The biocide producers have to cope with a highly variable demand of the biocidal product consuming industry, the heightened awareness of the danger of germ growth (bacteria, fungi, algae etc), increasing regulatory measures and fluctuating raw material costs.
Regulations with regard to the production and application of biocides are affecting the biocide market in several ways, as they are often restricting the use of biocidal products and increasing the costs of the time-consuming support of biocides under new regulations.
As a result, a couple of biocides are being withdrawn from some applications and traditional chemistries are being replaced with new products.
While the regulations in Europe, America, Asia and other parts of the world are becoming more stringent, officials agree these changes will benefit the global biocide industry. Meeting the additional regulatory requirements will protect consumers and, in the long term, will benefit all stakeholders, customers and product manufacturers.
All water-based coatings contain organic components, which are vulnerable to microbial degradation. Without appropriate preservation in their wet states the paints and coatings become unusable, resulting in customer complaints.
In addition, cured coatings are subject to microbiological attack from fungi, algae and lichens, particularly if the degree of atmospheric humidity is increased.
Dry-film preservatives serve to prevent spoilage in and on the applied and cured paint film. One of the biggest trends in the biocide market is the desire for more environmentally compatible but, at the same time, more cost-effective alternatives, such as no or only little VOC content and minor ecological toxicity of the components.
This directly leads to the need for a high understanding of the intrinsic properties of biocidal actives and the corresponding chemistries. As a consequence, the adequate choice out of a range of legally accepted biocides is of vital importance to prevent paints and coatings from microbial attack and to ensure environmental sustainability.
In this regard the variety of potential chemical compounds is fairly restricted and the allocation of appropriate products becomes more and more sophisticated and a balancing act in terms of product design.
The range of effectiveness of a microbiocide is another important factor to be considered. A full range covering all species of microbes is not always a must.
How far the application of a microbiocide represents a risk to human health and environment depends on the way a microbiocide is applied. In general, risks can be reduced either by using a microbiocide having a low potential to cause harm or by applications leading to low exposures.
Wet state Protection
Lanxess recently launched a set of products based upon the established actives (eg isothiazolinones (CMIT, MIT, BIT), bronopol or dibromodicyanobutane) that are free of any VOCs as well as organic solvents and formaldehyde. Formulated as aqueous dispersions, they are particularly suited for the production of environmentally compatible aqueous formulations, eg low emission wall paints. These products are sold under brand names Preventol, Biochek and Tektamer.
Modern Dry-Film Preservatives
Due to the upgrading of demands on paints and coatings with regard to environmental compliance – such as no or only a little VOC content and minor ecological toxicity – efforts are made from industry to replace biocides under discussion against alternatives, which can meet those requirements but without suffering from substantial losses of efficacy.
Today’s modern dry-film preservatives should provide:
* Broad fungicidal and / or algicidal activity.
* Low water solubility to reduce leaching out of the paint film.
* Low vapour pressure to minimise contamination of the environment.
* Temperature stability to avoid degradation of the active ingredient.
* Compatibility with common paint formulations (no discolouration, neutral odour, pH-value stability).
* Low toxicity/ecotoxicity to be in line with environmental legislation.
* Cost efficiency.
As it is normally not possible to cover all these demands by only one active ingredient, it is often useful to combine two or more actives in order to profit from synergistic effects of those mixtures.
Benchmark for Dry-Film Preservatives - Thiabendazole (TBZ)
In contrast to other fungicides in the market which are classified as ‘toxic’ or at least ‘harmful’, the fungicide Thiabendazole does not lead to classification of the coating, when applied in common dosages. It is therefore particularly appropriate for the formulation of environmental compliant coatings.
Besides film protection in coatings Thiabendazole is also used to control fruit and vegetable diseases such as mould, rot, blight and stain. Thiabendazole is also utilised medicinally as a chelating agent to bind metals.
The product is often used in combination with other fungicides and insecticides. A complete dossier under the Biocidal Products Directive is under preparation for product type 7 (film preservation). For product type 8 (wood preservation) the Standing Committee on Biocidal Products has already decided on the inclusion in Annex I of the Biocidal Product Directive.
There are gaps in efficacy of Thiabendazole against alternaria sp. and some aspergillus sp. that can be closed by a combination with other actives such as N-Octylisothiazolinone, which is highly efficient against the above mentioned fungi.
Thiabendazole is also an excellent supplement for systems where IPBC is used, because the amount of IPBC can be reduced and therefore the risk of yellowing can be decreased as well. Thiabendazole itself does not show such discolouration effects.
A white emulsion paint based upon acrylic binder for indoor use was equipped with 0.5% of a synergistic mixture of Thiabendazole and N-Octylisothiazolinone (approx 28% total active ingredient). The paint was then applied on cardboard and cured. Subsequently, ageing tests were carried out (leaching, wind channel) followed by a standard agar diffusion test on mould resistance. As a result, the samples containing 0.5% of the preservative are well protected against growth of fungi.
To provide environmentally compatible and, at the same time, highly efficient biocides, is of vital importance for the biocide consuming industry. To avoid critical components such as VOCs or formaldehyde in in-can formulations or to minimise the leaching tendency of dry-film preservatives by using modern formulation techniques is the precondition to provide a modern generation of biocidal products, which can meet the requirements of both environmental legislation and the demands of paint producers.