JP2022119747A - Base paper for liquid containers - Google Patents

Abstract

An object of the present invention is to provide a base paper for liquid containers having excellent edgewicking resistance to detergents containing amino acid-based surfactants. A base paper for liquid containers having edgewicking resistance to a cleaning agent containing an amino acid-based surfactant, wherein the base paper is resistant to an aqueous solution containing 2.0% by mass of the cleaning agent and 4.0% by mass of ethanol at 23°C. Base paper for liquid containers, which has an edgewick value of 3.5 g/1000 mm 2 or less. [Selection figure] None

Description

The present invention relates to base paper for liquid containers.

Conventionally, plastic products have been used as various containers for detergents, beverages, foods, etc. However, in order to reduce the burden on the environment, it is desired to switch to paper products.
For example, Patent Document 1 discloses a paper container in which both ends of a laminated sheet having a paper base material and a sealant layer made of a thermoplastic resin on at least the inner surface are fused to form a tubular shape, and both ends of the tubular shape are closed. describes a paper container having a break line that allows the cylindrical body and top to be folded and crushed to separate the top and body after the contents of the paper container are discharged. .

JP 2019-085137 A

In the paper container described in Patent Literature 1, a sealant layer made of a thermoplastic resin is provided on both sides of the paper substrate, which is insufficient in terms of reducing the environmental load.
An object of the present invention is to provide a base paper for liquid containers which is excellent in edgewick resistance to detergents containing amino acid surfactants. The base paper for liquid containers of the present invention comprises a paper base material and contributes to reducing the environmental load.

The present inventors have found that by setting the edgewick value in a specific measurement method to a specific value or less, it is possible to obtain a base paper having excellent edgewick resistance to detergents containing amino acid-based surfactants. The present invention relates to the following <1> to <13>.
<1> Base paper for liquid containers having edgewicking resistance to detergents containing amino acid-based surfactants, which is resistant to an aqueous solution containing 2.0% by mass of the detergent and 4.0% by mass of ethanol at 23°C Base paper for liquid containers, having an edgewick value of 3.5 g/1000 mm ² or less.
<2> Base paper for liquid containers having edgewicking resistance to detergents containing amino acid surfactants, which is 23 in an aqueous solution containing 2.0% by mass of betaine lauryldimethylaminoacetate and 4.0% by mass of ethanol. Base paper for liquid containers, having an edgewick value of 1.5 g/1000 mm ² or less at °C.
<3> The base paper for liquid containers according to <1> or <2>, wherein the base paper contains cationized starch as a paper strength enhancer.
<4> The base paper for liquid containers according to any one of <1> to <3>, wherein the base paper contains an alkylketene dimer as a sizing agent.
<5> The base paper for liquid containers according to any one of <1> to <4>, further comprising an anionic paper strength enhancer as the paper strength enhancer.
<6><1> to <5>, wherein the ratio of longitudinal elongation (%) to lateral elongation (%) of the base paper (longitudinal elongation/lateral elongation) is 0.30 or more The base paper for liquid containers according to any one of the above.
<7> The liquid according to any one of <1> to <6>, wherein the geometric mean of the longitudinal elongation (%) and the lateral elongation (%) of the base paper is 3.0% or more. Base paper for containers.
<8> Any one of <1> to <7>, wherein the geometric mean of the specific tensile strength in the machine direction and the specific tensile strength in the transverse direction of the base paper is 30.0 N m / g or more. Base paper for liquid containers.
<9> The base paper for liquid containers according to any one of <1> to <8>, wherein the base paper is a multi-layered paper having 3 to 7 layers.
<10> The base paper is multi-layered paper with three or more layers, and the mass ratio (NBKP/LBKP) of softwood bleached kraft pulp (NBKP) to hardwood bleached kraft pulp (LBKP) in the pulp constituting the surface layer is 10/90 or more and 60/40 or less, the content of bleached hardwood kraft pulp (LBKP) in the pulp constituting the middle layer is 50% by mass or more and 100% or less by mass, and the bleached hardwood in the pulp constituting the back layer The base paper for liquid containers according to any one of <1> to <9>, wherein the content of kraft pulp (LBKP) is 50% by mass or more and 100% by mass or less.
<11> The base paper for liquid containers according to any one of <1> to <10>, wherein the density of the bleached hardwood kraft pulp (LBKP) is lower than the density of the bleached softwood kraft pulp (NBKP).
<12> The mass ratio (NBKP/LBKP) of softwood bleached kraft pulp (NBKP) to hardwood bleached kraft pulp (LBKP) in the pulp constituting the surface layer is 30/70 or more and 50/50 or less, and constitutes the middle layer The liquid base paper according to any one of <1> to <11>, wherein the content of bleached hardwood kraft pulp (LBKP) in the pulp is 53% by mass or more and 98% by mass or less.
<13> The Canadian Standard Freeness (CSF) of the pulp constituting the back layer is greater than the Canadian Standard Freeness (CSF) of the pulp constituting the surface layer and the pulp constituting the intermediate layer, and the back layer <1> ~ The base paper for liquid containers according to any one of <12>.

According to the present invention, it is possible to provide base paper for liquid containers having edgewick resistance to detergents containing amino acid surfactants. The base paper for liquid containers of the present invention comprises a paper base material and contributes to reducing the environmental load.

[Base paper for liquid containers]
The first base paper for liquid containers of the present invention (hereinafter, "base paper for liquid containers" may be simply referred to as "base paper") is a cleaning agent containing an amino acid-based surfactant (hereinafter, also simply referred to as "cleaning agent"). ), the edgewick value at 23° C. for an aqueous solution containing 2.0% by mass of the detergent and 4.0% by mass of ethanol is 3.5 g/1000 mm ² or less is.
Further, the second base paper for liquid containers of the present invention is a base paper for liquid containers having edgewick resistance to detergents containing amino acid surfactants, comprising 2.0% by mass of betaine lauryldimethylaminoacetate, ethanol Edgewick value at 23° C. for an aqueous solution containing 4.0% by mass is 1.5 g/1000 mm ² or less.
ADVANTAGE OF THE INVENTION According to this invention, the base paper for liquid containers excellent in the edgewick resistance with respect to the detergent containing an amino acid type surfactant can be provided.
In the present invention, instead of measuring the edgewick value for the detergent itself, the edgewick value for an aqueous solution containing a specific amount of the detergent and ethanol, or the edgewick value for an aqueous solution containing specific amounts of betaine lauryldimethylaminoacetate and ethanol It has been clarified that the base paper has excellent edgewick resistance to detergents by setting the edgewick value to a specific value or less. Base paper with excellent edgewicking resistance to detergents or aqueous solutions containing betaine lauryldimethylaminoacetate and ethanol also has excellent edgewicking resistance to detergents containing amino acid-based surfactants. became.
Incidentally, conventional water-resistant paper does not necessarily have excellent edgewick resistance to detergents.
The present invention will be described in more detail below. In the following description, the term "base paper for liquid containers" or "base paper" simply means the first base paper for liquid containers of the present invention and the second base paper for liquid containers of the present invention.

<Edgewick value>
The first base paper for liquid containers of the present invention has an Edgewick value of 3.5 g/23° C. for an aqueous solution containing 2.0% by mass of a detergent containing an amino acid surfactant and 4.0% by mass of ethanol. 1000 mm ² or less. The Edgewick value is preferably 3.2 g/1000 mm ² or less, more preferably 3.0 g/1000 mm ² or less, even more preferably 2.8 g/1000 mm ² or less, and even more preferably 2.5 g/1000 mm ² or less. Particularly preferably, it is 2.0 g/1000 mm ² or less.
The Edgewick value is measured by the method described in Examples.

The second base paper for liquid containers of the present invention contains 2.0% by mass of betaine lauryldimethylaminoacetate and 4.0% by mass of ethanol from the viewpoint of obtaining excellent edgewicking resistance to detergents containing amino acid surfactants. The edgewick value for an aqueous solution containing is 1.5 g/1000 mm ² or less. The edgewick value is preferably 1.4 g/1000 mm ² or less, more preferably 1.2 g/1000 mm ² or less, even more preferably 0.8 g/1000 mm ² or less, and particularly preferably 0.4 g/1000 mm ² or less. .

(Amino acid surfactant)
The base paper for liquid containers of the present invention has edgewick resistance to detergents containing amino acid surfactants.
Amino acid-based surfactants are N-acyl amino acids obtained by N-acylating an amino acid using an amino acid as a raw material; salts, esters, and amides of N-acyl amino acids; higher alcohol esters of amino acids; -Alkyl amino acids and the like are exemplified.
In addition, compounds in which an amino acid skeleton is introduced into the molecule by reacting an N-alkylamine as a starting material with monochloroacetic acid, an acrylic acid ester, maleic acid, etc., or their N-methylated products and N,N-dimethylated products. may be In addition, the N-alkyl moiety may further have a long-chain fatty acid amidoalkyl group.
The number of carbon atoms in the alkyl group introduced as the N-acyl group or N-alkyl group is preferably 4 or more, more preferably 8 or more, preferably 22 or less, more preferably 18, from the viewpoint of imparting hydrophobicity. It is below.
The amino acid-based surfactant may be a cationic surfactant, an anionic surfactant, or an amphoteric surfactant, preferably an anionic surfactant or an amphoteric surfactant.

Specific examples of N-acylamino acids or salts thereof include N-capryloylglutamic acid, N-2-ethylhexanoylglutamic acid, N-lauroylglutamic acid, N-myristoylglutamic acid, N-palmitoylglutamic acid, N-stearoylglutamic acid, N- Cocoyl glutamic acid, N-palm oil fatty acid acyl glutamic acid, N-beef tallow fatty acid acyl glutamic acid, N-lauroyl aspartic acid, N-myristoyl aspartic acid, N-palmitoyl aspartic acid, N-stearoyl aspartic acid, N-cocoyl aspartic acid, N- Cocoylalanine, N-lauroylmethylalanine, N-myristoylmethylalanine, N-cocoylmethylalanine, N-lauroylsarcosine, N-myristoylsarcosine, N-cocoylsarcosine, and their sodium salts, potassium salts, arginine salts, tri Ethanolamine salts are exemplified.
In addition, betaine octyldimethylaminoacetate, betaine lauryldimethylaminoacetate, betaine myristyldimethylaminoacetate, betaine cetyldimethylaminoacetate, etc., betaine coconut amidopropyl betaine, betaine coconut alkyldimethylaminoacetate, betaine coconut amidodimethylpropyl betaine , betaine aminoacetate type amphoteric surfactants such as betaine lauramidopropyldimethylaminoacetate.

(cleaning fee)
The detergent containing an amino acid-based surfactant is not particularly limited as long as it contains the amino acid-based surfactant described above. Specifically, liquid cleansers such as hair cleansers (shampoos) and skin cleansers (body shampoos, facial cleansers) are preferred, and among these, hair cleansers (shampoos) are particularly preferred.

<Structure of base paper for liquid containers>
The base paper for liquid containers of the present invention is preferably multi-layered paper having a surface layer, a back layer, and at least one middle layer. The base paper is preferably three-layered or more paper consisting of at least a surface layer, a back layer and an intermediate layer. On the other hand, it is preferable that the paper is made of 7 layers or less in which the middle layer has a multi-layer structure. It is more preferable that the paper has 3 layers or more and 6 layers or less. It is preferable that the middle layer has a multi-layer structure according to the basis weight of the base paper. When the middle layer has a multi-layer structure, the layer in contact with the surface layer is also referred to as the surface layer. The paper material used for the lower surface layer may be the same as or different from that of the middle layer excluding the lower surface layer.
The pulp constituting the base paper includes chemical pulp such as bleached hardwood kraft pulp (LBKP) and bleached softwood kraft pulp (NBKP); groundwood pulp (GP), pressure groundwood pulp (PGW), refiner mechanical pulp (RMP), thermo Mechanical pulp such as mechanical pulp (TMP), chemi-thermomechanical pulp (CTMP), chemi-mechanical pulp (CMP), chemi-grand pulp (CGP); waste paper pulp; non-wood fiber pulp such as kenaf, bagasse, bamboo, cotton; Pulp etc. are mentioned. These pulps may be used individually by 1 type, and may be used in combination of 2 or more type.
Among these, it is preferable to use bleached hardwood kraft pulp (LBKP) and bleached softwood kraft pulp (NBKP) in combination, and in addition, recycled pulp such as waste paper may be contained as necessary.

As a preferred form of the present embodiment, the base paper for liquid containers is three-layered or more multi-layered paper having a surface layer, a back layer and at least one or more middle layers, and hardwood in the pulp constituting the surface layer The mass ratio of softwood bleached kraft pulp (NBKP) to bleached kraft pulp (LBKP) (NBKP/LBKP) is 10/90 or more and 60/40 or less, and the content of hardwood bleached kraft pulp (LBKP) in the pulp constituting the middle layer The content of hardwood bleached kraft pulp (LBKP) in the pulp constituting the back layer is 50% by mass or more and 100% by mass or less.
By blending an appropriate amount of NBKP as the pulp constituting the surface layer, it is possible to secure the paper strength necessary for the base paper for liquid containers, and to suppress the occurrence of creases during processing, which is preferable. From the above viewpoint, the mass ratio of NBKP to LBKP (NBKP/LBKP) in the pulp constituting the surface layer is preferably 10/90 or more, more preferably 15/85 or more, still more preferably 20/80 or more, and particularly preferably is 25/75 or more, most preferably 30/70 or more, and preferably 60/40 or less, more preferably 55/45 or less, even more preferably 50/50 or less, particularly preferably 45/55 or less .
In addition, it is preferable that the content of LBKP in the pulp constituting the intermediate layer and the back layer is 50% by mass or more, because the intermediate layer and the back layer can be easily crushed and workability can be improved.
From the above viewpoint, the content of LBKP in the pulp constituting the middle layer is preferably 50% by mass or more, more preferably 53% by mass or more, still more preferably 55% by mass or more, and even more preferably 60% by mass or more, especially It is preferably 65% by mass or more and 100% by mass or less, preferably 98% by mass or less, more preferably 90% by mass or less, still more preferably 85% by mass or less, and particularly preferably 83% by mass or less. .
In addition, the content of LBKP in the pulp constituting the back layer is preferably 50% by mass or more, more preferably 55% by mass or more, still more preferably 60% by mass or more, particularly preferably 65% by mass or more, and It is 100% by mass or less.

The content of NBKP in the pulp that constitutes the surface layer is preferably equal to or greater than the content of NBKP in the pulp that constitutes the middle layer, from the viewpoint of suppressing the occurrence of crease cracks in the surface layer and from the viewpoint of improving workability. .
In addition, the content of NBKP in the pulp constituting the surface layer is equal to or greater than the content of NBKP in the pulp constituting the back layer, from the viewpoint of suppressing the occurrence of crease cracks in the surface layer and improving workability. preferable from this point of view.
The relationship between the NBKP content in the pulp forming the middle layer and the NBKP content in the pulp forming the back layer is not particularly limited.

The density of the bleached hardwood kraft pulp (LBKP) is preferably lower than the density of the bleached softwood kraft pulp (NBKP).
By making the density of LBKP smaller than that of NBKP, the density of the middle layer and the back layer can be made smaller than that of the surface layer. It is preferable because it becomes easier and workability improves.
The difference between the density of LBKP and the density of NBKP (density of NBKP - density of LBKP) is preferably 0.01 g/ ^cm3 or more, more preferably 0.01 g/cm3 or more when the Canadian Standard Freeness (CSF) of the pulp component is 400 mL. is 0.02 g/cm ³ or more, more preferably 0.03 g/cm ³ or more, and is preferably 0.20 g/cm ³ or less, more preferably 0.10 g/cm ³ or less, and still more preferably 0.20 g/cm 3 or less. 08 g/cm ³ or less.
Also, the density of LBKP is preferably 0.50 g/cm ³ or more, more preferably 0.55 g/cm ³ or more, still more preferably 0.60 g/cm ³ or more, and preferably 1.00 g/cm 3 or more. ³ or less, more preferably 0.80 g/cm ³ or less, still more preferably 0.70 g/cm ³ or less.
The densities of LBKP and NBKP are measured by the method described in Examples.

The beating degree of the pulp is not particularly limited, but is preferably 200 mL or more, more preferably 300 mL or more, still more preferably 330 mL or more, and preferably 650 mL or less, in terms of Canadian Standard Freeness (CSF). It is more preferably 600 mL or less, still more preferably 550 mL or less, and particularly preferably 500 mL or less. If the CSF of the pulp is within the above range, the edgewick resistance is excellent, and the required paper strength can be easily obtained when the base paper is processed into a container for use. Further, when the CSF is 200 mL or more, the interfiber bond does not become too high, and good processability can be maintained in the bending process in the molding process. Moreover, if it is 650 mL or less, the smoothness of the paper surface becomes favorable, and printability can be maintained.
CSF is measured according to JIS P 8121-2:2012 "Pulp - Freeness Test Method - Part 2: Canadian Standard Freeness Method".

It is also preferred that the Canadian Standard Freeness (CSF) of the pulp that makes up the back layer is greater than the Canadian Standard Freeness (CSF) of the pulp that makes up the surface layer and the pulp that makes up the middle layer. By making the CSF of the pulp composing the backing layer larger than the CSF of the pulp composing the surface layer and the pulp composing the middle layer, the backing layer has a lower density and is more likely to be crushed. It is preferable because the back layer is easily crushed and the workability is excellent.
The difference between the CSF of the pulp constituting the back layer and the CSF of the pulp constituting the surface layer or the pulp constituting the middle layer is preferably 150 mL or less, more preferably 120 mL or less, and still more preferably 100 mL or less. Yes, and preferably 10 mL or more, more preferably 30 mL or more, and even more preferably 50 mL or more.

Examples of additives to the base paper include pH adjusters, dry strength agents (polyacrylamide, starch, etc.), wet strength agents (polyamide polyamine epichlorohydrin resin, melamine-formaldehyde resin, urea-formaldehyde resin, etc.). any), internal sizing agent (rosin type, alkyl ketene dimer, etc.), fixing agent (sulfuric acid aluminum, etc.), bulking agent, drainage retention agent, antifoaming agent, filler (calcium carbonate, talc, etc.), dye, etc. are mentioned. These additives may be used singly or in combination of two or more.

Examples of pH adjusters include sodium hydrogen carbonate and sodium hydroxide, with sodium hydrogen carbonate being preferred.
As the dry paper strength enhancer, any of an anionic paper strength enhancer, a cationic paper strength enhancer, and an amphoteric paper strength enhancer may be used, and two or more thereof may be used in combination. Among these, anionic paper strength enhancers and cationic paper strength enhancers are preferred, and it is more preferable to use at least cationic paper strength enhancers. Combined use is more preferable.
Examples of cationic paper strength agents include cationic starch and Hoffmann-modified polyacrylamide resin, and at least cationic starch is preferably used. Examples of Hoffmann-modified polyacrylamide resins include DH4160 and DH4162 (manufactured by Seiko PMC Co., Ltd.).
Examples of anionic paper strength agents include anionic polyacrylamide resins, such as Polystrone 117 (manufactured by Arakawa Chemical Industries, Ltd.), Hermide C-10, and Hermide B-15 (manufactured by Harima Chemicals Group Co., Ltd.). ) and the like are exemplified.
Amphoteric polyacrylamide resins such as DS4326 and DS4433 (manufactured by Seiko PMC Co., Ltd.) are exemplified as amphoteric paper strength agents.
The dry paper strength agent preferably contains at least cationic starch, and more preferably contains an anionic paper strength agent in addition to the cationic starch.

Polyamide polyamine epichlorohydrin resin (PAE) is preferred as the wet strength agent.
Examples of the internal sizing agent include alkylketene dimer and rosin, and among these, alkylketene dimer is preferred.
Examples of bulking agents include inorganic bulking agents and organic bulking agents. Examples of organic bulking agents include fatty acid ester bulking agents and fatty acid amide bulking agents. Among these, fatty acid amide-based bulking agents are preferable from the viewpoint of being able to impart sizing properties.
The content of the additive is not particularly limited, and may be within a commonly used range.

(basis weight)
Although the basis weight of the base paper for liquid containers is not particularly limited, it is preferably 180 g/m ² from the standpoint of easily obtaining the required paper strength and excellent workability when the base paper is processed into a container and used. above, more preferably 200 g/m ² or more, still more preferably 220 g/m ² or more, particularly preferably 235 g/m ² or more, and preferably 450 g/m ² or less, more preferably 400 g/m ² or less, More preferably, it is 350 g/m ² or less.
The basis weight of base paper is measured according to JIS P 8124:2011.

(paper thickness)
The thickness of the base paper for liquid containers is not particularly limited, but when the base paper is processed into a container and used, the necessary paper strength can be easily obtained, and from the viewpoint of excellent processability, it is preferably 200 μm or more, or more. It is preferably 230 μm or more, more preferably 250 μm or more, and preferably 450 μm or less, more preferably 400 μm or less, still more preferably 350 μm or less.
The paper thickness of the base paper is measured according to JIS P 8118:2014. Also, the paper thickness of the base paper can be calculated from the density and basis weight.

(density)
Although the density of the base paper for liquid containers is not particularly limited, it is preferably 0.70 g/cm from the viewpoint that the necessary paper strength can be easily obtained when the base paper is processed and used for containers, and the processability is excellent. ³ or more, more preferably 0.75 g/cm ³ or more, still more preferably 0.80 g/cm ³ or more, and preferably 1.5 g/cm ³ or less, more preferably 1.2 g/cm ³ or less, More preferably, it is 1.0 g/cm ³ or less.

(stretch)
The base paper for liquid containers has a ratio of longitudinal elongation (%) to lateral elongation (%) (longitudinal elongation/lateral directional elongation) is preferably 0.30 or more, more preferably 0.35 or more, and still more preferably 0.40 or more. Although the upper limit is not particularly limited, it is preferably 0.70 or less, more preferably 0.65 or less, and still more preferably 0.60 or less from the viewpoint of production.
The vertical direction means the papermaking direction, and the horizontal direction means the direction orthogonal to the papermaking direction.
The elongation of the liquid container base paper is measured according to JIS P 8113:2006.

The longitudinal elongation of the base paper for liquid containers is preferably 1.5% or more, more preferably 2.0% or more, from the viewpoint of making the base paper more excellent in edgewick resistance and suppressing cracking during molding. On the other hand, it is preferably 6.0% or less, more preferably 5.0% or less, still more preferably 4.0% or less.
In addition, the geometric mean of the longitudinal elongation and the transverse elongation is preferably 3.0% or more, more preferably 3.0% or more, from the viewpoint of obtaining a base paper that is resistant to edgewicking, cracking during molding is suppressed, and has excellent workability. It is 3.2% or more, more preferably 3.5% or more, and even more preferably 3.8% or more. On the other hand, it is preferably 6.0% or less, more preferably 5.5% or less, still more preferably 5.0% or less.

(Specific tensile strength)
Base paper for liquid containers has a ratio of the vertical specific tensile strength (N m/g) to the horizontal specific tensile strength (N m/g) (specific tensile strength in the vertical direction / specific tensile strength in the horizontal direction). strength) is preferably 4.0 or less, more preferably 3.5 or less, still more preferably 3.0 or less, and more preferably 3.0 or less, from the viewpoint of obtaining a base paper that suppresses edgewick resistance and cracking during molding and has excellent workability. More preferably 2.5 or less, particularly preferably 2.3 or less, and the lower limit is not particularly limited, but preferably 1.0 or more, more preferably 1.2 or more, further preferably 1.4 or more, Even more preferably, it is 1.6 or more.
The specific tensile strength (N·m/g) is measured according to JIS P 8113:2006, and is the value obtained by dividing the tensile strength by the basis weight.

The specific tensile strength in the longitudinal direction of the base paper for liquid containers is preferably 50 N·m/g or more, more preferably 60 N·m, from the viewpoint of obtaining a base paper that is resistant to edgewicking, cracking during molding is suppressed, and has excellent workability. /g or more, more preferably 70 N·m/g or more, and preferably 100 N·m/g or less, more preferably 90 N·m/g or less. Here, the specific tensile strength is a value obtained by dividing each tensile strength by the basis weight.
In addition, the geometric mean of the specific tensile strength in the longitudinal direction (N m / g) and the specific tensile strength in the transverse direction (N m / g) suppresses edgewick resistance and cracking during molding, improving workability. From the viewpoint of obtaining excellent base paper, it is preferably 70.0 N·m/g or less, more preferably 65.0 N·m/g or less, still more preferably 60.0 N·m/g or less, and preferably 30. It is 0 N·m/g or more, more preferably 40.0 N·m/g or more, still more preferably 45.0 N·m/g or more, and particularly preferably 50.0 N·m/g or more.

(stiffness)
The longitudinal stiffness (mN·m) of the base paper for liquid containers is preferably 3.0 mN·m or more, more preferably 5.0 mN·m or more, more preferably 5.0 mN·m or more, from the viewpoint of obtaining a base paper excellent in workability by suppressing edge wicking resistance and body swelling. It is 0 mN·m or more, more preferably 6.0 mN·m or more, and even more preferably 6.7 mN·m or more. The upper limit of the longitudinal rigidity (mN·m) of the base paper for liquid containers is not particularly limited, and may be appropriately adjusted depending on the size of the container, suitability for creasing, and the like.
The stiffness (mN·m) of base paper for liquid containers is measured according to JIS P 8143:2009.

The ratio of the longitudinal stiffness (mN・m) to the lateral stiffness (mN・m) of the base paper for liquid containers (vertical stiffness/lateral stiffness) suppresses edgewicking resistance and bulging. From the viewpoint of obtaining a base paper with excellent processability, it is preferably 1.2 or more, more preferably 1.4 or more, still more preferably 1.6 or more, and preferably 5.0 or less, more preferably 4.0. It is 0 or less, more preferably 3.5 or less, even more preferably 3.0 or less, and particularly preferably 2.5 or less.

(Smoother smoothness)
The base paper for liquid containers preferably has a smoother smoothness of 75 kPa or less, more preferably 70 kPa or less, still more preferably 60 kPa or less, from the viewpoint of obtaining a smooth surface with excellent printability, and Although the lower limit is not particularly limited, it is preferably 10 kPa or more, more preferably 20 kPa or more, and still more preferably 30 kPa or more from the viewpoint of ease of production. The Smoother smoothness of the base paper is determined according to JAPAN TAPPI No. 5:2000.
Further, the surface of the base paper for liquid containers means the outer side, that is, the surface that becomes the visible side when used as a container.

(ratio of bending resistance)
The ratio (front/back) of the bending resistance when the base paper for liquid containers is folded to the surface layer side and the bending resistance when it is folded to the back layer side is 1.00 or more in the longitudinal direction and the lateral direction. , is preferable from the viewpoint of being excellent in processability to a liquid container.
The bending resistance ratio (front/back) is more preferably 1.01 or more, still more preferably 1.05 or more, and particularly preferably 1.10 or more, and the upper limit is not particularly limited. From the viewpoint of sexuality, it is preferably 1.20 or less, more preferably 1.15 or less.
Preferably, at least one of the longitudinal direction and the lateral direction satisfies the preferable value of the bending resistance, and more preferably the above preferable range is satisfied in both the longitudinal direction and the lateral direction.
The bending resistance can be adjusted by adjusting the ratio of the pulp constituting the surface layer, middle layer and back layer, the density of the LBKP and NBKP contained, the CSF of the pulp, and the like.
Bending resistance is measured by the method described in Examples.

[Method for producing base paper for liquid containers]
As a method for producing the base paper for liquid containers, there is a method of making paper stock containing pulp. The paper material may further contain additives. Examples of the additive include those listed above.
Stock can be prepared by adding additives to the pulp slurry.
Pulp slurry is obtained by beating pulp in the presence of water. The pulp beating method and beating apparatus are not particularly limited, and may be the same as known beating methods and beating apparatus.
The content of pulp in the stock is not particularly limited, and may be within a range commonly used. For example, it is 60% by mass or more and less than 100% by mass with respect to the total mass of the stock (solid content).

Papermaking of stock can be carried out by a conventional method. For example, there is a method in which a paper stock is cast on a wire or the like, dewatered to obtain a wet paper web, a plurality of wet paper webs are stacked as necessary, and this single-layer or multi-layer wet paper web is pressed and dried. . At this time, when a plurality of wet paper webs are not stacked, a single-layer paper is obtained, and when a plurality of wet paper webs are stacked, a multi-layer paper is obtained.
In the present invention, it is preferable that the ratio of the elongation in the machine direction and the transverse direction, the specific tensile strength, and the stiffness are small. This is preferable because the difference in physical properties between the direction and the lateral direction can be reduced.
When stacking a plurality of wet paper webs, an adhesive may be applied to the surface of the wet paper web (the surface on which other wet paper webs are stacked).

The base paper for liquid containers of the present invention is excellent in edgewick resistance, and is therefore suitably used for various liquid containers. Among these, it is suitable as a container for the liquid detergent because it is excellent in edgewick resistance to detergents (liquid detergents) containing amino acid-based surfactants.

The base paper for liquid containers of the present invention may be used as it is by molding into various liquid containers, or may be molded into various liquid containers after forming a water-resistant layer, a heat-sealing layer, etc. on the base paper. It is not particularly limited.

[Evaluation method]
The first evaluation method of the present invention is a method for evaluating edgewick resistance to a detergent containing an amino acid-based surfactant, which contains 2.0% by mass of the detergent and 4.0% by mass of ethanol. This is a method for confirming that the Edgewick value at 23° C. for an aqueous solution is 3.5 g/1000 mm ² or less.
The second evaluation method of the present invention is a method for evaluating edgewick resistance to detergents containing amino acid-based surfactants, comprising 2.0% by mass of betaine lauryldimethylaminoacetate and 4.0% by mass of ethanol. This is a method for confirming that the Edgewick value at 23° C. for an aqueous solution containing % is 1.5 g/1000 mm ² or less.
Detergents are generally highly viscous, making it difficult to evaluate edgewick resistance in a short period of time. In the present invention, when evaluating edgewick resistance to a cleaning agent containing an amino acid-based surfactant to be evaluated, such as base paper, 2.0% by mass of the cleaning agent or betaine lauryldimethylaminoacetate and 4.0% by mass of ethanol. %, it is possible to evaluate edgewick resistance to detergents.
A specific method for measuring the Edgewick value is as described in Examples.

EXAMPLES The characteristics of the present invention will be described more specifically with reference to examples and comparative examples below. Materials, usage amounts, proportions, processing details, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the gist of the present invention. Therefore, the scope of the present invention should not be construed to be limited by the specific examples shown below.

The measurement methods in Examples and Comparative Examples are as follows. Humidity conditioning was carried out by standing for 12 hours under conditions of 23° C. and 50% RH.
[Measuring method]
<Basis Weight>
The basis weight of the base paper was measured according to JIS P 8124:2011.
<Paper thickness>
The paper thickness of the base paper was measured according to JIS P 8118:2014.
<Density>
The density of the base paper was calculated according to JIS P 8118:2014.
In addition, the density of the pulp is JIS P 8221-2: 2018 PFI mill method for single hardwood bleached kraft pulp (LBKP) or softwood bleached kraft pulp (NBKP) with a Canadian standard freeness (CSF) of 540 mL, It was beaten to 420 mL and 300 mL, hand-made paper with a basis weight of 60 g / m ² was produced according to JIS P 8222: 2015, and after humidity conditioning for 24 hours according to JIS P 8111: 1998, each hand-made paper obtained. The density was calculated by measuring the mass of the paper and the thickness according to JIS P 8118:2014. The densities of LBKP and NBKP are obtained by interpolating the density when the Canadian standard freeness (CSF) is 400 mL from the approximate straight line obtained by the vertical axis being the density and the horizontal axis being the Canadian standard freeness (CSF). rice field.

<Smoother smoothness>
The Smoother smoothness of the base paper is determined according to JAPAN TAPPI No. 5:2000.
<Specific tensile strength>
The specific tensile strength (N·m/g) of the base paper was measured according to JIS P 8113:2006.
<Elongation>
The elongation (%) of the base paper was measured according to JIS P 8113:2006.
<Rigidity>
The stiffness (mN·m) of the base paper was measured according to JIS P 8143:2009.
<Bending resistance>
Bending resistance was measured according to the bending test method described in ISO2493-2:2011. For the measurements, an L&W bend tester from Lorentzen & Wettre, Sweden - code 160 was used. The sample had a width of 38 mm and a clamp length of 50 mm. Measure in the longitudinal direction (T) and the transverse direction (Y) of the base paper.Furthermore, when bending to the back layer side (back side) and bending to the surface side (front side), 5 points each are measured, and the ratio of the average values (front / back).

[Example 1]
(Preparation of stock used for surface layer and back layer)
As a pulp component used for the surface layer and the back layer, a pulp slurry with a mixing ratio of NBKP/LBKP=30/70 beaten to a Canadian standard freeness (CSF) of 400 mL was obtained. The resulting pulp slurry was added with 0.1% by mass of an anionic paper strength enhancer (trademark: Polystrone 117, manufactured by Arakawa Chemical Industries, Ltd.) and 0.3% by mass of cationized starch as dry paper strength agents, and wet paper strength. 0.3% by mass of polyamide polyamine epichlorohydrin resin (PAE) as a reinforcing agent and 0.3% by mass of alkyl ketene dimer as an internal sizing agent were added to 100% by mass of the dry mass of the pulp, and the surface layer and the back were added. A stock for the layer was obtained.

(Preparation of paper stock used for middle layer)
As a pulp component used for the middle layer, a pulp slurry was beaten to a Canadian standard freeness (CSF) of 350 mL and had a mixing ratio of NBKP/LBKP = 20/80. The resulting pulp slurry contains 0.2% by mass of cationized starch, 0.2% by mass of polyamide polyamine epichlorohydrin resin (PAE) as a wet strength agent, and 0.2% by mass of alkyl ketene dimer as an internal sizing agent. was added to 100% by mass of the dry mass of the pulp to obtain a paper stock used for the middle layer.

(papermaking)
Using the obtained stock for the surface and back layers and the stock for the middle layer, paper was made by a multi-layer paper machine. The middle layer was 4-layered paper, and a total of 6 layers were made multi-layered paper. Further, a smoothing treatment was performed using a machine calender to obtain base paper A with a basis weight of 250 g/m ² and a paper thickness of 280 µm.

[Example 2]
In the preparation of the paper stock used for the surface layer and the back layer of Example 1, the Canadian standard freeness (CSF) was changed from 400 mL to 350 mL, and 0.2% by mass of Hoffmann-modified polyacrylamide resin was added as a dry strength agent. was added in the same manner as in Example 1, except that 0.1% by mass of Hoffmann-modified polyacrylamide resin was added as a dry paper strength enhancer in the preparation of the paper stock used for the middle layer, and the basis weight was 250 g. /m ² and a paper thickness of 260 μm.

[Example 3]
In Example 1, instead of an anionic paper strength agent and cationic starch as a dry paper strength agent, amphoteric polyacrylamide resin was used in the surface layer and back layer in the preparation of the stock, and 0.4% by mass was used in the middle layer. A base paper C having a basis weight of 250 g/m ² and a thickness of 280 μm was obtained in the same manner as in Example 1, except that 0.3 mass % was added in the preparation of the stock used.

[Example 4]
Base paper D having a basis weight of 320 g/m ² and a paper thickness of 340 μm was obtained in the same manner as in Example 2, except that the middle layer had a four-layer structure and a total of six layers were made, and the basis weight was adjusted. .

[Example 5]
Base paper E having a basis weight of 290 g/m ² and a paper thickness of 320 μm was obtained in the same manner as in Example 3, except that the middle layer had a four-layer structure and a total of six layers were made, and the basis weight was adjusted. .

[Example 6]
In Example 1, except that the pulp component, Canadian standard freeness (CSF), basis weight and paper thickness used for each layer were changed according to Table 3, the same procedure as in Example 1 was carried out, and the basis weight was 245 g/m ² , A base paper F having a paper thickness of 278 μm was obtained.

[Example 7]
Base paper G was obtained in the same manner as in Example 1, except that the pulp component, Canadian standard freeness (CSF), basis weight and paper thickness used in each layer were changed according to Table 3.
When Example 7 was evaluated for edgewick resistance-2, the result was good at 0.281 g/1000 mm ² .

[Example 8]
(Preparation of stock used for surface layer and back layer)
LBKP pulp slurry beaten to 420 mL of Canadian standard freeness (CSF) was obtained as a pulp component used for the surface layer and the back layer. To the resulting pulp slurry was added 1.0% by mass of an anionic paper strength agent (trademark: Polystrone 117, manufactured by Arakawa Chemical Industries, Ltd.) as a dry paper strength agent and 2.0% by weight of aluminum sulfate as a fixing agent. 0.5% by mass of rosin emulsion (as an active ingredient) was added as an additive sizing agent to 100% by mass of the dry mass of the pulp to obtain paper stocks to be used for the surface layer and the back layer.

(Preparation of paper stock used for middle layer)
As a pulp component used for the middle layer, a pulp slurry was beaten to a Canadian standard freeness (CSF) of 390 mL and had a mixing ratio of LBKP=100. To the resulting pulp slurry was added 1.0% by mass of an anionic paper strength agent (trademark: Polystrone 117, manufactured by Arakawa Chemical Industries, Ltd.) as a dry paper strength agent and 2.0% by weight of aluminum sulfate as a fixing agent. 0.5% by mass of rosin emulsion (as an active ingredient) was added as an additive sizing agent to 100% by mass of the dry mass of the pulp to obtain a stock used for the middle layer.

(papermaking)
Using the obtained stock for the surface and back layers and the stock for the middle layer, paper was made by a multi-layer paper machine. Further, a smoothing treatment was performed by a machine calender to obtain base paper H having a basis weight of 275 g/m ² and a paper thickness of 304 μm.

[Example 9]
(Preparation of stock used for surface layer and back layer)
As a pulp component for the surface layer and the back layer, a pulp slurry was beaten to a Canadian standard freeness (CSF) of 420 mL and had a mixing ratio of NBKP/LBKP = 30/70. To the resulting pulp slurry was added 1.0% by mass of an anionic paper strength agent (trademark: Polystrone 117, manufactured by Arakawa Chemical Industries, Ltd.) as a dry paper strength agent and 2.0% by weight of aluminum sulfate as a fixing agent. 0.7% by mass of rosin emulsion (as an active ingredient) was added as an additive sizing agent to 100% by mass of the dry mass of the pulp to obtain paper materials used for the surface layer and the back layer.

(Preparation of paper stock used for middle layer)
As a pulp component used for the middle layer, a pulp slurry was beaten to a Canadian standard freeness (CSF) of 390 mL and had a mixing ratio of NBKP/LBKP=10/90. The resulting pulp slurry was added with 0.3% by mass of an anionic paper strength agent (trademark: Polystrone 117, manufactured by Arakawa Chemical Industries, Ltd.) as a dry paper strength agent and 2.0% by weight of aluminum sulfate as a fixing agent. 0.5% by mass of rosin emulsion (as an active ingredient) was added as an additive sizing agent to 100% by mass of the dry mass of the pulp to obtain a stock used for the middle layer.

(papermaking)
Using the obtained stock for the surface and back layers and the stock for the middle layer, paper was made by a multi-layer paper machine. Further, a smoothing treatment was performed using a machine calender to obtain base paper I having a basis weight of 250 g/m ² and a paper thickness of 293 μm.

[Example 10]
(Preparation of stock used for surface layer and back layer)
As a pulp component for the surface layer and the back layer, a pulp slurry was beaten to a Canadian standard freeness (CSF) of 460 mL and had a mixing ratio of NBKP/LBKP=35/65. To the obtained pulp slurry, 1.0% by mass of an amphoteric polyacrylamide-based paper strength agent (trademark: DS4326, manufactured by Seiko PMC Co., Ltd.) as a dry paper strength agent and 1.0% by weight of aluminum sulfate as a fixing agent were added internally. 0.7% by mass of rosin emulsion (as an active ingredient) as a sizing agent was added to 100% by mass of the dry mass of the pulp to obtain stocks used for the surface layer and the back layer.

(Preparation of paper stock used for middle layer)
As a pulp component used for the middle layer, a pulp slurry was beaten to have a Canadian standard freeness (CSF) of 420 mL and had a mixing ratio of NBKP/LBKP = 45/55. The resulting pulp slurry was added with 0.5% by mass of an anionic paper strength agent (trademark: Polystrone 117, manufactured by Arakawa Chemical Industries, Ltd.) as a dry paper strength agent and 2.0% by weight of aluminum sulfate as a fixing agent. 0.4% by mass of rosin emulsion (as an active ingredient amount) as a sizing agent and 0.3% by mass of size pine DL-FA20 as a bulking agent are added to 100% by mass of the dry mass of the pulp, and paper used for the middle layer got the fee.

(papermaking)
Using the obtained stock for the surface and back layers and the stock for the middle layer, paper was made by a multi-layer paper machine. Further, a smoothing treatment was performed by a machine calender to obtain base paper J having a basis weight of 300 g/m ² and a paper thickness of 379 μm.

The physical properties of the obtained base papers A to E and F to J were as shown in Tables 1 and 3.

[Comparative example]
In a comparative example, a commercially available milk carton was used as base paper a.

[evaluation]
The base papers A to C, the base papers F to J, and the comparative base paper a were evaluated as follows.
<Edgewick Resistance -1>
Edgewick resistance to detergents was evaluated by the following method.
The base paper was cut to a width of about 10 cm and a length of about 7 cm. At this time, the vertical direction was set to be the papermaking direction (flow direction). The thickness of the cut base paper was measured at three points, and the average value was taken as the paper thickness.
The cut base paper is pouched using a laminator (product name “MS Pouch THS330”, manufactured by Meiko Shokai Co., Ltd.) and a laminate film (manufactured by Ako Brands Japan Co., Ltd., product number: YP70100Z). The four sides were cut so as to have a length of 6 cm to obtain a sample. The pouched sample was weighed.
Cleansing agent (trade name “Ichikami Dense W Moisturizing Care Shampoo”, manufactured by Kracie Home Products Co., Ltd., containing amino acid-based surfactant), 2.0% by mass, ethanol 0.2% to 4.0% by mass A mixed liquid (23°C ± 2°C) was prepared by adding tap water containing % food coloring (food red No. 102).
The sample was immersed in the mixed solution for 20 minutes, and after removing the mixed solution adhering to the surface, the mass of the sample was measured. ² ) was calculated.
The results are shown in Tables 2 and 3.

<Edgewick resistance -2>
An edgewick value (g/1000 mm ² ) was obtained in the same manner as in edgewick resistance-1, except that betaine lauryldimethylaminoacetate was used as the detergent in edgewick resistance-1.
The results were as shown in Table 2.

<Cracked ruled lines>
A ruled line is drawn on the surface of the obtained base paper, and the surface of the three base papers with the ruled line is placed face up and glued with tape glue (product name: "DOTLINER WIDE", manufactured by Kokuyo Co., Ltd.) so that the ruled line part overlaps. It was conditioned according to P 8111, folded at 90 degrees with the ruled surface facing outward, and then folded at 180 degrees with a coach roll specified in JIS P 8222: 2015 without applying extra pressure. . Cracking of the outermost ruled line portion of the superimposed base papers was visually evaluated according to the following criteria.
A: No problem at all.
B: Partially wrinkled, but no problem.
C: There are wrinkles on the whole, but there is no practical problem.
D: Remarkable cracking of ruled lines is a problem.

Base papers A to C and base papers F to J of Examples have an edgewick value of 3 at 23° C. for an aqueous solution containing 2.0% by mass of a detergent containing an amino acid-based surfactant and 4.0% by mass of ethanol. 0.5 g/1000 mm ² or less, and base papers A to C and base papers F to J were also excellent in edgewick resistance to detergents containing amino acid-based surfactants.
Base papers A to C and G had an edgewick value of 1.5 g/1000 mm ² or less at 23° C. in an aqueous solution containing 2.0% by mass of betaine lauryldimethylaminoacetate and 4.0% by mass of ethanol.
Furthermore, the base paper F can suppress cracking of the ruled lines of the outermost layer during the molding of the paper container.
On the other hand, for the comparative base paper a, the Edgewick value at 23° C. for an aqueous solution containing 2.0% by mass of a detergent containing an amino acid surfactant and 4.0% by mass of ethanol is 4.622 g/1000 mm. ² and exceeded 3.5 g/1000 mm ² . In addition, the edgewick value at 23° C. for an aqueous solution containing 2.0% by mass of betaine lauryldimethylaminoacetate and 4.0% by mass of ethanol is 1.671 g/1000 mm ² , exceeding 1.5 g/1000 mm ² . there were. Base paper a for comparison was inferior in edgewick resistance to detergents.
Further, in the base papers H to J, wrinkles were formed on the entire ruled line of the outermost layer during the molding of the paper container, but there was no practical problem.

Claims (13)

A base paper for liquid containers having edgewick resistance to detergents containing amino acid-based surfactants,
The edgewick value at 23° C. for an aqueous solution containing 2.0% by mass of the cleaning agent and 4.0% by mass of ethanol is 3.5 g/1000 mm ² or less.
Base paper for liquid containers. A base paper for liquid containers having edgewick resistance to detergents containing amino acid-based surfactants,
Edgewick value at 23 ° C. for an aqueous solution containing 2.0% by mass of betaine lauryldimethylaminoacetate and 4.0% by mass of ethanol is 1.5 g / 1000 mm ² or less.
Base paper for liquid containers. 3. Base paper for liquid containers according to claim 1, wherein said base paper contains cationized starch as a paper strength enhancer. Base paper for liquid containers according to any one of claims 1 to 3, wherein said base paper contains an alkylketene dimer as a sizing agent. The base paper for liquid containers according to any one of claims 1 to 4, further comprising an anionic paper strength enhancer as a paper strength enhancer. 6. The method according to any one of claims 1 to 5, wherein the ratio of longitudinal elongation (%) to lateral elongation (%) of the base paper (longitudinal elongation/lateral elongation) is 0.30 or more. Base paper for liquid containers as described. The base paper for liquid containers according to any one of claims 1 to 6, wherein the geometric mean of the elongation (%) in the longitudinal direction and the elongation (%) in the transverse direction of the base paper is 3.0% or more. The base paper for liquid containers according to any one of claims 1 to 7, wherein the geometric mean of the specific tensile strength in the machine direction and the specific tensile strength in the transverse direction of the base paper is 30.0 N·m/g or more. The base paper for liquid containers according to any one of claims 1 to 8, wherein the base paper is multi-layered paper with 3 to 7 layers. The base paper is multi-layered paper with three or more layers,
The mass ratio (NBKP/LBKP) of bleached softwood kraft pulp (NBKP) to bleached hardwood kraft pulp (LBKP) in the pulp constituting the surface layer is 10/90 or more and 60/40 or less,
The content of hardwood bleached kraft pulp (LBKP) in the pulp constituting the middle layer is 50% by mass or more and 100% by mass or less,
The content of hardwood bleached kraft pulp (LBKP) in the pulp constituting the back layer is 50% by mass or more and 100% by mass or less.
The base paper for liquid containers according to any one of claims 1 to 9. The base paper for liquid containers according to any one of claims 1 to 10, wherein the density of the bleached hardwood kraft pulp (LBKP) is lower than the density of the bleached softwood kraft pulp (NBKP). The mass ratio (NBKP/LBKP) of softwood bleached kraft pulp (NBKP) to hardwood bleached kraft pulp (LBKP) in the pulp constituting the surface layer is 30/70 or more and 50/50 or less, and the pulp constituting the middle layer The liquid base paper according to any one of claims 1 to 11, wherein the content of bleached hardwood kraft pulp (LBKP) is 53% by mass or more and 98% by mass or less. The Canadian Standard Freeness (CSF) of the pulp that constitutes the back layer is greater than the Canadian Standard Freeness (CSF) of the pulp that constitutes the surface layer and the pulp that constitutes the intermediate layer, and constitutes the back layer. Any one of claims 1 to 12, wherein the difference between the Canadian Standard Freeness (CSF) of the pulp and the Canadian Standard Freeness (CSF) of the pulp constituting the surface layer or the pulp constituting the intermediate layer is 150 mL or less. 1. The base paper for liquid containers according to 1.