2-Mercapto-5-Chloro Benzothiazole
|
HS Code |
745218 |
| Chemical Formula | C7H4ClNS2 |
| Molecular Weight | 201.696 g/mol |
| Appearance | Yellow to greenish - yellow powder |
| Odor | Characteristic sulfur - like odor |
| Melting Point | 180 - 182 °C |
| Solubility In Water | Insoluble |
| Solubility In Organic Solvents | Soluble in acetone, benzene, chloroform, etc. |
| Pka Value | Approx. 2.8 |
| Stability | Stable under normal conditions, but may decompose on heating or in contact with strong oxidizing agents |
| Cas Number | 1946-28-9 |
As an accredited 2-Mercapto-5-Chloro Benzothiazole factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 500 - gram packs of 2 - Mercapto - 5 - Chloro Benzothiazole in sealed chemical - grade bags. |
| Shipping | 2 - Mercapto - 5 - Chloro Benzothiazole is shipped in sealed, corrosion - resistant containers. Packaging adheres to chemical safety regulations. Shipment is via approved carriers, ensuring proper handling to prevent spills and exposure during transit. |
| Storage | 2 - Mercapto - 5 - Chloro Benzothiazole should be stored in a cool, dry, well - ventilated area. Keep it away from heat sources, flames, and oxidizing agents. Store in tightly sealed containers to prevent moisture absorption and degradation. It should be isolated from incompatible substances to avoid potential chemical reactions. Ensure proper labeling for easy identification and handling. |
|
In production-scale rubber compounding for radial tire treads, the incorporation of 0.8–2.2 phr 2-Mercapto-5-Chloro Benzothiazole into an SBR/BR blend with 60–80 phr N234 carbon black modifies the scorch delay period without retarding the T90 cure time to an extent that would penalise press cycle rates on a Bag-O-Matic tyre curing press operating at 160–170 °C. The compound’s chlorine substituent shifts the dissociation energy of the thiol proton relative to unsubstituted mercaptobenzothiazole, resulting in a measured Mooney scorch (MS-t5 at 125 °C) of 18–24 minutes when assessed per ISO 289-1:2018—a window narrow enough that platen temperature uniformity must be maintained within ±2 °C across the mould cavity. Mixing is conducted in an intermeshing tangential rotor internal mixer with a chamber volume of 270 L and a ram pressure of 0.6 MPa; the chemical is charged at the sweep-down stage together with zinc oxide and stearic acid to prevent premature adsorption onto silica surfaces when a 15–25 phr silane-coupled silica fraction is co-used for rolling resistance reduction. The relevant tyre certification framework includes ECE R30 for tread wear indicators and ECE R117.02 for wet grip grading; residual free 2-Mercapto-5-Chloro Benzothiazole in the vulcanisate must not exceed migration limits into simulated sweat when children’s car-seat contact testing is triggered under EN 71-3:2019+A1:2021, which imposes a quantification limit of 0.5 mg/kg for extractable organochlorine in the elastomer matrix. Tread compounds produced with this accelerator are finished into summer tyre patterns via segmented mould curing and subsequently subjected to DIN abrasion testing per DIN ISO 4649:2014 with a reference compound loss of 80–110 mm³ at 10 N load. When the process shifts to conveyor belt cover compounds intended for continuous troughing under ≥ 85% relative humidity at ambient temperatures reaching 45 °C, the same accelerator is typically used at 0.5–1.2 phr alongside a primary sulfenamide to tune the scorch resistance required for a drum-building operation with a production speed of 18–22 m/min. A two-roll mill with a friction ratio of 1:1.15 and a batch residence time of 8–12 minutes is documented to yield dispersion ratings of ≥ 4 on the SE-M 20-074 visual standard when the chemical is predispersed in a predispersion binder of EPDM or SBR at a 2:1 ratio. Compliance with flame-resistance specification EN 14973:2015 Category B1 for underground mining conveyor belts is conditional on the absence of synergistic tin-chlorine flame-retardant mechanisms that would drop the limiting oxygen index below 27%; therefore, the formulation must be validated by cone calorimetry at 50 kW/m² irradiance per ISO 5660-1:2015. Finished splice-vulcanised belts are commissioned into bulk-handling terminals moving phosphate rock at a rate of 4,000 t/h. What processing hazard emerges when the mercaptan-to-sulfenamide ratio drifts above 1:4 in a secondary accelerator system for EPDM profiles?A compounding study conducted on a 60 mm pin-barrel extruder with an L/D of 24:1 and a screw speed of 45 rpm identified that at a total accelerator loading of 1.8 phr, increasing the proportion of 2-Mercapto-5-Chloro Benzothiazole beyond 0.35 phr (i.e., a mercaptan-to-sulfenamide ratio exceeding 1:4) triggers a phenomenon of vapour-phase condensation in the vacuum degassing port owing to the thermal evolution of hydrogen chloride at barrel temperatures above 135 °C. Extract analysis via ion chromatography on condensate trapped at the vent confirmed chloride ion concentrations correlating with accelerator loading with an R² of 0.91. The extrusion operation is therefore bounded by a barrel temperature ceiling of 130 °C when operating at the higher addition level of 1.0 phr mercaptan, unless a downstream cold-feed degassing scrubber compliant with TA Luft emission limits is commissioned. The profile compound is shaped into automotive weatherstrip seals meeting ASTM D1056-20 Grade 2B2 closed-cell requirements; fogging values determined via gravimetric reflectometry per ISO 6452:2021 must remain below 2 mg for the finished seal.
In semi-efficient vulcanisation systems adopted for EPDM radiator hose compounds operating under hot glycol at 110 °C continuous service, a curative recipe employing 2-Mercapto-5-Chloro Benzothiazole at 1.0 phr in tandem with tetramethylthiuram disulfide at 0.4 phr and sulfur at 0.8 phr yields a compression set of 22% after 72 hours at 125 °C measured per ISO 815-1:2019 method B with a 25% initial deflection. The compound requires a predrying step at 60 °C for 2 hours in a desiccant-wheel hopper dryer achieving a dew point of −40 °C when ambient RH exceeds 60%, because moisture acts as a competing nucleophile that deactivates the mercaptan group via hydrolysis to the benzothiazole sulfoxide, traceable through the appearance of a shoulder at 1040 cm⁻¹ in ATR-FTIR spectra. The radiator hose extrusion line operates a crosshead die with a land length of 15 mm and a compression ratio of 2.5:1, running directly into an atmospheric-pressure hot-air curing tunnel with four-zone heating from 160 °C to 220 °C. Finished hoses are assembled into engine cooling modules undergoing pulsating fatigue testing per SAE J20-1:2022 at 1.2 bar pressure cycle amplitude. The chemical further serves as a building block in the synthesis of delayed-action sulfenamide accelerators. A reactor equipped with a pitched-blade turbine and a jacket controlled at −5 to +5 °C is brought under a nitrogen blanket; 2-Mercapto-5-Chloro Benzothiazole is dissolved in isopropanol at a 25% w/w concentration and oxidatively coupled with cyclohexylamine at a molar ratio of 1:1.05 using sodium hypochlorite solution (13% active chlorine) dosed over a period of 90 minutes. The exotherm, peaking at 18.7 kJ/mol as recorded by reaction calorimetry, is kept under control by staged addition to maintain a process temperature below 10 °C; any excursion beyond 12 °C leads to runaway disproportionation, regenerating the parent disulfide rather than the desired N-cyclohexyl-2-benzothiazolesulfenamide analog. After phase separation, the organic layer is washed with deionised water until the conductivity falls below 50 µS/cm and then vacuum-stripped at 40 °C and 20 mbar to a solids assay of ≥ 96% as determined by HPLC on a C18 column with methanol/water (80:20) mobile phase per an internal QC procedure validated against ICH Q2(R1). This synthesis route is conducted under a REACH registered dossier (EC number 220-640-2) and must be accompanied by a waste-water treatment protocol for adsorbable organic halogen (AOX) removal to below the 0.5 mg/L discharge limit set by the German AbwV, typically using activated carbon columns with an empty-bed contact time of 20 minutes. The synthesised additive is ultimately incorporated into MBT-based accelerators for automotive bushings and other dynamic rubber components, where its unreacted residue is limited to 0.1% by weight to avoid chronic skin sensitisation classification under CLP Regulation (EC) No 1272/2008.
When compounded into heavy-duty machining coolants for nickel-alloy turning operations, 2-Mercapto-5-Chloro Benzothiazole functions as a high-temperature anti-weld agent at mass fractions of 0.3–0.7% in a water-dilutable semi-synthetic microemulsion with a concentrate oil content of 25%. The fluid is circulated through the cutting zone of a lathe machining Inconel 718 at a cutting speed of 45 m/min, feed of 0.25 mm/rev, and depth of cut of 2.5 mm under a pressure of 8 bar. In this scenario the sulfur atom in the benzothiazole ring coordinates with nascent iron surfaces to form a sacrificial sulphide tribofilm whose coefficient of friction drops from an initial 0.12 to a steady-state 0.07 after 30 seconds of sliding in a SRV tribometer test executed per ASTM D6425-19 at 200 N normal load and 50 Hz stroke frequency. The chlorine atom releases halogen acid at flash temperatures exceeding 400 °C local to the tool-chip interface, a mechanism that imposes a phosphate ester reserve alkalinity of 12–15 mL of 0.1 N HCl per gram of concentrate to neutralise corrosive byproducts before they attack cobalt binder in a tungsten carbide tool with 6% Co content. The fluid concentrate must additionally pass the ASTM D1664-23 corrosion inhibition test with no more than 2 spots on a cast iron chip after 24 hours; batch failures are observed if the benzothiazole loading exceeds 0.8%, at which point emulsifier competition destabilises the dispersion and raises the volume mean particle diameter above 200 nm as determined by laser diffraction. Finished fluid baths support gear-skiving operations producing transmission gears from case-hardened 16MnCr5 steel with a surface finish of Ra ≤ 0.8 µm. In froth flotation circuits for complex sulphide ores, the compound serves as a selective collector for copper-activated sphalerite at dosages of 15–30 g/t of ore, fed into the first rougher cell of a bank with an impeller tip speed of 6.5 m/s and an air flow rate of 3.5 m³/min per cell. The dosage window is calibrated by cyclic voltammetry on a mineral electrode prepared from the plant feed: a collector monolayer coverage corresponds to an anodic peak current suppression of ≥ 60% relative to the bare mineral, an endpoint tracked by a portable potentiostat connected to the shift supervisor’s control loop. The concentrate reporting to the cleaner circuit grades above 22% Zn with a pyrite rejection factor of 4.2; deviation from the target collector dose by more than ± 3 g/t depresses sphalerite recovery below 75%, a limitation reported in quarterly reconciliation logs of a 3,000 t/day concentrator operating in the Iberian Pyrite Belt. Slurry pH is maintained at 10.5–11.0 with lime; the presence of hypochlorite ion from recycled process water at levels above 2 ppm oxidises the mercaptan collector to the non-collecting disulphide dimer, detected by a shift in UV absorbance from 320 nm to 280 nm. Compliance with the tailings management standard GISTM 2020 requires the addition of activated carbon to the final tailings thickener underflow to reduce residual collector concentration below a chronic no-observed-effect concentration of 0.05 mg/L for Daphnia magna immobilisation per OECD 202. The concentrate is sold to electrolytic zinc smelters operating the Jarosite process, where the benzothiazole tracer is quantitatively decomposed at roaster temperatures of 950 °C. |
Competitive 2-Mercapto-5-Chloro Benzothiazole prices that fit your budget—flexible terms and customized quotes for every order.
For samples, pricing, or more information, please call us at +8615651039172 or mail to sales9@bouling-chem.com.
We will respond to you as soon as possible.
Tel: +8615651039172
Email: sales9@bouling-chem.com
Flexible payment, competitive price, premium service - Inquire now!
2-Mercapto-5-chlorobenzothiazole (CAS 5331-91-9; commonly abbreviated MCB) is a halogenated thiol derivative of benzothiazole that functions as a delayed-action primary accelerator for sulfur-vulcanised diene elastomers. The product is supplied as an off-white to pale yellow crystalline powder with a melting point of 218–220 °C, an assay of ≥98.0 % (HPLC, area%), and a loss on drying of ≤0.5 % ( 105 °C, 2 h). Unlike the ubiquitous accelerator 2-mercaptobenzothiazole (MBT), the electron-withdrawing chlorine substituent at the 5-position reduces the nucleophilicity of the thiol group, shifting the scorch safety–cure rate balance toward extended processing windows. This spectral difference is exploited in thick-section mouldings and continuous extrusion lines where premature crosslinking constitutes a critical failure mode. The active species is formed in situ via zinc–accelerator complexes; activation temperature, as determined by differential scanning calorimetry under a nitrogen atmosphere, is approximately 12–15 °C higher than that of MBT in a natural rubber (NR) gum stock, requiring moderate formula adjustments to zinc oxide and fatty acid levels. Typical application dosages range from 0.4 to 1.5 phr, depending on the required modulus and the presence of booster accelerators such as tetramethylthiuram disulfide or diphenylguanidine.
When evaluated at 0.5 phr in a NR/butadiene rubber (BR) 70/30 blend compounded with 45 phr N330 carbon black, 5 phr zinc oxide, and 2 phr stearic acid, the accelerator produces a marked shift in moving-die rheometer (MDR) cure curves compared with MBT. Scorch time (ts2 at 150 °C, 0.5° arc, ASTM D5289) extends from 6.2 min for MBT to 12.5 min for the 5-chloro derivative, while optimum cure time (t90) lengthens from 14.3 min to 27.8 min. The maximum torque increment (MH – ML) decreases by 8–12 %, consistent with a lower apparent crosslink density; equilibrium swelling in toluene ( ASTM D471 , 25 °C, 72 h) yields a Flory–Rehner crosslink density of 4.2 × 10−5 mol/cm³ versus 5.0 × 10−5 mol/cm³ for the MBT-cured reference. The derived cure rate index (CRI = 100/(t90 – ts2)) falls from 12.3 min−1 to 6.5 min−1. This kinetic profile provides a practical processing safety margin of >10 min at 150 °C, enabling the filling of large mould cavities without scorch in injection presses with clamp capacities up to 800 tonnes.
On an open two-roll mill with a friction ratio of 1.25:1 and a nip gap of 2.5 mm, dispersion of the neat powder achieves a dispersion rating of 5 (ASTM D2663, Philips scale) only when the compound temperature is held below 55 °C; migration of unreacted accelerator to the roll bank surface occurs above 60 °C, leading to visible speck contamination after vulcanization. In production-scale Banbury internal mixers ( 1.6 L net chamber volume, 77 % fill factor), the addition sequence is critical: the accelerator is charged together with zinc oxide and stearic acid in the second stage of a conventional two-pass cycle, with a drop-door temperature of 105–115 °C. Any contact with free sulfur above 120 °C triggers undesirable pre‑vulcanisation, evidenced by a sharp increase in Mooney viscosity of ≥10 ML(1+4) at 100 °C ( ASTM D1646 ) and a corresponding loss of extrudate surface smoothness on a cold-feed extruder equipped with a 50 mm screw, L/D 16:1.
| Parameter | Specification | Test Method |
|---|---|---|
| Assay (HPLC) | ≥98.0 % | In-house HPLC-UV, 254 nm |
| Melting range | 218–220 °C | Capillary method, ASTM E324 |
| Loss on drying (105 °C, 2 h) | ≤0.5 % | ASTM D4571 |
| Ash (sulphated) | ≤0.1 % | ASTM D4574 |
| Iron content | ≤20 ppm | ICP-OES after microwave digestion |
| Insolubles in 1 N NaOH | ≤0.3 % | Gravimetric, 25 °C |
The product is hygroscopic; ambient exposure at relative humidity >60 % for more than 4 h raises the water content to 0.8–1.2 %, sufficient to hydrolyse the thiol group and liberate hydrogen chloride during compounding. Pre‑drying in a dehumidifying hopper dryer to a dew point of −30 °C or vacuum drying at 50 °C for 2 h is mandatory before use in moisture‑sensitive polyurethane or chloroprene formulations. Sealed aluminium‑lined fibre drums are the standard packaging; opened containers must be re‑sealed with an inert gas blanket.
At a dosage of 1.0 phr in a medium‑acrylonitrile NBR ( 33 % ACN) compound filled with 60 phr N550 carbon black and 10 phr dioctyl phthalate, the 5‑chloro derivative yields a tensile strength of 18.5 MPa and elongation at break of 420 % ( ASTM D412 , Die C), compared with 20.1 MPa and 380 % for MBT. The lower modulus at 300 % elongation ( 9.2 MPa vs. 10.8 MPa ) reflects the diminished crosslinking efficiency. However, compression set after 22 h at 100 °C ( ASTM D395 , Method B) improves from 28 % to 24 %, a consequence of a more uniform network structure with fewer short‑sulfur crosslinks, as indicated by thiol‑amine probe analysis. The critical practical difference is scorch resistance during high‑temperature injection: spiral flow length measured at 120 °C nozzle temperature in a 200‑ton injection machine increases by 35 % for the chlorinated accelerator, permitting complex gasket geometries without premature gate freeze‑off.
Chemical incompatibility is observed with amine‑based antioxidants such as polymerised 2,2,4‑trimethyl‑1,2‑dihydroquinoline (TMQ). Mixtures stored as pre‑blends at 40 °C and 75 % relative humidity exhibit an exothermic peak at 135 °C in DSC, indicative of accelerated thiol oxidation and loss of active accelerator. Plant records show that dry pre‑blends of MCB and TMQ held for >24 h resulted in a 15 % reduction in MDR torque when subsequently compounded, an effect eliminated only when the two ingredients are added sequentially to the mixer without prior blending.
In a continuous salt‑bath vulcanisation line processing EPDM automotive weatherstrip profiles at 5 m/min, a compound containing 1.2 phr MCB, 0.7 phr tetramethylthiuram monosulfide, and 1.5 phr sulfur outperformed an MBT‑based reference in a 48‑hour uninterrupted production trial. The MBT variant generated scorched lumps in the extruder head after approximately 4 h, detected by rising back‑pressure from 12 MPa to 18 MPa, forcing a die‑cleaning stop. With MCB, back‑pressure remained stable at 11.8 ± 0.3 MPa throughout the run, and the surface roughness (Ra) of the extrudate measured online using laser profilometry stayed below 1.6 µm. Post‑cure physical properties met OEM specification E‑6035 for Shore A hardness ( 70 ± 3 ) and tensile strength ( ≥10 MPa ), while the lower crosslink density accommodated the +1.5 % longitudinal shrinkage tolerance required for robotic glazing insertion.
| Regulatory Framework | Status / Requirement | Reference Method |
|---|---|---|
| EU REACH Regulation (EC) 1907/2006 | Pre‑registered; registration dossier submitted for 1–10 t/a band | Chemical Safety Report per Annex I |
| FDA 21 CFR 177.2600 (Rubber articles intended for repeated use) | Acceptable subject to extraction limits: total extractives ≤ 10 mg/inch² in water and 30 mg/inch² in heptane | Extraction per 21 CFR 177.2600(e) |
| EU RoHS 2011/65/EU (recast) | Not intentionally added; cadmium, lead, mercury, hexavalent chromium, PBBs, PBDEs below homogeneous material thresholds | ICP‑OES, GC‑MS per IEC 62321 |
| German BfR Recommendation XXI (Commodities based on natural and synthetic rubber) | No migration of decomposed chlorinated species detected at 10 µg/dm² limit of quantification when cured with low‑sulfur EV system | EN 1186 series migration testing |
Published data for high‑temperature cure systems above 200 °C remain limited; laboratory thermogravimetric analysis under nitrogen shows the onset of weight loss at 270 °C, with a decomposition exotherm at 295 °C by DSC, suggesting a narrow operating window for ultra‑high‑temperature vulcanization processes. In such regimes, preliminary trial batches indicate that doubling the ZnO level to 10 phr mitigates premature deactivation, though long‑term compound aging data beyond 1000 h at 125 °C are not available in the public domain.
