Fiber Properties Modification Technologies
De-Inking Technology (Paper Recycling)
1. What Are De-Inking Agents?
A de-inking agent is a detergent designed for use in wastepaper recycling. The de-inking process mainly involves the detachment of ink from the surface of recovered newsprint and magazines (the ink removal process) and the floating away of that ink using foam (the ink collection process). A de-inking agent has two primary functions: reducing the surface tension between the pulp fiber and ink during the ink removal process to facilitate the detachment of ink and foaming a froth that floats the ink off during the ink collection process, thereby separating the ink from the pulp slurry.
| Before use | Ink removal process |
Removal process |
After use |
|---|---|---|---|
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2. Lion’s De-Inking Agents
● LIPTOL S series ● LIPTOL SA series, others
3. The Composition of De-Inking Agents
In general, a de-inking agent primarily consists of a nonionic surfactant with a chemical structure in which alkylene oxide (AO) has been added to a fatty alcohol. In addition, the agent may be combined with various auxiliary agents that facilitate the removal of ink. Other auxiliary agents that can be incorporated to aid flotation may have such functions as, causing ink to aggregate, improving the interaction between the bubbles of foam and the ink and regulating foam volume.
Fatty alcohol AO adduct, the primary component of a de-inking agent, is a nonionic surfactant and thus sensitive to temperature. For example, its dynamic surface tension, indicated by the shape of its meniscus, is drastically different at 40°C, which is close to the cloud point, and at 55°C, which is well beyond the cloud point. This difference affects foaming power and other properties. However, there are also some other factors that affect the effectiveness of de-inking agents, among them the inclusion of other ingredients and type of wastepaper being treated.
4. Tips for Selecting De-Inking Agents
When selecting an appropriate de-inking agent, the most essential consideration is its flotation mechanism. Floatation involves the ink that has been removed from wastepaper attaching to bubbles that then rise to the surface to form a froth. The ink is then removed as the froth is skimmed and separated from the floater. This complex process is affected by a variety of factors. In particular, foaming power is largely affected by the type of wastepaper being treated, the type of floater used, the vigor of white water circulation, temperature, pH and other factors. Therefore, we recommend that your first consideration in selecting a de-inking agent be based on foaming power to ensure stable operations.
For example, when recycling old magazines or when using a high-foaming type floater with a high G/L (Gas/Liquid) ratio, there is a risk of a deterioration in operational efficiency and thus a lower yield ratio due to the generation of excess froth. In such cases, the use of de-inking agents with low-foaming power is recommended to control foam volume and thus minimize risk. In contrast, when a low-foaming type floater with a low G/L ratio, is used or when the density of solid content undergoing the flotation process is high, the targeted quality of DIP (De-Inked Pulp) might not be achieved because of an insufficient froth volume. In such cases, using de-inking agents with high-foaming power is recommended.
| Low-foaming type ← | → High-foaming type | ||||
| Product name | SA-640 | SA-520 SA-370 |
SA-630 | SA-510 S-8100 |
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|---|---|---|---|---|---|
| Foaming power | Foam volume*1 （g／5min.） |
280 | 300～320 | 320～330 | 350～400 |
| Basic physical property | Appearance | Homogeneous liquid | Colorless or pale yellow transparent homogeneous liquid with a distinctive odor | ||
| Water content(%) | 9～10 | ||||
| pH (10% aqueous solution, 25°C) |
4.5～5.5 | 4.0～6.0 | 5.0～8.5 | ||
| Viscosity (mN/m, 25°C) | 420 | 500～600 | 700 | 480～850 | |
