2-Benzothiazolethiol,Zincsalt(2:1)
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HS Code |
552916 |
| Chemical Formula | C14H8N2S4Zn |
| Molar Mass | 397.87 g/mol |
| Appearance | Yellow - green powder |
| Odor | Faint sulfur - like odor |
| Solubility In Water | Insoluble |
| Solubility In Organic Solvents | Soluble in some organic solvents like toluene |
| Melting Point | 270 - 280 °C |
| Density | Approx. 1.6 g/cm³ |
| Stability | Stable under normal conditions |
| Cas Number | 155-04-4 |
As an accredited 2-Benzothiazolethiol,Zincsalt(2:1) factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 25 - kg bags of 2 - Benzothiazolethiol, Zinc salt(2:1) with tight - sealed packaging. |
| Shipping | 2 - Benzothiazolethiol, Zinc salt(2:1) is shipped in accordance with strict chemical transport regulations. Packaged securely to prevent leakage, it's transported by approved carriers ensuring safe delivery to destinations. |
| Storage | 2 - Benzothiazolethiol, Zinc salt(2:1) should be stored in a cool, dry place away from direct sunlight and heat sources. Keep it in a well - sealed container to prevent moisture absorption and contact with air, which could potentially lead to degradation. Store it separately from incompatible substances like strong acids and oxidizing agents to avoid chemical reactions. |
In passenger car tire tread compounds where the balance between scorch safety, modulus development, and reversion resistance dictates the accelerator selection at multi-stage mix lines, zinc 2-mercaptobenzothiazole (ZMBT) is introduced at 1.2–1.8 phr in combination with 0.6–0.9 phr TBBS to displace sulfenamide-only packages. The mixing sequence employs a 270 L intermeshing internal mixer with a drop temperature held below 155°C, adding ZMBT in the second non-productive pass to prevent premature crosslinking induced by residual heat and shear. Compliance for global original equipment tire specifications is anchored to REACH Annex XVII entries for PAH limitation (EU 1272/2013), the absence of N-nitrosatable amines per EU Directive 93/11/EEC migration limits, and material conformity with ASTM D3489 test recipes for carbon black–filled NR/BR blends. The downstream operation processes the masterbatch through a twin-screw roller die extruder feeding a 14-inch two-roll mill that maintains a friction ratio of 1:1.08 before calendering into tread profiles; curing is conducted in a 1,500 mm × 3,000 mm multi-opening hydraulic press at 160°C over 8 minutes, producing passenger car radial tire treads targeting shore A hardness of 64±2 and tensile strength exceeding 18 MPa when tested per ISO 37:2017. Production batch logs from dual-cavity mold lines record Mooney scorch (MS-t5, 127°C) consistently between 19–23 minutes, a processing window that permits safe extrusion without requiring retrofitted cooling jackets on screw barrels.At Which Crosslink Density Does ZMBT Outperform Sulfenamides in EPDM Compression Molded Seals?Experimental data generated on a 1.5 L laboratory internal mixer (Haake Rheomix type) using an EPDM formulation containing 55 phr carbon black N550 and 8 phr paraffinic oil reveals that partial replacement of MBTS with ZMBT at an equimolar sulfur-donor equivalent shifts the critical crosslink density plateau. When ZMBT is dosed at 1.0–1.6 phr alongside 0.6 phr ZDBC, the compound attains a delta torque (MH − ML) of 18.3 dN·m versus 14.7 dN·m for the sulfenamide-only control as measured on a moving die rheometer per ASTM D5289 at 175°C. This architecture addresses the persistent compression set failure of EPDM static seals tested under ISO 815-1:2019 (25% compression, 150°C for 72 h), where ZMBT-based vulcanizates record set values below 22% compared to 31% for the reference CBS-accelerated compound. Regulatory compliance for automotive coolant seals relies on FDA 21 CFR §177.2600 (rubber articles for repeated food contact with a migration ceiling of 1.5 wt% ZMBT in the finished article) and the German BfR Recommendation XXI Category 3, simultaneously meeting RoHS 2.0 (2011/65/EU) threshold limits for lead and cadmium. The manufacturing process involves a two-stage mixing cycle on a 120 L tangential Banbury-type mixer followed by sheet-out on an open mill with a nip gap of 6 mm; the blanks are then fed into a 500-ton clamping force injection molding machine with a cold-runner block maintained at 85°C and vulcanized in a multi-cavity mold at 185°C with a cure time of 150 seconds. Finished goods—O-rings per ISO 3601 and grommet seals for engine thermal management modules—are post-cured in a forced-air oven at 150°C for 4 hours to drive off volatile residues and stabilize crosslink architecture.Latex Dipping Line Preservative and Vulcanization Activator SystemIn natural rubber latex dipping operations where ammonium preservation falls short against reversion-driven viscosity drift and zinc oxide activation kinetics require tight control, ZMBT added as a 50% aqueous dispersion at a rate of 0.15–0.4 phr based on dry rubber content serves a dual preservative–secondary accelerator function without elevating zinc leaching levels measured under EN 71-3:2019 migration protocols. The dispersion is charged into pre-vulcanized latex compound after the primary post-prevulcanization cool-down phase at 38°C, ensuring that residual ammonia (0.2–0.3%) does not destabilize the thiol-zinc complex prior to film formation. The production line comprises a continuous chain-driven dipping machine with porcelain formers passing through a coagulant tank containing 15% calcium nitrate solution, followed by a dwell time of 45 seconds in the compounded latex bath maintained at 28±1°C, and then a three-zone drying tunnel with progressive air temperatures of 80°C / 100°C / 120°C. Vulcanization is accomplished in a hot-air circulating oven at 110°C for 25 minutes, producing examination gloves compliant with ASTM D3578 and with extractable protein levels below 50 µg/g per ASTM D5712. Biocidal efficacy data run according to ISO 11930 show a 4-log reduction in Bacillus subtilis spore count within 72 hours when ZMBT is present at the minimum recommended concentration, a relevant benchmark for lines that operate under intermittent production schedules without in-line preservative re-dosing systems. The compound also demonstrates no detectable N-nitrosamine formation when evaluated via GC-TEA following the method of EN 12868, supporting compliance with European medical device regulation (EU) 2017/745 for single-use gloves classified as Class I devices.When Steel Cord Adhesion Retention Requires Delayed-Action Synergy with Cobalt SaltsSteel cord skim compounds for heavy-duty conveyor belts operating under sustained tension of 10% of breaking strength demand a vulcanization system that does not sacrifice initial adhesion build-up to the brass coating while preserving sufficient scorch delay for calendar-fed continuous pressing lines. A ZMBT content of 1.1–1.4 phr deployed together with 0.5 phr DCBS and 1.0 phr cobalt boroacylate adhesion promoter extends the MDR scorch time (ts2) to 4.5 minutes at 150°C compared to 2.8 minutes for an equivalent thiuram-accelerated control, measured under ASTM D5289 on an NR/BR blend filled with 52 phr N330 carbon black and 12 phr resorcinol-formaldehyde precondensate. The processing route threads the skim compound through a four-roll Z-type calender with roll temperatures held at 75°C top, 80°C middle, and 70°C bottom, embedding the steel cords (7×19 construction, 4.0 mm diameter) between two 1.2 mm rubber sheets at a line speed of 18 m/min. Curing occurs in a double-belt press with a heated platen length of 12 meters, applying 2.5 MPa pressure at 155°C for 22 minutes. Adhesion force, determined per ISO 7623:2015 with pull-out testing, exceeds 90 N/mm after hot-salt aging at 95°C in 5% NaCl solution for 7 days—a test protocol frequently cited in procurement specifications for mining-grade belts. Finished belts conform to the mechanical and flame-resistance requirements of ISO 22768:2017 and include ground-edge profiles for coal handling applications where electrostatic discharge safety per ISO 284:2012 must be maintained.For lubrication formulators seeking an ash-containing extreme-pressure additive that provides secondary antioxidant functionality without triggering copper corrosion beyond 1b rating under ASTM D130 at 150°C, the incorporation of 1.5–2.5 wt% ZMBT into lithium 12-hydroxystearate grease thickener systems creates a synergistic anti-wear film distinct from that of conventional ZDDP-bearing packages. The additive is introduced during the cool-down phase at 90–100°C after the saponification of 12-hydroxystearic acid with lithium hydroxide monohydrate in a 1,500 kg contactor reactor, dispersed under a high-shear rotor-stator mill operating at 3,000 rpm until Hegman gauge fineness reads below 20 µm. Four-ball extreme pressure testing per ASTM D2596 records a weld point of 250 kg and a load-wear index of 42, while the wear scar diameter measured via ASTM D2266 (40 kg, 75°C, 1,200 rpm, 1 h) contracts to 0.38 mm relative to 0.62 mm for the base grease. Regulatory acceptance for industrial bearing greases intended for food-processing environments is supported by NSF H1 registration where the formulation meets incidental food contact criteria under 21 CFR 178.3570 with a total additive limit of 5 wt%. The terminal product is a NLGI Grade 2 grease, filled into 400 g cartridges or 180 kg drums, deployed in centralized lubrication systems of textile weaving looms where prolonged thermal exposure at 120°C demands oxidation stability exceeding 400 hours per ASTM D942 at 99°C. Long-term storage data collected from bulk containers stored at ambient conditions in Southeast Asian warehouse facilities confirms that ZMBT-thickened greases exhibit oil separation below 4% per ASTM D1742 after 12 months, a performance boundary that degrades if charging temperature exceeds 105°C during milling.
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2-Benzothiazolethiol, zinc salt (2:1) (CAS 155-04-4), commonly designated ZnMBT or zinc mercaptobenzothiazole, is supplied as an off‑white to light yellow powder with a melting point in excess of 240 °C accompanied by thermal decomposition. The stoichiometric formula Zn(C7H4NS2)2 yields a molecular weight of 397.8 g mol−1 and a zinc content of 15.0–16.5 % (determined by EDTA titration in accordance with ISO 248‑1). Typical commercial lots exhibit a bulk density between 0.35 g cm−3 and 0.55 g cm−3, an assay of ≥ 97.0 % by HPLC area normalization, free 2‑mercaptobenzothiazole below 1.0 %, and moisture ≤ 0.5 % (Karl Fischer coulometry, ISO 760). The powder disperses readily in natural and synthetic diene rubbers on a two‑roll mill (friction ratio 1:1.2, nip gap 0.5–0.8 mm) and in internal mixers with a fill factor of 0.75, achieving a Mooney viscosity reduction of 3–5 units (ML 1+4 at 100 °C, ISO 289‑1) relative to an equimolar addition of MBT, an effect attributed to the zinc‑mediated peptization during mastication.
In a reference natural rubber compound (SMR CV60: 100 phr, N330 carbon black 50 phr, sulfur 2.0 phr, accelerator 1.2 phr), ZnMBT positions its cure kinetics between the fast‑acting free mercaptan and the delayed‑action disulfide. Moving‑die rheometer data obtained at 140 °C (ISO 6502) give a scorch time ts2 of 5.5 min for the zinc salt, versus 3.2 min for MBT and 7.1 min for MBTS. The lower acidity of the zinc thiolate (aqueous slurry pH 6.5–7.5) retards the activation of elemental sulfur, providing a broader processing safety window than MBT while retaining a cure rate index (CRI = 100/(t90 − ts2)) of 8.2 min−1, notably higher than the 6.1 min−1 recorded for MBTS. The zinc cation supplied by the accelerator partially fulfills the activator requirement, reducing the additional ZnO charge by 20–30 % without a statistically significant loss in crosslink density (equilibrium swelling in toluene per ISO 1817, νe maintained at 1.35 ± 0.05 × 10−4 mol cm−3).
| Property | ZnMBT | MBT | MBTS |
|---|---|---|---|
| Melting range (°C) | >240 (decomp.) | 177–181 | 175–182 |
| ts2 at 140 °C (min, ISO 6502) | 5.5 | 3.2 | 7.1 |
| Cure rate index (min−1) | 8.2 | 9.0 | 6.1 |
| Bloom tendency in SBR/BR (visual rating, 7 d/40 °C) | Low | Moderate | Very low |
| Typical dosage in NR (phr) | 0.8–2.0 | 0.5–1.5 | 1.0–2.5 |
| Synergism with dithiocarbamates | Strong | Moderate (risk of scorch) | Moderate |
In prevulcanized natural rubber latex systems, ZnMBT is introduced as a 50 % aqueous dispersion (particle size D90 ≤ 5 µm, stabilised with 0.5 % caseinate) alongside zinc diethyldithiocarbamate (ZDEC). A compound containing 1.0 phr ZnMBT, 0.5 phr ZDEC, and 1.5 phr sulfur develops a chloroform number of 3.5–4.0 (80 °C water bath, 25 min) corresponding to a lightly crosslinked gel suitable for dip‑moulded surgical gloves. When the ZnMBT fraction exceeds 1.5 phr, the post‑vulcanization network density becomes sensitive to calcium‑ion concentration in the process water; a calcium chloride stability threshold of 0.02 N must be maintained to prevent coagulum formation on continuous dipping lines.
Extruded EPDM radiator hoses co‑cured with a ZnMBT/sulfur/sulfenamide package display a characteristic torque increase (MH − ML) of 18–22 dNm at 160 °C in an MDR 2000 rheometer. The zinc salt contributes to the cure reversion resistance at the inner tube surface, where prolonged contact with glycol‑based coolant at 125 °C and 1.5 bar overpressure can reduce the conventional MBT‑activated network by 15 % within 1000 h. With ZnMBT the reversion‑induced drop in equilibrium modulus is limited to 5–7 % under identical ageing conditions (ISO 188, air‑oven at 125 °C extrapolated from 72 h data). The chloroform number of the uncured compound, targeted at 4.0–4.5, is monitored off‑line by solvent extraction titration to predict hose‑to‑mandrel tack before steam autoclave curing at 150 °C and 4.5 bar.
Injection‑moulded CVJ boots based on CR/EPDM blends benefit from the lower mould‑fouling tendency of ZnMBT relative to MBT. A 260‑tonne clamping press running a 32‑cavity cold‑runner mould at a stock temperature of 85 °C and injection pressure 90 MPa recorded a mould‑cleaning cycle extension from 2000 to 5000 shots after substituting 1.0 phr of MBT with the zinc salt. The reduction in mould deposit is correlated with the decreased volatility of ZnMBT (weight loss at 150 °C by TGA below 0.3 % over 60 min), whereas MBT exhibits a weight loss of 1.2 % under identical conditions.
Exposure of ZnMBT powder to ambient relative humidity exceeding 60 % at 23 °C for periods longer than 4 h raises the moisture content above 1.0 %, leading to agglomerate formation (soft agglomerates > 200 µm) that resist de‑agglomeration during single‑pass mixing on open mills. Microscopic examination of cured sheets (optical microscopy at 40×) reveals undispersed ZnMBT domains of 30–80 µm acting as stress concentrators; the tear strength (ISO 34‑1, trouser method) drops by 18–22 % compared to material blended with pre‑dried powder. Pre‑drying in a circulated‑air oven at 60 °C for 2 h restores dispersion quality, and feeding through a loss‑in‑weight gravimetric hopper fitted with a desiccant breather (silica gel, dew point ≤ −30 °C) maintains moisture below 0.3 % in continuous mixing lines.
ZnMBT does not exhibit the amine‑bloom discolouration characteristic of MBT when co‑vulcanised with aromatic amine antioxidants such as 6PPD. In a white sidewall compound (NR/BR, titanium dioxide 30 phr), ΔE colour change after QUV‑A exposure (340 nm, 168 h, ASTM G154) is 2.1 for the ZnMBT formulation versus 5.8 for an equivalent MBT‑based stock. The absence of free mercapto groups eliminates the formation of highly chromophoric zinc–amine complexes, a pathway confirmed by X‑ray photoelectron spectroscopy of the surface after ageing.
Occupational exposure monitoring during bulk‑bag discharging (FIBC with 500 kg capacity) indicates a respirable dust concentration below 0.05 mg m−3 (8‑h TWA) when a local exhaust ventilation system operating at a capture velocity of 0.5 m s−1 is employed. The product is classified as a skin sensitiser category 1B under EC 1272/2008; therefore enclosed transfer systems or full‑face respirators with P2 filters are mandated for operations where airborne dust generation cannot be contained.
| Regulation / Standard | Clause / Method | Limitation / Requirement |
|---|---|---|
| REACH (EC 1907/2006) | Annex XVII, entry 72 | Not restricted; registration dossier covers uses in rubber processing |
| FDA 21 CFR 177.2600 | Rubber articles intended for repeated use | ZnMBT permitted as an accelerator for food‑contact rubber; migration into food simulants ≤ 5 mg kg−1 (total organic extract) |
| EN 71‑3:2019 | Migration of certain elements | Zinc migration limit for toy materials: 3 750 mg kg−1 (category II); ZnMBT contributes to extractable zinc and must be quantified in formulation‑level risk assessment |
| RoHS (2011/65/EU) | Annex II | No restricted substances present above threshold concentrations |
| Oeko‑Tex Standard 100 | Product class I (baby articles) | Total extractable zinc ≤ 0.5 mg L−1; formulation guidance recommends ZnMBT dosage ≤ 1.5 phr with subsequent leaching validation |
ZnMBT is incompatible with strongly basic amine‑based co‑agents such as hexamethylenetetramine (HMT) in phenol‑formaldehyde cure systems. When dry‑blended prior to compounding, the zinc thiolate reacts exothermically with the tertiary amine, liberating the free mercaptan and forming a zinc–amine complex that precipitates as a non‑dispersible solid, evidenced by a DSC exotherm onset at 105–110 °C. The resulting compound exhibits premature scorch (ts2 ≤ 1.8 min at 140 °C) and a 25–30 % reduction in state of cure. For resorcinol‑formaldehyde‑latex (RFL) dip systems applied to polyester tyre cord, the ZnMBT accelerator is introduced as a separate aqueous dispersion, not pre‑blended with the RF resin component, to avoid latent gelation during dip‑tank hold times exceeding 8 h.
In factory operations manufacturing impact‑resistant polypropylene/EPDM TPVs via dynamic vulcanisation on a co‑rotating twin‑screw extruder (L/D 52, screw speed 400 rpm, barrel temperatures 180–210 °C), the zinc salt is fed downstream after the PP phase inversion to minimise parasitic crosslinking in the melt. At 0.3–0.5 phr, it generates an elastomer phase crosslink density sufficient to raise the gel content to 82–88 % (cyclohexane extraction, 72 h) while maintaining extrusion surface roughness (Ra) below 0.8 µm on a profile‑calibration table.
