Preparation method of heat insulation coating for air fryer

Abstract

The invention discloses a preparation method of a heat-insulating coating for an air fryer, composite heat-insulating particles are double-cavity particles, in the calcining process, polystyrene and polydopamine between a silicon dioxide shell layer and a hollow glass bead core material are removed to form cavities, and the cavities are matched with cavities of hollow glass beads to form particles with double-cavity structures. And when applied to a coating, the coating can improve the heat insulation performance and meet the use requirements.

Description

Technical Field

[0001] The present invention relates to the technical field of household electrical appliances, and in particular to a method for preparing a heat-insulating coating for an air fryer. Background Art

[0002] An air fryer is a machine that can "fry" food with air. It mainly uses air to replace the hot oil in the frying pan to cook the food. At the same time, the hot air blows away the moisture on the surface of the food, making the food almost fried. In order to avoid the phenomenon of overheating of the shell surface causing damage to furniture or injury to operators, air fryers generally need to be insulated. Common methods include changing the structure of the shell, placing a gap between the double-layer shell, or building other insulation mechanisms into the shell cavity.

[0003] The above method requires complex structural improvements to the shell or chamber. In response to this, structures that use coatings for insulation have also appeared on the market, such as forming an insulation coating on the periphery of the shell, such as a coating composed of silicone resin and thermal insulation fillers such as silica and hollow glass beads. The defect is that the insulation requirements can only be met when a large proportion of thermal insulation fillers are added, but it is easy to affect the mechanical and weather resistance properties of the coating, which needs to be improved. Summary of the invention

[0004] To solve at least one of the above technical defects, the present invention provides the following technical solutions:

[0005] The invention discloses a method for preparing a heat-insulating coating for an air fryer, comprising the following steps:

[0006] First, the preparation of composite thermal insulation particles

[0007] The hollow glass microspheres are first coated with polystyrene, then the polystyrene shell is coated with polydopamine, and then the polydopamine shell is coated with silicon dioxide for a second time to form prefabricated particles. Finally, the prefabricated particles are calcined to remove the polystyrene shell and the polydopamine shell to form composite insulation particles.

[0008] Second, by mass, 30-48 parts of silicone resin emulsion, 5-8 parts of acrylic emulsion, 5-15 parts of the above-mentioned composite heat-insulating particles, 1-3 parts of additives, and 15-25 parts of solvent are mixed to form a coating;

[0009] Third, the above-mentioned coating is applied and dried to form a heat-insulating coating.

[0010] The composite thermal insulation particles in the present invention are double-cavity particles. During the calcination process, the polystyrene shell layer and the polydopamine shell layer between the silica shell layer and the hollow glass microsphere core material are removed to form cavities, which cooperate with the cavities of the hollow glass microspheres to form particles with a double-cavity configuration. When applied to a coating, the thermal insulation performance can be improved to meet usage requirements.

[0011] The silicone resin emulsion and acrylic emulsion in the coating components are combined to form a film layer, which has the advantages of good mechanical properties, high adhesion strength and weather resistance. The function of the polydopamine shell layer is mainly to make the silicon dioxide more evenly coated on the corresponding polystyrene shell layer, increase the proportion of double-cavity composite particles, and help to further improve the thermal insulation performance.

[0012] Furthermore, in the first step, water, hollow glass microspheres and surfactant are mixed, the temperature is raised to above 40°C, styrene and initiator are added, the temperature is raised to above 65°C for a second time to react so that polystyrene is coated on the hollow glass microspheres to form a polystyrene shell layer, the polystyrene-coated hollow glass microspheres, trihydroxyaminomethane, dopamine and solvent are mixed and reacted so that polydopamine is coated on the polystyrene shell layer to form a polydopamine shell layer, polydopamine and polystyrene-coated hollow glass microspheres are dispersed in an alcohol solvent, ammonia water and an alcohol solution of tetraethyl orthosilicate are added, and the reaction is carried out at 25±5°C so that silicon dioxide is coated on the polydopamine shell layer, the obtained solid is dried after solid-liquid separation, and the dried solid is calcined to remove polystyrene and polydopamine, thereby obtaining the composite thermal insulation particles.

[0013] In the present invention, polystyrene is pre-coated on the peripheral wall of the hollow glass microspheres, and then polydopamine is used for secondary coating. Under the action of polydopamine, the silicon dioxide is coated more evenly. In the subsequent calcination process, the polystyrene shell layer and the polydopamine shell layer are removed to form double-cavity particles. The above scheme has the advantages of short process flow and convenient molding.

[0014] Furthermore, the mass ratio of styrene, surfactant, hollow glass microspheres, tetraethyl orthosilicate and dopamine is 4:0.2-0.7:0.8-1.2:6-9:1-1.2.

[0015] Furthermore, the hollow glass microspheres are mixed with water and a surfactant after coupling modification, and the coupling modification helps to improve the dispersibility of the hollow glass microspheres and reduce agglomeration and the like.

[0016] Furthermore, when the polystyrene shell layer is formed by the reaction, the temperature is raised to above 65° C. for a second time for reaction for 3-6 hours, and when the silica shell layer is formed by the reaction, the temperature is 25±5° C. for reaction for 10-16 hours. Limiting the reaction time helps the corresponding substances to fully form the coating.

[0017] Furthermore, the silicone resin emulsion is MP50E type, the acrylic emulsion is 2648A type, and the auxiliary agents include a defoamer and a wetting agent.

[0018] Furthermore, the diameter of the hollow glass microspheres is 20-60 μm, which facilitates coating of the coating on the shell.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The present invention designs composite thermal insulation particles with a double-cavity configuration and a preparation process. A small amount of composite thermal insulation particles can be added to make the coating meet application requirements, which helps to reduce costs. DETAILED DESCRIPTION

[0021] The present invention will be further described below in conjunction with specific embodiments.

[0022] Example 1

[0023] A method for preparing a heat-insulating coating for an air fryer comprises the following steps:

[0024] First, the preparation of composite thermal insulation particles

[0025] Hollow glass microspheres are coated with polystyrene. First, deionized water, hollow glass microspheres (diameter 40-60 μm, silane coupling agent modified), and surfactant (sodium dodecyl sulfate), the mass ratio of hollow glass microspheres to surfactant is 1:0.4, and the mass ratio of hollow glass microspheres to deionized water is 1:160. The three are mixed and ultrasonically vibrated for 15 minutes. The temperature is raised to 45° C. and styrene and initiator (potassium persulfate) are added. The amount of initiator is 1% of the mass of styrene, and the mass ratio of styrene to hollow glass microspheres is 4:1. The temperature is raised to 80° C. for a second time to react for 3 hours. During the reaction, polystyrene is deposited on the surface of the hollow glass microspheres to form a coating to form a polystyrene shell layer. The emulsion is extracted and filtered. The filtrate is washed and placed in an oven at 40° C. for drying. The dried reactant is ground to obtain hollow glass microspheres coated with polystyrene.

[0026] The above-mentioned polystyrene-coated hollow glass microspheres, trihydroxyaminomethane, dopamine, and deionized water are mixed and ultrasonically stirred for 15 minutes, and stirred at room temperature for 18 hours. The mass ratio of hollow glass microspheres to trihydroxyaminomethane, dopamine, and deionized water is 1:1:1:1. The reaction product is filtered and washed, and the filtered product is placed in an oven at 50°C and dried to form a double-layer hollow glass microsphere coated with a polydopamine shell layer and a polystyrene shell layer.

[0027] The double-layer coated hollow glass microspheres are dispersed in ethanol and ultrasonicated for 15 minutes, ammonia water is added and stirred evenly, the mass ratio of the double-layer coated hollow glass microspheres to ethanol is 1:10, and the mass ratio of the double-layer coated hollow glass microspheres to ammonia water is 10:1. An ethanol solution of tetraethyl orthosilicate (40%) is added to the ethanol dispersion, the mass ratio of styrene to tetraethyl orthosilicate is 4:7, and stirring is continued at room temperature for 14 hours. During the reaction, a silicon dioxide layer is secondary coated on the outside of the polydopamine shell layer. The reaction product is centrifuged, washed and dried, and the dried particles are calcined to remove the polystyrene shell layer and the polydopamine shell layer between the silicon dioxide layer and the hollow glass microspheres, so as to obtain double-cavity composite thermal insulation particles.

[0028] Second, by mass, 40 parts of silicone resin emulsion (MP50E), 7 parts of acrylic emulsion (2648A), 10 parts of the above-mentioned composite thermal insulation particles, 2 parts of additives, and 20 parts of deionized water were mixed and stirred for 40 minutes to form a coating. The additive was composed of a defoamer 681f and a wetting agent OP-10 in a ratio of 1:1 by mass.

[0029] Third, apply the paint on the surrounding wall of the air fryer shell and form a heat-insulating coating after drying at room temperature.

[0030] Example 2

[0031] A method for preparing a heat-insulating coating for an air fryer comprises the following steps:

[0032] First, the preparation of composite thermal insulation particles

[0033] Hollow glass microspheres are coated with polystyrene. First, deionized water, hollow glass microspheres (diameter 40-60 μm, silane coupling agent modified), and surfactant (sodium dodecyl sulfate), the mass ratio of hollow glass microspheres to surfactant is 1:0.5, and the mass ratio of hollow glass microspheres to deionized water is 1:150. The three are mixed and ultrasonically vibrated for 20 minutes, the temperature is raised to 42°C, styrene and initiator (potassium persulfate) are added, the amount of initiator is 1% of the mass of styrene, and the mass ratio of styrene to hollow glass microspheres is 4:1.1. The temperature is raised to 85°C for a second time to react for 3 hours. During the reaction, polystyrene is deposited on the surface of the hollow glass microspheres to form a coating to form a polystyrene shell layer. The emulsion is extracted and filtered. The filtrate is washed and placed in an oven at 40°C for drying. The dried reactant is ground to obtain hollow glass microspheres coated with polystyrene.

[0034] The above-mentioned polystyrene-coated hollow glass microspheres, trihydroxyaminomethane, dopamine, and deionized water are mixed and ultrasonically stirred for 20 minutes, and stirred at room temperature for 20 hours. The mass ratio of hollow glass microspheres to trihydroxyaminomethane, dopamine, and deionized water is 1:1:1.1:1.3. The reaction product is filtered and washed, and the filtered product is placed in an oven at 50°C and dried to form a double-layer hollow glass microsphere coated with a polydopamine shell layer and a polystyrene shell layer.

[0035] The double-layer coated hollow glass microspheres are dispersed in ethanol and ultrasonicated for 20 minutes, ammonia water is added and stirred evenly, the mass ratio of the double-layer coated hollow glass microspheres to ethanol is 1:12, and the mass ratio of the double-layer coated hollow glass microspheres to ammonia water is 12:1. An ethanol solution of tetraethyl orthosilicate (40%) is added to the ethanol dispersion, the mass ratio of styrene to tetraethyl orthosilicate is 4:8, and stirring is continued at room temperature for 15 hours. During the reaction, a silicon dioxide layer is secondary coated on the outside of the polydopamine shell layer. The reaction product is centrifuged, washed and dried, and the dried particles are calcined to remove the polystyrene shell layer and the polydopamine shell layer between the silicon dioxide layer and the hollow glass microspheres, so as to obtain double-cavity composite thermal insulation particles.

[0036] Second, by mass, 42 parts of silicone resin emulsion (MP50E), 8 parts of acrylic emulsion (2648A), 8 parts of the above-mentioned composite thermal insulation particles, 2 parts of additives, and 25 parts of deionized water are mixed and stirred for 40 minutes to form a coating. The additive is composed of a defoamer 681f and a wetting agent OP-10 in a ratio of 1:1 by mass.

[0037] Third, apply the paint on the surrounding wall of the air fryer shell and form a heat-insulating coating after drying at room temperature.

[0038] Example 3

[0039] A method for preparing a heat-insulating coating for an air fryer comprises the following steps:

[0040] First, the preparation of composite thermal insulation particles

[0041] Hollow glass microspheres are coated with polystyrene. First, deionized water, hollow glass microspheres (diameter 40-60 μm, silane coupling agent modified), and surfactant (sodium dodecyl sulfate), the mass ratio of hollow glass microspheres to surfactant is 1:0.6, and the mass ratio of hollow glass microspheres to deionized water is 1:160. The three are mixed and ultrasonically vibrated for 15 minutes. The temperature is raised to 43° C. and styrene and initiator (potassium persulfate) are added. The amount of initiator is 1% of the mass of styrene, and the mass ratio of styrene to hollow glass microspheres is 4:0.9. The temperature is raised to 80° C. for a second time to react for 4 hours. During the reaction, polystyrene is deposited on the surface of the hollow glass microspheres to form a coating to form a polystyrene shell layer. The emulsion is extracted and filtered. The filtrate is washed and placed in an oven at 40° C. for drying. The dried reactant is ground to obtain hollow glass microspheres coated with polystyrene.

[0042] The above-mentioned polystyrene-coated hollow glass microspheres, trihydroxyaminomethane, dopamine, and deionized water are mixed and ultrasonically stirred for 10 minutes, and stirred at room temperature for 24 hours. The mass ratio of hollow glass microspheres to trihydroxyaminomethane, dopamine, and deionized water is 1:1:1:1. The reaction product is filtered and washed, and the filtered product is placed in an oven at 50°C and dried to form a polydopamine shell layer and a polystyrene double-layer shell to coat hollow glass microspheres.

[0043] The double-layer coated hollow glass microspheres are dispersed in ethanol and ultrasonicated for 15 minutes, ammonia water is added and stirred evenly, the mass ratio of the double-layer coated hollow glass microspheres to ethanol is 1:13, and the mass ratio of the double-layer coated hollow glass microspheres to ammonia water is 11:1. An ethanol solution of tetraethyl orthosilicate (40%) is added to the ethanol dispersion, the mass ratio of styrene to tetraethyl orthosilicate is 4:9, and stirring is continued at room temperature for 16 hours. During the reaction, a silicon dioxide layer is secondary coated on the outside of the polydopamine shell layer. The reaction product is centrifuged, washed and dried, and the dried particles are calcined to remove the polystyrene shell layer and the polydopamine shell layer between the silicon dioxide layer and the hollow glass microspheres, so as to obtain double-cavity composite thermal insulation particles.

[0044] Second, by mass, 45 parts of silicone resin emulsion (MP50E), 6 parts of acrylic emulsion (2648A), 12 parts of the above-mentioned composite thermal insulation particles, 2 parts of additives, and 25 parts of deionized water were mixed and stirred for 40 minutes to form a coating. The additive was composed of a defoamer 681f and a wetting agent OP-10 in a ratio of 1:1 by mass.

[0045] Third, apply the paint on the surrounding wall of the air fryer shell and form a heat-insulating coating after drying at room temperature.

[0046] Comparative Example 1

[0047] Compared with Example 3, in this example, there is no step of coating the polystyrene shell layer with polydopamine, and silicon dioxide is directly coated on the polystyrene shell layer.

[0048] Comparative Example 2

[0049] Compared with Example 3, the components of the coating in this example are: 45 parts of silicone resin emulsion (MP50E), 6 parts of acrylic emulsion (2648A), 12 parts of hollow glass microsphere particles, 6 parts of silica aerogel, 3 parts of potassium hexatitanate whiskers, 2 parts of additives, and 35 parts of deionized water are mixed and stirred for 40 minutes to form a coating. The additive is composed of a defoamer 681f and a wetting agent OP-10 in a mass ratio of 1:1.

[0050] The thermal insulation coefficient of the coating prepared above was tested, as shown in Table 1.

[0051] Table 1

[0052] <![CDATA[Thermal conductivity W·(m·K) -1 > Example 1 0.030 Example 2 0.033 Example 3 0.028 Comparative Example 1 0.037 Comparative Example 2 0.034

[0053] It can be seen that the thermal conductivity of the coating formed by this scheme is significantly reduced, and the required thermal insulation effect can be achieved with a relatively small proportion of thermal insulation filler, which has little effect on the mechanical properties of the coating. The thermal insulation filler in the coating of Comparative Example 2 is much higher than the proportion in this scheme, and the thermal insulation effects of the two are similar. In Comparative Example 1, there is no polydopamine coating. It is found through testing that the silicon dioxide is scattered on the polystyrene shell layer and cannot be evenly adsorbed on the polystyrene shell layer. There is no obvious shell configuration or collapse under subsequent high-temperature calcination. The proportion of double-cavity particles formed is low, which leads to a decrease in subsequent thermal insulation performance.

[0054] The above are only preferred embodiments of the present invention. The protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a heat-insulating coating for an air fryer, characterized in that: The following steps are involved: First, the preparation of composite thermal insulation particles Firstly, hollow glass microspheres are coated with polystyrene, then the polystyrene shell is coated with polydopamine, and then the polydopamine shell is coated with silicon dioxide for a second time to form prefabricated particles, and finally the prefabricated particles are calcined to remove the polystyrene shell and the polydopamine shell to form composite thermal insulation particles; Second, by mass, 30-48 parts of silicone resin emulsion, 5-8 parts of acrylic emulsion, 5-15 parts of the above composite thermal insulation particles, 1-3 parts of additives, and 15-25 parts of solvent are mixed to form a coating; Third, the coating is applied and dried to form a heat-insulating coating.

2. The method for preparing the heat-insulating coating for an air fryer according to claim 1, characterized in that: In the first step, water, hollow glass microspheres and a surfactant are mixed, the temperature is raised to above 40°C, styrene and an initiator are added, and the temperature is raised to above 65°C for a second time to react so that polystyrene is coated on the hollow glass microspheres to form a polystyrene shell layer; the polystyrene-coated hollow glass microspheres, trihydroxyaminomethane, dopamine and a solvent are mixed and reacted so that polydopamine is coated on the polystyrene shell layer to form a polydopamine shell layer; polydopamine and polystyrene-coated hollow glass microspheres are dispersed in an alcohol solvent, and ammonia water and an alcohol solution of tetraethyl orthosilicate are added, and the reaction is carried out at 25±5°C so that silicon dioxide is coated on the polydopamine shell layer, and the obtained solid is dried after solid-liquid separation, and the dried solid is calcined to remove polystyrene and polydopamine, so as to obtain the composite thermal insulation particles.

3. The method for preparing the heat-insulating coating for an air fryer according to claim 2, characterized in that: The mass ratio of styrene, surfactant, hollow glass microspheres, tetraethyl orthosilicate and dopamine is 4:0.2-0.7:0.8-1.2:6-9:1-1.

2.

4. The method for preparing the heat-insulating coating for an air fryer according to claim 2, characterized in that: The hollow glass microspheres are mixed with water and a surfactant after being coupled and modified.

5. The method for preparing the heat-insulating coating for an air fryer according to claim 2, characterized in that: When the polystyrene shell layer is formed by the reaction, the temperature is raised to above 65°C for a second time to react for 3-6 hours. When the silica shell layer is formed by the reaction, the temperature is kept at 25±5°C for 10-16 hours.

6. The method for preparing the heat-insulating coating for an air fryer according to claim 1, characterized in that: The silicone resin emulsion is MP50E type, the acrylic emulsion is 2648A type, and the auxiliary agents include a defoamer and a wetting agent.

7. The method for preparing the heat-insulating coating for an air fryer according to claim 1, characterized in that: The diameter of the hollow glass microspheres is 20-60 μm.