A self-catalytic imide ring-containing phthalonitrile resin and its preparation method and application

Abstract

A self-catalytic imide ring-containing phthalonitrile resin and a preparation method and application thereof, relate to the technical field of aromatic heterocyclic resins, and specifically to a self-catalytic imide ring-containing phthalonitrile resin and a preparation method and application thereof. It is necessary to solve the problems of high melting point, inappropriate curing speed and complicated preparation process of existing self-catalytic phthalonitrile resins. Unsaturated double bonds and imide rings are introduced into the structure of the self-catalytic imide ring-containing phthalonitrile resin, and dimethyl is introduced on the benzene ring at the same time. Method: 4-amino-3,5-xylenol, 4-nitrophthalonitrile and anhydrous potassium carbonate are stirred in a non-protonic solvent, reacted, the product is washed with water, and dried to obtain 4-(4-amino-3,5-dimethylphenoxy)phthalonitrile; then glacial acetic acid is added, heated to reflux, cooled to precipitate the product, washed with water, and dried to obtain the target product. The resin has a moderate curing speed and a relatively low melting point. The resin of the present invention is used for modifying epoxy resins.

Description

Technical Field

[0001] The invention relates to the technical field of aromatic heterocyclic resins, and in particular to a self-catalytic imide ring-containing phthalonitrile resin and a preparation method and application thereof. Background Art

[0002] Phthalonitrile resin is a kind of aromatic heterocyclic resin. This kind of resin has excellent mechanical properties, thermal stability, flame retardant properties and chemical stability, and has wide application prospects in the fields of aerospace, electronics and electrical, chemical industry, automobile manufacturing, etc. However, the curing speed of this kind of resin is very slow, and it is necessary to add curing accelerators such as amine compounds, phenolic compounds, metal salts, acid anhydrides, carboxylic acids, etc. Domestic and foreign scholars have also designed the molecular structure of phthalonitrile resin grafted with amino, hydroxyl, benzimidazole or benzoxazine, and can realize autocatalytic curing without adding curing accelerator. This kind of resin is collectively referred to as autocatalytic phthalonitrile resin. Among them, amino autocatalytic phthalonitrile resin has high amino catalytic activity, narrow processing temperature window, and too fast curing speed, resulting in many pore defects in the product, and although phthalonitrile resin with hydroxyl and benzimidazole can also be cured by autocatalysis, its speed is very slow, and it is difficult to observe obvious exothermic peaks on differential scanning calorimetry (DSC) curve. In addition, the melting point of traditional phthalonitrile resin is relatively high, generally exceeding 190°C. Usually, researchers introduce flexible segments into the main chain of the resin molecule to lower the melting point, but this will sacrifice the heat resistance of the resin. Therefore, self-catalytic phthalonitrile resins with low melting point, wide processing temperature window and moderate curing speed have yet to be developed.

[0003] In terms of application, phthalonitrile resin is also often used to improve the thermal stability, thermomechanical properties and bonding properties of epoxy resin, but most of the mixing methods are solvent methods, and the solvent needs to be removed before curing; Zhao et al. prepared modified epoxy resin by melt mixing without solvent using E44 epoxy, non-self-catalytic bisphenol A type phthalonitrile, and 4,4'-diaminodiphenyl sulfone as raw materials (Journal of applied polymer science, 2013, 127 (6): 4873-4878), and the mixing temperature was as high as 200°C. Other scholars also prepared modified epoxy resin by melt mixing, but the temperature was generally above 150°C, and the phthalonitrile resin itself had to be above the melting point to be mixed evenly. Overall, the processing process is relatively complicated. Patent CN113201302B discloses a bisaminobisphthalonitrile modified epoxy resin adhesive and a preparation method thereof. The active diluent with a cyano group is used to mainly solve the problems of phthalonitrile modified epoxy resin adhesive being toxic, not environmentally friendly, and having low anti-aging performance, but the preparation process is also relatively complicated.

[0004] Therefore, the existing self-catalytic phthalonitrile resin has the problems of high melting point, unsuitable curing speed and complicated preparation process. Summary of the invention

[0005] The invention aims to solve the problems of high melting point, unsuitable curing speed and complicated preparation process of existing self-catalytic phthalonitrile resin, and provides a self-catalytic imide ring-containing phthalonitrile resin and a preparation method and application thereof.

[0006] The present invention provides a self-catalytic imide ring-containing phthalonitrile resin, the molecular structure of which is:

[0007]

[0008] The present invention also provides a method for preparing a self-catalytic imide ring-containing phthalonitrile resin, which specifically comprises the following steps:

[0009] Step 1: 4-amino-3,5-dimethylphenol, 4-nitrophthalonitrile and anhydrous potassium carbonate are stirred evenly in an aprotic solvent, heated to 35-80°C and reacted for 6-24 hours, then poured into an alkaline solution to precipitate the product, the product is washed with water until neutral, filtered and vacuum dried to obtain 4-(4-amino-3,5-dimethylphenoxy)phthalonitrile;

[0010] Step 2: Add maleic anhydride and 4-(4-amino-3,5-dimethylphenoxy)phthalonitrile to a reaction vessel filled with glacial acetic acid and stir, heat and reflux for reaction for 3-12 hours, cool to room temperature, pour into distilled water to precipitate the product, repeatedly wash the product with water until it is neutral, filter and vacuum dry to obtain the target product, the self-catalytic imide ring-containing phthalonitrile resin.

[0011] Furthermore, in step 1, the molar ratio of 4-amino-3,5-dimethylphenol, 4-nitrophthalonitrile and anhydrous potassium carbonate is 1:(1-1.1):(1.2-2).

[0012] Furthermore, the aprotic solvent in step 1 is dimethyl sulfoxide, N-methylpyrrolidone, N,N-dimethylformamide or N,N-dimethylacetamide; the amount of the aprotic solvent is 2-5 times the total weight of 4-amino-3,5-xylenol, 4-nitrophthalonitrile and anhydrous potassium carbonate.

[0013] Furthermore, the alkaline solution in step 1 is a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution, a calcium hydroxide aqueous solution or a barium hydroxide aqueous solution. Preferably, the molar concentration of the alkaline solution is 0.1-1.0 mol / L.

[0014] Furthermore, in step 2, the molar ratio of maleic anhydride to 4-(4-amino-3,5-dimethylphenoxy)phthalonitrile is (2-1.2):1.

[0015] Furthermore, in step 2, the amount of glacial acetic acid added is 3-5 times the total weight of maleic anhydride and 4-(4-amino-3,5-dimethylphenoxy)phthalonitrile.

[0016] In the above steps 1 and 2, stirring, precipitation, water washing, filtration and vacuum drying are all conventional operating methods in the art, and those skilled in the art can reasonably select tools and parameters according to actual conditions.

[0017] The invention provides the use of a self-catalytic imide ring-containing phthalonitrile resin as a modifier for epoxy resin.

[0018] Further, the specific method of epoxy resin modification is:

[0019] Aromatic amine curing agent is added to epoxy resin in an equal stoichiometric ratio, heated at 90-150°C to completely melt the aromatic amine curing agent, and then self-catalytic imide ring-containing phthalonitrile resin powder is added, and stirring is continued until it is clear and transparent, and programmed temperature is increased to cure to obtain a modified epoxy resin.

[0020] Furthermore, the epoxy resin is E44, E51, AG70 or TDE85 low-viscosity liquid epoxy resin.

[0021] Furthermore, the aromatic amine curing agent is 4,4'-diaminodiphenyl sulfone, 4,4'-bis(3-aminophenoxy)diphenyl or 4,4'-diaminobenzenesulfonylanilide.

[0022] Furthermore, the mass ratio of the epoxy resin to the self-catalytic imide ring-containing phthalonitrile resin is (0.6-1.5):1.

[0023] Furthermore, the temperature curing procedure is to keep the temperature at 180°C for 3 hours, and then heat to 250°C and keep the temperature for 2 hours.

[0024] Beneficial effects of the present invention:

[0025] 1. The self-catalytic imide ring-containing phthalonitrile resin provided by the present invention contains unsaturated double bonds, imide rings and cyano groups in the molecule. The succinimide generated by these structures after copolymerization will generate trace amounts of amines, such as aniline and benzylamine, at high temperatures, which can promote the curing reaction of cyano groups, have a relatively moderate curing speed, and are easy to prepare large-sized products with dense structures, which is conducive to industrial applications.

[0026] 2. The self-catalytic imide ring-containing phthalonitrile resin provided by the present invention has a relatively low melting point while having a relatively moderate curing speed, and is convenient for processing and use. Since the introduction of dimethyl groups on the benzene ring does not affect the rigidity of the main chain structure of the resin molecule, it can still maintain excellent thermal stability and thermomechanical properties.

[0027] 3. The method for preparing the self-catalytic imide ring-containing phthalonitrile resin provided by the present invention mainly realizes the preparation of the target resin based on operations such as stirring, heating and water washing, and does not require further refining and purification. The process is simple, the operation is convenient, and it has high production efficiency and low production cost.

[0028] 4. The self-catalytic imide ring-containing phthalonitrile resin provided by the present invention can be used as a modifier for epoxy resin. Based on the Michael addition reaction between amino groups and double bonds, the aromatic amine curing agent can "force melting" of the self-catalytic imide ring-containing phthalonitrile resin at a temperature lower than its own melting point, without the need for solvents, and the modification process is very simple. The melting temperature can be significantly lower than the melting point of the self-catalytic imide ring-containing phthalonitrile resin itself, and ultimately the glass transition temperature and high-temperature bonding performance of the epoxy resin are improved through multiple curing mechanisms. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is the DSC curve of the self-catalytic imide ring-containing phthalonitrile resin prepared in Example 1;

[0030] Figure 2 The H NMR spectrum of the self-catalytic imide ring-containing phthalonitrile resin prepared in Example 1 is ( 1 H NMR) spectrum;

[0031] Figure 3 This is the infrared (FT-IR) spectrum of the self-catalytic imide ring-containing phthalonitrile resin prepared in Example 1. DETAILED DESCRIPTION

[0032] The technical solution of the present invention is not limited to the specific implementation modes listed below, but also includes any combination of the specific implementation modes.

[0033] Specific implementation method 1: In this implementation method, the self-catalytic imide ring-containing phthalonitrile resin has a molecular structure of:

[0034]

[0035] From the perspective of molecular structure design, the resin is introduced simultaneously with unsaturated double bonds and imide rings through the imidization reaction of maleic anhydride and 4-(4-amino-3,5-dimethylphenoxy)phthalonitrile. The succinimide generated by these structures after copolymerization will generate trace amines at high temperature, such as aniline and benzylamine, which can promote the curing reaction of cyano groups. The reaction activity is much milder than that of the self-catalytic phthalonitrile resin directly with amino groups, but the reaction speed is much faster than that of the phthalonitrile resin with hydroxyl and benzimidazole. An obvious exothermic peak can be observed on the DSC curve. Therefore, the self-catalytic phthalonitrile resin containing imide rings of the present invention has a relatively moderate curing speed, and it is easy to prepare large-sized products with dense structures. At the same time, from the perspective of molecular structure design, dimethyl is introduced simultaneously on the benzene ring to destroy the structural symmetry and regularity of the phthalonitrile resin, weaken the interaction between molecules and within molecules, so that the self-catalytic phthalonitrile resin containing imide rings of the present invention has a relatively low melting point. The present invention does not affect the rigidity of the main chain structure of the phthalonitrile resin molecule as a whole, and thus can still maintain excellent thermal stability and thermomechanical properties.

[0036] Specific embodiment 2: The method for preparing the self-catalytic imide ring-containing phthalonitrile resin in this embodiment specifically includes the following steps:

[0037] Step 1: 4-amino-3,5-dimethylphenol, 4-nitrophthalonitrile and anhydrous potassium carbonate are stirred evenly in an aprotic solvent, heated to 35-80°C and reacted for 6-24 hours, then poured into an alkaline solution to precipitate the product, the product is washed with water until neutral, filtered and vacuum dried to obtain 4-(4-amino-3,5-dimethylphenoxy)phthalonitrile;

[0038] Step 2: Add maleic anhydride and 4-(4-amino-3,5-dimethylphenoxy)phthalonitrile to a reaction vessel filled with glacial acetic acid and stir, heat and reflux for reaction for 3-12 hours, cool to room temperature, pour into distilled water to precipitate the product, repeatedly wash the product with water until it is neutral, filter and vacuum dry to obtain the target product, the self-catalytic imide ring-containing phthalonitrile resin.

[0039] Specific embodiment 3: This embodiment differs from specific embodiment 2 in that the molar ratio of 4-amino-3,5-dimethylphenol, 4-nitrophthalonitrile and anhydrous potassium carbonate in step 1 is 1:(1-1.1):(1.2-2). Others are the same as specific embodiment 2.

[0040] Specific embodiment 4: This embodiment differs from specific embodiment 2 in that: the aprotic solvent in step 1 is dimethyl sulfoxide, N-methylpyrrolidone, N,N-dimethylformamide or N,N-dimethylacetamide; the amount of the aprotic solvent is 2-5 times the total weight of 4-amino-3,5-xylenol, 4-nitrophthalonitrile and anhydrous potassium carbonate. The rest is the same as specific embodiment 2.

[0041] Specific embodiment 5: This embodiment differs from specific embodiment 2 in that: the alkaline solution in step 1 is a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution, a calcium hydroxide aqueous solution or a barium hydroxide aqueous solution. Preferably, the molar concentration of the alkaline solution is 0.1-1.0 mol / L. Others are the same as specific embodiment 2.

[0042] Specific embodiment 6: This embodiment is different from specific embodiment 2 in that the molar ratio of maleic anhydride to 4-(4-amino-3,5-dimethylphenoxy)phthalonitrile in step 2 is (2-1.2): 1. The rest is the same as specific embodiment 2.

[0043] Specific embodiment 7: This embodiment differs from specific embodiment 2 in that the amount of glacial acetic acid added in step 2 is 3-5 times the total weight of maleic anhydride and 4-(4-amino-3,5-dimethylphenoxy)phthalonitrile. Others are the same as specific embodiment 2.

[0044] Specific implementation example eight: This implementation example is the use of a self-catalytic imide ring-containing phthalonitrile resin as a modifier for epoxy resins.

[0045] It can be evenly mixed with epoxy resin by simply heating and melting. Based on the Michael addition reaction between amino group and double bond, the melting temperature can be significantly lower than the melting point of the self-catalytic imide ring-containing phthalonitrile resin itself, and finally the glass transition temperature and high-temperature bonding performance of epoxy resin can be improved through multiple curing mechanisms.

[0046] Specific embodiment 9: This embodiment is different from specific embodiment 8 in that the specific method of epoxy resin modification is:

[0047] Aromatic amine curing agent is added to epoxy resin in an equal stoichiometric ratio, heated at 90-150°C to completely melt the aromatic amine curing agent, and then self-catalytic imide ring-containing phthalonitrile resin powder is added, stirred continuously until clear and transparent, and programmed temperature curing is performed to obtain modified epoxy resin. The rest is the same as the eighth embodiment.

[0048] It is preferred to heat at 100-130°C to completely melt the aromatic amine in the epoxy resin, otherwise the aromatic amine will precipitate during the curing process, resulting in unstable performance of the cured product. If the heating temperature is too high, the modified resin will gel. The conventional operation is to first melt the self-catalytic imide ring-containing phthalonitrile resin and the epoxy resin at high temperature, and then add the aromatic amine, which cannot be mixed evenly.

[0049] Specific embodiment 10: This embodiment differs from specific embodiment 9 in that the epoxy resin is E44, E51, AG70 or TDE85 low-viscosity liquid epoxy resin. Other aspects are the same as specific embodiment 9.

[0050] Specific embodiment 11: This embodiment differs from specific embodiment 9 in that the aromatic amine curing agent is 4,4'-diaminodiphenyl sulfone, 4,4'-bis(3-aminophenoxy)diphenyl or 4,4'-diaminobenzenesulfonylanilide. Other aspects are the same as specific embodiment 9.

[0051] Specific embodiment 12: This embodiment differs from specific embodiment 9 in that the mass ratio of epoxy resin to self-catalytic imide ring-containing phthalonitrile resin is (0.6-1.5): 1. Others are the same as specific embodiment 9.

[0052] When the mass ratio of epoxy resin to self-catalytic acylide-containing phthalonitrile resin is lower than 0.6:1, the proportion of self-catalytic acylide-containing phthalonitrile resin is too high, making the modified epoxy resin a hard solid at room temperature, with poor processability and inability to be used in paste adhesives; when the mass ratio of the two is higher than 1.5:1, the proportion of self-catalytic acylide-containing phthalonitrile resin is low, fewer heat-resistant cross-linking points are formed, and the performance of the modified epoxy resin does not change significantly.

[0053] Specific embodiment 13: This embodiment differs from specific embodiment 9 in that the temperature rise and curing procedure is to keep the temperature at 180°C for 3 hours, then heat to 250°C and keep the temperature for 2 hours. The rest is the same as specific embodiment 9.

[0054] The embodiments of the present invention are described in detail below. The following embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation schemes and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments.

[0055] The test instruments and methods used in the following examples are:

[0056] 1 H NMR: measured using a Bruker AVANCE III HD 600 MHz NMR spectrometer, with tetramethylsilane as the internal standard and deuterated dimethyl sulfoxide (DMSO-d 6 ) is a solvent.

[0057] DSC: TA Q20 differential scanning calorimeter was used for testing in a nitrogen atmosphere with a heating rate of 10°C / min.

[0058] Processing temperature window: The temperature difference between the curing exothermic peak temperature of the resin DSC curve and the resin melting point is defined as the processing temperature window, in degrees Celsius.

[0059] FT-IR: TENSOR-27 Fourier infrared spectrometer from Bruker was used for testing, potassium bromide tablets were used for sample preparation, and the scanning range was 4000-400 cm -1 , resolution 2cm -1 .

[0060] Glass transition temperature: tested using TA Q800 dynamic thermomechanical analyzer, single cantilever mode, heating rate 5°C / min.

[0061] Lap shear strength: Lap shear strength is one of the most basic and important indicators to characterize the bonding performance of materials. The lap shear strength at 300°C is measured according to the requirements of GJB 444-1988 standard.

[0062] Embodiment 1:

[0063] The method for preparing the autocatalytic imide ring-containing phthalonitrile resin of this embodiment comprises the following steps:

[0064] Step 1: 0.5 mol of 4-amino-3,5-xylenol, 0.52 mol of 4-nitrophthalonitrile and 0.7 mol of anhydrous potassium carbonate are stirred evenly in 540 g of N,N-dimethylformamide, heated to 35°C and reacted for 24 hours, then poured into a 0.5 mol / L sodium hydroxide aqueous solution to precipitate the product, washed with water until neutral, filtered and dried in vacuum at 60°C to obtain 4-(4-amino-3,5-dimethylphenoxy)phthalonitrile;

[0065] Step 2: Add 0.8 mol of maleic anhydride and 0.4 mol of 4-(4-amino-3,5-dimethylphenoxy)phthalonitrile to a three-necked flask containing 560 g of glacial acetic acid, stir, heat and reflux for 4 hours, cool to room temperature, pour into distilled water to precipitate the product, and repeatedly wash with water until neutral, filter and dry at 70° C. in vacuum to obtain the target product, self-catalytic imide ring-containing phthalonitrile resin, with a yield of 91% and a melting point of 150° C.

[0066] The molecular structure of the self-catalytic imide ring-containing phthalonitrile resin prepared in this embodiment is:

[0067]

[0068] The self-catalytic imide ring-containing phthalonitrile resin prepared in this example was subjected to DSC analysis. The results are as follows: Figure 1 From the DSC test results, it can be seen that the melting point of the self-catalytic imide ring-containing phthalonitrile resin is 150°C, and an obvious exothermic peak can be observed on the DSC curve. The exothermic peak temperature appears at 348°C, and the heating temperature window is 198°C, which has a moderate curing speed.

[0069] The self-catalytic imide ring-containing phthalonitrile resin prepared in this example is subjected to 1 H NMR analysis, the results are as attached Figure 2 As shown, the parsed data is: 1 H NMR (600MHz, DMSO-d6, δ, ppm) 8.13, 8.14 (d, 1H, Ar-H); 7.90, 7.91 (d, 1H, Ar-H); 7 .45-7.47 (dd, 1H, Ar-H); 7.27 (s, 2H, Ar-H); 7.05 (s, 2H, -CH=CH); 2.04 (s, 6H, -CH 3 ).

[0070] The self-catalytic imide ring-containing phthalonitrile resin prepared in this example was subjected to FT-IR analysis. The results are shown in the attached figure. Figure 3 As shown, the analytical data are: FTIR (KBr, cm -1 ): 698, 829 (C=C), 1718, 1780 (C=O), 2230 (-CN), 1093, 744 (CNC), 1250 (COC), 2968 (-CH 3 ).

[0071] from 1 The results of H NMR and FT-IR analysis show that the molecular structure of the prepared self-catalytic imide ring-containing phthalonitrile resin is consistent with the designed molecular structure, indicating that the target product has been successfully synthesized.

[0072] Embodiment 2:

[0073] The method for preparing the autocatalytic imide ring-containing phthalonitrile resin of this embodiment comprises the following steps:

[0074] Step 1: 0.5 mol of 4-amino-3,5-xylenol, 0.5 mol of 4-nitrophthalonitrile and 1 mol of anhydrous potassium carbonate are stirred evenly in 1400 g of dimethyl sulfoxide, heated to 65° C. and reacted for 10 h, then poured into a 0.2 mol / L potassium hydroxide aqueous solution to precipitate the product, washed with water until neutral, filtered and dried in vacuum at 60° C. to obtain 4-(4-amino-3,5-dimethylphenoxy)phthalonitrile;

[0075] Step 2: Add 0.64 mol of maleic anhydride and 0.4 mol of 4-(4-amino-3,5-dimethylphenoxy)phthalonitrile to a three-necked flask containing 672 g of glacial acetic acid, stir, heat and reflux for reaction for 10 h, cool to room temperature, pour into distilled water to precipitate the product, and repeatedly wash with water until neutral, filter and dry at 70° C. in vacuum to obtain the target product, self-catalytic imide ring-containing phthalonitrile resin, with a yield of 87% and a melting point of 150° C.

[0076] The DSC curve of the self-catalyzed imide ring-containing phthalonitrile resin in this example is the same as that in Example 1.

[0077] Embodiment 3:

[0078] The method for preparing the autocatalytic imide ring-containing phthalonitrile resin of this embodiment comprises the following steps:

[0079] Step 1: 0.5 mol of 4-amino-3,5-xylenol, 0.54 mol of 4-nitrophthalonitrile and 0.61 mol of anhydrous potassium carbonate are stirred evenly in 860 g of N,N-dimethylacetamide, heated to 75°C and reacted for 7 hours, then poured into a 0.8 mol / L calcium hydroxide aqueous solution to precipitate the product, washed with water until neutral, filtered and dried in vacuum at 60°C to obtain 4-(4-amino-3,5-dimethylphenoxy)phthalonitrile;

[0080] Step 2: Add 0.5 mol of maleic anhydride and 0.4 mol of 4-(4-amino-3,5-dimethylphenoxy)phthalonitrile to a three-necked flask filled with 710 g of glacial acetic acid, stir, heat and reflux for 7 hours, cool to room temperature, pour into distilled water to precipitate the product, and repeatedly wash with water until neutral, filter and dry at 70° C. in vacuum to obtain the target product, self-catalytic imide ring-containing phthalonitrile resin, with a yield of 90% and a melting point of 150° C.

[0081] The DSC curve of the self-catalyzed imide ring-containing phthalonitrile resin in this example is the same as that in Example 1.

[0082] Embodiment 4:

[0083] The method for preparing the autocatalytic imide ring-containing phthalonitrile resin of this embodiment comprises the following steps:

[0084] Step 1: 0.5 mol of 4-amino-3,5-xylenol, 0.53 mol of 4-nitrophthalonitrile and 0.79 mol of anhydrous potassium carbonate are stirred evenly in 675 g of dimethyl sulfoxide, heated to 60° C. and reacted for 16 hours, then poured into a 0.4 mol / L sodium hydroxide aqueous solution to precipitate the product, washed with water until neutral, filtered and dried under vacuum at 60° C. to obtain 4-(4-amino-3,5-dimethylphenoxy)phthalonitrile;

[0085] Step 2: Add 0.68 mol of maleic anhydride and 0.4 mol of 4-(4-amino-3,5-dimethylphenoxy)phthalonitrile to a three-necked flask filled with 774 g of glacial acetic acid, stir, heat and reflux for reaction for 9 hours, cool to room temperature, pour into distilled water to precipitate the product, and repeatedly wash with water until neutral, filter and dry in vacuum at 70° C. to obtain the target product, self-catalytic imide ring-containing phthalonitrile resin, with a yield of 88% and a melting point of 150° C.

[0086] The DSC curve of the self-catalyzed imide ring-containing phthalonitrile resin in this example is the same as that in Example 1.

[0087] Comparative Example 1:

[0088] This embodiment provides another self-catalytic imide ring-containing phthalonitrile resin. Compared with the self-catalytic imide ring-containing phthalonitrile resin in Example 1, the benzene ring thereof lacks a dimethyl structure. The specific molecular structure is:

[0089]

[0090] The preparation steps of this comparative example are as follows:

[0091] Step 1: 0.5 mol 4-aminophenol, 0.5 mol 4-nitrophthalonitrile and 0.7 mol anhydrous potassium carbonate are stirred evenly in 852 g dimethyl sulfoxide, heated to 65° C. and reacted for 9 h, then poured into a 0.2 mol / L sodium hydroxide aqueous solution to precipitate the product, washed with water until neutral, filtered and dried in vacuum at 60° C. to obtain 4-(4-aminophenoxy)phthalonitrile;

[0092] Step 2: Add 0.64 mol of maleic anhydride and 0.4 mol of 4-(4-aminophenoxy)phthalonitrile into a three-necked flask filled with 695 g of glacial acetic acid, stir, heat and reflux for 6 h, cool to room temperature, pour into distilled water to precipitate the product, and repeatedly wash with water until neutral, filter and dry in vacuum at 70° C. to obtain the target product, autocatalytic imide ring-containing phthalonitrile resin, with a yield of 90% and a melting point of 210° C.

[0093] The melting point of the self-catalytic imide ring-containing phthalonitrile resin is 213°C, and a clear exothermic peak can be observed on the DSC curve, with the exothermic peak temperature appearing at 328°C, and the heating temperature window is 115°C, which is relatively narrow. Compared with Examples 1-4, the self-catalytic imide ring-containing phthalonitrile resin in the comparative example has a higher melting point and a too fast curing speed, and a large-sized product with a dense structure cannot be prepared.

[0094] Embodiment 5:

[0095] In this example, the self-catalytic imide ring-containing phthalonitrile resin prepared in Example 1 is used as a modifier for epoxy resin to prepare modified epoxy resin. The specific operation is as follows:

[0096] Add 3.2 g of aromatic amine curing agent 4,4'-diaminodiphenyl sulfone to 10 g of E51 epoxy resin, heat at 130°C to completely melt the aromatic amine, then add 8.2 g of self-catalytic imide ring-containing phthalonitrile resin powder, continue stirring until clear and transparent, keep warm at 180°C for 3 h, then raise the temperature to 250°C and keep warm for 2 h to cure to obtain modified epoxy resin A.

[0097] Embodiment 6:

[0098] In this example, the self-catalytic imide ring-containing phthalonitrile resin obtained in Example 1 is used as a modifier for epoxy resin to prepare modified epoxy resin. The specific operation is as follows:

[0099] Add 3.2 g of aromatic amine curing agent 4,4'-diaminodiphenyl sulfone to 10 g of E51 epoxy resin, heat at 130°C to completely melt the aromatic amine, then add 15 g of self-catalytic imide ring-containing phthalonitrile resin powder, continue stirring until clear and transparent, keep warm at 180°C for 3 h, then raise the temperature to 250°C and keep warm for 2 h, and cure to obtain modified epoxy resin B.

[0100] Comparative Example 2:

[0101] This comparative example is a blank control test, and the self-catalytic imide ring-containing phthalonitrile resin obtained in Example 1 is not added. The specific operation is:

[0102] 3.2 g of aromatic amine curing agent 4,4'-diaminodiphenyl sulfone was added to 10 g of E51 epoxy resin, heated at 130°C to completely melt the aromatic amine, kept at 180°C for 3 h, and then heated to 250°C for 2 h to cure to obtain modified epoxy resin C.

[0103] Comparative Example 3:

[0104] In this comparative example, the self-catalytic imide ring-containing phthalonitrile resin obtained in comparative example 1 is used as a modifier for epoxy resin to prepare modified epoxy resin. The specific operation is as follows:

[0105] 3.2 g of aromatic amine curing agent 4,4'-diaminodiphenyl sulfone was added to 10 g of E51 epoxy resin, and the mixture was heated at 130°C to completely melt the aromatic amine. Then 8.2 g of self-catalytic imide ring-containing phthalonitrile resin powder was added and stirring was continued.

[0106] During the experiment, it was found that since the melting point of the self-catalytic imide ring-containing phthalonitrile resin obtained in Comparative Example 1 was as high as 213°C, the resin could only be melted in a small amount in the epoxy resin, resulting in uneven mixing. If the stirring time was further extended or the heating temperature was increased, gelation occurred, that is, the modified epoxy resin could not be prepared by the solvent-free method provided by the present invention.

[0107] Embodiment 7:

[0108] In this example, the self-catalytic imide ring-containing phthalonitrile resin obtained in Example 1 is used as a modifier for epoxy resin to prepare modified epoxy resin. The specific operation is as follows:

[0109] 4.8 g of aromatic amine curing agent 4,4'-bis(3-aminophenoxy)diphenyl sulfone was added to 10 g of E44 epoxy resin, and the mixture was heated at 110°C to completely melt the aromatic amine. Then, 9.6 g of self-catalytic imide ring-containing phthalonitrile resin powder was added, and stirring was continued until the mixture became clear and transparent. The mixture was kept at 180°C for 3 h, and then the mixture was heated to 250°C for 2 h to cure and obtain modified epoxy resin D.

[0110] Embodiment 8:

[0111] In this example, the self-catalytic imide ring-containing phthalonitrile resin obtained in Example 1 is used as a modifier for epoxy resin to prepare modified epoxy resin. The specific operation is as follows:

[0112] Add 4.6 g of aromatic amine curing agent 4,4'-diaminobenzenesulfonylanilide to 10 g of AG70 epoxy resin, heat at 100°C to completely melt the aromatic amine, then add 13.8 g of self-catalytic imide ring-containing phthalonitrile resin powder, continue stirring until clear and transparent, keep warm at 180°C for 3 h, then raise the temperature to 250°C and keep warm for 2 h, and cure to obtain modified epoxy resin E.

[0113] Embodiment 9:

[0114] In this example, the self-catalytic imide ring-containing phthalonitrile resin obtained in Example 1 is used as a modifier for epoxy resin to prepare modified epoxy resin. The specific operation is as follows:

[0115] Add 5.6 g of aromatic amine curing agent 4,4'-diaminobenzenesulfonylanilide to 10 g of TDE85 epoxy resin, heat at 100°C to completely melt the aromatic amine, then add 8.8 g of self-catalytic imide ring-containing phthalonitrile resin powder, continue stirring until clear and transparent, keep warm at 180°C for 3 h, then raise the temperature to 250°C and keep warm for 2 h, and cure to obtain modified epoxy resin F.

[0116] The modified epoxy resins prepared in Examples 5-9 and Comparative Example 2 were tested for performance, and the results are shown in Table 1.

[0117] Table 1

[0118]

[0119] As can be seen from Table 1, the modified epoxy resin C prepared in Comparative Example 2 did not add the self-catalytic imide ring-containing phthalonitrile resin, and the glass transition temperature after curing by programmed temperature increase was 234°C, and the lap shear strength at 300°C was only 1.9MPa. On this basis, after introducing different portions of self-catalytic imide ring-containing phthalonitrile resin, the glass transition temperature and high-temperature bonding performance of the prepared modified epoxy resin A and modified epoxy resin B were greatly improved. In particular, the lap shear strength of modified epoxy resin B at 300°C was increased by 389% compared to modified epoxy resin C. The modified epoxy resins prepared in Examples 7-9 also added self-catalytic imide ring-containing phthalonitrile resins, all of which had higher glass transition temperatures and high-temperature bonding performance. This is mainly attributed to the fact that the epoxy, double bond, cyano, amino and other reactive groups in the modified resin system generate heat-resistant crosslinking points of various structures through multiple curing mechanisms, which hinder the movement and slippage of molecular chains. The presence of multiple polar reactive groups also strengthens the bonding effect and bonding stability on the interface, thereby improving the high-temperature bonding performance. In addition, the preparation process of the modified epoxy resin in the present invention is very simple, without the need for complex equipment, and there is no sedimentation and precipitation phenomenon during the curing process, and the performance of the cured product is very stable.

Claims

1. A self-catalytic imide ring-containing phthalonitrile resin, Features The molecular structure of the self-catalytic imide ring-containing phthalonitrile resin is:

2. The method for preparing the self-catalytic imide ring-containing phthalonitrile resin according to claim 1, Features The method comprises the following steps: Step 1: 4-amino-3,5-dimethylphenol, 4-nitrophthalonitrile and anhydrous potassium carbonate are stirred evenly in an aprotic solvent, heated to 35-80°C and reacted for 6-24 hours, then poured into an alkaline solution to precipitate the product, the product is washed with water until neutral, filtered and vacuum dried to obtain 4-(4-amino-3,5-dimethylphenoxy)phthalonitrile; Step 2: Add maleic anhydride and 4-(4-amino-3,5-dimethylphenoxy)phthalonitrile to a reaction vessel filled with glacial acetic acid and stir, heat and reflux for reaction for 3-12 hours, cool to room temperature, pour into distilled water to precipitate the product, repeatedly wash the product with water until it is neutral, filter and vacuum dry to obtain the target product, the self-catalytic imide ring-containing phthalonitrile resin.

3. The method for preparing the self-catalytic imide ring-containing phthalonitrile resin according to claim 2, Features In step 1, the molar ratio of 4-amino-3,5-dimethylphenol, 4-nitrophthalonitrile and anhydrous potassium carbonate is 1:(1-1.1):(1.2-2).

4. The method for preparing the self-catalytic imide ring-containing phthalonitrile resin according to claim 2 or 3, Features The aprotic solvent in step 1 is dimethyl sulfoxide, N-methylpyrrolidone, N,N-dimethylformamide or N,N-dimethylacetamide; the amount of the aprotic solvent is 2-5 times the total weight of 4-amino-3,5-xylenol, 4-nitrophthalonitrile and anhydrous potassium carbonate.

5. The method for preparing the self-catalytic imide ring-containing phthalonitrile resin according to claim 4, Features The alkaline solution in step 1 is a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution, a calcium hydroxide aqueous solution or a barium hydroxide aqueous solution, and the molar concentration of the alkaline solution is 0.1-1.0 mol / L.

6. The method for preparing the self-catalytic imide ring-containing phthalonitrile resin according to claim 5, Features In step 2, the molar ratio of maleic anhydride to 4-(4-amino-3,5-dimethylphenoxy)phthalonitrile is (2-1.2):

1.

7. The method for preparing the self-catalytic imide ring-containing phthalonitrile resin according to claim 6, Features In step 2, the amount of glacial acetic acid added is 3-5 times the total weight of maleic anhydride and 4-(4-amino-3,5-dimethylphenoxy)phthalonitrile.

8. Use of the self-catalytic imide ring-containing phthalonitrile resin as claimed in claim 1 as an epoxy resin modifier; The specific method of epoxy resin modification is: An aromatic amine curing agent is added to the epoxy resin in an equal stoichiometric ratio, and the aromatic amine curing agent is completely melted by heating at 90-150° C., and then a self-catalytic imide ring-containing phthalonitrile resin powder is added, and stirring is continued until it becomes clear and transparent, and programmed temperature curing is performed to obtain a modified epoxy resin; the mass ratio of the epoxy resin to the self-catalytic imide ring-containing phthalonitrile resin is (0.6-1.5):1.

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