Comparison of the performance of common anti-mold actives in water-based building coatings.

performance of common anti-mold actives in water-based building coatings
Zhang Yeping 1,2, Liu Mingqiu 2
(1. Tol Special Chemicals (Zhenjiang) Co., Ltd., Zhenjiang, Jiangsu 212006;2. Fudan University School of Life Sciences, Shanghai, 200433) 0 Introduction
Bactericides as a necessary additive to the formulation of water-based building coatings, the application of water-based architectural coatings include preservatives and mold inhibitors. Preservatives are used to protect coatings from microbial contamination when wet, and mold inhibitors are used to protect coatings from microbial contamination. This paper mainly discusses the anti-mold agent in water-based building coatings. When the coating is applied to the wall, in a humid environment, the coating film is easily contaminated with mold and algae. Mold may also cause damage to the coating film, the appearance of the wall we usually see black, green, yellowing, cracking, peeling and other phenomena, affecting the visual effects of the coating, and may endanger human health. The coating film contains emulsion polymers, pigments, fillers, as well as film-forming, wetting and other additives, providing nutrients for the growth of microorganisms. When a small amount of mold spores or mold mycelium is attached to the coating through air and other media, in a certain relative humidity, temperature, spores will absorb nutrients and water, and then germinate, the production of substitutable mycelium. The substring mycelium will go deep into the film's internal absorption of nutrients, and will also grow into the air, producing gas-based mycelium. Gas mycelium develops to a certain stage, spores will be produced, and then multiply rapidly and in large quantities, destroying the coating both inside and outside the coating.active ingredient in the coating can act simultaneously or separately on the cell walls, nuclei, or inoculators of mold cells, killing mold spores or inhibiting mold reproduction. Ideal for water-based building coatings mold inhibitors should generally have the following characteristics: (1) broad-spectrum bactericidal activity, especially mold;in a modern industrial environment with a growing concept of sustainability, the architectural coatings market is paying more and more attention to the environmental performance of coatings. Coupled with the introduction of relevant laws and regulations and standards, low volatile organic compounds (VOCs) of water-based building coatings accounted for more than 80% of the market. Water-based building coatings commonly used anti-mold agents according to the active ingredients can be broadly divided into: isoprene, benzodiaxel, iodine propylene, pyrithione and so on. There are mainly 2-hinkyl-4-isopyroid-3-ketones (OIT) and 4,5-dichlorine-N-hinkyl-4-isopyroid-3-ketones (DCOIT). OIT has good anti-mold properties, is a broad-spectrum anti-mold agent, excellent anti-mold performance, good thermal stability, pH stability range (4 to 9.5), water solubility than other common anti-mold agent active substances, is currently widely used as a mold inhibitor. At present, the market also appeared in the use of polymer-wrapped OIT, can greatly improve its weather resistance. DCOIT is also a broad-spectrum anti-mold agent, it has different degrees of effect on bacteria, fungi and algae, the minimum antibacterial concentration (MIC) of the microorganisms tested can be under 20 x 10-6. Because of its certain algae killing properties, the ingredient is also widely used in marine anti-fouling coatings. It is high temperature resistance, anti-UV resistance is very good, because more than OIT two hydrophobic Cl-, so its water solubility is relatively small, because it contains halogens, so the skin irritation is greater. Benzodialyc refers mainly to benzodiaminolamide (BCM), commonly referred to as polybacterial spirit, as a commonly used in-absorption fungicide is widely used in the prevention and control of fruit and vegetable pests and diseases. Its composition light stability is good, thermal stability is good, water solubility is low, but the anti-mold performance is not broad enough. Because of its potential teratogenicity, it is now increasingly restricted in coating-related green regulations. Iodine-propylene mainly refers to 3-iodine-2-propylene butyl acetate (IPBC), IPBC on mold and yeast has a good inhibitory effect, low toxicity, relatively mild, water solubility is relatively high. Because it contains iodine, it is easy to form other compounds under conditions such as lighting, resulting in color change of the paint film. In addition, IPBC is also an excellent wood mold-resistant active ingredient because of its obvious inhibition of common molds in wood. IpBC, which is also specially processed and capsuleized, can also improve its performance in all aspects. It has been shown in the literature that IPBC, which has been specially treated, can also achieve a good rate of loss resistance.To the current market common anti-mold agents are zinc pyrithione (ZPT), copper pyrithione (CuPT) and sodium nithione NaPT), is more used in water-based building coatings for mold inhibitor use is mainly ZPT. ZPT in the application of water-based architectural coatings has only been developed in recent years, it has the effect of killing bacteria, fungi and algae, but its killing effect on certain bacteria and fungi is not strong, and ZPT at low temperatures easy to precipitate lumps, storage requirements are higher. Because it is sensitive to light, there is a certain risk of color change when adding at high doses. At present, water-based building coatings commonly used anti-mold agents are mainly OIT, DCOIT, IPBC, BCM, these kinds of anti-mold agent active ingredients are often used alone or compound.Whether a mold-proof agent has a good anti-mold effect, not only need to consider its mold resistance, but also need to consider its thermal stability and weather resistance, coating on the wall, weather, light, temperature and other environmental factors will affect the effectiveness of mold-proof agent. The purpose of this paper is to make a comprehensive and detailed comparative study of the effects of OIT, DCOIT, IPBC and BCM, which are active ingredients of anti-mold agents in the same formulation system, such as anti-mold, antibacterial, in-tank thermal stability and weather resistance.1 Experimental Part
1.1 Experimental Materials
Microbicide Actives: 2-Hinkie-4-Isopromycin-3-Ketone (OIT), 4,5-Dichlorine-N-Hinkie-4-Isopromycin-3-Ketone (DCOIT), Polybacterial (BCM) and 3-Iodine-2-acetylene butyl acetate (IPBC); GB/T 1741-2007-related mold, ATCC6538 Staphylococcus aureus; potato glucose agar culture (PDA); water-based acrylic elastic wall coating; water, phosphate buffer, methanol, acetylene, tethinfuran, acetic acid.
1.2 Experimental equipment
biosecurity cabinet, culture box, thermostat culture shaker, pipenut gun, oven, high-efficiency liquid chromatography, UV light box, microscope, chroma meter, paint dry film flushing device, refrigerator, blood cell counting board, petri dish, inoculation ring, centrifuge tube, gun head, sample bottle, film manufacturer, plastic film, etc.1.3 Experimental Method
1.3.1 Anti-mold effect test of individual anti-mold agent active ingredients
adding 100 x 10 -6, 200 x 10 -6, 300 x 10 -6, 400 x 10 - 6, 500 in blank water-based acrylic elastic facade coatings OIT, DCOIT, IPBC, BCM, reference GB/T 1741-2007 method, in order to strengthen the harsh conditions of the experiment, the culture base from inorganic salt culture base to PDA (potato, glucose, agar) culture base for testing, because PDA culture is more nutritious, microorganisms (mold) grow more vigorously on it, so that the challenge of mold inhibitors is stronger.
The specific experimental method is: the paint sample on the special piece of paper prepared into a 300 m thick wet film, drying, and then cropped into 50 mm x 50 mm square block, inoculated mold mixed spore suspension and uniformly coated, and then placed the sample block in the middle of the PDA culture base plate. Place the plate in the culture box and culture for 4 weeks at a relative humidity of 25 degrees C and 85%. Scores are made based on the growth of mold on the surface of the sample. Inoculation of mold can be found in Table 1.1.3.2 4 kinds of anti-mold agent active ingredients of the surface antibacterial effect test
in the blank water-based building coatings, respectively, added 500 x 10-6OIT, DCOIT, IPBC, BCM, with reference to JIS Z 2801 method, the use of ATCC6538 Staphylococcus acobacteria test 4 kinds of mold-resistant surface antibacterial effect. The experimental method is as follows: the coating sample is prepared on special paper sheets into a 300 m thick wet film, dried, and then cropped into a 50 mm x 50 mm square block. Prepare fresh Staphylococcus aegypti at ATCC6538, dilute to (0.25 to 1) x 106 cfu/mL, suck 0.4mL to the dry film surface and cover with a 40 mm x 40 mm PE film.
the plate into the culture box, 37 degrees C, 90% of the relative humidity after culture 24 h, through gradient dilution to count bacterial residues.1.3.3 4 types of anti-mold agents in the coating thermal stability test
in the coating, respectively, added about 1,000 x 10-6 OIT, DCOIT, IPBC, BCM these four anti-mold agents, sealed and placed in a 55 oC oven aging for 4 weeks, respectively, to detect the aging samples OIT, DCOIT, IPBC, BCM content.1.3.4 4 anti-mold agent active ingredients weather resistance test
in the blank water-based building coatings, respectively, add about 1,000 x 10-6 of the 4 active ingredients of anti-mold agents, and then use a film reader to prepare 300 m thickness of wet film, room temperature drying. After taking part of the UV aging of the dry film, ultraviolet light box (253 nm) for one month. After the end of aging, the yellowing of the dry film after aging and aging was tested with a color meter, and 3 points were averaged. Then evenly take a few pieces on the non-aging and aging dry film, after solvent extraction, the retention of anti-mold agent in the dry film is tested with high-efficiency liquid chromatography. Take another part of the dry film to simulate the process of rainwater flushing the wall: in one box, the paint film is suspended and soaked in tap water, which flows from the inflow to the exit end at a constant flow rate of 800 to 1,000 mL per minute. After washing 1 d and 12 d respectively, remove the paint film to dry, and then test the content of anti-mold agent in the initial and post-flush paint film with an efficient liquid chromatography method by solvent extraction.2 Results and Discussion
2.1 Anti-mold Efficiency Test
In order to compare the anti-mold efficacy and broad spectrum of the active ingredients in water-based coatings, the experimental reference to the national standard GB/T 1741-2007 conducted anti-mold experiments. The specific scoring criteria for this method can be found in Table 2. The rating is measured by the size of the area where mold grows on the paint film. The results showed that the mold growth area on the paint film was less than 10% when the OIT concentration in the coating was 300 x 10-6, the IPBC concentration was 400 x 10-6, and the DCOIT concentration was 500 x 10-6, while the mold growth area on the paint film was less than 10%, while the BCM concentration was less than 10% on the paint film. It is shown that OIT has the highest anti-mold efficiency of dry film, while BCM has the relatively poor anti-mold efficiency. The specific results of the test can be found in Table 3.2.2 Antibacterial test
If the environment relative humidity is low, the coating's dry film does not have the moisture needed for bacterial growth, so after the coating is applied to the wall, we do not consider its surface anti-bacterial performance. But in some special places, such as public places or hospitals, we would like the coating to have certain antibacterial properties. In order to test the antibacterial properties of each active substance in the coating, we conducted antibacterial tests based on the JISZ2801 method.Antibacterial activity s l g (24 h blank paint sample bacteria residue /24 h added mold inhibitor sample bacteria residue);
sterilization rate s (24 h blank paint sample bacteria residue -24 h added mold sample bacteria residue) / 24 h blank paint sample bacteria residue;
in this method, the antibacterial activity value of 2, i.e. sterilization rate of 99% shows that there is an effective surface antibacterial effect, the specific experimental results can be found in Table 4.results show that the coating containing DCOIT reached 99% sterilization rate under the same 500 x 10-6 active added amount, while the coating containing the active substance OIT, IPBC and BCM was not achieved. It is explained that DCOIT can provide good surface antibacterial properties for the dry film coating of the system at 500 x 10-6, while the surface antibacterial effect of OIT, IPBC and BCM under the system is not obvious. 2.3 4 anti-mold agents are tested for thermal stability in coatings
the stability of mold-resistant agents in the tank affects the shelf life of the coating and the mold resistance of its coating coating after the coating is walled. The thermal stability of several different mold inhibitors in the tank is also compared in this paper, the specific results can be seen in Table 5. In this experiment, after aging at 55 degrees C4 weeks, both OIT and DCOIT had more than 90% of the residue compared to the initial values added, BCM had about 70% of the residue, and IPBC had the lowest residue, at about 67%. Therefore, in this experimental system, OIT and DCOIT show good stability, while BCM and IPBC thermal stability is relatively poor. 2.4 weather resistance test
weather resistance refers to the paint dry film due to sunlight exposure, temperature changes, wind and rain and other external conditions, and the appearance of yellow change, cracking and anti-mold anti-algae antibacterial capacity decline, such as a series of aging phenomena. 2.4.1 Coating dry film high temperature and UV aging performance test
paint on the wall every day under the sun's rays, wherein the temperature and ultraviolet light may cause the color of the coating film to change, the yellow change of the coating film is generally detected with a chromometer, wherein the b-value can be indicated yellow change, b-value higher, yellow change more serious. In order to detect the yellowing of paint film caused by high temperature and UV ultraviolet radiation of each active substance, the coating dry film is made high in this paper.