JPH07114753B2 - Heating container and manufacturing method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating container for heating a liquid containing polar molecules such as water. In particular, a film containing at least one component of fluororesin is formed on the inner surface of the container, and the surface of the film is The present invention relates to a heating container that has been subjected to high-frequency discharge treatment or high-frequency corona discharge treatment, and a method for manufacturing the heating container.

[0002]

2. Description of the Related Art Conventionally, a container for containing a liquid such as water and a heat source for heating the outer surface of the container are provided, and at least a portion of the inner surface of the container facing the heat source is bonded more than a substance forming the container. There has been proposed an attempt to reduce the boiling noise of a liquid by forming a coating film made of a substance having a small energy, for example, a fluorine resin (Japanese Patent Publication No. 52-14665).

[0003]

However, the fact that the boiling sound of a liquid does not become so small by simply forming a coating film on the inner surface of the container made of a substance having a smaller adhesive energy than the substance forming the container, It is known from experiments and research conducted by the present inventors. For example, a fluororesin or the like having excellent weather resistance and non-adhesiveness has a hydrophobic surface, and is known as a substance having a relatively small adhesive energy with water which is a polar molecule. Here, the adhesion energy means the work amount required to separate the liquid contacting the surface of the solid from the solid.

Here, when water is put into a container having a coating made of a fluororesin and heated to the boiling point, the boiling phenomenon will be described by paying attention to a minute portion in the container. Part of the heated container rises in temperature and transfers heat to the surrounding water, and when part of its water molecules reaches the boiling point, it becomes water vapor and undergoes a phase transition from liquid to gas. As shown in FIG. 2a, when it becomes water vapor, the volume expands to generate bubbles 6, and until the buoyancy of the bubbles 6 becomes larger than the adhesive energy between the fluororesin 3 and the bubbles 6,
The state of being attached to the fluororesin 3 continues. At this time, since the hydrophobicity of the fluororesin 3, that is, the adhesive energy between the fluororesin 3 and the water 5 is small, the water 5 existing around the bubble 6 tends not to enter the gap between the bubble 6 and the fluororesin 3, and 6
Due to the increase in the adhesiveness between the fluororesin 3 and the fluorine resin 3, the bubbles 6 adhere to the inner surface of the container until the volume of the bubbles 6 becomes considerably large.

By the way, when a temperature sensor is provided at the bottom of the container to detect the boiling point of water to control a heating source such as a heater, if large bubbles adhere to the inner bottom of the container as described above, Due to the adiabatic effect of the bubbles, the thermal resistance between the water and the temperature sensor increases, and the temperature sensor detects the temperature of the bubbles even though the actual temperature of the water is much lower than the boiling point. However, there is a problem that it is difficult to detect the temperature accurately. For example, a cartridge heater formed in a planar shape on the bottom of a cylindrical container and a temperature sensor arranged at the center of the bottom, and when the temperature sensor outputs a signal corresponding to the boiling point of water, the cartridge heater is energized. When the temperature was detected to stop, the output of the temperature sensor was detected as a signal corresponding to about 100 ° C, even though the actual temperature of the water in the container was about 80 ° C, and the current flowed. since thus cut, problem of undesirable condition can not be heated to a higher temperature
There was In addition, large bubbles are generated,
Withdrawal, and have you in the process of rupture or the like in the liquid surface, the larger boiling
Produces sound. Therefore, the inner surface of the container is made of fluororesin
It is difficult to reduce the volume of boiling noise by simply forming a film
There was a problem that was.

In order to solve the above-mentioned conventional problems , the present invention forms a coating film made of a fluororesin on the inner surface of a container,
By imparting hydrophilic properties to the surface of the coating,
It is an object of the present invention to provide a heating container capable of accurately detecting the temperature of water and reducing the volume of boiling noise, and a manufacturing method thereof.

[0007]

In order to solve the above-mentioned problems, the heating container of the present invention is a heating container in which a coating film containing at least one component of a fluororesin is formed on the inner surface of the container, and at least the coating film is formed. It is characterized in that the surface of the heating portion has cracks and has a hydrophilic property.

Further, in the method for manufacturing a heating container according to the present invention, a resin containing at least one component of a fluororesin is baked and coated on the inner surface of the container to form a film, and then the surface of the film is subjected to a high frequency discharge treatment. Alternatively, high frequency corona discharge treatment is performed to form cracks on at least the surface of the heating portion of the coating film and impart hydrophilicity thereto.

[0009]

According to the above-mentioned configuration of the present invention, the fluorine of the heating container is
At least the surface of the heated portion of the base resin coating has cracks and
By being hydrophilic, the volume of bubbles when boiling is
Get smaller. That is, the synergy between hydrophilic treatment and cracking
Due to the action, the bubbles generated during heating become fine and
As a result, the temperature sensor installed at the bottom of the container
It becomes possible to detect with high accuracy, and the temperature control operation
Stabilize. You can also reduce the volume of the boiling sound.
Wear. More specifically, the inner surface of the container is made of fluororesin.
And a high frequency discharge treatment or
Is subjected to high-frequency corona discharge treatment, the surface of the fluororesin, which was hydrophobic, is dissected from the molecular chains or the surface gradually collapses.
Due to cross-linking, oxidation, hydrogen bonding, ozonation, etc., the surface tension is increased, the hydrophilic property is imparted or enhanced, and minute cracks are formed. Therefore, as shown in FIG. 2b, when the adhesion energy with water 5 which is a polar molecule becomes large and bubbles 6 are generated on the inner surface of the container,
The water 5 existing around the bubbles 6 immediately becomes the bubbles 6 and the fluororesin 3
The bubbles 6 will enter the gap and will be removed from the container while the volume of the bubble 6 is small .

Therefore, since the surface of the fluororesin has a hydrophilic property, it becomes difficult for bubbles to adhere to the container, and it is possible to prevent an increase in thermal resistance between the water and the temperature sensor. Further, since the wettability with water is improved, the temperature sensor provided at the bottom of the container can detect the temperature of water with high accuracy. In addition, since the growth of bubbles is suppressed,
In the process of foam generation, separation from the container, rupture on the liquid surface, etc.
The volume of the boiling sound is reduced.

In addition, for example, since a coating made of a fluororesin is formed on the surface of a metal container, the container has good chemical resistance, non-adhesiveness, hydrophobicity, weather resistance and stain resistance,
It also has a long life.

Further, in the method for producing a heating container of the present invention, a resin containing at least one component of a fluororesin is baked and coated on the inner surface of the container to form a film, and then the surface of the film is subjected to a high frequency discharge treatment or a high frequency treatment. By the corona discharge treatment, hydrophilicity and wettability can be imparted to the surface of the fluororesin to improve the surface energy easily.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the heating container of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of the heating container of the present invention.

A coating 3 made of a fluororesin is formed on the inner surface of the container body 2 made of metal such as stainless steel or aluminum. In order to facilitate understanding, the thickness of the resin cross section is exaggerated in the drawing. In reality, the thickness of the container body 2 is about 1 mm, and the thickness of the coating film 3 is 5 μm to 100 μm.
The range of μm is preferred.

The fluororesin used in the present invention is polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (PEP),
Ethylene-tetrafluoroethylene copolymer (ETF
E), tetrafluoroethylene-perfluoroalkylvinylether copolymer (PFA), ethylene-chlorotrifluoroethylene copolymer (ECTFE), tetrafluoroethylene-hexafluoropropylene-perfluoroalkylvinylether copolymer (PEPE),
There are polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVdF), etc., especially P
PTFE or PFA for TFE, PFA and heat resistant resin
Modified PTFE, modified PFA and the like in which are dispersed are preferable.

The surface of the coating film 3 is subjected to high-frequency discharge treatment or high-frequency corona discharge treatment to impart properties such as hydrophilicity and wettability. Here, the scanning electron microscope (SE
The result of observing the surface state of the coating film using M) will be described. FIG. 3 is a copy of the SEM photograph of the coating surface before the high frequency discharge treatment, and FIG. 4 is a copy of the SEM photograph of the coating surface after the high frequency discharge treatment.

Observing FIG. 3a before the treatment, it can be seen that the pock-shaped depressions are uniformly distributed in the irregularities having a large period in which shaded portions are shaded. FIG. 3b is a copy of an SEM photograph enlarged about 7 times as large as that of FIG. 3a. A shadow corresponding to a pock-shaped depression is seen in the shaded area, and thin and small crack-like cracks are newly formed. Observed as a structure.

Next, when observing FIG. 4A after the treatment, FIG.
Similar to “a”, pit-shaped depressions are uniformly distributed in the irregularities having a large period. However, FIG. 4 enlarged about 7 times.
Looking at b, it can be seen that a large number of thick and large-scale cracks are formed by the high frequency discharge treatment. Such large-scale cracks indirectly indicate the presence of molecular chain incision or surface disintegration, cross-linking, oxidation, hydrogen bonding, ozonation, etc. on the surface of the resin.

FIG. 5 shows how water is heated by providing a temperature sensor and a heater at the bottom of such a heating container. The temperature sensor 11 is fixed to a depression at the bottom of the heating container and detects the temperature of the bottom of the container and indirectly detects the temperature of water.
The output of the temperature sensor 11 is input to the temperature control circuit 14. The cartridge heater 12 is provided so that the entire bottom of the heating container is heated, and its lead wire is connected to a power supply source such as a commercial power source via a switching device 15 such as a relay. When the water in the container reaches the boiling point when the energization is started, the output of the temperature sensor 11 changes to the reference value generator 1.
3, the temperature control circuit 14 commands the switching device 15 to stop energization. When the temperature of the water in the container falls below another reference value due to natural heat radiation or the like, the temperature control circuit 14 commands the switching device 15 to start energization. In this way, the temperature of the water in the container is set near the boiling point.

Here, the state in which water is actively boiling will be described. The hydrophilic property is imparted or enhanced by the high-frequency discharge treatment of the coating film containing at least one component of the fluororesin. Therefore, as shown in FIG. 2b, the adhesion energy between the resin 3 and the water 5 becomes large, and when the bubbles 5 are generated on the inner surface of the container, they are separated from the container while the volume is small. Therefore, the volume of the boiling sound during the process of bubble generation, separation from the container, rupture on the liquid surface, etc. became extremely small.

Further, since the wettability between the surface of the resin and water becomes good, the temperature sensor provided at the bottom of the container can detect the temperature of water with high accuracy because the heat insulating property of bubbles is reduced. It was possible to realize stable temperature control.

Next, one embodiment of the method for manufacturing a heating container according to the present invention will be described with reference to the drawings. Polyethersulfone, which is a heat-resistant resin, is mixed with polytetrafluoroethylene, which is a fluorine resin, in an amount of 5% by weight to 70% by weight,
A coating was formed by coating the inner surface of a container made of metal so as to have a predetermined thickness, drying, and baking.

Then, the surface of the coating is rendered hydrophilic by using a high frequency discharge treatment apparatus as shown in FIG. Here, the outline of the high frequency discharge processing will be described. The oscillator 21 is
It outputs a voltage of about 175 V at a frequency of 18 kHz to 25 kHz and is connected to the primary side of the step-up transformer 23. The secondary side of the step-up transformer 23 outputs a voltage of about 50 kV by connecting two coils in series. One output is connected to the discharge electrode 24, and the other output is connected to the counter electrode 25.

A work such as a container is inserted between the two electrodes and the switch 22 is turned on. Then, a high voltage electric field is generated around the discharge electrode 24, and free electrons in the air are accelerated and collide with gas molecules in the air to generate ions to emit electrons, and the number of electrons is increased one after another to accelerate. "Avalanche phenomenon" occurs. The electrons activated in the discharge collide with the surface of the coating film formed on the surface of the work, and the molecular chains on the surface of the coating film are dissociated or broken down, cross-bonded, oxidized, hydrogen-bonded, ozonized, etc. Cause Therefore, the hydrophilic property is imparted or enhanced, and the surface tension of the coating surface becomes large. As described above, by using the method of subjecting the resin coating of the heating container to the high frequency discharge treatment, it is possible to easily provide the coating surface with hydrophilicity.

Further, instead of the above-mentioned high frequency discharge treatment,
The hydrophilicity can be easily imparted to the surface of the coating film also by performing the high frequency corona discharge treatment. FIG. 7 is a schematic view of an example of a high frequency corona discharge treatment device used in the method for manufacturing a heating container according to the present invention. It differs from the high-frequency discharge treatment apparatus shown in FIG. 6 in that an insulating coating 26 made of glass, ceramics or the like is formed on the entire surface of the discharge electrode 24. The discharge electrode 24 in FIG. 7 has a shape in which a conductive wire is connected from the center of a disk-shaped conductive plate, but it is preferable to use an electrode shape according to the shape of the container. In particular, when the member to be processed has a planar shape, as shown in FIG. 8, the discharge electrode 24 having the insulating coating 26 formed on the surface of the U-shaped conductive wire can be used.

Corona discharge occurs between the insulating coating 26 and the container 1, and similarly to the high frequency discharge treatment, the activated electrons in the discharge collide with the coating surface to dissect molecular chains or gradually collapse the surface. , Cross-linking, oxidation, hydrogen bonding, ozonation, etc. are caused, and hydrophilic property is imparted to the film surface.

Next, specific examples of the method of manufacturing the heating container of the present invention will be described in detail. After degreasing the surface of the container made of aluminum and roughening the surface by sandblasting, a transparent fluororesin paint (TC manufactured by Daikin Industries, Ltd.
-7808GY) was applied to a thickness of about 15 μm, dried at about 100 ° C., and then baked at about 380 ° C.

Next, using a discharge treatment device as shown in FIG. 6, the distance between the heating container and the discharge electrode was set to about 4 cm, and a high frequency voltage of about 40 kV was applied for about 5 to 10 seconds. In this way, the heating container of the present invention could be easily obtained.

[0029]

As described in detail above, the heating container of the present invention has a coating film containing at least one component of a fluororesin formed on the inner surface of the container, and the surface of the coating film is subjected to high-frequency discharge treatment, which causes cracks. When formed , the adhesive energy with water is increased to impart or enhance the hydrophilic property, and the volume of bubbles during boiling is reduced. That is,
Due to the synergistic effect of hydrophilic treatment and cracks,
The resulting bubbles become finer and, as a result, can be placed at the bottom of the container.
The built-in temperature sensor can detect the temperature of water accurately.
This enables the temperature control operation to be stabilized. Further , the volume of the boiling sound can be reduced.

Further, in the method of manufacturing the heating container of the present invention, the surface of the resin containing at least one component of the fluororesin is hydrophilic,
Since it is easy to provide the wettability and improve the surface energy, the product price of the heating container of the present invention can be reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a heating container according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing how bubbles are generated during boiling.
2A shows the case where the resin coating is untreated, and FIG. 2B shows the case where the resin coating of one embodiment of the present invention is subjected to the high frequency discharge treatment.

FIG. 3 is a copy of an SEM photograph of the surface of the coating film before the high frequency discharge treatment according to the embodiment of the present invention.

FIG. 4 is a copy of an SEM photograph of the surface of the coating film after the high frequency discharge treatment according to the embodiment of the present invention.

FIG. 5 is an example of how water is heated by providing a temperature sensor and a heater at the bottom of the heating container of the present invention.

FIG. 6 is a schematic view of an example of a high-frequency discharge treatment device used in the method for manufacturing a heating container according to the present invention.

FIG. 7 is a schematic view of an example of a high-frequency corona discharge treatment device used in the method for manufacturing a heating container according to the present invention.

FIG. 8 is an example of a discharge electrode of a high frequency corona discharge treatment device.

[Explanation of symbols]

 1 Heating Container 2 Container Body 3 Resin Coating 5 Water 6 Bubbles 11 Temperature Sensor 12 Cartridge Heater 13 Reference Value Generator 14 Temperature Control Circuit 15 Switching Device 21 Oscillator 22 Switch 23 Boost Transformer 24 Discharge Electrode 25 Counter Electrode 26 Insulating Coating

Claims (2)

[Claims] 1. A heating container in which a coating film containing at least one component of a fluororesin is formed on the inner surface of the container, wherein at least the surface of the heating portion of the coating film has cracks and has a hydrophilic property. And heating container. 2. An inner surface of a container is baked and coated with a resin containing at least one component of a fluororesin to form a coating film, and then the surface of the coating film is subjected to a high frequency discharge treatment or a high frequency corona discharge treatment to form the coating film. A method for producing a heating container, which comprises forming a crack on at least the surface of the heating portion and imparting hydrophilicity thereto.