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Description  |
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BACKGROUND OF THE INVENTION
The present invention relates to an azeotropic like composition comprising
95 to 93% (% by weight) of tetrachlorodifluoroethane (hereinafter referred
to as "Flon-112") and 5 to 7% of isooctane. The composition has a boiling
point of 92.5.degree. to 92.7.degree. C.
Recently, importance of washing process is increasing with advance in
miniturization and precision of parts in electronic field. For washing
them, chlorofluorohydrocarbon solvents are employed because of their
various advantages such as incombustibility, low toxity and selective
solubility that they can dissolve fats, oils, grease and the like without
erosion of high molecular compounds such as rubbers and plastics.
Examples of the chlorofluorohydrocarbon solvents used for washing are
trichlorotrifluoroethane (hereinafter referred to as "Flon-113") which is
chemically stable and safe, an azeotropic mixed solvent thereof and the
like.
When temporarily fixing silicon wafers used for semiconductors, quartz,
ceramics and the like in their processing such as cutting or polishing,
waxes are used. Removal of the waxes by dissolving or peeling off,
however, is essentially impossible by employing Flon-113 or an admixtures
thereof because Flon-113 has a relatively low boiling point of
47.6.degree. C.
Flon-112 is a suitable solvent to the waxes of a relatively high melting
point used for the temporary fixing because Flon-112 has a high boiling
point of 92.8.degree. C. However, since Flon-112 has a high freezing point
and becomes solid at a low temperature, it is hard to use in winter
season, which limits width of its use. In addition, Flon-112 cannot be
used as an extraction solvent for purifying waxes having a high melting
point such as bees wax and Japan wax, because Flon-112 becomes solid on
cooling.
Heretofore though there has been proposed a method for lowering the
freezing point of Flon-112 in which various organic solvents such as
alcohols, ketones or esters are admixed with Flon-112 to form mixed
solvents of two-component system or three-component system which include
an azeatropic system, many solvents obtained by the method sacrifice one
or more useful advantageous properties of Flon-112. That is, those
solvents are chemically unstable, flammable, or have a relatively high
toxity. Azeotropic solvents of Flon-112 with solvents having a high
solubility have a danger that they harm materials made of rubbers or
plastics.
The present invention has done to provide an azeotropic like composition
which can solve the disadvantages derived from the high freezing point of
Flon-112 while keeping the above-mentioned excellent properties of
Flon-112, and does not harm materials made of rubbers or plastics, and
also is incombustible, chemically stable, and has an essentially constant
boiling point.
SUMMARY OF THE INVENTION
According to the present invention, there is provided an azeotropic like
composition comprising 95 to 93% of Flon-112 and 5 to 7% of isooctane.
The composition has a freezing point of 9.degree. to 5.degree. C. and a
boiling point of 92.5.degree. to 92.7.degree. C.
The words "azeotropic like composition" as used herein means a liquid
composition which has a constant boiling point lower than every boiling
point of each component, and does not change in proportion of components
when the composition is distilled.
DETAILED DESCRIPTION OF THE INVENTION
The composition of the present invention has excellent electrical
properties such as electroinsulating property and breakdown voltage, and
does not harm materials made of rubbers or plastics, and has almost the
same chemical stability as that of Flon-112, and also can provide a
solvent having a high boiling point. Accordingly the composition can
remove the above-mentioned waxes and other greases having a high boiling
point, and also is usable as an extraction solvent for waxes having a high
boiling point such as bees wax. Further since the composition can form an
azeotropic mixture which is incombustible and has an essentially constant
boiling point, it is very easy to control the liquid composition and to
recover by distillation.
Though the composition of the present invention has almost the same
chemical stability as that of Flon-112, the stability is slightly lower
than that of Flon-113. Therefore stabilizers may be added to the
composition.
It is preferred that the stabilizers can be distilled together with the
composition, more desirably can form an azeotropic system, in addition
that the stabilizers have a large stabilizing effect against the
composition.
Examples of the stabilizers are, for instance, aliphatic nitro compounds
such as nitromethane, nitroethane and nitropropane; acetylene alcohols
such as 3-methyl-1-butyne-3-ol and 3-methyl-1-pentyne-3-ol; epoxides such
as glycidol, methyl glycidyl ether, allyl glycidyl ether, phenyl glycidyl
ether, 1,2-butylene oxide, cyclohexene oxide and epichlorohydrin; ethers
such as dimethyoxymethane, 1,2-dimethoxyethane, 1,4-dioxane and
1,3,5-trioxane; unsaturated hydrocarbons such as hexene, heptene, octene,
2,4,4-trimethyl-1-pentene, pentadiene, octadiene, cyclohexene and
cyclopentene; olefinic alcohols such as allyl alcohol, 1-butene-3-ol and
3-methyl-1-butene-3-ol; acrylates such as methyl acrylate, ethyl acrylate
and butyl acrylate; and the like. These stabilizers can be used alone or
in an admixture. In addition, other compounds may be used together with
the above stabilizers. In such case synergic stabilizing effect can be
obtained. Examples of the other compounds are, for instance, phenols such
as phenol, trimethylphenol, cyclohexylphenol, thymol,
2,6-di-t-butyl-4-methylphenol, butylhydroxyanisole and isoeugenol; amines
such as hexylamine, pentylamine, dipropylamine, diisopropylamine,
diisobutylamine, triethylamine, tributylamine, pyridine,
N-methylmorpholine, cyclohexylamine, 2,2,6,6-tetramethylpyridine and
N,N'-diallyl-p-phenylenediamine; and the like.
Amount of the stabilizers varies on kinds of the stabilizers, and is
generally 0.1 to 10%, preferably 0.5 to 5% to the composition.
According to the present invention, there can be provided a mixed solvent
of Flon-112, which can solve the disadvantages derived from the high
freezing point of Flon-112 while maintaining the excellent properties
similar to Flon-112, such as chemical stability, incombustibility, high
boiling point, good cleaning power and safety against materials of rubbers
or plastics.
The composition of the present invention is useful as a cleaning solvent
for the above-mentioned temporary fixing waxes, and also-useful as an
extraction solvent for bees wax and Japan wax. Further there can be
advantageously used as a dispersing medium for powders such as carbon
powder, silicon powder, ceramic powder and aluminium metal powder because
the composition can form stable dispersions due to its high specific
gravity. The composition can be preferably used as a solvent of paints and
printing inks, as a kneading solvent of car waxes, and as a dispersing
medium of liquid abrasives for boring.
The present invention is more specifically described and explained by means
of the following Examples. It is to be understood that the present
invention is not limited to the Examples and various changes and
modifications may be made in the invention without departing from the
spirit and scope thereof.
EXAMPLE 1
A distillation flask was charged with a mixture of Flon-112 and isooctane
(90:10 by weight). The mixture was distilled under normal pressure by
using a distillation tower having a theoritical plate number of 20 to
obtain a distillate having a boiling point of 92.5.degree. to 92.7.degree.
C. which is lower than the boiling points of Flon-112 and isooctane.
As the result of gaschromatography analysis, the distillate consisted of 95
to 93% of Flon-112 and 5 to 7% of isooctane.
EXAMPLE 2
A beaker was charged with 100 cc of the distillate obtained in Example 1
and was heated on a hot plate to boil the distillate. A silicon wafer of 2
inch diameter to which was adhered a sticky wax in polishing process as a
temporary fixing wax was dipped into the boiling distillate for two
minutes, and then washed the wafer by dipping it in the boiling distillate
of the same composition.
The washed silicon wafer was observed with a microscope of 20
magnifications. There was no wax on the surface.
EXAMPLE 3
A beaker was charged with 100 cc of the disillate obtained in Example 1,
and an active carbon which adsorbed bees wax was dipped thereto, and then
allowed to stand for 5 minutes at a temperature of 90.degree. to
93.degree. C. After cooling, the active carbon was separated from the
liquid phase, and the content of the bees wax in the liquid phase was
measured. As the result 97% of the bees wax was extracted.
COMPARATIVE EXAMPLE 1
The same washing procedures as in Example 2 were repeated except that
Flon-113 and a solvent containing Flon-113 such as an azeotropic mixed
solvent of Flon-113/methylene chloride (50.5/49.5 by weight) were used
instead of the distillate in Example 1. Almost of the sticky wax was not
removed.
COMPARATIVE EXAMPLE 2
The same extraction procedures as in Example 3 were repeated except that
Flon-112 was used instead of the distillate in Example 1. The active
carbon could not be separated from Flon-112 which was solidified at the
cooling because of its high freezing point.
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