Résumé : |
Microbiological spoilage of aqueous based surface coatings can result in severe economic loss to the manufacturer if it happens during production, with even greater problems occuring if such growth is not noticed until the paint reaches the end user.
The effects of bacterial and fungal activity are viscosity loss, gassing, malodour and visible surface growth. In addition, discolouration and alteration in the rheology of the formulation can result in the product being unacceptable to the customer.
As well as these obvious problems, caused by growth of bacteria and fungi, the presence of microbially producted enzymes can lead to changes in the product long after manufacture. Breakdown of cellulosic thickening agents may, therefore, result in viscosity loss even after the micro-organisms causing it have been destroyed by the addition of a biocide.
In addition, changes in manufacturing practice, product types and raw material composition during the pasto two decades have resulted in paint formulations becoming more susceptible to bacterial and fungal growth in the wet state.
These factors, combined with the continuing trend towards lower toxicity, more environmentally acceptable biocides, which tend to be less persistent in the manufactured product, have resulted in increased incidences of microbial infection.
The use of ever increasing concentrations of more highly active biocides is not the complete answer to these problems. Instead, the producer, with the help of the biocide manufacturer product, have resulted in increased incidences of microbial infection.
The use of ever increasing concentrations of more highly active biocides is not the complete answer to these problems. Instead, the producer, with the help of the biocide manufacturer, must critically look at the whole production operation from a microbiological point of view.
Improvements in plant hygiene, including examination and possible modification of plant design and more frequent and thorough cleaning, including a biocidal wash, will help of the biocide mnaufacturer, must critically look at the whole production operation from a microbiological point of view.
Improvements in plant hygiene, including examination and possible modification of plant design and more frequent and thorough cleaning, including a biocidal wash, will help to alleviate problems. Changes in production practices, such as avoiding storage of stock thickener solutions and careful monitoring of raw materials will bring about further improvements.
These activities, allied with the use of effective broad spectrum biocides, will at least decrease incidences of microbiological contamination and at best eliminate such infection altogether. |