Enamel composition, preparation method therefor, and cooking appliance

Abstract

The present invention relates to an enamel composition, a preparation method therefor, and a cooking appliance. The enamel composition according to the present invention comprises: 20-30 wt% of P2O5 , 16-23 wt% of SiO2, 14-20 wt% of Al2O3, 10-16 wt% of B2O3, 15-30 wt% of at least one of Na2O, K2O, and Li2O, 0.5-4 wt% of TiO2, 2-8 wt% of Fe2O3, 1-2 wt% of Co3O4, and 0.5-8 wt% of MeO, and thus can lower the temperature for heating required for cleaning existing enamel coatings and significantly reduce the heating time, and enables cleaning without soaking using water.

Description

Enamel composition, method for producing the same, and cooking apparatus

[0001] The present invention relates to a novel enamel composition, a method for manufacturing the same, and a cooking appliance, which lowers the heating temperature required for cleaning a coating layer and also shortens the heating time required for cleaning a coating layer.

[0002] Enamel is a glassy glaze applied to the surface of a metal plate. Common enamels are used in cooking appliances such as microwave ovens and ovens. Cooking appliances such as electric ovens and gas ovens are appliances that cook food using a heat source. Since contaminants generated during the cooking process adhere to the inner walls of the cavity of the cookware, the inner walls of the cavity need to be cleaned. Enamel is coated on the inner walls of the cavity of the cookware to facilitate the removal of contaminants on the cookware. A commonly known technology for easily cleaning the inner walls of the cavity is the pyrolysis method, which burns contaminants at high temperatures to turn them into ash. As an enamel composition to which the pyrolysis method is applied, an enamel composition containing components such as P2O5, SiO2, and B2O3 is known.

[0003] However, existing known enamel compositions require heating at high temperature pyrolysis conditions of 450 to 500 ℃ for about 3 to 5 hours to be cleaned, which results in high energy consumption.

[0004] In addition, existing enamel compositions require a soaking process in water for a certain period of time to remove oil contaminants such as beef, pork, and poultry fat, which makes the cleaning process cumbersome.

[0005] In addition, the enamel composition must not be deformed or damaged at high temperatures of 450 to 500°C, but existing enamel compositions have the problem of reduced durability at high temperatures.

[0006] The present invention aims to provide a novel enamel composition capable of lowering the temperature required for cleaning an enamel coating layer and shortening the heating time.

[0007] In addition, the present invention aims to provide a novel enamel composition that does not require water soaking when removing oil-based contaminants.

[0008] In addition, the present invention aims to provide a novel enamel composition having excellent durability, such as heat resistance and chemical resistance, as well as excellent cleaning performance.

[0009] The present invention provides an enamel composition capable of lowering the temperature required for cleaning existing enamel coating layers and shortening the required heating time, and of cleaning oil-based contaminants at room temperature without a moisture soaking process. To this end, the enamel composition according to the present invention increases the solubility limit of a metal oxide that acts as a catalyst through the compositional design of the matrix component.

[0010] Specifically, the enamel composition of the present invention comprises 20 to 30 wt% of P2O5, 16 to 23 wt% of SiO2, 14 to 20 wt% of Al2O3, 10 to 16 wt% of B2O3, 15 to 30 wt% of at least one of Na2O, K2O and Li2O, 0.5 to 4 wt% of TiO2, 2 to 8 wt% of Fe2O3, 1 to 2 wt% of Co3O4 and 0.5 to 8 wt% of MeO.

[0011] Here, the MeO is Cu2O, CeO2, Bi2O3, Y2O3, La2O 3, Contains at least one of Ta2O5, V2O5, WO3, MoO3, and MnO4.

[0012] Preferably, the enamel composition of the present invention may further include ZrO22.5 wt% or less and AlF22.5 wt% or less.

[0013] Additionally, the MeO may contain 6 wt% or more of Cu2O or MnO4.

[0014] The enamel composition according to the present invention can significantly reduce the heating temperature and heating time required for cleaning existing enamel coating layers. Accordingly, the enamel composition according to the present invention has the effect of reducing the heating temperature and heating time required for cleaning, thereby saving energy used during cleaning.

[0015] Furthermore, the enamel composition according to the present invention can be cleaned at room temperature without water, particularly for oil-based contaminants. Therefore, users can easily clean the enamel composition. Furthermore, the enamel composition according to the present invention can improve the sanitary properties of cooking appliances.

[0016] Furthermore, the enamel composition according to the present invention increases the solubility limit of the metal oxide acting as a catalyst through optimal phosphate composition design. Accordingly, the enamel composition of the present invention exhibits both superior cleaning performance and durability, including heat and chemical resistance.

[0017] Figure 1 is a front view showing a cooking appliance according to an embodiment of the present invention.

[0018] Fig. 2 is an enlarged cross-sectional view of a portion of the inner cavity of the cooking appliance according to Fig. 1.

[0019] Fig. 3 is an enlarged cross-sectional view of a portion of the inner surface of the door of the cooking appliance according to Fig. 1.

[0020] Figure 4 is a photograph showing the surface of an enamel coating according to an example and a comparative example.

[0021]

[0022] The aforementioned objectives, features, and advantages are described in detail below, so that those skilled in the art can readily implement the technical concepts of the present invention. In describing the present invention, detailed descriptions of known technologies related to the present invention will be omitted if they are deemed to unnecessarily obscure the gist of the invention. Hereinafter, preferred embodiments of the present invention will be described in detail.

[0023] The present invention is not limited to the embodiments disclosed below, but can be implemented in various different forms. These embodiments are provided solely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention. Hereinafter, the enamel composition, the manufacturing method thereof, and the cooking appliance according to the present invention will be described in detail.

[0024]

[0025] <Enamel composition>

[0026]

[0027] The enamel composition according to the present invention comprises 20 to 30 wt% of P2O5, 16 to 23 wt% of SiO2, 14 to 20 wt% of Al2O3, 10 to 16 wt% of B2O3, 15 to 30 wt% of at least one of Na2O, K2O and Li2O, 0.5 to 4 wt% of TiO2, 2 to 8 wt% of Fe2O3, 1 to 2 wt% of Co3O4 and 0.5 to 8 wt% of MeO.

[0028] P2O5 is a component that forms an alkali phosphate glass structure. In addition, P2O5 is a glass former that facilitates the addition of a large amount of transition metal oxide in the enamel composition, and has the function of helping water penetrate between the enamel surface and the contaminants, thereby easily removing the contaminants. The P2O5 is contained in the range of 20 to 30 wt%. If the P2O5 exceeds 30 wt%, vitrification of the enamel composition may become difficult and the thermal properties of the enamel composition may deteriorate. If the P2O5 is less than 20 wt%, the amount of transition metal oxide added may decrease, thereby deteriorating the cleaning function. More preferably, the enamel composition of the present invention may contain 21 to 29 wt% of the P2O5.

[0029] SiO2 is a component that forms a glass structure, strengthening the skeleton of the glass structure to improve the chemical resistance of the enamel composition and facilitating the expression of the properties of a metal oxide that acts as a catalyst. Since the catalytic metal oxide has inferior heat and chemical resistance compared to other components, it cannot be contained in large amounts in the enamel composition. However, since SiO2 has a structure with a large pore size, if SiO2 is included in an appropriate amount in the glass composition, the solubility of the catalytic metal oxide in the glass can be increased. Accordingly, by appropriately controlling the content ratio of SiO2 and the catalytic metal oxide, it is possible to exhibit excellent heat and chemical resistance while also expressing the properties of the catalytic metal oxide. The SiO2 is contained in the enamel composition in the range of 16 to 23 wt%. If the SiO2 exceeds 23 wt%, it may interfere with the addition of other components, which may cause a problem of reduced cleaning function. If the SiO2 is less than 16 wt%, the glass composition according to the present invention may be broken. More preferably, the enamel composition of the present invention may contain 16 to 20 wt% of SiO2.

[0030] B2O3 acts as a glass former and is a component that allows each component of the enamel composition to melt evenly. In addition, B2O3 improves coating performance by controlling the coefficient of thermal expansion and fusion flow of the enamel composition. In addition, B2O3 maintains an appropriate viscosity during the enamel firing process and controls the glass composition from crystallizing. The B2O 3- is contained in the enamel composition in the range of 10 to 16 wt%. If the B2O3 exceeds 16 wt%, it may interfere with the addition of other components, which may cause a problem of reduced cleaning function. If the B2O3 is less than 10 wt%, the glass composition may collapse or crystallization of the glass composition may occur. More preferably, the enamel composition of the present invention may contain 11 to 14 wt% of B2O3.

[0031] Li2O, Na2O, and K2O play a role in improving the cleaning performance of the enamel composition. At least one of Li2O, Na2O, and K2O is contained in the enamel composition in the range of 15 to 30 wt%. If the content of at least one of Li2O, Na2O, and K2O exceeds 30 wt%, there is a problem that the thermal expansion coefficient of the glass increases drastically, resulting in a deterioration in coating performance. If the content of at least one of Li2O, Na2O, and K2O is less than 15 wt%, there may be a problem that the cleaning function is deteriorated.

[0032] Next, the enamel composition according to the present invention contains 14 to 20 wt% of Al2O3. The Al2O3 has the effect of complementing the weak durability of the alkali phosphate glass structure and improving the hardness of the enamel surface. If the Al2O3 exceeds 20 wt%, the melting temperature increases and the fusion flow increases, which may reduce the adhesion of the enamel coating layer. In addition, if the Al2O3 is less than 14 wt%, the durability of the enamel coating layer may be reduced.

[0033] In addition, the enamel composition according to the present invention contains 0.5 to 4 wt% of TiO2. The TiO2 complements the weak durability of the alkali phosphate glass structure and has the effect of improving the hardness of the enamel surface. Accordingly, the enamel composition of the present invention contains the TiO2 as an essential component. If the TiO2 exceeds 4 wt%, the melting temperature increases and the fusion flow increases, which may reduce the adhesion of the enamel coating layer. In addition, if the TiO2 is less than 0.5 wt%, the durability of the enamel coating layer may be reduced.

[0034] In addition, the enamel composition according to the present invention contains 2 to 8 wt% of Fe2O3 and 1 to 2 wt% of Co3O4. Fe2O3 and Co3O4 are components that promote the carbonization of contaminants attached to the surface of the enamel coating layer and also improve the adhesion of the enamel coating layer. If Fe2O3 and Co3O4 are contained in amounts less than the minimum content described above, the cleaning performance and adhesion of the enamel coating layer may be reduced. Conversely, if Fe2O3 and Co3O4 are contained in amounts exceeding the maximum content described above, the chemical durability of the glass structure may be reduced.

[0035] Next, the enamel composition of the present invention contains 0.5 to 8 wt% of MeO. Here, MeO refers to a metal oxide that acts as a catalyst in the enamel composition. The MeO is Cu2O, CeO2, Bi2O3, Y2O3, La2O. 3,It contains at least one of Ta2O5, V2O5, WO3, MoO3, and MnO4. If the MeO exceeds 8 wt%, it may interfere with the addition of other components, which may cause a problem of reduced durability such as heat resistance and chemical resistance. On the other hand, if the MeO is contained in an amount of less than 0.5 wt%, the carbonization performance of contaminants in the enamel coating layer may be reduced and the cleaning performance may be worsened. More preferably, in order to improve both the cleaning performance and durability of the enamel composition, the MeO may contain Cu2O or MnO4 in an amount of 6 wt% or more.

[0036] Meanwhile, the enamel composition of the present invention may contain ZrO2 in an amount of 2.5 wt% or less to increase the chemical durability of the enamel coating layer and also to improve adhesion. In addition, the enamel composition of the present invention may further contain AlF in an amount of 2 wt% or less to control the surface tension of the enamel coating layer and thereby improve the surface properties of the enamel coating layer.

[0037]

[0038] As mentioned above, conventional enamel compositions require heating for about 3 to 5 hours under high-temperature pyrolysis conditions of 450 to 500°C to be cleaned, which results in high energy consumption. However, the enamel composition according to the present invention has a newly designed matrix component composition to increase the solid solution limit of the metal oxide acting as a catalyst. Accordingly, the enamel composition of the present invention can clean sugar-containing contaminants even when heated at a temperature 100°C lower than the high-temperature conditions required for cleaning in less than about 1 hour. Accordingly, when the enamel composition according to the present invention is used, there is an effect of saving energy and shortening the cleaning time. In addition, the enamel composition according to the present invention has the advantageous advantage of allowing immediate cleaning of oil-based contaminants at room temperature without soaking in water, making it easy to maintain the hygiene of the cooking appliance.

[0039]

[0040] <Method for producing enamel composition>

[0041]

[0042] Next, a method for manufacturing an enamel composition according to the present invention includes the steps of providing the above-described enamel composition material; melting the enamel composition material; and quenching the melted enamel composition material to form an enamel composition.

[0043] After sufficiently mixing the above enamel composition material, the enamel composition material is melted. Preferably, the enamel composition material can be melted at a temperature range of 1200 to 1400°C. Additionally, the enamel composition material can be melted for 1 to 2 hours.

[0044] Thereafter, the melted enamel composition material can be rapidly cooled by a quenching roller using a chiller or the like. Accordingly, the enamel composition can be formed.

[0045]

[0046] Cooking equipment

[0047] Next, the enamel composition according to the present invention can be coated on one surface of a target object to be coated with the enamel composition. The target object can be a metal plate, a glass plate, a portion of a cooking appliance, or the entirety of the cooking appliance. Preferably, the coating can be applied to the inner surface of the cavity of the cooking appliance or the inner surface of the door of the cooking appliance.

[0048] Referring to FIG. 1, a cooking appliance (1) according to the present invention includes a cavity (11) in which a cooking chamber is formed, a door (14) for selectively opening and closing the cooking chamber, at least one heating source (13, 15, 16) for providing heat for heating food in the cooking chamber, and a coating layer formed by an enamel composition according to the present invention coated on the inner surface of the cavity (11) or the inner surface of the door (14).

[0049] The cavity (11) may be formed in a hexahedral shape with an open front. The heating source (13, 15, 16) may include a convection assembly (13) that discharges heated air into the cavity (11), an upper heater (15) disposed at an upper portion of the cavity (11), and a lower heater (16) disposed at a lower portion of the cavity (11). The upper heater (15) and the lower heater (16) may be provided inside or outside the cavity (11). Of course, the heating sources (13, 15, 16) do not necessarily have to include the convection assembly (13), the upper heater (15), and the lower heater (16). That is, the heating sources (13, 15, 16) may include at least one of the convection assembly (13), the upper heater (15), and the lower heater (16).

[0050] Meanwhile, referring to FIGS. 2 and 3, the enamel composition according to the present invention can be coated on the inner surface of the cavity (11) or the inner surface of the door (14) of the cooking appliance (1) by a dry process or a wet process. The cavity (11) and the door (14) can be formed of a metal plate, and the coating layer (17)(18) using the enamel composition according to the present invention can be directly coated as a single layer on the metal plate.

[0051] In the above dry process, the enamel composition material is dispersed in an organic binder, and the mixed enamel composition material and the organic binder are milled in a ball mill, thereby producing a glass frit. On the other hand, in the above wet process, the enamel composition material is dispersed in water (H2O) and a pigment, and the mixed enamel composition material, water (H2O), and pigment are milled in a ball mill, thereby producing a glass frit.

[0052] Thereafter, the glass frit according to the dry process and the wet process can be applied to the inner surface of the cavity (11) of the cooking appliance (1) or the inner surface of the door (14) by a spray method. The applied glass frit can be coated on the inner surface of the cavity (11) of the cooking appliance (1) or the inner surface of the door (14) by being fired at a temperature range of 600 to 900°C for 100 to 450 seconds.

[0053]

[0054] Hereinafter, specific aspects of the present invention will be examined through examples.

[0055]

[0056] <Example>

[0057]

[0058] <Manufacture of enamel composition>

[0059] An enamel composition having the composition ratios described in Table 1 below was prepared. The raw materials of each component were sufficiently mixed for 3 hours in a V-mixer. Here, the raw materials of Na2O, K2O, and Li2O were Na2CO3, K2CO3, and Li2CO3, respectively, and the remaining components were the same as those described in Table 1. The mixed materials were sufficiently melted at 1300°C for 1 hour and 30 minutes, and then rapidly cooled using a quenching roller to obtain a glass cullet.

[0060] The glass cullet obtained through the above process was subjected to initial particle size control using a ball mill, then ground for approximately 5 hours using a jet mill and passed through a 325 mesh sieve (ASTM C285-88). The particle size was controlled so that 1 to 3 g of frit remained that did not pass through the mesh sieve, and the powder that passed through the mesh sieve was used as the enamel composition frit.

[0061]

[0062] Ingredients (% by weight)ExampleComparative Example12345123P2O522.522.525272425.52416SiO21616181819151515Al2O3141416151419.31720ZrO2220012.466Na2O8867814.21010K2O1010810910.155Li2O002012.8500B2O312121111105.522Zn O000005.151111TiO22211.50.5000Fe2O35544.54000Co3O41.51.5111000AlF110.500.5000Cu2O603440 00MnO406212000Bi2O3002.500000V2O500001.50715MoO300000.5030Total100100100100100100100100

[0063]

[0064] <Manufacturing of enamel composition specimens>

[0065] Frits manufactured using the enamel compositions according to Examples 1 to 5 and Comparative Examples 1 to 3 were sprayed onto low-carbon steel sheets each having a size of 200×200 (mm) and a thickness of 1 (mm) or less using a corona discharge gun. The voltage of the discharge gun was controlled to 40 kV to 100 kV, and the amount of frit sprayed onto the low-carbon steel sheet was 300 g / ㎡. The low-carbon steel on which the frit was sprayed was fired at a temperature of 830°C to 870°C for 300 to 450 seconds to form a coating layer on one surface of the low-carbon steel. At this time, the coating layer was formed to a thickness of about 80 μm to 250 μm. Through this, specimens according to Examples 1 to 5 and Comparative Examples 1 to 3 were manufactured.

[0066]

[0067] <Experimental Example>

[0068] Performance evaluation was performed on the specimens according to the above examples and comparative examples as follows, and the results are shown in Table 5.

[0069]

[0070] 1. Evaluation of cleaning performance for chicken fat contaminants

[0071] 1 g of chicken fat as a contaminant was evenly and thinly applied to the surface of a specimen coated with an enamel composition on a metal substrate (100 × 100 (mm)) using a brush, and the specimen coated with the contaminant was placed in a thermostat and the contaminant was fixed for 1 hour at a temperature range of 250 to 290°C. After the contaminant was fixed, the specimen was naturally cooled and the degree of hardening was checked, and then the hardened chicken fat was wiped off with a frying pan-specific scrubber soaked in room temperature water at a force of less than 3 kgf. The area to be wiped off on the surface of the contaminated specimen was uniformly wiped using a flat-bottomed stick with a diameter of 5 cm.

[0072]

[0073] 2. Cleaning performance against cherry pie contaminants

[0074] Cherry Pie 1g as a contaminant was evenly and thinly applied with a brush to the surface of a specimen coated with an enamel composition on a metal substrate (100×100 (mm)), and then the specimen coated with the contaminant was placed in a thermostat and the contaminant was fixed at a temperature range of approximately 220℃ for 30 minutes. After the contaminant was fixed, the specimen was naturally cooled and the contaminant was burned at 350℃ for 1 hour. Afterwards, the hardened cherry pie contaminant was wiped off with a frying pan-specific scrubber soaked in room temperature water at a force of less than 3 kgf. The area to be wiped off on the contaminated specimen surface was uniformly wiped off using a flat-bottomed stick with a diameter of 5 cm.

[0075]

[0076] The number of round trips wiped in the above specimens was measured and defined as the number of cleaning round trips, and the cleaning performance evaluation index is listed in Table 3.

[0077]

[0078] Number of cleaning round trips Level (LEVEL) 1 ~ 5 LV. 56 ~ 15 LV. 416 ~ 25 LV. 326 ~ 50 LV. 251 ~ LV. 1

[0079]

[0080] 3. Durability Evaluation

[0081] Specimens that completed the cleaning tests described in item 2 above were evaluated for durability, including heat and chemical resistance. The durability of each specimen was assessed by examining the staining phenomenon. The surface of each specimen was examined and the staining phenomenon was evaluated by quantifying the ratio of the remaining residue or trace area to the total surface area. The evaluation criteria for the staining phenomenon are as shown in Table 3.

[0082]

[0083] Stain Area Ratio Level (LEVEL) 0 %LV.5~ 20 %LV.4~ 50 %LV.3~ 80 %LV.280 % ~LV.1

[0084]

[0085] Example Comparative Example 12345123 Chicken fat cleaning performance LV. 5LV. 5LV. 5LV. 5LV. 1LV. 3LV. 2 Cherry pie cleaning performance LV. 5LV. 5LV. 5LV. 5LV. 1LV. 3LV. 1 Stain level LV. 5LV. 5LV. 5LV. 5LV. 1LV2LV. 2

[0086]

[0087] As described in Table 4 above, it was confirmed that the examples according to the present invention not only had excellent cleaning performance but also had excellent durability.

[0088] In particular, referring to FIG. 4, it can be confirmed that the enamel coating using the enamel composition according to Examples 1 and 2 of the present invention has all contaminants removed after cleaning. However, it can be confirmed that the enamel coating according to Comparative Example 1 still has contaminants not removed after cleaning.

[0089] The above comparative examples were found to have poor cleaning performance and very unsatisfactory durability due to unstable glass compositions because they did not have the optimal composition compared to the examples.

[0090] While the present invention has been described as above, it is clear that the present invention is not limited to the embodiments disclosed herein, and that various modifications can be made by those skilled in the art within the scope of the present invention's technical concept. Furthermore, even if the operational effects according to the configuration of the present invention have not been explicitly described while describing the embodiments of the present invention, it is natural that the effects predictable by the corresponding configuration should also be acknowledged.

[0091]

[0092] [Explanation of symbols]

[0093] 1: Cooking appliances

[0094] 11: Cavity

[0095] 12: Kitchen

[0096] 13: Convection assembly

[0097] 14: Door

[0098] 15: Top heater

[0099] 16: Lower heater

[0100] 17, 18: Coating layer

Claims

1. P2O520~30 wt%; SiO2 16~23 wt%; Al2O314~20 wt%; B2O310~16 wt%; 15 to 30 wt% of at least one of Na2O, K2O and Li2O; TiO20.5~4 wt%; Fe2O3 2~8 wt%; Co3O4 1~2 wt%; and Containing MeO 0.5~8 wt%; Enamel composition. (Here, the above MeO is Cu2O, CeO2, Bi2O3, Y2O3, La2O 3, (Contains at least one of Ta2O5, V2O5, WO3, MoO3, and MnO4) 2. In paragraph 1, The above enamel composition Containing ZrO22.5 wt% or less Enamel composition.

3. In paragraph 1 The above enamel composition Containing AlF 2 wt% or less Enamel composition.

4. In paragraph 1 The above MeO is Containing 6 wt% or more of Cu2O or MnO4 Enamel composition. 5.P2O520~30 wt%; SiO2 16~23 wt%; Al2O314~20 wt%; B2O310~16 wt%; 15 to 30 wt% of at least one of Na2O, K2O and Li2O; TiO20.5~4 wt%; Fe2O3 2~8 wt%; Co3O4 1~2 wt%; and A step of providing an enamel composition material comprising MeO 0.5 to 8 wt%; A step of melting the above enamel composition material; and A step of forming an enamel composition by quenching the melted enamel composition material is included. Method for producing an enamel composition.

6. In paragraph 5, The above enamel composition material Containing ZrO22.5 wt% or less Method for producing an enamel composition.

7. In paragraph 5 The above enamel composition material is Containing AlF 2 wt% or less Method for producing an enamel composition.

8. In paragraph 5 The above MeO is Containing 6 wt% or more of Cu2O or MnO4 Method for producing an enamel composition.

9. Cavity where the cooking chamber is formed; A door for selectively opening and closing the above cooking room; At least one heating source providing heat for heating food in the cooking chamber; A buffer layer coated on the inner surface of the cavity or the inner surface of the door; and A coating layer coated on the buffer layer and formed by the enamel composition of any one of claims 1 to 4; Cooking appliances.

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