JP2009034378A - Heating vessel for cooking and method for manufacturing heating vessel for cooking - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heating vessel for cooking with a fluorocarbon resin coating layer capable of generating minute foams. <P>SOLUTION: The coating layer made to be hydrophilic by compounding PFA (tetrafluoroethylene perfluoroalkoxyvinylether copolymer) or PTFE (tetrafluoroethylene resin) and a filler more hydrophilic than the PFA or the PTFE is arranged on the inner face of at least the bottom wall of a base material forming the bottom wall and a peripheral wall, the compounding rate of the filler in the coating layer is 20 wt.% to 80 wt.%, and a part of the filler is exposed in the surface of the coating layer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a cooking container for cooking and a method for producing the same, and is suitably used as an inner pot of an electromagnetic induction heating type or an electric rice cooker. Particularly, a large number of small bubbles are generated from the bottom wall side to improve convection, and up and down. Cook rice without uneven heating.

Conventionally, in a heating container for cooking, a water-repellent fluororesin coating layer has been provided from the viewpoints of preventing sticking (non-adhesive) of cooked food such as cooked rice filled in the container, preventing contamination of the inner surface, and preventing rust. Often formed on the inner surface of the container.
However, in the container provided with the fluororesin coating layer, since the water contact angle of the coating layer is 100 ° or more and rich in water repellency, the generated bubbles tend to grow into relatively large bubbles. When the bubbles become large, it becomes difficult to convection during cooking, and large bubbles tend to remain on the surface of the fluororesin coating layer. In this case, the fluororesin coating layer on the bottom wall in the vicinity of the heat source and the rice are blocked by the bubbles and the heat conduction is reduced. As described above, if large bubbles are generated inside the rice cooking container and water is not sufficiently convected, the temperature in the container is not uniform, cooking of the upper layer is insufficient, and rice cooking unevenness is likely to occur.
In addition, if there is a fluororesin coating layer on the bottom wall of the container near the heat source, bumping phenomenon is likely to occur, and the bottom wall surface where bubbles are generated due to bumping is overheated, causing malfunction of the temperature sensing unit. There are also problems that are easy to invite.

  As described above, when the water contact angle of the fluororesin coating layer is large, the bubbles are likely to be large. Therefore, if the water contact angle is reduced to make it hydrophilic, the bubbles can be made small. When small bubbles are generated, it becomes easy to generate multiple fine convections during cooking, and the occurrence of bumping can be suppressed. As a result, the temperature inside the container can be made uniform and cooked without unevenness. Become.

In order to solve the problem of bumping, the applicant of the present invention disclosed in Japanese Patent Application Laid-Open No. 8-256913 (Patent Document 1) irradiated with ultraviolet rays or ultraviolet laser light in a state where the surface of the fluororesin coating layer of the liquid heating container is in contact with water. Thus, a liquid heating container is provided that is hydrophilized so that the contact angle with water is in the range of 40 ° to 110 °.
Further, the present applicant has disclosed in JP-A-11-178715 (Patent Document 2) a liquid heating container that has been hydrophilized by irradiating with ultraviolet rays or an ultraviolet laser in a state in which a methylcellulose aqueous solution is in contact with the surface of the fluororesin coating layer. providing.

JP-A-8-256913 JP-A-11-178715

In each of Patent Documents 1 and 2, the surface of the fluororesin coating layer is irradiated with ultraviolet rays or ultraviolet laser light to make it hydrophilic, so that there is a problem that the process becomes complicated and the cost increases.
Furthermore, since Patent Documents 1 and 2 are intended for liquid heating containers such as electric pots, the durability required for rice cooking containers and the like, and the anti-sticking function (non-adhesiveness) are not required. A function to prevent sticking is also required.
According to the experiments of the present inventors, when the hydrophilization method of the fluororesin coating layer of Patent Documents 1 and 2 is used, there is a problem that the durability and the anti-sticking function required for the rice cooking container cannot be satisfied.

  The present invention has been made in view of the above problems, and provides a cooking container that can generate a large number of small bubbles, has durability and a function to prevent sticking, and can be easily manufactured. Is an issue.

  In order to solve the above-mentioned problems, the present invention provides PFA (tetrafluoroethylene perfluoroalkoxy vinyl ether copolymer) or PTFE (tetrafluoroethylene resin) on at least the inner surface of the bottom wall of the base material forming the bottom wall and the peripheral wall. And providing a coating layer hydrophilized by blending a filler more hydrophilic than PFA or PTFE, the blending ratio of the filler in the coating layer is 20% by mass to 80% by mass, There is provided a heating container for cooking, wherein a part of the filler is exposed on the surface of the coating layer.

As described above, in the present invention, in the cooking container suitably used as an inner pot or the like of a rice cooker, the maximum continuous use temperature is 260 ° C. so that the function of preventing sticking and durability can be maintained on the bottom wall inner surface side. PFA or PTFE with excellent heat resistance and durability, non-adhesiveness and water repellency, and a filler more hydrophilic than PFA or PTFE so that small bubbles can be generated. Or the coating-film layer mix | blended with PTFE is provided.
When the coating layer is made of only PFA or PTFE, the water contact angle is about 110 °, and as described above, large bubbles are likely to be generated on the surface of the coating layer. However, in the present invention, it is more hydrophilic than PFA or PTFE. By blending 20% by mass to 80% by mass of the filler having the property, the water contact angle of the coating layer is reduced, and the coating layer is made hydrophilic compared to the simple substance of PFA or PTFE. As a result, compared to the case of a single coating layer of PFA or PTFE, the growth of bubbles can be suppressed and a large number of small bubbles can be generated, and the bubbles can be convected from the bottom side of the container to the upper side. Can do.
The blending ratio of the filler in the coating layer is set to 20% by mass to 80% by mass. If it is less than 20% by mass, it is difficult to make the contact angle with water less than 100 °, and it is impossible to make it hydrophilic. When the amount exceeds mass%, the amount of PFA or PTFE becomes too small, the binder action of the filler by PFA or PTFE is reduced, the filler is easily peeled off from the coating layer, and the non-adhesiveness of the coating layer is reduced. This makes it easier for rice to stick.
The blending ratio of the filler in the coating layer is preferably 40% by mass to 60% by mass.

As a filler having higher hydrophilicity than PFA or PTFE to be blended in the coating layer, the filler to be blended in the coating layer has a granular, flaky shape and / or hollow bead shape to increase the surface area. preferable.
Specifically, the filler is made of an inorganic material, silica, iron zirconia (iron zirconia ceramics composed of iron oxide and zirconium oxide), ceramics such as titanium oxide, diatomaceous earth, glass, metal such as aluminum, titanium coat, etc. It is preferable that the inorganic material such as mica is composed of one or more kinds selected from those having a hydrophilic coating on the surface.

As the ceramic, a broadly defined ceramic powder, hollow beads or flakes made of a nonmetallic inorganic material obtained through processes such as molding and firing can be used.
For example, an oxide containing at least one of aluminum oxide, chromium oxide, iron oxide, cobalt oxide, nickel oxide, silicon oxide (silica), titanium oxide, vanadium oxide, zinc oxide, zirconium oxide, and magnesium oxide; diatomaceous earth, kaolin Natural clay minerals such as natural mica (mica); other aluminosilicates such as synthetic mica and zeolite; glass; nitrides or carbides such as silicon, boron and titanium, borides, etc. Is mentioned.
The silica may be a solid powder or colloidal silica.
Moreover, metal flakes, such as aluminum, stainless steel, gold | metal | money, silver, titanium, can be used as said metal.
Those having an average particle diameter of 0.1 to 20 μm are preferably used.

The surface of the inorganic material made of ceramic or metal may be coated with metal or metal oxide. For example, a ceramic having a hydrophilic coating such as hydrophilic titanium oxide is suitably used. Instead of the hydrophilic titanium oxide, zinc, iron, aluminum or zirconium may be used, and titanium oxide, zinc oxide, iron oxide, aluminum oxide or zirconium oxide whose surface is coated with silica or aluminum hydroxide is used. May be.
Among these, titanium-coated mica in which mica is coated with hydrophilic titanium oxide is preferably used.

Among the fillers described above, one or more kinds selected from glass powder, hollow glass beads, hollow ceramic beads, iron zirconia powder, titanium oxide powder, diatomaceous earth powder, aluminum flakes, and titanium-coated mica powder are preferably used. be able to.
Among these, diatomaceous earth and iron zirconia having an average particle diameter of 0.1 μm to 20 μm are most preferably used. This is because when a coating film layer is formed by blending with PFA, it is likely to be distributed on the surface side of the coating film layer and exposed to the surface of the coating film layer.

The surface occupancy ratio of the filler on the surface of the coating layer is balanced with the surface occupancy ratio of PFA or PTFE, and is adjusted so as to generate a large number of small bubbles and have an anti-sticking function together. Preferably it is.
That is, it is the surface of the coating layer that comes into contact with water at the time of cooking rice, and the larger the surface occupancy is, the more the filler that is blended to reduce the contact angle with water is exposed on the surface. The water contact angle can be reduced to increase the degree of hydrophilicity, and the growth of bubbles can be suppressed to generate a large number of small bubbles. On the other hand, if the surface occupation ratio of PFA or PTFE becomes too small, non-adhesiveness is lowered and stickiness is inferior.

In the coating layer in which the filler other than the diatomaceous earth and iron zirconia is blended with PFA or PTFE, the surface side of the coating layer tends to have a large distribution of PFA or PTFE and the surface occupancy tends to be high. Since the film often sinks to the side, it is preferable to polish the coating layer about 1/3 from the surface to expose the filler to the surface of the coating layer.
By this polishing, the surface occupancy of the filler on the surface of the coating layer can be increased.
In addition, if the surface is roughened during polishing, the generation of small bubbles can be promoted.
In this case, the surface roughness is preferably 1 to 10 μm.
In addition, although unevenness may be formed on the surface of the coating layer during embossing or hot pressing, in this case, the unevenness is likely to increase, so that roughing by polishing is better.

In the heating container for cooking according to the present invention, the coating layer is provided on the inner surface of the bottom wall of the base material. However, a fluororesin coating layer is formed on the entire inner surface of the bottom wall and the peripheral wall of the container. The coating layer may be provided on the surface of the resin coating layer.
That is, when the material that is the base material is relatively non-adhesive and has a function of preventing sticking, it is only necessary to provide the coating layer on the inner surface of the bottom wall. When the fluororesin coating layer is formed on the entire inner surface of the container, non-adhesiveness, rust prevention and durability can be imparted to the entire inner surface of the container.
The fluororesin coating layer is not limited as long as it is a fluororesin system, but PFA or PTFE is also preferably used from the viewpoint of good binding properties with the coating layer.
In addition, the fluororesin coating layer formed on the surface of the base material of the container is not limited to one layer of the fluororesin coating layer made of PFA or PTFE, but a fluororesin coating layer made of PTFE is provided as a base layer. It is good also as a structure which provides the fluororesin coating layer which consists of said PFA.

  The cooking container according to the present invention is suitable for use as an inner pot of a rice cooker because it is easy to generate many small bubbles on the inner surface of the bottom wall and has a function of preventing sticking.

The rice cooker may be an electric rice cooker, but is preferably used as an electromagnetic induction heating rice cooker. When the inner pot of the electromagnetic induction heating rice cooker is used, the base material of the inner pot may be a nonmagnetic metal plate such as aluminum, aluminum alloy, nonmagnetic stainless steel, a carbon sintered plate, ceramics, It may be a sintered product of earth components such as diatomaceous earth.
In addition, a magnetic metal plate made of magnetic stainless steel, iron, iron alloy, nickel, nickel alloy, copper, copper alloy, cobalt, cobalt alloy or the like is provided at a position corresponding to at least the outer surface of the bottom wall of the base material serving as the inner pot. I have.
When the magnetic metal plate is provided on the entire surface of the bottom wall and the outer peripheral surface of the peripheral wall, a composite material made of a clad material of a nonmagnetic metal plate and a magnetic metal plate can be used as the base material.

The present invention further provides a method for producing the heating container for cooking,
A fluororesin coating layer made of PFA or PTFE is formed on the surface of a base material punched into a disk shape,
A coating solution containing PFA or PTFE and a filler is coated on the entire surface of the fluororesin coating layer on the surface of the fluororesin coating layer at a central portion of the base material or at intervals, and then baked and applied. Forming a membrane layer,
Thereafter, the present invention provides a method for manufacturing a cooking container for cooking, characterized in that the container is provided with a bottom wall and a peripheral wall by drawing press molding or hot press molding.

As described above, in this production method, a fluororesin coating layer made of PFA or PTFE is formed on the surface of the substrate in advance, and a coating liquid in which PFA or PTFE and a filler are blended on the coating layer. After coating, it is sintered to easily form a coating layer.
The coating is preferably performed by screen printing or spraying.
When a coating film layer is formed on a plate material as in this production method, and the bottom wall and the peripheral wall are formed by post-processing press, dot printing is possible, and screen printing is preferable because the coating range can be clearly controlled. In this case, since it is difficult to screen-print using PTFE, it is preferable to use PFA. In the present invention, since the particle size of the filler is reduced, it is advantageous for screen printing.
In addition, when apply | coating a coating liquid by a spray system and forming a coating film layer, both PFA and PTFE can be used suitably.

Furthermore, as another manufacturing method of the heating container for cooking of the present invention,
The coating layer is formed by coating at least the bottom wall of the substrate with a coating solution containing the PFA or PTFE and a filler over the entire surface or at intervals, followed by baking. The manufacturing method of the heating container for cooking is provided.

According to this manufacturing method, it is also possible to form a coating film layer directly on a container such as an earthen pot provided with a bottom wall and a peripheral wall in advance. That is, if the base material is preliminarily subjected to primer treatment to ensure the affinity between the base material and the coating film layer, the coating film layer can be formed without providing the fluororesin coating layer. Therefore, this manufacturing method can further simplify the formation of the coating layer, and can greatly reduce the manufacturing cost.
However, when a highly hydrophilic material such as a clay pot is used as the base material, the fluororesin coating layer is provided on the base material that has been subjected to the primer treatment in order to further enhance the durability. A coating layer may be provided.

As described above, in the heating container for cooking used as the inner pot of the rice cooker of the present invention, a coating layer containing a hydrophilic filler in PFA or PTFE is provided on the inner surface of the bottom wall. The water contact angle of the coating layer can be reduced, the growth of bubbles generated on the inner surface of the bottom wall can be suppressed, and a large number of small bubbles can be generated. Since these small bubbles can convection upward between the cooked rice, it is possible to equalize the temperature between the upper side and the lower side, and cook rice without uneven cooking.
Furthermore, sticking prevention function, durability and rust prevention can be provided by PFA or PTFE serving as a binder for the filler.

  Further, according to the method for manufacturing a heating container of the present invention, the coating layer is formed by coating on the upper surface of the central portion that becomes the bottom wall of the disk-shaped base material that forms the bottom wall and the peripheral wall by post-processing press. Therefore, processing is simplified, and the manufacturing cost can be reduced.

  Furthermore, according to another production method of the present invention, the coating layer can be formed on a base material having a bottom wall and a peripheral wall in advance. A film layer can be provided, and the application range of a base material can be expanded. Further, since it is possible to form a coating film layer without providing a fluororesin coating layer, the processing can be simplified and the manufacturing cost can be greatly reduced.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
The heating container for cooking of 1st Embodiment consists of the inner pot 1 of an electromagnetic induction heating type rice cooker.

  As shown in FIGS. 1 and 2, the inner pot 1 is a disk-shaped sintered plate obtained by sintering a clad material of a nonmagnetic metal plate 3 and a magnetic metal plate 4 provided with a fluororesin coating layer 2 made of PFA. A blank 6 is formed by punching, and a coating solution containing PFA and a filler is screen-printed at the center of the fluororesin coating layer 2 of the blank 6 and then baked to form a coating layer 7. Is processed into a shape having a bottom wall 10 and a peripheral wall 11 by hot pressing. The coating layer 7 is located on the inner surface of the bottom wall.

The coating layer 7 is blended with PFA using diatomaceous earth as a filler. In this embodiment, the blending ratio is 40 mass% PFA and the filler is 60 mass%.
In addition, it is good also considering the compounding quantity of a filler as 40 mass%, and the compounding quantity of PFA as 60 mass%.
The diatomaceous earth has an average particle size of 0.1 μm to 20 μm.

  200 parts by mass of PFA powder, 174 parts by mass of PFA dispersion (47% by mass of PFA spherical particles, 6% by mass of surfactant, 47% by mass of water), surfactant (“Otapol 45” manufactured by Sanyo Chemical Co., Ltd.) Product name) ") 500 parts by mass and 125 parts by mass of filler are blended to prepare a coating solution in which PFA and filler are dispersed in a liquid medium, and the coating solution is screen printed. . In the present embodiment, the coating liquid is printed on the entire surface of the portion that becomes the bottom wall 10 to form the coating layer 7 having a thickness of 20 μm.

  Since diatomaceous earth is used as the filler in the coating layer 7, a part of the diatomaceous earth is exposed on the surface of the coating layer 7, but the surface of the coating layer 7 is further roughened and polished. Diatomaceous earth is exposed, and the surface occupancy of diatomaceous earth is increased on the surface of the coating layer 7.

  After forming the coating layer 7, the blank 6 is hot-pressed to form the inner pot 1 shown in FIG.

In the inner pot having the above structure, the water contact angle on the surface of the coating layer 7 is 100 ° to 90 °, which is smaller than the water contact angle 110 ° when the coating layer is made of PFA alone, and is hydrophilic. Was achieved.
Further, since the surface of the coating layer 7 is exposed by dispersing the filler made of diatomaceous earth in PFA serving as a binder, the surface of the coating layer 7 has a local difference in thermal conductivity, The surface of the coating layer 7 is roughened and microscopic irregularities are formed.

Thus, by making the coating layer 7 hydrophilic and further roughening the surface, the growth of bubbles generated on the surface of the coating layer 7 on the inner surface of the bottom wall 10 during rice cooking is suppressed, and small bubbles are generated. Will occur in large numbers.
Therefore, the generation of large bubbles generated when a coating layer is formed from a single PFA can be suppressed, large bubbles can be prevented from staying on the surface of the coating layer, and the small bubbles can smoothly convection upward. Thus, the internal temperature of the inner pot 1 can be made uniform, and cooking with no uneven cooking can be performed.

In 2nd Embodiment, the filler mix | blended with PFA which forms the coating-film layer 7 is made into titanium coat mica, and the compounding quantity with respect to PFA is the same as that of 1st Embodiment.
A coating solution containing titanium-coated mica is applied to the fluororesin coating layer 2 to form a coating layer having a thickness of 30 μm. Since the surface of the coating layer is rich in PFA and the titanium-coated mica is sinking inside, 10 μm is polished from the surface to expose the titanium-coated mica on the surface of the coating layer 7.

  FIG. 3 shows a third embodiment, in which a coating layer 7 containing diatomaceous earth and PFA of the first embodiment is formed. The coating layer is formed by dot printing on the bottom wall 10 in the form of polka dots. ing.

FIG. 4 shows the inner pot 20 of the fourth embodiment, and the base 21 of the inner pot 20 is a clay pot made of diatomaceous earth sintered body or ceramics. A magnetic metal plate 4 is provided on the outer surface of the bottom wall of the earthenware pot for use in an electromagnetic induction heating rice cooker. In the present embodiment, the fluororesin coating layer 2 is not formed on the inner surfaces of the bottom wall and the peripheral wall, and the coating layer 7 of the first embodiment is directly formed on the base material 21. The coating layer 7 is formed in a dot shape on the inner surface of the bottom wall by spraying a coating solution through a masking plate having a large number of holes. In addition, the primer is previously apply | coated to the bottom wall inner surface of the earthenware pot which forms the coating-film layer 7, and the affinity with a coating-film layer is raised.
In the case of an earthenware pan, sticking of cooked rice is likely to occur, but in this embodiment, since a coating layer containing PFA is provided on the inner surface of the bottom wall, sticking of cooked rice to the bottom wall can be prevented.
Furthermore, since the coating layer is provided in a dot shape, a large number of small bubbles can be generated from the clay pot.
Further, a carbon sintered plate may be used as the base material 21 and the inner pot may be formed from a material made of a carbon sintered plate.

In 5th Embodiment, only the coating liquid which forms the coating-film layer 7 of 4th Embodiment is changed.
That is, in the present embodiment, a coating liquid containing PTFE is used instead of PFA. The blending amount of the filler with respect to PTFE is the same as the blending amount with respect to the PFA of the first embodiment.
Even if the resin blended in the coating layer is PTFE as in this embodiment, a cooking heating container in which a hydrophilic coating layer is formed on a base made of a clay pot made of diatomaceous earth sintered body or ceramics by a spray method. Can be produced.

In any of the first to fifth embodiments, the coating layer is provided only on the inner surface of the bottom wall, but may be provided on the inner surface of the peripheral wall.
In the first to fifth embodiments, one coating layer is formed, but two or three coating layers composed of PFA or PTFE and a filler may be formed.

  This invention can be used suitably not only for the inner pot of an electromagnetic induction heating type rice cooker but for an electric rice cooker. Furthermore, the present invention can be applied to various cooking heating containers such as a gas microwave oven, an electric microwave oven, a cooking heating container for an electromagnetic range, a frying pan, a Genghis Khan pan, and a hot plate plate.

It is a schematic sectional drawing of the inner hook of 1st Embodiment. It is drawing which shows the formation process of the inner hook of FIG. It is drawing which shows the formation process of the inner hook of 3rd Embodiment. It is a schematic sectional drawing of the inner hook of 4th Embodiment.

Explanation of symbols

1, 20 Inner pot 2 Fluorine resin coating layer 3 Non-magnetic metal plate 4 Magnetic metal plate 7 Coating layer

Claims (10)

  PFA (tetrafluoroethylene perfluoroalkoxy vinyl ether copolymer) or PTFE (tetrafluoroethylene resin) and more hydrophilic than PFA or PTFE are formed on the inner surface of at least the bottom wall of the base material forming the bottom wall and the peripheral wall. A coating layer that is made hydrophilic by blending a filler is provided, and the blending ratio of the filler in the coating layer is 20% by mass to 80% by mass, and a part of the filler is formed on the surface of the coating layer. A heating container for cooking, characterized in that is exposed.   The heating container for cooking according to claim 1, wherein the filler to be blended in the coating layer is in the form of particles, flakes or / and hollow beads and is made of an inorganic material.   The filler is one selected from ceramics such as silica, iron zirconia and titanium oxide, metals such as diatomaceous earth, glass and aluminum, and those obtained by applying a hydrophilic coating on the surface of the inorganic material such as titanium-coated mica. Or the heating container for cooking of Claim 2 which consists of multiple types.   The surface occupancy ratio of PFA or PTFE of the coating layer is roughened and polished, and the surface occupancy ratio of the filler on the polished coating layer surface is increased. The heating container for cooking according to any one of 3.   5. The method according to claim 1, further comprising: a fluororesin coating layer on an inner surface of the bottom wall and the peripheral wall of the base material, and the coating film layer provided on a surface of the fluororesin coating layer on the bottom wall. The heating container for cooking as described.   The heating container for cooking according to any one of claims 1 to 5, comprising an inner pot of a rice cooker.   It consists of an inner pot of an electromagnetic induction heating rice cooker, and the substrate is made of a non-magnetic metal plate, a carbon sintered plate, a sintered product of ceramics or ceramics, and a magnetic metal plate on at least the bottom wall outer surface of the inner pot The heating container for cooking according to any one of claims 1 to 6, comprising: It is a manufacturing method of the cooking container for cooking according to any one of claims 1 to 7,
The coating layer is formed by coating at least the bottom wall of the substrate with a coating solution containing the PFA or PTFE and a filler over the entire surface or at intervals, followed by baking. The manufacturing method of the heating container for cooking. It is a manufacturing method of the cooking container for cooking according to any one of claims 1 to 7,
A fluororesin coating layer made of PFA or PTFE is formed on the surface of a base material punched into a disk shape,
A coating solution containing PFA or PTFE and a filler is coated on the entire surface of the fluororesin coating layer on the surface of the fluororesin coating layer at a central portion of the base material or at intervals, and then baked and applied. Forming a membrane layer,
Then, the manufacturing method of the heating container for cooking characterized by making it the container provided with the bottom wall and the surrounding wall by drawing press molding or hot press molding.   The manufacturing method of the cooking container for cooking of Claim 8 or Claim 9 which grind | polishes and roughens the surface of the said coating-film layer.

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