JP7301007B2 - Refractory heating element manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a fire-resistant heating element, and more particularly to a method for manufacturing a fire-resistant heating element capable of generating heat by irradiating microwaves.

A heating element capable of generating heat by irradiating microwaves can rapidly heat the entire heating element by irradiating microwaves using, for example, a microwave oven or an industrial microwave irradiation apparatus. In addition, when heating, no flame is used and there is no need to use a liquid (water or oil) as a heat medium. In view of these advantages, heating elements capable of generating heat by irradiating microwaves are used in various applications such as cooking plates that generate heat in microwave ovens. Moreover, since such a heating element generates heat by absorbing microwaves, it can also be used as an electromagnetic wave absorber.

For example, Patent Literature 1 discloses a technique for a magnetite-containing silicone rubber composition in which magnetite is compounded into silicone rubber and further compounded with zinc oxide to prevent discoloration. For example, it is disclosed that discoloration of the composition can be suppressed when used in a high-temperature environment.

Japanese Patent Application Laid-Open No. 2009-149800

By the way, when such a heating element capable of generating heat by irradiating microwaves is used for a cooking plate heated by using a microwave oven, the user normally uses such a cooking plate only in the microwave oven. Inadvertently, such cooking pans may be used in hot gas ovens or exposed to open flames such as gas stoves.

Since the heat-generating part of the cooking plate is made of, for example, a silicone rubber composition in which magnetite is contained in silicone rubber, when exposed to high temperatures such as being exposed to an open flame, the rubber component decomposes and becomes a flammable gas. may occur, and the heat-generating part may foam, collapse, or peel off.

SUMMARY OF THE INVENTION An object of the present invention is to provide a fire-resistant heating element that is suppressed from deteriorating or deforming when exposed to high temperatures such as flames or open flames. Another object of the present invention is to improve the manufacturing quality of such refractory heating elements.

As a result of intensive studies, the inventors have found that at least one of the above problems can be solved by cross-linking an uncross-linked silicone rubber composition containing a microwave absorber and then sintering it to form a ceramic. perfected the invention.

The present invention relates to a method for producing a refractory heating element capable of generating heat by microwave irradiation, wherein a powdery or particulate microwave absorber that generates heat by microwave irradiation is added to an uncrosslinked silicone rubber composition. A first step of kneading, a second step of molding the uncrosslinked silicone rubber composition containing the microwave absorber obtained in the first step into a predetermined shape, and then a second step of crosslinking; A method for producing a refractory heating element, comprising a third step of firing a silicone rubber composition containing a crosslinked microwave absorber to form a ceramic (first invention).

In the first invention, the baking treatment in the third step is preferably performed at 270° C. to 330° C. (second invention). In the first invention, preferably, in the first step, the uncrosslinked silicone rubber composition is kneaded so that 50 to 1000 parts by weight of the microwave absorber is blended with 100 parts by weight of the uncrosslinked silicone rubber. (third invention). In any one of the first to third inventions, the microwave absorber preferably contains nickel zinc (NiZn) ferrite or manganese zinc (MnZn) ferrite (fourth invention).

According to the method for producing a refractory heating element of the present invention (first invention), the heating element capable of generating heat by microwaves is prevented from being altered or deformed when exposed to high temperatures such as flames or open flames. A refractory heating element is obtained. In addition, manufacturing defects such as cracks are less likely to occur in the obtained refractory heating element, and the manufacturing quality of the refractory heating element is improved.

Furthermore, in the case of the second invention, the fire resistance and manufacturing quality of the resulting heating element are further enhanced. In addition, in the case of the third invention, leanness in the baking process is particularly reduced, and the manufacturing quality of the refractory heating element is particularly improved. Further, in the case of the fourth invention, a refractory heating element is obtained whose heating properties are less likely to deteriorate even when exposed to high temperatures.

It is a sectional view showing the structure of the cooking plate of a 1st embodiment. It is a flowchart which shows a part of manufacturing process of the cooking plate of 1st Embodiment.

Embodiments of the invention will be described below with reference to the drawings, taking as an example a cooking plate capable of generating heat in a microwave oven and a method of manufacturing the same. The invention is not limited to the individual embodiments shown below, and can be implemented by changing the form.

FIG. 1 is a cross-sectional view showing the structure of the cooking plate 1 of the first embodiment. The cooking plate 1 has a metal plate 11 and a refractory heating element 12 attached to the bottom surface of the metal plate 11. - 特許庁The refractory heating element 12 is configured to generate heat by irradiating microwaves. When food is placed on the cooking plate 1 and irradiated with microwaves inside the microwave oven, the refractory heating element 12 generates heat. As a result, the temperature of the adjacent metal plate 11 becomes high, and the food can be grilled.

The metal plate 11 is made of a metal material such as a steel plate. The metal material is not particularly limited as long as it does not cause damage even when the cooking plate 1 is exposed to an open flame, and may be an aluminum plate or the like. An iron-based metal material such as is particularly preferable. It is preferable that the upper surface of the metal plate 11 is coated with a fluorine-based resin or the like by baking so that the food is less likely to stick to the cooking plate 1.例文帳に追加The shape of the metal plate 11 is not particularly limited as long as it is determined according to the shape of the heating chamber of the microwave oven, the shape of the food, and the like.

The refractory heating element 12 contains a powdery or particulate microwave absorber that generates heat when irradiated with microwaves. As will be described later, the refractory heating element 12 is formed by molding an uncrosslinked silicone rubber composition containing a powdery or particulate microwave absorber that generates heat when irradiated with microwaves, crosslinks the composition, and then bakes the composition. obtained by

As the powdery or particulate microwave absorber that generates heat by microwave irradiation, a heating substance that generates heat by absorbing microwaves of 900 to 5000 megahertz can be preferably used. In particular, it is preferable to select and use a material having high heat generation performance by microwaves around 2450 MHz, which is used in household microwave ovens and the like.

The microwave absorber is not particularly limited as long as it can be kneaded with the uncrosslinked silicone rubber. The microwave absorber is powdered or particulated so as to be kneaded and dispersed in the uncrosslinked silicone rubber. If necessary, the microwave absorber may be subjected to surface treatment such as coating or coupling agent treatment for the purpose of facilitating kneading with uncrosslinked silicone rubber.

Exothermic substances contained in the microwave absorber include metal compounds such as magnetite, ferrite, and conductive metal oxides, conductive carbon, carbon fiber, and the like. These exothermic substance powders can be directly used as microwave absorbers, and exothermic substance powders can also be used in the form of particles that are hardened with a binder or the like.

Among the exothermic substances contained in the microwave absorber, metal compounds can be preferably used in terms of good temperature rise characteristics, and in particular, nickel zinc (NiZn) ferrite, manganese zinc (MnZn) ferrite, and magnetite can be preferably used. . Also, if the microwave absorber contains nickel zinc (NiZn) ferrite or manganese zinc (MnZn) ferrite, the microwave absorber is not easily denatured even when exposed to high temperatures, so it is not exposed to direct flames. The heat generation performance of the refractory heating element 12 is likely to be maintained even if the

A method of manufacturing the cooking plate 1, particularly a method of manufacturing the refractory heating element 12 will be described. FIG. 2 is a flow chart showing part of the manufacturing process of the cooking plate 1 of the first embodiment. As shown in FIG. 2, the manufacturing process of the cooking dish 1 includes a first step of kneading an uncrosslinked silicone rubber composition containing a microwave absorber, and After forming the uncrosslinked silicone rubber composition into a predetermined shape, the second step of crosslinking is performed, and the silicone rubber composition containing the microwave absorber crosslinked by the second step is calcined to produce ceramics. and a third step of transforming. The refractory heating element 12 is manufactured by a structure including these first, second and third steps.

In the first step, a powdery or particulate microwave absorber that generates heat when irradiated with microwaves is kneaded into uncrosslinked silicone rubber to form an uncrosslinked silicone rubber composition. For kneading, ordinary kneading means such as a kneading roll and a Banbury mixer can be used. If necessary, a cross-linking agent and a cross-linking aid are kneaded into the uncrosslinked silicone rubber composition so that cross-linking is possible in a later step. Other materials such as fillers may also be kneaded into the uncrosslinked silicone rubber composition.

The uncrosslinked silicone rubber used in the first step is not particularly limited, and various silicone rubbers can be used. As the uncrosslinked silicone rubber, for example, a millable type or a liquid type can be used. It may be a silicone rubber in which a plurality of silicone rubber polymers having different types, average molecular weights, functional groups, etc. are mixed. As the uncrosslinked silicone rubber, mineralized silicone rubber may be used so that it can be easily converted to ceramics in the later-described firing step. The mineralized silicone rubber is obtained by blending a platinum compound and an inorganic filler (kaolinite, talc, mica, silica, aluminum silicate, etc.) with silicone rubber as a base polymer.

The microwave absorber used in the first step preferably contains nickel zinc (NiZn) ferrite or manganese zinc (MnZn) ferrite. Different types of microwave absorbers may be used together and kneaded.

The mixing ratio of the uncrosslinked silicone rubber and the powdery or particulate microwave absorber to be kneaded in the first step is preferably 50 to 1000 parts by weight of the microwave absorber per 100 parts by weight of the uncrosslinked silicone rubber. More preferably, the amount of the microwave absorber is 100 to 600 parts by weight per 100 parts by weight of the uncrosslinked silicone rubber. When the amount of the microwave absorber is more than 50 parts by weight, defects such as cracks are less likely to occur in the refractory heating element in the baking process. Further, when the amount of the microwave absorber to be blended is 1000 parts by weight or less, uniform kneading of the uncrosslinked silicone rubber composition and molding in the second step are facilitated.

In the second step, the microwave absorber-containing uncrosslinked silicone rubber composition obtained in the first step is molded into a predetermined shape and then crosslinked. Although the cross-linking system is not particularly limited, it is preferably an organic peroxide-based cross-linking system.

The molding is preferably molding in which the uncrosslinked silicone rubber composition is pressurized, such as roll molding or press molding. When manufacturing the cooking dish 1 of the above embodiment, the uncrosslinked silicone rubber composition containing a microwave absorber is pressed onto the metal dish 11 by pressing the uncrosslinked silicone rubber composition onto the metal dish 11. It is preferable to mold to a predetermined thickness and size so that objects can be brought into close contact with each other. It is preferable to roughen the surface of the metal plate 11 or treat it with a binder so that the metal plate 11 and the refractory heating element 12 are well integrated.

The uncrosslinked silicone rubber composition that has been molded and brought into close contact with the metal plate 11 is crosslinked. If it is an organic peroxide-based cross-linking system, it will be cross-linked by heating. The cross-linking agent and cross-linking aid used for cross-linking can be those for cross-linking systems capable of cross-linking silicone rubber. peroxide, 2-4-dichlorobenzoyl peroxide, ditertiarybutyl peroxide, etc.) and a cross-linking aid can be used.
When it is desired to integrate the metal plate 11 and the refractory heating element 12 as in this embodiment, the metal plate 11 is heated under pressure so that the uncrosslinked silicone rubber composition adheres to the metal plate 11 during crosslinking. cross-linking is preferred. In the case of an organic peroxide-based cross-linking system, cross-linking is preferably carried out in an oxygen-blocked environment using a mold or the like so as not to cause cross-linking failure.

When the crosslinking is completed through the second step, the microwave absorber-containing silicone rubber composition molded into a predetermined shape and crosslinked is crosslinked and adhered to the metal plate 11 .
In the third step, the silicone rubber composition containing the microwave absorber crosslinked in the second step is sintered to be ceramics.

The firing treatment is preferably performed at a firing temperature of 270°C to 330°C. If the firing temperature is 250° C. or less, the firing tends to be insufficient, and the resulting refractory heating element may have insufficient fire resistance. If the firing temperature is 400° C. or higher, the firing reaction will proceed rapidly during the firing process, generating a large amount of gas, causing the silicone rubber composition to foam or blister, and possibly causing the metal plate to crack. Manufacturing defects such as peeling off from 11 are likely to occur. Although the firing temperature may be constant, the firing temperature may be changed. For example, the firing temperature may be lowered at the start of firing and raised as the firing progresses.

Although the atmosphere for the firing treatment is not particularly limited, it is preferable to perform the firing treatment in air at approximately atmospheric pressure in order to facilitate diffusion of the generated gas and to avoid manufacturing defects such as foaming. In addition, it is preferable that the firing treatment is performed while appropriately ventilating the air so that the concentration of the gas released from the silicone rubber composition does not increase.

The firing process is performed for a firing time sufficient for the firing to proceed sufficiently. A higher firing temperature tends to shorten the firing time. However, if the firing temperature is high, problems such as foaming are likely to occur, and if the firing time is short, the fire resistance may be lowered. If the molded and crosslinked silicone rubber composition is thick, it is difficult for the gas to escape, so it is necessary to bake the composition for a longer time than if it is thin.
For example, if the molded body has a thickness of 3 mm, the crosslinked silicone rubber composition containing the microwave absorber is sufficiently sintered at a sintering temperature of 280° C. for a sintering time of about 100 hours to form a ceramic. be able to.

By firing, gases and monomer components are released from the crosslinked silicone rubber composition, and the silicone rubber composition turns into a ceramic. Gases generated in the baking process include gases generated when the silicone rubber decomposes/denatures. When a silicone rubber composition containing a microwave absorber is ceramized, the composition loses its elasticity and becomes hard ceramics such as pottery or roof tiles.

The silicone rubber composition containing the microwave absorber becomes the refractory heating element 12 through the baking treatment. As will be described later, the refractory heating element 12 is a stable ceramic that does not deform or deteriorate even when exposed to direct fire. In addition, since the silicone rubber composition containing the microwave absorber was in close contact with the metal plate 11 and vulcanized before the baking treatment, the refractory heating element 12 and the metal plate 11 remained in contact with each other even after the baking treatment. It is integrated in a state of close contact and adhesion.

The action and effects of the invention will be described.
The refractory heating element 12 manufactured by the manufacturing method of the above embodiment contains a microwave absorber, and the entire refractory heating element 12 generates heat when irradiated with microwaves. Moreover, when the fire-resistant heating element 12 is manufactured by the manufacturing method of the above embodiment, the fire-resistant heating element 12 molded into a desired shape can be obtained.

Further, in the molding in the second step, if the uncrosslinked silicone rubber composition containing the microwave absorber is pressurized so as to adhere to the metal plate 11 and is crosslinked, the refractory heating element 12 is formed on the metal plate 11. can be integrated in close contact.

In addition, since the refractory heating element 12 manufactured by the manufacturing method of the above embodiment is made into a ceramic by firing, even if it is exposed to an open flame, it may smoke, ignite, deform, crack, It is hard to collapse and has excellent fire resistance.
Regarding this point, in the case of a conventionally known heating element made of a crosslinked silicone rubber composition containing a microwave absorber, when exposed to an open flame such as a flame, the portion exposed to the flame swells like a blister. , peeled off, and combustible gas was emitted and smoked.

Further, according to the method for manufacturing the refractory heating element of the above-described embodiment, the ceramic refractory heating element having a predetermined shape can be manufactured with high accuracy without causing defects in shape such as cracks and cracks. can. In the manufacturing method of the refractory heating element of the above embodiment, since the powdery or particulate microwave absorber is kneaded and dispersed in the silicone rubber composition, the baking treatment is performed. This is because it acts like an aggregate in the material, and even if the silicone rubber portion becomes thin during the baking process, the aggregate serves as a support and suppresses dimensional change and shrinkage of the composition. .

In addition, in the method of manufacturing the refractory heating element of the above embodiment, if the firing treatment in the third step is performed at 270° C. to 330° C., the firing reaction will proceed sufficiently and the ceramics will be more completely formed. As a result, the fire resistance of the fire-resistant heating element 12 is further improved, and manufacturing defects such as cracks, foaming, blistering, and peeling of the fire-resistant molding due to rapid progress of the firing reaction are suppressed.

Further, in the method for manufacturing the fire-resistant heating element of the above-described embodiment, in the first step, uncrosslinked silicone rubber is added so that 50 parts by weight or more of the microwave absorber is blended with 100 parts by weight of the uncrosslinked silicone rubber. By kneading the rubber composition, the function of the microwave absorber as an aggregate is enhanced, and the effect is that the crosslinked silicone rubber composition containing the microwave absorber shrinks and shrinks during the baking process. The occurrence of manufacturing defects such as cracks, cracks, blisters, air bubbles, and peeling in the resulting refractory heating element 12 is effectively suppressed. From the same point of view, it is particularly preferable to blend 50 parts by weight or more of the microwave absorber as a magnetite or ferrite microwave absorber.

Further, in the method for manufacturing the fire-resistant heating element of the above-described embodiment, in the first step, uncrosslinked silicone is added so that 1000 parts by weight or less of the microwave absorber is blended with 100 parts by weight of the uncrosslinked silicone rubber. If the rubber composition is kneaded, kneading in the first step and molding in the second step can be easily performed, and production efficiency can be enhanced.

Moreover, in the manufacturing method of the refractory heating element of the above embodiment, the microwave absorber preferably contains nickel zinc (NiZn) ferrite or manganese zinc (MnZn) ferrite. These microwave absorbers do not denature even when exposed to high temperatures up to about 500° C., and when the temperature drops, the heat generation property due to microwaves is restored. This is because even if the heat generating material is exposed to a direct flame such as a flame and becomes high temperature, the heat generating property as a refractory heat generating element is hardly deteriorated, and it is easy to reuse.

The results of evaluating the fire resistance performance of the fire resistant heating element manufactured by the manufacturing method of the above embodiment are shown below.

(Example)
100 parts by weight of silicone rubber (TSE2570-4U manufactured by Momentive), 100 parts by weight of manganese zinc (Mn-Zn) ferrite (LD-M manufactured by JFE Chemical Co., Ltd.), a cross-linking agent, etc. are kneaded (first step). , to obtain an uncrosslinked silicone rubber composition containing a microwave absorber. This uncrosslinked silicone rubber composition was crosslinked by heating while being press-molded to a thickness of 3 mm so as to adhere to an iron plate (second step) to obtain a crosslinked silicone rubber composition containing a microwave absorber. . Furthermore, in a state in which the crosslinked silicone rubber composition containing the microwave absorber is integrated with the steel plate, they are placed in a gear oven heated to 280° C. and baked for 100 hours to convert the silicone rubber composition. It was made into ceramics (third step) to obtain the refractory heating element 12 of the example.

The refractory heating element 12 of the obtained example was in the form of hard ceramics without elasticity, and was integrated with the iron plate. The obtained refractory heating element 12 has substantially the same shape and dimensions as the crosslinked silicone rubber composition containing the microwave absorber before sintering, and has cracks, splits, blisters, and the like. No manufacturing defects such as peeling were observed.

(Comparative example 1)
A crosslinked silicone rubber composition containing a microwave absorber was obtained by carrying out the first and second steps of the above example. This was subjected to a test as a heating element integrated with an iron plate of Comparative Example 1 as it was without firing treatment.

(Comparative example 2)
The silicone rubber of Comparative Example 1 was changed to acrylonitrile butadiene rubber (JSR N239SV manufactured by JSR Corporation), mixed with 100 parts by weight of manganese zinc ferrite, kneaded, molded, and crosslinked to contain a microwave absorber. A crosslinked acrylonitrile butadiene composition was obtained. This was subjected to the test as a heating element integrated with the iron plate of Comparative Example 2 as it was without firing treatment.

The heating elements of these Examples and Comparative Examples were subjected to a fire resistance test. In the fire resistance test, the iron plate is placed at an angle of 45°C with respect to the vertical direction so that the heating element side faces down, and the heating element is heated for 1 minute so that the flame of the gas burner hits it directly. We observed the state of the heating element of

In the refractory heating element of the example, even when the flame of the gas burner hit the heating element, no gas was generated or the heating element was deformed, and there was no particular change in appearance. Moreover, even when observed after the test was completed, there was no particular change in appearance from before the test.

In the heating element of Comparative Example 1, when the flame of the gas burner hit the heating element, gas was generated from the portion exposed to the flame, and smoke was generated. Also, the part exposed to the flame swelled like a blister. Even after the test was completed, the swollen portion did not return to its original state and had a scorched appearance compared to the surroundings. In addition, the bulging portion was fragile and easily crumbled.

In the heating element of Comparative Example 2, when the flame of the gas burner hit the heating element, gas was generated from the portion exposed to the flame, and smoke and fire occurred. And the ignited part swelled like a blister. Observation after the test was completed showed that the bulging portion had become quite brittle and the heating element was easily lost.

As described above, it was shown that the fire-resistant heating element obtained by the firing treatment by the manufacturing method of the above embodiment has excellent fire resistance.

The invention is not limited to the above embodiments, and can be implemented with various modifications. Other embodiments of the invention will be described below, but in the following description, differences from the above embodiment will be mainly described, and detailed descriptions of the same parts will be omitted. Moreover, these embodiments can be implemented by combining some of them with each other or replacing some of them.

In the description of the above embodiment, the refractory heating element is a cooking plate used in a microwave oven, but the specific application is not limited to the cooking plate. The fire-resistant heating element manufactured by the manufacturing method of the above embodiment may be used by being attached to a resin mold or mold for manufacturing carbon fiber reinforced plastic (CFRP) products, for example. The refractory heating element manufactured by the manufacturing method of the above embodiment generates heat by microwaves and is excellent in fire resistance, so it is suitable as a heating element used at high temperatures.

The refractory heating element manufactured by the manufacturing method of the above embodiment can be used, for example, in a cooking dish that can be heated in a microwave oven, and has a high industrial utility value.

1 cooking plate 11 metal plate 12 refractory heating element

Claims (4)

A method for producing a refractory heating element capable of generating heat by irradiating microwaves,
A first step of kneading a powdery or particulate microwave absorber that generates heat by microwave irradiation into an uncrosslinked silicone rubber composition;
A second step of molding the uncrosslinked silicone rubber composition containing the microwave absorber obtained in the first step into a predetermined shape and then crosslinking;
a third step of firing the silicone rubber composition containing the microwave absorber crosslinked in the second step to form a ceramic;
A method for manufacturing a refractory heating element. The firing treatment of the third step is performed at 270 ° C. to 330 ° C.,
The method for manufacturing the refractory heating element according to claim 1. 2. The fire-resistant heating element according to claim 1, wherein in the first step, the uncrosslinked silicone rubber composition is kneaded so that 50 to 1000 parts by weight of the microwave absorber is blended with 100 parts by weight of the uncrosslinked silicone rubber. manufacturing method. the microwave absorber comprises nickel zinc (NiZn) ferrite or manganese zinc (MnZn) ferrite;
4. The method for manufacturing the fire-resistant heating element according to claim 1.

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