JP2002085257A - Electric hot water heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric hot water heater which suppresses the adhesion of dirt to the inside surface of a container, does not degrade the taste and smell of hot water, has a metallic luster feel and is excellent in appearance. SOLUTION: A film which consists essentially of a fluororesin or at least one kind of a polyimide resin and polysulfone resin and does not contain pigments, is formed at a thickness of 05 to 3.0 μm on the inside surface of the container which has an arithmetical mean deviation of profile of <=2.0 μm and has such a gentle corrugated shape as to attain H<W when the mean height of ruggedness is defined as H and the mean width as W as the rugged shape of the surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric water heater used in general households and the like. The present invention relates to an electric kettle that provides easy-to-drink water or hot water.

[0002]

2. Description of the Related Art Ferritic stainless steel having excellent corrosion resistance is mainly used for a container of a conventional electric water heater. However, such a configuration has a problem that dirt such as water scale adheres when used, and a problem that the adhered dirt is very difficult to remove.

For this reason, recently, a substance such as a fluororesin or a silicon resin having a smaller adhesive energy than the substance constituting the container is coated on the inner surface of the container with a polyimide resin (hereinafter referred to as “P”).
I ") or polyether sulfone resin (hereinafter" P ").
It has been proposed to form a film layer using a heat-resistant resin having excellent adhesiveness such as ES ") and has been put to practical use (see Japanese Patent Publication No. 52-14665).

[0004] Further, there has been proposed an electric water heater in which the smoothness of the film surface is increased by increasing the ratio of PES to the fluororesin, and the antifouling property is more excellent.

[0005]

However, even in such an improved electric water heater, the color tone remains the same as that of the conventional electric water heater and is colored gray or brown. This is because, in a conventional coating method such as spray coating, the film thickness is 5 to 20 μm or more, and therefore, it is necessary to add a pigment as a constitutional agent in order to prevent sagging. As a result, the metallic feeling of the base material was completely impaired, and the marketability was reduced.

[0006] In addition, since the conventional paint contains several additives such as pigments in addition to the resin as the main component, the smell and taste of hot water that comes into direct contact with the water at the time of boiling and keeping the temperature (hereinafter referred to as “water quality”) ).

On the other hand, since a blast treatment is generally performed with crushed alumina particles as a base treatment for ensuring the adhesion of the film, even if a clear paint excluding pigment is applied, the color Had no metallic luster and was rather a dull image.

An object of the present invention is to solve such a conventional problem, and an object of the present invention is to provide an electric water heater in which the merchantability is ensured and the odor and taste of hot water are suppressed as much as possible.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a method for reducing the blast roughness on the inner surface of a container by securing the roughness required for adhesion and suppressing the extreme roughness. A film having a glossy feeling was formed. This makes it possible to provide an electric water heater with improved commercial value.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of an electric water heater having a container for storing a liquid according to an embodiment of the present invention; At least one of
0.5 ~
It is formed with a thickness of 3.0 μm, and the surface shape of the inner surface of the container in contact with the film has a center line average roughness of 2.0
An electric water heater having a shape of irregularities on the surface of not more than μm and having an average width of the irregularities larger than an average height of the irregularities.

The invention according to claims 2 and 3 is achieved by performing a blast treatment with a bead-like blast material, particularly a blast material containing zirconium oxide as a main component, in order to form the surface shape of the inner surface of the container. Things.

By performing the blasting treatment with the bead-like blasting material in this manner, the average roughness of the blast surface on the inner surface of the container represented by Ra is maintained at a constant value and, for example, the maximum roughness (Rmax) or the like is determined. Extremely large roughness represented by ten point average roughness (Rz) can be suppressed. In addition to ensuring the properties, it is possible to keep the metallic luster of the base material and to suppress defects that lead to the deterioration of the physical properties of the film as much as possible. In addition, by using a blast material containing zirconium oxide as a main component as a bead-like blast material, a decrease in adhesion and corrosion resistance due to the composition of the blast material when general stainless beads or glass beads are used. It is difficult to occur, and a film having more excellent durability can be obtained. Further, by forming a film containing no pigment, it is possible to leave a metallic luster of the base material and to suppress a decrease in the quality of the hot water.

[0013] Then, after securing a constant value of the average roughness of the blast surface of the inner surface of the container represented by Ra, an extremely large average represented by, for example, the maximum roughness (Rmax) or the ten-point average roughness (Rz). Since the roughness can be suppressed, the adhesion of the film can be ensured, and the metallic luster of the base material can be left, and defects that reduce the physical properties of the film can be suppressed as much as possible.

The invention according to claim 4 is a method of firing a film by firing in a furnace in a reducing atmosphere.

When the metal is heated in a normal furnace during the firing of the film, an oxide film is generally formed on the surface and the color tone changes. When cleaning with citric acid, which is recommended as a care for the electric water heater, is performed, the oxide film is reduced only in the portion where the citric acid is immersed, and the color tone is restored to cause an uncomfortable feeling. If this is fired in a furnace in a reducing atmosphere, the initial color tone change can be suppressed, and a series of phenomena can be suppressed.

The invention according to claims 5 to 7 uses an airless low-pressure atomization coating method as a method for forming a film, rotates a container at a high speed of 600 rpm or more at the time of coating, or performs intermittent coating. This is done by using a method.

By using an airless low-pressure atomization coating method in which atomization particles are small as compared with a normal spray coating method, a dense film is formed.
Even if there is no pigment or a thin film, it is possible to suppress the deterioration of film properties.

Further, by coating the container by rotating the container at a high speed, sagging can be suppressed and a uniform and stable film can be formed even with a thin film.

Further, by performing the coating intermittently, the drying can be promoted during the coating.
Even with paint that is easy to sag without a pigment, the sagging limit is raised, the range of coatable film thickness is widened, and a wide range of film thickness requirements can be met.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a sectional view of an electric water heater according to a first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes an outer case, in which a bottomed cylindrical container 2 is housed. A water level line 3 indicating the amount of water supply is engraved on a side surface of the container 2, and a heater 4 is integrated on a lower side. Further, a film 13 is formed on the inner surface of the container 2. Reference numeral 5 denotes an upper cover that covers the container 2. Further, a temperature sensor 11 for measuring the liquid temperature is attached so as to be in contact with the lower side of the container 2, and this temperature sensor is connected to a temperature control function unit 12 to control the temperature of hot water. When the tapping button 6 is pressed, the number of rotations of the electric pump 8 connected to the liquid outlet 7 from the container changes depending on the degree of pressing, and the tapping means through which the liquid is discharged from the discharge port 10 through the tapping pipe 9. It has.

A container was prepared in which the blast roughness and the film thickness of the inner surface of the container 2 of the electric water heater were as shown in Table 1 below. As the blast material, beads of zirconium oxide were used, and each surface roughness was realized by changing the conditions of the particle size of the blast material and the blast pressure. As the film, a dispersion (clear) containing a fluororesin as a main component was used. The coating was performed with a manual spray gun so as to have a predetermined film thickness, and baked at 320 ° C. for 10 minutes.

The evaluation results of these prototype containers are also shown in Table 1. Here, "corrosion resistance" indicates the corrosion state of the film after 4% saline was put in a container and left in a warm state for 20 days (hereinafter referred to as "4% salt water test"). ○ indicates “significant corrosion and no hole in the container”, Δ indicates “slightly corroded and no hole in the container”, and X indicates “significant corrosion or hole in the container”.

The "adhesion" was determined by placing a 4% saline solution in the same container as the corrosion resistance and evaluating the adhesion of the film by a cellotape (registered trademark) peel test. ◎ indicates no peeling even after repeating cellophane tape peeling 10 times in the same place, ○ indicates 1 point or less peeling of 1 mm ² or less (no practical problem), △ indicates 1 time of cellophane tape 1m by peeling
When a plurality of point-like peelings having a size of m ² or less occurred, × indicates that a surface peeling of 1 mm ² or more occurred.

The term “water quality” is a symbol indicating the average value of the taste and smell of hot water boiled by an electric water heater using each container, as judged by a plurality of panelists based on sensory evaluation.

"Appearance" indicates the level of metallic glossiness.
Indicated by x.

The comprehensive evaluation shows the sum of the results of these evaluations.

[0028]

[Table 1]

As can be seen from the results of (Table 1), No.
Although the corrosion resistance and adhesion of No. 2 were poor, it is considered that this was because the leveling of the film was insufficient due to the thin film thickness and the bonding force in the lateral direction was weak.

In the case of the thick film No. Sample No. 6 formed a film by repeating recoating, since sagging occurred in the coating method in which a predetermined amount was applied to the inner surface of the container at one time. As the evaluation results, the items of adhesion and water quality were poor, but this was weakened due to the weakening of the bonding force in the thickness direction due to the repeated coating, and also a somewhat disadvantageous direction for the thick water distribution. Is considered as a factor.

On the other hand, no. In No. 8, it is considered that the film could not completely cover the surface of the base material because the surface of the base material was rough, and the corrosion resistance was lowered due to the portion.

The hot water tapping means of this embodiment is configured to discharge the hot water inside the container by the electric pump 8 interlocked with the pressing and pressing of the tapping button 6. However, it is needless to say that the air pump is used. There is no restriction on the means of the present embodiment, such as a method of tapping or a method of direct pouring.

Example 2 An electric water heater similar to that of Example 1 was used, except that the main component of the film on the inner surface of the container was a fluororesin to which a pigment was added. The processing conditions and the evaluation results of the appearance are shown in No. 1 of Example 1. The results are shown in Table 2 in comparison with No. 1.

[0034]

[Table 2]

As can be seen from (Table 2), the sample containing no pigment had a metallic luster. In No. 9, even when the film thickness was 1 μm, which was considerably thinner than the conventional product, the metallic luster was lost. However, if you adjust the color tone and film thickness of the pigment to be added,
It is considered possible to give a metallic luster.

(Embodiment 3) In an electric water heater similar to that of Embodiment 1, the main component of the coating on the inner surface of the container is PI or PES.
Created. Table 3 shows the processing conditions and evaluation results.
Shown in

[0037]

[Table 3]

No. 10 does not perform blast processing,
This is a film in which PI is the main component. No. Nos. 11 and 12 are formed by forming a coating mainly composed of PI or PES.

These samples satisfied all of the basic evaluation items listed in (Table 3). In particular, regarding the color tone of the appearance, No. 10 had a metallic luster and was very good. No. 11 and 12 all have metallic luster, but slightly different colors were obtained as listed in (Table 3).

In this embodiment, only the resin which is the main component is used alone. However, it goes without saying that each resin can be used by mixing at an arbitrary ratio without being limited to this. .

(Embodiment 4) In an electric water heater similar to that of the first embodiment, No. No. 1 (fired in a normal batch furnace), 13 was fired using a furnace in a reducing atmosphere. Each of these samples was painted by an air spray method.

Table 4 shows the color tone after baking and the presence or absence of color tone change after washing with citric acid. The conditions for washing with citric acid were such that 80 g of citric acid was added to 3.3 L of water, heated for 2 hours after boiling, and the color tone was confirmed after 30 cycles. ○ indicates no discoloration, Δ indicates partial discoloration (bleaching), and X indicates complete discoloration (bleaching). Other conditions are the same as in the first embodiment.

[0043]

[Table 4]

The color tone of No. 1 is considered to be a discoloration due to a so-called temper color in which an oxide film is formed on the surface of the base material by heating during firing. Discoloration (decolorization) by citric acid
The mechanism of this is that the citric acid solution enters through minute pinholes in the film, reduces the oxide film on the surface of the base material, and returns the color tone. As a result, the color after firing is discolored.

On the other hand, no. Since No. 13 was fired in a reducing atmosphere, no oxide film was formed, and the color tone of the base material was kept as it was after firing. Therefore, it is considered that discoloration (decolorization) by citric acid does not occur.

(Embodiment 5) In an electric water heater similar to that in Embodiment 1, basically, No. Samples were prepared with the same specifications as in Example 1 except that the coating method was changed to the airless low-pressure atomization method (Table 5).

Here, the airless low-pressure atomization method will be described.
I will tell. In general, airless air is compressed air inside the nozzle.
While supplying and atomizing the paint, the nozzle shape is modified.
Husband and also apply pressure to paint (liquid) to atomize
Low-pressure atomization means that pressure is conventionally applied to liquid paint.
100 kg / cm^TwoNeed about
However, by raising the liquid temperature, the pressure applied to the paint
30-50Kg / cm ^TwoAtomization with a moderate pressure
is there. The airless low-pressure atomization method has a higher fog than the conventional method.
Particles become very small, forming a dense coating film
Liquids such as citric acid solution are difficult to permeate
You.

These samples were tested for citric acid washing in the same manner as in Example 4, and the results of the discoloration at that time are also shown in (Table 5).

[0049]

[Table 5]

As is clear from Table 5, when the rotation speed of the container at the time of coating was 600 rpm or more, no discoloration due to washing with citric acid was observed, and good results were obtained. This is thought to be because the airless low-pressure atomization method paints very fine particles over and over again, and fills the pinholes existing in the film, compared to those applied by air spray. . However, when the rotation speed was 300 rpm, the effect was not sufficient, and the color was removed by washing with citric acid.

(Embodiment 6) In an electric water heater similar to that of Embodiment 1, A sample was prepared under the same conditions as in Example 15 except that the film thickness was changed. Each processing condition (Table 6)
Shown in

These samples were evaluated for “appearance” and “wear resistance”. Here, “abrasion resistance” was evaluated as ○ when the base was not exposed after rubbing 600 times with a nylon scourer soaked in water. Table 6 also shows these evaluation results.

[0053]

[Table 6]

As is clear from Table 6, Example 5
Sample no. For No. 15, coating was performed to 2 μm by the same method (continuous ejection) (No. 17), but sagging occurred after drying and firing, and sufficient characteristics could not be obtained in appearance. Further, the abrasion resistance is slightly poor due to uneven coating such as sagging.

On the other hand, no. 18 is ON for 0.2 seconds
The coating was performed by intermittent discharge for /0.8 seconds OFF. This is referred to as an intermittent coating method, in which the discharge of paint is performed intermittently at intervals. In this way, by providing an interval, drying of the paint was promoted, and a good film could be formed without sagging. The abrasion resistance for the specified number of times was also good. In addition, the film can be made thicker.

[0056]

As is clear from the above examples, according to the present invention, the adhesion of the film is ensured, the deterioration of the film is suppressed as much as possible, and the deterioration of the physical properties is suppressed, and the metallic luster of the substrate is reduced. It is possible to provide an electric kettle having high residual merchantability.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an electric water heater showing an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Outer case 2 Container 4 Heater 5 Top lid 6 Tapping button 7 Liquid outlet 8 Electric pump 9 Tapping pipe 10 Discharge port 11 Temperature sensor 12 Temperature control unit 13 Coating

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B24C 3/32 B24C 3/32 Z 11/00 11/00 D (72) Inventor Satoshi Shimizu Kadoma, Osaka No. 1006, Ojimon, Matsushita Electric Industrial Co., Ltd. DA23 DB01 DC38 EB16 EB39

Claims (7)

[Claims] 1. An electric water heater having a container for storing a liquid, wherein an inner surface of the container is provided with a coating containing at least one of a fluorine resin, a polyimide resin and a polyether sulfone resin as a main component and containing no pigment. 5-3.
Formed at a thickness of 0 μm, and the surface shape of the inner surface of the container in contact with the film has a center line average roughness of 2.0 μm
An electric water heater having a shape in which the average width of the unevenness is larger than the average height of the unevenness as the shape of the unevenness on the surface. 2. The electric water heater according to claim 1, wherein the inner surface of the container is blasted using a bead-like blast material to form the surface shape. 3. The electric water heater according to claim 2, wherein the blast treatment is performed with a blast material containing zirconium oxide as a main component. 4. The electric water heater according to claim 1, wherein the film is fired in a reducing atmosphere. 5. The electric water heater according to claim 1, wherein the film is formed by an airless low-pressure atomization coating method. 6. When forming a film, the container is rotated 600 times /
The electric water heater according to any one of claims 1 to 5, wherein the coating is performed by rotating at a high speed for at least minutes. 7. The method according to claim 1, wherein an intermittent coating method is employed when forming the film.
An electric kettle according to the item.