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Phosphate Esters for Agrochemicals

Updated: Sep 14, 2021

The Lanphos range of phosphate esters is a versatile class of surfactants, possessing many of the surfactant properties useful in the formulation of Agrochemical formulations 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 Agrochemicals. 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. Chemistry Lanphos phosphate esters are produced 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 pentoxide b) 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 + H3PO4 Monoester This reaction produces monoester phosphate predominately. If carried out at a mole ratio of 3:1, as above, results in a mole of free phosphoric acid being formed, this typically relates to 5-10% on a weight/weight basis. With TPA phosphate esters, the mole ratio can be adjusted; however, in this case, it only has the effect of changing the free nonionic content. Affect of Phosphorylating Route

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

Phosphorous Pentoxide

Polyphosphoric Acid

Monoester %

30 - 75

80- 90

Diester %

20 - 60


Phosphoric acid %


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:






Electrolyte tolerance










Excellent (emulsion polymer)

Excellent (oils)







Choice of hydrophobe The choice of hydrophobe has a significant 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 are obtained with the various hydrophobes available:

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:

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 Agrochemicals applications:

Emulsifiers - Phosphate esters find use in the formulation of emulsifiable concentrates. However, they more commonly find application in more specialised formulations such as suspo-emulsions (suspension concentrates produced in an emulsion). In these formulations the combination of good emulsification with dispersing make them an ideal surfactant. Products used include: Lanphos PE35 Lanphos PE36 Dispersants - Phosphate esters find use as the primary dispersant in the formulation of suspension concentrates and water-dispersible granules. They allow the formulation of stable dispersions with high solid contents.

Products used include: Lanphos PET22 Lanphos PE35

Compatibility Agents - Phosphate esters can be used to allow the spray application of pesticide at the same time as micronutrients such as manganese sulphate. In this application, it is the hydrotropic and electrolyte tolerance that makes phosphate esters suitable.

Products used include: Lanphos TEP4 Lanphos TEP4K Lanphos PE310

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