JPH03280868A - Thermal sterilization process with microwave - Google Patents

Abstract

PURPOSE:To sterilize a packaged object while preventing the rupture of the package by sealing a heating object in a package, putting the package in a space formed by assembling supporting plates composed of specific formed articles and irradiating the package with microwave. CONSTITUTION:Supporting plates 1 made of molded articles of a sheet molding compound of a polyester resin containing preferably 50-70wt.% of glass fiber (cured at 140-170 deg.C) are assembled with each other to form a supporting member 2 having a cavity (a) with the shape similar to the shape of a package containing a sealed object to be heated. The package is put into the cavity (a) and the object is sterilized by heating at 100-150 deg.C with microwave radiation. After sterilization, the package is quenched by immersing in water. The supporting member 2 can be repeatedly used since it endures a number of repeated microwave irradiation treatments.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method of microwave heating sterilization of a sealed package filled with an object to be heated.

(Prior art) When carrying out high temperature sterilization of a sealed package filled with an object to be heated at a temperature of 100°C or higher under normal pressure, support plates are stacked on top of each other as a support to prevent the package from breaking. A method of storing the package in this support and heating it is carried out by microwave heat sterilization or the like.

(Japanese Patent Publication No. 58-26949) Two supporting plates are usually used, and by overlapping the two supporting plates, a package accommodating portion is formed between them. FIG. 2 is a cross-sectional view at this time, in which (11) and (12) are support plates, and (a) is a package storage section. With the two support plates stacked on top of each other, insert the ring-shaped holder (2) from both the left and right sides.
This prevents the package from expanding and bursting due to microwave heating.

In this state, the object to be heated is irradiated with microwaves from outside the support to heat and sterilize it, and then forcedly cooled to complete the heat sterilization. Heating is about 100 to 150"C, and forced cooling is done by immersing the entire support in water. Note that the support is reused.

(Intelligence to be Solved by the Invention) By the way, in the above heating step, for example, when heated at 130°C, the expansion pressure inside the package is approximately 3 kg/cm.
'' pressure is applied to the support, which is then immediately cooled with water.For this reason, there is a problem in that the above-mentioned support will crack if used several to ten times or more, making it unusable.

(Means for Solving the Problem) In order to solve this problem, the present invention provides a microwave heat sterilization method using a sheet mold compound (SMC) molded article of unsaturated polyester resin containing glass fiber as a support. do.

The support body according to the present invention is composed of a pair of support plates, and by overlapping the support plates with each other, a housing portion having substantially the same shape as the package is formed inside the support body.

For example, if the package is bag-shaped, the support plate 1 shown in FIGS. 1A and 1B can be used. That is, FIG. 1A is a perspective view of the support plate 1, the outer surface of which consists of a flat top surface 16 and a slope 1c continuous to the top surface via a step 1d. On the other hand, FIG. 1B is a perspective view of the support plate 1 when it is overturned.
A recess 1a for accommodating a package is provided on its inner surface. By stacking two such support plates 1 so that their inner surfaces face each other, a package accommodating part a is formed by the recess 1a (FIG. 2).

By the way, since the package and the package accommodating section a have substantially the same shape, the support absorbs the expansion pressure of the package due to microwave irradiation, thereby preventing the package from breaking. In order to prevent the support from opening due to expansion of the package, heat-resistant holders 2 are fitted from both sides and fixed by coming into contact with the step 1d.

Microwave irradiation is possible, for example, by the method shown in FIG.

That is, the support body 10 containing the package is transported to the conveyor 1.
1 and introduced into the microwave irradiation device,
It is discharged. The microwave irradiation device is divided into several cavities, and in the illustrated example, it is divided into a first heating section 21 consisting of six cavities and a second heating section 22 consisting of one cavity. Each cavity of the first heating section 21 includes waveguides 12a, 13a, 14a, 15a, and 16a.

Through 17a, microwave oscillators 12b, 13b,
14b, 15b, 16b, and 17b are connected, and microwaves are selectively irradiated to a part of the package, for example, the center part, to selectively heat this part. A microwave oscillator 18b is connected to the second heating section 22 via a waveguide 18a, and here uniformly irradiates the entire surface of the package with microwaves. Such first heating section 21 and second heating section 22
As a result, the entire package is heated to a uniform temperature of 100 to 150°C.

The heat-sterilized package is first cooled to a temperature of 100"C or less to bring the pressure inside the package to atmospheric pressure, and then taken out from the support. After heating, it is kept warm before cooling to maintain the sterilization effect. It is also possible to improve.

Cooling is by water cooling to improve the cooling rate. Water cooling can be done by immersing the package in water while it is housed in the support, but in order to improve the cooling rate of the package, slide the holder 2 toward the end to create a gap between the support plates 1. established,
It is desirable that the water contacts the package from here. A method for continuously performing such cooling is disclosed in Japanese Patent Application No. 63-3.
No. 35502.

By the way, since the support plate 1 is reused, it is necessary to use an SMC molded product of unsaturated polyester containing glass fiber in order to withstand repeated cold and heat cycles.

If it does not contain glass fiber, it will not have sufficient resistance to repeated cold and heat cycles. It is sufficient to contain glass fiber in an amount of 20% by weight, but it is desirable to contain it in an amount of 50% by weight or more in order to withstand repeated heating and cooling many times, for example, 100 times or more. Note that if it exceeds 70% by weight, the glass fibers will be exposed on the surface of the molded product, resulting in poor appearance and difficulty in handling, so it is preferably 70% by weight or less.

In addition, in the case of block mold compound (BMC), the glass fibers do not reach every corner of the molded product, and the glass fibers do not intertwine with each other sufficiently, so the resistance to repeated cold and heat cycles is insufficient, so SMC is used. There is a need.

In SMC, for example, glass fibers are spread on a removable carrier sheet, a sheet of unsaturated polyester resin is layered on top of this, and the two are dried and integrated, and the resulting sheet-like composite is applied to a predetermined area. Stack many sheets in a mold, 1
The unsaturated polyester resin may be cured by heating to a temperature of 40 to 170°C.

Further, during such curing, if a glass cloth is placed between the sheet-like composites or on the outermost surface and compression molded together, a support plate with even better heat and pressure resistance can be obtained. In particular, when glass cloth is placed on the outermost surface, the resistance of the outermost surface to the heat associated with microwave sterilization, the expansion pressure of the package, and repeated contractions due to cooling is improved, and cracks are less likely to occur on the outer surface of the support.

(Example) A large number of sheets of unsaturated polyester containing 59% by weight of glass fiber were stacked, a glass cloth was placed on top of the sheets,
The whole is pressurized and heated to 140-170°C,
A support plate having the shape shown in FIGS. 1A and 1B was manufactured (Example 1).

Further, a sheet of unsaturated polyester resin containing 30% by weight of glass fiber is used as the potash of the sheet,
A support plate was manufactured in the same manner (Example 2).

The bending strength of these support plates was measured and the &l! Visually check the damage status &1! At the same time, the bag-shaped package containing water was housed in a pair of support plates, and microwave heat sterilization was repeated 100 times using the apparatus shown in FIG.

For comparison, a diallylphthalate support (Comparative Example 1), a silicone resin support containing 30% glass powder (Comparative Example 2), and an unsaturated polyester BMC molding containing 20% glass fiber were used. Using the product (Comparative Example 3),
A similar test was conducted.

The results are shown in Table 1.

Table 1 (Effects) As described above, according to the present invention, a support that can withstand multiple microwave irradiations and can be used repeatedly can be obtained.

[Brief explanation of the drawing]

FIGS. 1A and 1B are perspective views of the support plate, FIG. 2 is a sectional view of the support, and FIG. 3 is an explanatory diagram of the microwave irradiation device. 1...Support plate 10...Support patent application Hitotopyohan Printing Co., Ltd. Condolence map for Kazuo Suzuki] Diagram/Figure 2

Claims (1)

[Claims] (1) The package in which the object to be heated is sealed is made of a sheet mold compound molded product of unsaturated polyester resin containing glass fiber, and is stacked on top of each other to form a housing section having approximately the same shape as the package inside. A microwave heat sterilization method characterized by irradiating a support body with microwaves while the support body is accommodated in the above-mentioned accommodating portion of a support body consisting of a pair of support plates.