Influential Factors on Raindrop Imprint Resistance of Exterior Wall Latex

Ding Shuai, Gao Xitian, Lin Lisa, Chu Huilai, Xue Xiaoqian (Hebei Chenyang Industrial & Trade Group Co., Ltd., Baoding, Hebei 072550, China)

Abstract : Some experiments in terms of wetting agent, dispersant, filler, PVC, emulsion and colorant, etc. have been carried out. Thus, the influential factors on raindrop imprint resistance of exterior wall latex have been provided.

0 Introduction
With the improvement of people’s aesthetic requirements, architecture The colors painted on the objects also become gorgeous. Although dark paint looks dull in color, the paint film has a long life and is not easy to change color and lose light. Due to long-term consideration of the performance of the paint film, most of the building exterior walls have chosen to paint with dark paint as the decorative color. Rain marks, the ill known as “wall cancer” by the paint industry, have been accompanied by architectural exterior wall paint. Especially shortly after construction, the wall was exposed to light rain. After the rain, the wall will bloom, which greatly affects the decorative effect of the paint film. The effect of rain marks will not improve until after several rains, until they disappear. This problem is related to many factors that form the coating. This article tests and discusses the factors such as additives, filler varieties and particle sizes, and the amount of PVC, emulsion, and colorant added, and draws some conclusions.

1 Experimental
1.1 Experimental materials and instruments
Wetting agent A (non-ionic alkoxylated alcohol), wetting agent C (special alcohol surfactant): The Dow Chemical Company; wetting agent B (alkyl polyoxylate) Vinyl ether): Shenzhen Hairun Chemical Co., Ltd .; Wetting agent D (fatty alcohol alkoxylate): Sasol Chemical Co., Ltd .; Kaolin: Inner Mongolia Sanhe Calcined Kaolin Co., Ltd .; Wollastonite powder: Dalian Dadingshan Silicon Greystone powder factory; Talc powder: Beijing Liguo Weiye Superfine Powder Co., Ltd .; Calcium: Wuhan Guangfu Building Material Co., Ltd .; Mica powder: Shenzhen Haiyang Powder Technology Co., Ltd .; Emulsion 1: BASF styrene-acrylic emulsion; Emulsion 2: Hebei Xinguang styrene-acrylic emulsion; Emulsion 3: Yantai Baolijia styrene-acrylic emulsion. Frequency modulation type disperser, model QSJ-Ⅲ: Tianjin Yonglida Material Testing Machine Co., Ltd .; digital display electrothermal constant temperature blast drying oven, type 101-2 A: Shanghai Jinping Instrument Co., Ltd .; scraper fineness meter, 0- 100um: Tianjin Yonglida Material Testing Machine Co., Ltd .; electronic balance, model YP20002: Shanghai Guangzheng Medical Instrument Co., Ltd .; KU viscosity meter, model KU-2: BROOKFTELD.

1.2 Test formula and preparation process
1.2.1 Basic formula.
The basic formula of the test is shown in Table 1.

Basic formula

1.2.2 Preparation process
First, add the water in the formula to the container, slowly add hydroxyethyl cellulose under low speed stirring, add the amine neutralizer after homogeneous dispersion, and stir for 2 min. Then add wetting agent, dispersing agent, propylene glycol, bactericide, and defoaming agent in order, and mix for 2 minutes. Then slowly add powders such as titanium dioxide, kaolin, wollastonite, and heavy calcium, and then disperse at high speed for 30 minutes to a fineness of ≤55 μm. After adding the emulsion, disperse the alcohol ester, defoaming agent, antifungal agent, thickener, etc. slowly after the dispersion is uniform, and adjust to the proper viscosity.

2 Results and discussion
Many of the rain marks are bright spots or slight changes in color where there is rain on the surface. In order to determine whether the rain marks are caused by the precipitation of surfactants, first perform a verification experiment: place the test panel after painting flat, drip a little tap water, and collect the water in a small bottle after a certain time, and another small bottle Fill ordinary tap water into the bottle and shake two bottles of water at the same time. It can be found that a large number of bubbles are generated in the water bottle collected on the test panel, and the bubbles are not easy to eliminate; while ordinary tap water generates fewer bubbles and is quickly eliminated.
From this, it can be determined that surfactant precipitation does occur after soaking in rainwater. Three major sources of surfactant precipitation: wetting and dispersing agents added to coatings; surfactants in emulsions; surfactants in color pastes.

First look at the effect of wetting and dispersing agents on rain marks.
2.1 Influence of Wetting Agent Types In
this experiment, four kinds of wetting agents A, B, C, and D were used to test the influence of different wetting agents on rain marks.
The glass plate was used in the experiment to eliminate the influence of the substrate on the rain marks. After 2 times of roller coating application, bake at 50 ℃ for 30 min. Lay the test panel flat, drip water with a wash bottle, and observe the degree of rain marks after the water is dry. The results are shown in Figure 1.

Effects of wetting agents on rain marks

It can be seen from Figure 1 that the effects of rain marks from good to bad are: D, C, A, B.

2.2 Effect of
dispersant addition amount When the dispersant addition amount is 0.6% and 1% respectively, the degree of influence on rain marks is shown in Figure 2.

The effect of the amount of dispersant added on rain marks

It can be seen from Figure 2 that the addition of 0.6% dispersant is better than the rain mark of 1%. Increased dispersive dose, severe rain marks. This conclusion is also consistent with the theory. Because the dispersant contains more surface active ingredients, the more the amount of dispersant added, the more surfactants are brought in, and the more severe the rain mark phenomenon.

2.3 Effect of Filler Types The effects of
five kinds of fillers, kaolin, wollastonite, talc, heavy calcium, and mica powder, on rain marks were tested. The test formula is shown in Table 2. The degree of influence of filler types on rain marks is shown in Figure 3.

Effect of Filler Type
Effects of filler types on rain marks

It can be seen from Figure 3 that wollastonite is the best, mica powder is the worst, and kaolin, talc and heavy calcium are not much different.

2.4 Impact of PVC
By adjusting the amount of heavy calcium added, the rain marks at 35%, 40%, and 45% of PVC were tested. The test formula is shown in Table 3. The effect of filler PVC on rain marks is shown in Figure 4.

Test formulations for different PVCs
Impact of filler PVC on rain marks

It can be seen from Figure 4 that when the filler content is 35%, the rain marks are bright; when 40% and 45%, the rain marks are not bright and the color is different. Rain marks work better at high PVC.

2.5 Impact of filler particle size
Replace CC700 and 800 mesh talc powder with CC500 and 425 mesh talc powder, respectively, and test for rain marks. The test formula is shown in Table 4.

Test formula for different filler particle sizes

The effect of filler particle size on rain marks is shown in Figure 5.

Effect of filler particle size on rain marks

It can be seen from Fig. 5 that the coarse particle size filler is not as good as the fine particle size filler.

2.6 Effects of
emulsions Styrene-acrylic emulsions for exterior wall paints from three different manufacturers were selected and tested at the same dosage. The test results of rain marks are shown in Figure 6.

Effects of emulsions on rain marks

It can be seen from Figure 6 that the effect of the same type of styrene-acrylic emulsion on rain marks is not much different.

2.7 Effect of Addition of
Color Paste Fig. 7 shows the rain marks when Hyde color paste is added at 6%, 8%, and 10%, respectively.

Effect of the amount of colorant addition on rain marks

It can be seen from Fig. 7 that 10% color paste addition amount is the worst, followed by 8%, and 6% is the best. Therefore, the rain mark phenomenon becomes more serious with the increase of the amount of color paste.

3 Conclusions The
above experiments tested the influence of the amount of wetting and dispersing agent, filler type, PVC, emulsion, color paste on the rain marks. It can be seen from the experimental results:
(1) Wetting agents have a greater effect on rain marks, and the effects of different wetting agents on rain marks are different. Consider using a professional anti-rain mark wetting agent to prevent rain marks The effect is good, and the most appropriate wetting agent should be selected after experimental observation before use.
(2) The higher the amount of dispersant added, the more severe the rain marks. Therefore, the effect of the amount of dispersant on rain marks should be considered during the experiment, and the amount of dispersant added should be controlled;
(3) The effect of different fillers on rain marks The experiment shows that wollastonite is the best, mica powder is the worst, kaolin and talc Not much different from heavy calcium. For other commonly used fillers, you can also refer to this method for testing, and try to avoid using powders with poor rain marks as fillers. When selecting the particle size of the powder, the rain marks of fine particles are better than those of coarse particles;
(4) PVC also has a certain effect on the rain marks of the coating. In the above experiment, when the filler amount is 35%, the rain marks are bright; at 40% and 45%, the rain marks are not bright, but the color is different. It can be seen that the effect of rain marks at high PVC is better than that at low PVC, and it can also be used as a reference when designing the formula;
(5) Three manufacturers of the same type of styrene-acrylic emulsion were selected for testing, but the rain marks were not much different. It can be seen that the effect of the same type of styrene-acrylic emulsion on rain marks is not much different; the amount of surfactant added in the color paste formula is quite different. The higher the amount of colorant added during color mixing, the more surfactants are brought in, and the more severe the rain marks, so the maximum amount of colorant added must be controlled when coloring, especially when adjusting dark paint. To control the occurrence of rain marks.

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