Color Part I

Color in plastics is achieved in numerous ways but the mixing in or compounding of the color in the material is key along with using the right ingredients. This series hopes to look at color from the processing point of view.  In this part let’s discuss terms and or definitions.

Pre-color:
The material has the color already in it when you the processor receive it.
The basic steps are that the material is manufactured and than sent to a color house, compounder, or some other source. Pigments are than added and the material is mixed, run through an extrusion process, re-pelletized and we now have pellets that have the hopeful color we desire. In most but now all cases we can now process the material in our own way, and the results are good. Due to the amount of handling and volume minimums the price is usually higher then what people like. From an inventory standpoint I now have one material in color and if multiple colors I have the same material in many colors.

Natural Plus:
What is meant here is that we will blend at the machine. Basically taking natural materials and than adding color concentrates of one form or another at the press. We than depend on the machine, screw and barrel combination to mix to a uniform color.  In most cases we have no problems, (discussion later). From the inventory stand point I now have one material, and smaller quantities of color concentrates of one form or another.
 
Concentrates:
What is meant here is that we have a concentrated material usually pigments carried by a carrier, that when heated will soften or melt and disperse though out the materials it is being mixed with. Understand that there is a carrier, and pigments. Though concentrates are manufactured for one basic resin type there are some that may be used in multiple resins. One factor of concentrates is what is the pigment loading is in the concentrate. This then results in what let down ratio is necessary to achieve the desired effect in our plastic.

Carrier:
The carrier is the material used to hold together the pigments. If it is a critical color and or material the carrier may be the same material as you are molding thus achieving the compatibility for the color system and resin. They could be general-purpose wax types, or a high flow base grade, so it melts or softens first, ensuring the mix of the pigment. The compatibility of the carrier with the resin trying to be colored is very important.

To be continued:
Thanks for the time

Steven L Silvey
Sr. Technical Service
General Polymers Division
Ashland Distribution