + 350 °C / 6 h + 375 °C / 4 h.

[0080] The above-mentioned cured products were subjected to TGA tests in nitrogen and air atmospheres at a heating rate of 10 °C / min, and the thermal decomposition temperature (T d5 ) at which the mass loss was 5% and the mass retention rate at 1000 °C are shown in the following table

[0081]

[0082]

[0083] As can be seen from the above table, using o-carborane as a catalyst to modify phthalonitrile resin can make the retention rates of the cured phthalonitrile resin in air and nitrogen and the T d5 both increase significantly, indicating that the oxidation resistance and heat resistance of the o-carborane modified phthalonitrile resin have been significantly improved.

[0084] All documents mentioned in this invention are cited herein for reference as if each document was individually cited for reference. In addition, it should be understood that after reading the above teachings of this invention, those skilled in the art can make various changes or modifications to this invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

Claims

1. A high-heat and oxidation-resistant modified phthalonitrile resin prepolymer, characterized in that: The raw materials of the modified phthalonitrile resin prepolymer are phthalonitrile resin monomer and o-carborane, wherein the o-carborane catalyst has the structure shown below:

2. The prepolymer according to claim 1, characterized in that The phthalonitrile resin monomer is selected from the following group: biphenyl phthalonitrile resin, benzophenone phthalonitrile resin, bisphenol A phthalonitrile resin, bisphenol AF phthalonitrile resin, bisphenol F phthalonitrile resin, bisphenol S phthalonitrile resin, or a combination thereof; Preferably, the phthalonitrile resin monomer has the structure shown below:

3. A method for preparing the modified phthalonitrile resin prepolymer according to claim 1, characterized in that: The steps include: Under an inert atmosphere, a phthalonitrile resin monomer, an orthocarborane catalyst and an organic polar solvent are prepolymerized at 160° C. to 240° C. for 1 to 5 hours; a precipitant is poured in to precipitate a product, namely a modified phthalonitrile resin prepolymer; Wherein, the ortho-carborane catalyst has the structure shown below 4. The preparation method according to claim 3, characterized in that: The phthalonitrile resin monomer is selected from the following group: biphenyl phthalonitrile resin, benzophenone phthalonitrile resin, bisphenol A phthalonitrile resin, bisphenol AF phthalonitrile resin, bisphenol F phthalonitrile resin, bisphenol S phthalonitrile resin, or a combination thereof; Preferably, the phthalonitrile resin monomer has the structure shown below:

5. The preparation method according to claim 3, characterized in that: The organic polar solvent is selected from the following group: aromatic solvents, amide solvents, or a combination thereof; preferably N,N-dimethylformamide, N-methylpyrrolidone, N,N-dimethylacetamide, diphenyl ether, or a combination thereof; more preferably N-methylpyrrolidone and diphenyl ether.

6. The preparation method according to claim 3, characterized in that: The precipitant is selected from the group consisting of water, methanol, ethanol, or a combination thereof; preferably water and methanol.

7. The preparation method according to claim 3, characterized in that: The mass ratio of the phthalonitrile resin monomer to the o-carborane catalyst is 100:(1-50), preferably 100:(3-30); more preferably 100:(5-20).

8. The preparation method according to claim 3, characterized in that: The reaction temperature is 180-220°C.

9. The preparation method according to claim 3, characterized in that: The reaction time is 2 to 4 hours.

10. A cured product of the modified phthalonitrile resin prepolymer according to claim 1, characterized in that: The solidified product is obtained by solidifying a modified phthalonitrile resin prepolymer.

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