CA1080686A - Compositions for curing epoxide resins - Google Patents

Abstract

Abstract of the Disclosure To accelerate the curing of epoxide resins by particular curing agents. i.e., polyamines, polyaminoamides, polycarboxylic acids, or polycarboxylic acid anhydrides, there is employed an aliphatic or araliphatic monocarboxylic acid of 2 to 8 carbon atoms, bearing on the carbon atom adjacent to the carboxyl group at least two halogen atoms chosen from fluorine and chlorine atoms, or a salt thereof, such as magnesium trifluoroacetate and magnesium trichloroacetate.

Description

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Basel (Schweiz) Canada BACKGROUND OF THE INVENTION

This invention relates to compositions for curing epoxide resins, to curable mixtures of these compositions and epoxide resins, and to cured products obtained by curing the aforesaid mixtures.

It is known that epoxide resins, i.e., substances containing on average more ~han one 1,2-epoxide group per molecule, may be cured by reaction with various classes of substances to form cross-linked, infusible, insoluble products having valuable technical properties.
Typical curing agents include aromatic, aliphatic, heterocyclic, and cycloaliphatic polyamines and polyaminoamides, and polycarboxylic acids and their anhydrides.

Some of these agents are suitable for curing at room temperature whilst others are suitable only at elevated temperatures. The chief drawback with curing agents at present in use is that they often cure the resin only slowly. The use of accelerators alleviates .nis ~raw-back to some extent but the accelerating effect which the acceleratcrs presently employed impart is relatively modest, particularly when amine curing agents are employed.

United States Patent Specification 3 278 ~05 discloses a process for theyhotochemicai crosslinking of polymers ~-hich comprises e~posing to actinic light selected portior.s of a photo-sensitive mixt~re containing a polymeric material carrying groups which are reactive ~ith photochemical'y ormed isocyan~tes and a polycarboxylic acid azide capable of for&ir.g crosslinks with the pol~eric materi21.
Among the polymeric materia s mentioned a.e epoxide resins. It is ~f ~

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stated that, under tlle influence of light, the polycarboxylic acid azides are probably converted into polyisocyanates. Compounds which are known to accele-rate the photochemical conversion of the acid azide group into an isocyanate group, such as trichloroacetic acid, may be added to the photosensitive com-position.
We have now found that certain fluorinated or chlorinated carboxylic acids and their salts very markedly accelerate the cure of epoxide resins by polyamines, polyaminoamides, polycarboxylic acids, and polycarboxylic acid anhydrides.
One aspect of this invention therefore relates to composition com-prising ta) a curing agent for epoxide resins, which is a polyamine, a polyamino-amide, a polycarboxylic acid, or a polycarboxylic acid anhydride, and (b) a lithium, sodium, calcium, zinc, barium, copper, cobalt, nickel, manganese, vanadyl vanadium, chromic chromium, or magnesium salt of a saturat-ed aliphatic monocarboxylic acid of 2 to 8 carbon atoms, bearing on the carbon atom adjacent to the carboxyl group at least two halogen atoms chosen from fluorine and chlorine atoms.

Another aspect of this invention comprises a curable composition in which (b) is the lithium, sodium, calcium, zinc, barium, copper, cobalt, nickel, manganese, vanadylvanadium, chromic chromium, or magnesium salt of a perfluorinated or perchlorinated acid.
Preferred is also a composition, in which (b) is the lithium, sodium, calcium, zinc, barium, copper, cobalt, nickel, manganese, vanadyl vanadium, chromic chromium, or magnesium salt of dichloroacetic acid, ,~-dichloro-propionic acid, perfluoropropionic acid, perfluoro-~-butyric acid, trifluoro-acetic acid, or trichloroacetic acid.

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~ referred is furthcr a composition, in which (b) is dissolved in an inert organic solvent.

Preferably said solvent is 2-methoxyethanol, ethylene glycol, diethylene glycol, N-methylpyrrolidone, y-butyrolactone, benzyl alcohol, dibutyl phthalate, butane-1,4-diol, or ethyl methyl ketone.

The curing agent (a) preferably is an aromatic polyamine.

According to the invention the composition may further con-tain (c) an epoxide resin.

This epoxide resin (c) preferably contains, per average molecule, at least one group of formule .0 -CH - C ~--- CH
R Ll R2 directly attached to an atom of oxygen, nitrogen, or sulfur, where either R and R each represent a hydrogen atom, in which case denotes a hydrogen atom or a methyl group, or R and R together represent -CH2CH2-, in which case R denotes a hydrogen atom.

This epoxide resin (c) preferably is a polyglycidyl ester, a polyglycidyl ether, or an N,N'-diglycidyl-hydantoin.

The composition according to this invention preferably con-tains from 0.2 to 2 parts by weight of tne comp~nen. ~b) ?er 100 parts of the combined weights of the curing agent (a) and the epc-xide resin (c).

A further aspect cf this invention is a method cf preparing a ~ ~ . . _ . _ . , . . . . _ _ . _ . _ _ _ . . _ _ _ . . . .
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l()ffv~ff~j cured epoxide composition, which comprises permitting the compo-sition to cure.

The preferred halogenated acids are fluorinated or chlorinated, especially perfluorinated or perchlorinated, saturated aliphatic acids of from 2 to 6 carbon atoms, more particularly of from 2 to 4 carbon atoms, such as dichloroacetic, a,a-dichloropropionic, per-fluoropropionic, and perfluoro-n-butyric ~cids. Trifluoroacetic acid and trichloroacetic acid are especially preferred.

The salt of the halogenated acid may be those of light or heavy metals, i.e., of metals of Groups I~, IB, IIA, IIB, IIIB, IVB, VB, VIB, VIIB, or VIII of the Periodic Table (as shown on p.
60-61 in Handbook of Chemistry, ed. Lange, Revised Tenth Edition, published by McGraw-Hill). The metals may be trivalent, e.g., chromic chromium, but preferably they are mono- or divalent, such as lithium, sodium, calcium, zinc, barium, copper, cobalt, nickel, manganese, vanadyl vanadium (V0 ), and magnesium, tne lithium, sodium, calcium, and magnesium salts being particularly preferred for use with aro-matic amines and the zinc, manganese, vanadyl, and magnesium salts being particularly preferred for use wi~h aliphatic amines.

- - The salts may also be ammonium salts, including quaternary ammonium salts, or amine salts such as those of aromatic, aliphatic~
or heterocyclic amines, preferably those amines having a basic strenght, -log Kl, of 5 or less. Typical such amines include mono-, di-, and tri-methylamine,mono-,ordi- and tri-ethylamine, ethanolamine, , .: ` ` `' - ~

~ O~ ti the butylamines, bcnzylaminc, 2-phcnyletllylamine, N,N-dimethyl-bcnzylamine, ethylenediamine, pipcrazine, piperidine, bis(4-amino-phenyl)-methane, 3-ethyl-4,4'-diaminodiphenylmethane, and bis(3-ethyl-4-aminophenyl)methane.
As examples of such resins may be mentioned polyglycidyl and poly(e-methylglycidyl) esters obtainable by reaction of a compound containing two more carboxylic acid groups per molecule with epichlorohydrine, glycerol dichlorohydrin, or e-methylepichloro-hydrin in the presence of an alkali. Such polyglycidyl esters may be derived from aliphatic polycarboxylic acids, e.g., oxalic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, or dimerised or trimerised linoleic acid; from cycloaliphatic polycarboxylic acids, such as tetrahydro-phthalic acid, 4-methyltetrahydrophthalic acid, hexahydrophthalic acid, and 4-methylhexahydrophthalic acid; and from aromatic poly-carboxylic acids such as phthalic acid, isophthalic acid, and tere-phthalic acid.
Further examples are polyglycidyl and poly~e-methylglycidyl) ethers obtainable by reaction of a compound containing at least two free alcoholic hydroxyl and/or phenolic hydroxyl groups per molecule 108V~

witll the appropriate epichlorohydrinunder alkaline conditions or, alternatively, in the presence of an acidic catalyst and subse~uent treatment with alkali. These ethers may be made from acyclic alcohols such as ethylene glycol, diethylene glycol, and higher poly(oxyethylene) glycols, propane-1,2-diol and poly(oxypropylene) glycols, propane-1,3-diol, butane-1,4-diol, poly(oxytetramethylene) glycols, pentane-1,5-diol, hexane-~6-diol, hexane-2,4,6-triol, glycerol, l,l,l-tri-methylolpropane, pentaerythritol, sorbitol, and poly(epichlorohydrin);
from cycloaliphatic alcohols such as resorcitol, quinitol, bis(4-hydroxycyclohexyl)methane, 2,2-bis(4-hydroxycyclohexyl)-propane, and 1,1-bis(hydroxymethyl)cyclohex-3-ene; and from alcohols having aromatic nuclei, such as N,N-bis(2-hydroxyethyl)aniline and p,p'-bis(2-hydroxy-ethylamino)dipher,ylmethane. Or they may be made from mononuclear phen-ols, such as resorcinol and hydroquinone, and from polynuclear phenols, such as bis(4-hydroxyphenyl)methane, 4,4'-dihydroxydiphenyl, bis~4-hydroxyphenyl) sulphone, 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane,

2,2-bis(4-hydroxyphenyl)propane (otherwise known as bisphenol A), 2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane, and novolaks formed from aldehydes such as formaldehyde, acetaldehyde, chloral, and furfur-aldehyde, with phenols such as phenol itself, and phenol substituted in the ring by chlorine atoms or by alkyl groups each containing up to nine carbon atomes, such as 4-chlorophenol, 2-~ethylphenol, and 4-tert.butylphenol.

Poly(N-glycidyl) compounds include, for example, those obtai-ned by dehydrochlorination of the reaction products of epichlorohydrin with Emines containing at least two amino-hydrogen atoms such as ani-line, n-butylamine, bis~4-aminophenyl)methane, and bis(4-methylamino-phenyl)methane; triglycidyl isocyanurate; and N,N'-diglycidyl deri-Yatives of cyclic alkylene ureas, such as ethyleneurea and 1,3-propyleneureae, and of hydantoins such as 5,5-dimethylhydantoin.

Examples of poly~S-glycidyl) compo-mds are di-S-glycidyl deri-.
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vatives of dithiols such as ethane-1,2-dithiol and bis(4-mercapto-methylphenyl) ether.

Exa~ples of epoxide resins having groups of formula I where R
and R conjointly denote a -CH2CH2- group are bis(2,3-epoxycyclo-pentyl) ether, 2,3-epoxycyclopentyl glycidyl ether, and 1,2-bis(2,3-epoxycyclopentyloxy)ethane.

Epoxide resins having the 1,2-epoxide groups attached to diffe-rent kinds of hetero atoms may be employed, e.g., the N,N,0-triglyci-dyl derivative of 4-aminophenol, the glycidyl ether-glycidyl ester of salicylic acid, N-glycidyl-N'-(2-glycidyloxypropyl)-5,5-dimethyl-hydantoin, and 2-glycidyloxy-1,3-bis(5,5-dimethyl-1-glycidylhydantoin-

3-yl)propane.

Epoxide resins in which some or all of the epoxide groups are not terminal may also be employed, such as vinylcyclohexene dioxide, limonene dioxide, dicyclopentadiene dioxide, 4-oxotetracyclo 16,2.1.0 '7.0 '5] undec-9-yl glycidyl ether, the bis(4-oxatetra-cyclo [6.2.1.0 '7.03'5]undec-9-yl) ether of ethylebe glycol, 3,4-epo-xycyclohexylmethyl 3',4'-epoxycyclohexanecarboxylate and its 6,6'-dimethyl derivative, the bis(3,4-epoxycyrlohexanecarboxylate) of ~thyleneglycol~ 3-(3,4-epoxycyclohexyl)-8,9-epoxy-2,4-dioxaspiro 15,5] undecane, and epoxidised butadienes or copolymers of butadiene with ethylenic compounds such as styrene and vinyl acetate.

If desired, a mixture of epoxide resins may be used.

Preferred epoxide resins are polyglycidyl ethers, polyglycidyl esters, and N,N-diglycidylhydantoins. Specific preferred, resins are polyglycidyl ethers or 2,2-bis(4-hydroxyphenyl)propane, of bis(4-hy-droxyphenyl)methane, or of a novola~ formed from formaldehyde ar.d pherol, or phenol substituted in the ring by one chlorine atom or by .

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~o~o~tj 9 _ one alkyl hydrocarbon group containing from one to nine carbon atoms, and having a 1,2-epoxide content of more than 0.5 equivalent per kilo-gram.

As examples of polyamines suitable for use as the curing agent may be mentioned aliphatic, cycloaliphatic, aromatic, and hetero-cyclic amines such as m- and p-phenylenediamine, bis(4-aminophenyl) methane, aniline-formaldehyde resins, bis(4-aminophenyl) sulphone, ethylenediamine, propane-1,2-diamine, propane-1,3-diamine, N,N-di-ethylethylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, N-(2-hydroxyethyl)-, N-(2-hydroxypropyl)-, and N-~2-cyanoethyl)diethylenetriamine, 2,2,4-trimethylhexane-1,6-diamine, 2,4,4-trimethylhexane-1,6-diamine, m-xylylenediamine, N,N-dimethyl- and N,N-diethylpropane-1,3-diamine, bis(4-aminocyclohexyl)methane, 2,2-bis(4-aminocyclohexyl)propane, 2,2-bis(4-amino-3-methylcyclohexyl)-propane, 3-aminomethyl-3,5,5-trimethylcyclohexylamine (isophoronediamine), and N-(2-aminoethyl)pi-perazne, and adducts of such polyamines wiht a stoichiometric defi-cit of a polyepoxide such as a diglycidyl ether. Suitable polyamino-amides include those prepared from aliphatic polyamines and dimerised or trimerised unsaturated fatty acids. Suitable polycarboxylic acids and their anhydrides include phthalic anhydride, tetrahydro- and hexahydro-phthalic anhydride, methylendomethylenetetrahydrophthalic anhydride, nonenylsuccinic anhydride, dodecenylsuccinic anhydride, hexachloroendomethylenetetrahydrophthalic anhydride and endomethylene-tetrahydrophthalic anhydride and their mixtures, maleic anhydride, succinic anhydride, pyromellitic acid dianhydride, benzophenone-3.3',4,4'-tetracarboxylic acid dianhydride, polysebacic anhydride, polyazelaic anhydride, the acids corresponding to the afore-mentioned anhydrides, and also isophthalic acid, terephthalic acid, citric acid, and mellitic acid. Particularly preferred polycarboxylic acid or anhydride curing agents are those which, in admixture if necessary, are liquid at temperatures below 60~.
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The preferred curing ~gcnts are polyamines, especiallv aromatic polyamines.

An effective amount of the curing agent is employed. The propor-tion will depend on the chemical nature of the curing agent and the properties sought of the curable composition and its cured product;
the optimum proportion can readily be determined by methods familiar to those skilled in the art. By way of illustration, however, when the curing agent is an amine there will normally be used from about 0.75 to 1.25 amino-hydrogen equivalents of the amine per 1,2-epoxy equivalent of the epoxide resin. When polyc~rboxylic acids or their anhydrides are used, usually from about 0.4 to 1.1 carboxylic acid, or carboxylic acid anhydride, equivalents are taken per 1,2-epoxy equivalent.

The amount of the accelerator (b), too, may vary according to such factors as those just mentioned, but usually from 0.2 to 2 parts by weight are employed per 100 parts of the combined weights of the epoxide resin ar.d the curing agent.

The accelerator is best incorporated dissolved in an inert organic solvent such as 2-methoxyethanol, ethylene glycol, diethylene glycol, N-methylpyrrolidone, y-butyrolactone, benzyl alcohol, dibutyl phthalate, butane-1,4-diol, or ethyl methyl ketone.
~.

Curing can be carried out, depending on the nature of the curing agent, at room temperature (say, 18 to 25C) or lower (e.g. 0 to 5C) or at higher temperatures (50 to 180C, for example).

The new compositions may further contain suitable plasticizers such as dibutyl phthalate, dioctyl phthalate, and tricresyl phosphate, inert diluents such as tars and bitumen and so-called reactive dilu-ents, especially monoepoxides such as n-butyl glycidyl ether, iso-octyl glycidyl ether, phenyl glycidyl ether, cresyl glycidyl ethers, . . .

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glycidyl esters of tertiary, aliphatic, monocarboxylic acids, glyci-dyl acrylate, and glycidyl mcthacrylate. They may also contain additives such as fillers, reinforcing materials, colouring matter, flow control agents, flame inhibitors, and mould lubricants.Suitable extenders, fillers, and reinforcing materials are, for example, glass fibres, carbon fibres, ballotini, mica, quartz flour, calcium carbon-ate, cellulose, kaolin, wollastonite, colloidal silica having a large specific surface area, powdered poly(vinyl chloride), and powdered polyolefin hydrocarbons such as polyethylene and polypropylene.

The curable compositions of this invention may be used as la-minating resins, paints and lacquers, sinter powders, impregnating and casting resins, moulding compositions, putties and sealing com-pounds, potting and insulating compounds for the electrical industry, and adhesives, and also in the manufacture of such products.

They may be supplied as a two-part pack, one part containing the epoxide resin and the other the curing agent, the accelerator being ir. either or both parts, but avantageously only in the curing agent part, because some epoxide resins tend to polymerise slowly, over a period of some months, when kept in contact with the halo-genated acid or its salts at room temperature.

The following Examples illustrate the invention. Temperatures are in degrees Celsius and, unless otherwise specified, parts are by weight. The accelerating effect is shown, as is conventional in this art, by the redcution in the time taken for the com~osition to gel, prior to curing; gelation times were determined by means of a "Techne" gelation timerl available from Techne (Cambridge) ~td., Duxford, Cambridge, England.

The salts were prepared by any of the follouing methods:

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a) The acid was mixed with lO parts by volume of water and the ammonium, amine, or metal carbonate was addcd to bring the pH to 7.
If the carbonate was insoluble in water, an excess over the theoreti-cal amount was added and, when effervescence ceased, the excess was filtered off.

The resultant solution was evaporated, and the salt was dried at 100/13 mm Hg.

b) The amine, ammonium, or metal nitrate was dissolved in ethanol and treated an equivalent of the barium salt of the acid, also dissol-- ved in ethanol. Barium nitrate precipitated from solution and was filtered off. The solution was evaporated and the product was dried as above.

c) The amine, ammonium, or metal sulphate was dissolved in water and treated with an equivalent of the barium salt of the acid, dissol-ved in water. Barium sulphate precipitated and was filtered off. The solution was evaporated and the product was dried as above.

- "Epoxide resin I" denotes a polyglycidyl ether of 2,2-bis(4-hydroxyphenyl)propane having a 1,2-epoxide content of 5.16 equivalents per kilogram and a viscosity at 21 of 245 poises.
"Epoxide resin II" denotes the diglycidyl ether of butane-1,4-diol.
"Epoxide resin III" denotes N,N-diglycidyl-5,5-dimethylhydan-toin.
~` "Epoxide resin IV" denotes N-glycidyl-N'-(2-glycidyloxypropyl)-5,5-dimethylhydantoin.
"Epoxide resin V" denotes the tetraglycidyl ether of penta-erythritol, advanced with 2,2-bis~4.hydroxyphenyl)propane to an epoxide content of 8,5 equiv.'kg.
"Epoxide resin VI" denotes diglycidyl tetrahydrophthalate; its lO~

1,2-epoxide content was 6.0 equiv./kg.
"Epoxide resin VII" denotes the tetrakis(N-glycidyl) deriva-tive o~ bis(4-aminophenyl)methane.
"Epoxide resin VIII" denotes 3,4-epoxycyclohexylmethyl 3',4'-epoxycyclohexanecarboxylate.
"Hardener I" denotes a commercially available liquid curing agent, composed essentially of bis(4-aminophenyl)methane.
"Hardener II" denotes triethylenetetramine.
"Hardener III" denotes a 54% solution of bis(4-aminophenyl)me-thane in y-butyrolactone.
"Hardener IV" denotes bis(4-amino-3-methylcyclohexyl)methane.
"Hardener V" denotes a polyaminoamide made from dimerised linoleic acid and triethylenetetramine, and is described as Sample 3 of Example 2 in British Patent Specification No. 847028.
"Hardener VI" denotes hexahydrophthalic anhydride.

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EXA~LF 1 Epoxide resin I (50 g) was mixed at room temperature with Hardener I (16 g). The gel time was 2682 minutes. Next, the experiment was repeated, incorporating in each case 0.5 g of a 50Z solution of a trifluoroacetate or a trichloroacetate in 2-methoxyethanol, and the corresponding gel times were recorded.

Table I shows the results obtained.

TABLE I

Gel Time (minutes with Salt trifluoroacetate Itrichloroacetate Mg2+ 22 19 Li 51 813 NH2+ 1226 1253 Ca 704 756 Ba 1391 1453 ~ ' ~

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- denotes t'nat the experiment was not carried out ' .

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EXA~LE 2 The procedure of Example 1 was repeated, but Hardener I was replaced by Hardener II (6 g). The gel time for the unaccelerated mixture was 54 minutes. The results for the accelerated mixes are shown in Table II.

TABLE II

Gel time (minutes) with Salt trifluoroacetate trichloroacetate Li 34 36 Ca 36 33 Cu21 34 36 `~ The procedure of Example 1 was repeated, using various epoxide - resins and hardeners. Magnesium trifluoroacetate and trichloroacetate, added as 50~ solutions in 2-methoxyethanol (0.5 g) were incorporated as accelerators. The results are given in Table III.

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_ 16 -TABLE III
Resin Hardener Gel time (minutes) with accelerator Type g Type g None Trifluoroacetate Trichloroacetate _ II 50 I 22.8 8075 25 2650 _ V - 50 _ 20 3436_ _ l6~ _ 14 VI 50 I 19,6 4580 47 68 VII 50 III 38.3 61592011 2539 VIII 50 I 22 ~75000 5856 736 Epoxide resin I (50 g) and Hardener VI (37,5 g) were mixed toge-ther at 120: they gelled after 2358 minutes at 120. A similar mixture, containing also 0.5 g of a 50~ solution of magnesium tri-fluoroacetate in 2-methoxyethanol, gelled after 1298 minutes, and one containing 0.5 g o~ a 50Z solution of magnesium trichloroacetate in 2-methoxyethanol gelled after 505 minutes, both mixtures being maintained at 120.

EXU~PLE 5 _ Example 1 was repeated, the solutions of haloacetate salts ,. ~

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_ 17 _ being replaced by 0.5 g of a 50% solution in 2-methoxyethanol of magnesium salts of other halogenated acids. The resultant gel times were as follows:
magnesium heptafluoro-n-butyrate - 58 minutes magnesium pentafluoropropionate - 19 minutes magnesium dichloroacetate - 71 minutes magnesium a,a-dichloropropionate - 39 minutes Example 2 was repeated, the solutions of haloacetate salts being replaced by 0.5 g of a 50% solution in 2-methoxyethanol of magnesium salts of other halogenated acids. The resultant gel times were as follows:
magnesium heptafluoro-n-butyrate - 33 minutes magnesium pentafluoropropionate - 38 minutes magnesium dichloroacetate - 39 minutes magnesium pentadecafluoro-octanoate- 38 minutes Example 1 was repeated, the haloacetate salt accelerators being - replaced by 0.25 g of trifluoroacetic acid. The gel time was 257 minutes.

In this Example, the efficzcy of the accelerators of this in-vention is compared with those of cor.ventional accelerators.

A mixture comprising 87% of Epoxide resin I and 13% of iso-octyl glycidyl ether (50 g) was mixed at room temperature with Hardener I (16 g). The gel time at room temperature was 257 minutes.

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The experiment was repeated, using two conventional accelerators.
When 2-methoxyethyl hydrogen maleate (0,5 g) was incorporated, the corresponding gel time was 379 minutes: when salicylic acid (0.5 g) was incorporated, the gel time at room temperature was 117 minutes.

Finally, the experiment was repeated with 0.5 g of a 50~ solu-tion of magnesium trichloroacetate in 2-methoxyethanol incorporated.
The gel time at room temperature was only ~5 minutes.

Claims (11)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A composition comprising (a) a curing agent for epoxide resins, which is a polyamine, a polyaminoamlde, a polycarboxylic acid, or a polycarboxylic acid anhydride, and (b) a lithium, sodium, calcium, zinc, barium, copper, cobalt, nickel, manganese, vanadyl vanadium, chromic chromium, or magnesium salt of a saturated aliphatic monocarboxylic acid of 2 to 8 carbon atoms, bearing on the carbon atom adjacent to the carboxyl group at least two halogen atoms chosen from fluorine and chlorine atoms.

2. The composition of claim 1, in which (b) is the lithium, sodium, calcium, zinc, barium, copper, cobalt, nickel, manganese, vanadylvanadium, chromic chromium,or magnesium salt of a perfluorina-ted or perchlorinated acid.

3. The composition of claim 1, in which (b) is the lithium, sodium, calcium, zinc, barium, copper, cobalt, nickel, manganese, vanadyl vanadium, chromic chromium, or magnesium salt of dichloro-acetic acid, .alpha.,.alpha.-dichloropropionic acid, perfluoropropionic acid, perfluoro-n-butyric acid, trifluoroacetic acid, or trichloroacetic acid.

4. The composition of claim 1, in which (b) is dissolved in an inert organic solvent.

5. The composition of claim 4, in which the said solvent is 2-methoxyethanol, ethylene glycol, diethylene glycol, N-methylpyrroli-done, y-butyrolacetone, benzyl alcohol, dibutyl phthalate, butane-1,4-diol, or ethyl methyl ketone.

6. The composition of claim 1, in which the curing agent (a) is an aromatice polyamine.

7. The composition of claim 1, which further contains (c) an epoxide resin.

8. The composition of claim 7, in which the epoxide resin (c) contains, per average molecule, at least one group of formula directly attached to an atom of oxygen, nitrogen, or sulfur, where either R
and R2 each represent a hydrogen atom, in which case R1 denotes a hydrogen atom or a methyl group, or R and R2 together represent -CH2CH2-, in which case R1 denotes a hydrogen atom.

9. The composition of claim 7, in which the epoxide resin (c) is a polyglycidyl ester, a polyglycidyl ether, or an N,N'-diglycidylhydantoin.

10. The composition of claim 7, containing from 0.2 to 2 parts by weight of the component (b) per 100 parts of the combined weights of the curing agent (a) and the epoxide resin (c).

11. Method of preparing a cured epoxide composition, which comprises forming the composition of claim 7 and permitting the composition to cure.