Cationic starches represent a unique class of high performance starch derivatives which have gained commercial acceptance because of their affinity towards negatively charged substrate such as cellulose, aqueous suspensions of minerals and slimes and biologically active macromolecules. They have already found extensive use in the paper manufacture in which they function as internal binders and retention aids for various fillers and emulsions and are added to the paper furnish before the sheet is formed. They are effective for improving such physical properties of paper as bursting and tensile strength, elongation, fold endurance, and pick resistance. Usually 0.5% to 1% addition of cooked cationic starch, gives the same improvement in the paper as does 1.5% to 2% addition of corn starch. Other benefits of the cationic starches are improved drainage on the wire, better sheet formation and enhancement of the sizing efficiency of an alum rosin size. Cationic starches also improve the retention of fillers such as titanium dioxide, clay, calcium carbonate which are frequently incorporated in the furnish to improve the opacity of high grade printing papers, fine writing papers, light weight papers such as bread wraps, glassine, etc.
