Filled packaging body and vinylidene chloride-based resin stretched film

Abstract

Provided is a filled packaging body that stably exhibits easy-openability at a longitudinal seal part and a vinylidene chloride-based resin stretched film that provides the filled packaging body.　A filled packaging body according to the present invention comprises a longitudinal seal part extending in the longitudinal direction and is obtained by filling and enclosing content in a cylindrical vinylidene chloride-based resin stretched film having both longitudinal directional end parts closed, wherein: the vinylidene chloride-based resin stretched film includes a resin composition containing a vinylidene chloride-based resin and an ethylene-based resin; the proportion of an ethylene-derived structural unit in the ethylene-based resin is not less than 50 mass%; the T-peel strength of the longitudinal seal part is 7-13 N / 15 mm; and among the total number of dispersed phases of the ethylene-based resin in the vinylidene chloride-based resin stretched film, the proportion of dispersed phases having a long width of not less than 2 μm is 20-50%.

Description

Filled packaging body and vinylidene chloride resin stretched film

[0001] The present invention relates to a filled package and a stretched vinylidene chloride resin film.

[0002] In cylindrical filled packages, which are produced by filling a cylindrical film with the contents of solid or paste-like processed foods such as sausages, stick cheese, and kamaboko (fish cake), and tying both ends, a strip of film roll is often wrapped into a cylindrical shape, and the front surface of one side edge of the film is overlapped with the back surface of the other side edge to seal it, a process known as envelope sealing.

[0003] As the strip-shaped raw film, a cylindrical film formed by inflation of a vinylidene chloride resin is often folded to form a flat two-layer film, which is then slit to the desired width to form a long film.

[0004] In recent years, studies have been conducted to improve the openability of cylindrical filled packages. Patent Document 1 describes an easy-open package that is opened by pinching the outer edge of the cylindrical package made of two layers of film with the fingers and cutting the seal, and Patent Document 2 describes an easy-open package that uses a resin composition made of vinylidene chloride resin and ethylene-vinyl acetate copolymer to exhibit an easy-open function by peeling off the vertical seal.

[0005] Furthermore, Patent Document 3 describes that a filled package comprising a vinylidene chloride resin film containing ultra-low density polyethylene resin or ionomer resin and a lipid-containing content overcomes the problem of insufficient color retention period of the content before and after retort treatment, but does not describe the film configuration that leads to improved openability or the openability mechanism of the tubular filled package.

[0006] JP 2021-1027 A International Publication No. 2023 / 032632 International Publication No. 2022 / 209039

[0007] In current filled packages, there is a large variation in the opening performance of the vertical seal portion (the seal portion in the longitudinal direction of the tubular shape). For example, when pinching and opening the outer ear portion of a tubular filled package made of two layers of two-ply film as shown in Figures 1 and 2, the seal portion of the radially inner layer of film in the outer ear portion may not peel off, and only the radially outer layer of film in the outer ear portion may peel off, resulting in a defective opening condition (sometimes called single-layer peeling). It is difficult to say that current filled packages exhibit stable easy-open properties in the vertical seal portion, which poses a major problem that could lead to a decrease in product value.

[0008] The present invention has been made in view of the above problems, and its object is to provide a filled package that stably exhibits easy-open properties at the vertical seal portion, and a vinylidene chloride resin stretched film that provides such a filled package.

[0009] The present inventors have discovered that in a stretched vinylidene chloride resin film containing an ethylene-based resin, the dispersion state of the dispersed phase of the ethylene-based resin relative to the vinylidene chloride resin is significantly related to the aforementioned poor opening or unstable opening of the vertical seal. They have also discovered that the above-mentioned problems can be solved by controlling the proportion of dispersed phases having a major width of 2 μm or more to the total number of dispersed phases of the ethylene-based resin in a stretched vinylidene chloride resin film to 20 to 50% and by controlling the T-peel strength of the vertical seal to 7 to 13 N / 15 mm, thereby completing the present invention. Specifically, the present invention provides the following:

[0010] (1) A filled package comprising a cylindrical stretched vinylidene chloride resin film having a longitudinal seal extending in the longitudinal direction and both longitudinal ends converged, filled with and sealed with contents, wherein the stretched vinylidene chloride resin film is made of a resin composition containing a vinylidene chloride resin and an ethylene resin, the ethylene resin contains ethylene-derived structural units in an amount of 50 mass% or more relative to all structural units constituting the ethylene resin, the vertical seal has a T-peel strength of 7 to 13 N / 15 mm, and the proportion of dispersed phases having a major width of 2 μm or more in the total number of dispersed phases of the ethylene resin in the stretched vinylidene chloride resin film is 20 to 50%.

[0011] (2) The filled package described in (1) that has been retorted.

[0012] (3) A stretched vinylidene chloride resin film made of a resin composition containing a vinylidene chloride resin and an ethylene resin, wherein the ethylene resin contains ethylene-derived structural units in an amount of 50% by mass or more relative to all structural units constituting the ethylene resin, the amount of the ethylene resin is 2.0 to 3.0 parts by mass relative to 100 parts by mass of the vinylidene chloride resin, the melt flow rate of the ethylene resin is 0.1 to 10 g / 10 min, and the peak melting temperature of the ethylene resin is 100 to 130°C.

[0013] (4) The stretched vinylidene chloride resin film according to (3), wherein the ethylene resin is an ethylene homopolymer.

[0014] According to the present invention, it is possible to stably achieve easy-open properties in the vertical seal portion of a filled package filled with contents such as processed fish paste foods, and it is also possible to provide a stretched vinylidene chloride resin film that can be used to produce such a filled package.

[0015] 1 is an example of a schematic diagram of a filled package. FIG. 2 is an example of a schematic cross-sectional view of the vicinity of a vertical seal portion of a cylindrical filled package made of two laminated two-layer films. (a) is a cross-sectional view taken along the line A-A' in FIG. 1. (b) is an enlarged view of region B in (a), showing the dispersion state of an ethylene-based resin dispersed phase in a cross section perpendicular to the longitudinal direction of a stretched vinylidene chloride resin film. FIG. 3 is a schematic cross-sectional image of a stretched vinylidene chloride resin film of Example 3. FIG. 4 is a schematic cross-sectional image of a stretched vinylidene chloride resin film of Comparative Example 9.

[0016] The present invention will be described in detail below, but the following description is an example of an embodiment of the present invention, and the present invention is not limited to the following description as long as it does not deviate from the gist of the present invention, and can be implemented by any modification within the scope of the gist of the present invention. Note that in this specification, when an expression is expressed using "~" with a numerical value or physical property value before and after it, the values ​​before and after it are included.

[0017] <<Filled Package>> The filled package is formed by filling and sealing a cylindrical vinylidene chloride resin stretched film having a longitudinal seal extending in the longitudinal direction and both longitudinal ends converged, with the contents filled and sealed inside. The vinylidene chloride resin stretched film is made of a resin composition containing a vinylidene chloride resin and an ethylene resin. The T-peel strength of the longitudinal seal is 7 to 13 N / 15 mm. In the vinylidene chloride resin stretched film, the proportion of dispersed phases having a major width of 2 μm or more out of the total number of dispersed phases of the ethylene resin is 20 to 50%.

[0018] The mechanism by which a filled package can stably achieve easy-open properties is presumed to be as follows. The inventors presumed that the mechanism by which a filled package including a stretched vinylidene chloride resin film containing an ethylene-based resin peels from a vertical seal is that the force of opening causes fracture initiation points at the interface between the vinylidene chloride resin and the ethylene-based resin, and cracks due to the fracture propagate radially. The inventors then discovered that the dispersion state of the ethylene-based resin in a cross section perpendicular to the longitudinal direction of the stretched vinylidene chloride resin film, as shown in FIG. 3( b), affects the generation of fracture initiation points. When the dispersed phases of the ethylene-based resin are relatively large, the number of dispersed phases is reduced, and the opening force tends to concentrate stress at the interfaces, making fracture initiation points more likely to be generated. On the other hand, when the dispersed phases of the ethylene-based resin are too small, the number of dispersed phases is increased, and the opening force is dispersed to many interfaces, resulting in no stress concentration and less likely generation of fracture initiation points. By controlling the proportion of dispersed phases having a major width of 2 μm or more to 20 to 50% of the total number of dispersed phases of the ethylene-based resin, the size and number of dispersed phases become appropriate, and easy-open properties can be stably achieved. In this specification, the "dispersed phase" of the ethylene-based resin refers to a structure in which the ethylene-based resin is phase-separated from the vinylidene chloride-based resin in the form of domains (dispersed islands) in a cross section perpendicular to the longitudinal direction of the stretched vinylidene chloride-based resin film. Furthermore, the "major width" refers to the maximum width of the dispersed phase in a direction perpendicular to the thickness direction of the stretched vinylidene chloride-based resin film (the radial direction of the cylindrical stretched vinylidene chloride-based resin film) in a cross section perpendicular to the longitudinal direction of the stretched vinylidene chloride-based resin film (the shortest distance between two lines parallel to the thickness direction when the dispersed phase is sandwiched between two lines).

[0019] <Stretched vinylidene chloride resin film> The tubular stretched vinylidene chloride resin film is made of a resin composition containing a vinylidene chloride resin and an ethylene resin.

[0020] [Vinylidene chloride resin] The vinylidene chloride resin (hereinafter sometimes referred to as "PVDC") may be a homopolymer of vinylidene chloride, or a copolymer of 60% by mass or more and 98% by mass or less of vinylidene chloride and 2% by mass or more and 40% by mass or less of another monomer copolymerizable with vinylidene chloride. Examples of other monomers copolymerizable with vinylidene chloride include vinyl chloride; alkyl acrylate esters (alkyl group having 1 to 18 carbon atoms) such as methyl acrylate, ethyl acrylate, butyl acrylate, and lauryl acrylate; alkyl methacrylate esters (alkyl group having 1 to 18 carbon atoms) such as methyl methacrylate, butyl methacrylate, and lauryl methacrylate; vinyl cyanide such as acrylonitrile; aromatic vinyl such as styrene; vinyl esters of aliphatic carboxylic acids having 1 to 18 carbon atoms such as vinyl acetate; alkyl vinyl ethers having 1 to 18 carbon atoms; vinyl-polymerizable unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, and fumaric acid; and alkyl esters (including partial esters, alkyl group having 1 to 18 carbon atoms) of vinyl-polymerizable unsaturated carboxylic acids such as maleic acid, fumaric acid, and itaconic acid. More preferred is at least one selected from vinyl chloride, methyl acrylate, and lauryl acrylate. The other monomer copolymerizable with vinylidene chloride may be used alone or in combination of two or more. The copolymerization ratio of the other monomer is more preferably 3% by mass or more and 35% by mass or less, and even more preferably 10% by mass or more and 30% by mass or less. When the copolymerization ratio of the other monomer is 3% by mass or more, melt processability is less likely to be reduced, while when the copolymerization ratio of the other monomer is 35% by mass or less, gas barrier properties are less likely to be reduced. Furthermore, two or more types of PVDC may be mixed to improve melt processability. PVDC can be synthesized by any polymerization method, such as suspension polymerization, emulsion polymerization, or solution polymerization.In particular, when the other monomer copolymerizable with vinylidene chloride is vinyl chloride, from the viewpoints of melt processability, gas barrier properties, etc., the PVDC is preferably a copolymer of 60% by mass or more and 95% by mass or less of vinylidene chloride and 5% by mass or more and 40% by mass or less of vinyl chloride, more preferably a copolymer of 63% by mass or more and 90% by mass or less of vinylidene chloride and 10% by mass or more and 37% by mass or less of vinyl chloride, even more preferably a copolymer of 66% by mass or more and 85% by mass or less of vinylidene chloride and 15% by mass or more and 34% by mass or less of vinyl chloride, and particularly preferably a copolymer of 69% by mass or more and 83% by mass or less of vinylidene chloride and 17% by mass or more and 31% by mass or less of vinyl chloride.

[0021] [Ethylene-Based Resin] The ethylene-based resin contains ethylene-derived structural units in an amount of 50% by mass or more relative to the total structural units constituting the ethylene-based resin. The amount of ethylene-derived structural units in the ethylene-based resin is preferably 70% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, particularly preferably 97% by mass or more, and may even be 100% by mass. Examples of ethylene-based resins include ethylene homopolymers and copolymers of ethylene and other monomers copolymerizable with ethylene. Among these, ethylene homopolymers are preferred because they have low affinity with vinylidene chloride-based resins and low interfacial strength with vinylidene chloride-based resins, which makes fracture initiation and crack propagation more likely, and they are less responsive to high-frequency weldering used in vertical sealing, making their dispersion state less likely to change during high-frequency welder welding. Examples of other monomers copolymerizable with ethylene include vinyl esters of aliphatic carboxylic acids having 1 to 18 carbon atoms, such as vinyl acetate; vinyl-polymerizable unsaturated carboxylic acids, such as acrylic acid, methacrylic acid, maleic acid, and fumaric acid; and the like. The other monomers copolymerizable with ethylene may be used singly or in combination of two or more.

[0022] The melt flow rate (MFR) of the ethylene-based resin is preferably 0.1 to 10 g / 10 min, more preferably 0.2 to 5 g / 10 min, even more preferably 0.3 to 2 g / 10 min, and particularly preferably 0.3 to 1 g / 10 min. When the MFR is 0.1 g / 10 min or more, the ethylene-based resin is easily dispersed in the vinylidene chloride-based resin during stretched film formation, reducing the likelihood of appearance defects such as fisheyes and foreign matter, and of weak points in the film physical properties. When the MFR is 10 g / 10 min or less, the ethylene-based resin is not too finely dispersed in the vinylidene chloride-based resin during stretched film formation, making it difficult to disperse stress generated by opening the film and facilitating the generation of fracture initiation points, thereby improving ease of opening. In this specification, the MFR of the ethylene-based resin is measured by the method described in the Examples section below.

[0023] The melting peak temperature (Tpm) of the ethylene-based resin is preferably 100 to 130°C, more preferably 103 to 125°C, and even more preferably 105 to 120°C. An ethylene-based resin with a Tpm of 100°C or higher does not melt or deform due to heat transfer from the vinylidene chloride-based resin heated during high-frequency welder welding, and therefore tends to maintain its original dispersed phase shape. As a result, the propagation direction of cracks that occur upon opening tends to be stable, and opening is less likely to be incomplete. An ethylene-based resin with a Tpm of 130°C or lower melts sufficiently during stretched film formation, making it easy to disperse the ethylene-based resin in the vinylidene chloride-based resin, and less likely to cause appearance defects such as fisheyes and foreign matter, and weak points in the film physical properties. In this specification, the Tpm of the ethylene-based resin is measured by the method described in the Examples section below.

[0024] The density of ethylene resin is 885 kg / m ３ Larger, 940 kg / m ３ Preferably, it is less than 900 to 930 kg / m ３ More preferably, it is 918 to 928 kg / m ３ It is more preferable that the density is 885 kg / m ３Larger ethylene-based resins are not too finely dispersed in the vinylidene chloride-based resin during stretched film formation, so stress generated during opening is not easily dispersed, and starting points for fracture are easily generated, which makes it easier to develop easy-open properties. In particular, in the case of homopolymers of ethylene-based resins, they do not melt or deform due to heat transfer from the vinylidene chloride-based resin heated during high-frequency welder welding, so the original dispersed phase shape is easily maintained, and as a result, the propagation direction of cracks generated during opening is easily stabilized, making it less likely for opening to be incomplete. Density: 940 kg / m ３ An ethylene-based resin having a density of less than 1 / 2 mm melts sufficiently during stretching to form a film, and therefore the ethylene-based resin is easily dispersed in the vinylidene chloride-based resin, and defects in appearance such as fish eyes and foreign matter and weak points in the film properties are unlikely to occur. In this specification, the density of the ethylene-based resin is measured by the method described in the Examples below.

[0025] In the vinylidene chloride resin composition, the amount of the ethylene resin is preferably 2.0 to 3.0 parts by mass, more preferably 2.3 to 2.8 parts by mass, and even more preferably 2.4 to 2.6 parts by mass, per 100 parts by mass of the vinylidene chloride resin. When the amount is 2.0 parts by mass or more, the number of dispersed phases of the ethylene resin in the vinylidene chloride resin composition is sufficient, and the initiation point of fracture caused by the force of opening the package is easily propagated. When the amount is 3.0 parts by mass or less, the proportion of the ethylene resin in the vinylidene chloride resin composition is not large, and therefore the fusion strength in the high-frequency welder process (a sealing process using high-frequency dielectric heating) is not weakened, and the problem of the seal peeling during the retort process after filling, preventing the package from fulfilling its function, is unlikely to occur.

[0026] [Proportion of Dispersed Phases Having a Longitudinal Width of 2 μm or More] In the vinylidene chloride resin stretched film of the filled package after retort treatment, the proportion of the number of dispersed phases having a longitudinal width of 2 μm or more out of the total number of dispersed phases of the ethylene-based resin is 20 to 50%. This proportion is preferably 21 to 48%, more preferably 22 to 46%. When it is 20% or more, the dispersed phases are relatively large and the number of dispersed phases is relatively small, so that the opening force causes stress concentration at the interface between the dispersed phases and the vinylidene chloride resin, which is likely to generate a fracture starting point. When it is 50% or less, the dispersed phases are relatively small and the number of dispersed phases is relatively large, so that opening with a small force is unlikely, and the package can easily function as a package. In this specification, the proportion of the number of dispersed phases having a longitudinal width of 2 μm or more out of the total number of dispersed phases of the ethylene-based resin is measured by the method described in the Examples below. The proportion of the number of dispersed phases having a major width of 2 μm or more to the total number of dispersed phases in the ethylene-based resin can be adjusted by, for example, the type and amount of the ethylene-based resin, MFR, melting peak temperature, screw diameter when melt-extruding the vinylidene chloride-based resin composition, draw ratio, etc.

[0027] [Additives] The vinylidene chloride resin composition may optionally contain various additives, such as heat stabilizers, plasticizers, processing aids, colorants, UV absorbers, pH adjusters, and dispersing aids, which are typically added to cylindrical packaging films used in filled packaging products to improve various properties and moldability. Examples of heat stabilizers include epoxy compounds such as epoxidized vegetable oils, epoxidized animal oils, epoxidized fatty acid esters, and epoxy resin prepolymers; epoxy group-containing resins, and the like, with epoxidized vegetable oils being preferred. The type and amount of additives may be selected in the same manner as for the various additives typically used in cylindrical packaging films used in filled packaging products. The additives may be used alone or in combination of two or more. Furthermore, some or all of the additives may be incorporated into the monomer composition during the PVDC polymerization process, or may be blended into the PVDC after polymerization.

[0028] 1 , for example, a filled package is a cylindrical stretched vinylidene chloride resin film in which both side edge portions of the stretched vinylidene chloride resin film are overlapped so that the front and back surfaces of the stretched vinylidene chloride resin film face each other and longitudinally sealed, and contents are filled into the cylindrical stretched vinylidene chloride resin film and both ends are sealed, and the side edge portions of the stretched vinylidene chloride resin film form outer ear portions that protrude in a strip-like shape outside the cylindrical stretched vinylidene chloride resin film. With this filled package, when the outer ear portions are pinched and opened with fingers, incomplete opening is unlikely to occur even if the two films arranged radially inside are welded together with the two films arranged radially outside.

[0029] [Production of Strip-Shaped Stretched Vinylidene Chloride Resin Film] The stretched vinylidene chloride resin film may be composed of a single film having a thickness of 10 to 300 μm made of a vinylidene chloride resin composition, or may be composed of two overlapping films. A two-ply structure is preferred, since the effects of the present invention are more readily achieved when defects such as peeling off of one film are more likely to occur upon opening. The strip-shaped stretched vinylidene chloride resin film used to form the cylindrical stretched vinylidene chloride resin film is not particularly limited in its production method. Typically, a sheet-like or tubular extruded film is produced by extrusion molding, and the film is stretched to impart heat shrinkability. In the case of a tubular extruded film, two sheets are stacked (two-layer laminate) with their insides facing each other to obtain a strip-shaped stretched vinylidene chloride resin film having a predetermined width. This can then be further cut longitudinally as necessary to produce a strip-shaped stretched vinylidene chloride resin film having a desired width. The stretching ratio in the machine direction (MD) is not particularly limited, but is, for example, 2 to 4 times, 2.1 to 3.5 times, or 2.2 to 3 times. The stretching ratio in the transverse direction (TD) is preferably 2 to 5 times, more preferably 3 to 4.8 times, and even more preferably 3.5 to 4.5 times. The thickness of a single film constituting the strip-shaped vinylidene chloride resin stretched film is determined taking into consideration the strength and barrier properties of the film depending on the contents to be filled, but is in the range of 10 to 300 μm, with a range of 12 to 100 μm in many cases and a range of 15 to 80 μm being widely adopted. When the cylindrical vinylidene chloride resin stretched film is to be printed, the obtained strip-shaped vinylidene chloride resin stretched film may be printed.

[0030] [Longitudinal Sealed Portion] The longitudinally extending longitudinally sealed portion provided on a tubular vinylidene chloride-based resin stretched film is formed by winding a strip of vinylidene chloride-based resin stretched film into a cylindrical shape so that the backsides of both longitudinally extending edge portions face each other (palm-sealed) or so that the front and back sides of both edge portions face each other (envelope-sealed) as shown in Figures 1 and 2, and then continuously sealing (welding) both edge portions of the tubular film in the longitudinal direction (longitudinal direction) by a conventional method such as high-frequency dielectric heating, thereby forming a tubular vinylidene chloride-based resin stretched film. The longitudinally sealed portion is provided over the entire longitudinal length of the tubular vinylidene chloride-based resin stretched film, thereby allowing the contents filled and enclosed in the tubular vinylidene chloride-based resin stretched film to be stored in a sealed state. The width of the longitudinal seal portion provided on the cylindrical vinylidene chloride resin stretched film and extending in the longitudinal direction can be determined appropriately.

[0031] In the filled package after retort treatment, the T-peel strength of the vertical seal is 7 to 13 N / 15 mm, preferably 8 to 13 N / 15 mm, and more preferably 9 to 13 N / 15 mm. If it is 7 N / 15 mm or more, the filled package is difficult to open even with a small impact during transportation, packing, or shipping. If it is 13 N / 15 mm or less, easy-open properties are easily exhibited. In this specification, the T-peel strength of the vertical seal is measured by the method described in the Examples below. The T-peel strength of the vertical seal can be adjusted, for example, by the type and amount of the ethylene-based resin, MFR, etc.

[0032] [Longitudinal Outer Ears] The tubular vinylidene chloride-based resin stretched film has longitudinally extending outer ears. The longitudinally extending outer ears are unsealed portions of the tubular vinylidene chloride-based resin stretched film, formed by sealing (welding) both side edges of the tubular vinylidene chloride-based resin stretched film in the longitudinal direction (longitudinal direction) according to a conventional method, but leaving the ends of the exposed side edges perpendicular to the longitudinal direction unsealed. The width of the outer ears is not particularly limited, but is typically within the range of 1 to 10 mm, and often 2 to 6 mm. The longitudinally extending outer ears (unsealed portions) are typically formed with a uniform width throughout the entire longitudinal length of the tubular vinylidene chloride-based resin stretched film, but may be formed with different widths. The cylindrical vinylidene chloride resin stretched film has an outer ear portion and a vertical seal portion extending in the longitudinal direction, and the outer ear portion can be pinched and pulled to peel off the vertical seal portion and open the package. The outer ear portion extending in the longitudinal direction may be printed, and may have scars, indentations, cuts, notches, through holes, blind holes, etc.

[0033] [Gathering of both longitudinal ends] The filled package includes a tubular stretched vinylidene chloride resin film with both longitudinal ends gathered. That is, the filled package is formed by filling the tubular stretched vinylidene chloride resin film with contents such as processed food and then gathering both longitudinal ends of the tubular stretched vinylidene chloride resin film, thereby allowing the contents to be stored in a sealed state. The gathering of both longitudinal ends of the tubular stretched vinylidene chloride resin film can be performed using a method for gathering both longitudinal ends that has traditionally been used for tubular stretched vinylidene chloride resin films provided in filled packages, such as using metal wire clips such as aluminum wire clips, a horizontal seal film (clip tape), or other means.

[0034] [Contents filled and sealed in a cylindrical stretched vinylidene chloride resin film] The contents filled and sealed in a cylindrical stretched vinylidene chloride resin film are not particularly limited, and can be any contents conventionally filled in filled packages, such as solid or paste-like processed foods such as sausage, cheese, butter, hamburger steak, Uiro, Yokan, jelly, etc. Furthermore, contents other than foods, such as construction materials such as caulking materials and cosmetics, can also be used. The composition and shape of the contents can be selected appropriately. Particularly preferred contents include, for example, fish sausage made by blending fish paste with ordinary additives such as oil, salt, and starch.

[0035] [Retort Processing] After filling the contents, the filled package is retorted. Retort processing is a method of pressure sterilizing microorganisms such as mold, yeast, and bacteria, generally for food preservation. Typically, the filled package is pressure sterilized at 105 to 140°C, 0.15 to 0.3 MPa, and for 5 to 120 minutes. Retort devices include steam types that use heated steam and hot water types that use pressurized superheated water, and are used appropriately depending on the sterilization conditions of the food contents.

[0036] [Sensory evaluation of openability] The sensory evaluation value of the seal strength of the filled package after retort treatment is preferably 2.5 to 3.5 points, more preferably 2.6 to 3.4 points, and even more preferably 2.7 to 3.3 points. If it is 2.5 points or more, the filled package is difficult to open even with a small impact during transportation, packing, or shipping. If it is 3.5 points or less, easy opening is likely to occur. In this specification, the sensory evaluation of openability is carried out by the method described in the Examples below.

[0037] [Normal Opening Rate] The normal opening rate of the filled package after retort treatment is preferably 60% or more, more preferably 70% or more, and even more preferably 80% or more. When it is 60% or more, the easy-opening property tends to be sufficient. In this specification, the normal opening rate is measured by the method described in the examples below.

[0038] <<Stretched Vinylidene Chloride Resin Film>> The stretched vinylidene chloride resin film is made of a resin composition containing a vinylidene chloride resin and an ethylene resin. The amount of the ethylene resin is 2.0 to 3.0 parts by mass per 100 parts by mass of the vinylidene chloride resin. The melt flow rate of the ethylene resin is 0.1 to 10 g / 10 min. The peak melting temperature of the ethylene resin is 100 to 130°C. By using such a stretched vinylidene chloride resin film, the above-mentioned filled package can be obtained.

[0039] The preferred embodiments of the stretched vinylidene chloride resin film are the same as those of the stretched vinylidene chloride resin film in the "filled package".

[0040] EXAMPLES The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0041] [Melt Flow Rate (MFR)] The MFR (g / 10 min) of the ethylene-based resin was measured at a temperature of 190°C, a load of 2.16 kg, and for 10 minutes in accordance with ISO 1133:1997 Conditions M. The results are shown in Table 1.

[0042] [Melting Peak Temperature (Tpm)] The Tpm (°C) of an ethylene-based resin was measured using a differential scanning calorimeter (DSC) in accordance with JIS K7121 by the following method. The results are shown in Table 1. The temperature was once raised to 190°C to erase the thermal history, then the temperature was lowered to -10°C at a rate of 10°C / min, and then raised again at a rate of 10°C / min, and the measurement was performed. The temperature at the top of the endothermic peak was taken as Tpm.

[0043] [Proportion of Dispersed Phases with a Longitudinal Width of 2 μm or More] A cylindrical film, obtained by removing the contents from a filled package after retort treatment, was cut from the center of a cross section perpendicular to the longitudinal direction of the film. The sample was embedded in epoxy resin, flattened using a cryo-ultramicrotome, and observed using a scanning electron microscope (SU-8020, manufactured by Hitachi High-Technologies Corporation) at an acceleration voltage of 0.8 to 1.0 keV and a magnification of 5000x. Next, an arbitrary 22 μm x 16 μm region was selected from the obtained image, and the gradation was changed using Photoshop to clarify the boundaries of the dispersed phases of the ethylene-based resin. Data on the longitudinal width of the dispersed phases in the region was extracted using image processing software (WinROOF, manufactured by Mitani Shoji Co., Ltd.). Schematic diagrams of the processed images obtained in Example 3 and Comparative Example 9 are shown in Figures 4 and 5, respectively. The total number of dispersed phases of the ethylene-based resin and the number of dispersed phases having a major width of 2 μm or more were counted, and the ratio of the number of dispersed phases having a major width of 2 μm or more to the total number of dispersed phases of the ethylene-based resin was calculated using the following formula. The results are shown in Table 1. However, in counting the total number of dispersed phases, the ratio of the number of dispersed phases having a major width of 0.003 μm or less and an area of ​​0.009 μm ２ Dispersed phases that fall into at least one of the following categories were excluded: a width of 0.001 μm or less, and a short width of 0.001 μm or less. The term "short width" refers to the maximum width of the dispersed phase in the thickness direction of the stretched vinylidene chloride resin film in a cross section perpendicular to the longitudinal direction of the stretched vinylidene chloride resin film (the shortest distance between two lines when the dispersed phase is sandwiched between two lines parallel to the direction perpendicular to the thickness direction). For example, the dispersed phase in the upper right of Figure 4 has a long width of 1 and a short width of w. The proportion (%) of the number of dispersed phases with a long width of 2 μm or more out of the total number of dispersed phases in the ethylene resin = (number of dispersed phases with a long width of 2 μm or more / total number of dispersed phases) × 100

[0044] [Density of ethylene-based resin] Density of ethylene-based resin (kg / m ３ The results are shown in Table 1.

[0045] [T-shaped (T-type) Peel Strength] The T-shaped peel strength of the vertical seal portion of a filled package was measured in accordance with JIS K6854 using a Tensilon universal material testing machine manufactured by Orientec Co., Ltd., as follows. The results are shown in Table 1. A tubular film from which the contents were removed from the filled package after retort treatment was clamped between the clamps of the testing machine at a 15 mm long section along the longitudinal direction of the outer edge portion at approximately the center of the longitudinal direction of the film, and at a 15 mm long section along the longitudinal direction of the body portion (the portion of the tubular film other than the vertical seal portion), and the strength when peeled at a pulling rate of 300 mm / min was measured at a temperature of 23°C.

[0046] [Sensory evaluation of openability] The seal strength of the filled packages after retort treatment was sensorily evaluated according to the following method. The results are shown in Table 1. Ten subjects, each of whom was a panel of five filled packages, pinched the outer edge of each filled package with their fingers and pulled off the vertical seal, measuring the strength of the peel resistance felt and assigning a score (ranging from 1 to 5 points) according to the following criteria. The average score (expressed to one decimal place) assigned to a total of 50 filled packages was calculated. (Evaluation criteria) 5 points: The vertical seal cannot be peeled even with strong force, or the vertical seal or outer edge is torn 4 points: The vertical seal peels off with strong force 3 points: The vertical seal peels off with moderate force 2 points: The vertical seal peels off with weak force 1 point: The vertical seal peels off with just a light touch

[0047] [Normal Opening Rate] The ease of opening the filled packages was evaluated using the following method. The results are shown in Table 1. Ten subjects each opened five filled packages (50 in total) by pinching the outer edge of the filled package with their fingers. The opening rate was calculated using the following formula: Opening rate (%) = ((number of packages in which the two films located on the outside in the radial direction peeled from the vertical seal) / 50) × 100 (rounded to one decimal place).

[0048] [Ethylene-based resins] LDPE1: UBE Polyethylene R300 manufactured by Ube Maruzen Polyethylene Co., Ltd. LDPE2: NUC-8350 manufactured by ENEOS NUC Corporation LDPE3: DNDJ-0405 manufactured by ENEOS NUC Corporation LDPE4: Novatec LD LF280 manufactured by Japan Polyethylene Corporation EVA: Evaflex V5274 manufactured by Mitsui Dow Polychemicals VLDPE: Tafmer A4085S manufactured by Mitsui Chemicals, Inc. Ionomer: Surlyn 1707 manufactured by Dow

[0049] Example 1 (Production of a stretched vinylidene chloride resin film) A copolymer (85 parts by mass) polymerized at a monomer charge mass ratio (VD / VC) of 81 / 19 during polymerization of vinylidene chloride (VD) and vinyl chloride (VC), at a polymerization temperature of 34° C. or higher and 49° C. or lower for 44 hours, and a copolymer (15 parts by mass) polymerized at a VD / VC ratio of 71 / 29, at a polymerization temperature of 43° C. or higher and 58° C. or lower for 37 hours were mixed with 100 parts by mass of a polyvinylidene chloride resin, and a total of 5.4 parts by mass of acetyl tributyl citrate (ATBC), dibutyl sebacate (DBS), and epoxidized vegetable oil was further added, and a total of 1.83 parts by mass of an epoxy group-containing polymer, an antioxidant, a surfactant, erucic acid amide, and calcium carbonate was further added. Finally, a stretched film having a density of 920 kg / m was produced. ３ 2.5 parts by mass of ethylene homopolymer LDPE1 having a melt flow rate (MFR) of 0.35 g / 10 min and a peak melting temperature of 109°C was added to the mixture, and melt extrusion molding was performed using an extrusion screw with a diameter of 40 mm to obtain a vinylidene chloride resin composition. Subsequently, a tubular film was formed by inflation biaxial stretching at room temperature under conditions of 2.5 times in the MD (longitudinal direction) and 4.1 times in the TD (transverse direction), and then folded into a flat two-ply (two-layer) film to obtain a vinylidene chloride resin stretched film (two-layer laminate film) a having a total thickness of 40 μm (the thickness of two 20 μm-thick films).

[0050] (Production of Filled Package) A base film (vinylidene chloride-based resin stretched film a) cut to a width of 84 mm was set in an automatic filling and packaging machine (manufactured by Kureha Corporation, product name: KAP8000 automatic filling and packaging machine). This base film was rolled into a cylindrical shape so that the front and back surfaces of both longitudinally extending edge portions overlapped and faced each other to form a cylindrical PVDC film. While the cylindrical PVDC film was running downward, the overlapping side edges of the cylindrical PVDC film were passed between a seal electrode (external electrode with a semicircular tip having a radius of 1 mm) and an earth electrode (internal electrode) of a high-frequency dielectric heating device to which high-frequency power based on a predetermined voltage and current was applied (a force of 500 g was used to press the external electrode against the internal electrode). The two films located radially inside the side edges of the cylindrical PVDC film were welded together with the two films located radially outside, forming a cylindrical PVDC film with an outer edge and a vertical seal extending in the longitudinal direction, each 8 mm wide. Subsequently, the vertically sealed PVDC film was filled with fish sausage paste from a filling device via a nozzle. Two pairs of cylindrical feed rollers, which are a feed device located downstream of the nozzle, continuously clamped and conveyed the film downward while pressing the contents. The two pairs of feed rollers completely pressed the film, and each pair of feed rollers separated the film by approximately 16 mm. ２ The area of ​​the filled package was pressed. Then, both longitudinal ends of the cylindrical PVDC film were bundled with clip tape and cut to a predetermined length to produce a filled package with a circumference of 72 mm and a length of 215 mm. When forming the base film into a cylindrical shape, the conditions were adjusted so that the folded width (half the circumference) was 36 mm, the cut length (the length measured in the longitudinal direction after removing the contents from the filled package and flattening the cylindrical PVDC film) was 215 mm, and the mass was 64 g. The obtained filled package was then heated at a temperature of 120°C and a pressure of 2.0 kg / cm. ２ (gauge pressure) for 10 minutes to carry out retort heat sterilization, and then the container was taken out to prepare an evaluation sample.

[0051] Example 2 A stretched vinylidene chloride resin film and a filled package were obtained in the same manner as in Example 1, except that the amount of ethylene homopolymer LDPE1 added was changed to 2.0 parts by mass.

[0052] [Example 3] A vinylidene chloride resin stretched film and a filled package were obtained in the same manner as in Example 1, except that a vinylidene chloride resin composition was obtained by melt extrusion molding using an extrusion molding screw with a diameter of 90 mm.

[0053] [Example 4] Instead of the ethylene homopolymer LDPE1, ３ A stretched vinylidene chloride resin film and a filled package were obtained in the same manner as in Example 1, except that an ethylene homopolymer LDPE4 having a melt flow rate of 0.7 g / 10 min and a peak melting temperature of 115°C was used.

[0054] Comparative Example 1 A stretched vinylidene chloride resin film and a filled package were obtained in the same manner as in Example 1, except that the ethylene homopolymer LDPE1 was not added.

[0055] [Comparative Example 2] Instead of the ethylene homopolymer LDPE1, ３ A stretched vinylidene chloride resin film and a filled packaging body were obtained in the same manner as in Example 1, except that an ethylene-vinyl acetate copolymer EVA having a vinyl acetate content of 17% by mass, a melt flow rate of 0.8 g / 10 min, and a peak melting temperature of 89°C was used.

[0056] [Comparative Example 3] Instead of the ethylene homopolymer LDPE1, ３ A stretched vinylidene chloride resin film and a filled package were obtained in the same manner as in Example 1, except that a very low density linear polyethylene VLDPE having a melt flow rate of 3.6 g / 10 min and a peak melting temperature of 66°C was used.

[0057] [Comparative Example 4] Instead of the ethylene homopolymer LDPE1, ３A stretched vinylidene chloride resin film and a filled packaging body were obtained in the same manner as in Example 1, except that Ionomer, a sodium ion neutralized ethylene-methacrylic acid copolymer having a melt flow rate of 0.9 g / 10 min and a melting peak temperature of 92°C, was used.

[0058] Comparative Example 5 A stretched vinylidene chloride resin film and a filled package were obtained in the same manner as in Example 1, except that the amount of ethylene homopolymer LDPE1 added was changed to 1.5 parts by mass.

[0059] Comparative Example 6 A stretched vinylidene chloride resin film and a filled package were obtained in the same manner as in Example 1, except that the amount of ethylene homopolymer LDPE1 added was changed to 3.5 parts by mass.

[0060] [Comparative Example 7] Instead of the ethylene homopolymer LDPE1, ３ A stretched vinylidene chloride resin film and a filled packaging body were obtained in the same manner as in Example 1, except that an ethylene homopolymer LDPE2 having a melt flow rate of 17 g / 10 min and a melting peak temperature of 107°C was used.

[0061] [Comparative Example 8] Instead of the ethylene homopolymer LDPE1, ３ A stretched vinylidene chloride resin film and a filled packaging body were obtained in the same manner as in Example 1, except that an ethylene homopolymer LDPE3 having a melt flow rate of 25 g / 10 min and a peak melting temperature of 106°C was used.

[0062] [Comparative Example 9] Instead of the ethylene homopolymer LDPE1, ３ A vinylidene chloride resin stretched film and a filled package were obtained in the same manner as in Example 1, except that an ethylene homopolymer LDPE3 having a melt flow rate of 25 g / 10 min and a peak melting temperature of 106°C was used and melt-extruded using an extruder having a diameter of 90 mm to produce a stretched film to obtain a vinylidene chloride resin composition.

[0063]

[0064] From Table 1, it can be seen that the filled packaging bodies of the examples in which the T-peel strength of the vertical seal portion and the proportion of the number of dispersed phases with a long width of 2 μm or more out of the total number of dispersed phases of the ethylene-based resin are each within a specific range have good sensory evaluations of openability and normal opening rates, and consistently exhibit easy-openability.

[0065] S: Filled package 1: Cylindrical vinylidene chloride resin stretched film 21: Vertical seal portion 22: Outer ear portion 3A, 3B: Both ends 41: Two films arranged radially outward 41A: Surface layer portion (one film located outermost in the radial direction) 42: Two films arranged radially inward 51: Vinylidene chloride resin 52: Ethylene resin 9: Contents 1: Long width of ethylene-based resin dispersed phase w: Short width of ethylene-based resin dispersed phase

Claims

1. A filled package comprising a cylindrical stretched vinylidene chloride resin film having a longitudinal seal extending in the longitudinal direction and both longitudinal ends converged, filled with and sealed with contents, wherein the stretched vinylidene chloride resin film is made of a resin composition containing a vinylidene chloride resin and an ethylene resin, the proportion of ethylene-derived structural units in the ethylene resin being 50 mass% or more relative to all structural units constituting the ethylene resin, the T-peel strength of the longitudinal seal being 7 to 13 N / 15 mm, and the proportion of dispersed phases of the ethylene resin in the stretched vinylidene chloride resin film having a major width of 2 μm or more being 20 to 50% of the total number of dispersed phases.

2. The filled package according to claim 1, which has been retorted.

3. A stretched vinylidene chloride resin film made of a resin composition containing a vinylidene chloride resin and an ethylene resin, wherein the proportion of ethylene-derived structural units in the ethylene resin is 50% by mass or more relative to all structural units constituting the ethylene resin, the amount of the ethylene resin is 2.0 to 3.0 parts by mass per 100 parts by mass of the vinylidene chloride resin, the melt flow rate of the ethylene resin is 0.1 to 10 g / 10 min, and the peak melting temperature of the ethylene resin is 100 to 130°C.

4. The stretched vinylidene chloride resin film according to claim 3, wherein the ethylene resin is an ethylene homopolymer.

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