JP6870973B2 - Electron irradiation sterilization method of containers, plastic film used in the method, container packaging used in the method, automatic filling method - Google Patents

Description

The present invention relates to an electron beam irradiation sterilization method for a container. Further, the present invention relates to a plastic film used as a packing material in the method, a container / packing body used in the method, and a method of taking out a container from the container / packing body and automatically filling the container.

Containers filled with foods, pharmaceuticals, etc. are usually sterilized prior to filling the contents. Known methods for sterilizing containers include, for example, high-pressure steam sterilization, ethylene oxide sterilization, and radiation sterilization such as γ-rays and electron beams. Sterilization by irradiation does not require the container to be heated to a high temperature unlike high-pressure steam sterilization, and does not generate harmful residues or by-products unlike ethylene oxide sterilization.

Patent Document 1 is an invention relating to a method for sterilizing an inner bag for a bag-in-box (double bag with a mouth) and the like, characterized in that ultraviolet rays and radiation are used in combination. Ultraviolet rays have a weak penetrating power and can only sterilize the surface. Radiation such as γ-rays or electron beams requires high-dose irradiation when the number of bacteria is large, so that there is a problem that the physical properties of the packaging material are likely to change and a decomposed odor is generated. Patent Document 1 is characterized in that such defects due to ultraviolet rays and defects due to radiation are compensated for by combining both.

Conventionally, the inner bag for a bag-in-box has often been sterilized by γ-ray irradiation. This is because the film constituting the inner bag for the bag-in-box is thick, and many of them have a double bag structure. Since γ-rays have excellent penetrating power, γ-ray irradiation sterilization has less restrictions on the packaging form and less variation in dose, and products such as inner bags for bag-in-boxes can be sterilized, but the processing speed is slow.
On the other hand, electron beam irradiation sterilization is not as strong as γ-rays in penetrating power, but the processing speed is high. In recent years, an electron beam irradiation device having a penetrating power close to that of γ-rays has been developed, and in the sterilization process of the inner bag for a bag-in-box, the case where the electron beam irradiation sterilization with a high processing speed is adopted is increasing.

Patent Document 2 is an invention for the purpose of surely sterilizing the inner surface and the outer surface of a continuous container (continuous packaging bag) composed of a large number of packaging bags. After radiation treatment of each inner surface of the pair of continuous films, the pair of films are laminated to form a continuous container, and then the outer surface is sterilized.
When the packaging bag is sterilized, as described in Patent Document 2, the sterilization process may be performed in the state of continuous containers (a group of containers in which a plurality of containers are connected in a long shape via a scheduled line to be separated). There are many. The continuous container wound in a roll shape is sterilized by irradiating it with radiation while being unwound from the roll, and then wound up on the roll again.

In the bag-in-box inner bag with a spout, since the spout is installed in advance, it cannot be rolled into a roll, and it is difficult to perform the above-mentioned sterilization. For such a container that cannot be rolled into a roll, a plurality of containers are covered with a packing material to form a single container package, and then the container package is irradiated with radiation to sterilize the container. There is.

Japanese Unexamined Patent Publication No. 57-25855 Japanese Unexamined Patent Publication No. 2006-232381

The present inventors fold the inner bag for a bag-in-box with a spout in a continuous container state and put it in a bag-shaped packing material (a bag made of a plastic film) (see FIG. 3) to prepare a container packing body. The container and packaging body was sterilized by irradiating it with an electron beam. Then, a spark was generated between the continuous container and the packing material, and a pinhole was generated in the packing material. If pinholes occur in the packaging material, the cleanliness of the continuous container may deteriorate. In addition, if sparks occur between the continuous container and the packaging material, a part of the continuous container may melt out.
After the sterilization process, when the continuous container was taken out from the packing material, the overlapping inner bags for bag-in-box were in close contact with each other, and it was not possible to take out smoothly.

The problem to be solved by the present invention is that in a method of sterilizing a container in which a plurality of containers are coated with a packing material to form a container packing body and then the container packing body is irradiated with an electron beam, between the container and the packing material This is to prevent sparks from being generated in the container, and further to prevent the containers from coming into close contact with each other when the container is taken out from the container packaging body.

As a result of investigating the cause of sparks during electron beam irradiation sterilization and the cause of the containers sticking to each other when the containers are taken out, the present inventors have determined that the cause is static electricity accumulated in the container due to electron beam irradiation. I guessed. Then, they have found that the above-mentioned problems can be solved by imparting antistatic properties to the packaging material that covers the container in the container packaging body.

That is, according to the present invention, in the electron beam irradiation sterilization method of a container including a step of covering a plurality of containers with a packing material to prepare a container packing body and a step of irradiating the container packing body with an electron beam, the packing. Provided is an electron beam irradiation sterilization method for a container, characterized in that the surface resistance of the surface of the material in contact with the container is 1.0 × 10 ^{14 Ω / □ or less.}
Further, an electron beam irradiation sterilization method for the container is provided, wherein the surface resistivity of the surface of the packaging material in contact with the container is 1.0 × 10 ^{13 Ω / □ or less.}
Further, an electron beam irradiation sterilization method for the container, characterized in that the packaging material is a plastic film, is provided.

Furthermore, there is provided an electron beam irradiation sterilization method for the container, which comprises forming the plastic film into a bag shape.
Furthermore, an electron beam irradiation sterilization method for the container is provided, wherein the container is a bag with a spout.
Furthermore, there is provided an electron beam irradiation sterilization method for the container, which is characterized in that the container is in the state of a continuous container connected via a scheduled line to be separated.
Furthermore, there is provided an electron beam irradiation sterilization method for the container, wherein the container / packing body is a container in which the plurality of containers are coated with the packing material and further stored in the box body.

In addition, a plastic film having a surface resistivity of at least one surface of 1.0 × 10 ¹⁴ Ω / □ or less, which is used as a packaging material for an electron beam irradiation sterilization method for the container. Film is provided.
Further provided, the plastic film is characterized in that at least one surface layer is made of a resin composition containing an antistatic agent.

Further, it is a container packaging body formed by covering a plurality of containers with a packaging material having at least one surface resistivity of 1.0 × 10 ¹⁴ Ω / □ or less, and is used in the electron beam irradiation method of the container. A container packaging body characterized by this is provided.
Further, there is provided an automatic filling method characterized in that a container sterilized by an electron beam irradiation sterilization method of the container is taken out from a container package, introduced into an automatic filling machine, and the contents are filled in the container. Will be done.

In the electron beam irradiation sterilization method for containers according to the present invention, since the container is covered with a packaging material having a low surface resistivity prior to electron beam irradiation, static electricity is unlikely to accumulate in the container even if electron beam irradiation sterilization is performed. As a result, sparks generated between the packaging material and the container are suppressed. In addition, after electron beam irradiation sterilization, the problem that each container is in close contact and difficult to take out is reduced.
If the packing material is a bag-shaped plastic film, the work of covering the container with the packing material is easy. In addition, it is easy to carry the container when carrying it into a clean room or the like.
When the container to be sterilized according to the present invention is a continuous container connected via a scheduled separation line, the work of introducing the sterilized container into the automatic filling machine becomes easy. Furthermore, if the container is covered not only with a packaging material such as a plastic film but also with a box body, the container can be easily stored and transported, and the container packaging body can be stacked and irradiated with an electron beam. It becomes.

It is a figure for demonstrating the electron beam irradiation sterilization method of this invention, and is the schematic diagram of the packing step (A) and the irradiation step (B). It is a schematic cross-sectional view (A) (B) which shows an Example of the plastic film which is a packing material used in this invention. It is a schematic diagram for demonstrating the electron beam irradiation sterilization method of this invention. It is a graph which shows the variation of the charge amount of each container after the electron beam irradiation of Examples 1 and 2.

Hereinafter, the present invention will be described in more detail based on the drawings.
FIG. 1 is a schematic view for explaining an electron beam irradiation sterilization method for a container of the present invention. In the electron beam irradiation sterilization method of the present invention, a step (hereinafter referred to as a packing step) (A) in which a plurality of containers 10 are covered with a packing material 11 to prepare a container packing body X, and an electron beam is applied to the container packing body. It includes a step of irradiating (hereinafter, referred to as an irradiation step) (B).

[Packing step]
<Container>
In the packing step, the plurality of containers 10 are covered with the packing material 11.
Although the container 10 in FIG. 1 is a glass bottle, the electron beam irradiation sterilization method of the present invention can also be applied to other containers. Examples of the container 10 sterilized according to the present invention include a plastic bottle, a flat bag, a standing pouch, a gusset bag, an inner bag for a bag-in-box, and the like. In the packing step, the number of containers 10 covered with one packing material 11 is not particularly limited, but the container 10 already has a certain bulk before filling the contents, such as a glass bottle or a plastic bottle. In the case of, it is generally about ten to several tens. Further, when the container is a flat container such as a standing pouch, a gusset bag, an inner bag for a bag-in-box, etc. before filling the contents, it is generally about several tens to several hundreds. Further, the container may be in the state of a continuous container in which each container is connected via a scheduled line to be separated.

<Packing materials>
The packaging material 11 that wraps the plurality of containers 10 is ^{a film having a surface resistivity of at least one surface of 1.0 × 10 14} Ω / □ or less. If the resistivity exceeds 1.0 × 10 ¹⁴ Ω / □, it is difficult to suppress the spark between the packaging material 11 and the container 10. The surface resistivity is particularly preferably 1.0 × 10 ¹³ Ω / □ or less, particularly preferably 1.0 × 10 ¹² Ω / □ or less, and further preferably 1.0 × 10 ¹¹ Ω / □. □ It is desirable that it is less than or equal to. When the resistivity is 1.0 × 10 ¹¹ Ω / □ or less, it is difficult for each packaging bag to adhere to each other when the container is a continuous container connected via a planned disconnection line, and the packaging material 11 is continuous. The container can be easily taken out. In the case of irradiating an electron beam at a high dose, for easy container 10 is particularly charged, it is preferable that the surface resistivity of the packaging material 11 to 1.0 × 10 ⁸ Ω / □ or less.

The packing material 11 may be, for example, a plastic case or the like, but it is desirable that the packing material 11 is a flexible plastic film because the container 10 and the packing material 11 are easily in contact with each other.
The packaging material 11 can be obtained, for example, by molding a resin composition in which an antistatic agent is mixed with a resin conventionally used for a plastic film. Conventionally, resins used for plastic films include low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polypropylene, and the like. Olefin resin, polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate and other ester resins, polyamide, polyimide, polystyrene, polycarbonate, polyacrylonitrile, polyvinyl alcohol, polyvinylidene chloride and the like can be exemplified. The packaging material 11 of the present invention can be obtained by forming a film of a resin composition containing one or more of these resins and an antistatic agent. Considering the flexibility and price of the packaging material 11, it is desirable to use low-density polyethylene, linear low-density polyethylene, polypropylene, or the like, and to use a plastic film formed into a film as the packaging material 11. ..

Examples of the antistatic agent include a polymer-type antistatic agent, a surfactant-type antistatic agent, a conductive fine powder, and the like, and one or more of these can be selected and adopted. be able to. When transparency is required, it is preferable to use a polymer-type antistatic agent or a surfactant-type antistatic agent.
The polymer-type antistatic agent is a polymer-type antistatic agent called a persistent antistatic agent or a permanent antistatic agent, which is difficult to bleed out and has excellent transparency and long-lasting antistatic effect. Examples of the polymer type antistatic agent include polyethylene oxide, polypropylene oxide, polyethylene glycol, polyesteramide, polyetheramide, polyether esteramide, ionoma such as ethylene-methacrylic acid copolymer, and polyethylene glycol methacrylate-based agents. Molecular chains in one or a mixture of two or more kinds selected from quaternary ammonium salts such as polymers, or two or more kinds of copolymers, and copolymers of them and other resins. Examples of resins having a polar group therein and capable of copolymerizing or copolymerizing an inorganic salt or a low molecular weight organic protonate can be exemplified. Among these, polyether polyolefins and polyether ester amides are preferable, and polyether polyolefins are particularly preferable, from the viewpoint of compatibility with olefin resins and antistatic performance.

As the surfactant-type antistatic agent, conventionally known cationic surfactants, anionic surfactants, nonionic surfactants, amphoteric surfactants and the like can be used. As the cationic surfactant, for example, a quaternary ammonium salt, a pyridine derivative, or the like can be used. Further, as the anionic surfactant, for example, an alkyl sulfate ester salt, an alkyl aromatic sulfonate, a succinate sulfonate, a phosphoric acid ester salt and the like can be used. Examples of the nonionic surfactant include alcohol type (polyethylene glycol, etc.), ether type (polyoxyethylene alkyl ether, polyoxyalkylene alkyl ether, polyoxyethylene alkyl phenyl ether, etc.), and ester type (sorbitan fatty acid ester, poly). Oxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, glycerin fatty acid ester, etc.), amine type (polyoxyethylene alkylamine, alkyldiethanolamine, hydroxyalkylamine monoethanolamine, etc.), glycerin type (polyoxyethylene glyceride, etc.), The amide type (alkyl alkanol amide, alkyl diethanol amide, polyoxyethylene alkyl amide, etc.) can be used. Furthermore, as the amphoteric tenside, alkyl betaine, alkyl imidazolium betaine, hydroxyalkyl imidazoline sulfate ester, betaine-type carboxylic acid derivative, imidazoline derivative and the like can be used.

When irradiating an electron beam with a high dose, it is necessary to significantly reduce the surface resistivity of the packaging material 11. In such a case, it is desirable to use a conductive fine powder as an antistatic agent.
As the conductive fine powder, one kind or two or more kinds can be selected and adopted from tin oxide, zinc oxide, indium oxide, carbon black, an organic conductive compound and the like.

The amount of the antistatic agent contained in the resin composition forming the packaging material 11 is not particularly limited, and may be appropriately determined so that ^{the surface resistivity is 1.0 × 10 14 Ω / □ or less.} In order to achieve such a resistivity, it is desirable to add an antistatic agent in an amount of about 5 to 35% by weight, and particularly preferably about 10 to 25% by weight, in the resin composition forming the packaging material 11. .. When the amount of the antistatic agent compounded is small, the desired antistatic performance cannot be obtained, and it is difficult to prevent static electricity from staying in the container to be sterilized by electron beam irradiation. Further, if the amount of the antistatic agent compounded is large, the surface resistivity of the film surface decreases, but the film becomes expensive.

The packing material 11 shown in FIG. 1 is a single-layer plastic film made of the above-mentioned resin or antistatic agent, but the packing material 11 of the present invention has a surface resistance of 1 as shown in FIG. 2 (A). It may be a two-layer plastic film composed of a layer of 0.0 × 10 ¹⁴ Ω / □ or less (hereinafter referred to as an antistatic layer) 21a and another layer 21b, and further as shown in FIG. 2 (B). , A three-layer plastic film in which another layer 21'b is arranged between two antistatic layers 21'a may be used. The plastic films 21 and 21'shown in FIGS. 2 (A) and 2 (B) require a smaller amount of antistatic agent to achieve the same effect as compared with the single-layer plastic films having the same film thickness. ..
When the surface resistivity of one surface layer and the surface resistivity of the other surface layer are different as in the plastic film 21 shown in FIG. 2 (A), the layer having a low resistivity becomes the inner surface (the surface in contact with the contents). In addition, it is desirable to cover the container with the plastic film 21 because it can effectively prevent the container from being charged.

<Container packaging>
A plurality of containers may be coated with the above-mentioned packing material 11 and sterilized by electron beam irradiation as the container packing body X, but the container packing body X shown in FIG. 1 further includes a box body 12. As the box body 12, a box body conventionally used as a packaging material can be appropriately used, and for example, a corrugated cardboard box or the like may be used. When the container / packing body X is composed of only the container 10 and the packing material 11 such as a plastic film, the plastic film is flexible and difficult to carry. In addition, the container 10 may be cracked or deformed. Therefore, it is preferable that the container / packing body X of the present invention includes a box body 12 having a shape-retaining property.

<Coating method (method of making container packaging)>
The method of covering the plurality of containers 10 with the packing material 11 or the box body 12 to create the container packing body X is not particularly limited. For example, the box body 12 is opened, the packing material 11 is laid, and the center of the packing material 11 is laid. It is preferable to arrange the container 10 in the portion, fold the four sides of the packing material 11, and further fold the four flaps of the box body 12. It is desirable that the packaging material 11 made of a plastic film is previously molded into a bag shape. When the packing material 11 is made of a plastic film and has a bag shape, the work of covering the plurality of containers 10 and the work of taking out the plurality of containers 10 from the box body 12 at one time become easy.

[Irradiation step]
When the container / packing body X is completed, the packing body X is irradiated with an electron beam. The method of irradiating the electron beam is not particularly limited, and the same method as the conventional method can be adopted. In FIG. 1B, the container / packaging body X is supplied to the electron beam irradiation device Y by a belt conveyor or the like (not shown), and the electron beam is irradiated from above the container / packaging body X. The irradiation amount of the electron beam is not particularly limited, but irradiation of 2 to 60 kGy, particularly 5 to 30 kGy is common. Further, the electron beam irradiation of the container / packaging body X may be performed a plurality of times. For example, if the container / packaging body X is irradiated with an electron beam, the container / packaging body X is turned upside down, and the container / packaging body X is sterilized by electron beam irradiation again, the container / packaging body X can uniformly perform the electron beam irradiation.

[Another Embodiment]
FIG. 3 is a schematic diagram for explaining another embodiment of the electron beam irradiation sterilization method of the present invention.
The container 30 in FIG. 3 is a bag with a spout 30s used as an inner bag for a bag-in-box, and is stored in the packing material 31 in the state of a continuous container in which each container 30 is connected.
Bags with spouts cannot be rolled up because they have spouts. As shown in FIG. 3, such a container 30 may be folded in a continuous container state and covered with a packing material 31. In the sterilization method shown in FIG. 3, the container (bag with spout) 30 is covered with the packing material 31 and the box body 32 made of a cardboard box to prepare the container packing body X (packing step), and then the container packing body is electronically charged. The container 30 is sterilized by electron beam irradiation by irradiating the wire (irradiation step).
When filling the container 30, it is preferable to pull out the earliest container from the container package sterilized by electron beam irradiation and introduce it into the automatic filling machine. Since the container is stored in the packing material 31 in the state of a continuous container, when the first container is introduced into the automatic filling machine, other containers are sequentially supplied to the automatic filling machine. The containers sterilized by the electron beam irradiation sterilization method of the present invention are difficult to adhere to each other, so that the containers can be smoothly supplied to the automatic filling machine.

Hereinafter, the effects of the present invention will be shown based on Examples. The evaluation methods in each of the examples and comparative examples are as follows.
[Easy to take out the container]
After electron beam irradiation sterilization, the containers (bags with spouts) are sequentially taken out from the container package. Those that could be taken out smoothly without the containers sticking to each other were ○, those with some sticking between the containers were △, and the containers were often sticking to each other, so it seems that they are not suitable for introduction to the automatic filling machine. The thing is x.
[Presence / absence of spark]
After electron beam sterilization, the packaging material (bag-shaped plastic film) is taken out, the bag-shaped film is cut open in a flat state, and then the packaging material is placed on paper. Alcohol is sprayed on the surface of the packaging material, and it is confirmed whether or not the alcohol permeates the packaging material and reaches the paper. If there are traces of alcohol on the paper, it is determined that the packaging material has pinholes. If the packaging material has pinholes, it is probable that sparks have occurred between the container and the packaging material during electron beam irradiation sterilization.

[Example 1]
A resin composition obtained by adding 20% by weight of a glycerin fatty acid ester antistatic agent to 80% by weight of a polyethylene-based resin is formed to produce a 50 μm single-layer film, and the film is used as a packaging material. The surface resistivity of the packaging material was 1.0 × 10 ¹² Ω / □.
The packaging material is molded into a bag shape, which is stored in a cardboard box, and 200 containers (bags with spouts) are stored in a continuous container, the opening of the packaging material is folded, and the cardboard box Fold the flaps to get the packaging. Next, the container package is irradiated with an electron beam of 10 kGy, the container package is turned upside down and irradiated with an electron beam of 10 kGy, the container package is further inverted and irradiated with an electron beam of 10 kGy, and the container package is further irradiated with an electron beam of 10 kGy. The container was inverted and irradiated with an electron beam of 10 kGy, and the container was sterilized by irradiation with an electron beam (irradiated with an electron beam of 10 kGy each on the front and back twice).
After irradiation, the container (bag with spout) was taken out from the container package, and the ease of taking out the container was confirmed. After removing the container, it was confirmed that there were no pinholes in the packaging material. The results are shown in Table 1.

[Example 2]
A layer (A) made of a propylene resin, a layer (B) made of an ethylene resin, 75% by weight of an ethylene resin, 20% by weight of a polyether olefin polymer type antistatic agent, and a nonionic surfactant. A three-layer film of 80 μm provided with an antistatic layer (C) made of 5% by weight of the antistatic agent in this order is produced, and the film is used as a packing material. The surface resistivity of the antistatic layer (C) of the packaging material was 1.0 × 10 ¹⁰ Ω / □.
In the same manner as in Example 1, 200 containers (bags with spouts) were sterilized by electron beam irradiation. When the plastic film was molded into a bag shape, the antistatic layer (C) of the packaging material (plastic film) was placed inside.
After irradiation, the container (bag with spout) was taken out from the container package, and the ease of taking out the container was confirmed. After removing the container, it was confirmed that there were no pinholes in the packaging material. The results are shown in Table 1.

[Comparative Example 1]
Electron beam irradiation sterilization was carried out in the same manner as in Example 1 except that an antistatic agent was not added when the packaging material was produced. The surface resistivity of the packaging material was 1.0 × 10 ¹⁶ Ω / □. Table 1 shows the ease of taking out the container and the presence or absence of sparks.

In Examples 1 and 2 in which electron beam irradiation sterilization was performed using a packaging material containing an antistatic agent, no pinholes were observed in the packaging material. Therefore, it is probable that no sparks were generated during the sterilization process. On the other hand, a large number of pinholes were confirmed in the packaging material used in Comparative Example 1. Therefore, it is considered that sparks were generated during the sterilization process. Further, as the surface resistivity of the packaging material decreased, the number of containers that were in close contact with each other at the time of taking out decreased.

In Examples 1 and 2, when the containers were taken out, the amount of charge on the front and back sides of each container was measured. The electrostatic position difference of each container of Example 1 was within ± 20 kV, and that of Example 2 was within ± 15 kV. The variation in the charge amount of each container is shown in FIG. When the standard deviation values of the charged amounts of Examples 1 and 2 were obtained, they were 8.02 (Example 1) and 6.14 (Example 2). It was confirmed that the smaller the surface resistivity of the packaging material, the less likely it is that the container will be charged.

10 containers (glass bottles)
11, 21, 21', 31 Packaging material (plastic film)
12, 32 Boxes 21a, 21'a Antistatic layers 21b, 21'b Other layers 30 Containers (bag with spout / continuous container)
30s Spout X Container Package Y Electron beam irradiation device

Claims (6)

The present invention includes a step of covering a plurality of containers in a continuous state connected via a planned separation line with a packing material made of a plastic film to create a container packing body, and a step of irradiating the container packing body with an electron beam. In the electron beam irradiation sterilization method for containers,
A method for sterilizing a container by electron beam irradiation, wherein the surface resistivity of the surface of the packaging material in contact with the container is 1.0 × 10 ^{11 Ω / □ or less.} The method for sterilizing a container by electron beam irradiation according to claim 1, wherein the plastic film is molded into a bag shape. The method for sterilizing a container by electron beam irradiation according to claim 1 or 2, wherein the container is a bag with a spout. The electron of the container according to any one of claims 1 to 3, wherein the container packaging body is a container in which the plurality of containers are coated with the packaging material and further stored in the box body. Radiation sterilization method. At least one surface resistivity is 1.0 × 10 ¹¹ A packaging material made of a plastic film of Ω / □ or less, which covers a plurality of containers in a continuous state connected via a planned separation line, and is any one of claims 1 to 4. A container packaging body, which is used in the method for irradiating an electron beam of a container according to the above item. A plurality of containers that have been sterilized by the electron beam irradiation sterilization method for the container according to any one of claims 1 to 4 and are in a continuous state connected via a scheduled separation line are automatically taken out from the container package. An automatic filling method characterized by being introduced into a filling machine and filling the contents in the container.

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