Coumarone (benzofunin) (I) and indene (II) occur in coal tar naphtha (b.p.
150-200??C) together with various other compounds (mainly xylenes and cumenes). In the preparation of polymers, no attempt is made to isolate these
monomers and they are polymerized in situ. Indeed, resinification is used as a
means of separating these substances from the other components of the cut
which are subsequently distilled and sold as solvents. Polymerization of the
coumarone-indene mixture is accomplished by adding concentrated sulphuric acid to the naphtha at 0??C. Reaction is stopped after 5-10 minutes by
the addition of water and any sludge is removed. The solution is then
neutralized and washed and residual napththa is distilled off to leave the resin.
Depending on the relative proportions of coumarone and indene (the coumarone content is usually less than 10%) and the polymerization conditions,
resins may vary from hard and brittle to soft and sticky materials. The resins
have molecular weights of about 1000-3000 and are commonly assumed to
be a random copolymer of the following type:
Coumarone-indene polymers are chemically inert and are used as binders
in cheaper grades of floor tiles. They are also used as additives in various
surface coating formulations.
