JP2020007445A - Food packaging film and food packaging - Google Patents

Abstract

To provide a packaging film for a food, with small thickness unevenness and improved water vapor barrier property.SOLUTION: The film for packaging a food is provided that comprises a biaxially stretched film layer including a propylene-based polymer, wherein when successively performing a first differential scanning calorimetry (1'st run) composed of a process of raising a temperature of the biaxially stretched film layer from -50°C to 250°C at a temperature-raising rate of 10°C/min. using a differential scanning calorimeter, an isothermal process of keeping the temperature of the biaxially stretched film layer at 250°C for 10 min., and a process of reducing the temperature of the same from 250°C to -50°C at a temperature-reducing rate of 10°C/min., and a second differential scanning calorimetry (2'nd run) composed of a process of raising a temperature of the biaxially stretched film layer from -50°C to 250°C at a temperature-raising rate of 10°C/min., an endothermic peak is observed on a DCS curve 2 obtained by the second differential scanning calorimetry within a range of 150°C or higher and 180°C or lower, and a heat quantity of the endothermic peak A is 95 J/g or more and 120 J/g or less.SELECTED DRAWING: None

Description

  The present invention relates to a food packaging film and a food packaging.

  A biaxially stretched polypropylene film (hereinafter also referred to as an OPP film) is excellent in workability, water vapor barrier property, transparency, mechanical strength, rigidity, etc. and is used as a packaging film for packaging food. Have been.

  As a technique relating to a food packaging film using such an OPP film, for example, those described in Patent Literature 1 (JP-A-2008-73926) and Patent Literature 2 (JP-A-2004-82499) are exemplified. Can be

Patent Document 1 discloses that a biaxially stretched film composed of a propylene polymer composition containing 75 to 90% by weight of a propylene homopolymer (A) and 25 to 10% by weight of a tackifier (D) has a melting point of 155 ° C. A layer comprising a propylene / α-olefin random copolymer (C) having a melting point in the range of 125 to 145 ° C via a layer comprising the propylene-based polymer (B) as described above; Describes a biaxially stretched multilayer polypropylene film having a layer made of a propylene-based polymer (E) on one side of the film.
Patent Document 1 describes that a biaxially stretched multilayer polypropylene film having the above-described configuration can suppress seepage of a film of a petroleum resin or the like and is excellent in lamination strength and moisture resistance.

Patent Document 2 discloses that a biaxially stretched polypropylene-based resin layer containing 10 to 40% by weight of a highly crystallized resin and 6 to 15% by weight of a petroleum resin is provided with an adhesive layer on at least one surface thereof. A multilayer resin film further comprising a polyvinyl alcohol-based resin layer, wherein the relative humidity is 85% RH, the oxygen permeability at a temperature of 23 ° C. is 600 mL / m ² · day · MPa or less, and the relative humidity is 90% A multilayer resin film is described in which the water vapor permeability at RH and a temperature of 40 ° C. is 3.5 g / m ² · day · 20 μm or less.
Patent Literature 2 describes that a multilayer resin film having the above configuration has excellent oxygen gas barrier properties and moisture proof properties.

JP 2008-73926 A JP-A-2004-82499

The OPP film is required to further improve the water vapor barrier property from the viewpoint of reducing the environmental load. When the water vapor barrier property is improved, the thickness of the OPP film can be reduced, so that the amount of the propylene-based polymer used can be reduced, and the environmental load can be reduced.
Here, according to the study of the present inventors, it has been found that when a highly crystalline propylene-based polymer is used as the propylene-based polymer constituting the OPP film, the water vapor barrier property of the OPP film can be improved. . However, it has been found that when such a highly crystalline propylene-based polymer is used, stretching unevenness is likely to occur, and the thickness unevenness of the OPP film obtained after the biaxial stretching step may be large.
As described above, the present inventors have found that there is a trade-off between the water vapor barrier property and the thickness unevenness in the OPP film. In other words, the present inventor has found that there is room for improvement in the OPP film from the viewpoint of improving both the water vapor barrier property and suppressing thickness unevenness in a well-balanced manner.

  The present invention has been made in view of the above circumstances, and provides a food packaging film having small thickness unevenness and improved water vapor barrier properties.

The present inventors have made intensive studies to solve the above problems. As a result, in the DSC curve at 2nd Run of the differential scanning calorimetry, the measure of the calorific value of the endothermic peak A observed in the range of 150 ° C. or more and 180 ° C. or less was used to improve the balance between the improvement in water vapor barrier property and the suppression of thickness unevenness. We found that it is effective as a design guide.
The present inventors have conducted further studies based on the above findings, and by using a biaxially stretched film layer in which the calorific value of the endothermic peak A observed in the range of 150 ° C or more and 180 ° C or less is in a specific range, The present inventors have found that a food packaging film having small thickness unevenness and improved water vapor barrier properties can be obtained, and the present invention has been accomplished.

  That is, according to the present invention, a food packaging film and a food packaging shown below are provided.

[1]
A film for packaging food,
With a biaxially stretched film layer containing a propylene-based polymer,
For the biaxially stretched film layer, using a differential scanning calorimeter,
From the process of raising the temperature from −50 ° C. to 250 ° C. at a rate of 10 ° C./min, the isothermal process of maintaining the temperature at 250 ° C. for 10 minutes, and the process of decreasing the temperature from 250 ° C. to −50 ° C. at a rate of 10 ° C./min. The first differential scanning calorimetry (1stRun)
A second differential scanning calorimetry (2ndRun) comprising a process of raising the temperature from -50 ° C to 250 ° C at a rate of 10 ° C / min,
When I went to
In DSC curve 2 obtained by the second differential scanning calorimetry, endothermic peak A is observed in the range of 150 ° C. or more and 180 ° C. or less,
A food packaging film having a heat quantity of the endothermic peak A of 95 J / g or more and 120 J / g or less.
[2]
In the food packaging film according to the above [1],
In the DSC curve 1 obtained by the first differential scanning calorimetry, a food package in which an endothermic peak B is observed in a range of 150 ° C or more and 165 ° C or less and an endothermic peak C is observed in a range of 165 ° C or more and 180 ° C or less, respectively. the film.
[3]
In the food packaging film according to the above [2],
A food packaging film wherein the ratio (C / B) of the peak height C of the endothermic peak C to the peak height B of the endothermic peak B is 1.0 or more and 3.0 or less.
[4]
In the food packaging film according to any one of the above [1] to [3],
A food packaging film in which an exothermic peak D is observed in a range of 100 ° C. or more and 130 ° C. or less in a DSC curve 1 obtained by the first differential scanning calorimetry.
[5]
In the food packaging film according to the above [4],
A food packaging film having a half width of the exothermic peak D of 2.0 ° C. or more and 6.0 ° C. or less.
[6]
In the food packaging film according to any one of the above [1] to [5],
According to JIS K7127 (1999), the tensile strength in the MD direction of the food packaging film is measured using a tensile tester at a measurement temperature of 23 ± 2 ° C., 50 ± 5% RH, and a tensile speed of 5 mm / min. A food packaging film having a total value (T ₁ + T ₂ ) of the elastic modulus T ₁ and the tensile elastic modulus T _{2 in the} TD direction of 5,000 MPa or more and 10,000 MPa or less.
[7]
The food packaging film according to any one of the above [1] to [6],
A food packaging film further comprising a heat seal layer on at least one surface of the biaxially stretched film layer.
[8]
In the food packaging film according to the above [7],
A food packaging film, wherein the heat seal layer is provided so as to directly contact the one surface of the biaxially stretched film layer.
[9]
In the food packaging film according to the above [7] or [8],
A food packaging film in which the heat seal layer contains one or more selected from homopolypropylene and a random copolymer of propylene and an α-olefin having 2 to 10 carbon atoms.
[10]
In the food packaging film according to any one of the above [1] to [9],
A food packaging film further comprising a surface layer on one surface of the biaxially stretched film layer.
[11]
In the food packaging film according to the above [10],
The surface layer is a food packaging film containing an anti-blocking agent.
[12]
In the food packaging film according to the above [10] or [11],
The above-mentioned surface layer is a food packaging film containing one or more selected from homopolypropylene and a random copolymer of propylene and an α-olefin having 2 to 10 carbon atoms.
[13]
In the food packaging film according to any one of the above [1] to [12],
A food packaging film, wherein the content of the tackifier contained in the biaxially stretched film layer is 10% by mass or less when the whole of the biaxially stretched film layer is 100% by mass.
[14]
In the food packaging film according to any one of the above [1] to [13],
Food packaging film water vapor transmission rate as measured by the following method is 6.0g ^/ (m 2 · 24h) or less.
(Measuring method)
The food packaging film is folded back so that the heat seal layer is on the inner surface, and the two sides are heat sealed to form a bag. Thereafter, calcium chloride is added as the contents. Next, the other side is heat-sealed to prepare a bag so that the surface area becomes 0.01 m ² . Next, the obtained bag is stored at 40 ° C. and a humidity of 90% RH for 72 hours. Measuring the weight of calcium chloride before and after storage, it calculates a water vapor transmission rate of ^{(g / (m 2 · 24h} )) from the difference.
[15]
In the food packaging film according to any one of the above [1] to [14],
Food packaging film used for outer packaging bags.
[16]
A food package using the food packaging film according to any one of [1] to [15].

  ADVANTAGE OF THE INVENTION According to this invention, the thickness nonuniformity is small and the packaging film for foods which the water vapor barrier property improved can be provided.

It is sectional drawing which showed typically an example of the structure of the packaging film for foods of embodiment which concerns on this invention. It is sectional drawing which showed typically an example of the structure of the packaging film for foods of embodiment which concerns on this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the figure is a schematic diagram and does not match the actual dimensional ratio. In addition, "~" between numbers in a sentence represents the following from the above unless otherwise specified.

<Food packaging film>
1 and 2 are cross-sectional views schematically showing an example of the structure of a food packaging film 100 according to an embodiment of the present invention.
The food packaging film 100 according to the present embodiment is a film for packaging food, and includes a biaxially stretched film layer 101 containing a propylene-based polymer. Using a calorimeter, a process of raising the temperature from -50 ° C to 250 ° C at a heating rate of 10 ° C / minute, an isothermal process of keeping the temperature at 250 ° C for 10 minutes, and a process of decreasing the temperature from 250 ° C to -50 ° C at a rate of 10 ° C / minute. The first differential scanning calorimetry (1stRun) consisting of the step of decreasing the temperature to 2 ° C and the second differential scanning calorimetry (2ndRun) consisting of the step of raising the temperature from -50 ° C to 250 ° C at a rate of 10 ° C / min. And, in the DSC curve 2 obtained by the second differential scanning calorimetry, an endothermic peak A is observed in the range of 150 ° C. or more and 180 ° C. or less, and the endothermic peak A The amount is equal to or less than 95J / g or more 120J / g. As a result, a food packaging film with small thickness unevenness and improved water vapor barrier properties can be realized.
The lower limit of the calorific value of the endothermic peak A is 95 J / g or more, but from the viewpoint of further improving the water vapor barrier property of the food packaging film 100, preferably 100 J / g or more, more preferably 105 J / g or more, and still more preferably. Is 110 J / g or more.
The upper limit of the calorific value of the endothermic peak A is 120 J / g or less, but from the viewpoint of further suppressing thickness unevenness, it is preferably 118 J / g or less, more preferably 115 J / g or less.
Here, the calorific value of the endothermic peak A is calculated by obtaining an area surrounded by a melting endothermic curve including the endothermic peak A and a base line. The baseline is obtained by differentiating the Heat Flow with respect to time before and after the endothermic peak A, displaying the Deriv. Heat Flow, and the point where the change of the Deriv. Heat Flow starts (ie, the point where the flat region of the Deriv. Heat Flow ends). ) And a point where the change of the Deriv. Heat Flow ends (that is, a point where the Deriv. Heat Flow enters the flat region).
When a plurality of endothermic peaks are observed in the range of 150 ° C. or more and 180 ° C. or less, the maximum peak is taken as endothermic peak A.

As described above, the OPP film is required to further improve the water vapor barrier property from the viewpoint of reducing the environmental load. When the water vapor barrier property is improved, the amount of the propylene-based polymer used can be reduced, and the environmental load can be reduced.
Here, according to the study of the present inventors, it has been found that when a highly crystalline propylene-based polymer is used as the propylene-based polymer constituting the OPP film, the water vapor barrier property of the OPP film can be improved. . However, it has been found that when such a highly crystalline propylene-based polymer is used, stretching unevenness is likely to occur, and the thickness unevenness of the OPP film obtained after the biaxial stretching step may be large.
As described above, the present inventors have found that there is a trade-off between the water vapor barrier property and the thickness unevenness in the OPP film. In other words, the present inventor has found that there is room for improvement in the OPP film from the viewpoint of improving both the water vapor barrier property and suppressing thickness unevenness in a well-balanced manner.

The present inventors have made intensive studies to solve the above problems. As a result, in the DSC curve 2 at 2ndRun of the differential scanning calorimetry, the measure of the calorific value of the endothermic peak A observed in the range of 150 ° C. or more and 180 ° C. or less is to improve the balance between the improvement of the water vapor barrier property and the suppression of thickness unevenness. It was found that it was effective as a design guideline.
The present inventors have conducted further intensive studies based on the above findings. As a result, the biaxial stretching in which the calorific value of the endothermic peak A observed in the range of 150 ° C. or more and 180 ° C. or less is in the range of 95 J / g or more and 120 J / g or less. It has been found that by using the film layer 101, a food packaging film having small thickness unevenness and improved water vapor barrier properties can be obtained.
That is, according to the food packaging film 100 according to the present embodiment, a food packaging body with small thickness unevenness and improved water vapor barrier properties can be realized.
Moreover, according to the food packaging film 100 according to the present embodiment, since the water vapor barrier property can be improved, a sufficient water vapor barrier property can be obtained even when the thickness of the biaxially stretched film layer 101 is made thinner. Therefore, according to the food packaging film 100 according to the present embodiment, the amount of the propylene-based polymer used in the food packaging film or the package can be reduced, and the environmental load can be reduced.
From the above, according to the present embodiment, a food packaging having a sufficient water vapor barrier property and being able to realize an environmentally friendly food packaging, having small thickness unevenness, and having excellent appearance, packaging suitability, and excellent bag making properties. A film 100 can be provided.

The biaxially stretched film layer 101 containing the propylene-based polymer according to this embodiment has an endothermic peak observed in the range of 150 ° C. or more and 180 ° C. or less in the DSC curve 2 obtained by the second differential scanning calorimetry. The heat amount of A is controlled so as to be 95 J / g or more and 120 J / g or less. This makes it possible to improve both the water vapor barrier property and the thickness unevenness in a well-balanced manner. Although the reason for this is not clear, the following may be considered.
First, when the calorific value of the endothermic peak A is equal to or more than the lower limit, the crystallinity of the biaxially stretched film layer 101 can be increased. As a result, the water vapor barrier property of the food packaging film 100 according to the present embodiment can be improved. It is thought that it can be improved. Further, when the calorific value of the endothermic peak A is equal to or less than the upper limit, stretching unevenness due to crystallization of the biaxially stretched film layer 101 can be reduced, and as a result, the thickness generated when the biaxially stretched film layer 101 is stretched. It is considered that unevenness can be reduced.
Here, the calorific value of the endothermic peak A of the biaxially stretched film layer 101 can be achieved by, for example, adjusting the content ratio of the propylene-based polymer contained in the biaxially stretched film layer 101 and various conditions at the time of stretching. . More specifically, as the propylene polymer constituting the biaxially stretched film layer 101, two or more propylene polymers having different melting points, crystallinities, stereoregularities, etc. are used in combination, and the proportions thereof are adjusted. It can be adjusted by appropriately adjusting the stretching ratio during stretching, the temperature during stretching, the temperature and time of heat treatment, and the like.

In the DSC curve 1 obtained by the first differential scanning calorimetry in the food packaging film 100 according to the present embodiment, for example, an endothermic peak B in a range of 150 ° C. or more and 165 ° C. or less and a temperature exceeding 165 ° C. and 180 ° C. or less It is preferable that the endothermic peak C is observed in the range of each.
By having the endothermic peak B in the range of 150 ° C. or more and 165 ° C. or less, the stretching unevenness of the biaxially stretched film layer 101 can be further reduced. It can be even smaller. In addition, by having an endothermic peak C in the range from 165 ° C. to 180 ° C., the crystallinity of the biaxially stretched film layer 101 can be further increased, and as a result, the water vapor of the food packaging film 100 according to the present embodiment can be improved. The barrier properties can be further improved.

In the food packaging film 100 according to the present embodiment, the ratio (C / B) of the peak height C of the endothermic peak C to the peak height B of the endothermic peak B determines the water vapor barrier property of the packaging film 100 for food. From the viewpoint of further improvement, it is preferably 1.0 or more, more preferably 1.2 or more, and still more preferably 1.5 or more.
Further, in the food packaging film 100 according to the present embodiment, the ratio (C / B) of the peak height C of the endothermic peak C to the peak height B of the endothermic peak B is determined by the thickness unevenness of the food packaging film 100. Is more preferably 3.0 or less, more preferably 2.5 or less, and still more preferably 2.3 or less, from the viewpoint of further suppressing.
Here, the peak height B of the endothermic peak B and the peak height C of the endothermic peak C are represented by a straight line P−, where Q is the intersection of a line drawn perpendicularly to the X axis from the peak top P and the base line. Q is the Heat Flow value. The baseline is obtained by differentiating the Heat Flow with respect to time before and after the endothermic peak B and the endothermic peak C, displaying the Deriv. Heat Flow, and the point where the change of the Deriv. Heat Flow starts (that is, the flat area of the Deriv. Heat Flow). End point) and the point where the change of Deriv. Heat Flow ends (that is, the point where Deriv. Heat Flow enters the flat region).

  In the packaging film 100 for food according to the present embodiment, in the DSC curve 1 obtained by the first differential scanning calorimetry, for example, a range of 100 ° C to 130 ° C, preferably a range of 100 ° C to 120 ° C It is preferable that an exothermic peak D is observed. Thereby, the crystallinity of the biaxially stretched film layer 101 can be further increased, and as a result, the balance between the improvement of the water vapor barrier property and the suppression of thickness unevenness of the food packaging film 100 according to the present embodiment can be further improved. it can.

The half width of the exothermic peak D is, for example, 2.0 ° C. or more and 6.0 ° C. or less, and preferably 3.0 ° C. or more and 5.0 ° C. or less.
By setting the half width of the heat generation peak D to the lower limit or more, the internal strain of the biaxially stretched film layer 101 can be further reduced. It can be even smaller.
In addition, by setting the half width of the heat generation peak D to be equal to or less than the upper limit, the crystallinity of the biaxially stretched film layer 101 can be further increased, and as a result, the water vapor of the food packaging film 100 according to the present embodiment can be improved. The barrier properties can be further improved.
Here, the half width of the heat generation peak D can be calculated by, for example, the following method. First, let S be the intersection of a line drawn vertically from the peak top R of the exothermic peak D toward the X-axis and the baseline. Then, through the midpoint of the straight line R-S, and, when obtained by subtracting the straight line parallel to the X axis, the point of intersection with the exothermic peak D and T ₁ and T _2, respectively. Then, the length of the straight line T ₁ -T ₂ is defined as a half width. The baseline is the point at which the Heat Flow is differentiated with time before and after the exothermic peak D, the Deriv. Heat Flow is displayed, and the point at which the change of the Deriv. Heat Flow starts (that is, the point at which the flat region of the Deriv. Heat Flow ends). ) And a point where the change of the Deriv. Heat Flow ends (that is, a point where the Deriv. Heat Flow enters the flat region).

The food packaging film 100 according to the present embodiment is measured at a measurement temperature of 23 ± 2 ° C., 50 ± 5% RH, and a tensile speed of 5 mm / min using a tensile tester in accordance with JIS K7127 (1999). The total value (T ₁ + T ₂ ) of the tensile modulus T _{1 in the} MD direction and the tensile modulus T _{2 in the} TD direction is preferably 5000 MPa or more, more preferably 6000 MPa or more, and more preferably 7000 MPa or more. More preferably, it is more preferably 7100 MPa or more, and it is preferably 10000 MPa or less, more preferably 9000 MPa or less, further preferably 8000 MPa or less, and particularly preferably 7500 MPa or less.
MD direction tensile modulus T ₁ and the total value of the tensile modulus T ₂ of the TD direction when the (T 1 _{+ T 2)} is not less than the above lower limit, the heat sealable food packaging films 100 according to this embodiment , The balance between water vapor barrier properties and transparency can be improved. Further, the stiffness of the food packaging film 100 according to the present embodiment can be improved, and as a result, the film can be prevented from being displaced during heat sealing, and the occurrence of poor sealing can be suppressed. .
That is, when the total value of the tensile modulus T ₂ of the tensile modulus T ₁ and TD direction MD direction (T 1 _{+ T 2)} is not less than the above lower limit, the heat of the food packaging film 100 according to this embodiment The balance between the sealing property, the water vapor barrier property, the transparency and the packaging suitability can be improved.
This addition, when the total value of the tensile modulus T ₂ of the tensile modulus T ₁ and TD direction MD direction (T 1 _{+ T 2)} is less than the above upper limit, without increasing the amount of the antistatic agent The surface specific resistance of the food packaging film 100 according to the embodiment can be effectively reduced, and as a result, the antistatic property can be improved while maintaining the good heat sealing property of the food packaging film 100. .
Such a tensile modulus is a substitute value for quantitatively measuring the stiffness of the film, for example, by adjusting the content ratio of the propylene-based polymer contained in the biaxially stretched film layer 101 and various conditions during the stretching treatment. And so on. More specifically, using a plurality of propylene-based polymers having different melting points and heats of fusion as propylene-based polymers constituting the biaxially stretched film layer 101, or a stretching ratio during stretching, a temperature during stretching, By appropriately adjusting the temperature and time of the heat treatment, the elastic modulus can be adjusted, and the tensile elastic modulus of the food packaging film 100 can be adjusted.

  Here, the food packaging body manufactured using the food packaging film 100 according to the present embodiment has sufficient performance with respect to the water vapor barrier property. Therefore, it can be particularly suitably used as a film constituting a food package for packaging food (eg, dried food), which is required to have a water vapor barrier property but is not required to have a high oxygen barrier property.

A food package produced using the food packaging film 100 according to the present embodiment has a sufficient water vapor barrier property. In food packaging film 100, from the viewpoint of obtaining an excellent food package by water vapor barrier property stably, is water vapor transmission rate as measured by the following methods 6.0g / (m 2 · ^24h) or less it is preferred, more preferably 5.5g ^/ (m 2 · 24h) or less, and more preferably 5.0g ^/ (m 2 · 24h) or less.
(Measuring method)
The food packaging film 100 is folded back so that the heat seal layer 103 is on the inner surface, and the two sides are heat sealed to form a bag. Thereafter, calcium chloride is added as the contents. Next, the other side is heat-sealed to prepare a bag so that the surface area becomes 0.01 m ² . Next, the obtained bag is stored at 40 ° C. and a humidity of 90% RH for 72 hours. Measuring the weight of calcium chloride before and after storage, it calculates a water vapor transmission rate of ^{(g / (m 2 · 24h} )) from the difference.
Such a water vapor transmission rate is determined, for example, by the DSC characteristics of the biaxially stretched film layer 101 such as the endothermic peak characteristics and the exothermic peak characteristics described above, the content ratio of the propylene-based polymer contained in the biaxially stretched film layer 101, heat sealing. This can be achieved by adjusting the constituent material, thickness, and the like of the layer 103.

The thickness of the food packaging film 100 according to the present embodiment is not particularly limited, but can be arbitrarily set according to desired purposes such as water vapor barrier property, cost, mechanical strength, and transparency, and is not particularly limited. For example, it is 5 μm or more and 100 μm or less, preferably 10 μm or more and 50 μm or less, and more preferably 15 μm or more and 40 μm or less.
When the thickness of the food packaging film 100 is within the above range, the balance between bag making properties, mechanical properties, handling properties, appearance, transparency, moldability, lightness, and the like is more excellent.

  Hereinafter, each layer constituting the food packaging film 100 will be described.

[Biaxially stretched film layer]
The biaxially-stretched film layer 101 (also referred to as a biaxially-stretched polypropylene-based film layer) according to this embodiment is formed by, for example, biaxially stretching a film composed of a propylene-based polymer composition containing a propylene-based polymer. It is formed by:

  The biaxially stretched film layer 101 according to the present embodiment may be a single layer, or may have a configuration in which a plurality of layers composed of a propylene-based polymer composition are laminated, but may be formed by biaxial stretching. is necessary.

  In the food packaging film 100, the ratio of the thickness of the biaxially stretched film layer 101 to the entire thickness of the food packaging film 100 is preferably 50% or more and 100% or less, more preferably 60% or more and 99%. Or less, more preferably 70% or more and 97% or less, and particularly preferably 75% or more and 95% or less.

(Propylene polymer composition)
The propylene-based polymer composition according to the present embodiment contains a propylene-based polymer.
The content of the propylene-based polymer composition according to the present embodiment, that is, the content of the propylene-based polymer contained in the biaxially stretched film layer 101 is preferably 50% by mass when the entire propylene-based polymer composition is 100% by mass. % To 100% by mass, more preferably 70% to 100% by mass, still more preferably 90% to 100% by mass, and particularly preferably 95% to 100% by mass. Thereby, the balance of the stiffness, the water vapor barrier property, the mechanical properties, the handleability, the appearance, the moldability and the like of the film can be further improved.

(Propylene polymer)
The propylene-based polymer according to the present embodiment includes, for example, a propylene homopolymer, a copolymer of propylene and ethylene or an α-olefin having 4 to 20 carbon atoms, and the like. Examples of the α-olefin having 4 to 20 carbon atoms include 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, Examples thereof include 1-hexadecene, 1-octadecene, and 1-eicosene. Among them, ethylene or an α-olefin having 4 to 10 carbon atoms is preferable, and ethylene is more preferable. These α-olefins may form a random copolymer with propylene, or may form a block copolymer. The content of the structural unit derived from ethylene or an α-olefin having 4 to 20 carbon atoms is preferably 5 mol% or less, and preferably 2 mol% or less, when the entire propylene-based polymer is 100 mol%. Is more preferable. The propylene-based polymer in the biaxially stretched film layer 101 may be used alone or in a combination of two or more.
Among these, a propylene homopolymer is preferable as the propylene-based polymer, from the viewpoint of obtaining a biaxially stretched film layer 101 that is more excellent in performance balance such as heat resistance, water vapor barrier properties, mechanical properties, and rigidity.

Here, in order to satisfy the DSC characteristics such as the endothermic peak characteristic and the exothermic peak characteristic of the biaxially stretched film layer 101, it is important to select an appropriate propylene-based polymer.
More specifically, the biaxially stretched film layer 101 according to the present embodiment uses, for example, two or more types of propylene-based polymers having different melting points, crystallinities, stereoregularities, and the like, and adjusts the proportions thereof. By doing so, it is possible to adjust the DSC characteristics such as the above-mentioned endothermic peak characteristics and exothermic peak characteristics.

For example, the propylene-based polymer contained in the biaxially stretched film layer 101 according to the present embodiment has a first propylene-based polymer having a melting point in the range of 130 ° C. or more and 162 ° C. or less in DSC measurement, and a melting point in DSC measurement. And a second propylene-based polymer in a range from 162 ° C to 180 ° C.
In this case, when the total amount of the first propylene-based polymer and the second propylene-based polymer contained in the biaxially stretched film layer 101 is 100% by mass, the content of the second propylene-based polymer is From the viewpoint of improving the water vapor barrier property of the film 100, the content is preferably 1% by mass or more, more preferably 10% by mass or more, still more preferably 25% by mass or more, and preferably 35% by mass or more. Is still more preferable, and it is particularly preferable that it is 50 mass% or more.
Further, when the total amount of the first propylene-based polymer and the second propylene-based polymer contained in the biaxially stretched film layer 101 is 100% by mass, the content of the second propylene-based polymer is defined as a food packaging film. From the viewpoint of further suppressing thickness unevenness of 100, the content is preferably 85% by mass or less, more preferably 75% by mass or less, and even more preferably 70% by mass or less.

In this embodiment, the second propylene-based polymer is preferably a highly stereoregular propylene-based polymer. Here, the high stereoregularity propylene polymer refers to a propylene polymer having an isotactic mesopentad fraction (mmmm) of 96.0% or more, which is an index of stereoregularity.
The isotactic mesopentad fraction (mmmm) of the highly stereoregular propylene polymer according to this embodiment is preferably 96.5% or more, and more preferably 97.0% or more. The upper limit of the isotactic mesopentad fraction (mmmm) of the highly stereoregular propylene polymer is not particularly limited, but is preferably 99.5% or less, more preferably 99.5%, from the viewpoint of easy production. It is at most 3%, more preferably at most 99.0%.
The isotactic mesopentad fraction (mmmm) can be determined from a ¹³ C-nuclear magnetic resonance (NMR) spectrum by a known method.

  The propylene-based polymer according to this embodiment can be produced by various methods. For example, it can be produced using a known catalyst such as a Ziegler-Natta catalyst or a metallocene catalyst.

  According to ASTM D1238, the melt flow rate (MFR) of the propylene-based polymer according to the present embodiment measured under the conditions of 230 ° C. and a load of 2.16 kg is preferably 0. It is at least 5 g / 10 min, more preferably at least 1 g / 10 min, even more preferably at least 2 g / 10 min, and from the viewpoint of further stabilizing moldability, preferably at most 20 g / 10 min, more preferably at most 10 g / 10. Min, more preferably 7 g / 10 min or less.

(Other components)
In the propylene polymer composition according to the present embodiment, if necessary, a tackifier, a heat stabilizer, a weather stabilizer, an antioxidant, an ultraviolet absorber, a lubricant, a slip agent, a nucleating agent, an antiblocking agent Various additives such as an antistatic agent, an antifogging agent, a pigment, a dye, and an inorganic or organic filler may be added within a range that does not impair the purpose of the present embodiment.

As the tackifier according to the present embodiment, a resinous substance having the property of imparting tackiness, which is generally manufactured and sold as a tackifier, can be used.
Such tackifiers include, for example, chroman resins such as chroman / indene resins; phenolic resins such as phenol / formaldehyde resins and xylene / formaldehyde resins; terpenes / phenolic resins; terpene resins (α, β-pinene resins) ), Terpene resins such as aromatic modified terpene resins and hydrogenated terpene resins; synthetic polyterpene resins, aromatic hydrocarbon resins, aliphatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic and alicyclic resins Petroleum hydrocarbon resins such as petroleum-based petroleum resins, aliphatic / aromatic petroleum resins, unsaturated hydrocarbon polymers and hydrocarbon-based tackifying resins; hydrogenated products of the above petroleum-based hydrocarbon resins (hydrogenated petroleum-based carbon Rosin pentaerythritol ester, rosin glycerin ester, hydrogenated rosin And rosin resins such as hydrogenated rosin esters, special rosin esters and rosin tackifiers.
Among them, from the viewpoint of good compatibility with the propylene-based polymer, from the viewpoint of more effectively improving the water vapor barrier properties of the food packaging film 100, from the petroleum-based hydrocarbon resin and the hydrogenated petroleum-based hydrocarbon resin At least one selected is preferable, and a hydrogenated petroleum hydrocarbon resin is more preferable.
Here, the hydrogenation rate of the hydrogenated petroleum hydrocarbon resin is not particularly limited, but is preferably 90% or more, more preferably 95% or more, and still more preferably 99%, from the viewpoint of being more compatible with the propylene polymer. % Or more.

  Here, the content of the tackifier contained in the propylene-based polymer composition according to the present embodiment, that is, the biaxially stretched film layer 101 is selected from the viewpoints of recyclability and cost reduction of the food packaging film 100, and From the viewpoint of suppressing a decrease in bending elasticity of the packaging film 100 and improving workability, dimensional stability, transparency, and the like, when the entire biaxially stretched film layer 101 is 100% by mass, preferably 10% by mass. It is at most 5% by mass, more preferably at most 5% by mass, further preferably at most 3% by mass, particularly preferably at most 1% by mass.

(Method for preparing propylene-based polymer composition)
The propylene polymer composition according to the present embodiment is obtained by mixing or melting / kneading the components by dry blending, a tumbler mixer, a Banbury mixer, a single-screw extruder, a twin-screw extruder, a high-speed twin-screw extruder, a hot roll, or the like. Can be prepared.

[Heat seal layer]
The food packaging film 100 according to the present embodiment preferably includes a heat seal layer 103 on at least one surface of the biaxially stretched film layer 101 in order to impart heat sealability. The heat seal layer 103 may be provided on both surfaces of the biaxially stretched film layer 101.
The heat seal layer 103 is preferably provided on the outermost layer of the food packaging film 100 according to the present embodiment, from the viewpoint of improving the heat sealing property of the food packaging film 100.

  Further, it is preferable that the heat seal layer 103 is provided so as to be in direct contact with the surface of the biaxially stretched film layer 101. Thereby, the manufacturing process of the food packaging film 100 can be simplified.

In the food packaging film 100, the thickness of the heat seal layer 103 is preferably 0.1 μm or more and 10 μm or less, more preferably 0.2 μm or more and 9 μm or less, further preferably 0.5 μm or more and 8 μm or less, and particularly preferably 1 μm or more and 8 μm or less. It is as follows. Here, the thickness of the heat seal layer 103 refers to the thickness of the heat seal layer 103 provided on one surface of the biaxially stretched film layer 101.
When the thickness of the heat seal layer 103 is equal to or more than the lower limit, the heat seal property of the food packaging film 100 can be further improved.
When the thickness of the heat seal layer 103 is equal to or less than the upper limit, the blocking property and the slip property required for the food packaging film can be further improved.
That is, by providing the heat seal layer 103 so as to be in direct contact with the surface of the biaxially stretched film layer 101, the manufacturing process of the food packaging film 100 can be simplified.
Here, in the present embodiment, when the heat seal layers 103 are provided on both surfaces of the biaxially stretched film layer 101, the thickness of the heat seal layer 103 is equal to the thickness of the heat seal layer 103 provided on one surface of the biaxially stretched film layer 101. Shows the thickness of

  In the food packaging film 100, the heat seal layer 103 provided on one surface is preferably a single layer. Thereby, the manufacturing process of the food packaging film 100 can be further simplified.

  Further, it is preferable that the heat seal layer 103 is formed by being biaxially stretched at the same time as the film in the state before the biaxially stretching of the biaxially stretched film layer 101. Thereby, since the food packaging film 100 can be produced using a molding method such as a co-extrusion molding method, that is, a laminated film produced by a single molding, the manufacturing process of the food packaging film 100 is further simplified. can do. Therefore, the heat seal layer 103 is preferably biaxially stretched.

(Polyolefin)
The heat seal layer 103 according to the present embodiment is made of, for example, a polyolefin-based resin composition (A) containing a polyolefin. Examples of the polyolefin constituting the heat seal layer 103 include homo- or copolymers of α-olefins such as ethylene, propylene, butene-1, hexene-1, 4-methyl-pentene-1, and octene-1; High-pressure low-density polyethylene; linear low-density polyethylene (LLDPE); high-density polyethylene; polypropylene; random copolymer of propylene with an α-olefin having 2 to 10 carbon atoms; ethylene-vinyl acetate copolymer (EVA) ); Ionomer resins and the like.
Among them, as the polyolefin constituting the heat seal layer 103, homopolypropylene and propylene have 2 or more and 10 or less carbon atoms from the viewpoint that the adhesiveness with the biaxially stretched film layer 101 and the balance of heat sealability and the like are excellent. At least one selected from random copolymers with α-olefins is preferred.
Further, from the viewpoint of the heat sealability and the stability of the heat seal strength, the heat seal layer 103 preferably contains an olefin-based elastomer among the above-mentioned polyolefins.

The propylene / α-olefin random copolymer according to the present embodiment is a random copolymer of propylene and an α-olefin (however, the α-olefin is not propylene). Examples of the α-olefin include ethylene. , 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene and the like. These copolymers may be used alone or as a mixture of two or more.
Among propylene / α-olefin random copolymers, propylene / ethylene random copolymer, propylene / ethylene / 1-butene random copolymer, and propylene / 1-butene random copolymer are preferable.

The melting point of the polyolefin constituting the heat seal layer 103 according to the present embodiment is preferably in the range of 60 ° C to 175 ° C, more preferably 65 ° C to 170 ° C, and even more preferably 70 ° C to 167 ° C. When the melting point of the polyolefin is equal to or more than the lower limit, stickiness on the surface of the heat seal layer 103 can be suppressed, and the blocking resistance of the food packaging film 100 can be improved.
When the melting point of the polyolefin is equal to or less than the upper limit, the heat sealing property of the food packaging film 100 can be further improved.

Examples of the olefin-based elastomer include, for example, an α-olefin polymer having a melting point of preferably 110 ° C. or lower, more preferably 100 ° C. or lower, and further preferably 80 ° C. or lower or a C 2 to C 20 polymer having no observable melting point or ethylene. And an α-olefin; a copolymer of ethylene and an unsaturated carboxylic acid or an unsaturated carboxylic acid ester; and the like.
Specifically, ethylene / propylene copolymer, ethylene / 1-butene copolymer, ethylene / 1-hexene copolymer, ethylene / 4-methylpentene-1 copolymer, ethylene / 1-octene copolymer , Propylene homopolymer, propylene / ethylene copolymer, propylene / ethylene / 1-butene copolymer, 1-butene homopolymer, 1-butene / ethylene copolymer, 1-butene / propylene copolymer, 4-methylpentene-1 homopolymer, 4-methylpentene-1 · propylene copolymer, 4-methylpentene-1 / 1-butene copolymer, 4-methylpentene-1-propylene / 1-butene copolymer Copolymer, propylene / 1-butene copolymer, ethylene / vinyl acetate copolymer, ethylene / methacrylic acid copolymer, ethylene / methyl methacrylate copolymer It can be mentioned.
From the viewpoint of heat sealability and stability of heat seal strength, a propylene / 1-butene copolymer is particularly preferred.

  In accordance with ASTM D1238, the melt flow rate (MFR) of the polyolefin constituting the heat seal layer 103 according to the present embodiment measured at 230 ° C. under a load of 2.16 kg is determined from the viewpoint of fluidity and moldability. It is preferably at least 0.5 g / 10 min, more preferably at least 1 g / 10 min, even more preferably at least 2 g / 10 min, and from the viewpoint of more stabilizing moldability, preferably at most 20 g / 10 min, more preferably Is 10 g / 10 min or less, more preferably 7 g / 10 min or less.

The polyolefin resin composition (A) according to the present embodiment, that is, the content of the polyolefin in the heat seal layer 103 is preferably 50% by mass or more when the entire polyolefin resin composition (A) is 100% by mass. It is 100% by mass or less, more preferably 70% by mass or more and 100% by mass or less, further preferably 90% by mass or more and 100% by mass or less, particularly preferably 95% by mass or more and 100% by mass or less. Thereby, the balance between the adhesiveness to the biaxially stretched film layer 101 and the heat sealing property can be further improved.
In addition, the content of the polyolefin-based resin composition (A) according to the present embodiment, that is, the content of the olefin-based elastomer in the heat seal layer 103 is assuming that the content of the polyolefin contained in the biaxially stretched film layer 101 is 100% by mass. It is preferably from 10% by mass to 50% by mass, more preferably from 15% by mass to 45% by mass, and still more preferably from 20% by mass to 40% by mass.

(Other components)
The polyolefin-based resin composition (A) constituting the heat seal layer 103 according to the present embodiment includes, as necessary, a tackifier, a heat stabilizer, a weather stabilizer, an antioxidant, an ultraviolet absorber, a lubricant, Various additives such as a slip agent, a nucleating agent, an antiblocking agent, an antistatic agent, an antifogging agent, a pigment, a dye, an inorganic or organic filler, and the like may be added within a range that does not impair the purpose of the present embodiment. In particular, the heat seal layer 103 according to the present embodiment preferably contains an anti-blocking agent from the viewpoint of improving the blocking resistance of the food packaging film 100 according to the present embodiment.
Examples of the anti-blocking agent include talc, silica, clay, calcium carbonate, synthetic zeolite, starch, aluminum oxide, acrylic resin, methacrylic resin, silicone resin, polytetrafluoroethylene resin and the like.

Further, from the viewpoint of improving the heat sealing property of the heat seal layer 103, it is preferable that the heat seal layer 103 does not substantially contain a tackifier. More specifically, the content of the tackifier in the heat seal layer 103 is preferably equal to or less than 0.5% by mass, more preferably equal to or less than 0.1% by mass, and still more preferably equal to or less than 0.01% by mass. Preferably, it is 0% by mass.
Here, the tackifier is a resinous substance having the property of imparting tackiness, which is generally manufactured and sold as a tackifier.
Such tackifiers include, for example, chroman resins such as chroman / indene resins; phenolic resins such as phenol / formaldehyde resins and xylene / formaldehyde resins; terpenes / phenolic resins; terpene resins (α, β-pinene resins) ), Terpene resins such as aromatic modified terpene resins and hydrogenated terpene resins; synthetic polyterpene resins, aromatic hydrocarbon resins, aliphatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic and alicyclic resins Petroleum hydrocarbon resins such as petroleum-based petroleum resins, aliphatic / aromatic petroleum resins, unsaturated hydrocarbon polymers and hydrocarbon-based tackifying resins; hydrogenated products of the above petroleum-based hydrocarbon resins (hydrogenated petroleum-based carbon Rosin pentaerythritol ester, rosin glycerin ester, hydrogenated rosin And rosin resins such as hydrogenated rosin esters, special rosin esters and rosin tackifiers.

(Method for Preparing Polyolefin Resin Composition (A))
The polyolefin-based resin composition (A) according to the embodiment is, for example, mixed with a dry blend, a tumbler mixer, a Banbury mixer, a single-screw extruder, a twin-screw extruder, a high-speed twin-screw extruder, a hot roll, and the like. Alternatively, it can be prepared by melting and kneading.

[Surface layer]
The food packaging film 100 according to the present embodiment has a surface opposite to the surface on which the heat seal layer 103 of the biaxially stretched film layer 101 is provided as shown in FIG. 2 in order to improve the printability of the surface. It is preferable to further include a surface layer 105.
The surface layer 105 is preferably provided on the outermost layer of the food packaging film 100 according to the present embodiment, from the viewpoint of improving the printability of the food packaging film 100.

  Further, it is preferable that the surface layer 105 is provided so as to be in direct contact with the surface of the biaxially stretched film layer 101. Thereby, the manufacturing process of the food packaging film 100 can be simplified.

In the food packaging film 100, the thickness of the surface layer 105 is preferably 0.1 μm or more and 10 μm or less, more preferably 0.2 μm or more and 9 μm or less, further preferably 0.5 μm or more and 8 μm or less, and particularly preferably 1 μm or more and 8 μm or less. It is. Here, the thickness of the surface layer 105 refers to the thickness of the surface layer 105 provided on one surface of the biaxially stretched film layer 101.
When the thickness of the surface layer 105 is equal to or more than the lower limit, the printability of the food packaging film 100 can be further improved.
When the thickness of the surface layer 105 is equal to or less than the upper limit, the blocking property and the slip property required at the time of printing can be further improved.
That is, by providing the surface layer 105 so as to be in direct contact with the surface of the biaxially stretched film layer 101, the manufacturing process of the food packaging film 100 can be simplified.

  In the food packaging film 100, the surface layer 105 is preferably a single layer. Thereby, the manufacturing process of the food packaging film 100 can be further simplified.

  The surface layer 105 is preferably formed by being biaxially stretched at the same time as the film in a state before the biaxially stretched film layer 101 is biaxially stretched. Thereby, since the food packaging film 100 can be produced using a molding method such as a co-extrusion molding method, that is, a laminated film produced by a single molding, the manufacturing process of the food packaging film 100 is further simplified. can do. Therefore, it is preferable that the surface layer 105 is biaxially stretched.

  The surface layer 105 may be subjected to a surface treatment from the viewpoint of improving the printability of the food packaging film 100. Specifically, a surface activation treatment such as a corona treatment, a flame treatment, a plasma treatment, a primer coating treatment, and an ozone treatment may be performed.

(Polyolefin)
The surface layer 105 according to this embodiment is made of, for example, a polyolefin-based resin composition (B) containing a polyolefin. Examples of the polyolefin constituting the surface layer 105 include homopolymers or copolymers of α-olefins such as ethylene, propylene, butene-1, hexene-1, 4-methyl-pentene-1, and octene-1; Low-density polyethylene; Linear low-density polyethylene (LLDPE); High-density polyethylene; Polypropylene; Random copolymer of propylene and α-olefin having 2 to 10 carbon atoms; Ethylene / vinyl acetate copolymer (EVA) An ionomer resin and the like.
Among these, as the polyolefin constituting the surface layer 105, homopolypropylene and propylene and α having at least 2 and at most 10 carbon atoms are preferable in terms of excellent balance between adhesiveness with the biaxially stretched film layer 101 and printability. -At least one selected from random copolymers with olefins is preferred.

The propylene / α-olefin random copolymer according to the present embodiment is a random copolymer of propylene and an α-olefin (however, the α-olefin is not propylene). Examples of the α-olefin include ethylene. , 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene and the like. These copolymers may be used alone or as a mixture of two or more.
Among propylene / α-olefin random copolymers, propylene / ethylene random copolymer, propylene / ethylene / 1-butene random copolymer, and propylene / 1-butene random copolymer are preferable.

  The melting point of the polyolefin constituting the surface layer 105 according to the present embodiment is preferably in the range of 90 ° C to 175 ° C, more preferably 95 ° C to 170 ° C, and still more preferably 100 ° C to 167 ° C. When the melting point of the polyolefin is equal to or higher than the lower limit, stickiness on the surface of the surface layer 105 can be suppressed, and the blocking resistance of the food packaging film 100 can be improved.

  In accordance with ASTM D1238, the melt flow rate (MFR) of the polyolefin constituting the surface layer 105 according to the present embodiment, which is measured under the conditions of 230 ° C. and a load of 2.16 kg, is preferably from the viewpoint of fluidity and moldability. Is at least 0.5 g / 10 min, more preferably at least 1 g / 10 min, even more preferably at least 2 g / 10 min, and from the viewpoint of more stabilizing moldability, preferably at most 20 g / 10 min, more preferably It is 10 g / 10 minutes or less, more preferably 7 g / 10 minutes or less.

  The polyolefin resin composition (B) according to the present embodiment, that is, the content of the polyolefin in the surface layer 105 is preferably 50% by mass or more and 100% by mass when the entire polyolefin resin composition (B) is 100% by mass. % By mass, more preferably from 70% by mass to 100% by mass, still more preferably from 90% by mass to 100% by mass, particularly preferably from 95% by mass to 100% by mass. Thereby, the balance between the adhesiveness to the biaxially stretched film layer 101 and the printability can be further improved.

(Other components)
The polyolefin-based resin composition (B) constituting the surface layer 105 according to the present embodiment may contain a tackifier, a heat stabilizer, a weather stabilizer, an antioxidant, an ultraviolet absorber, a lubricant, a slip, if necessary. Various additives such as an agent, a nucleating agent, an anti-blocking agent, an antistatic agent, an anti-fogging agent, a pigment, a dye, and an inorganic or organic filler may be added within a range that does not impair the purpose of the present embodiment.
In particular, the surface layer 105 according to the present embodiment preferably contains an anti-blocking agent from the viewpoint of improving the blocking resistance of the food packaging film 100 according to the present embodiment.
As the antiblocking agent, for example, those similar to the antiblocking agent used for the heat seal layer 103 described above can be mentioned.

(Preparation method of polyolefin resin composition (B))
The polyolefin-based resin composition (B) according to the present embodiment is, for example, mixed with a dry blend, a tumbler mixer, a Banbury mixer, a single-screw extruder, a twin-screw extruder, a high-speed twin-screw extruder, a hot roll, and the like. Alternatively, it can be prepared by melting and kneading.

<Production method of food packaging film>
The food packaging film 100 according to this embodiment includes, for example, a resin composition (P) for forming a biaxially stretched film layer 101 and a polyolefin-based resin composition for forming a heat seal layer 103 as necessary. A product obtained by co-extruding the product (A) and the polyolefin-based resin composition (B) for forming the surface layer 105 into a film is formed by a known simultaneous biaxial stretching method or sequential biaxial stretching method. It can be obtained by biaxially stretching using a biaxially stretched film production method such as the method.
The molding apparatus and molding conditions are not particularly limited, and conventionally known molding apparatuses and molding conditions can be employed. As a molding device, a T-die extruder, a multilayer T-die extruder, an inflation molding machine, a multilayer inflation molding machine, or the like can be used. For the biaxial stretching conditions, for example, known OPP film manufacturing conditions can be adopted. More specifically, in the sequential biaxial stretching method, for example, the longitudinal stretching temperature is 100 ° C. to 145 ° C., the longitudinal stretching ratio is in the range of 4.5 to 6 times, the transverse stretching temperature is 130 ° C. to 190 ° C., and the transverse stretching is performed. The magnification may be in the range of 9 to 11 times.
In addition, the food packaging film 100 according to the present embodiment is obtained by separately forming the biaxially stretched film layer 101, the heat seal layer 103 and the surface layer 105 as necessary, laminating these layers, and performing heat molding. Can also be obtained by

<Uses of food packaging film>
The food packaging film 100 according to the present embodiment can be suitably used as a film constituting a food packaging body. The food package according to the present embodiment is, for example, a packaging bag itself used for storing food or a package in which food is stored. Further, the food packaging film according to the present embodiment may use the food packaging film 100 for a part thereof depending on the use, or may use the food packaging film 100 for the whole food packaging material. .

The food packaging film 100 according to the present embodiment is preferably used for an outer packaging bag that requires a water vapor barrier property.
Further, when the food packaging film 100 according to the present embodiment is used for an integrated package composed of food, an individual packaging bag for individually packaging food, and an outer packaging bag for packaging a plurality of individual packaging bags, It is preferable to use the packaging film 100 for an outer packaging bag in which a water vapor barrier property is required in an integrated package. Thus, an integrated package having a sufficient water vapor barrier property can be obtained.

  The embodiments of the present invention have been described with reference to the drawings. However, these are merely examples of the present invention, and various configurations other than those described above can be adopted.

  Hereinafter, the present embodiment will be described in detail with reference to examples and comparative examples. Note that the present embodiment is not limited to the description of these examples.

1. Raw Materials Raw materials used in Examples and Comparative Examples are shown below.
(1) Propylene polymer PP1: high stereoregularity propylene homopolymer (MFR: 3 g / 10 min, melting point: 167 ° C., isotactic mesopentad fraction (mmmm): 98.5%)
PP2: propylene homopolymer (MFR: 3 g / 10 min, melting point: 161 ° C., isotactic mesopentad fraction (mmmm): 92%)

2. Measurement and evaluation method (1) Isotactic mesopentad fraction of propylene polymer (mmmm)
The measurement of the isotactic mesopentad fraction (mesopentad fraction, (mmmm)) was performed using ¹³ C-NMR. The isotactic mesopentad fraction was determined according to the method described in Zambelli et al., Macromolecules, vol. 6, p. 925 (1973). C. Calculated according to the method described by Randall in “Polymer Sequence Distribution”, Chapter 2 (1977) (Academic Press, New York).

(2) MFR of propylene polymer
According to ASTM D1238, it was measured at 230 ° C. under a load of 2.16 kg.

(3) Differential Scanning Calorimetry A test piece of about 5.0 mg was cut out from the food packaging films obtained in Examples and Comparative Examples. Next, the sample is heated from −50 ° C. to 250 ° C. at a heating rate of 10 ° C./min under a nitrogen stream using a differential scanning calorimeter (product name: Q200 DSC TA Instruments). The first differential scanning calorimetry (1stRun) consisting of a process, an isothermal process of keeping at 250 ° C. for 10 minutes, and a process of decreasing the temperature from 250 ° C. to −50 ° C. at a temperature decreasing rate of 10 ° C./min; The second differential scanning calorimetry (2ndRun), which is a process of raising the temperature from −50 ° C. to 250 ° C./min, was continuously performed.
From the obtained DSC curve, the calorie (J / g) of endothermic peak A, the presence or absence of endothermic peaks B and C, and the ratio of peak height C of endothermic peak C to peak height B of endothermic peak B (C / B) , The presence or absence of an exothermic peak D, and the half width of the exothermic peak D were determined.

(4) Tensile Modulus A 15 mm × 15 cm test piece was cut out from the food packaging films obtained in Examples and Comparative Examples. Then, using a tensile tester manufactured by Orientec Co., in accordance with JIS K7127 (1999), in the MD direction of the test piece at a measurement temperature of 23 ± 2 ° C., 50 ± 5% RH, and a tensile speed of 5 mm / min. tensile modulus T ₁ and TD direction tensile modulus T ₂ were measured.

(5) Evaluation of thickness unevenness Using a sequential biaxial stretching machine, a biaxially oriented polypropylene-based film having a width of about 1 m in a direction perpendicular to the flow direction was produced by the method described below. Ten films were stacked and divided into nine equal parts in the direction of 1 m width, and the thickness at eight places except both ends was measured. X was calculated by applying the measured value to the following equation. The smaller the X, the better the thickness unevenness.
X = (maximum thickness−minimum thickness) / (maximum thickness + minimum thickness)
Next, the thickness unevenness of the food packaging film was evaluated according to the following criteria.
◎: X is less than 2% Δ: X is 2% or more and less than 4% Δ: X is 4% or more and less than 6% X: The value of X is 6% or more

(6) Evaluation of stretch unevenness The appearance of the stretched film was confirmed, and it was visually checked whether or not a clearly thick portion remained in portions except for 150 mm at both ends. If the thick portion remains, it means that stretching unevenness has occurred, and the physical properties of the film are not stable.
：: No stretching unevenness ×: Stretching unevenness

(7) Water Vapor Barrier Property The food packaging film was folded so that the heat seal layer was on the inner surface, and heat sealed on two sides to form a bag. Thereafter, calcium chloride was added as the content. Next, the other side was heat-sealed to produce a bag having a surface area of 0.01 m ² . Next, the obtained bag was stored at 40 ° C. and a humidity of 90% RH for 72 hours. The weight of calcium chloride before and after the storage were measured, water vapor permeability from the difference a ^{(g / (m 2 · 24h} )) was calculated.
Here, a heat seal layer was formed on one surface of the biaxially stretched polypropylene-based films obtained in the examples and comparative examples.
Next, the water vapor barrier property of the packaging film for food was evaluated according to the following criteria.
◎◎: water vapor permeability of 5.0g ^/ (m 2 · 24h) or less ◎: water vapor permeability of 5.0g ^/ (m 2 · 24h) exceeding 5.5g ^/ (m 2 · 24h) or less ○: water vapor permeability degrees is 5.5g ^/ (m 2 · 24h) exceeding 6.0g ^/ (m 2 · 24h) or less ×: water vapor permeability is 6.0g ^/ (m 2 · 24h) exceeded

[Examples 1 to 7 and Comparative Examples 1 to 3]
Each of the biaxially stretched polypropylene-based films was extrusion-molded with the composition shown in Table 1 and then subjected to biaxial stretching treatment to produce food packaging films, and each evaluation was performed. Extrusion molding conditions and biaxial stretching treatment conditions are as follows.
Extruder: 60 mmφ multilayer T-die extruder (screw: L / D = 27, manufactured by Screw Seiki)
Extrusion setting temperature: 230-250 ° C, processing speed: 20 m / min (winding speed)
Longitudinal stretching temperature: 115-130 ° C
Vertical stretching ratio: 5 times Horizontal stretching temperature: 140 to 175 ° C
Lateral stretching ratio: 10 times

  Each of the food packaging films of the examples had smaller thickness unevenness than the food packaging film of the comparative example. In addition, when the food packaging film of the example was used, a food packaging having improved water vapor barrier properties could be obtained as compared with the case of using the food packaging film of the comparative example.

Reference Signs List 100 Food packaging film 101 Biaxially stretched film layer 103 Heat seal layer 105 Surface layer

Claims (16)

A film for packaging food,
With a biaxially stretched film layer containing a propylene-based polymer,
For the biaxially stretched film layer, using a differential scanning calorimeter,
From the process of raising the temperature from −50 ° C. to 250 ° C. at a rate of 10 ° C./min, the isothermal process of maintaining the temperature at 250 ° C. for 10 minutes, and the process of decreasing the temperature from 250 ° C. to −50 ° C. at a rate of 10 ° C./min. The first differential scanning calorimetry (1stRun)
A second differential scanning calorimetry (2ndRun) comprising a process of raising the temperature from -50 ° C to 250 ° C at a rate of 10 ° C / min,
When I went to
In the DSC curve 2 obtained by the second differential scanning calorimetry, an endothermic peak A is observed in a range of 150 ° C. or more and 180 ° C. or less,
A food packaging film having a heat quantity of the endothermic peak A of 95 J / g or more and 120 J / g or less. The food packaging film according to claim 1,
In the DSC curve 1 obtained by the first differential scanning calorimetry, a food package in which an endothermic peak B is observed in a range of 150 ° C or more and 165 ° C or less and an endothermic peak C is observed in a range of 165 ° C or more and 180 ° C or less. the film. The food packaging film according to claim 2,
A food packaging film wherein the ratio (C / B) of the peak height C of the endothermic peak C to the peak height B of the endothermic peak B is 1.0 or more and 3.0 or less. The food packaging film according to any one of claims 1 to 3,
A food packaging film in which an exothermic peak D is observed in a range of 100 ° C. or more and 130 ° C. or less in a DSC curve 1 obtained by the first differential scanning calorimetry. The food packaging film according to claim 4,
A food packaging film having a half width of the exothermic peak D of 2.0 ° C. or more and 6.0 ° C. or less. The food packaging film according to any one of claims 1 to 5,
According to JIS K7127 (1999), the tensile strength in the MD direction of the food packaging film is measured using a tensile tester at a measurement temperature of 23 ± 2 ° C., 50 ± 5% RH, and a tensile speed of 5 mm / min. A food packaging film having a total value (T ₁ + T ₂ ) of the elastic modulus T ₁ and the tensile elastic modulus T _{2 in the} TD direction of 5,000 MPa or more and 10,000 MPa or less. The food packaging film according to any one of claims 1 to 6,
A food packaging film further comprising a heat seal layer on at least one surface of the biaxially stretched film layer. The food packaging film according to claim 7,
The food packaging film, wherein the heat seal layer is provided so as to directly contact the one surface of the biaxially stretched film layer. The food packaging film according to claim 7 or 8,
A food packaging film in which the heat sealing layer contains one or more selected from homopolypropylene and a random copolymer of propylene and an α-olefin having 2 to 10 carbon atoms. The food packaging film according to any one of claims 1 to 9,
A food packaging film further comprising a surface layer on one surface of the biaxially stretched film layer. The food packaging film according to claim 10,
The surface layer is a food packaging film containing an anti-blocking agent. The food packaging film according to claim 10 or 11,
A food packaging film, wherein the surface layer comprises one or two or more selected from homopolypropylene and a random copolymer of propylene and an α-olefin having 2 to 10 carbon atoms. The food packaging film according to any one of claims 1 to 12,
A food packaging film, wherein the content of the tackifier contained in the biaxially stretched film layer is 10% by mass or less when the whole of the biaxially stretched film layer is 100% by mass. The food packaging film according to any one of claims 1 to 13,
Food packaging film water vapor transmission rate as measured by the following method is 6.0g ^/ (m 2 · 24h) or less.
(Measuring method)
The food packaging film is folded back so that the heat sealing layer is on the inner surface, and the two sides are heat sealed to form a bag. Thereafter, calcium chloride is added as the contents. Next, the other side is heat-sealed to prepare a bag so that the surface area becomes 0.01 m ² . Next, the obtained bag is stored at 40 ° C. and a humidity of 90% RH for 72 hours. Measuring the weight of calcium chloride before and after storage, it calculates a water vapor transmission rate of ^{(g / (m 2 · 24h} )) from the difference. The food packaging film according to any one of claims 1 to 14,
Food packaging film used for outer packaging bags.   A food package using the food packaging film according to any one of claims 1 to 15.

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