To provide a polymer in which a functional monomer is grafted to an isotactic polypropylene obtained using a metallocene catalyst and a binder composition for coextrusion containing the grafted polymer.

The composition contains (a) 10 to 100 wt.% of an isotactic homopolymer or copolymer (miPP) of a propylene obtained using a metallocene catalyst, (b) 0 to 90 wt.% of a homopolymer or copolymer (A) of ethylene, (c) 0 to 90 wt.% of an isotactic homopolymer or copolymer (B1) of polyproylene obtained using a Ziegler-Natta catalyst, a 1-butene homopolymer or copolymer (B2), a homopolymer or copolymer (B3) of styrene and a polymer (B) selected from a mixture thereof, wherein a functional monomer is grafted to each of the polymers.