CH672493A5 - - Google Patents

Description

DESCRIPTION The invention relates to storage-stable, heat-curable substance mixtures which contain certain di- and polyfunctional epoxy resins, diphenols and / or dihydroxynaphthalenes as hardeners and accelerators, and their use for the production of shaped articles, in particular prepregs for fiber-reinforced composites and adhesive films.

A variety of curable epoxy resin mixtures, which include also contain phenolic hardeners is known. For example, JP-OS 76/129 498 substance mixtures containing polyfunctional epoxy resins, phenolic hardeners and accelerators and 5 their use for the production of prepregs for special electrical insulating materials. US 4,322,456 discloses mixtures of epoxy resins, phenolic hardeners and accelerators, preferably the functionality of the epoxy resins and /

or the hardener is greater than 2, which are suitable for the production of curable coatings, particularly as powder coatings. No. 4,288,565 describes mixtures of epoxy resins with high and low epoxy equivalent weight and phenolic hardeners, which are at least 30% compounds with 3 or more hydroxyl groups per molecule.

15 US Pat. No. 4,216,304 describes liquid, curable epoxy resin mixtures which contain a glycidyl ether of a phenolic novolak which is liquid at room temperature and contains 2,6-dihydroxytoluene as curing agent and curing accelerator.

DE-OS 28 07 666 describes liquid polymer mixtures 20 containing a polymer containing terminal carboxyl groups, an epoxy resin, a plasticizer, a dihydroxy compound as a hardener for the epoxy resin and 2-ethyl-4-methylimidazole as a curing accelerator. Bisphenols and dihydroxynaphthalene 25 are also mentioned as dihydroxy compounds. The polymer containing terminal carboxyl groups is preferably an elastomer and the polymer mixtures are used for the production of rubber bubbles for game balls.

No. 3,661,828 describes molding compositions containing a copolymer of glycidyl methacrylate, (meth) acyl nitrile and methyl methacrylate with an average molecular weight of approx. 1500-16 000 and a diphenol as hardener. The molding compositions can also contain low molecular weight diepoxides as reactive diluents. Bisphe-35 noie and 2,7-dihydroxynaphthalene are also mentioned as suitable diphenol hardeners.

The present invention relates to storage-stable, curable substance mixtures according to claim 1.

(c2) 100-20% by weight of a dihydroxynaphthalene, and

40 d) 0.05-5% by weight, based on the epoxy resins (a) and (b), of an accelerator.

The mixtures according to the invention are suitable for the production of shaped objects, prepregs and adhesive films, and the cured products are distinguished by excellent thermal and mechanical properties, in particular by high heat resistance and excellent flexural strength. The particularly good strength properties are achieved if the proportion of the compounds of the formula I or II is at most 80% by weight and the proportion of the dihydroxynaphthalene is at least 20% by weight of the diphenol hardener (c).

Furthermore, the mixtures have excellent processing properties, e.g. a high degree of homogeneity, a long pot life (“pot life”) and a favorable stickiness (“tack”), which is retained even after long storage at room temperature 55.

They are also characterized in particular by a low viscosity even at room temperature, so that they are particularly well suited for solvent-free applications.

Suitable epoxy resins (a) and (b) for the present 60 mixtures are all those which have a functionality of at least 3 or 2-2.5 and which are cured with diphenols (c) in the presence of accelerators (d) can be.

Epoxy resins with a functionality of 3, for example 65, are understood to mean those resins which have an average of 3 epoxy groups per molecule.

Suitable as epoxy resins (a) and (b) are e.g. Di- or poly-glycidyl ethers of cycloaliphatic polyols, such as 2,2-bis (4'-

hydroxycyclohexyl) propane, di- or polyglycidyl ether of polyhydric phenols, such as resorcinol, bis (4'-hydroxyphenyl) methane (bisphenol F), 2,2-bis (4'-hydroxyphenyl) propane (bisphenol A), 2,2- Bis- (4'-hydroxy-3 ', 5'-dibromophenyl) propane, 1,1,2,2-tetra-kis (4'-hydroxyphenyl) ethane, or condensation products of phenols with formaldehyde, such as phenol novolaks and cresol -Novolake; furthermore di- or poly (β-methylglycidyl) ether of the above-mentioned polyalcohols and polyphenols;

Polyglycidyl esters and poly (β-methylglycidyl) esters of polyvalent carboxylic acids, such as phthalic acid, terephthalic acid, tetra-hydrophthalic acid and hexahydrophthalic acid;

Glycidyl derivatives of aminophenols, e.g. Triglycidyl-p-aminophenol;

N-glycidyl derivatives of amines, amides and heterocyclic nitrogen bases, such as N, N-diglycidylaniline, N, N-diglycidyl-toluidine, N, N, N ', N'-tetraglycidyl-bis (4-aminophenyl) methane, triglycidyl isocyanurate, N, N-diglycidyl-N, N'-ethylene urea, N, N'-diglycidyl-5,5-dimethylhydantoin, N, N'-diglycidyl-5-iso-propylhydantoin, N, N'-diglycidyl-5,5- dimethyl-6-isopropyl-5,6-dihydrouracil;

Multi-functional epoxy resins, such as the 2,6-disubstituted 4-epoxypropylene phenyl glycidyl ether and their adducts described in EP 205 409 and EP 204 659;

Bisphenols substituted with two glycidyloxy and 2,3-epoxypropyl groups, e.g. the 2,2-bis (3'-epoxypropyl-4'-epoxypropylphenyl) propane described in GB 828 364;

Glycidyl derivatives of tetramethylol-substituted cyclohexanols, cyclohexanones, cyclopentanols and cyclopentanones, such as the compounds described in US Pat. No. 4,549,008;

Glycidyloxy-substituted benzophenones and glycidyloxydi-ketones, such as the compounds described in US 4,649,181.

In general, mixtures of two or more epoxy resins can also be used as component (a) and / or as component (b) in the compositions according to the invention.

Particularly suitable as epoxy resins (a) and (b) are compounds which have an epoxy content of 5-11 equivalents / kg and which are glycidyl ethers, glycidyl esters or N-glycidyl derivatives of a cycloaliphatic, an aromatic or heterocyclic compound. Particularly preferred epoxy resins (a) and (b) are epoxynovolaks or glycidyl derivatives of a bisphenol, a hydantoin or a tetramethylolcyclohexane.

Particularly suitable epoxy resin (a) are epoxiphenolno-volatile or glycidyl derivatives of hydantoins or tetramethylolcyclohexanes. They preferably have a functionality of 3 to 4. Epoxy-phenol novolaks or glycidyl derivatives of bisphenol A or bisphenol F are particularly suitable as epoxy resin (b). They preferably have a functionality of 2 to 2.2.

Mixtures according to the invention in which the hydroxyl substituents of the compound of the formula I are in the 4,4'-position and the symbol T denotes O, S, methylene or isopropylidene are preferred.

Mixtures according to the invention in which the compound of the formula II is a dihydroxytoluene, in particular, are also preferred

Is 2,6-dihydroxytoluene.

Component (c2) of the substance mixtures according to the invention is a dihydroxynaphthalene, e.g. 1.5, 1.7, 2.6 or

2,7-dihydroxynaphthalene. Component (c2) is preferably 2,6- and in particular 2,7-dihydroxynaphthalene.

Mixtures are preferred in which the diphenol (c) consists of 20-60% by weight of component (cl) and 80-40% by weight of component (c2), and in particular those

wherein the diphenol (c) consists of 50% by weight of components (cl) and (c2). Mixtures in which the diphenol (c) consists of 2,6-dihydroxytoluene and 2,7-dihydroxynaphthalene are particularly preferred.

Particularly good results are achieved if the same

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Amounts of weight of these compounds are mixed in the melt at about 180 ° C., the product obtained after the melt solidifies is ground to a fine powder and this is then used as a hardener.

The present invention also relates to a hardener for epoxy resins containing a compound of the formula I or II and a dihydroxynaphthalene.

If appropriate, in addition to the diphenols (c), the substance mixtures according to the invention can also contain a certain amount of one or more tri- or polyphenols, such as 2,4,6-tris [2 '- (p-hydroxyphenyl) -2'-propyl] benzene (“Tris-TC” from Mitsui Petrochemical). In general, however, at most 30% of the phenolic hydroxyl groups should come from a tri- or polyphenol, and the rest of the hydroxyl groups should belong to a diphenol. Phenol or cresol novolaks are generally not suitable as phenolic hardeners for the mixtures according to the invention. It goes without saying that when using both diphenols and tri- or polyphenols, the amount of the total phenolic hardener (c) is chosen such that a total of 0.7-1.2 hydroxyl equivalents of the phenols used per epoxy equivalent of epoxy resins used are contained in the mixture according to the invention.

Suitable accelerators (d) of the curable substance mixtures are all compounds known to the person skilled in the art for accelerating the crosslinking reaction of epoxy resins with phenolic hardeners, such as e.g. tertiary amines, their salts or quaternary ammonium compounds such as tetramethylammonium chloride, phosphonium salts, alkali metal alcoholates, such as e.g. Sodium hexanetriolate, Lewis acids e.g. BF3 or SnCU, and nitrogen-containing heterocycles such as pyridines, imidazoles and their derivatives. Imidazoles and N-acylimidazoles (imidazolides) are particularly suitable as accelerators (d).

Examples of suitable imidazoles are compounds of the formula III

R »yR2

(III),

h wherein R1, R2 and R3 independently of one another are hydrogen, Q-Cj2-alkyl, C5-Ci0-cycloalkyl or Q-Qo-alyl. In particular, 2-methyl-, 2-ethyl-, 2-phenyl- and 2-ethyl-4-methyl-imidazole are preferred.

Suitable N-acylimidazoles (imidazolides) are e.g. the compounds described in US 4,436,892, US 4,587,311 and JP-OS 74/7599. Compounds of the formula IV are particularly suitable

r6 ~ "\) - ^ ^ (iv), i1

wherein R1 to R3 have the meaning given above and R4 to R8 are independently hydrogen, Ci-C12-alkyl, halogen, nitro or trifluoromethyl. Examples of suitable imidazolides are 1- (2 / s4 ', 6'-trimethylbenzene) -2-ethylimidazole, 1- (2'36 / -dichlorobenzene) -2-methylimidazole, 1 - (2 / s4 / s6'-trimethylbenzene ) -2-methylimidazole and l- (2'54 ^ 6'-trimethylbenzene) -2-phenylimidazole.

If appropriate, the curable substance mixtures according to the invention can, in addition to components (a) to (d), also (e) 10-120, preferably 20-70 parts by weight, based on 100

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Parts by weight of components (a) to (c), a thermoplastic with a glass transition temperature of at least 180 ° C included. The cured products produced with the thermoplastic mixtures are characterized by excellent thermal and mechanical properties, in particular by high heat resistance, excellent fracture toughness, bending and impact resistance as well as very high ductility.

All those known polymers which have a sufficiently high glass transition temperature, i. E., Can be used as thenmoplastics (e) in the curable material mixtures according to the invention. Have> 180 ° C and are miscible with the epoxy resin hardener system according to the invention.

Based on their properties as thermoplastics, polyimides, polyetherimides, polyamideimides, polysulfones or polyethersulfones are preferably used, in particular those with a glass transition temperature of 180-350 ° C. Thermoplastics with a glass transition temperature of 190-250 ° C. are particularly preferred.

If a polysulfone is used as the thermoplastic, the compounds described in EP-A194 232 as polysulfone component (c) are particularly suitable. These connections are e.g. available under the designation “Polysulfone Udel P1800”, “Polysulfone 2300” or “Polysulfonate 3500” (from Union Carbide Corporation).

According to the invention, mixtures of two or more thermoplastics can also be used as component (e).

Also particularly suitable as thermoplastics (e) are polyimides,

how

Polyimides with phenylindane units, such as those e.g. are described in US 3,856,752 and EP-A 92 534,

- Homo- and copolyimides from at least one aromatic tetracarboxylic acid and at least one aromatic diamine, such as. B. disclosed in US 4,629,777 and

- Homo- and copolyimides, e.g. in EP-A 162 017, EP-A 181 837 and US 4,629,685.

Preferred thermoplastics (e) are also polyetherimides, e.g. the products from General Electric offered under the name Ultem® (e.g. Ultem® 1000). Other preferred thermoplastics are polyether sulfones, e.g. Victrex PES 100 P from ICI or Udel P 1800 from Union Carbide.

Suitable polyamideimides are, for example, the compounds described in US Pat. Nos. 3,894,114, 3,948,835, 3,926,911 and 3,950,408.

Components (a) to (e) used in the mixtures according to the invention are all known compounds and can be prepared in a known manner.

Particularly preferred curable mixtures according to the invention are those containing 10 to 60 parts by weight of the epoxy resin (a), 90 to 40 parts by weight of the epoxy resin (b), an amount of the diphenol (c), so that 0.8-1.1, preferably 0.9 -1.0, hydroxyl equivalents of diphenol are used per epoxy equivalent of resins (a) and (b), and 0.1-1% by weight of accelerator (d) based on the amount of (a) and (b).

The mixtures according to the invention can be provided by thoroughly mixing or dissolving all of the components together, the individual components being able to be added in a different order. If the mixtures also contain a thermoplastic, this can e.g. be dissolved in the epoxy resin and in the phenolic hardener while heating, and after cooling the accelerator and, if appropriate, further additives can be added. However, a solution of the thermoplastic in an inert solvent, such as e.g. in methylene chloride, and mix them with the epoxy resin hardener mixture.

The mixtures according to the invention can be used in a variety of ways and are suitable, for example, as casting resins, laminating or impregnating resins, molding compounds, sealing compounds,

Bedding and insulating compounds for electrical engineering and preferably as adhesives and as matrix resins for composite materials, in particular for the production of fiber-reinforced plastics.

If desired, in particular when modifiers are used, the mixtures according to the invention can be dissolved in an organic solvent, such as toluene, xylene, methyl ethyl ketone, methylene chloride or a similar solvent or solvent mixture customary in the paint industry. Such solutions are particularly suitable as impregnating agents or coating agents.

Before the hardening in any phase, customary modifiers, such as extenders, fillers and reinforcing agents, pigments, dyes, organic solvents, plasticizers, leveling agents, thixotropic agents, flame retardants or mold release agents, are added. Examples of extenders, reinforcing agents, fillers and pigments which can be used in the curable mixtures according to the invention include called: liquid coumarone-inden-Haize, textile fibers, glass fibers, asbestos fibers, boron fibers, carbon fibers, polyethylene powder, polypropylene powder, quartz powder, mineral silicates such as mica, asbestos powder, slate powder, kaolin, chalk powder, antimony trioxide, bentone, iithopone, heavy spar , Carbon black, graphite, oxide paints, such as iron oxide, or metal powder, such as aluminum powder or iron powder. If the mixtures according to the invention are used for the production of prepregs, addition of short fibers is particularly desirable.

As a leveling agent when using the curable mixtures, especially in surface protection, one can e.g. Add silicones, liquid acyl resins, cellulose acetobutyrate, polyvinyl butyral, waxes, stea rates, etc. (some of which are also used as mold release agents).

As plasticizers for the modification of the curable mixtures e.g. Dibuthyl, dioctyl and dinonyl phthalate, tri-cresyl phosphate, trixylenyl phosphate and diphenoxyethyl formal can be used.

The mixtures according to the invention are preferably cured by heating them to a temperature in the range from 120 to 250 ° C., in particular 150 ° to 200 ° C. The curing can also be carried out in two or more stages in a known manner, the first curing stage being carried out at a low temperature and the post-curing at a higher temperature.

If desired, active curable thinners such as e.g. Add neopen tylglycol, butanediol or hexanediol diglycidyl ether.

The present invention also relates to the use of the mixtures according to the invention for the production of hardened moldings, and the use for the production of prepregs for fiber-reinforced composites or for the production of adhesive films. The prepregs and the adhesive films can be produced in a manner known per se, e.g. in the impregnation process in the presence of one of the solvents mentioned above, a halogenated solvent such as e.g. Methylene chloride, or in the so-called "hot melt" process.

The molding materials according to the invention are generally distinguished by high glass transition temperatures and high mechanical strengths.

The following examples explain the invention in more detail.

Components (a) - (e) used in the following examples are as follows:

Epoxy resin al: An epoxy phenol novolak with a functionality of 3.6 with an epoxy content of 5.6 equivalents / kg and a viscosity at 50 ° C of about 40 Pa s.

Epoxy resin a2: tetraglycidyl ether of 2,2,6,6-tetramethylol-cyclohexanol (produced according to Example 2 of US Pat. No. 4,549,008) with an epoxy equivalent weight of 129.

Epoxy resin a3: A triglycidyl-bis-hydantoin of formula VI with an epoxy content of 5.6 equivalents / kg and a viscosity at 80 ° C of about 13 Pa • s.

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H3C,

\

h3

çh3

0 o | / CH3

• r •

C ^ 2 — CH-CHz-N ^ ^ N-GH2 — CH-ÇH2— ^ M-CHz-Cf {-pCHz 0 • Ò •

ä L Ä

(VI)

; h2

<

Epoxy resin bl: An epoxy phenol novolak liquid at room temperature with a functionality of 2.2 with an epoxy content of 5.7 equivalents / kg and a viscosity at 50 ° C of 1.4 Pa • s.

Epoxy resin b2: A bisphenol F-diglycidyl ether with an epoxy content of 6.1 equivalents / kg and a viscosity at 25 ° C of 6.0 Pa • s.

: h2

Polyimide 1: A polyimide with phenylindane units with a glass transition temperature of 305 ° C. and an average molecular weight of ~ 65,000 (Matrimid® 5218, i5 Ciba-Geigy).

Polyetherimide 1: A polyetherimide with repeating units of the formula

/ V \

-NT I II

W "

/ "V

\ /

ÇHa ch3

V

\ / • SS *

ss À

• Nl

II I

"\ A

^ \ i H

V

and a glass transition temperature of 219 ° C (Ultem® 1000 from General Electric).

Polysulfone 1: Polysulfone Udel PI 800® (Union Carbide Corporation) with a melting point in the range of 350-370 ° C., a heat resistance (according to ASTM D 648) of 175 ° C., a glass transition temperature of 200 ° C. and a molecular weight range of about 22 000-35,000.

Example 1:

a) 15 g of epoxy resin al and 85 g of epoxy resin bl are mixed at 120 ° C. At this temperature, 17.7 g of 2,6-dihydroxytoluene and 17.7 g of 2,7-dihydroxynaphthalene are added and dissolved with stirring. After the mixture has cooled to 80 ° C., 0.1 g of 2-phenylimidazole is added. After cooling to room temperature, a solution of 81.2 g of polyimide 1 in 82 g of methylene chloride is added to the mixture and the mixture is stirred well until a homogeneous mixture is formed. Using a doctor blade, a 0.1 mm thick film is poured onto the siliconized paper with the mixture and the solvent is evaporated at room temperature. Several pieces of film measuring 30 x 30 mm are stacked on top of one another, pressed into a 1 mm thick molded body at 180 ° C. and cured at 180 ° C. for 1 h. The molded body has a Tg (measured by means of thermometric analysis) of 142 ° C with secondary conversion at 160 ° C.

b) If Example la) is repeated, but using 135.4 g of polyimide 1 as thermoplastic, a Tg of 153 and 182 ° C. is measured after curing.

Example 2:

If Example la is repeated, but using 44.7 g of polysulfone 1 as the thermoplastic, a Tg of 164 ° C. with pre-softening at 96 ° C. is measured after curing.

Example 3:

a) 35 g of epoxy resin a2 and 65 g of epoxy resin b2 are mixed at 120 ° C. with 20.5 g of 2,6-dihydroxytoluene and 20.5 g of 2,7-dihydro-xynaphthalene. 0.1 g of 2-phenylimidazole is added to the mixture, it is cooled to room temperature and then, as described in Example 1, 84.5 g of polyimide 1 in methylene chloride are added and processed. After curing, a Tg of 194 ° C with weak pre-softening is measured at 104 ° C 30.

b) When using 60.4 g of polyimide 1 and otherwise the same composition and processing as in a), a film-shaped body with a Tg of 210 and 105 ° C is obtained. With a part of the film, 2 Al plates are glued together at 180 ° C 35 and post-cured at 200 ° C for 1 h. The cured resin has a fracture toughness (GiC) of 794 J / m 2, measured using the double torsion test according to "Journal of Materials Science, 10, 1334 (1975) and 14.776 (1979)". Two aluminum plates Extradai 050 AlMgSi 0.5) with the dimensions 200 x 40 20 x 5 mm, which are treated with chromosulphuric acid, are glued to the hardenable mixture and the glue is hardened using light pressure. With this measurement method, the crack propagation in the bond is measured, i.e. the 45 fracture energy in J / m2 is calculated from the maximum load for the crack propagation.

Example 4:

50 g of epoxy resin a3 and 30 g of epoxy resin b2 are mixed and processed with 19 g of 2,6-dihydroxytoluene, 19 g of 2,7-dihydroxynaphthalene, 0.1 g of 2-50 phenylimidazole and 138 g of polyetherimide 1, as described in Example 1 . After curing, a Tg of 188 ° C with a low pre-softening at 100 ° C is measured.

55 Example 5:

a) 35 g epoxy resin a2.65 g epoxy resin b2.22 g 2,6-dihydroxy toluene, 22 g 2,7-dihydroxynaphthalene, 0.1 g l- (2 ', 4', 6'-trimethylbenzene) -2 -phenylimidazole and 96 g of polyimide 1 are processed according to Example 3a. After curing for 1 h at

6o 180 0 C and 1 h at 200 ° C a Tg of 212 ° C is measured.

b) When the test was repeated using 71 g of polyimide 1, a Tg of 222 ° C. (slight pre-softening at 100 ° C.) and a fracture toughness Gic (double torsion test) of 976 J / m2 were measured.

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Example 6:

a) 15 g epoxy resin al, 85 g epoxy resin bl, 17.7 g 2,6-dihydroxytoluene, 17.7 g 2,7-dihydroxynaphthalene, and a solution

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6

0.1 g of 2-phenylimidazole and 44.7 g of polysulfone 1 are processed as described in Example 1 and cured at 180 ° C. for 2 hours. The hardened molded body has a Tg of 164 ° C with pre-softening at 96 ° C.

b) When the experiment is repeated using 80.4 g of polyimide 1 instead of the polysulfone, the hardened molded body has a Tg of 142 ° C.

Example 7:

100 g of a mixture consisting of 35 parts by weight of epoxy resin al, 65 parts by weight of epoxy resin bl, 20.5 parts by weight of 2,6-dihydroxytoluene, 20.5 parts by weight of 2,7-dihydroxynaphthalene, 0.2 parts by weight of l- (2 ', 4', 6 '-Trimethylbenzene) -2-phenylimidazole and 80.4 g of polyimide 1 are processed and cured as described in Example 1. The hardened molded body has a Tg of 194 ° C with low pre-softening at 101 ° C.

Example 8:

33.3 g epoxy resin a2, 33.3 g epoxy resin bl, 33.3 g epoxy resin b2.45.9 g 2,7-dihydroxynaphthalene and 0.1 g 2-phenylimidazole are processed according to Example 1. The hardened moldings have the following properties:

Tg (IMA) 122 ° C

Flexural strength (ISO 178) 152 MPa

Edge elongation (ISO 178) 6.9%

Impact resistance (ISO R179) 38 kJ / m2

Example 9:

a) 50 g of epoxy resin a2, 50 g of epoxy resin b, 2.21 g of 2,6-dihydroxytoluene, 21 g of 2,7-dihydroxynaphthalene and 0.1 g of 2-phenylimidazole are processed according to Example 1. The hardened moldings have the following properties:

Tg (IMA) 113 ° C

Flexural strength (ISO 178) 140 MPa

Edge elongation (ISO 178) 12.1%

Impact resistance (ISO R179) 68 kJ / m2

b) When the test is repeated using 17.5 g of 2,6-dihydroxytoluene and 17.5 g of 2,7-dihydroxynaphthalene as the phenolic hardener, the hardened moldings have the following properties:

Tg (IMA) 96 ° C

Flexural strength (ISO 178) 140 MPa

Edge expansion (ISO 178)> 14%

Impact resistance (ISO R179) 67 kJ / m2

Example 10:

a) 35 g of epoxy resin a2.65 g of epoxy resin b2.20.5 g of 2,6-dihydroxytoluene and 20.5 g of 2.7 dihydroxynaphthalene are processed as described in Example 1. The moldings have the following properties:

Tg (IMA) 106 ° C

Flexural strength (ISO 178) 151 MPa

Edge expansion (ISO 178)> 13%

Impact resistance (ISO R179) 91 kJ / m2

Fracture toughness (double torsion test) 454 J / m2

Example 11:

15 g of epoxy resin al and 85 g of epoxy resin bl are heated to 120 ° C., a mixture of 17.7 g of 2,6-dihydroxytoluene and 17.7 g of 2,7-dihydroxynaphthalene is added and mixed to form a homogeneous mixture. After cooling to 80 ° C 0.1 g of 2-phenylimidazole are added and the mixture is briefly evacuated to remove the air bubbles. The mixture has a viscosity of t] 310 mPa ■ s at 70 ° C. Part of the mixture is used to measure the fracture toughness after the double torsion test. The majority of the mixture is poured into molds made of Extradai 050 (AlMgSi 0.5) measuring 80 x 60 x 4 mm and hardened for 2 hours at 140 ° C and 2 hours at 180 ° C. The following results are obtained:

Tg (IMA) 105 ° C

Flexural strength (ISO 178) 128 MPa

Edge expansion (ISO 178)> 14%

Impact resistance (ISO R 179) 86 kJ / m2

Fracture toughness (double torsion test) 726 J / m2

After storage of the resin mixture for 2 weeks at room temperature, the resin still shows good tack ("tack").

Example 12:

a) When Example 11 is repeated using 40.3 g of 2,7-dihydroxynaphthalene as hardener, molded bodies with the following properties are obtained:

Tg (IMA) 120 ° C

Flexural strength (ISO 178), 145 MPa

Edge elongation (ISO 178) 13%

Impact resistance (ISO R 179) 86 kJ / m2

b) When Example 11 is repeated using 20.3 g of bisphenol A and 20.3 g of 2,7-dihydroxynaphthalene as hardener, molded bodies with the following properties are obtained:

Tg (IMA) 94 ° C

Flexural strength (ISO 178) 125 MPa

Edge expansion (ISO 178)> 14%

Impact resistance (ISO R179) 83 kJ / m2

Fracture toughness (double torsion test) 783 J / m2

Example 13:

50 g epoxy resin a3, 50 g epoxy resin bl, 42.1 g 2,7-dihydroxynaphthalene and 0.1 g 2-phenylimidazole are processed according to Example 11. Shaped bodies with the following properties are obtained:

Tg (TAM) 133 ° C

Flexural strength (ISO 178) 158 MPa

Edge expansion (ISO 178) 12%

Impact resistance (ISO R179) 53 kJ / m2

Example 14:

20 g epoxy resin al, 20 g epoxy resin a3.60 g epoxy resin b2, 19.5 g 2,6-dihydroxytoluene, 19.5 g 2,7-dihydroxynaphthalene and 0.1 g 2-phenylimidazole are processed according to Example 11. Shaped articles with the following properties are obtained:

Tg (IMA) 107 ° C

Flexural strength (ISO 178) 153 MPa

Edge expansion (ISO 178)> 14%

Impact resistance (ISO R179) 44 kJ / m2

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Claims (11)

672 493 PATENT CLAIMS 1. Storage-stable, curable mixture comprising a) 10-80 parts by weight of at least one epoxy resin with a functionality of at least 3, b) 90-20 parts by weight of at least one epoxy resin with a functionality of 2-2.5, c) at least one diphenol, the amount of the diphenol being such that 0.7-1.2 hydroxyl equivalents of the diphenol (c) are present per epoxy equivalent of the epoxy resins (a) and (b), and wherein the diphenol consists of (cl) 0-80% by weight of a compound of the formula I or II . . , 0H x K (I) * (^ ~ R (II) ' H0 0H tu where T is the direct bond, methylene, isopropylidene, O, S, CO or S02 and R is hydrogen or Ci-C4-alkyl, and (c2) 100-20% by weight of a dihydroxynaphthalene, and d) 0.05-5% by weight, based on the epoxy resins (a) and (b), of an accelerator. 2. Mixture according to claim 1, wherein the epoxy resin (a) has a functionality of 3 to 4 and is an epoxiphenol novolak or a glycidyl derivative of a hydantoin or a tetramethyl-olcyclohexane. 3. Mixture according to claim 1, wherein the epoxy resin (b) has a functionality of 2 to 2.2 and is an epoxiphenol novolak or a glycidyl derivative of bisphenol A or bisphenol F. 4. Mixture according to claim 1, wherein the hydroxyl substituents of the compound of formula I are in the 4,4'-position and the symbol T O, S, methylene, or isopropylidene. 5. A mixture according to claim 1, wherein the diphenol (c) consists of 2,6-dihydroxytoluene and 2,7-dihydroxynaphthalene. 6. Mixture according to claim 1, which, in addition to components (a) to (d), also (e) 10-120 parts by weight, based on 100 parts by weight of components (a) to (c), of a thermoplastic with a glass transition temperature of at least Holds 180 ° cents. 7. Mixture according to claim 1 containing 10 to 60 parts by weight of the epoxy resin (a), 90 to 40 parts by weight of the epoxy resin (b), an amount of the diphenol (c), so that 0.8-1.1 preferably 0.9-1 , 0, hydroxyl equivalents of diphenol per epoxy equivalent of resins (a) and (b) are present, and 0.1-1 wt .-% of accelerator (d) based on the amount of (a) and (b). 8. Use of the mixture according to claim 1 for the production of hardened moldings. 9. Use of the mixture according to claim 1 for the production of prepregs for fiber-reinforced composites. 10. Use of the mixture according to claim 1 for the production of adhesive films. 11. Hardener for epoxy resins containing a compound of formula I or II according to claim 1 and a dihydroxynaphthalene.