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Styrene Maleic anhydride copolymers are crosslinking agents as well
as chemical intermediates that find use in powder coating at the
maximum level of 10%. They also contribute significantly when used
at 5-10% level in water or solvent based coatings. The aesthetic
quality imparted by SMA in coatings cannot be easily matched by
other chemical additives or polymers. However, the coating industry
finds difficult to use SMA, particularly in those applications where
the inherent smell of SMA due to the presence of acetophenone is
very objectionable or irritating. SMA resins have been manufactured
from Styrene and Maleic anhydride using an initiator that produces
acetophenone as a by-product. Acetophenone, even after removal/extraction,
remains at the level of 0.2 - 0.4% in the final products.
A new free radical initiator has been used in a
new manufacturing process. The by-products from the free radical
initiator form low molecular weight light ends. These light ends
having low boiling point are removed, as a result of which the by-products
in the final SMA resin can be below 5ppm level.
The irritating odour of acetophenone is absent in the final SMA
product. The volatiles content reduce significantly below 0.25%
level. The purer SMA resins called SMA-LO available at the same
price as the conventional SMA polymers can be used as drop-in replacements
of the existing SMA resins.
The powder coating manufacturers would find these new SMA-LO copolymers
very attractive for use in Epoxy, Polyester as well as Epoxy hybrid
systems. These new SMA-LO coploymers are available from ATOFINA,
the major producer of SMA copolymers.
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