Guilin Hongkaolin vertical mill

Guilin Hongcheng grinding equipment manufacturers learned that calcined kaolin grinding products are mainly used in the coating industry, which is used as a filler in the paint, on the one hand plays the role of physical filling, on the other hand has a certain dry covering force. So, what are the index requirements of calcined kaolin grinding products?

The product indexes of calcined kaolin for coating mainly include whiteness, particle size, covering force, dispersion, 325 mesh sieve residue, oil absorption value, deposition volume, pH value, weather resistance and so on:

1.White degree

whiteness is the primary index of calcined kaolin, the higher the better. The color paint is also made with white paint as the base paint and the color mother.whiteness should be at least greater than 90%, some manufacturers even require greater than 93%. White degree stability is very important, if the fluctuation is too large to affect the optical performance of the coating, resulting in the color difference of different batches of products under the same formula.

2.Granularity

Particle size is actually an index of representation, coating manufacturers rarely directly to detect the particle size. However, because other indicators of calcined kaolin are directly related to the particle size, if the particle size is not fine enough, or unqualified, it will be reflected through other indicators. For the calcined kaolin manufacturer, the inspection index of the finished product should be-2 μ m at about 80%. Of course, the performance of the products produced by different raw materials will be different, and if the other indicators are qualified, the particle size requirements can also be reduced.

The particle size is mainly affected by the wear of raw ore and the temperature of calcination. The wear ability is determined by the quality of raw ore, which mainly affects the particle size of the raw material stage, and the calcination temperature mainly affects the particle size of the powder after the kiln. For coating calcination kaolin, medium temperature calcination (1000~1200℃), the optimal calcination temperature is selected in the amorphous phase just changed into silicon aluminum spinel phase, which produces porous expansion structure, resulting in pore development, and the abrasion value of the product is relatively low.

3.Cover force

Covering power is the most important index of calcined kaolin. The finer the powder, the more interface formed in the coating, the stronger the refraction and reflection of the light, especially when the particle size is equal to the wavelength of visible light, has the strongest scattering effect, can produce the largest covering force, when less than this value, the covering force will become smaller because of the diffraction of the light.

For too fine kaolin, whether it can be fully dispersed in the coating is also an important factor affecting its covering power. Although calcination improves the covering power of kaolin in water-based coating, it is not significant. In some cases, it is easy to sintering and form coarse particles, but makes the covering force decrease, and it cannot be used for coating at all.Another problem is that calcination below 1000℃ sometimes produces a light red phase, which is very bad for white pigments.1050℃ and superfine powder.

4.Disperssiveness

The domestic coating industry said dispersion, and the concept is the same. Although the calcined kaolin has undergone ultrafine powder, with an average particle size of 1 μ m or less, in the paint, in the high viscosity parent liquor, the particles are not separate but grouped together. The ability of calcined kaolin to disperse in a coating system is called dispersion. The dispersion of calcined kaolin is good. If the grinding grade meets the final requirements, it can be dispersed within the coating system.

The dispersion of calcined kaolin is related to the final effect of grinding. If 45 μ m or larger particles are contained in the superfine processing process, it will not be dispersed in the coating system. The requirement for this index is less than 45 μ m, and the smaller, the better. If the dispersion of titanium dioxide can reach 25 μ m, corresponding to the grinding grade should be selected as 4 or more.

5.325 mesh sieve residue

325 mesh sieve residue is an important index, the requirement of coating to this index is <0.02%, and the smaller the better.325 mesh sieve is also mainly related to the final effect of grinding, requiring no 45 μ m or larger particles during ultrafine processing. Another influencing factor is impurities, mixed with impurities have the most obvious impact on the screening content of 325 mesh.

6.Oil absorption value

The oil absorption value of calcined kaolin is 50g / 100g~60g / 100g is moderate, the oil absorption amount is too high, the coating viscosity made with the same formula is large, in order to reduce the viscosity, the amount of paint base must increase the cost; the oil absorption value is too low, the coating made is easy to settle, and the opening performance is not good. The oil absorption value of kaolin is particle size distribution, porosity, specific surface area, and the grain type of particles. The particle size is small, the specific surface area is larger, and the oil absorption value is

7.Settlement volume

The oil absorption value of calcined kaolin is 50g / 100g~60g / 100g is moderate, the oil absorption amount is too high, the coating viscosity made with the same formula is large, in order to reduce the viscosity, the amount of paint base must increase the cost; the oil absorption value is too low, the coating made is easy to settle, and the opening performance is not good. The oil absorption value of kaolin is particle size distribution, porosity, specific surface area, and the grain type of particles. The particle size is small, the specific surface area is larger, and the oil absorption value is higher.

8.pH value

The pH value reflects the acid and alkalinity of calcined kaolin, and the pH value should be between 6 and 8, basically close to neutral. The PH of the calcined kaolin itself is neutral, so the PH modification is not required in the coating industry.

9.Weather resistance

After the pigment is made of paint and daub, the paint film through the sun and rain, will turn yellow, lose light and powder. The ability of pigments to resist these changes is called weather resistance. Calcined kaolin has no strong chemical activity on light, so it has good weather resistance.

10.Other indicators

ther index requirements for calcined kaolin, acid and alkali resistance, mixing performance, wet performance, density, etc., these are the common characteristics of all calcined kaolin, some are not digital indicators. It is worth paying attention to that, no matter which index of kaolin, the stability of the index is the most important, if the fluctuation is too big, it will bring bad influence to the paint users, affect the overall performance of the paint. As the production equipment of calcined kaolin mill products, it has an important influence on the whiteness, particle size and 325 mesh residue of calcinined kaolin mill products. Guilin Hongcheng grinding equipment can be ground kaolin to 80-2500 mesh for the production of coating, grinding equipment with high output, low energy consumption, consulting equipment price can contact the email:mkt@hcmilling.com