Flame-retardant polyamide material and preparation method thereof

Abstract

The invention discloses a flame-retardant polyamide material and a preparation method thereof, 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and maleic anhydride react to obtain a flame retardant DOPO-MA, the flame retardant DOPO-MA, a prepared polyamide monomer and 4-dimethylaminopyridine are mixed and react to prepare a modified hydroxyl polyamide monomer, then 3, 6-dioxa-1, 2, 3-triazole is added, and the flame-retardant polyamide material is obtained. The preparation method comprises the following steps: carrying out nitrogen purging reaction on 1, 8-octyldithiol, azodiisobutyronitrile and anhydrous tetrahydrofuran to obtain a polyamide solid, carrying out melt blending on the polyamide solid, dioctyl diphenylamine and stearic acid, and carrying out extrusion, granulation and drying to obtain the flame-retardant polyamide material. According to the preparation method, the problem of poor compatibility of the flame retardant and the polyamide monomer is effectively solved, combustible gas generated in the thermal degradation process is reduced, the environment-friendly requirement is better met, the preparation process is simple, the production efficiency is high, and the obtained polyamide material has excellent flame retardant property and mechanical property and has important practical application value.

Description

Technical Field

[0001] The invention belongs to the field of polymer materials, and in particular relates to a flame retardant polyamide material and a preparation method thereof. Background Art

[0002] Flame retardant polyamide is a material whose flame retardant properties are improved by adding specific flame retardants, which effectively improves the fire resistance of polyamide materials, enables it to suppress the spread of flames when encountering a fire source, and has the ability to self-extinguish fire. This feature makes flame retardant polyamide widely used in many fields such as electronics, automobiles, construction, aerospace, etc. In recent years, with people's increasing attention to safety performance and the continuous advancement of technology, the flame retardant polyamide market has shown explosive growth. According to market research organization QYResearch, by 2030, the global flame retardant polyamide market will reach approximately US$1.85 billion, with an annual compound growth rate (CAGR) of up to 8.2%. This growth trend not only reflects the market's urgent demand for efficient and safe materials, but also indicates the important position of flame retardant polyamide in the future field of materials science. Therefore, it is necessary to develop flame retardant polyamide materials with superior performance to meet the growing market demand.

[0003] To this end, researchers have developed a variety of flame-retardant polyamide materials, but existing flame-retardant polyamides still have several defects and are difficult to meet the growing demand for high-performance materials. For example, after adding a large amount of flame retardants, the compatibility is low, and the mechanical properties of the polyamide matrix, such as tensile strength and impact strength, are significantly reduced, which limits its application in high-strength structural parts; some flame retardants (such as halogen-containing flame retardants) will release harmful gases and smoke during combustion, causing harm to the environment and human health; the price of high-performance flame retardants is usually high, which leads to an increase in the overall cost of flame-retardant polyamides, limiting their large-scale application.

[0004] CN114231024A discloses a flame-retardant polyamide composite material, a preparation method and an application thereof, the material comprising the following components: 80 parts of short carbon chain polyamide; 5-30 parts of red phosphorus powder; 5-30 parts of a compound toughening / yellowing resistance agent; the compound toughening / yellowing resistance agent comprises component A and component B, wherein component A is maleic anhydride grafted polyolefin or epoxy group grafted polyolefin, and component B is ethylene / methacrylic acid copolymer zinc salt; the invention mainly achieves the improvement of toughening effect and color stability, and the mechanical properties of the composite material are limited.

[0005] CN112480398A discloses a flame-retardant polyamide resin and a preparation method and application thereof. The raw materials for preparing the flame-retardant polyamide resin include a polymerization monomer, a diamine and a reactive phosphorus-containing flame retardant. The reactive phosphorus-containing flame retardant contains a carboxyl or anhydride reaction group. After the reactive phosphorus-containing flame retardant is salified with the diamine, it participates in the polycondensation reaction in the synthesis of the polyamide resin as a polymerization monomer, and finally exists in the polyamide resin in the form of molecular chain fragments, thereby avoiding the precipitation of small molecules, water solubility or hydrolysis.

[0006] Based on the defects of the current flame-retardant polyamide preparation method, the development of a flame-retardant polyamide with good compatibility, excellent flame retardant effect and meeting the needs of different markets plays an important role in the transformation and upgrading of the flame-retardant polyamide industry. Summary of the invention

[0007] The present invention overcomes the deficiencies of the above-mentioned prior art, and provides a flame retardant polyamide material and a preparation method thereof, wherein 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and maleic anhydride (MA) are reacted to obtain a flame retardant DOPO-MA, which is mixed with the prepared polyamide monomer and 4-dimethylaminopyridine to prepare a modified hydroxy polyamide monomer, and then 3,6-dioxa-1,8-octanedithiol and azobisisobutyronitrile are added for nitrogen purge reaction to obtain a polyamide solid, which is melt-blended with dioctyl diphenylamine and stearic acid, and then extruded, granulated, and dried to obtain a flame retardant polyamide material. The preparation process of the present invention effectively avoids the problem of poor compatibility between the flame retardant and the polyamide monomer, and secondly reduces the combustible gas generated during the thermal degradation process, and the obtained polyamide material has excellent flame retardant properties and mechanical properties.

[0008] In order to achieve the above object, the present invention adopts the following technical solution:

[0009] A method for preparing a flame retardant polyamide material comprises the following steps:

[0010] (1) Under an inert atmosphere, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is dissolved in ethanol, maleic anhydride is added for reaction, and DOPO-MA is obtained after cooling, filtering and washing;

[0011] (2) mixing 1,3-diamino-2-propanol, 10-undecenoic acid methyl ester, anhydrous tetrahydrofuran, and sodium methoxide and reacting them under a nitrogen atmosphere to obtain a hydroxy polyamide monomer;

[0012] (3) mixing the DOPO-MA prepared in step (1), the hydroxy polyamide monomer prepared in step (2), 4-dimethylaminopyridine, and anhydrous tetrahydrofuran, adding a tetrahydrofuran aqueous solution to react, and obtaining a mixed solution; pouring the mixed solution into dichloromethane, washing, standing and separating the layers, and taking the upper layer to obtain a modified polyamide monomer;

[0013] (4) mixing the modified polyamide monomer obtained in step (3), 3,6-dioxa-1,8-octanedithiol, azobisisobutyronitrile, and anhydrous tetrahydrofuran, and reacting them after nitrogen purging to prepare a polyamide solid;

[0014] (5) The polyamide prepared in step (4) is melt-blended with dioctyl diphenylamine and stearic acid, and then extruded, granulated and dried to obtain a flame-retardant polyamide material.

[0015] Furthermore, in step (1), the mass ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, ethanol and maleic anhydride is 1:6-10:1-3; the reaction temperature is 75-85°C, and the reaction time is 10-15h; and the washing is 2-4 times of washing with anhydrous ethanol.

[0016] Furthermore, in step (2), the mass ratio of 1,3-diamino-2-propanol, 10-undecenoic acid methyl ester, anhydrous tetrahydrofuran and sodium methoxide is 5:8-12:3-4:0.1-0.2; the reaction temperature is 55-70°C, and the reaction time is 20-30h.

[0017] Furthermore, in step (3), the mass ratio of DOPO-MA, hydroxypolyamide monomer, 4-dimethylaminopyridine and anhydrous tetrahydrofuran is 7-10:7-10:0.25:5; the mixing temperature is 55-65° C., and the mixing time is 20-30 h.

[0018] Furthermore, in step (3), the mass ratio of DOPO-MA to tetrahydrofuran aqueous solution is 8.5:15-20, and the reaction time is 3-5h; the mass ratio of tetrahydrofuran to water in the tetrahydrofuran aqueous solution is 5:9-11.

[0019] Furthermore, in step (3), the volume ratio of the mixed solution to dichloromethane is 1:1-3; the washing is performed 2-4 times with a mixed aqueous solution of NaHCO3 and NaCl, the volume of the mixed aqueous solution of NaHCO3 and NaCl is 1-2 times the volume of the mixed solution and dichloromethane, and the concentrations of NaHCO3 and NaCl in the mixed aqueous solution of NaHCO3 and NaCl are 0.5-2 mol / L and 1-3 mol / L, respectively.

[0020] Furthermore, in step (4), the mass ratio of the modified polyamide monomer, 3,6-dioxa-1,8-octanedithiol, azobisisobutyronitrile, and anhydrous tetrahydrofuran is 2:1-3:0.05-0.1:2-3; the nitrogen purge time is 8-12 min; the reaction temperature is 60-70° C., and the reaction time is 20-30 h.

[0021] Furthermore, in step (5), the polyamide, dioctyl diphenylamine and stearic acid are 850-950 parts, 3-8 parts and 2-5 parts by mass respectively.

[0022] Furthermore, the temperature of the melt blending in step (5) is 200-220°C, and the time is 0.5-1h; the extrusion conditions are: the temperatures of zones 1 to 9 of the extruder are: 180°C, 190°C, 200°C, 200°C, 210°C, 220°C, 225°C, 230°C, 230°C, the head section temperature is 235°C, and the screw speed is 20Hz; the drying temperature is 90-110°C, and the time is 3-5h.

[0023] Beneficial effects:

[0024] (1) The present invention introduces maleic anhydride as a highly efficient reactive monomer, which can undergo graft copolymerization reaction with polyamide monomers. Based on this feature, the present invention reacts the phosphorus-containing flame retardant DOPO with maleic anhydride to form a stable blend flame retardant DOPO-MA. The synergistic effect between the phosphorus-containing flame retardant and the functional groups introduced by maleic anhydride promotes the fusion of the phosphorus-containing flame retardant and the polyamide monomer, thereby improving the heat resistance and flame retardant properties of the material. At the same time, maleic anhydride can enhance the crosslinking density between polyamide molecular chains and introduce more functional groups containing carboxyl and anhydride groups. The presence of these functional groups significantly improves the polarity and interfacial compatibility of the polyamide material, improves the mechanical strength, and obtains a polyamide material with excellent flame retardant and mechanical properties.

[0025] (2) The introduction of maleic anhydride in the preparation process of the present invention makes the material more stable at high temperatures, reduces the combustible gas generated during thermal degradation, further improves the flame retardant properties of the material, and is more in line with environmental protection requirements. The preparation process is simple and the production efficiency is high. The obtained polyamide material can be applied to the automotive industry, electronic products, synthetic fibers, packaging materials, building manufacturing and other fields, and has important practical application value. DETAILED DESCRIPTION

[0026] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be specifically described below in conjunction with the embodiments of the present invention. The described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0027] The experimental materials used in the present invention are all commercially available.

[0028] Example 1

[0029] A method for preparing a flame retardant polyamide material comprises the following steps:

[0030] (1) Under an inert atmosphere, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) was dissolved in ethanol at room temperature, and maleic anhydride (MA) was added after it was completely dissolved, wherein the mass ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, ethanol and maleic anhydride was 1:9:1, and the reaction was carried out at 80° C. for 12 h. After the reaction was completed, the reaction was cooled to room temperature, filtered with qualitative medium-speed filter paper, and the precipitate was washed with anhydrous ethanol for 3 times to obtain DOPO-MA;

[0031] (2) adding 1,3-diamino-2-propanol, 10-undecenoic acid methyl ester, anhydrous tetrahydrofuran (THF) and sodium methoxide in a mass ratio of 5:10:3.7:0.18 into a reaction kettle, and reacting at 60° C. for 24 hours under a nitrogen atmosphere to obtain a hydroxy polyamide monomer;

[0032] (3) Preparation of modified polyamide monomer:

[0033] ① Add DOPO-MA obtained in step (1), the hydroxypolyamide monomer obtained in step (2), 4-dimethylaminopyridine (DMAP) and THF into a reactor in a mass ratio of 8.5:8:0.25:5, react at 60° C. for 24 hours, inject THF aqueous solution (wherein the mass ratio of THF to pure water is 5:10) into the reaction system, wherein the mass ratio of the THF aqueous solution to DOPO-MA is 15:8.5, and continue to react for 4 hours to obtain a mixed solution;

[0034] ② Pour the mixed solution into 1.5 times the volume of dichloromethane, then wash it three times with a mixed aqueous solution of NaHCO3 and NaCl (the concentration of NaCl in the mixed aqueous solution is 2 mol / L, and the concentration of NaHCO3 is 1 mol / L) with the mixed solution and 1.5 times the volume of dichloromethane, let it stand for stratification, and take the upper layer to obtain the modified polyamide monomer;

[0035] (4) placing the modified polyamide monomer obtained in step (3) at a mass ratio of 2:2:0.06:2.5, 3,6-dioxa-1,8-octanedithiol, azobisisobutyronitrile (AIBN) and anhydrous THF into a reaction kettle, purging with nitrogen for 10 minutes, and reacting at 65° C. for 24 hours to obtain a polyamide solid;

[0036] (5) Add 900 parts of the polyamide prepared in step (4), 5 parts of dioctyl diphenylamine (antioxidant) and 3 parts of stearic acid (lubricant) into a mixer, melt blend at 210°C for 1 hour, and then transfer to a screw extruder for extrusion. Set the extruder temperature as follows: the temperatures of zones 1 to 9 are 180°C, 190°C, 200°C, 200°C, 210°C, 220°C, 225°C, 230°C, 230°C, the head section is 235°C, the screw speed is 20 Hz, and after extrusion, the mixture is air-dried and pelletized, and placed in a drying oven at 100°C for 4 hours to obtain a flame-retardant polyamide material.

[0037] Example 2

[0038] A method for preparing a flame retardant polyamide material comprises the following steps:

[0039] (1) Under an inert atmosphere, DOPO was dissolved in ethanol at room temperature, and MA was added after it was completely dissolved, wherein the mass ratio of DOPO, ethanol, and maleic anhydride was 1:9:1, and the reaction was carried out at 80°C for 12 hours. After the reaction was completed, the mixture was cooled to room temperature, filtered with qualitative medium-speed filter paper, and the precipitate was washed with anhydrous ethanol for three times to obtain DOPO-MA;

[0040] (2) adding 1,3-diamino-2-propanol, 10-undecenoic acid methyl ester, anhydrous THF and sodium methoxide in a mass ratio of 5:11:3.7:0.18 into a reaction kettle, and reacting at 60° C. for 24 hours under a nitrogen atmosphere to obtain a hydroxy polyamide monomer;

[0041] (3) Preparation of modified polyamide monomer:

[0042] ① Add DOPO-MA obtained in step (1) and the hydroxy polyamide monomer obtained in step (2) in a mass ratio of 8:9:0.25:5, DMAP and THF into a reaction kettle, react at 60° C. for 24 hours, inject THF aqueous solution (wherein the mass ratio of THF to pure water is 5:10) into the reaction system, and the mass ratio of THF aqueous solution to DOPO-MA is 15:8.5. Continue to react for 4 hours to obtain a mixed solution;

[0043] ② Pour the mixed solution into 1.5 times the volume of dichloromethane, then wash it three times with a mixed aqueous solution of NaHCO3 and NaCl (the concentration of NaCl in the mixed aqueous solution is 2 mol / L, and the concentration of NaHCO3 is 1 mol / L) with the mixed solution and 1.5 times the volume of dichloromethane, let it stand for stratification, and take the upper layer to obtain the modified polyamide monomer;

[0044] (4) placing the modified polyamide monomer obtained in step (3) in a mass ratio of 2:2.2:0.08:2.5, 3,6-dioxa-1,8-octanedithiol, AIBN and anhydrous THF into a reaction kettle, purging with nitrogen for 10 minutes, and reacting at 65° C. for 24 hours to obtain a polyamide solid;

[0045] (5) Add 850 parts of the polyamide prepared in step (4), 3 parts of dioctyl diphenylamine and 3.5 parts of stearic acid into a mixer, melt blend at 210°C for 1 hour, and then transfer to a screw extruder for extrusion. Set the extruder temperature as follows: the temperatures of zones 1 to 9 are 180°C, 190°C, 200°C, 200°C, 210°C, 220°C, 225°C, 230°C, 230°C, the head section is 235°C, the screw speed is 20Hz, and after extrusion, the mixture is air-dried and pelletized, and placed in a drying oven at 100°C for 4 hours to obtain a flame-retardant polyamide material.

[0046] Example 3

[0047] A method for preparing a flame retardant polyamide material comprises the following steps:

[0048] (1) Under an inert atmosphere, DOPO was dissolved in ethanol at room temperature, and MA was added after it was completely dissolved, wherein the mass ratio of DOPO, ethanol, and maleic anhydride was 1:9:1, and the reaction was carried out at 80°C for 12 hours. After the reaction was completed, the mixture was cooled to room temperature, filtered with qualitative medium-speed filter paper, and the precipitate was washed with anhydrous ethanol for three times to obtain DOPO-MA;

[0049] (2) adding 1,3-diamino-2-propanol, 10-undecenoic acid methyl ester, anhydrous THF and sodium methoxide in a mass ratio of 5:9:3.7:0.18 into a reaction kettle, and reacting at 60° C. for 24 hours under a nitrogen atmosphere to obtain a hydroxy polyamide monomer;

[0050] (3) Preparation of modified polyamide monomer:

[0051] ① Add DOPO-MA obtained in step (1), the hydroxy polyamide monomer obtained in step (2), DMAP and THF in a mass ratio of 8:8:0.25:5 into a reactor, react at 60° C. for 24 hours, inject THF aqueous solution (wherein the mass ratio of THF to pure water is 5:10) into the reaction system, the mass ratio of THF aqueous solution to DOPO-MA is 15:8.5, continue to react for 4 hours, and obtain a mixed solution;

[0052] ② Pour the mixed solution into 1.5 times the volume of dichloromethane, then wash it three times with a mixed aqueous solution of NaHCO3 and NaCl (the concentration of NaCl in the mixed aqueous solution is 2 mol / L, and the concentration of NaHCO3 is 1 mol / L) with the mixed solution and 1.5 times the volume of dichloromethane, let it stand for stratification, and take the upper layer to obtain the modified polyamide monomer;

[0053] (4) placing the modified polyamide monomer obtained in step (3) in a mass ratio of 2:2.1:0.05:2.5, 3,6-dioxa-1,8-octanedithiol, AIBN and anhydrous THF into a reaction kettle, purging with nitrogen for 10 minutes, and reacting at 65° C. for 24 hours to obtain a polyamide solid;

[0054] (5) Add 950 parts of the polyamide prepared in step (4), 8 parts of dioctyl diphenylamine and 4.5 parts of stearic acid into a mixer, melt blend at 210°C for 1 hour, and then transfer to a screw extruder for extrusion. Set the extruder temperature as follows: the temperatures of zones 1 to 9 are 180°C, 190°C, 200°C, 200°C, 210°C, 220°C, 225°C, 230°C, 230°C, the head section is 235°C, the screw speed is 20Hz, and after extrusion, the mixture is air-dried and pelletized, and placed in a drying oven at 100°C for 4 hours to obtain a flame-retardant polyamide material.

[0055] Comparative Example 1

[0056] The difference between this comparative example and Example 1 is that only acetic anhydride is used to modify the hydroxypolyamide monomer.

[0057] A method for preparing a polyamide material specifically comprises the following steps:

[0058] (1) adding 1,3-diamino-2-propanol, 10-undecenoic acid methyl ester, THF and sodium methoxide in a mass ratio of 5:10:3.7:0.18 into a reaction kettle, reacting at 60° C. for 24 hours under a nitrogen atmosphere to obtain a hydroxy polyamide monomer;

[0059] (2) Preparation of modified polyamide monomer:

[0060] ① Add the hydroxy polyamide monomer, acetic anhydride, DMAP and THF obtained in step (1) in a mass ratio of 8:8.5:0.25:5 into a reaction kettle, react at 60° C. for 24 hours, inject a THF aqueous solution (wherein the mass ratio of THF to pure water is 5:10) into the reaction system, and the mass ratio of the THF aqueous solution to acetic anhydride is 15:8.5. Continue to react for 4 hours to obtain a mixed solution;

[0061] ② Pour the mixed solution into 1.5 times the volume of dichloromethane, then wash it three times with a mixed aqueous solution of NaHCO3 and NaCl (the concentration of NaCl in the mixed aqueous solution is 2 mol / L, and the concentration of NaHCO3 is 1 mol / L) with the mixed solution and 1.5 times the volume of dichloromethane, let it stand for stratification, and take the upper layer to obtain the modified polyamide monomer;

[0062] (3) placing the modified polyamide monomer obtained in step ②, 3,6-dioxa-1,8-octanedithiol, AIBN and THF in a mass ratio of 2:2:0.06:2.5 into a reaction kettle, purging with nitrogen for 10 minutes, and reacting at 65° C. for 24 hours to obtain a polyamide solid;

[0063] (4) Add 900 parts of polyamide, 5 parts of dioctyl diphenylamine and 3 parts of stearic acid into a mixer, melt blend at 210°C for 1 hour, and then transfer to a screw extruder for extrusion. Set the extruder temperature as follows: the temperatures of zones 1 to 9 are 180°C, 190°C, 200°C, 200°C, 210°C, 220°C, 225°C, 230°C, 230°C, head section 235°C, screw speed 20Hz, and after extrusion, air-dry and pelletize, and place in a drying oven at 100°C for 4 hours to obtain a polyamide material.

[0064] Comparative Example 2

[0065] The difference between this comparative example and Example 1 is that maleic anhydride is used to modify the hydroxypolyamide monomer.

[0066] A method for preparing a polyamide material specifically comprises the following steps:

[0067] (1) adding 1,3-diamino-2-propanol, 10-undecenoic acid methyl ester, THF and sodium methoxide in a mass ratio of 5:10:3.7:0.18 into a reaction kettle, reacting at 60° C. for 24 hours under a nitrogen atmosphere to obtain a hydroxy polyamide monomer;

[0068] (2) Preparation of modified polyamide monomer:

[0069] ① Add hydroxy polyamide monomer, maleic anhydride, DMAP and THF in a mass ratio of 8:8.5:0.25:5 into a reactor, react at 60°C for 24 hours, inject THF aqueous solution (wherein the mass ratio of THF to pure water is 5:10) into the reaction system, the mass ratio of THF aqueous solution to maleic anhydride is 15:8.5, continue to react for 4 hours, and obtain a mixed solution;

[0070] ② Pour the mixed solution into 1.5 times the volume of dichloromethane, then wash it three times with a mixed aqueous solution of NaHCO3 and NaCl (the concentration of NaCl in the mixed aqueous solution is 2 mol / L, and the concentration of NaHCO3 is 1 mol / L) with the mixed solution and 1.5 times the volume of dichloromethane, let it stand for stratification, and take the upper layer to obtain the modified polyamide monomer;

[0071] (3) adding a modified polyamide monomer, 3,6-dioxa-1,8-octanedithiol, AIBN and THF in a mass ratio of 2:2:0.06:2.5 into a reaction kettle, purging with nitrogen for 10 minutes, and reacting at 65° C. for 24 hours to obtain a polyamide solid;

[0072] (4) Add 900 parts of polyamide, 5 parts of dioctyl diphenylamine and 3 parts of stearic acid into a mixer, melt blend at 210°C for 1 hour, and then transfer to a screw extruder for extrusion. Set the extruder temperature as follows: the temperatures of zones 1 to 9 are 180°C, 190°C, 200°C, 200°C, 210°C, 220°C, 225°C, 230°C, 230°C, head section 235°C, screw speed 20Hz, and after extrusion, air-dry and pelletize, and place in a drying oven at 100°C for 4 hours to obtain a polyamide material.

[0073] Test example

[0074] The polyamide materials prepared in the above embodiments and comparative examples were tested for performance, and the testing methods for various performance indicators are as follows:

[0075] Mechanical properties testing: simply supported beam notch impact is tested in accordance with GB / T 1043-2008 "Determination of impact properties of simply supported beams of plastics"; tensile strength is tested in accordance with GB / T 1040-2006 "Determination of tensile properties of plastics"; flexural strength is tested in accordance with GB / T 9341-2008 "Determination of flexural properties of plastics";

[0076] Flame retardant grade detection: The flame retardant grade is determined by referring to the UL94 plastic material combustion test standard. According to the UL94 standard, the flame retardant grade is divided into several grades: V-2: After the sample is subjected to two 10-second combustion tests, the flame goes out within 60 seconds, and the burning material can fall off; V-1: After the sample is subjected to two 10-second combustion tests, the flame goes out within 60 seconds, and no burning material can fall off; V-0: After the sample is subjected to two 10-second combustion tests, the flame goes out within 30 seconds, and no burning material can fall off.

[0077] Table 1 Performance test results of polyamide materials

[0078]

[0079]

[0080] As shown in Table 1, Comparative Examples 1 and 2, compared with the use of acetic anhydride to modify the hydroxy polyamide monomer, the flame retardant grade of the flame retardant polyamide material prepared by modifying the polyamide monomer with maleic anhydride can reach V-1, and has better mechanical properties. As shown in Examples 1-3 and Comparative Example 2, the present invention further introduces DOPO-MA obtained by reacting the phosphorus-containing flame retardant intermediate DOPO with maleic anhydride to modify the polyamide monomer, and the flame retardant grade of the flame retardant material is increased to V-0. This is because the phosphorus-containing flame retardant DOPO reacts with maleic anhydride to form a stable blend DOPO-MA, and the synergistic effect between the functional groups introduced by the phosphorus-containing flame retardant and maleic anhydride promotes the fusion of the phosphorus-containing flame retardant and the polyamide monomer, improves the heat resistance and flame retardant properties of the material, and further optimizes its mechanical properties. The preparation process of Example 1 obtains the best flame retardant properties and mechanical properties.

Claims

1. A method for preparing a flame retardant polyamide material, characterized in that: The method comprises the following steps: (1) Under an inert atmosphere, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is dissolved in ethanol, maleic anhydride is added for reaction, and DOPO-MA is obtained after cooling, filtering and washing; (2) mixing 1,3-diamino-2-propanol, 10-undecenoic acid methyl ester, anhydrous tetrahydrofuran, and sodium methoxide and reacting them under a nitrogen atmosphere to obtain a hydroxy polyamide monomer; (3) mixing the DOPO-MA prepared in step (1), the hydroxy polyamide monomer prepared in step (2), 4-dimethylaminopyridine, and anhydrous tetrahydrofuran, adding a tetrahydrofuran aqueous solution to react, and obtaining a mixed solution; pouring the mixed solution into dichloromethane, washing, standing and separating the layers, and taking the upper layer to obtain a modified polyamide monomer; (4) mixing the modified polyamide monomer obtained in step (3), 3,6-dioxa-1,8-octanedithiol, azobisisobutyronitrile, and anhydrous tetrahydrofuran, and reacting them after nitrogen purging to prepare a polyamide solid; (5) The polyamide prepared in step (4) is melt-blended with dioctyl diphenylamine and stearic acid, and then extruded, granulated and dried to obtain a flame-retardant polyamide material.

2. The preparation method according to claim 1, characterized in that: In step (1), the mass ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, ethanol and maleic anhydride is 1:6-10:1-3; the reaction temperature is 75-85° C., and the reaction time is 10-15 h; and the washing is performed by washing with anhydrous ethanol 2-4 times.

3. The preparation method according to claim 1, characterized in that: In step (2), the mass ratio of 1,3-diamino-2-propanol, 10-undecenoic acid methyl ester, anhydrous tetrahydrofuran and sodium methoxide is 5:8-12:3-4:0.1-0.2; the reaction temperature is 55-70° C. and the reaction time is 20-30 h.

4. The preparation method according to claim 1, characterized in that: In step (3), the mass ratio of DOPO-MA, hydroxypolyamide monomer, 4-dimethylaminopyridine and anhydrous tetrahydrofuran is 7-10:7-10:0.25:5; the mixing temperature is 55-65°C and the reaction time is 20-30h; the mass ratio of DOPO-MA and tetrahydrofuran aqueous solution is 8.5:15-20 and the reaction time is 3-5h; the mass ratio of tetrahydrofuran to water in the tetrahydrofuran aqueous solution is 5:9-11.

5. The preparation method according to claim 1, characterized in that: In step (3), the volume ratio of the mixed solution to dichloromethane is 1:1-3; and the washing is performed by washing with a mixed aqueous solution of NaHCO3 and NaCl for 2-4 times.

6. The preparation method according to claim 5, characterized in that: The volume of the mixed aqueous solution of NaHCO3 and NaCl in step (3) is 1-2 times the volume of the mixed solution and dichloromethane, and the concentrations of NaHCO3 and NaCl in the mixed aqueous solution of NaHCO3 and NaCl are 0.5-2 mol / L and 1-3 mol / L, respectively.

7. The preparation method according to claim 1, characterized in that: In step (4), the mass ratio of the modified polyamide monomer, 3,6-dioxa-1,8-octanedithiol, azobisisobutyronitrile and anhydrous tetrahydrofuran is 2:1-3:0.05-0.1:2-3; the nitrogen purge time is 8-12 minutes; the reaction temperature is 60-70° C., and the reaction time is 20-30 hours.

8. The preparation method according to claim 1, characterized in that: In step (5), the polyamide, dioctyl diphenylamine and stearic acid are respectively 850-950 parts, 3-8 parts and 2-5 parts by mass.

9. The preparation method according to claim 1, characterized in that: The temperature of the melt blending in step (5) is 200-220°C, and the time is 0.5-1h; the extrusion conditions are: the temperatures of zones 1 to 9 of the extruder are: 180°C, 190°C, 200°C, 200°C, 210°C, 220°C, 225°C, 230°C, 230°C, the head section temperature is 235°C, and the screw speed is 20Hz; the drying temperature is 90-110°C, and the time is 3-5h.

10. The flame retardant polyamide material prepared according to the preparation method according to any one of claims 1 to 9.

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