JP5931354B2 - Film for gusset folded packaging bags - Google Patents

Description

The present invention relates to a gusset fold packaging bag film, in particular with that at moderate slip properties to control the frictional force of the film surface on the side in contact with the articles to be packaged, the original shape of the bag-like objects formed from the film was also inhibited Gazette folded about the packaging bag film.

  For example, when foods (packaged items) such as confectionery breads (boiled bread, etc.) or Japanese confectionery (such as dorayaki) are coated and packaged with a film for packaging bags, the packaging of a single packaged item can be opened as it is after being packed. The part is sealed. The packaging bag film is often sealed by heat sealing to fuse the films together. This is because heat sealing is simple and the processing speed is high. Therefore, an olefin resin excellent in heat sealability is frequently used for the packaging bag film.

  Here, when a plurality of articles to be packaged are arranged in series and are accommodated in the packaging bag film, the objects to be packaged may be misaligned during the accommodating operation and cannot be packaged well. In other words, after the article to be packaged arrives at the planned storage position, when the film is sealed by the heat seal device, the article to be packaged is displaced by the film. In such a case, when the heat sealing device is operated, the heat generating portion of the device bites the package object together with the packaging bag film. As a result, not only the sealing failure but also the contamination of the apparatus is caused, and the efficiency of the packaging work is remarkably lowered. For this reason, it is common to place an article in a tray made of polystyrene or the like, place the tray itself in a packaging bag film, and seal the film by heat sealing.

  However, the demand for non-use of trays is increasing due to the demand for resource saving of packaging materials accompanying the reduction of environmental burden and the reduction of material costs. The inventors have previously made slipping between a package and an article to be packaged against the non-use of trays in the packaging of confectionery such as rice confectionery (rice crackers, arare, etc.) and baked confectionery (cookies, etc.). As a result of intensive studies on the resin composition of the packaging bag film, focusing on the improvement of the stopper properties, the inventors have proposed a packaging bag film with improved slip resistance (see Patent Document 1).

  However, when foods such as confectionery bread and Japanese confectionery are to be packaged, there are many differences from the confectionery targeted by the film of Patent Document 1 such as the size and weight of the packaged items and the presence or absence of individual packaging. is there. For this reason, the film for packaging bags of patent document 1 cannot be applied directly.

  Furthermore, when a plurality of items to be packaged such as breads are arranged in series and accommodated in a packaging bag film, if the tray is not used, the packaged film bag is likely to bend in the longitudinal direction. Become. It is not preferable at the time of store display because it looks bad due to the folding of the bag. In addition, it is necessary to avoid an object to be packaged such as breads accommodated in the bag because the bag is bent.

  Therefore, it was also considered to change the thickness of the film itself used for packaging to a rigid type. However, the heat seal characteristics of the film were hindered and good results could not be obtained. Considering the number of products manufactured per unit time, heat sealing at low temperatures is required.

For this reason, in a packaging form in which a plurality of articles to be packaged such as breads are arranged in series and accommodated in a packaging bag film without using a tray, an appropriate slipperiness of the article to be packaged, a bag after packaging Thus, a packaging bag film that takes into consideration the overall shape maintenance and heat sealing performance has been demanded.

JP 2008-307779 A

  Thereafter, the inventor conducted intensive studies on how to fold the film when making it into a bag, as well as the blending of the constituent resins and the slipperiness of the film for packaging bags. Therefore, as a result of forming the packaging bag by incorporating the gusset fold, the tray can be omitted when packaging the packaged object, and the film has the rigidity of the film corresponding to the actual use and also has the heat sealability. I came to get.

The present invention has been proposed in view of the above-described circumstances, exhibits moderate slipperiness in a packaging bag film, and maintains shape when a packaged article is accommodated in two or more in series to form a bag-like article. Even if it overlaps the double seal part which arises by heat seal of the film for packaging bags corresponding to gusset folding, and the quadruple seal part which arises by the heat seal of the four-stage folding part of the film for packaging bags such comprising a heat seal characteristics, it provides a gusset fold packaging bag film unnecessary to use the tray.

  That is, the invention of claim 1 forms a cylindrical body by laminating a flat packaging bag film along the longitudinal direction which is the winding direction, and becomes both ends in the longitudinal direction of the predetermined length of the cylindrical body. A part of the part to be sealed is folded into a W-shape in a longitudinal sectional view by gusset folding to form a four-stage folded part on the part to be sealed, and the four-stage folded part is heated together with the part to be sealed A bag comprising a double seal portion produced by heat-sealing between the packaging bag films of the sealing bag portion to be sealed and a quadruple seal portion produced by heat sealing of the four-stage folded portion of the packaging bag film A packaging bag film for forming a product and storing two or more packages in series in the longitudinal direction of the bag, wherein the packaging bag film is in contact with the package The first inner resin layer Olefin copolymer composition, second α-olefin copolymer composition on outer resin layer which is subjected to corona treatment and is on outer side of packaging, and base resin arranged between inner resin layer and outer resin layer The layer has a polypropylene resin composition, is provided with at least three resin layers, is formed by biaxial stretching, the heat sealing temperature of the outer resin layer is 120 ° C. to 160 ° C., and the second α-olefin copolymer The F5 value, which is the strength when the coalescence is an ethylene-propylene copolymer polymerized by a metallocene catalyst, and when the winding direction (MD) of the packaging bag film is stretched by 5% is the F5 value measurement of the following (I) In the winding direction of the film for packaging bags in the method, the static friction coefficient of the inner resin layer of the film for packaging bags is static friction by the gradient method of the following (II) The loop stiffness value of the center seal portion formed by bonding along the longitudinal direction which is the winding direction in the bag-like material is 0.1 to 0.8 in the coefficient measurement method, and the loop of the following (III) It relates to a film for a gusset folded packaging bag, which is 50 mN to 150 mN in measuring a stiffness value.

  F5 value measurement method (I) is a method for cutting a packaging bag film as a sample to 150 mm in the film winding direction and 15 mm in the width direction, setting the distance between chucks of the tensile tester to 100 mm, and then at a tensile speed of 200 mm / min. It is characterized by reading the stress value when it is pulled and stretched 5% from the length in the winding direction of the film before tension.

The static friction coefficient measurement method (II) by the tilt method is such that the packaging bag film is pasted on a moving block having a width of 63 mm, a length of 100 mm, and a mass of 1000 g and placed on a fine puffed SUS304 plate. The value of tan θ is obtained from the angle θ when the moving block starts to slide by changing the sliding slope at 7 ^o / sec.

  The loop stiffness value measurement (III) is performed by forming the cylindrical body including the center seal portion by bonding the inner resin layers to each other by heat sealing the packaging bag film along the longitudinal direction. A strip having a width of 15 mm is cut, and both ends of the strip are fixed to a loop stiffness tester so that the strip has a circumferential length of 95 mm, bent into an annular shape, and the annular product is formed into the loop stiffness tester. The stress (mN) at the time when the distance between the pressing parts is 20 mm after being pressed by the pressing part is read.

  Invention of Claim 2 concerns on the film for gusset fold packaging bags of Claim 1 whose said to-be-packaged goods are bread or confectionery bread.

  In the measurement of the heat shrinkage area ratio of the following (IV) based on the heat shrinkage test based on JIS Z 1712 (2009), the invention of claim 3 has a heat shrinkage area ratio of the packaging bag film of 5% or less. It concerns on the film for gusset folding packaging bags of Claim 1 or 2.

In the measurement (IV) of the heat shrinkage area ratio, the distance between marked lines before heating in the winding direction (MD) of the film for packaging bag is M ₁ , the distance between marked lines after heating is M ₂ , and the packaging bag The width direction (TD) perpendicular to the winding direction of the film for heating is T ₁ , the distance between marked lines before heating is T ₁ , the distance between marked lines after heating is T _2, and the thermal shrinkage area ratio (%) according to the following equation (i) ).

  According to the film for a gusset folded packaging bag according to the invention of claim 1, a cylindrical body is formed by laminating a planar packaging bag film along a longitudinal direction which is a winding direction, and a predetermined length of the cylindrical body. A four-stage folded portion is formed in the planned sealing portion by folding a part of the planned sealing portion which becomes both ends in the longitudinal direction into a W-shape in a longitudinal sectional view by gusset folding, and together with the planned sealing portion, It is generated by heat sealing the four-stage folded portion and heat-sealing the four-stage folded portion of the packaging bag film and the double-sealed portion produced by heat-sealing the packaging bag films of the planned sealing portion. Forming a bag-like article having a quadruple seal portion, and a packaging bag film for containing two or more articles to be packaged in series in the longitudinal direction of the bag-like article, wherein the packaging bag film is With the package A first α-olefin copolymer composition on the inner resin layer that becomes the side to be processed, a second α-olefin copolymer composition on the outer resin layer that is subjected to corona treatment and becomes the outer surface of the package, the inner resin layer, and the outer resin The base resin layer disposed between the layers has a polypropylene resin composition, is provided with at least three resin layers, is formed by biaxial stretching, and the heat sealing temperature of the outer resin layer is 120 ° C. to 160 ° C. F5 value which is strength when the second α-olefin copolymer is an ethylene-propylene copolymer polymerized by a metallocene catalyst and the winding direction (MD) of the packaging bag film is extended by 5%. However, in the F5 value measurement method of (I) below, 16N to 28N are satisfied in the winding direction of the packaging bag film, and the static friction coefficient of the inner resin layer of the packaging bag film is: The loop stiffness of the center seal portion formed by bonding along the longitudinal direction which is the winding direction in the bag-like material in the static friction coefficient measurement method by the gradient method of (II) Since the value is 50 mN to 150 mN in the measurement of the loop stiffness value of (III) below, it exhibits an appropriate slipperiness in the packaging bag film, and the shape when the packaged material is accommodated to become a bag-like product A film for a gusset folded packaging bag that has excellent maintenance performance, has good heat-sealing characteristics even if the films are overlapped in response to gusset folding, and does not use a tray can be obtained.

  Moreover, it is possible to objectively evaluate the difficulty of bending the bag-shaped object after accommodating the packaged object, and at the same time, it is excellent in maintaining the shape as the bag-shaped object. Furthermore, the efficiency at the time of heat sealing increases. Excellent low temperature heat sealability even after corona treatment. In addition, while the packaging form does not use a tray, the packaged item is fixed, and the bag-like item after receiving and packaging the packaged item is prevented from bending in the longitudinal direction, and the appearance of the bag-like item itself is maintained. can do.

  According to the film for a gusset fold packaging bag according to the invention of claim 2, in the invention of claim 1, since the article to be packaged is bread or confectionery bread, the bag-like article formed from the film without using a tray Mold loss can be suppressed.

  According to the film for a gusset folded packaging bag according to the invention of claim 3, in the invention of claim 1 or 2, in the measurement of the heat shrinkage area ratio based on the heat shrinkage test based on JIS Z 1712 (2009), the packaging bag Since the thermal shrinkage area ratio of the film is 5% or less, it becomes easy to predict the appearance after sealing by grasping the amount of thermal deformation of the film itself.

It is a 1st schematic process drawing of bag-shaped object formation using the film for gusset folding packaging bags. It is a 2nd schematic process drawing of bag-shaped object formation using the film for gusset folding packaging bags. It is a whole perspective view of a bag-like thing. It is a cross-sectional schematic diagram of the film for packaging bags. It is a cross-sectional schematic diagram of the 4-step folding part before heat sealing. It is a cross-sectional schematic diagram of the 4-step folding part after heat sealing. It is a schematic diagram which shows the measurement of a loop stiffness value. It is a schematic diagram which shows the measurement of a heat shrink area ratio.

The film for gusset folded packaging bags of the present invention is a film used for applications in which both ends in the longitudinal direction are sealed and processed into a bag shape (pillow shape). In particular, it is a film to be formed into a bag shape having gusset folds that form “towns” at both ends sealed in a bag shape .

  First, the process of processing into a bag-like product, which is the intended use of the film for gusset folded packaging bags, will be described with reference to the schematic process diagrams of FIGS. In addition, since it is before the process to a bag shape, in order to avoid confusion, it demonstrates from now on as the film 10 for packaging bags. From FIG. 1A, the packaging bag film 10 is pulled out from the original film 1 by a predetermined length (amount used). In the packaging bag film 10, the film winding direction is a winding direction MD (machine direction, flow direction), and the direction orthogonal to the winding direction MD is a width direction TD (vertical direction). The planar packaging bag film 10 is bent along the longitudinal direction as the winding direction MD from FIG. And the both ends of the width direction TD side are bonded together by heat seal from FIG.1 (c), and the center seal | sticker part 11 arises. Thus, the cylindrical body 13 is formed. In the drawing, the cylindrical body 13 is taken out for explanation.

  As shown in FIG. 2A, the cylindrical body 13 is longitudinally cut by gusset folding on a part of the planned sealing portion 12 which is both ends in the longitudinal direction of the predetermined length 13 under pressure from the folding jigs 15 and 15. It is folded into a W shape when viewed from the front. The part that is folded into a W shape in the longitudinal section is a four-stage folded portion 14. As can be seen from this figure, when the opening part (scheduled sealing part 12) of the cylindrical body 13 is a circle, the four-stage folded parts 14 and 14 are formed to face each other in the diameter direction of the circle of the opening part. The For convenience of illustration, only one of the cylindrical bodies 13 is opened. Therefore, a four-stage folded portion is formed on the opposite side of the cylindrical body in a portion that is folded in the same W-shape in a longitudinal sectional view.

  As shown in FIG. 2 (b), the four-stage folded portions 14 and 14 formed in the planned sealing portion 12 together with the planned sealing portions 12 at both ends in the longitudinal direction of the cylindrical body 13 are both heat of the heat seal device. It is pressed by the board parts 16 and 16. Finally, as shown in FIG. 2 (c), the heat seal sealing is completed by fusing the resin constituting the packaging bag film 10, and the sealing portion 21 is obtained. A bag-like object 20 is formed by heat sealing at both ends of the cylindrical body 13 together with the filling of the article to be packaged into the cylindrical body 13. Along with this heat sealing, intrusion portions 22 and 22 are formed that are folded inside the bag on the four-stage folded portions 14 and 14 side. Of course, the sealing portion and the entering portion are similarly formed on the side of the cylindrical body not shown.

  In the sealing part 21 formed in the bag-like product 20 by heat sealing the sealing part 12 of the cylindrical body 13, there are portions having different numbers of layers. Specifically, from FIG. 2 (c), the double seal portion 23, which is the central portion of the sealing portion 21 and is generated by heat sealing between the packaging bag films 10 of the planned sealing portion 12, and the packaging bag This is a quadruple seal portion 24 generated by heat sealing the four-stage folded portions 14 and 14 of the film 10.

  In actual bag making, the film from the packaging bag film 10 to the cylindrical body 13 and the subsequent heat sealing are continuously performed without a break. The filling (insertion) of the article to be packaged into the cylindrical body 13, the heat sealing to the sealing portion 12, and the subdividing into individual bag-like objects by cutting the sealing portion 21 are also performed continuously.

  An article to be packed filled in the bag-like product 20 made of the packaging bag film 10 is exclusively food, although it is appropriate for food, miscellaneous goods, machine products, and the like. The packaging bag film 10 is mainly used for packaging foods as described in detail in the background art, and is particularly used for packaging confectionery bread, Japanese confectionery, and the like. In consideration of bag production from film for packaging bags on a mass production scale, followed by confectionery bread and bagging of Japanese confectionery (formation of bag-like products), in addition to making bags with good heat sealing performance, surface friction control Ease of filling (packing) the packaged material by means of is important. This is because it greatly affects the production efficiency per unit time.

  FIG. 3 is an overall perspective view showing an example of the appearance of the bag-like product 20 (gazette folded bag-like product). The packaged goods W are assumed to be breads of an appropriate shape having a size (diameter or length of one side) of 5 cm to 10 cm. In the figure, a state (containing contents) in which two or more packages W are serially arranged in the longitudinal direction of the bag-like object 20 formed by heat sealing and the tray is omitted is shown. The illustrated articles W to be packaged are two (W1, W2), and contact the packaging bag film 10 directly, not via the tray. In the figure, reference numeral 25 denotes a printing surface, and reference numeral 40 denotes a printing unit, which is printing using a known dedicated printing ink.

  As shown in the figure, in the case of the form in which the articles to be packaged W are accommodated in series, the bag-like article 20 easily breaks or bends in the middle of the longitudinal direction due to its own weight even in the case of breads. For this reason, the article to be packaged W is pressed and looks bad. From the viewpoint of distribution and display, it is also important to look at the bag-like product itself after containing the packaged items. As shown in the figure, since the packaging form does not use a tray, it is necessary to generate an appropriate rigidity by the strength of the packaging bag film itself and the bag-like material.

  In view of the properties required as a packaging bag film, the composition and structure of the resin in the film will be described with respect to the packaging bag film 10 for use in the bag-like product 20 provided with a gusset fold. FIG. 4 is a schematic cross-sectional view of the packaging bag film 10. The side in contact with the object to be packaged is the inner resin layer 31, which is formed mainly of the first α-olefin copolymer composition (R1). The side that is subjected to corona treatment and becomes the outer packaging surface is the outer resin layer 32, and is formed mainly of the second α-olefin copolymer composition (R2). The corona treatment applied to the outer resin layer 32 is a process for improving the degree of attachment of the printing ink when forming the printing unit 40 and the like. And between the inner side resin layer 31 and the outer side resin layer 32, the base material resin layer 33 which becomes a base material of the said packaging bag film 10 itself and exhibits "strain (rigidity)" is arranged. The base resin layer 33 is formed mainly of a polypropylene resin composition (R3). The film formation of the packaging bag film 10 can be expressed as {inner resin layer 31 (R1)} / {base resin layer 33 (R3)} / {outer resin layer 32 (R2)}.

  The film formation of the packaging bag film 10 is mainly performed by a tenter biaxial stretching method, and specifically, sequential biaxial stretching or simultaneous biaxial stretching. The composition resin of each resin layer 31, 33, 32 is simultaneously discharged (co-extruded) from the T-die, and is manufactured through stretching, heat setting, slow cooling, etc. in various rollers and tenters. By forming the film by biaxial stretching, the orientation and heat shrinkability in any direction (machine direction MD, width direction TD) of the film are stabilized. As a result, it is effective for maintaining the strength (strain strength) as a film material for packaging. As shown in the figure, the packaging bag film is formed with three resin layers, four base resin layers (not shown) with a base resin layer increased to two layers, and more multilayers. It is also possible. The film thickness of the packaging bag film 10 comprising the resin layers 31, 33, 32 shown in the figure is preferably 35 to 50 μm.

  Since the 1st alpha olefin copolymer composition (R1) used for the inner side resin layer 31 needs to form the center seal part 11 and the sealing part 21 by heat sealing as above-mentioned, favorable heat-sealing performance is carried out. Desired. For this reason, olefin-based resins such as propylene-ethylene random copolymer and ethylene-propylene-1 butene polymer are used for the first α-olefin copolymer composition (R1) in consideration of low-temperature melting.

  The second α-olefin copolymer composition (R2) used for the outer resin layer 32 is desirably a resin composition that enables good printing after corona treatment. For example, ethylene homopolymer, random or block copolymer of ethylene and one or more α-olefins such as propylene, 1-butene, 1-pentene, 1-hexene and 4-methyl-1-pentene , One or more random or block copolymers of ethylene and vinyl acetate, acrylic acid, methacrylic acid, methyl acrylate, propylene homopolymer, ethylene other than propylene and propylene, 1-butene, 1-pentene , 1-hexene, 4-methyl-1-pentene, etc., or a random or block copolymer with two or more α-olefins, 1-butene homopolymer, ionomer resin, and the above-described polymers. Polyolefin resin such as a mixture.

  As understood from FIGS. 2 (c) and 3, four-stage folded portions 14, 14 are formed in the planned sealing portion 12 of the packaging bag film 10. More specifically, it can be roughly seen as shown in the schematic cross-sectional views of FIGS. FIG. 5 shows a four-stage folded portion 14 formed on the planned sealing portion 12 of the packaging bag film 10. Since it is W-shaped in longitudinal section, the inner resin layers 31 face each other and the outer resin layers 32 face each other in the bent state (the center in the figure). FIG. 6 shows a quadruple seal portion 24 portion of the sealing portion 21 after the heat sealing of the planned sealing portion 12. This is a four-layer stack of packaging bag films 10, which is a total of 12 layers.

  Usually, when forming a bag-like article from a packaging bag film, a composition resin is selected so that the inner resin layer corresponds to heat sealing performance and the outer resin layer corresponds to printing performance. Further, corona treatment is performed in order to improve printability with printing on the outer resin layer surface. Therefore, in general, when the corona treatment is performed on the film surface, the heat seal performance tends to be lowered.

  However, as is apparent from these drawings, in the packaging bag film 10, not only heat seal formation between the inner resin layers 31 (see the double seal portion 23) but also good heat seal between the outer resin layers 32. Formation (see quadruple seal portion 24) is also required. In this case, it is important to maintain both printability with corona treatment and good heat sealability in the outer resin layer 32.

  At the time of heat sealing the planned sealing portion 12, the hot platen portions 16 and 16 (see FIG. 2) of the heat sealing device are pressure-bonded to the planned sealing portion and the upper and lower resins are melted by heating. In other words, in order to achieve a good heat seal, the heating temperature of the hot platen is appropriately controlled on the high temperature side (generally 140 ° C. to 160 ° C.), or the pressure bonding time of the hot platen. Is a combination of these. In this case, taking into consideration the specific heat and melting temperature of the resin of the film, the time required for the heat sealing of one part to be sealed tends to be long for strong heat sealing. However, there is a demand for shortening the time required for heat-sealing to the part to be sealed from the viewpoint of the efficiency of bag making and product production by heat-sealing per unit time.

  Therefore, a resin having a low melting point is used as the resin of the outer resin layer 32, and the constituent resin is selected so that the heat sealing temperature when the outer resin layer 32 is heat sealed converges to 120 ° C to 160 ° C. This is because it is desirable for the production efficiency of the heat seal as described above. Therefore, it is desirable to use an ethylene-propylene copolymer, which is known to have a small temperature change even when subjected to corona treatment, as the second α-olefin copolymer composition (R2). Among them, an ethylene-propylene copolymer polymerized with a metallocene catalyst is selected because of its excellent low temperature heat sealability. In addition, regarding an outer surface layer, you may contain various additives, such as an antiblocking agent, a heat stabilizer, antioxidant, a light stabilizer, a crystal nucleating agent, and an ultraviolet absorber, according to a use and the objective.

  Since the polypropylene resin composition (R3) used for the base resin layer 33 is a part to be a base layer in the packaging bag film 10, a polypropylene resin composition is used. For example, homopolypropylene, 1-butene homopolypropylene, random polypropylene and the like. Further, the polypropylene resin composition (R3) includes aliphatic amine compounds such as lauryl diethanolamine, myristyl diethanolamine, and oleyl diethanolamine, aliphatic amide compounds such as lauryl diethanolamide, myristyl diethanolamide, and oleyl diethanolamide, and polyvalent compounds. Various antistatic agents such as alcohol are appropriately added.

  As described above, the first α-olefin copolymer composition (R1) is formed on the inner resin layer 31 of the packaging bag film 10, the second α-olefin copolymer composition (R2) is formed on the outer resin layer 32, and the base resin layer 33. A polypropylene resin composition (R3) is used. The bag-like product 20 formed from the packaging bag film 10 is difficult to bend in the longitudinal direction after the packaged product is accommodated so that the bag-like product 20 can be grasped from the direction of bag making in FIGS. There is a need to. That is, even if the tray on which the package object is placed is omitted, it is necessary to maintain the shape of the bag-shaped object after the package object is accommodated as much as possible.

  Since the winding direction MD of the packaging bag film 10 is the longitudinal direction of the bag-like product 20, an appropriate strength in the same direction MD is required. At the same time, when the packaging bag film is loaded into an apparatus for filling and packaging the packaged object, a tensile force is always generated in the winding direction of the packaging bag film. Without proper tensile strength, the film will tear apart. Therefore, the F5 value, which is the strength of the film when the packaging bag film 10 is stretched 5% in the winding direction MD, can be used as an evaluation index.

  In the F5 value measurement method (I), a packaging bag film 10 as a sample is cut out by 150 mm in the winding direction MD and 15 mm in the width direction TD, and fixed at a setting where the distance between chucks of the tensile tester is 100 mm. . At this time, two marked lines at intervals of 50 mm are drawn in the width direction TD at the center of the sample. After fixing the sample, it is pulled at a pulling speed of 200 mm / min. And the stress value at the time (1.05 times) when the distance between the two marked lines is extended by 5% from before the tension is read.

  As will be apparent from the following examples, the F5 value of the film for packaging bags of the present invention is in a range satisfying 16N to 28N. When the F5 value is less than 16N, the sagging and mold deformation of the bag-like material increase due to the softness of the film. When the F5 value exceeds 28N, the film becomes hard and the formation of the four-stage folded portion on the planned sealing portion becomes worse. As a result, the productivity of gusset folding is reduced. Obviously, the F5 value varies greatly depending on the film thickness of the packaging bag film itself. Moreover, the film thickness of the film varies greatly depending on the packaging object and application. However, considering the production of bag-like products on a mass production scale, it is important to achieve both the hardness of the film and the ease of folding. Therefore, the F5 value is considered as an appropriate range.

  Further, for the packaging bag film 10, when the packaged object is filled in the cylindrical body 13, the efficiency of filling (bagging) of the packaged object is that the packaged object appropriately slides on the surface of the inner resin layer 31. Increase. At the same time, the object to be packaged receives an appropriate frictional resistance with the inner resin layer 31, so that the object to be packaged does not shift in the filling or heat sealing process, and is defined in the cylindrical body 13. Can be stationary. When the packaged item is too slippery or not slipped, the position shift is likely to occur, the packaged product reaches the sealing target portion 12, and the packaged product is heat sealed while being bitten by the packaging bag film 10. It will be pressed by the hot platen 16 of the apparatus. As a result, the bag making and bagging apparatus may be damaged or contaminated, and the operation of the apparatus is stopped and the cleaning is performed.

For this reason, in the inner side resin layer 31 (the surface) of the film 10 for packaging bags, control of the slipperiness with a to-be-packaged item becomes an indispensable element. Therefore, the slipperiness of the surface on the inner resin layer 31 side can be evaluated as a static friction coefficient measurement method (II) by the tilt method. That is, the packaging bag film 10 is bonded to a moving block that becomes a weight of 63 mm in width, 100 mm in length, and 1000 g in mass. The moving block is placed on a fine puffed SUS304 plate. The slope θ is changed at an inclination speed of 2.7 ^° / sec, and the angle θ when the moving block starts to slide is read. The value of tan θ is obtained from this angle θ, and this value becomes the static friction coefficient. In the static friction coefficient measurement method (II) by the tilt method, some items were changed with reference to the tilt method measurement of JIS P 8147 (2010).

  In the static friction coefficient measurement method (II) by the gradient method, the static friction coefficient satisfies 0.1 to 0.8, preferably 0.15 to 0.35. When the static friction coefficient is less than 0.1, it becomes too slippery as described above. When the coefficient of static friction exceeds 0.8, the frictional resistance is too large, and it is difficult to slip with respect to the packaging equipment, and the flow of the packaged object on the film surface tends to deteriorate.

  Next, a part of the center seal portion 11 formed by bonding along the longitudinal direction which is the winding direction MD in the bag-like object 20 is cut out, and a loop stiffness value is obtained. This value is 50 mN to 150 mN in the loop stiffness value measurement (III). The loop stiffness value is convenient for objective evaluation of the difficulty of bending the bag-like object after the packaged object is accommodated. And it becomes high evaluation for the shape maintenance of a bag-like thing by being included in the above-mentioned range value as an after-mentioned example.

  The measurement (III) of the loop stiffness value will be described with reference to the schematic diagram of FIG. As described in detail in FIGS. 1 to 3, first, the packaging bag film 10 is formed in the cylindrical body 13 including the center seal portion 11 by bonding the inner resin layers 31 together by heat sealing along the longitudinal direction. A bag-like product 20 is completed.

  As shown in FIGS. 7A and 7B, a strip-like piece 26 having a width of 15 mm is cut from the center seal portion 11 of the bag-like object 20. As shown in FIG. 7C, the belt-like piece 26 is an annular object 27 having a circumferential length of 95 mm, and both ends of the belt-like piece are fixed to the loop stiffness tester. 7D, the annular object 27 is pressed by the pressing portions 28, 28 of the loop stiffness tester, and when the distance between the pressing portions 28, 28 becomes 20 mm, the stress value (mN) of the loop stiffness tester. Is read. This stress value is the loop stiffness value.

  Next, it is inevitable that the film is thermally deformed by heating during heat sealing. However, if the amount of thermal deformation of the film itself after sealing is large, the appearance after bag making will be poor. In addition, the sealing accuracy tends to deteriorate. Therefore, it is necessary to control the amount of thermal deformation of the film itself. From this, the heat shrink test based on JIS Z 1712 (2009) is performed with respect to the film 10 for packaging bags. This result is expressed as the heat shrinkage area ratio HS (unit%) by the following measurement (IV) of the heat shrinkage area ratio.

In the measurement of the heat shrinkage area ratio (IV), as shown in FIG. 8, the distance M ₁ between marked lines before heating in the winding direction MD of the packaging bag film 10 (the distance between the origin O and the marked line Lm before heating). ) And the distance M ₂ between the marked lines after heating (distance between the origin O and the marked line Lm after the heating). At the same time, the distance T ₁ between the marked lines before heating in the width direction TD of the packaging bag film 10 (distance between the origin O and the marked line Lt before heating) and the distance T ₂ between the marked lines after heating (the origin O and the heating) The distance to the later marked line Lt) is obtained. As shown in equation (i), the area before and after heating is determined from the product of the distance between the marked lines before and after heating. That is, the area before heating (M ₁ · T ₁ ) and the area after heating (M ₂ · T ₂ ). The heat shrinkage area ratio HS (%) is calculated from the area ratio from before the heating.

  The heat shrinkage area ratio HS of the packaging bag film 10 calculated from the formula (i) is suppressed to 5% or less, more preferably 4.5% or less. In particular, because of the heat shrinkage area ratio, it is possible to grasp both the winding direction MD and the width direction TD, which is convenient for grasping the heat shrinkage of the film. When this value is exceeded, the shrinkage of the sealing part due to heat sealing tends to be often observed, and the appearance is likely to deteriorate.

  The packaging bag film 10 having the above-described resin material and physical properties is formed into a bag-like material 20 as understood from the processing steps shown in FIGS. That is, the film for gusset folded packaging bags (film 10 for packaging bags) is bonded together along the longitudinal direction that is the winding direction to form a cylindrical body. A part of the part to be sealed which becomes both ends in the longitudinal direction of the predetermined length of the cylindrical body is folded into a W shape in a longitudinal sectional view by gusset folding. A four-stage folded portion is formed in the planned sealing portion, and the four-stage folded portion is sealed together with the planned sealing portion by heat sealing. In this way, the bag-like product 20 shown in FIG. 3, i.e., the gusset folded bag-like product is completed.

  When the bag 20 is described again with reference to FIG. 3, the printing surface 25 that is the outermost surface is the outer resin layer 32. Corona treatment is performed on the surface of the outer resin layer 32 at the time of the packaging bag film 10. At the same time, the printing unit 40 displaying various contents including a product name, various patterns, a manufacturer name, and a raw material name is printed on the surface of the outer resin layer 32. In FIG. 3, there are two exemplary packages W (W 1, W 2), which are in direct contact with the packaging bag film 10, not via the tray. Of course, the number of items to be packaged is not limited to two, and may be three or more. In the examples described later, five breads were arranged in series.

  As a series of explanations, in the gusset folded bag-like product (bag-like product 20 in FIG. 3) formed from the film for gusset folded packaging bags (packaging bag film 10), a portion is provided at both ends in the longitudinal direction of the bag-like product. A gusset fold can be created by overlapping the films. In other words, in the four-stage folded portion of the film that is W-shaped when viewed in the longitudinal cross section, an entering portion that is folded inside the bag is generated. Due to the overlap of the films, a part of the side surface of the bag-like material changes into a corrugated shape (wave shape). In this case, the structural strength on the longitudinal direction side of the bag-like material is increased by providing the corrugated structure, compared to the case where the bag-like material is a simple cylindrical body, and the folding resistance of the bag-like material is somewhat increased. Therefore, it is possible to obtain a gusset folded bag-like product formed from a film for gusset folded packaging bags, which can maintain the shape of the bag without using a tray.

[Creation of film for gusset folded packaging bags]
For the films for gusset folded packaging bags of Examples 1 to 8 and Comparative Examples 1 to 6, based on the blending ratios (parts by weight) shown in Tables 1 to 3 below, the raw material resin is melted and various additives are added. The mixture was kneaded together and formed into a film using a three-layer coextrusion T-die film forming machine and a tenter biaxial stretching machine. When forming the film of each Example and Comparative Example, the draw ratio in the winding direction (MD draw ratio) (times) in the table below, the draw ratio in the width direction (TD draw ratio) (times), stretching The temperature (heat setting temperature) (° C.) and the temperature (° C.) for heat sealing the outer resin layer of the film were used. Moreover, the film thickness of the film was created for each of the examples and comparative examples.

[Raw materials (raw resin)]
The following raw materials 1 to 6 were used as the raw material resin.
Raw material 1: ethylene-propylene-1 butene copolymer (manufactured by Nippon Polypro Co., Ltd .: trade name “FX4G”, melting point 129 ° C.)
Raw material 2: ethylene-propylene-1-butene copolymer (manufactured by Nippon Polypro Co., Ltd .: trade name “FX8877”, melting point 131 ° C.)
Raw material 3: ethylene-propylene copolymer polymerized by metallocene catalyst (Nippon Polypro Co., Ltd .: trade name “Wintech WFX4”, melting point 125 ° C.)
Raw material 4: ethylene-propylene copolymer polymerized by metallocene catalyst (melting point 115 ° C., MFR = 7)
Raw material 5: ethylene-propylene copolymer (manufactured by Nippon Polypro Co., Ltd .: trade name “EG7F”, melting point 142 ° C.)
Raw material 6: polypropylene polymer (manufactured by Nippon Polypro Co., Ltd .: trade name “FL100A”, melting point 160 ° C.)

[Raw materials (additives)]
The following raw materials 7 to 9 were used as additives.
Raw material 7: Powdered synthetic silica (manufactured by Fuji Silysia Chemical Ltd .: trade name “Silicia 430”, average particle size 2.5 μm)
Raw material 8: Silicone resin powder (Shin-Etsu Chemical Co., Ltd .: trade name “KMP-701”)
Raw material 9: Antistatic agent (manufactured by Toho Chemical Co., Ltd .: trade name “Anstex SA-300F”)
Raw material 10: hydrogenated styrene butadiene rubber (JSR Corporation: trade name “DYNARON1320P”)

[Measurement of F5 value]
As F5 value measurement method (I), the film for gusset folded packaging bags of Examples and Comparative Examples serving as samples was cut out by 150 mm in the winding direction MD and 15 mm in the width direction TD. The film of the sample was fixed to a chuck portion of a strograph (manufactured by Toyo Seiki Seisakusho, V1-B) with a setting of a distance between chucks of 100 mm. At this time, two marked lines at intervals of 50 mm were drawn in advance in the width direction TD at the center of each sample. After fixing the sample, the chuck part is pulled at a pulling speed of 200 mm / min, and the stress value (unit N) when the distance between the two marked lines is extended by 5% (1.05 times longer) than before pulling. I read it. This was performed on each sample.

[Measurement of static friction coefficient]
As a static friction coefficient measuring method (II), the film for gusset fold packaging bags of the example and the comparative example, which are samples, were bonded to a moving block having a width of 63 mm, a length of 100 mm, and a mass of 1000 g. Then, a fine puffed stainless steel plate (SUS304 plate) was mounted on a static friction coefficient measuring machine (manufactured by Sagawa Seisakusho Co., Ltd., DFA-02), and a moving block with a sample film was placed on the steel plate.

In the static friction coefficient measuring machine, the sliding slope was changed while the inclination speed of the steel sheet was 2.7 ^° / sec, and the angle θ when the moving block started to slide was read. The value of tan θ (that is, the static friction coefficient) was obtained from this angle θ. In addition, in the static friction coefficient measurement method (II) by the tilt method, some items such as a moving block were changed with reference to the tilt method measurement of JIS P 8147 (2010).

[Measurement of loop stiffness value]
When measuring the loop stiffness value (III), first, each sample film for the gusset fold packaging bag of the example and the comparative example was loaded into a horizontal pillow packaging machine (FW3410) manufactured by Fujikikai Co., Ltd. A packaging bag having a total length of about 25 cm and a width of about 10 cm provided with a seal portion (see the shape in FIG. 3 and the like) was prepared. The center seal portion generated by heat sealing is the longitudinal direction of the packaging bag and coincides with the film winding direction MD.

  After the film of each sample was processed by the packaging machine into a bag-like product, a strip having a predetermined length with a width of 15 mm was cut from the center seal portion of the bag-like product. One strip of each sample was made into a ring by fixing both ends to a fixing part of a loop stiffness tester (manufactured by Toyo Seiki Seisakusho). All of the annular objects had a circumferential length of 95 mm (diameter: about 30 mm). This annular object was pressed with a measurement terminal (dial gauge) and pressed to a position where the distance between the fixed part and the measurement terminal was 20 mm and maintained for 10 seconds. The stress value (mN) of the loop stiffness tester at this time was read and used as the loop stiffness value of the sample film.

[Measurement of heat shrinkage area ratio]
In measurement (IV) of the heat shrinkage area ratio, each of the film for the gusset fold packaging bag of the example and the comparative example based on the heat shrinkage test based on JIS Z 1712 (2009) is heated and cured, The distance between marked lines before and after heating was measured. _First , for each of the sample films, the distance between the marked lines M _{1, which} is the distance between the origin and the marked line before heating before heating in the winding direction MD, and the marked line before and heated before the heating in the width direction TD. The distance T ₁ between the marked lines, which is the distance between Subsequently, for each film of the same sample, after heating in the winding direction MD, the distance between the marked lines M _{2, which} is the distance between the origin and the marked line after heating, and after heating in the width direction TD, A distance T ₂ between the marked lines that is a distance from the marked line was obtained. By substituting the distance between the marked lines before and after heating into the above formula (i), the heat shrinkage area ratio (unit%) of each sample was measured.

[Preparation of bag-like materials and filling and packaging of packages]
In the preparation of the bag-like material and the filling and packaging of the packaged material, about 45 g of bread per package is used for each of the films for the gusset fold packaging bags of the examples and comparative examples as samples, By wrapping five pieces in series using the film of each sample, a gusset folded bag-like material containing an article to be packaged (bread) corresponding to each sample film was created. The bag-like product was provided with a center seal portion for heat seal formation and had a total length of about 25 cm and a width of about 10 cm.

[Comprehensive evaluation of films for gusset folded packaging bags]
Based on the above-described results of creating the bag-like product accompanying the filling and packaging of the packaged material, the quality of each of the films for the gusset-folded packaging bag of the example and the comparative example, which are samples, was determined in four stages as a comprehensive evaluation.
A sample film having no hindrance to the packaging of the packaged object and having a very good appearance of the packaging bag after packaging (no bending and good appearance of the heat-sealed portion) was designated as “A”.
The film of the sample, which has no hindrance to the packaging of the package and has a good appearance (no bending) after packaging, was designated as “B”.
Although there was no hindrance to the packaging of the packaged item, the film of the sample having a bad appearance (folded) after packaging was designated as “C”.
The sample film that interfered with the packaging of the packaged product itself was designated as “D”.

[result]
Tables 1 to 3 show the raw materials used, the results of various measurements, the overall evaluation, and the like for each of the films for gusset folded packaging bags of Examples and Comparative Examples. In each table, the inner resin layer, the base resin layer, the outer resin layer, MD stretch ratio (times), TD stretch ratio (times), stretching temperature (° C.), thickness (μm), F5 value (N), The order of the static friction coefficient, the heat sealing temperature (° C.) of the outer resin layer, the loop stiffness value (mN), the heat shrinkage area ratio (%), and the comprehensive evaluation. Since Comparative Example 1 is non-stretched, there is no temperature during stretching.

[Discussion]
The evaluation result of the film for a gusset fold packaging bag of an Example and a comparative example is considered. Evaluations suitable as products are “A” and “B”, and other “C” and “D” are insufficient or ineligible. Examples 1 to 7 are good, and in particular, Examples 1 to 5 are stable and excellent. Hereinafter, the details of the resin layer in the film and the details of the physical property values will be examined.

<Selection of resin layer constituent materials>
In consideration of the composition of the inner resin layer, an example in which the raw material 7 and the powdery synthetic silica of the raw material 7 were used as the first α-olefin copolymer composition after the use of the raw material 1 and the raw material 2 of ethylene-propylene-1 butene copolymer is appropriate. The static friction coefficient is kept.

  Considering the composition of the base resin layer, the example using the polypropylene polymer of raw material 6 as the polypropylene resin composition showed an appropriate F5 value. From Comparative Example 1, it is clear from the fact that the F5 value decreases when the ethylene-propylene-1-butene copolymer of the raw material 2 is used.

  Considering the composition of the outer resin layer, the second α-olefin copolymer composition is ethylene-propylene-1 butene copolymer of raw material 1 or raw material 2, and ethylene-polymerized by metallocene catalyst of raw material 3 or raw material 4. In the example using the propylene copolymer and the ethylene-propylene copolymer of the raw material 5, the outer resin layer could be heat sealed. On the other hand, Comparative Example 4 using the polypropylene polymer of raw material 6 was not heat sealable. From this point, it can be said that the polypropylene polymer alone is insufficient for the composition of the outer resin layer.

  Next, in the case of using an ethylene-propylene copolymer polymerized by the metallocene catalyst of raw material 3 or raw material 4, various physical properties can be satisfactorily satisfied while satisfying a heat seal temperature of around 135 ° C. Therefore, the use of an ethylene-propylene copolymer polymerized with a metallocene catalyst as the second α-olefin copolymer composition is advantageous.

<Select thickness>
Generally, as the thickness increases, the stiffness (rigidity) of the film itself increases. It is clear from the increase in F5 value and loop stiffness value. For this reason, the present invention seems to meet the desired purpose. However, contrary to the strength of the film, it may be troublesome to fold, particularly to form a four-stage folded portion. In addition, the amount of resin used increases. Therefore, in the case where the packaging of an object to be packaged (bread) which is expected in the future is assumed in the experiment, the thickness of the film itself is suppressed to some extent while being processed to a desired gusset folded bag shape to 35 μm or less. A film thickness of 50 μm is reasonable.

<F5 value>
It is necessary to define the tensile strength in the film winding direction MD in consideration of the operation by the filling and packaging machine. As a result, an F5 value exceeding 15.0 N of Comparative Example 2 is desirable. If the F5 value becomes extremely high as in Comparative Example 3, it may be time-consuming to form the 4-step folded portion. Therefore, an F5 value range of 16N to 28N is appropriate.

<Static friction coefficient>
Since this invention is a packaging form which does not use a tray, the inner surface layer of the film for gusset fold packaging bags is in direct contact with the object to be packaged. For this reason, an appropriate frictional force is necessary for the object to be packaged to move while sliding on the film surface, and an appropriate static friction coefficient is approximately 0.1 to 0.8. More desirably, it is 0.15 to 0.35. As in Comparative Example 5, when the silicone resin powder of the raw material 8 is added, the static friction coefficient is extremely lowered, which is not preferable.

  The raw material 10 is a raw material selected to further increase the frictional force. According to Comparative Example 6 using the raw material 10, the static friction coefficient was extremely increased. That is, since the slipperiness of the inner resin layer is deteriorated, it is not suitable for use as a film for packaging and filling purposes of the present invention.

<Heat seal temperature of outer resin layer>
Except for Comparative Example 4 where heat sealing could not be performed, the heat sealing temperature converges to 120 ° C to 160 ° C. In particular, from the viewpoint of continuous production efficiency of packaging and bag making, it is desirable to exhibit heat sealing performance in the lowest possible temperature range. Therefore, a heat seal temperature of 120 ° C. to 140 ° C. (because Example 7 is 138 ° C.) is desired.

<Loop stiffness value>
The loop stiffness value for grasping the strain (rigidity) of the film itself needs to be at least 50 mN from the numerical values of Comparative Examples 1 and 2. However, when the value becomes high and the film becomes extremely hard, the film itself becomes stiff and the F5 value becomes high, so that the efficiency of packaging and bag making by the apparatus tends to deteriorate. Therefore, 150 mN was made the upper limit on the basis of 148.2 mN of Example 3. Of course, as described above, since the loop stiffness value depends on the film thickness, the film thickness of 35 μm to 40 μm can be set to 75 mN to 95 mN in consideration of the numerical values of the respective examples.

<Heat shrinkage area ratio>
By grasping the heat shrinkage area ratio, the heat shrinkage of the film accompanying heat sealing can be predicted to some extent. If the heat shrinkage area ratio is large, the appearance as a bag-like product that can be made large in degree of shrinkage tends to deteriorate. Since 5 to 6% is within an acceptable range, Examples 1 to 8 are appropriate. Furthermore, in order to suppress the thermal shrinkage of the film itself, it was specified as 5.0% or less as selected in Examples 1 to 7. More preferably, it is 4.0% or less from the numerical value of each Example.

<Comprehensive evaluation>
As a result of the creation of the bag-like material, as well as the results of the compositional raw materials mentioned so far and the measured physical property values, the film for gusset folded packaging bags that converged to an appropriate level for all the indicators was “B” or higher in the comprehensive evaluation. Examples 1 to 8. Examples 1 to 7 are preferable. Further, Examples 1 to 5 of the overall evaluation “A” are stable and excellent.

  In addition, the inventors also confirmed the quality of the packaging bag after packaging according to the presence or absence of gusset folding. Specifically, using the film for a gusset fold packaging bag prepared in Example 1 above, omitting the original gusset fold process (no gusset fold), and the article to be packaged (bread) as in the example A bag-like product was created. The size of the bag is the same. The bag-like product without the gusset fold was evaluated as “C” because the outer appearance was bent. Therefore, in order to exhibit shape retention performance without using a tray, it is indispensable to form a gusset fold on the bag-like material in addition to the improvement of the film itself.

  When the film for a gusset fold packaging bag of the present invention is used, it is possible to suppress the deformation of a bag-shaped product formed from the film without using a tray when filling and packaging a plurality of packages. Therefore, it can contribute to resource saving of packaging materials.

DESCRIPTION OF SYMBOLS 1 Film original fabric 10 Film for packaging bags 11 Center seal part 12 Sealing planned part 14 Four-step folding part 20 Bag-shaped thing 21 Sealing part 22 Enclosing part 23 Double seal part 24 Quadruple seal part 25 Printing surface 26 Band shape Piece 31 Inner resin layer 32 Outer resin layer 33 Base resin layer 40 Printing part W (W1, W2) Package MD Take-up direction (machine direction, flow direction)
TD Width direction perpendicular to winding direction

Claims (3)

A flat packaging bag film (10) is bonded along the longitudinal direction of the winding direction (MD) to form a cylindrical body (13), which becomes both ends of the cylindrical body in the longitudinal direction of a predetermined length. A part of the planned sealing portion (12) is folded into a W-shape in a longitudinal sectional view by gusset folding to form a four-stage folded portion (14) in the planned sealing portion, and together with the planned sealing portion, the 4 A heat-sealing of the double-folded portion (23) generated by heat-sealing the step-folding portion and heat-sealing the packaging bag films of the portion to be sealed, and heat sealing of the four-step folding portion of the packaging bag film A packaging bag film for forming a bag-like article (20) having a quadruple seal portion (24) generated by the above-described method and accommodating two or more articles (W) in series in the longitudinal direction of the bag-like article. There,
The packaging bag film comprises a first α-olefin copolymer composition (R1) and a corona treatment on the inner resin layer (31) on the side in contact with the article to be packaged, and an outer resin layer (on the outer packaging side). 32) having the polypropylene resin composition (R3) in the second α-olefin copolymer composition (R2) and the base resin layer (33) disposed between the inner resin layer and the outer resin layer. It is formed by biaxial stretching with at least three resin layers,
The heat sealing temperature of the outer resin layer is 120 ° C to 160 ° C,
The second α-olefin copolymer is an ethylene-propylene copolymer polymerized by a metallocene catalyst,
The F5 value, which is the strength when the winding direction (MD) of the packaging bag film is extended by 5%, is 16N to 28N in the winding direction of the packaging bag film in the F5 value measurement method of (I) below. Meet,
The static friction coefficient of the inner resin layer of the packaging bag film is 0.1 to 0.8 in the static friction coefficient measurement method by the slope method of (II) below,
The loop stiffness value of the center seal portion formed by bonding along the longitudinal direction that is the winding direction in the bag-like material is 50 mN to 150 mN in the measurement of the loop stiffness value of (III) below. Film for gusset folded packaging bags.
(I) F5 value measurement method: A packaging bag film as a sample is cut out by 150 mm in the film winding direction and 15 mm in the width direction, the distance between chucks of the tensile tester is set at 100 mm, and then pulled at a pulling speed of 200 mm / min. Then, the stress value when the film is pulled 5% from the length in the winding direction of the film before being pulled is read.
(II) Measuring method of static friction coefficient by tilt method: The packaging bag film is pasted on a moving block having a width of 63 mm, a length of 100 mm, and a mass of 1000 g, and placed on a fine puffed SUS304 plate, and the tilt speed is 2.7. The value of tan θ is obtained from the angle θ when the moving block starts to slide by changing the sliding slope at ^o / sec.
(III) Measurement of loop stiffness value: After forming the cylindrical body provided with a center seal portion by bonding the inner resin layers to each other by heat sealing the film for packaging bags along the longitudinal direction, the width from the center seal portion A strip of 15 mm is cut out, both ends of the strip are fixed to a loop stiffness tester so that the strip has a circumference of 95 mm, bent into an annular shape, and the annular material is pressed by the loop stiffness tester. The stress (mN) at the time when the distance between the pressing parts is 20 mm by pressing with the part is read.   The film for a gusset folded packaging bag according to claim 1, wherein the article to be packaged is bread or confectionery bread. In the measurement of the thermal shrinkage area ratio of the following (IV) based on the thermal shrinkage test based on JIS Z 1712 (2009), the thermal shrinkage area ratio (HS) of the packaging bag film is 5% or less. The film for gusset folding packaging bags of 2.
(IV) Measurement of heat shrinkage area ratio: the M ₁ the gauge length before heating in the winding direction of the packaging bag film (MD), the gauge length after heating and M _2, for the packaging bag The width direction (TD) perpendicular to the film winding direction T _{1 is} the distance between marked lines before heating, T ₂ is the distance between marked lines after heating, and T ₂ is the thermal shrinkage area ratio (HS) according to the following equation (i) (%) Is calculated.

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