JPH08256913A - Liquid heating vessel and its production - Google Patents

Abstract

PURPOSE: To provide a liquid heating vessel which is formed with a bumping preventive layer by the higher hydrophilic nature of a fluororesin coating layer, is free from malfunction by early lack of liquid and has excellent contamination resistance and its production. CONSTITUTION: This liquid heating vessel 2 is formed with the fluororesin coating layer on the inside surface of a metallic vessel body. At least the part forming the heating part surface of the front surface of the fluororesin coating layer 5 is imparted with the high hydrophilic nature within a range of 40 to 110 deg. in the contact angle θ with water by irradiation with active rays. The part forming at least the heating part surface on the front surface of the fluororesin coating layer is irradiated with UV rays or UV laser beams in the state of bringing the part into contact with the water or is irradiated with synchrotron radiation light in vacuum, by which the part is imparted with the high hydrophilic nature in such a manner that the contact angle with the water of the irradiated part attains the value within the range of 40 to 110 deg. in the part to be irradiated in the process for producing the liquid heating vessel 2 consisting of a metallic base material formed with the fluororesin coating layer 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid heating container, and more specifically, it has an anti-swelling layer formed by hydrophilization of the surface of a fluororesin coating layer to prevent malfunction due to premature disconnection and excellent stain resistance. Liquid heating container and its manufacturing method. The liquid heating container of the present invention is used as a container of an electric liquid heater such as an electric pot.

[0002]

2. Description of the Related Art An electric liquid heater is widely used as an electric pot, a liquor or the like because it can easily and safely heat or keep the liquid warm. The electric liquid heater includes a container (liquid heating container) for containing the liquid to be heated and a heat source, and further heats the liquid to a desired temperature.
A temperature sensor (temperature sensor, temperature sensor) is provided to keep warm. These heat sources and temperature sensing parts are
Usually, it is placed in close contact with the outer surface of the bottom of the liquid heating container. One of the problems in the electric liquid heater is the bumping phenomenon that occurs on the inner surface of the container near the heat source. When bumping occurs, a loud noise is generated, and the surface inside the container where the bubbles are generated due to bumping is overheated and the surface temperature rises.
It causes malfunction of the temperature sensor.

Various proposals have hitherto been made to deal with the problem of bumping of a liquid heating container. For example,
(1) A method of forming a fluororesin coating layer on the inner surface of the container (Japanese Patent Publication No. 52-14665), (2) A method of spraying a metal oxide on the inner surface of the container to form a bumping prevention layer (Japanese Patent Publication No. 63-51003). Gazette), (3) a method of providing a boiling agent layer such as an inorganic powder or an organic polymer on the fluororesin coating layer (JP-A-5-123246), (4) high-frequency discharge treatment or high-frequency treatment on the fluororesin coating layer surface. There has been proposed a method of imparting hydrophilicity to the surface of the treated film by corona discharge treatment (JP-A-4-371116).

In general, in order to quickly heat the liquid by the electric liquid heater without temperature unevenness, it is preferable to provide a heat source on the outer surface of the bottom of the container. However, in order to heat the liquid with the heat source at the bottom of the container, the electric capacity of the heat source must be increased, which makes it even more difficult to prevent bumping on the inner surface of the container near the heat source. Therefore, for example, even if the fluororesin coating layer is provided on the inner surface of the container by the method (1), the bubbles become large and an overheated state occurs.
When this overheated state occurs on the temperature sensor, the temperature sensor operates regardless of the hot water temperature, causing so-called premature disconnection. If the temperature sensor is provided on the side of the container away from the heat source, the liquid temperature cannot be sensed when the amount of liquid is small.

By providing the bumping prevention layer by the metal oxide spraying by the method (2), the bumping itself can be considerably reduced, but the surface roughness of the bumping prevention layer is 50 to 150 μm.
It is necessary to increase the thickness and increase the layer thickness to 50 to 400 μm. However, when the surface roughness is high, stains such as water stains are likely to adhere to the recesses on the surface, and the stain resistance is reduced. Moreover, if the bumping prevention layer is thickened, the thermal conductivity of that portion is lowered. Although the anti-boiler agent layer according to the method (3) can reduce the layer thickness, it is poor in stain resistance and has a large amount of water stains. ) Increases to 10 mg / cm ² or more.

In the method (4) of subjecting the surface of the fluororesin coating layer to high-frequency discharge treatment or high-frequency corona discharge treatment, cracks are always generated on the surface to be treated, and strength deterioration of the fluororesin coating layer is unavoidable. Only about 70% of the strength of the untreated material can be retained. Moreover, a corrosive component or the like permeates through the generated cracks, and as a result, the fluororesin coating layer peels off and swells at the interface with the container, which lowers the durability of the container.

Recently, the binding energy with a fluorine atom is 1
There has been proposed a method for producing a hydrophilic fluororesin film, which comprises irradiating a fluororesin film with ultraviolet rays to make it hydrophilic in the presence of a compound having 28 kcal / mol or more atoms and a hydrophilic group (JP-A-7- 3057 publication). In this method, by irradiating the fluororesin film with ultraviolet rays in the presence of a compound such as aluminum hydroxide, boric acid, ammonium borate, lithium hydroxide, calcium hydroxide, or barium hydroxide, the fluorine in the fluororesin is changed. Some of the atoms are replaced with hydrophilic functional groups. According to this method, the fluororesin film can be hydrophilized, and it is possible to hydrophilize even the inside of the porous fluororesin film. However, if this method is applied to the method for hydrophilizing a liquid heating container having a fluororesin coating layer, stains such as water stains tend to adhere to the treated part, and as the number of boiling times increases, the contact angle of the treated part increases. Is significantly reduced.

[0008]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a liquid heating container in which a swelling prevention layer is formed by hydrophilization of a fluororesin coating layer, has no malfunction due to premature disconnection, and has excellent stain resistance. It is to provide a manufacturing method. The inventors of the present invention have conducted extensive studies as a result of overcoming the above-mentioned problems of the prior art. As a result, in a container having a fluororesin coating layer formed on the inner surface, at least the inner surface of the container corresponding to the heating source and the temperature sensing unit (heating unit It was found that the above object can be achieved by irradiating the surface of the fluororesin coating layer (the surface) with an actinic ray such as an ultraviolet ray, an ultraviolet laser beam or a synchrotron radiation ray to form a hydrophilic layer. When irradiating with ultraviolet light or ultraviolet laser light, the irradiated part is irradiated with water in contact with it, while when irradiating with synchrotron radiation, by irradiating in vacuum, the fluororesin coating The surface of the layer can be made hydrophilic so as to have a desired contact angle, and the stain resistance originally possessed by the fluororesin coating layer can be highly retained. The present invention has been completed based on these findings.

[0009]

According to the present invention, there is provided a liquid heating container in which a fluororesin coating layer is formed on the inner surface of a metal container body, wherein at least the heating portion surface of the fluororesin coating layer surface is formed. There is provided a liquid heating container, characterized in that the portion to be hydrophilized by irradiation with actinic rays has a contact angle with water θ of 40 to 110 °. Further, according to the present invention, in a method for producing a liquid heating container from a metal substrate on which a fluororesin coating layer is formed, at least a portion of the surface of the fluororesin coating layer that forms the heating portion surface is covered with water. The contact angle to water of the irradiated portion is 40 to 110 by irradiating with ultraviolet light or ultraviolet laser light in a state of being in contact with or by irradiating synchrotron radiation in vacuum.
There is provided a method for manufacturing a liquid heating container, which is characterized in that it is hydrophilized so as to be within a range of °.

The liquid heating container obtained by the production method of the present invention has a contact angle θ of water with respect to the surface of the fluororesin coating layer.
Is made hydrophilic so that it falls within the range of 40 to 110 °, and the surface modification rate R of the surface is expressed by the formula R ≦ 135−θ.
Satisfying the above requirement, the stain resistance is excellent, and the decrease in contact angle over time is suppressed. The surface modification rate R is expressed by the formula R
= (1-C [CH ₂ ] / C [total]) × 100. Here, C [total] is the total area of the C1s spectrum obtained by measurement by photoelectron spectroscopy, and C [CH ₂ ] is a value of the peak area derived from CF ₂ obtained by waveform separation processing. is there. Also,
When irradiating with ultraviolet rays or ultraviolet laser light in a state in which at least the portion forming the surface of the heating portion of the fluororesin coating layer is in contact with water, the temperature of water is 50 to 10
When the temperature is raised to 0 ° C and irradiation is performed, the irradiation efficiency can be increased.

[0011]

According to the present invention, even if the heat source and the temperature sensing portion are provided on the outer surface of the bottom of the liquid heating container, the temperature sensor is not prematurely cut off due to bumping, and the film strength of the fluororesin coating layer is high. A liquid heating container that is strong and has dramatically better stain resistance than conventional products is provided. The liquid heating container of the present invention is used as a container for storing and heating a liquid in an electric liquid heater. The basic configuration of the electric liquid heater is as shown in FIG. That is, the fluororesin coating layer 5 is formed on the inner surface of the metal container 2.
Is provided, and the heat source 3 and the temperature sensing unit 4 are arranged in close contact with each other on the outer surface of the bottom of the container. The heat source 3 and the temperature sensing unit 4 may be integrated with the container body 2 or may be separated separately. As shown in FIGS. 1 and 2, at least the surface of the heating portion of the fluororesin coating layer 5 inside the container 2 is
A layer 6 in which the surface of the fluororesin coating layer is hydrophilized is formed.

The liquid heating container body is made of a metal substrate such as aluminum (including aluminum alloy) or stainless steel. A fluororesin coating layer is provided on the inner surface of the container. Examples of the fluororesin include polytetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), and the like.

The fluororesin coating layer can be formed by coating a fluororesin paint by a conventional method, drying and sintering. In order to create a liquid heating container, the surface of a metal disk such as stainless steel or aluminum is usually roughened by blasting, electrolytic etching, chemical etching, or a primer coating process, and then a fluororesin paint is applied. Is coated, dried, and fired to form a disk having a fluororesin coating layer, which is pressed into the shape of a container.

In the present invention, at least the portion of the surface of the fluororesin coating layer on the inner surface of the container that forms the surface of the heating portion is irradiated with an actinic ray to make it hydrophilic so that the contact angle with water falls within the range of 40 to 110 °. To do. The heating surface is usually the bottom inner surface of the container. The hydrophilic treatment by irradiation with actinic rays is carried out by irradiating actinic rays on at least a portion of the metal disk having the fluororesin coating layer to be the surface of the heating portion, and then press-working into a container shape. . When there is a possibility that the hydrophilicity of the surface may be deteriorated by pressing, after pressing into the shape of the container, the surface of the fluororesin coating layer that will be the heating part surface of the container is irradiated with actinic rays to make it hydrophilic. It can be performed.

The actinic rays include ultraviolet rays (UV), ultraviolet laser light (laser light that pulsates in the ultraviolet region), and synchrotron radiation (Synchrotron).
Radiation) light (SR light) and the like.
As the ultraviolet rays, those having a wavelength range of 200 to 300 nm are preferable. As the ultraviolet laser light, KrF excimer laser light (248 nm) is preferable.

To carry out the hydrophilic treatment by irradiating the surface of the fluororesin coating layer with these actinic rays, the surface of the fluororesin coating layer is irradiated with ultraviolet rays or ultraviolet laser light in a state of being in contact with water, or Irradiate SR light in a vacuum. In the method of irradiating with ultraviolet light or ultraviolet laser light in a state where at least a portion forming the surface of the heating portion of the fluororesin coating layer is in contact with water, the temperature of water is preferably 50 to 100 ° C., more preferably 80 to 100 ° C. When the temperature is raised to 0 ° C and irradiation is performed, the hydrophilicity-improving reactivity is improved, and the irradiation time can be shortened when the same contact angle with water is to be obtained. For example, water temperature is 100 ℃
When the temperature is raised to near (boiling water state), it will reach room temperature (20
The same contact angle with respect to water can be obtained in about 1/10 the time of irradiation treatment at (° C.), and the cost can be reduced.

The degree of hydrophilicity due to irradiation with actinic rays can be quantitatively expressed by the contact angle with water θ. The contact angle with water is determined by measuring the contact angle with water using a contact angle meter (CA-A) manufactured by Kyowa Interface Science Co., Ltd. by a liquid proper method. In the present invention, the hydrophilic treatment is carried out so that the contact angle with water falls within the range of 40 to 110 °. If the irradiation amount of actinic rays is too small and the contact angle with water is too large, the hydrophilicity is not sufficient and the temperature sensing unit may malfunction easily. Conversely, the irradiation amount is too large and the contact angle with water is too large. If the value is too small, the film strength (tensile strength) of the fluororesin coating layer will decrease, and the amount of contaminants attached will increase. The preferred range of the contact angle with water is anti-jumping property, cost and time (productivity) of irradiation treatment with actinic rays, amount of attached contaminants, tensile strength,
It is determined by comprehensively evaluating the premature disconnection prevention property. The preferred contact angle with water is 50 to 105 °, more preferably 70 to 95.
°.

When an ultraviolet laser light (eg, KrF excimer laser light) is irradiated, the irradiation amount is usually 0.5 to 2000 J / cm ² , preferably 5 to 50.
It is prepared to be about 0 J / cm ² . When using UV light, the irradiation time is adjusted to about 60 to 3000 seconds. When SR light is used, it has a peak wavelength of usually 1 to 200 nm, preferably 1 to 100 nm. In addition, in order to contact the irradiated portion of the surface of the fluororesin coating layer with water and irradiate it with ultraviolet rays or ultraviolet laser light, a water layer portion using quartz glass as a window material is formed on the irradiated portion of the fluororesin coating disc. There is a method of setting. When irradiation is performed after press-molding a fluororesin-coated disk into a container shape, similarly, provide a water layer part using quartz glass as a window material in the irradiated part, or irradiate by putting water in the bottom part of the container. To do. To raise the water temperature, a method of heating from the side opposite to the surface to be irradiated by a suitable heating means is convenient.

The fluororesin coating layer 5 is for the purpose of preventing stains, but the formation of the hydrophilic layer 6 by irradiation with actinic rays facilitates the generation of air bubbles and prevents a jump or overheating. You can Compared with the conventional method of providing a boiling agent layer such as an inorganic powder or an organic polymer on the fluororesin coating layer, in the present invention, since only the surface of the fluororesin coating layer is made hydrophilic,
The hydrophilic layer can be made extremely thin, usually less than 1 μm, to prevent deterioration of thermal conductivity, almost no deterioration of film strength (tensile strength), excellent stain resistance, and take advantage of the inherent advantages of the fluororesin coating layer. ing. Further, in the present invention, a boiling agent is unnecessary, and the treatment can be performed at low cost. Unlike conventional high-frequency discharge treatment or high-frequency corona discharge treatment, cracks that cause strength deterioration or corrosion do not occur on the surface of the fluororesin coating film.

According to the hydrophilization method disclosed in JP-A-7-3057, the surface of the fluororesin coating layer is treated with aluminum hydroxide, boric acid, ammonium borate, lithium hydroxide, calcium hydroxide, or hydroxide. When an aqueous solution of a compound such as barium is brought into contact and irradiated with ultraviolet rays, hydrophilicity can be obtained, but the stain resistance of the irradiated portion deteriorates. As a result of examining the surface structure of the fluororesin coating layer by photoelectron spectroscopy, it was found that a modified fluororesin coating layer having a different surface structure was obtained by the production method of the present invention and the hydrophilization method described in the publication. found.

That is, according to the production method of the present invention, the following relational expressions and are established between the contact angle θ of water and the surface modification rate R of the irradiated portion of the surface of the fluororesin coating layer. To do. R ≦ 135−θ 40 ≦ θ ≦ 110 These relational expressions are graphed in FIG. According to the production method of the present invention, as shown by A, B and C in FIG. 4, a hydrophilized fluororesin coating layer satisfying the above relational expressions and can be obtained. On the other hand, according to the hydrophilization method disclosed in JP-A-7-3057, as shown by D and E in FIG.
A hydrophilized fluororesin coating layer satisfying the above relational expressions and cannot be obtained.

Here, the surface modification rate R (%) is obtained by evaluating the surface structure of the fluororesin coating layer (in the range of about 1 nm below the surface) by photoelectron spectroscopy (XPS). , Can be defined by the following formula. R = (1-C [CH 2] / C [total]) × 100 C [total] is the total area of C1s spectrum obtained by measuring a photoelectron spectroscopy, C [CH _2]
Is the value obtained by the waveform separation process of the peak area derived from CF ₂ . Specific measurement conditions are shown in the examples. In the sample before modification (all CF ₂ bonds), R = 0, and in the completely modified state (CF ₂ bond disappeared), R = 100. As shown in FIG. 4, in the case of the same contact angle to water, the surface modification ratio R is different, and therefore the modified fluororesin coating layer of the present invention having both high hydrophilicity and stain resistance (water stain resistance). The surface structure of
It can be presumed that it is different from that obtained by the hydrophilization method disclosed in JP-A-3057.

[0023]

EXAMPLES The present invention will be described more specifically below with reference to Examples and Comparative Examples. The evaluation methods of various physical properties are as follows.

(1) Water contact angle θ Using a contact angle meter (CA-A) manufactured by Kyowa Interface Science Co., Ltd.
The contact angle with water was measured by a liquid method. (2) Amount of attached contaminants A sample of 5 cm × 10 cm was immersed in an aqueous solution in which 5 g of calcium carbonate and 5 g of magnesium carbonate were dissolved in 90 g of pure water, discharged at 85 to 95 ° C. for 20 days, taken out, washed with water, dried, and attached. The amount of kimono was measured. (3) Tensile strength Sample length (chuck interval): 30 mm Sample width: 10 mm Tensile speed: Tested under the conditions of 100 mm / min. (4) Presence or absence of premature cutting 1 liter of water was put into each sample pot and heated, and the temperature at which the boiling completion alarm sounded was measured. When the temperature at that time was 99 ° C. or lower, it was evaluated as early cutting. (5) Surface modification rate R (%) Using the following apparatus, measurement by photoelectron spectroscopy was performed under the following conditions. Each sample was cut into 1 cm square, subjected to ultrasonic cleaning with acetone (5 minutes), dried, and immediately introduced into the sample chamber for measurement. An electron neutralization gun was used to prevent charge up of the sample. The surface modification rate R was calculated from the obtained spectrum according to the above formula. Equipment: ESCA5400 X-ray source: MgKα Central energy: 1253.6 eV Accelerating voltage: 15 kV, 400 W (used without monochromatization) Sample chamber pressure: 2.0 × 9 Torr or less Photoelectron take-off angle: 10 °

[Example 1] An aluminum disk was subjected to electrochemical etching in an aqueous sodium chloride solution at an electric quantity of 30 Q / cm ² to form fine irregularities on the surface.
Further, this surface was anodized in 15% sulfuric acid at 15 V for 5 minutes to form a hard layer on the etched surface. A fluororesin paint (Polyflon D-1F manufactured by Daikin Industries, Ltd.) was applied to this surface so as to have a thickness of about 25 μm, dried at about 100 ° C., and then sintered at 380 ° C. for 15 minutes. Next, when this fluororesin-coated plate was press-molded, a water layer was formed by using quartz glass as a window material on the surface of the bottom surface of the container to bring it into contact with water. (Wavelength: 248 nm) was irradiated at different irradiation doses of 0.05, 0.5, ⁵ , 50, 500, 2000, and 5000 J / cm ² , respectively. As a reference, the laser was irradiated in air, but the contact angle with water did not change. After irradiation, the contact angle against water, the stain resistance, and the tensile strength (tensile strength was carried out in the same lot for destructive testing) were measured. Next, after pressing this into the shape of a heating container, a heat source and a temperature sensing unit are attached to the bottom of the container, and a liquid heating container (electric pot)
I got 1 liter of water was placed in this electric pot and heated to carry out an early cut test. Table 1 shows various characteristics of the samples with different irradiation doses.

[0026]

[Table 1]

From the results shown in Table 1, it was found that the contact angle with water was 110 ° or less and the film did not break prematurely. 40 ° water contact angle
Irradiation until the amount becomes less than 1 deteriorates the film strength and increases the amount of attached contaminants. Observation of the hydrophilized surface revealed that the fluororesin coating film did not show any deterioration such as cracking, indicating that there was no problem in durability. Similar results were obtained even with the type in which the container, heat source, and temperature sensing part could be separated.

Example 2 An aluminum disc was roughened by sandblasting, and then a transparent fluororesin paint (TC-7808GT manufactured by Daikin Industries, Ltd.) was applied to a thickness of about 20 μm, and then about 100 μm. Dry at 0 ° C and sinter at about 380 ° C for 15 minutes. Then, using an ultraviolet lamp (UV lamp manufactured by Eye Graphics Co., Ltd .; metal halide type, M03-L31), a fluororesin-coated aluminum plate, which is in contact with water by providing a water layer portion with quartz glass as a window material, is subjected to UV. The light was irradiated at different irradiation times of 3, 30, 60, 300 and 3000 seconds, respectively. When the irradiation time is increased and the irradiation amount is increased,
The contact angle with water decreased from 118 ° of the original to 70 °, and hydrophilicity could be imparted. Irradiation with UV light in air as a reference did not change the contact angle with water. After that, it was pressed into the shape of a heating container, and a heat source and a temperature sensing part were attached to form an electric pot, and various characteristics were measured. When 1 liter of water was placed in this electric pot and heated, when the contact angle against water was 110 ° or less, it became hydrophilic when it boiled, and the bubbles on the surface were released smoothly, and the occupied area of the bubbles was reduced. It became smaller and the volume of the boiling noise could be lowered, and at the same time it did not cut off prematurely.

[0029]

[Table 2]

Next, the water temperature was raised to 100 ° C. for examination. The contact angle with water was about 10 ° lower than that at room temperature.
Therefore, when trying to obtain the same contact angle with water, it was found that the irradiation time was about 1/10 of the room temperature, and the cost could be reduced.

[Example 3] An aluminum disk was subjected to electrochemical etching in an aqueous sodium chloride solution at an electric quantity of 30 Q / cm ² to form fine irregularities on the surface.
Further, this surface was anodized in 15% sulfuric acid at 15 V for 5 minutes to form a hard layer on the etched surface. A fluororesin paint (Polyflon D-1F manufactured by Daikin Industries, Ltd.) was applied to this surface so as to have a thickness of about 25 μm, dried at about 100 ° C., and then sintered at 380 ° C. for 15 minutes. Furthermore, PTFE colored paint (component ratio after drying and sintering: PTFE / PFA 78%, adhesive 3%, pigment 19
%) Was applied thereon to give a thickness of about 10 μm. Next, using a UV lamp (manufactured by Eye Graphics Co., Ltd., metal halide type, M03-L31),
UV light is applied to a fluororesin-coated aluminum plate that is made of quartz glass as a window material and provided with a water layer portion and is brought into contact with water.
Irradiation was performed by changing the irradiation time to 3, 30, 60, 300, and 3000 seconds, respectively. As a result, the contact angle with water was lowered from the original 128 ° to 81 °, and hydrophilicity could be imparted. Then, it was pressed into the shape of a heating container, a heat source and a temperature sensing part were attached to obtain an electric pot, and various characteristics were examined. Table 3 shows the results.

[0032]

[Table 3]

From the results shown in Table 3, when the contact angle against water is within the range defined by the present invention (110 ° -40 °), the amount of adhered contaminants is small, the tensile strength is high, and premature breakage does not occur. Recognize. When 1 liter of water was placed in a pot satisfying the requirements of the present invention and heated, when it boils, since it becomes hydrophilic, bubbles on the surface smoothly separate, the occupied area of the bubbles becomes smaller, and the volume of the boiling sound increases. Can be made small, and at the same time, it no longer cuts prematurely.

[Example 4] An aluminum disk was subjected to electrochemical etching in a sodium chloride aqueous solution at an electric quantity of 30 Q / cm ² to form fine irregularities on the surface.
Further, this surface was anodized in 15% sulfuric acid at 15 V for 5 minutes to form a hard layer on the etched surface. A fluororesin paint (Polyflon D-1F manufactured by Daikin Industries, Ltd.) was applied to this surface so as to have a thickness of about 25 μm, dried at about 100 ° C., and then sintered at 380 ° C. for 15 minutes. When pressed, the surface of the part that will be the bottom of the container,
Quartz glass is used as a window material to provide a water layer and contact it with water.
SR (SynchrotronRad)
irradiation) at the time of peak wavelengths of 1, 5, 100, 150, 200, and 220 nm, respectively.
Was changed (the irradiation time was constant at 150 seconds). The results are shown in Table 4.

[0035]

[Table 4] If the peak wavelength exceeds 200 nm, the contact angle with water will be 11
Premature cutting occurs when the angle exceeds 0 °.

[Embodiment 5] An electric pot with a power consumption of 800 W (capacity 2.
A hydrophilic layer was formed on the inner surface of the bottom of a 2 liter container (made of SUS431) by the following procedure. After roughening the inner surface of the container with sandplast, a transparent fluororesin paint (TC-7808GT manufactured by Daikin Industries, Ltd.) is applied to a thickness of about 2
The coating was applied so as to have a thickness of 0 μm, dried at about 100 ° C., and then sintered at about 380 ° C. for 15 minutes. Next, SR light having a peak wavelength of 150 nm was irradiated in vacuum of 10 ⁻⁵ torr or less only on the bottom surface of the container for 150 seconds to prepare a heating container in which only the surface of the bottom coating portion was made hydrophilic. The contact angle of water thus obtained on the bottom surface is 8
It was 5 °, and as a result of analyzing this irradiated surface by X-ray photoelectron spectroscopy, it was found that --COO
It was found that oxygen-containing groups such as H and —CO were formed and the hydrophilicity was dramatically improved. No deterioration of the coating film such as cracks was observed on the irradiated surface. When 1 liter of water was placed in an electric pot prepared from this sample and heated, 100 ° C. was reached after 8 minutes and 30 seconds. When boiling, the bottom surface was made hydrophilic and the contact angle with water was small, so that the bubbles were smoothly separated from the bottom surface, the volume of the bubbles was reduced, and the volume of the boiling sound could be reduced. Further, since the surface of the fluororesin coating layer has hydrophilicity, the temperature sensor provided at the bottom of the container accurately detected the temperature of water and did not malfunction (no premature disconnection).

Example 6 An aluminum disk was subjected to electrochemical etching in an aqueous sodium chloride solution at an electric quantity of 30 Q / cm ² to form fine irregularities on the surface.
Further, this surface was anodized in 15% sulfuric acid at 15 V for 5 minutes to form a hard layer on the etched surface. A fluororesin paint (Polyflon D-1F manufactured by Daikin Industries, Ltd.) was applied to this surface so as to have a thickness of about 25 μm, dried at about 100 ° C., and then sintered at 380 ° C. for 15 minutes. Then, the surface of the portion which will be the bottom surface when this fluororesin-coated plate is press-molded is left in the state of a disk, and SR light having a peak wavelength of 150 nm is applied at 10 ⁻⁵ torr.
Irradiation was performed for 150 seconds in the following vacuum. After pressing this into the shape of a heating container, a heat source and a temperature sensor were attached to the outer surface of the bottom of the container. When 1 liter of water was put into the obtained electric pot and heated, 100 minutes after 8 minutes and 40 seconds.
Reached ℃. The bubbles were released smoothly from the bottom surface, and there was no sudden rise or the temperature sensor was cut off prematurely. The contact angle of water with respect to the hydrophilized surface was 88 °, and the amount of attached contaminants was 0.04 mg / cm ² .

Example 7 SR having a peak wavelength of 4.3 nm
A hydrophilic treatment was performed in the same manner as in Example 6 except that light irradiation was performed to prepare an electric pot. When 1 liter of water was placed in this electric pot and heated, 100 minutes later, 100
Reached ℃. The bubbles were released smoothly from the bottom surface, and there was no sudden rise or the temperature sensor was cut off prematurely. The contact angle of water on the hydrophilized surface was 67 °, and the amount of attached contaminants was 0.05 mg / cm ² .

[Embodiment 8] In each of the above-mentioned embodiments, the irradiation treatment was carried out at room temperature (20 ° C.).
The water contact angle was measured by changing the water temperature during irradiation. 30 Q /
Electrochemical etching was performed with an electric quantity of cm ² to form fine irregularities on the surface. Further, this surface was anodized in 15% sulfuric acid at 15 V for 5 minutes to form a hard layer on the etched surface. About 25 μm of fluororesin paint (Polyflon D-1F manufactured by Daikin Industries, Ltd.) on this surface
It is applied to a thickness of m and dried at about 100 ° C, then 3
Sintered at 80 ° C for 15 minutes. Next, using a UV lamp (UV lamp manufactured by Eye Graphics Co., Ltd .; metal halide type, M03-L31), a fluororesin-coated aluminum plate in which a water layer portion was provided using quartz glass as a window material and brought into contact with water was subjected to UV treatment. It was irradiated with light for 60 seconds,
Water temperature is 20 ℃, 60 ℃, and 10 during irradiation.
Irradiation was performed after changing the temperature to 0 ° C. (boiling state). The results are shown in Table 5.

[0040]

[Table 5]

As is clear from the experimental results shown in Table 5, as the temperature of the water to be contacted with the surface of the fluororesin coating layer is increased, the degree of decrease in the contact angle with water decreases even with the same UVV irradiation time. It turns out to be big. Room temperature (2
Compared to irradiation at 0 ° C), a significant difference was observed in the contact angle with water at a water temperature of 60 ° C, and when it was around 100 ° C, the reactivity was remarkably improved, and the same contact angle with water was tried to be obtained. About 1
Irradiation time of / 10 is sufficient.

[Example 9] An aluminum disk was subjected to electrochemical etching in an aqueous sodium chloride solution at an electric quantity of 30 Q / cm ² to form fine irregularities on the surface.
Further, this surface was anodized in 15% sulfuric acid at 15 V for 5 minutes to form a hard layer on the etched surface. A fluororesin paint (Polyflon D-1F manufactured by Daikin Industries, Ltd.) was applied to this surface so as to have a thickness of about 25 μm, dried at about 100 ° C., and then sintered at 380 ° C. for 15 minutes. Next, UV lamp (UV lamp manufactured by Eye Graphics Co., Ltd .; metal halide type, M03-L3)
Using 1), the fluororesin-coated aluminum plate, which was provided with a water layer part using quartz glass as a window material and was in contact with water, was irradiated with UV light at room temperature, and the irradiation time was adjusted to adjust the contact angle with water. Samples of 50 ° (Sample A), 67 ° (Sample B), and 80 ° (Sample C) were prepared. On the other hand, instead of water, a 4.1% by weight aqueous boric acid solution was used according to the hydrophilization method of JP-A-7-3057, and UV irradiation conditions were adjusted in the same manner as described above, so that the contact angle with water was changed. Each sample of 50 ° (Sample D) and 67 ° (Sample E) was prepared. For these samples A to E, the surface modification rate R
Was measured. The results are shown in Table 6.

[0043]

[Table 6]

The relationship between the contact angle θ with respect to water and the surface modification rate R of these samples A to E is plotted in FIG. As is clear from FIG. 3, in the case of the same contact angle to water (A and D, B and E), according to the production method of the present invention, JP-A-7-3057 is used.
It can be seen that the surface modification rate is small as compared with the method using the hydrophilization method described in Japanese Patent Laid-Open Publication No. Next, samples A and B (invention products),
Samples D and E (comparative products) were pressed into the shape of a heating container. A heat source and a temperature sensor were attached to the outer surface of the bottom of each container. 1 liter of water was placed in each of the obtained electric pots and heated to boil. The number of times of boiling water was set to once, new water was replaced, and the same boiling water experiment was conducted. The contact angle of water with respect to the UV irradiation treated surface was measured every time the water was boiled once. Then, the relationship between the number of boiling times and the measurement result of the contact angle with water is graphed and shown in FIG.

As is clear from FIG. 4, the products of the present invention (Samples A and B) are stable with almost no change in the contact angle with water even if the number of times of boiling is increased. That is, the product of the present invention has excellent durability. On the other hand, Japanese Patent Laid-Open No. 7-3
Those obtained by the hydrophilization method of 057 (Samples D and E) have an original water contact angle of 50 ° (Sample D) and a water contact angle of 40 after about 3 times of boiling.
When the contact angle of the original is 67 ° (Sample E), the contact angle with water becomes smaller than 40 ° after about 10 times of boiling. As described above, in the case of Samples D and E, it is presumed that the contact angle with water rapidly decreases due to the adhesion of scales.

[0046]

EFFECTS OF THE INVENTION According to the present invention, there is provided a liquid heating container which is free from malfunction due to premature disconnection, and which is excellent in stain resistance, and a method for producing the same, because a surface for preventing a rise is formed by hydrophilicizing the surface of the fluororesin coating layer. Provided. In the production method of the present invention, the fluororesin coating layer is subjected to hydrophilic treatment by irradiation with active rays such as ultraviolet rays, ultraviolet laser light, and synchrotron irradiation light, so that bumping is prevented while suppressing deterioration of the strength of the fluororesin coating layer. It is possible to obtain a liquid heating container that can be completely prevented, does not cause a malfunction of the transient sensor, improves bubble breakage, and has excellent stain resistance.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing the structure of an embodiment of an electric liquid heater using a liquid heating container of the present invention.

FIG. 2 is a schematic sectional view of an embodiment showing the structure of the bottom portion of the liquid heating container of the present invention.

FIG. 3 is a graph showing the relationship between the contact angle θ of water and the surface modification rate R on the surface of the hydrophilized fluororesin coating layer.

FIG. 4 is a graph showing the relationship between the number of boiling times and the water contact angle measured for an electric pot obtained by pressing a metal substrate having a hydrophilized fluororesin coating layer.

[Explanation of symbols]

 1: Electric Liquid Heater 2: Liquid Heating Container (Main Body) 3: Heat Source 4: Temperature Sensing Part 5: Fluororesin Coating Layer 6: Light Irradiation Hydrophilic Layer A: Present Invention Product B: Present Invention Product C: Present Invention Product D: Comparative product E: Comparative product

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiroyuki Nakaishi Inventor Hiroyuki Nakage 1431-12 Kindeji, Kamigori-cho, Ako-gun, Hyogo Prefecture Harima Research Institute, Sumitomo Electric Industries, Ltd. Address Sumitomo Electric Industries, Ltd., Kumatori Factory (72) Inventor Takuma Yoshizaka, Kumatori-cho, Sennan-gun, Osaka Prefecture 950 Noda, Sumitomo Electric Industries, Ltd. Kumatori Factory (72) Inventor, Kenichiro Miyatake Shimaya, Konohana-ku, Osaka City, Osaka Prefecture 1-3 1 Sumitomo Electric Industries, Ltd. Osaka Works

Claims (4)

[Claims] 1. A liquid heating container in which a fluororesin coating layer is formed on the inner surface of a metal container body, wherein at least a portion of the surface of the fluororesin coating layer forming the surface of the heating portion is exposed by irradiation with actinic rays. Water contact angle θ is 4
A liquid heating container, which is hydrophilized within a range of 0 to 110 °. 2. The formula R = (1-C [CH ₂ ] / C [total]) × on the surface of the fluororesin coating layer hydrophilized within a contact angle of water θ of 40 to 110 °.
The surface modification ratio R of the fluororesin layer defined by 100 [where C [total] is the total area of the C1s spectrum obtained by measurement by photoelectron spectroscopy, and C [C]
H ₂ ] is a value obtained by waveform separation processing of the peak area derived from CF ₂ among these. ] Satisfy | fills Formula R <= 135- (theta), The liquid heating container of Claim 1 characterized by the above-mentioned. 3. A method for producing a liquid heating container from a metal substrate having a fluororesin coating layer formed thereon, which comprises contacting at least a portion of the surface of the fluororesin coating layer forming a surface of a heating portion with water. By irradiating with ultraviolet light or ultraviolet laser light in the above state, or by irradiating with synchrotron radiation in a vacuum, the irradiated portion is made hydrophilic so that the contact angle with water is in the range of 40 to 110 °. A method for manufacturing a liquid heating container, comprising: 4. The temperature of water is raised to 50 to 100 ° C. in the step of irradiating with ultraviolet rays or ultraviolet laser light in a state where at least the portion forming the surface of the heating portion of the surface of the fluororesin coating layer is in contact with water. The method for manufacturing a liquid heating container according to claim 3, wherein the irradiation is performed by irradiating the liquid heating container.