The trend of waterborne and powdered coatings is more and more obvious. With the wide application of waterborne coatings, how to solve the quality problem of waterborne coatings and choose the appropriate anti mildew agent?
The traditional fungicides in coatings include formaldehyde, heavy metal salts, phenol, sodium pentachlorophenol, etc. There are mainly the following fungicides on the market: isothiazolinone; benzoisothiazolinone; formaldehyde slow release agents: organic bromine; organic amines; guatriazine. Formaldehyde releasing agent is one of the most attractive fungicides. Formaldehyde releasing agent is a kind of polymerized hydroxymethyl organic substance, which can depolymerize slowly in a certain period of time and release a small amount of formaldehyde, so as to achieve a certain antibacterial effect. Its dosage is very low, and it will not produce irritating smell in the final product. It is especially suitable for the coating industry with poor sealing and secondary pollution. Formaldehyde releasing agent is the only one of all bactericides with gas-phase bactericidal ability and obvious bacteriostatic effect.
The important index to determine the bactericidal ability of bactericide is the minimum effective concentration (MIC), which is to introduce 1-2 million bacteria / M1 into the agar culture medium, and then test the bactericide concentration when the killing rate reaches 99.9%. Generally speaking, the concentration used in the actual formula should be greater than or equal to MIC. The selection of mildew inhibitor and fungicide is discussed with latex paint as an example. In order to select a suitable fungicide, first of all, it is required to be able to meet the characteristics of the coating and meet its relevant requirements.
1. It has good compatibility with various components in the paint, and will not cause changes in color, smell, stability, etc. after being added.
2. Stable storage in the range of ph6-10.
3. It is suitable for long-term storage at 40 ℃ and processing temperature of 60-70 ℃ is allowed in a short time.
4. Due to the small capacity of the packaging barrel and the poor sealing of the packaging barrel, there is a large space between the top layer of the coating and the top of the barrel, which may lead to secondary pollution. Therefore, the ideal anti mildew fungicide should have the ability of gas-phase sterilization.
5. Good water solubility is required, because microorganisms grow in the water phase, so as to ensure better contact and faster sterilization effect.
6. It is required that the sterilization spectrum is comprehensive and has good sterilization effect on the vast majority of molds and bacteria growing in weak alkaline environment.
7. It is required to have good biodegradability and low environmental toxicity, and minimize the irritation to operators.
Source: paint ink net
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