A high temperature resistant and easy-to-process benzoxazole resin and its preparation method and application

Abstract

The present invention discloses a high temperature resistant and easy-to-process benzoxazole resin and a preparation method and application thereof. The high temperature resistant and easy-to-process benzoxazole resin has a structure as shown in the following formula: wherein n is selected from any integer between 0 and 10. The high temperature resistant and easy-to-process benzoxazole resin provided by the present invention has the characteristics of good solubility, good fluidity and high heat resistance, and solves the technical problem that the existing linear polybenzoxazole is insoluble, infusible and cannot be used as a matrix resin for preparing composite materials.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and in particular relates to a high temperature resistant and easy to process benzoxazole resin and a preparation method and application thereof. Background Art

[0002] Polybenzoxazole (PBO) is a kind of rigid conjugated polymer material with extremely excellent mechanical properties, thermal stability, dimensional stability and dielectric properties. Its thermal decomposition temperature can reach up to 650°C. However, linear PBO can only be dissolved in strong proton acids but not in any organic solvents, nor can it be melted, and its processability is extremely poor. Therefore, it is of great significance to develop benzoxazole resins with both high heat resistance and excellent molding processability. In recent years, the research on soluble and fusible thermosetting benzoxazole resins has received great attention. Domestic researchers first used 2,2-bis (3-amino-4-hydroxyphenyl) hexafluoropropane monomers to prepare phenylethynyl-terminated imide precursors, and then obtained polybenzoxazole by thermal rearrangement reaction at high temperature (Chemical Engineering Journal 2019, 359, 641). However, the thermal rearrangement reaction temperature must be as high as 400°C or even 450°C to complete the reaction, and small molecular volatiles are released during the reaction process, which is extremely unfavorable for material molding and its mechanical properties. Recently, researchers have synthesized acetylene- and cyano-terminated benzoxazole resins using an aqueous medium method. The solubility of the resin in organic solvents has been significantly improved, and the cured resin has excellent thermal stability (Journal of East China University of Science and Technology, 2021, 0, 1). However, the acetylene- or cyano-terminated resins have a short shelf life and a narrow processing window, and the cross-linking density of the cured resin is too high, resulting in poor mechanical properties. Therefore, providing a high-temperature resistant and easy-to-process benzoxazole resin is an urgent problem to be solved. Summary of the invention

[0003] The main purpose of the present invention is to provide a high temperature resistant and easy to process benzoxazole resin and a preparation method and application thereof, so as to overcome the deficiencies of the prior art.

[0004] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention includes:

[0005] The embodiment of the present invention provides a high temperature resistant and easy-to-process benzoxazole resin having a structure as shown in formula (I):

[0006]

[0007] Wherein, R1 is selected from the structure shown in any one of the following formulae:

[0008]

[0009] R2 is selected from the structure shown in any one of the following formulae:

[0010]

[0011] R3 is selected from the structure shown in any one of the following formulae:

[0012]

[0013] n is any integer selected from 0 to 10.

[0014] The present invention also provides a method for preparing the aforementioned high temperature resistant and easy-to-process benzoxazole resin, which comprises:

[0015] Under a protective atmosphere, reacting a first mixed reaction system comprising aromatic bis(o-aminophenol), aromatic diformyl chloride, a basic catalyst and an organic solvent at 5 to 10° C. for 4 to 8 hours;

[0016] Adding a capping agent to the first mixed reaction system and continuing the reaction for 2 to 4 hours to obtain a hydroxyamide oligomer;

[0017] And, under a protective atmosphere, a second mixed reaction system comprising the hydroxyamide oligomer, a dehydrating agent, an acidic catalyst and an organic solvent is reacted at 140-180° C. for 10-20 hours to obtain a high temperature resistant and easy-to-process benzoxazole resin.

[0018] The embodiment of the present invention also provides the use of the above-mentioned high temperature resistant and easy-to-process benzoxazole resin as a base resin in preparing a composite material.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The present invention innovatively prepares a high temperature resistant and easy-to-process benzoxazole resin, wherein the prepared high temperature resistant and easy-to-process benzoxazole resin has a soluble solid content of more than 30% in an organic solvent, a melt viscosity adjustable in the range of 0 to 10000 Pa·s, a 5wt% thermal weight loss temperature of the resin solidified material in air of more than 550°C, and an elongation at break of more than 2%;

[0021] (2) The present invention uses aromatic bis(o-aminophenol), aromatic diformyl chloride and phenylacetylene or naphthylethynylbenzoyl chloride to obtain benzoxazole resin through a two-step polycondensation method, which has a simple preparation process, is easy to operate, and has strong resin structure designability;

[0022] (3) The high temperature resistant and easy-to-process benzoxazole resin prepared by the present invention has the characteristics of high solubility, high fluidity and high heat resistance, which solves the technical problem that the existing polybenzoxazole is insoluble, non-meltable and cannot be used as a matrix resin for preparing composite materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 This is an infrared spectrum of the high temperature resistant and easy-to-process benzoxazole resin obtained in Example 1 of the present invention;

[0025] Figure 2 This is the hydrogen nuclear magnetic spectrum of the high temperature resistant and easy to process benzoxazole resin obtained in Example 1 of the present invention;

[0026] Figure 3 This is a dissolution test diagram of the high temperature resistant and easy-to-process benzoxazole resin obtained in Example 1 of the present invention;

[0027] Figure 4 This is a rheological curve of the high temperature resistant and easy-to-process benzoxazole resin obtained in Example 1 of the present invention;

[0028] Figure 5 is a differential scanning calorimetry diagram of the high temperature resistant and easy-to-process benzoxazole resin obtained in Example 1 of the present invention;

[0029] Figure 6 This is a thermogravimetric diagram of the cured product of the high temperature resistant and easy-to-process benzoxazole resin obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0030] In view of the defects of the prior art, the inventors of this case have proposed the technical solution of the present invention after long-term research and extensive practice. The technical solution mainly adopts aromatic bis(o-aminophenol), aromatic diformyl chloride and phenylacetylene or naphthylethynylbenzoyl chloride to obtain a high-temperature resistant and easy-to-process benzoxazole resin through a two-step polycondensation method, so that the high-temperature resistant and easy-to-process benzoxazole resin has the characteristics of high solubility, high fluidity and high heat resistance, which solves the technical problem that the existing polybenzoxazole is insoluble, non-meltable and cannot be used as a matrix resin for preparing composite materials.

[0031] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Specifically, as one aspect of the technical solution of the present invention, a high temperature resistant and easy-to-process benzoxazole resin has a structure as shown in formula (I):

[0033]

[0034] Wherein, R1 is selected from the structure shown in any one of the following formulae:

[0035]

[0036] R2 is selected from the structure shown in any one of the following formulae:

[0037]

[0038] R3 is selected from the structure shown in any one of the following formulae:

[0039]

[0040] n is any integer selected from 0 to 10.

[0041] Another aspect of the embodiments of the present invention further provides a method for preparing the aforementioned high temperature resistant and easy to process benzoxazole resin, which comprises:

[0042] Under a protective atmosphere, reacting a first mixed reaction system comprising aromatic bis(o-aminophenol), aromatic diformyl chloride, a basic catalyst and an organic solvent at 5 to 10° C. for 4 to 8 hours;

[0043] Adding a capping agent to the first mixed reaction system and continuing the reaction for 2 to 4 hours to obtain a hydroxyamide oligomer;

[0044] And, under a protective atmosphere, a second mixed reaction system comprising the hydroxyamide oligomer, a dehydrating agent, an acidic catalyst and an organic solvent is reacted at 140-180° C. for 10-20 hours to obtain a high temperature resistant and easy-to-process benzoxazole resin.

[0045] In some preferred embodiments, the aromatic bis(o-aminophenol) includes any one or a combination of two or more of 4,6-diaminoresorcinol, 3,3'-dihydroxybenzidine, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, 3,3'-diamino-4,4'-dihydroxydiphenylmethane, 2,2-bis(3-amino-4-hydroxyphenyl)propane, 9,9-bis(3-amino-4-hydroxyphenyl)fluorene, and 3,3'-diamino-4,4'-dihydroxydiphenyl sulfone, wherein the 4,6-diaminoresorcinol The structural formulas of (R1-1), 3,3'-dihydroxybenzidine (R1-2), 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (R1-3), 3,3'-diamino-4,4'-dihydroxydiphenylmethane (R1-4), 2,2-bis(3-amino-4-hydroxyphenyl)propane (R1-5), 9,9-bis(3-amino-4-hydroxyphenyl)fluorene (R1-6), and 3,3'-diamino-4,4'-dihydroxydiphenyl sulfone (R1-7) are shown in formulas (R1-1) to (R1-7), respectively:

[0046]

[0047] In some preferred embodiments, the aromatic diformyl chloride includes any one or a combination of two or more of terephthaloyl chloride, 2,6-naphthalene diformyl chloride, 2,2'-bis(trifluoromethyl)-diformyl chloride biphenyl, 2,2-bis(benzoyl chloride)hexafluoropropane, 2,2'-dimethyl-diformyl chloride biphenyl, 2,6-bis(4-formyl chloride phenoxy) naphthalene, and 4,4'-diformyl chloride diphenyl ether, wherein the terephthaloyl chloride (R2-1) , 2,6-naphthalene dicarboxylic acid chloride (R2-2), 2,2'-bis(trifluoromethyl)-dicarboxylic acid biphenyl chloride (R2-3), 2,2-bis(benzoyl chloride)hexafluoropropane (R2-4), 2,2'-dimethyl-dicarboxylic acid biphenyl chloride (R2-5), 2,6-bis(4-carboxylic acid phenoxy) naphthalene (R2-6), 4,4'-dicarboxylic acid diphenyl ether (R2-7) have structural formulae as shown in formulae (R2-1) to (R2-7), respectively:

[0048]

[0049] In some preferred embodiments, the alkaline catalyst includes any one of N,N-dimethylbenzene, pyridine, triethylamine, and lutidine, but is not limited thereto.

[0050] In some preferred embodiments, the molar ratio of the basic catalyst to the acyl chloride group in the aromatic dicarboxylic acid chloride is (1-3):1.

[0051] In some preferred embodiments, the molar ratio of the aromatic diformyl chloride, aromatic bis(o-aminophenol) and the capping agent is n:(n+1):2, wherein n is selected from any integer between 0 and 10.

[0052] In some preferred embodiments, the preparation method comprises: after the first mixed reaction system completes the reaction, adding a capping agent and controlling the solid content of the obtained mixed solution to be 20-40 wt %, and then continuing the reaction for 2-4 hours to obtain the hydroxyamide oligomer.

[0053] In some preferred embodiments, the end-capping agent includes any one or a combination of two or more of 4-phenylethynylbenzoyl chloride, 3-phenylethynylbenzoyl chloride, 2-phenylethynylbenzoyl chloride, 4-(1-ethynylnaphthalene)benzoyl chloride, 4-(2-ethynylnaphthalene)benzoyl chloride, 3-(1-ethynylnaphthalene)benzoyl chloride, 3-(2-ethynylnaphthalene)benzoyl chloride, 2-(1-ethynylnaphthalene)benzoyl chloride and 2-(2-ethynylnaphthalene)benzoyl chloride, wherein the 4-phenylethynylbenzoyl chloride (EC-1), 3-phenylethynylbenzoyl chloride, 2-(2-ethynylnaphthalene)benzoyl chloride, 4-(1-ethynylnaphthalene)benzoyl chloride, 4-(2-ethynylnaphthalene)benzoyl chloride, 3-(1-ethynylnaphthalene)benzoyl chloride, 3-(2-ethynylnaphthalene)benzoyl chloride, 2-(1-ethynylnaphthalene)benzoyl chloride and 2-(2-ethynylnaphthalene)benzoyl chloride. The structural formulas of ethynylbenzoyl chloride (EC-2), 2-phenylethynylbenzoyl chloride (EC-3), 4-(1-ethynylnaphthalene)benzoyl chloride (EC-4), 4-(2-ethynylnaphthalene)benzoyl chloride (EC-5), 3-(1-ethynylnaphthalene)benzoyl chloride (EC-6), 3-(2-ethynylnaphthalene)benzoyl chloride (EC-7), 2-(1-ethynylnaphthalene)benzoyl chloride (EC-8), and 2-(2-ethynylnaphthalene)benzoyl chloride (EC-9) are shown in formulas (EC-1) to (EC-9), respectively:

[0054]

[0055] Furthermore, the resin terminated with phenylethynyl or naphthylethynyl in the present application mainly forms a polyene structure during thermal crosslinking, and due to the steric hindrance of the benzene ring or naphthalene ring, the crosslinking speed can be regulated, so that the oligomers with lower molecular weight can be obtained by controlling the curing conditions to obtain similar linear polymers, thereby making the material have good toughness, and at the same time, the curing temperature of phenylethynyl or naphthylethynyl is high, and the resin has a wider processing window. Therefore, the benzoxazole resin terminated with phenylethynyl or naphthylethynyl has more excellent molding processability and mechanical toughness.

[0056] In some preferred embodiments, the preparation method comprises: placing the hydroxyamide oligomer and the acidic catalyst in an organic solvent under a protective atmosphere, and controlling the solid content of the obtained mixed solution to be 20-40 wt %, and then adding a dehydrating agent to form the second mixed reaction system.

[0057] Further, the acidic catalyst includes any one or a combination of two or more of 4-bromopyridine hydrochloride, pyridine hydrochloride, and p-toluenesulfonic acid monohydrate, but is not limited thereto.

[0058] Furthermore, the dehydrating agent includes any one of toluene, xylene, and o-dichlorobenzene or a combination of two or more thereof, but is not limited thereto.

[0059] Furthermore, the molar ratio of the acidic catalyst to the hydroxyamide oligomer is 1:(5-15).

[0060] Furthermore, the mass ratio of the dehydrating agent to the organic solvent is 1:(2-6).

[0061] In some preferred embodiments, the protective atmosphere includes a nitrogen atmosphere, but is not limited thereto.

[0062] In some preferred embodiments, the organic solvent includes any one or a combination of two or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and N-methylpyrrolidone (NMP), but is not limited thereto.

[0063] In some more specific embodiments, the method for preparing the high temperature resistant and easy to process benzoxazole resin comprises:

[0064] S1. Under nitrogen protection, aromatic bis(o-aminophenol), aromatic diformyl chloride and alkaline catalyst are placed in an organic solvent at 5-10°C for 4-8h;

[0065] S2. Add a capping agent to the reaction system of step S1, and continue the reaction for 2 to 4 hours to obtain a hydroxyamide oligomer;

[0066] S3. Under nitrogen protection, the hydroxyamide oligomer obtained in step S2, a dehydrating agent, and an acidic catalyst are placed in an organic solvent and reacted at 140 to 180° C. for 10 to 20 hours to obtain a high temperature resistant and easy-to-process benzoxazole resin.

[0067] Furthermore, step S2 specifically includes: after the reaction in step S1 is completed, adding a capping agent to the reaction system, and controlling the solid content of the obtained mixed solution to be 20wt% to 40wt%, and then continuing the reaction for 2 to 4h.

[0068] Furthermore, step S3 specifically includes: under nitrogen protection, placing the hydroxyamide oligomer and the acidic catalyst obtained in step S2 in an organic solvent, and controlling the solid content of the obtained mixed solution to be 20wt% to 40wt%, and then adding a dehydrating agent to react at 140 to 180° C. for 10 to 20 hours to obtain the high temperature resistant and easy-to-process benzoxazole resin.

[0069] Furthermore, after the reaction in step S2 is completed, the obtained mixed solution is poured into an alcohol / water mixed solvent, solids are precipitated, filtered, washed, and vacuum dried at 100-120° C. for 10-20 h to obtain hydroxyamide oligomers.

[0070] Furthermore, after the reaction in step S3 is completed, the obtained mixed solution is poured into an alcohol solvent, solids are precipitated, filtered, washed, and vacuum dried at 150-200° C. for 6-12 hours to obtain the high temperature resistant and easy to process benzoxazole resin.

[0071] Furthermore, the alcohol solvent is ethanol or methanol.

[0072] Another aspect of the embodiments of the present invention further provides the use of the aforementioned high temperature resistant and easy to process benzoxazole resin as a base resin in preparing a composite material.

[0073] The technical solution of the present invention is further described in detail below in conjunction with several preferred embodiments and drawings. This embodiment is implemented on the premise of the technical solution of the invention, and a detailed implementation method and specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments.

[0074] Unless otherwise specified, the experimental materials used in the following examples can be purchased from conventional biochemical reagent companies.

[0075] Example 1

[0076] Under nitrogen protection, 10.00 g R1-3 and 4.32 g pyridine were added to a three-necked flask containing 109.84 g NMP, and then 13.14 g EC-1 was added, and the reaction temperature was maintained at 10°C for 4 h. The reaction solution was poured into a mixed solvent of methanol / water, and solids precipitated. The solids were filtered, washed, and vacuum dried at 110°C for 15 h to obtain hydroxyamide oligomers.

[0077] Under nitrogen protection, 15.00g of hydroxyamide oligomer, 0.39g of p-toluenesulfonic acid monohydrate and 61.56g of NMP were placed in a three-necked flask, and then 15.39g of toluene was added and reacted at 140°C for 20 hours. The reaction solution was poured into methanol, and solids precipitated. The solids were filtered, washed, and vacuum dried at 150°C for 12 hours to obtain a high temperature resistant and easy-to-process benzoxazole resin.

[0078] The infrared spectrum of the high temperature resistant and easy-to-process benzoxazole resin prepared in this example is as follows: Figure 1 As shown; the hydrogen nuclear magnetic spectrum is as shown Figure 2 As shown; the dissolution test diagram of high temperature resistant and easy to process benzoxazole resin is as follows Figure 3As shown, the resin has good solubility, and the solid content in nitrogen methyl pyrrolidone, tetrahydrofuran, dimethylacetamide and dioxane can reach more than 30%; the rheological curve of high temperature resistant and easy to process benzoxazole resin is shown in Figure 4 As shown in the figure, the rheological curve shows that the melt viscosity of the resin is low, indicating that it has good melt fluidity; the differential scanning calorimetry diagram of the high temperature resistant and easy to process benzoxazole resin is shown in the figure Figure 5 As shown in the DSC curve, there is a temperature range of more than 100°C between the melting point of the resin and the crosslinking temperature, and the processing window is very wide; the thermal weight loss diagram of the cured product of the high temperature resistant and easy to process benzoxazole resin is shown in Figure 6 As shown, the thermogravimetric curve shows that the cured resin has good thermal oxidation stability.

[0079] Example 2

[0080] Under nitrogen protection, 5 g R2-1, 18.041 g R1-3 and 7.79 g pyridine were added into a three-necked flask containing 64.03 g NMP, and the reaction temperature was maintained at 5° C. for 6 h.

[0081] Add 11.855 g EC-1 to a three-necked flask and keep the reaction temperature at 5°C for 3 h. Pour the reaction solution into a mixed solvent of ethanol / water, solids precipitate, filter, wash, and vacuum dry at 120°C for 10 h to obtain hydroxyamide oligomers.

[0082] Under nitrogen protection, 20g of hydroxyamide oligomer, 0.212g of p-toluenesulfonic acid monohydrate and 30.32g of NMP were placed in a three-necked flask, and then 5.05g of xylene was added and reacted at 160°C for 10h. The reaction solution was poured into ethanol, and solids precipitated. The solids were filtered, washed, and vacuum dried at 180°C for 10h to obtain a high temperature resistant and easy to process benzoxazole resin.

[0083] Example 3

[0084] Under nitrogen protection, 10.00 g R1-2 and 13.38 g lutidine were added to a three-necked flask containing 109.84 g NMP, and then 22.26 g EC-2 was added, and the reaction temperature was maintained at 8°C for 3 h. The reaction solution was poured into a mixed solvent of methanol / water, and solids precipitated. The solids were filtered, washed, and vacuum dried at 100°C for 20 h to obtain hydroxyamide oligomers.

[0085] Under nitrogen protection, 20.00g of hydroxyamide oligomer, 1.29g of p-toluenesulfonic acid monohydrate and 39.54g of NMP were placed in a three-necked flask, and then 19.77g of o-dichlorobenzene was added and reacted at 180°C for 15 hours. The reaction solution was poured into methanol, and solids precipitated. The solids were filtered, washed, and vacuum dried at 200°C for 6 hours to obtain a high temperature resistant and easy-to-process benzoxazole resin.

[0086] Example 4

[0087] Under nitrogen protection, 5 g R2-3, 6.11 g R1-6 and 9.73 g N,N-dimethylbenzene were added into a three-necked flask containing 91.07 g DMAc, and the reaction temperature was maintained at 5°C for 8 h.

[0088] Add 1.93 g EC-3 to a three-necked flask and keep the reaction temperature at 5°C for 4 hours. Pour the reaction solution into a methanol / water mixed solvent, solids precipitate, filter, wash, and vacuum dry at 115°C for 10 hours to obtain hydroxyamide oligomers.

[0089] Under nitrogen protection, 8g of hydroxyamide oligomer, 0.04g of pyridine hydrochloride and 32.16g of DMAc were placed in a three-necked flask, and then 10.72g of toluene was added and reacted at 145°C for 10h. The reaction solution was poured into ethanol, and solids precipitated. The solids were filtered, washed, and vacuum dried at 140°C for 10h to obtain a high temperature resistant and easy to process benzoxazole resin.

[0090] Example 5

[0091] Under nitrogen protection, 50 g of R2-7, 58.26 g of R1-4 and 69.43 g of triethylamine were added into a three-necked flask containing 327.70 g of DMF, and the reaction temperature was maintained at 10° C. for 5 h.

[0092] Add 49.26g EC-4 to a three-necked flask and keep the reaction temperature at 10°C for 3h. Pour the reaction solution into a methanol / water mixed solvent, solids precipitate, filter, wash, and vacuum dry at 105°C for 18h to obtain hydroxyamide oligomers.

[0093] Under nitrogen protection, 100g of hydroxyamide oligomer, 1.50g of pyridine hydrochloride and 236.83g of DMF were placed in a three-necked flask, and then 47.37g of xylene was added and reacted at 140°C for 15h. The reaction solution was poured into ethanol, and solids precipitated. The solids were filtered, washed, and vacuum dried at 160°C for 12h to obtain a high temperature resistant and easy to process benzoxazole resin.

[0094] Example 6

[0095] Under nitrogen protection, 20 g R2-5, 18.92 g R1-5 and 69.43 g triethylamine were added into a three-necked flask containing 327.70 g DMF, and the reaction temperature was maintained at 10° C. for 5 h.

[0096] Add 49.26g EC-5 to the three-necked flask and keep the reaction temperature at 10℃ for 3h. Pour the reaction solution into a mixed solvent of methanol / water, solid precipitates, filter, wash, and vacuum dry at 105℃ for 18h to obtain hydroxyamide oligomer.

[0097] Under nitrogen protection, 100g of hydroxyamide oligomer, 1.50g of pyridine hydrochloride and 236.83g of DMF were placed in a three-necked flask, and then 47.37g of xylene was added and reacted at 140°C for 15h. The reaction solution was poured into ethanol, and solids precipitated. The solids were filtered, washed, and vacuum dried at 160°C for 12h to obtain a high temperature resistant and easy to process benzoxazole resin.

[0098] Example 7

[0099] Under nitrogen protection, 30 g R2-6, 27.64 g R1-3 and 32.56 g pyridine were added into a three-necked flask containing 167.51 g NMP, and the reaction temperature was maintained at 5° C. for 7 h.

[0100] Add 7.84 g EC-6 to a three-necked flask and keep the reaction temperature at 5°C for 2 h. Pour the reaction solution into a mixed solvent of ethanol / water, solids precipitate, filter, wash, and vacuum dry at 115°C for 12 h to obtain hydroxyamide oligomers.

[0101] Under nitrogen protection, 40g of hydroxyamide oligomer, 0.10g of p-toluenesulfonic acid monohydrate and 120.30g of NMP were placed in a three-necked flask, and then 20.05g of toluene was added and reacted at 160°C for 18h. The reaction solution was poured into ethanol, and solids precipitated. The solids were filtered, washed, and vacuum dried at 180°C for 8h to obtain a high temperature resistant and easy-to-process benzoxazole resin.

[0102] Example 8

[0103] Under nitrogen protection, 50 g of R2-2, 110.76 g of R1-7 and 159.93 g of triethylamine were added into a three-necked flask containing 970.18 g of DMAc, and the reaction temperature was maintained at 10° C. for 8 h.

[0104] Add 95.10 g EC-2 into a three-necked flask and keep the reaction temperature at 10°C for 4 hours. Pour the reaction solution into a methanol / water mixed solvent, solids precipitate, filter, wash, and vacuum dry at 120°C for 10 hours to obtain hydroxyamide oligomers.

[0105] Under nitrogen protection, 100g of hydroxyamide oligomer, 0.67g of pyridine hydrochloride and 151.00g of DMAc were placed in a three-necked flask, and then 38.00ger of toluene was added and reacted at 155°C for 10h. The reaction solution was poured into methanol, and solids precipitated. The solids were filtered, washed, and vacuum dried at 150°C for 10h to obtain a high temperature resistant and easy to process benzoxazole resin.

[0106] Example 9

[0107] Under nitrogen protection, 30 g R2-4, 51.21 g R1-3 and 28.39 g triethylamine were added into a three-necked flask containing 350.58 g NMP, and the reaction temperature was maintained at 5° C. for 7 h.

[0108] Add 40.65 g EC-7 to a three-necked flask and keep the reaction temperature at 5°C for 4 hours. Pour the reaction solution into a methanol / water mixed solvent, solids precipitate, filter, wash, and vacuum dry at 110°C for 10 hours to obtain hydroxyamide oligomers.

[0109] Under nitrogen protection, 60g of hydroxyamide oligomer, 0.75g of p-toluenesulfonic acid monohydrate and 142g of NMP were placed in a three-necked flask, and then 35g of toluene was added to react at 150°C for 15h. The reaction solution was poured into methanol, and solids precipitated. The solids were filtered, washed, and vacuum dried at 200°C for 10h to obtain a high temperature resistant and easy-to-process benzoxazole resin.

[0110] Example 10

[0111] Under nitrogen protection, 40 g R2-5, 57.23 g R1-3 and 49.37 g pyridine were added into a three-necked flask containing 168 g DMF, and the reaction temperature was maintained at 7° C. for 4 h.

[0112] Add 15.14 g EC-8 to a three-necked flask and keep the reaction temperature at 7°C for 2 h. Pour the reaction solution into a mixed solvent of ethanol / water, solids precipitate, filter, wash, and vacuum dry at 120°C for 20 h to obtain hydroxyamide oligomers.

[0113] Under nitrogen protection, 50g of hydroxyamide oligomer, 0.50g of 4-bromopyridine hydrochloride and 200g of DMF were placed in a three-necked flask, and then 30g of xylene was added and reacted at 160°C for 10h. The reaction solution was poured into ethanol, and solids precipitated. The solids were filtered, washed, and vacuum dried at 180°C for 8h to obtain a high temperature resistant and easy-to-process benzoxazole resin.

[0114] Embodiment 11

[0115] Under nitrogen protection, 50 g of R2-7, 70.90 g of R1-6 and 130 g of lutidine were added into a three-necked flask containing 390 g of DMAc, and the reaction temperature was maintained at 10° C. for 8 h.

[0116] Add 9.85 g EC-9 to a three-necked flask and keep the reaction temperature at 10°C for 2 h. Pour the reaction solution into a methanol / water mixed solvent, solids precipitate, filter, wash, and vacuum dry at 100°C for 15 h to obtain hydroxyamide oligomers.

[0117] Under nitrogen protection, 100g of hydroxyamide oligomer, 0.12g of pyridine hydrochloride and 150g of DMAc were placed in a three-necked flask, and then 35g of o-dichlorobenzene was added and reacted at 165°C for 20h. The reaction solution was poured into methanol, and solids precipitated. The solids were filtered, washed, and vacuum dried at 190°C for 10h to obtain a high temperature resistant and easy to process benzoxazole resin.

[0118] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments with other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

[0119] It should be understood that the technical solution of the present invention is not limited to the above-mentioned specific implementation cases. Any technical deformation made according to the technical solution of the present invention without departing from the scope of protection of the purpose of the present invention and the claims shall fall within the protection scope of the present invention.

Claims

1. A method for preparing a high temperature resistant and easy-to-process benzoxazole resin, characterized in that: include: Under a protective atmosphere, a first mixed reaction system comprising an aromatic bis(o-aminophenol), an aromatic diformyl chloride, an alkaline catalyst and an organic solvent is reacted at 5 to 10° C. for 4 to 8 hours; wherein the aromatic bis(o-aminophenol) is selected from 4,6-diaminoresorcinol, 3,3'-dihydroxybenzidine, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, 3,3'-diamino-4,4'-dihydroxydiphenylmethane, 2,2-bis(3-amino-4-hydroxyphenyl)propane, 9,9- Any one or a combination of two or more of di(3-amino-4-hydroxyphenyl)fluorene and 3,3'-diamino-4,4'-dihydroxydiphenyl sulfone; the aromatic diformyl chloride is selected from any one or a combination of two or more of terephthaloyl chloride, 2,6-naphthalene diformyl chloride, 2,2'-bis(trifluoromethyl)-diformyl biphenyl chloride, 2,2-bis(benzoyl chloride)hexafluoropropane, 2,2'-dimethyl-diformyl biphenyl chloride, 2,6-bis(4-formyl chloride phenoxy) naphthalene and 4,4'-diformyl chloride diphenyl ether; Adding a capping agent to the first mixed reaction system and continuing the reaction for 2 to 4 hours to obtain a hydroxyamide oligomer; wherein the capping agent is selected from any one of 4-phenylethynylbenzoyl chloride, 3-phenylethynylbenzoyl chloride, 2-phenylethynylbenzoyl chloride, 4-(1-ethynylnaphthalene)benzoyl chloride, 4-(2-ethynylnaphthalene)benzoyl chloride, 3-(1-ethynylnaphthalene)benzoyl chloride, 3-(2-ethynylnaphthalene)benzoyl chloride, 2-(1-ethynylnaphthalene)benzoyl chloride, and 2-(2-ethynylnaphthalene)benzoyl chloride, or a combination of two or more thereof; and, under a protective atmosphere, reacting a second mixed reaction system comprising the hydroxyamide oligomer, a dehydrating agent, an acidic catalyst and an organic solvent at 140 to 180° C. for 10 to 20 hours to obtain a high temperature resistant and easy-to-process benzoxazole resin; The high temperature resistant and easy-to-process benzoxazole resin has a structure as shown in formula (I): Wherein, R1 is selected from the structure shown in any one of the following formulae: R2 is selected from the structure shown in any one of the following formulae: R3 is selected from the structure shown in any one of the following formulae: n is any integer selected from 0 to 10.

2. The preparation method according to claim 1, characterized in that: The alkaline catalyst is selected from any one of N,N-dimethylbenzene, pyridine, triethylamine and lutidine.

3. The preparation method according to claim 1, characterized in that: The molar ratio of the alkaline catalyst to the acyl chloride group in the aromatic diformyl chloride is (1-3):

1.

4. The preparation method according to claim 1, characterized in that: The molar ratio of the aromatic diformyl chloride, aromatic bis(o-aminophenol) and the end-capping agent is n:(n+1):2, wherein n is selected from any integer between 0 and 10.

5. The preparation method according to claim 1, characterized in that include: After the first mixed reaction system completes the reaction, a capping agent is added and the solid content of the obtained mixed solution is controlled to be 20-40 wt %, and then the reaction is continued for 2-4 hours to obtain the hydroxyamide oligomer.

6. The preparation method according to claim 1, characterized in that include: Under a protective atmosphere, the hydroxyamide oligomer and the acid catalyst are placed in an organic solvent, and the solid content of the obtained mixed solution is controlled to be 20-40 wt %, and then a dehydrating agent is added to form the second mixed reaction system.

7. The preparation method according to claim 6, characterized in that: The acidic catalyst is selected from any one of 4-bromopyridine hydrochloride, pyridine hydrochloride, and p-toluenesulfonic acid monohydrate, or a combination of two or more thereof.

8. The preparation method according to claim 6, characterized in that: The dehydrating agent is selected from any one of toluene, xylene and o-dichlorobenzene or a combination of two or more thereof.

9. The preparation method according to claim 6, characterized in that: The molar ratio of the acid catalyst to the hydroxyamide oligomer is 1:(5-15).

10. The preparation method according to claim 6, characterized in that: The mass ratio of the dehydrating agent to the organic solvent is 1:(2-6).

11. The preparation method according to claim 1, characterized in that: The protective atmosphere is selected from a nitrogen atmosphere.

12. The preparation method according to claim 1, characterized in that: The organic solvent is selected from any one of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone, or a combination of two or more thereof.

13. Use of the high temperature resistant and easy-to-process benzoxazole resin prepared by the preparation method according to any one of claims 1 to 12 as a matrix resin in preparing a composite material.

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