High heat-resistant oxidatively modified phthalonitrile resin prepolymer and preparation method thereof

Abstract

The application discloses a high-heat-oxidation-resistant modified phthalonitrile resin prepolymer and a preparation method thereof. Specifically, the application discloses a phthalonitrile resin prepolymer modified by o-carborane, and the main raw material is phthalonitrile resin monomer. The modified phthalonitrile resin prepolymer prepared by the application has improved heat-oxidation resistance and can be widely applied to the fields of high-tech industries such as aerospace, high-performance composite materials and the like.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials. Specifically, this invention relates to a high heat-resistant oxidative modified phthalonitrile resin prepolymer and its preparation method. Background Technology

[0002] Phthalonil resin is a high-performance engineering resin with excellent thermal stability and mechanical properties. However, its thermo-oxidative stability remains one of its major drawbacks; its performance degrades significantly at high temperatures, with a mass retention rate of 0% at 800°C in a conventional air atmosphere, greatly limiting its applications in aerospace, automotive, and electronics industries.

[0003] Therefore, there is an urgent need in the field to develop phthalonitrile resins with superior thermal stability. Summary of the Invention

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

[0005] Another object of the present invention is to provide a method for preparing a highly heat-resistant, oxidatively modified phthalonitrile resin prepolymer.

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

[0007] In a first aspect of the present invention, a heat- and oxidation-resistant modified phthalonitrile resin prepolymer is provided, wherein the raw materials for the modified phthalonitrile resin prepolymer are phthalonitrile resin monomer and o-carborane, wherein the o-carborane catalyst has the following structure.

[0008] In another preferred embodiment, 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 combinations thereof.

[0009] In another preferred embodiment, the phthalonitrile resin monomer has the following structure:

[0010]

[0011] R:

[0012]

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

[0014] Under an inert atmosphere, phthalonitrile resin monomer, o-carborane catalyst and organic polar solvent are prepolymerized at 160℃~240℃ for 1~5h; a precipitant is added and the product is precipitated, namely the modified phthalonitrile resin prepolymer.

[0015] The ortho-carborane catalyst has the following structure.

[0016] In another preferred embodiment, 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 combinations thereof.

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

[0018]

[0019] R:

[0020]

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

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

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

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

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

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

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

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

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

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

[0031] In another preferred embodiment, the solidified material is subjected to a nitrogen atmosphere at a T d5 The temperature is 543-560℃; the temperature in the air is T d5 The temperature ranges from 543 to 562℃.

[0032] In another preferred embodiment, the cured product has a mass retention rate of 75.2-81.8% at 1000°C under a nitrogen atmosphere and a mass retention rate of 14.7-75.6% under an air atmosphere.

[0033] It should be understood that, within the scope of this invention, the above-described technical features of this invention and the technical features specifically described below (such as in the embodiments) can be combined with each other to form new or preferred technical solutions. Due to space limitations, they will not be described in detail here. Attached Figure Description

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

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

[0036] Figure 3 The images show the DSC spectra of the biphenyl-type phthalonitrile resin before and after prepolymerization in Example 1.

[0037] Figure 4 This is a schematic diagram of the structure of phthalonitrile resin catalyzed by ortho-carborane.

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

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

[0040] Figure 7 The TGA curve of the cured bisphenol S-type phthalonitrile resin prepared in Example 3 is shown. Detailed Implementation

[0041] Through extensive and in-depth research, the inventors have, for the first time, provided a novel high-heat-resistant, oxidation-modified phthalonitrile resin prepolymer and its preparation method. Compared to traditional phthalonitrile resin systems, this invention, based on the boron-nitrogen coordination principle of carboranes, significantly improves the heat resistance and heat oxidation resistance of the phthalonitrile system, enhances resin processing performance, and is suitable for various molding processes. It is also soluble in a variety of low-boiling-point solvents, which is beneficial for preparing various high-performance composite materials. Based on these findings, the inventors completed this invention.

[0042] Carborane-modified phthalonitrile resin prepolymer

[0043] o-Carboranes are a special class of compounds. Their unique cage-like structure and elemental composition give them strong electrophilicity, high thermal stability, and high chemical stability. They are not easily thermally degraded or cracked, nor are they easily chemically reacted or degraded. Through organic combination with the resin matrix, they can effectively improve the high temperature resistance and heat oxidation resistance of the resin matrix.

[0044] To address the thermal stability issue of phthalonitrile resin, this invention introduces a novel catalyst, o-carborane, to react with phthalonitrile resin to prepare a highly heat-resistant, oxidation-modified phthalonitrile resin prepolymer. Through the catalytic action of the BH bonds in o-carborane and the boron-nitrogen coordination mechanism, the carborane structure is organically combined with the resin matrix via coordinate bonds, introducing inorganic components into the resin system. This improves the overall heat and oxidation resistance of the resin. Furthermore, the prepolymer exhibits good processability, is soluble in various low-boiling-point solvents, and is suitable for a variety of molding processes.

[0045] Because o-carboranes readily sublimate when heated to above 150°C in air, and their catalytic cyano reaction typically requires temperatures above 180°C, this system is unsuitable for traditional melt processes. To address this issue, a solution prepolymerization process was designed. By co-dissolving o-carboranes and phthalonitrile resin in an organic solvent, the sublimation behavior of o-carboranes was effectively suppressed. Simultaneously, by increasing the concentration of the reaction system, the catalytic efficiency was significantly improved, successfully achieving the preparation of phthalonitrile resin prepolymers catalyzed by o-carboranes at high temperatures. This process provides a new solution for the application of o-carboranes in high-temperature catalytic systems.

[0046] The modification method of this 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, and bisphenol S-type phthalonitrile resin, with the following structural formula:

[0047]

[0048] R:

[0049]

[0050] In the method for preparing the high heat-resistant oxidatively modified phthalonitrile resin prepolymer of the present invention, the catalyst used has the following structural formula:

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

[0052] Under inert gas protection, phthalonitrile resin monomer and o-carborane catalyst are dissolved in an organic polar solvent at a mass ratio of 100:(1-50), and prepolymerized at 160℃-240℃ for 1-5 hours. After the reaction is completed, the mixture is cooled to room temperature, and the reaction solution is added to a precipitant. The product precipitates to obtain the prepolymer of highly heat-resistant oxidative modified phthalonitrile resin.

[0053] The inert gas mentioned is a common inert gas in the art, including but not limited to nitrogen and argon.

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

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

[0056] (2) The modified phthalonitrile resin of the present invention is suitable for various molding processes, is soluble in a variety of low boiling point solvents, and is beneficial for the preparation of various high performance composite materials.

[0057] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. Percentages and parts are by weight unless otherwise stated.

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

[0059] Example 1

[0060] Preparation steps of cured high heat-resistant oxidative modified phthalonitrile resin:

[0061] (1) Add 15g of biphenyl-type phthalonitrile monomer, 3g of o-carborane, and 10g of N-methylpyrrolidone to a dry four-necked flask. Under nitrogen protection, heat to 200℃ and react at high speed for 2.5h. After the reaction is complete, 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 the solution and wash the filter residue with deionized water and ethanol solution multiple times. Dry the solution under vacuum to obtain a black solid, namely the high heat-resistant oxidative modified phthalonitrile resin prepolymer.

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

[0064] (4) The sample obtained in step (3) is cured in a muffle furnace by step heating at 220℃ / 1h+260℃ / 1h+300℃ / 3h. After the muffle furnace is cooled to room temperature, the cured product of high heat resistance oxidative modified phthalonitrile resin is obtained.

[0065] Example 2

[0066] Preparation steps of cured high heat-resistant oxidative modified phthalonitrile resin:

[0067] (1) Add 15g of bisphenol A phthalonitrile monomer, 1.5g of o-carborane, and 10g of N-methylpyrrolidone to a dry four-necked flask. Under nitrogen protection, heat to 190℃ and react at high speed for 3h. After the reaction is complete, 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 the solution and wash the filter residue with deionized water and ethanol solution multiple times. Dry the solution under vacuum to obtain a black solid, namely the high heat-resistant oxidative modified phthalonitrile resin prepolymer.

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

[0070] (4) The sample obtained in step (3) is cured in a muffle furnace by step heating at 220℃ / 1h+260℃ / 1h+300℃ / 3h+350℃ / 3h. After the muffle furnace is cooled to room temperature, the cured product of high heat resistance oxidative modified phthalonitrile resin is obtained.

[0071] Example 3

[0072] Preparation steps of cured high heat-resistant oxidative modified phthalonitrile resin:

[0073] (1) Add 15g of bisphenol S-type phthalonitrile monomer, 0.45g of o-carborane, and 10g of diphenyl ether to a dry four-necked flask. Under nitrogen protection, heat to 220℃ and react at high speed for 3h. After the reaction is complete, cool to room temperature.

[0074] (2) Pour the product solution obtained in step (1) into 200 ml of H2O. A large amount of brown precipitate appears. Filter the solution and wash the filter residue with deionized water and ethanol solution multiple times. Dry the solution under vacuum to obtain a black solid, namely the high heat-resistant oxidative modified phthalonitrile resin prepolymer.

[0075] (3) After grinding the prepolymer from step (2), take a small amount of powder and place it in a ceramic crucible.

[0076] (4) The sample obtained in step (3) is cured in a muffle furnace by step heating at the following conditions: 220℃ / 1h+260℃ / 1h+300℃ / 2h+350℃ / 4h+400℃ / 2h. After the muffle furnace is cooled to room temperature, the cured product of the high heat-resistant oxidative modified phthalonitrile resin is obtained.

[0077] Comparative Example 1

[0078] (1) Add 100g of bisphenol A phthalonitrile resin to a 200mL beaker, place the beaker in an oil bath and heat it to 200℃ until the monomer is completely melted, then place it in a 200℃ vacuum oven and evacuate for 30min.

[0079] (2) Add 3g of 4,4'-bis(4-aminophenoxy)diphenyl sulfone (p-BAPS) to the resin in step (1), stir rapidly for 2min and then slowly pour it into a crucible for curing treatment. The curing regime is 270℃ / 12h+300℃ / 3h+350℃ / 6h+375℃ / 4h.

[0080] The cured material was subjected to TGA testing in nitrogen and air atmospheres at a heating rate of 10 °C / min, yielding the thermal decomposition temperature (T0) with a 5% mass loss. d5 The mass retention rates at 1000℃ and 1000℃ are shown in the following tables.

[0081]

[0082]

[0083] As can be seen from the table above, modifying phthalonitrile resin with o-carborane as a catalyst can improve the retention rate and T of the cured phthalonitrile resin in air and nitrogen. d5 The significant increase indicates that the oxidation resistance and heat resistance of the phthalonitrile resin modified with o-borane are significantly improved.

[0084] All documents mentioned in this invention are incorporated herein by reference as if each document were individually incorporated by reference. Furthermore, it should be understood that after reading the foregoing teachings of this invention, those skilled in the art can make various alterations or modifications to this invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A heat- and oxidation-resistant modified phthalonitrile resin prepolymer, characterized in that, The raw materials for the modified phthalonitrile resin prepolymer are phthalonitrile resin monomer and o-carborane, and the preparation method of the phthalonitrile resin prepolymer includes the following steps: Under an inert atmosphere, phthalonitrile resin monomer, o-carborane catalyst, and organic polar solvent undergo a prepolymerization reaction at 160℃~240℃ for 1~5 hours; a precipitant is then added, and the product, namely the modified phthalonitrile resin prepolymer, precipitates out; wherein the o-carborane catalyst has the structure shown below. The precipitant is selected from the group consisting of water, methanol, ethanol, or combinations thereof. The mass ratio of the phthalonitrile resin monomer to the o-carborane catalyst is 100:(1~50). The organic polar solvent is selected from the group consisting of aromatic solvents, amide solvents, or combinations thereof; 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 combinations thereof.

2. The prepolymer as described in claim 1, characterized in that, The phthalonitrile resin monomer has the following structure: 。 3. A method for preparing the modified phthalonitrile resin prepolymer according to claim 1, characterized in that, Includes the following steps: Under an inert atmosphere, phthalonitrile resin monomer, o-carborane catalyst and organic polar solvent are prepolymerized at 160℃~240℃ for 1~5h; a precipitant is added and the product, namely modified phthalonitrile resin prepolymer, is precipitated. The ortho-carborane catalyst has the following structure. .

4. The preparation method according to claim 3, characterized in that, 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 combinations thereof.

5. The preparation method according to claim 3, characterized in that, The phthalonitrile resin monomer has the following structure: 。 6. The preparation method according to claim 3, characterized in that, The organic polar solvent is selected from the group consisting of aromatic solvents, amide solvents, or combinations thereof.

7. The preparation method according to claim 3, characterized in that, The organic polar solvent is selected from the group consisting of N,N-dimethylformamide, N-methylpyrrolidone, N,N-dimethylacetamide, diphenyl ether, or combinations thereof.

8. The preparation method according to claim 3, characterized in that, The organic polar solvent is selected from the following group: N-methylpyrrolidone, diphenyl ether.

9. The preparation method according to claim 3, characterized in that, The precipitant is selected from the group consisting of water, methanol, ethanol, or combinations thereof.

10. The preparation method according to claim 3, characterized in that, The precipitant is water and methanol.

11. 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).

12. 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:(3~30).

13. 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:(5-20).

14. The preparation method according to claim 3, characterized in that, The reaction temperature is 180~220℃.

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

16. A cured product of the modified phthalonitrile resin prepolymer according to claim 1, characterized in that, The cured product is obtained by curing a modified phthalonitrile resin prepolymer.

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