The composition of this type of leveling agent is a copolymer or homopolymer of some polyacrylic esters. The ideal polyacrylate leveling agent should have a narrow relative molecular weight distribution, low surface tension, low glass transition temperature, appropriate relative molecular weight, and limited compatibility with film-forming resins. This allows for partial migration to the surface of the coating due to lower surface tension and incomplete miscibility than the coating, thereby forming a single-molecule thin film on the wet film surface, weakening surface flow, promoting uniform surface tension of the coating, suppressing solvent evaporation rate, and giving the wet film more leveling time. As a result, it can alleviate or eliminate surface defects such as orange peel brush marks, roller marks, floating colors, and flower marks, making the coating smooth and even. The compatibility between polyacrylate leveling agent and film-forming material is very important. If the compatibility is too good, it will not form a monolayer on the surface of the coating and affect the leveling effect.
However, leveling agents with poor compatibility can also cause adverse phenomena such as fogging, reduced gloss, and loss of gloss in the coating. Acrylic homopolymers have poor compatibility with some resins. So acrylic copolymers are often used. By using different acrylic monomers to participate in copolymerization, the miscibility and glass transition humidity of the coating can be adjusted to maintain good flowability at room temperature.
Compared with modified polydimethylsiloxane leveling agents, polyacrylate leveling agents are relatively safe. Even if added excessively, it will not affect recoating and interlayer adhesion. As the dosage increases, the surface tension decreases, the shrinkage decreases, and the gloss and clarity improve. However, continuing to increase the dosage does not help further improve the leveling performance. On the contrary, it will also bring side effects. Such as fogging and loss of gloss on the paint film. In addition, the dosage of leveling agent is related to the type of film-forming resin, and the dosage varies for different resins, usually not exceeding 2% of the total coating amount. So the optimal dosage of leveling agent is best determined through experimentation.
Polyacrylate leveling agents can be used for solvent based coatings, water-based coatings, and powder coatings. Reactive polyacrylic esters can be divided into two types: non reactive and reactive. Water based coatings generally use non reactive materials. Solvent based coatings and powder coatings can be used both non reactive and reactive. But currently, non reactive leveling agents are commonly used in China.
