Novel bio-based compounds containing phenols suitable for the synthesis of
polyurethanes were prepared. The direct alkylation of phenols with different
vegetable oils in the presence of superacids (HBF4, triflic acid) as
catalysts was studied. The reaction kinetics was followed by monitoring the
decrease of the double bond content (iodine value) with time. In order to
understand the mechanism of the reaction, phenol was alkylated with model
compounds. The model compounds containing one internal double bond were
9-octadecene and methyl oleate and those with three double bonds were
triolein and high oleic safflower oil (82% oleic acid). It was shown that
the best structures for phenol alkylation are fatty acids with only one
double bond (oleic acid). Fatty acids with two double bonds (linoleic acid)
and three double bonds (linolenic acid) lead to polymerized oils by a Diels
Alder reaction, and to a lesser extent to phenol alkylated products. The
reaction product of direct alkylation of phenol with vegetable oils is a
complex mixture of phenol alkylated with polymerized oil (30-60%), phenyl
esters formed by transesterification of phenol with triglyceride ester bonds
(<10 %) and unreacted oil (30%). The phenolated vegetable oils are new
aromatic-aliphatic bio-based raw materials suitable for the preparation of
polyols (by propoxylation, ethoxylation, Mannich reactions) for the
preparation of polyurethanes, as intermediates for phenolic resins or as
bio-based antioxidants.
Phenolation of vegetable oils
