Every time fibre is recycled it gets shorter and stiffer. After a few cycles, the same basis weight gives noticeably lower burst and tensile – and the only traditional fix was to add more virgin pulp or raise GSM. Both cost money.
What dry strength resin does
Dry strength resin (DSR) is a polymer that builds extra bonds between fibres as the sheet dries. More bonds mean a stronger sheet at the same weight.
Benefits
- Higher burst, tensile and ring crush – often enough to meet specs without extra virgin fibre.
- Lower GSM for the same strength – saving fibre and steam.
- Better runnability – fewer breaks on the machine and the converter.
- More freedom with furnish – use cheaper recycled grades with confidence.
Where it is used
- Kraft paper and test liners for corrugated boxes.
- Duplex board middle plies.
- Corrugated medium (fluting).
- Writing papers with high recycled content.
Dosing tips
- Add to the thick stock, after cationic starch, with enough mixing time.
- Keep charge balance in mind – very dirty recycled stock may need a fixative first.
- Increase in small steps and measure strength on reels, not just lab sheets.
DSR and starch – friends, not rivals
Cationic starch gives the first lift in strength at low cost. DSR takes over where starch alone stops working. Many mills run both, each at a lower dose than either would need alone.
A real example of the saving
A kraft mill making 120 GSM liner might find that with DSR it meets the same burst at 110 GSM. On a machine making 60 tonnes a day, that is a meaningful drop in fibre use every month – and the converter gets a sheet that runs the same or better.
Want stronger sheets from recycled fibre? Tell us your grade and current strength results – we will suggest a DSR programme and trial. Get a quote →