A high-transparency leveling agent and its preparation method

Abstract

The present invention belongs to the technical field of coatings, and particularly relates to a high-transparency leveling agent and a preparation method thereof. The method includes: 1) adding reactants and carrier powder into a reaction vessel to carry out a polycondensation reaction, and obtaining a prepolymer after the reaction is completed; 2) mixing the prepolymer with a catalyst and silicone and carrying out a constant-temperature reaction, and then centrifugally separating to obtain a solid powder leveling agent. The leveling agent of the present invention has high compatibility, can be effectively compatibly combined with coatings, and can avoid caking under high temperature or exposure conditions, effectively improving the flatness of film formation, while maintaining the high transparency of the formed coating film. It is particularly suitable for film formation of surface protective films or anti-reflection coating paints on solar photovoltaic panels, and can greatly reduce the actual light scattering loss.

Description

Technical Field

[0001] The present invention belongs to the technical field of coatings, and particularly relates to a high-transparency leveling agent and a preparation method thereof. Background Art

[0002] After a long period of development, China has become the world's largest coating producer and consumer, and has entered the mainstream of the world coating industry development. In coatings, leveling agents are essential auxiliaries. During the film-forming process, the solid powder is melted by heating, the air between the powder particles is discharged, and it gradually levels and cures into a film.

[0003] At present, most leveling agents are divided into solvent-based and solid-based. One type of solvent-based leveling agent acts by adjusting the film viscosity and leveling time, while the second type acts by adjusting the surface properties of the film. The second type of solvent leveling agent affects surface properties such as the interfacial tension of the film to enable the film to obtain good leveling, which is also a common type of leveling agent. However, solvent-based leveling agents are prone to surface shrinkage pores during actual use, especially when the surface conditions of the coating surface are poor and the cleanliness is low, and are greatly affected by temperature. When the temperature is too low, the shrinkage pore phenomenon is likely to be aggravated.

[0004] Conventional solid leveling agents are acrylic acid ester homopolymers, acrylic acid ester copolymers, organosilicon-modified acrylic acid ester polymers, polyhydrosilanes, etc. Although they have good leveling effects, they are prone to orange peel. When the equipment for manufacturing powder coatings has low precision or is aged, resulting in slightly poor grinding and dispersion effects, and when in contact with substances with low surface tension during the manufacture or application of powders, serious orange peel will occur. In addition, most existing solid leveling agents are non-transparent material particles and are difficult to be used for leveling coatings on the surface of solar panels. Currently, when solar panels are privately used in solar power generation bases, since the surrounding environment is relatively harsh, a protective coating needs to be coated on their surfaces to form a protective layer. However, the protective coating needs to maintain high transparency and extremely high flatness. High transparency ensures the light transmittance, and flatness is conducive to reducing light scattering loss. At present, solid leveling agents do not have high transparency, so when used, although they can produce good leveling effects, the actual light transmittance and scattering loss are extremely large, and their applications are extremely limited. For ordinary solvent-based leveling agents, because most solar power generation bases are located in remote areas, such as vast sprayed coatings and desert areas, it is difficult to preserve them during transportation, and shrinkage pores and component segregation are also extremely likely to increase the problem of light scattering loss of the protective coating, and their use is also limited.

[0005] Therefore, in view of this, it is very important to develop a high-transparency leveling agent that can be effectively used for the surface of solar panels. Summary of the Invention

[0006] To solve the problem that existing solid leveling agents are difficult to be applied to transparent coatings, especially difficult to be used as transparent coating additives on the surface of solar panels, and there are problems such as easy increase in scattering loss of the protective coating and reduction in light transmittance, the present invention provides a high-transparency leveling agent.

[0007] The object of the present invention is:

[0008] First, it can be effectively used in transparent coatings and reduce the light transmittance as little as possible;

[0009] Second, the leveling effect is excellent, and it can effectively reduce the scattering loss caused by the leveling agent.

[0010] To achieve the above object, the present invention adopts the following technical solutions.

[0011] A preparation method of a high-transparency leveling agent,

[0012] The method includes:

[0013] 1) Add reactants and carrier powder to a reaction vessel, carry out polycondensation reaction, and obtain a prepolymer after the reaction is completed;

[0014] 2) React the prepolymer with a catalyst and silicone at a constant temperature, and then centrifuge to separate to obtain a solid powder leveling agent.

[0015] Preferably,

[0016] The reactants in step 1) are 1,3-bis(4-nitrophthalimido)benzene and 2,2-bis(4-hydroxyphenyl)propane;

[0017] The polycondensation reaction process in step 1) is as follows:

[0018]

[0019] Preferably,

[0020] The mass ratio of the amount of 1,3-bis(4-nitrophthalimido)benzene to 2,2-bis(4-hydroxyphenyl)propane is 1:(1.2 - 1.4).

[0021] Preferably,

[0022] The carrier powder in step 1) is carbon powder;

[0023] The mesh number of the carbon powder is 1300 - 1500 meshes;

[0024] The amount of the carbon powder used is 0.3 - 0.7 g / g of the reactants.

[0025] Preferably,

[0026] The polycondensation reaction is carried out in a protective atmosphere at 160 - 180 °C for 45 - 75 min.

[0027] Preferably,

[0028] The catalyst in step 2) is a platinum on carbon catalyst;

[0029] The dosage of the platinum on carbon catalyst is 0.01 - 0.03 g / g of the prepolymer;

[0030] The average particle size of the platinum on carbon catalyst is 5 - 10 nm.

[0031] Preferably,

[0032] The organosilicon in step 2) is 2-(trimethylsilyl)ethanol;

[0033] The dosage of the 2-(trimethylsilyl)ethanol is 3 - 5 mL / g of the prepolymer.

[0034] Preferably,

[0035] The constant temperature reaction in step 2) is carried out at 60 - 65 °C for 4 - 6 h;

[0036] The reaction process is as follows:

[0037]

[0038] In the formula: R is a silanol with C≥3.

[0039] A high transparency leveling agent.

[0040] In the technical solution of the present invention, a polymer with high molecular weight is prepared by a polymerization reaction. The reactant has a characteristic structure of "imide ring". Due to the electron-withdrawing effect of the imide ring, substituents such as halogen or nitro on the benzene ring adjacent to the imide ring are easily replaced by nucleophiles, so polycondensation reaction is likely to occur. In the art, leveling agents are usually added to resins at a concentration of 5 - 10 wt% or precipitated onto fumed silica at a concentration of 60 - 70 wt% to form masterbatches, so that they can be more easily metered and uniformly dispersed in the premixing stage of powder coatings. However, the leveling agents prepared in this way have too high costs.

[0041] The core of the present invention is to control the viscosity of the polymer by modifying the prepolymer and increasing the side chains. Since the -OH on 2-(trimethylsilyl)ethanol is a strong electron-donating group, the adjacent C atom is negatively charged and is easily attached to the 6 α-H sites (R groups) shown in the illustration. As the amount of 2-(trimethylsilyl)ethanol increases, the relative molecular mass of the polymer increases, which is manifested as an increase in the activity of the branched-chain reactive groups on the molecular chain after heating, resulting in an increase in density and a gradual increase in its viscosity. Although theoretically all the α-H sites adjacent to -O- have considerable activity and can also be attached with silanol or other polar groups, when the electron clouds of the atomic nucleus and electrons overlap, due to the superposition of wave functions, the electrons are bound within a certain space. Therefore, the electron probability density between the two bonding atoms in the bonding orbital becomes larger, leading to a decrease in the energy that can bind electrons. As a result, the activities of the adjacent α-H sites are different. When these positions are successfully incorporated with silanol, the present invention obtains a leveling agent with higher compatibility using relatively less organosilicon. At the same time, it is made into a solid powder, which can be directly applied to powder coatings to improve the adhesion of the powder coatings on target substrates such as glass and metal, and can effectively spread after being compatible with the coatings during use to maintain the transparency of the coatings. At the same time, if the viscosity is too high, it will cause difficulty in leveling. Not only will there be defects on its surface, but it will also lead to excessive rigidity of the coating, resulting in problems such as easy peeling, poor abrasion resistance, difficulty in resisting impact, and a decrease in the light transmittance of the coating film after film formation. At the same time, too high a degree of branching will also cause the reaction to be difficult to control and is not conducive to the thermal stability of the leveling agent. Therefore, the amount of 2-(trimethylsilyl)ethanol used in the present invention should be controlled.

[0042] In addition, due to the large surface tension difference of some coatings, during the film-forming process, they tend to flow towards the direction with higher surface tension, resulting in a very rough surface of the coating film, thus producing orange peel or shrinkage holes. Generally, the leveling property is comprehensively considered based on the surface tension and the melt viscosity. At a certain temperature, the surface tension drives the molten resin to flow, while the resistance comes from the melt viscosity of the resin. Theoretically speaking, when improving the fluidity of the coating, the surface tension of the coating should be controlled on the basis of ensuring good wettability and compatibility. Too low a surface tension during application makes the coating level quickly, but it is easy to cause the coating to flow away in all directions and is difficult to form. Too high a surface tension will obviously cause the surface tension of the coating to be non-uniform, thus forming orange peel.

[0043] The dosage of the leveling agent prepared by the present invention should be strictly controlled. Moreover, when the high polymer of the leveling agent of the present invention rises to the surface of the coating, its side chains tend to escape outward, while the polar main chain remains in the coating, making a certain stable equilibrium state in the coating. The present invention compensates the chemical potential energy between the coating and the target substrate, thereby improving the interfacial properties between the coating and the target substrate. Due to the relatively high concentration of the molecular structure arranged in an oriented manner on the coating surface, the surface tension of the coating tends to be average, thus avoiding the generation of wrinkling and cratering. In addition, activated carbon particles are evenly dispersed in the leveling agent, assisting in increasing the softening point of the leveling agent. In application, the porous structure improves the leveling property of the coating and also forms a heat conduction chain between materials, which can enhance the heat dissipation of the coating. Through experiments by the inventor, the coating surface using the leveling agent of the present invention has no obvious wrinkling and cratering defects, and the coating has no obvious cracking and bulging at 200 °C for 96 h.

[0044] In addition, it should also be noted that the leveling agent of the present invention uses carbon powder as the central carrier, and it has good compatibility with the high polymer formed by the reaction of the present invention. However, it also results in that although the granulated particles present a macroscopically nearly transparent particle morphology, carbon powder is dispersed therein. After the carbon powder forms a film on the surface protection film or antireflection film of the photovoltaic panel, it is also dispersed in the film itself, which is likely to cause an increase in light scattering loss. In this regard, the R & D personnel of the present invention also conducted in-depth research on this phenomenon during the R & D process and found that there are actual differences in the light scattering loss after the carbon powder of different mesh numbers actually forms a film, and it is not that the larger the mesh number of the carbon powder, the better the use effect. The reason also lies in that when the leveling agent particles of the present invention are used, the molecules of the high polymer disperse and are compatible with the coating, which can ensure the uniform and effective dispersion of the carbon powder core. Under this prerequisite, when the mesh number of the carbon powder is within a certain range, it is instead likely to increase the frontal carbon powder projection area after the formation of the protection film or antireflection film, which is not conducive to the photovoltaic panel receiving sunlight. Moreover, the peak of photovoltaic power generation is in the interval of 9:00 - 15:00, and the light angle continuously changes in this interval, and the mesh number of the carbon powder also leads to the ratio of actual different lateral light scattering losses. Therefore, after the R & D personnel of the present invention jointly conducted experiments with a photovoltaic power generation base, it was shown that the particle size of the carbon powder has a huge impact on the actual final use effect. When the mesh number of the carbon powder is ≥1650 mesh or ≤1200 mesh, the light scattering loss will be greatly increased. Therefore, the mesh number of the carbon powder also needs to be strictly controlled.

[0045] The beneficial effects of the present invention are:

[0046] The leveling agent of the present invention has high compatibility, can be effectively compatibly combined with the coating, and can avoid the occurrence of caking under high temperature or sunlight exposure conditions, effectively improving the flatness of the film formation and maintaining the high transparency of the formed coating film. It is especially suitable for the film formation of the surface protection film or antireflection film coating of the photovoltaic panel, and can greatly reduce the actual light scattering loss. Description of the Drawings

[0047] Figure 1 These are the graphs for characterizing and comparing the power generation efficiency of the anti-reflection coatings used on the surface of the solar photovoltaic panels in Examples 1 to 3 of the present invention, as well as the blank reference and the reference control solar photovoltaic panels.

[0048] Figure 2 These are the graphs for characterizing and comparing the relative hourly temperature on the surface of the solar photovoltaic panels after using the anti-reflection coatings in Examples 1 to 3 of the present invention, as well as the blank reference and the reference control solar photovoltaic panels.

[0049] Figure 3 These are the graphs for characterizing and comparing the power generation efficiency of the leveling agents prepared with carbon powders of different mesh numbers in Comparative Example 1 of the present invention, the anti-reflection coatings used on the surface of the solar photovoltaic panels in Example 1, as well as the blank reference and the reference control solar photovoltaic panels.

[0050] Figure 4 These are the graphs for characterizing and comparing the power generation efficiency of the anti-reflection coatings used on the surface of the solar photovoltaic panels in Example 1 of the present invention, a commercially available high-transparency leveling agent, as well as the blank reference and the reference control solar photovoltaic panels. Detailed Embodiments

[0051] The following further clearly and detailedly describes the present invention in combination with specific embodiments and the accompanying drawings of the specification. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. In addition, the embodiments of the present invention involved in the following descriptions are usually only a part of the embodiments of the present invention, rather than all of the embodiments. Therefore, all other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0052] Unless otherwise specified, the raw materials used in the embodiments of the present invention are all commercially available or raw materials that can be obtained by those skilled in the art; unless otherwise specified, the methods used in the embodiments of the present invention are all methods mastered by those skilled in the art.

[0053] Unless otherwise specified, the 1,3-bis(4-nitrophthalimido)benzene used in the embodiments of the present invention has a purity of ≥99 wt%.

[0054] Unless otherwise specified, the 2,2-bis(4-hydroxyphenyl)propane used in the embodiments of the present invention has a purity of ≥98 wt%.

[0055] Unless otherwise specified, the 2-(trimethylsilyl)ethanol used in the embodiments of the present invention has a purity of ≥98 wt%.

[0056] Unless otherwise specified, the average particle size of the platinum-carbon catalyst used in the embodiments of the present invention is 5 - 10 nm (GX series), and the water content is ≤25%.

[0057] Example 1

[0058] A preparation method of a high-transparency leveling agent, the method is as follows:

[0059] 1) Add 1,3-bis(4-nitrophthalimido)benzene, 2,2-bis(4-hydroxyphenyl)propane and carbon powder (mesh number 1500) to the reaction vessel according to the mass ratio of 5:6:4 and mix evenly. Under a nitrogen atmosphere, keep the reaction temperature at 160 °C for 75 min. After the reaction is completed, a prepolymer is obtained;

[0060] 2) Mix the prepolymer, platinum-carbon catalyst and 2-(trimethylsilyl)ethanol evenly according to the ratio of 1 g:0.02 g:5 mL, keep it at 60 °C for 6 h, centrifuge to separate the solid product, and ultrasonically wash it with deionized water and then dry it to obtain the high-transparency leveling agent.

[0061] Take the commercially available anti-reflection coating of a photovoltaic technology company in Hangzhou as the test coating, add the leveling agent of this example at a dosage ratio of 5 wt%, and then coat it on the surface of the standard solar photovoltaic power generation panel of a domestic photovoltaic power generation base at the standard dosage. After it is thermally cured into a film, perform characterization on it. The characterization includes adhesion characterization (cross-cut tape adhesion test), pencil hardness characterization, and power generation efficiency characterization from 9:00 to 15:00 every day. The power generation efficiency characterization experiment lasts for 7 days and records the average value of each characterization time and plots it into a graph.

[0062] Among them, the adhesion characterization result is a 5B grade adhesion, and the pencil hardness characterization result is a 3H grade hardness.

[0063] On the basis of not adding the leveling agent, take the commercially available anti-reflection coating of a photovoltaic technology company in Hangzhou as the test coating, coat it on the surface of the standard solar photovoltaic power generation panel of a domestic photovoltaic power generation base at the standard dosage. After it is thermally cured into a film, perform the same characterization on it (the characterization includes adhesion characterization, pencil hardness characterization, and power generation efficiency characterization from 9:00 to 15:00 every day). The characterization results show that the adhesion characterization result is a 5B grade adhesion, and the pencil hardness characterization result is a 3H grade hardness.

[0064] From the above two characterization test results, the leveling agent of the present invention does not affect the film-forming quality and can effectively maintain the good mechanical properties and good bonding effect of the film material.

[0065] Example 2

[0066] A preparation method of a high-transparency leveling agent, the method is as follows:

[0067] 1) Add 1,3-bis(4-nitrophthalimido)benzene, 2,2-bis(4-hydroxyphenyl)propane, and carbon powder (mesh number 1300) to the reaction vessel in a mass ratio of 5:7:4.8 and mix evenly. Under a nitrogen atmosphere, keep the reaction temperature at 180 °C for 50 min. After the reaction is completed, a prepolymer is obtained;

[0068] 2) Mix the prepolymer, platinum-carbon catalyst, and 2-(trimethylsilyl)ethanol evenly in a ratio of 1 g:0.02 g:5 mL. Keep the temperature at 60 °C for 6 h. Centrifuge to separate the solid product, ultrasonically wash it with deionized water, and then dry it to obtain a high-transparency leveling agent.

[0069] Perform the same characterization tests on the leveling agent prepared in this example as in Example 1. The characterization test results show that the adhesion is at the 5B level and the pencil hardness is at the 3H level.

[0070] Example 3

[0071] A preparation method of a high-transparency leveling agent, the method is as follows:

[0072] 1) Add 1,3-bis(4-nitrophthalimido)benzene, 2,2-bis(4-hydroxyphenyl)propane, and carbon powder (mesh number 1350) to the reaction vessel in a mass ratio of 5:6:3.9 and mix evenly. Under a nitrogen atmosphere, keep the reaction temperature at 170 °C for 60 min. After the reaction is completed, a prepolymer is obtained;

[0073] 2) Mix the prepolymer, platinum-carbon catalyst, and 2-(trimethylsilyl)ethanol evenly in a ratio of 1 g:0.02 g:5 mL. Keep the temperature at 60 °C for 6 h. Centrifuge to separate the solid product, ultrasonically wash it with deionized water, and then dry it to obtain a high-transparency leveling agent.

[0074] Perform the same characterization tests on the leveling agent prepared in this example as in Example 1. The characterization test results show that the adhesion is at the 5B level and the pencil hardness is at the 3H level.

[0075] Solar photovoltaic panel power generation test characterization

[0076] Take the blank standard solar photovoltaic power generation panel of the same specification as the blank control, record its power generation efficiency and relative period temperature as the blank comparison, take the power generation efficiency and relative period temperature recorded by the same specification standard solar photovoltaic power generation panel coated with an anti-reflection coating (the commercially available coating recorded in Example 1) without adding a leveling agent as the control (recorded as the reference control), and then record the power generation efficiency and relative period temperature of the same specification standard solar photovoltaic power generation panel coated with an anti-reflection coating (the commercially available coating recorded in Example 1) after adding the leveling agents prepared in Examples 1-3 (the addition amount is 5 wt%). The test results are as Figure 1 and Figure 2as shown

[0077] From Figure 1 and Figure 2 It can be clearly seen that commercially available antireflection coating materials do have the effect of reducing the surface reflection of photovoltaic panels to a certain extent and improving the power generation efficiency when exposed to oblique sunlight. However, as the sunlight angle approaches a right angle, the power generation efficiency of the reference control experimental group has decreased very significantly. This is mainly because of its poor leveling effect. When the efficiency of the bare board (blank comparison) reaches its peak, the reference control instead produces structural scattering, resulting in an increase in light scattering loss and a decrease in power generation efficiency, and the actual use effect is negative. After adding the leveling agents prepared in Examples 1 to 3 of the present invention, it can be clearly seen from Figure 1 that it is possible to greatly reduce the light scattering loss caused by the poor leveling effect of the antireflection coating during the period from about 12:00 to 15:00, so that its power generation efficiency is close to that of the bare board, indicating that the leveling agent of the present invention has good leveling effect and extremely high light transmittance, meeting the peak power generation light demand of photovoltaic power generation panels.

[0078] And from Figure 2 it can also be seen that while maintaining high light transmittance performance, the leveling agent of the present invention also has a certain heat dissipation ability. However, after the antireflection coating forms a film, the temperature of the photovoltaic power generation panel is higher than that of the bare board throughout the whole period, especially during the period from 12:30 to 15:00, the temperature rise is more significant. After adding the leveling agent of the present invention, the temperature rise in this time interval is significantly inhibited, reducing the amplitude of the temperature rise of the photovoltaic power generation panel caused by the antireflection coating, which also indicates that the leveling agent of the present invention can improve the heat dissipation ability of the formed film material to a certain extent while ensuring high light transmittance.

[0079] Comparative Example 1

[0080] Based on Example 1, during the R & D process of the present invention, the usage effects of carbon powders with different mesh numbers were also compared. Carbon powders with 800 mesh, 1000 mesh, 1200 mesh, 1350 mesh, 1650 mesh and 1800 mesh with the same dosage were respectively used to prepare the leveling agent, and the rest of the preparation processes and parameters were the same as those in Example 1.

[0081] The prepared leveling agents were characterized in the same way as in Example 1, and the characterization results showed that the adhesion was all at the 5B level and the pencil hardness was all at the 3H level. However, there are great differences in the power generation test results of solar photovoltaic panels.

[0082] As Figure 3 shown. From Figure 3It can be clearly seen from the test results that when carbon powder with a mesh size of 800 - 1200 is actually used, it causes a further increase in the light scattering loss of the anti-reflection coating during the period from 12:00 to 15:00. This is mainly because it forms a more obvious front projection area, directly resulting in light shielding. Moreover, from the actual macroscopic use effect, even the anti-reflection coating film of the carbon powder test group with a mesh size of 800 has a slightly grayish appearance and a slightly darker color after film formation, which also indicates that the actual use effect of carbon powder with too large a mesh size is not good. When the mesh size of the carbon powder is further increased to 1650 mesh, from Figure 3 it can be clearly seen that although it reduces the light scattering loss of the anti-reflection coating film during the period from 12:00 to 15:00, indicating that it has a good leveling promotion effect and also avoids the formation of direct shadow projections, however, during the period from 9:00 to 12:00, there is an obvious decrease in the power generation efficiency. This is mainly because carbon powder with too small a mesh size, when actually in oblique sunlight, due to its larger longitudinal distribution range and its own light impermeability, leads to a sharp increase in the lateral light scattering loss, resulting in a decrease in the actual use effect of the anti-reflection coating. Therefore, through experiments, the most suitable mesh size of the carbon powder should be in the range of 1300 - 1500 mesh, which can avoid the increase in the oblique light scattering loss of the coating while improving the leveling property of the coating, avoiding the formation of too large a shadow projection area, thus maintaining the high transparency of the coating and improving the use effect of the coating.

[0083] Comparative Example 2

[0084] A preparation method of a high-transparency leveling agent, the method is as follows:

[0085] 1) Add 1,3-bis(4-nitrophthalimido)benzene, 2,2-bis(4-hydroxyphenyl)propane and carbon powder (mesh size 1300 mesh) to the reaction vessel according to the mass ratio of 5:7:4.8 and mix evenly. Under a nitrogen atmosphere, keep the reaction temperature at 180 °C for 50 min. After the reaction is completed, a prepolymer is obtained;

[0086] 2) Mix the prepolymer, platinum-carbon catalyst and 2-(trimethylsilyl)ethanol evenly according to the ratio of 1 g:0.02 g:10 mL, keep it at 60 °C for 6 h, centrifuge to separate the solid product, and ultrasonically wash it with deionized water and then dry it to obtain the high-transparency leveling agent.

[0087] Perform the same characterization tests on the leveling agent prepared in this example as in Example 1. The characterization test results show that the adhesion is at the 4B level and the pencil hardness is at the 3H level.

[0088] Meanwhile, in the solar photovoltaic panel power generation test, it can be clearly seen that the local color of the anti-reflection coating film formed on its surface deepens, and the power generation efficiency decreases by about 3.2-6.6% compared with Example 1 during the entire experimental period. It can be seen that its permeability also decreases significantly. This shows that the excessive use of silicone results in too high and uncontrollable degree of branching of the polymerized components in the prepared leveling agent particles, and the actual bonding strength decreases. At the same time, it also causes a certain degree of agglomeration or segregation problem of the carbon powder center, and the actual preparation and use effects are very limited.

[0089] Comparative Example 3

[0090] Replace the leveling agent of the present invention with commercially available high-transparency leveling agents (respectively commercially available solvent-based leveling agent and solid-based leveling agent), and the dosage is 5wt% of the anti-reflection coating, and conduct the same solar photovoltaic panel power generation test as in Example 1.

[0091] The test results are as Figure 4 shown.

[0092] From Figure 4 it can be seen that the commercially available solvent-based leveling agent has relatively close permeability characteristics to the present invention. During the characterization process, except that its performance is weaker than that of the leveling agent of the present invention during the period from 9:00 to 11:00, it is close to the high-transparency leveling agent of the present invention in the remaining time periods. However, the problems of difficult transportation and storage of the solvent-based leveling agent are still difficult to solve. And in the subsequent additional tests, the performance of the leveling agent of the present invention is stable. During the nearly 2-month continuous operation, no yellowing occurs and the permeability hardly changes. The power generation efficiency of the test board remains basically stable. While the solvent-based leveling agent shows a certain color change after about 50 days. The R & D personnel guess that it has turned yellow, and the power generation efficiency of the test board decreases afterwards. Similarly, in the adhesion test, the solvent-based leveling agent causes a significant decrease in the adhesion grade of the anti-reflection coating film to the 3B grade, and the surface pencil hardness also decreases to the 2H grade, indicating that it may also have a certain adverse effect on the mechanical properties of the coating.

[0093] The commercially available solid-based leveling agent is also in a solid form like the present invention. Its macroscopic characterization before use is white transparent granular, but after use, due to poor compatibility, it is actually difficult to effectively and evenly disperse and combine in the anti-reflection coating film. Instead, it may cause component segregation or agglomeration, resulting in possible differences in refractive index in many places. Under the strong sunlight at noon, it can be seen with the naked eye that there are local areas with different brightness. It can be seen that the commercially available solid-based leveling agent has very obvious use defects. When it is used for promoting the leveling of the surface protection coating film or anti-reflection coating film of solar photovoltaic power generation panels, it will greatly affect the actual permeability of the coating film and the power generation efficiency of solar photovoltaic power generation panels.

[0094] Similarly, during the experiment, neither of them showed the effect of promoting heat dissipation of the coating film.

Claims

1. A preparation method of a high-transparency leveling agent, characterized in that, the method comprises: 1) adding reactants and carrier powder into a reaction vessel, carrying out polycondensation reaction, and obtaining a prepolymer after the reaction is completed; 2) mixing the prepolymer with a catalyst and silicone, carrying out a constant-temperature reaction, and then centrifuging to obtain a solid powder leveling agent; the reactants in step 1) are 1,3-bis(4-nitrophthalimido)benzene and 2,2-bis(4-hydroxyphenyl)propane; the carrier powder in step 1) is carbon powder; the mesh number of the carbon powder is 1300-1500 meshes; the dosage of the carbon powder is 0.35-0.40 g / g of reactants; the silicone in step 2) is 2-(trimethylsilyl)ethanol; the dosage of the 2-(trimethylsilyl)ethanol is 3-5 mL / g of prepolymer.

2. The preparation method of a high-transparency leveling agent according to claim 1, characterized in that, the mass ratio of the dosages of 1,3-bis(4-nitrophthalimido)benzene and 2,2-bis(4-hydroxyphenyl)propane is 1:(1.2-1.4).

3. The preparation method of a high-transparency leveling agent according to claim 1, characterized in that, the polycondensation reaction is carried out at 160-180 °C for 45-75 min under a protective atmosphere.

4. The preparation method of a high-transparency leveling agent according to claim 1, characterized in that, the catalyst in step 2) is a platinum-carbon catalyst; the dosage of the platinum-carbon catalyst is 0.01-0.03 g / g of prepolymer; the average particle size of the platinum-carbon catalyst is 5-10 nm.

5. The preparation method of a high-transparency leveling agent according to claim 1, characterized in that, the constant-temperature reaction in step 2) is carried out at 60-65 °C for 4-6 h.

6. A high-transparency leveling agent prepared by any one of the methods according to claims 1 to 5.

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