Masterbatch is a concentrated mixture of pigments and/or additives encapsulated during a heat process into a carrier resin which is then cooled and cut into a granular shape. Masterbatch allows the processor to colour raw polymer economically during the plastics manufacturing process.The polymers
There are two polymer resins to be considered:Carrier Resin
The resin in which the pigments and/or additives are carried and which forms the masterbatch.Dilution Resin
This is the polymer or polymers which make up the bulk of the plastic processor's finished product.The Colourants
There are three main types of colourant:Inorganic Pigments
This type of pigment is manufactured from natural raw materials and includes fundamental types such as titanium dioxide, iron oxides and ultramarine blue. However many are not suitable for some applications such as packaging due to their toxicity. Pigments in this category include lead chromium and cadmium.Organic Pigments
Organic pigment systems are synthesised and tend to have lower heat stability than inorganics. One of the big advantages of this type of pigment system is that they are normally non-toxic and conform to legislation relating to food contact and safety.Dyestuffs
These are man-made soluble dyes, which are used extensively in fibre colouring, for example. Their general use is limited due to their incompatibility with polyolefins, but they can be very effective in styrenics and engineering polymers. Dyestuffs have good colouring strength, but can be expensive.The additives
Different types include:Performance Additives:
To enhance the performance of the end product.Processing Additives:
To aid the efficiency of manufacture.
Using masterbatches allows the processor to maximize their purchasing power by buying larger amounts of natural polymer. That advantage, plus lower obsolescence costs invested in end of life colors as products change give masterbatches a great economic benefit over other modes of color delivery.
Processors can also take advantage of masterbatch cost incentives, but avoid difficulties associated with monitoring proper metering by using a cube blend.
A masterbatch is pre-dispersed concentrated color that is let down with natural polymer during molding. With a precolor all the polymer is entirely compounded with the proper amount of color and delivered ready-to-use, eliminating metering and dispersion difficulties. A masterbatch offers economic advantages associated with resin purchasing and color obsolescence. Additionally, since masterbatches are not fully compounded most of the polymer used does not exhibit an additional heat history, potentially deteriorating the properties of some polymers.
Masterbatches were greatly popular only in the late 1970’s and early 1980’s. Prior to that and even today the unorganized sector still uses dry pigments and blends the polymer, additive and pigment matrix in a tumble blender and then proceeds for processing. Here there is a problem of inconsistent dispersion of the pigment and article to article color shade variation. On the other hand when a Masterbatch is used, these problems aren’t faced. Plenty of time is saved.
For almost every known polymer! It is better to use resin specific masterbatches for engineering plastics in order to be able to retain the physical properties. For most polyolefins, a LDPE or LLDPE based Masterbatch is ok. Similarly for styrenes like GPPS and HIPS, a GPPS based Masterbatch is suitable.
It is mostly made from TiO2 (titanium dioxide) which is either rutile or anatase. TiO2 is the best whitener available however there are cheaper alternatives like barium sulphate, lithopone and calcium carbonate which can be used either directly or in combination with TiO2 to make a cheaper white Masterbatch. Maximum loading of TiO2 gives the best opacity results as TiO2 has the highest coloring power amongst other whiteners. Best loadings known in the industry are a Masterbatch with 75 – 80% pure TiO2 (for PE carrier). For Engineering plastics, it is better to have lesser loadings of TiO2 in the carrier resin.
Black Masterbatch is made with carbon black pigment. Here too several grades of carbon are available for the type of application for which the Black Masterbatch is prepared. Maximum loading possible of carbon in a PE carrier is 50%. For engineering plastics it is difficult to load beyond 30%.
Colour Masterbatches are made in several forms depending on the aesthetic required for the type of plastic it is being made for. These are the possibilities – opaque, transparent, translucent, special effects, etc. Color masterbatches uses TiO2, Organic Pigments, Inorganic Pigments, Dyes, Additives, etc depending on the application and the resin which they are designed for.
Additive Masterbatches can be of several types namely -
Filler Masterbatches are usually a combination of Talc / CaCO3 and PE resin (LLDPE or LDPE). These can also be made in PP resin. Filler masterbatches provide cost reduction and also depending on the design of the type of filler Masterbatch, offer better properties such as stiffness, anti-fibrilation, etc.