Chemistry Reference
In-Depth Information
molar ratios ranging between 1 and 5. The physicochemical properties of the resulting
resins were determined [37]. The possible structures of condensed products, prepared
at 150
o
C as shown in Scheme 2.3, indicate that the trimethylol derivatives of rosin
acids can be formed with a rosin acid:FA molar ratio of 3. At a higher molar ratio
(rosin acid:FA = 4), the methylol groups tend to form dimethyl ether type structures
as shown in Scheme 2.3, while at a lower molar ratios (rosin acids:FA = 2), methylene
links are more probable. The acid number values indicate that the carboxylic groups
of rosin acids do not participate in the condensation reaction with methyl groups. The
resins synthesised by the polycondensation of resin acid with FA at temperatures up
to 150 ºC release further quantities of water and carbon dioxide when the process is
continued at high temperature (up to 240 ºC). The resins formed by the condensation
of rosin acid with FA (molar ratio 3) at high temperatures are shown in Scheme 2.3.
The lower acid number values of the resins produced by condensation at high
temperatures indicate the participation of carboxylic groups in the condensation
reaction. This observation agrees with the data for the condensation of AbA with
FA at high temperature [37].
Product of condensation of rosin acid and formaldehyde at temperature 150
o
C.
a)
Product of condensation of rosin acid and formaldehyde at temperature 240
o
C.
b)
Scheme 2.3
Products of condensation of rosin acid with FA at different
temperatures
