Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
7~i311Ei~3
- l - 73661-8
REACTIVE CONCENq'RATED IRRADIArrED CATALYq'lC
COMPLEXES AS LOW TEMPERATURE CURIN~
AGENTS FOR ORGANIC RESINOUS MATE'RIALS
BACKGROU~D OF THE INVENTION
Carboxylic acid anhydride curing agents have been found
to be useful with epoxy resins for high voltage insulating
applications. Usually, the addition of an accelerator is required
to give reasonable gel times at elevated temperatures, but at room
temperature, even with hiyh concentrations of accelerators, very
slow gel times are experienced. Considerable effort has been
devoted in recent years to developing improved room temperature
curing agents for epoxy-anhydride resins.
Smith et al., in U.S. Patent 4,020,017, used minor
amounts of organotin compounds, such as triphenyl tin chloride, to
form apparent complexes with reactive epoxide diluents, for use as :.
additives for cycloaliphatic and glycidyl ester epoxy resins, to
provide resirour electrical
.
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~ 51,803I
insulating compositions without usin~ acid anhydrides
These compositions, however, required at least 120C curing
temperatureS, In a later improvement, Smlth et al., in
U.S. Patent 4,~73,914, fliscovered a low temperature, fast
S curing epoxy insulating composition, which consists of an
epoxy resin and a carboxylic acid anhydride complex. The
anhydride complex was made by the low temperature reaction
of a selected Lewis acid catalyst, such as antimony penta-
chloride, titanium ~etrachloride, boron trifluoride, tin
tetrachloride, or triphenyl tin chloride, with a carbox-
ylic acid anhydride. There, the catalyst and anhydride
were simply pre-reacted at a reacting mass temperature of
from 10C to about 45C. The complex allowed substantially
complete cure of the epoxy resin at 25C in about 48 hours.
Von Brachel et al., in U.S. Patent 3,499,077,
utilized a peroxide initiated, non-irradiated, free-radical
chain reaction of maleic anhydride and straight chain
polyalkylene ethers, at from about 80C to 160C, to
provide addition products, noting that the literature
showed successful reaction of maleic anhydride with tetra-
hydrofuran, but not dioxane, in the presence of radical
initiators. These addition products were found useful as
raw materials for lacquers, and as surface active anhydride
components in the production of polyesters. These addition
products were usually reacted at ~rom 100C to about 130C
with epoxies and the like.
What is needed is a room temperature curing agent
which will provide good gel and cure times, have extended
shelf life, and which will help provide good electrical
30 insulating properties to the resins it cures.
SUMMARY OF THE INVENTION
Th~ above problems have heen solved and the aboveneeds met by admixing an organic resinous material, such as
an epoxy resin or a vinyl resin, with a highly concentrated
reactive catalytic complex produced by admixing: (a) a
~arboxylic acid anhydride, selected from halide or short
chain alkyl substituted maleic anhydride, and preferably
: ~ . .: - .
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..
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~ 2'76~i9
3 51,803I
citraconic anhydride or maleic anhydride, and their mix-
tures, and (b) a carbon containing cyclic compound contain_
ing an electron deficient element, such as sulfur or
preferably oxygen and their mixtures, selected from t~e
group consisting of tetrahydrofuran, dioxane, trioxane, and
sulfolane, and their mixtures. This latter material acts
both as solvent and interactant. A reactive catalytic
complex i9 then formed between (a) and a portion of (b),
and then at least a part of the other portion of (b) is
removed. The weight ratio of (carboxylic acid anhy-
dride):(carbon containing cyclic compounfl) is preferably
from about (1):(0.6 to 2). In the interaction to form the
unconcentrated catalytic complex, no free radical initia-
tors are used, and the temperature is preerably kept below
about 40C.
The unconcentrated catalytic complex which will
always contain excess solvent then has solvent removed,
preferably without the use of heat in for example a vacuum
chamber or other vacuum means, to reduce its weight to from
about 55% to about 90% of its original weight. The highly
concentrated, highly reactive catalytic complex, when added
in a weight ratio of (resinous material~:(catalytic com-
plex) of from about (1~:(0.2 to 1.5~, will effect substan-
tially complete cure at 25C, in from about 2 hours to 144
hours. No additional curing agents are needed.
The irradiation that can be used to form th~
unconcentrated catalytic complex contains the wavele~gth
ran~e of from~about 2,000 Angstrom units to 5,200 Angstrom
units. The irradiation is effective only when both the
.
selected carboxylic acid anhydride and the s~lected carbon
containing cyclic compound are mixed togather, the irradia-
tion of the mixed product solution producing an active
species wh1ch is responsible for initiating resin polymer-
ization at room temperature.
The resins incorporating these catalytic complex-
es can be used to impregnate electrical coil insulation
tapes, to encapsulato electrical articles, to act as an
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4 51,803I
insulating adhesiv~ for polyurethane and other type arti-
cles, to act as a low viscosity room temperature curable
resin, and particularlY, to insulate coil connection~ of
high hors~power motors and similar hiyh voLta~e rotating
apparatus. These highly concentrated complex catalyzed
resins can be especially useful when insulatins temperature
sensitive materials that might be melted by application of
heat, or, with certain semiconductors, which might change
their characteristics upon heating. Also, these highly
concentrated complex catalyzed resins can be used where
heating the resin to cure it would also unduly cause
expansion of the wires or other components that are being
bonded or insulated.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the invention,
reference may be made to the preferred embodiments, exem-
plary of the invention, shown in ~he accompanying drawings,
in which:
Figure 1 shows one type of apparatus that can be
used to produce the catalytic complexes used in this
invention;
Fig. 2 shows a wrapped, resin-impregnated coil
made with the resinous composition of this invention;
Fig. 3 shows an encapsulated electrical article
! 25 made with the resinous composition of this invention; and
Fig. 4 shows an illustration of the resinous
composition of this invention used as a series coil connec-
tion stub insulation in high voltage rotating apparatus.
DESCRIPTION OF_THE PREFERRED EMBODIMENTS
30 It has been found that selected carbon containing
cyclic compounds, containing an electron deficient element,
can effectively interact and complex with selected carbox-
ylic acid anhydrides, through irradiation containing the
radiation wavelength range of from about 2,000 Angstrom
units to about 5,200 Angstrom units, preferably in the
ultraviolet portion of that range, i.e., from about 2,000
Angstrom units to about 3,900 Angstrom units. Laser
:
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51,803l
irradiation, for example with ar~ Argon laser at about 3,600
Angstrom units, is a very concentrated and en~rgy efficient
substitute for commol ult~aviolet (U-V-) lamp sources, and
allows the reaction to proceed at about ~5C without
cooling.
When a laser is used, 5 minutes to 60 minutes
irradiation will provide an effective amount of reactive
catalytic complex to cure organic resins; and when a 250
watt to 500 watt U.V. lamp is used, 15 minutes to 90
minutes will provide an effective amount of reactive
catalytic complex to cure organic resins, when, in each
case, the catalytic complex is to be further concentrated
in its solvent solution. In the case of the U.V. lamp, the
interacting mixture must usually be surrounded by a refrig-
eration means, so that the heat of the U.V. lamp does notcause undue evaporation of the materials before the com-
plexing is completed. In all cases, the temperature must
be kept below about 40C, to prevent evaporation of the
materials, for example, maleic anhydride has a sublimation
temperature of about 52C and tetrahydrofuran has a boiling
point of about 66C. These complexes formed by irradiation
are reactive species that are particularly effective in
curing epoxy, vinyl, polyester, and other organic resinous
systems, at temperatures below about 30C, with no ionic
contamination of the cured resin.
The useful carbon containing cyclic compounds ~or
these complexes contain one or more sulfur and/or oxygen,
preerably oxygen, electron deficient elements or compo-
nents, where th~ electron deficient element or component
ne~d not be present in the ring structure. Particularly
useful compounds of this type include sulfolane, trioxane,
and preferably dioxane (1,4 dioxane) a~d tetrahydrofuran,
whose respective chemical structures are shown below:
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6 51,803I
O o o O O
S/ \ / \ H C / \
H~C CH2 , O\ /O , H2C \ ~ ~ /C-C
H2C~CH CH2 o
Use~ul carboxylic acid anhydrides for these
complexes include a class of carboxylic acid anhydrides
having the chemical formula:
C ~ o
R'C'' ~
s- 1~ /o
~ C
~0 ;:
where R and R' = H, CH3, C2H5, Cl, Br or I, for example, R'
can = Cl and R can = CH3.
Use of a higher alkyl than C2H5 as R or R' will
slow the irradiation reaction with the carbon containing
cyclic compound. The most preferred carboxylic acid
anhydrid~s are those where R = H and R' - CH3, and where R
and R' - ~, i.e., citraconic anhydride, and preferably
maleic anhydride, respectively:
C ~ C~O
CH C~' \ HC'~ \
11 , 11 ~
HC ~C / C
~0 ~o
: 15 Other carboxylic acld anhydrides, such as hexa-
hydrophthalic anhydride, succinic anhydride, and dodecenyl
succinic anhydride, are not effective to provide catalytic
reactive æpecies. The double bond opposite the central,
single bonded oxygen, appears to be o critical importance
in providing catalytic reactive species with the above
described carbon containing cyclic compounds during irradi-
ation. The carbon containing cyclic compounds act a5 a
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7 51,803I
solvent for the selected acid anhydrides which are usually
in solid form. The most useful weight ran~e of (selected
carboxylic acid anhydride):(selected carbon containing
cyclic compound) is from about (1):(0.6 to 2), most preer-
S ably from about (1):(0.8 to 2~. Less than 0.6 part/l partacid anhydride, a solution will not usually result, even
with mild heating. Over 2 parts/l part acid ar~ydride, the
complex may not form.
Usually, the selected acid anhydride is added to
the selected liquid carbon containing cyclic compound,
acting as solvent, and mixed, at about 25C to 30C,
although they can be mixed at up to about 40C, until a
solution results. At this point there is no interaction
between the two ingredients other than solution formation,
i.e., the produc~ of the mixture contains no complexes or
reactive species. Then a reactive catalytic complex is
formed between the aci~ anhydride and a part of the sol-
vent. Preferably, a source of irradiation, such as a bank
of U.V. lamps or, for example, an Argon ion laser beam,
which provides concentrated radiation and fast interaction,
is directed into the solution to form the reactive catalyt-
ic complex. Fig. 1 of the Drawings, shows the use of a
coherent CR-18 Argon ion laser to produce useful complexes
for curing resins. In Fig. 1, mirrors 1 reflect laser beam
2, from laser source 3, through convex lens 4 into monomer
solution 5, attached to magnetic ~tirrer means 6, and
having optionaL nitrogen bubbler means 7.
Upon irradiation of the solution, with the
wavelength range containing radiation of about 2,000
3Q Angstrom units to about 5,200 Angstrom units, and prefera-
bly from about 2,000 Angstrom units to about 3,900 Angstrom
units, a complex forms. There will never be complete
interaction and complexing betwe~n the two components, so
that some solvent will always remain. Although applicants
are not to be held to any particular theory, using the
interaction between maleic anhydride and dioxane as an
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8 51,803I
example, the possible interactionS that, it is thought
might occur include:
HC ~ \ l ~ C~0 r , C~ *
H2C~ Ch ~ C~ ~ ~ hC ~ / ~ ~
O r C0 ,~0 HC ~ S
r ~ O ~ 0
O
~C C~O
/ ~ CH HC
. O I + I
2 .HC \ /
)C ~ ~ (II) ~O
12C ~ ~fCH2
(III)
~s shown in the previously described reactions,
i~ is believed that Argon ion laser action on the product
solution and mixture of maleic anhydride and dioxane in
step (A) produces a si~glet excited species which goes to
triplet excited state via step (B). The triplet excimer
thUS produced reacts with another maleic anhydride unit in
,
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g 51,803I
the ground state (step C) and produces a complex (after
step C). This compl~x then abstract~ a hydrogen atom from
dioxane. Th~s results in a color change between step (C)
and step (D) to provide catalytic char~e trans~er complexes
consisting essentially o reactive specieS, such as cation
(I), radical anion (II) and a free radical (III) containing
only an electron as a reactive component; which are capable
of initiating a cationic polymerization in epoxies and a
free radical polymerization in vinyl monomers. In addition
to the re~c$ive species shown, it has tlOW been found that a
substantial amount, i.e., from about 20% to about 50% of
carbon containing cyclic compound added as solvent-
interactant, i.e., such as dioxane, remains uncomplexed,
and acts as an undesirable plasticizer. No deliberate
heating is generally used, care being taken to react only
up to about 40C, with no ca~alysts, or initiators being
present, the complexing proceeding solely due to irradia-
tion effects.
The uncomplexed, carbon containing cyclic com-
pound remaining after catalytic complex production, be it
dioxane, sulfolane or tetrahydrofuran, has now been found
to provide a plasticizing effect on the resinous system it
is used~ with, slowing resin cure at 25C. Continued
irradiation has not been found to reduce substantially the
25 amount o~ carbon containing cyclic compound remaining.
Heating the catalytic complex over about 45C in an attempt
to reduce the amount of unreacted, car~on containing cyclic
compound usually causes decomposition of the already formed
catalytic complex. A method to remove a substantial amount
of the uncomplexed, r~maining carbon containing cyclic
solvent compound without decomposing or deactivating any
catalytic complex aIready foxmed, can involve passing a
stream of nitrogen gas over the catalytic complex at 25C
under about 45C, or preferably using a vacuum chamber at
3~ under about 45C, to remove a substantial amount of the
uncomplexed carbon containing cyclic solvent compound, and
reduce substantially the plasticizing effect of the unre
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51,803I
acted solvent, allcwing extremely fast re~in gel times and
commercially feasible cure times at 25C. It is also
speculated that the concentration may open up some rings of
the carbon containing cyclic compounds, proviclin~ addition-
al reactive species.
The solvent solution of catalytic complex is
concentrated to from about 55% to about 90%, preferably
from about 65% to abou~ 75% of its original weight.
Concentration below about 55% is very difficult, and not
concentrating below about ~0% does not yield much benefit
in terms of gel and cure times to justify the expense of
utilizing a concentrating means. Concentrating between 65%
and about 75% yields a very workable thick slurry material.
Concentration between about 55% and 65% yields a still
useful material of incr~a ing solidity as 55% is ap-
proached. The term "c~oncentrated" as used here means
concentration of the irradiated complex solution, wherein a
portion of the remaining carbon containing cyclic solvent
is removed, genarally in the temperature range of from
about 18C to about 45C, preferably below about 30C. The
term X% concentrated as used herein is defined as concen-
trated to X% of its original weight, i.e., 60% concentrated
means that 40% of the original solvent solution weight has
been evaporated. The solvent will evaporate but the
complex will not evaporate or decompose under the tempera-
ture conditions described above.
Epoxy resins are the preferred resinous materials
used with the highly concentrated catalytic complexes
previously described. One type of epoxy resin which may be
used as the base resin in the invention, or usad in combi-
nation with, for example, a cycloaliphatic epoxy, is a
bisphenol type obtainable by reacting epichlorohydrin with
a dihydric phenol in an alkaline medium at about 50C,
using 1 to 2 or more moles of epichlorohydrin per mole of
dihydric phenol. The heatin~ 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
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11 51,803I
single simple compoun~, is generally a complex mixture of
glycidyl polyethers, but the principal product may be
represented by the chemical structural formula:
, CH2-CH-CE2-0(R-O-CH2-CHOH-CH2-O)n-R-O-CH2-CH-CH2
where n is an integer of the series, O, 1, 2, 3..., and R
represents the divalent hydrocarbon radical of the dihydric
phenol. Typically R is:
to provide a diglycidyl ether of bisphenol A type epoxy
resin or
@~ C ~ ~.
H
to provide a diglyci~yl ether of bisphenol F type epoxy
resin.
; ~ The bisphenol epoxy resins used in the invention
have a 1,2 epoxy equivalency greater than one. They will
generally be diepoxides. By the epoxy equivalency, refer-
ence is made to the average number of 1,~ epoxy groups,
: ~0~
C~2 c
: ' . I
contained in the average molecule of the glycidylether.
Other epoxy resins that are useful in this
invention include polyglycidylethers of a novolac. The
polyglycidylethers of a novolac suitable for use in accor-
dance With this invention are prepared by reacting an
epihalohydrin with phenol formaldehyde condensates. While
the bisphenol~based resins contain a maximum of two epoxy
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12 51,803I
~roups 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 ~or the productlon of epoxy
novolac resins.
Other useful epoxy resins include glycidyl
esters, hydantoin epoxy resins, cycl~aliphatic epoxy resins
and diglycidyl ethers of aliphatic diols. Of these latter
four varieties of epoxies, cycloaliphatic epoxies are
particularly useful, used alone or blended with the other
epoxy types. The cycloaliphatic type epoxy resins that can
be amployed as the resin ingredient in the invention are
selected from nonglycidyl ether epoxy resins containing
more than one 1,2 epoxy group per molecule. These are
generally prepared by epoxidizing unsaturated hydrocarbon
compounds, such as cyclo olefins, using hydroyen peroxide
or peracids such as peracetic acid and perhenæoic acid.
The organic peracids are generally prepared by reacting
hydrogen peroxide with either carboxylic acids, acid
chloride ketones to give the compound R-COOOH.
Examples of cycloaliphatic epoxy resins would
include: 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexane
carboxylate ~containing two epoxide groups which are part
of ring structures, and an ester linkage); vinyl cyclo-
hexene dioxide (containing two epoxide groups, one of whichis part of a ring structure); and 3,4-epoxy-6-methylcyclo-
hexyl methyl~3,4-epoxy-6-methylcyclohexane carboxylate.
All o~ these epoxy resins are well known in the art, and
reference can be made to U.S. Patent 4,273,914 for addi~
tional de-tails in their production.
Other useful organic resinous materials that can
be used with the catalytic complexes previously described
include vinyl monomers, such as, styrene, 4-methoxy sty-
rene, vinyl toluene, methyl methacrylate, methyl vinyl
3S ketone, or 1,1 diphenyl ethylene and the like, and their
mixtures. Polyester resins should also work. Both of
these classes of resins are well known in the art. The
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~"2~71~3~9
13 51,803I
most useful weight ratio t`ange of (organic resinous
material):(concentrated catalytic complex) is from about
(1):(0.2 to 1.5), mo5t preferabJ.y from about (1):(0.4 to
0.60). Use of less than 0.2 parts concentrated catalytic
complex/l part organic resinous material will provide
little gel or cure time improvement- Use of over 1.5 parts
concentrated catalytic complex/l part organic resinous
material will result in minimal pot life or working time,
and air bubhles and voids .in the resin due to high exo-
therms resulting in lowering electrical properties. Therange between about (1):(0.60 to 1.5) can be especially
useful when a large quantity of filler is used, since
filler inclusion seems to substantially delay gel time.
Natural oil extenders, such as epoxidized linseed
or soybean oils, octyl epoxy tallate and reactive plasti-
cizers such as the conventional phthalates and phosphates
may also be used in small amounts, up to about 50 parts per
100 parts of resin to provide increased flexibility.
Thixotropic agents, such as fumed alumina or fumed silica,
having particle sizes of from about 0.005 micron to 0.025
micron, and pigments, such as TiO2, may be used in minor
amounts as aids in thickening the composition or enhancing
the color tones of the ~ured resins.
Similarly, various inorganic particulate fillers,
such as alumina trihydrate, silica, quartz, mica, chopped
glass fibers, beryllium aluminum silicate, lithium aluminum
~ilicat~, mixtures thereof, ànd the like, in average
particle sizes from about 5 microns to about 150 microns,
may be employed in amounts up to about 400 parts per 100
parts of resin, to improve electrical properties of the
resin formulation, to lower costs, and to provide thick
casting or pasting compositions. Photoinitiatoxs are
neither required nor desired, since they can provide an
impurity element in the composition.
Referring now to ~ig. 2, a closed full coil 10 is
shown which can be used in an electric motor or the like.
The coil comprises an end portion comprising a tangent 12,
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3~9
14 51,803I
a connecting loop ;4 and another tangent ~6 with bar leads
18 extending theref~om. Slot portions ~0 and 22 of the
- coil which sometimes are hot pressed to precure the resin
and to form them to predetermined s~lape and si7e are
connected to the tan~ents lZ and 16, respectively. These
slot portions are connected to other tangents 24 and 26
connected through another loop 28.
In the case of a motor, generally the entire
motor con-taining the coils would be placed in an impreg-
nating bath containing a low viscosity version of the resinof this invention, and vacuum impregnated. Thereafter the
impregnated motor could be removed from the impregnating
tank, drained, and air dried for about 100 hours.
Fig. 3 shows an insulated electrical member such
as a coil 30, which has conductors 32, potted or encapsu-
lated in a thick, cured, insulating casting 34, the casting
being the resinous composition of this invention applied to
the member in a casting or pasting operation and cured at
room temperature.
.20 Tha resin of this invention can be used to
adhesively bond coils together or adhesively bond plastic
articles, such as polyurethane or other plastic mountings,
to a variety of flat or tubular structures, without the use
of heat for curing. With filler added, the composition can
be used as a thick paste to coat a variety of articles.
Fig. 4 shows its use to bond coils together, where adjacent
coils 40, grouped in series are ~hown, and the resinous
insulation is used to saturate and coat tape fabric applied
over the joint connections 41, to provide insulated stub
42.
EXAMPLE 1
Several batches of cataly~ic complex solutionwere made, each containing 50 grams (0.51 mole) of maleic
anhydride (MAH) dissolved in 50 milliliters ~44.5 grams) of
tetrahydrofuran (THF) solvent-interactant. The MAH and THF
were well mixed in a stainless steel beaker with a magnetic
stirrer. The beaker was wrapped with copper tubing and the
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beaker was kept in a bath of ethylene glycol-water mixture.
Refri~erated ethylene glycol-water coolant, }cept at -20C
using an Endocol, Neslab refrigeration unit, was circulated
through the copper coil wrapped around the beaker and also
dipped in the ethylene glycol-water bath. The bath temper-
ature was about 2C. During stirring, the mixture was
subjected to U.V. irradiation from a 300 watt U.V.-D bulb
having a wav~length band between 2,000 Angstrom units and
4,000 Angstrom units, with primary wavelengths between
10about 3,600 Angstrom units and 3,900 Angstrom units. The
cooling arrangement was necessary to dissipate the heat
energy generated by the D bulb, so that the mixture compo-
nents would not evaporate before reaction. In all cases
the temperature must be maintained below about 40C.
15After 30 seconds of irradiation, the mixture
temperature increased from 18C to 35C, after which the D
bulb was shut off and the mixture was allowed to cool down
to 18C over a ~ to 3 minute period. Then the solution was
irradiated until a 35C temperature was reached, after
which it was again cooled to 18C. This irradiation and
cooling cycle was repeated until a total U.V. exposure time
of 15 minutes was obtained. During the 15 minutes irradia-
tion, the colorless MAH-THF solution turned to red, indi-
cating some interaction between the MAH and the THF. The
development of color was followed spectrophotometrically.
In the MAH-THF mixture, charge transfer complexes, having
an absorption maxima at a~out 4,480 Angstrom units, were
ormed.
The irradiated, highly fluid solution of MAH-THF,
the unconcentrated charge transfer complex, was found to
contain a substantial amount of uncomplexed tetrahydrofuran
solvent, the carbo~ containing cyclic compound~ from about
20% to about 50% of the T~F added. The unconcentrated
charge transfer complex solution was then placed in a small
~5 vacuum chamber apparatus, i.e., a vacuum desiccator at-
tached to a vacuum line drawing 0.5 Torr to 1.0 Torr, until
charge transfer complex solution weight was reduced to 65%
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16 51,803I
of its original weiaht. This concentration was carried out
at 25C, and produce~ a highly concentrated charge transfer
complex solution having s~lbstantially all of the uncom-
plexed THF removed without decomposin~ the already formed
charge transfer complex. The highly concentrated charge
transfer complex had a thick slurry consistency.
Varying amounts of the highly concentrated charge
transfer complex were added to 3,4-epoxy cyclohexyl-
methyl(3,~ epoxy)cyclohexane carboxylate, a cycloaliphatic
epoxy resin having an epoxy equivalent weight of 133 and a
viscosity at 25C of from 350 cps. to 450 cps. (sold
commercially by Union Carbide Corporation under the trade
name of ERL-4221), In several instances, filler, such as
chopped mica or glass iber, was added to the composition.
lS The gel time at 25C and the cure time at 25C for the
various compositions, which were placed in 2 inch diameter
aluminum dishes, were recorded as set forth in Table 1
below:
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17 51, 803I
___ _ _ ___ __
. . . . .
CC L L L L 0
t.~ 3 ~ t~
_ , .
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0 10 L .
L~ 1 0 L L 0 L
~ ~ o ~ u~ o e ~o
~o C~ o oL~ o
__ __ _ _ _
oZX ~ o o o o~
'2 ~ ~ ~ 3 u~ ~O L~
C~ ~ :L O O O O C~
t/~O _ _ _ ',
___ ____ __
CC 0 3 ~
~ ~ ~ ~a ~ B~* ~o ._
_ L -- ~ CD
L~ ~eCD CC L ._
. ____. ~ 2 ~..';'
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18 51,803I
As can be seen, epoxy resins can be yelled at
2SC at very reasondble valu~s and reach an intermediate
cure hardness, Shore D of 50, within reason~bLe commercial
times. Initial cure times, i.~., to a Shore D hardness of
35 to 37, occurred much sooner for Samples 1 through 5.
For e~ample, Sample 3 reached a Shore D of 35 to 37 in
about 23 hours and Sample 5 reached a Shore D of 35 to 37
in about 20 hours, both of which could be considered cured.
Upon further aging at 25C, all the Samples will. eventually
reach a Shore D hardness of 85 to 90. Of course, post-
curing for 3 to 5 hours at 75C to 125~C will bring the
Shore D value to 85 to 90 much sooner. It must be remem
bered, that, in most instances BF3 catalyzed epoxy resins
require from 12 hours to 18 hours at 75C to cure at all.
Also, increasing the U~V. lamp irradiation time to 30, 45,
or 90 minutes should provide a greater amount of reactive
species which after concentration would remain and provide
faster gel and cure times. In this example, an Argon
laser, for example, a coherent CR-18 VSG Argon ion laser
operated in the region of 3,600 Angstrom units, could be
used to form the charge transfer complex solutions with
equally good results as the U.V. lamp, in the fashion shown
in Fig. l of the drawings.
Sample 2 resinous compositions were allowed to
cure for 288 hours (12 days) at 25C, after which the
electrical properties were determined and compared to
ERL-4221 catalyzed by a mixture of 3 wt.% BF3 and methyl
ethyl amine (MEA) and a 3 wt.% addition of triphenyl tin
chloride (TPTCL), both of which are standard curing agents
in those amounts for cycloaliphatic epoxy resins. The
results are set forth in Table 2 below, where the higher
the value, the better the electrical properties:
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19 51,803I
TABI.E ~
_ ~ ~ ~
DIELECTRIC
C~RE TI~IE & BREAKDOWN STRENGTH-:t-/'
SAMPLE RESIN CATALYST TE~IPERATURE VOLTS/MII.__ ___ __ ____
2 ERL-4221 MAH:THF 288 hrs. 2;C 435
_ _ _ _ , ~
6* ERL-4221 BF3/~lEA 15 hrs. 75C 285 .
__ __ ~
7~,~ ERL-4221 TPTCL 15 hrs. 75C 260
_ _ ~ .
: ~':Comparative Examples
: *~Rate of voltage incre~se = 500 ~o1ts/second
As can be seen, if the insulation can be applied
in a situa~ion where a 2.5 hour gel period is practical and
a storage time of 12 days is feasible, dramatic improve-
ments in dielectric strength, at least a 50% increase, are
possi~le. It was found that the catalytic curing activity
of the complexes remained stable for over l year. In
addition to polymerizing epoxies, these catalytic complexes
were successfully used to initiate polymerization in vinyl
monomers such as styrene, p-methoxy styrene and 1,1 di-
phenyl ethylene. Hence, these catalytic complexes can be
used to polymerize a wide variety of monomers at room
temperature without exposing the epoxy or vinyl resin
itself to radiation, or exposing the electrical components
bonded or insulated with the complexed resins to excesses
of halide action.
EXAMPLE 2
The same amounts of ingredients and processes
were followed as in Example 1 to make the charge transfer
complex, except that the charge transfer complex solution
was concentrated to 75% of its original weight. The gel
time at 25~C, and the cure time at 25C was recorded as set
for-th in Table 3 below:
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21 51,803I
As can b~ seen, comparing the gel and cure times
of Sample 8 with Sam~le 3 in Table 1, where the Sample 3 is
a more concentrated solution, i.e., 65% concentrated--
having 35% o~ the solution cold vaporized, the Sample 3
charge transfer complex provided improved values. In both
Examples 1 and ~, the composition is considered to be
gelled when it reaches a soft, tacky, gel consistency
exhibiting no flow.
EXAMPLE 3
' ~ 10 One layer of Dacro~ polyethylene terephthalate)
b felt tape, 0.010 inch thick, was dry half lap wrapped
around the stub bar lead connections of cut adjacent motor
coils, as shown in Fig. 4 of the drawing. The tape was
then saturated with the insulating composition of Sample 3,
from Example 1, by a dipping and painting process, to
provide a total build of about 0.05 inch. The Sample 3
composition contained ERL-4221 resin and a 65% concentrated
complex of MRH:THF, with a resin:concentrated complex
weight ratio of 1:0.50. A similar tape was wrapped around
a similar coil stub and saturated and painted with an
insulating composition containing ERL-4221 resin and an
alkyl amine catalyst, capable of providing room temperature
epoxy cure. The Sample 3 composition was cured for 288
hours ~12 days) at 25C and the comparative Sample 9
25 composition was also cured for 288 hours at 25C. The
dielectric strength of each Sample was then measured while
immersed in a 5% salt solution--a very drastic test. The
results are shown below in Table 4, where the higher the
value, the better the electrical properties:
.. . . .
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22 51,803I
TA~LE 4
____~___ __________ _ _ _ TOTAL ~ __ __ __ __ __
INSUL. DTELECTRIC
CURE TIME THICKNESS BREAKDOWN STRENGT}I**
5 SAMPLE RESIN CATALYST & TEMP. INC}IES VOLTS/MIL
___ , _ -,. . ~ __ _
3 ERL-4221 MAH:THF 288 hours 0.05" 352.9
=.,. ___ ___ . _
9~ ERL-4221 Alkyl 288 hours 0.05" 19.5
amine 25C
__ . _ _ . __ ,~ L _
~Comparative Example
~Rate of increase = 500 volts/second
As can be seen, the c~mposition of this invention
provides outstanding insulating and electrical properties
even under highly rigorous testing.
. .
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