High-latency hardeners for epoxy resins
The present invention relates to novel high-latency liquid hardeners for hardening of curable polymer resins, especially epoxy resins, and to epoxy resin compositions comprising liquid hardeners for the production of fiber composite materials.
1. A liquid hardener for curing curable polymer resins, comprising:
a) cyanamide;
b) at least one urea derivative of the formula (III) or formula (IV)
wherein the following applies to the radicals, in each case simultaneously or independently of one another:
R 1 , R 2 =simultaneously or independently of one another hydrogen, C1- to C15-alkyl, C3- to C15-cycloalkyl or together form C3- to C10-alkylene;
R 4 , R 4′ , R 5 , R 5′ , R 6 , R 6′ , R 7 , R 7′ , R 8 , R 8′ =simultaneously or independently of one another hydrogen, halogen, C1- to C15-alkyl, C3- to C15-cycloalkyl, aryl, arylalkyl, —CF 3 , —NHC(O)NR′R 2 ,
—NHC(O)NR 1 R 2 -substituted C1- to C15-alkyl,
—NHC(O)NR 1 R 2 -substituted aryl or
—NHC(O)NR 1 R 2 -substituted arylalkyl; and,
c) at least one stabiliser comprising inorganic or organic acids,
wherein the hardener includes cyanamide and at least one urea derivative of the formula (III) or formula (IV) in a molar ratio of cyanamide: the at least one urea derivative of 1:1 to 4:1.
2. The liquid hardener of claim 1 , wherein the hardener, besides cyanamide, the at least one urea derivative and the stabiliser, includes no solvents or solubilisers or is free of the solvents or the solubilisers.
3. The liquid hardener of claim 1 , wherein the inorganic or the organic acid is an acid selected from the group consisting of salicylic acid, phthalic acid, toluene sulfonic acid, sulfuric acid, phosphoric acid, anhydrides thereof and mixtures thereof.
4. An epoxy resin composition comprising at least one curable epoxy resin and at least one of the liquid hardeners of claim 1 .
5. A polyurethane resin composition comprising at least one curable polyurethane resin and at least one of the liquid hardeners of claim 1 .
6. A composite material comprising a support material, at least one curable epoxy resin or curable polyurethane resin and at least one of the liquid hardeners of claim 1 .
7. The liquid hardener of claim 1 , wherein the polymer resins are epoxy resins.
8. The composite material of claim 6 , wherein the support material is a fibre material.
9. The liquid hardener of claim 1 , wherein the liquid hardener has a melting point S m of <20° C. at normal pressure.
10. The liquid hardener of claim 1 , wherein the hardener is liquid at a temperature of 20° C. at normal pressure and has a viscosity less than 1 Pa·s.
11. The liquid hardener of claim 1 , wherein the hardener includes at least two different urea derivatives of the at least one urea derivative.
12. A method for curing compositions comprising at least one curable epoxy resin or curable polyurethane resin, comprising employing the liquid hardener of claim 1 .
13. A method for curing impregnated fibre materials or impregnated woven fabrics, knitted fabrics or braiding, comprising employing the liquid hardener of claim 1 .