Modifying starch with cationic polymers and use of the modified starches as dry-strength agent

A process for modifying starch, comprising:

• heating starch with at least one cationic polymer in an aqueous medium to temperatures above the gelatinization temperature of said starch, wherein the starch is selected from the group consisting of the native starches, the oxidized native starches, the starch ethers, the starch esters, the oxidized starch ethers, the oxidized starch esters, the cationic modified starches and the amphoteric starches and effecting said modifying of said starch in the presence of a combination of
• (a) a polymeric cationizer selected from the group consisting of polymers containing vinylamine units and having molecular weights Mw of up to 1 million, polyethyleneimines, polydiallyldimethylammonium chlorides, condensates of dimethylamine with epichlorohydrin or dichloroalkanes, condensates of dichloroethane and ammonia, and mixtures thereof;
• and
• (b) a polymeric papermaking drainage aid selected from the group consisting of a water-soluble crosslinked polyamidoamine with or without an ethyleneimine graft, a polymer containing acrylamide and/or methacrylamide units and having a molecular weight Mw of more than 1 million, a polymer containing vinylamine units and having a molecular weight Mw of more than 1 million, and mixtures thereof.