WO2018198794A1

WO2018198794A1 - Sealant film and packaging material

Info

Publication number: WO2018198794A1
Application number: PCT/JP2018/015358
Authority: WO
Inventors: 桂輔浜崎; 達彦薄井
Original assignee: Dic株式会社
Priority date: 2017-04-26
Filing date: 2018-04-12
Publication date: 2018-11-01
Also published as: KR102654522B1; KR20190139833A; JPWO2018198794A1; JP6424997B1

Abstract

Provided is a sealant film, characterized in that: the sealant film comprises a laminated film in which an outer layer, an intermediate layer, and an inner layer are laminated; the outer layer and the inner layer contain a polyethylene-based resin; the intermediate layer contains a straight-chain low-density polyethylene and a cyclic olefin-based resin; the cyclic olefin-based resin content in the resin constituents contained in the intermediate layer is 20–40% by mass; and the standardized molecular orientation Morc value, when the reference thickness measured using a microwave molecule orientation meter is 60 µm, is at least 1.025. Through the use of the sealant film, outstanding ease of tearing and straight cutting properties can be achieved, and during high-temperature processing, inner-surface fusion of a packaging material and an uneven exterior-appearance thereof can be suppressed.

Description

Sealant film and packaging material

The present invention relates to a sealant film used for retort packaging that can be sterilized and cooked by heating or pressurization in a state where food or the like is packaged, and a packaging material using the sealant film.

Flexible packaging using plastic materials is used worldwide as a packaging material for food, and it is showing an increasing trend as it spreads to emerging countries. Under such circumstances, the demand for retort food that has been pressurized and heat sterilized (retort sterilization) at high temperatures is expected to increase in the future food packaging market due to its convenience. Retort food can be distributed at room temperature, and is easy to handle and easy to handle in distribution, and is expected to expand into areas where cold chain development is insufficient.

∙ When eating retort food, it is often heated in hot water, and after heating, the film is torn and opened from the notch provided at the upper end of the packaging bag. For this reason, the easy tear property is calculated | required by the resin film used for retort packaging. As a film for retort having easy tearability, for example, a propylene film in which a resin in which a low crystalline ethylene elastomer is blended with a propylene-ethylene block copolymer is used and the birefringence is controlled within a specific range is disclosed. (See Patent Document 1).

In addition, as a packaging material having easy cutability, a cyclic olefin-based resin and a linear low-density polyethylene resin are contained as a packaging material used for a soft bag filled with a chemical solution such as physiological saline or an electrolytic solution. A packaging material having an intermediate layer and an inner layer and an outer layer of a linear low-density polyethylene resin is disclosed (see Patent Document 2).

JP 2011-162667 A JP 2009-172902 A

The propylene-based film that promotes the above birefringence has a reduction in tear strength due to the improved rigidity of the film, but the direction of tearing is not sufficiently controlled, and the straight cut ability to tear straight There was a need for improvement. In addition, packaging materials using an ethylene-propylene copolymer as a sealant for heavy loads for business use or distribution in cold regions, etc., are not sufficient in impact resistance and may cause bag breakage accidents.

Although the packaging material used for the above-mentioned soft bag has easy-cutting properties and straight-cutting properties, it has been desired to further improve the cutting properties when applied to retort applications.

The problem to be solved by the present invention is to provide a sealant film and a packaging material having suitable bag breaking resistance and excellent in easy tearability and straight cut ability.

Furthermore, in addition to the said subject, in this invention, it makes it a subject to provide the sealant film which has suitable sealing performance.
Furthermore, in the present invention, in addition to the above-described problems, it is an object to provide a sealant film that does not cause inner surface fusion or appearance unevenness of a packaging material during high-temperature processing.

The present invention comprises a laminated film in which an outer layer (A), an intermediate layer (B) and an inner layer (C) are laminated, the outer layer (A) and the inner layer (C) contain a polyethylene resin, and the intermediate layer (B) Contains linear low density polyethylene (b1) and 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 The above-mentioned problem is solved by a sealant film having a normalized molecular orientation MORc value of 1.025 or more when the reference thickness measured by a microwave molecular orientation meter is 60 μm and is 40 mass%. is there.

Further, the present invention is a method for producing a sealant film comprising a laminated film in which an outer layer (A), an intermediate layer (B) and an inner layer (C) are laminated by a coextrusion inflation method, wherein the outer layer (A) The outer layer resin to be formed and the inner layer resin to form the inner layer (C) contain a polyethylene resin, and the intermediate layer resin to form the intermediate layer (B) is linear low density polyethylene (b1) and cyclic The olefin resin (b2) is contained, 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 1.0 to 2.3. The above-described problems are solved by a method for producing a sealant film which is co-extrusion blow molded at a blow ratio of 20 to 60 and a drawdown ratio of 20 to 60.

Since the sealant film of the present invention has a suitable easy tearing property and straight cut ability due to the above-described configuration, the packaging bag using the sealant film of the present invention is spilled from the contents at the time of opening or after opening has started to occur. And scattering is difficult to occur. In particular, when applied to retort packaging applications, it is possible to cut with simple and suitable straightness. Moreover, it can implement | achieve suitable bag-breaking resistance, especially the bag-breaking resistance suitable under low temperature, and has suitable distribution | circulation aptitude.

In addition, the sealant film of the present invention easily realizes a packaging material that does not cause inner surface fusion or appearance irregularity during high-temperature treatment such as retort sterilization treatment while achieving suitable tearability. For this reason, the sealant film of the present invention can be suitably applied to high-temperature processing packaging materials such as retort food packaging materials that require high-temperature sterilization. Furthermore, the sealant film of the present invention is suitable for these packaging materials because it can easily achieve suitable sealing properties.

The sealant film of the present invention comprises a laminated film in which an outer layer (A), an intermediate layer (B) and an inner layer (C) are laminated in 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 the linear low density polyethylene (b1) and the cyclic olefin resin (b2), and the resin component contained in the intermediate layer (B) The content of the cyclic olefin resin (b2) in the sealant film is 20 to 40% by mass. Further, the normalized molecular orientation MORc value is 1.025 or more when the reference thickness measured by the microwave molecular orientation meter is 60 μm.

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

As the linear low density polyethylene, an ethylene monomer is a main component by a low-pressure radical polymerization method using a single site catalyst, and butene-1, hexene-1, octene-1, 4-methylpentene, etc. are used as comonomers. The α-olefin was copolymerized. The comonomer content in LLDPE is preferably in the range of 0.5 to 20 mol%, 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 Group IV or V transition metal of the periodic table and an organoaluminum compound and / or an ionic compound. In addition, the single-site catalyst has a uniform active site, so the molecular weight distribution of the resulting resin is sharper than a multi-site catalyst with a non-uniform active site. This is preferable because a resin having physical properties excellent in stability of seal strength and impact resistance can be obtained.

In the outer layer (A), since it is easy to obtain suitable impact resistance, the polyethylene resin is preferably contained in an amount of 60% by mass or more with respect to the total amount of the resin components forming the layer, and 80% by mass or more. It is more preferable to contain, and it is further more preferable to contain 90 mass% or more. Among them, it contains only a polyethylene resin as a resin component, and preferably 60% by mass or more in the resin component is a linear low density polyethylene, more preferably 80% by mass or more, and 90% by mass or more. More preferably.

In the outer layer (A), other resins of the above polyethylene resin may be used in combination as long as the effects of the present invention are not impaired. Examples of other resin types that can be used in combination include polyolefin resins other than the above polyethylene resins, and include propylene homopolymers, propylene-ethylene copolymers, propylene-butene-1 copolymers, propylene-ethylene- Examples include polypropylene resins such as butene-1 copolymer and metallocene catalyst polypropylene.

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

In the outer layer (A) used in the sealant film of the present invention, the average density of the resin component used in the layer is preferably 0.940 g / cm ³ or more, more preferably 0.940 to 0.945 g / cm ³ layer. By setting the average density of the resin component in the above range, appearance unevenness during high-temperature treatment such as retort sterilization treatment can be suitably suppressed. The average density resin used for the layer of the resin a, resin b, and when a resin c · · ·, using the density of these resins _{_{d a, d b, d c}} ···, in the layer the mass of the resin _W _{_a,} _W _b, upon the _W c · · _·, in _{_{_{_{(d a W a + d b}}}} W b + d c W c ···) / (W a + W b + W c ···) This is the calculated density.

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 in the polyethylene resin, it is preferably 0.880 g / cm ³ or more, It is more preferably 0.920 g / cm ³ or more, particularly preferably 0.940 to 0.950 g / cm ³ . In addition, it is preferable to use other resins having 0.920 g / cm ³ or more.

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

[Intermediate layer (B)]
The intermediate layer (B) of the sealant film of the present invention contains linear low density polyethylene (b1). By including the linear low-density polyethylene, it becomes easy to suitably suppress the appearance unevenness during the retort sterilization treatment during the high-temperature treatment as well as suitable impact resistance. The density of the linear low density polyethylene (b1) is preferably 0.937 g / cm ³ or more, more preferably 0.940 g / cm ³ or more, and even more preferably 0, because it is particularly preferable to suppress unevenness in appearance. 940 to 0.945 g / cm ³ . It is preferable that the average density of the resin component in the layer of the intermediate layer (B) is 0.940 g / cm ³ or more, and more preferably a layer of 0.940 ~ 0.945g / cm ^3.

The MFR of the linear low density polyethylene (b1) is 0.1 to 20 g / 10 min (190 ° C., 21.18 N), preferably 0.3 to 10 g / 10 min (190 ° C., 21.18 N), and more 0.5 to 5 g / 10 min (190 ° C., 21.18 N) is preferable. When the MFR is within this range, the compatibility with the cyclic olefin-based resin (b2) is excellent, and preferable film forming properties can be obtained in various multilayer film forming methods.

In the resin component contained in the intermediate layer (B), the content of the linear low density polyethylene (b1) in the intermediate layer (B) is easy to obtain suitable impact resistance and heat resistance during high-temperature treatment. It is preferably 60 to 80% by mass, and more preferably 65 to 75% by mass.

The intermediate layer (B) of the sealant film of the present invention contains the cyclic olefin resin (b2), so that excellent easy tearability and straight cut ability can be realized. Examples of the cyclic olefin-based resin (b2) include norbornene-based polymers, vinyl alicyclic hydrocarbon polymers, and cyclic conjugated diene polymers. Among these, norbornene-based polymers are preferable. The norbornene-based polymer includes a ring-opening polymer of a norbornene-based monomer (hereinafter referred to as “COP”), a norbornene-based copolymer obtained by copolymerizing a norbornene-based monomer and an olefin such as ethylene (hereinafter, referred to as “COP”). , “COC”). Also particularly preferred are hydrogenated products of COP and COC. In addition, the weight average molecular weight of the cyclic olefin resin is preferably 5,000 to 500,000, more preferably 7,000 to 300,000.

The norbornene polymer and the norbornene monomer used as a raw material are alicyclic monomers having a norbornene ring. Examples of such norbornene-based monomers include norbornene, tetracyclododecene, ethylidene norbornene, vinyl norbornene, ethylidetetracyclododecene, dicyclopentadiene, dimethanotetrahydrofluorene, phenyl norbornene, methoxycarbonyl norbornene, methoxy And carbonyltetracyclododecene. These norbornene monomers may be used alone or in combination of two or more.

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

The content of the cyclic olefin-based resin (b2) contained in the intermediate layer (B) is preferably 20 to 40% by mass, and 25 to 35% by mass in the resin component contained in the intermediate layer (B). More preferably. By setting the content of the cyclic olefin-based resin (b2) in the above range, it is possible to realize suitable easy tearability and straight cut performance without impairing impact resistance.

Further, 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 70 to 120 ° C. More preferably it is. By using the cyclic olefin resin (b2) having the glass transition temperature, it is easy to obtain good heat resistance and rigidity, and it is easy to improve the bag breaking resistance against dropping and the like. Moreover, it becomes easy to obtain good compatibility, and it becomes easy to suppress the appearance unevenness. The glass transition temperature (Tg) is a value obtained by measurement by DSC.

The MFR of the cyclic olefin resin (b2) is 0.2 to 17 g / 10 min (230 ° C., 21.18 N), preferably 3 to 15 g / 10 min (230 ° C., 21.18 N), more preferably 5 to 13 g / 10 min (230 ° C., 21.18 N). An MFR within this range is preferable in terms of excellent compatibility with the linear low-density polyethylene (b1) and good film formability in various multilayer film formation methods.

As a commercially available product that can be used as the cyclic olefin resin used in the present invention, as a ring-opening polymer (COP) of a norbornene monomer, for example, “ZEONOR” manufactured by Nippon Zeon Co., Ltd. can be mentioned. Examples of the copolymer (COC) include “Appel” manufactured by Mitsui Chemicals, Inc. and “TOPAS” manufactured by Polyplastics.

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-based resin (b2), but within the range not impairing the effects of the present invention. Other resins other than the resin component may be used in combination. Other resin types that can be used in combination include, for example, the polyethylene-based resin and the polypropylene-based resin exemplified in the outer layer (A).

When these other resins are used, the content is preferably 20% by mass or less, more preferably 10% by mass or less, in 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 according to desired properties.

[Inner layer (C)]
The inner layer (C) in the sealant film of the present invention is a layer containing a polyethylene resin, preferably a layer having an average density of resin components in the layer of 0.940 g / cm ³ or more. The said inner layer (C) is a layer used as the heat seal layer of a sealant film.

Examples of the polyethylene resin used for the inner layer (C) and the resin that can be used in combination with the polyethylene resin can be the same as those of the outer layer (A), and preferable ones are also the same. Moreover, about the content of the said polyethylene-type resin and other resin, and the density and average density of the resin component in an inner layer, the range similar to the said outer layer (A) can be illustrated as a preferable range.

In the inner layer (C), high density polyethylene (HDPE) is used in combination with medium / low density polyethylene such as ultra low density polyethylene, linear low density polyethylene, low density polyethylene, linear medium density polyethylene, etc. It is also preferable to do. When medium / low density polyethylene and high density polyethylene are used in combination, the content of medium / low density polyethylene in the resin component used in the inner layer (C) is 40 to 80% by mass, and the content of high density polyethylene. Is preferably 20 to 60% by mass, more preferably 45 to 75% by mass of medium / low density polyethylene and 25 to 55% by mass of high density polyethylene.

[Sealant film]
The sealant film of the present invention is a laminated film in which the outer layer (A), the intermediate layer (B), and the inner layer (C) are laminated in order. With this configuration, the sealant film of the present invention can realize a packaging material that does not cause inner surface fusion or appearance irregularity during high-temperature processing such as retort sterilization processing, while having suitable easy tearability and straight cut ability. Moreover, since it is easy to implement | achieve suitable sealing performance and bag breaking resistance, it is suitable for a retort packaging material use.

The sealant film of the present invention has a normalized molecular orientation MORc value of 1.025 or more, preferably 1.030 or more, more preferably when the reference thickness measured with a microwave molecular orientation meter is 60 μm. Is 1.035 or more. 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 within the above range, it is possible to realize excellent easy tearability and straight cut ability 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.
It arrange | positions so that the said sample surface (film surface) may become perpendicular | vertical to the advancing direction of a microwave in the microwave resonant waveguide of a known microwave type | system | group molecular orientation meter. Then, in a state where the sample is continuously irradiated with the microwave whose vibration direction is biased in one direction, the sample is rotated 0 to 360 ° in a plane perpendicular to the traveling direction of the microwave, and the microwave transmitted through the sample is transmitted. The degree of molecular orientation MOR is determined by measuring the strength.
The normalized molecular orientation MORc in the present embodiment is a MOR value when the reference thickness is tc, and can be obtained by the following equation.
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 film is represented.
The normalized molecular orientation MORc can be measured with a known molecular orientation meter, for example, a microwave molecular orientation meter MOA-2000A or MOA-2012A manufactured by Oji Scientific Instruments Co., Ltd. at a resonance frequency near 4 GHz.

The thickness of the sealant film of the present invention may be appropriately adjusted according to the application and mode to be used, but the total thickness is 20 from the viewpoint of heat resistance in packaging applications, resistance to bag breakage during distribution, heat sealability and the like. It is preferably ˜150 μm, more preferably 40 to 100 μm.

As the thickness ratio of each layer, 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, from the viewpoints of sealing properties, easy tearing properties, and laminating properties. % Is more preferable. The thickness ratio of the inner layer (C) is preferably in the range of 10 to 40%, more preferably in the range of 15 to 30%.

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

Specifically, the thickness of the outer layer (A) is preferably 2 to 60 μm, 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), the intermediate layer (B), and the inner layer (C) are laminated in this order, but the gas barrier layer is within the range that does not impair the effects of the present invention. Alternatively, any other layer such as an easy adhesion layer may be provided. Incidentally, the sealant film of the present invention preferably has an average density of the resin component in the layer of all layers is 0.940 g / cm ³ or more, more be a layer of 0.940 ~ 0.945g / cm ³ preferable. For this reason, when providing another layer, it is preferable that the average density of the resin component in the layer of the said other layer is also the said range.

Various additives may be blended in each layer of the sealant film of the present invention as long as the effects of the present invention are not impaired. Examples of the additive include an antioxidant, a weather resistance stabilizer, an antistatic agent, an antifogging agent, an antiblocking agent, a lubricant, a nucleating agent, and a pigment.

[Production method]
As a method for producing the sealant film of the present invention, for example, a resin (including a resin mixture containing two or more kinds of resins and additives) used for each layer of a multilayer film is heated and melted with a separate extruder. Examples include a coextrusion method in which a film is laminated in a molten state by a method such as an extrusion multilayer die method or a feed block method and then formed into a film shape by an inflation method. This coextrusion method is preferable because the thickness ratio of each layer can be adjusted relatively freely, and a film having excellent hygiene and cost effectiveness can be obtained. As the inflation method, an air-cooled inflation method is preferable, and an upward air-cooled inflation method can be particularly preferably used. Moreover, it can be set as a multilayer film by using several extruders and a multilayer circular die. After extruding the cylindrical molten resin upward using these, the cylindrical molten resin is expanded and taken out as necessary, and after cooling and solidifying the molten resin by air cooling, it is appropriately cut and cut as desired. A film can be obtained.

In the present invention, since it is easy to obtain a sealant film having a specific orientation, it is preferable to set the blow ratio during the coextrusion inflation molding to 1.0 to 2.3 and the drawdown ratio to 20 to 60. Easy to cut.

The drawdown ratio in the inflation method corresponds to the ratio between the line speed V _L (m / min) and the die outlet speed V ₀ (m / min), and is calculated as V _L / V ₀ . The blow ratio corresponds to the ratio between the diameter D0 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 20 to 60, preferably 25 to 50, and more preferably 30 to 40. 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 within the above-mentioned range, the resin discharged from the die is stretched predominantly in the flow direction, and excellent tearability and straight tearability are easily exhibited.

In the inflation method, the temperature of the extruder and the die is preferably 180 to 220 ° C. The diameter of the die is preferably 100 to 1200 mm, more preferably 100 to 800 mm, and even more preferably 150 to 500 mm. The lip opening of the die is preferably 0.5 to 5 mm, more preferably 1.5 to 4.5 mm, and further 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 diameter of the die, the blow ratio, and the discharge amount, but is preferably 10 to 150 m / min, and more preferably 20 to 100 m / min.

[Retort packaging materials]
When the sealant film of the present invention is used as a packaging material for retort, it can be used by bonding another base film to the outer layer (A) side surface of the sealant film. Although it does not specifically limit as another base film, From a viewpoint of making the effect of this invention express easily, it is preferable to use the plastic base material, especially the resin film stretched biaxially. For applications that do not require transparency, aluminum foil can be used in combination.

Examples of the stretched resin film include coextrusion using, as a central layer, biaxially stretched polyester (PET), biaxially stretched polypropylene (OPP), biaxially stretched polyamide (PA), and ethylene vinyl alcohol copolymer (EVOH). Biaxially stretched polypropylene, biaxially stretched ethylene vinyl alcohol copolymer (EVOH), alumina-deposited PET, silica-deposited PET, alumina-silica binary-deposited PET, silica-deposited PA, alumina-deposited PA and the like can be mentioned. These may be used alone or in combination.

As a method for bonding the sealant film of the present invention and various stretched base film, two processing methods are mainly used. One is to apply an anchor coating agent on the laminate surface of the sealant film of the present invention or the base film, if necessary, and to heat and melt the polymer film (polyethylene, polypropylene, etc.) with the sealant film of the present invention. This is an extrusion laminating method in which a thin film is extruded between the laminate surfaces of the material film, and is pressed and laminated. The other is a dry laminating method in which an adhesive is applied to the laminating surface of the base film, and then the sealant film of the present invention and the base film are pressure-bonded and laminated. preferable.

The adhesive for laminating is generally cured by polyol / isocyanate, and is widely used for high-functional applications such as retort applications. Conventionally, the combination of the aluminum foil and the sealant film was generally used for pasting, but various transparent vapor deposition films have come to be marketed. From the demand for improving the visibility of the contents, the transparent vapor deposition film and Bonding of sealant film is also increasing.

As a polyol used for the adhesive for laminating, for example, a polyol itself described later, or a polyester polyol obtained by reacting a polyol with a polycarboxylic acid described later, or ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, Ethylene oxide, propylene oxide, butylene starting from compounds having two active hydrogen atoms such as trimethylene glycol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, etc. Examples thereof include polyethers obtained by addition polymerization of monomers such as oxide, 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-cyclohexanediol, 1 , 4-cyclohexanedimethanol, triethylene glycol, polycaprolactone diol, dimer diol, bisphenol A, hydrogenated bisphenol A, and other glycols Polyesters obtained by ring-opening polymerization reaction of cyclic ester compounds such as propiolactone, butyrolactone, ε-caprolactone, δ-valerolactone, β-methyl-δ-valerolactone, ethylene glycol, diethylene glycol, triethylene glycol, propylene Ethylene oxide, propylene oxide starting with compounds having two active hydrogen atoms such as glycol, trimethylene glycol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, etc. , Polyethers obtained by addition polymerization of monomers such as butylene oxide, styrene oxide, epichlorohydrin, tetrahydrofuran, and cyclohexylene.

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. 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 anhydrides or ester-forming derivatives of these dicarboxylic acids; p-hydroxybenzoic acid, p- (2-hydroxyethoxy) benzoic acid, ester-forming derivatives of these dihydroxycarboxylic acids, dimer acids, etc. Of the polybasic acids.

Examples of the polyisocyanate include organic compounds having at least two isocyanate groups in the molecule. Examples of the organic polyisocyanate include tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, 1,6-hexamethylene diisocyanate, isophorone diisocyanate, 4,4′-methylenebis (cyclohexyl isocyanate), lysine diisocyanate, trimethylhexamethylene diisocyanate, 1 , 3- (isocyanatomethyl) cyclohexane, 1,5-naphthalene diisocyanate, polyisocyanate such as triphenylmethane triisocyanate; adducts of these polyisocyanates, burettes of these polyisocyanates, or of these polyisocyanates Derivatives (modified products) of polyisocyanates such as isocyanurates are exemplified.

Further, a product obtained by reacting the isocyanate and the polyol with a mixing ratio in which an isocyanate group becomes excessive may be used.

In the adhesive, the equivalent ratio polyol / isocyanate of the hydroxyl group 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 laminates a base film on the outer layer (A) side of the sealant film, thereby realizing good sealing properties and good tearability due to suitable tearing properties. it can. In addition, since suitable heat resistance and resistance to bag breakage can be realized, it is possible to suppress fusion between the inner layers (C) serving as a heat seal layer and uneven appearance even during high-temperature sterilization treatment. For this reason, the packaging material formed by laminating the sealant film of the present invention with various base materials can be suitably applied as a packaging material for retort food.

The packaging material of the present invention can be suitably used as a packaging bag by making bags into various shapes such as a flat bag type, a self-supporting packaging bag (standing pouch) type, and a tube type. Specifically, for example, one film-like packaging material is folded so that the sealant layers face each other, or two film-like packaging materials of the present invention are piled so that the sealant layers face each other, The peripheral edge part can be heat-sealed to form a bag for a retort food or the like (retort pouch). Moreover, you may provide opening start parts, such as V notch and I notch, as needed.

The packaging material of the present invention and the packaging bag for retort foods using the packaging material can be suitably used for packaging foods that require treatment under high-temperature hot water conditions such as boiling and retort sterilization, such as curry, It can be suitably applied to various retort food packaging applications such as stew, soup, and cooking sauces.

Example 1
The resin mixture which forms each layer was prepared using the following resin as a resin component which forms each layer of an outer layer, an intermediate | middle layer, and an inner layer, respectively. These mixtures were each fed to three extruders and melted at 250 ° C. The melted resin is supplied to an air-cooled inflation co-extrusion multi-layer film production apparatus (die temperature: 200 ° C.) equipped with a spiral three-layer die, and co-melt extrusion is performed. A laminated film having a total thickness of 60 μm was obtained with a three-layer constitution of layer / inner layer and a thickness ratio (%) of each layer of 30/40/30. The blow ratio during molding was 1.3 and the drawdown ratio was 30.

Outer layer: linear low density polyethylene (hereinafter referred to as “LLDPE (1)”) having an MFR of 0.5 g / 10 min (190 ° C., 21.18 N) and a density of 0.944 g / cm ³ .
Intermediate layer: LLDPE (1) 70% by mass, glass transition temperature (Tg) 78 ° C., MFR 10 g / 10 min (230 ° C., 21.18 N) norbornene copolymer (hereinafter referred to as “COC”) 30 Mass% resin mixture Inner layer: LLDPE (1) 50 mass%, MFR 1 g / 10 min (190 ° C., 21.18 N), density 0.960 g / cm ³ high density polyethylene (hereinafter referred to as “HDPE”) 50 mass % Mixed resin.

(Example 2)
A laminated film was obtained in the same manner as in Example 1 except that the blow ratio was 1.5 and the drawdown ratio was 27.

(Example 3)
A laminated film was obtained in the same manner as in Example 1 except that the blow ratio was 1.8 and the drawdown ratio was 23.

Example 4
A laminated film was obtained in the same manner as in Example 1 except that the outer layer / intermediate layer / inner layer thickness ratio (%) 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 / intermediate 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 layer and inner layer were as follows.
Outer layer: MFR 0.9 g / 10 min (190 ° C., 21.18 N), linear low density polyethylene (hereinafter referred to as “LLDPE (2)”) having a density of 0.929 g / cm ³ , 60% by mass, HDPE 40 Mixed resin material of mass% Inner layer: Mixed resin material of 50% by mass of LLDPE (2) and 50% by mass of HDPE.

(Example 7)
A precision layer film was obtained in the same manner as in Example 2 except that the resin component used in the outer layer and the inner layer was LLDPE (2).

(Example 8)
A laminated film was obtained in the same manner as in Example 2 except that the resin component used in the intermediate layer was LLDPE (2) 70 mass% and COC 30 mass%.

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

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

(Comparative Example 3)
The resin components forming the outer layer, the intermediate layer, and the inner layer were the same as in Example 1, and these resin mixtures were respectively supplied to three extruders and melted at 250 ° C. The melted resin is supplied to a co-extruded multilayer film production apparatus (feed block and T-die temperature: 250 ° C.) using a T-die / chill roll method having a feed block, and co-melt extrusion is performed. A sealant film having a total thickness of 50 μm was obtained with a three-layer structure of / intermediate layer / inner layer and a thickness ratio of each layer of 25/50/25%.

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

(1) Normalized molecular orientation MORc
For each film of Examples and Comparative Examples, the normalized molecular orientation MORc was measured with a microwave molecular orientation meter MOA-2000 manufactured by Oji Scientific Instruments. The reference thickness tc was set to 60 μm.

(2) Tear Strength Tear strength in the flow direction was measured in a constant temperature room at 23 ° C. and 50% Rh according to JIS K7128-1 (trouser method).
1N or less: 〇 (Excellent tearability)
Over 1N: × (Tearability is inferior)

(2) Straight-cutting property Using a test piece having a length of 150 mm in the flow direction of the film and a length of 50 mm in the width direction, 10 mm of a 15 mm wide cut is made at the center in the width direction, and the width of the tip of the cut (W ₀ ) Is actually measured. A polyester sheet having a thickness of 0.3 mm, a width of 15 mm, and a length of 160 mm prepared in advance is attached to the tip of the cut with a tape. The attached polyester sheet is folded back in the direction of 180 °, the test piece excluding the notch on the side opposite to the tip is attached to a tensile tester, and it is torn 100 mm at a speed of 300 mm / min, and the width of the end point (W ₁ ) Is actually measured. At this time, the retention rate was obtained from the following equation, and used as an index of straight cut property.
Retention rate [%] = W ₁ / W ₀ × 100
100 ± 10%: 〇 (Excellent straight cut performance)
More than 100 ± 10%: × (poor straightness is poor)

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

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

(5) Appearance unevenness A laminate film was obtained in the same manner as in (3). Using the obtained film, the bag was processed so that the inner size was 100 mm × 150 mm (heat seal width 10 mm), and 200 ml of water was sealed. After the bag-making product enclosing water was retorted at 121 ° C. for 30 minutes, the appearance unevenness was visually evaluated.

As is clear from the above table, the sealant films of the present invention of Examples 1 to 8 had tear strength that was easy to tear and good straight-cut properties. The sealant films of Examples 1 to 6 and 8 all had a peel strength of 1 N / 15 mm or less in the evaluation of inner surface fusion. Further, the sealant films of Examples 1 to 6 were not visually recognized even in appearance evaluation. On the other hand, the sealant film of the comparative example did not have easy tearability and good straight cut property, and did not have suitable tear property.

Claims

It consists of a laminated film in which the outer layer (A), the intermediate layer (B) and the inner layer (C) are laminated,
The outer layer (A) and the inner layer (C) contain a polyethylene resin,
The intermediate layer (B) contains linear low density polyethylene (b1) and a cyclic olefin resin (b2), and the cyclic olefin resin (b2) in the resin component contained in the intermediate layer (B). The content is 20 to 40% by mass,
A sealant film having a normalized molecular orientation MORc value of 1.025 or more when a reference thickness measured by a microwave molecular orientation meter is 60 μm.
The sealant film according to claim 1, wherein the thickness of the intermediate layer (B) is 10 to 50% of the total thickness of the laminated film.
The average density of the resin component 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. The sealant film according to claim 1 or 2.
The sealant film according to any one of claims 1 to 3, 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.
The sealant film according to any one of claims 1 to 4, wherein the cyclic olefin resin (b2) has a glass transition temperature of 140 ° C or lower.
The sealant film according to any one of claims 1 to 5, having a total thickness of 20 to 150 µm.
7. The MFR of the linear low density polyethylene (b1) is 0.1 to 20 g / 10 minutes, and the MFR of the cyclic olefin resin (b2) is 0.2 to 17 g / 10 minutes. The sealant film according to crab.
A packaging material using the sealant film according to any one of claims 1 to 7.
A method for producing a sealant film comprising a laminated film in which an outer layer (A), an intermediate layer (B) and an inner layer (C) are laminated by a coextrusion inflation method,
The outer layer resin forming the outer layer (A) and the inner layer resin forming the inner layer (C) contain a polyethylene resin, and the intermediate layer resin forming the intermediate layer (B) is a linear low density. Containing polyethylene (b1) and a cyclic olefin resin (b2), and the content of the cyclic olefin resin (b2) in the resin component contained in the resin for the intermediate layer is 20 to 40% by mass,
A method for producing a sealant film, comprising coextrusion inflation molding at a blow ratio of 1.0 to 2.3 and a draw down ratio of 20 to 60
The method for producing a sealant film according to claim 9, wherein the MORc value of the laminated film is 1.025 or more.
The method for producing a sealant film according to claim 9 or 10, wherein the thickness of the intermediate layer (B) of the laminated film is 10 to 50% of the total thickness of the laminated film.
The average density of the resin component 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. The method for producing a sealant film according to any one of claims 9 to 11.
The process for producing a sealant film according to any one of claims 9 to 12, wherein the cyclic olefin resin (b2) has a glass transition temperature of 140 ° C or lower.
14. The method for producing a sealant film according to claim 9, wherein the total thickness is 20 to 150 μm.
The MFR of the linear low-density polyethylene (b1) is 0.1 to 20 g / 10 minutes, and the MFR of the cyclic olefin resin (b2) is 0.2 to 17 g / 10 minutes. A method for producing a sealant film according to claim 1.