Papermaking is one of the most chemically demanding processes in industry. The wet end carries fibers, fines, fillers and dissolved anionic “trash” that must be retained, drained and controlled — and cationic polyamine (CAS 42751-79-1) is a versatile tool for all three jobs. This article explains how polyamine is used in the paper mill, where it helps and how to dose it.
1. The Wet-End Chemistry Problem
Paper machines run at high speed with a dilute fiber suspension. To make paper efficiently you need:
- Retention: keep fibers, fines and fillers on the sheet instead of losing them to the white water.
- Drainage: remove water from the sheet quickly on the wire.
- Cleanliness: control anionic trash (dissolved and colloidal substances) and pitch/stickies that deposit on wires, felts and rolls.
Fines, fillers and most dissolved organics carry a negative charge. Cationic polymers are the standard answer — and polyamine is one of the most cost-effective of them.
2. How Polyamine Helps
2.1 Retention and drainage aid
Polyamine neutralizes the negative charge on fines and fillers, allowing them to aggregate with fibers and improving retention on the wire. Better retention means cleaner white water, lower furnish cost and better drainage.
2.2 Anionic trash catcher (ATC)
Dissolved and colloidal anionic substances (from pulping, bleaching, recycled fiber and broke) consume cationic additives and destabilize the wet end. Polyamine, with its high charge density, is an efficient and economical ATC that neutralizes this trash before it reaches the more expensive retention aids.
2.3 Pitch and stickies control
By fixing colloidal pitch and stickies onto fibers (instead of letting them deposit on machine surfaces), polyamine keeps the machine cleaner and reduces breaks and downtime.
3. Typical Application Points
- ATC dosing: added to the thin stock or thick stock before the retention aid system.
- With a dual-polymer system: polyamine + high-molecular-weight anionic PAM or a microparticle system for maximum retention.
- White water and broke treatment: polyamine clarifies white water for reuse and conditions broke for the pulper.
4. Dosing Practice
- Dose: typically 0.05-1 kg per ton of paper depending on the anionic demand of the furnish; measure the cationic demand (e.g. by charge titration) and dose to a target.
- Order of addition: dose polyamine upstream of the retention aid with good mixing; adjust injection points by trial.
- Combination: for high retention targets, use polyamine as the ATC/coagulant with anionic PAM as the bridging flocculant.
- Monitoring: track retention, drainage, first-pass ash retention and machine cleanliness; adjust dose when furnish changes (e.g. more recycled fiber).
5. FAQ
Is polyamine a retention aid?
It works as a coagulant/ATC in the retention system — it neutralizes charge and aggregates fines and fillers. For very high retention, it is normally combined with a high-molecular-weight flocculant (anionic PAM or a microparticle system).
Can polyamine be used with optical brighteners and dyes?
Generally yes, but cationic polymers can interact with anionic dyes and brighteners. Evaluate compatibility in the mill before full-scale use, and adjust addition points.
Does polyamine affect paper strength?
Used at normal doses as an ATC/retention chemical, polyamine has minimal direct effect on strength; its main benefit is a cleaner, more stable wet end.
Is food-grade polyamine available for paper contact?
For paper grades that contact food, use a polyamine grade certified for food-contact use and verify the residual monomer limits on the COA.
PolyblueChem supplies polyamine (CAS 42751-79-1) for papermaking and water treatment, with COA and MSDS. See also our polyamine overview and wastewater and sludge application guide. Contact us for grade selection and dosing support.