JP2022032459A - Oil resistant paperboard - Google Patents

Abstract

To provide an oil resistant paperboard having oil resistance and water repellency on a face to be in contact with a food product, capable of suppressing a deterioration of the oil resistance at a ridge-folding part, and also having adiabaticity.SOLUTION: The foregoing problem can be solved by: an oil resistant paperboard involving: base paper obtained by papermaking 3 or more layers consisting of a surface layer, a back layer, and one or more core layers between the surface layer and the back layer; one or more coating layers involving a white inorganic pigment and a binder on both sides of the base paper, respectively; and an oil resistant layer in the coating layer and on one side relative to the outermost coating layer positioned at the outermost based on the base paper, wherein the white inorganic pigment in the outermost coating layer on the side having the oil resistant layer involves kaolin, and the oil resistant layer involves a white inorganic pigment and an acrylic resin.SELECTED DRAWING: None

Description

The present invention relates to an oil resistant paperboard that can be used for packaging containers such as bags, trays and packaging boxes for storing food.

While absorbing and absorbing water such as water and steam, it suppresses the absorption of oils such as animal and vegetable oils, that is, it has moisture absorption and oil resistance, and is excellent in printability and recyclability, and there is no occurrence of ruled line cracks. As a paperboard that can be manufactured at low cost, in a paperboard in which the base paper is composed of at least two or more paper layers, a front layer and a back layer, at least acrylic resin and porous are formed on the surface of the surface layer and / or the surface of the back layer. A moisture-absorbing and oil-resistant paperboard provided with a coating layer by applying a coating liquid containing inorganic particles at a solid content of 2 to 40 g / m ² per side is known (see, for example, Patent Document 1).

In retail stores and take-out food stores, the food to be sold may be stored in packaging containers such as bags, trays and packaging boxes. As such a packaging container, a synthetic resin container is generally used. However, due to the recent tendency of deplasticization, traders tend to change the packaging container from a synthetic resin container to a paper packaging container.

Japanese Unexamined Patent Publication No. 2009-013506

Paperboard is often used for paper packaging containers. Paperboard has cellulose fibers of pulp as the main constituent material. Cellulose fibers have a drawback that they easily absorb oil and the like exuded from food between the fibers. For this reason, for example, take-out paper packaging containers used for hamburgers, pizzas, okonomiyaki, octopus grills, shumai, and fried foods need to be oil resistant so that they do not absorb oil on the surface of the paper packaging containers that come into contact with food. Is. Oil oozes out from the non-oil resistant paper packaging container and contaminates the outside with oil. Therefore, the paperboard used for the paper packaging container needs to have oil resistance in the surface in contact with food. For example, when an oil resistant agent is simply applied to a paperboard to obtain a paper packaging container, the oil resistant agent is buried between the cellulose fibers and the oil resistance cannot be sufficiently exhibited.

Further, in a paper packaging container for take-out, the paperboard may be bent for the purpose of supporting the food to be contained. Generally, the so-called "valley fold" is performed by folding the paperboard on the side where the food is stored. Even when the paper packaging container uses a paperboard having oil resistance, the oil resistance of the valley fold portion may deteriorate. Deterioration of oil resistance in the valley folds causes oil to penetrate from the valley folds. As a result, oil oozes out from the valley fold portion of the paper packaging container, and the outside is contaminated with oil. For example, in the oil-resistant paperboard disclosed in Patent Document 1, the oil resistance of the valley fold portion may deteriorate. Therefore, it is necessary for the paperboard used for the paper packaging container to suppress the deterioration of the oil resistance of the valley fold portion.

In addition, many foods contain water inside. The surface of the paper packaging container that comes into contact with food must be water repellent. This is because when the surface of the paper packaging container in contact with the food does not have water repellency, the moisture makes it easier for the food to stick to the paper packaging container. Therefore, the paperboard used for the paper packaging container needs to be water repellent on the surface in contact with food.
In addition, take-out paper packaging may contain relatively hot foods such as takoyaki and fried chicken. Therefore, the paperboard used for the paper packaging container needs to have heat insulating properties that can be used when storing relatively hot foods.

From the above, an object of the present invention is to provide an oil-resistant paperboard that can be used for a paper packaging container and that satisfies the following (1) to (4).
(1) Have oil resistance on the surface in contact with food.
(2) Have water repellency on the surface in contact with food.
(3) Deterioration of oil resistance can be suppressed at the valley fold.
(4) Have heat insulating properties that can accommodate relatively hot foods.

As a result of diligent studies by the present inventors, the object of the present invention is achieved by the following.

[1] A base paper obtained by laminating three or more layers having one or two or more core layers between the surface layer and the back layer and the surface layer and the back layer, and both sides of the base paper, respectively. An oil-resistant layer on one side with respect to one or more coating layers containing a white inorganic pigment and a binder, and the outermost coating layer in the coating layer located on the outermost side with respect to the base paper. An oil-resistant paperboard in which the white inorganic pigment of the outermost coating layer on the side having the oil-resistant layer contains kaolin, and the oil-resistant layer contains a white inorganic pigment and an acrylic resin.

[2] The oil-resistant paperboard according to the above [1], wherein the binder of the outermost coating layer contains a styrene-butadiene copolymer.

[3] In the oil-resistant layer, the content mass ratio of the white inorganic pigment to the acrylic resin is [white inorganic pigment: acrylic resin] = 4: 6 to 6: 4, the above [1] or the above [2]. Oil resistant paperboard described in.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide an oil-resistant paperboard having oil resistance and water repellency on a surface in contact with food, suppressing deterioration of oil resistance at a valley fold portion, and having heat insulating properties.

The oil-resistant paperboard is a base paper obtained by laminating three or more layers having one or two or more core layers between the surface layer and the back layer, the surface layer and the back layer, and both sides of the base paper. One or more coating layers containing a white inorganic pigment and a binder, respectively, and the outermost coating layer in the coating layer, which is located on the outermost side of the base paper, are oil resistant on one side. Has a layer. The side on which the oil resistant layer is provided may be either one having a large number of coating layers or one having a small number of coating layers, regardless of the number of coating layers. In the oil-resistant paperboard, the surface having the oil-resistant layer is the surface in contact with food.

Each layer of the base paper is made of chemical pulp such as LBKP (Leaf Bleached Kraft Pulp) and NBKP (Needle Bleached Kraft Pulp), GP (Groundwood Pulp), PGW (Pressure GroundWood pulp), RMP (Refiner Mechanical Pulp), and TMP (Thermo Mechanical Pulp). ), CTMP (ChemiThermoMechanical Pulp), CMP (ChemiMechanical Pulp), CGP (ChemiGroundwood Pulp) and other mechanical pulps, and DIP (DeInked Pulp) and other waste paper pulps. It can be obtained by making a paper material containing various fillers such as calcium carbonate, talc, clay and kaolin, and various additives such as sizing agent, yield agent, fixing agent and cationizing agent as needed.
The base paper can be obtained, for example, by making a paper material for each layer, and making and drying each layer of the surface layer, the back layer, and the core layer in a wet paper state. In some embodiments, starch, various modified starches and modifications thereof are made between the surface layer and the core layer, between the core layer and the back layer, and between the core layer and the core layer prior to the bonding. Apply adhesive such as objects. The reason for this is that the interlayer strength is improved.
In some embodiments, each layer of base paper has an LBKP of 50% by weight or more with respect to the pulp in each layer. The reason for this is considered to be as follows. Although NBKP with a long fiber length is advantageous if it is normal for the strength of paper, LBKP has an LBKP of 50% by mass or more for the strength of the paper after being sewn because the layer made of LBKP has excellent smoothness. On the other hand, it works in an advantageous way. The strength of the paper affects the oil resistance of the valley folds.

Paper making is performed using a conventionally known paper machine by adjusting the paper material to be acidic, neutral or alkaline. Examples of the paper machine include various paper machines capable of multi-layer paper making such as a long net multi-layer paper machine, a circular net multi-layer paper machine, and a long net circular net combination multi-layer paper machine.

In some embodiments, the basis weight of the base paper is 260 g / m ² or more. The reason for this is that the heat insulating property is improved. As will be described later, the outermost coating layer on the side having the oil resistant layer contains kaolin. Kaolin has a flat plate shape and has excellent shielding properties, so that it suppresses the permeation and diffusion of the oil resistant agent from the oil resistant layer to the base paper. On the other hand, kaolin has relatively high thermal conductivity because it contains a metal in its composition. Therefore, when the white inorganic pigment of the outermost coating layer on the side having the oil resistant layer contains kaolin, a certain basis weight of the base paper is required in order to obtain heat insulating properties.

Other additives such as pigment dispersants, thickeners, fluidity improvers, defoamers, foam suppressants, mold release agents, foaming agents, penetrants, colorants, fluorescent whitening agents, etc. One or more of UV absorbers, antioxidants, preservatives, antifoaming agents, water resistant agents, wet paper strength enhancers, dry paper strength enhancers, etc., within the range that does not impair the desired effect of the present invention. Then, it can be appropriately blended.

The filler is a white pigment conventionally known in the papermaking field. White pigments include, for example, light calcium carbonate, heavy calcium carbonate, kaolin, talc, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, silica, aluminum silicate, diatomaceous earth, active white clay, alumina, alumina. Examples thereof include white inorganic pigments such as hydrate, aluminum hydroxide, lithopone, zeolite, magnesium carbonate, and magnesium hydroxide. Further, white organic pigments such as styrene-based plastic pigments, acrylic-based plastic pigments, polyethylene-based plastic pigments, urea resins, melamine resins and microcapsules can be mentioned. The filler is one or more selected from the group consisting of the white inorganic pigment and the white organic pigment.

The sizing agent is an internal sizing agent conventionally known in the papermaking field. Examples of the internal sizing agent include rosin-based sizing agents for acid paper, alkenyl succinic anhydride, alkyl ketene dimer, neutral rosin-based sizing agents, and cationic styrene acrylic sizing agents for neutral paper. be able to.

The yield agent is conventionally known in the field of papermaking. Examples of the yield agent include aluminum sulfate, polyacrylamide, cationized starch, polyethyleneimine, polyamide and polyethylene oxide.

In some embodiments, when used in packaging containers for foodstuffs, each of the surface, back and core layers contains only sizing agents, yield agents and / or colorants as additives. Contains only sizing agents or does not contain additives. The reason for this is food safety.
Further, in at least one embodiment, the base paper contains a sizing agent in the surface layer corresponding to the side where the following oil resistant layer is provided. The reason for this is that oil resistance and water repellency are improved.

In some embodiments, the base paper contains a surface sizing agent. The reason for this is that the oil resistance and water repellency are improved.
The surface sizing agent is also referred to as an external sizing agent. Surface sizing agents are conventionally known in the field of papermaking. Examples of the surface sizing agent include various starches and modified products thereof, carboxymethyl cellulose, casein, various polyvinyl alcohols and modified products thereof, polyacrylamide, styrene acrylic copolymers and waxes. In at least one embodiment, the surface sizing agent is one or more selected from the group consisting of starch, various modified starches and modified products thereof and styrene acrylic copolymers.

The base paper contains a surface sizing agent by applying a surface sizing liquid containing a surface sizing agent to the base paper using a conventionally known size press device or a conventionally known coating device. Conventionally known size press devices include, for example, an inclined size press, a horizontal size press, a rod metering size press, a roll metering size press, and a blade metering size press as a film transfer method, and a simsizer for a rod metering size press. Optimizers, speed sizers, film presses, and roll metering size presses include gate roll coaters. Other examples include bill blade coaters, twin blade coaters, velva papa coaters, tab size presses, and calendar size presses. Conventionally known coating devices include, for example, a blade coater, a rod coater, an air knife coater, a comma coater (registered trademark), a gravure coater, a bar coater, an E bar coater, a curtain coater, and the like.
After coating, it can be dried using a conventionally known drying device. Examples of the drying device include a straight tunnel dryer, an arch dryer, an air loop dryer, a hot air dryer such as a sine curve air float dryer, an infrared heating dryer, and a dryer using microwaves.

Calendar processing can be applied to the base paper.
The calendering process is a process of averaging the smoothness and thickness by passing paper between rolls. Examples of the calendar processing device include a machine calendar, a soft nip calendar, a super calendar, a multi-stage calendar, and a multi-nip calendar.

The coating layer is one layer or two or more layers. Of the coating layers, the coating layer located on the outermost side of the base paper is called the outermost coating layer. When there is only one coating layer, the coating layer is the outermost coating layer. The outermost coating layer has a sealing effect of suppressing the penetration and diffusion of the oil resistant agent into the base paper when the following oil resistant layer is provided. In some embodiments, the coating layer is one or two layers. The reason for this is that it is advantageous in terms of manufacturing cost.
The coating layer including the outermost coating layer can be obtained by applying and drying the coating layer coating liquid on the base paper or the coating layer. The method of providing the coating layer including the outermost coating layer on the base paper or the coating layer is not particularly limited. For example, a method of applying and drying a coating layer coating liquid using a coating device and a drying device conventionally known in the papermaking field can be mentioned. Examples of the coating apparatus include a comma coater, a film press coater, an air knife coater, a rod blade coater, a bar coater, a blade coater, a gravure coater, a curtain coater, an E bar coater, and a film transfer coater. Examples of drying devices include hot air dryers such as straight tunnel dryers, arch dryers, air loop dryers, and sine curve air float dryers, infrared heating dryers, and various drying devices such as microwave dryers. Can be done.
The coating layer can be subjected to calendar processing.

The coating layer contains a white inorganic pigment. The white inorganic pigment is a white inorganic pigment conventionally known in the field of coated paper. White inorganic pigments include, for example, heavy calcium carbonate, light calcium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, diatomaceous earth, calcium silicate. , Magnesium silicate, silica, aluminum hydroxide, alumina, lithopon, zeolite, magnesium carbonate, magnesium hydroxide and the like. The white inorganic pigment is one or more selected from the group consisting of these.

The coating layer contains a binder. The binder is a binder conventionally known in the field of coated paper, and is not particularly limited. Examples of the binder include conjugated diene resins such as styrene butadiene copolymers and acrylonitrile butadiene copolymers, acrylic resins such as acrylic acid esters or methacrylic acid ester polymers or methacrylic acid ester butadiene copolymers, and ethylene acetic acid. Vinyl-based resins such as vinyl copolymers and vinyl chloride vinyl acetate copolymers, polyurethane resins, alkyd resins, unsaturated polyester resins, and functional groups made of functional group-containing monomers such as carboxyl groups of these various copolymers. Thermo-curable synthetic resins such as modified resins, melamine resins, urea resins, natural rubbers, starches, various processed starches and various modified starches, cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose, natural polymer resins such as casein, gelatin and soy protein. Alternatively, a derivative thereof, polyvinylpyrrolidone, polyvinyl alcohol and various modified polyvinyl alcohols thereof, polypropylene glycol, polyethylene glycol and the like can be mentioned. The binder is one or more selected from the group consisting of these.

The coating layer can contain the white inorganic pigment and the binder by blending the white inorganic pigment and the binder with the coating liquid of the coating layer.

The outermost coating layer on the side having the oil resistant layer contains kaolin as a white inorganic pigment. In some embodiments, the kaolin of the outermost coated layer is 80% by mass or more with respect to the white inorganic pigment in the outermost coated layer. The reason for this is that oil resistance, water repellency and oil resistance at the valley fold portion are improved.
Kaolin is sometimes referred to as kaolin clay. Kaolin is an industrially refined and processed kaolin ore that is naturally produced, and is produced through processes such as crushing, washing, iron removal and classification. In addition, highly processable products such as delaminated kaolin made into a thin plate by applying shear force to improve the aspect ratio, engineered kaolin adjusted to sharpen the particle size distribution, and calcined kaolin with improved cohesiveness. Is also included.

In some embodiments, the outermost coating layer comprises a styrene-butadiene copolymer as a binder. The reason for this is that deterioration of oil resistance can be further suppressed in the valley fold portion.

The coating layer including the outermost coating layer can contain various additives conventionally known in the field of coated paper, in addition to the white inorganic pigment and the binder. Examples of the additive include white organic pigments, thickeners, fluidity improvers, antifoaming agents, foaming agents, colorants, ultraviolet absorbers, antioxidants, preservatives and antibacterial agents. Additives that are not harmful to food safety are used.

The amount of coating of the coating layer including the outermost coating layer is not particularly limited. In some embodiments, the individual coating amount of each coating layer including the outermost coating layer is 2 g / m ^{2 or more and 10 g / m 2 or} less in terms of dry solid content. In at least one embodiment, the total coating amount per one side of the coating layer including the outermost coating layer is 2 g / m ² or more and 24 g / m ² or less. These reasons are that the deterioration of oil resistance can be further suppressed in the valley fold portion.

The oil resistant layer contains an acrylic resin. The acrylic resin is an acrylic resin conventionally known as an oil resistant agent having water repellency. The acrylic resin is one selected from the group consisting of the (meth) acrylic acid alkyl ester monomer (monomer a) or two or more kinds of monomers, or one selected from the group consisting of the monomer a. Or with one or more kinds of monomers selected from the group consisting of two or more kinds of monomers and a monomer (monomer b) containing ethylenically unsaturated carboxylic acid and / or the above-mentioned monomer a. It is a copolymer obtained from one or more kinds of monomers selected from the group consisting of other copolymerizable monomers (monomer c).

The (meth) acrylic acid alkyl ester monomer (monomer a) is, for example, methyl (meth) acrylic acid, ethyl (meth) acrylic acid, n-propyl (meth) acrylic acid, isopropyl (meth) acrylic acid, and the like. N-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, octyl (meth) acrylate, (meth) acrylic 2-Ethylhexyl acid, n-nonyl (meth) acrylate, isononyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, and (Meta) Dodecyl acrylate and the like can be mentioned.

The monomeric (monomeric b) containing ethylenically unsaturated carboxylic acid includes, for example, (meth) acrylic acid, crotonic acid, maleic acid, itaconic acid, fumaric acid, monoalkyl maleic acid, monoalkyl fumaric acid, and Examples thereof include monoalkylitaconic acid. Further, the monomer a includes, for example, a monomer in which a carboxylic acid forms a salt such as a sodium salt.

Other monomers (monomerc c) copolymerizable with the monomer a include, for example, styrene, vinyl acetate, vinyl chloride, vinylidene chloride, (meth) acrylonitrile, ethylene, propylene, and (meth) acrylic acid. 2-Hydroxyethyl, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxypropyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, 2 (meth) acrylate -Hydroxy-3-phenoxypropyl, glycerol mono (meth) acrylate, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, di (meth) acrylic acid ( Poly) ethylene glycol, di (meth) acrylic acid dipropylene glycol, di (meth) acrylic acid 1,2-propylene glycol, di (meth) acrylic acid 1,3-propylene glycol, di (meth) acrylic acid 1,3 -Butylene glycol, Trimethylolpropane tri (meth) acrylate, Tetramethylolmethane tetra (meth) acrylate, Divinylbenzene, Di (meth) acrylate 1,4-butanediol, Di (meth) acrylate 1,6- Hexadiol, di (meth) acrylate neopentylglycol, tri (meth) acrylate trimethylolpropane, (meth) acrylate diallyl, (meth) glycidyl acrylate, (meth) acrylate methylglycidyl, N-methylol (meth) ) Acrylic, N-methoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N, N'-methylenebis (meth) acrylamide, sodium vinyl sulfonate, sodium p-styrene sulfonate, 2-acrylamide-2- Methylpropanesulfonic acid, 3-allyloxy-2-hydroxypropanesulfonic acid sodium, polyoxyethylene styrenated phenylsulfate sodium, glycerin monoallyl ether monosulfosuccinate sodium, 2-sulfoethyl (meth) sodium acrylate, (meth) acrylamide stearer Sodium acrylate, n-amyl (meth) acrylate, isoamyl (meth) acrylate, benzyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, ethyl carbitol (meth) acrylate, caprolactone modification (meth) Acrylic acid ester, achlorine, diacetone (meth) a Crylamide, formylstyrene, vinylmethylketone, vinylethylketone, (meth) acrylooxyalkylpropenal, (meth) diacetone acrylate, (meth) acetonyl acrylate, (meth) acetoacetoxyethyl acrylate, (meth) acrylic Acrylic 3,4-epoxycyclohexyl, diallyl phthalate, triallyl cyanurate and the like can be mentioned.

The acrylic resin can be synthesized by a known emulsification polymerization method. The synthesis is, for example, a method in which various monomers, emulsifiers and water are mixed in a predetermined reaction vessel, a radical polymerization initiator is added, and the mixture is stirred and heated. Acrylic resins as water-repellent oil-resistant agents are commercially available from, for example, Henkel Japan, Daiichi Paint Mfg. Co., Ltd., Clariant Japan, BASF, and the like.

The oil resistant layer contains a white inorganic pigment. The white inorganic pigment is a white inorganic pigment conventionally known in the field of coated paper. White inorganic pigments include, for example, heavy calcium carbonate, light calcium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, diatomaceous earth, calcium silicate. , Magnesium silicate, silica, aluminum hydroxide, alumina, lithopon, zeolite, magnesium carbonate, magnesium hydroxide and the like. The white inorganic pigment is one or more selected from the group consisting of these.

By using the white inorganic pigment in combination with the acrylic resin, the migration of the acrylic resin can be suppressed because the acrylic resin is adsorbed on the white inorganic pigment, and as a result, the oil resistant layer has defects such as pinholes. It is possible to form a film that does not exist.
In some embodiments, the content mass ratio of the acrylic resin and the white inorganic pigment in the oil resistant layer is [acrylic resin: white inorganic pigment] = 6: 4 to 4: 6. Further, in at least one embodiment, the white inorganic pigment in the oil resistant layer is heavy calcium carbonate. These reasons are that the oil resistance, the water repellency and / or the suppression of the deterioration of the oil resistance in the valley fold portion are improved because the film can be formed satisfactorily.

The oil-resistant layer can contain various additives conventionally known in the field of coated paper, in addition to the acrylic resin and the white inorganic pigment. Examples of the additive include white organic pigments, thickeners, fluidity improvers, antifoaming agents, foaming agents, colorants, ultraviolet absorbers, antioxidants, preservatives and antibacterial agents. Additives that are not harmful to food safety are used.

The amount of oil-resistant layer applied is not particularly limited. In some embodiments, the coating amount of the oil resistant layer is 5 g / m ² or more and 20 g / m ² or less in terms of the dry solid content. These reasons are that the deterioration of the oil resistance can be further suppressed in the valley fold portion while having the oil resistance.

Hereinafter, the present invention will be described in more detail by way of examples. The present invention is not limited to these examples. Here, "parts by mass" and "% by mass" represent "parts by mass" and "% by mass", respectively, of the amount of dry solid content or the amount of substantial components. The coating amount of the coating layer represents the amount of dry solid content.

A pulp slurry containing the following pulp and internal chemicals was prepared to make a base paper. The paper machine used was a long net paper machine for the surface layer, a circular net 5-layer paper machine for the core layer, and a circular net 1-layer paper machine for the back layer, and the paper was made at a papermaking speed of 160 m / min. Commercially available starch was attached to each layer by spraying at 0.6 g / m ² each.

<Base paper 1>
(surface)
LBKP (drainage degree 450 mlcsf) 100 parts by mass Sulfate band 1.1 parts by mass Rosin-based sizing agent 0.7 parts by mass Basis weight 46 g / m ²
(Core layer)
LBKP (drainage degree 450 mlcsf) 40 parts by mass NBKP (drainage degree 450 mlcsf) 30 parts by mass CGP (drainage degree 400 mlcsf) 30 parts by mass Sulfate band 0.6 parts by mass Basis weight 148 g / m ²
(Back layer)
LBKP (drainage degree 450 mlcsf) 85 parts by mass NBKP (drainage degree 450 mlcsf) 15 parts by mass Sulfate band 0.5 parts by mass Basis weight 46 g / m ²

<Base paper 2>
(surface)
LBKP (drainage degree 450 mlcsf) 100 parts by mass Sulfate band 1.1 parts by mass Rosin-based sizing agent 0.7 parts by mass Basis weight 46 g / m ²
(Core layer)
LBKP (Drainage degree 450 mlcsf) 40 parts by mass NBKP (Drainage degree 450 mlcsf) 30 parts by mass CGP (Drainage degree 400 mlcsf) 30 parts by mass Sulfate band 0.6 parts by mass Basis weight 168 g / m ²
(Back layer)
LBKP (drainage degree 450 mlcsf) 85 parts by mass NBKP (drainage degree 450 mlcsf) 15 parts by mass Sulfate band 0.5 parts by mass Basis weight 46 g / m ²

<Base paper 3>
(surface)
LBKP (drainage degree 450 mlcsf) 100 parts by mass Sulfate band 1.1 parts by mass Rosin-based sizing agent 0.7 parts by mass Basis weight 56 g / m ²
(Core layer)
LBKP (Drainage degree 450 mlcsf) 40 parts by mass NBKP (Drainage degree 450 mlcsf) 30 parts by mass CGP (Drainage degree 400 mlcsf) 30 parts by mass Sulfate band 0.6 parts by mass Basis weight 168 g / m ²
(Back layer)
LBKP (drainage degree 450 mlcsf) 85 parts by mass NBKP (drainage degree 450 mlcsf) 15 parts by mass Sulfate band 0.5 parts by mass Basis weight 56 g / m ²

<Base paper 4>
(surface)
LBKP (Drainage degree 450 mlcsf) 30 parts by mass NBKP (Drainage degree 450 mlcsf) 70 parts by mass Sulfate band 1.1 parts by mass Rosin-based sizing agent 0.7 parts by mass Basis weight 56 g / m ²
(Core layer)
LBKP (Drainage degree 450 mlcsf) 20 parts by mass NBKP (Drainage degree 450 mlcsf) 50 parts by mass CGP (Drainage degree 400 mlcsf) 30 parts by mass Sulfate band 0.6 parts by mass Basis weight 168 g / m ²
(Back layer)
LBKP (drainage degree 450 mlcsf) 85 parts by mass NBKP (drainage degree 450 mlcsf) 15 parts by mass Sulfate band 0.5 parts by mass Basis weight 56 g / m ²

<Base paper 5>
(surface)
LBKP (Drainage degree 450 mlcsf) 30 parts by mass NBKP (Drainage degree 450 mlcsf) 70 parts by mass Sulfate band 1.1 parts by mass Rosin-based sizing agent 0.7 parts by mass Basis weight 112 g / m ²
(Back layer)
LBKP (Drainage degree 450 mlcsf) 85 parts by mass NBKP (Drainage degree 450 mlcsf) 15 parts by mass Sulfate band 0.5 parts by mass Basis weight 112 g / m ²

<Surface size agent>
Oxidized starch and a styrene-acrylic copolymer were used as the surface sizing agent.

<Coating layer coating liquid 1>
The coating layer coating liquid 1 was prepared according to the following contents.
Kaolin 10 parts by mass Heavy calcium carbonate 90 parts by mass Phosphoric acid esterified starch 10 parts by mass styrene butadiene copolymer 10 parts by mass Antifoaming agent 0.3 parts by mass Ammonia water 0.1 parts by mass Mix with the above contents, water The mixture was mixed and dispersed in 1 to adjust the concentration to 58% by mass.

<Coating layer coating liquid 2>
The coating layer coating liquid 2 was prepared according to the following contents.
Kaolin 0 parts by mass Light calcium carbonate 100 parts by mass Phosphoric acid esterified starch 1 part by mass styrene butadiene copolymer 14 parts by mass Antifoaming agent 0.3 parts by mass Ammonia water 0.1 parts by mass Mix with water It was mixed and dispersed to adjust the concentration to 60% by mass.

<Coating layer coating liquid 3>
The coating layer coating liquid 3 was prepared according to the following contents.
Kaolin 60 parts by mass Light calcium carbonate 40 parts by mass Phosphoric acid esterified starch 1 part by mass styrene butadiene copolymer 14 parts by mass Antifoaming agent 0.3 parts by mass Ammonia water 0.1 parts by mass Mix with water It was mixed and dispersed to adjust the concentration to 60% by mass.

<Coating layer coating liquid 4>
The coating layer coating liquid 4 was prepared according to the following contents.
Kaolin 80 parts by mass Light calcium carbonate 20 parts by mass Phosphoric acid esterified starch 1 part by mass styrene butadiene copolymer 14 parts by mass Antifoaming agent 0.3 parts by mass Ammonia water 0.1 parts by mass Mix with water It was mixed and dispersed to adjust the concentration to 60% by mass.

<Coating layer coating liquid 5>
The coating layer coating liquid 5 was prepared according to the following contents.
Kaolin 80 parts by mass Light calcium carbonate 20 parts by mass Phosphoric acid esterified starch 1 part by mass Polyvinyl alcohol (kensification degree 88%, average polymerization degree 3500) 14 parts by mass Antifoaming agent 0.3 parts by mass Ammonia water 0.1 parts by mass The mixture was blended with the above contents, mixed and dispersed with water, and adjusted to a concentration of 60% by mass.

<Oil resistant layer coating liquid>
The oil-resistant layer coating liquid was prepared according to the following contents.
The number of white inorganic pigments is shown in Table 1. The number of oil resistant agents is shown in Table 1. The above contents were blended, and the mixture was mixed and dispersed with water to adjust the concentration to 40% by mass.
As oil resistant agents, acrylic resin, which is a water-based varnish for food paper packaging, Harville (registered trademark) B-7 of Daiichi Paint Mfg. Co., Ltd., polyvinyl alcohol, which is a barrier agent for oil resistant paper for food packaging, and Kuraray's Excell (registered). Trademark) was used.

<Oil resistant paperboard>
Apply a horizontal size press to the base paper on both sides of the base paper so that the amount of coating is 3.0 g / m ² of oxidized starch and 0.05 g / m ² of styrene acrylic copolymer per side. And dried using a hot air dryer.
With respect to the base paper after size pressing, the coating layer coating liquid 1 was applied to the back layer side of the base paper using a blade coater and dried using a hot air dryer. The coating amount was adjusted to 10 g / m ² .
Next, with respect to the base paper provided with the coating layer, the coating layer coating liquid 3 is applied to the side provided with the coating layer using an air knife coater and dried using a hot air dryer. did. The coating amount was adjusted to 8 g / m ² .
Next, as the outermost coating layer on the surface layer side of the base paper, any one of the above coating layer coating liquids 2 to 5 was coated using an air knife coater and dried using a hot air dryer. The coating amount was adjusted to 4 g / m ² . The coating layer coating liquid used is shown in Table 1.
Next, the oil-resistant layer coating liquid was applied to the coating layer (outermost coating layer) provided on the surface layer side of the base paper using an air knife coater and dried using a hot air dryer. The coating amount was adjusted so that the oil resistant agent was 6 g / m ² .

The following evaluation was performed on the obtained oil-resistant paperboard.

<Oil resistance>
The evaluation of oil resistance was carried out by J. Mol. TAPPI Pulp Test Method No. 41: 2000 The test method for oil resistance of paper and paperboard (kit method) was followed. Based on the measurement results of the oiliness of the kit method, the evaluation was made according to the following criteria. In the present invention, the oil-resistant paperboard shall have oil resistance if it is evaluated as A, B or C.
A: The value is 10 or more.
B: The value is 8 or more and less than 10.
C: The value is 6 or more and less than 8.
D: The value is less than 6.

<Water repellency>
The water repellency was evaluated by the following method.
For a rectangular oil-resistant paperboard measuring 20 cm in length and 20 cm in width, place the surface of the oil-resistant paperboard (the side with the oil-resistant layer) at an upward angle of 45 degrees from the horizontal, and place it 10 mm away from the surface of the oil-resistant paperboard in the vertical direction. Ion-exchanged water was continuously dropped (1 drop = about 0.1 ml) and the state of the water drops was observed. Based on the observation results, evaluation was made according to the following criteria. In the present invention, the oil-resistant paperboard shall have water repellency if it is evaluated as A, B or C.
A: Water droplets roll down on the surface of the oil-resistant paperboard like a ball.
B: Although there are no traces of water droplets on the surface of the oil-resistant paperboard, the water droplets fall slightly from the spherical shape.
C: There are no traces of water droplets on the surface of the oil-resistant paperboard, but water flow streaks are shown.
D: Water droplet marks are observed on the surface of the oil-resistant paperboard.

<Oil resistance of valley folds>
The oil resistance of the valley fold is determined by J. TAPPI Pulp Test Method No. 41: 2000 The test method for oil resistance of paper and paperboard (kit method) was followed. The oil resistance of the valley fold portion was measured by folding the oil resistant paperboard once with the surface having the oil resistant layer inside and dropping the kit liquid onto the expanded valley fold portion. Based on the measurement results of the oiliness of the kit method, the evaluation was made according to the following criteria. In the present invention, if the oil-resistant paperboard is evaluated as A, B or C, deterioration of the oil resistance of the valley fold portion can be suppressed.
A: The value is 5 or more.
B: The value is 4 or more and less than 5.
C: The value is 3 or more and less than 4.
D: The value is less than 3.

<Insulation>
The heat insulating property was evaluated by the following method.
A petri dish was placed on the surface of the oil-resistant paperboard (the side having the oil-resistant layer), and 30 ml of boiling water at 90 ° C. was poured into the petri dish. At this time, the oil-resistant paperboard was placed on the palm from the back surface of the oil-resistant paperboard (the side having no oil-resistant layer), and the heat felt was evaluated by scoring according to the following criteria. The number of subjects was 6 (3 females and 3 males), and the average score was calculated and rounded off to the nearest whole number. In the present invention, the oil-resistant paperboard shall have heat insulating properties if the evaluation is 4, 3 or 2.
4: You can have it without any pain.
3: It feels a little hot, but I can hold it.
2: It's hot, but you can have it for a short time.
1: I can't have it.

The evaluation results are shown in Table 1.

From Table 1, Examples 1 to 11 corresponding to the present invention are oil-resistant paperboard having oil resistance and water repellency on the surface in contact with food, suppressing deterioration of oil resistance at the valley fold portion, and having heat insulating property. I know there is. On the other hand, it can be seen that Comparative Examples 1 to 5 which do not satisfy the configuration of the present invention cannot satisfy at least one of the effects of the present invention on oil resistance, water repellency, oil resistance and heat insulating property in the valley fold portion.
Mainly from the comparison between Example 3 and Example 6, in the oil-resistant paperboard, when the outermost coating layer on the side having the oil-resistant layer contains a styrene-butadiene copolymer as a binder, the oil resistance deteriorates at the valley break portion. Can be suppressed.
Mainly from the comparison between Examples 3, 7, 8, 9 and 10, the mass ratio of the white inorganic pigment and the acrylic resin in the oil resistant layer is [white inorganic pigment: acrylic resin] = 4: 6 to 6. When it is: 4, the oil resistance can be improved, and the deterioration of the oil resistance can be suppressed in the valley fold portion.

Further, the following additional notes are disclosed with respect to the above-described embodiment of the present invention.

<1>
A base paper obtained by laminating three or more layers having one or two or more core layers between the surface layer and the back layer, and between the surface layer and the back layer, and a white inorganic pigment on both sides of the base paper, respectively. And one layer or two or more coating layers containing a binder, and an oil resistant layer on one side with respect to the outermost coating layer located on the outermost side of the coating layer with respect to the base paper. An oil-resistant paperboard in which the white inorganic pigment of the outermost coating layer on the side having the oil-resistant layer contains kaolin, and the oil-resistant layer contains a white inorganic pigment and an acrylic resin.

<2>
The oil-resistant paperboard according to <1> above, wherein the binder of the outermost coating layer contains a styrene-butadiene copolymer.

<3>
The above <1> or the above <2>, wherein the content mass ratio of the white inorganic pigment and the acrylic resin in the oil resistant layer is [white inorganic pigment: acrylic resin] = 4: 6 to 6: 4. Oil resistant paperboard.

<4>
The oil-resistant paperboard according to <3> above, wherein the white inorganic pigment contains heavy calcium carbonate in the oil-resistant layer.

<5>
The oil-resistant paperboard according to any one of <1> to <4> above, wherein each layer of the base paper has an LBKP of 50% by mass or more with respect to the pulp in each layer.

<6>
The oil-resistant paperboard according to any one of <1> to <5>, wherein the base paper has a basis weight of 260 g / m ² or more.

<7>
Any of the above <1> to <6>, wherein the base paper contains one or more surface sizing agents selected from the group consisting of starch, various modified starches and modified products thereof, and styrene-acrylic copolymers. Oil resistant paperboard described in.

Claims (3)

A base paper obtained by laminating three or more layers having one or two or more core layers between the surface layer and the back layer, and between the surface layer and the back layer, and a white inorganic pigment on both sides of the base paper, respectively. And one layer or two or more coating layers containing a binder, and an oil resistant layer on one side with respect to the outermost coating layer located on the outermost side of the coating layer with respect to the base paper. An oil-resistant paperboard in which the white inorganic pigment of the outermost coating layer on the side having the oil-resistant layer contains kaolin, and the oil-resistant layer contains a white inorganic pigment and an acrylic resin. The oil-resistant paperboard according to claim 1, wherein the binder of the outermost coating layer contains a styrene-butadiene copolymer. The oil-resistant paperboard according to claim 1 or 2, wherein in the oil-resistant layer, the content mass ratio of the white inorganic pigment to the acrylic resin is [white inorganic pigment: acrylic resin] = 4: 6 to 6: 4.