Different types of leveling agents used in different coatings are not the same

Leveling agent is a commonly used coating additive, it can promote the coating in the drying process into a smooth, smooth, uniform coating film. There are many types of leveling agents, and the types of leveling agents used in different coatings are not the same.
of the
coating, there is a flow and drying of the film process, and then gradually form a flat, smooth, uniform coating film

. Whether the coating film can achieve the characteristics of flat and smooth, called leveling. Shrinking hole is one of the characteristic defects of coating in the process of leveling and film forming. In the actual construction process, due to poor leveling, brush marks when painting, rolling paint when rolling marks, spraying when orange peel, in the drying process accompanied by shrink holes, pinholes, flow hanging and other phenomena, are called poor leveling, the production of these phenomena reduce the decorative and protective functions of the paint.
There are many factors that affect paint leveling, the volatile gradient and solubility performance of solvents, the surface tensor pressure of the coating, the thickness and surface tensor gradient of the wet film, the fluidization of the coating, the construction process and the environment, among which the most important factors are the surface tensor pressure of the coating, the surface tensor gradient produced by the wet film during the film formation process, and the surface tensor homogenization ability of the wet film surface layer. Improving the leveling of coatings requires consideration of adjusting formulations and adding suitable additives to give the coating the right surface strength and the ability to reduce surface stress gradients.
the flow leveling agent
coating drying into a membrane too common defects are shrink holes, orange peel, brush marks, rolling marks, hanging and so on.
shrink hole refers to the irregular formation of the coating film, such as a small depression like a bowl, so that the coating film loses its flatness, often with a drop or a small piece of impurities as the center, around the formation of a ring of prisms. From the point of view of leveling, it is a special kind of "dot-type" flow uneven, resulting from the coating surface, its shape from the performance can be divided into flat- type, crater-type, dot-type, dew-type, bubble-type and so on.
commonly used anti-shrink hole leveling agent
solvent leveling agent is mainly a mixture of high boiling point solvents. Solvent-based coatings only use increased solvents to reduce viscosity to improve leveling, will reduce the solid content of the coating and lead to hang and other ills, or maintain solvent content, only add high boiling point solvents to adjust the volatility speed to improve the level, drying time is also extended accordingly. Therefore, neither option is ideal. Only the addition of a mixture of high boiling point solvents to show a variety of incremental characteristics (volatile index, distillation curve, solubility capacity) is ideal. The main component of solvent leveling agent is a variety of high boiling point of mixed solvents, with good solubility, but also a good pigment wetting agent. Temperature-cured coatings due to solvent evaporation too fast, paint viscosity increased too fast to hinder the flow of brush marks, solvent volatilization led to poor solubility of the substation caused by shrink holes, or in baking paint to produce boiling marks, foaming and other ills using such additives is very effective. In addition, the use of high boiling point leveling agent to adjust the volatilization speed, but also to overcome the ills of whitening.
chain resins with limited compatible are commonly used in polyacrylic acids, citric cellulose, etc. Their surface pressure is low, can reduce the surface pressure between the coating and the substrate and improve the wetting of the coating to the substrate, eliminate the gas molecules absorbed by the solid surface, prevent the adsorption of gas molecules from being removed too late and form a concave on the cured coating surface Holes, shrink holes, orange peels and other defects, in addition, they are not completely compatible with the resin, can quickly migrate to the surface to form a single molecular layer, to ensure that the surface of the surface of the homogenization of the surface, increase the anti-shrink hole effect, thereby improving the smooth flatness of the coating surface. Polyacrylate leveling agent can be divided into pure polyacrylates, modified polyacrylates (or flattened with silicone), acrylic alkali resin, etc., pure polyacrylate flow
In order to improve its compatible, it is usually used to have a better mixed compatible co-property.
chain silicone resins with limited compatible are commonly used in polydymethane, polymethylene benzene, organic-modified polysilica, etc. Such substances can improve the wetting of the substrate and control surface flow, play a role in improving the leveling effect, when the solvent evaporates, silicone resin on the surface of the coating film formed a single molecular layer, improve the gloss of the coating film. Modified polysilicae can also be divided into polyether modified silicone, polyester modified silicone, reactive silicone, the introduction of organic groups to help improve the compatible polysilicae and coating resin, even if the concentration increase will not produce incompatible and side effects, modified polysilica can reduce the interface between the coating and substrate, improve the wetting of the substrate, improve adhesion, prevent flowering, orange peeling, reduce the surface of the needle.
fluorine surfactant, its main component is polyfluorinated polyolefins, for many resins and solvents also have good compatibility and surf activity, help to improve wetting, dispersion and leveling, but also in solvent-based paint can adjust the speed of solvent evaporation.
the main function of the leveling agent
coating in the formulation of the coating is decoration and protection, if there are flow and level defects, not only affect the appearance, but also damage the protective function. If the formation of shrink holes resulting in insufficient thickness of the paint film, the formation of pinholes will lead to discontinuity of the paint film, which will reduce the protectiveness of the paint film.
coating in the construction and film-forming process, there will be some physical and chemical changes, these changes and the nature of the coating itself, will significantly affect the flow and leveling of the coating.
coating construction, a new interface will appear, typically the liquid/solid interface between the coating and the substrate and the liquid/gas interface between the coating and the air. If the interface of the liquid/solid interface between the coating and the substrate is higher than the critical surface stress of the substrate, the coating cannot spread on the substrate, and naturally there will be leveling defects such as fish eyes and shrink holes.
the evaporation of solvents during the drying of the paint film results in differences in temperature, density and surface pressure between the surface and interior of the paint film, which in turn results in turbulence movement within the paint film, forming a so-called Benard vortex. Benard vortex can lead to orange peels; in a system with more than one pigment, if there is a difference in the motion of pigment particles, Benard vortex is also likely to lead to floating colors and hair flowers, vertical surface construction can lead to silk.
the drying process of the paint film sometimes produces some insoluble gel particles, the production of insoluble gel particles will lead to the formation of surface stress gradient, often lead to the production of shrink holes in the paint film. For example, in cross-linked curing systems, the formula contains more than one resin, in the drying process of the paint film, with the evaporation of solvents, the less soluble resin may form insoluble particles. In addition, in formulations containing surfactants, if the surfactants are not compatible with the system, or in the drying process with the evaporation of solvents, the concentration changes leading to changes in solubility, the formation of incompatible droplets, will also form a surface tension difference. These can lead to shrink holes.
coating in the construction and film-forming process, if there are external pollutants, may also lead to shrink holes, fish eyes and other leveling defects. These pollutants are usually oil, dust, paint mist, water vapor, etc. from air, construction tools and substrates.
the paint itself, such as construction viscosity, drying time, etc., will also have a significant impact on the final level of the paint film. Excessive construction viscosity and too short drying times usually result in poorly leveled surfaces.
therefore, the coating must be helped to obtain a good level by adding leveling agents, by adjusting for some changes in the coating during construction and film-forming processes, and by adjusting the properties of the coating.
types of adhesives
are broadly divided into two broad categories.
one works by adjusting the viscosity and leveling time of the paint film, most of which are organic solvents with high boiling points or their mixtures, such as isofol, diprotonol, Solvesso150, etc.
another is by adjusting the surface properties of the paint film to play a role, generally referred to as leveling agents mostly refer to this class of leveling agents. This type of leveling agent through limited compatible migration to the paint film surface, affecting the paint film interface stress and other surface properties, so that the paint film to obtain a good level. Depending on the chemical structure, there are currently three main categories of such leveling agents: acrylics, silicones and fluorocarbons.
acrylic leveling agents
acrylic leveling agents include pure acrylic leveling agents and modified acrylic leveling agents.
pure acrylic leveling agents include traditional non-reactive acrylic leveling agents and new reactive acrylic leveling agents containing tube energy groups. This is a class of acrylic polymers or co-polymers of varying molecular weight, such leveling agents only slightly reduce the surface pressure of the coating, but can balance the surface pressure difference of the paint film, to obtain a truly flat, mirror-like paint film surface. If the molecular weight is high enough, this leveling agent also has the effect of degassing and deblistering. The disadvantage of traditional non-reactive acrylic leveling agents is that high molecular weight products may produce fog shadow in the paint film, low molecular weight products, and may reduce the hardness of the paint film surface. Acrylic leveling agent with reactive function group can solve this contradiction very well, provide good leveling, do not produce fog shadow or reduce surface hardness, and sometimes improve surface hardness.
varieties of modified acrylic leveling agents are fluorine modified acrylic leveling agent and phosphate modified acrylic leveling agent. Unlike pure acrylic leveling agents, modified acrylic leveling agents can significantly reduce the surface pressure of the coating, which will have a leveling at the same time with good substrate wetting.
silicone leveling agents
two significant properties of silicone leveling agents. First, it can significantly reduce the surface pressure of the coating, improve the coating substrate moisturizing capacity and the fluidity of the paint film, eliminate the Benard vortex to prevent flowering. The ability to reduce surface stress depends on its chemical structure. Another notable feature is the ability to improve the smoothness, anti-hanging injury and anti-adhesion of the coating. The disadvantage of this leveling agent is that there is a tendency to stabilize foam and affect inter-layer adhesion, and some also pollute the construction environment such as ovens. At present, there are three main types of structure: polydyl methylsilioxane, polymericane silica, organic modified polysilane, with organic modified polysilicaane is the most important, pure polydylsilisiloxane due to poor compatible with the coating system, is now rarely used.
. Fluorocarbon leveling agent
Fluorocarbon leveling agent is characterized by high efficiency, but expensive, generally used when acrylic leveling agent and silicone leveling agent difficult to function, however, there is also a tendency to stabilize foam, affect inter-layer adhesion.
application of a leveling agent
For a defined formulation system, the appropriate leveling agent variety should be selected according to the nature of the formulation and the performance of the desired leveling agent.
1, solvent-based coating
in primer and mid-lacquer formulation, usually using acrylic leveling agent. If degassing and substrate wetting are required, it is advisable to choose
medium molecular weight or high molecular weight acrylic leveling agent. In primers, if stronger substrate wetting is required, consider the use of silicone leveling agents and modified acrylic leveling agents (e.g. fluoro modified acrylic leveling agents and phosphate modified acrylic leveling agents) that significantly reduce surface stress, and if the silicone leveling agent and fluorine modified acrylic leveling agents appear to stabilize bubbles, affect inter-layer adhesion and other side effects, phosphate-modified acrylic leveling agents should be used.
In the paint and transparent paint formula, the appearance of the paint film requirements are relatively high, generally optional low molecular weight acrylic leveling agent, so that you will get good leveling, in the paint film is not easy to produce fog shadow. In cross-link curing systems, acrylic leveling agents with reactive erythropoies are often used to obtain better leveling, while improving the physical and chemical properties of paint film. Silicone leveling agents are required if the paint film is needed for better fluidity or if it requires smoothness and scratch resistance, in which case it is best to use silicone leveling agents and acrylic leveling agents.
it should be noted that when vertical surface construction, silicone leveling agents provide leveling properties while effectively reducing the tendency of the coating to hang. In addition, in the metal flash paint formula, silicone leveling agent should be used with caution, as this may lead to uneven arrangement of flaky aluminum pigments and uneven color of the paint film.
2, powder coating system
the leveling process of powder coating is divided into two stages. The first stage is the melting of powder particles, and the second stage of powder particles melts and flows into a flat paint film. Powder coatings are solvent-free and do not produce surface tensor gradients during film-forming processes, and the leveling is more related to the wetting of the substrate.
powder coatings often use acrylic leveling agents. If the leveling agent is liquid, it is generally pre-made into mastertenses before use. There are also acrylic leveling agents made into powders, specifically used in powder coatings, such products are liquid acrylic leveling agent adsorption on silicon dioxide powder, some low-grade leveling agents with calcium carbonate adsorption.
if powder coatings require smoothness and anti-hanging injury resistance, silicone leveling agents should be used, and silicone leveling agents have been made into powders specifically for powder coatings. Use silicone leveling agents to avoid shrink holes.
3, water-based coating system
water-based coating system is divided into water-soluble system and latex system.
In water-soluble systems, the surface pressure of the system needs to be strongly reduced, most commonly silicone leveling agents and fluorocarbonized
-class leveling agents, which work in the same way as they are used in solvent-based coating systems. Of course, acrylic leveling agents for water-based systems are necessary if a truly flat surface is required.
the latex system, the film-forming process is completely different, and the viscosity does not change with the volatility of the solvent. The use of leveling agents in the formulation may improve the wetting of the substrate of the coating, acrylic leveling agent can improve the flatness of the paint film, but the main fluidity of the coating, more by adding rheumor control agent to control and adjust.
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