Coatings are multi component systems and a synergy needs to exist between all the components for a uniform, defect-free and stable coating. One of the basic physical processes in coatings manufacture is the dispersion of fine solid particles in the vehicle (water or solvent) to form a uniform, stable, colloidal dispersion. Stabilization of these solid particles is crucial to ensure a defect free, uniform surface coat. Wetting and dispersing additives are used to ensure these characteristics and are hence crucial additives in the formulation of coatings.
The main steps that take place in the dispersion process are:
- Wetting of the particles
- Dispersing the agglomerates
Selection of wetting and dispersing additives involves many factors that should be taken into consideration which include the vehicle (water or solvent), type and surface area of pigment (organic or inorganic), application (decorative, industrial, coil coatings etc) and curing conditions.
We have a wide range of wetting and dispersing additives based on different chemistries that are designed to suit the needs of various applications. Our wetting and dispersing additives can be used in decorative coatings, universal strainers, industrial coatings, etc.
All these surfactants effectively stabilize the foam that is generated in the manufacturing process. Even though surfactants stabilize foam and gas bubbles, they are not solely responsible for the degree of foam formation. Aside from these ingredients, production & application methods (e.g. pigment grinding, milling, spray applications etc.) and the viscosity of the coating have a large influence on the foam characteristics.
Foam that is formed when manufacturing coatings leads to several problems. For example, containers cannot be optimally filled because of the increase in volume. Problems also arise when refilling the coatings into processing and sales containers. If the bubbles burst during drying of the film, it leads to unwelcome surface defects, such as craters or pinholes. The protective effect of the coating surface is also decreased to a large extent.
Although the tendency towards foam generation and stabilization can be limited during formulation through suitable component selection, the only really effective way of avoiding such defects is the addition of suitable defoamers and foam inhibiting agents.
Defoamer selection for a given formulation is based on finding a suitable balance between the defoaming efficiency and compatibility of the defoamer in the system. Often times the defoamer giving the best defoaming performance are highly incompatible leading to surface defects and the most compatible defoamers may not give effective foam control. Additionally, an increase in the use of defoamers in the formulations may lead to formation of craters and pinholes in the final coating. Defoamer selection involves many factors that should be taken into consideration which include the raw materials used, method of manufacture, application and curing conditions.
Waxes impart or improve various surface effects as slip and lubrication, abrasion resistance, anti-blocking, matting and water repellency – all critical properties in the coating and ink areas. These waxes are in the solid form and have to be emulsified in order to obtain a water based emulsion which can be easily formulated.
We have on offer wax emulsions which can be readily added to the coating formulation to impart the desired surface effect. These emulsions are carefully made in order to be compatible with the regular components in these formulations.