Substrate pretreatment with a metal-beta keto ester complex in the method of curing an anaerobic resin

A method of curing an anaerobic resin, which primarily contains acrylic resin, includes externally catalyzing the cure of the resin with a metal-beta keto ester complex having the structural formula: ##STR1## where M is a transition metal; R.sub.1 is selected from the group consisting of alkyl groups having from 1 to 20 carbon atoms, benzene, naphthalene, anthracene, and hydrocarbon substituted aromatic; R.sub.2 and R.sub.3 are selected from hydrogen, alkyl groups having from 1 to 20 carbon atoms, benzene, naphthalene, anthracene and hydrocarbon substituted aromatic; R.sub.4 is selected from alkyl groups having from 1 to 20 carbon atoms; and n is equal to the valence of the metal M.

BACKGROUND OF THE INVENTION 
The use of an anaerobic resin in tape insulation for copper electrical 
coils is taught by J. D. B. Smith et al., in U.S. Pat. Nos. 4,160,178 and 
4,239,802. These anaerobic resins, i.e., resins which will not cure in the 
presence of oxygen, were heretofore vacuum impregnated into uncatalyzed, 
sheet backed mica tape, which was already wound onto an electrical coil. 
The anaerobic resin was then cured, without the application of heat, 
preferably by introduction of a contacting, flowing stream of a selected 
oxygen free inert gas, such as nitrogen. 
While this method of applying and curing anaerobic resins provided deep 
cured insulation, improvements in storage stability, power factor values, 
resin drainage, and better utilization of pressurized, static, inert gas 
cure, would be highly advantageous. A method of easily applying and curing 
anaerobic resins on the surface of a glass, plastic, or metal base, would 
also be useful. 
SUMMARY OF THE INVENTION 
We have found that initially impregnating porous tape insulation, or 
coating a substrate made of, for example, paper, mica, glass, plastic or 
metal, with a composition containing an amount of a metal-beta keto ester 
complex, i.e., metal .beta. keto ester complex, effective to catalyze 
anaerobic resin subsequently applied, improves power factor values and gel 
times, and allows ease of pressurized, static, inert gas cure. The 
metal-beta keto ester complex can be utilized in a solvent carrier, or in 
some instances can be utilized in a resinous carrier. 
More specifically, in the case of impregnating a standard, resin bonded 
mica flake insulating tape wound on an electrical coil, as an initial 
step, in one embodiment of the method of this invention, the coil would be 
vacuum impregnated with a solvent solution of a metal-beta keto ester 
complex, such as, preferably, copper ethylacetoacetate, as a pretreatment 
step. The coil would be dried and then vacuum impregnated with an 
anaerobic resin. Alternatively, the bonding resin used in the mica tape 
could be of an acrylic based anaerobic type, and include a metal-beta keto 
ester complex, such inclusion in the bonding resin would still be 
considered a pretreatment of the mica tape. 
Thus the metal-beta keto ester complex is applied as part of a composition, 
where the carrier of the composition is a suitable solvent or a resin. The 
preferred anaerobic resin, used either as the mica bonding resin or as the 
final insulation, would contain at least one polyacrylic resin, such as 
neopentyl glycol diacrylate, tetraethylene glycol diacrylate and the like, 
and may contain minor amounts of initiators, such as cumene hydroperoxide; 
accelerators, such as triphenyl amine; coaccelerators; and stabilizers, 
such as hydroquinone. It is to be understood, that the term "anaerobic 
resin" is meant to include such minor amounts of initiators, accelerators, 
coaccelerators, stabilizers, and the like. Epoxy resins, along with 
optional associated anhydride or other curing agents and latent 
accelerators could also be added to the anaerobic resin. 
After vacuum impregnation with anaerobic resin and draining, the coil would 
be placed in a sealed tank, purged with a nitrogen stream and then 
pressurized with nitrogen at about 40 psig. After about 16 hours the 
anaerobic insulation would be completely cured by the nitrogen gas and the 
coil could be removed. 
By utilizing a metal-beta keto ester complex as an anaerobic resin catalyst 
in the porous tape insulation, or on the substrate to be coated, very high 
concentrations of the complex can be used, causing rapid gelation and 
complete cure of the anaerobic resin. In addition, very long resin storage 
lifetimes result, because the catalyst is external to the main portion of 
the insulating resin. The metal-beta keto ester complex is effective in 
providing outstanding gelation and cure, providing a very hard resin that 
resists debilitation upon aging. The metal-beta keto ester complex is 
capable of dissolution in suitable solvents to allow substrate 
pretreatment, with the ability of not leaching into the anaerobic resin 
during vacuum impregnation. Other materials, such as metal acetates and 
metal acetylacetonates are much less effective to pretreat substrates in 
the manner described above.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIG. 1 of the Drawings in order to better understand the 
invention, a copper or aluminum conductor 1, is shown. The conductor is 
wound with a plurality of layers of mica tape or other type of insulation 
2 and one layer of woven tape insulation 3, which helps hold the 
insulation 2 in place. The insulation 2 can, for example, consist of mica 
paper or mica flakes or splittings bonded to a sheet backing of cellulose 
paper, cotton cloth, woven glass cloth, or the like, i.e., mica tape, by 
an effective amount of bonding resin, that can itself be an anaerobic 
resin or that is compatible with anaerobic resin 4, which impregnates the 
insulation. The metal-beta keto ester complex used in this invention can 
be applied to the wound conductor prior to final anaerobic resin 
application, or it can be used in the bonding resin which adheres the mica 
to its sheet backing. Where it is used as a component of the bonding 
resin, it will still have the capability of intermixing and migrating to 
the subsequently applied anaerobic resin to provide a catalytic effect on 
the anaerobic resin. 
FIG. 2 of the Drawings shows a flat substrate 10, which can be a plastic, 
such as polycarbonate, polymethyl methacrylate or the like; metal, such as 
copper, brass, aluminum or plated steel; glass; wood; a decorative or 
industrial laminate such as phenolic, polyester or epoxy resin impregnated 
glass cloth, cotton cloth or cellulose paper; mica tape insulation; 
cellulose paper; cotton cloth; woven glass cloth; and the like, covered 
and/or impregnated on side 11 with an anaerobic resin insulating and/or 
protective and/or adhesive film 12. The film 12 may also cover the other 
side 13 or completely encapsulate the substrate 10. The film 12 may serve 
as an adhesive bond for a similar flat article disposed on the top of flat 
substrate 10, i.e., a composite or laminate of two flat sheets. The 
substrate 10 can be of a variety of shapes. The metal-beta keto ester 
complex of this invention can be applied to the side 11 prior to 
application of anaerobic resin 12. 
The anaerobic resin used in this invention is a resin which will not cure 
in the presence of oxygen dissolved therein. However, it is capable of gas 
penetration, and will deep cure, in the method of this invention, at room 
temperature, when placed in an oxygen free environment containing a gas 
effective to displace the dissolved oxygen. By "deep cure" is meant, 
curing to a solid state to depths of about 6 inches. 
The anaerobic insulating resins used in the method of this invention will 
preferably contain aliphatic polyacrylics such as diacrylate and 
triacrylate resins, which polymerize by addition through a double bond. 
Commonly used polyacrylic resins include neopentyl glycol diacrylate and 
tetraethylene glycol diacrylate. The anaerobic insulating resin may also 
contain aliphatic monoacrylic resins such as ethyl methacrylate and 
aromatic, reactive vinyl monomers such as styrene. Well known organic 
initiators, such as cumene hydroperoxide are used to help initiate cure. 
Small effective amounts of well known, organic accelerators, usually 
tertiary amines such as N,N-dimethyl-p-toluidine, and a small effective 
amount of organic coaccelerator, usually an organic sulfimide such as 
benzoic sulfimide, may be present to reduce curing time. The initiator is 
stabilized with a stabilizer such as hydroquinone. A variety of epoxy 
resins may be used in this invention to provide improved electrical, 
curing, shrinkage and high temperature stability properties. 
Although the chemistry of the anaerobic resins used in the method of this 
invention is very complex, and not completely understood even at this 
time, it is believed that the unique curing characteristic of the material 
of this invention is linked to the tendency for the organic peroxide 
initiator, i.e., hydroperoxide or perester, to be stabilized in an 
oxygen-rich atmosphere, or by dissolved oxygen in the resin itself: 
##STR2## 
An equilibrium is attained between the organic peroxide free radical 
initiator and its decomposition products in an air or an oxygen-containing 
environment. Presumably, the small amount of free radicals produced under 
these conditions are "quenched" or stabilized by organic reaction 
inhibitors such as hydroquinone. However, when the equilibrium is moved to 
the right, i.e., by decreasing the oxygen content, such as displacement by 
N.sub.2, the concentration of free radicals will increase sharply and the 
inhibitor is no longer able to quench all of them. 
At some critical point, the peroxide radicals or their by-products will 
begin to initiate polymerization. The function of accelerators or 
coaccelerators would be to speed up the rate of decomposition of the 
organic peroxide, thereby giving a faster gelation time for the 
impregnants. The gaseous atmosphere, such as nitrogen, functions as a 
resin permeable cure initiator. 
The anaerobic resins used in this invention contain a variety of components 
which allow a chain reaction mechanism to proceed, resulting in deep resin 
cure. Without using heat, reaction kinetics and component interaction are 
of prime importance in cure. All resin systems contain small quantities of 
dissolved O.sub.2, due to O.sub.2 permeation from the atmosphere i.e., 
about 1.0 to 10 volume %. A normal vacuum of about 3 to 5 mm. of Hg will 
not remove this O.sub.2 to a level of below about 0.5 volume %, which is 
required in the method of this invention. A vacuum of below 1 mm. of Hg 
might remove the dissolved O.sub.2 but would also probably eliminate some 
required reactive species, and is commercially unfeasible. 
Suitable diffusion gases, i.e., gases that are soluble in the resin and 
effective to permeate the resin and displace substantially all of the 
dissolved O.sub.2 therein, are preferably, argon, helium, carbon dioxide, 
methane, hydrogen, and most preferably nitrogen. By "displace" is meant 
removal of oxygen to a level below about 0.5 volume % i.e., below 0.5 
volume % O.sub.2. Below this amount, the chain reaction cure will proceed 
between the combination of ingredients in the resin. Argon, helium and 
carbon dioxide are the most effective to displace O.sub.2, but nitrogen is 
preferred because it is commercially available in pure form free of 
moisture. Of course, other gases or gas mixtures effective to act as 
defined above can be used. It is also possible that these diffusion gases 
might in some way interact with some components of the resin formulation 
to push the reaction to polymerization. 
It is thought that there is a complex interaction between all of the 
components present in the anaerobic resins described herein. The free 
radical initiator must be present in an amount effective to initiate 
acrylic or vinyl monomer cross linking or polymerization. The accelerator 
must be present in an amount effective to activate the peroxide to form a 
complex. The coaccelerator must be present in an amount effective to cause 
decomposition of the peroxide free radical initiator, and the reaction 
inhibitor must be present in an amount effective to prevent peroxide 
decomposition when O.sub.2 is present in the resin. 
However, a major problem in past systems has been the requirement of 
limiting the amount of accelerator and coaccelerator used in the anaerobic 
resin mixture, because excessive amounts of these ingredients drastically 
cut down the pot life of the resin to below about 3 weeks. Since 
commercial utilization of anaerobic resins for coil insulation 
impregnation requires large quantities of the resin in a dipping and 
vacuum impregnation step, storage stability of the resin is a very 
important consideration, and should last over about 8 weeks at ambient 
temperatures. 
This invention pretreats the article to be impregnated or coated, with a 
composition containing a metal complex of a beta keto ester, which, when 
the keto ester is added in an effective amount, acts as a catalyst for the 
anaerobic resin upon contact. This pretreatment accomplishes a result 
similar to drastically increasing the accelerator and coaccelerator 
content of the anaerobic resin, i.e., dramatically increasing gel time of 
the anaerobic resin, and substantially lowering resin loss through 
drainage, without, however, decreasing the pot life of the anaerobic 
resin. Use of this pretreatment also increases resin pick up, allows 
complete cure without heating, and importantly, provides a very hard resin 
that resists debilitation upon aging. Power factor values of anaerobic 
resins cured in conjunction with the pretreatment of this invention are 
shown to be outstanding. Only a very small class of compounds are 
effective, however, to pretreat the substrate and accomplish the above 
described results. 
As an initial step, the article to which an anaerobic resin is to be 
applied is painted, dipped, sprayed, or if porous, preferably vacuum 
impregnated with a concentrated amount of a metal-beta keto ester complex, 
preferably a metal alkylacetoacetate. An effective amount of the 
metal-beta keto ester complex to be in contact with an anaerobic resin, is 
a concentration of between about 10 mg. to about 1,000 mg. per liter of 
suitable solvent applied to the article, preferably between about 100 mg. 
to about 450 mg. per liter of suitable solvent. Below 10 mg. per liter and 
little catalytic effect on the contacting anaerobic resin is evidenced. 
Over 1,000 mg. per liter and leaching back into the impregnating or 
coating dip solution is probable. Suitable solvents include acetone, 
methylene chloride, toluol, and the like. Thus, the composition containing 
the metal-beta keto ester complex will coat and/or be carried into the 
interstices of the article to be coated or impregnated with anaerobic 
resin, and will be present in major amounts to contact the anaerobic resin 
and catalyze the anaerobic resin cure mechanism. 
As an alternative, the metal-beta keto ester complex may be included in the 
resin initially used as a first impregnant or bonding resin for the 
article, when the article is, for example, a mica tape or glass cloth. In 
this case an effective amount of metal-beta keto ester complex to be in 
contact with an anaerobic resin is a concentration of between about 10 mg. 
to about 1,000 mg., preferably between about 150 mg. to about 450 mg. per 
liter of suitable resin for the article; where the metal-beta keto ester 
complex solution is admixed with the bonding resin, in a weight ratio of 
(metal-beta keto ester complex):(bonding resin) of between about (0.5 to 
2):(10), said resin preferably having an acrylic base. 
The useful metal-beta keto ester complex, has the following structural 
formula: 
##STR3## 
where M is a transition metal such as titanium, vanadium, chromium, 
manganese, iron, cobalt, nickel, zinc, and preferably copper. R.sub.1 is 
selected from alkyl groups having from 1 to 20 carbon atoms, preferably 1 
to 4 carbon atoms, benzene, naphthalene, anthracene and hydrocarbon 
substituted aromatic; R.sub.2 and R.sub.3 are selected from hydrogen, 
alkyl groups having from 1 to 20 carbon atoms, preferably 1 to 4 carbon 
atoms, benzene, naphthalene, anthracene and hydrocarbon substituted 
aromatic; and R.sub.4 is selected from alkyl groups having from 1 to 20 
carbon atoms, preferably 1 to 4 carbon atoms. In the formula, n is equal 
to the valence of the metal used in the complex. The term "hydrocarbon 
substituted aromatic" is meant to include for example aralkyl groups, such 
as 
##STR4## 
where R.sub.5 is selected from alkyl groups having from 1 to 10 carbon 
atoms. 
The preferred catalyst, copper ethylacetoacetate has the following 
structural formula: 
##STR5## 
In structures (I) and (II), the metal in the complex is "bonded" to two 
and possibly three oxygen atoms. The key to catalytic activity is thought 
to be the --O--R.sub.4 group, which is though to act as an electron donor 
for the diketo group. Metal acetates on the other hand are strictly ionic, 
and metal acetylacetonates do not contain any oxygen bonding the R.sub.4 
radical to the diketo part of the molecular structure. 
The metal complex of a beta keto ester appears to be unique in its ability 
to dissolve in a suitable solvent, to remain on or in the article after 
pretreatment, to not leach back out into the anaerobic resin bath so that 
the bath retains its lengthy pot life, and to effect rapid gelation and 
very hard cure of the anaerobic resin. Other compounds, such as copper 
acetate, cobalt acetate, manganese acetate, copper acetylacetonate, cobalt 
acetylacetonate and manganese acetylacetonate are not effective in 
reducing the gel time and preventing resin loss through drainage, 
apparently having little or no catalytic effect on the anaerobic resin. 
The component R.sub.4 in structure (I) above, attached to the ester oxygen, 
appears to play some part in the catalytic effect which is not understood 
at this time. While not wanting to be held to any particular theory, the 
R.sub.4 component is thought to be an electron donor to both the attached 
keto oxygen, and to the ester oxygen, thereby increasing their 
nucleophilic (electron density) nature. This may cause the transition 
complex thought to be formed between the metal complex beta keto ester and 
the peroxide initiator to be more reactive, and promote a catalytic effect 
on the anaerobic resin polymerization rate. The --O--R.sub.4 group also 
appears to increase the solubility of the compound in a wide range of 
solvents. 
The solventless anaerobic resins used to coat or impregnate articles 
according to this invention have extremely useful and widespread 
applications. One of the obvious advantages of this pretreatment-anaerobic 
coating or impregnation method is that these resins would not require any 
heat treatment to completely gel. This would offer the possibility of 
eliminating baking ovens in the curing method thereby reducing capital 
expenditures and saving valuable floor space in manufacturing plants. 
Also, heat energy and hence fuel costs would be drastically curtailed. 
Other notable advantages of this method would be lower resin "run-off" from 
coils and stators, reduced air pollution arising from volatile substances 
in the curing oven, and the elimination of damaging mechanical stresses 
sometimes found in the manufacture of larger coils and stators, from 
copper expansion effects during the heat treatment of resins. On some 
articles, the reduction of "run off" would mean more uniform resin 
coverage, rather then coverage at the top of the article, where drainage 
has caused a high bottom resin concentration. 
The acrylic and acrylic-epoxy anaerobic resins of this invention can be 
formulated to have viscosities as low as 1 cps., making them uniquely 
applicable for coating and impregnation of multiple layered mica insulated 
high voltage coils. These resins can also be formulated for use as wire 
enamel resins. These acrylic and acrylic-epoxy anaerobic resins can also 
find particularly useful application as insulating potting resins for 
transformers and insulating casting resins for bushings which may be used 
in power circuit breakers, since they can be deep cured to 6 or more 
inches without requiring heat. Following cure by the static, pressurized, 
or flowing diffusion gas, the resins can be optionally post-cured in an 
oven for up to 48 hours at 100.degree. C. to 175.degree. C. In most 
instances the electrical properties of the diffusion gas cured resins are 
more than adequate, and post-curing is not necessary, due to inert gas 
contact in a manner effective to displace oxygen dissolved in the resin, 
causing cure initiation. 
The anaerobic resin will hereinafter be discussed primarily for use in an 
impregnating process, but it is to be understood that its use is not so 
limited. Referring again to FIG. 1 of the Drawings, the conductor 1 is 
preferably copper because it is most widely used conductor for electrical 
insulation although other metals can also be used. The primary insulation 
is preferably mica, especially for high voltages, as it has excellent 
electrical properties. Glass, polyester, Nomex, a polyamide believed to be 
made from meta phenylene diamine and isophtaloyl chloride, and other types 
of insulation could also be used, either alone, in mixtures, or in 
mixtures with mica. 
Mica insulation is usually made with a polyester fabric backing to hold the 
mica together. The insulation may be a tape which is wrapped around the 
conductor, the amount of insulation depending upon the voltage drop across 
the insulation. The mica is preferably coated with about 3% to 30%, 
preferably about 5% to about 12%, by weight based on the mica insulation 
weight, of a separate bonding resin which is compatible and co-reactive 
with the impregnated anaerobic resin, in order to insure a better bond 
between the mica and between the mica and the fabric backing. Such bonding 
resins include polyesters, polybutadienes, acrylic based resins also 
having anaerobic cure properties, and the like. 
The anaerobic resin used in this invention is an admixture comprising 
(acrylic resin):(aromatic reactive vinyl monomer):(epoxy 
resin):(anhydride) in a weight ratio of from about (10):(0 to 120):(0 to 
100):(0 to 60). This resin also contains, for 100 parts by weight of total 
resin: 0.001 to 10 parts initiator, 0.01 to 10 parts accelerator, 0.01 to 
10 parts coaccelerator, and 0.001 to 1 part free radical stabilizer. The 
acrylic resin will preferably contain a ratio of (aliphatic, poly, i.e., 
di, tri, or tetra acrylic resin):(monoacrylic resin) of from, about 
(10):(0 to 20), however the acrylic component can contain all monoacrylic 
resin. 
Polyacrylic resins that are useful and preferred in the insulating resin of 
this invention are selected from the group of aliphatic, organic 
diacrylates such as, for example, tetraethylene glycol dimethacrylate, 
tetraethylene glycol diacrylate, hexamethylene glycol dimethacrylate, 
neopentyl glycol diacrylate, neopentyl glycol dimethacrylate, 
hexamethylene glycol diacrylate, ethylene glycol dimethacrylate, 
trimethylene glycol diacrylate, bisphenol A dimethacrylate, ethoxylate 
bisphenol A diacrylate, and the like; aliphatic, organic triacrylates such 
as, for example, trimethylol propane triacrylate, and the like; and 
aliphatic, organic tetracrylates such as pentaerythritol tetracrylate, and 
the like; and their mixtures. The preferred acrylic resins are 
tetraethylene glycol diacrylate and neopentyl glycol diacrylate. 
Aliphatic or cyclic, monoacrylic resins, and aromatic, reactive vinyl 
monomers can be used with the preferred polyacrylics. Those particularly 
useful are, for example, organic aliphatic monoacrylates, such as ethyl 
acrylate, 2-ethyl acrylate, 2-ethylhexyl acrylate, ethyl methacrylate, 
glycidyl methacrylate, allylmethacrylate, and the like; cyclic monoacrylic 
resins, such as cyclohexyl methacrylate, and the like; vinyl acids such as 
acrylic acid, methacrylic acid and the like; and organic, aromatic, 
reactive vinyl monomers, such as vinyl pyridine, vinyl toluene, tertiary 
butyl styrene, styrene, and the like. The preferred monoacrylics and 
reactive vinyl monomers are ethyl methacrylate, 2-ethylhexyl acrylate and 
styrene. These materials act as reactants and diluents for the preferred 
polyacrylics and optional epoxy resin. 
The epoxy resins that can be used as a component of the anaerobic resins 
used in this invention, include diglycidyl ethers of bisphenol A, 
diglycidyl ethers of bisphenol F, polyglycidylethers of a novolac, 
glycidyl ester epoxy resins, hydantoin epoxy resins, cycloaliphatic epoxy 
resins, diglycidyl ethers of an aliphatic diol having from 2 to 12 carbon 
atoms, and mixtures thereof. 
All of the above described epoxy resins can be characterized by reference 
to their epoxy equivalent weight, which is defined as the mean molecular 
weight of the particular resin divided by the mean number of epoxy 
radicals per molecule. In the formulations used in the invention, all of 
the suitable epoxy resins will have a preferred epoxy equivalent weight of 
from about 100 to about 500, with a most preferred range of about 150 to 
about 250. All of these epoxy resins are well known in the art, and are 
described in detail, for example, in U.S. Pat. No. 4,160,178, herein 
incorporated by reference. 
In many instances, organic, carboxylic acid anhydrides reactive with the 
epoxy, are used in the resin formulation. These anhydrides include the 
conventional organic mono- and poly-functional anhydrides. Typical of the 
mono-functional anhydrides are hexahydrophthalic anhydride, 
1-methylhexahydrophthalic anhydride, tetrahydrophthalic anhydride, 
1-methyltetrahydrophthalic anhydride, phthalic anhydride, NADIC anhydride, 
NADIC methylanhydride, dodecenyl succinic anhydride and the like. 
Poly-functional anhydrides which may be employed include pyromellitic 
dianhydride, polyazelaic polyanhydride, the reaction product of 
trimellitic anhydride and an organic glycol, and benzophenone 
tetracarboxylic acid dianhydride. These organic anhydrides may be used 
singly or in admixture. 
In some instances, latent accelerators may also be used for improving the 
electrical properties of the anaerobic resins. These latent accelerators 
are well known in the epoxy resin curing art, and a number of them are 
described in U.S. Pat. Nos. 3,868,613, 4,020,017, and 4,254,351, herein 
incorporated by reference. They include organic quaternary ammonium salts, 
organic quaternary phosphonium salts, quaternary organo-tin compounds, and 
metal acetylacetonates, among others. Examples of some useful latent 
accelerators would include, for example, trimethyl ammonium chloride, 
methyltrioctyl phosphonium dimethyl phosphate, triphenyl tin acetate, 
chromium acetylacetonate, manganese acetylacetonate, and the like. They 
are well known in the art, and can be used between 0.001 to 2 parts per 
100 parts total resin. 
Free radical initiators particularly useful in the resin formulations used 
in this invention are, preferably, effective amounts of 2,2'-azobis 
(2-methyl propionitrile), or organic peroxides, such as, for example, 
cumene hydroperoxide, t-butyl perbenzoate, t-butyl hydroperoxide, benzoyl 
peroxide, 2,5-dimethyl-2,5 bis (benzoylperoxy) hexane, and the like. They 
are well known in the art, and can be used between 0.001 to 10 parts per 
100 parts total acrylate+aromatic vinyl monomer+epoxy+anhydride i.e., per 
100 parts total resin. 
Free radical reaction accelerators, used to initiate cure, which are 
particularly useful under the cure conditions of this invention are, 
preferably, organic amides and amines, such as, for example 
N,N'-diethylformamide, N,N-dimethyl-p-toluidine, N,N-diethyl-p-toluidine, 
triphenylamine, and the like. They are well known in the art, and can be 
used between 0.01 to 10 parts per 100 parts total resin. Organic 
elastomeric accelerators, such as mercapto benzothiazole, and the like are 
also useful, in the same amounts as above, in some instances. 
Free radical reaction coaccelerators, used to reduce curing time, which are 
particularly useful under the cure conditions of this invention are, 
preferably, organic sulfimides, such as, for example, benzoic sulfimide, 
and the like. They are well known in the art, and can be used between 0.01 
to 10 parts per 100 parts total resin. 
Free radical stabilizers, used to stabilize the initiator, particularly 
useful in the resin used in this invention, are effective amounts of 
organic reaction inhibitors such as, for example, hydroquinone, 
parabenzoquinone, acidic compounds such as di-nitrophenols, 
trinitrophenols, picric acid, cresylic acid, and the like. They are well 
known in the art, and can be used between 0.001 to 1 part per 100 parts 
total resin. 
The vacuum pressure impregnation process is a preferred method of 
insulating a wrapped conductor, because it leaves very few air gaps in the 
insulation. In this process, the pretreated mica tape wrapped conductor is 
placed in a tank or other type pressure container which is then evacuated 
to remove oxygen. The anaerobic resin is admitted under pressure, usually 
at least about 45 psi., although about 90 psi. to about 100 psi. is 
preferred. The resin should saturate the insulation. Typically, the 
insulation will contain about 5% to about 35%, by weight based on the 
insulation weight, of the resin, although about 20% to about 30% is 
preferred. The resin is then permitted to drain from the wrapped 
conductor. 
The resin impregnated insulation then is cured by contact with a gas which 
does not contain any significant amount of oxygen. This may be 
accomplished in the same tank, or the wrapped conductor may be cured in a 
separate tank. Oxygen is again evacuated from the tank and the inert gas 
is fed into the tank at 25.degree. C. Nitrogen, or carbon dioxide, or 
mixtures of these two gases are preferred as they are inexpensive, safe, 
and easy to handle, but other inert gases may also be used, such as argon, 
helium, methane or hydrogen. It has been found that if nitrogen or carbon 
dioxide are used, the rates of cure are optimum at a continuous inert gas 
stream flow of about 6 lpm to about 20 lpm (liters per minute). Instead of 
a gas flow across the insulation, a 20 psi. to 200 psi. static gas 
pressure can be maintained in a closed tank to cure the resin. Times 
involved in either instance are from about 4 to 24 hours for complete 
cure. 
Referring now to FIG. 3 of the Drawings, there is illustrated a coil 
suitable for use in high-voltage electric motors and generators. The full 
coil would be disposed within the slots of the metal stator surrounding 
the metal motor armature or generator rotor and could also be used in the 
armature and rotor slots. The coil comprises a plurality of turns of 
conductors 20. Each turn of the conductor 20 consists essentially of a 
copper bar or wire wrapped with insulation 21, such as glass fiber cloth, 
paper, mica paper, or aramid paper. 
The turn insulation is not adequate to withstand the severe voltage 
gradients that will be present between the conductor and ground when the 
coil is installed in a high-voltage electrical machine. Therefore, ground 
insulation for the coil is provided by wrapping plural layers of composite 
mica tape 22 about the turn 20. Such composite tape 22 can comprise a 
pliable backing sheet 24 of, for example, polyethylene terephthalate mat, 
having a layer of mica flakes 26 bonded thereto. The mica tape can have 
metal-beta keto ester complex therein as part of the bonding resin or can 
have metal-beta keto ester complex deposited from solution on and into the 
resin bonded mica. 
The tape may be applied half lapped, abutted or otherwise. Generally, a 
plurality of layers of the composite tape 22 are wrapped about the coil, 
with sixteen or more layers generally being used for high voltage coils. 
In such instances, anaerobic resins are particularly useful, since they 
can be formulated with viscosities as low as 1 cps. and can be deep cured. 
To impart better abrasion resistance and to secure a tighter insulation, a 
wrapping of an outer tape 28 of a tough fibrous material, for example, 
glass fiber or the like may be applied to the coil. 
The mica tape 22 for insulating the coils shown in FIG. 3 may be prepared 
from a sheet backing support material upon which is disposed a layer of 
mica in the form of integrated flake paper, flakes, splittings, or very 
fine particle size mica paper. The sheet backing and the mica are 
contacted and impregnated with the anaerobic resinous impregnant. This 
mica insulation is preferably in the form of a tape of the order of 
one-half inch to two inches in width, though sheet insulation of any other 
width may be prepared. 
For building electrical machines, such as motors and generators, the sheet 
backing 24 for the mica may comprise cellulose paper, cotton fabric, linen 
fabric, woven glass cloth, glass fibers, mats or fabrics prepared from 
nylon, polyester, polyethylene, linear polyethylene terephthalate, 
polyamide, and aramid fiber, or additional mica paper sheets. Sheet 
backing material of a thickness of approximately 1 mil (0.001 in.), to 
which there has been applied a layer of from 3 mils to 10 mils thickness 
of mica has been successfully employed. 
Mica flakes are generally about 1/16 inch to 3/4 inch square while mica 
splittings are generally about 3/4 inch to 3 inches square. Integrated 
mica flake paper is made of compacted mica particles about 1/32 inch to 
1/2 inch square, and fine mica paper is made of compacted mica particles 
about 1/64 inch to 1/16 inch square. 
The mica tape is wrapped around the coil and then is impregnated with the 
anaerobic resin in a vacuum so that there is complete saturation between 
mica layers. Then, an inert gas is introduced and forced to contact the 
anaerobic resin, which upon continued exposure to the penetrating 
non-oxygen containing atmosphere, will deep cure to provide a thermally 
stable, tough, cured insulation in the thermoset state. The same pressure 
container used for impregnation can be used to flow the inert gas or 
introduce it under 20 psi. to 200 psi. pressure. 
A closed full coil 30 is shown in FIG. 4 of the Drawings. It comprises an 
end portion comprising a tangent 31, a connecting loop 32 and another 
tangent 33 with bare leads 34 extending therefrom. Slot portions 35 and 36 
of the coil, which sometimes are hot pressed to form them to predetermined 
shape and size are connected to the tangents 31 and 33 respectively. These 
slot portions are connected to other tangents 37 and 38 connected through 
another loop 39. 
The acrylic or acrylic-epoxy resins of this invention are useful as 
insulation in motor armature and stator coils as well as stator coils and 
rotor field windings in generators. The acrylic or acrylic-epoxy resins of 
this invention are also particularly useful for encapsulating large 
electrical apparatus such as transformers, since they are highly fluid, 
having viscosities at 25.degree. C. of between about 1 cps. and about 
2,000 cps. Over 2,000 cps. and it would be difficult to impregnate thick 
mica windings. After encapsulation, the resin can be exposed to a gas 
effective to deep cure the resin. Thus, run-off of resin from coils can be 
minimized, to yield insulation having good electrical, shrinkage and 
thermal stability properties. The anaerobic resin can also contain up to 
about 100 parts of filler particles, such as alumina, alumina trihydrate, 
silica and the like, of average particle sizes of from about 10 microns to 
about 300 microns, per 100 parts of total resin. 
The electrical properties of the anaerobic resins described hereinabove can 
be further improved by post-curing for up to about 48 hours at 
temperatures of up to about 175.degree. C. This is an optional step that 
may be utilized when the end use is a high voltage application. The method 
of this invention is shown in diagram form is FIG. 4 of the Drawings, 
where article 40, be it a mica insulated coil or a polycarbonate sheet, is 
pretreated by pretreatment means 41, to apply metal alkylacetoacetate. 
Anaerobic resin is then applied by resin application means 42, after which 
the anaerobic resin is cured by an oxygen free inert gas in contact means 
43. 
EXAMPLE 1 
Six aluminum rods, 6 inches long and 1/2 inch in diameter, were 1/2 lap 
wrapped with three layers of glass cloth. Four of the glass covered rods 
were dipped at 25.degree. C. in a pretreatment bath of copper 
ethylacetoacetate (CuEA) for 5 minutes. The bath contained 100 mg. of 
copper ethylacetoacetate per liter of acetone solvent. After dipping the 
impregnated rods were air dried at 25.degree. C. Two glass covered rods 
were not pretreated with copper ethylacetoacetate. 
Two anerobic resin compositions were prepared. Composition 1 consisted of: 
375 grams of tetraethylene glycol diacrylate; 125 grams of styrene; 10 
grams of cumene hydroperoxide initiator; 0.75 gram of 
N,N'-dimethyl-p-toluidine accelerator; 2.0 grams of benzoic sulfimide 
coaccelerator; and 0.4 gram of hydroquinone inhibitor. This provided an 
anaerobic resin having a weight ratio of acrylic resin:aromatic reactive 
vinyl monomer of 10:3.3. The parts additives per 100 parts resin 
(acrylic+styrene) were: 2.0 parts total organic free radical initiator; 
0.15 part organic free radical accelerator; 0.40 part organic 
coaccelerator; and 0.08 part free radical stabilizer. The viscosity of the 
resin was about 75 cps at 25.degree. C. This provided a relatively simple, 
two component anaerobic resin composition. 
Composition 2 anaerobic resin consisted of: 175 grams of neopentyl glycol 
diacrylate; 175 grams of tetraethylene glycol diacrylate; 50 grams of 
trimethylol propane triacrylate; 25 grams of ethylmethacrylate; 50 grams 
of styrene; 25 grams of a liquid diglycidyl ether of bisphenol A epoxy 
resin having a viscosity at 25.degree. C. of about 8,000 to 10,000 cps. 
(sold commercially by Dow Chemical Co. under the tradename DER 828); 10 
grams of cumene hydroperoxide initiator; 0.75 gram of 
N,N'-dimethyl-p-toluidine accelerator; 2.0 grams of benzoic sulfimide 
coaccelerator; and 0.4 gram of hydroquinone inhibitor. This provided an 
acrylic:styrene:epoxy anaerobic resin. The anaerobic resin had 425 grams 
total acrylic resin, where the weight ratio of polyacrylic 
resin:monoacrylic resin was 400:25 or 10:0.62. The weight ratio of acrylic 
resin:aromatic reactive vinyl monomer:epoxy, resin was 10:1.2:0.6. The 
parts additive per 100 parts resin (acrylic+styrene+epoxy) were: 2.0 parts 
total organic free radical initiator; 0.15 part organic free radical 
accelerator; 0.40 part organic coaccelerator; and 0.08 part free radical 
stabilizer. The viscosity of the resin was about 100 cps., at 25.degree. 
C. 
Two of the copper ethylacetoacetate pretreated rods, Samples (1) and (2) 
and one of the untreated rods, Sample (3), were immersed in a pressure 
vessel containing a bath of Composition 1 anaerobic resin; and two of the 
copper ethylacetoacetate pretreated rods, Samples (4) and (5), and one of 
the untreated rods, Sample (6), were immersed in another pressure vessel 
containing a bath of Composition 2 anaerobic resin. In both cases the 
vessel was evacuated for 20 minutes. All the rods were then removed from 
the anaerobic resin, allowed to drain for 1/2 minute while standing in an 
upright position, during which time some resin drained off, and then 
Samples (1), (3), (4) and (6) were placed in a pressure vessel. The 
pressure vessel was then sealed, purged with oxygen free nitrogen gas for 
15 minutes, at a flow rate of about 15 liters/minute, and then pressurized 
with the oxygen-free nitrogen gas to 45 psig., for 24 hours at about 
25.degree. C., to displace substantially all oxygen. The nitrogen treated 
rods were then removed from the pressure vessel. Measurements for resin 
pickup and drainoff are shown below in Table I: 
TABLE I 
______________________________________ 
Initial Resin Final Observations 
Resin Run-Off Resin 24 hr. N.sub.2 
Sample Pick-Up 1/2 min. drain 
Pick-Up 
cure 
______________________________________ 
(1) CuEA+ 
7.02 g. 0.53 g. 6.49 Resin hard. 
Comp. 1 Evenly com- 
pletely 
cured. No 
odor of 
acrylate. 
(3)* 7.11 g. 0.83 g. 6.28 Resin hard. 
Comp. 1 Thin on top 
and heavy on 
bottom. 
Some odor. 
(4) CuEA+ 
7.21 g. 0.77 g. 6.44 Resin hard. 
Comp. 2 Evenly com- 
pletely 
cured. No 
odor of 
acrylate. 
(6)* 6.19 g. 1.21 g. 5.98 Resin hard. 
Comp. 2 Thin on top 
and heavy on 
bottom. Some 
odor. 
______________________________________ 
*Comparative Samples: no copper ethylacetoacetate pretreatment. 
No leach out of copper ethylacetoacetate into the resin bath was apparent. 
Sample (2), containing CuEA+Comp. 1, and Sample (5), containing CuEA+Comp. 
2, were not nitrogen cured and failed to gel in air over a 10 day period, 
showing that Compositions 1 and 2 were anaerobic and were cure inhibited 
by air. 
As can be seen from Table I, the copper ethylacetoacetate pretreated and 
nitrogen cured rods, Samples (1) and (4), exhibited greater final resin 
pickup and less resin runoff: for resin Composition 1, Sample (1) had 7.5% 
resin drain, while comparative Sample (3) had 11.7% resin drain. For resin 
Composition 2, Sample (4) had 10.6% resin drain, while comparative Sample 
(6) had 19.6% resin drain. The final results show a substantial increase 
in resin content for the glass cloth wrapped rod, for both Composition 1 
and 2 anaerobic resins, by pretreating with a metal-beta keto ester 
complex prior to impregnation with the anaerobic resin. This pretreatment 
allows even resin distribution upon cure, as in Samples (1) and (4), 
rather than thin resin coverage at the top of the rod and heavy resin 
coverage at the bottom of the rod, due to heavy drainage, as in 
comparative Samples (3) and (6). Additionally, pretreatment with the 
metal-beta keto ester complex eliminates heat energy requirements, reduces 
volatiles, and lowers air pollution. 
EXAMPLE 2 
Two, 24 inch long, 4.16 kV. stator coils, Samples (7) and (8), similar to 
those shown in FIG. 3 and FIG. 4 of the drawings, were each separately 
immersed, as a pretreatment step, in a pressure vessel containing a bath 
solution of copper ethylacetoacetate (CuEA). The coils were wrapped with 
mica splitting tape comprising polyester bonding resin and polyethylene 
terephthalate fabric backing. The copper ethylacetoacetate concentration 
was 200 mg. per liter of acetone solvent, and the bath temperature was 
about 25.degree. C. 
Each coil was evacuated for 20 minutes in the copper ethylacetoacetate 
solution, for complete impregnation. Each coil, impregnated with the 
copper ethylacetoacetate solution was then immediately placed in a 
separate pressure vessel and evacuated for 30 minutes until dry. Each 
coil, impregnated with copper ethylacetoacetate was next immersed in a 
pressure vessel containing a bath of anaerobic resin and evacuated for 30 
minutes. Each coil was then removed from the anaerobic resin bath, allowed 
to drain for 1/2 minute, during which time some resin drained off, and 
then placed in a separate pressure vessel. 
The pressure vessel was then sealed, purged with oxygen free nitrogen gas 
for 60 minutes at a flow rate of about 15 liters/minute, and then 
pressurized with the oxygen-free nitrogen gas to 40 psig. for 16 hours at 
about 25.degree. C., to displace substantially all oxygen. Each coil was 
then removed from the pressure vessel. However, the Sample (7) coil was 
immediately treated with anaerobic resin after copper ethyl acetoacetate 
impregnation, while Sample (8) was allowed to age for 7 days before 
treatment with anaerobic resin. In both cases, no heat was applied to 
cure. 
A third 24 inch, 4.16 kV. coil, Sample (9), wrapped with the same mica 
splitting tape described above, was impregnated with anaerobic resin and 
pressurized with oxygen-free nitrogen gas as described above for 16 hours. 
This comparative Sample (9) coil was not pretreated with a metal complex 
of a beta keto ester as had been done with Samples (7) and (8). After the 
16 hour pressure treatment with nitrogen, the resin on the Sample (9) coil 
was found to be slightly soft and tacky, and so was placed in an oven and 
subjected to an additional 3 hour cure at 40.degree. C. 
The anaerobic resin, Composition 3, used for coil Samples (7), (8) and (9) 
consisted of: 800 grams of neopentyl glycol diacrylate; 500 grams of 
tetraethylene glycol diacrylate; 200 grams of trimethylolpropane 
triacrylate; 100 grams of pentaerythritol tetracrylate; 200 grams of ethyl 
methacrylate; 200 grams of cyclohexylmethacrylate; 40 grams of 2,2'-azobis 
(2-methyl propionitrile) initiator; 30 grams of cumene hydroperoxide 
initiator; 4 grams of N,N'-diethylformamide accelerator; 4 grams of 
triphenylamine accelerator; 1 gram of N,N'-dimethyl-p-toluidine 
accelerator; 0.06 gram of chromium acetylacetonate latent accelerator; 4 
grams of benzoic sulfimide coaccelerator; 2 grams of cresylic acid 
inhibitor; and 0.8 gram of hydroquinone inhibitor. This provided an 
anaerobic resin having 2,000 grams total of acrylic resin where the weight 
ratio of polyacrylic resin:monoacrylic resin was 1,600:400 or 10:2.5. The 
parts additives per 100 parts resin were: 3.5 parts total organic free 
radical initiator; 0.45 part organic free radical accelerator; 0.20 part 
organic coaccelerator; 0.24 part free radical stabilizer; and 0.003 part 
latent accelerator. The viscosity of the resin was about 100 cps. at 
25.degree. C. 
The cured coils had been measured for resin pickup and drain off, and the 
results are shown below in Table II: 
TABLE II 
__________________________________________________________________________ 
Initial Resin 
Resin Run-Off 
Final Resin 
Observations 
Sample Pick-Up 
1/2 min. drain 
Pick-Up 
16 hr. N.sub.2 cure 
__________________________________________________________________________ 
(7) CuEA+ 
46.27 g. 
6.6 g. 39.6 g. 
Resin hard. 
Comp. 3 Completely cured 
on coil. Very 
slight odor of 
acrylate 
(8) CuEA+ 
48.5 g. 
8.2 g. 40.3 g. 
Resin hard. 
Comp. 3 Completely cured 
(aged) on coil. Very 
slight odor of 
acrylate. 
*(9) 40.46 g. 
10.2 g. 30.2 g. 
Resin slightly 
Comp.3 tacky; coil 
additionally 
cured 3 hr. at 
40.degree. C. No odor. 
__________________________________________________________________________ 
*Comparative Sample: no copper ethylacetoacetate pretreatment. 
No leach out of copper ethylacetoacetate into the resin bath was apparent, 
and the storage stability of the anaerobic resin after the coil 
pretreatment described above was about 4 months. 
The cured coils were also measured for 60 Hz power factors (100.times.tan 
.delta.) at 25.degree. C. (ASTM designation D150-65T) at applied voltages 
from 1 kV. to 4 kV., and the results are shown below in Table III: 
TABLE III 
__________________________________________________________________________ 
Metal-Beta Keto 
Metal-Beta Keto 
Ester Aging 
Ester Complex 
Tan .times. 1100 (25.degree. C. 60 Hz)** 
Sample Time Days 
In Solution 
1 kV 
1 KV 
2 kV 
2 kV 
4 kV 
4 KV 
__________________________________________________________________________ 
(7) CuEA + 
0 200 mg/liter 
2.5 
3.9 
8.6 
5.3 
9.2 
13.3 
Comp. 3 
(8) CuEA + 
7 200 mg/liter 
2.6 
3.6 
6.4 
6.4 
10.8 
10.1 
Comp. 3 
(aged) 
*(9) 0 none 16.9 
15.0 
19.3 
17.0 
26.0 
23.0 
__________________________________________________________________________ 
*Comparative Sample: no copper ethylacetoacetate pretreatment. 
**Measured on two different "legs" of each coil. 
As can be seen from Table II, the copper ethylacetoacetate pretreated coils 
exhibited greater final resin pickup and less resin runoff: Sample (7) had 
14% resin drain and Sample (8) had 17% resin drain while comparative 
Sample (9) had 25% resin drain. The final result shows a 10 gram increase 
in resin content of the coil, from about 30 to 40 grams by pretreating the 
coil with a metal-beta keto ester complex prior to impregnation with the 
anaerobic resin. The pretreatment process provides a hard cured resin, 
eliminates heat energy requirements, lowers resin runoff from coils and 
stators, reduces volatiles thus lowering air pollution, and lowers 
mechanical and thermal stresses caused by differential expansion between 
metal and the groundwall resin. 
As shown in Table III, dramatic improvement is achieved in power factor 
values by pretreating the coil with a metal-beta keto ester complex prior 
to impregnation with the anaerobic resin. The use of a high percentage of 
diacrylate 1,300 g./2,000 g=65%, as well as use of dual initiators, 
accelerators and inhibitors, served to help provide the outstanding power 
factor values of Samples (7) and (8). Use of higher concentration of 
metal-beta keto ester complexes in the pretreatment step should also lower 
power factor values. 
EXAMPLE 3 
A polycarbonate sheet 1/4 inch thick was cut into four, 1 inch squares. Two 
of the pieces, Samples (10) and (11) were surface brushed with a 
pretreatment solution of copper ethylacetoacetate at a concentration of 20 
mg. of copper ethylacetoacetate per liter of acetone solvent. The solvent 
was allowed to evaporate at room temperature, to give a dry non-tacky film 
of copper ethylacetoacetate. 
An anaerobic resin, Composition 4, was prepared, consisting of: 30 grams of 
neopentyl glycol diacrylate; 30 grams of epoxylated bisphenol A 
diacrylate; 20 grams of trimethylol propane triacrylate; 20 grams of 
cyclohexylmethacrylate; 1.0 gram of 2,2'-azobis (2-methyl propionitrile) 
initiator; 1.5 grams of cumene hydroperoxide initiator; 0.2 gram of 
N,N'-diethylformamide accelerator; 0.3 gram of triphenylamine accelerator; 
0.3 gram of mercaptobenzothiazole elastomeric accelerator; 0.01 gram of 
chromium acetylacetonate latent accelerator; 0.2 gram of benzoic sulfimide 
coaccelerator; and 0.08 gram of hydroquinone inhibitor. This provided an 
anaerobic resin having 100 grams total acrylic resin where the weight 
ratio of polyacrylic resin:monoacrylic resin was 80:10 or 10:1.25. The 
part additives per 100 parts resin were: 2.5 part total organic free 
radical initiator; 0.5 part accelerator; 0.2 part organic coaccelerator; 
0.08 part free radical stabilizer; and 0.01 part latent accelerator. The 
viscosity of the resin at 25.degree. C. was about 100 cps. 
All four pieces of polycarbonate were brushed with the anaerobic 
composition. The anaerobic resin was brushed on top of the copper 
ethylacetoacetate film of Samples (10) and (11). Two composites were made 
with the polycarbonate pieces by mating the two brushed surfaces together 
so that Samples (10) and (11) made up one composite, and Samples (12) and 
(13), which had not been pretreated with copper ethylacetoacetate, made up 
the second comparative composite. In all cases, the anaerobic resin was 
disposed between the polycarbonate squares. 
A 500 gram weight was placed on each of the three composites. Then, the two 
composites were placed in a dessicator under a flow of oxygen free 
nitrogen gas for 16 hours, at a flow rate of 13 liters/minute at 
25.degree. C. The adhesive strength between the polycarbonate composites 
were evaluated by attempting to pry the polycarbonate composites apart. 
The strongest adhesive bond was formed in the composite which had the 
polycarbonate surfaces pretreated with the metal-beta keto ester complex, 
i.e., composite comprising Samples (10) and (11). When the polycarbonate 
surfaces were finally pried apart, the fracture line of the Sample (10) 
and (11) composite occurred in the resin between the polycarbonate 
squares, rather than directly at the resin-polycarbonate interface, 
indicating that the bond between the anaerobic resin and the polycarbonate 
surface was extremely strong. 
The metal-beta keto ester complex could also be used to form a protective 
coating on the polycarbonate after cure in nitrogen gas, without adhesive 
application of a second polycarbonate square. 
In the examples above, other inert gases could be used to cure the 
anaerobic resins and various other formulations of anaerobic resins as 
well as other metal-beta keto ester complexes utilized in conformity with 
the specification above with equally outstanding results.