We are using plastic bags all the time and anywhere, shopping in supermarkets, buying vegetables, packing, loading garbage and so on. It is very practical and indispensable for human life. The bright color of plastic is more impact on people's vision. In order to make the plastic packaging products rich in color, colorants should be used in the production of plastic packaging.
Coloring agent is mainly divided into two kinds of pigment and dye. Pigment is a very fine granular colored pigment, which is insoluble in water and resin coloring agent, so it is necessary to obtain the ideal coloring property. It is necessary to disperse the pigment evenly in the resin or oil by mechanical method, and the color of the plastic products can be obtained. According to the structure, it can be divided into organic and inorganic pigments. Inorganic pigments (such as iron oxide pigments) have high thermal stability, good photostability and low price, but their coloring force is relatively poor and relative density is large; organic pigments have high coloring power, bright color, complete chromatography, and small relative density, which are not as good as inorganic pigments in heat resistance, weatherability and covering power. Dye is an organic compound soluble in water and most solvents and dyed plastics. It can make the dyed objects coloured inside and outside. The advantages are small density, high coloring power and good transparency, but its general molecular structure is small, and it is easy to migrate when coloring.
