Anionic polyacrylamide, though water-soluble, forms a transparent gel in water once its concentration exceeds 10%, losing its fluidity. If a large amount of anionic polyacrylamide is added instantaneously during the dissolution process, a dissolution system with a concentration greater than 10% can form in a specific area of the water, making it difficult to continue the dissolution. Therefore, it is necessary to first add a certain amount of clear water until it covers the stirrer blades, then start the stirrer to circulate the water solution before adding the anionic polyacrylamide. The stirrer blades should not have sharp edges or blades, as this can lead to poor effects such as material adherence and shearing of the anionic polyacrylamide molecular chains, causing inaccurate concentration and reduced dispersion. The dissolution concentration of anionic polyacrylamide should not be too high, generally around 0.5-1%. The stirring and dissolution time for anionic polyacrylamide should not be too long, ideally 1-1.5 hours, as otherwise it may damage its dispersion effect.
2. Anionic polyacrylamide should be dissolved immediately before use, as the aqueous solution of anionic polyacrylamide will autohydrolyze within 20-48 hours, losing its viscosity and ultimately its dispersing properties.
Anionic polyacrylamide cannot dissolve completely during dissolution, as there will always be a small amount of undissolved gel clusters. Therefore, a filtration device must be added during application to prevent these gel clusters from entering the paper machine, causing webbing and sticking to the felt or resulting in paper defects.
4. When the paper machine begins to run water, anionic polyacrylamide should be added first to prevent clumping of undispersed long fibers in the system, allowing production to quickly reach normal status. Since anionic polyacrylamide cannot be added in excess at once, it must be added evenly and at a constant rate. The addition speed should not be too fast, generally around 0.15 kg/min is appropriate. Simultaneously with the addition of anionic polyacrylamide to the water, a certain pressure of clean water should be injected at the addition point to ensure it is immediately diluted and dissolved upon entering the water, achieving a good dissolution effect.
5. When the dosage of anionic polyacrylamide changes, the dewatering speed of the pulp on the paper machine will vary accordingly. Excessive adjustment of the dosage of anionic polyacrylamide can lead to either overly rapid or slow dewatering, affecting the normal and stable production. Therefore, do not arbitrarily adjust the dosage of polyacrylamide excessively during normal paper machine production. For anionic polyacrylamide used in long fiber dispersants, the preferred ion type is anionic or non-ionic.
