阅读说明：本技术 碳纳米管改性涂料所需的改性导热填料的制备方法 (Preparation method of modified heat-conducting filler required by carbon nano tube modified coating ) 是由 段宝荣 王全杰 王辉强 唐志海 王琦研 王雪 刁屾 仇同济 于 2019-12-30 设计创作，主要内容包括：本发明涉及碳纳米管改性阻燃性水性聚氨酯涂料或胶粘剂所需的改性导热填料的制备方法,首先利用偶联剂、去离子水、单宁酸和氮化硼纳米片层制备改性导热填料；然后利用聚合物多元醇和改性导热填料制备A组分；最后利用A组分、异氰酸酯和二月桂酸二丁基锡,并加入改性剂、多元醇扩链剂、交联剂和填料聚合链制得聚氨酯A,在所得聚氨酯A中再加入增粘剂制得碳纳米管改性阻燃性聚氨酯涂料与胶粘剂。所得聚氨酯涂料与胶粘剂具有更好地降低燃烧烟雾性能及提高压敏性能的突出优势。(The invention relates to a preparation method of a modified heat-conducting filler required by a carbon nano tube modified flame-retardant waterborne polyurethane coating or an adhesive, which comprises the following steps of firstly preparing the modified heat-conducting filler by using a coupling agent, deionized water, tannic acid and a boron nitride nanosheet layer; then preparing a component A by using polymer polyol and modified heat-conducting filler; and finally, preparing polyurethane A by using the component A, isocyanate and dibutyltin dilaurate, adding a modifier, a polyol chain extender, a cross-linking agent and a filler polymeric chain, and adding a tackifier into the obtained polyurethane A to prepare the carbon nano tube modified flame-retardant polyurethane coating and adhesive. The obtained polyurethane coating and adhesive have the outstanding advantages of better reducing the combustion smoke performance and improving the pressure-sensitive performance.)

1. The preparation method of the modified heat-conducting filler required by the carbon nano tube modified flame-retardant waterborne polyurethane coating or adhesive is characterized by comprising the following steps of:

(1) preparing the modified heat-conducting filler, wherein the mass ratio of the modified heat-conducting filler to the modified heat-conducting filler is 1: (2-4): (1-2): (0.5-0.8) mixing and hydrolyzing the coupling agent, deionized water, tannic acid and boron nitride nanosheets for 30-40 min to obtain a hydrolysate A; subjecting the obtained hydrolysate to

And (C) adding the A into a high-speed mixer at the temperature of 80-90 ℃ to continue mixing for 30-40 min, cooling and discharging, and performing vacuum drying to obtain the modified heat-conducting filler.

2. The preparation method of the coating or the adhesive required by the carbon nano tube modified flame-retardant waterborne polyurethane coating or the adhesive is characterized by comprising the following steps of:

(1) preparing a component A, mixing polymer polyol and modified heat-conducting filler according to a mass ratio of (4-5) to 1, performing ultrasonic treatment for 1-2.5 hours, and performing reduced pressure dehydration for 1-2 hours at 100-110 ℃ to obtain the component A;

(2) preparing the coating and the adhesive, namely mixing the component A, isocyanate and dibutyltin dilaurate at the temperature of 50-60 ℃ according to the mass ratio of (2.5-3.0): 1: 0.02 reacting for 40-50 min at the rotating speed of 60-80 r/min, heating to 75-85 ℃, continuing to react for 1-3h, adding 0.1-0.2 time of a modifier, 0.21-0.32 time of a polyol chain extender, 0.02-0.04 time of a cross-linking agent, 0.02-0.05 time of a filler polymeric chain and 1.2 times of water, continuing to react for 1-2h at 80-90 ℃ to prepare polyurethane A, adding 0.04-0.06 time of a tackifier into the obtained polyurethane A, and uniformly mixing to prepare a polyurethane emulsion which is a carbon nano tube modified flame-retardant polyurethane coating or adhesive;

the times of the added modifier, the polyol chain extender, the cross-linking agent, the filler polymer chain and the water are all based on the weight of the isocyanate.

3. The preparation method of the modifier required by the carbon nano tube modified flame-retardant waterborne polyurethane coating or adhesive is characterized by comprising the following steps of:

the preparation method of the modifier comprises the following steps: adding 70-80 g of water into 0.1g of hydroxylated carbon nanotube, 20-30 g of polyvinyl alcohol and 4-60 g of catechin, stirring and reacting for 1-3h at 60-80 ℃, adding 2-3 g of butyrolactone, 0.4-0.6 g of 1, 2-dibromopropane and 5g of acetone, stirring and reacting for 1-2h at 40-60 ℃, and spray drying to obtain the modifier.

4. The preparation method of the hydroxylated carbon nanotube required by the carbon nanotube modified flame-retardant waterborne polyurethane coating or adhesive is characterized by comprising the following steps:

the preparation method of the hydroxylated carbon nanotube comprises the following steps: taking 1.1-1.5 g of carbon nano tube and 280-320 mL of concentrated sulfuric acid and concentrated nitric acid according to a volume ratio of 2: adding the mixed acid of 1 into a 500mL flask, reacting at 65-75 ℃, and condensing and refluxing for 2-4 h in an ultrasonic cleaner with ultrasonic power of 200W and ultrasonic frequency of 40 KHz; then transferring the mixture into a beaker, diluting the mixture with 250g of deionized water, performing suction filtration by using a microporous filter membrane with the diameter of 0.2 mu m, and repeatedly washing the mixture with the deionized water until the mixture is neutral; finally, drying the carbon nano tube after suction filtration at 105 ℃, and grinding the carbon nano tube into powder for later use to obtain a hydroxylated carbon nano tube; the carbon nano tube is a single-walled carbon nano tube produced by a chemical vapor deposition method, the diameter is 2nm, the tube length is 100 mu m, the purity is 99.5 wt%, the amorphous carbon impurity content is less than 5%,

ash impurity <3 wt%, specific surface area 700m 2/g.

5. The preparation method of the filler polymer chain required by the carbon nano tube modified flame-retardant waterborne polyurethane coating or adhesive is characterized by comprising the following steps:

the preparation method of the filler polymer chain comprises the following steps:

(1) vacuum drying 9-16g of nano silicon carbide at 105 ℃, dispersing the nano silicon carbide in 40g of N, N-dimethylformamide for ultrasonic dispersion at 30-60 ℃ for 30-45 min to prepare a solution A;

(2) dissolving 20-24g of diphenylmethane diisocyanate and 16-20g of polylactic acid in 40g of N, N-dimethylformamide to prepare solution B,

(3) and mixing nano silver, 1, 5-naphthalene disulfonic acid and 5-hydroxymethyl furfural according to the weight ratio of 1: 20: stirring for 1-2h at 50-70 ℃ in a proportion of 50-80 to prepare a solution C, wherein the weight of the nano silver is 1/100 of that of the nano silicon carbide;

(4) dropwise adding the solution B into the solution A, adding the solution C into the solution A, stirring and reacting at 50-60 ℃ for 2-3 h,

to produce a filler polymer chain.

Technical Field

The invention relates to the field of functional polymer materials, in particular to a preparation method of a carbon nano tube modified flame-retardant polyurethane coating and an adhesive.

Background

With the development of fields such as automobiles, electronic appliances, wind power generation devices, aviation and the like and the continuous improvement of performance requirements thereof, the adhesive is used as an important auxiliary material necessary for the fields, and the application of the adhesive is more and more extensive. Common pressure sensitive adhesive tape and label technology is mature, and the yield is over-demand; however, pressure-sensitive adhesive tapes and labels used in the fields of automobiles, electronic industries and the like are required to have good cohesive force, ensure that the adhesive layer is not damaged when the pressure-sensitive adhesive tapes and labels are subjected to peeling force or shearing force after bonding, and can conveniently repair or secondarily bond an adherend.

A pressure-sensitive adhesive is an adhesive that can wet the surface of an adherend and bond it firmly with only a certain pressure. Although the pressure-sensitive adhesive can be used directly for bonding, in general, the pressure-sensitive adhesive is applied to a substrate such as a plastic film, paper, metal foil, or fabric to prepare a pressure-sensitive adhesive product such as a pressure-sensitive adhesive label or a pressure-sensitive adhesive tape, and is used in practice.

With the continuous development of electronic science and technology, electronic components and integrated circuits tend to be dense and miniaturized continuously, and the use frequency of electronic equipment is increased rapidly, so that heat generated by the electronic equipment is accumulated and increased continuously, the temperature of the working environment of the electronic equipment is increased continuously, local high temperature is easily formed, and the stability and the service life of the electronic equipment are influenced. In order to ensure that the electronic components can work effectively for a long time, the temperature must be prevented from being increased continuously, and the heat dissipation of the electronic components becomes a problem to be solved urgently.

However, the heat dissipation problem of electronic components puts higher demands on the bonding between the electrons, and the bonding between the electrons is required to have not only better stability but also higher thermal conductivity. Materials with high thermal conductivity are widely applied to various fields of national defense and national economy. Conventional heat conducting materials are usually metals (e.g. Cu, Fe, Al, Ag, etc.), metal oxides (e.g. Al)₂O₃MgO, ZnO, etc.),Metal nitrides (e.g., AlN, BN, etc.) and other non-metallic materials (e.g., graphite, etc.). Although the metal material has good heat conductivity, the metal material is easily corroded by chemical substances and has poor electrical insulation. With the rapid development of science and technology, higher requirements are put forward on the chemical corrosion resistance, the electrical insulation performance, the impact resistance and the processing performance of heat conducting materials in many occasions, and the polymer has excellent mechanical property, chemical corrosion resistance and electrical insulation performance, so that the development of polymer-based heat conducting adhesives to replace traditional materials becomes a research hotspot.

The polyurethane adhesive is generally obtained by stepwise polymerization of an oligomer polyol such as polyester or polyether and a polyisocyanate, with a diol or diamine as a chain extender. Due to the special chemical structure of the polyurethane, the polyurethane has the following special properties: the hardness range is wide, the hardness range of polyurethane is from Shore A10 to Shore D80, and the hardness range of common rubber is from Shore A20 to Shore A90; the wear resistance is good, and the wear resistance of the polyurethane is 3-10 times that of natural rubber; the polyurethane has excellent solvent resistance and oil resistance, and is hardly etched in fuel oil and water; the low temperature resistance is good, the brittleness temperature of the polyester polyurethane is about minus 40 ℃, and the brittleness temperature of the polyether polyurethane can reach minus 70 ℃; and (4) strong adhesion. These properties are not available in many materials and polyurethane adhesives protect electronic components from vibration, corrosion and dust.

Chinese patent with application number CN201910899146.7 discloses a preparation method of bio-based polyurethane pressure-sensitive adhesive, which comprises the following steps: s1, adding polylactic acid polyol and a hydrophilic agent into a reaction container, carrying out reduced pressure dehydration at 100-120 ℃ for 1-2h, and then cooling to 40-60 ℃; s2, adding an isocyanate curing agent, uniformly mixing, and introducing inert gas at 40-60 ℃ for 1-2 hours; s3, adding a catalyst, adjusting the viscosity of the mixed solution by using acetone, and reacting at 50-80 ℃ for 6-8 h to generate a polymer; s4, adding a neutralizer into the reaction container, and reacting for 5-20 min to ionize the polymer; s5, dissolving the chain extender in water, adding the solution into a reaction vessel, and stirring to emulsify the polymer to form emulsion; s6, distilling and recovering acetone in the emulsion to obtain the bio-based polyurethane pressure-sensitive adhesive. The bio-based polyurethane pressure-sensitive adhesive and the adhesive tape prepared by the method are also provided. The bio-based polyurethane pressure-sensitive adhesive has the advantages of good degradation performance, wide peeling force range and low heat conductivity coefficient, and has the defects of small peeling force.

Chinese patent with application number CN201110364443.5 discloses a high-elasticity, heat-conducting and environment-friendly polyurethane sealant. The problems to be solved are as follows: the one-component polyurethane sealant has high elasticity, heat resistance, water resistance, heat conductivity and adhesiveness, and can well adhere various base materials such as various woods, concrete and the like, and a preparation method thereof. It is characterized by that it is made up by using 25-60% of prepolymer prepared from polyether glycol with high activity and high molecular weight and isocyanate, 15-30% of plasticizer, 15-35% of heat-conducting filler, 2-10% of thixotropic agent and 0.01-1% of amine or tin compound catalyst through a certain mixing process. The sealant is used for paving and bonding various wood floors, particularly for paving the wood floors of emerging floor heating mechanisms so as to replace the traditional wood keel paving mode. However, the addition of the heat-conducting filler is high, the heat-conducting filler and the polyurethane matrix are very different in physical form and molecular structure, and the heat-conducting filler and the polyurethane matrix have low dispersibility, small particles and large specific surface area, and are easy to agglomerate in application, so that the service performance of the adhesive is influenced.

Therefore, the preparation of the polyurethane pressure-sensitive adhesive with low addition of the heat-conducting filler and good heat-conducting property and mechanical property is a research hotspot at present.

Polyurethane releases a large amount of smoke in the combustion process, CO is one of toxic gases in the smoke, so that how to reduce the content of CO greatly in the smoke reducing process is realized, and silver catalysis is a new degradation direction.

Disclosure of Invention

The invention aims to solve the technical problem of providing a preparation method of a carbon nano tube modified flame-retardant waterborne polyurethane coating and an adhesive, which improves two main indexes of flame retardance and pressure sensitivity of the polyurethane coating and the adhesive, and the adhesive has small addition amount of a heat-conducting filler and also has good pressure-sensitive property, heat-conducting property and mechanical property.

In order to realize the purpose, the invention adopts the following technical scheme:

the preparation method of the carbon nano tube modified flame-retardant waterborne polyurethane coating and the adhesive is characterized by comprising the following steps of:

(1) preparing the modified heat-conducting filler, wherein the mass ratio of the modified heat-conducting filler to the modified heat-conducting filler is 1: (2-4): (1-2): (0.5-0.8) mixing and hydrolyzing the coupling agent, deionized water, tannic acid and the boron nitride nanosheet layer for 30-40 min to obtain a hydrolysate A; adding the hydrolysate A into a high-speed mixer at the temperature of 80-90 ℃ to continue mixing for 30-40 min, cooling, discharging and vacuum drying to obtain the modified heat-conducting filler;

(2) preparing a component A, mixing polymer polyol and modified heat-conducting filler according to a mass ratio of (4-5) to 1, performing ultrasonic treatment for 1-2.5 hours, and performing reduced pressure dehydration for 1-2 hours at 100-110 ℃ to obtain the component A;

(3) preparing the coating and the adhesive, namely mixing the component A, isocyanate and dibutyltin dilaurate at the temperature of 50-60 ℃ according to the mass ratio of (2.5-3.0): 1: 0.02 reacting for 40-50 min at the rotating speed of 60-80 r/min, heating to 75-85 ℃, continuing to react for 1-3h, adding 0.1-0.2 time of a modifier, 0.21-0.32 time of a polyol chain extender, 0.02-0.04 time of a cross-linking agent, 0.02-0.05 time of a filler polymeric chain and 1.2 times of water, continuing to react for 1-2h at 80-90 ℃ to prepare polyurethane A, adding 0.04-0.06 time of a tackifier into the obtained polyurethane A, and uniformly mixing to prepare a polyurethane emulsion, namely the carbon nanotube modified flame-retardant polyurethane coating and the adhesive;

the times of the added modifier, the polyol chain extender, the cross-linking agent, the filler polymer chain and the water are all based on the weight of the isocyanate.

The coupling agent is one or two of 3-aminopropyl triethoxysilane and monoalkoxy titanate coupling agent.

The polymer polyol is any one of polytetrahydrofuran ether glycol and polycarbonate glycol.

The polyol type chain extender is one or more of neopentyl glycol, diethylene glycol, 1, 4-butanediol, polyethylene glycol adipate glycol, 1, 4-butanediol adipate glycol and polyethylene glycol adipate glycol.

The isocyanate is one or more of TDI, MDI and PAPI.

The cross-linking agent is propylene oxide polyether triol or CX-100 cross-linking agent.

The preparation method of the modifier comprises the following steps: adding 70-80 g of water into 0.1g of hydroxylated carbon nanotube, 20-30 g of polyvinyl alcohol and 4-60 g of catechin, stirring and reacting for 1-3h at 60-80 ℃, adding 2-3 g of butyrolactone, 0.4-0.6 g of 1, 2-dibromopropane and 5g of acetone, stirring and reacting for 1-2h at 40-60 ℃, and spray drying to obtain the modifier.

The preparation method of the hydroxylated carbon nanotube comprises the following steps: adding 1.1-1.5 g of carbon nano tube and 280-320 mL of mixed acid (the volume ratio of concentrated sulfuric acid to concentrated nitric acid is 2: 1) into a 500mL flask, reacting at 65-75 ℃, and condensing and refluxing for 2-4 h in an ultrasonic cleaner with ultrasonic power of 200W and ultrasonic frequency of 40 KHz; then transferring the mixture into a beaker, diluting the mixture with 250g of deionized water, performing suction filtration by using a microporous filter membrane with the diameter of 0.2 mu m, and repeatedly washing the mixture with the deionized water until the mixture is neutral; finally, drying the carbon nano tube after suction filtration at 105 ℃, and grinding the carbon nano tube into powder for later use to obtain a hydroxylated carbon nano tube; the carbon nano tube is a single-walled carbon nano tube produced by a chemical vapor deposition method, the diameter of the carbon nano tube is 2nm, the tube length is 100 mu m, the purity is 99.5 wt%, and the amorphous carbon hetero<5% of ash impurities<3 wt%, specific surface area 700m²/g。

The tackifier is one or more of rosin resin, hydrogenated rosin resin (seven-color chemical industry Co., Ltd., Sterculia city), terpene resin and C5 petroleum resin.

The preparation method of the filler polymer chain comprises the following steps:

(1) vacuum drying 9-16g of nano silicon carbide at 105 ℃, dispersing the nano silicon carbide in 40g of N, N-dimethylformamide for ultrasonic dispersion at 30-60 ℃ for 30-45 min to prepare a solution A;

(2) dissolving 20-24g of diphenylmethane diisocyanate and 16-20g of polylactic acid in 40g of N, N-dimethylformamide to prepare solution B,

(3) and mixing nano silver, 1, 5-naphthalene disulfonic acid and 5-hydroxymethyl furfural according to the weight ratio of 1: 20: stirring for 1-2h at 50-70 ℃ in a proportion of 50-80 to prepare a solution C, wherein the weight of the nano silver is 1/100 of that of the nano silicon carbide;

(4) dropwise adding the solution B into the solution A, adding the solution C into the solution A, and stirring and reacting at 50-60 ℃ for 2-3 hours to obtain the filler polymer chain.

Compared with the prior art, the invention has the following beneficial effects:

(1) the basic principle of the polyurethane is that polymer polyol and isocyanate are subjected to polymerization reaction to generate polyurethane, and the polyurethane is modified by polyvinyl alcohol and catechin; forming hydrogen bond action between phenolic hydroxyl on the surface of catechin and hydroxyl on a polyvinyl alcohol main chain so as to form a first physical cross-linking network, forming a microcrystalline region by the hydrogen bond action of hydroxyl groups on a polyvinyl alcohol chain segment, and forming a physical cross-linking point so as to form a second physical cross-linking network; the cross-linked network between the catechin and the polyvinyl alcohol and the polyurethane are synchronously interpenetrated to form a third physical cross-linked network; the prepared polyurethane coating and the pressure-sensitive adhesive have better stability and higher tensile strength, toughness and tear resistance, the butyrolactone and the 1, 2-dibromopropane modified polyvinyl alcohol and the catechin enable a third physical cross-linked network to be formed quickly, the pressure-sensitive adhesive has good pressure-sensitive property, and meanwhile, the hydroxylated carbon nano, the polyvinyl alcohol and the catechin form hydrogen bond combination, so that the mechanical property and the flame retardant property of the polyurethane are improved.

(2) The filler polymeric chain is prepared from diphenylmethane diisocyanate and nano silicon nitride; the diphenylmethane diisocyanate is filled with the nano silicon nitride with high intrinsic heat conductivity coefficient, namely, the nano silicon carbide is connected in series through the diphenylmethane diisocyanate with a flexible structure, so that the heat conduction performance of the diphenylmethane diisocyanate is improved, and meanwhile, the continuous heat conduction path is formed by filling the silicon carbide with lower content in the diphenylmethane diisocyanate; the introduction of the filler polymer chain not only effectively improves the heat-conducting property and reduces the addition amount of the heat-conducting filler, but also maintains the mechanical property and the air permeability of the polylactic acid reinforced filler, thereby further enhancing the air permeability of the surface of polyurethane and facilitating the dissipation of heat in a porous manner, and the nano silver can emit gas under the modification of 1, 5-naphthalenedisulfonic acid and 5-hydroxymethylfurfural and be converted into complete combustion, thereby reducing the concentration of smoke.

(3) The heat conduction performance of the adhesive is enhanced by filling the carbon-based material with excellent mechanical property and heat conduction performance, and the heat conduction mechanism of the filling type heat conduction polymer adhesive is as follows: the heat in the adhesive is realized through the mutual contact among the heat-conducting fillers, the heat-conducting fillers and the polyurethane and the interaction between the heat-conducting fillers and the polyurethane; after the polyurethane matrix with poor heat conductivity is filled with the heat-conducting filler, the heat-conducting filler which is in contact with the polyurethane matrix and the interaction between the heat-conducting filler and the polyurethane matrix form a heat-conducting grid structure in the adhesive, which can be called as a heat-conducting network chain; the heat is effectively transferred from the heat conduction network chain.

(4) Because the heat-conducting filler has small particles and large specific surface area and is easy to agglomerate in the process of filling polyurethane, the heat-conducting filler is treated by the coupling agent so as to avoid the influence on the service performance of the adhesive caused by the agglomerated heat-conducting filler; meanwhile, a plurality of physical cross-linked networks and filler polymer chains are formed among the polyurethane, the catechin and the polyvinyl alcohol, so that the heat-conducting filler is filled in the network structure, the heat-conducting filler can be uniformly distributed, and the mechanical property of the polyurethane can be maintained.

(5) The polyurethane coating and the base pressure-sensitive adhesive prepared by the invention can be conveniently stripped and repeatedly pasted; the invention carries out surface treatment on the heat-conducting filler, takes polyurethane as a matrix to prepare the heat-sensitive adhesive with high heat conductivity, and the introduction of the filler polymer chain reduces the use amount of the heat-conducting filler, so that the heat-sensitive adhesive has the advantages of convenient use, excellent performance and low price, well meets the bonding requirements in the fields of electronic and electric appliances and the like, and can also be used for building outer walls.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

(1) Preparing the modified heat-conducting filler, wherein the mass ratio of the modified heat-conducting filler to the modified heat-conducting filler is 1: 2: 1: mixing and hydrolyzing 0.5 of 3-aminopropyltriethoxysilane coupling agent, deionized water, tannic acid and boron nitride nanosheet layer for 30min to obtain a hydrolysate A; adding the hydrolysate A into a high-speed mixer at 80 ℃ to continue mixing for 30min, cooling, discharging and vacuum drying to obtain the modified heat-conducting filler;

(2) mixing polytetrahydrofuran ether glycol and a modified heat-conducting filler according to a mass ratio of 4:1, performing ultrasonic treatment for 1h, and performing reduced pressure dehydration at 100 ℃ for 1h to obtain a component A;

(3) preparing the carbon nano tube modified flame-retardant polyurethane coating and adhesive by mixing the component A (all, the same below), TDI isocyanate and dibutyltin dilaurate according to the mass ratio of 2.5: 1: 0.02 reacting for 40min at the rotating speed of 60r/min, heating to 75 ℃ and continuing to react for 1h, adding 0.1 time of modifier, 0.21 time of neopentyl glycol, 0.02 time of propylene oxide polyether triol cross-linking agent, 0.02 time of filler polymeric chain and 1.2 times of water, and continuing to react for 1h at the temperature of 80 ℃ to prepare polyurethane A, wherein the weight of isocyanate is taken as the reference of the modifier, the neopentyl glycol polyol chain extender and the propylene oxide polyether triol cross-linking agent; adding 0.04 times of rosin resin tackifier into the polyurethane A, stirring and mixing; after being uniformly mixed, polyurethane emulsion is prepared, namely the carbon nano tube modified flame-retardant polyurethane coating and the adhesive; the tackifier, water, and filler polymeric chain are based on the weight of the isocyanate.

The preparation method of the modifier comprises the following steps: adding 70g of water into 0.1g of hydroxylated carbon nanotube, 20g of polyvinyl alcohol and 4g of catechin, stirring and reacting for 1h at 60 ℃, adding 2g of butyrolactone, 0.4g of 1, 2-dibromopropane and 5g of acetone, stirring and reacting for 1h at 40 ℃, and spray-drying to obtain the modifier.

The preparation method of the hydroxylated carbon nanotube comprises the following steps:

adding 1.1g of carbon nano tube and 280mL of mixed acid (the volume ratio of concentrated sulfuric acid to concentrated nitric acid is 2: 1) into a 500mL flask, reacting at 65 ℃, and condensing and refluxing for 2h in an ultrasonic cleaner with the ultrasonic power of 200W and the ultrasonic frequency of 40 KHz; then transferring the mixture into a beaker, diluting the mixture with 250g of deionized water, performing suction filtration by using a microporous filter membrane with the diameter of 0.2 mu m, and repeatedly washing the mixture with the deionized water until the mixture is neutral; finally, drying the carbon nano tube after suction filtration at 105 ℃, and grinding the carbon nano tube into powder for later use to obtain a hydroxylated carbon nano tube; the carbon nano tube is a single-walled carbon nano tube produced by a chemical vapor deposition method, the diameter of the carbon nano tube is 2nm, the tube length is 100 mu m, the purity is 99.5 wt%, and the amorphous carbon hetero<5% of ash impurities<3 wt%, specific surface area 700m²/g。

The preparation method of the filler polymer chain comprises the following steps:

(1) vacuum drying 9g of nano silicon carbide at 105 ℃, dispersing the nano silicon carbide in 40g of N, N-dimethylformamide and ultrasonically dispersing for 30min at 30 ℃ to prepare a solution A;

(2) dissolving 20g of diphenylmethane diisocyanate and 16g of polylactic acid in 40g of N, N-dimethylformamide to prepare a solution B,

(3) and mixing nano silver, 1, 5-naphthalene disulfonic acid and 5-hydroxymethyl furfural according to the weight ratio of 1: 20: stirring for 1h at 50 ℃ in a proportion of 50 to prepare a solution C, wherein the weight of the nano silver is 1/100 of the mass of the nano silicon carbide;

(4) dropwise adding the solution B into the solution A, adding the solution C into the solution A, and stirring at 50 ℃ for reaction for 2 hours to obtain the filler polymer chain.

Example 2

(1) Preparing the modified heat-conducting filler, wherein the mass ratio of the modified heat-conducting filler to the modified heat-conducting filler is 1: 4: 2: 0.8 of mono-alkoxy titanate coupling agent (Nanjing Quanxi chemical Co., Ltd., mono-alkoxy fatty acid titanate coupling agent), deionized water, tannic acid and boron nitride nanosheet layers, and mixing and hydrolyzing for 40min to obtain a hydrolysate A; adding the hydrolysate A into a high-speed mixer at 90 ℃ to continue mixing for 40min, cooling, discharging and vacuum drying to obtain the modified heat-conducting filler;

(2) mixing polycarbonate diol and modified heat-conducting filler according to the mass ratio of 5:1, performing ultrasonic treatment for 2.5 hours, and performing reduced pressure dehydration at 110 ℃ for 2 hours to obtain a component A;

(3) preparing a coating and an adhesive, namely mixing the component A, MDI isocyanate and dibutyltin dilaurate at the temperature of 60 ℃ according to the mass ratio of 3.0: 1: 0.02 reacting for 50min at the rotating speed of 80r/min, heating to 85 ℃ and continuing to react for 3h, adding 0.2 time of modifier, 0.32 time of diethylene glycol, 0.04 time of CX-100 cross-linking agent (trade company Limited in Zonen, Guangzhou), 0.05 time of filler polymer chain and 1.2 times of water and continuing to react for 2h at 90 ℃ to prepare polyurethane A, wherein the cross-linking agents of the modifier, the diethylene glycol and the CX-100 cross-linking agent take the weight of isocyanate as a reference; adding hydrogenated rosin resin (QICAI CHEMICAL Co., Ltd., Sterculia) tackifier 0.06 times into polyurethane A, stirring, and mixing; after being uniformly mixed, polyurethane emulsion is prepared, namely the carbon nano tube modified flame-retardant polyurethane coating and the adhesive; the polyurethane emulsion was coated and dried, and the hydrogenated rosin resin (seven color chemical, ltd., phoenix) tackifier, water were based on the weight of isocyanate.

The preparation method of the modifier comprises the following steps: adding 80g of water into 0.1g of hydroxylated carbon nanotube, 30g of polyvinyl alcohol and 60g of catechin, stirring and reacting for 3h at 80 ℃, adding 3g of butyrolactone, 0.6g of 1, 2-dibromopropane and 5g of acetone, stirring and reacting for 2h at 60 ℃, and spray-drying to obtain the modifier.

The preparation method of the hydroxylated carbon nanotube comprises the following steps:

adding 1.5g of carbon nano tube and 320mL of mixed acid (the volume ratio of concentrated sulfuric acid to concentrated nitric acid is 2: 1) into a 500mL flask, reacting at 75 ℃, and condensing and refluxing for 4h in an ultrasonic cleaner with the ultrasonic power of 200W and the ultrasonic frequency of 40 KHz; then transferring the mixture into a beaker, diluting the mixture with 250g of deionized water, performing suction filtration by using a microporous filter membrane with the diameter of 0.2 mu m, and repeatedly washing the mixture with the deionized water until the mixture is neutral; finally, drying the carbon nano tube after suction filtration at 105 ℃, and grinding the carbon nano tube into powder for later use to obtain a hydroxylated carbon nano tube; the carbon nano tube is a single-walled carbon nano tube produced by a chemical vapor deposition method, the diameter of the carbon nano tube is 2nm, the tube length is 100 mu m, the purity is 99.5 wt%, and the amorphous carbon hetero<5% of ash impurities<3wt％Specific surface area of 700m²/g。

The preparation method of the filler polymer chain comprises the following steps:

(1) 16g of nano silicon carbide is dried in vacuum at 105 ℃, and the nano silicon carbide is dispersed in 40g of N, N-dimethylformamide for ultrasonic dispersion for 45min at 60 ℃ to prepare a solution A;

(2) dissolving 24g of diphenylmethane diisocyanate and 20g of polylactic acid in 40g of N, N-dimethylformamide to prepare a solution B,

(3) and mixing nano silver, 1, 5-naphthalene disulfonic acid and 5-hydroxymethyl furfural according to the weight ratio of 1: 20: stirring for 2 hours at 70 ℃ in proportion of 80 to prepare solution C, wherein the weight of the nano silver is 1/100 of that of the nano silicon carbide;

(4) dropwise adding the solution B into the solution A, adding the solution C into the solution A, and stirring at 60 ℃ for reaction for 3 hours to obtain the filler polymer chain.

Example 3

(1) Preparing the modified heat-conducting filler, wherein the mass ratio of the modified heat-conducting filler to the modified heat-conducting filler is 1: 3: 1.5: mixing and hydrolyzing 0.65 parts of 3-aminopropyltriethoxysilane coupling agent, deionized water, tannic acid and boron nitride nanosheet layer for 35min to obtain a hydrolysate A; adding the hydrolysate A into a high-speed mixer at 85 ℃ to continue mixing for 35min, cooling, discharging and vacuum drying to obtain the modified heat-conducting filler;

(2) mixing polytetrahydrofuran ether glycol and the modified heat-conducting filler according to the mass ratio of 4.5:1, performing ultrasonic treatment for 1.5 hours, and performing reduced pressure dehydration at 105 ℃ for 1.5 hours to obtain a component A;

(3) preparing the component A, the PAPI isocyanate and the dibutyltin dilaurate according to the mass ratio of 2.75: 1: 0.02 reacting for 45min at the rotating speed of 70r/min, heating to 80 ℃ and continuing to react for 2h, adding 0.15 time of modifier, 0.26 time of 1, 4-butanediol, 0.03 time of propylene oxide polyether triol cross-linking agent, 0.035 time of filler polymer chain and 1.2 times of water, and continuing to react for 1.5h at the temperature of 85 ℃ to obtain polyurethane A, wherein the weight of the modifier, the 1, 4-butanediol polyalcohol chain extender and the cross-linking agent is used as the reference; adding terpene resin tackifier 0.05 times into polyurethane A, stirring, and mixing; after being uniformly mixed, polyurethane emulsion is prepared, namely the carbon nano tube modified flame-retardant polyurethane coating and the adhesive; the tackifier, filler polymeric chain, and water are based on the weight of the isocyanate.

The preparation method of the modifier comprises the following steps: adding 75g of water into 0.1g of hydroxylated carbon nanotube, 25g of polyvinyl alcohol and 32g of catechin, stirring and reacting for 2h at 70 ℃, adding 2.5g of butyrolactone, 0.5g of 1, 2-dibromopropane and 5g of acetone, stirring and reacting for 1.5h at 50 ℃, and spray-drying to obtain the modifier.

The preparation method of the hydroxylated carbon nanotube comprises the following steps:

adding 1.3g of carbon nano tube and 300mL of mixed acid (the volume ratio of concentrated sulfuric acid to concentrated nitric acid is 2: 1) into a 500mL flask, reacting at 70 ℃, and condensing and refluxing for 3h in an ultrasonic cleaner with the ultrasonic power of 200W and the ultrasonic frequency of 40 KHz; then transferring the mixture into a beaker, diluting the mixture with 250g of deionized water, performing suction filtration by using a microporous filter membrane with the diameter of 0.2 mu m, and repeatedly washing the mixture with the deionized water until the mixture is neutral; finally, drying the carbon nano tube after suction filtration at 105 ℃, and grinding the carbon nano tube into powder for later use to obtain a hydroxylated carbon nano tube; the carbon nano tube is a single-walled carbon nano tube produced by a chemical vapor deposition method, the diameter of the carbon nano tube is 2nm, the tube length is 100 mu m, the purity is 99.5 wt%, and the amorphous carbon hetero<5% of ash impurities<3 wt%, specific surface area 700m²/g。

The preparation method of the filler polymer chain comprises the following steps:

(1) drying 12.5g of nano silicon carbide in vacuum at 105 ℃, dispersing the nano silicon carbide in 40g of N, N-dimethylformamide for ultrasonic dispersion at 45 ℃ for 35min to prepare a solution A;

(2) dissolving 22g of diphenylmethane diisocyanate and 18g of polylactic acid in 40g of N, N-dimethylformamide to prepare a solution B,

(3) and mixing nano silver, 1, 5-naphthalene disulfonic acid and 5-hydroxymethyl furfural according to the weight ratio of 1: 20: stirring the mixture for 1.5h at the temperature of 60 ℃ according to the proportion of 65 to prepare a solution C, wherein the weight of the nano silver is 1/100 of that of the nano silicon carbide;

(4) dropwise adding the solution B into the solution A, adding the solution C into the solution A, and stirring at 55 ℃ for reaction for 2.5 hours to obtain the filler polymer chain.

Example 4

(1) Preparing the modified heat-conducting filler, wherein the mass ratio of the modified heat-conducting filler to the modified heat-conducting filler is 1: 2: 2: 0.6 of mono-alkoxy titanate coupling agent (Nanjing Quanxi chemical Co., Ltd., mono-alkoxy fatty acid titanate coupling agent), deionized water, tannic acid and boron nitride nanosheet layers are mixed and hydrolyzed for 35min to obtain a hydrolysate A; adding the hydrolysate A into a high-speed mixer at 85 ℃ to continue mixing for 35min, cooling, discharging and vacuum drying to obtain the modified heat-conducting filler;

(2) mixing polycarbonate diol and modified heat-conducting filler according to the mass ratio of 4:1, performing ultrasonic treatment for 1 hour, and performing reduced pressure dehydration at 100 ℃ for 2 hours to obtain a component A;

(3) preparing the carbon nano tube modified flame-retardant polyurethane coating and adhesive, namely mixing the component A, TDI isocyanate and dibutyltin dilaurate according to the mass ratio of 3.0: 1: 0.02 reacting for 45min at the rotating speed of 70r/min, heating to 80 ℃ and continuing to react for 1h, adding 0.1 time of modifier, 0.21 time of polyethylene glycol adipate glycol, 0.02 time of CX-100 cross-linking agent (Kyoho energy Co., Ltd., Guangzhou), 0.05 time of filler polymer chain and 1.2 times of water and continuing to react for 2h at 80 ℃ to prepare polyurethane A, wherein the modifier, the polyethylene glycol adipate glycol polyol chain extender and the CX-100 cross-linking agent (Kyoho energy Co., Ltd., Guangzhou) take the weight of isocyanate as a standard; adding 0.04 times of C5 petroleum resin tackifier (Ziboxinle chemical Co., Ltd.) into the polyurethane A, stirring, and mixing; after being uniformly mixed, polyurethane emulsion is prepared, namely the carbon nano tube modified flame-retardant polyurethane coating and the adhesive; the tackifier, filler polymeric chain, and water are based on the weight of the isocyanate.

The preparation method of the modifier comprises the following steps: adding 80g of water into 0.1g of hydroxylated carbon nanotube, 20g of polyvinyl alcohol and 60g of catechin, stirring and reacting for 3h at 80 ℃, adding 3g of butyrolactone, 0.6g of 1, 2-dibromopropane and 5g of acetone, stirring and reacting for 1h at 40 ℃, and spray-drying to obtain the modifier.

The preparation method of the hydroxylated carbon nanotube comprises the following steps:

adding 1.3g of carbon nano tube and 300mL of mixed acid (the volume ratio of concentrated sulfuric acid to concentrated nitric acid is 2: 1) into a 500mL flask, reacting at 65 ℃, and condensing and refluxing for 4h in an ultrasonic cleaner with the ultrasonic power of 200W and the ultrasonic frequency of 40 KHz; then transferring the mixture into a beaker, diluting the mixture with 250g of deionized water, performing suction filtration by using a microporous filter membrane with the diameter of 0.2 mu m, and repeatedly washing the mixture with the deionized water until the mixture is neutral; finally, drying the carbon nano tube after suction filtration at 105 ℃, and grinding the carbon nano tube into powder for later use to obtain a hydroxylated carbon nano tube; the carbon nano tube is a single-walled carbon nano tube produced by a chemical vapor deposition method, the diameter of the carbon nano tube is 2nm, the tube length is 100 mu m, the purity is 99.5 wt%, and the amorphous carbon hetero<5% of ash impurities<3 wt%, specific surface area 700m²/g。

The preparation method of the filler polymer chain comprises the following steps:

(1) vacuum drying 9g of nano silicon carbide at 105 ℃, dispersing the nano silicon carbide in 40g of N, N-dimethylformamide and ultrasonically dispersing for 45min at 60 ℃ to prepare a solution A;

(2) dissolving 24g of diphenylmethane diisocyanate and 20g of polylactic acid in 40g of N, N-dimethylformamide to prepare a solution B,

(3) and mixing nano silver, 1, 5-naphthalene disulfonic acid and 5-hydroxymethyl furfural according to the weight ratio of 1: 20: stirring for 2 hours at 70 ℃ in proportion of 80 to prepare solution C, wherein the weight of the nano silver is 1/100 of that of the nano silicon carbide;

(4) dropwise adding the solution B into the solution A, adding the solution C into the solution A, and stirring at 60 ℃ for reaction for 2 hours to obtain the filler polymer chain.

Example 5

(1) Preparing the modified heat-conducting filler, wherein the mass ratio of the modified heat-conducting filler to the modified heat-conducting filler is 1: 3: 1: mixing and hydrolyzing 0.8 parts of 3-aminopropyltriethoxysilane coupling agent, deionized water, tannic acid and boron nitride nanosheet layer for 40min to obtain a hydrolysate A; adding the hydrolysate A into a high-speed mixer at 90 ℃ to continue mixing for 40min, cooling, discharging and vacuum drying to obtain the modified heat-conducting filler;

(2) mixing polytetrahydrofuran ether glycol and a modified heat-conducting filler according to a mass ratio of 4:1, performing ultrasonic treatment for 1.5 hours, and performing reduced pressure dehydration at 100 ℃ for 2 hours to obtain a component A;

(3) preparing the carbon nano tube modified flame-retardant polyurethane coating and adhesive by mixing the component A, MDI isocyanate and dibutyltin dilaurate according to the weight ratio of 2.6: 1: 0.02 reacting for 45min at the rotating speed of 70r/min, heating to 75 ℃ and continuing to react for 1h, adding 0.1 time of modifier, 0.32 time of poly adipic acid-1, 4-butanediol ester diol, 0.04 time of propylene oxide polyether triol cross-linking agent, 0.05 time of filler polymer chain and 1.2 times of water and continuing to react for 2h at 90 ℃ to prepare polyurethane A, wherein the modifier, the poly adipic acid-1, 4-butanediol ester diol polyol chain extender and the propylene oxide polyether triol cross-linking agent are based on the weight of isocyanate; adding rosin resin tackifier 0.04 times into polyurethane A, stirring and mixing; after being uniformly mixed, polyurethane emulsion is prepared, namely the carbon nano tube modified flame-retardant polyurethane coating and the adhesive; the tackifier, filler polymeric chain, and water are based on the weight of the isocyanate.

The preparation method of the modifier comprises the following steps: adding 70g of water into 0.1g of hydroxylated carbon nanotube, 20g of polyvinyl alcohol and 40g of catechin, stirring and reacting for 2h at 70 ℃, adding 2.2g of butyrolactone, 0.45g of 1, 2-dibromopropane and 5g of acetone, stirring and reacting for 1h at 55 ℃, and spray-drying to obtain the modifier.

The preparation method of the hydroxylated carbon nanotube comprises the following steps:

adding 1.2g of carbon nano tube and 290mL of mixed acid (the volume ratio of concentrated sulfuric acid to concentrated nitric acid is 2: 1) into a 500mL flask, reacting at 70 ℃, and condensing and refluxing for 2.5h in an ultrasonic cleaner with the ultrasonic power of 200W and the ultrasonic frequency of 40 KHz; then transferring the mixture into a beaker, diluting the mixture with 250g of deionized water, performing suction filtration by using a microporous filter membrane with the diameter of 0.2 mu m, and repeatedly washing the mixture with the deionized water until the mixture is neutral; finally, drying the carbon nano tube after suction filtration at 105 ℃, and grinding the carbon nano tube into powder for later use to obtain a hydroxylated carbon nano tube; the carbon nano tube is a single-walled carbon nano tube produced by a chemical vapor deposition method, the diameter of the carbon nano tube is 2nm, the tube length is 100 mu m, the purity is 99.5 wt%, and the amorphous carbon hetero<5% of ash impurities<3 wt%, specific surface area 700m²/g。

The preparation method of the filler polymer chain comprises the following steps:

(1) drying 11g of nano silicon carbide in vacuum at 105 ℃, dispersing the nano silicon carbide in 40g of N, N-dimethylformamide and ultrasonically dispersing for 35min at 50 ℃ to prepare a solution A;

(2) dissolving 22g of diphenylmethane diisocyanate and 17g of polylactic acid in 40g of N, N-dimethylformamide to prepare a solution B,

(3) and mixing nano silver, 1, 5-naphthalene disulfonic acid and 5-hydroxymethyl furfural according to the weight ratio of 1: 20: stirring for 1.5h at the temperature of 60 ℃ in proportion of 70 to prepare a solution C, wherein the weight of the nano silver is 1/100 of that of the nano silicon carbide;

(4) dropwise adding the solution B into the solution A, adding the solution C into the solution A, and stirring at 55 ℃ for reaction for 2 hours to obtain the filler polymer chain.

The following are product performance tests and results and analyses.

1. Polyurethane adhesive bonding performance and thermal conductivity.

Preparing a pressure-sensitive adhesive tape, respectively taking a proper amount of the polyurethane emulsion prepared in the examples 1-5, uniformly coating the polyurethane emulsion on the surface of a polyester film by using a glass rod, then drying the polyester film in a 65 ℃ oven for 2 hours to prepare the pressure-sensitive adhesive tape with the thickness of 10mm, taking out the pressure-sensitive adhesive tape, attaching the pressure-sensitive adhesive tape on a test board for 24 hours, and testing.

Uniformly coating the pouring sealant prepared in the embodiment 1 with the publication number of CN201910899146.7 on the surface of a polyester film by using a glass rod, then drying the polyester film in an oven at 65 ℃ for 2 hours to prepare a pressure-sensitive adhesive tape with the thickness of 10mm, taking out the pressure-sensitive adhesive tape, attaching the pressure-sensitive adhesive tape on a test board for 24 hours, and testing; as comparative example 1.

Uniformly coating the sealant prepared in the embodiment 1 with the publication number of CN201110364443.5 on the surface of a polyester film by using a glass rod, then baking the polyester film in an oven at 65 ℃ for 2 hours to prepare a pressure-sensitive adhesive tape with the thickness of 10mm, taking out the pressure-sensitive adhesive tape, attaching the pressure-sensitive adhesive tape on a test board for 24 hours, and testing; as comparative example 2.

(1) And measuring initial viscosity: according to GB/T4852-2002, the steel ball is measured by an inclined plane rolling ball method, an inclined plane initial adhesion instrument is adopted, small steel balls with different diameters are freely put down from a position of 10cm above an inclined plane with an inclination angle of 30 degrees, and the rolling distance of the small balls on a horizontal adhesive tape and the maximum number of the steel balls are tested.

(2) Measurement of peel strength: the test was carried out according to GB/T2792-1998 with a strip width of 25mm, the free end of the test specimen and the test plate were clamped separately in a BLD-2005 electron stripper at a loading speed of 50mm/min and a test temperature of 20 ℃.

(3) And heat conductivity coefficient: according to the standard of ASTME1530-2006, the thermal conductivity coefficient of the polyurethane adhesive is detected by using a steady-state method thermal conductivity meter.

The results are shown in Table 1.

Table 1 polyurethane adhesive bond performance and thermal conductivity

As can be seen from Table 1, the polyurethane-based pressure-sensitive adhesives prepared according to the present invention are superior in performance index initial tack to comparative examples 1 and 2, because the present invention modifies polyurethane with polyvinyl alcohol and catechin; the phenolic hydroxyl on the surface of the catechin and the hydroxyl on the main chain of the polyvinyl alcohol form hydrogen bond action to further form a first physical crosslinking network, and the hydroxyl on the chain segment of the polyvinyl alcohol forms a microcrystalline region through hydrogen bond action to form a physical crosslinking point, so that cohesive energy is increased, the rigidity of the polymer is increased, and finally the viscosity and the peel strength of the polyurethane-based pressure-sensitive adhesive are increased.

2. Flame retardant properties of polyurethane coatings.

Comparative example 3A pressure-sensitive adhesive tape having a thickness of 10mm and a length of 5cm and a width of 5.2cm was prepared and tested using 201910643179.5, the product prepared in example two, using smoke density measurement methods specified in ASTME662 and GB 8323-87.

GB/T5455-1997 (vertical method for testing textile burning performance) determines the flame burning time (afterflame time) of the film formed by the polyurethane coating, and the test sample is 10cm multiplied by 10cm and has the thickness of 10 mm. The nano silver can emit gas under the modification of 1, 5-naphthalene disulfonic acid and 5-hydroxymethyl furfural, and the gas is converted into complete combustion, so that the concentration of smoke is reduced.

The test piece was analyzed and measured by ASTM E1354-1990(2004 standard) using a cone calorimeter 2000 of FTT, UK, 10cm X10 cm in thickness and 12kw/m in heat radiation power². The results of the flame retardant performance tests are shown in tables 2, 3 and 4.

TABLE 2 flame retardancy of polyurethane coatings

TABLE 3 flame retardancy of polyurethane coatings (without 1, 5-naphthalenedisulfonic acid)

TABLE 4 flame retardancy of polyurethane coatings (without 5-hydroxymethylfurfural addition)

As can be seen from table 2, the polyurethane coatings were low in flame burning time, smoke density, and CO concentration.

From tables 3 and 4, it can be seen that the resulting material without 1, 5-naphthalenedisulfonic acid and 5-hydroxymethylfurfural added corresponds to an increase in the concentration of CO, which needs to be controlled with great emphasis as a toxic gas in smoke.

3. The polyurethane adhesives prepared by different technical schemes of the invention have comparative bonding performance.

The above test methods were carried out to compare the adhesion properties of the products prepared according to the different technical solutions of the five examples of the present invention, and the results are shown in tables 5 and 6.

TABLE 5 polyurethane adhesive Properties (without butyrolactone)

TABLE 6 polyurethane adhesive Properties (without 1, 2-dibromopropane)

From tables 5 and 6, it can be found that butyrolactone and 1, 2-dibromopropane modify polyvinyl alcohol and catechin, so that a third physical cross-linked network is rapidly formed, and the polyurethane has good pressure sensitivity, and meanwhile, hydroxylated carbon nano-particles, polyvinyl alcohol and catechin form hydrogen bond combination, so that the mechanical property and flame retardant property of the polyurethane are improved.

The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.