Preparation method of flame-retardant reinforced polypropylene composite material

Abstract

The invention discloses a preparation method of a flame-retardant reinforced polypropylene composite material, and belongs to the technical field of polypropylene composite materials. The preparation method of the flame-retardant reinforced polypropylene composite material comprises the following steps: mixing the modified ammonium polyphosphate and the carbon microspheres for reaction to obtain a first mixture; polypropylene and modified hydrotalcite are mixed, and a second mixture is obtained; mixing and reacting the first mixture and the second mixture to obtain a third mixture; and finally, mixing the third mixture, melamine urate and an auxiliary agent, carrying out melt blending, extrusion and granulation on a double-screw extruder, and carrying out injection molding to obtain the composite material. Wherein the modified ammonium polyphosphate is obtained by modifying ammonium polyphosphate with a silane coupling agent; the modified hydrotalcite is obtained by modifying calcium aluminum hydrotalcite with 1, 10-bis (4-benzoic acid oxygen group) decane; the carbon microspheres are obtained by taking beer as a precursor, performing hydrothermal reaction and activating by adopting zinc chloride; the flame-retardant reinforced polypropylene composite material prepared by the preparation method disclosed by the invention is relatively good in flame retardance and relatively good in mechanical property.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method of a flame-retardant reinforced polypropylene composite material BACKGROUND

[0002] Polypropylene, as a kind of general-purpose thermoplastic resin, has the advantages of low density, strong chemical corrosion resistance, excellent processing performance and low cost, and is widely used in the fields of automobile, electronic and electrical appliances, packaging and building. However, due to the flammable characteristics of the carbon-hydrogen structure in the molecular chain of polypropylene, a large amount of heat and smoke will be released during the combustion process, and molten droplets are easy to produce, which limits its application in fields with high requirements for flame retardant performance. In addition, the mechanical properties of polypropylene, especially strength and stiffness, are difficult to meet the needs of some high-performance structural materials. Therefore, how to improve the flame retardant performance and mechanical properties of polypropylene material has become one of the current research focuses.

[0003] In order to improve the flame retardant performance of polypropylene, the traditional method mainly uses additive flame retardants, such as halogen-based flame retardants and phosphorus-based flame retardants. Although these flame retardants can improve the flame retardant effect of the material to a certain extent, halogen-based flame retardants will produce toxic and harmful gases during the combustion process, which poses a threat to the environment and human health; and some phosphorus-based flame retardants have the problem of poor compatibility with the polypropylene matrix, which easily leads to the decrease of the mechanical properties of the material, especially the significant decrease of the impact strength.

[0004] Therefore, it is urgent to develop a preparation method which can effectively improve the flame retardant performance of polypropylene composite material and significantly enhance its mechanical properties. SUMMARY

[0005] The purpose of the present application is to provide a preparation method of a flame-retardant reinforced polypropylene composite material to solve the technical problems mentioned in the background.

[0006] The technical scheme for achieving the purpose of the present application is:

[0007] The present application provides a preparation method of a flame-retardant reinforced polypropylene composite material, comprising the following preparation steps:

[0008] (1) The raw material components are weighed and prepared according to the corresponding mass fraction, and the raw material components mainly include modified ammonium polyphosphate, carbon microspheres, modified hydrotalcite, melamine cyanurate, polypropylene and additives;

[0009] (2) The modified ammonium polyphosphate and carbon microspheres weighed in step (1) are mixed and reacted to obtain a first mixture;

[0010] (3) The polypropylene and modified hydrotalcite are mixed to obtain a second mixture;

[0011] (4) mixing and reacting the first mixture and the second mixture to obtain a third mixture;

[0012] (5) mixing the third mixture, melamine urea salt and the auxiliary agent, melt blending and extruding to obtain granules, and then injection molding to obtain.

[0013] Further, the mass fractions of the components in step (1) are as follows: 6-7 parts by mass of modified ammonium polyphosphate, 1.5-2.5 parts by mass of carbon microspheres, 3.5-3.55 parts by mass of modified hydrotalcite, 19-20 parts by mass of melamine urea salt, 66.5-67.45 parts by mass of polypropylene, and 1.5 parts by mass of auxiliary agent.

[0014] Further, the modified ammonium polyphosphate is obtained by modifying ammonium polyphosphate with a silane coupling agent, and the specific preparation steps are as follows: 2-3 parts by mass of silane coupling agent is mixed with 50 parts by mass of water, then 3M hydrochloric acid is added to adjust the pH to 5-6, and then stirred and mixed uniformly, then heated to 84-86℃ while stirring, and kept at this temperature for 55-65 min, to obtain a mixed solution A; 50 parts by mass of ammonium polyphosphate is mixed with 160 parts by mass of absolute ethanol and stirred for 18-22 min to obtain a mixed solution B; mixed solution B is added to mixed solution A, then cooled to 48-52℃, and reacted for 1.5-2.5 h, then filtered, dried, crushed and passed through a 45μm sieve to obtain the modified ammonium polyphosphate.

[0015] Further, the silane coupling agent at least uses trimethoxy(3-(4-nitrophenoxy)propyl)silane.

[0016] Further, the modified hydrotalcite is obtained by modifying magnesium-aluminum hydrotalcite with 1,10-bis(4-benzoxy)decane, and the specific preparation steps are as follows: the hydrotalcite and 1,10-bis(4-benzoxy)decane are placed in an oven at 78-82℃ and dried for 28-32 min, then the dried hydrotalcite and 1,10-bis(4-benzoxy)decane are mixed in a mass ratio of 3.3-3.35:0.2, then reacted at 118-122℃ for 28-32 min to obtain the modified hydrotalcite.

[0017] Further, the carbon microspheres are obtained by hydrothermal reaction using beer as precursor and then activating with zinc chloride, and the specific steps are as follows: 80 parts by mass of commercial beer is stirred for 20 min to remove the dissolved carbon dioxide foam in the beer, then the beer is transferred to a polytetrafluoroethylene stainless steel reaction kettle, and reacted under hydrothermal conditions at 200℃ for 20 h; after natural cooling to room temperature, an orange-yellow supernatant and black precipitate are obtained, which are separated by centrifugation, the precipitate is repeatedly washed with deionized water and dried in a 60℃ oven to obtain carbon microsphere blanks; the carbon microsphere blanks are mixed with zinc chloride at a mass ratio of 1:3, dried at 80℃ for 12 h, then heated to 890-910℃ at a heating rate of 5℃ / min in a tube furnace, calcined for 2 h, and then naturally cooled to room temperature, followed by repeated washing with 2M hydrochloric acid solution for 4-6 times to remove metal residues, and then repeatedly washing with deionized water for 4-6 times, and drying in a 60℃ oven to obtain carbon microspheres.

[0018] Beer is a popular drink, which is rich in nutrients including maltose, amino acids, glutathione, vitamins and ethanol; in the hydrothermal reaction process, the ether ring in maltose is cleaved and rearranged, and polymerizes with free radical intermediates formed by dehydroxylation and dehydrogenation to form an aromatic ring type carbon skeleton; and the nucleophilicity of amino acids or glutathione introduces nitrogen and sulfur elements on the carbon skeleton, thereby generating carbon microspheres containing oxygen, nitrogen and sulfur, and the introduction of zinc chloride can promote the dehydration of the carbon skeleton, produce pores and structures similar to aromatic rings, and the composite material has a strong adsorption effect on the flue gas and acidic gas generated during combustion, thereby achieving excellent smoke suppression effect.

[0019] Further, the specific steps of step (2) are as follows: the modified ammonium polyphosphate weighed in step (1) is dispersed in 1257-1259 parts by mass of deionized water to obtain a mixed solution C; the mixed solution C is added to 4750-4770 parts by mass of a 1 mg / mL sodium borohydride solution, then carbon microspheres are added, stirred and reacted for 18-22 min, filtered, washed with deionized water for 2-4 times, and dried to obtain a first mixture.

[0020] In step (2), the modified ammonium polyphosphate is mixed with the carbon microspheres, and sodium borohydride is introduced during the mixing process, and under the joint action of the carbon microspheres and sodium borohydride, the nitrobenzene on the modified ammonium polyphosphate is reduced to form aniline.

[0021] Further, the specific steps of the step (3) are as follows: dispersing the weighed modified hydrotalcite in 180-200 parts by mass of xylene to ultrasonically disperse for 8-12 min to obtain a dispersion liquid of the modified hydrotalcite; dissolving the polypropylene weighed in step (1) in a solution of 10-20 times the mass of xylene, then adding the dispersion liquid of the modified hydrotalcite drop by drop at a drop rate of 1 drop / s under the condition of heating to 150 DEG C, and after condensation refluxing under stirring for 23-25 h, extracting by pouring into an equal volume of ethanol, and washing and filtering with ethanol, the flocculent material obtained is dried under vacuum for 23-25 h to obtain a second mixture.

[0022] Further, the specific steps of the step (4) are as follows: mixing the second mixture with the first mixture, 400-500 parts by mass of 1-methyl-2-pyrrolidone at 0-5 DEG C, ultrasonically dispersing for 8-12 min, adding 0.1-0.12 parts by mass of triethylamine and 0.0002-0.0004 parts by mass of anhydrous lithium chloride under stirring for 25-35 min, then heating to 70-80 DEG C under nitrogen protection, and reacting for 5.5-6.5 h, after the reaction, precipitating in ice water, filtering, washing with deionized water for 2-4 times, then adding 5-6 parts by mass of 4M sodium hydroxide, reacting at room temperature for 85-95 min, then pouring into 36% concentrated hydrochloric acid to adjust the pH to neutral, filtering, washing with deionized water for 2-4 times, and baking at 60 DEG C for 47-49 h to obtain a third mixture.

[0023] Further, the specific steps of the step (5) are as follows: putting the granulated polypropylene composite granules into an injection molding machine to injection mold at 225-235 DEG C, then cooling in a 20 DEG C vacuum cooling water tank for 12-20 s, then keeping warm at 60-120 DEG C for 120-200 s, and finally cooling in a 20 DEG C cooling water tank for 36-60 s.

[0024] By adopting the technical scheme, the present application has the following beneficial effects:

[0025] (1) The present application introduces modified ammonium polyphosphate, melamine cyanurate, carbon microspheres and modified hydrotalcite into polypropylene to make the polypropylene have good flame retardancy and impact toughness.

[0026] (2) The polyphosphoric acid ammonium generated by heating covers the surface of the polypropylene composite material, and can isolate part of the heat, oxygen and flammable gas, while the polyphosphoric acid is a strong acid and has strong dehydrating property, which can promote the dehydration of polypropylene into carbon, thereby improving the flame retardancy of the composite material in the condensed phase, and the nitrogen dioxide, ammonia, carbon dioxide and other non-combustible gases generated by heating melamine urea salt can dilute the flammable gas and reduce the oxygen concentration, and can also act as a gas source to form holes inside the carbon layer by foaming, thereby further improving the heat insulation, oxygen and flammable gas resistance of the carbon layer, and improving the overall flame retardancy of the composite material; The carbon microspheres can capture active free radicals generated during the combustion process in the gas phase flame retardant, and can also capture free radicals generated during the decomposition of polypropylene in the condensed phase flame retardant, forming an in-situ crosslinked network, and the carbon microspheres are temperature-resistant and non-combustible, which can compensate for the pores of the carbon layer and improve the sealing property of the carbon layer, thereby further improving the heat insulation, oxygen and flammable gas resistance, and improving the flame retardancy of the composite material; After the bimetallic hydroxide is heated in the fire, it decomposes and absorbs a large amount of heat, thereby reducing the temperature of the burning base material; In addition, the water and carbon dioxide gas released by the thermal decomposition of the bimetallic hydroxide dilutes the flammable gas, and also takes away part of the heat of the fire; Furthermore, the oxides generated by the thermal decomposition of the bimetallic hydroxide and the carbides formed during the combustion of the composite material can form a condensed phase protective film on the surface of the composite material, thereby preventing the combustion from further spreading and spreading; At the same time, the bimetallic hydroxide can be converted into a porous solid base oxide with a high specific surface area by thermal decomposition, which has a strong adsorption effect on the smoke and acidic gas generated during combustion, thereby achieving excellent smoke suppression effect; The modified polyphosphoric acid ammonium, melamine urea salt, carbon microspheres and modified hydrotalcite are simultaneously added to the polypropylene composite material, and the flame retardant effect is better; However, the dispersibility and compatibility of the polyphosphoric acid ammonium, melamine urea salt, carbon microspheres and hydrotalcite with polypropylene are poor, thereby reducing the mechanical properties of the polypropylene composite material.

[0027] (3) The polyphosphoric acid ammonium is modified by the silane coupling agent to form a uniform and dense silicon "protective layer" on the surface of the polyphosphoric acid ammonium, thereby further improving the flame retardancy of the polypropylene composite material.

[0028] (4) The invention introduces magnesium-aluminum hydrotalcite to induce the crystallization of polypropylene alpha crystal form by the effect of heterogeneous nucleation, and modifies the magnesium-aluminum hydrotalcite by 1,10-bis(4-benzoxy) decane, uses the variability of the metal composition of the hydrotalcite layer to introduce 1,10-bis(4-benzoxy) decane to combine with the divalent metal elements on the hydrotalcite layer to load 1,10-bis(4-benzoxy) decane on the hydrotalcite layer, effectively reduces the polarity of the hydrotalcite, and improves the compatibility of the hydrotalcite and polypropylene; when the subsequent polypropylene, the second mixture obtained by mixing the modified hydrotalcite, and the first mixture obtained by mixing the modified ammonium polyphosphate and carbon microspheres are mixed, the aniline in the first mixture reacts with the benzoic acid in the second mixture to form an aromatic amide compound, which induces the crystallization of polypropylene beta crystal form, and at the same time, the first mixture is grafted on the surface of the hydrotalcite to enhance the compatibility of the first mixture and PP, thereby effectively improving the mechanical properties of the polypropylene composite material while ensuring the mechanical properties of the polypropylene. DETAILED DESCRIPTION

[0029] In order to better understand the above technical solutions, the above technical solutions will be described in detail below in combination with specific embodiments.

[0030] Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application.

[0031] The present application will be further described below. The following examples are only used to more clearly illustrate the technical solutions of the present application, and cannot be used to limit the protection scope of the present application.

[0032] The chemical raw materials involved in the present application are commercially available.

[0033] Preparation of hydrotalcite: 6.4102 parts by mass of magnesium nitrate hexahydrate and 4.6891 parts by mass of aluminum nitrate nonahydrate were dissolved in 50 parts by mass of deionized water without carbon dioxide to obtain a mixed salt solution; 4 parts of sodium hydroxide were dissolved in 50 parts by mass of deionized water without carbon dioxide to obtain a sodium hydroxide solution; 2.65 parts by mass of sodium carbonate were dissolved in 50 parts by mass of deionized water without carbon dioxide to obtain a sodium carbonate solution; the sodium hydroxide solution and the mixed salt solution were simultaneously added to the sodium carbonate solution, continuously stirred and controlled at a pH of about 10, and after the addition of the mixed salt solution was completed, it was transferred to a pressure container for sealing, and after 24 h of reaction in a 150℃ oven, it was taken out, the obtained product was washed by centrifugation with a solution of ethanol and deionized water in a volume ratio of 1:1 until the pH was neutral, then washed with acetone three times, and vacuum dried at 60℃ for 48 h to obtain magnesium-aluminum hydrotalcite with a particle size of 200-300 nm.

[0034] The auxiliary includes 0.5 parts by mass of antioxidant 1010 and 1 part by mass of zinc stearate.

[0035] The polypropylene is pure random copolymer polypropylene, with a tensile strength of 22.49 MPa and an impact strength of 20.50 kJ / m 2 .

[0036] The beer is commercially available, with an original wort concentration of 11 °P and an alcohol content of ≥4.3%vol.

[0037] (Example 1)

[0038] A preparation method of a flame-retardant reinforced polypropylene composite material, comprising the following preparation steps:

[0039] (1) The raw material components are weighed and dosed according to the corresponding mass fractions: 6 parts by mass of modified ammonium polyphosphate, 1.5 parts by mass of carbon microspheres, 3.55 parts by mass of modified hydrotalcite, 20 parts by mass of melamine cyanurate, 67.45 parts by mass of polypropylene, and 1.5 parts by mass of auxiliary;

[0040] (2) The modified ammonium polyphosphate weighed in step (1) is dispersed in 1257 parts by mass of deionized water to obtain a mixed solution C; the mixed solution C is added to a 4750 parts by mass of 1 mg / mL sodium borohydride solution, followed by the addition of carbon microspheres, stirring for 18 min, filtration, washing with deionized water for 2 times, and drying to obtain a first mixture;

[0041] (3) The modified hydrotalcite weighed in step (1) is ultrasonically dispersed in 180 parts by mass of dimethylbenzene to obtain a dispersion of modified hydrotalcite; the polypropylene weighed in step (1) is dissolved in a solution of 10 times its mass in dimethylbenzene, then the dispersion of modified hydrotalcite is added dropwise at a drop rate of 1 drop / s while heating to 150°C, and after condensation refluxing under stirring for 23 h, it is extracted by pouring into an equal volume of ethanol, and the obtained flocculent material is dried under vacuum for 23 h to obtain a second mixture;

[0042] (4) The second mixture is mixed with the first mixture, 400 parts by mass of 1-methyl-2-pyrrolidone at 0°C, ultrasonically dispersed for 8 min, 0.1 parts by mass of triethylamine and 0.0002 parts by mass of anhydrous lithium chloride are added under stirring for 25 min, then the temperature is raised to 70°C under nitrogen protection and kept constant for 5.5 h, after the reaction is completed, the product is precipitated in ice water, filtered, washed with deionized water for 2 times, then 5 parts by mass of 4M sodium hydroxide is added, reacted at room temperature for 85 min, poured into 36% concentrated hydrochloric acid to adjust the pH to neutral, filtered, washed with deionized water for 2 times, and then dried at 60°C for 47 h to obtain a third mixture;

[0043] (5) the third mixture, melamine cyanurate, and the auxiliary agent are mixed and then melt blended and extruded to form granules in a twin-screw extruder at an extrusion temperature of 190-220 DEG C, followed by injection molding in an injection molding machine at 225 DEG C, and then cooled in a vacuum cooling water tank at 20 DEG C for 12 s, followed by incubation at 60 DEG C for 120 s, and finally cooled in a cooling water tank at 20 DEG C for 36 s, to obtain the flame-retardant reinforced polypropylene composite material.

[0044] The modified ammonium polyphosphate is obtained by modifying ammonium polyphosphate with a silane coupling agent, and the specific preparation steps are as follows: 2 parts by mass of trimethoxy(3-(4-nitrophenoxy)propyl)silane is mixed with 50 parts by mass of water, and then 3M hydrochloric acid is added to adjust the pH to 5, and the mixture is stirred and mixed uniformly, and then the temperature is increased to 84 DEG C while stirring, and the mixture is stirred and incubated for 55 min to obtain a mixed solution A; 50 parts by mass of ammonium polyphosphate is mixed with 160 parts by mass of absolute ethanol, and stirred for 18 min to obtain a mixed solution B; the mixed solution B is added to the mixed solution A, and then the temperature is lowered to 48 DEG C, and the reaction is carried out for 1.5 h, and then the mixture is filtered, dried, and crushed to pass through a 45 μm sieve to obtain the modified ammonium polyphosphate.

[0045] The modified hydrotalcite is obtained by modifying magnesium-aluminum hydrotalcite with 1,10-bis(4-benzoatoxy)decane, and the specific preparation steps are as follows: the hydrotalcite and 1,10-bis(4-benzoatoxy)decane are dried in an oven at 78 DEG C for 28 min, and then the dried hydrotalcite and 1,10-bis(4-benzoatoxy)decane are mixed in a mass ratio of 3.35:0.2, and then the mixture is reacted at 118 DEG C for 28 min to obtain the modified hydrotalcite.

[0046] The carbon microspheres are obtained by hydrothermal reaction of beer as a precursor and activation with zinc chloride, and the specific steps are as follows: 80 parts by mass of commercial beer is stirred for 20 min to remove the dissolved carbon dioxide foam in the beer, and then the beer is transferred to a polytetrafluoroethylene stainless steel reaction kettle, and reacted under hydrothermal conditions at 200 DEG C for 20 h; after natural cooling to room temperature, an orange-yellow supernatant and black precipitate are obtained, and the two are separated by centrifugation, the precipitate is repeatedly washed with deionized water and dried in an oven at 60 DEG C to obtain carbon microsphere blanks; the carbon microsphere blanks are mixed with zinc chloride at a mass ratio of 1:3, dried at 80 DEG C for 12 h, and then calcined in a tube furnace at a temperature increasing rate of 5 DEG C / min to 890 DEG C for 2 h, and then naturally cooled to room temperature, and then repeatedly washed with 2M hydrochloric acid solution for 4 times to remove metal residues, and then repeatedly washed with deionized water for 4 times, and dried in an oven at 60 DEG C to obtain the carbon microspheres.

[0047] (Example 2)

[0048] A preparation method of a flame-retardant reinforced polypropylene composite material, comprising the following preparation steps:

[0049] (1) The raw material components are weighed and mixed according to the corresponding mass fraction: 6.5 parts by mass of modified ammonium polyphosphate, 2 parts by mass of carbon microspheres, 3.52 parts by mass of modified hydrotalcite, 19.5 parts by mass of melamine cyanurate, 66.98 parts by mass of polypropylene, and 1.5 parts by mass of an auxiliary agent;

[0050] (2) The modified ammonium polyphosphate weighed in step (1) is dispersed in 1258 parts by mass of deionized water to obtain a mixed solution C; the mixed solution C is added to a 4760 parts by mass of 1 mg / mL sodium borohydride solution, and then the carbon microspheres are added, stirred and reacted for 20 min, filtered, washed with deionized water for 3 times, and dried to obtain a first mixture;

[0051] (3) The modified hydrotalcite weighed in step (1) is dispersed in 190 parts by mass of xylene to obtain a dispersion of the modified hydrotalcite; the polypropylene weighed in step (1) is dissolved in a solution of 15 times the mass of xylene, then the dispersion of the modified hydrotalcite is added dropwise at a drop rate of 1 drop / s while heating to 150°C, and after condensation refluxing under stirring for 24 h, the product is extracted by pouring into an equal volume of ethanol, washed with ethanol, filtered, and the obtained flocculent material is dried under vacuum for 24 h to obtain a second mixture;

[0052] (4) The second mixture is mixed with the first mixture, 450 parts by mass of 1-methyl-2-pyrrolidone at 5°C, ultrasonically dispersed for 10 min, 0.11 parts by mass of triethylamine and 0.0003 parts by mass of anhydrous lithium chloride are added under stirring, stirred for 30 min, then heated to 75°C under nitrogen protection, and reacted for 6 h, after which the reaction product is precipitated in ice water, filtered, washed with deionized water for 3 times, then 5.5 parts by mass of 4M sodium hydroxide is added, reacted at room temperature for 90 min, then poured into 36% concentrated hydrochloric acid to adjust the pH to neutral, filtered, washed with deionized water for 3 times, and then dried at 60°C for 48 h to obtain a third mixture;

[0053] (5) The third mixture, melamine cyanurate, and auxiliary agent are mixed, then melt blended and extruded on a twin-screw extruder to obtain granules, the extrusion temperature is 190-220°C, then the granules are put into an injection molding machine to be injection molded at 230°C, then cooled in a 20°C vacuum cooling water tank for 16 s, then kept at 90°C for 160 s, and finally cooled in a 20°C cooling water tank for 48 s to obtain a flame-retardant reinforced polypropylene composite material.

[0054] The modified ammonium polyphosphate is obtained by modifying ammonium polyphosphate with a silane coupling agent, and the specific preparation steps are as follows: 2.5 parts by mass of trimethoxy(3-(4-nitrophenoxy)propyl)silane is mixed with 50 parts by mass of water, then 3M hydrochloric acid is added to adjust the pH to 5.5, the mixture is stirred until uniform, then the temperature is raised to 85°C while stirring, and the mixture is stirred for 60 minutes to obtain a mixed solution A; 50 parts by mass of ammonium polyphosphate is mixed with 160 parts by mass of absolute ethanol, and stirred for 20 minutes to obtain a mixed solution B; the mixed solution B is added to the mixed solution A, then the temperature is lowered to 50°C, and the reaction is carried out for 2 hours, then the mixture is filtered, dried, crushed and passed through a 45μm sieve to obtain the modified ammonium polyphosphate.

[0055] The modified hydrotalcite is obtained by modifying magnesium-aluminum hydrotalcite with 1,10-bis(4-benzoatoxy)decane, and the specific preparation steps are as follows: the hydrotalcite and 1,10-bis(4-benzoatoxy)decane are placed in an oven at 80°C and dried for 30 minutes, then the dried hydrotalcite and 1,10-bis(4-benzoatoxy)decane are mixed in a mass ratio of 3.32:0.2, and then reacted at 120°C for 30 minutes to obtain the modified hydrotalcite.

[0056] The carbon microspheres are obtained by hydrothermal reaction of beer as a precursor and activation with zinc chloride, and the specific steps are as follows: 80 parts by mass of commercial beer is stirred for 20 minutes to remove the dissolved carbon dioxide foam in the beer, then the beer is transferred to a polytetrafluoroethylene stainless steel reaction kettle and reacted under hydrothermal conditions at 200°C for 20 hours; after natural cooling to room temperature, an orange-yellow supernatant and black precipitate are obtained, which are separated by centrifugation, the precipitate is repeatedly washed with deionized water and dried in an oven at 60°C to obtain carbon microsphere blanks; the carbon microsphere blanks are mixed with zinc chloride at a mass ratio of 1:3, dried at 80°C for 12 hours, then heated to 900°C at a heating rate of 5°C / min in a tube furnace and calcined for 2 hours, then naturally cooled to room temperature, then repeatedly washed with 2M hydrochloric acid solution for 5 times to remove metal residues, and then repeatedly washed with deionized water for 5 times, and dried in an oven at 60°C to obtain the carbon microspheres.

[0057] (Example 3)

[0058] A preparation method of a flame-retardant reinforced polypropylene composite material, comprising the following preparation steps:

[0059] (1) The raw material components are weighed and prepared according to the corresponding mass fraction: 7 parts by mass of modified ammonium polyphosphate, 2.5 parts by mass of carbon microspheres, 3.5 parts by mass of modified hydrotalcite, 19 parts by mass of melamine cyanurate, 66.5 parts by mass of polypropylene, and 1.5 parts by mass of auxiliary agent;

[0060] (2) The modified ammonium polyphosphate weighed in step (1) is dispersed in 1259 parts by mass of deionized water to obtain a mixed solution C; the mixed solution C is added to 4770 parts by mass of a 1 mg / mL sodium borohydride solution, and then carbon microspheres are added, and the reaction is stirred for 22 min, filtered, washed with deionized water for 4 times, and dried to obtain a first mixture;

[0061] (3) The modified hydrotalcite weighed in step (1) is ultrasonically dispersed in 200 parts by mass of xylene to obtain a dispersion of the modified hydrotalcite; polypropylene weighed in step (1) is dissolved in a solution of 20 times the mass of xylene, and then the dispersion of the modified hydrotalcite is added dropwise at a drop rate of 1 drop / s under the condition of heating to 150 ℃, and after condensation refluxing under stirring for 25 h, the product is extracted by pouring into an equal volume of ethanol, and then filtered after washing with ethanol, and the obtained flocculent material is dried under vacuum for 25 h to obtain a second mixture;

[0062] (4) The second mixture is mixed with the first mixture, 500 parts by mass of 1-methyl-2-pyrrolidone at 5 ℃, ultrasonically dispersed for 12 min, and then 0.12 parts by mass of triethylamine and 0.0004 parts by mass of anhydrous lithium chloride are added under stirring, and after stirring for 35 min, the temperature is raised to 80 ℃ under nitrogen protection, and the reaction is kept at 80 ℃ for 6.5 h; after the reaction is completed, the product is precipitated in ice water, filtered, washed with deionized water for 4 times, and then 6 parts by mass of 4M sodium hydroxide is added, and after reaction at room temperature for 95 min, the product is poured into 36% concentrated hydrochloric acid to adjust the pH to neutral, filtered, washed with deionized water for 4 times, and then dried at 60 ℃ for 49 h to obtain a third mixture;

[0063] (5) The third mixture, melamine cyanurate, and an additive are mixed, and then melt blended and extruded to form granules on a double-screw extruder, with an extrusion temperature of 190-220 ℃; then the product is injected into an injection molding machine at 235 ℃ to form a molded product, and then cooled in a vacuum cooling water tank at 20 ℃ for 20 s, kept at 120 ℃ for 200 s, and finally cooled in a cooling water tank at 20 ℃ for 60 s to obtain a flame-retardant and reinforced polypropylene composite material.

[0064] The modified ammonium polyphosphate is obtained by modifying ammonium polyphosphate with a silane coupling agent, and the specific preparation steps are as follows: 3 parts by mass of trimethoxy(3-(4-nitrophenoxy)propyl)silane is mixed with 50 parts by mass of water, and then 3M hydrochloric acid is added to adjust the pH to 6, and the mixture is stirred until uniform, and then the temperature is raised to 86 ℃ while stirring, and the reaction is kept at 86 ℃ for 65 min to obtain a mixed solution A; 50 parts by mass of ammonium polyphosphate is mixed with 160 parts by mass of anhydrous ethanol, and the mixture is stirred for 22 min to obtain a mixed solution B; the mixed solution B is added to the mixed solution A, and then the temperature is lowered to 52 ℃, and the reaction is kept at 52 ℃ for 2.5 h, and then the product is filtered, dried, and crushed to pass through a 45 μm sieve to obtain the modified ammonium polyphosphate.

[0065] The modified hydrotalcite is obtained by modifying magnesium-aluminum hydrotalcite with 1,10-bis(4-benzoxy)decane, and the specific preparation steps are as follows: the hydrotalcite and 1,10-bis(4-benzoxy)decane are placed in an oven at 82°C and dried for 32 min, then the dried hydrotalcite and 1,10-bis(4-benzoxy)decane are mixed according to a mass ratio of 3.3:0.2, and then reacted at 122°C for 32 min to obtain the modified hydrotalcite.

[0066] The carbon microspheres are obtained by hydrothermal reaction of beer as a precursor and then activated by zinc chloride, and the specific steps are as follows: 80 parts by mass of commercial beer is stirred for 20 min to remove the dissolved carbon dioxide foam in the beer, then the beer is transferred to a polytetrafluoroethylene stainless steel reaction kettle, and reacted under hydrothermal conditions at 200°C for 20 h; after natural cooling to room temperature, an orange-yellow supernatant and black precipitate are obtained, which are separated by centrifugation, the precipitate is repeatedly washed with deionized water and dried in an oven at 60°C to obtain carbon microsphere blanks; the carbon microsphere blanks are mixed with zinc chloride at a mass ratio of 1:3, dried at 80°C for 12 h, then heated to 910°C at a heating rate of 5°C / min in a tube furnace, calcined for 2 h, and then naturally cooled to room temperature, then repeatedly washed with 2M hydrochloric acid solution for 6 times to remove metal residues, and then repeatedly washed with deionized water for 6 times, and dried in an oven at 60°C to obtain carbon microspheres.

[0067] (Comparative Example 1)

[0068] The difference between Comparative Example 1 and Example 2 is that the flame-retardant reinforced polypropylene composite material comprises, by mass fraction: 6.5 parts of modified ammonium polyphosphate, 2 parts of carbon microspheres, 3.52 parts of hydrotalcite, 19.5 parts of melamine cyanurate, 66.98 parts of polypropylene, and 1.5 parts of auxiliary agent, and the remaining steps are the same as those of Example 2.

[0069] (Comparative Example 2)

[0070] The difference between Comparative Example 2 and Example 2 is that the flame-retardant reinforced polypropylene composite material comprises, by mass fraction: 6.5 parts of modified ammonium polyphosphate, 3.52 parts of modified hydrotalcite, 19.5 parts of melamine cyanurate, 66.98 parts of polypropylene, and 1.5 parts of auxiliary agent, and the remaining steps are the same as those of Example 2.

[0071] (Comparative Example 3)

[0072] The difference between Comparative Example 3 and Example 2 is that the flame-retardant reinforced polypropylene composite material comprises, by mass fraction: 6.5 parts of modified ammonium polyphosphate, 2 parts of carbon microspheres, 3.52 parts of hydrotalcite, 19.5 parts of melamine cyanurate, 66.98 parts of polypropylene, and 1.5 parts of auxiliary agent, and the remaining steps are the same as those of Example 2.

[0073] (Comparative Example 4)

[0074] Comparative Example 4 differs from Example 2 in that the raw material components of the flame-retardant reinforced polypropylene composite include, by mass fraction: 6.5 parts of modified ammonium polyphosphate, 2 parts of carbon microspheres, 19.5 parts of melamine cyanurate, 66.98 parts of polypropylene, 1.5 parts of auxiliary, and the remaining steps are the same as Example 2.

[0075] (Comparative Example 5)

[0076] Comparative Example 5 differs from Example 2 in that the flame-retardant reinforced polypropylene composite is directly mixed at high speed and placed into a twin-screw extruder for extrusion granulation and injection molding during preparation, and the remaining steps are the same as Example 2.

[0077] (Comparative Example 6)

[0078] Comparative Example 6 differs from Example 2 in that the modified ammonium polyphosphate is vinyl trimethoxysilane modified ammonium polyphosphate, and the remaining steps are the same as Example 2.

[0079] (Effect Example)

[0080] Limiting Oxygen Index (LOI): The flame-retardant reinforced polypropylene composite prepared in the examples and comparative examples was tested for LOI according to GB / T 2406.2-2009, with a sample size of 150mm*12.8mm*3.0mm.

[0081] Tensile Properties: The flame-retardant reinforced polypropylene composite prepared in the examples and comparative examples was tested for tensile properties according to GB / T 1040.1-2018.

[0082] Impact Resistance: The flame-retardant reinforced polypropylene composite prepared in the examples and comparative examples was tested for notched impact resistance according to GB / T 1843-2008.

[0083] Table 1 below shows the performance data of the flame-retardant reinforced polypropylene composite prepared in Examples 1-3 and Comparative Examples 1-6:

[0084] Table 1

[0085] LOI (%) Tensile strength (MPa) Impact strength (kJ / m 2 ) Example 1 36.72 27.56 31.15 Example 2 36.91 27.92 31.28 Example 3 36.81 27.64 31.21 Comparative Example 1 34.69 24.76 24.03 Comparative Example 2 34.61 21.13 24.00 Comparative Example 3 33.64 18.87 18.96 Comparative Example 4 33.21 20.54 19.24 Comparative Example 5 34.59 24.99 25.68 Comparative Example 6 36.89 27.86 24.01

[0086] As shown in Table 1, the flame-retardant reinforced polypropylene composite prepared in Examples 1-3 has better flame retardancy, tensile properties, and impact resistance.

[0087] Comparative Example 1 differs from Example 2 in that the ammonium polyphosphate in the flame-retardant reinforced polypropylene composite is not modified, and the flame-retardant reinforced polypropylene composite prepared has weaker flame retardancy, tensile properties, and impact resistance.

[0088] The difference between Comparative Example 2 and Example 2 is that no carbon microspheres are added to the flame-retardant reinforced polypropylene composite, and the flame retardancy, tensile property and impact resistance of the prepared flame-retardant reinforced polypropylene composite are weaker.

[0089] The difference between Comparative Example 3 and Example 2 is that the hydrotalcite in the flame-retardant reinforced polypropylene composite is not modified, and the flame retardancy, tensile property and impact resistance of the prepared flame-retardant reinforced polypropylene composite are weaker; the impact resistance of 1, 2, 5, 6 is better than that of Comparative Example 3, and the addition of modified hydrotalcite increases the impact resistance of the reinforced polypropylene composite to a certain extent.

[0090] The difference between Comparative Example 4 and Example 2 is that no modified hydrotalcite is added to the flame-retardant reinforced polypropylene composite, and the flame retardancy, tensile property and impact resistance of the prepared flame-retardant reinforced polypropylene composite are weaker; the tensile property of Comparative Example 4 is worse than that of Comparative Example 3, but the impact resistance is relatively better, and the addition of unmodified hydrotalcite can enhance the tensile property of the polypropylene composite, but its introduction directly weakens the impact resistance of the polypropylene composite.

[0091] The difference between Comparative Example 5 and Example 2 is that the raw material components are directly mixed at high speed, put into a double-screw extruder for extrusion granulation and injection molding during the preparation of the flame-retardant reinforced polypropylene composite, and the flame retardancy, tensile property and impact resistance of the prepared flame-retardant reinforced polypropylene composite are weaker.

[0092] The difference between Comparative Example 6 and Example 1 is that the silane coupling agent of the modified ammonium polyphosphate is vinyltrimethoxysilane instead of trimethoxy(3-(4-nitrophenoxy)propyl)silane, and the impact resistance of the prepared flame-retardant reinforced polypropylene composite is weaker.

[0093] The above specific examples further illustrate the purpose, technical solutions and advantages of the present application. It should be understood that the above description is only a specific embodiment of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A process for the preparation of a flame-retardant reinforced polypropylene composite material, characterized in that, The preparation steps include: (1) The raw material components are weighed and prepared according to the corresponding mass fraction, and the raw material components mainly include modified ammonium polyphosphate, carbon microspheres, modified hydrotalcite, melamine cyanurate, polypropylene, and additives; (2) The modified ammonium polyphosphate and carbon microspheres weighed in step (1) are mixed and reacted to obtain a first mixture; (3) The polypropylene and modified hydrotalcite are mixed to obtain a second mixture; (4) The first mixture and the second mixture are mixed and reacted to obtain a third mixture; (5) The third mixture, melamine cyanurate, and additives are mixed, then melt blended, extruded, and granulated on a twin-screw extruder, and then injection molded to obtain.

2. The process for the preparation of a flame retardant reinforced polypropylene composite according to claim 1, characterized in that, The corresponding mass fraction of each raw material component in step (1) is as follows: 6-7 parts by mass of modified ammonium polyphosphate, 1.5-2.5 parts by mass of carbon microspheres, 3.5-3.55 parts by mass of modified hydrotalcite, 19-20 parts by mass of melamine cyanurate, 66.5-67.45 parts by mass of polypropylene, and 1.5 parts by mass of additives.

3. The process for the preparation of a flame retardant reinforced polypropylene composite according to claim 1, characterized in that, The modified ammonium polyphosphate is obtained by modifying ammonium polyphosphate with a silane coupling agent, and the specific preparation steps are as follows: 2-3 parts by mass of silane coupling agent is mixed with 50 parts by mass of water, then 3M hydrochloric acid is added to adjust the pH to 5-6, and then stirred and mixed uniformly, then heated to 84-86℃ while stirring, and then kept stirring for 55-65 min to obtain a mixed solution A; 50 parts by mass of ammonium polyphosphate is mixed with 160 parts by mass of absolute ethanol, and stirred for 18-22 min to obtain a mixed solution B; then the mixed solution B is added to the mixed solution A, then cooled to 48-52℃, and then reacted for 1.5-2.5 h, then filtered, dried, and crushed to pass through a 45μm sieve to obtain the modified ammonium polyphosphate.

4. The process for the preparation of a flame retardant reinforced polypropylene composite according to claim 3, characterized in that, The silane coupling agent at least uses trimethoxy(3-(4-nitrophenoxy)propyl)silane.

5. The process for the preparation of flame retardant reinforced polypropylene composites as claimed in claim 1, wherein, The modified hydrotalcite is obtained by modifying calcium-aluminum hydrotalcite with 1,10-bis(4-benzoxy)decane, and the specific preparation steps are as follows: the hydrotalcite and 1,10-bis(4-benzoxy)decane are placed in an oven at 78-82℃ and dried for 28-32 min, then the dried hydrotalcite and 1,10-bis(4-benzoxy)decane are mixed according to a mass ratio of 3.3-3.35:0.2, then reacted at 118-122℃ for 28-32 min to obtain the modified hydrotalcite.

6. The process for the preparation of flame retardant reinforced polypropylene composites as claimed in claim 1, wherein, The specific steps of step (2) are as follows: the modified ammonium polyphosphate weighed in step (1) is dispersed in 1257-1259 parts by mass of deionized water to obtain a mixed solution C; the mixed solution C is added to a 1mg / mL sodium borohydride solution of 4750-4770 parts by mass, then the carbon microspheres are added, and then stirred and reacted for 18-22 min, then filtered, washed with deionized water for 2-4 times, and then dried to obtain the first mixture.

7. The process for the preparation of flame retardant reinforced polypropylene composites as claimed in claim 1, wherein, The specific steps of the step (3) are as follows: the weighed modified hydrotalcite in step (1) is dispersed in 180-200 parts by mass of xylene and ultrasonically dispersed for 8-12 min to obtain a dispersion of the modified hydrotalcite; the weighed polypropylene in step (1) is dissolved in a solution of 10-20 times the mass of xylene, then the dispersion of the modified hydrotalcite is added dropwise at a drop rate of 1 drop / s under heating to 150℃, and after condensation refluxing under stirring for 23-25 h, the resultant is poured into an equal volume of ethanol for extraction, and the resultant flocculent material is washed with ethanol, filtered, and dried under vacuum for 23-25 h to obtain a second mixture.

8. The process for the preparation of flame retardant reinforced polypropylene composites as claimed in claim 1, wherein, The specific steps of the step (4) are as follows: the second mixture is mixed with the first mixture and 400-500 parts by mass of 1-methyl-2-pyrrolidinone at 0-5℃, ultrasonically dispersed for 8-12 min, and then 0.1-0.12 parts by mass of triethylamine and 0.0002-0.0004 parts by mass of anhydrous lithium chloride are added under stirring for 25-35 min, and then the temperature is raised to 70-80℃ under nitrogen protection, and the resultant is kept at the temperature for 5.5-6.5 h, after which the resultant is precipitated in ice water, filtered, washed with deionized water for 2-4 times, then 5-6 parts by mass of 4M sodium hydroxide is added, and the resultant is reacted at room temperature for 85-95 min, then the resultant is poured into 36% concentrated hydrochloric acid to adjust the pH to neutral, filtered, washed with deionized water for 2-4 times, and then dried at 60℃ for 47-49 h to obtain a third mixture.

9. The process for the preparation of flame retardant reinforced polypropylene composites as claimed in claim 1, wherein, The specific steps of the injection molding of the step (5) are as follows: the granulated polypropylene composite granules are put into an injection molding machine for injection molding at 225-235℃, then cooled in a vacuum cooling water tank at 20℃ for 12-20 s, then kept at 60-120℃ for 120-200 s, and finally cooled in a cooling water tank at 20℃ for 36-60 s.