Wastewater Treatment Glossary: What Is Isothiazolinone?
What Is Isothiazolinone?
Isothiazolinone mainly consists of 5-chloro-2-methyl-4-isothiazolin-3-one (CIT) and 2-methyl-4-isothiazolin-3-one (MIT). Its vapor pressure is 0.328 mmHg at 25 °C and its boiling point is 200.2 °C at 760 mmHg.
Mechanism of Action
Isothiazolinone kills microorganisms by breaking the protein bonds of bacteria and algae. Upon contact with microorganisms it rapidly and irreversibly inhibits their growth, leading to the death of microbial cells. It therefore has a strong inhibitory and biocidal effect on common bacteria, fungi and algae. It offers high biocidal efficiency and good degradability, with the advantages of leaving no residue, safe handling, good compatibility, strong stability and low cost of use. It is miscible with chlorine and with most anionic, cationic and nonionic surfactants. At high doses, isothiazolinone is remarkably effective at stripping biological slime (biofilm).
Properties and Uses
Isothiazolinone is a broad-spectrum, highly efficient, low-toxicity, non-oxidizing biocide. It is widely used in oilfields, papermaking, pesticides, cutting fluids, leather processing, printing inks, dyes, tanning and other industries.
For Class 2 isothiazolinone products (CMI/MI mass fraction as specified by the standard), the typical dosage is 150-300 mg/L when used as a slime stripper. When used as a bactericide, it is dosed once every 3-7 days at 80-100 mg/L. It can be used simultaneously with oxidizing biocides such as chlorine, but must not be used in cooling water systems containing sulfides. Combining isothiazolinone with quaternary ammonium salts gives the best results. When used as an industrial fungicide and mildew preventive, the usual concentration is 0.05-0.4%.
Isothiazolinone is packaged in plastic drums of 25 kg each or as required by the customer. It should be stored indoors in a cool place and has a shelf life of ten months.
Safety Precautions
Isothiazolinone is corrosive and irritating to skin and eyes. Operators should wear protective goggles and rubber gloves. If it contacts skin or eyes, flush immediately with plenty of clean water. If skin contact occurs, remove contaminated clothing and shoes at once and rinse with plenty of water for at least 15 minutes, apply urea acetic acid ointment or burn ointment to the affected area, and seek medical attention immediately.
History of Synthesis
In 1963, Goerdeler and Mittle published a preparation method for isothiazolinone, obtained by halogenating P-thioketone amides in an inert organic solvent.
In 1965, Grow and Leonard proposed that beta-thiocyanoacrylamide or thioacrylamide treated with an acid (such as sulfuric acid) can produce isothiazolinone.
In the 1970s, Rohm and Haas of the United States filed patents for preparing isothiazolinone homologs by reacting 3-hydroxyisothiazolinone with a halogenating agent.
In 1973, Rohm and Haas proposed a new preparation route for isothiazolinone homologs: reacting dithiodiamide with a halogenating agent in an inert solvent.
In 1974, Rohm and Haas again proposed a method using mercaptoamide as the feedstock to prepare isothiazolinone.
A commonly used synthesis route is ring-closure from dithiodipropionyl chloride to produce isothiazolinone biocides.
Isothiazolinone compounds can also be synthesized by ring closure from ortho-N-substituted benzamides.
