Gilsonite Solubility:
Chemical Group |
Item |
Solubility |
Aliphatic Hydrocarbons |
VM&P Naphtha |
S |
---- |
Mineral Spirits |
S |
---- |
Solvents with KB Values of 30 or more |
S |
Aromatic Hydrocarbons |
All |
S |
Alcohols |
All |
I |
Chlorinated Hydrocarbons |
All |
S |
Esters |
Methyl Acetate |
I |
---- |
Ethyl Acetate |
Slight |
---- |
n-Butyl Acetate |
Slight |
Glycols |
All |
I |
Glycol Ethers |
All |
I |
Glycol Ether Esters |
All |
I |
Ketones |
Acetone |
I |
---- |
MEK |
I |
---- |
MIBK |
I |
Other Solvents |
Carbon Disulfide |
S |
---- |
Carbon Tetrachloride |
S |
S=soluble I=insoluble
slight=slightly soluble
Gilsonite Solutions
Gilsonite is an important component of
today's printing inks, paints &
industrial coatings. Gilsonite is used
as a hard resin and carbon black
dispersant in a variety of coatings.
Solutions of Gilsonite (sometimes called
cutbacks or varnishes) are an excellent
starting point for blending Gilsonite
with other components of a final product
formulation. Some formulators convert
dry Gilsonite into liquid solution in
their own facilities. Others will
request a pre-made solution.
Converting dry, granular Gilsonite to a
liquid solution also provides the
opportunity to remove the small amount
of abrasive grit that occurs in natural
asphaltums. Stabilizing additives can
also be added if a poor solvent is used
or if high concentrations of Gilsonite
are desired.
• Solubility: Gilsonite is soluble in
aliphatic, aromatic and chlorinated
hydrocarbon solvents. It has limited
solubility in most ketones, but is
soluble in mixed aromatic solvents that
contain a ketone component. Gilsonite is
not soluble in water, alcohols, or
acetone.
Solution Preparation: Three basic
procedures are used to dissolve
Gilsonite. In each case, precautions for
flammable materials should be used.
• Cold-cutting: Gilsonite is generally
soluble in aliphatic and aromatic
solvents at ambient temperatures. Some
agitation should be used. The rate of
solution will depend on the type of
solvent, the type and severity of
mixing, and the grade of Gilsonite. The
solution rate can be increased by using
a high shear mixer, such as a Cowles
disperser. When a ball mill or a paddle
mixer is used, lump grade Gilsonite is
recommended. When high energy mixing is
available, either lump or pulverized
grades may be used. Care must be taken
to avoid "dry balls" of undissolved
solid when using pulverized grades.
• Hot-cutting: The rate of solution can
be increased by heating. Steam coils or
hot oil is preferred. Direct-fired
heating can be hazardous. Care must be
taken to avoid or make up for vaporized
solvent. Facilities for solvent
containment are often necessary. The
maximum processing temperature will
depend on the boiling range of the
solvent.
• Hot fluxing: Gilsonite can be hot
fluxed into asphalts and high boiling
oils. Once blended, the combination can
then be let down with a solvent to reach
the desired viscosity. This hot fluxing
with another product can help overcome
limitations of solubility. Selecting the
correct blend or co-solvent can yield
compatibility with a solvent that is
normally of limited solubility.
Hot Fluxing Procedure: Heat the oil to
200°F or more. Most of the high boiling,
law aromatic ink oils in use today will
require a temperature of at least
300-330°F. With good agitation, add dry
Gilsonite at a rate that maintains
constant dispersion of the particles
until they dissolve. Be alert for
foaming that can be caused by traces of
moisture in the Gilsonite. Continue to
agitate for 15 to 30 minutes beyond the
point when the last of the Gilsonite
particles is detected. The Gilsonite
should now be completely dissolved and
the solution ready for discharge.
Filtration: The varnish must be filtered
to remove the grit that is a natural
component of Gilsonite. There are two
common filtration methods. Each provides
a different degree of cleanliness. Both
methods are normally preceded by passing
the hot varnish through a course wire
screen (approx. 1/4") to remove any
large stones.
For a normal degree of cleanliness, the
prescreened, hot varnish is passed
through wire screen baskets of about 200
mesh (74 microns). Cloth bag filters can
also be used, at a higher cost, when the
company doesn’t have the personnel to
clean the wire baskets. Disposal of the
bags is also a consideration. Be careful
to use bags that can tolerate elevated
temperatures if hot cutting is
performed.
For extra cleanliness, the prescreened,
hot varnish is passed through cartridge
filters of about 5 to 25 microns. These
filters are also disposable.
• Viscosity Modification: Some Gilsonite
solutions can be quite viscous at
ambient temperature. Also, some
solutions can steadily increase in
viscosity over time. These
characteristics are usually observed
when using law aromatic oils with poor
solvent power or when high percentages
of Gilsonite are used. In these cases,
small amounts of viscosity modifiers are
often added to (1) keep the hot varnish
sufficiently fluid for easy filtration
and (2) to reduce and stabilize the
ambient viscosity so the solution
remains fluid until it is used.
The following is a partial list of
modifiers that are effective at
stabilizing the viscosity of Gilsonite
solutions.
1. Soft asphalt flux. This is often
substituted for 15 to 20 % of the
Gilsonite in the varnish. At this level,
it reduces the softening point of the
Gilsonite by about 30°F. It should not
be used when maximum hardness and rub
resistance is desired, or when fast
solvent release is required, or when
restrictive health safety regulations
are in effect.
2. Tridecyl alcohol (TDA). More volatile
than some modifiers (a flash point of
180°F), but effective. Generally used at
3-10%, based on the Gilsonite content.
3. Low molecular weight alcohols.
Examples are n-propanol and n-butanol.
These are effective, but their high
volatility usually restricts their use
to fast drying systems or products that
are stored and used at ambient
temperature.
4. Tall oil fatty acids. These are
mainly oleic and linoleic acids with
small amounts of rosin acids present.
They are used for their high flash point
and law volatility. In some cases,
stearic or oleic acid, or vegetable oils
such as linseed or soya bean oil, can be
substituted for tall oil fatty acids
with comparable performance.
5. Surfactants. A wide variety of
commercial surfactants are also
effective. Care must be taken to avoid
any undesirable side effects on the
performance of the final product.
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