JP7199688B2 - Tubular coextruded film - Google Patents

Description

The present invention relates to tubular coextruded films.

Conventionally, containers such as glass bottles and plastic bottles have been widely used for packaging liquids such as liquid seasonings, beverages and liquid detergents. Such a container has a problem that it becomes bulky as garbage after use. In recent years, as an improvement measure, flexible packaging bags that can be rolled or folded after use have been used.

For example, tubular films are sometimes used for soft packaging bags used for servers for mineral water, juice, etc. (water servers, etc.) and large bags for business use. A bag filled with a liquid using a tubular film can be produced, for example, by sealing one opening of the tubular film to form a bag and filling the bag with a liquid.

Such a packaging bag includes, for example, a polyethylene resin layer as an outer layer, a polyamide resin layer as an intermediate layer or a resin layer mainly composed of a saponified ethylene-vinyl acetate copolymer, and a polyethylene resin layer as an inner layer. A tubular coextruded film is known, which is a film for packaging beverages to be distributed, the additive compounded in the inner layer is aspherical particles, and the peel strength between the inner layers of the tube is within a specific range (Patent Document 1 reference). Patent Literature 1 describes that the tubular coextruded film can keep the inner layer of the film from coming into contact with the atmosphere and maintain hygiene until the liquid flows in.

JP 2017-145026 A

However, with the beverage packaging film described in Patent Document 1, the outer surfaces of the film may rub against each other during transportation in the bag after the beverage is filled, and the surface of the outer layer may be damaged. When the outer layer of a tubular film is damaged, the film appears white. For this reason, for example, after the beverage is filled, the beverage looks cloudy, and there is a risk that the beverage may be misidentified as having a quality problem. Moreover, such a problem becomes more conspicuous when filling mineral water, which requires high transparency. For this reason, the inner layer surfaces (inner surfaces) are in close contact with each other so that sanitation can be maintained until the liquid is filled. At present, there is a demand for a tubular film whose outer surface is resistant to scratches.

Also, the tubular coextruded film is produced in a long tubular shape and continuously wound into a roll. The tubular coextruded film is unwound and used when liquid is filled. For this reason, the tubular coextruded film is required to have excellent mechanical aptitude, such as little blocking between outer layer surfaces during unwinding.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a tubular coextruded film which has moderate blocking properties between inner layer surfaces, excellent mechanical aptitude, and which can make the outer surface less likely to be damaged.

As a result of intensive studies to achieve the above object, the present inventors have found that the outer layer is a resin layer containing a polyethylene resin as a main component, an average particle size of 2 to 10 μm, and a spherical antiblocking agent of 3000 to 20000 ppm by mass. an intermediate layer which is a resin layer mainly composed of a polyamide resin or saponified ethylene-vinyl acetate copolymer; According to the tubular coextruded film having a laminated structure containing in this order the inner layer, which is a resin layer containing 2000 to 6000 mass ppm, the blocking property between the inner layer surfaces is moderate, the mechanical aptitude is excellent, and the outer surface is hard to damage. We have found that it is possible to obtain a film. The present invention has been completed based on these findings.

That is, the present invention provides a liquid packaging film having a laminated structure comprising an outer layer, an intermediate layer, and an inner layer in this order,
The outer layer is a resin layer mainly composed of polyethylene resin, having an average particle diameter of 2 to 10 μm and containing 3000 to 20000 mass ppm of a spherical antiblocking agent,
The intermediate layer is a resin layer mainly composed of a polyamide resin or saponified ethylene-vinyl acetate copolymer,
Provided is a tubular coextruded film in which the inner layer is a resin layer containing polyethylene resin as a main component, an average particle size of 2 to 10 μm, and a spherical antiblocking agent of 2000 to 6000 mass ppm.

The antiblocking agent contained in the inner layer is preferably inorganic particles.

The total thickness of the outer layer and inner layer is preferably 70 to 80% of the total thickness of the tubular coextruded film.

The polyethylene resin in the outer layer preferably has a density of 0.930 to 0.950 g/cm ³ .

The polyethylene resin in the inner layer preferably has a density of 0.900 to 0.930 g/cm ³ .

According to the tubular coextruded film of the present invention, the blocking property between the inner layer surfaces is moderate, the mechanical aptitude is excellent, and it is possible to make the outer surface less likely to be damaged. Therefore, by using the tubular film, it is possible to obtain a bag that is excellent in sanitation, can be easily unwound, and has an outer surface that is less likely to be damaged.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic sectional drawing which shows one Embodiment of the tubular coextrusion film of this invention. 2 is an enlarged view (schematic cross-sectional view) of part of the tubular coextruded film 1 shown in FIG. 1. FIG.

The tubular coextruded film of the present invention has a laminated structure comprising an outer layer, an intermediate layer and an inner layer in this order. The outer layer is the outermost layer of the tube in the tubular coextruded film of the present invention, and is exposed to the outside air. The inner layer is the innermost layer of the tube in the tubular coextruded film of the present invention, and is the layer in contact with liquid in the bag filled with liquid such as beverage. The intermediate layer is a layer located between the outer layer and the inner layer.

The tubular coextruded film of the present invention is a tubular film formed by a coextrusion method, for example, by a resin melt extrusion method such as a tubular method or an inflation method. Since the tubular coextruded film of the present invention is a film formed by coextrusion in a tubular shape, it does not have a connecting portion such as a film bonding portion or a joint in the circumferential direction of the tube (cylindrical body). .

(outer layer)
The outer layer is a resin layer containing polyethylene-based resin as a main component. In the present specification, the resin layer constituting the tubular coextruded film of the present invention (for example, the outer layer, the intermediate layer, the inner layer, the adhesive layer described later, etc.) is the "main component" of the resin. The most abundant resin in terms of mass among the constituent resins. The content of the polyethylene resin in the outer layer is preferably 50% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably It is 95% by mass or more. The upper limit of the content ratio is not particularly limited as long as it is within a range in which the antiblocking agent can be included. Only one type of polyethylene-based resin may be used in the outer layer, or two or more types may be used.

In the present specification, the polyethylene-based resin is a polymer composed of a monomer component containing ethylene as a main component, that is, it contains a structural unit derived from ethylene in the molecule (in one molecule) as a main component. It is a polymer. Examples of polyethylene resins include homopolymers of ethylene, copolymers composed of ethylene and one or more monomer components (monomer components other than ethylene) as essential monomer components (ethylene copolymer coalescence) and the like. In the present specification, the term "main component" in a resin refers to the monomer component or structural unit that is the most abundant in terms of mass among the monomer components or structural units of the resin that constitute the resin.

Examples of monomer components other than ethylene include α-olefins; vinyl monomers such as vinyl chloride and vinyl acetate; (meth)acrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, citraconic acid; -unsaturated carboxylic anhydrides such as norbornene-2,3-dicarboxylic acid; unsaturated carboxylic anhydrides such as maleic anhydride, citraconic anhydride, 5-norbornene-2,3-dicarboxylic anhydride, and tetrahydrophthalic anhydride; meth)methyl acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, (meth)acrylic Unsaturated carboxylic acid esters such as 3-hydroxypropyl acid, glycidyl (meth)acrylate, monoethyl maleate, and diethyl maleate; unsaturated amides or imides such as acrylamide, methacrylamide, and maleimide; sodium (meth)acrylate, ( Unsaturated carboxylates such as zinc meth)acrylate and the like are included. Only one kind of monomer component other than ethylene may be used, or two or more kinds thereof may be used.

Examples of the α-olefins include propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, and the like. 3 to 20 α-olefins (preferably 1-butene, 1-pentene, 1-hexene and 1-octene, more preferably 1-pentene, 1-hexene and 1-octene) and the like. The α-olefin may be used alone or in combination of two or more.

Examples of the ethylene copolymer include copolymers (ethylene-α-olefin copolymers) composed of ethylene and one or more α-olefins as essential monomer components; ethylene-vinyl acetate copolymers; Coalescence (EVA); ethylene-acrylic acid copolymer (EAA), ethylene-carboxylic acid copolymer such as ethylene-methacrylic acid copolymer (EMAA); ethylene-ethyl acrylate copolymer (EEA) , ethylene-methyl methacrylate copolymer (EMMA) and other ethylene-carboxylic acid ester copolymers; ionomers;

Examples of the polyethylene-based resin include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE). The LDPE is, for example, a low-density polyethylene containing structural units derived from ethylene as a main component and produced by a high-pressure method. The LLDPE is, for example, a low-density polyethylene containing ethylene-derived structural units as a main component, produced by a medium-low pressure method, and having short chain branches.

As the polyethylene-based resin contained in the outer layer, ethylene homopolymers and ethylene-α-olefin copolymers are particularly preferred.

The density of the polyethylene resin contained in the outer layer is not particularly limited, but is preferably 0.925 to 0.950 g/cm ³ , more preferably 0.930 to 0.948 g/cm ³ , still more preferably 0.935. ~0.945 g/cm ³ or more.

The weight average molecular weight (Mw) of the polyethylene resin contained in the outer layer is not particularly limited, but is preferably 50,000 to 500,000, more preferably 60,000 to 300,000, and still more preferably 70,000 to 250,000. In this specification, the weight-average molecular weight and number-average molecular weight of a resin are determined by gel permeation chromatography (GPC) using polystyrene as a standard substance.

The molecular weight distribution (weight average molecular weight/number average molecular weight) of the polyethylene resin contained in the outer layer is not particularly limited, but is preferably 3.0 to 6.0, more preferably 3.5 to 5.8, and further It is preferably 4.0 to 5.5. When the molecular weight distribution is 3.0 or more, the rigidity of the polyethylene-based resin is high, and the outer layer surfaces are less likely to be damaged even if the outer layer surfaces are rubbed against each other during bag making, packaging, transportation, or the like. When the molecular weight dispersity is 6.0 or less, the impact resistance of the polyethylene-based resin tends to be excellent, and thus the impact resistance of the film is excellent.

The polyethylene-based resin contained in the outer layer is not particularly limited, but is preferably a polyethylene-based resin obtained using a single-site catalyst such as a Ziegler-Natta catalyst or a metallocene catalyst (single-site catalyst-based polyethylene-based resin). The polyethylene-based resin obtained in this way has a low amount of wax components, low-density components, low-molecular-weight components, and catalyst residues used in the manufacturing process, so it has high thermal stability, low volatile organic substances, and low odor. It is flexible and tends to have high stiffness and impact resistance. In particular, when used for mineral water, even a slight odor from the film is easily transferred to the contents of the bag, and the taste of the contents may change. . As the Ziegler-Natta catalyst and the metallocene catalyst, known or commonly used catalysts for olefin polymerization can be used.

The outer layer has an average particle size of 2 to 10 μm and contains a spherical antiblocking agent as an essential component. In this specification, the "anti-blocking agent having an average particle size of 2 to 10 µm and having a spherical shape" may be referred to as "anti-blocking agent A". When the outer layer contains a specific amount of the anti-blocking agent A, blocking between the outer layer surfaces is made difficult to occur, thereby improving the slipperiness. Even when rubbed against each other, the surface of the outer layer is less likely to be damaged, and has excellent blocking resistance and excellent mechanical suitability.

As the antiblocking agent A, known or commonly used agents for films can be used as long as they do not impair the effects of the present invention and the function as the outer layer. Examples include silica, zeolite, talc, smectite, vermiculite, mica, Clay compound particles such as kaolin and inorganic particles such as glass; acrylic resins such as PMMA, polyolefin resins such as ultrahigh molecular weight PE, polystyrene resins, polyurethane resins, polyester resins, silicone resins, fluorine resins Examples include organic particles such as copolymers of monomers constituting these resins. Among them, inorganic particles are preferred, more preferably silica and zeolite, and still more preferably silica and zeolite, from the viewpoints of more suppressing damage to the outer layer surface, more excellent blocking resistance between the outer layer surfaces, and suppressing change in taste of the liquid to be filled. Zeolite. As silica, both natural silica and synthetic silica can be used, but synthetic silica is preferable from the viewpoint of easily obtaining spherical silica. As zeolite, both natural zeolite and synthetic zeolite can be used, but synthetic zeolite is preferable from the viewpoint of easily obtaining spherical zeolite. Only one type of antiblocking agent A may be used, or two or more types may be used.

The antiblocking agent A contained in the outer layer has an average particle size of 2 to 10 μm, preferably 3 to 9 μm, more preferably 4 to 8 μm. When the average particle size is 2 μm or more, the blocking resistance between the surfaces of the outer layers is excellent. When the average particle size is 10 μm or less, the surface of the outer layer is less likely to be damaged. In addition, in this specification, the average particle size of the antiblocking agent shall mean the volume average particle size measured by the Coulter method.

Antiblocking agent A is spherical. In this specification, the term “spherical” does not have to be a perfect sphere, and includes elliptical spheres and particles with rounded corners generated by pulverization. The diameter (aspect ratio) is 1.2 or less, preferably 1.1 or less. Note that the lower limit is 1. An anti-blocking agent marketed as "spherical" corresponds to the "spherical" anti-blocking agent in this specification. The spherical antiblocking agent may have slight unevenness on the surface.

The content of the antiblocking agent A in the outer layer is 3000 to 20000 mass ppm (3000 mass ppm to 20000 mass ppm), preferably 4000 to 10000 mass ppm, relative to the total mass (100 mass%) of the outer layer. , More preferably 4000 mass ppm or more and less than 10000 mass ppm, more preferably 4000 to 8000 mass ppm. When the above content is 3000 ppm by mass or more, the outer layer surfaces have excellent blocking resistance, and when the tubular coextruded film is unwound, the resistance between the outer layer surfaces is low and the film can be easily unwound. When the content is 20,000 ppm by mass or less (especially, less than 10,000 ppm by mass), the surface of the outer layer is less likely to be damaged even when rubbed against each other. Moreover, it is excellent in transparency.

The outer layer may contain components other than the polyethylene-based resin and the antiblocking agent A within a range that does not impair the effects of the present invention. Examples of the other components include resins other than polyethylene resins, antioxidants, ultraviolet absorbers, light stabilizers, antiblocking agents other than antiblocking agent A, lubricants, flame retardants, fillers, and colorants. etc. Only one kind of each of the other components may be used, or two or more kinds thereof may be used.

The content ratio of the polyethylene-based resin to the total amount (100% by mass) of the resin components contained in the outer layer is preferably 90% by mass or more, more preferably 95% by mass or more, and still more preferably 99% by mass or more. Moreover, the upper limit of the content ratio may be 100% by mass.

The content of the antiblocking agent A with respect to the total mass (100% by mass) of the particles contained in the outer layer is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and particularly preferably It is 99% by mass or more. Moreover, the upper limit of the content ratio may be 100% by mass. When the content is 80% by mass or more, it is possible to further suppress damage to the outer layer surfaces even if the outer layer surfaces rub against each other by suppressing the inclusion of non-spherical particles.

The total content of the polyethylene resin and the antiblocking agent A in the outer layer is not particularly limited, but is preferably 70% by mass or more, more preferably 80% by mass or more, relative to the total mass (100% by mass) of the outer layer. , more preferably 90% by mass or more. In addition, the upper limit of the said content rate may be 100 mass %.

The thickness of the outer layer is preferably 5-50%, more preferably 10-40%, of the total thickness of the film. When the thickness is 5% or more, the film formability is excellent. When the thickness is 50% or less, the abrasion resistance of the film is excellent.

(middle layer)
The intermediate layer is a resin layer mainly composed of a polyamide resin or saponified ethylene-vinyl acetate copolymer. That is, the intermediate layer is a resin layer containing a polyamide resin as a main component, or a resin layer containing an ethylene-vinyl acetate copolymer saponified product as a main component. Each of the polyamide-based resin and saponified ethylene-vinyl acetate copolymer may be used alone, or two or more of them may be used.

The tubular coextruded film of the present invention may have only one intermediate layer, or may have two or more intermediate layers. When two or more intermediate layers are provided, for example, a resin layer containing a polyamide resin as a main component and a resin layer containing an ethylene-vinyl acetate copolymer saponified product as a main component may be used in combination. When there are two or more intermediate layers, the polyamide resin or the saponified ethylene-vinyl acetate copolymer used for each layer may be the same or different.

When it has an intermediate layer containing a polyamide-based resin (particularly containing a polyamide-based resin as a main component), the tubular coextruded film of the present invention is excellent in strength, particularly in pinhole resistance. Polyamide resins that can be contained in the intermediate layer include, for example, 4 nylon, 6 nylon, 7 nylon, 11 nylon, 12 nylon, 46 nylon, 66 nylon, 69 nylon, 610 nylon, 611 nylon, 6T nylon, 6I nylon, MXD6 nylon, 6-66 nylon, 6-610 nylon, 6-611 nylon, 6-12 nylon, 6-612 nylon, 6-6T nylon, 6-6I nylon, 6-66-610 nylon, 6-66-12 nylon, 6-66-612 nylon, 66-6T nylon, 66-6I nylon, 6T-6I nylon, 66-6T-6I nylon and the like. Among these, 6 nylon and 6-66 nylon are preferable from the viewpoint of better pinhole resistance.

In the case of having an intermediate layer containing a saponified ethylene-vinyl acetate copolymer (particularly containing a saponified ethylene-vinyl acetate copolymer as a main component), the tubular coextruded film of the present invention has excellent oxygen gas barrier properties. . In the saponified ethylene-vinyl acetate copolymer that can be contained in the intermediate layer, from the viewpoint of excellent film-forming stability of the film, the content ratio of structural units derived from ethylene is the total amount of structural units of the saponified product (100 mol %), preferably 27 to 47 mol %, more preferably 29 to 44 mol %, still more preferably 32 to 38 mol %. The degree of saponification of the saponified ethylene-vinyl acetate copolymer is preferably 90 mol % or more, more preferably 95 mol % or more.

When the intermediate layer is a resin layer containing a polyamide-based resin as a main component, the content of the polyamide-based resin in the intermediate layer is preferably 50% by mass or more with respect to the total mass (100% by mass) of the intermediate layer, More preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably 95% by mass or more. The upper limit of the content ratio may be 100% by mass.

When the intermediate layer is a resin layer containing a saponified ethylene-vinyl acetate copolymer as a main component, the content of the saponified ethylene-vinyl acetate copolymer in the intermediate layer is the total mass of the intermediate layer (100 mass% ), preferably 50% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably 95% by mass or more. The upper limit of the content ratio may be 100% by mass.

The intermediate layer may contain components other than the polyamide-based resin or the saponified ethylene-vinyl acetate copolymer within a range that does not impair the effects of the present invention. Examples of the other components include resins other than polyamide resins, resins other than ethylene-vinyl acetate copolymer saponified products, antioxidants, ultraviolet absorbers, light stabilizers, flame retardants, fillers, and colorings. agents and the like. Only one kind of each of the other components may be used, or two or more kinds thereof may be used.

When the intermediate layer is a resin layer containing a polyamide-based resin as a main component, the thickness of the intermediate layer is preferably 10 to 30%, more preferably 15 to 20%, of the total thickness of the film. When the thickness is 10% or more, the pinhole resistance of the film is more excellent. When the thickness is 30% or less, the flexibility is excellent, and the manufacturing cost can be suppressed. In addition, when the intermediate layer has a plurality of resin layers containing a polyamide-based resin as a main component, the above thickness is the total thickness of all the resin layers.

When the intermediate layer is a resin layer mainly composed of a saponified ethylene-vinyl acetate copolymer, the thickness of the intermediate layer is preferably 3 to 20%, more preferably 5%, of the total thickness of the film. ~18%, more preferably 7-15%. When the thickness is 3% or more, the oxygen barrier property of the film is more excellent. When the thickness is 20% or less, it is possible to suppress the deterioration of the pinhole resistance of the film and the manufacturing cost. In the case where the intermediate layer has a plurality of resin layers containing saponified ethylene-vinyl acetate copolymer as a main component, the above thickness is the total thickness of all the resin layers.

(inner layer)
The inner layer is a resin layer containing polyethylene-based resin as a main component. The content of the polyethylene-based resin in the inner layer is preferably 50% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably It is 95% by mass or more. The upper limit of the content ratio is not particularly limited as long as it is within a range in which the antiblocking agent can be included. Only one type of polyethylene-based resin may be used in the inner layer, or two or more types may be used.

The inner layer preferably has heat sealability in order to facilitate the production of a bag from the tubular coextruded film of the present invention. Therefore, LDPE, LLDPE, EVA, EAA, and ionomer are preferable as the polyethylene resin contained in the inner layer. Among them, LDPE and LLDPE are preferable from the viewpoint of having less odor and further suppressing the transfer of odor to the liquid to be filled, and LLDPE is more preferable from the viewpoint of excellent sealing strength between inner layer surfaces and excellent heat resistance of the seal portion. In particular, when used for mineral water, even a slight odor from the film is easily transferred to the contents of the bag, which may change the taste of the contents. , From the viewpoint of less odor and more suppressing the transfer of odor to the liquid to be filled, and from the viewpoint of better drop resistance, polyethylene resin obtained by polymerization using a metallocene catalyst (metallocene catalyst-based polyethylene resin) is used. Especially preferred.

The density of the polyethylene resin contained in the inner layer is not particularly limited, but is preferably 0.900 to 0.930 g/cm ³ , more preferably 0.910 to 0.928 g/cm ³ , still more preferably 0.915. ˜0.925 g/cm ³ . When the density is 0.900 g/cm ³ or more, the slipping property between the inner layer surfaces is improved, and the blocking property between the inner layer surfaces becomes more moderate. In addition, since the film does not stretch excessively when filled with liquid, it is easy to measure the amount of contained liquid. When the density is 0.930 g/cm ³ or less, the film becomes flexible and the surfaces of the inner layers tend to be in close contact with each other until the liquid is filled. In addition, it is easy to suppress the occurrence of pinholes due to bending fatigue.

The inner layer has an average particle size of 2 to 10 μm and contains a spherical antiblocking agent (antiblocking agent A above) as an essential component. By containing a specific amount of the anti-blocking agent A in the inner layer, blocking between the inner layer surfaces is made moderately difficult to occur, thereby improving lubricity. In addition, the blocking property (adhesion) between the inner layer surfaces becomes appropriate, and the inner layer surfaces do not come into contact with the air until the liquid is filled, making it possible to maintain hygiene. The antiblocking agent A contained in the outer layer and the antiblocking agent A contained in the inner layer may be the same or different.

As the anti-blocking agent A contained in the inner layer, those known or commonly used for films can be used, and examples thereof include those exemplified as the anti-blocking agents contained in the outer layer. Among them, inorganic particles are preferable, more preferably silica and zeolite, and still more preferably zeolite, from the viewpoint of moderate blocking between inner layer surfaces and suppression of change in taste of the liquid to be filled. As silica, both natural silica and synthetic silica can be used, but synthetic silica is preferable from the viewpoint of easily obtaining spherical silica. As zeolite, both natural zeolite and synthetic zeolite can be used, but synthetic zeolite is preferable from the viewpoint of easily obtaining spherical zeolite. Only one type of antiblocking agent A may be used, or two or more types may be used.

The antiblocking agent A contained in the inner layer has an average particle size of 2 to 10 μm, preferably 3 to 9 μm, more preferably 4 to 8 μm. When the average particle size is within the above range, the blocking property between the inner layer surfaces becomes appropriate.

The content of the antiblocking agent A in the inner layer is 2000 to 6000 ppm by mass, preferably 2500 to 5000 ppm by mass, more preferably 2600 to 4000 ppm by mass relative to the total mass (100% by mass) of the inner layer. be. When the above content is 2000 ppm by mass or more, the blocking property between the inner layer surfaces becomes appropriate, and the inner layer surfaces are easily opened when the liquid to be filled is poured, resulting in excellent sanitation. When the content is 6000 ppm by mass or less, the blocking property between the inner layer surfaces becomes appropriate, and the inner layer surfaces do not come into contact with the air until the liquid is filled, and hygiene can be maintained. Moreover, it is excellent in transparency.

The inner layer may contain components other than the polyethylene-based resin and the antiblocking agent A within a range that does not impair the effects of the present invention. Examples of the other components include resins other than polyethylene resins, antioxidants, ultraviolet absorbers, light stabilizers, antiblocking agents other than antiblocking agent A, lubricants, flame retardants, fillers, and colorants. etc. Only one kind of each of the other components may be used, or two or more kinds thereof may be used. In general, fatty acid amides, which are organic compounds, are often used as lubricants in tubular coextruded films used in packaging bags. However, there are problems such as slippery and easy separation, contamination of the roll of the film processing machine, generation of odor, and migration into the liquid of the contents. From these points of view, the inner layer preferably does not substantially contain organic compound additives such as fatty acid esters, hydrocarbon oils, fatty acids, and fatty acid amides (for example, 500 mass ppm or less, preferably 100 mass ppm or less).

The content of the polyethylene-based resin with respect to the total amount (100% by mass) of the resin components contained in the inner layer is preferably 90% by mass or more, more preferably 95% by mass or more, and still more preferably 99% by mass or more. Moreover, the upper limit of the content ratio may be 100% by mass.

The content of the antiblocking agent A is preferably 70% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more relative to the total mass (100% by mass) of the particles contained in the inner layer. Moreover, the upper limit of the content ratio may be 100% by mass.

The total content of the polyethylene resin and the antiblocking agent A in the inner layer is not particularly limited, but is preferably 80% by mass or more, more preferably 90% by mass or more, relative to the total mass (100% by mass) of the inner layer. , more preferably 95% by mass or more, more preferably 99% by mass or more, and particularly preferably 99.5% by mass or more. In addition, the upper limit of the said content rate may be 100 mass %.

The thickness of the inner layer is preferably 30-80%, more preferably 40-70%, still more preferably 45-65% of the total thickness of the film. When the thickness is 30% or more, stable sealing strength can be obtained when a packaging bag is formed. When the thickness is 80% or less, the total thickness of the film is prevented from becoming too thick, and the flexibility is excellent.

The tubular coextruded film of the present invention may have layers (other layers) other than the outer layer, the intermediate layer, and the inner layer. Examples of the other layers include a layer (adhesion layer) for improving adhesion between layers.

The tubular coextruded film of the present invention preferably has an adhesive layer between the outer layer and the intermediate layer, and between the inner layer and the intermediate layer. The adhesive layer that may be provided on the outer layer side of the intermediate layer and the adhesive layer that may be provided on the inner layer side of the intermediate layer may each be a single layer or multiple layers. . Further, each adhesive layer in the case of having a plurality of adhesive layers may be the same adhesive layer (e.g., adhesive layer having the same composition and thickness), or may be a different adhesive layer (e.g., different composition or thickness). adhesive layer).

The adhesive layers (the adhesive layer adjacent to the outer layer and the adhesive layer adjacent to the inner layer) each preferably contain a modified polyolefin resin having adhesive properties. Specifically, the adhesive layer is preferably a resin layer containing a polyolefin resin as a main component and containing the modified polyolefin resin, or a resin layer containing the modified polyolefin resin as a main component.

The polyolefin-based resin is a polymer composed of an olefin as an essential monomer component, and is a polymer containing at least a structural unit derived from an olefin in its molecule (per molecule). Examples of the olefin include, but are not limited to, α-olefins such as ethylene, propylene, 1-butene, and 4-methyl-1-pentene.

Examples of the polyolefin-based resin include polyethylene-based resins, polymers composed of propylene as an essential monomer component (polypropylene-based resins), amorphous cyclic olefin-based polymers, and olefin-based elastomers. Polyolefin-based resins such as polyethylene-based resins and homopolypropylene are preferable as the polyolefin-based resins. As the polyethylene-based resin, LDPE, LLDPE, MDPE, HDPE, EVA, EMMA, EEA, EMA, ethylene-ethyl acrylate-maleic anhydride copolymer (E-EA-MAH), EAA, and ionomer are preferable.

Examples of the modified polyolefin resin include those obtained by copolymerizing the above polyolefin resin with a modifying component. Examples of the modifying component include monobasic unsaturated fatty acids such as acrylic acid and methacrylic acid; dibasic fatty acids such as maleic acid, fumaric acid and itaconic acid; and anhydrides of the above dibasic fatty acids. Among them, maleic acid and maleic anhydride are preferred. That is, maleic acid-modified polyolefin-based resins and maleic anhydride-modified polyolefin-based resins are preferable as the modified polyolefin-based resins.

The content of the polyolefin resin or modified polyolefin resin as the main component in the adhesive layer is preferably 50% by mass or more, more preferably 80% by mass or more, relative to the total mass (100% by mass) of the adhesive layer. , more preferably 90% by mass or more, and particularly preferably 95% by mass or more. In the case of a resin layer containing a modified polyolefin resin as a main component, the upper limit of the content may be 100% by mass.

The adhesive layer may contain components other than the polyolefin-based resin and the modified polyolefin-based resin within a range that does not impair the effects of the present invention. Examples of the other components include other resins, antioxidants, ultraviolet absorbers, light stabilizers, lubricants, flame retardants, fillers, colorants, and the like. Only one kind of each of the other components may be used, or two or more kinds thereof may be used. However, from the viewpoint of increasing the adhesion between the layers, the content of other components in the adhesive layer is preferably 1% by mass or less, more preferably 0%, based on the total mass (100% by mass) of the adhesive layer. .5% by mass or less.

The thickness of each adhesive layer is preferably 3 to 30 μm, more preferably 5 to 25 μm, still more preferably 8 to 20 μm. When the thickness is 3 μm or more, the adhesion between layers is further improved. When the thickness is 30 µm or less, it is possible to suppress deterioration of transparency, an increase in the total thickness of the film, and an increase in manufacturing cost.

<Tubular co-extruded film>
One embodiment of the tubular coextruded film of the present invention is shown in FIGS. 1 and 2. FIG. FIG. 1 is a schematic cross-sectional view of a tubular coextruded film 1 of the present invention. The tubular coextruded film 1 of the present invention is flattened, and inner layer surfaces are in close contact with each other to form a boundary B. are doing. FIG. 2 is an enlarged view (schematic sectional view) of the region R shown in FIG. The tubular coextruded film 1 of the present invention has a laminated structure of outer layer 11/adhesive layer 12/intermediate layer 13/adhesive layer 14/inner layer 15 in order from the outside of the tube (cylindrical body).

The total thickness of the tubular coextruded film of the present invention (for example, the distance from the outer surface of the outer layer 11 to the boundary B in FIG. 1) is appropriately determined according to the mass of the liquid to be filled in the bag, impact resistance, and cost. It can be adjusted, for example 50-200 μm, preferably 80-180 μm, more preferably 100-150 μm. When the total thickness is 50 µm or more, the impact resistance of the bag produced from the tubular coextruded film of the present invention is improved. When the total thickness is 200 μm or less, the flexibility and sealability of the bag are excellent, and the cost can be suppressed.

In the tubular coextruded film of the present invention, the total thickness of the outer layer and the inner layer is preferably 60 to 90%, more preferably 65 to 85%, still more preferably 70 to 80% of the total thickness of the film. %. When the total thickness is 60% or more, the flexibility of the tubular coextruded film can be maintained at a high level. When the total thickness is 90% or less, the effect of having the intermediate layer can be exhibited more effectively, and the adhesive strength between the layers when having an adhesive layer is excellent.

The tubular coextruded film of the present invention is preferably an unstretched film. In this specification, the term "unstretched film" refers to a film that is not intentionally stretched in the manufacturing process, and is slightly stretched as a result of roll-to-roll transport or winding ( For example, a draw ratio of 1.05 times or less) is included.

In the tubular coextruded film of the present invention, each of the inner layer and the outer layer contains a specific spherical antiblocking agent in a specific content ratio, so that the inner layer surfaces can block each other without using a nonspherical antiblocking agent. is appropriate, it is excellent in mechanical aptitude, and it is possible to make the surface of the outer layer less likely to be damaged. Specifically, the inner layer and the outer layer each contain a specific spherical anti-blocking agent in a specific content ratio, and a non-spherical anti-blocking agent that is relatively excellent in blocking resistance but easily scratches the contact surface. By not using it or suppressing the blending amount to a minimum (for example, 1000 mass ppm or less, particularly 500 mass ppm or less), the blocking property between the inner layer surfaces is moderate, and the mechanical aptitude is excellent, and the outer layer surface is A scratch-resistant tubular film can be obtained.

The tubular coextruded film of the present invention is a film for filling liquid (liquid packaging film), preferably a bag film for filling liquid. Examples of the liquid include beverages, liquid seasonings, liquid detergents, and the like. Among them, from the viewpoint of being able to form a bag with excellent sanitation, it is particularly preferable to be a beverage, and from the viewpoint of being able to form a bag having excellent transparency with an outer layer surface that is less likely to be damaged, a transparent beverage, especially a beverage Water (especially mineral water for drinking) is preferred. In particular, it is suitable for liquid packages for drink servers such as water servers.

Examples of bags obtained by filling the tubular coextruded film of the present invention with a liquid include pillow pouch packaging bags, standing pouch packaging bags, three side seal bags, four side seal bags and the like.

EXAMPLES The present invention will be described in more detail below based on examples, but the present invention is not limited only to these examples. The compounding amounts shown in the table are the compounding amounts of each component, and are expressed on a mass basis unless otherwise specified.

The conditions for co-extrusion by the insulation method are as follows.
<Conditions of the Inflation Law>
・Extrusion equipment: Co-extrusion water cooling inflation equipment ・Extrusion temperature: 210°C (high density polyethylene), 200°C (linear low density polyethylene), 250°C (6 nylon), 180°C (maleic anhydride-modified polyolefin)
・Cooling water temperature: 20 to 40°C

Example 1
As the raw material for the outer layer (outer layer raw material), linear low-density polyethylene (density: 0.931 g/cm ³ ) and synthetic zeolite (spherical, average particle size: 7 μm) as an anti-blocking agent were added at 5000 mass ppm. A mixture was used.
100% by mass of 6 nylon (6NY) was used as a raw material for forming the intermediate layer (raw material for intermediate layer).
As the raw material for the inner layer (raw material for inner layer), a mixture of linear low-density polyethylene (density: 0.915 g/cm ³ ) and synthetic zeolite (spherical, average particle size: 7 μm) at 3000 mass ppm is used. board.
100% by mass of a maleic anhydride-modified polyolefin resin was used as a raw material for forming the adhesive resin layer (raw material for the adhesive resin layer).
Lamination of [outer layer (35 μm)/adhesive resin layer (7 μm)/intermediate layer (28 μm)/adhesive resin layer (7 μm)/inner layer (63 μm)] by a coextrusion inflation method using the raw materials for each layer prepared above. A tubular coextruded film consisting of the structure was produced (total thickness: 140 μm).

Example 2
Example 1, except that 100% by mass of saponified ethylene-vinyl acetate copolymer (EVOH) (degree of saponification: 38 mol%) was used as the raw material for the intermediate layer, and that the thickness of each layer was changed. Similarly, by the co-extrusion inflation method, tubular co-extrusion having a laminated structure of [outer layer (24 μm)/adhesive resin layer (6 μm)/intermediate layer (18 μm)/adhesive resin layer (6 μm)/inner layer (66 μm)] A film was produced (total thickness: 120 μm).

Example 3
[Outer layer ( 35 μm)/adhesive resin layer (7 μm)/intermediate layer (28 μm)/adhesive resin layer (7 μm)/inner layer (63 μm)] (total thickness: 140 μm).

Example 4
[ A tubular coextruded film having a laminated structure of outer layer (35 µm)/adhesive resin layer (7 µm)/intermediate layer (28 µm)/adhesive resin layer (7 µm)/inner layer (63 µm)] was produced (total thickness: 140 µm). .

Example 5
[ A tubular coextruded film having a laminated structure of outer layer (24 µm)/adhesive resin layer (6 µm)/intermediate layer (18 µm)/adhesive resin layer (6 µm)/inner layer (66 µm)] was produced (total thickness: 120 µm). .

Comparative example 1
Synthetic silica (non-spherical, average particle size: 5 μm) was used as an anti-blocking agent mixed with the raw material for the outer layer, and synthetic silica (non-spherical, average particle size: 10 μm) was used as an anti-blocking agent mixed for the inner layer. ) in the same manner as in Example 1, by a coextrusion inflation method, [outer layer (35 μm) / adhesive resin layer (7 μm) / intermediate layer (28 μm) / adhesive resin layer (7 μm) / inner layer ( 63 μm)] was produced (total thickness: 140 μm).

Comparative example 2
As a raw material for the outer layer, high-density polyethylene (density: 0.940 g/cm ³ ) produced using a metallocene catalyst was mixed with 20,000 mass ppm of synthetic silica (non-spherical, average particle size: 10 μm) as an anti-blocking agent. I used what I did.
As a material for the intermediate layer, saponified ethylene-vinyl acetate copolymer (EVOH) (degree of saponification: 38 mol %) was used in an amount of 100% by mass.
As a raw material for the inner layer, 10,000 mass ppm of synthetic silica (spherical, average particle size: 10 μm) mixed with linear low-density polyethylene (density: 0.920 g/cm ³ ) was used.
100% by mass of a maleic anhydride-modified polyolefin resin was used as a raw material for forming the adhesive resin layer (raw material for the adhesive resin layer).
Lamination of [outer layer (24 μm)/adhesive resin layer (6 μm)/intermediate layer (18 μm)/adhesive resin layer (6 μm)/inner layer (66 μm)] by a coextrusion inflation method using the raw materials for each layer prepared above. A tubular coextruded film consisting of the structure was produced (total thickness: 120 μm).

Comparative example 3
As the raw material for the outer layer, linear low-density polyethylene (density: 0.930 g/cm ³ ) was mixed with 20000 ppm by mass of synthetic silica (non-spherical, average particle size: 10 μm) as an anti-blocking agent. .
100% by mass of 6 nylon (6NY) was used as the raw material for the intermediate layer.
As a raw material for the inner layer, 3000 ppm by mass of synthetic silica (non-spherical, average particle size: 10 μm) was mixed with linear low-density polyethylene (density: 0.920 g/cm ³ ).
100% by mass of a maleic anhydride-modified polyolefin resin was used as a raw material for forming the adhesive resin layer (raw material for the adhesive resin layer).
Lamination of [outer layer (35 μm)/adhesive resin layer (7 μm)/intermediate layer (28 μm)/adhesive resin layer (7 μm)/inner layer (63 μm)] by a coextrusion inflation method using the raw materials for each layer prepared above. A tubular coextruded film consisting of the structure was produced (total thickness: 140 μm).

Comparative example 4
[Outer layer (35 μm)/adhesive resin layer (7 μm)/intermediate layer (28 μm)/adhesive A tubular coextruded film having a laminate structure of resin layer (7 μm)/inner layer (63 μm) was produced (total thickness: 140 μm).

Comparative example 5
[ A tubular coextruded film having a laminated structure of outer layer (35 µm)/adhesive resin layer (7 µm)/intermediate layer (28 µm)/adhesive resin layer (7 µm)/inner layer (63 µm)] was produced (total thickness: 140 µm). .

Comparative example 6
[Outer layer (35 μm)/adhesive resin layer (7 μm)/intermediate layer ( 28 μm)/adhesive resin layer (7 μm)/inner layer (63 μm)] (total thickness: 140 μm).

(evaluation)
Each tubular coextruded film obtained in Examples and Comparative Examples was evaluated as follows.

(1) Blocking property of inner layer surface Each tubular coextruded film obtained in Examples and Comparative Examples was cut to 50 cm to obtain a tubular body having openings at both ends, and from one opening of the tubular body, An attempt was made to add 100 mL of water. Then, the blocking property of the inner layer surface was evaluated based on the following criteria.
◯ (good): The inner surfaces are blocked and easily open as water is injected.
Δ (Possible): Blocking is relatively strong and water injection stops in the middle, or blocking occurs before water injection but blocking is relatively weak and opens before water injection.
x (improper): Blocking is too strong to inject water, or no blocking at all.

(2) Scratch resistance of outer layer surface Using each tubular coextruded film obtained in Examples and Comparative Examples, a packaging bag (31 cm × 31 cm) prepared by heat-sealing the inner layers was filled with 7 L of water. made the body. Three bags made in the same manner are stacked and packed in a box of 32 cm × 32 cm × 35 cm, and after a 1000 km transportation vibration test using a transportation packaging tester (trade name “BF-50UT”, manufactured by IDEX Co., Ltd.) I checked the appearance. Then, the scratch resistance of the outer layer surface was evaluated based on the following criteria.
◯ (Good): Almost no change in appearance before and after the transportation vibration test.
(triangle|delta) (acceptable): Appearance becomes slightly whitish before and after transportation vibration test.
x (improper): The appearance was white before and after the transportation vibration test, and the see-through of the contents was remarkably poor.

(3) Machine Suitability Each tubular coextruded film obtained in Examples and Comparative Examples was wound into a roll, and was wound from the roll at a winding tension of 45 N/m using a rewinding machine. Then, machine suitability was evaluated based on the following criteria.
◯ (Good): The resistance during unwinding was small, and the film could be easily unwound.
× (improper): The resistance during unwinding was too large, and unwinding was not easy.

(4) Haze For each tubular coextruded film obtained in Examples and Comparative Examples, the surface of the outer layer was measured using a haze meter (trade name "HM-150", manufactured by Murakami Color Research Laboratory Co., Ltd.), and measured according to JIS K7136. Measured according to Then, haze was evaluated based on the following criteria.
○ (good): haze is 7% or less △ (acceptable): haze is over 7% and 8% or less × (improper): haze is over 8%

The tubular coextruded films of the present invention (Examples) had moderate blocking properties between the inner layer surfaces, and were excellent in mechanical aptitude and scratch resistance of the outer layer surfaces. For this reason, it is possible to manufacture a liquid-filled bag that is excellent in sanitation, can be easily unrolled, and has an outer layer surface that is less likely to be damaged. On the other hand, when a non-spherical antiblocking agent was used in the outer layer (Comparative Examples 1 to 3), and when the content of the antiblocking agent in the outer layer was large (Comparative Example 6), a spherical antiblocking agent The scratch resistance of the outer layer surface was inferior to the case of using . Also, when a non-spherical antiblocking agent was used in the inner layer (Comparative Examples 1 and 3), and when a spherical antiblocking agent was contained in a large proportion (Comparative Example 2), the blocking property was weak. Moreover, when the antiblocking agent was not mixed in the inner layer (Comparative Example 4) and when the content of the antiblocking agent in the inner layer was small (Comparative Example 5), the blocking property was too strong. Moreover, when the content of the antiblocking agent in the outer layer was small (Comparative Example 5), the mechanical suitability was poor.

REFERENCE SIGNS LIST 1 tubular coextruded film of the present invention 11 outer layer 12 adhesive resin layer 13 intermediate layer 14 adhesive resin layer 15 inner layer

Claims (5)

Having a laminated structure including an outer layer, an intermediate layer, and an inner layer in this order,
The outer layer contains a polyethylene-based resin as the most abundant resin in terms of mass among the resins constituting the layer, and has an average particle size of 2 to 10 μm and an anti-blocking agent having a major axis/minor axis of 1.2 or less in a plan projection view. is a resin layer containing 3000 to 20000 mass ppm,
The intermediate layer is a resin layer containing a polyamide-based resin or saponified ethylene-vinyl acetate copolymer as the resin having the largest amount in terms of mass among the resins constituting the layer,
The inner layer contains a polyethylene resin as the most abundant resin in terms of mass among the resins constituting the layer, and has an average particle size of 2 to 10 μm and an anti-blocking agent having a major axis/minor axis of 1.2 or less in a plan projection view. is a resin layer containing 2000 to 6000 ppm by mass ,
A tubular coextruded film for liquid packaging , wherein the content of the antiblocking agent is 70% by mass or more relative to the total mass of the particles contained in the inner layer . 2. The tubular coextruded film according to claim 1, wherein the antiblocking agent contained in the inner layer is inorganic particles. 3. The tubular coextruded film according to claim 1, wherein the total thickness of the outer layer and the inner layer is 70-80% of the total thickness of the tubular coextruded film. The tubular coextruded film according to any one of claims 1 to 3, wherein the polyethylene resin in the outer layer has a density of 0.930 to 0.950 g/cm ³ . The tubular coextruded film according to any one of Claims 1 to 4, wherein the polyethylene resin in the inner layer has a density of 0.900 to 0.930 g/ ^cm3 .

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