Note: Descriptions are shown in the official language in which they were submitted.
~ ~0~35
1 51,153C
LASER IRRADIATED CATALYTIC COMPLEXES
AS LOW TEMPERATURE CURING AGENTS
FOR ORGANIC RESINS
sACKGROUND 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
high concentrations of accelerators, very slow gel times
are experienced. Considerable effort has been devoted in
recent years to devéloping 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
15 ~ glycidyl ester epoxy resins, to provide resinous electrical
insulating compositions wi-thout using acid anhydrides.
These compositions, however, required at least 120C curing
temperatures. In a later improvement, Smith et al., in
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2 51,153C
U.S~ Patent 4,273,91~ dlscovered a low temperature, fast
curinq epoxy insulating composition which consists of an
epoxy resin a~d a carboxylic acid anhydride complex. The
anhydride ~omplex was made by the low temperature reaction
of a selected Lewis acid catalyst, such as antimony
pentachloride, titanium tetrachloride, boron trifluoride,
tin tetra chloride, or triphenyl tin chloride, with a
carboxylic acid anhydride. There, the catalyst and anhy-
dride were simply pre-reacted at a reacting mass tempera-
ture of from 10C to about 45C. The complex allowedsubstantially 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 chained
polyalkylene ethers, at from about 80C to 160C, to
provide addition products, noting that the literature
showed successful reaction of maleic anhydride with
tetrahydrofuran, 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 from 100C
to about 130C with epoxies and the like.
What is needed is a room temperature curable
resin system or catalytic curing agent which will also have
extended shelf life, -and wh~ch will help provide good
electrical insulatiny properties to the resins it cures.
SUMMARY OF THE INVENTION
The above problems have been solved and the above
needs met, most broadly, by admixing an epoxy resin or
vinyl resin with a selected carboxylic acid anhydride and
irradiating the mixture with a laser having a wavelength
range of from about 2,000 Angstrom units to about 3,900
Angstrom units, most preerably an Argon ion laser operated
in the region of about 3,600 Angstrom units. This provides
an in-situ, two component, laser curable composition. In a
.
3 51,153C
preferred embodiment, the above problems have been solved
by admixing an organic resin, such as an epoxy resin or a
vinyl resin, with a catalytic complex produced by irradiat-
ing a mixture of: (a) a selected carboxylic acid anhy-
dride, and (b) a carbon containing cyclic stabilizingcompound containing an electron deficient element, such as
sulfur or preferably oxygen and their mixtures, selected
from the group consisting of tetrahydrofuran, dioxane,
trioxane, and sulfolane, and their mixtures. The weight
ratio of (carboxylic acid anhydride): (carbon containing
cyclic compound) is from about (1):~0.8 to 2). In both
cure reactions, no free radical U.V. photGinitiators are
used or desired, no additional curing ayents are needed,
and the temperature is kept below about 40C during
irradiation.
In the preferred three component system, the
catalytic complex, when added in a weight ratio of
(resin):(catalytic complex) of from about (1):(0.2 to 1),
will effect substantially complete cure at 25C in from
about 60 hours to 144 hours. The irradiation in the
preferred three component system is within the wavelength
range of from about 2,000 to about 5,200 Angstrom units.
The irradiation is effective only when both the selected
carboxylic acid anhydride and the selected carbon contain-
ing cyclic compound are mixed together, the irradiation of
the mixed product solution producing an active species
which is responsible for initiating resin polymerization at
room temperature.
The in-situ resin system, using only epoxy resin
plus selected anhydride, is particularly useful to coat
flat surfaces haviny patte~rned conductive circuitry, where
only the resin covering the metal pattern is laser irradi-
ated to cause cure, after which the rest of the resin can
be washed off with solvent or the like, to Ieave an insu-
lated conductiny metal pattern on the flat surface, whichmay be a printed circuit board of some type. This does
require sophisticated laser technology, however. In the
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preferred resin system, the resins incorporating the
catalytic complexes can be used to impregnate electrical
coll insulation, to encapsulate electrical articles, to act
as an insulating adhesive for polyurethane and other type
articles, to act as a low viscosity room temperature
curable resin, and the like. Both of these complex
catalyzed resins can be especially useful when insuLating
temperature sensitive materials that might be melted by
application of heat, or, as in certain semiconductors,
which might change their characteristics upon heating.
Also, these complex catalyzed resins can ba 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 the accompanying drawings,
in which:
Fig. 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 preferred resinous composition of this
~5 invention; and
Fig. 3 shows an encapsulated electrical article
made with the preferred resinous composition of this
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The first sections of this description will deal
with the preferred three component, curable system, which
includes a carbon containing cyclic stabilizer which is
mixed with anhydride and irradiated before addition to the
resin; with later sections dealing with the two component
system, which is appropriately applied to a substrate and
irradiated in-sltu.
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51,153C
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 in 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 to about
3,900 Angstr~.l units. Laser irradiat;on, for example ~ith
an Argon laser at about 3,600 Angstrom units, is a very
concentrated and energy efficient substitute for common
ultraviolet (U.V.) lamp sources, and allows the reaction to
proceed at about 25C without coo~ing.
When a laser is used, 10 to 90 minutes irradia-
tion will provide an effective amount of reactive species
to cure organic resins. When a 250 to 500 U.V. watt lamp
is used, 30 to 120 minutes will provide an effective amount
of reactive species to cure organic resins, but the react-
ing mixture must be surrounded by a refrigeration means, so
that the heat of the U.V. lamp doesn't cause undue evapora-
tion. In all cases, the temperature must be kept below
about 40C, to prevent evaporation of reactants, for
example, maleic anhydride has a sublimation temperature of
about 52C and tetrahydrofuran has a boiling point of about
60C. These complexes formed by irradiatlon are reactive
species that are particularly effective in curing epoxy,
vinyl, polyester, and other organic resin systems, at
temperatures below about 30C, with no ionic contamination
of the cured resin.
The useful carbon containing cyclic stabilizing
compounds for these complexes contain one or more sulfur
and/or oxygen, preferably oxygen, electron deficient
elements or components, where the electron deficient
element or component need not be present in the rin~
structure. Particularly useful compounds of this type
3S include sulfolane, trioxane, and preferably dioxane
(1,4-dioxane) and tetrahydrofuran, whose respective chemi-
cal structures are shown below:
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6 51,153C
O O , O O O
~ /\ /\ /\
S H2CI fH2 H2CI C~H2
H2C CH2 ~ O / , H2C\ / 2 C-C
H2 C ~CH2 CH2 0
Usef~ll carboxylic acid anhydrides for these
complexes include a class of carboxylic acid a~hydrides
having the chemical formula:
C ~o
R'C~ \
11 0
RC
~ C~o
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
anhydrides are those where R - H and R' = CH3, and where R
and R' = H, i.e., citraconic anhydride, and preferably
maleic anhydride, respectively:
C~ ~
~ "
CH3~C \ HC
ll O, 11 ~
HC ~ C / ~o
Other carboxylic acid anhydrides, such as hexa-
hydrophthalic anhydride, succinic anhydride, and dodecenyl
succinic anhydride, are not effective to provide catalytic
reactiv species. The~ double bond opposite the central,
~ :
single bonded oxygen, appears to be of critical importance
in providing ~catalytic reactive species with the above
described carbocyclic compounds during irradiation. The
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7 51,153C
carboc~clic com~ounds act as a solvent for the selected
acid anhydrides which are usually in solid form. The
useful weight range of (selected carboxylic acid
anhydride):(selected carbon containing cyclic compound~ is
from about (1):(0.8 to 2). ~ess than o.a part/l part acid
anhydride, a solution will not result. Over 2 parts/l part
acid anhydride, the complex may not form.
Usually, the selected acid anhydride is added
the selected liquid carbon containing cyclic compound,
acting as solvent, and mixed, at about 25C to 30C, until
a solution results. At this point there is no interaction
between the two ingredients other than solution formation,
i.e., the product of the mixture contains no complexes- or
reactive species. Then a source o ultraviolet light
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. 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 in contact with magnetic stirrer means 6 and
having optional nitrogen bubbler means 7.
Upon irradiation of the solution, within the
wavelength range of from about 2,000 Angstrom units to
~ about 5,200 Angstrom units, and preferably from about 2,000
; Angstrom units to about 3,900 Angstrom units, a complex
forms. Although applicants are not to be held to any
particular theory, using the interaction between maleic
anhydride and dioxane as an example, the possible reactions
that, it is thought, might occur include:
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851,153C
C~O
~0 h'~
--` ~L C ~ L c j c
r ~c c --Hl
l c ~
r O'c~+O~~c`,0~ 1~
H2C ~ ~CH2
~C C~
/ ~ CH HC
O I + I
\ / 2 \ C /
0~ (I) ,,0 ~ (II) ~0
.HC fH2
H2C~ ,~CH2
: O
(III)
As shown in the previously described reactions,
it i5 believed that argon ion laser action on the product
:solution admixture of maleic anhydride and dioxane in step
(A) produces a singlet excited species which goes to
triplet excited state via step (B). The triplet excimer
thus produced reacts with another maleic anhydride unit in
: the g-ound state (step C) and produces a reactive charge
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9 51,153C
transfer complex (after step C). This charge transfer
complex then abstracts a hydrogen atom from dioxane. This
results in a color change between step (C) and step (D)
indicating the presence of catalytic complexes consisting
essentially of reactive species such a.s cation (I), radical
anion (II) and a free radical (III) containing only an
electron as a reactive component. The catalytic com~lexes
are capable of initiating a cationic polymerization in
epoxies and a free radical polymerization in vinyl mono-
mers. In addition to the reactive species shown, someunreacted carbon containing cyclic compound, i.e., dioxane
is thought to remain. No deliberate heating is used, care
being taken to react only up to about 40C, with no cata-
lysts, or initiators being present, the reaction proceeding
solely due to irradiation effects.
Epoxy resins are the most preferred resins used
with the catalytic complexes previously described. One
type of epoxy resin which may be used as the base resin in
the invention, or used in combination 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
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:
O
CH2-C~-cH2 O(R-o-cH2-cHOH-cH2-o)n~R-o-cH2-c~-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:
C ~0}
CH3
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51,153C
to provide a diglycidyl ether of bisphenol A type epoxy
resin or
~ H ~
to provide a diglycidyl ether of bisphenol F type epoxy
resin.
The ~ sphenol 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 th average number of 1, 2 epoxy groups,
CH2 \ C -- -
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 anepihalohydrin with phenol formaldehyde condensates. While
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.
Other useful epoxy resins include glycidyl
esters, hydantoin epoxy resins, cycloaliphatic 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 employed 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
general~ly prepared by epoxidizing unsaturated aromatic
hydrocarbon compounds, such as cyclo-olefins, using hydro-
- carbon compounds, such as cyclo-olefins, using hydrogen
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11 51,153C
peroxide or peracids such as peracetic acid and perbenzoic
acid. The organic peracids are generally prepared by
reacting hydrogen peroxide with either carboxylic acids,
acid chlorides ketones to give the compound R-COOOH.
Examples of cycloaliphatic epoxy resins ~ould
include: 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane
carboxylate (containing two epoxide groups which are part
of ring structures, and an ester linkage); ~ nyl cyclo-
hexene dioxide (containing two epoxide groups, one of
which is part of a ring structure); 3,4-epoxy-6-methyl-
cyclohexyl methyl-3,4-epoxy-6-methylcyclohexane carboxy
late and dicyclopentadiene. All of these epoxy resins are
well known in the art, and reference can be made to U~S.
Patent 4,273,914 for additional details in their produc-
tion.
Other useful resins that can be used with thecatalytic complexes previously described include, prefera-
bly, vinyl monomers, such as, styrene, 4-methoxy styrene,
vinyl toluene, methyl methacrylate, methyl vinyl ketone,
1,1 diphenyl ethylene and the like, and their mixtures.
Unsaturated polyester resins should also work. Both of
these classes of resins are well known in the art.
Natural oil extenders, such as epoxidized linseed
or soy bean oils, octyl epoxy tallate and reactive plasti-
cizers such as the conventional phthalates and phosphatesmay also be used in small amounts, up to about 50 parts per
100 parts of resin to provide increased flexibility.
Thixotropic agents, such as SiO2 and pigments, such as
TiO2, may ba used as aids in fluidizing the composition or
enhancing the color tones of the cured resins.
Similarly, various inorganic particulate fillers,
such as silica, quartz, mica, chopped glass, beryllium
aluminum silicate, lithium aluminum silicate and mixtures
thereof, in average particle sizes from about 10 microns to
about 100 microns, may be employed in amounts up to about
; lOO parts per 100 parts of resin, to improve electrical
properties of the resin formulation, to lo~Jer costs, and to
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12 51,153C
provide thick casting or pasting compositi.ons. Photoini-
tiators are neither requir~d nor desired, since they can
provide an impurity element in the composition.
Regarding the broad two component, in-situ
composition, irradiation must be in the ultraviolet range
of from about 2,000 to about 3,900 Angstrom units, prefera-
bly from about 3,300 Angstrom units to about 3,900 Angstrom
units, most preferably, an Argon ion laser, or a suitable
eximer laser, operated in the region of about 3,600 Ang-
strom units. Ultraviolet (U.V.) lamp sources were notfound to be practical in this in-situ embodiment, since
they required almost 2,000 times more energy to cure this
resin system than a laser. When a laser is used, 1 to 45
minutes laser irradiation will usually produce an efective
amount of reactive species to cause gellation and eventual
cure of the resin system at 25C. In all cases, the
temperature must be kept below about 40C, to prevent
evaporation of maleic or other anhydride.
In this in-situ embodiment, carbon containing
cyclic compounds are not used. The useful carboxylic acid
anhydrides are those described previously with the most
preferred being citraconic anhydride and maleic anhydride.
Other carboxylic acid anhydrides, such as hexahydrophthalic
anhydride, succinic anhydride, and dodecenyl succinic
anhydride are not effective to provide catalytic reactive
species. Useful epoxy resins include bisphenol A type
epoxy resins, bisphenol F type epoxy resins and cycloali-
phatic type epoxy reslns, all described previously in
detail. Included within the useful epoxy resins is the
diglycidyl ether of an aliphatic diol, such as neopentyl
glycol (DGENPG), and cyclohexene oxide, having the respec
tlve structures:
O CH O
/ \ 13 / \
CH - CH - CH2OCH2 - C - CH2OCH2 2
CH3
.
.
13 51,153C
A very preferred cycloaliphatic epoxy is 3,4-epoxy
cyclohexymethyl (3,4 epoxy) cyclohexane carboxylate. Other
useful resins include vinyl monomers, such as, styrene,
4-methoxy styrene, vinyl toluene, methyl methacrylate,
methyl vinyl ketone, 1,1 diphenyl ethylene and the like.
Epoxy resins are the most preferred resins. Oil extenders
and fillers described previously may also be added to the
com~osition. U.V. photoinitiators are neither need-1 nor
desirable, since they may add ionic impurities to the
resin, and are excluded.
The epoxy or vinyl resin are mixed together, at
under 40C, in the weight ratio of (resin):(anhydride) of
from about (1):(0.1 to 1) with (1):(0.2 to O.S) preferred,
to form a solution. Use of less than about 0.10 part per 1
part epoxy or vinyl will result in very long gel times. At
this point no catalytic complex is formed. Upon irradia-
tion of the solution, within the wavelength range of from
about 2,000 Angstrom units to about 3,900 Angstrom units,
prefarably using an Argon ion laser, a complex forms which
causes direct cure of the epoxy or vinyl resin. Although
applicants are not to be held to any particular theory,
using the interaction between maleic anhydride and
cyclohexene dioxide as an example, the possible reactions
that, it is thought might occur i~clude:
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14 51,153C
~;0
~C 1 _ *
0~ 0~
~'
(IV)
C~
L~~o~ c c;
As shown, it is believed that the Argon ion laser
action in step (A) produces a singlet excited species which
:~ :goes to triplet excited stage via step (B). This, in turn,
~: :: 5 proceeds to charge transfer complex (IV) via step (C). In
~ the initial stages of polymerization, during step (D),
: polyether linkage (V) is probable. This suggests that the
electron donor: cyclohexene oxide undergoes a cationic
polymer:ization in the presence of a counteranion-radical.
:~ lO At longer irradiation times the maleic anhydride adduct of
a polyether is formed via step (E). A color change from
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51,153C
clear to yellow or oranye indicates formation of charge
transfer complex (IV).
Referring now to Fig. 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 comprlsing a tangent 12,
a connecting loop 14 and another tan~ent 16 with bar leads
18 extending therefrom. Slot portions 20 and 22 of the
coil which som imes are hot pressed to precure the resin
and to form them to predetermined shape and size are
connected to the tangents 12 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 containing the coils would be placed in an impreg-
nating bath containing a low viscosity version o 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.
Eig. 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 reslno~s composition of this invention applied to
the mem~er in a casting or pasting operation and cured at
room temperature.
The 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 o articles.
The in-situ composition of this invention can be used to
selectively insulate patterned areas of a substrate or
patterned conductors on a substrate.
EXAMPLE 1
Three catalyic complexes were made and used as a
curing agent and then used with epoxy resin, to illustrate
; the preferred three component system. In a 40 ml. glass
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!35
16 ~1,153C
beaker, 0.0~ mole (1.96 grams) of maleic anhydride (MAH)
and 2.0 ml. (1.78 grams) of tetrahydrofuran (THF) were
added and well mixed with a magnetic stirrer. Into another
40 ml. glass beaker, 0.02 mole of maleic anhydride (MAH)
and 2.0 ml. (2.07 grams) of dioxane (DOX) were added and
well mixed with a magnetic stirrer. Into a third 40 ml.
gl~ss beaker, 0.02 mole of maleic anhydride (MAH) and 2.0
m_. (2.52 grams) of sulfolane (SOL) were added ~nd well
mixed with a magnetic stirrer. At this point a simple
solution occurred with no color change or apparent reac-
tion. The solution temperature was ~5C. An argon ion
laser beam was directed into each beaker separately with
the help of reflecting mirrors, as shown in Fig. 1 of the
Drawings. An optional flow of Nitrogen gas was bubbled
through the solutions. The temperature of the solution was
maintained at 25C during irradiation.
The laser was a coherent radiation CR-18 USG
Argon ion laser, tunable over a number of discr te wave-
lengths. The laser was operated in the re~ion of about
20 3,600 Angstrom Units at a power level of 1.3 watts. The
irradiation was continued for 30 minutes during which the
colorless MAH/~HF solution turned to deep red and the
colorless MAH/DOX solution turned to yellow-red, indicating
some interaction between the MAH and the THF, and the MAH
and the DOX.
The development of the color in the beakers was
followed spectrophotometrically. No absorption was ob-
served in the visible region until these mixture solutions
were irradiated with argon ion laser. In case of maleic
anhydride/tetrahydrofuran and maleic anhydride/dioxane
systems, charge transfer complexes, having an absorption
maxima at 4,480 Angstrom Units were formed. Maleic
anhydride/sulfolane showed an absorption maxima at 4,000
Angstrom Units. ~he UV-visible spectrum of maleic
anhydride/tetrahydrofuran shows a linear increase in the
concentration of the charge transfer complex with the
:rradlation time~ A~ similar behavior was observed in
17 51,153C
maleic anhydride~dioxane and maleic anhydride~sulfolane.
The colored complexes formed in all these systems can be
closely related to the active species, which would initiate
the polymerization of epoxies or vinyl monomers.
One gram of each compLex was then added separate-
ly at 25C to 2.0 grams of 3,4-epoxy cyclohexylmethyl (3,4
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 Corp. under the tradename of
ERL-4221), and one gram of MAH/THF was also added at 25C
to 2.0 grams of a diylycidyl ether of neopentyl glycol, a
low visco~sity epoxy resin of the diglycidyl ether of- an
aliphatic dlol type, having a viscosity at 25C of from 5
cps. to 100 cps. (sold commercially by Ciba Geigy Co.
under the tradename XU-193). The gel time at 25C and cure
time at 25C for these four resin systems were then record-
ed as set forth in TABLE 1 below:
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18 51, 153t:~
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~ L r a~ S
L .1: ~ o tO 3
_ _ _
. E o~ L L L L
--C :1' 0 N 3
O O tO 0 0
L ~
O 5~
- d~ c c ~ c
L E E E E E
J X ._ _
e t~ O o o o o
...' ~
3;J
O ~
~ - ~ T C~ O C:~ ~ N
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As can be seen, epoxy resins can be catalyzed and
cured at 25C using the complexes of this invention.
Cycloaliphatic epoxy resins such as ERL-4221 show excellent
results, curing at 25C in Sample 1 within 3 days, noting,
that in some instances, BF3 catalyzed epoxies may require
12 to 18 hours cure at 75C to cure. The XU-193 required a
substantial cure time, but it must be remembered that it is
an extremel- lo~ vi~cosity epoxy resin. Cure time of
bisphenol A and other type epoxies could be improved by
blending with cycloaliphatic epoxies. Eleckrical proper
ties of the ERL-4221 epoxy 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). The results are set forth in TABLE 2
below:
:
:::
.;
' ~ . ,.: ''"
. .
~0 51, 153C
__ _ .
5~
o L _
. , L U~ E N r-- N N
L
__ __
>U :~-0'0 0
--E X X X X
N O N O ~i O
~ ::~
~ _ _
~e~
__
.~ ~ ~ ~;
: : __
~ N~ -
`
~ ~ :
`: '
,
: ' ' ~ . : '-
.
~: ' `, ' ' .'' ` '' ~ . , :
'
8~
21 51,153C
The higher the resistivity and breakdown strength
the better the insulating effect. As can be seen, break
dcwn strength of the catalytic complex, Samples 1 and 3, is
very good and resistivity i5 adequate. Samples 5 and 6 do
not show much detrimental effect of halide since only minor
amounts were used. However, even such minor amo~nts were
used. However, even such minor amounts could attack
elec:rical c aponents of the apparatus beiny insulate~ or
bonded.
In order to determine if irradiation time of the
catalytic complex would lower cure time of the resin
system, cyclohexene oxide, 0 = 0, which is an epoxy
model, was used as a base resin for MAH/THF complexes.
Here 0.02 mole (1.96 grams) of MAH and 2.0 ml. (1.78 grams)
of THF were irradiated at 25C as previously described for
15, 30, and 40 minutes usiny different resin:catalytic
complex weiyht ratios. The results of gel and cure times
at 25C are set forth in TABLE 3 below:
_ TABLE 3 ~ ___________
Wt. ratio
cyclohexene
oxide Irradiation Gel Time Cure Time
Sample :MAH/THF Timehours hours
6 1:0.25 30 min.4.5 hr.15 hrs.
7 1:0.50 30 minØ2 hr.8 hrs.
8 1:0.50 20 min.6 hr. 18 hrs.
9 1:0.50 40 minØ1 hr.6 hrs.¦
As can be seen, a 40 minute irradiation time
lowered cure time substantially over a 30 minute irradia-
tion time, and so the cure times of TABLE 1 should also belowered if more irradiation time is used to produce strony-
er complexes. The cure times of TABLE 1 should also be
lowered if the weight ratio of resin:complex is raised to
l:0.75 or possibly l:l.
~ ': ,. ~
.
`' '' ~
~L~
22 51,153C
It was found that the catalytic curing activity
of the complexes remained stabl.e for about 4 months. The
pot life of the resin system into which the complexes are
incorporated are, naturally, only about 12 hours at 25C.
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 diphenyl ethylene. Hence .hese 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.
EXAM~LE 2
Eight, clear, in-situ polymerizable co~positions
were made with maleic anhydride and an epoxy resin, and
gelled using the CR-18 USG Argon ion laser o~ Example l,
operated in the region of about 3,600 Angstrom units at 1.2
watts. The Argon ion laser was directed into the sample as
shown in Fig. 1 with help of reflecting mirrors. A con-
stant flow of N2 was bubbled through the solution. The
irradiation was continued until the magnetic stirrer
stopped stirring and the composition gelled. Table 4
illustrates the results:
.
.
: :. -
`:
.' . . .
,
8~
23 5l,lo3G
TABLE 4
__ _ ~ _
W . Ratio
Maleic Laser
Epoxy Anhydride IrradiAtion Color After
S~pleResin (~AH) Time Gel Time Irratiation
__ _ ~ _ __
10Cyclohexene 1:0.253.3 min. 3.3 ~in. Yellow
11Cyclohexene 1:0.502.5 min. 2.5 min. Yellow
-oxide
12ERL-4221 1:0.36 16 ~in. 16 min. Orange
13ERL-4221 1:0.17 30 min. 30 ~in. Or;nge-
14ERL-4221 1:0.10 47 min. 47 min. OrangP-
Yellow
15DGENPG 1:0.46 25 min. 25 min. OR~ndge'
16DGENPG 1:0.31 41 min. 41 min. Orsnge-
20 . 17DGENPG 1:0.23 62 min. j62 min. Red
At the point of gellation there was polymeriza-
Sion of the composition. After an additional 3 to 5
minutes, the cyclohexene oxide cured at 25~C. After an
additional 20 to 60 minutes, the ERL-4221 completely cured
at 25C, with the DGENPG taking somewhat longer.
,
