Dioctyl phthalate is an organic compound with the chemical formula of C24H38O4. It is a colorless oily liquid. Dioctyl phthalate is the most common member of the class of phthalates, which are used as plasticizers. Dioctyl phthalate is soluble in oil but not water. Dioctyl phthalate accounts for more than 54% of the market share for plasticizers and is considered a high production volume chemical.
Dioctyl phthalate is produced by the esterification of phthalic anhydride with 2-ethylhexyl alcohol using an acidic catalyst. The first 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 step is reversible and slower than the first step. High temperature and catalyst will increase the reaction speed. Depending on the catalyst used, the optimal temperature may range from 140 ℃ to 165 ℃ if using an acid catalyst and 200 ℃ to 250 ℃ if using an amphoteric catalyst.
Dioctyl phthalate is used as a general purpose plasticizers. It is highly cost effective and also widely available. Its broad range of characteristics such as high plasticizing efficiency, low volatility, UV-resistance, water-extracting proof, cold-resisting property, softness and electric property makes it suitable for making a wide range of products. It is widely used in PVC and ethyl cellulose resins to make plastic film, imitation leather, electric wire, etc.
Dioctyl phthalate is used in the production of synthetic rubber. Dioctyl phthalate is used as a softening agent to make the synthetic rubber easier to rebound and harder to undergo form change under pressure.