Phenolphthalein structure-containing imide chain segment phthalonitrile, preparation method thereof, prepolymer and cured product

Abstract

The invention provides phenolphthalein structure-containing imide chain link phthalonitrile, a preparation method thereof, a prepolymer and a cured product, the phenolphthalein structure-containing imide chain link phthalonitrile has a structure as shown in a formula 1: # imgabs0 #, R1-R6 are the same or different and are respectively and independently hydrogen atoms, halogen atoms or nitro groups, and at least one of R1-R6 is a halogen atom or nitro group, and the phenolphthalein structure-containing imide chain link phthalonitrile is a phenolphthalein structure-containing imide chain link phthalonitrile or a phenolphthalein structure-containing imide chain link phthalonitrile or a phenolphthalein structure-containing imide chain link phthalonitrile or a phenolphthalein structure-containing imide chain link phthalonitrile or a phenolphthalein structure-containing imide chain link phthalonitrile. The matrix resin prepared by using the phenolphthalein structure-containing imide chain segment phthalonitrile as a monomer has excellent processability, thermal performance and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and particularly relates to a phthalonitrile containing a phenolphthalein-structured imide link, a preparation method thereof, a prepolymer and a cured product. Background Art

[0002] As a class of high-performance materials, phthalonitrile resins have aromatic heterocycles formed by thermal addition polymerization of cyanide groups at both ends of their monomer structures, making their cross-linked cured products have excellent thermal stability (temperature resistance grade exceeding 300 °C), mechanical properties, high glass transition temperature, chemical resistance and flame retardant characteristics. This enables phthalonitrile resins to be applied in the field of high-temperature resistant materials, such as aerospace and mechanical manufacturing. However, the curing of phthalonitrile monomers without a curing agent is an extremely slow process, resulting in difficult processing and thus limiting the application of such resins. Moreover, the post-curing temperature of phthalonitrile resins needs to be as high as 375 °C, which also makes the processing cost of such resins relatively high. It has been reported that catalytic groups containing active hydrogen such as amino or hydroxyl groups are introduced into the phthalonitrile monomer structure, enabling phthalonitrile to have a self-catalytic reaction for cyanide groups, thus eliminating the need for external addition of a curing agent and reducing the generation of volatile small molecule by-products. On the other hand, phthalonitrile resins have the problem of relatively high melting temperatures of monomers (close to or higher than 200 °C), and a high melting temperature leads to a narrow processing window, which brings inconvenience to molding processing. Research shows that the length of the bridging chain segment between end groups can effectively affect the monomer melting point. A longer chain segment reduces the molecular crystallinity, melting point or glass transition temperature, but a longer chain segment also requires higher curing conditions (such as exceeding 400 °C).

[0003] Phenolphthalein is a bisphenol compound containing a lactone structure, with advantages such as strong structural designability, simple synthesis, low price and wide sources. Commercially available ones include phenolphthalein, o-cresolphthalein, thymolphthalein, etc., and it can also be prepared by reacting a phenolic anhydride with a substituted phenol under acidic conditions (such as preparing phenolphthalein containing a naphthalene ring by reacting phthalic anhydride with α-naphthol and zinc chloride under heating conditions). Therefore, phenolphthalein and its derivatives are often used as monomers for synthesizing high-performance aromatic polymers.

[0004] Patent CN202211487355.9 provides a shape memory phthalonitrile resin and its preparation method, belonging to the technical field of shape memory polymers. The phthalonitrile resin is prepared from a flexible phthalonitrile monomer, a rigid phthalonitrile monomer, and a curing agent with a molar ratio of (0.2 - 1):(0 - 1):(0.02 - 0.2); the flexible phthalonitrile monomer contains a flexible chain segment; the rigid phthalonitrile monomer contains a rigid chain segment. The glass transition temperature of the shape memory phthalonitrile resin provided by the present invention is >300°C, and the storage modulus of the resin is <100 MPa when the temperature reaches above the glass transition temperature, having good shaping and memory capabilities.

[0005] Patent CN115745856A discloses a cyclohexyl-containing phthalonitrile monomer and its preparation method and application. The cyclohexyl-containing phthalonitrile monomer has a significantly reduced melting point and a relatively wide processing window. Applying this monomer to prepare phthalonitrile resin can not only ensure the crosslinking degree of the resin, but also the non-coplanar structure brought by the cis-trans isomerism centered on cyclohexyl is more conducive to the movement of molecular chains in space, enabling sufficient curing and crosslinking at a lower temperature.

[0006] Patent CN115650879A relates to an aminophenoxy phthalonitrile resin, polymer, and its preparation method. It can not only solve a series of problems brought by introducing catalysts / curing agents during the processing and molding of existing phthalonitrile resins, simplify the molding process of polymers, and improve production efficiency. At the same time, the energy consumption in the resin synthesis and preparation process is low, safe and controllable, and the polymer has excellent electrical properties, providing a new type of resin for high-performance materials for electronic information and being suitable for market promotion and application. Summary of the Invention

[0007] The purpose of the present invention is to provide a phthalonitrile containing a phenolphthalein-structured imide link, its preparation method, prepolymer, and cured product. The matrix resin prepared from the phthalonitrile containing a phenolphthalein-structured imide link as a monomer has excellent processing properties, thermal properties, etc.

[0008] To achieve the above purpose, the present invention provides a phthalonitrile containing a phenolphthalein-structured imide link, having the structure shown in Formula 1:

[0009]

[0010] Wherein, R 1 -R 6 are the same or different, each independently being a hydrogen atom, a halogen atom, or a nitro group, and at least one of R 1 -R 6 is a halogen atom or a nitro group.

[0011] To achieve the above object, the present invention also provides a preparation method of the phthalonitrile containing a phthalimide chain segment with a phenolphthalein structure, comprising the following steps:

[0012] S1, Dissolve the bismaleimide BCP containing a phenolphthalein structure and the aminophenoxyphthalonitrile APN in an organic solvent, add a catalyst, and then introduce an inert gas, and carry out the reaction under an inert gas atmosphere;

[0013] S2, After the reaction is completed, wash the reaction solution, carry out solid-liquid separation, filtration, and drying to obtain the product phthalonitrile containing a phthalimide chain segment with a phenolphthalein structure.

[0014] In the preparation method of the phthalonitrile containing a phthalimide chain segment with a phenolphthalein structure according to the present invention, the molar ratio of the bismaleimide BCP containing a phenolphthalein structure to the aminophenoxyphthalonitrile APN is 1:1.8 to 1:2.5, preferably 1:2.2.

[0015] In the preparation method of the phthalonitrile containing a phthalimide chain segment with a phenolphthalein structure according to the present invention, the total volume ratio of the bismaleimide BCP containing a phenolphthalein structure and the aminophenoxyphthalonitrile APN to the organic solvent is 1:15 to 1:25.

[0016] In the preparation method of the phthalonitrile containing a phthalimide chain segment with a phenolphthalein structure according to the present invention, the organic solvent is one or more of m-cresol, N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide, preferably m-cresol.

[0017] In the preparation method of the phthalonitrile containing a phthalimide chain segment with a phenolphthalein structure according to the present invention, the catalyst is glacial acetic acid and / or triethylamine, preferably glacial acetic acid, and the catalyst dosage is 6% to 8% of the total mass of the bismaleimide BCP containing a phenolphthalein structure and the aminophenoxyphthalonitrile APN, preferably 6%.

[0018] In the preparation method of the phthalonitrile containing a phthalimide chain segment with a phenolphthalein structure according to the present invention, the reaction temperature in step S1 is 100 to 110 °C, preferably 100 °C, and the reaction time is 28 to 32 h, preferably 32 h.

[0019] In the preparation method of the phthalonitrile containing a phthalimide chain segment with a phenolphthalein structure according to the present invention, step S2 is washed with distilled water, and the number of washing times is 3 to 5 times.

[0020] In the preparation method of the phthalonitrile containing a phthalimide chain segment with a phenolphthalein structure according to the present invention, step S2 further includes a step of washing the solid obtained after solid-liquid separation with methanol, the number of washing times is 3 to 5 times, and then filtration and drying are carried out, and the drying conditions are: drying at 75 to 85 °C for 10 to 14 h.

[0021] The preparation method of phthalonitrile containing a phthalimide chain segment with a phenolphthalein structure also includes a step of recrystallizing the solid obtained after solid-liquid separation in a methanol-chloroform solution. The number of recrystallization times is 1 to 3 times. After crystallization, filtration and drying are carried out. Among them, the volume ratio of methanol to chloroform in the methanol-chloroform solution is 0.8:1 to 1:1. The drying conditions are: drying at 75 to 85 °C for 10 to 14 h.

[0022] To achieve the above object, the present invention also provides a phthalonitrile prepolymer containing a phthalimide chain segment with a phenolphthalein structure, which is obtained by melt-prepolymerizing the phthalonitrile containing a phthalimide chain segment with a phenolphthalein structure at 100 to 140 °C for 10 to 90 min, preferably at 110 to 130 °C for 20 to 40 min.

[0023] To achieve the above object, the present invention also provides a cured product of phthalonitrile containing a phthalimide chain segment with a phenolphthalein structure, which is prepared by casting and heat treatment of the prepolymer.

[0024] 13. The cured product of phthalonitrile containing a phthalimide chain segment with a phenolphthalein structure according to claim 12, wherein the heat treatment conditions are treatment at 195 to 325 °C for 5 to 15 h; preferably, the heat treatment process adopts stepwise temperature increase, and the heat treatment conditions are: 195 to 205 °C / 1 to 3 h, 235 to 245 °C / 1 to 3 h, 275 to 285 °C / 1 to 3 h, and the post-treatment procedure is: 295 to 305 °C / 1 to 3 h, 315 to 325 °C / 1 to 3 h.

[0025] The beneficial effects of the present invention:

[0026] The present invention introduces an imide chain segment into the phthalonitrile monomer, increases the length of the bridge chain segment between the monomer end-capping groups, and reduces the melting point of the resin monomer. The phthalonitrile resin containing a phthalimide chain segment with a phenolphthalein structure obtained has characteristics such as a wider processing temperature window (Δ>150 °C), a low melt processing viscosity (<0.2 Pa·s), and excellent heat resistance (the initial decomposition temperature is 350 to 385 °C, and the char yield at 800 °C in a nitrogen atmosphere is 68 to 70%). At the same time, by adjusting the processing temperature and processing time, different conditions can be selected for the resin during molding processing to be suitable for different fields such as aerospace and mechanical manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a non-isothermal viscosity curve of the phthalonitrile monomer containing a phthalimide chain segment with a phenolphthalein structure in Example 1.

[0028] Figure 2 It is an isothermal viscosity curve of the phthalonitrile monomer containing a phthalimide chain segment with a phenolphthalein structure at different temperatures in Example 1. Detailed Embodiments

[0029] The present invention will be specifically described below through embodiments. It is necessary to point out here that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the protection scope of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention according to the above content of the present invention.

[0030] In the following embodiments, (1) 1 1H NMR test was performed using a Bruker AMX-400 instrument from Germany, and the test solvent was DMSO-d 6 6; (2) FTIR test was performed using a Shimadzu FTIR8400S instrument, and dry KBr powder was pressed into tablets for testing; (3) Rheological test data was obtained through a plate rotational rheometer (TA Instruments Rheometer AR-G2); (4) DSC data was obtained through a TA Instruments Modulated DSC-Q100 under a heating condition of 10 °C / min in a nitrogen atmosphere; (5) TGA, T 5％ : refers to the temperature at which the sample loses 5% of its weight in a thermogravimetric analyzer TG under a heating condition of 20 °C / min in a nitrogen atmosphere; (6) The char yield refers to the residual weight of the sample when it reaches 800 °C in a thermogravimetric analyzer TG under a heating condition of 20 °C / min in a nitrogen atmosphere; (7) The glass transition temperature was measured by DMA test after the sample was completely cured, and it was the temperature value at the maximum loss tangent.

[0031] Example 1 Synthesis of Phthalonitrile Monomer with Chlorophenolphthalein Structure Imide Linkage

[0032] Weigh the raw materials according to the following molar ratio: Chlorophenolphthalein Structure Bismaleimide: 3-Aminophenoxyphthalonitrile = 1:1.8; Measure the solvent according to the following volume ratio: Raw materials: m-Cresol = 1:15; The catalyst is glacial acetic acid, and the dosage is 6% of the total mass of the raw materials; Dissolve the raw materials in the solvent to obtain a reaction solution, slowly add the catalyst to the reaction solution, and after the addition is complete, slowly introduce nitrogen; React the above reaction solution at 110 °C for 30 h; Wash the obtained reaction solution 3 times in a methanol solution and then perform solid-liquid separation. The separated solid is recrystallized 2 times in a methanol-chloroform solution, and after crystallization, it is filtered and dried. The volume ratio of the methanol-chloroform solution is 1:1; The drying condition is: drying at 80 °C for 12 h. The finally obtained yellowish-brown solid product is the phthalonitrile monomer with chlorophenolphthalein structure imide linkage, and the structural formula of the product is shown as follows:

[0033]

[0034] The softening point of this resin is approximately 132.7 °C, and its melting temperature is reduced by approximately 70 - 130 °C compared with bisphenol A phthalonitrile or biphenyl phthalonitrile. The processing performance is shown in Table 1:

[0035] Table 1 Processing Performance Table of Phthalonitrile Resin with Chlorophenolphthalein Structure Imide Link

[0036]

[0037] Synthesis of Phthalonitrile Monomer with Nitrophenolphthalein Structure Imide Link in Example 2

[0038] Weigh the raw materials according to the following molar ratio: nitrophenolphthalein structure bismaleimide: 3 - aminophenoxyphthalonitrile = 1:2.5; measure the solvent according to the following volume ratio: raw materials: m - cresol = 1:25; select triethylamine as the catalyst, and its dosage is 8% of the total mass of the raw materials; dissolve the raw materials in the solvent to obtain a reaction solution, slowly add the catalyst to the reaction solution, and after the addition is complete, slowly introduce nitrogen; react the above reaction solution at 110 °C for 32 h; wash the obtained reaction solution 3 times in methanol solution and then separate the solid and liquid. The separated solid is recrystallized 2 times in methanol - chloroform solution with a volume ratio of 1:1 for the methanol - chloroform solution; the drying conditions are: drying at 80 °C for 12 h. The finally obtained yellow - brown solid product is phthalonitrile monomer with chlorophenolphthalein structure imide link, and the product structural formula is shown as follows:

[0039]

[0040] The softening point of this resin is approximately 139.5 °C, and its melting temperature is reduced by approximately 70 - 130 °C compared with bisphenol A phthalonitrile or biphenyl phthalonitrile. The processing performance is shown in Table 2:

[0041] Table 2 Processing Performance Table of Phthalonitrile Resin with Nitrophenolphthalein Structure Imide Link

[0042]

[0043] Example 3

[0044] Same as Example 1, except that chlorophenolphthalein structure bismaleimide: 3 - aminophenoxyphthalonitrile = 1:2.2.

[0045] The obtained resin has a softening point of approximately 129 °C, and its melting temperature is reduced by approximately 70 - 130 °C compared with bisphenol A phthalonitrile or biphenyl phthalonitrile. The processing performance is shown in Table 3:

[0046] Table 3 Processing Performance Table of Phthalonitrile Resin with Chlorophenolphthalein Structure Imide Link

[0047]

[0048]

[0049] Example 4 Preparation of Phthalonitrile Curing Agent Containing Chlorophenolphthalein Structure Imide Linkage

[0050] The phthalonitrile monomer containing chlorophenolphthalein structure imide linkage in Example 1 was melt-prepolymerized at 100 °C for 20 min to obtain a prepolymer. The prepolymer was cast and heat-treated to obtain a cured product.

[0051] After melting, it was cast into a self-made aluminum box mold, and the heat treatment conditions were 200 - 320 °C for 10 h; the heat treatment process adopted stepwise heating, specifically: 200 °C / 2 h, 240 °C / 2 h, 280 °C / 2 h, and the post-treatment procedure was: 300 °C / 2 h, 320 °C / 2 h. After curing was completed, it was naturally cooled to room temperature to obtain a phthalonitrile cured product containing imide linkage. The cured resin T 5％ > 429 °C, the char yield > 63% (TGA) under a nitrogen atmosphere, and the glass transition temperature > 378 °C (DMA). With the change of different post-treatment temperatures, the single-lap interlaminar shear strength of the metal stainless steel sheet can reach 3.76 MPa (after post-treatment at 320 °C / 2 h).

[0052] Table 4 Properties of Phthalonitrile Resin Containing Chlorophenolphthalein Structure Imide Linkage

[0053]

[0054] Example 5 Preparation of Phthalonitrile Curing Agent Containing Nitrophenolphthalein Structure Imide Linkage

[0055] The phthalonitrile monomer containing nitrophenolphthalein structure imide linkage in Example 2 was melt-prepolymerized at 140 °C for 40 min to obtain a prepolymer. The prepolymer was cast and heat-treated to obtain a cured product.

[0056] After melting, it was cast into a self-made aluminum box mold, and the heat treatment conditions were 200 - 320 °C for 10 h; the heat treatment process adopted stepwise heating, specifically: 200 °C / 2 h, 240 °C / 2 h, 280 °C / 2 h, and the post-treatment procedure was: 300 °C / 2 h, 320 °C / 2 h. The obtained cured resin T 5％ > 417 °C, the char yield > 60% (TGA) under a nitrogen atmosphere, and the glass transition temperature > 370 °C (DMA). With the change of different post-treatment temperatures, the single-lap interlaminar shear strength of the metal stainless steel sheet can reach 3.69 MPa (after post-treatment at 320 °C / 2 h).

[0057] Table 6 Properties of Phthalonitrile Resin Containing Chlorophenolphthalein Structure Imide Linkage

[0058]

[0059] Example 6

[0060] Same as Example 4, except that the monomers of Example 3 are used to prepare the cured product.

[0061] The obtained cured resin T 5％ > 445 °C, char yield > 67% (TGA) under nitrogen atmosphere, glass transition temperature > 385 °C (DMA). With the change of different post-treatment temperatures, the single-lap shear strength of the metal stainless steel sheet can reach 3.85 MPa (after post-treatment at 320 °C / 2 h).

[0062] Table 5 Properties of phthalonitrile resin containing methylphthalein-structured imide linkages

[0063]

[0064] The above examples show that: the phthalonitrile monomer containing phthalein-structured imide linkages provided by the present invention has a low softening temperature, a wide processing temperature window, a low raw material cost, and the obtained polymer has excellent heat resistance. The phthalonitrile resin containing imide linkages obtained by this method not only improves the shortcoming of the narrow processing window of traditional phthalonitrile resins, reduces the production cost of products, but also maintains excellent heat resistance, and can be applied to the preparation of composite materials, insulating materials, adhesives, electronic packaging materials, etc. in the fields of aerospace, mechanical manufacturing, etc.

[0065] Of course, the present invention may also have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and deformations according to the present invention, but these corresponding changes and deformations should all fall within the protection scope of the claims of the present invention.

Claims

1. A phthalonitrile containing a phthalimide chain segment with a phenolphthalein structure, characterized in that, it has the structure shown in Formula 1: Among them, R 1 -R 6 are the same or different and each independently is a hydrogen atom, a halogen atom or a nitro group, and at least one of R 1 -R 6 is a halogen atom or a nitro group.

2. A preparation method of the phthalonitrile containing a phthalimide chain segment with a phenolphthalein structure according to Claim 1, characterized in that, it includes the following steps: S1, Dissolve bismaleimide BCP containing a phenolphthalein structure and aminophenoxyphthalonitrile APN in an organic solvent, add a catalyst, then introduce an inert gas, and carry out the reaction under an inert gas atmosphere; S2, After the reaction is completed, wash the reaction solution, carry out solid-liquid separation, filtration, and drying to obtain the product phthalonitrile containing a phthalimide chain segment with a phenolphthalein structure.

3. The preparation method of the phthalonitrile containing a phthalimide chain segment with a phenolphthalein structure according to Claim 2, characterized in that, the molar ratio of bismaleimide BCP containing a phenolphthalein structure to aminophenoxyphthalonitrile APN is 1:1.8 to 1:2.5, preferably 1:2.

2.

4. The preparation method of the phthalonitrile containing a phthalimide chain segment with a phenolphthalein structure according to Claim 2, characterized in that, the volume ratio of the total volume of bismaleimide BCP containing a phenolphthalein structure and aminophenoxyphthalonitrile APN to the volume of the organic solvent is 1:15 to 1:

25.

5. The preparation method of the phthalonitrile containing a phthalimide chain segment with a phenolphthalein structure according to Claim 2, characterized in that, the organic solvent is one or more of m-cresol, N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide, preferably m-cresol.

6. The preparation method of the phthalonitrile containing a phthalimide chain segment with a phenolphthalein structure according to Claim 2, characterized in that, the catalyst is glacial acetic acid and / or triethylamine, preferably glacial acetic acid, and the dosage of the catalyst is 6% to 8% of the total mass of bismaleimide BCP containing a phenolphthalein structure and aminophenoxyphthalonitrile APN, preferably 6%.

7. The preparation method of the phthalonitrile containing a phthalimide chain segment with a phenolphthalein structure according to Claim 2, characterized in that, in step S1, the reaction temperature is 100 to 110 °C, preferably 100 °C, and the reaction time is 28 to 32 h, preferably 32 h.

8. The preparation method of the phthalonitrile containing a phthalimide chain segment with a phenolphthalein structure according to Claim 2, characterized in that, in step S2, it is washed with distilled water, and the number of washing times is 3 to 5 times.

9. The preparation method of the phthalonitrile containing a phthalimide chain segment with a phenolphthalein structure according to Claim 2, characterized in that, step S2 further includes a step of washing the solid obtained after solid-liquid separation with methanol, the number of washing times is 3 to 5 times, then filtering and drying, and the drying conditions are: drying at 75 to 85 °C for 10 to 14 h.

10. The preparation method of the phthalonitrile containing a phthalimide chain segment with a phenolphthalein structure according to Claim 2, characterized in that, step S2 further includes a step of recrystallizing the solid obtained after solid-liquid separation in a methanol-chloroform solution, the number of recrystallization times is 1 to 3 times, and after crystallization, filtering and drying; wherein, the volume ratio of methanol to chloroform in the methanol-chloroform solution is: 0.8:1 to 1:1; the drying conditions are: drying at 75 to 85 °C for 10 to 14 h.

11. A phthalonitrile prepolymer containing an imide link with a phenolphthalein structure, characterized in that, it is obtained by melt-prepolymerizing the phthalonitrile containing an imide link with a phenolphthalein structure described in claim 1 at 100 - 140 °C for 10 - 90 min, preferably at 110 - 130 °C for 20 - 40 min.

12. A cured product of phthalonitrile containing an imide link with a phenolphthalein structure, characterized in that, it is prepared by casting and heat treatment of the prepolymer described in claim 11.

13. The cured product of phthalonitrile containing an imide link with a phenolphthalein structure according to claim 12, characterized in that, the heat treatment conditions are treatment at 195 - 325 °C for 5 - 15 h; preferably, the heat treatment process uses stepwise heating, and the heat treatment conditions are: 195 - 205 °C / 1 - 3 h, 235 - 245 °C / 1 - 3 h, 275 - 285 °C / 1 - 3 h, and the post-treatment procedure is: 295 - 305 °C / 1 - 3 h, 315 - 325 °C / 1 - 3 h.

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