Paper container

Abstract

To provide a paper packing material that is used to store and convey refrigerated goods that are typical in a bag-in-box application, in which strength in compressing a box does not decrease even when a difference in temperature between the inside and the outside of a box is large so that dew condensation occurs on contents and the box.SOLUTION: An excellent paper packing material is configured to store and convey refrigerated goods, by using sheet constituting an inner container and / or an outer container, where a degree of water repellency stipulated in a paper / pulp testing method No.68 of at least one surface of the surfaces is R4 or higher.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a paper container. [Background technology]

[0002] Containers and packaging materials using paper substrates have been widely used for storing and transporting goods. In particular, when transporting liquid or gel-like substances as contents, a plastic bag is often used inside the box. Patent Document 1 describes a paper container with an inner bag, which has a 30-minute Cobb water absorbency of 40 g / m2 measured from the waterproof layer side. 2 The following describes a paper container with an inner bag having a waterproof layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-098685 Summary of the Invention [Problem to be solved by the invention]

[0004] As mentioned above, the applicant has developed a paper container with an inner bag, which has a 30-minute Cobb water absorbency of 40 g / m2 measured from the waterproof layer side. 2 We have invented the following paper container with a paper inner bag having a waterproof layer (Patent Document 1). However, regardless of whether the inner bag is present or not, when the contents are transported in contact with the paper container, the greater the temperature difference between the contents and the surrounding environment, the more likely it is that condensation will form on the surface of the inner bag due to the temperature difference between the packaged items and the paper container. This condensation will penetrate into the paper container, causing a decrease in the strength of the paper container. Therefore, the object of this invention is to provide a box that can stably transport the contents without causing the paper container to deteriorate, even if condensation occurs due to the temperature difference between the contents and the surrounding environment. [Means for solving the problem]

[0005] After extensive research into the above-mentioned problems, the inventors were able to create a paper container that can transport the contents stably without deterioration of the paper container, even if condensation occurs due to the temperature difference between the contents and the surrounding environment, by making one surface of at least one of the outer container or inner container water-repellent.

[0006] The present invention includes, but is not limited to, the following aspects. [1] A paper container having (a) a paper outer container and (b) a paper inner container attached to the inside of the outer container, characterized in that at least one of the inner container or the outer container uses a sheet having a surface with a water repellency of R4 or higher as specified in Paper Pulp Testing Method No. 68. [2] The paper container according to [1], wherein at least the outer container is box-shaped. [3] At least one of the inner container or outer container has a 30-minute Cobb water absorption of 155 g / m2 measured from the waterproof layer side. 2 The paper container according to [1] or [2], characterized in that it uses a sheet having a waterproof layer surface as follows: [4] The paper container according to [3], wherein the waterproof layer is provided by coating. [5] The paper container according to [3] or [4], wherein the waterproof layer is a waterproof resin layer containing at least one resin selected from the group consisting of styrene-based resin, acrylic-based resin, and polyolefin resin, and water-repellent wax. [6] The paper container according to any one of [1] to [5], wherein the sheet constituting the inner container and / or the outer container is a cardboard sheet. [7] A method for using a paper container, in which an inner container is placed inside an outer container to store an object, characterized in that at least one of the inner container or the outer container uses a sheet having a surface with a water repellency of R4 or higher as specified in Paper Pulp Testing Method No. 68. [8] A method for manufacturing a paper container having a double structure, comprising: (a) preparing a paper container for an inner container and / or an outer container using a sheet having a surface with a water repellency of R4 or higher as specified in Paper Pulp Test Method No. 68; and (b) placing the inner container inside the outer container. [Effects of the Invention]

[0007] According to the present invention, by imparting water repellency to one of the sheets that make up the paper container, a paper container whose strength does not decrease even when condensation occurs inside the container can be obtained. Furthermore, the present invention broadens the range of uses of paper containers, and makes it possible to provide paper containers that are suited to various applications. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view showing an inner container of a paper container according to the present invention. [Figure 2] This is a photograph taken when evaluating the condensation resistance of paper containers. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention relates to a paper container. The paper container according to the present invention is characterized in that at least one of the outer container and inner container uses a sheet having a surface with a water repellency of R4 or higher as defined in Paper Pulp Test Method No. 68. The paper container according to the present invention is not particularly limited as long as it is used for transporting in a refrigerated or frozen environment, and can be used for, for example, storing food such as meat, fish, or vegetables, or liquid or gel-like chemicals in the form of a waterproof liner or bag-in-box. If necessary, a cooling agent (refrigerant) may be placed inside the paper container to maintain a refrigerated state inside the paper container when the surrounding temperature reaches room temperature.

[0010] The type of paper used in the paper container of the present invention is not particularly limited, and may be appropriately selected from wrapping paper, processed base paper, corrugated board, paperboard for paper containers, miscellaneous paperboard, thick paper, etc. In a preferred embodiment, the paper container is made of corrugated board. By using corrugated board, accidents such as collapse of cargo during handling, such as transportation, do not occur even when stacked in multiple layers. Furthermore, the paper container of the present invention is preferably in the form of a multiple-structure paper container, in which each paper container is formed using multiple corrugated boards, and then an inner paper container (inner container) is inserted inside the outer paper container (outer container) to form a single paper container.

[0011] Although the thickness of the cardboard sheet is not particularly limited, reducing the thickness of the cardboard sheet improves the temperature adaptability to the surrounding environment in which the paper container is placed and improves loading efficiency. In a preferred embodiment, the thickness of the cardboard sheet used for the paper container is 0.2 to 15 mm, more preferably 0.4 to 5 mm. In addition, when a paper container is made with multiple structures, in a preferred embodiment, the thickness of the cardboard sheet used for the inner container is equal to or less than the thickness of the cardboard sheet used for the outer container. Corrugated cardboard sheets are made by gluing together flat paper (liner) and corrugated paper (core) and are suitable for a variety of uses, including packaging and cushioning for goods, transporting luggage, and storing items.

[0012] The corrugated cardboard sheets used in the paper container of the present invention can generally be produced by bonding a liner and a corrugated medium together using a corrugator. Any known corrugator can be used without limitation, but a typical corrugator is composed of a single facer, a double backer, and a cutter. A glue-making device for bonding the liner and medium base paper, as well as a device for generating heat to melt the glue, are also used.

[0013] Furthermore, when manufacturing the corrugated cardboard sheet used in the paper container of the present invention, an adhesive is used to bond the liner and the corrugating medium. While known adhesives can be used, it is preferable to use a water-resistant adhesive, as this prevents the strength of the corrugated cardboard box from being reduced by water wetting, condensation, humidity, etc., on the cross section of the corrugated cardboard sheet. A water-resistant adhesive is a standard corrugated cardboard adhesive to which a water-resistant agent has been added. The water-resistant agent is not particularly limited, and examples include those containing synthetic resin emulsions, ketone aldehyde resins, etc.

[0014] The liner used for the cardboard sheet will be described later, but depending on the application and the part to be used, kraft liner, jute liner, etc. can be used. The basis weight of the liner is not particularly limited, and for example, the basis weight of the entire liner can be 70 to 550 g / m 2 and can be set to 100 to 500 g / m 2 Or 150~450g / m 2 It may also be possible to use the following.

[0015] The corrugating material that makes up the cardboard can be A-flute, B-flute, C-flute, E-flute, F-flute, G-flute, AAA-flute, AA-flute, W-flute, etc., depending on the application and the part to be used, but as mentioned above, by selecting the configuration of the corrugating material so that the overall thickness of the cardboard sheet can be reduced, the temperature adaptability to the surrounding environment in which the paper container is placed will be good and loading efficiency will also be improved. There are also no particular restrictions on the basis weight of the corrugating material, and it is recommended to use a material with a weight of 120 g / m. 2 , 160g / m 2 , 180g / m 2 , reinforced 180g / m 2 , reinforced 200g / m 2 It is preferable to reduce the basis weight of the liner and / or the medium within a range that ensures the effects of the present invention and that ensures the strength of the paper container at a certain level or above.

[0016] The paper container according to the present invention is produced from a cardboard sheet by, for example, folding a single blank sheet and, if necessary, laminating it with an adhesive. The type of adhesive is not particularly limited, and examples include aqueous, water-dispersed, solution-based, solventless, and solid-based adhesives, which can be selected appropriately depending on the surface condition of the paper material to be bonded.

[0017] The amount of adhesive used is not particularly limited as long as sufficient adhesive strength is obtained, but in the case of surface application, it is 0.5 to 2000 g / m 2 It can be 5 to 1500 g / m 2 It may be 10 to 1000 g / m 2 In the case of line application, the application width can be changed appropriately depending on the nozzle diameter of the applicator, the movement speed of the nozzle or paper material, the viscosity of the adhesive during application, the width of the paper to be adhered, etc., and the application amount per unit length is not particularly limited, but may be, for example, 0.1 to 30 g / m, 0.5 to 20 g / m, or 1 to 15 g / m.

[0018] The shape and size of the paper container used in the present invention are not particularly limited as long as they can adequately store the intended items and ensure strength. Examples include corrugated cardboard boxes exemplified in JIS Z 1507, watertight boxes formed by folding a single blank sheet, in which the bottom and all side walls are connected via fold lines and all side walls are connected via fold lines, polygonal containers or boxes, cylindrical containers or boxes, and curved container-shaped containers or boxes. When a paper container is made with multiple structures, the outer and inner containers may have the same shape, or inner and outer containers with different shapes may be combined. A preferred embodiment of a paper container with multiple structures is a set of paper containers in which the inner and outer dimensions of the outer container are set so that at least a portion of the inner surface of the outer container and a portion of the outer surface of the inner container are in contact with each other at the side of the paper container. In a more preferred embodiment, both the inner and outer containers are box-shaped. In an even more preferred embodiment, the inner container is a watertight box.

[0019] When paper materials are made into boxes to produce paper containers such as boxes, a box-making machine can be used. There are no particular restrictions on the type of box-making machine used, and for example, a vertical or horizontal box-making machine can be used.

[0020] The paper container according to the present invention is characterized in that at least one of the inner container and the outer container uses a sheet having a surface with a water repellency of R4 or higher as specified in Paper and Pulp Testing Method No. 68. By using a sheet with a water repellency of R4 or higher, the strength of the paper container is less likely to decrease even when the ambient temperature conditions around the paper container storing the contents suddenly change and condensation occurs. Furthermore, since paper is an environmentally friendly material, waste disposal also reduces the environmental burden. The water repellency of the paper substrate of this embodiment can be measured in accordance with JAPAN TAPPI Paper and Pulp Testing Method No. 68, "Paper and Paperboard - Water Repellency Testing Method," and is preferably R4 or higher, more preferably R6 or higher, and even more preferably R8 or higher.

[0021] Paper sheets that make up paper containers The paper sheet for constituting the paper container according to the present invention is preferably paperboard, more preferably a liner for corrugated cardboard. The basis weight of the paper sheet is not particularly limited, but may be, for example, 10 to 800 g / m 2 When the paper sheet is a single-ply paper, the basis weight is 10 to 300 g / m 2 It can be set appropriately within the range of 30 to 250 g / m 2 In addition, when the paper sheet is a multi-layer paperboard having two or more paper layers, the basis weight is 70 to 800 g / m 2 The paper sheet can be appropriately set within the range. The paper sheet can be appropriately selected depending on the use, structure, etc. of the paper container. Furthermore, when a paper container is made of multiple structures, the basis weight of the paper sheet for the inner container and the paper sheet for the outer container may be the same, or paper sheets of different basis weights may be used for the inner container and the outer container. In a preferred embodiment, from the viewpoint of improving the ease of assembling the inner container, the basis weight of the paper sheet for the inner container used in the present invention is smaller than the basis weight of the paper sheet for the outer container.

[0022] (Paper container sheet with water-repellent layer) In the paper container according to the present invention, the paper sheet provided with a water-repellent layer (water-repellent sheet) constituting at least one of the inner container and the outer container has water repellency, and in a preferred embodiment, the water repellency level defined in Paper Pulp Test Method No. 68 is R4 or higher, more preferably R6 or higher, and even more preferably R8 or higher. The higher the water repellency level, the smaller the contact area between the paper sheet and water droplets adhering to the surface of the sheet, making it more difficult for water to penetrate the paper, thereby preventing a decrease in the strength of the paper container.

[0023] In a preferred embodiment, the water-repellent sheet according to the present invention is also excellent in waterproofness, and in a more preferred embodiment, the 120-second Cobb water absorbency of the surface is 155 g / m 2 less than 100 g / m 2 Less than 50 g / m is more preferable. 2 The Cobb water absorbency of paper is measured in accordance with JIS P8140 (Cobb method) by contacting 100 ml of distilled water with the water-repellent layer and measuring the weight of water absorbed per unit area after a specified time. The lower the Cobb water absorbency, the lower the water absorbency of the water-repellent layer.

[0024] In a preferred embodiment, the water-repellent sheet according to the present invention is also excellent in moisture resistance, and for example, has a moisture permeability of 1500 g / m 2 24 hours or less, preferably 1000g / m 2 24 hours or less, preferably 500g / m 2 The moisture permeability of paper can be measured from the water-repellent layer side of the water-repellent sheet in accordance with JIS Z 0208, and the smaller the value, the higher the moisture resistance.

[0025] The water-repellent sheet according to the present invention also has excellent oil resistance, and in a preferred embodiment, the oil repellency on the water-repellent layer side is preferably kit number 7 or higher, more preferably 8 or higher, and even more preferably 9 or higher. Here, the oil repellency can be measured from the water-repellent layer side of the inner sheet in accordance with JAPAN TAPPI Paper and Pulp Test Method No. 41 "Paper and Paperboard - Oil Repellency Test Method - Kit Method," and the higher the kit number, the higher the oil resistance.

[0026] The water-repellent sheet according to the present invention preferably has an Oken smoothness of 15 seconds or more, more preferably 20 seconds or more, and even more preferably 25 seconds or more on the water-repellent surface. When the surface smoothness of the water-repellent layer of the water-repellent paper is in the above range, a high gloss can be obtained on the surface of the water-repellent layer, resulting in a water-repellent paper with superior aesthetic appeal.

[0027] (Water-repellent sheet paper substrate) The water-repellent sheet of the present invention has at least a paper substrate and a water-repellent layer provided on at least one surface of the paper substrate. In the present invention, the basis weight of the paper substrate is not particularly limited, and is, for example, 10 to 800 g / m 2 When the paper substrate is a single-ply paper, the basis weight is 10 to 300 g / m 2 For example, when the paper base material is kraft paper, the basis weight is 30 to 250 g / m 2 In addition, when the paper base material is a multi-layer paperboard having two or more paper layers, the basis weight is 70 to 800 g / m 2 The range can be appropriately set.

[0028] The paper substrate used in the water-repellent sheet is not particularly limited in terms of the 120-second Cobb water absorbency of the surface on which the water-repellent layer is to be formed, but it is preferably 25 g / m 2 Less than 20 g / m, more preferably 2 or less, more preferably 15 g / m 2 The paper substrate used for the water-repellent sheet may have a Cobb water absorbency of 5 g / m2 or less at 120 seconds. 2 or more, preferably 7 g / m 2More preferably, 10 g / m 2 That's all.

[0029] In a preferred embodiment, the paper substrate used in the water-repellent sheet has an oil drop absorbency of 5 seconds or more on the surface on which the water-repellent layer is to be formed, more preferably 7 seconds or more, and even more preferably 10 seconds or more. There is no particular upper limit, but it is preferably 80 seconds or less, more preferably 75 seconds or less, and even more preferably 70 seconds or less. Having an oil absorbency within the above range allows the wax contained in the water-repellent material to remain on the paper surface and not easily penetrate into the paper layer, thereby preventing a decrease in the strength of the paper container. The oil absorbency of the paper substrate is measured by using a microsyringe equipped with an H5 needle to drop a drop of diesel No. 1, adjusted to a dynamic viscosity of 3 cSt, onto the sample surface, and measuring the time until the surface gloss disappears.

[0030] In a preferred embodiment, the paper substrate used in the water-repellent sheet has a moisture permeability of 1500 g / m2 measured from the side where the water-repellent layer is provided. 2 24 hours or more, preferably 1750 g / m 2 24 hours or more, preferably 2000g / m 2 The upper limit of the moisture permeability is not particularly limited, but in a preferred embodiment, it is 5000 g / m 2 24 hours or less, preferably 4500g / m 2 24 hours or less, more preferably 4000g / m 2 By having the moisture permeability of the surface on which the water-repellent layer is to be formed within the above range, the water in the water-repellent material and / or the water in the solvent of the water-repellent material can be efficiently evaporated to the paper layer side during the drying process after coating, allowing for the formation of a uniformly coated water-repellent layer.

[0031] The physical properties of the paper substrate used in the water-repellent sheet are not particularly limited and can be appropriately set depending on the application and structure of the paper container. In the present invention, for example, the longitudinal elongation is 1.0 to 15.0%, the transverse elongation is 2.0 to 12.0%, and the specific compressive strength is 100 to 350 N m 2 / g, specific burst strength 2.80~5.00kPa·m 2 / g.

[0032] (Paper sheets used for other parts) The physical properties of the paper sheets used in the other parts, excluding the part using the water-repellent sheet, are not particularly limited. For example, the surface has a 120-second Cobb water absorbency of 50 g / m 2 It may be less than 45 g / m 2 It may be less than 40 g / m 2 In the present invention, the Cobb water absorbency is measured in accordance with JIS P8140 (Cobb method) by bringing 100 ml of distilled water into contact with the surface layer and measuring the weight of water absorbed per unit area after a specified time.

[0033] The moisture permeability of the paper sheet is not particularly limited, and is 10,000 g / m 2 24 hours or less is acceptable, 7500g / m 2 24 hours or less is acceptable, 5000g / m 2 The moisture permeability of paper can be measured from the surface layer side in accordance with JIS Z 0208, and the smaller the value, the higher the moisture resistance.

[0034] The drop oil absorbency of the surface of the paper sheet is not particularly limited, and may be 1 second or more, 2 seconds or more, or 3 seconds or more. The oil absorbency is measured by dropping one drop of diesel No. 1, whose dynamic viscosity coefficient has been adjusted to 3 cSt, onto the surface of the sample using a microsyringe equipped with an H5 needle, and measuring the time until the surface no longer becomes glossy.

[0035] Other physical properties of the paper sheet are not particularly limited and can be set appropriately depending on the use and structure of the paper container. For example, the Oken smoothness of the surface side is 1 second to 100 seconds, the longitudinal elongation is 1.0 to 15.0%, the transverse elongation is 2.0 to 12.0%, and the specific compressive strength is 100 to 350 N m 2 / g, specific burst strength 2.80~5.00kPa·m 2 / g. In the case of a paper sheet, a waterproof layer, which will be described later, may be provided on the surface layer.

[0036] (Paper sheet raw materials and manufacturing) As for the raw pulp of the paper sheet, as will be described later, known materials can be used without any particular restrictions for both the water-repellent sheet and the paper sheets used in other parts. The paper sheet may contain recycled paper pulp or may not contain recycled paper pulp. When recycled paper pulp is contained, for example, when the paper sheet is a single-ply paper, the recycled paper pulp content of the total pulp can be preferably 10% by mass or more, more preferably 25% by mass or more, even more preferably 50% by mass or more, and most preferably 70% by mass or more, or can be 100% by mass (consisting only of pulp derived from recycled paper). Furthermore, kraft pulp can be blended as a pulp other than recycled paper pulp, or the entire amount can be kraft pulp. Furthermore, when the paper sheet is a multi-layer paperboard having two or more paper layers, the recycled paper pulp content per layer can be as described above, and the recycled paper pulp content in each layer can be different.

[0037] In the papermaking process for paper sheets, sizing agents and water repellents can be added internally or externally, and furthermore, paper strength agents can be added internally or externally to improve strength. Examples of sizing agents include rosin-based sizing agents, rosin emulsion-based sizing agents, α-carboxymethyl saturated fatty acids, neutral rosin-based sizing agents, alkyl ketene dimers (AKD), alkenyl succinic anhydrides (ASA), cationic polymer-based sizing agents, etc. Furthermore, examples of water repellents include fluorine-based resins, polyamide-based resins, waxes, etc. Furthermore, examples of paper strength agents include conventionally used paper strength agents such as polyacrylamide (PAM) and modified starch. When externally added, the coating amount is not particularly limited, and can be, for example, 10 g / m 2 It may be less than 5g / m 2 It may be less than 3g / m 2 It may be less than 2 g / m 2 The following may also be used.

[0038] If necessary, known fillers can be added to the paper sheet, such as inorganic fillers such as kaolin, calcined kaolin, delaminated kaolin, clay, calcined clay, delaminated clay, illite, heavy calcium carbonate, light calcium carbonate, light calcium carbonate-silica composite, magnesium carbonate, barium carbonate, titanium dioxide, zinc oxide, silicon oxide, amorphous silica, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, and zinc hydroxide, and organic fillers such as urea-formalin resin, polystyrene resin, and phenolic resin.

[0039] Furthermore, aluminum sulfate, aluminum chloride, sodium aluminate, basic aluminum compounds, water-soluble aluminum compounds, polyvalent metal compounds, silica sol, etc. may be added internally to the extent that the quality of the paper sheet is not affected.

[0040] The paper sheet is produced by a known papermaking method, for example, using a Fourdrinier paper machine, a gap former paper machine, a hybrid former paper machine, an on-top former paper machine, a cylinder paper machine, or the like, but is not limited to these.

[0041] Furthermore, to adjust the smoothness of the paper sheet, a smoothing treatment may be carried out as necessary. For the smoothing treatment, a smoothing treatment device such as a normal calender, super calender, gross calender, soft calender, thermal calender, or shoe calender can be used. The smoothing treatment device may be adjusted as appropriate in terms of the form of the pressure device, the number of pressure nips, heating, line pressure, etc. Furthermore, a coating agent such as latex, starch, pigment, water repellent, or waterproofing material (described below) may be applied to the outermost layer of the paper sheet using a known coating method in a manner depending on the intended use of the paper sheet.

[0042] In the present invention, depending on the use and structure of the paper container, the raw materials, chemicals, papermaking methods, etc. described above may be the same as or different from those of the paper sheets used in other parts of the water-repellent sheet. In a more preferred embodiment, the water-repellent sheet may be in the form of paper (waterproof paper) provided with a waterproof layer having waterproof properties as described below.

[0043] Cord base paper The corrugated board of the present invention can be obtained by laminating corrugated medium base paper to the obtained paper sheet (liner). Generally, medium base paper is corrugated using a corrugator, and liners are laminated to the front and back of the medium to produce high-strength corrugated board, but multi-layered corrugated board and single-faced corrugated board with corrugated medium base paper exposed on the surface are also known. In a preferred embodiment of the present invention, the corrugated board is one in which liners are laminated to both sides of the medium, or one in which the corrugated board is laminated to multiple layers.

[0044] The basis weight of the medium base paper is not particularly limited, but is preferably 60 to 250 g / m 2 is preferred, and 70 to 240 g / m 2 More preferably, 80 to 230 g / m 2 Furthermore, depending on the application and structure of the double-walled paper container, the corrugated cardboard sheet for the inner container and the corrugated cardboard sheet for the outer container may have the same basis weight, or corrugated cardboard sheets of different basis weights may be used.

[0045] In the present invention, it is preferable to use reinforced corrug in the corrugated cardboard sheet, and it is more preferable to use water-resistant reinforced corrug. Reinforced corrug refers to a corrug that has improved compressive strength compared to a general corrug that satisfies the performance of corrug base paper specified in JIS P 3904 by adding a paper strength agent or the like during the papermaking process. Furthermore, water-resistant reinforced corrug refers to a corrug that has improved not only compressive strength but also water resistance by further adding a waterproofing agent during the reinforced corrug manufacturing process. Polyacrylamide (PAM) may be used as an internal paper strength agent, and in this case, the amount added is preferably 0.1% to 5.0% of the paper stock solids, more preferably 0.2% to 2.0%.

[0046] The medium base paper may have a clear (transparent) coating layer formed on one or both sides of the base paper by applying a coating liquid containing a starch-based compound. Starch coating refers to applying a coating liquid (surface treatment liquid) containing a starch-based compound onto the base paper using a coater (coating machine) such as a pond-type two-roll size press, a gate roll coater or rod metering size press which are film transfer coating methods, or a curtain coater or spray coater which are non-contact coating methods.

[0047] There are no particular restrictions on the amount of starch coating as long as it does not impair the strength of the medium, and the lower limit is 0.2 g / m2 in solids per side. 2 It may be more than 0.8g / m 2 It may be 2.0 g / m or more. 2 It may be more than 3.0 g / m 2 It may be more than 4.0 g / m 2 There is no particular upper limit to the coating amount, but if the coating amount is increased, it is necessary to reduce the basis weight of the base paper before the starch clear coating, which reduces the tensile strength and tear strength of the base paper before the starch coating, making it more likely to break. Therefore, the coating amount of the starch-based compound is set to 8.0 g / m per side. 2 Less than 6.0 g / m is preferred 2 The following may also be used.

[0048] In the present invention, various auxiliaries that are typically incorporated into starch coatings, such as dispersants, thickeners, water retention agents, antifoaming agents, water-resistant agents, and colorants, can be used as needed.

[0049] Examples of coaters that can be used to apply the starch-based compound to the medium base paper include a two-roll size press, a gate roll coater, a rod metering size press, a blade coater, a bar coater, a spray coater, an air knife coater, and a curtain coater. In the present invention, film transfer type coaters such as a gate roll coater and a rod metering size press can also be used to produce the desired effect.

[0050] As the raw material pulp for the corrug base paper, any known pulp can be used without any particular restrictions, as will be described later. It is preferable that a large amount of recycled paper pulp is blended as the raw material pulp for the corrug base paper used in the present invention. In the present invention, the blending ratio of recycled paper pulp to the total pulp is preferably 50% by weight or more, more preferably 70% by weight or more, even more preferably 80% by weight or more, and may be 90% by weight or more.

[0051] Fillers and additives to be added to the corrug base paper will be described later, but known ones can be used, and known papermaking methods can also be used. Various surface treatments can be applied to the corrug base paper, for example, surface treatment can be performed by calendering, or a lubricant can be applied to the corrug base paper. Wax-based lubricants are particularly preferred, and the application amount is 0.005 g / m. 2 ~0.1g / m 2 In the present invention, it is preferable to spray the lubricant onto the calender rolls and transfer it to the paper when the base paper is passed through the calender. This is because, in addition to applying the lubricant, this method can prevent dirt from adhering to the surface of the calender rolls. As described above, applying a lubricant can more effectively prevent dirt from adhering to the surface of the calender rolls.

[0052] The obtained corrugating medium base paper can be corrugated (fluted) using a known corrugator. Any known corrugation process can be used depending on the application, and for example, A flute, B flute, C flute, E flute, F flute, G flute, AAA flute, AA flute, etc. may be applied to the corrugating medium base paper.

[0053] Processing into cardboard sheets The corrugated cardboard sheet used in the paper container of the present invention is obtained by laminating a paper sheet (liner) and a corrugated medium together using a corrugator.

[0054] Any known corrugator can be used without limitation, but a typical corrugator is composed of a single facer, a double backer, and a cutter. It also uses a glue-making device for bonding the liner and the core paper, and a device for generating heat to melt the glue.

[0055] Furthermore, when producing the corrugated cardboard sheet used in the paper container of the present invention, an adhesive is used to bond the liner and the core. However, it is preferable to use a water-resistant adhesive from the viewpoint of preventing a decrease in the strength of the corrugated cardboard box due to water wetting, condensation, humidity, etc. on the cross section of the corrugated cardboard sheet, and it is particularly preferable to use a water-resistant adhesive when producing a corrugated cardboard sheet using a water-repellent sheet. A water-resistant adhesive is a normal corrugated cardboard adhesive to which a water-resistant agent has been added. The water-resistant agent is not particularly limited, and examples include those containing synthetic resin emulsion, ketone aldehyde resin, etc.

[0056] Raw material for paper sheets for paper containers and corrugated cardboard cores for paper containers The raw material pulp for the paper sheet (liner) and medium (hereinafter referred to as "paper material") used in paper containers can be any known pulp, without particular limitation, depending on the part to be used and the application. Specific examples include various wood-derived pulps such as bleached softwood kraft pulp (NBKP), bleached hardwood kraft pulp (LBKP), unbleached softwood kraft pulp (NUKP), unbleached hardwood kraft pulp (LUKP), groundwood pulp (GP), refiner ground pulp (RGP), chemical pulp (CP), thermomechanical pulp (TMP), and chemithermomechanical pulp (CTMP), as well as non-wood pulps obtained from kenaf, bagasse, bamboo, hemp, straw, etc.

[0057] The paper material may contain recycled paper pulp, or may not contain recycled paper pulp. When recycled paper pulp is contained, for example, when the paper material is single-ply paper, the recycled paper pulp content of the total pulp is preferably 10% by mass or more, more preferably 25% by mass or more, even more preferably 50% by mass or more, and most preferably 70% by mass or more, or may be 100% by mass (consisting only of pulp derived from recycled paper). Furthermore, kraft pulp may be blended as a pulp other than recycled paper pulp, or the entire amount may be kraft pulp.

[0058] Examples of waste paper pulp that can be used include waste paper pulp obtained by disintegrating unprinted waste paper such as cardboard, white paper, extra white paper, medium white paper, and white damage; printed waste paper such as fine paper, fine coated paper, medium paper, medium coated paper, and recycled paper; written waste paper; paper such as discarded confidential documents; and deinked pulp (DIP) obtained by disintegrating waste magazines and newspapers.

[0059] In the papermaking process, sizing agents and water repellents can be added internally or externally, and paper strength agents can be added internally to improve strength. Examples of sizing agents include rosin-based sizing agents, rosin emulsion-based sizing agents, α-carboxymethyl saturated fatty acids, neutral rosin-based sizing agents, alkyl ketene dimers (AKD), alkenyl succinic anhydrides (ASA), and cationic polymer-based sizing agents. Examples of water repellents include fluorine-based resins, polyamide-based resins, and waxes. Examples of paper strength agents include traditionally used paper strength agents such as polyacrylamide (PAM) and modified starch.

[0060] Furthermore, known fillers can be added to the paper stock as needed, and inorganic and organic fillers can be used without restriction. Examples of inorganic fillers include kaolin, calcined kaolin, delaminated kaolin, clay, calcined clay, delaminated clay, illite, heavy calcium carbonate, light calcium carbonate, light calcium carbonate-silica composite, magnesium carbonate, barium carbonate, titanium dioxide, zinc oxide, silicon oxide, amorphous silica, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, and zinc hydroxide. Examples of organic fillers include urea-formalin resin, polystyrene resin, and phenolic resin.

[0061] Furthermore, aluminum sulfate, aluminum chloride, sodium aluminate, basic aluminum compounds, water-soluble aluminum compounds, polyvalent metal compounds, silica sol, etc. may be added internally to the extent that the quality of the paper material is not affected.

[0062] The paper stock can be produced by a known papermaking method, for example, using a Fourdrinier paper machine, a gap former paper machine, a hybrid former paper machine, an on-top former paper machine, a cylinder paper machine, or the like, but is not limited to these.

[0063] Furthermore, to adjust the smoothness of the paper material of the present invention, a smoothing treatment may be carried out as necessary. For the smoothing treatment, a smoothing treatment device such as a normal calender, super calender, gross calender, soft calender, thermal calender, or shoe calender can be used. The smoothing treatment device may be adjusted as appropriate by adjusting the shape of the pressure device, the number of pressure nips, heating, line pressure, etc.

[0064] Water-repellent sheet, water-repellent layer In the water-repellent sheet of the present invention, a water-repellent layer is formed by known methods, such as applying a water-repellent agent such as an acrylic emulsion or a polyester emulsion to a paper substrate, or providing a porous layer containing a polymer of a radically polymerizable monomer on an anchor layer primarily composed of a pigment and a binder. In a more preferred embodiment, the water-repellent layer of the present invention contains a wax. Examples of waxes that can be contained in the water-repellent layer include polyethylene wax, Fischer-Tropsch wax, synthetic oil-based waxes (fatty acid esters, fatty acid amides, ketones, and amines), synthetic waxes such as hydrogenated oils, and natural waxes such as beeswax, Japan wax, paraffin wax, and microcrystalline wax. These waxes can be used alone or in combination of two or more types. Hydrocarbon waxes containing paraffin are particularly preferred.

[0065] waterproof paper, waterproof layer Waterproof paper may be used as the water-repellent sheet constituting the paper container of the present invention. Waterproof paper has a waterproof layer provided on a paper material. In a preferred embodiment, the waterproof layer of the present invention is provided by coating, and in a more preferred embodiment, the waterproof layer contains a synthetic resin and wax. The synthetic resin preferably contains at least one of a styrene-based resin, an acrylic-based resin, and a polyolefin-based resin. In particular, the synthetic resin is preferably a styrene-based resin and / or an acrylic-based resin.

[0066] The styrene-based resin that can be contained in the waterproof layer constituting the present invention preferably has a copolymerization ratio of 50 mass% or more of a styrene-based monomer having a styrene skeleton in its structure, and may be composed only of a polymer of a styrene-based monomer.

[0067] Examples of styrene-based monomers include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, ethylstyrene, p-tert-butylstyrene, α-methylstyrene, and α-methyl-p-methylstyrene.

[0068] Examples of monomers copolymerizable with styrene monomers include alkyl methacrylates such as methyl methacrylate, cyclohexyl methacrylate, and methylphenyl methacrylate, alkyl acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate, and cyclohexyl acrylate, unsaturated carboxylic acids such as methacrylic acid and acrylic acid, unsaturated dicarboxylic anhydrides such as maleic acid and itaconic acid, unsaturated nitriles such as acrylonitrile and methacrylonitrile, and conjugated dienes such as 1,3-butadiene and 2-methyl-1,3-butadiene. These can be used alone or in combination of two or more.

[0069] The acrylic resin that can be contained in the waterproof layer of the present invention is a resin in which the copolymerization ratio of acrylic acid, methacrylic acid, and acrylic monomers that are derivatives of these is 50% by mass or more, and it may be composed only of polymers of acrylic monomers.

[0070] Examples of acrylic monomers include methacrylic acid esters such as cyclohexyl methacrylate, t-butylcyclohexyl methacrylate, and methyl methacrylate, and acrylic acid esters such as methyl acrylate, ethyl acrylate, butyl acrylate, and isopropyl acrylate, and the acrylic resin may be a polymer of one or more monomers selected from these acrylic monomers.

[0071] Examples of monomers copolymerizable with acrylic monomers include aromatic vinyl compounds such as styrene, o-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, ethylstyrene, p-tert-butylstyrene, α-methylstyrene, and α-methyl-p-methylstyrene, unsaturated nitriles such as acrylonitrile and methacrylonitrile, maleimides such as N-phenylmaleimide and N-cyclohexylmaleimide, unsaturated dicarboxylic anhydrides such as maleic anhydride, and unsaturated carboxylic acids such as methacrylic acid and acrylic acid. These may be used alone or in combination of two or more.

[0072] In the present invention, the waterproof layer contains a wax. Examples of waxes that can be contained in the waterproof layer include synthetic waxes such as polyethylene wax, Fischer-Tropsch wax, oil-based synthetic waxes (fatty acid esters, fatty acid amides, ketones, and amines), and hydrogenated oils, as well as natural waxes such as beeswax, Japan wax, paraffin wax, and microcrystalline wax. These waxes can be used alone or in combination of two or more, with paraffin-containing hydrocarbon waxes being particularly preferred.

[0073] In the present invention, a pigment may be incorporated into the waterproof layer to improve whiteness, provided that the waterproofing properties are not impaired. In this case, the incorporation of the pigment preferably increases the whiteness of the waterproof layer surface by at least 1% compared to the whiteness of the paper substrate. Examples of such pigments include inorganic pigments such as calcium carbonate, titanium oxide, kaolin, clay, engineered kaolin, delaminated clay, talc, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicates, colloidal silica, satin white, mica, and montmorillonite. These pigments can be used alone or in combination of two or more. Among these pigments, kaolin, calcium carbonate, and mica, which have flat particles, are particularly suitable because they do not impair waterproofing properties. Such flat-shaped inorganic pigments preferably have an aspect ratio of 10 or greater. The pigment content in the waterproof layer is preferably 5 to 40% by mass, more preferably 10 to 35% by mass. If the pigment content is less than 5% by mass, the whiteness improvement effect will not be sufficient, and if it exceeds 40% by mass, the moisture-proof and waterproof functions of the waterproof layer due to the synthetic resin component may not be fully exhibited, which is undesirable.In addition, other coating agents such as binders, stabilizers, antifoaming agents, viscosity improvers, water-retaining agents, preservatives, and colorants may also be contained.

[0074] In the present invention, the waterproof layer can be formed by coating a waterproof material containing the above-mentioned components on a paper substrate and drying it. The coating amount of the waterproof layer is 4 to 20 g / m 2 It is preferable to set the thickness to 5 to 15 g / m 2 It is more preferable to set the thickness to 20 g / m 2 If the temperature exceeds this range, further improvement in waterproofness cannot be expected, and the manufacturing cost may increase.

[0075] In a preferred embodiment, the waterproof layer provided on the waterproof paper constituting the present invention has an average thickness of 5.5 to 20 μm, more preferably 5.6 to 15 μm, and even more preferably 5.7 to 12.5 μm. Here, the average thickness of the waterproof layer is the average value of the thicknesses of the waterproof layer measured by cutting a sample into strips and observing the cross section at any 10 points using an electron microscope.

[0076] In addition, the waterproof paper constituting the present invention has a moisture permeability of 15 (g / m 2 24h) / μm or less is preferable, and 10 (g / m 2 24h) / μm or less is more preferable, and 7 (g / m 2 ·24h) / μm or less is even more desirable. Here, the moisture permeability per unit thickness of the waterproof layer is calculated by dividing the moisture permeability measured from the waterproof layer side of the waterproof paper in accordance with JIS Z 0208 by the average waterproof layer thickness.

[0077] The waterproof paper of the present invention can be produced by coating at least one side of a paper stock with a waterproofing material and drying the coated waterproofing material. The waterproof layer can be formed by applying a coating agent using a known coating method, such as air knife coating, curtain coating, blade coating, gate roll coating, or die coating. The coating layer may be a single layer or multiple layers. Multiple coating layers may be applied sequentially, or two or more layers may be applied simultaneously using curtain coating or other methods. When multiple coating layers are applied, at least one layer must be waterproof, and it is preferable for the waterproofing material to be applied as the outermost coating layer. When drying the coating layer, the temperature of the coating layer at the exit of the drying process is preferably adjusted to be less than 120°C. The coating speed when applying the coating agent can be appropriately set taking into account the viscosity of the coating agent and the target coating weight.

[0078] In a preferred embodiment, the coating agent is applied to the paper stock by a contour coating method such as air knife coating or curtain coating, which ensures a uniform amount of coating agent on the paper stock surface, resulting in a uniform coating film thickness and preventing the occurrence of blisters in the coating layer during the subsequent drying process. Furthermore, the amount of coating agent used can be reduced compared to contact coating methods, thereby reducing production costs.

[0079] The coating agent applied to the paper stock is dried to form a coating layer. In this drying process, the coating temperature at the exit is preferably less than 120°C, and may be adjusted to 100°C or less. If the coating temperature at the exit is 120°C or higher, the incidence of blisters in the coating layer may increase, and blocking may occur in the waterproof paper that is wound after the coating layer has been formed. On the other hand, the coating temperature at the exit is preferably 60°C or higher, more preferably 70°C, and can also be 80°C or higher. If the coating temperature at the exit is less than 60°C, not only may blocking occur in the waterproof paper that is wound after the coating layer has been formed, but the coating may not dry sufficiently, resulting in insufficient waterproof and moisture-proof performance.

[0080] The coating temperature at the drying process exit can be set taking into account the basis weight and thickness of the paper stock. For example, paper stock with a high basis weight and thickness requires more heat for drying than paper stock with a low basis weight and thickness, but it also tends to be more susceptible to blisters on the coating surface. The reason for this is not limited to specific factors, but thick paper often has a higher basis weight and thickness and lower air permeability than thin paper. Even with the same moisture content, much of the moisture vaporized inside the paper stock during the drying process cannot fully escape, making it more likely to develop blisters on the coating surface. Therefore, the greater the basis weight and thickness of the paper stock, the higher the coating temperature at the drying process exit, within the above range, and the lower the temperature at the drying process entrance.

[0081] Here, the outlet of the drying process refers to the outlet of the drying zone when there is one drying zone in the drying process, and refers to the outlet of the drying zone on the most downstream side when there are multiple drying zones in the drying process.

[0082] The temperature of the coating layer at the exit of the drying process can be adjusted by adjusting the drying time and the temperature of the drying zone. The drying time is determined by the paper material feed speed, the number and length of the drying zones, and the equipment capacity of the drying zones (air volume, infrared output), etc. Furthermore, any known drying method can be used, such as a steam cylinder heating drying method, a hot air drying method, a gas-type infrared drying method, or an electric infrared drying method. Any one of these methods can be used alone or in combination of two or more. [Example]

[0083] The present invention will be described in more detail below using specific examples, but the present invention is not limited to the following specific examples. In this specification, unless otherwise specified, concentrations and the like are based on weight, and numerical ranges include their endpoints.

[0084] Liner and corrug base paper manufacturing (1) Liner sample A A back layer made of 100% recycled corrugated paper pulp, a middle layer made of 100% recycled paper pulp, and a top layer made of 70% unbleached kraft pulp and 30% recycled corrugated paper pulp were combined in a weight ratio of back layer: middle layer: top layer = 25:60:15. After drying with a dryer, a water repellent agent containing paraffin wax and rosin was applied to one side of the top layer. After drying with a dryer again, the surface was smoothed using a calender to produce liner sample A (basis weight: 282.6 g / m). 2 , 120-second Cobb water absorption of the surface: 39.4 g / m 2 , Water repellent coating amount: approx. 1g / m 2 ). (2) Liner sample B A waterproofing agent consisting of 100 parts styrene-acrylic resin (Michaelman MC1548A) and 5 parts wax emulsion (Seiko PMC WR3932) was applied to the surface of liner sample A using an air knife at a rate of 10.0 g / m. 2 The coating was applied and then dried with hot air so that the temperature of the coating layer at the exit of the drying process was 80°C, to obtain liner sample B (basis weight: 291.4 g / m 2 , 120-second Cobb water absorption of the surface: 0.1 g / m 2 ). (3) Liner sample C A back layer made of 100% recycled corrugated paper pulp, a middle layer made of 100% recycled paper pulp, and a surface layer made of 70% unbleached kraft pulp and 30% recycled corrugated paper pulp were combined in a weight ratio of back layer:middle layer:surface layer = 25:60:15. After drying in a dryer, the surface was smoothed using a calender to produce liner sample C (basis weight: 281.3 g / m 2 , 120-second Cobb water absorption of the surface: 27.7 g / m 2 ). (4) Liner sample D A 10 μm thick polyethylene film was laminated on the surface of liner sample C, and then the film was adhered and laminated using a roller heated to 80°C to obtain liner sample D (basis weight: 289.7 g / m 2 ). (5) Cord base paper A pulp slurry containing 100% recycled corrugated pulp by weight was mixed with 0.4% waterproofing material to prepare a paper stock. Next, a single layer of paper was made from this paper stock, dried in a dryer, and smoothed using a calender to produce corrugating base paper (basis weight: approximately 200 g / m 2 ).

[0085] Evaluation of liner and corrugating materials. The paper quality of the liner samples and medium base paper is shown in Table 1. (Basis Weight) Measured in accordance with JIS P 8124. (Average coating layer thickness, moisture permeability per unit coating layer thickness) The sample was cut into strips, and the thickness of the coating layer (waterproof layer) was measured at 10 random points on the cross section using an electron microscope. The average value was calculated as the average coating layer thickness. The moisture permeability per unit coating layer was also calculated by dividing the moisture permeability by the average coating layer thickness. (Oken Smoothness) Oken Smoothness was measured in accordance with JIS P 8155 using a digital Oken air permeability smoothness tester (Asahi Seiko). (Longitudinal elongation, transverse elongation) Measured in accordance with JIS P 8113. (Specific Compressive Strength) The compressive strength was measured in accordance with JIS P 8126, and the compressive strength was divided by the basis weight to calculate the specific compressive strength. (Burst Ratio) Burst strength was measured in accordance with JIS P 8131, and the burst ratio was calculated by dividing the burst strength by the basis weight. (Wet burst strength residual rate) Each sample was placed in water and left for 60 minutes (1 hour), and then the water was wiped off. The burst strength of the sample was measured in accordance with JIS P 8131, and the burst strength index was calculated by dividing this value by the basis weight. The value obtained by dividing this value by the burst strength index (the burst strength index of the sample before contact with water) was taken as the wet burst strength residual rate. (Cobb Water Absorbency) Measurement was carried out by the Cobb method in accordance with JIS P 8140. That is, 100 ml of distilled water was brought into contact with the surface (coated surface), and the weight of water absorbed per unit area after a specified time was measured. Note that the measurement time was the usual specified time of 120 seconds (2 minutes), and also 30 minutes. (Moisture permeability) Measured from the surface side (coated side) in accordance with JIS Z 0208. (Water repellency) The surface side (coated side) was measured in accordance with JAPAN TAPPI Paper and Pulp Test Method No. 68 "Paper and Paperboard - Water Repellency Test Method." (Contact Angle) One drop (50 μl) of distilled water was dropped onto the sample surface, and the contact angle was measured one second later using a contact angle measuring device (DAT1100 manufactured by FIBRO System AB). (Oil repellency) The surface side (coated side) was measured in accordance with JAPAN TAPPI Paper and Pulp Test Method No. 41 "Paper and paperboard - Oil repellency test method - Kit method." (Drop oil absorbency) Using a microsyringe equipped with an H5 needle, one drop of diesel No. 1, whose dynamic viscosity coefficient was adjusted to 3 cSt, was dropped onto the surface of the sample, and the time until the surface no longer became glossy was measured.

[0086] [Table 1]

[0087] Corrugated cardboard sheet manufacturing Corrugated cardboard sheets for boxes were produced from each liner sample. Specifically, for liner samples A to D, the front and back liners were used in the combinations shown in Table 2, and the front and back liners were bonded together via medium base paper so that the front layer side (the water-repellent layer or waterproof layer side) was on the outside of the cardboard sheet to produce the cardboard sheet. The thickness of the cardboard sheet was 5 mm (A flute) for the sheet for the outer container and 3 mm (B flute) for the sheet for the inner container.

[0088] Manufacturing of double-walled paper containers The resulting cardboard sheets were placed with the outer liner (water-repellent or waterproof layer) facing inward to create an A-type (JIS Z 1507 0201 format) cardboard box (external dimensions: 28.1 cm length x 24.6 cm width x 23.5 cm height, internal dimensions: 27.1 cm length x 23.6 cm width x 22.5 cm depth) for the outer container. Furthermore, a B-flute (3 mm thick) sheet was used as the inner container to create a cardboard container (external dimensions: 23.8 cm length x 23.6 cm width x 22.3 cm height, internal dimensions: 23.2 cm length x 23 cm width x 21.7 cm depth) as shown in Figure 1. The inner container was then placed inside the A-type cardboard box, which served as the outer container, to produce a double-walled paper container. The inner / external volume ratio of the double-walled paper container was 71.3%. As a comparative example, a paper container was produced in the same manner as above, without using an A-type cardboard box as the outer container, but as an inner container only.

[0089] [Table 2]

[0090] Evaluation of each container (1) Condensation resistance A vinyl bag containing a carboxymethyl cellulose solution (Sunrose (registered trademark) manufactured by Nippon Paper Industries Co., Ltd., product number: F350HC, concentration 1%) that had been sufficiently cooled in advance in a refrigerator at 5°C was placed into each cardboard container, and the lid was then sealed. The sealed cardboard container was left in an environment of 30°C and 85% humidity, and the box compressive strength was measured and evaluated after 1 day, 2 days, and 5 days. The box compressive strength was measured according to the following procedure in accordance with JIS Z 0212. (a) Place the box with the lid on in the center of the compression tester. (b) Start the compression testing machine and gradually apply a downward force evenly across the entire top surface of the box. (c) Read the load when the side of the box is deformed and use this as the box compressive strength. (d) The rate of decrease in box strength before and after storage (=box compressive strength after storage / box compressive strength before storage x 100) was calculated, and the condensation resistance was evaluated based on the following criteria. ○: Box strength reduction rate is less than 50% ×: Box strength reduction rate is 50% or more

[0091] (2) Mixed recyclability Paper sheet samples for the outer and inner containers (outer and inner cardboard) were cut into 25mm squares, and weighed out in a ratio of 30g of paper sample for the outer container to 10g of paper sample for the inner container. 1.5L of 45°C water was added to dilute the mixture to 2%, and the mixture was then disintegrated for 30 minutes using a Tappi disintegrator. Next, a wet sheet was formed and pressed according to JIS P 8222, and then dried for 2 hours on a plate heated to 50°C to produce a hand-made sheet (basis weight: approximately 50g / m2). 2 ). Next, the surface appearance of the hand-made sheet was visually evaluated based on the following criteria. ○: There is no noticeable foreign matter on the paper surface, and there are no particular issues with regard to recycling. ×: Foreign matter is noticeable on the paper surface, which poses a problem in terms of recycling. The results are shown in Table 3.

[0092] [Table 3]

[0093] The above results demonstrate that the paper container of the present invention has sufficient box compressive strength, regardless of the location of the sheet with the water-repellent layer, compared to box sample ccCC, which uses only ordinary corrugated board, and when the inner container is used alone. The liner used in the present invention can be suitably used as a liner for manufacturing boxes for bag-in-box applications. [Explanation of symbols]

[0094] 1 box 2 Flat plate part 3 1st fold line 4 First side wall 5 Second fold line 6 Second side wall 7 Third fold line 8 4th fold line 9 5th fold line 10 Folding section 11a,11b Projection piece 12 recess 13a, 13b protrusion 14 6th fold line 15 Locking piece 16a,16b fitting opening 17 Connection part 18 Cut 19 7th fold line

Claims

1. (a) a paper outer container; (b) A paper container having a paper inner container provided inside the outer container, A paper container, wherein at least one of the inner container and the outer container uses a sheet having a surface with a water repellency of R4 or more as defined in Paper Pulp Test Method No.

68.

2. The paper container according to claim 1, wherein at least the outer container is box-shaped.

3. At least one of the inner container and the outer container has a 30-minute Cobb water absorbency of 155 g / m2 measured from the waterproof layer side. ２ 3. The paper container according to claim 1 or 2, characterized in that a sheet having a waterproof layer surface is used.

4. The paper container according to claim 3, wherein the waterproof layer is provided by coating.

5. 5. The paper container according to claim 4, wherein the waterproof layer is a waterproof resin layer containing at least one resin selected from the group consisting of a styrene-based resin, an acrylic-based resin, and a polyolefin resin, and a water-repellent wax.

6. 3. The paper container according to claim 1, wherein the sheet constituting the inner container and / or the outer container is a cardboard sheet.

7. A method for using a paper container, in which an inner container is placed inside an outer container to contain an object, characterized in that at least one of the inner container or the outer container uses a sheet having a surface with a water repellency of R4 or higher as defined in Paper Pulp Test Method No.

68.

8. A method for manufacturing a paper container having a double structure, comprising: (a) Producing a paper container for an inner container and / or an outer container using a sheet having a surface with a water repellency of R4 or more as defined in Paper Pulp Test Method No. 68; (b) Placing the inner container inside the outer container; The above method, comprising:

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