Use of N,N′-(dimethyl) urones and method for curing epoxy resin compositions

1. A method for the controlled curing of epoxy resin compositions comprising

(i) providing an epoxy resin composition comprising:

(a) at least one curable epoxy resin; and

(b) at least one curing agent for epoxy resins selected from the group consisting of bis- or multi-functional N,N′-(dimethyl)-urones of the general formula (I) or mixtures thereof

R—(NH—CO—N(CH 3 ) 2 ) n   Formula (I)

wherein

R=a linear or branched aliphatic radical, or

a cycloaliphatic radical, or

an unsubstituted, halo-substituted and/or alkyl-substituted aromatic radical, and

n =a number from 2 to 20,

wherein the epoxy resin composition has a layer thickness of at least 10 mm, and

wherein the epoxy resin composition does not comprise any further curing agents, co-curing agents, curing accelerators or other catalysts for the curing of epoxy resins apart from the N,N′-(dimethyl)-urone of the general formula (I) or mixtures thereof, and wherein the epoxy resin composition comprises the N,N′-(dimethyl)-urone of the general formula (I) or mixtures thereof in an amount of from 0.1 to 8 wt. % based on the mass of the epoxy resin composition, that during curing at a temperature of from 60 to 160° C., generates a maximum heat flow in the epoxy resin composition of from 0.05 to 0.99 W/g (based on the mass of the epoxy resin composition), so that the epoxy resin composition cures fully; and

(ii) curing the epoxy resin composition at a temperature of from 60 to 160° C. so that the epoxy resin composition cures fully,

wherein the proportion of unreacted epoxy groups in the cured epoxy resin composition is <2%.

2. The method of claim 1 , wherein the epoxy resin composition has a layer thickness of at least 20 mm.

3. The method of claim 1 , wherein the epoxy resin is at least one epoxy resin from the group of the epoxy resins based on glycidyl polyether of 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), its bromine-substituted derivative (tetrabromobisphenol A), glycidyl polyether of 2,2-bis(4-hydroxyphenyl)-methane (bisphenol F) and/or glycidyl polyether of novolak resins.

4. The method of claim 1 , wherein the N,N′-(dimethyl)-urones of the general formula (I) is bis[4-(N,N-dimethylurea)cyclohexyl]methane (H12MDI-urone), 1,1′-hexamethylenebis[3,3-dimethylurea] (HDI-urone), N,N″-1,5-naphthalenediylbis[N′,N′-dimethylurea] (NDI-urone), 1,1′-m-xylylenebis(3,3 -dimethylurea) (MXDI-urone), N,N″-1,4-phenylenebis[N′,N′-dimethylurea] (PDI-urone), 4,4′-methylenediphenylene bis(dimethylurea) (MDI-urone) and/or 1-(N,N-dimethylurea)-3-(N,N-dimethylureamethyl)-3,5,5-trimethylcyclohexane (IPDI-urone).

5. The method of claim 1 , wherein at least two different N,N′-(dimethyl)-urones of the general formula (I) are used as curing agent.

6. The method of claim 1 , wherein the epoxy resin composition comprises from 0.01 to 10 wt. % (based on the mass of the epoxy resin composition) N,N′-(dimethyl)-urone according to formula (I) or mixtures thereof.

7. The method of claim 1 for producing mouldings having a layer thickness or wall of from 10 mm to 1000 mm.

8. The method of claim 1 for producing hollow articles having a layer thickness or wall of from 10 to 1000 mm.

9. The method of claim 1 , wherein the epoxy resin composition cures to the extent of ≧98%.

10. A method for the controlled curing of epoxy resin compositions comprising

(i) providing an epoxy resin composition comprising

(a) at least one curable epoxy resin; and

(b) at least one curing agent for epoxy resins selected from the group consisting of bis- or multi-functional N,N′-(dimethyl)-urones of the general formula (I) or mixtures thereof

R—(NH—CO—N(CH 3 ) 2 ) n   Formula (I)

wherein

R=a linear or branched aliphatic radical, or

a cycloaliphatic radical, or

an unsubstituted, halo-substituted and/or alkyl-substituted aromatic radical, and

n=a number from 2 to 20,

wherein the epoxy resin composition has a layer thickness of at least 10 mm, and

wherein the epoxy resin composition does not comprise any further curing agents, co-curing agents, curing accelerators or other catalysts for the curing of epoxy resins apart from the N,N′-(dimethyl)-urone of the general formula (I) or mixtures thereof, wherein the epoxy resin composition comprises the N,N′-(dimethyl)-urone of the general formula (I) or mixtures thereof in an amount of from 0.1 to 8 wt. % based on the mass of the epoxy resin composition, that during curing at a temperature of from 60 to 160° C., generates a maximum heat flow in the epoxy resin composition of from 0.05 to 0.99 W/g (based on the mass of the epoxy resin composition), so that the epoxy resin composition cures fully; and

(ii) curing the epoxy resin composition at a temperature of from 60 to 160° C. so that the epoxy resin composition cures fully, wherein the epoxy resin composition cures to the extent of ≧98%.

11. The method of claim 1 , wherein the epoxy resin composition has a layer thickness of at least 50 mm.

12. The method of claim 10 , wherein the epoxy resin composition has a layer thickness of at least 50 mm.

13. The method of claim 1 for producing mouldings having a layer thickness or wall of from 50 mm to 1000 mm.

14. The method of claim 1 for producing hollow articles having a layer thickness or wall of from 50 mm to 1000 mm.