Applications herbicide manufacture

The technology can be used in agricultural applications, the manufacture or use of herbicides, munitions manufacturing, and in the manufacture and use of pesticides. 

Phenoxyalkanoic acids, introduced in the middle of the 1940s, are even today the most important selective herbicides, manufactured and used in the largest quantity. Owing to their particular selectivity, their wide field of applicability and their economy, demand for this type of herbicide continues to increase. In 1974 and 1975, 200 000 to 300 000 tons, yearly about 55-60% of the world herbicide production, was phenoxy acid compounds. 

In the practical experience of manufacturers and applicators, herbicidal 5-triazines have proved to be virtually nontoxic. Consistent evidence of toxic effects has not been reported (Deutsche Forschungsgemeinschaft 1986 Loosli 1994 Velvart 1993). It is particularly pertinent that the health files of major manufacturing plants have no record of triazine poisoning, although safety precautions in the early years of production prevented worker exposure to a limited extent only (Ciba-Geigy 1993, personal communication). 

Chlorinated aromatics, including monochlorobenzene (MCB), o-dichloroben-zene (o-DCB), and p-dichlorobenzene (p-DCB), are the major chlorinated aromatic species produced on an industrial scale. MCB is used as both a chemical intermediate and a solvent. As an intermediate, it is used to produce chloroni-trobenzene, pesticides, and pharmaceutical products. In solvent applications, MCB is used in the manufacture of isocyanates. Its high solvency allows it to be used with many types of resins, adhesives, and coatings. The o-dichlorobenzene is used primarily for organic synthesis, especially in the production of 3,4-dichlo-roaniline herbicides. Like MCB, it can be used as a solvent, especially in the production of isocyanates. It is also used in motor oil and paint formulations. The p-dichlorobenzene is used as a moth repellent and for the control of mildew and fungi. It also is used for odor control. It is a chemical intermediate for the manufacture of pharmaceuticals and other organic chemicals. 

Borax pentahydrate occurs in nature as mineral tincalconite, formed by dehydration of borax. It has several industrial applications, mostly the same as its decahydrate. The pentahydrate is used in the manufacture of borosili-cate glass. It also is used in cleaning agents ceramic glaze adhesives cosmetics antifreeze and herbicide formulations. It is added to fertihzers to provide boron as a nutrient to the plants. 

In addition to borax, which can be applied directly as a fertilizer, special borate products are manufactured for fertilizer use. These include granulated beads for blending with other common fertilizer products and soluble borates for application as liquid foliar sprays. Boron fertilizers are typically applied at a rate equivalent to about one to two pounds elemental boron per acre, depending on the specific crop and soil conditions. As with most fertilizers, excessive application can have adverse results. Borate fertilizers are phyotoxic at high levels and are sometimes used as non-selective herbicides. 

In addition to the construction industry, phenol has many other applications. It is used in pharmaceuticals, in herbicides and pesticides, and as a germicide in paints. It can be used to produce caprolactam, which is the monomer used in the production of nylon 6. Another important industrial compound produced from phenol is bisphenol A, which is made from phenol and acetone. Bisphenol A is used in the manufacture of polycarbonate resins. Polycarbonate resins are manufactured into structural parts used in the manufacture of various products such as automobile parts, electrical products, and consumer appliances. Items such as compact discs, reading glasses, sunglasses, and water bottles are made from polycarbonates. 

Sulfamic acid has a unique combination of properties that makes it particularly well suited for scale removal and chemical cleaning operations, the main commercial applications. Sulfamic acid is also used in sulfation reactions, pH adjustment, preparation of synthetic sweeteners (qv), and a variety of chemical processing applications. Salts of sulfamic acid are used in electroplating (qv) and electroforming operations as well as for manufacturing flame retardants (qv) and weed and brush killers (see Herbicides). 

Chlorine adds to ketene to form chloroacetyl chloride [79-04-9] (78). Chloroacetyl chloride (CAC) is used inlatge volume in the manufacture of the pre-emergence herbicides alachlor [15972-60-8] and butachlor [23184-66-9]. It is estimated that the CAC requirement for this application was in excess of 45,000 metric tons in 1992. Significant volumes of CAC are also used in pharmaceutical manufacture, such as anesthetics of the lidocaine type, and in the production of the tear gas chloroacetophenone [532-27-4]. Other commercial methods for the manufacture of CAC have been described (79). 

Up to the late 1960s, only dry formulations of atrazine were available. Ciba-Geigy Corporation later developed the first water-based, flowable concentrate formulation of an herbicide, AAtrex 4L, which was approved on January 15, 1970. This development launched a new era in herbicide formulation technology. The water-based formulation improved the manufacturing process, minimized dust, was easier to package and to load into application equipment, and easier to mix. Gradually, more and more farmers who used atrazine switched to the liquid formulation, which is now the preferred formulation. 

In general, workers involved in the manufacture of 2,4,5-TCP and subsequent products were exposed to far greater levels of 2,3,7,8-TCDD than those involved in the handling and application of chlorinated pesticides containing CDDs. Current serum lipid levels of 2,3,7,8-TCDD in a small number of U.S. Air Force veterans who were directly involved in the aerial spraying of herbicides (Agent Orange contaminated with 2,3,7,8-TCDD) in Vietnam as part of Operation Ranch Hand,... 

Occupational Exposure. Exposures to 2,3,7,8-TCDD, one of the most potent of the CDD congeners, have occurred occupationally in workers involved in the manufacture and application of trichlorophenols and the chlorophenoxy acid herbicides 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichloro-phenoxyacetic acid (2,4,5-T). Holmstedt (1980) has reviewed the history of industrial exposures that have occurred between 1949 and 1976, and Kogevinas et al. (1997) summarized recent data on these cohorts. 

TCDD or 2,3,7,8-TCDD-contaminated chemicals, workers involved in manufacturing or application of phenoxy herbicides and/or chlorophenols, and Vietnam veterans. In most of the human studies, exposure was poorly characterized. 

The carcinogenicity of 2,3,7,8-TCDD in humans has been assessed in numerous case-control and mortality cohort studies of chemical manufacturing and processing workers and phenoxy herbicide and chlorophenols applicators, Vietnam veterans exposed to Agent Orange, and residents of Seveso, Italy. A major weakness in many of these studies is the lack of adequate exposure data. Exposure levels or... 

TCDD. Another major weakness of most of the human cancer data is concomitant exposure to other compounds. The focus of this discussion on the carcinogenic potential of 2,3,7,8-TCDD and other CDDs will be on studies that have documented exposure by measuring blood levels or in which exposure can be reasonably presumed. The section is divided into four parts 1) the effect of CDD exposure on overall cancer risk in workers involved in the manufacture or application of phenoxy herbicides or chlorophenols followed by a discussion of specific types of cancer in this group, 2) cancer risks in Vietnam veterans, 3) cancer risks in Seveso residents, and 4) conclusive statement. 

Case-control studies have been designed to determine if 2,3,7,8-TCDD exposure results in increased risks for site-specific cancers. Case-control studies have found significant increases in the risk of soft-tissue sarcomas in Swedish agricultural, forestry, and horticultural workers (Eriksson et al. 1981, 1990 Hardell and Eriksson 1988 Hardell and Sandstrom 1979), workers involved in manufacturing and application of phenoxy herbicides (Kogevinas et al. 1995), and New Zealand farmers (Smith et al. 1984a). In the Eriksson et al. (1990) study, the risk ratio of soft-tissue sarcoma was 1.80 (95% 0=1.02-3.18) in subjects exposed to phenoxyacetic acid herbicides and/or chlorophenols. In subjects exposed to phenoxyacetic acid herbicides only or chlorophenols only, the risk ratios were 1.34 (95% 0=0.7-2.56) and 5.25 (95%... 

Diisobutylamine production (isobutanol and ammonia) for use in the manufacture of herbicides is the largest single chemical intermediate market for isobutanol. It represented approximately 32 percent of U.S. demand for the alcohol in 1979 This application is growing at a rate of roughly 3 percent per year. 

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