Process for electrodepositing mica on coil or bar connections and resulting products

A process for electrodepositing mica and a water soluble anionic resin binder, such as a modified polyester resin, is disclosed as a means for applying a heavy coating of a high-voltage, mica-bearing electrical insulation onto uninsulated and insulated portions of electrical connections in dynamoelectric machines. The electrodeposited mica coating is subsequently impregnated with a suitable resin, such as an epoxy or polyester resin, concurrently with the impregnation of other conventional insulations in the machine. Alternatively, deposition and impregnation of the connection insulation can be performed prior to installing the connection into the machine.

FIELD OF THE INVENTION 
The present invention relates generally to the art of electrophoretic 
deposition, and is more particularly concerned with a novel process for 
electrodepositing micaceous insulating coatings on end connections for 
electrical conductors, especially end connections for electrical coils and 
the like, and with the resulting novel insulated articles and assemblies. 
CROSS REFERENCE 
This invention is related to that of patent application Ser. No. 672,776, 
entitled Formulation For Electrodeposition of Mica, filed Nov. 19, 1984 in 
the names of Richard K. Elton and William R. Schultz, Jr. and assigned to 
the assignee hereof, from which U.S. Pat. No. 4,533,694 was issued Aug. 6, 
1985 and which discloses and claims a novel mica-containing composition 
having special utility in providing insulating coatings on electrical 
conductors. 
BACKGROUND OF THE INVENTION 
The connections in a small dynamoelectric machine are typified by the 
lengths of bare copper wires which join the stator coils in electric 
motors to each other and to external motor terminals. Insulation of those 
small connections is usually accomplished by application of micaceous 
insulating tape after the connections are made from a few strands of wire 
and fastened together, for example, by brazing. Because in many cases, the 
actual connection is only several inches long, has an irregular geometry, 
and is located in crowded part of the machine, the insulation normally has 
to be applied manually, a very slow and laborious process. 
In larger machines, such as hydroelectric or steam turbine-generators, 
connections are often made using large copper tubes or bars. These 
connecting parts may be taped and impregnated prior to installation. In 
any case, however, because of the irregular shapes involved, much or all 
of the work must be done by hand. 
A less complicated, yet effective technique of applying micaceous 
insulation, without the need for taping, would be of great benefit in the 
manufacture of dynamoelectric equipment. In addition to savings in labor 
and time, the cost of materials could be substantially reduced because 
insulating tape production involving mica paper fabrication, lamination, 
etc., would be avoided. Also, less expensive wet ground mica might be used 
instead of the fluid-split or calcined mica required for tape manufacture. 
Heretofore, electrodeposition of mica has been a recognized means of 
providing an electrical insulation coating or covering. Thus, Shibayama et 
al, U.S. Pat. No. 4,058,444 discloses such a process for providing 
insulation for coils of rotary machines, mica and a water dispersion 
varnish being used in a coating bath formulation. Other patents describe 
the electrophoretic deposition of mica with the use of water dispersion 
resins in similar manner to bind the deposited mica particles. Japanese 
patents issued to Mitsubishi Electric Corp. (Japanese Pat. Nos. 77 126438; 
81 05,868 and 81 05,867) are directed along this same line, but none of 
them disclose the in situ electrodeposition of mica on electrical 
connections. 
German Pat. No. 1,018,088 issued to H. W. Rotter describes the use of 
electrodeposited mica for insulating electrical connections, and sets 
forth a coating bath formulation wich contains extremely finely divided 
mica (&lt;1 micron). In addition, the possibility of using a silicone resin 
emulsion to aid in binding the flakes of mica together is mentioned. 
Other applications of electrodeposited mica appear in the patent literature 
which involve the use of a binder either in the form of a water dispersion 
polymer or an aqueous emulsion. Objects to be coated such as wires, 
plates, and perforated plates are mentioned. 
None of these prior art procedures have proven to be satisfactory enough to 
displace the manual technique with all of its drawbacks. For one reason, 
the resultant coating compositions are unable to withstand conditions of 
the manufacturing environment, coalescing or coagulating when agitated or 
allowed to stand for prolonged periods. Additionally, the emulsions and 
dispersions used heretofore result in coatings which are not of uniform 
thickness, particularly on irregularly shaped conductor substrates because 
the different levels of electrical field strengths cause corresponding 
variations in insulating coating thickness. 
The generally recognized, long-standing demand for answers to these 
problems, having not been met through any of the concepts disclosed in the 
foregoing patents or elsewhere in the patent art, has persisted to the 
present time. 
SUMMARY OF THE INVENTION 
By virtue of the present invention which is predicated upon the discoveries 
and concepts set out below, the shortcomings of the prior art can be 
avoided and new results and advantages can be obtained. Further, these 
gains can be made and realized without penalty of offsetting disadvantages 
of economy or efficiency of production, or of product quality, utility or 
value. 
A key concept underlying this invention, as well as the invention of 
aforesaid U.S. Pat. No. 4,533,694, is to use in producing by 
electrodeposition thick (greater than 50 mils) insulation coatings, a 
formulation in which the binder is contained in solution rather than being 
dispersed or emulsified in the liquid vehicle of the deposition 
formulation. 
When such a solution is employed instead of a dispersion or emulsion of the 
prior art, the problem of thick and thin spots in the electrodeposited 
mica coatings is minimized as coatings of substantially more uniform 
thickness are consistently produced. Apparently, this is the result of 
self-limiting effect arising from the fact that depositions on a conductor 
from a coating bath containing mica and a water soluble binder result in 
the conductor becoming increasingly passivated which in turn results in 
decay of the deposition rate exponentially with time. The decay constant 
of this system, which determines how rapidly this effect develops, can be 
controlled by varying the concentration of water soluble binder and/or 
electrolyte in the coating bath. Thus, the high field strength areas of 
the conductor will begin to accumulate a heavier coating than the low 
field regions, but will also more quickly become passivated. The low field 
strength regions do not become passivated as quickly and, consequently, 
will continue to acquire a coating at an increasingly greater relative 
rate than the higher field strength regions. More uniform coating 
thickness is the result. 
It has been further found that coating quality can be enhanced and coating 
deposition rate can be controlled by adding a relatively small amount of 
an electrolyte to the aqueous coating bath. 
As set forth in the aforesaid referenced patent application, the water 
soluble resin binder must have anionic functionality, that is, only 
anionic polymers are useful for my purposes and are therefore contemplated 
by the appended claims. Cationic or nonionic water soluble polymers, 
unlike anionic-type polymers, are not compatible with mica 
electrodeposition formulations because they are not attracted to the anode 
with the mica which in water dispersion acquires a net negative charge. 
Water soluble anionic resins having special utility in this invention are 
polyesters, epoxyesters, acrylics and carboxy-terminated 
butadiene/acrylonitrile resins. It will be understood, however, that 
others may be used together with or in place of these, and that typically 
such a resin has an acid number (indicating carboxy group content) from 20 
to 120 and that it is rendered water soluble by reaction with a 
substituted amine or other suitable base. 
Still another concept of the invention is to impregnate the porous, dry, 
micaceous coating resulting from the electrodeposition from the aqueous 
mica containing bath. Thus, with the mica flakes being held together as 
deposited as a coating, resin varnish is applied to the coating and the 
impregnated coating is baked to cure the resin varnish. 
I have further discovered that when the process of this invention is 
carried out on a conductor which is insulated as by tape wrapped over a 
portion of the conductor length, the uninsulated bare portion and the 
immediately adjacent part of the conductor are covered with a continuous 
crack-free coating of electrodeposited insulating material. This discovery 
led me to the novel concept of insulating the series leads of motor coil 
assemblies by the process of immersing the bare lead portions and adjacent 
insulated lead portions in an electrodeposition bath and then 
electrodepositing a coating of insulating material on not only the bare 
exposed coil connection parts of the assembly, but also on the adjacent 
insulated parts thereof to provide overlapped insulation at each coil end 
connection. A related new concept of mine is to apply insulation to other 
electrical conductor components of dynamoelectric machines such as pole 
jumpers for hydrogenerators and similar equipment in which high integrity 
of the insulating cover material is essential over the full length of the 
conductor component and its connections. 
Briefly stated, then, in its process aspect the present invention generally 
comprises the sequential steps of immersing bare electrical connections 
and/or terminals between an end portion of a wire member in coil form or 
otherwise and another conductor in an aqueous electrodeposition 
composition containing mica particles, a water soluble anionic resin 
binder, an electrolyte and a nonionic surfactant; electrodepositing a 
coating from the bath on the bare electrical connections to provide a 
micaceous coating which, when dried, is porous and contains sufficient 
binder to hold the particles together in place on the substrate; next, the 
porous coating is impregnated with resin varnish; and finally the 
impregnated coating is heated to an elevated temperature to cure the resin 
varnish. This process accordingly is a new combination of procedural steps 
including the new step involving the use of the new composition disclosed 
and claimed in the above-referenced patent application. 
In more specific terms this new process includes the preliminary step of 
wrapping a portion of the length of the conductor with insulating 
material, suitably in the form of tape, and immersing the so insulated 
part of the conductor and the uninsulated adjacent part in the 
electrodeposition formulation, and then electrodepositing a coating of 
insulating material from the said formulation on the bare portion and on 
the immediately adjacent insulation-covered portion of the conductor to 
provide a continuous crack-free coating of high integrity. 
In its product aspect this invention is in general the article or the 
assembly resulting from the application of the present novel process to 
electrical conductors generally and especially to those carrying an 
insulating cover over part of their lengths. Thus an electric motor 
assembly of insulated coils connected at their ends in series by coil 
leads which are in part bare and uninsulated as installed is provided with 
continuous crack-free insulation on each coil lead which overlaps and is 
bonded securely to the insulation on the coil lead as well as to the 
exposed metal surface thereof.

DETAILED DESCRIPTION OF THE INVENTION 
As illustrated in FIG. 1 a conductor in the form of a copper bar is 
provided with continuous, crack-free insulating cover 11 consisting of a 
combination of mica tape 12 wrapped around conductor 10 over a part of its 
length and electrodeposited mica insulation coating 13 covering and bonded 
directly to the unwrapped, bare part of the conductor. As an important 
consequence of electrodepositing insulation coating 13 in strict 
compliance with the process of this invention as described above, the 
interface between the taped and bare parts of conductor 10 is covered by 
coating 13. Thus the coating overlaps tape 12, extending approximately as 
far beyond the said interface as the thickness dimension of coating 13 on 
the bare part of the conductor. As shown, coating 13 is of substantially 
uniform thickness over the bare metal but tapers at about 45.degree. from 
the interface to the end over tape 12. Further, as indicated elsewhere 
herein, the thickness of coating 13 is largely a matter of the operator's 
choice as this invention enables electrodeposition of coatings of high 
integrity and uniformity of thickness 50 to 150 mils or more. 
In the case of series connection 20 of FIG. 2 lead portion 21 is wrapped 
with mica tape insulation and the central or junction portion 22 is 
covered with a coating 24 of electrodeposited mica insulation. Again the 
insulation over the full length of connection 20 is continuous and 
crack-free because coating 24 bridges over the interface region between 
wrapped and bare parts of the series connection and is securely bonded to 
both. In this instance the overlap is approximately 100 mils which is the 
thickness of coating 24 on the unwrapped or bare part of the element. 
Coil formette 30 of FIG. 3 comprises four coils 31, 32, 33 and 34 and three 
series connections 35, 36 and 37. As in the case of series connection 20 
of FIG. 2, these three are wrapped to some extent with the mica tape 
insulation which covers the four coils. The junctions of connections 35, 
36 and 37 are not wrapped at the stage of assembly illustrated in this 
view. 
Completion of the insulation system of the assembly of FIG. 3 is again 
accomplished in accordance with preferred practice of the process of this 
invention with the result shown in FIG. 4. Thus series connections 35, 36 
and 37 of formette 30 are insulated by electrodeposited coatings 40, 41 
and 42, respectively. Those coatings, like coating 24 on series connection 
20, are each of substantially uniform thickness about 100 mils and 
crack-free and continuous. Further, as a consequence of these coatings 
being formed as described above by an operation involving dipping of the 
formette in an electrodeposition bath of the kind specified herein, the 
ends of each coating have the geometry of coating 13 of FIG. 1, overlying 
the mica tape insulation and bridging across the interface between the 
taped and untaped parts of the series connection. 
The dipping operation just mentioned is illustrated in FIG. 5 in which an 
electric motor stator 50 is suspended in coating vessel 52 with series 
connections 54 of the motor coils immersed in electrocoating solution bath 
56. The depth of this immersion is sufficient to insure that the tape 
insulation on the series connections is submerged to at least the extent 
that overlap of electrodeposited insulation is desired, then D.C. 
potential is applied to the system with vessel 52 serving as the ground 
and the power source suitably being a D.C. generator. 
The compositional range of the electrodeposition bath in accord with the 
invention in weight percent is summarized below: 
______________________________________ 
Component Broad Range Preferred Range 
______________________________________ 
Mica 5-35% 10-16% 
Soluble Resin Binder 
0.2-2% 0.5-1.5% 
(as solids) 
Electrolyte 0.001-0.20% 0.002-0.05% 
Nonionic Surfactant 
0-0.3% 0.03-0.10% 
Water Balance Balance 
______________________________________ 
Mica types and particle sizes useful in the process of this invention 
include those specified in the above-referenced patent application. 
Likewise, soluble resin binders, electrolytes and polar solvents useful in 
this process include those set forth in that patent application. 
Accordingly, those portions of the specification of said above-referenced 
application describing those constituents of electrodeposition both useful 
in the present process are hereby incorporated herein by reference. 
The electrical connection or group of connections to be insulated are 
coated by electrodeposition. The connection is immersed in the 
aforementioned bath. A direct current (D.C.) potential is applied to the 
conductor in the connection, typically in the range of +20 to +150 volts. 
Simultaneously, a grounded counterelectrode must be present in the bath. 
The mica flakelets in suspension are attracted to the anodic connection 
and are deposited there as long as current flows from it. The organic 
binder also codeposits with the mica flakes. Typical deposition times 
range from 20 to 500 seconds, depending on the binder, electrolyte 
concentrations and the thickness of the insulation coating desired. 
The interface between the electrodeposited mica and the taped insulation is 
the region of greatest difficulty in achieving a consolidated, crack-free 
insulation, due to the properties of the two dissimilar insulation 
materials. In some instances depending on the type of mica tape used, 
better adhesion, between the electrodeposited mica and the tape, can be 
accomplished when a nonionic surfactant, i.e., one that does not undergo 
migration in an electric field, is incorporated into the deposition bath. 
A typical nonionic surfactant is Tergitol NPX (alkyl phenyl ether of 
polypropylene glycol), available from Union Carbide Corporation. 
When enough mica has been deposited, the D.C. current is switched off and 
the connection is removed from the bath. The initial wet coating on the 
connection is a composite of mica flakelets, binder solids and water. This 
coating is allowed to dry at a temperature greater than 0.degree. C. and 
less than 100.degree. C., but preferably from about 25.degree. C. to about 
75.degree. C. The residual water is baked out in an oven at an elevated 
temperature. At the same time the elevated temperature serves to cure the 
binder. The result is a dry, micaceous coating which is porous and 
contains enough binder to hold the mica flakes together. 
The next step is a post-impregnation treatment of the porous coating, in 
which the connection is either dipped into an impregnating varnish or, 
more preferably, treated by vacuum-pressure impregnation with a suitable 
epoxy or polyester resin. This impregnation treatment can, in many 
instances, be part of the same cycle whereby other conventional 
insulations in the dynamoelectric machine are also being resin treated. 
Frequently in the actual dynamoelectric machine there are two such post 
impregnation treatments. 
The final step consists of an elevated temperature bake to cure the 
impregnated resin. Generally, the curing step includes heating to a 
temperature of 150.degree. to 180.degree. C. for a time of four to six 
hours. Longer curing times can be used, but are usually not necessary. The 
higher the temperature the shorter the time required for a satisfactory 
cure. A typical curing step is at a temperature of 160.degree. C. for a 
time of six hours. 
The resulting product is a micaceous connection insulation, consolidated 
and void-free. This procedure has the advantages of using low-cost mica 
and eliminating all taping operations in the connection region. In 
instances in which a wire or coil terminal is to be connected to a wire or 
coil and then used as a connector, it may be taped over initially with a 
suitable tape and after the plating process is complete the underlying 
tape and the insulation deposited thereover may be removed. 
The invention is further described by the following examples in which all 
mesh is given in U.S. Standard sieve sizes and all percentages are given 
in weight percent. 
EXAMPLE I 
A representative model of a conventional high-voltage motor coil connection 
was made by overlapping two rectangular copper strips about 1/2" and 
brazing them together. This joined connection was then bent in the shape 
of a "U", and insulated with conventional mica tapes on the ends only. To 
insulate the bare copper portion, the connection model was immersed in a 
metal vessel containing a bath of the following composition: 900 grams of 
325 mesh wet ground muscovite mica powder; 170 grams of a water soluble 
polyester resin varnish, available as Sterling WS-200 WAT-A-VAR, from 
Reichold Chemicals, Inc.; 2 grams of ammonium nitrate electrolyte, and 
enough distilled water to bring the volume up to 2 gallons. 
The model was immersed in the bath for a period of 2 minutes to eliminate 
air from the submerged taped insulation portion. Using a metal vessel as 
the ground, an anodic potential of 60 volts D.C. was applied for 350 
seconds to deposit the mica and binder. Thereafter the model was dried for 
15 hours at 25.degree. C. and baked 6 hours at 160.degree. C. It was 
subsequently vacuum-pressure impregnated with an accelerated version of an 
epoxy resin consisting in weight percent of about a 60% cycloaliphatic and 
40% a liquid Bisphenol A-diglycidyl ether epoxy, as disclosed in Markovitz 
U.S. Pat. No. 3,812,214. Thereafter, the epoxy was cured 6 hours at 
160.degree. C. 
The result was the deposition of a smooth, uniform insulation, about 125 
mils thick, coating the bare portion, and two overlapping portions that 
rise over the conventionally taped insulation by about 120 mils. The mica 
content of the coating was determined to be 36.9%. The two overlapping 
portions between the electrodeposited and conventional insulation were 
wrapped with a 2" metal foil, and when subjected to electrical testing, it 
was found that over 35,000 volts at 60 Hz were applied, between the copper 
strips and foils, without failure of the insulation. 
EXAMPLE II 
A high-voltage connection model was prepared from a rectangular copper 
strip by insulating half of its length with conventional mica tape. The 
following bath was prepared for coating the bare copper portion of this 
strip: 7,500 grams of 325 mesh wet ground muscovite mica powder; 900 grams 
of a water soluble polyester varnish, available as Aquanel 513 from 
Schenectady Chemicals, Inc.; 17 grams of basic aluminum acetate 
(stabilized with boric acid); 7 grams of ammonium nitrate, and enough 
distilled water to bring the volume up to 32 liters. 
The model was immersed for several minutes to eliminate air from the taped 
insulation, and then an anodic potential of 60 volts D.C. was applied for 
105 seconds. The model was then removed and dried at 25.degree. C. 
overnight, and baked 6 hours at 160.degree. C. It was subsequently 
vacuum-pressure impregnated with an epoxy resin as described in Example I, 
and cured for 6 hours at 160.degree. C. 
The result was a uniform void-free micaceous insulation about 200 mils 
thick, and overlapping the upper portion of the mica tape insulation by 
about 200 mils. A metal foil was wrapped over the interface, and 
electrical failure did not occur until a potential of 40,000 volts at 60 
Hz was reached. 
EXAMPLE III 
A connection model for a large generator was prepared by soldering together 
3 lengths of 11/8" o.d. copper tubing in the shape of a "T". 
A bath for coating this object was prepared as follows: 5,600 grams of 325 
mesh wet ground muscovite powder; 560 grams of Aquanel 513 soluble 
polyester varnish; 17.5 grams of basic aluminum acetate (stabilized with 
boric acid), and enough distilled water to bring the volume up to 34 
liters. 
The "T" shaped object was then immersed in this bath, and an anodic 
potential of 60 volts D.C. was applied for a period of 300 seconds. 
Thereafter, the object was removed and allowed to dry at 25.degree. C. for 
24 hours. It was then baked 6 hours at 160.degree. C., and subsequently 
impregnated with the epoxy resin, as and according to the procedure 
described in Example I. The final cure was for 6 hours at 160.degree. C. 
This process resulted in a uniform micaceous insulation on the outside 
surface of the copper tubing which was about 75 mils thick and contained 
about 35% mica. When the region about the corners of the "T" were wrapped 
with metal foil, voltage was applied up to 25,000 volts without failure. 
EXAMPLE IV 
A multiple coil motor model, known as a formette, was constructed using 4 
motor coils placed in a fixture similar to the stator of a high-voltage 
motor. These coils were insulated with conventional mica tapes and 
wrappers, except for the leads, which consisted of bundles of six bare 
rectangular copper wire. The leads were joined in series from one coil to 
the next by brazing, resulting in 3 bare series connections. A bath for 
electrodeposition of mica onto these leads was prepared by mixing the 
following constituents: 1,800 grams of 325 mesh wet ground muscovite 
powder; 340 grams of Sterling WS-200 WAT-A-VAR water soluble polyester 
varnish; 4 grams ammonium nitrate electrolyte, and enough distilled water 
to bring the volume up to 4 gallons. 
The end region of the formette was immersed in the bath so that all of the 
bare copper connections were submerged. An anodic potential of 70 volts 
D.C. was applied for 270 seconds. Thereafter the formette was removed, 
dried at 25.degree. C. for 24 hours, and then baked for 6 hours at 
160.degree. C. Following this, the electrodeposited insulation along with 
the conventional taped insulation was impregnated with an epoxy resin as 
disclosed in Example I. The resin was then cured for 6 hours at 
160.degree. C. 
The result was a continuous insulation around the coil connections about 
110 mils thick and overlapping the taped insulation by about 100 mils. 
EXAMPLE V 
Three high-voltage motor connection models were prepared by bending 15" 
copper strips in the shape of a "U", and insulating the ends with mica 
tapes, similar to the method described in Example I. A coating formulation 
was prepared in a metal vessel by mixing the following constituents: 900 
grams of 325 mesh wet ground muscovite mica powder; 170 grams of Aquanel 
550 water soluble polyester varnish; 2 grams of ammonium nitrate; 4 grams 
of Tergitol NPX nonionic surfactant available from Union Carbide 
Corporation, and enough distilled water to bring the total volume up to 2 
gallons. 
The bare copper portion of each model was coated by immersing the model in 
the bath and applying an anodic potential of 60 volts D.C. for a period of 
180 seconds. Thereafter, the objects were allowed to dry overnight at 
25.degree. C., and then baked 6 hours at 160.degree. C. Following this, 
they were vacuum-pressure impregnated with an epoxy resin as described in 
Example I, and cured 6 hours at 160.degree. C. 
The foregoing resulted in a smooth uniform micaceous insulation about 120 
mils thick and overlapping the taped insulation by about 130 mils. The 
insulation integrity was tested by applying 9000 volts at 60 Hz between 
the outside surface and the copper, and found to pass without failure. 
Thereafter, the models were thermally cycled by repeatedly passing current 
through the copper to heat it to 190.degree. C., and subsequently 
permitted to cool in air to 30.degree. C. After 2000 such cycles, the 
models were tested by immersion in water containing a wetting agent for 30 
minutes. Then 4600 volts at 60 Hz were applied to the submerged samples 
without any dielectric failure occurring. 
EXAMPLE VI 
Three high-voltage motor connection models were prepared as described in 
Example V. A coating formulation was prepared by mixing the following 
constituents in a metal vessel: 900 grams of 325 mesh wet ground muscovite 
mica powder; 170 grams of Aquanel 513 water soluble polyester varnish; 2 
grams of ammonium nitrate; 4 grams of Tergitol NPX nonionic surfactant; 
and enough distilled water to bring the total volume up to 2 gallons. 
The bare copper and insulated portions of each model were coated by 
immersing the model in the bath, and applying an anodic potential of 60 
volts D.C. for a period of 140 seconds. Thereafter, the objects were 
allowed to dry overnight at 25.degree. C. and then baked 6 hours at 
160.degree. C. Following this they were vacuum-pressure impregnated with 
an epoxy resin as described in Example I, and cured 6 hours at 160.degree. 
C. 
This resulted in a smooth uniform micaceous insulation about 130 mils 
thick, and overlapping the taped insulation by about 130 mils. The 
insulation was tested by applying 9000 volts at 60 Hz as in Example V, 
without failure. The models were thermally cycled from 190.degree. C. to 
30.degree. C. for 2000 times as in Example V and tested at 4600 volts at 
60 Hz under water after 30 minutes submersion, without failure. One model 
was then placed back on the thermal cycling test for an additional 3136 
cycles, removed, and submerged under water. It passed the 4600 volt test. 
EXAMPLE VII 
A formulation of the coating composition of the present invention was 
prepared by mixing the following ingredients: 5,600 grams of 88 mesh 
muscovite mica powder available from Franklin Minerals, Inc., 560 grams 
Aquanel 513 water soluble insulating varnish available from Schenectady 
Chemicals, Inc. (28% solids of an oil modified polyester), 2.5 grams 
sodium chloride, and enough distilled water to bring the bath volume up to 
34 liters. 
A rectangular copper wire, 0.162".times.0.322" cross section, was immersed 
in the coating formulation coaxial with respect to a 3 inch copper tube at 
ground potential. Mica and binder were electrodeposited on the wire by 
applying an anodic potential of 60 volts D.C. for 80 seconds. The coated 
wire was removed from the bath and dried at 25.degree. C. for 15 hours, 
and the binder cured at 165.degree. C. for 4 hours, resulting in a porous 
micaceous coating. 
Thereafter, the coating was vacuum/pressure impregnated with an epoxy resin 
consisting of 60% cycloaliphatic and 40% Bisphenol A epoxy, as disclosed 
in Markovitz, U.S. Pat. No. 3,812,214. The epoxy was cured for 6 hours at 
160.degree. C. to yield a consolidated, void-free insulation 30 mils thick 
containing 40.4% mica. The insulation was voltage endurance tested by 
wrapping the insulated wire spirally with a 40 mil bare Cu wire and 
applying 7,500 volts at 60 Hz. The insulation survived the corona and 
voltage stress for 5,035 hours. 
EXAMPLE VIII 
Following the procedure of Example VII, a formulation was prepared 
consisting of 900 grams of 325 mesh muscovite powder, 200 grams of Aquanel 
513 water soluble polyester varnish, 2 grams ammonium nitrate, diluted to 
2 gallons with distilled water and stored in a tin coated steel container. 
A test sample was prepared from two parallel copper bars, having 
rectangular cross sections of 1 inch.times.1/4 inch, and 6 inches in 
length. The bars were separated by two 3/8 inch thick phenolic spacers 
placed at either end of the bars and the bars were bolted together. The 
sample was then immersed in the coating formulation. Mica and binder were 
deposited thereon by applying an anodic potential of 100 volts D.C. for a 
time of 400 seconds. The metal container was grounded and became the 
cathode of the electrical deposition system. The bars were removed and 
dried 15 hours at 25.degree. C., then 6 hours at 105.degree. C., and 
finally 6 hours at 160.degree. F. Thereafter, the bars were 
vacuum/pressure impregnated with an accelerated version of the epoxy resin 
disclosed in Example I, and the resin cured at 160.degree. C. for 6 hours. 
The resulting insulation measured 130-137 mils thick on the outside faces 
of the bars and 102-107 mils on the inner faces. This represents a 
reduction in insulation thickness of only about 15% in the electrically 
shielded region. 
This example demonstrates how an improved uniformity of insulation build 
can be achieved in regions where electrical shielding or enhancement 
occurs simply by adjusting the concentration of water soluble binder. 
As a comparison, the same copper bar configuration immersed in a bath 
containing the same constituents as in Example IV and 100 grams of Aquanel 
513 instead of 200 grams results in insulation builds of 252 mils and 85 
mils on the outer and inner faces, respectively. Here, a reduction in 
thickness of 66% occurs in the shielded region. 
EXAMPLE IX 
In order to compare the effects of using water soluble resins versus water 
dispersed resins in the electrodeposition of mica, test samples of two 
parallel copper bars (designed as bar X and bar Y) were prepared having 
the dimensions and configuation as described in Example VIII. 
Electrodeposition baths were prepared consisting of 2 pounds of 325 
muscovite, 2 grams of ammonium nitrate, 114 grams (on a solid basis) of 
resin and two gallons of distilled water. 
The resin systems compared in the above formulation were as shown in the 
following table. In the subsequent discussion and tabulation of the 
experimental results, the electrodeposited samples are identified by the 
designation of the resin system used. 
TABLE II 
______________________________________ 
Resin System 
______________________________________ 
A. Water Soluble Resins 
A1. Aquanel 513, a water soluble polyester, 
commercially available from Schenectady 
Chemical Company. 
A2. Aquanel 550, a water soluble polyester, 
commercially available from Schenectady 
Chemical Company. 
A3. GE 111-244, a water soluble polyester, 
available from General Electric Company. 
B. Water Dispersion Resins 
B1. Rhoplex TR-407, an acrylic dispersion 
resin, commercially available from Rohm 
and Haas Company. 
B2. Rhoplex AC-1533, an acrylic dispersion 
resin, commercially available from Rohm 
and Haas Company. 
B3. Rhoplex AC-1822, an acrylic dispersion 
resin, commercially available from Rohm 
and Haas Company. 
B4. Cavalite, an acrylic dispersion resin, 
commercially available from E. I. DuPont 
De Nemours and Company. 
______________________________________ 
Mica and binder were electrodeposited on the wire by applying an anodic 
potential of 80 volts D.C. for a time of 180 seconds with the exception 
that the time in sample B2 was 130 seconds and the sample B4 was 120 
seconds. 
In all cases the outer coating was thicker than the inside coating, due to 
an electrical shielding effect. In the case of water soluble resin 
coatings, improved thickness uniformity between the inside and the outside 
as indicated by the ratio of I/O resulted. Water dispersion resins, on the 
other hand were much more influenced by the electrical shielding effect as 
indicated by a significantly lower ratio of I/O. 
The results are shown in the following table: 
TABLE III 
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Resin System 
Inside Outside 
Thickness, 
Thickness, 
I O Ratio 
Bars (mils) (mils) I/O 
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A. Water Soluble Resins 
A1. Aquanel 513 
X 70 98 .71 
Y 78 99 .79 
A2. Aquanel 550 
X 57 98 .58 
Y 60 98 .61 
A3. GE 111-244 X 80 102 .78 
Y 88 112 .79 
B. Water Dispersion Resin 
B1. Rhoplex X 19 49 .39 
TR-407 Y 19 52 .37 
B2. Rhoplex X 42 135 .31 
AC-1533 Y 48 120 .40 
B3. Rhoplex X 45 105 .43 
AC-1822 Y 54 115 .47 
B4. Cavalite X * * * 
Y * * * 
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*Coating did not adhere to test bars and no measurements were possible. 
Similar test bars to those used in the thickness test were also prepared, 
and subjected to a rinse under running water from a faucet. Sample A1, A2 
and A3 remained adherent to the bars. Sample B4 could not be evaluated 
since it had insufficient adhesion to the bar. Sample B3 washed off 
easily. Samples B1 and B2 washed off partially, leaving exposed portions 
of copper, and reduced coating thicknesses in other places. 
EXAMPLE X 
The utility of water soluble epoxyesters in accordance with this invention 
was tested by preparing a one gallon aqueous bath of the following 
ingredients: 
1 lb. of 325 mesh mica 
110 grams Isopoxy 771 (Schenectady Chemicals) 
1 gram NH.sub.4 NO.sub.3 
2 grams Tergitol NP10 surfactant 
A copper bar was immersed in this bath at room temperature and maintained 
at +60 volts for 240 seconds whereupon the bar was removed, dried 24 hours 
at 25.degree. C. and then baked 6 hours at 160.degree. C. The bar was then 
impregnated by vacuum pressure impregnation technique with an epoxy resin 
and then baked at 160.degree. for 6 hours to cure the epoxy resin. The 
result was found to be a uniform coating of about 0.210 inch and was void 
free and of mica content approximating 40 percent. Thus, this coating 
compared favorably with that produced as described above in Example VII. 
EXAMPLE XI 
The suitability of water soluble acrylics was similarly tested in another 
experiment in which a two gallon aqueous bath was prepared by adding the 
following to water: 
2 lbs. of 325 mesh mica 
360 grams Acrysol WS-68 acrylic resin (Rohm and Haas) 
4 grams Tergitol NP10 surfactant 
2 grams Sodium Lauryl sulfate 
2 grams Dimethylaminoethanol 
Again, a copper bar was immersed in this bath and held at +60 volts for 300 
seconds whereupon the bar was removed and treated as in Example X with the 
consequence that a coating of uniform thickness approximating 0.200 inch 
was produced having a mica content of about 40 percent and being void free 
and comparing again favorably with the insulating coating described above 
in Example VII. 
EXAMPLE XII 
A one gallon aqueous bath was prepared by adding the following to water: 
1 lb. of 325 mesh mica 
65 grams Carboxy-terminated butadiene/acrylonitrile (B.F. Goodrich) 
2 grams NH.sub.4 NO.sub.3 
2 grams Tergitol NP10 
1 gram Sodium Lauryl sulfate 
This, thus, was a test of the suitability in accordance with this invention 
of the so called CTBN resins which are as described above blended in 65 
grams of butyl cellosolve and reacted with 4.6 grams dimethylaminoethanol 
to render them water soluble. As in Examples X and XI, a copper bar was 
immersed in this bath and held at 45 volts for 150 seconds then removed 
and processed as described in Example VIII with the result that a uniform 
coating of about 0.12 inch thickness resulted. This insulating coating was 
found to be void free and to have a mica content approximating 40 percent 
and to be therefore quite similar to those of Example VII, VIII and IX 
above. 
EXAMPLE XIII 
To test the suitability of combinations of these anionic water soluble 
resins for the purposes of this invention, a four gallon aqueous bath was 
prepared by adding Acrysol WS-68 and Aquanel 513 in a ratio to each other 
about 1.5 to 1, the actual formulation being as follows: 
480 grams Acrysol WS-68 acrylic resin 
340 grams Aquanel 513 polyester resin 
8 grams Tergitol NPID 
4 grams Sodium Lauryl Sulfate 
8 grams Dimethyl-amino-ethanol 
5 grams Ammonium Nitrate and the balance water. 
Once again, the copper bar test as described in Example VIII was carried 
out with successful results in terms of the resulting insulating coating 
being of uniform thickness approximating 0.21 inch and of mica content 
approximating 40 percent and being void free and altogether a superior 
electrical insulating coating of the sort described above in Example VII. 
EXAMPLE XIV 
The utility of non-ionic polymer in this invention was tested in an 
experiment involving the use of 
1 lb. of 325 mesh mica 
75 grams of polyethyleneglycol (average mica weight 6,000) 
1 gram of ammonium nitrate 
The mixture was added to one gallon of water and a copper bar test was run 
as described above in Examples X-XIII. Thus, the copper bar was immersed 
in this bath and a potential of 60 volts D.C. was applied for about one 
minute the bar being then removed and found to be completely clean. There 
was no mica adherence to the bar at all and the polymer was found of 
itself to be insufficient to hold the mica particles together. 
EXAMPLE XV 
The suitability of a cationic polymer was similarly tested in experiments 
which involved formulation of 
1 lb. of 325 mesh mica 
2 grams of NH.sub.4 NO.sub.3 
80 grams of Poly-2-vinylpyridine dissolved in 80 milliliters of butyl 
cellosolve 
20 grams of acetic acid 
The mixture was prepared in a volume of one gallon with water and agitated 
for 30 minutes in a paint shaker to allow the ingredients to disperse and 
the acid to react with the Poly-2-vinylpyridine to form a polyelectrolyte. 
Then two copper strips were immersed in the bath spaced about two inches 
apart, the potential of 60 volts D.C. was applied to the strips. 
Immediately mica was observed to begin accumulating about the anode while 
at the cathode a gelatinous accumulation was observed. After 60 seconds, 
the voltage was dropped to zero and the strips were removed. The mica 
deposit at the anode having no binder slipped off the wire and could not 
be removed from the bath, thus demonstrating the generic inability of 
cathodic deposition resins to bind or hold material deposited at the 
anode. 
The data obtained from these tests substantiate the fact that in 
electrodeposition of mica improved results can be obtained using anionic 
water soluble resins as compared to water dispersion resins and to 
non-ionic and cationic water soluble resins. 
In this specification and in the appended claims wherever percentage or 
proportion are stated, reference is to the weight basis unless otherwise 
specifically noted. 
It will be appreciated that the invention is not limited to the specific 
details shown in the illustrations, and that various modifications may be 
made within the ordinary skill in the art without departing from the 
spirit and scope of the invention.