Handbook of Solvents - George Wypych - ChemTech - Ventech!

406 Seung Su Kim, Jae Chun Hyun
Table 7.3.4
Component Weight fraction, % Initial coating amount, g/m 2
Pigment and binder 35.5 6.23
Methyl ethyl ketone 21.5 3.77
Toluene 21.5 3.77
Cyclohexanone 21.5 3.77
The solvent concentration of coating at the entrance of dryer is known with coating
formulation and the solvent concentration of final dried coating could be measured offline,
thus the percent evaporated solvent at each zone can be calculated. In this example of drying
of magnetic coated film, the final dried coating contains less than 1000 ppm solvent, so we
assumed that all the coated solvent was evaporated within the dryer. Finally, we estimated
how much percent of solvent that was evaporated at each zone. The fractional amount of the
evaporated solvent at zone, k, is
F
k
=
ER
n
∑
k = 1
k
ER
k
[7.3.11]
where:
F k
fractional evaporated solvent amount in zone k
ER k
evaporation rate at zone k
n number of zone
From these fractional solvent
evaporation data we estimate
the solvent concentration in the
coated film at the end of each
zone. The solvent content per unit
area decreases according to the
fractional solvent evaporation
data at each zone, for example, if
the fractional evaporation rate of
solvent is 50% in zone 1 and the
initial solvent content is given as
10 g/m 2 , then the solvent content
at the end of zone 1 should be 5
g/m 2 Figure 7.3.22. Measured coating composition changes with drying.
, thus we can find the solvent
concentration at the end of each
zone. Moreover the measurements
and calculations are applied to the
each solvent in multiple solvent systems, therefore we can find the solvent content of each
solvent at the end of zone. The resulting coating composition changes with drying are
shown in Figure 7.3.22.
The theoretical evaporation rate to dry a given solvent load at the specified line speed
can be calculated as in Figure 7.3.21. Theoretically and experimentally found evaporation