The thermoplastic, which can be reprocessed even after being brought to solid stage from plastic stage, like polyethylene. PVC, polystyrene, polyamides, cellulosic, acrylics, acetates etc. are hard, brittle & poor in mechanical properties where as when mixed with suitable plasticizer can be processed more conveniently by process like extrusion, injection & blow moulding. Just as fillers are absolutely essential for a thermosetting moulding powders, plasticizers are indispensable for termoplastics, particularly cellulosic.

Thus for plastic material to exhibit flexibility resilience & melt, flow, it must be `plasticizer'. Government of India has reserved the manufacture of D.E.P. in small scale sector only to secure small scale manufacturers. So all the facilities regarding raw materials procurement, marketability levies and taxes concessions etc are available to this unit also.

All the plant & machineries are also indigenously available. Therefore there is no hurdle in setting up this unit either within it or by the addition of an added substance which is knows as plasticizers. Without this, it would not be possible to make plastic sheeting, film & other flexible forms of plastics.

There are more than 350 types of plasticizers in the market all over the world and they are classified on the basis of chemical composition such as phthalates, phosphates, adipates epoxy etc. and on the basis of performance character such as primary secondary etc.

Among plasticizers, phthalates which are pthelic acid esters of boiling alcohols are the minor product of application & form nearly 70% of total plastisizer consumption. There are many type of phthalates which are used for this purposes, however their reprocessing is the same. The proposed scheme envisages the manufacture of diethylphthalate (DEP) in a small scale. The same set up of equipment may be utilisted for the manufacture of other, as necessary.

A plasticizer or softener is a substance or material incorporated in a material (usually a plastic or elastomer) to increase its flexibility, workability or distensibility. A plasticiser may reduce the melt viscosity, lower the temperature of the second order transition or lower the elastic modulus of the melt.

Diethyl phthalate (DEP) is a phthalate ester, namely the diethyl ester of phthalic acid. It is a clear substance that is liquid at room temperature and which does not occur in nature. It as a faint, disareeable odor and can be transferred from the plastics that contain it When burned, DEP produces toxic gases.

Since the compound is a suitable solvent for many organic molecules, it is often used to bind cosmetics and fragrances. Other industrial uses include plasticizers, detergent bases and aerosol sprays. Because of the frequent dermal exposure of humans to the chemical, the question of toxicity is crucial. Several studies suggest that DEP can cause damage to the nervous system as well as to the reproductive organs in males and females.

Exposure

Due to their use as plasticizers, diethyl phthalates are ubiquitous in the environment, especially near places of production and use. Biodegradation through microbially-mediated processes can result in products that can potentially harm microorganisms. There is also general evidence of widespread human exposure. Non-occupational exposure results from the diet, for example phthalate-coated medicines and nutritional supplements, and through consumer products. High occupational exposure was observed in workers directly manufacturing plasticizers. Studies suggest a high correlation between air and urine sample concentrations of short side-chain phthalates such as DEP, making inhalation an important route of exposure.

Structure and reactivity

Diethyl phthalate, or o-Benzenedicarboxylic acid diethyl ester consists of a benzene ring with two carboxylic acid ethyl esters attached to it in the ortho (1,2) pattern. It is a highly conjugated system, as the pi-cloud on the benzene ring, the p-orbitals on the carbonyl atoms and the lone pairs on the oxygens are all conjugated. The substituents are meta-directing, and they are ortho to each other, so all positions in the ring are more or less equally activated. Diethyl phthalate is likely to undergo biodegradation in the environment. Abiotic degradation processes such as hydrolysis, oxidation, and photolysis are unlikely to play significant roles in the environmental fate of diethyl phthalate.

Synthesis

Diethyl phthalate is produced by the reaction of phthalic anhydride with ethanol in the presence of a catalytic amount of concentrated sulfuric acid. Phthalic anhydride is produced by either the oxo process or the Ald- Ox process from ethanol and the oxidation of naphthalene or o-xylene. The purity of anufactured phthalate esters is reportedly between 99.70% and 99.97% with the main impurities being isophthalic acid, terephthalic acid and maleic anhydride.

Metabolism

Diethyl phthalate is hydrolyzed to monoester, monoethyl phthalate and ethanol after oral administration in the lumen of the gastrointestinal tract or in the intestinal mucosal cells. Hydrolysis of DEP also takes place at the kidney and liver after systemic absorption. After tissue distribution throughout the body, DEP accumulates in the liver and kidney. The metabolites are excreted in the urine. DEP is metabolized by carboxyl esterase, which is synthesized in the human liver. In vitro studies show that DEP reduces the glucuronyl transferase activity. It was also observed that the activity of peroxisomal enzyme carnitine acetyl transferase is increased in cultures of rat liver cells. Furthermore DEP induces the enzyme activity of catalase, which leads to hepatic peroxisome proliferation and possibly causes hyperplasia.

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