JPH0427101B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to a heat-resistant container, and more particularly to a heat-resistant container whose contents can be heated and cooked in a microwave oven, an electric oven, or a toaster oven. (Conventional technology) In recent years, advances in electronics have led to lower prices for microwave ovens, and because they allow faster and easier cooking, their penetration rate is remarkable, reaching 45-50% in the United States and even in Japan. 40-45%
If you add it to the ovens (electric or gas) that have been used up until now, the penetration rate will be considerable. Due to its excellent heat resistance, aluminum is the most commonly consumed tray for oven-heated cooked food. However, when aluminum trays are placed in a microwave oven, arcs may fly between the tray and the inner wall of the microwave oven, between the trays, and between the tray and other containers, causing damage to the inside of the oven, and the magnetron oscillating microwaves. cause damage to. Furthermore, if there is not much to be heated (food), the microwaves reflected from the aluminum surface may damage the magnetron or cause the inner wall of the microwave oven to reach an abnormally high temperature, making it unsuitable for use in microwave ovens. There is. For these reasons, dual ovenable trays that can be used in both ovens and microwaves have been developed, and mainly in the United States, paper + polyethylene terephthalate (PET) laminate, pulp mold + PET, unsaturated polyester, crystal Trays made from recycled PET have been commercialized. (Problems to be Solved by the Invention) Although the dual ovenable tray described above is said to be applicable to ovens, its heat resistance is at most 220 to 230°C, and it is only applicable to electric ovens equipped with a temperature control device. Can not. For example, in the toaster oven, which is the most popular in Japan and cannot be controlled, the tray temperature is
Because the temperature rises to 250-300℃, the tray may become deformed or damaged, making it unusable. Therefore, it is not a dual ovenable tray in the true sense, and there is a need for a microwave oven or dual ovenable tray that has excellent heat resistance, high heating efficiency, and is inexpensive. Therefore, the technical problem of the present invention is to solve the above-mentioned drawbacks of the conventional dual ovenable tray, and to avoid the generation of sparks and damage to the magneto when heated in a microwave oven, as seen in metal trays. On the other hand, it is an object of the present invention to provide a dual ovenable tray which has significantly superior heat resistance when heated in an oven compared to conventional non-metallic containers. (Means for Solving the Problems) According to the present invention, at least the outer surface of a tray-shaped container made of paper or organic resin is coated with
A heat-resistant coating film containing 25 to 90% by weight of scaly metal particles having an average diameter of 200 μm and an aspect ratio of 10 or more as a heat-reflecting coating layer, which reflects infrared rays and is microwave safe. A usable heat resistant container is provided. (Function) The first feature of the present invention is that a heat-resistant coating film containing scale-like metal particles is used as a heat ray reflective coating layer. These scaly metal particles are
When forming a coating film, it has the characteristic that it is arranged in a flat state and in a layered manner on the coating film surface. For this reason, heat-resistant paints containing scaly metal particles exhibit excellent heat ray (infrared) reflection properties, and for example, when irradiated with heat rays from an infrared heating lamp, the equilibrium temperature reached by the substrate is lower than that of heat resistant paints containing scaly metal particles. It is observed that the temperature is approximately 40°C lower than that of the one coated with paint. As described above, when the heat-resistant container of the present invention is used for heating in an oven, the heat rays are effectively reflected by the coating film containing scale-like metal particles, and the temperature rise of the container base is suppressed, thereby preventing deformation or damage of the container. This allows the container to withstand heating in an oven. Moreover, the scaly metal particles themselves have remarkable heat resistance, and their presence preferentially and layered on the paint film surface protects the paint film from attack by heat and oxygen. As a result, the heat resistance of the coating film itself is significantly improved. Thus,
According to the present invention, even if the base material of the container is made of a material with poor heat resistance, such as paper, organic resin, or a combination thereof, it is possible to impart heat resistance that can withstand oven heating. It is what it is. Furthermore, in a coating having a structure in which scaly metal particles are dispersed in a coating film, each particle is electrically independent, and as a result, the electrical resistance of the coating film surface is maintained at a relatively high level. As a result, the container of the present invention does not generate sparks during microwave heating in a microwave oven. Additionally, coatings containing scaly metal particles advantageously absorb microwaves, have a much lower tendency to damage the magnetrons that emit them, and can even increase heating efficiency. bring about action. It is also important that the scaly metal particles have an average diameter of 1 to 200 μm, especially 5 to 30 μm,
If this particle size is smaller than the above range, it will be difficult to obtain the above-mentioned distribution structure, and the heat ray reflection properties will deteriorate. Moreover, if the particle size exceeds the above range, the particles tend to lose their electrical independence from each other, and troubles such as spark generation tend to occur in a microwave oven. Further, in order to facilitate the development of a layered distribution structure, the aspect ratio (diameter/thickness ratio) should be 10 or more, particularly 35 or more. In addition, the scale-like metal particles are preferably blended in the heat-resistant coating film in an amount of 25 to 90% by weight, especially 30 to 60% by weight, and if the content is less than the above range, the content is within the range of the present invention. When the amount exceeds the above range, the density, smoothness, mechanical strength, etc. of the coating film decrease. (Description of Preferred Embodiments) The heat-resistant container of the present invention includes at least one surface, or preferably a part of at least one surface, of the covering material 1, that is, the base material 2 shown in the cross-sectional view of FIG. It is formed by press-molding a material provided with a coating film 3 containing scale-like metal particles into a tray shape. As shown in FIG. 2, this tray-shaped container is composed of a flat bottom portion 4, a short side wall portion 5, and a flange portion or curl portion 6. As described above, the base material 2 is made of paper, organic resin, or a combination thereof (laminate). As paper, one or two types of natural pulps such as softwood pulp and hardwood pulp, inorganic fibers such as glass fiber, rock wool, slag wool, asbestos, and ceramic fibers; and synthetic resin pulps such as polyolefin, polyester, polyamide, and polyimide are used.
Examples include natural or synthetic paper obtained by paper-making more than one type of paper. These papers can be blended with fuel-retardant fillers, such as aluminum hydroxide, magnesium hydroxide, calcium aluminate, dawsonite, and the like. In addition, silica,
Talc, clay, calcium carbonate, etc. can be blended, and an organic resin binder can also be used to improve paper formability and bond or fix fibers to each other. An advantage of the present invention is that even when ordinary paper obtained from wood pulp is used, it can provide significantly superior heat resistance.
The paper substrate has a basis weight of 100 to 600 g/m ² , especially 150 to 600 g/m 2 .
It is desirable that it be within the range of 400g/m ² . As the organic resin substrate, thermoplastic or thermosetting resins known per se can be used.
Thermoplastic resins include polypropylene, poly-
Polyolefins such as 4-methylpentene-1; polyesters such as polyethylene terephthalate;
Polyamides such as nylon 6, nylon 6,6;
Polycarbonates; polyarylates such as poly(bisphenol A terephthalate) and the like can be mentioned. Examples of thermosetting resins include phenolic resins, urea resins, melamine resins, epoxy resins, and unsaturated polyester resins. Moreover, those resins to which inorganic fillers are added can also be used. These resins are in the form of a film, and after providing a heat-resistant coating, they may be formed into a tray by press molding or vacuum forming into a container, or they may be formed into a tray by press molding, vacuum forming, or compressing in advance. It may be formed into a tray shape by injection molding, transfer molding, injection molding, etc., and a heat-resistant coating film may be provided thereon. A combination of paper and resin can also be used, for example, a paper substrate coated with the above-mentioned thermoplastic resin by extrusion, or a paper and resin film laminated together. Moreover, a prepreg obtained by impregnating paper with a thermosetting resin can also be used. The thickness of the base material mentioned above may be any thickness that allows the container to retain its shape. The scaly metal particles may be any metal as long as they satisfy the above-mentioned restrictions, and the constituent metal thereof may be any metal such as aluminum, copper, brass, etc., but aluminum is preferred from the viewpoint of hygiene. The scaly metal particles used in the present invention are coated with a dispersant, which allows them to noticeably develop a preferential layered distribution structure on the surface of the coating film, and also to maintain the electrical independence of each particle. Particularly desirable above. As the dispersant, higher fatty acids, resin acids, or metal salts thereof are preferably used, and it is desirable to coat the scale-like metal particles with these in an amount of 0.5 to 5% by weight. As the paint, thermosetting resins such as phenol-formaldehyde resin, furan-formaldehyde resin, xylene-formaldehyde resin,
Ketone formaldehyde resin, urea formaldehyde resin, melamine formaldehyde resin,
Paints made of alkyd resins, unsaturated polyester resins, epoxy resins, bismaleimide resins, triallyl cyanurate resins, thermosetting acrylic resins, silicone resins, oil-based resins, etc., or thermoplastic resins such as vinyl chloride-vinyl acetate copolymer Union,
partially saponified vinyl chloride-vinyl acetate copolymer,
Vinyl chloride-maleic acid copolymer, vinyl chloride-
Paints made of maleic acid-vinyl acetate copolymers, acrylic polymers, saturated polyester resins, etc., or combinations thereof, are used. If the thickness of the coating film is in the range of 1 to 50 μm, particularly 5 to 20 μm, satisfactory results can be obtained in terms of both heat resistance and workability. Moreover, this paint containing scale-like aluminum particles is applied onto a substrate by brush coating, spray coating, electrostatic coating, roller coding, dip coating, electrodeposition coating, or the like. It is desirable that the coating film be formed on both sides of the base material, but it may be formed on at least one surface of the base material. Or, if the contents are in the tray, the bottom part 4 and side wall part 5 that are in contact with the contents
a, 5b, 5c, 5d are toaster ovens, etc.
Since the temperature rise is small when hot wire heating is performed, it may be necessary to coat only the surface of the portion where the temperature rise is large, such as the upper part of the flange portion 6 and the side wall portions 5a, 5b, 5c, and 5d. For this purpose, part coating is carried out by spray painting or roller coating. The molding into the tray is done by the usual press molding method that uses a combination of a male die (punch) and a female die (die).
A vacuum forming method, a plug assist forming method, an injection molding, a compression molding, a transfer molding, etc. are performed as appropriate depending on the type of material. (Operations and Effects of the Invention) According to the present invention, a container that can be used in a microwave oven, a microwave oven, a toaster oven, etc. to heat and cook the contents on the spot has excellent heat resistance,
It was provided at a low price with high heating efficiency and safety. Example 1.2 Comparative Examples 1 to 3 Aluminum flaky aluminum particles have an average diameter of 14μ and a thickness of 0.27μ, and the content is 66% by weight, 32% by weight of mineral spirits, and 2% by weight of stearic acid. Paste and 24% solids
After mixing and stirring the epoxy-urea paint in various proportions as shown in Table 1, the basis weight was 200 g/m ²
Apply it to one side of acid-proof paper using a bar coater,
After drying with a hair dryer, it was baked in an oven at 170°C for 10 minutes. The coating amount was 10 g/m ² . Using the thus obtained paper having a coating film containing flaky aluminum particles, a rectangular tray measuring 18 cm long, 10 cm wide and 2 cm deep was formed by press molding, with the coating film facing down. . Using this tray, the degree of temperature rise of the container itself due to infrared absorption was investigated as follows. The tray and the infrared heating device were arranged so that the light source of the infrared heating device was located 10 cm from the lower surface (coated film surface) of the bottom 4 of the tray, and heating was performed using a 40 V power source. At this time, the temperature at the center of the upper surface of the bottom 4 of the tray was measured. At first, the temperature rose rapidly, but eventually reached an equilibrium state. The equilibrium temperature is shown in Table 1.

[Table] * Values determined from the mixture composition
** The aluminum flakes are peeling off.
Examples 3 to 5 Comparative Example 4 Aluminum paste consisting of scaly aluminum particles having various shapes as shown in Table 2 and containing 70% by weight, 29% by weight of mineral spirits, and 1% by weight of stearic acid. Mix 25% by weight of epoxy-urea paint with 75% by weight of epoxy-urea paint with a solid content of 24%, stir, apply on one side of acid-proof paper with a basis weight of 200 g/m ² using a bar coater, and dry with a hair dryer. Afterwards, it was baked at 170°C for 10 minutes. The application amount is 10
g/ ^m2 . The paper thus obtained, which has a coating on one side, is press-molded to a length of 18 cm, a width of 10 cm, and a depth of 2 cm.
A rectangular tray was formed so that the coating film was on the bottom surface. Using this tray, the equilibrium temperature reached by this tray was measured by infrared absorption in the same manner as in Example 1. The results are shown in Table 2.

[Table] Example 6 An aluminum paste consisting of 75% by weight of scaly aluminum particles with an average diameter of 7μ and a thickness of 0.15μ, 24% by weight of mineral spirits, and 1% by weight of stearic acid was mixed with 30% by weight and a solid content of 24% by weight. After mixing and stirring 70% by weight of epoxy-phenol paint, the mixture was coated on both sides of acid-proof paper with a basis weight of 300 g/m ² using a bar coater, dried with a hair dryer, and then baked at 180° C. for 5 minutes. The coating amount was 10 g/m ² on one side. The thus obtained paper, which has a coating surface on both sides, was press-molded to form a mold with a height of 18 cm and a width of 10 cm.
A rectangular tray with a depth of 2 cm was molded. Place 3 pieces of commercially available yakitori with a core temperature of 6°C in this square tray, and place them in a toaster oven for 4 minutes.
Heated for minutes. After heating, I took the tray out of the oven and measured the center temperature of the yakitori, which was 60.
It was warm at ℃. When I tasted it, it was just right, hot, and delicious. Although the temperature of the paper layer at the flange portion 6 of the tray reached 260° C. at the end of heating, there was no significant discoloration of the tray or decrease in paper strength. Comparative Example 5 When a square paper tray similar to that of Example 6 was formed using a paint that did not contain aluminum paste and the same test was conducted, the tray turned brown after heating. In addition, a decrease in paper strength was observed, and when force was applied manually, the side wall of the tray
was broken. Note that the temperature of the paper layer in the tray flange portion 6 had reached 300° C. at the end of the heating. Example 7 Comparative Example 6 Trays similar to those in Example 6 and Comparative Example 5 were molded, 100 ml of water was placed in each tray, and the two trays were heated together in a microwave oven. The relationship between water temperature and heating time at that time is shown in Figure 3. Microwave oven: Sharp Hikutuker RA-1 Heating conditions: Strong heating Example 8 Comparative Example 7 A square tray measuring 18 cm long, 10 cm wide and 2 cm deep was formed by press molding using 60 μm aluminum foil. In addition, a tray similar to that in Example 6 was molded,
100 ml of water was placed in each of these two types of trays and heated together in a microwave oven.The conditions are as shown in Example 7.
Same as. The relationship between water temperature and heating time at that time is shown in Figure 4. In addition, when we investigated whether sparks were generated when these two types of trays came into contact with the wall of the microwave, we found that the aluminum foil tray generated sparks, but the tray with the coating containing scaly aluminum particles did not. . Example 9 PET resin with an IV of 0.80 was extruded into a 1 mm thick sheet. After heating this sheet with a heater, it reaches 170℃.
A square tray measuring 15 cm x 10 cm x 1.5 cm was obtained. On both sides of the PET tray obtained in this way,
Scaly aluminum particles with an average diameter of 20μ and a thickness of 0.5μ
40% by weight of an aluminum paste consisting of 70% by weight of mineral spirits, 28% by weight and 2% of oleic acid and 60% by weight of an epoxy-phenol paint having a solid content of 24% by weight were mixed, stirred, and spray coated. Thereafter, it was dried and baked in an oven at 150°C for 15 minutes. The coating amount was 5 g/m ² . Put 100g of macaroni gratin in the tray obtained in this way and put it in a toaster oven for 15 minutes.
When heated for a minute, the container did not deform, and the macaroni gratin was sufficiently heated and delicious. Comparative Example 8 A similar test was conducted in Example 9 using a rectangular tray made of PET alone without coating. When the tray was taken out after heating, the flange portion 6 not in contact with the gratin was melted and deformed. was.
The temperature of the flange portion at the end of heating was 280°C.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional structural diagram of the container wall of the heat-resistant container of the present invention, FIG. 2 is a perspective view showing the heat-resistant container of the present invention, and FIG. 3 is a heating time in Example 7 and Comparative Example 6. FIG. 4 is a diagram showing the relationship between heating time and water temperature in Example 8 and Comparative Example 7. FIG. The reference numbers are 1 for the covering material, 2 for the base material, 3a,
3b is a heat ray reflective coating layer, 4 is a bottom portion, 5a, 5b,
5c and 5d are side wall portions, and 6 is a flange portion or curl portion.

Claims (1)

[Claims] 1. 25 to 90% by weight of scaly metal particles having an average diameter of 1 to 200 μm and an aspect ratio of 10 or more on at least the outer surface of a tray-shaped container based on paper or organic resin. 1. A heat-resistant container that reflects infrared rays and can be used in a microwave oven, characterized by having a heat-resistant coating film containing the same as a heat-ray reflective coating layer. 2. The heat-resistant container according to claim 1, wherein the scale-like metal particles are coated with a fatty acid, a resin acid, or a metal salt thereof.