JPH0953831A - Microwave heating body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an efficient heating body by mixing needle titanium oxide powder or ferrite powder in thermosetting resin and by molding the mixture by heating. SOLUTION: Needle titanium oxide powder or ferrite powder of a tri-iron tetroxide or the like and thermosetting resin such as phenolic resin or melamine resin as a prepolymer are mixed in the ratio of 1 of the former to 0.2-50, preferably about 0.5-20, of the latter by a method of a ball mill or the like. The mixture is subjected to heat molding at 50-500 deg.C by a method of injection molding, heating press or the like and thereby a heating body is obtained. A substance to be heated is brought into contact with the heating body thus obtained and then a microwave is cast thereon for several seconds to several minutes by using an electronic oven or the like. By using the thermosetting resin, a heating value is made large, a material to be heated can be heated efficiently and it is also possible to form a scorch on a site in contact on the occasion of heating foodstuff or the like.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a microwave heating element. Specifically, it relates to a microwave heating element using a thermosetting resin in which a specific inorganic compound powder is dispersed.

[0002]

2. Description of the Related Art A method of irradiating a microwave is widely adopted as one of methods for heating an object, but it is usually heated by exciting the water contained in the object to be heated by the microwave. However, not everything can be effectively heated. On the other hand, a method of using a dispersion of conductive fine particles as a heating element by microwave irradiation was previously proposed (Japanese Patent Application No. 5-32374).
Five).

[0003]

The method of heating by using a microwave is an excellent method capable of heating and melting only a desired portion under non-contact conditions. In particular, the method of using a resin molded product in which the conductive fine particles are dispersed as a heating element is an excellent method that can be applied to any resin.

However, in order to obtain a large calorific value, it is necessary to disperse a large amount of electroconductive fine particles if it is simply electroconductive, and the fluidity of the resin in which the electroconductive fine particles are dispersed is poor. The problem that it is difficult to mold a resin molded product in which conductive fine particles are dispersed,
Furthermore, when a large amount of electrically conductive particles are dispersed, the resin molded product becomes electrically conductive in the macro as well, and there is the problem that an induced current is generated and sparks fly and ignite. is not.

An object of the present invention is to provide an efficient microwave heating element that solves the above problems.

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have completed the present invention.

That is, the present invention relates to a microwave heating element obtained by mixing needle-shaped titanium oxide powder or ferrite powder with a thermosetting resin and then heat-molding and curing the mixture.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, as the thermosetting resin, phenol resin, urea resin, melamine resin, unsaturated polyester resin, epoxy resin, silicone resin, polyurethane resin, diallyl phthalate resin, thermosetting polyimide, poly A carbodiimide resin or the like can be used. The thermosetting resin is used as a prepolymer before three-dimensional crosslinking, and is used by mixing a prepolymer and acicular titanium oxide powder or ferrite powder with a curing agent as needed. The shape of the prepolymer, the curing agent, and the curing method are known for each resin, but it is preferable to use it as a powdery or liquid prepolymer because the operation is simple and preferable.

Specifically, in the phenol resin, various structures such as resole, novolak, which is a condensate of formaldehyde with phenol or a derivative thereof, methylol melamine, which is a condensate of melamine and formaldehyde, and a condensate of xylene and formaldehyde are used as prepolymers. Things are available. It is preferable to use the melamine resin in the form of methylol melamine from the viewpoints of heat resistance, price, operability, and effect of heating element.

By using a thermosetting resin, a large amount of heat is generated, and an object to be heated can be efficiently heated, and when food is selected as the object to be heated, it is possible to very efficiently burn the contacted portion. Is.

In the present invention, as the acicular titanium oxide powder, acicular or columnar aspect ratios of about 5 to 1000 and minor axis lengths of about 0.01 to 10 μm can be used. A material doped with another metal oxide such as magnesium or calcium, or a material doped with tin oxide, indium oxide or the like to make it conductive, or a commercially available material can be used as it is. As the crystal form of titanium oxide, an anatase type having a high degree of crystallinity may be particularly preferable.

As the ferrite, oxides containing iron with various valences are used, and particularly, iron tetroxide is preferably used. Commercially available ferric oxide can be used, and natural magnetite is finely pulverized, or iron is calcined in air, iron (III) oxide reduced with hydrogen containing water vapor, red heat Examples thereof include those synthesized by finely pulverizing iron obtained by allowing water vapor to act on the iron. The particle size of such ferric oxide is 1000 μm.
m or less, preferably about 0.01 to 100 μm, is preferably used.

In the present invention, the method of mixing the acicular titanium oxide powder or the ferrite powder with the thermosetting resin is not particularly limited as long as it can be uniformly dispersed, and a known mixing method such as a ball mill, a homogenizer or a Henschel mixer is used. It can be achieved by mixing. The mixing ratio of acicular titanium oxide powder or ferrite powder is 1 to thermosetting resin of 0.2 to 50, preferably 0.5 to 20.
It is a degree. If it is too small, the physical properties of the molded product will be poor,
On the other hand, if the amount is too large, a sufficient calorific value cannot be obtained.

The molding method is not particularly limited, and a method used for a usual thermosetting resin can be adopted, and examples thereof include a method of injection molding in a heated mold and a method of hot pressing. The heating temperature is usually 50 to 500 ° C.
It is common to do in. The shape of the molded article is not particularly limited and may be a preferred shape according to the purpose. For the purpose of obtaining a sufficient calorific value, the thickness of the molded product is preferably 0.01 mm or more, particularly 0.1 mm or more, because the calorific value is large.

A substance to be heated is brought into contact with the heating element thus obtained, and then microwave is irradiated. Microwaves can be heated to 100 ° C. or higher with a wavelength and energy that are commercially available as microwave ovens for home use, and are heated to a device of 500 w to 1 kw at a frequency of 2450 MHz which is commercially available in Japan. May be placed on the above-mentioned heating element, and if necessary, the object to be heated may be covered with a heat-resistant non-microwave absorbing material and irradiated with microwaves for several seconds to several minutes.

[0016]

The present invention will be further described with reference to examples.

Example 1 100 parts by weight of melamine resin molding material (manufactured by Taiwa Co., Ltd., W5085) per 50 parts by weight of needle titanium oxide (anatase type, brand name NT-100) manufactured by Fuji Titanium Industry Co., Ltd. Mix and hot press equipment, 200x200x
It was set to be 1 mm and heated at 180 ° C. for 5 minutes to be cured. Place this sheet on an alumina plate, put a commercially available frozen dumpling, put it on a commercially available microwave oven (Toshiba microwave oven ERT-540F made by Toshiba), and irradiate it with microwaves for 3 minutes under defrosting conditions. There was a brown eye on the side.

Example 2 Iron tetraoxide (Wako Pure Chemical Industries, Ltd.) was used instead of acicular titanium oxide.
A sheet prepared in the same manner as in Example 1 except that the same was used, was placed on an alumina plate in the same manner, a commercially available frozen hamburger was placed, and microwaves were irradiated for 6 minutes under the defrosting condition. The melamine resin side had a brown mark.

Comparative Example 1 15 g of the needle-shaped titanium oxide used in Example 1 and 15 g of polypropylene (brand name J3H-G) manufactured by Mitsui Toatsu Chemicals, Inc. were used in Labo Plastomill R type (manufactured by Toyo Seiki Seisakusho Co., Ltd.). In 2
After mixing well at 40 ° C, press at 240 ° C to obtain a thickness of 1
I made a mm sheet. When the same procedure as in Example 1 was carried out except that this sheet was used, it was not sufficiently heated and was not browned.

[0020]

By using the heating element of the present invention, various objects can be easily heated by irradiating them with microwaves, which is extremely valuable industrially.

Claims (1)

[Claims] 1. A microwave heating element obtained by mixing acicular titanium oxide powder or ferrite powder with a thermosetting resin, followed by thermoforming and curing.