Benzoxazine resin containing aryl ether nitrile chain segment and preparation method thereof

Abstract

The invention discloses a preparation method of benzoxazine resin containing aryl ether nitrile chain segments, and belongs to the technical field of synthesis and processing technologies of special high polymer materials. The preparation method comprises the following steps: synthesizing amino-terminated poly (arylene ether nitrile) (PEN) with different molecular weights by adopting nucleophilic substitution reaction, forming a film with a benzoxazine polymer hot solution synthesized by bisphenol A, melamine and paraformaldehyde by adopting a solution pouring method, and curing at high temperature to obtain the poly (arylene ether nitrile) / benzoxazine film. Wherein the synthesized amino-terminated poly (arylene ether nitrile) (PEN) with different molecular weights participates in synthesis of benzoxazine as an amine source, and can effectively catalyze a cross-linking reaction of cyano groups, so that the cross-linking degree and the thermal stability of a polymer are improved. Therefore, the wide application of the special high polymer material in the comprehensive field is realized. In addition, PEN with low molecular weight can effectively toughen and reinforce the benzoxazine composite material in a copolymerization system.

Description

Technical Field

[0001] The present invention belongs to the technical field of synthesis and processing technology of polymer materials, and particularly relates to a preparation method of a benzoxazine resin containing an aromatic ether nitrile chain segment. Background Art

[0002] Benzoxazine, as a new type of phenolic resin, is a six-membered heterocyclic compound composed of oxygen atoms and nitrogen atoms. Such compounds retain the excellent electrical properties, flame retardancy, and mechanical properties of traditional phenolic resins. The curing process does not require a strong acid as a catalyst, and polymerization can occur with Lewis acid or heating. The polymer has a relatively high glass transition temperature and thermal-oxidative stability. It overcomes the disadvantage of traditional phenolic resins volatilizing small molecules during polymerization. Products prepared using raw materials with different structures can meet different actual needs. Therefore, this resin has broad application prospects in the fields of aerospace, electronic information, etc. Although benzoxazine resin has many advantages, there are also some problems. For example, its dielectric properties are not particularly excellent, and its dielectric constant is generally about 3.5. Due to the characteristics of the molecular structure of bifunctional benzoxazine, the toughness of the polymer is poor.

[0003] Polyarylether nitrile (PEN) is a class of semi-crystalline aromatic ring compounds with nitrile groups on the side chains. It has excellent properties such as good mechanical properties, flame retardancy, dielectric properties, and dimensional stability, and has broad application prospects in the fields of aerospace, mechanical manufacturing, electronic appliances, etc. Based on this, PEN is selected as a modification material for benzoxazine, hoping to achieve the characteristics of toughening and strengthening while maintaining the heat resistance of benzoxazine, and improving the mechanical properties of benzoxazine.

[0004] In addition, melamine is a triazine-based nitrogen-containing heterocyclic organic compound, which is used as a chemical raw material. It was initially used to manufacture melamine resins, and then gradually expanded to be widely used in fields such as adhesives, crosslinking agents, and flame retardants. It has characteristics such as low corrosion, low smoke generation, low cost, high thermal stability, and good synergistic effect, making the research and development and improvement of its products highly regarded and having broad application prospects. Summary of the Invention

[0005] The object of the present invention is to propose a preparation method of a benzoxazine resin containing an aromatic ether nitrile segment in view of the problems existing in the background art. The present invention proposes a polyarylether nitrile / benzoxazine film obtained by a simple nucleophilic substitution reaction, high and low molecular weight copolymerization, and a method combining solution casting and post-solid state chemical reaction. By synthesizing amino-terminated polyarylether nitrile with different molecular weights as the amine source to synthesize benzoxazine resin, the glass transition temperature of the polyarylether nitrile / benzoxazine resin is increased, the polymerization reaction degree of benzoxazine is reduced, the violent exothermic behavior of benzoxazine resin is alleviated, and it is convenient for production and processing. By introducing melamine, the production cost is reduced and the flame retardant performance is improved, providing a basic theory and operation basis for large-scale production of the polyarylether nitrile / benzoxazine resin with excellent performance.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A preparation method of a benzoxazine resin containing an aromatic ether nitrile segment, comprising the following steps:

[0008] Step 1, synthesize amino-terminated polyarylether nitrile:

[0009] 1.1 Add bisphenol A and 2,6-dichlorobenzonitrile as reactants into a three-necked flask equipped with a thermometer, a water separator, a condensing reflux device and a mechanical stirring device, add potassium carbonate as a catalyst to obtain a mixture powder; inject 25 mL of toluene and 15 mL of water into the water separator;

[0010] 1.2 Add the mixture powder obtained in step 1.1 into a mixed solvent of N-methylpyrrolidone (NMP) and toluene to obtain a mixed solution A; wherein, (1-1.5) mL of the mixed solvent is added per 1 g of the mixture powder, and in the mixed solvent, the volume ratio of N-methylpyrrolidone (NMP) to toluene is 3:1;

[0011] 1.3 The mixed solution A obtained in step 1.2 is heated in an electric heating mantle at a heating rate of 5 °C / min to a temperature of 145-150 °C, and is kept at a constant temperature of 145-150 °C for 2 h; then it is heated at a heating rate of 5 °C / min to continue heating to 170 °C, and is kept at a constant temperature of 170 °C for 1 h; open the water separator and drain 5 mL of toluene within 3-5 seconds, and then heat it at a heating rate of 10 °C / min to a temperature of 180-190 °C, add p-aminophenol at 180-190 °C and keep it at a constant temperature for 30 min-60 min; finally cool it to 150 °C, pour the obtained reaction solution into a 0.2 mol / L hydrochloric acid solution, stir to obtain a strip-shaped solid A;

[0012] 1.4 The strip-shaped solid A obtained in Step 1.3 is soaked in a 0.2 mol / L hydrochloric acid solution for 12 h, then crushed, and washed 3 - 5 times by boiling with tap water until the solution is neutral. The washed powder is dried in a vacuum oven for 12 h, and the resulting brown powder is the amino-terminated polyarylether nitrile.

[0013] Step 2: Synthesis of amino-terminated polyarylether nitrile / benzoxazine resin: Different molecular weight amino-terminated polyarylether nitriles obtained in Step 1 and melamine are used as amine sources in different ratios, and reacted with bisphenol A and paraformaldehyde in the solvent N,N-dimethylformamide by stirring at 80 °C for 5 h to obtain a polyarylether nitrile / benzoxazine polymer hot solution. Among them, the molar ratio of phenol, aldehyde to amine is 1:1:4.

[0014] Step 3: The polyarylether nitrile / benzoxazine polymer hot solution obtained in Step 2 is formed into a film by solution casting to obtain an amino-terminated polyarylether nitrile / benzoxazine film. Among them, the heating process of the solution casting method is: keep warm at 80 °C, 100 °C, 120 °C, 160 °C, 180 °C and 200 °C for 1 h respectively, and then keep warm at 220 °C for 2 h.

[0015] Step 4: The amino-terminated polyarylether nitrile / benzoxazine film obtained in Step 3 is kept warm at 340 - 360 °C for 1 - 2 h for high-temperature curing treatment. The amino-terminated polyarylether nitrile / benzoxazine film after high-temperature curing treatment is naturally cooled to room temperature to obtain the benzoxazine film containing aryl ether nitrile segments.

[0016] Furthermore, in Step 1.1, the molar ratio of bisphenol A, 2,6-dichlorobenzonitrile and potassium carbonate is 2:(1.5 - 1.87):2.4. Preferably, the molar ratio of bisphenol A, 2,6-dichlorobenzonitrile and potassium carbonate is 2:1.5:2.4, 2:1.75:2.4 or 2:1.87:2.4.

[0017] A preparation method of a benzoxazine resin containing an aromatic ether nitrile segment provided by the present invention synthesizes amino-terminated polyaryl ether nitrile (PEN) by nucleophilic substitution reaction, and forms a film with a benzoxazine polymer hot solution synthesized from bisphenol A, melamine, and paraformaldehyde through solution casting method and then cures it at high temperature to obtain a polyaryl ether nitrile / benzoxazine film. Among them, the synthesized amino-terminated polyaryl ether nitrile (PEN) with different molecular weights participates in the synthesis of benzoxazine as an amine source and serves as a catalyst under high-temperature curing reaction. The active hydrogen in the amino group can effectively catalyze the cross-linking reaction of cyanide groups, improving the cross-linking degree and thermal stability of the polymer. Although the amino group is a hydrophilic group, most of it acts on cyanide groups and is consumed at high temperature, so it will not affect its water absorption rate. Thus, the wide application of this special polymer material in comprehensive fields is realized. In addition, low-molecular-weight PEN can act as a plasticizer in the copolymer system, effectively toughening and reinforcing the melt viscosity of the benzoxazine composite material, reducing the torque during processing, and improving the processing fluidity of the material.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] A preparation method of a benzoxazine resin containing an aromatic ether nitrile segment provided by the present invention synthesizes amino-terminated polyaryl ether nitrile by nucleophilic substitution reaction, and forms a film with a benzoxazine polymer hot solution synthesized from bisphenol A, melamine, and paraformaldehyde through solution casting method and then cures it at high temperature to obtain a polyaryl ether nitrile / benzoxazine film. It can more effectively improve the cross-linking reaction rate, mechanical properties and heat resistance of the system in a high-temperature environment; at the same time, the molecular chain segment of amino-terminated polyaryl ether nitrile contains a large number of ether bonds, endowing the polymer with toughness. In summary, a preparation method of a benzoxazine resin containing an aromatic ether nitrile segment provided by the present invention synthesizes amino-terminated polyaryl ether nitrile by nucleophilic substitution reaction, and forms a film with a benzoxazine polymer hot solution synthesized from bisphenol A, melamine, and paraformaldehyde through solution casting method and then cures it at high temperature to obtain a polyaryl ether nitrile / benzoxazine film that is easy to process, has high modulus, high strength, high glass transition temperature and excellent dielectric stability at high temperature. The preparation process is simple, the effect is obvious, and large-scale production and application can be realized. Description of the Drawings

[0020] Figure 1 It is the structural formula of the amino-terminated polyaryl ether nitrile synthesized in Step 1;

[0021] Figure 2 It is the structural formula of the polyaryl ether nitrile / benzoxazine hot solution synthesized in Step 2;

[0022] Figure 3 It is the gelation time of polyaryl ether nitrile / benzoxazine films with different ratios;

[0023] Figure 4 It is the mechanical curve of polyaryl ether nitrile / benzoxazine films with different ratios at a curing temperature of 220 °C; Detailed implementation manners

[0024] The technical solution of the present invention will be described in detail below in conjunction with the accompanying drawings and embodiments.

[0025] Embodiment 1

[0026] A preparation method of a benzoxazine resin containing an aromatic ether nitrile segment, comprising the following steps:

[0027] Step 1, synthesize amino-terminated polyarylether nitrile:

[0028] 1.1 Add bisphenol A and 2,6-dichlorobenzonitrile as reactants, and potassium carbonate as a catalyst into a three-necked flask equipped with a thermometer, a water separator, a condensation reflux device and a mechanical stirring device to obtain a mixture powder; wherein, the molar ratio of bisphenol A, 2,6-dichlorobenzonitrile and potassium carbonate is 2:1.5:2.4. Inject 15 mL of toluene and 15 mL of water into the water separator;

[0029] 1.2 Add the mixture powder obtained in step 1.1 into a mixed solvent of N-methylpyrrolidone (NMP) and toluene to obtain a mixed solution A; wherein, 1.5 mL of the mixed solvent is added per 1 g of the mixture powder, and in the mixed solvent, the volume ratio of N-methylpyrrolidone (NMP) to toluene is 3:1;

[0030] 1.3 The mixed solution A obtained in step 1.2 is heated in an electric heating mantle at a heating rate of 5 °C / min to 150 °C, and kept at a constant temperature of 150 °C for 2 h; then continue to heat at a heating rate of 5 °C / min to 170 °C, and keep at a constant temperature of 170 °C for 1 h; open the water separator and drain 5 mL of toluene within 3 - 5 seconds, then continue to heat at a heating rate of 10 °C / min to 180 °C, add p-aminophenol at 180 °C and keep the reaction at a constant temperature for 50 min; finally cool down to 150 °C, pour the obtained reaction solution into a 0.2 mol / L hydrochloric acid solution, stir to obtain a strip-shaped solid A;

[0031] 1.4 The strip-shaped solid A obtained in step 1.3 is soaked in a 0.2 mol / L hydrochloric acid solution for 12 h, crushed, and then washed by boiling with tap water 3 - 5 times until the solution is neutral; the washed powder is placed in a vacuum oven and dried for 12 h, and the obtained white powder is the amino-terminated polyarylether nitrile;

[0032] Step 2, synthesize amino-terminated polyarylether nitrile / benzoxazine resin: Use the amino-terminated polyarylether nitrile with different molecular weights and melamine obtained in step 1 as phenolic sources in different proportions, react with bisphenol A and paraformaldehyde in the solvent N,N-dimethylformamide at 80 °C with stirring for 5 h to obtain a polyarylether nitrile / benzoxazine polymer hot solution; wherein, the molar ratio of phenol, aldehyde and amine is 1:1:4;

[0033] Step 3: Cast the poly(aryl ether nitrile) / benzoxazine polymer hot solution obtained in Step 2 into a film by solution casting to obtain an amino-terminated poly(aryl ether nitrile) / benzoxazine film; wherein, the heating process of the solution casting method is as follows: keep the temperature at 80°C, 100°C, 120°C, 160°C, 180°C and 200°C for 1 h respectively, and then keep the temperature at 220°C for 2 h;

[0034] Step 4: Keep the amino-terminated poly(aryl ether nitrile) / benzoxazine film obtained in Step 3 at 340 - 360°C for 1 - 2 h for high-temperature curing treatment; after the high-temperature curing treatment, the amino-terminated poly(aryl ether nitrile) / benzoxazine film is naturally cooled to room temperature to obtain the benzoxazine resin containing aryl ether nitrile segments.

[0035] The properties of the amino-terminated poly(aryl ether nitrile) / benzoxazine film obtained in Example 1 are as follows: the gelation temperature is 5 min at 140°C, Td 5 is 420°C, the char yield is 54%, and the flexural strength is 690 GPa.

[0036] Example 2

[0037] Compared with Example 1, the difference in this example is that: in Step 1.1, the molar ratio of bisphenol A, 2,6-dichlorobenzonitrile and potassium carbonate is 2:1.75:2.4. The remaining steps are exactly the same as those in Example 1.

[0038] The properties of the amino-terminated poly(aryl ether nitrile) / benzoxazine film obtained in Example 2 are as follows: the gelation temperature is 7 min at 140°C, Td 5 is 424°C, the char yield is 54.55%, and the flexural strength is 700 GPa.

[0039] Example 3

[0040] Compared with Example 1, the difference in this example is that: in Step 1.1, the molar ratio of bisphenol A, 2,6-dichlorobenzonitrile and potassium carbonate is 2:1.87:2.4. The remaining steps are exactly the same as those in Example 1.

[0041] The properties of the amino-terminated poly(aryl ether nitrile) / benzoxazine film obtained in Example 3 are as follows: the gelation temperature is 8.5 min at 140°C, Td 5 is 430°C, the char yield is 56.43%, and the flexural strength is 728 GPa.

[0042] Control case

[0043] Compared with Example 1, the difference in this example is that: melamine, paraformaldehyde and bisphenol A are used as raw materials to synthesize benzoxazine, and the remaining steps are exactly the same as those in Example 1.

[0044] The properties of the benzoxazine film obtained from the control case are as follows: the gelation temperature is 140 °C for 1 min, Td 5 is 409 °C, the char yield is 52.43%, and the flexural strength is 560 GPa.

Claims

1. A method for preparing a benzoxazine resin containing an aromatic ether nitrile segment, characterized in that: The following steps are involved: Step 1, synthesizing amino-terminated poly(arylene ether nitrile) with different molecular weights; Step 2, using different molecular weight amino-terminated poly(arylether nitrile) and melamine obtained in step 1 as amine sources in different proportions, and reacting with bisphenol A and polyformaldehyde in a solvent of NN dimethylformamide at 80° C. for 5 hours under stirring to obtain a hot solution of a benzoxazine polymer containing an arylether nitrile segment; wherein the molar ratio of phenol, aldehyde and amine is 1:1:4; Step 3, forming a film of the hot solution of the benzoxazine polymer containing aromatic ether nitrile chain segments obtained in step 2 by solution casting method to obtain an amino-terminated poly(arylether nitrile) / benzoxazine film; wherein the temperature rising process of the solution casting method is: keeping the temperature at 80° C., 100° C., 120° C., 160° C., 180° C. and 200° C. for 1 hour respectively, and then keeping the temperature at 220° C. for 2 hours; In step 4, the benzoxazine film obtained in step 3 is kept at 340-360° C. for 1-2 hours for high temperature curing treatment; the amino-terminated poly(arylether nitrile) / benzoxazine film after high temperature curing treatment is naturally cooled to room temperature to obtain the benzoxazine film containing the arylether nitrile chain segment.

2. The method for preparing the amino-terminated poly(arylene ether nitrile) / benzoxazine film according to claim 1, characterized in that: The process of synthesizing amino-terminated poly(arylene ether nitrile) in step 1 is as follows: 1.1 Add 2,6-dichlorobenzonitrile and bisphenol A in a set ratio as reactants into a three-necked flask equipped with a mechanical stirrer, a water separator and a thermometer, and add potassium carbonate as a catalyst to obtain a mixture powder; 1.2 Add the mixture powder obtained in step 1.1 to a mixed solvent of N-methylpyrrolidone and toluene to obtain a mixed solution A; wherein (1 to 1.5) mL of the mixed solvent is added to every 1 g of the mixture powder, and the volume ratio of N-methylpyrrolidone to toluene in the mixed solvent is 3:1; 1.3 The mixed solution A obtained in step 1.2 is heated to 145-150° C. in an electric heating mantle, and reacted at 145-150° C. for 2 hours; after dehydration, the temperature is raised to 190-200° C., p-aminophenol is added at 190-200° C. and reacted at a constant temperature for 100-120 minutes; finally, the temperature is lowered to 150° C., the obtained reaction solution is poured into a 0.2 mol / L hydrochloric acid solution, stirred, and a strip-shaped solid A is obtained; 1.4 The strip solid A obtained in step 1.3 is soaked in a 0.2 mol / L hydrochloric acid solution for 12 hours, crushed, and then washed 3 to 5 times until the solution is neutral; the washed powder is placed in a vacuum oven and dried for 12 hours to obtain the amino-terminated polyarylethernitrile.

3. The method for preparing the amino-terminated poly(arylene ether nitrile) / benzoxazine film according to claim 1, characterized in that: Step 2 The process of synthesizing the poly(arylethernitrile) / benzoxazine film is as follows: 2.1 The amino-terminated poly(arylether nitrile) with different molecular weights and melamine obtained in step 1 were used as amine sources in different proportions, and reacted with bisphenol A and polyformaldehyde in a solvent of NN dimethylformamide at 80°C for 5 hours under stirring to obtain a poly(arylether nitrile) / benzoxazine polymer hot solution; wherein the molar ratio of phenol, aldehyde and amine was 1:1:4; 2.2 The poly(arylether nitrile) / benzoxazine polymer hot solution obtained in step 2.1 is subjected to a solution casting method to form a film to obtain an amino-terminated poly(arylether nitrile) / benzoxazine film; wherein the temperature rise process of the solution casting method is: heat preservation at 80°C, 100°C, 120°C, 160°C, 180°C and 200°C for 1 hour respectively, and then heat preservation at 220°C for 2 hours; 2.3 The amino-terminated poly(arylether nitrile) / benzoxazine film obtained in step 2.2 is kept at 340-360°C for 1-2 hours for high-temperature curing treatment; the amino-terminated poly(arylether nitrile) / benzoxazine film after high-temperature curing treatment is naturally cooled to room temperature to obtain the benzoxazine film containing aromatic ether nitrile chain segments.

4. The method for preparing the amino-terminated poly(arylene ether nitrile) / benzoxazine film according to claim 2, characterized in that: In step 1.1, the molar ratio of bisphenol A, 2,6-dichlorobenzonitrile and potassium carbonate is 2:(1.5-1.87):2.4.

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