Preparation method of a flame-retardant graphene polyamide 6 composite material

Abstract

The present invention belongs to the technical field of the preparation of polyamides, and particularly relates to a method for preparing a flame-retardant graphene polyamide 6 composite material. In the present invention, graphene, small molecule polyamide, 2-phenyl-1,3-propanediol phosphoric anhydride, ethylenediamine, oxalic acid and caprolactam are mixed, and an auxiliary agent and a solvent are added, and ring-opening and polymerization reactions are carried out, and at the same time, a substitution reaction between 2-phenyl-1,3-propanediol phosphoric anhydride and ethylenediamine is carried out to obtain the flame-retardant graphene polyamide 6 composite material. A flame retardant is generated by the reaction of 2-phenyl-1,3-propanediol phosphoric anhydride and ethylenediamine, and the flame retardant is generated while polymerization is carried out, which improves the dispersion of the flame retardant in the polyamide 6 material. At the same time, 2-phenyl-1,3-propanediol phosphoric anhydride can also participate in the polymerization reaction as a capping agent, so that the compatibility between the flame retardant and the polymer matrix is better, the stability of the flame retardant in polyamide 6 is improved, the situation of flame retardant migration is reduced, and the strength performance of the composite material is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of polyamides, and particularly relates to a method for preparing a flame-retardant graphene polyamide 6 composite material. Background Art

[0002] Polyamides, commonly known as nylons, are one of the five major engineering plastics, characterized by a wide variety of types, large production volumes, and extensive applications. Polyamide 6 is the most widely used type among polyamides, having excellent properties such as high mechanical strength, wear resistance, oil resistance, resistance to weak acids and alkalis, and can be processed into plastics, fibers, and films. However, the limiting oxygen index of polyamide 6 is only about 21%, and there is a serious melt dripping phenomenon during combustion, which severely limits the application of polyamide 6. Therefore, the flame-retardant and anti-melt dripping modification of polyamide 6 is of great significance.

[0003] The flame retardants applicable to polyamide 6 mainly include halogen-based, nitrogen-based, inorganic, and phosphorus-based flame retardants. Different flame retardants vary greatly in terms of flame retardant mechanism, flame retardant efficiency, and the impact on material properties. Among them, halogen-based flame retardants are the most widely used, with the largest usage amount and the best flame retardant effect. However, halogen-based flame retardants release a large amount of smoke and toxic gases during combustion, causing great harm to the environment and the human body. Inorganic flame retardants are widely used in the flame retardant field due to their advantages such as good thermal stability, low volatility, low corrosivity, and almost no toxicity. However, usually a relatively high addition amount is required to achieve a good flame retardant effect. Compared with halogen-based flame retardants and inorganic flame retardants, nitrogen-based flame retardants have advantages such as good stability and environmental friendliness. However, most nitrogen-based flame retardants are introduced into polyamides in a physical form, suffering from problems such as a large addition amount and easy precipitation. Phosphorus-based flame retardants have advantages such as good thermal stability, low volatility, no generation of corrosive gases, long-lasting flame retardancy, and low toxicity, and have been widely used in the field of flame-retardant polyamides in recent years. However, currently, they are mainly added to polyamide 6 in a physical addition form.

[0004] Currently, the commonly used preparation methods for flame-retardant polyamide 6 are the blending method and the polymerization method. Among them, the polymerization method includes the copolymerization method and the in-situ polymerization method. The blending method has a simple processing technology, but has a high addition amount of the flame retardant, uneven dispersion, and easy precipitation, which has a great impact on the mechanical properties of the material. Copolymerization flame retardant modification is an important way of its flame retardant modification. There is relatively little research on the preparation of flame-retardant polyamides by the copolymerization method. The flame retardant process of the copolymerization method is complex, and when the addition amount is large, the mechanical properties of the polyamide decrease significantly. The in-situ polymerization method introduces a flame retardant during the synthesis process of the polymer and disperses it between the matrix molecular chains, which can effectively avoid the degradation caused by the secondary processing of the blending method. However, a relatively large addition amount is also required to achieve the flame retardant purpose, and the flame retardant is easy to precipitate. Summary of the Invention

[0005] In order to solve the above problems in the prior art, the present invention provides a method for preparing a flame-retardant graphene polyamide 6 composite material.

[0006] A preparation method of a flame-retardant graphene polyamide 6 composite material, comprising the following steps:

[0007] S1: React ethylenediamine and dicarboxylic acid dichloride to generate a small molecule polyamide;

[0008] S2: React 2-phenyl-1,3-propanediol with phosphorus oxychloride, and then hydrolyze to obtain 2-phenyl-1,3-propanediol phosphate anhydride;

[0009] S3: Mix graphene, small molecule polyamide, 2-phenyl-1,3-propanediol phosphate anhydride, ethylenediamine, oxalic acid and caprolactam, and add an auxiliary agent and a solvent, and carry out ring-opening and polymerization reactions, and at the same time carry out a substitution reaction of 2-phenyl-1,3-propanediol phosphate anhydride and ethylenediamine to obtain the flame-retardant graphene polyamide 6 composite material.

[0010] Preferably, S1 is specifically: under a nitrogen atmosphere, dissolve ethylenediamine and an acid-binding agent in a good solvent, add dicarboxylic acid dichloride at 0-10 °C, react for 1-2 h, after the reaction is completed, through precipitation, extraction and drying, obtain a small molecule aromatic polyamide; the molar ratio of ethylenediamine to dicarboxylic acid dichloride is (1.05-1.3):1.

[0011] Preferably, the good solvent is an amide solvent-salt system, wherein the amide solvent is N-methylpyrrolidone or dimethylacetamide, and the salt is lithium chloride or calcium chloride; the acid-binding agent is pyridine or 2-methylpyridine.

[0012] Preferably, S2 is specifically as follows: under a nitrogen atmosphere, mix 2-phenyl-1,3-propanediol with dichloroethane solvent, heat up to 50-60 °C, add phosphorus oxychloride, and heat up to 80-85 °C to react for 2-3 hours; after the reaction is completed, cool down to 0-2 °C, add a mixed solution of deionized water and ether; then heat up to 40-45 °C to react for 3-4 hours, and obtain 2-phenyl-1,3-propanediol phosphate anhydride through purification.

[0013] Preferably, the molar dosage ratio of 2-phenyl-1,3-propanediol, phosphorus oxychloride and deionized water is 1:1:0.5.

[0014] Preferably, the purification specifically includes concentration, cooling crystallization, filtration and recrystallization.

[0015] Preferably, the ring-opening reaction conditions in S3 are a temperature of 255-275 °C, a pressure of 0.15-0.85 MPa, and a reaction time of 1.5-4 h; the polymerization reaction conditions are a temperature of 240-255 °C, a pressure of -0.05--0.20 MPa, and a reaction time of 3-10 h.

[0016] Preferably, the dosage of graphene in S3 accounts for 0.1%-1% of the total mass of the reactants in S3; the dosage of small molecule polyamide accounts for 3%-5%; the dosage of 2-phenyl-1,3-propanediol phosphoric anhydride accounts for 0.5-1.2%.

[0017] Preferably, the solvent in S3 is xylene; the auxiliary agent is composed of one or more of antioxidant, anti-aging agent, heat stabilizer, antistatic agent, etc.

[0018] Preferably, the mixing method in S3 adopts high-shear ultrasonic coupling technology, the ultrasonic power is 1-20kW, the shear rate is 4500-20000rpm, the dispersion time is 2-24h, and the dispersion temperature is 60-90°C.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: In the present invention, ethylenediamine is not only a reaction substrate for polyamide 6, but also a reaction raw material for synthesizing a flame retardant. The flame retardant is generated by the reaction of 2-phenyl-1,3-propanediol phosphoric anhydride and ethylenediamine, and the flame retardant is generated while polymerization, which improves the dispersion of the flame retardant in the polyamide 6 material. 2-Phenyl-1,3-propanediol phosphoric anhydride can also participate in the polymerization reaction as a capping agent, so that the compatibility between the flame retardant and the polymer matrix is better, the stability of the flame retardant in polyamide 6 is improved, and the migration of the flame retardant is reduced. Moreover, by adding small molecule polyamide, the uniformity of the polyamide 6 composite material segments is improved, and the strength performance of the composite material is improved. Specific Embodiments

[0020] The present invention will be further described below in conjunction with specific embodiments.

[0021] The graphene in the present invention is graphene oxide. In the following examples, the graphene oxide is purchased from Changzhou Sixth Element Materials Technology Co., Ltd., and the model is SE2430W-N.

[0022] Example 1

[0023] Under the protection of high-purity nitrogen, first dissolve 50g of ethylenediamine and the acid-binding agent pyridine in a good solvent (N-methylpyrrolidone-calcium chloride system), control the system temperature at 5°C, and then add 150g of terephthaloyl chloride to the reaction system dropwise for reaction. The reaction time is 2h. After the reaction is completed, the reaction solution is subjected to precipitation, extraction and drying to obtain 154g of small molecule aromatic polyamide powder.

[0024] Add 0.20 mol of 2-phenyl-1,3-propanediol to 200 mL of dichloroethane. Pass nitrogen and stir while heating up to 60 °C. Start dropping 0.2 mol of POCl3, and finish dropping in about 1.5 h. Continue to pass nitrogen and slowly heat up to 80 °C, and maintain the reaction for 2.5 h. After cooling the reaction solution to 0 - 2 °C with an ice bath, slowly drop a mixture of 0.10 mol of deionized water and 5 mL of diethyl ether. After finishing dropping in about 0.5 h, remove the ice bath and let the reaction solution gradually warm up to 40 °C and react for 4 h. After concentrating the reaction solution to remove the solvent, let it cool and crystallize naturally. The crude product obtained after filtration is recrystallized with dichloromethane to obtain 24.32 g of colorless flaky crystals, which is 2-phenyl-1,3-propanediol phosphoric anhydride.

[0025] Mix 7.5 g of graphene, 60 g of small molecule polyamide, 15 g of 2-phenyl-1,3-propanediol phosphoric anhydride, 270 g of ethylenediamine, 500 g of terephthalic acid, 530 g of caprolactam, 5 g of benzoic acid, 100 g of xylene, and 5 g of antioxidant, and disperse them with high-shear ultrasonic coupling technology. The ultrasonic power is 20 kW, the shear rate is 4500 rpm, the dispersion time is 24 h, and the dispersion temperature is 60 °C. After dispersion is completed, add it into the polymerization reactor, and control the ring-opening reaction conditions as temperature 265 °C, pressure 0.60 MPa, and reaction time 3 h; the polymerization reaction conditions are temperature 250 °C, pressure -0.10 MPa, and after the equilibrium reaction time of 7 h, a polyamide 6 composite material is obtained.

[0026] Example 2

[0027] Under the protection of high-purity nitrogen, first dissolve 50 g of ethylenediamine and the acid-binding agent pyridine in a good solvent (N-methylpyrrolidone-calcium chloride system), control the system temperature at 0 °C, and then add 130 g of terephthaloyl chloride to the reaction system by dropping for reaction. The reaction time is 1.8 h. After the reaction is completed, after subjecting the reaction solution to precipitation, extraction, and drying, 135 g of small molecule aromatic polyamide powder is obtained.

[0028] Add 0.20 mol of 2-phenyl-1,3-propanediol to 200 mL of dichloroethane. Pass nitrogen and stir while heating up to 55 °C. Start dropping 0.2 mol of POCl3, and finish dropping in about 1.5 h. Continue to pass nitrogen and slowly heat up to 85 °C, and maintain the reaction for 3 h. After cooling the reaction solution to 0 - 2 °C with an ice bath, slowly drop a mixture of 0.10 mol of deionized water and 5 mL of diethyl ether. After finishing dropping in about 0.5 h, remove the ice bath and let the reaction solution gradually warm up to 45 °C and react for 3 h. After concentrating the reaction solution to remove the solvent, let it cool and crystallize naturally. The crude product obtained after filtration is recrystallized with dichloromethane to obtain 24.32 g of colorless flaky crystals, which is 2-phenyl-1,3-propanediol phosphoric anhydride.

[0029] Mix 1.5 g of graphene, 45 g of small molecule polyamide, 7.5 g of 2-phenyl-1,3-propanediol phosphoric anhydride, 270 g of ethylenediamine, 500 g of terephthalic acid, 530 g of caprolactam, 5 g of benzoic acid, 100 g of xylene, and 5 g of antioxidant, and disperse them using high-shear ultrasonic coupling technology. The ultrasonic power is 10 kW, the shear rate is 10000 rpm, the dispersion time is 12 h, and the dispersion temperature is 90 °C. After dispersion is completed, add it to the polymerization reactor, and control the ring-opening reaction conditions as temperature 275 °C, pressure 0.85 MPa, and reaction time 1.5 h; the polymerization reaction conditions are temperature 255 °C, pressure -0.20 MPa, and after the equilibrium reaction time of 3 h, a polyamide 6 composite material is obtained.

[0030] Example 3

[0031] Under the protection of high-purity nitrogen, first dissolve 50 g of ethylenediamine and the acid-binding agent pyridine in a good solvent (N-methylpyrrolidone-calcium chloride system), control the system temperature at 10 °C, and then add 160 g of terephthaloyl chloride to the reaction system dropwise for reaction. The reaction time is 1.5 h. After the reaction is completed, the reaction solution is subjected to precipitation, extraction, and drying to obtain 160 g of small molecule aromatic polyamide powder.

[0032] Add 0.20 mol of 2-phenyl-1,3-propanediol to 200 mL of dichloroethane, pass nitrogen and stir to raise the temperature to 50 °C, and start to dropwise add 0.2 mol of POCl3, which is added dropwise in about 1.5 h. Continue to pass nitrogen and slowly raise the temperature to 83 °C, and maintain the reaction for 2 h. After cooling the reaction solution to 0 - 2 °C with an ice bath, slowly add dropwise a mixed solution of 0.10 mol of deionized water and 5 mL of ether, and after adding dropwise in about 0.5 h, remove the ice bath and let the reaction solution gradually warm up to 42 °C for reaction for 3.5 h. After the reaction solution is concentrated to remove the solvent, it is naturally cooled and crystallized, and the crude product obtained after filtration is recrystallized with dichloromethane to obtain 24.32 g of colorless flaky crystals, which is 2-phenyl-1,3-propanediol phosphoric anhydride.

[0033] Mix 15 g of graphene, 75 g of small molecule polyamide, 18 g of 2-phenyl-1,3-propanediol phosphoric anhydride, 270 g of ethylenediamine, 500 g of terephthalic acid, 530 g of caprolactam, 5 g of benzoic acid, 100 g of xylene, and 5 g of antioxidant, and disperse them using high-shear ultrasonic coupling technology. The ultrasonic power is 1 kW, the shear rate is 20000 rpm, the dispersion time is 2 h, and the dispersion temperature is 70 °C. After dispersion is completed, add it to the polymerization reactor, and control the ring-opening reaction conditions as temperature 255 °C, pressure 0.15 MPa, and reaction time 4 h; the polymerization reaction conditions are temperature 240 °C, pressure -0.05 MPa, and after the equilibrium reaction time of 10 h, a polyamide 6 composite material is obtained.

[0034] Comparative Example 1

[0035] 0.20 mol of 2-phenyl-1,3-propanediol was added to 200 mL of dichloroethane. Nitrogen was passed through and the mixture was stirred and heated to 60 °C. Then, 0.2 mol of POCl3 was added dropwise, and the addition was completed in about 1.5 h. Nitrogen was continuously passed through and the temperature was slowly raised to 80 °C, and the reaction was maintained for 2.5 h. After the reaction solution was cooled to 0-2 °C with an ice bath, a mixed solution of 0.10 mol of deionized water and 5 mL of diethyl ether was slowly added dropwise. After the addition was completed in about 0.5 h, the ice bath was removed, and the reaction solution was gradually heated to 40 °C and reacted for 4 h. After the reaction solution was concentrated to remove the solvent, it was naturally cooled and crystallized. The crude product obtained after filtration was recrystallized with dichloromethane to obtain 24.32 g of colorless flaky crystals, which was 2-phenyl-1,3-propanediol phosphoric anhydride.

[0036] 7.5 g of graphene, 15 g of 2-phenyl-1,3-propanediol phosphoric anhydride, 270 g of ethylenediamine, 500 g of terephthalic acid, 530 g of caprolactam, 5 g of benzoic acid, 100 g of xylene, and 5 g of antioxidant were mixed and dispersed by high-shear ultrasonic coupling technology. The ultrasonic power was 20 kW, the shear rate was 4500 rpm, the dispersion time was 24 h, and the dispersion temperature was 60 °C. After dispersion, it was added to a polymerization reactor. The ring-opening reaction conditions were controlled as temperature 265 °C, pressure 0.60 MPa, and reaction time 3 h; the polymerization reaction conditions were temperature 250 °C, pressure -0.10 MPa, and the equilibrium reaction time was 7 h to obtain a polyamide 6 composite material.

[0037] Comparative Example 2

[0038] Under the protection of high-purity nitrogen, first 50 g of ethylenediamine and the acid-binding agent pyridine were dissolved in a good solvent (N-methylpyrrolidone-calcium chloride system), and the system temperature was controlled at 5 °C. Then, 150 g of terephthaloyl chloride was added to the reaction system by dropwise addition for reaction. The reaction time was 2 h. After the reaction was completed, the reaction solution was subjected to precipitation, extraction, and drying to obtain 154 g of small molecule aromatic polyamide powder.

[0039] 7.5 g of graphene, 60 g of small molecule polyamide, 270 g of ethylenediamine, 500 g of terephthalic acid, 530 g of caprolactam, 5 g of benzoic acid, 100 g of xylene, and 5 g of antioxidant were mixed and dispersed by high-shear ultrasonic coupling technology. The ultrasonic power was 20 kW, the shear rate was 4500 rpm, the dispersion time was 24 h, and the dispersion temperature was 60 °C. After dispersion, it was added to a polymerization reactor. The ring-opening reaction conditions were controlled as temperature 265 °C, pressure 0.60 MPa, and reaction time 3 h; the polymerization reaction conditions were temperature 250 °C, pressure -0.10 MPa, and the equilibrium reaction time was 7 h to obtain a polyamide 6 composite material.

[0040] The polyamide 6 composite materials obtained in Examples 1-3 and Comparative Examples 1 and 2 were tested for limiting oxygen index, melting point and strength properties. The test results are shown in Table 1; the limiting oxygen index test was carried out with reference to GB / T 2406.2-2009.

[0041] Table 1 Test results of the properties of polyamide 6 composite materials

[0042]

[0043] It can be seen from the data in Table 1 that the flame retardant properties and strength properties of the polyamide 6 materials obtained in Comparative Example 1 are lower than those of the polyamide 6 obtained in Examples 1-3, and the flame retardant properties and strength properties of the polyamide 6 materials obtained in Comparative Example 2 are also poorer than those in Examples 1-3. This shows that simply adding small molecule polyamide or simply through the copolymerization reaction of flame retardant and polyamide has little effect on the improvement of the properties of polyamide 6 materials, while the synergistic effect of the two enables the polyamide 6 materials to have excellent flame retardant properties and good strength properties at the same time.

[0044] The above specific embodiments are only explanations of the present application, and they do not limit the present application. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A preparation method of a flame-retardant graphene polyamide 6 composite material, characterized in that: It includes the following steps: S1: React ethylenediamine with dicarboxylic acid dichloride to generate small molecule polyamide; S2: React 2-phenyl-1,3-propanediol with phosphorus oxychloride, and then hydrolyze to obtain 2-phenyl-1,3-propanediol phosphate anhydride; S3: Mix graphene, small molecule polyamide, 2-phenyl-1,3-propanediol phosphate anhydride, ethylenediamine, oxalic acid and caprolactam, add additives and solvents, carry out ring-opening and polymerization reactions, and at the same time carry out substitution reaction of 2-phenyl-1,3-propanediol phosphate anhydride with ethylenediamine to obtain the flame-retardant graphene polyamide 6 composite material.

2. The preparation method of a flame-retardant graphene polyamide 6 composite material according to claim 1, wherein: Specifically, S1 is as follows: Under a nitrogen atmosphere, dissolve ethylenediamine and an acid-binding agent in a good solvent, add dicarboxylic acid dichloride at 0-10 °C, react for 1-2 h, after the reaction ends, carry out precipitation, extraction and drying to obtain small molecule polyamide; the molar ratio of ethylenediamine to dicarboxylic acid dichloride is (1.05-1.3):

1.

3. The preparation method of a flame-retardant graphene polyamide 6 composite material according to claim 2, wherein: The good solvent is an amide solvent-salt system, where the amide solvent is N-methylpyrrolidone or dimethylacetamide, and the salt is lithium chloride or calcium chloride; the acid-binding agent is pyridine or 2-methylpyridine.

4. The preparation method of a flame-retardant graphene polyamide 6 composite material according to claim 1, characterized in that: Specifically, S2 is as follows: Under a nitrogen atmosphere, mix 2-phenyl-1,3-propanediol with dichloroethane solvent, heat up to 50-60 °C, add phosphorus oxychloride, and heat up to 80-85 °C to react for 2-3 hours; after the reaction ends, cool down to 0-2 °C, add a mixture of deionized water and ether; then heat up to 40-45 °C to react for 3-4 hours, and obtain 2-phenyl-1,3-propanediol phosphate anhydride through purification.

5. The preparation method of a flame-retardant graphene polyamide 6 composite material according to claim 4, characterized in that: The molar dosage ratio of 2-phenyl-1,3-propanediol, phosphorus oxychloride and deionized water is 1:1:0.

5.

6. The preparation method of a flame-retardant graphene polyamide 6 composite material according to claim 4, characterized in that: The purification specifically includes concentration, cooling crystallization, filtration and recrystallization.

7. The preparation method of a flame-retardant graphene polyamide 6 composite material according to claim 1, characterized in that: The ring-opening reaction conditions in S3 are temperature 255-275 °C, pressure 0.15-0.85 MPa, and reaction time 1.5-4 h; the polymerization reaction conditions are temperature 240-255 °C, pressure -0.05--0.20 MPa, and reaction time 3-10 h.

8. The preparation method of a flame-retardant graphene polyamide 6 composite material according to claim 1, characterized in that: In S3, the dosage of graphene accounts for 0.1%-1% of the total mass of the reactants in S3; the dosage of small molecule polyamide accounts for 3%-5%; the dosage of 2-phenyl-1,3-propanediol phosphate anhydride accounts for 0.5-1.2%.

9. The preparation method of a flame-retardant graphene polyamide 6 composite material according to claim 1, characterized in that: The solvent in S3 is xylene; the additives are composed of one or more of antioxidant, anti-aging agent, heat stabilizer and antistatic agent.

10. The preparation method of a flame-retardant graphene polyamide 6 composite material according to claim 1, characterized in that: The mixing method in S3 adopts high-shear ultrasonic coupling technology, with ultrasonic power of 1-20 kW, shear rate of 4500-20000 rpm, dispersion time of 2-24 h, and dispersion temperature of 60-90 °C.

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