Polyacrylamide for papermaking manufactured by Chinese producers is a white granular linear high-molecular polymer, widely applied as retention aid, drainage aid and uniformity agent in the papermaking industry. It generally has no peculiar odor, appearing as white powder, translucent beads or flakes, and some products are milky white. Featuring excellent thermal stability and solubility, it can be miscible with water in any proportion to form a homogeneous transparent solution.
Under dry conditions, the product exists as discrete non-sticky particles. It effectively improves paper quality, enhances pulp dewatering performance, raises the retention rate of fine fibers and fillers, and cuts raw material consumption as well as environmental pollution.
1. Main Applications
Polyacrylamide serves as dry strength agent, retention aid, drainage aid and flocculant in papermaking.
- Non-ionic polyacrylamide: improves pulp drainability, boosts dry paper strength and increases retention rate of fibers and fillers.
- Anionic polyacrylamide copolymer: acts as wet and dry paper strength enhancer and retention aid.
- Cationic polyacrylamide copolymer: mainly used for papermaking wastewater treatment and drainage promotion, and delivers favorable effects on filler retention.
In terms of retention performance, cationic polyacrylamide outperforms non-ionic type, while non-ionic polyacrylamide is superior to anionic type. It is also adopted for papermaking wastewater treatment and fiber recovery.
2. Drainage Mechanism
The favorable drainage capacity of the papermaking additive relies on the following principles:
- Uniform molecular weight and molecular structure form evenly sized flocs. The distribution of such flocs on paper mesh differs distinctly from uneven flocs generated without high-molecular flocculants or by products with inconsistent molecular weight.
- Without flocculants, fibers and fillers of varying particle sizes distribute naturally on the mesh under gravity. Fine particles fill gaps between large particles and form a dense barrier, drastically slowing down water filtration.
- Flocs hinder dense stacking of particles. Fine particles that originally fill gaps are agglomerated, creating more passages for water permeation and accelerating drainage. Uneven flocs formed by products with vastly different molecular weights still allow small flocs to settle into gaps of large flocs, restraining water filtration efficiency.
3. Precautions Avoid filter mesh clogging caused by incomplete dissolution of polyacrylamide during papermaking. Insoluble substances such as plant fibers and auxiliary additives accumulate in process water and block filtering facilities, lowering production efficiency. Operators shall strictly control the solubility, viscosity and dissolving time of polyacrylamide in practical production.