EP1799745A1

EP1799745A1 - Aging-resistant coatings and adhesive composites

Info

Publication number: EP1799745A1
Application number: EP05798088A
Authority: EP
Inventors: Olaf Lammerschop; Steve DÖRING; Michael Kux; Andreas Ferencz; Stefan Kreiling
Original assignee: Henkel AG and Co KGaA
Current assignee: Henkel AG and Co KGaA
Priority date: 2004-10-11
Filing date: 2005-10-10
Publication date: 2007-06-27
Also published as: US7462658B2; JP2008516064A; US20070231582A1; CA2583916A1; WO2006040108A1; DE102004049717A1

Abstract

The invention relates to hardening compositions, comprising a hardening component and a m-hydroxybenzene derivative of general formula (I): where Y = carboxyl, carboxylate, or straight-chain or branched alkyl, optionally substituted with hydroxy, amino, carboxyl and/or carboxylate groups and R1, R2 and R3 independently = H or OH, where R1 and R3 are not simultaneously OH, with the proviso that when the hardening composition is a thermally-hardening component of a multi-component epoxy-based system, the hardening composition is free of transition metal oxides of the copper and zinc groups and, when the hardening component is an epoxy-based thermally-hardening component, the above is not a self-hardening component. The invention further relates to the use of the m-hydroxybenzene derivative as aging inhibitor in coating agents and adhesives and a method for coating or gluing of substrates.

Description

Aging resistant coatings and adhesive bonds

The present invention relates to curable compositions that are resistant to aging in a cured state, especially in a humid environment. In particular, the invention relates to coating compositions and adhesives containing aging resistance-imparting additives, as well as the use of these additives in coating compositions and adhesives.

The adhesion of a surface coating agent on a substrate surface is of great importance in view of a permanent function of the coating composition. In particular, to adhesives that should connect two substrates as permanently as possible, high demands are made in this regard. The bond strength of such an adhesive depends on the compatibility between the adhesive and the substrate to which the adhesive is to be applied, d. h., Adhesion between adhesive and substrate. However, adhesion also relies on the cohesion of the adhesive itself. Even small changes in the composition of the adhesive can produce a drastic reduction in bond strength, either rendering the adhesive unusable in the first place or weakening, or even weakening, an adhesive bond obtained using such an adhesive completely destroy.

Therefore, it must be ensured in the formulation of adhesives that individual components supplied to the adhesive do not adversely affect the adhesive force of such an adhesive. In addition, an adhesive bond due to environmental influences and thus as a result of aging of the adhesive, their bond strength over a certain period of time such a loss that a firm connection between two parts is no longer guaranteed.

Especially the adhesion of cured epoxy resins on metals z. As in the structural bonding of metals with epoxy resin adhesives, decreases considerably by aging processes, especially under the influence of moisture. The main reason is an ingress of water into the adhesive bond, which reduces the adhesion of the adhesive to the metal surface.

To improve the adhesion under moist conditions, metallic surfaces are usually pretreated with so-called primers. This, in turn, requires a further step that prolongs glueing operations and causes increased costs. In many cases, for example in accident repairs in the body area, these pretreatment methods are beyond limited use. This is especially true with regard to steel or aluminum components frequently used in body construction, since the adhesion of 2K epoxy resin adhesives to steel or aluminum, in particular in the case of insufficient substrate pretreatment, is often very poor.

As a result of these aging processes, the adhesive may lose flexibility, cohesion or adhesion or one or more other important properties.

In particular, when an adhesive is to be used outdoors, it must be ensured that, for example, caused by moisture changes that lead to the loss of adhesive force, not or only inevitably occur to a small extent.

This need has led to the suggestion of various ways of giving adhesive bonds improved long-term stability even under the influence of environmental conditions such as moisture.

Thus, for example, heat-curing epoxy resin adhesives are known from the state of the art which have sufficient adhesion to aluminum surfaces under customary conditions. A disadvantage of these adhesives, however, is often that the aging resistance for applications under extreme conditions is not sufficient. GB 2 222 592 A describes the pretreatment of metallic surfaces with polyhydroxylated benzene derivatives. To avoid this further working step, the addition of additives to the adhesive composition is sometimes recommended. Thus GB 2 222 592 A describes the coating of metallic surfaces with heat-curable 1-component systems, ie systems which are self-curing without the addition of a further component, for example a chemical hardener under the action of heat, and their hardening at temperatures of at least 100 ° C, wherein the compositions may contain polyhydroxylated benzene derivatives.

From EP 0,458,521 A2 is known to use metal oxides in combination with Polyhydroxyarylverbindungen in thermosetting compositions for the improvement of aging resistance, which also temperatures of at least 100 ⁰ C in the curing are required. In this case, EP 0 458 521 A2 delimits the metal oxides to be used according to claim 1 of EP 0 458 521 A2 from oxides which have other functions, such as, for example, thixotroping of the composition or serve as fillers. EP 0 458 521 describes oxides of the transition metals of the Periodic Table, in particular those of the copper and zinc subgroups, as the metal oxides to be used. However, the use of such transition metal oxides is undesirable for various, especially economic reasons.

JP 08198945 (Abstract) discloses amine-curing epoxy resins containing aromatic hydroxy compounds and fillers.

WO 00/34405 A discloses adhesive compositions containing an aromatic carboxylic acid and a hydroxyl-containing polymer, the latter having to contain a small amount of carboxy-functional monomer units for the adhesive composition to possess corrosion resistance.

WO 03/014236 A2 describes binder components which contain compounds with chelating properties. In particular, be Compounds having chelating properties are disclosed as containing amino or mercapto groups.

The object underlying the invention was, in particular, to increase the aging resistance of adhesive composites even under extreme conditions, such as high humidity, by providing adhesives which can be used without the use of primers on many substrates, but in particular on metals, and are excellent Adhesion to the substrate and have an excellent cohesion. Furthermore, it should be possible, for example, to dispense with the use of additive combinations with transition metal oxides, in particular those of the copper and zinc groups, and moreover also the use in 2-component adhesive systems (2K adhesives), i. be possible in usually without heat-curing systems.

Surprisingly, it has been found that m-hydroxybenzene derivatives of the general formula (I):

wherein Y is a carboxyl group, a carboxylate group or a straight-chain or branched, optionally substituted with hydroxyl groups, amino groups, carboxyl groups and / or carboxylate groups alkyl group; and R ¹ , R ² and R ^{3 are} independently the same or different and represent hydrogen or a hydroxyl group, and R ¹ and R ^{3 are} not simultaneously a hydroxyl group; with the proviso that, if the curable component is a thermosetting component of an epoxy-based multi-component system, the curable composition is free of transition metal oxides of the copper and zinc group, and if so curable component is an epoxy-based thermosetting component, it is not a self-curing component, are extremely suitable to increase the aging resistance of adhesive bonds and coatings.

In none of the documents known from the prior art, the importance of the 1-Y-3-hydroxy substitution pattern of the above compounds for the use according to the invention is recognized or even taught.

Particularly preferred as aging inhibitors are those in which one or two of the radicals R ¹ , R ² and R ^{3 represent} a hydroxyl group.

Examples of suitable aging inhibitors in which Y represents a carboxyl group or carboxylate group are, in particular, 3-hydroxybenzoic acid, 3-hydroxysalicylic acid, 3,5-dihydroxybenzoic acid and 3,4,5-

Trihydroxybenzoic acid, and salts thereof. Suitable salts are, in particular, the alkali metal salts, such as sodium salts and potassium salts or ammonium salts of the acids mentioned.

Examples of suitable aging inhibitors in which Y represents a straight-chain or branched alkyl group are in particular those in which the alkyl group contains 1 to 12, more preferably 1 to 6, and most preferably 1 to 4 carbon atoms. Very particularly preferred are the methyl, ethyl, n-propyl, iso-propyl, n-butyl, isobutyl and tert-butyl radicals. These may preferably be further substituted and carry one or more of the following radicals selected from the group hydroxy, amino, carboxyl and carboxylate. By way of example, mention may be made of 3-ethylphenol, 5- (hydroxymethyl) benzene-1, 3-diol, 4-isobutylbenzene-1,2-diol or 4-alanylbenzene-1,2-diol.

In addition to the inventive use of the aging inhibitors described above in curable compositions, such as adhesives or coating compositions, the curable compositions thus obtained are also subject of the invention. Both in the inventive use of the above-described aging inhibitors in curable compositions, such as adhesives or coating compositions, as well as in the curable compositions thus obtained, it is preferred that the compound of general formula (I) interacts with iron (III), wherein it is particularly preferred if said compound of general formula (I) is in the form of an iron (III) complex. The same applies to the method described in the context of the present application.

In this context, wherever aging inhibitors of the general formula (I) are used in the context of the present invention, it is particularly preferred if they interact with iron (III), it being particularly preferred if the said compound of general formula (I) is in the form of an iron (III) complex.

According to the invention, therefore, a curable composition comprising a curable component and at least one m-hydroxybenzene derivative of the general formula (I):

wherein Y is a carboxyl group, a carboxylate group or a straight-chain or branched, optionally substituted with hydroxyl groups, amino groups, carboxyl groups and / or carboxylate groups alkyl group; and R ¹ , R ² and R ^{3 are} independently the same or different and represent hydrogen or a hydroxyl group, and R ¹ and R ^{3 are} not simultaneously a hydroxyl group; with the proviso that, if the curable component is a thermosetting component of an epoxy-based multi-component system, the curable composition is free of transition metal oxides of the copper and zinc group, and if the curable component is an epoxy-based thermosetting component is, it is not a self-curing component, provided by the invention.

It is again pointed out that it is to be regarded as a preferred embodiment of the present invention, when the compound of the general formula (I) interacts with iron (III), it being particularly preferred if said compound of the general formula (I ) in the form of an iron (III) complex.

The curable component contained in the compositions of the present invention may be cured by radiation, heat, catalytic or a chemical hardener and includes, for example, epoxy compounds, (meth) acrylates (which term means both acrylates and methacrylates), (meth) acrylic acid or polyol-curing polyisocyanates ,

Among the so-called multi-component systems, ie those which contain one or more hardeners in addition to one or more curable components and which are mostly cold-curing, 2-component systems have the greatest importance. In such 2K systems, the curable component is usually one that is curable by means of a chemical hardener.

For example, 2-component epoxy adhesives may be amine-cured epoxy systems wherein the curing component is an epoxy component and the curing agent is an amine.

Polyepoxides containing on average at least two epoxide groups per molecule are usually used as the epoxy component in such systems. These epoxy compounds can be both saturated and unsaturated and aliphatic, cycloaliphatic, aromatic or heterocyclic and also have hydroxyl groups.

These epoxy components are preferably polyglycidyl ethers based on polyhydric, preferably dihydric alcohols, phenols, hydrogenation products of these phenols and / or novolacs (reaction products of mono- or polyhydric phenols with aldehydes, in particular formaldehyde in the presence of acidic catalysts).

The polyglycidyl ethers of polyhydric alcohols are also suitable. Examples of such polyhydric alcohols are ethylene glycol, diethylene glycol, triethylene glycol, 1, 2-propylene glycol, polyoxypropylene glycols (n = 1-20), 1, 3-propylene glycol, 1, 4-butylene glycol, 1,5-pentanediol, 1, 6-hexanediol , 1, 2,6-hexanetriol, glycerol and bis- (4-hydroxycyclohexyl) -2,2-propane.

Polyglycidyl ethers of polycarboxylic acids can also be used, which are obtained by the reaction of epichlorohydrin or similar epoxy compounds with an aliphatic, cycloaliphatic or aromatic polycarboxylic acid such as oxalic, succinic, adipic, glutaric, phthalic, terephthalic, hexahydrophthalic, 2,6-naphthalenedicarboxylic and dimerized Linolenic acid, receives. Examples are adipic acid diglycidyl ester, phthalic acid diglycidyl ester and hexahydrophthalic acid diglycidyl ester.

Particularly suitable epoxy compounds are those based on reaction products between epichlorohydrin and bisphenol A or bisphenol F.

A detailed list of suitable epoxy compounds can be found in A.M. Paquin, Handbuch "Epoxy Compounds and Epoxy Resins", Springer-Verlag, Berlin 1958, Chapter V, pages 308 to 461 and further Lee, Neville "Handbook of Epoxy Resins", 1967, Chapter 2, pages 2-1 to 2-33.

As amine hardeners in 2K epoxy systems are primary and / or secondary amines for use. The amines used are preferably polyamines having at least two nitrogen atoms and at least two active amino hydrogen atoms per molecule. Aliphatic, aromatic, aliphatic-aromatic, cycloaliphatic and heterocyclic di- and polyamines can be used.

Examples of suitable amine hardeners are straight-chain or branched polyalkyleneamines, such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, 1,2-propylenediamine, 1,3-propylenediamine, 1,4-butanediamine, 1,5-pentanediamine, 1,3-pentanediamine, 1 , 6-hexanediamine, 3,3,5-trimethyl-1,6-hexanediamine, 3,5,5-trimethyl-1,6-hexanediamine, 2-methyl-1,5-pentanediamine, bis (3-aminopropyl) amine , N, N'-bis (3-aminopropyl) -1, 2-ethanediamine, N- (3-aminopropyl) -1,2-ethanediamine, cycloaliphatic polyamines, such as 1,2-diaminocyclohexane, 1,3-diaminocyclohexane, 1 , 4-diaminocyclohexane, aminoethylpiperazine,

Poly (alkylene oxide) diamines and triamines, such as. Jeffamine D-230, Jeffamine D-400, Jeffamine D-2000, Jeffamine D-4000, Jeffamine T-403, Jeffamine EDR-148, Jeffamine EDR-192, Jeffamine C-346, Jeffamine ED-600, Jeffamine ED. 900, Jeffamine ED-2001, aromatic polyamines such as, meta-xylylenediamine, phenylenediamine, 4,4'-diaminodiphenylmethane, toluenediamine, isophoronediamine, S.S'-dimethylM '' - diaminodicyclohexylmethane, 4,4'-diaminodicyclohexylmethane, 2,4 ' Diaminodicyclohexylmethane, the mixture of poly (cyclohexyl aromatic) amines linked via a methylene bridge (also known as MBPCAA) and polyaminoamides.

In the event that the curing component is a (meth) acrylate or (meth) acrylic acid, the curing is usually carried out by free-radical polymerization, initiated by radical-forming substances, such as peroxides, hydroperoxides or azo compounds or photochemically, indziert with help of photoinitiators in combination with ultraviolet light.

However, it is also possible ionic polymerization, especially the anionic polymerization by means of suitable bases. In some cases, a polymerization can already be done by the admission of humidity. The aging inhibitors according to the invention can also be used in polyurethane adhesive systems. Curing takes place here in particular by polycondensation of polyisocyanates, preferably diisocyanates with polyols, in particular diols.

By polyisocyanates are meant compounds having at least two isocyanate groups. The polyisocyanates used are preferably the aromatic isocyanates, for example diphenylmethane diisocyanate, either in the form of the pure isomers, as isomer mixture of the 2,4 '- / 4,4'-isomers or else the diphenylmethane diisocyanate (MDI) liquefied with carbodiimide, for example under the trade name Isonate 143 L is known. In addition, the so-called "crude MDI", ie, the isomers / oligomer mixture of MDI can be used, as they are commercially available, for example, under the trade name PAPI or Desmodur VK. Furthermore, so-called quasi-prepolymers, ie reaction products of MDI or toluene diisocyanate (TDI) with low molecular weight diols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol or triethylene glycol can be used. Although the aforementioned isocyanates are the most preferred isocyanates, it is also possible to use aliphatic or cycloaliphatic di- or polyisocyanates, for example the hydrogenated MDI (H 12MDI) ₁ tetramethylxylylene diisocyanate (TMXDI), 1-isocyanatomethyl-3-isocyanato-1,5,5 trimethylcyclohexane (IPDI), hexane-1,6-diisocyanate (HDI), biuretization product of HDI, isocyanuration product of HDI or dimer fatty acid diisocyanate.

Suitable polyols are compounds having at least two hydroxyl groups. Suitable polyols are preferably the liquid polyhydroxy compounds having two or three hydroxyl groups per molecule, such as di- and / or trifunctional polypropylene glycols in the molecular weight range from 200 to 6000, preferably in the range of 400 to 3000. It may also be random and / or block copolymers of Ethylene oxide and propylene oxide are used. Another group of preferably used polyether polyols are the polytetramethylene glycols, for example by the acidic Polymerization of tetrahydrofuran, wherein the molecular weight range of the polytetramethylene glycols is preferably between 200 and 6000, more preferably in the range of 400 to 4000. Further suitable polyols are the liquid polyesters obtained by condensation of di- or tricarboxylic acids, such as adipic acid, sebacic acid, glutaric acid with low molecular weight diols or triols such as ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, 1, 4-butanediol, 1, 6-hexanediol, glycerol or trimethylolpropane can be prepared. Another group of usable polyols are the lactones-based polyesters, such as caprolactone or valerolactone. However, it is also possible to use polyester polyols of oleochemical origin. Such polyester polyols can be prepared, for example, by complete ring opening of epoxidized triglycerides of a fat mixture containing at least partially olefinically unsaturated fatty acid with one or more alcohols having 1 to 12 carbon atoms and subsequent partial transesterification of the triglyceride derivatives to alkyl ester polyols having 1 to 12 carbon atoms in the alkyl radical. Other suitable polyols are polycarbonate polyols and dimer diols, and in particular castor oil and its derivatives. The hydroxy-functional polybutadienes, such as those obtainable, for example, under the trade name "poly-BD", can also be used as polyols for the compositions according to the invention.

Irrespective of the example systems listed above, the aging inhibitors can be used independently of the adhesive system according to the invention. As described, both epoxy-based systems and polyurethane or (meth) acrylate adhesive systems are particularly suitable.

Although use in heat-curable 1 K and / or 2K systems, ie adhesive systems having a curing temperature of 100 ⁰ C and more, is possible, a particular advantage of the aging inhibitors according to the invention is therein, even in 2K systems, for example at temperatures below 100 ⁰ C, preferably at a temperature between 15 ⁰ C and 95 ⁰ C, more preferably 50 ⁰ C to 90 ⁰ C to develop their effect. In particular, the invention usable, aging inhibitor-containing, epoxy-polyamine-based 2K systems show excellent aging resistance.

Even small amounts of the additive of less than 10 wt .-% based on the curable composition are usually sufficient to increase the aging resistance according to the invention. In individual cases, however, even much smaller amounts, of about 0.1% by weight, are sufficient to develop the properties according to the invention. Preferably, 0.5 to 9 wt .-%, more preferably 2 to 8 wt .-%, most preferably 2 to 6 wt .-% based on the curable composition.

The aging inhibitor may be premixed with either the curable component or, if a chemical hardener component is required for curing, may be supplied by blending it with the curable composition of the present invention. However, in 2K systems, the aging inhibitor may also be present in both components or, if the processing time permits, may be added to the 2K system only after mixing the two components.

The aging inhibitors can also be used in systems containing more than two components. Thus, these are also applicable in systems with multiple curable components and / or multiple curing agents.

Preferably, the curable composition is a coating agent or an adhesive. In particular, the composition is characterized in that there is no need for transition metal oxides as a co-component to the aging inhibitor necessary to act according to the invention.

The invention further provides a process which comprises coating a substrate with a curable composition, the curable composition comprising a curable component and at least one m-hydroxybenzene derivative of the general formula (I):

wherein Y is a carboxyl group, a carboxylate group or a straight-chain or branched, optionally substituted with hydroxyl groups, amino groups, carboxyl groups and / or carboxylate groups alkyl group; and R ¹ , R ² and R ^{3 are} independently the same or different and represent hydrogen or a hydroxyl group, and R ¹ and R ^{3 are} not simultaneously a hydroxyl group; with the proviso that, if the curable component is a thermosetting component of an epoxy-based multi-component system, the curable composition is free of transition metal oxides of the copper and zinc group, and if the curable component is an epoxy-based thermosetting component is, it is not a self-curing component.

The curable composition used in the process according to the invention is preferably one which is curable by a chemical hardener or by heat or radiation and cured after application.

When the method is used to produce adhesive composites, the curable composition preferably contains a chemical hardener and / or is thermosetting. The coating located on the substrate is then brought into contact with another substrate prior to curing so that the curable coating lies between the two substrates and, in a further step, the coating is cured. The substrates used in the process according to the invention may in principle be any desired substrates, for example metallic substrates, plastics, glass and ceramic substrates or wood. The substrates used are preferably metallic substrates such as, for example, light metals, aluminum, copper or steel such as, for example, ZE steel, ZEP steel or phosphated steel, the metallic substrates also being able to be used in the form of their alloys or in galvanized or oiled form Shape.

The invention will be illustrated by the following examples.

EXAMPLES

Epoxy-based compositions

Cold-curing of an epoxy-based composition

For the preparation of the epoxy adhesives, the hardenable binder component was an epoxy resin of bisphenol A and epichlorohydrin having a number average molecular weight of about 700 g / mol (DE R 331 P, available from The Dow Chemical Company) and, as a hardener, a terminal diaminofunctional polypropylene glycol having one molecular weight of 400 g / mol (Jeffamine® D400, available from Huntsman Chemical Company). The composition according to the invention additionally contains 3,4,5-trihydroxybenzoic acid (see Example 2a) as an aging inhibitor. Using an adhesive prepared in this way, cleaned and degreased ZE steel sheets (or aluminum sheets or CRS steel sheets) of the dimension 100 × 25 mm (bond area 25 × 10 mm) were bonded and cured at 90 ^° C. or 80 ^° C. for 180 minutes. The bonded sheets were then examined for the tensile shear strength of the bond (determined according to DIN 53283 "Determination of the bond strength of single-lapped adhesive bonds" at a speed of 100 mm / min). Identically prepared further specimens were subjected to a Cataplasmatest at 70 ⁰ C and examined immediately after removal in the wet state to their tensile shear strength.

To perform the cataplasm test, the test specimens were wrapped in a paper towel soaked in distilled water. This arrangement was then enclosed with aluminum foils and stored in an airtight plastic container at 70 ⁰ C for one week, two weeks or four weeks. After the corresponding storage time the samples were taken in - frozen at -20 ⁰ C, thawed and then tested immediately at room temperature on their tensile shear strength. As can be seen from Table 1, further epoxy adhesives according to the invention (Examples 2b and 2c) were made available on the same binder and hardener base already described above, the inventive composition being used instead of 3,4,5-trihydroxybenzoic acid (Example 2a ) 3,4-dihydroxyphenylalanine (Example 2b) or 3,4-dihydroxyphenylalanine plus Fe (III) (Example 2c) as aging inhibitor.

Using the adhesives prepared according to Examples 2b and 2c, cleaned and degreased CRS steel sheets of dimensions 100 × 25 mm (bonding area 25 × 10 mm) were bonded and cured at 90 ^° C. for 180 minutes. The examination of the bonded sheets with regard to the tensile shear strength of the bond was carried out as already described (DIN 53283 "Determination of the Adhesive Strength of Single-Sided Adhesions" at a Speed of 100 mm / min). The results can be found in Table 4 again.

Likewise, for Example 2b and 2c produced in another identical test specimens were subjected to a Kataplasmatest at 70 ⁰ C and examined immediately after removal in the wet state to their tensile shear strength. The results can also be found in Table 4 again.

The Kataplasmatests was also carried out as already described above.

To prepare the aging inhibitor [3,4-dihydroxyphenylalanine plus Fe (III)] used in Example 2c, 0.035 mol of 3,4-dihydroxyphenylalanine were initially charged at RT in 100 ml of ethanol. Thereafter, about 50 ml of an ethanolic solution of 0.038 mol of Fe (III) nitrate were added with stirring.

After about 15 minutes, a strongly colored precipitate forms. This is filtered off after a further 15 minutes, washed with ethanol and finally dried in a drying oven.

To verify the effectiveness of the adhesives of the invention, the adhesives shown in the following table were prepared. Table 1

Example 1 is not according to the invention

Table 2

Tensile shear strength (in MPa) for adhesive composites with ZE steel after

Kataplasmabehandlung

Table 3

Tensile shear strength (in MPa) for adhesive bonds with aluminum after

Kataplasmabehandlung

Table 4

Tensile shear strength (in MPa) for adhesive bonds with CRS steel after

Kataplasmabehandlung

Heat curing of a 2-component composition based on epoxy at 120 ⁰ C without the addition of transition metal oxides of copper and zinc

To carry out the experiments from Tables 5 and 6 compositions were prepared according to Table 1, but with different inventive and non-inventive additives, these applied to a degreased aluminum test specimen AI6016 (100 x 25 x 0.8 mm), at 120 ⁰ C for 1 hour hardened and stored partly under cataplasm conditions. Table 5 shows the use of additives according to the invention, while Table 6 shows the use of additives not according to the invention. Table 5

Even after 28 days of aging under cataplasmic conditions, the tensile shear strengths of the adhesives made using the additives of the present invention hardly fall below their starting values (Table 5). In contrast, the values of the tensile shear strengths when using additives which are not inventive according to cataplasmic conditions are already lower than the additives used according to the invention after 28 days aging (see Table 5 and Table 6). Table 6

Polyurethane-based compositions

For the preparation of the PU adhesives, the hydroxyl-containing organic compounds Macroplast UK 8202 (density: 1.45 +/- 0.05 g / cm ³ ; viscosity (Brookfield RVT, 20 ^° C.): 27000 +/- 4000 were used as the curable binder component mPas; manufacturer: Henkel KGaA) and, as hardener, the isocyanate Macroplast UK 5400 (density: 1.22 +/- 0.05 g / cm ³ ; viscosity (Brookfield RVT, 20 ^° C.): 250 +/- 100 mPas; manufacturer : Henkel KGaA). The composition according to the invention additionally contains 3,4,5-trihydroxybenzoic acid as an aging inhibitor. With an adhesive prepared in this way, aluminum sheets of dimensions 100 × 25 mm pretreated without chromium (bonding area 25 × 10 mm) bonded. The test specimens obtained were stored at 20 ^° C. for 14 days. The bonded sheets were then examined for the tensile shear strength of the bond (determined according to DIN 53283 "Determination of the bond strength of single-lapped adhesive bonds" at a speed of 100 mm / min). Identically prepared further specimens were subjected to a Cataplasmatest at 70 ⁰ C and examined immediately after removal in the wet state to their tensile shear strength.

Table 7

Example 15 is not according to the invention

Macroplast UK 8202, Macroplast UK 5400 and 3,4,5-trihydroxy benzoic acid were mixed at 20 ⁰ C. The additional amount of curing agent used over Example 3 was calculated so that the benzene derivative used was compensated on the basis of its hydroxyl number by an equivalent amount of hardener based on its NCO number.

Table 8

Tensile shear strength (in MPa) for PU adhesive composites with aluminum after

Kataplasmabehandlung

Claims

claims

A curable composition comprising a curable component and at least one m-hydroxybenzene derivative of the general formula (I):

2. A curable composition according to claim 1, characterized in that it is curable by radiation, heat, catalytic or a chemical hardener.

The curable composition of claim 2, wherein the chemical curing agent is one which reacts with the curable component to cure the composition.

4. A curable composition according to one or more of claims 1 to 3, characterized in that the curable component is selected from the group consisting of epoxy compounds, (meth) acrylic acid and their esters and polyols.

A curable composition according to claim 4, characterized in that the curable component is an amine-curing epoxy compound or a polyisocyanate-curing polyol.

A curable composition according to claim 5, characterized in that the epoxy compound is a bisphenol A-epichlorohydrin adduct.

7. A curable composition according to any one of claims 5 or 6, characterized in that a polyamine having at least two nitrogen atoms and at least two active amino hydrogen atoms per molecule is used as the curing agent.

8. A curable composition according to any one of claims 1 to 7, characterized in that one or two of the radicals R ¹ , R ² or R ^{3 are} hydroxyl groups.

9. A curable composition according to any one of claims 1 to 8, characterized in that the compound of the general formula (I) is contained in an amount of less than 10 wt .-%, based on the total curable composition.

10. A curable composition according to claim 9, characterized in that the compound of general formula (I) in an amount of 0.5 to 9 Wt .-%, preferably, 2 to 6 wt .-%, based on the total curable composition.

11. A curable composition according to one or more of claims 1 to 10, characterized in that the compound of the general formula (I) interacts with iron (III).

12. A curable composition according to claim 11, characterized in that the compound of general formula (I) is in the form of an iron (III) complex.

A curable composition according to one or more of claims 1 to 12, characterized in that the curable composition is a coating composition or an adhesive.

14. A curable composition according to one or more of claims 1 to 13, characterized in that it is cold-curing.

15. A curable composition according to one or more of claims 1 to 14, characterized in that it is curable at temperatures below 100 ⁰ C.

16. A curable composition according to claim 15, characterized in that it is curable at a temperature between 15 ⁰ C and 95 ⁰ C.

17. A curable composition according to one or more of claims 1 to 16, characterized in that it is curable below 100 ⁰ C and comprises as the curable component an epoxy compound and a hardener as an amine having at least two amino groups.

18. A curable composition according to claim 17, characterized in that Y is a carboxyl group.

19. Use of a m-ydroxybenzene derivative of the general formula (I):

as an aging inhibitor in coating compositions or adhesives, wherein Y represents a carboxyl group, a carboxylate group or a straight-chain or branched, optionally with hydroxyl groups,

Substituted amino groups, carboxyl groups and / or carboxylate groups

Alkyl group; and R ¹ , R ² and R ^{3 are} independently the same or different and represent hydrogen or a hydroxyl group, and R ¹ and R ^{3 are} not simultaneously a hydroxyl group; with the proviso that, if the Beschichtungsmttel or the adhesive as a curable component, a thermosetting component of a

Multi-component system based on epoxy, the

Coating agent or the adhesive free of transition metal oxides of

Copper and zinc group is and that, provided that the coating agent or the adhesive as a curable component, a thermosetting component

Epoxy-based, it is not a self-curing component.

20. Use according to claim 19, characterized in that said compound of general formula (I) interacts with iron (III).

21. Use according to claim 20, characterized in that said compound of general formula (I) is in the form of an iron (III) complex.

22. A method comprising coating a substrate with a curable composition, the curable composition comprising a curable component and at least one m-hydroxybenzene derivative of the general formula (I):

where Y is a carboxyl group, a carboxylate group or a straight-chain or branched, optionally with hydroxyl groups,

Substituted amino groups, carboxyl groups and / or carboxylate groups

Alkyl group; and R ¹ , R ² and R ^{3 are} independently the same or different and represent hydrogen or a hydroxyl group, and R ¹ and R ^{3 are} not simultaneously a hydroxyl group; with the proviso that if the curable component is a thermosetting one

Component of a multi-component epoxy-based system, the curable composition is free of transition metal oxides of the copper and zinc group, and that if the curable component is an epoxy-based thermosetting component, it is not a self-curing component.

The method of claim 22, wherein the curable composition contains a hardener or is curable by heat or radiation and cured.

24. The method of claim 23, wherein the curable composition contains a hardener or is curable by heat and is brought into contact with another substrate so that the curable coating between the two substrates and in a further step, the curing of the coating takes place.

25. The method according to one or more of claims 22 to 24, wherein a metallic substrate is used as the substrate.

26. The method of claim 25, wherein the metallic substrate is selected from the group consisting of aluminum, steel, copper, or alloys thereof, wherein said metallic substrates may be galvanized or oiled.

27. The method according to one or more of claims 22 to 26, characterized in that said compound of general formula (I) interacts with iron (III).

28. A curable composition according to claim 27, characterized in that said compound of general formula (I) is in the form of an iron (III) complex.