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Yuan lei small class | craft is wrong, everything is in vain! Powder surface modification 3 categories of typical process

Release time:

2024-01-29 09:35

 

Yuan lei small class | craft is wrong, everything is in vain! Powder surface modification 3 categories of typical process

 

The surface modification process varies according to the method, equipment and powder preparation method of surface modification. At present, the surface modification process applied in industry mainly includesDry process, wet process, composite processthree major categories.

 

 

1. Dry process

This is one of the most widely used non-metallic mineral powder surface modification process. Currently for non-metallic mineral fillers and pigments, suchHeavy and light calcium carbonate, kaolin and calcined kaolin, talc, wollastonite, silica micropowder, glass beads, aluminum hydroxide and light magnesium oxide, clay, ceramic pigmentsMost of the dry surface modification process. The reason is that the dry process is simple, flexible operation, less investment and good applicability of the modifier.

(1) Intermittent dry process

The characteristic is that the surface modification time (I. e. residence time) can be flexibly adjusted in a large range, but the particle surface modifier is difficult to coat evenly, the unit product consumption is more, the production efficiency is low, the labor intensity is high, there is dust pollution, it is difficult to adapt to large-scale industrial production, and is generally used in small-scale production.

(2) Continuous modification process

It is characterized by better dispersion of powder and surface modifier, more uniform coating of particle surface, less consumption of modifier per unit product, low labor intensity, high production efficiency, suitable for large-scale industrial production. The continuous dry surface modification process is often placed after the dry powder preparation process, and the large-scale continuous production of various non-metallic mineral active powders, especially inorganic fillers and pigments for plastics, rubber, adhesives and other polymer-based composites.

2. Wet process

Compared with the dry process, it has the characteristics of good dispersion of surface modifiers and uniform surface coating, but requires subsequent dehydration (filtration and drying) operations. Generally used for water-soluble or hydrolysable organic surface modifiers and the previous stage for wet powder (including wet mechanical ultra-fine grinding and chemical powder) process and the latter section needs to be dried, such.Light calcium carbonate (especially nano calcium carbonate), wet fine ground heavy calcium carbonate, ultrafine aluminum hydroxide and magnesium hydroxide, ultrafine silicaThis is because the slurry generated after the chemical reaction is filtered and dried even without wet surface modification, and the surface modification before filtering and drying can also make the material dry without forming a hard agglomeration and improve its dispersibility.

Inorganic precipitation coating modification is also a wet modification process. It includes pulping, hydrolysis, precipitation reaction and subsequent washing, dehydration, calcination or roasting process or process.

3、composite process

(1) Mechanochemical/chemical coating composite modification process.

The surface modifier is added in the process of mechanical force action or fine grinding and ultra-fine grinding, and the surface chemical coating modification of the particles is carried out at the same time as the particle size of the powder is reduced. The characteristic of this composite surface modification process is that it can simplify the process, and some surface modifiers also have a certain degree of grinding aid, which can improve the crushing efficiency to a certain extent.

The disadvantage is that the temperature is not well controlled. In addition, due to the continuous crushing of particles during the modification process, new surfaces are generated, and the particle coating is difficult to be uniform. The addition method of surface modifier must be designed to ensure uniform coating and high coating rate. In addition, if the heat dissipation of the crushing equipment is not good, the local excessive temperature rise during the strong mechanical force may cause some surface modifiers to decompose or the molecular structure to be destroyed.

(2) Inorganic precipitation reaction/chemical coating composite modification process

Surface chemical coating modification after precipitation reaction modification is essentially an inorganic/organic composite modification process. This composite modification process has been widely used in the surface modification of composite titanium dioxide, that is, in the precipitation coated SiO.2or Al2O3On the basis of the film, TiO is then treated with titanate, silane and other organic surface modifiers.2/SiO2or Al2O3The surface of the composite particles was modified by organic coating.

(3) Physical coating/chemical coating composite modification process

The process of surface organic chemical modification after physical coating of particles, such as metal coating or film coating.

 

 

 

 

















Process, modification, surface, modifier, composite, dry, proceed, wet, particle

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