Non-stick cookware and method of making same

Abstract

Provided are a non-stick cookware and a manufacturing method thereof. The non-stick cookware comprises a substrate, a material layer comprising metal arranged on the substrate layer, and a fatty acid modified layer arranged on the substrate layer. Due to the arrangement of the fatty acid modified layer on the material layer comprising metal, fatty acid salt is formed by fatty acid and metal atoms, on one hand, the surface fatty acid salt can isolate food and the cookware in micro contact, on the other hand, the fatty acid salt can firmly lock edible oil to form an oil film as a lipophilic group, thereby avoiding food sticking to the cookware.

Description

Technical Field

[0001] This invention relates to the field of non-stick technology, and more specifically, to a non-stick cookware and its manufacturing method. Background Technology

[0002] There are three main directions for achieving non-stick technology: 1) low surface energy; 2) forming a hydrophobic and oleophobic surface similar to the surface of a lotus leaf through micro-uneven structure; 3) forming a stable oil film by storing oil in a porous structure, so as to use oil as a medium to achieve non-stick.

[0003] Currently, the main non-stick materials for cookware include fluoropolymer coatings, ceramic coatings, and silicone resins. These three types of non-stick materials are mainly applied by spraying to form a non-stick coating on the inner surface of the cookware to achieve the purpose of preventing food from sticking when heating. Fluoropolymer coatings mainly include PTFE (polytetrafluoroethylene), PFOA (perfluorooctanoic acid), PFA (a copolymer of perfluoropropyl perfluorovinyl ether and polytetrafluoroethylene), FEP (perfluoroethylene propylene copolymer), ETFE (ethylene-tetrafluoroethylene copolymer), etc. Their non-stick principle is mainly due to the extremely low surface free energy of fluoropolymers. Ceramic coatings are mainly composed of inorganic silicon with a silicon-oxygen bond structure. They achieve a non-stick effect by forming a nanostructure on the surface of the cookware. Silicone resins mainly utilize their low surface energy to achieve a non-stick effect. While all three types of coatings offer non-stick properties, they all have significant drawbacks: Fluoropolymer coatings are not wear-resistant, so they cannot be cleaned with metal spatulas, steel wool, or scouring pads when cooking. They may decompose at high temperatures, producing harmful substances, and their non-stick properties decrease after wear. Ceramic coatings are less effective at non-sticking than fluoropolymer coatings, primarily utilizing silicone oil in their coating system for non-sticking. However, their non-stick properties are not durable, and the coating tends to peel off after 3-6 months of use. Silicone coatings are also less effective at non-sticking than fluoropolymer coatings. They tend to yellow or gray after exposure to high temperatures or open flames, and their hardness decreases at high temperatures, making them prone to "re-sticking."

[0004] This shows that non-stick materials generally have poor long-lasting non-stick properties and are not resistant to high temperatures and can be stir-fried at will. Summary of the Invention

[0005] To address at least one of the problems in the prior art, this invention provides a non-stick cookware and its preparation method. This invention utilizes the metal atoms on the surface of a metal material layer to form fatty acid salts with fatty acids. On one hand, the surface fatty acid salts can isolate the food from microscopic contact with the cookware; on the other hand, the fatty acid salts, as lipophilic groups, can firmly lock in edible oil to form an oil film, thereby preventing food from sticking to the cookware.

[0006] According to one aspect of the present invention, a non-stick cookware includes: a substrate; a material layer comprising metal disposed on the substrate; and a fatty acid modified layer disposed on the material layer.

[0007] According to an exemplary embodiment, the metal-containing material layer may include at least one of titanium, titanium alloys, stainless steel, cast iron, and their oxides.

[0008] According to an exemplary embodiment, the fatty acid modified layer may include a fatty acid salt formed by an organic acid and metal atoms included in a metal material layer.

[0009] According to an exemplary embodiment, the organic acid may include at least one of stearic acid, palmitic acid, oleic acid, linoleic acid, lauric acid, and linolenic acid.

[0010] According to another aspect of the present invention, a method for manufacturing a non-stick cookware includes the following steps: providing a substrate; depositing a material layer comprising a metal on the substrate; and contacting the material layer comprising the metal on the substrate with an organic acid to form a fatty acid modified layer.

[0011] According to an exemplary embodiment, the included metal material layer may include at least one of titanium, titanium alloy, stainless steel, cast iron, and oxides thereof.

[0012] According to an exemplary embodiment, a material layer including metal can be applied to a substrate by spraying.

[0013] According to an exemplary embodiment, the spraying method can be arc spraying.

[0014] According to an exemplary embodiment, the step of forming the fatty acid modified layer may include immersing a substrate on which a material layer including a metal is formed in a fatty acid solution to form the fatty acid modified layer.

[0015] According to an exemplary embodiment, during the contact between the metal material layer on the substrate and the organic acid, the temperature of the organic acid solution can be controlled at 100°C-150°C and maintained for 50-120 minutes. Detailed Implementation

[0016] The invention will now be described more fully below; however, it may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0017] What will be understood is that when an element is referred to as being "on" another element, the element may be directly on the other element, or there may be an intermediate element between them. Conversely, when an element is referred to as being "directly on" another element, there is no intermediate element.

[0018] Exemplary embodiments of the present invention will now be described in detail below.

[0019] During cooking, food often sticks to the cookware. The foods that stick are mainly starches and proteins. Specifically, during cooking, starch undergoes a series of processes: water absorption, swelling, gelatinization, and finally carbonization. Proteins, on the other hand, undergo peptide chain dissociation and denaturation, hydrolysis and inactivation, and finally dehydration and carbonization. During these processes, starch gels and protein gels bind to the cookware surface, thus initiating the sticking (sticking). The adhesion reaches its peak after the food contact surface carbonizes. Based on the above, the adhesion mechanism mainly includes the following theories:

[0020] 1) Mechanical bonding theory: The adhesive force comes from the mechanical interlocking of the two surfaces, which are connected by anchoring, hooking, wedging and other actions. In fact, this force does not play a major role.

[0021] 2) Adsorption theory: It is caused by molecular contact and interfacial forces between two materials. The main source of adhesive force is intermolecular forces, including hydrogen bonding and van der Waals forces. These forces play a dominant role in the gelation process.

[0022] 3) Chemical bond theory: Atoms of two materials form chemical bonds. The bond energy of chemical bonds is much greater than that of intermolecular forces, resulting in stronger adhesion. This force dominates the process of food burning.

[0023] In the above theory, mechanical bonding can be solved by improving the surface roughness of the cookware, and surface adsorption and chemical bonding can be solved by oil. In other words, by forming a strong oil film on the surface of the cookware, the food and metal atoms can bond and adhere to each other, so that the food and oil can come into contact without sticking, thus achieving the purpose of non-stick coating.

[0024] Furthermore, since the formation of a strong oil film requires increased oleophilicity of the metal surface, according to the present invention, the metal surface can be grafted with fatty acids to achieve oleophilicity. Here, fatty acids are products of normal hydrolysis in natural oils and fats, dissolved in the oils. They can form fatty acid salts with metal atoms, which allows the surface fatty acid salts to isolate the food from microscopic contact with the cookware, and the fatty acid salts, as oleophilic groups, can firmly lock in the edible oil to form an oil film, thereby preventing food from sticking to the pan.

[0025] Therefore, the non-stick cookware conceived according to the present invention may include a substrate, a material layer including metal, and a fatty acid modified layer.

[0026] The substrate serves to provide a space for operations such as cooking within the cookware. Therefore, the substrate can be manufactured into various shapes using metallic materials. For example, according to exemplary embodiments, the substrate may include stainless steel, cast iron, aluminum alloy, titanium alloy, copper alloy, magnesium alloy, or a composite material composed of two or more of these, and may have a single-layer or multi-layer structure; the inventive concept is not limited thereto. Furthermore, the substrate may be formed into angled and / or rounded shapes depending on the process, aesthetic appearance, and specific requirements.

[0027] A metallic material layer can be conformally formed on at least part or all of the inner surface of the substrate to facilitate the subsequent formation of a fatty acid-modified layer. Here, the metallic material layer can include at least one of titanium, titanium alloys, stainless steel, cast iron, and their oxides. Specifically, a metallic material layer can be formed by spraying a metallic material onto part or all of the inner surface of the substrate using a spraying process. During the spraying process, due to process conditions, some of the metallic material used to form the metallic material layer may be oxidized to form oxides. Therefore, the formed metallic material layer may also include oxides of the metallic material.

[0028] According to an exemplary embodiment, the material layer including metal can have a thickness of 40 μm to 300 μm.

[0029] A fatty acid modified layer can be applied to a metal-containing material layer to at least partially or completely cover the substrate on which the metal-containing material layer is applied. The fatty acid modified layer can be formed by the reaction of an organic acid with the metal atoms of the metal-containing material layer. Specifically, an organic acid can be brought into contact with the aforementioned metal-containing material layer to cause a reaction. Due to the reaction, the metal atoms on the surface of the metal-containing material layer readily form fatty acid salts with the organic acid, thus forming the fatty acid modified layer. In this case, on the one hand, the surface fatty acid salts can isolate the food from microscopic contact with the cookware; on the other hand, the fatty acid salts are lipophilic groups, which can firmly lock in edible oil to form an oil film, thereby preventing food from sticking to the pan.

[0030] According to an exemplary embodiment, the organic acid forming the fatty acid modified layer may include at least one of the natural fatty acids stearic acid, palmitic acid, oleic acid, linoleic acid, lauric acid and linolenic acid, and is preferably a saturated fatty acid.

[0031] The above description, in conjunction with exemplary embodiments, describes a non-stick cookware with a three-layer structure according to the present invention. Below, a method for manufacturing a non-stick cookware according to the present invention will be described in detail with reference to exemplary embodiments.

[0032] Ideally, a matrix can be provided.

[0033] The substrate serves to provide space for operations such as cooking within the cookware. Therefore, the substrate can be manufactured into various shapes using suitable metallic materials. The substrate has already been described in detail above; therefore, to avoid redundancy, it will not be described further here.

[0034] After providing the substrate, it can be pretreated. Pretreatment may include degreasing, sanding, or wiping the substrate surface with alcohol to provide excellent surface properties, thereby facilitating the formation and adhesion of material layers, including those comprising metals, which will be described below. However, the inventive concept is not limited thereto; that is, the substrate pretreatment step may be omitted.

[0035] Subsequently, a metal-containing material layer can be formed on the surface of the pre-treated or untreated substrate. According to an exemplary embodiment, a metal-containing material layer can be conformally formed on at least part or all of the substrate surface using a cold spraying or thermal spraying method. Here, the phrase "at least part or all" can mean that the metal material can be applied only at the desired locations on the inner surface of the cookware substrate, or that the metal material can be applied to the entire inner surface of the cookware substrate; that is, the metal material can be applied at appropriate locations as needed. Furthermore, the metal material forming the metal-containing material layer can include titanium, titanium alloys, stainless steel, and cast iron, and these metal materials may be partially oxidized into metal oxides during the spraying process. Therefore, the final metal-containing material layer may further include oxides of metals such as titanium, titanium alloys, stainless steel, and cast iron.

[0036] For example, according to a preferred embodiment, an arc spraying method can be used to form a metal material layer on the surface of the substrate because: arc spraying is low-cost, and the metal is partially oxidized during the arc spraying process, and the resulting oxide is more likely to react and bond with the fatty acids described later. However, the exemplary embodiments are not limited thereto. When an arc method is used to form a metal material layer, the diameter of the metal wire can be 0.8 mm to 1.2 mm, the spraying voltage can be 25 V to 50 V, the spraying current can be 100 A to 300 A, the spraying distance can be 120 mm to 180 mm, and the atomization pressure can be 0.6 MPa to 1.0 MPa.

[0037] After forming the metal-containing material layer, the surface of the formed metal-containing material can be surface-treated. This surface treatment can include sanding and polishing. For example, a process using Scotch 96 polishing agent can be employed. #A scouring pad is used to sand the surface of materials, including metals, until its roughness is Ra 4μm-6μm. Finally, a cloth wheel can be used to polish the surface to make it smooth. However, the exemplary embodiments are not limited to this, and this surface treatment step can be omitted.

[0038] After forming a metal-containing material layer, the material layer can be contacted with an organic acid under predetermined conditions, thereby enabling the metal atoms on the surface of the material layer to react with the organic acid to form a fatty acid salt. Here, the predetermined conditions may include a temperature of 100°C-150°C and a contact time of 50-120 minutes.

[0039] According to the example, a substrate including the material layer can be immersed in an organic acid solution of a predetermined concentration, and then the organic acid solution is heated to a temperature of 100°C-150°C and maintained for 50-120 minutes. Here, an ethanol solution of the organic acid can be used as the organic acid solution, and the mass concentration of the organic acid can be in the range of 30%-80%. However, the exemplary embodiments are not limited thereto. In other words, other methods can be used to contact and react the organic acid (e.g., organic acid vapor) with the material layer, and the inventive concept does not limit the contact method between the organic acid and the material layer.

[0040] After the reaction, the cookware can be cleaned and dried, thus finally obtaining the non-stick cookware of the present invention.

[0041] Forming a fatty acid salt non-stick layer on a metal surface can transform the adhesion between food and metal atoms into a non-stick effect where food and oil come into contact without sticking, thus achieving a coating-free non-stick coating. However, due to the smoothness of the metal substrate, the metal surface area is small, resulting in a relatively thin fatty acid salt non-stick layer. Furthermore, cost constraints make certain special materials (e.g., titanium) too expensive for cookware substrates. Therefore, according to the present invention, by applying a substrate containing materials such as iron or aluminum, for example, by hot or cold spraying titanium, titanium alloys, stainless steel, or cast iron, the desired metal surface can be obtained at a lower cost. On the other hand, a micron-level uneven structure can be formed on the surface, followed by sanding to increase the surface area and form a spatially thicker fatty acid salt non-stick layer. Moreover, the pores created by hot or cold spraying make it easier to store cooking oil during later use, improving non-stick properties and facilitating the continuous replenishment of fatty acid salts lost from the cookware surface by the fatty acids in the cooking oil.

[0042] The beneficial effects of the present invention will be described below with reference to specific examples.

[0043] Example 1

[0044] The cookware according to Example 1 is manufactured by the following method.

[0045] Step 1: Prepare the cookware base material: deep drawing of iron sheet, surface alkaline washing to remove oil, and drying;

[0046] Step 2, Arc spraying: Two titanium wires with a diameter of 0.8 mm are used. The spraying voltage is 25 V, the spraying current is 300 A, the spraying distance is 140 mm, and the atomization pressure is 1.0 MPa, so as to form a material layer containing metallic titanium with a thickness of 80 μm on the inner wall of the iron pot.

[0047] Step 3, Sanding + Polishing: Use Scotch 96 # The surface is sanded with a scouring pad to a roughness of Ra4μm, and finally polished with a cloth wheel;

[0048] Step 4, Fatty acid modification: Place the polished cookware in a high-pressure reactor, purge with nitrogen to remove oxygen, continue for 10 minutes until the oxygen content is below 0.1%, then add an ethanol solution of 50% stearic acid (as an organic acid) to immerse the cookware in it, heat to 150°C and keep warm for 2 hours, keep the reactor rotating at 10 r / min, then remove it, wash with distilled water and dry it to obtain the non-stick metal cookware with surface fatty acid modification, thus completing the manufacture of the cookware in Example 1.

[0049] Example 2

[0050] Except that the base material is aluminum, the cookware according to Comparative Example 1 was manufactured using the same method as in Example 1.

[0051] Example 3

[0052] Except for the use of stainless steel wire for arc spraying, the cookware according to Example 3 is manufactured using the same method as in Example 1.

[0053] Example 4

[0054] Except that the organic acid is oleic acid, the cookware according to Example 4 is manufactured using the same method as in Example 1.

[0055] Example 5

[0056] Except that the organic acid is lauric acid, the cookware according to Example 5 is manufactured using the same method as in Example 1.

[0057] Example 6

[0058] Except for the heating temperature of 100°C in step four, the cookware according to Example 6 is manufactured using the same method as in Example 1.

[0059] Example 7

[0060] Except for the heating temperature of 130°C in step four, the cookware according to Example 7 is manufactured using the same method as in Example 1.

[0061] Example 8

[0062] Except for the heat preservation time of 50 minutes in step four, the cookware according to Example 8 is manufactured using the same method as in Example 1.

[0063] Example 9

[0064] Except for the heat preservation time of 90 minutes in step four, the cookware according to Example 9 is manufactured using the same method as in Example 1.

[0065] Comparative Example 1

[0066] The cookware according to Comparative Example 1 was manufactured using the same method as in Example 1, except that it was not sanded or polished.

[0067] Comparative Example 2

[0068] Except for the absence of fatty acid modification (i.e., step four is omitted), the cookware according to Comparative Example 2 was manufactured using the same method as in Example 1.

[0069] Performance metrics testing

[0070] The performance of the cookware obtained above was tested and recorded in the table below. The specific performance testing methods are as follows:

[0071] I. Non-stickiness test: The test is conducted in accordance with the requirements of GB32095.1-2015 and is divided into three levels: I, II and III. Level I has the best non-stickiness and Level III has the worst non-stickiness.

[0072] II. Durable non-stick test: The test is conducted in accordance with GB32388-2015 requirements. The unit is the number of cycles. The higher the number of cycles, the longer the lifespan. The non-stick result is evaluated once every 1000 cycles. The number of cycles is recorded up to the point of reaching Level III.

[0073] III. Evaluation of the non-stickiness of the dish:

[0074] 1) Pan-fried tofu

[0075] Ingredients: 150g firm tofu (cut into cubes, about 10 pieces), 20mL oil;

[0076] Steps: 1. Wash the surface of the pot with tap water, a rag or steel wool, then heat it to 200°C on the highest heat. Pour in cooking oil and heat until a small amount of oil smoke is produced. Rotate the pot to make sure the oil fully submerges the entire inner surface of the pot. Add the tofu and adjust to medium heat.

[0077] 2. Once one side is lightly browned, flip the tofu over and continue frying until both sides are golden brown.

[0078] 2) Stir-fried shredded potatoes

[0079] Ingredients: 200g shredded potatoes (shredded with a slicer, soaked in water for 5 minutes before use), 20mL oil, 25g vinegar, 5g light soy sauce;

[0080] Steps: 1. Wash the surface of the pot with tap water, a rag or steel wool, and heat it to 200°C on the highest heat. Pour in cooking oil and heat it until a small amount of oil smoke is produced. Rotate the pot to make the oil fully submerge the entire inner surface of the pot. Add the shredded potatoes and stir-fry them with a spatula until the shredded potatoes are half-cooked.

[0081] 2. Add vinegar and light soy sauce and continue to stir-fry until fully cooked, then stop.

[0082] 3) Shredded pork with green peppers

[0083] Ingredients: 100g lean pork (shredded), 50g green bell pepper (shredded), 20mL oil, 3g dark soy sauce;

[0084] Steps: 1. Wash and drain the shredded pork, add 10g of light soy sauce and stir well, then add 10g of cornstarch and stir well, finally add 3g of cooking oil and stir well, set aside.

[0085] 2. After washing the surface of the pot with tap water, a rag or steel wool, heat it to 200℃ over the highest heat. Pour in cooking oil and heat until a small amount of oil smoke is produced. Rotate the pot to make the oil fully submerge the entire inner surface of the pot. Add the shredded meat and stir-fry until cooked. Add the green peppers and continue to stir-fry until the green peppers are half-cooked. Add dark soy sauce and stir-fry evenly. Finally, add 25g of water and stir-fry evenly. Stop cooking.

[0086] Evaluation method:

[0087] Grade A: Normal stir-frying results in minimal sticking, and the pan remains relatively clean.

[0088] Grade B: Slightly sticky after normal stir-frying, with a small amount of residue;

[0089] Grade C: Normal stir-frying results in sticking to the pan, with a large amount of residue remaining inside.

[0090] The table below shows the performance test data for Examples 1-9 and Comparative Examples 1-2;

[0091]

[0092] In summary, the cookware with a fatty acid modified layer according to the present invention exhibits good initial non-stick properties and long-lasting non-stick properties, meeting national standards. Compared to ordinary cookware without a fatty acid modified layer, it has better initial non-stick properties and excellent long-lasting non-stick properties, and the resulting coating has a longer non-stick lifespan.

[0093] While one or more embodiments of the invention have been described, those skilled in the art will understand that various changes in form and detail may be made therein without departing from the spirit and scope defined by the claims.

Claims

1. A non-stick cookware characterized by, The non-stick cookware comprises: a substrate; a material layer comprising metal formed by spraying, disposed on the substrate; a fatty acid modified layer disposed on the material layer, wherein the fatty acid modified layer comprises fatty acid salts with lipophilic groups formed by fatty acids and metal atoms in the material layer at the contact with the material layer, and wherein the fatty acids comprise at least one of stearic acid, palmitic acid, oleic acid, linoleic acid, lauric acid and linolenic acid.

2. The non-stick cookware of claim 1, wherein the material layer comprising metal comprises at least one of titanium, titanium alloy, stainless steel, cast iron and oxides thereof; and / or the material layer comprising metal has a thickness of 40-300 microns; and / or the material layer comprising metal has a surface roughness Ra of 4-6 microns; and / or the material layer comprising metal is formed by cold spraying or thermal spraying.

3. The non-stick cookware of claim 1, wherein, the material layer comprising metal is formed by arc spraying.

4. The non-stick cookware of any one of claims 1-3, wherein the fatty acid modified layer is used to lock edible oil to form an oil film.

5. A method of manufacturing a non-stick cookware, characterized by, The method comprises the following steps: providing a substrate; spraying a material layer comprising metal on the substrate; contacting the material layer comprising metal on the substrate with fatty acids to form a fatty acid modified layer, wherein the fatty acid modified layer comprises fatty acid salts with lipophilic groups formed by fatty acids and metal atoms in the material layer at the contact with the material layer, and wherein the fatty acids comprise at least one of stearic acid, palmitic acid, oleic acid, linoleic acid, lauric acid and linolenic acid.

6. The method of claim 5, wherein, the spraying comprises cold spraying or thermal spraying; and / or the material layer comprising metal comprises at least one of titanium, titanium alloy, stainless steel, cast iron and oxides thereof.

7. The method of claim 5, wherein, the mass concentration of the fatty acids is 30-80%.

8. The method of claim 5, wherein, the spraying mode is arc spraying.

9. The method of any one of claims 5 to 8, wherein, the step of forming the fatty acid modified layer comprises: immersing the substrate with the material layer comprising metal formed thereon in a fatty acid solution to form the fatty acid modified layer.

10. The method of any one of claims 5 to 8, wherein, controlling the temperature of the fatty acid solution at 100-150°C during the contacting of the material layer comprising metal on the substrate with the fatty acids, and maintaining for 50-120 min.

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