PRODUCTS BY FUNCTION
FUNCTION.05Lubricants and Releasing Agents
- From vehicles and metalworking to the production and processing of fiber and the fields of plastic and rubber, lubricants and releasing agents are essential additives used in every industry today. Their purpose is to maintain and preserve equipment and to improve operational capacity.
Our lubricants and releasing agents are the dispersion type made from hydrophobic lubricating components dispersed in water. Adding them to coating materials, such as a coating or paint, prevents the coating film from adhering to metal as well as blocking.
Lubricants and Releasing Agents for Coating
One of several important industrial agents, the lubricants and releasing agents for coated paper used in the paper-making industry carry a wide range of functions, such as releasing and slippage properties as well as hydrophobic properties. Two of the main usages of these agents are for improving operability during the manufacturing process as well as the quality of the coated paper itself. The former can be seen in the anti-dusting of calendars (anti-adhesion of coating colors) and stain prevention of the guide roll, while the latter consists of blocking prevention and the adding of slipping properties to the paper.
Stacking coated products such as coated paper or construction materials on top of each other may lead to blocking of the coating films, making their separation impossible. Attempts to rip them off may further cause a removal of the coating film. In such cases, adding an anti-blocking agent to the paint can eliminate troubles related to blocking. Since our anti-blocking agents are of the dispersing type, they are easy to handle and can be easily added to aqueous paints.
Lubrication and Releasing Mechanisms
The following are 4 mechanisms associated with lubricants and releasing agents.
- 1. Providing a coating of components with a low critical surface tension
- Critical surface tension (γC) is a parameter indicating the ease of wetting an object. Objects can only be wetted by liquids with a surface tension lower than the γC of the object, eliminating the threat of wetting from liquids with a higher surface tension than γC. As releasing agents are composed of components with a low γC value, covering a metallic surface in these components provides the metal surface itself with releasing properties.
A common problem during the manufacturing of coated paper is dusting, in which the coating color adheres to the metal roll. By covering the surface of the roll in a releasing agent of components with a low γC value, adhesive factors such as latex and starch are prevented from wetting and spreading across the metal roll’s surface, decreasing the overall area of adhesion. With a lower area of adhesion, the metal roll’s overall adhesiveness is reduced and dusting is suppressed.
The relationship between critical surface tension and peeling strength for releasing agents is shown in figure 2. Peel strength refers to the force used in removing the coated paper from the surface of the metal roll. From the figure, it can be seen that the lower the lubricant’s critical surface tension, the weaker the peel strength. The weaker the peel strength, the easier it is to remove the coated paper, increasing the dusting resistance.
Fig. 1 Critical surface tension γC for each material
Relationship between critical surface tension and peeling strength
- 2.Suppressing the formation of hydrogen bonds
- As the hydrophilic group of starches and latexes on the coating layer’s surface form a hydrogen bond with the surface of the metal roll, the components of these materials easily adhere to the metal roll causing it to become dirty. As shown in figure 3, applying lubricants to the surface of the coating layer and metal roll suppresses the formation of hydrogen bonds on both objects and prevents dirt form adhering to the metal roll. And by suppressing the formation of hydrogen bonds on these surfaces, the slippage of the coating layer is increased as well.
Fig. 3 Model for the suppression of hydrogen bond formations by lubricants
- 3. Lowering the friction coefficient
- By lowering the friction coefficient of the coating layer surface, lubricants provide the coating layer with slippage properties. As shown in figure 4, increases in the carbon number for lubricants in the aliphatic group correspond with decreasing friction coefficients.
Fig. 4 Relationship between friction coefficients and carbon numbers for the aliphatic group
- 4. Surface orientation and protrusion
- The lubricant’s hydrophobic particles are largely oriented near the surface of the coating layer (Fig. 5). A portion of them protrude out from the surface of the coating layer, providing the layer with slippage properties.
Fig. 5 Lubricant distribution