Di(2-ethylhexyl) phthalate (DEHP) is one of the most cost effective and widely available general purpose plasticisers. It is used mainly for making PVC soft and pliable and it accounts for around 18% of all plasticiser usage in Western Europe .
DEHP (CAS No [117-81-7]) is also known as di-octyl phthalate (DOP). It is the phthalate ester of the alcohol 2-ethyl hexanol, which is normally manufactured by the dimerisation of butyraldehyde, the butyraldehyde itself being synthesised from propylene.
DEHP is a plasticiser which offers a good all-round performance and is therefore used for a great many cost-effective, general purpose products including building material such as flooring, cables, profiles and roofs, as well as medical products such as blood bags and dialysis equipment.
DEHP possesses reasonable plasticising efficiency, fusion rate and viscosity (of great importance for plastisol applications).
The content of DEHP in flexible polymer materials varies but is often around 30% (w/w).
Production process
All manufacturers of phthalate esters use similar processes. 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 batchwise.
DEHP → Bis(2-ethylhexyl) phthalate
From Wikipedia
Bis(2-ethylhexyl)phthalate, commonly abbreviated DEHP, is anorganic compound with the formulaC6H4(C8H17COO)2. It is sometimes called dioctyl phthalate and abbreviated DOP. It is the most important "phthalate," being thediester of phthalic acid and the branched-chain 2-ethylhexanol. This colourless viscous liquid is soluble in oil, but not in water. It possesses good plasticizing properties. Being produced on a massive scale by many companies, it has acquired many names and acronyms, including BEHP and di-2-ethyl hexyl phthalate.
Production
The process entails the reaction of phthalic anhydride with 2-ethylhexanol:
C6H4(CO)2O + 2 C8H17OH → C6H4(CO2 C8H17)2 + H2O
Approximately three billion kilograms are produced annually.[1]
Use
Due to its suitable properties and the low cost, DEHP is widely used as a plasticizer in manufacturing of articles made of PVC.[1] Plastics may contain 1% to 40% of DEHP. It is also used as a hydraulic fluid and as a dielectric fluid in capacitors. DEHP also finds use as a solvent in lightsticks.
Environmental exposure
DEHP has a low vapor pressure, but the temperatures for processing PVC articles are often high, leading to release of elevated levels, raising concerns about health risks (see outgassing). It can be absorbed from food and water. Higher levels have been found in milk and cheese. It can also leach into a liquid that comes in contact with the plastic; it extracts faster into nonpolar solvents (e.g. oils and fats in foods packed in PVC). Food and Drug Administration (FDA) therefore permits use of DEHP-containing packaging only for foods that primarily contain water. In soil, DEHP contamination moves very slowly because of its low solubility in water. Therefore, leaching from disposed plastics in landfills is generally slow. The US EPA limits for DEHP in drinking water is 6 ppb. The U.S. agency OSHA's limit for occupational exposure is 5 mg/m3 of air.
Use in medical devices
DEHP has been used as a plasticiser in medical devices such as intravenous tubing and bags, catheters, nasogastric tubes, dialysis bags and tubing, and blood bags and transfusion tubing, and air tubes. For this reason, concern has been expressed about leachates transported into the patient, especially for those requiring extensive infusions, e.g. newborns in intensive care nursery settings, hemophiliacs, and kidney dialysis patients. According to the European Commission Scientific Committee on Health and Environmental Risks (SCHER), exposure to DEHP may exceed the tolerable daily intake in some specific population groups, namely people exposed through medical procedures such as kidney dialysis.[2] The American Academy of Pediatrics has advocated not to use medical devices that can leach DEHP into patients and, instead, to resort to DEHP-free alternatives.[citation needed] In July 2002, the U.S. FDA issued a Public Health Notification on DEHP, stating in part, "We recommend considering such alternatives when these high-risk procedures are to be performed on male neonates, pregnant women who are carrying male fetuses, and peripubertal males" noting that the alternatives were to look for non-DEHP exposure solutions;[3] they mention a database of alternatives.[4] The CBC documentary The Disappearing Male raised concerns about sexual development in male fetal development, miscarriage (as DEHP is a pseudo-estrogen and a hormone modifier found in most plastic products such as PVC, polycarbonate, nearly all cosmetic chemical products, and many others), and as a cause of dramatically lower sperm counts in men. [5]
Metabolism
DEHP hydrolyzes to MEHP (mono-ethylhexyl phthalate) and subsequently to phthalate salts. The released alcohol is susceptible to oxidation to the aldehyde and carboxylic acid.[1]
Effects on living organisms
Smaller penis size and other feminizing links
DEHP metabolites measured from the blood of pregnant women have been significantly associated with the decreased penis width, shorter anogenital distance, and the incomplete descent of testes of their newborn sons, replicating effects identified in animals.[6] Approximately 25% of US women have phthalate levels similar to those in the study.[6]
Obesity
A study on CDC data published in Environmental Health Perspectives (EHP), revealed that American men with abdominal obesity or insulin resistance (a precursor todiabetes) were more likely to have high levels of DEHP and DBP metabolites in their urine than men without those problems.[7]
Toxicity
The acute toxicity of DEHP is 30g/kg in rats (oral) and 24g/kg in rabbits (dermal).[1] Concerns instead focus on its potential as an endocrine disruptor. Some countries have banned DEHP from toys; see phthalate for legal status.
Cardiotoxicity
A clinically relevant dose and duration of exposure to DEHP has been shown to have a significant impact on the behavior of cardiac cells in culture. This includes an uncoupling effect that leads to irregular rhythms in vitro. This is observed in conjunction with a significant decrease in the amount of gap junctional connexin proteins incardiomyocytes treated with DEHP.[8][9]
Alternative plasticizers
Manufacturers of flexible PVC articles can choose among several alternative plasticizers offering similar technical properties as DEHP. These alternatives include other phthalates such as DINP, DPHP, DIDP and non-phthalates e.g. DINCH and Citrates.
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