Dibenzothiazole Disulfide Research Articles

Effect of water on the accelerated sulfur vulcanization of natural rubber

Water present in natural rubber was found to play a role in forming carbon-carbon crosslinking junctions before forming carbon-sulfur crosslinking junctions when its effect on the accelerated sulfur vulcanization was investigated by analyzing low–molecular weight products through various instrumental analytical techniques. Samples were prepared by mixing deproteinized natural rubber (DPNR) with various moisture contents with stearic acid, ZnO, sulfur, and N-tert-butylbenzothiazole-2-sulfenamide, and they were vulcanized at 150 °C for various cure times. Low–molecular weight products such as 2,2′-dibenzothiazole disulfide (MBTS), 2-mercaptobenzothiazole (MBT), ZnMBT, Zn2+ and sulfur linked to the rubber were extracted from the vulcanized natural rubbers using benzene and dioxane, and subsequently measured by high-performance liquid chromatography, UV–visible spectroscopy, inductively coupled plasma atomic emission spectroscopy, and combustion analysis. The water present in natural rubber was found to strongly affect the production and formation rate of the low–molecular weight products in the accelerated sulfur vulcanization of natural rubber. As the result it suggests that the water promotes the formation of the C-C linkages, and then it sequentially promotes the formation of the C-S linkages.

An integrated system of a microreactor with a Taylor–Couette reactor for 2,2′‐dibenzothiazole disulfide synthesis

AbstractAn integrated microreaction system of a microreactor with a Taylor–Couette reactor (TCR) for continuous synthesis of 2,2′‐dibenzothiazole disulfide has been developed, so as to improve the process efficiency and the stability with solid product generation compared with the current batch process. The homogeneous oxidation with hydrogen peroxide catalyzed by phosphotungstic acid was applied. In the microreaction system, two feedstocks can be rapidly mixed through the microreactor; stable particle flow ability and high conversion can be achieved through the TCR, due to the flow characteristics of high shear stress and limited back‐mixing. Under the conditions of stable operation, the conversion can reach over 90%. The purity of the product is over 99%. The space–time yield can reach 160 g L−1 h−1, which is much higher than that in the batch reactor. The microreaction system is stable for long‐term running, which provides an effective design strategy for continuous flow processes with solid generation.

A Much Cleaner Oxidation Process for 2,2′-Dibenzothiazole Disulfide Synthesis Catalyzed by Phosphotungstic Acid

A novel homogeneous oxidation of 2-mercaptobenzothiazole (MBT) to 2,2′-dibenzothiazole disulfide (MBTS) with almost no emissions has been developed. The oxidation with hydrogen peroxide catalyzed by phosphotungstic acid (PTA) was applied to MBTS synthesis for the first time. The reaction efficiency and product quality are improved. Also, the problem of high salinity organic wastewater treatment in industrial production can be effectively solved. Under certain reaction conditions, the conversion ratio and reaction selectivity could be over 98.0 and 99.0%, respectively. The purity of the solid product is equivalent to that of pharmaceutical grade. Based on the observed reaction kinetics, two parallel reaction pathways in the catalytic process are proposed. The mother liquor containing catalyst was recycled for five times under the optimized conditions with high utilization of hydrogen peroxide over 93.0% in each cycle. A much greener synthesis of MBTS with high quality and without a side product is successfully achieved.

Main Reaction Network and Kinetics in the Synthesis of 2,2′-Dibenzothiazole Disulfide

Main Reaction Network and Kinetics in the Synthesis of 2,2′-Dibenzothiazole Disulfide

Cross-Linked Density Determination of Natural Rubber Compounds by Different Analytical Techniques

This paper investigated the formation of crosslinks in natural rubber compounds in the vulcanization systems: conventional (CV), semi-efficient (SEV), and efficient (EV), processed with three types of accelerators: MBTS (dibenzothiazole disulfide), TMTD (tetramethylthiuram disulfide) and CBS (n-cyclohexyl 2-benzothiazole sulfenamide). The cross-linked densities were determined by organic solvent swelling, dynamic mechanical analysis (DMA), stress vs strain, and low-field nuclear magnetic resonance, the latter being the reference technique for comparison with the other results. It was found that the choice of accelerator type influences the processing time and the cross-linked density of the vulcanizate. The four techniques showed close values of cross-linked density for natural rubber compounds, demonstrating that the analytical techniques studied can be applied to determine cross-linked density.

Reactive Sintering of Ground Tire Rubber (GTR) Modified by a Trans-Polyoctenamer Rubber and Curing Additives.

The proposed method of ground tire rubber (GTR) utilization involves the application of trans-polyoctenamer rubber (TOR), a commercially available waste rubber modifier. The idea was to investigate the influence of various curing additives (sulfur, N-cyclohexyl-2-benzothiazole sulfenamide (CBS), dibenzothiazole disulfide (MBTS) and di-(2-ethyl)hexylphosphorylpolysulfide (SDT)) on curing characteristics, physico-mechanical, thermal, acoustic properties as well as the morphology of modified GTR, in order to evaluate the possibility of reclaiming GTR and the co-cross-linking between applied components. The results showed that the presence of the modifier without the addition of curing additives hinders the physico-mechanical properties of revulcanized GTR. The addition of SDT, CBS, MBTS and sulfur change the melting kinetics of TOR, indicating partial degradation and/or co-cross-linking between components. In the studied conditions, the best mechanical properties were obtained by the samples cured with sulfur. The morphology analysis, combined with the physico-mechanical results, indicated that when the surface of the GTR is more developed, obtained by the addition of TOR, the properties of the GTR improve.

A chemical looping technology for the synthesis of 2,2′-dibenzothiazole disulfide

A novel chemical looping technology for the synthesis of 2,2′-dibenzothiazole disulfide (MBTS) with zero emissions.

Synthesis and characterization of natural rubber/clay nanocomposite to develop electrical safety gloves

This research focuses on the synthesis of natural rubber (NR)/clay nanocomposites to develop electrical safety gloves. The mixture included sulfur as a cross-linked agent, dibenzothiazole disulfide (MBTS) as catalysis of the vulcanizing processes, zinc oxide (ZnO), and stearic acid (SA) as chemical activators to control the reaction. The manufacturing process of the sample compounds was developed to evaluate the optimal processing parameters. The main criteria were the formulation quantities, temperature conditions, curing time, mixing speed and mixing time. This method allowed the absence of lumps, bubbles or pores to evaluate the texture, color, strength, and elongation in the samples. Some samples simulate a finger form and size. The NR/clay nanocomposites were synthesized, with organo-clay reinforcements in 0.5, 1 and 2 wt% fractions. The nanocomposites were characterized by different methods. SEM was used to observe the morphology and distribution of the clay in the matrix. The NR crystallinity was accessed via XRD. The main functional groups of the nanocomposite were identified by FTIR spectroscopy, and DSC distinguished the glass transition temperature.

The multiple roles of an organic corrosion inhibitor on copper investigated by a combination of electrochemistry-coupled optical in situ spectroscopies

The interaction of the organic corrosion inhibitor 2-mercaptobenzothiazole (MBT) with copper in alkaline solution was investigated by in situ infrared (IR) and Raman spectroscopy, and in situ spectroscopic ellipsometry, coupled to cyclic voltammetry (CV). At negative potentials, MBT monolayers relax on a minute time scale through MBT reorientation, leading to MBT-copper binding via S and N-atoms. After copper dissolution becomes thermodynamically feasible, including at open circuit, formation of a multilayer CuMBT complex sets in, in which thiol dominates over thione. Multilayer films effectively inhibit oxide formation. Instead, MBT oxidatively dimerises to 2,2′-dibenzothiazole disulfide (DBTA), which remains protective.

Aerobic oxidative radical coupling catalyzed by TEMPO for the preparation of 2,2′-dibenzothiazole disulfide

BACKGROUND: 2,2′-disbenzothiazole disulfide is widely used as a vulcanization accelerator in rubber production and as an intermediate in the drug industry. Its current industrial process, the oxidation of 2-mercaptobenzothiazole by sodium nitrite in acidic solution, produces large quantities of liquid waste water. A novel and green synthetic method was developed, which used dioxygen as the oxidant and 2,2,6,6-tetramethylpiperidyl-1-oxyl (TEMPO) as the catalyst without any metallic compounds. RESULTS: The conditions, including temperature, solvents, amount of catalyst, dioxygen pressure and time, were optimized. Thus 94% yield of 2,2′-disbenzothiazole disulfide was obtained at 60 °C in acetonitrile under 0.2 MPa oxygen pressure for 3 h. Theoretical calculations and UV spectra showed that hydrogen-transfer reaction between 2-mercaptobenzothiazole and TEMPO was the key step, and 2,2′-disbenzothiazole disulfide was generated by the coupling of the formed thiyl radical of 2-mercaptobenzothiazole. CONCLUSION: 2,2′-disbenzothiazole disulfide was prepared efficiently by aerobic oxidative coupling of 2-mercaptobenzothiazole with TEMPO as the catalyst. This ‘environmentally friendly’ approach with easy handling, mild reaction conditions and simple separation represents a viable means of producing 2,2′-disbenzothiazole disulfide. Copyright © 2011 Society of Chemical Industry

Synthesis of new Bismuth (III) compound and adducts of benzothiazol disulfide derivatives and their complexes with Co(II), Ni(II) and Cu(II)

Bismuth metal react with dibenzothiazole disulfide (C7H4NS2)2 in refluxing toluene to give the compound Bi(S2C7H4N)3 through oxidative addition reaction, similary, a mixture of bismuth, (C7H4NS2)2 and iodine in 1:1:0.5 molar ratio in refluxing toluene lead to the formation of Bi(S2C7H4N)2I. Adducts of new bismuth compounds with triphenyl-phosphine and 1,10-phenanthroline have been synthesized by direct reaction between the bismuth compounds and the neutral ligand. Trinuclear complexes of the general formula[Bi(S2C7H4N)3(MCl2)2] were prepared by a direct reaction of CoCl2.6H2O, NiCl2.6H2O or CuCl2.4H2O with bismuth compound. The bismuth compounds their adducts and the complexes have been characterized physico-chemically and spectro-scopically.

Improvement in the synthesis of 2-(5-amino-1,2,4-thiadiazol-3-yl)-2-(Z)-methoxyiminoacetic acid 2-benzothiazolyl thioester

2-(5-Amino-1,2,4-thiadiazol-3-yl)-2-(Z)-methoxyiminoacetic acid 2-benzothiazolyl thioester(III), an important intermediate of the fourth generation cephalosporins, was efficiently synthesized by reacting 2-(5-amino-1,2,4-thiadiazol-3-yl)-2-(Z)-methoxyiminoacetic acid (I) with 2,2′-dibenzothiazole disulfide (II) in the presence of triphenylphosphine. Effects of reaction time, temperature, solvents, catalysts and feeding molar ratio on the yield and quality of products were investigated, and an improved procedure suitable for industrial production was established. Using 1,2-dichloroethane as solvent, triphenylphosphine as reducer, and triethylamine as catalyst, n(I): n(II): n(triphenylphosphine)51.0: 1.0: 1.0, the product was obtained at room temperature in 98.1% yield. The purity of the product without further purification is 98.7% determined by HPLC method. This procedure could be a suitable alternative to the traditional processes because of its easy handling, high yield and low cost.

Synthesis and ring‐opening polymerization of macrocyclic aromatic sulfide oligomers

AbstractA series of macrocyclic(arylene sulfide) oligomers were synthesized by reaction of 4,4′‐oxybis(benzenethiol) with a number of difluoro compounds in dimethylformamide (DMF) in the presence of anhydrous K2CO3 under high dilution conditions. The difluoro compound can be 4,4′‐difluorobenzophenone, bis(4‐fluorophenyl)sulfone or 1,3‐bis(4‐fluorobenzoyl)benzene. Detailed structural characterization of these oligomers by matrix‐assisted laser desorption and ionization‐time of flight‐mass spectroscopy (MALDI‐TOF‐MS) demonstrated their cyclic nature. The MALDI‐TOF‐MS technique has proved to be a powerful tool to analyze these cyclics. These cyclic oligomers are amorphous and highly soluble in DMF and N,N′‐dimethyl acetamide. Moreover, these cyclic(arylene sulfide) oligomers readily underwent ring‐opening polymerization in the melt at 285 °C in the presence of 2,2′‐dibenzothiazole disulfide, affording linear, high molecular weigh poly(aromatic sulfide)s. These polymers are insoluble in most common solvents. Copyright © 2004 Society of Chemical Industry

Prevalence of upper and lower respiratory symptoms in workers exposed to colophony and MBTS

Rationale We assessed the prevalence of upper and lower work-related (WR) respiratory symptoms in 66 male subjects (mean age 37.4, SD 7.8) exposed to colophony and Dibenzothiazole Disulfide (MBTS), an occupational irritant, while working in linoleum production and in 17 nonexposed control subjects. Methods All completed a questionnaire and underwent skin prick test (SPT) for common allergens, and nasal peak inspiratory flow. Spirometry was carried-out only in exposed workers. Results Mean exposure duration was 6.3 (SD 3.9). SPT were positive in 40% of exposed and in 50% of control subjects. WR asthma was found in one subject, WR rhino-conjunctivitis in 5 (7.6%), WR cough/breathlessness in 5 (7.6%), and WR upper airway irritation in 21 (31.8%). A mild airway obstruction was found in 10 subjects (15.2%) 5 of whom were nonsmokers. 6 of the subjects with mild airway obstruction had WR symptoms: 2 had asthma and rhino-conjunctivitis, 2 rhino-conjunctivitis, and 2 upper airway irritation. Nasal peak inspiratory flow measurements were not different in exposed and control subjects, or in symptomatic and asymptomatic workers, but were lower in subjects with mild airway obstruction (100.7 L/min, SD 24.1) than in those with normal spirometry (122.8 L/min, SD 48.0). Conclusions Subjects with a simultaneous exposure to colophony and MBTS tend to have a high prevalence of upper respiratory symptoms associated with a mild airway obstruction. Nasal peak inspiratory flow measurements had a low sensitivity in detecting work-related nasal symptoms.

Studies on the Combined Use of Some Different Organic Accelerators. IV. Diphenylguanidine and Dibenzothiazole Disulfide

Abstract 1. Diphenylguanidine and dibenzothiazole disulfide do not form a molecular compound or eutectic mixture, as judged by their melting and softening point curve. 2. The effects of scorching were studied by the use of various proportions of diphenylguanidine and dibenzothiazole disulfide; the maximum scorching was found with the mixture which had the lowest melting point in the curve. 3. These proportions were also studied for their vulcanizing power. 4. Diphenylguanidine and dibenzothiazole disulfide form a molecular compound through the medium of hydrogen sulfide. 5. This molecular compound was prepared and tested for its vulcanizing properties.