What is zinc pyrithione?
Zinc pyrithione is a well-known anti-microbial additive. It is suitable for a variety of applications and has a wide range of uses. It has excellent anti-microbial properties. It is used as a biocide and preservative in metalworking fluids, lubricants, cosmetics, and toiletries.
Zinc pyrithione can be reacted with zinc salts (e.g. ZnSO4) by reaction of 1-hydroxy-2-mercaptopyridine or its soluble salt. It is produced by forming a precipitate of zinc pyrithione.
Zinc pyrithione is used as a broad-spectrum anti-microbial agent and preservative in metalworking fluids, plastics, paints, adhesives, and cosmetics. Its main uses are as an anti-dandruff agent in hairdressing products, as a preservative in various cosmetics, and as an anti-fouling agent in marine paints. Industrial applications of zinc mercaptosulfide in paints, adhesives, blocking agents, and sealants are growing.
The Discoloration Problems
Composites containing zinc mercaptooxypyridine tend to turn blue in the presence of high iron ions. Similarly, in the presence of ultraviolet radiation in sunlight, the pyrimethoprim part may undergo photodegradation. This discoloration is undesirable for aesthetic reasons as well as for some functional reasons involving unwanted color formulations.
Given the aesthetics of paints, adhesives, blocking agents and sealants. After drying to form a dry coating on the substrate, a certain desired color is usually required. And since every effort is made to achieve a specific color effect in the formulation of such products. Therefore, any component that would cause the formulation to differ significantly from the desired color would make the colorant formulator’s task very difficult.
In the past, various methods have been proposed by some experts to solve the problem of turning blue. In the United States, experts have solved the problem by adding alkali metal or alkaline earth metal salts of 1-hydroxyethane-1 1-dilinic acid to paints or functional fluids. In this way, the above-mentioned discoloration problem is solved. However, these solutions are not always as cost-effective or durable as desired.
In addition to discoloration problems, harmful ions can affect the anti-microbial properties of zinc pyrithione. Such as the high iron ion. These performance problems are caused by the fact that zinc pyrithione tends to form blue precipitates in the presence of high iron ions. And also reduces the amount of zinc pyrithione available in the overall composition, thus weakening its biocidal protective properties.
When the paint dries to form a dry film on the substrate, the presence of large amounts of zinc oxide in the paint containing zinc pyrithione will inhibit the short-term (or initial) anti-microbial efficacy that zinc pyrithione confers on the paint. This reduced short-term efficacy can have a negative impact on the performance of the paint, particularly in terms of the film’s resistance to mold growth.
How to Solve Discoloration Problems?
New methods for solving discoloration problems in various aqueous coating compositions containing zinc pyrithione are much needed. This is especially true in paints, adhesives, plugging agents, and sealants.
Preferred solutions should include the ability to enable the use of zinc pyrithione in coating compositions containing iron or copper. And cheaper, more durable, and/or with lower amounts of additives than required by the prior art described above. That is a method that would enable the coating composition to produce improved short and long-term anti-microbial properties and make the resulting coating resistant to microbial attack. It must be much needed by the industry of paints, adhesives, blocking agents, and sealants.
For more details, please refer to the following articles.
Discoloration Prevention in Pyrithione-containing Coating Compositions – https://patents.google.com/patent/EP1348743A1/en