JP5705635B2 - Gas permeable film, method for producing the same, and container using the gas permeable film - Google Patents

Description

  The present invention relates to a gas permeable film that allows gas such as oxygen, carbon dioxide, and water vapor to pass through, a manufacturing method thereof, and a container using the gas permeable film. This gas-permeable film is particularly suitable for use in packaging materials such as fruits and vegetables, fermented foods, and containers (bags) for heating a microwave oven.

  A gas permeable film that has a gas permeable part on a film base and allows gas such as oxygen, carbon dioxide, and water vapor to pass through the gas permeable part is mainly used as a packaging material for products in a wide range of food and medical fields. It is used. For example, when vegetables, fruits and the like are packaged using this gas permeable film, they can be stored while maintaining freshness for a relatively long period of time. This type of gas-permeable film generally uses a polymer film as the film base and has fine holes that pass through the base in the film base, or non-through holes that do not pass through the base. They are broadly divided into those provided.

For example, Patent Document 1 below discloses a storage bag in which a polymer film having a predetermined thickness is provided with micropores having a predetermined opening area. This storage bag stores citrus fruits. Patent Document 2 below discloses a microwave heating bag provided with non-through holes. This heating bag is composed of a laminated film in which an inner layer and an outer layer are bonded together by an intermediate layer (adhesive layer), and a non-through hole is formed in the inner layer. In this microwave heating bag, when frozen food is stored and heated in a microwave oven, water vapor is generated from the frozen food, and this water vapor permeates through the thin part at the bottom of the non-through hole and enters the intermediate layer. The intermediate layer is peeled off and released to the outside. Further, a gas permeable film provided with the same non-through hole is also described in Patent Document 3 below. This permeable film has an average hole area of 10 ⁻⁶ to 10 ⁻² cm ² and a depth of 1 to 99.0% relative to the thickness of the base film on one side of a single layer or multilayer basic film. The non-through hole is provided.

JP 2006-158254 A (paragraphs [0013] to [0015]) Japanese Patent Laying-Open No. 2006-27627 (paragraphs [0014] and [0015], FIG. 3) JP-A-8-52816 (paragraphs [0014] to [0019])

  Since the storage bag of Patent Document 1 is a polymer film provided with a through-hole penetrating the polymer film, depending on the use environment, unnecessary materials (for example, dust, dust, bacteria, etc.) may enter the bag. There is a risk of intrusion. In addition, this storage bag is not suitable for packaging such moisture-containing bags because if moisture-containing items are put inside, moisture may ooze out to the outside through the through holes. There are problems such as limited applications. On the other hand, since the film of the said patent document 2 and 3 is a non-through-hole (hole), even if what contains a water | moisture content is blocked | prevented while an intrusion of an unnecessary object is prevented, it will ooze out to the exterior naturally. There is nothing. Moreover, when the microwave oven heating bag of Patent Document 2 is heated in the microwave oven, water vapor is generated from the frozen food in the bag, and this water vapor permeates through a thin portion at the bottom of the non-through-hole. The water vapor enters and is discharged to the outside. At this time, the water vapor is transmitted through the thin portion at the bottom of the non-through hole and discharged due to the increase in internal pressure in the bag.

  The present inventors created a film provided with the same non-through hole with reference to the inner layer constituting the laminated film of Patent Document 2 above, and confirmed the gas permeation effect by experiments. FIG. 13A is an enlarged cross-sectional view of a non-through hole portion of a film in which a non-through hole is provided in the film base, and FIG. 13B is a cross-sectional view illustrating a permeation effect when gas permeates due to an increase in internal pressure. As shown in FIG. 13A, the non-through hole 21 is formed of a recessed hole in which one surface of the film base material 20 is recessed toward the other surface, and the recessed hole has a thickness of the bottom portion 21a substantially uniform. The shape does not protrude outward. The recessed hole 21 in this figure is in a state where no internal pressure is applied. When pressure is applied to the recessed hole from the arrow direction A in this state, as shown in FIG. 13B, the bottom of the recessed hole 21 extends, expands, and swells, and the wall thickness of the bottom becomes thin due to this swelling. Gas is transmitted from 21a. That is, the gas is permeated from the thin portion 21a ′ whose bottom is stretched and expanded, and hardly permeates in a state where it is not stretched and expanded.

  The permeation of this gas depends on the thickness of the bottom, and the thinner the wall, the greater the amount of permeation. On the other hand, if the wall is too thin, fine holes that penetrate this part, that is, pinholes, are generated. And the same subject as the subject which the film of the above-mentioned patent document 1 has becomes obvious by this fine hole. Therefore, even if an attempt is made to reduce the thickness, the thickness of the thickness is limited, and it is extremely difficult to make the thickness 8 μm or less with the current processing technology.

  Therefore, it is difficult to adjust the gas permeation amount to obtain a desired permeation amount for the gas permeable film provided with such a recessed hole 21 and cannot be used for applications that require it. In addition, although the structure of a non-through-hole is not specified in the gas permeable film of the said patent document 3, it is estimated that it is a structure substantially the same as the recessed hole of FIG. 13A, and the same subject is latent.

  In recent years, the gas permeable film of this type has been required to further improve the gas permeation performance while further expanding its application. Conventional gas permeable films have been used in citrus packaging or microwave oven heating bags, but even in these packaging, citrus fruits and foods have many types and storage methods. Therefore, if it is going to apply to these, the packaging material (film) with higher performance will be needed. In addition, since the applications are expanding, a packaging material (film) having a wider gas permeation performance is required in order to adapt to those applications.

  The amount of oxygen permeation required for foods such as vegetables varies greatly depending on the type. For example, lettuce, leaf onion, leek, eringi, cut vegetables (mix), bean sprouts, asparagus, spinach, etc., their oxygen permeation amounts differ greatly. Moreover, the gas amount which kimchi, Chinese cabbage pickles, and rakkyo pickles differ, respectively, and these gas permeation amounts are larger than vegetables.

  For example, fruits and vegetables containing vegetables still breathe after harvesting. That is, the harvested fruits and vegetables are taking more breaths, i.e. more active breathing than when they are in the field to repair the fruits and vegetables themselves. However, when this breathing becomes active, the nutrients of fruits and vegetables are consumed and maturation and aging progress more rapidly. However, the packaging of fruits and vegetables is usually sealed packaging in which a bag is packed and the bag mouth is sealed. In this sealed packaging, oxygen that was present in the bag at the time of packaging is consumed over time, so the bag is anaerobic with almost no oxygen and cannot breathe, causing the fruits and vegetables to rot. . Regarding the breathing of fruits and vegetables, the ratio of oxygen and carbon dioxide is 20.9% oxygen and 0% carbon dioxide before packaging (open packaging), but it is almost oxygen in anaerobic conditions (unbreathing). 0% and 20% or more of carbon dioxide, and in the hibernation state described later, it is said that 5 to 10% oxygen and 15 to 20% carbon dioxide are optimal. Therefore, in the packaging of fruits and vegetables, it is necessary to adjust the gas permeability of the bag according to the fruits and vegetables and the distribution conditions (especially temperature) according to the difference in the respiration rate of the fruits and vegetables.

  MA (Modified Atmosphere) packaging balances the air in the bag with the breathing performed by the fruits and vegetables themselves, so that the fruits and vegetables become hibernating in a high concentration carbon dioxide and low concentration oxygen atmosphere. This is a method of delaying growth and deterioration and extending quality. In other words, it is a method of maintaining the quality by delaying the speed of quality degradation by keeping the respiration rate as low as possible. For this MA packaging, a unidirectional packaging material is preferred, but there is no such packaging material, that is, a gas permeable film.

Moreover, double packaging is performed depending on food. This double package is a double package in which a small inner bag is filled with an article A and sealed, and the inner bag filled with the article A is put in a large outer bag and sealed. In this double packaging, an article B different from the article A of the inner bag may be packed in a large outer bag. These articles A and B are usually packed with the following items.
(I) Foods such as sweets in the inner bag article A, alcohol / inert gas, flavoring, etc. in the outer bag article B, storage and flavoring agents (ii) alcohol, flavoring etc. in the inner bag article A Preservation / fragrance, food such as confectionery in the outer bag article B The double packaging of (i) above, the article B of the outer bag permeates into the inner bag and preserves or scents the article A. In the double packaging of (ii) above, the article A of the inner bag permeates the inner bag and enters the outer bag, and the article B is preserved or scented. In these double packaging, if the gas in the inner bag permeates into the outer bag in the packaging of (i) above, the quality of the article A is deteriorated, and the packaging in the above (ii) If the gas permeates and escapes to the inner bag, the quality of the article B is deteriorated. Therefore, in order to maintain the quality of the article in such double packaging, the gas permeable film needs gas permeability in one direction. However, no conventional gas permeable film has been developed from this point of view. Of course, the films of Patent Documents 2 and 3 do not have such unidirectionality.

  The present invention has been made on the basis of the above-mentioned needs and solves the problems of the conventional techniques, and the object of the present invention is to improve the gas permeation performance, and to achieve a wide range of applications, particularly a wide variety of applications. An object of the present invention is to provide a gas permeable film that can be used as a packaging film suitable for packaging articles and the like, a manufacturing method thereof, and a container using the gas permeable film. In particular, packaging films suitable for (i) MA packaging, (ii) double packaging, (iii) degassing packaging such as kimchi, pickles, etc. (iv) other, for example, air-permeable packaging materials for fungi cultivation It is in providing the manufacturing method and container.

In order to solve the above problems, the gas permeable film according to the first aspect of the present invention is a gas permeable film provided with a gas permeable portion that allows gas to permeate a plastic film substrate having a predetermined thickness.
The gas permeation part is composed of an unpenetrated dent part in which a bottom part is inflated by indenting a predetermined depth from one surface to the other surface of the plastic film substrate, and the dent part is The thickness is gradually reduced from the upper opening toward the bottom, and the bottom is formed to be the thinnest.

  Moreover, in the gas permeable film of the 2nd aspect, the said recessed part is formed by the slit or recessed hole which made cross-sectional shape U shape or V shape, It is characterized by the above-mentioned.

  In the gas permeable film of the third aspect, the slit is formed by a discontinuous slit group in which a plurality of short and long slits are arranged at a predetermined interval or a relatively long continuous slit. Features.

  Moreover, in the gas permeable film of the 4th aspect, the slit of the said discontinuous slit group has the shape of either a straight line, a curve, or a bending by planar view, It is characterized by the above-mentioned.

  In the gas permeable film of the fifth aspect, a virtual line having a predetermined length is drawn on one surface of the plastic film substrate, and the plurality of slits of the non-continuous slit are spaced from each other by a predetermined interval. It is characterized by being arranged along or intersecting the virtual line.

  In the gas permeable film of the sixth aspect, the plurality of slits of the discontinuous slit intersect with the longitudinal direction of the imaginary line at a predetermined angle.

  In the gas permeable film of the seventh aspect, the plastic film substrate is a single-layer or multilayer film of any one of PP, PE, PET, and PA, and has a thickness of 15 It is characterized in that the thickness of the bottom of the recess is 2 to 70 μm.

  In the gas permeable film of the eighth aspect, the plastic film substrate is a single-layer film of any one of PP, PE, PET, and PA, and the plastic film on which the recess is formed Another plastic film is laminated on either the front or back surface of the substrate.

Moreover, the method for producing a gas permeable film according to the ninth aspect of the present invention is a method for producing a gas permeable film that forms a gas permeable portion that allows gas to pass through a plastic film having a predetermined thickness.
The gas permeation part, the plastic film substrate is set to a temperature that exceeds the glass transition temperature of the film and less than the melting point, is pressed and stretched from one side of the film to the other side, and is recessed by a predetermined depth, It is characterized in that the thickness is gradually reduced from the upper opening toward the bottom, and the bottom is the thinnest so that the bottom is formed by a recess that bulges outward from the other surface.

  In the method for producing a gas permeable film according to the tenth aspect, after the recess is formed in the plastic film substrate, another plastic film is laminated on either the front or back surface of the plastic film substrate. It is characterized by that.

  Moreover, in the manufacturing method of the gas permeable film of the 11th aspect, the said recessed part pinches | interposes the said plastic film between the other rotary rolls which provided the protrusion of the predetermined shape in one rotary roll, and these rotations. The plastic film is formed in a process including a process in which the plastic film travels as the roll rotates.

  Moreover, in the manufacturing method of the gas permeable film of the twelfth aspect, the rotating roll provided with the protrusions has a lower hardness than other rotating rolls to form the recess. To do.

  In the gas permeable film manufacturing method of the thirteenth aspect, the plastic film substrate is a single-layer or multilayer film of any one of PP, PE, PET, and PA, and has a thickness of the film. Is 15 to 100 μm, and the thickness of the bottom of the recess is 2 to 70 μm.

  Moreover, the container of the 14th aspect of this invention consists of a bag body heat-welded in the location containing at least 1 dent part using one of the said gas-permeable films.

  Further, the container of the fifteenth aspect is characterized by comprising a bag body made by using any one of the gas permeable films so that the dent portion faces inward or outward.

  In the container of the sixteenth aspect of the present invention, the opening is sealed with any one of the gas permeable films.

  According to the present invention, the bottom of the recess can be thinned from the thickness of the film base material to almost the limit (for example, about 2.0 μm), and this thinning widens the range of gas permeability and widens It can be used in the field. In particular, it is useful as a packaging material. That is, it is useful for packaging materials such as vegetables and fermented foods, and containers for fermented foods and microwave oven heating. Moreover, since gas permeation is improved from one direction and difficult from the opposite direction, it is effective for MA packaging, double packaging, and the like.

  Further, according to the present invention, when a microwave oven heating container is made of a gas permeable film, the container can be prevented from being ruptured by being broken from the slit portion at or near a portion that overlaps the seal portion.

  Furthermore, according to this invention, a gas-permeable film can be produced at low cost without using a special material.

  Furthermore, according to the present invention, the gas permeable film is useful for making a container for a microwave oven.

  Furthermore, according to the present invention, the bottom of the recess can be thinned from the thickness of the film base material to almost the limit (for example, about 2.0 μm), and this thinning increases the range of gas permeability. A gas permeable film that can be used in a wide range of fields can be produced.

  Furthermore, according to this invention, the container created with the film which has said effect can be provided.

1 shows a gas permeable film according to an embodiment of the present invention, FIG. 1 is a plan view, and FIG. 1B is an enlarged view of a portion IB in FIG. 2 is a cross-sectional view taken along line II-II in FIG. FIG. 3 is a schematic view of a production apparatus for producing the gas permeable film of FIG. 4A and 4B illustrate the gas permeation action of the slit, FIG. 4A is a cross-sectional view of the slit, FIG. 4B is a cross-sectional view of the slit shape during gas permeation, and FIG. 4C is a cross-section of the slit shape during gas permeation from the reverse direction. FIG. FIG. 5 is a plan view of a gas permeable film according to another embodiment. FIG. 6 is a cross-sectional view of a slit portion of a gas permeable film according to another embodiment. FIG. 7 is a schematic view of a production apparatus for producing the gas permeable film of FIG. FIG. 8 is a perspective view of a packaging bag made using a gas permeable film. FIG. 9 is a perspective view of another packaging bag made using a gas permeable film. FIG. 10 is a perspective view of still another packaging bag made using a gas permeable film. FIG. 11 is a perspective view of still another packaging bag made using a gas permeable film. FIG. 12 is a perspective view of a container whose opening is covered with a gas permeable film. FIG. 13 is a cross-sectional view of a recessed hole provided in a gas permeable film of the prior art.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the embodiment described below exemplifies a gas permeable film for embodying the technical idea of the present invention, a manufacturing method thereof, and a container using the gas permeable film. And is equally applicable to other embodiments within the scope of the claims.

  In the gas permeable film of the present invention, a gas permeable portion that allows gas to permeate is provided on a film substrate made of a plastic film having a predetermined thickness. This gas permeation part consists of a dent in which the bottom part bulges from the other surface by indenting a predetermined depth from one side to the other side in the longitudinal direction of the film substrate. The thickness is gradually reduced from the opening to the bottom, and the bottom is formed thinnest. The dent part is configured by a slit or a dent hole having a predetermined shape.

  Hereinafter, with reference to FIG. 1, FIG. 2, the gas-permeable film which concerns on embodiment of this invention is demonstrated. 1 shows a gas permeable film according to an embodiment of the present invention, FIG. 1 is a plan view, FIG. 1B is an enlarged view of a portion IB in FIG. 1, and FIG. 2 is a cross-sectional view taken along the line II-II in FIG. It is.

  The recessed part of the gas permeation | transmission part which concerns on embodiment of this invention is comprised by the slit group 3L which arrange | positioned the several short slit 3 at predetermined intervals. These slits 3 have the same structure, and the thickness is gradually reduced from the upper opening toward the bottom, and the bottom is formed thinnest. In addition, although this recessed part was formed with the slit group which consists of the slit 3 of predetermined length, ie, a discontinuous slit group, you may form it with a comparatively long continuous slit.

  The film substrate 2 uses a long film substrate having a predetermined width, thickness and length, and a plurality of short slits 3 are arranged in a line at predetermined intervals in the longitudinal direction. It is arranged. A plurality of short slits 3 constitute a slit group 3L. Although the space | interval of the slit 3 which adjoins 3 L of slit groups is made into arbitrary space | intervals by the use of a gas-permeable film, an equal space | interval is preferable for packaging. The slit group 3L is not limited to one row, and may be two or more rows.

  As the film substrate 2, a single layer or multilayer plastic film such as polypropylene (PP), biaxially stretched polypropylene film (OPP), polyethylene (PE), polyethylene terephthalate (PET), nylon (PA) or the like is used. In addition, this base material is not limited to these, Another plastic film may be sufficient. The slit 3 may be provided in one layer or all layers of the multilayer structure film. That is, after forming a slit in a single layer of film, lamination may be performed to form a multilayer structure, or a slit may be formed in a multilayer structure film. These processing methods are appropriately selected depending on the type or application of the resin constituting the film. As an example of a multilayer structure, for example, a film having both high gas barrier properties and sealing properties can be obtained by laminating PE having a good sealing function on PA and PET having high gas barrier properties. First, an example in which slits are formed in these films using a single layer or multilayer structure film will be described.

  A film base material consists of a film material of a single layer or a multilayer structure, Although the thickness is not specifically limited, The range of 15-100 micrometers is preferable. If the thickness is less than 15 μm, it is difficult to form a slit, and for example, when used with a packaging film, sufficient strength may not be obtained. Moreover, when it exceeds 100 micrometers or more, a process will become difficult. Therefore, the thickness of the film substrate is appropriately selected depending on the type of film resin, the use, and the like within these ranges.

  The plurality of slits 3 are non-penetrating grooves made of narrow grooves having the same shape. These slits 3, as shown in FIG. 2, gradually swell from the upper opening groove 3 a toward the bottom so that the thickness gradually swells in a mountain-like shape, and the bottom is swelled outward from the other surface. The bottom portion 3c is thinned so that the cross-sectional shape is substantially U-shaped. Specifically, as shown in FIGS. 1B and 2, the film base 2 has a width W in the longitudinal direction and a length L ′ and a predetermined depth in a direction perpendicular to the longitudinal direction. Although the width length, length, and depth are not particularly limited, the width length W is preferably 100 to 500 μm and the length L ′ is preferably 1.2 to 2.6 mm. Further, the depth is about 1.2 to 2.2 times as measured from the film surface, and even with these magnifications, the depth is preferably 1.2 to 2.2 times the thickness. Furthermore, it is preferable that the thinnest wall thickness of the bottom 3c is 2 μm to 70 μm. This thickness is the same for both single-layer and multi-layer films. Moreover, although the space | interval between adjacent slits of the slit group 3L is not specifically limited, About 1.5-3.0 mm is preferable. Therefore, this slit is appropriately selected depending on the type and use of the film resin.

  The slit 3 has a substantially U-shaped cross section, but is not limited to this, and may have another shape, for example, a V-shaped cross section or other shapes. In the slit group 3L, a plurality of slits having a predetermined length are arranged discontinuously, but may be made continuous. In the case of continuous slits, the arrangement of continuous slits can be linear, polygonal, or curved. The amount of gas permeation of the slit and slit group can be adjusted by changing the shape and thickness of the bottom. In place of the slit, a recessed hole may be used. The recessed hole is a hole having a circular or elliptical opening and depth. In the case of a round hole, the diameter is, for example, 30-1500 μm, and the thickness of the thinnest part at the bottom is 2-70 μm. The oval opening is also substantially the same as the substantially circular hole.

  Next, with reference to FIG. 3, the manufacturing method of a gas-permeable film is demonstrated. 3A is a schematic view of a production apparatus for producing the gas permeable film of FIG. 1, FIG. 3B is an enlarged view of IIIB in FIG. 3A, and FIG. 3C is an enlarged view of IIIC in FIG.

  As shown in FIG. 3A, the manufacturing apparatus 4 includes a pretreatment device 5 that pretreats the film substrate 2 and a slit forming device 6 that forms the slit 3 in the film substrate 2. The pretreatment device 5 is a temperature adjusting device that treats the film substrate 2 so that the temperature exceeds the glass transition point of the substrate and is lower than the melting point.

  The temperature adjustment in the pretreatment device 5 is important for forming slits in the film substrate. The film substrate 2 is made of a plastic film material, that is, a polymer material. The polymer material is in a state where a crystalline portion and an amorphous portion coexist at a low temperature, and is in a glass state with a small molecular motion. Yes. When heated from this state and the temperature rises, the molecular motion increases to become a rubber state, and when further heated, it becomes a molten state. The boundary from the glass state to the rubber state is the glass transition point, and the boundary from the rubber state to the molten state is the melting point. Therefore, by heating the film substrate to a temperature exceeding the glass transition point and softening, the slit can be rolled up and the bottom can be rolled thinnest. Further, at this temperature, rolling can be performed while maintaining gas barrier properties, so that a thin slit can be formed without impairing the properties of the film. In addition, a slit having no pinholes can be formed.

  The glass transition point and melting point vary depending on the material of the film substrate. When PP is used for the film substrate, the PP has a glass transition point of minus 18 ° C. and a melting point of 163 ° C., so the temperature is adjusted to 40 to 120 ° C., which is higher than normal temperature. Similarly, since PET has a glass transition point of 81 ° C. and a melting point of 264 ° C., the temperature is about 85 to 200 ° C., while LDPE has a glass transition point of −125 ° C. and a melting point of 115 ° C. Since it is ° C., the temperature is adjusted to 20 to 100 ° C. higher than normal temperature. Moreover, in the multilayer structure film which laminated PET and LDPE mentioned later, it adjusts to the range of 85-100 degreeC of temperature.

  PP and PE already exceed the glass transition point at room temperature, but the melting point is 130 ° C., so the degree of processing is adjusted within that range. Even in the same base material, the softness of the film varies depending on the temperature in the range exceeding the glass transition point and less than the melting point. Therefore, in the next slit forming apparatus, the slit can be easily formed by raising the temperature even with light pressing.

  The slit forming device 6 is a disc-shaped pressing roll 6A in which a plurality of slit forming teeth 7 are arranged at a predetermined interval on the outer periphery, and a receiving roll for sandwiching the film substrate 2 between the pressing rolls. 6B. The pressing roll 6A is formed of a metallic disk-shaped gear having a predetermined diameter, thickness, and hardness. The pressing roll 6A rotates around the shaft 6a and moves the film substrate 2 in the X direction while forming the slit 3. Send it out. As shown in FIG. 3B, the plurality of slit forming teeth 7 are substantially saw-toothed teeth having a predetermined pitch p and a height h. The slit forming teeth 7 are provided with a predetermined R2 at the top tip 7a and R at R1 at the bottom 7b. The pitch p is not particularly limited, but is 2.094 mm and the height h is 2.0 mm. R2 is in the range of 0.05 to 1.0 mm, and even in this range, 0.1 to 0.2 mm is preferable. If the thickness is 0.1 mm or less, if the mechanical wear is severe, the film base material is damaged and pinholes are easily formed. If it is 1.0 mm or more, the pressing area can be widened. R1 is 0.5 mm. Note that the teeth may be continuous with a pitch of zero. In this case, the width is further reduced in order to ensure a sufficient pressing force. That is, when the number of teeth is increased, the number of teeth increases, and as a result, the unit area increases and the overall pressing force decreases. Therefore, the desired pressing force is ensured by reducing the width and reducing the area.

  The pressing roll 6A is a disc-shaped gear in the present embodiment, but may be a roll, that is, a cylindrical body or a columnar body. By making it into a roll shape, a long slit and a continuous slit can be formed. Although the gear provided with the slit forming teeth is not particularly limited, for example, it is preferable to use a gear provided with spur teeth. The flat teeth are rectangular in a plan view, have a length of 1.5 to 2.6 mm, a width of 30 to 500 μm, and 1.2 to 2.4 times the film thickness in an elevation view. Use one. When this flat tooth is used, if the total thickness of the film substrate is 50 μm, the thickness from the bottom of the film substrate is 60 to 120 μm up to the top of the mountain. This degree is determined by the amount of gas to be permeated. Further, depending on the shape of the slit, a gear having another shape, for example, a gear provided with helical teeth is used. For example, a slit as shown in FIG. 5B is formed using such a gear.

  Similarly to the pressing roll 6A, the receiving roll 6B receives pressure when the slit 3 is formed in the film base 2 by the pressing roll 6A while rotating around the shaft 6b, and moves the film base 2 in the X direction. Send it out. The pressing roll 6A has a hardness of 60 to 63 and is formed of a metal material having a hardness lower than that of the receiving roll 6B. The receiving roll 6B is formed of a metallic cylindrical body or cylindrical body having a predetermined diameter and hardness, and the hardness is set to 63 to 67. The pressing roll 6A is not scraped even if it is processed by, for example, 1 million m when the receiving roll 6B is pressed by the pressing roll 6A by making the hardness lower than that of the roll 6B.

  The manufacturing apparatus 4 processes the film substrate 2 to a temperature exceeding the glass transition point by the pretreatment device 5 and sends the film substrate 2 to the slit forming device 6, and the film substrate 2 that has reached a predetermined temperature by the slit forming device 6. The film base 2 is rolled between the pressing roll 6A and the receiving roll 6B, and a predetermined pressing force is applied to the pressing roll 6A to form a slit (see FIG. 3C). The slit is formed by adjusting the pretreatment temperature of the substrate and the pressing force of the pressing roll according to the type and thickness of the film substrate. When the bottom of the slit is thinned, the gas permeability is increased by the thinned portion, but the strength is decreased. The degree is determined by adjusting at least one of the pretreatment temperature and the pressing force. For example, if the glass transition point of the film substrate is 50 ° C. and the melting point is 215 ° C., if the pretreatment temperature is 60 ° C. or 120 ° C., the latter is softer than the former, while the pressing force is lower than the former. Can be formed with a light pressing force. The degree of pressing is adjusted, for example, between 0 and 0.5 MPa, and is preferably around 0.2 MPa. In addition, 0.5 MPa is 5 kg / square centimeter.

  In this manufacturing apparatus 4, the pretreatment temperature of the film base material 2 and the pressing force of the pressing roll are adjusted according to the application, and a slit suitable for each application is formed. For example, in vegetable packaging, a single film of an OPP antifogging film having a thickness of 25 μm is used, and a recess is formed in the film from the inside of the bag. The minimum thickness of the recess is about 2 μm. Depending on the vegetables, the degree of pressing differs, for example, with Komatsuna, pressing at 0.2 MPa, and the shape of the portion pressed with flat teeth with a pitch of 2 mm is rectangular, 2 mm long × 200 μm wide. For a bag size of 200 mm × 320 mm, the slit group is only in one horizontal row.

  With reference to FIG. 4, the gas permeation | transmission effect | action of a slit is demonstrated. 4A and 4B are diagrams for explaining the gas permeation action of the slit, FIG. 4A is a cross-sectional view of the slit, FIG. 4B is a cross-sectional view of the slit shape during gas permeation, and FIG. 4C is a gas permeation from the reverse direction. It is sectional drawing of slit shape.

  In this example, a gas permeable film 1 is used to create a packaging bag of a predetermined size, and when the article is stored in the packaging bag, gas (such as steam) is released from the article and pressure is applied to the packaging bag. The permeation effect will be described. The slit 3 in FIG. 4A is in a state where no internal pressure is applied. 4A is the same as FIG.

When an internal pressure is applied to the slit 3 from the direction of the arrow A, as shown in FIG. 4B, the bottom of the slit is stretched and expanded by the pressure, and expands into a balloon shape. Gas permeates from 3c ₁ . The slit 3 has gas permeation that makes it easier to adjust the amount of permeation than the slits of the prior art, and provides other effects.
Specifically, since the thickness of the bottom of the conventional recess 21 (see FIG. 13) is substantially uniform, it cannot be made as thin as possible, and the current processing technology has a limit of about 8 μm. Since the slit 3 can be thinned to a substantially limit (about 2.0 μm), the amount of transmission can be easily adjusted.

Further, as shown in FIG. 4C, the pressure from the opposite direction is applied, but the bottom 3c ₂ of the slit is pressed in the opposite direction, the gas permeation amount is much smaller than in the direction of FIG. 4B. This phenomenon has been confirmed by experiments. When the amount of transmission from the opening side is 10, the amount of transmission from the reverse direction is about 1 to 2. As a result, the gas permeable film 1 has good gas permeability from one direction and is difficult to gas from the opposite direction. For example, the gas permeable film 1 has a remarkable effect when used in MA packaging or double packaging. Play. That is, for the MA packaging, a packaging bag is prepared and used so that the opening of the gas permeable film 1 is located on the inner side and the bottom is located on the outer side. Further, in double packaging, a packaging bag is prepared and used so that the opening of the gas permeable film 1 is inside or outside and the bottom is outside or inside depending on the article to be packed. For example, an alcohol gas-permeable confectionery package has an outer bag and a large number of inner bags, and an anti-mold (which generates alcohol gas) is placed in the outer bag, and the inner bag is pressed and processed from the outside. Then, a lot of alcohol gas goes into the inner bag. The outer bag is a gas barrier bag, and the inner bag uses a film of 20 μm OPP alone, and the size of the bag is 50 mm × 70 mm.

  Although the gas permeable film 1 according to the embodiment of the present invention has been described with a plurality of slits 3 disposed substantially parallel to each other at a predetermined interval, the present invention is not limited to this, and other arrangements and shapes are used. May be. FIG. 5 is a plan view of a gas permeable film according to another embodiment.

  The gas permeable film 1A is a film in which a virtual line L is drawn in the longitudinal direction of the film substrate 2, and a plurality of slits 3A are arranged along the straight line with a predetermined interval to form a slit group 3AL. is there. Moreover, the gas permeable film 1B draws a virtual line L in the longitudinal direction of the film substrate 2, and a plurality of slits 3B are arranged so as to intersect with the straight line to form a slit group 3BL. Further, the gas permeable film 1C is a slit group 3CL in which a plurality of mountain-shaped slits are arranged on the virtual line L with a predetermined interval. Furthermore, the gas permeable film 1D is a slit group 3DL in which a plurality of curved slits 3D are arranged on a virtual line L with a predetermined interval. These imaginary lines L can be straight lines, broken lines, curves, and the like.

  With reference to FIG. 6, FIG. 7, the gas-permeable film which concerns on other embodiment of this invention, and its manufacturing method are demonstrated. 6 is an enlarged cross-sectional view of a slit portion obtained by laminating another film on either side of the front and back surfaces of the film provided with slits, and FIG. 7 is a schematic view of a manufacturing apparatus for manufacturing the gas permeable film of FIG. is there.

The gas permeable film 10 is obtained by bonding another film to the bulging side of the slit of the film 11 provided with the slit S with an adhesive. The slit S has the same structure as the slit 3, and the wall thickness gradually inflates from the upper opening groove 11 a toward the bottom so that the bottom portion bulges outward from the other surface. In addition, the bottom portion 11c is made thinnest, and the cross-sectional shape is formed in a substantially U shape or V shape.

  As an example of a combination of films to be bonded, PE can be used for the film 11, and PA and PET can be used for the film 13. By bonding PE having a good sealing function to PA and PET having a high gas barrier property, a film having both a high gas barrier property and a sealing property can be obtained. The bottom thickness of the gas permeable film 10 is obtained by adding the thickness of the film 13 (15 to 100 μm) and the thickness of the adhesive layer to the bottom thickness (2 to 70 μm) of the slit S of the film 11. It has become. The gas permeable film 10 is formed by joining another film 13 with an adhesive 12 on the bulging side of the slit of the film 11 provided with the slit S. The manufacturing apparatus 9A for the gas permeable film 10 is obtained by adding a film bonding apparatus 8 to the manufacturing apparatus 4 (see FIG. 7A).

  This gas permeable film 10 is suitable for a microwave heating container. When a microwave heating container using the gas permeable film 10 is heated in a microwave oven, water vapor is generated from the contents, the internal pressure of the container rises, and water vapor passes through the slit S of the film 11. At this time, since the slit S is laminated with another film 13, the water vapor transmitted through the slit S peels off the adhesive 12 between the films 11 and 13 and accumulates in this gap. This water vapor is released to the outside when the film 13 is torn or further passes through the gap between the films 11 and 13 and permeates from the seal portion provided at the end of the container. Thereby, it can prevent that the container for microwave oven heating bursts.

  In addition, the gas permeable film 10A is obtained by bonding another film with an adhesive to the concave side of the slit of the film 14 provided with the slit S. The slit S has the same structure as the slit 3. Another film 16 is bonded with an adhesive 15 on the slit recess side of the film 14 provided with the slit S. The bottom wall thickness of the gas permeable film 10A is the same as that of the gas permeable film 10, and the thickness (15 to 100 μm) and adhesion of the film 16 to the bottom wall thickness (2 to 70 μm) of the slit S of the film 14. The thickness is the sum of the thickness of the agent 15. Moreover, the manufacturing apparatus 9B of the gas permeable film 10A is obtained by adding a film bonding apparatus 8 to the manufacturing apparatus 4 (see FIG. 7B).

  This gas permeable film 10A is also suitable for a microwave heating container. When a microwave heating container using the gas permeable film 10A is heated in a microwave oven, water vapor is generated from the contents and the container expands, and water vapor is transmitted from the film 14 by internal pressure, or the film 14 is torn and water vapor is generated. Is released. At this time, the film 14 is laminated with another film 16, but since the slit 16 is provided in the film 16, water vapor accumulates in the space 14 a of the slit S, and the slit S breaks when the internal pressure further increases. As a result, water vapor is released. Thereby, it can prevent that the container for microwave oven heating bursts.

  These gas permeable films 1, 1 </ b> A to 1 </ b> D, 10, and 10 </ b> A can be used as a cover that covers a packaging container (packaging bag) or an opening of the container. Hereinafter, some examples of packaging bags and covers will be described with reference to FIGS.

  The packaging bag 17 in FIGS. 8 and 9 uses the gas permeable film 1. As shown in FIG. 8, the packaging bag 17 is first heat-sealed on three sides so that the gas permeable film 1 is cut into a predetermined length and bent so that one end becomes a bag mouth. Next, the packaging bag 17 is filled with food or the like, and the bag mouth is sealed with a heat seal. FIG. 9A shows a state in which a bag mouth is sealed by filling food in the bag. In the packaging bag 17, the slits 3 positioned at both ends of the slit group 3 </ b> L are sealed by the seal portion 18, and the slit 3 is positioned in the vicinity of the seal portion 18.

The packaging bag 17 can be used to pack various articles such as fruits and vegetables, but can also be used as a microwave heating bag by packing frozen food. When used as a bag for a microwave oven, when the packaging bag 17 is heated in a microwave oven, water vapor is generated from food, etc., the internal pressure in the bag rises, passes through the slit group 3L, and is released to the outside. When the amount of steam increases, the internal pressure rises exceeding the amount of permeation that passes through the slit group 3L, and the slit 3 in the vicinity of the seal portion 18 has a narrower gap with the seal portion. A large amount of vapor is released from the part (see FIG. 9B). For example, when the distance _{L 1} between the slits 3 to 2.2 mm, distance _{L 2} of the seal portion 18 near the slit 3 narrows the range of 0～2.2Mm. The distance L _2, liable to break strength of this portion becomes weak, thereby preventing the rupture of the packaging bag.

The packaging bag 17A in FIG. 10 uses a gas permeable film 1B (see FIG. 5).
By providing the slit 3B having such a shape, the slit 3B is always formed across the boundary with the seal portion 18 of the packaging bag. Therefore, for example, when using in a microwave oven, if it is necessary to break due to the generated water vapor, the portion where the slit is formed can be surely broken. Will be able to. Further, similarly to the above, since the gap between the slit 3B near the seal portion 18 and the seal portion becomes narrow in this portion, a break is caused from this portion and a large amount of vapor is released from this portion (see FIG. 10B). FIG. 10B is an enlarged view of the XB portion of FIG. 10A.

The packaging bag 17B in FIG. 11 uses a gas permeable film 1B (see FIG. 5).
Since the gap between the slit 3C in the vicinity of the seal portion 18 and the seal portion 18 becomes narrow, a break is caused from this portion, and a large amount of vapor is released from this portion (see FIG. 11B). FIG. 11B is an enlarged view of the XIB portion of FIG. 10A.

  In addition, a double packaging container (bag) is used by creating a packaging bag so that the opening of the gas permeable film is inside or outside and the bottom is outside or inside depending on the article to be packed.

  FIG. 12 shows the case where the opening of the container is covered with a gas permeable film and sealed. The container 19 is obtained by sealing an opening 19b of a bottomed container body 19a having an opening 19b on the upper side with a gas permeable film 1 with a seal portion 18. This container is suitable for fermented foods such as kimchi. In the gas permeable film 1 used for this kimchi packaging, for example, 12 μm thick PET is laminated by laminating PE that can be easily peeled off from a PET container, and the slit group 3L is placed on the inside of the container. It is formed by pressing from the surface. The minimum thickness of the bottom of the slit group 3L is about 2 μm. By sealing the gas permeable film 1 with the opening 19b of the container main body 19a made of PET by heat welding, carbon dioxide generated from kimchi which is a fermented food can be permeated through the slit group 3L moderately.

  As described above, according to the gas permeable film of the present invention, the bottom of the recess can be thinned from the thickness of the film base material to almost the limit (for example, about 2.0 μm). The range of degrees will be expanded, allowing use in a wide range of fields. In particular, it is useful as a packaging material. That is, it is useful for packaging materials such as vegetables and fermented foods, and containers for fermented foods and microwave oven heating. Moreover, since gas permeation is improved from one direction and difficult from the opposite direction, it is effective for MA packaging, double packaging, and the like.

1-1B, 10, 10A Gas permeable film 2 Plastic film base material 3, 3A-3D, S Slit 3L, 3AL, 3BL, 3CL, 3DL Slit group 4 Manufacturing device 5 Pretreatment device 6 Slit forming device 6A Pressing roll 6B Receiving roll 7 Slit forming tooth 8 Joining device 9A, 9B Manufacturing device 11, 14 Plastic film

Claims (16)

In the gas permeable film provided with a gas permeable portion that allows gas to permeate the plastic film substrate of a predetermined thickness,
The gas permeation part is composed of an unpenetrated dent part in which a bottom part is inflated by indenting a predetermined depth from one surface to the other surface of the plastic film substrate, and the dent part is A gas permeable film characterized in that the thickness is gradually reduced from the upper opening toward the bottom, and the bottom is formed to be the thinnest.   The gas permeable film according to claim 1, wherein the concave portion is formed by a slit or a concave hole having a U-shaped or V-shaped cross section.   The gas permeable film according to claim 2, wherein the slit is formed of a discontinuous slit group in which a plurality of short slits are arranged at a predetermined interval or a relatively long continuous slit.   The gas permeable film according to claim 3, wherein the slits of the non-continuous slit group have a straight, curved, or bent shape in plan view.   An imaginary line having a predetermined length is drawn on one surface of the plastic film substrate, and a plurality of slits of the non-continuous slit are arranged along the imaginary line or intersecting the imaginary line at a predetermined interval. The gas permeable film according to claim 4, wherein   The gas permeable film according to claim 5, wherein the plurality of slits of the discontinuous slit intersect with the longitudinal direction of the virtual line at a predetermined angle.   The plastic film substrate is a single-layer or multi-layer film of any one of PP, PE, PET, and PA, and has a wall thickness of 15 to 100 μm and a bottom wall thickness of 2 to 70 μm. The gas permeable film according to claim 1, wherein the gas permeable film is a gas permeable film.   The plastic film substrate is a single-layer film of any one of PP, PE, PET, and PA, and another plastic film is formed on either side of the plastic film substrate on which the recess is formed. The gas permeable film according to claim 1, wherein the gas permeable film is laminated. In the method for producing a gas permeable film for forming a gas permeable portion that allows gas to permeate the plastic film having a predetermined thickness,
The gas permeation part, the plastic film substrate is set to a temperature that exceeds the glass transition temperature of the film and less than the melting point, is pressed and stretched from one side of the film to the other side, and is recessed by a predetermined depth, Manufacture of a gas permeable film characterized in that the thickness is gradually reduced from the upper opening toward the bottom, and the bottom is the thinnest and the bottom is formed by a dent that bulges outward from the other surface. Method.   The gas permeable film according to claim 9, wherein after forming the recess in the plastic film base material, another plastic film is laminated on either the front or back surface of the plastic film base material. Method.   The concave portion is formed in a process including a process in which the plastic film travels in accordance with the rotation of the rotary rolls by sandwiching the plastic film between the rotary rolls provided with projections having a predetermined shape on one rotary roll. The method for producing a gas permeable film according to claim 9 or 10, wherein:   The method for producing a gas permeable film according to claim 11, wherein the dent is formed by using a rotating roll provided with the protrusion having a lower hardness than other rotating rolls.   The plastic film substrate is a single-layer or multi-layer film of any one of PP, PE, PET, and PA, and has a wall thickness of 15 to 100 μm and a bottom wall thickness of 2 to 70 μm. It exists, The manufacturing method of the gas-permeable film in any one of Claims 9-12 characterized by the above-mentioned.   A container comprising a bag body heat-sealed at a location including at least one indentation using the gas permeable film according to any one of claims 1 to 8.   A container comprising a bag formed by using the gas permeable film according to any one of claims 1 to 8 so that the dent portion faces inward or outward.   A container having an opening sealed with the gas permeable film according to claim 1.

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