U.S. patent application number 09/356977 was filed with the patent office on 2002-01-24 for high voltage capable non-volatile low viscosity insulating resins.
Invention is credited to EMERY, FRANKLIN T., SMITH, JAMES D.B..
Application Number | 20020010289 09/356977 |
Document ID | / |
Family ID | 23403776 |
Filed Date | 2002-01-24 |
United States Patent
Application |
20020010289 |
Kind Code |
A1 |
SMITH, JAMES D.B. ; et
al. |
January 24, 2002 |
HIGH VOLTAGE CAPABLE NON-VOLATILE LOW VISCOSITY INSULATING
RESINS
Abstract
An insulating resin is made, containing an epoxy system of resin
and epoxy diluent, with phenolic accelerator selected from catechol
and pyrogallol and organotin latent catalyst selected from
triphenyltin chloride, tribenzyltin chloride, tribenzyltin
hydroxide and triphenyltin acetate; where the insulating resin is
solventless and has a viscosity of from 10 centipoise to 450
centipoise at 25.degree. C. for up to eight weeks, where the
insulating resin can be used as an impregnating resin in slot
portions (15) and 16 of an electrical coil (10), usually in
combination with mica tape, in a motor (20) or a generator
(30).
Inventors: |
SMITH, JAMES D.B.;
(MONROEVILLE, PA) ; EMERY, FRANKLIN T.; (FORT
PAYNE, AL) |
Correspondence
Address: |
SIEMENS CORPORATION
186 WOOD AVENUE
SOUTH ISELIN
NJ
08830
|
Family ID: |
23403776 |
Appl. No.: |
09/356977 |
Filed: |
July 19, 1999 |
Current U.S.
Class: |
525/524 |
Current CPC
Class: |
H01B 3/40 20130101 |
Class at
Publication: |
525/524 |
International
Class: |
C08L 063/00 |
Claims
What is claimed is:
1. An insulating resin comprising: (1) an epoxy system consisting
essentially of: (a) an epoxy resin component, and (b) an epoxy
reactive diluent having 1,2 epoxy groups in its chain structure,
(2) a phenolic accelerator selected from the group consisting of
catechol, pyrogallol, and mixtures thereof, and (3) an organotin
latent catalyst selected from the group consisting of triphenyl tin
chloride, tribenzyltin chloride, tribenzyltin hydroxide,
triphenyltin acetate, and mixtures thereof, where the insulating
resin is solventless and has a viscosity of from 10 centipoise to
450 centipoise at 25.degree. C.
2. The insulating resin of claim 1, where the resin has a storage
stability at 25.degree. C. of over 4 month.
3. The insulating resin of claim 1, where the epoxy reactive
diluent constitutes from 30 wt. % to 70 wt. % of the epoxy
system.
4. The insulating resin of claim 1, where the phenolic accelerator
concentration is from 0.001 wt. % to 0.4 wt. % based on the epoxy
system.
5. The insulating resin of claim 1, where the organotin latent
catalyst concentration is from 0.01 wt. % to 0.1 wt. % based on the
epoxy system.
6. The insulation resin of claim 1, where the epoxy resin component
is a blend of cycloaliphatic epoxy and an epoxy resin selected from
the group consisting of bisphenol A epoxy, bisphenol F epoxy, epoxy
novolac, multi-functional epoxy and mixtures thereof, where the
cycloaliphatic epoxy constitutes at least 50 wt. % of the
blend.
7. The insulating resin of claim 1, where the epoxy resin component
is a cycloaliphatic epoxy.
8. The insulating resin of claim 1, where the epoxy diluent is a
diglycidylether of neopentyl glycol.
9. The insulating resin of claim 1, where the epoxy reactive
diluent constitutes from 55 wt. % to 65 wt. % of the epoxy system
and where both the organotin latent catalyst concentration and the
phenolic accelerator concentration is from 0.05 wt. % to 0.15 wt. %
based on the epoxy system.
10. The insulating resin of claim 1, used as part of the insulation
of an electrical coil member.
11. The insulating resin of claim 1, used in combination with a
mica as part of the insulation of an electrical coil member in a
motor.
12. The insulating resin of claim 1, used in combination with mica
as part of the insulation of an electrical coil member in a
generator.
13. An electrical coil member insulated with the insulating resin
of claim 1.
14. An electrical coil member containing mica insulation also
insulated with the insulating resin of claim 1.
15. An electrical coil member for use in a motor or generator
insulated with a resin comprising: (1) an epoxy system consisting
essentially of: (a) an epoxy resin component, and (b) an epoxy
reactive diluent having 1,2 epoxy groups in its chain structure,
(2) a phenolic accelerator selected from the group consisting of
catechol, pyrogallol, and mixtures thereof, and (3) an organotin
latent catalyst selected from the group consisting of triphenyl tin
chloride, tribenzyltin chloride, tribenzyltin hydroxide,
triphenyltin acetate, and mixtures thereof, where the insulating
resin is solventless and has a viscosity of from 10 centipoise to
450 centipoise at 25.degree. C.
16. The electrical coil member of claim 15 also containing mica
insulation.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to new and improved epoxide
insulating resins, which utilize a combination of selected phenol
accelerators and selected organotin latent catalysts, and which are
non volatile, solventless and cold-blendable and also have low
viscosity and long storage life.
[0003] 2. Background Information
[0004] Organotin catalysts are well known in the insulating resin
art as latent catalysts for epoxy resins, for example, U.S. Patent
Specification Nos. 4,020,017 and 4,112,183 (Smith et al. and
Smith), taught epoxy compositions containing organotin compounds
with chlorine, hydroxide, acetate, butyrate, propionate or
dimethylphosphate, as well as phenyl, naphthyl, Br or NO.sub.2
substituted aryl, and benzyl groups, among others, as components,
and listed twenty nine preferred compounds. Smith et al., '017,
specifically excluded phenolic; anhydride or amine compounds from
the epoxy, and utilized reactive diluents containing 1, 2 epoxy
groups. Smith, '183, required use of a solvent such as a ketone or
aromatic hydrocarbon, preferably a dual solvent system, which had
to be removed by heating at over 65.degree. C. (149.degree. F.),
and lists about twenty six preferred organotin catalysts.
[0005] In U.S. Patent Specification Nos. 4,296,018 and 4,356,417
(both Smith et al.) the phenols catechol, C.sub.6H.sub.4
(OH).sub.2, and pyrogallol, C.sub.6H.sub.3 (OH).sub.3 were used
with epoxy resins and organotin compounds, but both teachings
required use of a solvent such as a ketone or aromatic hydrocarbon,
preferably a dual solvent system, which had to be removed by
heating at over 85.degree. C. (185.degree. F.). Both of these
patents list seventeen preferred organotin compounds, and
specifically exclude anhydride, amine, phenol or amide curing
agents.
[0006] U.S. Patent Specification No. 3,716,598 (Markovitz) taught
control of the cure rate of epoxy resins by use of specific bis
(triorganotin) oxides, and from 0.1 to 15 wt. %, based on total
epoxy resin system, of a phenolic accelerator, such as pyrogallol,
hydroxy-benzaldehydes, catechol, resorcinol and hydroquinone, among
others. The bis (triorganotin) oxide had the formula:
(R.sub.1).sub.3Sn--O--Sn(R.sub.2).s- ub.3, where R was an alkyl,
cycloalkyl, aryl, or alkaryl group. One preferred material was bis
(tri-n-butyltin) oxide.
[0007] While all of these resinous epoxy insulating compositions
each have their own advantages, what is still needed is a resinous
system having a unique cure system that provides: (1) a
solventless, cold-blendable resin admixture not requiring volatile
and flammable monomers such as styrene or vinyl toluene (2) a low
viscosity resin (below about 120 centipoise at 25.degree. C.)
suitable for vacuum pressure impregnation ("VPI") in high voltage
insulation for coils of motors and generators (3) a resin
compatible with mica tape, and importantly, (4) a resin which has a
long storage life and that does not require special equipment or
pre-cooking, and which uses raw material components readily
commercially available world-wide.
SUMMARY OF THE INVENTION
[0008] Therefore, it is one of the main objects of this invention
to provide a high voltage capable insulating resin that can be
manufactured with ease in almost any country without highly
specially trained personnel or expensive oven equipment, and which,
during manufacture, would have minimum emission health
problems.
[0009] It is another main object of this invention to provide a
solventless, cold-blendable, low viscosity insulating resin that
can be used to impregnate mica tape in motor and generator
coils.
[0010] These and other objects of the invention are accomplished by
providing an insulating resin consisting essentially of: an epoxy
system having an epoxy resin component and an epoxy reactive
diluent having 1,2 epoxy groups in its chain structure; a phenolic
accelerator selected from the group consisting of catechol,
pyrogallol and mixtures thereof; and an organotin latent catalyst
selected from the group consisting of triphenyltin chloride,
tribenzyltin chloride, tribenzyltin hydroxide, triphenyltin acetate
and mixtures thereof, where the insulating resin is solventless and
has a viscosity of from 10 centipoise to 150 centipoise at
25.degree. C.
[0011] This means that the viscosity at 25.degree. C. will remain
below 450 cps. for at least eight weeks. The insulating
impregnating resin can be cold-blended at from 20.degree. C. to
35.degree. C. Preferably the epoxy resin component will be a
cycloaliphatic epoxy resin or a blend of cycloaliphatic epoxy resin
plus other type epoxy resins where the cycloaliphatic epoxy
constitutes at least 50 wt. % of the blend. The preferred reactive
diluent is the diglycidyl ether of neopentyl glycol. In all cases
both cycloaliphatic epoxy and epoxy reactive diluent will be
present in the epoxy system.
[0012] Preferably the reactive diluent will constitute from 30 wt.
% to 70 wt. % of the epoxy system, the phenolic accelerator
component concentration will range from 0.001 wt. % to 0.4 wt. %,
preferably from 0.01 wt. % to 0.4 wt. %, of the insulating resin,
based on the total weight of the epoxy system (epoxy resin
component and reactive diluent). The organotin component
concentration will range from 0.01 wt. % to 0.1 wt. %, preferably
from 0.05 wt. % to 0.1 wt. %, of the insulating resin, based on the
total weight of the epoxy system. Both the selected phenolic
accelerator and the organotin catalyst must be present in the
insulating resin.
[0013] These insulating resins have a long storage stability at
25.degree. C. of over about 4 months, and can be used to pot or
encapsulate electrical components or to impregnate mica or glass
tape used on coils for electrical machines, such as motors or
generators. Where a "medium viscosity" resin ranges from about
16,000 cps. to 20,000 cps., these ultra low viscosity resins (up to
450 cps. for eight weeks at 25.degree. C.) have excellent
penetration ability and are excellent impregnating resins even
after substantial storage. These resins are extremely easy to
manufacture, utilizing a cold blending admixture of ingredients and
not requiring a hot flash step for solvent removal, with attendant
venting problems.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] For a better understanding of the invention, reference may
be made to the preferred embodiments, exemplary for the invention,
shown in the accompanying drawings, in which:
[0015] FIG. 1 is a plan view of a closed electrical coil member
having two slot portions;
[0016] FIG. 2 is a cross-sectional view of a motor, containing
coils insulated with the resinous composition of this invention;
and
[0017] FIG. 3 is a cross-sectional view of a generator, containing
coils insulated with the resinous composition of this
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0018] Throughout the specification the terms "epoxy" and "epoxide"
are interchangeable. The preferred epoxy, or epoxide, resin used in
the epoxy resin component of this invention is a cycloaliphatic
type, selected from non-glycidyl ether epoxides containing more
than one 1,2 epoxy group per molecule. These are well known in the
art and are generally prepared by epoxidizing unsaturated aromatic
hydrocarbon compounds, such as cyclo-olefins, using hydrogen
peroxide or peracids such as peracetic acid and perbenzoic acid.
The organic peracids are generally prepared by reacting hydrogen
peroxide and either carboxylic acids, acid chlorides, or ketones,
to give the compound R-COOOH.
[0019] Such non-glycidyl ether cycloaliphatic epoxides are here
characterized by the absence of the ether oxygen bond, i.e.
-.largecircle.-, near the epoxide group, and are selected from
those which contain a ring structure as well as more than one
epoxide group in the molecule. The epoxide group may be part of the
ring structure or may be attached to the ring structure. These
epoxides may also contain ester linkages. These ester linkages are
generally not near the epoxide group and are relatively unreactive,
therefore these type materials are properly characterized as
cycloaliphatic epoxides.
[0020] Examples of non-glycidyl ether cycloalyphatic epoxides would
include 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate
(containing two epoxide groups which are part of ring structures,
and an ester linkage); vinyl cyclohexene dioxide (containing two
epoxide groups, one of which is part of a ring structure);
3,4-epoxy-6-methylcyclohexyl methyl-3,4-epoxy-6-methylcyclohexane
carboxylate and dicyclopentadiene, having the following respective
structures: 1
[0021] Other useful cycloaliphatic epoxides include
2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy) cyclohexanemetadioxane
and 3,4-epoxy-6-methylcyclohexyl-methyl adipate.
[0022] A distinguishing feature of many of the non-glycidyl ether
cycloaliphatic epoxides is the location of the epoxy group(s) on a
ring structure rather than on an aliphatic side chain. Generally,
the cycloaliphatic epoxide particularly useful in this invention
will have the formula selected from the group consisting of: 2
[0023] where S stands for a saturated ring structure, R is selected
from the group consisting of CHOCH.sub.2, O(CH.sub.2), CHOCH.sub.2
and OC(CH.sub.3).sub.2 CHOCH.sub.2 radicals where n=1 to 5, R' is
selected from the group consisting of hydrogen, methyl, ethyl,
propyl, butyl and benzyl radicals and "R" is selected from the
group consisting of CH.sub.2OOC, and CH.sub.2OOC(CH.sub.2).sub.4
COO radicals.
[0024] Use of an epoxy reactive diluent having 1,2 epoxy groups in
its chain structure is particularly advantageous in combination
with the above described cycloaliphatic resins. Useful reactive
epoxy diluents include diglycidyl ethers of a glycol having from
3-12 carbon atoms between the glycidyl ether units, that is, 3-12
carbons in the glycol unit, for example, diglycidylether of
neopentyl glycol ("DGENPG"), and diglycidylether of 1,4 butanediol.
Below 3 carbons in the glycol unit and effective complexing would
not take place with the orgono-tin compound. Other useful reactive
diluents include epoxidized oils made from triesters of glycerol
and long chain unsaturated acids. The number of epoxy groups per
chain will vary, but for epoxidized oils such as modified soybean
oils there are an average of about 4 per chain and for epoxidized
linseed oils there are an average of about 6 per chain. The
epoxidized natural oils should have from about 3 to 12% by weight
oxirane (epoxy) oxygen content.
[0025] DGENPG is the preferred reactive diluent. DGENPG has two 1,2
epoxy groups and is prepared by a two step process. The initial
step reacts neopentyl glycol and epichlorohydrin in the presence of
BF.sub.3 to produce a chlorohydrid intermediate which is then
dehydrohalogenated by sodium hydroxide or sodium aluminate to
provide: 3
[0026] These reactive diluents can be used in the range of 30 wt. %
to 70 wt. % of the epoxy system weight. That is, if 100 parts by
weight of combined epoxy resin component plus reactive diluent is
used, 30 to 70 parts by weight of reactive diluent can be used in
that system. These reactive diluents as well as the cycloaliphatic
epoxy resins described are well known, and taught for example in
the Smith et al. '017 patent.
[0027] Other types of epoxy, or epoxide, resin can be used as the
epoxy resin component in this invention, with the previously
described reactive diluents. One type of epoxy resin which may be
used is obtainable by reacting epichlorohydrin with a dihydric
phenol an alkaline medium at about 50.degree. C., using 1 to 2 or
more moles of epichlorohydrin per mole of dihydric phenol. The
heating is continued for several hours to effect the reaction, and
the product is then washed free of salt and base. The product,
instead of being a single simple compound, is generally a complex
mixture of glycidyl polyethers, but the principal product may be
represented by the chemical structural formula: 4
[0028] where X is, for example R--O--CH.sub.2--CHOH--CH.sub.2--O,
where n is an integer of the series 0, 1, 2, 3 . . . , and R
represents the divalent hydrocarbon radical of the dihydric phenol.
Typically R is: 5
[0029] to provide a diglycidyl ether of bisphenol A type expoxide
or 6
[0030] to provide a diglycidyl ether of bisphenol F type epoxide
resin.
[0031] The bisphenol epoxides used in the invention have a 1, 2
epoxy equivalency greater than one. They will generally be
diepoxides. By the epoxy equivalency, reference is made to the
average number of 1, 2 epoxy groups: 7
[0032] Other glycidylether resins that are useful in this invention
include polyglycidylethers of a novolac. These resins are prepared
by reacting an epihalohydrin with phenol formaldehyde condensates,
which the bisphenol-based resins contain a maximum of two epoxy
groups per molecule, the epoxy novolacs may contain as many as
seven or more epoxy groups per molecule. In addition to phenol,
alkyl-substituted phenols such as o-cresol may be used as a
starting point for the production of epoxy novolac resins. The
product of the reaction is generally a massive oxidation resistant
aromatic compound.
[0033] Although epoxy novolac resins from formaldehyde are
generally the preferred novolac type resin, epoxy novolac resins
from any other aldehyde such as, for example, acetaldehyde,
chloraldehyde, butyaldehyde or fufuraldehyde, can also be used.
Completely epoxidized novolacs or other epoxy novolacs which are
only particularly epoxidized can be useful in this invention. An
example of a suitable epoxy novolac is 2, 2, bis
[p-(2-3-epoxypropoxy)-phenyl]-methane. Multi-functional epoxy
resins are also useful epoxy resins in this invention. These resins
are somewhat similar to epoxy novolacs, and can be mixtures of
epoxy novolacs with bisphenol A or bisphenol F epoxides. These
resins generally have extremely high temperature resistance and are
commercially available as polyfunctional epoxy resins.
[0034] These bisphenol A, bisphenol F, novolac and multi-functional
epoxy resins are widely commercially available and taught, for
example, in the Smith et al. '018 patent. When bisphenol A,
bisphenol F, novolac or multi-functional epoxies are desired, for
example, to provide certain enhanced mechanical, tensile, or
thermal stability properties, they will be blended with the
cycloaliphatic resin. The term "epoxy resin component" is herein
defined to mean cycloaliphatic epoxy resin alone, or in combination
with one or more of such other epoxy resins previously described,
not including epoxy diluents. Any blend should constitute at least
50 wt. % cycloaliphatic resin so that cure of the epoxy resin
system is not sluggish. The term "epoxy system" is herein defined
as such epoxy resin component plus reactive diluent.
[0035] There are only two phenolic accelerator compounds found
useful in the particular insulating composition of this, invention,
and they are catechol (1,2 benzene diol, C.sub.6 H.sub.4
(OH).sub.2) and pyrogallol (1, 2, 3, tri hydroxy benzene, C.sub.6
H.sub.3 (OH).sub.3). These phenolic accelerators can be used alone
or in a mixture and are particularly effective when used in the
range of 0.001 wt. % to 0.4 wt. % of the epoxy system weight
(including reactive diluent). At accelerator concentrations over
about 0.45 wt. %, the storage stability of the epoxy insulation
resin definitely begins to be severely impaired. With high
concentrations of organotin compounds the upper range of phenolic
accelerator can drop to 0.2 wt % of epoxy system weight.
[0036] Results show that the selected phenolic acceleration effect
is confined to only specific organotin latent catalyst compounds.
Most organotin compounds do not show beneficial coreactivity
properties with catechol and pyrogallol. This is probably because
they do not form an intermediate reaction compound which is thought
to be necessary for the initiation of the polymerization step. The
useful latent catalysts for this particular resin system are
covalently bonded organo-tin compounds having the general chemical
structural formula:
(R).sub.3 SNX
[0037] where each R is independently selected from the group
consisting of phenyl, that is, 8
[0038] and alkaryl groups, such a benzyl groups, 9
[0039] where the X constituent is selected from the group
consisting of chloride, hydroxide and acetate. Examples of suitable
tin chlorides are triphenyl chloride ("TPTCL") and tribenzyltin
chloride ("TBTCL"). Others are tribenzyltin hydroxide ("TBTH") and
triphenyltin acetate ("TPTA"). These four organotin compounds can
be used alone or in combination.
[0040] The useful organotin compound should be used in the range of
0.01 wt. % to 0.10 wt. % of epoxy system weight. These materials
are highly reactive with mica and facilitate good bonding and
interaction with mica tapes, as is discussed in detail by the Smith
'183 patent. Organotin compounds which do not show coacceleration
effect with catechol and pyrogallol are: tetrabutyltin (TBTN),
tetraphenyltin (TPHT), bis(tri-n-butyltin oxide) (TBTO) and
methyltin chloride (MTCI). In addition, the acceleration effect
appears to be confined to catechol and pyrogallol. Other phenolic
additives, such as resorcinol and straight bisphenol "A", will not
accelerate cure in the presence of these organotin catalysts. This
certainly demonstrates that not all phenolic accelerators or
organotin compounds are equivalents.
[0041] The mechanism responsible for the coacceleration effect of
catechol and pyrogallol with the "active" organotin compounds
probably involves some type of charge-transfer complex formation
between the accelerator and the organotin compound. This is shown
by the formation of a deep-yellow coloration when both catechol (or
pyrogallol) and the organotin compound are added to a
cycloaliphatic epoxy resin. The coloration is absent when
accelerator and organotin compound are added separately to the
epoxy resin.
[0042] It is also interesting to speculate why catechol and
pyrogallol are so specific as accelerators with organotin
catalysts, whereas other phenolic materials, such as picric acid,
resorcinol and bisphenol A, are not. The only common feature shown
by catechol and pyrogallol is the presence of adjacent OH groups in
the aromatic ring structure. The other phenolic compounds evaluated
did not possess these adjacent OH groups. It may be that the
adjoining OH groups might be necessary for the formation of a
stable charge-transfer complex with the organotin compounds
(probably by electron donation to the Sn atom). Attempts to make
catechol/organotin complexes in the absence of epoxy resin (that
is, in an inert solvent) have, so far, been unsuccessful. This
suggests that the presence of cycloaliphatic epoxy molecules may be
necessary to aid or stabilize complex formation between catechol
and the organotin compound.
[0043] The insulating resins of this invention use the unique cure
chemistry described previously to provide a "family" of
cold-blendable, low-viscosity, epoxy resins suited for vacuum
pressure impregnation applications in high voltage insulation. The
viscosities obtainable with this family of resins (<100 cps),
would appear to be adequate for efficient impregnation of the
present by used mica tapes. These formulations will provide an
alternative to the presently used styrene based epoxy resins. The
preparation of these resins does not require special equipment or
pre-cooking as is the case with styrene based epoxy resins, and the
raw material components required to make the compositions are
readily available from large company, multiple world-wide suppliers
such as Shell, Ciba and Dow Chemical. Another advantage of these
new VPI resin formulations is that no volatile vinyl monomers such
as styrene and vinyl-toluene are needed to achieve low viscosity
levels.
[0044] It should also be mentioned that epoxy resin flexibilizers
such as aliphatic polyols, epoxidized polybutadienes, epoxidized
oils such as linseed oil, and fillers such as alumina
(Al.sub.2O.sub.3) and silica (SiO.sub.2) can also be included
without materially effecting the fundamental character of the
insulating resin. While the term "consisting essentially of" has
been used here and is taken to mean excluding materials of a
different nature that would materially change the fundamental
character of the insulating resin, the use of the further limiting
term "consisting of" is reserved, consistent with U.S.
practice.
[0045] One type of a closed full coil 10 which may be prepared
using the VPI insulating resin of the present invention is
illustrated in FIG. 1. The full coil comprises an end portion
comprising a tangent 11, a connecting loop 12, and another tangent
13 with bare leads 14 extending therefrom. Straight slot portions
15 and 16 of the coil, usually are wrapped mica tape or possibly
glass fiber cloth, which is then vacuum pressure impregnated with a
resin, such as the insulating resin of this invention the slot
portions 15 and 16 which have been hot pressed to form them to
predetermined shape and size, are connected to the tangents 11 and
13 respectively. These slot portions are connected to other
tangents 17 and 18 connected through another loop 19.
[0046] The complete full coils are placed within the slots of the
stator or rotor of an electrical machine and the end windings are
wrapped and tied together. The uninsulated leads are then soldered,
welded or otherwise connected to each other or to the commutator.
Thereafter, the entire machine will be placed in an oven and heated
to a temperature effective to cure the completely reactive
composition in the mica tape insulating the coil.
[0047] FIG. 2 shows one embodiment of a motor 20 in cross section.
The motor comprises a metal armature 21 having slots 22 therein,
containing insulated coils 23, surrounded by a metal stator 24
having slots 25 therein about the stator circumference at 26. The
stator slots contain insulated coils 27. All the insulation on the
coils 23 and 27 can compose the resinous compositions of this
invention. FIG. 3 shows one embodiment of a generator 30 in cross
section. The generator comprises a metal rotor 31 having slots 32
therein, containing insulated coils, 33, surrounded by a metal
stator 34 having slots 35 therein about the stator circumference at
36. The stator slots contain insulated coils 37 and may also
contain inner cooling channels not shown. All the insulation on the
coils 33 and 37 can comprise the resinous compositions of this
invention.
[0048] The following specific examples are presented to help
illustrate the invention. They should not be considered in any way
limiting. They should not be considered in any way limiting.
EXAMPLE I
[0049] A series of insulating resins were formulated by
cold-blending the epoxy resin component, a reactive epoxy diluent,
an organotin catalyst and catechol phenolic accelerator.
[0050] Most of the work has been done using blends of a
3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate
cycloaliphatic epoxy sold commercially by Union Carbide Plastics
Division under the Tradename, ERL 4221, also available from Ciba
Products Co. as CY-179 and having an epoxy equivalent weight of
about 133-140 and a viscosity at 25.degree. C. of 350-450
centipoises, and the reactive diluent DGENPG (diglycidylether of
neopentyl glycol), available from Shell Chemical Co. under the
Tradename "Heloxy 68".
[0051] Gel time data were obtained with 10-20g resin samples in
aluminum dishes (5 cm. diam.) or with 5g samples in small test
tubes at 135.degree. C. and 150.degree. C. The latter test closely
simulated the cure condition for the impregnate formulations in a
silicate-rich environment. Catalyzed storage tests were carried out
using a Gardner-Holdt bubble viscometer at 25.degree. C. (ASTM
D154-56). The "shelf-life" was measured by the time taken (at
25.degree. C.) for the viscosity of the impregnate to reach 1000
cps. Some of these storage data were obtained by extrapolation of
the viscosity curve to 1000 cps. Electrical properties were
obtained on 0.32 cm.-0.64 cm. castings made with some of the
formulations. Power factor (100.times.tan) and dielectric constant
(.epsilon.) data were obtained at 150.degree. C.
[0052] In many instances, comparisons are made of the properties of
the insulating resin of this invention versus a longtime standard
epoxy impregnating resin having outstanding gel, pot life and
electrical insulating characteristics taught in. U.S. Patent
Specification No. 4254351 (Smith et al.) hereinafter "Sample 351."
Comparative Sample 351 is a solventless, bisphenol A, epoxy-styrene
composition with an amine catalyst and also using maleic anhydride
and a metal acetylacelonate latent accelerator. Comparative sample
351 was made by mixing: (1) the product of the reaction of (a) 1
part of an epoxy resin mixture, comprising solid epoxy resin and
liquid epoxy resin wherein the weight ratio of solid epoxy: liquid
epoxy is between 1:1 to 1:10; with (b) between about 0.01 part to
0.06 part of malecic anhydride and (c) a catalyst; under such
conditions that the epoxy diester formed has an acid number of
between about 0.5 to 3.0; with (2) styrene; and between about
0.0003 part to 0.004 part of a room temperature stabilizer (3)
between about 0.3 part to 1.2 part of a polycarboxylic anhydride,
which is soluble in the mixture of (1) and (2) and an amount of
free radical catalyst that is effective to provide a catalytic
effect on the impregnating varnish and to cure it at temperatures
of over about 85.degree. C., and with (4) between 0.0005 part to
0.005 part of a metal acetylacetonate, of chromium (III)
acetylacetonate, manganese (III) acetylacetonate acting as latent
accelerator. As can be seen, this is a rather complicated admixture
compared to insulating resin of this invention.
[0053] Table 1 gives a list of different compositions evaluated,
samples 1-7 and comparative samples C1, C2 and 351, showing
viscosity, gel time and storage stability data.
1TABLE 1 THE EFFECT OF VARIOUS AMOUNTS OF DGENPG AND TRIPHENYLTIN
ACETATE (TPTA) CATALYST/CATECHOL ACCELERATOR ON THE VISCOSITY, GEL
TIME AND STORAGE STABILITY OF CYCLOALIPHATIC EPOXY IMPREGNANTS
Impregnant Epoxy Organotin Viscosity Gel Time.sup.c Storage.sup.d
Sample Cycloaliphatic Diluent.sup.b Catalyst Catechol at 25.degree.
C. (cps.) at 150.degree. C. Stability No. Epoxy (parts).sup.a
(parts) (parts) (parts) initial 8 weeks (min) at 25.degree. C. 1 50
50 0.10 TPTA 0.10 41 55 40-50 >6 mos 2 40 60 0.10 TPA 0.10 27 40
>100 >6 mos 3 50 50 0.10 TPA 0.20 41 200 20-25 21 wks 4 40 60
0.10 TPA 0.20 27 90 30-35 39 wks 5 65 35 0.10 TPTA 0.10 57 140
<20 >24 wks 6 60 40 0.10 TPA 0.20 50 380 <15 23 wks 7 55
45 0.10 TPA 0.20 41 430 <15 20 wks C1 45 55 0.10 TPA 0.50 32
>1000 <10 <7 wks C2 45 55 0.20 TPTA 0.20 32 >1000 10-20
<7 wks 351 -- -- -- -- 10 15 -- >6 mos .sup.aUsing ERL 4221
(3,4-epoxy cyclohexyl-methyl-3,4-epoxy cyclohexane carboxylate).
.sup.bUsing diglycidylether of neopentyl glycol (DGENPG). .sup.c20
g sample cured in 5 cm. diam. aluminum dish (covered with a
watch-glass). .sup.dTime for viscosity to reach 1000 cps. at
25.degree. C.
[0054] The most preferred composition shown in Table 1 is an
insulating resin containing 55 wt. % to 65 wt. % of epoxy diluent
and 0.05 wt. % to 0.15 wt. % each of organotin and phenolic
accelerator.
[0055] As can be seen, the viscosity of the insulating resin of
this invention starts to increase dramatically at about 35 wt. %
diluent, so that the lower range of diluent is estimated to be
about 30 wt. % of the epoxy system weight. Also, a storage
stability of at least 4 months is realistically required for
insulating resin to be considered commercially viable in many
countries. Comparative samples C1 and C2 provide poor shelf life
compositions due to either high organotin concentration or a
combination of high total organotin plus phenolic accelerator
concentration. Useful upper limits for the organotin latent
catalyst appear to be up to 0.1 wt. % of epoxy system weight.
Useful upper limits for the phenolic accelerator appear to be up to
0.4 wt. % of epoxy system weight. All the gel times were acceptable
except for C1. Commercial requirements would require some time
before impregnation and gellation, usually over 10 minutes up to
about 2 hours.
[0056] The correlation between gel times and tribenzyltin chloride
concentration as well as the correlation between gel times and
catechol concentration is shown in Table 2:
2TABLE 2 Cyclo- aliphatic Epoxy Organotin Gel Time.sup.c Impregnant
Epoxy Diluent Catalyst Catechol at 150.degree. Sample No.
(parts).sup.a (parts).sup.b (parts) (parts) (min) 8 50 50 0.10
TBTCL 0.10 15 9 50 50 0.05 TBTCL 0.10 35 10 50 50 0.01 TBTCL 0.10
70 11 50 50 0.10 TBTCL 0.005 80 12 50 50 0.10 TBTCL 0.001 110
.sup.aUsing ERL 4221 .sup.bUsing EGENPG .sup.c20 g Sample cured in
5 cm. diam. aluminum dish (covered with a watch-glass).
[0057] All gel times were acceptable, that is over 10 minutes up to
2 hours, as mentioned previously. Useful lower limits for the
phenolic accelerator appear to be 0.001 wt. % when used with a
substantial amount of TBTCL, but would preferably appear to be
0.010 wt. %. Useful lower limits for the organotin latent catalyst
appear to be 0.01 when used with a substantial amount of phenolic
accelerator, but would preferably appear to be 0.05 wt. %. Both the
selected phenolic accelerator and the organotin catalyst must be
present in the insulating resin.
[0058] Electrical properties (100.times.tan.delta. and dielectric
constant values) for several cured resin samples were taken and are
shown in Table 3 and compared to Sample 351, which has excellent
electrical properties.
3TABLE 3 ELECTRICAL PROPERTIES OF CURED SAMPLES OF CYCLOALIPHATIC
EPOXY IMPREGNANTS CONTAINING ORGANOTIN CATALYST AND CATECHOL
ACCELERATOR Sample Electrical Thick- Properties Impregnant ness at
150.degree. C. Sample No. (cm.) Cure 100 .times. tans E. 5 .353 16h
at 100.degree. C. + 8h at 150.degree. C. 2.1 5.6 6a .695 16h at
100.degree. C. + 8h at 150.degree. C. 17.0 6.7 7b .622 16h at
100.degree. C. + 8h at 150.degree. C. 42.0 6.9 351c .706 16h at
100.degree. C. + 8h at 150.degree. C. 6.8 4.3 .sup.aSame
composition as 6 except 0.10 part catechol. .sup.bSame composition
as 7 except 0.10 part catechol. .sup.cContains 0.1% chromium
acetylacetonate.
[0059] Sample 5 had an even better (lower) 100.times.tan s value
than Sample 351c at 150.degree. C. While the electrical properties
of both 6a and 7b are acceptable at 150.degree. C. cure, there is a
strong indication that they would have had lower values if the post
cure temperature had been raised to 160.degree. C.
[0060] Although the initial formulations employ cycloaliphatic
epoxy and epoxy reactive diluent in their preparation, it is
envisioned that modification with other reactive epoxy components,
such as bisphenol "A" epoxy, bisphenol "F" epoxy, epoxy-novolacs
and multi-functional epoxy can be easily carried out to give
enhanced mechanical, tensile and thermal stability properties if
required. Also, the other organotin compounds as well as pyrogallol
would provide equally good results when used in the wt. % ranges
previously described.
[0061] Also, as mentioned previously, organotin compounds which do
not show coacceleration effect with catechol and pyrogallol are
tetrabutyltin (TBTN), Tetraphenyltin (TPHT), bis(tri-n-butyltin
oxide) (TBTO), and methyltin chloride (MTC1). In addition, the
acceleration effect appears to be confined to catechol and
pyrogallol. Other phenolic additives, such as resorcinol and
straight bisphenol "A", will not accelerate cure in the presence of
these organotin catalysts as shown by the data in Table 4.
[0062] The data in Table 4 shows the effect of various potential
accelerators on the gel time of a cycloaliphatic epoxy formulation
containing tribenzyltin chloride catalyst. It is noted that, in the
silicate-rich environment (that is, glass test tube), only catechol
and pyrogallol showed useful acceleration effects at concentrations
up to 0.10%. Trifluoroacetic acid caused some "popcorn" gelation at
room temperature. It should also be noted that phenolic
accelerators such as picric acid, bisphenol "A" and resorcinol did
not exhibit any significant acceleration effect with tribenzyltin
chloride catalyst.
4TABLE 4 THE EFFECT OF VARIOUS ACCELERATORS ON THE GEL TIME OF
CYCLOALIPHATIC EPOXY IMPREGNANT CONTAINING TRIBENZYLTIN CHLORIDE
(TBTCl) CATALYST Cyclo- TBTCL aliphatic Epoxy Organotin Gel
Time.sup.c Epoxy Diluent.sup.b Catalyst Accelerator Added at
150.degree. C. (parts).sup.a (parts) (parts) (parts) (min) 70 30
0.10 TBTCl None 120-135 " " " 1.0 Acetic Acid 120-135 " " " 1.0
Hexanoic Acid 105-120 " " " 1.0 Trifluorocetic " " " Acid d " " "
0.1 Catechol 15-30 " " " 1.0 Acetylacetone >1000 " " " 1.0
Ethylene Glycol 210-240 " " " 1.0 Trifluoroacetic 105-120 Anhydride
" " " 0.01 Benzoquinone 120-135 " " " 0.01 Pyrogallol 60-70 " " "
0.01 Bisphenol `A` >85 " " " 0.01 Picric Acid >70 " " " 0.01
Resorcinol >85 " " " 0.10 Pyrogallol <15 " " " 0.10 Bisphenol
`A` >90 " " " 0.10 Resorcinol 75-90 .sup.aUsing ERL 4221
(3,4-epoxy cyclohexyl-methyl-3,4-epoxy cyclohexane carboxylate).
.sup.bUsing diglycidylether of neopentyl glycol (DGENPG).
.sup.cMeasured (5 g) in glass test tube in oven. .sup.dSome
gelation occurred at room temperature.
[0063] While specific embodiments of the invention have been
described in detail, it will be appreciated by those skilled in the
art that various modifications and alternatives to those details
could be developed in light of the overall teachings of the
disclosure. Accordingly, the particular arrangements disclosed are
meant to be illustrative only and not limiting as to the scope of
invention which, is to be given the full breadth of the claims
appended and any and all equivalents thereof.
* * * * *