Agents synthetic suspending

Pretreatment Chemicals Even though the suspended solids concentration of the slurry to be tested may be correct, it is frequently necessary to modify the sluriy in order to provide an acceptable filtration rate, washing rate, or final cake moisture content. The most common treatment, and one which may provide improvement in all three of these categories, is the addition of flocculating agents, either inorganic chemicals or natural or synthetic polymers. The main task at this point is to determine which is the most effective chemical and the quantity of chemical which should be used. 

Emulsion polymerisation represents the next stage in development from the suspension technique and is a versatile and widely used method of polymerisation. In this technique droplets of monomer are dispersed in water with the aid of an emulsifying agent, usually a synthetic detergent. The detergent forms small micelles 10-100 /im in size, which is much smaller than the droplets that can be formed by mechanical agitation in suspension polymerisation. These micelles contain a small quantity of monomer, the rest of the monomer being suspended in the water without the aid of any surfactant. 

Accdg to Riegel (Ref 2), the commercial synthetic detergents were devised originally as improved wetting agents (substances dissolved or suspended in water that cause water to penetrate... 

Cellulose (Figure 8.19) may be extracted from wood pulp, and is usually partially hydrolysed with acid to give microcrystalline cellulose. These materials are used as tablet diluents. Semi-synthetic derivatives of cellulose, e.g. methylcellulose, hydroxymethylcellulose, and carboxymethylcellulose, are used as emulsifying and suspending agents. Cellulose acetate phthalate is cellulose with about half the hydroxyl groups acetylated, and the remainder esterified with phthalic acid. It is used as an acid-resistant enteric coating for tablets and capsules. 

---