Production principle and application of precipitated silica

* Source: * Publication time: 2021/09/16 13:43:40 * Browse: 72

The chemical formula of white carbon black is SiO2nH2O, because its use is similar to carbon black and white, hence the name of white carbon black. According to the different production methods, silica can be divided into precipitated silica (precipitated hydrated silica) and gas phase silica (gas phase silica). The production methods of the two products are different, and their properties and uses are also very different. Gas phase production is mainly the use of silicon tetrachloride and air combustion of silica, fine particles, the median particle size of up to 5 microns. The precipitation process uses sodium silicate to precipitate silica by adding sulfuric acid. The median particle size is about 7-12 microns. Gas phase silica is expensive, it is not easy to absorb moisture, and it is more used in paint as a extinction agent. Precipitated silica is cheap and easy to absorb moisture. Mainly used as filler and reinforcing agent in rubber and plastic products. The products introduced below are produced by sulfuric acid precipitation method, also known as precipitated white carbon black. The white carbon black involved in the following are precipitated white carbon black.

White carbon black

First, the production principle of precipitated silica

Sodium silicate reacts with sulfuric acid to form hydrated silicate Na2O·mSiO2+H2SO4+nH2o-→Na2SO4+mSiO2· (N +1) H2O↓

(The reaction process needs heating). The reaction finishing liquid was dehydrated by pressure filtration, washed and beaten to get the white carbon black slurry, which was spray dried to get the white carbon black finished product.

Two, the main use of silica precipitation method

Since the industrial production in the 1940s, silica products have been widely used in rubber products as reinforcing agent, in addition to the pharmaceutical industry, pesticide, ink, paint, coating, toothpaste, paper, food, feed, cosmetics, battery and other industries. Now the main application industries of white gray black are briefly introduced:

1. Tire industry

Using white carbon black in tire tread glue, especially high dispersive precipitation method and coupling agent can simultaneously improve tire life (improve wear resistance) and safety (improve skid resistance), reduce fuel consumption (reduce rolling resistance). In addition, the precipitation method of silica used in tire body and belt layer can improve the adhesive force between rubber material and steel cord; Using white carbon black to partially replace carbon black in tire side glue can greatly improve the durability of rubber material, improve flexure resistance and impact resistance.

Rubber shoes and other rubber products

(1) white carbon black white, fine particles, the use of white carbon black vulcanized rubber transparency is high, but also can improve the comprehensive physical properties of rubber material. Therefore, as the main reinforcing filler, white carbon black is widely used in the production of rubber shoes, especially in transparent and translucent sole rubber materials.

(2) In the production of adhesive tape, in order to improve its wear resistance, a large amount of white carbon black is added. At the same time, the silanol on the surface of white carbon black plays a role in improving the wettability of adhesive material and fabric, which is conducive to the diffusion and penetration of adhesive material. In addition to the above products, white carbon black is also used for rubber roller, rubber hose, rubber plate, wire and cable and household appliances, stationery rubber parts and so on.

3, silicone rubber

The application of silicone rubber began with the appearance of silica. Silicone rubber has high heat resistance and excellent cold resistance, ozone resistance, aging resistance and atmospheric aging resistance, and has excellent electrical insulation. Because of the above characteristics of silicone rubber, it is widely used in aerospace, electronics and other industries. Gas phase silica has a high price, and gas phase silica can be replaced by relatively cheap precipitated silica, which can be used for the production of low-grade silicone rubber.

4. Pharmaceutical industry

White carbon black has physiological inertia, high absorbability, dispersity and thickening, and has been widely used in pharmaceutical preparations. For example, a large number of pseudo-biogenic E powder now uses white carbon black as a carrier.

5. Pesticide industry

The main role of white carbon black in the pesticide industry is as a carrier, improve liquidity and prevent caking, at present, white carbon black is mainly used in all kinds of wettable powder.

6, in the application of ink

White carbon black in ink mainly thickens, used to control the flow of printing ink. Also used to control the flow of printer ink, so that it can not be arbitrary flow or flow hanging, in order to obtain a clear print.

Three, the significance of various indicators of silica in application

1, the specific surface area The size of the white carbon black reinforcing effect, depending on its specific surface with the increase of specific surface area, the general rubber products of the various strength indexes, but resilience reduces, tear strength is reduced, and do not wear, mixing scattered difficult, high heat, rubber Mooney viscosity, scorch easily, therefore, different formula, different purposes, Specific surface area requirements are not the same, specific surface area on the physical and mechanical properties of vulcanized rubber is not consistent.

2, oil absorption value of oil absorption value is reflected in the height of the structure, oil absorption value is large, small structure, vulcanized rubber extension strength is generally large, tensile strength and hardness is large, especially the wear resistance is small, but the elongation is low.

3, 900℃ burning reduction reflects the surface hydroxyl. When the surface hydroxyl group is too much, it is easy to cause the structure of rubber composite material and make the material brittle. Affect the processing performance, and vulcanizate easy to drop blocks, and the surface hydroxyl on the vulcanization accelerator has strong adsorption, prolong the curing time.

4, 105℃ heating reduction reflects the amount of free water in the particle gap. When it is too small, the structure of the rubber material is high and the mixing of rubber becomes difficult. If the heating reduction is zero, the white carbon black is useless, and generally controlled at about 6% is more appropriate.

5. The PH value is generally about 7, and the PH value increases (the acidity decreases), and the vulcanization rate of the rubber increases.

6. The less soluble salt content the better, but if the soluble salt content is greatly reduced, the production cost will be greatly increased.

Throughout the world, the number of new silicon compounds has not increased much in recent years, and the development of inorganic silicon compounds is more attention. From the current trend, white carbon black will enter a large number of light industry, food, medicine, construction, electronics, metallurgy, machinery industry and many other fields, will have a great development prospect.

News Sort

Production principle and application of precipitated silica