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PP, currently commanding almost 25% share of the total plastics
consumption and still growing at 2 - 3 x GDP growth around the world,
plays a significant role in developments of several additives such
as clarifying agents or nucleants. Similarly, a huge volume of injection
moulded products that find an usage in automobiles, consumer durable
as well as non durable segments need PP products in several different
colours.
Because of its basically non polar nature, PP, like other Polyolefins
is difficult to colour. This in particular is true in comparison
with stryenics, the other group of plastics that plays a dominant
role in the consumer products sector. It is not only the nature
of PP, but also the nature of the pigments that contribute to the
colouring factor. Pigments tend to agglomerate easily. Some pigments
also have tendency to reagglomerate after getting mixed in the melting
process during the conversion process.
To eliminate these agglomeration problems and achieve better dispersion
of individual pigment particle, chemicals known as dispersion agents
are required. These dispersion agents need to however be compatible
with PP matrix. The PP waxes having excellent compatibility with
PP obviously meets the primary requirement of a dispersion agent
for PP. The finer particle size of PP wax is also desirable to effectively
segregate particles of pigments. They also help in reducing binding
force of pigments and thus prevents agglomeration. The formation
of film across pigments prevents formation of reagglomeration.
The faster melting by lower viscosity wax would help in improving
dispersion. No wonder that Micronised PP wax acts as an efficient
dispersion agent.
The recent development of Metallocene catalysts has also been adapted
for PP wax. Due to uniform control of chain length and sharper melt
and drop points, Metallocene PP waxes are found to provide better
dispersion compared to micronized PP wax based on Z - N catalysts
of same particle size.
It is expected that use of Metallocene PP micronised wax would
grow to meet the evergrowing penetration of PP in consumer products
to meet the challenge of several colours in the PP products.
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