JP2828008B2 - Liquid heating container and method of manufacturing the same - Google Patents

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 particularly, to a liquid heating container, in which a rising prevention layer is formed by hydrophilizing the surface of a fluororesin coating layer, there is no malfunction due to premature breakage, and the contamination resistance is excellent. Liquid heating container and a method for manufacturing the same. The liquid heating container of the present invention is used as a container for an electric liquid heater such as an electric pot.

[0002]

2. Description of the Related Art Electric liquid heaters are widely used as electric pots and sake brewers because they can easily and safely heat or maintain liquid. The electric liquid heater is provided with a container (liquid heating container) for storing 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 the temperature warm. These heat sources and temperature sensors are
Usually, it is arranged 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, loud noise is generated, and the surface inside the container where the bubbles are generated due to bumping is overheated and the surface temperature increases,
This could lead to malfunction of the temperature sensor.

Conventionally, various proposals have been made to deal with the bumping problem of the liquid heating container. For example,
(1) A method of providing a fluorine resin coating layer on the inner surface of a container (Japanese Patent Publication No. 52-14665), and (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). JP-A-5-123246, (3) a method of providing a boiling agent layer of an inorganic powder, an organic polymer, or the like on a fluororesin coating layer (JP-A-5-123246); A method of imparting hydrophilicity to the surface of the treated film by corona discharge treatment (Japanese Patent Application Laid-Open No. 4-371116) has been proposed.

Generally, in order to heat a liquid quickly and uniformly with an electric liquid heater, 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 more difficult to prevent bumping on the inner surface of the container near the heat source. For this reason, for example, even if a fluororesin coating layer is provided on the inner surface of the container by the method (1), bubbles become large and an overheating state occurs.
When this overheating condition occurs on the temperature sensor, the temperature sensor operates regardless of the hot water temperature, causing a 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.

When the bumping prevention layer formed by spraying a metal oxide is provided by the method (2), the bumping itself can be considerably reduced, but the surface roughness of the bumping prevention layer is reduced to 50 to 150 μm.
And the layer thickness must be as large as 50 to 400 μm. However, when the surface roughness increases, dirt such as water scale easily adheres to the recesses on the surface, and thus the stain resistance decreases. Moreover, if the bumping prevention layer is made thicker, the thermal conductivity at that portion is reduced. Although the boiling preventive agent layer obtained by the method (3) can be reduced in thickness, it has poor stain resistance and an increased amount of water residue. ) Is as high as 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 formed on the surface to be treated, and deterioration of the strength of the fluororesin coating layer is inevitable. Only about 70% of the strength of the untreated material can be maintained. In addition, corrosion components and the like penetrate from the generated cracks, and as a result, the fluororesin coating layer peels off at the interface with the container and swells, so that the durability of the container decreases.

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 in the presence of a compound having at least 28 kcal / mol of atoms and a hydrophilic group to hydrophilize the film (Japanese Patent Application Laid-Open No. 7-1995). No. 3057). In this method, by irradiating a fluororesin film with ultraviolet rays in the presence of a compound such as aluminum hydroxide, boric acid, ammonium borate, lithium hydroxide, calcium hydroxide, barium hydroxide, etc. Some of the atoms have been replaced with hydrophilic functional groups. According to this method, the fluororesin film can be hydrophilized, and it is possible to hydrophilize the inside of the porous fluororesin film. However, when this method is applied to a method for hydrophilizing a liquid heating container having a fluororesin coating layer formed thereon, dirt such as water scale easily adheres to a portion to be treated, and as the number of boiling water increases, the contact angle of the portion to be treated increases. Is significantly reduced.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a liquid heating container which is provided with a rising prevention layer due to hydrophilicity of a fluororesin coating layer, does not malfunction due to premature breakage, and is excellent in stain resistance. It is to provide a manufacturing method. The present inventors have conducted intensive studies to overcome the problems of the prior art, and as a result, in a container having a fluororesin coating layer formed on the inner surface, at least the inner surface of the container (heating portion) corresponding to a heating source and a temperature sensing portion. It has been found that the above object can be achieved by irradiating the surface of the fluororesin coating layer (surface) with actinic light such as ultraviolet light, ultraviolet laser light, or synchrotron radiation to form a hydrophilized layer. When irradiating with ultraviolet light or ultraviolet laser light, the irradiated part is irradiated in contact with water, while when irradiating with synchrotron radiation, it is irradiated in a vacuum to obtain a fluororesin coating. The surface of the layer can be made hydrophilic so as to have a desired contact angle, and the contamination resistance inherent to the fluororesin coating layer can be maintained at a high level. 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 an inner surface of a metal container main body, wherein at least a heating portion surface of the fluororesin coating layer surface is formed. The liquid heating container is characterized in that the portion to be treated is hydrophilized by irradiation with actinic rays so that the contact angle θ with respect to water is in the range of 40 to 110 °. Further, according to the present invention, in a method for manufacturing a liquid heating container from a metal substrate on which a fluororesin coating layer is formed, water is applied to at least a portion of the fluororesin coating layer surface which forms a heating portion surface. Irradiation with ultraviolet light or ultraviolet laser light in a state of being in contact with, or irradiation with synchrotron radiation in a vacuum, the water contact angle of the irradiated portion is 40 to 110.
The method for producing a liquid heating container is characterized in that the container is made hydrophilic so as to fall within the range of °.

The liquid heating container obtained by the production method of the present invention has a water contact angle θ on the surface of the fluororesin coating layer.
Is in the range of 40 to 110 °, and the surface modification rate R of the surface is represented by the formula R ≦ 135−θ.
Is satisfied, whereby the stain resistance is excellent and the decrease in the 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 the value of the peak area derived from CF ₂ obtained by waveform separation processing. is there. Also,
When irradiating an ultraviolet ray or an ultraviolet laser beam in a state where at least a portion of the surface of the fluororesin coating layer which forms the surface of the heating section is in contact with water, the temperature of the water is 50 to 10
When the temperature is raised to 0 ° C. for irradiation, the irradiation efficiency can be increased.

[0011]

According to the present invention, even if a heat source and a temperature sensing portion are provided on the outer surface of the bottom of the liquid heating container, the temperature sensor does not prematurely break due to bumping, and the film strength of the fluororesin coating layer is increased. A liquid heating container is provided which is strong and has a much higher contamination resistance than conventional products. The liquid heating container of the present invention is used as a container for storing and heating 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.
The heat source 3 and the temperature sensing unit 4 are arranged on the outer surface of the bottom of the container in close contact with each other. 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 section of the fluororesin coating layer 5 inside the container 2 includes:
The layer 6 in which the surface of the fluororesin coating layer is hydrophilized is formed.

The liquid heating vessel main body is manufactured using a metal base material such as aluminum (including aluminum alloy) and stainless steel. A fluorine resin coating layer is provided on the inner surface of the container. Examples of the fluororesin include polytetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkylvinyl ether copolymer (PFA), and tetrafluoroethylene / hexafluoropropylene copolymer (FEP).

The fluororesin coating layer can be formed by coating a fluororesin paint, drying and sintering in a conventional manner. To make a liquid heating vessel, the surface of a metal disk such as stainless steel or aluminum is usually roughened by blasting, electrolytic etching, chemical etching, etc. Is dried and fired to form a disc having a fluororesin coating layer, which is pressed into the shape of a container.

In the present invention, at least a portion of the surface of the fluororesin coating layer on the inner surface of the container, which forms the surface of the heating portion, is irradiated with an actinic ray so as to be hydrophilized so that the contact angle with water is in the range of 40 to 110 °. I do. The heating section surface is usually the inner bottom surface of the container. The hydrophilic treatment by irradiation with actinic rays is performed by irradiating actinic rays on at least a portion of the metal disk on which the fluororesin coating layer is formed, which is to be the surface of the heating section, and then press-forming into a container shape. . When there is a possibility that the hydrophilicity of the surface may be degraded by the press working, after the press working into the shape of the container, the surface of the fluororesin coating layer in the portion to be the surface of the heating portion of the container is irradiated with actinic rays to make it hydrophilic. It can be performed.

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

In order to perform 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 vacuum. In the method of irradiating an ultraviolet ray or an ultraviolet laser beam in a state where at least a portion of the surface of the fluororesin coating layer which forms the surface of the heating section is in contact with water, the temperature of the water is preferably 50 to 100 ° C, more preferably 80 to 100 ° C. When irradiation is carried out at a temperature raised to ° C., the hydrophilicity is improved, and the irradiation time can be shortened in the case of obtaining the same contact angle with water. For example, if the water temperature is 100 ° C
(The state of boiling water)
C), the same contact angle with water can be obtained in about 1/10 of the time when the irradiation treatment is performed at the same temperature, and the cost can be reduced.

The degree of hydrophilization by irradiation with actinic rays can be quantitatively expressed by the contact angle θ with water. The contact angle with water is determined by measuring the contact angle with water by a liquid method using a contact angle meter (CA-A) manufactured by Kyowa Interface Science Co., Ltd. In the present invention, the hydrophilic treatment is performed so that the contact angle with water is in the range of 40 to 110 °. If the irradiation amount of the actinic ray is too small and the contact angle with water is too large, the hydrophilicity is not sufficient and a malfunction of the temperature sensing unit tends to occur, and conversely, the irradiation amount is too large and the contact angle with water is large. Is too small, the film strength (tensile strength) of the fluororesin coating layer decreases, or the amount of adhered contaminants increases. The preferable range of the contact angle with respect to water is as follows.
Comprehensively evaluate the ability to prevent premature breaks and determine. Preferred contact angles with water are 50-105 °, more preferably 70-95.
°.

When irradiating with ultraviolet laser light (for example, KrF excimer laser light), the irradiation amount is usually 0.5 to 2000 J / cm ² , preferably 5 to 50 J / cm ² .
It is adjusted 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, one having a peak wavelength of usually 1 to 200 nm, preferably 1 to 100 nm is used. To irradiate ultraviolet rays or ultraviolet laser light by bringing the irradiated portion of the fluororesin coating layer surface into contact with water, a water layer portion made of quartz glass as a window material is applied to the irradiated portion of the fluororesin coating disc. There is a method of providing. When irradiating after pressing a fluororesin-coated disk into the shape of a container, similarly, provide an aqueous layer with quartz glass as a window material at the irradiated part, or irradiate with water at the bottom of the container. I do. In order to raise the water temperature, a method of heating from a side opposite to the surface to be irradiated by an appropriate heating means is simple.

The fluororesin coating layer 5 is intended to prevent contamination. However, the formation of the hydrophilized layer 6 by irradiation with actinic rays facilitates the generation of air bubbles and does not cause a sudden rise or overheating. You can do so. Compared to the conventional method of providing a boiling agent layer of an inorganic powder or an organic polymer on the fluororesin coating layer, in the present invention, only the surface of the fluororesin coating layer is made hydrophilic,
The hydrophilized layer can be made extremely thin, typically 1 μm or less, preventing a decrease in thermal conductivity, hardly deteriorating film strength (tensile strength), excellent in stain resistance, and taking advantage of the inherent advantages of the fluororesin coating layer. ing. Further, in the present invention, a boiling agent is not required, and the treatment can be performed at low cost. Unlike the conventional high-frequency discharge treatment or high-frequency corona discharge treatment, the surface of the fluororesin coating film does not have cracks that cause strength deterioration and corrosion.

The surface of the fluororesin coating layer is coated with aluminum hydroxide, boric acid, ammonium borate, lithium hydroxide, calcium hydroxide, and hydroxide according to the hydrophilization method disclosed in JP-A-7-3057. When an aqueous solution of a compound such as barium is brought into contact and irradiated with ultraviolet rays, hydrophilicity can be achieved, 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 between the production method of the present invention and the hydrophilization method described in the publication. found.

That is, according to the manufacturing method of the present invention, the following relational expression is established between the water contact angle θ of the irradiated portion on the surface of the fluororesin coating layer and the surface modification rate R. I 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 that satisfies 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 that satisfies the above relational expressions and cannot be obtained.

Here, the surface modification rate R (%) is obtained by evaluating the surface structure (range of about 1 nm or less below the surface) of the fluororesin coating layer by photoelectron spectroscopy (XPS). , Can be defined by the following equation. R = (1−C [CH ₂ ] / C [total]) × 100 C [total] is the total area of the C1s spectrum obtained by photoelectron spectroscopy, and C [CH ₂ ]
Is the value of the peak area derived from CF ₂ obtained by the waveform separation processing. Specific measurement conditions are shown in Examples. In the sample before reforming (all CF ₂ bonds), R = 0, and in the completely reformed state (without CF ₂ bonds), R = 100. As shown in FIG. 4, in the case of the same contact angle with respect to water, since the surface modification ratio R is different, the modified fluororesin coating layer according to the present invention, which has both high hydrophilicity and stain resistance (adhesion resistance to water scale). The surface structure of
It can be presumed that this is different from that obtained by the hydrophilization method disclosed in JP-A-3057.

[0023]

The present invention will be described below more specifically with reference to examples and comparative examples. In addition, the evaluation method of various physical properties is as follows.

(1) Contact angle θ with water 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) Adhesion amount of 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 and dried, and then attached. The amount of the kimono was measured. (3) Tensile strength Sample length (chuck interval): 30 mm Sample width: 10 mm Test speed: 100 mm / min. (4) Presence or absence of premature expiration One liter of water was put into each sample pot, heated, and the temperature at the time of sounding the alarm of completion of boiling was measured. The case where the temperature at that time was 99 ° C. or less was evaluated as having prematurely cut off. (5) Surface modification ratio R (%) Measurement was performed by photoelectron spectroscopy using the following apparatus under the following conditions. Each sample was cut into 1 cm square, subjected to acetone ultrasonic cleaning (5 minutes), dried, and immediately introduced into a sample chamber for measurement. An electron neutralizing gun was used to prevent sample charge-up. The surface modification ratio R was calculated from the obtained spectrum according to the above equation. Apparatus: ESCA5400 X-ray source: MgKα Central energy: 1253.6 eV Acceleration voltage: 15 kV, 400 W (used without monochromatization) Sample chamber pressure: 2.0 × 9 Torr or less Photoelectron extraction angle: 10 °

Example 1 An aluminum disk was subjected to electrochemical etching in an aqueous solution of sodium chloride with an amount of electricity of 30 Q / cm ² to form fine irregularities on the surface.
Further, this surface was subjected to anodizing treatment in 15% sulfuric acid at 15 V for 5 minutes to provide a hard layer on the etched surface. A fluororesin paint (Polyflon D-1F manufactured by Daikin Industries, Ltd.) was applied to the 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 is press-formed, a water layer is provided on the surface of the portion serving as the bottom surface of the container using quartz glass as a window material and is brought into contact with water. (Wavelength: 248 nm) with 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 with water, stain resistance, and tensile strength (the tensile strength was measured in the same lot for a destructive test) were measured. Next, after this is pressed 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 One liter of water was put into the electric pot, heated and a quick-off test was performed. Table 1 shows various characteristics of the sample in which the irradiation amount was changed.

[0026]

[Table 1]

From the results shown in Table 1, it was found that the contact angle with water was 110 ° or less, and it did not prematurely break. Water contact angle is 40 °
When the irradiation is carried out to less than the above, the film strength is deteriorated, and the amount of contaminants attached increases. Observation of the hydrophilized surface showed that no deterioration such as cracking was observed in the fluororesin coating film, indicating that there was no problem in durability. Comparable results were obtained with a type in which the container and the heat source or the temperature sensor could be separated.

Example 2 An aluminum disk 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 applied to about 100 μm. C. and dried at about 380.degree. C. for 15 minutes. Next, using an ultraviolet lamp (UV lamp manufactured by Eye Graphics Co., Ltd .; metal halide type, M03-L31), a water layer portion was provided using quartz glass as a window material, and a fluororesin-coated aluminum plate was brought into contact with water. Light was applied for 3, 30, 60, 300, and 3000 seconds, respectively, with different irradiation times. By increasing the irradiation time and the irradiation amount,
The water contact angle was reduced from the original 118 ° to 70 °, and hydrophilicity could be imparted. Irradiation with UV light in air as a reference did not change the contact angle with water. Then, it was pressed into the shape of a heating container, and a heat source and a temperature sensing unit were attached to form an electric pot, and various characteristics were measured. When 1 liter of water was put into the electric pot and heated, when the contact angle with water became 110 ° or less, the water became hydrophilic when boiling, so that the bubbles on the surface proceeded smoothly and the area occupied by the bubbles was reduced. It became smaller, and the volume of the boiling sound could be reduced, and at the same time, it did not prematurely cut.

[0029]

[Table 2]

Next, the water temperature was raised to 100 ° C. and examined. The contact angle with respect to water was lower by about 10 ° than at room temperature.
Therefore, when trying to obtain the same contact angle with respect to water, the irradiation time may be about 1/10 of normal temperature, and it has been found that the cost can be reduced.

Example 3 An aluminum disk was subjected to electrochemical etching in an aqueous solution of sodium chloride with an amount of electricity of 30 Q / cm ² to form fine irregularities on the surface.
Further, this surface was subjected to anodizing treatment in 15% sulfuric acid at 15 V for 5 minutes to provide a hard layer on the etched surface. A fluororesin paint (Polyflon D-1F manufactured by Daikin Industries, Ltd.) was applied to the 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. Further, a PTFE colored paint (component ratio after drying and sintering: PTFE / PFA 78%, adhesive 3%, pigment 19
%) Was applied thereon to a thickness of about 10 μm. Next, using a UV lamp (Metal halide type, M03-L31, manufactured by Eye Graphics Co., Ltd.)
UV light is applied to a fluororesin-coated aluminum plate that has been provided with an aqueous layer using quartz glass as a window material and 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 water contact angle was reduced from the original 128 ° to 81 °, and hydrophilicity could be imparted. Then, it was pressed into the shape of a heating container, and a heat source and a temperature sensing unit 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 with water is within the range specified in the present invention (110 ° to 40 °), the amount of contaminants attached is small, the tensile strength is high, and premature breakage does not occur. Recognize. When 1 liter of water is put into a pot that satisfies the requirements of the present invention and heated, when boiling, since it is hydrophilic, bubbles on the surface are smoothly separated, the area occupied by bubbles is reduced, and the volume of boiling sound is reduced. Can be made smaller, and at the same time, it no longer cuts quickly.

Example 4 An aluminum disk was subjected to electrochemical etching in an aqueous solution of sodium chloride with an amount of electricity of 30 Q / cm ² to form fine irregularities on the surface.
Further, this surface was subjected to anodizing treatment in 15% sulfuric acid at 15 V for 5 minutes to provide a hard layer on the etched surface. A fluororesin paint (Polyflon D-1F manufactured by Daikin Industries, Ltd.) was applied to the 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,
A water layer is provided with quartz glass as a window material and brought into contact with water,
SR (SynchrontronRad)
irradiation), with peak wavelengths of 1, 5, 100, 150, 200, and 220 nm, respectively.
(The irradiation time was constant at 150 seconds). Table 4 shows the results.

[0035]

[Table 4] If the peak wavelength exceeds 200 nm, the contact angle with water becomes 11
Beyond 0 °, premature cutting occurs.

[Embodiment 5] An electric pot with a power consumption of 800 W equipped with a heat source and a temperature sensor on the bottom outer surface (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.) having a thickness of about 2
It was coated to a thickness of 0 μm, dried at about 100 ° C., and then sintered at about 380 ° C. for 15 minutes. Next, by irradiating SR light having a peak wavelength of 150 nm to only the bottom surface of the container for 150 seconds in a vacuum of 10 ^-5 torr or less, a heating container was prepared in which only the surface of the bottom coating portion was made hydrophilic. The water contact angle of the bottom surface thus obtained is 8
5 °, and the irradiated surface was analyzed by X-ray photoelectron spectroscopy. As a result, -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 generation of cracks was observed on the irradiated surface. When 1 liter of water was put into an electric pot prepared from this sample and heated, the temperature reached 100 ° C. after 8 minutes and 30 seconds. At the time of boiling, since the bottom surface was made hydrophilic and the contact angle with water was reduced, 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. In addition, since the surface of the fluororesin coating layer is hydrophilic, the temperature sensor provided at the bottom of the container accurately detects the temperature of water, and does not malfunction (no premature disconnection).

Example 6 An aluminum disk was subjected to electrochemical etching in an aqueous solution of sodium chloride with an amount of electricity of 30 Q / cm ² to form fine irregularities on the surface.
Further, this surface was subjected to anodizing treatment in 15% sulfuric acid at 15 V for 5 minutes to provide a hard layer on the etched surface. A fluororesin paint (Polyflon D-1F manufactured by Daikin Industries, Ltd.) was applied to the 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 becomes the bottom surface when the fluororesin coated plate is press-molded, the SR light having a peak wavelength of 150 nm is irradiated with 10 ^-5 torr while the surface of the disk is kept in a disk shape.
Irradiation was performed for 150 seconds in the following vacuum. After this was 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 the container. When 1 liter of water was put into the obtained electric pot and heated, 100 minutes after 8 minutes and 40 seconds,
° C was reached. Air bubbles from the bottom surface proceeded smoothly, and did not rise, nor did the temperature detector cut off prematurely. The water contact angle of the hydrophilized surface was 88 °, and the amount of contaminants attached 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 put in this electric pot and heated, 100 minutes after 8 minutes
° C was reached. Air bubbles from the bottom surface proceeded smoothly, and did not rise, nor did the temperature detector cut off prematurely. The contact angle with water of the hydrophilized surface was 67 °, and the amount of contaminants attached was 0.05 mg / cm ² .

[Embodiment 8] In each of the above embodiments, the irradiation treatment was performed at normal temperature (20 ° C.).
The water contact angle was measured by changing the water temperature during irradiation. An aluminum disk is placed in an aqueous sodium chloride solution at 30 Q /
Electrochemical etching was performed with an amount of electricity of cm ² to form fine irregularities on the surface. Further, this surface was subjected to anodizing treatment in 15% sulfuric acid at 15 V for 5 minutes to provide a hard layer on the etched surface. Fluorine resin paint (Polyflon D-1F manufactured by Daikin Industries, Ltd.)
m and dried at about 100 ° C.
Sintered at 80 ° C. for 15 minutes. Next, using an ultraviolet lamp (UV lamp manufactured by Eye Graphics Co., Ltd .; metal halide type, M03-L31), a water layer portion was provided using quartz glass as a window material, and a fluororesin-coated aluminum plate was brought into contact with water. Light was irradiated for 60 seconds,
Upon irradiation, the water temperature was set at 20 ° C., 60 ° C. and 10 ° C., respectively.
Irradiation was performed after the temperature was changed to 0 ° C. (boiling state). Table 5 shows the results.

[0040]

[Table 5]

As is evident from the experimental results in Table 5, as the temperature of the water to be brought into contact with the surface to be treated of the fluororesin coating layer is increased, the degree of decrease in the contact angle with respect to water is reduced even with the same UVV irradiation time. It turns out that it is big. Room temperature (2
0 ° C.), a significant difference is observed in the contact angle with water at a water temperature of 60 ° C., and when the temperature is around 100 ° C., the reactivity is remarkably improved, and an attempt is made to obtain the same contact angle with water. About 1 in case
An irradiation time of / 10 is sufficient.

Example 9 An aluminum disk was subjected to electrochemical etching in an aqueous solution of sodium chloride with an amount of electricity of 30 Q / cm ² to form fine irregularities on the surface.
Further, this surface was subjected to anodizing treatment in 15% sulfuric acid at 15 V for 5 minutes to provide a hard layer on the etched surface. A fluororesin paint (Polyflon D-1F manufactured by Daikin Industries, Ltd.) was applied to the 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, an ultraviolet lamp (UV lamp manufactured by Eye Graphics Co., Ltd .; metal halide type, M03-L3)
1) Using a quartz glass window material as a window material, providing a water layer portion and irradiating UV light at room temperature to a fluororesin-coated aluminum plate that has been brought into contact with water, adjusting the irradiation time, so that the contact angle with water is Samples of 50 ° (sample A), 67 ° (sample B), and 80 ° (sample C) were prepared. On the other hand, in accordance with the hydrophilization method of JP-A-7-3057, instead of water, a 4.1% by weight aqueous solution of boric acid was used, and the UV irradiation conditions were adjusted in the same manner as described above, so that the contact angle with respect to water was respectively increased. 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. Table 6 shows the results.

[0043]

[Table 6]

The relationship between the contact angle θ with respect to water and the surface modification ratio R of the samples A to E is plotted in FIG. As is clear from FIG. 3, in the case of the same contact angle with water (A and D, B and E), according to the production method of the present invention, JP-A-7-3057
It can be seen that the surface modification ratio is smaller than that obtained by the hydrophilization method in Japanese Patent Application Laid-Open No. H10-260,086. Next, samples A and B (products of the present invention),
Each of the samples D and E (comparative products) was pressed into a heating container. A heat source and a temperature sensor were attached to the outer surface of the bottom of each container. One liter of water was put in each of the obtained electric pots, heated and boiled. The number of times of water boiling was set to one, and water was newly replaced, and a similar water heating experiment was performed. The water contact angle of the UV-irradiated surface was measured each time the water was heated. FIG. 4 is a graph showing the relationship between the number of water heaters and the measurement result of the contact angle with water.

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 respect to water even when the number of boiling waters is increased. That is, the product of the present invention is excellent in durability. On the other hand, Japanese Patent Application Laid-Open No. 7-3
No. 057 obtained by the hydrophilization method (samples D and E) show that when the original contact angle with water is 50 ° (sample D), the contact angle with water is 40 with the number of boilings of about three times.
When the contact angle of the original is 67 ° (sample E), the contact angle with water becomes smaller than 40 ° with the number of boiling waters of about 10 times. As described above, in the case of the samples D and E, the rapid decrease in the contact angle with respect to water is presumed to be due to adhesion of water scale and the like.

[0046]

According to the present invention, there is provided a liquid heating container which is provided with a rising prevention layer due to hydrophilization of the surface of a fluororesin coating layer, does not malfunction due to premature breakage, and has excellent contamination resistance, and a method of manufacturing the same. Provided. In the production method of the present invention, since the fluororesin coating layer is subjected to hydrophilic treatment by irradiation with actinic rays such as ultraviolet rays, ultraviolet laser light, and synchrotron irradiation light, bumping is suppressed while suppressing deterioration in the strength of the fluororesin coating layer. It is possible to obtain a liquid heating container which can be completely prevented, does not cause a malfunction of the excessive sensor, can improve bubble elimination, and has excellent contamination resistance.

[Brief description of the drawings]

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

FIG. 2 is a schematic cross-sectional view of one embodiment showing the structure of the bottom 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 a fluororesin coating layer subjected to a hydrophilic treatment.

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

[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 product B: Present product C: Present invention Product D: Comparative product E: Comparative product

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroyuki Nakaishi 1431-12 Kotoge, Kaneji-cho, Kamigori-cho, Ako-gun, Hyogo Prefecture Inside the Harima Research Laboratory, Sumitomo Electric Industries, Ltd. Address Sumitomo Electric Industries, Ltd.Kumatori Works (72) Inventor Takuma Yoshisaka 950, Kojiri-cho, Kumatori-cho, Sennan-gun, Osaka Prefecture Sumitomo Electric Industries, Ltd.Kumatori Works (72) Inventor Kenichiro Miyatake 1-chome Shimaya, Konohana-ku, Osaka-shi, Osaka No. 1-3 Sumitomo Electric Industries, Ltd. Osaka Works (56) References JP-A-6-98828 (JP, A) JP-A-3-269024 (JP, A) JP-A-6-228343 (JP, A) (58) Field surveyed (Int.Cl. ⁶ , DB name) A47J 27/00-27/13 A47J 27/20-27/64 A47J 29/00-29/06 A47J 33/00 A47J 36/00-36 / 42 C18J 7/00 304

Claims (4)

(57) [Claims] 1. A liquid heating container in which a fluororesin coating layer is formed on an inner surface of a metal container main body, wherein at least a portion of the surface of the fluororesin coating layer which forms the surface of the heating section is activated 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 θ of 40 to 110 ° with respect to water.
The surface modification rate R of the fluororesin layer defined by 100 [where C [total] is the total area of the C1s spectrum obtained by photoelectron spectroscopy, and C [C
H ₂ ] is the value of the peak area derived from CF ₂ obtained by the waveform separation processing. Satisfies the formula: R ≦ 135−θ. The liquid heating container according to claim 1, wherein 3. A method for producing a liquid heating container from a metal substrate having a fluororesin coating layer formed thereon, wherein said portion is brought into contact with water at least at a portion of the surface of said fluororesin coating layer which forms the surface of a heating portion. By irradiating ultraviolet light or ultraviolet laser light in a state of being irradiated, or by irradiating synchrotron radiation light in a vacuum, so that the irradiated portion becomes hydrophilic so that the contact angle with water is in the range of 40 to 110 °. A method for producing a liquid heating container, comprising: 4. A step of irradiating an ultraviolet ray or an ultraviolet laser beam in a state where at least a portion of the surface of the fluororesin coating layer which forms the surface of the heating section is in contact with water, raising the temperature of the water to 50 to 100 ° C. 4. The method for producing a liquid heating container according to claim 3, wherein the irradiation is performed.