Dry-Strength Resins DSR

Many water soluble, hydrogen bonding polymers will act as dry strength additives. In fact, wood fibers contain their own natural dry strength additive in the form of hemicelluloses. It is well-known that the removal of hemiceUuloses from wood fibers makes it more difficult to develop their bonding characteristics. 

Polyacrylamide- and polyvinylamine-based DSRs are mainly supplied as ready to use aqueous solutions or emulsions (10-40%) or as water soluble powders that must be dissolved prior to use. No other preparatory steps are necessary. The most beneficial way of application is to meter them continuously to the thick paper stock at a point of thorough mixing, e. g. at stock dilution. Addition rates of 0.1 to 0.5% of solid material are adequate for most uses. Excessive use can overcationize the stock suspension and reduce the effectiveness of the DSR and of other cationic additives. 

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Fig. 3.28 Flowsheet of paper production process with integrated metering points and addition sequences of various chemical additives. (DSR = dry strength resin, DSR-PAM = dry strength resin - poiacryiamide, OBA = opticai brightening agent, PAC = polyaiuminum chioride, RDA = retention drainage aid, WSR = wet strength resin.)...

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