Preparation of alkyds
Four different alkyds having oil contents of 35% (w/w), 47% (w/w), 60% (w/w) and 78% (w/w) were prepared
using a two-stage alcoholysis-polyesterification method. [16,17]
The alkyds were labeled as follows: J-AKD 1 (36% oil); J-AKD 2 (47% oil); J-AKD 3 (59% oil); J-AKD 4 (78%
oil). In preparing each of the alkyd, a known weight of jojoba seed oil was heated to a temperature between 220°C
and 240°C. Glycerol (14.8 g), and 0.2 g calcium carbonate were added while maintaining the temperature at about
240°C.
The completion of alcoholysis was monitored by taking samples of the reaction mixture every 5 min. Each sample
was mixed with anhydrous methanol in a 1:1 volume ratio until a clear solution was obtained which indicated the
end of alcoholysis process. [18]
After completion of the alcoholysis stage, phthalic anhydride (25g) and benzoic acid (4.8g) were added and the
reaction continued at about 240°C. The reaction was moinitored by acid value determination every one hour until a
value of 10 was reached, then the reaction was quenched by immersing the reaction vessel in cold water. Benzoic
acid was included in the preparation of alkyds to obtain products with reduced drying times, and since it is
monofunctional it also acts as chain terminating agent thus preventing the tendency towards gelling. Nitrogen was
used to blanket the surface of the reaction mixture during the reaction. The amount of the various ingredients are
shown in table 2.
T