CH672492A5 - - Google Patents

Description

DESCRIPTION The invention relates to storage-stable, heat-curable substance mixtures which contain tetraglycidyl ethers of certain tetramethylol compounds, epoxy resins with a functionality of 2-2.5, phenolic 35 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, 40 describes JP-OS 76/129 498 substance mixtures containing polyfunctional epoxy resins, phenolic hardeners and accelerators and their use for the production of prepregs for special electrical insulating materials. U.S. Patent 4,322,456 discloses mixtures of epoxy resins, phenolic hardeners and 45 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, especially as powder coatings.

The present invention relates to storage-stable, heat-curable mixtures of substances according to claim 1.

The mixtures according to the invention are suitable for the cooking, positioning of shaped objects, prepregs and adhesive films, and the cured products are distinguished by excellent thermal and mechanical properties, in particular by a high heat resistance and excellent impact resistance.

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.

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. 65 The tetraglycidyl ethers (a) of the formula I and their use as epoxy resins are known. These compounds and their preparation and use are described in U.S. Patent 4,549,008.

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672 492

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

Epoxy resins with a functionality of 2 are understood to mean, for example, those resins which have an average of 2 epoxy groups per molecule.

Suitable as epoxy resins (b) are e.g. Di- or polyglycidyl ethers of cycloaliphatic polyols, such as 2,2-bis (4'-hydroxycy-clohexyl) propane, di- or polyglycidyl ethers 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, or condensation products of phenols with formaldehyde, such as phenol Novolaks and cresol novolaks; 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;

N-glycidyl derivatives of amines, amides and heterocyclic nitrogen bases, such as N, N-diglydidylaniline, N, N-diglycidyl-toluidine, N, N-diglycidyl-N, N'-ethylene urea, N, N'-diglycidyl-5, 5-dimethylhydantoin, N, N'-diglycidyl-5-isopropylhydantoin, N, N'-diglycidyl-5,5-dimethyl-6-isopropyl-5,6-dihydrouracil;

Multifunctional epoxy resins, such as the 2,6-disubstituted 4-epoxypropylphenyl glyddyl 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;

Glycidyloxy-substituted benzophenones and glycidyloxydi-ketones, such as the compounds described in U.S. Patent 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 tetraglycidyl ethers (a) of the mixtures according to the invention are compounds of the formula I in which the symbol X denotes the group

-ÌH-0H or -i = 0

means. Also preferred are compounds in which R is hydrogen and n is 2 or 3. The tetraglycidyl ether of 2,2,6,6-tetramethylolcyclohexanol is very particularly preferred as component (a).

As epoxy resin (b) of the mixtures according to the invention, compounds having an epoxy content of 5-11 equivalents / kg are preferred which are glycidyl ethers, glycidyl esters or N-glycidyl derivatives of cycloaliphatic, aromatic or heterocyclic compounds.

Particularly preferred as component (b) are epoxinovolaks or glycidyl derivatives of a bisphenol or a hydantoin, in particular those which have a functionality of 2-2.2 and are an epoxiphenol novolak or a glydidyl derivative of bisphenols or bisphenol F.

Suitable diphenols (c) are e.g. mononuclear and multinuclear dihydroxyaromatic compounds which may contain condensed benzene rings. Compounds of the formulas II or III are particularly suitable

HO '

y w

✓ S.

N - =. \

(II)

X '

(m),

wherein T is the direct bond, methylene, isopropylidene, O, S, CO or S02 and R is hydrogen or Q-C4-alkyl, io dihydroxynaphthalene or mixtures of these compounds. Preferred compounds of the formula I are those in which the hydroxyl groups are bonded in the 4,4'-position.

Particularly preferred diphenols (c) are bisphenol A, bisphenol F, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphe-15-nyl sulfide, 2,6-dihydroxytoluene, 2,6-dihydroxynaphthalene or 2,7-dihydroxynaphthalene.

A mixture of 2,6-dihydroxytoluene and 2,7-dihydroxynaphthalene is particularly suitable as a phenolic hardener. Particularly good results are achieved if equal amounts of 20 of these compounds are mixed in the melt at approximately 180 ° C., the product obtained after the melt solidifies is ground to a fine powder and this is then used as a hardener.

If appropriate, the substance mixtures according to the invention can also act as hardeners in addition to the diphenols (c), a certain amount of one or more tri- or polyphenols, such as, for example, B. 2,4,6-Tris [2 '- (p-hydroxyphenyl) -2'-propyl] benzene ("Tris-TC" from Misui Petrochemical). In general, however, at most 30% of the phenolic hydroxyl groups should come from a 3o 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 both diphenols and tri- or poly-35 phenols are used, 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 epoxide equivalent of the epoxy resins used are contained in the mixture according to the invention.

Suitable accelerators (d) of the curable material 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 he-45 xantriolate, Lewis acids e.g. BF3 or SnCl4, 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 For-50 mei IV

55

R3 ^ <>

i1

(IV),

65

OH

wherein R1, R2 and R3 independently of one another are hydrogen, Q-C12-alkyl, C5-C10-cycloalkyl or C6-CI0-aryl. In particular, 2-methyl, 2-ethyl, 2-phenyl and 2-ethyl-4-methylimidazole are preferred.

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

672 492

4th

^ = / 2

R5- \) —S— \ (V),

R? / = 'V

A1

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 ', 4', 6'-trimethylbenzoyl) -2-ethylimidazole, 1- (2 ', 6'-dichlorobenzoyl) -2-methylimidazole, 1- (2', 4 ', 6' -Trimethyl-benzoyl) -2-methylimidazole and l- (2 ', 4', 6'-trimethylbenzoyl) -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 parts by weight of components (a) to (c), of 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 resistance, bending and impact resistance as well as very high ductility.

As thermoplastics (e), all those known polymers can be used in the curable material mixtures according to the invention which have a sufficiently high glass transition temperature, i.e. Have> 180 ° C and are miscible with the epoxy resin curing system according to the invention.

Based on their properties, the thermoplastics used are preferably polyimides, polyetherimides, polyamideimides, polysulphones or polyether sulfones, 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-A 194 232 as polysulfone component (c) are particularly suitable. These connections are e.g. available under the designation "Polysulfone Udel PI800", Polysulfone 2300 "or" Polysulfone 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 Pat. No. 3,856,752 and EP-A 92 524,

- Homo- and copolyimides from at least one aromatic tetracarboxylic acid and at least one aromatic diamine, such as e.g. in U.S. Patent 4,629,777 and

- Homo- and copolyimides, e.g. in EP-A

162 017, EP-A 181 837 and U.S. Patent 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 30 to 60 parts by weight of the triglycidyl ether (a), 70 to 40 parts by weight of the epoxy resin (b), one

Amount of 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 wt .-% 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 compositions, sealing compositions, embedding and insulating compositions for electrical engineering and preferably as adhesives and as matrix resins for composites, 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.

The hardenable mixtures according to the invention can furthermore be mixed in any phase with conventional modifiers, such as extenders, fillers and reinforcing agents, pigments, dyes, organic solvents, plasticizers, flow control agents, thixotropic agents, flame retardants or mold release agents, before the hardening. Examples of extenders, reinforcing agents, fillers and pigments which can be used in the curable mixtures according to the invention include called: liquid coumarone indene resins, 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, anti-montrioxide, bentone, lithopone, heavy spar , Titanium dioxide, 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. Dibutyl, dioctyl and dinonyl phthalate, tricresyl 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

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672 492

be prepared 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, 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:

Tetraglycidyl ether 1: Tetraglycidyl ether of 2,2,6,6-tetramethylcyclohexanol (prepared according to Example 2 of US Pat. No. 4,549,008) with an epoxy equivalent weight of 129.

Epoxy resin b 1: An epoxy-nol 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 x 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 paxs.

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

Example 1:

a) 35 g of tetraglycidyl ether 1 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-dihydroxynaphthalene. After cooling to 100 ° C., 0.1 g of 2-phenylimidazole is added to the mixture, it is cooled to room temperature and then a solution of 84.5 g of polyimide 1 in 82 g of methylene chloride is added and stirred well until a homogeneous mixture is formed . With the mixture, a film 0.1 mm thick is poured onto siliconized paper using a doctor blade 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 thermomechanical analysis) of 194 ° C with weak pre-softening at 104 ° C.

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 part of the film, 2 Al plates are glued together at 180 ° C and post-cured at 200 0 C for 1 h. The cured resin has a fracture toughness (Grc) 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 Extradai 050 (AlMgSi 0.5) aluminum plates are dimensioned

200 x 20 x 5 mm, which are treated with chromosulphuric acid, glued to the hardenable mixture and the glue hardened using light pressure. With this measuring method the crack propagation is measured in the bond, i.e., the breaking energy in J / m2 is calculated from the maximum load for the crack propagation.

Example 2:

Example la is repeated by using 59.2 g of 4,4'-dihydroxydiphenyl ether as the hardener instead of the 2,6-dihydroxytoluene / 2,7-dihydroxynaphthalene mixture used therein. The cured mixture has a Tg of 192 ° C with little pre-softening at 80 ° C.

Example 3:

a) 35 g tetraglycidyl ether 1, 65 g epoxy resin b2, 22 g 2,6-dihydroxytoluene, 22 g 2,7-dihydroxynaphthalene, 0.1 g 1- (2 ', 4', 6'-trimethylbenzene) -2-phenylimidazole and 96 g of polyimide 1

are processed according to example la. After curing for 1 h at 180 ° 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.

Example 4:

33.3 g of tetraglycidyl ether 1, 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) 38kJ / m2

Example 5:

a) 50 g of tetraglycidyl ether 1, 50 epoxy resin b2, 38 g of 2,6-dihydroxytoluene and 0.1 g of 2-phenylimidazole are processed according to Example 1. The hardened moldings have the following properties:

Tg (TAM) 103 ° C

Flexural strength (ISO 178 135 MPa

Edge expansion (ISO 178)> 14%

Impact resistance (ISO R179) 86 kJ / m2

b) When the test is repeated using 68 g of bisphenol A as a phenolic hardener, the following properties are determined on the hardened moldings:

Tg (TAM) 109 ° C

Flexural strength (ISO 178) 121 MPa

Edge elongation (ISO 178) 13%

Impact resistance (ISO R179) 93 kJ / m2

c) When the test is repeated using 21 g of 2,6-dihydroxytoluene and 21 g of 2,7-dihydroxynaphthalene as the phenolic hardener, the hardened moldings have the following properties:

Tg (TAM) 113 ° C

Flexural strength (ISO 178) 140 MPa

Edge elongation (ISO 178) 12.1%

Impact resistance (ISO R179) 68 kJ / m2

d) 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 (TMA) 96 ° C

Flexural strength (ISO 178) 140 MPa

Edge expansion (ISO 178)> 14%

Impact resistance (ISO R179) 67 kJ / m2

Example 6:

a) 35 g of tetraglycidyl ether 1, 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 hardened moldings have the following properties:

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672 492

Tg (IMA)

Flexural strength (ISO 178)

Edge elongation (ISO 178) Impact resistance (ISO R 179) Fracture toughness (double torsion test)

6

106 ° C b) If the experiment is repeated using

151 MPa 59 g of 4,4'-dihydroxydiphenyl ether as a phenolic hardener

> 13% the hardened molded body has the following properties:

91 kJ / m2

454 J / m2 s Tg (IMA) 93 ° C

Flexural strength (ISO 178) 113 MPa

Edge elongation (ISO 178)> 14%

Impact resistance (ISO R179) 103 kJ / m2

Claims (10)

672 492 PATENT CLAIMS 1. Storage-stable, heat-curable mixture of substances, containing a) 10-80 parts by weight of at least one tetraglycidyl ether of the formula I , CH2-0-CHZ-Cfi-CH2 'CH2-0-CH2-dl- CHa (I), where X is a group -è = 0, —ÌH-QH. or -Ìh-0-CH2-c1ì— CH2 means R is hydrogen or methyl and n is an integer from 2 to 4. b) 90-20 parts by weight of at least one epoxy resin with a functionality of 2-2.5 c) at least one phenolic hardener, the amount of hardener being chosen such that 0.7-1.2 hydroxyl equivalents of hardener (c) are present per epoxy equivalent of epoxy resins (a) 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 symbol X in the formula I is the group -ÌH-OH or -è = 0 means. 3. Mixture according to claim 1, wherein the epoxy resin (a) is the tetraglycidyl ether of 2,2,6,6-tetramethylolcyclohexanol. 4. Mixture according to claim 1, wherein the epoxy resin (b) has an epoxy content of 5-11 equivalents / kg and is a glycidyl ether, glycidyl ester or an N-glycidyl derivative of a cycloaliphatic, an aromatic or a heterocyclic compound. 5. A mixture according to claim 1, wherein the hardener (c) is a compound of formula II or III 15 8. Mixture according to claim 1, containing 30 to 60 parts by weight of the tetraglycidyl ether (a), 70 to 40 parts by weight of the epoxy resin (b), an amount of the hardener (c), so that 0.8-1.1 preferably 0.9 -1.0 hydroxy equivalents of the hardener are present per epoxy equivalent of the Haize (a) and (b), and 20 0.1-1 wt .-% of the accelerator (d) based on the amount of (a) and (b). 9. Use of the mixture according to claim 1 for the production of hardened moldings. 10. Use of the mixture according to claim 1 for the manufacture of prepregs for fiber-reinforced composites. 11. Use of the mixture according to claim 1 for the production of adhesive films. HO ' y \ —T- / \ \ =. \ (II) OH 1h in which T is the direct bond, methylene, isopropylidene, O, S, CO or S02 and R is hydrogen or Ci-C4-alkyl, a dihydroxynaphthalene or a mixture of these compounds. 6. Mixture according to claim 1, wherein the hardener (c) bisphenol A, bisphenol F, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfide, 2,6-dihydroxytoluene or 2,6- or 2,7- Is dihydroxynaphthalene. 7. Mixture according to claim 1, which, in addition to components (a) to (d), also (e) 10 to 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 180 0C contains.