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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is concerned with novel compositions which are
capable of removing both hydrophilic and hydrophobic contaminants from
surfaces. More particularly, it is concerned with compositions which are
especially suited for cleaning and refinishing electrical equipment and
tools, and to this end the compositions have a number of unique
properties. Principal among these properties are the ability to dissolve
water and organic materials, coupled with high evaporation rates and
resistance to flaming.
2. Description of the Prior Art
Equipment and tools used by electrical utilities often become contaminated
with a large variety of materials such as grease, dirt, salt and water.
Such equipment and tools thus need to be cleaned and refinished
periodically, in order to maintain safe operating conditions. Popular
cleaners heretofore used for this purpose have generally included
chlorinated solvents such as perchloroethylene and trichloroethane. These
solvents do not, however, remove water or wet contamination that may be
tightly held on the surface of a well-used tool. Removal of such water is
important not only to maximize the electrical integrity of the tool, but
also to ensure a good bond when the tool is recoated.
There are of course solvents that can readily remove water, such as alcohol
or acetone. These solvents are highly flammable however, having flash
points well below 100.degree. F., and thereby present a danger during use.
Heretofore known solvents which dissolve water and have flash points
greater than 100.degree. F. evaporate far too slowly for practical use as
a cleaner-dryer.
Prior patents describing various types of cleaning compositions include:
U.S. Pat. Nos. 3,592,691, 3,625,763, 3,743,542, 3,546,304, 3,574,123,
3,789,007 and 4,023,984.
SUMMARY OF THE INVENTION
Greatly improved cleaning and drying compositions which overcome the
problems noted above have now been discovered. Broadly speaking, the
compositions comprise, wherein all percentages are by weight, based upon
the total weight of the composition taken as 100%, a basic mixture having
therein from about 25 to 35% ethanol and from about 40 to 70% of a
compound selected from the group consisting of methylene chloride, Freon
11 and mixtures thereof. In addition, from about 0 to 35% of an adjunct
admixed with the basic mixture can be included which has one or more
chlorinated hydrocarbons therein. The adjunct should be such as to not
substantially lower the flame resistance of the basic mixture, however.
In more preferred forms, the ethanol should be present at a level of about
30% and the adjunct should include 1,1,1-trichloroethane and
perchloroethylene, in order to increase the solvent properties of the
overall composition.
Compositions in accordance with the invention have flash points of greater
than 100.degree. F., can remove water and various other materials such as
organic contaminants, and give a visual indication of when the composition
should be replaced. This unique combination of properties has heretofore
not been available in any known composition.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The compositions of the present invention are in liquid form and are
particularly adapted for cleaning and drying surfaces such as those on
electrical equipment and tools. The compositions are capable of removing
both hydrophilic and hydrophobic contaminants from surfaces, and have a
variety of desirable properties. The basic mixture of the compositions of
the invention have therein from about 25 to 35% ethanol and from about 40
to 70% of a compound selected from the group consisting of methylene
chloride, Freon 11 and mixtures thereof. From about 0 to 35% of an adjunct
can be admixed with the basic mixture and includes one or more chlorinated
hydrocarbons; the adjuncts should be such as to not substantially lower
the flame resistance of the basic mixture (i.e., flash point should be
higher than about 100.degree. F.) and should not evaporate at an
excessively slow rate (the rate should be less than about 2, with the
evaporation rate of butyl acetate taken as 1). Throughout the instant
specification and claims, all percentages are given on a weight basis,
based upon the total weight of the composition taken as 100%.
The ethanol component of the compositions of the invention is most
preferably present at a level of about 30%. The function of the alcohol is
believed to be as a dryer and water remover. Below about 25%, the overall
compositions have been found to be inefficient at removing water; on the
other hand, above about 35% ethanol, the flame resistance of the
compositions is excessively lowered. Therefore, a certain degree of
criticality exists with respect to the use of ethanol, and the percentages
of use.
It will also be understood that denatured ethyl alcohol has actually been
used in the invention. The denaturant in the alcohol is a combination of
methyl isobutyl ketone and heptane, and the alcohol is 95% ethanol and 5%
denaturant. Although the specific chemical identity of the denaturant is
not critical, it is preferred that the denaturants have relatively rapid
evaporation rates, i.e., greater than about 1.5, with n-butyl acetate
being taken as 1. For example, kerosene or gasoline as denaturants would
not evaporate with sufficient rapidity and should not be used for this
purpose. Of course, pure ethanol could also be used in the invention if
available.
The other component of the basic mixture is selected from the group
consisting of methylene chloride and Freon 11 and mixtures thereof. This
component serves as a vapor phase flame retardant for the ethanol, and in
effect raises the flash point of the latter. Here again, the amount of
this component used in the basic mixture is of some importance in order to
obtain adequate flame protection. Methylene chloride is the preferred
component and not only functions as a flame retardant because of its high
relative evaporation rate but because it itself is not flammable. Freon 11
has these properties as well, but methylene chloride is nevertheless
preferred because of its higher boiling point. The most preferred level of
use of methylene chloride is about 50%.
The adjunct can be used at a level of from about 0 to 35%, most preferably
about 20%. The adjunct includes a chlorinated hydrocarbon selected from
the group consisting of 1,1,1-trichloroethane, perchloroethylene,
1,1,2-trichloroethane and propylene dichloride. In particularly preferred
forms, the adjunct consists essentially of about 15% 1,1,1-trichloroethane
and about 5% perchloroethylene. The adjunct serves to add variety of
chemical types to the compositions so that they will be solvent for a
greater variety of materials. Furthermore, the evaporation rates of the
particular chlorinated hydrocarbons listed are closer to that of the
preferred ethyl alcohol. These features increase the quality of the
cleaner, but do not necessarily add to the properties of water solubility,
rapid evaporation and flame retardancy. This unusual combination of
properties can be obtained in a composition which includes only ethanol
and methylene chloride (preferably 30% alcohol, 70% methylene chloride).
The chlorinated hydrocarbons used in the adjunct should all be of a
so-called vapor degreasing grade, in order that catalytic decomposition
does not occur during storage of the composition. However, this is not an
absolute essential to the invention.
In preparative procedures, the selected ingredients are simply admixed at
ambient temperatures to yield the final composition. No special steps or
mixing procedures are required.
The most preferred composition of the invention as described above has a
flash point of about 116.degree. F., and a water solvency (ml.H.sub.2 O
per 100 grams of composition) of 4.5; however, if the composition is
slightly altered, e.g., to 40% methylene chloride, 20% ethyl alcohol, 30%
1,1,1-trichloroethane and 10% perchloroethylene, the flash point drops to
82.degree. F., and the water solvency power is reduced by more than half,
to 2.2.
The compositions of the invention exhibit a number of unique properties in
combination. As noted above, the compositions dissolve water and a wide
variety of other contaminants; the flame resistance of the compositions is
high (flash point of greater than about 100.degree. F.); the compositions
evaporate rapidly; and the compositions give a visual indication of the
need for recleaning and recoating by becoming cloudy upon absorption of
sufficient amounts of moisture. This combination of properties is highly
advantageous and novel.
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