Liquid hardeners for hardening epoxide resins (II)

1. A liquid curing agent for curing polymer resins, comprising:

a) cyanamide;

b) at least one urea derivative of formula (I)

wherein

R 1 and R 2 are each independently selected from the group consisting of hydrogen, C1- to C15-alkyl, and C3- to C15-cycloalkyl; or R 1 and R 2 together are C3- to C10-alkylene, thereby forming a ring together with the nitrogen atom to which they are attached;

R3 is selected from the group consisting of hydrogen, C1- to C15-alkyl, C3- to C15-cycloalkyl, aryl, arylalkyl, C1- to C15-alkyl substituted by —NHC(O)NR 1 R 2 , C3- to C15-cycloalkyl substituted by —NHC(O)NR 1 R 2 , aryl substituted by —NHC(O)NR 1 R 2 , and arylalkyl substituted by —NHC(O)NR 1 R 2 ;

provided that at least one of R 1 , R 2 , and R 3 is not hydrogen; and

c) at least one curing accelerator selected from the group consisting of imidazolines according to formula (II) and imidazoles according to formula (III)

wherein

R 30 is selected from the group consisting of hydrogen, C1- to C15-alkyl, C3- to C15-cycloalkyl, aryl, and arylalkyl;

R 32 and R 34 are each independently selected from the group consisting of hydrogen, C1- to C15-alkyl, and C3- to C15-cycloalkyl; or R 32 and R 34 together are C3- to C15-alkylene, thereby forming a ring together with the carbon atoms to which they are attached;

R 33 and R 35 are each independently selected from the group consisting of hydrogen, C1-to C15-alkyl, and C3- to C15-cycloalkyl; or R 33 and R 35 together are C3- to C15-alkylene, thereby forming a ring together with the carbon atoms to which they are attached.

2. The liquid curing agent of claim 1 , wherein the cyanamide and the at least one urea derivative of formula (I) are provided in a molar ratio of from 1:1 to 4:1.

3. The liquid curing agent of claim 2 , wherein R 3 is represented by the general formula (V),

wherein R 1 and R 2 are each independently selected from the group consisting of hydrogen, C1- to C15-alkyl, and C3- to C15-cycloalkyl; or R 1 and R 2 together are C3- to C10-alkylene, thereby forming a ring together with the nitrogen atom to which they are attached;

R 4 , R 5 , R 6 , R 7 and R 8 are each independently selected from the group consisting of hydrogen, halogen, C1- to C15-alkyl, C3- to C15-cycloalkyl, aryl, arylalkyl, —CF 3 , —NHC(O)NR 1 R 2 , C1- to C15-alkyl substituted by —NHC(O)NR 1 R 2 , aryl substituted by —NHC(O)NR 1 R 2 , and arylalkyl substituted by —NHC(O)NR 1 R 2 ;

R 9 and R 10 are each independently selected from the group consisting of hydrogen and C1- to C15-alkyl;

n is a number between 0 and 10.

4. The liquid curing agent of claim 1 , wherein R 3 is represented by the general formula (V),

wherein R 1 and R 2 are each independently selected from the group consisting of hydrogen, C1- to C15-alkyl, and C3- to C15-cycloalkyl; or R 1 and R 2 together are C3- to C10-alkylene, thereby forming a ring together with the nitrogen atom to which they are attached;

R 4 , R 5 , R 6 , R 7 and R 8 are each independently selected from the group consisting of hydrogen, halogen, C1- to C15-alkyl, C3- to C15-cycloalkyl, aryl, arylalkyl, —CF 3 , —NHC(O)NR 1 R 2 , C1to C15-alkyl substituted by —NHC(O)NR 1 R 2 , aryl substituted by —NHC(O)NR 1 R 2 , and arylalkyl substituted by —NHC(O)NR 1 R 2 ;

R 9 and R 10 are each independently selected from the group consisting of hydrogen and C1- to C15-alkyl;

n is a number between 0 and 10.

5. The liquid curing agent of claim 1 , wherein

R 1 and R 2 are each independently selected from the group consisting of hydrogen and C1- to C15-alkyl; and

R 3 is selected from the group consisting of hydrogen, C1-C15-alkyl, C3- to C15-cycloalkyl, C1- to C15-alkyl substituted by —NHC(O)NR 1 R 2 , and C3- to C15-cycloalkyl substituted by —NHC(O)NR 1 R 2 .

6. The liquid curing agent of claim 1 , wherein the at least one urea derivative according to formula (I) is selected from the group consisting of 1-methylurea, 1,1-dimethylurea, 1,3-dimethylurea, 3-(3-chloro-4-methylphenyl)-1,1-dimethylurea, 3-(p-chlorophenyl)-1,1-dimethylurea, 3-phenyl-1,1-dimethylurea, 3-(3,4-dichlorophenyl)-1,1-dimethylurea, 1,1′-(methylenedi-p-phenylene)-bis-(3,3-dimethylurea), 3-(3-trifluoromethylphenyl)-1,1-dimethylurea, 1,1′-(2-methyl-m-phenylene) -bis-(3,3-dimethylurea), 1,1′-(4-methyl-m-phenylene)-bis-(3,3-dimethylurea), and mixtures thereof.

7. The liquid curing agent of claim 1 , wherein

R 30 is selected from the group consisting of hydrogen, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decanyl and phenyl;

R 32 and R 34 are each independently selected from the group consisting of hydrogen, C1- to C5-alkyl and phenyl; and

R 33 and R 35 are each independently selected from the group consisting of hydrogen, C1- to C5-alkyl and phenyl.

8. The liquid curing agent of claim 1 , wherein the curing agent further comprises d) at least one viscosity modifier selected from the group consisting of the monools, diols, polyols, ethers, polyethers, polyether polyols, ketones, aldehydes, nitriles, carboxylic acid esters, and mixtures thereof.

9. The liquid curing agent of claim 1 , wherein the curing agent further comprises d) at least one viscosity modifier selected from the group consisting of the monools, diols, polyols, ethers, ether alcohols, polyethers, polyether polyols, and mixtures thereof according to the general formula (VII),

wherein

R 11 and R 22 are each independently selected from the group consisting of hydrogen, —OH, and C1- to C15-alkyl;

R 12 , R 14 , R 16 , R 18 and R 20 are each independently selected from the group consisting of hydrogen, —OH, and C1- to C5-alkyl;

R 13 , R 15 , R 17 , R 19 and R 21 are each independently selected from the group consisting of hydrogen, —OH, —NH 2 , and C1- to C5-alkyl;

u is a number from 1 to 10;

s and t are independently a number from 0 to 10, provided that at least one of s and t is a number from 1 to 10;

m is a number from 0 to 10, provided that m is a number from 1 to 10 when s is a number 1 to 10;

p is a number from 0 to 10, provided that p is a number from 1 to 10 when t is a number from 1 to 10;

n, o and q are independently a number from 0 to 10.

10. The liquid curing agent of claim 1 , wherein the curing agent further comprises e) a stabiliser selected from the group of inorganic and organic acids.

11. The liquid curing agent of claim 1 , wherein the curing agent further comprises e) a stabiliser selected from the group consisting of salicylic acid, phthalic acid, toluenesulfonic acid, sulfuric acid, phosphoric acid, anhydrides thereof, and mixtures thereof.

12. The liquid curing agent of claim 1 , wherein the curing agent comprises:

from 1 to 50 parts by weight of the cyanamide;

from 1 to 50 parts by weight of the at least one urea derivative of formula (I); and

from 0.01 to 50 parts by weight of the at least one curing accelerator selected from the group consisting of the imidazolines of formula (II) and of the imidazoles of formula (III).

13. The liquid curing agent of claim 1 , further comprising

from 0 to 10 parts by weight of at least one viscosity modifier; and

from 0 to 10 parts by weight of at least one stabiliser.

14. An epoxy resin composition comprising:

a) at least one curable epoxy resin; and

b) the liquid curing agent of claim 1 .

15. A polyurethane resin composition comprising:

a) at least one curable polyurethane resin; and

b) the liquid curing agent of claim 1 .

16. A composite material comprising:

a) a carrier material;

b) at least one of a curable epoxy resin and a curable polyurethane resin; and

c) the liquid curing agent of claim 1 .

17. The composite material of claim 16 , wherein the carrier material is a fibre material.

18. A method of making a composite material comprising:

impregnating a carrier material with a curable composition; and curing the impregnated carrier material; wherein the carrier material is selected from the group consisting of woven fabrics, knitted fabrics and meshes; and wherein the curable composition comprises a curable polymer resin and the liquid curing agent of claim 1 .

19. The method of claim 18 , wherein the curable polymer resin is at least one of a curable epoxy resin and a curable polyurethane resin.

20. A liquid curing agent for curing epoxy resins comprising:

a) cyanamide;

b) at least one urea derivative of formula (I)

wherein

R 1 and R 2 are each independently selected from the group consisting of hydrogen, C1- to C15-alkyl, and C3- to C15-cycloalkyl; or R 1 and R 2 together are C3- to C10-alkylene, thereby forming a ring together with the nitrogen atom to which they are attached;

R 3 is selected from the group consisting of hydrogen, C1- to C15-alkyl, C3- to C15-cycloalkyl, aryl, arylalkyl, C1- to C15-alkyl substituted by —NHC(O)NR 1 R 2 , C3- to C15-cycloalkyl substituted by —NHC(O)NR 1 R 2 , aryl substituted by —NHC(O)NR 1 R 2 , and arylalkyl substituted by —NHC(O)NR 1 R 2 ;

provided that at least one of R 1 , R 2 and R 3 is not hydrogen; and

c) at least one curing accelerator selected from the group consisting of imidazolines according to formula (II) and imidazoles according to formula (III)

wherein:

R 30 is selected from the group consisting of hydrogen, C1- to C15-alkyl, C3- to C15-cycloalkyl, aryl, and arylalkyl;

R 32 and R 34 are each independently selected from the group consisting of hydrogen, C1- to C15-alkyl, and C3- to C15-cycloalkyl; or R 32 and R 34 together are C3- to C15-alkylene, thereby forming a ring together with the carbon atoms to which they are attached;

R 33 and R 35 are each independently selected from the group consisting of hydrogen, C1- to C15-alkyl, and C3- to C15-cycloalkyl; or R 33 and R 35 together are C3- to C15-alkylene, thereby forming a ring together with the carbon atoms to which they are attached.