JP5258254B2 - Packaging film - Google Patents

Description

  The present invention relates to a novel packaging film comprising a biaxially stretched polypropylene resin film. Specifically, in a packaging film in which an opening tape is provided in the width direction (hereinafter sometimes abbreviated as TD) of a biaxially stretched polypropylene-based resin film, the packaging film in which the tear directionality of TD is remarkably improved. It is to provide.

  Packaging films made of plastic films, especially biaxially oriented polypropylene resin films, are used for packaging such as sandwiches, rice balls, caramels, and other luxury goods such as tobacco, CDs, DVDs because of their strength, packaging characteristics, and economy. It is used for packaging various packages such as daily goods such as cassette tapes.

  The packaging film is usually packaged by heat-sealing or fusing-seal etc. to wrap the packaged body, but when taking out the packaged body which is the contents, the necessary part can be easily torn and broken. Are devised.

  For example, in the packaging film, many are provided with an opening tape (also referred to as “tier tape”) in order to easily tear the film (see Patent Documents 1 to 4). . In general, in the case of a packaging film made of a biaxially stretched polypropylene resin film, the opening tape is laminated in the longitudinal direction of the film (hereinafter sometimes abbreviated as MD) from the end of the film. At the end, a notch (notch) is provided with an opening tape interposed therebetween. The packaging body provided with such an opening tape can tear the packaging film (packaging body) along the tape from the notch of the packaging film by pulling the opening tape. Moreover, since the base film which comprises an opening tape normally uses what has high tensile strength, it does not cut in the middle of opening, and this opening tape also plays the role which prevents miscutting.

  By the way, in the packaging film using the said biaxially-stretched polypropylene-type resin film, depending on the usage form of a film, it may be required to laminate | stack the opening tape on TD which becomes a right angle with conventional MD. is there.

  However, when the opening tape is provided on the TD of the film as described above, it has been found that if a general-purpose biaxially stretched polypropylene resin film is used, the tear direction to TD is not stable.

  For example, when pulling the opening tape without pressing the packaging bag (packaging body) by the packaging film firmly or when the pulling speed of the opening tape is fast, the film is obliquely separated from the guiding direction by the opening tape. A state of tearing in the direction occurred, and the contents (packaged body) sometimes jumped out. In particular, when the opening distance by the opening tape is relatively long (about 80 to 120 mm) and the contents are soft like a sandwich packaging bag, there is no tightness between the contents and the package, and the opening tape When tearing the package, the package itself may move slightly, and the above problem may occur frequently.

  Such a phenomenon is caused by a heat-seal type biaxially stretched laminated polypropylene in which a low melting point, low crystalline, and amorphous polyolefin-based resin is laminated as a heat seal layer, among biaxially oriented polypropylene resin films. In the case of the resin-based resin film, the tear directionality becomes unstable due to the flexible characteristics of the resin constituting the heat seal layer, and the above-mentioned problem tends to occur more easily.

JP-A-3-28959 Japanese Utility Model Publication No. 6-42689 Registered Utility Model No. 3014696 JP 2005-53508 A

  Accordingly, an object of the present invention is to provide a packaging film having an extremely good tearing directionality with an opening tape when the opening tape is provided on the TD of the film in a packaging film made of a biaxially stretched polypropylene resin film. There is to do.

  The inventors of the present invention have made extensive studies to achieve the above object. As a result, a biaxially stretched polypropylene resin film that is highly molecularly oriented so that the tensile elongation of MD is below a specific value is unexpectedly opened to a TD perpendicular to the direction of the molecular orientation. It has been found that by laminating the film, a tearable directionality by the opening tape is remarkably improved. Furthermore, even when such a biaxially stretched polypropylene resin film is a laminate of heat seal layers, it has been found that the above-mentioned effects can be sufficiently exerted, and the present invention has been completed.

That is, the present invention has at least a biaxially stretched base material layer made of a polypropylene resin, has a longitudinal tensile elongation of 80 to 170%, and a longitudinal tensile strength of 155 to 230 MPa. A packaging film comprising a polypropylene-based resin film and comprising an opening tape laminated in the width direction of the biaxially stretched polypropylene-based resin film.

  In the packaging film, the biaxially oriented polypropylene resin film preferably has a tensile elongation in the width direction of 40 to 90%. When the tensile elongation in the width direction satisfies the above range, the balance of mechanical strength is excellent, and the use thereof is preferable.

  In the packaging film, the biaxially stretched polypropylene resin film is a heat seal made of a polyolefin resin having a melting point lower than that of the polypropylene resin on at least one surface of a biaxially stretched base material layer made of a polypropylene resin. It is preferable that the layers are laminated. Since the biaxially stretched polypropylene resin film having such a structure has excellent molding processability, it can be used as a packaging film for various applications.

  Further, in the packaging film, the total thickness of the heat seal layer (in the case where the heat seal layer is laminated on both sides of the base material layer, the total thickness of the heat seal layers on both sides) is a biaxially oriented polypropylene resin. It is preferably 0.8 to 25% of the thickness of the film in order to exhibit the effects of the present invention more remarkably.

  The present invention also provides a sandwich packaging bag formed of the packaging film.

  The packaging film of the present invention eliminates the instability of tearability of TD, which has been a problem in the past, and can be torn stably along the opening tape. In addition, when the opening tape is laminated on the biaxially stretched polypropylene resin film in which the heat seal layer is laminated on at least one side of the base material layer, and this is constituted, the heat seal layer is present. Although instability of tearability of TD was likely to occur, the present invention can be stably torn along the opening tape even in such a packaging film.

  Therefore, this invention can eliminate the restriction | limiting of the direction which laminates an opening tape in the packaging film which uses a biaxially-stretched polypropylene-type resin film. That is, it is possible to satisfy the requirements when the opening tape must be laminated on the TD due to restrictions such as the printing pitch, the printing direction, the packaging form, or the improvement in the yield of the packaging bag. As a result, the utilization rate of the biaxially stretched polypropylene resin film in the packaging field can be improved, and the industrial contribution is extremely large.

  The present invention is a packaging film in which an opening tape is laminated on a TD of a biaxially stretched polypropylene resin film having at least a biaxially stretched base material layer made of a polypropylene resin. And this invention can tear a film to TD linearly and stably by this opening tape by making the tensile elongation of the longitudinal direction of this biaxially stretched polypropylene resin film 170% or less. “Tear directionality” is improved.

[Polypropylene resin constituting the base material layer]
The packaging film of the present invention comprises a biaxially stretched polypropylene resin film having at least a biaxially stretched base material layer made of a polypropylene resin.

  The polypropylene resin may have any crystallinity that can achieve a tensile elongation of MD of 170% or less by a biaxial stretching method to be described later. % Resin is used. Specific examples of the polypropylene resin include a propylene homopolymer, a propylene-α-olefin copolymer having a monomer unit based on an α-olefin other than propylene of less than 30% by mass, and propylene-ethylene-1-butene. Examples include terpolymers and mixtures thereof. Examples of the α-olefin include ethylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 4-methyl-1-pentene, and the like. It is done. Furthermore, the copolymer may be any of a random copolymer, a block copolymer, and a graft copolymer. In addition, although the heat seal layer mentioned later is comprised from the polyolefin-type resin whose melting | fusing point is lower than the polypropylene resin which comprises a base material layer, melting | fusing point of the polypropylene resin which comprises the base material layer of this invention is the said polypropylene type When mixing and using resin, it is based on melting | fusing point of polypropylene resin with many compounding ratios. When the blending ratio is the same, a polypropylene resin having a high melting point is used as a reference.

  In the present invention, among the polypropylene resins, a propylene homopolymer, propylene-ethylene having an ethylene content of 0.2 to 5.0% by mass in order to obtain a film having better film forming properties and openability. It is preferable to use a random copolymer and a mixture of a propylene homopolymer and a propylene-ethylene random copolymer adjusted so that the ethylene content is 0.2 to 5.0% by mass.

  Moreover, in order to improve the functionality of the obtained biaxially stretched polypropylene resin film, the following resins can be added to the polypropylene resin. Examples of these resins to be added are low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene, polybutene, petroleum resin, ethylene-α-olefin copolymer, 1-butene-α-olefin copolymer. Examples include polymers and various elastomers. By forming a film by adding the above resin to a polypropylene resin, easy stretchability, high transparency, high moisture resistance, additive bleed acceleration, easy improvement of surface roughness, film matting, easy Effects such as film-forming properties, heat-sealing properties, and surface modification properties by corona discharge treatment can be enhanced.

  In addition, the melt mass flow rate of the polypropylene resin is preferably 0.5 to 15.0 g / 10 min at 230 ° C., more preferably 1.0 to 10.0 g / 10, considering the film-forming property. Minutes are preferred. Moreover, it is preferable that the melt mass flow rate of the polypropylene resin to which the resin for enhancing the functionality is added is 1.0 to 20.0 g / 10 min at 230 ° C.

[Biaxially stretched polypropylene resin film]
The packaging film of the present invention is composed of a biaxially stretched polypropylene resin film having at least a biaxially stretched base material layer made of the polypropylene resin. The base layer of this biaxially stretched polypropylene resin film may be composed of a single layer using any of the polypropylene resins exemplified above, and different types of resins and additives depending on the purpose. You may comprise from the several layer which consists of resin from which these differ. If an example composed of a plurality of layers is specifically shown, a base layer made of a polypropylene resin in which an additive having a specific function is blended is laminated on a main layer made of a polypropylene resin to form a base material layer. An example can be given. In addition, although the heat seal layer mentioned later is comprised from the polyolefin-type resin whose melting | fusing point is lower than the polypropylene resin which comprises a base material layer, when a base material layer is comprised from several layers, a base material layer Of the polypropylene resin having the highest blending ratio among the polypropylene resins constituting the base. Moreover, when the compounding ratio of the polypropylene resin constituting the base material layer is the same, the polypropylene resin having a high melting point is used as a reference.

  In the present invention, the base material layer may contain a known additive. Of course, when the base material layer is composed of a plurality of layers (for example, when the base material layer is composed of a main layer and a surface layer), each layer can contain a known additive. Specific examples of known additives include antioxidants, lubricants, antiblocking agents, antifogging agents, chlorine scavengers, antistatic agents, crystal nucleating agents and the like. In particular, when the packaging film of the present invention is used for packaging foods such as sandwiches, fogging due to condensation on the film after packaging may become a problem. It is preferable to add.

  Especially, in order for the packaging film of this invention to exhibit the outstanding antifogging property, it is preferable to contain 0.5-1.5 mass% of antifogging agents in the said base material layer. When the base material layer is composed of a main layer and a surface layer, the antifogging agent contained in the main layer is 0.5 to 1.5% by mass, and the total thickness of the surface layer (surface layers exist on both sides) In this case, the sum of the thicknesses of the surface layers on both sides is preferably 3 to 20% of the thickness of the base material layer. Furthermore, it is preferable to perform surface treatment such as corona treatment on the base material layer on the side where it is desired to impart antifogging properties. When the packaging film of the present invention is made of a biaxially stretched polypropylene resin film having only a base material layer on which a heat seal layer is not laminated, or a biaxially stretched polypropylene resin film having a heat seal layer laminated thereon In any case, it is preferable that the blending ratio of the antifogging agent satisfies the above range in order to exhibit excellent antifogging properties.

  In the present invention, a known functional layer, for example, an adhesive layer, a gas barrier layer, a light shielding layer, a UV cut layer, or the like can be provided on the surface of the base material layer as long as the effects of the present invention are not impaired.

  The greatest feature of the packaging film of the present invention is that the MD tensile elongation of the biaxially stretched polypropylene resin film having at least a biaxially stretched base material layer made of the polypropylene resin is 170% or less, preferably 160. % Or less. That is, when the tensile elongation exceeds 170%, as shown in a comparative example described later, the tearability to TD is lowered, and when tearing with the opening tape, it can be torn linearly along the opening tape. It becomes difficult.

  The lower limit of the tensile elongation of MD is not particularly limited, but is preferably 80% in consideration of productivity, physical properties as a packaging film, and the like.

  Usually, the biaxially stretched polypropylene resin film used for packaging has the property of being easily torn in both the vertical and horizontal directions. Tear. Conventionally, such a biaxially stretched polypropylene-based resin film generally has a MD tensile elongation exceeding 180%. When a heat seal layer is laminated thereon, particularly when the thickness is thick, the tensile elongation tends to be further increased.

  On the other hand, this invention uses the biaxially-stretched polypropylene-type resin film whose molecule | numerator more orientated to MD whose tensile elongation of MD is 170% or less.

  Thus, by setting the MD tensile elongation of the biaxially stretched polypropylene resin film to 170% or less, the tearability of TD by the opening tape described later is remarkably improved, and the film is stably and linearly torn. Can do.

  In the packaging film of the present invention, the mechanism by which the tearing directionality is remarkably improved by the opening tape laminated on the TD is not clear, but the present inventors presume as follows. That is, in the packaging film of the present invention in which the tensile elongation of MD of the film is 170% or less, the molecular chain of the biaxially stretched polypropylene-based resin film constituting the film is oriented by MD, and there is a margin to extend to MD. There is no molecular orientation. And the shearing force by the opening tape laminated | stacked on the orthogonal | vertical direction with respect to this orientation adds to this, The destruction of the molecular chain of this part arises. It is presumed that the opening tape leads to “tearing” by the opening tape by breaking a molecular chain that cannot be extended to the MD, and tears the film linearly along the opening tape. That is, in order to improve the tearing direction of TD by using the opening tape, the tensile strength of MD is lowered (not in the state of molecular chain with no room to extend to MD) rather than lowering the tearing strength of TD. Is considered important. Such a mechanism is completely different from the conventional film tearing mechanism in which molecular chains are oriented by TD when, for example, the film is torn to TD.

  In the packaging film of the present invention, the biaxially stretched polypropylene-based resin film is not particularly limited with respect to other physical properties other than the tensile elongation of MD, but suitable physical properties include a tensile elongation of TD. It is preferable that it is 40 to 90%. Further, the difference between the tensile elongation of MD and the tensile elongation of TD is more preferably 30 to 120%. By satisfying these physical properties, it can be used in a wide range of applications.

Furthermore, it is preferable that the tensile strength of MD is 155 to 230 MPa , and the tensile strength of TD is 200 MPa or more, preferably 220 to 340 MPa.

  Further, the birefringence of MD and TD is preferably 0.01300 or less. When the biaxially stretched polypropylene resin film satisfies these physical properties, the tearing direction of TD can be further improved. The lower limit of the birefringence is not particularly limited, but is preferably 0.00050 in view of the physical properties of the film, film forming properties, and the like.

  The birefringence indicates the difference in the degree of molecular orientation between MD and TD in the film plane using the refractive index of light. That is, the higher the molecular orientation relative to the orientation direction in the film plane, the greater the refractive index of light in that direction. Here, the biaxially stretched polypropyne resin film of the present invention needs to have a tensile elongation of MD of 170% or less, and MD is more highly molecularly oriented than a general biaxially stretched polypropylene film. Therefore, the difference in orientation between MD and TD is reduced. As a result, birefringence, which is the difference in refractive index between MD and TD, is smaller than that of a general biaxially stretched polypropylene film.

  The thickness of the biaxially stretched polypropylene resin film constituting the packaging film of the present invention is not particularly limited, but is generally 15 to 80 μm, particularly preferably 20 to 60 μm. .

  In the packaging film of the present invention, the biaxially stretched polypropylene resin film may be a film composed only of a base material layer on which no heat seal layer is laminated. In this case, the biaxially stretched base material layer made of the polypropylene resin may be a biaxially stretched polypropylene resin film, and the tensile elongation in the longitudinal direction of the film may be 170% or less. Moreover, it is preferable that this film satisfies the above-mentioned various physical properties (for example, TD tensile elongation, MD, TD tensile strength, birefringence, film thickness, etc.).

  In addition, the packaging film of the present invention has a polypropylene resin on at least one surface of a base material layer made of the polypropylene resin as long as the tensile elongation in the longitudinal direction of the biaxially stretched polypropylene resin film is 170% or less. You may comprise from the biaxially-stretched polypropylene-type resin film by which the heat seal layer which consists of polyolefin resin with a lower melting | fusing point was laminated | stacked. By laminating a heat seal layer on at least one surface of the base material layer, the packaging film of the present invention has good secondary processing characteristics and can be used for packaging various packages. Hereinafter, a biaxially stretched polypropylene resin film in which a heat seal layer is laminated on at least one surface of the base material layer may be referred to as a “biaxially stretched laminated polypropylene resin film”.

  Next, the heat seal layer of the biaxially stretched laminated polypropylene resin film and the polyolefin resin constituting the heat seal layer will be described.

[Heat seal layer and polyolefin resin constituting heat seal layer]
In the packaging film of the present invention, the heat seal layer laminated on at least one side of the biaxially stretched base material layer has the required heat seal strength, depending on the contents to be packaged and the packaging suitability of the packaging machine, In consideration of the heat seal fusion start temperature, the thickness and the polyolefin resin to be formed may be appropriately selected.

  In particular, when the packaging film of the present invention is processed by heat sealing into a sandwich packaging bag, the biaxially oriented laminated polypropylene system having a heat seal strength of 2.5 N / 15 mm or more, preferably 3.0 N / 15 mm or more. It is preferable to use a resin film. Therefore, when using for the said use, it is preferable to select the polyolefin-type resin which satisfies the said heat seal intensity | strength.

  The polyolefin resin constituting the heat seal layer is a resin having a lower melting point than the polypropylene resin constituting the base material layer. In particular, a resin having a melting point lower by 15 to 60 ° C. than the polypropylene resin constituting the base material layer is suitable. Specific examples of the polyolefin resin constituting the heat seal layer include linear low density polyethylene, propylene-α-olefin copolymer having a monomer unit of less than 30% by mass based on α-olefin other than propylene, and propylene. -Ethylene-1-butene terpolymers and mixtures thereof. Examples of the α-olefin include ethylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 4-methyl-1-pentene, and the like. It is done. Furthermore, the copolymer may be any of a random copolymer, a block copolymer, and a graft copolymer. Among these, in order to obtain a film having better film forming properties, heat sealability, and antifogging properties, linear low density polyethylene having a melting point of 100 to 130 ° C., propylene-ethylene having a melting point of 110 to 140 ° C. It is preferable to use a random copolymer and a propylene-ethylene-1-butene terpolymer. In addition, when mixing and using the said polyolefin resin, it is based on melting | fusing point of polyolefin resin with many compounding ratios. When the blending ratio is the same, a polyolefin resin having a low melting point is used as a reference. When heat seal layers made of different polyolefin resins are laminated on both surfaces of the base material layer, the melting point of the polyolefin resin constituting each heat seal layer is used as a reference.

  When the heat seal layer is desired to have functions such as low temperature heat seal and accelerating bleeding of additives such as an antifogging agent, the polyolefin resin constituting the heat seal layer is added with an ethylene-α-olefin. It is preferable to mix a low melting point, low crystalline elastomer composed of 1-butene-α-olefin or the like at a ratio of 60% by mass or less.

  In addition, when it is desired to give the heat seal layer a matte appearance, the polyolefin resin constituting the heat seal layer may be a low density polyethylene, a medium density polyethylene, a high density polyethylene, a polybutene, a polypropylene, or the like. It is preferable to mix the incompatible resin consisting of appropriately.

  In this invention, the additive illustrated in the said base material layer can be especially added to a heat seal layer without a restriction | limiting.

  The polyolefin resin constituting the heat seal layer has an action of efficiently bleeding out the antifogging agent contained in the base material layer to the surface of the heat seal layer, and is extremely good on the surface of the heat seal layer. Antifogging properties can be imparted. Therefore, the packaging film of the present invention can be suitably used for applications such as sandwich packaging bags.

  In the biaxially stretched laminated polypropylene resin film, the heat seal layer may be formed on one side of the base material layer or on both sides of the base material layer depending on the use of the packaging film.

  In the packaging film of the present invention, the total thickness of the heat-seal layer of the biaxially stretched laminated polypropylene resin film (in the case where the heat-seal layer is laminated on both sides, the total thickness of the heat-seal layers on both sides) is 0 It is preferably 5 to 12.0 μm, and more preferably 0.5 to 10.0 μm.

  However, since the tensile elongation of MD of the biaxially stretched laminated polypropylene resin film, which is a feature of the packaging film of the present invention, is mainly determined by the characteristics of the base material layer, the thickness of the heat seal layer is determined by the base material. If it is too thick for the layer, the desired tensile elongation may not be achieved. That is, the biaxially stretched laminated polypropylene resin film must have an MD tensile elongation of 170% or less, but if the heat seal layer becomes too thick, the tensile elongation may not be satisfied.

  In general, it is considered that the MD molecular orientation of the base material layer on which the heat seal layer is laminated greatly affects the MD tensile elongation. Of course, since the heat-sealed layer laminated | stacked by the co-pressing method and in-line lamination method mentioned later passes a biaxial or uniaxial extending process, a molecule | numerator is orientated in the biaxial or uniaxial extending | stretching direction. However, as a matter of course, the TD stretching, which is the final stretching, needs to be set to a temperature at which the resin constituting the base material layer having a higher melting point can be stretched than the melting point of the resin constituting the heat seal layer. Therefore, especially at the heat treatment temperature of the tenter oven heat treatment, which is the final process of TD stretching, it is considered that the orientation of most molecules of the low melting point polyolefin resin constituting the heat seal layer is relaxed. In this way, the heat seal layer made of a low melting point polyolefin resin with relaxed molecular orientation has a large elongation of the heat seal layer itself. As a result, when the heat seal layer is too thick with respect to the base material layer, the tensile elongation of MD is also increased, and the tear directionality may be hindered.

  Therefore, the total thickness of the heat seal layer satisfies the above range and is limited to 25% or less, preferably 0.8 to 25% of the total thickness of the biaxially stretched laminated polypropylene resin film. It is preferable.

  Next, physical properties of a film on which the heat seal layer is laminated, that is, a biaxially stretched laminated polypropylene resin film will be described.

[Biaxially stretched laminated polypropylene resin film]
The biaxially stretched laminated polypropylene resin film can be laminated with a heat seal layer on at least one surface of the biaxially stretched base material layer by a method described later. The physical properties of the biaxially stretched laminated polypropylene resin film are such that the tensile elongation of MD is 170% or less, preferably 160% or less, as described in the biaxially stretched polypropylene resin film. That is, when the MD tensile strength exceeds 170%, as shown in a comparative example described later, the tear directionality to the TD is lowered, and when tearing with the opening tape, the MD is torn linearly along the opening tape. It becomes difficult. The lower limit of the tensile elongation of MD is not particularly limited, but is preferably 80% in consideration of productivity, physical properties as a packaging film, and the like.

  In the packaging film of the present invention, the tensile elongation of TD and the tensile strength of MD and TD of the biaxially stretched laminated polypropylene resin film are not particularly limited. It is preferable to satisfy the range described for the stretched polypropylene resin film. Specifically, the tensile elongation of TD is preferably 40 to 90%, and the difference between the tensile elongation of MD and the tensile elongation of TD is more preferably 60 to 120%. Furthermore, it is preferable that the MD tensile strength is 150 MPa or more, preferably 155 to 230 MPa, and the TD tensile strength is 200 MPa or more, preferably 220 to 310 MPa.

  In addition, the birefringence of MD and TD of the biaxially stretched laminated polypropylene resin film is preferably lower, specifically 0.01100 or less, and preferably 0.01000 or less. More preferred. As described above, this birefringence indicates the difference in molecular orientation between MD and TD in the film plane using the refractive index of light. Here, in the biaxially stretched laminated polypropyne resin film of the present invention, the tensile elongation of MD needs to be 170% or less, and the difference in orientation between MD and TD becomes small. As a result, the refraction of MD and TD Birefringence, which is a difference in rate, is reduced. In addition, as described above, in the heat seal layer, molecules are not easily oriented. Therefore, the birefringence of the biaxially stretched laminated polypropylene resin film is even smaller than the birefringence of the biaxially stretched polypropylene resin film on which no heat seal layer is laminated. The lower limit of the birefringence is not particularly limited, but is preferably 0.00050 in view of the physical properties of the film, film forming properties, and the like.

  Further, the thickness of the biaxially stretched laminated polypropylene resin film constituting the packaging film of the present invention is not particularly limited, but the thickness of the heat seal layer and the thickness ratio satisfy the above range, and It is preferable that it is 15-80 micrometers, especially 20-60 micrometers.

[Method for producing film]
Next, the manufacturing method of the biaxially stretched polypropylene resin film described above will be described. The manufacturing method of such a film differs depending on whether the heat seal layer is laminated or not. Therefore, first, the manufacturing method of the biaxially stretched polypropylene resin film which consists only of a base material layer which does not laminate | stack a heat seal layer is demonstrated.

[Method for producing film with no heat seal layer]
What will be described below is a manufacturing method in the case where a biaxially stretched base material layer made of the polypropylene resin is a biaxially stretched polypropylene resin film.

  In the packaging film of the present invention, the production method of the biaxially stretched polypropylene resin film in which the heat seal layer is not laminated is not particularly limited, but the following method can be exemplified as a suitable method. .

  That is, it is preferable to employ a method of producing a biaxially stretched base material layer by sequentially biaxially stretching a sheet made of the polypropylene resin. In particular, in this biaxial stretching, a method of stretching to MD more than 5.5 times is preferable.

  In a method for producing a biaxially stretched polypropylene resin film without a heat seal layer, the MD is stretched by 5.5 times or more in order to make the MD tensile elongation of 170% or less. Is preferred. In addition, the upper limit for stretching to MD is preferably 8.5 times in consideration of film-forming properties, physical properties of the packaging film, and the like.

  The operation of stretching to MD can be stretched to 5.5 times or more in one step, and can be stretched to 5.5 times or more in multiple steps. In particular, the film can be stably formed by stretching the MD to 5.5 times or more in multistage, generally in two stages. In addition, when extending | stretching in multistep, the final MD draw ratio, ie, the whole MD draw ratio, should just be 5.5 times or more.

  Further, in the stretching to TD, the stretching ratio is not particularly limited, but is preferably stretched 8 times or more. By setting the draw ratio of TD to 8 times or more, a biaxially stretched polypropylene resin film with high thickness accuracy can be obtained in consideration of the draw ratio of MD. In order to obtain a film with higher thickness accuracy, it is more preferable that the draw ratio of TD is 8.5 times or more. The upper limit of the stretching ratio of TD is preferably 13.0 times in view of stable film forming properties, physical properties of the packaging film, and the like.

  In the sequential stretching described above, stretching is performed by stretching a sheet extruded by an extruder to MD and then stretching to TD.

  Next, a method for producing a film on which the heat seal layer is laminated, that is, a biaxially stretched laminated polypropylene resin film will be described.

[Production method of biaxially stretched laminated polypropylene resin film]
Although the manufacturing method of the biaxially stretched laminated polypropylene resin film constituting the packaging film of the present invention is not particularly limited, the following method can be exemplified as a suitable method.

  That is, in the method of sequentially biaxially stretching a sheet made of the polypropylene resin, a method of laminating a polyolefin resin having a melting point lower than that of the polypropylene resin in any of the processes of producing a film by sequential stretching. preferable. In particular, in the sequential biaxial stretching, a method of stretching 6 times or more to MD is preferable. Since the tensile elongation of MD may be increased by laminating the heat seal layer, it is preferable to increase the MD stretch than a film in which the heat seal layer is not laminated.

  As a matter of course, as the raw material polypropylene resin and polyolefin resin, the resins exemplified in the description of the base material layer and the heat seal layer are used.

  In the method for producing a biaxially stretched laminated polypropylene resin film of the present invention, in order to satisfy the tensile elongation of MD of the obtained film of 170% or less, it is preferable to stretch MD 6 times or more. In addition, the upper limit for stretching to MD is preferably 8.5 times in consideration of film-forming properties, physical properties of the packaging film, and the like.

  The operation of stretching in the MD can be stretched 6 times or more in one stage, and can be stretched 6 times or more in multiple stages. In particular, the film can be stably formed by stretching 6 times or more to MD in multiple stages, generally in two stages. In addition, when extending | stretching in multistep, the draw ratio of final MD, ie, the whole MD draw ratio, should just be 6 times or more.

  Further, in the stretching to TD, the stretching ratio is not particularly limited, but is preferably stretched 8 times or more. By setting the draw ratio of TD to 8 times or more, a biaxially stretched laminated polypropylene resin film with high thickness accuracy can be obtained in consideration of the draw ratio of MD. In order to obtain a film with higher thickness accuracy, it is more preferable that the draw ratio of TD is 8.5 times or more. The upper limit of the stretching ratio of TD is preferably 13.0 times in view of stable film forming properties, physical properties of the packaging film, and the like.

  In the sequential stretching described above, stretching is performed by stretching a sheet extruded by an extruder to MD and then stretching to TD.

  In the method for producing a biaxially stretched laminated polypropylene resin film of the present invention, the formation of the heat seal layer may be performed in any of the steps of the sequential biaxial stretching.

  First, the case where the inline lamination method is employed will be described. By the T-die method, an unstretched sheet made of the polypropylene-based resin that finally becomes the base material layer is formed. Next, MD roll stretching is performed on the non-stretched sheet by a difference in roll speed to obtain an MD stretched sheet. Next, using a separately installed extruder, the polyolefin resin constituting the heat seal layer is extruded from a T-die, melt lamination is performed on one or both sides of the MD stretched sheet, and the laminated MD in which the heat seal layer is laminated A stretched sheet is obtained. Next, the laminated MD stretched sheet is guided to a tenter, both ends of the laminated MD stretched sheet are gripped with clips, and TD stretched to a predetermined width in a tenter oven to obtain a biaxially stretched laminated polypropylene resin film.

  Next, a case where the co-pressing method is adopted will be described. Using two or more extruders, the polypropylene resin and the polyolefin resin are co-extruded from each individual flow path from a co-extrusion die, and a heat seal made of a polyolefin resin is applied to the surface of an unstretched sheet made of the polypropylene resin. An unstretched laminated sheet in which the layers are laminated is formed. Next, the unstretched laminated sheet is subjected to MD roll stretching by a difference in roll speed to obtain a laminated MD stretched sheet. Next, the laminated MD stretched sheet is led to a tenter, both ends of the laminated MD stretched sheet are gripped with clips, and TD stretched to a predetermined width in a tenter oven to obtain a biaxially stretched laminated polypropylene resin film.

  Further, both the methods can be combined. For example, a laminated MD stretched sheet in which a heat seal layer is laminated only on one side is prepared in advance by the co-pressing method. Next, a laminated MD stretched sheet in which a heat seal layer is laminated on the opposite surface (surface of the base material layer) of the laminated MD sheet by the in-line lamination method, and the heat seal layer is laminated on both surfaces. Mold. Thereafter, a biaxially stretched laminated film in which heat seal layers are laminated on both sides by the TD stretching method can also be obtained.

  When the in-line lamination method is adopted, only the sheet constituting the base material layer is MD-stretched in advance, so that the melting point and crystallinity of the resin composing the base film are taken into consideration and sufficient preheating is performed before MD stretching. Can do. Therefore, even if MD draw ratio is 6 times or more, it can carry out without any problem.

  On the other hand, when the co-extrusion method is adopted, since the melting point of the polypropylene resin constituting the base material layer and the melting point of the polyolefin resin constituting the heat seal layer are different, a sheet in which resins having different melting points are laminated is obtained. . Therefore, in order to perform MD stretching at a high magnification stably, it is necessary to set an MD preheating temperature at which a polypropylene resin having a high melting point constituting the base material layer can be stretched. However, in this case, the melting point of the polyolefin resin constituting the heat seal layer may be exceeded, and the polyolefin resin may easily adhere to the MD preheating roll or MD stretching roll. Moreover, the extending | stretching damage | wound by MD extending | stretching becomes easy to generate | occur | produce on the sheet | seat surface which comprises a heat seal layer. However, in order to avoid these, the following method may be adopted.

  For example, when laminating the heat seal layer only on one side, first, the temperature of the preheating / stretching roll in contact with the heat seal layer is changed to the melting point and crystallinity of the polyolefin resin constituting the heat seal layer by the co-pressing method. Set accordingly. On the other hand, on the opposite sheet surface where the heat seal layer is not laminated, the temperature of the preheating / stretching roll in contact with the sheet surface is set according to the melting point and crystallinity of the resin constituting the sheet surface. For example, if the sheet surface on the opposite side is a base material layer, the temperature of the preheating / stretching roll is set around the maximum temperature at which it can be stretched according to the melting point and crystallinity of the polypropylene resin constituting the base material layer. To do. If such a setting is made, an MD stretched sheet having a good high stretch ratio can be obtained.

  Moreover, when laminating | stacking a heat seal layer on both surfaces by a co-pressing method, it is preferable to add resin with melting | fusing point or crystallinity lower than this polypropylene resin to the polypropylene resin which comprises a base material layer. By carrying out like this, a drawability can be improved and MD preheating roll and draw roll temperature can be made low. As a result, the heat seal layer can be prevented from sticking to various MD rolls and stretched scratches.

  Furthermore, when laminating heat seal layers on both sides by the co-pressing method, when the unstretched sheet formed by the co-pressing method is water-cooled with water of 40 ° C. or less, for example, the temperature of the MD preheating roll or stretching roll is set. It becomes possible to set significantly low, and a MD stretched sheet having a good high stretch ratio can be obtained. This is because the molten sheet-like material is rapidly cooled and solidified to solidify the polyolefin resin constituting the heat seal layer and the polypropylene resin constituting the base material layer while inhibiting crystal growth. Therefore, the MD preheating roll and the stretching roll temperature can be set low. As a result, the heat seal layer can be prevented from sticking to various MD rolls and stretched scratches.

  The biaxially stretched laminated polypropylene resin film of the present invention needs to have a MD tensile elongation of 170% or less. In order to obtain the tensile elongation of MD, the draw ratio of MD is stretched to a high ratio of 6 times or more, and the thickness of the heat seal layer laminated on the surface of the base material layer is adjusted as described above. It is preferable.

[Opening tape and lamination of opening tape]
In the packaging film of the present invention, an opening tape is laminated on the TD of a biaxially stretched polypropylene resin film (including a biaxially stretched laminated polypropylene resin film) constituting the film.

  A well-known thing can be used for the said opening tape without a restriction | limiting. In general, a film obtained by processing a film having a high tensile strength without tearing or elongation due to tension at the time of opening into a tape shape is used. Specific examples of the film include a polyester film and a uniaxially stretched or biaxially stretched polyolefin film.

  The surface on which the opening tape is laminated is not particularly limited, and may be laminated on any surface of a biaxially stretched polypropylene resin film (including a biaxially stretched laminated polypropylene resin film). For example, in the biaxially stretched laminated polypropylene resin film, when the heat seal layers are present on both surfaces of the base material layer, the heat seal layers may be laminated on the surface of any one of the heat seal layers. When the heat seal layer is present only on one side of the base material layer, it can be laminated on either the surface of the base material layer or the surface of the heat seal layer. Moreover, the opening tape may be laminated on either the inner surface or the outer surface of the packaging bag, but if the opening tape is laminated on the outer surface of the packaging bag, the opening tape is rarely crimped or heat-sealed. Occasionally wavy wrinkles may be visible, or printing applied to the outer surface of the packaging bag may be blurred. Therefore, it is preferable that the opening tape is laminated so as to be the inner surface of the packaging bag.

  Moreover, the space | interval of the opening tape laminated | stacked on TD of a film is suitably determined according to the packaging form etc. of the film for packaging. The method of laminating the opening tape can be performed by a known method such as a pressure bonding method or a heat fusion method.

  In the packaging film of the present invention, it is preferable that the end of the biaxially stretched polypropylene-based resin film on which the opening tape is laminated is notched with the opening tape interposed therebetween.

[Processing and use of packaging film (sandwich packaging bags)]
The packaging film of the present invention can be subjected to secondary processing (bag making processing) by fusing sealing and / or heat sealing to package a packaged body. Therefore, it can be suitably used for applications such as sandwich packaging bags. In particular, when the packaging film of the present invention is made of a biaxially stretched laminated polypropylene resin film, the heat seal layer laminated on at least one side is superposed so as to be the inner surface of the bag, and the bag is made by a fusing seal machine. Thus, a packaging bag having extremely stable fusing seal strength can be obtained. This is because the heat seal layer is made of a low melting point polyolefin resin. Therefore, the packaging film can be suitably used particularly as a sandwich packaging bag.

  FIG. 5 shows a schematic view of an example of a sandwich packaging bag using the biaxially stretched polypropylene resin film of the present invention. In FIG. 5, the opening tape N is provided along TD of this film, and the notch M is provided in the edge part of the film located in the opening of the opening tape.

  Examples are given below to specifically describe the present invention, but the present invention is not limited to these examples. First, the measurement methods used in the following examples will be described.

(1) Melt Mass Flow Rate Melt mass flow rate (hereinafter abbreviated as MFR) was measured according to JIS-K7210. The measurement temperature was 230 ° C. or 190 ° C.

(2) Melting point of resin Using a differential scanning calorimeter (DSC6200R manufactured by Seiko Denshi Kogyo Co., Ltd.), the resin was melted at 235 ° C. in a nitrogen atmosphere and held for 10 minutes, and then the temperature drop was measured at 10 ° C./min at 30 ° C. The peak temperature showing the maximum endotherm in the endothermic curve obtained when the temperature was lowered to 235 ° C. at a rate of temperature rise of 10 ° C./min was taken as the melting point.

(3) Copolymerization composition It measured on the following conditions using the nuclear magnetic resonance spectrometer (JNM-GSX-270 ( ^13C- nuclear resonance frequency 67.8MHz) by JEOL Co., Ltd.).
Measurement mode: ¹ H-complete decoupling pulse width: 90 degree pulse pulse repetition time: 3 seconds Integration number: 10,000 times Solvent: mixed solvent of trichlorobenzene / heavy benzene (76/24% by volume)
Sample concentration: 120 mg / 2.5 ml Solvent measurement temperature: 120 ° C.
The quantification of the copolymer composition is described in M.M. kakugo, Y. et al. Naito, K .; Mizunuma, T .; According to Miyatake, [Macromolecules, 15, 1150 (1982)].

(4) Film thickness The thickness (μm) was measured with a mechanical thickness meter (Micrometer OMV-25DM manufactured by Mitutoyo Corporation).

(5) Thickness of heat seal layer A biaxially stretched laminated polypropylene resin film was immersed in liquid nitrogen for 30 minutes and freeze fractured. The fracture surface of the film was photographed with a scanning electron microscope (JSM-5600LV, manufactured by JEOL Ltd.) at a magnification of 5000, and the thickness (μm) of the heat seal layer was calculated. From the thickness of this heat seal layer and the film thickness of (4), the ratio of the total thickness of the heat seal layer was calculated.

(6) Transparency Haze (cloudiness value) was measured according to JIS-K7105.

(7) Tensile strength, tensile elongation A strip-shaped sample having a width of 10 mm and a length of 150 mm was cut into MD and TD, respectively, and measured according to JIS-K7127 at a tensile speed of 300 mm / min.

(8) Birefringence Using an automatic birefringence meter (manufactured by Oji Scientific Instruments, KOBRA-21ADH), measurement was performed under the following conditions.
Measurement method: Parallel Nicol rotation method Measurement wavelength: 590 nm
The TD refractive index (Ntd) in the film plane, the MD refractive index (Nmd) in the film plane, the refractive index (Nz) in the thickness direction of the film, and the difference between the TD refractive index and the MD refractive index in the film plane (Ntd− Nmd) was calculated from the retardation at incident angles of 0 ° and 40 ° with the software attached to the device. The absolute value (| Ntd−Nmd |) of the difference between the TD refractive index and the MD refractive index in the film plane at this time was measured as birefringence (Δ (delta) n). The average refractive index value was 1.490.

(9) Tearability evaluation: 45 degree tearability test A MD and TD A4 size film as shown in FIG. 1 is cut out, and a 20 mm wide and 165 mm wide opening tape K is heated along the TD of the film L. It was heat-sealed by a sealing machine and laminated.

  Write 150mm length base lines A and A 'parallel to the opening tape K from the center of the opening tape K on the film L, and then open an opening B 25mm wide and 15mm long above the opening tape K. It was. The tearing start position from the opening B is G and G '. The distance between the base line A and the base line A ′ is 70 mm, and the positions of one end of the base line A′A and G and G ′ are the same in the TD of the film. Subsequently, the film L was fixed to the cardboard J with an adhesive tape E.

  The sample fixed to the cardboard J is tilted as shown in FIG. 2, and is gripped by the chucks C and C ′ of the tensile tester, and the chuck C ′ is moved in the direction of the arrow so that the tearing speed is 500 mm / min. It was. By carrying out like this, the tear test was done so that the force of the 45-degree direction may be applied to the opening tape. At this time, the upper chuck C grabbed the sample and cardboard, and the lower chuck C ′ grabbed the film of the opening B and the upper part of the opening tape K. Here, the distance (70 mm) between the base line A and the base line A ′ written to the left and right 35 mm from the center of the opening tape is a sandwich with a thin thickness (width) (about 70 mm) among commercially available sandwiches. It is a combination. That is, it is considered that when the opened portion extends beyond the base line, the sandwich is likely to jump out. FIG. 3 is a side view showing an outline when a sample is set on the chuck (the opening tape K laminated on the film, a part of the adhesive tape E, etc. are not shown).

FIG. 4 shows a sample after the 45-degree tear test. An example of a torn part is indicated by dotted lines F and F ′. A contact when the base line A or A ′ is reached from the tear starting position G or G ′ is indicated by a contact H. In addition, the I distance in FIG.
Evaluation A: 45 degree tear distance is 120 mm or more.
Evaluation (circle): 45 degree tear distance is 80 mm or more and less than 120 mm.
Evaluation Δ: 45-degree tear distance is 60 mm or more and less than 80 mm.
Evaluation x: 45 degree tear distance is less than 60 mm.

(10) Antifogging property 50 ml (18 ° C.) of water was put into a 100 ml beaker. Subsequently, the mouth of the beaker was covered with a film so as not to be wrinkled, and a sample fixed with a rubber band was prepared. Subsequently, after cooling this sample for 30 minutes in a refrigerator (5 degreeC), the state of the water droplet which condensed on the film surface (beaker inner surface side) was made into the following four-step evaluation.
Evaluation A: Condensed water is smoothly wetted on the surface, and the film is not clouded at all.
Evaluation ○: Condensed water is large and the film is not cloudy.
Evaluation Δ: Condensed water is small, and some portions of the film are cloudy.
Evaluation x: Condensed water is minimal and the film is clouded white.

(11) Fusing and sealing strength Using a fusing and sealing machine (PP-500 type manufactured by Kyoei Co., Ltd.), bag making was performed at a sealing blade temperature of 380 ° C. and 120 shots / min. A strip-shaped sample having a width of 15 mm and a length of 150 mm was cut out from the fusing seal portion of the obtained fusing seal bag. Next, the sample is subjected to a tensile test using a tensile tester (AG500 manufactured by Shimadzu Corporation) at a tensile speed of 100 mm / min, and the strength when the fusing seal part breaks is defined as fusing seal strength (unit: N / 15 mm). did.

(12) Heat seal strength Two strips of 15 mm wide and 150 mm long with MD as the longitudinal direction are aligned so that the heat seal surfaces overlap each other, using a heat seal machine (manufactured by YSS type Yasuda Seiki Co., Ltd.). The conditions were fixed at an upper metal heat-sieber temperature of 145 ° C., a lower Teflon rubber temperature of 90 ° C., a heat seal pressure of 0.1 Mpa, and a heat seal time of 1 second, and heat sealing was performed. The obtained heat seal sample was subjected to a tensile test at a tensile speed of 100 mm / min using a tensile tester (AG500 manufactured by Shimadzu Corporation), and the maximum strength when the heat seal portion was ruptured was determined as the heat seal strength (unit: N / 15 mm).

Example 1 (film not laminated with a heat seal layer)
A propylene homopolymer (melting point 161 ° C., MFR 3.2 g / 10 min (230 ° C.) prime polymer F301SPE / F301SPG: mixing ratio 60/40) was extruded from a single layer T die at an extrusion temperature of 245 ° C. to obtain an unstretched sheet It was. The sheet is stretched 5 times at 145 ° C. by stretching the first stage with an MD two-stage stretching machine, and the second stage is stretched at 135 ° C. to obtain an MD stretched sheet in which the overall MD stretching ratio is 7 times. It was. Next, the MD stretched sheet was stretched 11 times to TD by a tenter-type lateral stretching machine (preheating temperature 186 ° C., stretching temperature 164 ° C.) to obtain a 30 μm biaxially stretched film not subjected to corona treatment. The melt seal strength of the obtained biaxially stretched film was 23.9 N / 15 mm. Evaluation of antifogging property was x. Table 1 shows the transparency, stretch ratio, mechanical strength characteristics, birefringence, and tearability evaluation of the obtained biaxially stretched polypropylene resin film.

Example 2 (film without heat seal layer laminated)
A propylene homopolymer (melting point 161 ° C., MFR 3.2 g / 10 min (230 ° C.) prime polymer F301SPE / F301SPG: mixing ratio 60/40) was extruded from a single layer T die at an extrusion temperature of 245 ° C. to obtain an unstretched sheet It was. The MD is stretched 5.1 times at 142 ° C. by the MD two-stage stretching machine, and the second stage is stretched at 138 ° C., so that the overall MD stretching ratio is 7.1 times. A stretched sheet was obtained. Next, the MD stretched sheet was stretched 11 times to TD with a tenter-type lateral stretching machine (preheating temperature 180 ° C., stretching temperature 162 ° C.) to obtain a 25 μm biaxially stretched polypropylene resin film without corona treatment. . The melt seal strength of the obtained biaxially stretched polypropylene resin film was 22.2 N / 15 mm. Evaluation of antifogging property was x. Table 1 shows the transparency, stretch ratio, mechanical strength characteristics, birefringence, and tearability evaluation of the obtained biaxially stretched polypropylene resin film.

Example 3 (film with no heat seal layer laminated)
In Example 2, the same operation as in Example 2 was performed, except that a 22 μm biaxially stretched polypropylene resin film without corona treatment was used. The melt seal strength of the obtained biaxially stretched polypropylene resin film was 20.3 N / 15 mm. Evaluation of antifogging property was x. Table 1 shows the transparency, stretch ratio, mechanical strength characteristics, birefringence, and tearability evaluation of the obtained biaxially stretched polypropylene resin film.

Comparative Example 1 (film without a heat seal layer laminated)
Propylene homopolymer (melting point 161 ° C., MFR 2.2 g / 10 min (230 ° C.) prime polymer F201SPE / F201SPG: mixing ratio 60:40) Extruded from a single layer T die at an extrusion temperature of 230 ° C. to obtain an unstretched sheet . The MD is stretched 4.4 times at 143 ° C. by a two-stage MD stretcher, and the second stage is stretched at 138 ° C., so that the overall MD stretch ratio is 4.6 times. A stretched sheet was obtained. Next, the MD stretched sheet was stretched 10 times to TD with a tenter-type lateral stretching machine (preheating temperature 184 ° C., stretching temperature 161 ° C.) to obtain a 30 μm biaxially stretched film not subjected to corona treatment. The melt seal strength of the obtained biaxially stretched polypropylene resin film was 25.3 N / 15 mm. Evaluation of antifogging property was x. Table 1 shows the transparency, stretch ratio, mechanical strength characteristics, birefringence, and tearability evaluation of the obtained biaxially stretched polypropylene resin film.

Example 4 (film without heat seal layer laminated)
As a base material layer, a three-layer film having a structure of surface layer / main layer / surface layer was formed by the following method. First, as a raw material for the main layer, a propylene-ethylene random copolymer (melting point: 156 ° C., ethylene content: 0.4 mass%, MFR: 2.5 g / 10 min (230 ° C.), anti-fogging agent: 1.0 mass% PC412Z manufactured by Sun Allomer, resin 1 in Table 2) 75% by mass and propylene-ethylene random copolymer (melting point 144 ° C., ethylene amount 2.5% by mass, MFR 2.0 g / 10 min, Sumitomo Chemical FH3315 resin 2 in Table 2 ) 25% by mass was mixed. Next, as raw materials for both surface layers, 75% by mass of propylene-ethylene random copolymer (melting point 156 ° C., ethylene content 0.4% by mass, MFR 2.2 g / 10 min (230 ° C.), Sun Allomer PC412A) and propylene -Ethylene random copolymer (melting point 144 ° C., ethylene amount 2.5% by mass, MFR 2.0 g / 10 min, Sumitomo Chemical FH3315, resin 2 in Table 2) 20% by mass and antiblocking agent master batch (melting point 140 ° C. , Ethylene content 3.6 mass%, MFR 8.0 g / 10 min (230 ° C.), Sun Allomer PY630D Resin 7 in Table 2) 5 mass% were mixed. Subsequently, the raw material for the main layer and the raw material for both surface layers were co-pressed from a three-layer T die at an extrusion temperature of 260 ° C. to obtain an unstretched sheet. Next, the unstretched sheet was stretched 1.3 times at 140 ° C. by stretching the first stage with an MD two-stage stretching machine, and stretched at 146 ° C. at the second stage, and the overall MD stretching ratio was 5.5. A doubled MD stretched sheet was obtained. Subsequently, the MD stretched sheet was stretched 10.3 times to TD with a tenter-type transverse stretching machine (preheating temperature 187 ° C., stretching temperature 152 ° C.), and subjected to corona treatment on both sides, with a total thickness of 30 μm and the thickness of each surface layer. A biaxially stretched polypropylene resin film having a thickness of 1.0 μm and a main layer thickness of 28.0 μm was obtained. The melt seal strength of the obtained biaxially stretched polypropylene resin film was 18.2 N / 15 mm, and the evaluation of antifogging property was good. Table 1 shows the transparency, stretch ratio, mechanical strength characteristics, birefringence, and tearability evaluation of the obtained biaxially stretched polypropylene resin film.

Example 5 (film not laminated with a heat seal layer)
In Example 4, the total MD draw ratio was 6.0 times, the TD draw ratio was 10.2 times, the total thickness was 30 μm, and the thickness of each surface layer was 1.0 μm, and the main layer thickness was 28. The same operation as in Example 4 was performed except that a 0.0 μm biaxially stretched polypropylene resin film was used. The melt seal strength of the obtained biaxially stretched polypropylene resin film was 18.4 N / 15 mm, and the evaluation of antifogging property was ◎. Table 1 shows the transparency, stretch ratio, mechanical strength characteristics, birefringence, and tearability evaluation of the obtained biaxially stretched polypropylene resin film.

Example 6 (film with no heat seal layer laminated)
In Example 4, the total MD stretch ratio was 6.5 times, the TD stretch ratio was 10.0 times, the corona treatment was applied to both surfaces, the total thickness was 30 μm, the thickness of each surface layer was 1.0 μm, and the main layer thickness was 28 The same operation as in Example 4 was performed except that a 0.0 μm biaxially stretched polypropylene resin film was used. The melt seal strength of the obtained biaxially stretched polypropylene resin film was 17.8 N / 15 mm, and the evaluation of antifogging property was ◎. Table 1 shows the transparency, stretch ratio, mechanical strength characteristics, birefringence, and tearability evaluation of the obtained biaxially stretched polypropylene resin film.

Comparative Example 2 (film without a heat seal layer laminated)
In Example 4, the total MD stretch ratio was 4.6 times, the TD stretch ratio was 9.3 times, the total thickness of the corona treatment on both surfaces was 30 μm, the thickness of each surface layer was 1.0 μm, and the thickness of the base layer was 28. The same operation as in Example 4 was performed except that a 0 μm biaxially oriented polypropylene resin film was used. The melt seal strength of the obtained biaxially stretched polypropylene resin film was 19.4 N / 15 mm, and the evaluation of antifogging property was ◎. Table 1 shows the transparency, stretch ratio, mechanical strength characteristics, birefringence, and tearability evaluation of the obtained biaxially stretched polypropylene resin film.

Example 7 (film without heat seal layer laminated)
As a base material layer, a three-layer film having a structure of surface layer / main layer / surface layer was formed by the following method. First, as a raw material for the main layer, a propylene-ethylene random copolymer (melting point: 156 ° C., ethylene content: 0.4 mass%, MFR: 2.5 g / 10 min (230 ° C.), anti-fogging agent: 1.0 mass% PC412Z manufactured by Sun Allomer 25% by mass of resin 1 in Table 2 and propylene-ethylene random copolymer (melting point 144 ° C., 2.5% by mass of ethylene, MFR 2.0 g / 10 minutes, Sumitomo Chemical FH3315 Resin 2 in Table 2 ) 75% by mass was mixed. Next, as raw materials for both surface layers, propylene-ethylene random copolymer (melting point 156 ° C., ethylene content 0.4% by mass, MFR 2.2 g / 10 min (230 ° C.), Sun Allomer PC412A) 25% by mass and propylene -Ethylene random copolymer (melting point 144 ° C., ethylene amount 2.5% by mass, MFR 2.0 g / 10 min, Sumitomo Chemical FH3315, resin 2 in Table 2) 70% by mass and anti-blocking agent master batch (melting point 140 ° C. , Ethylene content 3.6 mass%, MFR 8.0 g / 10 min (230 ° C.), Sun Allomer PY630D Resin 7 in Table 2) 5 mass% were mixed. Subsequently, the raw material for the main layer and the raw material for both surface layers were co-pressed from a three-layer T die at an extrusion temperature of 260 ° C. to obtain an unstretched sheet. Next, the unstretched sheet was stretched 1.3 times at 139 ° C. in the first stage using an MD two-stage stretcher, and stretched at 144 ° C. in the second stage, with an overall MD stretch ratio of 6.0. A doubled MD stretched sheet was obtained. Next, the MD stretched sheet was stretched 9.5 times to TD with a tenter-type transverse stretching machine (preheating temperature 185 ° C., stretching temperature 150 ° C.), and subjected to corona treatment on both sides, with a total thickness of 30 μm and the thickness of each surface layer. A biaxially stretched polypropylene resin film having a thickness of 1.0 μm and a main layer thickness of 28.0 μm was obtained. The melt seal strength of the obtained biaxially stretched polypropylene resin film was 15.5 N / 15 mm, and the evaluation of antifogging property was x. Table 1 shows the transparency, stretch ratio, mechanical strength characteristics, birefringence, and tearability evaluation of the obtained biaxially stretched polypropylene resin film.

Example 8 (film with no heat seal layer laminated)
In Example 7, the total MD stretch ratio was 6.5 times, the TD stretch ratio was 9.3 times, the total thickness was 30 μm, and the thickness of each surface layer was 1.0 μm, and the main layer thickness was 28. The same operation as in Example 7 was performed except that a biaxially stretched polypropylene resin film of 0.0 μm was used. The melt seal strength of the obtained biaxially stretched polypropylene resin film was 15.3 N / 15 mm, and the evaluation of antifogging property was x. Table 1 shows the transparency, stretch ratio, mechanical strength characteristics, birefringence, and tearability evaluation of the obtained biaxially stretched polypropylene resin film.

Example 9 (film without heat seal layer laminated)
In Example 7, the total MD stretch ratio was 7.0 times, the TD stretch ratio was 9.2 times, the total thickness was 30 μm, and the thickness of each surface layer was 1.0 μm, and the main layer thickness was 28. The same operation as in Example 7 was performed except that a biaxially stretched polypropylene resin film of 0.0 μm was used. The melt seal strength of the obtained biaxially stretched polypropylene resin film was 15.0 N / 15 mm, and the evaluation of antifogging property was x. Table 1 shows the transparency, stretch ratio, mechanical strength characteristics, birefringence, and tearability evaluation of the obtained biaxially stretched polypropylene resin film.

Comparative Example 3
As a result of evaluating the fusing seal strength and antifogging property of a commercially available double-sided antifogging film product name KF51 # 30 double-sided corona-treated product (manufactured by Sun Tox Co., Ltd.), the fusing seal strength is 21.0 N / 15 mm. The antifogging property was ◎. Table 1 shows the transparency, mechanical strength characteristics, birefringence, and tearability evaluation of the film.

Comparative Example 4
Create a melt-sealed sealing bag so that the corona-treated surface of a commercially available biaxially stretched OPP film, product name PA20 # 30 single-sided corona-treated product (manufactured by Sun Tox Co., Ltd.) is inside the bag, and the melt-sealed sealing strength As a result of the measurement, the fusing seal strength was 13.3 N / 15 mm. Further, as a result of evaluating the antifogging property of the corona-treated surface, the antifogging property was x. Table 1 shows the transparency, mechanical strength characteristics, birefringence, and tearability evaluation of the film.

Example 10 (film having a heat seal layer)
A biaxially stretched laminated polypropylene resin film having a structure of heat seal layer / base material layer (the base material layer was a main layer and a surface layer) was formed by the following method. First, a resin (heat sealing resin) in which 95% by mass of the resin 5 shown in Table 2 and 5% by mass of the resin 7 shown in Table 2 were mixed as a resin constituting the heat seal layer was prepared. Next, as raw materials constituting the base material layer, 70% by mass of the resin 1 shown in Table 2 and 30% by mass of the resin 2 shown in Table 2 (main layer resin) and the resin shown in Table 2 are mixed. 4 and 97% by mass, and 3% by mass of the resin 8 shown in Table 2 (surface layer resin) were prepared. In this case, it is the resin 5 of the heat seal layer and the resin 1 of the main layer that compare the melting points.

  The resin of each layer is co-pressed by a three-layer T die from an individual extruder in the order of heat sealing resin / main layer resin / surface layer resin at an extrusion temperature of 220 to 240 ° C. After cooling and solidification, an unstretched sheet having a three-layer structure was formed. Next, the three-layer sheet is stretched 5.2 times at a preheating temperature of 135 ° C. by a MD two-stage stretching machine, and the second stage is stretched at a preheating temperature of 122 ° C. An MD stretched sheet having a stretching ratio of 6.8 times was obtained. Next, the MD stretched sheet was stretched 9.5 times to TD with a tenter-type lateral stretching machine (preheating temperature 186 ° C., stretching temperature 162 ° C.), and subjected to corona treatment on both sides. A biaxially stretched laminated polypropylene resin film having a thickness of 1.5 μm, a base layer thickness of 28.5 μm (main layer thickness of 26.5 μm, surface layer thickness of 2.0 μm) was formed.

  The biaxially stretched laminated polypropylene resin film thus obtained is cured at 40 ° C. for 2 days, and has a fusing seal strength, heat seal strength, antifogging properties, transparency, birefringence, tear directionality evaluation, mechanical strength properties. The measurement was performed and the results are shown in Table 3. Table 2 shows the detailed composition and melting point of the resin used.

Example 11 (film having a heat seal layer)
A biaxially stretched laminated polypropylene resin film having a structure of heat seal layer / base material layer (the base material layer was a main layer and a surface layer) was formed by the following method. First, a resin (heat sealing resin) in which 95% by mass of the resin 5 shown in Table 2 and 5% by mass of the resin 7 shown in Table 2 were mixed as a resin constituting the heat seal layer was prepared. Next, as raw materials constituting the base material layer, 70% by mass of resin 1 shown in Table 2 and 30% by mass of resin 2 shown in Table 2 (main layer resin), and resin 4 shown in Table 2 are mixed. A mixture (surface layer resin) in which 97% by mass and 3% by mass of the resin 8 shown in Table 2 was mixed was prepared. The resins whose melting points are compared are Resin 5 and Resin 1.

  The resin of each layer is co-pressed with a three-layer T die from an individual extruder in the order of heat sealing resin / main layer resin / surface layer resin at an extrusion temperature of 245 to 265 ° C., and cooled and solidified with a chill roll. A three-layer unstretched sheet was formed. Next, the three-layer sheet was stretched 1.2 times at a preheating temperature of 143 ° C. by the MD two-stage stretching machine, and the second stage was stretched at a preheating temperature of 143 ° C. An MD stretched sheet having a stretching ratio of 6.8 times was obtained. Next, the MD stretched sheet was stretched 9.0 times to TD with a tenter-type transverse stretching machine (preheating temperature 190 ° C., stretching temperature 155 to 164 ° C.), and subjected to corona treatment on both sides. A biaxially stretched laminated polypropylene resin film having a layer thickness of 2.5 μm and a base material layer thickness of 27.5 μm (main layer thickness of 25.5 μm, surface layer thickness of 2.0 μm) was formed.

  The biaxially stretched laminated polypropylene resin film thus obtained is cured at 40 ° C. for 2 days, and has a fusing seal strength, heat seal strength, antifogging properties, transparency, birefringence, tear directionality evaluation, mechanical strength properties. The measurement was performed and the results are shown in Table 3. The detailed composition of the resin used is shown in Table 2.

Example 12 (film having a heat seal layer)
A biaxially stretched laminated polypropylene resin film having a structure of heat seal layer / base material layer (the base material layer was a main layer and a surface layer) was formed by the following method. First, a resin (heat sealing resin) in which 95% by mass of the resin 6 shown in Table 2 and 5% by mass of the resin 7 shown in Table 2 were mixed as a resin constituting the heat seal layer was prepared. Next, as raw materials constituting the base material layer, 70% by mass of resin 3 shown in Table 2 and 30% by mass of resin 2 (main layer resin), 97% by mass of resin 4 and 3% by mass of resin 8 % (Surface layer resin) was prepared. Resins whose melting points are compared are Resin 6 and Resin 3.

  The resin of each layer is co-pressed by a three-layer T die from an individual extruder in the order of heat sealing resin / main layer resin / surface layer resin at an extrusion temperature of 220 to 240 ° C. The mixture was cooled and solidified to form a three-layer unstretched sheet. Next, the three-layer sheet is stretched 5.2 times at a preheating temperature of 135 ° C. by a MD two-stage stretching machine, and the second stage is stretched at a preheating temperature of 122 ° C. An MD stretched sheet having a stretching ratio of 6.8 times was obtained. Next, the MD stretched sheet was stretched 9.5 times to TD with a tenter-type lateral stretching machine (preheating temperature 186 ° C., stretching temperature 162 ° C.), and subjected to corona treatment on both sides. A biaxially stretched laminated polypropylene resin film having a thickness of 1.5 μm, a base layer thickness of 28.5 μm (main layer thickness of 26.5 μm, surface layer thickness of 2.0 μm) was formed.

  The biaxially stretched laminated polypropylene resin film thus obtained is cured at 40 ° C. for 2 days, and has a fusing seal strength, heat seal strength, antifogging properties, transparency, birefringence, tear directionality evaluation, mechanical strength properties. The measurement was performed and the results are shown in Table 3. The detailed composition of the resin used is shown in Table 2.

Comparative Example 5 (film having a heat seal layer)
A biaxially stretched laminated polypropylene resin film having a structure of heat seal layer / base material layer / heat seal layer was formed by the following method. First, as a resin constituting the heat seal layers on both sides, 80% by mass of the resin 5 shown in Table 2, 15% by mass of the resin 10 shown in Table 2, and 5% by mass of the resin 7 shown in Table 2 are mixed. (Resin for heat seal) was prepared. Next, 100% by mass of resin 1 shown in Table 2 (main layer resin) was prepared as a raw material constituting the base material layer. The resins whose melting points are compared are the resin 5 and the resin 10.

  Next, the resin of each layer is co-pressed by a three-layer T die at an extrusion temperature of 240 to 260 ° C. from an individual extruder in the order of heat sealing resin / main layer resin / heat sealing resin, It was cooled and solidified by a water-cooled cast method to form an unstretched sheet having a three-layer structure. Next, the first layer of the three-layer sheet is stretched 1.1 times at a preheating temperature of 128 ° C. and the second stage of preheating is performed at 128 ° C., and the entire MD stretching is performed. An MD stretched sheet having a magnification of 4.6 times was obtained. Next, the MD stretched sheet was stretched 9.5 times to TD with a tenter-type transverse stretching machine (preheating temperature 186 ° C., stretching temperature 162 ° C.), and subjected to corona treatment on both sides, with a total thickness of 30 μm, both heat seal layers A biaxially stretched laminated polypropylene resin film having a thickness of 1.5 μm and a base film thickness of 27.0 μm was formed.

  The biaxially stretched laminated polypropylene resin film thus obtained is cured at 40 ° C. for 2 days, and has a fusing seal strength, heat seal strength, antifogging properties, transparency, birefringence, tear directionality evaluation, mechanical strength properties. The measurement was performed and the results are shown in Table 3. The detailed composition of the resin used is shown in Table 2.

Example 13 (film having a heat seal layer)
A biaxially stretched laminated polypropylene resin film having a structure of heat seal layer / base material layer / heat seal layer was formed by the following method. First, a resin (heat sealing resin) in which 95% by mass of the resin 6 shown in Table 2 and 5% by mass of the resin 7 shown in Table 2 were mixed as a resin constituting the heat seal layers on both sides was prepared. Next, a material (main layer resin) in which 80% by mass of the resin 1 shown in Table 2 and 20% by mass of the resin 3 shown in Table 2 were mixed as raw materials constituting the base material layer was prepared. Resins whose melting points are compared are Resin 6 and Resin 1.

  The above-mentioned resins of each layer are co-pressed by a three-layer T die from an individual extruder in the order of heat sealing resin / main layer resin / heat sealing resin at an extrusion temperature of 200 to 240 ° C. And solidified by cooling to form a three-layer unstretched sheet. Next, the three-layer sheet is stretched 5.2 times at a preheating temperature of 122 ° C. by a MD two-stage stretching machine, and the second stage of stretching is performed at a preheating temperature of 121 ° C. An MD stretched sheet having a stretching ratio of 6.8 times was obtained. Next, the MD stretched sheet was stretched 10 times to TD by a tenter-type lateral stretching machine (preheating temperature 186 ° C., stretching temperature 166 ° C.), and then subjected to corona treatment on both sides. Thus, a biaxially stretched laminated polypropylene resin film having a total thickness of 30 μm, thicknesses of both heat seal layers of 1.5 μm and a base material layer thickness of 27.0 μm was formed. The obtained biaxially stretched laminated polypropylene resin film was cured at 40 ° C. for 2 days, and then subjected to fusing seal strength, heat seal strength, antifogging properties, transparency, birefringence, tear directionality evaluation, and measurement of mechanical strength properties. The results are shown in Table 3. The detailed composition of the resin used is shown in Table 2.

Example 14 (film having a heat seal layer)
A biaxially stretched laminated polypropylene resin film having a structure of heat seal layer / base material layer / heat seal layer was formed by the following method. First, as a resin constituting the heat seal layers on both sides, a resin (heat seal resin) in which 95% by mass of the resin 6 shown in Table 2 and 7% by mass of the resin shown in Table 2 were mixed was prepared. Next, a material (main layer resin) in which 80% by mass of the resin 1 shown in Table 2 and 20% by mass of the resin 3 shown in Table 2 were mixed as raw materials constituting the base material layer was prepared. The resin 6 and the resin 1 compare the melting points.

  The above-mentioned resins of each layer are co-pressed by a three-layer T die from an individual extruder in the order of heat sealing resin / main layer resin / heat sealing resin at an extrusion temperature of 200 to 240 ° C. And solidified by cooling to form a three-layer unstretched sheet. Next, the three-layer sheet is stretched 5.2 times at a preheating temperature of 122 ° C. by a MD two-stage stretching machine, and the second stage of stretching is performed at a preheating temperature of 121 ° C. An MD stretched sheet having a stretching ratio of 6.8 times was obtained. Next, the MD stretched sheet was stretched 10 times to TD by a tenter-type lateral stretching machine (preheating temperature 183 ° C., stretching temperature 163 ° C.), and then subjected to corona treatment on both sides. Thus, a biaxially stretched laminated polypropylene resin film having a total thickness of 20 μm, thicknesses of both heat seal layers of 1.5 μm and a base material layer thickness of 17.0 μm was prepared. The obtained biaxially stretched laminated polypropylene resin film was cured at 40 ° C. for 2 days, and then subjected to fusing seal strength, heat seal strength, antifogging properties, transparency, birefringence, tear directionality evaluation, and measurement of mechanical strength properties. The results are shown in Table 3. The detailed composition of the resin used is shown in Table 2.

Comparative Example 6 (film having a heat seal layer)
A biaxially stretched laminated polypropylene resin film having a structure of heat seal layer / base material layer (the base material layer was a main layer and a surface layer) was formed by the following method. First, a resin (heat sealing resin) in which 95% by mass of the resin 5 shown in Table 2 and 5% by mass of the resin 7 shown in Table 2 were mixed as a resin constituting the heat seal layer was prepared. Next, as raw materials constituting the base material layer, 70% by mass of the resin 1 shown in Table 2 and 30% by mass of the resin 2 shown in Table 2 (main layer resin) and the resin 4 shown in Table 2 are mixed. Was prepared by mixing 97% by mass and 3% by mass of the resin 8 shown in Table 2 (surface resin). The resin 5 and the resin 1 compare the melting points.

  The resin of each layer is co-pressed with a three-layer T die from an individual extruder in the order of heat sealing resin / main layer resin / surface layer resin at an extrusion temperature of 245 to 265 ° C., and cooled and solidified with a chill roll. A three-layer unstretched sheet was formed. Next, the three-layer sheet was stretched 1.2 times at a preheating temperature of 143 ° C. by the MD two-stage stretching machine, and the second stage was stretched at a preheating temperature of 143 ° C. An MD stretched sheet having a stretch ratio of 5.2 times was obtained. Next, the MD stretched sheet was stretched 8.7 times to TD with a tenter-type lateral stretching machine (preheating temperature 190 ° C., stretching temperature 155 to 164 ° C.), and then subjected to corona treatment on both sides.

  Thus, a biaxially stretched laminated polypropylene resin film having a total thickness of 30 μm, a heat seal layer thickness of 2.0 μm, and a base material layer thickness of 28.0 μm (main layer thickness of 26.5 μm, surface layer thickness of 1.5 μm) is manufactured. Filmed. The obtained biaxially stretched laminated polypropylene resin film was cured at 40 ° C. for 2 days, and then subjected to fusing seal strength, heat seal strength, antifogging properties, transparency, birefringence, tear directionality evaluation, and measurement of mechanical strength properties. The results are shown in Table 3. The detailed composition of the resin used is shown in Table 2.

Example 15 (film having a heat seal layer)
A total thickness of 30 μm, a heat seal layer thickness of 2.0 μm, except that the second stage draw ratio of the MD two-stage drawing machine was increased and the overall MD draw ratio was set to 6.3 times. A biaxially stretched laminated polypropylene resin film having a base material layer thickness of 28.0 μm (main layer thickness 26.5 μm, surface layer thickness 1.5 μm) was formed. The obtained biaxially stretched laminated polypropylene resin film was cured at 40 ° C. for 2 days, and then subjected to fusing seal strength, heat seal strength, antifogging properties, transparency, birefringence, tear directionality evaluation, and measurement of mechanical strength properties. The results are shown in Table 3. The detailed composition of the resin used is shown in Table 2.

Example 16 (film having a heat seal layer)
A total thickness of 30 μm was obtained in the same manner as in Comparative Example 6 except that the second stage draw ratio of the MD two-stage drawing machine was increased, the entire MD draw ratio was 6.8 times, and the TD was drawn 9.0 times. A biaxially stretched laminated polypropylene resin film having a heat seal layer thickness of 2.0 μm and a base film thickness of 28.0 μm (main layer thickness of 26.5 μm, surface layer thickness of 1.5 μm) was formed. The obtained biaxially stretched laminated polypropylene resin film was cured at 40 ° C. for 2 days, and then subjected to fusing seal strength, heat seal strength, antifogging properties, transparency, birefringence, tear directionality evaluation, and measurement of mechanical strength properties. The results are shown in Table 3. The detailed composition of the resin used is shown in Table 2.
Example 17 (film having a heat seal layer)
Biaxially stretched laminate in the same manner as in Comparative Example 6 except that the stretch ratio of the second stage of the MD2 stretcher is increased, the overall MD stretch ratio is 7.0 times, and the TD is stretched 9.2 times. A polypropylene resin film was formed. The obtained biaxially stretched laminated polypropylene resin film was cured at 40 ° C. for 2 days, and then subjected to fusing seal strength, heat seal strength, antifogging properties, transparency, birefringence, tear directionality evaluation, and measurement of mechanical strength properties. The results are shown in Table 3. The detailed composition of the resin used is shown in Table 2.

Example 18 (film having a heat seal layer)
In the same manner as in Example 16, except that the total thickness was 30 μm, the heat seal layer thickness was 5.0 μm, and the base material layer was 25.0 μm (main layer thickness 23.5 μm, surface layer thickness 1.5 μm). An axially stretched laminated polypropylene resin film was formed. The obtained biaxially stretched laminated polypropylene resin film was cured at 40 ° C. for 2 days, and then subjected to fusing seal strength, heat seal strength, antifogging properties, transparency, birefringence, tear directionality evaluation, and measurement of mechanical strength properties. The results are shown in Table 3. The detailed composition of the resin used is shown in Table 2.

Example 19 (film having a heat seal layer)
A biaxially stretched laminated polypropylene resin film having a structure of heat seal layer / base material layer (the base material layer was a main layer and a surface layer) was formed by the following method. First, a resin (heat sealing resin) in which 95% by mass of the resin 9 shown in Table 2 and 5% by mass of the resin 7 shown in Table 2 were mixed as a resin constituting the heat seal layer was prepared. Next, as raw materials constituting the base material layer, 70% by mass of resin 1 shown in Table 2 and 30% by mass of resin 2 shown in Table 2 (main layer resin), and resin 4 shown in Table 2 are mixed. A mixture (surface layer resin) in which 97% by mass and 3% by mass of the resin 8 shown in Table 2 was mixed was prepared. The resin 9 and the resin 1 compare the melting points.

  Next, the main layer resin and the surface layer resin constituting the base material layer described above are co-pressed with a two-layer T die from an individual extruder at an extrusion temperature of 245 to 265 ° C., and cooled and solidified with a chill roll. An unstretched sheet having a layer structure was formed. Next, the two-layer unstretched sheet is stretched 1.2 times at a preheating temperature of 153 ° C. by the MD two-stage stretching machine, and the second stage is stretched at a preheating temperature of 154 ° C. An MD stretched sheet comprising a base material layer (the base material layer was composed of a main layer and a surface layer) having an MD stretch ratio of 6.8 times was obtained. Next, a resin constituting the heat seal layer was extruded and laminated on the main layer surface of the MD stretched sheet at 250 ° C. using an in-line laminating machine additionally provided with a single-layer die. Next, the MD stretched sheet on which the heat seal layer was laminated was stretched 9.0 times to TD with a tenter-type transverse stretching machine (preheating temperature 190 ° C., stretching temperature 156 to 167 ° C.), and then subjected to corona treatment on both sides. gave.

  Thus, a biaxially stretched laminated polypropylene resin film having a total thickness of 30 μm, a heat seal layer thickness of 2.0 μm, and a base material layer thickness of 28.0 μm (main layer thickness of 26.5 μm, surface layer thickness of 1.5 μm) is manufactured. Filmed. The obtained biaxially stretched laminated polypropylene resin film was cured at 40 ° C. for 2 days, and then subjected to fusing seal strength, heat seal strength, antifogging properties, transparency, birefringence, tear directionality evaluation, and measurement of mechanical strength properties. The results are shown in Table 3. The detailed composition of the resin used is shown in Table 2.

Example 20 (film having a heat seal layer)
Biaxially oriented laminated polypropylene system in the same manner as in Example 19, except that the total thickness was 32 μm, the heat seal layer thickness was 4.0 μm, the base layer thickness was 26.5 μm, and the surface layer thickness was 1.5 μm. A resin film was prepared. The obtained biaxially stretched laminated polypropylene resin film was cured at 40 ° C. for 2 days, and then subjected to fusing seal strength, heat seal strength, antifogging properties, transparency, birefringence, tear directionality evaluation, and measurement of mechanical strength properties. The results are shown in Table 3. The detailed composition of the resin used is shown in Table 2.

Example 21 (film having a heat seal layer)
Biaxially stretched laminated polypropylene system in the same manner as in Example 19, except that the total thickness was 37 μm, the heat seal layer thickness was 9.0 μm, the base layer thickness was 26.5 μm, and the surface layer thickness was 1.5 μm. A resin film was formed. The obtained biaxially stretched laminated polypropylene resin film was cured at 40 ° C. for 2 days, and then subjected to fusing seal strength, heat seal strength, antifogging properties, transparency, birefringence, tear directionality evaluation, and measurement of mechanical strength properties. The results are shown in Table 3.
The detailed composition of the resin used is shown in Table 2.

Example 22 (film having a heat seal layer)
A biaxially stretched laminated polypropylene resin film having a configuration of heat seal I layer / base material layer (main layer) / heat seal II layer was formed by the following method. First, 95 mass% of resin 9 and 5 mass% of resin 7 are mixed as the resin constituting the heat seal I layer, and 95 mass% of resin 6 and the resin 7 are mixed as the resin constituting the heat seal II layer. What mixed 5 mass% was prepared. Next, a material (main layer resin) in which 70% by mass of resin 1 and 30% by mass of resin 2 were mixed as a raw material constituting the base film was prepared. It is Resin 9, Resin 6, and Resin 1 that compare the melting points.

  Next, the main layer resin constituting the base material layer was extruded with a single-layer T die at an extrusion temperature of 265 ° C., and cooled and solidified with a chill roll to prepare an unstretched sheet having a single-layer configuration. Next, the unstretched sheet is stretched 1.2 times at a preheating temperature of 153 ° C. by the MD two-stage stretching machine, and the second stage is stretched at a preheating temperature of 154 ° C. A single-layer MD stretched sheet having a stretching ratio of 6.8 times was obtained. Next, on one side of the MD stretched sheet, a resin constituting the heat seal I layer was extruded at 250 ° C. using an inline laminating machine provided with a single-layer die separately, laminated on the MD stretched sheet, and heat seal I on one side. The MD stretched sheet was obtained by laminating the layers. Next, the heat seal II layer was constructed using an inline laminating machine with a single-layer die separately attached to the other side where the heat seal I layer was not laminated. The resin to be extruded was extruded at 250 ° C. and laminated on the MD stretched sheet to obtain a three-layer laminated sheet which was a heat seal I layer / MD stretch sheet / heat seal II layer. Next, the three-layer laminated sheet was stretched 9.0 times to TD with a tenter-type lateral stretching machine (preheating temperature 190 ° C., stretching temperature 156 to 167 ° C.), and then subjected to corona treatment on both sides.

  Thus, a biaxially stretched laminated polypropylene resin film having a total thickness of 34 μm, a heat seal I layer thickness of 2.0 μm, a base material layer thickness of 28.0 μm, and a heat seal II layer thickness of 4.0 μm was formed. The obtained biaxially stretched laminated polypropylene-based resin film was cured at 40 ° C. for 2 days, and then the fusing seal strength with the heat seal I layer surface in the bag, the heat seal strength of the heat seal I layer surface, and the antifogging of the heat seal I layer surface , Biaxially stretched laminated polypropylene resin film, transparency, birefringence, tear direction evaluation, and mechanical strength characteristics were measured, and the results are shown in Table 3. The detailed composition of the resin used is shown in Table 2.

Plan view showing a state where a sample is set on cardboard in the tearing evaluation process Front view when the sample is attached to the chuck in the tearability evaluation process Side view of the sample attached to the chuck in the tearability evaluation process Plan view of the sample after the tensile test in the tearability evaluation process Schematic showing an example of a sandwich packaging bag using the packaging film of the present invention

Explanation of symbols

A Base line A 'Base line
B opening C chuck (upper)
C 'Chuck (downward)
E Adhesive tape F Tear mark F 'Tear mark G Tear start position G' Tear start position H Contact point I Tear distance J Cardboard K Opening tape L Biaxially stretched laminated film M Notch N on sandwich packaging bag Opening tape provided

Claims (5)

It comprises a biaxially stretched polypropylene resin film having at least a biaxially stretched base material layer made of a polypropylene resin, a tensile elongation in the longitudinal direction of 80 to 170%, and a tensile strength in the longitudinal direction of 155 to 230 MPa. And the packaging film characterized by being comprised by laminating | opening a tape in the width direction of this biaxially-stretched polypropylene resin film. The packaging film according to claim 1, wherein the biaxially oriented polypropylene resin film has a tensile elongation in the width direction of 40 to 90%. The biaxially stretched polypropylene resin film is a laminate in which a heat seal layer made of a polyolefin resin having a melting point lower than that of the polypropylene resin is laminated on at least one surface of a biaxially stretched base material layer made of a polypropylene resin. The packaging film according to claim 1 or 2. The packaging film according to claim 3, wherein the total thickness of the heat seal layer is 0.8 to 25% of the thickness of the biaxially stretched polypropylene resin film. A sandwich packaging bag formed by the packaging film according to any one of claims 1 to 4.

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