Starch in wet-end of papermaking as retention & strength aid

Author(s): Vipul S.Chauhan, Puskar Gupta, R.Varadhan

Papermakers use mainly two forms of starch for addition at the wet-end section of papermaking process viz., cationic and amphoteric starch. The starch added in the thick pulp stock mainly increases the strength properties, whereas it increases the filler retention when added in the thin pulp stock. With modern retention aid polymers and techniques, use of starch as retention aid chemical is almost discarded with time. This study was devised to see the effect of dosage and dosing point of three different starches on filler retention and paper properties. Out of three starch samples two were cationic having different degrees of substitution and one was amphoteric. All the starches were added into pulp stock in two different manners; in thin stock as retention aid and in thick stock as strength aid. The comparison of all the three starches added in thin stock was done with a typical polymeric retention aid. The amphoteric starch gave better retention as compared with cationic starch. The use of any of the starches in thin pulp stock as retention aid was not economical. The effect of amphoteric starch and cationic starches added in thick pulp stock as strength aid was also compared. Optimized dose and dosing point of some starches may improve the strength properties even at increased filler level in paper sheets.

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