JP2013237187A - Packaging material, and container for liquid formed of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a packaging material excelling in a non-adsorptive property and an aroma retention property, and including a sealant layer excelling in heat sealing property, and a container for liquid formed of the same.SOLUTION: In a packaging material formed with an outermost layer, a paper base material layer, a smoothing layer, an adhesive layer and a sealant layer in this order, and used for a container for liquid, the adhesive layer contains, as a main constituent, an epoxy resin composition containing an epoxy resin and an epoxy resin curing agent, and the sealant layer has a multilayer structure including a cyclic polyolefin-based resin layer.

Description

  The present invention relates to a packaging material and a liquid paper container comprising the same. The packaging material of the present invention is particularly excellent as a material for paper containers used for low-temperature distribution (chilled distribution) of milk, milk drinks, juices and the like.

Liquid paper containers such as paper-based gable-top type and brick type use laminates laminated with various material films in order to ensure sealing, storage, rigidity, strength, etc. It is formed. Laminates for liquid paper containers vary from low-temperature distribution types to types that can be distributed at room temperature and for long-term distribution, and their specifications are designed according to the contents, sterilization method, packaging method, expiration date setting, etc. Is done. The main components of the packaging material for paper containers used for low temperature distribution (chilled distribution) of conventional milk, milk drinks, juices, etc. are low density polyethylene resin / paper / low density polyethylene resin. (In this specification, when the layer structure of the laminate is described, the slash (/) means that adjacent layers are adjacent to each other.) Low density polyethylene resin (LDPE, density 0.90 to 0.925 g / cm ³ ) is most often used because it functions as a sealant and has good laminate processability when forming a laminate and heat sealability when molding a container.

  However, the packaging material described above is inferior in gas barrier properties and adsorbs organic compound components contained in the contents, for example, aroma components such as limonene and l-menthol, so the taste and smell of the contents. There was a problem that changed.

On the other hand, in some cases, a medium density polyethylene resin (MDPE, density 0.926 to 0.940 g / cm ³ ) is used as the sealant layer. However, MDPE has a disadvantage that a stable sealing temperature range cannot be obtained because the heat sealing temperature during box making (molding of paper containers) must be set higher than LDPE in order to obtain sufficient adhesion strength. Have. Further, when heat-sealing at such a high temperature, MDPE is oxidized and an oxidized odor is generated. Therefore, a paper container having a sealant layer made of MDPE as the innermost layer easily transfers the oxidized odor of the resin into the contents. Has drawbacks.

  It has also been proposed to use a polyester resin as a sealant layer (Patent Document 1). However, since the polyester-based resin has poor heat-sealability and is likely to cause a sealing failure at the time of box making, a paper container having a sealant layer made of such a resin has drawbacks such as leakage of contents.

JP-A-5-162737

  The present invention solves the above-mentioned problems and has excellent gas barrier properties and makes it difficult to adsorb organic compound components contained in the contents, that is, excellent non-adsorbability and aroma retention, and heat sealability. It is an object of the present invention to provide a packaging material having an excellent sealant layer and a liquid paper container comprising the same, particularly a liquid paper container used for low-temperature distribution (chilled distribution).

  As a result of various studies, the present inventor is a packaging material used for a liquid paper container in which an outermost layer, a paper base layer, a smoothing layer, an adhesive layer, and a sealant layer are provided in this order. And a layer formed by curing a composition mainly composed of an epoxy resin composition comprising an epoxy resin curing agent, and the sealant layer has a multilayer structure including a cyclic polyolefin resin layer. It has been found that a packaging material and a liquid paper container comprising the same, particularly a liquid paper container used for low-temperature circulation (chilled circulation), achieve the above-mentioned object.

  The present invention is characterized by the following points.

1. A packaging material used for a liquid paper container in which an outermost layer, a paper base layer, a smoothing layer, an adhesive layer, and a sealant layer are provided in this order, the adhesive layer comprising an epoxy resin and an epoxy resin curing agent A packaging material, which is a layer formed by curing a composition comprising a composition as a main component, and the sealant layer has a multilayer structure including a cyclic polyolefin resin layer.
2. 2. The packaging material according to 1 above, wherein the sealant layer is a layer composed of two layers, a linear low density polyethylene resin layer and a cyclic polyolefin resin layer.
3. 3. The packaging material according to 2 above, wherein the linear low-density polyethylene resin layer contains a cyclic polyolefin-based resin at a ratio of 30 to 70% by mass.
4). The sealant layer is a layer composed of three layers in which a first linear low density polyethylene resin layer, a cyclic polyolefin resin layer, and a second linear low density polyethylene resin layer are provided in this order, The packaging material according to 1 above, wherein one linear low-density polyethylene resin layer is adjacent to the paper base layer.
5. Of the first and second linear low density polyethylene resin layers, at least the second linear low density polyethylene resin layer contains a cyclic polyolefin-based resin in a ratio of 30 to 70% by mass. The packaging material according to 4 above.
6). The sealant layer includes a first low density polyethylene resin layer, a first linear low density polyethylene resin layer, a cyclic polyolefin-based resin layer, a second linear low density polyethylene resin layer, and a second low density. 2. The packaging material according to 1 above, wherein the packaging material is a five-layered polyethylene resin layer provided in this order, and the first low-density polyethylene resin layer is adjacent to the paper base material layer.
7). Of the first and second low-density polyethylene resin layers and the first and second linear low-density polyethylene resin layers, at least the second linear low-density polyethylene resin layer has a ratio of 30 to 70% by mass. The packaging material as described in 6 above, comprising a cyclic polyolefin resin.
8). The packaging material according to any one of 2 to 7 above, wherein a resin layer made of carboxylic acid-modified polyethylene is used instead of the linear low-density polyethylene resin layer.
9. The packaging material according to any one of 1 to 8 above, wherein the smoothing layer comprises a low-density polyethylene resin layer or a linear low-density polyethylene resin layer.
10. The packaging material according to any one of the above 1 to 8, wherein the smoothing layer comprises a clay coat layer.
11. 11. The packaging material according to any one of 1 to 10 above, wherein the epoxy resin curing agent contained in the epoxy resin composition of the adhesive layer is an epoxy resin curing agent containing an aromatic moiety in the molecule.
12 12. The packaging material according to any one of 1 to 11 above, wherein the epoxy resin contained in the epoxy resin composition of the adhesive layer is an epoxy resin having a glycidylamine moiety derived from metaxylenediamine.
13. 13. A liquid paper container formed by boxing the packaging material according to any one of 1 to 12 so that a sealant layer is an innermost layer.

  The packaging material of the present invention is characterized in that the sealant layer has a multilayer structure including a cyclic polyolefin resin layer.

  A generally known single-layer sealant film made of only a polyolefin resin has a thickness proportional to an organic compound adsorption amount and a sealing strength. Therefore, if the sealant film of the packaging material is thinned to prevent the adsorption of the organic compound contained in the contents, the sealing strength is lowered and the impact resistance of the bag is lowered. In addition, when the sealant film is thickened in order to improve impact resistance, the amount of adsorption of the organic compound contained in the contents increases.

On the other hand, the sealant layer of the present invention has a multilayer structure including a cyclic polyolefin resin layer. For example, a linear low density is formed on the paper base material layer side or contents side of the cyclic polyolefin resin layer. Since a polyethylene resin (LLDPE, density 0.880-0.940 g / cm ³ ) layer, a polyolefin resin layer such as a resin layer made of carboxylic acid-modified polyethylene, and the like are laminated, the adsorption amount of the organic compound component is increased. Low and high sealing strength. This tendency becomes more remarkable by co-extrusion of these layers, particularly by co-extrusion by the inflation method.

  That is, the sealant film of the present invention has a small amount of adsorption of organic compound components contained in the contents, for example, aroma components such as limonene and l-menthol. In addition, since the cyclic polyolefin resin exhibits a high intermolecular force and has a close surface structure in which the distance between the molecules is close, the sealant film of the present invention containing the resin suppresses the elution of low molecular weight components. Can do. Therefore, the packaging material of the present invention using the sealant film has excellent fragrance retention. Further, the packaging material of the present invention exhibits a sufficiently high sealing strength to form the innermost layer of a liquid paper container such as a gobel top type or a brick type.

  In general, it is known that a cyclic polyolefin-based resin has a high intermolecular force during melt film formation and causes aggregation between polymers. As a result, it is difficult to obtain a uniform film surface by agglomerating the resin throughout the film to form a knob-like gel mass. This tendency becomes more prominent at the time of film formation by the inflation method, and the cyclic polyolefin resin film obtained by the method generates innumerable gel lumps on the entire surface. However, according to the present invention, the cyclic polyolefin resin layer is formed into a multilayer structure together with the LLDPE layer, the LDPE layer, and the like, and the films are formed together, thereby suppressing uneven aggregation of the molecules of the cyclic polyolefin resin. Therefore, the sealant film constituting the packaging material of the present invention can be easily formed, and can form a beautiful film that is homogeneous and has good transparency. Moreover, the same effect can be obtained also at the time of high-speed film formation by the inflation method.

  Moreover, the packaging material of this invention has an adhesive layer. Here, the adhesive layer is formed by curing a composition mainly composed of an epoxy resin composition composed of an epoxy resin and an epoxy resin curing agent, and has an excellent gas barrier property. The paper container using the packaging material can prevent the entry of oxygen gas or the like from the outside, and can effectively prevent the contents from being modified due to the oxygen gas or the like.

  As described above, the packaging material of the present invention is suitable for forming a liquid paper container that is required to maintain the quality of contents, particularly a liquid paper container used for low-temperature circulation (chilled circulation).

It is a schematic sectional drawing which shows the example about the layer structure of the laminated body which comprises the cover material of this invention. It is a schematic sectional drawing which shows the example about the layer structure of the laminated body which comprises the cover material of this invention. It is a schematic sectional drawing which shows the example about the layer structure of the laminated body which comprises the cover material of this invention.

The present invention will be described in more detail below.
<1> Layer Configuration of Laminate Forming Packaging Material of the Present Invention FIGS. 1 to 3 are schematic sectional views showing an example of the layer configuration of the packaging material of the present invention.
As shown in FIGS. 1 to 3, the packaging material of the present invention basically has a configuration in which an outermost layer 1, a paper base layer 2, a smoothing layer 3, an adhesive layer 4, and a sealant layer 5 are laminated in this order. Here, the sealant layer 5 has a multilayer structure including a cyclic polyolefin resin layer.

  As an aspect of the packaging material of the present invention, as shown in FIG. 1, the sealant layer 3 is composed of two layers, an LLDPE layer (b) and a cyclic polyolefin resin layer (c), and the LLDPE layer is a paper base. Adjacent to the material layer.

As another aspect of the packaging material of the present invention, as shown in FIG. 2, the sealant layer 3 includes a first LLDPE layer (b ₁ ), a cyclic polyolefin-based resin layer (c), and a second LLDPE layer ( b ₂₎ the three layers provided in this order, the first LLDPE layer is adjacent to the paper substrate layer.

As still another embodiment of the packaging material of the present invention, as shown in FIG. 3, the sealant layer 3 includes a first LDPE layer (a ₁ ), a _first LLDPE layer (b ₁ ), and a cyclic polyolefin resin. The layer (c), the second LLDPE layer (b ₂ ), and the second LDPE layer (a ₂ ) are composed of five layers in this order, and the first LDPE layer is adjacent to the paper base layer.

  The examples given above illustrate the packaging material of the present invention, and the present invention is not limited thereto. For example, the sealant shown in FIGS. In the layer, a resin layer made of carboxylic acid-modified polyethylene can be used instead of the LLDPE layer.

  Hereinafter, the resin names used in the present invention are those commonly used in the industry. In the present invention, the melt flow rate (MFR) is a value measured by a method based on “JIS K6922” and is a value measured at 190 ° C. and a 2.16 kg load unless otherwise specified. Furthermore, the density referred to in the present invention is measured by a method based on “JIS K7112”.

<2> Outermost layer The outermost layer is a layer provided to protect the outside of the paper base layer and to be heated and bonded to the sealant layer at the end portion of the packaging material. Therefore, a polyethylene resin is usually used as the material for the outermost layer. Specific examples of the polyethylene resin used here include LDPE, MDPE, and LLDPE. LDPE is preferable from the viewpoints of sealability and processing suitability. As LDPE, a polymer of ethylene is preferable, and specifically, a high-pressure ethylene homopolymer is suitably used.

The density of the LDPE that constitutes the outermost layer is not particularly limited as long as it is usually referred to as a low density polyethylene resin, but it is 0.90 to 0.925 g / cm ³ , and its melt flow rate (MFR) is also particularly high. It is not limited, Usually, it is 1-20 g / 10min, and melting | fusing point is 100 to 120 degreeC.

  A method for forming the outermost layer is not particularly limited. For example, when a polyethylene resin is used as the outermost layer, the outermost layer is formed by extrusion coating on one surface of the paper base material layer. As processing conditions for extrusion coating, an extrusion temperature of 280 to 330 ° C. and a line speed of 100 to 300 m / min. It is set in the range. The thickness of the polyethylene resin is not particularly limited, but is usually 10 to 60 μm.

  The outermost layer is a layer that becomes the outer surface of the liquid paper container, but a printing layer may be further provided thereon. In order to improve the adhesion of the printing ink used for the printing layer, it is preferable to subject the surface of the outermost layer to surface treatment (for example, corona treatment).

<3> Paper base material layer Since the paper base material layer is a basic material constituting the liquid paper container of the present invention, a material having formability, bending resistance, rigidity, waist, strength, etc. should be used. Can do. As the paper, it is a main strength material, and various sized paper substrates such as a strong sized bleached or unbleached paper substrate, or pure white roll paper, kraft paper, paperboard, processed paper, and milk base paper can be used. .

The paper base layer may be a laminate of these papers. The paper to be used may be one having a basis weight of 80 to 600 g / m ² , preferably 100 to 450 g / m ² . The paper having a thickness of 110 to 860 μm, preferably 140 to 640 μm can be used. The basis weight of the paper base material layer is, for example, 300 g / m ² .

  Since paper used for the paper base layer 12 generally has fibrous burrs on both sides thereof, the paper base layer has rough surfaces on both sides. When the degree of the rough surface is measured based on JIS P8151, the surface roughness PPS (Parker Print Surf) is preferably 7 μm or less.

  Note that, for example, letters, figures, symbols, and other desired patterns can be arbitrarily formed on the paper base by a normal printing method.

<4> Smoothing layer The smoothing layer is provided between the paper base material layer and the adhesive layer, and smoothes the rough surface of the paper base material layer. The smoothing layer can be, for example, an LDPE layer, an LLDPE layer, or a clay coat layer.

  As the LDPE or LLDPE used as the smoothing layer, the same LDPE or LLDPE as the LDPE layer or LLDPE layer constituting the seal layer described later can be suitably used. By using LLDPE as the smoothing layer, the transport resistance is improved.

  In this case, the smoothing layer is formed by extrusion coating on the surface opposite to the outermost layer of the paper base material layer. As processing conditions for extrusion coating, an extrusion temperature of 280 to 330 ° C. and a line speed of 100 to 300 m / min. It is set in the range. Although the thickness of this smoothing layer is not specifically limited, Usually, it is 10-60 micrometers.

  The chill roll used in this case is a mirror-type or semi-mirror-type roll that has been subjected to wet blasting and drive blast treatment after chrome plating on the roll. By using this chill roll, a smoothing layer The smoothness can be increased.

  Specifically, a KRH type mirror or a semi-mirror type chill roll is preferable. Furthermore, in addition to the surface roughness of the smoothing layer, by increasing the smoothness of the paper substrate layer itself, the adhesive layer described later can be applied more uniformly, eliminating the loss of the adhesive layer film. Thus, the barrier property can be further improved.

  By providing such a smoothing layer on the paper base layer, the surface roughness PPS of the smoothing layer is 3 μm or less when measured according to JIS P8151.

  Moreover, as above-mentioned, a smoothing layer can also be used as a clay coat layer. By making the smooth layer a clay coat layer, the pinhole generated by hot air during sealing with a filling machine can be improved, and the thickness of the sealant layer can be reduced.

  Since the surface of the clay coat layer is usually smooth, the adhesion with the extruded laminated resin tends to be inferior. However, as described later, an epoxy resin composition comprising an epoxy resin and an epoxy resin curing agent is used as an adhesive layer. By using, the adhesiveness with the sealant layer is also improved. When further laminate strength is required, ozone treatment or the like may be performed when the sealant layer is extruded and laminated.

  The clay coat layer includes clay, and this clay can be used without particular limitation as long as it is generally called clay, clay, kaolin, talc, bentonite, smectite, vermiculite, mica, green mud. Stone, kibushi clay, gyrome clay, halloysite, mica, etc. can be used. Of these, kaolin and talc are preferably used as the clay. Kaolin has excellent concealability and water absorption, and talc has low hardness (Mohs hardness 1) and excellent heat resistance. Improvement in dimensional stability can be expected.

  The clay coat layer preferably contains calcium carbonate, titanium dioxide, amorphous silica, expandable barium sulfate, satin white and the like as a pigment in addition to clay. By using calcium carbonate or titanium dioxide as the pigment, the smoothness of the surface of the clay coat layer can be increased and the concealability can be increased. Furthermore, calcium carbonate is preferably used because it is inexpensive.

  A coating liquid (clay coating layer coating liquid) for coating the clay coat layer contains the clay, a binder, and, if necessary, other pigments and additives in a solvent. As the solvent, water, alcohol or the like is usually used. The binder is usually a latex binder (eg, styrene butadiene latex, acrylic latex vinyl acetate latex), water soluble binder (eg starch (modified starch, oxidized starch, hydroxyethyl etherified starch, phosphate ester). Modified starch), polyvinyl alcohol, casein, and the like. Examples of additives that can be used include pigment dispersants, antifoaming agents, antifoaming agents, viscosity modifiers, lubricants, water resistance agents, water retention agents, coloring materials, and printability improvers.

  The blending ratio of the clay coating layer coating solution is not particularly limited, but is preferably about clay: pigment: binder = 1-20%: 50-90%: 10-30%.

  The coating method of the clay coat layer is not particularly limited, and a conventionally known coating method is used, but a coating method such as air knife coating, blade coating, short dwell coating, cast coating or the like is used.

Although the coating amount and thickness of a clay coat layer are not specifically limited, Usually, the basic weight after drying is 5-40 g / m < ² >, and 10-40 g / m < ² > is preferable. When the basis weight after drying is less than 5 g / m ² , the smoothness may be inferior, and when the basis weight after drying exceeds 40 g / m ² , the container becomes too thick and the production suitability may be deteriorated. Moreover, since the adhesive strength tends to decrease, it is not preferable.

<5> Adhesive layer The adhesive layer is a layer provided on the smoothing layer and formed by curing a composition mainly composed of an epoxy resin composition composed of an epoxy resin and an epoxy resin curing agent. The adhesive layer adheres the sealant layer and the smoothing layer, and also functions as an anchor coat layer (AC layer) having excellent gas barrier properties.

  As an epoxy resin composition used for an adhesive bond layer, what was described in Unexamined-Japanese-Patent No. 2003-155465 and Unexamined-Japanese-Patent No. 2007-126627 is mentioned, for example.

Specifically, what consists of an epoxy resin and the epoxy resin hardening | curing agent which contains an aromatic site | part in a molecule | numerator can be used as said epoxy resin composition. Preferably, the epoxy resin composition used for the adhesive layer is an epoxy resin composition containing an epoxy resin and an epoxy resin curing agent, and the formula ( An epoxy resin composition characterized by containing 40% by weight or more of the skeleton structure shown in 1) can be used.

  Furthermore, the epoxy resin composition used for the adhesive layer is an epoxy resin composition containing an epoxy resin, an epoxy resin curing agent and a curing accelerator, and the above-mentioned (in the cured product formed from the resin composition ( 1) The epoxy resin composition characterized in that the content of the skeleton structure represented by the formula is 30% by weight or more can also be used.

  Examples of the epoxy resin include an epoxy resin having a glycidylamine moiety derived from metaxylylenediamine, an epoxy resin having a glycidylamine moiety derived from 1,3-bis (aminomethyl) cyclohexane, and a diaminodiphenylmethane derivative. Epoxy resin having glycidylamine moiety, epoxy resin having glycidylamine moiety and / or glycidyl ether moiety derived from paraaminophenol, epoxy resin having glycidyl ether moiety derived from bisphenol A, glycidyl derived from bisphenol F Epoxy resin having ether moiety, epoxy resin having glycidyl ether moiety derived from phenol novolac, glycidyl ether derived from resorcinol An epoxy resin having a site is exemplified. Among these resins, it is particularly preferable to use an epoxy resin having a glycidylamine moiety derived from metaxylenediamine. These resins can be used alone or in any combination of two or more.

Moreover, as said epoxy resin hardening | curing agent, although the epoxy resin hardening | curing agent which can be used generally can be used, in order to further improve gas barrier property, the epoxy resin hardening | curing agent which contains an aromatic site | part in a molecule | numerator is used. It is preferable to use an epoxy resin curing agent containing the skeleton structure of the above formula (1) in the molecule. Specifically, metaxylylenediamine or paraxylylenediamine, and a modification reaction product with an epoxy resin or a monoglycidyl compound, a modification reaction product with an alkylene oxide having 2 to 4 carbon atoms, addition with epichlorohydrin A reaction product, a reaction product with a polyfunctional compound having at least one acyl group, which can form an amide group site by reaction with these polyamines to form an oligomer, by reaction with these polyamines It is more preferable to use a reaction product of a polyfunctional compound having at least one acyl group capable of forming an amide group site to form an oligomer and a monovalent carboxylic acid and / or a derivative thereof.

Furthermore, when considering gas barrier properties and adhesion to a smoothing layer or a sealant layer, the following reaction products (A) and (B) or (A), (B ) And (C) are particularly preferred.
(A) Metaxylylenediamine or paraxylylenediamine
(B) A polyfunctional compound having at least one acyl group capable of forming an amide group site by reaction with a polyamine to form an oligomer
(C) C1-C8 monovalent carboxylic acid and / or derivative thereof

  Examples of the polyfunctional compound having at least one acyl group that can form an amide group site by reaction with the (B) polyamine to form an oligomer include acrylic acid, methacrylic acid, maleic acid, fumaric acid, succinic acid, Carboxylic acids such as malic acid, tartaric acid, adipic acid, isophthalic acid, terephthalic acid, pyromellitic acid, trimellitic acid and their derivatives such as esters, amides, acid anhydrides, acid chlorides, etc., especially acrylic acid Methacrylic acid and derivatives thereof are preferred.

  In addition, monovalent carboxylic acids having 1 to 8 carbon atoms such as formic acid, acetic acid, propionic acid, butyric acid, lactic acid, glycolic acid, benzoic acid, and derivatives thereof such as esters, amides, acid anhydrides, acid chlorides, etc. The polyfunctional compound may be used in combination with the starting polyamine. The amide group site introduced by the reaction has a high cohesive force, and the presence of the amide group site in a high proportion in the epoxy resin curing agent results in higher oxygen barrier properties and good adhesion to various film materials. Strength is obtained.

  The curing accelerator is not particularly limited as long as it shortens the curing time or increases the low-temperature curability. For example, in addition to a boron trihalide complex or an organic acid, phenol, m-cresol, p -Chlorophenol, p-nitrophenol, 2,4-dinitrophenol, o-chlorophenol, 2,4-dichlorophenol, o-aminophenol, p-aminophenol, 2,4,5-trichlorophenol, resorcinol, hydroquinone Phenols such as catechol, phloroglicinol, bisphenol A, trisdimethylaminophenol; methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, ethylene glycol, 1,3-propanediol , Glycerol, propylene glycol, thioglycenol, pentaerythritol, monoethanolamine, diethanolamine, triethanolamine, alcohols such as benzyl alcohol; imidazoles such as 2-ethyl-4-methylimidazole and 2-phenylimidazole; N-ethyl Morpholine, dibutyltin dilaurate, cobalt naphthenate, stannous chloride, triphenylphosphine, triphenyl phosphate, and the like can be used. Of these, boron trihalide complexes and organic acids are preferred. These curing accelerators can be used alone or in combination of two or more.

  As the boron trihalide complex, a boron trifluoride complex is particularly preferable, and specifically, boron trifluoride amine complex such as boron trifluoride monoethylamine complex; boron trifluoride dimethyl ether complex, trifluoride Boron diethyl ether complex, boron trifluoride di-n-butyl ether complex and other boron trifluoride ether complexes; boron trifluoride phenol complex, boron trifluoride acetic acid complex, boron trifluoride methanol complex, trifluoride Boron piperidine complex, boron trifluoride tetrahydrofuran complex, boron trifluoride phosphate complex, boron trifluoride acetonitrile complex etc. are mentioned, especially boron trifluoride amine complex, especially boron trifluoride monoethylamine complex is suitable. Used. These boron trihalide complexes can be used alone or in combination of two or more.

  Organic acids include p-toluenesulfonic acid, m-xylenesulfonic acid, benzoic acid, p-toluic acid, p-aminobenzoic acid, p-chlorobenzoic acid, 2,4-dichlorobenzoic acid, salicylic acid, phthalic acid, isophthalic acid Acid, terephthalic acid, malic acid, oxalic acid, succinic acid, malonic acid, fumaric acid, maleic acid, tartaric acid, citric acid, formic acid, acetic acid, lactic acid, glycolic acid, n-butyric acid, iso-butyric acid, propionic acid, caproic acid , Octanoic acid, n-heptylic acid, monochloroacetic acid, dichloroacetic acid, trichloroacetic acid and the like, and p-toluenesulfonic acid is particularly preferably used. These organic acids can be used alone or in combination of two or more.

  The adhesive layer can be formed on the smoothing layer or sealant layer by using a coating method such as gravure coating, roll coating, air knife coating, blade coating, short dwell, cast coating or the like.

  As an epoxy resin composition suitable for use in the present invention, MAXIVE (anchor coat agent) manufactured by Mitsubishi Gas Co., Ltd. may be mentioned.

  Hereinafter, the aspect at the time of using MAXIVE as an adhesive layer is demonstrated in detail.

When applying MAXIVE to the smoothing layer, the solid content is preferably adjusted to 20% or less. The coating amount of the smoothing layer of Makushibu is ^{preferably, 0.5g / m 2 ~5g / m} 2. When the coating amount is 0.5 g / m ² or less, the gas barrier property is inferior, and when it is 5 g / m ² or more, it is necessary to increase the solid content concentration. Since the Maxive coating solution has a short pot life, the workability is remarkably deteriorated when the solid content concentration is increased.

  Further, in coating, it is desirable to smooth the coated surface (smoothing layer) of MAXIVE. By smoothing the coating surface, the Maxive coating solution can be applied uniformly, so that the Maxive film is not lost, and the gas barrier is improved.

<6> Sealant Layer (i) Structure of Sealant Layer The sealant layer of the present invention has a multilayer structure including a cyclic polyolefin resin layer, and is provided on the paper base material layer side or contents side of the cyclic polyolefin resin layer. In consideration of film-forming properties, perfuming properties, sealing properties, and the like, for example, an LDPE layer, an LLDPE layer, a polyolefin-based resin layer such as a resin layer made of carboxylic acid-modified polyethylene, and the like are arbitrarily laminated.

  As one aspect of the present invention, the sealant layer is composed of two layers, an LLDPE layer and a cyclic polyolefin resin layer, and the LLDPE layer is adjacent to the paper base material layer. In the sealant layer having this configuration, since the cyclic polyolefin resin layer is the outermost layer of the packaging material of the present invention, that is, the innermost layer of the paper container, it can exhibit excellent non-adsorbability and aroma retention.

  In the said structure, the total thickness of a sealant layer is 25-80 micrometers, for example, More preferably, it is 30-60 micrometers. If the thickness of the sealant layer is thinner than this, it is impossible to fill a gap generated in the step portion of the paper container in heat sealing during box making, resulting in poor sealing performance. On the other hand, if it is thicker than this, the rigidity of the paper container is increased, which causes molding defects. The ratio of the layer thickness of the LLDPE layer to the cyclic polyolefin resin layer is suitably in the range of LLDPE layer: cyclic polyolefin resin layer = 1: 1 to 10: 1. If the layer thickness of the LLDPE layer is too thin, sufficient adhesive strength cannot be obtained, and the sealing performance of the paper container may be impaired. In addition, the thicker the thickness of the cyclic polyolefin-based resin layer, the higher the non-adsorptivity. However, if the thickness is too thick, sufficient adhesive strength cannot be obtained, and the sealing property of the paper container may be impaired. Absent.

  In still another embodiment of the present invention, the sealant layer is composed of three layers in which a first LLDPE layer, a cyclic polyolefin resin layer, and a second LLDPE layer are provided in this order, and the first LLDPE layer is a paper base material. Adjacent to the layer. The sealant layer with this structure is made of LLDPE, so it has excellent laminate strength and content resistance, and exhibits high sealing strength while maintaining good non-adsorption properties. can do.

  In the said structure, the total thickness of a sealant layer is 25-80 micrometers, for example, More preferably, it is 30-60 micrometers. If the thickness of the sealant layer is thinner than this, it is impossible to fill a gap generated in the step portion of the paper container in heat sealing during box making, resulting in poor sealing performance. On the other hand, if it is thicker than this, the rigidity of the paper container is increased, which causes molding defects. The ratio of each layer thickness is suitably in the range of first LLDPE layer: cyclic polyolefin resin layer: second LLDPE layer = 1: 1: 1 to 10: 1: 10. If the thickness of the first LLDPE layer is too thin, sufficient adhesive strength cannot be obtained, and the sealing performance of the paper container may be impaired, which is not preferable. In addition, the thicker the thickness of the cyclic polyolefin-based resin layer, the higher the non-adsorptivity. However, if the thickness is too thick, sufficient adhesive strength cannot be obtained, and the sealing property of the paper container may be impaired. Absent. Similarly, if the layer thickness of the second LLDPE layer is too thin, sufficient adhesive strength cannot be obtained, and the sealing performance of the paper container may be impaired. Furthermore, 5-30 micrometers is suitable for the layer thickness of a 2nd LLDPE layer. If the layer thickness of the second LLDPE layer is less than this, sufficient adhesive strength cannot be obtained, and if it exceeds this, the adsorbed amount of the aroma component of the contents in the layer increases, and the aroma retaining property is increased. It will be inferior.

  In still another embodiment of the present invention, the sealant layer is composed of five layers in which a first LDPE layer, a first LLDPE layer, a cyclic polyolefin resin layer, a second LLDPE layer, and a second LDPE layer are provided in this order. And the first LDPE layer is adjacent to the paper substrate layer. The sealant layer has an LLDPE layer between the LDPE layer and the cyclic polyolefin resin layer. Since LLDPE has good adhesion to both LDPE and cyclic polyolefin resin, the sealant layer having this structure has excellent laminate strength and content resistance, and has good non-adsorption properties. While maintaining, high sealing strength can be exhibited. Further, since the innermost layer is made of LDPE, the sealing performance of the liquid paper container after box making is superior to those made of cyclic polyolefin resin or LLDPE.

  In the said structure, the total thickness of a sealant layer is 25-80 micrometers, for example, More preferably, it is 30-60 micrometers. If the thickness of the sealant layer is thinner than this, it is impossible to fill a gap generated in the step portion of the paper container in heat sealing during box making, resulting in poor sealing performance. On the other hand, if it is thicker than this, the rigidity of the paper container is increased, which causes molding defects. The ratio of each layer thickness is the sum of the layer thicknesses of the first LLDPE layer and the first LDPE layer: the cyclic polyolefin resin layer: the sum of the layer thicknesses of the second LLDPE layer and the second LDPE layer = 1: 1: A range of 1-10: 1: 10 is suitable. If the sum of the thicknesses of the first LLDPE layer and the first LDPE layer is too thin, sufficient adhesive strength cannot be obtained, and the sealing property of the paper container may be impaired, which is not preferable. In addition, the thicker the thickness of the cyclic polyolefin-based resin layer, the higher the non-adsorptivity. However, if the thickness is too thick, sufficient adhesive strength cannot be obtained, and the sealing property of the paper container may be impaired. Absent. Similarly, if the sum of the layer thicknesses of the first LLDPE layer and the first LDPE layer is too thin, sufficient adhesive strength cannot be obtained, and the sealing performance of the paper container may be impaired. Furthermore, 5-30 micrometers is suitable for the sum of the layer thickness of a 2nd LLDPE layer and a 2nd LDPE layer. If the sum of the layer thicknesses of the second LLDPE layer and the second LDPE layer is less than this, sufficient adhesive strength cannot be obtained, and if it exceeds this, the adsorbed amount of the aromatic component of the contents in the layer Increases, resulting in poor incense retention.

  In the above configuration, a resin made of carboxylic acid-modified polyethylene can be used instead of LLDPE. In this case, delamination between the cyclic polyolefin-based resin layer and the layer in contact with the resin can be effectively prevented.

  Further, in the above configuration, in order to prevent permeation of a causative substance that causes delamination and further improve non-adsorbability, at least the LDPE layer on the side in contact with the contents, the LLDPE layer, or the carboxylic acid-modified polyethylene is used. It is preferable to add an arbitrary cyclic polyolefin resin to the resin layer. Suitable cyclic polyolefin-based resins can include those described in the following (v), and the amount added is 30 to 70% by mass, preferably 40 to 60% by mass of the whole. . If the addition amount is less than 30% by mass, or even less than 40% by mass, the permeation of the causative substance that causes delamination may not be completely prevented. On the other hand, if the addition amount exceeds 70% by mass, and further exceeds 60% by mass, the sealing property becomes poor. Furthermore, from the viewpoint of production efficiency, the cyclic polyolefin-based resin may be added to an LDPE layer other than the layer in contact with the contents, an LLDPE layer, or a resin layer made of carboxylic acid-modified polyethylene.

(Ii) Low density polyethylene resin (LDPE) layer In the present invention, the LDPE constituting the LDPE layer in the sealant layer has, for example, a density of about 0.90 to 0.925 g / cm ³ and a melt flow rate. A low density polyethylene having an (MFR) in the range of about 1.0 to 10.0 g / 10 min can be used. As said LDPE, as a monomer, ethylene, Furthermore, propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-nonene, Using α-olefins such as decene and others, for example, using high pressure method, slurry method, solution method, gas phase method, and other polymerization methods, ethylene is used alone or ethylene and other olefins are used together. A homopolymer of ethylene obtained by polymerization, a copolymer of ethylene and another olefin, or the like can be used.

  Examples of LDPE suitable for use in the present invention include “LC520” manufactured by Nippon Polyethylene Corporation.

(Iii) Linear low-density polyethylene resin (LLDPE) layer In the present invention, LLDPE constituting the LLDPE layer in the sealant layer is linear polyethylene having a density of 0.880 to 0.940 g / cm ³ , It is a copolymer obtained by copolymerizing ethylene and an α-olefin having 3 to 20 carbon atoms at low temperature and low pressure using a single site catalyst such as a metallocene catalyst or a multisite catalyst such as a Ziegler-Natta catalyst.

  Specific examples of the α-olefin having 3 to 20 carbon atoms include propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-nonene and 1-decene. , 1-dodecene and the like.

  Examples of the copolymerization method include ethylene and α-olefin polymerization methods such as a low pressure method, a slurry method, a solution method, and a gas phase method.

The LLDPE of the present invention has 3 to 25 short chain branches per 1000 carbon atoms as short chain branches, but is not distinguished from LDPE in that it does not have long chain branches exceeding about 20 carbon atoms. Usually, in LLDPE, the structural unit derived from ethylene is about 99.9 to 90 mol%, and the structural unit derived from α-olefin is about 0.1 to 10 mol%. In the present invention, LLDPE prepared with a metallocene catalyst can be suitably used because of excellent structural uniformity.

  Examples of LLDPE suitable for use in the present invention include “Sumikasen CW8003” manufactured by Sumitomo Chemical Co., Ltd.

  Further, the main component is LLDPE as described above, and if necessary, an antioxidant, an ultraviolet absorber, a light stabilizer, an antistatic agent, an antiblocking agent, a flame retardant, a crosslinking agent, a colorant, etc. One or more of these additives may be added.

(Iv) Resin layer made of carboxylic acid-modified polyethylene The resin layer made of carboxylic acid-modified polyethylene used in the present invention refers to a material obtained by modifying polyethylene with carboxylic acid or its anhydride.

  Here, the carboxylic acid modification means that a part of the monomer constituting the polyethylene is copolymerized in place of the α, β-unsaturated carboxylic acid or its anhydride monomer, or one of the side chains by graft reaction or the like. It is carried out by introducing α, β-unsaturated carboxylic acid or its anhydride monomer into the part.

  Examples of the α, β-unsaturated carboxylic acid or anhydride thereof used for the carboxylic acid modification include maleic acid, acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic anhydride, itaconic anhydride and the like. Among these, methacrylic acid (ethylene / methacrylic acid copolymer resin: EMAA) and maleic anhydride are preferably used.

Density of the resin consisting of the above carboxylic acid-modified polyethylene, from the viewpoint of bonding strength between adjacent layers, 0.80~0.94g / cm ^3, preferably, the 0.85~0.940g / cm ³ Those having a density are preferably used. In particular, when polyethylene modified with maleic anhydride is used as the carboxylic acid-modified polyethylene, the density is 0.80 to 0.91 g / cm ³ , preferably 0.85 to 0.905 g / cm ³ . Those are preferably used. When EMAA is used, one having a density of 0.93 to 0.94 g / cm ³ is preferably used.

  Examples of the resin made of carboxylic acid-modified polyethylene suitable for use in the present invention include “SF600” manufactured by Mitsui Chemicals, Inc., “Nucrel N0908C” manufactured by Mitsui DuPont Polychemicals, and the like.

(V) Cyclic polyolefin resin layer In the present invention, the cyclic polyolefin resin constituting the cyclic polyolefin resin layer includes a ring-opening metathesis polymer (COP) obtained by polymerizing a cyclic olefin by a metathesis ring-opening polymerization reaction, and a cyclic olefin. And a copolymer of α-olefin (chain olefin), that is, cyclic olefin copolymer (COC).

  As the cyclic olefin, any cyclic hydrocarbon having an ethylenically unsaturated bond and a bicyclo ring can be used, particularly those having a bicyclo [2.2.1] hept-2-ene (norbornene) skeleton. preferable.

Specifically, bicyclo [2.2.1] hept-2-ene and derivatives thereof, tricyclo [4.3.0.1 ^2.5 ] -3-decene and derivatives thereof, tricyclo [4.4.0.1 ^2.5] -3-undecene and derivatives thereof, tetracyclo [4.4.0.1 ^2.5 .1 ^7.10] -3-dodecene and derivatives thereof, pentacyclo ^{[6.5.1.1 3.6 .0 2.7 .0 9.13]} - 4 pentadecene and its derivatives, pentacyclo ^{[7.4.0.1 2.5 .1 9.12 .0 8.13]} -3- pentadecene and its derivatives, pentacyclo ^{[6.5.1.1 3.6 .0 2.7 .0 9.13]} - 4,10 penta decadiene and its derivatives, pentacyclo ^{[8.4.0.1 2.5 .1 9.12 .0 8.13]} -3- hexadecene and it derivatives, and the like, without limitation. The cyclic olefin may have a polar group such as an ester group, a carboxyl group, and a carboxylic anhydride group as a substituent.

  As the α-olefin copolymerized with the cyclic olefin, ethylene, an α-olefin having 3 to 20 carbon atoms can be used, and specifically, ethylene, propylene, 1-butene, 1-pentene, 3-methyl. Examples include -1-butene, 1-hexene, 4-methyl-1-pentene, and preferably ethylene.

  In the present invention, the production of the ring-opening metathesis polymer is not particularly limited as long as it is a known ring-opening metathesis polymerization reaction, and can be produced by ring-opening polymerization of the above cyclic olefin using a polymerization catalyst. .

  In the production of the cyclic olefin copolymer, 25 to 45 mol% of α-olefin and 55 to 75 mol% of cyclic olefin are randomly polymerized using a single site catalyst such as a metallocene catalyst or a multisite catalyst. Is made by

Ring-opening metathesis polymer and a cyclic olefin copolymer are preferably used in the present invention, some are commercially available, for example, Nippon Zeon Co., Ltd. of "ZEONOR ^(R)" and manufactured by Polyplastics Co., Ltd., "TOPAS ^{(R )} "And the like.

  In addition, in order to obtain the more uniform film | membrane surface in the said cyclic polyolefin resin in order to suppress the generation | occurrence | production of the gel lump by aggregation of cyclic polyolefin resin at the time of film forming, It can be added arbitrarily within a range not impairing the non-adsorption property. Examples of the olefin resin include arbitrary polyethylene and polypropylene, and those having a melt flow rate (MFR) of 5 to 40 g / 10 minutes, preferably 15 to 30 g / 10 minutes. Moreover, as an addition amount, it is good to mix | blend an olefin resin with the ratio of 3-50 mass% of the whole, Preferably 5-10 mass%.

  If necessary, one or more additives such as an antioxidant, an ultraviolet absorber, a light stabilizer, an antistatic agent, an antiblocking agent, a flame retardant, a crosslinking agent, and a colorant are added. May be.

(Vi) Method for producing sealant film In the present invention, as a method for producing a sealant film having a multilayer structure, a resin constituting an LLDPE layer and a cyclic polyolefin-based resin layer is used for coextrusion such as an inflation method or a cast method. Two layers are coextruded to form a film.

  Similarly, a three-layer sealant film including the second LLDPE layer can also be produced by coextrusion film formation. On the LLDPE film, a cyclic polyolefin resin layer and an LLDPE layer are formed in this order by an extrusion coating method. Can be manufactured. In order to increase the adhesive strength between the layers, any surface treatment such as ozone treatment may be performed on the laminated surface of the LLDPE film in advance.

  Further, in addition to the second LLDPE layer, the sealant film including the first and second LDPE layers can be similarly produced by extrusion coating on the LDPE film or by coextrusion film formation.

  High interlaminar adhesion and good film-forming stability are obtained, non-adsorbability and heat-sealability are further improved, and a beautiful film can be obtained. Therefore, LLDPE can be obtained by coextrusion, particularly by coextrusion film formation. It is preferable to form the layer and the cyclic polyolefin resin layer together. Furthermore, film formation by a coextrusion inflation method is particularly preferred because film formation at a low temperature is possible, there are few troubles of resin odor due to heating, and higher interlayer adhesion can be obtained.

<7> Use of packaging material The packaging material of the present invention is suitable for forming a liquid paper container that is required to maintain the quality of contents, particularly a liquid paper container used for low-temperature distribution (chilled distribution). Can be used.

  Production of a paper container from the packaging material of the present invention is usually performed as follows. That is, after printing as necessary on the surface of the packaging material of the present invention, it is punched out, and the end face is skived and hemmed so that the contents do not come into contact with the end face. Heat seal by heating, flame heating, etc. to make a paper container.

  The shape of the paper container may be determined as appropriate according to the use and purpose, and examples thereof include a gable top type, a brick type, a flat type, and a cylindrical paper such as a rectangular container or a round shape. A can etc. are mentioned. For example, a polyethylene cap, a pull tab-type opening mechanism, and the like may be appropriately provided at the spout of the paper container.

The contents of the paper container are not particularly limited, but those that circulate at low temperatures such as milk, milk drinks, and juice are preferable.
Next, the present invention will be specifically described with reference to examples.

[Example 1]
Frame processing is applied to both sides of a milk base paper having a basis weight of 320 g / m ² , and LDPE (LC520 manufactured by Nippon Polyethylene Co., Ltd.) having a thickness of 20 μm is laminated as an outermost layer on the printing surface side, and then reverse On the surface side, a low density polyethylene resin (LC520 manufactured by Nippon Polyethylene Co., Ltd.) was extrusion coated with a chill roll of KRH120-1.5 to form a smoothing layer having a thickness of 20 μm. Next, corona treatment was applied to the smoothing layer, and using a gravure roll, a laminating adhesive (Mc sieve manufactured by Mitsubishi Gas Chemical Co., Ltd.) mainly composed of an epoxy resin composition consisting of an epoxy resin and an epoxy resin curing agent was converted to dry. Was coated to 1.0 g / m ² and dried to form a barrier layer. Next, on the barrier layer surface, the sealant layer was LDPE 20 μm (LC520 from Nippon Polyethylene Co., Ltd.) / LLDPE 5 μm (Sumitomo Chemical CW8003) / Cyclic olefin copolymer 5 μm (TOPAS ^(R) 8007F-500 from Polyplastics Co., Ltd .; Melt flow rate (MFR) 1.9 g / 10 min; density 1.02 g / cm ³ )) / LLDPE 5 μm (Sumitomo Chemical CW8003) / LDPE 20 μm (Nippon Polyethylene Co., Ltd. LC520) laminated by coextrusion of 3 types and 5 layers The packaging material of the present invention was obtained.

[Example 2]
A packaging material of the present invention was produced in the same manner as in Example 1 except that LLDPE 5 μm (Sumitomo Chemical CW8003) in Example 1 was changed to a maleic anhydride-modified polyethylene resin (Mitsui Chemicals SF600).

[Example 3]
Cyclic olefin copolymer (TOPAS ^(R) 8007F-500 manufactured by Polyplastics Co., Ltd .; melt flow rate (MFR) 1.9 g / 10 min; density 1.02 g) for the LDPE layer and the LLDPE layer of the heat seal layer of Example 1 The packaging material of the present invention was produced in the same manner as in Example 1 except that 40 wt% of / cm ³ )) was blended.

[Comparative Example 1]
A packaging material was produced in the same manner as in Example 1 except that LLDPE (Sumitomo Chemical CW8003) was used instead of the cyclic olefin copolymer.

[Comparative Example 2]
A packaging material was prepared in the same manner as in Example 1 except that the smoothing layer was not laminated and the barrier layer was directly coated on the paper surface.

[Comparative Example 3]
A packaging material was prepared in the same manner as in Example 1 except that LDPE (LC520 manufactured by Nippon Polyethylene Co., Ltd.) was used instead of LLDPE 5 μm (Sumitomo Chemical CW8003).

[Adsorption test]
A menthol prepared by preparing a 1-L Gabel top type paper container with a side of 70 mm square using the packaging materials of Examples 1 to 3 and Comparative Examples 1 to 3 and having a menthol concentration of 5 μm / ml 1 L of ethanol solution was charged.

After storing for 2 weeks in an atmosphere at 50 ° C., the menthol content in the solution was measured by the GC / MS method. From the difference between the measured value and the menthol content before storage, the amount of menthol adsorbed per 1 cm ² of the inner wall of the paper container was determined. The results are shown in Table 1 below.

  In the paper containers comprising the packaging materials of Examples 1-2 and Comparative Examples 2, 3 having a cyclic olefin copolymer layer, the menthol adsorption amount was suppressed to a low value. In contrast, the paper container made of the packaging material of Comparative Example 1 without the cyclic olefin copolymer layer adsorbed a large amount of menthol.

[Oxygen gas barrier property test]
The oxygen barrier of each packaging material was measured using an oxygen barrier measuring machine manufactured by MOCON. The results are shown in Table 2 below.

The packaging materials of Examples 1 to 3 and Comparative Examples 1 and 3 having a barrier layer had excellent oxygen gas barrier properties.
On the other hand, since the packaging material of Comparative Example 2 coated the adhesive layer (barrier coat layer) on the paper surface, the adhesive layer was not formed.

[Lamination strength test]
The laminate strength between the cyclic olefin copolymer and the adjacent layer after storage evaluation was measured with a tensile tester under the condition that the tensile speed was 50 mm / min. The results are shown in Table 3 below.

  In the packaging materials of Examples 1 to 3 and Comparative Example 2 in which the layer adjacent to the cyclic olefin copolymer is LLDPE or acid-modified polyethylene resin, the two layers cannot be peeled off under the condition of 50 mm / min. It was confirmed to have laminate strength. On the other hand, the peel strength of Comparative Example 3 in which the layer adjacent to the cyclic olefin copolymer was LDPE was 0.5 N / 15 mm width, and it was confirmed that the laminate strength was inferior to that of the Example.

  Regarding Comparative Example 1, since there was no cyclic olefin copolymer layer, the laminate strength between the cyclic olefin copolymer and the adjacent layer was not measured. However, it was confirmed that the other layers could not be peeled.

[Heat sealability test]
Using the packaging materials of Examples 1 to 3 and Comparative Examples 1 to 3, the outermost layer surface is printed with a desired pattern, display, etc. by the offset printing method, and then punched into a predetermined shape and simultaneously necessary parts A ruled line was provided to make a blank sheet. Next, the body portions were bonded together by a frame seal method to form a cylindrical sleeve, and this cylindrical sleeve was supplied to a filling machine. The bottom part was heat-sealed with hot air from a filling machine, then the contents (mineral water) were filled, and finally the top part was heat-sealed to prepare a paperbell type paper container (1 L capacity).

  If the hot air temperature of the filling machine is too low, the adhesive strength becomes insufficient due to insufficient heating. On the other hand, if the temperature is too high, bubbling occurs in the seal portion due to overheating, and in either case, the contents leak or the container swells.

  When heat-sealing the bottom part and top part of the packaging material amount of each example and comparative example, the hot air temperature of the filling machine was changed every 10 ° C., and the hot air temperature adhered firmly without leaking the contents Range was measured. The results are shown in Table 4 below.

The packaging materials of Examples 1 to 3 can all be heat-sealed in a wide temperature range as in the comparative example, and exhibit sufficient sealing strength even at a low temperature of 320 to 340 ° C. Indicated.
From the above results, it was confirmed that the paper container formed using the packaging material of the present invention has both good non-adsorbability and oxygen barrier property and no problem with regard to suitability of the filling machine.

DESCRIPTION OF SYMBOLS 1 Outermost layer 2 Paper base material layer 3 Smoothing layer 4 Adhesive layer 5 Sealant layer a ₁ First LDPE layer a ₂ Second LDPE layer b LLDPE layer b ₁ First LLDPE layer b ₂ Second LLDPE layer c Cyclic polyolefin resin layer

Claims (13)

A packaging material used for a liquid paper container in which an outermost layer, a paper base layer, a smoothing layer, an adhesive layer, and a sealant layer are provided in this order,
The adhesive layer is a layer formed by curing a composition mainly composed of an epoxy resin composition composed of an epoxy resin and an epoxy resin curing agent, and the sealant layer has a multilayer structure including a cyclic polyolefin resin layer. A packaging material characterized by   The packaging material according to claim 1, wherein the sealant layer is a layer composed of two layers of a linear low density polyethylene resin layer and a cyclic polyolefin resin layer.   The packaging material according to claim 2, wherein the linear low-density polyethylene resin layer contains a cyclic polyolefin resin at a ratio of 30 to 70% by mass.   The sealant layer is a layer composed of three layers in which a first linear low density polyethylene resin layer, a cyclic polyolefin resin layer, and a second linear low density polyethylene resin layer are provided in this order, The packaging material according to claim 1, wherein one linear low density polyethylene resin layer is adjacent to the paper base layer.   Of the first and second linear low density polyethylene resin layers, at least the second linear low density polyethylene resin layer contains a cyclic polyolefin-based resin in a ratio of 30 to 70% by mass. The packaging material according to claim 4.   The sealant layer includes a first low density polyethylene resin layer, a first linear low density polyethylene resin layer, a cyclic polyolefin-based resin layer, a second linear low density polyethylene resin layer, and a second low density. The packaging material according to claim 1, wherein the packaging material is a layer composed of five layers in which a polyethylene resin layer is provided in this order, and the first low-density polyethylene resin layer is adjacent to the paper base material layer. .   Of the first and second low-density polyethylene resin layers and the first and second linear low-density polyethylene resin layers, at least the second linear low-density polyethylene resin layer has a ratio of 30 to 70% by mass. The packaging material according to claim 6, further comprising a cyclic polyolefin-based resin.   The packaging material according to any one of claims 2 to 7, wherein a resin layer made of carboxylic acid-modified polyethylene is used instead of the linear low-density polyethylene resin layer.   The packaging material according to any one of claims 1 to 8, wherein the smoothing layer comprises a low-density polyethylene resin layer or a linear low-density polyethylene resin layer.   The packaging material according to any one of claims 1 to 8, wherein the smoothing layer comprises a clay coat layer.   The epoxy resin curing agent contained in the epoxy resin composition of the adhesive layer is an epoxy resin curing agent containing an aromatic moiety in the molecule, according to any one of claims 1 to 10. Packaging material.   The epoxy resin contained in the epoxy resin composition of the adhesive layer is an epoxy resin having a glycidylamine moiety derived from metaxylenediamine, according to any one of claims 1 to 11. Packaging material.   A liquid paper container formed by boxing the packaging material according to any one of claims 1 to 12 so that a sealant layer becomes an innermost layer.

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