As we all know, the use of
titanium dioxide is very wide, its application range covers coatings, plastics, paper, ink, cosmetics, rubber and other fields, due to the application conditions in the field and the purpose of the use of titanium dioxide users are different, so different titanium dioxide manufacturers according to their own characteristics and market positioning to determine the different production process to meet the needs of different customer groups. This also leads to the difference in the application performance of different manufacturers or different brands of titanium dioxide.
Even if each
titanium dioxide manufacturer claims that a certain brand product is fully applicable to a certain type of coating production, but due to the process technology, production equipment, management level and other reasons of titanium dioxide manufacturers, there will still be differences in the scope of application and coating quality.
These differences are mainly manifested in the dispersion of titanium self-powder in the application system. This problem is an extremely important problem that needs to be solved first for every titanium dioxide manufacturer and coating manufacturer.
Therefore, in terms of the production and application process of
titanium dioxide, the dispersibility is often an extremely important indicator to evaluate the quality of the brand product, especially for rutile titanium dioxide.
A.The basic principle of titanium dioxide dispersion in aqueous phase
We can divide the grinding and dispersion process of
titanium dioxide into three steps that affect and restrict each other :
a)Wetting
b)Separation
c) Stabilization
In the actual process of grinding dispersion, these three steps are not gradual, but a link, complementary and mutually restrictive, that is, if one of the three can not achieve the purpose will make the grinding efficiency decline and even the product can not reach the required level, or return coarse.
The pigment dispersion stabilization mechanism has the following types:
a)Electric double layer stability theory;
b)Spatial stability theory;
c)Vacancy stability theory;
d)the above various stability mechanism of mutual composite.
The stability mechanism of electric double layer widely exists in various application systems. It is the most classical and reliable theoretical basis, and has very good applicability for pure water phase systems. The space stability theory and vacancy stability theory are involved in the role of polymers, so it is relatively more complex, but in the rutile titanium dioxide organic treatment, how to choose the appropriate organic treatment agent, how to control the appropriate amount of addition, it has a good guiding significance.
B.Main factors affecting the dispersion of rutile titanium dioxide in aqueous system
According to the above basic principles, combined with the production and preparation process of titanium dioxide and process control elements, after a large number of analysis and tests, we found that the control of the following indicators will have an important impact on the dispersion of rutile titanium dioxide in the aqueous system:
a)Salt content (electrical resistivity)
High salt content will not only have a bad effect on the dispersion of the aqueous system, but also on the dispersion of the oil system, just because the dominant principle of the dispersion of titanium dioxide in the oil and water two phases is not the same, the influence on the oil phase dispersion is usually relatively small.
b)The PH of the system
Although the PH value of titanium dioxide in the application system is not determined by the
titanium dioxide manufacturer, it is still necessary to fully understand the impact of this index.
Because the PH value itself in the preparation process of titanium dioxide is relatively large, understanding the impact of this index on the dispersion is conducive to controlling the PH value of titanium dioxide in a more effective range, and as far as possible to improve the dispersion performance of titanium dioxide in the aqueous system.
After practice, we found that in the aqueous phase system close to the ideal state, the PH value of the system will also become an important factor affecting the dispersion of rutile titanium dioxide, and the main mechanism of its influence is analyzed and we believe that it may be attributed to the reason of the double electric layer. Data show that different types of titanium dioxide due to their differences in surface properties, the so-called isoelectric point is very different.
c)Surface properties of titanium dioxideAs a titanium dioxide manufacturer, according to different product positioning and customer needs to adjust the surface properties of titanium dioxide is a very effective and very simple way. This adjustment can be achieved by means of inorganic envelopes, by means of organic treatments, or by a combination of both.
d)Particle characteristics of the product
When it comes to the dispersion of products, whether it is
rutile titanium dioxide, anatase titanium dioxide or kaolin, light calcium and other products, the glute characteristics are an important aspect of the product dispersion. For titanium dioxide, the more the shape of the particles tend to be spherical and the more concentrated the distribution, and the particle size is moderate, the better the dispersion performance of the product, especially the shape and distribution of the particles have a more obvious influence on the dispersion performance.
Poor shape and scattered distribution usually due to the boundary effect offset the effect of the electrical phase bed, which directly leads to the lower peak of the product dispersion. Therefore, whether it is the dispersion of the water phase or the oil phase, all the effects of the particle characteristics of the product need to be marked.
