Waterproof coating for loess silt dam and preparation method thereof

Abstract

The invention relates to a waterproof coating for a loess silt dam and a preparation method of the waterproof coating, the waterproof coating comprises the following components in parts by weight: 1.2-2.4 parts of polyvinyl butyral, 60-70 parts of alkoxy silane, 28.2-38.4 parts of a solvent and 0.05-0.1 part of a catalyst, and the waterproof coating forms a hydrophobic coating with a compact structure on the surface of loess. The loess has excellent water resistance, wear resistance, scouring resistance and long-term effect, so that the stability and safety of engineering are ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of waterproof coatings, and in particular relates to a waterproof coating for loess silt dams and a preparation method thereof. Background Art

[0002] Loess is composed of fine wind-blown sand and clay particles, accounting for about 10% of the Earth's land surface. It is widely distributed around the world, including Asia, Africa, Central and Southern Europe, northern Russia, the Midwest of the United States, and northern France. Loess is a natural inorganic mineral material with abundant water resources, non-toxic, economical and environmentally friendly. Its chemical composition mainly contains SiO2, Al2O3, CaO, Fe2O3 and MgO.

[0003] my country has abundant, high-quality and cheap loess resources, but so far, except as a carrier of plants, it has been basically undeveloped and utilized, and nearly 1.6 billion tons of loess are lost every year due to soil flow. There are a large number of gaps in the loess stacking structure, and they are basically through-holes. Such a high porosity makes loess susceptible to the same wet collapse damage process as natural soil, such as freeze-thaw cycles, soluble salt crystallization and water erosion.

[0004] Considering the above problems of loess, it is necessary to improve the strength and hydrophobicity of loess through artificial technology, enhance the anti-seepage, anti-disintegration and anti-erosion capabilities of loess, and make it meet the requirements of engineering construction. The selected waterproof coating needs to have the following properties: 1) Achieve appropriate penetration depth, which is related to the characteristics of loess (especially its pore size distribution) and the inherent characteristics of the consolidating agent (such as viscosity and surface tension); 2) No harmful by-products; 3) Good chemical, physical and mechanical compatibility with soil; 4) Good compatibility with the external environment.

[0005] Therefore, developing a waterproof coating that can block water and improve soil strength is the current research focus in this field. Summary of the invention

[0006] In view of the shortcomings of the prior art, the object of the present invention is to provide a waterproof coating for loess silt dams and a preparation method thereof, wherein the waterproof coating can effectively improve the impermeability, wear resistance, erosion resistance and waterproofness of loess.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a waterproof coating for a loess silt dam, wherein the waterproof coating comprises the following components in parts by weight: 1.2 to 2.4 parts of polyvinyl butyral (for example, 1.2 parts, 1.4 parts, 1.6 parts, 1.8 parts, 2 parts, 2.2 parts, 2.4 parts, etc.), 60 to 70 parts of alkoxysilane (for example, 60 parts, 62 parts, 64 parts, 66 parts, 68 parts, 70 parts, etc.), 28.2 to 38.4 parts of solvent (for example, 28.2 parts, 29 parts, 30 parts, 32 parts, 34 parts, 36 parts, 38 parts, 38.4 parts, etc.), and 0.05 to 0.1 part of catalyst (for example, 0.05 parts, 0.06 parts, 0.07 parts, 0.08 parts, 0.09 parts, 0.1 parts, etc.).

[0009] The present invention adopts specific contents of polyvinyl butyral, alkoxysilane, solvent and catalyst to prepare a waterproof coating for loess silt dam. The waterproof coating forms a dense cross-linked network structure on the surface of loess, which can effectively enhance the anti-permeability, wear resistance, erosion resistance and waterproofness of the loess.

[0010] In the present invention, the -Si(OCH3)3 group in the alkoxysilane is hydrolyzed to form silanol -Si(OH)3, which can undergo a condensation reaction with the hydroxyl group in polyvinyl butyral to form a -Si-O-Si- bond; at the same time, the silanol can also undergo a dehydration condensation reaction with the -OH on the surface of loess to form a -Si-O-Si- bond; in addition, the silanol itself can also undergo a dehydration condensation reaction to form a -Si-O-Si- bond, so that the waterproof coating can fully form a dense cross-linked network on the surface of the loess silt dam, so that it has excellent hydrophobicity, wear resistance, adhesion and long-term effectiveness. Therefore, the present invention compounds polyvinyl butyral with alkoxysilanes having greatly different characteristics, so that the two can play a synergistic role, thereby improving the comprehensive performance of the resulting waterproof coating, and can be well applied to the protection of loess silt dams.

[0011] Preferably, the alkoxysilane includes any one of dodecyltrimethoxysilane, hexadecyltrimethoxysilane or octadecyltriethoxysilane, or a combination of at least two thereof.

[0012] Preferably, the weight average molecular weight of the polyvinyl butyral is 40,000-70,000, for example, 40,000, 45,000, 50,000, 55,000, 60,000, 65,000, 70,000, etc.

[0013] Preferably, the solvent is selected from ethanol and / or acetone.

[0014] Preferably, the catalyst comprises dibutyltin dilaurate and / or dibutyltin diacetate.

[0015] In a second aspect, the present invention provides a method for preparing the waterproof coating according to the first aspect, the preparation method comprising:

[0016] The waterproof coating is obtained by mixing polyvinyl butyral, alkoxysilane, a solvent and a catalyst.

[0017] Preferably, the mixing temperature is 15-25°C, for example, 15°C, 18°C, 20°C, 22°C, or 25°C.

[0018] Preferably, the mixing comprises the following steps:

[0019] (1) mixing polyvinyl butyral and a solvent, stirring, and ultrasonically dispersing to obtain a mixed solution;

[0020] (2) Add the mixed solution and the catalyst into the alkoxysilane, and stir and disperse by ultrasonic.

[0021] Preferably, the mass fraction of polyvinyl butyral in the mixed solution of step (1) is 4-6wt%, for example, it can be 4wt%, 4.2wt%, 4.4wt%, 4.6wt%, 4.8wt%, 5wt%, 5.2wt%, 5.4wt%, 5.6wt%, 5.8wt%, 6wt% and the like.

[0022] Preferably, the stirring time in step (1) is 2 to 3 hours, for example, 2 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, 3 hours, etc.

[0023] Preferably, the stirring speed in step (1) and step (2) is 400-500 r / min, for example, 400 r / min, 420 r / min, 440 r / min, 460 r / min, 480 r / min, 500 r / min, etc.

[0024] Preferably, the ultrasonic dispersion time in step (1) and step (2) is 15 to 30 minutes, for example, 15 minutes, 20 minutes, 25 minutes, 30 minutes, etc.

[0025] Preferably, the power of the ultrasonic dispersion in step (1) and step (2) is 200-400 W, for example, 200 W, 250 W, 300 W, 350 W, 400 W, etc.

[0026] Preferably, the stirring time in step (2) is 1 to 2 h, for example, 1 h, 1.2 h, 1.5 h, 1.7 h, 2 h, etc.

[0027] Preferably, the preparation method comprises the following steps:

[0028] (1) mixing polyvinyl butyral and a solvent, stirring at 15 to 25° C. and 400 to 500 r / min for 2 to 3 hours, and then ultrasonically dispersing at 200 to 400 W for 15 to 30 minutes to obtain a mixed solution;

[0029] (2) adding the mixed solution and the catalyst into the alkoxysilane, stirring at 15-25° C. and 400-500 r / min for 1-2 hours, and ultrasonically dispersing at 200-400 W for 15-30 minutes to obtain the waterproof coating.

[0030] There is no particular limitation on the coating method of the waterproof coating of the present invention, and it can be, for example, roller coating, spray coating, brush coating, etc. The drying temperature after coating is 20-35°C, for example, it can be 20°C, 25°C, 30°C, 35°C, etc. The drying time is 3-8 days, for example, it can be 3 days, 4 days, 5 days, 6 days, 7 days, 8 days, etc. The drying environment humidity is 10-50%, for example, it can be 10%, 20%, 30%, 40%, 50%, etc.

[0031] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] In the waterproof coating for loess silt dams described in the present invention, -Si(OCH3)3 groups are hydrolyzed to form silanol -Si(OH)3, and silanol undergoes condensation reaction with -OH on the loess surface or hydroxyl groups in polyvinyl butyral to form -Si-O-Si- bonds. At the same time, silanol itself also undergoes dehydration condensation reaction to form -Si-O-Si- bonds, and the waterproof coating forms a dense cross-linked network on the surface of the loess silt dam, which has excellent hydrophobicity, wear resistance, adhesion and long-term effectiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a surface morphology image of a loess sample sprayed with the waterproof coating described in Example 1 under a scanning electron microscope at 300 times magnification;

[0035] Figure 2 This is a diagram of the water contact angle of the waterproof coating described in Example 1 after scraping off the hard coating on the surface of loess. DETAILED DESCRIPTION

[0036] For the convenience of understanding the present invention, the present invention lists the following embodiments. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0037] Unless otherwise specified, the polyvinyl butyral involved in the following embodiments is purchased from Shanghai MacLean Biochemical Technology Co., Ltd., P815775, with a weight average molecular weight of 40,000 to 70,000.

[0038] Example 1

[0039] The present embodiment provides a waterproof coating for loess silt dams, wherein 48 g of ethanol and 2 g of polyvinyl butyral are mixed and stirred at 25° C. and 500 r / min for 2 h, and then ultrasonically dispersed at 400 W for 20 min to obtain a 4 wt % polyvinyl butyral solution; 30 g of the polyvinyl butyral solution and 0.08 g of dibutyltin dilaurate are added to 70 g of dodecyltrimethoxysilane, mixed and stirred at 25° C. and 500 r / min for 1 h, and ultrasonically dispersed at 400 W for 20 min to obtain the waterproof coating for loess silt dams.

[0040] The surface morphology of the waterproof coating obtained in this example after spraying onto the loess sample under a scanning electron microscope at 300 times magnification is as follows Figure 1 As shown in FIG. 1 , it shows that the waterproof coating of the present invention exhibits a smooth hard surface after being applied. The water contact angle of the waterproof coating of this embodiment after scraping off the hard coating on the loess surface is as shown in FIG. Figure 2 shown.

[0041] Example 2

[0042] The present embodiment provides a waterproof coating for loess silt dams, wherein 47.5 g of acetone and 2.3 g of polyvinyl butyral powder are mixed and stirred at 20° C. and 400 r / min for 3 h, and then ultrasonically dispersed at 200 W for 30 min to obtain a 4.6 wt % polyvinyl butyral solution; 30 g of the polyvinyl butyral solution and 0.07 g of dibutyltin diacetate are added to 70 g of dodecyltrimethoxysilane, mixed and stirred at 20° C. and 400 r / min for 1.5 h, and ultrasonically dispersed at 200 W for 30 min to obtain the waterproof coating for loess silt dams.

[0043] Example 3

[0044] The present embodiment provides a waterproof coating for loess silt dams, wherein 47 g of ethanol and 3 g of polyvinyl butyral powder are mixed and stirred at 15° C. and 450 r / min for 2.5 h, and then ultrasonically dispersed at 300 W for 15 min to obtain a 6 wt % polyvinyl butyral solution; 30 g of the polyvinyl butyral solution and 0.05 g of dibutyltin dilaurate are added to 70 g of dodecyltrimethoxysilane, mixed and stirred at 15° C. and 450 r / min for 2 h, and ultrasonically dispersed at 300 W for 15 min to obtain the waterproof coating for loess silt dams.

[0045] Example 4

[0046] The present embodiment provides a waterproof coating for loess silt dams, wherein 47 g of ethanol and 3 g of polyvinyl butyral powder are mixed and stirred at 15° C. and 450 r / min for 2.5 h, and then ultrasonically dispersed at 300 W for 15 min to obtain a 6 wt % polyvinyl butyral solution; 40 g of the polyvinyl butyral solution and 0.1 g of dibutyl tin dilaurate are added to 60 g of hexadecyltrimethoxysilane, mixed and stirred at 25° C. and 450 r / min for 1.5 h, and ultrasonically dispersed at 300 W for 15 min to obtain the waterproof coating for loess silt dams.

[0047] Example 5

[0048] The present embodiment provides a waterproof coating for loess silt dams, wherein 47 g of ethanol and 3 g of polyvinyl butyral powder are mixed and stirred at 15° C. and 450 r / min for 2.5 h, and then ultrasonically dispersed at 300 W for 15 min to obtain a 6% polyvinyl butyral solution; 35 g of the polyvinyl butyral solution and 0.06 g of dibutyl tin dilaurate are added to 65 g of octadecyltrimethoxysilane, mixed and stirred at 25° C. and 450 r / min for 1.5 h, and ultrasonically dispersed at 300 W for 15 min to obtain the waterproof coating for loess silt dams.

[0049] Example 6

[0050] This embodiment provides a waterproof coating for loess silt dams, which differs from Example 1 only in that polyvinyl butyral with a weight average molecular weight of 20,000 (Shanghai McLean Biochemical Technology Co., Ltd., P832219) is used, and other raw materials, amounts and preparation methods are the same as those in Preparation Example 1.

[0051] Example 7

[0052] This embodiment provides a waterproof coating for loess silt dams. The only difference between this embodiment and Example 1 is that polyvinyl butyral with a weight average molecular weight of 90,000 (Shanghai McLean Biochemical Technology Co., Ltd., P815776) is used, and other raw materials, dosages and preparation methods are the same as those in Example 1.

[0053] Comparative Example 1

[0054] This comparative example provides a waterproof coating for loess silt dams, which differs from Example 1 only in that 80 g of dodecyltrimethoxysilane is used, and other raw materials, amounts and preparation methods are the same as those in Example 1.

[0055] Comparative Example 2

[0056] This comparative example provides a waterproof coating for loess silt dams, which differs from Example 1 only in that 50 g of dodecyltrimethoxysilane is used, and other raw materials, amounts and preparation methods are the same as those in Example 1.

[0057] Comparative Example 3

[0058] This comparative example provides a waterproof coating for loess silt dams, which differs from Example 1 only in that 75 g of ethanol is used, and other raw materials, amounts and preparation methods are the same as those in Example 1.

[0059] Comparative Example 4

[0060] This comparative example provides a waterproof coating for loess silt dams, which differs from Example 1 only in that an equal amount of polyvinyl butyral is replaced by tetraethyl orthosilicate, and other raw materials, amounts and preparation methods are the same as those in Example 1.

[0061] Comparative Example 5

[0062] This comparative example provides a waterproof coating for loess silt dams, which differs from Example 1 only in that an equal amount of dodecyltrimethoxysilane is replaced by polyvinyl butyral, and other raw materials, amounts and preparation methods are the same as those in Example 1.

[0063] Comparative Example 6

[0064] This comparative example provides a waterproof coating for loess silt dams. 28.8 g of ethanol and 0.08 g of dibutyltin dilaurate are added to 71.2 g of dodecyltrimethoxysilane, mixed and stirred at 25°C and 500 r / min for 1 h, and ultrasonically dispersed at 400 W for 20 min to obtain the waterproof coating for loess silt dams.

[0065] Performance Testing

[0066] The waterproof coating for loess silt dam prepared in the above-mentioned embodiments 1 to 7 and comparative examples 1 to 6 was evenly applied on the outer surface of the loess by brushing. After the surface coating was basically infiltrated into the loess, the coating was continued by brushing for 2 times in total. The samples were dried at 25° C. for 2 days. The waterproof performance was tested using the dried samples. The specific test method is as follows:

[0067] (1) Water contact angle and water rolling angle: The contact angle and rolling angle were measured using a DSA100 optical contact angle meter. The contact angle was measured using a 4 μL water droplet, and the rolling angle was measured using an 8 μL water droplet.

[0068] (2) Penetration depth: 3 mL of the waterproof coating was dropped vertically on a surface with a density of 1.7 g / cm2 for 3 min using the direct titration method. 3The penetration depth was measured at 10 points on the surface of the loess sample, and the average value was calculated.

[0069] (3) Adhesion: Use transparent tape to stick on the coating surface 100 times and weigh the weight of the sample after sticking. The smaller the weight reduction of the sample, the better the adhesion of the coating.

[0070] (4) Abrasion resistance and water contact angle reduction: Place the sample on a 200-grit sandpaper surface and use a 200g metal sheet as a weight to apply a certain amount of pressure on the sample. Slowly pull the sandpaper strip out from under the sample at a constant speed to allow the sample surface to rub against the sandpaper. A 50-cm back-and-forth cycle is recorded as one cycle. Repeat 50 times and measure the sample wear and water contact angle reduction.

[0071] (5) Water resistance: The sample was placed in a beaker filled with 1 L of clean water. The height of the solution was maintained at 150 mm from the upper surface of the sample. The sample was removed after 1, 7, 15, and 30 days, and the surface was wiped dry with absorbent paper and weighed. The weight gain rate of the sample after immersion in water was measured.

[0072] The performance test results are shown in Table 1:

[0073] Table 1

[0074]

[0075] Analysis of the data in Table 1 shows that, taking Examples 1 to 7 as examples, the waterproof coating for loess silt dams of the present invention has excellent hydrophobicity, impermeability, adhesion and wear resistance on the loess surface, with a water contact angle of 125 to 135°, a water rolling angle of 20 to 40°, a penetration depth of 8 to 10 mm, an adhesion (weight reduction) of 0 to 3 wt%, a wear amount of 30 to 35 wt%, a water contact angle reduction of 0 to 20°, and a water immersion weight gain rate of 3 to 34 wt%.

[0076] From the analysis of Examples 1 and 6-7, it can be seen that when polyvinyl butyral with a molecular weight other than that of a specific molecular weight is used, the water resistance and wear resistance of the loess surface coated with the waterproof coating are reduced. This is because the content ratio of polyvinyl butyral with other molecular weights and alkoxysilane is not good, resulting in uneven spraying during actual use, thus affecting its practicality.

[0077] From the analysis of Example 1 and Comparative Examples 1-2, it can be seen that when alkoxysilane is used outside the specific content, the wear resistance and hydrophobicity of the loess surface coated with the waterproof coating are reduced. This is because when the content of alkoxysilane exceeds the specific range, its specific content ratio with polyvinyl butyral is destroyed, resulting in a decrease in the overall performance of the resulting waterproof coating.

[0078] Analysis of Example 1 and Comparative Example 3 shows that the use of excessive solvent will reduce the water resistance and wear resistance of the loess surface coated with the waterproof coating. This is because the effective content of polyvinyl butyral is reduced, resulting in a significant decrease in the strength of the resulting coating, which in turn makes its wear resistance poor; at the same time, due to the reduction in the content of polyvinyl butyral, its specific ratio with alkoxysilane is destroyed, thereby significantly increasing the water rolling angle and immersion water weight gain rate of the resulting waterproof coating, thereby reducing its hydrophobicity.

[0079] From the analysis of Example 1 and Comparative Example 4, it can be seen that in the comparative example, polyvinyl butyral is replaced by tetraethyl orthosilicate, the water contact angle of the loess surface coated with the waterproof coating is reduced from 135° to 110°, the wear amount is increased from 30wt% to 55wt%, and the weight gain rate of immersion water is increased from 3wt% to 70wt%. This is because tetraethyl orthosilicate does not have the ability to match the performance of alkoxysilane, which makes the overall performance of the obtained waterproof coating poor.

[0080] From the analysis of Example 1, Comparative Example 5 and Comparative Example 6, it can be seen that if only one of polyvinyl butyral or alkoxysilane is added to the waterproof coating, the water contact angle of the loess surface coated with the waterproof coating is significantly reduced, and the water rolling angle, wear amount, water contact angle change value and immersion water weight gain rate are all significantly increased. At the same time, the weight reduction amount is also significantly increased. That is, this comparison fully illustrates that the compounding of polyvinyl butyral and alkoxysilane in the present invention can make the two play a synergistic role, thereby improving the comprehensive performance of the obtained waterproof coating, and then can be well applied to the protection of loess silt dams.

[0081] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A waterproof coating for loess silt dam, characterized in that: The waterproof coating comprises the following components in parts by weight: 1.2 to 2.4 parts of polyvinyl butyral, 60 to 70 parts of alkoxysilane, 28.2 to 38.4 parts of solvent, and 0.05 to 0.1 parts of catalyst.

2. The waterproof coating according to claim 1, characterized in that: The alkoxysilane includes any one of dodecyltrimethoxysilane, hexadecyltrimethoxysilane and octadecyltriethoxysilane, or a combination of at least two thereof.

3. The waterproof coating according to claim 1 or 2, characterized in that: The weight average molecular weight of the polyvinyl butyral is 40,000-70,000.

4. The waterproof coating according to any one of claims 1 to 3, characterized in that: The solvent is selected from ethanol and / or acetone.

5. The waterproof coating according to any one of claims 1 to 4, characterized in that: The catalyst includes dibutyltin dilaurate and / or dibutyltin diacetate.

6. A method for preparing a waterproof coating according to any one of claims 1 to 5, characterized in that: The preparation method comprises: The waterproof coating is obtained by mixing polyvinyl butyral, alkoxysilane, a solvent and a catalyst.

7. The preparation method according to claim 6, characterized in that: The mixing temperature is 15-25°C.

8. The preparation method according to claim 6 or 7, characterized in that: The mixing comprises the following steps: (1) mixing polyvinyl butyral and a solvent, stirring, and ultrasonically dispersing to obtain a mixed solution; (2) Add the mixed solution and the catalyst into the alkoxysilane, and stir and disperse by ultrasonic.

9. The preparation method according to any one of claims 6 to 8, characterized in that: The stirring time in step (1) is 2 to 3 hours; Preferably, the stirring speed in step (1) and step (2) is 400-500 r / min; Preferably, the ultrasonic dispersion time in step (1) and step (2) is 15 to 30 minutes; Preferably, the power of the ultrasonic dispersion in step (1) and step (2) is 200 to 400 W; Preferably, the stirring time in step (2) is 1 to 2 hours.

10. The preparation method according to any one of claims 6 to 9, characterized in that: The preparation method comprises the following steps: (1) mixing polyvinyl butyral and a solvent, stirring at 15 to 25° C. and 400 to 500 r / min for 2 to 3 hours, and then ultrasonically dispersing at 200 to 400 W for 15 to 30 minutes to obtain a mixed solution; (2) adding the mixed solution and the catalyst into the alkoxysilane, stirring at 15-25° C. and 400-500 r / min for 1-2 hours, and ultrasonically dispersing at 200-400 W for 15-30 minutes to obtain the waterproof coating.

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