Colorants are mainly divided into two types: pigments and dyes. Pigments are colorants that cannot be dissolved in ordinary solvents, so to obtain ideal coloring properties, it is necessary to use mechanical methods to evenly disperse the pigments in the plastic. Dyes are organic compounds that can be used in most solvents and dyed plastics. Their advantages are low density, high coloring power, and good transparency, but their general molecular structure is small and they are prone to migration during coloring.

Today, let's take a look at the advantages and disadvantages of 4 plastic colorants so that you can better choose and use different colorants during production.

There are four types of plastic colorants according to their physical form:

• Powdered colorant - color powder;
• Solid colorant - masterbatch;
• Paste colorant - color paste;
• Liquid colorant - color oil;

In the coloring of the plastic industry, color powder and masterbatch are relatively widely used.

Color Powder Coloring

The method of directly using color powder (pigment or dye) to add an appropriate amount of powdered additives to color plastic particles is also called dry coloring.

Advantages

1. Good dispersibility;

2. Suitable for small batch plastic processing;

3. Low cost, saving the consumption of manpower and material resources in the processing of masterbatch, color paste, etc.

Disadvantages

1. Flying dust pollution, pigments will fly during transportation, storage, weighing, and mixing, causing pollution, seriously affecting the working environment;

2. The hopper of the extruder is not easy to clean, and the color powder used for coloring adheres to the inner wall of the barrel (even on the screw) under the action of wetting agents such as white oil. When it is necessary to change the material, cleaning the barrel becomes a problem for the on-site operator;

3. It is not practical for blown film and spinning products. The use of color powder for coloring, because the pigment powder is evenly distributed in the resin to be colored, has better dispersibility. This conclusion can only be applied to injection molding products, especially thick-walled products, and it is another matter for blown film and spinning products. Because the color powder is generally not pre-treated, when it is mixed with the resin, it is completely impossible to ensure that the molecules of the pigment powder and the pigment molecules to be colored can be well combined with each other only by the distance from the extruder feed port, screw, to the discharge port and such a short plasticizing and mixing time, and there will be a "cold" phenomenon. However, this "cold" phenomenon will be covered up in thick-walled products, and it is obvious in blown film and spinning products. Therefore, the latter coloring method is still mainly based on masterbatch.

Masterbatch Coloring

Using a certain process and corresponding equipment, under the action of additives, the pigment (or dye) is mixed into the carrier, and through heating, plasticizing, stirring, and shearing, the molecules of the pigment powder and the molecules of the carrier resin are finally fully combined, and then made into particles of similar size to the resin particles.

Advantages

1. Improves the environmental pollution caused by flying toner;

2. Easy to change color during use, no need to clean the extruder hopper specially;

3. Strong targeting, simple color matching, easy quantitative;

4. Compared with batch resin dry dyeing and granulation before plastic parts, the use of masterbatch can reduce the aging of resin performance caused by secondary processing of plastic products, which is beneficial to the improvement of the service life of plastic products;

5. During the processing, the pigment is fully mixed and completely combined with the carrier resin under the action of the additive. When in use, it is placed in the resin to be processed in a certain proportion, and the compatibility is significantly better than that of toner coloring.

Disadvantages

1. Poor dispersibility. Due to the small amount of addition, the processing time of plastic products is short. Due to the limitation of the aspect ratio of the extruder screw, the dispersion of masterbatch is often not as good as that of color powder;

2. The cost is high. There is one more manufacturing process, and the dyeing cost is higher than that of color powder;

3. The performance requirements of masterbatch are high. When the performance of the carrier in the masterbatch is different from that of the resin to be colored, undispersed spots, color spots, and patterns often appear on the surface of plastic products. Therefore, the use of masterbatch is limited by its compatibility and dispersibility. Color paste coloring