We meant by dry strength additives, a number of natural and synthetic polymers that are mixed in paper mill industry with the stock at the wet end to improve some properties of the dry paper. Normally dry strength additives are water soluble.
Dry strength additives are used in paper mill to increase the strength of paper. It increases the strength of paper by increasing internal bond formation. Moreover dry strength additives improve bust strength, tear strength, wax pick values, folding endurance, stiffness, machine runability, increase levels of paper filler uses etc. Dry strength additives also reduced linting and dusting.
The polyelectrolyte’s dry strength additives become part of the existing complex colloid suspension of wet end side of paper mill industry and can be act as a retention aid. But this beneficiary is depends on a certain levels of uses. High addition rate can be brings negative effect, resulting poor retention and poor water removal.
Dry strength additives are used for greatly in printing and converting grades paper than in packaging grades. Dry strength additives are the highest uses in coating base papers, paper grades from recycled fiber and mechanical pulp.
Different gums, vegetable extractives and synthetic polymers are used in paper mill as dry strength additives. Such as cationic and amphoteric starches, natural gums (guar, locust bean or tamarind), cationic polyacrylamides, cationic glyoxylated resins, modified polyamines, carboxymethyl cellulose etc. The dry strength additives can be used individually or in combination.
This post explains the role of dry strength additives in a very practical way. The description of wet-end addition and internal bond formation clearly shows how dry strength resin becomes part of the paper structure rather than acting as a surface treatment. The point about controlled dosage is important, because excess dry strength resin for paper can affect retention and drainage. I also found the comparison between printing, converting, and packaging grades useful, as resin demand varies significantly across these applications. Overall, this is a realistic overview of how dry strength resin supports paper strength, runnability, and quality in actual paper mill operations.