Microwave oven metal cookware wave-absorbing and heat-generating coating and preparation method thereof

Abstract

This invention discloses a microwave-absorbing and heating coating for metal cookware used in microwave ovens and its preparation method. The microwave-absorbing and heating coating is prepared from layered Mxenes powder, magnetic iron tetroxide powder or γ-iron oxide powder, tungsten carbide powder, polyvinylidene fluoride powder, aluminosilicate powder, and a high-temperature resistant glass adhesive. This invention uses the microwave-absorbing and heating coating material as a heat source, utilizing the heat generated by the absorbing material under microwave action, which can solve the problem that metal cookware cannot heat the food inside the cavity in a microwave oven.

Description

Technical Field

[0001] This invention belongs to the field of microwave absorbing material manufacturing technology, and in particular relates to a microwave absorbing and heating coating for microwave oven metal cookware and its preparation method. Background Technology

[0002] Microwaves are a type of electromagnetic wave with significantly more energy than typical radio waves. They can penetrate insulating materials such as glass, ceramics, and plastics without consuming energy. Microwave heating works by directly penetrating the material and converting electromagnetic energy into heat through the interaction of molecules and the electromagnetic field. This is not limited by the thermal conductivity of conventional heating methods, allowing for volumetric heating with higher energy efficiency and shorter heating times, leading to their increasingly widespread application. When cooking in a microwave oven, the heat penetrates directly into the food, making cooking 4 to 10 times faster than other stoves, with a thermal efficiency exceeding 80%. Currently, no other type of stove can match its thermal efficiency. Because of the short cooking time, microwave ovens effectively preserve the vitamins and natural flavors of food. While modern people appreciate the convenience of microwave ovens, they also have higher demands for food preparation, as microwaved food often lacks the texture and flavor of grilled or roasted food.

[0003] However, the metal casing of most metal cookware makes them difficult to use in microwave ovens. This is because the electromagnetic shielding effect of metal causes microwaves to be reflected off the metal surface, preventing the food inside from receiving microwaves for heating.

[0004] Currently, some researchers both domestically and internationally have conducted research on microwave absorbing materials. For example:

[0005] Chinese patent document CN 115594401 A discloses a microwave absorbing heating material, its preparation method, and a ceramic vessel. This microwave absorbing heating material can be used on an open flame or in a microwave oven. It can reach 150-200°C within 5 minutes of microwave heating, without rapidly increasing the temperature in a short time and carbonizing or charring the food.

[0006] Chinese patent document CN 107011704 A provides a microwave heating coating that has a low solidification temperature, good coating adhesion, excellent heat generation and thermal conductivity, high microwave utilization rate, and low preparation cost, and has good practical significance.

[0007] Chinese patent document CN 116553599 A discloses a zinc oxide-based microwave heating material, its preparation method, and its application. This invention synthesizes zinc oxide, a microwave heating material, using a simple method. Furthermore, by selecting suitable preparation methods, zinc oxide-based composite materials with needle-like, petal-like, and rod-like micro / nano-structures are constructed using a zinc oxide matrix and modifiers. This effectively improves the microwave heating efficiency of various microwave-transparent or poorly heated inorganic metals or non-metals, enabling their application in microwave processing of carbon-containing materials.

[0008] Chinese patent document CN 107159887 A discloses a molding method for microwave-absorbing heating materials. This molding method utilizes microwaves for heating, shortening the heating time, improving the heating effect, and eliminating the defects of traditional molding methods.

[0009] However, none of the microwave-absorbing materials disclosed in the above literature pertain to the use of metal cookware in microwave ovens. Because the heating uniformity and temperature rise process of the bottom of metal cookware are difficult to control, these materials are not suitable for heating metal cookware in microwave ovens. Summary of the Invention

[0010] To address the problems existing in the prior art, this invention provides a microwave-absorbing heating coating for metal cookware and its preparation method. This invention uses a microwave-absorbing heating material as a heat source. After absorbing microwaves, the material heats up evenly, heating the metal cookware from the bottom. Furthermore, the coating exhibits good adhesion even at high temperatures and is not easily peeled off. This allows the metal cookware to be used for heating food in a microwave oven, producing the aroma of stir-fried dishes cooked in an iron wok without the oil fumes produced by ordinary iron woks and stoves.

[0011] To achieve the above objectives, the present invention adopts the following technical solution:

[0012] A microwave-safe metal cookware heat-absorbing coating is prepared from layered Mxenes powder, magnetic iron oxide powder or γ-iron oxide powder, tungsten carbide powder, polyvinylidene fluoride powder, aluminosilicate powder, and a high-temperature resistant glass adhesive. In this invention, the layered Mxenes powder, magnetic iron oxide powder or γ-iron oxide powder, tungsten carbide powder, and polyvinylidene fluoride powder are all microwave-absorbing materials. When the microwave-absorbing materials absorb microwaves, they convert the energy into heat. During microwave heating, the food inside cannot be heated due to the reflection from the metal surface. The heat generated by the microwave-absorbing material at the bottom of the cookware cooks the food. The aluminosilicate powder and high-temperature resistant glass adhesive serve as bonding materials to firmly adhere the microwave-absorbing heat-absorbing material to the bottom of the metal cookware. The adhesive material also serves to conduct and dissipate heat, preventing uneven heating and cracking of the adhesive layer due to localized overheating.

[0013] In this invention, adjusting the ratio of layered Mxenes powder, magnetic iron oxide powder or γ-iron oxide powder, and tungsten carbide powder can control the efficiency of microwave heating. Magnetic iron oxide powder or γ-iron oxide powder has a lower heating efficiency, while layered Mxenes powder and tungsten carbide powder have a higher heating efficiency, resulting in excessively rapid heating in the microwave oven. Using magnetic iron oxide powder or γ-iron oxide powder prevents dangerous overheating. Polyvinylidene fluoride powder, aluminosilicate powder, and high-temperature resistant glass adhesive have dispersing and adhesive effects.

[0014] Furthermore, the mass ratio of layered Mxenes powder, magnetic iron oxide powder or γ-iron oxide powder, tungsten carbide powder, polyvinylidene fluoride powder, and aluminosilicate powder is 20-60:40-70:10-20:1-5:2-10.

[0015] Furthermore, the total mass ratio of layered Mxenes powder, magnetic iron oxide powder or γ-iron oxide powder, tungsten carbide powder, polyvinylidene fluoride powder, and aluminosilicate powder to the mass ratio of the high-temperature resistant glass adhesive is 90-75:10-25. The high-temperature resistant glass adhesive can withstand temperatures above 800 degrees Celsius for up to 30 minutes.

[0016] Furthermore, the layered Mxenes powder is obtained by etching titanium carbide; the magnetic iron oxide powder has a particle size of 10-200 nm; the tungsten carbide powder has a particle size of 100 nm-5000 nm; and the polyvinylidene fluoride powder has a number average molecular weight of 250,000-500,000 and a viscosity of <3000 mPa·s.

[0017] Furthermore, the preparation method of layered Mxenes powder is as follows: Titanium carbide powder is boiled in sodium hydroxide solution for 10-40 minutes, ultrasonically vibrated for 5-10 minutes, and allowed to stand for 4-8 hours. The supernatant is then discarded, and the distilled water is replaced 3-5 times. After discarding the excess supernatant, the powder is frozen and vacuum-dried to obtain the powder for later use. This preparation method enables the Mxenes powder to achieve high heating efficiency when microwaved in a microwave oven.

[0018] Furthermore, the magnetic iron oxide powder or γ-iron oxide powder must be ferromagnetic; otherwise, it would not have a microwave heating effect.

[0019] Furthermore, the layered Mxenes powder, magnetic iron oxide powder or γ-iron oxide powder, tungsten carbide powder, polyvinylidene fluoride powder, and aluminosilicate powder and high-temperature resistant glass adhesive are mixed in a specified ratio, and a certain amount (the above mass-volume ratio is 10g / 50mL) of DMF (nitrogen-nitrogen-dimethylformamide) / water mixture is added and stirred at high speed to obtain a viscous mixture.

[0020] The present invention also discloses a method for preparing the microwave oven metal cookware heat-absorbing coating as described above, specifically: layered Mxenes powder, magnetic iron oxide powder or γ-iron oxide powder, tungsten carbide powder, polyvinylidene fluoride powder, aluminosilicate powder, high-temperature resistant glass adhesive, DMF (nitrogen-nitrogen-dimethylformamide), and water are mixed and stirred evenly.

[0021] Furthermore, mechanical stirring is employed for 5-40 minutes at a stirring speed of 800-1500 rpm.

[0022] Furthermore, the mixture is applied to the bottom of the metal cookware, with the coating thickness controlled between 1.0mm and 8.0mm.

[0023] Furthermore, invert the metal cookware and allow the coating to cure naturally at room temperature for 24-48 hours. Then heat it to 50°C to cure for 2-4 hours, and continue heating it to 120°C to cure for 0.5-4 hours.

[0024] Furthermore, coating includes one or more of spraying, dipping, or hand coating.

[0025] Furthermore, the heating coating is wrapped with a high-temperature resistant insulating material, such as asbestos, high-temperature resistant ceramic fiber paper, or glass wool. This high-temperature resistant insulating material is then covered with an engineering plastic shell, which can be made of ABS, PC, PSF, PEEK, nylon, or other plastic varieties. This prevents burns to hands or damage to tabletops after use.

[0026] High-temperature resistant glass adhesives can withstand temperatures of 800-1400℃ after curing without softening or cracking.

[0027] Furthermore, to ensure safe heat dissipation during use, the metal cookware lid has a hole. When using it in a microwave oven, always cover it with the lid. The hole diameter should be at least 8mm. Otherwise, poor heat dissipation inside the cookware may lead to a hazard.

[0028] Placing a coated metal cookware in a microwave oven and heating it on medium for 5-8 minutes or on high for 2-5 minutes will heat the food inside to 100°C. Because this heating method uses a bottom heat source, it simulates the heating process of an iron pot in a microwave oven without causing the food to harden due to microwave heating. This invention has the following technical features:

[0029] 1) This invention uses a microwave-absorbing heating coating material as a heat source. The microwave-absorbing material generates heat under the action of microwaves, which can solve the problem that metal cookware cannot heat the food inside the cavity in a microwave oven.

[0030] 2) The microwave absorbing material of this invention uses layered Mxenes powder, magnetic iron oxide powder or γ-iron oxide powder, tungsten carbide powder, and polyvinylidene fluoride powder as absorbing materials. The absorption principle of layered Mxenes powder and tungsten carbide powder is the absorption of microwaves through multiple reflections and scattering within their layered structure; the absorption principle of magnetic iron oxide powder or γ-iron oxide powder is eddy current loss; and the absorption principle of polyvinylidene fluoride is its polar structure. The use of multiple composite absorbing materials achieves maximum heat dissipation.

[0031] 3) The present invention uses high-temperature resistant glass glue as an adhesive, which makes the uniform heating of the coating easier to control and prevents local overheating from causing thermal stress cracking of the coating. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the structure of a microwave oven metal cookware using the microwave absorbing and heating coating of the present invention. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the protection scope of the present invention.

[0034] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0035] like Figure 1 As shown, the structure of a microwave oven metal cookware using the microwave absorbing and heating coating of the present invention has small ventilation holes on the top cover, microwave heating material coated on the bottom, heat insulation material wrapped on the outside, and an engineering plastic shell on the outermost layer.

[0036] Example 1

[0037] Preparation of Mexenes powder: 1.0 kg of titanium carbide powder was placed in 0.2 M (i.e., mol / L) NaOH solution, and heated to 100 °C while stirring at 800 rpm for 40 minutes. After cooling, it was ultrasonically vibrated for 10 minutes. The precipitate was filtered off, and the filtrate was freeze-dried to obtain Mexenes powder for later use.

[0038] The prepared Mexnes powder was mixed with magnetic iron oxide powder (particle size 200 nm), tungsten carbide powder (particle size 1 μm), polyvinylidene fluoride powder (molecular weight 300,000), and aluminosilicate powder in a mass ratio of 30:45:15:2:8 to obtain microwave absorbing and heating powder.

[0039] The microwave-absorbing heat-generating powder was mixed with high-temperature resistant glass adhesive (1400℃) (mixing ratio 90:10), and 50 ml of DMF (nitrogen-dimethylformamide) / water mixture (50:50 volume ratio) was added and stirred at high speed to obtain a viscous mixture. The mixture was then mechanically stirred at high speed at room temperature (1200 rpm) for 25 minutes, and then coated onto the bottom of a metal cookware to a thickness of 1.5 mm. It was cured at room temperature for 48 hours, then heated to 50℃ for 4 hours, and finally heated to 120℃ for 2 hours.

[0040] The microwave-absorbing heating coating is wrapped with high-temperature resistant ceramic fiber paper, and the outermost layer is a polyetheretherketone (PEEK) injection-molded shell. The edge of the metal cookware lid has six evenly distributed small circular holes, each 8mm in diameter.

[0041] Metal cookware with a microwave-safe heat-absorbing coating can be used in a microwave oven and can heat 600mL of 20°C water to 100°C in 5 minutes on medium power to meet cooking needs.

[0042] Example 2

[0043] Preparation of Mexenes powder: 2.0 kg of titanium carbide was placed in 0.1 M NaOH solution and heated to 100 °C while stirring at 1000 rpm for 20 minutes. After cooling, it was ultrasonically vibrated for 10 minutes. The precipitate was filtered off, and the filtrate was freeze-dried to obtain Mexenes powder for later use.

[0044] The prepared Mexnes powder was mixed with γ-iron oxide powder (particle size 400 nm), tungsten carbide powder (particle size 10 μm), polyvinylidene fluoride powder (molecular weight 400,000) and aluminosilicate powder in a mass ratio of 40:60:15:1:9 to obtain microwave absorbing and heating powder.

[0045] The microwave-absorbing and heat-generating powder was mixed with high-temperature resistant glass adhesive (1200℃ resistance) (mixing ratio 85:15) and a thermally conductive and heat-dissipating agent. Then, 40 ml of DMF (nitrogen-dimethylformamide) / water mixture (60:40 volume ratio) was added and stirred at high speed to obtain a viscous mixture. The mixture was mechanically stirred at room temperature at high speed (1000 rpm) for 20 minutes, and then coated onto the bottom of a metal cookware to a thickness of 2.0 mm. It was cured at room temperature for 36 hours, then heated to 50℃ for 2 hours, and finally heated to 120℃ for 4 hours.

[0046] The microwave-absorbing and heating coating is wrapped with asbestos-resistant material, and the outermost layer is a PEEK injection-molded shell. The edge of the metal cookware lid has two evenly distributed small circular holes, each 1.0mm in diameter.

[0047] Metal cookware with a microwave-safe heat-absorbing coating can be used in a microwave oven and can heat 600mL of 20°C water to 100°C in 2 minutes on high power to meet cooking needs.

[0048] Example 3

[0049] Preparation of Mexenes powder: 1.5 kg of titanium carbide was placed in a 0.2 M NaOH solution and heated to 100 °C while stirring at 1000 rpm for 30 minutes. After cooling, the solution was ultrasonically vibrated for 8 minutes. The precipitate was filtered off, and the filtrate was freeze-dried to obtain Mexenes powder for later use.

[0050] The prepared Mexnes powder was mixed with magnetic iron oxide powder (particle size 100 nm), tungsten carbide powder (particle size 50 μm), polyvinylidene fluoride powder (molecular weight 500,000), and aluminosilicate powder in a mass ratio of 40:40:10:2:8 to obtain microwave absorbing and heating powder.

[0051] The microwave-absorbing and heat-generating powder was mixed with high-temperature resistant glass adhesive (1000℃ resistance) (mixing ratio 85:15) and a thermally conductive and heat-dissipating agent. Then, 50 ml of DMF (nitrogen-dimethylformamide) / water mixture (50:50 volume ratio) was added and stirred at high speed to obtain a viscous mixture. The mixture was mechanically stirred at room temperature at high speed (1500 rpm) for 30 minutes, and then coated onto the bottom of a metal cookware to a thickness of 2.5 mm. It was cured at room temperature for 36 hours, then heated to 50℃ for 2 hours, and finally heated to 120℃ for 4 hours.

[0052] The microwave-absorbing heating coating is wrapped with high-temperature resistant ceramic fiber paper, and the outermost layer is a polysulfone (PSF) injection-molded shell. The edge of the metal cookware lid has two evenly distributed small circular holes, each 1.5mm in diameter.

[0053] Metal cookware with a microwave-safe heat-absorbing coating can be used in a microwave oven and can heat 600mL of 20°C water to 100°C in 3 minutes on medium power to meet cooking needs.

[0054] This invention discloses a microwave-absorbing and heating coating for metal cookware used in microwave ovens and its preparation method. This invention has the advantages of rapid heating, uniform heating, and controllable temperature when heated in a microwave oven.

[0055] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A microwave oven metal cookware heat-absorbing coating, characterized in that, The materials of the microwave absorbing and heating coating include layered Mxenes powder, magnetic iron oxide powder or γ-iron oxide powder, tungsten carbide powder, polyvinylidene fluoride powder, aluminosilicate powder and high-temperature resistant glass adhesive. The mass ratio of the layered Mxenes powder, magnetic iron oxide powder or γ-iron oxide powder, tungsten carbide powder, polyvinylidene fluoride powder, and aluminosilicate powder is 20-60:40-70:10-20:1-5:2-10. The total mass ratio of the layered Mxenes powder, magnetic iron oxide powder or γ-iron oxide powder, tungsten carbide powder, polyvinylidene fluoride powder and aluminosilicate powder to the high-temperature resistant glass adhesive is 75-90:10-25.

2. The microwave oven metal cookware microwave-absorbing and heating coating as described in claim 1, characterized in that, The layered Mxenes powder is obtained by etching titanium carbide; the magnetic iron oxide powder has a particle size of 10-200 nm; the tungsten carbide powder has a particle size of 100 nm-5000 nm; the polyvinylidene fluoride powder has a number average molecular weight of 250,000-500,000 and a viscosity of <3000 mPa·s.

3. A method for preparing a microwave oven metal cookware microwave-absorbing and heating coating as described in any one of claims 1-2, characterized in that, Layered Mxenes powder, magnetic iron oxide powder or γ-iron oxide powder, tungsten carbide powder, polyvinylidene fluoride powder, aluminosilicate powder, high-temperature resistant glass adhesive, DMF, and water are mixed and stirred evenly.

4. The method for preparing a microwave oven metal cookware microwave-absorbing and heating coating as described in claim 3, characterized in that, Use mechanical stirring for 5-40 minutes at a stirring speed of 800-1500 rpm.

5. The method for preparing a microwave oven metal cookware microwave-absorbing and heating coating as described in claim 3 or 4, characterized in that, Apply the mixed material to metal cookware to a thickness of 1.0mm-8.0mm; cure at room temperature for 24-48 hours, then heat to 50℃ for 2-4 hours, and continue heating to 120℃ for 0.5-4 hours.

6. The method for preparing a microwave oven metal cookware microwave-absorbing and heating coating as described in claim 5, characterized in that, The coating includes one or more of spraying, dipping, or manual coating.

7. The method for preparing a microwave oven metal cookware microwave-absorbing and heating coating as described in claim 5, characterized in that, The heating coating is wrapped with a high-temperature resistant insulating material, and the high-temperature resistant insulating material is covered with an engineering plastic shell.

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