3. Blackness of carbon black


The blackness of carbon black is a very important topic in the study of dispersants, and it is also the most frequently discussed topic.


So far, the practice shows that the detection of the instrument is not as accurate as the visual inspection; the blackness changes under different light; the blackness also changes under different angles; different dispersants will choose different carbon black to give different blackness; the carbon black mother with high blackness will not necessarily improve the coloring power.


It's all easy to explain. Because carbon black's transparent sheet structure + carbon black's ability to absorb light. The size and orientation of the transparent sheet structure under the particle size of less than 1 μ m will inevitably lead to the transmission, reflection, refraction and scattering of light. And the derived color light will be conditionally absorbed by carbon black, and the other part will continue its journey. This is a complex and variable superposition effect. Therefore, 100% of the black is not, that is, there is no darkest, only darker than the back. Although understandable, control is extremely difficult.






4. Titanium dioxide


At first, everyone thought that titanium dioxide was so easy to disperse that it could be used without dispersant.


However, when mixed with other hard to disperse pigments, titanium white will participate in floating color;


In the preparation of high-level pure white, there will be fog shadow in titanium white;


In the products with special requirements, titanium white needs excellent covering and whiteness, and it is not allowed to turn yellow at high temperature; many ordinary industrial occasions are not willing to use expensive high-grade titanium white, or even use titanium white as a substitute pigment; the above problems have aroused the attention of the auxiliary industry to titanium white dispersion.


According to its surface structure and treatment, it has been tested that the dispersed titanium white can be used as follows:


- traditional wetting and dispersing agents, including organic carboxylic acid with acid value AV, ammonia value AMV, amine salt with phosphoric acid and wetting and dispersing agent with controlled flocculation for its floating color


- organophosphate


- special PU high dispersant


- special vinyl polymer type titanium white dispersant


- widely effective polymer surfactants in water properties


Among them, wetting dispersant is a general choice. It has a wide range of adaptability to the system, but it can not adapt to special requirements.


Organic phosphates are often recommended to prepare high-grade pure white to remove haze, while high-quality dispersants consider the ability to control floating color and whiteness. The new technology of dispersant in the water-based system helps the factory's self-made reference white to accept the commercial color masterbatch. Therefore, it is common sense to use dispersants in titanium dioxide.






5. Transparent iron oxide


The particle size of transparent iron oxide is at nanometer level, and its surface is amphoteric. It seems easy to disperse when the pigment concentration is low, and the viscosity of color paste is very low, but the transparency is not easy to get the best. Once the pigment concentration slightly exceeds the critical concentration, the color paste immediately thickens to the point where it cannot be stirred, resulting in the efficiency of sand mill.


The transparency of iron oxide, some like the blackness of carbon black, always seems to be able to improve its transparency. Our experimental results show that a sample that we have considered to be transparent may still have heavy fog shadow when observed at 45 °;


So, what's the best way to use it? This question is another uncertainty.


In addition to the selectivity caused by different resin systems, more than one scheme is recommended.


For example, the method of using phosphate ester, the method of using highly dispersing agent with acid end group wetting agent, and the independently designed highly dispersing agent, etc. They show adaptability to the same transparent iron oxide pigment in different systems.


Source: core chemistry