Zeolites and novel silicates as raw materials for detergents

Special crystalline and amorphous silicates soda/silicate compounds as well as zeolite P are offered as an alternative to zeolite A. These builders have in common that they contribute to the softening of water and thus to the inhibition of coarse precipitations which may lend to incrustations on textiles The mechanisms of these builders are however quite different. Whereas the builder efficacy of zeolites is essentially due to the ion exchange capacity, the builder properties of the special silicates are largely determined by the dissolution kinetics and the structure of the formed silicate anions. Physicochemical investigations and washing tests show that zeolite P as well as the special silicates may partially or completely substitute zeolite A. A benefit of zeolite P is, that the calcium binding is quicker and substantially stronger in comparison to zeolite A. As a consequence, the amount of organic cobuilders (e.g. polycarboxylates) that have to be used in combination with Zeolite A can be reduced in the detergent formulas. Furthermore, zeolite P exhibits a superior uptake for non-ionic surfactants in comparison to zeolite A. This is essentially due to the smaller particle size of zeolite P and may be of potential advantage for special production technologies. Additionally, zeolite P shows a better compatibility with bleach components in some detergent formulas. All silicates are distinguished from the heterogeneous zeolites by several properties: they are principally soluble, they contribute to the alkalinity of the washing liquor and they are generally more compatible to sensitive bleach components like percarbonate. Soda/silicate compounds are especially suited for the partial substitution of zeolite A. On the other hand crystalline layered silicates (like delta-sodium disilicate) and especially certain amorphous silicates with reduced solubility may completely substitute zeolite due to their superior antiincrustation efficiency. A prerequisite for the maintainance of the good builder efficiency of the silicates is a gentle processing with a far reaching preservation of the silicate or granule structure. The possibilities to process zeolites are surely more versatile. The future market development of the silicates as well as of zeolite P depends particularly on the price development.