What is a leveling agent? What are the types?

Admin · 1 What is a leveling agent? What are the types? Mon Jun 21, 2021 10:07 am

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Leveling agents are roughly divided into two categories. One works by adjusting the viscosity of the paint film and the leveling time. Most of these leveling agents are high-boiling organic solvents or their mixtures, such as isophorone, diacetone alcohol, Solvesso150, etc.; the other It works by adjusting the surface properties of the paint film. Generally speaking, the leveling agent refers to this type of leveling agent. This type of leveling agent migrates to the surface of the paint film through limited compatibility, which affects the surface properties such as the interfacial tension of the paint film, and enables the paint film to achieve good leveling. According to different chemical structures, there are three main types of this type of leveling agents: acrylics, silicones and fluorocarbons. classification: Silicone type Silicone oil Commonly used silicone oils are polydimethylsiloxane and polymethylphenylsiloxane. Polydimethylsiloxane is used in coatings and inks. Although polymethylphenylsiloxane has good compatibility, it does not have the ability to control the surface state, so it is basically not used in leveling agents and is mostly used for high temperature resistance. Polydimethylsiloxane Although it has a good surface condition control ability, it has many shortcomings. The compatibility is not good, which will affect the gloss of the coating film, and there will often be shrinkage and interlayer adhesion problems. The molecular weight of polydimethylsiloxane is different, and its compatibility and use are also different. Compared with silicone oil, organically modified polydimethylsiloxane has obvious advantages. It not only retains the advantages of siloxane, but also overcomes its shortcomings with modified compounds and exerts many special functional effects. The key to the performance and application of modified siloxane is the molecular weight, type, type of modified compound and position in the molecule of siloxane. There are many ways to modify it. Polyether polyester modified organosiloxane It is an organopolysiloxane with a comb-like structure. n+m is about 50-250, and the molecular weight is controlled between 1000-150000. The compatibility is adjusted by polyether and polyester. The longer the chain, the better the compatibility. Polyethers of this type are mostly modified, propylene oxide are usually used. As the content of ethoxy groups increases, its compatibility with water also increases, so it is also possible to synthesize water-soluble siloxane leveling agents. Propylene oxide can be used alone or mixed to control the hydrophilicity and lipophilicity. If it contains both ethoxy group and propoxy group, it is made into a water-oil dual-use siloxane leveling agent, such as: MOON Chemical's 1080 and 1090 series products. The larger the molecular weight, the stronger the ability to control the surface state, and the better the slippage and anti-blocking properties. For example, the 1070 and 1071 series products of Moneng Chemical. There are two ways to link the modified polyester or polyether with siloxane: one is a silicon-oxygen bond; the other is a silicon-carbon chain. Generally speaking, the thermal stability and water resistance of the former are not as good as the latter. The compatibility of polyether and polyester modified siloxane with resin has been greatly improved, the surface tension is reduced, the ability to control surface flow, slippage, anti-cratering, and anti-blocking effects are also very good. , Individual products still have problems with adhesion between layers. Especially polyether-modified polysiloxanes have poor thermal stability and are easy to stabilize foam. ***Pay attention to the negative effects of these products when applying. Alkyl modified organosiloxane As mentioned earlier, polyether-modified polysiloxanes have some shortcomings; alkyl-modified polysiloxanes have exactly these advantages. This series of polysiloxane products also belong to the comb structure. The molecular weight of this type of product is relatively small, about 10,000, and n+m is about 30-50. The purpose of modification with alkyl is mainly to improve thermal stability, compatibility and unstable foam, and even has a defoaming function. But as the modified alkyl chain grows, its ability to reduce surface tension also decreases. The relationship between alkyl chain length. Generally, the carbon chain is controlled between C1-C14, so the molecular weight is not too large. The three modification methods of polydimethylsiloxane are introduced above. The modification methods are different, the amount and structure of the modifier are different, and the performance of the product is also different. The leveling agent produced by the three different modification methods, Its heat resistance is also very different. Monon Chemical’s 1060 silicone modified polysiloxane has good heat resistance and can be used in the temperature range of 200-220℃. End group modified silicone End-group-modified silicones that impart excellent smoothness In order to impart good smoothness to the coating film, Moneng Chemical has introduced some terminal-modified silicones. Reactive leveling agent In radiation-cured coatings and ink systems, there are defects such as poor substrate wetting, insufficient slippage, easy scratching, and poor leveling. In response to these problems, Monon Chemical Co., Ltd. provides a series of reactive organically modified polysiloxane acrylic leveling agents, including Monon Chemical's 1073, 1074 and other products. The former has good compatibility and poor slippage. The latter has poor compatibility and good smoothness. It can be seen from the structural formula that the modified organic substance is acrylate, which is used to adjust its fluidity and compatibility. Its smoothness is determined by siloxane. The double bond of the acrylic group can participate in the polymerization reaction of the free radicals, and together with the resin form a coating film firmly anchored on the surface of the coating film. Acrylic type product description Resin-based surface flow control agents are mostly linear resin polymers, mainly acrylic resins, urea-formaldehyde resins and melamine-formaldehyde resins. In the general system, the compatibility of these resins is limited. They will accumulate to the surface to form a new resin film, making the surface tension of the coating film balanced, but they will not reduce the surface tension, so it does not affect The flow of paint is often referred to as a flow promoter. In this type of leveling agent, acrylic resin is the main body. Acrylic leveling agents can not only promote the flow and leveling of the coating film, but also will not affect the interlayer adhesion of the coating film, and also have the effect of defoaming. Leveling principleThe compatibility of acrylic leveling agents is an important indicator of its ability to control the surface state of the coating film. The compatibility is too good, dissolving in the coating film, will not form a new interface on the coating film surface, and can not provide leveling effect; the compatibility is too poor, it is impossible to evenly distribute on the coating film surface, and will gather together , Easy to produce shrinkage-shaped defects. It will reduce the gloss of the coating film and produce undesirable side effects such as haze. Only with ideal controlled compatibility can a new interface layer be formed on the surface of the coating film, which plays a role of leveling. product category The controllability of acrylic leveling agents is achieved by changing the molecular weight and polarity. The compatibility of homopolymers is not as good as that of copolymers. For example, homopolymer acrylics usually have poor compatibility with resins used in epoxy, polyester, polyurethane and other coatings. If they are physically mixed, they will form a surface. A matte coating film in poor condition, so acrylic homopolymer is not suitable as a leveling agent. Ideal leveling agents mostly use copolymers, which can be terpolymers or modified copolymers. Only copolymers can change the polarity and glass flower temperature of the polymer through different monomers. Generally, the number average molecular weight of acrylic leveling agents is controlled between 6000-20000, the molecular weight distribution is relatively narrow, the glass flower temperature is controlled below -20°C, and the surface tension is below 25-26mN/m. This acrylic copolymer with limited compatibility is considered a good leveling agent. Acrylic leveling agents can be homopolymers or copolymers; they can be linear or branched; they can also be random copolymers or block copolymers. 1) Fluorine-modified acrylate-based leveling agent. This type of leveling agent is widely used. The use of fluorine-modified acrylic acid makes the advantages and disadvantages of fluorine and acrylic acid complement each other, making this type of leveling agent more prone to vulnerabilities. The advantages and disadvantages of acrylic. The modified leveling agent has good surface control ability, unstable foam, can be recoated, and has good anti-crater and substrate wetting ability. Representative products are 1154 from Moneng Chemical. 2) Application of acrylate leveling agent Pure acrylate leveling agent has little effect on surface tension, so it is mostly used as flow and leveling aids, especially for printing iron coatings and coil coatings, to eliminate roll marks Is helpful. And brushed wood lacquer is also helpful to eliminate brush marks. Pay special attention to the compatibility with the coating during application. Generally speaking, the compatibility with large molecular weight is poor, but the flow and leveling are good; the compatibility with small molecular weight is good, but the flow and leveling are worse. Acrylic <a href="https://www.pc-additive.com/leveling-agent.html" rel="noopener noreferrer" target="_blank">leveling agents</a> can be used not only in oil-based coatings, water-based coatings, but also in powder coatings. These products include Monon Chemical's 1153.

What is a leveling agent? What are the types?

1 What is a leveling agent? What are the types? Mon Jun 21, 2021 10:07 am

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