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What is "water-based paint thickener"? Divided into several categories?

Views: 1     Author: Site Editor     Publish Time: 2022-11-23      Origin: Site

Water-based paint is a paint that uses water as a dispersion medium and does not contain organic solvents. The characteristics of its water-based formula determine the characteristics of its system with low viscosity and poor fluidity. Therefore, in the configuration process, in order to ensure the good viscosity and fluidity required for its construction, water-based paint thickeners are added to check the viscosity of the system. Control, so that the water-based paint has good performance and construction performance, convenient construction and storage and transportation.

Therefore, thickeners are generally added during the configuration of water-based paints. Thickeners are a type of rheological additives. The amount added in the configuration of water-based paints is small, but it can significantly improve the performance of water-based paints. An integral part of the configuration process. Thickeners can increase the viscosity of water-based paints, adjust the fluidity of the formula, prevent sagging during construction, and endow water-based paints with good mechanical properties and storage properties, which can prevent flocculation or sedimentation during storage.

However, there are many types of thickeners on the market, and different types of thickeners have different thickening properties and use environments. Thickeners mainly include cellulose thickeners, inorganic thickeners, associative polyurethane thickeners and polyacrylates.

1. The use history of cellulose thickener is long and there are many varieties, such as methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, etc., which used to be the first choice of thickener The mainstream, of which the more commonly used is hydroxyethyl cellulose. Cellulosic thickeners have high thickening efficiency, especially for the thickening of the water phase; they have less restrictions on coating formulations and are widely used; they can be used in a wide range of pH. Since it has low viscosity under high shear and high viscosity under static and low shear, the viscosity increases rapidly after coating, which can prevent sagging. Studies have shown that as the relative molecular weight of the thickener increases, the spattering of latex paint also increases. Cellulosic thickeners are prone to splashing due to their large relative molecular mass. And because cellulose is more hydrophilic, it will reduce the water resistance of the paint film.

2. Inorganic thickener is a kind of gel mineral that absorbs water and expands to form thixotropy. There are mainly bentonite, attapulgite, aluminum silicate, etc., among which bentonite is more commonly used. Inorganic thickeners have the advantages of strong thickening, good thixotropy, wide pH range, and good stability. However, since bentonite is an inorganic powder with good light absorption, it can significantly reduce the surface gloss of the coating film and act like a matting agent.

3. Associative polyurethane thickener The associative structure is destroyed under the action of shear force, and the viscosity decreases. When the shear force disappears, the viscosity can be restored, which can prevent the sagging phenomenon during the construction process. And its viscosity recovery has a certain hysteresis, which is conducive to the leveling of the coating film. The relative molecular mass (thousands to tens of thousands) of polyurethane thickeners is much lower than the relative molecular mass (hundreds of thousands to millions) of the first two types of thickeners, and will not promote splashing. Polyurethane thickener molecules have both hydrophilic and hydrophobic groups, and the hydrophobic groups have a strong affinity with the matrix of the coating film, which can enhance the water resistance of the coating film.

4. Polyacrylate thickeners can basically be divided into two types: one is water-soluble polyacrylate, and the other is homopolymer or copolymer emulsion thickener of acrylic acid and methacrylic acid. The thickener itself is acidic and must be neutralized with alkali or ammonia water to pH 8-9 to achieve the thickening effect. It is also called acrylic acid alkali swelling thickener. Polyacrylic acid thickeners have strong thickening and leveling properties, and good biological stability, but are sensitive to pH and have slightly poorer water resistance.

Cellulosic thickeners, inorganic thickeners, associative polyurethane thickeners and polyacrylate thickeners have their own advantages and characteristics. They are also the four types of thickeners commonly used in the preparation of water-based paints. The choice is to choose a suitable thickener according to the thickening environment and thickening performance requirements.