The action mechanism and types of anti-mildew agents for coating are described （一））
2 Performance requirements of anti-mildew agent for coating
The ideal anti-mildew agent should meet the following conditions in the practical application: it has a very high killing ability for the erosion of the coating and the coating of various molds, a small amount, a wide range of application, lasting effect; Harmless to humans and animals, low toxicity or non-toxic, no irritation to the skin and eyes; Does not affect the physical and chemical properties of coating and film; High stability, good heat resistance, light resistance and chemical resistance, small sublimation, not easy to be extracted by water, oil or solvent; Good compatibility with resins and other auxiliaries, no harmful chemical reactions; No corrosion of metal or various materials, no electrical corrosion; No odor, light color, no pollution; Easy to use, low price. It is difficult, sometimes even impossible, to develop mildew protection agents that fully meet the above requirements. All kinds of mildew prevention agents have their own characteristics, some aspects show advantages, others show deficiencies. The synergistic effect of two or more kinds of compound mildew inhibitor can be played by preparation of compound mildew inhibitor.
3 Classification, characteristics and applications
At the beginning of World War II, foreign countries have attached great importance to the research of mildew prevention agents. There is a considerable amount of coating and coating material loss in the world every year on the problem of spoilage and mildew, coating with mildew inhibitor development quickly. Europe and the United States pay attention to the development of organic system, Japan focuses on the development of inorganic system, our country started late, all kinds of systems of mildew prevention agents have been studied, new results and new products have been reported. From the perspective of chemical structure and source, anti-mildew agent can be divided into natural anti-mildew agent, inorganic anti-mildew agent, organic anti-mildew agent and compound anti-mildew agent.
3.1 Natural mildew prevention agent
Most natural mildew prevention agents are refined from animals and plants, including chitosan, serum protein, cinnamon oil, arhan tar, allicin and natural phenols. Chitosan was obtained by removing N-acetyl from the hard parts of shell of natural shells, crabs, shrimp, fish bones and insects. In the process of production and use of natural mildew prevention agent, no pollution to the environment, good biocompatibility. However, the heat resistance of natural anti-mildew agent is poor, and the carbonization decomposition begins at 160 ~ 180℃. The duration of the drug effect is relatively short, and the application scope is greatly limited, and the large-scale commercialization is still some time away.
3.2 Inorganic mildew prevention agent
Inorganic mildew prevention agents are widely used, more kinds, usually silver, copper, zinc and other metal ion antibacterial agents and metal oxides (such as titanium dioxide, zinc oxide and other nano antibacterial agents). The antibacterial mechanism includes contact reaction hypothesis and catalytic reaction hypothesis. The contact response hypothesis is that the contact reaction between metal ions and bacteria causes the destruction or dysfunction of the inherent components of bacteria, leading to the death of bacteria. The catalytic reaction hypothesis is that under the action of light, metal ions and nanoparticles play the role of catalytic active center, activate the oxygen in water molecules and air to produce hydroxyl radicals and reactive oxygen ions, destroy the proliferation ability of bacteria for a short time, resulting in cell death, and play an antibacterial role.
Inorganic mildew inhibitor has wide antibacterial spectrum, safe use, heat resistance and good sustainability, and has become a research hotspot in the field of antibacterial mildew inhibitor. Some inorganic anti-mildew agents have poor performance. It has been reported in recent years that nano zinc oxide has certain anti-mildew performance, but in practical application, its anti-mildew performance is limited.
Cuprous oxide is a red or dark red octahedral cubic crystalline powder, which is widely used for ship anti-mildew and has low use cost. It is especially suitable for military anti-mildew coating, and the dosage is about 40% of the total quality of the coating. Barium metaborate is a white rhombic crystalline powder, mainly used for mildew prevention of water-based latex coatings, the general dosage is 1 ~ 2%.
3.3 Organic mildew prevention agent
Organic mildew inhibitor has wide spectrum, fast action, good bacteriostatic and mildew control effect, but some organic mildew inhibitor has poor heat resistance, short duration of mildew control, and certain toxicity. Organic anti-mold agents mainly include phenolic compounds (substituted aromatics), elemental organic compounds, nitrogen organic compounds, halogenated organic compounds, sulfur-containing organic compounds, etc. This classification method is not rigorous enough, the same compound can be classified into different categories. When organic mildewproof agents contact the cell membrane of microorganisms, they fuse with the cell membrane and gradually enter the cell. Through the action of organelles, proteins, nucleic acids and other structural substances, the cell contents, enzymes, proteins, nucleic acids are damaged, and the propagation of bacteria and molds is inhibited to achieve the purpose of bacteriostasis and sterilization.
I believe that through the above introduction, we have a further understanding of the mechanism and type of coating mildew inhibitor in detail. Please visit our official website for more information about mildew prevention agent, welcome to inquire and negotiate with the factory.
