BIT (CAS 2634-33-5) is a heterocyclic organic compound from the isothiazolinone family, widely established as a high-performance, broad-spectrum industrial biocide and preservative. Its technical profile is defined by exceptional thermal and pH stability, a distinctive solubility limitation, and potent antimicrobial efficacy against bacteria, fungi, yeasts, and algae.
1. PHYSICAL AND CHEMICAL PROPERTIES
| Parameter | Characteristic / Value | Comments / Source |
|---|---|---|
| Appearance | White to off-white / pale yellow powder (pure) or clear liquid (formulated) | Powder is standard for high-purity grades (98%); liquid products are commercial solutions. |
| Molecular Formula | C₇H₅NOS | Molecular weight: ~151.18. |
| Solubility (Critical Limitation) | 0.14% at 25°C; 1.5% at 90°C | Poor water solubility is the primary technical constraint of neat BIT. Readily soluble in alkaline solutions and organic solvents (ethanol, glycol) . |
| Melting Point | 155–160°C | Confirms solid state at room temperature . |
| pH Stability | 2 – 14 (exceptional range) | Stable in both acidic and highly alkaline media; suitable for diverse formulations. |
| Thermal Stability | Stable up to 100°C (liquid formulations); powder stable to 180°C | Allows incorporation in processes with elevated temperatures. |
| VOC Status | Formaldehyde-free; options for VOC-free, solvent-free | Compliant with modern low-emission regulatory requirements. |
2. MECHANISM OF ACTION & PERFORMANCE CHARACTERISTICS
Antimicrobial Spectrum:
BIT is a broad-spectrum biocide, exhibiting high efficacy against:
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Bacteria: Both Gram-positive and Gram-negative strains, including Sulfate-Reducing Bacteria (SRB) Prevent microbial degradation during storage.Adhesives & SealantsWater-based, casein, PVA adhesives; tackifiersSpoilage prevention.Metalworking FluidsCutting fluids, cooling lubricantsTankside addition; stability at high pH.Pigments & FillersCalcium carbonate slurries, Kaolin, pigment pastes, dye suspensionsPreservation of aqueous slurries.Construction MaterialsConcrete admixtures, plasters, building material preservationMicrobial control.Paper & TextilesPaper coatings, textile printing/dyeing, photographic lotionsFungicide/bactericide.Household & I&I CleanersDetergents, cleaning agents, fountain solutionsIn-can stability.Leather ProcessingTreatment solutionsMold prevention.Cosmetics (Restricted)Personal care products (historical use)Preservative; subject to stringent concentration limits.
3.2 Typical Use Concentrations (Active BIT Basis)
Dosage is highly dependent on formulation, raw material susceptibility, and intended storage life. Field testing is mandatory for optimization.
Application Area Recommended Dosage (Product Weight %) Notes / Source Paints, Adhesives, Polymers 0.10 – 0.50% General in-can preservation. Metalworking Fluids 0.15 – 0.50% (tankside) Pigment / Filler Slurries 0.03 – 0.30% Household / Institutional Products 0.012 – 0.40% General Industrial Preservation 0.05 – 0.25% Nipacide BIT 20 (20% soln) 0.10 – 0.25% Equivalent to 200-500 ppm active BIT. 3.3 Processing & Handling Guidelines
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Incorporation: Best added at the feed water stage for immediate protection. For processes >60°C or pH >10, add at the cooling-down phase (below 60°C/140°F) to prevent degradation.
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Mixing: Ensure uniform distribution by stirring after addition.
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Solubility Management: Due to low water solubility, commercial products utilize:
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Glycol-based solutions (e.g., 20% BIT in dipropylene glycol) for easy dosing.
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Alkaline salts (Sodium BIT, Tetramethylammonium BIT) to achieve true water solubility and low-temperature stability.
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4. SAFETY, REGULATORY & ENVIRONMENTAL PROFILE
4.1 Hazard Classification (GHS & EPA NZ)
BIT is classified as hazardous, requiring strict handling protocols:Hazard Class Code Hazard Statement Concentration Limit / Note Acute Toxicity (Oral) H302 Harmful if swallowed LD50 1020 mg/kg (rat). Skin Irritation H315 Causes skin irritation Irritant at ≥20% concentration. Eye Damage H318 Causes serious eye damage Corrosive at ≥10%; irritant at 5-10% . Skin Sensitization H317 May cause allergic skin reaction Sensitizer down to 0.05%; significant regulatory trigger. Aquatic Toxicity H400 / H410 Very toxic to aquatic life (acute & chronic) EC50 (algae) 0.15 mg/L; not readily biodegradable. Signal Word: DANGER.
Personal Protection: Mandatory use of goggles, rubber gloves, protective clothing. Avoid all skin/eye contact. Wash immediately with soap and copious water if contact occurs.4.2 Regulatory Approvals & Compliance
Despite its hazardous nature, BIT is globally accepted for industrial use with specific concentration limits:-
FDA (USA): Permitted for adhesives (21 CFR 175.105) and paper/paperboard components (21 CFR 176.170, 176.180).
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German BfR: Recommendations XIV (plastic dispersions) and XXXVI (paper preservation) .
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EPA (NZ): Approved under Group Standards for industrial use; carries specific concentration limits for sensitization (0.05%) and eye damage (10%) .
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VOC Regulations: BIT formulations are available as solvent-free and VOC-free, compliant with strict emission standards.
5. SUMMARY
BIT is a highly effective, thermally stable, and pH-versatile industrial preservative, ideally suited for protecting aqueous formulations in the paint, polymer, adhesive, metalworking, and construction sectors. Its primary technical limitation—low water solubility—is routinely overcome through formulated glycol solutions or soluble alkaline salts. While BIT offers a favorable low acute toxicity profile compared to older technologies, it is a potent skin sensitizer and eye irritant. Mandatory concentration limits (e.g., 0.05% for sensitization labeling) and personal protective equipment are non-negotiable for safe industrial use.
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