Note: Descriptions are shown in the official language in which they were submitted.
9~79
1 --
ACCELERATED CYCLOAL I PHAT I C
EPOXIDE~AF~OMATIC AMINE RESIN SYSTEMS
B~CKGROIJND OF THE INVENTION
~ mine curable epoxy resin formulations are
widely used as coatings, adhesi~es, sealants, and
matrices for fiber-reinforced composites. For many
applications, a ~ast rate of cure is desira~le.
Many additives have been tested as cure
accelerators for epoxy/amine mixtures. Several
references teach that additives with phenolic
hydroxyl groups are efEective with epoxy resins
derived from epihalohydrins and active hydrogen
compounds, such as bisphenol A epoxy resins. For
example, Shechter et al in Industrial and
Engineering Chemistry, Volume g~, No. 1, pages 94 to
97, 1956, disclosed that phenol was more effectiv0
than aliphatic alcohols in accelerating the reaction
of phenyl glycidyl ether with diethylamine. ~owen
et al in the American Che~ical Society Advances in
Chemistry Series, Volume 92, pages 48 to 59, 1970,
disclosed that a variety of hydroxyl containing
compounds decreased ~he gel time of a bisphenol A
epoxy~triethylenetetramine mixture. ~owen et al
disclosed tha~ 4,4'-dihydroxydiphenyl sulfone,
glycerin, phenol, ~etrabromobisphenol A, and
bisphenol A a~celerated the cure with a similar
degree of effectiveness.
Epoxy compositions containing resorcinol
are described in the prior art. For example, Gough
et al lin ~he Journ~l of Oil and Color Chemists
2099~79
Association, volume 43, pages 409 to 418, 1961),
Nagy (in Adhesive~ Age, pages 20 to 27, April,
1967), and Parten~ky (in the American Chemical
Society Advances in Chemistry S~ries, Volume 92,
pages 29 to 47, 1970~ disclo~ed that resorcinol and
many other phenolic compounds accelerate the cure of
glycidyl epoxy/amine mixture~. Markovitz in
"Chemical Properties of Crosslinked Polymers,"
American Chemical Society 5ympo~ium 1976, S.S.
Labana, Ed., page~ 49 to 58 described curable
compositions containing cycloaliphatic epoxides,
resorcinol and metal salts as coaccelerator~. No
reference was found to cycloaliphatic
epoxide/aromatic amine mixtures containing
resorcinol as an accelerator.
In many epoxy/amine formulations,
cycloaliphatic epoxides ar~ used as the epoxy
component ~ince they impart improved mechanical and
thermal properties to the cured compositions. For
example, unreinforced castings of bis(2,3-epoxy-
cyclopentyl) ether cured with m-phenylenediamine
have tensile strengths and tensile ~oduli which are
among ~he highes~ of any ~hermosetting material.
Similarly, as described by McLean et. al. in Report
No. 14450 of the National Research Council o
~9917~
-- 3 --
Canada, November, 1974, high mechanical properties
can be achieve~ in unreinforced castings made by
curing 3,4-epoxycyclohexylmethyl
3,4-epoxycyclohexane carboxylate with methylene
dianiline. ~owever, resin systems containing
bis(2,3-epoxycyclopentyl) ether or
3,4-epoxycyclohexylmethyl 3,~-epoxycyclohexane
carboxylate cure more slowly with aromatic amines
than ~imilar compositions containing bisphenol A
epoxy resins. This characteristic limit~ their
utility in composite fabrication processe6 such as
filament winding and reaction injection moldi~g.
Thus ~here i~ a need for cure accelerators for
cycloaliphatic epoxide/amine re~in systems2
Moreover~ in commercial practîce it is desirable
that the mixture of the accelerator and epoxy resin
have good storage stability in the absence of the
amine hardener. Thi~ chara~,teri~tic fa~ ta~es
handling in a production environment.
It has now been found that a select group
of phenolic compounds are highly effec~ive cure
accelera~ors for cycloaliphatic/aromatic amine resin
sy~tems. Under a fixed cure schedule, the
accelerated compositions afford improved properties
compared to compositions which do not contain the
accelerator, ~uch as higher mechanical propereies
and/or increased heat deflection temperature~ in
unreinforced ca6tings.
~ urther~ a method for accelerating the cure
of cycloaliphatic epoxide/aromatic amine mixture6 at
low temperatures has been found which comprises
adding a 601id solution of a high melting
20~9~7C3
_ 4
accelerator in a low melting solid cycloaliphatic
epoxy resin.
THE INVENTION
This invention is directed to a compo~ition
comprising:
ta) a cycloaliphatic epoxy resin
containing two or more epoxide groups,
(b) an aromatic amine hardener, and
(c) a cure accelerator selected from
(i) HO ~ ~ ~ ~ and/or
HO OH
(ii) Ra ~
wherein ~ is selected from SO2, SO,
OH O O
C(CF3)2, CN, C, CO, R i~ selected from haloyen
O ;.
or alkyl of 1 to 4 carb~n at.om~, or ~ C.-and a i~ O
to ~.
The composition may optionally contain a
thermoplastic polymer and/or a s~ructural ~iber.
The preferred cure accelerator~ are one or
more of the following: 4,4'-dihydroxydiphenyl
sulfone, re~orcinol, 2,2-bis(~-hydroxyphenyl~
hexafluoropropane, 4,4~-dihydroxydiphenyl sulfo~ide,
2,4 dihydroxybenzophenone,
4,4'-dihydroxybenzophenone, and 4,4'-dihydroxy-
3,3-dichlorodiphenyl sulone.
2 ~ 7 ~
~ 5 --
The cycloaliphatic epoxide~ of ~his
invention are prepared by epoxidation of dienes or
polyenes. Resin~ of this type include bi~(2,3-
epoxycyclopentyl) ~her, I,
~~ ~
I II
reaction products of I with e~hylene glycol which
are described in U.S. Patent 3,398,102,
5(6)-glycidyl-2-(1,2-epoxyethyl)bicyclo[2.2.1]
heptane, II, and dicyclopentadiene diepoxide~
Commercial examples o these epoxides include vinyl
cyclohexene diepoxide. e.g., "ERL-4206" (obtained
from Union Carbide Corp.), 3,g-epoxycyclohexylmethyl
3,4-epoxycyclohexane carboxylate, e.g., "ERL-4221
(obtained from Union Carbide Corp.) t 3,4-epoxy-6-
methylcyclohexylmethyl 3,4-epoxy-6-methyl-
cyclohexane carboxylate, e.g., ~'ER~-4201" (obtained
from Union Carbide Corp.), bis(3,4-epoxycyclo-
hexylme~yl)adipa~e, e.g., "ERL-4299" ~obtained from
Union Carbide Corp.), dipentene dioxide, e.g.,
"ERL-4269~' (obtained from Union Carbide Corp.~
2-(3,q-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclo-
hexane meta-dioxane, e.g., "ERL-4234" (obtained from
Union Carbide Corp.) and epoxidized poly-butadiene,
e.g., "Oxiron 2001" (obtained from FMC Corp.)
Other 6uitable cycloaliphatic epoxides
include those described in U.S. Patents Z,750,395;
2,890,194; and 3,318,822 ~hich are incorporated
~erein by referenoe, and ~he following:
--"` 2~9~179
, ~al~ , ~p ~\o\~
~C--o~ ~
~c ..o L}
Other suitable epoxide6 include:
O
~ ~ b ~ J b
whers b is 1 to 4, m is ~5-b), and Rl is H,
halogen, or Cl to C4 alkyl.
Coepoxides may be used with the
cycloaliphatic epoxide of this invention. These
coepoxides are called polyglycidyl compounds. They
contain a plurality of l,2-epoxide groups derived
from the reaction of a polyfunctional active
hydrogen coneaining compound with an excess of an
epihalohydrin under basic conditions. ~hen the
active hydrogen compound i~ a polyhydric alcohol or
phenol, the r~sulting e~oxide resin con~ains
glycidyl ~ther groups~ A preferred group of
polyglycidyl compounds are made via condensation
reactions ~i~h 2,~-bis(4-hydroxyphenyl)propane~ also
2~99179
.
_ 7
known as bisphenol A, and have structure~ such as
H C - CH - CH - O ~ C ~ ~ CH2
l 'H - CH - O ~ C ~ O ~ CH2- CH - H2
OH C~3
III
where c has a value from about 0 to about 15. These
epoxides are bisphenol-A epoxy r0sins. They are
available commercially under the trade name~ such as
"Epon 828," "Epon 1001", and "Epon 1009" from Shell
Chemical Co., and as ~DER 331", and "DER 334" from
Dow Chemical Co. The most preferred bisphenol A
epoxy resins have an "c" value between O and 10.
Polyepoxides which are polyglycidyl ethers
of q,g'-dihydroxydiphenyl methane~
4,4'-dihydroxydiphenyl sulfone, 4,q'-biphenol,
4,4'-dihydroxydiphenyl sulfide, phenolphthalein,
resorcinol, 4,2'-biphenol, or tris(4-hydroxyphenyl)
methane and the like, are useful in this invention.
In addition, EPON 1031 (a tetraglycidyl derivative
of 1,1,2,Z-~etraki6(hydroxyphenyl)ethane from Shell
Chemical Company), and Apogen 101, (a methylolated
bisphenol A resin fro~ Schaefer Chemical Co.) may
also be used. Halogenated poly~lycidyl compounds
such a~ D.E.R. 580 (a bromina~ed bisp~eno~ A epoxy
resin from Dow Chemical Company) are also useful.
---`` 209~ 79
-- 8
Other suitable epoxy resin~ incl~de pslyepoxide~
-prepar~d fro~ polyols such as pentaerythritol,
glycerol, butanediol or trimethylolpropane and an
epihalohydrin.
Polyglycidyl derivatives of
phenol-formaldehyde novolaks ~uch a~ IV where d =
0.1 to 8 and cresol-formaldehyde novolak~ such as V
where d = O.l to ~ are al~o useable.
R 2 ~ ]
IV R2 = H
V R2 = C~3
The former are commercially available as D.E.N 931,
D.E.N. 438, and D.E.N. 485 from Dow Chemical
Company. The latter are available a~, for example,
ECN 1235, ECN 1273, and ECN 1299 (obtained ~rom
Ciba-Geigy Corporation, Ardsley, NY). Other
epoxidized novolaks such as SU-8 (ob~ained ~rom
Celanese Polymer 5pecialties Company, ~ouisville,
KY) are also suitable.
Other poly~unctional active hydrogen
compounds besides phenols and alcohols may be used
to prepare the polyqlycidyl adduc~s oE t~is
invention. They include amines, aminoalcohols and
polycarboxylic acids.
Adducts derived from amines include
N,N-diglycidyl aniline, N,N-diglycidyl toluidine,
N~N,N',N'-tetraglycidylxylylene diamine, (i.e.~ VI)
N,N,N',N'-~etraglycidyl-bis (methylamino)
~-- 2099179
_ 9 _
cyclohexdne (i.e. VII) , N,N,M',N'-tetraglycidyl-
4,4`-diaminodiphenyl methane, (i.e. VIII)
N,N,N',N'-tetraglycidyl-3,3'-diaminodiphenyl
sulfone, and N,N' dimethyl-N,N'-diglycidyl-
4,q'-diaminodiphenyl methane. Commercially
available resins of this type include Glyamins 135
and Glyamine 125 (obtained fro~ F.I.C. Corporation,
San Francisco, CA.), Araldite MY-720 (obtained from
Ciba Geigy Corporation) and PGA-~ and PGA-C
(obtained from The Sherwin-Williams Co., Chica~o,
Illinois).
~0
/CH2 rH_CHZ
T CH2 CH\ ~CH2
CH
~CH~H2
H2
CH - N
2 ~ CH2 - ~ ~ ~ CH2
Vl
CH - ~ ~ ~ C~2
~H - ~
~ ~CEI2 C~ 2
CH ~ ~2
CH2~
~C~2 SH~ ~ H2
VII
-- - 2~99179
- 10 ~
" 0 - / C~2-CH-C~2
CH2 ~\ f ~A2 N~
CH2 -CH~H2
CH2
O~
VIII
Suitable polyglycidyl adduc~s derived from
amino alcohols include O,N,N-triglycidyl-4-amino-
phenol, availa~le as Araldite 0500 or Araldite 0510
(obtained from Ciba Geigy Corporation) and O,N,N-
triglycidyl-3-aminophenol (available as Glyamine 115
from F.I.C. Corporation).
Also sui~able for use herein are the
glycidyl esters of carboxylic acids. Such glycidyl
ester~ include, for example, diglycidyl phthalate,
diglycidyl terephthala~e, diglycidyl isophthalate,
and diglycidyl adipate. There may also be used
polyepoxides such as triglycidyl cyanurates and
isocyanurates, N,N-diglycidyl oxamides,
N,N'-diglycidyl derivatives of hydantoins such as
"XB 2793" tobtained f~om Ciba Geigy Corporation),
diglycidyl esters of cycloaliphatic dicarboxylic
acids, and polyglycidyl thioethers of pslythiols.
Other epoxy-containing materials are
copolymers oP acrylic dCi~ es~er~ of glyridol such
as glycidyl acrylate and glycldyl methacrylate with
~ 2~9~17~
11
one or more copolymerizable ~inyl compounds.
-Examples of such copolymers are lul styrene-glycidyl
methacrylate, 1:1 methyl methacrylate-glycidyl
acrylate and 62.5:24:13.5 methyl methacrylate:ethyl
acrylate:glycidyl methacrylate.
Silicone resins containing epoxy
functionality, e.g., 2,4,6,~,10-pentakis
[3-(2,3-epoxypropoxy)propyl]-2,4,6,fl,10-pentamethyl-
cyclopen~asiloxane and the diglycidyl ether of
1,3-bis-(3-hydroxypropyl)tetramethyldisiloxane are
also useable.
Reactive diluents containinq one epoxide
group such as t-butylphenyl glycidyl ether, may also
be used. The reactive diluent may comprise up to 25
percent by weight of the epoxide component.
The reactive diluent dnd coepoxide are used
in amounts of up to 40, preferably 30 percent by
weight.
The preferred epoxy resins are
bis~2,3-epoxycyclopentyl)ether, vinyl cyclohexene
diepoxide, 2-(3,9-expoxycyclohexyl-5,5-spiro-3~4
epoxy)cyclohexane meta-dioxane, the diepoxides of
allyl cyclopentenyl ether, l,q-cyclohexadiene
diepoxide, 3,4-epoxycyclohexylmeehyl
3,4-epoxycyclohexane carboxylate, and
bis~3,4-epoxycyclohexylmethyl~adipate.
Th~ hardeners which may be used in the
composition of this invention are selected ~rom one
or more of the following: 4,~'-diaminodiphenyl
ether, 4,4'-diaminodiphenyl methane,
3,3'-diaminodiphenyl methane, 4,4'-diaminodlphenyl
sulfone, m-phenylenediamine, p-phenylenediami~e,
4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl
209~7~
- 12 -
sulfide, l,9-bis(p-aminophenoxy)benzene, alkylated
derivatives of 4,4'-diaminodiphenyl methane su~h as
3,3'-dii~opropyl-4,4;-diaminodiphenyl methane,
1,3-bis(m-aminophenoxy)benzene,
diethyltoluenediamine, l,3-bis(p-aminophenoxy)
benzene, adducts of epoxy re~ins with the above
diamines, such as the adduce formed by reacing one
mole of a liquid bisphenol-A epoxy resin with 2 to 4
moles of m-phenylenediamine by itself or in
combination with 4,4'-diaminodiphenyl methane or the
adducts of a bisphenol-A epoxy resin with a molar
excess of g,q-diaminodiphenyl sulfone, as described
in U.S. Patent 4,330,659,
9,4'-bis(3-aminophenoxy)diphenyl sulfone,
2,2-bis(~-aminophenoxyphenyl) propane and
trimethylene glycol di-para-aminobenzoate.
The pre~erred hardeners are m-phenylene-
diamine, 4,4'-~iamino~iphenyl met.hane, low mel~ing
mixtures o~ m-phenylenediamine and 4.~-diamino-
diphenyl methane, 2,2-bis(4-aminophenoxyphenyl~
propane and the adduc~ formed by reac~ing one mole
of a liquid bisphenol-A epoxy with 2 to 4 moles of
m-phenylenediamine.
The compositions of this invention may
optionally contain a thermoplastic polymer~ These
materials have beneficial effec~ on the viscosity
and film strength characteristics of the
epoxy~ardener/accelerator mixture.
The thermopla~tic polymers used in ~his
inven~ion i~clude polyarylethers of formula I~ wh;ch
are described in U.S. Paten~s 4,lO8,B37 and
4,175,175,
`` 209~179
- 13 -
~ -O-R3-0-R4-~e
. IX
wherein R3 is a residuum of a dihydric phenol such
as bisphenol A, hydroquinone. resorcinol,
4,9-biphenol, q,4'-dihydroxydiphenyl sulfone,
4,4'-dihydroxy-3,3' 5,5'-t.etramethyldiphenyl
sulfide, 4,4'-dihydroxy-3,3',5.5'-
tetramethyldiphenyl sulfone and the like. R4 is a
residuum of a benzenoid compound susceptible to
nucleophilic aromatic substitution reactions such as
4,4'-dichlorodiphenyl sulfone,
~,~'-difluorobenæophenone, and the like. The
average value of e is from about 8 to about 120.
These polymers may have terminal groups
which react with epoxy resins, such as hydroxyl or
carboxyl, or terminal groups which do not react.
Other suitable polyarylethers are described
in U,S, Patent 3,332,209.
Also suitable are polyhydroxyethers of
formula X.
-~0 - R3 0 - CHz CH -CH
OH
X
where R3 has the same meaning as for Formula I~
and the average value of f is between about 8 and
about 300; and polycarbonates such as those based on
bisphenol A, tetramethyl bisphenol A,
4,4'-dihydroxydiphenyl sulfone,
4,4l-dibydroxy-3,3',5,5'tetramethyldiphenyl sulfo~e,
hydroquinone, resorcinol,
4,4l-dihydroxy-3,3l,5,5~-tetramethyldiphenyl
-. :
.
'
-- 2~99179
sulfide, 4,4'biphenol, 4,4'-dihydroxydiphenyl
sulfide, phenolphthalein, 2,2,4,4-tetramethyl-1,3-
cyclobutan~ diol. and the like. Other suitable
thermoplastic6 include poly (~-caprolactone);
polybutadiene: polybutadiene/acrylonitrile
copolymers, including those optionally con~aining
amine, carboxyl, hydroxyl, or -SH groups;
polyesters, such as poly(butylene terepht~alate);
poly(e~hylene terephthalate); polyetherimides such
as the Ultem resins (obtained from the General
Electric Company); acrylonitrile~ butadiene~styrene
terpolymers, polyamides such as nylon 6, nylon 6,6,
nylon 6,12, and Trogamid T (obtained from Dynamit
Nobel Corporation); poly(amide imides) such as
Torlon poly(amide imide) (obtained from Amoco
Chemical Corporation, Napierville, IL); polyolefins:
polyethylene oxid~; poly(butyl me~hacrylate);
impact-modified polystyrene; sulfonated
polyethylene: polyarylates such as those derived
from bisphenol A and isophthalic and terephthalic
acid; poly(2,6- dimethyl phenylene oxide); polyvinyl
chloride and its copolymers; polyacetals;
polyphenylene sulfide and ~he like.
The compositions of this inv~ntion may
include a structural fiber. The structural fibers
which are useful in this invention include carbon,
graphite, glass, silicon carbide,
poly(benzothiazole), poly(benzimidazole~,
poly(benzoxazole~, alumina, titania, boron, and
aromatic polyamide fibers. These fibers are
characterized by a tensile strengt~ of greater than
100,000 psi, a tensile modulus of g~eater than two
million psi, and a decomposition temperature of
` -` 2~93~7~
- 15 ~
greater than 200C. The fiber~ may be used in the
form of contin~ous tows ~1000 to 400,000 filaments
each), woven cloth, whiskers, chopped fiber or
random mat. The preferred fibers are carbon fiber6,
aromatic polyamide fibers, such as Kevldr 49 fiber
(ohtained from E.I. duPont de Nemour~, Inc.,
Wilmingeon~ DE), and silicon carbide fibers.
The composition contain6 from about 20 to
about 90 percent by weight of cycloaliphatic
epoxide, fro~ about 15 to about 80, preferably fro~
about 20 to about 70 percent by weight of hardener.
The composition also contains from 0.1 to about 10,
prefer~bly from 0.1 to about 8 percent by weight of
the accelerator. The thermoplastic polymer may be
used in amounts up to Z0 percent by weight of the
total composition. The structural fiber may be u~ed
in amounts of up to 90, preferably between about 20
and about 85 percènt by we~ht o~ the total
composite.
In the compositions of this invention, the
molar ratio of amine NH groups to epoxy groups i5
0.5 to 2.0, preferably 0.6 to 1.7.
Preimpregnated reinforcement may be made
from the compositions of this invention by combining
epoxy resins, hardener, accelerator, and optionally
~hermoplastic polymer with the structural fiber.
Preimpregnated reinforcement ~ay be
prepared by ~everal techniques known in the art,
such as wet winding or hot melt. In wet winding, a
continuous tow of reinPorcement is passed through a
resin bath cvntaining a mix~ure of the
cycloaliphatic epoxide, the amine hardener,
accelerator and optionally, the thermoplastic
.
--~ 2~9~79
- 16 -
polymer. After the tow is impregnated with the
resin, i~ i8 p~ssed through squeeze rolls to remove
excess resin. Preferably, because of the fast
curing characteristics of these compositions. the
preimpregnated reinPorcement is used to make a
composite article soon after it is prepared.
Composites may be preparea by curing
preimpregnated reinforcement using heat and
pressure. Vacuum bag~autoclave cures work well with
these compositions. Laminates may also be prepared
via wet layup followed by compression molding, resin
transfer molding, or by resin injection, as
described in European Patent Application 0019149
published November 26, 1980. Typical cure
temperatures are from about 100F to about 500F,
preferably from about 180F to about 450F. Cure
times may be as short as from about 1 to about 2
minutes depending on the composition utilized.
The compositions of this inventisn are well
suited for filament windin~. In this composite
fabrication process, continuous reinforcement in the
form of tape or tow--either previously impregnated
with resin or impregnated during winding--is placed
over a rotating and removable form or mandrel i~ a
previou~ly determined pattern. Generally the shape
is a surface of revolution and contain~ end
clo~ure~. ~hen the proper number of layers are
applied, the wound form is cured in an oYen or
autoclave and the mandrel removed.
The composition of this inven~ion may be
used as aircraft parts such as wing skins,
wing-to-bsdy fairingE, flo~r panels, ~laps, radomes;
., .
1 7 ~
- 17 -
as au~omotive parts such as driveshaft~, bumpers,
and spring~: and as pressure vessels, tanks and
pipes. ~hey are also suitable or sporeing go~ds
applications such as golf shafts, tennis rackets,
and fishing rods.
In addition to structural fibers~ the
composi~ion may also ccntain particulate fillers
such as talc, mica, calcium carbonate, aluminum
trihydrate, glass microballoons, phenolic
thermospheres, and carbon black. Up to hal~ of the
weight struct~ral fibers in the composition may be
replaced by filler. Thixotropic agents such as
fumed silica may also be used.
Further, the compositions may be used in
adhesives, potting and encapsulation compounds, and
in coating applications.
EXAMPLES
The following examples serve to give
specific illustrations of the practice of this
invention but they are not intended in any way to
limit the scope of this invention.
In the Exameles which follow, the epoxy
equivalent weight (EEW) is defined as the grams of
epoxy resin per mole of 1,2 epoxide ~roup.
Examples 1 through ~ and Controls A through
H describe effects of accelerators on the viscosity
of cycloaliphatic epoxide/aromatic amine mixtures.
ExamPle 1
A 250 ml, three necked flask equipped with
a paddle stirrer, thermometer with a Therm-0-~atch
Controller, an inlet and outlet for nitrogen9 and an
electric heating mantle was charged with 190 g o-f
2099179
- 18 -
bis(2,3-epoxycyclopentyl) ether and 10 g of
4,4'-aihydroxyaiphenyl sulfone. The mixture was
heated and s~irred at a temperature of 100C for 1
hour to dissolve the bisphenol.
A lO0 g portion of the dihydroxydiphenyl
sulfone/bis(2,3-epoxycyclopentyl ether solution was
placed in a 4 ounce jar in an oil ba~h maintained a~
a temperature of 66C. Then 30.7 g sf
m-phenylenediamine (MPDA) was added. The mixture
was stirred for about five minutes uneil the diamine
dissolYed. The viscosity of the solution was
measured with a Brookfield viscometer (obtained from
Brookfield ~ngineering Laboratories, Stoughton, MA)
at fixed intervals. The viscosity was 25
centipoises after Q.5 hours and 35 centipoises after
l.0 hour. After 1.5 hours, the mixture gelled and
increased in temperature.
ExamPle 2
A flask equipped as in Example l was
charged with lO g of resorcinol and 190 g of
bis(2,3-epoxycyclop0ntyl~ ether. ~he mixture was
stirred and heated at a tempera~ure of ~0C ~or 1
hour to dissolve the resorcinol. Then a lO0 g
portion of ~he solution wa~ transferred to a 4 ounce
jar in an oil bath at a tempera~ure of 66C and
treated with 30.7 g of MPDA. The viscosity of the
mixture at various times is shown in Table I.
F.xamPle 3
A flask equipped as in Example l was
charged with lO g of 4,4l-dihydroxybenzophenone and
l90 g o bis(2,3-epoxycyclopentyl~ether. ~he
mixture was heated at a temperature of 120~C for l
hour to dissolve the diphenol. T~en a lO0 g poreion
2099~79
- 19 -
of the solution was tran~ferred ~o a 9 ounce jar in
an oil bat~ at a temperature of 66C and treated
with 30.7 9 of MPDA. The viscosity of the mixture
at various times i~ shown in Table I.
Control~ A throuqh F
A series of other hydroxyl compounds were
screened as accelerators for bis(2,3-epoxycyclo-
pentyl) ether/MPD~ mixtures using the procedure
descr;bed in Example 1. As shown by the data i~
Table I, none of these additives caused the mixture
to gel in 1.5 hours. To determine if additional
heating would cause gelation, samples which had been
held at 66C for 1.5 hours were removed from the
bath and allowed to stand for 16 hours at room
temperature (23C). They were then replaced in the
66C bath. After an additional hour, the viscosity
of each mixture was measured. None had gelled.
2~9~179
-- 20 --
U U~; o
o o o E
.~7 .
~ N D .
_ _ _ t~
~ m I U O N
Ul ID _I N r
_l I` s:
Q~
~n
~,
Q) a
O Ln r~
,C: . ~ r) N
_ _I ~ N N ~ r~ N
_ .R ~
O
a~ F ~1
e .~ ol ~ N ~ ~
O O ~ ) ~I N Nt~ N N O
~1
C~ ~O 0
. ~
M
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20~9179
- 21 -
Example ~ and Control G describe vi6c06ity
versus time behavior of 3,4-epoxycyclohexylmethyl
3 J 4-epoxycyclohexane carboxylate/MPDA mixtures.
Viscosity measurements were made on samples in the
chamber of a Brookfield Thermosel viscometer
(obtained from Brookfield Engineering Laboratories)
maintained a~ a temperature of 66C. The
accelera~ing effect of 4,4'-dihydroxydiphenyl
sulfone on the cure of this epoxy formulation wa~
demonstrated by adding this compound in an ea~ily
dissolvable form. A ~olution containing 20 percent
by weight of 4,4'-dihydroxydiphenyl sulfone was
prepared by heating the diphenol in Bakelite
ERRA-0300 epoxy resin for 1 hour at a temperature of
120C. ERRA-0~00, obtained from Union Carbide, was
a mixture of the solid isomers of
bis(2,3-epoxycyclopentyl) ether. The solution was
allowed to cool to room temperature and solidify.
This compo~ition had good stability a~ room
~emperature and was a convenient means for adding
4,4'-dihydroxydiphenyl sulfone to epoxy/amine
mix~ures at moderate temperatures.
Exam~le 4
An accelerated thermosetting epoxy
composition was prepared by combining:
14.0 g of 3,4-epoxycyclohexylmethyl
3,4-epoxycyclohexane carboxylate,
3.0 g of the solid solut;on of
4,4'-dihydroxydiphenyl ~ulfone in bis~
(2,3-epoxycyclopentyl) ether described
above, and
3.79 9 o~ m-phenylenediamine.
2099179
- 22 -
at a temperature o 66C. This mixture had an
NH~epoxide ~toichiometry of 1.10. Its viscosity wa~
measured as a ~unction of time. The results as
shown in Table II.
Control G
A thermosetting mixture wa~ prepared by combining
19.0 g of 3,4-epoxycyclohexylmethyl
3,9-epoxycyclohexane carboxylate.
and 4.2 g of m-~henylenediamine.
The NH/epoxide stoichiometry of this
mixture was 1.10. Its viscosity at a temperature of
66C was measured periodically as described in
Example 4. The results are ~hown in Table II.
- 23 - 2~99~79
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` 2~9917~
- 24 -
Comparison of the viscosity versus ~ime
data for ~xample ~ with that of Control G and
Control A ~i.e., a bis(2,3-epoxycyclopentyl)
ether/MPDA mixture~ shows that
4,4'-dihydroxydiphenyl sulfone is an effective
accelerator when added a8 a solid solution in
bis(2,3-epoxycyclopentyl) ether~
Example 5 demonstrates the storage
stabili~y of bis (2,3-epoxycyclopentyl)
ether/g,4'-dihydroxydiphenyl sulfone solutions.
ExamPle 5
A 100 g portion of the solution of
4,q'-dihydroxydiphenyl sulfone in bis-
(2,3-epoxycyclopentyl) ether prepared a~ in Example
1 was maintained at a temperature of 66C for 96
hours. At the end of that period, the solution was
a clear low viscosity fluid. Analysis of the final
solution by liquid chromatography showed ~hat le~s
than 2 percent of the epoxide had reacted with the
diphenol.
Examples 6 through 11 and Controls M
through K describe the preparation and properties of
unreinforced castings. Casting dimensions were 1/8
x 8 x 4 to 8 inches. Typically they weighed 80 to
160 g.
The general procedure for making castings
was the following: The epoxy resin and accelera~or
~ere charged ~o a 3-necked flask equipped wi~h a
paddle stirrer. The contents of the flask were
s~irred and heated at a temperature of 85 to 100C
~til t~e accelerator aissolved. The solution was
- ` 20~9~79
then cooled to a temperature of 70C. The amine
hardener was a~ded to this solution. It dissolved
in about 2 eo 5 minute~. The resulting solution wa~
subjected to a vacuum of about 28 inches of mercury
to remove air bubbles for about 3 minutes. It was
then poured into a preheated glass mold with a
cavity of dimensions of 1/8 x 8 x ~ inches.
Casting~ were tested to determine tensile
properties and heat deflection temperature. Ten ile
properties were measured a~cordinq to AST~ D-63~
using a Type I dogbone specimen. Heat deflection
tempera~ure was measured according eO ASTM D-648
(264 psi stress).
Examples 6 through 8 and Control H describe
unreinforced castings made with the following cure
schedule: 2 hours at 85C; 85~ to 150C at
1C~minute: 1 hour at 150C.
ExamPle 6
A solution containing 190 g of bis-
(2,3-epoxycyclopentyl) ether and 10 9 of
~,4'-dihydroxydiphenyl sulfone was prepared as
described in Example 1. A 60 g por~ion of this
solution was blended with 18.4 9 of MPDA, poured
into a mold, and cured as described above. The
tensile properties and heat deflection temperature
of the cured casting are given in Table III.
ExamPle 7
The pxocedure in Example 6 was repeated
excep~ that the amount of 4,4'-dihydroxydiphenyl
sulrone was reduced by one half. The data on this
casting are sho~n in Ta~le III.
. .
2~99179
.
- 26 -
Control H
A thermosetting composition was prepared by
blending 60 g of bis(2,3-epoxycyclopentyl) ether
with 18.g g of MPDA. A casting was then prepared
by the procedure as de~cribed above. The propertie~
of the casting made from this composition are shown
in Table III.
ExamDle 8
A copolymer of bis(2,3-epoxycyclopentyl)
ether and ethylene glycol (i.e. ERLA-~617 obtained
from Union Carbide Corporation), 93.7 g, and 6.4 g
of 4,4'-dihydroxydiphenyl sulfone were heated at a
temperature of 100C for 0.5 hours with stirring ~o
dissolve the diphenol. This solution was cooled to
a temperature of 80~C and treated with 21.2 g of
MPDA. This solution was poured into a mold and
cured. The properties of the casting are shown in
Table III.
---`"` 2~179
-- 27 --
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`` 2~9~179
- 28 -
Examples 9 through 11 and Control I
describe other unreinforced castings. Resin
formulations, casting properties, and cure sch~dul0s
are shown in Table IV.
The data in Tables III and IV show that the
cure accelerators of this invention may be used with
a wide variety of epoxides and aromatic amines.
In Table III, higher heat deflection
temperatures are obtained in bis-
(2,3-epoxycyclopentyl) ether~MPDA castings
containing 4,4'-dihydroxydiphenyl sul~one than in
the Con~rol. In Example 8, a high level of
properties are also ob~ained with the ethylene
glycol~bi~2,3-epoxycyclopentyl) ether copolymer
resin. Note that the tensile strengths of all
castings in Table III are very high. Other
accelerators such as borontri~loride:
~onoethyla~ine complexes do not produce unrein~orcad
castings wit~ such high mechanical propertie~.
Tensile strength and elongation measurements are
sensitive to defects in the sample so that small
difEersnces between sample6 (e.g., tensile streng~h6
of 14,000 psi versus l6,000 psi) do no~ serve as a
basis of diPferen~iation. In contra6t, hea~
deflection temperature is a bulk property of the
material and is much less affected by d~fects.
In Table IV, the cas~ing in Control I was
so severely undercured that it could no~ be ~ested.
In contrast, the aceelerated composition of Exam21e
9 afforded a casting with good mechanical
propertie~. Example 10 shows ~hat mix~ures of
cycloaliphatic epoxides and glycidyl epoxides can be
cured wi~h the accelerators of ~hi~ inven~ion.
:--`` 2 ~ 7 ~
-- 29 --
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--" 2~9~179
. - .
_ 30 -
ExamPle 12
- Example 12 describes the preparation of a
unidirectional carbon fi~er composite using the
composition o~ this invention. The prepreg is made
using a polyacrylonitrile-based carbon fiber with a
tensile strength of 6.6 x 10 psi and a tensile
modulus of 36 X 106 pci.
A tow of carbon ~iber containing 6000
filaments is drawn through a resin bath contain;ng
the resin formulation shown in E~ample 6. The
impregnated fiber i6 wound on an 8 inch square frame
to a thickness of approximately lJ8 inch. The
impregnated fiber in the frame contains
approximately 35 percent by weight of resin. The
resin is cured by placing the frame in an oven and
heating wieh a programmed cure cycle. The cure
cycle is 2 hours at 85C to 160C at 1C/minute,
hold 2 hours at 160C. The frame is removed from
the oven and the cured carbon fiber composite is
removed erom the frame. The composite has a high
level of longitudinal and transverse tensile
properties.
