OUR TECHNOLOGY


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POLYBLEND
MASTERBATCH:
Masterbatch is a concentrate generally consisting of a thermoplastic resin with a high loading of pigments and/or other special additives. The resin in the Masterbatch is selected to give optimum wetting and dispersion of the pigment as well as to ensure complete compatibility with the resin to be coloured.
In order to incorporate high pigment loading, specially designed extruder machines are required.

PROPERTIES OF MASTERBATCH MANUFACTURING MACHINES:
The requirement for producing good Masterbatch must be able to perform the process of:
Wetting – Separation – Distribution, which are essential for good dispersion.
a) It must achieve excellent longitudinal and transverse mixing in order to wet and distribute the pigment and additive particles homogeneously.
b) It must generate sufficiently high shearing stresses in the material to make separation of the agglomerates possible.
Hence further requirements are:
a) It must provide for intensive heat exchange for cooling the product so that the energy introduced into the material by shearing does not cause the product to become overheated and its viscosity simultaneously reduced.
b) The energy input must be effected sparingly and at a uniform rate so that the pigments and additives, which are sensitive to temperatures, are not damaged.
The required equipment must have facilities for degassing the melt to remove volatiles which hinder wetting of the pigments and additives.
The required equipment must be easy to clean so that it is out of action for short periods only, for example when changing colours

TWIN SCREW EXTRUDER

KNEADER

PROPER SELECTION OF PIGMENTS & ADDITIVES

THE BLUE WOOL SCALE

The Masterbatch, in general, contains two types of pigments: organic and inorganic.

The organic pigments have good colour strength and high brilliance, but low opacity. For example, the colours are bright but often transparent. The inorganic pigments have the opposite characteristics: less colour strength but high opacity. By combining these two groups, a bright colour with greater opacity is often achieved.

The following factors are to be considered while selecting the pigments:

The pigment suitability for the actual resin with regards to:
a) Resistance to migration.
b) Temperature resistance.
c) Dispersion & Light stability.
d) Opacity.
e) Cost.
f) The pigments, dye additives and resins’ suitability for coloring articles to be used for food containers, packaging etc.

The following information is given for each illustration:
1) Products
The product name is indicated.


2) Additional level
In actual practice, addition level will be different depending upon opacity requirements of the user.
• For Film: 7 to 8%
• For Moulding: 1 to 2%
(by weight)


3) Heat stability
Heat resistance is of course dependent on the properties of the polymer itself. The indication given corresponds to the maximum temperature in degrees centigrade at which no colour change was observed after a residence time of 10 minutes.

4) Light fastness:
Light fastness is expressed according to the Blue Wool Scale where 8 is excellent and 1 is very poor.
Light fastness Rating
Excellent 7 – 8
Good 5 – 6
Fair 3 – 4
Poor 1 – 2

Light fastness ratings depend on the addition level of the Masterbatch, type of product, and the base polymer. Higher addition levels and thicker products generally give higher fastness ratings.
5) Migration Resistance:

Pigments and additives used in the production of Masterbatch sometimes migrate to the surface of the plastic products. Migration Resistance is generally measured from 5 to 1 scale. A rating of 5 indicates excellent stable condition and that the pigment used in the Masterbatch will not migrate from the polymer to any external material.

A rating of 1 implies poor migration resistance.
Migration resistance Rating
Excellent 5
Good 3 – 4
Fair 2
Poor 1
6) Approval for food packing use:
Some of Masterbatches are recommended for food and pharmaceutical packaging where pigment and polymer required for food packing are considered during manufacturing of Masterbatch. However, food packing mainly depends at end-user level since it also requires proper understanding of conditions of polymer being used in food packing.