Indicator for cure of two-component-epoxy adhesives

1. Cold-curing two-component-epoxy adhesive, comprising

(a) an epoxy-resin-component and

(b) a curing agent-component, comprising a mercaptan curing agent present in a range of 5.0 to 95.0 wt. %, based on the total weight of the curing agent-component (b), yielding a ratio of 1 thiol equivalent of the mercaptan curing agent per 1 to 2 epoxy equivalents of the epoxy-resin-component (a),

in which the epoxy-resin-component comprises a color change indicator, wherein said cold-curing two-component-epoxy adhesive is capable of curing at a temperature as low as 0° C.

2. Adhesive according to claim 1 , wherein the color change indicator is selected from the group consisting of an inorganic dye, an organic dye, azo compounds, azo dyes, Solvent Red 26 {1-[[2,5-dimethyl-4-[(2-methylphenyl)azo]-phenyl]azo]-2-naphthol}, Solvent Red 164 {1-[[4-[phenylazo]-phenyl]azo]-2-naphthol} and combinations thereof.

3. Adhesive according to claim 1 , comprising a color change indicator that demonstrates a pH dependency.

4. Adhesive according to claim 1 , comprising a color change indicator demonstrating a pH dependency, selected from the group consisting of methyl violet, eosin yellow, malachite green, thymol blue, methyl yellow, bromophenol blue, congo red, methyl orange, bromocresol green, methyl red, litmus, bromocresol purple, bromophenol red, bromothymol blue, phenol red, neutral red, naphtholphthalein, cresol red, phenolphthalein, thymolphthalein, alkali blue, Alizarin Yellow R, indigo carmine, and combinations thereof.

5. Adhesive according to claim 1 , wherein the color change indicator is present in a range of 0.05 to 5.0 wt. %, based on the total weight of the epoxy-resin-component (a).

6. Adhesive according to claim 1 , wherein the color change indicator is present in a range of 0.15 to 1.5 wt. %, based on the total weight of the epoxy-resin-component (a).

7. Adhesive according to claim 1 , wherein the curing agent-component also comprises a tertiary amine, which is present in a quantity from 0 to 20 wt. %, based on the total weight of the curing agent-component (b).

8. Adhesive according to claim 7 , wherein the tertiary amine is Tris(dimethylaminomethyl)phenol.

9. Adhesive according to claim 1 , wherein the curing agent-component also comprises a tertiary amine, which is present in a quantity from 0.1 to 15 wt. %, based on the total weight of the curing agent-component (b).

10. Adhesive according to claim 1 , wherein the curing agent-component also comprises a tertiary amine, which is present in a quantity from 2 to 10 wt. %, based on the total weight of the curing agent-component (b).

11. Adhesive according to claim 1 , wherein the mercaptan curing agent is present in a range of 25.0 to 75.0 wt. %, based on the total weight of the curing agent-component (b).

12. Adhesive according to claim 1 , wherein the mercaptan curing agent is selected from the group consisting of pentaerythritol tetrakis(3-mercaptobutylate); dipentenedimercaptan; Mercaptized Soy Oil; Mercaptized Castor Oil; glycol dimercaptoacetate; trimethylpropane trimercaptoacetate; pentaerythritol tetramercaptoacetate; trimethylopropane tris-3-mercaptopropionate; pentaerythritol tetra-3-mercaptopropionate; ethoxylated trimethylpropane tris-3-mercaptopropionate; 3,6-dioxa-1,8-octanedithiol; 3-oxa-1,5-pentanedithiol; 1,2-ethanedithiol T; 1,3-propanedithiol; 1,2-propanedithiol; 1,4-butanedithiol; 1,3-butanedithiol; 2,3-butanedithiol; 1,5-pentanedithiol; 1,3-pentanedithiol; 1,6-hexanedithiol; 1,3-dithio-3-methylbutane; ethylcyclohexyldithiol; methylcyclohexyldithiol; methyl-substituted dimercaptodiethyl sulfide; dimethyl-substituted dimercaptodiethyl sulfide; 2,3-dimercapto-1-propanol; bis-(4-mercaptomethylphenyl) ether; and 2,2′-thiodiethanethiol.

13. Adhesive according to claim 1 , further comprising an amine selected from the group consisting of aminoethylpiperazine, diethylenetriamine, triethylenetetramine, tetraethylenepentaamine, and pentaethylenehexamine.

14. Dispensing system, comprising two separate containers which, separately from one another, contain the components (a) and (b) of the adhesive according to claim 1 , as well as a dispensing apparatus.

15. Method for monitoring the curing progress of cold-curing two-component-epoxy adhesive via color change of the adhesive, comprising the mixing of

(a) an epoxy-resin-component and

(b) a curing agent-component, comprising a mercaptan curing agent present in a range of 5.0 to 95.0 wt. %, based on the total weight of the curing agent-component (b), yielding a ratio of 1 thiol equivalent of the mercaptan curing agent per 1 to 2 epoxy equivalents of the epoxy-resin-component (a),

in which the epoxy-resin-component comprises a color change indicator, wherein said cold-curing two-component-epoxy adhesive is capable of curing at a temperature as low as 0° C.

16. Cold-curing two-component-epoxy adhesive, comprising

(a) an epoxy-resin-component and

(b) a curing agent-component, comprising a mercaptan curing agent,

in which the epoxy-resin-component comprises a color change indicator, wherein said cold-curing two-component-epoxy adhesive is capable of curing at a temperature as low as 0° C.; and wherein the color change indicator is selected from the group consisting of Solvent Red 26 {1-[[2,5-dimethyl-4-[(2-methylphenyl)azo]-phenyl]azo]-2-naphthol}, Solvent Red 164 {1-[[4-[phenylazo]-phenyl]azo]-2-naphthol} and combinations thereof.

17. Cold-curing two-component-epoxy adhesive comprising

(a) an epoxy-resin-component, comprising:

(i) at least one polyepoxide, in an amount between 50-80 wt. %,

(ii) at least one filler, in an amount between of 20-50 wt. %,

(iii) a color change indicator selected from the group consisting of Solvent Red 26 {1-[[2,5-dimethyl-4-[(2-methylphenyl)azo]-phenyl]azo]-2-naphthol }, Solvent Red 164 {1-[[4-[phenylazo]-phenyl]azo]-2-naphthol} and combinations thereof, in an amount between 0.05% to 5.0% wt. %, said amounts being based on the total weight of the epoxy-resin-component, and

(b) a curing agent-component, comprising:

(i) a mercaptan epoxy hardener in amounts of 40-80 wt. %,

(ii) a tertiary amine, in amounts of 0.1-20 wt. %,

(iii) at least one filler, in amounts of 20-50 wt. %, said amounts based on the total weight of the curing agent-component.

18. Cold-curing two-component-epoxy adhesive comprising

(a) an epoxy-resin-component, comprising:

(i) a polyepoxide selected from the group consisting of Bisphenol F diglycidyl ether (BFDGE) and Bisphenol A diglycidyl ether (BADGE), in an amount between 50-80 wt. %,

(ii) quartz powder, in an amount between 20-50 wt. %,

(iii) a color change indicator selected from the group consisting of Solvent Red 26 {1-[[2,5-dimethyl-4-[(2-methylphenyl)azo]-phenyl]azo]-2-naphthol }, Solvent Red 164 {1-[[4-[phenylazo]-phenyl]azo]-2-naphthol} and combinations thereof, in an amount between 0.05% to 5.0% wt. %, said amounts are based on the total weight of the epoxy-resin-component, and

(b) curing agent-component, comprising:

(i) a mercaptan epoxy hardener in an amount between 40-80wt. %,

(ii) Tris(dimethylaminomethyl)phenol, in an amount between 0.1-20 wt. %,

(iii) quartz powder, in an amount between of 20-50 wt. %, said amounts based on the total weight of the curing agent-component.