JP6476597B2 - Packaging materials for paper containers - Google Patents

Description

  The present invention relates to a paper container packaging material, a paper container comprising the same, and a package formed by filling a liquid into the paper container. More specifically, the present invention has excellent sealing properties and can reduce the sealing temperature during box making. In addition, the present invention relates to a packaging material for paper containers, a paper container, and a packaging body having a wide sealing temperature range during box making.

Conventionally, various packaging materials for paper containers and paper containers made thereof have been developed and proposed for filling and packaging liquid foods and drinks such as liquor, juice, mineral water, and liquid seasonings.
As such a paper container, a packaging material for a paper container having an outer surface thermoplastic resin layer, a paper base material layer, and an inner surface thermoplastic resin layer is used as a gable top type shown in FIG. 4 or a flat top shown in FIG. Products made in various shapes such as molds are used.

These paper containers are required to have a very high sealing property in order to prevent penetration of contents and liquid leakage, or to prevent deterioration of contents and enable long-term storage.
However, since the paper base material has a certain thickness and rigidity, a paper container using the paper base material generally has a poor sealing property due to a gap generated in the joint portion or a repulsive force of the paper against bending. easy. For example, in the case of a gable-top type paper container, it has been difficult to obtain a reliable sealing property at the upper portion, bottom portion, and trunk portion, particularly at the upper portion.

Therefore, in order to increase the sealing performance of the joint, it is performed to increase the adhesive strength by increasing the sealing temperature during box making. However, when the sealing temperature is high, there is a problem that the thermoplastic resin is oxidized and the oxidized odor is transferred to the contents. In particular, regarding the vapor deposition specifications, although the adhesive strength is increased, there is a problem that pinholes are generated and the sealing performance and the airtightness are impaired at those portions (Patent Document 1).
Therefore, there is a need for a paper container packaging material that can provide high adhesive strength and sealing performance even when the sealing temperature during box making is set low.

JP 2001-31005 A

  The present invention solves the above problems, is excellent in sealability at the time of box making, that is, excellent in low-temperature sealability and can be sealed in a wide temperature range, and has excellent sealing properties, in particular, a step in a joint portion of a container. It aims at providing the packaging material for paper containers which is excellent in the sealing performance of a part and a center seal part, the paper container consisting thereof, and the package formed by filling this with a liquid.

  The present inventors have intensively studied to solve the above problems, and are at least a packaging material for paper containers laminated in the order of an outer surface thermoplastic resin layer, a paper base material layer, and an inner surface thermoplastic resin layer, The inner surface thermoplastic resin layer has a multilayer structure of three layers or more, and in the multilayer structure of three layers or more, a layer (bonding layer) located closest to the paper substrate layer is: The layer (wetted layer) that is made of low-density polyethylene (LDPE) and is located farthest from the paper substrate layer is made of linear low-density polyethylene (LLDPE) and is an intermediate layer that is located between these layers. Is made of any polyethylene having a prescribed density, and the density of the thermoplastic resin forming each layer decreases as the distance from the paper substrate layer increases, and the paper container packaging material, Paper container, And it has developed a package which is filled with a liquid in it.

In the present invention, low-density polyethylene is a high-pressure ethylene homopolymer, and linear low-density polyethylene uses a multi-site catalyst typified by a Ziegler catalyst or a single-site catalyst typified by a metallocene catalyst. And a copolymer of ethylene and α-olefin, all of which have a density of 0.930 g / cm ³ or less. Examples of the α-olefin which is a comonomer of the linear low density polyethylene include α-olefins having 3 to 20 carbon atoms such as propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-nonene, 4 -Methylpentene etc., and mixtures thereof.

More specifically, the present invention is characterized by the following points.
(1) A packaging material for a paper container in which at least an outer surface thermoplastic resin layer, a paper base material layer, and an inner surface thermoplastic resin layer are laminated in this order, and the inner surface thermoplastic resin layer has three or more layers. A layer having a multilayer structure, wherein the layer located closest to the paper base layer in the three or more layers is made of low density polyethylene and is located farthest from the paper base layer Is made of linear low density polyethylene, and the intermediate layer located between these layers is made of polyethylene, and the density of the thermoplastic resin forming each layer decreases as the distance from the paper base layer increases. The packaging material for paper containers.
(2) The packaging material for paper containers according to (1) above, wherein the polyethylene forming the intermediate layer is linear low density polyethylene.
(3) The above-mentioned (1) or (), wherein the inner surface thermoplastic resin layer has a three-layer structure in which the first, second and third layers are laminated in order from the side closer to the paper base material layer. The packaging material for paper containers as described in 2).
(4) The packaging material for paper containers according to any one of (1) to (3) above, wherein a barrier layer is laminated between the paper base material layer and the inner surface thermoplastic resin layer.
(5) A paper container obtained by boxing the packaging material for a paper container according to any one of (1) to (4) so that the inner surface thermoplastic resin layer becomes the innermost layer.
(6) A package formed by filling the paper container according to (5) with a liquid.

  The packaging material for a paper container of the present invention has a multilayer structure in which an inner surface thermoplastic resin layer made of polyethylene is composed of three or more layers, and in this multilayer structure, a layer located at a position farthest from the paper base material layer, That is, the wetted layer that is the innermost layer of the paper container is made of linear low-density polyethylene, and the density of the thermoplastic resin forming each layer gradually decreases as the distance from the paper substrate layer increases. Is. With this configuration, it is possible to lower the seal temperature during box making and to widen the seal temperature range during box making. Furthermore, since the bonding layer and the intermediate layer are superior in heat resistance as compared to the liquid contact layer, the occurrence of pinholes can be suppressed when the packaging material for paper containers is heated for box making.

  In the multilayer structure of the inner surface thermoplastic resin layer, the bonding layer is made of low-density polyethylene having a density higher than that of the liquid contact layer and the intermediate layer. The bonding layer made of low-density polyethylene exhibits a low viscosity suitable for sealing, and flows into the stepped portion and the center seal portion of the joint portion of the paper container to fill the gap, thereby improving the sealing property of the container and the contents Can prevent leakage.

It is a schematic sectional drawing which shows an example about the layer structure of the packaging material for paper containers of this invention. It is a schematic sectional drawing which shows an example about the layer structure of the packaging material for paper containers of this invention. It is a top view which shows an example of the blank board of a gable top type | mold paper container. It is a perspective view which shows an example of a gable top type | mold about the paper container of this invention. It is a perspective view which shows an example of a flat top type | mold about the paper container of this invention. It is a perspective view which shows an example of a gable top type | mold about the paper container of this invention. It is WW section sectional drawing which shows (a) DS part of FIG. 6, and (b) CS part. It is a reference figure which shows the evaluation criteria of a sealing test. It is a reference photograph which shows the state which the penetrating solution has reached to the screw formed in the container upper part in a sealing test.

The above-described present invention will be described in more detail below. Hereinafter, the resin names used in the present invention are those commonly used in the industry.
<1> Layer Configuration of Paper Container Packaging Material of the Present Invention and Shape of Paper Container FIGS. 1-2 are schematic cross-sectional views showing an example of a layer configuration of the paper container packaging material of the present invention.
As shown in FIG. 1, the packaging material for paper containers of the present invention has an outer surface thermoplastic resin layer (1), a paper base material layer (2), and an inner surface thermoplastic resin layer (3) as a basic structure. Here, the inner surface thermoplastic resin layer (3) has a multilayer structure of three layers or more, and is at least a layer (bonding layer) (3a) located at a position closest to the paper base material layer, an intermediate layer (3b) and a layer (wetted layer) (3c) located farthest from the paper base material layer. The outer surface thermoplastic resin layer (1) forms the outer surface of the paper container, and the innermost thermoplastic resin layer (3), the layer (3c) located farthest from the paper substrate layer, is the outermost layer of the paper container. It becomes the inner layer. A printing layer or the like can be optionally provided between the outer surface thermoplastic resin layer (1) and the paper base material layer (2). Moreover, a printing layer can also be provided on the further surface of the outer surface thermoplastic resin layer (1).

  Moreover, as shown in FIG. 2, you may provide a barrier layer (5) through a contact bonding layer (4) between a paper base material layer (2) and an inner surface thermoplastic resin layer (3). Alternatively, additional layers may be arbitrarily laminated according to the packaging purpose of the paper container, the contents to be filled and packaged, the purpose of use, the application, and the like.

  Further, the paper container packaging material of the present invention is punched into a predetermined shape to produce a blank plate having a paste margin as shown in FIG. This end face is treated by skive hemming or the like, and the inner surface thermoplastic resin layer of the adhesive margin is melted by frame treatment or hot air treatment, and sealed to produce a cylindrical sleeve. Next, sealing is performed in the same manner in the content filling machine, and the bottom and top are formed to form a paper container.

The shape of the paper container may be appropriately determined according to the use and purpose, and may be any shape other than the gable top type shown in FIGS. 4 and 6 and the flat top type shown in FIG. . In addition, 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.
As an embodiment of the present invention, the sealing performance in the stepped portion and the center seal portion of the joint portion will be described by taking a gable top type paper container as an example.

  As shown in FIG. 3 and FIG. 4, the paper container seals the panels that form the upper surface (10), the body portion (30), and the bottom portion (50) through the adhesive margin (90), Shaped sleeves. Next, the bottom part (50) is manufactured by the bottom panel (51, 52, 53, 54). Further, after filling the contents, the upper joint 15 is formed by sealing through the adhesive margin (11b) of the inclined panel (11a) and the adhesive margin (13b) of the folding panel (13a), and the inclined portion (11). And the upper part (10) including the folding part (13). Further, as shown in FIG. 4, the paper container may include a spout 71 and may further include a cap 72.

  FIG. 6 is a perspective view showing another example of the gable top type for the paper container of the present invention. 7 is a cross-sectional view taken along the line WW in FIG. 6. FIG. 7A shows the step portion DS and FIG. 7B shows the center seal portion CS.

  Needless to say, in the sealed paper container P, particularly when the contents are liquid, there should be no liquid leakage from any part. For example, in the case of a gobeltop type paper container, as shown in FIG. 7 (a), the gap X in the upper joint portion and the portion where the airtightness is likely to be lost due to the structure of the container, as shown in FIG. As shown in FIG. 7B, the gap Y is in the center seal portion CS of the upper joint portion. This is a part to be particularly noted when the gaps X and Y formed in the step part DS and the center seal part CS are reliably sealed with molten resin.

  Further, in the structure of the container as described above, the surface sealing property (glue allowance surface) due to the repulsive force against the folding of the folding panel, especially in the upper joining portion which is the joining portion of the glue margin of the upper inclined panel and the folding panel. Adhesive strength between each other) is impaired, and seal failure is likely to occur. Furthermore, the center seal portion CS of the upper joint portion is likely to be in a seal thin state where the thickness of the seal portion is reduced.

  Although it demonstrated in the site | part of the upper part of the paper container P, the site | part which is easy to leak similarly in the bottom part, or is easy to impair airtightness exists. During transportation, these parts may be damaged by impact or the like, causing liquid leakage. In particular, the danger is high in the case of long-distance transportation.

  In addition to the usual seal, a screw is further provided at the joint where these leaks are likely to occur. Specifically, in the stepped portion and the center seal portion, a portion (screw) bonded with higher adhesive strength is provided by partially applying extra pressure. However, in the conventional paper container, it is known that the contents travel through the gap and leak beyond the screw.

<2> Outer surface thermoplastic resin layer In the present invention, the outer surface thermoplastic resin layer is laminated on one surface of the paper base material layer and has any adhesive property with the wetted layer of the inner surface thermoplastic resin layer. It may be made of resin.
Examples of such thermoplastic resins include polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ionomer resin, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer, and ethylene-methacrylic acid copolymer. Polyethylene resins such as ethylene-methyl methacrylate copolymer, methylpentene polymer, polybutene polymer, polyethylene or polypropylene, and unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid and itaconic acid Resins such as acid-modified polyolefin resin, polyvinyl acetate resin, poly (meth) acrylic resin, and polyvinyl chloride resin modified with the above can be used alone or in admixture of two or more. It is particularly preferable to use low-density polyethylene or linear low-density polyethylene because it exhibits particularly good adhesion with the linear low-density polyethylene forming the liquid contact layer.

  The outer surface thermoplastic resin layer is a layer that becomes the surface of the paper container, but a printing layer can also be provided on the surface, and in this case, in order to improve the adhesion of the printing ink used for the printing layer The surface is preferably subjected to surface treatment such as corona treatment.

  The layer thickness of the outer surface thermoplastic resin layer may be a thickness that provides sufficient sealing strength to form a paper container, and can be appropriately set by those skilled in the art. Is in the range of 15-30 μm.

  The outer surface thermoplastic resin layer is formed by extrusion coating a molten thermoplastic resin on one surface of the paper base material layer through a corona treatment / frame treatment or an anchor coating agent layer, etc. It can laminate | stack by laminating | stacking the resin film which consists of a plastic resin by arbitrary methods.

<3> Paper base material layer In the present invention, as the paper base material layer, any paper having various formability, flex resistance, rigidity, waist, strength, etc. is used depending on the application of the paper container to be applied. Can be used, for example, the main strength material, and use various types of paper such as strong size bleached or unbleached paper, or pure white roll paper, kraft paper, paperboard, processed paper, milk base paper, etc. Can do. The paper base material layer may be obtained by laminating a plurality of layers of these papers. An arbitrary thickness can be used. For example, the basis weight is 80 to 600 g / m ² , preferably the basis weight is 100 to 500 g / m ² , and the thickness is 110 to 860 μm, preferably 140 to 640 μm. It is a range. 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> Inner surface thermoplastic resin layer In the present invention, the inner surface thermoplastic resin layer has a multilayer structure composed of three or more thermoplastic resins, and in this multilayer structure, the density of the thermoplastic resin forming each layer is It becomes gradually smaller as the distance from the paper base material layer increases. That is, in the multilayer structure of the inner surface thermoplastic resin layer, the thermoplastic resin forming the layer (bonding layer) located closest to the paper base material layer has the highest density and is farthest from the paper base material layer. The thermoplastic resin that forms the layer located in place (the wetted layer) has the lowest density.

  With this configuration, it is possible to lower the seal temperature during box making and to widen the seal temperature range during box making. In addition, if the packaging material for paper containers is blown with hot air during box making, the layer located inside when the liquid contact layer on the surface melts and softens to a degree sufficient to exhibit sealing properties and adhesiveness. Withstands the water vapor pressure generated from the paper base material layer and retains the strength to prevent foaming and film breakage, while melting and softening to such an extent that it contributes to improving the adhesive strength. Therefore, it is possible to suppress the occurrence of twisting pinholes.

  Also, the low-density polyethylene that forms the bonding layer flows into the stepped part and center seal part of the joint part of the paper container at the time of sealing and fills the gap, thereby improving the sealing performance of the container and preventing leakage of the contents. prevent.

  That is, in the multilayer structure of the inner surface thermoplastic resin layer, high pinhole resistance is exhibited by gradually changing the interlayer density from the wetted layer to the bonding layer through the intermediate layer. However, the sealing performance can be improved.

Therefore, the thermoplastic resin forming the liquid contact layer has the smallest density in the multilayer structure and is a linear low density polyethylene. With this configuration, good sealing performance is exhibited. Therefore, the packaging material for paper containers of the present invention can be sealed even at low temperatures, can be packaged at high speed, and can be applied to a wide variety of uses. The density of the linear low density polyethylene forming the wetted layer is preferably 0.890 to 0.909 g / cm ³ . If it is less than 0.890 g / cm ³ , the slipperiness of the surface is inferior and the suitability for producing cartons is deteriorated.

  As the linear low density polyethylene, it is particularly preferable to use a linear low density polyethylene polymerized using a single site catalyst typified by a metallocene catalyst. Linear low-density polyethylene polymerized with a metallocene catalyst is superior in mechanical properties such as tensile strength, tear strength, and piercing strength compared to those polymerized using a multisite catalyst typified by a Ziegler-Natta catalyst. Can be used particularly preferably. Here, a single site catalyst (including a metallocene catalyst, so-called Kaminsky catalyst) has a feature that the active sites are uniform (single site). This single-site catalyst is a catalyst composed of a metallocene transition metal compound and an organoaluminum compound, and is sometimes used while being supported on an inorganic substance.

  Here, as the metallocene-based transition metal compound, for example, a transition metal selected from group IVB [titanium (Ti), zirconium (Zr), hafnium (Hf)], cyclopentadienyl group, substituted cyclopentadienyl group , An indenyl group, a substituted indenyl group, a tetrahydroindenyl group, a substituted tetrahydroindenyl group, a fluoronyl group or a substituted fluoronyl group having 1 to 2 bonds, or two of these groups are covalently crosslinked Other than these, a hydrogen atom, an oxygen atom, a halogen atom, an alkyl group, an alkoxy group, an aryl group, an acetylacetonate group, a carbonyl group, a nitrogen molecule, an oxygen molecule, a Lewis base, a substituent containing a silicon atom, What has ligands, such as unsaturated hydrocarbon, is mentioned.

  In addition, examples of the organoaluminum compound include alkylaluminum, chain-like or cyclic aluminoxane, and the like. Here, examples of the alkylaluminum include triethylaluminum, triisobutylaluminum, dimethylaluminum chloride, diethylaluminum chloride, methylaluminum dichloride, ethylaluminum dichloride, dimethylaluminum fluoride, diisobutylaluminum hydride, diethylaluminum hydride, ethylaluminum sesquichloride, and the like. Can be mentioned.

  The chain or cyclic aluminoxane is produced by bringing alkyl aluminum into contact with water. For example, it can be obtained by adding alkylaluminum at the time of polymerization and adding water later, or by reacting crystallization water of a complex salt or adsorbed water of an organic / inorganic compound with alkylaluminum.

Moreover, the thermoplastic resin which forms a bonding layer has the largest density in a multilayer structure, and is a low density polyethylene. With this configuration, the bonding layer moves to the step of the seal part of the paper container and fills the gap, so that the sealing property of the container, that is, the step part and the center seal part at the top and bottom is improved, Content leakage can be prevented. The density of the low-density polyethylene forming the bonding layer is preferably 0.910 to 0.930 g / cm ³ . When it is larger than 0.930 g / cm ³ , the sealing performance is deteriorated, which is not preferable.

  Furthermore, the intermediate layer located between the bonding layer and the liquid contact layer is polyethylene and may have a single layer structure or a multilayer structure of two or more layers. In particular, the polyethylene is preferably composed of linear low density polyethylene, more preferably linear low density polyethylene polymerized using a single site catalyst typified by a metallocene catalyst. Thereby, a sealing performance can be improved further.

The density of the thermoplastic resin that forms the intermediate layer is a value between the density of the low-density polyethylene that forms the bonding layer and the density of the linear low-density polyethylene that forms the wetted layer, and is preferably 0. 0.909 to 0.925 g / cm ³ . If it is less than 0.909 g / cm ³ , sufficient pinhole resistance cannot be obtained. On the other hand, if it is larger than 0.925 g / cm ³ , sufficient low-temperature sealability cannot be obtained.

  A person skilled in the art can appropriately set the total thickness of the inner surface thermoplastic resin layer, but it is preferably 30 to 100 μm, and more preferably 40 to 80 μm. By setting it to 40 μm or more, excellent sealing properties and low temperature sealing properties are exhibited. Moreover, since the internal surface thermoplastic resin layer of this invention shows sufficient adhesive strength at 100 micrometers or less, it is excellent in a moldability.

  The total thickness of the liquid contact layer and the intermediate layer is preferably larger than the thickness of the bonding layer. With this configuration, the low-temperature sealing property can be further enhanced. The thickness of each layer can be appropriately set by those skilled in the art. For example, the thickness of the bonding layer is 15 to 25 μm, the total thickness of the intermediate layer is 15 to 30 μm, and the thickness of the wetted layer is 10 It can be set to ˜25 μm. When the bonding layer and the intermediate layer are too thick, the low temperature sealing property is impaired. Conversely, if the bonding layer is too thin, sufficient sealing properties cannot be obtained. On the other hand, if the intermediate layer is too thin, the pinhole resistance is impaired. If the wetted layer is too thin, the low temperature sealing property is impaired, which is not preferable.

  The inner surface thermoplastic resin layer is laminated on the paper base layer or the barrier layer described later by the coextrusion coating of the bonding layer / intermediate layer / wetted layer via the anchor coating agent layer, etc. Is done. Alternatively, a coextruded film formed in the layer configuration of a bonding layer / intermediate layer / wetted layer is laminated on the paper base layer or barrier layer by any method, for example, by dry lamination via an adhesive. May be. Moreover, you may laminate | stack the coextruded film formed by the layer structure of the intermediate | middle layer / wetted layer by the sandwich lamination method through the bonding layer. The coextruded film can be manufactured using a T-die or an inflation method. As another lamination method, a co-extruded film formed by a T-die method with a layer structure of a bonding layer / intermediate layer / wetted layer is bonded inline using an adhesive and a dry lamination method. They can also be combined (the so-called Neram method). Lamination by the co-extrusion coating method is particularly preferred in that it is excellent in productivity, can be produced at low cost, and has little elution of the adhesive component into the container.

When an anchor coat agent is used, a urethane-based adhesive or the like can be used, and the coating amount can be about 0.01 to 1.0 g / m ² . When laminating by the dry lamination method, urethane adhesive, vinyl adhesive, acrylic adhesive, epoxy adhesive, etc. can be used as the adhesive, and the coating amount is, for example, 2.0 g / m ² or more It is good to be.

<5> Barrier layer In the present invention, a barrier layer may be provided between the paper base material layer and the inner surface thermoplastic resin layer. The barrier layer may be any barrier film that exhibits a barrier property against oxygen and water vapor. Specifically, a metal film such as an aluminum foil, a vapor deposition film obtained by depositing a metal such as aluminum or an inorganic oxide such as silicon oxide, aluminum oxide, or magnesium oxide on a film made of polyester, polyamide, polypropylene, or the like, ethylene-vinyl Examples thereof include a layer formed of a resin exhibiting gas barrier properties such as an alcohol copolymer, polyamide, polyvinylidene chloride, and polyacrylonitrile. Two or more of these may be laminated.

  The barrier layer can be laminated on the paper base layer by a sandwich lamination method through an adhesive resin. As the adhesive resin, any thermoplastic resin that can be melted by heat and fused to each other can be used. For example, ethylene-acrylic acid copolymer (EAA), ethylene-ethyl acrylate copolymer , Ethylene-methacrylic acid copolymer (EMAA), ethylene-methyl methacrylate copolymer, ethylene-maleic acid copolymer, linear low density polyethylene, low density polyethylene, ionomer resin, polyethylene with acrylic acid, methacrylic acid, Examples thereof include acid-modified polyolefin resins modified with unsaturated carboxylic acids such as maleic acid, maleic anhydride, fumaric acid, and itaconic acid, and maleic anhydride. The thickness of the adhesive resin layer can be appropriately set by those skilled in the art depending on the type of barrier film to be bonded, and may be, for example, 15 to 60 μm, preferably 20 to 30 μm. If it is thicker than 60 μm, the cost increases, which is not preferable.

  The barrier layer may also be laminated by a dry lamination method or the like via an arbitrary adhesive. As the adhesive, thermosetting resins such as urethane adhesives, vinyl adhesives, acrylic adhesives, and epoxy adhesives can be used.

<6> Paper container packaging material and paper container In order to produce the paper container packaging material of the present invention, an outer surface thermoplastic resin layer is laminated on one surface of the paper base material layer, and on the opposite surface. In some cases, a barrier layer is laminated, and an inner surface thermoplastic resin layer is further laminated. Or you may manufacture by bonding together the paper base material layer which laminated | stacked the outer surface thermoplastic resin layer on one surface, and the barrier layer which laminated | stacked the inner surface thermoplastic resin layer on one surface.

The paper container made of the packaging material of the paper container method of the present invention can be filled and packaged with various articles such as various foods and drinks, chemicals such as adhesives and adhesives, cosmetics, general goods such as pharmaceuticals, and the like. Is. In particular, for example, it is useful as a liquid paper container for filling and packaging various liquid foods and drinks such as juices such as liquor and fruit juices, mineral water, soy sauce, sauces and soup, or curry, stew and soup. Is.
EXAMPLES The present invention will be specifically described below with reference to examples, but these do not limit the present invention.

<Example 1>
Low-density polyethylene (LC520, manufactured by Nippon Polyethylene Co., Ltd.) was extrusion coated so as to have a thickness of 20 μm on the surface side of a milk carton base paper having a basis weight of 400 g / m ² . Next, while extruding an ethylene-methacrylic acid copolymer (N0908C, manufactured by Mitsui DuPont Polychemical Co., Ltd.) to a thickness of 20 μm on the back side of the milk carton base paper, a deposited film is formed using a sandwich lamination method. The provided biaxially stretched polyethylene terephthalate film having a thickness of 12 μm was bonded. Finally, after drying the urethane adhesive (EL-540 (main agent) / CAT-RT32 (curing agent), manufactured by Toyo Morton Co., Ltd.) on a 12 μm thick biaxially stretched polyethylene terephthalate film provided with a deposited film After coating so that the coating amount of 0.1 g / m ² becomes low density polyethylene (bonding layer, LC520, density 0.923 g / m ³ , manufactured by Nippon Polyethylene Co., Ltd.), linear low density Polyethylene (intermediate layer, FV403, density 0.918 g / m ³ , manufactured by Sumitomo Chemical Co., Ltd.) and linear low density polyethylene (wetted layer, 057FA, density 0.902 g / m ³ , Ube Maruzen Polyethylene Co., Ltd.) Were manufactured by coextrusion coating so that the thickness was 20 μm, 25 μm, and 10 μm, respectively, and the packaging material for paper containers of the present invention was produced.

<Example 2>
As the resin for forming the wetted layer, linear low density polyethylene (057FA, density 0.902 g / m ³ , manufactured by Ube Maruzen Polyethylene Co., Ltd.) was used instead of linear low density polyethylene (FV401, density 0.904 g / m). m ^3, except for using Sumitomo chemical Co., Ltd.) in the same manner as in example 1 to prepare a paper container for packaging materials of the present invention.

<Comparative Example 1>
In the same manner as in Example 1, low density polyethylene was extrusion coated on the front side of the milk carton base paper, a vapor deposition film was bonded to the back side, and a urethane adhesive was applied on the vapor deposition film. Thereafter, low density polyethylene (bonding layer, LC520, density 0.923 g / m ^3, Nippon Polyethylene Co., Ltd.) and linear low density polyethylene (intermediate layer, 057FA, density 0.902 g / m ^3, Ube Maruzen Polyethylene Co., Ltd.) and linear low-density polyethylene (wetted layer, FV403, density 0.918 g / m ³ , manufactured by Sumitomo Chemical Co., Ltd.) so that the thicknesses are 20 μm, 25 μm, and 10 μm, respectively. Co-extrusion coating was carried out to produce a packaging material for paper containers.

<Comparative example 2>
In the same manner as in Example 1, low density polyethylene was extrusion coated on the front side of the milk carton base paper, a vapor deposition film was bonded to the back side, and a urethane adhesive was applied on the vapor deposition film. Thereafter, low density polyethylene (bonding layer, LC520, density 0.923 g / m ^3, Nippon Polyethylene Co., Ltd.) and linear low density polyethylene (intermediate layer, 057FA, density 0.902 g / m ^3, Ube Maruzen Polyethylene) and linear low density polyethylene (wetted layer, 057FA, density 0.902 g / m ³ , Ube Maruzen Polyethylene Co., Ltd.) have thicknesses of 35 μm, 10 μm, and 10 μm, respectively. Co-extrusion coating was performed as described above to prepare a packaging material for paper containers.

<Comparative Example 3>
In the same manner as in Example 1, low density polyethylene was extrusion coated on the front side of the milk carton base paper, a vapor deposition film was bonded to the back side, and a urethane adhesive was applied on the vapor deposition film. Thereafter, low density polyethylene (bonding layer, LC520, density 0.923 g / m ^3, Nippon Polyethylene Co., Ltd.) and linear low density polyethylene (intermediate layer, 057FA, density 0.902 g / m ^3, Ube Maruzen Polyethylene Co., Ltd.) and linear low density polyethylene (057FA, density 0.902 g / m ³ , Ube Maruzen Polyethylene Co., Ltd.) are co-extruded to a thickness of 20 μm, 15 μm, and 20 μm, respectively. Coating was performed to prepare a packaging material for paper containers.

<Evaluation criteria>
(Pinhole resistance test)
Using the packaging materials for paper containers prepared in Examples 1-2 and Comparative Examples 1-3, the sealing temperature (air temperature) was changed between 280-360 ° C every 10 ° C, and after passing through the heater, the carton Were sampled, and the penetrant was applied to the inner surface of the packaging material for paper containers, wiped off after 5 minutes, and pinholes were confirmed visually.

Next, the packaging material for the paper container is agglomerated and separated at the milk carton base paper to separate it into two sheets, and the surface of each of the milk carton base paper in a flat state is observed, and the permeate penetrates to the milk carton base paper. It was confirmed visually whether or not.
(Sealing test / Seal test)
Using the packaging materials for paper containers prepared in Examples 1 and 2 and Comparative Examples 1 to 3, the seal temperature (air temperature) was changed between 280 to 360 ° C. every 10 ° C. A sample of a 1800 ml gable top paper container filled with water was prepared. The adhesive margin of the upper inclined panel was set to 17 mm in width, and the adhesive margin of the folded panel was overlapped and sealed to provide the upper joint 15. Here, in the stepped portion, a screw is provided at a position above 2 mm from the broken line (boundary line with the non-glue part), and in the center seal part, 2. from the broken line (boundary line with the non-glue part). A screw was provided at a position above 5 mm. Similarly, a bottom joint portion was provided at the bottom portion, and a screw was provided at the bottom joint portion.

  After filling the obtained gable-top paper container with water, discard the water in the gable-top paper container, cut off the top and bottom of the container, apply the penetrant inside, and heat the joint 30 minutes later After peeling off into a flat plate state, the sealing performance is evaluated from the level of penetration of the penetrant liquid in the stepped portion and the center seal portion of the upper joint portion 15 and the portion other than the stepped portion of the upper joint portion 15 and the center seal. The sealing property was evaluated from the degree of penetration of the penetrating liquid in parts other than the part. In the blank plate of FIG. 3, the sealability of the stepped portion of the upper joint portion 15 was evaluated by confirming the vicinity of the connecting portion of the folding panel paste margin 13 b and the paste margin 90. Moreover, in the blank board of FIG. 3, the sealing performance of the center seal portion of the upper joint portion 15 was evaluated by confirming the vicinity of the center portion of the inclined panel paste margin 11b and the folded panel paste margin 13b.

In addition, since it was known that if the sealing property of the upper joint portion 15 satisfies the evaluation criteria, the sealing property of the bottom joint portion also satisfies the evaluation criteria, the sealing performance and the sealing performance of the upper joint portion 15 were evaluated here. Only the results will be described.
The results are shown in Table 2 below.

  In Table 2 above, the “pinhole” column represents the occurrence of pinholes. In the table, “◯” represents a state where there is no pinhole and the penetrating liquid has not penetrated into the paper, and “Δ” represents a pinhole. A state in which a hole is generated in the inclined panel adhesive margin 11b and the folded panel adhesive margin 13b (above the broken line of the inclined panel adhesive margin 11b and the folded panel adhesive margin 13b and the side panels 31, 32, 33, 34). X represents a state in which leakage due to pinholes occurs.

  Moreover, in the column of “sealing”, as shown in the OK example of FIG. 8, ○ indicates a state where the penetrant does not reach the lower ends of the screws formed on the inclined panel paste margin 11b and the folded panel paste margin 13b. △ represents a state in which the permeated liquid permeates through the lower ends of the screws formed in the inclined panel paste margin 11b and the folded panel paste margin 13b as shown in the NG example of FIG. 8 and FIG. 9. The symbol x represents a state in which the leakage of the penetrating liquid has occurred from the inclined panel paste margin 11b and the folded panel paste margin 13b.

  In the “Seal” column, “◯” represents a state in which the penetrating liquid has not penetrated into the inclined panel paste margin 11b and the folded panel paste margin 13b, and “Δ” represents the penetrating liquid into the tilted panel paste margin 11b and the folded panel paste margin. Represents the state of permeating into the margin 13b (above the broken line of the slope panel glue margin 11b and the folding panel glue margin 13b and the side panels 31, 32, 33, 34), and x represents the slope panel glue margin 11b. And the state where the leakage of the penetrant has occurred from the folding panel paste margin 13b is shown.

  As is apparent from the evaluation results shown in Table 2, the occurrence of pinholes was not confirmed even when the packaging materials for paper containers of Examples 1 and 2 were sealed at a high temperature of 350 ° C. Further, it showed good sealing properties and sealing properties even at a low temperature of 290 ° C., and could be manufactured in a wide heat sealing temperature range of 325 ° C. ± 25 ° C.

1. 1. Outer surface thermoplastic resin layer 2. Paper base material layer Inner surface thermoplastic resin layer 3a. Layer located at the location closest to the paper base layer (bonding layer)
3b. Intermediate layer 3c. Layer located at the furthest place from the paper base layer (wetted layer)
4). 4. Adhesive layer Barrier layer 10. Upper part 11. Inclined portion 11a. Inclined panel 11b. Inclined panel glue margin13. Folding part 13a. Folding panel 13b. Insert panel glue allowance15. Upper joint 30. Torso 31, 32, 33, 34. Side panel 50. Bottom 51,52,53,54. Bottom panels 52b, 53b, 54b. Bottom panel glue allowance 70. Gripping tab 71. Spout 72. Cap 90. Adhesive margins L1, L2. Line P.P. Paper container DS. Stepped portion CS. Center seal

Claims (7)

At least a packaging material for paper containers laminated in the order of an outer surface thermoplastic resin layer, a paper base material layer, and an inner surface thermoplastic resin layer,
The inner surface thermoplastic resin layer has a multilayer structure of three layers or more, and in the multilayer structure of three layers or more,
The layer located closest to the paper substrate layer is made of low-density polyethylene, and the wetted layer that is located farthest from the paper substrate layer and is the innermost layer is a linear low density Made of polyethylene,
An intermediate layer having a single layer structure or a multilayer structure of two or more layers located adjacent to each other is made of polyethylene (except when these intermediate layers are resins containing a cyclic olefin as a raw material). ),
The density of the thermoplastic resin forming each layer of the inner surface thermoplastic resin layer is:
The density of the low density polyethylene is 0.910 to 0.930 g / cm ³ ;
The density of the polyethylene forming the intermediate layer is a value between the density of the low density polyethylene and the density of the linear low density polyethylene described below , and is 0.909 to 0.925 g / cm ³ .
The density of the linear low density polyethylene is 0.890 to 0.909 g / cm ³ ;
It becomes smaller as it gets away from the paper base layer,
The packaging material for paper containers described above.   The packaging material for paper containers according to claim 1, wherein the polyethylene forming the intermediate layer is linear low-density polyethylene.   The paper according to claim 1 or 2, wherein the inner surface thermoplastic resin layer has a three-layer structure in which the first, second, and third layers are laminated in order from the side closer to the paper base material layer. Packaging material for containers.   The packaging material for paper containers according to any one of claims 1 to 3, wherein a barrier layer is laminated between the paper base material layer and the inner surface thermoplastic resin layer. A paper container obtained by box-packaging the packaging material for a paper container according to any one of claims 1 to 4 so that an inner surface thermoplastic resin layer becomes an innermost layer.   A package formed by filling the paper container according to claim 5 with a liquid. At least a method for producing a packaging material for paper containers laminated in the order of an outer surface thermoplastic resin layer, a paper base material layer, and an inner surface thermoplastic resin layer ,
The inner surface thermoplastic resin layer has a multilayer structure of three layers or more, and in the multilayer structure of three layers or more,
The layer located closest to the paper substrate layer is made of low-density polyethylene, and the wetted layer that is located farthest from the paper substrate layer and is the innermost layer is a linear low density Made of polyethylene,
An intermediate layer having a single layer structure or a multilayer structure of two or more layers located adjacent to each other is made of polyethylene (except when these intermediate layers are made of a resin containing a cyclic olefin as a raw material). ),
The density of the thermoplastic resin forming each layer of the inner surface thermoplastic resin layer is:
The density of the low density polyethylene is 0.910 to 0.930 g / cm ³ ;
The density of the polyethylene forming the intermediate layer is a value between the density of the low density polyethylene and the density of the linear low density polyethylene described below , and is 0.909 to 0.925 g / cm ³ .
The density of the linear low density polyethylene is 0.890 to 0.909 g / cm ³ ;
A method for producing a packaging material for a paper container that decreases as the distance from the paper substrate layer increases.
Said manufacturing method characterized by laminating | stacking this inner surface thermoplastic resin layer by co-extrusion coating.