There are four types of plastic colorants according to their physical forms: powder colorants-toner; solid colorants-masterbatch; paste colorants-color paste; liquid colorants-color oil; In coloring of plastics industry, toners and color masterbatches are relatively widely used.

 

Method of coloring plastic particles directly with toner (pigment or dye) and adding an appropriate amount of powdery additives, also known as dry coloring.

1. Good dispersion;
2. Suitable for small batch plastic processing;
3. Cost is low, eliminating need for manpower and material resources in processing of color masterbatches and color pastes.

1. Fly dust pollution, pigments will fly during transportation, storage, weighing, mixing, causing pollution and seriously affecting working environment.
2. Hopper of extruder is not easy to clean. Toner used for coloring is attached to inner wall of barrel (or even on screw) under action of a wetting agent such as white oil. When material needs to be changed, cleaning barrel becomes a problem for on-site operators.
3. Blown film and spinning products are not practical. Toner is used for coloring. Because pigment powder is evenly distributed in resin to be colored, its dispersibility is better.

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

1. Improved environmental pollution caused by flying toner
2. It is easy to change color during use, so there is no need to clean hopper of extruder.
3. Strong pertinence, simple color matching, and easy quantification.
4. Compared with batch resin dry dyeing and granulation, use of color masterbatch can reduce resin performance aging caused by secondary processing of plastic products, which is conducive to improvement of service life of plastic products.
5. In process of processing, color masterbatch is fully mixed with carrier resin under action of additives. When in use, it is placed in resin to be processed in a certain proportion, compatibility is obviously better than that of toner coloring.

1. Dispersibility is poor. Due to small amount of addition, processing time of plastic products is short. Due to limitation of extruder screw length-to-diameter ratio, dispersion of color masterbatch is often not as good as that of toner.
2. Cost is high, one more manufacturing process, and dyeing cost is higher than toner coloring.
3. Performance requirements of color masterbatch are relatively high. When performance of carrier in color masterbatch is different from that of resin to be colored, undispersed spots, color spots and patterns often appear on the surface of plastic product. Therefore, use of color masterbatch is limited due to its compatibility and dispersibility.

Color paste is a semi-finished product made of pigments and fillers dispersed in paint. According to purpose of classification, it can be divided into paint color paste, tape color paste, paper color paste, textile color paste, mechanical color paste, toy color paste, latex product color paste, etc.

1. It is easy to use and can be directly used in processing technology for forming and coloring of plates;
2. Generally, it has good high temperature resistance, convenient storage and no precipitation;
3. It can reduce dust pollution problem in use of toner, can also solve lack of compatibility and dispersibility of masterbatch;
4. Color paste is easy to control amount of input in use, reduce color difference, improve coloring power and color brightness.
5. Environmental protection type meets requirements of EU REACH and other regulations.

1. At present, the biggest restriction on development of color pastes is production process of domestic color pastes. High-quality color pastes have higher requirements for process and raw material quality, their cost will be higher than that of color masterbatches and toners.
2. Screw may slip when added amount is large;
3. When stored for a long time, precipitation will occur, it is better to stir before use.

Color oil is a liquid pigment concentrate without resin carrier. At present, color oil is mainly used in preforms in my country.

1. Low addition ratio, usually 0.1~0.5% for transparent series, 0.3~3.0% for pearlescent/solid color series.
2. Excellent dispersion, color is more uniform, color is more brilliant, product has a higher gloss; color is stable, and coloring defect is reduced.
3. Material passes through a high temperature process only once, physical properties of raw material resin are kept unaffected.
4. The best inventory management, only a small space is needed to complete storage of color oil. Compared with color masterbatch, it saves three-quarters of storage space. Reduce overall inventory and working capital pressure.
5. Color oil adding equipment is simple, cost is low, color changing process is simple and fast, which improves freedom of production scheduling and saves personnel time, machinery and energy consumption;
6. Suitable for all polyolefins (such as PP/PE), polystyrene resin (PS), PET resin and other engineering resins.

1. Do not add antistatic agents to color oil, which will cause product to be dust-proof on shelf or in storage;
2. Shelf life of color oil products is shorter than that of color masterbatch products;
3. Color oil needs special color oil adding equipment, that is, color oil metering pump can supply color oil to injection molding machine to produce products of desired color.