What is the difference between drying agent and curing agent of car paint coating

For two-component paint, paint (A component) and desiccant (B component) are packed separately. The paint itself will not be cured, only after adding desiccant (also called curing agent), it can be dried and form a hard paint film through chemical reaction.

The amount of desiccant should be in accordance with the regulations of the paint manufacturer. If the amount is too much, the paint film will be easily cracked; if the amount is not enough, the paint film will be difficult to dry. For the atomic ash, the B component is called curing agent.

Micron-sized precipitated silica
Precipitated silica is formed by the flocculation of multiple primary particles. There is no regular three-dimensional spatial network structure, and it can be imagined as a bunch of grapes. Precipitated silica matting agent is made by grinding the dried product.

It can be clearly seen that the particle size of HK450 is larger than that of HK460.
Typical products include Degussa’s HK and OK series, as shown in Table 12-6. In addition to Degussa, the manufacturers of precipitated silica matting agents also include PPG in the United States. The representative brand is the Lover series, the Nipos il series of Nippon Sila in Japan, and Rodia in France.

The domestic output of this type of matting agent is the largest, but most of them are small factories with an annual output of 100 to 400 tons. Due to the serious surplus of domestic precipitated silica, the price is very low. After the product is pulverized by jet mill, it is sold as a paint matting agent, with low investment and large profit margins. It has been launched one after another. At present, there are dozens of companies. Excess production capacity. Due to the different sources of raw materials, the overall quality cannot be controlled, the price competition is fierce, and the quality is more difficult to improve. It is only used for low-grade coatings. Individual manufacturers choose raw materials from fixed sources, and those with better particle size control can be used for mid-range coatings.

Fumed silica
At present, only Degussa’s TS 100 and TT 600 matting agents are produced by hydrolysis wax emulsion basf in gas phase synthesis (1400°C). Its technical indicators are made of silicon tetrachloride in hydrogen and oxygen baking.
Good matting, high transparency of the coating film, eliminating blue phase. The disadvantage is that it is expensive, more than twice the OK series, and needs to be combined with hydrophobic fumed silica R972 to prevent the formation of hard precipitates. Domestic manufacturers have developed fumed silica matting agents, but they have not yet appeared on the market.