Nitrosatable compounds

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). 

Nitrosamines form as a result of the reaction of nitrosating agents with secondary amines in the rubber. One of the main sources of secondary amines is a number of the accelerators that are used in sulphur-based cure systems, the amines being breakdown products produced as a result of the chemical reactions taking place during vulcanisation. Specific examples of these accelerators, their secondary amine products (i.e. the nitrosatable compounds) and the nitrosamines derived from them, are given in Table 12.7. 

The main approaches that have been taken to ensure that the concentration of nitrosamines (and nitrosatable compounds) in a given rubber is as low as possible are as follows ... 

Singer G.M. and Lijinsky W. (1976) Naturally occurring nitrosatable compounds. I. Secondary amines in foodstuffs. J. Agric. Food Chem. 24, 550-3. 

Almost any class of reduced nitrogen compound can serve as the nitrosatable precursor of an N-nitroso compound. To make matters worse, every nitrogen coordination state from primary to quaternary has been converted to a nitrosamine. A glance at the list of some of the known nitrosatable substrates given in Table II illustrates what a wide variety of N-nitroso compounds analysts might expect to encounter in our complex environment. 

Rhone-Poulenc Chemicals). Preparation of Fluoro Compounds by Treatment of the Corresponding Amines with Hydrogen Fluoride and a Nitrosat-ing Agent Under Ultrasound or Micro-wave Irradiation. PCT International Application WO 41,083, 1997 (GB Application 96/9, 154, 1 May 1996) Chem. 

Challis, B. C. (1981). The chemistry of formation of N-nitroso compounds. In Safety Evaluation of Nitrosatable Drugs and Chemicals (G. G. Gibson and C. loannides, eds.), pp. 16-55. Taylor Francis, London. 

Natural rubber has been the traditional material for elastomeric meat netting for many years and this has led to a number of studies into the levels of N-nitrosamines, nitrosatable and other compounds. Work carried out in the US A ° using a typical product produced from natural rubber latex contacted with a 50% ethanol simulant for 150 minutes at 152 °C produced the data shown in Table 12.5. 

A study in Japan looked at the migration of dimethylamine (DMA) into water and hydrochloric acid from 25 rubber articles (including stoppers, chopping boards, spatulas and teats). After one hour of refluxing, the water extracts contained 3 to 1280 mg of DMA per kg of rubber. The study also showed that the thiuram accelerators that were present (TMTD and TMTM) were almost totally decomposed to DMA (a nitrosatable substance). However, in the case of dimethyl dithiocarbamate salts (sodium, zinc, copper and lead examples were included), the decomposition to DMA depended on the solvent used and the salt compound. 

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