What is Dioctyl Phthalate
Dioctyl phalate (DOP) or Bis(2-ethylhexyl) phthalate is a colorless, odorless, and oily organic compound with the chemical formula of C24H38O4. It is a famous plasticizer that has been used for flexible polyvinyl chloride (PVC) plastic production due to its low price. DOP as a plasticizer is known for its good stability to heat and ultraviolet light and its compatibility to use with PVC resins. Dioctyl phthalate is soluble in oil but not water. The density of DOP is less than water, hence it floats on the surface of 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 a homogeneous acid catalyst such as concentrated sulfuric acid. The process can be performed in batch reactors with controlled condition of temperature for 16-20 hours. 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. After the esterification, the catalyst and unreacted phthalic anhydride is neutralized with alkaline solution and the alcohol-containing wastewater is recovered. 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.
The Uses of Dioctyl Phthalate
Dioctyl phthalate is often 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. As a softening agent, DOP makes the product easier to rebound and to maintain its form under pressure. DOP 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.
DOP is used to increase the performance properties of wood coating formulations.
DOP as a plasticizer is also used in the production of medical and sanitary products, such as blood bags and dialysis equipment. DOP has a significant role in blood bags due to it really helps to prolong the life of the blood itself. Besides that, DOP also stabilizes the membranes of red blood cells and allows them to be stored for several weeks.