Phthalates, use as plasticizers

The substances detected included herbicides, such as Alachlor, butachlor, atrazine, cyanazine, propazine, and simazine insecticides, such as chlordane, heptachlor, dield-rin, eldrin, and DDE as a DDT metabolite and industrial organics, which included alkylbenzenes such as toluene, xylenes, ethylbenzene alkanes such as decane through pentadecane naphtalene and methylnaphtalenes alkyl phthalates, used as plasticizers chlorinated methanes and ethanes, especially CHCI3 chlorinated benzenes and chlorinates phenols benzaldehyde dicyclopentadiene, etc. Of these compounds, the hydrocarbons are typical of oil refinery operations, and the chlorinated benzenes and phenols are associated with herbicide and insecticide production. 

Phthalates, used as plasticizers in PVC (annual world production 6.4... 

Oestrogenic activity has been demonstrated in a number of other anthropogenic substances. An example is bisphenol A (see Section 12.9.2), a monomer of polycarbonate and epoxy resins, which can be leached from lacquered plates for cans or dental compositions and seals. Oestrogenic activity is also exhibited by some halogenated pesticides, polychlorinated biphenyls and certain of their hydroxy-lated metabolites, phthalates (used as plastic softeners), veterinary pharmaceuticals and some other xenobiotics, which are referred to in Chapter 12. 

Commodity Phthalate Esters. The family of phthalate esters are by far the most abundandy produced woddwide. Both orthophthaUc and terephthahc acid and anhydrides are manufactured. The plasticizer esters are produced from these materials by reaction with an appropriate alcohol (eq. 1) terephthalate esterification for plasticizers is performed more abundandy in the United States. Phthalate esters are manufactured from methanol (C ) up to Qyj alcohols, although phthalate use as PVC plasticizers is generally in the range to The lower molecular weight phthalates find use in nitrocellulose the higher phthalates as synthetic lubricants for the automotive industries. 

One principal use of cyclohexanol has been in the manufacture of esters for use as plasticizers (qv), ie, cyclohexyl and dicyclohexyl phthalates. In the finishes industry, cyclohexanol is used as a solvent for lacquers, shellacs, and varnishes. Its low volatiUty helps to improve secondary flow and to prevent blushing. It also improves the miscibility of cellulose nitrate and resin solutions and helps maintain homogeneity during drying of lacquers. Reaction of cyclohexanol with ammonia produces cyclohexylamine [108-91-8], a corrosion inhibitor. Cyclohexanol is used as a stabilizer and homogenizer for soaps and synthetic detergent emulsions. It is used also by the textile industry as a dye solvent and kier-boiling assistant (see Dye carriers). 

Plasticizers. Plasticizers are materials that soften and flexibilize inherently rigid, and even britde polymers. Organic esters are widely used as plasticizers in polymers (97,98). These esters include the benzoats, phthalates, terephthalates, and trimeUitates, and aUphatic dibasic acid esters. Eor example, triethylene glycol bis(2-ethylbutyrate) [95-08-9] is a plasticizer for poly(vinyl butyral) [63148-65-2] which is used in laminated safety glass (see Vinyl POLYMERS, poly(vinyl acetals)). Di(2-ethyUiexyl)phthalate [117-81-7] (DOP) is a preeminent plasticizer. Variation of acid and/or alcohol component(s) modifies the efficacy of the resultant ester as a plasticizer. In phthalate plasticizers, molecular sizes of the alcohol moiety can be varied from methyl to tridecyl to control permanence, compatibiUty, and efficiency branched (eg, 2-ethylhexyl, isodecyl) for rapid absorption and fusion linear (C6—Cll) for low temperature flexibiUty and low volatility and aromatic (benzyl) for solvating. Terephthalates are recognized for their migration resistance, and trimeUitates for their low volatility in plasticizer appHcations. 

Plasticizers can be classified according to their chemical nature. The most important classes of plasticizers used in rubber adhesives are phthalates, polymeric plasticizers, and esters. The group phthalate plasticizers constitutes the biggest and most widely used plasticizers. The linear alkyl phthalates impart improved low-temperature performance and have reduced volatility. Most of the polymeric plasticizers are saturated polyesters obtained by reaction of a diol with a dicarboxylic acid. The most common diols are propanediol, 1,3- and 1,4-butanediol, and 1,6-hexanediol. Adipic, phthalic and sebacic acids are common carboxylic acids used in the manufacture of polymeric plasticizers. Some poly-hydroxybutyrates are used in rubber adhesive formulations. Both the molecular weight and the chemical nature determine the performance of the polymeric plasticizers. Increasing the molecular weight reduces the volatility of the plasticizer but reduces the plasticizing efficiency and low-temperature properties. Typical esters used as plasticizers are n-butyl acetate and cellulose acetobutyrate. 

To minimize the gradual embrittlement that can occur on aging of cyanoacrylate adhesives, plasticizers are added. Some of the materials, which have been used as plasticizers, include phthalates, phosphonates, acyl esters, succinates, and cyano-acetates. The use of allyl, methallyl, and crotyl phthalates is also claimed to improve thermal resistance properties in addition to plasticizing the adhesive [23]. 

The chemical industry uses esters for a variety of purposes. Ethyl acetate, for instance, is a commonly used solvent, and dialkyl phthalates are used as plasticizers to keep polymers from becoming brittle. You may be aware that there is current concern about possible toxicity of phthalates at high concentrations, although a recent assessment by the U.S. Food and Drug Administration found the risk to be minimal for most people, with the possible exception of male infants. 

Organotin compounds such as monobutyltin oxide, the main substance used, accounting for 70% of consumption, dibutyltin oxide, monooctyltin oxide, and dioctyltin oxide are used in certain esterification and transesterification reactions, at concentrations between 0.001% and 0.5% by weight. They are used in the production of substances such as phthalates, polyesters, alkyd resins, fatty acid esters, and adipates and in trans-esterifications. These substances are in turn used as plasticizers, synthetic lubricants, and coatings. Organo-tins are used as catalysts to reduce the formation of unwanted by-products and also provide the required colour properties (ETICA, 2002). 

Phthalate esters, particularly, di-2-ethylhexyl phthalate (DEHP), are widely used as plasticizers. The total annual U.S. production of phthalate esters was over h00,000 tons in 1970 (1). Many of the applications of phthalate esters such as in construction, home furnishings, the automobile industry, etc. make it likely that they reach the aquatic environment. Since the initial report of the presence of phthalate esters in natural waters and fish in the United States by Mayer and coworkers (2), there have been reports of these chemicals in fish in Canada (3, t) and in Japan (5). The presence of phthalate esters in the ocean waters off the United States and in Gulf of Mexico biota has also been noted (6. ... 

As previously mentioned, phthalates are mainly used as plasticizers, but they are also used as solubilizing or stabilizing agents in other applications. They are components of many plastics products such as food wraps, detergents, building... 

Other oxygenated organic components reported in air include dihydroxybenzene and phthalates (e.g., Appel et al., 1980). The latter may arise from direct emissions, since phthalates are used as plasticizers. 

Salthammer et al. (1999) examined emissions from commonly available coatings used on furniture and identified numerous oxidation products. These were observed without the addition of oxidants such as ozone, indicating that oxidation in air (perhaps including photodecomposition for some compounds) under typical conditions is sufficient to generate such products. For example, emissions of 2-ethylhexanol were identified from di-2-ethylhexyl phthalate, used as a plasticizer in many coatings. 

Since cellulose nitrate is intractable, in 1870 John W. Hyatt added camphor as a plasticizer to flexibilize this plastic. Some 60 years later, Waldo Semon used tricresyl phosphate as a plasticizer for PVC. Dialkyl phthalates, such as dioctyl phthalate (DOP) and other alkyl phthalates which replaced the more toxic tricresyl phosphate, are now used as plasticizers primarily for PVC at an annual rate of 1 million tons. 

Although environmentally persistent, most of the common phthalates have low toxicity ratings of 2 or 3, based on acute toxic effects. There is particular concern with regard to di-2-ethylhexyl phthalate used as a plasticizer in polyvinyl chloride plastic medical devices.12 Dialysis patients and hemophiliacs who receive frequent blood transfusions are especially likely to receive potentially harmful levels of di-2-ethylhexyl phthalates from contact of fluids with such devices. 

DEHP exposure of humans might result from intravenous administration of blood that has been stored in plastic containers, or through hemodialysis. Under situations such as these, in which DEHP is introduced directly into the blood, it is possible to evaluate exposure by measuring blood DEHP concentrations. DEHP metabolites, MEHP and phthalic acid, are also measured in the blood to determine exposure from medical products or devices (Barry et al. 1989 Sjoberg and Bondesson 1985). If the total amount of phthalate is to be monitored, the phthalate esters are first de-esterified (Liss et al. 1985). Techniques that measure total phthalic acid are not specific for DEHP exposure since other alkyl phthalic acid esters that are used as plasticizers will also produce phthalic acid after de-esterification. 

Benzyl Chloride. The principal method for producing benzyl chloride involves the photochlorination of toluene, followed by neutralization and distillation. In 1999, 75 million lb of benzyl chloride were produced in the United States. About two-thirds was used to manufacture benzyl phthalates (mainly butyl benzyl phthalate), which are widely used as plasticizers. The other use was to make benzyl quarts. Benzyl chloride can also be used as raw material in the manufacture of benzyl alcohol, for use in photography, perfumes, and cosmetics. The production has increased considerably in Western Europe because of the greater use in solvents such as benzyl esters. But the U.S. production was stopped in 1999. 

The desired a-alkenes in the C10-C20 range are used as feedstock in the production of detergent alcohols and in the synthesis of lubricants, the C6-Q0 alkenes are used as plasticizer alcohols in phthalates for PVC, and as comonomers in low-density polyethylene, and a variety of other products. The internal by-products are mainly used for the production of alcohols via a cobalt-catalyzed hydroformylation. 

The major use of phthalic anhydride is for ester derivatives used as plasticizers in the manufacture of flexible poly(vinyl chloride), e.g., wallpaper. The largest volume plasticizer is the di(2-ethylhexyl)phthalate. Other uses of phthalic anhydride are for unsaturated polyester and alkyd resins, for dye intermediates, and for isatoic anhydride (for the production of saccharin). 

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