NO870604L - EPOXY / AROMATIC AMINHARPIX SYSTEMS CONTAINING AROMATIC TRIHYDROXY COMPOUNDS AS Curing Accelerators. - Google Patents

Description

The present invention relates to a curable epoxy/aromatic diamine resin system containing a defined group of aromatic trihydroxy compounds as curing accelerators.

The three-dimensional epoxy/amine networks formed by curing amine/epoxy resin formulations are known to provide desirable mechanical and thermal properties. As a result, amine-curable epoxy resin systems are frequently used as coatings, adhesives, sealants and matrices for fiber-reinforced preparations. For each application, the epoxy/amine resin formulation must have a particular degree of reactivity. In many cases, the reaction rate must be increased and curing accelerators added. Typically, additives that increase the cure rate will seriously reduce the mechanical and thermal properties of the cured resin. Thus, there is a need to increase the cure rate of the epoxy/amine formulations while maintaining or preferably increasing the high mechanical properties (such as tensile strength and modulus) achieved with the non-accelerated resin systems. This improvement is particularly desirable in high performance applications such as composite materials.

Accordingly, considerable efforts have been made to improve epoxy/amine resin systems by the addition of various additives.

ABOUT. May and Y. Tanaka, Epoxy Resins Chemistry and Technology. Marcel Dekker, New York, 1973 for example describes the addition of various Lewis acids, Lewis bases and numerous salts and complexes as accelerators for epoxy/amino systems. Such accelerators, while found to improve cure rate, have also been found to adversely affect mechanical properties due to homopolymerization of the epoxy groups, which is facilitated by the presence of such accelerators.

It is also disclosed that various mono- and dihydroxy substituted aromatic compounds are effective in increasing the cure rate of certain epoxy resins. For example, Schecter et al describe in Industrial and Engineering Chemistry. Volume 48, No. 1, pages 94 to 97, 1956, that phenol was more effective than aliphatic alcohols in accelerating the reaction of phenyl glycidyl ether with diethylamine. Bowen et al describe in the American Chemical Society Advances in Chemistry Series. Volume 92, pages 48 to 59, 1970, that 4,4'-dihydroxydiphenyl sulfone, phenol, tetrabromobisphenol A and bisphenol A reduced the gel time of bisphenol A epoxy/triethylenetetramine systems with similar degrees of effectiveness.

Resorcinol, phenol and various halogenated and nitrated derivatives of these compounds are also by Gough et al, Journal of Oil and Color Chemists Association. Volume 43, pages 409 to 418, 1960, Nagy, Adhesives Age, pages 20 to 27, April 1967 and Partensky American Chemical Society Advances in Chemistry Series. Volume 92, pages 29 to 47, 1970, and accelerate the cure of glycidyl epoxy/amine blends. In addition, Markovitz in "Chemical Properties of Crosslinked Polymers", American Chemical Society Symposium 1976, S.S. Labana, Ed, pages 49 to 58, described the use of resorcinol and metal salts as coaccelerators for curable compositions containing cycloaliphatic epoxides.

Thus, while resorcinol and phenol have been found to provide desirable improvements in the cure rate of certain epoxy/amine resin systems, further improvements in the cure rate of such systems, particularly with regard to cycloaliphatic epoxy/amine resin formulations, are still desirable.

In many epoxy/amine formulas, cycloaliphatic epoxides are used as an epoxy component because they provide improved mechanical and thermal properties to the cured preparations. For example, unreinforced castings of bis(2,3-epoxycyclopentyl)ether, cured with m-phenylenediamine, have tensile strengths and tensile moduli that are among the highest for thermosetting substances.

Furthermore and as described by McLean et al in Report No. 14450 in The National Research Council of Canada, November 1974, high mechanical properties can be obtained for unreinforced castings by curing 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexane carboxylate with methylene-dianiline. However, resin systems containing bis(2,3-epoxycyclopentyl)ether or 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexane carboxylate cure more slowly with aromatic amines than corresponding preparations containing bisphenol A epoxy resins. This characteristic limits their applicability in composite manufacturing such as filament winding and reaction injection molding. Thus, there is a need for improved cure accelerators for cycloaliphatic epoxy/amine resin systems.

From Japanese Kokai No. 82/192428 of 26 November 1982, there are known additive preparations comprising 3,4-epoxycyclohexyl-methyl 3,4-epoxycyclohexane carboxylate, triethanolamine borate and pyrogallol in a weight ratio of 100:1:3. Triethanolamine borate promotes the homopolymerization of the epoxy groups present in the formulation. When curing, according to this publication, the mixtures primarily have a cross-linked epoxy homopolymer structure which has poorer mechanical properties compared to thermosetting systems which are characterized by an epoxy-amine network structure, i.e. the epoxy/aromatic diamine formulations. As a result, the mixtures according to this literature reference have limited application possibilities and are not usable in high performance applications such as in composite materials.

DE-OS 2924717 describes the use of approximately stoichiometric amounts of pyrogallol to cure 1,3-diglycidyl-5,5-dimethylhyd-antoin. This system does not contain any aromatic amine curing agent. Furthermore, in this system, pyrogallol does not act as a curing accelerator but cross-links with the epoxy resin. Thus, in this system, pyrogallol acts as a curing agent giving a cured mixture with an ether network structure.

GB-PS 1 054 045 describes the use of pyrogallol to cure bisphenol A type epoxy materials. In the compositions of this countermeasure, an approximately stoichiometric amount of pyrogallol with a small amount of methylene dianiline (1.5 parts/100 parts resin) as a co-curing agent is used to crosslink a bisphenol A type epoxy with an epoxy equivalent of 500. Because of the large amount of pyrogallol present in this system, the pyrogallon acts as the primary cross-linking agent and leads to a hardened mixture with primarily an ether network structure.

Thus, while the prior art has described various mono- and dihydroxyaromatic compounds as curing accelerators for epoxy/amine resin systems and has described the use of pyrogallol as a cross-linking agent (hardener) for epoxy resins, the prior art lacks any description of the use of aromatic trihydroxy compounds as curing accelerators for epoxy/ aromatic resin systems.

As is well known to those skilled in the art, curing accelerators act in a truly catalytic manner and increase the reaction rate between the epoxy resin and the amine curing agent without even reacting to a significant extent with the epoxy resin such as e.g. shown by solvent extraction studies. This result stands in contrast to the use of these compounds as curing agents where the trihydroxyaromatic compound is chemically incorporated into the resin network structure. The use of trihydroxy aromatic compounds as hardeners (i.e. as curing agents or crosslinkers) requires stoichiometric amounts (i.e. from about 0.4 to 1.0 equivalents of hydroxy/equivalent epoxy groups in the epoxy resin), while cure acceleration is based on the use of only small amounts of accelerator from approx.

0.01 to approx. 0.35 equivalents of hydroxy/equivalent epoxy groups in the epoxy resin, together with the simultaneous presence of an aromatic diamine hardener in an amount within the general range of approx. 0.4 to approx. 2.0 equivalents of amine N-H per equivalent 1,2-epoxy groups in the epoxy resin. Curing acceleration is thus a rather different function from pure curing and involves different amounts of additive, different amounts of action and the presence of a primary hardener in preferably stoichiometric excess.

The invention is directed to curable thermosetting epoxy mixtures comprising: a) an epoxy resin containing at least two 1,2 epoxy-c! e j groups- epr .x ano leekyle^ a et. blandinømeé r- r y jts» r t. er ». r e r r ■-- 'h r - b) an aromatic diamine hardener in an amount sufficient to give from approx. 0.4 to approx. 2.0 equivalents of amine N-H per

equivalent 1,2-epoxy groups in the epoxy resin; and

c) an aromatic trihydroxy curing accelerator of formula I

0 0 0

where R is hydrogen, aryl, alkyl, -C-R, -C0R<1>, -CNHR<1>, SO2R<1>, or SO2NHR<1> and R<1> is alkyl or aryl with from 1 to 12 carbon atoms, in an amount sufficient to give approx. 0.01 to approx. 0.35 equivalents of hydroxy per equivalent 1,2-epoxy groups in the epoxy resin.

Optionally, the mixtures according to the invention may also contain a thermoplastic polymer, a structural fiber and/or modifying agents to increase the modulus of the hardened epoxy resin.

According to the invention, it has been discovered that the compositions according to the invention combine not only improved curing rates compared to e.g. with epoxy/aromatic diamine resin systems containing mono- and dihydroxyaromatic compounds as curing accelerators, but in addition have excellent mechanical properties. Cured compositions based on bis(2,3-epoxycyclopentyl)ether, a preferred epoxy resin for use herein, an aromatic diamine hardener and the aromatic trihydroxy cure accelerators of formula (I) e.g. have been found to have tensile strengths in excess of 18,000 psi and tensile moduli in excess of 700,000 psi. This combination of mechanical properties, especially a combination with the high reactivity and cure rates characteristic of the compositions according to the invention, is unique and makes the compositions ideal for use in filament winding systems.

Achieving both the aforementioned outstanding mechanical properties and the high cure rates for the present compositions is unexpected and contrary to what one would expect with cure accelerators. It is also unexpected that the accelerators according to the invention increase the curing speed more than the aromatic dihydroxy accelerators and that the modulus of hardened castings containing the trihydroxy accelerators is higher than that of analogous castings containing a) the aromatic dihydroxy accelerators, or b) no accelerator. Generally, the use of curing accelerators has been found to have an adverse effect on the mechanical properties of cured mixtures. Without wishing to be bound by any particular theory or method, it is believed that the improvements in the mechanical properties resulting from the use of the curing accelerators according to the invention originate from the fact that the accelerators of formula (I) exhibit an anti-softening effect on the resin. In any case, it has been found that the mixtures according to the invention generally show improved physical properties such as tensile modulus and tensile strength, compared to corresponding mixtures containing e.g. bisphenol S as curing accelerator.

In addition to the various advantages mentioned above, the mixtures in question have good stability, i.e. that accelerator and epoxy resin can be mixed in advance up to weeks or months before without significant changes in properties. This characteristic facilitates processing during manufacture.

As a result of this, the mixtures according to the invention find particular application in the production of composite materials by e.g. filament winding and reaction injection molding. In another embodiment, the invention thus provides composite materials comprising the mixtures as mentioned above containing structural fibers with a tensile strength of more than 100,000 psi, a tensile modulus of more than approx. two million psi and a decomposition temperature of more than approx. 200°C.

Other embodiments, features and advantages of the invention will become apparent to the person skilled in the art from a closer study of the description. The cure accelerators of formula (I) include 1,3,5-trihydroxybenzene (phloroglucinol); 1,2,3-trihydroxybenzene (pyrogallol); C± to C12 derivatives thereof; aryl derivatives thereof containing up to 12 carbon atoms in the aryl group such as the phenyl, benzyl and tolyl derivatives; hydrates such as phloroglucinol dihydrate; C± to C12 alkylene ethers of gallic acid (3,4,5-trihydroxybenzoic acid) such as methyl gallate, ethyl gallate, n-propyl gallate, butyl gallate, etc.; the aryl esters of gallic acid in which the aryl group contains up to 12 carbon atoms such as phenyl gallate, benzyl gallate and tolyl gallate; phenones such as 2,4,6-trihydroxy acetophenone, 2,3,4-trihydroxy acetophenone and 2,3,4-trihydroxy benzophenone; and the various N-C 1 to C 12 alkyl amides of gallic acid; The N-aryl amides of gallic acid in which the aryl group contains up to 12 carbon atoms such as the N-phenyl, N-benzyl and N-tolylamide of gallic acid; (3,4,5-1rihydroxyphenyl)- C ± to C 12 alkyl sulfones, and aryl analogs thereof in which the aryl group contains up to 12 carbon atoms; and corresponding sulfonamide analogues. Preferred curing accelerators include the various positional isomers of trihydroxybenzene, the hydrates thereof and the C1 to C-L2 alkyl esters of gallic acid, of which phloroglucinol, n-propyl gallate and pyrogallol are particularly preferred.

The epoxy resins that can be used contain two or more epoxy groups with the formula: The epoxy groups can be terminal epoxy groups or internal epoxy groups. The epoxy groups are of two general types: polyglycidyl compounds or products derived from epoxidation of dienes or polyenes. The polyglycidyl compounds contain a number of 1,2-epoxide groups derived from the reaction of a polyfunctional active hydrogen-containing compound with an excess of an epihalogen hydrin under basic conditions. When the active hydrogen compound is a polyhydroxy alcohol or phenol, the resulting epoxide mixture contains glycidyl ether groups. A preferred group of polyglycidyl compounds are prepared via condensation reactions with 2,2-bis(4-hydroxyphenyl) propane, also known as bisphenol A, and have structures such as (II),

where n has a value from approx. 0 to 15. These epoxies are bisphenol-A epoxy resins. They are commercially available

under designations such as "Epon 828", "Epon 1001" and "Epon 1009" and as "DER 331", "DER 332" and "DER 334". The most preferred bisphenol A epoxy resin has an "n" value between 0 and 10.

Polyepoxides which are polyglycidyl ethers of 4,4'-fihydroxy-phenyl methane, 4,4'-dihydroxyphenyl sulfone, 4,4'-biphenol, 4,4'-dihydroxyphenyl sulfide, phenolphthalein, resorcinol, 4,2'-biphenol or tris (4-Hydroxyphenyl)methane such as "Tactix 742" and the like are useful according to the invention. In addition, "EPON 1031" (a tetraglycidyl derivative of 1,1,2,2-tetrakis(hydroxyphenyl)ethane and "Apogen 101" (a methylolated bisphenol A resin) can also be used. Halogenated polyglycidyl compounds such as "D.E.R. 580" (a brominated bisphenol A epoxy resin) are also useful.Other suitable epoxy resins include polyepoxides prepared from polyols such as pentaerythritol, glycerol, butanediol or trimethylolpropane and an epihalohydrin.

Polyglycidyl derivatives of phenol-formaldehyde novolaks such as III where n=0.1 to 8 and cresol-formaldehyde novolaks such as IV where n=0.1 to 8 are also usable.

The former are commercially available as "D.E.N. 431", "D.E.N. 438" and "D.E.N. 485". The latter are available as "ECN 1235", "ECN 1273" and "ECN 1299". Epoxidized novolaks made from bisphenol A and formaldehyde such as "SU-8" are also usable.

Other polyfunctional active hydrogen compounds besides phenols and alcohols can be used to prepare the polyglycidyl adducts according to the invention. These include amines, amino alcohols and polycarboxylic acids.

Adducts derived from amines include N,N-diglycidyl aniline, N,N-diglycidyl toluidine, N,N,N',N'-tetraglycidylxylylene di amin., N., N' ,N-tetraglycidyl.-bls(me.tyLamiiio )-cyclohexane, N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenyl methane, N,N,N',N'-tetraglycidyl-3 , 3 '-diaminodiphenyl sulfone and N,N<*- >dimethyl-N , N '-diglycidyl-4,4'-diaminodiphenyl methane. Commercially available resins of this type include "Glyamin iQ5tii3ageV'5Glyamln. 125?', "Araldite MY-7-20:" cogr''PGA-sX^and A'PGA-C". Suitable polyglycidyl adducts derived from amino alcohols include O,N,N-triglycidyl-4-aminophenol, available as "Araldite 0500" or "Araldite 0510". O.N.N-triglycidyl-3-aminophenyl can also be used. Also suitable for use herein are the glycidyl esters of carboxylic acids. Such glycidyl esters include e.g. diglycidyl phthalate, diglycidyl terephthalate, diglycidyl isophthalate and diglycidyl adipate. Polyepoxides such as triglycidyl cyanurates and -isocyanurates, N,N-diglycidyl oxamides, N,N'-diglycidyl derivatives of hydantoin such as "XB 2793" diglycidyl esters of cycloaliphatic diglycidyl carboxylic acids and polyglycidyl thioethers of polythiols can also be used. Other epoxy-containing substances are copolymers of acrylic acid esters of glycidol such as glycidyl acrylate and glycidyl methacrylate with one or more copolymerizable vinyl compounds. Examples of such copolymers are 1:1 styrene-glycidyl methacrylate, 1:1 methyl methacrylate-glycidyl acrylate and 62.5:24-:13.5 methyl methacrylate:ethyl acrylate:glycidyl methacrylate. Si 1 icon resins containing epoxy functionality such as e.g. 2, 4,6,8,10-pentakis[3-(2,3-epoxypropoxy)propyl]-2,4,6,8,10-pentamethylcyclopentasiloxane and the diglycidyl ether of 1,3-bis-(3-hydroxypropyl)tetramethyldisiolkane are also usable. ;The second group of epoxy resins is that produced by epoxidizing dienes or polyenes. Resins of this type include bis(2,3-epoxycyclopentyl) ether: ; copolymers between V and ethylene glycol as described in US-PS 3,398,102, 5(6)-glycidyl-2-(1,2-epoxyethyl)bicyclo[2,2,1]heptane, VI; and d in cycle open ad in a diepoxide. Commercial examples of these types of epoxides include vinylcyclohexene dioxide, e.g. "ERL-4206", 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexane carboxylate, e.g. "ERL-4221", 3,4-epoxy-6-methylcyclohexylmethyl 3,4-epoxy-6-methylcyclohexane carboxylate, e.g. "ERL-4201", bis(3,4-epoxy-6-methylcyclohexylmethyl) adipate, e.g. "ERL-4289", dipentene dioxide, e.g. "ERL-4269", 2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexane meta-dioxane, e.g. "ERL-4234" and epoxidized polybutadiene, e.g. "Oxiron 2001". Other suitable cycloaliphatic epoxides include those described in US-PS 2,750,395; 2,890,194 and 3,318,822, and the following: ; Other suitable epoxies include: ; where b is 1 to 4, m is (5-b) and R 2 is H, halogen or C 1 to C 4 alkyl. The preferred epoxy resins, especially for use in composite applications, include the previously mentioned cycloaliphatic epoxides, especially bis(2,3-epoxycyclopentyl)ether, vinyl cyclohexene diepoxide, 2-(3,4-epoxycyclohexyl-5,5-spiro- 3,4-epoxy)cyclohexane meta-dioxane, the diepoxides of allyl cyclopentyl ether, 1,4-cyclohexadiene diepoxide, 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexane carboxylate and bis(3,4-epoxycyclohexylmethyl)adipate, of which bis- (2,3-epoxycyclopentyl) ether and 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexane carboxylate are particularly preferred. Where desired, up to 40% and preferably up to 30% by weight of a cow epoxide can be used instead of the cycloaliphatic epoxide, calculated on the combined weight of cycloaliphatic epoxide and cow epoxide. Preferred co-epoxides for this purpose include the bisphenol A epoxy resins of formula II, wherein n is between 0 and 15, epoxidized novolak resins of formulas III and IV wherein n is between 0.1 and 8, and N,N,N',N'-tetraglycidyl 4,4'-diaminodiphenyl methane. ;Other preferred resin formulations will characteristically contain a diglycidyl ether of bisphenol A, N,N,N',N'-tetra-glyci dy lxy lylene diamine, 0,N,N-triglycidyl-3-aminophenol , 0 , N , N-triglycidyl -4-aminophenol, glycidyl glycidate, N,N-diglycidyl aniline and N,N-diglycidyl toluidine as resin component. The aromatic diamine hardeners which can be used in the preparations according to the invention include any of the aromatic diamine hardeners which are conventionally used to harden epoxy resins. Examples of such hardeners include 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfone, p-phenylenediamine, 4,4'-diaminodiphenyl propane, 4,4'-diaminodiphenyl sulfide, 1,4-bis(p-aminophenoxy ) benzene, 1,4-bis(m-aminophenoxy)benzene, 3,3'-diaminodiphenylmethane, m-phenylenediamine, 1,3-bis-(m-aminophenoxy)benzene, eutectic mixtures of m-phenylenediamine and 4,4' -diaminodiphenyl methane, 4,4'-diaminodiphenyl methane, 3, 4'-diaminodiphenyl ether, bis(4-aminocyclohexyl)methane, 4,4'-(3-phenylend iisopropylidene)bisaniline, 4, 4'-(4-phenylenediisopropylidene) bisaniline, 4,4'-(3-phenylenediisopropylidene) bis-(3-toluide), 4,4'-bis(3-aminophenoxy)-diphenyl sulfone, 2,2-bis[ 4-(4-aminophenoxy)phenyl] propane, trimethylene glycol di-p-aminobenzoate, 4,4'-diaminodiphenyl sulfone, 4 , 4'-bis(4-aminophenoxy) diphenyl sulfone, 4,4'-bis(4- aminophenoxy)-3,3',5,5'-tetramethyl diphenyl sulfone, 4,4'-bis(4-amino-3-methylphenoxy)di f phenyl sulfone, ring alkylated derivatives of m-phenylenediamine, adducts of epoxy harp ics with the preceding diamines such as the adduct formed by reacting 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, adducts of bisphenol A epoxy resin with a molar excess of 4,4'-diaminodiphenyl sulfone and the various aromatic diamines described in US-SN 534 649 and 564 393 as well as US-PS 4 517 321. Preferred diamines for use according to the invention include m-phenylenediamine, the ring alkylated derivatives thereof, adducts of epoxy resins and m-f phenylenediamine, eutectic mixtures of m-f phenylenediamine and -4 ,-4-'— diaminodiphenyl -methane 4 , 4 '-bis(3-aminophenoxy) diphenyl sulfone, 2 , 2 '-bis[4-( 4-aminophenoxy)phenyl]propane and trimethyleneglycol di-para-aminobenzoate. The mixtures - according to the invention can optionally contain a thermoplastic polymer. These substances have beneficial effects on the viscosity and film strength properties of the epoxy/hardener/accelerator mixture. The thermoplastic polymers used according to the invention include polyaryl ethers of formula VII as described in US-PS 4,108,837 and 4,175,175, ; ; wherein R3 is a residue of a dihydroxyphenol such as bisphenol A, hydroquinone, resorcinol, 4,4'-bisphenol, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxy-3,3',5,5'-tetramethyldiphenyl sulfide , 4,4'-dihydroxy-3,3',5,5'-tetramethyldiphenyl sulfone and the like. R4 is a residue of a benzenoid compound capable of nucleophilic aromatic substitution such as 4,4'-dichlorodiphenyl sulfone, 4,4'-difluorobenzophenone and the like. The average value for e is from approx. 8 to approx. 120. ;These polymers may have terminal groups that react with epoxy resins such as hydroxyl or carboxyl, or terminal groups that do not react. Other suitable polyaryl ethers are described in US-PS 3,332,209. Also suitable are polyhydroxy ethers of formula (VIII); ; where R3 has the same meaning as in formula VII and the average value for f is between approx. 8 and approx. 300; and polycarbonates such as those based on bisphenol A, tetramethyl bisphenol A, 4,4'-dihydroxydiphenyl sulfone, hydroquinone, resorcinol, 4,4'-dihydroxy-3,3',5,5'-tetramethyldiphenyl sulfide, 4,4'-biphenol, 4,4'-dihydroxydiphenyl sulphide, phenolphthalein, 2,2,4,4-tetramethyl-1,3-cyclobutane diol and the like. Other suitable thermoplastics include poly(c-caprolactone); polybutadiene; polybutadiene/acrylonitrile copolymers including those optionally containing amine, carboxyl, hydroxyl or -SH groups; polyesters such as poly(butylene terephthalate); poly(ethylene terephthalate); polyetherimides such as the Ultem resins; acrylonitrile/butadiene/styrene terpolymers, polyamides such as nylon 6, nylon 6,6, nylon 6,12 and "Trogamide T"; poly(amidimide) such as polyolefins, polyethylene oxide; poly(butyl methacrylate); impact modified polystyrene; sulfonated polyethylene; polyarylates such as those derived from bisphenol A and isophthalic and terephthalic acids; poly(2,6-dimethyl phenylene oxide); polyvinyl chloride and copolymers thereof; polyacetals; polyphenylene sulfide and the like. The preferred thermoplastic polymers for use in the invention include the polyhydroxyethers, the polyetherimides and the polyarylethers. The mixtures according to the invention may include a structural fiber. Structural fibers that can be used include carbon, graphite, glass, silicon carbide, poly(benzothiazole), poly(benz imidazole), poly(benzoxazole), alumina, titanium oxide, boron and aromatic polyamide fibers. These fibers are characterized by a tensile strength of more than 100,000 psi, a tensile modulus of more than 2 million psi and a decomposition temperature of more than 200° C. The fibers can be used in the form of continuous ropes (1000 - 400,000 filaments each), woven fabrics, chopped fibers, random mats or whiskers. The preferred fibers are carbon fibers, aromatic polyamide fibers such as "Kevlar 49" fibers and silicon carbide fibers. The mixtures according to the invention can also include modifiers which increase the modulus of the hardened epoxy resins. Examples of such agents include antiplasticizers such as dibutyl phthalate, the phenol adducts of bisphenol A epoxy resins, polyhalogenated biphenyls, azobenzers, hydroxy diphenyl, tricresyl phosphate; enhancers such as the various reaction products between a suitable aromatic amine or amide and a monoepoxide or diepoxide as described by P.D. McLean et al in The British Polymer Journal, Volume 15, Maren 1983, pages 66-70, as well as other modifiers known to those skilled in the art. Preferred modifiers for use in the compositions according to the invention include the strengthening agents described in US-PS 4,480,082. These include the reaction product of (i) an aromatic amide with the amine group on the amide bound to the aromatic ring, and (ii) a mono- or diepoxide. A particularly preferred agent of this type consists of the reaction product of phenyl glycidyl ether and 4-hydroxyacetanilide. This is commercially available under the name "Fortifier I" and contains approx. 80 to 98% by weight of adducts of 4-hydroxyacetanilide and phenyl glycidyl ether in the molar ratio 1:4.3, 0 to 12% unreacted phenyl glycidyl ether and 0 to &% unreacted 4-hydroxyacetanilide. The epoxy equivalent weight for "Fortifier I" is greater than or equal to 900 g/mol. Also preferred is the commercially available "Fortifier C", consisting of the reaction product of aniline and vinylcyclohexene dioxide. In the mixtures according to the invention, the aromatic diamine hardener is used in an amount sufficient to provide 0.4 to 2.0, preferably 0.6 to 1.9 and preferably 0.7 to 1.7 equivalents of amine N-H per equivalent epoxy group in the epoxy resin. The curing accelerator is generally used in an amount sufficient to provide from 0.01 to 0.35, preferably 0.03 to 0.3 and preferably 0.04 to 0.25 equivalents of hydroxy groups per equivalent epoxy groups in the resin. Typical formulations within these areas will include from approx. 30 to 90 and preferably from 40 to 80 wt # of epoxy resin, from approx. 10 to 70 and preferably 15 to 65% by weight hardener and 0.1 to 10 and preferably 0.5 to 7 and most preferably approx. 1 to 6 wt-$ cure accelerator. When a thermoplastic polymer is incorporated into the mixture, the amount of this is up to 20$ and preferably less than 15$ by weight. The modifier comprises when used up to 35 and preferably less than 30% by weight. All of these are calculated on the combined weight of resin, hardener, cure accelerator, optional modifier and optional thermoplastic polymer, collectively referred to herein as the "resin portion of the composite material". Where structural fibers are incorporated into the mixture, the amount thereof is from up to 85 and generally from 20 to 80 and preferably from 30 to 80 weight-$ of the total mixture, that is, the combined weight of structural fibers and the resin part of the composite material. A particularly preferred formulation for use in the production of composite materials comprises as resin part of this bis(2,3-epoxycyclopentyl) ether; from 5 to 40 wt-$ "Fortifier I" modifier; f loroglucinol, pyrogallol and/or n-propyl gallate in an amount to provide 0.03 to 0.3 equivalents of hydroxy group per equivalent epoxy group; and m-phenylene diamine in an amount sufficient to provide from 0.6 to 1.9 equivalents of amine N-H groups per equivalent epoxy group. ;The compositions of the invention can be prepared by combining the curing accelerator with either epoxy or amine to create a premix which is then mixed with the remaining components to complete the composition. Composite materials can be produced by a any of the known procedures such as wet winding or hot melt-ing. During the wet winding, a continuous reinforcing rope is passed through a resin bath containing a mixture of epoxy, amide hardener, accelerator and any modification-raid part and .f thermoplastic-; polymer s After -that- -the rope-? re&-impreg-; nerted with the resin, it is passed through press rollers to remove excess resin. Preferably, and because of the rapid curing properties of these mixtures, prepreg is used to produce a composite article soon after it is produced. ;The composite materials can be produced by curing pre-impregnated reinforcement using heat and possibly pressure. Heat bag/autoclave hardeners work well with these mixes. Laminates can also be produced via wet laying followed by compression molding, resin transfer molding or by resin injection as described in European application 0019149 with curing temperatures from 100 to approx. 500°F and preferably from 180 to approx. 450°F. Curing times depend on the manufacturing process and can be up to several hours or down to approx. 1-2 minutes, depending on the mixture used. The mixtures according to the invention are well suited for filament winding. In this composite manufacturing process, continuous reinforcement in the form of ribbon or rope, optionally pre-impregnated with resin or impregnated during winding, is placed over a rotating and removable mold or spindle in a predetermined pattern. In general, the mold is a surface of revolution and contains end closures. When the correct number of layers have been applied, the winding is cured in an oven or autoclave and the spindle is removed. The mixtures according to the invention can be used as aircraft parts such as wing skins, wing-body gaskets, floor plates, flaps, radomes; as car parts such as drive shafts, shock absorbers and springs, and as pressure tanks, tanks and pipes. They are also suitable for sports items such as golf clubs, tennis rackets and fishing rods. In addition to structural fibres, the mixtures may also contain particulate fillers such as talc, mica, calcium carbonate, aluminum trihydrate, glass microspheres, phenolic thermospheres and carbon black. Up to half of the weight of the structural fibers in the mixture can be replaced by filler. Thixotropic agents such as fumed silica can also be used. Furthermore, the mixtures can be used as adhesives, enveloping or encapsulating compounds and in coating applications. The following examples shall provide an illustration of the implementation of the invention without limiting it. In the examples that follow, the epoxy equivalent weight, EEW, is defined as the amount of grams of epoxy resin per mole 1,2-epoxy group. ;Examples 1 and 2 and Controls A and B. ;Examples 1 and 2 and Controls A and B describe viscosity versus time for bis(2,3-epoxycyclopentyl) ether/meta-phenylenediamine, MPDA, mixtures alone and with florglucinol, n- propyl gallate and bisphenol-S as curing accelerators. The procedure used is as follows: A 250 ml three-necked flask equipped with blade stirrer, thermometer with Therm-O-Watch control, inlet and outlet for nitrogen and an electric cooling jacket was charged with 100 g and 5 g of accelerator. The mixture was heated and stirred at 120°C for 115 minutes. During this time, the accelerator was dissolved. After the solution was cooled to 65°C, 47 g of m-phenylenediamine was added. The mixture was then stirred for 12 minutes until the amine hardener was dissolved. In control B, 100 g . bis(2,3-epoxycyclopentyl)ether mixed with . 47 g of MPDA at 65°C. In all cases, 15 to 20 g of solution were charged to a sample cup in a Brookfield thermosel viscometer. Viscosity versus time was then carried out at 66°C. The results of these tests are shown in Table 1. These results show that florglucinol and n-propyl gallate are significantly more active accelerators than the dihydroxy aromatic compound bisphenol S. a) Concentration for all accelerators: 5 phr. ;b) After addition of MPDA.;c) The viscosity measured in centipoises. EEW for bis(2,3-epoxycyclopentyl)ether - 92 g/mol. ;Example 3. ;A 30 g portion of a solution of fluoroglucinol in bis(2,3-epoxycyclopentyl)ether as described in Example 1 was kept at a temperature of 60° C. for 45 days. The viscosity of the finished solution at room temperature was similar to that of the original mixture. However, the EEW of the bis(2,3-epoxycyclopentyl)ether resin/phloroglucinol mixture did not change after 45 days. These results demonstrate the excellent storage stability of the epoxy resin/cure accelerator compositions of the invention in the absence of amine curing agents. Examples 4 to 9 and controls C to E describe the production and properties of unreinforced hardened castings. The dimensions of the pieces were 1/8x8x4 by 8 inches. Characteristic weight of these pieces was in the range of 8 to 160 g. The pieces produced in these experiments were tested to determine the tensile properties and heat deflection temperature. The tensile properties were measured according to ASTM D-638 using a type I dog bone specimen. Heat deflection temperatures were measured according to ASTM D-648 at 264 psi load. ;Example 4;A 250 mL round-bottomed flask equipped with a paddle stirrer, thermometer with Therm-O-Watch control, inert gas inlet and outlet, and an electrical cooling jacket was charged with 100 g of bis(2,3-epoxycyclopentyl)ether and 5.0 g phloroglucinol. The mixture was heated and stirred at 110°C for 115 minutes. During this time the florglucinols were dissolved. After the bis(2,3-epoxycyclopentyl)ether fluoroflucinol solution had cooled to 60° C., 47 g of m-phenylene diamine was charged to the flask. The resulting mixture was stirred for 12 minutes at 60°C until the diamine was dissolved. This solution was then poured into a mold preheated to 100°C. The mold was placed in an oven and heated for 4 hours to 85°C. The temperature in the oven was then raised from 85 to 179°C over 100 minutes followed by 2 hours at 179°C. After the mold had cooled to room temperature, a hard, clear solid piece of casting was removed. The properties are shown in Table II. ;Example 5. ;The procedure in Ex. 4 was repeated except that 5.0 g of n-propyl gallate was used instead of fluoroglucolnol. The properties are given in Table II. ;Example 6. ;The procedure in Ex. 4 was again repeated except that 5.0 g pyjrorga Ilso ]epcf$eK rfrænyt te t * i s tfe~detr rf or? ~f luor andluc~ijrrol=.~ T "Egen - cabinets are indicated in Table II.

Control C.

The procedure in Ex. 4 was repeated except that bisphenol-S was used instead of phloroglucinol.

Control D.

The procedure described in Ex. 4 was repeated except that no accelerator was used for the production of this test casting.

As can be seen from Table I, the castings containing phloroglucinol and n-propyl gallate showed higher strength and modulus than the controls without accelerator or with bisphenol S. At 5 phr (based on 100 parts of epoxy resin) phloroglucinol, the tensile strength was increased from approx. 127 to 139 MPa and the modulus increased from 4,600 to 5,490 MPa. The heat distortion temperature, which was somewhat lower than that of pieces produced without an accelerator, 157 versus 166°C, was nevertheless still good and similar to that of bisphenol S based casting. Phloroglucinol and n-propyl gallate thus act not only as accelerators for epoxy/amine systems but also as modulus and strength modifiers for such systems as well.

Control E.

A homogeneous mixture was prepared by combining 100 g of bis(2,3-epoxycyclopentyl) ether with 20 g of "Fortifier I" at 100° C. for 30 minutes. This solution was mixed with 47 g of MPDA at 60°C. The mixture was stirred, degassed, poured into a mold and cured as described in Table II.

Example 7.

A solution containing 100 g of bis(2,3-epoxycyclopentyl) ether and 5.0 g of phloroglucinol was prepared as in Ex. 1. This mixture was mixed with 20 g "Fortifier I" and then mixed with 47 g MPDA at 60°C; the homogeneous mixture was degassed and poured into a mold and cured as described in Ex. 2. The tensile properties and the heat deflection temperature are given in Table II.

As can be seen from Table II, this mixture provides excellent mechanical properties. The tensile strength increased from 127 to 161 MPa and the modulus from 4,600 to 5,930 MPa. The system also gave higher reactivity than controls C and D.

Example 8.

A solution containing 100 g of bis(2,3-epoxycyclopentyl) ether and 3.0 g of phloroglucinol was prepared as in Ex. 1. The solution was mixed with 12.5 g of "Fortifier I" and then mixed with 47 g of MPDA at 60° C. The homogeneous mixture was degassed and poured into a mold and cured as described in Table

II.

Example 9.

The procedure from Ex. 6 was repeated except that 5.0 g of pyrogallol was used instead of phloroglucinol. The properties are shown in Table II.

Examples 7 to 9 and Control E show the effect of phloroglucinol and pyrogallol on compositions containing a modifier. As can be seen from Table II, the addition of phloroglucinol and pyrogallol further improves the tensile modulus of the mixtures compared to that achieved by the addition of "Fortifier I", which gives castings with an exceptionally high modulus. Examples 1 through 12 and Controls F, G, H and K describe unreinforced castings made from various other epoxy/aromatic amine resin systems. Resin formulations, casting properties and curing schemes are given in Tables III and

IV.

Data given in Tables III and IV show that the curing accelerators according to the invention can be used with a wide range of epoxides and aromatic amines to improve modulus, strength and in some cases the heat deflection temperature.

Example- 10. A 250 ml flask equipped as described in Ex. 1 was charged with 100 g of 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexane carboxylate "ERL-4221", "EEW-137" and 5.0 g of loroglucinol. The mixture was heated with stirring to 110°C for 80 minutes to dissolve the phloroglucinol. After the solution had cooled to 65° C., 28 g of MPDA were added. The mixture was stirred, degassed, poured into a mold and cured as described in Table III.

Controls F and G.

The procedure as described in Ex. 10 was repeated for control F except that bisphenol S was used instead of phloroglucinol. Control G was similarly produced but without an accelerator.

Example 11

A solution containing 100 g of bis(2,3-epoxycyclopentyl) ether and 8.0 g of loroglucinol was prepared as described in Ex. 1. This solution was mixed with 114 g of trimethylene glycol di-para-aminobenzoate at 119°C. The resulting homogeneous mixture was then degassed and poured into a mold and cured as described in Table IV.

Control H

The procedure in Ex. 11 was repeated except that no accelerator was used.

Control K

A homogeneous solution was prepared by combining 100 g diglycidyl ether of bisphenol A epoxy resin "EEW-180" with 52 g trimethylene glycol di-para-aminobenzoate at 110°C.

The solution was degassed and then poured into a mold and cured as described in Table IV.

Example 12.

A solution containing 100 g of diglycidyl ether of bisphenol A epoxy resin "EEW-180" with 5.0 g of phloroglucinol was prepared sonorbe.sk-revet in Ex. 1. The solution was mixed with 52 g of trimethylene glycol di-para-aminobenzoate. An unreinforced casting was then prepared from this mixture as described in Control K.

It appears from Table IV that the pieces produced in Ex. 12 had a higher modulus and higher heat distortion temperature than the equivalent cast which did not contain fluoroglucinol, i.e. Control K. Examples 13 and 14 "describe the production of unidirectional carbon fiber composite materials using the compositions of the invention. Each of the described compositions was manufactured using a polyacrylic nitrile based carbon fiber with a tensile strength of 7.8 x IO<5>psi and a tensile modulus of 41 x IO<6>psi.

Example 13

A carbon fiber rope containing 12,000 filaments was drawn through a resin bath containing the resin formulation of Ex. 8. The impregnated fiber was wound on a 20 cm square frame to a thickness of approx. 1/8 inch. The impregnated fiber in the frame contained approx. 30 wt-$ resin. The resin was cured by placing the frame in an oven and heating according to a programmed curing cycle comprising 4 hours at 85°C, 85 - 120°C at 1°C/minute, hold for 2 hours at 120° C, 120 - 179°C with 1°C/minute and stay for 2 hours at 179°C. The frame was then removed from the furnace after which the cured carbon fiber composite material was removed and tested for transverse strength and modulus in accordance with ASTM D-3039. The transverse tensile modulus of the composite material was found to be 1.78 million psi. The fiber volume fraction was 70.2$.

Example 14.

The impregnated fiber prepared as in Ex. 13 was wound on a 5 3/4 inch diameter steel spindle. Four layer fibers were laid in a band with a length of approx. 10 cm. The fiber area weight was approx. 206 g/m². Spindle and impregnated fiber were cured using the scheme in Ex. 13. After the resin was cured, cylindrical cured composite material was removed from the mandrel and divided into 12.7 mm wide rings for loop tensile testing according to ASTM D-2290. The fiber volume fraction was $68.3.

The average loop tensile strength for five rings was 489,000 psi. This result indicates that the mixtures according to the invention can be advantageously used in the production of high-strength composite materials via filament winding.

Claims (27)

©f Curable, thermosetting epoxy compound comprising: a) an epoxy resin containing at least two 1,2-epoxy groups per molecule; b) an aromatic diamine hardener in an amount sufficient to give from approx. 0.4 to approx. 2.0 equivalents of amine N-H per equivalent 1,2-epoxy group in the epoxy resin; and c) an aromatic trihydroxy cure accelerator of the formula: 0 0 0 in which R is hydrogen, aryl, alkyl, -C-R', -C0R <1> , -CNHR <1> , SO2 R', or SO2 NHR and R' is alkyl or aryl with 1 to 12 carbon atoms, in a quantity sufficient to give from approx. 0.01 to approx. 0.35 equivalents of hydroxy per equivalent 1,2-epoxy group in the epoxy resin. 2. Mixture according to claim 1, characterized in that the curing accelerator is f loroglucinol, n-propyl gallate, pyrogallol or mixtures thereof. 3. Mixture according to claim 2, characterized in that the curing accelerator is phloroglucinol. 4. Mixture according to claim 2, characterized in that the curing accelerator is n-propyl gallate. 5. Mixture according to claim 2, characterized in that the hardening accelerator is pyrogallol. 6. Mixture according to claim 2, characterized in that the epoxy resin is a cycloaliphatic epoxide. 7. Mixture according to claim 6, characterized in that the aromatic diamine hardener is m-f phenylenediamine, an autectic mixture of a phenylenediamine and 4,4 <1-> diaminodiphenyl methane, 4 , 4 1-diamindiphenyl methane, 4,4 <1-> bis( 3-aminophenoxy)-diphenyl sulfone, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, trimethylene glycol di-para-aminobenzoate, 4 ,4-diaminodiphenyl sulfone, 4 , 41-bis(4-aminophenoxy) diphenyl sulfone, adducts of epoxy resin-.with m-phenylenediamine> 4,4'-bis(4-aminophenoxy)-3 , 3 1 ,5,51-tetramethyl diphenyl sulfone, 4,4 <1-> bis(4-amino -3-methylphenoxy) diphenyl sulfone, ring alkylated derivatives of m-phenylenediamine or mixtures thereof. 8. Mixture according to claim 6, characterized in that the aromatic diamine hardener is m-phenylenediamine, ring alkylated derivatives thereof, adducts of epoxy resins and m-phenylenediamine, autectic mixtures of m-phenylenediamine and 4,4<1-> diaminodiphenylmethane or mixtures thereof. 9. Mixture according to claim 6, characterized in that the cycloaliphatic epoxide is bis(2,3-epoxycyclopentyl) ether. 10. Mixture according to claim 6, characterized in that the cycloaliphatic epoxide is vinylcyclohexene diepoxide, 2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexane meta-dioxane, 3,4-epoxycyclohexyl-methyl 3, 4-epoxycyclohexane carboxylate, 3,4-epoxy-6-methylcyclohexylmethyl 3,4-epoxy-6-methylcyclohexane carboxylate, dipentene dioxide, epoxidized polybutadiene, bis(3,4-epoxy cyclohexylmethyl)adipate or mixtures thereof. 11. Mixture according to claim 6, characterized in that the cycloaliphatic epoxide is selected from one or more of where b is 1 to 4, m is (5-b) and R 2 is H, halogen or C 1 to C 4 alkyl. 12. Mixture according to claim 6, characterized in that it further contains up to 40% by weight of a co-epoxy resin. 13 . Mixture according to claim 12, characterized in that the co-epoxy resin is selected from one or more of where n is from 0 to approx. 15; where n is from 0.1 to approx. 8 and R is hydrogen; and where n is from 0.1 to approx. 8 and R is CH 3 . 14. Mixture according to claim 6, characterized in that it further comprises up to approx. 20% by weight of a thermoplastic polymer. 15. Mixture according to claim 14, characterized in that the thermoplastic polymer is a polyhydroxyether, a polyetherimide, a polyarylether, a polysulfone, a polycarbonate or mixtures thereof. 16. Mixture according to claim 6, characterized in that it further comprises up to 35% by weight of a modifier which increases the modulus of the epoxy resin. 17. Mixture according to claims 1, 2, 6, 14 or 16, characterized in that it further comprises a structural fiber with a tensile strength of over approx. 100,000 psi, a tensile modulus of more than approx. 2 million psi and the decomposition temperature of over approx. 200|C. 18. Mixture according to claim 17, characterized in that the structural fiber is selected from carbon, graphite, glass, silicon carbide, poly(benzothiazole), poly(benzimidazole), poly(benzoxazole), aluminium, titanium, boron, aromatic polyamides and mixtures thereof. 19. Mixture according to claim 17 in the form of a composite material. 20. Composite material, characterized in that it includes: a) a cycloaliphatic epoxy resin containing at least two 1,2-epoxy groups per molecule; b) an aromatic diamine hardener in an amount sufficient to æ give from approx. 0.4 to 2.0 equivalents of amine N-H per equivalent 1,2-epoxy groups in the epoxy resin; c) an aromatic trihydroxy curing accelerator selected from phloroglucinol, n-propyl gallate, pyrogallol and mixtures thereof in an amount sufficient to give from approx. 0.01 to approx. 0.35 equivalents of hydroxy per equivalent of 1,2-epoxy in the epoxy resin; and d) up to approx. 85% by weight, based on the total weight of the mixture, of a structural fiber with a tensile strength of over approx. 100 . 000 psi, a tensile modulus of over approx. 2 million psi and a decomposition temperature of over approx.200|C. 21. Mixture according to claim 20, characterized in that the cycloaliphatic epoxide is bis(2,3-epoxycyclopentyl) ether. 22 . Composite material according to claim 20, characterized in that the cycloaliphatic epoxide is vinylcyclohexene diepoxide, 2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexane meta-dioxane, 3,4-epoxycyclohexylmethyl 3,4- epoxycyclohexane carboxylate, 3,4-epoxy-6-methylcyclohexylmethyl 3,4-epoxy-6-methylcyclohexane carboxylate, dipentene dioxide, epoxidized polybutadiene, bis (3,4-epoxy cyclohexylmethyl) adipate or mixtures thereof. 23 . Composite material according to claim 20, characterized in that the cycloaliphatic epoxide is selected from one or more of: where b is 1 to 4, m is (5-b) and R 2 is H, halogen or C± to C 4 alkyl. 24. Composite material according to claims 21, 22 or 23, characterized in that the aromatic diamine hardener is m-f phenylenediamine, the ring alkylated derivatives thereof, adducts of epoxy resins and m-phenylene diamine, autectic mixtures of m-phenylenediamine and 4,4 <1-> diaminodi-phenylmethane or mixtures thereof. 25. Composite material according to claim 24, characterized in that it further contains up to 40% by weight of a co-epoxy resin, based on the combined weight of the cycloaliphatic epoxy resin and the co-epoxy resin. 26. Composite material according to claim 24, characterized in that it comprises up to approx. 35% by weight, calculated on the total weight of the resin part of composite material, of a modifier that increases the modulus of the epoxy resin. 27. Composite material according to claim 24, characterized in that it further contains up to approx. 20% by weight, calculated on the total weight of the resin portion of the composite material, of a thermoplastic polymer.