SUSTAINABLE GLOBAL BIOCIDE SOLUTIONS

Transcription

1 SUSTAINABLE GLOBAL BIOCIDE SOLUTIONS Dave Alexander Thor Group Limited ABSTRACT The number of antimicrobial actives available for industrial preservation around the world has been severely limited over the past ten to fifteen years, due mainly to European and US legislation. As a result, biocide formulators have been forced to formulate blends of approved actives in the hope that they will provide the performance required, and conform to increasingly restrictive regulations. Actives used for both in-can and dry film preservation have various favourable and unfavourable attributes. Although unfavourable attributes can be reduced by co-formulating with other actives, there is still a need for innovation to arrive at the ideal solution within the bounds of current and future legislation. The novel in-can blend presented in the current paper is capable of offering superior performance against a wide range of microbial contaminants (including tolerant species) than current benchmark biocides, whilst meeting the strictest current legislative requirements. This blend of manipulated approved actives is proving to be the next major innovative step in the development of a biocide suitable for global demand. Dry film actives are also typically blended together for optimal performance and reducing unfavourable attributes. In addition to combining actives, innovative technology restricting the immediate availability of active in the wet product and dry film, provide a means of further enhancing performance or longevity, whilst further reducing unfavourable effects related to humans or the environment. INTRODUCTION All industrial preservatives are inherently toxic to some form of life. The task of the biocide formulator is to focus the harmful effects against target organisms and minimise harm against other species, including humans, higher animals and the environment. Over the past 25 years ever increasing legislation has focussed on protecting humans and the environment, pressurizing formulators into creating antimicrobial products with maximum benefit and minimum risk. As the title of this paper suggests, biocides have to be sustainable well into the future, causing minimal harmful effects but still controlling spoilage organisms which are responsible for millions of dollars of damage to industrial products. Preservatives should be suitable for application globally, adding value without being cost-prohibitive in the end product. All aqueous based compounds are susceptible to microbiological deterioration in the wet form due to the water content and presence of essential organic compounds and trace elements necessary for the metabolism of micro-organisms, in the form of bacteria, moulds and yeasts. Paint has all of the elements to sustain microbial proliferation in the packaging: water, nutrients from binders, extenders and rheological agents, and trace elements from all raw materials. Moist surfaces will support the proliferation of fungi provided nutrients are present. In addition, in the presence of sunlight, algae will establish and grow. Once applied, the dry paint film provides the ideal environment for fungi and algae, provided moisture and nutrients are present. Prevention of biological spoilage is most cost effectively and efficiently achieved by chemical means. Antimicrobial actives are added to compounds during their manufacture and in-can and / or dry film preservation is achieved. Thor Group July 2015 Page 1 of 12

2 INFLUENCE OF EUROPEAN LEGISLATION ON GLOBAL BIOCIDE APPLICATION Global biocide demand is strongly influenced by European and North American requirements and legislation. As the Globally Harmonised System (GHS) extends its influence further around the world, so the use of hazardous chemicals, including preservatives, becomes more restricted. Biocide producers are in a perpetual race to keep abreast or ahead of regulations which are the primary driver of innovative technology today. Regulation (EC) No 1272/2008 is commonly known as the classification, labelling and packaging (CLP) regulation and is based on the Globally Harmonised System (GHS) of classification and labelling of chemicals. Limits on the content of hazardous chemicals that could harm humans and the environment are prescribed, above which hazard labels are required. Changes to the legislation are instituted from time to time, known as Adaptations to Technical Progress (ATP). The most significant change in recent years was the 2 nd ATP (widely known as EUH208), whereby limits for labelling of sensitizing chemicals were significantly reduced, forcing biocide manufacturers and end users to re-think biocide strategies to avoid cautionary labelling on end product containers (Table 1). Any products containing active ingredient levels above the prescribed limits require the phrase Contains XYZ substance. May cause allergic reactions on the label. This also applies to non-biocide raw materials with sensitizing potential. Table 1. EUH 208 phrase limits Active Specific concentration limit (SCL) before 1 June 2015 Concentration limit for EUH208 effective 1 st June 2015 BIT 500 ppm 50 ppm CIT/MIT 15 ppm 1,5 ppm MIT ppm 100 ppm OIT 500 ppm 50 ppm The next significant change will be the 7 th ATP, where the use of formaldehyde will be severely limited in Europe with new labelling restrictions effective 1 January This will have a major impact on its use around the world. Classification as a carcinogen effectively excludes its use, with many countries already banning the substance from consumer products. Current classification at 1.0 % : carcinogen 2, H351 (Suspected of causing cancer) Future classification at 0.1 % : carcinogen 1b, H350 (May cause cancer), Future classification at 1.0 % : mutagen 2, H341 (Suspected of causing genetic defects) The Biocidal Products Regulation (BPR Directive 528/2012), previously Biocidal Products Directive, dictates which actives are available for sale in European member states. The purpose is to limit the number of hazardous compounds e.g. carcinogenic, mutagenic and compounds toxic for mammalian reproduction (CMR) and allow substances from approved sources only to be sold. Actives are approved first, then biocidal products or formulated biocides, with the process expected to extend beyond Levels of volatile organic compounds (VOC) have also become a significant concern over the past few years, aimed primarily at reducing the levels of solvents used, but also affecting some biocidal actives such as formaldehyde. Paint producers ask that the levels of VOC in biocides are reduced such that they do not contribute further VOC content to their paint formulations. Increased awareness of biocides that emit from the dry paint film into the air has led to nonemitting actives becoming more popular. This is particularly pertinent where sensitising biocides occupy indoor airspace, potentially causing an allergic reaction in previously sensitised Thor Group July 2015 Page 2 of 12

3 individuals. Although this affects a very small sector of the population, it is sufficient to stimulate paint producers to avoid biocides with high emission potential in certain product lines. Carbendazim (BCM) has been declared a CMR and PBT (persistent, bioaccumulative, toxic) substance in Europe, hence is under pressure to be substituted with a less harmful substance. In Europe there is already a strong swing away from BCM in favour of fungicides such as OIT, IPBC and ZPT. LEGISLATIVE CHALLENGES IN LESS REGULATED MARKETS The Globally Harmonised System (GHS) is becoming more important in less or non-regulated markets. In order to compete on a global scale, companies based in such markets wishing to export to regulated markets are faced with conforming to the destination country s legislation. Manufacturers are often forced by European holding companies to comply with EU legislation. In Europe conformance with REACH (Registration, Evaluation, Authorisation of Chemical substances) for non-biocidal actives and the BPR have to be achieved. Increasing consumer awareness also puts pressure on manufacturers to restrict the use of hazardous chemicals. Table 2. Summary of EU legislation affecting biocide use in Europe Regulation common name Regulation Influence Biocide type affected Classification, Labelling and Packaging (CLP) Regulation (EC) No 1272/2008 Labelling limits set for all biocides All EUH208 2 nd ATP to Regulation (EC) No 1272/2008 Reduced levels requiring statement Sensitising biocides Formaldehyde reclassification 7 th ATP to Regulation (EC) No 1272/2008 Classification as carcinogen Formaldehyde, formaldehyde donors Biocidal Products Regulation (BPR) Directive 528/2012 Limit on types of substances / biocide product availability All IN-CAN PRESERVATION: THE NEXT GENERATION Legislation continues to restrict the availability and use levels of in-can preservatives. Fewer actives are available compared to the past and the approval process for new actives is expensive and may take many years. Thor Group July 2015 Page 3 of 12

4 Figure 1. Progression of in-can actives towards lower toxicity, less reactive compounds Overcoming these challenges requires careful blending of existing compounds to comply with regulations, and maintain efficacy. Furthermore, all compounds have inherent advantages and disadvantages (Table 3). IN-CAN ACTIVES Table 3. In-can actives advantages and disadvantages 5-Chloro-2- methylisothiazolin-3-one + 2- Methylisothiazolin-3-one 2-Methylisothiazolin-3-one 1,2-Benzisothiazolin-3-one ACTIVE POSITIVE NEGATIVE CMIT / MIT MIT BIT Bactericide / fungicide High efficacy Bactericide Good stability Bactericide / fungicide Good stability Low toxicity Formaldehyde donors HCHO Bactericide 2-Bromo-2-nitropropane-1,3- diol (Bronopol) BNPD Bactericide Low toxicity 2-n-octyl-4-isothiazolin-3-one OIT Fungicide Reactive unstable at high ph, amines, nucleophiles Sensitiser Poor fungicide Combine for best effect Gaps in spectrum Combine for best effect Weak fungicide Toxic CMR substance* Volatile Weak fungicide Nitrosamine formation Poor alkaline stability Reacts with amines, nucleophiles 3-iodopropynyl butylcarbamate IPBC Fungicide Poor stability Zinc 2-pyridinethiol-1-oxide ZPT Fungicide Low toxicity *CMR carcinogenic, mutagenic, toxic for reproduction THOR NOVEL BLEND COMPARATIVE DATA Weak bactericide High concentration for efficacy Thor Group July 2015 Page 4 of 12

5 Direct comparison of the novel Thor blend with commercially available products (Fig. 2) has shown exceptional performance, an average of at least twice as effective as the traditional MIT- BIT derivative benchmark. In order to accurately simulate industry conditions, it is essential that testing includes tolerant industrial contaminants, that are known to be difficult to control. In this case, wild strains of Ps. putida, Ps. aeruginosa and Gluconacetobacter sp were included. Elevated levels of single actives are usually required to control these types of species. Minimum inhibitory (MIC) data alone does not provide a complete picture of the actual efficacy. Further tests in the application must be done to compliment MIC data as reactions in the final product will affect biocide performance. In this case pure acrylic paints were tested using bacteria and yeasts in the ula (see Tables 4-6 below). The Thor Novel Blend performed best with the lowest total active content. Multiple ulations (eight in this case) would not be expected in the production environment, hence good preservation will be achieved under normal production conditions. At the levels tested both products are approved for use in the EU, without the need for hazard labels. The Thor Novel Blend is VOC, formaldehyde and CIT free and degrades to innocuous compounds. Figure 2. Comparison of efficacy values of the new Thor Novel Blend with a standard industry MIT-BIT derivative product. Lower figures indicate higher efficacy. Table 4. In-can test against bacteria and yeast in standard acrylic EU paint Dose level Product(s) 1 st 2 nd 3 rd 4 th 5 th 6 th 0.20% Thor Novel Blend Pass Pass Pass Pass Pass Pass 0.20% *MIT-BIT Derivative Pass Pass Pass Pass Pass Fail MIT Methylisothiazolinone, BIT - Benzisothiazolinone Thor Group July 2015 Page 5 of 12

6 Table 5. In-can test against bacteria in alkaline acrylic USA based paint Active (ppm) Product 1 st 2 nd 3 rd 4 th 5 th 6 th 7 th 8 th 0 Blank Fail Fail Fail Fail Fail Fail Fail Fail 150 MIT-BIT Pass Pass Pass Pass Pass Pass Pass Fail 88 *MIT/M-BIT Pass Pass Pass Pass Pass Pass Fail Fail 115 **BIT/ZPT Pass Pass Pass Pass Pass Fail Fail Fail 75 Thor Novel Blend Pass Pass Pass Pass Pass Pass Pass Pass * MIT Methylisothiazolinone, M-BIT Methyl benzisothiazolinone ** BIT Benzisothiazolinone, ZPT Zinc pyrithione Table 6. In-can test against yeast (wild type Candida) in alkaline acrylic USA based paint Active (ppm) Product 1 st 2 nd 3 rd 4 th 5 th 6 th 7 th 8 th 0 Blank Fail Fail Fail Fail Fail Fail Fail Fail 150 MIT-BIT Pass Pass Pass Pass Pass Pass Pass Fail 88 MIT/M-BIT Pass Pass Pass Pass Pass Pass Pass Fail 115 BIT/ZPT Pass Pass Pass Pass Pass Pass Pass Pass 75 Thor Novel Blend Pass Pass Pass Pass Pass Pass Pass Pass DRY FILM SOLUTIONS: ADVANCED MICRO MATRIX EMBEDDING (AMME ) Dry film biocides are essentially microbistatic, preventing the proliferation of deteriogenic organisms on a surface. They are highly effective but performance tends to be hampered by various negative attributes (Table 7). Blending of actives has partially reduced the disadvantages of the single actives. The next step has been to reduce release by confining active molecules in an organic matrix. Restricted/controlled active release is not a new concept. The pharmaceutical and agricultural industries have employed this technology for decades. But numerous attempts to apply the principle to dry film fungicides and algicides have not yielded satisfactory results: the active may be too well bound in the application reducing its efficacy or may not be adequately controlled resulting in rapid release from the paint film or even prior to application. The concept employed by Thor has shown exceptional results, beyond initial expectations. A novel method of encapsulation in an organic matrix has been developed and perfected over the last 14 years, effectively overcoming these challenges. Long term efficacy and stability are some of the advantages already proven in practical use in climates around the globe. Thor Group July 2015 Page 6 of 12

7 Table 7. Dry film compounds advantages and disadvantages ACTIVE POSITIVE NEGATIVE 2-n-octyl-4-isothiazolin-3-one OIT Fungicide Broad spectrum High water solubility EUH phrase 4,5-dichloro-2-n-octyl-4- isothiazolin-3-one DCOIT Fungicide Low water solubility Good envirotoxicity profile Broad spectrum Strong sensitiser Poor in-can stability esp. high ph EUH phrase Strong labelling 3-iodopropynyl butylcarbamate IPBC Fungicide Broad spectrum Poor alkaline stability Discolouration High water solubility Methyl-N-(2-benzimidazolyl) carbamate (Carbendazim) BCM Fungicide Low water solubility Gaps in activity spectrum CMR & PBT substance Zinc-bis(2-thiolpyridine-Noxide) 3-(3,4-dichlorophenyl)-1,1- dimethylurea (Diuron) 2-tert-butylamino-4- ethylamino-6-methylthio1,3,5- triazine (Terbutryn) ZPT DIU Fungicide Low toxicity Low environmental toxicity Algicide Discolouration High levels required Poor ecotoxicity profile Poor in-can stability in certain formulations Carcinogen cat. 2 TERB Algicide Poor ecotoxicity profile Negative attributes of certain actives, such as excessive leaching due to water solubility can be overcome with Advanced Micro Matrix Embedding (AMME ), giving new life and possibilities to preservatives. Extensive testing and practical experience has elevated AMME products to one of the most widely used dry film product types. Advantages include lower active content required, enhanced longevity / performance, reduced human and environmental toxicity, lower leaching, improved in-can and dry film stability (Fig. 3 and 4). Figure 3. Reduction in actives and long term retention AMME vs Standard formulations Thor Group July 2015 Page 7 of 12

8 Standard biocide formulations tend to be added to applications in excess to compensate for loss of active through in-can or dry film degradation, emission and leaching. AMME based biocides can be dosed at lower levels whilst maintaining performance for longer. Figure 4. Advantages of AMME Improved efficacy against fungi and algae Lower active levels required Reduced leaching Reduced release Reduced air emissions Efficacy Release Toxicity Stability Reduced environmental toxicity Reduced mammalian toxicity Improved biological degradability Improved alkali stability Improved thermal stability / tolerance Improved UV stability Reduced risk of discolouration Reduced in-can degradation AMME SUCCESS IN PRACTICE Both laboratory and practical exterior exposure studies were employed to evaluate the efficacy of AMME based preservatives. Exposure sites in Germany, Sweden, United Kingdom, Japan, Malaysia, USA and Australia were selected and various biocides evaluated in exterior coatings. Thor Group July 2015 Page 8 of 12

9 Microbiological and analytical data were collected over 3 to 5 years and the most effective AMME blends identified. Figure 5. Silicone paint 1,500 ppm Standard and AMME OIT 24 months outdoor exposure (facing north-north east, 45o) Blank AMME OIT Standard OIT Due to the high water leachability / solubility it would be expected that OIT would rapidly leach from the paint film. The retention mechanism of AMME prevented excessive loss of OIT providing extended efficacy compared to the active in the standard form (Fig. 5). Figure 6. Exterior roof paint after 3 years exterior exposure In this evaluation, the standard algicide used was Terbutryn and the AMME actives consisted of OIT, ZPT and Terbutryn (Fig. 6). Optimal ratios of fungicides and algicides in the AMME form provided better performance at lower levels compared to excessive levels of standard Thor Group July 2015 Page 9 of 12

10 active. The levels of active could be reduced, as well as leaching into the environment, providing a far safer product with improved performance. Figure 7. Exterior exposure Malaysia AMME Diuron vs standard Diuron after 24 months Blank Standard Diuron AMME Diuron The tropical climate of Malaysia is conducive to excessive and rapid fungal and algal growth. Coatings normally require elevated levels of dry film biocides in such challenging conditions, but AMME technology enhances the performance of Diuron, a common algicide used in the region (Fig. 7) resulting in better active retention and performance. Figure 8. Exposure trial north-west Australia after 21 months Thor Group July 2015 Page 10 of 12

11 Key: AMME based preservatives Standard OIT/BCM/Diuron DCOIT/IPBC and IPBC/Terbutryn types Blank Preservative free Two paint types were used in this evaluation: low sheen (top two rows) and gloss pure acrylic (lower 2 rows). Panels were placed at an angle of 45 o facing south. High solar radiation, approx. 320 days a year, and a high dew factor promote excessive growth of fungi and algae. AMME based products performed the same or better, at lower total active levels, than the benchmark OIT/BCM/Diuron (Fig. 8). Figure 9. Reduced environmental toxicity of AMME vs standard algicides Traditional algicides are under close scrutiny due to their ecotoxicity. The European Water Framework Directive lists terbutryn and diuron as priority substances, requiring monitoring in natural water courses. Although not banned, some manufacturers prefer to exclude algicides from their formulations. AMME versions of these algicides are significantly less ecotoxic than their standard countertypes (Fig. 9). Bioavailability, or the degree of availability a substance has at the film surface, is subsequently reduced. This allows for reduced environmental labelling, alleviating the need for hazard symbols on paint packaging. Where algicides are not permitted, in spite of reduced ecotoxicity, the next generation of dry film biocides available are algicidal without the use of a traditional algicide. This is only possible through the use of AMME technology. CONCLUSION In order to fulfil the concept of sustainability on a global scale, various criteria need to be considered. Chemicals are expected to be increasingly safer for humans and the environment whilst still maintaining their core function. The biocidal solutions discussed in this paper are already commercially available and are expected to fulfil the requirements of the coatings industry now and in the future. References Alexander, D.G. Beneficial dry film biocides. PPCJ. Jan 2012 Guidance on the Application of the CLP Criteria, ECHA Guidance to Regulation (EC) No 1272/2008 on classification, labelling and packaging (CLP) of substances and mixtures Thor Group July 2015 Page 11 of 12

12 Version 4.0, November 2013 Paulus, W.E. Directory of microbicides for the protection of materials a handbook. 2005, Springer REGULATION (EU) No 528/2012 OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 22 May 2012 concerning the making available on the market and use of biocidal products Thor Group July 2015 Page 12 of 12