NITROSAMINE-FREE

The various effects of the Toxic Substances Control Act (TSCA) on the metalworking fluids Industry is presented, with emphasis placed on nitrosamine contamination of the fluids. A review of the literature on the effects of various metalworking fluid additives on nitrosamine formation is also presented to aid the industry in dealing with the nuisance of nitrosamine contamination. It is concluded that with increased awareness of nitrosamine contamination as a result of the implementation of TSCA and careful consideration of the factors described in this paper, it may be possible to design and control a nitrosamine-free metalworking fluid. 

Poly-tert-amylphenol disulfide Brown, slightly Liquid density at 25 C = 1150-1200 kg/m Nitrosamine-free... 

N,N -Dibutylthiourea is a nitrosamine free accelerator, antidegradant, and corrosion inhibitor. Ultra-accelerator for mercaptan-modified CR. It is slightly safer than DETU. It is also used as a secondary accelerator for NR and synthetic rubbers. It disperses easily in rubber. It is non-staining and does not bloom. It is practically odorless. Antioxidant for NR, antiozonant for NR and SR, particularly SBR. 

In all cases, nitrosamine free or safe alternatives are looked for. Eor System 1, the following alternative was suggested ... 

Manchester, 7th-10th June 1999, Environment paper 4. NITROSAMINE FREE CURING SYSTEMS FOR MODERN RUBBER COMPOUNDS... 

DITHIOATES ARE MORE THAN JUST NITROSAMINE FREE... 

Studies were made of nitrosamine formation by a number of accelerators in EPDM compounds, and of the effects of nitrosamine-free accelerators on cure characteristics and heat resistance and compression set of vulcanisates. The results showed the possibility of reducing cure times and compression set values through the use of combinations of different nitrosamine-free accelerators. 

In the concluding part of this study, a critical discussion is presented of the legally permissible N-nitrosamine concentrations, nitrosamine-free vulcanising systems are studied and evaluated, the activation of zinc dithiophosphate is described, and the BG 187 systems are compared with other systems. 73 refs. Articles from this]oumal can be requested for translation by subscribers to the Rapra produced International Polymer Science and Technology. 

There is an industry trend to supply SBR certifiably free of volatile nitrosamines or nitrosatable compounds. This has generally been accomplished by replacing shortstop systems based on carbamates and hydroxyl amines with products that are not based on secondary amines or are secondary amines of high molecular weight, such as dibenzyldithiocarbamate. A more recendy issued patent for ESBR shortstop is based on isopropyUiydroxylamine, a primary amine that does not form nitrosamine (46). 

By using modem production methods it is possible to reduce the amounts of 1,4-dioxane to a level that is barely detectable with the best current analytical methods. Free ethylene oxide is now below detectable levels. Furthermore, volatile and nonvolatile nitrosamines ( NDELA ) both seem to be below detection limits of ppb in the alkanolamide-based sulfosuccinates. A good overview of modern analytical methods for the detection of 1,4-dioxane and ethylene oxide as well as nitrosamines and formaldehyde is given in Ref. 60. 

Nitrite concentration The kinetics of N-nitrosamine formation in vitro has been studied at length (, ) and, in moderately acidic media, the reaction rate is directly proportional to the concentration of the free amine (non-protonated) and to the square of the concentration of the undissociated nitrous acid. Therefore, it is not surprising that the amount of nitrite permitted in bacon has received considerable attention. Although, there have been suggestions that it is the initial and not the residual nitrite that influences N-nitrosamine formation in bacon (41), recent evidence seems to indicate that the lowest residual nitrite gives the least probability of N-nitrosamines... 

In tobacco, we found the highest NDELA values for fresh and aged snuff with 6.8 and 3.2 ppm, respectively. The fermentation process appears to increase NDELA, as was also observed for VNA concentrations. There was clear evidence that tobaccos which had not been treated with MH-30, and cigarette smoke obtained from these tobaccos, were free of NDELA, whereas all MH-30 treated tobaccos and cigarette smoke derived from them showed measurable quantities of this nitrosamine (19). 

In order to ascertain that the NDELA formation does not occur as a result of trapping of the smoke or during the analysis, we added diethanolamine to tobacco prior to extraction with ethyl acetate in the presence of ascorbic acid. The control value for NDELA was 121 ppb and the experiment with 5.5 iqg diethanolamine addition yielded 113 ppb NDELA. For control of the smoke analysis we added 5.5 mg of DELA in the solvent trap and smoked cigarettes known to be free of DELA. Analysis of the trapped material showed no significant quantities of NDELA, so that artifactual formation of this nitrosamine during smoke collection and analysis can be ruled out. 

Saliva of 3 non-snufMipping women (controls) was free of nicotine and tobacco-specific N-nitrosamines. 

The experimental details describe the use of a free secondary amine for the preparation of a nitrosamine. Identical results are, of course, obtained by employing solid diethylamine hydrochloride. 

Hietanen, E. and Bartsch, H. (1992). Gastrointestinal cancers role of nitrosamines and free radicals. Eur. J. Cancer Prev. 1 (Suppl. 3), 51-54. 

Surfactants that form micelles have also been shown to accelerate the formation of nitrosamlnes from amines and nitrite (33.) A rate enhancement of up to 80 0-fold was observed for the nitrosation of dihexylamine by nitrite in the presence of the cationic surfactant decyltrimethylammonium bromide (DTAB) at pH 3.5. A critical micelle concentration (CMC) of 0.08% of DTAB was required to cause this effect, which was attributed to a micelle with the hydrocarbon chains buried in the interior of the micelle. The positively-charged ends of the micelle would then cause an aggregation of free nitrosatable amine relative to protonated amine and thus lead to rate enhancements. Since surfactants are commonly used in water-based fluids (25-50% lubricating agent or 10-2 0% emulsifier in concentrates), concentrations above the CMC of a micelle-forming surfactant could enhance the formation of nitrosamines. 

The massive contamination of NDE1A in alkaline synthetic fluids (3%) found by Fan et al Q) cannot be explained by known nitrosation kinetics of di- or triethanolamine. Instead, more powerful nitrosation routes, possibly involving nitrogen oxide (N0X) derivatives (e.g., N02> N O t) may be responsible for the amounts of NDE1A in these products (34). In fact, a nitrite-free commercial concentrate was shown to accumulate NDE1A up to about 10 0 days at which time the levels dropped dramatically (19). Inhibition of N0X contaminants may be an effective route to the inhibition of nitrosamine formation in metalworking fluids. 

A review of the literature has revealed that several factors associated with metalworking fluids may enhance or control the formation of nitrosamines in metalworking fluids. If nitrite is present in the concentrate with appropriate amines the nitrosamine levels can reach the part-per-hundred level Yet even nitrite-free metalworking fluid concentrates have been shown to contain part-per-million quantities of nitrosamines. 

It will he noticed that by this reaction the nitrosamines of the corresponding diarylamines are formed. The nitrogen radicles also combine with triphenylmethyl and other radicles, with mutual saturation of the free valencies. 

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