Laminated paper and liquid container

Abstract

To provide: laminated paper in which interlayer peeling is suppressed and which exhibits excellent processability; and a liquid container made using the laminated paper.SOLUTION: Laminated paper comprises a paper substrate, an optional first adhesive resin layer, a nylon layer, a second adhesive resin layer, and a thermoplastic resin layer in this order. The air permeation resistance in the thickness direction is 350 seconds or more and 2000 seconds or less. The moisture content is 4.0 mass% or more and 8.0 mass% or less. Also provided is a liquid container produced using the laminated paper.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a laminated paper and a liquid container made using the laminated paper. [Background technology]

[0002] Paper containers (liquid containers) for liquid beverages and the like are made of paper base materials that have been given water resistance by various methods. Typical methods for giving water resistance to paper base materials include adding a sizing agent to the paper base material and laminating a thermoplastic resin onto the surface of the paper base material.

[0003] Liquid containers using nylon as an oxygen barrier material to maintain the quality of contents such as liquid beverages are known. For example, Patent Document 1 discloses a paper liquid container made of a container material having a layered structure in which, from the surface side, at least a thermoplastic resin layer, a paperboard layer, a nylon layer, an adhesive polyolefin resin layer, and an innermost low-density polyethylene resin layer are arranged in this order, wherein the coating weight of the innermost low-density polyethylene resin layer is equal to or greater than a specific value, the coating weight of the resin layer consisting of the innermost low-density polyethylene resin layer and the adhesive polyolefin resin layer is equal to or greater than a specific value, and the coating weight of the resin layer consisting of these resin layers and the nylon layer is equal to or less than a specific value. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-335375 Summary of the Invention [Problem to be solved by the invention]

[0005] When the container material of a paper liquid container has a nylon layer, pinholes tend to be less likely to occur when heat-sealing the top or bottom of the liquid container, but there is a problem in that peeling is likely to occur between the nylon layer and adjacent layers.

[0006] The present invention has been made in view of the existence of the above-mentioned problems. That is, an object of the present invention is to provide a laminated paper that is inhibited from delaminating and has excellent processability, and a liquid container made using the laminated paper. [Means for solving the problem]

[0007] The inventors have discovered that for a laminated paper having a paper base material, an optional first adhesive resin layer, a nylon layer, a second adhesive resin layer, and a thermoplastic resin layer, in that order, by setting the cross-sectional air resistance within a specific range and the moisture content within a specific range, interlayer delamination is suppressed and the paper has excellent processability. That is, the present invention has the following configuration. <1> A laminated paper having a paper base material, an optional first adhesive resin layer, a nylon layer, a second adhesive resin layer, and a thermoplastic resin layer in this order, wherein the air resistance in the cross-sectional direction is 350 seconds or more and 2000 seconds or less, and the moisture content is 4.0 mass% or more and 8.0 mass% or less. <2> The smoothness of the paper substrate on the side where the nylon layer is to be provided is 20 seconds or less. <1> 2. The laminated paper according to claim 1. <3> The nylon layer has a thickness of 3 μm or more and 35 μm or less, and the first adhesive resin layer and the second adhesive resin layer each have a thickness of 15 μm or less. <1> or <2> 1. The laminated paper according to any one of the preceding items. <4> The absolute value of the difference between the melt volume rate of the nylon constituting the nylon layer and the melt volume rate of the adhesive resin constituting the first adhesive resin layer, measured in accordance with JIS K 7210:1999 at 280°C and a load of 2.16 kg, is 0 cm 3 / 100cm for more than 10 minutes 3 / 10 minutes or less, <1> ~ <3> 1. The laminated paper according to any one of the preceding items. <5> The melt volume rate of the nylon constituting the nylon layer, measured in accordance with JIS K 7210:1999 at 280°C and a load of 2.16 kg, is 10 cm 3 / 500cm for more than 10 minutes 3 / 10 minutes or less, and the melt volume rate of the adhesive resin constituting the first adhesive resin layer is 5 cm 3 / 500cm for more than 10 minutes 3 / 10 minutes or less, <1> ~ <4> 1. The laminated paper according to any one of the preceding items. <6> The paper substrate further has a thermoplastic resin layer on the side opposite to the side where the nylon layer is provided. <1> ~ <5> 1. The laminated paper according to any one of the preceding items. <7> For liquid containers, <1> ~ <6> 1. The laminated paper according to any one of the preceding items. <8> <1> ~ <7> A liquid container comprising the laminated paper according to any one of the above. [Effects of the Invention]

[0008] According to the present invention, there are provided laminated paper that is inhibited from delaminating and has excellent processability, and a liquid container made using said laminated paper. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail. The following description of the constituent elements may be based on representative embodiments or specific examples, but the present invention is not limited to such embodiments. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​written before and after "to" as the lower and upper limits. When a numerical range is written in stages, the upper and lower limits of each numerical range can be combined in any way.

[0010] [Laminated paper] The laminated paper of this embodiment comprises a paper substrate, an optional first adhesive resin layer, a nylon layer, a second adhesive resin layer, and a thermoplastic resin layer, in this order. The laminated paper has an air resistance in the cross-sectional direction of 350 seconds to 2000 seconds, and a moisture content of 4.0% by mass to 8.0% by mass. This embodiment provides a laminated paper that can suppress delamination and has excellent processability. Here, "delamination" refers to delamination between the nylon layer and the paper substrate layer or the first adhesive resin layer (hereinafter also referred to as the adjacent layer). When delamination is suppressed, the laminated paper can suppress leakage of contents when a liquid container is fabricated, making it suitable for use in liquid containers. Furthermore, "excellent processability" means that peeling within the paper base material due to ironing, particularly when laminated paper is printed, is suppressed, and / or that surface cracks (crease breaks) that occur at the score lines after the laminated paper is creasing processed and the score lines are folded are suppressed. The mechanism by which this effect is achieved is unclear, but is presumed to be as follows. The presence of a nylon layer in laminated paper makes it less likely to develop pinholes when heat-sealing the top or bottom of a liquid container (it has pinhole resistance). However, when a liquid container is made from the laminated paper, water vapor from the moisture contained in the paper substrate can accumulate between the nylon layer and its adjacent layer, causing delamination. By setting the cross-sectional air resistance of the laminated paper to 2000 seconds or less, the water vapor can easily escape from the edge (cross section) of the laminated paper, thereby preventing delamination of the laminated paper when it is made into a liquid container. Furthermore, by setting the cross-sectional air resistance of the laminated paper to 350 seconds or more, the interior of the paper substrate is appropriately filled with pulp fibers, strengthening the interfiber bonds and preventing delamination within the paper substrate due to ironing during printing. Furthermore, by setting the moisture content of the laminated paper to 8.0% by mass or less, the generation of water vapor and the retention of water vapor between the nylon layer and its adjacent layer are less likely to occur, thereby suppressing delamination of the laminated paper. Furthermore, by setting the moisture content of the laminated paper to 4.0% by mass or more, the laminated paper does not become too hard, suppressing delamination within the paper base due to ironing during printing processing, and also reducing the occurrence of cracks when the score lines are folded. The effects of the present invention are not limited to the above mechanism.

[0011] Specifically, the laminated paper of this embodiment may have a layer structure of paper substrate / first adhesive resin layer / nylon layer / second adhesive resin layer / thermoplastic resin layer, or paper substrate / nylon layer / second adhesive resin layer / thermoplastic resin layer. In addition to the above layers, the paper substrate may further have a thermoplastic resin layer on the other side opposite the side on which the nylon layer is provided, or may have other layers as described below.

[0012] <Air permeability resistance> In this embodiment, the air resistance in the cross-sectional direction of the laminated paper is 350 seconds or more, preferably 400 seconds or more, more preferably 450 seconds or more, even more preferably 470 seconds or more, and even more preferably 480 seconds or more, from the viewpoint of suppressing interlayer delamination between the nylon layer and its adjacent layer, and thereby obtaining a laminated paper that suppresses leakage of the contents when a liquid container is manufactured, and is 2000 seconds or less, preferably 1800 seconds or less, and more preferably 1700 seconds or less. The air resistance in the cross-sectional direction of laminated paper can be adjusted by adjusting the pulp beating conditions, press processing conditions during papermaking, etc. for the paper base material that constitutes the laminated paper. Specifically, increasing the degree of beating of the pulp or increasing the press pressure tends to increase the air resistance. The air resistance in the cross-sectional direction of laminated paper is measured as follows. If the laminated paper further has a thermoplastic resin layer (printed side) on the side opposite the side where the nylon layer is provided, as described below, the thermoplastic resin layer on the printed side is peeled off to expose the paper substrate. In accordance with JIS P 8117:2009, the Oken air resistance of gas escaping horizontally from the underside of the edge (cross-section) of the side where the paper substrate is exposed is measured. Specifically, it is measured by the method described in the Examples.

[0013] <Moisture content> In this embodiment, the moisture content of the laminated paper is 4.0% by mass or more, preferably 5.0% by mass or more, from the viewpoint of obtaining laminated paper with excellent processability, and is 8.0% by mass or less, preferably 7.0% by mass or less, from the viewpoint of suppressing interlayer delamination. The moisture content of the laminated paper can be adjusted by adjusting the drying temperature and drying time when producing the laminated paper. The moisture content of the laminated paper is measured in accordance with JIS P 8127:2010.

[0014] <Basic weight> The basis weight of the laminated paper is preferably 100 g / m from the viewpoint of preventing delamination and suitability for processing. 2 More preferably, 200 g / m 2More preferably, 300 g / m 2 More preferably, 350 g / m 2 and preferably 600 g / m 2 Less than 500 g / m 2 or less, more preferably 450 g / m 2 The following is the result. The basis weight of laminated paper is measured in accordance with JIS P 8118:2014.

[0015] <Thickness> From the viewpoint of preventing delamination and processability, the thickness of the laminated paper is preferably 200 μm or more, more preferably 250 μm or more, even more preferably 300 μm or more, and even more preferably 350 μm or more, and is preferably 1000 μm or less, more preferably 800 μm or less, even more preferably 600 μm or less, and even more preferably 500 μm or less. The thickness of the laminated paper is measured in accordance with JIS P 8118:2014. Specifically, it is measured by the method described in the examples.

[0016] Each layer constituting the laminated paper of this embodiment will be described below. <Paper base material> In this embodiment, the paper substrate is mainly made of paper, and there are no particular limitations on the paper substrate as long as it is a commonly used paper containing plant-derived wood pulp as its main component. The paper base preferably has a multilayer structure with two or more pulp layers. The number of layers in the paper base is preferably three or more, more preferably four or more, and is preferably seven or fewer, more preferably six or fewer, and particularly preferably five, from the viewpoint of making it easy to adjust the interlayer strength of the paper base to a desired range and thereby obtaining a laminated paper with better processability. The basis weights of the pulp layers in the paper base may be the same or different.

[0017] (Basic weight) The basis weight of the paper base material (all layers) is preferably 200 g / m from the viewpoints of preventing delamination, suitability for processing, and strength when used as a liquid container.2 More preferably, 250 g / m 2 More preferably, 300 g / m 2 More preferably, 310 g / m 2 More preferably, 320 g / m 2 and preferably 500 g / m 2 Less than 400 g / m 2 or less, more preferably 350 g / m 2 That's all below. The basis weight of the paper substrate is measured in accordance with JIS P 8118:2014.

[0018] (Thickness) The thickness of the paper base material (all layers) is preferably 100 μm or more, more preferably 200 μm or more, even more preferably 300 μm or more, even more preferably 400 μm or more, even more preferably 420 μm or more, from the viewpoints of preventing delamination, processability, and strength when made into a liquid container, and is preferably 600 μm or less, more preferably 500 μm or less, and even more preferably 480 μm or less. The thickness of the paper substrate is measured in accordance with JIS P 8118:2014.

[0019] (density) The density of the paper base material (all layers) is preferably 0.4 g / cm from the viewpoints of preventing delamination, suitability for processing, and strength when used as a liquid container. 3 More preferably, 0.5 g / cm 3 More preferably, 0.6 g / cm 3 More preferably, 0.7 g / cm 3 and preferably 1.2 g / cm 3 or less, more preferably 1.1 g / cm 3 or less, more preferably 1.0 g / cm 3 or less, even more preferably 0.9 g / cm 3 or less, even more preferably 0.8 g / cm 3 The following is the result. The density of the paper base material is calculated from the basis weight and thickness of the paper base material measured in accordance with JIS P 8118:2014.

[0020] (Smoothness) The smoothness of the paper substrate on the side where the nylon layer described below is provided (the side that comes into contact with the liquid when made into a liquid container) is preferably 2 seconds or more, more preferably 4 seconds or more, and preferably 20 seconds or less, more preferably 18 seconds or less, from the viewpoint of more effectively increasing adhesion to the nylon layer, etc., and as a result, further suppressing interlayer delamination. The smoothness of the paper substrate is measured in accordance with JIS P 8155:2010. When measuring laminated paper, the measurement is performed as follows: The laminated paper is immersed in xylene and heated in a 98°C water bath for 1 hour to remove all resin layers except for the paper substrate. After heating, it is removed from the xylene, thoroughly dried, and measured in accordance with JIS P 8155:2010.

[0021] When the paper substrate has a multilayer structure, an adhesive component may be applied between each layer. Furthermore, an adhesive layer containing an adhesive component may be provided between each layer of the paper substrate. Examples of adhesive components include starch, polyacrylamide, polyamide-polyamine-epichlorohydrin resin, etc. These may be used alone or in combination of two or more. The adhesive component preferably contains one or more components selected from the group consisting of starch, polyacrylamide, and polyamide-polyamine-epichlorohydrin resin, more preferably one or more components selected from the group consisting of starch and polyacrylamide, and even more preferably starch. Applying (coating) an adhesive component between each layer of the paper substrate can improve the interlayer strength of the paper substrate, resulting in a laminated paper with superior processability. The amount of adhesive component applied between each layer of the paper base is preferably 2.0 g / m from the viewpoint of improving the interlayer strength of the paper base and, as a result, obtaining a laminated paper that can further suppress interlayer peeling, particularly due to ironing. 2 More preferably, 2.5 g / m 2 More preferably, 3.0 g / m2 From the viewpoint of further suppressing cracking of the laminated paper, it is preferable that the thickness is 8.0 g / m 2 Less than 7.0 g / m 2 or less, more preferably 6.0 g / m 2 or less, even more preferably 5.0 g / m 2 The following is the result.

[0022] (pulp) The paper base preferably contains pulp (preferably cellulose pulp) as its main component. Here, the term "main component" refers to a component that accounts for 50% by mass or more of the total mass of the paper base. The pulp content is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more of the total mass of the paper base.

[0023] Examples of pulp constituting the paper base include softwood kraft pulps (NKP) such as softwood bleached kraft pulp (NBKP) and softwood unbleached kraft pulp (NUKP), hardwood kraft pulps (LKP) such as hardwood bleached kraft pulp (LBKP) and hardwood unbleached kraft pulp (LUKP), and other wood-based pulps, and non-wood pulps such as hemp pulp. These pulps can be used alone or in combination of two or more. Among these, from the standpoints of quality and cost, the pulp preferably contains one or more selected from the group consisting of LKP and NKP, and more preferably contains LBKP and NBKP.

[0024] In this embodiment, the mass ratio of hardwood bleached kraft pulp to softwood bleached kraft pulp (LBKP:NBKP) in the paper base material is preferably 10:90 to 100:0, more preferably 40:60 to 70:30, and even more preferably 50:50 to 65:45, from the viewpoint of more effectively increasing the adhesion between the paper base material and the adhesive resin layer, nylon layer, or thermoplastic resin layer described below, thereby further suppressing interlayer delamination, and from the viewpoint of strength when made into a liquid container. From the viewpoint of printability when used to make a liquid container, the content of softwood bleached kraft pulp and hardwood bleached kraft pulp in the pulp constituting the paper base material is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 100% by mass. From the same viewpoint, the content of recycled paper pulp or unbleached kraft pulp is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less, even more preferably 5% by mass or less, and even more preferably less than 1% by mass, and it is particularly preferable that they are not contained at all.

[0025] When the pulp contains LBKP, the Canadian Standard Freeness (CSF) of the pulp constituting the paper base material is preferably 400 mL or more, more preferably 420 mL or more, even more preferably 450 mL or more, and preferably 500 mL or less, more preferably 490 mL or less, from the viewpoints of preventing delamination and processability. When the pulp contains NBKP, the Canadian Standard Freeness (CSF) is preferably 580 mL or more, more preferably 600 mL or more, even more preferably 620 mL or more, and preferably 700 mL or less, from the viewpoints of preventing delamination and processability. The CSF of pulp is measured in accordance with JIS P 8121-2:2012.

[0026] (Various internal additives) Various known internal additives can be added to the paper substrate. Examples of internal additives include fillers such as titanium dioxide, kaolin, talc, and calcium carbonate, sizing agents, paper strength agents, wet strength agents, retention aids, drainage aids, water-resistant agents, softeners, antistatic agents, defoamers, bulking agents, coloring dyes, coloring pigments, fluorescent whitening agents, pH adjusters, pitch control agents, preservatives, and slime control agents. These can be used alone or in combination of two or more. Among these, it is preferable for the paper substrate to contain a sizing agent in order to obtain laminated paper with superior water resistance. Furthermore, in order to more effectively increase the strength of the paper substrate, it is preferable for the paper substrate to contain, in addition to the sizing agent, one or more selected from the group consisting of paper strength agents and wet strength agents, and it is more preferable for the paper substrate to contain a paper strength agent and a wet strength agent.

[0027] <Sizing agent> Examples of sizing agents include various known paper sizing agents such as rosin-based, alkyl ketene dimer-based, alkenyl succinic anhydride-based, maleic anhydride-based, styrene-acrylic acid-based, and styrene-acrylic-based. These can be used alone or in combination of two or more. Among these, it is preferable that the sizing agent contains an alkyl ketene dimer-based sizing agent. When the paper base material contains a sizing agent, the content of the sizing agent (in terms of solids content) is preferably 0.001 parts by mass or more, more preferably 0.01 parts by mass or more, even more preferably 0.1 parts by mass or more, and preferably 4.0 parts by mass or less, more preferably 2.0 parts by mass or less, even more preferably 1.0 parts by mass or less, still more preferably 0.5 parts by mass or less, and even more preferably 0.3 parts by mass or less, per 100 parts by mass (dry mass) of pulp contained in the paper base material, from the viewpoint of more effectively improving the water resistance of the paper base material and, as a result, obtaining a laminated paper with better water resistance. Note that, from the viewpoint of production efficiency, it is preferable that the content of the sizing agent in each layer of the paper base material is the same.

[0028] <Paper strength enhancer> Examples of paper strength agents (dry strength agents) include polyacrylamide polymers, starches such as cationized starch, urea resins, polyamide-polyamine resins, polyethyleneimine, polyamines, polyvinyl alcohol, and polyethylene oxide. These can be used alone or in combination of two or more. Among these, the paper base material preferably contains one or more paper strength agents selected from the group consisting of cationized starch and polyacrylamide polymers, and more preferably contains polyacrylamide polymers. When the paper base material contains a paper strength agent, the content of the paper strength agent (in terms of solid content) is, from the viewpoint of more effectively increasing the strength of the paper base material, preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, even more preferably 0.2 parts by mass or more, and even more preferably 0.3 parts by mass or more, per 100 parts by mass (dry mass) of pulp fiber contained in the paper base material, and is preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, and even more preferably 1.5 parts by mass or less.

[0029] <Wet strength agent> Examples of wet strength agents include melamine resins, urea resins, polyamide-polyamine-epichlorohydrin resins, etc. These can be used alone or in combination of two or more. When the paper base material contains a wet strength agent, the content of the wet strength agent (in terms of solid content) is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, and preferably 1.0 part by mass or less, more preferably 0.5 part by mass or less, and even more preferably 0.3 part by mass or less, per 100 parts by mass (dry mass) of pulp contained in the paper base material, from the viewpoint of more effectively increasing the wet strength of the paper base material.

[0030] In order to increase the surface strength and further suppress peeling of the adhesive resin layer, nylon layer, or thermoplastic resin layer, which is laminated on the paper base material and will be described later, when the laminated paper is ironed, the paper base material preferably contains, in addition to the internal additives described above, one or more selected from the group consisting of surface sizing agents and surface paper strength agents. Examples of surface sizing agents include alkylketene dimer compounds. Examples of surface strength agents include modified starches such as oxidized starch, enzyme-treated starch, and acid-treated starch; aqueous resins such as polyvinyl alcohol (PVA); styrene-acrylic acid copolymers; and styrene-methacrylic acid copolymers. These can be used alone or in combination of two or more. Among these, the surface strength agent preferably contains one or more selected from the group consisting of modified starch and aqueous resin, more preferably contains one or more selected from the group consisting of oxidized starch and polyvinyl alcohol, and even more preferably contains polyvinyl alcohol. When one or more selected from the group consisting of surface sizes and surface strength agents are used in the size press process, it is preferable to use an adhesive aid such as a vinyl resin, epoxy resin, urethane resin, polyester resin, or polyethyleneimine resin mixed into the size press liquid in order to more effectively improve adhesion to the adhesive resin layer, nylon layer, or thermoplastic resin layer (described later) laminated to the paper substrate. In other words, it is preferable that the paper substrate has applied to at least one side thereof one or more selected from the group consisting of surface sizes and surface strength agents and an adhesive aid. Among the above, the adhesive aid preferably contains one or more selected from the group consisting of vinyl resins and polyethyleneimine resins, and more preferably contains polyethyleneimine resin. The amount of the surface sizing agent and the surface paper strength agent to be applied is preferably 0.01 g / m in terms of solid content, from the viewpoint of increasing the surface strength of the paper substrate. 2 More preferably, 0.1 g / m 2 More preferably, 0.3 g / m 2 More preferably, 0.4 g / m 2 From the viewpoint of obtaining a laminated paper having an appropriate surface strength of the paper base material and excellent processability, it is preferable that the thickness is 5.0 g / m 2 Less than 3.0 g / m, more preferably 3.0 g / m 2 or less, more preferably 1.5 g / m 2 When a surface sizing agent and a surface strength agent are used in combination, the amounts of each agent applied are preferably within the above ranges. The amount of adhesive aid applied is preferably 0.01 g / m in terms of solid content, from the viewpoint of improving adhesion to the adhesive resin layer, nylon layer or thermoplastic resin layer to be described later, which is laminated on the paper substrate. 2 More preferably, 0.05 g / m 2 More preferably, 0.1 g / m 2 From the viewpoint of recyclability of the laminated paper, it is preferably 5.0 g / m 2 Less than 3.0 g / m, more preferably 3.0 g / m 2 or less, more preferably 1.5 g / m 2 or less, even more preferably 1.0 g / m 2 or less, even more preferably 0.7 g / m 2 or less, even more preferably 0.4 g / m 2 The following is the result.

[0031] (Paper base material manufacturing method) The paper base material is preferably produced by a manufacturing method including a papermaking step in which two or more pulp layers are laminated. Multilayer paper, which is constructed by laminating multiple pulp layers, is used as a manufacturing technique for paperboard, etc., and can generally be produced using a multilayer papermaking machine such as a cylinder-type papermaking machine or a Fourdrinier-type papermaking machine. Furthermore, the pH during papermaking may be in the acidic range (acidic papermaking), pseudo-neutral range (pseudo-neutral papermaking), neutral range (neutral papermaking), or alkaline range (alkaline papermaking).

[0032] In the papermaking of paper substrates, a known wet papermaking machine (e.g., a Fourdrinier papermaking machine, a gap former papermaking machine, a cylinder papermaking machine, a short wire papermaking machine, etc.) can be appropriately selected and used. The paper layer formed by the papermaking machine can be transported on a felt and dried in a dryer. A multi-stage cylinder dryer may be used as a pre-dryer before drying in the dryer.

[0033] As described above, from the viewpoint of increasing the surface strength of the paper base material, it is preferable to apply one or more selected from the group consisting of surface sizing agents and surface strength agents to one or both sides of the paper base material obtained as described above. Furthermore, from the viewpoint of effectively increasing adhesion to the adhesive resin layer, nylon layer or thermoplastic resin layer described below, it is more preferable to apply a mixture of one or more selected from the group consisting of surface sizing agents and surface strength agents and an adhesive aid. A known size press or the like can be used as an application device for the surface sizing agent, surface strength agent, and / or adhesion aid. Furthermore, from the viewpoint of effectively enhancing adhesion to the adhesive resin layer, nylon layer, or thermoplastic resin layer described below, it is preferable to subject the paper substrate obtained as described above to a surface treatment using a calendar to achieve uniform thickness and profile. A known calendaring machine can be appropriately selected and used for the calendaring treatment. Furthermore, a size press agent may be applied before the calendaring treatment.

[0034] <First adhesive resin layer> The first adhesive resin layer is a layer for further improving the adhesion between the paper substrate and the nylon layer. The first adhesive resin layer can be optionally laminated on one side of the paper substrate. From the viewpoint of making the laminated paper suitable for manufacturing liquid containers under higher temperature conditions, it is preferable that the laminated paper has the first adhesive resin layer on one side of the paper substrate. From the viewpoint of cost, the laminated paper does not necessarily have to have the first adhesive resin layer on one side of the paper substrate.

[0035] The adhesive resin constituting the first adhesive resin layer is not particularly limited, and known adhesive thermoplastic resins can be used. Examples of adhesive resins include acid-modified polyolefins obtained by modifying olefin resins with unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, and maleic anhydride. These can be used alone or in combination of two or more. Among these, it is preferable that the adhesive resin contains one or more selected from the group consisting of ethylene / methacrylic acid copolymers and maleic anhydride-modified polyethylenes.

[0036] The melt volume rate (MVR) of the adhesive resin constituting the first adhesive resin layer, measured in accordance with JIS K 7210:1999 at 280°C and a load of 2.16 kg, is preferably 5 cm from the viewpoint of improving adhesion with the nylon layer described later and further suppressing interlayer delamination. 3 / 10 minutes or more, preferably 8cm 3 / 10 minutes or more, and preferably 500 cm 3 / 10 minutes or less, preferably 400cm 3 / 10 minutes or less, more preferably 380cm 3 / 10 minutes or less, even more preferably 170cm 3 / 10 minutes or less, even more preferably 140cm 3 / 10 minutes or less, even more preferably 100cm 3 The adhesive resin constituting the first adhesive resin layer can be appropriately selected in consideration of the molecular weight and the like so as to have a desired MVR.

[0037] When the laminated paper has a first adhesive resin layer, the thickness of the first adhesive resin layer is preferably 0.5 μm or more, more preferably 0.8 μm or more, and even more preferably 1.0 μm or more from the viewpoint of ease of production, and is preferably 15 μm or less, more preferably 13 μm or less, even more preferably 12 μm or less, and even more preferably 10 μm or less from the viewpoint of cost and further suppressing interlayer delamination.

[0038] The method for laminating the first adhesive resin layer on the paper substrate can be appropriately selected from various known methods such as melt extrusion lamination, coating method, etc. Although not particularly limited, among these, the melt extrusion lamination method is preferred, and lamination by melt co-extrusion with nylon constituting the nylon layer described below is more preferred.

[0039] <Nylon layer> The nylon layer is laminated on one side of the paper substrate or on any first adhesive resin layer. Examples of nylons constituting the nylon layer include aliphatic nylons such as nylon 6, nylon 66, nylon 6 / 66, nylon 6 / 9, nylon 6 / 10, nylon 11, and nylon 12, and aromatic nylons such as nylon MXD6. These can be used alone or in combination of two or more. Among these, it is preferable that the nylon contains at least one selected from the group consisting of nylon 6 and nylon MXD6. The nylon layer may further contain components other than nylon.

[0040] The melt volume rate of the nylon constituting the nylon layer, measured in accordance with JIS K 7210:1999 at 280°C and a load of 2.16 kg, is preferably 10 cm from the viewpoint of improving adhesion with the first adhesive resin layer and further suppressing interlayer delamination when the laminated paper has a first adhesive resin layer. 3 / 10 minutes or more, preferably 13cm 3 / 10 minutes or more, and preferably 500 cm 3 / 10 minutes or less, preferably 400cm 3 / 10 minutes or less, more preferably 350cm 3 / 10 minutes or less, even more preferably 300cm 3 From the above viewpoint, it is preferable that the time is 20 cm / 10 minutes or less. 3 / 10 minutes or more, preferably 30cm 3 / 10 minutes or more, preferably 40cm 3 / 10 minutes or more, and preferably 200 cm 3 / 10 minutes or less, preferably 150cm 3 / 10 minutes or less, more preferably 100cm 3 / 10 minutes or less, even more preferably 60cm 3 The nylon constituting the nylon layer can be appropriately selected in consideration of the molecular weight and the like so as to have a desired MVR.

[0041] When the laminated paper has a first adhesive resin layer, the absolute value of the difference between the melt volume rate of the nylon constituting the nylon layer and the melt volume rate of the adhesive resin constituting the first adhesive resin layer is preferably 0 cm from the viewpoint of improving the adhesion between the first adhesive resin layer and the nylon layer and further suppressing interlayer peeling. 3 / 10 minutes or more, and preferably 350 cm 3 / 10 minutes or less, preferably 300cm 3 / 10 minutes or less, more preferably 200cm 3 / 10 minutes or less, or even better 150cm 3 / 10 minutes or less, even more preferably 100cm 3 / 10 minutes or less, even more preferably 50cm 3 / 10 minutes or less, even more preferably 25cm 3 / 10 minutes or less, even more preferably 10cm 3 / less than 10 minutes.

[0042] The thickness of the nylon layer is preferably 3 μm or more, more preferably 4 μm or more, even more preferably 5 μm or more, and even more preferably 6 μm or more from the viewpoint of pinhole resistance, and is preferably 35 μm or less, more preferably 30 μm or less, even more preferably 25 μm or less, even more preferably 20 μm or less, even more preferably 15 μm or less, and particularly preferably 10 μm or less from the viewpoint of preventing delamination and / or improving processability. When the thickness of the nylon layer is below the above upper limit, the hardness of the laminated paper is appropriate, no unnecessary load is applied to the paper substrate during ironing, delamination within the paper substrate due to ironing is suppressed, and processability is excellent. Furthermore, when the thickness of the nylon layer is below the above upper limit, the force applied to the surface when the laminated paper is folded is appropriate, preventing crease cracking and improving processability.

[0043] The method for laminating the nylon layer onto the paper substrate or the first adhesive resin layer can be selected from various known methods, such as melt extrusion lamination, dry lamination, wet lamination, and thermal lamination. While not particularly limited, melt extrusion lamination is preferred. When the laminated paper has a first adhesive resin layer, it is more preferable to laminate the nylon layer and the adhesive resin constituting the first adhesive resin layer by melt co-extrusion. In this case, by setting the absolute value of the difference between the MVR of the nylon constituting the nylon layer and the MVR of the adhesive resin constituting the first adhesive resin layer within the above-mentioned range, the adhesion between the first adhesive resin layer and the nylon layer is further improved, resulting in a laminated paper with better suppressed interlayer delamination.

[0044] <Second adhesive resin layer> The second adhesive resin layer is laminated on the nylon layer. The adhesive resin constituting the second adhesive resin layer can be one of those exemplified as the adhesive resin constituting the first adhesive resin layer. When the laminated paper has a first adhesive resin layer, the adhesive resin constituting the second adhesive resin layer may be the same as or different from the adhesive resin constituting the first adhesive resin layer, but it is preferable that they are the same.

[0045] The MVR of the adhesive resin constituting the second adhesive resin layer is preferably 8 cm from the viewpoint of improving the adhesiveness with the nylon layer. 3 / 10 minutes or more, preferably 10cm 3 / 10 minutes or more, and preferably 500 cm 3 / 10 minutes or less, preferably 400cm 3 / 10 minutes or less, more preferably 380cm 3 / less than 10 minutes. The MVR of the adhesive resin constituting the second adhesive resin layer is measured in accordance with JIS K 7210:1999 at 280° C. and a load of 2.16 kg.

[0046] From the viewpoint of ease of production, the thickness of the second adhesive resin layer is preferably 0.5 μm or more, more preferably 0.8 μm or more, even more preferably 1.0 μm or more, and even more preferably 1.5 μm or more, and from the viewpoint of cost, it is preferably 15 μm or less, more preferably 13 μm or less, and even more preferably 10 μm or less.

[0047] The method for laminating the second adhesive resin layer on the nylon layer can be appropriately selected from various known methods such as melt extrusion lamination, coating, etc. Although not particularly limited, among these, melt extrusion lamination is preferred.

[0048] <Thermoplastic resin layer> The thermoplastic resin layer is laminated on the second adhesive resin layer and may be a single layer or multiple layers.

[0049] The thermoplastic resin constituting the thermoplastic resin layer can be either crystalline or amorphous, depending on the application. Examples of thermoplastic resins include polyethylenes such as low-density polyethylene (LDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), and linear low-density polyethylene (LLDPE), polyolefin resins such as polypropylene and polymethylpentene, polyester resins such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), polyamide resins, biodegradable resins such as polylactic acid (PLA), polyhydroxybutyrate (PHB), polybutylene succinate (PBS), poly(butylene adipate-co-butylene terephthalate) (PBAT), polycaprolactone (PCL), and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene (ABS) resin, acrylic resin, and modified polyphenylene ether (PPE). These thermoplastic resins may be used singly or in combination of two or more. Among these, the thermoplastic resin is preferably one or more selected from the group consisting of polyolefin resins and polylactic acid (PLA), more preferably one or more selected from the group consisting of polyethylene and polypropylene, and even more preferably one or more selected from the group consisting of polyethylene.

[0050] The thermoplastic resin layer may be formed as a single layer of a single resin, or as a single layer of a mixture of multiple resins, or as a multi-layer structure of these (e.g., single resin layer / single resin layer, single resin layer / mixed resin layer, mixed resin layer / mixed resin layer).

[0051] The thickness of the thermoplastic resin layer is not particularly limited, but from the viewpoint of preventing the liquid filled in the liquid container from penetrating into the paper substrate, it is preferably 5 μm or more, more preferably 10 μm or more, and preferably 150 μm or less, more preferably 100 μm or less, even more preferably 50 μm or less, and even more preferably 40 μm or less.

[0052] The laminated paper of this embodiment preferably further has a thermoplastic resin layer on the side (printing surface) opposite to the side where the nylon layer is provided of the paper substrate. That is, the thermoplastic resin layers are preferably laminated on both sides of the paper substrate. In this specification, the terms "laminated on the surface" and "laminated on" mean that they may be laminated directly or indirectly via another layer.

[0053] The thickness of the thermoplastic resin layer on the side of the paper substrate opposite to the side where the nylon layer is provided (printing side) may be the same as or different from the thickness on the side where the nylon layer is provided (liquid-contacting side). The thickness of the thermoplastic resin layer on the side of the paper substrate opposite to the side where the nylon layer is provided (printing side) is not particularly limited, but is preferably 5 μm or more, more preferably 10 μm or more, and preferably 150 μm or less, more preferably 100 μm or less, even more preferably 50 μm or less, and even more preferably 40 μm or less.

[0054] In addition to the above-mentioned paper substrate, first adhesive resin layer, nylon layer, second adhesive resin layer, and thermoplastic resin layer, other layers may be present depending on the application. Examples of other layers include a water-soluble polymer (such as polyvinyl alcohol (PVA)) layer, a pigment coating layer mainly composed of a pigment and a binder, an aluminum foil (Al foil), a metal vapor deposition layer, an inorganic oxide (such as silica or alumina) vapor deposition layer, a barrier layer such as an EVOH (ethylene-vinyl alcohol copolymer) layer, a printed layer, and an adhesive layer.

[0055] [Laminated paper manufacturing method] The laminated paper of this embodiment is produced by a manufacturing method including a laminating step of laminating an optional first adhesive resin layer, a nylon layer, a second adhesive resin layer, and a thermoplastic resin layer in this order on one side of a paper substrate. Specifically, the manufacturing method of laminated paper preferably includes a papermaking step of a paper substrate, and a laminating step of laminating an optional first adhesive resin layer, a nylon layer, a second adhesive resin layer, and a thermoplastic resin layer on at least one side of the paper substrate.

[0056] As a method for laminating an optional first adhesive resin layer, a nylon layer, a second adhesive resin layer, and a thermoplastic resin layer onto a paper substrate in this order, various known methods such as melt extrusion lamination, dry lamination, wet lamination, and thermal lamination can be appropriately selected and used. Among these, melt extrusion lamination is preferred. Although not particularly limited, when the laminated paper has a first adhesive resin layer, for example, the adhesive resin constituting the first adhesive resin layer and the nylon constituting the nylon layer can be melt-extruded and laminated onto the paper substrate. Furthermore, when the laminated paper does not have a first adhesive resin layer, the nylon constituting the nylon layer can be melt-extruded and laminated onto the paper substrate. Furthermore, the second adhesive resin layer and the thermoplastic resin layer can be melt-extruded and laminated onto the nylon layer. During lamination, the paper substrate may be subjected to oxidation treatment such as corona treatment or ozone treatment, if necessary. These treatments generate polar groups on the surface of the paper substrate, improving adhesion. These treatments may be performed on either one or both of the paper substrates, and may be performed once or multiple times.

[0057] In the papermaking process, it is preferable to make the paper base material using a multi-layer papermaking machine. The papermaking process is as described above.

[0058] [Liquid container] The laminated paper of this embodiment is preferably used for liquid containers. The present invention also provides a blank sheet or liquid container made using the above-mentioned laminated paper. The blank sheet and liquid container can be manufactured by appropriately selecting a known method.

[0059] The laminated paper of this embodiment can be used for various purposes, such as liquid containers such as paper cartons, paper cups, and aseptic containers, paper containers such as foam cups, ice cups, insulated cups, and packaging containers, as well as packaging materials and heat insulating materials. Among these, the laminated paper of this embodiment is suitable for use as a liquid container. The shape of the liquid container is not particularly limited, and examples include gable-top containers, rectangular parallelepiped containers (brick, straight, flat top), triangular pyramid-shaped containers, cup containers, slant-top containers, regular tetrahedron-shaped containers, etc. Therefore, another embodiment of the present invention is the use of the above-mentioned laminated paper in the production of paper containers (preferably paper containers for liquids). The method for producing a gable-top liquid container is not particularly limited, but for example, the surface (printing surface) of laminated paper is printed, creasing and punching are performed, and the container is further folded and frame-sealed in the vertical direction, and then provided in a folded carton shape. The provided folded carton goes through the steps of bottom sealing (heat-sealing the bottom), sterilization, filling, and top sealing (heat-sealing the top), and is then distributed as a gable-top liquid-filled product. The liquid contained in the liquid container may be either food or non-food. Liquids that can be contained in the liquid container are not particularly limited and include alcoholic beverages such as sake, shochu, and wine; dairy beverages such as milk; beverages such as juice, coffee, tea, and black tea; liquid foods such as beverages (yogurt, jelly, pudding, etc.) and prepared dishes; pharmaceuticals; and chemical products such as car wax, shampoo, conditioner, detergent, bath additives, hair dye, and toothpaste. [Example]

[0060] The effects of the present invention will be described in detail below using examples. The materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the specific examples shown below. Furthermore, in the examples and comparative examples, "parts" and "%" refer to "parts by mass" and "% by mass," respectively, unless otherwise specified. Furthermore, the operations of the examples and comparative examples were carried out at room temperature (20-25°C) and normal humidity (40-50% RH), unless otherwise specified.

[0061] [measurement] <Pulp> (Canadian Standard Freeness) The Canadian Standard Freeness (CSF) of the pulp was measured in accordance with JIS P 8121-2:2012.

[0062] <Paper base material> (Thickness) The thickness of the paper substrate is measured according to JIS P 8118:2014, and a pressure of 100 kPa ± 10 kPa is applied to the circular area (200 mm 2 The thickness of the film was measured when it was applied to the substrate.

[0063] (Basic weight) The basis weight of the paper substrate was measured in accordance with JIS P 8118:2014.

[0064] (density) The density of the paper substrate was calculated from the thickness and basis weight of the paper substrate obtained in accordance with JIS P 8118:2014.

[0065] (Smoothness) The smoothness of the paper substrate was measured in accordance with JIS P 8155:2010.

[0066] <Thermoplastic resin layer> (Thickness) The thickness of each resin layer was measured by observing the cross section of the laminated paper with a scanning electron microscope. The specimens for observation were prepared by embedding the laminated paper in resin and cutting it with an ultramicrotome.

[0067] <Laminated paper> (basis weight, thickness and density) The basis weight, thickness and density of the laminated paper were measured in the same manner as for measuring the basis weight, thickness and density of the paper substrate, respectively.

[0068] (moisture content) The moisture content of the laminated paper was measured in accordance with JIS P 8127:2010.

[0069] (Air resistance in cross-sectional direction) The cross-sectional air resistance of the laminated paper was measured by cutting a piece of laminated paper measuring 12 cm in the machine direction (the direction corresponding to the paper substrate's papermaking direction) and 8 cm in the cross-sectional direction (the direction corresponding to the paper substrate's width). The thermoplastic resin layer on the side opposite the nylon layer (the printed side) of the paper substrate was peeled off to expose the paper substrate. The thermoplastic resin layer on the printed side was peeled off from one edge of the laminated paper cut to a specified size, creating a peel initiation point between the thermoplastic resin layer and the paper substrate. The laminated paper with the peel initiation point was fixed to a Tensilon (manufactured by A&D Co., Ltd.) jig and the test was continued at a peel rate of 50 mm per minute until at least 9 cm of the adhesive length had peeled off, exposing the paper substrate. The exposed paper substrate was cut to a size of 8 cm in the MD (the direction corresponding to the papermaking direction of the paper substrate) x 8 cm in the CD (the direction corresponding to the width direction of the paper substrate). Using an EYBO-type digital Oken air permeability and smoothness tester manufactured by Asahi Seiko Co., Ltd., the cylinder-driven pressure reducing valve was set to 0.25 MPa, and the Oken air resistance was measured at a measuring pressure of 0.05 MPa in accordance with JIS P 8117:2009 to measure the air permeability resistance in the cross-sectional direction. Note that a resin layer such as a nylon layer is present on the side of the paper substrate where the nylon layer is to be formed (the liquid-contacting side), preventing air from passing through. Therefore, specifically, a laminated paper from which the thermoplastic resin layer on the side opposite the side where the nylon layer is to be formed (the printed side) of the paper substrate was peeled off was placed in the measuring device, and air was blown into the laminated paper from the paper substrate side, and the number of seconds until the air escaped in the cross-sectional direction was measured.

[0070] (MVR of resin) The MVR of resins (adhesive resin and nylon) was measured in accordance with JIS K 7210:1999 at 280°C and a load of 2.16 kg.

[0071] (peel strength between resins) Laminated paper was cut to a width of 25 mm and a length of 200 mm and subjected to a T-peel test using a Tensilon tensile tester (manufactured by A&D Co., Ltd.). One edge of the laminated paper cut to the specified size was peeled to create a peel initiation point between the resin and the adhesive. The laminate was then fixed to the Tensilon jig and the test was continued at a peel rate of 10 mm per minute until at least 150 mm of the adhesive length had peeled. Peel tests were performed five or more times for each laminated paper, and the average peel force (unit: kN) required to peel the adhesive was calculated from the curve recording at least 100 mm of peel (excluding the first and last 25 mm). The average peel force was calculated using the best-fit method. When the peel strength between the resins was strong, no peel occurred between the resins and the paper substrate was destroyed; therefore, this is indicated as "substrate failure" in Tables 1 and 2. On the other hand, when the peel strength between the resins was slightly poor, peeling progressed between the resins, and the strength was measurable, so the average peel force was recorded.

[0072] [evaluation] (pinhole) The laminated paper obtained in the Examples and Comparative Examples was cut into 150 mm squares, and the thermoplastic resin layer on the nylon side (liquid-contacting side) of the laminated paper was exposed to hot air at the temperatures shown in Tables 1 and 2 for 5 seconds. The laminated paper was then immersed in a Scarlett Moo red dye solution for 1 minute. The laminated paper was then removed from the dye solution and washed with tap water for 1 minute to remove the dye from the surface. Finally, the laminated paper was dried in a dryer. Note that the red dye penetrates into the fibers immediately if there are pinholes in the coating, leaving red dot-shaped marks after drying. Pinholes are typically less than 3 mm in size. Therefore, the degree of formation of red dots less than 3 mm in size was evaluated according to the following criteria. A: Pinholes (red dots less than 3 mm) are 0-1 per cm 2 B: Pinholes (red dots less than 3 mm) 2-3 / cm 2 C: Pinholes (red dots less than 3 mm) 4-7 / cm 2 D: Pinholes (red dots less than 3 mm) 8 or more / cm 2

[0073] (delamination) The peeling between the nylon layer and its adjacent layer (paper substrate layer or first adhesive resin layer) was evaluated using the following method. The laminated paper obtained in the Examples and Comparative Examples was cut into 150 mm squares, and hot air at the temperatures shown in Tables 1 and 2 was applied to the thermoplastic resin layer on the nylon layer side (liquid-contacting side) of the laminated paper for 5 seconds. The laminated paper was then immersed in a Scarlett Moo red dye solution for 1 minute. The laminated paper was then removed from the dye solution and washed with tap water for 1 minute to remove the dye from the surface. Finally, the laminated paper was dried in a dryer. Note that the red dye penetrates into the fibers immediately if there is any blistering of the coating due to delamination, leaving a mark in the shape of a red dot after drying. The blistering is usually 3 mm or larger. Therefore, the degree of red dot formation of 3 mm or larger was evaluated according to the following criteria. The blistering evaluation was performed on 10 sheets of the same sample. A grade of C or higher according to the following criteria was considered acceptable. A: 0 swellings (red dots 3mm or larger) out of 10 B: 1 blister (red dot over 3mm) out of 10 sheets C: Blisters (red dots over 3mm) 2 out of 10 D: 3 or more swellings (red dots 3mm or larger) out of 10 sheets

[0074] (Exercise test) During printing, laminated paper travels along the curved surfaces of various rollers under tension. The direction of curvature of the laminated paper constantly changes from front to back, resulting in the laminated paper being subjected to a tensile stress. Therefore, even if the laminated paper meets the strength criteria before printing, the tensile stress experienced by the laminated paper during printing can reduce its strength, potentially resulting in peeling during or at a later stage. Therefore, the resistance to tensile stress during printing was evaluated using the following method. Laminated paper was cut into pieces 25 mm wide and 300 mm long. Using the measuring device (squeezing tester) described in JP 2010-127623, a tensile stress test was conducted at a load of 10 kg for the number of times shown in Tables 1 and 2. The presence or absence of peeling was visually confirmed. Laminated paper that showed no peeling in this evaluation is particularly resistant to tensile stress during printing and has excellent processability.

[0075] (Crack test) The occurrence of cracks (cracks on the surface of the score line) when the score line was folded was evaluated using the following method. A laminated paper was placed on top of the score lined underlay board and fixed so that the liquid-contacting side of the laminated paper (the side with the nylon layer) was the fixing surface to the underlay board (hereinafter, the laminate of the underlay board and the laminated paper is referred to as the test sample). The size of the underlay board was the same as that of the laminated paper, measuring 150 mm x 150 mm. The score line (also referred to as the center line) was a line drawn passing through the midpoint of one side of the underlay board and the center of the underlay board, and was 15 cm long. The test sample was folded along the crease so that the printed surface of the laminated paper was on the crest side of the crease and the liquid-contacting surface of the laminated paper was on the valley side of the crease. The folded test sample had two planes, including the crease, at a certain angle (in other words, the test sample was V-shaped with the crease as the boundary). Furthermore, there was still room for further folding of the test sample. Next, the test sample was placed on a table surface so that one of the two planes containing the crease of the folded test sample was parallel to the table surface. Next, tape was applied to one of the two flat surfaces in a folded state, securing three edges of the surface to the table. Next, a metal roller weighing 13 kg and measuring at least 15 cm wide was placed on the table so that its width (length) was parallel to the crease in the test sample. The roller was then rolled over the table, passing over the test sample. The test sample was pressed down from the crease side, and the roller was passed over the entire width of the test sample. Furthermore, only force was applied in the direction of travel while the roller was moving. The test sample, which still had room to be folded, was further folded by the operation of the roller. The test sample was then released from its fixed position, and the laminated paper was removed. The total length (TL) of the folded laminated paper, and the length of the cracked portion (BL) if the laminated paper was cracked along the score line, were measured. The ratio of the length of the cracked portion of the laminated paper to the total length of the folded laminated paper (BL / TL) x 100 [%] was calculated and evaluated according to the following criteria. Grades C and D in this evaluation indicate that there were many cracks on the surface when the score line was folded, and condensation could penetrate into the paper base through the cracks, resulting in a decrease in strength, making this undesirable for practical use. A: BL / TL is 0% to 25% (no practical problems) B: BL / TL is over 25% and 50% or less (no practical problems) C: BL / TL is over 50% and 75% or less (problems in practical use) D: BL / TL exceeds 75% (problems in practical use)

[0076] Example 1 (Paper base material) As pulp raw materials, 60 parts of LBKP and 40 parts of NBKP were beaten using a double-disc refiner (Canadian Standard Freeness (CSF) of 470 mL for LBKP after beating, and CSF of 660 mL for NBKP after beating) to obtain a pulp slurry. An internal strength agent, an internal sizing agent, and a wet strength agent were added to the pulp (dry mass) in the obtained pulp slurry to prepare a paper stock. This paper stock was used to make a five-layer paper using a multi-layer Fourdrinier paper machine. During the papermaking process, interlayer starch was sprayed between each layer using an interlayer spray, and after the five layers were combined, a surface strength agent and an adhesive aid were applied to both sides of the paper base, and the paper was calendered to a basis weight of 333 g / m 2 , density is 0.757g / cm 3 The paper substrate thus obtained had different smoothness on the front and back sides. The measurement results for the smoothness of the less smooth side (liquid-contacting side) are shown in Table 1. (laminated paper) LDPE (low-density polyethylene) was laminated onto the smooth side (printing side) of the resulting paper substrate using the melt-extrusion lamination method. On the less smooth side (liquid-contacting side) of the resulting paper substrate, the adhesive resin (maleic anhydride-modified polyethylene A) that constitutes the first adhesive resin layer, the nylon layer (nylon A, nylon type: nylon 6), the adhesive resin (maleic anhydride-modified polyethylene A) that constitutes the second adhesive resin layer, and the LDPE that constitutes the thermoplastic resin layer were laminated using the melt-extrusion lamination method from the paper substrate side to obtain laminated paper. The measurement and evaluation results are shown in Table 1.

[0077] Example 2 Laminated papers were obtained in the same manner as in Example 1, except that the thickness of the first adhesive resin layer was changed as shown in Table 1. The measurement results and evaluation results are shown in Table 1.

[0078] Example 3 Laminated paper was obtained in the same manner as in Example 1, except that the first adhesive resin and the second adhesive resin were changed to maleic anhydride-modified polyethylene B and the thickness of the first adhesive resin layer was changed as shown in Table 1. The measurement results and evaluation results are shown in Table 1.

[0079] Examples 4, 5 and 14 Laminated papers were obtained in the same manner as in Example 1, except that the thickness of the nylon layer was changed as shown in Table 1. The measurement results and evaluation results are shown in Table 1.

[0080] Example 6 (Paper base material) A paper base was prepared in the same manner as in Example 1, except that the CSF of the beaten LBKP was 510 mL and the CSF of the beaten NBKP was 690 mL, and the pressing conditions were adjusted to obtain a paper base with a basis weight of 325 g / m. 2 , density 0.730g / cm 3 A paper substrate of 100g was obtained. (laminated paper) LDPE was laminated onto the smooth side (printing side) of the resulting paper substrate using the melt extrusion lamination method. On the less smooth side (liquid-contacting side) of the resulting paper substrate, a nylon layer (nylon B, nylon type: nylon 6), an adhesive resin (maleic anhydride-modified polyethylene A) constituting the second adhesive resin layer, and LDPE constituting the thermoplastic resin layer were laminated in this order from the paper substrate side using the melt extrusion lamination method to obtain laminated paper. The measurement and evaluation results are shown in Table 1.

[0081] Examples 7 to 9 Laminated papers were obtained in the same manner as in Example 6, except that the thickness of the nylon layer was changed as shown in Table 1. The measurement results and evaluation results are shown in Table 1.

[0082] Example 10 Except for changing the first adhesive resin and the second adhesive resin to maleic anhydride-modified polyethylene C and changing the nylon to nylon C (nylon type: nylon 6), laminated paper was obtained in the same manner as in Example 1. The measurement results and evaluation results are shown in Table 1.

[0083] Example 11 A laminated paper was obtained in the same manner as in Example 1, except that the first adhesive resin and the second adhesive resin were changed to maleic anhydride-modified polyethylene B and the nylon was changed to nylon D (nylon type: nylon 6). The measurement results and evaluation results are shown in Table 1.

[0084] Example 12 Except for changing the first adhesive resin and the second adhesive resin to ethylene / methacrylic acid copolymer, laminated paper was obtained in the same manner as in Example 1. The measurement results and evaluation results are shown in Table 1.

[0085] Example 13 Except for changing the nylon to nylon MXD6, laminated paper was obtained in the same manner as in Example 1. The measurement results and evaluation results are shown in Table 1.

[0086] Example 15 The conditions for the calendaring process were adjusted to a basis weight of 333 g / m 2, density 0.774g / cm 3 Except for obtaining a paper base material of the above formula, a laminated paper was obtained in the same manner as in Example 1. The measurement results and evaluation results are shown in Table 1.

[0087] [Table 1]

[0088] Comparative Example 1 The CSF of the beaten LBKP was changed to 355 mL, and the CSF of the beaten NBKP was changed to 560 mL, and the press conditions were adjusted to a basis weight of 350 g / m 2 , density 0.814g / cm 3 Except for obtaining a paper base material of the above formula, a laminated paper was obtained in the same manner as in Example 1. The measurement results and evaluation results are shown in Table 2.

[0089] Comparative Example 2 The CSF of the beaten LBKP was changed to 510 mL, and the CSF of the beaten NBKP was changed to 700 mL, and the press conditions were adjusted to a basis weight of 320 g / m 2 , density 0.706g / cm 3 Except for obtaining a paper base material of the above formula, a laminated paper was obtained in the same manner as in Example 1. The measurement results and evaluation results are shown in Table 2.

[0090] Comparative Example 3 Except for changing the drying conditions and obtaining a paper base material so that the moisture content of the laminated paper was 8.3% by mass, a laminated paper was obtained in the same manner as in Example 1. The measurement results and evaluation results are shown in Table 2.

[0091] Comparative Example 4 Except for changing the drying conditions and obtaining a paper base material so that the moisture content of the laminated paper was 3.9% by mass, a laminated paper was obtained in the same manner as in Example 1. The measurement results and evaluation results are shown in Table 2.

[0092] Comparative Example 5 A laminated paper was obtained in the same manner as in Example 6, except that the paper base material obtained in Comparative Example 2 was used. The measurement results and evaluation results are shown in Table 2.

[0093] Comparative Example 6 A laminated paper was obtained in the same manner as in Example 6, except that the drying conditions were changed to obtain a paper base material so that the moisture content of the laminated paper was 8.3% by mass. The measurement results and evaluation results are shown in Table 2.

[0094] Comparative Example 7 Except for changing the drying conditions and obtaining a paper base material so that the moisture content of the laminated paper was 3.9% by mass, a laminated paper was obtained in the same manner as in Example 6. The measurement results and evaluation results are shown in Table 2.

[0095] [Table 2]

[0096] As can be seen from Tables 1 and 2, laminated paper having an air resistance in the cross-sectional direction of 350 seconds or more and 2000 seconds or less and a moisture content of 4.0 mass% or more and 8.0 mass% or less suppressed delamination and had excellent processability. On the other hand, the laminated paper of Comparative Example 1, which had an air resistance in the cross-sectional direction of more than 2000 seconds, was particularly prone to delamination. The laminated papers of Comparative Examples 2 and 5, which had an air resistance in the cross-sectional direction of less than 350 seconds, experienced delamination in the ironing test and were poor in processability. The laminated paper of Comparative Example 3, which had a moisture content of more than 8.0% by mass, was prone to pinholes and delamination. The laminated papers of Comparative Examples 4 and 7, which had a moisture content of less than 4.0% by mass, experienced delamination in the ironing test and also had many creases in the crease test, indicating poor processability. The laminated paper of Comparative Example 6, which had a moisture content of more than 8.0% by mass, was prone to pinholes and delamination. [Industrial Applicability]

[0097] The laminated paper of the present invention is inhibited from delaminating and has excellent processability, and can be suitably used for liquid containers such as paper cartons, paper cups, and aseptic containers, paper containers such as foam cups, ice cups, insulated cups, and packaging containers, as well as packaging materials, insulating materials, etc.

Claims

1. A laminated paper having a paper substrate, an optional first adhesive resin layer, a nylon layer, a second adhesive resin layer, and a thermoplastic resin layer in this order, The air resistance in the cross-sectional direction is 350 seconds or more and 2000 seconds or less, The moisture content is 4.0% by mass or more and 8.0% by mass or less. Laminated paper.

2. 2. The laminated paper according to claim 1, wherein the smoothness of the paper substrate on the side where the nylon layer is to be provided is 20 seconds or less.

3. 3. The laminated paper according to claim 1, wherein the nylon layer has a thickness of 3 μm or more and 35 μm or less, and the first adhesive resin layer and the second adhesive resin layer each have a thickness of 15 μm or less.

4. The absolute value of the difference between the melt volume rate of the nylon constituting the nylon layer and the melt volume rate of the adhesive resin constituting the first adhesive resin layer, measured in accordance with JIS K 7210:1999 at 280°C and a load of 2.16 kg, is 0 cm ３ / 100cm for more than 10 minutes ３ 3. The laminated paper according to claim 1, wherein the drying time is 10 minutes or less.

5. The melt volume rate of the nylon constituting the nylon layer, measured in accordance with JIS K 7210:1999 at 280°C and a load of 2.16 kg, is 10 cm ３ / 500cm for more than 10 minutes ３ / 10 minutes or less, and the melt volume rate of the adhesive resin constituting the first adhesive resin layer is 5 cm ３ / 500cm for more than 10 minutes ３ 3. The laminated paper according to claim 1, wherein the drying time is 10 minutes or less.

6. 3. The laminated paper according to claim 1, further comprising a thermoplastic resin layer on the side of the paper substrate opposite to the side on which the nylon layer is provided.

7. 3. The laminated paper according to claim 1, which is for use in a liquid container.

8. A liquid container made using the laminated paper according to claim 1 or 2.

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