CA2099179A1 - Accelerated cycloaliphatic epoxide/aromatic amine resin systems - Google Patents

Abstract

ABSTRACT
High modulus matrix resins for composites comprising a cycloaliphatic epoxy resin, an aromatic diamirle hardener and a particular cure accelerator.

94, 342

Description

9~79 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~

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 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 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 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~

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~

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 ~ -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 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 ~

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 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 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 U U~; o o o o E
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20~9179 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.

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.

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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 .

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.

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`` 2~9~179 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.

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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.

Claims (6)

1. A composition comprising a cycloaliphatic epoxide containing two or more epoxide groups, an aromatic amine hardener and a cure accelerator selected from:resorcinol, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfoxide,

2,2-bis(4-hydroxyphenyl) hexafluoropropane, 2,4-dihydroxybenzophenone, 4,4'-dihydroxybenzophenone, and 4,4'-dihydroxy-3,3'-dichlorodiphenyl sulfone.
2. The composition of Claim 1 wherein said hardener is selected from one or moreof the following: 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl methane,

3,3'-diaminodiphenyl methane, 4,4'-diaminodiphenyl sulfone, m-phenylenediamine, p-phenylenediamine, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl sulfide, 1,4-bis(p-aminophenoxy) benzene, 1,3-bis(m-aminophenoxy) benzene, 1,3-bis(p-aminophenoxy) benzene, 4,4'-bis(3-aminophenoxy) diphenyl sulfone,2,2-bis(4-aminophenoxyphenyl) propane, and diethyltoluene diamine.
3. The composition of Claims 1 or 2 wherein said cycloaliphatic epoxide is bis(2,3-epoxycyclopentyl) ether.

4. The composition of Claims 1-3 further comprising a structural fiber selected from the group consisting of carbon, graphite, glass boron, silicon carbide and aromatic polyamides.

5. The composition of Claim 4 in the form of a prepreg.

6. The composition of Claims 1 or 4 further comprising a therrnoplastic selectedfrom the group consisting of polysulfone, polyhydroxyether, and polyamide.

94, 342