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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 it 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 volatile contents 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.
Powder coating manufacturers would find these new SMA-LO copolymers
very attractive for use in Epoxy, Polyester as well as Epoxy hybrid
systems.
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