Abstract: A process for improving the qualities of paper which comprises making co-exist (a) a water-soluble polymer containing hydrazide group or its adduct with a water-soluble inorganic salt of an alkaline earth metal and (b) a heavy metal ion capable of chelating with the polymer or its adduct in a pulp slurry in paper making. The use of the water-soluble polymer or its adduct in combination with the heavy metal ion improves markedly the paper strength, the retention of sizing agents and the retention of fillers at a pH value around neutrality.

Abstract: A bonding composition for incombustible fibrous materials comprising (a) a water-soluble polymer containing hydrazide groups or its adduct with a water-soluble alkaline earth metal salt of an inorganic acid and (b) a heavy metal ion capable of forming chelate with the water-soluble polymer or its adduct. The bonding composition is employed as bonding agents to prepare incombustible sheet materials from incombustible fibrous materials by adding the components (a) and (b) to an aqueous dispersion of the fibrous materials and forming sheets or by forming wet or dry sheets containing the component (b) and then making the component (a) contain in the sheets. The bonding composition has excellent bonding effect and the polymer itself becomes incombustible, so incombustible sheet materials having excellent strength can be economically obtained.