Handbook of Solvents - George Wypych - ChemTech - Ventech!

102 Valery Yu. Senichev, Vasiliy V. Tereshatov
The KB value is primarily a measure of the aromaticity of solvents. Using KB value, it
is possible to arrange solvents in sequence: aliphatic hydrocarbons < naphthenic hydrocarbons
< aromatic hydrocarbons.
Dilution ratio, DR, is used to express the tolerance of solvents to diluents, most frequently,
toluene. DR is the volume of a solvent added to a given solution that causes precipitation
of the dissolved resin. This ratio can characterize the compatibility of a diluent with a
resin solution in primary solvent. When compatibility is high, more diluent can be added.
Only a multi-parameter approach provides a satisfactory correlation with solubility parameters.
2-3 DR depends on the polymer concentration. With polymer concentration increasing,
DR increases as well. Temperature influences DR in a similar manner. Determination of DR
must be performed at standard conditions. DR can be related to the solubility parameters but
such correlation depends on concentration.
Aniline point, AP, is the temperature of a phase separation of aniline in a given solvent
(the volume ratio of aniline : solvent = 1:1) in the temperature decreasing mode. AP is a critical
temperature of the aniline - solvent system. AP can be related to KB value using the following
equations:
At KB50
⎛ ⎞
KB = 177 7 −10 6 − 0 249AP + 010⎜358 − Tb ⎟
⎝ ⎠
5
. . ρ . .
[4.1.3]
9
where:
Tb a solvent boiling point.
AP depends on the number of carbon atoms in the hydrocarbon molecule. AP is useful
for describing complex aromatic solvents.
The solvent power can also be presented as a sum of factors that promote solubility or
decrease it: 4
S = H + B −A−C − D
[4.1.4]
where:
H a factor characterizing the presence of active sites of opposite nature in solvent and
polymer that can lead to formation of hydrogen bond between polymer and solvent
B a factor related to the difference in sizes of solute and solvent molecules
A a factor characterizing solute “melting”
C a factor of the self-association between solvent molecules
D a factor characterizing the change of nonspecific cohesion forces in the course of transfer
of the polymer molecule into solution.
The equations for calculation of the above-listed factors are as follows:
B ( b) ( )
Vm
= α + 1 −ϕp
[4.1.5]
V
s