Adhesive with improved adhesion on epoxy resin adhesive remnants

Abstract

The invention relates to the use of an epoxy resin adhesive for adhesively bonding a substrate at least partially coated with a cured epoxy resin adhesive, characterised in that the adhesive comprises a resin component containing at least one epoxy resin and a curing agent component containing at least one amine with at least one aliphatic amino group, wherein the amine is selected from polyetheramines and linear or branched, but not cyclical, aliphatic polyamines, wherein the amine makes up at least 50% by weight of all the amine curing agents contained in the curing agent component with at least one amine hydrogen, based on all amine curing agents in the curing agent component. The use according to the invention enables substrates at least partially coated with a cured epoxy resin adhesive to be adhesively bonded such that a stable, weather-resistant adhesive bond is formed, and is particularly suitable for the repair of rotor blades in wind turbines.

Description

[0001] ADHESIVE WITH IMPROVED ADHESION TO EPOXY RESIN ADHESIVE RESIDUE

[0002] Technical area

[0003] The invention relates to the use of an adhesive for bonding a substrate at least partially coated with a cured epoxy resin adhesive and to an adhesive bond obtained from this use.

[0004] State of the art

[0005] Wind turbines are playing an increasingly important role in energy supply, particularly as an increasingly important environmentally friendly energy source in terms of sustainability. Wind turbines are by far the most important form of wind energy utilization. Today's wind turbines almost exclusively have three rotor blades, which are positioned at a sufficient height within the wind flow. These rotor blades extract energy from the wind flow and feed it into a generator to generate electricity. Rotor blades are typically made of glass-fiber-reinforced plastic (GRP) and are usually manufactured in a half-shell sandwich construction with stiffening spars or webs inside. During rotor blade production, the half-shells are usually bonded together using a structural adhesive, such as SikaPower®-830 from Sika.Epoxy resin adhesives, in particular, are highly suitable for such structural bonding due to their robust mechanical properties and adhesive strength, especially when they contain an impact modifier (toughener), which imparts sufficient impact strength and toughness to the otherwise often brittle epoxy adhesives. Today's adhesives are particularly suitable for the production of new rotor blades.

[0006] Epoxy resin adhesives are satisfactory for this purpose. However, wind turbine rotor blades are exposed to very strong forces and damaging environmental influences such as collisions with ice particles and water droplets, which lead to damage to the rotor blades over the course of their use. From an economic perspective, it is not desirable to continually replace the rotor blades with new replacement blades; instead, attempts are made to repair damage and, at most, replace or repair parts of the rotor blade. The goal of such replacement or repair operations is to restore the damaged area to its original structural integrity, as it was after the rotor blade was manufactured. During repairs, it is common for adhesive residues from the original bond from the initial production process to remain. These often cannot be removed completely.However, such cured epoxy adhesive residues are much more difficult to rebond or re-bond than a clean, new substrate. Since these adhesive residues are almost impossible to remove completely, they can significantly weaken a second bond. A freshly applied epoxy resin adhesive, even if the same adhesive is used in the original production, cannot develop sufficient adhesion to the possibly contaminated, cured adhesive residue to withstand the high mechanical stress. Furthermore, the goal with the repair adhesive after repair is to achieve a bond equivalent to that achieved during the original production. This is a major problem when repairing wind turbine rotor blades, since repaired rotor blades are exposed to the same influences and must meet the same mechanical stability requirements as newly manufactured ones.

[0007] There is therefore a need for an adhesive that easily adheres to residues of cured epoxy resin adhesives and that can be used for such structural bonding.

[0008] Description of the invention

[0009] The object of the present invention is therefore to provide an adhesive for bonding a substrate at least partially coated with a cured epoxy resin adhesive, which enables a resilient adhesive bond with high resistance to weathering and mechanical stress, even without complex pretreatment or complete removal of the cured epoxy resin adhesive. Surprisingly, this object is achieved by using an adhesive according to claim 1.The epoxy resin adhesive used comprises a hardener component containing at least one amine A1 having at least one aliphatic amino group, wherein amine A1 is selected from polyetheramines and linear or branched, but not cyclic, aliphatic polyamines, and wherein the amine A1 makes up at least 50% by weight of all amine hardeners A containing at least one amine hydrogen in the hardener component, based on all amine hardeners A in the hardener component.

[0010] Surprisingly, an epoxy resin adhesive with such a hardener component enables excellent, strong adhesion to substrates that are at least partially coated with a cured epoxy resin adhesive. Conventional state-of-the-art epoxy resin adhesives are usually unable to establish sufficient adhesion to such substrates, as the bond between the freshly applied epoxy resin adhesive and the residues of the original, fully cured epoxy resin adhesive lacks sufficient adhesion strength.

[0011] The inventive use enables the bonding of substrates such as those found, for example, in wind turbine rotor blades that are to be repaired. This allows for the production of adhesive bonds that are sufficiently strong and durable that the repaired rotor blade can exhibit a similar stability and service life to a newly manufactured one. With the inventive use, cost-effective repairs can be carried out instead of complete replacement measures, which not only makes economic sense but also supports current efforts toward increased sustainability in terms of raw material and energy consumption and reduced downtime of the wind turbine.

[0012] The adhesives according to the invention in the process according to the invention enable adhesive bonds with tensile shear strengths, measured according to DIN EN 1465, of at least 10 MPa, preferably at least 15 MPa, in particular at least 20 MPa or higher.

[0013] Ways to implement the invention

[0014] The invention relates to the use of an adhesive for bonding a substrate at least partially coated with a cured epoxy resin adhesive, characterized in that the adhesive comprises a resin component containing at least one epoxy resin and a hardener component containing at least one amine A1 having at least one aliphatic amino group, wherein amine A1 is selected from polyetheramines and linear or branched, but not cyclic, aliphatic polyamines, wherein the amine A1 makes up at least 50% by weight of all amine hardeners A containing at least one amine hydrogen in the hardener component, based on all amine hardeners A in the hardener component.

[0015] The hydrogen atoms of primary and secondary amine groups are called “amine hydrogen”.

[0016] The "amine hydrogen equivalent weight" is the mass of an amine or amine-containing compound containing one molar equivalent of amine hydrogen. It is expressed in the unit "g / eq."

[0017] A “primary amino group” is an amino group that is bonded to a single organic residue and carries two hydrogen atoms; a “secondary amino group” is an amino group that is bonded to two organic residues, which may also together be part of a ring, and carries one hydrogen atom; and a “tertiary amino group” is an amino group that is bonded to three organic residues, which may also be part of one or more rings in twos or threes, and does not carry a hydrogen atom.

[0018] The term "cured epoxy resin adhesive" with which the substrate is coated in the inventive use refers to an epoxy resin adhesive that has been fully cured by heat treatment for several hours and / or storage for at least one month at room temperature. This cured epoxy resin adhesive is already present on the substrate in this cured state when the inventive use is carried out.

[0019] The "epoxide equivalent weight" is the mass of an epoxy-containing compound or composition that contains one molar equivalent of epoxy groups. It is expressed in the unit "g / eq." Substance names beginning with "poly," such as polyamine or polyepoxide, refer to substances that formally contain two or more of the functional groups mentioned in their name per molecule.

[0020] A “thinner” is a substance that is soluble in an epoxy resin and reduces its viscosity, but which is not chemically bound into the epoxy resin polymer during curing.

[0021] The “pot life” of an adhesive is the maximum period of time from mixing the components and applying the adhesive during which the mixed adhesive is in a sufficiently flowable state and can wet the substrate surfaces well.

[0022] The “open time” of an adhesive is the maximum possible time period for a force-locking connection between mixing the adhesive and joining the parts to be bonded.

[0023] The term “molecular weight” refers to the molar mass (in grams per mole) of a molecule. The term “average molecular weight” refers to the number average M na polydisperse mixture of oligomeric or polymeric molecules, which is usually determined by gel permeation chromatography (GPC) against polystyrene as a standard.

[0024] “Room temperature” is defined as a temperature of 23 °C.

[0025] All industry standards and norms mentioned in this document refer to the versions valid at the time of filing the initial application, unless otherwise stated.

[0026] Percentages by weight (% by weight) refer to the mass fraction of a component of a composition relative to the total composition, unless otherwise stated. The terms "mass" and "weight" are used synonymously in this document.

[0027] The resin and hardener components of the adhesive are stored separately in separate containers and mixed together only shortly before or during application. A suitable epoxy resin is obtained in a known manner, particularly from the oxidation of olefins or from the reaction of epichlorohydrin with polyols, polyphenols, or amines.

[0028] Aromatic epoxy resins are preferred, in particular the glycidyl ethers of:

[0029] - Bisphenol-A, bisphenol-F, or bisphenol-A / F, where A stands for acetone and F for formaldehyde, which served as starting materials for the production of these bisphenols. In the case of bisphenol-F, positional isomers may also be present, in particular derived from 2,4'- or 2,2'-hydroxyphenylmethane.

[0030] - Dihydroxybenzene derivatives such as resorcinol, hydroquinone or pyrocatechol,

[0031] - weiteren Bisphenolen oder Polyphenolen wie Bis(4-hydroxy-3-methylphenyl)- methan, 2,2-Bis(4-hydroxy-3-methylphenyl)propan (Bisphenol-C), Bis(3,5- dimethyl-4-hydroxyphenyl)methan, 2,2-Bis(3,5-dimethyl-4-hydroxyphenyl)pro- pan, 2,2-Bis(3,5-dibromo-4-hydroxyphenyl)propan, 2,2-Bis(4-hydroxy-3-tert.bu- tylphenyl)propan, 2,2-Bis(4-hydroxyphenyl)butan (Bisphenol-B), 3,3-Bis(4- hydroxyphenyl)pentan, 3,4-Bis(4-hydroxyphenyl)hexan, 4,4-Bis(4-hydroxy- phenyl)heptan, 2,4-Bis(4-hydroxyphenyl)-2-methylbutan, 2,4-Bis(3,5-dimethyl-4- hydroxyphenyl)-2-methylbutan, 1 ,1-Bis(4-hydroxyphenyl)cyclohexan (Bisphe- nol-Z), 1 ,1-Bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexan (Bisphenol-TMC),

[0032] 1,1-Bis(4-hydroxyphenyl)-1-phenylethane, 1,4-Bis[2-(4-hydroxyphenyl)-2-propyl]benzene (Bisphenol-P), 1,3-Bis[2-(4-hydroxyphenyl)-2-propyl]benzene (Bisphenol-M), 4,4'-Dihydroxydiphenyl (DOD), 4,4'-Dihydroxybenzophenone, bis(2-hydroxynaphth-1-yl)methane, bis(4-hydroxynaphth-1-yl)methane, 1,5-dihydroxynaphthalene, tris(4-hydroxyphenyl)methane, 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane, bis(4-hydroxyphenyl)ether or bis(4-hydroxyphenyl)sulfone,

[0033] - Novolaks, which are in particular condensation products of phenol or cresols with formaldehyde or paraformaldehyde or acetaldehyde or crotonaldehyde or isobutyraldehyde or 2-ethylhexanal or benzaldehyde or furfural,

[0034] - aromatic amines, such as aniline, toluidine, 4-aminophenol, 4,4'-methylenediphenyldiamine, 4,4'-methylenediphenyldi-(N-methyl)amine, 4,4'-[1,4-phenylenebis(1-methylethylidene)]bisaniline (bisaniline-P) or 4,4'-[1,3-phenylenebis(1-methylethylidene)]bisaniline (bisaniline-M). Other suitable epoxy resins are aliphatic or cycloaliphatic polyepoxides, especially

[0035] - Glycidyl ethers of saturated or unsaturated, branched or unbranched, cyclic or open-chain di-, tri- or tetrafunctional C2 to C50 alcohols, in particular ethylene glycol, propylene glycol, butylene glycol, hexanediol, octanediol, polypropylene glycols, dimethylolcyclohexane, neopentyl glycol, dibromoneopentyl glycol, castor oil, trimethylolpropane, trimethylolethane, pentaerythrol, sorbitol or glycerol, or alkoxylated glycerol or alkoxylated trimethylolpropane;

[0036] - a hydrogenated bisphenol-A, -F or -A / F liquid resin, or the glycidylation products of hydrogenated bisphenol-A, -F or -A / F;

[0037] - an N-glycidyl derivative of amides or heterocyclic nitrogen bases, such as triglycidyl cyanurate or triglycidyl isocyanurate, or reaction products of epichlorohydrin with hydantoin.

[0038] - Epoxy resins from the oxidation of olefins, such as in particular vinylcyclohexene, dicyclopentadiene, cyclohexadiene, cyclododecadiene, cyclododecatriene, isoprene, 1,5-hexadiene, butadiene, polybutadiene or divinylbenzene.

[0039] Other suitable epoxy resins are those resulting from the reaction of bio-based hydroxy-functional raw materials with epichlorohydrin, in particular vanillin-based epoxy resins such as diglycidyl ethers of vanillin alcohol, or glycerol-based epoxy resins.

[0040] Preferably, the epoxy resin is a liquid resin or a mixture containing two or more epoxy liquid resins.

[0041] An “epoxy liquid resin” is a technical polyepoxide with a glass transition temperature below 25°C.

[0042] If necessary, the resin component also contains portions of solid epoxy resin.

[0043] The resin component particularly preferably contains at least one aromatic liquid epoxy resin, in particular a bisphenol A diglycidyl ether, a bisphenol F diglycidyl ether, or a phenol-formaldehyde novolak glycidyl ether, with the phenol-formaldehyde novolak glycidyl ether preferably having an average functionality in the range of 2.3 to 4, preferably 2.5 to 3. These epoxy resins are very hydrophobic and have a low viscosity for an epoxy resin. They enable good processability, rapid curing, and high adhesive strengths.

[0044] The aromatic epoxy liquid resin preferably has an average epoxy equivalent weight of 150 to 250 g / eq.

[0045] The resin component preferably additionally contains at least one reactive diluent containing epoxy groups.

[0046] Particularly suitable for this purpose are 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane di- or triglycidyl ether, phenyl glycidyl ether, cresyl glycidyl ether, guaiacol glycidyl ether, 4-methoxyphenyl glycidyl ether, pn-butylphenyl glycidyl ether, p-tert. butylphenyl glycidyl ether, 4-nonylphenyl glycidyl ether, 4-dodecylphenyl glycidyl ether, cardanol glycidyl ether, benzyl glycidyl ether, allyl glycidyl ether, butyl glycidyl ether, hexyl glycidyl ether, 2-ethylhexyl glycidyl ether, or glycidyl ethers of natural alcohols such as in particular Cs to C10 or C12 to C14 or C13 to C15 alkyl glycidyl ether.

[0047] Preferred reactive diluents are 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, p-tert-butylphenyl glycidyl ether, cardanol glycidyl ether or Cs to C10 or C12 to C14 or C13 to C18 alkyl glycidyl ether.

[0048] 1,4-Butanediol diglycidyl ether and / or 1,6-hexanediol diglycidyl ether are particularly preferred. Such an adhesive enables particularly high adhesive strengths with good water resistance.

[0049] The weight ratio between aromatic epoxy liquid resins and reactive diluents containing epoxy groups is preferably in the range from 60 / 40 to 95 / 5, in particular 70 / 30 to 95 / 5.

[0050] The hardener component contains at least one amine A1 with at least one aliphatic amino group, in particular an aliphatic primary amino group, where amine A1 is selected from polyetheramines and linear or branched, but not cyclic, aliphatic polyamines. Amine A1 makes up at least 50% by weight, preferably at least 55% by weight, in particular at least 60% by weight, in particular at least 75% by weight of all amine hardeners A containing at least one amine hydrogen contained in the hardener component, based on all amine hardeners A in the hardener component. In some embodiments, the amine A1 makes up at least 80% by weight, in particular at least 90% by weight, preferably at least 95% by weight, particularly preferably at least 99% by weight, most preferably 100% by weight of all amine hardeners A containing at least one amine hydrogen in the hardener component, based on all amine hardeners A in the hardener component.Amine A1 can also represent a mixture of several different amines A1.

[0051] Suitable amines as A1 include, for example, commercially available polyamines with aliphatically bonded amino groups, such as those commonly used for curing epoxy resins. However, similarly common cycloaliphatic polyamines such as isophoronediamine (IPDA) or arylaliphatic polyamines such as m-xylylenediamine (MXDA) are surprisingly unsuitable as A1, as they do not provide the desired adhesive strength and resistance for the inventive use.

[0052] The amine A1 preferably contains at least two amine hydrogens, in particular at least three amine hydrogens.

[0053] Amine A1 is preferably selected from the group consisting of 2-dimethylaminoethylamine, 3-dimethylaminopropylamine (DMAPA), 4-dimethylaminobutylamine, 6-dimethylaminohexylamine, 2-(2-dimethylaminoethylamino)ethylamine, 2-(3-dimethylaminopropylamino)ethylamine, 3-(2-dimethylaminoethylamino)propylamine, 3-(3-dimethylaminopropylamino)propylamine (DMAPAPA), bis(2-dimethylaminoethyl)amine, bis(3-dimethylaminopropyl)amine, and bis(6-dimethylaminohexyl)amine. 3-(3-dimethylaminopropylamino)propylamine (DMAPAPA) is particularly preferred as amine A1. It is low-odor, toxicologically advantageous, commercially readily available, and enables very high adhesive strengths with good water resistance of the bond.

[0054] Another preferred amine A1 is 3-dimethylaminopropylamine (DMAPA). It has a particularly high concentration of dimethylamino groups and is readily available commercially.

[0055] Likewise preferably, the amine A1 is selected from the group consisting of 1,5-diamino-2-methylpentane (MPMD), 1,6-hexanediamine, 2,2(4),4-trimethyl-1,6-hexanediamine (TMD), 2-butyl-2-ethyl-1,5-pentanediamine (C11-neodiamine), diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), dipropylenetriamine (DPTA), N-(2-aminoethyl)-1,3-propanediamine (N3-amine), N,N'-bis(3-aminopropyl)ethylenediamine (N4-amine), bis(1,6-hexylene)triamine (BHMT), and combinations of two or more of these amines.

[0056] In particularly preferred embodiments of the use according to the present invention, the amine A1 is selected from the group consisting of 2-dimethylaminoethylamine, 3-dimethylaminopropylamine, 4-dimethylaminobutylamine, 6-dimethylaminohexylamine, 2-(2-dimethylaminoethylamino)ethylamine, 2-(3-dimethylaminopropylamino)ethylamine, 3-(2-dimethylaminoethylamino)propylamine, 3-(3-dimethylaminopropylamino)propylamine, 1,5-diamino-2-methylpentane, 1,6-hexanediamine, 2,2(4),4-trimethyl-1,6-hexanediamine, 2-butyl-2-ethyl-1,5-pentanediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, dipropylenetriamine, N-(2-aminoethyl)-1 ,3-propanediamine, N,N'-bis(3-aminopropyl)ethylenediamine, bis(1,6-hexylene)triamine, polyetheramines, and combinations of two or more of these amines.

[0057] In the same or other particularly preferred embodiments of the use according to the present invention, amine A1 comprises at least one polyetheramine, which is preferably a polyoxyalkylenediamine or polyoxyalkylenetriamine, in particular a polyoxyalkylenediamine, preferably with a number-average molecular weight between 170 and 500 g / mol. In some preferred embodiments thereof, amine A1 consists of at least one polyetheramine.

[0058] Suitable polyetheramines for amine A1 are, for example, aliphatic primary diamines which contain ether groups, e.g. bis(2-aminoethyl) ether, 3,6-dioxaoctane-1,8-diamine, 4,7-dioxadecane-1,10-diamine, 4,7-dioxadecane-2,9-diamine, 4,9-dioxadodecane-1,12-diamine, 5,8-dioxadodecane-3,10-diamine, 4,7,10-trioxatridecane-1,13-diamine and higher oligomers of these diamines, bis-(3-aminopropyl)polytetrahydrofurans and other polytetrahydrofuran diamines with molecular weights in the range of, for example, 350 to 2000, and also polyoxyalkylenediamines. The latter are typically products of the amination of polyoxyalkylenediols and can, for example, They can be purchased, for example, under the name Jeffamine® (from Huntsman), under the name Polyetheramine (from BASF) or under the name PC Amine® (from Nitroil).Particularly suitable polyoxyalkylenediamines are Jeffamine® D-230, Jeffamine® D-400, Jeffamine® D-2000, Polyetheramine D 230, Polyetheramine D 400 and Polyetheramine D 2000, PC Amine® DA 250, PC Amine® DA 400, PC Amine® DA 650 and PC Amine® DA 2000.

[0059] Most preferred polyetheramines are available, for example, under the trade name Jeffamine® from Huntsman, in particular Jeffamine® D-230.

[0060] The hardener component contains amine hardener A with at least one amine hydrogen, where amine A1 must constitute at least 50% by weight of amine hardener A. In some embodiments, amine hardener A can consist entirely of amines A1.

[0061] Amine hardener A can, however, preferably also contain other amine hardeners with at least one amine hydrogen, which are not amine hardeners A1. These other amine hardeners can make up to 50% by weight, preferably up to 45% by weight, in particular up to 40% by weight or less of all amine hardeners A with at least one amine hydrogen. Preferably, the hardener component contains, in addition to amine A1, other amine hardeners, which, together with amine A1, make up the total of amine hardeners A with at least one amine hydrogen.

[0062] Further preferred amine hardeners are cycloaliphatic or arylaliphatic polyamines having at least 2, in particular at least 3, amines, such as in particular 1,2-, 1,3- or 1,4-diaminocyclohexane, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, bis(4-aminocyclohexyl)methane, bis(4-amino-3-methylcyclohexyl)methane, bis(4-amino-3-ethylcyclohexyl)methane, bis(4-amino-3,5-dimethylcyclohexyl)methane, bis(4-amino-3-ethyl-5-methylcyclohexyl)methane, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane (isophoronediamine or IPDA), 2(4)-methyl-1,3-diaminocyclohexane, 2,5(2,6)-bis(aminomethyl)bicyclo[2.2.1]heptane (NBDA), 3(4),8(9)-bis(aminomethyl)tricyclo[5.2.1 .0 2 6]-decane, 1,4-diamino-2,2,6-trimethylcyclohexane (TMCDA), 1,8-menthanediamine, 3,9-bis(3-aminopropyl)-2,4,8,10-tetraoxaspiro[5.5]undecane, 1,3-bis(aminomethyl)-benzene (MXDA), 1 ,4-Bis(aminomethyl)benzene, bis(2-aminoethyl)ether, 3,6-dioxa-octane-1,8-diamine, 4,7-dioxadecane-1,10-diamine, 4,7-dioxadecane-2,9-diamine, 4,9-dioxadodecane-1,12-diamine, 5,8-dioxadodecane-3, 10-diamine, 4,7, 10-trioxatridecan-1, 13-diamine or higher oligomers of these diamines, cycloaliphatic ether group-containing diamines from the propoxylation and subsequent amination of 1,4-dimethylolcyclohexane, available in particular as Jeffamine® RFD-270 (from Huntsman), 2-aminoethylpiperazine, N-benzyldiethylenetriamine, N-benzyltriethylenetetramine, N,N'-dibenzyltriethylenetetramine, N"-benzyl-N,N'-bis(3-aminopropyl)ethylenediamine, N",N"'-dibenzyl-N,N'-bis(3-aminopropyl)ethylenediamine, N-benzyl-1,2-propanediamine, N,N'-dibenzyl-1,2-propanediamine, N-benzyl-1,3-bis(aminomethyl)benzene, N,N'-dibenzyl-1,3-bis(aminomethyl)benzene, N-(2-ethylhexyl)-1,3-bis(aminomethyl)benzene, N,N'-bis(2-ethylhexyl)-1,3-bis(aminomethyl)benzene, styrenated MXDA (available as Gaskamine® 240 from Mitsubishi Gas Chemical), adducts of the above-mentioned or further polyamines with epoxides or epoxy resins, in particular adducts with diepoxides or monoepoxides, or polyamidoamines, in particular reaction products of a mono- or polybasic carboxylic acid or its ester or anhydride, in particular a dimer fatty acid, with an aliphatic, cycloaliphatic or aromatic polyamine used in stoichiometric excess, in particular a polyalkyleneamine such as DETA or TETA, or Mannich bases, in particular phenalkamines, i.e. reaction products of phenols, in particular cardanol, with Aldehydes, especially formaldehyde, and polyamines.

[0063] The amine hardener A preferably contains at least one further amine selected from the group consisting of TMD, 1,2-, 1,3- or 1,4-diaminocyclohexane, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, bis(4-aminocyclohexyl)methane, IPDA, 2(4)-methyl-1,3-diaminocyclohexane, MXDA, and phenalkamines.

[0064] Preferred among these are TMD, 1,3-bis(aminomethyl)cyclohexane, IPDA, MXDA, and phenalkamine.

[0065] Particularly suitable phenalkamines are reaction products of cardanol with formaldehyde and polyamines. Phenalkamines that also contain amide groups are particularly suitable as phenalkamides. Particularly suitable polyamidoamines are reaction products of dimer fatty acids with polyalkyleneamines, such as DETA, TETA, or TEPA.

[0066] In particularly preferred embodiments of the use according to the present invention, the amine A comprises at least one phenalkamine, which is a reaction product of cardanol with formaldehyde and at least one aliphatic polyamine, in particular an aliphatic polyamine as described above as amine A1.

[0067] Cardanol (CAS Registry Number: 37330-39-5) is a phenolic lipid derived from anacardic acid, the main component of cashew nut shell liquid (CNSL), a byproduct of cashew nut processing. The name of the substance is derived from the genus Anacardium, which includes the cashew tree, Anacardium occidentale. The structure is shown in formula (I).

[0068] R - CisH3i-n; n - 0,2, 4, 6

[0069] The term cardanol is used for the decarboxylated derivatives obtained by thermal decomposition of one of the naturally occurring anacardic acids. This compound is more than one, as the side chain composition varies in its degree of unsaturation. The triunsaturated cardanol, the major component (41%), is shown in formula (II) below. The remaining cardanol is 34% monounsaturated, 22% diunsaturated, and 2% saturated.

[0070] Particularly preferred are phenalkamines or phenalkamides, in particular solvent-free phenalkamines or phenalkamides as marketed commercially by Cardolite, in particular phenalkamines such as Cardolite® NC-658, Cardolite® NC-540, Cardolite® NC-558, Cardolite® LITE 2002, and phenalkamides such as Cardolite® LITE 3025, LITE 3040 or LITE 3060 (all from Cardolite).

[0071] Hardener A can preferably contain a combination of two or more of the mentioned further amines. In the most preferred embodiment, the hardener component contains, as amine A1, a combination of 3-(3-dimethylaminopropylamino)propylamine (DMAPAPA) and at least one polyetheramine.

[0072] In the same or other particularly preferred embodiments of the use according to the present invention, the hardener component contains between 20% by weight and 75% by weight, preferably between 25% by weight and 70% by weight, in particular between 30% by weight and 60% by weight, of amine A1, based on the total hardener component.

[0073] The preferred amines and amounts enable adhesives with particularly high adhesive strengths and high resistance to moisture.

[0074] The adhesive preferably contains additional ingredients, which are present as part of the resin and / or hardener component and / or as another separate component. Components reactive toward amine hydrogens are preferably present as part of the resin component. Components reactive toward epoxy groups are preferably present as part of the hardener component.

[0075] The adhesive preferably contains at least one further ingredient selected from thinners, fillers, adhesion promoters, accelerators and surface-active compounds.

[0076] Suitable thinners are particularly those with a boiling point of at least 200 °C at atmospheric pressure, in particular 2-phenoxyethanol, 2-benzyloxyethanol, benzyl alcohol, ethylene glycol dibutyl ether, ethylene glycol diphenyl ether, diethylene glycol, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol di-n-butylyl ether, propylene glycol phenyl ether, dipropylene glycol, dipropylene glycol di-n-butyl ether, diphenylmethane, diisopropylnaphthalene, propylated biphenyl, tert-butylphenol, nonylphenol, dodecylphenol, cardanol (from cashew shell oil, containing as main components 3-(7-pentadecenyl)phenol, 3-(7, 10, 14-pentadecatrienyl)phenol and 3-(7,10-pentadecadienyl)phenol), styrenated phenol, bisphenols, aromatic hydrocarbon resins, in particular types containing phenol groups, adipates, sebacates, phthalates, benzoates, organic phosphoric or sulfonic acid esters or sulfonamides.

[0077] Preferred are benzyl alcohol, styrenated phenol, ethoxylated phenol such as in particular 2-phenoxyethanol, aromatic hydrocarbon resins containing phenol groups, in particular the Novares® types LS 500, LX 200, LA 300 or LA 700 (from Rütgers), diisopropylnaphthalene, propylated biphenyl or cardanol.

[0078] Preferably, the adhesive contains only a low content of thinners.

[0079] The adhesive preferably contains a maximum of 30 parts by weight, preferably a maximum of 20 parts by weight, particularly preferably a maximum of 10 parts by weight, and especially a maximum of 5 parts by weight, of thinner per 100 parts by weight of the sum of all epoxy and amine group-containing components. This enables bonds with particularly high moisture resistance.

[0080] Suitable fillers are, in particular, ground or precipitated calcium carbonates, which may be coated with fatty acids, in particular stearates, barite (barite), talc, quartz flour, quartz sand, silicon carbide, iron mica, dolomite, wollastonite, kaolin, mica (potassium aluminum silicate), molecular sieve, aluminum oxide, aluminum hydroxide, magnesium hydroxide, silica, cement, gypsum, fly ash, carbon black, graphite, metal powders such as aluminum, copper, iron, zinc, silver or steel, PVC powder or hollow spheres.

[0081] The adhesive preferably contains mineral fillers, in particular selected from calcium carbonate, barite, talc, silica, quartz flour, quartz sand, kaolin, and combinations of these fillers. A particularly preferred filler is the combination of calcium carbonate (lime) and silica.

[0082] The adhesive preferably contains 10 to 60% by weight, in particular 15 to 50% by weight, of mineral fillers based on the total adhesive.

[0083] Suitable accelerators are, in particular, acids or compounds hydrolyzable to acids, in particular organic carboxylic acids such as acetic acid, benzoic acid, salicylic acid, 2-nitrobenzoic acid, lactic acid, organic sulfonic acids such as methanesulfonic acid, p-toluenesulfonic acid or 4-dodecylbenzenesulfonic acid, sulfonic acid esters, other organic or inorganic acids or acid esters; furthermore, nitrates such as, in particular, calcium nitrate; tertiary amines, imidazoles, ammonium salts, amidines, guanidines, phenols, phenol resins or Mannich bases such as, in particular, 2,4,6-tris(dimethylaminomethyl)phenol, or compounds containing mercapto groups.

[0084] Preferred accelerators are acids, nitrates, tertiary amines or Mannich bases, in particular salicylic acid, calcium nitrate or 2,4,6-tris(dimethylaminomethyl)phenol or a combination of these accelerators.

[0085] Suitable surface-active compounds are in particular thickeners, wetting agents, defoamers or deaerators.

[0086] The adhesive is preferably not water-based. It preferably contains less than 5% by weight, in particular less than 1% by weight, of water based on the total adhesive.

[0087] The composition preferably comprises, in particular in the resin component, at least one impact modifier, preferably a polyurethane-based impact modifier.

[0088] In this document, "impact modifier" refers to an additive to an epoxy resin matrix that, even at low concentrations in the composition, e.g., from 1 to 25 wt.%, based on the total composition, significantly increases the toughness of the cured matrix, allowing it to withstand higher bending, tensile, impact, and / or impact loads before the cured composition cracks or breaks. The measurement method according to ISO 11343 is typically used as a measure of impact strength.

[0089] Suitable impact modifiers I include so-called core-shell polymers. Core-shell polymers consist of an elastic core polymer and a rigid shell polymer. Particularly suitable core-shell polymers consist of a core of elastic acrylate or butadiene polymer wrapped around a rigid shell of a stiff thermoplastic polymer. This core-shell structure forms either spontaneously through demixing of a block copolymer or is predetermined by polymerization as a latex or suspension polymerization with subsequent grafting.

[0090] Preferred core-shell polymers are so-called MBS polymers, which are commercially available under the trade names Clearstrength® from Arkema, Paraloid® from Dow (formerly Rohm and Haas), or F-351® from Zeon. Core-shell polymer particles that are already in the form of dried polymer latex are particularly preferred. Examples are GENIOPERL® M23A from Wacker with a polysiloxane core and acrylate shell, radiation-crosslinked rubber particles of the NEP series manufactured by Eliokem, or Nanoprene® from Lanxess or Paraloid® EXL from Dow. Other comparable examples of core-shell polymers are offered under the name Albidur® by Evonik Hanse GmbH, Germany. Also suitable are nanoscale silicates in an epoxy matrix, such as those offered under the trade name Nonopox® by Evonik Hanse GmbH.

[0091] Another suitable impact modifier is a liquid rubber which is a carboxyl- or epoxy-terminated acrylonitrile / butadiene copolymer or a derivative thereof. Such liquid rubbers are commercially available, for example, under the name Hypro® (formerly Hycar®) CTBN and CTBNX and ETBN from Emerald Performance Materials LLC. Derivatives which are, in particular, epoxy-containing, elastomer-modified prepolymers, such as those from the Polydis® product line, Struktol® (Schill + Seilacher Group, Germany) or from the Albipox® product line (Evonik Hanse GmbH, Germany). In another embodiment, the impact modifier is a polyacrylate liquid rubber which is fully miscible with liquid epoxy resins and only breaks down into microdroplets when the epoxy resin matrix cures. Such polyacrylate liquid rubbers are, for example, B. available under the name 20208-XPA from Dow (formerly Rohm and Haas).

[0092] A reaction product of a carboxylated nitrile solid rubber with excess epoxy resin is also suitable as an impact modifier. A polymer of formula (III) is also suitable and preferred as an impact modifier.

[0093] In this formula, n and n' are independently values ​​from 0 to 7, preferably 0 or 1 or 2, with the proviso that n + n' is a value from 1 to 8, in particular 1 or 2.

[0094] In addition, R 1 a linear or branched polyurethane prepolymer with n+n' isocyanate groups after removal of all terminal isocyanate groups. R 2 and R 3 are independently aliphatic, cycloaliphatic, aromatic or arylaliphatic groups having 1 to 20 C atoms and optionally heteroatoms selected from O, N and S, in particular O and N.

[0095] If the substituents R 2 and R 3reactive towards epoxy groups, the impact modifier of formula (III) is part of the hardener component. If the substituents R 2 and R 3 reactive towards amino groups, the impact modifier of formula (III) is part of the resin component.

[0096] Impact modifiers that are non-reactive or compatible with both components can be incorporated into either one or both components. This principle applies to all impact modifiers, not just those of formula (III).

[0097] In a preferred embodiment of an impact modifier according to formula (V), R 1 a linear polyurethane prepolymer containing at least n+n' terminal isocyanate groups, after removal of n+n' terminal isocyanate groups;

[0098] R 2 and R 3are residues of cardanol after removal of the hydroxyl hydrogen atom and are bonded via the oxygen atom. These types of impact modifiers are particularly preferred for the compositions of this invention. Cardanol is described above in connection with formulas (I) and (II).

[0099] The polyurethane prepolymers used for polyurethane-based impact modifiers can be produced from all commercially available polyisocyanates, especially diisocyanates, and all commercially available polyols, especially diols. These are preferably produced from the raw materials and according to the manufacturing processes described in WO / 2020 / 249741 on pages 20-27. Polyether diols and 4,4'-, 2,4'-, or 2,2'-diphenylmethane diisocyanates (MDI) are particularly preferred as raw materials.

[0100] In a particularly preferred use according to the present invention, the impact modifier is prepared from the reaction of an isocyanate-functional polyurethane polymer with cardanol. The isocyanate-functional polyurethane polymer is preferably prepared from a polyether diol and 4,4'-, 2,4'-, or 2,2'-diphenylmethane diisocyanate (MDI).

[0101] The adhesive may contain other auxiliary substances and additives, such as

[0102] - other reactive diluents, in particular epoxidized soybean oil or linseed oil, compounds containing acetoacetate groups, butyrolactone, carbonates, aldehydes, isocyanates or silicones containing reactive groups,

[0103] - solvents,

[0104] - other compounds containing dimethylamino groups, in particular (meth)acrylamides such as 3-dimethylaminopropylmethacrylamide,

[0105] - Compounds containing mercapto groups, in particular liquid mercaptan-terminated polysulfide polymers, mercaptan-terminated polyoxyalkylene ethers, mercaptan-terminated polyoxyalkylene derivatives, polyesters of thiocarboxylic acids, 2,4,6-trimercapto-1,3,5-triazine, triethylene glycol dimercaptan or ethanedithiol, - Polymers, in particular polyamides, polysulfides, polyvinyl formal (PVF), polyvinyl butyral (PVB), polyurethanes (PUR), polymers with carboxyl groups, polyamides, butadiene-acrylonitrile copolymers, styrene-acrylonitrile copolymers, butadiene-styrene copolymers, homo- or copolymers of unsaturated monomers, in particular from the group comprising ethylene, propylene, butylene, isobutylene, isoprene, vinyl acetate or alkyl (meth)acrylates, in particular chlorosulfonated polyethylenes or Fluorine-containing polymers or sulfonamide-modified melamines,

[0106] - fibres, in particular glass fibres, carbon fibres, metal fibres, ceramic fibres, plastic fibres such as polyamide fibres or polyethylene fibres or bio-based fibres such as wood fibres, cellulose fibres, hemp fibres, flax (linen), jute or coconut fibres,

[0107] - Nanofillers, especially carbon nanotubes,

[0108] - Pigments, in particular titanium dioxide, iron oxides or chromium(III) oxide,

[0109] - adhesion promoters, especially organoalkoxysilanes,

[0110] - flame-retardant substances or

[0111] - other additives, in particular stabilizers against oxidation, heat, light or UV radiation or biocides.

[0112] A preferred adhesive for use according to the invention contains, based on the resin component

[0113] 40 to 90% by weight, preferably 50 to 90% by weight of aromatic epoxy liquid resins, optionally up to 15% by weight, preferably 1 to 10% by weight of reactive diluent containing epoxy groups,

[0114] 5 to 25% by weight, preferably 10 to 20% by weight impact modifier, optionally up to 5% by weight, preferably 0.1 to 3% by weight adhesion promoter, and optionally up to 55% by weight, preferably 5 to 20% by weight mineral fillers, and optionally further ingredients, and based on the hardener component 30 to 90% by weight, preferably 25 to 70% by weight amine A1, optionally up to 45% by weight, preferably 10 to 35% by weight further amine hardener A, optionally up to 10% by weight, preferably 1 to 5% by weight accelerator, and optionally up to 60% by weight, preferably 20 to 50% by weight mineral fillers, and optionally further ingredients.

[0115] The substrate in the use according to the invention is a substrate of any kind at least partially coated with a cured epoxy resin adhesive. This is normally the case when a substrate originally bonded or coated with an epoxy resin adhesive, for example in an article to be repaired, is newly bonded with an adhesive according to the invention for the use according to the invention.

[0116] On the adhesive surface where the adhesive according to the invention is applied, at least partial residues of the epoxy resin adhesive originally used and, in particular, which has long since completely cured are present.

[0117] As such, a substrate coated at least partially with a particularly fully cured epoxy resin adhesive is particularly suitable for the use according to the invention

[0118] - a plastic such as rigid and soft PVC, polycarbonate, polystyrene, polyester, polyamide, PMMA, ABS, SAN, epoxy resins, phenolic resins, PUR, POM, TPO, PE, PP, EPM or EPDM, in each case untreated or surface-treated, for example by means of plasma, corona or flames;

[0119] - Concrete, mortar, cement screed, fiber cement, brick, tile, plaster, natural stones such as granite or marble, glass or glass ceramic;

[0120] - asphalt or bitumen;

[0121] - Repair or leveling compounds based on PCC (polymer-modified cement mortar) or ECC (epoxy resin-modified cement mortar); - Fiber-reinforced plastics, such as carbon fiber-reinforced plastics (CFRP), glass fiber-reinforced plastics (GRP), natural fiber-reinforced plastics (NFRP), or sheet molding compounds (SMC);

[0122] - leather, textiles, paper, wood, wood materials bonded with resins, for example phenolic, melamine or epoxy resins, resin-textile composites or other so-called polymer composites;

[0123] - Metals or alloys such as aluminum, iron, steel, copper, other non-ferrous metals, including surface-treated metals or alloys such as galvanized or chrome-plated metals;

[0124] - insulating foams, in particular made of EPS, XPS, PUR, PIR, rock wool, glass wool or foamed glass (foam glass);

[0125] - coated or painted substrates, in particular painted tiles, painted concrete, powder-coated metals or alloys or painted sheets, in particular sheets coated with polyvinylidene fluoride;

[0126] - Coatings, paints or varnishes, especially coated floors.

[0127] The substrate, at least partially coated with a cured epoxy resin adhesive, may be pretreated if necessary before applying the adhesive, in particular by physical and / or chemical cleaning processes or by applying an activator or primer. It is preferably not pretreated other than surface cleaning, in particular removing dust.

[0128] Preferably, the substrate at least partially coated with a cured epoxy resin adhesive is selected from plastics, metals and alloys, and in particular fiber-reinforced plastics.

[0129] Most preferably, the substrate at least partially coated with a cured epoxy resin adhesive is a fiber-reinforced plastic, in particular a glass fiber-reinforced plastic.

[0130] Most preferably, the substrate at least partially coated with a cured epoxy resin adhesive is a rotor blade or part of a rotor blade of a wind turbine. The epoxy resin adhesive, in particular the fully cured one, with which the substrate to be bonded is at least partially coated is not particularly limited. It can be a commercially available epoxy resin adhesive suitable for structural bonding of the respective substrate. In particular, it is a commercially available two-component epoxy resin adhesive, such as SikaPower®-830 or SikaPower®-1200 from Sika. However, it is important that the adhesive is at least partially, preferably completely, cured. Typically, such adhesives present on a component to be repaired are already fully cured due to the component's long service life.

[0131] For the inventive use, the resin and hardener components, and any other components present in the adhesive, are mixed using a suitable method. The mixing ratio is preferably selected such that the molar ratio of the groups reactive toward epoxy groups to the epoxy groups is in the range of 0.5 to 1.5, in particular 0.7 to 1.2. In parts by weight, the mixing ratio between the resin and hardener components is typically in the range of approximately 1:2 to 20:1, in particular 1:1 to 5:1.

[0132] The components are mixed continuously or batchwise using a suitable process, ensuring that the time between mixing the components and applying the mixed adhesive is not too long, so that the application is completed within the adhesive's pot life. Mixing and application of the adhesive preferably take place at ambient temperature, which typically ranges from approximately 5 to 40°C, preferably approximately 10 to 35°C.

[0133] For the use according to the invention, the mixed adhesive is applied to the substrate within the pot life.

[0134] The adhesive is preferably applied by hand using a spatula or trowel. Application from a cartridge or with a hydraulic conveyor system is also possible. The adhesive is preferably applied in such a quantity that, after joining and pressing the substrates, the adhesive joint has a thickness of 0.1 to 30 mm, preferably 0.2 to 5 mm.

[0135] The substrate can be bonded over its entire surface or only in one or more partial areas. Bonding is preferably done in one or more partial areas.

[0136] Following application of the mixed adhesive, the bond is assembled within the adhesive's open time. The pot life and open time of the adhesive depend on its ingredients, the presence of accelerators, and the temperature. At room temperature, the open time is typically about 5 minutes to about 2 hours.

[0137] Depending on the geometry of the bond, it is advantageous to fix the bond after joining using a suitable method to prevent the joined parts from shifting as long as the adhesive has not yet cured enough to hold the joined parts in the selected position.

[0138] After the bond is formed, the adhesive cures. The adhesive preferably cures under ambient conditions.

[0139] The adhesive cures through a chemical reaction between its ingredients. The amine hydrogens of primary and secondary amino groups, and any other epoxy-reactive groups present, react with epoxy groups, causing their ring opening. Any accelerators present catalyze these chemical reactions. As a result of these reactions, the adhesive polymerizes and thus cures. Curing typically takes several hours to several days. The duration depends, among other things, on the temperature, the reactivity of the components, their stoichiometry, and the presence or amount of accelerators.

[0140] The invention further relates to an adhesive composite obtained from the use as described above. The adhesive composite preferably has an adhesive layer thickness of 0.1 to 30 mm, in particular 0.2 to 5 mm.

[0141] The resulting adhesive bond is preferably part of an object or structure, in particular part of a rotor blade of a wind turbine. The resulting adhesive bond is preferably produced as part of a repair or partial replacement measure.

[0142] The resulting adhesive bond is able to connect the bonded parts reliably and durably and enables reliable sealing against penetrating water and gases such as methane or radon.

[0143] Another object of the invention is an adhesive for the use according to the invention as described above, wherein the resin component

[0144] 40 to 90% by weight, preferably 50 to 90% by weight of aromatic epoxy liquid resins, optionally up to 15% by weight, preferably 1 to 10% by weight of reactive diluent containing epoxy groups,

[0145] 5 to 25% by weight, preferably 10 to 20% by weight impact modifier, optionally up to 5% by weight, preferably 0.1 to 3% by weight adhesion promoter, and optionally up to 55% by weight, preferably 5 to 20% by weight mineral fillers, and optionally further ingredients, and the hardener component

[0146] 30 to 90% by weight, preferably 25 to 70% by weight of amine A1, optionally up to 45% by weight, preferably 10 to 35% by weight of further amine hardener A, optionally up to 10% by weight, preferably 1 to 5% by weight of accelerator, and optionally up to 60% by weight, preferably 20 to 50% by weight of mineral fillers, and optionally further ingredients.

[0147] Preferred embodiments of this adhesive correspond without restriction to the preferred embodiments according to the inventive use as described above and are thus also valid for the adhesive itself as long as they concern the definition of the adhesive.

[0148] Examples

[0149] The following are exemplary embodiments intended to further illustrate the described invention. Of course, the invention is not limited to these described exemplary embodiments.

[0150] The “standard climate” (“NK”) is defined as a temperature of 23±1 °C and a relative humidity of 50±5%.

[0151] Unless otherwise stated, the chemicals used were from Sigma-Aldrich Chemie GmbH.

[0152] Substances and abbreviations used:

[0153] BADGE Bisphenol-A diglycidyl ether, EEW approx. 187 g / eq (Araldite®

[0154] GY 250, from Huntsman)

[0155] BDDGE 1,4-butanediol diglycidyl ether, reactive diluent (Araldite®

[0156] DY-D, by Huntsman)

[0157] Ancamine 1769 Hydroxyalkylated aliphatic polyamine Amine A1 (Ancamine® 1769, from Evonik)

[0158] Ancamine 2167 Cycloaliphatic polyamine (amine hardener) with aromatic structural elements (Ancamine® 2167, from Evonik)

[0159] D-230 Polyoxypropylenediamine with a number average molecular weight of

[0160] 230 g / mol; Amine A1 (Jeffamine® D-230, ex Huntsman)

[0161] NC-558 Phenalkamine (Cardolite® NC-558, from Cardolite)

[0162] NC-658 Phenalkamine (Cardolite® NC-658, from Cardolite)

[0163] TMD Isomer mixture of 2,2,4- and 2,4,4-trimethylhexamethylenediamine, Amine A1 (Vestamin® TDM, from Evonik) IPDA Isophoronediamine, cycloaliphatic amine hardener, (Vestamin®

[0164] IPD, from Evonik)

[0165] MXDA m-xylylenediamine (1,3-bis-(aminomethyl)-benzene), arylaliphatic amine hardener

[0166] 1922A [3,3'-(oxybis(2,1-ethanediyloxy))bis-1-popanamine], amine A1

[0167] (Ancamine® 1922 A, from Evonik)

[0168] LITE 2002 Phenalkamin (Cardolite® LITE 2002, from Cardolite)

[0169] Impact modifier Cardanol-endcapped polyurethane polymer; prepared as described below

[0170] Accelerator Tris-(dimethylaminomethyl)phenol (Ancamine® K54, from Evonik)

[0171] Adhesion promoter 3-glycidoxypropyltrimethoxysilane

[0172] Filler 1 precipitated, surface-treated chalk

[0173] Filler 2 fumed silica

[0174] Impact modifier:

[0175] Under a nitrogen atmosphere, 5687 g of Acclaim® 4200 polyol (polyetherdiol from Bayer Materialscience), 712 g of diphenylmethane diisocyanate (MDI) with the trade name Desmodur 44 MC L (Covestro), and 0.6 g of catalyst DABCO 33 LV (Air Products) were heated to 80 °C with continuous stirring and maintained at this temperature to produce an NCO-terminated prepolymer. After one hour of reaction, the free NCO content was determined by titration. It had reached an isocyanate group content of 1.9 wt.%. Subsequently, 910 g of cardanol with the trade name Cardolite NC-700 (Cardolite) were added, and stirring was continued for a further 2 hours at 80 °C. The reaction was stopped as soon as no free isocyanate was detectable by IR spectroscopy (wavenumbers 2275 - 2230 cm'). 1 ).

[0176] Production of adhesives and bondings:

[0177] Examples 1 to 13: For each example, an identical resin component was prepared by mixing the resin component ingredients listed in Table 1 in the specified amounts (in parts by weight) using a centrifugal mixer (SpeedMixer™ DAC 150, FlackTek Inc.) and storing under exclusion of moisture.

[0178] Table 1 : Resin component for the example compositions.

[0179] Furthermore, an individual hardener component was prepared for each example by mixing the ingredients of the respective hardener component listed in Tables 2 and 3 in the specified amounts (in parts by weight) using a centrifugal mixer and storing the components in a dry, moisture-free environment. The hardener components of each example differed only in the type of amine hardener used. The type of the remaining components and the amounts of all components were always identical. Table 2 shows the general formulation of each hardener component, and Table 3 shows which amine(s) was used as Amine A in each specific hardener component.

[0180] Table 2: Hardener component for the example compositions.

[0181] For each example, the resin component and the hardener component were then processed into a homogeneous paste using a centrifugal mixer, with the respective amount of each hardener component in each mixture being measured to achieve a molar ratio of epoxy groups of the resin component to amine hydrogens of the hardener component of 1:1. The mixtures thus prepared were immediately tested as follows:

[0182] The tensile shear strength was tested on glass fiber-reinforced epoxy resin panels from Rocholl (Germany) measuring 100 x 25 x 10 mm. These panels were coated with a two-component epoxy resin adhesive (SikaPower®-830, a solvent-free, amine-cured epoxy resin adhesive for wind turbine rotor blades) prior to testing. SikaPower®-830 was applied to both panels required for testing with a visible thickness of 0.5 mm and allowed to cure for 4 hours at 70°C. The panels were then cooled to 23°C. Composite specimens were prepared for the test by bonding two panels coated with SikaPower®-830 using the adhesive compositions C1 to C14 to form an overlapping bond measuring 12.5 x 25 mm and 3 mm thick. The bonding was applied to the side coated with SikaPower®-830 on both panels.After storing the composites for 7 days under standard conditions, the tensile shear strength was tested according to DIN EN 1465 at a tensile speed of 10 mm / min.

[0183] The results are shown in Table 3.

[0184] Table 3: Amine hardeners A used in the respective hardener component of each example composition and results of the tensile shear strength measurements. "(Ref.)" denotes reference compositions not according to the invention.

[0185] The results in Table 3 show that the adhesives according to the invention enable adhesive bonds with very high tensile shear strength. They all exhibit a tensile shear strength of at least 10 MPa or higher. In contrast, the reference compositions without or with insufficient amounts of Amine A1 exhibit inadequate tensile shear strengths in direct comparison.

Claims

Patent claims: 1 . Use of an adhesive for bonding a substrate at least partially coated with a cured epoxy resin adhesive, characterized in that the adhesive - a resin component containing at least one epoxy resin and - a hardener component containing at least one amine A1 having at least one aliphatic amino group, wherein amine A1 is selected from polyetheramines and linear or branched, but not cyclic, aliphatic polyamines, wherein the amine A1 makes up at least 50% by weight of all amine hardeners A containing at least one amine hydrogen in the hardener component, based on all amine hardeners A in the hardener component.

2. Use according to claim 1, characterized in that the resin component contains at least one aromatic epoxy liquid resin.

3. Use according to one of claims 1 or 2, characterized in that the amine A1 is selected from the group consisting of 2-dimethylaminoethylamine, 3-dimethylaminopropylamine, 4-dimethylaminobutylamine, 6-dimethylaminohexylamine, 2-(2-dimethylaminoethylamino)ethylamine, 2-(3-dimethylaminopropylamino)ethylamine, 3-(2-dimethylaminoethylamino)propylamine, 3-(3-dimethylaminopropylamino)propylamine, 1,5-diamino-2-methylpentane, 1,6-hexanediamine, 2,2(4),4-trimethyl I-1,6-hexanediamine, 2-butyl-2-ethyl I-1,5-pentanediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, dipropylenetriamine, N-(2-aminoethyl)-1,3-propanediamine, N,N'-bis(3-aminopropyl)ethylenediamine, bis(1,6-hexylene)triamine, polyetheramines, and combinations of two or more of these amines.

4. Use according to one of claims 1 to 3, characterized in that the amine A1 comprises at least one polyetheramine, in particular a polyoxyalkylenediamine, preferably with a number-average molecular weight between 170 and 500 g / mol.

5. Use according to one of claims 1 to 4, characterized in that in addition to amine A1, further amine hardeners A are contained in the hardener component, in particular selected from phenalkamines, cycloaliphatic polyamines, aromatic polyamines, and / or amine-functional adducts of polyamines with epoxy resins.

6. Use according to one of claims 1 to 5, characterized in that the amine A1 makes up at least 55% by weight, preferably at least 60% by weight, in particular at least 75% by weight of all amine hardeners A containing at least one amine hydrogen in the hardener component, based on all amine hardeners A in the hardener component.

7. Use according to one of claims 1 to 6, characterized in that the mixing ratio of the resin component and the hardener component is selected such that the molar ratio of the groups reactive towards epoxy groups to the epoxy groups is in the range from 0.5 to 1.5, in particular 0.7 to 1.

2.

8. Use according to one of claims 1 to 7, characterized in that the hardener component contains between 25% by weight and 75% by weight, preferably between 30% by weight and 70% by weight, in particular between 40% by weight and 60% by weight, of amine A1, based on the total hardener component.

9. Use according to one of claims 1 to 8, characterized in that the adhesive contains at least one further ingredient selected from thinners, fillers, adhesion promoters, accelerators and surface-active compounds.

10. Use according to one of claims 1 to 9, characterized in that the resin component comprises at least one impact modifier, preferably a polyurethane-based impact modifier.

11. Use according to claim 10, characterized in that the impact modifier is prepared from the reaction of an isocyanate-functional polyurethane polymer with cardanol.

12. Use according to one of claims 1 to 11, characterized in that the resin component - 40 to 90% by weight aromatic epoxy liquid resins, - optionally up to 15% by weight of reactive diluent containing epoxy groups, - 5 to 25% by weight impact modifier, - optionally up to 5% by weight adhesion promoter, as well as - optionally up to 55% by weight of mineral fillers, and optionally other ingredients, and the hardener component - 30 to 90 wt% Amine A1 - optionally up to 45 wt.% further amine hardener A, - optionally up to 10% by weight accelerator, as well as - optionally contains up to 60% by weight of mineral fillers, and possibly other ingredients.

13. Use according to one of claims 1 to 12, characterized in that the substrate at least partially coated with a cured epoxy resin adhesive is a fiber-reinforced plastic, in particular a glass-fiber-reinforced plastic.

14. Adhesive composite obtained from the use according to one of claims 1 to 13, in particular on or in a rotor blade of a wind turbine.

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