Sodium Tripolyphosphate

What is Sodium Tripolyphosphate (STPP)?

Molecular Formula (Sodium Tripolyphosphate); Na₅P₃O₁₀.nH₂O(n=0

Molecular Weight; 367.86 g/mol

Chemical Name; Sodium Tripolyphosphate

CAS Number; 7558-29-4

It has many industrial applications, from cleaning products to its use as a food preservative. Sodium Tripolyphosphate (STPP) is also known by names such as pentasodium salt and triphosphoric acid.

Its chemical structure consists of 5 Sodium atoms, 3 Phosphorus atoms, and 10 Oxygen atoms.

Sodium Tripolyphosphate E Code is E 450.

Other names include the following;

• Sodium Triphosphate
• Triphosphoric Acid
• Pentasodium Salt
• Sodium Salt Triphosphoric Acid
• Tripolyphosphate
• Sodium Tripolyphosphate anhydrous
• Tetrasodium tripolyphosphate
• Triphosphate
• Sodium Phosphate
• Pentasodium(oxido-phosphonatooxyphosphoryl) phosphate
• Sodium Tripolyphosphate Penta Basic
• E 450

How is it Produced?

The primary method for industrial production of Sodium Tripolyphosphate (STPP) is the recrystallization method. The production here occurs as a result of a 2-stage reaction.

Soda Ash (Na₂CO₃) and food-grade Phosphoric Acid (H₃PO₄) with a concentration between 50%-60% are sent to the neutralization tank after reaction. The neutralized liquid is then sent to an intermediate storage tank. The resulting powder is conveyed to a rotary polymerization furnace. It is heated to between 540 °C and 580 °C. Dehydration polymerization powder is obtained through air cooling. During the production process, Sodium Tripolyphosphate (STPP) precipitates under water in an aqueous and anhydrous ethanol solution.

The production reactions are as follows;

1. 1st Reaction

5Na₂CO₃ + 6H₃PO₄ 》4Na₂HPO₄ + 2NaH₂PO₄ + 5CO₂ + 5H₂O

2. 2nd Reaction

4Na₂HPO₄ + 2NaH₂PO₄ 》 2Na₅P₃O₁₀ + 4H₂O

The production reaction is outlined here in general terms. However, internal process details are not shared due to being commercial information.

What are the Physical and Chemical Properties of Sodium Tripolyphosphate?

It exists as white and colorless crystalline granules and powder.

Sodium Tripolyphosphate (STPP) is completely soluble in water. Its aqueous solution is alkaline.

Its density at 20 °C is 2.52 g/cm3.

Its pH is between 9-10 (at 25 °C).

It is stable. It is not compatible with strong oxidizing agents and strong acids. It has hygroscopic properties.

In terms of solubility, it has a strong dissolution capacity in water. This solubility effect varies with pH and temperature.

Melting Point: 622 °C

Boiling Point: Information not available.

What are its Effects on Human Health?

Ingestion may be harmful. STPP causes skin irritation. It may cause serious eye irritation. Inhalation of its fumes may cause irritation to internal organs.

What is the Chelating Effect of Sodium Tripolyphosphate?

Water contains some metal ions that cause hardness. Since metal ions are positively charged, they bind to the dirt and lumps that have penetrated textile products. This is because dirt and lumps generally have negatively charged ions. Another factor is that the +2 valence structure of the hardness-causing ions forms a bridge.

STPP quickly binds both Ca+2 and Mg+2 ions. Additionally, it provides an excellent suspension/dispersion effect, capable of breaking down insoluble lumps.

Factors Affecting the Solubility of Sodium Tripolyphosphate

This chemical is used in many fields. It is the most widely used phosphate salt in sectors like the food industry, detergent industry, and cosmetics industry.

Due to some impurities present in STPP, this phosphate salt cannot exhibit its full effect. Therefore, its solubility decreases. If this chemical does not dissolve sufficiently, it cannot fully demonstrate its chemical effects.

Especially if even trace amounts of Potassium (+K) ions are present in the solution, Sodium Tripolyphosphate cannot show its effect.

What are the Usage Areas of Sodium Tripolyphosphate?

• It is one of the excellent detergent additives. There are 4 main reasons for its use here.
• STPP creates an ion chelation effect with heavy metals. This way, during the washing water process, heavy metal ions combine with detergent molecules to form an insoluble metal salt. This reduces the washing power and can even lead to a loss of function. It converts water containing heavy metal ions into harmless substances in the detergent. Sodium Tripolyphosphate (STPP) forms strong chelates and seals heavy metal ions, thereby eliminating their negative effects on washing.
• It is used to adjust the pH value of liquid soap. This helps in the decomposition of dirt. It has solubility on dirt protein. In this process, emulsification in oil is promoted.
• When used in detergent formulations, sodium tripolyphosphate is used to help prevent clogging caused by moisture absorption by maintaining the dry granular structure of synthetic absorbents.
• It contains a larger-sized buffer alkaline solution, and the pH is stabilized around 9.4. This helps in removing acidic dirt.
• It is used in the meat processing industry, synthetic detergent production, textile dyeing industry, and in the manufacture of solvents.
• This phosphate salt is used to provide soft water in confectionery production. Its effect here is to remove the hardness-causing metal ions in the water by forming a chelate structure, creating a complex.
• Sodium triphosphate (STPP) is used as a water softening agent in power plants, locomotive vehicles, fertilizer plant cooling waters, and treatment systems.
• It is used as a modifier, emulsifying agent, sequestering agent, and stabilizing agent.
• It is used for the precipitation and blooming of bar soap fat. It has a strong emulsifying capacity for lubricating oil.
• It is used as an anti-grease agent in the paper industry.
• STPP is used to improve the quality of food by complexing metal ions, increasing the pH value, and enhancing ionic strength.
• Technical grade sodium tripolyphosphate is used in dishwashing detergents, as well as in the manufacture of industrial glass cleaning products, along with a surfactant such as alkyl aryl sulfonate. It is also dissolved in a few solvents to obtain a liquid solution.
• It is used in fish products, poultry, and dairy products. It is also used in ice cream and instant noodle products.
• In the sausage, ham, and meat processing industry, it functions as a curing agent along with Sodium Ascorbate, Sodium Erythorbate, and Tetra Sodium Pyrophosphate (TSPP).
• It is used for chelating Magnesium and Calcium salts found in hard water in cleaning compositions produced with Magnesium Salts.
• In the marination process of seafood, it is used to improve the texture and enhance the flavor of the products.
• It is used in paper bleaching products along with Hydrogen Peroxide.
• In swimming pools, it controls water hardness by binding Calcium and Magnesium salts, ensuring a clearer pool.

What Factors Affect its Prices?

The price of Sodium Tripolyphosphate (STPP) is directly linked to the prices of the chemicals used in its production. For example, when the price of Soda Ash (Na₂CO₃) increases, the price of Sodium STPP will also increase.

When the price of Phosphoric Acid increases, its price will also increase.

As the number of companies producing in this field increases, the price of STPP may experience a short-term decrease, but it reaches a stable level in the long run.

Prices have shown a standard increase over many years. Companies that wholesale Sodium Tripolyphosphate (STPP) can control the market. Wholesaling companies keep their prices balanced according to their profit and loss systems.

At the beginning of the 2000s, Europe banned the use of sodium tripolyphosphate in detergents. This led to a contraction in the market for this substance, causing its price to fall.