Li Wei （Shanghai Saiguan Construction Developing Group Co., Ltd., Shanghai 201708，China）
Abstract：Compared with the commonly used water-in-water multi-color coatings，the water-in-sand multicolor coatings can form a three-dimensional granite-like effect without a moulding layer in a single coat. However，due to the addition of a large number of sand in the basecoatings，which caused a greater adverse impact on its performance. In this paper，the preparation of sand-in-water multicolor coatings was studied experimentally. Parallel experiments were carried out on the influence of amount of protective glue，types and dosages of wetting agents，types and dosages of cellulose ethers. When the dosage of protective glue GS was 10%~12%，wetting agent 399 was 0. 4%~0. 6%，and the dosage of cellulose 250HHBR was 1. 2%~1. 4%，respectively，the sand-in-water multicolor coatings provided excellent bleeding resistance，blushing resistance and stability
Compared with real stone paint and texture paint, multicolor coating has won more and more users’ favor with its advantages of high degree of simulation, light weight, fast construction speed and low cost. However, the multicolor coating has a flat effect and does not have the texture of real stone paint. In order to make the multicolor coating have a texture effect, the current commonly used method is to use real stone paint as a modeling layer, and then spray multicolor coating on it, which not only adds a process but also adds materials. cost. For this reason, water-in-sand multicolor coatings have emerged at the historic moment, and they can have the simulation degree of multicolor coatings and the texture effect of real stone paints in one spray. Because the dispersed phase in the sand-in-water multicolor coating contains sand with a higher density, the stability is poor. Due to the large particle size of the sand, the flexible continuous film formed by the gelation of the protective gel on the surface of the color point has defects. As a result, the color point is fragile, and the color paste in the color point is precipitated, which causes serious bleeding and affects the hue. Moreover, the color point in the finished product is liable to sink to the bottom. In addition, due to the addition of sand, the water whitening resistance of sand-in-water multicolor coatings also deteriorates. Due to the above-mentioned shortcomings of sand-in-water multicolor coating, its use in building exterior walls is restricted.
Because the water-in-sand multicolor coating is an emerging paint variety, the related research literature is less. Su Guohui and other preferred protective gums, emulsions, aggregates, and cellulose ethers, to prepare sandy colorful coating products with excellent long-term storage stability. In order to store the color point without sinking to the bottom, hollow microbeads with lower density are added to improve suspension. However, because the hollow glass microspheres have a small particle size, they can be easily inhaled into the lungs of production personnel and cause harm. This study is based on the existing research results of sand-in-water sands and their shortcomings. The main influence factors on bleeding, whiteness and stability in sand-in-water sand formulas are the amount of protective gel GS, the type and amount of wetting agent. In parallel experiments with cellulose ether types and dosages, the formula was optimized, and the performance of sand-in-water colorful coatings was tested. Finally, sand-in-water colorful coatings with excellent bleeding resistance, water resistance, and stability were prepared.
1 Experimental part
1.1 Raw materials and instrument
protective glue GS, wetting agent (wetter390, weter396, weter399): Shanghai Grid International Trade Co., Ltd .; Hydroxyethyl cellulose (250HBR, 250HHBR, HE10K): Ashland (China ) Investment Co., Ltd .; Other additives: commercially available.
SFJ-400 Inverter Disperser, STM-V Stormer Viscometer, GFX Blast Dryer: Shanghai Modern Environment Co., Ltd .; DC type colorful granulator: Jiangyin Xiongwei Chemical Machinery Co., Ltd .; W77 type multicolor coating spray gun: Shanghai Iwata Industrial Co., Ltd.
1. 2 Preparation of sand-in-water multicolor coating
1. 2. 1 Preparation of protective glue solution
The composition of the protective glue solution is shown in Table 1.
Pour the weighed deionized water into the dispersion tank, adjust the speed of the disperser to 1 000 ~ 1 200 r / min, and then slowly pour the weighed protective glue GS into the dispersion tank to avoid agglomeration. Disperse for 30 ~ 60 minutes to obtain a protective gum solution, ready for use.
1. 2. 2 Preparation of tinting base paint
The formula of tinting base paint is shown in Table 2.
At a speed of 300 ~ 600 r / min, add the cellulose ether, dispersant, wetting agent, defoamer, pigment and filler listed in Table 2 in turn, and adjust the speed to 1 300 ~ 1 as the viscosity of the system increases. 500 r / min, high-speed dispersion for 20-30 minutes, measuring speed ≤50 μm, then reduce the speed to 700-900 r / min, add emulsion, protective glue and remaining additives in sequence, and finally adjust the base paint with a thickener To the appropriate viscosity, add quartz sand and continue to stir for about 10 minutes to obtain the color base paint.
1. 2. 3 Preparation of continuous phase emulsion
The formulation of continuous phase emulsion is shown in Table 3.
Add the raw materials in Table 3 in sequence at a speed of 500 ~ 800 r / min, adjust the viscosity with a thickener, and continue stirring for about 5 minutes to obtain a continuous phase.
1. 2. 4 Granulation of water-in-sand multicolor coating granulation
The formulation of water-in-sand multicolor coating granulation is shown in Table 4.
Add deionized water and protective gum solution in sequence at a speed of 200 ~ 300 r / min, and then add each color paint according to the proportion of the color point of the colorful template. After pre-cutting, use a granulator to granulate to obtain multi-colored particles of appropriate size. .
1. 2. 5 Preparation of finished product of colorful water-in-sand coatings Table 5 shows the formula of finished product of colorful water-sands coating.
Slowly add the continuous phase emulsion to the particles of each color according to the ratio in Table 5. Stir with a three-blade paddle at a low speed of 50 to 100 r / min, and then use a thickener to adjust the system to a suitable viscosity. Mix at 100 r / min for about 10 minutes to make it uniform.
1.3 Test method
Anti-bleeding: Add the tinted base paint to the protective glue solution in proportion, cut with a three-bladed paddle at a speed of 500 r / min for 5 minutes, and observe the protective glue solution after cutting. The color change after the color paste oozes out, and the grade is evaluated, grade 5 is the worst, grade 3 is qualified, and grade 0 is the best.
Water resistance whiteness: The test panel of the spray-painted multicolor coating is placed in an oven at 5 ℃ for 16 hours, and then it is soaked in water for 2 hours. The water resistance is evaluated and the grade is the worst. The grade 5 is the worst. The grade 3 is qualified. Level 0 is the best. The size of the asbestos cement board is 150 mm × 70 mm × 3 mm.
Color point shape and storage stability of multicolor coatings: Store in an oven at 55 ℃ for one week, and observe the broken point of the color point and the change of softness and hardness.
2 Results and discussion
2.1 Effect of the amount of protective gum solution on the anti-bleeding properties of sand-in-water colorful coatings
The main component of protective gum is artificial lithium lithium silicate, which is a trioctahedral layered silicate mineral. Due to the negative charge on the sheet layer and the positive charge on the end face, the separated end face of the sheet is attracted to the layer of another sheet, thereby quickly forming a three-dimensional space colloid structure, that is, a card palace structure, which forms so-called gel-protected color particles. Role. Due to the presence of quartz sand with a large particle size in the color point of the water-in-water sand coating, it is difficult for the protective glue to form a continuous gel film to cover the color particles during the granulation of the cut point, which in turn causes the substances in the base paint and The colorant spills into the continuous phase, affecting its performance and hue. Based on the characteristics of sand-in-water coatings, a commercially available protective glue is used for comparison. Experiments have found that organically modified grid protective glue GS is used to form a card palace structure on the surface of multi-color particles through a special surface treatment process, which increases the organism. The formed cross-linked network body has better protection effect on multi-colored particles with larger particle size in the sand-in-water coating, and makes the sand-in-water colorful coating have better resistance to bleeding.
The effect of the protective gum solution against bleeding is shown in Figure 1.
It can be seen from Figure 1 that due to the different structures of iron red, iron yellow, and carbon black, different wetting and dispersing agents are used, so the compatibility with the base paint and protective glue is also different, resulting in different amounts of protective glue added. The degree of bleeding is different. When the amount of GS reaches 12%, except for iron red which has slight bleeding, the other two color pastes basically do not bleed. Continue to increase the amount of GS, the color bleeding is not significantly improved, and it is added in the protective gum solution. The slight bleeding at the amount of 10% ~ 12% has not affected the overall hue of the sand-in-water multicolor coating. Based on the cost and the stability of the multicolor coating, when the content of GS in the protective gum solution is 10% ~ 12%, A sand-in-water multicolor coating with excellent bleeding resistance was obtained.
2.2 Effect of Types and Dosages of Wetting Agents on Water Whiteness of Sand-in-Water Multicolor Coatings
When the amount of protective glue is 10% ~ 12%, three kinds of grid wetting agents, weter390, weter396, and weter399 are used for comparison, and the effects of different types of wetting agents on the water-white resistance of sand-in-water colorful coatings are discussed. Test method: The test panel (the size of asbestos cement board is 150 mm × 70 mm × 3 mm) just sprayed with multicolor coating was placed in an oven at 5 ℃ for 16h, then it was soaked in water for 2h to examine its water resistance and whiteness. The results are shown in Figure 2.
It can be seen from Figure 2 that wetter399 has the best water resistance whiteness, followed by wetter396, and wetter390 is the worst. This may be because the active ingredient of wetter390 is a nonionic surfactant, and the active ingredient of wetter396 is a specially modified nonionic surfactant, which has better permeability and therefore has better water whitening resistance. In the experiment, the anionic wetting agent wetter 399 has the best water resistance. This is because in the coating formulation, the non-ionic wetting agent is resistant to water because the anion is hydrophilic instead of the ionic being hydrophobic. The whiteness is better than the anionic wetting agent, but in the water-in-sand coating formulation, it is just the opposite. This may be because the main substance of the water-in-sand colorful coating is magnesium trisilicate, which is a trioctahedral silicate. Minerals, due to the negative charge on the lamellar layer and the positive charge on the end face, are inherently ionic. According to similar compatibility principles, minerals have better compatibility with anionic wetting agents, so they have higher water resistance. Whiteness. In summary, when the added amount of wetter399 is selected from 0.4% to 0.6%, the obtained sand-in-water multicolor coating has the best water resistance.
2.3 The effect of the type and amount of cellulose ether on the stability of sand-in-water colorful coatings.
The amount of protective glue is 10% ~ 12%, and the amount of wetting agent weter399 is 0.4% ~ 0. 6%. 3 kinds of hydroxyethyl cellulose ethers 250HBR, 250HHBR and HE10K were selected, and the effects of cellulose ethers with different relative molecular weights and treatment methods on the color point shape and storage stability of multicolor coatings (storage at 55 ° C for 1 week) were discussed. The results are shown in Table 6.
It can be known from Table 6 that the color point of the sand-in-water coating prepared with HE10K will harden during storage. This may be because HE10K is a hydrophobically modified cellulose. Due to the addition of a large amount of sand, it crosslinks with the protective glue. The reaction is slow, and continued to cause the color point to harden during storage. When 250HBR is used, the color point is fragile with a small amount of addition. After reaching a certain amount, the color point is not brittle but becomes hard after storage. When 250HHBR is used, the color point is not fragile and it does not harden during storage, but when it exceeds a certain amount, the color point will also become hard during storage. This may be caused by the difference in the relative molecular mass of the two. The relative molecular mass of 250HBR is 30 000, the molecular chain is relatively short, and the color point is fragile when the amount is small, but when the amount is large, there are more cross-linking points with the protective glue. , Causing subsequent thermal storage to harden. The relative molecular mass of 250HHBR is 100,000, and the molecular chain is relatively long. It can achieve the balance between encapsulation and crosslinkability with the protective glue at the proper dosage, and obtain a water-in-water coating that is not brittle and has no hardening during heat storage. . In summary, when the addition amount of 250HHBR is selected from 1.2% to 1.4%, the obtained sand-in-water multicolor coating has good stability.
(1) When GS is used as the protective glue, the content of GS in the protective glue solution is 10% ~ 12%. The sand-in-water multicolor coating has excellent resistance to bleeding.
(2) The type and amount of wetting agent have a greater impact on the water-resistant whiteness of sand-in-water colorful coatings. The water-in-water-colored colorful coatings obtained by adding 0.4% to 0.6% of wetter399 have excellent water-whitening resistance. .
(3) The type and amount of cellulose ether have a great influence on the color point shape and storage stability of the sand-in-water multicolor coating. Adding 1.2% to 1.4% of 250HHBR, the water-in-water multicolor coating does not harden and Less broken points.