Nitrile rubber blends for fixing metal parts to plastics

1. An adhesive sheet comprising at least one heat-activatable adhesive, said adhesive comprising a blend of

at least one nitrile rubber S1 and at least one nitrile rubber S2, said at least one nitrile rubber S1 having an acrylonitrile fraction of not more than 25% by weight and said at least one nitrile rubber S2 having an acrylonitrile fraction of not less than 30% by weight, and

at least one phenol-novolak resin.

2. The adhesive sheet of claim 1 , wherein the acrylonitrile fraction of said at least one nitrile rubber S1 is between 15% and 25% by weight.

3. The adhesive sheet of claim 1 , wherein the acrylonitrile fraction of said at least one nitrile rubber S2 is between 30% and 60% by weight.

4. The adhesive sheet of claim 1 , wherein nitrile rubbers S1 and S2 are selected such that when measured by DSC the blend exhibits at least two different glass transition temperatures, one of which is at least 10° C. and one of which is not more than −20° C.

5. The adhesive sheet of claim 1 , wherein the weight ratio of nitrile rubber S1 to nitrile rubber S2 is between 20 to 80 and 80 to 20.

6. The adhesive sheet of claim 1 , wherein said at least one phenol-novolak resin is present in a fraction of between 30% and 75% by weight relative to the weight of the blend.

7. The adhesive sheet of claim 1 , wherein tackifying resins are added to the blend in an amount of up to 30% by weight, relative to the weight of the blend.

8. A method for bonding metal parts in electronics articles, which comprises bonding said metal parts with the adhesive sheet of claim 1 .

9. The adhesive sheet of claim 5 , wherein said ratio is between 40 to 60 and 60 to 40.

10. The adhesive sheet of claim 9 , wherein said ratio is about 50 to 50.