Water-based thermal insulation coating and preparation method thereof

Abstract

The invention provides a water-based thermal insulation coating and a preparation method thereof. The water-based thermal insulation coating comprises the copolymer coated modified glass bead and sodium polyacrylate modified bentonite, and the copolymer coated modified glass bead comprises a hollow glass bead and a hydroxyl-containing acrylate copolymer coating layer coated on the surface of the hollow glass bead. The copolymer coating layer is mainly prepared by taking methyl methacrylate, butyl acrylate and hydroxyethyl acrylate as monomers, mixing the monomers according to the mass ratio of (4.7-6.0): (3.0-4.3): 1 and carrying out copolymerization reaction. The copolymer coated modified glass beads and the sodium polyacrylate modified bentonite can form hydrogen-bond interaction and electrostatic interaction to form a three-dimensional network structure, so that the hollow glass beads in the water-based thermal insulation coating are prevented from floating upwards for a long time, and a thermal insulation coating product has relatively good stability; and the phenomena of layering and surface hardening are avoided after at least one month of heat storage.

Description

Technical Field

[0001] The present invention relates to the application field of hollow glass microspheres, and in particular to a water-based thermal insulation coating and a preparation method thereof. Background Art

[0002] Hollow glass microspheres are widely used in water-based thermal insulation coatings due to their low density and low thermal conductivity. They have the functions of reflection, radiation and insulation. As the main functional filler of water-based thermal insulation materials, hollow glass microspheres are generally added in an amount of ≥10% and the system volume fraction is ≥50%. The density of hollow glass microspheres used in water-based thermal insulation coatings is usually ≤0.5 g / cm 3 , which is far less than the density of water, the dispersion medium. Therefore, hollow glass microspheres are particularly prone to floating during storage of finished coatings, causing coating delamination. At the same time, because hollow glass microspheres are rigid materials, the evaporation of water from the film-forming material on the surface causes the floating hollow glass microspheres to bond together, greatly increasing the intensity of the secondary stirring in the barrel before use of water-based thermal insulation coatings. Therefore, how to control the floating of hollow glass microspheres in water-based thermal insulation coatings is of great significance to the construction and application of water-based thermal insulation coatings.

[0003] Currently, the commonly used methods are: 1) adding thickening agents such as cellulose to increase the viscosity of the system to prevent the hollow glass microspheres from floating up. However, since the hollow glass microspheres account for a large volume of the entire system, in order to obtain a coating with better thermal insulation performance, more microspheres need to be added to reduce the thermal conductivity of the system. If the system viscosity is high, the amount of microspheres added will be limited; this makes it difficult to ensure that the coating has good thermal conductivity while effectively preventing the coating from delamination. 2) Adding thixotropic agents such as bentonite to reduce the viscosity under high shear conditions such as production. After production is completed and the coating is barreled, the system viscosity increases rapidly after the shear force disappears. However, since there is no interaction between commonly used thixotropic agents and hollow glass microspheres, the microspheres will still float up after a period of time. Summary of the Invention

[0004] In view of this, the present invention adopts copolymer-coated modified glass microspheres in water-based thermal insulation coatings. The modified glass microspheres are prepared by coating the surface of hollow glass microspheres with a hydroxyl-containing acrylate copolymer; hydrogen bonds and electrostatic effects are formed between the modified glass microspheres and bentonite modified with sodium polyacrylate to achieve long-term prevention of the hollow glass microspheres in the coating from floating up; therefore, the present invention provides a water-based thermal insulation coating and a preparation method thereof.

[0005] Specifically, a water-based thermal insulation coating includes the following raw materials per 100 parts by weight: 20-30 parts of water-based acrylic emulsion, 1-10 parts of aerogel powder, 10-20 parts of copolymer-coated modified glass microspheres, 0.2-1 part of sodium polyacrylate-modified bentonite, 0.6-1.5 parts of propylene glycol, 1-1.5 parts of a film-forming aid, 0.1-0.4 parts of a dispersant, 0-0.2 parts of a thickener, 0.2-0.4 parts of a defoaming agent, and the balance is water; wherein the copolymer-coated modified glass microspheres include hollow glass microspheres and a hydroxyl-containing acrylate copolymer coating layer coated on the surface of the hollow glass microspheres.

[0006] The copolymer coating layer is mainly prepared by mixing methyl methacrylate, butyl acrylate and hydroxyethyl acrylate as monomers in a mass ratio of 4.7-6.0:3.0-4.3:1 and undergoing copolymerization reaction.

[0007] The copolymer-coated modified glass microspheres are mainly prepared by the following method: Pre-modification: first use silane coupling agent to modify the hollow glass microspheres to obtain double-bond modified glass microspheres; Copolymer modification: using methyl methacrylate, butyl acrylate and hydroxyethyl acrylate as polymer monomers, a copolymerization reaction occurs on the surface of the double-bond modified glass microspheres to form a hydroxyl-containing acrylate copolymer coating layer on the surface of the hollow glass microspheres, thereby obtaining copolymer-coated modified glass microspheres.

[0008] The primary purpose of the pre-modification step is to form double bonds on the surface of the hollow glass microspheres, facilitating the subsequent formation of a copolymer coating thereon. To form sufficient double bonds on the surface of the hollow glass microspheres, the pre-modification step may include: first, uniformly mixing 5-10 parts of hollow glass microspheres, 40-50 parts of anhydrous ethanol, and 5-10 parts of a silane coupling agent to form a premix; then, dropwise adding 15-30 parts of pure water to the premix within 3-6 minutes, allowing the mixture to react for 0.5-1.0 hours, and filtering to obtain the double-bond-modified hollow glass microspheres.

[0009] In order to allow copolymerization between monomers with different polymerization rates and prevent hydrophilic monomers such as hydroxyethyl acrylate from forming copolymers by themselves, a seed emulsion polymerization method is used to coat the hollow glass microspheres with the polymer. The copolymer modification step may include: uniformly mixing methyl methacrylate, butyl acrylate and hydroxyethyl acrylate to form a polymer monomer mixture, and uniformly mixing it with the double-bond modified glass microspheres; under the action of an initiator, copolymerizing on the surface of the double-bond modified glass microspheres to form a hydroxyl-containing acrylate copolymer coating layer on the surface of the hollow glass microspheres, thereby producing the copolymer-coated modified glass microspheres; wherein the mass ratio of the double-bond modified glass microspheres, the polymer monomer mixture and the initiator is 2-8:35-45:0.03-0.06, and the mass ratio of methyl methacrylate, butyl acrylate and hydroxyethyl acrylate in the polymer monomer mixture is 4.7-6.0:3.0-4.3:1, so that the copolymer can better coat the hollow glass microspheres.

[0010] The emulsifier is mainly a mixture of anionic emulsifier and nonionic emulsifier. Preferably, the emulsifier is prepared by uniformly mixing sodium lauryl sulfate and fatty alcohol polyoxyethylene ether AEO-3 in a mass ratio of 1.5-2.5:1.

[0011] According to HG / T 2248-2012, when the sodium polyacrylate-modified bentonite is made into a slurry with a concentration of 6 wt%, the 4# rotor of the LC-NDJ-8S Pro digital rotational viscometer is selected for detection: the viscosity at 6 rpm is 27,000-40,000 mP•s; the viscosity at 60 rpm is 3,000-4,000 mP•s, and the shear thinning index is 9-10.

[0012] A preparation method of the above-mentioned water-based thermal insulation coating includes the steps of: first, uniformly mixing the sodium polyacrylate modified bentonite, dispersant, aerogel powder and water to obtain a uniformly dispersed aerogel slurry; then, uniformly mixing the aerogel slurry, propylene glycol, film-forming aid, defoaming agent, water-based acrylic emulsion, copolymer-coated modified glass microspheres and thickener.

[0013] Therefore, the above technical solution provided by the present invention has the following advantages: 1) The copolymer-coated modified glass microspheres provided by the present invention include a hydroxyl-containing acrylate copolymer coating layer. Since the hydroxyethyl acrylate in the copolymer contains hydrophilic hydroxyl groups and the sodium polyacrylate-modified bentonite contains carboxyl groups, hydrogen bonds and electrostatic interactions can form between the copolymer-coated modified glass microspheres and the sodium polyacrylate-modified bentonite to form a three-dimensional network structure, thereby achieving long-term prevention of floating of the hollow glass microspheres in the water-based thermal insulation coating. This ensures that the thermal insulation coating product has good stability and will not delaminate or harden the surface after at least one month of hot storage. 2) Since the surface of the copolymer-coated modified glass microspheres contains hydroxyl groups, it does not affect their dispersibility in water, but reduces the water absorption rate of the hollow glass microspheres. Therefore, the water-based thermal insulation coating using the copolymer-coated modified glass microspheres can reduce the water absorption rate of the coating after film formation to no more than 30%, thereby improving its waterproof performance. 3) When copolymer-coated modified glass microspheres are used in the preparation of water-based thermal insulation coatings, they can avoid or reduce the breakage of hollow glass microspheres during production and use stirring, which affects the thermal insulation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 These are photographs of the thermal stability test results of the water-based thermal insulation coatings provided in Example 1 (A) and Comparative Examples 1-3 (BD) of the present invention, wherein the red frame in Figure BD shows stratification. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solutions and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0016] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to form one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed in the present invention.

[0017] In the present invention, unless otherwise specified and / or explained, all numerical values ​​involving component amounts are by weight. Unless otherwise specified, the terms used in the present invention are commonly used in the relevant field. The preparation processes, testing methods, etc. used in the various embodiments are conventional means well known to those skilled in the art unless otherwise explained. The raw materials and equipment used are all available from public commercial sources.

[0018] The main purpose of the present invention is to solve the problem of hollow glass microspheres floating in water-based thermal insulation coatings by providing a copolymer-coated modified glass microsphere that can form hydrogen bonds and electrostatic interactions with sodium polyacrylate-modified bentonite. The specific embodiments of the present invention are as follows: A copolymer-coated modified glass microsphere comprises hollow glass microspheres and a hydroxyl-containing acrylate copolymer coating layer coated on the surface of the hollow glass microspheres. The copolymer-coated modified glass microspheres are formed on the microsphere surfaces using an emulsion polymerization method. The monomers of the copolymer coating layer include hydroxyethyl acrylate (HEA), a hydrophilic monomer, such that the copolymer coating layer contains hydroxyl groups. The preparation method of the copolymer-coated modified glass microspheres comprises: Pre-modification: 15-30 parts of pure water are added dropwise to a mixture of 5-10 parts of hollow glass microspheres, 40-50 parts of anhydrous ethanol, and 5-10 parts of a silane coupling agent. The mixture is allowed to drip within 3-6 minutes, reacted for 0.5-1.0 hours, and filtered to obtain double-bond modified glass microspheres. In this step, anhydrous ethanol is used as a dispersion medium and water is used as a reaction substance. The silane coupling agent contains a double bond at one end and a silicon-oxygen bond at the other end. The silicon-oxygen bond is easily hydrolyzed to form a silicon hydroxyl group, which undergoes a condensation reaction with the hydroxyl group on the surface of the microspheres, thereby grafting a double bond on the surface of the microspheres. Therefore, pure water needs to be added dropwise to the mixture and dripped within 3-6 minutes. Copolymer modification: First, 40-60 parts of deionized water, 2-8 parts of the double-bond modified hollow glass microspheres, 2-5 parts of emulsifier, and 0.3-0.6 parts of sodium bicarbonate buffer are uniformly mixed and heated to 45-55°C. After maintaining the temperature for 20-40 minutes, the temperature is further increased to 70-75°C. Simultaneously, 0.3-0.6 parts of a 10 wt% initiator solution and 35-45 parts of the polymerization monomer mixture are slowly added dropwise for 1-2 hours. The reaction is continued for 2-3 hours to form a hydroxyl-containing acrylate copolymer coating layer on the surface of the hollow glass microspheres. The material is filtered to obtain copolymer-coated modified glass microspheres. The emulsifier is prepared by uniformly mixing sodium lauryl sulfate and fatty alcohol polyoxyethylene ether AEO-3 in a mass ratio of 1.5-2.5:1. The polymer monomer mixture is prepared by mixing methyl methacrylate, butyl acrylate, and hydroxyethyl acrylate in a mass ratio of 4.7-6.0:3.0-4.3:1.

[0019] During the copolymer modification process, the initial heating followed by holding is performed to form seed latex micelles within this temperature range. The slow addition of the solution is intended to promote copolymerization between monomers with different reactivity ratios, preventing hydrophilic monomers such as hydroxyethyl acrylate from forming copolymers on their own. The initial heating temperature is 45-55°C, and the holding time is 20-40 minutes. This is primarily because this is the seed polymerization stage. Lower temperatures facilitate the formation of small latex particles and the copolymerization of monomers with different reactivity ratios. Excessively high temperatures will result in the formation of overly large latex particles or even gels, causing the reaction to fail.

[0020] The density of the hollow glass microspheres is 0.12-0.60 g / cm 3 , particle size 55-120 μm; preferably, its model can be HL15, HL20, HL25, HL30, HL35, HL38. The silane coupling agent can be γ-methacryloxypropyltrimethoxysilane KH570, vinyl tris (2-methoxyethoxysilane), vinyl triethoxysilane, vinyl trimethoxysilane, etc.

[0021] A water-based thermal insulation coating comprises the following raw materials in parts by weight based on 100 parts by weight: 20-30 parts of water-based acrylic emulsion, 1-10 parts of aerogel powder with a particle size of 15-50 μm, 10-20 parts of copolymer-coated modified glass microspheres, 0.2-1 part of sodium polyacrylate-modified bentonite, 0.6-1.5 parts of propylene glycol, 1-1.5 parts of a film-forming aid, 0.1-0.4 parts of a dispersant, 0-0.2 parts of a thickener, 0.2-0.4 parts of a defoaming agent, and the balance being water.

[0022] Among them, the preparation method of the sodium polyacrylate modified bentonite is an existing technology, which may include: first stirring and mixing the acid-washed bentonite and sodium polyacrylate at a mass ratio of 100:1-15 at 20-70°C, then continuing to stir for 1-2 hours under the condition of pH reaching 8-10, so that the sodium polyacrylate is inserted into the interlayer of the acid-washed bentonite, filtering and drying to obtain the sodium polyacrylate modified bentonite.

[0023] The acid-washed bentonite refers to the original bentonite that has been acid-washed. The main purposes of this treatment are: 1) to remove impurities such as carbonates, iron oxides, and organic matter that are commonly contained in the bentonite by chemically reacting with acid; 2) acid washing will dissolve some metal cations such as calcium and magnesium on the surface of the bentonite, increasing the negative charge on the surface and enhancing its ability to adsorb cations; 3) acid etching forms micropores on the surface of the bentonite, increasing its specific surface area and porosity.

[0024] Specifically, the preparation method of the sodium polyacrylate modified bentonite comprises the steps of: S01: Bentonite is first stirred and mixed in a hydrochloric acid solution to form a slurry with a bentonite content of 2-15%. The slurry is then washed with water, dried, and heated to 175-185°C for 5-10 minutes. The temperature is then raised to 305-315°C and kept at this temperature for 10-15 minutes. Finally, the acid-washed bentonite is obtained. S02: 100 parts of acid-washed bentonite and 1-15 parts of sodium polyacrylate are stirred at a constant temperature of 20-70°C for 1-10 hours; then the pH is adjusted to 8-10 with 1-5 wt% NaOH solution, and stirring is continued for 1-2 hours. The mixture is filtered and dried to obtain sodium polyacrylate-modified bentonite.

[0025] Since hollow glass microspheres are the main functional filler that plays a role in thermal insulation in water-based thermal insulation coatings, the mass proportion of copolymer-coated modified glass microspheres is limited to 10-20 parts. If the amount of copolymer-coated modified glass microspheres is too low, the thermal insulation effect will be poor; if it is excessive, the system PVC will be too large, causing serious powdering of the coating.

[0026] Since bentonite plays a role in preventing hollow glass microspheres from floating in water-based thermal insulation coatings, the amount of sodium polyacrylate modified bentonite is limited to 0.2-1 parts; if the amount of sodium polyacrylate modified bentonite is too low, the microspheres will float during the storage of the coating; if it is excessive, the viscosity of the system will be too high, making it difficult to produce and increasing costs.

[0027] The acrylic emulsion is one or more of water-based acrylic elastic emulsion and water-based acrylic emulsion.

[0028] The film-forming aids include ester-12, PC6800, and dipropylene glycol butyl ether, preferably ester-12.

[0029] The dispersant is an aerogel powder dispersant, including ZKYT-1000, CA-2500, PE-100, BYK163, BYK9076, and AT-204.

[0030] The thickener is a hydrophobically modified alkali swelling thickener, including A406 and Rheovis HS 1152.

[0031] The defoaming agents include SN-345, BYK052, and defoaming agent NXZ.

[0032] The preparation method of the above-mentioned water-based thermal insulation coating comprises the steps of: (1) Add water, modified bentonite and dispersant in this order, disperse at high speed of 800-1200 rpm for 10-20 minutes, add aerogel powder, and continue to disperse at high speed for 10-20 minutes until the aerogel powder is completely and evenly wetted and dispersed to obtain aerogel slurry; (2) The rotation speed is adjusted to 600-800 rpm, and propylene glycol, film-forming aid, defoaming agent, water-based acrylic emulsion, polymer-coated modified hollow glass microspheres and thickener are added to the above-mentioned aerogel slurry in sequence, and stirred evenly to prepare a water-based thermal insulation coating.

[0033] The technical solution of the present invention is further described in detail below through specific implementation methods.

[0034] Example 1 This embodiment provides a copolymer-coated modified glass microsphere, which is mainly prepared by the following method: Pre-modification: 5 parts of particle size 120μm, density 0.15g / cm 3 20 parts of pure water were added dropwise to a mixture of hollow glass microspheres, 40 parts of anhydrous ethanol, and 5 parts of KH570, and the mixture was added over 5 minutes. The mixture was reacted for 1.0 hour and filtered to obtain double bond modified glass microspheres. Copolymer modification: In a four-necked flask equipped with an electric stirrer, a thermometer, a condenser, and a dropping funnel, add 50 parts of deionized water, 5 parts of the double-bond modified glass microspheres, 3 parts of an emulsifier, and 0.5 parts of a sodium bicarbonate buffer. Stir and heat to 50°C. Keep warm for 0.5 hours, then heat to 75°C. Simultaneously, slowly add dropwise 0.5 parts of a 10 wt% aqueous solution of ammonium persulfate and 40 parts of a polymer monomer mixture. The addition time is 1.5 hours. Continue the reaction for 3 hours, filter the material, and obtain hydroxyl-containing acrylate copolymer-coated modified glass microspheres. The emulsifier is prepared by uniformly mixing sodium lauryl sulfate and AEO-3 in a mass ratio of 2:1, and the polymer monomer mixture is prepared by uniformly mixing methyl methacrylate, butyl acrylate, and hydroxyethyl acrylate in a mass ratio of 5:4:1.

[0035] This embodiment also provides a water-based thermal insulation coating, which comprises, by weight, 40 parts of water, 0.8 parts of sodium polyacrylate-modified bentonite, 0.2 parts of ZKYT-1000, 0.3 parts of aerogel powder with a particle size of 45 μm, 1 part of propylene glycol, 1 part of a film-forming aid alcohol ester-12, 0.3 parts of a defoamer SN-345, 22 parts of a water-based acrylic elastic emulsion, and 15 parts of the copolymer-coated modified glass microspheres. The preparation method of the sodium polyacrylate-modified bentonite comprises: S01: Bentonite was first stirred and mixed in a hydrochloric acid solution to form a slurry with a bentonite content of 8%. The slurry was then washed with water and dried. The temperature was then raised to 180°C at a rate of 5°C / min and kept at this temperature for 10 min. The temperature was then raised to 310°C at a rate of 5°C / min and kept at this temperature for 15 min. The slurry was finally cooled in air to room temperature to obtain the acid-washed bentonite. S02: 100 parts of the acid-washed bentonite obtained in step S01 and 10 parts of sodium polyacrylate were stirred at a constant temperature of 50° C. for 5 hours; the pH was then adjusted to 9 with a 2% NaOH solution, and the stirring was continued for 2 hours. The mixture was filtered and dried to obtain sodium polyacrylate-modified bentonite.

[0036] The preparation method of the above-mentioned water-based thermal insulation coating includes: adding 40 parts of water, 0.8 parts of modified bentonite and 0.2 parts of dispersant to an open dispersion tank in sequence, dispersing at a high speed of 1000 rpm for 20 minutes, adding 0.3 parts of aerogel powder, and continuing to disperse at a high speed for 20 minutes until the aerogel powder is completely and evenly wetted and dispersed to obtain an aerogel slurry; adjusting the speed to 800 rpm, and adding 1 part of propylene glycol, 1 part of a film-forming aid, 0.3 parts of a defoaming agent, 22 parts of a water-based acrylic emulsion, and 15 parts of copolymer-coated modified glass microspheres in sequence to the above-mentioned aerogel slurry, and stirring evenly to prepare the water-based thermal insulation coating.

[0037] Example 2 This embodiment provides a copolymer-coated modified glass microsphere, which is mainly prepared by the following method: Pre-modification: 7 parts of particle size 100μm, density 0.25g / cm 3 23 parts of pure water were added dropwise to a mixture of hollow glass microspheres, 45 parts of anhydrous ethanol, and 7 parts of vinyltriethoxysilane. The mixture was allowed to drip over for 5 minutes, reacted for 0.6 hours, and filtered to obtain double-bond modified glass microspheres. Copolymer modification: In a four-necked flask equipped with an electric stirrer, a thermometer, a condenser, and a dropping funnel, add 60 parts of deionized water, 2 parts of the double-bond modified glass microspheres, 2 parts of an emulsifier, and 0.3 parts of a sodium bicarbonate buffer. Stir and heat to 50°C. After holding for 0.5 hours, heat to 75°C. Simultaneously, slowly add dropwise 0.3 parts of a 10 wt% aqueous solution of ammonium persulfate and 35 parts of a polymer monomer mixture. The addition time is 1 hour. Continue the reaction for 2 hours, filter the material, and obtain hydroxyl-containing acrylate copolymer-coated modified glass microspheres. The emulsifier is prepared by uniformly mixing sodium lauryl sulfate and AEO-3 in a mass ratio of 2:1, and the polymer monomer mixture is prepared by uniformly mixing methyl methacrylate, butyl acrylate, and hydroxyethyl acrylate in a mass ratio of 4.7:4.3:1.

[0038] This embodiment also provides a water-based thermal insulation coating, which comprises, by weight, 45 parts of water, 0.25 parts of sodium polyacrylate modified bentonite, 0.15 parts of dispersant ZKYT-1000, 10 parts of aerogel powder with a particle size of 45 μm, 0.65 parts of propylene glycol, 1.2 parts of film-forming aid alcohol ester-12, 0.2 parts of defoamer SN-345, 30 parts of water-based acrylic elastic emulsion, and 10 parts of the copolymer-coated modified glass microspheres. The preparation method of the sodium polyacrylate modified bentonite comprises: S01: Bentonite was first stirred and mixed in a hydrochloric acid solution to form a slurry with a bentonite content of 4%. The slurry was then washed with water and dried. The temperature was then raised to 175°C at a rate of 5°C / min and kept at this temperature for 5 min. The temperature was then raised to 305°C at a rate of 5°C / min and kept at this temperature for 10 min. The slurry was finally cooled in air to room temperature to obtain the acid-washed bentonite. S02: 100 parts of the acid-washed bentonite obtained in step S01 and 3 parts of sodium polyacrylate were stirred at a constant temperature of 30° C. for 3 hours; then the pH was adjusted to 8 with 1.5% NaOH solution, and the stirring was continued for 1 hour. The sodium polyacrylate-modified bentonite was filtered and dried to obtain the sodium polyacrylate-modified bentonite.

[0039] The preparation method of the above-mentioned water-based thermal insulation coating includes: adding 45 parts of water, 0.25 parts of modified bentonite and 0.15 parts of dispersant to an open dispersion tank in sequence, dispersing at a high speed of 800 rpm for 10 minutes, adding 10 parts of aerogel powder, and continuing to disperse at a high speed for 10 minutes until the aerogel powder is completely and evenly wetted and dispersed to obtain an aerogel slurry; adjusting the speed to 600 rpm, and adding 0.65 parts of propylene glycol, 1.2 parts of a film-forming aid, 0.2 parts of a defoaming agent, 30 parts of a water-based acrylic elastic emulsion, and 10 parts of a copolymer-coated modified glass microspheres in sequence to the above-mentioned aerogel slurry, and stirring evenly to prepare a water-based thermal insulation coating.

[0040] Example 3 This embodiment provides a copolymer-coated modified glass microsphere, which is mainly prepared by the following method: Pre-modification: 10 parts of particle size 70μm, density 0.35g / cm 3 30 parts of pure water were added dropwise to a mixture of hollow glass microspheres, 50 parts of anhydrous ethanol, and 10 parts of vinyltrimethoxysilane. The mixture was added over 6 minutes, reacted for 1.0 hour, and filtered to obtain double-bond modified glass microspheres. Copolymer modification: In a four-necked flask equipped with an electric stirrer, a thermometer, a condenser, and a dropping funnel, add 45 parts of deionized water, 8 parts of the double-bond modified glass microspheres, 5 parts of an emulsifier, and 0.6 parts of a sodium bicarbonate buffer. Stir and heat to 55°C. After keeping warm for 40 minutes, heat to 75°C. Simultaneously, slowly add dropwise 0.6 parts of a 10 wt% aqueous solution of ammonium persulfate and 40 parts of a polymer monomer mixture. The addition time is 2.5 hours. Continue the reaction for 3 hours, filter the material, and obtain hydroxyl-containing acrylate copolymer-coated modified glass microspheres. The emulsifier is prepared by uniformly mixing sodium lauryl sulfate and AEO-3 in a mass ratio of 2:1, and the polymer monomer mixture is prepared by uniformly mixing methyl methacrylate, butyl acrylate, and hydroxyethyl acrylate in a mass ratio of 6:3:1.

[0041] This embodiment also provides a water-based thermal insulation coating, which comprises, by mass, 45 parts of water, 1 part of sodium polyacrylate modified bentonite, 0.2 parts of CA-2500 dispersant, 0.2 parts of PE-100 dispersant, 1 part of aerogel powder, 1.5 parts of propylene glycol, 1.5 parts of dipropylene glycol butyl ether, 0.4 parts of defoamer NXZ, 30 parts of water-based acrylic elastic emulsion, and 20 parts of the copolymer-coated modified glass microspheres. The preparation method of the sodium polyacrylate modified bentonite comprises: S01: Bentonite was first stirred and mixed in a hydrochloric acid solution to form a slurry with a bentonite content of 14%. The slurry was then washed with water and dried. The temperature was then raised to 185°C at a rate of 5°C / min and kept at this temperature for 10 min. The temperature was then raised to 315°C at a rate of 5°C / min and kept at this temperature for 15 min. The slurry was finally cooled in air to room temperature to obtain the acid-washed bentonite. S02: 100 parts of the acid-washed bentonite obtained in step S01 and 15 parts of sodium polyacrylate were stirred at a constant temperature of 70° C. for 10 hours; then the pH was adjusted to 10 with a 2% NaOH solution, and the stirring was continued for 2 hours. The mixture was filtered and dried to obtain sodium polyacrylate-modified bentonite.

[0042] The preparation method of the above-mentioned water-based thermal insulation coating includes: adding 45 parts of water, 1 part of modified bentonite, 0.2 parts of CA-2500 dispersant, 0.2 parts of PE-100 dispersant, and dispersant into an open dispersion tank in sequence, dispersing at a high speed of 1200 rpm for 20 minutes, adding 0.3 parts of aerogel powder, and continuing to disperse at a high speed for 20 minutes until the aerogel powder is completely and evenly wetted and dispersed to obtain an aerogel slurry; adjusting the speed to 800 rpm, and then adding 1.5 parts of propylene glycol, 1.5 parts of film-forming aid, 0.4 parts of defoaming agent, 30 parts of water-based acrylic emulsion, and 20 parts of copolymer-coated modified glass microspheres to the above-mentioned aerogel slurry in sequence, stirring evenly to prepare the water-based thermal insulation coating.

[0043] Comparative Example 1 This comparative example provides a water-based thermal insulation coating, which is basically the same as the water-based thermal insulation coating provided in Example 1, with the main difference being that unmodified bentonite is used in this comparative example to replace the sodium polyacrylate modified bentonite in Example 1, and unmodified hollow glass microspheres are used to replace the copolymer-coated modified glass microspheres in Example 1, and the amounts of bentonite and hollow glass microspheres in the two are the same.

[0044] Comparative Example 2 This comparative example provides a water-based thermal insulation coating, which is basically the same as the water-based thermal insulation coating provided in Example 1. The main difference is that unmodified hollow glass microspheres are used in this comparative example to replace the copolymer-coated modified glass microspheres in Example 1, and the amount of hollow glass microspheres used in the two is the same.

[0045] Comparative Example 3 This comparative example provides a water-based thermal insulation coating, which is basically the same as the water-based thermal insulation coating provided in Example 1, with the main difference being that: in this comparative example, unmodified hollow glass microspheres are used to replace the copolymer-coated modified glass microspheres in Example 1, and the amount of hollow glass microspheres used in the two is the same; at the same time, in this comparative example, unmodified bentonite and sodium polyacrylate of equal mass are used to replace the sodium polyacrylate modified bentonite in Example 1.

[0046] Comparative Example 4 This comparative example provides a water-based thermal insulation coating, which is basically the same as the water-based thermal insulation coating provided in Example 1. The main difference is that the unmodified bentonite in this comparative example replaces the sodium polyacrylate modified bentonite in Example 1, and the amount of bentonite in both is the same.

[0047] Comparative Example 5 This comparative example provides a water-based thermal insulation coating, which is basically the same as the water-based thermal insulation coating provided in Example 1, with the main difference being that the unmodified bentonite in this comparative example replaces the sodium polyacrylate modified bentonite in Example 1, and the amount of bentonite used in the two is the same; at the same time, hollow glass microspheres and copolymers of equal mass are used in this comparative example instead of the copolymer-coated modified glass microspheres in Example 1.

[0048] Performance Testing The storage stability (GB / T6753.3-1986), water absorption (HG / T 3344-2012), thermal conductivity and other properties of the water-based thermal insulation coatings provided in Examples 1-3 and Comparative Examples 1-5 were tested. The results are shown in Tables 1 and Figure 1 The properties of the bentonite used in each embodiment and comparative example (HG / T 2248-2012) were tested using the 4# rotor of the LC-NDJ-8S Pro digital display rotational viscometer, as shown in Table 1.

[0049] Table 1 Performance test results of water-based thermal insulation coatings and various bentonite used therein project Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Example 2 Example 3 Storage stability There is no stratification after 30 days of hot storage and the surface does not harden After 1 day of hot storage, the upper and lower layers are separated and the surface becomes hard. After 5 days of hot storage, the upper and lower layers are separated and the surface becomes hard. After 3 days of hot storage, the upper and lower layers are separated and the surface becomes hard. After 1 day of hot storage, the upper and lower layers are separated and the surface becomes hard. After 3 days of hot storage, the upper and lower layers are separated and the surface becomes hard. No delamination after 30 days, and the surface does not become hard No delamination after 30 days, and the surface does not become hard Water absorption rate / 7 days 7.2% 221% 123% 225% 62.9% 83.1% 15.31% 3.6% Thermal conductivity 0.038 0.038 0.038 0.038 0.039 0.039 0.046 0.035 Bentonite viscosity at low speed 32007 mP·s 6379 mP·s 32007 mP·s 6579 mP·s 6379 mP·s 6379 mP·s 27701mP·s 39180mP·s High speed bentonite viscosity 3334 mP·s 1724 mP·s 3334 mP·s 1724 mP·s 1724 mP·s 1724 mP·s 3011 mP·s 3998 mP·s Bentonite shear thinning index 9.6 3.7 9.6 3.6 3.7 3.7 9.2 9.8 In the table, “low-speed bentonite viscosity” refers to the bentonite viscosity measured when a 6 wt% bentonite slurry was stirred with a 4# rotor at 6 rpm; “high-speed bentonite viscosity” refers to the bentonite viscosity measured when a 6 wt% bentonite slurry was stirred with a 4# rotor at 60 rpm. The unit of thermal conductivity is w / (m·K).

[0050] Table 1 shows that the thermal conductivity of the water-based thermal insulation coating provided by the embodiment of the present invention is 0.035-0.046 w / (m·K). While having good thermal insulation performance, it has good thermal stability and can achieve thermal storage for 30 days without delamination and the surface does not harden. The water absorption rate is between 3.6-15.31%, not exceeding 20%.

[0051] It can be seen from Example 1 and Comparative Examples 1-5 that: 1) From the perspective of stability, combined with Table 1 and Figure 1 It can be seen that since the bentonite in Comparative Example 1 (1 B), Comparative Example 3 (1 D), Comparative Example 4 and Comparative Example 5 has not been purified and modified with sodium polyacrylate, and the microbeads in Comparative Example 1, Comparative Example 2 (1 C), Comparative Example 3 and Comparative Example 5 have not been modified by polymer coating, a three-dimensional network structure formed by hydrogen bonding and electrostatic action cannot be formed between the microbeads and the bentonite, so the storage stability is poor and the microbeads float up. Therefore, Example 1 (1 A) provides a water-based thermal insulation coating with good thermal stability, which can prevent the hollow glass microbeads therein from floating up for a long time and the surface does not harden.

[0052] 2) From the perspective of water absorption, since the microbeads in Comparative Examples 1, 2, 3 and 5 were not modified by polymer coating, the water absorption rate of the coating after film formation was relatively large. Among them, in Comparative Example 5, the copolymer was directly added instead of coating modification, and the water absorption rate was second only to that in Comparative Example 5. Therefore, Example 1 provides a water-based thermal insulation coating with lower water absorption after film formation and better water resistance.

[0053] 3) From the perspective of thermal conductivity, since the microbeads in Comparative Examples 1, 2, and 3 were not modified by polymer coating, their thermal conductivity was consistent with that of Example 1. Comparative Example 4 coated the microbeads with a layer of organic copolymer, and Comparative Example 5 added an organic copolymer to the microbeads, so the thermal conductivity was slightly higher than that of Example 1.

[0054] 4) From the perspective of bentonite viscosity, i.e., shear thinning index, the bentonite in Comparative Examples 1, 3, 4, and 5 was not purified or modified with sodium polyacrylate, resulting in a low viscosity. Therefore, the shear thinning index of the bentonite was low, indicating a thickening type. The modified bentonite had a shear thinning index of 9 or greater, indicating a rheological type. Therefore, the microspheres had the best storage stability. Therefore, Example 1 provides a water-based thermal insulation coating with the best storage stability.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solutions of the present invention. They should all be included in the scope of the technical solutions claimed for protection by the present invention.

Claims

1. A water-based thermal insulation coating, characterized in that: The invention comprises the following raw materials based on 100 parts by weight: 20-30 parts of aqueous acrylic emulsion, 1-10 parts of aerogel powder, 10-20 parts of copolymer-coated modified glass microspheres, 0.2-1 part of sodium polyacrylate-modified bentonite, 0.6-1.5 parts of propylene glycol, 1-1.5 parts of a film-forming aid, 0.1-0.4 parts of a dispersant, 0-0.2 parts of a thickener, 0.2-0.4 parts of a defoaming agent, and the balance being water; wherein the copolymer-coated modified glass microspheres comprise hollow glass microspheres and a hydroxyl-containing acrylate copolymer coating layer coated on the surface of the hollow glass microspheres.

2. The water-based thermal insulation coating according to claim 1, characterized in that: The hydroxyl-containing acrylate copolymer coating layer is mainly prepared by mixing methyl methacrylate, butyl acrylate and hydroxyethyl acrylate as polymer monomers in a mass ratio of 4.7-6.0:3.0-4.3:1 and undergoing copolymerization reaction.

3. The water-based thermal insulation coating according to claim 2, characterized in that: The copolymer-coated modified glass microspheres are mainly prepared by the following method: Pre-modification: first use silane coupling agent to modify the hollow glass microspheres to obtain double-bond modified glass microspheres; Copolymer modification: using the methyl methacrylate, butyl acrylate and hydroxyethyl acrylate as polymer monomers, a copolymerization reaction occurs on the surface of the double-bond modified glass microspheres to form a hydroxyl-containing acrylate copolymer coating layer on the surface of the hollow glass microspheres.

4. The water-based thermal insulation coating according to claim 3, characterized in that: Copolymer modification: Methyl methacrylate, butyl acrylate, and hydroxyethyl acrylate are uniformly mixed to form a polymer monomer mixture, which is then uniformly mixed with the double-bond modified glass microspheres. Under the action of an initiator, a copolymerization reaction occurs on the surface of the double-bond modified glass microspheres, forming a hydroxyl-containing acrylate copolymer coating layer on the surface of the hollow glass microspheres, thereby producing copolymer-coated modified glass microspheres. The mass ratio of the double-bond modified glass microspheres to the polymer monomer mixture and the initiator is 2-8:35-45:0.03-0.

06.

5. The water-based thermal insulation coating according to claim 4, characterized in that: The copolymer modification step may include: first, uniformly mixing 40-60 parts of deionized water, 2-8 parts of the double-bond modified hollow glass microspheres, 2-5 parts of an emulsifier, and 0.3-0.6 parts of a sodium bicarbonate buffer, heating the mixture to 45-55° C., then maintaining the temperature for 20-40 minutes, and then continuing to heat the mixture to 70-75° C., while slowly adding dropwise 0.3-0.6 parts of a 10 wt% initiator solution and 35-45 parts of the polymerization monomer mixture, the addition time being 1-2 hours, and continuing the reaction for 2-3 hours to form a hydroxyl-containing acrylate copolymer coating layer on the surface of the hollow glass microspheres, and filtering the material.

6. The water-based thermal insulation coating according to claim 5, characterized in that: The emulsifier is prepared by uniformly mixing sodium lauryl sulfate and fatty alcohol polyoxyethylene ether in a mass ratio of 1.5-2.5:

1.

7. The water-based thermal insulation coating according to claim 3, characterized in that: The pre-modification step includes: first, uniformly mixing 5-10 parts of hollow glass microspheres, 40-50 parts of anhydrous ethanol and 5-10 parts of the silane coupling agent to form a raw material premix; adding 15-30 parts of pure water to the raw material premix within 3-6 minutes, reacting for 0.5-1.0 hours, and filtering to obtain the double bond modified hollow glass microspheres.

8. The water-based thermal insulation coating according to claim 3 or 7, characterized in that: The silane coupling agent is γ-methacryloxypropyltrimethoxysilane KH570, vinyl tris(2-methoxyethoxysilane), vinyl triethoxysilane or vinyl trimethoxysilane.

9. The water-based thermal insulation coating according to claim 1, characterized in that: When the sodium polyacrylate-modified bentonite is prepared into a slurry with a concentration of 6 wt%, the viscosity is 27,000-40,000 mP·s at 6 rpm using the 4# rotor of the LC-NDJ-8S Pro digital rotational viscometer; the viscosity is 3,000-4,000 mP·s at 60 rpm, and the shear thinning index is 9-10.

10. The method for preparing the water-based thermal insulation coating according to any one of claims 1 to 9, comprising the steps of: first uniformly mixing the sodium polyacrylate modified bentonite, a dispersant, aerogel powder and water to obtain a uniformly dispersed aerogel slurry; then uniformly mixing the aerogel slurry, propylene glycol, a film-forming aid, a defoaming agent, a water-based acrylic emulsion, copolymer-coated modified glass microspheres and a thickener.

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