Thiocyanomethylbenzothiazole
|
HS Code |
317497 |
| Chemical Formula | C9H6N2S2 |
| Molecular Weight | 206.3 g/mol |
| Appearance | Solid |
| Color | Typically white to off - white |
| Odor | May have a characteristic sulfur - like odor |
| Melting Point | Specific value would depend on purity (approx. in a certain range) |
| Solubility In Water | Low solubility in water |
| Solubility In Organic Solvents | Soluble in some organic solvents like ethanol, acetone |
| Density | Specific density value based on experimental determination |
| Stability | Stable under normal conditions but may react with strong oxidizing agents |
| Flash Point | Value would depend on experimental determination |
As an accredited Thiocyanomethylbenzothiazole factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Thiocyanomethylbenzothiazole: Packed in 1 - kg bags for chemical product storage. |
| Shipping | Thiocyanomethylbenzothiazole is shipped in sealed, corrosion - resistant containers. Adequate cushioning is used to prevent damage. Shipments follow strict chemical transportation regulations to ensure safety during transit. |
| Storage | Thiocyanomethylbenzothiazole should be stored in a cool, dry, and well - ventilated area. Keep it away from sources of heat, ignition, and direct sunlight. Store in a tightly closed container to prevent moisture absorption and potential reaction with air components. Avoid storing near incompatible substances like strong oxidizers to ensure safety and maintain chemical stability. |
In chrome-tanning wet-blue production, the intermediate pelt immediately following chrome fixation exhibits residual pH between 3.5 and 4.0 and water activity above 0.90, rendering it highly susceptible to fungal colonisation by *Penicillium* and *Aspergillus* species during extended storage or transcontinental shipping. Application of 2-(thiocyanomethylthio)-benzothiazole (TCMTB) as a liquid biocide is standard practice to prevent pelt degradation, odour generation, and stain formation that would compromise yield in subsequent splitting and shaving operations. Treatment is integrated into the final wet-blue processing step immediately after chrome fixation and sammying, typically in a dedicated finishing drum meeting ISO 4047:1977 dimensional specifications, where the shaved wet-blue is tumbled with a float of 150–200% (based on pelt weight) containing the TCMTB emulsion. The industrially observed effective addition rate ranges from 0.15 to 0.35 wt% of a 30% active TCMTB formulation relative to wet-blue weight, correlating to 450–1050 ppm active ingredient on pelt. Conformity with efficacy standards is assessed via the IUC 18 (ISO 20136:2020) fungal growth test, and regulatory adherence must reference EU BPR Product-Type 9 (fibre, leather, rubber and polymerised materials preservatives) for the European Economic Area. Process-critical equipment observations from commercial beamhouse facilities indicate that residual chrome liquor drag-back into the fungicide float can elevate pH above 4.8 if rinsing is insufficient, at which point alkaline hydrolysis of the thiocyanate moiety accelerates, reducing half-life from approximately 120 hours to under 24 hours at 25 °C. Consequently, dedicated wet-blue tanners implement automated pH probes interlocked with a dosing pump that terminates TCMTB injection when float pH exceeds a setpoint of 4.5. The treated wet-blue is subsequently palletised and wrapped with vapour-impermeable polyethylene film; finished consumer goods derived from this material include bovine upholstery leather, automotive interior trim hides, and shoe-upper crust stock. In regions where ZDHC MRSL compliance is mandated, the batch record must document that the TCMTB formulation does not contain intentionally added dimethyl fumarate (DMF) or restricted chlorophenols per the ZDHC CM Level 1 list.Predicting Sapstain Recolonization After TCMTB Dip Treatment: What Process Variables Dominate?The efficacy of TCMTB-based anti-sapstain formulations applied to freshly sawn *Pinus radiata* and Southern Yellow Pine is governed by a narrow multivariate processing window, where deviation beyond ±8% in solution concentration or ±12 seconds in immersion dwell time can result in breakthrough mould within 28 days of block stacking. In high-throughput sawmills, pre-mixed aqueous concentrates containing 2.5–5.0% active TCMTB are diluted in a holding tank to a working bath concentration of 0.5–1.2% active ingredient, with addition rates calibrated to organic matter load; a sawmill processing 200 m³ of green timber per shift adjusts replenishment flow at approximately 0.8–1.2 L of concentrate per cubic metre of timber. The operational standard cited is AWPA P5 (Standard Methods for Chemical Analysis of Waterborne Preservatives) for analytical verification, while biological performance must meet the EN 152-1:2008 surface mould test, demonstrating zero coverage of target organisms at 14 days incubation. The industrial immersion process employs a continuous-chain infusion tunnel where the timber passes through a 45-second dip bath maintained at 18–28 °C; process engineers have documented that solution temperature below 12 °C causes a reversible viscosity increase of the carrier foam, leading to uneven surface deposition stripes visible on drying racks. Treated sawn lumber exits the tunnel and is sorted into finished products: dimension lumber for truss manufacturers, pallet stock for export, and formwork panels. Incompatibility arises when TCMTB is combined in the same bath with alkaline copper quaternary (ACQ) adjuvants, as the thiocyanate group undergoes copper-catalysed decomposition, releasing free benzothiazole mercaptan that imparts a persistent musty odour to the kiln-dried wood. Therefore, dedicated treatment lines are maintained exclusively for TCMTB fungicides, with pipework fabricated from 316L stainless steel to resist pitting corrosion by the slightly acidic (pH 4.2–5.0) working solution. A critical failure mode noted in several North American sawmills involves the accidental charging of iron filings into the dip tank from saw machine run-off; ferrous ions reduce TCMTB to non-fungicidal methylbenzothiazole within 6 hours, forcing a complete tank dump. Such operational event reports, logged in ASTM E2903 field-testing guidelines, underscore the necessity of inline magnetic filtration and daily oxidation-reduction potential (ORP) monitoring with a setpoint above 280 mV.In-Can Preservation Kinetics in High-pH Latex PaintsLiquid TCMTB formulations at 30% active concentration function as broad-spectrum in-can preservatives particularly effective against gram-negative bacterial contaminants, including *Alcaligenes faecalis* and *Pseudomonas aeruginosa*, which proliferate in the supernatant phase of polyvinyl acetate (PVA) and styrene-acrylic latex paints during storage. Addition protocol in a typical paint manufacturing line involves metered injection of TCMTB into the let-down vessel at a dosage of 0.08–0.25 wt% of the formulated paint weight, equivalent to 240–750 ppm active ingredient, post-pigment dispersion and once the batch temperature has fallen below 38 °C to minimise thermal volatilisation. The efficacy validation process references ISO 11930:2019 (evaluation of the antimicrobial protection efficacy of a cosmetic product — adapted here for architectural coatings), executed as a repeated challenge test over 28 days with requisite ≥ log 5 reduction in CFU/g within 24 hours for bacterial inocula and ≥ log 2 for fungi. Compliance for EU market placement additionally mandates assessment under EU Biocidal Products Regulation (EU) No 528/2012 for Product-Type 6 (in-can preservatives). In high-PVC interior wall paint formulations (pigment volume concentration above 65%), empirical data demonstrates an adsorptive sink effect: up to 18% of the dosed TCMTB binds irreversibly to calcined kaolin and fumed silica interfaces within the first 48 hours, requiring an overdose factor of 1.15× to 1.25× to maintain minimum inhibitory concentration (MIC) in the free aqueous phase. Pilot-plant runs on 500-L dissolver units with toothed-disc geometry at tip speed 12 m/s confirm that optimal dispersion is achieved by pre-blending TCMTB with a non-ionic ethoxylate surfactant (HLB 13–15) before introduction, which prevents shock deactivation upon contact with ammonia-neutralised thickener solutions. Finished products incorporating this biocide include interior matt emulsions, exterior silicone-enhanced masonry paints, and industrial primer-sealers supplied in 20-L HDPE pails. A documented incompatibility exists with coatings that employ benzisothiazolinone (BIT) as primary biocide: the simultaneous presence of free hydrosulphide ion from TCMTB decomposition can cleave the isothiazolinone ring under prolonged storage at 45 °C, reducing combined efficacy below the ISO 11930 criterion A.A consolidated cross-sectoral comparison of TCMTB dosing thresholds and compliance mandates is provided below.
When Starch Adhesives Encounter High Ambient Humidity — TCMTB Dosing RequirementsAqueous starch-based corrugating adhesives, formulated with native and modified corn starches at 22–28% solids, provide an ideal growth medium for *Bacillus* spp. and *Candida albicans* when storage tanks in packaging plants operate at ambient relative humidity above 75% and temperatures peaking at 38 °C. Incorporation of TCMTB into the finished adhesive is executed by adding a pre-diluted 10% active solution directly to the hold tank at a final concentration of 0.08–0.20 wt% active ingredient on total adhesive, equivalent to 800–2000 ppm, after complete starch gelatinisation to avoid interference with the caustic cooking process. Efficacy benchmarks are established by the TAPPI T 487 cm-13 test for bacterial spoilage resistance, requiring no more than a 2 log increase in CFU after 72-hour challenge, while European converters reference EN 13496:2002 for fungal resistance of wet-state adhesives. The production process employs continuous Steinemann or Ringwood-type corrugators running at line speeds of 120–250 m/min; the TCMTB pre-blend is injected 50 cm upstream of the glue roll doctor blade to ensure uniform film formation on the flute tips. Field service reports from Southern European box plants note that TCMTB exhibits a synergistic effect with benzyl alcohol (BA) at mass ratios from 1:2 to 1:4, extending mould-free open time for starch tanks from 48 to 120 hours. However, an operational limitation is the incompatibility of TCMTB with polyvinyl alcohol (PVOH) homopolymer adhesive systems that have been crosslinked with amine-hardened boric acid complexes; the thiocyanate moiety participates in ligand exchange with the boron-hydroxy network, causing instantaneous gelation and catastrophic viscosity spikes above 20,000 cP on a Brookfield RV viscometer, leading to ropy, unprocessable adhesive. End-product specifications comprise single-wall and double-wall corrugated fibreboard packaging intended for fresh produce export, frozen food boxes, and heavy-duty shipping containers. Regulatory compliance for indirect food contact must be validated under 21 CFR 176.170 for components that migrate to aqueous and fatty food simulants, with migration limits typically 0.5 mg/kg in the simulant as an Acceptable Daily Intake consideration.Confronting Biocide Adaptation in Closed Water Loops with TCMTB Pulse DosingModern paperboard mills operating with zero-discharge water systems accumulate dissolved and colloidal organic matter reaching COD values of 8,000–15,000 mg/L, forming resilient biofilms composed predominantly of *Pseudomonas putida* and *Geotrichum candidum* on headbox surfaces, press felts, and wire foils. TCMTB is applied as a shock-dose biocide into the short-circulation whitewater loop at an initial concentration of 15–30 ppm active ingredient based on total water volume, delivered via a metering pump calibrated to inject over a 30-minute cycle, repeated every 8–12 hours depending on online fouling sensor readings that monitor pressure drop across suction couch rolls. The industrial guideline for microbial control in papermaking systems is TAPPI TIP 0416-03 for mill experience in microbiological deposit control, with quantitative microbiological analysis performed according to ISO 9308-1:2014 (enumeration of *E. coli* as indicator organisms). The dosing point is critically positioned after the centrifugal cleaner rejects and before the fan pump to maximise residence time in the approach piping, which is typically of 8-inch diameter stainless steel schedule 10 construction. One pervasive failure mechanism encountered in newsprint mills adopting TCMTB programmes is the rapid biodegradation of residual active in the sludge water due to aerobic microbial adaptation; after approximately six to eight weeks of continuous use, specific TCMTB-degrading *Bacillus* strains enriched in the backwater can reduce the half-life of the biocide to 2 hours, necessitating alternation with an oxidising biocide such as chlorine dioxide (ClO₂) at 2 ppm residual to break the adaptation cycle. Therefore, the additive protocol mandates rotation with a halogen-based biocide every 4 weeks to maintain efficacy. Finished paper and board grades produced under this programme include recycled linerboard (RP-10), white-top testliner, and gypsum face paper for wallboard manufacturing. Compliance documentation for end-use in food-contact paperboard must satisfy BfR Recommendation XXXVI and EN 15519:2014, with migration testing demonstrating that TCMTB residuals are below the detection limit of 0.01 µg/dm² under the EN 646 cold-water extraction protocol. The formulation cannot be used in combination with post-consumer broke that has been treated with enzymatic starch conversion agents containing proteases, as the enzyme residual rapidly cleaves the thioester bond of TCMTB, nullifying preservative activity within a single machine chest residence time. |
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The thiocyanate ester of 2-mercaptobenzothiazole, commonly designated TCMTB, is supplied industrially as a broad-spectrum microbicide under the CAS registry 21564-17-0. Its molecular formula (C₉H₆N₂S₃) integrates a benzothiazole ring with a reactive thiocyanomethyl moiety, conferring electrophilic disruption of fungal cytochrome c oxidase and non-specific membrane lysis in Gram-positive bacteria. The neat compound is a pale amber liquid with a density of 1.38 g/cm³ at 20 °C, a pour point below -10 °C, and a water solubility of approximately 33 mg/L. Commercial formulations are typically rendered as 30% w/w aqueous dispersions or 50% w/w solutions in dipropylene glycol monomethyl ether, with the choice of carrier materially influencing low-temperature stability and shear tolerance during automated dosing. Unlike many isothiazolinone preservatives, TCMTB does not liberate formaldehyde under storage, and its activity spectrum is skewed heavily toward Ascomycota and deuteromycete fungi responsible for cellulosic degradation and hide protein colonization.
| Parameter | Method | TCMTB 30% Aqueous Dispersion | TCMTB 50% Solvent-Based Concentrate |
|---|---|---|---|
| Active content (wt%) | HPLC-UV, proprietary | 29.0–31.0 | 49.0–51.0 |
| Density at 20 °C (g/cm³) | DIN 51757 | 1.13–1.17 | 1.27–1.31 |
| pH (1% in distilled water) | ISO 4316 | 4.0–6.5 | 5.5–7.0 |
| Freeze-thaw stability | Internal protocol; 5 cycles, -5 °C/25 °C | Viscosity reversal upon warming; no coalescence | Remains homogeneous; no crystal precipitation |
| Flash point (°C) | ASTM D93 | > 100 | 64–72 |
| Microbial challenge test (mixed fungi, 0.05% dose) | ISO 11930:2019, criterion A | 7-day log reduction > 3 | 7-day log reduction > 4 |
In wet-blue processing drums with typical loading capacities of 12,000–18,000 kg of delimed bovine hides, direct substitution of pentachlorophenate (PCP) by TCMTB 30% aqueous dispersion at 0.15–0.30% on wet-blue weight introduces a narrower operational window for float pH. Preservative fixation occurs primarily during the final 40–60-minute drumming cycle at 28–32 °C, with a float ratio of 1:1 (hide to water). At pH values exceeding 9.0, nucleophilic hydroxyl ions cleave the thiocyanomethyl ester, accelerating hydrolysis to 2-mercaptobenzothiazole and reducing the half-life of active fungicide to less than 90 minutes. This pH sensitivity is absent in PCP and its sodium salt, which retain stability up to pH 12. Consequently, plants that previously buffered floated with soda ash must now maintain a pH ceiling of 8.2 using a sodium acetate/acetic acid system. Field observations from processing lines in Tamil Nadu and the Rio Grande do Sul region indicate that a deviation of only ±0.4 pH units above this ceiling results in Aspergillus niger colonisation visible as black spot within 14 days of warehousing at 35 °C and 85% relative humidity. Accelerated shelf-life monitoring per IULTCS/IUC 3 protocol reinforces that TCMTB-treated wet-blue retains tensile strength above 18 N/mm² and tear resistance within 5% of control for at least 180 days, provided the float pH during application was monitored by inline glass-electrode probes calibrated against NIST-traceable buffers. The absence of chlorinated phenols eliminates the formation of polychlorinated dibenzodioxins during subsequent incineration of shavings, aligning waste streams with EU Directive 2010/75/EU and REACH Annex XVII entry 22. The compound’s moderate octanol-water partition coefficient (log Kow 3.1) also reduces the biomagnification risk observed with highly lipophilic agents like o-phenylphenol.
The inherent yellow chromophore of TCMTB—originating from the benzothiazole nucleus—creates a visible tinting risk when dosed above 0.08% on total formulation weight into titanium dioxide-pigmented styrene-acrylic dispersions. Spectrophotometric measurements according to ASTM D2244-16 reveal a ΔE*ab shift of 2.8–4.2 units at 0.15% loading in a 23% PVC interior matt paint, rendering it unacceptable for RAL 9010 pure-white topcoats. In contrast, 2-methyl-4-isothiazolin-3-one (MIT)/benzisothiazolinone (BIT) combinations maintain ΔE*ab below 1.0 at equivalent active concentrations. Nevertheless, in coloured, deep-tone, and clear wood coatings, TCMTB 30% is applied as an in-can preservative at 0.05–0.20% because of its superior efficacy against Amorphotheca resinae and Cladosporium spp., which are pervasive in waterborne alkyd and polyurethane systems. Activation is immediate upon incorporation without the latency period characteristic of zinc pyrithione, which requires partial dissolution to exert fungistasis. A critical incompatibility emerges in formulations containing primary amines, polyamide curing agents, or ammonia as a pH adjuster: the thiocyanomethyl group is susceptible to nucleophilic displacement, generating mercaptobenzothiazole and thiocyanate ions. This degradation pathway is accelerated at temperatures above 50 °C, which restricts TCMTB to cold-blend addition in high-speed dispersers operating at tip speeds below 15 m/s. The coating formulator must verify compatibility through a 28-day storage stability protocol at 40 °C (as prescribed in ISO 11930:2019, Annex C) with periodic fungal challenge using Chaetomium globosum and quantification of the active moiety via reverse-phase HPLC. Systems that pass the protocol demonstrate a microbial recovery below 10 CFU/g after 7-day inoculation, a margin seldom achieved by sodium benzoate in pH-neutral matrices.
In open-recirculating cooling towers with continuous make-up water alkalinity between 150 and 350 mg/L as CaCO₃, the biostatic efficacy of TCMTB oscillates sharply with bulk-water chemistry. Shock doses of 15–25 mg/L active substance are introduced via side-stream injection using positive-displacement diaphragm pumps synchronized to blowdown cycles. The transient concentration spike of 25 mg/L must be sustained for a minimum contact time of 4 hours; shorter residence intervals due to excessive drift eliminator losses reduce the kill rate of sessile Fusarium hyphae embedded in biofilm matrices. Operating experience across multiple 30,000–60,000 m³/h cross-flow towers in petrochemical complexes reveals that TCMTB’s penetration into biofilms is hindered when the biofilm thickness exceeds 1.2 mm, necessitating preliminary dispersal with terpene-based biodispersants dosed at 5–8 mg/L. A notable advantage over glutaraldehyde lies in the persistence of activity in hydrocarbon-contaminated blowdown: TCMTB retains 70% of its 24-hour fungal control at 50 mg/L diesel contamination (measured by ATP photometry per ASTM E2190-10), whereas dialdehyde biocides are consumed by nucleophilic coupling with petroleum fractions. The compound demonstrates a post-treatment residual effect against sulfate-reducing bacteria (SRB) for 48–72 hours, effectively bridging the interval between weekly shock treatments. However, TCMTB is incompatible with standard halogen oxidisers. Simultaneous feeding of sodium hypochlorite or bromochlorodimethylhydantoin (BCDMH) results in rapid oxidation of the thioether sulfur and the thiocyanate group, with monitored free-halogen residuals as low as 0.2 mg/L Cl₂ cutting the half-life of TCMTB to under 20 minutes. Therefore, oxidising biocide programs must be decoupled by at least 12 hours. Substitution for methylenebisthiocyanate (MBT) in cooling-tower applications is driven by TCMTB’s markedly lower acute dermal toxicity (rat dermal LD₅₀ > 2,000 mg/kg versus 200–400 mg/kg for MBT), which relaxes the PPE tier from Level B to Level C under OSHA HAZWOPER classification.
In sawmill dip lines treating freshly sawn Pinus radiata dimension stock, a 0.5–1.2% w/v working solution of TCMTB 30% applied at 60–80 L/m³ spray volume provides 12–16 weeks of protection against sapstain fungi (Lasiodiplodia theobromae, Ceratocystis spp.) under covered outdoor storage in subtropical climates. The formulation is often co-applied with 0.3% w/v of a quaternary ammonium compound to extend antibacterial coverage to moulds that TCMTB alone controls only at higher doses. A decisive distinction from the historically used 2,4,6-tribromophenol is the absence of dip bath pH drift; TCMTB does not consume alkalinity, so bath maintenance is reduced to fortnightly specific gravity correction rather than daily pH titration. Leaching experiments conducted per EN 84 (accelerated ageing, 14-day water immersion) on pressure-treated Scots pine sapwood show that TCMTB retention after leaching is 42–55% of the initially impregnated 0.8 kg/m³, whereas MBT retention falls below 25% under identical conditions. This superior fixation derives from the hydrophobic benzothiazole moiety partitioning into the resinous extractives of the softwood ray parenchyma. The primary limitation encountered in high-throughput line applications is the minimum dipping temperature: at 10 °C and below, the viscosity of the 30% aqueous dispersion rises to 400–600 mPa·s, causing uneven film build and localized over-retention pockets that later exude in kiln-drying schedules exceeding 70 °C dry-bulb. Plants operating in Nordic winter conditions therefore require trace-heated recirculation loops maintaining bath temperature at 18–22 °C.
| Attribute | TCMTB | Benzisothiazolinone (BIT) | Methylenebisthiocyanate (MBT) |
|---|---|---|---|
| Fungal MIC₉₀ (ppm) for A. niger (ISO 11930) | 5–25 | 100–500 | 1–10 |
| pH stability window | 3.0–8.5 | 2.0–12.5 | 5.0–8.0 |
| Half-life at pH 10, 25 °C | < 2 hours | > 30 days | 6–24 hours |
| Acute oral toxicity (rat LD₅₀, mg/kg) | 250–400 | 1,200–1,400 | 50–80 |
| Vapour pressure at 25 °C (Pa) | 4.6 × 10⁻² | 2.7 × 10⁻³ | 1.1 |
| Typical application sector risk phrase under GHS | Acute Tox. 4, Eye Irrit. 2, Skin Sens. 1 | Skin Sens. 1, Eye Irrit. 2 | Acute Tox. 2, Eye Corr. 1, Aquatic Acute 1 |
The practical consequence of this profile is that TCMTB occupies an intermediate position between the broad alkaline tolerance of BIT and the rapid kill kinetics of MBT. Its substitution into existing MBT-based leather or wood programs requires re-certification of waste-stream ecotoxicology, because TCMTB degrades to 2-mercaptobenzothiazole, a compound classified under GHS as a respiratory and skin sensitiser at concentrations above 0.1%, though its aquatic partitioning profile (log Kow 2.4 for the metabolite) reduces bioaccumulation risk relative to the parent molecule. Dip/spray operators transitioning from MBT to TCMTB must also replace galvanised steel nozzles with 316L stainless steel: the acidic micro-environment generated by the hydrolysis of the thiocyanomethyl group accelerates zinc etching, leading to nozzle clogging within 150–200 operating hours at 0.5% w/v concentration.
