阅读说明：本技术 一种耐臭氧再生塑料及其加工工艺 (Ozone-resistant regenerated plastic and processing technology thereof ) 是由 李嘉荣 谭远胜 杨茗棋 于 2020-08-03 设计创作，主要内容包括：本申请涉及一种耐臭氧再生塑料及其加工工艺,属于再生材料技术领域,再生塑料所用原料包括以下重量份的组分：回收聚苯乙烯76.79-82.79份、聚苯乙烯6.97-12.97份、聚苯乙烯丁二烯共聚物8.00-11.94份、炭黑0.08-0.18份、硬脂酸镁0.10-0.16份、玄武岩纤维5.72-7.72份、纳米二氧化硅8-12份、纳米氧化铝11.8-13.8份、木粉14.68-16.68份、超分散剂0.035-0.045份、1-乙基-3-甲基咪唑磷酸二甲酯盐0.15-0.25份、二氢黄酮甙0.1-0.2份、微晶纤维素0.08-0.10份,本申请的再生塑料具有较强的耐臭氧能力、力学性能及耐热性。(The application relates to an ozone-resistant regenerated plastic and a processing technology thereof, belonging to the technical field of regenerated materials, wherein the raw materials used by the regenerated plastic comprise the following components in parts by weight: recovered polystyrene 76.79-82.79 parts, polystyrene 6.97-12.97 parts, polystyrene butadiene copolymer 8.00-11.94 parts, carbon black 0.08-0.18 part, magnesium stearate 0.10-0.16 part, basalt fiber 5.72-7.72 parts, nano silicon dioxide 8-12 parts, nano alumina 11.8-13.8 parts, wood powder 14.68-16.68 parts, hyperdispersant 0.035-0.045 part, 1-ethyl-3-methylimidazole dimethyl phosphate 0.15-0.25 part, dihydroflavone glycoside 0.1-0.2 part and microcrystalline cellulose 0.08-0.10 part.)

1. An ozone-resistant recycled plastic is characterized in that: the raw materials comprise the following components in parts by weight: 76.79-82.79 parts of recycled polystyrene, 6.97-12.97 parts of polystyrene, 8.00-11.94 parts of polystyrene butadiene copolymer, 0.08-0.18 part of carbon black, 0.10-0.16 part of magnesium stearate, 5.72-7.72 parts of basalt fiber, 8-12 parts of nano silicon dioxide, 11.8-13.8 parts of nano aluminum oxide, 14.68-16.68 parts of wood powder, 0.035-0.045 part of hyperdispersant, 0.15-0.25 part of 1-ethyl-3-methylimidazole dimethyl phosphate, 0.1-0.2 part of dihydroflavone glycoside and 0.08-0.10 part of microcrystalline cellulose.

2. The ozone-resistant recycled plastic as claimed in claim 1, wherein: the raw materials comprise the following components in parts by weight: 79.00-80.58 parts of recycled polystyrene, 8.97-10.97 parts of polystyrene, 9.00-10.94 parts of polystyrene butadiene copolymer, 0.10-0.16 part of carbon black, 0.11-0.15 part of magnesium stearate, 6.00-7.44 parts of basalt fiber, 9.5-10.5 parts of nano silicon dioxide, 12.0-13.6 parts of nano aluminum oxide, 15.00-16.36 parts of wood powder, 0.038-0.042 parts of hyper-dispersant, 0.18-0.22 part of 1-ethyl-3-methylimidazole dimethyl phosphate, 0.13-0.17 part of flavanone glycoside and 0.085-0.095 part of microcrystalline cellulose.

3. The ozone-resistant recycled plastic as claimed in claim 1, wherein: the weight ratio of the nano silicon dioxide to the nano aluminum oxide is 1: (1.25-1.35).

4. An ozone resistant recycled plastic as claimed in claim 1 or 2, wherein: the nano silicon dioxide is prepared by the following method:

uniformly mixing ethanol, water, tetraethyl orthosilicate and ammonia water, stirring and reacting for 7.5-8.5h at the temperature of 26-28 ℃ and the rotating speed of 290-310r/min, centrifuging, washing, drying at the temperature of 62-64 ℃, and grinding to obtain the nano silicon dioxide, wherein the weight ratio of the ethanol to the water to the tetraethyl orthosilicate to the ammonia water is (46-50): (0.6-1.0): (0.7-1.0): (3.6-3.9).

5. The ozone-resistant recycled plastic as claimed in claim 4, wherein: the nano silicon dioxide is modified by adopting the following method:

drying the nano-silica at the temperature of 120-125 ℃, mixing with ethanol, performing ultrasonic dispersion for 30-35min to obtain nano-silica suspension with the mass concentration of 4.8-5.0%, mixing with dichlorodimethylsilane, refluxing for 50-60min at the temperature of 130-132 ℃, washing, and drying at the temperature of 120-122 ℃ to obtain the modified nano-silica, wherein the weight ratio of the nano-silica suspension to the dichlorodimethylsilane is 1: (0.075-0.080).

6. An ozone resistant recycled plastic as claimed in claim 1 or 2, wherein: the nano alumina is modified by adopting the following method:

firstly, drying nano alumina for 1.5-2.0h at the temperature of 118-122 ℃, then mixing the dried nano alumina with ethanol, ultrasonically dispersing for 25-30min, then dropwise adding a silane coupling agent at the temperature of 80-90 ℃, reacting for 50-55min, cooling to 20-23 ℃, washing for 2-3 times, pouring out supernatant, and drying for 11-12h at the temperature of 80-82 ℃ to obtain modified nano alumina; wherein the weight ratio of the nano alumina to the ethanol is 1: (13-15); the weight ratio of the nano alumina to the silane coupling agent is 1: (0.02-0.03).

7. The ozone-resistant recycled plastic as claimed in claim 1, wherein: the hyperdispersant comprises acrylic acid and allyl alcohol, wherein the weight ratio of the acrylic acid to the allyl alcohol is (8-12): (10-14).

8. A process for preparing an ozone-resistant recycled plastic as claimed in any one of claims 1 to 7, wherein the process comprises the following steps: the method comprises the following steps:

s1: drying all the raw materials at the temperature of 155-165 ℃ for 1.5-2.5 h;

s2: mixing the dried raw materials at a rotation speed of 45-55r/min for 10-15min to obtain a mixture;

s3: and melting, blending and extruding the mixture to obtain the recycled plastic.

9. The process for processing the ozone-resistant recycled plastic as claimed in claim 8, wherein the process comprises the following steps: the device used in the step S3 is a screw extruder; the temperature of each section of the screw extruder is as follows: the temperature of the head is 215-; the rotating speed of the screw in the screw extruder is 1590-1610 r/min.

Technical Field

The application relates to the technical field of recycled materials, in particular to an ozone-resistant recycled plastic and a processing technology thereof.

Background

At present, with the development of economy, the usage amount of plastics is higher and higher, but because plastics can not be naturally degraded, the environment can be greatly polluted, so in order to achieve environmental protection and energy saving, waste plastics are generally subjected to resource recovery, processing and recycling, and resources are not lost.

Plastic is used as an insulating material to manufacture a shell, a toner cartridge and other positions of a printer, and when the printer is in an operating state, a high-voltage discharge arc is generated, oxygen in air generates ozone under the stimulation of the high-voltage discharge arc, and the ozone has strong oxidizing property, so that the plastic is easily oxidized to generate phenomena such as fading, strength reduction and the like after long-time use.

Disclosure of Invention

The aim of the application is to provide an ozone-resistant recycled plastic which has oxidation resistance and reduces the possibility of discoloration or strength reduction caused by oxidation of the plastic.

The second purpose of the application is to provide a processing technology of the ozone-resistant recycled plastic, which is simple in technology and enables the produced recycled plastic to have strong ozone resistance.

The above object of the present application is achieved by the following technical solutions:

the ozone-resistant regenerated plastic comprises the following raw materials in parts by weight: 76.79-82.79 parts of recycled polystyrene, 6.97-12.97 parts of polystyrene, 8.00-11.94 parts of polystyrene butadiene copolymer, 0.08-0.18 part of carbon black, 0.10-0.16 part of magnesium stearate, 5.72-7.72 parts of basalt fiber, 8-12 parts of nano silicon dioxide, 11.8-13.8 parts of nano aluminum oxide, 14.68-16.68 parts of wood powder, 0.035-0.045 part of hyperdispersant, 0.15-0.25 part of 1-ethyl-3-methylimidazole dimethyl phosphate, 0.1-0.2 part of dihydroflavone glycoside and 0.08-0.10 part of microcrystalline cellulose.

By adopting the technical scheme, in order to save resources and reduce production cost, the recycled polystyrene in the range is added and mixed with polystyrene to be used to prepare the recycled plastic, and the mechanical property of the recycled polystyrene is poor, so that the mechanical property of the recycled polystyrene is enhanced by adding the wood flour in the range, and the wood flour are mutually crossed and wound to form a good wrapping phenomenon with the recycled polystyrene so as to generate good mechanical interlocking. The mesh number of the wood powder used in the application is 100-200 meshes, the specific surface area of the wood powder in the mesh number range is larger, the contact area of the wood powder and the recycled polystyrene is increased, the bonding force between the wood powder and the recycled polystyrene is increased, and the mechanical property of the recycled polystyrene is enhanced.

The carbon black is light, loose and superfine black powder with large specific surface area, and is added in the range, so that the carbon black is dispersed in the recycled plastic, the mechanical property of the recycled plastic can be enhanced, and the effects of coloring and toning are achieved. Since the higher the degree of dispersion of carbon black in recycled plastics, the higher the coloring strength, carbon black is used in combination with magnesium stearate and a hyperdispersant within this range, and the coloring property of carbon black in recycled plastics is improved.

The polystyrene butadiene copolymer has uniform quality, less foreign matters and excellent mechanical stability, and the polystyrene butadiene copolymer is added into the plastic in the range and matched with the recycled polystyrene for use, so that the toughness of the recycled plastic can be improved, the bearing strength is increased, and the brittleness of the recycled plastic is reduced.

Magnesium stearate and hyperdispersant are used as dispersing agents, and the dispersing property of carbon black in the recycled plastic and the dispersing property of other components in the recycled plastic can be improved when the magnesium stearate and hyperdispersant are added into the recycled plastic. The molecular structure of the hyperdispersant is composed of two parts with different performances and functions, one part is an anchoring group, the other part is a solvation polymerization chain, and the hyperdispersant can be better compatible with polymers such as recycled polystyrene, polystyrene and polystyrene butadiene copolymer, so that the hyperdispersant is added into the recycled plastic according to the range, all the components in the recycled plastic can be better dispersed in the recycled plastic, the compatibility and the stability between the components are improved, the agglomeration or flocculation phenomenon is not easy to occur, and the mechanical property of the recycled plastic is improved.

Since the oxidation rate of the recycled plastic is accelerated by the increase of the temperature, and the oxidation rate of the recycled plastic is accelerated if the heat resistance of the recycled plastic is poor, the heat resistance of the recycled plastic needs to be improved in order to make the recycled plastic have a strong oxidation resistance even in a high-temperature environment. The nano silicon dioxide has higher heat resistance value, better heat resistance and higher strength, the heat resistance and the mechanical property of the recycled plastic can be obviously improved by adding the nano silicon dioxide into the recycled plastic according to the range, if the addition amount of the nano silicon dioxide is too much, the integral hardness of the recycled plastic is too high, the brittleness is increased, the recycled plastic is easy to impact and break, and the anti-cracking property of the recycled plastic is reduced;

the basalt fiber is a fiber obtained by melting natural basalt ore at high temperature of about 1500 ℃, then forming the molten basalt ore through a platinum-rhodium alloy bushing plate and drawing the molten basalt fiber at high speed by a wire drawing machine, so that the basalt fiber has high tensile strength, high temperature resistance, heat insulation and other excellent performances, the use tolerance temperature range of the basalt fiber is-260 ℃ to 700 ℃, the tolerance temperature range of the glass fiber and the like is generally 60 ℃ to 450 ℃, and the mechanical property and the heat resistance of the plastic can be obviously improved by adding the basalt fiber into the regenerated plastic according to the range;

therefore, the nano silicon dioxide and the basalt fiber are added into the recycled plastic according to the range, so that the heat resistance and the mechanical property of the recycled plastic can be obviously improved; meanwhile, the nano silicon dioxide can improve the tensile strength of the basalt fiber and can enable Fe in the basalt fiber to be contained²⁺Conversion to Fe³⁺The heat resistance of the basalt fiber is improved, and the phenomenon that the strength of the basalt fiber is reduced at a higher temperature is reduced, so that the heat resistance of the recycled plastic is improved.

The nano alumina is added into the recycled plastic according to the range, so that the binding force among all components in the recycled plastic can be enhanced, the nano alumina is matched with nano silicon dioxide and basalt fiber and mutually matched, the mechanical property and the heat resistance of the recycled plastic are improved, and the oxidation resistance of the recycled plastic can be improved by adding the nano alumina into the recycled plastic.

The 1-ethyl-3-methylimidazole dimethyl phosphate belongs to an ionic liquid, has good thermal stability, and can improve the oxidation resistance and heat resistance of the regenerated plastic by adding the 1-ethyl-3-methylimidazole dimethyl phosphate into the regenerated plastic according to the range; the flavanone glycoside is also called as hesperidin, has high thermal stability, can be matched with 1-ethyl-3-methylimidazole dimethyl phosphate in the regenerated plastic to play a synergistic effect, and can improve the oxidation resistance and the heat resistance of the regenerated plastic together;

the microcrystalline cellulose is a powdery substance obtained by hydrolyzing natural fibers to the limit polymerization degree, has low polymerization degree, large specific surface area and good adsorbability, and is matched with 1-ethyl-3-methylimidazole dimethyl phosphate and flavanone glycoside in the regenerated plastic to reduce the possibility of breakage of double bonds of polymers in the regenerated plastic, thereby achieving the effect of improving the oxidation resistance of the regenerated plastic and improving the ozone resistance of the regenerated plastic.

Preferably, the raw materials comprise the following components in parts by weight: 79.00-80.58 parts of recycled polystyrene, 8.97-10.97 parts of polystyrene, 9.00-10.94 parts of polystyrene butadiene copolymer, 0.10-0.16 part of carbon black, 0.11-0.15 part of magnesium stearate, 6.00-7.44 parts of basalt fiber, 9.5-10.5 parts of nano silicon dioxide, 12.0-13.6 parts of nano aluminum oxide, 15.00-16.36 parts of wood powder, 0.038-0.042 parts of hyper-dispersant, 0.18-0.22 part of 1-ethyl-3-methylimidazole dimethyl phosphate, 0.13-0.17 part of flavanone glycoside and 0.085-0.095 part of microcrystalline cellulose.

By adopting the technical scheme, the recycled polystyrene and the polystyrene are matched to prepare the recycled plastic according to the range, so that the resource is saved, and the production cost is reduced; simultaneously adding carbon black in the range as a coloring agent into the recycled plastic; simultaneously, nano silicon dioxide, nano aluminum oxide, 1-ethyl-3-methylimidazole dimethyl phosphate, flavanone glycoside, basalt fiber, wood powder and microcrystalline cellulose are added according to the range to be mixed and matched for use, so that the oxidation resistance, the heat resistance and the mechanical property of the regenerated plastic are further improved; meanwhile, the magnesium stearate and the hyperdispersant in the range are added to be used as the dispersant in a matching way, so that the dispersibility of each component in the recycled plastic is enhanced, the effect of each component in the recycled plastic is improved, and the oxidation resistance, the heat resistance and the mechanical property of the recycled plastic are improved.

Preferably, the weight ratio of the nano silicon dioxide to the nano aluminum oxide is 1: (1.25-1.35).

By adopting the technical scheme, the nano silicon dioxide and the nano aluminum oxide are mixed and matched according to the proportion range, so that the nano silicon dioxide and the nano aluminum oxide can play a synergistic effect with each other, the nano silicon dioxide can effectively inhibit the nano aluminum oxide from high-temperature phase change at high temperature, the nano aluminum oxide can make up the oxidation resistance of the nano silicon dioxide, and the oxidation resistance, the heat resistance and the mechanical property of the regenerated plastic are improved together.

If the proportion range of the nano silicon dioxide and the nano aluminum oxide is lower than the range, the synergistic effect between the nano silicon dioxide and the nano aluminum oxide cannot be exerted, so that the oxidation resistance, the heat resistance and the mechanical property of the regenerated plastic are reduced; if the ratio range of the nano silicon dioxide and the nano aluminum oxide is higher than the range, the nano silicon dioxide cannot fully play a role in inhibiting the high-temperature phase change of the nano aluminum oxide, so that the oxidation resistance and the thermal stability of the nano aluminum oxide are reduced, and the oxidation resistance and the heat resistance of the regenerated plastic are further reduced.

Preferably, the nano silicon dioxide is prepared by the following method:

uniformly mixing ethanol, water, tetraethyl orthosilicate and ammonia water, stirring and reacting for 7.5-8.5h at the temperature of 26-28 ℃ and the rotating speed of 290-310r/min, centrifuging, washing, drying at the temperature of 62-64 ℃, and grinding to obtain the nano silicon dioxide, wherein the weight ratio of the ethanol to the water to the tetraethyl orthosilicate to the ammonia water is (46-50): (0.6-1.0): (0.7-1.0): (3.6-3.9).

By adopting the technical scheme, the particle size of the prepared nano silicon dioxide can be influenced by the factors of the addition amount of the ammonia water, the reaction temperature and the reaction time, and the particle size of the nano silicon dioxide is controlled within a proper range, so that the dispersity of the nano silicon dioxide in the regenerated plastic can be obviously improved, and the effect of the nano silicon dioxide in the regenerated plastic is enhanced. Therefore, the conditions such as the addition amount of ammonia water, the reaction temperature, the reaction time and the like are controlled within the range, the particle size of the prepared nano silicon dioxide can be controlled to be about 40-45nm, the dispersibility of the nano silicon dioxide in the recycled plastic is obviously improved, and the mechanical property of the recycled plastic is improved.

If the addition amount of the ammonia water is less than the range, the particle size of the nano silicon dioxide is too small, and if the addition amount of the ammonia water is more than the range, the particle size of the nano silicon dioxide can not be increased continuously, and the cost is increased; if the reaction temperature is lower than the range, the particle size of the nano silicon dioxide is too large, and if the reaction temperature is higher than the range, the particle size of the nano silicon dioxide is too reduced, and the interaction between the nano silicon dioxide with small particle size is too strong and easy to agglomerate; if the reaction time is less than this range, the particle size of the nano-silica is too small, and if the reaction time is more than this range, the particle size of the nano-silica cannot be increased further and the cost is increased.

Preferably, the nano-silica is modified by the following method:

drying the nano-silica at the temperature of 120-125 ℃, mixing with ethanol, performing ultrasonic dispersion for 30-35min to obtain nano-silica suspension with the mass concentration of 4.8-5.0%, mixing with dichlorodimethylsilane, refluxing for 50-60min at the temperature of 130-132 ℃, washing, and drying at the temperature of 120-122 ℃ to obtain the modified nano-silica, wherein the weight ratio of the nano-silica suspension to the dichlorodimethylsilane is 1: (0.075-0.080).

By adopting the technical scheme, dichlorodimethylsilane is used as a modifier to modify the nano-silica, so that the modified nano-silica has stronger hydrophobicity, the dispersibility of the nano-silica in the regenerated plastic is improved, the dosage of the dichlorodimethylsilane is controlled within the range, the contact angle of the modified nano-silica can be maximized, the hydrophobicity is highest, the dispersing capacity of the modified nano-silica is best, the contact angle cannot be maximized when the dosage of the dichlorodimethylsilane is lower than or higher than the range, and the dispersibility of the modified nano-silica is reduced.

Preferably, the nano alumina is modified by the following method:

firstly, drying nano alumina for 1.5-2.0h at the temperature of 118-122 ℃, then mixing the dried nano alumina with ethanol, ultrasonically dispersing for 25-30min, then dropwise adding a silane coupling agent at the temperature of 80-90 ℃, reacting for 50-55min, cooling to 20-23 ℃, washing for 2-3 times, pouring out supernatant, and drying for 11-12h at the temperature of 80-82 ℃ to obtain modified nano alumina; wherein the weight ratio of the nano alumina to the ethanol is 1: (13-15); the weight ratio of the nano alumina to the silane coupling agent is 1: (0.02-0.03).

By adopting the technical scheme, the nanometer alumina serving as inorganic particles in the regenerated plastic has poor compatibility with polymers in the regenerated plastic, and the aggregation phenomenon is easy to occur in the regenerated plastic, so the nanometer alumina needs to be organized. According to the range, the silane coupling agent is used as the modifying agent to modify the nano alumina, the temperature range and other conditions are controlled, and after the reaction is finished, unreacted substances on the surface of the nano alumina are washed away, so that the silane coupling agent is grafted to the surface of the nano alumina, the compatibility of the nano alumina and an organic phase in the regenerated plastic is enhanced, the dispersibility of the nano alumina in the regenerated plastic is improved, and the effects of improving the oxidation resistance and the heat resistance of the nano alumina in the regenerated plastic can be fully exerted. Meanwhile, the nano alumina is dried within the temperature range, so that the influence of moisture contained in the nano alumina on the modification process is reduced.

Preferably, the hyperdispersant comprises acrylic acid and allyl alcohol, and the weight ratio of the acrylic acid to the allyl alcohol is (8-12): (10-14).

By adopting the technical scheme, the acrylic acid belongs to the representative of anionic dispersing agents and has good dispersibility, but the structure of the acrylic acid has hydrophilic groups, so that the particles are easy to desorb and are caused to be flocculated again, and the lipophilic groups can not play a role in space stabilization. In addition, the excessive high or low proportion of the allyl alcohol in the hyperdispersant can reduce the dispersibility of the hyperdispersant, so that the oxidation resistance, the heat resistance and the mechanical property of the recycled plastic are influenced.

The second purpose of the application is to provide a processing technology of ozone-resistant recycled plastic, which comprises the following steps:

s1: drying all the raw materials at the temperature of 155-165 ℃ for 1.5-2.5 h;

s2: mixing the dried raw materials at a rotation speed of 45-55r/min for 10-15min to obtain a mixture;

s3: and melting, blending and extruding the mixture to obtain the recycled plastic.

By adopting the technical scheme, all the raw materials are dried within the temperature range, the moisture in all the raw materials is fully eliminated, the possibility of decomposition of the raw materials in the melting process is reduced, all the raw materials are uniformly mixed, and then are melted, blended and extruded, the process is simple, and the obtained regenerated plastic has higher oxidation resistance, heat resistance and mechanical property.

Preferably, the device used in the process of step S3 is a screw extruder; the temperature of each section of the screw extruder is as follows: the temperature of the head is 215-; the rotating speed of the screw in the screw extruder is 1590-1610 r/min.

Through adopting above-mentioned technical scheme, the temperature in the control screw extruder in this within range can obviously increase the mobility of reclaimed plastic fuse-element, improves reclaimed plastic's elongation at break to improved reclaimed plastic's mechanical properties, if the high temperature in the screw extruder, can make the energy consumption of preparation reclaimed plastic increase, thereby make manufacturing cost improve.

In summary, the present application includes at least one of the following beneficial technical effects:

1. the recycled plastic prepared by the processing technology has higher oxidation resistance, heat resistance and mechanical property by virtue of the synergistic effect among the components in the raw materials;

2. the processing technology of the recycled plastic has the advantages that the operation process is simple, the ratio of the recycled polystyrene to the polystyrene in the used raw materials is high, and the production cost is low;

3. the compatibility among all components in the regenerated plastic is enhanced by adopting the modified nano silicon dioxide and the modified nano aluminum oxide.

Detailed Description

The present application will be described in further detail with reference to examples.

In the following examples and comparative examples:

recovered polystyrene was purchased from Fpico;

polystyrene was purchased from taiwan gaofu;

polystyrene butadiene copolymers are available from LG;

carbon black is available from ORION;

magnesium stearate was purchased from the chinese science;

1-Ethyl-3-methylimidazole dimethyl phosphate salt was purchased from Shanghai Chengjie Ionic liquids, Inc.;

flavanone glycosides were purchased from Hechengjing chemical Co., Ltd, Hubei;

microcrystalline cellulose was purchased from Jiangsu Caosheng Biotech limited;

the wood flour is purchased from the wood processing factory in Benzhou province in Fisher county, and the mesh number is 100-200 meshes.

Preparation example 1

The nano silicon dioxide is prepared by the following method:

uniformly mixing 46g of ethanol, 0.6g of water, 0.7g of tetraethyl orthosilicate and 3.6g of ammonia water, stirring and reacting for 7.5h at the temperature of 26 ℃ and the rotating speed of 290r/min, centrifuging, washing, removing unreacted substances, drying at the temperature of 62 ℃, and grinding to obtain the nano silicon dioxide with the particle size of 40 nm.

Preparation example 2

The nano silicon dioxide is prepared by the following method:

the preparation method comprises the steps of uniformly mixing 48g of ethanol, 0.8g of water, 0.85g of tetraethyl orthosilicate and 3.75g of ammonia water, stirring and reacting for 8 hours at the temperature of 27 ℃ and the rotating speed of 300r/min, centrifuging, washing, removing unreacted substances, drying at the temperature of 63 ℃, and grinding to obtain the nano silicon dioxide with the particle size of 42.5 nm.

Preparation example 3

The nano silicon dioxide is prepared by the following method:

50g of ethanol, 1g of water, 1g of tetraethyl orthosilicate and 3.9g of ammonia water are uniformly mixed, stirred and reacted for 8 hours at the temperature of 27 ℃ and the rotating speed of 300r/min, centrifuged, washed, unreacted substances are removed, and the nano silicon dioxide with the particle size of 45nm is obtained by drying and grinding at the temperature of 64 ℃.