Dimethyl Phthalate

Infobox on Dimethyl Phthalate
Example of Dimethyl Phthalate
Facts
Origin	-
Stowage factor (in m3/t)	-
Humidity / moisture	-
Ventilation	-
Risk factors	See text

Dimethyl Phthalate

Description

Dimethyl phthalate is a colorless oily liquid with a slightly sweet odour. Dimethyl phthalate is a phthalate with molecular formula (CH3)2(C6H4(COO)2). It is the methyl ester of phthalic acid.

Dimethyl phthalate is an ectoparasiticide and has many other uses, including in solid rocket propellants, plastics, and insect repellents.

Phthalates are easily released into the environment because there is no covalent bond between the phthalates and plastics in which they are mixed. As plastics age and break down, the release of phthalates accelerates. Because phthalate plasticizers are not chemically bound to PVC, they can easily leach and evaporate into food or the atmosphere. Phthalate exposure can be through direct use or by indirect means through leaching and general environmental contamination. Diet is believed to be the main source of di(2-ethylhexyl) phthalate (DEHP) and other phthalates in the general population. Fatty foods such as milk, butter, and meats are a major source.

Phthalate esters are the dialkyl or alkyl aryl esters of phthalic acid (also called 1,2-benzenedicarboxylic acid, not be confused with the structurally isomeric terephthalic or isophthalic acids ); the name phthalate derives from phthalic acid, which itself is derived from word "naphthalene". When added to plastics, phthalates allow the long polyvinyl molecules to slide against one another. The phthalates have a clear syrupy liquid consistency and show low water solubility, high oil solubility, and low volatility. The polar carboxyl group contributes little to the physical properties of the phthalates, except when R and R' are very small (such as ethyl or methyl groups). They are colorless, odorless liquids produced by reacting phthalic anhydride with an appropriate alcohol (usually 6- to 13-carbon).

The mechanism by which phthalates and other molecules afford plasticisation to polar polymers has been a subject of intense study since the 1960's. The mechanism is one of a polar interactions between the polar centres of the phthalate molecule (the C=O functionality) and the positively charged areas of the vinyl chain, typically residing on the carbon atom of the carbon-chlorine bond. In order for this to be established, the polymer needs to be heated in the presence of the plasticizer, first above the Tg of the polymer and then into a melt state. This enables an intimate mix of polymer and plasticizer to be formed, and for these interactions to occur. When cooled, these interactions remain and the network of PVC chains cannot reform (as is present in unplasticised PVC, or PVC-U). The alkyl chains of the phthalate then screen the PVC chains from each other as well. This explains why small changes in the length of these chains produce small changes in the level of plasticisation.

In studies of rodents exposed to certain phthalates, high doses have been shown to change hormone levels and cause birth defects.

Application

A colourless, oily liquid used in the manufacture of lacquers, plastics, coating agents, safety glass, moulding powders and insect repellents.

Phthalates are by far the most widely used plasticisers, primarily to make soft and flexible polyvinyl chloride (PVC) for the applications in the industry of automotive, building & construction material, cable, flooring, medical device and toys. Phthalates make the long polyvinyl molecules to slide against one another. Minor quantity of phthalates are used in adhesives, caulk, sealants, paint to improve work performance. Small molecule phthalates are used as solvents in perfumes to provide longer linger longer and in nail polish to prevent chipping. They are also used as ingredients of insect repellents, as solvents in lacquer and pesticides, and as dye carrier. They are used as textile lubricating agents and as solid rocket propellents. Phthalates are produced by the reaction of phthalic anhydride with appropriate alcohols from methanol up to isodecanol (C13), either as a straight chain or with some branched in the presence of concentrated sulphuric acid as a catalyst. Excess alcohols are recovered and recycled and phthalates are purified by vacuum distillation and/or Activated Charcoal. A wide range of phthalates of varying chain length and structure provides each adequate properties and cost-effective for various processing and mechanical requirements. C8 - C9 phthalates, such as di-2-ethyl hexyl phthalate (DEHP or called DOP), diisodecyl phthalate (DIDP) and diisononyl phthalate (DINP) are the most widely used general purpose phthalates. DOP is the dominant plasticizer used in PVC, providing low cost. Short chain phthalates (C3 - C7) are used when rapid setting and stain resistance is required. 2-Ethyl hexanol, produced by the dimerisation of butyraldehyde obtained from propylene, is cheaper than isononyl alcohol which are prepared by the carbonylation of an olefin. Long chain phthalates (C11 - C13) are used when high temperature stability is required. C1 and C2 phthalates are used as solvents. Special phthalates which contain aromatic ring in the side chain are used when fast-fused is required. Diallyl phthalate is used as a crosslinking agent, plasticizer or dying carrier for polyesters.

Phthalates are used in a large variety of products, from enteric coatings of pharmaceutical pills and nutritional supplements to viscosity control agents, gelling agents, film formers, stabilizers, dispersants, lubricants, binders, emulsifying agents, and suspending agents. End-applications include adhesives and glues, agricultural adjuvants, building materials, personal-care products, medical devices, detergents and surfactants, packaging, children's toys, modelling clay, waxes, paints, printing inks and coatings, pharmaceuticals, food products, and textiles. Phthalates are also frequently used in soft plastic fishing lures, caulk, paint pigments, and sex toys made of so-called "jelly rubber". Phthalates are used in a variety of household applications such as shower curtains, vinyl upholstery, adhesives, floor tiles, food containers and wrappers, and cleaning materials. Personal-care items containing phthalates include perfume, eye shadow, moisturizer, nail polish, liquid soap, and hair spray. They are also found in modern electronics and medical applications such as catheters and blood transfusion devices. The most widely used phthalates are the di(2-ethylhexyl) phthalate (DEHP), the diisodecyl phthalate (DIDP), and the diisononyl phthalate (DINP). DEHP is the dominant plasticizer used in PVC due to its low cost. Benzylbutylphthalate (BBP) is used in the manufacture of foamed PVC, which is mostly used as a flooring material. Phthalates with small R and R' groups are used as solvents in perfumes and pesticides.

Shipment / Storage

If damaged by water or contaminated with foreign matter may be reconditoned by experts. It is slightly soluble in water.

Auto-Ignition Temperature	490°C
Flash points, closed cup	146°C
Flammable limits, lower	0.9%
Flammable limits, upper	8.03%
Boiling point	283,7°C
Melting point	5,5°C
Specific gravity	1,194

Keep container dry. Keep in a cool place. Keep container tightly closed. Keep in a cool, well-ventilated place. Combustible materials should be stored away from extreme heat and away from strong oxidizing agents.

Risk factors

Stable. Combustible. Incompatible with strong oxidizing agents, strong acids, strong bases, nitrates. Sensitive to prolonged exposure to light.

For overseas carriage aspects of Chemicals, the readers are recommended to acquire or have access to a good chemical dictionary, and a copy of the International Maritime Dangerous Goods (IMDG) Code, issued by the International Maritime Organisation. Also consult the applicable MSDS sheet.

Environmentally hazardous substance.