Super-hydrophobic and zero-energy-consumption cooling bifunctional phosphogypsum coating and preparation method thereof

Abstract

The invention discloses a preparation method of an ardealite coating with super-hydrophobic and radiation refrigeration functions. The coating comprises the following main components: phosphogypsum (PG), a silane coupling agent, polymethyl methacrylate (PMMA), stearic acid (SA), polydimethylsiloxane (PDMS) and a curing agent thereof, slurry is prepared by adopting a simple blending method, and film coating is carried out by adopting a scraper method, so that the phosphogypsum coating with excellent super-hydrophobic and radiation refrigeration functions can be prepared.

Description

Technical Field

[0001] The invention belongs to the technical field of functional coatings, and in particular relates to a method for preparing a phosphogypsum coating with super-hydrophobic and radiation cooling functions. Background Art

[0002] ‌Phosphogypsum is the main by-product in the production of high-concentration phosphate fertilizers, compound fertilizers or wet phosphoric acid. Its annual output is huge and contains a variety of impurities such as phosphorus, fluorine, and organic matter. This limits the direct use of phosphogypsum and reduces its resource utilization rate. According to statistics, China emits a huge amount of phosphogypsum each year, and the surface stockpile has exceeded hundreds of millions of tons, which not only occupies a large amount of arable land, but also damages the surface ecological environment. Therefore, the efficient utilization technology of phosphogypsum has become a global problem, and improving its utilization rate has become an urgent need.

[0003] Superhydrophobic modification of phosphogypsum is an effective way to utilize phosphogypsum in a high-value manner. Through superhydrophobic modification, the water absorption rate of phosphogypsum products can be significantly reduced, and their water resistance and durability can be improved, thereby expanding the application scope of phosphogypsum in the fields of building materials and the like. Among various superhydrophobic modification methods, organic modification of phosphogypsum improves the hydrophobicity of phosphogypsum products without affecting the appearance of phosphogypsum products, and is currently a commonly used modification method. However, organic hydrophobic agents usually only affect gypsum with small pore size and low porosity, while the modification effect on phosphogypsum with large pore size and high porosity is not obvious.

[0004] At the same time, radiative cooling technology is an extremely attractive new zero-energy cooling technology. This technology releases the heat energy of surface objects in the form of electromagnetic waves to the external space with a temperature close to absolute zero through the atmospheric window (such as the 8-13 micron band), thereby achieving the purpose of self-cooling. To achieve the best zero-energy cooling effect, the refrigeration material is usually required to have a high reflectivity in the solar spectrum band (0.3 ~ 2.5 μm) to prevent heat absorption; at the same time, it has a high emissivity in the atmospheric transparent window (ATW 8~ 13 μm) to transfer heat to the cold outer space, thereby achieving a quiet cooling function without power consumption while absorbing as little heat as possible. If the cooling function of phosphogypsum can be modified to obtain zero-energy cooling phosphogypsum, it will further broaden the application field of phosphogypsum and promote the high-value utilization and development of phosphogypsum. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing a phosphogypsum coating with super-hydrophobic and radiation cooling functions, so as to solve the problems of existing phosphogypsum disposal and efficient utilization.

[0006] The technical solution of the present invention: The synergistic effect of polydimethylsiloxane (PDMS), stearic acid (SA) and polymethyl methacrylate (PMMA) is utilized to reduce the surface energy of PG and make its surface hydrophobic. Meanwhile, PMMA and SA give PG a significant cooling effect under the action of ultrasound. A method for preparing a phosphogypsum coating having super-hydrophobic and radiation cooling functions comprises the following steps: Step 1: Add PG, NaOH and Na2SO4 into deionized water in proportion, and stir and disperse to obtain a mixed suspension; Step 2: filtering, washing and drying the mixed suspension obtained in step 1 to obtain hydroxylated PG powder; Step 3: Add the silane coupling agent into a mixed solvent of deionized water and anhydrous ethanol, and heat and stir to obtain a dispersant; Step 4: adding the hydroxylated PG powder obtained in step 2 to the dispersant obtained in step 3, and stirring to obtain a mixed suspension; Step 5: filtering, washing and drying the mixed suspension obtained in step 4 to obtain hydrophobically modified PG powder; Step 6: Grind the hydrophobically modified PG powder obtained in step 5, and pass it through a sieve to obtain hydrophobically modified PG powders of different particle sizes; Step 7: Add PMMA and SA in proportion to a mixed solvent of N,N-dimethylformamide (DMF) and tetrahydrofuran (THF), and stir thoroughly to obtain a cooling modifier; Step 8: adding the hydrophobic modified PG powder obtained in step 6 to the cooling modifier obtained in step 7, stirring sufficiently, ultrasonically treating, and then adding PDMS and its curing agent to obtain a super-hydrophobic-radiation cooling dual-functional modified phosphogypsum coating; Step 9: The coating obtained in step 8 is coated on the substrate by a scraper method, and after the solvent is dried, a phosphogypsum coating with super-hydrophobic and radiation cooling functions is obtained.

[0007] In the step 1, the mass concentration of PG is 0.1-0.5 g / mL, the mass concentration of NaOH is 0.05-0.25 g / mL, the mass concentration of Na2SO4 is 0.005-0.04 g / mL, the stirring temperature is room temperature, and the stirring time is 20-30 min.

[0008] In step 2, the drying temperature is 60° C. and the drying time is 12 h.

[0009] In the step 3, the silane coupling agent is any one of KH550, KH560, and KH570; by volume, deionized water: anhydrous ethanol = 3:4-6, and the mass concentration of the silane coupling agent in the silane coupling agent mixture is 0.03-0.06 g / mL.

[0010] In step 4, the stirring temperature is 60-80° C., and the stirring time is 1.0-2.5 h.

[0011] In step 5, the drying temperature is 60-80° C. and the drying time is 10-12 hours.

[0012] In step 6, the mesh size of the sieve is 90-110 meshes.

[0013] In step 7, the volume ratio of DMF:THF in the mixed solvent is 1:1-5, the mass concentration of PMMA added is 0.015-0.1 g / mL, and the mass concentration of SA is 0.02-0.1 g / mL. In the step 8, the mass ratio of hydrophobically modified PG powder to cooling modifier is 1:3-4, the PDMS mass concentration is 0.03-0.1 g / ml, the ultrasonic power is 50-100 w, preferably 80 w, the ultrasonic time is 5-30 minutes, preferably 10 min, the stirring temperature is room temperature, and the stirring time is 3-10 min, preferably 5 min.

[0014] In the step 9, the scraping film thickness of the scraping method is 300-400 μm, and the material of the substrate includes any one of a glass sheet, an aluminum sheet, a copper sheet, and a carbon steel sheet.

[0015] Beneficial effects of the present invention: 1. Good water resistance. The surface hydrophobic modification of small-pore particles in phosphogypsum is carried out using silane coupling agent, and PMMA and SA are used to penetrate into the large pores, so that phosphogypsum has excellent super-hydrophobic and anti-seepage properties, extending the service life of phosphogypsum materials.

[0016] 2. Good zero-energy cooling effect. The synergistic effect of PMMA and SA is used to optimize the reflectivity and emissivity of phosphogypsum, significantly improving the zero-energy cooling effect of phosphogypsum. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 Graph showing the water drop contact angle test results of the coatings in Examples 1, 2, 3, 4, and 5.

[0017] Figure 2 The graphs are the test results of water droplet rolling angle of the coatings in Examples 1, 2, 3, 4, and 5.

[0018] Figure 3 This is a graph showing the temperature change results of the radiant cooling test of the coatings in Examples 1, 2, and 3 on the same day.

[0019] Figure 4 This is a comparison chart of the radiant cooling test temperature and cavity temperature of the coatings in Examples 1, 2, and 3 on the same day.

[0020] Figure 5This is a graph showing the temperature change results of the radiant cooling test of the coatings in Examples 1, 4, and 5 on the same day.

[0021] Figure 6 This is a comparison chart of the radiant cooling test temperature and cavity temperature of the coatings in Examples 1, 4, and 5 on the same day.

[0022] Figure 7 This is a graph showing the test results of the water drop contact angle and rolling angle of the coating in Example 1 in a 20g gravel 40cm height cyclic impact test.

[0023] Figure 8 The graph shows the test results of the water drop contact angle and rolling angle of the coating in Example 1 in the cyclic friction test on 1000-grit sandpaper with a load of 100g.

[0024] Fig. 9 This is a graph showing the test results of the water drop contact angle and the rolling angle in a water drop impact test of the coating in Example 1, when the droplet falling speed was adjusted to 1 drop / s at 30 cm below the faucet. DETAILED DESCRIPTION

[0025] In order to further understand the content and features of the present invention, embodiments of the present invention are given below. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0026] The experimental methods in the following examples are conventional methods unless otherwise specified.

[0027] Example 1 A method for preparing a phosphogypsum coating having super-hydrophobic and radiation cooling functions comprises the following steps: Step 1: Add 6 g PG, 3 g NaOH, and 0.5 g Na2SO4 to 30 g deionized water, and stir magnetically at room temperature for 30 min to obtain a mixed suspension; Step 2: The mixed suspension obtained in step 1 was filtered, washed with deionized water and anhydrous ethanol for three times, and dried at 60° C. for 12 h to obtain 4.2 g of hydroxylated PG powder; Step 3: Add 0.43 g KH570 to a mixed solvent of 1 mL deionized water and 13.4 mL anhydrous ethanol, heat at 60 °C with magnetic stirring for 10 min to obtain a dispersant; Step 4: Grind 4.2 g of hydroxylated PG powder obtained in step 2 and add it to the dispersant obtained in step 3, heat at 60° C. and stir magnetically for 2.5 h to obtain a mixed suspension; Step 5: Filter the mixed suspension obtained in step 4, wash it with deionized water and anhydrous ethanol for three times, and dry it at 60° C. for 12 h to obtain a hydrophobically modified PG powder; Step 6: Grind the hydrophobically modified PG powder obtained in step 5, and pass it through a 90-mesh sieve to obtain a hydrophobically modified PG powder with a particle size of 90 mesh; Step 7: Add 0.6 g of PMMA and 1.0 g of SA into a mixed solvent of 10 mL of DMF and 10 mL of THF, and stir at room temperature until all the solids are dissolved to obtain a cooling modifier; Step 8: Add 0.5 g of the hydrophobically modified PG powder obtained in step 6 to the cooling modifier obtained in step 7, use a magnetic stirrer, stir at room temperature at a speed of 500-700 r / min for 10 min, and then perform ultrasonic treatment with an ultrasonic power of 80 w and an ultrasonic time of 10 min to obtain a super hydrophobic coating; Step 9: Add 0.6g PDMS and 0.06g curing agent to 0.5g hydrophobically modified PG powder obtained in step 8, add it to the cooling modifier obtained in step 7, use a magnetic stirrer, stir at room temperature for 10min at a speed of 500-700r / min, and then perform ultrasonic treatment with an ultrasonic power of 80w and an ultrasonic time of 10min to obtain a super-hydrophobic-radiation cooling dual-functional modified phosphogypsum coating; Step 10: Place the aluminum substrate in a plasma cleaning machine and clean it for 2 minutes. At room temperature, use a scraper with a height of 400 μm to scrape the film. Place it in an oven at 80°C to dry for 4 hours. Place it at room temperature for 3 days to obtain a phosphogypsum coating with super-hydrophobic and radiation cooling functions.

[0028] Through the above steps, the water contact angle of the coating prepared on the aluminum substrate reached a maximum of 160.2° ( Figure 1 ), the roll angle is 2.25° ( Figure 2 ).

[0029] Compared with the ambient temperature, the temperature difference ΔT on the sample surface of this embodiment can reach up to 24.5°C, and the average temperature drop is 20°C ( Figure 5 , Figure 6 ), has excellent cooling effect.

[0030] Compared with the surface temperature of commercial white paint, the temperature difference ΔT of the sample surface in this embodiment can reach up to 8°C, and the average temperature drop is 5.38°C ( Figure 5 , Figure 6 ), has excellent cooling effect.

[0031] The sample of this embodiment has been subjected to 30 cycles ( Figure 7 ) can maintain a contact angle of about 155° and a rolling angle of about 6°; in a cyclic friction test with a load of 100g on 1000-grit sandpaper, after 22 cycles ( Figure 8) can maintain a contact angle of about 155° and a rolling angle of less than 10°; at 30cm below the faucet, the droplet falling speed is adjusted to 1 drop / s for 10h ( Fig. 9 ) can maintain a contact angle of about 155° and a rolling angle of about 5°.

[0032] Example 2 The method and steps are the same as those in Example 1, except that 1.5 g of SA is added in step 6, and the rest is the same as in Example 1. The water contact angle of the tested coating is 157.74° ( Figure 1 ), roll angle 2° ( Figure 2 ).

[0033] Compared with the ambient temperature, the sample surface temperature difference ΔT of the sample in this embodiment can reach up to 18.8℃, and the average temperature drop is 13.2℃ ( Figure 3 , Figure 4 ).

[0034] Compared with the surface temperature of commercial white paint, the temperature difference ΔT of the sample surface in this embodiment can reach up to 6.7°C, and the average temperature drop is 4.86°C ( Figure 3 , Figure 4 ).

[0035] Example 3 The method and steps are the same as those in Example 1, except that 2.0 g SA is added in step 6, and the rest is the same as in Example 1. The water contact angle of the tested coating is 159° ( Figure 1 ), roll angle 2° ( Figure 2 ).

[0036] Compared with the ambient temperature, the sample surface temperature difference ΔT of the sample in this embodiment can reach up to 19.99℃, and the average temperature drop is 13.99℃ ( Figure 3 , Figure 4 ).

[0037] Compared with the surface temperature of commercial white paint, the temperature difference ΔT of the sample surface in this embodiment can reach up to 7.9°C, and the average temperature drop is 5.53°C ( Figure 3 , Figure 4 ).

[0038] Example 4 The method and steps are the same as those in Example 1, except that 1.0 g of PMMA is added in step 7, and the rest is the same as in Example 1. The water contact angle of the tested coating is 158.29° ( Figure 1 ), rolling angle 3.25° ( Figure 2 ).

[0039] Compared with the ambient temperature, the sample surface temperature difference ΔT of the sample in this embodiment can reach up to 21.9℃, and the average temperature drop is 18.08℃ ( Figure 5 , Figure 6 ).

[0040] Compared with the surface temperature of commercial white paint, the temperature difference ΔT of the sample surface in this embodiment can reach up to 6.8°C, and the average temperature drop is 4°C ( Figure 5 , Figure 6 ).

[0041] Example 5 The method and steps are the same as those in Example 1, but in step 7, a scraper with a height of 400 μm is used for scraping the film, and the film is placed at room temperature for 5 days to obtain a phosphogypsum radiation cooling multifunctional super hydrophobic coating, and the rest is the same as in Example 1. The water contact angle of the coating tested is 149.04° ( Figure 1 ), roll angle 18° ( Figure 2 ).

[0042] Compared with the ambient temperature, the sample surface temperature difference ΔT of the sample in this embodiment can reach up to 24.3℃, and the average temperature drop is 19.45℃ ( Figure 5 , Figure 6 ), has excellent cooling effect.

[0043] Compared with the surface temperature of commercial white paint, the temperature difference ΔT of the sample surface in this embodiment can reach up to 8.1°C, and the average temperature drop is 5.93°C ( Figure 5 , Figure 6 ), has excellent cooling effect.

Claims

1. A method for preparing a phosphogypsum coating having super-hydrophobic and radiation cooling functions, characterized in that: The following steps are involved: Step 1: Add phosphogypsum PG, NaOH and Na2SO4 into deionized water in proportion, and stir and disperse to obtain a mixed suspension; Step 2: filtering, washing and drying the mixed suspension obtained in step 1 to obtain hydroxylated PG powder; Step 3: Add the silane coupling agent into a mixed solvent of water and anhydrous ethanol, and heat and stir to obtain a dispersant; Step 4: adding the hydroxylated PG powder obtained in step 2 to the dispersant obtained in step 3, and stirring to obtain a mixed suspension; Step 5: filtering, washing and drying the mixed suspension obtained in step 4 to obtain hydrophobically modified PG powder; Step 6: Grind the hydrophobically modified PG powder obtained in step 5, and pass it through a sieve to obtain hydrophobically modified PG powders of different particle sizes; Step 7: Add PMMA and SA in proportion to a mixed solvent of N,N-dimethylformamide and tetrahydrofuran, and stir thoroughly to obtain a cooling modifier; Step 8: adding the hydrophobic modified PG powder obtained in step 6 to the cooling modifier obtained in step 7, stirring sufficiently, ultrasonically treating, and then adding PDMS and its curing agent to obtain a super-hydrophobic-radiation cooling dual-functional modified phosphogypsum coating; Step 9: The coating obtained in step 8 is coated on the substrate by a scraper method, and after the solvent is dried, a phosphogypsum coating with super-hydrophobic and radiation cooling functions is obtained.

2. The method for preparing the phosphogypsum coating having super-hydrophobicity and radiation cooling function according to claim 1, characterized in that: In the step 1, the mass concentration of PG is 0.1-0.5 g / mL, the mass concentration of NaOH is 0.05-0.25 g / mL, the mass concentration of Na2SO4 is 0.005-0.04 g / mL, the stirring temperature is room temperature, and the stirring time is 20-30 min.

3. The method for preparing the phosphogypsum coating having super-hydrophobicity and radiation cooling function according to claim 1, characterized in that: In step 2, the drying temperature is 60-80° C. and the drying time is 10-12 hours.

4. The method for preparing the phosphogypsum coating having super-hydrophobicity and radiation cooling function according to claim 1, characterized in that: In the step 3, the silane coupling agent is any one of KH550, KH560, and KH570; by volume, water: anhydrous ethanol = 3:4-6, and the mass concentration of the silane coupling agent in the silane coupling agent mixture is 0.03-0.06 g / mL.

5. The method for preparing the phosphogypsum coating having super-hydrophobicity and radiation cooling function according to claim 1, characterized in that: In step 4, the stirring temperature is 60-80° C., and the stirring time is 1.0-2.5 h.

6. The method for preparing the phosphogypsum coating having super-hydrophobicity and radiation cooling function according to claim 1, characterized in that: In step 5, the drying temperature is 60-80° C. and the drying time is 10-12 hours.

7. The method for preparing the phosphogypsum coating having super-hydrophobicity and radiation cooling function according to claim 1, characterized in that: In step 6, the mesh size of the sieve is 90-110 meshes.

8. The method for preparing the phosphogypsum coating having super-hydrophobicity and radiation cooling function according to claim 1, characterized in that: In step 7, the volume ratio of DMF:THF in the mixed solvent is 1:1-5, the mass concentration of PMMA added is 0.015-0.1 g / mL, and the mass concentration of SA is 0.02-0.1 g / mL.

9. The method for preparing the phosphogypsum coating having super-hydrophobicity and radiation cooling function according to claim 1, characterized in that: In the step 8, the mass ratio of hydrophobically modified PG powder to cooling modifier is 1:3-4, the PDMS mass concentration is 0.03-0.1 g / ml, the ultrasonic power is 50-100 w, preferably 80 w, the ultrasonic time is 5-30 minutes, preferably 10 min, the stirring temperature is room temperature, and the stirring time is 3-10 min, preferably 5 min.

10. The method for preparing the phosphogypsum coating having super-hydrophobicity and radiation cooling function according to claim 1, characterized in that: In the step 9, the scraping film thickness of the scraping method is 300-400 μm, and the material of the substrate includes any one of a glass sheet, an aluminum sheet, a copper sheet, and a carbon steel sheet.

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