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Mixed solvents
To obtain a low solution viscosity for S-LEC B/K,
it is better to employ a mixed solvent than a
single solvent. In addition, the viscosity of
a mixed solvent is more stable when stored. Typical
combinations of alcohol-, aromatic-, ketone- and
ester-base solvents are shown in Fig. 1 below.
The desirable mixing rate for alcohol base and
aromatic-base solvents is 4 : 6, which assures
a low-viscosity solution. We particularly recommend
a mixture of ethanol/toluene as a solvent. If
you use methanol or ethanol as the alcohol-based
solvent, there is a chance that the coating may
be whitened. To prevent this, add about 5% n-butanol.
Water content
in solution
S-LEC B/K has a larger allowable range of water
content than any other synthetic resin. Except
for high Butyral content types (S-LEC BL-5, BL-SH,
BM-SH, BL-S, BM-S and BH-S), the existence of
3% to 8% of water lowers the solution viscosity.
This is of great practical use.
Dissolving S-LEC
B/K
Stir the solvent continuously, and gradually pour
in the S-LEC B/K. It dissolves at ambient temperature,
but if the solvent is heated the dissolution is
accelerated. Do not apply heat immediately after
putting S-LEC B/K into the solvent, as this may
cause agglomeration. Wait until the S-LEC B/K
is saturated with solvent before heating. When
using a mixed solvent, first swell S-LEC B/K with
a solvent that does not dissolve butyral resins
alone, such as aromatic-, ester-, ketone-, or
chlorinated hydrocarbon-based solvents, and then
add an alcohol-base solvent which dissolves S-LEC
B/K. The dissolving speed of the BL types is so
high that you can mix the solvent before adding
the resin. The solvent must be tested carefully
in advance, because it heavily influences the
solution viscosity, dissolving speed, the condition
of coatings after application, and costs.
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