Classification of additives for powder coatings

Powder coatings exist in solid powder form. Powder generally refers to solid particles less than 1 mm in diameter. The production of powder coatings is a process of pre-mixing synthetic resins, pigment fillers, additives and other raw materials, melt extrusion, tablet conveying, crushing and sieving, etc. The coating is mainly electrostatic spraying. Due to its excellent energy-saving and environmental protection performance, powder coatings are the fastest-growing coatings at home and abroad in recent years. Some data show that, if compared by pure solids, the amount of powder coatings in 2010 will be ranked in the top three of coatings. At the same time, the raw materials and milling equipment related to powder coatings have made great progress. Below we mainly discuss the additives in powder coating raw materials.

Classification of additives for powder coating

Auxiliary is an auxiliary material for powder film formation. It cannot be formed into a film alone. The amount of the auxiliary agent in the coating is small. The total amount of the auxiliary agent is generally within 5%, but it can change the performance of the coating or coating in a targeted manner. The additives used in powder coatings are mostly solid, or absorbed by the carrier to become solid, which has the characteristics of relatively stable performance and high temperature resistance. Therefore, powder additives are different from similar paint additives, and are self-contained. With the rapid development of powder coatings, the varieties of powder additives are also increasing. According to the production and application of auxiliaries, we divide auxiliaries into the following three categories.

Conventional additives
Conventional additives are the necessary additives for the production of ordinary flat powder coatings, mainly including leveling agents, brightening agents, benzoin, matting agents, dry powder flow agents, etc. Some of these additives can change the leveling of the coating film, some can change the gloss of the coating film, some can change the flow properties of the powder during construction, and some can improve the storage stability of the powder. The commonly used leveling agents are mostly polyacrylates, and Tsinghua castor oil, polyvinyl butyral, and butyl cellulose are also used as auxiliary leveling agents. Brighteners are coupling agents, dispersants, etc. used to improve the dispersion of pigments and fillers. There are many varieties of powder matting agents, and there are chemical types that participate in the reaction, such as the commonly used models B68, 208; physical types that do not participate in the reaction, such as matting wax 823, 3329, etc. The dry powder flow agent uses more fine powder, and adds it to the finished powder, such as fumed silica M-5, alumina C.

Texture Aids:
Texture additive is a powder additive developed to cover the surface roughness of the workpiece or achieve a beautiful coating effect. It optimizes the previous cumbersome formulas and makes the powder achieve a relatively stable artistic decoration effect. The main varieties are wrinkle agent, hammer pattern agent, sand pattern agent, cotton wool agent, foaming agent, moiré pattern agent, dot flower diffuser, three-dimensional pattern agent and so on. The amount of texture aid is small, all in a few thousandths, and is generally re-dispersed after extrusion. And these additives have strict requirements on the performance of the resin, such as viscosity, reactivity, glass transition temperature, content of impurities and so on. Ordinary wrinkle powder, if the content of catalyst in the resin is high, the texture is small or no texture. To make cotton grain powder, the organic chlorine content of epoxy resin is required not to exceed 0.1%.

Functional additives:
Functional additives are additives that improve and expand the function of coating films. These additives are the fastest growing and the most diverse in several categories of additives, such as anti-yellowing agents, ultraviolet absorbers, electrifiers, Foaming agent, light stabilizer, anti-blocking agent, hardening agent, coupling agent, adhesion promoter, antistatic agent, conductive agent, dispersant, antifungal agent, catalyst, heat stabilizer, flame retardant, wear-resistant agent, etc. These additives used in powder coatings can be borrowed from coatings or plastics as long as they do not affect the powder properties.