WO2012123403A1 - Epoxy resin system with visual monitoring of the hardening state - Google Patents

Abstract

The present invention relates to an epoxy resin system comprising a dye which indicates the progress or the end point of the hardening of the epoxy resin by a color change in the course of hardening of the epoxy resin system. The invention further relates to components coated with an inventive epoxy resin system and additionally describes the use of the epoxy resin system as a thermally hardenable adhesive. In accordance with the present invention, a process is likewise defined for indicating the progress or the end point of the hardening reaction of an epoxy resin system. In addition, the present invention describes the use of a dye which reacts with a color change with an epoxy resin system as an indicator for the progress or the end point of the hardening of an epoxy resin system.

Description

 Epoxy resin systems with visual inspection of the

 Aushärtezustandes

The present invention relates to an epoxy resin system which includes a dye which indicates the course or the end point of the curing of the epoxy resin as the epoxy resin system is cured by color change. The invention further relates to components which are coated with an epoxy resin system according to the invention and also describes the use of the epoxy resin system as a thermally curable adhesive. Also according to the present invention, a method is defined for indicating the course or end point of the curing reaction of an epoxy resin system. In addition, the present invention describes the use of a reacting with an epoxy resin system with color change dye as an indicator for the course or, the end point of the curing of an epoxy resin system,

One-component epoxy adhesives consist in most cases of an epoxy resin and a curing agent which is reacted at temperatures well above the storage temperature of the adhesive. At the storage temperature of the adhesive, the hardener reacts only very slowly. The storage stability of such adhesives is limited. The curing state of the adhesive Stoffes can often only be determined with elaborate analytical methods.

From US 6,017,983 a thermosetting adhesive is known which is based on an epoxy resin. This adhesive composition includes an anhydride curing agent and a dye that forms a reversible complex with the anhydride curing agent. The dye changes its color as soon as the anhydride hardener is used up.

From EP 2 223 966 AI an epoxy resin composition is known which is based on aliphatic and cycloaliphatic amines as a curing agent. This composition may include a dye. However, an indication of the curing process is not mentioned in this patent application.

Proceeding from this, it is an object of the present invention to visualize a universal indication of the course of the curing process or the end of the curing process in epoxy resin systems without being limited to certain epoxy resin systems. It should also be apparent here whether the adhesive for the application is still sufficiently fresh,

that is not superimposed, which is not possible with the system according to US Pat. No. 6,017,983, since here the color change only shows the complete consumption of the hardener.

This object is achieved with respect to an epoxy resin system having the features of patent claim 1 and with respect to a component coated with the epoxy resin system with the features of patent claim 8. Uses of the epoxy resin system are given in claim 9. Claim 11 describes a method for indicating the course or the end point of the curing reaction of an epoxy resin system according to the invention, while with claim 12 relates to uses of a dye as an indicator for indicating the curing process or end point in epoxy resins. The respective dependent claims are advantageous developments.

According to the invention, therefore, a particular thermosetting epoxy resin system is specified which comprises the following constituents: a) at least one epoxy resin,

b) at least one curing agent or accelerator for the epoxy resin selected from the group consisting of imidazole derivatives, aziridine derivatives, triazine derivatives, imidazoline derivatives, o-tolylbiguanide, cyclic amidines, substituted guanidines, dicyandiamide, aromatic amines, room temperature solid polyamines and / or mixtures thereof, wherein the at least one curing agent or accelerator for the epoxy resin to at least 0.2 wt., Based on the total epoxy resin system is included, as well as

c) at least one dye which reacts with the epoxy resin with the color change on curing of the epoxy resin system.

By using an epoxy resin adhesive containing a dye which changes color with the progress of curing of the adhesive, a visualization of the progress of the curing, the curing state and the further processability can be made visually.

Thus, e.g. determine whether an adhesive has already hardened due to improper storage or interference and therefore can no longer be used for a particular application,

Even more important is the control of the state of the adhesive when it is already precoated on the component and thus form the components to be stored and the adhesive together. In general, such precoated adhesives are solid adhesives, so that an overlay is not even recognizable by increasing solidification. Components which include a precoated epoxy resin, which preferably forms a solid layer, are e.g. Adhesive bolts and other fasteners or reinforcing sheets to be fastened by gluing.

According to the invention thus dyes are used which can react with the epoxy resin with color change ie have a reactivity to epoxy resins, the reaction with the epoxy resins causes the color change. It has been found that dyes which have, for example, amino groups, such as Sudan Red 7b,

 Sudan Red 7b show no color change when curing epoxy resins.

Likewise, chemical dyes, such as Ponceau BS (Acid Red 66) are not suitable because no color change could be detected in the curing of the epoxy resin system,

Dyes present as the ammonium or sulfonic acid salt are generally not or only sparingly soluble in organic systems. Thus, when using the ionic dye Ponceau BS (Acid Red 66) no

Color change in the curing of the adhesive described above are determined.

Ponceau BS (Acid Red 66) Particularly preferred dyes are nonionic dyes which have an -OH functionality, ie hydroxyl group-containing dyes.

Epoxy resin system according to claim 1, characterized in that

 a) the at least one epoxy resin to 20. to 99 parts by weight, preferably 40 to 95 wt .-%, particularly preferably 50 to 60 wt .-%, based on the total epoxy resin, and / or b) the at least one Hardener or accelerator for the epoxy resin to at least 0.2 to 30 wt .-%, preferably 2 to 10 wt .-%, particularly preferably 3 to 6 wt .-%, based on the total epoxy resin system,

is included.

In particular, the at least one dye is selected from the group consisting of at least one -OH functionality having azo dyes, Triphenylmethanfarbstoffen, anthraquinone dyes, xanthenfarbstoffen, phthalein dyes and / or mixtures thereof.

Particularly preferred azo dyes are selected from the group consisting of 1-phenylazo-naphthalene-2-ol {Sudan * I), 1- (2,4-dimethyl-phenylazo) -naphthalen-2-ol (Sudan * II), l - (4-phenylazo-phenylazo) -naphthalene-2-ol (Sudan * III), 1- (2-methyl-4-o-tolylazo-phenylazo) -naphthalen-2-ol (Sudan * IV), 1- [ 4- (3-methylphenylazo) -3-methylphenylazo] naphthalen-2-ol (Sudan * Red B), 1- (2-methoxy-phenylazo) -naphthalen-2-ol (Sudan * Red G), 4-phenylazo resorcinol (Sudan * Orange G), 4 - [[4- (phenylazo) -l-naphthalenyl] azo] phenol (Disperse Orange 13), 1- (o-tolylazo) -2-naphthol (Orange OT), l- ( 4-nitrophenylazo) -2-naphthol (para-red), 1- (4-chloromercuriophenylazo) -2-naphthol (cerium orange), 1- [4- (o-tolylazo) -2,5-xylylazo] - 2-naphthol (Oil Red EGN), 1- {4-methyl-2-nitrophenylazo) -2-naphthol (toluidine Red), 3-hydroxy-4- (2-hydroxyphenylazo) -2-naphthoyl-2,4-dimethylanilide (Magone) 1 - ([4- (Xylylazo) xylyl] azo) -2-naphthol (Oil Red O) and / or mixtures thereof.

Structural formulas of some of the preferred azo dyes described above are given below: 

Sudan Orange 6

Preferred representatives of the triphenylmethane dyes are selected from the group consisting of 4- [bis (4-hydroxyphenyl) methylene] -2,5-cyclohexadienone (aurin), phenolphthalein, thymolphthalein and / or mixtures thereof.

Advantageous anthraquinone dyes are selected from the group consisting of 1,2-dihydroxyanthraquinone {alizarin), 1,2,3-trihydroxyanthraquinone

(Alizarin R), 1,2,4-trihydroxyanthraquinone (purpurin), 1,2,5,8-tetrahydroxyanthraquinone (alizarin Bordeaux, quinalizarin) and / or mixtures thereof.

It is likewise possible to use mixtures and / or combinations of the abovementioned dyes,

It is believed that a color change occurs by deprotonation of the dyes, which is triggered by reaction with the epoxy resins. The color change occurs e.g. in the deprotonation of the OH group on the naphthalene, which take place in reaction with the epoxy resins or by changing the pH. With the dye Sudan III, which also has the naphthol group, a color change from red to blue could also be observed. Non-OH dyes (e.g., Sudan 7b) showed no color change under the conditions described above.

In a further advantageous embodiment, the at least one of dye, based on the total weight of components a) and b), from 0.001 to 0.5 wt .-%, preferably from 0.005 to 0.25 wt .-%, particularly before ^¬ Trains t from 0.01 to 0.05 wt .-%. Particularly preferred hardeners are imidazole hardeners, ie hardeners based on imidazole derivatives. Particularly preferred imidazole derivatives are selected from the group consisting of 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, l Benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2 -phenylimidazole, 1-cyanoethyl-2-undecylimidazolium-trimellitate, 1-cyanoethyl-2-phenylimidazolium-trimellitate, 2,4-diamino-6- [2'-methylimidazolyl-1 ')] -ethyl-s-triazine , 2 _/ 4-diamino-6- [2'-undecyl-imidazolyl- (1 ')] -ethyl-s-triazine, 2,4-diamino-6- [2'-ethyl-4'-methyl-imidazolyl (I') ] -ethyl-s-2,4-diamino-6- [2'-methylimidazolyl (1 ')] - ethyl-s-triazine, 2-phenylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl- 4-methyl-5-hydroxyiriethylimidazole, 2,3-dihydro-1H-pyrrolo [1,2-a] benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, 2- Phenylimidazoline o the adducts or mixtures of these compounds.

In a preferred embodiment, aromatic amines are excluded as curing agents, more preferably, the hardener or the epoxy resin system used according to the invention is completely free of primary or secondary aliphatic or cycloaliphatic amines. However, tertiary amines can be included as catalytically active amines. Imidazoles in general are not expected according to the invention to the amines. With respect to the epoxy resin, which is used according to the invention, the present invention is not particularly limited, it can be used all common epoxy resins, Preferred representatives are, for example, aliphatic, cycloaliphatic or aromatic epoxy resins. Likewise, bi-, tri- or polyfunctional epoxy resins can be used.

Particularly preferred representatives of aliphatic epoxy resins are selected from the group consisting of alkanediol glycidyl ether, in particular butanediol and / or hexanediol diglycidyl ether; 1, 2: 4,5-diepoxy-3,3-dimethylpentane (dimethylpentane dioxide), 2,2'-bioxirane (butadiene diepoxide); Di-, tri- or poly-ethylene glycol diglycidyl ether; Di-, tri- or poly-propylene glycol diglycidyl ethers and / or mixtures thereof. As cycloaliphatic epoxy resins in particular epoxy resins are selected from the group consisting of 3-cyclohexenylmethyl-3-cyclo hexylcarboxylatdiepoxid, 3,4-epoxy cyclo hexane carboxylic acid (3,4-epoxycyclohexyl-methyl ester), 3,4-epoxy 6-methylcyclohexylmethyl-3 ', 4'-epoxy-6-methylcyclohexanecarboxylate, 4-vinyl-1-cyclohexene diepoxide (vinylcyclohexane dioxide), bis (3,4-epoxycyclohexylmethyl) adipate, dicyclopentadiene dioxide , 1,2-epoxy-6- (2,3-epoxypropoxy) hexa-hydro-4,7-methanoindane and / or mixtures thereof.

Further advantageous aromatic epoxy resins are in particular selected from the group consisting of bisphenol A epoxy resins, bisphenol F epoxy resins, phenol novolac epoxy resins, cresol novolac epoxy resins, Biphenylepoxidharzen, Biphenolepoxidharzen, 4,4'-biphenyl epoxy resins, Di-vinylbenzene dioxide, 2-glycidylphenyl glycidyl ether, tetraglycidylmethylenedi- aniline and / or mixtures thereof.

Likewise, combinations of the above-mentioned epoxy resins are possible.

The epoxy resin system of the present invention may include other additives such as toughening modifiers. The additives are in the case of their presence in a preferred amount of 20 to 99 wt .-% _; preferably from 45 to 95% by weight, preferably from 0.1 to 99% by weight, more preferably from 50 to 60% by weight, based on said epoxy resin system. Particularly suitable toughening modifiers are selected from the group consisting of carboxyl-terminated butadiene-acrylonitrile liquid rubber, amine-terminated butadiene-acrylonitrile liquid rubber, maleic acid-treated polybutadiene or butadiene-styrene copolymer, hydroxyl-functional polybutadiene oligomers, epoxy-terminated urethane prepolymers, and epoxy-terminated polysulfides, epoxidized polybutadiene, core-shell particles (eg Genioperl ^® from Wacker), thermoplastic silicone elastomers (eg Geniomer * from Wacker), elastomers, siloxanes, polyethers having functional groups, nanoparticles, and mixtures and / or combinations thereof. Particularly preferred toughening modifiers are, for example, carboxyl-terminated butadiene-acrylonitrile liquid rubbers (CTBN), which are available in liquid form under the name Hypro from Emerald Performance Materials LLC. These have molecular weights between about 2,000 and about 5,000 and acrylonitrile contents between about 10% and about 30

Wt. Specific examples are Hypro CBTN 1300 X8, 1300 X13 or 1300 X15.

In addition, it is also possible that the epoxy resin system according to the present invention comprises at least one filler, wherein the at least one filler is preferably selected from the group consisting of calcium carbonate, silica, alumina, aluminum hydroxide, aluminum powder, talc, kaolin, barium sulfate, calcium sulfate Potymer powder, glass bubbles, carbon black, feldspar, mica, quartz and mixtures and / or combinations thereof. The at least one filler is in the case of his

Presence in a preferred amount of 0.1 to 50 wt .-%, preferably from 5 to 30 wt .-%, particularly preferably from 7 to 20 wt .-%, based on said epoxy resin system. Likewise, accelerators can be contained in epoxy resin systems according to the invention. These accelerators are different from the outset be ^¬ signed curing agents or accelerators for epoxy resins. These accelerators are in the case of its presence in a preferred amount of 0.2 to 10 parts by weight, preferably from 0.5 to 5 wt .-%, particularly preferably from 0.5 to 2 wt .-%, based on the mentioned epoxy resin system included. In addition, the adhesive may contain reactive diluents or other raw materials typical in epoxy resin formulations, each in the case of their presence in a preferred amount of 0.1 to 30 wt .-%, preferably from 0.2 to 10 wt .-%, particularly preferably from 0 , 5 to 5 wt .-%, based on said epoxy resin system included.

The epoxy resin may be present in all major forms of preparation here, ie as a single component, in which all components use ^¬ ready present in a mixture together, Such a composition only needs to be applied to the application and can be ordered at elevated temperatures, for example at temperatures ranging between room temperature and 200 ° C, are cured.

Likewise, however, it is possible to formulate the epoxy resin system as a two-component system, so that at least the epoxy resin and the hardener are present separately from one another. Immediately before application of the epoxy resin system, the individual components of the epoxy resin system are then mixed together. According to the invention, a component coated with an epoxy resin system according to the invention is likewise provided, wherein the component is preferably selected from the group consisting of fastening elements, bolts, grab handles or reinforcing plates. However, the aforementioned preferred components are merely exemplary in nature. In particular, in the event that epoxy resin and hardener are coordinated so that the

Epoxy resin system is fixed at temperature and tack-free, the pre-coated components can be independently prefabricated and sold. For an application, then only heating of the components or the epoxy resin system thereon is necessary to cure the epoxy resin system, e.g. by melting the epoxy resin system with subsequent chemical crosslinking.

According to the invention, the use of the epoxy resin system described above is further specified as a thermally curable adhesive. The thermally curable adhesive can, depending on which epoxy resins or

Hardeners are used, be designed so that a cure between room temperature and 200 ° C, for example, with melting takes place. The uses of the epoxy resin system are e.g. the bonding of components, in particular fasteners, bolts, handles or reinforcing plates.

Further, the present invention relates to a method for indicating the progress and / or the end point of a Aushärungsreaktion erfindungsge ^¬ MAESSEN epoxy resin, wherein the epoxy resin provided on the temperature required for curing is heated and a color change is determined, the color change indicating the progress and / or the end of the curing. Before curing, the epoxy resin system can of course be applied to components to be bonded together. Particularly preferably, the color reaction serves to determine whether the adhesive is still fresh or already reacted (control of storage stability or pot life)

Furthermore, the present invention relates to the use of a dye which reacts with the epoxy resin with color change upon curing of an epoxy resin system, as an indicator of the course and / or the end point of the curing of the epoxy resin.

Particular preference may be given to all the dyes described above, in particular the dyes mentioned in claims 2 to 4.

The present invention will be described in more detail with reference to the following exemplary embodiments, without limiting the invention to the specific parameters shown there.

example 1

An adhesive (see Table 1) was prepared containing a dye (Sudan IV) with a reactive OH group. The freshly prepared adhesive had a red color. When the adhesive was stored in the oven (50 ° C), the color changed from red to purple to blue. The change in hue is related to the degree of cure of the adhesive. If the adhesive has not cured yet, it shows a red color. If the adhesive has already partially hardened (significantly higher viscosity), the color changes to purple. The fully cured adhesive shows a blue ^¬ black color. Table 1

Composition of an epoxy resin adhesive

The discoloration was also evident with various other imidazole hardeners. The greater the curing speed of the adhesive, the faster a color change could be detected.

The color change could also be detected in addition to the use of imidazoles as a curing agent and in the use of imidazole adducts as a hardener. The discoloration occurred in all experiments, but to varying degrees.

When using an anhydride hardener (with and without imidazole accelerator), no color change occurred on storage in the oven at 100 ° C, with the adhesive curing. In the mixture, in which all the ingredients from Table 1 except the

Contained epoxy resin (Araldite GY 250}, no color change occurred when stored in the oven at 100 ° C.

In the mixture where all the ingredients in Table 1 except the 2- Methylimidazoles (Dyhard MI-FF) contained no change in color when stored in an oven at 100 ° C.

Claims

claims An epoxy resin system comprising  a) at least one epoxy resin,  b) at least one curing agent or accelerator for the epoxy resin selected from the group consisting of imidazole derivatives, aziridine derivatives, triazine derivatives, imidazoline derivatives, o-tolyl biguanide, cyclic amidines, substituted guanidines, dicyandiamide, aromatic amines, room temperature solid polyamines and / or mixtures from this, wherein the at least one hardener or accelerator for the epoxy resin to at least 0.2 wt .-%, based on the total epoxy resin system, is included, as well as  c) at least one dye which reacts to change color during curing of the epoxy resin system. 2. Epoxy resin system according to claim 1, characterized in that a) the at least one epoxy resin to 20 to 99 wt .-%, preferably 40 to 95 wt .-%, particularly preferably 50 to 60 wt .-%, based on the entire epoxy resin system, and / or b) the at least one curing agent or accelerator for the epoxy resin to at least 0.2 to 30 wt .-%, preferably 2 to 10 wt .-%, particularly preferably 3 to 6 wt .-% based on the entire epoxy resin system, is included. 3. Epoxy resin system according to one of the preceding claims, characterized in that the dye is a non-ionic dye having a -OH functionality. 4. Epoxy resin system according to one of the preceding claims, ^¬ characterized in that the selected at least one dye is from the group consisting of at least one -OH-functional azo dyes, triphenylmethane dyes, anthraquinone dyes, xanthene dyes, phthalein dyes and / or mixtures thereof. Epoxy resin system according to the preceding claim, characterized in that a) the at least one azo dye is selected from the group consisting of 1-phenylazo-naphthalen-2-ol (Sudan "I), 1- (2,4-dimethyl-phenylazo) -naphthalen-2-ol (Sudan ^* II) , 1- (4-phenylazo-phenylazo) -naphthalen-2-ol (Sudan ^* III), 1- (2-methyl-4-o-tolylazo-phenylazo) -naphthalen-2-ol (Sudan ^* IV), l [4- (3-methylphenylazo) -3-methylphenylazo] naphthalen-2-ol (Sudan ^* Red B), 1- (2-methoxy-phenylazo) -naphthalen-2-ol (Sudan ^* Red G), 4- Phenylazoresorcinol (Sudan ^* Orange G), 4 - [[4- (phenylazo) -l-naphthalenyl] azo] phenol (Disperse Orange 13), 1- (o-tolylazo) -2-naphthol (Orange OT), 1- (o-tolyl) 4-nitrophenylazo) -2-naphthol (pararotene), 1- (4-chloromercuriophenyl-azo) -2-naphthol (Mercury Orange), 1- [4- (o-tolylazo) -2,5-xylylazo] -2- naphthol (OH Red EGN), 1- (4-methyl-2-nitrophenylazo) -2-naphthol (toluidine Red), 3-hydroxy-4- (2-hydroxyphenylazo) -2-naphthoyl-2,4-dimethylanilide (Magon ) l - ([4- (xylylazo) xylyl] azo) -2-naphthol (Oil Red 0) and / or mixtures thereof; b) the at least one triphenylmethane dye is selected from the group consisting of 4- [bis (4-hydroxyphenyl) methylene] -2,5-cyclohexadienone (aurin), phenolphthalein, thymolphthalein and / or mixtures thereof; c} the at least one anthraquinone dye is selected from the group consisting of 1,2-dihydroxyanthraquinone (alizarin), 1,2,3-trihydroxyanthraquinone (alizarin R), 1,2,4-trihydroxyanthraquinone (purpurin), 1,2,5 , 8-tetrahydroxyanthraquinone (alizarin Bordeaux, Chinalizarin) and / or mixtures thereof, d) and mixtures and / or combinations of the aforementioned dyes. 11 Epoxy resin system according to one of the preceding claims, characterized in that the at least one dye, based on the total by weight of components a) and b), from 0.001 to 0.5 wt .-%, preferably from 0.005 to 0.25 wt .-% , particularly preferably from 0.01 to 0.05 wt .-% is contained. Epoxy resin system according to one of the preceding claims, characterized in that the imidazole derivatives are selected from the group consisting of 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4 metylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6- [2'-methylimidazolyl (1 ')] - ethyl-s-triazine, 2,4-diamino-6- [2'-undecylimidazolyl- (1 ')] - ethyl-s-triazine, 2,4-diamino-6- [2'-ethyl-4'-methylimidazolyl - (l ')] - ethyl-s-2,4-diamino-6- [2'-methylimidazolyl (l')] - ethyl-s-triazine, 2-phenylimidazole, 2-phenyl-4,5-dihydroxymethyl imide - azole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo [1,2-a] benzimidazole, 1-dodecyl-2-methyl-3-benzyl-imidyl zo) ium chloride, 2-methylimidazoline, 2-phenylimidazoline or adducts or mixtures of these compounds. Epoxy resin system according to one of the preceding claims, characterized in that the at least one epoxy resin is selected from the group consisting of aliphatic, cycloaliphatic or aromatic bi-, tri- or polyfunctional epoxy resins, in particular a) the aliphatic epoxy resins are selected from the group consisting of alkanediol diglycidyl ether, in particular butane and / or hexanediol diglycidyl ether; 1, 2: 4,5-diepoxy-3,3-dimethylpentane (dimethylpentane dioxide), 2,2'-bioxirane (Butadiene diepoxide); Di-, tri- or poly-ethylene glycol diglycidyl ether; Di-, tri- or poly-propylene glycol diglycidyl ether; and / or mixtures thereof, b) the cycloaliphatic epoxy resins are selected from the group consisting of 3-cyclohexenylmethyl-3-cyclohexylcarboxylate diepoxide, 3,4-epoxycyclohexanecarboxylic acid (3,4-epoxycyclohexyl methyl ester), 3,4-epoxy-6-methylcyclohexylmethyl S '^' - epoxy-e-methylcyclohexanecarboxylate, 4-vinyl-1-cyclohexenediepoxide (vinylcyclohexanedioxide), bis {3,4-epoxycyclohexylmethyl) adipate, dicyclopentadiene dioxide, 1,2-epoxy-6- (2,3-epoxypropoxy ) hexahydro-4,7-methanoindane and / or mixtures thereof, c) the aromatic epoxy resins are selected from the group consisting of bisphenol A epoxy resins, bisphenol F epoxy resins, phenol novolac epoxy resins, cresol novolac epoxy resins, Biphenylepoxidharzen, Biphenolepoxidharzen, 4,4'-biphenyl epoxy resins, divinylbenzene dioxide , 2-Glycidylphenylglycidylether, tetraglycidylmethylenedianiline and / or mixtures thereof, as well as d) combinations of the above-mentioned epoxy resins. With a epoxy resin according to any one of the preceding claims coated component, wherein the component is in particular selected from the group consisting of fasteners, bolts, handles or reinforcing plates. Use of an epoxy resin system according to any one of the preceding claims as an adhesive thermally curable between room temperature and 200 ° C. Use according to the preceding claim for the bonding of components, in particular fasteners, bolts, handles or reinforcing sheets. Method for indicating the course and / or end point of the curing reaction of an epoxy resin system according to one of claims 1 to 7, in which the epoxy resin system is heated, heated to the temperature required for curing and a color change is determined, the color change being the progress and / or or the end of curing indicated. Use of a dye which reacts with the epoxy resin with color change on curing of an epoxy resin system as an indicator of the course and / or the end point of the curing of the epoxy resin.