Epoxy-terminated isocyanate prepolymers, and process for the preparation thereof

Abstract

The present invention relates to a process for preparing an epoxy-group-terminated impact modifier, in which process one or more polyisocyanates (a) are mixed with two or more polyols (b), containing at least one polyether polyol (b1) and at least one OH-terminated rubber (b2), in a molar ratio of isocyanate groups to OH groups of 10:1 to 1.5:1, and reacted to form an isocyanate-terminated prepolymer, and the isocyanate-terminated prepolymer is reacted with a polyepoxide (c) in the presence of an ionic liquid to form the epoxy-group-terminated impact modifier. The present invention also relates to: an epoxy-group-terminated impact modifier, which can be obtained in accordance with a process according to the invention; the use of an epoxy-group-terminated impact modifier in a single-component or two-component epoxy resin composition, preferably in a single-component or two-component epoxy resin adhesive, for increasing the impact strength of the cured epoxy resin matrix; and to a single-component or two-component epoxy resin composition comprising at least one epoxy-group-terminated impact modifier according to the invention.

Description

[0001] Epoxy-terminated isocyanate prepolymers and processes for their preparation

[0002] Description

[0003] The present invention relates to processes for producing an epoxy group-terminated impact modifier, in which one or more polyisocyanates (a) are mixed with two or more polyols (b), containing at least one polyether polyol (b1) and at least one OH-terminated rubber (b2), at a molar ratio of isocyanate groups to OH groups of 10:1 to 1.5:1 and reacted to form an isocyanate-terminated prepolymer and the isocyanate-terminated prepolymer is reacted with a polyepoxide (c) in the presence of an ionic liquid to form the epoxy group-terminated impact modifier.Furthermore, the present invention relates to an epoxy group-terminated impact modifier obtainable by a process according to the invention, the use of an epoxy group-terminated impact modifier in a one-component or two-component epoxy resin composition, preferably in a one-component or two-component epoxy resin adhesive, for increasing the impact strength of the cured epoxy resin matrix and a one-component or two-component epoxy resin composition comprising at least one epoxy group-terminated impact modifier according to the invention.

[0004] In the manufacture of vehicles and add-on parts, as well as machines and equipment, high-quality adhesives are increasingly being used instead of or in combination with conventional joining methods such as screwing, riveting, punching, or welding. This creates advantages and new possibilities in production, for example the production of composite and hybrid materials or greater freedom in the design of components. For use in vehicle manufacturing, the adhesives must exhibit good adhesion to all substrates used, in particular electrogalvanized, hot-dip galvanized, and subsequently phosphated steel sheets, oiled steel sheets, and various, possibly surface-treated aluminum alloys. These good adhesion properties must be maintained without significant loss of quality, especially after aging (alternating climates, salt spray baths, etc.).When the adhesives are used as body-in-white adhesives in automotive construction, the resistance of these adhesives to cleaning baths and dip painting (so-called washout resistance) is of great importance so that process reliability can be guaranteed at the manufacturer.

[0005] Adhesives for the bodyshell should cure under standard curing conditions, ideally 30 minutes at 180°C, in the case of 1K adhesives. In the case of 2K adhesives, curing should occur at room temperature over the course of a few days to approximately 1 week, but an accelerated curing regime, such as 4 hours at room temperature followed by 30 minutes at 60°C or 85°C, should also be applicable. Furthermore, they should also be resistant to temperatures up to approximately 220°C. Further requirements for such a cured adhesive or bond include ensuring operational reliability both at high temperatures up to approximately 90°C and at low temperatures down to approximately -40°C.Since these adhesives are structural adhesives and therefore bond structural parts, high strength, such as high peel strength and high tensile shear strength, reduced crack propagation and high impact strength of the adhesive are of utmost importance.

[0006] Conventional epoxy adhesives are characterized by high mechanical strength, particularly tensile strength. However, when subjected to sudden stress on the bond, they are usually too brittle and therefore fall far short of the requirements, particularly in the automotive industry, under crash conditions where both high tensile and peel stresses occur. In this regard, the strengths at high temperatures, but especially at low temperatures, for example, below 20 °C or below 10 °C, are often inadequate.

[0007] Two methods are known from the literature for reducing the brittleness of epoxy adhesives and thus increasing impact strength: Firstly, this goal can be achieved by adding at least partially cross-linked, high-molecular-weight compounds such as latices of core / shell polymers or other flexibilizing polymers and copolymers. One such method is described, for example, in US 5290857. Secondly, a certain increase in toughness can also be achieved by introducing soft segments, e.g., by appropriately modifying the epoxy components. For example, US 4952645 describes epoxy resin compositions that have been flexibilized by reaction with carboxylic acids, in particular di- or trimeric fatty acids, and with carboxylic acid-terminated diols.

[0008] EP 0353190 relates to a flexibilizing component for epoxy resins based on monophenol- or epoxy-terminated polymers. EP 1574537 A1 and EP 1602702 A1 describe epoxy resin adhesive compositions containing monophenol- or epoxy-terminated polymers as impact modifiers.

[0009] EP 2060592 describes heat-curing epoxy resin compositions, one example of which describes the preparation of a toughener from a mixture of a polyalkylene glycol and a hydroxyl-terminated polybutadiene and isophorone diisocyanate and cardanol as blocking agent.

[0010] EP 0383505 relates to a reactive hot melt adhesive comprising a urethane prepolymer made of a polyisocyanate and a polyether polyol and a thermoplastic elastomer, wherein hydroxy-terminated polybutadienes can additionally be used for the production of the urethane prepolymer.

[0011] EP 1741734 relates to a thermosetting epoxy resin composition comprising a solid epoxy resin and an impact modifier obtainable by the reaction of a monohydroxyl epoxy compound and an isocyanate-terminated polyurethane polymer, wherein in one example for the preparation of the polyurethane polymer a mixture of polyalkylene glycols and hydroxyl-terminated polybutadiene is used as polyol.

[0012] WO2014 / 072515 relates to an epoxy-terminated impact modifier obtained by preparing a urethane prepolymer containing isocyanate groups and reacting this prepolymer with an epoxy resin containing an epoxy compound containing a primary or secondary hydroxy group. To prepare the urethane prepolymer, isophorone diisocyanate can be used as the isocyanate component, and a polyol mixture comprising at least one polyether polyol and at least one OH-terminated rubber can be used as the polyol component. A disadvantage of urethane-linked impact modifiers is reduced temperature stability. Furthermore, the compatibility of the impact modifiers according to the invention with the epoxy matrix is ​​improved, which leads to improved impact properties.

[0013] US Pat. No. 5,480,958 describes the reaction of NCO-terminated prepolymers with epoxides to form oxazolidone structural elements. In this case, potassium acetate is used as a catalyst for the reaction. However, the property profile of these impact modifiers still requires improvement, particularly with regard to impact strength, fracture toughness, and fracture energy Gic.

[0014] The object of the present invention was therefore to provide an improved impact modifier that, in epoxy resins such as epoxy adhesives, results in excellent impact strength with high tensile shear strength, peel strength, and reduced crack propagation. Furthermore, such an impact modifier should, if possible, not lower the glass transition temperature of the epoxy resin and should not excessively increase the viscosity of the epoxy resin formulation, in order to ensure easy processability.

[0015] The object of the present invention is achieved by an epoxy group-terminated impact modifier, preparable by a process in which one or more polyisocyanates (a) are mixed with two or more polyols (b), containing at least one polyether polyol (b1) and at least one OH-terminated rubber (b2), at a molar ratio of isocyanate groups to OH groups of 10:1 to 1.5:1 and reacted to form an isocyanate-terminated prepolymer and the isocyanate-terminated prepolymer is reacted with a polyepoxide (c) in the presence of an ionic liquid to form the epoxy group-terminated impact modifier.Furthermore, the present invention relates to such a method, the use of an epoxy group-terminated impact modifier in a one-component or two-component epoxy resin composition, preferably in a one-component or two-component epoxy resin adhesive, for increasing the impact strength of the cured epoxy resin matrix, and a one-component or two-component epoxy resin composition comprising at least one epoxy group-terminated impact modifier according to the invention.

[0016] To produce the epoxy group-terminated impact modifier according to the invention, an isocyanate prepolymer is obtained in a first step from one or more polyisocyanates (a) with two or more polyols (b).

[0017] All polyisocyanates known for the production of polyurethanes can be used as isocyanates (a). These include the aliphatic, cycloaliphatic, and aromatic di- or polyfunctional isocyanates known from the prior art, as well as any mixtures thereof. Examples are 2,2'-, 2,4'-, and 4,4'-diphenylmethane diisocyanate, mixtures of monomeric diphenylmethane diisocyanates and higher-nuclear homologues of diphenylmethane diisocyanate (polymer MDI), isophorone diisocyanate (IPDI) or its oligomers, 2,4- or 2,6-tolylene diisocyanate (TDI) or mixtures thereof, tetramethylene diisocyanate or its oligomers, hexamethylene diisocyanate (HDI) or its oligomers, naphthylene diisocyanate (NDI), or mixtures thereof. Furthermore, modified isocyanates, such as isocyanurate-, uretdione-, allophanate- or uretonimine-modified polyisocyanates can also be used.Other possible isocyanates are listed, for example, in the "Plastics Handbook, Volume 7, Polyurethanes", Carl Hanser Verlag, 3rd edition 1993, Chapters 3.2 and 3.3.2.

[0018] The isocyanate (a) used is preferably isophorone diisocyanate (IPDI), optionally in a mixture with modified isophorone diisocyanate, and preferably isophorone diisocyanate, in particular exclusively isophorone diisocyanate.

[0019] Two or more polyols (b), containing at least one polyether polyol (b1) and at least one OH-terminated rubber (b2), are used as polyols.

[0020] Polyols that can be used include all compounds known in polyurethane chemistry with at least two, preferably two to eight, isocyanate-reactive groups. These include polyethers, polyesters, polyamines, OH-terminated polymers such as OH-terminated rubber, and compounds known as chain extenders and crosslinking agents. Such compounds are described, for example, in "Kunststoffhandbuch, Volume 7, Polyurethane," Carl Hanser Verlag, 3rd edition 1993, Chapters 3.1 and 3.4.3.

[0021] The polyetherols (b1) preferably have an OH number of 20 to 100 mg KOH / g, particularly preferably 35 to 80 mg KOH / g and in particular 45 to 65 mg KOH / g and a functionality of preferably 2 to 3, in particular 2.

[0022] The polyether polyols usable according to the invention are prepared by known processes. For example, they can be prepared by anionic polymerization of alkylene oxides with alkali metal hydroxides, such as sodium or potassium hydroxide, or alkali metal alcoholates, such as sodium methylate, sodium or potassium ethylate, or potassium isopropylate, as catalysts and with the addition of at least one starter molecule, which preferably has 2 to 3 reactive hydrogen atoms, or by cationic polymerization with Lewis acids, such as antimony pentachloride, boron fluoride etherate, among others, or bleaching earth, as catalysts. Polyether polyols can also be prepared by double metal cyanide catalysis from one or more alkylene oxides having 2 to 4 carbon atoms in the alkylene radical. Tertiary amines can also be used as catalysts, for example triethylamine, tributylamine, trimethylamine, dimethylethanolamine, imidazole, or dimethylcyclohexylamine.

[0023] Suitable alkylene oxides are, for example, ethylene oxide, propylene oxide, 1,2-butylene oxide, 1,3-propylene oxide, 2,3-butylene oxide, styrene oxide, tetrahydrofuran, or mixtures thereof, preferably ethylene oxide, propylene oxide, 1,2-butylene oxide, tetrahydrofuran, or mixtures thereof, and especially tetrahydrofuran. The alkylene oxides can be used individually, alternately, or as mixtures.

[0024] Examples of suitable starter molecules include: water, aliphatic and aromatic, optionally N-mono-, N,N- and N,N'-dialkyl-substituted diamines having 1 to 4 carbon atoms in the alkyl radical, and in particular polyhydric alcohols, such as ethanediol, 1,2- and 2,3-propanediol, diethylene glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, glycerol, trimethylolpropane; pentaerythritol, and mixtures thereof. For the purposes of the present invention, the functionality of the polyetherol (b1) is considered to be the functionality of the starter molecule, even if in reality the actual functionality of the polyether polyol may be lower due to side reactions. Fractional functionalities can be obtained by mixing starter molecules with different functionalities.

[0025] Polytetrahydrofuran (poly-THF polyols) can also be used as the polyetherol. The number-average molecular weight of the polytetrahydrofuran is typically 550 to 4000 g / mol, preferably 750 to 3000 g / mol, particularly preferably 800 to 2500 g / mol.

[0026] The polyether polyols can be used individually or in the form of mixtures.

[0027] One or more OH-terminated rubbers can be used as OH-terminated rubber (b2). OH-terminated rubbers are understood to mean all rubbers which contain hydroxyl groups, for example nitrile rubbers containing hydroxyl groups, as described for example in US 3551472, and preferably hydroxyl-terminated polybutadienes (HTPB).

[0028] Liquid hydroxyl-terminated polybutadienes (HTPB) have long been known and are used as polyol components in polyurethanes. Commercial products can be obtained by radical polymerization (see US 3965140) or ionic polymerization (see DD 160223) of 1,3-butadiene. Obtaining HTPB requires specific initiation and termination reagents. Depending on the manufacturing process, polyols with varying numbers of functional groups are obtained. The polybutadienes obtained by polymer-analogous reactions contain different amounts of reactive hydroxyl groups, depending on the degree of epoxidation and epoxide opening, and therefore exhibit different functionalities. To improve compatibility with polyethers (b1) and isocyanates (a), the hydroxyl-terminated polybutadienes can also be modified with alkylene oxides or cyclic esters, such as ε-caprolactone. Such compounds are described, for example, in EP 3183282.Non-functionalized HTPBs are preferably used.

[0029] Commercially available hydroxyl-terminated polybutadienes include the Poly bd® and Krasol® products from Cray Valley, such as Krasol® LBH-P 2000 or Poly bd® R45V. Castor oil-based polyols include the Albodur® products from Alberdingk Boley, such as Albodur®901, or the Polycine® products from Baker Castor Oil Company, such as Polycine®-GR80.

[0030] The OH functionality of the hydroxyl-terminated rubbers used is preferably in the range from 1.7 to 2.2 for anionically produced types or from 2.2 to 2.8 for radically produced types. If the epoxy group-terminated impact modifier is used in a 2-component epoxy resin adhesive, preference is given to using a hydroxyl-terminated rubber, in particular a hydroxyl-terminated butadiene, with an OH functionality of less than or equal to 2. If the epoxy group-terminated impact modifier is used in a 1-component epoxy resin adhesive, preference is given to using a hydroxyl-terminated rubber, in particular a hydroxyl-terminated butadiene, with an OH functionality in the range from 2.4 to 2.8. The mentioned preferred OH functionality for 2K and 1K epoxy resin adhesives can also be achieved in a mixture of two hydroxyl-terminated rubbers, in particular hydroxyl-terminated polybutadienes.The weight ratio of polyether polyol to hydroxyl-terminated rubber is preferably in the range of 7:3 to 2:8, particularly preferably 7:3 to 4:6, more preferably 7:3 to 5:5, even more preferably in the range of 6:4 to 2:8, and especially preferably 6:4 to 3:7. In this way, the mechanical properties of the cured adhesive can be improved, in particular the impact peel resistance at -30°C.

[0031] Preferably, polyols, in particular polyols (b1) and (b2), are selected for which a mixture of polyol and an epoxy liquid resin made from bisphenol A and epichlorohydrin, such as Epikote 828 LVEL, in a weight ratio of 40 to 60 has a haze value measured according to ASTM D1003-11e1 in the range from 50 to 100 for hydroxy-terminated rubber (b2) as polyol and / or in the range from 0 to 5 for polyether polyol as polyol (b1).

[0032] The polyisocyanates (a) and the polyols (b) are then reacted to form the isocyanate-terminated prepolymer. For this purpose, the polyisocyanates (a) and the polyols (b) are mixed together in a ratio such that the molar ratio of isocyanate groups to OH groups is from 10:1 to 1.5:1, preferably from 5:1 to 1.8:1, particularly preferably from 3:1 to 1.9:1. The reaction is typically carried out at temperatures from 30 to 100 °C, preferably at about 80 °C, preferably in the presence of conventional polyurethane catalysts. Such catalysts are described, for example, in "Kunststoffhandbuch, Volume 7, Polyurethane," Carl Hanser Verlag, 3rd edition 1993, Chapter 3.4.1.

[0033] Examples of suitable catalysts include organic metal compounds, preferably organic tin compounds, such as tin(II) salts of organic carboxylic acids, e.g., tin(II) acetate, tin(II) octoate, tin(II) ethylhexanoate, and tin(II) laurate, and the dialkyltin(IV) salts of organic carboxylic acids, e.g., dibutyltin diacetate, dibutyltin dilaurate, dibutyltin maleate, and dioctyltin diacetate, as well as bismuth carboxylates, such as bismuth(III) neodecanoate, bismuth 2-ethylhexanoate, and bismuth octanoate, or mixtures thereof. Other possible catalysts include strongly basic amine catalysts.Examples of these are amidines such as 2,3-dimethyl-3,4,5,6-tetrahydropyrimidine, tertiary amines such as triethylamine, tributylamine, dimethylbenzylamine, N-methyl-, N-ethyl-, N-cyclohexylmorpholine, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetramethylbutanediamine, N,N,N',N'-tetramethylhexanediamine, pentamethyldiethylenetriamine, tetramethyldiaminoethyl ether, bis(dimethylaminopropyl)urea, dimethylpiperazine, 1,2-dimethylimidazole, 1-azabicyclo-(3,3,0)octane and preferably 1,4-diazabicyclo-(2,2,2)octane and alkanolamine compounds such as triethanolamine, triisopropanolamine, N- Methyl- and N-ethyldiethanolamine, and dimethylethanolamine. The catalysts can be used individually or as mixtures. Particular preference is given to using exclusively metal catalysts to produce the prepolymer.

[0034] The content of free isocyanate groups in the isocyanate prepolymer is usually between 1 and 6 wt.% NCO, preferably 1.5 to 4 wt.% free NCO groups.

[0035] The isocyanate-terminated prepolymer is then reacted in a further step in the presence of an ionic liquid with a polyepoxide (c) to form the epoxy-terminated impact modifier. The reaction preferably takes place at temperatures of 120 to 250 °C. Any aliphatic, cycloaliphatic, aromatic, and / or heterocyclic compounds containing at least two epoxy groups can be used as polyepoxide (c). The preferred epoxides suitable as component (c) have 2 to 4, preferably 2, epoxy groups per molecule and an epoxy equivalent weight of 90 to 500 g / eq, preferably 140 to 220 g / eq.

[0036] Suitable polyepoxides are, for example, polyglycidyl ethers of polyhydric phenols, for example of pyrocatechol, resorcinol, hydroquinone, 4,4'-dihydroxydiphenylpropane (bisphenol A), of 4,4'-dihydroxy-3,3'-dimethyldiphenylmethane, of 4,4'-dihydroxydiphenylmethane (bisphenol F), 4,4'-dihydroxydiphenylcyclohexane, of 4,4'-dihydroxy-3,3'-dimethyldiphenylpropane, of 4,4'-dihydroxydiphenyl, of 4,4'-dihydroxydiphenylsulfone (bisphenol S), of tris-(4-hydroxyphenyl)methane, the chlorination and bromination products of the above-mentioned diphenols, of novolaks (ie reaction products of mono- or polyhydric phenols and / or cresols with aldehydes, in particular formaldehyde, in the presence of acidic catalysts in an equivalent ratio of less than 1: 1), of diphenols obtained by esterification of 2 moles of the sodium salt of an aromatic oxycarboxylic acid with one mole of a dihaloalkane or dihalodialkyl ester (cf.British Patent 1 017 612) or of polyphenols obtained by condensation of phenols and long-chain halogenated paraffins containing at least two halogen atoms (cf. GB-PS 1 024 288). Also mentioned are polyepoxide compounds based on aromatic amines and epichlorohydrin, e.g. N-di-(2,3-epoxypropyl)aniline, N,N'-dimethyl-N,N'-diepoxypropyl-4,4'-diaminodiphenylmethane, N,N-diepoxypropyl-4-aminophenyl glycidyl ether (cf. GB-PS 772 830 and 816 923).

[0037] Also suitable are: glycidyl esters of polyvalent aromatic, aliphatic and cycloaliphatic carboxylic acids, for example diglycidyl phthalate, diglycidyl isophthalate, diglycidyl terephthalate, diglycidyl adipic acid and glycidyl esters of reaction products of 1 mol of an aromatic or cycloaliphatic dicarboxylic acid anhydride and 1 / 2 mol of a diol or 1 / n mol of a polyol with n hydroxyl groups or diglycidyl hexahydrophthalate, which may optionally be substituted by methyl groups.

[0038] Glycidyl ethers of polyhydric alcohols, such as 1,4-butanediol (Araldite® DY-D, Huntsman), 1,4-butenediol, glycerin, trimethylolpropane (Araldite® DY-T / CH, Huntsman), pentaerythritol, and polyethylene glycol, can also be used. Of further interest are triglycidyl isocyanurate, N,N'-diepoxypropyloxyamide, polyglycidyl thioethers of polyhydric thiols, such as bismercaptomethylbenzene, diglycidyltrimethylenetrisulfone, and polyglycidyl ethers based on hydantoins.

[0039] Finally, epoxidation products of polyunsaturated compounds can also be used, such as vegetable oils and their conversion products. Epoxidation products of di- and polyolefins, such as butadiene, vinylcyclohexane, 1,5-cyclooctadiene, 1,5,9-cyclododecatriene, polymers and copolymers that still contain epoxidizable double bonds, e.g., based on polybutadiene, polyisoprene, butadiene-styrene copolymers, divinylbenzene, dicyclopentadiene, unsaturated polyesters, and epoxidation products of olefins, which are accessible by Diels-Alder addition and subsequently converted into polyepoxides by epoxidation with per compound, or of compounds containing two cyclopentene or cyclohexene rings linked via bridge atoms or bridge atom groups, can also be used.

[0040] In addition, polymers of unsaturated monoepoxides can also be used, for example from methacrylic acid glycidyl ester or allyl glycidyl ether.

[0041] According to the invention, the following polyepoxide compounds or mixtures thereof are preferably used as component (c):

[0042] Polyglycidyl ethers of polyhydric phenols, in particular bisphenol A (Araldit® GY250, Huntsman; Ruetapox® 0162, Bakelite AG; Epikote® Resin 162, Hexion Specialty Chemicals GmbH; Eurepox 710, Brenntag GmbH; Araldit® GY250, Hunstman, DER™ 332, The Dow Chemical Company; Epilox® A 18-00, LEUNA-Harze GmbH) or bisphenol F (4,4'-dihydroxydiphenylmethane, Araldit® GY281 , Huntsman; Epilox® F 16-01 , LEUNA-Harze GmbH; Epilox® F 17-00, LEUNA-Harze GmbH) polyepoxide compounds based on aromatic amines, in particular bis(N-epoxypropyl)aniline, N,N'-dimethyl-N,N'-diepoxypropyl-4,4'-diaminodiphenylmethane and N,N-diepoxypropyl-4-aminophenyl glycidyl ether; Polyglycidyl esters of cycloaliphatic dicarboxylic acids, in particular hexahydrophthalic acid diglycidyl ester and polyepoxides from the reaction product of n moles of hexahydrophthalic anhydride and 1 mole of a polyol having n hydroxyl groups (n = integer from 2-6), in particular 3 moles of hexahydrophthalic anhydride and one mole of 1,1,1-trimethylolpropane; 3,4-epoxycyclohexylmethane-3,4-epoxycyclohexanecarboxylate.

[0043] Polyglycidyl ethers of bisphenol A and bisphenol F as well as of novolaks and mixtures thereof are very particularly preferred, in particular polyglycidyl ethers of bisphenol F.

[0044] Liquid polyepoxides or low-viscosity diepoxides, such as bis(N-epoxypropyl)aniline or vinylcyclohexane diepoxide, can, in special cases, further reduce the viscosity of already liquid polyepoxides or convert solid polyepoxides into liquid mixtures. Preferably, the polyepoxides (c) contain as few OH-containing by-products as possible, such as glycols. The proportion of OH-containing by-products is expressed as the OH number of the polyepoxide (c). The OH number of the polyepoxides (c) is particularly preferably less than 20 mg KOH / g, particularly preferably less than 10 mg KOH / g.

[0045] Ionic liquids are well known, widely described, and commercially available. For example, ionic liquids suitable for improving the conductivity of polyurethanes are described in EP 2038337. These ionic liquids are salts of the general formula (I)

[0046] [Al- [YF where n stands for 1, 2, 3 or 4, [A] + represents a quaternary ammonium cation, an oxonium cation, a sulfonium cation or a phosphonium cation and [Y] n- represents a mono-, di-, tri- or tetravalent anion; (B) mixed salts of the general formulas (II)

[0047] [A 1 p[A 2 P [Yp- (Ha), where n = 2;

[0048] [A 1 ] + [A 2 ] + [A 3 ] + [Yp- (Hb), where n = 3; or

[0049] [A 1 p[A 2 P[A 3 p[A 4 P [Y] n- (llc), where n = 4 and where [A 1 ] + , [A 2 ] + , [A 3 p and [A 4 ] + independently from the [A] + mentioned groups are selected and [Y] n ~ has the meaning given under (A); or

[0050] (C) mixed salts of the general formulas (III)

[0051] [A 1 ] + [A 2 ] + [A 3 ] + [M 1 ] + [Yp- (Illa), where n = 4;

[0052] [A 1 ] + [A 2 ] + [M 1 ] + [M 2 ] + [Yp- (lllb), where n = 4;

[0053] [A 1 ] + [M 1 ] + [M 2 ] + [M 3 ] + [Yp- (Ille), where n = 4;

[0054] [A 1 ] + [A 2 ] + [M 1 ] + [Y] n- (II Id), where n = 3;

[0055] [A 1 ] + [M 1 ] + [M 2 ] + [Yp- (Ille), where n = 3;

[0056] [A 1 ] + [M 1 ] + [Y] n - (Ulf), where n = 2;

[0057] [A 1 p[A 2 p[M 4 ] 2+ [Yp- (Illg), where n = 4;

[0058] [A 1 ] + [M 1 ] + [M 4 ] 2+ [Yp- (lllh), where n = 4;

[0059] [A 1 ] + [M 5 ] 3+ Yp- (Illi), where n = 4; or

[0060] [A 1 p[M 4 ] 2+ [Yp- (lllj), where n = 3 and where [A 1 ] + , [A 2 p and [A 3 ] + independently from the [A] + mentioned groups, [Yp- has the meaning given under (A) and [M 1 p, [M 2p, [M 3 p monovalent metal cations, [M 4 ] 2+ divalent metal cations and [M 5 ] 3+ trivalent metal cations.

[0061] The ionic liquids used in the present invention have a melting point in a range from -50°C to 150°C, more preferably in the range from -20°C to below 100°C, and even more preferably from -20°C to below 80°C. The melting point of the ionic liquid is particularly preferably below 50°C; in particular, ionic liquids according to the invention are liquid at room temperature. Ionic liquids that are liquid at room temperature are easy to process and have an excellent antistatic effect.

[0062] Compounds that combine to form the cation [A] +of ionic liquids are known, for example, from DE 102 02 838 A1. Such compounds can contain oxygen, phosphorus, sulfur or, in particular, nitrogen atoms, for example at least one nitrogen atom, preferably 1-10 nitrogen atoms, more preferably 1-5, most preferably 1-3 and in particular 1-2 nitrogen atoms. If desired, further heteroatoms such as oxygen, sulfur or phosphorus atoms can also be present. The nitrogen atom is a suitable carrier of the positive charge in the cation of the ionic liquid, from which a proton or an alkyl radical can then be transferred to the anion in equilibrium to produce an electrically neutral molecule. The positive charge can also be delocalized in a mesomeric system.If the nitrogen atom carries the positive charge in the cation of the ionic liquid, a cation can be generated during the synthesis of the ionic liquids by quaternization at the nitrogen atom, for example, of an amine or nitrogen heterocycle. Quaternization can be achieved by alkylating the nitrogen atom. Depending on the alkylating reagent used, salts with different anions are obtained. In cases where it is not possible to form the desired anion during quaternization, this can be done in a further synthesis step. Starting from an ammonium halide, for example, the halide can be reacted with a Lewis acid, whereby a complex anion is formed from the halide and Lewis acid. Alternatively, the exchange of a halide ion for the desired anion is possible.This can be achieved by adding a metal salt to precipitate the resulting metal halide, via an ion exchanger, or by displacing the halide ion with a strong acid (releasing the hydrohalic acid). Suitable methods are described, for example, in Angew. Chem. 2000, 112, pp. 3926-3945 and the literature cited therein.

[0063] In principle, any anion can be used. Preferred anions are described, for example, in EP 2038337.

[0064] As ionic liquids within the meaning of the invention, substances with a soft cation and / or a soft anion are preferably used. This means that cations and / or anions are well stabilized, for example, by inductive and / or mesomeric effects. Cations preferably have electron-donating substituents. The cation preferably contains exclusively electron-donating substituents. The anions preferably have electron-withdrawing substituents. Particular preference is given to using an ionic liquid in which the charge of the cation, the anion, or the cation and the anion is delocalized by mesomeric effects. Therefore, imidazolium, guanidinium, or pyrazolium derivatives, in particular imidazolium derivatives, are preferred as cations.Ionic liquids according to the invention particularly preferably have cations selected from the group comprising 1,2,3-trimethylimidazolium, 1,3,4,5-tetramethylimidazolium, 1,3,4-dimethylimidazolium, 1,3,4-trimethylimidazolium, 1,3-dibutyl-2-methylimidazolium, 1,3-dibutylimidazolium, 1,2-dimethylimidazolium, 1,3-dimethylimidazolium, 1-benzyl-3-methylimidazolium, 1-butyl-2,3-dimethylimidazolium.

[0065] 1-Butyl-2-ethyl-5-methylimidazolium, 1-Butyl-2-ethylimidazolium, 1-Butyl-2-methylimidazolium, 1-Butyl-3,4,5-trimethylimidazolium, 1-Butyl-3,4-dimethylimidazolium, 1-Butyl-3-ethylimidazolium, 1-Butyl-3-methylimidazolium, 1-Butyl-4-methylimidazolium, 1-Butylimidazolium, 1-Decyl-3-methylimidazolium, 1-Dodecyl-3-methylimidazolium, 1-Ethyl-2,3-dimethylimidazolium, 1-Ethyl-3-methylimidazolium, 1-Hexadecyl-2,3-dimethylimidazolium, 1-Hexadecyl-3-methylimidazolium, 1-hexyl-2,3-dimethylimidazolium,

[0066] 1 -Hexyl-3-methylimidazolium, 1 -Methyl-2-ethylimidazolium, 1 -Methyl-3-octylimidazolium, 1-Methylimidazolium, 1-Pentyl-3-methylimidazolium, 1-Phenylpropyl-3-methylimidazolium,

[0067] 1-Propyl-2,3-dimethylimidazolium, 1-Tetradecyl-3-methylimidazolium, 2,3-Dimethylimidazolium,

[0068] 2-Ethyl-3,4-dimethylimidazolium, 3,4-Dimethylimidazolium, 1,2-Dimethylpyridinium, guanidinium, hexamethylguanidinium, N,N,N',N'-tetramethyl-N"-ethylguanidinium, N-pentamethyl-N-isopropylguanidinium, N-pentamethyl-N-propylguanidinium, benzyltriphenylphosphonium, tetrabutylphosphonium, trihexyl(tetradecyl)phosphonium and tri-isobutyl(methyl)phosphonium. The anions for the process according to the invention are preferably selected from the group containing acetate, bis(2,4,4-trimethylpentyl)phosphinate, bis(malonato)borate, bis(oxalato)borate, bis(pentafluoroethyl)phosphinate, bis(phthalato)borate, bis(salicylato)borate, Bis(trifluoromethanesulfonyl)imidate, bis(trifluoromethyl)imidate, borate, bromide, bromoaluminates, carbonate, chloroaluminates, decylbenzenesulfonate, dichlorocuprate, dicyanamide, didecylbenzenesulfonate, didodecylbenzenesulfonate, diethyl phosphate, dihydrogen phosphate, dodecylbenzenesulfonate, ethyl sulfate, Ethyl sulfonate, fluoride, hexafluorophosphate, hydrogen carbonate, hydrogen phosphate,Hydrogen sulfate, hydrogen sulfite, iodide, methyl sulfate, methyl sulfonate, nitrate, nitrite, phosphate, sulfite, tetracyanoborate, tetrafluoroborate, tetrakis(hydrogensulfato)borate, tetrakis(methylsulfonato)borate, thiocyanate, tosylate, trichlorozincate, trifluoroacetate, trifluoromethyl sulfonate, T ris(heptafluoropropyl)trifluorophosphate, Tris(nonafluorobutyl)trifluorophosphate, Tris(pentafluoroethyl)trifluorophosphate, Tris(pentafluoroethylsulfonyl)trifluorophosphate.,

[0069] Particularly preferred anions are hexafluorophosphate, tetrafluoroborate, thiocyanate and dicyanamide, ethyl sulfate, diethyl phosphate, methyl sulfate, bromide, iodide, p-toluenesulfonate and methanesulfonate, in particular based on ethyl sulfate, thiocyanate bromide or dicyanamide, very particularly preferably bromide.

[0070] Vorzugsweise werden als Ionische Flüssigkeiten im Sinn der Erfindung 1 -Ethyl-3- methylimidazoliumchlorid, 1- Butyl-3-methylimidazoliumchlorid, 1-Ethyl-3- methylimidazoliummethylsulfonat, 1-Butyl-3-methylimidazoliummethansulfonat, 1-Ethyl-3- methylimidazoliumethylsulfat, 1- Butyl-3-methylimidazoliummethylsulfat, 1- Ethyl-3- methylimidazoliumdiethylphosphat, 1- Butyl-3-methylimidazoliumdimethylphosphat, 1-Ethyl-3- methylimidazoliumdicyanamid, 1- Butyl-3-methylimidazoliumdicyanamid, 1-Ethyl-3- methylimidazoliumacetat, 1-Butyl-3-methylimidazoliumacetat, 1 -Ethyl-3- methylimidazoliumthiocyanat, 1- Butyl-3-methylimidazoliumthiocyanat, 1-Ethyl-3- methylimidazoliumtetrafluoroborat, 1 -Butyl-3-methylimidazoliumtetrafluoroborat, 1 -Ethyl-3- methylimidazoliumtrifluormethansulfonat, 1-Butyl-3-methylimidazoliumtrifluormethansulfonat, 1- Ethyl-3-methylimidazoliumbis(trifluormethansulfonyl)imid, 1-Butyl-3- methylimidazoliumbis(trifluormethansulfonyl)imid,1-Ethyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium bromide, 1-ethyl-3-methylimidazolium p-toluenesulfonate and / or 1-butyl-3-methylimidazolium p-toluenesulfonate are used.

[0071] Particularly preferably, the ionic liquid within the meaning of the invention is selected from the group consisting of 1-ethyl-3-methylimidazolium methylsulfonate, 1-ethyl-3-methylimidazolium ethylsulfate, 1-ethyl-3-methylimidazolium dicyanamide, 1-ethyl-3-methylimidazolium thiocyanate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium bromide, and mixtures of at least two members of this group. In particular, 1-butyl-3-methylimidazolium bromide is used as the ionic liquid.

[0072] The ionic liquid is preferably present in the antistatic or conductive polyurethane according to the invention in an amount of 0.001 to 2 weight percent, more preferably 0.01 to 1.5 weight percent, even more preferably 0.05 to 1.0 weight percent, particularly preferably 0.05 to 0.5 weight percent, based in each case on the total weight of the isocyanate-terminated prepolymer and the polyepoxide (c). The ionic liquids employed can be used individually or in the form of mixtures.

[0073] The reaction of the isocyanate-terminated prepolymer with a polyepoxide (c) in the presence of an ionic liquid to form the epoxy-terminated impact modifier can be partial or complete, with a complete reaction resulting in essentially all isocyanate groups of the prepolymer being reacted with epoxy groups, and a partial reaction resulting in isocyanate groups still remaining. The proportion of unreacted isocyanate groups in the impact modifier according to the invention is preferably less than 1% by weight, preferably less than 0.1% by weight, and in particular less than 0.01% by weight, based on the total weight of the epoxy-terminated impact modifier. In a particularly preferred embodiment, the epoxy-terminated impact modifier contains no isocyanate groups.

[0074] The epoxy-terminated impact modifier producible by a process according to the invention can be added to a one-component or two-component epoxy resin composition, preferably in a one-component or two-component epoxy resin adhesive, to increase the impact strength of the cured epoxy resin matrix. A further area of ​​application for the epoxy-terminated impact modifier according to the invention is its use in epoxy-containing polyurethanes and polyisocyanurates. Such compounds are described, for example, in WO 2015078740.

[0075] The epoxy group-terminated impact modifier according to the invention is preferably used by adding it to one of the liquid starting components of the epoxy resin composition; alternatively, the impact modifier can also be added as a standalone component to the epoxy resin composition. The proportion of the impact modifier according to the invention is preferably 1 to 75, particularly preferably 10 to 60, and in particular 25 to 55 wt. %, based on the total weight of the epoxy resin composition. The resulting epoxy resin composition according to the invention has improved impact resistance, at least constant tensile strength, and reduced crack propagation. The glass transition temperature is only insignificantly affected compared to an epoxy resin composition without impact modifier, i.e. the glass transition temperature decreases when using 20 wt.-% impact modifier, based on the total weight of epoxy resin composition and impact modifier, preferably by less than 20°C, more preferably by less than 10°C, and in particular by less than 5°C, based on the epoxy resin composition without impact modifier. Furthermore, the viscosity of the epoxy resin composition according to the invention containing 20 wt.% impact modifier at 40°C increases preferably by less than 50% of the initial value without impact modifier, more preferably by less than 30%, and in particular by less than 10%.

[0076] The invention will be illustrated below using examples. Description of the determination of oxirane groups (EEW ​​determination):

[0077] To characterize the content of oxirane groups ("epoxide groups") in compounds, an epoxide titration was performed. The resulting epoxide number (%EpO) indicates how many grams of oxirane oxygen are contained in 100 grams of a sample.

[0078] Crystal violet is used as an indicator. The determination requires the absence of water, bases, and amines.

[0079] Reagents:

[0080] (1) 0.1-N-perchloric acid (Merck) in glacial acetic acid

[0081] (2) Tetraethylammonium bromide (Fluka) in the form of a solution of 100 g of tetraethylammonium bromide in 400 ml of glacial acetic acid

[0082] (3) Crystal violet (Merck); to prepare the indicator solution, 0.2 g of crystal violet was dissolved in 100 mL of glacial acetic acid.

[0083] Implementation:

[0084] 0.2 to 0.5 g of the sample containing oxirane rings is placed in an Erlenmeyer flask. The sample is dissolved in 50 ml of anhydrous acetone. Then, 10 ml of tetraethylammonium bromide solution and 3 drops of crystal violet solution are added. The mixture is titrated with a 0.1 N solution of perchloric acid in glacial acetic acid. The endpoint is reached when the color changes from blue to green.

[0085] Before carrying out the actual titration, a blank test is carried out (this does not contain any oxirane compound) to exclude measurement errors.

[0086] Evaluation:

[0087] The epoxy content %EpO is calculated as follows: % EpG=[(ab)+0.160] / E a: = Consumption ml 0.1 N perchloric acid during titration b: = Consumption ml 0.1 N perchloric acid during blank test

[0088] E: = Sample weight in grams

[0089] The epoxy equivalent weight (EEW) is calculated using the following formula:

[0090] EEW = 1600 / % EpO

[0091] The dimension of the EEW is g / eq.

[0092] The NCO content was determined in wt. % by back-titration of the corresponding samples with an excess of 1M di-n-butylamine in chlorobenzene with 1 molar hydrochloric acid. Tensile strength, modulus of elasticity, and elongation at break were determined from tensile tests according to DIN EN ISO 527 at a test speed of 20 mm / min.

[0093] Charpy impact strength according to DIN EN ISO 179-1 / 1fU.

[0094] Fracture toughness Kic and fracture energy G measured by OCT (optical crack tracing) according to ISO 13586 and ASTM D5045 at the Frauenhofer IAP - PYCO.

[0095] The following raw materials were used to produce the epoxy resins: Example 1: NCO-terminated prepolymer 1

[0096] 416.61 g of PolyTHF 2000 and 416.61 g of Polyvest EP HT were dried at 90 °C with stirring for 1 hour under vacuum. Subsequently, 0.14 g of Fomrez UL 28 was added and stirred for 5 minutes. 166.64 g of Vestanat IPDI was added, and the reaction was carried out for 2 hours under vacuum at 90 °C. A product with a free NCO content of 3.08% (theoretical NCO content: 3.00%) was obtained. Example 2: NCO-terminated Prepolymer 2

[0097] 498.71 g of PolyTHF 2000 and 332.47 g of Polyvest EP HT were dried at 90 °C with stirring for 1 hour under vacuum. Subsequently, 0.08 g of Fomrez UL 28 was added and stirred for 5 minutes. 168.73 g of Vestanat IPDI was added, and the reaction was carried out for 2 hours under vacuum at 90 °C. A product with a free NCO content of 3.15% (theoretical NCO content: 3.00%) was obtained.

[0098] Example 3: NCO-terminated prepolymer 3

[0099] 495.82 g of PolyTHF 2000 and 330.54 g of Krasol LBH-P 2000 were dried at 90 °C with stirring for 1 hour under vacuum. Subsequently, 0.10 g of Fomrez UL 28 was added and stirred for 5 minutes. 173.54 g of Vestanat IPDI was added, and the reaction was carried out for 2 hours under vacuum at 90 °C. A product with a free NCO content of 3.03% (theoretical NCO content: 3.00%) was obtained.

[0100] Example 4

[0101] In a 1L four-neck round-bottom flask equipped with a precision glass stirrer, thermocouple, dropping funnel (heatable to 80°C), and condenser, with N2 purge via a condenser, 440 g of DER 330 and 0.46 g of EMIM-Br were placed and heated to 160°C under N2 purge. 220 g (0.0770 equivalents of NCO) of the NCO-terminated prepolymer 1 from Example 1 were added dropwise via a dropping funnel over a period of 2 hours, while the reaction temperature was kept constant at 160-170°C. After the addition was complete, the mixture was stirred for 30 minutes at reaction temperature, and a sample was taken for IR spectroscopy. Complete conversion of the isocyanate was confirmed by the disappearance of the band at 2270 cm-1 (NCO vibration). The reaction mixture was cooled to approximately 100 °C and bottled. A viscous product with an EEW of 308.5 and a viscosity of 4250 mPas (measured at 80 °C) was obtained.

[0102] Example 5

[0103] In a 1L four-neck round-bottom flask equipped with a precision glass stirrer, thermocouple, dropping funnel (heatable to 80°C), and condenser, with N2 purge via a condenser, 440 g of DER 330 and 0.46 g of EMIM-Br were placed and heated to 160°C under N2 purge. Using a dropping funnel, 220 g (0.0770 equivalents of NCO) of the NCO-terminated prepolymer 2 from Example 2 were added dropwise over a period of 2 hours, while the reaction temperature was kept constant at 160-170°C. After the addition was complete, the mixture was stirred for 30 minutes at reaction temperature, and a sample was taken for IR spectroscopy. Complete conversion of the isocyanate was confirmed by the disappearance of the band at 2270 cm-1 (NCO vibration). The reaction mixture was cooled to approximately 100 °C and bottled. A viscous product with an EEW of 286.9 and a viscosity of 3340 mPas (measured at 80 °C) was obtained.

[0104] Example 6

[0105] In a 1L four-neck round-bottom flask equipped with a precision glass stirrer, thermocouple, dropping funnel (heatable to 80°C), and condenser, with N2 purge via condenser, 440 g of DER 330 and 0.46 g of EMIM-Br were placed and heated to 160°C under N2 purge. Using a dropping funnel, 220 g (0.0770 equivalents of NCO) of the NCO-terminated prepolymer 3 from Example 3 were added dropwise over a period of 2 hours, while the reaction temperature was kept constant at 160-170°C. After the addition was complete, the mixture was stirred for 30 minutes at reaction temperature, and a sample was taken for IR spectroscopy. Complete conversion of the isocyanate was confirmed by the disappearance of the band at 2270 cm-1 (NCO vibration). The reaction mixture was cooled to approximately 100 °C and bottled. A viscous product with an EEW of 297.0 and a viscosity of 4018 mPas (measured at 80 °C) was obtained.

[0106] Comparative Example 1 : Phenol-blocked prepolymer

[0107] 254.44 g of PolyTHF 2000 and 254.44 g of Polyvest EP HT were dried at 90 °C with stirring for 1 hour under vacuum. Subsequently, 0.08 g of Fomrez UL 28 was added and stirred for 5 minutes. 102.62 g of Vestanat IPDI was added, and the reaction was carried out for 2 hours under vacuum at 90 °C. A sample was taken and a free NCO content of 3.05% (theoretical NCO content: 3.00%) was determined. 138.24 g of Cardolite NX 2026 and 0.17 g of Fomrez UL 28 were added, and the reaction was carried out for 2 hours at 110 °C under vacuum. The conversion of the NCO-terminated prepolymer was verified by measuring the NCO content (<0.3%).

[0108] Comparative example 2: Toughness modifier according to US005480958

[0109] 123.58 g of Lupranat T 80 A and 676.42 g of Lupranol 1000 / 1 were mixed and heated to 80 °C under nitrogen. The reaction was carried out at 90 °C for 9 h. A prepolymer with a free NCO content of 3.74% (theoretical NCO content 3.80%) was obtained. 197.29 g of the resulting prepolymer were mixed with 452.57 g of Epikote 828 and 0.13 g of potassium acetate and heated to 160 °C. After one hour at 160 °C, a sample was taken, and the conversion of the prepolymer was verified by measuring the NCO content (0.01%). A viscous product with an EEW of 280.6 was obtained.

[0110] The following examples illustrate the use of the described toughening modifiers in 1-component, hot-curing adhesives.

[0111] For preparation, Epikote 828 LVEL, the appropriate toughener, Precal 30 S, and Omyacarb 5 GU were pre-mixed in a planetary mixer in the proportions shown in the table and heated to 80 °C. After mixing the solids, Araldite GT 6071 was added and cooled to 60 °C. HDK H18, Dyhard 100SF, and Dyhard UR700 were then added and stirred in the planetary mixer for 1 hour. The adhesives were cured at 175 °C for 30 minutes.

[0112] REPLACEMENT SHEET (RULE 26)

[0113] The comparison of Example 7 with Comparative Example 3 (containing the same amount of toughener) and the comparison of Example 8 with Comparative Example 4 (containing the same amount of toughener) shows that the tougheners described in the invention report show significantly better performance in both cases than the toughener according to

[0114] US005480958. Both impact strength and K1C and G1C show significantly higher values.

[0115] A comparison of Examples 7, 8, and 9 with Comparative Example 5, which represents the prior art as a phenol-blocked toughener, demonstrates the advantages of the tougheners described in this invention disclosure. The epoxy-terminated prepolymers described here allow direct reaction with the epoxy matrix in the adhesive formulation. The phenol-blocked prepolymers must first deblock at the curing temperature before they can react with the epoxy matrix. Both the Tg and the Young's modulus of Examples 7, 8, and 9 are significantly higher than Comparative Example 5.

[0116] REPLACEMENT SHEET (RULE 26)

Claims

Patent claims 1. A process for the preparation of an epoxide-terminated impact modifier, in which a) one or more polyisocyanates are mixed with b) two or more polyols, terminating at least one polyether polyol (b1) and at least one OH-terminated rubber (b2), at a molar ratio of isocyanate groups to OH groups of 10:1 to 1.5:1 and reacted to form an isocyanate-terminated prepolymer, and c) the isocyanate-terminated prepolymer is reacted with a polyepoxide (c) in the presence of an ionic liquid to form the epoxide-terminated impact modifier.

2. The method according to claim 1, characterized in that polyisocyanate (a) comprises an aliphatic polyisocyanate.

3. Method according to claim 1 or 2, characterized in that the OH-terminated rubber (b2) is hydroxyl-terminated polybutadiene.

4. Method according to one of claims 1 to 3, characterized in that the OH-terminated rubber (b2) has an OH functionality in the range of 1.7 to 2.

8.

5. A method according to any one of claims 1 to 4, characterized in that the polyether polyol (b1) is the alkoxylation product of a two- to three-functional starter molecule, wherein the alkylene oxide is selected from the group consisting of ethylene oxide, propylene oxide, 1,2-butylene oxide, tetrahydrofuran or mixtures thereof.

6. Method according to any one of claims 1 to 5, characterized in that the polyether polyol (b1) is polytetrahydrofuran.

7. Method according to any one of claims 1 to 6, characterized in that the polyether polyol (b1) has an OH number of 20 to 100 mg KOH / g.

8. Method according to any one of claims 1 to 7, characterized in that the polyepoxide is selected from the group consisting of polyglycidyl ethers of bisphenol A, bisphenol F, novolacs or mixtures thereof.

9. Method according to any one of claims 1 to 8, characterized in that the ionic liquid is selected from the group consisting of 1-Ethyl-3-methylimidazoliumchlorid, 1- Butyl-3-methylimidazoliumchlorid, 1-Ethyl-3- methylimidazoliummethylsulfonat, 1-Butyl-3-methylimidazoliummethansulfonat, 1-Ethyl-3- methylimidazoliumethylsulfat, 1- Butyl-3-methylimidazoliummethylsulfat, 1- Ethyl-3- methylimidazoliumdiethylphosphat, 1- Butyl-3-methylimidazoliumdimethylphosphat, 1- Ethyl-3-methylimidazoliumdicyanamid, 1- Butyl-3-methylimidazoliumdicyanamid, 1-Ethyl- 3-methylimidazoliumacetat, 1-Butyl-3-methylimidazoliumacetat, 1-Ethyl-3- methylimidazoliumthiocyanat, 1- Butyl-3-methylimidazoliumthiocyanat, 1-Ethyl-3- methylimidazoliumtetrafluoroborat, 1-Butyl-3-methylimidazoliumtetrafluoroborat, 1-Ethyl-3- methylimidazoliumtrifluormethansulfonat, 1-Butyl-3- methylimidazoliumtrifluormethansulfonat, 1 -Ethyl-3- methylimidazoliumbis(trifluormethansulfonyl)imid, 1-Butyl-3- methylimidazoliumbis(trifluormethansulfonyl)imid, 1-Ethyl-3- methylimidazoliumhexafluorophosphat, 1-Butyl-3-methylimidazoliumhexafluorophosphat,1-Ethyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium bromide, 1-ethyl-3-methylimidazolium p-toluenesulfonate and 1-butyl-3-methylimidazolium p-toluenesulfonate., 10. Method according to claim 9, characterized in that the ionic liquid contains 1-ethyl-3-methylimidazolium bromide.

11. Method according to any one of claims 1 to 10, characterized in that the conversion of the isocyanate-terminated prepolymer to the epoxy group-terminated impact modifier is carried out at temperatures of 120 to 250 °C.

12. Epoxy group-terminated impact modifier, obtainable according to any one of the preceding claims 1 to 11.

13. Use of an epoxy group-terminated impact modifier according to claim 12 in a one-component or two-component epoxy resin composition, preferably in a one-component or two-component epoxy resin adhesive, to increase the impact strength of the cured epoxy resin matrix.

14. One-component or two-component epoxy resin composition comprising at least one epoxy group-terminated impact modifier according to claim 12.

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