All-solid-waste-based inorganic coating with flame retardance, heat insulation and hydrophobicity and preparation method of all-solid-waste-based inorganic coating

Abstract

The invention relates to the technical field of functional coatings, and particularly discloses an all-solid-waste-based inorganic coating with flame retardance, heat insulation and hydrophobicity and a preparation method of the all-solid-waste-based inorganic coating. The preparation method of the all-solid-waste-based inorganic coating comprises the following steps: uniformly mixing fly ash, ardealite and silica fume, adding water glass, uniformly stirring and dispersing, adding fly ash hollow microspheres, continuously stirring to obtain coating slurry, and uniformly coating the surface of a sample with the coating slurry to obtain the inorganic coating; and finally, spraying or brushing the hydrophobic modified solution on the surface of the inorganic coating, and drying. The inorganic coating prepared by the invention takes all solid wastes as raw materials, so that resource utilization of industrial solid wastes is realized; the coating can generate crystallization transformation from aluminosilicate to mullite at high temperature, oxygen and heat are isolated through the stable inorganic glaze layer, and good fireproof and heat-insulating performance is kept; the hydrophobic solution forms a hydrophobic layer on the surface of the coating, surface energy is reduced, moisture permeation is blocked, the hydrophobic effect is achieved, and the coating can serve as a protective coating of various types of base materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional materials, and particularly relates to an all-solid waste-based inorganic coating with flame retardancy, heat insulation and hydrophobic properties and a preparation method thereof. Background Art

[0002] As a special functional coating, inorganic coatings have played an important role in the fields of fire prevention, anti-corrosion, waterproofing, etc., and are widely used in building materials, electronic devices, industrial protection and environmental engineering. However, inorganic coatings have problems such as complex processes, high costs, easy cracking or peeling, single functions, and poor universality.

[0003] In the prior art, Patent No. CN103740284B uses aluminum dihydrogen phosphate and zirconium sol as the main components to prepare a fireproof coating, which can withstand high temperatures of 2000°C for a long time. However, it requires specific temperature control conditions for preparation, the production process is relatively complex, and the mechanical properties at high temperatures still need to be further enhanced. Patent No. CN110128918B combines two-dimensional nano-fillers and polar polymers to design a flame retardant protective coating for rubber and plastic products, which has good fire prevention and heat insulation effects. However, the flame retardant performance may decrease after friction or washing, the durability is poor, and the universality is low. Patent No. WO2020233027A1 prepares a high heat insulation and high peel strength composite coating through a polyvinyl chloride substrate and a multi-layer flame retardant coating, which is applicable to the building and industrial fields. However, the coating process requirements are strict, resulting in high production costs. Patent No. CN105789523B uses an inorganic / organic composite porous separator containing inorganic ceramic particles and a polymer binder to improve the thermal stability and hydrophobic properties of the separator by adjusting the composition, and is widely used in the field of lithium batteries. However, the coating preparation process is complex, the material ratio requirements are strict, and the surface performance of the coating may be damaged by external forces and decrease. Therefore, there is an urgent need to develop an all-solid waste-based inorganic coating with flame retardancy, heat insulation and hydrophobic properties and a preparation method thereof to solve the above technical problems. Summary of the Invention

[0004] The purpose of the present invention is to provide an all-solid waste-based inorganic coating with flame retardancy, heat insulation and hydrophobic properties and a preparation method thereof, aiming at the above deficiencies of the prior art. The all-solid waste-based inorganic coating has flame retardancy, heat insulation and hydrophobic properties.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions: The first aspect of the present invention is to provide a preparation method of an all-solid waste-based inorganic coating, including the following steps: S1. Prepare liquid-phase raw materials: Dissolve sodium silicate powder in deionized water, add NaOH solution, and configure water glass with a certain modulus to obtain component A; S2. Preparation of solid-phase raw materials: Mix fly ash, phosphogypsum, and silica fume evenly to obtain Component B. S3. Preparation of inorganic coating: Add Component B to Component A, mechanically stir to disperse evenly, add fly ash hollow microspheres and continue stirring to obtain a coating slurry, and evenly coat it on the surface of the sample to obtain an inorganic coating. S4. Hydrophobic modification of the coating: Spray or brush the hydrophobic modification solution on the surface of the inorganic coating, and a solid-waste-based inorganic coating with flame retardancy, heat insulation, and hydrophobic properties is obtained after drying.

[0006] Further, the modulus of sodium silicate is the molar ratio of SiO 2 and Na 2 O, and its range is (1~1.6):1.

[0007] Further, in step S2, the mass ratio of fly ash, phosphogypsum, and silica fume is 10:1:(3.4~6.8).

[0008] Further, the fly ash belongs to F-class low-calcium fly ash. In its chemical composition, the total amount of SiO 2 , Al 2 O 3 , Fe 2 O 3 is greater than 70%, and the CaO content is less than 10%.

[0009] Further, the phosphogypsum is an industrial by-product generated in the production process of wet-process phosphoric acid, and its main component is CaSO 4 ·2H 2 O.

[0010] Further, the main component of the silica fume is SiO 2 , and the purity is greater than 98%.

[0011] Further, in step S3, the mass ratio of Component B to Component A is (0.92~1.59):1, and the mass ratio of Component B to fly ash hollow microspheres is (2.89~4.43):1.

[0012] Further, the thickness of the inorganic coating is 0.5~10 mm.

[0013] Further, in step S4, the hydrophobic modification solution is any one or more of polydimethylsiloxane, triethoxysilane, and sodium methylsilicate.

[0014] The second object of the present invention is to provide a solid-waste-based inorganic coating with flame retardancy, heat insulation, and hydrophobic properties prepared by the above preparation method.

[0015] Compared with the prior art, the beneficial effects brought by the technical solution provided by the present invention are: (1) The all-solid waste-based inorganic coating provided by the present invention will undergo a crystallization transformation from aluminosilicate phase to mullite at high temperatures, improving the high-temperature mechanical strength and thermal stability. At high temperatures, oxygen and heat are isolated by a stable inorganic glaze layer, maintaining good fireproof and heat-insulating properties; the hydrophobic modified solution migrates and accumulates on the coating surface to form a hydrophobic layer, while reducing the surface energy and blocking water penetration, achieving a hydrophobic effect.

[0016] (2) The method adopted by the present invention uses all-solid waste as raw materials, realizes the resource utilization of industrial solid waste, solves the problem of stacking pollution, reduces the consumption of natural raw materials, and endows the coating with a high fire resistance limit and excellent flame retardant properties through the synergistic effect of multiple components in the solid waste. Moreover, it has strong operability, low preparation cost, and simple coating method, and is suitable for the fire safety protection of various flammable and non-flammable substrates; the raw materials used in the present invention exhibit low toxicity or non-toxic characteristics, meeting the development requirements of green chemistry. Description of the Drawings

[0017] Figure 1 HRR image of the inorganic coating on the surface of the plywood prepared in Example 1; Figure 2 THR image of the inorganic coating on the surface of the plywood prepared in Example 1; Figure 3 HRR image of the inorganic coating on the surface of the polyurethane foam prepared in Example 2; Figure 4 THR image of the inorganic coating on the surface of the polyurethane foam prepared in Example 2; Figure 5 Back surface temperature-time image of the inorganic coating on the surface of the cement board prepared in Example 3; Figure 6 Back surface temperature-time image of the inorganic coating on the surface of the steel plate prepared in Example 4; Figure 7 Water contact angle images of the inorganic coatings prepared in Examples 1-4 and Comparative Example 1 before and after hydrophobic modification; Figure 8 Saturated water absorption images of the inorganic coatings prepared in Examples 1-4 and Comparative Example 1 before and after hydrophobic modification; Figure 9 Scanning electron microscope images of the inorganic coating prepared in Example 1 at different scales; Figure 10 Scanning electron microscope images of the inorganic coating prepared in Comparative Example 1 at different scales. Detailed Description of the Invention

[0018] To make the objectives, technical solutions, and advantages of the present invention clearer, the following further describes in detail the specific implementation manners of the present invention in combination with specific embodiments and the accompanying drawings. For embodiments where specific test methods, instrument equipment, or conditions are not specified, they shall all be carried out according to the techniques or conditions described in the literature in this field or according to the product instructions. For reagents or instruments where the manufacturer is not specified, they are all conventional products that can be obtained through commercial purchase.

[0019] An embodiment of the present invention provides an all-solid waste-based inorganic coating with flame retardancy, heat insulation, and hydrophobic properties and a preparation method thereof, including the following steps: (1) Take an appropriate amount of sodium silicate powder and dissolve it in deionized water, add an appropriate amount of NaOH, and configure sodium silicate water glass with a modulus of 1 to 1.6. After ultrasonic dispersion, transfer it to an oil bath at 80 to 120 °C and continue stirring for 1 h. After it becomes a colorless or light yellow transparent liquid, pour it into a beaker, seal it, and cool it for standby, denoted as component A.

[0020] (2) Add an appropriate amount of deionized water to the pre-configured water glass according to the solid-liquid ratio of (2.5 to 4):1. (3) Take an appropriate amount of fly ash, phosphogypsum, and silica fume, mix them evenly, denoted as component B, add them to the liquid-phase raw material in step (2), stir for 3 to 5 min, and according to the mass ratio of component B to fly ash cenospheres of (2.89 to 4.43):1, add an appropriate amount of fly ash cenospheres and continue stirring for 1 to 3 min, and mix them thoroughly to obtain a coating slurry.

[0021] (4) Use the brushing method to coat the coating slurry on the substrate and cure it at room temperature until the surface is dry.

[0022] (5) Spray or brush the hydrophobic modification solution on the surface of the inorganic coating, and after drying, an all-solid waste-based inorganic coating with flame retardancy, heat insulation, and hydrophobic properties is obtained. The hydrophobic modification solution can be selected from one or more of polydimethylsiloxane (PDMS), triethoxyoctylsilane (TTOS), and sodium methyl silicate, dissolved in n-hexane, with a concentration of 2% to 30%.

[0023] The fly ash used in the present invention: In the chemical composition, the total amount of SiO 2 , Al 2 O 3 , Fe 2 O 3 is greater than 70%, and the CaO content is less than 10%. According to the standard GB / T1596-2017, it belongs to F-class low-calcium fly ash, with a particle size of about 30 μm.

[0024] Phosphogypsum: It is an industrial by-product generated during the production of wet-process phosphoric acid, with the main component being CaSO 4 ·2H 2O, with a particle size of about 50 μm.

[0025] Silica fume: The main component is SiO 2 , with a purity greater than 98% and a particle size of about 10 μm.

[0026] Fly ash cenospheres: The main components are SiO 2 , Al 2 O 3 , with a particle size of about 400 μm.

[0027] In the research and development or use process of the embodiments of the present invention, some positive effects have been achieved, and there are indeed great advantages compared with the prior art. The following content will be described in combination with the data, charts, etc. of the test process.

[0028] Example 1 (1) Take 43.9 g of sodium silicate powder and dissolve it in deionized water. Add NaOH according to a mass ratio of 1:2.6 to prepare sodium silicate water glass with a modulus of 1. After ultrasonic dispersion, transfer it to an oil bath at 120 °C and continue stirring for 1 h. After it becomes a colorless or light yellow transparent liquid, pour it into a beaker, seal it, and cool it for later use.

[0029] (2) Add 61 g of deionized water to the pre-prepared water glass according to a solid-liquid ratio of 2.5:1. (3) Take 100 g of fly ash, 10 g of phosphogypsum, and 34 g of silica fume, mix them evenly, add them to the liquid-phase raw material in step (2), stir for 5 min, add 40 g of fly ash cenospheres, and continue stirring for 3 min to mix them thoroughly to obtain a coating slurry.

[0030] (4) Use the brushing method to coat the coating slurry on the wooden board, control the thickness at 0.5 - 2 mm, and cure it at room temperature until the surface is dry.

[0031] (5) Dissolve 1.25 g of PDMS in 48.75 g of n-hexane to obtain a hydrophobic modification solution with a concentration of 2.5%. Brush it on the surface of the inorganic coating, and after drying, a solid waste-based inorganic coating with flame retardant, heat insulation, and hydrophobic properties is obtained.

[0032] Example 2 (1) Take 44.08 g of sodium silicate powder and dissolve it in deionized water. Add NaOH according to a mass ratio of 1:6.09 to prepare sodium silicate water glass with a modulus of 1.4. After ultrasonic dispersion, transfer it to an oil bath at 120 °C and continue stirring for 1 h. After it becomes a colorless or light yellow transparent liquid, pour it into a beaker, seal it, and cool it for later use.

[0033] (2) Add 61 g of deionized water to the pre-prepared water glass according to a solid-liquid ratio of 2.5:1. (3) Take 100 g of fly ash, 10 g of phosphogypsum, and 43 g of silica fume. After mixing them evenly, add them to the liquid-phase raw materials in step (2), stir for 5 min, add 40 g of fly ash hollow microspheres, and continue stirring for 3 min. Mix them thoroughly to obtain a coating slurry.

[0034] (4) Apply the coating slurry onto the polyurethane foam by the brushing method, control the thickness to be 0.5 - 2 mm, and cure at room temperature until the surface is dry.

[0035] (5) Dissolve 2.5 g of PDMS in 47.5 g of n-hexane to obtain a 5% hydrophobic modification solution, brush it on the surface of the inorganic coating, and after drying, a fully solid-waste-based inorganic coating with flame retardancy, heat insulation, and hydrophobic properties is obtained.

[0036] Example 3 (1) Take 43.9 g of sodium silicate powder and dissolve it in deionized water. Add NaOH according to a mass ratio of 1:2.6 to prepare sodium silicate water glass with a modulus of 1. After ultrasonic dispersion, transfer it to an oil bath at 120 °C and continue stirring for 1 h. After it becomes a colorless or light yellow transparent liquid, pour it into a beaker, seal it, and cool for later use.

[0037] (2) Add 82 g of deionized water to the pre-prepared water glass according to a solid-liquid ratio of 2.5:1. (3) Take 100 g of fly ash, 10 g of phosphogypsum, and 43 g of silica fume. After mixing them evenly, add them to the liquid-phase raw materials in step (2), stir for 5 min, add 40 g of fly ash hollow microspheres, and continue stirring for 3 min. Mix them thoroughly to obtain a coating slurry.

[0038] (4) Apply the coating slurry onto the cement by the brushing method, control the thickness to be 2 - 8 mm, and cure at room temperature until the surface is dry.

[0039] (5) Dissolve 5 g of PDMS in 45 g of n-hexane to obtain a 10% hydrophobic modification solution, brush it on the surface of the inorganic coating, and after drying, a fully solid-waste-based inorganic coating with flame retardancy, heat insulation, and hydrophobic properties is obtained.

[0040] Example 4 (1) Take 43.9 g of sodium silicate powder and dissolve it in deionized water. Add NaOH according to a mass ratio of 1:2.6 to prepare sodium silicate water glass with a modulus of 1. After ultrasonic dispersion, transfer it to an oil bath at 120 °C and continue stirring for 1 h. After it becomes a colorless or light yellow transparent liquid, pour it into a beaker, seal it, and cool for later use.

[0041] (2) Add 82 g of deionized water to the pre-prepared water glass according to a solid-liquid ratio of 2.5:1. (3) Take 100 g of fly ash, 10 g of phosphogypsum, and 43 g of silica fume. After mixing them evenly, add them to the liquid-phase raw materials in step (2), stir for 5 min, add 40 g of fly ash hollow microspheres, and continue to stir for 3 min. Mix them thoroughly to obtain a coating slurry.

[0042] (4) Apply the coating slurry on the steel plate by the brushing method, control the thickness to be 2 - 8 mm, and cure at room temperature until the surface is dry.

[0043] (5) Dissolve 10 g of PDMS in 40 g of n-hexane to obtain a hydrophobic modification solution with a concentration of 20%. Brush it on the surface of the inorganic coating, and after drying, a fully solid waste-based inorganic coating with flame retardancy, heat insulation, and hydrophobic properties is obtained.

[0044] Comparative Example 1 The difference between this comparative example and Example 1 is that after the inorganic coating is prepared, the hydrophobic solution is not brushed on its surface, and the preparation process does not include step (5); other preparation methods are the same as those in Example 1.

[0045] Comparative Example 2 The difference between this comparative example and Example 1 is that the solid-phase raw materials in step (3) do not contain phosphogypsum; other preparation methods are the same as those in Example 1.

[0046] Conduct cone calorimeter tests, heat insulation tests, water contact angle tests, water absorption tests, and scanning electron microscope tests on the inorganic coatings prepared in Examples 1 - 4 and Comparative Examples 1 - 2 respectively.

[0047] As Figure 1 and Figure 2 shown, they are respectively the heat release rate (HRR) and total heat release (THR) images of the cone calorimeter test of the plywood coated with 0.5 - 2 mm inorganic coating in Example 1. It can be seen from the figure that the peak heat release rate (PHRR) and THR of the plywood without the inorganic coating reach 266.13 kW / m 2 and 26.58 MJ / m 2 , respectively. After the plywood is coated with the inorganic coating, the flame retardancy of the plywood increases with the increase of the coating thickness. The lowest PHRR is 118.52 kW / m 2 , a decrease of 55.47%, and the lowest THR is 12.25 MJ / m 2 , a decrease of 53.91%. Moreover, the time to reach the peak of heat release is significantly delayed, effectively improving the fire safety of the plywood.

[0048] As Figure 3 and Figure 4As shown, they are the HRR and THR images of the cone calorimeter test of the polyurethane foam coated with an inorganic coating of 0.5 - 2 mm in Example 2. It can be seen from the figure that the PHRR and THR of the polyurethane foam without the inorganic coating reached 234.38 kW / m 2 and 13.12 MJ / m 2 . After the polyurethane foam was coated with the inorganic coating, the PHRR and THR of the polyurethane foam decreased simultaneously with the increase of the coating thickness. When the coating thickness reached 2 mm, the PHRR and THR of the polyurethane foam were 120.90 kW / m 2 and 8.74 MJ / m 2 , which were decreased by 48.41% and 33.38% respectively, and the time to reach the peak of heat release was significantly delayed, effectively improving the fire safety of the polyurethane foam.

[0049] As Figure 5 and Figure 6 shown, they are the back surface temperature - time images of the heat insulation test of the non - combustible substrates coated with an inorganic coating of 2 - 8 mm in Examples 3 and 4 respectively. It can be seen from the figure that the maximum back surface temperatures of the cement board and the steel plate without the inorganic coating reached 352.8 °C and 290.5 °C respectively. After the substrates were coated with the inorganic coating, the heat insulation performance of the substrates improved with the increase of the coating thickness. When the coating thickness increased to 8 mm, the maximum back surface temperatures of the cement board and the steel plate were 223.8 °C and 183.5 °C respectively, which were decreased by 33.97% and 36.83% respectively, and the fire safety performance was significantly improved.

[0050] As Figure 7 and Figure 8 shown, they are the waterproof performance test images of the inorganic coatings in Examples 1 - 4 and Comparative Example 1 respectively. It can be seen from Figure 7 that the inorganic coating in Comparative Example 1 showed hydrophilicity, and the water contact angle was 38.114°. After the inorganic coatings in Examples 1 - 4 were hydrophobically modified, the surfaces of the coatings showed hydrophobicity, and the water contact angle increased with the increase of the PDMS concentration, reaching up to 124.008°. It can be seen from Figure 8 that the waterproof performance of the inorganic coating in Comparative Example 1 was poor, while PDMS could effectively reduce the water absorption rate of the coating. In Example 4, the saturated water absorption rate of the inorganic coating was decreased by 74.69% compared with that in Comparative Example 1, which confirmed that PDMS could endow the inorganic coating with excellent hydrophobic properties.

[0051] As Figure 9 and Figure 10 shown, they are the scanning electron microscope images of the inorganic coatings in Example 1 and Comparative Example 2 respectively. It can be seen from Figure 9 that the microstructure of the inorganic coating containing phosphogypsum was flat and dense, a large number of N - A - S - H gels could be observed, and the reaction of fly ash was relatively complete. It can be seen from Figure 10It can be seen that the overall structure of the inorganic coating without the addition of phosphogypsum is relatively loose, and there are many unreacted fly ashes and incompletely cross-linked N-A-S-H gel networks. The results show that phosphogypsum can promote the polymerization reaction of the inorganic coating and make the coating structure more dense.

[0052] In the case of no conflict, the above embodiments and the features in the embodiments in this article can be combined with each other.

[0053] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a solid waste-based inorganic coating having flame retardant, heat insulating and hydrophobic properties, characterized in that: The following steps are involved: S1. Prepare liquid raw materials: dissolve sodium silicate powder in deionized water, add NaOH solution, and prepare water glass with a certain modulus to obtain component A; S2. preparing solid raw materials: stirring and mixing fly ash, phosphogypsum and silica fume to obtain component B; S3, preparing an inorganic coating: adding component B to component A, mechanically stirring to make it evenly dispersed, adding fly ash hollow microbeads and continuing to stir to obtain a coating slurry, and evenly coating the slurry on the sample surface to obtain an inorganic coating; S4. Hydrophobic modification of coating: Spray or brush the hydrophobic modified solution on the surface of the inorganic coating. After drying, a solid waste-based inorganic coating with flame retardant, heat insulating and hydrophobic properties is obtained.

2. The preparation method according to claim 1, characterized in that In step S1, the water glass modulus is the molar ratio of SiO2 to Na2O, which ranges from (1 to 1.6):

1.

3. The preparation method according to claim 2, characterized in that: In step S2, the mass ratio of fly ash, phosphogypsum and silica fume is 10:1:(3.4-6.8).

4. The preparation method according to claim 3, characterized in that: The fly ash is Class F low-calcium fly ash.

5. The preparation method according to claim 4, characterized in that: The phosphogypsum is an industrial byproduct produced in the production process of wet phosphoric acid, and its main component is CaSO4·2H2O.

6. The preparation method according to claim 5, characterized in that: The main component of the silica ash is SiO2, and the purity is greater than 98%.

7. The preparation method according to claim 6, characterized in that: In step S3, the mass ratio of component B to component A is (0.92-1.59):1, and the mass ratio of component B to fly ash hollow microspheres is (2.89-4.43):

1.

8. The preparation method according to claim 7, characterized in that: The thickness of the inorganic coating is 0.5-10 mm.

9. The preparation method according to claim 8, characterized in that: In step S4, the hydrophobic modified solution is any one or more of polydimethylsiloxane, triethoxyoctylsilane, and sodium methyl silicate.

10. An all-solid waste-based inorganic coating having flame retardant, heat insulating and hydrophobic properties, prepared by the preparation method according to any one of claims 1 to 9.

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