Curing agent for epoxy resin coating

Abstract

The present invention relates to a curing agent for epoxy resins, which contains 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane and N-benzyl-1,2-ethylenediamine in such amounts that the ratio of the number of their amine hydrogens is in the range of 90 / 10 to 20 / 80. The curing agent according to the invention enables an epoxy resin composition suitable as a coating material, which has excellent processability and rapid curing, has almost no defects caused by clouding even under wet and cold conditions, and has a particularly high hardness, a high glass transition temperature and a surprisingly low yellowing tendency after curing.

Description

Field of the Invention

[0001] The present invention relates to a curing agent for epoxy resin compositions, which epoxy resin compositions are particularly suitable as coatings, especially for floors. Prior Art

[0002] Epoxy resin-based coatings are widely used in the construction industry. They consist of a liquid resin and a curing agent component, which are mixed before application and cured at ambient temperature in the range of about 5 - 35 °C. When applied, the viscosity of the coating should be as low as possible so that they flow well at ambient temperature. After application, they should cure as quickly and problem-free as possible, even under wet and cold conditions, and form a defect-free surface without cloudiness, spots, stickiness or pits. After curing, they should have high hardness plus low brittleness and a high glass transition temperature in order to withstand mechanical stress as well as possible. For applications with high visual requirements, such as the top covering of floors, they should additionally have a high gloss and a minimal tendency to yellow under the influence of light.

[0003] However, such epoxy resin coatings often have a tendency to surface defects such as cloudiness, spots, roughness or stickiness, which is also referred to as "blushing". Blushing is caused by the formation of salts of amines contained in the curing agent component with carbon dioxide from the air and occurs especially at high air humidity and low temperature. Many curing agents for epoxy resin coatings contain adducts of diamines and epoxy resins. This can reduce the blushing phenomenon and also allow for faster curing. However, diamine-epoxy resin adducts are significantly stickier than free diamines, which means that such curing agents often contain large amounts of diluents and / or can only be appropriately filled with inorganic fillers. Diluents are not incorporated into the resin matrix during curing and can be released into the environment by evaporation or diffusion processes. However, there is an increasing need today for low-emission products with a low content of releasable substances after curing. For low-emission or emission-free epoxy resin compositions, diluents can therefore only be used in small amounts or not at all.

[0004] EP 3 344 677 discloses an epoxy resin composition which contains N-benzyl-1,2-ethanediamine in the curing agent and allows the coating to have a good surface. The coating contains diamine-epoxy resin adducts which significantly increase their stickiness or polyoxypropylenediamines which result in an undesirably low glass transition temperature. Summary of the Invention

[0006] The object of the present invention is therefore to provide a curing agent for epoxy resins which enables a very low-viscosity, easily processable epoxy resin composition with little or no use of diluents, which has rapid curing, high final hardness and a high glass transition temperature, and is suitable for coatings which result in a defect-free, glossy surface even at wet and cold ambient temperatures.

[0007] This is achieved by a curing agent described in the following text. The curing agent contains 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane (IPDA) and N-benzyl-1,2-ethylenediamine in such an amount that the ratio of the number of amine hydrogens is in the range of 70 / 30 - 20 / 80. At the ratio according to the invention, the curing agent enables a favorable combination of a high glass transition temperature, a high final hardness, a good surface, and rapid curing under cold conditions. A higher content of IPDA results in slow curing, an undesired dull surface under cold conditions, and an increased tendency to yellowing, while a higher content of N-benzyl-1,2-ethylenediamine results in an undesired low glass transition temperature and final hardness.

[0008] Surprisingly, the coating containing the curing agent according to the invention shows a particularly low tendency to yellowing under the influence of light.

[0009] The curing agent of the invention enables an epoxy resin composition suitable as a coating, which has excellent processability and rapid curing, and has a tendency to have few defects related to clouding even under wet and cold conditions, and has a high hardness, a high glass transition temperature, and surprisingly a low tendency to yellowing after curing. Detailed Description of the Invention

[0011] The present invention provides a curing agent for epoxy resins, which contains 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane (IPDA) and N-benzyl-1,2-ethylenediamine in free form and / or in adduct form with an epoxy resin, and the amount contained is such that the ratio of the number of amine hydrogens is in the range of 90 / 10 - 20 / 80.

[0012] "Primary amino group" refers to an amino group that is connected to only one organic group and carries two hydrogen atoms; "secondary amino group" refers to an amino group that is connected to two organic groups (which may also be part of a ring together) and carries one hydrogen atom; and "tertiary amino group" refers to an amino group that is connected to three organic groups (where two or three of them may also be part of one or more rings), and does not carry any hydrogen atoms.

[0013] "Amine hydrogen" refers to the hydrogen atoms of primary and secondary amino groups.

[0014] "Amine hydrogen equivalent" refers to the mass of an amine or amine-containing composition that contains one molar equivalent of amine hydrogen. It is expressed in the unit of "g / Eq".

[0015] "Epoxide equivalent" refers to the mass of an epoxy group-containing compound or composition that contains one molar equivalent of epoxy groups. It is expressed in the unit of "g / Eq".

[0016] Substances whose names start with "poly-" such as polyamines or polyepoxides refer to substances that formally contain two or more functional groups appearing in their names in each molecular form.

[0017] A "diluent" refers to a substance that is soluble in epoxy resin and reduces its viscosity, and is not chemically incorporated into the epoxy resin polymer during the curing process.

[0018] "Molecular weight" refers to the molar mass of a molecule (in g / mol). "Average molecular weight" refers to the number-average molecular weight Mn of a polydisperse mixture of oligomer or polymer molecules n , which is usually determined by gel permeation chromatography (GPC) using polystyrene as a standard.

[0019] "Gel time" is the time period from mixing the components of the epoxy resin composition until its gelation.

[0020] "Room temperature" refers to a temperature of 23 °C.

[0021] The IPDA contained in the curing agent is preferably in a commercially available quality, such as in the form of IPD (from Evonik) or EC 201 (from BASF).

[0022] The IPDA contained in the curing agent is preferably in a free form, not adducted with the epoxy resin. The curing agent preferably contains less than 10% by weight, more preferably less than 5% by weight, especially less than 1% by weight of IPDA adducted with the epoxy resin. Most preferably, the curing agent does not contain IPDA adducted with the epoxy resin. Such a curing agent has a particularly low viscosity.

[0023] The N-benzyl-1,2-ethylenediamine contained in the curing agent preferably has a purity of at least 80% by weight, more preferably at least 90% by weight, especially at least 95% by weight. Optionally, N,N'-dibenzyl-1,2-ethylenediamine is additionally contained. Preferably, it contains less than 2% by weight, especially less than 1% by weight of 1,2-ethylenediamine.

[0024] The N-benzyl-1,2-ethylenediamine contained in the curing agent is preferably in a free form, not adducted with the epoxy resin. The curing agent preferably contains less than 10% by weight, more preferably less than 5% by weight, especially less than 1% by weight of N-benzyl-1,2-ethylenediamine adducted with the epoxy resin. Most preferably, the curing agent does not contain N-benzyl-1,2-ethylenediamine adducted with the epoxy resin. Such a curing agent has a particularly low viscosity.

[0025] N-benzyl-1,2-ethylenediamine is preferably prepared by partial alkylation of 1,2-ethylenediamine with at least one benzylating agent.

[0026] The alkylation is preferably a reductive alkylation using hydrogen and benzaldehyde as the benzylating agent.

[0027] The reductive alkylation is preferably carried out in the presence of a suitable catalyst. Preferred catalysts are palladium on carbon (Pd / C), platinum on carbon (Pt / C), Adams catalyst or Raney nickel, especially palladium on carbon or Raney nickel.

[0028] When using molecular hydrogen, the reductive alkylation preferably operates in a pressure apparatus at a hydrogen pressure of 5 to 150 bar, especially 10 to 100 bar. This can be carried out in a batch process or preferably in a continuous process.

[0029] The reductive alkylation is preferably carried out at a temperature in the range of 40 - 120 °C, especially 60 to 100 °C.

[0030] Preferably, 1,2 - ethylenediamine is used in a stoichiometric excess relative to benzaldehyde and removed from the reaction mixture after alkylation, especially by stripping to remove some or all of the unreacted 1,2 - ethylenediamine.

[0031] If desired, the reaction mixture can subsequently be further purified, more particularly by distillation to remove at least part of the N,N'-dibenzyl - 1,2 - ethylenediamine from the obtained N - benzyl - 1,2 - ethylenediamine. This enables the curing agent to have a particularly high reactivity and the epoxy resin composition to have a particularly high glass transition temperature.

[0032] The ratio of the number of amine hydrogens from IPDA and N - benzyl - 1,2 - ethylenediamine is preferably in the range of 80 / 20 - 25 / 75, especially 75 / 25 to 30 / 70. Such a curing agent enables a particularly good combination of rapid curing, high hardness, high glass transition temperature and good surface for the epoxy resin composition.

[0033] The ratio of the number of amine hydrogens from IPDA and N - benzyl - 1,2 - ethylenediamine is particularly preferably in the range of 80 / 20 - 30 / 70, especially 70 / 30 to 50 / 50. Such a curing agent can achieve a particularly high glass transition temperature as well as a good surface.

[0034] It is also particularly preferred that the ratio of the number of amine hydrogens from IPDA and N - benzyl - 1,2 - ethylenediamine is in the range of 70 / 30 - 20 / 80. Such a curing agent can achieve particularly rapid curing within 24 hours under cold conditions.

[0035] The curing agent of the present invention preferably comprises at least one additional component selected from additional amines, accelerators and diluents.

[0036] Suitable additional amines are in particular N-benzyl-1,2-propanediamine, N-benzyl-1,3-bis(aminomethyl)benzene, N-(2-ethylhexyl)-1,3-bis(aminomethyl)benzene or N-(2-phenylethyl)-1,3-bis(aminomethyl)benzene, 2,2-dimethyl-1,3-propanediamine, 1,3-pentanediamine (DAMP), 1,5-pentanediamine, 1,5-diamino-2-methylpentane (MPMD), 2-butyl-2-ethyl-1,5-pentanediamine (C11-neodiamine), 1,6-hexanediamine, 2,5-dimethyl-1,6-hexanediamine, 2,2(4),4-tetramethyl-1,6-hexanediamine (TMD), 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, undecane-1,11-diamine, dodecane-1,12-diamine, 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, 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), menthane-1,8-diamine, 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-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 or higher oligomers of these diamines, bis(3-aminopropyl)polytetrahydrofuran or other polytetrahydrofuran diamines, polyoxyalkylene diamines or triamines, in particular polyoxypropylene diamines or polyoxypropylene triamines such as for example D-230, D-400 or T-403 (all from Huntsman), diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), pentaethylenehexamine (PEHA), dipropylenetriamine (DPTA), N-(2-aminoethyl)-1,3-propanediamine (N3-amine), N,N'-bis(3-aminopropyl)ethylenediamine (N4-amine), N,N'-bis(3-aminopropyl)-1,4-diaminobutane, N5-(3-aminopropyl)-2-methyl-1,5-pentanediamine, N3-(3-aminopentyl)-1,3-pentanediamine, N5-(3-amino-1-ethylpropyl)-2-methyl-1,5-pentanediamine, N,N'-bis(3-amino-1-ethylpropyl)-2-methyl-1,5-pentanediamine, 3-(2-aminoethyl)aminopropylamine, bis(hexamethylene)triamine (BHMT), N-aminoethylpiperazine, 3-dimethylaminopropylamine (DMAPA) or 3-(3-(dimethylamino)propylamino)propylamine (DMAPAPA) and also adducts of these polyamines with epoxy resins or monoxides, or adducts of 1,2-ethylenediamine or 1,2-propylenediamine with epoxy resins or monoxides and subsequent removal of the excess 1,2-ethylenediamine or 1,2-propylenediamine by distillation.

[0037] It may be advantageous for the curing agent of the present invention to comprise a combination of two or more additional amines.

[0038] Preferably the additional amines are selected from the following: TMD, 1,2-diaminocyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, bis(4-aminocyclohexyl)methane, 2(4)-methyl-1,3-diaminocyclohexane, MXDA, polyoxypropylenediamine with an average molecular weight M n in the range of 200 - 500 g / mol, polyoxypropylenetriamine with an average molecular weight M n in the range of 300 - 500 g / mol, DMAPAPA, BHMT, DETA, TETA, TEPA, PEHA, DPTA, N3-amine, N4-amine, adducts of MXDA, DETA, TETA or TEPA with epoxy resins, and adducts of MPMD, 1,2-ethylenediamine or 1,2-propylenediamine with tolyl glycidyl ether, where the unreacted MPMD, 1,2-ethylenediamine or 1,2-propylenediamine is removed by distillation after the reaction.

[0039] Among these, preferred are 1,2-diaminocyclohexane, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, 2(4)-methyl-1,3-diaminocyclohexane, MXDA, average molecular weight M nPolyoxypropylene diamine in the range of 200 - 500 g / mol and an average molecular weight M n Polyoxypropylene triamine in the range of 300 - 500 g / mol.

[0040] Particularly preferred are 1,3 - bis(aminomethyl)cyclohexane or MXDA, especially 1,3 - bis(aminomethyl)cyclohexane. These amines enable particularly fast curing.

[0041] Also particularly preferred are polyoxypropylene diamine or polyoxypropylene triamine. These enable particularly low brittleness.

[0042] Suitable accelerators are especially acids or compounds that can be hydrolyzed to acids, especially 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, such as especially phosphoric acid, or mixtures of the above acids and acid esters; nitrates, such as especially calcium nitrate; tertiary amines such as especially 1,4 - diazabicyclo[2.2.2]octane, benzyldimethylamine, α - methylbenzyldimethylamine, triethanolamine, dimethylaminopropylamine, imidazoles such as especially N - methylimidazole, N - vinylimidazole or 1,2 - dimethylimidazole, salts of these tertiary amines, quaternary ammonium salts such as especially benzyltrimethylammonium chloride, amidines such as especially 1,8 - diazabicyclo[5.4.0]undec - 7 - ene, guanidines such as especially 1,1,3,3 - tetramethylguanidine, phenols, especially bisphenols, phenolic resins or Mannich bases, such as especially 2 - (dimethylaminomethyl)phenol, 2,4,6 - tris(dimethylaminomethyl)phenol or polymers prepared from phenol, formaldehyde and N,N - dimethylpropane - 1,3 - diamine, phosphite esters such as especially diphenyl phosphite or triphenyl phosphite, or compounds having a mercapto group.

[0043] Preferred are acids, nitrates, tertiary amines or Mannich bases, especially salicylic acid, calcium nitrate or 2,4,6 - tris(dimethylaminomethyl)phenol or combinations of these accelerators.

[0044] Particularly preferably, the curing agent contains salicylic acid, especially in an amount in the range of 1 - 15 parts by weight, preferably 2 to 12 parts by weight, especially 3 to 10 parts by weight, relative to the sum of 100 parts by weight of IPDA and N - benzyl - 1,2 - ethylenediamine. Such a curing agent can achieve a particularly good surface when curing under cold conditions.

[0045] Most preferably, the curing agent comprises a combination of salicylic acid and 2,4,6-tris(dimethylaminomethyl)phenol. There is 2,4,6-tris(dimethylaminomethyl)phenol present, especially in an amount in the range of 1 to 15 parts by weight, preferably 2 to 12 parts by weight, especially 3 to 10 parts by weight, relative to the sum of 100 parts by weight of IPDA and N-benzyl-1,2-ethylenediamine. Such a curing agent enables particularly rapid curing and a particularly good surface when curing under cold conditions.

[0046] Suitable diluents are especially xylene, 2-methoxyethanol, dimethoxyethanol, 2-ethoxyethanol, 2-propoxyethanol, 2-isopropoxyethanol, 2-butoxyethanol, 2-phenoxyethanol, 2-benzyloxyethanol, benzyl alcohol, ethylene glycol, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, ethylene glycol diphenyl ether, diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monon-butyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol di-n-butyl ether, propylene glycol butyl ether, propylene glycol phenyl ether, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, dipropylene glycol di-n-butyl ether, diphenylmethane, diisopropylnaphthalene, mineral oil fractions such as grade (from Exxon), alkylphenols such as tert-butylphenol, nonylphenol, dodecylphenol, cardanol (from cashew nut shell liquid, containing 3-(8,11-pentadecadienyl)phenol as the main component), styrenated phenol, bisphenol, aromatic hydrocarbon resins, especially of the type containing phenolic groups, alkoxylated phenols, especially ethoxylated or propoxylated phenols, especially 2-phenoxyethanol, adipates, sebacates, phthalates, benzoates, organic phosphates or organic sulfonates or sulfonamides.

[0047] Diluents preferably having a boiling point greater than 200 °C are preferred.

[0048] The diluent is preferably selected from the following: benzyl alcohol, styrenated phenol, ethoxylated phenol, aromatic hydrocarbon resins containing phenolic groups, especially LS 500, LX 200, LA 300 or LA 700 products (from Rütgers), diisopropylnaphthalene and cardanol.

[0049] Particularly preferred is benzyl alcohol.

[0050] Diluents containing phenolic groups also show effectiveness as accelerators.

[0051] The curing agent may contain additional components, especially the following:

[0052] - Monoamines such as especially benzylamine or furfurylamine;

[0053] - reaction products of polyaminoamines, especially mono- or polycarboxylic acids, or their esters or acid anhydrides, especially dimer fatty acids, with polyamines (especially DETA or TETA) used in stoichiometric excess;

[0054] - Mannich bases, especially phenolic amines, i.e., reaction products of phenols (especially cardanol) with aldehydes (especially formaldehyde) and polyamines;

[0055] - aromatic polyamines such as especially 4,4'-, 2,4'- and / or 2,2'-diaminodiphenylmethane, 2,4- and / or 2,6-toluenediamine, 3,5-dimethylthio-2,4- and / or -2,6-toluenediamine, 3,5-diethyl-2,4- and / or -2,6-toluenediamine;

[0056] - compounds having a mercapto group, especially liquid thiol-terminated polysulfide polymers, thiol-terminated polyalkylene oxides, thiol-terminated polyalkylene derivatives, polyesters of thioacids, 2,4,6-trimercapto-1,3,5-triazine, triethylene glycol dithiol or ethylene dithiol.

[0057] The curing agent preferably has only a low content of additional amines.

[0058] In particular, at least 30%, preferably at least 40%, more preferably at least 50%, especially at least 60% of all amine hydrogens contained in the curing agent are derived from N-benzyl-1,2-ethylenediamine and IPDA. Such a curing agent can achieve an attractive combination of rapid curing, a tendency towards little turbidity effect, high hardness and high glass transition temperature.

[0059] The curing agent preferably has only a small amount of diluent, more particularly from 0 wt% to 50 wt%, preferably from 0 wt% to 30 wt% of diluent, especially benzyl alcohol.

[0060] The curing agent of the present invention is preferably not water-based. It especially contains less than 15 wt%, preferably less than 10 wt% of water. Such a curing agent is suitable for non-aqueous epoxy resin products, especially floor coatings.

[0061] Another subject of the present invention is to provide an epoxy resin composition comprising

[0062] - a resin component comprising at least one epoxy resin, and

[0063] - a curing agent component comprising the curing agent of the present invention.

[0064] Suitable epoxy resins are obtained in a known manner, especially from the reaction of epichlorohydrin with polyols, polyphenols or amines.

[0065] Suitable epoxy resins are especially aromatic epoxy resins, especially the following glycidyl ethers:

[0066] - Bisphenol A, bisphenol F or bisphenol A / F, where A represents acetone and F represents formaldehyde, which are used as reactants for the production of these bisphenols. In the case of bisphenol F, positional isomers may also be present, especially those derived from 2,4'- or 2,2'-hydroxyphenylmethane.

[0067] - Dihydroxybenzene derivatives such as resorcinol, hydroquinone or catechol;

[0068] - Further bisphenols or polyphenols such as bis(4-hydroxy-3-methylphenyl)methane, 2,2-bis(4-hydroxy-3-methylphenyl)propane (bisphenol C), bis(3,5-dimethyl-4-hydroxyphenyl)methane, 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane, 2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane, 2,2-bis(4-hydroxy-3-tert-butylphenyl)propane, 2,2-bis(4-hydroxyphenyl)butane (bisphenol B), 3,3-bis(4-hydroxyphenyl)pentane, 3,4-bis(4-hydroxyphenyl)hexane, 4,4-bis(4-hydroxyphenyl)heptane, 2,4-bis(4-hydroxyphenyl)-2-methylbutane, 2,4-bis(3,5-dimethyl-4-hydroxyphenyl)-2-methylbutane, 1,1-bis(4-hydroxyphenyl)cyclohexane (bisphenol Z), 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane (bisphenol TMC), 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'-dihydroxybiphenyl (DOD), 4,4'-dihydroxybenzophenone, bis(2-hydroxynaphthalen-1-yl)methane, bis(4-hydroxynaphthalen-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;

[0069] - Novolacs, which are especially condensation products of phenol or cresol with formaldehyde or paraformaldehyde or acetaldehyde or crotonaldehyde or isobutyraldehyde or 2-ethylhexanal or benzaldehyde or furfural;

[0070] - Aromatic amines such as aniline, toluidine, 4-aminophenol, 4,4'-methylenediphenyldiamine, 4,4'-methylenediphenyldi(N-methyl)amine, 4,4'-[1,4-phenylenebis(1-methylethylidene)]dianiline (dianiline P) or 4,4'-[1,3-phenylenebis(1-methylethylidene)]dianiline (dianiline M).

[0071] Other suitable epoxy resins are aliphatic or cycloaliphatic polyepoxides, especially

[0072] - glycidyl ethers of the following substances: saturated or unsaturated, branched or unbranched, cyclic or open-chain di-, tri- or tetra-functional C2-C 30 alcohols, especially ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, octylene glycol, polypropylene glycol, dimethylolcyclohexane, neopentyl glycol, dibromoneopentyl glycol, castor oil, trimethylolpropane, trimethylolethane, pentaerythritol, sorbitol or glycerol, or alkoxylated glycerol or alkoxylated trimethylolpropane;

[0073] - hydrogenated bisphenol A, F or A / F liquid resins, or glycidylated products of hydrogenated bisphenol A, F or A / F;

[0074] - N-glycidyl derivatives of amides or heterocyclic nitrogen bases, such as triglycidyl cyanurate or triglycidyl isocyanurate, or reaction products of epichlorohydrin and hydantoin.

[0075] The epoxy resin is preferably a liquid resin or a mixture comprising two or more liquid epoxy resins.

[0076] "Liquid epoxy resin" means an industrial polyepoxide having a glass transition temperature of less than 25 °C.

[0077] The resin component may optionally additionally contain partially solid epoxy resin.

[0078] The epoxy resin is especially a bisphenol-based liquid resin, especially bisphenol A-diglycidyl ether and / or bisphenol F-diglycidyl ether, such as those commercially available from Olin, Huntsman or Momentive, for example. These liquid resins have a relatively low viscosity for epoxy resins and enable rapid curing and high hardness. They may contain partially solid bisphenol A resin or novolac glycidyl ether.

[0079] The resin component may contain a reactive diluent.

[0080] Preferred reactive diluents are reactive diluents containing epoxy groups, especially butanediol diglycidyl ether, hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether or triglycidyl ether, phenyl glycidyl ether, tolyl glycidyl ether, guaiacol glycidyl ether, 4-methoxyphenyl glycidyl ether, p-n-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 especially C8-C 10 or C12 -C 14 or C 13 -C 15 alkyl glycidyl ether.

[0081] The epoxy resin composition preferably contains at least one additional component selected from diluents, accelerators, and fillers.

[0082] Suitable accelerators are those already mentioned, in particular salicylic acid, calcium nitrate, or 2,4,6-tris(dimethylaminomethyl)phenol or combinations thereof. Particularly preferred is salicylic acid, especially in combination with 2,4,6-tris(dimethylaminomethyl)phenol.

[0083] Suitable diluents are those already mentioned, in particular those having a boiling point greater than 200 °C.

[0084] Preferably, the diluent is selected from the following: benzyl alcohol, styrenated phenol, ethoxylated phenol, aromatic hydrocarbon resins containing phenolic groups, in particular LS 500, LX 200, LA 300, or LA 700 products (from Rütgers), diisopropylnaphthalene, and cardanol.

[0085] Particularly preferred is benzyl alcohol.

[0086] Suitable fillers are especially ground or precipitated calcium carbonate, optionally coated with fatty acids, especially stearic acid, barite (Schwerspat), talc, quartz powder, quartz sand, silicon carbide, iron mica, dolomite, wollastonite, kaolin, mica (potassium aluminosilicate), molecular sieves, alumina, 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 beads.

[0087] Preferred are calcium carbonate, quartz powder, quartz sand, or combinations thereof.

[0088] The epoxy resin composition optionally contains additional auxiliaries or additives, especially the following:

[0089] - reactive diluents, especially those already mentioned, or epoxidized soybean or linseed oil, compounds containing acetoacetate groups, especially acetoacetylated polyols, butyrolactone, carbonates, aldehydes, isocyanates, or silicones containing reactive groups;

[0090] - Polymers, especially polyamides, polysulfides, polyvinyl formal (PVF), polyvinyl butyral (PVB), polyurethanes (PUR), polymers with carboxyl groups, polyamides, butadiene-acrylonitrile copolymers, styrene-acrylonitrile copolymers, butadiene-styrene copolymers, homopolymers or copolymers of unsaturated monomers, said unsaturated monomers especially selected from ethylene, propylene, butene, isobutene, isoprene, vinyl acetate or alkyl (meth)acrylates, especially chlorosulfonated polyethylene or fluoropolymers or sulfamide-modified melamine;

[0091] - Fibers, especially glass fibers, carbon fibers, metal fibers, ceramic fibers or plastic fibers such as polyamide fibers or polyethylene fibers;

[0092] - Pigments, especially titanium dioxide, iron oxide or chromium(III) oxide;

[0093] - Rheological modifiers, especially thickeners or anti-settling agents;

[0094] - Adhesion improvers, especially organic alkoxysilanes;

[0095] - Flame retardant substances, especially the fillers aluminum hydroxide or magnesium hydroxide already mentioned, antimony trioxide, antimony pentoxide, boric acid (B(OH)3), zinc borate, zinc phosphate, melamine borate, melamine cyanurate, ammonium polyphosphate, melamine phosphate, melamine pyrophosphate, polybrominated diphenyl ethers or diphenyl ethers, phosphate esters such as especially diphenyl cresyl phosphate, resorcinol-bis(diphenyl phosphate), resorcinol diphosphate oligomer, tetraphenyl resorcinol diphosphite, ethylenediamine diphosphate, bisphenol A bis(diphenyl phosphate), tris(2-chloroethyl) phosphate, tris(2-chloropropyl) phosphate, tris(2,3-dichloroisopropyl) phosphate, tris[3-bromo-2,2-bis(bromomethyl)propyl] phosphate, tetrabromobisphenol A, bis(2,3-dibromopropyl ether) of bisphenol A, brominated epoxy resins, ethylene-bis(tetrabromophthalimide), ethylene-bis(dibromonorbornane dicarboximide), 1,2-bis(tribromophenoxy)ethane, tris(2,3-dibromopropyl) isocyanurate, tribromophenol, hexabromocyclododecane, bis(hexachlorocyclopentadienyl) cyclooctane or chlorinated paraffin; or

[0096] - Additives, especially dispersed paraffin wax, film-forming aids, wetting agents, leveling agents, defoamers, degassing agents, stabilizers against oxidation, heat, light or UV radiation or biocides.

[0097] The epoxy resin composition preferably contains additional auxiliaries or additives, especially pigments, wetting agents, leveling agents and / or defoamers.

[0098] The epoxy resin composition preferably has only a low content of diluent. Preferably, it contains less than 20% by weight, more preferably less than 15% by weight, and especially less than 10% by weight of diluent. This enables a low-emission or emission-free epoxy resin product.

[0099] The epoxy resin composition preferably has only a low content of water, preferably less than 5% by weight and especially less than 1% by weight of water.

[0100] In the epoxy resin composition, the ratio of the number of groups reactive with epoxy groups to the number of epoxy groups is preferably in the range of 0.5 - 1.5, especially in the range of 0.7 - 1.2.

[0101] The primary amine groups and secondary amine groups present in the epoxy resin composition and optionally other groups reactive with epoxy groups react with the epoxy groups, causing them to open-ring (addition reaction). Mainly as a result of this reaction, the composition polymerizes and thus cures.

[0102] The resin component and the curing agent component of the epoxy resin composition are stored in separate containers from each other. Additional components of the epoxy resin composition can be present as components of the resin component or the curing agent component, and additional components reactive with epoxy groups are preferably components of the curing agent component. It is also possible for the additional components to be present as separate additional components.

[0103] Suitable containers for storing the resin component or the curing agent component are in particular drums, pails, bags, bladders, tanks, cartridges, cassettes or tubes. The components are storable, which means that they can be stored for several months up to a year or longer before use without their respective properties changing to an extent relevant to their use. For using the epoxy resin composition, the components are mixed with each other shortly before application or during application. The mixing ratio between the resin component and the curing agent component is preferably selected such that the groups reactive with epoxy groups of the curing agent component are in a suitable ratio to the epoxy groups of the resin component, as described above. By weight parts, the mixing ratio between the resin component and the curing agent component is generally in the range of 1:10 - 10:1.

[0104] The components are mixed by means of a suitable method; this mixing can be carried out continuously or batchwise. If the mixing is not carried out immediately before application, it must be noted that not too much time elapses between mixing the components and applying them and that the application is carried out within the pot life. The mixing is carried out especially at ambient temperature, which is generally in the range of about 5 - 40°C, preferably about 10 to 35°C.

[0105] Through a chemical reaction, curing begins upon mixing of the two components, as described above. Curing typically occurs at a temperature in the range of 0 - 150 °C. It is preferably cured at ambient temperature and usually lasts for several days to several weeks. The duration depends in particular on the temperature, the reactivity of the components and their stoichiometric ratio, and on the presence of a promoter.

[0106] In the freshly mixed state, the epoxy resin composition has a low viscosity. The viscosity after the resin component and the curing agent component have been mixed for 10 minutes is preferably in the range of 100 - 4000 mPa·s, preferably 200 to 3000 mPa·s, more preferably 200 to 2000 mPa·s, particularly 200 to 1500 mPa·s at 20 °C, measured using a cone and plate viscometer at a shear rate of 10 s -1 .

[0107] When cured under cold conditions of 8 °C and 80% relative humidity, the Shore D hardness is preferably at least 11 after 24 hours. This is particularly achieved using a curing agent in which the ratio of the number of amine hydrogens from IPDA and N - benzyl - 1,2 - ethylenediamine is in the range of 70 / 30 - 20 / 80, and which particularly additionally contains salicylic acid.

[0108] The epoxy resin composition is applied to at least one substrate, and the following substrates are particularly suitable:

[0109] - glass, glass ceramics, concrete, mortar, cement screed, fibre cement, bricks, tiles, gypsum or natural stone such as granite or marble;

[0110] - repair materials or levelling materials based on PCC (polymer - modified cement mortar) or ECC (epoxy - modified cement mortar);

[0111] - metals or alloys, such as aluminium, iron, steel, copper, other non - ferrous metals, including surface - treated metals or alloys, such as galvanized or chrome - plated metals;

[0112] - tar or asphalt;

[0113] - leather, fabric, paper, wood, wood materials bonded with resins (such as phenolic resins, melamine resins or epoxy resins), resin - fabric composites or other so - called polymer composites;

[0114] - plastics, such as rigid and flexible PVC, polycarbonate, polystyrene, polyester, polyamide, PMMA, ABS, SAN, epoxy resin, phenolic resin, PUR, POM, TPO, PE, PP, EPM or EPDM, in each case untreated or surface - treated, for example by plasma, corona or flame treatment;

[0115] - Fiber-reinforced plastics, such as carbon fiber-reinforced plastics (CFK), glass fiber-reinforced plastics (GFK), and sheet molding compounds (SMC);

[0116] - Insulating foams, especially those made of EPS, XPS, PUR, PIR, rock wool, glass wool, or foam glass;

[0117] - Coated or painted substrates, especially painted nonwovens, coated concrete, powder-coated metals or alloys, or painted metal sheets;

[0118] - Coatings, paints, or varnishes, especially coated floors, which are top-coated with additional floor coverings.

[0119] If required, the substrate can be pretreated before application, especially by physical and / or chemical cleaning methods or by applying an activator or primer.

[0120] The cured composition is obtained by curing the epoxy resin composition.

[0121] Once cured, the epoxy resin composition has a high glass transition temperature.

[0122] Preferably, after a curing time of 14 days at room temperature, the glass transition temperature is at least 45 °C, preferably at least 50 °C, during the first heating (first run), and at least 60 °C, preferably at least 65 °C, during the second heating (second run), as determined by DSC using the measurement program of (1) -10 °C for 2 min, (2) heating rate of 10 K / min from -10 to 200 °C (= first run), (3) cooling rate of -50 K / min from 200 to -10 °C, (4) -10 °C for 2 min, (5) heating rate of 10 K / min from -10 to 180 °C (= second run).

[0123] The epoxy resin composition is preferably used as a coating, primer, adhesive, sealant, potting compound, casting resin, impregnating resin, or as a matrix for fiber composites such as especially CFK or GFK.

[0124] The epoxy resin composition is particularly preferably used as a coating. By coating is here understood all types of coatings applied in a planar manner, especially floor coverings, brush coatings, varnish layers, sealants, undercoats, primers, or protective coatings, especially also those for heavy corrosion protection.

[0125] This epoxy resin composition is particularly suitable as a floor covering or floor coating for indoor areas such as offices, production halls, sports halls or cold storages, or for outdoor areas such as balconies, terraces, parking slabs, bridges or roofs, as a protective coating for concrete, cement, metal, plastic or wood, for example for surface sealing of wooden structures, vehicles, load areas, tanks, silos, shafts, pipes, pipelines, machines or steel structures, such as surface sealing of ships, docks, offshore platforms, gates, hydropower stations, water conservancy projects, swimming pools, wind turbines, bridges, chimneys, cranes or sheet pile walls, or as a primer, binder, anticorrosive primer or hydrophobization for surfaces.

[0126] This epoxy resin composition is particularly advantageously used in low-emission coatings with environmentally friendly quality seals, such as environmentally friendly quality seals according to Emicode (EC1Plus), AgBB, DIBt, Blue Angel (Der Blaue Engel), AFSSET, RTS (M1) and the US Green Building Council (LEED).

[0127] For use as a coating, the epoxy resin composition advantageously has a fluid consistency with low viscosity and good leveling properties. During its pot life, the mixed composition is usually applied planar to the substrate at ambient temperature as a film with a layer thickness of about 50 μm to about 5 mm. It is applied in particular by pouring onto the substrate to be coated and then spreading evenly with the aid of, for example, a squeegee or a toothed trowel. It can also be applied in the form of brushing or rolling or spraying, for example as an anticorrosive coating on steel. Curing usually forms a substantially uniform, glossy and non-sticky high-hardness film, which has good adhesion to a variety of different substrates.

[0128] The present invention thus also provides a coating method, comprising the following steps:

[0129] (i) mixing the components of the epoxy resin composition,

[0130] (ii) applying the mixed composition to the substrate during its pot life,

[0131] and then curing the mixed composition.

[0132] An additional coating can be applied to the fully or partially cured composition, in which case the additional layer can likewise be an epoxy resin composition, or another material, in particular a polyurethane or polyurea coating.

[0133] It is also preferred to use an epoxy resin composition as an adhesive. When used as an adhesive, the epoxy resin composition generally has a paste-like consistency and structural viscosity properties after the components have been mixed. During application, the mixed adhesive is applied to at least one of the substrates to be bonded within the pot life, and the two substrates are joined within the open time of the adhesive to form an adhesive bond.

[0134] The mixed adhesive is applied or dispensed in particular by means of a brush, roller, spatula, doctor blade, trowel, or from a tube, cartridge or metering device.

[0135] The adhesive is particularly suitable for use in the construction industry, especially for strengthening building structures by means of steel plates or sheets made of carbon fiber-reinforced composite plastics (CFK), for buildings containing bonded precast concrete elements, especially bridges or concrete towers, such as for wind turbines, shafts, pipes or tunnels, or for buildings containing bonded natural rocks, ceramic elements or components made of fiber cement, steel, cast iron, aluminum, wood or polyester, for anchoring pins or steel bars in drill holes, for fixing, for example, handrails, balustrades or door frames, for repairing, for example, filling edges, holes or joints especially in concrete curing, or for bonding polyvinyl chloride (PVC), toughened polyolefins or adhesion-modified chlorosulfonated polyethylene films.

[0136] Further fields of application relate to structural bonding in the construction or manufacturing industries, especially as bonding mortar, assembly adhesives, reinforcing adhesives, for example especially for bonding sheets made of CFK or steel to concrete, brickwork or wood, as element adhesives, sandwich element adhesives, facade element adhesives, reinforcing adhesives, body adhesives or semi-shell adhesives for wind turbine rotor blades, such as for bridge elements.

[0137] Such an epoxy resin adhesive is also suitable for filling cavities such as gaps, cracks or drill holes, where the adhesive is filled or injected into the cavity and fills it after curing, and connects or bonds the sides of the cavity to each other in a force-locking manner.

[0138] The present invention therefore also provides an adhesive method, comprising the steps of:

[0139] (i) mixing the components of the epoxy resin composition,

[0140] (ii) applying the mixed composition within the pot life,

[0141] - to at least one of the substrates to be bonded and joining the substrates to form an adhesive bond within the open time, or

[0142] - into the cavity or gap between one or more substrates, and optionally inserting an anchor into the cavity or gap during the open time,

[0143] The mixed composition is then cured.

[0144] "Anchor" here particularly refers to steel bars, screws or bolts. Such an anchor is adhesively bonded or anchored in a wall, wall, ceiling or foundation in such a way that a part of it is adhesively bonded in a force-locking manner and a part of it protrudes and can withstand building loads.

[0145] The same or different substrates can be bonded.

[0146] An article is obtained by the application and curing of the epoxy resin composition.

[0147] The present invention thus also provides an article obtained by using the epoxy resin composition.

[0148] The article is preferably a building structure or a part thereof, especially a building, office, production hall, sports hall, cold storage, silo, bridge, roof, staircase, floor, balcony, terrace or parking floor slab of an above-ground or underground building, or an industrial article or consumer article, especially a dock, offshore platform, gate, crane, sheet pile wall, pipeline or rotor blade of a wind turbine, or a means of transportation, such as especially a car, truck, rail vehicle, ship, aircraft or helicopter, or an installable part thereof.

[0149] The epoxy resin composition is characterized by advantageous properties. It has a particularly low viscosity and thus excellent processability, and cures reliably and quickly, especially even under wet and cold conditions, where a coating with high mechanical quality having high hardness, high glass transition temperature, good surface and surprisingly little yellowing tendency is formed. Such an epoxy resin composition is particularly suitable as a coating, especially for floors. Examples

[0150] Some examples are given below to further illustrate the invention described. Of course, the present invention is not limited to these described examples.

[0151] "AHEW" stands for amine hydrogen equivalent.

[0152] "EEW" stands for epoxy equivalent weight.

[0153] "Standard climatic conditions" ("NK") means a temperature of 23 ± 1 °C and a relative air humidity of 50 ± 5%.

[0154] Unless otherwise stated, the chemicals used are from Sigma-Aldrich Chemie GmbH.

[0155] Measurement method description:

[0156] Viscosity was measured on a Rheotec Rc30 cone-plate viscometer at constant temperature (cone diameter 50 mm, cone angle 1°, cone tip - plate distance 0.05 mm, shear rate 10 s -1 ).

[0157] The amine value was determined by titration (using 0.1 N HClO4 in acetic acid with crystal violet as the indicator).

[0158] Substances and abbreviations used:

[0159] GY 250: Bisphenol A - diglycidyl ether, EEW 187 g / Eq (from Huntsman)

[0160] DY - E: C 12 - C 14 Mono - glycidyl ether of alcohol, EEW approximately 290 g / Eq (from Huntsman)

[0161] IPDA: 1 - Amino - 3 - aminomethyl - 3,5,5 - trimethylcyclohexane, AHEW 42.6 g / Eq( IPD from Evonik)

[0162] B - EDA: N - Benzyl - 1,2 - ethanediamine, prepared as described below, 150.2 g / mol, AHEW 50 g / Eq

[0163] BAC 1,3 - Bis(aminomethyl)cyclohexane, AHEW 35.5 g / Eq (from Mitsubishi Gas Chemical)

[0164] MXDA 1,3 - Bis(aminomethyl)benzene, AHEW 34 g / Eq (from Mitsubishi Gas Chemical)

[0165] TMD 2,2(4),4 - Tetramethylhexamethylenediamine, AHEW 39.6 g / Eq( TMD from Evonik)

[0166] TEPA Tetraethylenepentamine, AHEW approximately 30 g / Eq (technical grade, from Huntsman)

[0167] K54 2,4,6 - Tris(dimethylaminomethyl)phenol (from Air Products)

[0168] N - Benzyl - 1,2 - ethanediamine (B - EDA):

[0169] 180.3 g (3 mol) of 1,2-ethylenediamine were placed in a round-bottom flask at room temperature under a nitrogen atmosphere. A solution of 106.0 g (1 mol) of benzaldehyde in 1200 ml of isopropanol was slowly added dropwise with thorough stirring, and stirring was continued for another 2 hours. The reaction mixture was then hydrogenated in a continuous hydrogenation apparatus using a Pd / C fixed bed catalyst at a hydrogen pressure of 80 bar, a temperature of 80° C. and a flow rate of 5 ml / min. To monitor the reaction, it was checked by means of IR spectroscopy whether the peak at about 1665 cm -1 The imine band at has disappeared. The hydrogenated solution is then concentrated on a rotary evaporator at 65° C. to remove unreacted 1,2-ethylenediamine, water and isopropanol. The reaction mixture thus obtained is a clear, pale yellow liquid having an amine number of 678 mg KOH / g and containing approximately 85% by weight of N-benzyl-1,2-ethylenediamine determined by means of GC (retention time 8.47-8.57 min).

[0170] 120 g of this reaction mixture were purified by distillation at 80° C. under reduced pressure, resulting in the collection of 75.1 g of distillate (N-benzyl-1,2-ethylenediamine) at a vapor temperature of 60 to 65° C. and 0.06 mbar. A colorless liquid with a viscosity of 8 mPa·s at 20° C., an amine number of 750 mg KOH / g and a purity of >97% determined by GC was obtained. This was used for the further examples.

[0171] Preparation of curing agent and epoxy resin composition:

[0172] Embodiments 1 to 18:

[0173] For each example, the components of the resin components specified in Tables 1 to 3 were mixed in the specified amounts (in parts by weight) by means of a centrifugal mixer (SpeedMixer TM DAC 150, FlackTek Inc.) and stored under moisture exclusion conditions.

[0174] The ingredients of the hardener component specified in Tables 1 to 3 were likewise processed and stored.

[0175] The two components of each composition were then processed into a homogeneous liquid with the aid of a centrifugal mixer and immediately tested as follows:

[0176] Ten minutes after mixing, the viscosity was measured at 20° C. (“Viscosity (10′)”).

[0177] The gel time was determined under standard climatic conditions by occasionally stirring the mixed composition (25 g) with a spatula until it started to gel.

[0178] For the determination of the Shore D hardness, two cylindrical test specimens (diameter 20 mm, thickness 5 mm) are prepared in each case in accordance with DIN 53505. One is stored under standard climatic conditions and the hardness is measured after 1 day and after 2 days (1d NK and 2d NK); the other is stored at 8 °C and 80 % relative humidity and the hardness is measured in the cold state after 1 day and after 2 days (1d 8° / 80 % and 2d 8° / 80 %).

[0179] The first film is applied to a glass plate with a layer thickness of 500 μm and is stored / cured under standard climatic conditions. On this film, the hardness (1d NK)” is measured after 1 day, the hardness (2d NK)” is measured after 2 days, the hardness (4d NK)” is measured after 4 days, the hardness (7d NK)” is measured after 7 days, and the hardness (14d NK)” is measured after 14 days hardness ( pendulum hardness, measured in accordance with DIN EN ISO 1522). After 14 days, the appearance of the film is evaluated (marked as “appearance (NK)” in the table). If the film has a smooth, shiny and non-sticky surface, the film is described as “good”. “Texture” means any type of stripe or pattern on the surface. A film with reduced gloss is called “matte”.

[0180] The second film is applied to a glass plate with a layer thickness of 500 μm and is immediately stored / cured at 8 °C and 80 % relative humidity for 7 days after application and then stored / cured under standard climatic conditions for 2 weeks. 24 hours after application, a polypropylene bottle cap is placed on the film and a wet sponge is placed under the cap. After another 24 hours, the sponge and the cap are removed and placed at a new location on the film, and they are removed from this location and re-placed after 24 hours, this is done a total of 4 times. Then the appearance of this film is evaluated in the same way as described for appearance (NK) (marked as “appearance (8° / 80 %)” in the table). In each case, the number and nature of the visible marks formed in the film due to the wet sponge or the cap placed thereon are also reported here. The number of white spots is reported as “cloudiness”. Slightly white spot marks are marked as “(1)”. Clear white spot marks are marked as “1”. If there is an annular imprint due to the sinking of the first cap placed 24 hours after application, the mark “ring” is reported. Such an annular imprint indicates that the coating is not yet suitable for walking. Very small annular imprints are marked as “(yes)”. Clear annular imprints are marked as “yes”. The Hardness, in each case after 7 days at 8 °C and 80 % relative humidity (“ Hardness (7d 8 ° / 80 %)”), then after a further 2 days at NK (“ Hardness (+2d NK)”), after 7 days at NK (“ Hardness (+7d NK)”) and after 14 days at NK (“ Hardness (+14d NK)”) was determined.

[0181] The Tg value (glass transition temperature) was determined by means of DSC on cured samples stored for 14 days under standard climatic conditions using a Mettler Toledo DSC 3+700 instrument and the following measurement program: (1) -10 °C for 2 min, (2) heating rate of 10 K / min from -10 to 200 °C (= first run), (3) cooling rate of -50 K / min from 200 to -10 °C, (4) -10 °C for 2 min, (5) heating rate of 10 K / min from -10 to 180 °C (= second run).

[0182] As a measure of yellowing, the color change after loading in a climatic tester was also determined. For this, a further film was applied to a glass plate with a layer thickness of 500 µm and stored or cured for 2 weeks under standard climatic conditions, then loaded in a Q-Sun Xenon Xe-1 type climatic tester with a Q-SUN Daylight-Q filter and a xenon lamp with a light intensity of 0.51 W / m 2 at 340 nm for 72 h (Q-Sun (72 h)). The color difference ΔE of the loaded film relative to the corresponding unloaded film was then determined using an NH310 colorimeter from Shenzen 3NH Technology Co., LTD equipped with a silicon photodiode detector, light source A, and color space measurement interface CIE L*a*b*C*H*.

[0183] The results are reported in Tables 1 to 3.

[0184] The examples marked “(Ref.)” are comparative examples.

[0185]

[0186] Table 1: Composition and properties of Examples 1 to 7. 1 Ratio of amine hydrogen equivalents of IPDA and B-EDA

[0187] Table 2: Composition and properties of Examples 8 to 11.

[0188]

[0189] Table 3: Composition and properties of Examples 12 to 18.

[0190] 1 Amine hydrogen equivalent ratio of IPDA and B-EDA

[0191] Examples 19 to 21:

[0192] For these examples, the filled commercially available resin components were used in the amounts shown in Table 4: Component A RAL 5005 (from Sika).

[0193] The components of the curing agent shown in Table 4 were processed and stored as described above. Then the two components were processed into a homogeneous liquid as described above and tested as specified in Example 1.

[0194] The results are reported in Table 4.

[0195]

[0196] Table 4: Composition and properties of Examples 19 to 21.

[0197] 1 Amine hydrogen equivalent ratio of IPDA and B-EDA

Claims

1. A curing agent for epoxy resin, comprising 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane and N-benzyl-1,2-ethylenediamine in such amounts that the ratio of the number of their amine hydrogens is in the range of 75 / 25 to 30 / 70.

2. The curing agent according to claim 1, characterized in that it contains less than 10% by weight of 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane adducted with epoxy resin.

3. The curing agent according to claim 1, characterized in that it contains less than 5% by weight of 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane adducted with epoxy resin.

4. The curing agent according to claim 1, characterized in that it contains less than 1% by weight of 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane adducted with epoxy resin.

5. The curing agent according to any one of claims 1 to 4, characterized in that N-benzyl-1,2-ethylenediamine has a purity of at least 80% by weight.

6. The curing agent according to any one of claims 1 to 4, characterized in that it contains less than 10% by weight of N-benzyl-1,2-ethylenediamine adducted with epoxy resin.

7. The curing agent according to any one of claims 1 to 4, characterized in that it contains less than 5% by weight of N-benzyl-1,2-ethylenediamine adducted with epoxy resin.

8. The curing agent according to any one of claims 1 to 4, characterized in that it contains less than 1% by weight of N-benzyl-1,2-ethylenediamine adducted with epoxy resin.

9. The curing agent according to any one of claims 1 to 4, characterized in that it contains at least one additional component selected from additional amines, accelerators, and diluents.

10. The curing agent according to any one of claims 1 to 4, characterized in that at least 30% of all the amine hydrogens contained in the curing agent are derived from 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane and N-benzyl-1,2-ethylenediamine.

11. The curing agent according to any one of claims 1 to 4, characterized in that at least 40% of all the amine hydrogens contained in the curing agent are derived from 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane and N-benzyl-1,2-ethylenediamine.

12. The curing agent according to any one of claims 1 to 4, characterized in that at least 50% of all the amine hydrogens contained in the curing agent are derived from 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane and N-benzyl-1,2-ethylenediamine.

13. The curing agent according to any one of claims 1 to 4, characterized in that at least 60% of all the amine hydrogens contained in the curing agent are derived from 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane and N-benzyl-1,2-ethylenediamine.

14. The curing agent according to any one of claims 1 to 4, characterized in that it contains salicylic acid.

15. An epoxy resin composition, comprising: - a resin component, the resin component comprising at least one epoxy resin, and - a curing agent component, the curing agent component comprising the curing agent according to any one of claims 1 to 14.

16. The epoxy resin composition according to claim 15, characterized in that it has a viscosity in the range of 100 to 4000 mPa·s at 20 °C after the resin component and the curing agent component have been mixed for 10 minutes, measured at a shear rate of 10 s -1 by means of a cone-plate viscometer.

17. The epoxy resin composition according to claim 16, characterized in that it has a viscosity in the range of 200 to 3000 mPa·s at 20 °C after the resin component and the curing agent component have been mixed for 10 minutes.

18. The epoxy resin composition according to claim 16, characterized in that it has a viscosity in the range of 200 to 2000 mPa·s at 20 °C after the resin component and the curing agent component have been mixed for 10 minutes.

19. The epoxy resin composition according to claim 16, characterized in that it has a viscosity in the range of 200 to 1500 mPa·s at 20 °C after the resin component and the curing agent component have been mixed for 10 minutes.

20. The epoxy resin composition according to any one of claims 15 to 19, characterized in that after the components have been mixed and after a curing time of 14 days at room temperature, it has a glass transition temperature of at least 45 °C during the first heating period and at least 60 °C during the second heating period, determined by means of DSC using the following measurement program: (1) -10 °C for 2 min, (2) heating from -10 to 200 °C at a heating rate of 10 K / min, (3) cooling from 200 to -10 °C at a cooling rate of -50 K / min, (4) -10 °C for 2 min, (5) heating from -10 to 180 °C at a heating rate of 10 K / min.

21. The epoxy resin composition according to claim 20, characterized in that after the components have been mixed and after a curing time of 14 days at room temperature, it has a glass transition temperature of at least 50 °C during the first heating period.

22. The epoxy resin composition according to claim 20, characterized in that after the components have been mixed and after a curing time of 14 days at room temperature, it has a glass transition temperature of at least 65 °C during the second heating period.

23. Use of the epoxy resin composition according to any one of claims 15 to 22 as a coating, primer, adhesive, sealant, potting compound, casting resin, impregnating resin or as a matrix for fiber composites.

24. Coating method, comprising the following steps: (i) mixing the components of the epoxy resin composition according to any one of claims 15 to 22, (ii) applying the mixed composition to a substrate within the pot life, and then curing the mixed composition.

25. Bonding method, comprising the following steps: (i) mixing the components of the epoxy resin composition according to any one of claims 15 to 22, (ii) applying the mixed composition - to at least one of the substrates to be bonded and joining the substrates to form a bond within the open time, or - into a cavity or gap between a plurality of substrates, and optionally inserting an anchor into the cavity or gap within the open time, and then curing the mixed composition.

26. An article obtained by the use according to claim 23 or by the method according to any one of claims 24 and 25.

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