Flame-retardant polypropylene composite material for insulator sheath and preparation process of flame-retardant polypropylene composite material

Abstract

The invention relates to the technical field of insulators, in particular to a flame-retardant polypropylene composite material for an insulator sheath and a preparation process of the flame-retardant polypropylene composite material. The invention relates to a preparation process of a flame-retardant polypropylene composite material for an insulator sheath. The preparation process comprises the following steps: preparing a modified flame retardant; preparing grafted modified mica powder; preparing a zinc oxide composite material; and preparing the polypropylene composite material. Ethylene-methyl acrylate-glycidyl methacrylate reacts with 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, so that the 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is grafted on the ethylene-methyl acrylate-glycidyl methacrylate, a modified flame retardant is prepared, and the flame retardant has the advantages that the flame retardant can be used for preparing the flame retardant, and the flame retardant can be used for preparing the flame retardant. After the 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is prepared from the 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and homo-polypropylene resin and the like, the problem of flame retardance failure caused by migration and volatilization in the processing and using processes of the 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide can be fundamentally solved, and the flame retardance of the polypropylene composite material is lasting and stable.

Description

Technical Field

[0001] This invention relates to the field of insulator technology, specifically to a flame-retardant polypropylene composite material for insulator sheaths and its preparation process. Background Technology

[0002] As a key protective component of power transmission systems, insulator sheaths are primarily used to isolate conductors from the external environment, preventing safety hazards such as leakage and short circuits. Their service environments are mostly outdoor, requiring them to withstand long-term exposure to ultraviolet radiation, extreme temperature differences, biological damage, and potential fire risks, placing stringent demands on the comprehensive performance of the materials. Traditional sheath materials are typically based on silicone rubber, which, while possessing excellent hydrophobic properties, suffers from insufficient tear resistance and bird-pecking impact resistance under long-term mechanical stress, extreme weather conditions, and increasingly frequent bird damage.

[0003] Polypropylene has become the mainstream substrate for insulator sheaths due to its advantages such as lightweight, good processing fluidity, low cost and excellent chemical stability. However, it is easily combustible under the action of high voltage arc or external fire source, and may produce molten droplets during combustion, which can expand the fire range. Although traditional halogenated flame retardants have high flame retardant efficiency, they release toxic and harmful gases during combustion, which does not meet environmental protection requirements. Halogen-free flame retardant systems (such as DOPO) have a large difference in polarity with the polypropylene matrix, resulting in insufficient compatibility between the two, and migration and failure are likely to occur during processing and use.

[0004] In addition, strong outdoor ultraviolet radiation can cause polypropylene molecular chains to degrade and break, leading to cracking and brittleness on the material surface, a significant decrease in mechanical properties, a shortened service life of the insulator sheath, and even safety accidents. Furthermore, in terms of bird pecking resistance, bird pecking is a common form of damage to insulator sheaths, which can cause damage to the sheath surface, thinning of the sheath, damage to insulation integrity, and faults such as leakage and arc discharge.

[0005] Therefore, there is a need to propose a flame-retardant polypropylene composite material for insulator sheaths that is both resistant to bird pecking and UV aging, as well as its preparation process, in order to extend its service life. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a flame-retardant polypropylene composite material for insulator sheaths and its preparation process.

[0007] This invention provides a process for preparing a flame-retardant polypropylene composite material for insulator sheaths, comprising the following steps: S1: Preparation of modified flame retardants Ethylene-methyl acrylate-glycidyl methacrylate and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were dried and dissolved in anhydrous ethanol, and then heated to react and obtain a modified flame retardant. S2: Preparation of grafted modified mica powder S2.1: Add mica powder to anhydrous toluene at a mass ratio of 1g:(8-10)mL, and ultrasonically disperse for 20-30min to obtain a mica dispersion. Then add diacetone acrylamide to anhydrous toluene at a mass ratio of 1g:(6-8)mL, and stir thoroughly to dissolve to obtain a diacetone acrylamide solution. S2.2: Add the above diacetone acrylamide solution to the above mica dispersion, sonicate homogenize in an ice bath at 1-3℃ for 30-40 min, then centrifuge, wash and vacuum dry to obtain modified mica; S2.3: Add the above modified mica to anhydrous toluene at a ratio of 1g:(10-20)mL, disperse ultrasonically for 20-30min, add azobisisobutyronitrile, stir and mix, then add maleic anhydride-grafted polypropylene benzene solution, and heat and stir under nitrogen protection at 120-130℃ for 1-2h. After cooling, centrifuge, wash and vacuum dry to obtain grafted modified mica powder. S3: Preparation of zinc oxide composite materials After dissolving alkali lignin, 3-chloro-2-hydroxypropyltrimethylammonium chloride was added to quaternize it. Then, the quaternized alkali lignin was dissolved and added to zinc acetate solution to react, thus obtaining zinc oxide composite material. S4: Preparation of polypropylene composite materials After thoroughly mixing the homopolymer polypropylene resin, the modified flame retardant, the grafted modified mica powder, the zinc oxide composite material, the nucleating agent, and the toughening agent, the mixture is added to a twin-screw extruder for compounding, extrusion granulation, and polypropylene composite material is obtained.

[0008] Furthermore, S1 includes the following steps: S1.1: Ethylene-methyl acrylate-glycidyl methacrylate and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were placed in a vacuum drying oven and dried at 50-60℃ for 1-2 hours to obtain dried ethylene-methyl acrylate-glycidyl methacrylate and dried 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide; S1.2: The above-mentioned dried ethylene-methyl acrylate-glycidyl methacrylate and dried 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were added to anhydrous ethanol, stirred thoroughly to dissolve, and then heated and stirred under nitrogen protection at 120-130℃ for 4-6 hours. After cooling, the mixture was poured into ice-cold diethyl ether to precipitate, and then filtered, washed and vacuum dried to obtain the modified flame retardant.

[0009] Furthermore, S3 includes the following steps: S3.1: Dissolve alkali lignin in a 20% sodium hydroxide solution at a ratio of 1 g: (6.2-6.4) mL, then add 3-chloro-2-hydroxypropyltrimethylammonium chloride while stirring, heat and stir at 80-90℃ for 3-4 h, cool, purify by dialysis and freeze dry to obtain quaternized alkali lignin; S3.2: Dissolve zinc acetate monohydrate in deionized water at a ratio of 1g:(45-50)mL to obtain a zinc acetate solution. Then dissolve the above-mentioned quaternized alkali lignin and sodium hydroxide in deionized water at a ratio of 1g:(4.8-5)g:(120-130)mL to obtain a quaternized alkali lignin solution. S3.3: Add the above quaternized alkali lignin solution to the above zinc acetate solution, heat and stir at 80-90℃ for 4-5 hours, cool, add 20% sulfuric acid solution to adjust the pH to 7-7.5, then heat and age at 40-50℃ for 1-2 hours, cool, centrifuge, wash and dry to obtain zinc oxide composite material.

[0010] Furthermore, the ratio of ethylene-methyl acrylate-glycidyl methacrylate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to anhydrous ethanol is (4.3-4.5) g: 1 g: (25-30) mL.

[0011] Furthermore, the volume ratio of diacetone acrylamide solution to mica dispersion is 1:(1.6-1.8), and the amount of azobisisobutyronitrile added is 0.4-0.6% of the mass of modified mica.

[0012] Furthermore, the maleic anhydride-grafted polypropylene benzene solution is prepared by mixing maleic anhydride-grafted polypropylene and toluene at a mass ratio of 1:(5-6), and the mass ratio of maleic anhydride-grafted polypropylene to modified mica is 1:(1.2-1.4).

[0013] Furthermore, the amount of 3-chloro-2-hydroxypropyltrimethylammonium chloride added is 82-84% of the alkali lignin content.

[0014] Furthermore, the mass ratio of quaternized alkali lignin to zinc acetate monohydrate is 1:(2.7-2.8).

[0015] Further, by weight, the raw material composition of the polypropylene composite material is as follows: 70-80 parts homopolymer polypropylene resin, 8-10 parts modified flame retardant, 16-20 parts grafted modified mica powder, 3-5 parts zinc oxide composite material, 0.1-0.3 parts nucleating agent and 5-10 parts toughening agent, wherein the molecular weight of the homopolymer polypropylene resin is 100,000-200,000, the nucleating agent is a β-crystal nucleating agent, and the toughening agent is any one of ethylene-octene copolymer, ethylene-butene copolymer or EPDM rubber.

[0016] A flame-retardant polypropylene composite material for insulator sheaths, which is prepared by the preparation process of a flame-retardant polypropylene composite material for insulator sheaths as described in any one of the above claims.

[0017] The present invention has the following advantages: 1. In this invention, ethylene-methyl acrylate-glycidyl methacrylate is reacted with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to graft 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide onto ethylene-methyl acrylate-glycidyl methacrylate, thus preparing a modified flame retardant. After being combined with homopolymer polypropylene resin to form a polypropylene composite material, the flame retardant failure caused by migration and volatilization during processing and use can be fundamentally solved because 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is covalently anchored to the polymer chain, making the flame retardant performance of the polypropylene composite material long-lasting and stable.

[0018] 2. In this invention, mica is first organically modified with diacetone acrylamide, and then maleic anhydride-grafted polypropylene is covalently grafted onto the surface of the organically modified mica under the action of an initiator to obtain grafted modified mica. After being made into a polypropylene composite material with homopolymer polypropylene resin, the compatibility between mica and polypropylene resin can be effectively improved, eliminating the inherent "weak interface" problem between inorganic fillers and plastic matrix. This helps mica to be uniformly dispersed in the polypropylene matrix. When the polypropylene composite material is impacted, the stress can be effectively transferred from the soft polypropylene matrix to the high modulus and high strength mica sheets through the strong chemical interface, absorbing a large amount of impact energy, thereby effectively improving the impact resistance of the polypropylene composite material and achieving the effect of preventing bird pecking. In addition, since mica has excellent ultraviolet light blocking properties, the uniformly dispersed mica sheets can reflect and scatter ultraviolet light, effectively delaying the damage of ultraviolet light to the polypropylene molecular chain, thereby effectively improving the anti-ultraviolet aging performance of the polypropylene composite material.

[0019] 3. In this invention, alkali lignin is first converted into quaternized alkali lignin using 3-chloro-2-hydroxypropyltrimethylammonium chloride. Then, using the quaternized alkali lignin as a template, zinc oxide nanoparticles are generated and composited in situ to form a zinc oxide composite material. This composite material is then combined with homopolymer polypropylene resin to form a polypropylene composite material. The quaternized alkali lignin ensures that the encapsulated zinc oxide nanoparticles are uniformly dispersed at the nanoscale within the polypropylene matrix, forming a dense protective network. When the energy of ultraviolet light exceeds the band gap energy of zinc oxide, electrons are excited to transition from the valence band to the conduction band, thereby converting harmful ultraviolet light energy. By converting ultraviolet rays into harmless heat or fluorescence, the ultraviolet rays are fundamentally "filtered out," thereby improving the UV aging resistance of polypropylene composites. In addition, mica mainly reflects or scatters ultraviolet rays through physical means, while zinc oxide mainly absorbs them through chemical means, absorbing and converting the remaining ultraviolet rays that are transmitted. When zinc oxide composites are used in combination with grafted modified mica powder, the uniformly dispersed flaky mica can prolong the propagation path of ultraviolet rays inside the composite material, increasing the chances of ultraviolet rays being repeatedly absorbed by zinc oxide, thereby achieving a synergistic effect in improving the UV aging resistance of polypropylene composites. Attached Figure Description

[0020] Figure 1 This is a process flow diagram of the preparation process of flame-retardant polypropylene composite material used for insulator sheaths in an embodiment of the present invention. Detailed Implementation

[0021] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this invention.

[0022] Example 1: A preparation process for a flame-retardant polypropylene composite material for insulator sheaths, such as... Figure 1 As shown, it includes the following steps: S1: Preparation of modified flame retardants S1.1: Ethylene-methyl acrylate-glycidyl methacrylate and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were placed in a vacuum drying oven and dried at 50°C for 1 hour to obtain dried ethylene-methyl acrylate-glycidyl methacrylate and dried 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide; S1.2: The above-mentioned dried ethylene-methyl acrylate-glycidyl methacrylate and dried 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were added to anhydrous ethanol, stirred thoroughly to dissolve, and then heated and refluxed at 120°C for 4 hours under nitrogen protection. After cooling, the precipitate was poured into ice-cold diethyl ether, filtered, washed, and vacuum dried to obtain the modified flame retardant. The ratio of ethylene-methyl acrylate-glycidyl methacrylate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to anhydrous ethanol was 4.3 g: 1 g: 25 mL. S2: Preparation of grafted modified mica powder S2.1: Add mica powder to anhydrous toluene at a mass ratio of 1g:8mL, and ultrasonically disperse for 20min to obtain a mica dispersion. Then add diacetone acrylamide to anhydrous toluene at a mass ratio of 1g:6mL, and stir thoroughly to dissolve to obtain a diacetone acrylamide solution. S2.2: The above diacetone acrylamide solution was added to the above mica dispersion, and the mixture was ultrasonically homogenized for 30 min in an ice bath at 1°C. After centrifugation, washing and vacuum drying, modified mica was obtained. The volume ratio of the diacetone acrylamide solution to the mica dispersion was 1:1.6. S2.3: The modified mica was added to anhydrous toluene at a ratio of 1g:10mL. After ultrasonic dispersion for 20min, azobisisobutyronitrile was added and stirred. Then, maleic anhydride-grafted polypropylene benzene solution was added. Under nitrogen protection, the mixture was heated and stirred under reflux at 120℃ for 1h. After cooling, the mixture was centrifuged, washed, and vacuum dried to obtain grafted modified mica powder. The amount of azobisisobutyronitrile added was 0.4% of the mass of the modified mica. The maleic anhydride-grafted polypropylene benzene solution was prepared by mixing maleic anhydride-grafted polypropylene and toluene at a mass ratio of 1:5, and the mass ratio of maleic anhydride-grafted polypropylene to modified mica was 1:1.2. S3: Preparation of zinc oxide composite materials S3.1: Dissolve alkali lignin in a 20% sodium hydroxide solution at a ratio of 1 g: 6.2 mL, then add 3-chloro-2-hydroxypropyltrimethylammonium chloride while stirring. Heat and stir at 80°C for 3 h. After cooling, purify by dialysis and freeze-dry to obtain quaternized alkali lignin, wherein the amount of 3-chloro-2-hydroxypropyltrimethylammonium chloride added is 82% of the mass of alkali lignin. S3.2: Dissolve zinc acetate monohydrate in deionized water at a ratio of 1g:45mL to obtain a zinc acetate solution. Then dissolve the above-mentioned quaternized alkali lignin and sodium hydroxide in deionized water at a ratio of 1g:4.8g:120mL to obtain a quaternized alkali lignin solution. S3.3: The above quaternized alkali lignin solution was added to the above zinc acetate solution, and the mixture was heated and stirred at 80°C for 4 hours. After cooling, a 20% sulfuric acid solution was added to adjust the pH to 7. Then, the mixture was heated and aged at 40°C for 1 hour. After cooling, the mixture was centrifuged, washed, and dried to obtain the zinc oxide composite material. The mass ratio of quaternized alkali lignin to zinc acetate monohydrate was 1:2.7. S4: Preparation of polypropylene composite materials 70 parts by mass of homopolymer polypropylene resin with a molecular weight of 100,000, 8 parts by mass of the above-mentioned modified flame retardant, 16 parts by mass of the above-mentioned grafted modified mica powder, 3 parts by mass of the above-mentioned zinc oxide composite material, 0.1 parts by mass of β-crystal nucleating agent and 5 parts by mass of ethylene-octene copolymer are thoroughly mixed and then added to a twin-screw extruder for compounding, extrusion granulation to obtain polypropylene composite material.

[0023] Example 2: A preparation process for a flame-retardant polypropylene composite material for insulator sheaths, such as... Figure 1 As shown, it includes the following steps: S1: Preparation of modified flame retardants S1.1: Ethylene-methyl acrylate-glycidyl methacrylate and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were placed in a vacuum drying oven and dried at 55°C for 1.5 h to obtain dried ethylene-methyl acrylate-glycidyl methacrylate and dried 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide; S1.2: The above-mentioned dried ethylene-methyl acrylate-glycidyl methacrylate and dried 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were added to anhydrous ethanol, stirred thoroughly to dissolve, and then heated and refluxed at 125°C for 5 hours under nitrogen protection. After cooling, the precipitate was poured into ice-cold diethyl ether, filtered, washed, and vacuum dried to obtain the modified flame retardant. The ratio of ethylene-methyl acrylate-glycidyl methacrylate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to anhydrous ethanol was 4.4 g: 1 g: 27.5 mL. S2: Preparation of grafted modified mica powder S2.1: Add mica powder to anhydrous toluene at a mass ratio of 1g:9mL, and ultrasonically disperse for 25min to obtain a mica dispersion. Then add diacetone acrylamide to anhydrous toluene at a mass ratio of 1g:7mL, and stir thoroughly to dissolve to obtain a diacetone acrylamide solution. S2.2: The above diacetone acrylamide solution was added to the above mica dispersion, and the mixture was ultrasonically homogenized for 35 min in an ice bath at 2°C. After centrifugation, washing and vacuum drying, modified mica was obtained. The volume ratio of the diacetone acrylamide solution to the mica dispersion was 1:1.7. S2.3: The modified mica was added to anhydrous toluene at a ratio of 1 g: 15 mL. After ultrasonic dispersion for 25 min, azobisisobutyronitrile was added and stirred. Then, maleic anhydride-grafted polypropylene-benzene solution was added. Under nitrogen protection, the mixture was heated and stirred under reflux at 125 °C for 1.5 h. After cooling, the mixture was centrifuged, washed, and vacuum dried to obtain grafted modified mica powder. The amount of azobisisobutyronitrile added was 0.5% of the mass of the modified mica. The maleic anhydride-grafted polypropylene-benzene solution was prepared by mixing maleic anhydride-grafted polypropylene and toluene at a mass ratio of 1:5.5, and the mass ratio of maleic anhydride-grafted polypropylene to modified mica was 1:1.3. S3: Preparation of zinc oxide composite materials S3.1: Dissolve alkali lignin in a 20% sodium hydroxide solution at a ratio of 1 g: 6.3 mL, then add 3-chloro-2-hydroxypropyltrimethylammonium chloride while stirring. Heat and stir at 85°C for 3.5 h. After cooling, purify by dialysis and freeze-dry to obtain quaternized alkali lignin, wherein the amount of 3-chloro-2-hydroxypropyltrimethylammonium chloride added is 83% of the mass of alkali lignin. S3.2: Dissolve zinc acetate monohydrate in deionized water at a ratio of 1g:47.5mL to obtain a zinc acetate solution. Then dissolve the above-mentioned quaternized alkali lignin and sodium hydroxide in deionized water at a ratio of 1g:4.9g:125mL to obtain a quaternized alkali lignin solution. S3.3: The above quaternized alkali lignin solution was added to the above zinc acetate solution, and the mixture was heated and stirred at 85°C for 4.5 h. After cooling, a 20% sulfuric acid solution was added to adjust the pH to 7, and then the mixture was heated and aged at 45°C for 1.5 h. After cooling, the mixture was centrifuged, washed and dried to obtain the zinc oxide composite material, wherein the mass ratio of quaternized alkali lignin to zinc acetate monohydrate was 1:2.75. S4: Preparation of polypropylene composite materials 75 parts by mass of homopolymer polypropylene resin with a molecular weight of 150,000, 9 parts by mass of the above-mentioned modified flame retardant, 18 parts by mass of the above-mentioned grafted modified mica powder, 4 parts by mass of the above-mentioned zinc oxide composite material, 0.2 parts by mass of β-crystal nucleating agent and 7.5 parts by mass of ethylene-butene copolymer are thoroughly mixed and then added to a twin-screw extruder for compounding, extrusion granulation to obtain polypropylene composite material.

[0024] Example 3: A preparation process for a flame-retardant polypropylene composite material for insulator sheaths, such as... Figure 1 As shown, it includes the following steps: S1: Preparation of modified flame retardants S1.1: Ethylene-methyl acrylate-glycidyl methacrylate and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were placed in a vacuum drying oven and dried at 60°C for 2 hours to obtain dried ethylene-methyl acrylate-glycidyl methacrylate and dried 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide; S1.2: The above-mentioned dried ethylene-methyl acrylate-glycidyl methacrylate and dried 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were added to anhydrous ethanol, stirred thoroughly to dissolve, and then heated and refluxed at 130°C for 6 hours under nitrogen protection. After cooling, the precipitate was poured into ice-cold diethyl ether, filtered, washed, and vacuum dried to obtain the modified flame retardant. The ratio of ethylene-methyl acrylate-glycidyl methacrylate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to anhydrous ethanol was 4.5 g: 1 g: 30 mL. S2: Preparation of grafted modified mica powder S2.1: Add mica powder to anhydrous toluene at a mass ratio of 1g:10mL, and ultrasonically disperse for 30min to obtain a mica dispersion. Then add diacetone acrylamide to anhydrous toluene at a mass ratio of 1g:8mL, and stir thoroughly to dissolve to obtain a diacetone acrylamide solution. S2.2: The above diacetone acrylamide solution was added to the above mica dispersion, and the mixture was ultrasonically homogenized at 3°C ​​in an ice bath for 40 min. After centrifugation, washing and vacuum drying, modified mica was obtained. The volume ratio of the diacetone acrylamide solution to the mica dispersion was 1:1.8. S2.3: The modified mica was added to anhydrous toluene at a ratio of 1g:20mL. After ultrasonic dispersion for 30min, azobisisobutyronitrile was added and stirred. Then, maleic anhydride-grafted polypropylene-benzene solution was added. Under nitrogen protection, the mixture was heated and stirred under reflux at 130℃ for 2h. After cooling, the mixture was centrifuged, washed, and vacuum dried to obtain grafted modified mica powder. The amount of azobisisobutyronitrile added was 0.6% of the mass of the modified mica. The maleic anhydride-grafted polypropylene-benzene solution was prepared by mixing maleic anhydride-grafted polypropylene and toluene at a mass ratio of 1:6, and the mass ratio of maleic anhydride-grafted polypropylene to modified mica was 1:1.4. S3: Preparation of zinc oxide composite materials S3.1: Dissolve alkali lignin in a 20% sodium hydroxide solution at a ratio of 1 g: 6.4 mL, then add 3-chloro-2-hydroxypropyltrimethylammonium chloride while stirring. Heat and stir at 90°C for 4 h. After cooling, purify by dialysis and freeze-dry to obtain quaternized alkali lignin, wherein the amount of 3-chloro-2-hydroxypropyltrimethylammonium chloride added is 84% ​​of the mass of alkali lignin. S3.2: Dissolve zinc acetate monohydrate in deionized water at a ratio of 1g:50mL to obtain a zinc acetate solution. Then dissolve the above-mentioned quaternized alkali lignin and sodium hydroxide in deionized water at a ratio of 1g:5g:130mL to obtain a quaternized alkali lignin solution. S3.3: The above quaternized alkali lignin solution was added to the above zinc acetate solution, and the mixture was heated and stirred at 90°C for 5 hours. After cooling, a 20% sulfuric acid solution was added to adjust the pH to 7.5. Then, the mixture was heated and aged at 50°C for 2 hours. After cooling, the mixture was centrifuged, washed, and dried to obtain the zinc oxide composite material. The mass ratio of quaternized alkali lignin to zinc acetate monohydrate was 1:2.8. S4: Preparation of polypropylene composite materials 80 parts by mass of homopolymer polypropylene resin with a molecular weight of 200,000, 10 parts by mass of the above-mentioned modified flame retardant, 20 parts by mass of the above-mentioned grafted modified mica powder, 5 parts by mass of the above-mentioned zinc oxide composite material, 0.3 parts by mass of β-crystal nucleating agent and 10 parts by mass of EPDM rubber are thoroughly mixed and then added to a twin-screw extruder for compounding, extrusion granulation to obtain polypropylene composite material.

[0025] Comparative Example 1 differs from Example 1 in that the modified flame retardant in step S4 is replaced with an equal amount of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide.

[0026] Comparative Example 2 differs from Example 1 in that the grafted modified mica powder in step S4 is replaced with an equal amount of mica powder.

[0027] Comparative Example 3 differs from Example 1 in that the zinc oxide composite material in step S4 is removed.

[0028] Comparative Example 4 differs from Example 1 in that the zinc oxide composite material in step S4 is replaced with an equal amount of grafted modified mica powder.

[0029] Comparative Example 5 differs from Example 1 in that the grafted modified mica powder in step S4 is replaced with an equal amount of zinc oxide composite material.

[0030] Test example: Test 1: The polypropylene composite materials prepared in Examples 1-3 and Comparative Example 1 were made into samples, and their initial limiting oxygen index and the limiting oxygen index after accelerated thermal aging in an 80°C oven for 500 hours were measured. Each group was tested three times, and the average value was taken. The results are shown in Table 1.

[0031] Table 1: Limiting Oxygen Index Test Results

[0032] As shown in Table 1, when 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide was directly added in Comparative Example 1, the initial limiting oxygen index of the polypropylene composite material was slightly lower than that in Example 1, but the rate of decrease in limiting oxygen index after 500 hours of heat aging was significantly higher than that in Example 1. This indicates that reacting ethylene-methyl acrylate-glycidyl methacrylate with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to remove 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is effective in reducing the limiting oxygen index of polypropylene composites. Grafting 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide onto ethylene-methyl acrylate-glycidyl methacrylate produces a modified flame retardant. This modified flame retardant is then combined with homopolymer polypropylene resin to form a polypropylene composite material. Because 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is covalently anchored to the polymer chain, the flame retardant failure caused by migration and volatilization during processing and use is fundamentally solved, resulting in long-lasting and stable flame retardant performance of the polypropylene composite material.

[0033] Test 2: The notched impact strength of the polypropylene composite materials prepared in Examples 1-3 and Comparative Example 2 was tested according to GB / T1043.2-2018 standard. Each group was tested three times, and the average value was taken. The results are shown in Table 2.

[0034] Table 2: Notched Impact Strength Test Results

[0035] As shown in Table 2, when mica powder without any modification was directly added in Comparative Example 2, the notched impact strength of the resulting polypropylene composite material was significantly lower than that in Example 1. This indicates that by first organically modifying mica with diacetone acrylamide, and then covalently grafting maleic anhydride-grafted polypropylene onto the surface of the organically modified mica under the action of an initiator, grafted modified mica can be obtained. After this grafted modified mica is made into a polypropylene composite material with homopolymer polypropylene resin, the compatibility between mica and polypropylene resin can be effectively improved, which helps the mica to be uniformly dispersed in the polypropylene matrix, thereby effectively improving the impact strength of the polypropylene composite material and achieving the effect of preventing bird pecking.

[0036] Test 3: The polypropylene composite materials prepared in Examples 1-3 and Comparative Examples 2-5 were made into samples, and then ultraviolet light aging tests were carried out using UVA-340 lamps with an irradiation intensity of 0.76W / m² and a blackboard temperature of 60℃. The surface color difference after 500h of the test was measured using a colorimeter. Each group was tested three times, and the average value was taken. The results are shown in Table 3.

[0037] Table 3: Color difference test results after 500 hours of UV aging

[0038] As shown in Table 3, when mica powder without any modification was directly added in Comparative Example 2, the color difference value of the polypropylene composite material after 500 hours of UV aging was significantly higher than that in Example 1. This shows that preparing polypropylene composite materials by grafting modified mica with homopolymer polypropylene resin helps to uniformly disperse mica in the polypropylene matrix, and uniformly dispersed lamellar mica can effectively improve the UV aging resistance of polypropylene composite materials.

[0039] Furthermore, in Comparative Example 3, without the addition of zinc oxide composite material, the color difference value of the polypropylene composite material after 500 hours of UV aging was significantly higher than that in Example 1. This shows that by first converting alkali lignin into quaternized alkali lignin using 3-chloro-2-hydroxypropyltrimethylammonium chloride, and then using quaternized alkali lignin as a template to generate and composite zinc oxide nanoparticles in situ to produce zinc oxide composite material, and then combining it with homopolymer polypropylene resin to produce polypropylene composite material, the effect of improving the UV aging resistance of polypropylene composite material can be achieved. In Comparative Examples 4 and 5, when only grafted modified mica powder or zinc oxide composite material was added, the color difference values ​​of the polypropylene composite material after 500 hours of UV aging were higher than those in Example 1. This shows that when zinc oxide composite material is used in combination with grafted modified mica powder, the effect of synergistically improving the UV aging resistance of polypropylene composite material can be achieved.

[0040] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims. Parts not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. A preparation process for a flame-retardant polypropylene composite material for insulator sheaths, characterized in that, Includes the following steps: S1: Preparation of modified flame retardants Ethylene-methyl acrylate-glycidyl methacrylate and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were dried and dissolved in anhydrous ethanol, and then heated to react and obtain a modified flame retardant. S2: Preparation of grafted modified mica powder S2.1: Add mica powder to anhydrous toluene at a mass ratio of 1g:(8-10)mL, and ultrasonically disperse for 20-30min to obtain a mica dispersion. Then add diacetone acrylamide to anhydrous toluene at a mass ratio of 1g:(6-8)mL, and stir thoroughly to dissolve to obtain a diacetone acrylamide solution. S2.2: Add the above diacetone acrylamide solution to the above mica dispersion, sonicate homogenize in an ice bath at 1-3℃ for 30-40 min, then centrifuge, wash and vacuum dry to obtain modified mica; S2.3: Add the above modified mica to anhydrous toluene at a ratio of 1g:(10-20)mL, disperse ultrasonically for 20-30min, add azobisisobutyronitrile, stir and mix, then add maleic anhydride-grafted polypropylene benzene solution, and heat and stir under nitrogen protection at 120-130℃ for 1-2h. After cooling, centrifuge, wash and vacuum dry to obtain grafted modified mica powder. S3: Preparation of zinc oxide composite materials After dissolving alkali lignin, 3-chloro-2-hydroxypropyltrimethylammonium chloride was added to quaternize it. Then, the quaternized alkali lignin was dissolved and added to zinc acetate solution to react, thus obtaining zinc oxide composite material. S4: Preparation of polypropylene composite materials After thoroughly mixing the homopolymer polypropylene resin, the modified flame retardant, the grafted modified mica powder, the zinc oxide composite material, the nucleating agent, and the toughening agent, the mixture is added to a twin-screw extruder for compounding, extrusion granulation, and polypropylene composite material is obtained.

2. The preparation process of a flame-retardant polypropylene composite material for insulator sheaths according to claim 1, characterized in that, S1 includes the following steps: S1.1: Ethylene-methyl acrylate-glycidyl methacrylate and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were placed in a vacuum drying oven and dried at 50-60℃ for 1-2 hours to obtain dried ethylene-methyl acrylate-glycidyl methacrylate and dried 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide; S1.2: The above-mentioned dried ethylene-methyl acrylate-glycidyl methacrylate and dried 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were added to anhydrous ethanol, stirred thoroughly to dissolve, and then heated and stirred under nitrogen protection at 120-130℃ for 4-6 hours. After cooling, the mixture was poured into ice-cold diethyl ether to precipitate, and then filtered, washed and vacuum dried to obtain the modified flame retardant.

3. The preparation process of a flame-retardant polypropylene composite material for insulator sheaths according to claim 2, characterized in that, S3 includes the following steps: S3.1: Dissolve alkali lignin in a 20% sodium hydroxide solution at a ratio of 1 g: (6.2-6.4) mL, then add 3-chloro-2-hydroxypropyltrimethylammonium chloride while stirring, heat and stir at 80-90℃ for 3-4 h, cool, purify by dialysis and freeze dry to obtain quaternized alkali lignin; S3.2: Dissolve zinc acetate monohydrate in deionized water at a ratio of 1g:(45-50)mL to obtain a zinc acetate solution. Then dissolve the above-mentioned quaternized alkali lignin and sodium hydroxide in deionized water at a ratio of 1g:(4.8-5)g:(120-130)mL to obtain a quaternized alkali lignin solution. S3.3: Add the above quaternized alkali lignin solution to the above zinc acetate solution, heat and stir at 80-90℃ for 4-5 hours, cool, add 20% sulfuric acid solution to adjust the pH to 7-7.5, then heat and age at 40-50℃ for 1-2 hours, cool, centrifuge, wash and dry to obtain zinc oxide composite material.

4. The preparation process of a flame-retardant polypropylene composite material for insulator sheaths according to claim 2, characterized in that, The ratio of ethylene-methyl acrylate-glycidyl methacrylate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to anhydrous ethanol is (4.3-4.5) g: 1 g: (25-30) mL.

5. The preparation process of a flame-retardant polypropylene composite material for insulator sheaths according to claim 1, characterized in that, The volume ratio of diacetone acrylamide solution to mica dispersion is 1:(1.6-1.8), and the amount of azobisisobutyronitrile added is 0.4-0.6% of the mass of modified mica.

6. The preparation process of a flame-retardant polypropylene composite material for insulator sheaths according to claim 1, characterized in that, The maleic anhydride-grafted polypropylene benzene solution is prepared by mixing maleic anhydride-grafted polypropylene and toluene at a mass ratio of 1:(5-6), and the mass ratio of maleic anhydride-grafted polypropylene to modified mica is 1:(1.2-1.4).

7. The preparation process of a flame-retardant polypropylene composite material for insulator sheaths according to claim 3, characterized in that, The amount of 3-chloro-2-hydroxypropyltrimethylammonium chloride added is 82-84% of the alkali lignin quality.

8. The preparation process of a flame-retardant polypropylene composite material for insulator sheaths according to claim 3, characterized in that, The mass ratio of quaternized alkali lignin to zinc acetate monohydrate is 1:(2.7-2.8).

9. The preparation process of a flame-retardant polypropylene composite material for insulator sheaths according to claim 1, characterized in that, By weight, the raw material composition of the polypropylene composite material is as follows: 70-80 parts homopolymer polypropylene resin, 8-10 parts modified flame retardant, 16-20 parts grafted modified mica powder, 3-5 parts zinc oxide composite material, 0.1-0.3 parts nucleating agent and 5-10 parts toughening agent. Among them, the molecular weight of the homopolymer polypropylene resin is 100,000-200,000, the nucleating agent is a β-crystal nucleating agent, and the toughening agent is any one of ethylene-octene copolymer, ethylene-butene copolymer or EPDM rubber.

10. A flame-retardant polypropylene composite material for insulator sheaths, characterized in that, It is prepared by the preparation process of a flame-retardant polypropylene composite material for insulator sheaths as described in any one of claims 1-9.

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