polyfosfater

Polyfosfater, or polyphosphates, are salts or esters of polyphosphoric acids characterized by chains of phosphate units linked by oxygen atoms. They can be linear polymers, such as triphosphates and longer chains, or cyclic metaphosphates such as hexametaphosphate. In water solutions they are typically highly soluble and exhibit strong affinity for divalent metal ions, enabling them to sequester calcium and magnesium.

Common forms include diphosphates, tripolyphosphates, and longer polyphosphates, with cyclic metaphosphates also used. The exact composition depends on the process and the cation (for example sodium or potassium salts). In practice, they are employed as water-softening agents, sequestrants, stabilizers, and thickening or gelling agents in various industries.

Industrial production involves condensation of phosphoric acid or phosphate salts under controlled conditions to yield alkali metal salts of varying chain length. They are widely used in detergents and cleaning products to improve cleaning efficiency and prevent scale, in paper, textile, ceramics, and oilfield applications, and in some cosmetics.

In the food industry, polyphosphates are used as additives under the E numbers E450 (diphosphates), E451 (tripolyphosphates), and E452 (polyphosphates). They help retain moisture, improve texture and tenderness, and stabilize emulsions.

Environmental and regulatory aspects: polyphosphates can release orthophosphate upon hydrolysis, contributing to nutrient loading and eutrophication in aquatic systems. Consequently, many regions regulate their use in detergents and limit phosphate discharge. In food contact and consumer products, safety is evaluated by authorities and usage is allowed within approved limits.