Color powder, color masterbatch, color paste, color oil - the advantages and disadvantages of different coloring methods of plastics

Types of plastic colorants

The types of plastic colorants are divided into four types according to their physical form:

powdered colorants – pigments;

Solid colorants – masterbatches;

paste colorant – color paste;

liquid colorants – colored oils;

In the coloring of the plastic industry, pigments and masterbatches are used relatively extensively.

 

1. Color powder coloring

The method of directly adding an appropriate amount of powder additives to color plastic particles with color powder (pigment or dye), also known as dry coloring.

 

Advantage:

1. Good dispersion;

2. Suitable for small batch plastic processing;

3. The cost is low, which saves the consumption of manpower and material resources in the processing of color masterbatch and color paste.

 

Shortcoming:

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

2. The hopper of the injection molding machine or extruder is not easy to clean, and the toner used for coloring is attached to the inner wall of the barrel (even on the screw) under the action of a wetting agent such as white oil. When refueling is required, cleaning the barrel becomes a difficult problem for field operators;

3. Blown film and spinning products are not practical, use toner for coloring, because the pigment powder is evenly distributed in the resin to be colored, so its dispersibility is better. This conclusion can only be used for injection molding products, especially thick-walled products, but it is another matter for blown film and spinning products. Because the toner is generally not pretreated, after it is mixed with the resin, only relying on such a distance from the feed port of the extruder, the screw, to the discharge port and such a short plasticizing and mixing time, It is completely impossible to ensure that the molecules of the pigment powder are fully combined with the pigment molecules to be colored.There will be "sandwich" phenomenon. However, this "sandwich" phenomenon will be covered up in thick-walled products, and it is obvious in blown film and spinning products. Therefore, the coloring method of the latter is still dominated by color masterbatch.

 

2. Masterbatch coloring

Using a certain process and corresponding equipment, under the action of additives,

Mix the pigment (or dye) into the carrier, and through heating, plasticizing, stirring, and shearing, the molecules of the pigment powder are finally fully combined with the molecules of the carrier resin, and then made into particles similar in size to the resin particles.

 

 

Advantage:

1. Improve the environmental pollution caused by flying toner;

2. It is easy to change the color during use, and there is no need for special cleaning of the hopper of the injection molding machine or extruder;

3. Strong pertinence, simple color matching and easy quantification;

4. Compared with making plastic parts after dry dyeing and granulation of batches of resin, the use of color masterbatch can reduce the aging of resin properties caused by secondary processing of plastic products, which is conducive to improving the service life of plastic products;

5. In the process of processing, under the action of additives, the color masterbatch is fully mixed with the carrier resin. When in use, it is placed in the resin to be processed in a certain proportion, and the compatibility is obviously better than that of toner coloring.

 

Shortcoming:

1. The dispersibility is poor. Due to the small amount of addition, the processing time of plastic products is short, and the dispersibility of the color masterbatch is often not as good as that of the toner due to the limitation of the length-to-diameter ratio of the extruder screw;

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

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

 

 

3. Color paste coloring

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

 

Advantage:

1. It is easy to use and can be directly put into the processing technology for forming and coloring of plates;

2. Generally, good high temperature resistance, convenient storage, no precipitation;

3. It can reduce the problem of dust pollution in the use of toner, and can also solve the lack of compatibility and dispersibility of masterbatches;

4. It is easy to control the input amount of color paste during use, reduce color difference, improve tinting strength and color brightness;

5. Environmentally friendly, in line with EU REACH and other regulations.

 

Shortcoming:

1. At present, the biggest restriction on the development of color paste is the production process of domestic color paste. High-quality color paste has higher requirements on the process and raw material quality, and its cost will be higher than that of color masterbatch and toner;

2. When adding a large amount, the screw may slip;

3. When stored for a long time, precipitation will occur, it is better to stir before use.

 

4. Color oil coloring

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

 

Advantage:

1. Low addition ratio, usually 0.1-0.5% for transparent series, 0.3-3.0% for pearlescent/solid color series;

2. Excellent dispersibility, more uniform color, brighter color, higher gloss of the product; stable color, reducing coloring defects;

3. The material only goes through a high-temperature process once, keeping the physical properties of the raw material resin unaffected;

4. The best inventory management, only need a small space to complete the storage of color oil. Compared with color masterbatch, it saves three quarters of the storage space. Reduced pressure on overall inventory and working capital;

5. The color oil adding equipment is simple, the cost is low, and the color changing process is simple and fast, which improves the freedom of production scheduling and saves man-hours, machine and energy consumption;

6. Applicable to all polyolefins (such as PP/PE), polystyrene resin (PS), PET resin and other engineering resins.

 

Shortcoming:

1. Antistatic agents cannot be added to color oils, resulting in products that cannot be dust-proof on shelves or in storage;

2. The shelf life of color oil products is shorter than that of color masterbatch products;

3. The color oil needs special color oil adding equipment, that is, the color oil metering pump to supply the color oil to the injection molding machine to produce the desired color product.

Haisi Extrusion supply twin screw extruder for color masterbatch making.

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