Properties of detergent phosphates and their effects on detergent processing

Phosphates are usually key ingredients in detergent formulations ranging from liquids to free-flowing powdery material to hard cakes. Their functional properties, which contribute to the over-all detergency by controlling the alkalinity, lowering the critical micelle concentration, sequestering metal ions, and decreasing soil redeposition, are generally considered to be the reason for their wide use. Another important but less recognized reason is their versatile role in improving the handling properties and lowering the cost of the finished products. The sophistication of the phosphate manufacturing processes makes it possible to turn out a large number of phosphates with different properties and physical forms. Trisodium orthophosphate, tetrapotassium pyrophosphate, and sodium phosphate glass are for the specialties. Sodium tripolyphosphate, the work-horse of the detergent phosphates, has many grades. Some are designed to give the desired hydration properties for different detergent-processing conditions. Size and density are varied for granular grades to reduce segregation and degradation in dry-blended detergents. Sodium trimetaphosphate, which converts rapidly into tripolyphosphate, offers a new detergent-processing technology. Effervescent phosphate is an intriguing new detergent phosphate with many possible new applications. The properties of these phosphates and their effect on the detergent products and processes are discussed in detail.