Note: Descriptions are shown in the official language in which they were submitted.
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SPECIFICATION
BACKGROUND OF THE INVENTION
This invention relates to a liquid electrical tape
formulation and more particularly, to a liquid electrical
tape formulation that is vinyl resin based and which is
solubilized into a mixture of organic solvents, and further
includes a thixotropic agent, a plasticizer and a
stabilizer, preferably an epoxy stabilizer.
Liquid electrical tape formulations have been developed
in recent years to achieve an insulating coating, for
instance, for protecting electrical connections, although
such formulations have uses that range far beyond electrical
connections, namely, to any object or area where an
insulating or protective coating is desired, particularly
where it is difficult to use conventional insulating tape.
A particular field where liquid electrical tape
formulations have become popular, is in the marine or
boating field.
However, it has been determined that the liquid
electrical tape formulations heretofore known tended either
to have poor spreading or film forming characteristics or
tended to become brittle after application as time goes by.
Yet another problem with prior liquid electrical
formulations is that of shelf life. Long shelf life has
been difficult to obtain since prior liquid electrical tape
formulations normally had the property of quick hardening.
Thus, such formulations would tend to set, harden or
polymerize in the container.
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OBJECTS OF THE INVENTION
Accordingly, it is a principal object of the present
invention to provide a liquid electrical tape formulation,
possessing all of the desirable features of a liquid
electrical tape formulation, but yet also having significant
shelf life.
Yet another object of the present invention is to
provide a liquid electrical tape formulation which can be
brushed on or dipped onto various types of electrical
connections, objects and other areas to be protected.
Still another object of the present invention is to
provide a liquid electrical tape formulation that quickly
dries to a tough, yet flexible, ultraviolet resistant,
dielectric coating which seals out dirt, moisture and water,
thereby preventing corrosion.
Yet another object of the present invention is to
provide a liquid electrical tape formulation that forms a
protective dielectric coating of flexible vinyl material.
A further object of the present invention is to provide
a liquid electrical tape formulation that adheres to metal,
plastic, vinyl, rubber and composite surfaces.
Still another object of the present invention is to
provide a liquid electrical tape which will hold wires and
terminals together, thereby preventing loose connections due
to vibration.
A further object of the present invention is to provide
an economical liquid electrical tape that is safe and easy
to use and is also fast drying.
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BRIEF STATEMENT OF INVENTION
The foregoing as well as other objects of the invention
are achieved by providing a liquid electrical tape
formulation that was originally developed for the boat
building industry where electrical connections are
continuously exposed to vibration and moisture or, in some
cases, are actually under water. In such harsh environment,
standard electrical tape or shrink tubing does not perform
well and can actually promote corrosion by allowing water to
be trapped around electrical connections.
Moreover, standard electrical tape or shrink tubing
cannot be used on very thin wiring, screw terminals or
difficult to reach connections.
Examples of usage of the liquid electrical tape
formulation of the present invention include bilge pumps,
outdoor exposed wiring, sprinkler pumps, timers, underground
wiring, outdoor lighting fixtures, instruments, computers
and other places where a weatherproof and dependable
connection is needed or where irregular shapes are involved.
In the preferred embodiment of the present invention,
the liquid electrical tape formulation is a vinyl resin that
is solubilized into a mixture of organic solvents, with the
further presence of a thixotropic agent, a plasticizer and a
stabilizer, preferably an epoxy stabilizer.
DESCRIPTION OF PREFERRED EMBODIMENT
The foregoing basic formulation is preferably comprised
of a copolymer of vinyl compounds, namely, polyvinyl
chloride and polyvinyl acetate wherein the polyvinyl
chloride is present in a significant majority amount. For
ease of reference, these and other polyvinyl materials will
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be referred to as "vinyl" or "vinyl material". The second
component of the present invention is a thixotropic agent,
the third component is a plasticizer and the fourth
component is a stabilizer. Also, in the preferred
embodiment there is a mixture of three solvents, namely
methyl ethyl ketone, toluene and methylene chloride.
A preferred formulation in accordance with the present
invention is in weight percentages:
1) vinyl copolymer (23.68%) - VYHH
2) AC 4 Pliolite (1.52%) - thixotrope
(Pliolite is a trade mark)
3) Dioctyl phthalate (9.31%) - plasticizer
4) epoxy stabilizer (ERL 42-21 (Union Carbide)) (5%)
(ERL is a trade mark)
5) methyl ethyl ketone (38.5296)
6) toluene (13.88%)
7) methylene chloride (13.10%)
The first component is preferably a mixture of vinyl
compounds, since the film forming protective features for
satisfying the objectives of the invention basically flow
from the presence of at least one vinyl compound. A
preferred vinyl copolymer is identified as VYHH that is made
by the Union Carbide Company. The VYHH is a vinyl copolymer
that is a basic coating agent which provides good adhesion.
It should be understood that other vinyl materials may be
employed in the present formula. The VYHH copolymer is
composed of 86% by weight of polyvinyl chloride units and
14% by weight of polyvinyl acetate units. It has an
approximate specific gravity of 1.36 and is normally
presented in a solid granular form that is readily soluble
in solvents used with the present invention. This will be
covered in the method of preparing the formulation of the
present invention. If the vinyl component is substantially
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entirely vinyl chloride, the vinyl component will be less
soluble in the other components, particularly, the solvents
and will also be too crystalline. The presence of some
polyvinyl acetate will facilitate the formation of a good
clear solution in the overall formulation.
The percentage of the vinyl copolymer component may
vary from about 10% to 60% by weight of the total mix.
However, the preferred amount is about 25% by weight. This
amount will contribute sufficient vinyl material to make for
a durable film of protective vinyl on the wire or junction
or article to which the formulation of the present invention
is applied.
The next ingredient is thixotropic agent, exemplified
by AC 4 Pliolite (manufactured by the Goodyear Corporation
of Akron, Ohio) which may vary in the preferred liquid
electrical tape formulation from about 1% to 2% by weight.
The AC 4 Pliolite is manufactured by the Goodyear Company.
Other compatible thixotropic agents may be used in place of
the specific AC 4 Pliolite. AC 4 Pliolite is a modified
vinyl toluene acrylate copolymer having a melting point of
54~C and a specific gravity of 2.08. The purpose of the
thixotropic agent is to lend body or thickness to the
overall liquid electrical tape formulation. This will bring
about not only better film forming properties, but more
importantly, will prevent the formulation from running.
Rather, the formulation will tend to adhere to the surface
to which it has been applied. If too much thixotropic agent
is used, the overall formulation will not pour well. If too
little is used, the formulation may be thin and runny.
Examples of other thixotropic agents that will function
satisfactorily in the present formulation are organic clays,
fumed silicas and aluminum compounds.
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The next component is a plasticizer exemplified by
dioctyl phthalate. This plasticizer affords to the dried or
set liquid electrical tape formulation, the property of
being flexible. Thus, the finished or set "tape" will not
crack or separate under the force of vibration. The
plasticizer may vary in the preferred liquid electrical tape
formulation from about 5% to 15% by weight. If too much
plasticizer is used, the formulation will "weep" as the
plasticizer migrates to the surface. Examples of other
plasticizers that will function satisfactorily in the
present formulation are castor oil, other phthalates and soy
bean based plasticizers.
It is important that the ratio of vinyl component to
dioctyl phthalate or other plasticizer be in the vicinity of
2.5:1 Increases beyond this ratio will result in a
relatively rigid final coating that will fracture and
separate from the substrate on which the liquid electrical
tape formulation is coated. Should the ratio drop to 2:1 or
less, then the formulation may not harden well.
Then, there is the stabilizer exemplified by the epoxy
stabilizer. The preferred epoxy stabilizer is known as ERL
42-21 and is made by Union Carbide Co. It is preferred that
this stabilizer be present in an amount of about 5% in the
overall formulation. Another epoxy stabilizer, used in an
amount of about 3% in the overall formulation is made by
Shell Corporation and is known as Shell Epon 828 (Epon is a
trade mark). It has been determined that the formulation of
the present invention without the stabilizer will in storage
at elevated temperatures, tend to release acid which will
interact with the inside surface of a metal container.
These in turn will initiate unwanted polymerization of the
vinyl copolymer. The epoxy stabilizer is comprised of one
or more functional liquid epoxy resins and may vary in the
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preferred liquid electrical tape formulation from about 1/2%
to 6% by weight. Non-epoxy stabilizers, compatible with
other ingredients in the present formulation may be used to
prevent premature polymerization of the formulation.
Finally, there are the solvents. Toluene is present
because it is a very effective drying agent. However, it is
a significantly flammable product whose flammability is
controlled with the presence of the methylene chloride
component. There is also a significant amount of methyl
ethyl ketone in the preferred formulation as it is an
effective solvent for both the vinyl component and the
thixotropic agent to keep these two components in solution.
Also, methyl ethyl ketone affords additional quick drying
properties to the overall formulation although it is quite
flammable.
The preferred range of methyl ethyl ketone is from
about 20% to 40% by weight. When the levels of methyl ethyl
ketone are reduced to a level of approximately 20% it would
be near impossible to keep the vinyl and rubber based resin
in solution and you would get a seeding out or thickening of
a percentage of the mass. When the level of the methyl
ethyl ketone is increased over 40%, a dramatic increase in
the dry rate will be noted and stability in small quantities
will be reduced significantly.
The preferred range of toluene is from about 10% to 15%
by weight. If the amount of toluene exceeds 20%, the
overall formulation will "skin" immediately and/or flash too
quickly. It may even dry on the brush. Where toluene falls
to less than about 10%, the vinyl component could
precipitate out of solution.
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The final solvent is methylene chloride which has good
flammability resistance (raises flashpoint to exceed 20~F).
Methylene chloride adds good film forming or coating
properties. It is preferably present in a weight percentage
range of from 10 to 20%.
PREPARATION METHOD
The liquid electrical tape formulation of the present
invention is prepared by first introducing methyl ethyl
ketone and toluene in a closed vessel. Then, the
thixotropic agent such as AC 4 Pliolite and the vinyl
copolymer are slowly fed into the closed vessel under
continuous agitation that is sufficient enough to insure
proper dispersion. Mixing should continue for at least 30
minutes and then there should be a check for completeness of
dispersion. This can be done by obtaining a sample from the
closed vessel and pouring some of it on a glass plate such
that particles that are not dissolved in the formulation are
easily observable.
Then, the methyl chloride is added, followed by another
15 minutes of mixing action. This is followed by the slow
addition of the dioctyl phthalate so as not to shock the
solution.
After the dioctyl phthalate has been added, the
viscosity should be checked. Here, a satisfactory of
viscosity is between 2,000 and 2,500 centipoise on a
Brookfield viscometer at 78~F, 20 RPM and a #4 spindle.
This reading should be taken after five revolutions. Any
adjustments to viscosity should be made usin~ a combination
of methyl ethyl ketone and toluene in a proper ratio of
about 3:1 as set forth in the preferred formula. Such
adjustment of viscosity continues until the target of 2,000
to 2,500 centipoise is achieved.
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In testing the present formulation has consistently
formed excellent coatings even after having been maintained
in 4 fluid ounce (240 ml) metal containers for at least 3
months at a temperature in the range of 60~F to 80~F. When
applied as a coating the formulation did not run or drip
even when coated on a wire, cable or object maintained at
250~F. After exposure at 0~F for 72 hours the coating
maintained its flexibility and adhesion to the substrate.
N~l~lNG
The basic formulation produced is colorless. Should it
be desired that the formula have color, it is necessary to
prepare a coloring material that will be used in a ratio of
about 3 parts by weight to 97 parts of the basic liquid
electrical tape formulation.
The coloring material has the following formulation by
weight:
23.4% VYHH
1.50% AC 4
36.70% Methyl Ethyl Ketone
13% Toluene
12% Methylene Chloride
9.30% Dioctyl Phthalate
3.1% Talc
The talc in the foregoing formulation is a dispersant.
The mixture for the colorant to tint the base is as
follows:
White, Red and Green should encompass:
66.30% Dioctyl Phthalate
.70% Neosperse / 657 Cosperse (dispersant)
(Neosperse and Cosperse are trade marks)
33% Titanium Dioxide (for white color only), or 33%
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Phthalo Green (for green color only) or 33% Red 2B
(for red color only)
The f~regoing should be prepared in a high speed
disperser and should be checked to insure proper dispersion.
Black tinting base is as follows:
58.70% Dioctyl Phthalate
1.97% Neosperse / 657 Cosperse (codispersant)
39.40% Carbon Black
The evaluation of the viscosity is as set forth in the
preparation method for the basic formulation as previously
described.
From the foregoing, it can be seen that there is
provided, a liquid electrical tape formulation which has
excellent shelf life and yet when applied to a desired
surface, will form a vinyl resin film that is sufficiently
flexible to be durable under the stress of vibration and
will not readily crack for any other reason.
Without further elaboration, the foregoing will so
fully illustrate our invention that others may, by applying
future knowledge, adopt the same for use under various
conditions of service.
