BIOCIDE AND NEUTRALIZING AMINE ANTIMICROBIAL SYNERGY IN PAINT FORMULATIONS

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1 BIOCIDE AND NEUTRALIZING AMINE ANTIMICROBIAL SYNERGY IN PAINT FORMULATIONS Autors: Débora Takahashi, Eduardo Lima (presenter), Fernando Mesquita, Jackeline Silva and Vanessa Sarra. Company: Dow Chemical ABSTRACT Biocides, bactericides and fungicides are important to prevent the deterioration on architectural paints. There are two different applications in paints: a) To prevent the rottenness in wet phase during warehousing and transportation ( in can protection); b) To assure the longlasting performance of paints on dried film phase, after the application on the substrate. In the paint formulation, due to the presence of a considerable quantity of water, bacteria and yeasts are the most often contamination observed. Microbial growth in wet phase ( in can ) usually can be noticed by the product functionality lost, like generation of gas, non-pleasant odor, change of ph, viscosity or color. During the choice of the most functional biocide in order to prevent the paint, ph, process temperature and amines presence must be count on. Regularly biocides used to prevent architectural paints are those which are based on chloro methyl isothiazolinone and methyl isothiazolinone (CMIT/MIT) normally combined with formaldehyde or formaldehyde releaser. It is known that some neutralizers such as ammonia, sodium hydroxide and MEA may inactivate, in different levels, the biocides based on isothiazolinone. In this work was evaluated the antagonist effect on biocides, like CMIT/MIT, benzoisothiazolinone (BIT), combined or not with formaldehyde or formaldehyde releaser, of some agents used to neutralize the final ph of the paint. It was made microbial challenge tests in paints using the Taunovate High Throughput technique to determine the exact concentration of biocides needed to preserve the paint. The results showed that when associated amino alcohols to isothiazolinone (CMIT/MIT) based biocides there is a synergic effect, improving the performance of the paint preservatives. This effect is more evident using amine of a high molecular weight and zero VOC as a neutralizer. The synergy can be used to guarantee the microbial quality of the paints. 1. INTRODUCTION/ BACKGROUND Amines utilized for the neutralization of paint formulations can act synergistically with biocides to enhance the preservation and protection of coatings from in-can microbial contamination. Several commonly utilized paint neutralizers were utilized to demonstrate this effect. Specifically, paint preserved with isothiazolinone biocide chemistries and formulated with different neutralizers was subjected to bacterial challenge tests to evaluate the extent of synergy of BIT and CMIT/MIT with various paint neutralizers.

2 2. EXPERIMENTAL METHODS 2.1. Challenge Test using Taunovate High Throughput (HTP) The challenge test Taunovate High Throughput (HTP) is a method developed by Dow Microbial Control Application Centre in the USA, is a modification in the traditional method, which evaluates the effectiveness of the biocides in control of the contamination caused by bacteria and fungi. This new method utilizes equipment capable of dosing the biocides accurately, as well, making serial dilutions necessary to perform the microorganism counts in conventional tests. Thus, in addition to allowing greater precision in dosages of biocides, greatly increases the ability of test execution. This method can be used to optimize dosages of biocides, preservatives assessment of synergy in formulations as well as for checking the optimal dosage of biocide for the treatment of shock Procedures Preparation of 96-well plates The test is conducted in deep-well plates containing 96 wells, which would allow the implementation of 96 tests, but tests were performed in triplicate, that is, each plate 4 is used to test different systems with 8 different dosages. These plates were used evaluated paints added and biocides tested inoculum of bacteria and fungi Quantification of microorganisms (CFU / ml) The concentration of bacteria present in the sample is determined by using serial dilution (1:10) of the sample inoculated into culture medium with a special dye. After the 24 hour incubation for bacteria and 48 hours for fungi where there is contamination of culture medium changes color and is easily detected by the naked eye. The ranking of the results is done by estimation of viable organisms present in the sample (according to Table 1 below for CFU / ml). For example: If a sample shows contamination up to 4 dilutions of 1:10, this will receive a grade 4, which represents between 5 x 10 4 and 5 x 10 5 viable microorganisms in the total sample. Table 1 - Legend of the results for Challenge Test. 2

3 The counts are done in triplicate on TSB medium for bacteria and YMB for fungi. 3. RESULTS The follow results represents the amount of biocide BIT or CMIT/ MIT necessary to preserve the paint against 4 sequential weekly contamination and different neutralizers used at it study. The paint formulation, containing various neutralization agents and biocide chemistries, was challenged in parallel experiments with separate organism pools (laboratory strains vs. wild strains). The following biocide concentrations were required to protect the paint formulation from four bacterial challenges in the presence of a specific neutralizing agent: Table 2 Final results for Challenge Test. Biocide concentration (ppm) required for protection against four bacterial challenges BIT BIT Paint Neutralizer CMIT/MIT CMIT/MIT lab wild lab strains wild strains strains strains 2-Amino-2-ethyl-1,3-propanediol < Amino-2- Methil-1- Propanol < 100 < Ammonia < NaOH < KOH < NaCO 3 < >25 25 KCO 3 < >25 >25 3

4 A) B) * IV Cycles x ppm of biocide IV Cycles x ppm of biocide Figure 1 Concentration of biocides (ppm of active) effective to control bacteria contamination after 4 innoculation in paints applied different neutralization systems. A) BIT (benzoisothiazolinone) ; B) CMIT/MIT (chloro methyl isothiazolinone + methyl isothiazolonone) 4. CONCLUSIONS CMIT / MIT and BIT are inactivated in different levels by neutralizing agents used in the paint, so from these results is possible conclude that it below sequence of neutralizer showed better performance in synergism with biocides used at the study: 2-Amino-2-ethyl-1,3-propanediol<2-Amino-2- Methil-1- Propanol <Ammonia <KOH <NaOH <KCO3 <NaCO3 The results also showed a synergistic effect mainly with 2-Amino-2-ethyl-1,3-propanediol + BIT, and is possible consider a optimization of BIT levels, obtaining a formulation more preserved and with reduced costs. 4

5 CMIT / MIT is not the most suitable for paints, the best recommendation found from the study is BIT, which is related to the stability and lower deactivation of molecules at ph's which was submitted in an paint formulation 6. REFERENCES Banov, 1978A. Banov - Paints and coatings handbook Wilfried,PAULUS - Directory of Microbicides for the Protection of Materials. A handbook. Allsopp et al., 2004bD. Allsopp, K. Seal, C. Gaylarde - Introduction to biodeterioration ABNT Standardization references: - Challenge test ABNT Dry Film Fungos ABNT Dry Film algas ainda não temos ABNT publicada, utilizamos a ASTM