TCC’s ChemFlexx DOP di-2-ethylhexyl phthalate (DEHP, a.k.a. DOP) is the commercial name and abbreviation for the organic compound (DEHP) which is commonly known as “DOP”, which is a misnomer. The organic compound is a light-colored, non-toxic syrupy liquid that is used as a plasticizer for many resins and elastomers. DEHP is slightly soluble in water (0.285mg/L at 240c ) but soluble in alcohols, hexane etc., and is miscible and compatible with all the monomeric plasticizers of PVC compounding.
DEHP is the phthalate ester of the alcohol 2-ethyl hexanol, which is normally manufactured by the dimerisation of n-butyraldehyde, the butyraldehyde itself being synthesized from propylene. DEHP is a plasticizer that offers a good all-round performance and is therefore used for a great many cost-effective, general-purpose products that include building materials and some medical supplies and equipment. DEHP possesses reasonable plasticizing efficiency, fusion rate and viscosity, which is of great importance for plasitsol applications.
DEHP is produced by the esterfication of phthalic anhydride with 2-ethyl-hexanol. This reaction occurs in two successive steps. The first reaction step results in the formation of monoester by alcoholysis of phthalic acid. This step is rapid and proceeds to completion. The second step involves the conversion of the monoester to the di-ester. This is a reversible reaction and proceeds more slowly than the first. To shift the equilibrium towards the di-ester, the reaction water is removed by distillation. Elevated temperatures and a catalyst accelerate the reaction rate. Depending on the catalyst used, the temperature in the second step varies from 140°C to 165°C with acid catalysts and from 200°C to 250°C with amphoteric catalysts. Variations in purity may occur depending on catalyst, reactant alcohol and process type. Excess alcohol is recovered and recycled and DEHP is purified by vacuum distillation and/or activated charcoal. The reaction sequence is performed in a closed system. This process can be run continuously or in batches.