Plastic Extruder Tips 10: Color Masterbatch Formulation Research

Color Masterbatch Formulation Research

Posted by Andy

When you get an order from your customer for a new color masterbatch, if you have no experience, you need to research the approx. formulation first. So actually, the most important thing is you have a good color blending engineer.

Now we example as PE-based red color masterbatch:

Before we start the formulation, we should know the application of color masterbatch, like injection machine using or blowing machine using. Because of that the requirement of pigment dispersibility and moisture, blowing machine > injection machine, especial for high pigment filling masterbatch. 

As we know, the color masterbatch is made by Carrier(PE) + Pigment (red color) + Additives (dispersant, lubricant, anti-UV etc.) + Filler material (sometimes). So the most important thing is confirming the color matching and how many percents of pigment we will use.


Masterbatch production can choose the corresponding carrier according to the customer’s needs and application fields. The carrier material must be strictly guaranteed to have sufficient blending properties with the plastic material to be colored. Moreover, it is most reasonable that the carrier needs to be 30 degrees or lower than the heated melting point of the raw material. If the carrier does not blend with the plastic, the plastic will be peeled off after the coloring process is formed, or the performance of the product will be degraded. However, the carrier is too good and the melting point is too high, which will cause the product to have streaks, color mixing, and other adverse reactions that affect the appearance of the product, which are unqualified carriers.

2.Color matching:

Red, blue, yellow is the three primary color, and other colors can synthesize through these three colors.

  • Big red = red + yellow
  • Orange = red + yellow
  • Almond = red + yellow
  • Purple = red + blue
  • Rose = red + blue
  • Green = blue + yellow
  • Lake Blue = blue + yellow
  • Light green = blue + yellow
  • Grass green = yellow + blue
  • Emerald= yellow + blue
  • Brown = orange + purple
  • Olive = green + orange
  • Light brown = yellow + blue + red
  • Dark brown = yellow + blue + red
  • Beige = red + yellow + black
  • Gray = green + purple
  • Gray-green = gray + olive
  • Black = gray-green + dark brown

Normally it will add some TiO2 during the color matching. The more TiO2 is added, the lighter the color; the less added, the darker the color.

3.Percentage of Pigment:

When you confirmed the color number is the same as the requirement of the product, we also need to confirm the percentage of pigment you will add to make the color masterbatch. This need to confirm the color masterbatch addition ratio during making the product.

The basis of determining the proportion of color masterbatch is to obtain satisfactory coloring effect. As long as the product has a uniform color and no stripes and spots, it can be recognized. The usage ratio of masterbatch can be selected as follows: 1:100, unless the mixing of equipment is very good, it is easy to appear the phenomenon of uneven pigment dispersion, generally do not recommend customers to use this ratio. However, due to price pressures, some customers especially want to use this proportion of masterbatches, for the sake of customers, but also more to produce such a low proportion of concentrated masterbatches, and pigment dispersion can generally meet the requirements. 1:50 for coloring requirements of general plastic products, PE, PP Color Masterbatch more use this ratio. 1:33–1:25 is used for coloring demanding PO products, low coloring requirements or general ABS products. 1:20 for advanced plastic products, including PO, ABS, can be widely used in injection molding, blow molding, spinning and other processes. More than 1:20 is generally used for the coloring of high-grade cosmetic containers, and is mainly used for small injection molding machines.

If the color is right, but the color of the product is lighter than the sample, it indicates that the amount of pigment in the product is low. We need to add more ratio color masterbatch or producing more ratio color masterbatch.

For example, we decide to use 1:25 ratio color masterbatch to make the product. First, we need the engineer to confirm the approx ratio of pigment(formulation) we use and record it. Second, using small twin screw extruder(like our KTE-20) testing to make the color masterbatch. Third, using the color masterbatch to make the product and comparing the color with the sample. If it’s lighter than the sample, we need to add more pigment; otherwise, decrease the pigment ratio.

We can use the golden section method to find the best ratio. Such as, we confirmed that the best ratio of pigment is between 10% to 20%, according to the gold principle, the first time we can test with ratio 13.82%, the second time with 16.18%. Then testing again to find the best ratio.

The most important thing during producing color masterbatch is color matching, then the ratio of pigment confirming. The more experienced engineer, the fewer times the color adjusting, and the product requirements may be achieved two or three times. However, the first time production, the color will still change, so the production inspection adjustment is essential.

4.Extruder Clean

After the production of one color masterbatch, the cleaning work is also very important. For example, if you produce dark blue, then making red, or white, you must clean the machine so that it does not affect the color of the next color.

According to our experience, the energy-saving cleaning machine method is to mix 5 kg(according to the extruder size) of PE resin with calcium carbonate to the machine, let the color go down, and then use 2 kg of the high filling rate calcium carbonate masterbatch(80%-90%) to pass the machine. After that, take out the screw and clean it with a brush. The calcium carbonate does not stick to the screw, it is dropped with a light brush, and the screw can be quickly cleaned up. Calcium carbonate is also very cheap. 

The high-speed mixer cleaning method is also very simple, that is, first remove the inner blade and clean it with steel ball with calcium carbonate, then clean the mixing bucket with calcium carbonate powder, then assemble it, then pour a packet of clean calcium carbonate powder into it. , stir for 5 minutes and let it out.

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