JP7841839B2 - Steam-permeable pouch - Google Patents

Description

This invention relates to a steam-permeable pouch whose opening can be easily torn open by hand, and which can also be used as a food container after opening.

For example, microwave pouches containing contents to be heated, such as retort foods and frozen foods, are widely used. When these pouches are heated in a microwave, the water in the contents evaporates, increasing the pressure inside the pouch. This increased pressure can cause the pouch to rupture, scattering the contents and contaminating the microwave. Therefore, steam-release pouches equipped with a steam venting mechanism are known to release the increased pressure inside the pouch.

A steam-permeable pouch includes a sealed sheet that forms a containment space capable of holding contents, and a steam-permeable section where a portion of the sheet is sealed to open as the pressure in the containment space increases. When heating causes the pressure in the containment space to rise to a certain level, the seal constituting the steam-permeable section detaches, forming a passage connecting the containment space to the outside space. Therefore, moisture in the containment space is discharged to the outside of the pouch through the passage formed in the steam-permeable section, suppressing the rise in pressure within the containment space.

Patent Document 1 discloses a microwave-safe pouch, which is an example of a conventional steam-heated pouch. As shown in Patent Document 1, this microwave-safe pouch comprises a laminated sheet. The laminated sheet includes a base layer, a printed layer, other layers, and a sealant layer. When heating of the microwave-safe pouch containing the contents by the heating means is completed, the laminated sheet is torn from the opening, and the contents are removed from the storage space.

Japanese Patent Publication No. 2018-127257

However, with the microwave pouch described in Patent Document 1, when attempting to tear the laminated sheet from the opening by hand, the innermost sealant layer stretches during the tearing process, preventing a straight tear, causing fuzzing or wavy deformation at the tear point. This results in an insufficient opening, making it difficult to easily remove the contents from the opening.

This invention was made in view of the above problems, and aims to provide a steam-permeable pouch in which the opening can be neatly and cleanly torn by hand or other means, allowing for easy removal of the contents.

According to claim 1 of the present invention, the product comprises opposing body member sheets and a bottom member sheet that is folded into the bottom surface, and the peripheral edges of the left side, right side, and bottom surface are sealed, and the top surface is sealed after the contents are filled, thereby providing a storage space for the contents.
A steam-permeable pouch comprising, at least one of the sealing portions on the left and right sides, a steam-permeable portion for releasing steam from the containment space during heating, and an opening portion on the bottom or top side of the steam-permeable portion that is substantially parallel to the bottom surface,
The aforementioned body member sheet and bottom member sheet have the outermost layer, intermediate layer, and sealant layer reduced, respectively.
This also includes,
The outermost layer is made of transparent vapor-deposited polyethylene terephthalate,
The aforementioned intermediate layer is made of a material that has excellent heat resistance and easy tearing properties in the width direction.
The opening portion is further provided with a guide portion that guides the cutting of the sheet from the right end of the left side seal portion to the left end of the right side seal portion, and the guide portion includes a cutting line provided only in the intermediate layer.
The sealant layer of the aforementioned body member sheet is made of a material that has excellent heat resistance and easy tearing in the width direction.
The sealant layer of the bottom member sheet is made of unstretched polypropylene.

When a steam-permeable pouch is heated with contents inside, a passage connecting the contents to the outside space is formed in the steam-permeable section as the pressure inside the contents increases. Therefore, water vapor from the contents inside the contents passes through the passage formed in the steam-permeable section and is discharged to the outside of the steam-permeable pouch, suppressing the increase in pressure inside the contents. Furthermore, since the sealant layer of the body sheet is made of a material that is easily torn in the width direction, the sheet can be easily torn in that direction. Therefore, the contents can be easily removed from the torn portion of the body sheet. Also, since the sealant layer of the bottom sheet is made of a material with appropriate stiffness and bottom-opening properties, the container's suitability for filling is ensured.

Furthermore, according to claim 2 of the present invention, the sealant layer of the body member sheet contains 3 to 10 parts by weight of low-crystallinity ethylene-based elastomer per 100 parts by weight of propylene-ethylene block copolymer, wherein the low-crystallinity ethylene-based elastomer is made of unoriented polypropylene having a density in the range of 0.865 to 0.890 g/ ^cm³ and a heat absorption amount at melting in the range of 5 to 30 J/g as defined in JIS standard 7122, and the sealant layer of the bottom member sheet is made of unoriented polypropylene. Polypropylene is a resin with excellent heat resistance and can be suitably used as a material for microwave pouches that require boiling and retort suitability.

Furthermore, the sealant layer of the body sheet has easy tearing properties in the width direction, allowing the sheet to be easily torn in that direction. While short, thread-like fibers may sometimes remain in the torn area, this phenomenon is almost nonexistent with polypropylene. Therefore, the contents can be easily removed from the torn portion of the sheet.

Furthermore, the sealant layer of the bottom sheet is made of unstretched polypropylene. Unstretched polypropylene is a film molded without stretching the polypropylene material. Because it stretches when pulled, it is not easily torn and unsuitable for body components. However, it is flexible and has bottom-opening properties, making it suitable for filling and resistant to tearing when pulled.

Furthermore , both or at least one of the body sheet and the bottom sheet further include an intermediate layer laminated between the outermost layer and the sealant layer. This increases the strength of the permeable pouch.

Furthermore , the intermediate layer is made of a material that has excellent heat resistance and ease of tearing in the width direction. Because the intermediate layer is made of a material that has excellent ease of tearing in the width direction, the sheet can be easily torn. Therefore, the contents can be easily removed from the torn part of the sheet.

Furthermore , the opening portion has a notch in at least one of the sealing portions on the left and right sides, and further includes a guide portion that guides the cutting of the sheet from the right end of the left side sealing portion to the left end of the right side sealing portion. With the above-described steam-permeable pouch, the notch can be used as the starting point for tearing, and the sheet can be easily torn along the guide portion.
Therefore, the contents can be easily removed from the torn portion of the sheet.

Furthermore , the guide portion includes a perforated line provided in the intermediate layer. With the above-described steam-permeable pouch, even when the intermediate layer is present, the sheet can be easily torn. Therefore, the contents can be easily removed from the torn portion of the sheet.

According to the steam-permeable pouch of the present invention, the opening can be neatly and cleanly torn open by hand or other means, allowing for easy removal of the contents.

A front view of a steam-permeable pouch, illustrating an example of an embodiment of the present invention. A cross-sectional view showing the layer structure of the body sheet and the bottom sheet. Enlarged view of the steam passage and its surroundings in an open state. Front view of an opened steam-permeable pouch.

The following describes an example of an embodiment of the present invention. Figure 1 shows an example of a steam-permeable pouch 10 capable of containing contents 15 suitable for heating and discharging steam generated from the contents 15. The contents 15 are a heated object that generates steam when heated. An example of the contents 15 is food. An example of food is a fluid food such as stew and soup. The steam-permeable pouch 10 is configured to allow long-term storage while maintaining the quality of the contents 15. Examples of shapes that the steam-permeable pouch 10 can take include self-standing types such as standing type and gusset type. The shape of the steam-permeable pouch 10 exemplified in Figure 1 is a standing type. Hereinafter, the left-right direction of the steam-permeable pouch 10 in a front view will be referred to as the standard width direction, and the direction perpendicular to the standard width direction will be referred to as the standard height direction.

The steam-permeable pouch 10 includes a body sheet 20, a bottom sheet 23, a top sealing section 31, a bottom sealing section 32, a right side sealing section 33, a left side sealing section 34, an opening section 50, and a steam-permeable section 60. The body sheet 20 consists of a front sheet 21 and a back sheet 22. The front sheet 21 and the back sheet 22 are facing each other such that a storage space 11 for containing the contents 15 is formed between the sheets 21 and 22. The bottom sheet 23 is folded around its periphery to seal the space between the bottom of the front sheet 21 and the bottom of the back sheet 22.

The body member sheets 20 (21, 22) and the bottom member sheet 23 have a layered structure with multiple layers laminated together. Figure 2(a) is a cross-sectional view showing the layered structure of the body member sheet, and Figure 2(b) is a cross-sectional view showing the layered structure of the bottom member sheet. The body member sheets 20 (21, 22) include an outermost layer 20A, an intermediate layer 20B, a sealant layer 20C, a first adhesive layer 20D, and a second adhesive layer 20E. Similarly, the bottom member sheet 23 includes an outermost layer 23A, an intermediate layer 23B, a sealant layer 23C, a first adhesive layer 23D, and a second adhesive layer 23E. One example of a manufacturing method for each sheet 21-23 is dry lamination. The first adhesive layer of each sheet 21-23 is provided between the outermost layer and the intermediate layer, and the second adhesive layer is provided between the intermediate layer and the sealant layer.

The outermost layer 20A of the body member sheet 20 (21, 22) is mainly excellent in gas barrier properties, printability, and heat resistance. The outermost layer 20A is, for example, a transparent vapor-deposited layer. An example of the material constituting the outermost layer 20A is polyethylene terephthalate with an inorganic thin film vapor-deposited on it (hereinafter referred to as "vapor-deposited PET"). The intermediate layer 20B is mainly excellent in heat resistance and moisture resistance. The material constituting the intermediate layer 20B is nylon (hereinafter referred to as "veneer") which has easy tearing properties in the width direction of the body member sheet 20.
This is referred to as "Easy-Cut Ny". Hereinafter, the orientation direction of the material constituting each sheet 21, 22 will be referred to as the MD (Machine Direction) direction, and the direction perpendicular to the MD direction will be referred to as the TD (Transverse Direction) direction. The MD direction of each sheet 21, 22 is the direction along the standard width direction. The TD direction of each sheet 21, 22 is the direction along the standard height direction. An example of the material constituting the first adhesive layer 20D is a polyester adhesive. An example of the material constituting the second adhesive layer 20E is a polyester adhesive.

Regarding the bottom sheet 23, the outermost layer 23A is made of the same material as the outermost layer 20A of the body sheet 20, but an example of the material for the intermediate layer 23B is unstretched nylon that is not easily cut.

The sealant layer 20C of the body sheet 20 exhibits excellent heat resistance, heat sealability, and impact resistance. An example of the material constituting the sealant layer 20C is unoriented polypropylene (hereinafter referred to as "easy-cut CPP") with excellent tear resistance in the MD direction.

Excellent tear resistance in the MD direction refers to a tear force of 1.2 N or less, as defined by the trouser tear test method specified in JIS standard K7128-1. In the trouser tear test method, a rectangular test specimen with a length of 50 mm in the TD direction and 150 mm in the MD direction was cut 75 mm in the center, and the tear force in the MD direction was measured at a speed of 200 mm/min in a constant temperature room at 23°C.

The easily cut CPP contains, for example, 3 to 10 parts by weight of a low-crystallinity ethylene-based elastomer per 100 parts by weight of propylene-ethylene block copolymer. The low-crystallinity ethylene-based elastomer has, for example, a density in the range of 0.865 to 0.890 g/ ^cm³ and a heat absorption during melting in the range of 5 to 30 J/g as defined in JIS standard 7122.

The sealant layer 23C of the bottom sheet 23 has excellent heat resistance, heat sealability, and flexibility, and is suitable for bottom opening. Furthermore, it is an unstretched film, has the property of stretching when pulled, and is not easily cut.

The sealing portions 31-34 shown in Figure 1 join the sheets 21-23 together to prevent them from separating. One example of a method for forming the sealing portions 31-34 is heat sealing. The outer shape of the permeable pouch 10 in a front view can be arbitrarily selected. In the example shown in Figure 1, the outer shape of the permeable pouch is rectangular.

The opening section 50 has a notch 51 on at least one of the left and right side seal sections, and a guide section 52 is provided on the body member sheet 20 at the same height as the notch 51 in the standard height direction, guiding the cutting of the body member sheet 20 from the right end of the left side seal section to the left end of the right side seal section. The position of the opening section 50 (notch 51, guide section 52) in the standard height direction can be arbitrarily selected. In one example shown in Figure 1, the opening section 50 is provided between the steam passage section 60 and the bottom member sheet 23 in the standard height direction. In a preferred example, it is provided closer to the steam passage section 60 than to the bottom member sheet 23 in the standard height direction. In another example, the opening section 50 is provided between the steam passage section 60 and the top seal section 31 in the standard height direction.

The guide portion 52 is a collection of perforations formed on the body member sheet 20, and is formed to follow the MD direction of the body member sheet 20. The notch 51 is formed on at least one of the right side seal portion 33 and the left side seal portion 34 such that the tip of the notch 51 lies on a virtual line extending from the guide portion 52. Figure 1 shows an example where the notch 51 is formed on the left side seal portion 34.

The opening portion 50, where the guide portion 52 is formed, has lower tear strength than other parts of the body sheet 20 where the guide portion 52 is not formed. Therefore, when force is applied to the opening portion 50 in the direction along the guide portion 52, the body sheet 20 is easily torn along the guide portion 52. The guide portion 52 includes a plurality of discontinuously formed notches 52A in the standard width direction. A means for forming the guide portion 52 is, for example, a perforation machine.

The shape of the notch 52A can be straight, curved, perforated, or dashed, and the number of notches can be one or more in the standard height direction. In this invention, it is sufficient that the notch 52A portion is weakened and acts as a cut in the opening portion 50.

In a preferred example, the notch 52A does not penetrate all three layers of the body member sheet 20—the outermost layer 20A, the intermediate layer 20B, and the sealant layer 20C—but is formed in one or two of the three layers. Because the notch 52A does not penetrate the three layers of the body member sheet 20, the contents 15 contained in the containment space 11 do not pass through the guide portion 52 to the outside. In this embodiment, the notch 52A is provided to penetrate only the intermediate layer 20B of the body member sheet 20.

The steam-permeable pouch 10 is heated by a heating means to heat the contents 15. An example of a heating means is a microwave oven. As the steam-permeable pouch 10 is heated, steam is generated from the contents 15. The pressure in the containment space 11 increases as steam is generated. The steam vent 60 opens as the pressure in the containment space 11 rises, allowing the steam from the containment space 11 to be discharged to the outside of the steam-permeable pouch 10. In a preferred example, the steam vent 60 is configured to open when the pressure in the containment space 11 rises to a pressure within a predetermined pressure range.

The steam passage section 60 can take various forms. In one example, the steam passage section 60 is provided on at least one of the right side seal section 33 and the left side seal section 34. In another example, the steam passage section 60 is provided inside the seal section, independently of the right side seal section 33 and the left side seal section 34. Figure 1 shows an example where it is provided only on the right side seal section 33.

The shape of the steam passage section 60 is recessed from the outside in the standard width direction. The tip 61, which is the innermost part of the steam passage section 60 in the standard width direction, is located where strong stress concentration occurs when the pressure in the containment space 11 of the body member sheet 20 rises. It opens when the pressure in the containment space 11 rises to a predetermined pressure range.

Specifically, as the pressure in the containment space 11 increases, the front sheet 21 and the back sheet 22, which are joined at the tip 61 of the steam vent section 60, separate, and a steam vent passage 62 is formed in the steam vent section 60, connecting the containment space 11 to the outside of the steam-permeable pouch 10, as shown in Figure 3. The extent to which the steam vent section 60 separates varies depending on the pressure in the containment space 11. If the pressure in the containment space 11 is high, the separation may progress to the base of the steam vent section 60. The passage area of the steam vent passage 62 widens as the separation of the steam vent section 60 progresses. When the steam vent section 60 opens, the water vapor in the containment space 11 passes through the steam vent passage 62 and is discharged to the outside of the steam-permeable pouch 10. The discharge of water vapor suppresses the increase in pressure in the containment space 11, preventing the steam-permeable pouch 10 from rupturing.

Figure 4 shows a steam-permeable pouch 10 with the opening section 50 opened after cooking. When opening the opening section 50, the body sheet 20 is torn from the tip of the notch 51, and force is applied to the body sheet 20 so that the tearing progresses along the guide section 52, thereby opening the entire opening section 50. The user can then use the opened steam-permeable pouch 10 as a container and consume the contents 15.

Using samples from the examples and comparative examples, tests were conducted to confirm the relationship between the layer structure of the body sheet 20 and the bottom sheet 23 and their tearability and bottom opening properties. The samples were retort pouches containing curry. After heating the samples in a 600W microwave for 1 minute, the tearability (hereinafter referred to as "cutability") and bottom opening properties of the body sheet 20 were evaluated using a 5-point scoring system. The scoring scale was as follows: 5: Good > 4: Fairly Good > 3: Average > 2: Fairly Poor > 1: Poor. Table 1 shows the layer structure and the scoring results for cutability and bottom opening properties of the samples.

The meanings of the material-related terms shown in Table 1 are as follows:

<Transparent vapor-deposited PET12>
A transparent vapor-deposited film made by depositing aluminum oxide onto a polyethylene terephthalate film (12 μm thick).
<Easy-cut PET12>
A polyethylene terephthalate film (12 μm thick) with excellent tear resistance in the MD direction. Excellent tear resistance in the MD direction means, for example, that the tear force conforming to the trouser tear test specified in JIS standard K7128-1 is 1.2 N or less.
<Easy-cut CPP60>
An unstretched polypropylene film (60 μm thick) comprising 3 to 10 parts by weight of a low-crystallinity ethylene-based elastomer per 100 parts by weight of propylene-ethylene block copolymer, wherein the low-crystallinity ethylene-based elastomer has a density in the range of 0.865 to 0.890 g/cm³ and a heat absorption during melting in the range of 5 to 30 J/g as defined in JIS standard 7122.
<Easy-cut NY15>
A polyamide film (15 μm thick) with excellent tear resistance in the MD direction.
<PET12>
A polyethylene terephthalate film (12 μm thick) with poor tear resistance in the MD direction. Poor tear resistance in the MD direction means, for example, that the tear force according to the trouser tear test specified in JIS standard K7128-1 is greater than 1.2 N.
<CPP60>
An unoriented polypropylene film (60 μm thick) with poor tear resistance in the MD direction.
<Ny15>
A polyamide film (15 μm thick) with poor tear resistance in the MD direction.

As can be seen in Table 1, when the sealant layer of the body sheet is made of easily cuttable CPP and the sealant layer of the bottom member is also made of CPP, the best steam-permeable pouch with the best cutability and bottom opening suitability is obtained.

Based on the above, the steam-permeable pouch of the present invention provides the following actions and effects. When the contents are contained in the storage space and the sealed steam-permeable pouch is heated, a steam vent passage connecting the storage space to the outside is formed in the steam-permeable section as the pressure in the storage space increases. Therefore, the water vapor in the storage space is discharged to the outside of the steam-permeable pouch through the steam vent passage, suppressing the increase in pressure in the storage space.

Furthermore, since the sealant layer of the body sheet is made of a material with excellent tear resistance in the MD direction, the body sheet can be easily torn by hand from the opening. Therefore, the contents can be easily removed from the opening. Also, the sealant layer of the bottom sheet is M
Because it is made of a material that does not have excellent tear resistance in the D direction, it is flexible and has bottom-opening properties, making it possible to provide a steam-permeable pouch suitable for filling.

10...Steam-permeable pouch 11...Storage space 15...Contents 20...Body sheet 20A...Outermost layer of body sheet 20B...Intermediate layer of body sheet 20C...Sealant layer of body sheet 20D...First adhesive layer of body sheet 20E...Second adhesive layer of body sheet 21...Front sheet 22...Back sheet 23...Bottom sheet 23A...Outermost layer of bottom sheet 23B...Intermediate layer of bottom sheet 23C...Sealant layer of bottom sheet 23D...First adhesive layer of bottom sheet 23E...Second adhesive layer of bottom sheet 31...Top seal section 32...Bottom seal section 33...Right side seal section 34...Left side seal section 50...Opening section 51...Notch 52...Guide section 52A...Cut 60...Steam passage 61...Tip of steam passage 62...Steam vent passage

Claims (2)

It consists of opposing body sheet members and a bottom sheet member that is folded into the bottom surface.
The left side, right side, and bottom edges are sealed, and after filling with contents, the top surface is sealed to create a storage space for the contents.
A steam-permeable pouch comprising, at least one of the sealing portions on the left and right sides, a steam-permeable portion for releasing steam from the containment space during heating, and an opening portion that is substantially parallel to the bottom surface only on the upper side of the steam-permeable portion,
The body member sheet and the bottom member sheet each include at least an outermost layer, an intermediate layer, and a sealant layer.
The outermost layer is made of transparent vapor-deposited polyethylene terephthalate,
The intermediate layer of the body member sheet is made of polyethylene terephthalate having a widthwise tear force of 1.2 N or less, in accordance with the trouser tear method specified in JIS K7128-1.
The intermediate layer of the body member sheet is composed of a single layer.
The opening portion is further provided with a guide portion that guides the cutting of the sheet from the right end of the left side seal portion to the left end of the right side seal portion, and the guide portion includes a cutting line provided only in the intermediate layer of the body member sheet .
The sealant layer of the body member sheet is made of a material having a widthwise tear force of 1.2 N or less, in accordance with the trouser tear test specified in JIS K7128-1.
The sealant layer of the bottom member sheet is made of unstretched polypropylene.
The intermediate layer of the bottom sheet is a breathable pouch made of nylon with a widthwise tear force exceeding 1.2 N, conforming to the trouser tear method specified in JIS K7128-1 . The steam-permeable pouch according to claim 1, wherein the sealant layer of the body sheet contains 3 to 10 parts by weight of a low-crystallinity ethylene-based elastomer per 100 parts by weight of propylene-ethylene block copolymer, and the low-crystallinity ethylene-based elastomer is made of unstretched polypropylene having a density in the range of 0.865 to 0.890 g/cm³ ^and a heat absorption amount at melting in the range of 5 to 30 J/g as defined in JIS K 7122.