Preparation and modification method of white carbon black

26/08/2021

White carbon black is a general term for fine powder or ultrafine particle anhydrous and hydrated silicon dioxide or silicate. It is a white, non-toxic, amorphous fine powder or granular substance, and its silicon dioxide content is greater than 90%, the original particle size is generally 5-40nm, because the surface contains more hydroxyl groups, it is easy to absorb water and become aggregated fine particles.

White carbon black products can be divided into precipitation method white carbon black and gas phase method white carbon black according to the manufacture, and can be divided into gas phase method white carbon black, ordinary precipitated white carbon black and highly dispersed precipitated white carbon black according to the market.

The gas-phase white carbon black has small particle size (15-25nm), low impurities and high purity, superior water resistance, good dielectric properties, great flying properties, and superior reinforcement, but the process is complex and the price is high.

The precipitated silica has a large particle size (20-40nm), low purity, poor reinforcement and dielectric properties, but it can change the flexure and cracking properties of the rubber, and has good process performance and low price.

Preparation of white carbon black

The traditional method of preparing white carbon black is to use sodium silicate, silicon tetrachloride, and ethyl orthosilicate as the silicon source. Except for sodium silicate, other costs are very high. The new method uses cheap non-metallic minerals as the silicon source, which greatly reduces the production cost of white carbon black.

The use of non-metallic minerals to produce white carbon black is technically feasible and has good economic benefits. Commonly used raw materials are diatomite, serpentine, bentonite, kaolin, wollastonite, quartz sand, sepiolite, and bumps. Rod stone, fly ash, axonite, coal gangue, yellow phosphorite, etc.

Surface modification of white carbon black

The surface modification of white carbon black is to use the modifier to make the hydroxyl groups on the white carbon black surface react with the modifier through a chemical process to eliminate or reduce the silanol group on the surface to achieve the purpose of changing the surface properties.

There are three types of hydroxyl groups on the surface of white carbon: isolated and undisturbed isolated hydroxyl groups, adjacent hydroxyl groups that form hydrogen bonds with each other, and two hydroxyl groups connected to a Si atom.

The dry modification process is simple, the post-processing procedures are few, and the large-scale production is easy. The wet modification production process is simple, uses less equipment and lower production cost.