Moisture-proof paper, its manufacturing method, and corrugated cardboard sheet using the same

Abstract

To provide a moisture-proof paper capable of imparting high moisture-proof performance to a paper-made packaging box, a manufacturing method thereof, and a cardboard sheet using the same.SOLUTION: The invention relates to a moisture-proof paper 1 provided with a moisture-proof composition layer 11 containing a planar pigment, a granular pigment, and a synthetic resin latex on at least one side of a paper support medium 10, and is characterized by that the moisture-proof composition layer 11 is composed of at least two layers.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to moisture-proof paper, a method for producing the same, and a corrugated cardboard sheet using the same. [Background technology]

[0002] Conventionally, paper packaging boxes (e.g., cardboard boxes) have been widely used for transportation and storage, but ordinary paper packaging boxes have the drawback of being vulnerable to water. Therefore, there is a need for packaging boxes that can prevent water and moisture from entering from the outside to prevent items from getting wet, and to prevent moisture from escaping from the inside to maintain freshness.

[0003] Therefore, for example, Patent Document 1 describes a cardboard box that has moisture-proof properties achieved by coating the liner with a moisture-proof paint whose main components are synthetic resin and flat pigment, mixed with granular pigment. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-131865 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, the demand for maintaining the freshness of perishable foods during transportation and storage has become even stronger. To achieve high moisture-proof performance, it is considered necessary to increase the amount of coating applied to the surface of the packaging box and provide a thicker moisture-proof layer. However, simply increasing the amount of coating applied to the surface to thicken the moisture-proof layer can lead to unevenness of the coated surface and the need for equipment with high drying capabilities, which is expected to increase the effort required for quality control and the costs associated with installing such equipment. This point is not taken into consideration in the cardboard box described in Patent Document 1, and there is still room for improvement in the structure of the surface of paper packaging boxes with high moisture-proof performance.

[0006] Therefore, an object of the present invention is to provide moisture-proof paper that can impart high moisture-proof performance to paper packaging boxes, a method for manufacturing the same, and a corrugated cardboard sheet using the same. [Means for solving the problem]

[0007] The moisture-proof paper of the present invention is characterized in that it has a moisture-proof composition layer containing a tabular pigment, a granular pigment, and a synthetic resin latex formed on at least one side of a paper support, and that the moisture-proof composition layer comprises at least two layers.

[0008] In addition, the manufacturing method of the present invention is for producing the moisture-proof paper of the present invention, and further, the cardboard sheet of the present invention is characterized in that the moisture-proof paper of the present invention is laminated to at least one side as a liner. [Effects of the Invention]

[0009] According to the present invention, the moisture-proof paper has at least two moisture-proof composition layers, each of which has sufficient moisture-proof properties, so that the paper substrate can be imparted with high moisture-proof properties.Furthermore, if the moisture-proof paper is used as the surface of a packaging box, the packaging box can be imparted with high moisture-proof properties. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic cross-sectional view of moisture-proof paper according to one embodiment of the present invention. [Figure 2] 1 is a schematic cross-sectional view of a cardboard sheet using moisture-proof paper according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described in detail with reference to Figures 1 and 2. However, the present invention is not limited to this embodiment. The present invention relates to moisture-proof paper in which a moisture-proof composition layer is formed by applying a moisture-proof coating containing a tabular pigment, a granular pigment, and a synthetic resin latex to at least one side of a paper substrate, and the moisture-proof composition layer is configured to have at least two layers, thereby making it possible to impart high moisture-proof performance to the paper substrate.

[0012] In the present invention, the granular pigment preferably has an aspect ratio of 3 or less. The granular pigment with an aspect ratio of 3 or less used in the present invention is incorporated into a moisture-proof coating material that is applied to a paper support to form a moisture-proof composition layer, thereby exposing the pigment on the surface of the moisture-proof composition layer, roughening the surface, reducing the contact area between the coating layer surface and the calender roll surface, and preventing the moisture-proof coating material from sticking to the calender surface. Furthermore, the aspect ratio of the granular pigment is preferably in the range of 3 to 1, and more preferably as close to 1 as possible, such as 2 to 1. If the aspect ratio exceeds 3, the pigment is not exposed on the coating surface of the moisture-proof composition layer, which can result in a problem in which the moisture-proof composition layer does not achieve its anti-sticking effect.

[0013] The average particle size of the granular pigment must be in the range of 5 to 15 μm. If the average particle size is less than 5 μm, the granular pigment is not sufficiently exposed on the coated surface, increasing the contact area between the coated surface and the machine calender, making it impossible to obtain anti-tack effects. If the average particle size exceeds 15 μm, the surface properties of the coated surface of the moisture-proof composition layer deteriorate, reducing moisture-proof properties.

[0014] The granular pigment is preferably blended in an amount of 3 to 15% by weight based on the total solids content of the coating material. If the amount is less than 3% by weight, the amount of granular pigment is too small, and there is a risk that the anti-sticking effect during machine calendering will not be sufficient. If the amount is more than 15% by weight, the surface properties of the coating surface of the moisture-proof composition layer will deteriorate, and moisture resistance may be reduced. Furthermore, since the granular pigment protects the coating surface from the heat and pressure of the machine calender, it is desirable that it itself be heat-resistant.

[0015] Specifically, such granular pigments include calcium carbonate, heavy calcium carbonate, silica, clay, etc. Heavy calcium carbonate is particularly preferred.

[0016] The average particle size in the present invention is measured by a laser diffraction method. The aspect ratio is the value obtained by dividing the average particle size by the average thickness of the plate-like particles. Particle size measurement by the laser diffraction method can be performed using a laser diffraction particle size distribution analyzer, such as the SALD2000J manufactured by Shimadzu Corporation.

[0017] Next, in the present invention, tabular pigments having an aspect ratio of 5 or more are preferably used, and those having an aspect ratio of 10 or more are more preferably used. Pigments with an aspect ratio of less than 5 lack flatness and are therefore less able to orient parallel to the coating surface during coating, making it difficult to achieve excellent moisture-proof properties. Here, "parallel orientation" means that the pigments are arranged in a flat, scale-like pattern. The larger the aspect ratio, the more parallel the tabular pigments are oriented, and the greater the number of layers of tabular pigments in the moisture-proof composition layer, resulting in higher moisture-proof performance.

[0018] Specific examples of tabular pigments include phyllosilicate compounds (layered silicate compounds having a layered structure). Phyllosilicate compounds are plate-like or flaky with clear cleavage, and include micas, pyrophyllite, talc, chlorite, septe chlorite, serpentine, stilpnomelane, and clay minerals. Among these, micas and talc are preferred. Examples of micas include muscovite, sericite, phloxopite, biotite, fluorphlogopite (artificial mica), red mica, soda mica, vanadium mica, illite, zinc mica, paragonite, and brittle mica. Among these phyllosilicate compounds, muscovite, phloxopite, and sericite are more preferred in terms of particle size, aspect ratio, and the like. As the tabular pigment of the present invention, those described in JP-A-09-291499 can be used.

[0019] The average particle size of the tabular pigment preferably used in the present invention is 1 to 100 μm, more preferably 5 to 50 μm. Tabular pigments with an average particle size of less than 5 μm are less likely to be oriented parallel to the support in the coating layer, while those with an average particle size of 50 μm or more may cause some of the tabular pigment to protrude from the coating layer, and as the thickness of the tabular pigment decreases to around several μm, the number of layers of oriented tabular pigment in the coating layer decreases, reducing the effect of improving moisture-proof performance.

[0020] Examples of synthetic resins used in the synthetic resin latex of the present invention include styrene-butadiene copolymers, acrylic-styrene copolymers, methacrylate-butadiene copolymers, acrylonitrile-butadiene copolymers, acrylic copolymers, polyester copolymers, and polyurethane copolymers. Among these, styrene-butadiene copolymers are preferred. The synthetic resin latex used in the present invention has low moisture permeability, and the moisture permeability of the synthetic resin latex is 50 g / m or less in order to achieve the effects of the present invention. 2 Preferably 24 hours or less.

[0021] Styrene-butadiene copolymers (SBR) are copolymer latexes obtained by emulsion polymerization of monomers consisting of aromatic vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, pt-butylstyrene, and chlorostyrene, conjugated diene compounds such as butadiene, 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, and 1,3-pentadiene, as well as other compounds copolymerizable with these. Styrene is a preferred aromatic vinyl compound, and 1,3-butadiene is a preferred conjugated diene compound. The synthetic resins are not particularly limited in terms of glass transition temperature (Tg), particle size, gel fraction (weight of the insoluble portion when tetrahydrofuran is used as a solvent), molecular weight, etc., but generally, Tg is −10°C to 40°C, more preferably −5°C to 35°C, particle size is 50 to 500 nm, and gel fraction is 10 to 90%, with 90% or higher being preferred for improved disintegration properties. The mixing ratio (solids weight) of "plate-shaped pigment:synthetic resin" used in the present invention is 30:70 to 70:30, preferably 35:65 to 60:40. If the plate-shaped pigment is less than 30%, the synthetic resin is present in large amounts, and sufficient disintegration properties cannot be obtained. If the plate-shaped pigment is more than 70%, the coating film condition of the paint deteriorates and sufficient moisture resistance cannot be obtained.

[0022] To enhance the moisture-proof effect of the moisture-proof coating material of the present invention, it is preferable to use a coupling agent. Examples of such coupling agents include silane coupling agents containing Si in the hydrophilic group portion, titanate coupling agents containing Ti in the hydrophilic group portion, and aluminum coupling agents containing Al in the hydrophilic group portion. Examples of such coupling agents include γ-glycidoxypropyltrimethoxysilane, N-β(aminoethyl)γ-aminopropylmethyldimethoxysilane, and isopropyltri(N-aminoethylaminoethyl)titanate.

[0023] Coupling agent structures can be broadly divided into hydrophilic groups that interact with inorganic compounds, such as platelet-shaped pigments like phyllosilicate compounds, and hydrophobic groups that interact with organic compounds, such as resins. The hydrophilic groups are obtained by hydrolysis of alkoxy groups bonded to metal elements like Ti and Al or Si. Regarding the hydrophobic group portion of the coupling agent, if the hydrophobic group portion is an organic oligomer, it forms a polymeric organic coating on the surface of the inorganic compound, completely hydrophobizing the surface and enhancing adhesion to the resin matrix. Furthermore, if the hydrophobic group portion contains a reactive organic functional group, such as an epoxy group, vinyl group, or amino group, the functional group crosslinks with the reactive functional group of the resin matrix, further enhancing adhesion to the resin matrix.

[0024] The flat pigment is surface-treated with such a coupling agent using an integral blending method or a pretreatment method before use. The integral blending method is a method in which the coupling agent is directly added to a coating material containing the flat pigment and a synthetic resin latex. The pretreatment method is a method in which the flat pigment is pre-treated with the coupling agent. The amount of coupling agent added is 0.1 to 5 parts by weight, preferably 0.5 to 2 parts by weight, per 100 parts by weight of the flat pigment. Addition of less than 0.1 part by weight is undesirable because the surface of the flat pigment is not sufficiently covered by the coupling agent, while addition of more than 5 parts by weight is uneconomical because the effect of the coupling agent reaches a plateau.

[0025] The above materials are mixed to form a moisture-proof paint, and at this time, dispersants such as polycarboxylic acids, antifoaming agents, surfactants, and color adjusters can be added if necessary.

[0026] The paper support of the present invention is a paper substrate to which a moisture-proof coating material is applied to form a moisture-proof composition layer, and the moisture-proof paper of the present invention is, as described above, a paper support to which two or more moisture-proof composition layers are formed. The moisture-proof paper can be used, for example, as liner paper for cardboard sheets.

[0027] The moisture-proof coating material prepared in this manner can be applied using on-machine coating equipment. That is, a coating equipment is installed between the dryer part and the calendar part of the papermaking machine that produces the paper substrate, and the moisture-proof coating material is applied using this coating equipment. There are no particular limitations on the coating equipment that can be used in the present invention, and any known equipment can be used. However, coating methods that scrape the coated surface, such as blade coaters, bar coaters, and air knife coaters, are more preferred because they tend to promote the orientation of the plate-like pigments. In particular, bar coating using a bar coater allows for coating to produce a smooth surface, and is therefore preferred for achieving the effects of the present invention. Furthermore, the coating weight of this moisture-proof coating material when applied twice to the paper substrate is 5 to 35 g / m2 in terms of solids per side. 2 , and more preferably 7 to 30 g / m 2 In this way, moisture-proof paper that has been coated once with the moisture-proof coating material of the present invention on the machine, dried typically at 110 to 150°C for 1 to 20 seconds, and then coated and dried a second time in the same process as the first time can be used in normal operations because it does not experience adhesion problems due to the moisture-proof coating material when passed through a machine calender (typically a linear pressure of about 10 to 30 kg / cm).

[0028] FIG. 1 is a schematic cross-sectional view of a moisture-proof paper 1 according to one embodiment of the present invention. As shown in FIG. 1, the moisture-proof paper 1 according to this embodiment comprises a paper substrate 10 on at least one side of which a moisture-proof coating containing a tabular pigment, a granular pigment, and a synthetic resin latex is applied to form a moisture-proof composition layer 11. The moisture-proof composition layer 11 is a two-layer structure including a first moisture-proof composition layer 111 and a second moisture-proof composition layer 112. In the present invention, the moisture-proof composition layer 11 may be formed on both sides of the paper substrate 10, or the moisture-proof composition layer may have three or more layers. Furthermore, the moisture-proof composition layer may be formed on only a portion of the paper substrate 10, rather than the entire surface. The number of moisture-proof composition layers may be increased in areas where higher moisture resistance is desired compared to other areas. The amount of moisture-proof coating applied to each moisture-proof composition layer may also be varied.

[0029] In one embodiment of the present invention, in a first coating step, a first moisture-proof composition layer 111 is formed thinly and dried, and then in a second coating step, a second moisture-proof composition layer 112 is further formed thinly on the dried first moisture-proof composition layer 111 and dried, thereby forming two moisture-proof composition layers 11 on the paper support 10.

[0030] According to this embodiment, the moisture-proof composition layer 11 formed on the moisture-proof paper 1 is divided into two layers, a first moisture-proof composition layer 111 and a second moisture-proof composition layer 112, and each layer has sufficient moisture-proof performance, making it possible to impart high moisture-proof performance to the paper base material that is the paper support 10. Furthermore, if the moisture-proof paper 1 is used as the surface of a packaging box, it becomes possible to impart high moisture-proof performance to the packaging box. Furthermore, because each layer of the moisture-proof composition layer 11 is thin and can be sufficiently dried, blocking is less likely to occur even when the moisture-proof paper 1 is rolled or when moisture-proof paper 1 is stacked on top of another moisture-proof paper 1.

[0031] As the paper support used in the present invention, any paper support that is commonly used can be used, but in order to impart greater water resistance, it is also possible to use a paper support that has water resistance obtained by, for example, blending a water-resistant agent before papermaking or impregnating the paper with a water-resistant agent before drying in a papermaking machine.

[0032] The moisture permeability of the moisture-proof paper in the present invention is preferably 50 g / m2 as measured by JAPAN_TAPPI No. 7 A method. 2 24 hours or less, more preferably 20 g / m 2 - Less than 24 hours.

[0033] The moisture-proof paper obtained as described above is used as liner paper to produce the moisture-proof corrugated cardboard sheet of the present invention. To manufacture a corrugated cardboard sheet, it is necessary to bond the liner paper to the core paper, and this bonding is carried out in a corrugated cardboard sheet manufacturing device called a corrugator. The corrugator is mainly composed of an SF section where the liner paper is bonded to the core paper, and a DF section where further liner paper is bonded to the core side of the single corrugated cardboard sheet bonded in the SF section. During bonding in the corrugator, the corrugated cardboard sheet is pressed in the press roll section of the SF section at a temperature of 150-200°C and a linear pressure of 20-40 kg / cm. 2 Pressurization time: 0.01 to 0.20 seconds, temperature at the hot platen of the DF section: 150 to 200°C, linear pressure: 0.3 kg / cm 2 However, since the liner base paper of the present invention has a roughened surface with the granular pigment exposed on the moisture-proof composition layer, the contact area of ​​the coated surface with the press roll and hot plate of the corrugator is small, and since it has heat resistance, there are no problems with the coated surface fusing to the press roll or hot plate, and it can be manufactured in exactly the same way as ordinary liner base paper. When manufacturing such moisture-proof corrugated board sheets, it is preferable to use liner base paper with a moisture-proof composition layer on one side, and then laminate the core base paper to the uncoated side of the moisture-proof paint using a corrugator to produce a corrugated board sheet. Furthermore, the liner base paper obtained by the present invention can be used as a liner on both the SF and DF sides of a corrugated board sheet. It is also possible to use it as a liner on one side and use a conventional liner on the other. The corrugated board sheet obtained in this way can be printed, punched, and glued using an FFG (flexo folder gluer) to produce moisture-proof corrugated board boxes.

[0034] FIG. 2 is a schematic cross-sectional view of a cardboard sheet 100 using moisture-proof paper 1 according to one embodiment of the present invention as a liner. As shown in FIG. 2, the cardboard sheet 100 according to this embodiment is formed by laminating the moisture-proof paper 1 as a moisture-proof liner 1011 to one side of core raw paper. In FIG. 2, for ease of distinction, the moisture-proof liner 1011 is represented by a thick double line, and the liner 1012 not coated with moisture-proof paint is represented by a thick single line. As shown in FIG. 2, the cardboard sheet 100 according to this embodiment is produced by laminating the liner 1011, liner 1012, and core 102 together so that the core 102 is sandwiched between the moisture-proof liner 1011 and the liner 1012 not coated with moisture-proof paint. In the present invention, the cardboard sheet may have moisture-proof paper 1 laminated on both sides as liners. Furthermore, when manufacturing a cardboard box using moisture-proof paper 1 as a liner on one side of a cardboard sheet, the moisture-proof paper 1 may be on the inside surface or on the outside surface. Furthermore, in a cardboard sheet having multiple flutes such as double flutes, the moisture-proof paper 1 may be used as a liner located between the flutes.

[0035] In addition, in this embodiment, the moisture-proof paper 1 is used as a liner for a cardboard sheet, but the present invention is not limited to this, and it may also be used for cardboard that does not have a flute structure, and packaging boxes may be manufactured using that cardboard.

[0036] Conventionally, cardboard boxes and other paper packaging boxes usually have the drawback of being weak against water, and therefore it is required to prevent water and moisture from entering from the outside and to keep the packed items from getting wet, and to prevent moisture from escaping from the inside to maintain freshness. Therefore, for example, Patent Document 1 describes a cardboard box that has been given moisture-proof properties by coating the liner with a moisture-proof paint whose main components are synthetic resin and flat pigment, mixed with granular pigment.

[0037] In recent years, there has been an increasing demand for preserving the freshness of perishable foods during transportation and storage, and in order to achieve high moisture-proof performance, it is thought that it will be necessary to increase the amount of coating applied to the surface of the packaging box and provide a thick moisture-proof layer. However, simply increasing the amount of coating applied to the surface to make the moisture-proof layer thicker will cause the coated surface to become rough and will require equipment with high drying capabilities, which is expected to increase the effort required for quality control and the costs associated with introducing such equipment.

[0038] According to the present invention, the moisture-proof paper has at least two moisture-proof composition layers, each of which has sufficient moisture-proof properties, so that the paper substrate can be imparted with high moisture-proof properties.Furthermore, if the moisture-proof paper is used as the surface of a packaging box, the packaging box can be imparted with high moisture-proof properties.

[0039] Furthermore, according to the present invention, the moisture-proof composition layer formed on the moisture-proof paper is divided into two or more layers, which makes it possible to reduce the problems mentioned above that can occur when simply increasing the coating weight and forming a thick moisture-proof layer on a paper substrate, namely, problems such as coating surface disorder and the need for equipment with high drying capabilities. That is, according to the present invention, the moisture-proof composition layer can be applied in separate layers, and when a single layer applied so that the total coating weight is the same is compared with a layer applied in two or more layers as in the present invention, the latter can achieve higher moisture resistance (see the comparative evaluation below).

[0040] Furthermore, according to the present invention, when paper is coated once with a moisture-proof paint, as long as the basic composition is the same as in the first layer, the same or similar moisture-proof paint can be used for the second and subsequent layers. This makes it possible to impart further moisture-proof performance to the paper that has been coated once, and also makes it possible to efficiently upgrade inventory.

[0041] The cardboard box according to the present invention can be used, for example, to store high-quality vegetables containing sawdust for freshness preservation purposes, or to store floor tiles and the like for transporting building materials.

[0042] <Comparative evaluation> The moisture permeability of the examples and comparative examples according to the present invention was compared and evaluated. Regarding the process of applying a moisture-proof coating material to a paper substrate to form a moisture-proof composition layer, the moisture-proof composition layer was formed in one application in the comparative examples, whereas the moisture-proof composition layer was formed in two applications in the examples. The paper substrate was NRK220, a liner base paper manufactured by Oji Paper Co., Ltd., and a moisture-proof coating material prepared according to the formulation detailed below was applied on-machine to the surface of the paper substrate using a Mayer bar. The first application in the examples and the comparative examples was performed by drying at 160°C on a hot platen. The second application in the examples was also performed in the same manner as the first application in the examples. The coating weight in the examples is the total of the two applications. The moisture permeability of the surface liner of each example and comparative example was measured in accordance with JAPAN_TAPPI No. 7 A method.

[0043] Example 1 A moisture-proof paint was prepared with the following formulation. Next, the moisture-proof paint was applied by bar coating to a coating weight of 17.3 g / m2 after drying. 2 The moisture-proof composition of the present invention was coated twice on the surface of the base paper of the liner base paper in the same amount so that the moisture-proof composition of the present invention was formed on two layers. 2 The weight parts listed below are based on 100 parts of moisture-proof paint.

[0044] [Moisture-proof paint] SBR (synthetic resin latex) 46.2 parts by weight (Nipol S1X3: manufactured by Nippon Zeon) Muscovite (plate-like pigment) 46.2 parts by weight (W40H, aspect ratio 20-30, average particle size 22μm: Repco) Heavy calcium carbonate (granular pigment) 4.62 parts by weight (BF-300, aspect ratio 1-2, average particle size 8 μm: manufactured by Bihoku Powder Industries) Coupling agent 0.46 parts by weight (KBM-603: Aoki Oil Industry Co., Ltd.)

[0045] <Example 2> The coating weight of the moisture-proof paint after drying is 18.8 g / m 2 A liner was obtained in exactly the same manner as in Example 1, except that the moisture permeability of the sample in this example was 32 g / m 2 It was 24 hours.

[0046] Example 3 The coating weight of the moisture-proof paint after drying is 21.2 g / m 2 A liner was obtained in exactly the same manner as in Example 1, except that the moisture permeability of the sample in this example was 28 g / m 2 It was 24 hours.

[0047] Example 4 The coating weight of the moisture-proof paint after drying is 21.5 g / m 2 A liner was obtained in exactly the same manner as in Example 1, except that the moisture permeability of the sample in this example was 28 g / m 2 It was 24 hours.

[0048] <Example 5> The coating weight of the moisture-proof paint after drying is 27.5 g / m 2 A liner was obtained in exactly the same manner as in Example 1, except that the moisture permeability of the sample in this example was 11 g / m 2 It was 24 hours.

[0049] <Comparative Example 1> A moisture-proof paint was prepared with the same composition as in Example 1-5 above, and the moisture-proof paint was applied to the surface of the same liner base paper as in Example 1-5 above by bar coating so that the coating amount after drying was 3.6 g / m 2 The moisture permeability of the sample of this comparative example was 1030 g / m 2 It was 24 hours.

[0050] <Comparative Example 2> The coating weight of the moisture-proof paint after drying is 4.8 g / m 2 A liner was obtained in exactly the same manner as in Comparative Example 1, except that the moisture permeability of the sample in this comparative example was 690 g / m 2 It was 24 hours.

[0051] <Comparative Example 3> The coating weight of the moisture-proof paint after drying is 6.1 g / m 2 A liner was obtained in exactly the same manner as in Comparative Example 1, except that the moisture permeability of the sample in this comparative example was 650 g / m 2 It was 24 hours.

[0052] <Comparative Example 4> The coating weight of the moisture-proof paint after drying is 8.6 g / m 2 A liner was obtained in exactly the same manner as in Comparative Example 1, except that the moisture permeability of the sample in this comparative example was 250 g / m 2 It was 24 hours.

[0053] <Comparative Example 5> The coating weight of the moisture-proof paint after drying is 9.5 g / m 2 A liner was obtained in exactly the same manner as in Comparative Example 1, except that the moisture permeability of the sample in this comparative example was 180 g / m 2 It was 24 hours.

[0054] <Comparative Example 6> The coating weight of the moisture-proof paint after drying is 11.2 g / m 2 A liner was obtained in exactly the same manner as in Comparative Example 1, except that the moisture permeability of the sample in this comparative example was 100 g / m 2 It was 24 hours.

[0055] <Comparative Example 7> The coating weight of the moisture-proof paint after drying is 12.1 g / m 2 A liner was obtained in exactly the same manner as in Comparative Example 1, except that the moisture permeability of the sample in this comparative example was 130 g / m 2 It was 24 hours.

[0056] <Comparative Example 8> The coating weight of the moisture-proof paint after drying is 20.7 g / m 2 A liner was obtained in exactly the same manner as in Comparative Example 1, except that the moisture permeability of the sample in this comparative example was 54 g / m 2 It was 24 hours.

[0057] <Comparative Example 9> The coating weight of the moisture-proof paint after drying is 27.4 g / m 2A liner was obtained in exactly the same manner as in Comparative Example 1, except that the moisture permeability of the sample in this comparative example was 40 g / m 2 It was 24 hours.

[0058] <Test Results> The measured moisture permeability and coating amount of the surface liner of each example and each comparative example are shown in Table 1 below.

[0059] [Table 1]

[0060] Referring to Table 1 above, in liners coated with a moisture-proof paint to form a moisture-proof composition layer, the coating weights of Examples 3 and 4 (two coatings) were approximately the same as the coating weight of Comparative Example 8 (one coating), and the coating weight of Example 5 (two coatings) was approximately the same as the coating weight of Comparative Example 9 (one coating), but the moisture permeability was lower and moisture proofness was higher. In other words, it can be seen that by forming two moisture-proof composition layers instead of one, higher moisture proofness can be obtained even with the same total coating weight. [Explanation of symbols]

[0061] 1. Moisture-proof paper 10 Paper support 11 Moisture-proof composition layer 111 First moisture-proof composition layer 112 Second moisture-proof composition layer 100 cardboard sheets 1011 Moisture-proof liner 1012 Liner without moisture-proof paint 102 Core

Claims

1. A moisture-proof paper having a moisture-proof composition layer containing a tabular pigment, a granular pigment, and a synthetic resin latex formed on at least one side of a paper support, characterized in that the moisture-proof composition layer comprises at least two layers.

2. 2. The moisture-proof paper according to claim 1, wherein the aspect ratio of the tabular pigment is 5 or more.

3. 3. The moisture-proof paper according to claim 1, wherein the granular pigment has an aspect ratio of 3 or less and an average particle size of 5 to 15 μm.

4. Moisture permeability is 50g / m 2 The moisture-proof paper according to any one of claims 1 to 3, characterized in that the durability is 24 hours or less.

5. A method for producing the moisture-proof paper according to any one of claims 1 to 4.

6. A corrugated cardboard sheet, comprising the moisture-proof paper according to any one of claims 1 to 4 as a liner, pasted on at least one surface of core raw paper.

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