Composite nano-silver-graphene antibacterial plastic master batch and preparation method thereof

Abstract

The application relates to the field of plastic master batches, and provides a composite nano-silver-graphene antibacterial plastic master batch and a preparation method thereof; the master batch is composed of surface-modified silver / graphene composite fillers, a polypropylene matrix resin, maleic anhydride grafted polypropylene, polyvinylpyrrolidone and SEBS thermoplastic elastomer. The silver / graphene composite fillers are in-situ grown on the surface of doped graphene in the form of silver nanowires, and are modified by 3-aminopropyl triethoxysilane coupling agent to improve the interface compatibility. The components are blended and dispersed through a double-screw extrusion processing technology, and finally, the functional master batch with excellent mechanical properties and broad-spectrum antibacterial properties is obtained. The application solves the problems of poor antibacterial property and weak mechanical property of the existing plastic, and has good processing adaptability and application popularization potential.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of plastic master batch, in particular to a composite nano-silver-graphene antibacterial plastic master batch and a preparation method thereof. BACKGROUND

[0002] With the increasing demand for material safety and functionality in the fields of medical protection, food packaging, household appliance shell, children's products and other consumer goods, thermoplastic polymer materials with antibacterial properties have gradually become the focus of research and development in related industries. Especially in the context of frequent public health incidents and increasing consumer health awareness, plastic products that can achieve antibacterial protection and inhibit bacterial growth at the material level are being widely used in mask holders, antibacterial tableware, medical device shells, refrigerator liners, public transportation handrails and other scenarios. The above application scenarios have put forward dual performance requirements for plastic materials: on the one hand, the materials are required to have excellent mechanical properties in conventional use environment to ensure their structural stability and durability during long-term use; on the other hand, they are required to have broad-spectrum and efficient antibacterial ability to effectively inhibit the reproduction of bacteria on the surface and inside the material, thereby improving the safety and hygiene level of the product. On this basis, improving the mechanical properties and antibacterial properties of plastic materials has become a key factor in promoting their breakthrough in high-end functional applications, meeting the above composite properties can not only significantly improve the overall performance of the product, but also expand its application boundaries in medical health, smart home and public facilities and other diversified scenarios, reflecting the important development value of new antibacterial plastic materials in the modern functional material system.

[0003] Although antibacterial plastic materials have been widely concerned in recent years, and functional expansion is carried out by adding inorganic antibacterial agents, organic antibacterial agents or functional fillers, etc., but at present most of the antibacterial masterbatch is still difficult to achieve effective balance between mechanical properties and antibacterial properties, often one side is improved and the other side is decreased. For example, the Chinese patent with publication number CN104804320A discloses a kind of nano composite antibacterial masterbatch, although the material surface is endowed with antibacterial ability to a certain extent, but due to the poor dispersibility of filler, weak interface bonding force and other problems, its tensile strength and impact toughness cannot meet the demand of high strength application, and further limits its popularization and application in structural products and high durability occasions. The main reason for the above problems is that the traditional antibacterial filler has single structure, poor interface compatibility with polymer matrix, and lacks effective microstructure control means, which leads to uneven distribution and serious agglomeration of antibacterial components in the material, affecting the release of antibacterial activity and weakening the mechanical property transmission path. In addition, some organic antibacterial additives have poor thermal stability and easy migration, which further shortens the service cycle of the product. Therefore, it is urgent to develop a new antibacterial functional filler with structural stability, high dispersibility and interface activity, and to realize the synchronous improvement of mechanical properties and antibacterial properties through synergistic construction strategy, in order to meet the urgent demand of modern high performance plastic products for functional integration. SUMMARY

[0004] (1) Technical problems to be solved

[0005] The purpose of the present application is to provide a kind of composite nano silver-graphene antibacterial plastic masterbatch and its preparation method, solve the problem of insufficient mechanical properties and antibacterial properties of current plastics.

[0006] (2) Technical scheme

[0007] In order to achieve the above purpose, the present application provides the following technical scheme:

[0008] A kind of composite nano silver-graphene antibacterial plastic masterbatch, comprising the following weight parts of raw materials: surface modified silver / graphene composite filler 1.5~10.0 parts, polypropylene matrix resin 80~120 parts, maleic anhydride grafted polypropylene 2.0~8.0 parts, polyvinylpyrrolidone 0.5~0.9 parts, SEBS thermoplastic elastomer 2.0~8.0 parts;

[0009] The surface modified silver / graphene composite filler is obtained by surface modification of silver / graphene composite filler with 3-aminopropyl triethoxysilane coupling agent;

[0010] The silver / graphene composite filler is composed of doped graphene and silver nanowires doped on the surface of graphene;

[0011] The doped graphene is silver doped graphene, and the doping amount is 0.05~0.5wt%.

[0012] The silver nanowires are in-situ grown on the doped graphene surface by a liquid-phase reduction method.

[0013] Further, the mass ratio of the doped graphene and the silver nanowires in the silver / graphene composite filler is 1:(2.0-5.0).

[0014] Further, the preparation method of the surface-modified silver / graphene composite filler is as follows: 1.0-1.5 parts of the silver / graphene composite filler is dispersed in 80-100 parts of anhydrous ethanol, and a uniform suspension system is formed by ultrasonic treatment at a frequency of 40-60 kHz for 20-30 min; then, 1.0-2.0 parts of 3-aminopropyl triethoxysilane and 2-5 parts of deionized water are added, and 0.1-0.2 parts by weight of glacial acetic acid is added to adjust the pH to 4.0-5.0; a hydrolysis reaction is carried out at a magnetic stirring rate of 300-500 rpm for 30-60 min to form a silanol solution; the mixed system is transferred to a reaction kettle, heated to 60-80 ℃ at a heating rate of 2-5 ℃ / min, and kept for 20-24 h under nitrogen protection; after the reaction is completed, the system is cooled to room temperature, and the unreacted reagents and by-products in the supernatant are removed by centrifugation at a speed of 8000-12000 rpm; the remaining modified filler is washed with an ethanol / water mixture (volume ratio of 1:1) for 3-5 times; and finally, the surface-modified silver / graphene composite filler is obtained by vacuum drying at 50-60 ℃ for 8-12 h.

[0015] Further, the preparation method of the silver / graphene composite filler is as follows: 0.01-0.03 parts of porous silver-doped graphene is dispersed in 100-150 parts of ethylene glycol, and a uniform suspension system is formed by ultrasonic treatment at a frequency of 40-60 kHz for 20-40 min; then, 0.1-0.3 parts of silver nitrate and 0.3-0.8 parts of polyvinylpyrrolidone are added, and 0.0001-0.0005 parts of copper chloride is added as a morphology control agent; the mixture is dissolved and mixed at a magnetic stirring rate of 300-500 rpm for 30-60 min to form a precursor solution; the mixed system is transferred to a reaction container, heated to 160-170 ℃ at a heating rate of 5-10 ℃ / min, and kept for 30-90 min to make silver ions in-situ reduce and grow on the silver seeds of the porous graphene skeleton to form silver nanowires; after the reaction is completed, the system is naturally cooled to room temperature, and the free silver nanoparticles and residual reactants in the supernatant are removed by centrifugation at a speed of 8000-12000 rpm for 3-5 times; the remaining silver nanowire / graphene composite is washed with deionized water and anhydrous ethanol in sequence, and then vacuum dried at 50-70 ℃ for 12-24 h to obtain the silver / graphene composite filler.

[0016] Further, the preparation method of the porous silver-doped graphene is as follows: 0.02-0.05 parts of doped graphene powder is dispersed in 80-100 parts of deionized water by weight, 0.1-0.5 parts of polyvinylpyrrolidone is added as a dispersant, and the system is treated by ultrasonic frequency of 40-60 kHz for 20-40 min to form a uniform dispersion liquid; the obtained dispersion liquid is injected into a freeze-drying mold, frozen at-70--80℃ for 18-24 h to form ice crystal templates, then transferred to a freeze-drying machine, and maintained at-50--40℃ under the condition of vacuum degree≤10 Pa for 36-48 h to remove ice crystals, and finally porous silver-doped graphene is obtained.

[0017] Further, the preparation method of the doped graphene is as follows: first, 0.04-0.1 parts of graphene oxide is dispersed in 20-200 parts of deionized water by weight, and the system is treated by ultrasonic dispersion with ultrasonic frequency of 40-60 kHz and mechanical stirring with stirring rate of 300-500 rpm simultaneously for 60-120 min to form a uniform suspension; then, 0.005-0.05 parts of silver nitrate is added, and the system is continuously stirred at 25-40℃ with magnetic stirring rate of 200-400 rpm and ultrasonic assisted dispersion for 60-90 min; after the pH value of the system is adjusted to 9-11 by adding 0.1-0.5 mol / L sodium hydroxide solution dropwise, a reducing solution containing 0.02-0.1 parts of ascorbic acid by weight is slowly added and reacted in a water bath at 85-95℃ for 180-240 min; after the reaction is completed, the system is centrifuged at 8000-12000 rpm for 3-5 times to remove ion impurities and ethanol-soluble by-products in the supernatant in turn, and the remaining precipitate is vacuum dried at 50-70℃ for 12-24 h to obtain doped graphene.

[0018] The application adopts a composite filler design of in-situ growth of silver nanowires on the surface of doped graphene, and is mainly used for enhancing mechanical properties and antibacterial properties. Silver ions are introduced into the doped graphene skeleton, and silver nanowires are grown on the surface by a liquid phase reduction method, forming a three-dimensional network structure of a silver / graphene composite system. The structure improves the overall mechanical properties of the material and further enhances the antibacterial activity. The doped graphene provides excellent mechanical support and conductive channels, and the silver nanowires serve as high-efficiency antibacterial components to achieve sterilization function. The synergistic effect of the two makes the composite filler have significant advantages in structural stability, functional uniformity and interface interaction. Further, in order to improve the interface compatibility and dispersibility between the composite filler and the polymer matrix, the silver / graphene composite material is surface-modified by 3-aminopropyl triethoxysilane. Under the action of the silane coupling agent, a stable organosilanol layer is formed on the surface of the composite filler, effectively improving the distribution uniformity and interface bonding strength of the composite filler in a non-polar matrix such as polypropylene, so as to ensure that the composite master batch maintains good structural stability and mechanical transmission efficiency during the processing. The pretreatment process of the doped graphene realizes effective doping of silver by controlling the oxidation-reduction reaction and pH environment, and constructs a porous structure by means of freeze-drying technology, which significantly improves the in-situ growth space and nucleation efficiency of the silver nanowires, so that the finally formed composite filler realizes the overall consideration of function construction and skeleton support at the microstructure level. The overall design strategy starts from the aspects of material structure, performance control and interface engineering, and realizes the integration of mechanical enhancement and antibacterial function through the synergistic cooperation of various sub-components, which is suitable for various polymer application scenarios with high requirements for strength and hygiene performance.

[0019] The application also provides a preparation method of the composite nano-silver-graphene antibacterial plastic master batch.

[0020] S1. The surface-modified silver / graphene composite filler and polyvinylpyrrolidone are pre-mixed in a high-speed mixer. The equipment type is a conventional powder mixer, the mixing speed is controlled at 500-800 rpm, and the mixing time is 10-15 min, so as to ensure that the filler surface is uniformly coated with the dispersant.

[0021] S2. The polypropylene matrix resin and maleic anhydride grafted polypropylene are vacuum dried at 80-90°C for 4-6 h, the water content is controlled to be less than 0.05wt%, and then are added into the first feeding area of a twin-screw extruder, the screw temperature is set to be 180-220°C, and the screw rotation speed is 200-400 rpm, so as to perform melt plasticization treatment.

[0022] S3. The pre-mixed filler obtained in S1 is added into the second feeding area of the twin-screw extruder through a side feeding device, the screw rotation speed is controlled to be in the range of 300-400 rpm, the screw working length is 40-50D, and the effective residence time of the material in the melting zone is 2-5 min under the protection of nitrogen.

[0023] S4. Introducing SEBS thermoplastic elastomer from the third feeding area into the extrusion system, forming a high shear zone in the local melt blending zone by configuring three kneading blocks to enhance the interface bonding of SEBS and the matrix;

[0024] S5. Extruding through a Φ1.5~2.5mm die, using 15~25℃ water cooling draw bar to cut the particles, controlling the length of the particles to be 2~3mm, and obtaining cylindrical master batch with a particle size of 1.5~2.5mm;

[0025] S6. Placing the master batch in a 50~60℃ vacuum drying box for 4~6h, controlling the water content to be less than 0.1wt%, and finally obtaining the finished product of the antibacterial plastic master batch.

[0026] (3) Beneficial technical effects

[0027] 1. The application realizes the double promotion of antibacterial and mechanical properties through the synergistic construction of silver nanowires and doped graphene, significantly enhances the structural stability and interface compatibility, and is suitable for high-performance antibacterial polymer products. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The morphology diagram of the porous silver-doped graphene prepared for the embodiment 1 of the application.

[0029] Figure 2 The transmission electron microscope morphology diagram of the porous silver-doped graphene prepared for the embodiment 1 of the application.

[0030] Figure 3 The morphology diagram of the surface-modified silver / graphene composite filler prepared for the embodiment 1 of the application.

[0031] Figure 4 The XRD phase analysis diagram of the surface-modified silver / graphene composite filler prepared for the embodiment 1 of the application. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical scheme and advantages of the embodiments of the application more clear, the technical scheme in the embodiments of the application will be described clearly and completely below with reference to the drawings in the embodiments of the application.

[0033] Embodiment 1

[0034] A composite nano-silver-graphene antibacterial plastic master batch, comprising the following raw materials in parts by weight: surface-modified silver / graphene composite filler 1.5 parts, polypropylene matrix resin 80 parts, maleic anhydride grafted polypropylene 2.0 parts, polyvinylpyrrolidone 0.5 parts, SEBS thermoplastic elastomer 2.0 parts;

[0035] The surface-modified silver / graphene composite filler is obtained by surface modification of the silver / graphene composite filler with 3-aminopropyl triethoxysilane coupling agent; the silver / graphene composite filler is composed of doped graphene and silver nanowires on the surface of the doped graphene; the doped graphene is silver-doped graphene, and the doping amount is 0.05wt%; the silver nanowires are in-situ grown on the surface of the doped graphene by liquid-phase reduction method.

[0036] The mass ratio of the doped graphene and the silver nanowires in the silver / graphene composite filler of the embodiment is 1:2.0;

[0037] The preparation method of the surface-modified silver / graphene composite filler of the embodiment is as follows: 1.0 part of the silver / graphene composite filler is dispersed in 80 parts of anhydrous ethanol, and a uniform suspension system is formed by ultrasonic treatment at a frequency of 40 kHz for 20 min, then 1.0 part of 3-aminopropyl triethoxysilane and 2 parts of deionized water are added, 0.1 part of glacial acetic acid is further added to adjust the pH to 4.0, and a hydrolysis reaction is carried out under the condition of a magnetic stirring rate of 300 rpm for 30 min to form a silanol solution; the mixed system is transferred to a reaction kettle, heated to 60℃ at a heating rate of 2℃ / min, and kept for reaction under nitrogen protection for 20 h; after the reaction is completed, the system is cooled to room temperature, and the unreacted reagents and by-products in the supernatant are separated and removed by centrifugation at a speed of 8000 rpm, and the remaining modified filler is washed with an ethanol / water mixture (volume ratio of 1:1) for 3 times, and finally dried at 50℃ under vacuum for 8 h to obtain the surface-modified silver / graphene composite filler.

[0038] The preparation method of the silver / graphene composite filler of the embodiment is as follows: 0.01 parts of porous silver-doped graphene is dispersed in 100 parts of ethylene glycol, and a uniform suspension system is formed by ultrasonic treatment at a frequency of 40 kHz for 20 min, then 0.1 parts of silver nitrate and 0.3 parts of polyvinylpyrrolidone are added, and 0.0001 parts of copper chloride is further added as a morphology control agent, and the mixture is dissolved and mixed under the condition of a magnetic stirring rate of 300 rpm for 30 min to form a precursor solution; the mixed system is transferred to a reaction container, heated to 160℃ at a heating rate of 5℃ / min, and kept for 30 min to make silver ions in-situ reduce and grow silver nanowires on the silver seeds of the porous graphene skeleton, and after the reaction is completed, the system is naturally cooled to room temperature, and the free silver nanoparticles and residual reactants in the supernatant are removed by centrifugation at a speed of 8000 rpm for 3 times, and the remaining silver nanowire / graphene composite is washed with deionized water and anhydrous ethanol in sequence, and then dried at 50℃ under vacuum for 12 h to obtain the silver / graphene composite filler.

[0039] The preparation method of the porous silver-doped graphene of the embodiment is as follows: 0.03 parts of doped graphene powder is dispersed in 86 parts of deionized water by weight, 0.2 parts of polyvinylpyrrolidone is added as a dispersant, and the system is treated by ultrasonic frequency of 46 kHz for 26 min to form a uniform dispersion liquid; the obtained dispersion liquid is injected into a freeze-drying mold, frozen for 20 h at a low temperature environment of-73℃ to form ice crystal templates, and then transferred to a freeze dryer to maintain-47℃ and a vacuum degree of ≤10 Pa for 40 h to sublimate the ice crystals to remove the final porous silver-doped graphene.

[0040] The preparation method of the doped graphene of the embodiment is as follows: first, 0.06 parts of graphene oxide is dispersed in 74 parts of deionized water by weight, and the system is treated by ultrasonic dispersion with ultrasonic frequency of 46 kHz and mechanical stirring with stirring rate of 360 rpm synchronously for 78 min to form a uniform suspension; then, 0.019 parts of silver nitrate is added, and the system is continuously treated by magnetic stirring with stirring rate of 260 rpm and ultrasonic assisted dispersion at 30℃ for 69 min; after the pH value of the system is adjusted to 10 by adding 0.22 mol / L sodium hydroxide solution dropwise, a reducing solution containing 0.04 parts of ascorbic acid is slowly added and reacted in a 87℃ water bath for 198 min; after the reaction is completed, the ion impurities and ethanol-soluble byproducts in the supernatant are removed by centrifugal separation at 9200 rpm for 4 times, and the remaining precipitate is vacuum dried at 56℃ for 16 h to obtain the doped graphene.

[0041] The preparation method of a composite nano-silver-graphene antibacterial plastic master batch of the embodiment is as follows:

[0042] S1. The surface modified silver / graphene composite filler and polyvinylpyrrolidone are premixed in a high-speed mixer, the equipment type is a conventional powder mixer, the mixing speed is controlled at 590 rpm, and the mixing time is 12 min to ensure that the filler surface is uniformly coated with the dispersant;

[0043] S2. The polypropylene matrix resin and maleic anhydride grafted polypropylene are vacuum dried at 83℃ for 5 h to control the water content to be less than 0.05 wt%, and then added to the first feeding area of the twin-screw extruder, and the screw temperature is set to 192℃ and the screw rotation speed is 260 rpm for melt plasticization treatment.

[0044] S3. The premixed filler obtained in S1 is added to the second feeding area of the twin-screw extruder through a side feeding device, the screw rotation speed is controlled within 330 rpm, the screw working length is 43D, and the effective residence time of the material in the melt zone is 3 min under nitrogen protection;

[0045] S4. Introducing the SEBS thermoplastic elastomer from the third feeding zone into the extrusion system, forming a high shear zone in the local melt blending zone by configuring three kneading blocks to enhance the interface bonding of the SEBS and the matrix;

[0046] S5. Extruding through a Φ1.8mm die, using 18℃ water cooling draw bar to cut the particles, controlling the length of the particles to be 2.3mm, obtaining cylindrical master batch with a particle size of 1.8mm;

[0047] S6. Placing the master batch in a 53℃ vacuum drying box for 5h, controlling the water content to be less than 0.1wt%, finally obtaining the finished product of the antibacterial plastic master batch.

[0048] From Figure 1 and Figure 2 It can be seen that the porous silver-doped graphene prepared in Embodiment 1 has obvious porous structure and uniform sheet morphology, which is beneficial to the nucleation and distribution of silver nanowires; Figure 3 The XRD pattern of the surface-modified silver / graphene composite filler further verifies the crystal structure integrity of the silver nanowires and the existence of the graphene skeleton, which comprehensively indicates that the composite filler prepared in the application has good controllability and synergy in structure formation and component stability, and provides a structural basis and phase support for realizing excellent mechanical enhancement and antibacterial performance. Figure 4

[0049] Embodiment 2

[0050] A composite nano-silver-graphene antibacterial plastic master batch, comprising the following raw materials in parts by weight: surface-modified silver / graphene composite filler 4 parts, polypropylene matrix resin 92 parts, maleic anhydride grafted polypropylene 4 parts, polyvinylpyrrolidone 0.6 parts, SEBS thermoplastic elastomer 4 parts.

[0051] The surface-modified silver / graphene composite filler is obtained by surface modification of the silver / graphene composite filler with 3-aminopropyl triethoxysilane coupling agent; the silver / graphene composite filler is composed of doped graphene and silver nanowires on the surface of the doped graphene; the doped graphene is silver-doped graphene, and the doping amount is 0.19wt%; the silver nanowires are in-situ grown on the surface of the doped graphene by liquid phase reduction method.

[0052] The mass ratio of the doped graphene and the silver nanowires in the silver / graphene composite filler of the embodiment is 1:2.9;

[0053] ​The preparation method of the surface-modified silver / graphene composite filler in this embodiment is as follows: 1.2 parts of silver / graphene composite filler is dispersed in 86 parts of anhydrous ethanol, and a uniform suspension system is formed by ultrasonic treatment at a frequency of 46 kHz for 23 min, then 1.3 parts of 3-aminopropyl triethoxysilane and 3 parts of deionized water are added, 0.13 parts by weight of glacial acetic acid is added to adjust the pH to 4.3, and a hydrolysis reaction is carried out at a magnetic stirring rate of 360 rpm for 39 min to form a silanol solution; the mixed system is transferred to a reaction kettle, heated to 66°C at a heating rate of 3°C / min, and reacted for 21 h under nitrogen protection; after the reaction is completed, it is cooled to room temperature, and the unreacted reagents and by-products in the supernatant are removed by centrifugation at a speed of 9200 rpm, and the remaining modified filler is washed with an ethanol / water mixture (volume ratio 1:1) for 4 times, and finally dried at 53°C under vacuum for 9 h to obtain the surface-modified silver / graphene composite filler.

[0054] The preparation method of the silver / graphene composite filler in this embodiment is as follows: first, 0.02 parts of porous silver-doped graphene is dispersed in 115 parts of ethylene glycol, and a uniform suspension system is formed by ultrasonic treatment at a frequency of 46 kHz for 26 min, then 0.16 parts of silver nitrate and 0.45 parts of polyvinylpyrrolidone are added, and 0.0002 parts of copper chloride is added as a morphology control agent, and the mixture is dissolved at a magnetic stirring rate of 360 rpm for 39 min to form a precursor solution; the mixed system is transferred to a reaction container, heated to 163°C at a heating rate of 7°C / min, and kept for 48 min to make silver ions in situ reduce and grow silver nanowires on the silver seeds of the porous graphene skeleton, and then naturally cooled to room temperature, and the free silver nanoparticles and residual reactants in the supernatant are removed by centrifugation at a speed of 9200 rpm for 4 times, and the remaining silver nanowire / graphene composite is washed with deionized water and anhydrous ethanol, and then dried at 56°C under vacuum for 17 h to obtain the silver / graphene composite filler.

[0055] The preparation method of the porous silver-doped graphene in this embodiment is as follows: 0.02 parts of doped graphene powder is dispersed in 80 parts of deionized water, 0.1 parts of polyvinylpyrrolidone is added as a dispersant, and the system is treated by ultrasonic treatment at a frequency of 40 kHz for 20 min to form a uniform dispersion liquid; the obtained dispersion liquid is injected into a freeze-drying mold, frozen at -70°C for 18 h to form an ice crystal template, then transferred to a freeze-drying machine and maintained at -50°C and a vacuum degree of ≤10 Pa for 36 h to sublimate the ice crystals and remove the final porous silver-doped graphene.

[0056] The preparation method of the doped graphene of the embodiment is as follows: first, 0.04 parts of graphene oxide is dispersed in 20 parts of deionized water by weight, and is subjected to ultrasonic dispersion at a frequency of 40 kHz and synchronous treatment at a mechanical stirring rate of 300 rpm for 60 min to form a uniform suspension; then, 0.005 parts of silver nitrate is added and is subjected to magnetic stirring at a rate of 200 rpm and ultrasonic auxiliary dispersion for 60 min at 25°C; after the pH value of the system is adjusted to 9 by dropwise adding 0.1 mol / L sodium hydroxide solution, a reducing solution containing 0.02 parts of ascorbic acid by weight is slowly added and is reacted in a water bath at 85°C for 180 min; after the reaction is completed, the ion impurities and ethanol-soluble byproducts in the supernatant are removed by centrifugal separation at a speed of 8000 rpm for three times; and the retained precipitate is vacuum dried at 50°C for 12 h to obtain the doped graphene.

[0057] The preparation method of the composite nano-silver-graphene antibacterial plastic master batch of the embodiment is as follows:

[0058] S1. The surface-modified silver / graphene composite filler is pre-mixed with polyvinylpyrrolidone in a high-speed mixer, the type of the equipment is a conventional powder mixer, the mixing speed is controlled at 500 rpm, and the mixing time is 10 min to ensure that the filler surface is uniformly coated with the dispersant.

[0059] S2. The polypropylene matrix resin and maleic anhydride grafted polypropylene are vacuum dried at 80°C for 4 h to control the water content to be less than 0.05 wt%, and then are added to the first feeding area of a twin-screw extruder, the screw temperature is set to 180°C, and the screw speed is 200 rpm for melt plasticizing treatment.

[0060] S3. The pre-mixed filler obtained in S1 is added to the second feeding area of the twin-screw extruder through a side feeding device, the screw speed is controlled within the range of 300 rpm, the working length of the screw is 40D, and the effective residence time of the material in the melt zone is 2 min under nitrogen protection.

[0061] S4. The SEBS thermoplastic elastomer is introduced into the extrusion system from the third feeding area, and a three-section kneading block is configured to form a high-shear zone in the local melt blending zone to enhance the interface bonding between SEBS and the matrix.

[0062] S5. Extrusion is performed through a Φ1.5 mm die, water cooling is performed at 15°C, and the length of the cut particles is controlled to be 2 mm to obtain cylindrical master batches with a particle size of 1.5 mm.

[0063] S6. The master batch is placed in a vacuum drying oven at 50°C for 4 h to control the water content to be less than 0.1 wt%, and finally the antibacterial plastic master batch product is obtained.

[0064] Example 3

[0065] The composite nano-silver-graphene antibacterial plastic master batch comprises the following raw materials in parts by weight: 7 parts of surface modified silver / graphene composite filler, 104 parts of polypropylene matrix resin, 6 parts of maleic anhydride grafted polypropylene, 0.7 parts of polyvinylpyrrolidone, and 6 parts of SEBS thermoplastic elastomer.

[0066] The surface modified silver / graphene composite filler is obtained by surface modification of the silver / graphene composite filler with 3-aminopropyl triethoxysilane coupling agent; the silver / graphene composite filler is composed of doped graphene and silver nanowires on the surface of the doped graphene; the doped graphene is silver-doped graphene, and the doping amount is 0.32wt%; the silver nanowires are in-situ grown on the surface of the doped graphene by liquid phase reduction method.

[0067] The mass ratio of the doped graphene and the silver nanowires in the silver / graphene composite filler of the embodiment is 1:3.8.

[0068] The preparation method of the surface modified silver / graphene composite filler of the embodiment is as follows: 1.3 parts of silver / graphene composite filler is dispersed in 92 parts of anhydrous ethanol, and a uniform suspension system is formed by ultrasonic treatment at a frequency of 52 kHz for 26 min; then 1.6 parts of 3-aminopropyl triethoxysilane and 4 parts of deionized water are added, and 0.16 parts by weight of glacial acetic acid is added to adjust the pH to 4.6; a silanol solution is formed by hydrolysis reaction under the condition of a magnetic stirring speed of 420 rpm for 48 min; the mixed system is transferred to a reaction kettle, heated to 72℃ at a heating rate of 4℃ / min, and reacted under nitrogen protection for 22 h; after the reaction is completed, the system is cooled to room temperature, and the unreacted reagents and by-products in the supernatant are removed by centrifugation at a speed of 10400 rpm; the remaining modified filler is washed with a mixture of ethanol and water in a volume ratio of 1:1 for 4 times, and finally dried at 56℃ under vacuum for 10 h to obtain the surface modified silver / graphene composite filler.

[0069] The preparation method of the silver / graphene composite filler of the embodiment is as follows: first, 0.02 parts of porous silver-doped graphene is dispersed in 130 parts of ethylene glycol, and a uniform suspension system is formed by ultrasonic treatment at a frequency of 52 kHz for 32 min; then, 0.22 parts of silver nitrate and 0.6 parts of polyvinylpyrrolidone are added, and 0.0003 parts of copper chloride is added as a morphology control agent; the mixture is dissolved and mixed for 48 min under the condition of a magnetic stirring rate of 420 rpm to form a precursor solution; the mixed system is transferred to a reaction container, heated to 166℃ at a heating rate of 8℃ / min, and kept for 66 min to make silver ions in-situ reduce and grow silver nanowires on the silver seeds of the porous graphene skeleton; after the reaction is completed, the system is naturally cooled to room temperature; free silver nanoparticles and residual reactants in the supernatant are removed by centrifugation at a speed of 10400 rpm for 4 times; the retained silver nanowire / graphene composite is washed with deionized water and anhydrous ethanol in sequence, and then vacuum dried at 62℃ for 19 h to obtain the silver / graphene composite filler.

[0070] The preparation method of the porous silver-doped graphene of the embodiment is as follows: 0.05 parts of doped graphene powder is dispersed in 100 parts of deionized water, 0.5 parts of polyvinylpyrrolidone is added as a dispersant, and a uniform dispersion liquid is formed by ultrasonic treatment at a frequency of 60 kHz for 40 min; the obtained dispersion liquid is injected into a freeze-drying mold, frozen for 24 h at a low temperature of-80℃ to form an ice crystal template, and then transferred to a freeze-drying machine to maintain at-40℃ and a vacuum degree of≤10 Pa for 48 h to sublimate the ice crystals and remove the final porous silver-doped graphene.

[0071] The preparation method of the doped graphene of the embodiment is as follows: first, 0.1 parts of graphene oxide is dispersed in 200 parts of deionized water, and a uniform suspension is formed by ultrasonic dispersion at a frequency of 60 kHz and mechanical stirring at a speed of 500 rpm in sequence for 120 min; then, 0.05 parts of silver nitrate is added and continuously dispersed under the condition of magnetic stirring at a speed of 400 rpm and ultrasonic assistance at 40℃ for 90 min; after the pH value of the system is adjusted to 11 by adding 0.5 mol / L sodium hydroxide solution dropwise, a reducing solution containing 0.1 parts of ascorbic acid is slowly added and reacted in a 95℃ water bath for 240 min; after the reaction is completed, ion impurities and ethanol-soluble byproducts in the supernatant are removed by centrifugal separation at a speed of 12000 rpm for 5 times in sequence, and the retained precipitate is vacuum dried at 70℃ for 24 h to obtain the doped graphene.

[0072] The preparation method of a composite nano-silver-graphene antibacterial plastic master batch of the embodiment is as follows:

[0073] S1. The surface-modified silver / graphene composite filler is pre-mixed with polyvinylpyrrolidone in a high-speed mixer, the device type is a conventional powder mixer, the mixing speed is controlled at 800 rpm, and the mixing time is 15 min to ensure uniform coating of the filler surface with the dispersant;

[0074] S2. The polypropylene matrix resin and maleic anhydride grafted polypropylene are vacuum dried at 90°C for 6h to control the water content below 0.05wt%, and then added to the first feeding zone of the twin-screw extruder, with the screw temperature set at 220°C and the screw speed at 400 rpm for melt plasticization treatment.

[0075] S3. The pre-mixed filler obtained in S1 is added to the second feeding zone of the twin-screw extruder through a side feeding device, with the screw speed controlled within 400 rpm and the screw working length of 50D, and the effective residence time of the material in the melt zone is 5 min under nitrogen protection;

[0076] S4. The SEBS thermoplastic elastomer is introduced into the extrusion system from the third feeding zone, and the local melt blending zone is formed into a high shear zone by configuring three kneading blocks to enhance the interface bonding between SEBS and the matrix;

[0077] S5. Extruded through a Φ2.5mm die, and cut into particles with a water cooling bar at 25°C, with the particle length controlled at 3mm, to obtain cylindrical masterbatch with a particle size of 2.5mm;

[0078] S6. The masterbatch is placed in a vacuum drying oven at 60°C for 6h to control the water content below 0.1wt%, and finally the antibacterial plastic masterbatch product is obtained.

[0079] Example 4

[0080] A composite nano-silver-graphene antibacterial plastic masterbatch, comprising the following raw materials by weight: surface-modified silver / graphene composite filler 10.0 parts, polypropylene matrix resin 120 parts, maleic anhydride grafted polypropylene 8.0 parts, polyvinylpyrrolidone 0.9 parts, SEBS thermoplastic elastomer 8.0 parts;

[0081] The surface-modified silver / graphene composite filler is obtained by surface modification of silver / graphene composite filler with 3-aminopropyl triethoxysilane coupling agent; the silver / graphene composite filler is composed of doped graphene and silver nanowires doped on the surface of the graphene; the doped graphene is silver-doped graphene, and the doping amount is 0.5wt%; the silver nanowires are in-situ grown on the surface of the doped graphene by liquid phase reduction method.

[0082] The mass ratio of doped graphene and silver nanowires in the silver / graphene composite filler of this example is 1:5.0;

[0083] The preparation method of the surface-modified silver / graphene composite filler in this embodiment is as follows: 1.5 parts of silver / graphene composite filler is dispersed in 100 parts of anhydrous ethanol, and a uniform suspension system is formed by ultrasonic treatment at a frequency of 60 kHz for 30 min, then 2.0 parts of 3-aminopropyl triethoxysilane and 5 parts of deionized water are added, 0.2 parts by weight of glacial acetic acid is added to adjust the pH to 5.0, and a hydrolysis reaction is carried out under the condition of a magnetic stirring rate of 500 rpm for 60 min to form a silanol solution; the mixed system is transferred to a reaction kettle, heated to 80°C at a heating rate of 5°C / min, and kept at 80°C for 24 h under nitrogen protection; after the reaction is completed, it is cooled to room temperature, the unreacted reagents and by-products in the supernatant are removed by centrifugation at a speed of 12000 rpm, and the remaining modified filler is washed with a mixture of ethanol / water (volume ratio 1:1) for 5 times, and finally dried at 60°C under vacuum for 12 h to obtain the surface-modified silver / graphene composite filler.

[0084] The preparation method of the silver / graphene composite filler in this embodiment is as follows: first, 0.03 parts of porous silver-doped graphene is dispersed in 150 parts of ethylene glycol, a uniform suspension system is formed by ultrasonic treatment at a frequency of 60 kHz for 40 min, then 0.3 parts of silver nitrate and 0.8 parts of polyvinylpyrrolidone are added, and 0.0005 parts of copper chloride is added as a morphology control agent, and the mixture is dissolved and mixed at a magnetic stirring rate of 500 rpm for 60 min to form a precursor solution; the mixed system is transferred to a reaction container, heated to 170°C at a heating rate of 10°C / min, and kept at 170°C for 90 min to make silver ions in situ reduce and grow silver nanowires on the silver seeds of the porous graphene skeleton, and then naturally cooled to room temperature; the free silver nanoparticles and residual reactants in the supernatant are removed by centrifugation at a speed of 12000 rpm for 5 times, and the remaining silver nanowire / graphene composite is washed with deionized water and anhydrous ethanol, and then dried at 70°C under vacuum for 24 h to obtain the silver / graphene composite filler.

[0085] The preparation method of the porous silver-doped graphene in this embodiment is as follows: 0.04 parts of doped graphene powder is dispersed in 92 parts of deionized water, 0.3 parts of polyvinylpyrrolidone is added as a dispersant, and a uniform dispersion liquid is formed by ultrasonic treatment at a frequency of 52 kHz for 32 min; the obtained dispersion liquid is injected into a freeze-drying mold, frozen at -76°C for 22 h to form an ice crystal template, then transferred to a freeze-drying machine, and maintained at -44°C and a vacuum degree of ≤10 Pa for 43 h to sublimate the ice crystals and remove them, and finally obtain the porous silver-doped graphene.

[0086] The preparation method of the doped graphene of the embodiment is as follows: first, 0.08 parts of graphene oxide is dispersed in 128 parts of deionized water by weight, and is subjected to ultrasonic dispersion at a frequency of 52 kHz and synchronous treatment at a mechanical stirring rate of 420 rpm for 96 min to form a uniform suspension; then, 0.032 parts of silver nitrate is added and is subjected to magnetic stirring at a rate of 320 rpm and ultrasonic auxiliary dispersion at 35℃ for 78 min; after the pH value of the system is adjusted to 10 by dropwise adding 0.34 mol / L sodium hydroxide solution, a reducing solution containing 0.07 parts of ascorbic acid by weight is slowly added and is reacted in a 91℃ water bath for 216 min; after the reaction is completed, the retained precipitate is subjected to centrifugal separation at a speed of 10400 rpm for 4 times to remove ion impurities and ethanol-soluble byproducts in the supernatant in sequence, and is subjected to vacuum drying at 62℃ for 20 h to obtain the doped graphene.

[0087] The preparation method of the composite nano-silver-graphene antibacterial plastic master batch of the embodiment is as follows:

[0088] S1. The surface-modified silver / graphene composite filler is pre-mixed with polyvinylpyrrolidone in a high-speed mixer, the equipment type is a conventional powder mixer, the mixing speed is controlled at 680 rpm, and the mixing time is 13 min to ensure uniform coating of the filler surface with the dispersant;

[0089] S2. The polypropylene matrix resin and maleic anhydride grafted polypropylene are vacuum dried at 86℃ for 5 h to control the water content to be less than 0.05 wt%, and then are introduced into the first feeding zone of a twin-screw extruder, the screw temperature is set to 204℃, and the screw speed is 320 rpm for melt plasticizing treatment.

[0090] S3. The pre-mixed filler obtained in S1 is introduced into the second feeding zone of the twin-screw extruder through a side feeding device, the screw speed is controlled within the range of 360 rpm, the working length of the screw is 46D, and the effective residence time of the material in the melt zone is 4 min under nitrogen protection;

[0091] S4. The SEBS thermoplastic elastomer is introduced into the extrusion system from the third feeding zone, and a three-section kneading block is configured to form a high-shear zone in the local melt blending zone to enhance the interface bonding between SEBS and the matrix;

[0092] S5. Extrusion is performed through a Φ2.1 mm die, water cooling is performed at 21℃, and the length of the cut particles is controlled to be 2.6 mm to obtain cylindrical master batches with a particle size of 2.1 mm;

[0093] S6. The master batch is placed in a vacuum drying oven at 56℃ for 5 h to control the water content to be less than 0.1 wt%, and finally the antibacterial plastic master batch product is obtained.

[0094] Comparative Example 1

[0095] The same as example 1, except that the surface-modified silver / graphene composite filler is not surface-modified with 3-aminopropyl triethoxysilane coupling agent, but the unmodified silver / graphene composite filler is directly used for subsequent processing.

[0096] Comparative Example 2

[0097] The same as example 1, except that the doped graphene is not silver-doped graphene, but original graphene oxide.

[0098] Comparative Example 3

[0099] The same as example 1, except that polyvinylpyrrolidone is not added as a dispersant in the S1 step of the preparation method, but the surface-modified silver / graphene composite filler is directly added to the extrusion system.

[0100] Comparative Example 4

[0101] The same as example 1, except that in the preparation process of the surface-modified silver / graphene composite filler, glacial acetic acid is not added to adjust the pH value, but the hydrolysis reaction is carried out under neutral conditions (pH = 7.0).

[0102] Comparative Example 5

[0103] The same as example 1, except that copper chloride is not added as a morphology control agent in the preparation process of the silver / graphene composite filler, resulting in irregular morphology of the silver nanowires.

[0104] Comparative Example 6

[0105] The same as example 1, except that in the preparation process of the doped graphene, sodium borohydride is used instead of ascorbic acid as a reducing agent, and the reduction reaction is carried out at room temperature (25°C).

[0106] Comparative Example 7

[0107] The same as example 1, except that in the S4 step, a three-section kneading block is not configured to form a high-shear zone, but a conventional screw configuration is used for mixing.

[0108] Comparative Example 8

[0109] The same as example 1, except that in the preparation process of the surface-modified silver / graphene composite filler, glacial acetic acid is not added to adjust the pH value, but the hydrolysis reaction is carried out under neutral conditions (pH = 7.0).

[0110] Comparative Example 9

[0111] The same as example 1, except that in the preparation process of the doped graphene, ascorbic acid is not added as a reducing agent.

[0112] Performance test:

[0113] Antibacterial performance test (ISO 22196 standard): during the test, the master batch sample is injection molded into a test piece, and then cut into a 50mmx50mm test sample, inoculated with E. coli (ATCC 8739) and S. aureus (ATCC 6538) suspension (initial concentration 1.0x10 5 CFU / mL), covered with sterile polyethylene film and cultured at 37℃, 90%RH for 24h, then washed with PBS and diluted and plated for counting, and the antibacterial rate was calculated.

[0114] Mechanical properties: tensile strength test can be carried out according to GB / T 1040.2-2006 "Determination of tensile properties of plastics", polypropylene material added with the master batch of the application is injection molded into a standard dumbbell-shaped test sample, and the maximum tensile strength and elongation at break are tested by using an electronic universal material testing machine at a constant tensile speed, so as to evaluate the influence of the master batch on the mechanical support of the matrix material.

[0115] The properties of the plastics of examples 1-4 and comparative examples 1-9 are summarized in table 1, it can be seen from the table that the silver / graphene composite filler without surface modification by silane coupling agent leads to poor interfacial compatibility between the filler and the polymer matrix, affecting the uniformity of dispersion and the interfacial bonding force, and causing the antibacterial performance and mechanical properties to decrease simultaneously; using original graphene oxide instead of silver-doped graphene significantly weakens the antibacterial activity of the material, while the mechanical properties are less affected; the lack of polyvinylpyrrolidone dispersant during preparation leads to agglomeration of the nanofiller, forming stress concentration points, which significantly reduces the elongation at break; the lack of silane coupling reaction under acidic conditions reduces the coupling efficiency, affecting the surface modification effect of the filler and its antibacterial performance; the lack of copper chloride morphology regulator during the preparation of silver nanowires leads to irregular morphology of the silver nanowires, reducing the antibacterial efficiency; the use of a substitute reducing agent during the preparation of doped graphene and the reaction under low temperature conditions lead to incomplete reduction, affecting the doping effect of silver; the lack of high shear region during the extrusion blending stage leads to uneven mixing of the material, forming a microphase separation structure, which causes the mechanical properties to decrease; the lack of reducing agent leads to failure of graphene doping, and the antibacterial activity is significantly reduced.

[0116] Table 1: Properties of plastics of examples 1-4 and comparative examples 1-9

[0117] Sample No. Antibacterial rate (%) against E. coli Antibacterial rate (%) against S. aureus Tensile strength (MPa) Elongation at break (%) Example 1 95.8 94.2 32.6 156 Example 2 97.5 96.8 34.3 162 Example 3 99.3 99.1 35.8 178 Example 4 99.8 99.6 33.2 143 Comparative Example 1 92.6 91.3 28.1 130 Comparative Example 2 75.4 73.2 29.5 145 Comparative Example 3 94.2 93.5 25.6 110 Comparative Example 4 89.1 88.7 31.8 152 Comparative Example 5 93.5 92.6 32.0 155 Comparative Example 6 92.1 91.4 33.0 160 Comparative Example 7 94.9 93.7 29.3 125 Comparative Example 8 89.5 88.5 31.5 150 Comparative Example 9 72.8 71.5 30.2 148

[0118] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application and not to limit it, although the present application has been described in detail with reference to the above examples, those skilled in the art should understand that any equivalent structural transformation made within the concept of the present application, using the contents of the present application specification and drawings, should be covered within the protection scope of the claims of the present application.

Claims

1. A composite nano-silver-graphene antibacterial plastic master batch, characterized in that, The surface modified silver / graphene composite filler, 1.5-10.0 parts by weight, polypropylene matrix resin, 80-120 parts by weight, maleic anhydride grafted polypropylene, 2.0-8.0 parts by weight, polyvinylpyrrolidone, 0.5-0.9 parts by weight, and SEBS thermoplastic elastomer, 2.0-8.0 parts by weight are included. The surface modified silver / graphene composite filler is obtained by surface modification of silver / graphene composite filler with 3-aminopropyl triethoxysilane coupling agent; The silver / graphene composite filler is composed of doped graphene and silver nanowires on the surface of the doped graphene; The doped graphene is silver-doped graphene, and the doping amount is 0.05-0.5wt%; The silver nanowires are in-situ grown on the surface of the doped graphene by liquid phase reduction method; The preparation method of the surface modified silver / graphene composite filler is as follows: 1.0-1.5 parts of silver / graphene composite filler is dispersed in 80-100 parts of anhydrous ethanol, and a uniform suspension system is formed by ultrasonic treatment at a frequency of 40-60 kHz for 20-30 min; then 1.0-2.0 parts of 3-aminopropyl triethoxysilane and 2-5 parts of deionized water are added, and 0.1-0.2 parts by weight of glacial acetic acid is added to adjust the pH to 4.0-5.0; hydrolysis reaction is carried out under the condition of magnetic stirring speed of 300-500 rpm for 30-60 min to form a silanol solution; the mixed system is transferred to a reaction kettle, heated to 60-80℃ at a heating rate of 2-5℃ / min, and reacted for 20-24 h under nitrogen protection; after the reaction is completed, the system is cooled to room temperature, and the unreacted reagents and by-products in the supernatant are removed by centrifugation at a speed of 8000-12000 rpm; the remaining modified filler is washed with 1:1 ethanol / water mixture for 3-5 times, and finally dried at 50-60℃ under vacuum for 8-12 h to obtain the surface modified silver / graphene composite filler. The preparation method of the silver / graphene composite filler is as follows: first, 0.01-0.03 parts of porous silver-doped graphene is dispersed in 100-150 parts of ethylene glycol by weight, and a uniform suspension system is formed by ultrasonic treatment at a frequency of 40-60 kHz for 20-40 min, then 0.1-0.3 parts of silver nitrate and 0.3-0.8 parts of polyvinylpyrrolidone are added, and 0.0001-0.0005 parts of copper chloride is added as a morphology control agent, and the mixture is dissolved under the condition of a magnetic stirring rate of 300-500 rpm for 30-60 min to form a precursor solution; the mixed system is transferred to a reaction container, heated to 160-170℃ at a heating rate of 5-10℃ / min, and kept for 30-90 min to make silver ions in-situ reduce and grow silver nanowires on the silver crystal seeds of the porous graphene skeleton, and then naturally cooled to room temperature; the supernatant is removed by centrifugation at a speed of 8000-12000 rpm for 3-5 times to remove free silver nanoparticles and residual reactants in the supernatant, and the retained silver nanowire / graphene composite is washed with deionized water and anhydrous ethanol in sequence, and then vacuum dried at 50-70℃ for 12-24 h to obtain the silver / graphene composite filler.

2. The composite nano-silver-graphene antibacterial plastic master batch according to claim 1, characterized in that, The mass ratio of the doped graphene and the silver nanowires in the silver / graphene composite filler is 1:(2.0-5.0).

3. The composite nano-silver-graphene antibacterial plastic master batch according to claim 1, characterized in that, The preparation method of the porous silver-doped graphene is as follows: 0.02-0.05 parts of doped graphene powder is dispersed in 80-100 parts of deionized water by weight, 0.1-0.5 parts of polyvinylpyrrolidone is added as a dispersant, and the system is uniformly dispersed by ultrasonic treatment at a frequency of 40-60 kHz for 20-40 min; the obtained dispersion is injected into a freeze-drying mold, frozen at-70--80℃ for 18-24 h to form an ice crystal template, then transferred to a freeze-drying machine, and maintained at-50--40℃ under a vacuum degree of ≤10 Pa for 36-48 h to sublimate the ice crystals and remove the final porous silver-doped graphene.

4. The composite nano-silver-graphene antibacterial plastic master batch according to claim 3, characterized in that, The preparation method of the doped graphene is as follows: first, 0.04-0.1 parts of graphene oxide is dispersed in 20-200 parts of deionized water by weight, and then ultrasonic dispersion at a frequency of 40-60 kHz and synchronous mechanical stirring at a rate of 300-500 rpm are sequentially performed for 60-120 min to form a uniform suspension; Subsequently, 0.005-0.05 parts of silver nitrate is added and the stirring is continued at a magnetic stirring speed of 200-400 rpm and ultrasonic-assisted dispersion at 25-40℃ for 60-90 min. The pH value of the system is adjusted to 9-11 by dropwise addition of 0.1-0.5 mol / L sodium hydroxide solution, then a reducing solution containing 0.02-0.1 parts by weight of ascorbic acid is slowly added and reacted at 85-95℃ for 180-240 min. After the reaction is completed, the supernatant is removed by centrifugation at 8000-12000 rpm for 3-5 times to remove ionic impurities and ethanol-soluble byproducts, and the remaining precipitate is vacuum dried at 50-70℃ for 12-24 h to obtain the doped graphene.

5. The method for preparing a composite nano-silver-graphene antibacterial plastic master batch according to claim 1, characterized in that, The method comprises the following steps: S1. The surface-modified silver / graphene composite filler is premixed with polyvinylpyrrolidone in a high-speed mixer, the type of the equipment is a conventional powder mixer, the mixing speed is controlled at 500-800 rpm, and the mixing time is 10-15 min to ensure uniform coating of the dispersant on the surface of the filler; S2. The polypropylene matrix resin and maleic anhydride grafted polypropylene are vacuum dried at 80-90℃ for 4-6 h to control the water content to be less than 0.05 wt%, and then introduced into the first feeding zone of a twin-screw extruder, the screw temperature is set to 180-220℃, and the screw speed is 200-400 rpm for melt plasticization treatment; S3. The premixed filler obtained in S1 is introduced into the second feeding zone of the twin-screw extruder through a side feeding device, the screw speed is controlled in the range of 300-400 rpm, the screw working length is 40-50D, and the effective residence time of the material in the melt zone is 2-5 min under nitrogen protection; S4. The SEBS thermoplastic elastomer is introduced into the third feeding zone of the extrusion system, and a three-section kneading block is configured to form a high-shear zone in the local melt blending zone to enhance the interface bonding between SEBS and the matrix; S5. Extruded through a Φ1.5-2.5 mm die, and cut into particles using a 15-25℃ water cooling puller, the particle length is controlled at 2-3 mm to obtain cylindrical master batches with a particle size of 1.5-2.5 mm; S6. The master batch is placed in a vacuum drying oven at 50-60℃ for 4-6 h to control the water content to be less than 0.1 wt%, and finally the antibacterial plastic master batch product is obtained.

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