What is Phosphate Ester Surfactants and Why Do We Use Them?

21 Apr.,2025

 

The 411 on Phosphate Esters

Phosphate esters are a standout among surfactants due to their valuable functional properties and remarkable versatility. As demand for them continues to grow, Ethox Chemicals is proud to offer extensive expertise in phosphate ester production to our customers.

Goto Sancolo to know more.

Read on to learn more about these advantageous surfactants – and how we use them to customize high-performance products for specific applications in a multitude of sectors.

WHAT ARE PHOSPHATE ESTERS?

Organic esters of phosphoric acid, phosphate esters are a versatile class of anionic surfactants. Superior wetting and dispersing agents for a variety of end uses, they improve the dispersion of pigments during processing while also enhancing surface wetting and reducing flash rusting. Because of their versatility, phosphate esters have applications in many industries. For example, they are used in the coatings industry to improve gloss, color acceptance, and water sensitivity in waterborne paint and coatings.

Prepared via a phosphation process in which either phosphoric anhydride (P2O5) or polyphosphoric acid (PPA) is reacted with the hydroxyl group (-OH) of a hydrophobe-containing material, phosphate esters are strong acids. While they are often used in the acid form, they can also be partially or fully neutralized with various bases—such as potassium hydroxide or amines—to form anionic phosphate ester salts, which are much more water soluble than the acid form. The degree of neutralization determines the water solubility and surface activity of the phosphate ester, thus they may be ‘tuned’ to optimize their performance in your application.

A Leader in the Production of Phosphate Esters

Ethox Chemicals has more than 50 years of experience producing phosphate esters from these four major chemical groups:

  • Fatty alcohols
  • Ethoxylated and/or propoxylated fatty alcohols
  • Glycerides, such as castor oil
  • Ethoxylated alkyl phenols

They have a broad range of applications, and are used as the following:

  • Extreme pressure additives
  • Anti-static agents
  • Wetting and scouring agents
  • Oil and water dispersible emulsifiers
  • Lubricants
  • Pigment dispersants

Contact Ethox For Your Phosphate Ester Needs

A leading provider of surface-modifying products, we serve customers in a wide breadth and depth of industries. Using our extensive knowledge and experience in custom synthesis and product development, we employ a wide range of chemistries including alkoxylation, esterification, phosphation, sulfation, and quaternization.

As specialists in the manufacturing of phosphate esters, we make more than 100 phosphate ester products using different combinations of hydrophobe-to-acid group content—each optimized for its own specific end use.

Phosphate Esters for Industrial & Institutional Cleaning - Lankem Ltd

The Lanphos range of phosphate esters is a versatile class of surfactants, possessing many of the surfactant properties useful in the formulation of Industrial and Institutional cleaners than other anionic surfactants, including:

  • Detergency

  • Foaming

  • Emulsification

  • Dispersing

  • Wetting

  • Solubilising

In addition to these, the Lanphos phosphate esters also possess properties not as commonly found in other classes of anionic surfactant, which include:

  • Defoaming

  • Hydrotropiicity

  • High electrolyte tolerance

  • Lubricity

  • Corrosion inhibition

Because of the unique chemical structure of phosphate esters, it is possible to design multifunctional surfactants with the required balance of the above properties to give optimum performance in a wide range of applications in the formulation of Industrial and Institutional Cleaners.

The following is a brief introduction to the parameters which you can change in the manufacturing process and chemical composition of phosphate esters that gives rise to these properties. CHEMISTRYYou can produce Lanphos phosphate ester by reacting a hydroxyl containing molecule, typically an ethoxylated nonionic surfactant, with a phosphorylating agent. There are two main phosphorylating agents used in the preparation of phosphate esters:

a) Phosphorus pentoxideb) Polyphosphoric acid (TPA)

Phosphorus pentoxide phosphorylation conforms to the following general reaction:P2O5 + 3ROH ------> (RO) 2PO3H + (RO)2PO3H2

Diester Monoester

This reaction, if carried out at a 3:1 mole ratio (as above), gives equimolar amounts of monoester and diester phosphates, which relates to a ratio of approximately 65:35 on a weight/weight basis. However, by manipulating the reaction mole ratio and conditions, it is possible to achieve any ratio down to 20:80 (weight/weight).This reaction route also produces phosphoric acid as a by-product, however, the level is usually low, at below 1%.

Polyphosphoric acid is a complex mixture of orthophosphoric acid with pyro, tri, tetra, penta, and higher phosphoric acids. However, the grade commercially used has an average of four phosphoric acid groups and is sometimes referred to as tetra phosphoric acid (TPA). If for simplicity, we assume that the reaction is with tetra phosphoric acid, it follows the general reaction:HO-(PO3H)4-H + 3ROH -----> ROPO3H2 + H3PO4MonoesterThis reaction produces predominately, monoester phosphate. If carried out at a mole ratio of 3:1, as above, results in a mole of free phosphoric acid forming, this typically relates to 5-10% on a weight/weight basis. With TPA phosphate esters, you can adjust the mole ratio; however, in this case, it only has the effect of changing the free nonionic content

Affect of Phosphorylating RouteThese two phosphorylating agents give products with entirely different compositions. The following table provides typical compositions (in % weight/weight) of products made by these routes.

Phosphorus pentoxide

Polyphosphoric acid

Monoester %

30 - 75%

80 - 90%

Diester %

60 - 20%

2%

Phosphoric acid %

0.50%

5 - 10%

Free nonionic %

5 - 15%

1 - 10%

The choice of phosphorylating agent is essential as the monoester and diester phosphate esters have differing properties. The following table lists the typical differences:

Monoester

Diester

Hydrotropicity

Excellent

Poor

Electrolyte tolerance

The company is the world’s best Phosphate Ester Surfactants supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.

Excellent

Poor

Detergency

Fair

Good

Wetting

Fair

Excellent

Emulsification

Excellent (emulsion polymer)

Excellent (oils)

Foaming

Higher

Lower

Dispersing

Fair

Excellent

The choice of hydrophobe has as significant an effect on the performance of phosphate esters as does the synthesis route. As previously stated, you can base phosphate esters on ethoxylated nonionic surfactants; however, there are some applications where unethoxylated products are used, such as fatty alcohols. The following table lists some of the properties that you can obtain with the various hydrophobes available:

Hydrophobe

Properties

Fatty alcohol's (C8 - C18)

Very low foaming/defoaming

Fatty alcohol ethoxylates

(C8 - C10)

Excellent wetting, good detergency low(ish) foaming

(C10 - C14)

Fair wetting, good detergency, high(ish) foaming, good emulsification (emulsion polymer)

(C14 - C18)

Poor wetting, poor detergency, excellent lubricity, good emulsification (oil)

Aromatic & polyaromatic ethoxylates

Phenol

Excellent hydrotropicity, good lubricant additive

Polyaromatic

Excellent dispersing

In addition to the chemical nature of the hydrophobe, the degree of ethoxylation also greatly effects the performance of phosphate esters. The following table lists some of the general trends observed when changing the level of ethylene oxide:

Ethylene oxide content

Properties

1 - 5 moles ethylene oxide

Good wetting, good emulsification (oils)

5 - 15 moles ethylene oxide

Good emulsification (emulsion polymer), good dispersing, high electrolyte tolerance

The Lanphos range of phosphate esters is specially developed optimising the above parameters to give exceptional performance in a wide range of applications using the expertise gained over many years of product development. Lankem is open to developing products that meet specific customer needs.

Lanphos phosphate ester recommended for Industrial and Institutional Cleaners

Electrolyte Tolerant Detergents - Phosphate esters can commonly find use in the formulation of highly built detergents. The high electrolyte solubility of these products allows detergents containing high levels of builders, such as caustic soda, silicates and sequestrants, to be formulated without the need for a hydrotrope. Products for this application include:

  • Lanphos PE245

  • Lanphos PE36

  • Lanphos TE43

Hydrotropes - Phosphate esters based hydrotrope are amongst the most effective products, allowing the formulation of product containing up to 30% caustic soda.

The following products are in our current range:

Want more information on Castor Oil Ethoxylates? Feel free to contact us.