Non-stick cookware and method of making same

Abstract

Provided are a non-stick cookware and a manufacturing method thereof. The non-stick cookware includes a metal base, a surface of the base forming a containing space is electrolytically polished, and a fatty acid modified layer is disposed on the electrolytically polished surface of the metal base. As the fatty acid modified layer is disposed on the electrolytically polished surface of the metal base, 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 is as lipophilic group and can firmly lock edible oil to form an oil film, avoiding food sticking to the cookware.

Description

TECHNICAL FIELD

[0001] The present inventive concept is in the field of non-stick technology, and more particularly, to a non-stick cookware and a method of manufacturing the same. BACKGROUND

[0002] There are mainly three directions to realize non-stick technology: 1) low surface energy of itself; 2) forming a hydrophobic and oleophobic surface similar to the surface of a lotus leaf through micro concave-convex structure; and 3) forming a stable oil film by porous oil storage to use oil as an intermediary to realize non-stick.

[0003] Currently, the non-stick materials for cookware mainly include fluorine coating, ceramic coating and silicone resin. These three non-stick materials mainly form a non-stick coating on the inner surface of the cookware in the form of spraying to achieve the purpose of non-stick when heating food. Fluorine coating mainly includes PTFE (polytetrafluoroethylene), PFOA (ammonium perfluorooctanoate), PFA (copolymer of perfluoropropyl perfluorovinyl ether and polytetrafluoroethylene), FEP (polyperfluoroethylene-propylene copolymer), ETFE (ethylene-tetrafluoroethylene copolymer) and the like. The non-stick principle of fluorine-containing polymers is that they have extremely low surface free energy. Ceramic coating mainly refers to a coating with a silicon-oxygen bond structure and inorganic silicon as the main component. The ceramic coating achieves non-stick effect by forming a nano structure on the surface of the cookware. Silicone resin achieves non-stick effect by using the low surface energy of silicone resin. Although these three coatings have non-stick effect, they all have obvious defects: the fluorine coating is not resistant to wear and tear, so it cannot be used with an iron spatula when frying, nor can it be cleaned with a steel ball or a scouring pad. Harmful substances may be produced under high temperature, and the non-stick property decreases after wear and tear. The non-stick effect of ceramic coating is poorer than that of fluorine coating. The ceramic coating uses silicone oil in the coating system to achieve non-stick, but its durable non-stick property is not good, and the coating is easy to fall off after 3 to 6 months of use. The non-stick effect of silicone coating is also poorer than that of fluorine coating. The color of the silicone coating is easy to turn yellow or gray after being in contact with high temperature or open flame, and the hardness decreases under high temperature, which easily causes the phenomenon of "sticking back".

[0004] As can be seen, the non-stick materials generally have poor durable non-stick property and are not resistant to high temperature and explosive frying. SUMMARY

[0005] In order to solve at least one of the problems in the prior art, the present inventive concept provides a non-stick cookware and a method of manufacturing the same. The present inventive concept forms a fatty acid salt by using metal atoms on the surface of a metal substrate that is electrolytically polished to form a fatty acid salt with a fatty acid. On the one hand, the surface fatty acid salt can isolate the food from the microscopic contact with the pot, and on the other hand, the fatty acid salt as an oleophilic group can firmly lock the edible oil to form an oil film, thereby avoiding the food from sticking to the pot.

[0006] According to an aspect of the present application, a non-stick cookware includes a metal base whose surface forming a receiving space is electrolytically polished, and a fatty acid modified layer provided on the electrolytically polished surface of the metal base.

[0007] According to an exemplary embodiment, the fatty acid modified layer can include a fatty acid salt formed of the fatty acid and metal atoms included in the base.

[0008] According to an exemplary embodiment, the fatty acid can include at least one of stearic acid, palmitic acid, oleic acid, linoleic acid, lauric acid, and linolenic acid.

[0009] According to an exemplary embodiment, the metal of the base can include at least one of iron, aluminum, copper, tin, titanium, titanium alloy, stainless steel such as antibacterial stainless steel, and cast iron.

[0010] According to another aspect of the present application, a method of manufacturing a non-stick cookware includes the steps of providing a metal base, electrolytically polishing a surface of the base providing a receiving space, and contacting the electrolytically polished surface of the base with a fatty acid to form a fatty acid modified layer.

[0011] According to an exemplary embodiment, the fatty acid can include at least one of stearic acid, palmitic acid, oleic acid, linoleic acid, lauric acid, and linolenic acid.

[0012] According to an exemplary embodiment, the step of forming the fatty acid modified layer can include immersing the base in a fatty acid solution to form the fatty acid modified layer.

[0013] According to an exemplary embodiment, the fatty acid modified layer can include a fatty acid salt formed of the fatty acid and metal atoms included in the base.

[0014] According to an exemplary embodiment, during the contacting of the base with the fatty acid, the temperature of the fatty acid solution can be controlled to be 100°C to 200°C and maintained for 1h to 3h.

[0015] According to an exemplary embodiment, the metal of the base can include at least one of iron, aluminum, copper, tin, titanium, titanium alloy, stainless steel, antibacterial stainless steel, and cast iron. DETAILED DESCRIPTION

[0016] The present application now will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the application are shown. The present application may, however, 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 application to those skilled in the art.

[0017] Exemplary embodiments of the present application will now be described in detail below with reference to the accompanying drawings.

[0018] During cooking, food often sticks to the cookware. The food that sticks to the cookware is mainly starch and protein. Specifically, during cooking, starch undergoes a series of processes of water absorption, swelling, gelatinization, and finally carbonization, while protein undergoes a series of processes of peptide chain dissociation and denaturation, hydrolysis and inactivation, and finally dehydration and carbonization. During the series of processes, starch gel and protein gel are combined with the surface of the cookware, thereby starting to stick to the cookware (sticking to the pot), and the sticking force reaches a peak when the food contact surface is carbonized. Based on the above aspects, the sticking mechanism mainly includes the following theories:

[0019] 1) Mechanical combination theory: the sticking force comes from the mechanical interlocking of the two surfaces, which are connected by anchoring, hooking, and wedging, and in fact, this force does not play a major role.

[0020] 2) Adsorption theory: the sticking force is mainly caused by the molecular contact and interfacial force between the two materials, including hydrogen bond force and van der Waals force, which plays a dominant role in the gelatinization process.

[0021] 3) Chemical bond theory: atoms between the two materials form chemical bonds, and the bond energy of the chemical bond is much larger than that of the intermolecular force, and the sticking force is stronger, which plays a dominant role in the process of food charring.

[0022] In the above theories, mechanical combination can be solved by improving the surface roughness of the cookware, and surface adsorption and chemical bonds can be solved by oil, that is, by forming a firm oil film on the surface of the cookware, the food and metal atom bonding can be changed to food and oil contact non-stick, thereby achieving the purpose of non-coating non-stick.

[0023] Fatty acids are the normal hydrolysis products of natural oils, and their general formula is RCOOH, where R is a long-chain alkyl group, which is an oleophilic group and is compatible with oil, and the other end is a carboxyl group, which is a hydrophilic group and can form a fatty acid salt with metal atoms on the metal surface. Therefore, on the one hand, the R group on the surface can prevent the food from coming into contact with the pot, preventing the food from forming a chemical bond with the pot; on the other hand, the R group is an oleophilic group that can firmly lock edible oil to form an oil film, ultimately achieving the effect of non-stick. Therefore, the present concept achieves the effect of non-coating non-stick by applying a fatty acid modification layer on the surface of the metal substrate subjected to electrolytic polishing, and grafting and modifying the metal surface with fatty acid. That is, the present concept analyzes the mechanism of metal and food sticking to the pot from the bottom principle, and realizes the organic combination of metal cookware and non-stick by electrolytic polishing and organic modification of the metal surface.

[0024] The non-stick cookware according to the present concept can include a substrate and a fatty acid modification layer formed on the substrate.

[0025] The base is used to provide a containing space for an operation such as cooking of a cookware. Accordingly, the base can be manufactured in various shapes using a metal material. For example, according to an exemplary embodiment, the base can include at least one of iron, aluminum, copper, tin, titanium, titanium alloy, stainless steel such as antibacterial stainless steel, and cast iron, and can have a structure of a single layer or multiple layers, but the inventive concept is not limited thereto. In addition, the base can be formed to have an angled shape and / or a rounded shape according to a process, an aesthetic appearance, a specific requirement.

[0026] As described above, in order to achieve non-stick, it is necessary to provide a fatty acid modification layer on the metal base. However, the formation of a firm fatty acid modification layer requires an increase in the lipophilic effect of the metal surface of the base. Specifically, the metal atoms of the surface of the base form a bond with the metal atoms inside that is relatively stable, and has an adsorption effect with free radicals in the external environment or generates an oxide, thereby maintaining an inert surface state; while the fatty acid is relatively weak in acidity, to bond with the fatty acid efficiently, the metal atoms must be in an activated state, that is, the chemical bond of the surface metal atoms with other atoms or groups needs to be broken open.

[0027] Accordingly, according to the inventive concept, before the fatty acid modification layer is formed, the surface of the metal base exposed to the outside can be treated by an electrolytic polishing method. Through electrolytic polishing, the surface of the base is subjected to chemical corrosion, and the current density is higher in the micro-protruding part of the surface and the dissolution is faster, while the current density is lower in the micro-recessed part and the dissolution is slower. Therefore, through electrolytic polishing, on the one hand, the surface roughness is reduced, making the surface of the base smooth and bright, and on the other hand, the metal atoms exposed after the surface corrosion and dissolution can be activated, and the surface metal atoms can have more active sites to react and bond with the subsequent fatty acid forming the fatty acid modification layer.

[0028] The fatty acid modification layer can be provided on the electrolytically polished surface of the metal base to at least partially or entirely cover the surface. The fatty acid modification layer can be formed by the reaction of fatty acid with the exposed metal atoms in the metal base. Specifically, the fatty acid can be brought into contact with the exposed surface of the metal base to react between them, and as a result of the reaction, the metal atoms on the metal surface of the base are prone to form a fatty acid salt as the fatty acid modification layer, in which case, on the one hand, the surface fatty acid salt can isolate the micro-contact between the food and the pot, and on the other hand, the fatty acid salt is a lipophilic group that can firmly lock the cooking oil to form an oil film, thereby avoiding food sticking to the pot.

[0029] According to an exemplary embodiment, the fatty acid forming the fatty acid modification layer can include at least one of natural fatty acids of stearic acid, palmitic acid, oleic acid, linoleic acid, lauric acid, and linolenic acid, and is preferably a saturated fatty acid.

[0030] The non-stick cookware according to the inventive concept has been described above in connection with exemplary embodiments, and below, a method of manufacturing the non-stick cookware according to the inventive concept will be described in detail in connection with exemplary embodiments.

[0031] First, a base body can be provided.

[0032] The base body serves to provide a receiving space for an operation such as cooking of the cookware. Accordingly, the base body can be manufactured in various shapes using a suitable metal material. The base body has been described in detail above, and thus, to avoid redundancy, the base body will not be described in detail here.

[0033] After the base body is provided, a pre-treatment can be performed on the base body. Here, the pre-treatment can include a treatment such as degreasing, sanding, alcohol wiping, etc. on the surface of the base body to provide excellent surface properties, thereby facilitating the formation and adhesion of a material layer including a metal to be described below. However, the inventive concept is not limited thereto, that is, the pre-treatment step of the base body can be omitted.

[0034] Thereafter, electrolytic polishing can be performed on a surface of the base body that provides the receiving space, to increase the lipophilic effect of the metal surface. Here, the process of electrolytic polishing can include, but is not limited to, the following steps: the cookware base body is used as an anode, a lead material is used as a cathode, the power supply voltage can be set to 12V-15V, the electrolysis can use an environmentally friendly formula: 10%-15% by mass of nitric acid, 8%-10% of perchloric acid, the balance of glacial acetic acid, the temperature is controlled at 90°C-100°C, the current density is 10A / dm 2 -30A / dm 2 , and the time is controlled at 3min-5min. Through electrolytic polishing, the metal surface of the base body is subjected to chemical corrosion, and the current density is higher at the micro-protruding part of the surface and the dissolution is faster, while the current density is lower at the micro-recessed part and the dissolution is slower. Accordingly, the electrolytic polishing process reduces the surface roughness on the one hand, and the exposed metal atoms after the surface corrosion and dissolution can be activated on the other hand, so that the surface metal atoms have more active sites to react and bond with fatty acids.

[0035] After the electrolytic polishing, a fatty acid-modified layer can be formed on the surface of the base body. Specifically, the exposed inner surface of the base body subjected to the electrolytic polishing can be brought into contact with various forms of fatty acids under predetermined conditions, thereby allowing the metal atoms on the exposed surface of the metal base body to react with the fatty acids to form a fatty acid salt. Here, the predetermined conditions can include a temperature of 100°C-150°C and a contact time of 50min-120min.

[0036] According to an example, the base including the material layer can be immersed in a fatty acid solution of a predetermined concentration, and then the fatty acid solution can be heated to a temperature of 100°C to 200°C and maintained for 1 hour to 3 hours. Here, an ethanol solution of fatty acid can be used as the fatty acid solution, and the mass concentration of the fatty acid can be in the range of 30% to 80%, but exemplary embodiments are not limited thereto. In other words, other methods can be used to react the fatty acid (e.g., fatty acid vapor) with the metal base, and the inventive concept is not limited to the manner of contacting the fatty acid with the material layer.

[0037] After the reaction, the cookware can be cleaned and dried, thereby finally obtaining the non-stick cookware according to the inventive concept.

[0038] By forming a fatty acid salt non-stick layer on the metal surface, the adhesion of food to metal atoms can be changed to non-stick contact of food to oil, thereby achieving non-coated non-stick. However, due to the smoothness of the metal base, the surface area of the metal is small, and thus the finally formed fatty acid salt non-stick layer is relatively weak. In addition, due to cost constraints, using some special materials (e.g., titanium) to make a cookware base can result in a high cost. Therefore, according to the inventive concept, the surface of the metal base is treated by electrolytic polishing, so that under the action of chemical corrosion, the current density of the micro convex part of the surface of the metal base is high, and the dissolution is fast, while the current density of the micro concave part is low, and the dissolution is slow. Therefore, by electrolytic polishing, on the one hand, the surface roughness is reduced to make the surface of the base smooth and bright, and on the other hand, the exposed metal atoms after surface corrosion and dissolution can be activated, so that the surface metal atoms have more active sites to react and bond with the fatty acid.

[0039] In the following, the beneficial effects of the inventive concept will be described in connection with specific examples.

[0040] Example 1

[0041] A pot according to Example 1 is manufactured by the following method.

[0042] Step 1, prepare the pot base: stainless steel sheet deep drawing forming, surface alkali washing to remove oil, and drying;

[0043] Step 2, electrolytic polishing: the pot base is used as the anode, and the cathode is lead material. The power voltage is 12V, and the electrolysis uses an environmentally friendly formula (by mass fraction): 12% nitric acid, 8% perchloric acid, and the balance is glacial acetic acid. The temperature is 100°C, the current density is 25A / dm 2 , and the time is 3 minutes to remove the surface passivation film and impurities and reduce the surface roughness.

[0044] Step three, fatty acid modification: the electrolytically polished pot body was placed in a high pressure reactor, nitrogen was introduced to remove oxygen, which lasted for 10 min, until the oxygen content was less than 0.1%, then a 50% by mass fatty acid ethanol solution was added to soak the pot body, then heated to 150°C and kept for 2h, the reactor was kept rotating at 10r / min, then removed and washed with distilled water and dried, thus the surface fatty acid modified metal non-stick pot was obtained, and the pot of example 1 was completed.

[0045] Example 2

[0046] The pot according to example 2 was manufactured by the same method as example 1, except that the base was iron.

[0047] Example 3

[0048] The pot according to example 3 was manufactured by the same method as example 1, except that the base was titanium.

[0049] Example 4

[0050] The pot according to example 4 was manufactured by the same method as example 1, except that the fatty acid was oleic acid.

[0051] Example 5

[0052] The pot according to example 5 was manufactured by the same method as example 1, except that the fatty acid was lauric acid.

[0053] Example 6

[0054] The pot according to example 6 was manufactured by the same method as example 1, except that the heating temperature in step three was 100°C.

[0055] Example 7

[0056] The pot according to example 7 was manufactured by the same method as example 1, except that the heating temperature in step three was 200°C.

[0057] Example 8

[0058] The pot according to example 8 was manufactured by the same method as example 1, except that the holding time in step three was 1 min.

[0059] Example 9

[0060] A pot according to Example 9 was manufactured in the same manner as Example 1 except that the holding time in Step three was 3h.

[0061] Example 10

[0062] A pot according to Example 10 was manufactured in the same manner as Example 1 except that the power supply voltage in Step two was 15V.

[0063] Example 11

[0064] A pot according to Example 11 was manufactured in the same manner as Example 1 except that the power supply voltage in Step two was 13V.

[0065] Example 12

[0066] A pot according to Example 12 was manufactured in the same manner as Example 1 except that the mass fraction of nitric acid in Step two was 10%.

[0067] Example 13

[0068] A pot according to Example 13 was manufactured in the same manner as Example 1 except that the mass fraction of nitric acid in Step two was 15%.

[0069] Example 14

[0070] A pot according to Example 14 was manufactured in the same manner as Example 1 except that the mass fraction of perchloric acid in Step two was 9%.

[0071] Example 14'

[0072] A pot according to Example 14' was manufactured in the same manner as Example 1 except that the mass fraction of perchloric acid in Step two was 10%.

[0073] Example 15

[0074] A pot according to Example 15 was manufactured in the same manner as Example 1 except that the temperature control in Step two was 90°C.

[0075] Example 16

[0076] A pot according to Example 16 was manufactured in the same manner as Example 1 except that the temperature control in Step two was 95°C.

[0077] Example 17

[0078] Except that the current density in step two was controlled at 10 A / dm 2 A pot according to Example 17 was manufactured using the same method as Example 1 except that the current density in step two was controlled at 10 A / dm

[0079] Example 18

[0080] Except that the current density in step two was controlled at 30 A / dm 2 A pot according to Example 18 was manufactured using the same method as Example 1 except that the current density in step two was controlled at 30 A / dm

[0081] Example 19

[0082] A pot according to Example 19 was manufactured using the same method as Example 1 except that the electrolytic polishing time in step two was controlled at 4 min.

[0083] Example 20

[0084] A pot according to Example 20 was manufactured using the same method as Example 1 except that the electrolytic polishing time in step two was controlled at 5 min.

[0085] Comparative Example 1

[0086] A pot according to Comparative Example 1 was manufactured using the same method as Example 1 except that no electrolytic polishing was performed.

[0087] Comparative Example 2

[0088] A pot according to Comparative Example 2 was manufactured using the same method as Example 1 except that no fatty acid modification was performed (i.e., step three was omitted).

[0089] Performance Index Test

[0090] The performance of the pots obtained above was tested and recorded in the following table, and the specific performance test methods are as follows:

[0091] I. Non-stick test: tested according to GB32095.1-2015, divided into I, II, III levels, I level non-stick best, III level non-stick worst;

[0092] II. Durability non-stick test: tested according to GB32388-2015, unit is times, the higher the number of times, the longer the service life, 1000 times to evaluate the non-stick result, record the number of times to use to III level.

[0093] III. Dish non-stick evaluation:

[0094] 1) Fried tofu

[0095] Ingredients: old tofu 150g (cut into cubes, about 10), oil 20ml;

[0096] Step: 1. After cleaning the surface of the pot with tap water, a cloth or a steel ball, heat it to 200°C with maximum fire, pour in cooking oil and heat it until a small amount of smoke is generated, rotate the pot to make the oil fully immerse the entire inner surface of the pot, put in the tofu, adjust to medium heat;

[0097] 2. After frying one side to light yellow, turn over the tofu and continue frying, until both sides are yellow, stop;

[0098] 2) Fried potato strips

[0099] Ingredients: potato strips 200g (cut with a slicing knife, soak in water for 5 minutes before use), vinegar 25g, soy sauce 5g;

[0100] Step: 1. After cleaning the surface of the pot with tap water, a cloth or a steel ball, heat it to 200°C with maximum fire, pour in cooking oil and heat it until a small amount of smoke is generated, rotate the pot to make the oil fully immerse the entire inner surface of the pot, add potato strips, and stir-fry with an iron shovel until the potato strips are half cooked;

[0101] 2. Add vinegar and soy sauce and continue frying until cooked through, stop;

[0102] 3) Green pepper and shredded pork

[0103] Ingredients: lean pork 100g (cut into shreds), green pepper 50g (cut into shreds), oil 20ml, dark soy sauce 3g;

[0104] Step: 1. Wash the pork shreds and dry them, add 10g of soy sauce, stir well, then add 10g of cornstarch, stir well, and finally add 3g of cooking oil, stir well, and set aside;

[0105] 2. After cleaning the surface of the pot with tap water, a cloth or a steel ball, heat it to 200°C with maximum fire, pour in cooking oil and heat it until a small amount of smoke is generated, rotate the pot to make the oil fully immerse the entire inner surface of the pot, put in the pork shreds, fry until cooked, add green pepper, continue to stir-fry until the green pepper is half cooked, add dark soy sauce, stir-fry evenly, finally add 25g of water and stir-fry evenly, stop;

[0106] Evaluation method:

[0107] A: normal stir-frying, basically not sticky, pot is relatively clean;

[0108] B: normal stir-frying, slightly sticky, with a small amount of residue;

[0109] C: normal stir-frying, sticky pot, with a large amount of residue.

[0110] The following table shows the performance index test data of Examples 1-20 and Comparative Examples 1-2;

[0111]

[0112] In summary, the cookware comprising the fatty acid modified layer according to the inventive concept has good initial non-stickiness and persistent non-stickiness, which can meet the requirements of the national standard. Compared with the ordinary cookware without the fatty acid modified layer, the cookware has good initial non-stickiness and excellent persistent non-stickiness, and the formed coating has a longer non-stick life.

[0113] While one or more embodiments of the application have been described above, it is understood that those having ordinary skill in the art will readily conceive of modifications to the forms and details of the embodiments without departing from the spirit and scope of the claims.

Claims

1. A non-stick cookware, characterized in that, The non-stick cookware includes: A metallic matrix, wherein the surface of the matrix forming the accommodating space is electrolytically polished; and A fatty acid modified layer is disposed on an electrolytically polished surface of a metal substrate, wherein the fatty acid modified layer comprises a fatty acid salt having a lipophilic group formed by the reaction of fatty acids with metal atoms included in the substrate.

2. The non-stick cookware as described in claim 1, characterized in that, The fatty acids include at least one of stearic acid, palmitic acid, oleic acid, linoleic acid, lauric acid, and linolenic acid.

3. The non-stick cookware as described in claim 1, characterized in that, The base metal includes at least one of iron, aluminum, copper, tin, titanium, titanium alloys, stainless steel, and cast iron.

4. The non-stick cookware as described in any one of claims 1 to 3, characterized in that, The fatty acid modified layer is used to lock in edible oil to form an oil film.

5. A method for manufacturing non-stick cookware, characterized in that, The method includes the following steps: Provides a metal matrix; The surface of the substrate that provides the accommodating space is electropolished; The electropolished surface of the substrate is brought into contact with fatty acids, which react with metal atoms included in the substrate to form a fatty acid-modified layer with lipophilic groups.

6. The method as described in claim 5, characterized in that, The steps for forming the fatty acid modified layer include: The substrate is immersed in a fatty acid solution to form a fatty acid modified layer.

7. The method as described in claim 5, characterized in that, The fatty acids include at least one of stearic acid, palmitic acid, oleic acid, linoleic acid, lauric acid, and linolenic acid.

8. The method as described in claim 5, characterized in that, The mass concentration of the fatty acid is in the range of 30%-80%.

9. The method as described in claim 5, characterized in that, During the contact between the matrix and fatty acids, the temperature of the fatty acid solution is controlled at 100℃-200℃ and maintained for 1h-3h.

10. The method as described in claim 5, characterized in that, The base metal includes at least one of iron, aluminum, copper, tin, titanium, titanium alloys, stainless steel, and cast iron.

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