Adhesive of epoxy resin, diene copolymer-modified epoxy resin, phenolic-terminated elastomeric toughener and polyester segment polymer

1. An epoxy adhesive composition comprising

a) a first epoxy resin,

b) a second epoxy resin modified with a copolymer based on a 1,3-diene and a polar, ethylenically unsaturated comonomer,

c) a toughener selected from the group consisting of compounds of formula I

wherein m is 1 or 2, n is 2 to 6, R 1 is an n-valent radical of an elastomeric prepolymer after the removal of the terminal isocyanate, amino or hydroxyl group, the elastomeric prepolymer being soluble or dispersible in epoxy resin, W and X are independently —O— or —NR 3 —, at least one of W and X being —NR 3 —, R 2 is an m+1-valent radical of a polyphenol or aminophenol after the removal of the phenolic hydroxyl group and optionally of the amino group, and R 3 is hydrogen, a C 1 to C 6 alkyl or phenol,

and compounds of formula II

wherein p is 1 or 2, q is 2 to 6, Y is —O—, —S— or —NR 6 —, Z is a radical selected from the group consisting of —OH, —NHR 6 , —OCN,

R 4 is a residue of a hydroxyl-, mercapto- or amino-terminated polyether prepolymer or of a hydroxyl-, mercapto- or amino-terminated prepolymeric, segmented polyester, polythioester or polyamide R 5 is a carbocyclic aromatic or araliphatic p+1-valent radical with groups Z bonded directly to the aromatic ring, R 6 is hydrogen, C 1 to C 6 alkyl or phenyl, and R 7 is methyl or hydrogen,

and mixtures thereof and

d) a polymer comprising a polyester segment, said polymer being at least partially crystalline at room temperature and having a softening temperature in the range of 40° to 125° C.

2. A composition according to claim 1 , wherein component d) comprises a polyester.

3. A composition according to claim 1 comprising 5 to 15 weight percent of component d).

4. A composition according to claim 2 wherein component d) comprises at least one polymer selected from the group consisting of a hydroxyl-group terminated polyester, a carboxyl-group terminated polyester and an epoxy polyester resin.

5. A composition according to claim 1 wherein component d) has a softening temperature in the range of 40° to 90° C.

6. A composition according to claim 1 wherein component d) has a molecular weight in the range of 2,000 to 5,000 g/mol, preferably in the range of 3,000 to 4,000 g/mol, most preferably of about 3,500 g/mol.

7. A composition according to claim 1 wherein component a) comprises a mixture of at least two different epoxy resins.

8. A composition according to claim 1 wherein component a) comprises at least one epoxy resin which is solid at room temperature.

9. A composition according to claim 1 comprising 10 to 20 weight percent of component b).

10. A composition according to claim 1 wherein component b) comprises an epoxy resin modified with an acrylonitrile-butadiene rubber.

11. A composition according to claim 1 wherein component b) comprises at least one of the acrylonitrile-butadiene rubbers selected from the group of:

b 1 ) comprising about 10 weight percent of acrylonitrile,

b 2 ) comprising about 17 weight percent of acrylonitrile, and

b 3 ) comprising about 26 weight percent of acrylonitrile, or a mixture thereof.

12. A composition according to claim 1 comprising 10 to 20 weight percent of component c).

13. A composition according to claim 1 comprising a gelling agent.

14. A vehicle, parts of which are bonded by the epoxy adhesive composition according to claim 1 .