Anionic-cationic starches, applications

Cationic starches, for instance 2-hydroxy-3-trimethylammoniopropyl starch chloride, can be combined with anionic fluorescent whitening agents, such as di-aminostilbenedisulfonate, in order to produce fluorescent starch.2491 Unfortunately, despite their low cost and easy application, cationic starches have little prospect for use as soil stabilizers because of their low activity, which is independent of the metal ions present in the soil.2492... 

Cationic starch is the major wet-end starch. The phenomena involved in starch adsorption and the selection of cationic starch need careful consideration, as do the proper preparation and application of starch. The criteria for the use of native, anionic and amphoteric starches are also considered. 

Anionic trash catchers are either inorganic salts (aluminium, zirconium) or high charged cationic polymers. Extranely high DS, low molecular weight cationic starches are available for use in this application and are found to quench OBAs much less than polymers such as poly-DADMAC or polyacrylamide. 

This chapter describes the main properties and methods for the characterization of polyelectrolytes derived from the biomass. The most important sources are plants, with cellulose and starch, which turn to polyelectrolytes after chemical modifications. CarboxymethylceUulose is the main cellulose derivative used in many industrial applications as good thickener and hydrophilic polymer for aqueous media. Cationic starches are mainly used in the paper industry for fiUa- retention or paper wet-strength. Natural polyelectrol5des are produced by algae with anionic alginates and carrageenans as the major representatives, which are used in food applications and for biomedical devices. In this respect, alginates are often associated in an electrostatic complex with a pseudo-natural polyelectrolyte (chitosan), a cationic polymer extracted from crustaceous shells. 

Special cationic pol5miers, which react with starch [native or anionic] by fixation and/or precipitation, proved to be even more effective in dry-strength improvement than cationic starch. Pol5nnnylamine was found to be especially useful in such applications. It forms a very stable complex with starch and paper fibers, which results in very good retention [23]. 

Starch, cooked in the paper mill or supplied as - pregelatinized starch, is used also. Modified starches (- oxidized starch, - cationic starch or - starch ethers) are common in that application. Sodium - carboxymethyl cellulose is also effective, but as an anionic polymer, it requires a retention aid such as alum. 

For practical uses see - anionic starches, car-boxymethyl starch, - cationic starches, - cross-linked starches, - hydrophobic starches, - oxidized starches, - starch industrial applications. 

Anionic starches are obtained by reaction with phosphoric acid and alkali metal phosphates or by derivatization with carboxymethyl groups.30,31 This modification is primarily used to introduce amphoteric properties into cationic com starch for application on the wet end of the paper machine. Anionic starches with carboxymethyl substitution are used as thickeners in coating colors or as binders in coatings for specialty paper grades. Oxidized starches are inherently anionic but without thickening action. Potato starch already carries sufficient natural anionic charge to provide amphoteric properties after cationization.32... 

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