JP2019006463A - Food product packaging film and food product packaging body - Google Patents

Abstract

To provide a food product packaging film having sufficient steam barrier property and transparency, and capable of achieving a food product packaging body excellent in balance of heat seal property and antistatic property.SOLUTION: A food product packaging film 100 of the invention is a film for packaging a food product and comprises: a biaxial oriented film layer 101 including a propylene polymer and polyethylene; and a heat seal layer 103 provided on one face of the biaxial oriented film layer 101, in which a content of polyethylene included in the biaxial oriented film layer 101 is 0.5 mass% or more and 25 mass% or less, when a total amount of the propylene polymer and polyethylene included in the biaxial oriented film layer 101 is 100 mass%.SELECTED DRAWING: Figure 1

Description

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

  Biaxially stretched polypropylene film (hereinafter also referred to as OPP film) is excellent in performance balance such as processability, water vapor barrier property, transparency, mechanical strength and rigidity, and is used as a packaging film for packaging foods. It has been.

  As a technique regarding the packaging film for foods using such an OPP film, the thing as described in patent document 1 (Unexamined-Japanese-Patent No. 2008-73926) and patent document 2 (Unexamined-Japanese-Patent No. 2004-82499) is mentioned, for example. It is done.

In Patent Document 1, the melting point is 155 ° C. on one side of 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). It has a layer made of a propylene / α-olefin random copolymer (C) having a melting point of 125 to 145 ° C. through a layer made of the above propylene polymer (B), and other than the above biaxially stretched film A biaxially stretched multilayer polypropylene film characterized by having a layer made of a propylene-based polymer (E) on one side is described.
Patent Document 1 describes that a biaxially stretched multilayer polypropylene film having the above-described configuration can suppress the seepage of petroleum resin or the like onto the film surface and is excellent in laminate strength and moisture resistance.

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

JP 2008-73926 A JP 2004-82499 A

Although the OPP film has sufficient water vapor barrier properties and transparency, it has a high surface resistivity and is inferior in antistatic properties. Therefore, when the OPP film is used for a food packaging body such as a food packaging bag, it is necessary to increase the addition amount of the antistatic agent. By increasing the amount of the antistatic agent added to the OPP film, the surface specific resistance of the resulting food packaging body is lowered, and the antistatic property can be improved.
However, when the amount of the antistatic agent added to the OPP film is increased, the antistatic agent bleeds out to the film surface, and heat sealability may be deteriorated or transparency may be deteriorated. Therefore, the OPP film used for the food packaging has room for improvement in terms of improving the antistatic property while suppressing the addition amount of the antistatic agent.

  The present invention has been made in view of the above circumstances, and has a sufficient water vapor barrier property and transparency, and a food packaging film capable of realizing a food packaging body having an excellent balance of heat sealability and antistatic properties. Is to provide.

  The present inventors diligently studied to solve the above problems. As a result, by mixing polyethylene with the propylene polymer at a specific ratio, the surface resistivity of the film can be effectively reduced without increasing the addition amount of the antistatic agent while satisfying sufficient water vapor barrier properties and transparency. It has been found that the heat sealability can be improved while reducing the temperature, and the present invention has been achieved.

  That is, according to the present invention, the following food packaging film and food packaging are provided.

[1]
A film for packaging food,
A biaxially stretched film layer comprising a propylene polymer and polyethylene;
A heat seal layer provided on one surface of the biaxially stretched film layer;
With
When the total amount of the propylene polymer and the polyethylene contained in the biaxially stretched film layer is 100% by mass, the content of the polyethylene contained in the biaxially stretched film layer is 0.5% by mass or more and 25% by mass or more. A food packaging film having a mass% or less.
[2]
In the food packaging film according to the above [1],
According to JIS K7127 (1999), the tensile force in the MD direction of the food packaging film is measured using a tensile tester under the conditions of a measurement temperature of 23 ± 2 ° C., 50 ± 5% RH, and a tensile speed of 300 mm / min. A food packaging film having a total value (T ₁ + T ₂ ) of an elastic modulus T ₁ and a tensile elastic modulus T _{2 in the} TD direction of 3000 MPa or more and 6000 MPa or less.
[3]
In the food packaging film according to the above [1] or [2],
A food packaging film having a heat shrinkage rate of 4.5% or less in the TD direction of the food packaging film when heated at 120 ° C. for 15 minutes.
[4]
In the food packaging film according to any one of [1] to [3] above,
When the heat shrinkage rate in the TD direction and the heat shrinkage rate in the MD direction of the food packaging film when heat-treated at 120 ° C. for 15 minutes are respectively X _TD [%] and X _MD [%],
X _TD -X _MD food packaging film is not more than 5.0% more than -5.0%.
[5]
In the food packaging film according to any one of the above [1] to [4],
A packaging film for food, further comprising a surface layer on a surface opposite to the surface on which the heat seal layer of the biaxially stretched film layer is provided.
[6]
In the food packaging film according to the above [5],
The said surface layer is a food packaging film containing 1 type, or 2 or more types selected from the random copolymer of homopolypropylene and propylene, and C2-C10 alpha-olefin.
[7]
In the food packaging film according to any one of [1] to [6] above,
The food sealing film is provided such that the heat seal layer is in direct contact with the one surface of the biaxially stretched film layer.
[8]
In the food packaging film according to any one of the above [1] to [7],
Food packaging film used for exterior packaging bags.
[9]
In the food packaging film according to any one of the above [1] to [8],
A food packaging film, wherein the heat seal layer includes one or more selected from a random copolymer of homopolypropylene and propylene and an α-olefin having 2 to 10 carbon atoms.
[10]
A food packaging body using the food packaging film according to any one of [1] to [9].

  ADVANTAGE OF THE INVENTION According to this invention, while having sufficient water vapor | steam barrier property and transparency, the food packaging film which can implement | achieve the food packaging body excellent also in the balance of heat-sealing property and antistatic property can be provided.

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

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the figure is a schematic diagram and does not match the actual dimensional ratio. In addition, "-" between the numbers in a sentence represents the following from the above, unless there is particular notice.

<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.
A food packaging film 100 according to this embodiment is a film for packaging food, and is provided on one surface of a biaxially stretched film layer 101 containing a propylene polymer and polyethylene and a biaxially stretched film layer 101. When the total content of the propylene polymer and polyethylene contained in the biaxially stretched film layer 101 is 100% by mass, the polyethylene content contained in the biaxially stretched film layer 101 is 100% by mass. 0.5 mass% or more and 25 mass% or less.

As described above, the OPP film has a sufficient water vapor barrier property and transparency, but has a high surface resistivity and is inferior in antistatic property. Therefore, when the OPP film is used for a food packaging body such as a food packaging bag, it is necessary to increase the addition amount of the antistatic agent. By increasing the amount of the antistatic agent added to the OPP film, the surface specific resistance of the resulting food packaging body is lowered, and the antistatic property can be improved.
However, when the amount of the antistatic agent added to the OPP film is increased, the antistatic agent bleeds out to the film surface, and heat sealability may be deteriorated or transparency may be deteriorated. Therefore, the OPP film used for the food packaging has room for improvement in terms of improving the antistatic property while suppressing the addition amount of the antistatic agent.

The present inventors diligently studied to solve the above problems. As a result, by mixing polyethylene with the propylene polymer at a specific ratio, the surface resistivity of the film can be effectively reduced without increasing the addition amount of the antistatic agent while satisfying sufficient water vapor barrier properties and transparency. It has been found that the heat sealability can be improved while being able to lower. Here, since the propylene polymer is a thermally decomposable polymer and polyethylene is a thermally cross-linked polymer, when both are melt-mixed, a gel component is likely to be generated, and fish eyes and the like are formed on the resulting molded product. It was thought to be easy to generate. Therefore, in the field of resin processing, mixing propylene polymer with polyethylene has not been actively performed.
However, according to the study by the present inventors, by mixing polyethylene with a specific ratio in a propylene polymer, the surface resistivity of the film can be effectively reduced without increasing the addition amount of the antistatic agent. As a result, the antistatic property of the film is improved, and an unexpected effect that a food packaging body having an excellent balance of heat sealability and antistatic property while satisfying sufficient water vapor barrier property and transparency can be obtained. It was found that can be obtained.
That is, according to the food packaging film 100 according to the present embodiment, by providing a biaxially stretched film layer containing a propylene polymer and polyethylene at a specific ratio, it has sufficient water vapor barrier properties and transparency and is heat sealed. Food package excellent in the balance between antistatic properties and antistatic properties. Moreover, the food packaging film 100 according to the present embodiment is excellent in antistatic properties on the surface. Therefore, it is possible to improve the printability of the surface of the food packaging body, or to prevent foreign matters such as dust from adhering to the surface of the food packaging body.
As described above, according to the present embodiment, a food packaging body that can realize a food packaging body having sufficient water vapor barrier properties and transparency, and can also realize a food packaging body that has an excellent balance of heat sealability and antistatic properties. A packaging film 100 can be provided.

  Here, the food packaging body produced using the food packaging film 100 according to the present embodiment exhibits sufficient performance for water vapor barrier properties. Therefore, it can be particularly suitably used as a film constituting a food package for packaging foods (for example, dried foods) that require water vapor barrier properties but not so much oxygen barrier properties.

The food packaging film 100 according to this embodiment is measured in accordance with JIS K7127 (1999) using a tensile tester under the conditions of a measurement temperature of 23 ± 2 ° C., 50 ± 5% RH, and a tensile speed of 300 mm / min. preferably the sum of the MD direction of the tensile modulus _{T 1} and TD direction of the tensile modulus _{T 2} is _(T 1 + _{T 2)} is less than 6000MPa or more 3000MPa that, more preferably less than 3500 MPa 5800MPa, More preferably, it is 4000 MPa or more and 5700 MPa or less.
When the MD direction of the tensile modulus T ₁ and the total value of the tensile modulus T ₂ of the TD direction (T 1 _{+ T 2)} satisfies the above range, the stiffness of the food packaging film 100 according to this embodiment further good As a result, it is possible to suppress misalignment of the film at the time of heat sealing, and to prevent the occurrence of poor sealing. 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)} satisfies the above range, the water vapor barrier properties of the food packaging film 100 according to this embodiment And the suitability for packaging can be further improved.
Such tensile elastic modulus is a substitute value for quantitatively measuring the stiffness of the film. For example, the content ratio of polyethylene and propylene polymer contained in the biaxially stretched film layer 101 and various conditions during stretching are adjusted. In addition, this can be achieved by adjusting the constituent materials and thicknesses of the heat seal layer 103 and the surface layer 105. More specifically, the presence / absence and ratio of functional groups copolymerized with the propylene polymer contained in the biaxially stretched film layer 101, the stretching ratio during stretching, the temperature during stretching, the temperature and time of heat treatment, etc. By appropriately adjusting the elastic modulus, the tensile elastic modulus of the food packaging film 100 can also be adjusted.

In the food packaging film 100 according to this embodiment, the heat shrinkage rate in the TD direction when heat-treated at 120 ° C. for 15 minutes is preferably 4.5% or less, and more preferably 4.2% or less. preferable.
Thereby, the position shift of the seal part in the food packaging body, generation of wrinkles in the food packaging body, breakage of the food packaging body itself, and the like can be more effectively suppressed.
Such a heat shrinkage rate can be achieved, for example, by adjusting the content ratio of the propylene polymer and polyethylene contained in the biaxially stretched film layer 101, the constituent materials and thicknesses of the heat seal layer 103 and the surface layer 105, and the like.

In the food packaging film 100 according to the present embodiment, the heat shrinkage rate in the TD direction and the heat shrinkage rate in the MD direction when heat-treated at 120 ° C. for 15 minutes were set to X _TD [%] and X _MD [%], respectively. _when, it is preferable that X TD _{-X MD} is less than 5.0% or more -5.0%, more preferably 3.0% or less than -4.0%, -3.5% to 2 It is more preferably 0.0% or less, and particularly preferably −3.0% or more and 1.0% or less.
When X _TD -X _MD is within the above range, occurrence of displacement and food packaging body wrinkles of the seal portion of the food packaging body, is possible to more effectively suppress the damage of food packaging itself it can.
Such X _TD -X _MD, for example, accomplished by adjusting two propylene polymer and the content of the polyethylene shaft contained in the stretched film layer 101, the material and thickness of the heat seal layer 103 and the surface layer 105 or the like it can.
Further, _X TD [%] of the food packaging film 100 according to this embodiment and the _X MD [%] is calculated by the following method.
First, a 10 cm × 10 cm test piece is cut out from the food packaging film 100, and the test piece is heat-treated at 120 ° C. for 15 minutes. Next, when the length in the TD direction of the test piece after the heat treatment is TD ₁ [cm] and the length in the MD direction of the test piece after the heat treatment is MD ₁ [cm], X _TD [%] is It is calculated by 100 × (10−TD ₁ ) / 10, and X _MD [%] is calculated by 100 × (10−MD ₁ ) / 10.

The food packaging body produced using the food packaging film 100 according to this embodiment has a sufficient water vapor barrier property. In the food packaging film 100, from the viewpoint of stably obtaining a food packaging excellent in water vapor barrier properties, the water vapor permeability measured by the following method is 8.0 g / (m ² · 24 h) or less. Is more preferably 7.0 g / (m ² · 24 h) or less, and particularly preferably 6.5 g / (m ² · 24 h) or less.
(Measuring method)
The food packaging film 100 is folded so that the heat seal layer 103 is on the inner surface, and the two sides are heat sealed to form a bag. Then, calcium chloride is added as the contents. Next, the other side is heat-sealed to produce a bag so that the surface area becomes 0.01 m ² . Next, the obtained bag is stored for 72 hours under the conditions of 40 ° C. and humidity 90% RH. The weight of calcium chloride before and after storage is measured, and the water vapor permeability (g / (m ² · 24h)) is calculated from the difference.
Such water vapor permeability can be achieved, for example, by adjusting the content ratio of the propylene polymer and polyethylene contained in the biaxially stretched film layer 101, the constituent materials and thicknesses of the heat seal layer 103 and the surface layer 105, and the like.

The food packaging film 100 according to this embodiment is excellent in heat sealability. In the food packaging body produced using the food packaging film 100, from the viewpoint of further improving the sealing strength, the heat sealing layers 103 of the food packaging film 100 are 115 ° C., pressure 1.0 kgf, and sealing time 0.5. The heat seal strength of the part heat-sealed under the condition of seconds is preferably 2.5 N / 15 mm or more, more preferably 3.0 N / 15 mm or more, and particularly preferably 3.5 N / 15 mm or more.
Here, the heat seal strength can be measured by the following method. First, a laminated film is obtained by thermally fusing the heat seal layers 103 of the two food packaging films 100 under the conditions of 115 ° C., a pressure of 1.0 kgf, and a seal time of 0.5 seconds. Next, the two food packaging films 100 are peeled off under the conditions of 15 mm width, 90 degree peeling, and peeling speed of 300 mm / min, and the peel strength at that time is defined as heat seal strength.
Such heat seal strength can be achieved, for example, by adjusting the content ratio of the propylene polymer and polyethylene contained in the biaxially stretched film layer 101, the constituent materials and thicknesses of the heat seal layer 103 and the surface layer 105, and the like.

In the food packaging film 100 according to this embodiment, it is preferable that the haze measured using a haze meter is less than 2.5% in accordance with JIS K7105 from the viewpoint of improving transparency. More preferably, it is less than 0.0%.
Such haze can be achieved, for example, by adjusting the content ratio of the propylene polymer and polyethylene contained in the biaxially stretched film layer 101, the constituent materials and thicknesses of the heat seal layer 103 and the surface layer 105, and the like.

In addition, from the viewpoint of improving the antistatic property on both surfaces of the food packaging film 100 according to the present embodiment, in accordance with JIS C2139, using a digital ultrahigh resistance microammeter, 20 ± 2 ° C., 50 The surface specific resistance of the sample after storage for 24 hours or more under the condition of ± 5% RH is preferably 1.0 × 10 ¹⁴ Ω or less, more preferably 5.0 × 10 ¹³ Ω or less. It is particularly preferably 0 × 10 ¹² Ω or less.
Such surface specific resistance can be achieved by adjusting, for example, the content ratio of polyethylene and propylene polymer contained in the biaxially stretched film layer 101, the constituent materials and thicknesses of the heat seal layer 103 and the surface layer 105, and the like.

The thickness of the food packaging film 100 according to this embodiment is not particularly limited, but can be arbitrarily set according to desired purposes such as water vapor barrier properties, cost, mechanical strength, transparency, etc., but is not particularly limited. Usually, 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 of bag-making properties, mechanical properties, handleability, appearance, transparency, moldability, lightness, etc. is more excellent.

  Hereinafter, each layer which comprises the food packaging film 100 is demonstrated.

[Biaxially stretched film layer]
The biaxially stretched film layer 101 according to this embodiment is formed, for example, by biaxially stretching a film composed of a resin composition (P) containing a propylene polymer and polyethylene.

  The biaxially stretched film layer 101 according to the present embodiment may be a single layer or a structure in which a plurality of layers composed of the resin composition (P) are laminated, but may be biaxially stretched. is necessary.

  In the food packaging film 100, the ratio of the thickness of the biaxially stretched film layer 101 to the total thickness of the food packaging film 100 is preferably 0.50 or more and 0.998 or less, more preferably 0.60. It is 0.99 or less, More preferably, it is 0.70 or more and 0.97 or less, Especially preferably, it is 0.75 or more and 0.95 or less.

(Resin composition (P))
The resin composition (P) according to this embodiment contains a propylene polymer and polyethylene.
Here, when the biaxially stretched film layer 101 contains polyethylene, the balance between the heat sealability and the antistatic property of the biaxially stretched film layer 101 can be improved.

Although the lower limit of the content of polyethylene contained in the resin composition (P), that is, the biaxially stretched film layer 101 according to the present embodiment is 0.5% by mass or more, the heat sealability and charging of the food packaging film 100 From the viewpoint of further improving the balance of prevention, when the total amount of propylene polymer and polyethylene contained in the biaxially stretched film layer 101 is 100% by mass, it is preferably 1.0% by mass or more, more preferably Is 2.0% by mass or more, particularly preferably 3.0% by mass or more.
Moreover, although the upper limit of content of the polyethylene contained in the resin composition (P) which is this embodiment, ie, the biaxially stretched film layer 101, is 25 mass% or less, the fall of the bending elasticity of the food packaging film 100 is reduced. From the viewpoint of further suppressing or further improving heat sealability, water vapor barrier properties, transparency and the like, when the total amount of propylene polymer and polyethylene contained in the biaxially stretched film layer 101 is 100% by mass, Preferably it is 20 mass% or less, More preferably, it is 15 mass% or less, Most preferably, it is 10 mass% or less.

  The total content of the propylene polymer and polyethylene contained in the resin composition (P), that is, the biaxially stretched film layer 101 according to the present embodiment is preferably when the entire resin composition (P) is 100% by mass. Is 50% by mass to 100% by mass, more preferably 70% by mass to 100% by mass, further preferably 90% by mass to 100% by mass, and particularly preferably 95% by mass to 100% by mass. Thereby, balance, such as water vapor | steam barrier property, mechanical characteristics, a handleability, an external appearance, a moldability, transparency, heat seal property, and antistatic property, can be made more favorable.

(Propylene polymer)
The resin composition (P) according to this embodiment, that is, the biaxially stretched film layer 101 contains a propylene polymer. Thereby, it becomes possible to obtain the biaxially stretched film layer 101 excellent in performance balance such as heat resistance, water vapor barrier property, transparency, mechanical properties and rigidity.
Examples of the propylene polymer according to the present embodiment include homopolypropylene, a copolymer of propylene and ethylene or an α-olefin having 4 to 20 carbon atoms. 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, 1-hexadecene, 1-octadecene, 1-eicosene and the like can be mentioned. Among these, 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 structural units derived from ethylene or an α-olefin having 4 to 20 carbon atoms is preferably 5 mol% or less, preferably 2 mol% or less when the entire propylene polymer is 100 mol%. More preferably. The propylene polymer in the biaxially stretched film layer 101 may be used alone or in combination of two or more.
Among these, homopropylene is preferable as the propylene 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. Polypropylene has a content of structural units derived from propylene of 99.0 mol% or more, preferably 99.5 mol% or more, when the total content of structural units constituting homopolypropylene is 100 mol%. Preferably it is 99.9 mol% or more, Most preferably, it is 100.0 mol%.

  The propylene 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.

  The melting point of the propylene polymer according to this embodiment is preferably 150 ° C. or higher and 170 ° C. or lower from the viewpoint of further improving the balance of heat resistance, transparency, mechanical properties, rigidity, fluidity, moldability, and the like. More preferably, it exists in the range of 155 degreeC or more and 168 degrees C or less.

  Based on ASTM D1238, the melt flow rate (MFR) of the propylene polymer according to this embodiment measured at 230 ° C. and a load of 2.16 kg is preferably 0.5 g from the viewpoint of fluidity and moldability. / 10 min or more, more preferably 1 g / 10 min or more, further preferably 2 g / 10 min or more, and from the viewpoint of further stabilizing the moldability, preferably 20 g / 10 min or less, more preferably 10 g / 10 min. Hereinafter, it is more preferably 7 g / 10 min or less.

(polyethylene)
Examples of the polyethylene according to this embodiment include high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, and ultrahigh molecular weight polyethylene. Among these, low density polyethylene and linear low density polyethylene are preferable, and linear low density polyethylene is more preferable. One type of polyethylene may be used, or two or more types may be used in combination.

  The melting point of the polyethylene according to this embodiment is preferably 95 ° C. or more and 135 ° C. or less, more preferably from the viewpoint of further improving the balance of heat resistance, transparency, mechanical properties, rigidity, fluidity, moldability, and the like. Is in the range of 100 ° C. or higher and 130 ° C. or lower.

Density polyethylene according to the present embodiment, heat resistance, transparency, mechanical properties, rigidity, from the viewpoint of even more favorable balance of such fluidity and moldability, is 900 kg / m ³ or more 965 kg / m ³ or less Preferably, 900 kg / m ³ or more and 940 kg / m ³ or less are more preferable. Here, the density of the polyethylene according to the present embodiment can be measured according to JIS K7112 (1999).

  According to ASTM D1238, the melt flow rate (MFR) of the polyethylene according to this embodiment measured under conditions of 190 ° C. and 2.16 kg load is preferably 0.5 g / 10 from the viewpoint of fluidity and moldability. Min or more, more preferably 1 g / 10 min or more, further preferably 2 g / 10 min or more, and from the viewpoint of further stabilizing the moldability, preferably 30 g / 10 min or less, more preferably 20 g / 10 min or less, More preferably, it is 10 g / 10 minutes or less.

  The method for producing polyethylene according to this embodiment is not particularly limited, and can be produced by a known method. Further, commercially available polyethylene may be used.

(Other ingredients)
In the resin composition (P) according to the present embodiment, a tackifier, a heat stabilizer, a weather stabilizer, an antioxidant, an ultraviolet absorber, a lubricant, a slip agent, a nucleating agent, and an antiblocking agent are added as necessary. Various additives such as an antistatic agent, an antifogging agent, a pigment, a dye, and an inorganic or organic filler may be added as long as the object of the present embodiment is not impaired.

(Preparation method of resin composition (P))
In the resin composition (P) according to this embodiment, for example, each component is mixed or melted by dry blending, tumbler mixer, Banbury mixer, single screw extruder, twin screw extruder, high speed twin screw extruder, hot roll, etc. -It can be prepared by kneading.

[Heat seal layer]
The food packaging film 100 according to this embodiment 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.
Moreover, it is preferable that the heat seal layer 103 is provided in the outermost layer of the food packaging film 100 according to the present embodiment from the viewpoint of making the heat sealing property of the food packaging film 100 better.

  The heat seal layer 103 is preferably provided so as to be in direct contact with the surface of the biaxially stretched film layer 101. Thereby, the manufacturing process of the packaging film 100 for foodstuffs can be simplified.

In the food packaging film 100, the thickness of the heat seal layer 103 is preferably 0.1 μm to 10 μm, more preferably 0.2 μm to 9 μm, still more preferably 0.5 μm to 8 μm, and particularly preferably 1 μm to 8 μm. 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 side of the biaxially stretched film layer 101.
When the thickness of the heat seal layer 103 is equal to or greater than the lower limit, the heat sealability of the food packaging film 100 can be further improved.
Moreover, when the thickness of the heat seal layer 103 is not more than the above upper limit value, the adhesiveness with the biaxially stretched film layer 101 is improved, and the heat seal layer 103 is formed on the biaxially stretched film layer 101 without using an adhesive. It becomes easy to laminate.
That is, since it becomes easy to provide 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 this embodiment, when the heat seal layer 103 is provided on both surfaces of the biaxially stretched film layer 101, the thickness of the heat seal layer 103 is the heat seal layer 103 provided on one surface of the biaxially stretched film layer 101. The thickness of is shown.

  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 packaging film 100 for foodstuffs can be simplified further.

  The heat seal layer 103 is preferably formed by being biaxially stretched at the same time as the film in the state before biaxial stretching of the biaxially stretched film layer 101. Thereby, since the packaging film 100 for foodstuffs can be produced using shaping | molding methods, such as a coextrusion molding method, ie, the laminated | multilayer film produced by one shaping | molding, the manufacturing process of the packaging film 100 for foods is simplified further. 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 resin composition (A) containing polyolefin. Examples of the polyolefin constituting the heat seal layer 103 include homopolymers or copolymers of α-olefins such as ethylene, propylene, butene-1, hexene-1, 4-methyl-pentene-1, and octene-1. High pressure method 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) ); Ionomer resins and the like.
Among these, as the polyolefin constituting the heat seal layer 103, homopolypropylene and propylene and the number of carbon atoms are 2 or more and 10 or less from the viewpoint of excellent balance such as adhesion to the biaxially stretched film layer 101 and heat sealability. Of these, at least one selected from random copolymers with α-olefins is preferred.

The propylene / α-olefin random copolymer according to the present embodiment is a random copolymer of propylene and α-olefin (wherein α-olefin excludes propylene). As the α-olefin, for example, ethylene 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene and the like. These copolymers may be used alone or in combination of two or more.
Among the propylene / α-olefin random copolymers, propylene / ethylene random copolymers, propylene / ethylene / 1-butene random copolymers, and propylene / 1-butene random copolymers are preferable.

The melting point of the polyolefin constituting the heat seal layer 103 according to this embodiment is preferably in the range of 60 ° C. or higher and 175 ° C. or lower, more preferably 65 ° C. or higher and 170 ° C. or lower, and further preferably 70 ° C. or higher and 167 ° C. or lower. When the melting point of the polyolefin is equal to or higher than the lower limit, the surface stickiness of the heat seal layer 103 can be suppressed, and the blocking resistance of the food packaging film 100 can be improved.
Further, when the melting point of the polyolefin is not more than the above upper limit value, the heat sealability of the food packaging film 100 can be improved.

  Based on ASTM D1238, the melt flow rate (MFR) of the polyolefin constituting the heat seal layer 103 according to this embodiment measured under the conditions of 230 ° C. and 2.16 kg load is from the viewpoint of fluidity and moldability. Preferably it is 0.5 g / 10 min or more, more preferably 1 g / 10 min or more, further preferably 2 g / 10 min or more. From the viewpoint of further stabilizing the moldability, it is preferably 20 g / 10 min or less, more preferably Is 10 g / 10 min or less, more preferably 7 g / 10 min or less.

  The polyolefin resin composition (A) according to this embodiment, that is, the polyolefin content in the heat seal layer 103 is preferably 50% by mass or more when the entire polyolefin resin composition (A) is 100% by mass. 100 mass% or less, More preferably, it is 70 mass% or more and 100 mass% or less, More preferably, it is 90 mass% or more and 100 mass% or less, Most preferably, it is 95 mass% or more and 100 mass% or less. Thereby, balance, such as adhesiveness with the biaxially stretched film layer 101, heat seal property, can be made more favorable.

(Other ingredients)
In the polyolefin resin composition (A) constituting the heat seal layer 103 according to the present embodiment, 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, and an inorganic or organic filler may be added as long as the object of the present embodiment is not impaired.

(Preparation method of polyolefin resin composition (A))
In the polyolefin resin composition (A) according to the present embodiment, for example, each component is mixed by dry blend, tumbler mixer, Banbury mixer, single screw extruder, twin screw extruder, high speed twin screw extruder, hot roll, etc. 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.
Moreover, it is preferable that the surface layer 105 is provided in 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.

  The surface layer 105 is preferably provided so as to be in direct contact with the surface of the biaxially stretched film layer 101. Thereby, the manufacturing process of the packaging film 100 for foodstuffs 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 side of the biaxially stretched film layer 101.
When the thickness of the surface layer 105 is not less than the above lower limit value, the printability of the food packaging film 100 can be further improved.
Moreover, when the thickness of the surface layer 105 is not more than the above upper limit value, the adhesion with the biaxially stretched film layer 101 is improved, and the surface layer 105 is laminated on the biaxially stretched film layer 101 without using an adhesive. It becomes easy to make.
That is, since it becomes easy to provide the surface layer 105 so that it may contact | connect directly on 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 packaging film 100 for foodstuffs can be simplified further.

  The surface layer 105 is preferably formed by being biaxially stretched simultaneously with the film in the state before biaxial stretching of the biaxially stretched film layer 101. Thereby, since the packaging film 100 for foodstuffs can be produced using shaping | molding methods, such as a coextrusion molding method, ie, the laminated | multilayer film produced by one shaping | molding, the manufacturing process of the packaging film 100 for foods is simplified further. can do. Therefore, the surface layer 105 is preferably biaxially stretched.

  Further, 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, surface activation treatment such as corona treatment, flame treatment, plasma treatment, primer coating treatment, ozone treatment, etc. may be performed.

(Polyolefin)
The surface layer 105 according to the present embodiment is made of, for example, a polyolefin resin composition (B) containing 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; high pressure 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 or the like.
Among these, as the polyolefin constituting the surface layer 105, α, which is homopolypropylene and propylene, and has 2 to 10 carbon atoms in terms of excellent balance between adhesion to the biaxially stretched film layer 101 and printability. -At least 1 type selected from the random copolymer with an olefin is preferable.

The propylene / α-olefin random copolymer according to the present embodiment is a random copolymer of propylene and α-olefin (wherein α-olefin excludes propylene). As the α-olefin, for example, ethylene 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene and the like. These copolymers may be used alone or in combination of two or more.
Among the propylene / α-olefin random copolymers, propylene / ethylene random copolymers, propylene / ethylene / 1-butene random copolymers, and propylene / 1-butene random copolymers are preferable.

  The melting point of the polyolefin constituting the surface layer 105 according to this embodiment is preferably in the range of 90 ° C. or higher and 175 ° C. or lower, more preferably 95 ° C. or higher and 170 ° C. or lower, and further preferably 100 ° C. or higher and 167 ° C. or lower. When the melting point of the polyolefin is equal to or higher than the above lower limit, the surface of the surface layer 105 can be prevented from sticking, 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 this embodiment measured at 230 ° C. and a load of 2.16 kg is preferably from the viewpoint of fluidity and moldability. Is 0.5 g / 10 min or more, more preferably 1 g / 10 min or more, and further preferably 2 g / 10 min or more. From the viewpoint of further stabilizing the moldability, it is preferably 20 g / 10 min or less, more preferably It is 10 g / 10 min or less, more preferably 7 g / 10 min or less.

  The polyolefin resin composition according to the present embodiment, that is, the polyolefin content in the surface layer 105 is preferably 50% by mass or more and 100% by mass or less when the entire polyolefin resin composition (B) is 100% by mass. More preferably, it is 70 mass% or more and 100 mass% or less, More preferably, it is 90 mass% or more and 100 mass% or less, Most preferably, it is 95 mass% or more and 100 mass% or less. Thereby, balance, such as adhesiveness with the biaxially stretched film layer 101, printability, can be made more favorable.

(Other ingredients)
In the polyolefin resin composition (B) constituting the surface layer 105 according to the present embodiment, a tackifier, a heat stabilizer, a weather stabilizer, an antioxidant, an ultraviolet absorber, a lubricant, and a slip are included as necessary. Various additives such as an agent, a nucleating agent, an antiblocking agent, an antistatic agent, an antifogging agent, a pigment, a dye, and an inorganic or organic filler may be added as long as the object of the present embodiment is not impaired.

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

<Method for producing food packaging film>
The food packaging film 100 according to this embodiment includes, for example, a resin composition (P) for forming the biaxially stretched film layer 101 and a polyolefin resin composition (A) for forming the heat seal layer 103. And a polyolefin-based resin composition (B) for forming the surface layer 105 as necessary, and a laminated film obtained by co-extrusion molding into a film shape, a known simultaneous biaxial stretching method or sequential biaxial It can be obtained by biaxially stretching using a biaxially stretched film manufacturing method such as a stretching 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 apparatus, a multilayer T-die extruder, a multilayer inflation molding machine, or the like can be used. As the biaxial stretching conditions, for example, known production conditions for an OPP film can be employed. More specifically, in the sequential biaxial stretching method, for example, the longitudinal stretching temperature ranges from 100 ° C. to 145 ° C., the longitudinal stretching ratio ranges from 4.5 to 6 times, and the transverse stretching temperature ranges from 130 ° C. to 190 ° C. What is necessary is just to make a magnification into the range of 9-11 times.
In addition, the food packaging film 100 according to the present embodiment is formed by separately forming the biaxially stretched film layer 101, the heat seal layer 103, and the surface layer 105 as necessary, and laminating these layers, followed by heat forming. Can also be obtained.

<Applications for food packaging films>
The food packaging film 100 according to this embodiment can also be suitably used as a film constituting a food packaging body. The food packaging body according to the present embodiment is, for example, a packaging bag used for the purpose of containing food or a food containing the food in the bag. Moreover, the food packaging body according to the present embodiment may use the food packaging film 100 for a part of the food packaging body according to the application, or the food packaging film 100 may be used for the entire food packaging body. .

The food packaging film 100 according to the present embodiment is preferably used for an outer packaging bag in which water vapor barrier properties, transparency, and antistatic properties are particularly required.
In addition, when the food packaging film 100 according to the present embodiment is used in an integrated package composed of food, individual packaging bags for individually packaging foods, and outer packaging bags for packaging a plurality of individual packaging bags, The packaging film 100 is preferably used for an exterior packaging bag in which water vapor barrier properties, transparency, and antistatic properties are particularly required in an integrated package. Thereby, the accumulation | aggregation package which has sufficient water vapor | steam barrier property, transparency, and antistatic property can be obtained.

  As mentioned above, although embodiment of this invention was described with reference to drawings, these are the illustrations of this invention, Various structures other than the above are also employable.

  Hereinafter, the present embodiment will be described in detail with reference to examples and comparative examples. In addition, this embodiment is not limited to description of these Examples at all.

1. Raw materials The raw materials used in Examples and Comparative Examples are shown below.
(1) Polypropylene PP1: Homopolypropylene (MFR: 3 g / 10 min, melting point: 157 ° C., manufactured by Prime Polymer Co., Ltd.)
PP2: Propylene / α-olefin random copolymer (MFR: 7 g / 10 min, melting point: 137 ° C., manufactured by Prime Polymer Co., Ltd.)
PP3: Propylene / α-olefin random copolymer (MFR: 7 g / 10 min, melting point: 74 ° C., manufactured by Mitsui Chemicals)
PP4: Homopolypropylene (MFR: 3.5 g / 10 min, melting point: 159 ° C., manufactured by Prime Polymer Co., Ltd.)
(2) Polyethylene PE1: Polyethylene (MFR: 2.3 g / 10 min, density: 916 kg / m ³ , melting point: 126 ° C., manufactured by Braskem)
(3) Additive A1: Anti-blocking agent

2. Measurement and Evaluation Method (1) MFR of polypropylene
Based on ASTM D1238, the measurement was performed under the conditions of 230 ° C. and 2.16 kg load.

(2) Polyethylene MFR
Based on ASTM D1238, the measurement was performed under the conditions of 190 ° C. and 2.16 kg load.

(3) Melting point of polypropylene and polyethylene The melting point was the temperature of the maximum melting peak of the DSC curve of polypropylene and polyethylene obtained using DSC (differential scanning calorimeter).

(4) Tensile modulus A test piece of 15 mm × 15 cm was cut out from the food packaging film obtained in the examples and comparative examples. Next, using a tensile tester manufactured by Orientec, in accordance with JIS K7127 (1999), the test piece in the MD direction was measured under the conditions of a measurement temperature of 23 ± 2 ° C., 50 ± 5% RH, and a tensile speed of 300 mm / min. tensile modulus T ₁ and TD direction tensile modulus T ₂ were measured.

(5) Heat Shrinkage A test piece of 10 cm × 10 cm was cut out from the food packaging film obtained in Examples and Comparative Examples. Subsequently, the said test piece was heat-processed at 120 degreeC for 15 minute (s). Next, when the length in the TD direction of the test piece after the heat treatment is TD ₁ [cm] and the length in the MD direction of the test piece after the heat treatment is MD ₁ [cm], X _TD [%] is calculated by _{100 × (10-TD 1)} / 10, X MD [%] was calculated by _{100 × (10-MD 1)} / 10.

(6) Transparency Based on JIS K7105, the haze of the food packaging films obtained in Examples and Comparative Examples was measured using a haze meter (trade name: NDH300A, manufactured by Nippon Denshoku Industries Co., Ltd.).
Next, the transparency of the food packaging film was evaluated according to the following criteria.
A: Haze is less than 2.0% O: Haze is 2.0% or more and less than 2.5% X: Haze is 2.5% or more

(7) Antistatic property In accordance with JIS C2139, using a digital ultra-high resistance microammeter (trade name: 8340A, manufactured by Advantest Corporation), a heat seal layer for food packaging films obtained in Examples and Comparative Examples The surface resistivity on the side was measured. The measurement conditions are as follows.
Measurement conditions: after storage for 24 hours or more at 20 ± 2 ° C. and 50 ± 5% RH, measured under the conditions of 20 ± 2 ° C. and 50 ± 5% RH. The prevention was evaluated.
◎: Surface resistivity is 5.0 × 10 ¹² Ω or less ◎: Surface resistivity is 5.0 × 10 ¹² Ω excess 5.0 × 10 ¹³ Ω or less ◯: Surface resistivity is 5.0 × 10 ¹³ Ω Excess 1.0 × 10 ¹⁴ Ω or less ×: Surface resistivity exceeds 1.0 × 10 ¹⁴ Ω

(8) Water vapor barrier property The food packaging films obtained in the examples and comparative examples were folded so that the heat seal layer was the inner surface, and heat sealed on both sides to form a bag. Thereafter, calcium chloride was added as a content. Next, the other side was heat-sealed to produce a bag having a surface area of 0.01 m ² . Subsequently, the obtained bag was stored for 72 hours under the conditions of 40 ° C. and humidity 90% RH. The weight of calcium chloride before and after storage was measured, and the water vapor permeability (g / (m ² · 24 h)) was calculated from the difference.
Next, the water vapor barrier property of the food packaging film was evaluated according to the following criteria.
A: Water vapor permeability is 6.5 g / (m ² · 24 h) or less ○: Water vapor permeability is 6.5 g / (m ² · 24 h) excess 8.0 g / (m ² · 24 h) or less ×: Water vapor permeability Is over 8.0g / (m ² · 24h)

(9) Heat-sealing property A laminated film is obtained by heat-sealing heat-sealing layers of two food packaging films cut to a width of 15 mm under the conditions of 115 ° C., pressure 1.0 kgf, and sealing time 0.5 seconds. Obtained. Subsequently, two food packaging films were peeled off under the conditions of 15 mm width, 90 degree peeling, and peeling speed of 300 mm / min, and the peel strength at that time was defined as heat seal strength.
Next, the heat sealability of the food packaging film was evaluated according to the following criteria.
A: Heat seal strength is 3.5 N / 15 mm or more. O: Heat seal strength is 2.5 N / 15 mm or more and less than 3.5 N / 15 mm. X: Heat seal strength is less than 2.5 N / 15 mm.

[Examples 1-4 and Comparative Examples 1-2]
Each layer was coextruded with the layer structure shown in Table 1, and then a food packaging film was produced by biaxial stretching, and each evaluation was performed. The coextrusion molding conditions and the biaxial stretching treatment conditions are as follows.
Multi-layer extruder: 60 mmφ multi-layer T-die extruder (L / D = 27, manufactured by Screw Seiki Co., Ltd.)
Extrusion set temperature: 200 to 250 ° C., processing speed: 13.5 m / min
Longitudinal stretching temperature: 110-120 ° C
Longitudinal stretching ratio: 5.0 times Transverse stretching temperature: 140-170 ° C
Horizontal stretch ratio: 10.0 times

  When the food packaging film of the example was used, it was possible to obtain a food packaging body having sufficient water vapor barrier properties and transparency, and having an excellent balance of heat sealability and antistatic properties.

DESCRIPTION OF SYMBOLS 100 Food packaging film 101 Biaxially stretched film layer 103 Heat seal layer 105 Surface layer

Claims (10)

A film for packaging food,
A biaxially stretched film layer comprising a propylene polymer and polyethylene;
A heat seal layer provided on one surface of the biaxially stretched film layer;
With
When the total amount of the propylene polymer and the polyethylene contained in the biaxially stretched film layer is 100% by mass, the content of the polyethylene contained in the biaxially stretched film layer is 0.5% by mass or more and 25% by mass or more. A food packaging film having a mass% or less. In the food packaging film according to claim 1,
According to JIS K7127 (1999), the tensile force in the MD direction of the packaging film for food, measured using a tensile tester under the conditions of a measurement temperature of 23 ± 2 ° C., 50 ± 5% RH, and a tensile speed of 300 mm / min. A food packaging film having a total value (T ₁ + T ₂ ) of an elastic modulus T ₁ and a tensile elastic modulus T _{2 in the} TD direction of 3000 MPa or more and 6000 MPa or less. In the food packaging film according to claim 1 or 2,
A food packaging film having a thermal shrinkage in the TD direction of 4.5% or less when the food packaging film is heat-treated at 120 ° C for 15 minutes. In the food packaging film according to any one of claims 1 to 3,
When the heat shrinkage rate in the TD direction and the heat shrinkage rate in the MD direction of the food packaging film when heat-treated at 120 ° C. for 15 minutes are respectively X _TD [%] and X _MD [%],
X _TD -X _MD food packaging film is not more than 5.0% more than -5.0%. In the food packaging film according to any one of claims 1 to 4,
A food packaging film further comprising a surface layer on a surface opposite to a surface of the biaxially stretched film layer on which the heat seal layer is provided. In the food packaging film according to claim 5,
The said surface layer is a packaging film for foods containing 1 type, or 2 or more types selected from the random copolymer of a homopolypropylene and propylene, and C2-C10 alpha olefin. In the food packaging film according to any one of claims 1 to 6,
The food sealing film is provided such that the heat seal layer is in direct contact with the one surface of the biaxially stretched film layer. In the food packaging film according to any one of claims 1 to 7,
Food packaging film used for exterior packaging bags. In the food packaging film according to any one of claims 1 to 8,
A food packaging film, wherein the heat seal layer comprises one or more selected from a random copolymer of homopolypropylene and propylene and an α-olefin having 2 to 10 carbon atoms.   A food packaging body using the food packaging film according to any one of claims 1 to 9.

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