The dry powder coloring method is to directly add the powder colorant together with the small material into the rubber, and mix it on an open mill. The advantages of this method are simple operation and low cost, but the dust is large during mixing, which pollutes the environment, and is not easy to disperse uniformly, and has color difference. It is less used now. For ease of use, powdered colorants can be made into pre-dispersed colorants together with stearic acid, sulfate, etc., which have been sold in the market.

The method of color paste coloring is to first mix the colorant with the liquid compounding agent (such as plasticizer), grind it with a three-roller machine to make a paste or slurry, and then add it to the rubber in a certain proportion for mixing. This method can avoid dust flying, and is also conducive to the dispersion of colorants in the rubber, and the color is uniform. However, the content of colorant in the color paste is low, the coloring is not high, the transportation volume is large, the loss is large, and the user is inconvenient to use.

There are two main methods for preparing pellet colorant pellets. The first method is the same as other powdery compounding agent granulation methods. First, the powdery colorant is infiltrated with surfactant, and then granulated after being melted with wax or melted with resin; the second method is to use the colorant with After soaking with surfactant, the colorant particles are refined by mechanical force to make a dispersion of a certain concentration, which is then mixed with latex for co-precipitation, and rolled into granules after drying. Among them, the surfactants are mostly anionic and non-ionic, such as fatty acid salts, sulfonates, etc. The latex is usually natural latex.

The granular colorant is easy to use, has good dispersibility, has no dust flying, does not pollute the environment, has bright color, uniform hair color and no color difference, and is a promising coloring method. However, the preparation process of granular colorant is complicated and the cost is high, which limits its wide application.