KR102654522B1 - Sealant films and packaging materials - Google Patents

Abstract

It is made of a laminated film in which an outer layer, a middle layer, and an inner layer are laminated, the outer layer and the inner layer contain a polyethylene-based resin, the middle layer contains linear low-density polyethylene and a cyclic olefin-based resin, and the above-mentioned resin components contained in the middle layer include Excellent tear resistance due to a sealant film characterized by a content of 20 to 40% by mass of cyclic olefin resin and a standardized molecular orientation MORc value of 1.025 or more when the standard thickness measured with a microwave molecular orientation meter is 60㎛. However, straight cuts can be achieved, and internal fusion and appearance unevenness of packaging materials during high-temperature processing can be suppressed.

Description

Sealant films and packaging materials

The present invention relates to a sealant film used in retort packaging that allows sterilization and cooking by heating or pressurizing food, etc. in the packaged state, and a packaging material using the sealant film.

As a packaging material for food, flexible packaging using plastic materials is used globally, and is showing an increasing trend along with expansion into emerging countries. Meanwhile, demand for retort foods that have been pressurized and heat sterilized (retort sterilized) at high temperatures is expected to increase in the future food packaging market due to their convenience. Retort food can be distributed at room temperature, and in addition to being convenient to eat, it is also easy to handle during distribution, and is expected to expand into areas where cold chain development is insufficient.

When eating retort food, it is generally warmed by double boiling in boiling water, and after heating, the film is opened by tearing a notch provided at the top of the package. For this reason, tear resistance is required for resin films used in retort packaging. As a retort film with easy tearing properties, for example, a propylene-based film using a resin obtained by blending a low-crystalline ethylene-based elastomer with a propylene-ethylene block copolymer and controlling the birefringence to a specific range is disclosed ( (see patent document 1).

In addition, packaging materials having cut properties include packaging materials used in soft bags filled with chemical solutions such as physiological saline and electrolyte solutions, which include an intermediate layer containing a cyclic olefin resin and a linear low-density polyethylene resin, and a linear low-density polyethylene resin. A packaging material having an inner layer and an outer layer of low-density polyethylene resin is disclosed (see Patent Document 2).

Japanese Patent Laid-open No. 2011-162667 Japanese Patent Laid-open No. 2009-172902

In the propylene-based film that promotes the birefringence described above, a decrease in tear strength was confirmed as the rigidity of the film improved, but the control of the direction of tear was not sufficient, and improvement of straight cut properties that tears in a straight line was required. . In addition, packaging materials using ethylene-propylene copolymer as a sealant do not have sufficient impact resistance when used as heavy goods for business use or distribution in cold regions, and may cause bag breakage accidents.

The packaging material used for the above-mentioned soft bag has neat and straight cut properties, but for application to retort applications, further improvement in cut properties is required.

The problem that the present invention seeks to solve is to provide a sealant film and packaging material that has suitable bag resistance and is excellent in tear resistance and straight cut properties.

Furthermore, in the present invention, in addition to the above problems, the problem is to provide a sealant film having suitable sealing properties.

Furthermore, in the present invention, in addition to the above problems, the object is to provide a sealant film that does not cause internal fusion or appearance unevenness of the packaging material during high temperature processing.

The present invention consists of a laminated film in which an outer layer (A), a middle layer (B), and an inner layer (C) are laminated, the outer layer (A) and the inner layer (C) contain a polyethylene resin, and the middle layer (B) is, It contains linear low-density polyethylene (b1) and a cyclic olefin resin (b2), the content of the cyclic olefin resin (b2) in the resin component contained in the intermediate layer (B) is 20 to 40% by mass, and the microwave method The above problem is solved by a sealant film having a standardized molecular orientation MORc value of 1.025 or more when the standard thickness measured by a molecular orientation meter is 60 μm.

In addition, the present invention is a method of manufacturing a sealant film made of a laminated film in which an outer layer (A), a middle layer (B), and an inner layer (C) are laminated by a coextrusion inflation method, wherein the outer layer forming the outer layer (A) The resin for the inner layer and the inner layer resin forming the inner layer (C) contain a polyethylene-based resin, and the intermediate layer resin forming the intermediate layer (B) contains linear low-density polyethylene (b1) and a cyclic olefin-based resin (b2). and the content of the cyclic olefin resin (b2) in the resin component contained in the intermediate layer resin is 20 to 40% by mass, and the coextrusion inflation molding is performed at a blow ratio of 1.0 to 2.3 and a drawdown ratio of 20 to 60. The above problem is solved by a method for manufacturing a sealant film.

Since the sealant film of the present invention has suitable tear resistance and straight cut properties due to the above-described structure, it is difficult for the contents to overflow or scatter in the packaging bag using the sealant film of the present invention when opening or after opening begins to occur. Especially when applied to retort packaging applications, it is possible to cut simply and with suitable straightness. In addition, it can achieve suitable fracture resistance, especially at low temperatures, and has suitable distribution suitability.

In addition, the sealant film of the present invention is easy to realize a packaging material that realizes suitable thermal properties and does not cause internal fusion or appearance unevenness during high temperature processing such as retort sterilization. For this reason, the sealant film of the present invention can be suitably applied to packaging materials for high temperature processing, such as retort food packaging materials that require high temperature sterilization. In addition, the sealant film of the present invention is suitable for use in these packaging materials because it is easy to achieve suitable sealing properties.

The sealant film of the present invention is made of a laminated film in which an outer layer (A), a middle layer (B), and an inner layer (C) are laminated in that order, and the outer layer (A) and the inner layer (C) contain a polyethylene resin, The intermediate layer (B) between the outer layer (A) and the inner layer (C) contains linear low-density polyethylene (b1) and a cyclic olefin resin (b2), and the cyclic olefin resin is among the resin components contained in the intermediate layer (B). It is a sealant film containing 20 to 40 mass% of (b2). In addition, the standardized molecular orientation MORc value when the standard thickness measured with a microwave-type molecular orientation meter is 60 μm is 1.025 or more.

[Outer layer (A)]

The outer layer (A) of the sealant film of the present invention contains polyethylene-based resin. Examples of the polyethylene resin include polyethylene resins such as very low density polyethylene (VLDPE), linear low density polyethylene (LLDPE), low density polyethylene (LDPE), linear medium density polyethylene (LMDPE), and medium density polyethylene (MDPE), and ethylene- Vinyl acetate copolymer (EVA), ethylene-methyl methacrylate copolymer (EMMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl acrylate (EMA) copolymer, ethylene-ethyl acrylate-maleic anhydride Ethylene-based copolymers such as acid copolymer (E-EA-MAH), ethylene-acrylic acid copolymer (EAA), and ethylene-methacrylic acid copolymer (EMAA); Additionally, ionomers of ethylene-acrylic acid copolymers and ionomers of ethylene-methacrylic acid copolymers can be exemplified. These polyethylene-based resins may be used individually, or two or more types may be mixed and used. Among these, since it is easy to obtain suitable impact resistance, ultra-low-density polyethylene, linear low-density polyethylene, low-density polyethylene, and linear medium-density polyethylene can be preferably used, and linear low-density polyethylene is especially preferable. Additionally, it is also preferable to use high-density polyethylene (HDPE) in combination with these medium- and low-density polyethylenes.

As linear low-density polyethylene, ethylene monomer is used as the main component and α-olefins such as butene-1, hexene-1, and octene-1,4-methylpentene are added as comonomers by low-pressure radical polymerization using a single-site catalyst. It is copolymerized. The comonomer content in LLDPE is preferably in the range of 0.5 to 20 mol%, and more preferably in the range of 1 to 18 mol%.

Examples of the single site catalyst include various single site catalysts such as a metallocene catalyst system such as a combination of a metallocene compound of a transition metal of group IV or V of the periodic table, and an organoaluminum compound and/or an ionic compound. In addition, since single-site catalysts have uniform active sites, the molecular weight distribution of the resulting resin is sharp compared to multi-site catalysts with non-uniform active sites, so when deposited into a film, precipitation of low molecular weight components is less and the seal strength is improved. This is preferable because a resin with excellent physical properties such as stability and impact resistance can be obtained.

In the outer layer (A), since it is easy to obtain suitable impact resistance, it is preferable to contain 60% by mass or more of polyethylene resin, and more preferably 80% by mass or more, based on the total amount of resin components forming the layer. And, it is more preferable to contain it at 90% by mass or more. Among them, it is preferable that it contains only polyethylene resin as the resin component, and that 60% by mass or more of the resin component is linear low-density polyethylene, more preferably 80% by mass or more, and 90% by mass or more. It is more desirable.

In addition, in the outer layer (A), other resins of the above polyethylene resin may be used in combination, as long as the effect of the present invention is not impaired. Other resin species that can be used in combination include, for example, polyolefin-based resins other than the above-mentioned polyethylene-based resins, such as propylene homopolymer, propylene-ethylene copolymer, propylene-butene-1 copolymer, and propylene- Examples include polypropylene-based resins such as ethylene-butene-1 copolymer and metallocene catalyst-based polypropylene.

When using these other resins, the content of the resin component contained in the outer layer (A) is preferably 40% by mass or less, more preferably 20% by weight or less, and more preferably 10% by weight or less. . The lower limit is not particularly limited, but may be used appropriately at a content of 1% by mass or more depending on the desired properties.

The outer layer (A) used in the sealant film of the present invention is preferably a layer in which the average density of the resin component used in the layer is 0.940 g/cm3 or more, and more preferably 0.940 to 0.945 g/cm3. By setting the average density of the resin component within the range, appearance unevenness during high-temperature treatment such as retort sterilization can be appropriately suppressed. The average density is the density of the resins used in the layer, when the resins used in the layer are resin _a , resin _b , and resin _c ... When the masses are W _a , W _b , W _c ···, (d _a W _a +d _b W _b +d _c W _c ···)/(W _a +W _b +W _c ···) This is the density calculated as .

The density of each resin used in the outer layer (A) is not particularly limited as long as the average density of the resin components used is within the above range, but for polyethylene resins, it is preferably 0.880 g/cm3 or more, and 0.920 g/cm3 or more. It is more preferable, and 0.940 to 0.950 g/cm3 is particularly preferable. Also, for other resins, it is preferable to use 0.920 g/cm3 or more.

The MFR of the resin component used in the outer layer (A) is 0.1 to 20 g/10 min (190°C, 21.18N), preferably 0.3 to 10 g/10 min (190°C, 21.18N), more preferably 0.5 to 10 g/10 min (190°C, 21.18N). It is 5g/10min (190℃, 21.18N). If the MFR is within this range, it is preferable because good film forming properties can be obtained in various multilayer film forming methods.

[Middle layer (B)]

The intermediate layer (B) of the sealant film of the present invention contains linear low-density polyethylene (b1). By containing the linear low-density polyethylene, it becomes easy to appropriately suppress appearance unevenness during retort sterilization during high-temperature processing along with appropriate impact resistance. Since the density of linear low-density polyethylene (b1) is particularly easy to suppress appearance unevenness, it is preferably 0.937 g/cm3 or more, more preferably 0.940 g/cm3 or more, and still more preferably 0.940 to 0.945 g/cm3. It is ㎤. In addition, the average density of the resin component in the intermediate layer (B) is preferably 0.940 g/cm3 or more, and more preferably 0.940 to 0.945 g/cm3.

The MFR of linear low-density polyethylene (b1) is 0.1 to 20 g/10 min (190°C, 21.18N), preferably 0.3 to 10 g/10 min (190°C, 21.18N), more preferably 0.5 to 5 g/10 min. 10 minutes (190℃, 21.18N). If the MFR is within this range, it is preferable because it has excellent compatibility with the cyclic olefin resin (b2) and also provides good film forming properties in various multilayer film forming methods.

The content of linear low-density polyethylene (b1) in the middle layer (B) is preferably 60 to 80% by mass in the resin component contained in the middle layer (B), because it is easy to obtain appropriate impact resistance and heat resistance during high temperature treatment. , it is more preferable that it is 65 to 75 mass%.

By containing the cyclic olefin resin (b2) in the intermediate layer (B) of the sealant film of the present invention, excellent tear resistance and straight cut properties can be achieved. Examples of the cyclic olefin resin (b2) include norbornene polymers, vinyl alicyclic hydrocarbon polymers, and cyclic conjugated diene polymers. Among these, norbornene-based polymers are preferable. In addition, norbornene-based polymers include ring-opening polymers of norbornene-based monomers (hereinafter referred to as “COP”) and norbornene-based copolymers obtained by copolymerizing norbornene-based monomers with olefins such as ethylene (hereinafter referred to as “COC”). ), etc. Additionally, hydrogenated products of COP and COC are also particularly preferred. Moreover, the weight average molecular weight of the cyclic olefin resin is preferably 5,000 to 500,000, and more preferably 7,000 to 300,000.

The norbornene-based polymer and the norbornene-based monomer used as raw materials are alicyclic monomers having a norbornene ring. Examples of such norbornene monomers include norbornene, tetracyclododecene, ethylidene norbornene, vinyl norbornene, ethylidene tetracyclododecene, dicyclopentadiene, and dimethanotetrahydrofluorine. Orene, phenylnorbornene, methoxycarbonylnorbornene, methoxycarbonyltetracyclododecene, etc. are mentioned. These norbornene-based monomers may be used individually, or two or more types may be used together.

The norbornene-based copolymer is a copolymerization of the norbornene-based monomer and a copolymerizable olefin. Examples of such olefins include olefins having 2 to 20 carbon atoms, such as ethylene, propylene, and 1-butene. ; Cycloolefins such as cyclobutene, cyclopentene, and cyclohexene; and non-conjugated dienes such as 1,4-hexadiene.

The content of the cyclic olefin resin (b2) contained in the intermediate layer (B) is preferably 20 to 40% by mass, and more preferably 25 to 35% by mass, of the resin component contained in the intermediate layer (B). By setting the content of cyclic olefin resin (b2) within the range, suitable tear resistance and straight cut properties can be achieved without impairing impact resistance.

Moreover, the cyclic olefin resin (b2) used in the intermediate layer (B) preferably has a glass transition temperature of 140°C or lower, more preferably 50 to 140°C, and even more preferably 70 to 120°C. By using a cyclic olefin resin (b2) having the glass transition temperature, it is easy to obtain good heat resistance and rigidity, and it is also easy to improve bag resistance against dropping, etc. In addition, it becomes easy to obtain good compatibility, and it becomes easy to suppress unevenness in appearance. Glass transition temperature (Tg) is a value obtained by measuring by DSC.

The MFR of the cyclic olefin resin (b2) is 0.2 to 17 g/10 min (230°C, 21.18N), preferably 3 to 15 g/10 min (230°C, 21.18N), more preferably 5 to 13 g/ 10 minutes (230℃, 21.18N). If the MFR is within this range, it is preferable because it has excellent compatibility with linear low-density polyethylene (b1) and also provides good film forming properties in various multilayer film forming methods.

As a commercial product that can be used as the cyclic olefin resin used in the present invention, ring-opening polymers (COP) of norbornene monomers include, for example, “ZEONOR” manufactured by Nippon Zeon Co., Ltd.; Examples of the norbornene-based copolymer (COC) include “Apel” manufactured by Mitsui Chemicals Co., Ltd. and “TOPAS” manufactured by Polyplastics Corporation.

As the resin component in the intermediate layer (B), it is preferable to contain only the linear low-density polyethylene (b1) and the cyclic olefin resin (b2), but other resins other than these resin components may be used within the range that does not impair the effect of the present invention. You can use it together. Other resin species that can be used in combination include, for example, the polyethylene-based resin and polypropylene-based resin exemplified in the outer layer (A).

When using these other resins, the amount is preferably 20% by mass or less, and more preferably 10% by mass or less of the resin component contained in the intermediate layer (B). The lower limit is not particularly limited, but may be appropriately used at a content of 1% by mass or more depending on the desired characteristics.

[Inner layer (C)]

The inner layer (C) in the sealant film of the present invention is a layer containing a polyethylene resin, and is preferably a layer in which the average density of the resin component in the layer is 0.940 g/cm3 or more. The inner layer (C) is a layer that serves as a heat seal layer of the sealant film.

The polyethylene-based resin used in the inner layer (C) and the resin that can be used in combination with the polyethylene-based resin can be the same as those for the outer layer (A), and are also preferred. In addition, the content of the polyethylene resin or other resin, and the density or average density of the resin component in the inner layer can be exemplified as a preferable range similar to that of the outer layer (A).

In addition, for the inner layer (C), it is also preferable to use high-density polyethylene (HDPE) in combination with medium- and low-density polyethylene such as ultra-low-density polyethylene, linear low-density polyethylene, low-density polyethylene, and linear medium-density polyethylene. When using medium and low density polyethylene and high density polyethylene together, the content of medium and low density polyethylene in the resin component used in the inner layer (C) is set to 40 to 80% by mass, and the content of high density polyethylene is set to 20 to 60% by mass. It is preferable, and it is more preferable that the content of medium-low density polyethylene is 45 to 75% by mass, and the content of high density polyethylene is 25 to 55% by mass.

[Sealant film]

The sealant film of the present invention is a laminated film in which the outer layer (A), middle layer (B), and inner layer (C) are laminated in that order. Due to the configuration, the sealant film of the present invention can realize a packaging material that has suitable tear resistance and straight cut properties and does not cause inner surface fusion or appearance unevenness during high temperature processing such as retort sterilization. In addition, it is easy to achieve suitable sealing properties and anti-bag properties, making it suitable for use as retort packaging material.

The sealant film of the present invention has a standardized molecular orientation MORc value of 1.025 or more, preferably 1.030 or more, and more preferably 1.035 or more when the standard thickness measured with a microwave molecular orientation meter is 60 ㎛. The upper limit is not particularly limited, but is preferably 1.20 or less, more preferably 1.080 or less. In the present invention, by setting the MORc value of the sealant film to the above range, it is possible to achieve excellent tear resistance and straight cut properties along with suitable bag breaking resistance.

The MORc value is a value indicating the degree of molecular orientation, and is measured by the following measurement method.

In the microwave resonance waveguide of a known microwave molecular orientation system, the sample surface (film surface) is placed perpendicular to the direction of microwave travel. Then, while the sample is continuously irradiated with microwaves whose vibration direction is deflected in one direction, the sample is rotated from 0 to 360° in a plane perpendicular to the direction of movement of the microwaves, and the molecular orientation MOR is determined by measuring the intensity of the microwaves transmitted through the sample. Save.

The normalized molecular orientation MORc in this embodiment is the MOR value when tc is the reference thickness, and can be obtained by the following formula.

MORc = (tc/t)×(MOR-1)+1

(tc: reference thickness to be corrected, t: sample thickness)

Here, the closer the MORc value is to 1.000, the more isotropic the film is.

The standardized molecular orientation MORc can be measured at a resonance frequency around 4 GHz using a known molecular orientation meter, for example, a microwave molecular orientation meter MOA-2000A or MOA-2012A manufactured by Ojigaisokuki Co., Ltd. there is.

The thickness of the sealant film of the present invention may be appropriately adjusted depending on the intended use or mode of use, but from the viewpoint of heat resistance in packaging applications, bag resistance during distribution, heat sealing properties, etc., the total thickness should be 20 to 150 ㎛. It is preferable, and it is more preferable that it is 40-100 micrometers.

As for the thickness ratio of each layer, from the viewpoint of sealing properties, tear resistance, and lamination properties, the thickness ratio of the outer layer (A) is preferably in the range of 10 to 40% of the total thickness of the sealant film, and more preferably 15 to 30%. do. Additionally, the thickness ratio of the inner layer (C) is preferably in the range of 10 to 40%, and more preferably in the range of 15 to 30%.

Additionally, the thickness ratio of the intermediate layer (B) is preferably 10 to 80%, more preferably 15 to 60%, and especially preferably 20 to 50%. In addition, in the sealant film of the present invention, suitable cut properties can be achieved even when the thickness ratio of the intermediate layer (B) is low (for example, 40% or less, more preferably 30% or less), so it is suitable. Cuttable sealant film can be obtained at low cost.

As a specific thickness, the thickness of the outer layer (A) is preferably 2 to 60 μm, and more preferably 3 to 45 μm. The thickness of the intermediate layer (B1) is preferably 4 to 120 μm, and more preferably 8 to 100 μm. The thickness of the inner layer (C) is preferably 2 to 60 μm, and more preferably 3 to 45 μm.

The sealant film of the present invention is a laminated film in which the outer layer (A), middle layer (B), and inner layer (C) are laminated in that order, but a gas barrier layer or a gas barrier layer or the like is added between the layers to the extent that the effect of the present invention is not impaired. Any other layer, such as an adhesive layer, may be provided. In addition, the sealant film of the present invention preferably has an average density of the resin component in all layers of 0.940 g/cm3 or more, and more preferably 0.940 to 0.945 g/cm3. For this reason, when providing another layer, it is preferable that the average density of the resin component in the other layer is also within the above range.

In each layer of the sealant film of the present invention, various additives may be mixed within a range that does not impair the effect of the present invention. Examples of the additive include antioxidants, weathering stabilizers, antistatic agents, antifogging agents, antiblocking agents, lubricants, nucleating agents, pigments, and the like.

[Manufacturing method]

In the method for producing the sealant film of the present invention, for example, the resins (including resin mixtures containing two or more types of resins or additives) used in each layer of the multilayer film are heated and melted in separate extruders, and the An example is the coextrusion method of laminating in a molten state by a method such as an extrusion multilayer die method or a feed block method and then forming it into a film shape by an inflation method. This coextrusion method is preferable because it is possible to relatively freely adjust the ratio of the thickness of each layer, and a film with excellent hygiene and cost-effectiveness is obtained. As an inflation method, the air-cooled inflation method is preferable, and the upward air-cooled inflation method can be used particularly preferably. Additionally, a multilayer film can be obtained by using a plurality of extruders and a multilayer circular die. After extruding the cylindrical molten resin upward using these, if necessary, the cylindrical molten resin is expanded and taken out, and the molten resin is cooled and solidified by air cooling, and then cut appropriately to form the desired film. You can get it.

In the present invention, since it is easy to obtain a sealant film with a specific orientation, suitable cut properties can be achieved by setting the blow ratio to 1.0 to 2.3 and the drawdown ratio to 20 to 60 during coextrusion inflation molding.

The drawdown ratio in the inflation method corresponds to the ratio of the line speed V _L (m/min) and the die exit speed V ₀ (m/min), and is calculated as V _L /V ₀ . Additionally, blowby corresponds to the ratio of the diameter D ₀ of the die and the final diameter D _L of the bubble, and is calculated from D _L /D ₀ . In the present invention, the drawdown ratio is set to 20 to 60, but is preferably set to 25 to 50, and more preferably set to 30 to 40. Additionally, the blow ratio is preferably 1.0 to 2.3, more preferably 1.1 to 2.0, and still more preferably 1.2 to 1.5. By adjusting these values to the above range, the resin discharged from the die is predominantly stretched in the flow direction, and excellent tear properties and straight tear properties are easily developed.

In the inflation method, the temperature of the extruder and die is preferably 180 to 220°C. The diameter of the dice is preferably 100 to 1200 mm, more preferably 100 to 800 mm, and still more preferably 150 to 500 mm. The lip opening of the dice is preferably 0.5 to 5 mm, more preferably 1.5 to 4.5 mm, and still more preferably 2.0 to 4.0 mm. The discharge amount is preferably 10 to 400 Kg/h, more preferably 20 to 300 Kg/h, and still more preferably 50 to 250 Kg/h. The line speed varies depending on the die diameter, blow ratio, and discharge amount, but is preferably 10 to 150 m/min, and more preferably 20 to 100 m/min.

[Packaging material for retort]

When the sealant film of the present invention is used as a retort packaging material, another base film can be bonded to the outer layer (A) side surface of the sealant film. Other base films are not particularly limited, but from the viewpoint of easily demonstrating the effects of the present invention, it is preferable to use a plastic base film, especially a biaxially stretched resin film. Additionally, in the case of applications that do not require transparency, aluminum foil can be used in combination.

Stretched resin films include, for example, biaxially oriented polyester (PET), biaxially oriented polypropylene (OPP), biaxially oriented polyamide (PA), and coextruded biaxially with ethylene vinyl alcohol copolymer (EVOH) as the center layer. Examples include stretched polypropylene, biaxially stretched ethylene vinyl alcohol copolymer (EVOH), alumina-deposited PET, silica-deposited PET, alumina-silica dual-deposited PET, silica-deposited PA, and alumina-deposited PA. These may be used individually or in combination.

As a method for bonding the sealant film of the present invention and various stretched base films, two processing methods are mainly used. One is to apply an anchor coat agent as needed to the laminate surface of the sealant film of the present invention or the base film, and apply the heat-melted polymer film (polyethylene, polypropylene, etc.) to the laminate of the sealant film of the present invention and the base film. It is an extrusion lamination method in which a thin film is extruded, pressed, and laminated between surfaces. The other is a dry lamination method in which an adhesive is applied to the laminate surface of the base film and then the sealant film of the present invention and the base film are pressed and laminated. However, when used in retort packaging, the dry lamination method is preferable.

Adhesives for laminates are generally cured with polyol/isocyanate, and are widely used in high-performance applications such as retort applications. In addition, conventionally, the combination of aluminum foil and sealant film was common for bonding, but various transparent vapor deposition films are commercially available, and due to the demand for improved visibility of contents, the bonding of transparent vapor deposition films and sealant films has also increased.

Polyols used in laminate adhesives include, for example, polyol itself, which will be described later, or polyester polyol obtained by reacting polyol with polycarboxylic acids, which will be described later, or ethylene glycol, diethylene glycol, triethylene glycol, and propylene glycol. , trimethylene glycol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, and other compounds having two active hydrogen atoms as initiators such as ethylene oxide, propylene oxide, and butylene oxide. , polyethers obtained by addition polymerization of monomers such as styrene oxide, epichlorohydrin, tetrahydrofuran, and cyclohexylene.

Examples of the polyol include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, and 1,6-hexane. Diol, neopentyl glycol, methylpentanediol, dimethylbutanediol, butylethylpropanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, bishydroxyethoxybenzene, 1,4-cyclo Glycols such as hexanediol, 1,4-cyclohexanedimethanol, triethylene glycol, polycaprolactone diol, dimer diol, bisphenol A, hydrogenated bisphenol A, propiolactone, butyrolactone, ε-caprolactone, δ -Polyesters obtained by ring-opening polymerization of cyclic ester compounds such as valerolactone and β-methyl-δ-valerolactone, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, trimethylene glycol, 1, Compounds having two active hydrogen atoms, such as 3-butanediol, 1,4-butanediol, 1,6-hexanediol, and neopentyl glycol, are used as initiators such as ethylene oxide, propylene oxide, butylene oxide, styrene oxide, and epichlorohyde. Polyethers obtained by addition polymerization of monomers such as polyethylene, tetrahydrofuran, and cyclohexylene can be mentioned.

Examples of the polycarboxylic acids include succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, maleic anhydride, fumaric acid, 1,3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, Terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, naphthalic acid, biphenyldicarboxylic acid, 1,2-bis(phenoxy)ethane- p,p'-dicarboxylic acids and anhydride or ester-forming derivatives of these dicarboxylic acids; Examples include polybasic acids such as p-hydroxybenzoic acid, p-(2-hydroxyethoxy)benzoic acid, ester-forming derivatives of these dihydroxycarboxylic acids, and dimer acid.

Examples of the polyisocyanate include organic compounds having at least two isocyanate groups in the molecule. Examples of organic polyisocyanates include tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, 1,6-hexamethylene diisocyanate, isophorone diisocyanate, and 4,4'-methylenebis(cyclohexylisocyanate). , polyisocyanates such as lysine diisocyanate, trimethylhexamethylene diisocyanate, 1,3-(isocyanatomethyl)cyclohexane, 1,5-naphthalene diisocyanate, and triphenylmethane triisocyanate; Derivatives (modified products) of polyisocyanates such as adduct forms of these polyisocyanates, biuret forms of these polyisocyanates, or isocyanurate forms of these polyisocyanates, etc. can be mentioned.

Additionally, a product obtained by reacting the isocyanate with the polyol in a mixing ratio that results in an excess of isocyanate groups may be used.

In the adhesive, the equivalent ratio polyol/isocyanate between the hydroxyl equivalent of the polyol and the isocyanate equivalent of the polyisocyanate is preferably 0.5 to 5.0.

The packaging material of the present invention uses the above-mentioned sealant film as a sealant, and has a configuration of laminating a base film on the outer layer (A) side of the sealant film, thereby providing good sealing properties and good opening properties due to suitable thermal properties. It can be realized. In addition, since suitable heat resistance and bag resistance can be achieved, fusion of the inner layers (C) forming the heat seal layer and appearance unevenness can be suppressed even during high-temperature sterilization treatment. For this reason, packaging materials formed by laminating the sealant film of the present invention with various substrates can be suitably applied as packaging materials for retort foods.

The packaging material of the present invention can be packaged into various shapes such as a flat table, a stand-up pouch, or a tube, and can be suitably used as a packaging table. Specifically, for example, one sheet of film-shaped packaging material is folded so that the sealant layers face each other, or two sheets of film-shaped packaging material of the present invention are overlapped so that the sealant layers face each other, and the peripheral edges are heat-sealed. , can be used as a packaging bag (retort pouch) for retort food, etc. Additionally, if necessary, an opening start portion such as a V notch or an I notch may be provided.

The packaging material of the present invention and the packaging stand for retort food using the packaging material can be suitably used for packaging foods that require processing under high-temperature hydrothermal conditions such as boiling and retort sterilization, for example, curry, stew, soup, It can be suitably applied to various retort food packaging applications such as cooking sauce.

(Example)

(Example 1)

As the resin component forming each layer of the outer layer, middle layer, and inner layer, the following resins were respectively used to prepare the resin mixture forming each layer. These mixtures were supplied to each of three extruders and melted at 250°C. The molten resin is supplied to a co-extrusion multilayer film manufacturing apparatus using an air-cooled inflation method equipped with a spiral three-layer die (die temperature: 200°C), and co-melt extrusion is performed, so that the layer composition of the film is outer layer/middle layer/inner layer. A laminated film with a total thickness of 60 ㎛ was obtained with a three-layer structure and a thickness ratio (%) of each layer of 30/40/30. The blow ratio during molding was set to 1.3, and the drawdown ratio was set to 30.

Outer layer: MFR 0.5g/10min (190℃, 21.18N), linear low-density polyethylene (hereinafter referred to as “LLDPE(1)”) with density 0.944g/cm3.

Middle layer: 70% by mass of LLDPE (1) and 30% by mass of norbornene-based copolymer (hereinafter referred to as “COC”) with a glass transition temperature (Tg) of 78°C and an MFR of 10g/10min (230°C, 21.18N). resin mixture of

Inner layer: mixed resin material containing 50% by mass of LLDPE (1), MFR 1g/10min (190°C, 21.18N), and 50% by mass of high-density polyethylene (hereinafter referred to as “HDPE”) with a density of 0.960g/cm3.

(Example 2)

A laminated film was obtained in the same manner as in Example 1 except that the blow ratio was set to 1.5 and the drawdown ratio was set to 27.

(Example 3)

A laminated film was obtained in the same manner as in Example 1 except that the blow ratio was set to 1.8 and the drawdown ratio was set to 23.

(Example 4)

A laminated film was obtained in the same manner as in Example 1 except that the thickness ratio (%) of the outer layer/middle layer/inner layer was 40/25/35, the blow ratio was 1.2, and the drawdown ratio was 35.

(Example 5)

A laminated film was obtained in the same manner as in Example 1 except that the thickness ratio (%) of the outer layer/middle layer/inner layer was 35/30/35.

(Example 6)

A laminated film was obtained in the same manner as in Example 2, except that the resin components used for the outer and inner layers were changed.

Outer layer: mixed resin of 60% by mass of linear low-density polyethylene (hereinafter referred to as “LLDPE (2)”) with an MFR of 0.9g/10min (190°C, 21.18N) and a density of 0.929g/cm3 and 40% by mass of HDPE. water

Inner layer: mixed resin material of 50% by mass of LLDPE (2) and 50% by mass of HDPE.

(Example 7)

A laminated film was obtained in the same manner as in Example 2, except that the resin component used in the outer and inner layers was LLDPE (2).

(Example 8)

A laminated film was obtained in the same manner as in Example 2, except that the resin components used in the middle layer were 70% by mass of LLDPE (2) and 30% by mass of COC.

(Comparative Example 1)

A laminated film was obtained in the same manner as in Example 1 except that the blow ratio was set to 2.5 and the drawdown ratio was set to 15.

(Comparative Example 2)

A laminated film was obtained in the same manner as in Example 2, except that the resin component used in the middle layer was LLDPE (1).

(Comparative Example 3)

The resin components forming the outer layer, middle layer, and inner layer were the same as in Example 1, and these resin mixtures were each supplied to three extruders and melted at 250°C. The molten resin is supplied to a coextrusion multilayer film manufacturing apparatus using the T die/chilled roll method having a feed block (feed block and T die temperature: 250°C), and comelt extrusion is performed, so that the layer composition of the film is outer layer/middle layer. /A sealant film with a total thickness of 50㎛ was obtained, which consists of three inner layers and the thickness ratio of each layer is 25/50/25%.

The following evaluation was performed on the laminated films (sealant films) obtained in the above examples and comparative examples. The obtained results are shown in the table below.

(1) Standardized molecular orientation MORc

For each film of Examples and Comparative Examples, the standardized molecular orientation MORc was measured using a microwave molecular orientation meter MOA-2000 manufactured by Ojigaisokuki Co., Ltd. The reference thickness tc was set to 60 μm.

(2) Tear strength

According to JIS K7128-1 (Trouser method), tear strength in the flow direction was measured in a constant temperature room at 23°C and 50% Rh.

1N or less: ○ (excellent tear resistance)

Exceeding 1N: × (less tearing)

(2) Straight cut quality

Using a test piece with a length of 150 mm in the film flow direction and 50 mm in the width direction, a 15 mm wide slit of 10 mm is inserted in the center of the width direction, and the width (W ₀ ) of the tip of the slit is actually measured. . A previously prepared polyester sheet with a thickness of 0.3 mm, a width of 15 mm, and a length of 160 mm is attached to the tip of the slit with tape. The attached polyester sheet is folded back in the 180° direction, the test piece excluding the tip and the slit on the opposite side is attached to a tensile tester, and it is torn by 100 mm at a speed of 300 mm/min, and the width (W1) of the end point is measured. Take actual measurements. At this time, the retention rate was obtained from the following equation and was used as an index of straight cut properties.

Retention rate [%] = W ₁ /W ₀ ×100

100±10%: ○ (excellent straight cut performance)

Exceeding 100±10%: × (lack of straightness)

(3) Seal strength

On a biaxially stretched polyamide film with a thickness of 25 μm, a polyester adhesive is applied using a wire bar so that the application thickness is 3.5 g/m 2 . After drying the adhesive, a sealant film was attached and dried at 40°C for 24 hours to obtain a laminate film for heat seal testing. Using the obtained film, a test piece was created that was heat-sealed under the conditions of 160°C, 0.2 MPa, and 1 second, and heat treatment was performed at 121°C for 30 minutes using an autoclave. The test piece after heat treatment was cut to a width of 15 mm, and the seal strength was measured using a tensile tester. If it is 40N/15mm or more, it can be used normally.

(4) Internal fusion

A laminated film was obtained in the same manner as (3). The seals of the obtained films were overlapped, and heat treatment was performed at 121°C for 30 minutes using an autoclave. The test piece after the heat treatment was cooled to room temperature, cut into 15 mm width pieces, and the peel strength was measured using a tensile tester. Those with a peel strength of 1 N/15 mm or less were evaluated as having excellent heat resistance.

(5) Appearance unevenness

A laminated film was obtained in the same manner as (3). Using the obtained film, it was processed into a bag so that the inner dimension was 100 mm x 150 mm (heat seal width 10 mm), and 200 ml of water was sealed. After the water-encapsulated umbilical cord product was retorted at 121°C for 30 minutes, the appearance unevenness was visually evaluated.

[Table 1]

[Table 2]

As is clear from the table above, the sealant films of the present invention in Examples 1 to 8 had tear strength that allowed easy tearing and good straight cut properties. Additionally, the peeling strength of the sealant films of Examples 1 to 6 and 8 in the inner surface fusion evaluation was 1 N/15 mm or less. Additionally, in the sealant films of Examples 1 to 6, no unevenness in appearance was recognized even in the appearance evaluation. On the other hand, the sealant film of the comparative example did not have good tearing properties or good straight cut properties, and did not have appropriate tearing properties.

Claims (15)

It is made of a laminated film in which an outer layer (A), a middle layer (B), and an inner layer (C) are laminated,
The outer layer (A) and inner layer (C) contain polyethylene resin,
The inner layer (C) includes medium- and low-density polyethylene and high-density polyethylene (HDPE),
The intermediate layer (B) contains linear low density polyethylene (LLDPE) (b1) and a cyclic olefin resin (b2), and the content of the cyclic olefin resin (b2) in the resin component contained in the intermediate layer (B) is 20 to 40 mass%,
A sealant film characterized by a standardized molecular orientation MORc value of 1.025 or more when the standard thickness measured by a microwave-type molecular orientation meter is 60㎛. According to paragraph 1,
A sealant film wherein the thickness of the intermediate layer (B) is 10 to 50% of the total thickness of the laminated film. According to claim 1 or 2,
A sealant film wherein the average density of the resin components in the outer layer (A) and the inner layer (C) is 0.940 g/cm 3 or more, and the density of the linear low-density polyethylene (b1) is 0.937 g/cm 3 or more. According to claim 1 or 2,
A sealant film wherein the content of the linear low-density polyethylene (b1) in the resin component contained in the intermediate layer (B) is 60 to 80% by mass. According to claim 1 or 2,
A sealant film in which the glass transition temperature of the cyclic olefin resin (b2) is 140°C or lower. According to claim 1 or 2,
Sealant film with a total thickness of 20 to 150㎛. According to claim 1 or 2,
A sealant film wherein the linear low-density polyethylene (b1) has an MFR of 0.1 to 20 g/10 min, and the cyclic olefin resin (b2) has an MFR of 0.2 to 17 g/10 min. A packaging material using the sealant film according to claim 1 or 2. A method of manufacturing a sealant film made of a laminated film in which an outer layer (A), a middle layer (B), and an inner layer (C) are laminated by a coextrusion inflation method, comprising:
The outer layer resin forming the outer layer (A) and the inner layer resin forming the inner layer (C) contain a polyethylene-based resin, and the middle layer resin forming the middle layer (B) is linear low-density polyethylene (b1). and a cyclic olefin resin (b2), and the content of the cyclic olefin resin (b2) in the resin component contained in the intermediate layer resin is 20 to 40% by mass,
A method of manufacturing a sealant film characterized by coextrusion inflation molding with a blow ratio of 1.0 to 2.3 and a drawdown ratio of 20 to 60. According to clause 9,
A method of manufacturing a sealant film wherein the laminated film has a MORc value of 1.025 or more. According to claim 9 or 10,
A method for producing a sealant film, wherein the thickness of the intermediate layer (B) of the laminated film is 10 to 50% of the total thickness of the laminated film. According to claim 9 or 10,
A method for producing a sealant film, wherein the average density of the resin components in the outer layer (A) and the inner layer (C) is 0.940 g/cm 3 or more, and the density of the linear low-density polyethylene (b1) is 0.937 g/cm 3 or more. According to claim 9 or 10,
A method for producing a sealant film wherein the cyclic olefin resin (b2) has a glass transition temperature of 140° C. or lower. According to claim 9 or 10,
Method for manufacturing a sealant film with a total thickness of 20 to 150㎛. According to claim 9 or 10,
A method for producing a sealant film wherein the linear low-density polyethylene (b1) has an MFR of 0.1 to 20 g/10 min, and the cyclic olefin resin (b2) has an MFR of 0.2 to 17 g/10 min.