by softening water, dispersing soils, stabilizing surfactants, and preventing dirt from re-depositing onto fabrics or hard surfaces.
Key functions of STPP in washing applications
- Softens hard water by binding calcium and magnesium ions.
- Acts as a builder to boost surfactant cleaning efficiency.
- Disperses and suspends soils to prevent re-deposition.
- Helps control pH in alkaline detergent systems.
- Stabilizes formulations and improves storage performance.
1. How STPP Works in Detergent and Washing Formulations
In washing systems, minerals such as calcium and magnesium ions react with surfactants and reduce their cleaning power. STPP complexes these hardness ions, keeping them in solution and
protecting surfactants from precipitation. At the same time, its dispersing properties help break down particulate soils and keep them suspended in the wash liquor.
- Water softening: STPP chelates Ca2+ and Mg2+, preventing soap scum and improving surfactant efficiency.
- Builder effect: enhances detergency by allowing the use of less surfactant for the same or better cleaning performance.
- Soil dispersion: keeps loosened dirt in suspension, avoiding a grey or dull appearance on fabrics.
- pH buffering: helps maintain an alkaline environment that is favorable for many washing processes.
2. Typical STPP Dosage in the Washing Industry (Visual Guide)
The dosage of STPP in detergents depends on the formulation type, water hardness, and cleaning requirements. The chart below shows typical dosage ranges as a percentage of the total
formulation.
* These values are general reference ranges. Actual dosage should be optimized according to
local regulations, water hardness, surfactant system, and target performance.
Example: Basic Powder Laundry Detergent Formula with STPP
| Component | Function | Typical dosage (%) |
|---|---|---|
| Linear alkylbenzene sulfonate (LAS) | Primary anionic surfactant | 8–15% |
| Nonionic surfactant | Secondary surfactant, emulsifier | 3–6% |
| Sodium Tripolyphosphate (STPP) | Builder, water softener, soil dispersant | 20–30% |
| Alkaline salts (soda ash, silicate) | pH control, corrosion inhibition | 10–20% |
| Bleaching agents & stabilizers | Stain removal, whitening | 5–15% |
| Enzymes, optical brighteners, fragrance, etc. | Performance & sensory enhancement | Balance |
This example illustrates how STPP works alongside surfactants and other functional additives
as a central part of the washing formulation.
3. Application Areas of STPP in the Washing Industry
3.1 Household Laundry Detergents
In household powders and some liquid detergents, STPP is used to secure high cleaning efficiency even in hard water areas. It improves stain removal on cotton, synthetic fabrics,
and blends, while helping keep colors bright and whites clear.
3.2 Industrial & Institutional Cleaning
Heavy-duty detergents for hotels, hospitals, food processing, and metal cleaning often rely on STPP is a builder and dispersant. It helps remove oils, particulate soils, and protein-based
stains under demanding conditions and high wash temperatures.
3.3 Dishwashing & Hard-Surface Cleaning
In automatic dishwashing powders and machine cleaning agents, STPP contributes to scale control, improved rinsability, and prevention of film or spot formation caused by hard water
minerals and redeposited soils.
4. Practical Tips for Using STPP in Detergent Formulation
- Choose the right grade of STPP according to application (household, I&I, industrial).
- Check compatibility with surfactant system and other builders (zeolite, carbonate, citrate, etc.).
- Adjust dosage based on local water hardness and washing temperature.
- Monitor bulk density, flowability, and caking properties in powder formulations.
- Ensure compliance with local regulations and environmental guidelines.
5. Safety, Regulatory, and Environmental Considerations
STPP has been widely used in detergents for decades. However, in some markets, the use of phosphates in household laundry detergents is restricted due to concerns about nutrient
loading in water bodies. Many regions still allow STPP in industrial and institutional cleaners or in controlled applications.
Detergent manufacturers should always confirm current regulations in their target markets and design formulas that balance performance, cost, and environmental profile.
FAQ: STPP in the Washing Industry
1. Why is STPP used as a builder in detergents?
STPP binds calcium and magnesium ions, softens water, and protects surfactants from inactivation. This boosts the overall cleaning efficiency of the detergent, especially in
hard water conditions.
2. Can STPP be used in both powder and liquid detergents?
Yes. STPP is commonly used in powder detergents and can also be used in certain liquid detergents formulations, provided solubility and stability are properly managed in the formula.
3. Is STPP suitable for industrial and institutional cleaning?
STPP is widely applied in industrial and institutional cleaning products, where high performance, strong soil removal, and reliable water softening are required.
4. Are there regulatory limits on STPP in detergents?
In some regions, phosphates in household detergents are restricted or regulated. Many industrial applications are still permitted. Manufacturers should always follow local
regulations when designing formulations.
5. What type of STPP should I choose for detergent production?
High-purity, low-impurity STPP with good bulk properties is recommended for detergent manufacturing. Consistent quality helps ensure stable performance and efficient processing.
