Sulfur containing benzothiazoles

For some produets, elemental sulfur or sulfur-containing benzothiazole compounds are added to flie eompound as a euring agent. Sulfur reacts to form C-S-C bonds. This is an inexpensive reaetion seheme and it is useful for production of rubber compounds across a very wide hardness range. Residual sulfur eompounds lead to odors and acid products that are not well suited to applieations where elean materials are desired. Thiazole compounds provide better handling and more eontrollable erosslinking proeesses, with low residual odor and extraetables. 

A number of complexes of zinc with benzothiazole and other sulfur-containing ligands have been described and the crystal structure of [NBuJ [ZnQ CNMe (02CMe), which contains a square pyramidal ZnS40 unit, has been reported.91 ... 

Many sulfur dyes contain benzothiazole, thiazone or thianthrene groups, and almost the whole range of shades can be obtained. The number of commercially available sulfur dyes is small but their production volume is large. Sulfur Black T with all conceivable variations may be the biggest synthetic dye which is used as a penetrating dye on leather Sulphur Black 1, 53185 [1326-82-5] (18 most probable structure). 

Volatile profiles of raw and cooked-beef flavor samples, prepared by the procedures of Figure 1, were obtained after capillary GC and FPD. Although the identification of these sulfur containing compounds is as yet incomplete, the chromatograms demonstrated that there were a number of new sulfur compounds produced on cooking that were not present in the raw beef. Three prominent sulfur compounds were identified as markers in subsequent meat flavor deterioration experiments, namely, methional (13.2 min), methyl sulfone (13.8 min), and benzothiazole (25.3 min). Each compound produced an adequate mass spectrum for spectral library search and positive identification. 

Barnes and co-workers [21] describe a HPLC-MS method for the determination of sulfur containing vulcanising agents in acidic acetonitrile extracts of foodstnffs which have been in contact with crosslinked rubbers. The detection limit was between 0.005 and 0.043 mg/kg for 2-mercaptobenzothiazole and benzothiazole. No trace of these two compounds and other vulcanising agents was found in any retail foodstuffs. 

Oxygen can be transferred from the arene oxides to nitrogen-, sulfur-, or phosphorus-containing substrates like pyridine, thiourea, N-methyl-benzothiazol-2-thione, thioacetamide, thiosemicarbazide, thiols, thio ethers, triphenylphosphine,21,160,161 etc. Parent hydrocarbons are formed as products.162 Thus the dimethoxycarbonyl oxide 269 on heating with pyridine produces 9,10-dimethoxycarbonylphenanthrene (270). The reaction of 1 or its... 

Reduction of dinitrobenzothiadiazoles 280 with iron dust in acetic acid gave diamines 281 (Scheme 39). The reaction of diamines 281 with selenium dioxide gave [l,2,5]selenadiazo[4,5-c]-2,l,3-benzothiazole derivatives containing a hypervalent sulfur atom 82 and 83 in 40% and 82% yields, respectively <1997T10169>. 

Figure 12.5a shows the effect of filler loading on the volume resistivity of MWNTs and CB (CB Ensaco 250G from Timcal) filled composites based on insulating styrene-butadiene rubber. The styrene-butadiene rubber contains 25 w% of styrene units. The microstructure of the butadiene phase is the following 10% cis, 17% trans, 73% 1,2. It was compounded with sulfur (1.1 phr), cyclohexyl benzothiazole sulfenamide (1.3 phr), diphenyl guanidine (1.45 phr), stearic acid (1.1 phr), zinc oxide (1.82 phr) (phr = parts per hundred parts of rubber). The unfilled and filled samples are cured into films (around 200 pm thick) at 170°C during 10 min under a pressure of 150 bar in a standard hot press. 

An important feature of these results concerns the sulfur content. A large part of the sulfur accompanies the basic fraction. This fact could reasonably be explained by the presence of components containing the thiazole ring (probably as benzothiazoles). Furthermore, comparison of the sulfur content of the bases and the nonbasic residues with that of the original material shows a net decrease. This may, in fact, be attributable to the removal of water-soluble inorganic sulfur compounds during the precipitation procedure. 

Because of the low level of C=C imsatiu-ation in the polsrmer compared to, eg, natural rubber (NR) and SBR, EPDM needs significant amoimts of highly active accelerators for sulfur vulcanization. Usually, combinations of benzothiazole derivatives or sulfenamides with so-called ultra-accelerators like thiuram compoimds or dithiocarbamates are used. Because of the limited soluhihty of these various accelerators in EPDM versus the large quantities needed to obtain a sufficient level of vulcanization, an EPDM compoimd often contains four or more... 

Vulcanization by sulfur alone is of little help as it is too slow. The vulcanizing systems currently used contain accelerators like thiuram sulfides (R2N-CS-S-S-CS-NR2), zinc dithiocarbamates [(R2N-CS-S)2Zn], thiourea (H2N-CS-NH2), or zinc benzothiazoles,... 

Although natural rubber (crepe) and nitrile rubber soles (common in the manufacturing of safety shoes due to its chemical inertness) are used, sulfur vulcanized styrene-butadiene (SBR) rubbers are the most common sole materials. The vulcanization system contains sulfur and activators (N-cyclohexyl-2-benzothiazole suffenamide, dibenzothiazyl disulfide, hexamethylene tetramine, zinc oxide) and fillers (silica and/or carbon black, calcium... 

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