Summer
2002 - Article 3
From
The Lab
How Aliphatic Urethanes Are Made
Essential
Industries has been manufacturing various water-based (aliphatic) urethanes
for a number of years. These polymers are used in a variety of our floor
coatings. We use them because they impart toughness, excellent flexibility
(repairability) and abrasion resistance. The process involved in making
urethanes is fascinating since it blends a lot of science with a little
bit of art.
The first step in production is called the pre-polymer stage. Here we
react a polyol (alcohol-containing compound) with an isocyanate in the
presence of heat and/or a catalyst in a solvent. An internal surfactant
is also incorporated into the mix at this stage. The pre-polymer is
then neutralized with a suitable base (alkaline material) prior to dispersing
in water. At this point, the size of the urethane polymer is relatively
small. Under vigorous agitation, a chain extender is added in the presence
of water to "build" the final, high molecular weight urethane
polymer (called the polymer stage). The final product is filtered to
a clear, faint blue material that is ready for use in formulating products
like Eccothane™ (#274)
and Sport Kote ®(#222).
|
