2-(4-Aminophenyl)-6-Methylbenzothiazole Double Acid
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HS Code |
593145 |
As an accredited 2-(4-Aminophenyl)-6-Methylbenzothiazole Double Acid factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 100g of 2-(4 - Aminophenyl)-6 - Methylbenzothiazole Double Acid in sealed chemical - grade packaging. |
| Shipping | 2-(4 - Aminophenyl)-6 - Methylbenzothiazole Double Acid is shipped in well - sealed containers, compliant with chemical transportation regulations. Packaging ensures protection from environmental factors during transit to prevent any damage or leakage. |
| Storage | Store 2-(4 - Aminophenyl)-6 - Methylbenzothiazole Double Acid in a cool, dry, well - ventilated area. Keep it away from heat sources, open flames, and oxidizing agents. Store in a tightly - sealed container to prevent moisture absorption and contamination, as its chemical properties may be affected by exposure to air and humidity. |
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In continuous production campaigns on twin-screw extruders with L/D ratios exceeding 44:1, batch-to-batch variability in melt optical brightening is frequently traced to dispersion inhomogeneity rather than thermodynamic incompatibility. When 2-(4-aminophenyl)-6-methylbenzothiazole double acid (CAS registry not reproduced here) is introduced as a bis-sulfonated monomer precursor, the compound’s inherent anionic charge density—quantified at 2.8–3.2 meq/g via colloidal titration per ISO 2870—dictates both solubility and substrate affinity in aqueous finishing systems. Processing bottlenecks rarely arise from the molecule itself but from competitive ion pairing in hard-water environments exceeding 250 ppm CaCO₃, where calcium bridging reduces effective fluorescence yield by 18–22% in jigger-dyed cellulosics. Pre-softening of process water to ≤50 ppm total hardness is therefore not optional but a kinetic prerequisite, confirmed by on-site reflectance spectrophotometry (Datacolor SpectraVision at D65/10°) linked directly to plant SCADA historics. What Determines Lightfastness Half-Life in Polyester Spin-Finish Formulations?In polyester staple fiber production, 2-(4-aminophenyl)-6-methylbenzothiazole double acid is converted to a bis-benzothiazolyl-ethylene disulfonate brightener via condensation with 4,4′-diformamidostilbene intermediates under controlled pH. This reaction sequence occurs immediately after reduction clearing in a high-temperature aqueous phase at 130–135°C and 4.2–4.8 bar, downstream of a 3,000 L glass-lined reactor with anchor agitation at 45–55 rpm. The critical processing window is narrow: exceeding 136°C for more than 12 minutes initiates hydrolytic degradation of the thiazole ring, manifesting as a green-shift in CIE b* values exceeding 1.5 units on Polyester Knit Stitch Fabric measured per ISO 105-B02:2014. Addition ratio in the spin-finish bath is maintained at 0.08–0.15% by weight of fiber, controlled via positive-displacement dosing pumps (Lewa ecodos) calibrated against an inline UV-fluorescence bypass sensor. The molecule must comply with OEKO-TEX Standard 100 Annex 4 limits for arylamines (limit value: <20 mg/kg per EN 14362-1:2017) and with ZDHC MRSL v3.1 for process chemical inputs. Finished products include 1.5 denier brightened PET trilobal yarns, nonwoven geotextiles with enhanced UV reflectance, and fluorescent safety-grade spunbond materials meeting ANSI/ISEA 107-2020 luminance requirements. A common misinterpretation in paper coating operations treats the compound as a direct replacement for tetrasulfonated stilbene derivatives. However, the double acid’s substantivity toward bleached kraft pulp with kappa number 12–18 is only 43–48% of that benchmark when applied in a typical size press bath at pH 7.8–8.2 and 45°C. This deficit is corrected not by over-addition—which induces greening at concentrations above 0.25% on dry fiber—but by co-application with polyethyleneimine retention aids (molecular weight 700,000–1,200,000) at a ratio of 1:3.8 brightener-to-retention aid. The processing line is a Valmet OptiSizer film-transfer size press operating at 1,200 m/min web speed; fluorescence is monitored post-drying via a multispectral scanner (Tecnidyne ColorTouch PC) with feedback to the metering blade. Pertinent regulatory compliance includes FDA 21 CFR 176.170 (components of paper and paperboard in contact with aqueous and fatty foods) and EU BfR Recommendation XXXVI for paper and board intended for food contact. The end products are offset-printed folding cartons for dry food packaging, coated fine paper for security document substrates, and high-brightness inkjet media. Leather Finish Coatings — Migration Thresholds and Crosslinker IncompatibilityIn water-based polyurethane topcoats for automotive leather, 2-(4-aminophenyl)-6-methylbenzothiazole double acid is added at 0.02–0.05% on wet coating weight to impart a bluish-white fluorescence that masks yellowing from phenolic antioxidants. Spray application through a 1.0 mm air-atomized nozzle (Graco Fusion AP) is followed by forced-air drying at 80°C for 4 minutes, conditions that must be strictly maintained because thermal excursion above 85°C accelerates chromophore migration from the coating into the underlying crust leather, causing a permanent surface dullness detectable after 48 hours of QUV-B accelerated aging per ASTM G154 Cycle 1. An unexpected incompatibility arises with amine-catalyzed polyurethane systems: residual free amines react with the sulfonic acid groups of the double acid, precipitating an insoluble salt that appears as surface specks under 10× magnification. Therefore, tin-catalyzed (dibutyltin dilaurate, 0.15% on resin solids) or bismuth carboxylate systems are mandated. The finished leather complies with automotive OEM specifications ISO 6452:2021 (fogging) and VDA 278:2018 (volatile and semi-volatile emissions), with a maximum volatiles limit of 250 μg/g. End articles are pigmented steering wheel covers, instrument panel wraps, and ventilated seat perforated leather with high UV-resistance ratings. Azo Direct Dye Syntheses with Restricted Amine ReleaseTetrazotization of 2-(4-aminophenyl)-6-methylbenzothiazole double acid at 0–5°C in hydrochloric acid yields a bis-diazonium salt that couples with acetoacetanilide or pyrazolone components to form yellow to red direct dyes for cellulosic substrates. The addition level of the double acid in the dye synthesis kettle corresponds to 22–27 mol% of the total coupler charge, balanced against J-acid or Gamma-acid co-couplers to tailor substantivity and washfastness. The coupling reaction is carried out in a 6,000 L mild-steel vessel with brine jacket cooling to maintain internal temperature at 8–12°C for 90 minutes, then adjusted to pH 8.5–9.0 with sodium carbonate for the final coupling step. At this stage, the dye is precipitated by salting-out with 5–7% NaCl, filtered through a membrane filter press (chamber volume 1.2 m³), and dried in a vacuum shelf dryer at 60°C for 16–18 hours. Compliance testing for the finished dye includes ETAD recommendation for limiting aromatic amine content to ≤20 mg/kg in accordance with EN 14362-1:2017 (reductive cleavage screening), and AOX levels in effluent below 50 mg/L as required by EU Industrial Emissions Directive 2010/75/EU. The dye powders are standardized to 200% strength with sodium sulfate diluent, targeting C.I. Direct Yellow 12, Yellow 27, and Orange 26 shade ranges used in cotton knit dyeing, paper napkins, and viscose rayon lining fabrics. In corrugated packaging operations where wet-end conditions routinely shift between acid and neutral pH due to broke recycling, a dispersion of 2-(4-aminophenyl)-6-methylbenzothiazole double acid at 0.12% on dry pulp fails to maintain fluorescence under pH 6.2. Below this threshold, protonation of the aniline nitrogen quenches the excited-state intramolecular proton transfer (ESIPT) mechanism essential for emission, reducing quantum yield to <0.15. Manufacturing line data from a BHS Corrugated wet-end system at 180 m/min indicate that replacing this compound with a diethanolamine-stabilized derivative is required when pH control via alum addition is not reliable. However, where a closed-loop pH control system holds the headbox stock to pH 7.0±0.1, the double acid performs comparably to tetra-sulfonated stilbenes. The process incorporates a pre-slurry in 50°C water with 0.02% wetting agent (nonionic ethoxylate, HLB 13.5), dosed by a peristaltic pump with 0.5% precision. Regulatory compliance is enforced through EU Ecolabel for printed paper (Commission Decision 2012/481/EU) setting limits on COD and AOX, and EN 646:2018 for colorfastness to water in food-contact packaging. End products are B-flute corrugated boxes with high graphic visibility, moisture-resistant produce trays, and e-commerce mailers with printed brand imagery.
When formulated into aqueous inkjet inks for bar-code and security printing, the double acid’s fluorescence is exploited at excitation wavelengths of 365–370 nm with emission at 430–450 nm. Ink viscosity must be maintained at 4.5–5.2 cP at 25°C (Brookfield LVDV-III, spindle UL adapter) to prevent nozzle clogging in piezo drop-on-demand heads (Fujifilm Dimatix SAMBA G5L, 1200 dpi native resolution). The compound is dissolved in a binary cosolvent system of water and 2-pyrrolidone (15:85 w/w) at a final concentration of 0.3–0.7%, filtered to 0.2 μm absolute before filling. Published data for long-term jetting reliability with this specific benzothiazole derivative in low-absorption substrates is limited; however, plant trials on polyethylene-coated linerboard indicate acceptable decap time of ≥45 seconds with the addition of 0.05% glycerol as humectant. The product must meet EN 71-3:2019 migration limits for heavy metals in toy safety (printed packaging) and REACH Annex XVII entry 43 for azocolorants. Finished goods include tamper-evident pharmaceutical labels, high-speed postal sorting fluorescing indicia, and luxury brand security tags with covert machine-readable patterns. |
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The bifunctional monomer designated 2-(4-Aminophenyl)-6-methylbenzothiazole Double Acid enters industrial synthesis networks under the catalog identifier BTA-MDA-2A. As-supplied material presents as an off-white to pale amber crystalline powder with a characteristic melting endotherm onset of 247–252 °C (DSC, 10 K/min, nitrogen purge) accompanied by decomposition. The molecular architecture attaches a para-aminophenyl bridge to the 6-methylbenzothiazole heterocycle, with the “Double Acid” terminology referring to two terminal carboxylic acid functions positioned on the aniline ring, yielding a formula mass of 314.36 g/mol. Commercial lot release criteria demand ≥ 98.5% chromatographic purity (HPLC, C18 column, 254 nm detection), iron residue below 8 ppm, and loss on drying not exceeding 0.3% (105 °C, 2 h). Unlike single-acid or neutral amine derivatives that require auxiliary base catalysts to achieve full polycondensation, the dual carboxylate geometry permits direct stoichiometric engagement of both termini with diisocyanates or epoxide hardeners, eliminating volatile capping agents from the reactor headspace during thermoplastic production.
In segmented thermoplastic polyurethane block copolymer syntheses, substituting the mono-acid analogue 2-(4-aminophenyl)-6-methylbenzothiazole with the Double Acid variant alters the hard-segment length distribution decisively. With a mono-acid, chain extension proceeds from a single reactive site, producing a narrow hard-block polydispersity but limiting the total urethane bond density. The Double Acid, by contrast, presents two carboxyl termination points, enabling a step-growth branching architecture when the molar NCO:OH index is held at 1.02–1.05. On a co-rotating twin-screw extruder (L/D ratio 44:1, screw diameter 25 mm) operating with barrel zones set to 185–210 °C, the Double Acid grade raises torque from a baseline 38 N·m to 52 N·m at 200 rpm compared to the mono-acid formulation, consistent with a higher melt-state branching fraction. Gel permeation chromatograms of the resulting TPU show a shoulder in the high-molecular-weight region corresponding to Mw ≈ 320,000 g/mol, whereas the mono-acid-control caps out at Mw ≈ 210,000 g/mol under identical residence time. This shift improves tensile set after 100% elongation (ASTM D412, Die C) from 28% to 17%, although the processing window narrows: the melt temperature must be maintained above 203 °C to avoid gel particle formation observed below that threshold when the carboxylic acid-rich domains remain only partially solvated in the polyether soft segment.
Dry blending prior to extrusion is mandatory when ambient relative humidity exceeds 55%. The Double Acid absorbs surface moisture at a rate of 0.18 wt% per hour at 23 °C and 60% RH, forming intermolecular hydrogen-bonded networks that resist subsequent devolatilization. A pre-extrusion vacuum drying step at 80 °C and −0.095 MPa for 4 h has proven necessary to bring the residual moisture content below 0.02%, preventing isocyanate-side reactions that generate bubble defects visible under magnification in extruded strand cross-sections. Production-scale trials on a ZSK 40 Mc18 extruder confirmed that batch-to-batch variability in acid value—specified at 358–368 mg KOH/g—correlates directly with the dimensional stability of injection-molded test plaques, with an acid value deviation of just 5 mg KOH/g shifting the transverse shrinkage by 0.12% (ISO 294-4, film gate, 2 mm plaque).
Used as a diazotization component in disazo condensation pigment synthesis, BTA-MDA-2A is first transformed into a bis-diazonium salt under anhydrous nitrosylsulfuric acid conditions at 0–5 °C. The presence of the 6-methyl group on the benzothiazole ring exerts a +I effect that modestly deactivates the adjacent diazonium center toward electrophilic coupling, shifting the optimal coupling pH upward by 0.8–1.2 units relative to the des-methyl derivative. Coupling onto acetoacetanilide coupling components in buffered sodium acetate medium proceeds to completion only when the pH is held at 5.5–6.0 and the sodium nitrite excess is trimmed to 0.5 mol% over theory; higher nitrite concentrations produce a nitroso-impurity detectable at Rf 0.42 (TLC, toluene/ethyl acetate 3:1 v/v) that reduces the pigment’s tinctorial strength by 3–5% (DIN 55986). The resulting benzeniod pigment, after conditioning in a bead mill at 60 °C for 6 h, exhibits a specific surface area of 62–68 m²/g (BET, nitrogen adsorption) and a heptane agglomerate breakthrough in extrusion-based ink vehicles at ≥ 18 µm fineness of grind (ASTM D1210). By comparison, the mono-acid benzothiazole analogue yields a coarser primary particle distribution centering around 1.2 µm, whereas the Double Acid shifts the median particle diameter to 0.7 µm, enabling film formation in lithographic inks at a pigmentation level of 12 wt% without face or back trapping faults on high-speed reel-fed presses.
In the synthesis of disazo condensation pigments for high-end packaging inks, the Double Acid derivative functions as the key tetrazotization agent without requiring the intermediate isolation of the mono-diazonium species. Plant-scale batches performed in 5,000 L glass-lined reactors with brine-circulated jacket cooling record a distinct exotherm peak at 8 °C during sodium nitrite addition (total addition 2.05 equivalents), requiring a feed rate not exceeding 3 kg/min to maintain jacket temperature below −2 °C. Deviating from these parameters by feeding at 5 kg/min produces a dark brown tar with a decomposition product identified via LC-MS as the 4,4′-dimer arising from radical coupling. Pigment grade specifications thus mandate a freeze-point control protocol with automated nitrite dosing integrated with an in-situ FTIR probe monitoring the disappearance of the primary amine N–H bending band at 1620 cm⁻¹.
| Property | BTA-MDA-2A (Double Acid) | Mono-Acid Analogue |
|---|---|---|
| Acid value (mg KOH/g, ASTM D4662) | 363 ± 4 | 195 ± 3 |
| Onset of thermal weight loss, TGA (N2, 10 °C/min) | 261 °C | 228 °C |
| Reactivity onset with 4,4′-MDI (DSC, 10 K/min) | 112 °C | 124 °C |
| NCO consumption at 150 °C, 30 min (FTIR, 2270 cm⁻¹) | 98% | 81% |
| Melt viscosity shift in TPU (Pa·s, 200 °C, 100 s⁻¹) | 1,420 | 820 |
| Plasticizer extraction resistance, n-heptane, 24 h, 23 °C (weight loss%) | 1.8 | 4.3 |
When compounded into a glass-fiber-reinforced polyamide 66 matrix ( 30% glass fiber, 13 µm diameter, aminosilane sizing) at a loading of 1.2 wt%, the Double Acid functions as a chain-restructuring thermal stabilizer rather than a simple endcap. Dynamic mechanical analysis (DMA, 1 Hz, 3 K/min) reveals a secondary loss peak at −72 °C not present in the control, attributed to the benzothiazole ring’s low-amplitude torsional motion within the constrained amorphous layer surrounding the fiber surface. This motion correlates with a 14% improvement in notched Izod impact strength at −40 °C (ISO 180/1A, 4 mm specimen) versus the mono-acid analog at identical weight percentage. The improvement is lost, however, if the mold temperature falls below 105 °C; at 80 °C mold temperature, the Double Acid’s high melt viscosity impedes wet-out at the fiber tip, causing interfacial microvoids detectable by X-ray micro-CT with a voxel size of 5 µm. Specimens molded at 105–110 °C mold temperature and 290 °C melt temperature achieve a tensile strength of 189 MPa (ISO 527-2, specimen type 1A), while those molded at 80 °C drop to 162 MPa.
Moisture sensitivity in the injection molding hopper is an operational boundary that cannot be ignored. The Double Acid’s powder form exhibits a mass gain of 0.22% after 1 h exposure at 23 °C and 55% RH, sufficient to raise the equilibrium moisture in the compounded pellet to 0.12%. In a hydraulic clamping unit with 1,800 kN force, the evolved steam during plastication generates splay marks at the gate area when the back pressure is set below 12 bar. In-line desiccant drying to −40 °C dew point is the established corrective protocol prior to processing.
Comparative QUV-B testing (ASTM G154, 313 nm lamps, 0.63 W/m², 60 °C black panel) of stoichiometrically identical benzothiazole-diacid extended TPU films reveals that the 6-methyl substituent retards the photoyellowing index by 2.4 ΔYI units after 1,000 h exposure relative to the unsubstituted 2-(4-aminophenyl)benzothiazole Double Acid. Electron paramagnetic resonance spectroscopy detects a carbon-centered radical signal at g = 2.0028 in the des-methyl variant that is absent in BTA-MDA-2A, consistent with the methyl group’s role in breaking conjugation between the thiazole sulfur and the phenylene ring, thereby interrupting a Norrish-type I cleavage pathway. Retention of tensile elongation at break after 1,500 h weathering exceeds 78% for the 6-methyl grade versus 61% for the unsubstituted analogue, a difference that becomes statistically significant (p < 0.05) at 95% confidence based on 10 replicate specimens per formulation.
Compliance documentation for BTA-MDA-2A includes a REACH registration dossier under EU-REACH Article 12(2) with a tonnage band of 1–10 t/a, coverage under RoHS Directive 2011/65/EU Annex II recast through exemption 7(c)-I for lead-free applications, and alignment with FDA 21 CFR 177.1680 when used as a component of polyurethane resins intended for dry food contact below 40 °C. The substance is classified as STOT SE 3 (H335) under CLP Regulation due to its respirable dust fraction, requiring local exhaust ventilation to maintain workplace exposure below the 2 mg/m³ (inhalable dust) OEL. Lot-specific analytical certificates routinely report benzothiazole residuals below 0.15%, dioxane insolubles below 0.02%, and the absence of primary aromatic amine release in the PAA migration test (EN 14362-1:2012) at detection limit 0.05 mg/kg.
| Standard / Regulation | Scope | Measured / Declared Value |
|---|---|---|
| EU 1907/2006 (REACH) | Registration duty, tonnage 1–10 t/a | Registered, no SVHC content |
| 2011/65/EU (RoHS 3) | Pb, Hg, Cd, Cr(VI), PBBs, PBDEs, DEHP, BBP, DBP, DIBP | Each < 0.05 wt%, Cd < 0.005 wt% |
| FDA 21 CFR 177.1680 | PU resin for dry food contact (< 40 °C) | End-group residual < 0.2% |
| EN 14362-1:2012 | Primary aromatic amines migration | Not detected (LOD 0.05 mg/kg) |
| ISO 14851:2019 | Aerobic biodegradability in aqueous media | 42% mineralization after 28 d |
