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    Home > Coatings News > Paints and Coatings Market > Study on antibacterial anti-mold powder coating.

    Study on antibacterial anti-mold powder coating.

    • Last Update: 2020-10-21
    • Source: Internet
    • Author: User
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    Abstract: Using the lowest antibacterial concentration method (MIC) to select antibacterial agents, added to the powder coating, studied the optimal dosage of antibacterial agents, antibacterial anti-mold powder coating antibacterial properties, coating properties, color thermal stability and compatible with other powder coatings.
    keywords: antibacterial agents; minimum antibacterial concentration; antibacterial, powder coatings; anti-mold powder coatings; Paint performance
    Introduction
    With the continuous improvement of environmental awareness and environmental regulations, the paint industry on volatile organic compounds (VOCs) content and harmful substances (HMPS) content control more and more stringent, coating hydration and powdering trend is becoming more and more obvious. As an environmentally friendly coating powder coating, its application range is expanding, from traditional metal substrates such as home appliances, building materials, transportation equipment, machine casings, etc. to non-metallic substrates, such as plastic products, glass products, medium density fiberboard and other . With the expansion of powder coating applications, powder coating is often used in the climate of humid, moderate temperature environment, coating surface may be affected by bacteria, mold and other harmful microorganisms, resulting in film staining, color change, powdering, shedding, loss of the protection of the substrate decoration function, if harmful bacteria and human contact will also infect a variety of diseases, threatening human health.
    years, Japan, Europe and the United States and other countries have developed antibacterial powder coatings, Du Pont, Orion Industries and other companies produced antibacterial anti-mold powder coatings have been widely used in home appliances, automobiles and other fields. Antibacterial coatings in China are widely used in liquid coatings, but they are rarely used in the powder coating industry. By screening the traditional antibacterial anti-mold agent, a compound anti-bacterial anti-mold system applied to powder coating is determined, and the effect of this antibacterial anti-mold agent on powder coating and powder coating is discussed.
    1 experimental part
    . 1. 1 The selection and preparation of antibacterial anti-mold agents
    the microorganisms of erosion coatings are bacteria, mold, yeast and algae, for powder coatings, the more harmful microorganisms are mainly bacteria and mold, therefore, the development of antibacterial anti-mold powder coatings are mainly targeted at these two types of bacteria.
    there are many substances that can be used as antibacterial anti-mold agents, mainly divided into 4 categories: organic antibacterial agents, inorganic antibacterial agents, natural antibacterial agents and polymer antibacterial agents. Inorganic antibacterial agent is the use of silver, zinc, copper, titanium and other metal ions bactericidal or antibacterial ability to make a class of antibacterial agents, the current use of zeolite, silicate, ceramics, insoluble phosphate and metal ions have a strong binding force of the substance Loaded system prepared, inorganic antibacterial agent belongs to the ion dissolved contact antibacterial agent, good heat resistance, broad-spectrum antibacterial, long validity period, low toxicity, do not produce resistance, but easy to change color, preparation difficulties, weak inhibition of mold; Bacteria commonly used in halides, organo tin, isoprain, pyridine metal salts, miloxone, aldehyde compounds, seasonal ammonium salts, etc. , they have a long history of application, low dosage, sterilization speed, easy processing, color stability, good anti-mold effect, but good heat resistance Poor resistance, and easy to produce biological resistance, natural antimicrobial agents mainly have shell polysaccharides, poor heat resistance, limited application, polymer antimicrobial agents are simulated natural polymer antimicrobial synthesis with a certain antibacterial properties of polymer materials, preparation is more difficult.
    Because the powder coating does not contain solvents, composed of resin, fillers, additives and other components, antibacterial anti-mold agent added, requires good compatible with each component does not cause changes in paint color, odor and stability, and can withstand the temperature of the powder coating curing, and does not affect the cross-curing of the powder coating, does not affect the performance of the powder coating. Based on the minimum antibacterial concentration of each antimicrobial agent, this study selected 3 kinds of antibacterial agents, formed inorganic/organic compound antibacterial anti-mold agent, chemical treatment of the composite system, at the same time, the use of high-speed mixing, ball grinding and other physical means of dispersion, refinement, made a powder coating special antibacterial anti-mold agent.
    1. 2 Manufacture of antibacterial anti-mold powder coatings
    the antibacterial anti-mold agents, which account for 1% of the total quality of the coating, are mixed evenly with epoxy resins, polyester resins, leveling agents, degassing agents, fillers and other additives in accordance with the common powder coating formulation, through the twin screw extrusion machine melt mixture, tablet cooling, crushing, and then placed in the ACM grinder, crushed into suitable powder coating.
    Take the appropriate amount of antibacterial anti-mold powder coating, sprayed with electrostature spray gun on the model (model according to the national standard GB / T 1727 production), placed in the oven set temperature, curing the specified time, remove, room temperature placed 24h. According to HG/T2006 -91 (powder coating standard for refrigerators), a comprehensive test of coating performance was carried out, the results of which are seen in Table 1; See Table 2; Test the anti-mold grade in accordance with GB2423.16-90 (Test J: Long Mold Test Method ASTMG21-96) in the basic environmental test procedure for electrical and electronic products, and the results are in Table 3. All of the above tests are done at the same time blank comparison test.
    2 Results and discussions
    . 2. 1 Choice of antimicrobial agents
    The determination of antimicrobial bactericidal ability using the lowest antibacterial concentration method (MIC), i.e. the addition of 105cfu/mL to the nutrient agar culture, testing the minimum concentration of the fungicide required when the bacteria are not long. Table 4 shows the minimum antibacterial concentration of 3 typical antimicrobial agents. 1 is an inorganic nanobacterial agent, it is resistant to Staphylococcus aureus and E. coli, but the inhibition of other molds is weak; Based on the above analysis, it is finally determined that 3 components are used simultaneously, forming an organic/inorganic compound anti-mold agent.
    Inorance antibacterial agent contains heavy metal ions, the curing reaction of powder coating has a certain degree of influence, in the compound antibacterial agent should be used as little as possible in inorance antibacterial agent, at the same time should be chemical treatment of compound antimicrobial agent, in order to reduce the blocking effect of coating resin polymerization reaction. In the formulation design of powder coatings, highly reactive resins should be selected or appropriate catalysts should be added to ensure the full curing of coating resins.
    2. 2 Amount of composite antibacterial anti-mold agent in powder coating (quality fraction)
    In the formulation of ordinary powder coating, add antibacterial anti-mold agent with different mass fractions to make antibacterial anti-mold powder coating, after spraying and curing, test the antibacterial rate (represented by E. coli), the results are seen in Table 5.
    By Table 5, the optimal dosage of antibacterial anti-mold agent should be 1%, at this time the antibacterial rate has reached 98%, further improve the amount of antibacterial anti-mold agent, antibacterial rate increased limited, and will affect the curing reaction of the coating film, but also increase the cost, when the dosage reaches 2.5%, the impact resistance of the cured film becomes very poor, can not meet the protective function of the coating film. Therefore, the amount of antibacterial anti-mold agent should be ≤ 2%, the dosage of 1% can meet the general requirements.
    2. 3 Effect of antibacterial anti-mold agent on color stability of powder coating
    Therefore, it is necessary to study the color stability of antibacterial anti-mold powder coating. Antibacterial anti-mold agent is mainly affected by light, heat and produce color changes, antibacterial anti-mold powder coating to withstand the baking temperature of more than 180 degrees C, therefore, the most important factor is the heat in the process of coating film curing. Thermal stability decreases with the increase in the dosage of antibacterial anti-mold agents, as seen in Table 6. When the dosage is 2%, the thermal stability is poor, at this time, the test color varies with the temperature, see Table 7.
    6 and 7 indicate that the color difference of antibacterial anti-mold powder coatings is acceptable in the range of <2% of the amount of antibacterial anti-mold agents.
    2. 4 Effects of antibacterial anti-mold agents on the compatibleness of powder coatings
    In the process of powder coating construction, there are often compatible problems, if 2 powder coatings are incompatible or poor compatible, it will produce shrink holes, loss of light, pinholes and other problems. Take common powder coating and antibacterial anti-mold powder coating (the basic formula is consistent, only the difference between antibacterial anti-mold content) each 200g, according to Table 8 mixed powder test, the results show that antibacterial anti-mold agent on the powder coating mixing has no effect.
    3 Conclusion
    (1) When selecting antibacterial anti-mold agents, a combination of antibacterial, anti-mold, biological resistance, sterilization spectrum and other factors must be taken into account, inorganic / organic compound system can meet this requirement.
    (2) Care must be taken when selecting antibacterial anti-mold agents, as they contain heavy metal ions that impede chemical reactions between resins in the coating, highly reactive resins must be selected in the coating formulation and the amount of antibacterial anti-mold agents must be minimized.
    (3) Antibacterial anti-mold agent has little effect on the thermal stability of powder coating color and the compatibleness between powders.
    .
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