Solving the difficulty in color spreading in powder mixing

Depending on various final products, many customers need to add pigment color into their powder formula. However, the pigment color is very little percentage around 0.5-1% compared with total ingredients. For example, color cement, essence and pharma are most common product which needs to add different colors in their formula. Because adding percentage is very little and some basic powders are not easy to be coated by colors, it needs high requirement and something special treatment to powder mixers. Recently, we have one essence manufacturer came to our laboratory to do the test for their new formula which needs to add colors in their basic product.

In May 2016, an essence manufacturer from Thailand sent inquiry to us and explained their problems in their existing mixer. They are partner with Firmenich and Rhodia company. In their factory, they are using vertical mixer with paddle agitator but they think the mixing time is longer and homogeneity is not ideal. Our engineer director though it is better to do the test in our laboratory to use our ploughshare mixer and vertical ribbon mixer.

Finally, the customer delivered two batches of their product to our factory in the beginning of June and then their product manager Mr. Pakorn flied to Shanghai to witness the mixing result. We did test first in vertical ribbon mixer. The basic powder ingredients are put into mixer and put color into it at last but we found that the color can not be fully spread and coated on white basic powder even if we run the mixer for 40 mins. Then, we used ploughshare mixer to do the same test. The result was much better than vertical ribbon mixer but Mr. Pakorn think the mixing time is a little longer. Furthermore, it is not very clean to discharge.

Through our analysis and discussion with customer, we provided some suggestion and improvement in our lab mixer. We want to make following improvement in our lab mixer and would like to do the second test.

Improvement for Vertical Ribbon Mixer:
1. Considering the color percentage is very little, we think if we increase the shaft speed and chopper speed, the mixing movement will be more violent and color will be better to be coated and spread throughout the basic white powder.
2. Because the chopper position is at the bottom part of vessel, there are some materials can not touch with chopper and those materials would be not totally mixed. That lead to color can not touch with all white powder. Our engineer decided to increase the size of chopper blade and baffle plate in order to let basic white powder totally touch with chopper and color will be coated on white powder.
3. For vertical shape mixer, gap between agitator and vessel is very important. So, it needs high precision to keep minimum gap between agitator and vessel.

Improvement for Ploughshare Mixer:
1. Our existing ploughshare mixer is already high speed, it is not necessary to do anything for shaft speed. However, we also increase the size of chopper to make better spreading for color into basic white powder.
2. We also adjusted the gap between plough shovel and vessel.

After finish above improvement for our mixers, we let customer to deliver another two batches of their product and ready for the second test. This time, we did the same procedure as last time. Looking from mixed product, the mixing result is much better than last time. Mr. Pakorn took samples from each mixer and tested the mixing homogeneity. After two weeks, we got good news and they were satisfied with our mixing result. Both two mixers are ok for mixing their product. However, the mixing time of ploughshare mixer was 20 mins and 30 mins for vertical ribbon mixer. The customer prefer vertical ribbon mixer because it is clean to discharge and simple mixing structure. Now, they are discussing our proposal internally and will make final decision at the beginning of September.