Why STPP can be used in detergent
- Hydration performance. At room temperature, stpp chemical is quite stable, and it will slowly undergo hydrolysis in humid air, eventually producing sodium orthophosphate. Under the same conditions, the high-temperature type hydration generates high heat quickly and is prone to agglomeration when dissolved in water. This is due to the presence of sodium ions of the quadridentate ligand, which has a strong affinity for water. On the contrary, the low-temperature type forms hexahydrate at a low speed in water.
- Chelating ability to metal ions. STPP chemical has complexation action with metal ions, such as, calcium, magnesium and Fe dissolved in water to form soluble complexes. The complexing capacity of sodium tripolyphosphate is generally expressed by calcium value, that is, the grams of calcium ions complexed by 100g phosphate. The theoretical value is 13.4.
- Buffer effect. The aqueous solution of STPP is weakly alkaline. It forms a suspension liquid in water with the PH value ranging from 4.3 to 14. This is its dispersion effect. In addition, it can also make the liquid and solid particles better soluble in the liquid medium, so that the appearance of the solution is completely transparent, just like the real solution, this is its solubilization effect.
This is precisely because of its unique properties that make stpp powder an important ideal raw material in washing powder and detergents.
The Function of STPP in Synthetic Detergents
- The main ingredients of synthetic detergents are surfactants. The surface active agents have wetting effect, penetration effect, emulsifying effect, dispersing effect and foaming effect, etc… Decontamination is a comprehensive result of these effects. Although the surfactant alone has decontamination effect, it doesn’t get satisfactory results in all cases. For example, the effect is poor in hard water, the price is high, the washing effect is good at high PH, but the high PH value will have an erosive effect on the washing clothes and machine. Therefore, in order to make the synthetic detergent have good washing effect and better adaptability, and become a washing product that people are willing to use, it is necessary to add washing aid. Auxiliaries can be divided into organic auxiliaries and inorganic auxiliaries. The organic type can prevent dirt from redeposition, the inorganic type can reduce the concentration of synthetic pectin in synthetic detergent, and can make the synthetic detergent exert its washing performance at a lower concentration. In addition, these inorganic auxiliaries can also improve the decontamination effect of synthetic detergents under alkaline conditions. Sodium tripolyphosphate is the best inorganic auxiliary, which has many performances.
- It can make powder detergent products have good mobility. Sodium tripolyphosphate hydration can form a stable hydrate Na5P3O10.6H2O, which has a low steam pressure at room temperature and is very stable, thus preventing the powder detergent product from absorbing water and agglomerating, making the powder detergent have better fluidity when it contains higher moisture.
- Complexing action. There are usually high calcium and magnesium ions in tap water, which is called hard water. During washing, calcium and magnesium ions can react with the detergent in the synthetic detergent to form viscous metal soap, which reduces the detergency of the synthetic detergent, and it is easy to make the fabric recontaminated with metal soap. The metal soap deposited on the washed object will make the fabric hard and brittle.STPP can chelate with calcium and magnesium ions to form soluble complexes, which can soften hard water.
- STPP chemical itself has a certain washing effect. The washing effect of stpp is due to its dispersing, emulsifying, and peptizing effects on fine inorganic particles or fat droplets. The combination of these functions can improve the ability to suspend the dirt from redepositing on the fabric, and thus improve the cleaning effect of the detergent.