0 Introduction
With the improvement of people's living standards, people have put forward higher and higher requirements for the living environment. While satisfying the comfortable and healthy needs, fashion beauty has gradually become the goal of people's pursuit. Natural stone is a kind of building material with a long history, which can be made into various styles according to personal preferences. However, with the strengthening of the concept of energy conservation and environmental protection, as well as the limitation of natural stone resources, it is of great significance to study natural stone coatings with high simulation. Waterborne multi-color paint is a kind of coating which is the closest to natural granite in the decorative material of civil building at present. It is a kind of pure water-borne, pollution-free, granite-rich texture polymer materials, this kind of paint decoration on the surface of buildings can produce natural smooth granite texture, with decorative, practical, economic and many other properties. Since the 1990s, waterborne multi-color coatings have been popularized in China, waterborne multi-color coatings have gradually won the favor of the market with high stone simulation, high environmental protection and specific functionality. I believe that in the next long period of time, this paint will be much loved by consumers.
1 factors affecting the simulation degree of waterborne multicolor coatings
At present, the formulation of waterborne multi-color coatings has been relatively mature, people gradually agree that waterborne multi-color coatings, because it has a very high degree of similarity with natural stones, that is, what we call simulation. The color similarity, which is a necessary condition for waterborne multi-color coatings to imitate natural stone, is involved in the simulation first. However, the influence of substrate color, color particle coverage, color particle transparency, substrate smoothness, overcoat paint, spraying process and the stability of colorful particles in finished coatings on the simulation degree are often overlooked. This paper discusses the factors affecting the simulation of waterborne multicolor coatings from the above aspects.
1.1 substrate color
Waterborne multicolor coatings are multiphase suspensions composed of small droplets of waterborne latex coatings as dispersing phase and protective glue solution as continuous phase. The colorful particles are sprayed on the substrate with a special spray gun, showing the primer color through the different coverage of the substrate, producing the effect of simulating natural stone, so the selection and matching of the base color is very important. Natural stone has different color systems. When we get a stone sample, the color of the sample observed at a distance of 3-5m, that is, the primary color for us to determine, that is, the determination of the so-called same color primer. Choosing the color of the same color not only can increase the final fidelity of the waterborne multi-color paint, but also can reduce the amount of waterborne multi-color paint and reduce the risk of hanging because of too much spraying. The same color background also needs to take into account the main color of the colorful dispersed phase particles, the contrast can not be too strong, and eventually the color to be adjusted is slightly lighter than the template itself looks.
1.2 color particle coverage rate
There is a problem of color particle coverage in waterborne multi-color coatings. The area and color of the substrate will be different under different coverage, which will inevitably affect the simulation of waterborne multi-color coatings. Figure 1 shows the effect of water-based multicolor coating under different coverage rates. Fig. 1-a, the coverage rate is about 80%, the color of the substrate is more covered, the color particles are more dense, showing a denser pattern and more hierarchical three-dimensional characteristics of granite; Fig. 1-b, the coverage rate is about 40%, more showing the color of the substrate, the pattern is sparse, the overall appearance is more elegant.

Taking the Karamari gold granite (Fig. 2-c) as an example, it can be seen from Fig. 2 that the whole type of granite is yellow series, and the yellow-brown series is usually chosen as the background color. By observing this kind of rock, five color spots can be extracted, that is, the color grains to be prepared in the preparation of waterborne multi-color paint, namely yellow, orange-red, green, brown and black. In order to embody the sense of color, two brown species, deep brown and light brown, are usually modulated. The final colors are black, dark brown, light brown, light orange red, light yellow and green. According to the calculation, their proportions are 6%, 24%, 16%, 14%, 31% and 8%, respectively. This is also considered to be the most similar color distribution (Fig. 2-d). The pattern of this kind of stone is relatively dense, according to the calculation results, the coverage rate of color grains should reach about 80% to achieve a higher degree of simulation. Moreover, the floating rate of coverage should not exceed 5%. If we go beyond this range, the simulation will decrease.

On the basis of similar color matching, adjusting the coverage rate is a necessary condition to improve the simulation degree, but the simulation degree of colorful coatings can not be judged simply by the coverage rate. And according to the characteristics of the stone itself, combine and
Other elements can be optimized to improve the simulation degree.
1.3 transparent and opaque multicolor granules
Natural stone color level is natural and smooth, and some patterns are clear and transparent, and some are simple and heavy. In order to highlight the characteristics of various patterns of natural granite materials, the transparency of multi-color grains is controlled by controlling the amount of titanium dioxide added in the matrix in the formulation. This is also an important factor affecting the degree of simulation. As can be seen from Figure 2, the brown series of Carla Merih Kim is striped and crystal clear. The color particles do not need to add titanium dioxide to adjust its transparency; the yellow series of markings present a translucent state, usually with 0.5% titanium dioxide added to adjust the transparency. The total amount of titanium dioxide will not exceed 1.5% of the total base material. If the amount of titanium dioxide is too much, it will not only increase the cost, but also affect the size of color particles and the difficulty of color modulation.
1.4 substrate flatness
By spraying waterborne multi-colored coatings on different substrates, such as plane or concave-convex surface, can reflect the characteristics of different stones. Figure 3-E is the effect of spraying on the sand wall paint with concave and convex feel. The color particles attached to the uneven substrate appear more casual, the shape of the particles are different, the overall three-dimensional sense; Figure 3-F for the general flat coating effect, the color particles look clearer, full, complete, close to observe the color dots spread more open, highlighting the overall color effect of the color particles. Figures 4-g and 4-h show that the general plane and concave convex effect of imitation are all higher. According to experience for polished stone multi-purpose plane effect imitation, unpolished rough stone multi-purpose concave-convex effect imitation, can achieve the best simulation.

1.5 top coat
In order to improve the acid rain resistance, weather resistance and stain resistance of the coatings, it is necessary to cover the multi-color coatings. The commonly used varnish has two kinds: high mask and subsurface. Under normal circumstances, a gloss of 60 degrees above 85 degrees is called high gloss, and less than 20 is called matte. The main component of the gloss varnish is the emulsion. The smaller the particle size of the emulsion is, the higher the transparency and luster of the film will be. Therefore, gloss varnish will also have a greater impact on its color. High-gloss varnish can increase the gloss of the color particles by means of mirror reflection, after the wall after the gloss appears as clean as new, brighter color (Fig. 5-k); Matt after the wall color is more gentle, simple and elegant (Fig. 5-j). For the imitation of polished stone, high-gloss mask can be selected to achieve a higher degree of simulation, while for the effect of no polished concave-convex surface, the use of Matt mask can better reflect the characteristics of stone.

1.6 spraying process
Spraying process and simulation also have a direct relationship, in the absence of a reasonable grasp of the spraying process, it is difficult to fully show its true charm. The special spray gun must be used in the spraying of colorful coatings. The discharging rate can be adjusted by controlling the pressure in the tank, the discharging quantity can be adjusted by controlling the gap between the ejector needle and the discharging port, and the spraying speed can be adjusted by controlling the pressure component of the spraying gun. If the discharge volume is too fast, the air pressure component of the spray gun is insufficient, it may lead to flow sagging, and when the pressure is too high, it may lead to the breakage of colorful particles. To a certain extent, the discharge volume is too slow, which reduces the construction difficulty, but increases the construction time and reduces the operation efficiency. Usually, when the control viscosity is 70 ~ 85KU and the air pressure component of spray gun is 0.03 ~ 0.1MP, the workability and coating simulation effect are the best.
1.7 stability of multi colored particles in finished lacquer
The stability of multicolor particles has always been an important factor limiting the development of waterborne multicolor coatings. The finished lacquer produced newly can exhibit perfect stone imitation effect under reasonable background color and suitable spraying process. However, in fact, the paint in the tank until the final construction, there is a very long time between, as short as 10 days and a half months, up to several months, so the stability of multi-color particles has become an important factor affecting the simulation.
In the storage process of waterborne multi-color coatings, the hardening, infiltration and even dissolution of multi-color particles are very easy to occur. After hardening, under the same operating pressure, multi-color particles are difficult to spread out, which leads to a thicker film, and the color is relatively deep, compared with the normal construction effect, there will be obvious color difference. Similarly, the dissolution of multi-color particles directly changes the color composition of waterborne multi-color coatings, and its impact on stone-like effect is fatal. If the color infiltration occurs during storage, not only the color of the multi-color particles will become lighter, but also the overall tone will change after spraying, the color will no longer be clear and bright and appear dark and turbid. In addition, such as in the storage process, the finished paint layer, water separation phenomenon, spraying before mixing improper, will change the size of color particles, and even lead to its color particles completely unrecognizable, and can not complete the spraying. Therefore, the stability of multi-color particles in finished coatings can not be ignored, which is directly related to the finished waterborne multi-color coatings, and ultimately can achieve the desired effect. Therefore, to shorten the storage period as far as possible, to regulate the coating before the construction, to strictly control the parameters during the construction, and to improve the skilled degree of the construction personnel are all worthy of attention, and to be adjusted and controlled.
2 Conclusion
To sum up, in addition to color similarity, the factors affecting the simulation of waterborne multi-color coatings include the selection of background color, color coverage, color transparency, substrate smoothness, gloss of overcoat, stability of finished products and construction technology. At present, waterborne multi-color coatings is still a product to be improved, but it still relies on its unique advantages, in the field of building coatings widely used. To continuously improve the waterborne multicolor paint and coating system will be the focus of the work in the coming period.