Film and laminate of the same

Abstract

To provide a film which has low water vapor permeability and odor permeability, and prevents odor inherent to a resin from being absorbed.SOLUTION: A film is composed of a mixture of a polyester resin and a polyethylene resin, wherein intrinsic viscosity of the polyester resin is 0.7 to 1.0 dl / g, a melt flow rate of the polyethylene resin is 0.1 to 1.0 g / 10 min, and the film has such a sea-island structure that an island phase of the polyethylene resin is dispersed in a sea phase of the polyester resin.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a film used primarily as a packaging material or container material, a laminate formed by laminating a film with a substrate such as paper, packaging or containers using the same, and methods for producing the same. [Background technology]

[0002] In recent years, films made of polyethylene resin have been widely used for packaging and containers for food, detergents, daily necessities, waste, etc. These films are not only used as films, but also processed into laminates by laminating them with substrates such as paper, nonwoven fabrics, and foam sheets. They are not limited to film shapes, but are also processed into container shapes such as bags, cylinders, boxes, and bottles.

[0003] The purposes for using polyethylene resins in packaging and container materials include reducing water vapor permeability and heat sealing in the processing of bags and other containers. Therefore, even when used as a laminate, polyethylene resins are often used in the innermost layer that comes into contact with the contents of the package or container.

[0004] However, polyethylene resin has a unique odor known as an olefin odor, and there is a problem in that the odor transfers to the contents, particularly when the contents are food.

[0005] Furthermore, while polyethylene resin has low water vapor permeability, it has high permeability to gases such as oxygen and carbon dioxide, as well as odorous components found in our daily lives, making it a poor gas barrier. This has led to problems such as odors leaking from the packaging or container during distribution or storage at home, as well as odor transfer, where odorous components from external foods or insect repellents placed near the packaging or container are transferred to the contents.

[0006] The following methods have been disclosed as a way to solve the problem of odor transfer.

[0007] For example, Patent Document 1 discloses a deodorizing laminate comprising an odor barrier layer using nylon 6 / 66 copolymer, polyvinyl alcohol, or polyethylene terephthalate as an odor barrier resin, an adhesive layer, and a deodorizing layer containing a deodorizing agent made of an inorganic porous material.

[0008] Patent Document 2 discloses a packaging material for food containers that has an odor barrier layer on the inner side of a paper substrate and a deodorizing agent-containing polyolefin resin layer on the outer side of the paper substrate. The odor barrier layer is made of aluminum foil or polyvinyl alcohol. The deodorizing agent-containing polyolefin resin layer is said to use hydrophobic zeolite as a deodorizing agent.

[0009] Patent Document 3 discloses a multilayer sheet for a heat-insulating paper container body member, in which a low-melting-point thermoplastic resin layer made of low-density polyethylene is disposed on one surface of a paper base material, a thermoplastic aromatic polyester resin layer made of a biaxially oriented polyethylene terephthalate film is disposed on the other surface of the paper base material via an adhesive layer, and a high-melting-point thermoplastic resin layer made of medium-density polyethylene or the like is disposed on the surface of the thermoplastic aromatic polyester resin layer. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2020-164737 [Patent Document 2] Japanese Patent Application Publication No. 07-76338 [Patent Document 3] Japanese Patent Application Laid-Open No. 2010-208174 Summary of the Invention [Problem to be solved by the invention]

[0011] As described in the above patent documents, gas barrier properties can be achieved by providing a layer of a material other than polyethylene resin, such as aluminum foil, polyvinyl alcohol, or polyethylene terephthalate. However, these materials are more expensive than polyethylene resin, and as a single layer, they lack properties such as water vapor permeability and heat sealability, so polyethylene resin layers are laminated. Such lamination requires the use of adhesive layers, which increases the number of layers and manufacturing steps, thereby increasing manufacturing costs. Another approach has been to blend deodorants or deodorizing agents, such as inorganic porous materials or hydrophobic zeolites, into polyethylene resin. However, this requires technology to highly disperse the deodorants or deodorizing materials. Furthermore, blending deodorants or deodorizing agents into polyethylene resin does not achieve gas barrier properties, so they are only used as a supplementary measure.

[0012] The present invention aims to provide a film that is primarily used as a packaging or container material and can be laminated with a substrate such as paper, and that has a sufficiently low water vapor permeability, is minimal odor transfer due to the resin used, and is resistant to leakage of odors from the contents of the package or container, and is resistant to odor transfer from the outside of the package or container to the contents, all with a smaller number of layers. Another object of the present invention is to provide a method for producing the film. [Means for solving the problem]

[0013] The above-mentioned problems are solved by a film comprising a mixture of polyester resin and polyethylene resin, wherein the polyester resin has an intrinsic viscosity of 0.7 to 1.0 dL / g and a melt flow rate of 0.1 to 1.0 g / 10 min, and wherein the film has a sea-island structure in which island phases of the polyethylene resin are dispersed in a sea phase of the polyester resin.The above-mentioned problems are also solved by a method for producing a film, wherein the polyester resin having an intrinsic viscosity of 0.7 to 1.0 dL / g and the polyethylene resin having a melt flow rate of 0.1 to 1.0 g / 10 min are melt-extruded into a film, and the film thus produced has a sea-island structure in which island phases of the polyethylene resin are dispersed in a sea phase of the polyester resin.

[0014] The mixture preferably contains 55 to 65% by mass of polyester resin and 35 to 45% by mass of polyethylene resin. The film is preferably laminated with paper to form a laminate. The film is suitable as a material for packaging or containers. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a film having a single layer structure, which sufficiently suppresses the permeation of water vapor, is less permeable to odors, and does not transfer odors peculiar to resins, such as the odor of olefins. Furthermore, the film can be laminated with a substrate such as paper, and can be used as a packaging material or container material for food, etc. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 10 is a cross-sectional cut view of the film layer of Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0017] The present invention relates to a film made of a mixture of polyester resin and polyethylene resin. Preferred embodiments for carrying out the present invention will be described below. The embodiments described below are merely limited examples of the present invention, and the technical scope of the present invention is not limited to the exemplified embodiments.

[0018] The polyester resin may be either an aliphatic polyester or an aromatic polyester. Examples of aromatic polyesters include polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, and copolymers thereof. From the viewpoint that the present invention is mainly used for packaging materials and container materials, it is preferable to use polyethylene terephthalate or a copolymer of polyethylene terephthalate. Polyethylene terephthalate has excellent gas barrier properties, is widely used as a beverage container, and has a proven track record in terms of safety when in contact with food. From the viewpoint of use as a packaging or container material, it is preferable to use a biomass raw material.

[0019] To facilitate the processing of materials using the film of the present invention into containers and the like, it is desirable for the material to be heat-sealable at low temperatures, more specifically, within the range of 100 to 160°C. When the polyester resin and polyethylene resin are not mixed, even homopolymer polyethylene terephthalate with a melting point of 250 to 260°C can be heat-sealed within the above temperature range by molding the material in a state where crystallization is suppressed. However, since the film is composed of a mixture of polyester resin and polyethylene resin, if homopolymer polyethylene terephthalate is used as the polyester resin, it has a high melting point and a high crystallization rate, and the formation of a sea-island structure with the polyethylene resin rapidly accelerates its crystallization, making it difficult to achieve heat-sealability. Therefore, it is preferable to use a polyethylene terephthalate copolymer rather than homopolymer polyethylene terephthalate to reduce the crystallinity and lower the melting point and softening point. Examples of polyethylene terephthalate copolymers include those in which part of the acid component is replaced with an acid component such as isophthalic acid or naphthalenedicarboxylic acid, and those in which part of the glycol component is replaced with an alcohol component such as 1,4-cyclohexanedimethanol or butanediol. The melting point of the polyethylene terephthalate copolymer is preferably in the range of 210 to 240° C. Copolymers of the above-mentioned polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, and polybutylene naphthalate can also be obtained by applying the above substitution.

[0020] The polyethylene resin may be low-density polyethylene (including ethylene-α-olefin copolymer), medium-density polyethylene, or high-density polyethylene, and its manufacturing method may be a high-pressure method, low-pressure method, or the like, but is not limited thereto. If a high-density polyethylene is used, the resulting film will be hard and brittle, making it difficult to mold into a container shape. Furthermore, if the melting point is too high, the heat-sealing temperature will be high, making processing difficult. In such cases, it is preferable to use low-density polyethylene or medium-density polyethylene. On the other hand, if the density is too low, the heat resistance of the container will also be reduced accordingly. In consideration of heat resistance, the density of the polyethylene resin should be 0.910 to 0.935 g / cm. 3 It is preferable that the melting point is in the range of 105 to 125° C. From the viewpoint of use as a material for packaging or containers, it is preferable that biomass raw materials are used.

[0021] The film of the present invention has a sea-island structure of polyester resin and polyethylene resin. This sea-island structure can be obtained by kneading the polyester resin and polyethylene resin in a molten state. This melt kneading can be carried out using an extruder commonly used for film production. This extruder is not limited to a twin-screw extruder but may be a single-screw extruder. The shape of the die is not particularly limited, and the extruder may have either a multilayer structure or a single-layer structure, and may be a T-die or inflation method. In order to obtain the sea-island structure, it is preferable to consider the properties of the polyester resin and polyethylene resin in a molten state, such as viscosity and tension.

[0022] The polyester resin used has an intrinsic viscosity (IV value) in the range of 0.7 to 1.0 dl / g. The IV value can be measured by the method described in JIS K 7367-1:2002 and JIS K 7367-5:2000. If the IV value is less than 0.7, when the resin is mixed with a polyethylene resin and extruded into a film, the melt tension of the molten resin extruded from the die decreases, causing draw resonance and other phenomena, making it difficult to form the film stably. Furthermore, if the IV value is small, the shear stress during melt kneading decreases, which can result in the polyethylene resin not being sufficiently finely dispersed, resulting in striped or streaky dispersion defects on the film surface. If the IV value is greater than 1.0, the extruder is likely to be overloaded, making it difficult to knead the resin sufficiently.

[0023] The polyethylene resin used has a melt flow rate (MFR: JIS K6922-2, measured at 190°C and loaded at 2.16 kg) in the range of 0.1 to 1.0 g / min. More preferably, a melt flow rate in the range of 0.2 to 0.5 g / 10 min is used. When extruding a mixture of polyethylene and polyester resins, the extrusion temperature is set to match the polyester resin with a higher melting point. If the MFR exceeds the above range, the difference in melt viscosity between the polyester and polyethylene resins at the extrusion temperature becomes too large, making it difficult for the two resins to disperse uniformly within the extruder. This can lead to discharge abnormalities such as melt fracture at the nozzle outlet, resulting in loss of thickness uniformity and a poor appearance of the film. Furthermore, unless the polyester and polyethylene resins are uniformly dispersed to form an island-sea structure, sufficient odor barrier properties cannot be achieved.

[0024] The film has a sea-island structure with the polyester resin as the sea phase and the polyethylene resin as the island phase, so it is preferable to mix the polyester resin at a mass fraction of more than 50% by mass. The polyester resin is dispersed as the sea phase and the polyethylene resin as the island phase, making it difficult for odorous gases to permeate. This is thought to be because the polyester resin, which is impermeable to odorous components, forms the sea phase, and the polyethylene resin, which is permeable to odorous components, forms the island phase. Even if a small amount of odorous component attempts to permeate the polyester resin as the sea phase, the micro-dispersed polyethylene resin as the island phase captures and stores the odorous component, functioning as a so-called odor component capture material. Therefore, if the polyethylene resin becomes the sea phase, odorous components will permeate through the sea phase, and sufficient odor barrier performance will not be achieved.

[0025] In the film, it is preferable to mix the polyethylene resin so that its mass fraction is greater than 30% by mass. If the polyethylene resin is micro-dispersed as island phases, the more island phases there are, the lower the water vapor permeability. Therefore, it is more preferable to mix the polyester resin and polyethylene resin so that their mass fractions are 55 to 65% by mass and 35 to 45% by mass, respectively.

[0026] The film may contain a compatibilizer for the polyester resin and the polyethylene resin. Examples of the compatibilizer include, but are not limited to, maleic anhydride-modified polyethylene resin and copolymers of olefins and highly polar monomers, such as ethylene-acrylic acid copolymer. Additionally, colorants, antioxidants, light stabilizers, antistatic agents, lubricants, antiblocking agents, etc. may be added to the mixture of polyester resin and polyethylene resin, provided that the object of the present invention is not impaired.

[0027] The film may be used as a single-layer film, or may be laminated with a substrate such as paper, nonwoven fabric, metal foil, foam sheet, or other film to form a laminate. The film can be used as a packaging or container material for food, detergent, daily necessities, waste, etc. When the film is laminated with a paper substrate such as cup base paper, fine paper, coated paper, or recycled paper, it is preferable to use an extrusion lamination method. The extrusion lamination method is a method in which a molten film extruded from a T-die is laminated onto a substrate. The film may be laminated on one side or both sides of the substrate. For example, two or more types of substrates may be bonded together via a film, such as paper, film, and foam sheet, in that order from one side to the other of the laminate.

[0028] The thickness of the film is not particularly limited and is determined appropriately depending on the application. As a material for packaging or containers, the thickness is preferably in the range of 10 to 250 μm, and when laminated with a paper substrate, the thickness is preferably in the range of 10 to 100 μm.

[0029] Single-layer films can be molded into bags using a heat-sealing machine. A laminate of a film and a paper substrate can be made into a paper container by punching out a container body blank and a container bottom blank and combining them in a cup-forming machine. [Example]

[0030] The present invention will be described in more detail below with reference to examples, but the technical scope of the present invention is not limited to the following examples. The resins used in these examples, their physical properties, and the test methods for the obtained films are as follows.

[0031] 1. Test Method (1) Film appearance: The state of the film during extrusion was visually evaluated. (Evaluation criteria) 〇...The entire surface is uniformly white and opaque ×: There are stripes or streaks of white shading, or film cannot be collected (2) Water vapor permeability: A 10cm x 20cm piece of film was sealed on three sides with a heat sealer to create a bag, after which 60g of water was poured into it and the remaining edge was heat sealed to create a water-tight bag. The initial mass of the resulting bag was measured, and it was then hung in a thermostatic chamber at 50°C to measure the mass loss rate after 10 days (240 hours). (3) Odor permeability: A 5cm square piece of film was sealed on three sides with a heat sealer to create a bag, after which the odorous component was placed inside and the remaining edge was heat sealed to create a bag with the odorous component sealed in. This bag was placed in a 100cc glass bottle with a lid, and the odor leaking from the bag into the glass bottle over time was subjected to a sensory evaluation at room temperature. (Odor components) Odor component 1: Soothing anti-inflammatory plaster (Salonpas (registered trademark) manufactured by Hisamitsu Pharmaceutical Co., Ltd.) Odor component 2: Insect repellent (Parazol (registered trademark) manufactured by Hakugensha Earth Co., Ltd.) Odor-causing component 3: Liquid detergent (Kao Corporation New Beads (registered trademark)) (Evaluation criteria) A: No odor at all B: Slight odor C. I smell an odor (4) Olefin odor: A 10 mm square film was sealed on three sides with a heat sealer to create a bag, after which 60 g of water was placed inside and the remaining edge was heat sealed to create a bag with the water sealed in. The resulting bag was left at room temperature for 3 days, then opened and the odor inside the bag was subjected to a sensory evaluation. (Evaluation criteria) A: No odor at all B: Slight odor C. I smell an odor (5) Heat sealability: The minimum temperature at which two films could be tightly sealed using a heat sealer (OPL-450-5, manufactured by Fuji Impulse Co., Ltd.) was determined.

[0032] 2. Resin (1) Polyester resin PET1: Polyethylene terephthalate (INDRAMA N1B, intrinsic viscosity (IV value) 0.8 dl / g, melting point 255°C) PET2: Polyethylene terephthalate (INDRAMA BF3067, intrinsic viscosity (IV value) 0.645 dl / g, melting point 255°C) PET3: Copolymerized polyethylene terephthalate (IFG8L manufactured by Bell Polyester Products, Inc., intrinsic viscosity (IV value) 0.8 dl / g, melting point 224°C) (2) Polyethylene resin LDPE1: Low-density polyethylene (SEB853 manufactured by Braskem, MFR 2.7 g / 10 min, density 0.923 g / cm 3 , melting point 111℃) LDPE2: Low-density polyethylene (Braskem SBC818, MFR 8.3 g / 10 min, density 0.918 g / cm 3 , melting point 106℃) LDPE3: Low-density polyethylene (Braskem SBF0323HC, MFR 0.32 g / 10 min, density 0.923 g / cm 3 , melting point 111℃) LDPE4: Low-density polyethylene (LF161 manufactured by Japan Polyethylene Co., Ltd., MFR 0.4 g / 10 min, density 0.928 g / cm 3 , melting point 115℃) LDPE5: Low-density polyethylene (LC520 manufactured by Japan Polyethylene Co., Ltd., MFR 3.6 g / 10 min, density 0.923 g / cm 3 , melting point 111℃)

[0033] [Examples 1 and 2, Comparative Examples 1 to 9] The resin pellets of PET1, 2, and 3 and LDPE1, 2, 3, 4, and 5 were mixed in the mass ratios shown in Table 1, and fed into a 25 mm diameter, L / D 32 co-rotating twin-screw extruder. While removing moisture through a vacuum vent, the mixture was extruded through a 450 mm wide T-die at an extrusion temperature of approximately 280°C and cooled on a cooling roll set at approximately 40°C to produce a 60 μm thick film. The resulting films were designated Examples 1 and 2, and Comparative Examples 1 to 9, respectively. The evaluation results of the film appearance are shown in Table 1.

[0034] [Table 1]

[0035] Next, the films of Examples 1 and 2 and Comparative Examples 8 and 9, which had good evaluation results for film appearance, were evaluated for performance in terms of water vapor permeability, odor permeability, olefin odor, and heat sealability. The evaluation results are shown in Table 2.

[0036] [Table 2]

[0037] Although both Examples 1 and 2 had a single-layer structure, when a polyester resin was used as a single layer, the water vapor permeability, odor permeability, and olefin odor permeability showed performance that was equal to or better than when a polyethylene resin was used as a single layer. In particular, Example 2 could be heat-sealed at a low sealing temperature.

[0038] [Example 3] The same resin pellets as in Example 2 were mixed in a mass ratio, charged into a single-screw extruder with a bore of 119 mm, and extruded from a T-die with a width of 1150 mm at an extrusion temperature of approximately 280°C to form cup base paper (manufactured by Nippon Paper Industries Co., Ltd., basis weight 230 g / m 2 The film was laminated onto a sheet of paper (786 mm wide) at a take-up speed of 60 m / min so that the film layer had a thickness of 60 μm. The resulting laminate was designated Example 3.

[0039] The laminate of Example 3 was evaluated for its water vapor permeability, odor permeability, olefin odor, and heat sealability. The evaluation results are shown in Table 2. In each test, the film layers were sealed so that they adhered to each other.

[0040] [Table 3]

[0041] The film layer of the laminate obtained in Example 3 was uniformly white and opaque over the entire surface, as in Example 2. A cut cross section of the film layer of Example 3 was observed under an electron microscope. A photograph of the obtained cut cross section is shown in Figure 1. A sea-island structure was observed, with polyethylene terephthalate resin as the sea phase and polyethylene resin as the island phase. It can be said that the white opaque color was exhibited because the polyethylene resin that forms the island phase was uniformly dispersed at a microscopic level.

[0042] Example 3 was good in all of the water vapor permeability, odor permeability, olefin odor, and heat sealability, and showed sufficient performance even when laminated with paper.

Claims

1. It is made of a mixture of polyester resin and polyethylene resin, The intrinsic viscosity of the polyester resin is 0.7 to 1.0 dl / g, The melt flow rate of the polyethylene resin is 0.1 to 1.0 g / 10 min, A film characterized by having a sea-island structure in which polyethylene resin island phases are dispersed in a polyester resin sea phase.

2. The mixture comprises: Contains 55 to 65% by mass of polyester resin, 2. The film according to claim 1, wherein the film contains 35 to 45% by mass of a polyethylene resin.

3. A laminate comprising the film according to claim 1 or 2 and paper.

4. A package or container comprising the film according to claim 1 or 2 as a material.

5. A polyester resin having an intrinsic viscosity of 0.7 to 1.0 dl / g and a polyethylene resin having a melt flow rate of 0.1 to 1.0 g / 10 min are melt-extruded into a film, The method for producing a film is characterized in that the formed film has a sea-island structure in which island phases of polyethylene resin are dispersed in a sea phase of polyester resin.

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