Preparation method of antistatic and antibacterial modified polypropylene particles

Abstract

The present invention discloses a preparation method of antistatic and antibacterial modified polypropylene particles, which relates to the technical field of polymer materials. In the present invention, hydrogen peroxide is used to hydroxylate the terminal group of 3-bromo-4-vinylpyridine, so as to carry out an esterification reaction with carboxyl-terminated polypropylene to form an amphiphilic block copolymer, and quaternization is achieved through bromoethane, thereby realizing antibacterial and antistatic properties. Thus, polypropylene is blended and modified to achieve long-term antibacterial and antistatic properties. Multi-walled carbon nanotubes are modified by instantaneous oxidative flame, so as to interact with silver ions to enhance the antistatic and antibacterial properties, filled in the polypropylene matrix, and annealed to promote the dispersion of the filler in the matrix. At the same time, through pressurization, the stability of the whole system is enhanced, and the durability of antistatic and antibacterial properties is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and specifically to a preparation method of antistatic and antibacterial modified polypropylene particles. Background Art

[0002] Polypropylene (PP) is a colorless, odorless, non-toxic, semi-transparent thermoplastic general plastic polymerized from propylene. Due to its practical economy, it has currently developed into the second largest thermoplastic resin globally and has been widely used in industries such as automotive, household appliances, packaging, medical, fibers, and building materials. One of the biggest defects of ordinary PP is that it is extremely prone to generating static electricity. Due to the non-polar structure and excellent electrical insulation properties of polypropylene, during industrial production and applications, static electricity is easily accumulated on its surface, leading to dust absorption, electric shock, combustion, and even explosion, which brings harm to industrial and agricultural production and daily life. According to relevant research, static electricity is one of the main causes of fires and explosions, and the losses caused by static electricity worldwide reach up to billions of dollars annually.

[0003] Therefore, how to reduce and eliminate the static electricity hazards of polypropylene plastics and their products has become an urgent technical issue to be solved currently. At the same time, with the development of plastic modification technology, polypropylene is widely used in fields such as food packaging, textiles, biomedicine, and medical equipment, and these fields require avoiding bacterial infection and disease transmission. Moreover, with the gradual penetration of the concept of healthy consumption into people's hearts, the market prospect of using antibacterial polypropylene and other plastic products is broad. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method of antistatic and antibacterial modified polypropylene particles to solve the problems existing in the prior art.

[0005] To solve the above technical problems, the present invention provides the following technical solution: A preparation method of antistatic and antibacterial modified polypropylene particles, comprising the following preparation steps:

[0006] (1) Heat deionized water to 78 - 90 °C, and simultaneously dropwise add hydrogen peroxide and 3-bromo-4-vinylpyridine, react at 80 °C for 2.5 - 4 h, cool to room temperature, first dissolve with methanol, then precipitate with anhydrous ether, pour off the supernatant, and vacuum dry at 60 °C for 18 - 30 h to obtain hydroxylated 3-bromo-4-vinylpyridine;

[0007] (2) Dissolve carboxyl-terminated polypropylene with a molecular weight of 4×10 3 and hydroxylated 3-bromo-4-vinylpyridine in cyclohexanone, add 2-chloro-1-methylpyridinium iodide and triethylamine, heat to 120 °C, react for 8.5 - 11 h, cool to room temperature, filter, take the solid, use methanol as the extraction agent, extract for 40 - 60 h, and vacuum dry at 60 °C for 18 - 30 h to obtain a block copolymer;

[0008] (3) Dissolve the block copolymer in cyclohexanone, add ethyl bromide, reflux for 4 h, filter, take the solid, dry at 60 °C for 5 - 10 h, add polypropylene with a molecular weight of 9×10 4 and xylene, heat to 80 - 110 °C, stir at 30 - 70 rpm for 30 - 50 min, dry at 120 °C for 2 - 5 h to obtain modified polypropylene;

[0009] (4) Conduct instantaneous oxidation flame treatment on multi - walled carbon nanotubes, with the flame temperature being 1500 - 2800 °C. Subsequently, add an aqueous solution of 10 wt% potassium sodium tartrate with a mass 50 - 100 times that of the multi - walled carbon nanotubes, ultrasonicate at 21 kHz for 8 - 15 min, heat to 40 °C, stir at 60 - 120 rpm for 20 - 40 min, add a silver ammonia solution with a mass 5 - 10 times that of the multi - walled carbon nanotubes dropwise at 4 mL / min, continue stirring for 10 - 20 min, wash with deionized water 3 - 8 times, and vacuum - dry at 70 °C for 10 - 15 h to obtain carbon nanotube - supported silver nanoparticles;

[0010] (5) Mix the carbon nanotube - supported silver nanoparticles and modified polypropylene in a mass ratio of 10:0.5 - 1.5, heat to 170 - 188 °C, conduct melt blending at a rotation speed of 15 - 30 rpm for 10 - 20 min, and then anneal and extrude into pellets to obtain antistatic and antibacterial modified polypropylene pellets.

[0011] Further, the dropping rate in step (1) is 1 - 3 mL / min.

[0012] Further, the mass ratio of deionized water, hydrogen peroxide, and 3 - bromo - 4 - vinylpyridine in step (1) is 15:8 - 11:2.5 - 3.5.

[0013] Further, the preparation method of the carboxyl - terminated polypropylene with a molecular weight of 4×10 3 in step (2): Mix polypropylene with a molecular weight of 9×10 4 and 95 wt% nitric acid aqueous solution in a mass ratio of 1:4, heat to reflux at 110 °C, stir at 150 - 300 rpm for 8 h, cool to room temperature, rinse with water and acetone in sequence until the pH of the washing liquid is 6, and dry at 50 - 80 °C for 7 - 10 h to obtain it.

[0014] Further, the mass ratio of the carboxyl - terminated polypropylene with a molecular weight of 4×10 3 , hydroxylated 3 - bromo - 4 - vinylpyridine, cyclohexanone, 2 - chloro - 1 - methylpyridinium iodide, and triethylamine in step (2) is 1:2 - 3:50:2 - 3:2.

[0015] Further, the block copolymer, cyclohexanone, ethyl bromide, and polypropylene with a molecular weight of 9×10 4The mass ratio of polypropylene to xylene is 0.3:6:0.6:8 to 10:50 to 100.

[0016] Further, the preparation method of the silver ammonia solution described in step (4): Mix 2wt% silver nitrate aqueous solution and 2wt% ammonia aqueous solution according to a mass ratio of 1:0.5, then adjust the pH of the solution to 11 with ammonia water, heat up to 35 - 45°C, and mix evenly to obtain.

[0017] Further, the vacuum degree of the vacuum drying described in step (1), step (2) and step (4) is all 0.2 - 1 kPa.

[0018] Further, the process parameters of the annealing described in step (5): The temperature is 120 - 180°C, the pressure is 270 - 370 MPa, and the time is 80 - 150 min.

[0019] Further, the process parameters of the extrusion granulation described in step (5): The screw diameter is 20 mm, the length - diameter ratio is 25:1, the temperatures of the three sections and the head are 170, 180, 200, 220°C respectively, and the shear rate is 80 - 150 rpm.

[0020] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0021] The modified polypropylene particles of the present invention are first prepared by modifying polypropylene with an amphiphilic block copolymer, then filled with carbon nanotubes loaded with nano - silver, and finally annealed to achieve the effects of antibacterial and antistatic.

[0022] First, 3 - bromo - 4 - vinylpyridine is initiated by hydrogen peroxide to undergo free - radical polymerization, and at the same time, its terminal groups are oxidized to achieve hydroxylation. Then, it undergoes an esterification reaction with low - molecular - weight polypropylene with double - terminal carboxyl groups, introducing a chain segment of 3 - bromo - 4 - vinylpyridine into the polypropylene main chain to form an amphiphilic block copolymer. Through bromoethane, it reacts with the nitrogen atom on the pyridine ring in the 3 - bromo - 4 - vinylpyridine chain segment to generate a quaternary ammonium salt, thereby realizing the antibacterial and antistatic properties of the matrix. Thus, the polypropylene is blended and modified. Due to the presence of the polypropylene chain segment, the macromolecular modifier is difficult to detach from the matrix, achieving long - term antibacterial. And during the processing process, it is enriched and arranged on the side facing the air, and through absorbing moisture and the action of its own ions, a continuous and uniform conductive layer is formed on the surface of the matrix, achieving long - term antistatic.

[0023] Secondly, flame heat treatment is used to modify the surface of multi-walled carbon nanotubes. Through an instantaneous high-temperature oxidation flame, low-molecular substances, oil stains, and weak interfacial layers adsorbed on the surface are removed, generating a large number of free radicals and plasmas on the surface, and then polar groups are formed, which interact with silver ions, thereby loading silver nanoparticles. The two come into contact with each other to form a tunneling effect, enhancing the conductivity of the matrix and improving the antistatic and antibacterial properties. Then, it is filled into the polypropylene matrix and annealed. At a relatively high annealing temperature, the molecular chains in some amorphous regions of polypropylene gradually thaw over time, resulting in the slippage of solid chains and the formation of crystalline chains in a helical shape. The stronger the mobility of the molecular chains in the amorphous region, the more rearrangement crystallization occurs, thus promoting the good dispersion of the filler in the polypropylene matrix and forming smaller micro-interfaces, achieving long-term antistatic and antibacterial properties. At the same time, through pressurization, the bromine atoms on 3-bromo-4-vinylpyridine are decomposed, thereby enhancing the antibacterial property of the matrix. Meanwhile, the system density is increased, the molecular chain spacing is reduced, the nano-filler is fixed, and the stability of the entire system is enhanced, further improving the durability of antistatic and antibacterial properties. Detailed implementation mode

[0024] The following will combine the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0025] In order to more clearly illustrate the method provided by the present invention, the following examples are used for detailed description. The test methods for each index of the antistatic and antibacterial modified polypropylene particles prepared in the following examples are as follows:

[0026] The antistatic and antibacterial modified polypropylene particles are hot-pressed into a film with a thickness of 500 μm at 150 °C.

[0027] Antibacterial property: Samples of the same size from the examples and comparative examples are taken and the antibacterial rate is detected with reference to GB / T 21510, and then left standing for 60 days, and the antibacterial rate is detected again.

[0028] Antistatic property: Samples of the same size from the examples and comparative examples are taken and the surface resistivity is detected with reference to GB 1410, and then left standing for 60 days, and the surface resistivity is detected again.

[0029] Example 1; (1) Heat deionized water to 78 °C, and at the same time, dropwise add hydrogen peroxide and 3-bromo-4-vinylpyridine at a rate of 1 mL / min. React at 80 °C for 2.5 h, cool to room temperature, first dissolve with methanol, then precipitate with anhydrous ether, pour off the supernatant, and dry at 60 °C under a vacuum of 0.2 kPa for 18 h to obtain hydroxylated 3-bromo-4-vinylpyridine; the mass ratio of deionized water, hydrogen peroxide, and 3-bromo-4-vinylpyridine is 15:8:2.5;

[0030] (2) Mix polypropylene with a molecular weight of 9×10 4 and 95 wt% aqueous nitric acid solution in a mass ratio of 1:4, heat to 110 °C for reflux, stir at 150 rpm for 8 h, cool to room temperature, wash successively with water and acetone until the pH of the washing liquid is 6, and dry at 50 °C for 7 h to obtain carboxyl-terminated polypropylene with a molecular weight of 4×10 3 ; Dissolve carboxyl-terminated polypropylene with a molecular weight of 4×10 3 and hydroxylated 3-bromo-4-vinylpyridine in cyclohexanone, add 2-chloro-1-methylpyridinium iodide and triethylamine, heat to 120 °C, react for 8.5 h, cool to room temperature, filter, take the solid, use methanol as the extraction agent, extract for 40 h, and dry at 60 °C under a vacuum of 0.2 kPa for 18 h to obtain a block copolymer; the mass ratio of carboxyl-terminated polypropylene with a molecular weight of 4×10 3 , hydroxylated 3-bromo-4-vinylpyridine, cyclohexanone, 2-chloro-1-methylpyridinium iodide, and triethylamine is 1:2:50:2:2;

[0031] (3) Dissolve the block copolymer in cyclohexanone, add bromoethane, reflux and react for 4 h, filter, take the solid, dry at 60 °C for 5 h, add polypropylene with a molecular weight of 9×10 4 and xylene, heat to 80 °C, stir at 30 rpm for 30 min, and dry at 120 °C for 2 h to obtain modified polypropylene; the mass ratio of the block copolymer, cyclohexanone, bromoethane, polypropylene with a molecular weight of 9×10 4 and xylene is 0.3:6:0.6:8:50;

[0032] (4) Mix an aqueous solution of 2 wt% silver nitrate and an aqueous solution of 2 wt% ammonia water at a mass ratio of 1:0.5, then adjust the pH of the solution to 11 with ammonia water, heat up to 35 °C, mix well to obtain a silver ammonia solution; conduct an instantaneous oxidation flame treatment on multi-walled carbon nanotubes with a flame temperature of 1500 °C, then add an aqueous solution of 10 wt% potassium sodium tartrate which is 50 times the mass of the multi-walled carbon nanotubes, ultrasonicate at 21 kHz for 8 min, heat up to 40 °C, stir at 60 rpm for 20 min, add dropwise the silver ammonia solution which is 5 times the mass of the multi-walled carbon nanotubes at 4 mL / min, continue stirring for 10 min, wash 3 times with deionized water, and dry at 70 °C under a vacuum of 0.2 kPa for 10 h to obtain carbon nanotube-supported silver nanoparticles;

[0033] (5) Mix carbon nanotube-supported silver nanoparticles and modified polypropylene at a mass ratio of 10:0.5, heat up to 170 °C, conduct melt blending at a rotation speed of 15 rpm for 10 min, then anneal for 80 min under the conditions of a temperature of 120 °C and a pressure of 270 MPa, and then extrude and pelletize. Its process parameters: the screw diameter is 20 mm, the length-diameter ratio is 25:1, the temperatures of the three sections and the die head are 170, 180, 200, 220 °C respectively, and the shear rate is 80 rpm to obtain antistatic antibacterial modified polypropylene particles.

[0034] Example 2; (1) Heat deionized water to 82 °C, and at the same time add dropwise hydrogen peroxide and 3-bromo-4-vinylpyridine at 2 mL / min, react at 80 °C for 3 h, cool to room temperature, first dissolve with methanol, then precipitate with anhydrous ether, pour off the supernatant, and dry at 60 °C under a vacuum of 0.5 kPa for 24 h to obtain hydroxylated 3-bromo-4-vinylpyridine; the mass ratio of the deionized water, hydrogen peroxide, and 3-bromo-4-vinylpyridine is 15:9.5:3;

[0035] (2) Mix polypropylene with a molecular weight of 9×10 4 and 95 wt% nitric acid aqueous solution at a mass ratio of 1:4, heat up to 110 °C for reflux, stir at 230 rpm for 8 h, cool to room temperature, wash successively with water and acetone until the pH of the washing solution is 6, and dry at 65 °C for 8 h to obtain end-carboxyl polypropylene with a molecular weight of 4×10 3 ; Dissolve end-carboxyl polypropylene with a molecular weight of 4×10 3 and hydroxylated 3-bromo-4-vinylpyridine in cyclohexanone, add 2-chloro-1-methylpyridinium iodide and triethylamine, heat up to 120 °C, react for 9 h, cool to room temperature, filter, take the solid, use methanol as the extraction agent, extract for 50 h, and dry at 60 °C under a vacuum of 0.5 kPa for 24 h to obtain a block copolymer; the molecular weight of the 3The mass ratio of the carboxyl-terminated polypropylene, hydroxylated 3-bromo-4-vinylpyridine, cyclohexanone, 2-chloro-1-methylpyridinium iodide, and triethylamine is 1:2.5:50:2.5:2;

[0036] (3) Dissolve the block copolymer in cyclohexanone, add ethyl bromide, reflux for 4 h, filter, take the solid, dry at 60 °C for 7 h, add polypropylene with a molecular weight of 9×10 4 and xylene, heat up to 90 °C, stir at 50 rpm for 40 min, dry at 120 °C for 4 h to obtain modified polypropylene; the mass ratio of the block copolymer, cyclohexanone, ethyl bromide, polypropylene with a molecular weight of 9×10 4 and xylene is 0.3:6:0.6:9:75;

[0037] (4) Mix the 2 wt% silver nitrate aqueous solution and 2 wt% ammonia aqueous solution in a mass ratio of 1:0.5, then adjust the pH of the solution to 11 with ammonia water, heat up to 40 °C, and mix well to obtain a silver ammonia solution; perform an instantaneous oxidation flame treatment on the multi-walled carbon nanotubes, with the flame temperature being 2200 °C, then add a 10 wt% potassium sodium tartrate aqueous solution 75 times the mass of the multi-walled carbon nanotubes, ultrasonicate at 21 kHz for 11 min, heat up to 40 °C, stir at 90 rpm for 30 min, dropwise add a silver ammonia solution 8 times the mass of the multi-walled carbon nanotubes at 4 mL / min, continue to stir for 15 min, wash 5 times with deionized water, and dry at 70 °C and a vacuum degree of 0.5 kPa for 12 h to obtain carbon nanotube-supported silver nanoparticles;

[0038] (5) Mix the carbon nanotube-supported silver nanoparticles and the modified polypropylene in a mass ratio of 10:1, heat up to 180 °C, perform melt blending at a rotation speed of 20 rpm for 15 min, then anneal at a temperature of 150 °C and a pressure of 320 MPa for 110 min, and then extrude and pelletize. The process parameters are: the screw diameter is 20 mm, the length-diameter ratio is 25:1, the temperatures of the three sections and the die head are 170, 180, 200, 220 °C respectively, and the shear rate is 110 rpm to obtain antistatic and antibacterial modified polypropylene pellets.

[0039] Example 3; (1) Heat the deionized water to 90 °C, and at the same time dropwise add hydrogen peroxide and 3-bromo-4-vinylpyridine at 3 mL / min, react at 80 °C for 4 h, cool to room temperature, first dissolve with methanol, then precipitate with anhydrous ether, pour out the supernatant, and dry at 60 °C and a vacuum degree of 1 kPa for 30 h to obtain hydroxylated 3-bromo-4-vinylpyridine; the mass ratio of the deionized water, hydrogen peroxide, and 3-bromo-4-vinylpyridine is 15:11:3.5;

[0040] (2) Polypropylene with a molecular weight of 9×10 4Polypropylene and 95 wt% aqueous nitric acid solution were mixed at a mass ratio of 1:4, heated to 110 °C for reflux, stirred at 300 rpm for 8 h, cooled to room temperature, rinsed successively with water and acetone until the pH of the washing solution was 6, and dried at 80 °C for 10 h to obtain carboxyl-terminated polypropylene with a molecular weight of 4×10 3 The carboxyl-terminated polypropylene with a molecular weight of 4×10 3 The carboxyl-terminated polypropylene and hydroxylated 3-bromo-4-vinylpyridine were dissolved in cyclohexanone, 2-chloro-1-methylpyridinium iodide and triethylamine were added, the temperature was raised to 120 °C, and the reaction was carried out for 11 h. After cooling to room temperature, filtration was carried out. The solid was taken, and methanol was used as the extraction agent for extraction for 60 h, and dried at 60 °C and a vacuum degree of 1 kPa for 30 h to obtain a block copolymer; the mass ratio of the carboxyl-terminated polypropylene with a molecular weight of 4×10 3 The carboxyl-terminated polypropylene, hydroxylated 3-bromo-4-vinylpyridine, cyclohexanone, 2-chloro-1-methylpyridinium iodide, and triethylamine was 1:3:50:3:2;

[0041] (3) The block copolymer was dissolved in cyclohexanone, bromoethane was added, and the reflux reaction was carried out for 4 h. After filtration, the solid was taken, dried at 60 °C for 10 h, polypropylene with a molecular weight of 9×10 4 and xylene were added, the temperature was raised to 110 °C, stirred at 70 rpm for 50 min, and dried at 120 °C for 5 h to obtain modified polypropylene; the mass ratio of the block copolymer, cyclohexanone, bromoethane, polypropylene with a molecular weight of 9×10 4 and xylene was 0.3:6:0.6:10:100;

[0042] (4) A silver ammonia solution was obtained by mixing 2 wt% silver nitrate aqueous solution and 2 wt% ammonia aqueous solution at a mass ratio of 1:0.5, and then adjusting the pH of the solution to 11 with ammonia water, heating to 45 °C and mixing evenly. The multi-walled carbon nanotubes were subjected to instantaneous oxidation flame treatment with a flame temperature of 2800 °C. Subsequently, 10 wt% potassium sodium tartrate aqueous solution 100 times the mass of the multi-walled carbon nanotubes was added, ultrasonicated at 21 kHz for 15 min, heated to 40 °C, stirred at 120 rpm for 40 min, and the silver ammonia solution 10 times the mass of the multi-walled carbon nanotubes was added dropwise at 4 mL / min, and stirring was continued for 20 min. It was washed 8 times with deionized water and dried at 70 °C and a vacuum degree of 1 kPa for 15 h to obtain carbon nanotube-supported silver nanoparticles;

[0043] (5) Mix carbon nanotube-supported silver nanoparticles and modified polypropylene in a mass ratio of 10:1.5, heat up to 188 °C, carry out melt blending at a rotation speed of 30 rpm for 20 min. Subsequently, under the conditions of a temperature of 180 °C and a pressure of 370 MPa, anneal for 150 min, and then extrude and pelletize. Its process parameters are as follows: the screw diameter is 20 mm, the length-diameter ratio is 25:1, the temperatures of the three sections and the die head are 170, 180, 200, and 220 °C respectively, and the shear rate is 150 rpm, to obtain antistatic and antibacterial modified polypropylene particles.

[0044] Comparative Example 1; The difference between Comparative Example 1 and Example 2 lies in that step (2) is different. Modify step (2) as follows: Mix polypropylene with a molecular weight of 9×10 4 and 95 wt% nitric acid aqueous solution in a mass ratio of 1:4, heat up to 110 °C for reflux, stir at 230 rpm for 8 h, cool to room temperature, wash successively with water and acetone until the pH of the washing liquid is 6, and dry at 65 °C for 8 h to obtain polypropylene with carboxyl end groups having a molecular weight of 4×10 3 ; Dissolve polypropylene with carboxyl end groups having a molecular weight of 4×10 3 and hydroxylated 3-bromo-4-vinylpyridine in cyclohexanone, add triethylamine, heat up to 120 °C, react for 9 h, cool to room temperature, filter, take the solid, use methanol as an extraction agent, extract for 50 h, and dry at 60 °C and a vacuum degree of 0.5 kPa for 24 h to obtain a block copolymer; The mass ratio of polypropylene with carboxyl end groups having a molecular weight of 4×10 3 , hydroxylated 3-bromo-4-vinylpyridine, cyclohexanone, and triethylamine is 1:2.5:50:2; The remaining steps are the same as those in Example 2.

[0045] Comparative Example 2; The difference between Comparative Example 2 and Example 2 lies in that there are no step (1), step (2), and step (3); The remaining steps are the same as those in Example 2.

[0046] Comparative Example 3; The difference between Comparative Example 3 and Example 2 lies in that step (4) is different. Modify step (4) as follows: Mix 2 wt% silver nitrate aqueous solution and 2 wt% ammonia aqueous solution in a mass ratio of 1:0.5, and then adjust the pH of the solution to 11 with ammonia water, heat up to 40 °C, and mix well to obtain a silver ammonia solution; Mix multi-walled carbon nanotubes with a 10 wt% potassium sodium tartrate aqueous solution 75 times the mass of the multi-walled carbon nanotubes, ultrasonicate at 21 kHz for 11 min, heat up to 40 °C, stir at 90 rpm for 30 min, dropwise add a silver ammonia solution 8 times the mass of the multi-walled carbon nanotubes at 4 mL / min, continue stirring for 15 min, wash 5 times with deionized water, and dry at 70 °C and a vacuum degree of 0.5 kPa for 12 h to obtain carbon nanotube-supported silver nanoparticles; The remaining steps are the same as those in Example 2.

[0047] Comparative Example 4; The difference between Comparative Example 4 and Example 2 lies in step (4). Step (4) is changed to: subject the multi-walled carbon nanotubes to instantaneous oxidation flame treatment at a flame temperature of 2200 °C, wash with deionized water 5 times, and dry at 70 °C under a vacuum of 0.5 kPa for 12 h to obtain modified carbon nanotubes; the remaining steps are the same as in Example 2.

[0048] Comparative Example 5; The difference between Comparative Example 5 and Example 2 lies in step (5). Step (5) is changed to: anneal the modified polypropylene at a temperature of 150 °C and a pressure of 320 MPa for 110 min, and then extrude and pelletize. The process parameters are: screw diameter of 20 mm, length-to-diameter ratio of 25:1, temperatures of the three zones and the die head of 170, 180, 200, 220 °C respectively, and shear rate of 110 rpm to obtain antistatic and antibacterial modified polypropylene pellets; the remaining steps are the same as in Example 2.

[0049] Comparative Example 6; The difference between Comparative Example 6 and Example 2 lies in step (5). Step (5) is changed to: mix carbon nanotube-supported silver nanoparticles and modified polypropylene in a mass ratio of 10:1, heat up to 180 °C, carry out melt blending at a rotation speed of 20 rpm for 15 min, and then anneal at a temperature of 150 °C for 110 min, and then extrude and pelletize. The process parameters are: screw diameter of 20 mm, length-to-diameter ratio of 25:1, temperatures of the three zones and the die head of 170, 180, 200, 220 °C respectively, and shear rate of 110 rpm to obtain antistatic and antibacterial modified polypropylene pellets; the remaining steps are the same as in Example 2.

[0050] Comparative Example 7; The difference between Comparative Example 7 and Example 2 lies in step (5). Step (5) is changed to: mix carbon nanotube-supported silver nanoparticles and modified polypropylene in a mass ratio of 10:1, heat up to 180 °C, carry out melt blending at a rotation speed of 20 rpm for 15 min, and then extrude and pelletize. The process parameters are: screw diameter of 20 mm, length-to-diameter ratio of 25:1, temperatures of the three zones and the die head of 170, 180, 200, 220 °C respectively, and shear rate of 110 rpm to obtain antistatic and antibacterial modified polypropylene pellets; the remaining steps are the same as in Example 2.

[0051] Effect Example

[0052] The following Table 1 gives the performance analysis results of the antistatic and antibacterial modified polypropylene pellets of Examples 1 to 3 and Comparative Examples 1 to 7 of the present invention.

[0053] Table 1

[0054]

[0055] From the comparison of the experimental data of the examples and comparative examples in Table 1, it can be found that the present invention uses hydrogen peroxide to initiate and oxidize 3-bromo-4-vinylpyridine to hydroxylate its terminal group. Then, it reacts with polypropylene with low molecular weight and double-terminal carboxyl groups to form an amphiphilic block copolymer, and quaternization is achieved through bromoethane, thereby enabling the matrix to have antibacterial and antistatic properties. Thus, the polypropylene is blended and modified. Due to the presence of polypropylene segments, the macromolecular modifier is difficult to separate from the matrix, achieving long-term antibacterial effect. And during the processing, it accumulates and arranges on the side facing the air, forming a continuous and uniform conductive layer on the surface of the matrix to achieve long-term antistatic effect. Then, the multi-walled carbon nanotubes are surface-modified by flame heat treatment. Through the instantaneous high-temperature oxidation flame, a large number of free radicals and plasmas are generated on the surface, and then polar groups are formed, which interact with silver ions to load silver nanoparticles. The two contact with each other to form a tunneling effect, enhancing the antistatic and antibacterial properties. Then, it is filled into the polypropylene matrix and annealed. At a higher annealing temperature, the molecular chains in the amorphous region have stronger mobility and undergo rearrangement and crystallization, thereby promoting the good dispersion of the filler in the polypropylene matrix and forming smaller micro-interfaces to achieve long-term antistatic and antibacterial properties. At the same time, through pressurization, the bromine atoms on 3-bromo-4-vinylpyridine are decomposed, thereby enhancing the antibacterial property of the matrix. At the same time, the stability of the whole system is enhanced, and the durability of antistatic and antibacterial properties is further improved.

[0056] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-mentioned exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claimed claim.

Claims

1. A preparation method of antistatic and antibacterial modified polypropylene particles, characterized in that, It includes the following preparation steps: (1) Heat deionized water to 78 - 90 °C, and simultaneously dropwise add hydrogen peroxide and 3 - bromo - 4 - vinylpyridine. React at 80 °C for 2.5 - 4 h, cool to room temperature, first dissolve with methanol, then precipitate with anhydrous ether, pour off the supernatant, and vacuum dry at 60 °C for 18 - 30 h to obtain hydroxylated 3 - bromo - 4 - vinylpyridine; (2)Dissolve the carboxyl-terminated polypropylene with a molecular weight of 4×10 3 and hydroxylated 3-bromo-4-vinylpyridine in cyclohexanone, add 2-chloro-1-methylpyridinium iodide and triethylamine, raise the temperature to 120 °C, react for 8.5 - 11 h, cool to room temperature, filter, take the solid, use methanol as the extraction agent, extract for 40 - 60 h, and dry in vacuo at 60 °C for 18 - 30 h to obtain the block copolymer; (3) Dissolve the block copolymer in cyclohexanone, add ethyl bromide, reflux for 4 h, filter, take the solid, dry at 60 °C for 5 - 10 h, add polypropylene with a molecular weight of 9×10 4 and xylene, heat to 80 - 110 °C, stir at 30 - 70 rpm for 30 - 50 min, dry at 120 °C for 2 - 5 h to obtain modified polypropylene; (4) Conduct instantaneous oxidation flame treatment on multi - walled carbon nanotubes, with the flame temperature being 1500 - 2800 °C. Subsequently, add an aqueous solution of 10 wt% potassium sodium tartrate with a mass 50 - 100 times that of the multi - walled carbon nanotubes, ultrasonicate at 21 kHz for 8 - 15 min, heat to 40 °C, stir at 60 - 120 rpm for 20 - 40 min, dropwise add a silver ammonia solution with a mass 5 - 10 times that of the multi - walled carbon nanotubes at a rate of 4 mL / min, continue stirring for 10 - 20 min, wash with deionized water 3 - 8 times, and vacuum dry at 70 °C for 10 - 15 h to obtain carbon nanotube - supported silver nanoparticles; (5) Mix carbon nanotube - supported silver nanoparticles and modified polypropylene at a mass ratio of 10:0.5 - 1.5, heat to 170 - 188 °C, conduct melt blending at a rotational speed of 15 - 30 rpm for 10 - 20 min, then perform annealing and extrusion granulation to obtain antistatic and antibacterial modified polypropylene particles; the process parameters of the annealing: temperature is 120 - 180 °C, pressure is 270 - 370 MPa, and time is 80 - 150 min.

2. The preparation method of an antistatic and antibacterial modified polypropylene particle according to claim 1, characterized in that, The dropping rate in step (1) is 1 - 3 mL / min.

3. The preparation method of an antistatic and antibacterial modified polypropylene particle according to claim 1, characterized in that The mass ratio of the deionized water, hydrogen peroxide, and 3 - bromo - 4 - vinylpyridine in step (1) is 15:8 - 11:2.5 - 3.

5.

4. The preparation method of an antistatic and antibacterial modified polypropylene particle according to claim 1, characterized in that, The preparation method of the carboxyl-terminated polypropylene with a molecular weight of 4×10 3 : Mix polypropylene with a molecular weight of 9×10 4 and 95wt% nitric acid aqueous solution at a mass ratio of 1:4, heat to 110°C for reflux, stir at 150 - 300 rpm for 8 h, cool to room temperature, rinse successively with water and acetone until the pH of the washing liquid is 6, and dry at 50 - 80°C for 7 - 10 h to obtain it.

5. The preparation method of an antistatic and antibacterial modified polypropylene particle according to claim 1, wherein, The mass ratio of the carboxyl-terminated polypropylene with a molecular weight of 4×10 3 , hydroxylated 3-bromo-4-vinylpyridine, cyclohexanone, 2-chloro-1-methylpyridinium iodide, and triethylamine described in step (2) is 1:2 to 3:50:2 to 3:

2.

6. The preparation method of an antistatic and antibacterial modified polypropylene particle according to claim 1, characterized in that, The mass ratio of the block copolymer, cyclohexanone, bromoethane, polypropylene with a molecular weight of 9×10 4 to xylene described in step (3) is 0.3:6:0.6:8 - 10:50 - 100.

7. The preparation method of an antistatic and antibacterial modified polypropylene particle according to claim 1, characterized in that, The preparation method of the silver ammonia solution in step (4): Mix a 2 wt% silver nitrate aqueous solution and a 2 wt% ammonia aqueous solution at a mass ratio of 1:0.5, then adjust the pH of the solution to 11 with ammonia water, and heat to 35 - 45 °C and mix evenly.

8. The preparation method of an antistatic and antibacterial modified polypropylene particle according to claim 1, characterized in that, The vacuum degree of the vacuum drying in steps (1), (2), and (4) is all 0.2 - 1 kPa.

9. The preparation method of an antistatic and antibacterial modified polypropylene particle according to claim 1, wherein The process parameters of the extrusion granulation in step (5): The screw diameter is 20 mm, the length - diameter ratio is 25:1, the temperatures of the three sections and the die head are 170, 180, 200, 220 °C respectively, and the shear rate is 80 - 150 rpm.

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