2-Octyl-3(2H)-isothiazolinone OIT(CAS#26530-20-1)–Mildewcide & Dry Film Fungicide

1. Properties:

• Appearance and Physical Form: 2-Octyl-3(2H)-isothiazolinone (OIT) is supplied as a colorless to light yellow clear liquid (technical grade and formulated solutions) or as an off-white to light yellow solid/crystalline powder (high purity grade). Commercial grades include neat OIT and formulated blends dispersed in plasticizers or solvents at 10–45% active content.
• Solubility: OIT is highly soluble in most organic solvents including toluene, ethyl acetate, glycols, alcohols, and aromatic hydrocarbons. It is miscible with plasticizers, PVC resins, and coating binders. The compound is practically insoluble in water (0.05–0.5 g/L), a property that confers excellent resistance to leaching and provides long-term dry film protection.
• Chemical Properties: OIT is a halogen-free, non-formaldehyde, isothiazolinone biocide and fungicide. Its structure features a five-membered heterocyclic ring containing sulfur and nitrogen, with an octyl chain that imparts strong hydrophobicity and oil solubility.
  • Mechanism of Action: OIT inhibits fungal growth by disrupting DNA/RNA synthesis and thiol-containing enzymes essential for cellular respiration and metabolism. The electrophilic sulfur in the isothiazolinone ring reacts rapidly with thiol (–SH) groups in fungal proteins, causing irreversible enzyme inhibition and cell death.
  • Antifungal Efficacy: OIT is highly effective against a broad spectrum of fungi at low concentrations.
    • Aspergillus niger (black mold): MIC 20 µg/mL
    • Penicillium spp. (common mold): MIC 25 µg/mL
    • Fusarium spp. (pink mold): MIC 25 µg/mL
    • Candida albicans (yeast): MIC 10 µg/mL
    • In wood preservation with soil contact, OIT dissipates 94–100% within 40 days, offering quantifiable environmental fate advantages over persistent biocides.
  • Broad-Spectrum Activity: While primarily a fungicide, OIT also provides moderate antibacterial activity against Pseudomonas aeruginosa (MIC 100 µg/mL) and other bacteria.
  • Stability: OIT exhibits excellent thermal stability and UV resistance. It is stable in strong light and high-temperature conditions commonly encountered in exterior coatings. The low water solubility imparts outstanding water leaching resistance, making OIT particularly suitable for exterior applications. The product is also formaldehyde-free and VOC-free, meeting stringent environmental regulations.
  • Compatibility: OIT is compatible with most resin systems, polymer emulsions (acrylic, styrene-acrylic, PVAc), plasticizers, and industrial base materials used in paint, coating, adhesive, and plastic formulations.

2. Applications:

Paints & Coatings Industry (Primary – Dry Film Preservation):

• Architectural Paints and Coatings: OIT is the preferred dry film preservative for interior and exterior architectural coatings, including latex paints, elastomeric wall coatings, masonry paints, and roof coatings. It prevents unsightly surface discoloration, mold growth, and fungal defacement on cured paint films, maintaining aesthetic appearance over extended service life.
• Industrial Coatings and Wood Stains: Provides effective dry film protection in industrial coatings, wood stains, varnishes, lacquers, and sealers against fungal and algal attack.
• In-Can Preservation: OIT-based blends are used as in-can preservatives for paints, polymer emulsions, pigment dispersions, and latex to prevent microbial spoilage during storage.
• Application Level: Recommended use level is 0.1–0.3% of total formulation (dry weight), depending on the product and exposure environment.

Adhesives, Sealants & Elastomers:

• Adhesives and Glues: OIT is incorporated into water-based and solvent-based adhesives (including food packaging adhesives under FDA 21 CFR 175.105) to prevent microbial attack during storage and in-service exposure to humid environments.
• Sealants and Caulks: Effective fungicide for PVC and silicone sealants, caulking compounds, and grouting materials. Intercide OBF 20 DINCH, based on OIT, provides long-term protection of PVC and silicone sealants.
• Roofing Materials: OIT protects bituminous and polymer roofing materials from mold and fungal degradation.

Wood Preservation & Cultural Heritage Conservation:

• Wood Preservative: OIT is used in wood preservation products to protect against fungal decay, sapstain, mold, and insect damage in above-ground applications, extending the service life of wooden structures and lumber.
• Cultural Heritage Conservation: Due to its high antifungal potency (10–500× lower MIC than benzalkonium chloride) and minimal interference with cultural heritage artifacts, OIT is used in the conservation of paintings, sculptures, and historic objects.

Textile, Leather & Paper Processing:

• Textile Finishing: OIT is used as a biocide in textile finishing treatments to impart antifungal and antibacterial properties to fabrics, preventing mildew and odor in finished goods and during storage.
• Leather Processing: Controls spoilage organisms in leather processing baths and provides protection against mold growth on finished leather.
• Paper & Pulp: Used as a slimicide in paper machine white water systems to control slime-forming bacteria, fungi, and algae.

Metalworking Fluids (MWF) & Industrial Lubricants:

• Metalworking and Cutting Fluids: OIT is added to water-miscible metalworking fluids (soluble oils, semi-synthetic, and synthetic MWFs) to extend fluid service life by suppressing bacterial and fungal contamination that causes emulsion breakdown, foul odors, reduced tool life, and operator dermatitis.
• Industrial Lubricants and Hydraulic Fluids: Protects industrial lubricants from microbial degradation, maintaining performance and preventing system corrosion.

Plastics, PVC & Polymer Compounding:

• PVC Plastisols and Flexible PVC: OIT is dispersed in plasticizers for incorporation into PVC plastisols, film & sheet, flooring, pool liners, roofing membranes, and other polymer products, providing long-term antimicrobial protection.
• Masterbatch and Polymer Extrusion: Used as an antimicrobial additive in polyolefins, engineering plastics, and silicone rubber for masterbatch applications and extrusion processes.

Water Treatment & Cooling Towers:

• Industrial Water Treatment: OIT-based biocides are used in recirculating cooling water towers, air washer systems, pulp and paper slime control, and oilfield injection waters to control algae, bacteria, and fungal growth.

Cosmetics & Personal Care:

• Preservative for Toiletries and Skin Care: OIT is used as a preservative in rinse-off cosmetic products including shampoos, liquid soaps, skin care preparations, and toiletries at regulated use levels.
• Regulatory Restrictions: OIT use in leave-on cosmetic products is restricted in the EU due to skin sensitization potential (Ref. EU 2014/370/EU, 1.5% limit for Kathon 893). Always check local regulations before formulating.

3. Preparation Method:

• Laboratory Method: OIT can be synthesized by reacting di-n-octyl dithiodipropionamide with a chlorinating agent (e.g., chlorine gas or sulfuryl chloride) under controlled conditions. The reaction proceeds via cyclization and oxidation to form the isothiazolinone ring, followed by purification via recrystallization or column chromatography. However, due to the hazardous nature of the reaction, laboratory synthesis should only be performed by qualified chemists.
• Industrial Process: Industrial production of high-purity OIT follows a multi-step process:
  1. Condensation: Octylamine is condensed with a suitable thioester or mercaptan precursor to form the dithiodipropionamide intermediate.
  2. Cyclization: The intermediate is cyclized using a chlorinating agent (chlorine gas or sulfuryl chloride) in an organic solvent at controlled temperatures (typically 40–60°C) to yield OIT hydrochloride.
  3. Neutralization: The hydrochloride salt is neutralized with a base (e.g., sodium bicarbonate or sodium hydroxide solution) to liberate the free OIT base.
  4. Extraction and Purification: The crude product is extracted with an organic solvent, washed to remove inorganic byproducts, and purified by vacuum distillation or recrystallization to achieve ≥98–99% purity.
  5. Formulation: The purified OIT is formulated as:
     • Neat 98–99% active compound (solid or liquid)
     • 45% active solution in organic solvents
     • Blended formulations with MIT, CMIT, or carbendazim for enhanced performance
     • Dispersions in plasticizers (e.g., DINCH, DIDP) at 10–20% OIT
  6. Quality Control: Key parameters analyzed include active content (by HPLC), purity (by GC-MS), pH, density, melting point (FTIR), water content (Karl Fischer), heavy metals, and microbiological efficacy (MIC testing against Aspergillus niger and Penicillium spp.)
  7. Packaging: The final product is packaged under inert gas in 25 kg drums, 200 kg drums, or 1000 kg IBC totes for shipment.

4. Safety Information:

• Hazard Classification: According to GHS/CLP Regulation (EC) No 1272/2008, OIT (octhilinone) is classified as a hazardous substance with the following hazard statements: H301 (Toxic if swallowed), H311 (Toxic in contact with skin), H314 (Causes severe skin burns and eye damage), H317 (May cause an allergic skin reaction), H330 (Fatal if inhaled), H331 (Toxic if inhaled), H370 (Causes damage to organs), H372 (Causes damage to organs through prolonged or repeated exposure), H400 (Very toxic to aquatic life), H410 (Very toxic to aquatic life with long-lasting effects). Hazard pictograms: GHS05, GHS06, GHS09, GHS08. Signal word: Danger. UN 3077 (Environmentally hazardous substance, solid, n.o.s.), Class 9, PG III.
• Health Hazards:
  • Acute Toxicity: Toxic if swallowed (LD₅₀ oral 550–681 mg/kg in rats), toxic in contact with skin (LD₅₀ dermal >2,000 mg/kg), and fatal if inhaled (LC₅₀ inhalation >2 mg/kg).
  • Skin/Eye Contact: Causes severe skin burns and eye damage (H314). Direct contact with the concentrated compound may cause chemical burns to skin and eyes and allergic skin reactions (H317). OIT is a well-known skin sensitizer. Sensitized individuals may develop allergic contact dermatitis upon repeated exposure.
  • Inhalation: Toxic if inhaled (H331). Inhalation of mists or vapors may cause respiratory tract irritation, coughing, and throat discomfort. High-concentration exposure may cause chemical pneumonitis.
  • Chronic Toxicity: May cause damage to organs (H370) and through prolonged or repeated exposure (H372) – primarily the liver, kidneys, and nervous system in high-dose animal studies.
• First Aid Measures:
  • Eye Contact: Rinse cautiously with plenty of water for at least 15 minutes. Remove contact lenses if present and easy to do. Continue rinsing. Immediately call a physician (P310).
  • Skin Contact: Take off immediately all contaminated clothing. Rinse skin with water/shower. Wash contaminated clothing before reuse. If skin irritation develops, seek medical advice. For chemical burns, cover the burned area and seek immediate medical attention.
  • Inhalation: Remove victim to fresh air. Keep at rest in a position comfortable for breathing. If breathing stops, immediately apply artificial respiration, if necessary also oxygen. Immediately call a physician.
  • Ingestion: Rinse mouth immediately. Do NOT induce vomiting (risk of aspiration). Give water to drink (two glasses at most) if conscious and able to swallow. Seek immediate medical attention.
• Personal Protective Equipment (PPE):
  • Respiratory protection: Use a full-face particle respirator (type N100 (US) or P3 (EN 143)) where risk assessment shows inadequate ventilation. In emergency situations, use a full-face supplied air respirator.
  • Eye protection: Chemical splash goggles and face shield (mandatory, due to risk of severe eye damage).
  • Skin protection: Chemical-resistant gloves (nitrile, neoprene), acid-resistant protective clothing, and closed-toe shoes.
  • General hygiene: Do not eat, drink, or smoke when using this product. Wash contaminated clothing before reuse. Obtain special instructions before use. Wash exposed skin thoroughly after handling.
• Fire & Explosion Hazards: Pure OIT has a low flash point (23°C) and is combustible. Formulated grades have higher flash points (>65°C). Development of hazardous combustion gases or vapors possible in the event of fire (carbon oxides, nitrogen oxides, sulfur oxides). Use water spray, alcohol-resistant foam, dry chemical, or carbon dioxide as extinguishing media. Prevent fire extinguishing water from contaminating surface water or groundwater systems.
• Environmental Precautions: OIT is very toxic to aquatic life (algal EC₅₀ 0.1–1 mg/L, Daphnia EC₅₀ 0.5–5 mg/L, fish LC₅₀ 1–10 mg/L) with long-lasting effects (H400/H410). Do not let product enter drains. Avoid release to the environment. In case of spillage, cover drains, collect and bind spills, and pump off. Clean up affected area and dispose of properly in accordance with local regulations. OIT is biodegradable in soil and aquatic environments under aerobic conditions.
• Storage & Stability: Store in tightly closed, air-tight, moisture-proof containers in a cool, dry, well-ventilated area away from direct sunlight, heat sources, and strong oxidizing agents. The product is stable in strong UV light and high temperature. Avoid storage above 50°C to prevent decomposition. Under recommended storage conditions (room temperature, low humidity, dark), OIT has a shelf life of 12–24 months from the date of manufacture in sealed original containers.
• Regulatory Compliance: OIT (2-Octyl-3(2H)-isothiazolinone, CAS#26530-20-1, EC#247-761-7) is listed on EINECS, TSCA, DSL, AICS, NZIoC, ENCS, KECI, and other regional chemical inventories. It is an EPA-registered biocide (U.S.) for use in paints, coatings, adhesives, sealants, wood preservation, and metalworking fluids under FIFRA Section 3. However, OIT is no longer approved for use as an active substance in pesticides (biocidal products) within the European Union under the Biocidal Products Regulation (EU) 528/2012 for certain product types (e.g., PT7, PT10 for preservatives for coatings and wood protection). Check local legislation for approval status before formulating (e.g., EU 2015/1759). In the US, OIT is approved for use in food packaging adhesives (FDA 21 CFR 175.105). In cosmetics, Kathon 893 (OIT) is restricted to a maximum use level of 1.5% active in the EU and other jurisdictions. Always consult the Safety Data Sheet (SDS) and local regulations for complete safety, environmental, and regulatory information specific to each product grade and application jurisdiction.