Chemistry Reference
In-Depth Information
O
O
H
2
CO
C
(CH
2
)
7
CH
CH
CH
2
CH
CH
(CH
2
)
4
CH
3
O
O
HC
O
C
(CH
2
)
7
CH
CH
CH
2
CH
CH
(CH
2
)
4
CH
3
O
O
H
2
C
O
C
(CH
2
)
7
CH
CH
CH
2
CH
CH
(CH
2
)
4
CH
3
Figure 1.3 The structure of the triglyceride of vernolic acid.
23
Figure 1.4 General conventional method for the introduction of epoxy groups into a
triglyceride.
19
promise as inexpensive, renewable monomers for photo-curing industrial
applications.
21,22
Some raw vegetable oil such as vernonia oil already contain
large numbers of epoxide groups.
23
The vernonia oil is extracted from the
seeds of Vernonia galamensis with petroleum ether or hexane after the seeds
are lipase-deactivated and coarse ground, and yields of up to 42% have been
reported.
24,25
One unique characteristic of vernonia oil is that about 80%
of the oil is the triglyceride of vernolic acid. The structure is shown in
Figure 1.3. Vernonia oil can be utilized as a polymerizable monomer directly
in cationic UV-curing coating due to its high content of epoxy groups.
23
Most of the multifunctional epoxy monomers for photo-curing based on
vegetable oils are prepared from the epoxidation of unsaturated fatty acids or
triglycerides. The epoxidation of triglycerides or unsaturated fatty acids can
be achieved in a straightforward fashion by reaction with molecular oxygen,
hydrogen peroxide, or by chemo-enzymatic reactions.
26
The chemistry of
the Prileshajev epoxidation of unsaturated fatty compounds is well known.
27
A short-chain peroxy acid, usually peracetic acid, is prepared from hydrogen
peroxide (H
2
O
2
) and the corresponding acid either in a separate step or
in situ (Figure 1.4).
This process is performed industrially on large scale, and more research is
currently focusing on how to improve the conversion rate.
28
An epoxidation
reaction of mahua oil using hydrogen peroxide was done by Goud et al. They
used H
2
O
2
as the oxygen donor and glacial acetic acid as the oxygen carrier
in the presence of sulfuric acid (H
2
SO
4
) and nitric acid (HNO
3
), and found
that H
2
SO
4
is the best inorganic catalyst for this system, producing a high
conversion of double bonds to epoxide groups.
29
Dinda et al. worked on the
epoxidation kinetics of cottonseed oil using H
2
O
2
and liquid inorganic acids
i.e. hydrochloric (HCl) and phosphoric (H
3
PO
4
) acids, and HNO
3
and H
2
SO
4
as catalysts. They used carboxylic acid i.e. CH
3
COOH and HCOOH as oxygen
carriers, but they found that acetic acid is a more effective oxygen carrier
