A new type of modified flame-retardant polyethylene material

Abstract

The present invention discloses a novel modified flame-retardant polyethylene material, belonging to the technical field of flame-retardant materials, which includes: S1 adding cobalt nitrate hexahydrate, sodium molybdate and urea into deionized water, washing with water and ethanol respectively, separating and drying to obtain CoMo-L nanosheets; S2 calcining the CoMo-L nanosheets in a N2 / NH3 mixed gas to obtain cobalt molybdenum nitride nanosheets; S3 adding the cobalt molybdenum nitride nanosheets into deionized water and stirring, adding magnesium nitrate hexahydrate, aluminum nitrate nonahydrate and urea, separating and drying to obtain a CoMoN / Mg-Al LDH heterojunction flame retardant; S4 adding the product prepared in S3 into a carbon nanotube dispersion, stirring, filtering and drying to obtain a pretreated flame retardant; S5 melt-blending the pretreated flame retardant, antioxidant and modified polyethylene, and extruding and granulating to obtain the novel modified flame-retardant polyethylene material. The flame-retardant material prepared by the present invention has good flame-retardant performance and mechanical properties.

Description

Technical Field

[0001] The present invention relates to the technical field of flame retardants, and particularly to a novel modified flame retardant polyethylene material. Background Art

[0002] Polyethylene is one of the main types of polyolefin products, having advantages such as diverse varieties, excellent properties, and rich monomer sources, and is considered one of the most useful polyolefin materials. However, the flammability of traditional polyethylene materials limits their applications in many occasions, especially in fields with high flame retardancy requirements such as building materials, wires and cables, and interior decorations of transportation vehicles.

[0003] In order to overcome this defect of flammability, flame retardant polyethylene materials have emerged in the market. Generally, inorganic flame retardants are compounded to improve the flame retardancy of the materials. Inorganic flame retardants have advantages such as small water solubility and high flame retardancy efficiency. However, the particle size of inorganic flame retardants prepared by current processes is generally 30 - 50 μm, with large particles, irregular shapes, and a wide particle size distribution. When used, they must be mechanically crushed or air-flow crushed to less than 10 μm, and the process is difficult. In addition, the compatibility between inorganic flame retardants and polymer materials is poor, and they are prone to agglomeration and difficult to be uniformly dispersed in the polymer, resulting in a rapid deterioration of the mechanical properties of the materials and affecting the comprehensive properties of the end products.

[0004] Therefore, how to develop a polyethylene material with a simple process and both mechanical strength and flame retardancy is an urgent problem to be solved currently. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides a novel modified flame retardant polyethylene material, which solves the problems raised in the above background art.

[0006] To achieve the above purposes, the present invention is realized through the following technical solutions:

[0007] A novel modified flame retardant polyethylene material, and its preparation method includes the following steps:

[0008] S1. By weight, add 5 parts of cobalt nitrate hexahydrate, 2 - 3 parts of sodium molybdate, and 1 - 2 parts of urea to 40 - 60 parts of deionized water, stir evenly for hydrothermal reaction, control the reaction temperature at 130 - 150 °C, and the reaction time at 6 - 10 h to obtain a precursor containing Co hydroxide and Mo hydroxide. Then wash it twice with water and once with ethanol respectively, separate the product, and dry it to obtain CoMo-L nanosheets;

[0009] S2. Calcinate the CoMo-L nanosheets prepared in S1 in a mixed gas of N2 / NH3 to obtain cobalt molybdenum nitride (CoMoN) nanosheets, where the volume ratio of N2 to NH3 in the mixed gas is 5:1 to 2, the calcination temperature is 500 to 600 °C, and the calcination time is 2 to 3 h;

[0010] S3. By weight, add the cobalt molybdenum nitride (CoMoN) nanosheets prepared in S2 to 40 to 60 parts of deionized water, stir evenly, then add 1 to 2 parts of magnesium nitrate hexahydrate, 3.5 to 4.5 parts of aluminum nitrate nonahydrate, and 3 to 4 parts of urea, and carry out a hydrothermal reaction. Control the reaction temperature to be 140 to 160 °C, and the reaction time to be 4 to 6 h. Separate and dry the product to obtain the CoMoN / Mg-AlLDH heterojunction flame retardant;

[0011] S4. Add the CoMoN / Mg-AlLDH heterojunction flame retardant prepared in S3 to 60 to 100 parts of carbon nanotube dispersion, stir ultrasonically for 10 to 20 min, filter and dry to obtain the pretreated flame retardant;

[0012] S5. Melt-blend the pretreated flame retardant, antioxidant, and modified polyethylene obtained in S4, and extrude and pelletize to obtain a novel modified flame-retardant polyethylene material.

[0013] Further, the carbon nanotube dispersion in S4 is a dispersion of carboxylated carbon nanotubes in N,N-dimethylformamide (DMF).

[0014] Further, the mass fraction of the carboxylated carbon nanotubes in the carbon nanotube dispersion is 0.5 to 1%.

[0015] Further, the preparation method of the modified polyethylene in S4 includes the following steps:

[0016] Q1. By weight, prepare the following raw materials: 100 parts of polyethylene, 0.8 to 1.2 parts of tert-butyl peroxybenzoate, and 4 to 6 parts of glycidyl methacrylate. Mix the above raw materials evenly to obtain a mixed material;

[0017] Q2: Melt-extrude the mixed material through a twin-screw extruder, and pelletize the extruded strip after cooling to obtain modified polyethylene.

[0018] Further, the mass ratio of the pretreated flame retardant, antioxidant, and modified polyethylene in S5 is 14 to 16:(1.5 to 2.5):100.

[0019] Further, the antioxidant is 6-ditert-butyl-p-cresol.

[0020] After adopting the above technical solution, compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The present invention prepares a CoMoN / Mg - Al LDH heterojunction flame retardant by a specific method. By loading carboxylated carbon nanotubes with the CoMoN / Mg - Al LDH heterojunction flame retardant and then acting together with modified polyethylene, a strong interfacial interaction is achieved between the inorganic flame retardant and the polymer matrix material, thereby obtaining a polyethylene material with both mechanical strength and flame retardancy.

[0022] 2. The CoMoN / Mg - Al LDH heterojunction flame retardant provided by the present invention has a small particle size and a uniform particle size distribution. At the same time, the surface of the flame retardant particles has fine villous protrusions, enabling it to be an excellent carrier for carbon nanotubes, realizing the uniform dispersion of carboxylated carbon nanotubes. On the one hand, the carboxylated carbon nanotubes can be used as reinforcing materials to improve the mechanical properties of modified polyethylene, and at the same time, they can effectively improve the interfacial force between the inorganic flame retardant and the resin matrix, and improve the heat insulation and flame retardant properties of the polyethylene material.

[0023] 3. By modifying polyethylene, a branched chain structure is introduced into the polyethylene molecular chain, endowing polyethylene with certain polarity and reactivity, thereby increasing the thermal decomposition temperature of the material and making it have higher heat resistance. At the same time, the carboxylated carbon nanotubes and the modified polyethylene can have a chemical interaction, enabling the inorganic particles in the flame retardant to form a stable inorganic composite barrier layer in the polyethylene matrix, which can isolate oxygen from contacting the matrix, prevent melting and dripping, and enhance the flame retardancy of the polyethylene material. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a scanning electron microscope image of the CoMoN / Mg - Al LDH heterojunction flame retardant in the preparation of a novel modified flame - retardant polyethylene material of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] The following will clearly and completely describe the technical solutions in the present invention in conjunction with the embodiments in the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. The description of at least one exemplary embodiment is actually only illustrative and in no way limits the present invention and its application or use. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0026] Example 1

[0027] A novel modified flame - retardant polyethylene material, and its preparation method includes the following steps:

[0028] S1. By weight, add 5 parts of cobalt nitrate hexahydrate, 2.5 parts of sodium molybdate and 1.5 parts of urea to 50 parts of deionized water, stir evenly and carry out hydrothermal reaction. Control the reaction temperature at 140 °C and the reaction time at 8 h to obtain a precursor containing Co hydroxide and Mo hydroxide. Then wash it twice with water and once with ethanol, separate the product and dry it to obtain CoMo-L nanosheets;

[0029] S2. Calcinate the CoMo-L nanosheets prepared in S1 in a N2 / NH3 mixed gas to obtain cobalt molybdenum nitride (CoMoN) nanosheets, where the volume ratio of N2 to NH3 in the mixed gas is 5:1, the calcination temperature is 550 °C, and the calcination time is 2 h;

[0030] S3. By weight, add the cobalt molybdenum nitride (CoMoN) nanosheets prepared in S2 to 50 parts of deionized water, stir evenly, then add 1.5 parts of magnesium nitrate hexahydrate, 3.5 parts of aluminum nitrate nonahydrate and 4 parts of urea, and carry out hydrothermal reaction. Control the reaction temperature at 150 °C and the reaction time at 5 h, separate the product and dry it to obtain CoMoN / Mg-Al LDH flame retardant;

[0031] S4. By weight, add the CoMoN / Mg-Al LDH flame retardant prepared in S3 to 80 parts of carbon nanotube dispersion liquid, stir ultrasonically for 15 min, filter and dry to obtain a pretreated flame retardant. The carbon nanotube dispersion liquid in S4 is a dispersion liquid of carboxylated carbon nanotubes in N,N-dimethylformamide (DMF), where the mass fraction of carboxylated carbon nanotubes is 0.8%;

[0032] S5. Melt-blend the pretreated flame retardant, antioxidant and modified polyethylene obtained in S4, extrude and pelletize to obtain a novel modified flame retardant polyethylene material; the antioxidant is 6-ditert-butyl-p-cresol.

[0033] The preparation method of the modified polyethylene in S4 includes the following steps:

[0034] Q1. By weight, prepare the following raw materials: 100 parts of polyethylene, 0.8 - 1.2 parts of tert-butyl peroxybenzoate and 4 - 6 parts of glycidyl methacrylate, mix the above raw materials evenly to obtain a mixed material;

[0035] Q2: Melt-extrude the mixed material through a twin-screw extruder, cool the extruded strip and pelletize to obtain modified polyethylene.

[0036] The mass ratio of the pretreated flame retardant, antioxidant and modified polyethylene in S5 is 15﹕2﹕100.

[0037] Example 2

[0038] A novel modified flame-retardant polyethylene material, and its preparation method comprises the following steps:

[0039] S1. By weight, add 5 parts of cobalt nitrate hexahydrate, 2 parts of sodium molybdate, and 1 part of urea to 40 parts of deionized water, stir evenly for hydrothermal reaction, control the reaction temperature at 130 °C, and the reaction time at 6 h to obtain a precursor containing Co hydroxide and Mo hydroxide. Then wash it twice with water and once with ethanol, separate the product, and dry it to obtain CoMo-L nanosheets;

[0040] S2. Calcinate the CoMo-L nanosheets prepared in S1 in a mixed gas of N2 / NH3 to obtain cobalt molybdenum nitride (CoMoN) nanosheets, where the volume ratio of N2 to NH3 in the mixed gas is 5:1, the calcination temperature is 500 °C, and the calcination time is 2 h;

[0041] S3. By weight, add the cobalt molybdenum nitride (CoMoN) nanosheets prepared in S2 to 40 parts of deionized water, stir evenly, then add 1 part of magnesium nitrate hexahydrate, 3.5 parts of aluminum nitrate nonahydrate, and 3 parts of urea for hydrothermal reaction, control the reaction temperature at 140 °C, and the reaction time at 4 h. Separate the product and dry it to obtain a CoMoN / Mg-Al LDH heterojunction flame retardant;

[0042] S4. By weight, add the CoMoN / Mg-Al LDH heterojunction flame retardant prepared in S3 to 60 parts of carbon nanotube dispersion, stir ultrasonically for 10 min, filter and dry to obtain a pretreated flame retardant;

[0043] S5. Melt-blend the pretreated flame retardant, antioxidant, and modified polyethylene obtained in S4, and extrude and pelletize to obtain a novel modified flame-retardant polyethylene material; the antioxidant is 6-ditert-butyl-p-cresol.

[0044] The carbon nanotube dispersion in S4 is a dispersion of carboxylated carbon nanotubes in N,N-dimethylformamide (DMF), where the mass fraction of carboxylated carbon nanotubes is 0.5%;

[0045] The preparation method of the modified polyethylene in S4 comprises the following steps:

[0046] Q1. By weight, prepare the following raw materials: 100 parts of polyethylene, 0.8 part of tert-butyl peroxybenzoate, and 4 - 6 parts of glycidyl methacrylate. Mix the above raw materials evenly to obtain a mixed material;

[0047] Q2: Melt-extrude the mixed material through a twin-screw extruder, cool the extruded strip and pelletize to obtain modified polyethylene.

[0048] In S5, the mass ratio of the pretreated flame retardant, antioxidant, and modified polyethylene is 14:1.5:100.

[0049] Example 3

[0050] A novel modified flame-retardant polyethylene material, and its preparation method includes the following steps:

[0051] S1. By weight, add 5 parts of cobalt nitrate hexahydrate, 3 parts of sodium molybdate, and 2 parts of urea to 60 parts of deionized water, stir evenly for hydrothermal reaction, control the reaction temperature at 150 °C, and the reaction time at 10 h to obtain a precursor containing Co hydroxide and Mo hydroxide. Then wash twice with water and once with ethanol, separate the product, and dry it to obtain CoMo-L nanosheets;

[0052] S2. Calcinate the CoMo-L nanosheets prepared in S1 in a N2 / NH3 mixed gas to obtain cobalt molybdenum nitride (CoMoN) nanosheets, where the volume ratio of N2 to NH3 in the mixed gas is 5:2, the calcination temperature is 600 °C, and the calcination time is 3 h;

[0053] S3. By weight, add the cobalt molybdenum nitride (CoMoN) nanosheets prepared in S2 to 60 parts of deionized water, stir evenly, then add 2 parts of magnesium nitrate hexahydrate, 4.5 parts of aluminum nitrate nonahydrate, and 4 parts of urea for hydrothermal reaction, control the reaction temperature at 160 °C, and the reaction time at 6 h. Separate the product and dry it to obtain a CoMoN / Mg-Al LDH heterojunction flame retardant;

[0054] S4. By weight, add the CoMoN / Mg-Al LDH heterojunction flame retardant prepared in S3 to 100 parts of carbon nanotube dispersion, stir ultrasonically for 20 min, filter and dry to obtain a pretreated flame retardant;

[0055] S5. Melt-blend the pretreated flame retardant, antioxidant, and modified polyethylene obtained in S4, and extrude and pelletize to obtain a novel modified flame-retardant polyethylene material; the antioxidant is 6-ditert-butyl-p-cresol.

[0056] The carbon nanotube dispersion in S4 is a dispersion of carboxylated carbon nanotubes in N,N-dimethylformamide (DMF), where the mass fraction of carboxylated carbon nanotubes is 1%;

[0057] The preparation method of the modified polyethylene in S4 includes the following steps:

[0058] Q1. By weight, prepare the following raw materials: 100 parts of polyethylene, 1.2 parts of tert-butyl peroxybenzoate, and 6 parts of glycidyl methacrylate. Mix the above raw materials evenly to obtain a mixed material;

[0059] Q2: The mixed materials are melt-extruded through a twin-screw extruder, and the extruded strips are cooled and pelletized to obtain modified polyethylene.

[0060] In S5, the mass ratio of the pretreated flame retardant, antioxidant, and modified polyethylene is 16:2.5:100 respectively.

[0061] Example 4

[0062] A new type of modified flame-retardant polyethylene material, and its preparation method includes the following steps:

[0063] S1: By weight, 5 parts of cobalt nitrate hexahydrate, 2.3 parts of sodium molybdate, and 1.2 parts of urea are added to 45 parts of deionized water, stirred evenly for hydrothermal reaction, the reaction temperature is controlled at 135 °C, and the reaction time is 7 h to obtain a precursor containing Co hydroxide and Mo hydroxide. Then it is washed twice with water and once with ethanol respectively, the product is separated and dried to obtain CoMo-L nanosheets;

[0064] S2: The CoMo-L nanosheets prepared in S1 are calcined in a N2 / NH3 mixed gas to obtain cobalt molybdenum nitride (CoMoN) nanosheets, where the volume ratio of N2 to NH3 in the mixed gas is 5:1.2, the calcination temperature is 520 °C, and the calcination time is 2.3 h;

[0065] S3: By weight, the cobalt molybdenum nitride (CoMoN) nanosheets prepared in S2 are added to 45 parts of deionized water, stirred evenly, then 1.2 parts of magnesium nitrate hexahydrate, 3.7 parts of aluminum nitrate nonahydrate, and 3.3 parts of urea are added for hydrothermal reaction, the reaction temperature is controlled at 145 °C, and the reaction time is 4.5 h. The product is separated and dried to obtain CoMoN / Mg-Al LDH heterojunction flame retardant;

[0066] S4: By weight, the CoMoN / Mg-Al LDH heterojunction flame retardant prepared in S3 is added to 70 parts of carbon nanotube dispersion, ultrasonically stirred for 12 min, filtered and dried to obtain the pretreated flame retardant;

[0067] S5: The pretreated flame retardant, antioxidant, and modified polyethylene obtained in S4 are melt-blended and extruded into pellets to obtain a new type of modified flame-retardant polyethylene material; the antioxidant is 6-ditert-butyl-p-cresol.

[0068] The carbon nanotube dispersion in S4 is a dispersion of carboxylated carbon nanotubes in N,N-dimethylformamide (DMF), where the mass fraction of carboxylated carbon nanotubes is 0.6%;

[0069] The preparation method of the modified polyethylene in S4 includes the following steps:

[0070] Q1: By weight, the following raw materials are provided: 100 parts of polyethylene, 0.9 part of tert-butyl peroxybenzoate, and 4.5 parts of glycidyl methacrylate. Mix the above raw materials evenly to obtain a mixed material.

[0071] Q2: Melt-extrude the mixed material through a twin-screw extruder, cool the extruded strip, and pelletize it to obtain modified polyethylene.

[0072] In S5, the mass ratio of the pretreated flame retardant, antioxidant, and modified polyethylene is 14.5:1.6:100.

[0073] Example 5

[0074] A novel modified flame-retardant polyethylene material, and its preparation method includes the following steps:

[0075] S1: By weight, add 5 parts of cobalt nitrate hexahydrate, 2.8 parts of sodium molybdate, and 1.7 parts of urea to 55 parts of deionized water, stir evenly for hydrothermal reaction, control the reaction temperature at 145 °C, and the reaction time at 9 h to obtain a precursor containing Co hydroxide and Mo hydroxide. Then wash it twice with water and once with ethanol, separate the product, and dry it to obtain CoMo-L nanosheets.

[0076] S2: Calcinate the CoMo-L nanosheets prepared in S1 in a mixed gas of N2 / NH3 to obtain cobalt molybdenum nitride (CoMoN) nanosheets, where the volume ratio of N2 to NH3 in the mixed gas is 5:1.8, the calcination temperature is 590 °C, and the calcination time is 2.8 h.

[0077] S3: By weight, add the cobalt molybdenum nitride (CoMoN) nanosheets prepared in S2 to 55 parts of deionized water, stir evenly, then add 1.7 parts of magnesium nitrate hexahydrate, 4.2 parts of aluminum nitrate nonahydrate, and 3.8 parts of urea, conduct hydrothermal reaction, control the reaction temperature at 155 °C, and the reaction time at 5.5 h. Separate the product and dry it to obtain a CoMoN / Mg-Al LDH heterojunction flame retardant.

[0078] S4: By weight, add the CoMoN / Mg-Al LDH heterojunction flame retardant prepared in S3 to 90 parts of carbon nanotube dispersion liquid, stir ultrasonically for 18 min, filter and dry to obtain a pretreated flame retardant.

[0079] S5: Melt-blend the pretreated flame retardant, antioxidant, and modified polyethylene obtained in S4, and extrude and pelletize to obtain a novel modified flame-retardant polyethylene material; the antioxidant is 6-ditert-butyl-p-cresol.

[0080] The carbon nanotube dispersion described in S4 is a dispersion of carboxylated carbon nanotubes in N,N-dimethylformamide (DMF), where the mass fraction of carboxylated carbon nanotubes is 0.9%;

[0081] The preparation method of the modified polyethylene described in S4 includes the following steps:

[0082] Q1; By weight, prepare the following raw materials: 100 parts of polyethylene, 1.1 parts of tert-butyl peroxybenzoate, and 4 - 6 parts of glycidyl methacrylate. Mix the above raw materials evenly to obtain a mixed material;

[0083] Q2: Melt-extrude the mixed material through a twin-screw extruder, and pelletize the extruded strip after cooling to obtain modified polyethylene.

[0084] The mass ratios of the pretreated flame retardant, antioxidant, and modified polyethylene in S5 are 14 - 16﹕1.5 - 2.5﹕100 respectively.

[0085] Comparative Example 1

[0086] The difference from Example 1 is only that in the preparation of the carbon nanotube dispersion in S4, the carboxylated carbon nanotubes are replaced by ordinary carbon nanotubes.

[0087] A novel modified flame-retardant polyethylene material, and its preparation method includes the following steps:

[0088] S1. By weight, add 5 parts of cobalt nitrate hexahydrate, 2.5 parts of sodium molybdate, and 1.5 parts of urea to 50 parts of deionized water, stir evenly for hydrothermal reaction, control the reaction temperature at 140 °C, and the reaction time at 8 h to obtain a precursor containing Co hydroxide and Mo hydroxide. Then wash it twice with water and once with ethanol, separate the product, and dry it to obtain CoMo-L nanosheets;

[0089] S2. Calcinate the CoMo-L nanosheets prepared in S1 in a N2 / NH3 mixed gas to obtain cobalt molybdenum nitride (CoMoN) nanosheets, where the volume ratio of N2 to NH3 in the mixed gas is 5:1, the calcination temperature is 550 °C, and the calcination time is 2 h;

[0090] S3. By weight, add the cobalt molybdenum nitride (CoMoN) nanosheets prepared in S2 to 50 parts of deionized water, stir evenly, then add 1.5 parts of magnesium nitrate hexahydrate, 3.5 parts of aluminum nitrate nonahydrate, and 4 parts of urea, conduct hydrothermal reaction, control the reaction temperature at 150 °C, and the reaction time at 5 h, separate the product, and dry it to obtain CoMoN / Mg-Al LDH heterojunction flame retardant;

[0091] S4. By weight, add the CoMoN / Mg-Al LDH flame retardant prepared in S3 into 80 parts of carbon nanotube dispersion, stir ultrasonically for 15 min, filter and dry to obtain the pretreated flame retardant. The carbon nanotube dispersion in S4 is a dispersion of carbon nanotubes in N,N-dimethylformamide (DMF), where the mass fraction of carbon nanotubes is 0.8%.

[0092] S5. Melt-blend the pretreated flame retardant, antioxidant and modified polyethylene obtained in S4, and extrude and pelletize to obtain a novel modified flame-retardant polyethylene material; the antioxidant is 6-ditert-butyl-p-cresol.

[0093] Comparative Example 2

[0094] The difference from Example 1 is only that in the preparation of the modified polyethylene in S4, glycidyl methacrylate is not added.

[0095] The preparation method of the modified polyethylene in S4 includes the following steps:

[0096] Q1. By weight, prepare the following raw materials: 100 parts of polyethylene and 0.8 - 1.2 parts of tert-butyl peroxybenzoate, mix the above raw materials evenly to obtain a mixed material;

[0097] Q2: Melt-extrude the mixed material through a twin-screw extruder, cool the extruded strip and pelletize to obtain the modified polyethylene.

[0098] Comparative Example 3

[0099] The difference from Example 1 is only that in the carbon nanotube dispersion in step 4, carboxylated carbon nanotubes are replaced by ordinary carbon nanotubes, and in addition, glycidyl methacrylate is not added in the preparation of the modified polyethylene.

[0100] A novel modified flame-retardant polyethylene material, the preparation method of which includes the following steps:

[0101] S1. By weight, add 5 parts of cobalt nitrate hexahydrate, 2.5 parts of sodium molybdate and 1.5 parts of urea into 50 parts of deionized water, stir evenly for hydrothermal reaction, control the reaction temperature at 140 °C, and the reaction time at 8 h to obtain a precursor containing Co hydroxide and Mo hydroxide, then wash twice with water and once with ethanol respectively, separate the product and dry to obtain CoMo-L nanosheets;

[0102] S2. Calcinate the CoMo-L nanosheets prepared in S1 in a N2 / NH3 mixed gas to obtain cobalt molybdenum nitride (CoMoN) nanosheets, where the volume ratio of N2 to NH3 in the mixed gas is 5:1, the calcination temperature is 550 °C, and the calcination time is 2 h;

[0103] S3. By weight, add the cobalt molybdenum nitride (CoMoN) nanosheets prepared in S2 to 50 parts of deionized water, stir evenly, then add 1.5 parts of magnesium nitrate hexahydrate, 3.5 parts of aluminum nitrate nonahydrate and 4 parts of urea, and carry out a hydrothermal reaction. Control the reaction temperature at 150 °C and the reaction time at 5 h. Separate and dry the product to obtain the CoMoN / Mg-Al LDH heterojunction flame retardant;

[0104] S4. By weight, add the CoMoN / Mg-Al LDH heterojunction flame retardant prepared in S3 to 80 parts of carbon nanotube dispersion liquid, stir ultrasonically for 15 min, filter and dry to obtain the pretreated flame retardant. The carbon nanotube dispersion liquid in S4 is a dispersion liquid of carbon nanotubes in N,N-dimethylformamide (DMF), and the mass fraction of carbon nanotubes is 0.8%;

[0105] S5. Melt-blend the pretreated flame retardant, antioxidant and modified polyethylene obtained in S4, and extrude and pelletize to obtain a novel modified flame-retardant polyethylene material; the antioxidant is 6-ditert-butyl-p-cresol.

[0106] The preparation method of the modified polyethylene described in S4 includes the following steps:

[0107] Q1. By weight, prepare the following raw materials: 100 parts of polyethylene and 0.8 - 1.2 parts of tert-butyl peroxybenzoate, mix the above raw materials evenly to obtain a mixed material;

[0108] Q2: Carry out melt extrusion on the mixed material through a twin-screw extruder, and cut the extruded strip into pellets after cooling to obtain modified polyethylene.

[0109] Performance test

[0110] Make the materials obtained in the examples and comparative examples into corresponding shapes according to different test standards, and carry out the following performance tests. The specific results are shown in Table 1:

[0111] 1. The limiting oxygen index is tested according to the standard of GB / T 2406.2-2009 "Test Method for Flammability of Plastics";

[0112] 2. The tensile strength is tested according to the standard of GB / T 1040-2006 "Determination of Tensile Properties of Plastics";

[0113] Table 1

[0114]

[0115] Result analysis:

[0116] Combined with Examples 1 to 5 and Table 1, it can be seen that the novel modified flame-retardant polyethylene material prepared by the present invention has good flame-retardant performance and good mechanical properties.

[0117] Compared with Example 1, in Comparative Example 1, the carboxylated carbon nanotubes were replaced with ordinary carbon nanotubes. As a result, the tensile strength and limiting oxygen index of the novel modified polyethylene material prepared in Comparative Example 1 both decreased significantly, indicating that replacing ordinary carbon nanotubes with carboxylated carbon nanotubes can improve the flame retardancy and mechanical properties of the prepared novel modified flame-retardant polyethylene material.

[0118] Combined with the content of Example 1 and the data in Table 1, it can be seen that the mechanical properties and flame retardancy of the novel modified flame-retardant polyethylene material prepared in Comparative Example 2 deteriorated, indicating that the addition of glycidyl methacrylate can improve the mechanical properties and flame retardancy of the prepared novel modified flame-retardant polyethylene material.

[0119] In the preparation of the novel modified flame-retardant polyethylene material in Comparative Example 3, the carboxylated carbon nanotubes were replaced with ordinary carbon nanotubes and glycidyl methacrylate was not added. Combining the content of Comparative Example 1, Comparative Example 2, Example 1 and the data in Table 1, it can be seen that the addition of carboxylated carbon nanotubes and glycidyl methacrylate can produce a synergistic effect in improving the mechanical properties and flame retardancy of the prepared novel modified polyethylene material.

[0120] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A novel modified flame-retardant polyethylene material, characterized in that: The preparation method comprises the following steps: S1. By weight, add 5 parts of cobalt nitrate hexahydrate, 2 - 3 parts of sodium molybdate, and 1 - 2 parts of urea to 40 - 60 parts of deionized water, stir evenly to carry out hydrothermal reaction, control the reaction temperature at 130 - 150 °C, and the reaction time at 6 - 10 h to obtain a precursor containing cobalt hydroxide and molybdenum hydroxide. Then wash it twice with water and once with ethanol respectively, separate the product, and dry it to obtain CoMo-L nanosheets; S2. Calcinate the CoMo-L nanosheets prepared in S1 in a mixed gas of N2 / NH3 to obtain cobalt molybdenum nitride nanosheets, where the volume ratio of N2 to NH3 in the mixed gas is 5:1 - 2, the calcination temperature is 500 - 600 °C, and the calcination time is 2 - 3 h; S3. By weight, add the cobalt molybdenum nitride nanosheets prepared in S2 to 40 - 60 parts of deionized water, stir evenly, then add 1 - 2 parts of magnesium nitrate hexahydrate, 3.5 - 4.5 parts of aluminum nitrate nonahydrate, and 3 - 4 parts of urea, and carry out hydrothermal reaction. Control the reaction temperature at 140 - 160 °C and the reaction time at 4 - 6 h, separate the product, and dry it to obtain the CoMoN / Mg-Al LDH heterojunction flame retardant; S4. Add the CoMoN / Mg-Al LDH heterojunction flame retardant prepared in S3 to 60 - 100 parts of carbon nanotube dispersion liquid, stir ultrasonically for 10 - 20 min, filter and dry to obtain the pretreated flame retardant; S5. Carry out melt blending of the pretreated flame retardant, antioxidant, and modified polyethylene obtained in S4, extrude and pelletize to obtain the novel modified flame retardant polyethylene material; The carbon nanotube dispersion liquid in S4 is a dispersion liquid of carboxylated carbon nanotubes in N,N-dimethylformamide (DMF); The preparation method of the modified polyethylene in S4 comprises the following steps: Q1. By weight, prepare the following raw materials: 100 parts of polyethylene, 0.8 - 1.2 parts of tert-butyl peroxybenzoate, and 4 - 6 parts of glycidyl methacrylate. Mix the above raw materials evenly to obtain a mixed material; Q2: Melt extrude the mixed material through a twin-screw extruder, cool the extruded strip and cut it into pellets to obtain the modified polyethylene.

2. A novel modified flame-retardant polyethylene material according to claim 1, characterized in that: The mass fraction of the carboxylated carbon nanotubes in the carbon nanotube dispersion liquid is 0.5 - 1%.

3. A novel modified flame-retardant polyethylene material according to claim 1, characterized in that: The mass ratio of the pretreated flame retardant, antioxidant, and modified polyethylene in S5 is (14 - 16):(1.5 - 2.5):100 respectively.

4. A novel modified flame-retardant polyethylene material according to claim 1, characterized in that: The antioxidant is 6-ditert-butyl-p-cresol.

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