Exterior wall latex paint is a kind of architectural paint that decorates and protects the surface of the building, makes the appearance of the building clean and beautiful, thereby beautifying the urban environment, and at the same time can protect the exterior walls of the building and extend its service life. According to the classification of film-forming substances, the main ones are styrene acrylic, pure acrylic, silicon acrylic, fluorocarbon, etc.

In recent years, the construction coating industry has developed rapidly. With the application of high-tech, new varieties have been continuously developed. Using novel synthesis technology, the development of high-performance (brushing, anti-resistance, alkali resistance, stain resistance, water rinsing resistance, etc.) latex paints that are completely free of organic solvents have attracted much attention. In the future, architectural paints will gradually focus on functionality, or they will need to take into account both decorative and functional. With the rise of modern buildings and the popularization of environmental protection awareness, people have increasingly demanded on latex paint for architectural paint. It can be foreseen that under the guidance of industry policies and the pull of the government, the output of paint will increase year by year, and the market development potential of China's construction and decoration industry is huge.

Sericca is a mineral of mica, a flaky fine-grained mica. It has complete cleavage and can be split into extremely thin sheets, with a large diameter and thickness ratio, elasticity, high temperature resistance (above 600℃), strong chemical corrosion resistance, has a shielding effect on ultraviolet rays, and has a silky luster on the outside, and a delicate and lubricating feel.

In addition, the chemical composition, structure and structure of mica are similar to that of kaolin, and have certain characteristics of clay minerals, namely, they are well dispersed and suspended in aqueous media and organic solvents, white color and fine particles, and have viscosity. Therefore, mica has many characteristics of mica minerals and clay minerals. Its application in coatings can greatly improve the weather resistance, water permeability of the coating film, enhance the adhesion between the coating film and the substrate and the coating film strength, and improve the appearance of the coating film. At the same time, dye particles can easily enter the lattice layer of mica, thus keeping the color from fading for a long time. Therefore, mica powder is a multifunctional filler with excellent price and performance for coatings.

1.1 Effect on the weather resistance of coating films

Use architectural paint with the same formula mixed with the same color ratio without mica powder to conduct artificial aging resistance test. The test results are shown in the table below:

Experimental test results show that adding mica to exterior wall latex paint can greatly improve the weather resistance index of the paint.

1.2 Effect on the water permeability of the coating

Use architectural coatings with the same formula mixed with the same color ratio without mica powder to conduct water resistance experiments. The test results are shown in the table below:

1.3 Wash-resistant experiment on coating film

Use the same formula of the same color-based ratio of the same color-based ratio without mica powder to prepare the same thickness coating film. Fix the upward test piece of the coating film in the test tank of the scrub resistance measuring instrument to conduct scrub resistance data detection. The specific test results are shown in the table below:

1.4 Determination of formula

After production experiments and product performance testing, a relatively good formula was determined, as shown in the following table:

Formula of wet sericaceous powder latex paint

Performance of wet mica powder in exterior wall latex paint

1. Wet mica powder can shield more than 80% of ultraviolet rays, thereby greatly improving the weather resistance of the paint; at the same time, pay attention to the shielding function of mica, which is the extinction effect. It is generally recommended that mica be not used or used less in high-gloss exterior walls.

2. The effect of inorganic minerals on coating film strength in coatings is related to the physical shape of the minerals. They generally decrease in the following order: sheet-like>fibrous>column>granules; mica has a crystal flake structure with a high aspect ratio, and no matter how thin it is, it is a flake structure. In addition, mica has an active hydroxyl group, which is easy to bind and entangle with molecular chains in latex liquid and solvents. Arranged in parallel in the coating film, overlapping up and down, forming a dense layer mesh structure inside the coating film, thereby greatly improving the strength, water resistance and scrubbing resistance of the coating film.

3. Wet mica powder can improve its water resistance in the coating film, and at the same time it can improve the breathable performance of the coating film, so that the bubbles are small or even no bubbles are generated during the construction process; the amount of defoaming agent can be reduced in the coating formulation test.

Application suggestions and precautions

1. The recommended amount of addition is 5%-7.5%.

2. Wet mica powder has certain thixotropic properties and can play a certain thickening effect when used in coatings. If the amount is used too large, the viscosity of the coating will increase greatly. In view of this, when using mica powder, it is advisable to conduct a good test and choose its appropriate amount to avoid thickening too strongly and affecting the quality of the coating.

3. The thixotropic properties of wet mica powder are related to the particle size of the product. The finer the particle size, the greater the thixotropic properties. It is recommended that when using fine mica powder, the appropriate amount of wetting dispersant should be increased in the formula system.