Non-stick coating and cooking utensil with non-stick coating

Abstract

A non-stick coating and a cooking utensil having the non-stick coating are provided. [Solution] The non-stick coating 2 is a multi-layer coating formed on one side of the substrate 1 that will serve as the cooking surface of the cooking utensil, and is composed of an undercoat layer 21 containing a silane coupling agent, an intermediate layer 22 containing ceramic microparticles, and a topcoat layer 23 made of enamel paint. The multi-layer non-stick coating system provides excellent non-stick properties without the use of fluororesin (PFAS), while also improving abrasion resistance, heat resistance, and corrosion resistance, and extending the usable life of the cooking utensil, contributing to society and the economy in light of restrictions on fluororesin materials.

Description

[Technical Field]

[0001] The present invention relates to a surface treatment technology for cooking utensils, and more particularly to a non-stick coating that does not use fluororesin (PFAS) and a cooking utensil equipped with a non-stick coating. [Background technology]

[0002] Conventional non-stick coatings for cookware are mainly made of PTFE (polytetrafluoroethylene), a fluororesin that has excellent non-stick (mold release) properties, as well as heat resistance and slip resistance.

[0003] For such cookware using fluororesin, it has been proposed to control the temperature of the cookware so that the initial temperature is sufficient for cooking baked or fried foods, but is within a temperature range that will not damage the fluororesin coating (see, for example, Patent Document 1). It has also been proposed to solve the problem of high-temperature yellowing of non-stick coated cookware without changing the performance of the non-stick coating layer (see, for example, Patent Document 2). It has also been proposed to obtain a coated metal cookware compatible with induction heating, which has a PTFE-type coating on the cooking surface that can be produced more economically than a coated metal cooking vessel including an aluminum body combined with ferromagnetic steel elements and is lighter than a coated metal cooking vessel made from cast steel (see, for example, Patent Document 3). Furthermore, a surface structure with multiple fine holes and a non-stick protective layer made of fluororesin has also been proposed, which can maintain high temperatures, suppress the generation of oily smoke, and maintain an intact state for a long period of time (see, for example, Patent Document 4).

[0004] However, coatings using fluororesins have the following problems. 1. The coating is prone to wear and peeling over time. 2. Poor alkali resistance and easy to be damaged when cleaning. 3. There is a limit to the adhesion to metal substrates, which affects the product life. 4. PFAS, a general term for fluororesin (more specifically, a general term for perfluoroalkyl and polyfluoroalkyl organic fluorine compounds), is difficult to decompose and is known in Europe as "forever chemicals," with its highly persistent nature restricting its use. For example, Denmark, Germany, the Netherlands, Norway, and Sweden announced proposals to restrict the use of PFAS in February 2023. Additionally, American PFAS manufacturers have announced that they will cease production by the end of 2025.

[0005] Therefore, a coating layer that does not use a fluororesin has been proposed. For example, it has been proposed to apply a non-stick layer including a primer layer in which graphene and / or a graphene derivative is uniformly distributed to the surface of a cooking utensil body (see, for example, Patent Document 5). It has also been proposed that a coating member in which at least one of metal ions and metals migrates from a lower coating layer to an upper coating layer can make it easier to remove substances (such as dirt) adhering to the surface (see, for example, Patent Document 6).

[0006] However, graphene is expensive to produce, it is difficult to achieve uniform, defect-free coatings, and there are environmental and health concerns. Furthermore, coatings containing metal ions or metals raise concerns about their corrosion and rust resistance. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-278905 [Patent Document 2] Patent No. 7656029 [Patent Document 3] Patent No. 7671763 [Patent Document 4] Registered Utility Model No. 3179347 [Patent Document 5] Japanese Patent Publication No. 2023-91715 [Patent Document 6] Japanese Patent Application Publication No. 2024-71321 Summary of the Invention [Problem to be solved by the invention]

[0008] This invention was made in consideration of the above circumstances, and aims to provide a multi-layered non-stick coating system that does not use fluororesin (PFAS) and has excellent non-stick properties, while also improving abrasion resistance, heat resistance, and corrosion resistance, and can extend the service life of cookware, thereby contributing to society and the economy through regulations on fluororesin materials. [Means for solving the problem]

[0009] In order to achieve the above object, the first aspect of the present invention is a non-stick coating, which is a coating layer formed on one side of a substrate, characterized by being composed of, in order from the one side, a primer layer containing a silane coupling agent, an intermediate layer containing ceramic fine particles, and a top coat layer containing enamel paint.

[0010] In addition, a second aspect of the present invention is a cooking utensil with a non-stick coating, characterized in that one side of a base material that serves as a cooking surface in the cooking utensil is provided with a three-layer non-stick coating formed by sequentially laminating a primer layer containing a silane coupling agent, an intermediate layer containing ceramic microparticles, and a top coat layer made of enamel paint. In this case, the cooking utensil may preferably have a base material of either an aluminum alloy or stainless steel. The cooking device may also have a bottom surface and a side surface as cooking surfaces. The thickness of the non-adhesive coating on the bottom surface is preferably 40 to 74 μm. The thickness of the non-adhesive coating on the side surface may be 22 to 48 μm.

[0011] Specifically, the cooking utensil can be a frying pan or pot made from either an aluminum alloy or stainless steel, characterized in that one side of the base material that serves as the cooking surface is provided with a three-layer non-stick coating consisting of a primer layer containing a silane coupling agent, an intermediate layer containing ceramic microparticles, and a top coat layer made of enamel paint.

[0012] Furthermore, a third aspect of the present invention is a method for applying a coating to one side of a substrate that will serve as a cooking surface in a cooking utensil according to the first or second aspect of the present invention, and is a non-stick coating method characterized by comprising at least the following steps: a first step of performing a surface treatment such as sandblasting and alkaline degreasing on one side of the substrate; a second step of applying a first coating agent containing a silane coupling agent to the surface-treated surface of the substrate to form a primer layer; a third step of applying a second coating agent containing ceramic fine particles on the primer layer to form an intermediate layer; a fourth step of applying a third coating agent containing an enamel material on the intermediate layer to form a top coat layer; and a fifth step of performing a heat treatment to bake and harden the primer layer, intermediate layer, and top coat layer. In this case, it is preferable to include an additional step of performing anodizing treatment after the first step and before the second step. In addition, the fifth step may be performed by firing at a high temperature of 300 to 330° C. for 5 to 10 minutes. [Effects of the Invention]

[0013] According to this invention, it is possible to provide a multi-layered non-stick coating system that does not use fluororesin (PFAS) and has excellent non-stick properties, while also improving abrasion resistance, heat resistance, and corrosion resistance, thereby extending the service life of cookware, thereby contributing to society and the economy through regulations on fluororesin materials. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view illustrating the structure of a multi-layered non-stick coating according to the present invention. [Figure 2] 1 is a schematic diagram illustrating a non-stick coating method according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an example of an embodiment of the non-stick coating and a cooking utensil equipped with the non-stick coating according to the present invention will be described with reference to the drawings. The embodiments described below are preferred examples of the present invention and are therefore subject to various technical limitations. However, the scope of the present invention is not limited to these embodiments unless otherwise specified in the following description.

[0016] As shown in Figure 1, the multilayered non-stick coating 2 in this embodiment has a three-layer structure formed on one surface of a substrate 1 that will become the cooking surface of the cooking utensil, and is made up of an undercoat layer 21, an intermediate layer 22, and a topcoat layer 23. In other words, the non-stick coating 2 is made up of the undercoat layer 21, the intermediate (intermediate) layer 22, and the topcoat layer 23 formed in this order from the side of the cooking surface of the substrate 1 that constitutes the cooking utensil.

[0017] The undercoat layer 21 contains a silane coupling agent. Silane coupling agents have functional groups in their molecules that bond with both organic and inorganic materials, acting to connect the organic and inorganic materials. Specifically, the hydrolyzable alkoxy group (-OR) bonds with the hydroxy group (-OH) of the substrate 1, and the reactive (organic) functional group, such as an amino group (-NH), reacts with the intermediate layer 22. Therefore, by forming the undercoat layer 21 containing a silane coupling agent on one surface of the substrate 1, strong adhesion and bonding can be achieved, increasing the adhesion between the substrate 1 and the intermediate layer 22. Examples of silane coupling agents that can be used include aminosilane, epoxysilane, and acrylicsilane.

[0018] The intermediate layer 22 contains ceramic nanoparticles. The ceramic nanoparticles serve to disperse stress and increase hardness. Therefore, by forming the intermediate layer 22 on the undercoat layer 21, the mechanical strength characteristics are improved and strengthened, and scratch resistance and slip resistance are imparted.

[0019] The top coat layer 23 contains an enamel material. That is, the top coat layer 23 is composed of an enamel paint called glaze. Enamel is an inorganic glassy glaze that is coated (baked onto the surface), making it resistant to rust and corrosion, odor-resistant, heat-resistant, and corrosion-resistant, increasing durability and enabling long-term use. In other words, metal deteriorates when it comes into contact with acids or alkalis, but by applying enameling, the glaze melts at high temperatures to form a dense protective layer that is highly inert to chemical corrosion caused by acids and alkalis, improving corrosion resistance.

[0020] It is desirable for the cooking utensil to have a bottom surface as a cooking surface and side surfaces that stand upright from the periphery of the bottom surface. Examples of cooking utensils that have a bottom surface and a side surface include frying pans, pots, kettles, and molds that are used primarily for cooking methods such as baking, frying, and boiling. The total thickness of the non-stick coating applied to the cooking surface is preferably 40 μm to 74 μm on the bottom and 22 μm to 48 μm on the side. If the bottom is less than 40 μm thick, the wear resistance life will decrease, while if it exceeds 74 μm, the heat conduction efficiency will decrease. Furthermore, if the side is less than 22 μm thick, the risk of corrosion at the edges increases, while if it exceeds 48 μm, the risk of the coating peeling increases.

[0021] Note that the cooking utensils used in this embodiment do not exclude flat cooking utensils with no or few side surfaces, and therefore include what is called a plate.

[0022] The base material 1 constituting the cooking utensil is not particularly limited, but is preferably made of either an aluminum alloy or stainless steel. That is, the cooking utensil may be an aluminum casting made from an aluminum alloy, or a stainless steel product made by press-forming a stainless steel plate. Alternatively, the base material 1 may be made by sandwiching aluminum or iron between two stainless steel plates.

[0023] Aluminum has a lower specific gravity than stainless steel, which allows for lighter cooking vessels and improved usability. An example of an aluminum casting is ADC12, an alloy used in aluminum die casting. Stainless steel is also desirable as a base material for cooking vessels because of its high corrosion resistance and toughness. An example of stainless steel is SUS304, the most widely used austenitic stainless steel.

[0024] Such a non-stick coating 2 can be formed, for example, as follows. First, in the first step, one surface of the base material 1, which will be the cooking surface of a cooking utensil made of cast aluminum or stainless steel, is subjected to surface treatments such as sandblasting and alkaline degreasing (Step S1). That is, sandblasting increases the specific surface area of ​​one surface (the surface to be treated) of the base material 1, improving the adhesion of the coating agent.

[0025] Sandblasting is known as a processing method in which a powdered abrasive is bombarded at high speed onto one surface (surface to be treated) of the substrate 1 to remove foreign matter from the surface and create irregularities. In addition, alkaline degreasing is used to remove (clean) dirt and oil adhering to one surface (the surface to be treated) of the substrate 1. This alkaline degreasing process has long been used as a solvent-free method for degreasing metals, and is said to be an inexpensive and safe degreasing method because it uses an aqueous solution.

[0026] Furthermore, as required, after the first step and before the second step, an additional anodizing process (including step α) may be carried out as a surface treatment on the base material 1 to form an anodized layer. That is, when the base material 1 constituting the cooking utensil is made of a non-ferrous metal such as aluminum, an anodizing technique is used to electrolyze one surface (the surface to be treated) of the base material 1 with an anode (positive electrode) to artificially generate an oxide film (aluminum oxide). This anodizing treatment is known as a treatment method that improves the performance of the substrate 1, such as its robustness, corrosion resistance, and abrasion resistance.

[0027] Next, before applying the coating agent, the substrate 1 is subjected to a preheating treatment. The preheating conditions can be, for example, 50 to 60° C. for 5 minutes, and then the coating agent is applied by spray coating. Subsequently, in the second step, a first coating agent containing a silane coupling agent is applied to one side of the substrate 1 that has been surface-treated in the first step to form an undercoat layer (base coat) 21 (step S2). In addition to the silane coupling agent, this first coating agent also contains a solvent and other additives to adjust the viscosity in order to strengthen adhesion.

[0028] In the third step, a second coating agent containing ceramic particles is applied to the undercoat layer 21 formed in the second step to form an intermediate layer (midcoat) 22 (step S3). In addition to the ceramic particles, this second coating agent also contains a dispersant to prevent aggregation.

[0029] Furthermore, in the fourth step, a third coating agent (enamel paint) containing an enamel material is applied on the intermediate layer 22 formed in the third step to form a top coat layer 23 (step S4). This third coating agent contains boron oxide (BO) to lower the melting point and cobalt oxide (CoO) to improve adhesion.

[0030] Then, in the fifth step, a heat treatment is performed by baking at a high temperature of 300 to 330°C for 5 to 10 minutes, and the undercoat layer 21 formed in the second step, the intermediate layer 22 formed in the third step, and the topcoat layer 23 formed in the fourth step are baked and hardened (step S5). This allows the non-stick coating 2 to be formed on one surface of the substrate 1, which will be the cooking surface of the cooking utensil.

[0031] In this fifth step, if the baking temperature is lower than 300°C, the glass (porcelain or enamel) will not melt, resulting in increased porosity and reduced corrosion resistance. On the other hand, if the baking temperature is higher than 330°C, the resin will decompose, adversely affecting the initial non-stick performance. Therefore, it is desirable to set the baking temperature to 300-330°C. Furthermore, in the fifth step, if the baking hardening time is less than 5 minutes, the crosslinking reaction will be insufficient, resulting in a decrease in hardness. On the other hand, if the baking hardening time exceeds 10 minutes, the crystal growth of the ceramic particles will be affected, increasing brittleness and decreasing impact resistance. Therefore, the baking hardening time is preferably 5 to 10 minutes.

[0032] As described above, the non-stick coating 2 in this embodiment does not contain PFAS, and is therefore a multi-layered non-stick coating system that contributes to society and the economy in response to regulations on fluororesin materials. [Example]

[0033] Next, tests were conducted to confirm that the non-stick coating applied according to this embodiment has abrasion resistance, heat resistance, and corrosion resistance while maintaining excellent non-stick properties. Specifically, the following tests were conducted on a frying pan made of die-cast aluminum alloy ADC12, on whose cooking surface the above-described three-layer coating according to this embodiment was applied using an electrostatic spray device.

[0034] First, to test the non-stick performance, fried eggs were cooked without oil in accordance with the Chinese national standard GB / T32095.2-2015 "Standard for non-stick and abrasion resistance of household metal cookware, Part 2: Test method for non-stick and abrasion resistance." As a result, the fried eggs easily peeled off the frying pan, achieving the highest level I.

[0035] Additionally, for the abrasion resistance test, a 3M Scotch-Brite Industrial Pad 7447, made of abrasive coated nylon nonwoven fabric, was rubbed back and forth 20,000 times at a pressure of 45 N against the cooking surface of the frying pan. As a result, it was confirmed that the non-stick properties were well maintained even in the non-stick performance test after the abrasion resistance test.

[0036] Additionally, as a corrosion resistance test, an alkali resistance test was conducted in which the frying pan was immersed in a 10% sodium hydroxide solution at 80°C for 24 hours, and no damage was observed to the coating. In addition, the adhesive performance was tested according to the American Society for Testing Materials (ASTM) standard D3359, and the adhesiveness achieved a grade of 5B.

[0037] In addition, for heat resistance testing, in accordance with Section 6.2.10 of the Chinese national standard GB / T32095.1-2015, the frying pan was heated to 250°C + / - 5°C in a constant temperature drying oven, held there for 5 minutes, then immediately cooled in room temperature water for 1 minute, then wiped clean and the non-stick surface was observed under a 4x magnifying glass. This cycle was repeated a total of 5 times. No distortion, cracks, or other deformations were observed.

[0038] Furthermore, feedback from multiple customers has revealed that even after six months of continuous use, there are no visible scratches when cleaned with a metal scrubber, that omelets made without oil peel off completely (residue rate less than 3%), and that no corrosion spots are found even after cooking with acidic ingredients such as tomatoes. This confirms that the coating exhibits stable performance and is particularly suitable for oil-free cooking.

[0039] Therefore, it can be seen that the baking cookware coated with the non-stick coating according to this embodiment maintains excellent non-stick properties without the use of PFAS, while also improving abrasion resistance, heat resistance, and corrosion resistance. That is, the ceramic microparticles improve abrasion resistance and extend the service life, the vitreous (enamel) coating improves heat resistance and non-stick stability, and the formation of a dense layer enhances corrosion resistance, resulting in a synergistic effect that achieves high durability. [Industrial Applicability]

[0040] The non-stick coating of the present invention is expected to be used on cooking utensils such as frying pans, pots, kettles, hot plates, and molds used for baking, frying, and boiling. [Explanation of symbols]

[0041] 1 Base material 2. Non-stick coating 21 Undercoat layer (base coat) 22 Midcourt 23 Top coat

Claims

1. A coating layer formed on one surface of a substrate, In order from the one surface side, an undercoat layer containing a silane coupling agent; an intermediate layer containing ceramic particles; A top coat layer containing an enamel material; A non-stick coating comprising:

2. On one side of the base material that will be the cooking surface in the heating cookware, an undercoat layer containing a silane coupling agent; an intermediate layer containing ceramic particles; A top coat layer made of enamel paint; A cooking utensil characterized by having a three-layer non-stick coating formed by stacking the above in order.

3. 3. The cooking utensil according to claim 2, wherein the cooking utensil is made of either an aluminum alloy or stainless steel as a base material.

4. 4. The cooking device according to claim 2, wherein the cooking device has a bottom surface and a side surface as cooking surfaces.

5. 5. The cooking utensil according to claim 4, wherein the thickness of the non-stick coating on the bottom surface is 40 to 74 μm.

6. 5. The cooking device according to claim 4, wherein the thickness of the non-stick coating on the side surface is 22 to 48 μm.

7. A frying pan or pot made of either an aluminum alloy or stainless steel is provided with a base material on one side that serves as a cooking surface. an undercoat layer containing a silane coupling agent; an intermediate layer containing ceramic particles; A top coat layer made of enamel paint; A cooking utensil characterized by having a three-layer non-stick coating consisting of:

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