Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
  • B32B27/10—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of paper or cardboard
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
  • B65D65/00—Wrappers or flexible covers; Packaging materials of special type or form
  • B65D65/38—Packaging materials of special type or form
  • B65D65/42—Applications of coated or impregnated materials
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H15/00—Pulp or paper, comprising fibres or web-forming material characterised by features other than their chemical constitution
  • D21H15/02—Pulp or paper, comprising fibres or web-forming material characterised by features other than their chemical constitution characterised by configuration
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H19/00—Coated paper; Coating material
  • D21H19/10—Coatings without pigments
  • D21H19/14—Coatings without pigments applied in a form other than the aqueous solution defined in group D21H19/12
  • D21H19/20—Coatings without pigments applied in a form other than the aqueous solution defined in group D21H19/12 comprising macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H19/00—Coated paper; Coating material
  • D21H19/36—Coatings with pigments
  • D21H19/44—Coatings with pigments characterised by the other ingredients, e.g. the binder or dispersing agent
  • D21H19/56—Macromolecular organic compounds or oligomers thereof obtained by reactions only involving carbon-to-carbon unsaturated bonds
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H19/00—Coated paper; Coating material
  • D21H19/80—Paper comprising more than one coating
  • D21H19/82—Paper comprising more than one coating superposed
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H19/00—Coated paper; Coating material
  • D21H19/80—Paper comprising more than one coating
  • D21H19/84—Paper comprising more than one coating on both sides of the substrate
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
  • D21H21/14—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties characterised by function or properties in or on the paper
  • D21H21/18—Reinforcing agents
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H27/00—Special paper not otherwise provided for, e.g. made by multi-step processes
  • D21H27/10—Packing paper
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
  • Y02W90/00—Enabling technologies or technologies with a potential or indirect contribution to greenhouse gas [GHG] emissions mitigation
  • Y02W90/10—Bio-packaging, e.g. packing containers made from renewable resources or bio-plastics

Definitions

• the present invention relates to waterproof paper and packaging containers made using the same.
• an object of the present invention is to provide a waterproof paper that is excellent in water resistance, printability and condensation resistance, and to provide a packaging container made using the waterproof paper.
• the water-resistant paper of this embodiment has a water-resistant layer 1 on one side of the paper base material, and an undercoat layer 2 and a water-resistant layer 2 on the other side of the paper base material in this order from the paper base material side, and the PPS smoothness of the surface of the water-resistant paper having the water-resistant layer 2 is 2.6 ⁇ m or less, and the Cobb water absorbency of water at 20° C. for a contact time of 30 minutes on the surface of the water-resistant paper having the water-resistant layer 2 is 15.0 g/m 2 or less.
• the water-resistant paper of this embodiment has excellent water resistance, printability, and condensation resistance. Furthermore, the water-resistant paper of this embodiment has excellent surface gloss on the other side.
• condensation resistance means that when a container is made from the water-resistant paper of this embodiment and cold contents are placed in it to cause condensation, there is no change in appearance and the decrease in elasticity is suppressed.
• the surface on which the water-resistant layer 1 is formed is preferably the surface that comes into contact with the contents (liquid-contacting surface, front surface) when used as a packaging container, etc.
• the surface on which the water-resistant layer 2 is formed is preferably the opposite surface, which is the surface on which printing is performed (printing surface, back surface).
• Papermaking from the stock can be carried out by a standard method.
• the stock can be cast onto a wire or the like, dehydrated to obtain a wet paper, and multiple wet papers can be stacked as necessary, and this single-layer or multi-layer wet paper can be pressed and dried.
• this single-layer or multi-layer wet paper can be pressed and dried.
• an adhesive can be applied to the surface of the wet paper (the surface on which other wet papers are stacked).
• the undercoat layer preferably contains latex and a pigment.
• latex refers to a polymer that can be stably dispersed in water. Latex is generally emulsified and dispersed with a surfactant or the like.
• At least one selected from the group consisting of styrene-butadiene copolymers and acrylic polymers is preferable, an acrylic polymer is more preferable, and a styrene-acrylic copolymer is even more preferable.
• the styrene-acrylic copolymer is preferably a copolymer of styrene and an alkyl (meth)acrylate ester.
• the latex either a commercially available product or a synthetic product may be used. Examples of commercially available products include Acronal S728ap and Acronal S504ap manufactured by BASF Corporation, and Luckstar 3307BE manufactured by DIC Corporation.
• the glass transition temperature of the latex is not particularly limited, but from the viewpoint of the adhesive strength between the water-resistant layer and the undercoat layer, it is preferably -50°C or higher and 60°C or lower, more preferably -20°C or higher, even more preferably 0°C or higher, and more preferably 40°C or lower.
• the glass transition temperature of the latex is measured by differential scanning calorimetry (DSC).
• the mass ratio of calcium carbonate to kaolin is not particularly limited, but is preferably 50/50 or more and 90/10 or less, more preferably 55/45 or more and 80/20 or less, and even more preferably 55/45 or more and 75/25 or less.
• the average particle size of the pigment is not particularly limited, but is preferably 0.1 ⁇ m or more and 20 ⁇ m or less, more preferably 0.3 ⁇ m or more, and more preferably 10 ⁇ m or less.
• the average particle size of the pigment can be determined using a laser diffraction particle size distribution measuring device based on the principles of the laser diffraction method, and the value measured from the measured particle size distribution is to be adopted.
• a pigment having an aspect ratio of 5 or more in combination with a pigment having an aspect ratio of less than 5 (pigment 2) as the pigment, from the viewpoint of improving the water resistance of the undercoat layer, adjusting the viscosity of the coating liquid for the undercoat layer, and from the viewpoint of cost.
• the aspect ratio of pigment 1 is 5 or more, preferably 50 or more and 500 or less, and more preferably 300 or less.
• An example of a pigment having the above aspect ratio is kaolin.
• the aspect ratio of pigment 2 is less than 5, preferably 4 or less, more preferably 3.5 or less, and is at least 1.
• An example of a pigment having the above aspect ratio is calcium carbonate.
• the particle size of pigment 2 is preferably 0.1 ⁇ m or more and 10 ⁇ m or less, more preferably 0.3 ⁇ m or more, and more preferably 3 ⁇ m or less, and even more preferably 1.5 ⁇ m or less, from the viewpoint of further improving water resistance, printability, and condensation resistance.
• the pigment 2 contained in the undercoat layer 2 be finer because this makes it possible to obtain a printing paper having better printability and condensation resistance.
• the pigment 2 contained in the undercoat layer 2 is even more preferably 1.0 ⁇ m or less, and even more preferably 0.8 ⁇ m or less.
• the total content of pigment and latex is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more, from the viewpoint of water resistance and heat sealability, and may be 100% by mass.
• the undercoat layer may be one layer or two or more layers on each side.
• the undercoat layer is one layer from the viewpoint of productivity, and two or more layers may be used from the viewpoint of improving waterproofness.
• the undercoat layer 2 has two or more layers. By having two or more undercoat layers 2, the surface of the undercoat layer 2 becomes smoother, and by providing the water-resistant layer 2 on the undercoat layer 2, the printability and condensation resistance are further improved.
• the undercoat layer 2 preferably has 2 to 5 layers, more preferably 2 to 3 layers, and further preferably 2 layers.
• the method for forming the undercoat layer is not particularly limited, but for example, the undercoat layer can be obtained by preparing a coating liquid for the undercoat layer containing latex, pigment, and other components as necessary, coating the paper substrate with the coating liquid, and drying the coating liquid.
• the undercoat layer 2 has two layers, it is preferable to apply the lower layer with a rod coater, a bar coater or a roll coater, and it is preferable to apply the upper layer with a blade coater or a rod blade coater.
• a rod coater a bar coater or a roll coater
• the upper layer a blade coater or a rod blade coater.
• the thickness of the undercoat paper is preferably the lower limit or more from the viewpoint of obtaining paper strength as a packaging container, and is preferably the upper limit or less from the viewpoint of ease of manufacture and formability of water-resistant paper.
• the thickness of the undercoat paper is measured in accordance with JIS P 8118:2014.
• the density of the undercoat paper is not particularly limited, but for example, in the case of a packaging container, preferably a paper cup, from the viewpoint of obtaining paper strength as a packaging container and flexibility during molding, it is preferably 0.4 g/ cm3 or more and 1.1 g/ cm3 or less, more preferably 0.6 g/ cm3 or more, even more preferably 0.7 g/ cm3 or more, and more preferably 1.0 g/ cm3 or less, even more preferably 0.95 g/ cm3 or less.
• the density of the undercoat paper is calculated from the basis weight and thickness of the undercoat paper obtained by the above-mentioned measurement methods.
• the Oken smoothness of the surface (liquid-contacting surface, front surface) of the undercoat paper on which the water-resistant layer 1 is formed is, from the viewpoint of obtaining a water-resistant paper having excellent water resistance, preferably 20 seconds or more, more preferably 25 seconds or more, and even more preferably 30 seconds or more; the upper limit is not particularly limited, but is, for example, 500 seconds or less.
• the Oken smoothness of the surface of the undercoat paper on which the waterproof layer 2 is formed is preferably 100 seconds or more, more preferably 200 seconds or more, even more preferably 400 seconds or more, and even more preferably 600 seconds or more, and the upper limit is not particularly limited, but is, for example, 2000 seconds or less.
• the Oken smoothness of the back surface is equal to or more than the above lower limit, the waterproof layer 2 can be applied uniformly, resulting in good condensation resistance.
• the Oken smoothness is measured in accordance with JIS P 8115:2010.
• the waterproof paper of this embodiment has a waterproof layer 1 on one side of a paper base material and a waterproof layer 2 on the other side of the paper base material.
• the waterproof layer 2 is formed on the paper base material via the undercoat layer 2.
• the waterproof layer is preferably provided as the uppermost layer on at least one surface of the paper base material, and more preferably provided as the uppermost layer on at least the liquid-contacting surface.
• the waterproof paper of this embodiment may have one or more waterproof layers on each side of the paper base material, and may have two or more waterproof layers on at least one side.
• the water-resistant layer preferably contains a water-based resin.
• water-based resin is meant a resin that can be dispersed or suspended in water.
• the aqueous resin include polyolefin resins and acrylic resins, and examples thereof include ethylene-(meth)acrylic acid copolymers, styrene-acrylic copolymers, and ethylene- ⁇ -olefin copolymers.
• the number of carbon atoms in the ⁇ -olefin is preferably 4 or more and 20 or less, more preferably 6 or more and 16 or less, and even more preferably 6 or more and 12 or less.
• the water-resistant layers on the front surface (liquid-contacting surface) and the back surface (printing surface) contain the same type of water-based resin.
• the heat sealability tends to be improved. Therefore, for example, as described above, when the water-resistant layer on the front side contains an ethylene-(meth)acrylic acid copolymer as the aqueous resin, and when the back side has a water-resistant layer, it is preferable that the water-resistant layer contains an ethylene-(meth)acrylic acid copolymer as the aqueous resin.
• the water-resistant layers on both sides may contain different types of water-based resins, but from the viewpoint of heat sealability, it is preferable that the polarities of the resins are similar.
• the ethylene-(meth)acrylic acid copolymer may be an ethylene-acrylic acid copolymer or an ethylene-methacrylic acid copolymer
• the styrene-acrylic copolymer may be a styrene-(meth)acrylic acid alkyl ester copolymer.
• water-based resin commercially available products may be used, for example, AQUENCE EPIX BC 9220HS manufactured by Henkel Japan Ltd., MP498345N, MP4983R, MP4990R, 201103PX manufactured by Michaelman Japan LLC.
• Examples of such a surfactant include S, MFHS1279, ZAIKXEN (registered trademark) A and ZAIKXEN (registered trademark) AC manufactured by Sumitomo Seika Chemicals Co., Ltd., the Chemipearl series (S100, S300, S500) manufactured by Mitsui Chemicals, Inc., MYE-30ER and MYE-30MAZ manufactured by Maruyoshi Chemical Co., Ltd., the Surlyn series manufactured by DuPont, the Hi-Milan series manufactured by Mitsui-Dow Polychemicals Co., Ltd., HYPOD2000, RHOBAR R320, and RHOBAR R325 manufactured by Dow Chemical Japan Co., Ltd., Hi-Tec SC-100 manufactured by Toho Chemical Industry Co., Ltd., AQUATEX AC-3100 manufactured by Chuo Rika Kogyo Co., Ltd., AQUENCE EPIX BC900F, BC905F, and BC910F manufactured by Henkel Japan, and Jon
• the content of the aqueous resin in the water-resistant layer is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 80% by mass or more, still more preferably 90% by mass or more, and even more preferably 95% by mass or more, and is 100% by mass or less, of the resin components of the water-resistant layer.
• the resin component of the water-resistant layer means a polymer component contained in the water-resistant layer, that is, a compound having a weight-average molecular weight of 1,000 or more.
• the water-resistant layer can be obtained by preparing a coating liquid for the water-resistant layer containing a water-based resin and coating the same.
• the coating liquid for the water-resistant layer is preferably an aqueous dispersion. More preferably, the coating liquid for the water-resistant layer is a self-emulsifying and dispersing coating liquid that does not contain an emulsifier such as a surfactant or a dispersant. By not containing an emulsifier such as a surfactant or a dispersant, it is preferable because it has better water resistance.
• the ethylene-(meth)acrylic acid copolymer blended in the coating liquid for the water-resistant layer may be in the form of an ionomer.
• the ionomer is a copolymer neutralized with a cation.
• ethylene-methacrylic acid copolymers and synthetic resins obtained by neutralizing ethylene-acrylic acid copolymers with a cation all fall under the category of ionomers.
• the ionomers may be used alone or in combination of two or more types. Examples of cations include metal ions such as sodium ions, potassium ions, calcium ions, and magnesium ions, ammonium ions (NH 4 + ), and organic ammonium ions.
• the basis weight of the water-resistant layer 1 (the coating amount when provided by coating) is preferably 4.0 g/ m2 or more and 20 g/ m2 or less, more preferably 4.5 g/ m2 or more, more preferably 15 g/ m2 or less, and even more preferably 10 g/ m2 or less.
• the coating amount of the water-resistant layer 1 is preferably the above-mentioned lower limit value or more, and from the viewpoints of formability, cost and recyclability, it is preferably the above-mentioned upper limit value or less.
• the coating amount of the water-resistant layer 1 refers to the total coating amount.
• the total coating amount of the water-resistant layers 1 and 2 i.e., the total coating amount of the water-resistant layers on the front and back sides, is, from the viewpoints of water resistance and condensation resistance, as well as heat sealability, preferably from 6 g/ m2 to 20 g/ m2 , more preferably from 8 g/ m2 or more, even more preferably from 10 g/ m2 or more, still more preferably from 11.0 g/ m2 or more, and more preferably from 15 g/ m2 or less, even more preferably from 12 g/ m2 or less.
• the waterproof paper of this embodiment is used for a packaging container (preferably a food container, e.g., a paper cup), and has a water-resistant layer on only one side (the liquid-contacting side), it is preferable that the total coating amount of the waterproof layer on the liquid-contacting side is within the above range.
• the waterproof paper of this embodiment is used for a packaging container (preferably a food container, e.g., a paper cup), and has a water-resistant layer on both sides (the liquid-contacting side and the printed side), it is preferable that the total coating amount of the waterproof layer on the liquid-contacting side and the total coating amount of the waterproof layer on the printed side are each within the above range, and it is also preferable that the total coating amount of the waterproof layer on both sides is within the above range.
• the waterproof paper of this embodiment has a PPS smoothness (Parker Print Surf smoothness) of 2.6 ⁇ m or less on the surface having the waterproof layer 2, for example, the printed surface (reverse surface).
• PPS smoothness of the surface is 2.6 ⁇ m or less, the paper has excellent printability.
• a smooth waterproof layer 2 is formed, and unevenness in the formation of the waterproof layer 2 is suppressed, and the paper has excellent condensation resistance.
• the PPS smoothness of the surface having the water-resistant layer 2 is preferably 1.0 ⁇ m or more and 2.6 ⁇ m or less, preferably 2.4 ⁇ m or less, preferably 2.2 ⁇ m or less, more preferably 2.1 ⁇ m or less, and more preferably 1.2 ⁇ m or more, and even more preferably 1.5 ⁇ m or more.
• the PPS smoothness of the surface having the water-resistant layer 2 is preferably equal to or less than the upper limit from the viewpoints of printability and glossiness, and is preferably equal to or more than the lower limit from the viewpoint of ease of production.
• the PPS smoothness of the surface having the water-resistant layer 2 can be adjusted to the desired range by adjusting the Runkel ratio of the pulp raw material constituting the paper base material, the coating amount, number of layers, formation method, composition of the undercoat layer 2, and the coating amount, number of layers, composition, etc. of the water-resistant layer 2.
• the PPS smoothness is measured in accordance with JIS P 8151:2004 at a measurement pressure of 1 MPa.
• the basis weight of the waterproof paper is not particularly limited, but for example, in the case of packaging containers, preferably food containers, and more preferably paper cups, it is preferably 220 g/m 2 or more and 500 g/m 2 or less, more preferably 240 g/m 2 or more, even more preferably 250 g/m 2 or more, and more preferably 450 g/m 2 or less, even more preferably 400 g/m 2 or less, even more preferably 350 g/m 2 or less, and particularly preferably 300 g/m 2 or less.
• the thickness of the water-resistant paper is not particularly limited, but for example, for packaging containers, preferably food containers, and more preferably paper cups, it is preferably 230 ⁇ m or more and 500 ⁇ m or less, more preferably 250 ⁇ m or more, even more preferably 270 ⁇ m or more, and more preferably 430 ⁇ m or less, even more preferably 400 ⁇ m or less, and even more preferably 350 ⁇ m or less.
• the thickness of the water-resistant paper is preferably equal to or more than the lower limit from the viewpoint of obtaining water resistance and strength as a packaging container, and is preferably equal to or less than the upper limit from the viewpoint of ease of production of the water-resistant paper, formability, and recyclability of the pulp that constitutes the paper base material.
• the thickness of the waterproof paper is measured in accordance with JIS P 8118:2014.
• the density of the waterproof paper is not particularly limited, but for example, when used for packaging containers, preferably paper cups, it is preferably 0.4 g/ cm3 or more and 1.1 g/ cm3 or less, more preferably 0.6 g/ cm3 or more, even more preferably 0.7 g/ cm3 or more, and more preferably 1.0 g/ cm3 or less, even more preferably 0.95 g/ cm3 or less.
• the density of the waterproof paper is preferably the lower limit value or more, and from the viewpoint of flexibility during molding, it is preferably the upper limit value or less.
• the density of the waterproof paper is calculated from the basis weight and thickness of the waterproof paper obtained by the above-mentioned measurement method.
• the waterproof paper of this embodiment has a Cobb water absorbency of 15.0 g/ m2 or less at 20°C after a contact time of 30 minutes on the surface having the waterproof layer 2, for example the printed surface (rear surface).
• the Cobb water absorbency of 15.0 g/ m2 or less is preferable because it has excellent condensation resistance.
• the Cobb water absorbency of water at 20° C. on the surface having the water-resistant layer 2 is preferably 10.0 g/m 2 or less, more preferably 8.0 g/m 2 or less, and even more preferably 5.0 g/m 2 or less (the lower limit is 0 g/m 2 ).
• the Cobb water absorbency in water at 20°C for a contact time of 30 minutes is, from the viewpoint of water resistance to cold water, preferably 15.0 g/ m2 or less, more preferably 10.0 g/ m2 or less, more preferably 8.0 g/ m2 or less, even more preferably 6.0 g/ m2 or less, and even more preferably 4.0 g/ m2 or less (the lower limit is 0 g/ m2 ).
• the water-resistant paper of the present embodiment can also be suitably used for food packaging applications.
• the waterproof paper of this embodiment has excellent resistance to condensation, and is therefore suitable for storing cold contents that may cause condensation.
• the water-resistant paper of this embodiment is suitable for packaging containers such as paper cups, paper plates, and paper trays.
• the contents of the packaging container may be either food or non-food.
• the contents of the packaging container may be liquid, solid, or gel.
• the contents of the packaging container are not particularly limited, and include, for example, coffee, tea, black tea, juice, carbonated drinks, and other beverages; alcoholic drinks such as sake, shochu, and wine; milk drinks such as milk; foods such as instant foods (instant noodles, etc.), microwaveable foods, beverages (yogurt, ice cream, jelly, pudding, etc.), and prepared foods; pharmaceuticals; car wax, shampoo, rinse, and chemical products such as detergent, bath additives, hair dye, and toothpaste; and the like.
• the packaging container made of the water-resistant paper of this embodiment uses less plastic than a packaging container made of conventional laminated paper.
• the packaging container made of the water-resistant paper of this embodiment can be pulp-pulped with a pulpper with normal pulp-pulping performance, and is therefore excellent in recyclability.
• the packaging container made of the water-resistant paper of this embodiment is washed, cut, pulped, etc. to prepare a pulp slurry, and the obtained pulp slurry can be used to manufacture paper.
• the type of paper to be made is not particularly limited, and examples of the paper include printing paper, packaging paper, sanitary paper, and cardboard. It is also possible to manufacture packaging containers (for example, tissue boxes, paper cup sleeves, etc.) by processing the paper made.
• the raw materials used in the examples and comparative examples are as follows.
• the detailed blend ratio is as follows. Eucalyptus A and B are different species and origins. Eucalyptus A: Runkel ratio 0.24, 15% by weight Eucalyptus B: Runkel ratio 0.31, 75% by weight Acacia A: Runkel ratio 0.25, 10% by weight LBKP2: Hardwood bleached kraft pulp (LBKP) made from acacia. Runkel ratio 0.60.
• the detailed blend ratios are as follows.
• Acacia A, B, and C are of different species and origins.
• Acacia B Runkel ratio 0.60, 50% by mass blend
• Acacia C Runkel ratio 0.60, 50% by mass blend
• NBKP Softwood bleached kraft pulp made from Radiata pine and Douglas fir. Runkel ratio 0.85.
• the detailed blend ratios are as follows: Radiata pine: Runkel ratio 0.80 40% by weight Douglas fir: Runkel ratio 0.88 60% by weight
• a pigment dispersion having a solid content of 70 mass% was prepared using 70 parts of heavy calcium carbonate and 30 parts of kaolin as the pigment.
• a styrene-acrylic copolymer latex was blended into this pigment dispersion to prepare a pigment/styrene-acrylic copolymer latex mixture having a pigment content of 85.0 mass% and a styrene-acrylic copolymer latex content of 15.0 mass% in the solid content.
• a defoamer was blended into the pigment/styrene-acrylic copolymer latex mixture to prepare a coating liquid A having a solid content of 62 mass% and a pigment/styrene-acrylic copolymer latex mixture content of 99.5 mass% and a defoamer content of 0.5 mass% in the solid content.
• Example 7 A waterproof paper was obtained in the same manner as in Example 1, except that a waterproof layer 1 was formed on the liquid-contacting surface side using Coating Solution E.
• a weak acidic rosin sizing agent 0.15 parts by mass of a wet strength agent, and 0.7 parts by mass of a dry strength agent (cationized starch) were added to 100 parts by mass (solid content equivalent) of a pulp slurry prepared by mixing beaten LBKP2 (CSF 425 mL) and beaten NBKP (CSF 525 mL) in a ratio of 80% by mass and 20% by mass to prepare paper material for the inner layers (second and fourth layers).
• a weak acidic rosin sizing agent 0.15 parts by mass of a wet strength agent, and 0.7 parts by mass of a dry strength agent (cationized starch) were added to 100 parts by mass (solid content equivalent) of a pulp slurry prepared by mixing beaten LBKP2 (CSF 475 mL) and beaten NBKP (CSF 600 mL) in a ratio of 70% by mass and 30% by mass, to prepare a paper stock for the inner layer (third layer).
• Waterproof paper was obtained in the same manner as in Example 1, except that these paper materials were used.
• a weakly acidic rosin sizing agent 0.15 parts by mass of a wet strength agent, and 0.7 parts by mass of a dry strength agent (cationized starch) were added to 100 parts by mass (solids content equivalent) of a pulp slurry prepared by mixing beaten LBKP1 (CSF 475 mL) and beaten NBKP (CSF 600 mL) in a ratio of 55% by mass and 45% by mass to prepare a paper stock for the inner layer (third layer).
• Waterproof paper was obtained in the same manner as in Example 1, except that these paper materials were used.

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• 2023
  • 2023-12-26 JP JP2024567882A patent/JPWO2024143393A1/ja active Pending
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