Application of Isothiazolinone Biocides in the Industrial Sector

Isothiazolinone biocides represent a class of broad-spectrum, highly efficient, and low-toxicity non-oxidizing biocides. Their core components, such as 5-chloro-2-methyl-4-isothiazolin-3-one (CMIT) and 2-methyl-4-isothiazolin-3-one (MIT), irreversibly inhibit the growth of bacteria, fungi, algae, and other microorganisms by disrupting protein bonds or DNA structures, ultimately leading to cell death. These biocides are widely and deeply applied across industrial sectors, as detailed below:

I. Key Application Areas

1. Industrial Water Treatment

• Cooling Water Systems: In industries like steel smelting, thermal power generation, and petrochemicals, isothiazolinones prevent microbial biofilm formation on heat exchangers, avoiding corrosion and deposit buildup while enhancing system efficiency. For example, their use in refinery cooling water systems inhibits sulfate-reducing bacteria (SRB), protecting equipment from corrosion.

• Oilfield Water Injection: By killing microorganisms in water injection systems, they reduce formation plugging and equipment corrosion, ensuring efficient oil recovery.

• Wastewater Treatment: In municipal wastewater treatment, isothiazolinones control sludge bulking, improve sedimentation performance, and mitigate foul odor emissions.

2. Pulp and Paper Industry

• Added during pulping, coating, and white water recycling, these biocides prevent microbial contamination of paper, avoiding issues like web breaks, spots, and black patches while stabilizing coatings and additives. China’s paper chemical preservative market exceeds 1 billion RMB, with isothiazolinone derivatives dominating the share.

3. Paints and Coatings

• MIT: Effective for in-can antimicrobial and antifungal protection in coatings, ensuring quality during production and storage.

• BIT: Provides broad-spectrum杀菌 (antimicrobial) efficacy for both in-can and interior coatings, compatible with all stages of paint manufacturing.

• OIT: Excels in antifungal protection for water-based paints, offering weather resistance for exterior coatings.

• As in-can preservatives, isothiazolinones extend the shelf life of coatings by preventing spoilage, deterioration, and discoloration. Examples include:

4. Plastics and Rubber

• In plastic production, isothiazolinones control microbial contamination on mold surfaces and within products, preventing degradation and extending service life.

5. Leather and Textiles

• In leather processing, these biocides prevent microbial-induced production issues, enhancing leather quality and shelf life.

• In textile dyeing and finishing, they protect water-based emulsions, adhesives, and other auxiliaries from microbial degradation.

6. Personal Care Products

• Isothiazolinones (e.g., MIT) are widely used in creams, lotions, shampoos, and hair conditioners due to their compatibility, broad-spectrum efficacy, low toxicity, and eco-friendliness. A mass fraction of 0.03%–0.1% effectively inhibits microbial growth.

II. Technical Advantages

1. Broad-Spectrum Efficacy: Effective against Gram-positive and Gram-negative bacteria, yeasts, molds, and algae.

2. Low-Concentration Effectiveness: Economical, reducing chemical discharge and aligning with sustainability goals.

3. Strong Compatibility: Mixable with chlorine, flocculants, scale inhibitors, and other water treatment chemicals without interfering with their functions.

4. High Stability: Remains active across a wide pH range (stable at pH ≤ 9) and under high temperatures, with excellent UV resistance.

5. Environmental Safety: Biodegrades into non-toxic substances, avoiding long-term accumulation risks.

III. Typical Application Cases

• Cooling Water Systems: A steel plant reduced equipment corrosion by 40% and improved system efficiency by 25% after adopting isothiazolinones.

• Paper White Water Recycling: Paper web breaks decreased by 60%, and coating spoilage was eliminated following biocide addition.

• Water-Based Coating Preservation: A paint manufacturer extended product shelf life to 18 months by replacing formaldehyde-based preservatives with BIT, meeting EU environmental standards.

IV. Usage Precautions

1. Dosage Control:

• For sludge stripping: 150–300 mg/L.

• For biocidal treatment: 80–100 mg/L every 3–7 days.

2. Compatibility: Avoid use with strong oxidizing/reducing agents or sulfide-containing cooling water systems, but synergize with quaternary ammonium compounds for enhanced efficacy.

3. Safety: High doses may irritate skin; personal protective equipment (PPE) is required during handling.

This translation preserves technical accuracy while ensuring clarity for an international audience in industrial and chemical sectors.