Industrial solvents methyl butyl ketone

Spencer PS, Schaumburg HH, Raleigh RL, et al Nervous system degeneration produced by the industrial solvent methyl -butyl ketone. Arch Neurol 32 219-222,... 

Nonmetallic neurotoxins are frequently used in industry in manufacturing of chemicals and resins or as solvents. Some examples are hydrogen sulfide (which paralyzes specifically the nervous centers that control respiratory movement), carbon disulfide, -hexane, methyl -butyl ketone, and acrylamide. Exposure to all of these substances may occur through inhalation of vapors. In addition, carbondisufide and acrylamide may enter the system by dermal absorption. -Hexane and methyl -butyl ketone are not toxic by themselves but are activated by cytochrome P-450 to the neurotoxic hexanedione (CH3COCH2CH2COCH3). 

Selkoe DJ, Luckenbill-Edds L, Shelanski ML. 1978. Effects of neurotoxic industrial solvents on cultured neuroblastoma cells methyl //-butyl ketone,n-hcxanc and derivatives. J. Neuropathol. Exp. Neurol. 37 768-89... 

The solvent hexane causes a different type of neurotoxicity, involving swelling and degeneration of motor neurones. This leads to paraesthesia and sensory loss in the hands and feet, and weakness in toes and fingers. Hexane has been widely used in industry as a solvent, and there have been many cases of neuropathy reported from different parts of the world. The toxicity is due to the metabolite 2,5-hexanedione which arises by co-1 oxidation at the 2- and 5-positions to 2,5-hexanediol, and then further oxidation to the diketone (figure 4.9). The 2,5-hexanedione then reacts with protein to form pyrrole adducts. The v-diketone structure is important, as 2,3- and 2,4-hexanedione are not neurotoxic. Methyl -butyl ketone also causes similar neurotoxic effects and is also metabolized to 2,5-hexanedione. The lipophilicity of the molecule allows distribution to many tissues including the nervous system. Thus, chemical structure and metabolism are important prerequisites for this toxicity. Exposure to the solvent carbon disulphide in industry causes neuronal damage in the central and peripheral nervous system. 

Ethyl acetate is used in production of acrylic plastics. Ethyl acetate and butyl acetate find wide usage as solvents for nitrocellulose and lacquers. Hthyl acetate is considered one of the least toxic of all industrial organic solvents. Buiyl acetate s chief industrial competitor is methyl isobutyJ ketone. Over lime, ethyl acetate and butyl acetate may suffer the same fate as methyl acetate, which hos been largely displaced by other solvents. 

Commonly used water-immiscible solvents in industrial-scale processes include alcohols (isobutanol, -butanol), ketones (particularly methyl isobutyl ketone), acetates (butyl, ethyl, isopropyl), hydrocarbons (toluene, hexanes), and methylene chloride. These solvents are inexpensive, readily available, and exhibit physical properties of low viscosity and density significantly different from water. Common water-miscible solvents are the alcohols (particularly methanol). For laboratory-scale processes, the selection is greater since selection is not constrained by economics. Craig and Sogn (16) have prepared an extensive compilation of such solvents. 

Nowadays, the most commonly used solvents are mineral or white spirits. Aromatic hydrocarbon solvents, such as xylene and toluene, are used in certain specialized industrial paints. Other solvents include a wide variety of alcohols (isobutanol, i-butanol), esters (ethyl acetate, butyl or isobutylacetate) and ketones (acetone, methyl ethyl ketone). Often, a mixture of different solvents is used to ensure the desired outcome, e.g., in thinners (Mathias 1984 Valsecchi et al. 1992 Rose and Vance 1997 Leira 1997). In Scandinavia, there has been a tendency for more than a decade to reduce the use of the more toxic solvents, including benzene, n-hexane and the chlorinated solvents, particularly carbon tetrachloride, chloroform, dichloroethane and trichloroethylene (Leira 1997). 

Solvent Extraction - Acetone is used to extract fats, oils, waxes, and resins from natural products, to dewax lubricating oils, and to extract certain essential oils. The pharmaceutical industry uses acetone to extract B-vitamin complexes, alkaloids, antibiotics and enzymes. Methyl ethyl ketone is used to dewax lube oil. Methyl isobutyl ketone is used to dewax mineral oil, refine tall oil, and in extractive distillation and separation of isopropyl alcohol from ethyl and butyl alcohols. The extraction and purification of antibiotics and other pharmaceutical products utilize MIBK. Methyl isobutyl ketone is used in the extraction of rosin from pine wood and the extraction of heavy metal ion complexes from water solutions. 

Methyl and ethyl methacrylate polymers, although extensively used in Industry, do not possess the solubility characteristics (low polarity) that would make them appropriate for use over traditional oil paintings and other organic-based museum objects that might be sensitive to polar solvents such as alcohols, ketones and esters. Poly(n-butyl methacrylate), offered as an artists varnish in the late 1930 s, did not become widely accepted in the war-disrupted decade that followed. Accordingly, early in 1951, our laboratory began a detailed study of the higher alkyl methacrylate polymers for potential use as picture varnishes (1). 

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