Flame-retardant polypropylene film and preparation method thereof

Abstract

The invention discloses a flame-retardant polypropylene film and a preparation method thereof, and relates to the technical field of high polymer materials. When the flame-retardant polypropylene film is prepared, dicyandiamide and 3-amino-1-propylene are subjected to a reaction, and allyl guanidine salt is prepared; polypropylene and allyl guanidine salt are subjected to a reaction, and modified polypropylene is prepared; the preparation method comprises the following steps: polymerizing trithio boroxane and diallyl chloride phosphite, and coating the surface of magnesium hydroxide with the polymerized trithio boroxane and diallyl chloride phosphite to prepare modified magnesium hydroxide; the preparation method comprises the following steps: sequentially reacting cellulose with 5-(chloromethyl)-2-pyridylaldehyde and benzoyl hydrazine to prepare modified cellulose; uniformly mixing the modified polypropylene, the modified magnesium hydroxide, the modified cellulose and methylbenzene, and curing and forming to obtain the flame-retardant polypropylene film. The flame-retardant polypropylene film prepared by the invention has excellent flame-retardant, anti-aging, antibacterial and mechanical properties.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, in particular to a flame-retardant polypropylene film and a preparation method thereof. Background Art

[0002] Polypropylene (PP), with its high melting point and excellent overall performance, is one of the most promising thermoplastic polymers today. Compared to other general-purpose thermoplastics, it offers advantages such as low price, low specific gravity, wear resistance, excellent chemical stability, ease of molding, and a wide range of applications. It has been widely used in the chemical, electrical, automotive, construction, and packaging industries. Polypropylene film can be used for packaging food, medicine, daily necessities, medical devices, and electrical appliances. It can also be used to manufacture adhesive tapes, vacuum metallization, radiation protection, anti-counterfeiting substrates, various labels, and printed materials.

[0003] However, polypropylene is highly flammable, releasing significant amounts of heat and smoke during combustion, posing a fire hazard. Furthermore, the tertiary carbon atoms in the polypropylene molecular chain, linked by pendant methyl groups, are susceptible to structural changes in the environment, leading to main chain breakage and subsequent aging of the matrix. Polypropylene's flammability and aging issues have also limited the development and application of polypropylene films. Therefore, it is necessary to improve existing technologies to enhance the flame retardancy and aging resistance of polypropylene films. Summary of the Invention

[0004] The object of the present invention is to provide a flame retardant polypropylene film and a preparation method thereof, so as to solve the problems existing in the prior art.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] A flame-retardant polypropylene film, characterized in that the flame-retardant polypropylene film is prepared by polymerizing trisulfide boroxine and diallyl chlorophosphite to coat the surface of magnesium hydroxide to obtain modified magnesium hydroxide; reacting pre-modified cellulose with benzoyl hydrazide to obtain modified cellulose; and uniformly mixing modified polypropylene, modified magnesium hydroxide, modified cellulose, and toluene, and curing and forming the film.

[0007] The modified polypropylene is prepared by reacting polypropylene and allylguanidine salt;

[0008] The allylguanidine salt is prepared by reacting dicyandiamide and 3-amino-1-propylene;

[0009] The pre-modified cellulose is prepared by reacting cellulose and 5-(chloromethyl)-2-pyridinecarboxaldehyde.

[0010] A method for preparing a flame-retardant polypropylene film, characterized in that the method for preparing the flame-retardant polypropylene film comprises the following preparation steps:

[0011] (1) Polypropylene, allylguanidine salt, and xylene are mixed uniformly in a mass ratio of 1:(0.3-0.4):(10-12), and heated to 128-132°C at a rate of 4-5°C / min under nitrogen protection and stirring at 80-100 r / min. Stirring is continued for 8-10 minutes, and dicumyl peroxide (0.03-0.05 times the mass of polypropylene) is added. Stirring is continued for 3-3.2 hours, and ethyl acetate (3-4 times the volume of xylene) is added and mixed uniformly. The mixture is allowed to stand for 2-3 hours, filtered, and dried at 70-80°C under vacuum for 7-8 hours to obtain modified polypropylene.

[0012] (2) Magnesium hydroxide, 1 / 4 of the polymerizable coating reaction liquid, and 1 / 4 of the catalyst solution are mixed uniformly in a mass ratio of 1:(16-18):(1-2), heated to 70-80°C, stirred at 100-200 r / min for 26-30 minutes, and the remaining polymerizable coating reaction liquid and catalyst solution are added dropwise at a uniform rate within 30 minutes. After the addition is completed, the mixture is stirred and reacted for 2-3 hours, filtered, washed with anhydrous ethanol 3-5 times, and dried at 60-70°C under vacuum conditions for 10-12 hours to obtain modified magnesium hydroxide;

[0013] (3) Pre-modified cellulose, benzoyl hydrazide, and N,N-dimethylacetamide were mixed uniformly in a mass ratio of 1:(2-3):(20-22), stirred at 50-60°C and 100-200 r / min for 2-3 hours, cooled to room temperature, and deionized water 3-4 times the volume of N,N-dimethylacetamide was added and mixed uniformly. The mixture was allowed to stand at 2-4°C for 1-2 hours, filtered, washed with deionized water 3-5 times, and dried at 55-65°C under vacuum conditions for 8-10 hours to obtain modified cellulose.

[0014] (4) Weigh 95-105 parts of modified polypropylene, 4-5 parts of modified magnesium hydroxide, 8-10 parts of modified cellulose, 0.3-0.5 parts of triethylamine, and 130-140 parts of toluene by mass; mix the modified polypropylene, modified magnesium hydroxide, modified cellulose, triethylamine, and toluene evenly, stir at 80-90°C and 50-60 r / min for 10-12 minutes, pour into a polytetrafluoroethylene mold, dry at 60-70°C under vacuum conditions for 8-10 hours, cool to room temperature, and demold to obtain a flame-retardant polypropylene film.

[0015] As an optimization, the preparation method of the allylguanidine salt in step (1) is as follows: dicyandiamide and deionized water are mixed uniformly in a mass ratio of 1: (2.5-2.7) to prepare a dicyandiamide aqueous solution; 3-amino-1-propylene, hydrochloric acid aqueous solution and anhydrous ethanol in an equal molar amount of dicyandiamide are mixed uniformly in a mass ratio of 1: (2-2.2): (8-10), placed in a high-pressure reactor, stirred at 10-30° C. and 100-200 r / min for 8-10 minutes, heated to 78-80° C., and the dicyandiamide aqueous solution is added dropwise at a uniform speed within 15 minutes. After the addition is completed, the stirring reaction is continued for 6-7 hours, and dried at 50-60° C. under vacuum conditions for 8-10 hours to obtain the allylguanidine salt.

[0016] As an optimization, the mass fraction of the hydrochloric acid aqueous solution is 10% to 12%.

[0017] As an optimization, the polypropylene model in step (1) is RP242G.

[0018] As an optimization, the preparation method of the polymerizable coating reaction liquid in step (2) is: trisulfide cycloboroxine and diallyl chlorophosphite are added in a molar ratio of 2:3 to N,N-dimethylformamide with a mass of 8 to 10 times that of trisulfide cycloboroxine to prepare a polymerizable coating reaction liquid.

[0019] As an optimization, the CAS number of the trisulfide boroxine is 28921-59-7; the structural formula is as follows:

[0020]

[0021] As an optimization, the preparation method of the catalyst solution in step (2) is: uniformly mix azobisisobutyronitrile and N,N-dimethylformamide in a mass ratio of 1:(6-8) to prepare a catalyst solution.

[0022] As an optimization, the particle size of the magnesium hydroxide in step (2) is 1000 mesh, the purity is 99.9%, and the manufacturer is Nangong Harbin Institute of Technology New Materials Technology Co., Ltd.

[0023] As an optimization, the preparation method of the pre-modified cellulose in step (3) is as follows: cellulose powder and N,N-dimethylacetamide are uniformly mixed in a mass ratio of 1:(30-40), stirred at 150-160°C and 100-200 r / min for 20-30 min under nitrogen protection, cooled to 98-100°C, anhydrous lithium chloride in an amount of 0.6-0.8 times the mass of cellulose powder is added, and stirring is continued for 1-2 h to obtain a cellulose solution; triethylamine in an amount of 0.02-0.03 times the mass of cellulose powder and 5-(chloromethyl)-2-pyridinecarboxaldehyde in an amount of 0.4-0.6 times the mass of cellulose powder are added to the cellulose solution, the mixture is stirred at 40-50°C and 100-200 r / min for 3-4 h, and dried at 55-65°C under vacuum conditions for 6-7 h to obtain pre-modified cellulose.

[0024] As an optimization, the particle size of the cellulose powder is 50 μm, and the manufacturer is Shanghai Aladdin Biochemical Technology Co., Ltd.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] When preparing the flame-retardant polypropylene film, the present invention comprises the following steps: reacting dicyandiamide and 3-amino-1-propylene to obtain allylguanidine salt; reacting polypropylene and allylguanidine salt to obtain modified polypropylene; polymerizing trisulfide boroxine and diallyl chlorophosphite to coat the surface of magnesium hydroxide to obtain modified magnesium hydroxide; reacting cellulose and 5-(chloromethyl)-2-pyridinecarboxaldehyde to obtain pre-modified cellulose; reacting the pre-modified cellulose and benzoylhydrazide to obtain modified cellulose; and uniformly mixing the modified polypropylene, modified magnesium hydroxide, modified cellulose and toluene, and performing solidification molding to obtain the flame-retardant polypropylene film.

[0027] First, the cyano group on dicyandiamide reacts with the amino group on 3-amino-1-propylene to produce allylguanidine salt. The allylguanidine salt is then grafted onto the molecular side chains of polypropylene via a solution grafting method to produce modified polypropylene, into which guanidine salt and amino groups are introduced. The introduction of guanidine salt can impart excellent antibacterial properties to the flame-retardant polypropylene film. The amino groups introduced into the side chains of the modified polypropylene can react with the P-Cl bonds introduced onto the surface of the modified magnesium hydroxide to form a cross-linked network structure, inhibiting the relative slip between the molecular chains and improving the mechanical properties of the flame-retardant polypropylene film.

[0028] Secondly, the thiol group on trisulfide boroxine reacts with the carbon-carbon double bond on diallyl chlorophosphite, and the reaction is carried out by polymerization and coating on the surface of magnesium hydroxide to obtain modified magnesium hydroxide; organic phosphorus and organic boron as well as P-Cl bonds are introduced into the modified magnesium hydroxide; the organic boron forms a glassy outer layer when the polymer burns, thereby isolating heat and combustible gases, and the organic phosphorus can form a free radical inhibitor in the gas phase, produce an insulating carbon layer, and cool the combustion environment; the introduction of organic phosphorus and organic boron can give the flame-retardant polypropylene film excellent flame retardant properties; the P-Cl bond introduced on the surface of the modified magnesium hydroxide can react with the modified polypropylene The amino groups introduced on the side chains of the molecules can also react with the hydroxyl groups on the modified cellulose to form a cross-linked network structure, inhibiting the relative slip between the molecular chains and giving the flame-retardant polypropylene film excellent mechanical properties. When magnesium hydroxide is decomposed by heat, it absorbs a large amount of heat and produces water vapor, which dilutes the oxygen concentration. The magnesium oxide produced by the decomposition forms a protective layer to block air and heat, thereby improving the flame retardant properties of the polymer. However, magnesium hydroxide is an inorganic material and will agglomerate when directly added to the resin. By polymerizing and coating an organic layer on the surface of the magnesium hydroxide, the compatibility of the magnesium hydroxide with the resin can be improved.

[0029] Finally, some hydroxyl groups on cellulose are reacted with chloromethyl groups on 5-(chloromethyl)-2-pyridinecarboxaldehyde to prepare pre-modified cellulose, and a 2-pyridinecarboxaldehyde structure is introduced into the pre-modified cellulose; the 2-pyridinecarboxaldehyde structure introduced into the pre-modified cellulose undergoes a Schiff base reaction with the amino group on benzoylhydrazide to prepare modified cellulose; a phenylpyridine-2-acylhydrazone structure is generated on the modified cellulose; the phenylpyridine-2-acylhydrazone structure undergoes cis-trans isomerization changes under ultraviolet light, changing from E configuration to Z configuration, and then changes from Z configuration to E configuration under light-proof or heating conditions. This reversible configuration change can absorb ultraviolet light, convert ultraviolet light into harmless energy and release it, thereby improving the anti-aging ability of the flame-retardant polypropylene film. DETAILED DESCRIPTION

[0030] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0031] Example 1:

[0032] A method for preparing a flame-retardant polypropylene film, comprising the following steps:

[0033] (1) Dicyandiamide and deionized water were mixed at a mass ratio of 1:2.5 to prepare a dicyandiamide aqueous solution; 3-amino-1-propylene with an equal molar amount of dicyandiamide, a 10% hydrochloric acid aqueous solution, and anhydrous ethanol were mixed at a mass ratio of 1:2:8, placed in a high-pressure reactor, stirred at 100 rpm for 10 minutes at 10°C, heated to 78°C, and the dicyandiamide aqueous solution was added dropwise at a uniform speed over 15 minutes. After the addition was completed, the reaction was continued with stirring for 7 hours, and dried at 50°C under vacuum conditions. 10h to obtain allylguanidine salt; polypropylene, allylguanidine salt and xylene were mixed uniformly in a mass ratio of 1:0.3:10, and under nitrogen protection, heated to 128°C at a rate of 4°C / min with stirring at 80r / min, and continued to stir for 10min, and dicumyl peroxide (0.03 times the mass of polypropylene) was added, and the stirring reaction was continued for 3.2h, and ethyl acetate (3 times the volume of xylene) was added and mixed uniformly, and the mixture was allowed to stand for 3h, filtered, and dried at 70°C under vacuum for 8h to obtain modified polypropylene;

[0034] (2) Trisulfide cycloboroxine and diallyl chlorophosphite are added in a molar ratio of 2:3 to N,N-dimethylformamide (8 times the mass of trisulfide cycloboroxine) to prepare a polymerizable coating reaction solution; azobisisobutyronitrile and N,N-dimethylformamide are mixed at a mass ratio of 1:6 to prepare a catalyst solution; magnesium hydroxide, 1 / 4 of the polymerizable coating reaction solution, and 1 / 4 of the catalyst solution are mixed at a mass ratio of 1:16:1, heated to 70°C, stirred at 100 r / min for 30 minutes, and the remaining polymerizable coating reaction solution and catalyst solution are added dropwise at a uniform speed within 30 minutes. After the addition is completed, the stirring reaction is continued for 3 hours, filtered, washed with anhydrous ethanol 3 times, and dried at 60°C under vacuum conditions for 12 hours to obtain modified magnesium hydroxide;

[0035] (3) Cellulose powder and N,N-dimethylacetamide were mixed uniformly in a mass ratio of 1:30, stirred at 150°C and 100 r / min for 30 min under nitrogen protection, cooled to 98°C, anhydrous lithium chloride was added in an amount 0.6 times the mass of cellulose powder, and stirred for 2 h to obtain a cellulose solution; triethylamine in an amount 0.02 times the mass of cellulose powder and 5-(chloromethyl)-2-pyridinecarboxaldehyde in an amount 0.4 times the mass of cellulose powder were added to the cellulose solution, and stirred at 40°C and 100 r / min. The pre-modified cellulose was stirred and reacted for 4 hours, and dried at 55°C for 7 hours under vacuum conditions to obtain pre-modified cellulose; the pre-modified cellulose, benzoyl hydrazide, and N,N-dimethylacetamide were mixed uniformly in a mass ratio of 1:2:20, stirred and reacted at 50°C and 100 r / min for 3 hours, cooled to room temperature, and deionized water 3 times the volume of N,N-dimethylacetamide was added and mixed uniformly, and allowed to stand at 2°C for 2 hours, filtered, washed with deionized water 3 times, and dried at 55°C for 10 hours under vacuum conditions to obtain modified cellulose;

[0036] (4) Weigh 95 parts of modified polypropylene, 4 parts of modified magnesium hydroxide, 8 parts of modified cellulose, 0.3 parts of triethylamine, and 130 parts of toluene by mass; mix the modified polypropylene, modified magnesium hydroxide, modified cellulose, triethylamine, and toluene evenly, stir at 80°C and 50 r / min for 12 minutes, pour into a polytetrafluoroethylene mold, dry at 60°C for 10 hours under vacuum conditions, cool to room temperature, and demold to obtain a flame-retardant polypropylene film.

[0037] Example 2:

[0038] A method for preparing a flame-retardant polypropylene film, comprising the following steps:

[0039] (1) Dicyandiamide and deionized water were mixed uniformly at a mass ratio of 1:2.6 to prepare a dicyandiamide aqueous solution; equimolar amounts of dicyandiamide, 3-amino-1-propylene, a hydrochloric acid aqueous solution with a mass fraction of 11%, and anhydrous ethanol were mixed uniformly at a mass ratio of 1:2.1:9, placed in a high-pressure reactor, stirred at 20°C and 150 r / min for 9 minutes, heated to 79°C, and the dicyandiamide aqueous solution was added dropwise at a uniform speed over 15 minutes. After the addition was completed, the stirring reaction was continued for 6.5 hours, and dried at 55°C under vacuum conditions for 9 hours. , to obtain allylguanidine salt; polypropylene, allylguanidine salt, and xylene were mixed uniformly in a mass ratio of 1:0.35:11, and under nitrogen protection, heated to 130°C at a rate of 4.5°C / min with stirring at 90 r / min, and continued to stir for 9 minutes, and dicumyl peroxide (0.04 times the mass of polypropylene) was added, and the stirring reaction was continued for 3.1 hours, and ethyl acetate (3.5 times the volume of xylene) was added and mixed uniformly, and the mixture was allowed to stand for 2.5 hours, filtered, and dried at 75°C under vacuum conditions for 7.5 hours to obtain modified polypropylene;

[0040] (2) Trisulfide cycloboroxine and diallyl chlorophosphite are added in a molar ratio of 2:3 to N,N-dimethylformamide (9 times the mass of trisulfide cycloboroxine) to prepare a polymerizable coating reaction solution; azobisisobutyronitrile and N,N-dimethylformamide are mixed in a mass ratio of 1:7 to prepare a catalyst solution; magnesium hydroxide, 1 / 4 of the polymerizable coating reaction solution, and 1 / 4 of the catalyst solution are mixed in a mass ratio of 1:17:1.5, heated to 75°C, stirred at 150r / min for 28min, and the remaining polymerizable coating reaction solution and catalyst solution are added dropwise at a uniform speed within 30min. After the addition is completed, the stirring reaction is continued for 2.5h, filtered, washed with anhydrous ethanol 4 times, and dried at 65°C under vacuum conditions for 11h to obtain modified magnesium hydroxide;

[0041] (3) Cellulose powder and N,N-dimethylacetamide were mixed in a mass ratio of 1:35, stirred at 155°C and 150 r / min for 25 min under nitrogen protection, cooled to 99°C, anhydrous lithium chloride was added in an amount 0.7 times the mass of cellulose powder, and stirred for 1.5 h to obtain a cellulose solution; triethylamine in an amount 0.025 times the mass of cellulose powder and 5-(chloromethyl)-2-pyridinecarboxaldehyde in an amount 0.5 times the mass of cellulose powder were added to the cellulose solution, stirred at 45°C and 150 r / min for 25 min, and the mixture was stirred for 1.5 h. The pre-modified cellulose was stirred for 3.5 hours and dried at 60°C for 6.5 hours under vacuum conditions to obtain pre-modified cellulose; the pre-modified cellulose, benzoyl hydrazide and N,N-dimethylacetamide were mixed uniformly in a mass ratio of 1:2.5:21, stirred at 55°C and 150r / min for 2.5 hours, cooled to room temperature, and deionized water 3.5 times the volume of N,N-dimethylacetamide was added and mixed uniformly, and allowed to stand at 3°C ​​for 1.5 hours, filtered, washed with deionized water 4 times, and dried at 60°C under vacuum conditions for 9 hours to obtain modified cellulose;

[0042] (4) Weigh 100 parts of modified polypropylene, 4.5 parts of modified magnesium hydroxide, 9 parts of modified cellulose, 0.4 parts of triethylamine, and 135 parts of toluene by mass; mix the modified polypropylene, modified magnesium hydroxide, modified cellulose, triethylamine, and toluene evenly, stir at 85°C and 55 r / min for 11 minutes, pour into a polytetrafluoroethylene mold, dry at 65°C under vacuum conditions for 9 hours, cool to room temperature, and demold to obtain a flame-retardant polypropylene film.

[0043] Example 3:

[0044] A method for preparing a flame-retardant polypropylene film, comprising the following steps:

[0045] (1) Dicyandiamide and deionized water were mixed at a mass ratio of 1:2.7 to prepare a dicyandiamide aqueous solution; equimolar amounts of dicyandiamide, 3-amino-1-propylene, a 12% hydrochloric acid aqueous solution, and anhydrous ethanol were mixed at a mass ratio of 1:2.2:10, placed in a high-pressure reactor, stirred at 30°C and 200 r / min for 8 minutes, heated to 80°C, and the dicyandiamide aqueous solution was added dropwise at a constant speed over 15 minutes. After the addition was completed, the stirring reaction was continued for 6 hours. Under vacuum conditions, 60 ℃ and dried for 8 hours to obtain allylguanidine salt; polypropylene, allylguanidine salt and xylene were mixed uniformly in a mass ratio of 1:0.4:12, and heated to 132℃ at a rate of 5℃ / min under nitrogen protection and stirring at 100r / min, and stirred for 8 minutes, and dicumyl peroxide (0.05 times the mass of polypropylene) was added, and the stirring reaction was continued for 3 hours, and ethyl acetate (4 times the volume of xylene) was added and mixed uniformly, and the mixture was allowed to stand for 2 hours, filtered, and dried at 80℃ under vacuum conditions for 7 hours to obtain modified polypropylene;

[0046] (2) Trisulfide cycloboroxine and diallyl chlorophosphite are added in a molar ratio of 2:3 to N,N-dimethylformamide (10 times the mass of trisulfide cycloboroxine) to prepare a polymerizable coating reaction solution; azobisisobutyronitrile and N,N-dimethylformamide are mixed at a mass ratio of 1:8 to prepare a catalyst solution; magnesium hydroxide, 1 / 4 of the polymerizable coating reaction solution, and 1 / 4 of the catalyst solution are mixed at a mass ratio of 1:18:2, heated to 80°C, stirred at 200 r / min for 26 minutes, and the remaining polymerizable coating reaction solution and catalyst solution are added dropwise at a uniform speed within 30 minutes. After the addition is completed, the stirring reaction is continued for 2 hours, filtered, washed with anhydrous ethanol 5 times, and dried at 70°C under vacuum conditions for 10 hours to obtain modified magnesium hydroxide;

[0047] (3) Cellulose powder and N,N-dimethylacetamide were mixed uniformly in a mass ratio of 1:40, stirred at 160°C and 200 r / min for 20 min under nitrogen protection, cooled to 100°C, anhydrous lithium chloride 0.8 times the mass of cellulose powder was added, and stirring was continued for 1 h to obtain a cellulose solution; triethylamine 0.03 times the mass of cellulose powder and 5-(chloromethyl)-2-pyridinecarboxaldehyde 0.6 times the mass of cellulose powder were added to the cellulose solution, and stirred at 50°C and 200 r / m The mixture was stirred for 3 hours and dried at 65°C under vacuum for 6 hours to obtain pre-modified cellulose; the pre-modified cellulose, benzoyl hydrazide and N,N-dimethylacetamide were mixed uniformly in a mass ratio of 1:3:22, stirred at 60°C and 200 r / min for 2 hours, cooled to room temperature, and deionized water 4 times the volume of N,N-dimethylacetamide was added and mixed uniformly, and allowed to stand at 4°C for 1 hour, filtered, washed with deionized water 5 times, and dried at 65°C under vacuum for 8 hours to obtain modified cellulose;

[0048] (4) Weigh 105 parts of modified polypropylene, 5 parts of modified magnesium hydroxide, 10 parts of modified cellulose, 0.5 parts of triethylamine, and 140 parts of toluene by mass; mix the modified polypropylene, modified magnesium hydroxide, modified cellulose, triethylamine, and toluene evenly, stir at 90°C and 60 r / min for 10 minutes, pour into a polytetrafluoroethylene mold, dry at 70°C under vacuum conditions for 8 hours, cool to room temperature, and demold to obtain a flame-retardant polypropylene film.

[0049] Comparative Example 1:

[0050] The method for preparing the flame-retardant polypropylene film of Comparative Example 1 differs from that of Example 2 in that step (1) is omitted and step (4) is modified as follows: 100 parts of polypropylene, 4.5 parts of modified magnesium hydroxide, 9 parts of modified cellulose, 0.4 parts of triethylamine, and 135 parts of toluene are weighed, by mass; the polypropylene, modified magnesium hydroxide, modified cellulose, triethylamine, and toluene are uniformly mixed, stirred at 85°C and 55 rpm for 11 minutes, poured into a polytetrafluoroethylene mold, dried at 65°C under vacuum for 9 hours, cooled to room temperature, and demolded to produce a flame-retardant polypropylene film. The remaining steps are the same as those of Example 2.

[0051] Comparative Example 2:

[0052] The method for preparing the flame-retardant polypropylene film of Comparative Example 2 differs from that of Example 2 in that step (2) is omitted and step (4) is modified as follows: 100 parts of modified polypropylene, 4.5 parts of magnesium hydroxide, 9 parts of modified cellulose, 0.4 parts of triethylamine, and 135 parts of toluene are weighed, by mass; the modified polypropylene, magnesium hydroxide, modified cellulose, triethylamine, and toluene are uniformly mixed, stirred at 85°C and 55 rpm for 11 minutes, poured into a polytetrafluoroethylene mold, dried at 65°C under vacuum for 9 hours, cooled to room temperature, and demolded to produce a flame-retardant polypropylene film. The remaining steps are the same as those of Example 2.

[0053] Comparative Example 3:

[0054] The method for preparing the flame-retardant polypropylene film of Comparative Example 3 differs from that of Example 2 in that step (2) is omitted and step (4) is modified as follows: 100 parts by mass of modified polypropylene, 9 parts of modified cellulose, 0.4 parts of triethylamine, and 135 parts of toluene are weighed; the modified polypropylene, modified cellulose, triethylamine, and toluene are uniformly mixed, stirred at 85°C and 55 rpm for 11 minutes, poured into a polytetrafluoroethylene mold, dried at 65°C under vacuum for 9 hours, cooled to room temperature, and demolded to produce a flame-retardant polypropylene film. The remaining steps are the same as those of Example 2.

[0055] Comparative Example 4:

[0056] The method for preparing the flame-retardant polypropylene film of Comparative Example 4 differs from that of Example 2 in that step (3) is omitted and step (4) is modified as follows: 100 parts of modified polypropylene, 4.5 parts of modified magnesium hydroxide, 9 parts of cellulose powder, 0.4 parts of triethylamine, and 135 parts of toluene are weighed, by mass; the modified polypropylene, modified magnesium hydroxide, cellulose powder, triethylamine, and toluene are uniformly mixed, stirred at 85°C and 55 rpm for 11 minutes, poured into a polytetrafluoroethylene mold, dried at 65°C under vacuum for 9 hours, cooled to room temperature, and demolded to produce a flame-retardant polypropylene film. The remaining steps are the same as those of Example 2.

[0057] Test Example 1

[0058] Flame retardant performance test

[0059] Test method: The examples and comparative examples were prepared into standard specimens according to GB / T 2406.2, and the limiting oxygen index of the standard specimens was tested. The results are shown in Table 1.

[0060] Table 1

[0061] Limiting oxygen index (%) Limiting oxygen index (%) Example 1 29.41 Comparative Example 1 29.38 Example 2 30.26 Comparative Example 2 24.67 Example 3 30.09 Comparative Example 3 18.13 Comparative Example 4 29.19

[0062] From the comparison of the experimental data of Examples 1 to 3 and Comparative Examples 1 to 4 in Table 1, it can be found that the flame-retardant polypropylene film prepared in the present invention has good flame-retardant properties.

[0063] By comparison, the limiting oxygen index of Examples 1 to 3 is greater than that of Comparative Examples 2 to 3, and the limiting oxygen index of Comparative Example 2 is greater than that of Comparative Example 3. This indicates that the thiol group on trisulfide boroxine reacts with the carbon-carbon double bond on diallyl chlorophosphite, and the polymer is coated on the surface of magnesium hydroxide to produce modified magnesium hydroxide; organic phosphorus and organic boron are introduced into the modified magnesium hydroxide; the organic boron forms a glassy outer layer when the polymer burns, thereby isolating heat and combustible gases, and the organic phosphorus can form a free radical inhibitor in the gas phase, producing an insulating carbon layer and cooling the combustion environment; the introduction of organic phosphorus and organic boron can impart excellent flame retardant properties to the flame-retardant polypropylene film. Adding magnesium hydroxide to the flame-retardant polypropylene film can improve the flame retardant properties of the flame-retardant polypropylene film; this is because when magnesium hydroxide decomposes under heat, it absorbs a large amount of heat and also produces water vapor, which dilutes the oxygen concentration. The magnesium oxide produced by the decomposition forms a protective layer that blocks air and heat, thereby improving the flame retardant properties of the polymer.

[0064] Test Example 2

[0065] Antibacterial performance testing

[0066] Test method: Cut the examples and comparative examples into 20mm×20mm samples and sterilize them with ultraviolet radiation for 5h; activate the Escherichia coli strain and prepare it to a concentration of 3×10 4 CFU / ml bacterial suspension; place the sample in the bacterial suspension and shake at 200 rpm for 10 minutes at room temperature. Dilute 1 ml of the bacterial suspension to 100-fold. Inoculate 1 ml of the diluted bacterial suspension onto agar medium and incubate at 37°C for 16 hours. Count the colonies according to the method in GB / T 15979 and calculate the inhibition rate. The results are shown in Table 2.

[0067] Table 2

[0068] Antibacterial rate (%) Antibacterial rate (%) Example 1 99.81 Comparative Example 1 74.33 Example 2 99.83 Comparative Example 2 99.76 Example 3 99.77 Comparative Example 3 99.65 Comparative Example 4 29.73

[0069] From the comparison of the experimental data of Examples 1 to 3 and Comparative Examples 1 to 4 in Table 2, it can be found that the flame-retardant polypropylene film prepared in the present invention has good antibacterial properties.

[0070] By comparison, the antibacterial rates of Examples 1 to 3 are greater than that of Comparative Example 1, indicating that the cyano group on dicyandiamide reacts with the amino group on 3-amino-1-propylene to prepare allylguanidine salt; the allylguanidine salt is grafted onto the molecular side chain of polypropylene by a solution grafting method to prepare modified polypropylene, and the guanidine salt is introduced into the molecular side chain of the modified polypropylene; the introduction of the guanidine salt can give the flame-retardant polypropylene film excellent antibacterial properties.

[0071] Test Example 3

[0072] Testing of mechanical properties and anti-aging performance

[0073] Test Method: Standard bars made from the examples and comparative examples were prepared according to GB / T 1040 and their tensile strength (M) was measured. The standard bars were then irradiated with a xenon arc lamp for 14 days and their tensile strength (N) was measured. The change in tensile strength of the examples and comparative examples before and after UV aging was calculated as (MN) / M × 100%. The results are shown in Table 3.

[0074] Table 3

[0075]

[0076] From the comparison of the experimental data of Examples 1 to 3 and Comparative Examples 1 to 4 in Table 3, it can be found that the flame-retardant polypropylene film prepared in the present invention has good mechanical properties and anti-aging properties.

[0077] By comparison, the tensile strength of Examples 1 to 3 is greater than that of Comparative Example 1, indicating that the cyano group on dicyandiamide reacts with the amino group on 3-amino-1-propylene to prepare allylguanidine salt; the allylguanidine salt is grafted onto the molecular side chain of polypropylene by a solution grafting method to prepare modified polypropylene, and amino groups are introduced into the molecular side chain of the modified polypropylene; the amino groups introduced into the side chain of the modified polypropylene can react with the P-Cl bond introduced on the surface of the modified magnesium hydroxide to form a cross-linked network structure, thereby inhibiting the relative slip between molecular chains and improving the mechanical properties of the flame-retardant polypropylene film.

[0078] By comparison, the tensile strength of Examples 1 to 3 is greater than that of Comparative Examples 2 to 3, indicating that the thiol group on trisulfide boroxine reacts with the carbon-carbon double bond on diallyl chlorophosphite and is polymerized and coated on the surface of magnesium hydroxide to prepare modified magnesium hydroxide; P-Cl bonds are introduced on the modified magnesium hydroxide; the P-Cl bonds introduced on the surface of the modified magnesium hydroxide can react with the amino groups introduced on the side chains of the modified polypropylene molecules, and can also react with the hydroxyl groups on the modified cellulose to form a cross-linked network structure, inhibit the relative slip between the molecular chains, and impart excellent mechanical properties to the flame-retardant polypropylene film.

[0079] By comparison, the rate of change of tensile strength in Examples 1 to 3 is less than that in Comparative Example 4, indicating that pre-modified cellulose is prepared by reacting some hydroxyl groups on cellulose with chloromethyl groups on 5-(chloromethyl)-2-pyridinecarboxaldehyde, and a 2-pyridinecarboxaldehyde structure is introduced into the pre-modified cellulose; the 2-pyridinecarboxaldehyde structure introduced into the pre-modified cellulose undergoes a Schiff base reaction with the amino group on benzoylhydrazide to prepare modified cellulose; a phenylpyridine-2-acylhydrazone structure is generated on the modified cellulose; the phenylpyridine-2-acylhydrazone structure undergoes cis-trans isomerization change from E configuration to Z configuration under ultraviolet light irradiation, and then changes from Z configuration to E configuration under light-proof or heating conditions. This reversible configuration change can absorb ultraviolet light, convert the ultraviolet light into harmless energy and release it, thereby improving the aging resistance of the flame-retardant polypropylene film.

[0080] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A flame retardant polypropylene film, characterized in that: The flame-retardant polypropylene film is prepared by polymerizing trithioboroxine and diallyl chlorophosphite on the surface of magnesium hydroxide to obtain modified magnesium hydroxide; reacting pre-modified cellulose and benzoyl hydrazide to obtain modified cellulose; and uniformly mixing modified polypropylene, modified magnesium hydroxide, modified cellulose and toluene, and curing and forming the film. The modified polypropylene is prepared by reacting polypropylene and allylguanidine salt; The allylguanidine salt is prepared by reacting dicyandiamide and 3-amino-1-propylene; The pre-modified cellulose is prepared by reacting cellulose and 5-(chloromethyl)-2-pyridinecarboxaldehyde.

2. A method for preparing a flame retardant polypropylene film, characterized in that: The method for preparing the flame retardant polypropylene film comprises the following preparation steps: (1) Polypropylene, allylguanidine salt and xylene are mixed uniformly in a mass ratio of 1:(0.3-0.4):(10-12), and the mixture is heated to 128-132°C at a rate of 4-5°C / min under nitrogen protection and stirring at 80-100 r / min, and the stirring is continued for 8-10 min. Diisopropyl peroxide in an amount of 0.03-0.05 times the mass of polypropylene is added, and the stirring reaction is continued for 3-3.2 h. Ethyl acetate in an amount of 3-4 times the volume of xylene is added and mixed uniformly, and the mixture is allowed to stand for 2-3 h, filtered, and dried at 70-80°C under vacuum conditions for 7-8 h to obtain modified polypropylene. (2) Mix magnesium hydroxide, 1 / 4 of the polymerizable coating reaction liquid, and 1 / 4 of the catalyst solution in a mass ratio of 1:(16-18):(1-2), heat to 70-80°C, stir at 100-200 r / min for 26-30 min, add the remaining polymerizable coating reaction liquid and catalyst solution dropwise at a uniform rate within 30 min, continue stirring for 2-3 h after the addition is complete, filter, wash with anhydrous ethanol 3-5 times, and dry at 60-70°C for 10-12 h under vacuum conditions to obtain modified magnesium hydroxide; (3) Pre-modified cellulose, benzoyl hydrazide, and N,N-dimethylacetamide are mixed uniformly in a mass ratio of 1:(2-3):(20-22), stirred at 50-60° C. and 100-200 r / min for 2-3 h, cooled to room temperature, deionized water 3-4 times the volume of N,N-dimethylacetamide is added and mixed uniformly, allowed to stand at 2-4° C. for 1-2 h, filtered, washed with deionized water 3-5 times, and dried at 55-65° C. under vacuum conditions for 8-10 h to obtain modified cellulose; (4) Weigh 95-105 parts of modified polypropylene, 4-5 parts of modified magnesium hydroxide, 8-10 parts of modified cellulose, 0.3-0.5 parts of triethylamine, and 130-140 parts of toluene by mass; mix the modified polypropylene, modified magnesium hydroxide, modified cellulose, triethylamine, and toluene evenly, stir at 80-90° C. and 50-60 r / min for 10-12 min, pour into a polytetrafluoroethylene mold, dry at 60-70° C. under vacuum conditions for 8-10 h, and demold after cooling to room temperature to obtain a flame-retardant polypropylene film.

3. The method for preparing a flame-retardant polypropylene film according to claim 2, characterized in that: The preparation method of the allylguanidine salt in step (1) is as follows: dicyandiamide and deionized water are mixed uniformly at a mass ratio of 1:(2.5-2.7) to prepare a dicyandiamide aqueous solution; 3-amino-1-propylene, hydrochloric acid aqueous solution and anhydrous ethanol in an equal molar amount of dicyandiamide are mixed uniformly at a mass ratio of 1:(2-2.2):(8-10), placed in a high-pressure reactor, stirred at 10-30° C. and 100-200 r / min for 8-10 min, heated to 78-80° C., and the dicyandiamide aqueous solution is added dropwise at a uniform speed within 15 min. After the addition is completed, the stirring reaction is continued for 6-7 h, and dried at 50-60° C. under vacuum conditions for 8-10 h to obtain the allylguanidine salt.

4. The method for preparing a flame retardant polypropylene film according to claim 3, characterized in that: The mass fraction of the hydrochloric acid aqueous solution is 10% to 12%.

5. The method for preparing a flame-retardant polypropylene film according to claim 2, characterized in that: The polypropylene model in step (1) is RP242G.

6. The method for preparing a flame retardant polypropylene film according to claim 2, characterized in that: The preparation method of the polymerizable coating reaction liquid in step (2) is as follows: trisulfide cycloboroxine and diallyl chlorophosphite are added in a molar ratio of 2:3 to N,N-dimethylformamide which is 8 to 10 times the mass of trisulfide cycloboroxine to prepare a polymerizable coating reaction liquid.

7. The method for preparing a flame-retardant polypropylene film according to claim 2, characterized in that: The preparation method of the catalyst solution in step (2) is as follows: azobisisobutyronitrile and N,N-dimethylformamide are uniformly mixed in a mass ratio of 1:(6-8) to prepare a catalyst solution.

8. The method for preparing a flame retardant polypropylene film according to claim 2, characterized in that: The particle size of the magnesium hydroxide in step (2) is 1000 mesh and the purity is 99.9%.

9. The method for preparing a flame-retardant polypropylene film according to claim 2, characterized in that: The preparation method of the pre-modified cellulose in step (3) is as follows: cellulose powder and N,N-dimethylacetamide are uniformly mixed in a mass ratio of 1:(30-40), stirred at 150-160°C and 100-200 r / min for 20-30 min under nitrogen protection, cooled to 98-100°C, anhydrous lithium chloride is added in an amount of 0.6-0.8 times the mass of the cellulose powder, and stirred for 1-2 h to obtain a cellulose solution; triethylamine in an amount of 0.02-0.03 times the mass of the cellulose powder and 5-(chloromethyl)-2-pyridinecarboxaldehyde in an amount of 0.4-0.6 times the mass of the cellulose powder are added to the cellulose solution, stirred at 40-50°C and 100-200 r / min for 3-4 h, and dried at 55-65°C under vacuum conditions for 6-7 h to obtain the pre-modified cellulose.

10. The method for preparing a flame retardant polypropylene film according to claim 9, characterized in that: The particle size of the cellulose powder is 50 μm.

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