Foam cross-linked with metal salt and process for production

A foam comprising an organic polymer expanded matrix (I) and at least one kind of inorganic substance (II) selected from the group consisting of metals, metal compounds and non-metal inorganic fillers, wherein

• said organic polymer is at least one polymer selected from the group consisting of radical-polymerization polymers containing metal salt-crosslinkable functional groups, epoxy resins containing metal salt-crosslinkable functional groups, and addition-condensation polymers containing metal salt-crosslinkable functional groups, and
• said expanded matrix (I) contains metal salt-crosslinks, and
• said inorganic substance (II) is at least one member selected from the group consisting of metal oxides and metal hydroxides, and
• the relation between the weight percentage (M) of the metal forming said metal salt-crosslinks in the expanded matrix (I) based on the total weight of the expanded matrix (I) and the inorganic substance (II) and the weight percentage (S) of the inorganic substance (II) based on the total weight of the expanded matrix (I) and the inorganic substance (II) satisfies the following expression:
• M≧10−S/4 (1)
• wherein M≦50, S≧5.