Messi Biology states that isothiazolinone preservatives (such as CMIT/MIT, BIT, OIT, etc.) possess broad-spectrum and highly effective antibacterial capabilities. They are widely used in coatings, adhesives, detergents, cosmetics, and water treatment agents. However, these active substances are prone to degradation under alkaline or high-temperature conditions. Simultaneously, their release rate in some systems is too fast, easily causing increased irritation or loss of activity. To solve these problems, the introduction of magnesium hydroxide (Mg(OH)₂) as a carrier or auxiliary component can achieve sustained release and pH stabilization, extending the duration of the isothiazolinone’s preservative activity.
I. Sustained-Release Performance Analysis
- Surface Adsorption:
- Magnesium hydroxide has a good specific surface area and porous structure, which can adsorb some isothiazolinone molecules.
- The adsorbed isothiazolinone is gradually released in the system, avoiding high concentrations in a short time that could lead to irritation or inactivation.
- Microenvironment Control:
- In compound systems, magnesium hydroxide can act as a carrier to control the pH of the micro-regions.
- This control helps reduce the decomposition of isothiazolinones caused by pH fluctuations, thereby achieving “dynamic sustained release.”
- Extended Shelf Life:
- Sustained release not only improves the utilization rate of preservatives but also extends the antibacterial cycle of products.
- It is especially suitable for water-based paints and emulsion systems that require long-term preservation.
II. Buffering Performance Analysis
- Gentle Alkaline Regulation:
- Isothiazolinones are sensitive to pH, and excessively acidic or alkaline conditions can lead to their deactivation.
- As a weakly alkaline substance, magnesium hydroxide releases OH⁻ slowly when reacting with water or acidic components, providing buffering capacity and maintaining the pH in a neutral or slightly alkaline range (pH 7~8.5).
- Inhibition of Degradation Reactions:
- Catalytic degradation reactions caused by metal ions, amines, etc., in certain formulations can be reduced by buffering pH fluctuations with magnesium hydroxide, reducing the probability of reactions.
- Especially during long-term storage, the buffering effect helps isothiazolinones maintain a stable state.
- Reduction of By-product Generation:
- In systems with large fluctuations in acidity and alkalinity, isothiazolinones are prone to react with amines, alcohols, and phenols to generate toxic by-products.
- Magnesium hydroxide indirectly inhibits these side reactions by stabilizing the pH, which is beneficial to improving product safety.
III. Application Examples
- Industrial Preservative Formula: Using magnesium hydroxide + BIT, suitable for inks or glues in hot and humid environments.
- Water Treatment Bactericide: Adding magnesium hydroxide to cooling circulating water can improve the service life of isothiazolinones and reduce the frequency of addition.
- In Water-Based Coatings: Mg(OH)₂ particles act as a dispersant, delaying CMIT release and reducing early irritation.