Solutions for mildew in architectural coatings

Solutions for mildew in architectural coatings

The weather in the south is relatively humid. The obvious impact on the home environment is the wall. If the wall is not waterproof or the quality of the decoration materials is not good, it will inevitably cause the coatings on the wall to become moldy and affect people's lives. For this reason, people have been trying to combat mould for a long time. 

iSuoChem Marketing Department / Edited by Jason 2024-03-05

In the past, people used lime water to paint walls, which had two main effects: sterilisation and decoration. This was the prototype of modern anti-mildew coatings. 

With the development of science, especially the rapid development of anti-mildew and fungicide production and technology, anti-mildew coatings have developed rapidly. Today's anti-mildew coatings are used in workshops such as cigarette factories, breweries and pharmaceutical factories with very harsh environments. For wall decoration, the coating is mould resistant and has a lifespan of more than several decades. The coating is beautiful, highly decorative and has low toxicity.

In the past two decades, China's anti-fungal coatings have developed rapidly, and the outstanding representative is Anhui i-Sourcing (Brand: iSuoChem, it's one of leading coating raw materials who can supply powder coating solutions for customers). They provide necessary solutions for China's anti-mildew coatings and promote the development of anti-mildew coatings.

Formula Design of Anti-mildew Coating

Anti-mildew paints are composed of anti-mildew fungicides, binders（resins）, pigments, fillers and additives. The task of formulation design is to produce anti-mildew coatings that have both qualified anti-mildew and anti-algae properties as well as excellent decorative properties. 

Of course, they must also have sufficient storage stability and construction properties, as well as production operability, etc. . Nowadays, excellent anti-mildew coatings should have the basic properties of conventional architectural coatings, including non-toxicity, no unpleasant odour, pleasing colours and long-lasting effectiveness, making them environmentally friendly decorative functional paints.

1. Selection criteria for antifungal fungicides

The anti-mildew function of anti-mildew coatings is mainly achieved by anti-mildew fungicides. An ideal anti-mildew fungicide must be 

High efficiency: Kills or inhibits the growth of micro-organisms with a small amount of chemical.

Broad spectrum: kills or inhibits a wide range of micro-organisms;
Low toxicity: high safety, does not harm humans or animals, does not pollute the environment, and does not cause irritation to skin, mucous membranes, eyes, etc. Chemicals must be approved by national authorities such as the US Food and Drug Administration (FDA) and the US Environmental Protection Agency (EPA);
Good stability: does not react with other ingredients in the paints, is unaffected by light, heat, acid, alkali and other factors, and is long lasting;
Good compatibility: easily dispersed in coating, but insoluble or difficult to dissolve in water to avoid loss with water, low volatility and difficult to migrate;
Colourless, odourless and non-corrosive: the addition of colour does not affect the quality and performance of the product;
Abundant sources, low prices and easy to use.

2. Binders (Resins) (acrylic resins for coatings)

Not all adhesives used in normal decorative coatings can be used well as binders for anti-mildew coatings.
Acrylic emulsions (iSuoChem® DT, WS series emulsions for coatings), including all-acrylic and styrene-acrylic copolymer emulsions, have excellent film-forming properties, adhesion, chemical resistance and ageing resistance. They are important raw materials for the formulation of architectural coatings (Equivalent to BASF architectural coatings and mp architectural coatings ) and should also be the preferred base material for anti-mildew coatings.

They can be used to produce low VOC or environmentally friendly products, which is highly commendable.

Tips: If you want to learn more about acrylic coatings(acrylic surface coatings), you can click "What is Acrylic coating?" to have a check.

3. Pigments and fillers
The role of pigments in coating formulations is to provide hiding and colour. Most of the actual anti-mildew coatings (Paints) used are light or white, so white pigments are mainly used. Commonly available white pigments include titanium dioxide, lithopone and zinc oxide. Of course, some effect paints also use pearlescent, fluorescent, luminescent or other special effect pigments to give architectural coatings different colours and sensory requirements.
Fillers provide hiding power, storage stability and workability. There are many types to choose from, including calcium carbonate, kaolin, talc, wollastonite and attapulgite. Ultra-fine fillers should be selected to improve the quality of the coating.

4. Additives (coating additives) - Coating Additives to add to coatings to make them stronger.

There are differences in the additives used between waterborne mould control coatings and other systems. Today we will discuss the formulations of the main waterborne Paints.
4.1. Thickeners
Thickeners are a type of important coating additives.

In order to improve the storage stability of the coating, to prevent precipitation and agglomeration of pigments and fillers, to improve the dispersion efficiency of pigments and to improve the rheological properties of waterborne mould control coatings, thickeners need to be added to the formulation. When selecting a thickener, in addition to good thickening power, good water resistance and good stability, particular attention should be paid to the mould resistance of the thickener.

Synthetic polymer thickeners are thickeners that do not cause mould. This type of thickener has developed rapidly in recent years. The types are divided into acrylic, polyurethane(PU thickener) and polyether thickeners.

4.2. Pigment dispersion and surfactant
4.2.1. The dispersion mechanism of a pigment dispersion system is quite complex. The first step in the dispersion process is to improve the infiltration of the pigment by the developer, i.e. to reduce the interfacial tension between the developer and the pigment powder and to increase the infiltration rate. Agglomeration or excessive flocculation, i.e. removing the layer of air that is mainly present on the surface of the pigment. Next, the particles are mechanically ground to reach the primary particle state. Finally, the separated particles are prevented from recombining and maintained in a stable dispersion state.

More knowledge, please refer to pigment dispersion in paint or water based pigment dispersions in our site.
4.2.2. The function of the wetting agent and dispersing agent is to adsorb at the above developer/pigment interface to form a more stable dispersion system more quickly.

Summary

The formulations of waterborne anti-mildew coatings (paints) are listed in Table 1.

5. Manufacture, Product Quality Control and Construction of Anti-Mould coatings (Production of mould protection coatings in protective coatings market).

The basic process of producing an anti-mildew coating is shown in Table 2. 

Firstly, water and additives related to pigment dispersion are evenly mixed in a mixing tank. Solid water-soluble additives should be dissolved beforehand or at this stage. 

Next, the fungicide, pigments and fillers are added and stirred thoroughly to ensure complete wetting of the pigments and fillers. The mixture is then sent to dispersing equipment, such as a sand mill or three-roller mill, for grinding and QC checks the fineness. The resulting slurry is transferred to the paint mixing tank and additives such as base material, defoamer, film forming aid, rheology modifier and pH adjuster are further added and continuously stirred to produce a white anti-mildew coating. If a coloured paint is to be produced, the tinting slurry is added to the white coating to carry out the colouring process. 

Finally, the finished product is filtered and packaged. The products should be stored in a ventilated, dry warehouse away from sunlight, rain, heat sources and frost.