JP6694539B1 - LAMINATED PAPER, LAMINATED PAPER PAPER BASE, PAPER CONTAINER, AND METHODS FOR PRODUCING THE SAME - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated paper excellent in water resistance on the end face and excellent in processability at the time of manufacturing, a manufacturing method thereof, a laminated paper paper base material and a manufacturing method thereof, and a paper container using the laminated paper. Kind Code: A1 A laminated paper having a paper base material containing cellulose pulp as a main component and a thermoplastic resin layer laminated on at least one surface of the paper base material, wherein the paper base material is pulp. It has a multilayer structure having three or more layers, the mass ratio of hardwood kraft pulp and softwood kraft pulp in the outer layer of the paper substrate is 50:50 to 100: 0, and the sizing agent of the inner layer of the paper substrate is The laminated paper is characterized in that the content is higher than the content of the sizing agent in the outer layer. Further, it is a method for manufacturing the laminated paper, a laminated paper paper base material and a method for manufacturing the same, and a paper container using the laminated paper. [Selection diagram] None

Description

  The present invention relates to a laminated paper and a manufacturing method thereof, a laminated paper base material and a manufacturing method thereof, and a paper container using the laminated paper.

  In liquid paper containers used for milk packs and the like, various techniques are used to impart water resistance to the paper base material that constitutes the paper container. Typical methods include a method of applying a sizing agent to a paper base material and a method of laminating a thermoplastic resin.

  When a laminated paper laminated with a thermoplastic resin is used, liquid does not come into direct contact with the surface of the paper, so that water resistance can be imparted to the surface of the paper. However, when a paper container is made of laminated paper, the end surface of the laminated paper comes into contact with the liquid, which causes a problem that the liquid permeates from the end surface. In order to improve the water resistance of the end surface of the laminated paper, it is necessary to improve the water resistance of the paper base material itself.

  As a technique for imparting water resistance to the end surface of the paper base material, for example, skive hemming processing for bending the end surface of the paper base material is known. Further, Patent Document 1 discloses a base paper for a paper container having a multi-layered structure, the outer layer having a blending ratio of softwood kraft pulp of 40% by mass or more, and the inner layer having a blending ratio of softwood kraft pulp of 30% by mass or less. A base paper is disclosed. Furthermore, in Patent Document 1, in order to prevent the liquid from penetrating from the cross section of the laminated sheet into the base paper, a method of setting the freeness (CSF) of the raw material pulp to a low numerical value and an internal sizing agent are added. A method is disclosed.

International Publication No. 2010/113849

  The base paper formed by the method disclosed in Patent Document 1 has some effect in improving the water resistance of the end face. However, the method of adjusting the freeness of the raw pulp has room for further improvement in the effect of improving water resistance. In addition, the method of adding the internally added sizing agent generally has a function of hydrophobizing the fibers of the paper, so that there arises a problem that the adhesion is hindered when laminating.

  Conventionally, a method of applying PVA (polyvinyl alcohol) has been used in order to improve the hydrophilicity of the paper surface or increase the smoothness of the surface and improve the suitability for lamination. However, in recent years, the regulation of raw materials for food contact has been advanced, and the use of PVA containing methyl acetate and the like as impurities tends to be withheld.

  The present invention has been made in view of the above situation. That is, an object of the present invention is to provide a laminated paper excellent in water resistance at the end face and also excellent in processability during manufacturing, a method for manufacturing the laminated paper base material and a method for manufacturing the laminated paper, and a paper container using the laminated paper. Is to provide.

  The inventors of the present invention used a multi-layered structured paper having three or more pulp layers as a paper base material, and contained more sizing agent in the inner pulp layer than in the outer pulp layer to improve the water resistance on the end face. It was found that it is also effective for workability. It was also found that the laminating adhesiveness is improved by adding a large amount of hardwood kraft pulp to the outer pulp layer of the paper substrate. The present invention has been completed based on these findings. That is, the present invention has the following configurations.

(1) A laminated paper having a paper base material containing cellulose pulp as a main component and a thermoplastic resin layer laminated on at least one surface of the paper base material, wherein the paper base material is a pulp layer. Having a multi-layer structure having 3 or more layers, the mass ratio of the hardwood kraft pulp and the softwood kraft pulp in the outer layer of the paper substrate is 50:50 to 100: 0, and the sizing agent in the inner layer of the paper substrate is contained. The content of the sizing agent in the outer layer of the paper base material is 0.08 to 1.25 mass%, and the content of the sizing agent in the inner layer of the paper base material is 0.04 to 0.30 mass%. The laminated paper is characterized in that the rate is higher than the content rate of the sizing agent in the outer layer.

(2) The laminated paper according to (1) above, wherein the content of the paper strengthening agent in the inner layer of the paper substrate is higher than the content of the paper strengthening agent in the outer layer.

(3) The content ratio of the wet strength agent in the inner layer of the paper substrate is higher than the content ratio of the wet strength agent in the outer layer, (1) or (2) above Laminated paper.

(4) The laminated paper according to any one of (1) to (3), wherein the content of aluminum in the inner layer of the paper substrate is higher than the content of aluminum in the outer layer.

(5) A paper container using the laminated paper according to any one of (1) to (4) above.

(6) The paper container according to (5), which is for liquid.

(7) The method for producing a laminated paper according to any one of (1) to (4) above, which comprises a step of making a paper substrate containing cellulose pulp as a main component and three or more pulp layers. And a laminating step of laminating a thermoplastic resin layer on at least one surface of the paper base material, wherein in the paper making step, the paper base material is made using a multi-layer papermaking machine. And a method of manufacturing laminated paper.

(8) A laminated paper paper base material containing cellulose pulp as a main component, having a multilayer structure having three or more pulp layers, and the mass ratio of hardwood kraft pulp to softwood kraft pulp in the outer layer is 50:50 to 100. 0, the content of the sizing agent in the inner layer is 0.08 to 1.25% by mass, the content of the sizing agent in the outer layer is 0.04 to 0.30% by mass, and the size of the inner layer is A laminated paper / paper base material , wherein the content of the agent is higher than the content of the sizing agent in the outer layer .

(9) The content of at least one additive selected from the group consisting of a paper strengthening agent, a wet paper strengthening agent and aluminum in the inner layer is higher than the content of the additive in the outer layer. The laminated paper paper base material according to (8) above.

(10) In the method of (8) or laminated paper sheet substrate according to (9), wherein the paper making process of laminating a main component cellulose pulp, the pulp layer three or more layers, wherein A method for producing a laminated paper / paper base material, characterized in that, in the paper making step, the paper base material is made using a multi-layer papermaking machine .

  The laminated paper of the present invention, the laminated paper paper base material, and the paper container using the laminated paper are excellent in water resistance on the end face and also in processability during manufacturing.

  Embodiments of the present invention will be described below. However, the embodiments of the present invention are not limited to the following embodiments.

  The laminated paper of the present embodiment has a paper base material containing cellulose pulp as a main component, and a thermoplastic resin layer laminated on at least one surface of the paper base material. Since the thermoplastic resin layers are laminated, water resistance is imparted to the surface of the laminated paper on the thermoplastic resin layer side.

The water resistance at the end face, which is the subject of the present embodiment, is the ability to prevent the phenomenon that liquid permeates from the end face of the laminated paper. The water resistance on the end face is quantified as an end face water absorption index, as described later.
Hereinafter, each material constituting the laminated paper will be described.

[Paper substrate]
As the paper base material, a paper having a multilayer structure having three or more pulp layers (multilayer paper) is used. The basis weight of each pulp layer may be the same or different.
The outer layer of the paper base material is the outermost two pulp layers of the multilayer structure, and the inner layer is the pulp layer sandwiched between them. The inner layer may be a single layer or two or more layers.

(Size agent)
In order to impart water resistance to a paper base material, the paper base material usually contains a sizing agent. As the sizing agent, various known sizing agents for paper such as rosin type, alkyl ketene dimer type, alkenyl succinic anhydride type, maleic anhydride type, styrene acrylic acid type and styrene acrylic type are used.

  The inventors of the present invention use a multi-layered paper having three or more pulp layers to change the content (mass%) of the sizing agent in the outer layer serving as the front and back surfaces and the inner layer serving as the central layer. It was investigated. As a result, when the content of the sizing agent in the inner layer is set to be larger than the content of the sizing agent in the outer layer, the end surface water absorption index tends to be mainly determined by the content of the sizing agent in the inner layer. I found it. Therefore, in order to improve the water resistance of the end surface, it is not necessary to increase the content of the sizing agent in all layers including the inner layer and the outer layer, and it is effective to increase the content of the sizing agent in the inner layer. Found.

  Further, as described later, when producing a laminated paper, a thermoplastic resin layer is laminated on the surface of the paper base material. In order for the thermoplastic resin layer to strongly adhere to the paper base material, it is preferable that the surface of the paper base material has a polar group. Therefore, when a sizing agent is added to the paper base material to impart water resistance, the surface of the paper base material becomes hydrophobic, which causes a problem that the adhesiveness at the time of laminating is reduced.

  However, if the content of the sizing agent in the inner layer is set to be higher than the content of the sizing agent in the outer layer, the content of the sizing agent in the outer layer can be reduced. As a result, they have found that it is possible to reduce the occurrence of the problem that the adhesiveness during lamination is reduced. Further, it has been found that when the content of the sizing agent in the outer layer is small, the papermaking stain derived from the sizing agent attached to the manufacturing apparatus during papermaking is reduced.

  The content of the sizing agent in the inner layer is preferably 0.08 to 1.25 mass%, and the content of the sizing agent in the outer layer is preferably 0.04 to 0.30 mass%.

  As a method of increasing the content of the sizing agent of the inner layer than the content of the sizing agent of the outer layer, the addition rate of the internally added sizing agent of the inner layer may be made larger than the addition rate of the internally added sizing agent of the outer layer, Broke pulp may be blended as a pulp raw material for the inner layer. It is preferable that the broke pulp is self-damaged as long as it is broke generated when paper is made by adding a sizing agent. Since the sizing agent is contained in the broked pulp, the sizing agent content of the inner layer is the same as that of the outer layer, even if the addition rate of the inner sizing agent of the inner layer is not made higher than the addition rate of the inner sizing agent of the outer layer. It is possible to achieve a situation in which the content ratio is higher than that of.

(pulp)
The paper base material is mainly composed of cellulose pulp. Here, the main component means a component accounting for 50% by mass or more of the components constituting the paper base material. Examples of the cellulose pulp include bleached kraft pulp of softwood (NBKP), softwood kraft pulp (NKP), bleached kraft pulp of hardwood (LBKP), hardwood kraft pulp (LKP), and other wood-based pulp, hemp pulp, etc. Examples include non-wood pulp. These pulps may be used alone or in combination of two or more. From the viewpoint of quality and cost, wood pulp such as acacia lumber and eucalyptus lumber, which are LKP, are suitable as the pulp constituting the paper base material.

  The present inventors have further studied the type of pulp constituting the paper base material in order to improve the adhesiveness of the paper base material during the laminating process. As the cellulose pulp constituting the paper base material, hardwood kraft pulp and softwood kraft pulp are usually used. It has been found that, by adding a large amount of hardwood kraft pulp among these, the texture can be improved, the surface smoothness can be increased, and the adhesiveness during laminating can be improved. That is, it is preferable that the hardwood kraft pulp is contained in a larger amount than the softwood kraft pulp as the cellulose pulp constituting the outer layer of the paper base material. Specifically, the mass ratio of the hardwood kraft pulp and the softwood kraft pulp in the outer layer of the paper substrate is 50:50 to 100: 0. The mass ratio of the hardwood kraft pulp and the softwood kraft pulp is more preferably 80:20 to 100: 0. The freeness (csf) of the cellulose pulp before papermaking is preferably 360 to 640 ml, and more preferably 380 to 550 ml.

(Paper strength agent, wet strength agent)
Various internal addition aids are added to the paper base during papermaking. Among them, the paper strengthening agent and the wet strength agent are added for strengthening the paper strength. These internal addition aids are usually polymeric substances, and when present in large amounts on the surface of the paper base material, there is a concern that unevenness in the texture may occur on the surface and the adhesiveness during laminating may deteriorate.

  Specific examples of the paper strengthening agent include polyacrylamide-based polymers, starches, polyacrylamide, urea resins, polyamide / polyamine resins, polyethyleneimine, polyamines, polyvinyl alcohol, polyethylene oxide and the like. Further, specific examples of the wet strength agent include melamine resin, urea resin, polyamide-polyamine-epichlorohydrin resin and the like.

  Therefore, similar to the above sizing agent, it was examined to change the content ratio (mass%) of the paper strength enhancer or the wet paper strength enhancer in the outer layer serving as the front and back surfaces and the inner layer serving as the center layer. As a result, when the content of the paper-strengthening agent or the wet paper-strengthening agent in the inner layer is set to be larger than the content of the paper-strengthening agent or the wet paper-strengthening agent in the outer layer, the adhesiveness during laminating is It has been found that the occurrence of the problem of the decrease of can be reduced. Furthermore, when the content of the paper strength enhancer or the wet paper strength enhancer in the outer layer is small, the problem that the paper strength enhancer or the wet paper strength enhancer adheres to the manufacturing apparatus during papermaking and causes papermaking stains is also reduced. I found that.

  The content of the paper strengthening agent in the inner layer is preferably 0.05 to 1.50% by mass, and the content of the paper strengthening agent in the outer layer is 0.00 to 1.00% by mass. preferable. When the content of the paper strength enhancer in the outer layer exceeds 1.00 mass%, the rigidity may become excessive when molded into a paper container.

  Similarly, the content of the wet strength agent in the inner layer is preferably 0.05 to 0.85% by mass, and the content of the wet strength agent in the outer layer is 0.00 to 0.50% by mass. Is preferred.

(aluminum)
Aluminum is added to the paper base material as an aluminum polyvalent metal compound as a fixing aid for a sizing agent. The aluminum polyvalent metal compound is specifically aluminum sulfate (sulfuric acid band), aluminum chloride, polyaluminum chloride (PAC), sodium aluminate, a basic aluminum compound, or the like.

  The higher the aluminum content, the higher the fixability of the sizing agent. Therefore, it has been found that by increasing the aluminum content (mass%) in the inner layer, the fixability of the sizing agent in the inner layer can be increased, and the transfer of the sizing agent from the inner layer to the outer layer can be suppressed. Here, the content rate of aluminum means the total content rate of the aluminum element calculated | required by converting from the content rate of the aluminum polyvalent metal compound added to a pulp layer. As a result, when the aluminum content of the inner layer is set to be higher than the aluminum content of the outer layer, the content of the sizing agent in the inner layer can be made larger than the content of the sizing agent in the outer layer. It has been found that it is possible to reduce the occurrence of the problem that the adhesiveness during processing is reduced.

The aluminum content of the inner layer is preferably 0.05 to 0.20% by mass, and the aluminum content of the outer layer is preferably 0.02 to 0.10% by mass.
Note that, for example, when aluminum sulfate (molecular weight 342) is used as the aluminum polyvalent metal compound, the content rate of aluminum can be converted from the following formula.
Aluminum content (mass%) = {aluminum sulfate content (mass%) / 342} × 54

  As described above, the content rate of at least one additive selected from the group consisting of a sizing agent, a paper strength agent, a wet paper strength agent, and aluminum in the inner layer is higher than the content rate of the additive in the outer layer. Preferably. A multi-layered paper base material having different content of additives in the inner layer and the outer layer can be produced using a multi-layer paper machine described later.

  Various internal addition aids other than those mentioned above are appropriately selected and added to the paper base material, if necessary. The filler may be any filler commonly used in the papermaking field, and is not particularly limited. Other auxiliary additives include retention aids, freeness improvers, various starches such as cationized starches, bulking agents, coloring dyes, color pigments, optical brighteners, pH adjusters, pitch control agents, Preservatives, slime control agents and the like can be mentioned.

The basis weight of the paper substrate is not particularly limited, but is preferably 150 to 500 g / m ² .

(Papermaking)
The paper base material is manufactured by a papermaking process in which three or more pulp layers are laminated. Multilayer paper with a structure in which a large number of pulp layers are laminated is used as a manufacturing technology for paperboard and the like, and generally, a multi-layer paper machine such as a cylinder paper machine and a fourdrinier paper machine is used. Can be manufactured. The pH during papermaking may be any of an acidic region (acidic papermaking), a pseudo-neutral region (pseudo-neutral papermaking), a neutral region (neutral papermaking), and an alkaline region (alkaline papermaking).

[Thermoplastic resin layer]
The thermoplastic resin layer is laminated on at least one surface of the paper base material. As the thermoplastic resin, either a crystalline resin or a non-crystalline resin can be used depending on the application. As the thermoplastic resin, polyethylene (LDPE, MDPE, HDPE, LLDPE, etc.), polypropylene, polyolefin resin such as polymethylpentene, polyester resin such as PET and PBT, polyamide resin, polylactic acid (PLA), PHB, PBS, PBAT. , PCL, PHBH, and other biodegradable resins, polystyrene, polyvinyl chloride, acrylonitrile butadiene styrene (ABS) resin, acrylic resin, modified polyphenylene ether (PPE), and the like.

  The thermoplastic resin layer may be formed as a single layer of a single resin, may be formed as a single layer by mixing a plurality of resins, or may be formed as a plurality of layers of the same kind or different kinds of resins. You may.

The thickness of the thermoplastic resin layer is not particularly limited, but is usually about 10 to 50 μm. Formation of the thermoplastic resin layer is not particularly limited, but is preferably ^{5~50g / m 2, 10~30g / m} 2 is more preferable. If the amount of the thermoplastic resin layer formed is too small, the liquid or the like filled in the container may penetrate into the paper base material, and if it is too large, the suitability for molding into the container may be reduced.

[Laminated paper]
The laminated paper includes a paper base material and a thermoplastic resin layer laminated on at least one surface of the paper base material. The thermoplastic resin layer may be laminated only on one side of the paper base material, or may be laminated on both sides of the paper base material. Laminated paper is manufactured by a laminating step in which a thermoplastic resin layer is laminated on at least one surface of a paper base material.

  As a method for laminating the thermoplastic resin layer on the paper substrate, various known methods such as an extrusion laminating method, a dry laminating method, a wet laminating method and a thermal laminating method can be appropriately used. When the thermoplastic resin layer is a single layer, the extrusion laminating method is preferable.

  During lamination, the thermoplastic resin layer or the paper base material layer may be subjected to an oxidation treatment such as corona treatment or ozone treatment, if necessary. By performing these treatments, polar groups are generated on the surface of the thermoplastic resin layer or the paper base material layer, and the adhesiveness can be improved. These treatments may be performed on either or both of the thermoplastic resin layer and the paper base layer, may be performed once, or may be performed multiple times.

The laminated paper composed of the paper base material and the thermoplastic resin layer preferably has a basis weight of 150 to 500 g / m ² , and more preferably 200 to 400 g / m ² . If the basis weight is too small, the rigidity may be insufficient when molded into a paper container, and if the basis weight is too large, a large amount of raw materials and chemicals may be used, resulting in high cost.

The laminated paper including the paper base material and the thermoplastic resin layer preferably has a thickness of 200 to 750 μm. The laminated paper comprising a paper base material and a thermoplastic resin layer preferably has a density of 0.60 to 1.20 g / cm ³ .

  The laminated paper is basically a laminated paper having a two-layer structure or a three-layer structure composed of a paper base material and a thermoplastic resin layer. Can be formed. For example, a thermoplastic resin layer of the same or different type may be further provided on a laminated paper consisting of a paper base material and a thermoplastic resin layer, or a layer other than the thermoplastic resin may be provided between the thermoplastic resin layer and the thermoplastic resin layer. It is also possible to provide a layer other than the thermoplastic resin layer between the paper base material and the thermoplastic resin layer. Layers other than the thermoplastic resin layer include a water-soluble polymer (PVA, etc.), a coating layer containing a pigment and an adhesive as a main component, an aluminum foil (Al foil), a printing layer, and the like.

[Paper container]
Various paper containers can be manufactured using the laminated paper of this embodiment. As a method of manufacturing the paper container, a known method can be appropriately selected and used.

[Liquid paper container]
Various liquid paper containers can be manufactured using the laminated paper of this embodiment. As a method of manufacturing the liquid paper container, a known method can be appropriately selected and used.

  Laminated paper of the present embodiment, the occurrence of the problem that the adhesiveness is reduced during laminating process is reduced, the problem that the internal additive aids and the like to cause paper stains during papermaking is also reduced, and processability during manufacturing is reduced. Are better. Further, the paper container using the laminated paper is excellent in water resistance at the end face when used as a liquid container. The laminated paper of the present embodiment may be further subjected to skive hemming for bending the end faces to improve water resistance.

  Laminated paper provided with a thermoplastic resin layer such as PE on both the outside and the inside of a paper substrate is heat-treated at a temperature higher than the boiling point of water and the melting point of the thermoplastic resin to form the thermoplastic resin layer on the paper base. By foaming with the water content of the material, a paper container having a heat insulating property can be obtained. The heat-insulating paper container can be used as, for example, a heat-insulating paper container whose contents are a heated liquid / solid or a cooled liquid / solid.

  The laminated paper of the present embodiment is a liquid paper container such as a milk carton, a paper cup, a foaming cup, an ice cup, a heat insulating cup, a coffee container, an aseptic container, a paper container such as a packaging container, and a variety of packaging materials, heat insulating materials, and the like. It can be used for various purposes.

  Hereinafter, the effects of the present invention will be described in detail with reference to Examples. Unless otherwise specified, "parts" and "%" in Examples and Comparative Examples represent "parts by mass" and "% by mass", respectively.

Materials and manufacturing conditions used in Examples and Comparative Examples are as follows.
(1) Pulp LBKP: Acacia pulp, eucalyptus pulp NBKP: Douglas fir, radiata pine, cedar (2) Thermoplastic resin PE: LDPE manufactured by Nippon Polyethylene Co., product number LC522
PLA: PLA manufactured by Nature Works, product number Ingeo PLA 2002D
(3) Internal addition agent Cationized starch: P-3T manufactured by Pillar Starch Co., Ltd.
Sizing agent: AD1612 manufactured by Seikou PMC
Paper Strengthening Agent: Arakawa Chemical Industries PS-NH20B
Wet paper strength enhancer: WS4024 manufactured by Starlight PMC
Sulfuric acid band: Liquid sulfuric acid band manufactured by Asahi Chemical Industry Co., Ltd.

  Below, the measuring method implemented about the paper base material and laminated paper is shown. Unless otherwise specified, the measurement was performed in an environment described in JIS P8111: 1998 at a temperature of 23 ° C. ± 1 ° C. and a humidity of 50% ± 2%.

(1) Basis weight: Measured according to JIS P8124: 2011.
(2) Thickness: According to JIS P8118: 2014, the thickness when a pressure of 100 kPa ± 10 kPa was applied to the circular region (200 mm ² ) of the test piece was measured.
(3) Density: Measured according to JIS P8118: 2014. The thickness was measured when a pressure of 100 kPa ± 10 kPa was applied to the circular region (200 mm ² ) of the test piece.

(4) Re-deagglomeration pulp freeness The obtained paper base material was disintegrated according to the method of JIS P 8220: 2012, and the obtained pulp slurry was measured for the disaggregation freeness by the method according to JIS P 8121: 2012. As a measuring machine, a Canadian freeness tester manufactured by Kumagai Riki Kogyo was used.

(5) Fiber length / coarseness The pulp slurry obtained by disaggregation is diluted to 0.01% by mass or more and 0.02% by mass or less to prepare a diluting solution. The projected length of the fiber component contained in 10 ml of this diluted solution was measured using a fiber length measuring device (Mayso Automation Co., Ltd., Kajaani Fiber Lab Ver4.0), and the length-weighted average value of the disaggregated fibers was calculated. The courseness (fiber roughness) was also measured using a fiber length measuring device (Metso Automation Co., Kajaani Fiber Lab Ver4.0).

[Example 1]
(Paper substrate)
As a pulp raw material, 100 parts of LBKP was beaten using a double disc refiner to obtain a pulp slurry. To 100 parts of the obtained pulp slurry (solid content conversion), 0.45 parts (solid content conversion) of cationized starch as an internal paper strength enhancer for each layer and polyacrylamide dry paper strength enhancer for the outer layer 0.2 part (solid content conversion), 0.3 part (solid content conversion) in the inner layer, 0.05 parts (solid content conversion) in the outer layer, and an alkyl ketene dimer sizing agent as an internally added sizing agent in the inner layer. 10 parts (as solid content), 0.2 parts (as solid content) of a polyamide / amine epichlorohydrin-based wet strength agent as a wet strength agent in the inner layer, and 0.1 part of sulfuric acid band in the outer layer ( A solid material was added), and 0.3 part (as solid content) was added to the inner layer to adjust the stock. Using this stock, a five-layer fourdrinier paper machine was used to make paper. During the papermaking process, 1.0 g / m ² of starch was applied between the layers by interlayer spray, and 2.3 g / m ² of oxidized starch was applied by a size press to obtain a paper base material having a basis weight of 420 g / m ² . .. Here, out of all five pulp layers, the outer layers are the first layer and the fifth layer, and the inner layers are the second layer, the third layer, and the fourth layer.

(Thermoplastic resin layer)
LDPE (LC522) as a thermoplastic resin was laminated on both the outer and inner surfaces of the obtained paper substrate. The lamination of the thermoplastic resin layer was performed by an extrusion laminating method at a laminating temperature of 330 ° C. and a laminating speed of 200 m / min. The thickness and mass of the thermoplastic resin layer were as described in Table 1, and laminated paper was obtained.

(Paper container)
After offset printing was performed on the surface of the obtained laminated paper, ruled lines were provided at necessary positions and punched into a predetermined shape to obtain a blank material. Next, a part of the resin material of the blank material was melted by frame sealing, and the body portion was bonded to obtain a cylindrical sleeve. Subsequently, this tubular sleeve was supplied to a liquid filling machine to form a bottom portion on the filling machine, and then the top portion was sealed to obtain a gable top type paper container.

[Example 2]
As a pulp raw material, 100 parts of LBKP was beaten using a double disc refiner to obtain a pulp slurry. To 100 parts of the obtained pulp slurry (solid content conversion), 0.45 parts (solid content conversion) of cationized starch as an internal paper strength enhancer for each layer and polyacrylamide dry paper strength enhancer for the outer layer 0.2 part (as solid content), 0.3 part (as solid content) in the inner layer, 0.15 parts (as solid content) in the outer layer of alkyl ketene dimer sizing agent as an internally added sizing agent, and 0. 30 parts (solid content conversion), 0.1 parts (solid content conversion) of the polyamide / amine epichlorohydrin-based wet strength agent as a wet paper strength enhancer in the outer layer and 0.2 parts (solid content conversion) in the inner layer. ), And a sulfuric acid band was added to the outer layer in an amount of 0.3 part (solid content conversion) and the inner layer in an amount of 0.5 part (solid content conversion) to prepare a paper stock. Using this stock, a five-layer fourdrinier paper machine was used to make paper. During the papermaking process, 1.0 g / m ² of starch was applied between the layers by interlayer spray, and 2.3 g / m ² of oxidized starch was applied by a size press to obtain a paper base material having a basis weight of 420 g / m ² . .. A gable-top type paper container was obtained in the same manner as in Example 1 using the obtained paper base material.

[Example 3]
As a pulp raw material, 100 parts of LBKP was beaten using a double disc refiner to obtain a pulp slurry. To 100 parts of the obtained pulp slurry (solid content conversion), 0.45 parts (solid content conversion) of cationized starch as an internal paper strength enhancer for each layer and polyacrylamide dry paper strength enhancer for the outer layer 0.2 part (as solid content), 0.3 part (as solid content) in the inner layer, 0.3 part (as solid content) of the alkyl ketene dimer sizing agent as an internally added sizing agent in the outer layer, and 0. 8 parts (solid content conversion), 0.07 part (solid content conversion) of the polyamide / amine epichlorohydrin-based wet paper strength additive as a wet paper strength enhancer in the outer layer, and 0.1 part (solid content conversion) in the inner layer. ), 0.2 part (as solid content) of the sulfuric acid band was added to the outer layer, and 0.5 part (as solid content) was added to the inner layer to adjust the stock. Using this stock, a five-layer fourdrinier paper machine was used to make paper. During the papermaking process, 1.0 g / m ² of starch was applied between the layers by interlayer spray, and 2.3 g / m ² of oxidized starch was applied by a size press to obtain a paper base material having a basis weight of 320 g / m ² . .. A gable-top type paper container was obtained in the same manner as in Example 1 using the obtained paper base material.

[Example 4]
100 parts of LBKP as the raw material for the outer layer and 70 parts of LBKP and 30 parts as the raw material for the inner layer were beaten using a double disc refiner to obtain a pulp slurry. To 100 parts of the obtained pulp slurry (solid content conversion), 0.45 parts (solid content conversion) of cationized starch as an internal paper strength enhancer for each layer and polyacrylamide dry paper strength enhancer for the outer layer 0.2 part (as solid content), 0.3 part (as solid content) in the inner layer, 0.15 parts (as solid content) in the outer layer of alkyl ketene dimer sizing agent as an internally added sizing agent, and 0. 15 parts (as solid content), 0.1 parts (as solid content) of the polyamide / amine epichlorohydrin-based wet strength agent as a wet strength agent in the outer layer, 0.2 parts as solid content (as solid content) ), And a sulfuric acid band was added to the outer layer in an amount of 0.3 part (solid content conversion) and the inner layer in an amount of 0.5 part (solid content conversion) to prepare a paper stock. Using this stock, a five-layer fourdrinier paper machine was used to make paper. During the papermaking process, 1.0 g / m ² of starch was applied between the layers by interlayer spray, and 2.3 g / m ² of oxidized starch was applied by a size press to obtain a paper base material having a basis weight of 320 g / m ² . .. A gable-top type paper container was obtained in the same manner as in Example 1 using the obtained paper base material.

[Example 5]
As a pulp raw material, 100 parts of LBKP was beaten using a double disc refiner to obtain a pulp slurry. To 100 parts of the obtained pulp slurry (solid content conversion), 0.45 parts (solid content conversion) of cationized starch as an internal paper strength enhancer for each layer and polyacrylamide dry paper strength enhancer for the outer layer 0.2 part (solid content conversion), 0.3 part (solid content conversion) in the inner layer, 0.1 part (solid content conversion) of the alkyl ketene dimer type sizing agent as an internally added sizing agent in the outer layer, and 1. 5 parts (solid content conversion), 0.2 parts (solid content conversion) of the polyamide / amine epichlorohydrin-based wet strength agent as a wet paper strength enhancer in the outer layer, 0.4 part (solid content conversion) in the inner layer ), 0.2 part (as solid content) of the sulfuric acid band was added to the outer layer, and 0.5 part (as solid content) was added to the inner layer to adjust the stock. Using this stock, a five-layer fourdrinier paper machine was used to make paper. During the papermaking process, 1.0 g / m ² of starch was applied between the layers by interlayer spray, and 2.3 g / m ² of oxidized starch was applied by a size press to obtain a paper base material having a basis weight of 250 g / m ² . .. A gable-top type paper container was obtained in the same manner as in Example 1 using the obtained paper base material.

[Example 6]
As a pulp raw material, 90 parts of LBKP and 10 parts of NBKP were beaten using a double disc refiner to obtain a pulp slurry. To 100 parts of the obtained pulp slurry (solid content conversion), 0.45 parts (solid content conversion) of cationized starch as an internal paper strength enhancer for each layer and polyacrylamide dry paper strength enhancer for the outer layer 0.05 part (as solid content), 0.10 part (as solid content) for the inner layer, 0.2 parts (as solid content) for the alkyl ketene dimer sizing agent as an internally added sizing agent for the outer layer, and 0. 3 parts (converted to solid content), 0.6 parts (converted to solid content) of polyamide / amine epichlorohydrin-based wet strength agent as a wet strength agent for the outer layer, and 0.8 parts (converted to solid content) to the inner layer ), 0.2 part (as solid content) of the sulfuric acid band was added to the outer layer, and 0.5 part (as solid content) was added to the inner layer to adjust the stock. Using this stock, a five-layer fourdrinier paper machine was used to make paper. During the papermaking process, 1.0 g / m ² of starch was applied between the layers by interlayer spray, and 2.3 g / m ² of oxidized starch was applied by a size press to obtain a paper base material having a basis weight of 250 g / m ² . .. A gable-top type paper container was obtained in the same manner as in Example 1 using the obtained paper base material.

[Example 7]
90 parts of LBKP and 10 parts of NBKP as the raw material for the outer layer and 60 parts of LBKP, 10 parts of the NBKP and 30 parts of the broke as the raw material of the inner layer were beaten using a double disc refiner to obtain a pulp slurry. To 100 parts of the obtained pulp slurry (solid content conversion), 0.45 parts (solid content conversion) of cationized starch as an internal paper strength enhancer for each layer and polyacrylamide dry paper strength enhancer for the outer layer 0.05 part (as solid content), 0.10 part (as solid content) for the inner layer, 0.2 parts (as solid content) for the alkyl ketene dimer sizing agent as an internally added sizing agent for the outer layer, and 0. 2 parts (as solid content), 0.6 parts (as solid content) of the polyamide / amine epichlorohydrin-based wet strength agent as a wet strength agent in the outer layer, 0.8 parts as solid content (as solid content) ), 0.2 part (as solid content) of the sulfuric acid band was added to the outer layer, and 0.5 part (as solid content) was added to the inner layer to adjust the stock. Using this stock, a five-layer fourdrinier paper machine was used to make paper. During the papermaking process, 1.0 g / m ² of starch was applied between the layers by interlayer spray, and 2.3 g / m ² of oxidized starch was applied by a size press to obtain a paper base material having a basis weight of 250 g / m ² . .. A gable-top type paper container was obtained in the same manner as in Example 1 using the obtained paper base material.

[Example 8]
As a pulp raw material, 90 parts of LBKP and 10 parts of NBKP were beaten using a double disc refiner to obtain a pulp slurry. To 100 parts of the obtained pulp slurry (solid content conversion), 0.45 parts (solid content conversion) of cationized starch as an internal paper strength enhancer for each layer and polyacrylamide dry paper strength enhancer for the outer layer 0.1 part (as solid content), 0.2 part (as solid content) for the inner layer, 0.2 part (as solid content) for the alkyl ketene dimer type sizing agent as an internally added sizing agent for the outer layer, and 0. 3 parts (as solid content conversion), 0.1 parts (as solid content conversion) and 1.0 part (as solid content conversion) of polyamide / amine epichlorohydrin-based wet strength composition as a wet strength agent for the outer layer ), 0.2 part (as solid content) of the sulfuric acid band was added to the outer layer, and 0.5 part (as solid content) was added to the inner layer to adjust the stock. Using this stock, a five-layer fourdrinier paper machine was used to make paper. During the papermaking process, 1.0 g / m ² of starch was applied between the layers by interlayer spray, and 2.3 g / m ² of oxidized starch was applied by a size press to obtain a paper base material having a basis weight of 200 g / m ² . .. A gable-top type paper container was obtained in the same manner as in Example 1 using the obtained paper base material.

[Example 9]
90 parts of LBKP and 10 parts of NBKP as raw materials for the outer layer, and 80 parts of LBKP and 20 parts of NBKP as the raw materials for the inner layer were beaten using a double disc refiner to obtain a pulp slurry. To 100 parts of the obtained pulp slurry (solid content conversion), 0.45 parts (solid content conversion) of cationized starch as an internal paper strength enhancer for each layer and polyacrylamide dry paper strength enhancer for the outer layer 0.1 part (solid content conversion), 0.3 part (solid content conversion) in the inner layer, 0.2 parts (solid content conversion) in the outer layer, and alkyl ketene dimer sizing agent as an internally added sizing agent in the inner layer. 3 parts (as solid content), 0.2 parts (as solid content) of a polyamide / amine epichlorohydrin-based wet strength agent as a wet strength agent in the inner layer, and 0.2 parts of sulfuric acid band in the outer layer ( Paper content was adjusted by adding 0.8 parts (as solid content) to the inner layer. Using this stock, a five-layer fourdrinier paper machine was used to make paper. During the papermaking process, 1.0 g / m ² of starch was applied between the layers by interlayer spray, and 2.3 g / m ² of oxidized starch was applied by a size press to obtain a paper base material having a basis weight of 200 g / m ² . ..
PLA (PLA manufactured by Nature Works, product number Ingeo PLA 2002D) was laminated as a thermoplastic resin on both the outer and inner surfaces of the obtained paper substrate. The lamination of the thermoplastic resin layer was performed by an extrusion laminating method under the conditions of a laminating temperature of 260 ° C. and a laminating speed of 200 m / min. The thickness and mass of the thermoplastic resin layer were as described in Table 1, and laminated paper was obtained. Using the obtained laminated paper, a gable-top paper container was obtained in the same manner as in Example 1.

[Example 10]
80 parts of LBKP and 20 parts of NBKP as raw materials for the outer layer, and 90 parts of LBKP and 10 parts of NBKP as the raw materials for the inner layer were beaten using a double disc refiner to obtain a pulp slurry. To 100 parts of the obtained pulp slurry (solid content conversion), 0.45 parts (solid content conversion) of cationized starch as an internal paper strength enhancer for each layer and polyacrylamide dry paper strength enhancer for the outer layer 0.4 part (as solid content), 0.5 part (as solid content) in the inner layer, 0.2 part (as solid content) in the outer layer of alkyl ketene dimer sizing agent as an internally added sizing agent, and 0. 3 parts (solid content conversion), 0.1 parts (solid content conversion) of the polyamide / amine epichlorohydrin-based wet strength agent as a wet strength agent in the outer layer and 0.2 parts (solid content conversion) in the inner layer. ), And a sulfuric acid band was added to the outer layer in an amount of 0.3 part (solid content conversion) and to the inner layer in an amount of 0.6 part (solid content conversion) to prepare a paper stock. Using this stock, a five-layer fourdrinier paper machine was used to make paper. During the papermaking process, 1.0 g / m ² of starch was applied between the layers by interlayer spraying, and 2.3 g / m ² of oxidized starch was applied by a size press to obtain a paper base material having a basis weight of 150 g / m ² . .. A gable-top type paper container was obtained in the same manner as in Example 9 using the obtained paper base material.

[Example 11]
80 parts of LBKP and 20 parts of NBKP as raw materials for the outer layer, and 60 parts of LBKP, 10 parts of NBKP and 30 parts of the broke as raw materials for the inner layer were beaten using a double disc refiner to obtain a pulp slurry. To 100 parts of the obtained pulp slurry (solid content conversion), 0.45 parts (solid content conversion) of cationized starch as an internal paper strength enhancer for each layer and polyacrylamide dry paper strength enhancer for the outer layer 0.4 part (as solid content), 0.5 part (as solid content) in the inner layer, 0.2 part (as solid content) in the outer layer of alkyl ketene dimer sizing agent as an internally added sizing agent, and 0. 25 parts (converted to solid content), 0.1 parts (converted to solid content) of polyamide / amine epichlorohydrin-based wet strength agent as a wet strength agent for the outer layer and 0.2 parts (converted to solid content) for the inner layer. ), And a sulfuric acid band was added to the outer layer in an amount of 0.3 part (solid content conversion) and to the inner layer in an amount of 0.6 part (solid content conversion) to prepare a paper stock. Using this stock, a five-layer fourdrinier paper machine was used to make paper. During the papermaking process, 1.0 g / m ² of starch was applied between the layers by interlayer spraying, and 2.3 g / m ² of oxidized starch was applied by a size press to obtain a paper base material having a basis weight of 150 g / m ² . .. A gable-top type paper container was obtained in the same manner as in Example 9 using the obtained paper base material.

[Example 12]
As a pulp raw material, 80 parts of LBKP and 20 parts of NBKP were beaten using a double disc refiner to obtain a pulp slurry. To 100 parts of the obtained pulp slurry (solid content conversion), 0.45 parts (solid content conversion) of cationized starch as an internal paper strength enhancer for each layer and polyacrylamide dry paper strength enhancer for the outer layer 0.8 parts (solid content conversion), 1.0 part (solid content conversion) in the middle layer, 0.2 parts (solid content conversion) of the alkyl ketene dimer type sizing agent as an internally added sizing agent in the outer layer, and 0. 3 parts (solid content conversion), 0.1 parts (solid content) of polyamide / amine epichlorohydrin-based wet paper strength additive as a wet paper strength enhancer in the outer layer, and 0.2 parts (solid content conversion) in the middle layer. ), And 0.5 part (as solid content) of the sulfuric acid band was added to the outer layer and 1.0 part (as solid content) was added to the middle layer to adjust the stock. Using this stock, a five-layer fourdrinier paper machine was used to make paper. During the papermaking process, 1.0 g / m ² of starch was applied between the layers by interlayer spraying, and 2.3 g / m ² of oxidized starch was applied by a size press to obtain a paper base material having a basis weight of 150 g / m ² . .. A gable-top type paper container was obtained in the same manner as in Example 9 using the obtained paper base material.

[Comparative Example 1]
As a pulp raw material, 100 parts of LBKP was beaten using a double disc refiner to obtain a pulp slurry. To 100 parts of the obtained pulp slurry (solid content conversion), 0.45 parts (solid content conversion) of cationized starch as an internal paper strength enhancer in each layer, and polyacrylamide dry paper strength enhancer in each layer. 0.2 parts (as solid content), 0.1 parts of alkyl ketene dimer type sizing agent as an internally added sizing agent (as solid content), 0.05 parts as inner layer (as solid content), wet paper strengthening As an agent, a polyamide / amine epichlorohydrin-based wet paper strength enhancer for each layer was 0.1 part (solid content), a sulfuric acid band was 0.3 part for the outer layer (solid content), and 0.1 part for the inner layer ( The solid content was added to adjust the stock. Using this stock, a five-layer fourdrinier paper machine was used to make paper. During the papermaking process, 1.0 g / m ² of starch was applied between the layers by interlayer spraying, and 2.3 g / m ² of oxidized starch was applied by a size press to obtain a paper base material having a basis weight of 620 g / m ² . .. A gable-top type paper container was obtained in the same manner as in Example 1 using the obtained paper base material.

[Comparative example 2]
As a pulp raw material, 100 parts of LBKP was beaten using a double disc refiner to obtain a pulp slurry. To 100 parts of the obtained pulp slurry (solid content conversion), 0.45 parts (solid content conversion) of cationized starch as an internal paper strength enhancer in each layer, and polyacrylamide dry paper strength enhancer in each layer. 0.2 parts (as solid content), 0.3 parts (as solid content) of an alkyl ketene dimer sizing agent as an internally added sizing agent as outer layer, 0.1 parts as solid content (as solid content), wet paper strength As an agent, a polyamide / amine epichlorohydrin-based wet paper strength enhancer for each layer was 0.1 part (solid content), a sulfuric acid band was 0.5 part for the outer layer (solid content), and 0.3 part for the inner layer ( The solid content was added to adjust the stock. Using this stock, a five-layer fourdrinier paper machine was used to make paper. During the papermaking process, 1.0 g / m ² of starch was applied between the layers by interlayer spraying, and 2.3 g / m ² of oxidized starch was applied by a size press to obtain a paper base material having a basis weight of 620 g / m ² . .. A gable-top type paper container was obtained in the same manner as in Example 1 using the obtained paper base material.

[Comparative Example 3]
As a pulp raw material, 100 parts of LBKP was beaten using a double disc refiner to obtain a pulp slurry. To 100 parts of the obtained pulp slurry (solid content conversion), 0.45 parts (solid content conversion) of cationized starch as an internal paper strength enhancer in each layer, and polyacrylamide dry paper strength enhancer in each layer. 0.5 parts (solid content conversion), 0.8 parts (solid content conversion) of an alkyl ketene dimer sizing agent as an internally added sizing agent for the outer layer, 0.3 parts (solid content conversion) for the inner layer, wet paper strength enhancement As an agent, a polyamide / amine epichlorohydrin-based wet paper strength enhancer was used in an outer layer of 0.1 part (solid content conversion), an inner layer of 0.07 part (solid content conversion), and a sulfuric acid band in each layer of 0.2 part ( The solid content was added to adjust the stock. Using this stock, a five-layer fourdrinier paper machine was used to make paper. During the papermaking process, 1.0 g / m ² of starch was applied between the layers by interlayer spray, and 2.3 g / m ² of oxidized starch was applied by a size press to obtain a paper base material having a basis weight of 280 g / m ² . .. A gable-top type paper container was obtained in the same manner as in Example 1 using the obtained paper base material.

[Comparative Example 4]
As a pulp raw material, 100 parts of NBKP was beaten using a double disc refiner to obtain a pulp slurry. To 100 parts of the obtained pulp slurry (solid content conversion), 0.45 parts (solid content conversion) of cationized starch as an internal paper strength enhancer in each layer, and polyacrylamide dry paper strength enhancer in each layer. 0.8 parts (as solid content), 1.5 parts of alkyl ketene dimer sizing agent as internal addition size (as solid content) in the outer layer, 0.1 parts as solid content (as solid content), wet paper strengthening As an agent, a polyamide / amine epichlorohydrin-based wet paper strength enhancer was used in an outer layer of 0.4 part (solid content), an inner layer of 0.2 part (solid content), and a sulfuric acid band of 0.5 part in each layer ( The solid content was added to adjust the stock. Using this stock, a five-layer fourdrinier paper machine was used to make paper. During the papermaking process, 1.0 g / m ² of starch was applied between the layers by interlayer spray, and 2.3 g / m ² of oxidized starch was applied by a size press to obtain a paper base material having a basis weight of 250 g / m ² . .. A gable-top type paper container was obtained in the same manner as in Example 1 using the obtained paper base material.

[Comparative Example 5]
As a pulp raw material, 10 parts of LBKP and 90 parts of NBKP were beaten using a double disc refiner to obtain a pulp slurry. To 100 parts of the obtained pulp slurry (solid content conversion), 0.45 parts (solid content conversion) of cationized starch as an internal paper strength enhancer for each layer and polyacrylamide dry paper strength enhancer for the outer layer 0.1 part (as solid content), 0.2 part (as solid content) of an alkyl ketene dimer sizing agent as an internally added sizing agent in the outer layer, polyamide / amine epichlorohydrin-based wet paper as a wet paper strength enhancer The paper stock was adjusted by adding 0.8 parts (solid content) to the outer layer, 0.6 parts (solid content) to the inner layer, and 0.5 parts (solid content) to the sulfuric acid band for each layer. .. Using this stock, a five-layer fourdrinier paper machine was used to make paper. During the papermaking process, 1.0 g / m ² of starch was applied between the layers by interlayer spray, and 2.3 g / m ² of oxidized starch was applied by a size press to obtain a paper base material having a basis weight of 250 g / m ² . .. A gable-top type paper container was obtained in the same manner as in Example 1 using the obtained paper base material.

[Comparative Example 6]
As a pulp raw material, 10 parts of LBKP and 90 parts of NBKP were beaten using a double disc refiner to obtain a pulp slurry. To 100 parts of the obtained pulp slurry (solid content conversion), 0.45 parts (solid content conversion) of cationized starch as an internal paper strength enhancer for each layer and polyacrylamide dry paper strength enhancer for the outer layer 0.2 parts (solid content), 0.1 part (solid content) for the inner layer, 0.2 parts (solid content) for each layer of alkyl ketene dimer sizing agent as an internally added sizing agent, strengthening wet paper strength As an agent, a polyamide / amine epichlorohydrin-based wet paper strength enhancer was added to the outer layer at 1.0 part (solid content conversion), the inner layer at 0.1 part (solid content conversion), and the sulfuric acid band at each layer at 0.8 part ( The solid content was added to adjust the stock. Using this stock, a five-layer fourdrinier paper machine was used to make paper. During the papermaking process, 1.0 g / m ² of starch was applied between the layers by interlayer spray, and 2.3 g / m ² of oxidized starch was applied by a size press to obtain a paper base material having a basis weight of 200 g / m ² . .. A gable-top type paper container was obtained in the same manner as in Example 1 using the obtained paper base material.

[Comparative Example 7]
10 parts of LBKP and 90 parts of NBKP as pulp materials for the outer layer and 20 parts of LBKP and 80 parts of NBKP as pulp materials for the inner layer were beaten using a double disc refiner to obtain a pulp slurry. To 100 parts of the obtained pulp slurry (solid content conversion), 0.45 parts (solid content conversion) of cationized starch as an internal paper strength enhancer for each layer and polyacrylamide dry paper strength enhancer for the outer layer 0.3 part (solid content conversion), 0.1 part (solid content conversion) in the inner layer, alkyl ketene dimer sizing agent as the internally added sizing agent 1.0 part (solid content conversion) in the outer layer, wet paper strengthening As an agent, a polyamide / amine epichlorohydrin-based wet paper strength enhancer for each layer was 0.3 part (solid content), a sulfuric acid band was 0.8 part for the outer layer (solid content), and 0.2 part for the inner layer ( The solid content was added to adjust the stock. Using this stock, a five-layer fourdrinier paper machine was used to make paper. During the papermaking process, 1.0 g / m ² of starch was applied between the layers by interlayer spray, and 2.3 g / m ² of oxidized starch was applied by a size press to obtain a paper base material having a basis weight of 200 g / m ² . .. A gable-top type paper container was obtained in the same manner as in Example 9 using the obtained paper base material.

[Comparative Example 8]
20 parts of LBKP and 80 parts of NBKP as pulp materials for the outer layer, and 10 parts of LBKP and 90 parts of NBKP as pulp materials for the inner layer were beaten using a double disc refiner to obtain a pulp slurry. To 100 parts of the obtained pulp slurry (solid content conversion), 0.45 parts (solid content conversion) of cationized starch as an internal paper strength enhancer for each layer and polyacrylamide dry paper strength enhancer for the outer layer 0.5 parts (as solid content), 0.4 parts (as solid content) for the inner layer, 0.2 parts (as solid content) for each layer of alkyl ketene dimer sizing agent as an internally added sizing agent, wet paper strength enhancement As an agent, a polyamide / amine epichlorohydrin-based wet paper strength enhancer was added to each layer in an amount of 0.3 part (solid content), a sulfuric acid band was used in an outer layer of 0.6 part (solid content), and an inner layer of 0.3 part ( The solid content was added to adjust the stock. Using this stock, a five-layer fourdrinier paper machine was used to make paper. During the papermaking process, 1.0 g / m ² of starch was applied between the layers by interlayer spray, and 2.3 g / m ² of oxidized starch was applied by a size press to obtain a paper base material having a basis weight of 140 g / m ² . .. A gable-top type paper container was obtained in the same manner as in Example 9 using the obtained paper base material.

[Comparative Example 9]
As a pulp raw material, 20 parts of LBKP and 80 parts of NBKP were beaten using a double disc refiner to obtain a pulp slurry. To 100 parts of the obtained pulp slurry (solid content conversion), 0.45 parts (solid content conversion) of cationized starch as an internal paper strength enhancer for each layer and polyacrylamide dry paper strength enhancer for the outer layer 1.0 part (solid content conversion), 0.8 part (solid content conversion) in the inner layer, alkyl ketene dimer sizing agent as an internally added sizing agent in each layer 0.5 part (solid content conversion), wet paper strengthening As an agent, a polyamide / amine epichlorohydrin-based wet paper strength enhancer for each layer is 0.5 part (solid content conversion), a sulfuric acid band is 1.0 part for the outer layer (solid content conversion), and 0.5 part for the inner layer ( The solid content was added to adjust the stock. Using this stock, a five-layer fourdrinier paper machine was used to make paper. During the papermaking process, 1.0 g / m ² of starch was applied between the layers by interlayer spray, and 2.3 g / m ² of oxidized starch was applied by a size press to obtain a paper base material having a basis weight of 140 g / m ² . .. A gable-top type paper container was obtained in the same manner as in Example 9 using the obtained paper base material.

  The following performance evaluation was performed on the paper base material and the laminated paper obtained as described above. The performance evaluation was judged to be acceptable when ⊚, ◯ or Δ. The evaluation results are shown in Tables 1 and 2. In the table, the numerical value for the internally added chemical agent represents the content (parts by mass) of each pulp layer in the paper base material after papermaking with respect to 100 parts by mass of the total pulp. The content (in terms of solid content) of each internal additive contained in the paper base material was determined by mass spectrometry using a pyrolysis GC / MS analyzer (Agilent Technology Co., Ltd.).

(Laminated adhesiveness)
With respect to the laminated papers obtained in Examples and Comparative Examples, the adhesive strength between the thermoplastic resin layer and the paper substrate was measured according to JIS K6854-3: 1999. The width of the test piece was 25 mm, the length of the bonded portion was 150 mm, and the degree of peeling in a 100 mm region excluding 25 mm at both ends of the bonded portion was visually evaluated by ⊚, ◯, Δ, and x. No peeling is observed and sufficient adhesion is indicated by ⊚, peeling is observed at a very small portion, ○, peeling is observed at a very small portion, and the peeling range is wide, △, peeling When was observed in multiple places, it was evaluated as x.

(Steecht size degree)
With respect to the paper base materials obtained in Examples and Comparative Examples, the Steckigt sizing degree was measured according to JIS P8122: 2004 with the surface on which the thermoplastic resin layer was laminated facing up. When the Steckigt sizing degree is 1000 seconds or more, it is indicated as ⊚, when 850 seconds or more is indicated as ◯, when 650 seconds or more is indicated as Δ, and when less than 650 seconds is indicated as ×.

(End face water absorption index):
First, the thickness (μm) of the paper base material of the laminated paper was measured. Next, MS pouches (manufactured by Meiko Shokai Co., Ltd.) were attached to both front and back surfaces of the paper base material and laminated to make water absorption from the front and back surfaces of the paper base material. A test piece was prepared by cutting it out in a length of 60 mm (horizontal direction of paper) and a width of 90 mm (vertical direction of paper) so that the cross section of the paper base material laminated on the front and back surfaces was exposed. After measuring the weight (g) of the cut-out test piece, it was immersed in water adjusted to 23 ° C. for 60 minutes. After the immersion, the water adhering to the test piece was sufficiently wiped off, and then the weight (g) of the test piece was measured. The end face water absorption index was determined by the following formula using the thickness of the paper substrate and the weight before and after immersion. The thickness was measured with an accuracy of 1 μm and the weight was measured with an accuracy of 0.001 g.
Edge water absorption index (g / 1000 mm ² ) = (((weight after immersion-weight before immersion) / 300) / thickness of paper substrate) × 1,000,000
Regarding the laminated papers obtained in Examples and Comparative Examples, ⊚ when the edge water absorption index is 0.35 or less, ◯ when 0.40 or less, Δ when 0.45 or less, and 0.45 or more Was x.

(Smoothness)
Regarding the laminated papers obtained in Examples and Comparative Examples, the Oken type smoothness of the surface having the thermoplastic resin layer was measured according to JIS P 8155: 2010. When the Oken type smoothness was 250 seconds or more, it was evaluated as ⊚, when it was 200 seconds or more, it was evaluated as ◯, when 100 seconds or more was evaluated as Δ, and when it was less than 100 seconds, it was evaluated as x.

(Amount of paper stain)
The degree of occurrence of paper stains when the paper substrates obtained in Examples and Comparative Examples were made was evaluated by ⊚, ◯, Δ, and x. The number of dust particles of 0.05 mm ² or more in an area corresponding to 100 g of the obtained paper base material was measured. If the number of dust particles was 0, it was ⊚; If it is 5 or more, it is marked with x.

  As can be seen from the results shown in Tables 1 and 2, the laminated papers of Examples 1 to 12 were excellent in all properties in terms of laminating adhesiveness, Stecht sizing degree, end surface water absorption index, smoothness, and degree of papermaking stain. Was excellent. On the other hand, the laminated papers of Comparative Examples 1 to 9 were inferior in any of the performances such as the laminating adhesiveness, the Steckigt sizing degree, the end surface water absorption index, the smoothness, and the degree of paper stain.

Claims (10)

A laminated paper having a paper base material mainly composed of cellulose pulp, and a thermoplastic resin layer laminated on at least one surface of the paper base material,
The paper substrate has a multilayer structure having three or more pulp layers,
The mass ratio of the hardwood kraft pulp and the softwood kraft pulp in the outer layer of the paper base is 50:50 to 100: 0,
The content of the sizing agent in the inner layer of the paper substrate is 0.08 to 1.25% by mass,
The content of the sizing agent in the outer layer of the paper base is 0.04 to 0.30% by mass,
Laminated paper, wherein the content of the sizing agent in the inner layer of the paper substrate is higher than the content of the sizing agent in the outer layer.   The laminated paper according to claim 1, wherein the content ratio of the paper strengthening agent in the inner layer of the paper substrate is higher than the content ratio of the paper strengthening agent in the outer layer.   The laminated paper according to claim 1 or 2, wherein the content of the wet strength agent in the inner layer of the paper substrate is higher than the content of the wet strength agent in the outer layer.   The laminated paper according to any one of claims 1 to 3, wherein the content of aluminum in the inner layer of the paper substrate is higher than the content of aluminum in the outer layer.   A paper container using the laminated paper according to claim 1.   The paper container according to claim 5, which is for a liquid. A method for producing a laminated paper according to any one of claims 1 to 4,
A paper-making process of a paper base material comprising cellulose pulp as a main component and laminating three or more pulp layers,
A laminating step of laminating a thermoplastic resin layer on at least one surface of the paper substrate,
A method for producing a laminated paper, characterized in that, in the paper making step, the paper base is made using a multi-layer paper making machine. A laminated paper paper base material mainly composed of cellulose pulp,
It has a multilayer structure having three or more pulp layers,
The mass ratio of the hardwood kraft pulp and the softwood kraft pulp in the outer layer is 50:50 to 100: 0,
The content of the sizing agent in the inner layer is 0.08 to 1.25 mass%,
The content of the sizing agent in the outer layer is 0.04 to 0.30 mass%,
A laminated paper / paper base material , wherein the content of the sizing agent in the inner layer is higher than the content of the sizing agent in the outer layer . The content of at least one additive selected from the group consisting of a paper strengthening agent, a wet paper strengthening agent and aluminum in the inner layer is higher than the content of the additive in the outer layer. Item 9. A laminated paper sheet base material according to item 8. A method for manufacturing a laminated paper base material according to claim 8 or 9,
A main component of cellulose pulp, comprising a paper making process of laminating a pulp layer three or more layers,
A method for producing a laminated paper / paper base material, characterized in that, in the paper making step, the paper base material is made using a multi-layer paper making machine .