A HGMs@Al 2 O 3 Composite microspheres and preparation method thereof and application in constructing three-dimensional thermal insulation structure water-based thermal insulation coating

Abstract

The present invention discloses an HGMs@Al2O3 composite microsphere, a preparation method thereof, and an application thereof in constructing a three-dimensional heat-insulating structure waterborne heat-insulating coating, belonging to the technical field of functional materials. In the present invention, PVP and boehmite sol are used to modify the surface of HGMs, and an HGMs@Al2O3 composite microsphere with a core-shell structure that is hydrophilic on the outside and hydrophobic on the inside is prepared, which improves the compatibility between the polymer resin matrix and HGMs. Moreover, the surface-enriched high-hard Al2O3 particles improve the brittleness of the spherical wall, solving the problems that the existing HGMs, as heat-insulating fillers, have a brittle spherical wall and weak interaction with waterborne substrates, resulting in poor heat preservation and heat insulation performance of waterborne coatings. The present invention uses HGMs@Al2O3 as a heat-insulating filler, and utilizes the internal hollow of HGMs and the gas cavity containing rare gases to closely arrange and construct a three-dimensional heat-insulating gas layer in the composite coating, effectively preventing the generation of heat convection after heating, improving the interfacial thermal resistance, and reducing the heat conduction efficiency.

Description

Technical Field

[0001] The present invention relates to a HGMs@Al 2 O 3 The invention relates to composite microspheres, a preparation method and application in constructing a three-dimensional heat-insulating structure water-based heat-insulating coating, belonging to the field of surface modification of hollow glass microspheres (HGMs) and heat-insulating structure design of water-based coatings. Background Art

[0002] Since the "global warming" was formally proposed in the late 1970s, its popularity has remained high. The main reason is the burning of fossil fuels by humans. With the over-exploitation of energy in recent years, the world is facing a serious energy crisis. Thermal insulation is a powerful measure to reduce energy consumption and improve energy utilization. Traditional thermal insulation materials include: mineral wool, glass fiber, polyurethane foam and extruded polystyrene (PS) foam insulation board and other materials, which often have defects such as complex preparation process, poor fire resistance, and large fluctuations in thermal conductivity. In recent years, thermal insulation coatings have been widely studied due to their advantages such as simple construction procedures and stable thermal conductivity. Thermal insulation coatings are a thermally inert material with low thermal conductivity and are not easy to expand when heated. It is coated on the surface of the substrate to form a dense vacuum layer. After curing, the thermal resistance of the substrate is increased, and the direct conduction and heat convection of phonons carrying heat are blocked to achieve the purpose of thermal insulation and thermal energy management. In recent years, a large number of scientific researchers have conducted many studies in the field of coatings. Nanofillers (aerogel nanopowder, TiO 2 , vermiculite, SiC, nano negative thermal expansion fillers, etc.) are considered to be effective means to improve the thermal barrier capacity of coatings.

[0003] Air is the substance with the worst thermal conductivity in nature, about 0.023W / m·K. Therefore, using a filler with a hollow structure to store gas is one of the effective ways to prepare thermal insulation coatings. Hollow glass microspheres (HGMs) are a high-temperature resistant thermal insulation material with a hollow cavity containing rare gases. They are widely used in industrial fields such as plastics, rubber, and coatings. They have low thermal conductivity, high melting point, good fluidity, and obvious wave absorption, sound insulation, and thermal insulation effects. The addition of HGMs has a positive effect on reducing the thermal conductivity of the composite coating. Due to the low thermal shrinkage coefficient and isotropy, the shrinkage of the composite coating can be effectively controlled, making the size of the coating product stable and without warping defects in all directions.

[0004] Although the thermal conductivity of HGMs-based composite coatings is extremely low, the unique spherical wall structure of HGMs itself leads to the lowest surface energy and a natural repulsion with the water-based matrix. The coating has only a small amount of chemical bonds coupled with the HGMs surface, and there is always an obvious two-phase separation gap, which leads to large fluctuations in the overall thermal conductivity of the composite material. At the same time, the HGMs spherical wall is brittle, and the HGMs skeleton structure will be broken under the condition of large impact load, which seriously reduces the thermal barrier effect of the coating. Based on this, it is very necessary to provide a method that can enhance the interaction between HGMs and water-based substrates, improve the brittle characteristics of the spherical wall, and prepare a water-based coating with excellent thermal insulation performance. Summary of the invention

[0005] The present invention aims to solve the problem that the existing HGMs as thermal insulation fillers have brittle ball walls and weak interaction with the water-based substrate, resulting in poor thermal insulation performance of water-based coatings. 2 O 3 Composite microspheres, preparation method and application in constructing three-dimensional thermal insulation structure water-based thermal insulation coating.

[0006] The technical solution of the present invention:

[0007] One of the purposes of the present invention is to provide a HGMs@Al 2 O 3 A method for preparing composite microspheres, the method comprising the following steps:

[0008] (1) After flotation treatment of HGMs, the HGMs are dispersed in ethanol, a PVP / ethanol solution is added dropwise, stirred and centrifuged, and the solid is dried to obtain the pretreated HGMs;

[0009] (2) The HGMs pretreated in (1) were placed in a three-necked flask, and isopropanol and deionized water were added in sequence. The mixture was ultrasonically dispersed and stirred and heated to 70 °C. The AIP / isopropanol solution was poured in and stirred for 4 h. The mixture was aged for 2 h and centrifuged to obtain composite particles. The composite particles were washed with deionized water until the pH was 7-8 and then dried to obtain HGMs@Al 2 O 3 Composite microspheres.

[0010] Further, the flotation treatment process of HGMs in (1) is as follows: 15 to 20 parts by weight of HGMs are added to 120 to 170 parts by weight of C 2 H 5 OH solution, stirred at 160-170 r / min and ultrasonically dispersed for 1 h to obtain a suspension, which was centrifuged at 4000 r / min for 15 min, and the upper solid was taken and dried at 60°C for 6 h.

[0011] Further defined, (1) the specific operation is: at 65°C, the HGM after flotation treatment is dispersed in ethanol, PVP / ethanol solution is added dropwise, stirred for 3 hours and then centrifuged, and the solid is dried at 60°C for 3 to 5 hours.

[0012] Further defined, the PVP / ethanol solution is composed of 1 to 2 parts by mass of PVP and 15 to 20 parts by mass of C 2 H 5 OH solution and ultrasonically dispersed for 1.5 h.

[0013] It is further defined that the time for adding the PVP / ethanol solution dropwise in (1) is 10 minutes.

[0014] It is further defined that (1) the centrifugal speed is 4000 r / min, the time is 10 min, and the number of times is at least 3 times.

[0015] It is further defined that the mass ratio of the pretreated HGMs, isopropanol and deionized water in (2) is 15-20 parts: 120-150 parts: 40-50 parts.

[0016] It is further defined that the amount of aluminum isopropoxide in the AIP / isopropanol solution is 5 to 7 parts by mass, and the amount of isopropanol is 15 to 20 parts by mass.

[0017] The second object of the present invention is to provide a HGMs@Al prepared by the above method. 2 O 3 Composite microspheres, the composite microspheres are based on HGMs as the core and Al 2 O 3 The core-shell structure microspheres have an average particle size of 24 μm.

[0018] The third object of the present invention is to provide a HGMs@Al 2 O 3 The application of composite microspheres is specifically used for preparing water-based thermal insulation coatings.

[0019] A fourth object of the present invention is to provide a method for preparing the above-mentioned water-based thermal insulation coating, the method comprising the following steps:

[0020] S1, HGMs@Al 2 O 3 The composite microspheres were dispersed in an ethanol / water solution, APTES was added, stirred, centrifuged, and the solid was dried to obtain the treated HGMs@Al 2 O 3 Composite microspheres;

[0021] S2, the treated HGMs@Al 2 O 3 Composite microspheres, mica flakes, CaCO3 The powder and dispersant are added to the acrylic emulsion, mixed thoroughly, and stirred in a high-speed disperser for 24 hours to obtain a mixed emulsion;

[0022] S3, adding a defoamer, a thickener, a film-forming aid, a leveling agent and ethylene glycol to the mixed emulsion obtained in S2 in sequence, stirring evenly to obtain a water-based thermal insulation coating.

[0023] It is further defined that the coating is composed of the following raw materials in parts by weight: 12 to 15 parts of the HGMs@Al described in claim 5 2 O 3 Composite microspheres, 2-3 parts APTES, 45-50 parts acrylic emulsion, 7-8 parts mica flakes, 6-7 parts CaCO 3 powder, 1 to 2 parts of dispersant, 1 to 2 parts of defoamer, 1 to 2 parts of thickener, 1 to 2 parts of film-forming aid, 1 to 2 parts of leveling agent and 4 to 5 parts of ethylene glycol.

[0024] It is further defined that the ethanol / water solution in S1 is a mixture of ethanol and water in a volume ratio of 2:1.

[0025] It is further defined that the dispersant is sodium polycarboxylate, the defoaming agent is dimethyl silicone oil, the thickener is sodium bentonite, the film-forming aid is PVA, and the leveling agent is water-based varnish.

[0026] The fifth object of the present invention is to provide an application method of the above-mentioned water-based thermal insulation coating, which comprises coating the water-based thermal insulation coating on the surface of a substrate, drying at room temperature for 3 hours, and obtaining the water-based thermal insulation coating.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The present invention uses polyvinyl pyrrolidone (PVP) and boehmite sol to modify the surface of HGMs to prepare HGMs@Al 2 O 3 Composite microspheres form a core-shell structure with hydrophilic outside and hydrophobic inside, forming a "bridge" between the aqueous matrix and HGMs, and enriching high-hardness Al on the surface of HGMs. 2 O 3 The particles improve the brittleness of the ball wall and solve the problem of brittleness of HGMs and two-phase separation when compounded with an aqueous matrix.

[0029] (2) The present invention adopts HGMs@Al 2 O 3As a thermal insulation filler, HGMs are hollow inside and contain air cavities containing rare gases. They are closely arranged in the composite coating to build a three-dimensional thermal insulation gas layer. The closely arranged HGMs can effectively prevent the generation of thermal convection after heating, improve the interface thermal resistance, form a buffer layer for the propagation of energy-carrying phonons, and reduce the heat conduction efficiency. Al2O3 converted from boehmite 2 O 3 The particles can improve the compatibility between the polymer resin matrix and HGMs, prevent gas from penetrating the coating, and improve the overall thermal insulation performance of the composite coating. Characterization test: The water-based thermal insulation coating of the present invention, which constructs a three-dimensional thermal insulation structure, has a thermal conductivity (λ) reduced by 58.7% to 0.097Wm -1 K -1 , which is 58.7% lower than that of latex film; in a thermal environment of 100°C, the coating can achieve a heat insulation effect of a temperature difference of 18.1°C.

[0030] (3) The water-based thermal insulation coating provided by the present invention for constructing a three-dimensional thermal insulation structure has a tensile strength of about 3.50 MPa, which is about 53% higher than that of pure acrylic emulsion film. The maximum thermal degradation temperature of the coating is 411.8°C, and the mass loss within 500°C is about 30.8%. The results of thermogravimetric analysis show that: HGMs@Al 2 O 3 Microspheres enhance the heat resistance of water-based thermal insulation coatings. This is because Al 2 O 3 The particles have excellent heat resistance, and the hydrophilic surface enhances the cohesion of the composite material, plays a "bonding" role, and the heat resistance of the coating is significantly improved.

[0031] (4) The water-based thermal insulation coating of the present invention, which constructs a three-dimensional thermal insulation structure, has high thermal insulation efficiency, low raw material cost, simple production equipment, and stable coating performance. Compared with existing water-based thermal insulation coatings, HGMs@Al 2 O 3 The invention provides a new method for surface treatment of HGMs and a new technology for thermal insulation of water-based coatings.

[0032] In addition, the water-based thermal insulation coating of the present invention that constructs a three-dimensional thermal insulation structure can be applied to equipment, oil pipelines, ships, warships, etc. that are sensitive to high temperatures. Application on the surface of building materials can delay changes in the surface temperature of the material, improve the thermal barrier effect of the substrate, and reduce heat loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1FTIR spectra of PVP, HGMs and pretreated HGMs;

[0034] Figure 2 HGMs and HGMs@Al prepared in Example 1 2 O 3 XRD patterns of composite microspheres;

[0035] Figure 3 The SEM images and TEM images of the particles obtained at different stages of the surface treatment of HGMs in Example 1, where (a) is the SEM image of HGMs, (b) is the SEM image of HGMs after pretreatment, and (c) is the SEM image of HGMs@Al 2 O 3 SEM images of composite microspheres, (d) HGMs@Al 2 O 3 TEM images of composite microspheres;

[0036] Figure 4 The water contact angle photos of water-based thermal insulation coatings with different filler contents obtained in different embodiments;

[0037] Figure 5 The tensile strength of water-based thermal insulation coatings with different filler contents obtained in different embodiments;

[0038] Figure 6 The elongation at break of water-based thermal insulation coatings with different filler contents obtained in different embodiments;

[0039] Figure 7 SEM images of water-based thermal insulation coatings with different filler contents obtained in different embodiments, where (a) is 0% HGMs@Al 2 O 3 Content, (b) 7% HGMs@Al 2 O 3 content;

[0040] Figure 8 The thermal conductivity of water-based thermal insulation coatings with different filler contents obtained in different embodiments;

[0041] Fig. 9 is the thermal conductivity variation index of water-based thermal insulation coatings with different filler contents obtained in different embodiments;

[0042] Fig.10 Infrared thermal imaging images of water-based thermal insulation coatings with different filler contents obtained in different embodiments under a 100°C thermal field;

[0043] Fig.11 The thermal imaging histograms of water-based thermal insulation coatings with different filler contents obtained from different embodiments at temperature equilibrium;

[0044] Fig.12 The center point temperature variation curves of water-based thermal insulation coatings with different filler contents obtained in different embodiments. DETAILED DESCRIPTION

[0045] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0046] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0047] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0048] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained through commercial channels by those skilled in the art.

[0049] Example 1

[0050] 1. Preparation of HGMs@Al in this Example 2 O 3 The method of composite microspheres is as follows:

[0051] Step 1: Take 8g HGMs and add 75mL 2 H 5 The suspension was dispersed ultrasonically in the OH solution for 1 hour to obtain a suspension, which was subjected to centrifugal flotation treatment at a rate of 4000 r / min for 15 minutes. The upper solid was taken and dried at 60°C for 6 hours for later use.

[0052] Step 2: 100 mL of 2 H 5 Heat the OH solution in a three-necked flask to 65°C while stirring and keep it warm for 1 hour.

[0053] Step 3: Take 5 g of HGMs obtained by centrifugal flotation and add it into a three-necked bottle.

[0054] Step 4: Then add C containing 1g PVP 2 H 5OH solution, and ultrasonically disperse and stir for 1 h

[0055] Step 5: Centrifuge the milky white dispersion in the three-necked flask in a centrifuge tube for 3 times at a centrifugal speed of 4000 r / min for 10 min. Take the solid and dry it at 60° C. for 12 h to obtain the pretreated HGMs.

[0056] Step 6: Take 5 g of the HGMs solid powder after drying and pretreatment in a three-necked bottle, add 40 mL of isopropanol solution and 15 mL of deionized water in sequence, disperse by ultrasound, stir and heat to 65-70°C.

[0057] Step 7: Dissolve 2 g of AIP in 8 mL of isopropanol solution, pour into the three-necked flask in step 5 by pouring method, continue stirring for 4 h, and age for 2 h.

[0058] Step 8: Place the milky white dispersion in the three-necked flask into a centrifuge tube for centrifugation, and repeatedly rinse the composite particles with deionized water until the pH is 7-8, and dry at 60°C for 8 hours to obtain HGMs@Al 2 O 3 Composite microspheres.

[0059] The HGMs@Al 2 O 3 The composite microspheres were characterized and the results are as follows:

[0060] (1) Figure 1 FTIR spectra of PVP, HGMs and pretreated HGMs (PVP modified HGMs). Figure 1 It can be seen that curve a is at 2941cm -1 and 2815cm -1 PVP-CH appears 2 - Symmetric and asymmetric stretching vibration peaks, 1641cm -1 The -CO- stretching vibration peak of PVP is at 464cm. Curves b and c have the same infrared characteristic peak: -1 There is a sharp and flat Si-O-Si bond bending vibration peak at 798cm -1 There is a sharp and narrow Si-O symmetric stretching vibration peak at 1082cm -1 There is a broad and strong peak of Si-O asymmetric stretching vibration at 3347cm -1 There is a Si-OH stretching vibration peak.

[0061] After the surface of HGMs was modified by PVP, a different infrared characteristic absorption peak appeared in curve c: 2941cm -1 A sharp and narrow -CH 2 -Symmetrical stretch absorption vibration peak; 2815cm-1 There is a weak -CH 2 -Asymmetric stretching vibration absorption peak; 1641cm -1 is the stretching vibration absorption peak of the -CO- functional group in PVP; 1362cm -1 The absorption peak of the hydroxyl group in the plane is 3455cm, which is the characteristic peak of PVP functional group. -1 The stretching vibration peak of Si-OH at 464 cm -1 Si-O-Si bending vibration peak at 1082cm -1 The Si-O asymmetric stretching vibration peak at the position becomes weaker and blue-shifted, indicating that the -OH functional groups on the surface of HGMs are coupled with the double bonds of PVP and consume the -OH functional groups, proving that PVP successfully activates HGMs.

[0062] (2) Figure 2 For HGMs and HGMs@Al 2 O 3 The XRD pattern of the composite microspheres is Figure 2 It can be seen that the HGMs curve has a broad diffraction peak (023) at 2θ = 22°, which is amorphous SiO 2 The X-ray characteristic diffraction peaks of HGMs were not observed in the range of 2θ = 22° to 55°, and no α / β-cristobalite and α / β-tridymite structures were found. This indicates that the sphere wall of HGMs is composed of amorphous silicon dioxide, and the surface of HGMs microspheres has SiO 4 Tetrahedron basic unit, showing isotropy. Comparison of HGMs curve and HGMs@Al 2 O 3 Composite microsphere curve, HGMs@Al 2 O 3 The composite microsphere curve shows the characteristic broad peaks (113) of α-Al2O3 trigonal crystal system and the characteristic broad peaks (113) of γ-Al2O3 trigonal crystal system at 2θ=44.48° and 66.78°. 2 O 3 The characteristic broad peak of cubic diffraction (214) and the peak intensity of the characteristic peak of amorphous SiO2 diffraction at 2θ=22° weakened, indicating that the boehmite sol was transformed into Al on the surface of HGMs. 2 O 3 The particles are chemically bonded to the HGMs sphere wall, and the amorphous SiO2 exposed to X-rays 2 As the components decrease, the peak intensity of the spectrum weakens.

[0063] (3) Figure 3The SEM images and TEM images of the particles obtained at different stages of HGMs surface treatment, where (a) is the SEM image of HGMs, (b) is the SEM image of HGMs after pretreatment, and (c) is the SEM image of HGMs@Al 2 O 3 SEM images of composite microspheres, (d) HGMs@Al 2 O 3 TEM images of composite microspheres. As can be seen from Figure (a), the surface of HGMs is uniform and smooth, without any particles or other loads. As can be seen from Figure (b), the surface of HGMs is coated with a thin layer of PVP and the wall thickness increases. PVP increases the surface viscosity of HGMs, making them more adsorbable to nanoparticles. Figure (c) shows the surface of the ball after calcination of HGMs coated with boehmite sol. Compared with Figure (a), the surface of HGMs is enriched with uniform and dense Al 2 O 3 The particles have a diameter of about 50 to 200 nm and present a core-shell structure. The particle formation can be explained by a cooperative self-assembly mechanism. From the TEM image in Figure (d), it can be seen that PVP covers a thin layer on the surface of HGMs with a thickness of about 130 nm. The surface-enriched nano-Al 2 O 3 The particles, PVP, and substrate surfaces formed a stable phase structure without phase separation, indicating that Al 2 O 3 , PVP, and HGMs produce chemical bond coupling. The above results show that: HGMs@Al 2 O 3 The composite microspheres have stable structure and stable interface.

[0064] 2. Using the HGMs@Al obtained above 2 O 3 The water-based thermal insulation coating is prepared using composite microspheres as raw materials. The specific preparation method is as follows:

[0065] Step 1: Get HGMs@Al 2 O 3 1g of composite microspheres in 75mL C 2 H 5 OH / H 2 O composite solution (C 2 H 5 OH / H 2 The O composite solution was prepared by mixing ethanol and water in a volume ratio of 2:1), and the temperature was raised to 65°C by ultrasonic dispersion and stirring, and kept warm for 1 hour.

[0066] Step 2: Add 0.5 g of γ-aminopropyltriethoxysilane (APTES) to the solution in step 1 and disperse by ultrasonic for 4 h. Put the milky white dispersion into a centrifuge tube, centrifuge for 3 times, take the solid in the centrifuge tube into a petri dish, and dry at 60°C for 12 h to obtain a solid powder for standby use.

[0067] Step 3: Take 20g of acrylic resin emulsion into a three-necked flask and add HGMs@Al 2 O 3 Composite microspheres 5g, mica flakes 3g, heavy calcium 3g, dispersant polycarboxylate sodium salt 0.5g.

[0068] Step 4: Add the mixed solution from step 3 into a high-speed disperser and stir for 2 hours.

[0069] Step 5: Take the mixed latex and add 0.5g of dimethyl silicone oil, 0.2g of PVA, 0.2g of leveling agent, and 0.2g of ethylene glycol in turn and stir for 30 minutes until uniform, to obtain a water-based thermal insulation coating with a three-dimensional thermal insulation structure, named 4% HGMs@Al 2 O 3 Water-based thermal insulation coating, recorded as 4% HA.

[0070] Example 2

[0071] The difference between this embodiment and embodiment 1 is that: in step 1, HGMs@Al 2 O 3 The amount of composite microspheres added was 1.5 g, and the remaining operation process and parameter settings were the same as in Example 1, to obtain a water-based thermal insulation coating with a three-dimensional thermal insulation structure, named 5% HGMs@Al 2 O 3 Water-based thermal insulation coating, recorded as 5% HA.

[0072] Example 3

[0073] The difference between this embodiment and embodiment 1 is that: in step 1, HGMs@Al 2 O 3 The amount of composite microspheres added was 2 g, and the rest of the operation process and parameter settings were the same as in Example 1, to obtain a water-based thermal insulation coating with a three-dimensional thermal insulation structure, named 6% HGMs@Al 2 O 3 Water-based thermal insulation coating, recorded as 6% HA.

[0074] Example 4

[0075] The difference between this embodiment and embodiment 1 is that: in step 1, HGMs@Al 2 O 3The amount of composite microspheres added was 2.5 g, and the remaining operation process and parameter settings were the same as in Example 1, to obtain a water-based thermal insulation coating with a three-dimensional thermal insulation structure, named 7% HGMs@Al 2 O 3 Water-based thermal insulation coating, recorded as 7% HA.

[0076] Example 5

[0077] The difference between this embodiment and embodiment 1 is that: in step 1, HGMs@Al 2 O 3 The amount of composite microspheres added was 3 g, and the remaining operation process and parameter settings were the same as in Example 1, to obtain a water-based thermal insulation coating with a three-dimensional thermal insulation structure, named 8% HGMs@Al 2 O 3 Water-based thermal insulation coating, recorded as 8% HA.

[0078] Comparative Example 1

[0079] The difference between this comparative example and Example 1 is as follows: 2. In step 1, HGMs@Al 2 O 3 The amount of composite microspheres added was 0 g, and the rest of the operation process and parameter settings were the same as in Example 1, to obtain a water-based thermal insulation coating with a three-dimensional thermal insulation structure, named 0% HGMs@Al 2 O 3 Water-based thermal insulation coating, recorded as 0%.

[0080] Comparative Example 2

[0081] The difference between this comparative example and Example 1 is as follows: 2. In step 1, HGMs is used instead of HGMs@Al 2 O 3 The remaining operation process and parameter settings are the same as those in Example 1, and a water-based thermal insulation coating with a three-dimensional thermal insulation structure is obtained, which is named 4% HGMs water-based thermal insulation coating, recorded as 4% H.

[0082] Comparative Example 3

[0083] The difference between this comparative example and Example 2 is as follows: 2. In step 1, HGMs is used instead of HGMs@Al 2 O 3 The remaining operation process and parameter settings are the same as those in Example 1, and a water-based thermal insulation coating with a three-dimensional thermal insulation structure is obtained, which is named 5% HGMs water-based thermal insulation coating, recorded as 5% H.

[0084] Comparative Example 4

[0085] The difference between this comparative example and Example 3 is as follows: 2. In step 1, HGMs is used instead of HGMs@Al2 O 3 The remaining operation process and parameter settings are the same as those in Example 1, and a water-based thermal insulation coating with a three-dimensional thermal insulation structure is obtained, which is named 6% HGMs water-based thermal insulation coating, recorded as 6% H.

[0086] Comparative Example 5

[0087] The difference between this comparative example and Example 4 is as follows: 2. In step 1, HGMs is used instead of HGMs@Al 2 O 3 The remaining operation process and parameter settings are the same as those in Example 1, and a water-based thermal insulation coating with a three-dimensional thermal insulation structure is obtained, which is named 7% HGMs water-based thermal insulation coating, recorded as 7% H.

[0088] Comparative Example 6

[0089] The difference between this comparative example and Example 5 is as follows: 2. In step 1, HGMs is used instead of HGMs@Al 2 O 3 The remaining operation process and parameter settings are the same as those in Example 1, and a water-based thermal insulation coating with a three-dimensional thermal insulation structure is obtained, which is named 8% HGMs water-based thermal insulation coating, recorded as 8% H.

[0090] The water-based thermal insulation coatings prepared in the above-mentioned Examples 1 to 5 and Comparative Examples 1 to 6 are coated on tinplate tinplate to obtain water-based thermal insulation coatings with different filler contents (the naming of the obtained water-based thermal insulation coatings is the same as the corresponding water-based thermal insulation coatings). The specific operation process is as follows: the water-based thermal insulation coatings prepared in Examples 1 to 5 and Comparative Examples 1 to 6 are loaded into a spray gun and sprayed on the tinplate sheet.

[0091] Effect example

[0092] (1) The basic properties of the water-based thermal insulation coatings obtained in different embodiments were characterized, and the results are shown in Table 1 below.

[0093] Table 1

[0094]

[0095]

[0096] As shown in Table 1 above, without adding HGMs@Al 2 O 3The coating adhesion of composite microspheres is level 1. As the filling amount of composite microspheres increases, the coating adhesion becomes level 0, that is, the adhesion is enhanced. When the filling amount exceeds 7%, the coating adhesion becomes level 1. This is because the acrylic resin emulsion contains a large number of -OH and -COOH functional groups, which are easy to form chemical bonds with oxygen atoms and hydrogen atoms on the surface of the substrate, and has strong fluidity and wettability, so that the coating is completely close to the pores on the surface of the substrate before curing, and diffuses with each other so that the interface disappears. Therefore, acrylic emulsion has strong adhesion. HGMs@Al 2 O 3 The addition of will enhance the cohesive force and bonding strength of the emulsion. When it is close to the surface of the substrate, van der Waals force will be generated, which will facilitate the penetration of the emulsion into the pores and cracks of the substrate, thereby improving the adhesion and peel strength of the substrate. However, too high a filling amount will result in insufficient wetting of the solid filler, thereby reducing the overall performance of the coating.

[0097] Follow HGMs@Al 2 O 3 The hardness and impact resistance of the coating are significantly improved with the increase of the composite particle filling amount. When HGMs is used as filler, the maximum hardness of the coating is 3H, while HGMs@Al 2 O 3 When used as filler, the maximum hardness of the coating reaches 6H, which is due to the nano-α / γ-Al 2 O 3 The particles have high hardness, which improves the HGMs ball wall structure morphology, allowing the high-hardness nanoparticles to play a role. The HGMs loaded with high-hardness particles are enriched on the surface of the composite coating, enhancing the overall hardness of the coating. 2 O 3 The particle size is small, and the active points on the surface can easily form chemical bonds with the -OH functional groups of the resin matrix, which enhances the interfacial compatibility between the large HGMs particles and the emulsion; the interfacial bonding force with the resin matrix is ​​enhanced, which greatly improves the impact resistance of the coating.

[0098] (2) The hydrophobic properties of the water-based thermal insulation coatings obtained in different embodiments were characterized. The results are as follows: Figure 5 As shown by Figure 5 It can be seen that without HGMs@Al 2 O 3 When the composite microspheres are added, the water contact angle CA of the composite coating is 70°, and the surface is hydrophilic (CA < 90°). 2 O 3 As fillers, the surface hydrophilicity and hydrophobicity change. It can be seen that with the increase of HGMs content, the surface of the composite coating changes from hydrophilic to hydrophobic, but the contact angle is around 90°, the hydrophobic effect is not obvious, and there is no obvious surface self-cleaning ability. 2 O 3As the filling amount of composite particles increases, the surface of the composite coating becomes hydrophobic. When the filling amount reaches 7%, the water contact angle of the composite coating reaches 120.5°. This is because HGMs have the lowest surface energy, which provides conditions for the formation of a hydrophobic surface. 2 O 3 The particles are enriched and coated on the surface of the HGMs sphere wall, making the HGMs sphere wall change from smooth to rough. After the composite coating is cured, the rough particles cover the coating surface to play a hydrophobic role. 2 O 3 When the particle content exceeds 8%, nanoparticle agglomeration occurs inside the polymer resin, reducing the water resistance of the composite coating.

[0099] (3) The mechanical properties of the water-based thermal insulation coatings obtained in different embodiments were characterized. The specific tensile strength and elongation at break were as follows: Figure 5 and 6 As shown by Figure 5 It can be seen that with the HGMs@Al 2 O 3 After addition, the tensile strength of the coating increased first and then decreased, and the tensile strength remained at 2.3MPa-3.52MPa. 2 O 3 When the doping amount is 7%, the tensile strength can be increased by up to 53%. However, pure HGMs does not significantly improve the tensile strength of the composite coating, and when the filling amount exceeds 6%, due to the relatively small amount of resin contained in the coating, the sealing effect on the filler is poor, the density of the coating system is reduced, defects exist inside the composite material, and stress concentration occurs under load, causing the tensile strength of the coating to drop sharply. Figure 6 It can be seen that when the thermal insulation filler content is 0%, the elongation at break of the coating is 152%, while when pure HGMs is used as a thermal insulation filler, the elongation at break of the coating decreases significantly. 2 O 3 When used as a thermal insulation filler, the elongation at break of the coating decreases slightly, and when the content exceeds 7%, it drops to 40%. This is because there is a repulsive force between the HGMs surface and the aqueous matrix, the mutual restraint mechanism between the molecular chains is "complex", and the disentanglement rate is slowed down when subjected to load. At the same time, the matrix and filler have poor wetting effects, large grains have a reverse effect on plastic deformation, and it is not easy to form a continuous and stable interface with acrylic resin emulsion. The compatibility is poor, resulting in a decrease in the mechanical properties of the composite coating. HGMs@Al 2 O 3 The addition of composite microspheres stabilizes the interface between the continuous phase and the dispersed phase, and the bonding strength of the coating increases relatively. The above results show that the rigidity of the coating increases and the toughness decreases. 2 O 3 , playing a "bridging" role between the polymer matrix and HGMs, delaying the decreasing trend of elongation at break.

[0100] (4) SEM images of water-based thermal insulation coatings with different filler contents obtained in different embodiments, such as Figure 7 As shown, (a) is 0% HGMs@Al 2 O 3 Content, (b) 7% HGMs@Al 2 O 3 Figure (a) shows that the resin and filler are tightly combined, with good wettability, no defects such as voids, and good bonding effect. Figure (b) shows that with the HGMs@Al 2 O 3 As the particle content increases, the cross-section of the composite coating appears spherical and rough, forming cross-links with the resin matrix, and the overall composite structure is well-arranged. 2 O 3 The composite microsphere coating is evenly distributed and has dense voids. Most of its particles are infiltrated with acrylic resin emulsion to form a three-dimensional air cavity high heat barrier structure, which extends the heat transfer path and helps to improve the thermal insulation performance of the composite coating.

[0101] (5) The thermal insulation performance of water-based thermal insulation coatings with different filler contents obtained in different embodiments was quantitatively studied using an LFA-447 laser thermal conductivity meter. The test results are as follows: Figure 8 As shown by Figure 8 It can be seen that with the increase of thermal insulation filler, the thermal conductivity of the composite coating decreases. Compared with pure HGMs as thermal insulation filler, HGM@Al 2 O 3 The thermal conductivity of water-based composite coatings decreases significantly; when the thermal insulation filler content is 0%, the thermal conductivity is 0.235Wm -1 K -1 In contrast, HGMs@Al 2 O 3 When the composite coating filler content reaches 8%, the thermal conductivity is reduced to 0.062Wm -1 K -1 This is because HGMs have extremely low thermal conductivity, are evenly dispersed in the coating system to extend the heat transfer path, and the internal air cavity contains rarefied gas, which constructs a three-dimensional heat-insulating air cavity inside the composite coating, improves the interfacial thermal resistance, forms a buffer layer for the propagation of energy-carrying phonons, and reduces the heat conduction efficiency; Al2O3 converted from boehmite sol 2 O 3 particles, enhance the compatibility of polymer resin matrix and HGMs, prevent gas from penetrating the coating, and improve the overall thermal insulation performance of the composite coating; it can be found that with the HGMs@Al 2 O 3As the amount of composite microspheres filled in the polymer matrix increases, the thermal conductivity of the composite material decreases more slowly. This is because the thermal conductivity of acrylic emulsion coating is 0.219Wm -1 K -1 ~0.263Wm -1 K -1 , while the thermal conductivity of HGMs is 0.070Wm -1 K -1 ~0.037Wm -1 K -1 Therefore, the minimum thermal conductivity of the composite coating is not less than 0.037Wm -1 K -1 When HGMs@Al 2 O 3 When the content exceeds the percolation threshold of 7%, the aqueous matrix and filler are no longer a unified continuous phase, the internal particles are agglomerated, and the thermal conductivity value fluctuates greatly and cannot represent the thermal conductivity of the composite coating.

[0102] The thermal conductivity variation index (n) is an important parameter that describes the relationship between the thermal insulation filler content and the thermal conductivity coefficient. It can quantitatively describe the change in the thermal insulation performance of the composite coating. The calculation formula is as follows:

[0103]

[0104] The calculation results are as follows Fig. 9 As shown by Fig. 9 It can be seen that with HGMs@Al 2 O 3 The thermal conductivity of water-based composite coatings decreased significantly with the increase of particle content. Compared with acrylic emulsion-based adhesive films, when the pure HGMs filling content reached 7%, the thermal conductivity of the composite coating decreased by 47.1%, and the thermal conductivity of HGMs@Al 2 O 3 When the composite microspheres are used as thermal insulation fillers, the thermal conductivity of the coating is reduced by 58.7%. This is due to the Al 2 O 3 Nanoparticles enhance the interfacial compatibility between the matrix and HGMs, making the air cavity structure introduced by the composite coating more stable. 2 O 3 There is a synergistic effect among the HGMs and the polymer matrix, which further reduces the thermal conductivity of the coating, reduces heat transfer, and helps to block external heat from the material.

[0105] (6) In order to further characterize the thermal insulation performance of the composite coating, an infrared thermal imager was used to qualitatively study the heat transfer rate of the water-based thermal insulation coatings with different filler contents obtained in different embodiments. The results are as follows: Fig.10 and Fig.11As shown in the figure, under a 100°C thermal environment, seven different circular samples of the same size were covered on the heating platform support plate. The infrared thermal imager recorded the surface temperature changing over time, observed the thermal conductivity of the samples, and compared the heat transfer rate of the samples. Blue, cyan, green, yellow, and red represent different temperatures. The results show that when the thermal insulation filler content is 0%, a red high temperature area appears after the composite coating is heated for 160 seconds. As the HGMs@Al 2 O 3 As the content increases, the time in the red area increases. This is because the increase in the content of thermal insulation fillers introduces more air cavity structures inside the coating, the thermal resistance in the low thermal conductivity area is high, the propagation free path of the heat-carrying phonons is enhanced, the heat conduction path is extended, and the time for the composite coating to enter the high temperature area is extended. Comparison of 4% HGMs and 4% HGMs@Al 2 O 3 From the disc of water-based thermal insulation coating, it can be seen that the modification of HGMs by boehmite sol slows down the rate of change of the coating to the high temperature area, enhances the compatibility of the air cavity structure with the polymer matrix, and increases the probability of phonon propagation to the high thermal resistance and low thermal conductivity area. Fig.11 It can be shown intuitively that HGMs@Al 2 O 3 Reduce the internal thermal conductivity of the coating.

[0106] (7) Fig.12 The center point temperature variation curves of water-based thermal insulation coatings with different filler contents obtained in different embodiments are shown in FIG. Fig.12 It can be seen that the surface temperature distribution of the samples is different during heating. The temperature of the composite coating is balanced after heating for 120s. At this time, the temperature of each sample is different, which proves that the HGMs@Al 2 O 3 The thermal insulation performance of the composite coating increases with the increase of the content. When the composite microsphere content is 7%, it has an insulation effect of 18.1℃ in a 100℃ atmosphere.

[0107] Although the present invention has been disclosed as above in the preferred embodiment, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A HGMs@Al 2 O 3 Preparation method of composite microspheres, It is characterized in that include: (1) After flotation treatment of HGMs, the HGMs are dispersed in ethanol, a PVP / ethanol solution is added dropwise, stirred and centrifuged, and the solid is dried to obtain the pretreated HGMs; (2) The pretreated HGMs were placed in a three-necked flask, and isopropanol and deionized water were added in sequence. The mixture was ultrasonically dispersed and stirred and heated to 70 °C. The AIP / isopropanol solution was poured in and stirred for 4 h. The mixture was aged for 2 h and centrifuged to obtain composite particles. The composite particles were washed with deionized water until the pH was 7-8 and then dried to obtain HGMs@Al 2 O 3 Composite microspheres.

2. HGMs@Al according to claim 1 2 O 3 Preparation method of micro-nano composite microspheres, It is characterized in that The flotation process of HGMs in (1) is as follows: 15-20 parts by mass of HGMs are added to 120-170 parts by volume of C 2 H 5 OH solution, stirred at 160-170 r / min and ultrasonically dispersed for 1 h to obtain a suspension, which was centrifuged at 4000 r / min for 15 min, and the upper solid was taken and dried at 60°C for 6 h.

3. HGMs@Al according to claim 1 2 O 3 Preparation method of composite microspheres, It is characterized in that (1) The specific operation is as follows: at 65°C, the HGM after flotation treatment is dispersed in ethanol, PVP / ethanol solution is added dropwise, stirred for 3 hours and then centrifuged, and the solid is dried at 60°C for 3-5 hours; the PVP / ethanol solution is composed of 1-2 parts by weight of PVP and 15-20 parts by weight of C 2 H 5 OH solution and ultrasonically dispersed for 1.5 h.

4. HGMs@Al according to claim 1 2 O 3 Preparation method of composite microspheres, It is characterized in that (2) The ratio of pretreated HGMs, isopropanol and deionized water is 15-20 parts by mass: 120-150 parts by volume: 40-50 parts by volume; the amount of aluminum isopropoxide in the AIP / isopropanol solution is 5-7 parts by mass, and the amount of isopropanol is 15-20 parts by volume.

5. HGMs@Al prepared by the method according to any one of claims 1 to 4 2 O 3 Composite microspheres, It is characterized in that The composite microspheres are composed of HGMs as core and Al 2 O 3 The core-shell structure microspheres have an average particle size of 24 μm.

6. The HGMs@Al according to claim 5 2 O 3 Application of composite microspheres, It is characterized in that Used to prepare water-based thermal insulation coatings.

7. A water-based thermal insulation coating, It is characterized in that The composition is composed of the following raw materials by weight: 12 to 15 parts of the HGMs@Al described in claim 5 2 O 3 Composite microspheres, 2-3 parts APTES, 45-50 parts acrylic emulsion, 7-8 parts mica flakes, 6-7 parts CaCO 3 powder, 1 to 2 parts of dispersant, 1 to 2 parts of defoamer, 1 to 2 parts of thickener, 1 to 2 parts of film-forming aid, 1 to 2 parts of leveling agent and 4 to 5 parts of ethylene glycol.

8. A method for preparing the water-based thermal insulation coating according to claim 7, It is characterized in that include: S1, HGMs@Al 2 O 3 The composite microspheres were dispersed in an ethanol / water solution, APTES was added, stirred, centrifuged, and the solid was dried to obtain the treated HGMs@Al 2 O 3 Composite microspheres; S2, the treated HGMs@Al 2 O 3 Composite microspheres, mica flakes, CaCO 3 The powder and dispersant are added to the acrylic emulsion, mixed thoroughly, and stirred in a high-speed disperser for 24 hours to obtain a mixed emulsion; S3, adding a defoamer, a thickener, a film-forming aid, a leveling agent and ethylene glycol to the mixed emulsion obtained in S2 in sequence, stirring evenly to obtain a water-based thermal insulation coating.

9. The method for preparing the water-based thermal insulation coating according to claim 8, It is characterized in that The ethanol / water solution in S1 is a mixture of ethanol and water in a mass ratio of 2:

1.

10. An application of the water-based thermal insulation coating according to claim 7, It is characterized in that The coating was applied on the substrate surface and dried at room temperature for 3 hours to obtain a water-based thermal insulation coating.

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