GB2207676A

GB2207676A - Curable epoxy resin/thermoplastic compositions

Info

Publication number: GB2207676A
Application number: GB08817081A
Authority: GB
Inventors: Rolf Schmid; Werner Stauffer
Original assignee: Ciba Geigy AG
Current assignee: Novartis AG
Priority date: 1987-07-23
Filing date: 1988-07-18
Publication date: 1989-02-08
Also published as: ES2007541A6; IT1226283B; CH672494A5; SE8802698L; SE8802698D0; NL8801859A; IT8821454A0; DE3824705A1; JPS6465118A; GB8817081D0; BR8803677A; FR2618444A1

Description

Curable epoxy resin/thermoplast compositions The invention relates to

hot-curable compositions of matter which-are stable on storage and contain certain di- and polyfunctional expoxy resins, phenolic curing agents, accelerators and certain thermoplastics and to the use thereof for the production of moulded articles in particular of prepregs for fibre-reinforced composite materials and of adhesive films.

Many curable epoxy resin compositions which, inter alia, also contain phenolic curing agents are known. Thus, for example, Japanese published application 76/129,498 describes compositions of matter containing polyfunctional epoxy resins, phenolic curing agents and accelerators and also the use thereof for the production of prepregs for special electrical insulating materials. US 4,322,456 discloses mixtures of epoxy resins, phenolic curing agents and accelerators for which the functionality of the epoxy resins and/or of the curing agents i's preferably greater than 2 and which are suitable for the production of curable coatings, especially in the form of powder coatings. US 4,288,565 describes mixtures consisting of epoxy resins having high and low epoxy equivalent weights and of phenolic curing agents containing at least 30% of compounds having 3 or more hydroxyl groups per molecule.

The present invention relates to hot-curable compositions of matter which are stable on storage containing a) 10 to 60 parts by weight of an epoxy resin having a functionality of at least 3, b) 90-40 parts by weight of an epoxy resin having a functionality of 2-2.5, c) a diphenol, the amount of the diphenol being chosen in such a way that 03-1.2 hydroxyl equivalents of the diphenol (c) are used per epoxy equivalent of the epoxy resins (a) and (b), d) 0.05-5% by weight, based on the epoxy resins (a) and (b), of an accelerator, and 4 e) 10-140 parts by weight, based on 100 parts by weight of components (a) to (c), of a thermoplastic having a glass transition temperature of at least 1800C.

The compositions according to the invention are suitable for the production of moulded articles, prepregs and adhesive films, and the cured,products are distinguished by Qutstanding thermal and mechanical properties, in particular by a high heat distortion resistance, a high fracture toughness, flexural and impact flexural strength and also a very high extensibility.

Furthermore, the compositions have very good processing properties, for example a high homogeneity, a long pot life and a favourable tack, which is maintained even after relatively long storage at room temperature.

The compositions of matter according to the invention give, after curing, crosslinked polymers having thermoplastic-like properties (high extensibility, fracture toughness and impact strength) without having to accept the problems which arise when high molecular weight thermoplastics are processed due to the very high viscosity of these materials. The compositions according to the invention have a relatively low viscosity and can be processed at low temperatures (120 to 200OC) without difficulties.

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

Epoxy resins having a functionality of 3 are to be understood as meaning, for example those resins which have, on average, 3 epoxy groups per molecule.

Suitable epoxy resins (a) and (b) are, for example di- or polyglycidyl ethers of cycloaliphatic polyols such as 2,2-bis(4'hydroxycyclohexyl)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-(41-hydroxy-31,51dibromophenyl)propane, 1,1,2,2,-tetrakis(4'-hydroxyphanyl)ethane, or condensation -1 1 4 i products of phenols with formaldehyde such as phenol novolaks and cresol novolaks; furthermore-, di- or poly(o-methylglycidyl) ethers of the abovementioned polyalcohols and polyphenols; Polyglycidyl esters and poly(o-methyl-lycidyl) esters of polybasic carb- 0 oxylic acids such as phthalic acid, terephthalic acid, tetrahydrophthali acid and-hexahydrophthalic acid; Glycidyl derivatives of amino phenols, for example triglycidyl p-amino phenol; N-Glycidyl derivatives of amines, amides and heterocyclic nitrogen bases such as N,N-diglyclLdylaniline, N,N-diglycidyltoluidine, N,N,W,W- tetraglycidyl-bis(4-aminophenyl)methane, triglycidyl isocyanurate, N,N- diglycidyl-N,NI-ethyleneurea, N,N'-diglycidyl-5,5dimethylhydantoin, N, Wdiglycidyl-5-isopropylhydantoin, N,N'-diglycidyl-S,S-dimethyl-6- isopropyl5,6-dihydrouracil; multifunctional epoxy resins such As the 2,6-disubstituted 4epoxypropylpheny1glycidyl ethers and adducts thereof described in EP 205, 409 and EP 204,659; Bisphenols which are substituted by two glycidyloxy and 2,3-epoxypropyl groups each, for example 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 compound described in US 4,549,008; Glycidyloxy-substituted benzophenones and glycidyloxy diketones 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 materials according to the invention.

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

Suitable-epoxy resins (a) are preferably glycidyl derivatives of hydantoins and in particular epoxy phenol novolaks or glycidyl derivatives of tetramethylolcyclohexane. These compounds preferably have a functionality of 3 to 4. Suitable epoxy resins (b) are in particular epoxy phenol novolaks or glycidyl derivatives of bisphenol A or of bisphenol F. Preferably, these compounds have a functionality of 2 to 2.2. _ Suitable diphenols (c) are, for example, mononuclear and polynuclear dihydroxyaromatics containing fused or nonfused benzene rings.--Particularly suitable compounds are those of the formula I or II OH -R H0-.X X\O, 1H in which T is the direct bond, methylene, isopropylidene, 0, S, CO or S02 and R is hydrogen or Cl-COlkyl, a dihydrorcynaD-hthalene or mixtures of these compounds. Of the compounds of the formula I, preference is given to those in which the hydroxyl groups are bound in the 4,41-position.

Particularly preferred diphenols (c) are bisphenol A, bisphenol F, 4, 41dihydroxydiphenyl sulfide, 2,6-dihydroxynaphthalene and in particular 2, 7-dihydroxynaphthalene, 4,41-dihydroxydiphenyl ether or 2,6dihydroxytoluene.

A particularly suitable phenolic curing agent is a mixture of 2,6dihydroxytoluene and 2,7-dihydroxynaphthalene. Particularly good results are 1 1 epmcy (a)-5=d th) aTe =mVmmds -wtrir-h have mm zy 2mntp-mt of -3-11 mre zi-yz--d3a -317zmyl caste= -0'r S-gl7C"3L1 -zd a -ZyclOaU-;&atlz, 0wúd A -t-1 3 -to 4. -%útabU c -restns sre in particular -epoxy 01 _rd -w A =,ji, mt, D1,7 aef-=.-ffily, -these ==pounds tave a -tinmal2ty - of 2 to 2-2.

Suút zl phe=ls =Z,, lux =znonucle= t t:icz cz-ataúnúug fused = nonfused tenze= =aSs- 2artlcnlaxly -=M5 -are xjmaa = Xte -1 ox '11 0 In h 1 1s---theACI-rect Imd, D, 5 1 'C 0 mx 502 and A Is hydimgen..-or Cl--r,4Rlkyl, m= -ni=tures nú these zmpo- P!! the z=pwmds of---thef ormula I,. -f-,p-rence Is given Tarticularly pre f eTred diphendis (c) are -Iisphenol -A, tdnhenol 7, -4, 4 jdl:,h7ddjLphenyl..Ai,If.ide, 2,thydxoxywdph-th-al 2ind --in -pa=lcul2x 2, 7--dny.droxynaphthalene, 4,4 1-úlih3dxzxyalpher-_vl, ---thex ex 2,6- dihydxoxyzolue".

A -pa=lcul=17 suitable -phe-nolle m=ing agent is a -n zt=e tl Ar=cyt&=ne and =-d-. -'' i '-117 -zmzul:ts Wre 4 Y -obtained by mixing equal amounts by weight of these compounds in the melt at about 1800C, grinding the product obtained after solidification of the melt to a fine powder and then using this powder as the curing agent.

If desired, the compositions of matter according to the invention can contain as curing agents also a certain amount of one or more tri- or polyphenols such as, for example 2,4,6-tris[21-(p-hydroxyphenyl)ZIpropyl]benzene ("tris-TC' from Mitsui Petrochemical) in addition to the diphenols (c). However, in general not more than 30% of the phenolic hydroxyl groups should come from a tri- or polyphenol and the remainder of the hydroxyl groups should belong to a diphenol. In general,'phenol or cresol novolaks are not suitable as phenolic curing agents of the compositions according to the invention. It goes without saying that in the case where not only diphenols but also tri- or polyphenols are used the total amount of phenolic curing agent (c) is chosen in such a way. that overall 0.7-1.2 hydroxyl equivalents of the phenols used per epoxy equivalent of the epoxy resins used are conta.ined the composition according to the invention.

Suitable accelerators (d) of the curable compositions of matter are all compounds which are known to a person skilled i the art for the acceleration of the crosslinking reaction of epoxy resins-by means of phenolic curing agents, for example tertiary amines, salts thereof or quaternary ammonium compounds such as tetramethylammonium chloride, phosphonium salts, alkali metal alcoholates, for example sodium hexanetriolate, Lewis acids, for example BF 3 or StIC14, and nitrogencontaining heterocycles such as pyridines, imidazoles and derivatives thereof. Particularly suitable accelerators (d) are imidazoles and Nacyllmidazoles (imidazolides).

Examples of suitable imidazoles are compounds of the formula III R3 /R' (III) 4 9 in which R1, R2 and R3 independently of one another are hydrogen, Cl- C12alkyl, CS-Clocycloalkyl or C6-Cloaryl. Preference is given in particular to 2-methyl-, 2-ethyl-, 2-phenyl- and 2-ethyl-4-methyl- imidazole.

Suitable N-acylimidazoles (imidazolides) are, for example the compounds described in US 43436,892, US 4,587,311 and Japanese preliminary published application 7417,59. Pairticularly suitable compounds are those of the formula IV R3 R2 R /R R6 R7 \R8 (IV) 1 in which R1 to R3 are as defined above and R4 to R8 independently of one another are hydrogen, Cl-C12alkyl, halogen, nitro or trifluoromethyl. Examples of suitable imidazolides are 1-(21,41,61-trimethylbenzoyl)-2- ethylimidazole, 1-(21,61-dichlorobenzoyl)-2-methylimidazole, 1(21,41, 6'trimethylbenzoyl)-2-methylimidazole and 1-(2'4'6'-trimethylbenzoyl)2phenylimidazole.

Thermoplastics (e) which can be used in the curable compositions of matter according to the invention are all the known polymers which have a sufficiently high glass transition temperature, that is, > 1800C, and are miscible with the epoxy resin/curing agent system according to the application. Based on their properties, particularly suitable thermoplastics are polyamide imides, polysulfones or polyether sulfones and in particular polyimides and polyether imides. Of these, preference is given in particular to thermoplastics having a glass transition temperature of 180 to 3509 in particular from 190 to 250 OC. In the case where polyether imides are used, preference is given in particular to polymers having a Tg of 220 to 2500C and, where polyimides are used, preference is given to those having a Tg from 280 to 3400C.

In the case where a polysulfone is used as thermoplastic (e), suitable 1 IF i compounds are, for example those having a repeating unit of the formula - A-S02in which A is a divalent aromatic group which can be uninterrupted or interrupted by ether oxygen atoms and/or divalent aliphatic groups.

The polysulfones to be used can be obtained in a known manner, for example by heating either (a) a sulfonyl halide.of the formula RA1S02X or (b) a mixture of a disulfonyl halide of the formula XS02AIS02X With a compound which does not contain a sulfonyl halide of the formula RA 2H in which A, and A2 are identical or different and are each.a divalent aromatic group which can be uninterrupted or interrupted by ether oxygen atoms and/ or divalent aliphatic groups and X is chlorine or bromine atom, in.an inert solvent in the presence of a Lewis acid catalyst. The--- polysulfones obtained by process (a) contain the repeating unit -A,-SO:!-, whereas the polysulfones prepared by process (b) have the repeating unit -Al-SO----%,k--so,- Polysulfone resins which are preferably used in the materials according to the invention are those which have ether groups in the repeating unit but are free of hydroxyl groups in the side chains. These polysulfones are in particular those having a repeating unit of the formula 1 ---0A30A4SO2A4-, in which A3 and A4 aredivalent arylene, in particular phenylene groups, which can be substituted by chlorine or Cl-C4alkyl, for example methyl groups. Polysulfones of this type are obtained in a known manner by reaction of a dialkali metal salt of a.dihydric phenol of the formula HOA30H with a bis(monochloroaryl) sulfone of the formula C1A4SO2A4C1 in dimethyl sulfoxide. More preferred sulfone resins are those having a repeating unit of the formula --OA 5 0A6-S 0 6in which AS and A6 are each a phenylene group which is unsubstituted or substituted by chlorine or Cl-C4alkyl groups, for example methyl groups, and Y is a carbon-carbon bond or is a -S02- or an aliphatic hydrocarbon group, in particular one which has not more than four carbon atoms, for example one of the formula -CHp- or H ' H3 Particular preference is given to thermoplastic polysulfone resins having the repeating units of the formula V H H 3 n where n has preferably an average value of 50-120.

(V) 1 Particularly advantageous polysulfones are for example the compounds available from Union Carbide Corporation, for example "polysulfone Udel P180W, which, 0 according to the data given by the manufacturer, has a melting point in the range from,350-3700C, a heat distortion resistance (ASTM specification D648) of 1750C and contains on the average 50-80 repeating units of the formula V per molecule, which implies a molecular weight range of about 22,000-35,000.

Also suitable are a similar substance available from Union Carbide Corporation under the name "polysulfone P230T which, according to the data given by the manufacturer, has a molecular weight range of 30,000-50, 000, which implies that the substance contains on-the average about 68- 113 repeating units of the formula V per molecule, and also a similar substance available from Union Carbide Corporation under the name polysulfone P35OW which,, according to the data given by the manufacturer, has a molecular weight range which is between that of "polysulfone UdelP18OW and that of "polysulfone P230W; its molecular weight is about 35,000.

1 According to the invention, mixtures of two or more thermoplastics can also be used as component (e).- Particularly suitable thermoplastics (e) are polyimides such as - Polyimides having phenylindane 'units such as have been described, for example in US 3,856,752 and EP-A 92,524, in particular those having a glass transition temperature of about 3050C and an average molecular weight of about 65,000 such as, for example MatrimicO 5218 from Ciba- Geigy, - homopolyimides and copolyimides consisting of at least one aromatic tetracarboxylic acid and at least one aromatic diamine such as have been disclosed, for example, in US 4,629,777 and homopolyimides and copolyimides such as have been described, for example in EP-A 162,017, EP- A-181,837 and US 4,629,685.

Further preferred thermoplastics (e) are polyether imides, for example the products from General Electric which are available under the name UltenD (for example UltedID 1000). Further preferred thermoplastics are polyether sulfones, for example Victrex PES 100 P from ICI or Udel P 1800 from Union Carbide.

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

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

Particularly preferred curable compositions according to the invention are those which contain 15 to 50 parts by weight of the epoxy resin (a), 85 to 50 parts by weight of the epoxy resin (b), an amount of the diphenol (c) such that 0.8-1.1, preferably 0.9-1.0, hydroxyl eqgivalents of the diphenol are used per epoxide equivalent of the resins (a) and (b), 0.1-1% by weight of the accelerator (d), based on the amount of (a) and (b), and 20-130, preferably 30-120, and in particular 80-120 parts by weight of the thermoplastic (e), based on 100 parts by weight of components (a) to (c).

The compositions according to the invention can be made available by thorough mixing or dissolution-of all components in one another, it being possible for the individual components to be added in different sequences. For example, the thermoplastic can be dissolved in the epoxy resin and in the phenolic curing agent with heating and after cooling the accelerator and, if desired, more additives can be added. However, a solution of the thermoplastic in an inert solvent, for example methylene chloride,- can be prepared and then mixed with the epoxy resin/curing agent composition.

The compositions according to the invention can be used for many purposes and are suitable, for example as casting resins, laminating or impregnating resins, moulding nompositions, sealants, embedding and insulating compositions for electrical engineering and preferably as adhesives and as matrix resins for composite materials, in particular for the production of fibre-reinforced plastics.

If desired, in particular in the case where modifying agents are also used, the compositions according to the invention can be dissolved in organic solvents such as toluene, xylene, methyl ethyl ketone, methylene chloride or a similar solvent or solvent mixture which is customary in the coatings industry. Such solutions are suitable in particular as impregnating agents or coating agents.

Before curing, the curable mixtures according to the invention can also be admixed at any time with customary modifying agents such as extenders, fillers, reinforcements, pigments, dyes, organic solvents, softeners, flow-improving agents, thixotropic agents, flame retardents or mould release agents. Extenders, reinforcements, fillers and pigments which can be used in the curable mixtures according to the invention are for example: liquid cumaronelindene resins, textile fibres, glass fibres, asbestos fibres. boron fibres, carbon fibres, polyethylene powder, polypropylene powder, quartz powder, mineral silicates such as mica, asbestos powder, slate powder, kaolin, chalk powder, antimony trioxide, bentone, lithopone, heavy spar, titanium dioxide, soot, graphite, oxide colours such as iron oxide or metal powders such as aluminium powder or iron powder. In the case where the mixtures according to the invention are h 11 - used for the production of prepregs, the addition of short fibres is. particularly desirable.

For the practical use of the curable mixtures, especially in surface protection, it is possible to add as flow-improving agents, for example silicones. liquid acrylic resins, cellulose acetobutyrate, polyvinylbuty ral, waxes, stearates and the like (which in some cases are also used as mould release agents).

Softeners which can be used for modifying the curable mixtures are, for example, dibutyl, dioctyl and dinonyl phthalate, tricresyl phosphate, trixylenyl phosphate and diphenoxyethyl formal.

The mixtures according to the invention are preferably cured by heating them to a temperature within the range from 120 to 2500C, in particular 160 to 2200C. The curing can be carried out in a known manner also in two or more stages, the first curing stage being carried out at lower temperature and the post-curing at higher temperatures.

If desired, active diluents, for example neopentyl glycol ether, butane diol diglycidyl ether or hexanediol diglycidyl ether can be added to the curable mixtures to reduce their viscosity.

The present invention also relates to the use of the compositions according to the invention for the production of cured moulded materials and also to the use for the production of prepregs for fibre-reinforced composite materials or for the preparation of adhesive films. The prepegs and the adhesive films can be prepared in a manner known per se, for example by the impregnation process in the presence of one of the abovementioned solvents, of a halogenated solvent, for example methylene chloride., or by the so-called "hot-melt" process.

The moulding materials are in general distinguished by high glass transition temperatures in combination with high mechanical strength and, in particular, by a very high fracture toughness, flexural and impact flexural strength and also a very high extensibility.

The Examples which follow illustrate the Invention in more detail Components (a)-(e) used in the E.xamples which follow are the following:

Epoxy resin al: An epoxy phenol novolak of a functionality of 3.6 having an epoxid e. content of 5.6 equivalents/kg and a viscosity at 500C of about 40 Pa.s.

Epoxy resin a2: Tetraglycidyl ether of 2,2,6,6-tetramethylolcyclohexanol (prepared according to Example 2 of US 4,549,008) having an epoxide equivalent weight of 129.

Epoxy resin a3: A tri.alycidylbishydantoin of the formula VI having an epoxide content of 5.6 equivalents/kg and a viscosity at 800C of about 13 Pa.s.

H /3 H3C 0 0 CH3 Ck,,,-_CH-C H -N/ '-N-CHz H-CH2-N" 'N-CHZ-C /Hz 0 / \ A / \ A / j (VI) - H2 / H '' H 2 0;7 Epoxy resin 4: A tetraglycidyl derivative of 4,4'-diaminodiphenylmethane having an epoxide content of 7.8 equivalents/kg and a viscosity at 500C of about 1.3 Pa.s.

Epoxy resin bl: An epoxy phenol novolak liquid at room temperature of a functionality of 2.2 having an epoxide content of 5.7 equivalents/kg and a viscosity at 500C of 1.4 Pa.s.

Epoxy resin b2: A bisphenol F diglycidyl ether having an epoxide content of 6.1 equivalents/kg and a viscosity at 250C of 6.0 Pa.s.

Polyimide 1: A polyimide containing phenylindane units having a glass I transition temperature of 3050C and an average molecular weight of about nD 65,000 (Matrimid-ly 5218, Ciba-Geigy) Polyether imide 1: A polyether imide having repeating units of the formula 9 1 j, / j / \?"-;;0\ -NII \.016\.

M/0\ fH3 and a glass transition temperature of 2190C (UltenO 1000 from General Electric).

n Polysulfone 1: Polysulfone Udel P1800 (Union Carbide Corporation) having a melting point in the range from 350 to 3700C, a heat distortion resistance (according to ASTM D 648) of 1750C, a glass transition temperature of 2000C and a molecular weight range of about 22,000-35,000.

Example 1:

a) 15 g of epoxy resin al and 85 g bf epoxy resin bl are mixed at 1200C. At this temperature, 17.7 g of 2,6-dihydroxytoluene and 17.7 g of 2, 7dihydroxynaphthalene are added and dissolved with stirring. After cooling of the mixture to 800C, 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 are added to the mixture, which is thoroughly stirred until a homogeneous. mixture is obtained. The mixture is used to cast a film, 0.1 mm in thickness, on silicone-treated paper by means of a doctor blade, and the solvent is evaporated at room temperature. Several film cuts, 30 x 30 mm, are placed on top of each other, compressed to a 1 mm thick moulding in a press at 1800C and cured at 1800C for 1 hour. The moulding has a T 9 (measured by means of thermomechanical analysis) of 1420C and a secondary transition at 1600C.

b) Example la) is repeated except that 135.4 g of the polyimide 1 is f usedas the thermoplastic to give, after curing, a material having a measured T 9 of 153 and 1820C.

d except that 44.7 of polysulfone 1 Example 2: Example la is repeate are used as the thermoplastic to give, after curing, a material having a measured T 9 of 1640C and a presoftening at 960C.

Example 3:

a) 35 g of epoxy resin a2 and 65 g of epoxy resin U are mixed at 1200C with 20.5 g of 2,6-dihydroxytoluene and 20.5 g of 2,7dihydroxynaphthalene. 0.1 g of 2-phenylimidazole is added to the mixture which is cooled to room temperature and to which are then added as described in Example 1 84.5 g of polyimide 1 in methylene chloride, aftgr which the mixture is processed. After curing, the material has a measured T 9 of 194oC and. a slight presoftening at 1040C.

b) Example 3a) is repeated except that 60.4 9 of polyimide 1 are used to give a film moulding having a T. of 210 dnd 1050c. One portion of the film is used to bond together 2 A1 sheets at 1800C and the product is post cured at 2000C for 1 hour. The cured resin has a fracture toughness (Gic) of 794 J/m2, measured by the double-torsion experiment according to "Journal of Materials Science, 10, 1334 (1975) and 14, 776 (1979)". In this procedure two aluminium sheets Extrudal 050 (AlMgSi 0.5), dimensions 200 x 20 x 5 mm. which have been treated with chromic sulfuric acid, are bonded using the curable mixture, and the bonded product is cured by applying a little pressure. This method measures the crack propagation in the bonded product, that is, the 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 with 19 g of 2,6-dihydroxytoluene, 19 g of 2,7-dihydroxynaphthalene, 0.1 g of 2-phenylimidazole and 138 g of polyether imide 1 as described in Example 1 and processed. After curing, the material has a measured T 9 of 1880C and slight presoftening at 1000C.

:t 1 1 - l:; - Example 5: Example 3a is repeated except that 59.2 g of 4,4'-dihydroxy- :diphenyl ether are used as thecuring agent instead of 2,6- dihydroxytoluene/ 2,7-dihydroxynaphthalene mixture used in that Example. The cured composition has a T of 1920C and sligh presoftening at 800C. 9 Example 6:

a) 35 g of epoxy resin a2, 65 g of epoxy resin b2, 22 g of 2,6dihydroxytoluene, 22 g of 2,7-dihydroxynaphthalene, 0.1 9 of 1-(2',41,61trimethylbenzoyl)-2-phenylimidazole and 96 g of polyimide 1 are processed according to Example 3a. After curing for 1 hour at 1800C and for 1 hour at 2000C, the material has a measured T 9 of 2120C.

b) The experiment is repeated using 71 g of polyimide 1 to give a material having a measured TG of 2220C (slight presoftening at 100OC) and a fracture toughness GIC (double-torsion experiment) of 976 J/m2.

Example 7:

a) 15 g of epoxy resin al, 85 g of epoxy resin bl, 17.7 g of 2,6dihydroxytoluene, 17.7 g of 2,7-dihydroxynaphthalene and a solution of 0. 1.g of 2-phenylimidazole and 44.7 g of polysulfone 1 are processed as described in Example 1 and cured for 2 hours at 1800C. The cured moulding has a T 9 of 1640C and a presoftening at 960C.

b) The experiment is repeated using 80.4 g of Polyimide 1 instead of the polysulfone to give a cured moulding having a T9 of 1420C.

Example 8: 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-d ihyd roxy toluene, 20.5 parts by weight of 2,7-dihydroxynaphthalene, 0.2 parts by weight of 1-(21,41,61-trimethylbenzoyl)-2-phenylimidazole and 80.4 g of polyimide 1 are processed as described in Example 1 and cured. The cured moulding has a T 9 of 1940C and a slight presoftening at 1010C.

Example 9: 15 g of epoxy resin al and 85 g of epoxy resin bl are added to a solution of 20 g of polyether imide land 50 g of methylene chloride.

X i The mixture is then slowly heated to about 1200C and the solvent is evaporated. After treatment at 1200C in a vacuum for 30 minutes, the mixture is heated to 1400C and 51.2 g of 4,4'-dihydroxydiphenyl ether and 0.1 g of 2-ethyl-4-methylimidazole are added and dissolved with stirring.The mixture is degassed, poured into a mould of 80 x 60 x 4 mm and subsequently cured for 2 hours at 1400C and for 2 hours at 1800C. The mouldings have the following properties:

Tg (TMA) Flexural strength (ISO 178) Flexural elongation (ISO 178) - 910C = 14 5 MPa = 13.3% Example 10: Example 9 is repeated using 30 g of epoxy resin a4 and 70 g of epoxy resin bl as the resin components.

The followino, results are obtained:

W T 9 (11MA) Flexural strength (ISO 178) Flexural elongation (ISO 178) = 87 and 1551C = 157 MPa = 11% Examples 11 - 14: Preparation of laminates Example ll: 151 g of polyether imide 1 are dissolved in 300 g of methylene chloride and then 30 g of epoxy resin a4 and 70 g of epoxy resin bl are added. To the homogeneous solution is added dropwise a solution of 60 g of 4,41-dihydroxydiphenyl ether, 0.1 g of 2-ethyl-4- methylimidazole in 60 g of methyl ethyl ketone. This solution is used to impregnate a quasi unidirectional carbon fibre fabric (G 827, Brochier SA) with 3% by weight of glass fibres in the weft direction followed by drying at 500C for 16 hours. After treatment at 900C in a vacuum for 30 minutes. the prepregs (11 layers) are placed on top of each other and compressed at 2000C for 2 hours at 8 bar to giv - e a laminate. The following results are obtained:

i Flexural strength (parallel to the fibre) (ISO 178) = 1460 MPa Flexural strength (transverse to the fibre) (ISO 178) = 97 MPa Flexural elongation (parallel to the fibre) (ISO 178) Flexural elongation (transverse to the fibre) (ISO 178) 1.4 % 1.3 % 7 2 MPa = (107) 1010C = 70.1% by weight Interlami;nar shear strength (ASUI D 2344) TS (TMA) Fibre content Exampl ' e 12: Example 11 is repeated using a solution of 70 g of polysulfone 1, 15 g of epoxy resin al and 85 g of epoxy resin bl in 150 g of methylene chloride. To this solution are added dropwise 51.2 g of 4, 41dihydroxydiphenyl ether and 0.1 g of 2-ethyl-4-methylimidazole in 60 g of methyl ethyl ketone. The resulting laminate has the following properties:

Flexural strength (parallel to the fibre) (ISO 178) 1510 MPa Flexural strength (transverse to the fibre) (ISO 178) 110 MPa Flexural elongation (parallel to the fibre) (ISO 178) = 1.3 % Flexural elongation (transverse to the fibre) (ISO 178) Interlaminar shear strength (ASTM D 2344) T. (TMA) Fibre content 1.3 % 7 7 MPa = 97 to 1780C = 71.7% by weight Example 13: Example 11 is repeated except that 146.3 g of polyimide 1, 300 g of methylene chloride, 40 g of epoxy resin a2 and 60 g of epoxy resin bl and also 46.3 g of 2,7-dihydroxynaphthalene and 0.1 g of 2ethyl4-methylimidazole in 50 g of methyl ethyl ketone as the curing component are used to give the following results:

T 9 (TMA) Fibre content Interlaminar shear strength = 2260C 80.6% by weight 60 MPa Example 14: Using the same solution as in Example 13, a unidirectional prepreg is prepared (resin content 37% by weight) from the carbon fibre T 300.(Toray) by winding on a drum winder. After trea tment at 900C and 50 mbar in a vacuum for 30 minutes, the prepregs (10 layers) are placed on top of each other and compressed for 1 hour at 2000 and 10 bar to give a unidirectional laminate. The laminate is post cured for 1 hour at 2000 and-1 hour at 2100C. The following values-are measured:

T.c, (Ti'IA) 2250C 0 Flexural strength (parallel to the fibre) (ISO 178) 1350 MPa Flexural strength (transverse to the fibre) (ISO 178) 85 MPa Flexural elongation (parallel to the fibre) (ISO 178) = Flexural elongation (transverse to the fibre) (iSO 178) = 1.3 % 1.3 % Example 15: 149 g of.polyether imide 1 are dissolved in 250 g of methylene chloride and then 50 9 of epoxy resin a2 and 50 9 of epoxy resin b2 are added and the mixture is thoroughly mixed. After evaporation of the solvent down to about 10%, 49 g of 2,7-dihydroxynaphthalene and 0. 1 g of 2-ethyl-4-methylimidazoledissolved in methyl ethyl ketone (50%) are added dropwise with vigorous stirring. This mixture is used to prepare a film on silicone paper which is dried for 12 hours at 500C (without vacuum) and 30 minutes at 900C in a vacuum. The film is then cut and alure of 2000C compressed on a laboratory press at a compressing temper for 2 minutes to give a pure resin platelet. After complete curing in an oven at 2000C for 2 hours. the moulding has a T 9 (TMA) of 1600C.

11

Claims

1 What is claimed is:

19 - 1. A hot-curable composition of matter which is stable on storage containing a) 10 to 60 parts by weight of an epoxy resin having a functionality of at least 3, b) 90-40 parts by weight of an epoxy resin having a functionality of 2-

2. 53 a diphenol, the amount of the diphenol being chosen in such a way that 0.7-1.2 hydroxyl equivalents of the diphenol (c) are used per epoxy equivalent of the epoxy resins (a) and (b), d) 0.05-5% by weight, based on the epoxy resins (a) and (b), of an accelerator, and e) 10-140 parts by weight, based on 100 parts by weight of components (a) to (c), of a thermoplastic having a glass transition temperature of at least 1800C.

c) 2. A composition according to claim 1 in which the epoxy resins (a) and (b) have an epoxide content of 5-11 equivalents/kg and are glycidyl ethers, glycidyl esters or N-glycidyl derivatives of a cycloaliphatic, an aromatic or heterocyclic compound.

3. A composition according to claim 1 in which the epoxy resins (a) and (b) are epoxy novolaks or glycidyl derivatives of a bisphenol, a hydantoin or of a tetramethylolcyclohexane.

4. A composition according to claim 1 in which epoxy resin (a) has a functionality of 3 to 4 and is an epoxy phenol novolak or a glycidyl derivative of a hydantoin or of a tetramethylolcyclohexane.

5. A composition according to claim 1 in which epoxy resin (b) has a functionality of 2 to 2.2 and is an.epoxy phenol novolak or a glycidyl derivative of bisphenol A or of bisphenol F.

6. A composition according to claim 1 in which diphenol (c) is a compound of the formula I or II 1 OH ---R HO /X./ OH H in which T is the direct bond, methylene, isopropylidene, 0, S, CO or S02 and R is hydrogen or Cl-C4alkyl, a dihydroxynaphthalene or a mixture of these compounds.

7. A composition according to claim 1 in which diphenol (c) is bisphenol A, bisphenol F, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfide. 2,6-dihydroxytoluene, 2,6-dihydroxynaphthalene or 2, 7dihydroxynaphthalene.

8. A composition accordng to clai- 7 in r-14-pienol (c) ij mixture of 2,6-dihydroxytoluene and 2,7-dihydroxynaphthalene.

5. A composition according to claim 1 in which accelerator (d) is an imidazole or an N-acylimidazole.

10. A composition according to claim 1 in which thermoplastic (e) is a polyimide, a polyether imide, a polyamide imide, a polysulfone or is a polyether sulfone.

11. A composition according to claim 1 in which thermoplastic (e) has a glass transition temperature of 180 to 3500c.

12. A composition according to claim 1 containing 15 to 50 parts by weight of the epoxy resin (a), 85 to 50 parts by weight of the epoxy resin (b), an amount of the diphenol (c) such that 0.8-1.1 hydroxyl equivalents of the diphenol are used per epoxide equivalent of the resins (a) and (b), 0.1-1% by weight of the accelerator (d), based on the amount of (a) and (b), and 20-130 parts by weight of the thermoplastic (e), based on 100 parts by weight of components (a) to (c).

11. Use of a composition according to claim 1 for the production of cured mouldings.

14. Use of a composition according to claim 1 for the production of 0 prepregs for fibre-reinforced composite materials or for the preparation of adhesive films.. - Published 1988 at The Patent Office, State House, 66,71 High Holborn, London WC1R 4TP. Further copies may be obtained from The Patent Office, Sales Branch, St Mary Cray, orpington, Kent BR5 3RD. Printed by Multiplex techniques ltd, St Maxy Cray, Kent. Con. 1187.