WO2020116465A1

WO2020116465A1 - Coating paper for tableware

Info

Publication number: WO2020116465A1
Application number: PCT/JP2019/047281
Authority: WO
Inventors: 公人関
Original assignee: 大王製紙株式会社
Priority date: 2018-12-05
Filing date: 2019-12-03
Publication date: 2020-06-11
Also published as: KR20210097136A; JP2020090739A; JP6754417B2; CN113195829B; CN113195829A

Abstract

The present invention pertains to a coating paper that is for tableware, and that is provided with a pair of superficial layers and a plurality of intermediate layers disposed between the pair of superficial layers, wherein: the superficial layers and the intermediate layers contain, as main components, bleached softwood kraft pulp and bleached hardwood kraft pulp; the mass ratio of the bleached softwood kraft pulp to the bleached hardwood kraft pulp in the superficial layers is 5/95 to 15/85, while the mass ratio of the bleached softwood kraft pulp to the bleached hardwood kraft pulp in the intermediate layers is 30/70 to 40/60; and the respective superficial layers have, at the surface thereof, a surface coating layer that contains a totally saponified polyvinyl alcohol. The amount at which the surface coating layer is coated is preferably 1-5 g/m². The proportion of the sum of basis weight of the pair of superficial layers with respect to the total basis weight is preferably 25.0-35.0%.

Description

Coated paper for tableware

The present invention relates to coated paper for tableware.

Conventionally, as disposable tableware, molded plastic resin is widely used. In addition, conventional plastic resins, bamboo, and wood have a problem of high manufacturing cost because they need to be specially molded for knife applications. Further, since plastic products affect marine pollution and the ecosystem of marine organisms, in recent years, establishment of an alternative technique for plastic tableware has been required from the viewpoint of environmental protection. Especially in Europe, there is a demand for environmentally friendly paper products that can be recycled. On the other hand, in the prior art, a paper stirring stick or spoon with improved water resistance and hot water resistance has been proposed as an alternative material (see, for example, Patent Document 1).

JP, 2003-79505, A

However, the above-mentioned conventional techniques are still insufficient in imparting the toughness and durability required for cutlery applications such as tableware and knives. Therefore, in order to use paper for cutlery such as tableware and knives, it is required to improve toughness and durability.

The present invention has been made based on the above circumstances, excellent in toughness and durability, to provide a coated paper for tableware that can be used for paper tableware replacing conventional plastic paper knives To aim.

The invention made to solve the above problems comprises a pair of surface layers and a plurality of middle layers arranged between the pair of surface layers, and the surface layers and the middle layers are bleached softwood kraft pulp and bleached hardwood kraft pulp. And the mass ratio of the bleached softwood kraft pulp to the bleached hardwood kraft pulp in the surface layer is 5/95 or more and 15/85 or less, and the mass of the bleached softwood kraft pulp to the bleached hardwood kraft pulp in the middle layer. It is a coated paper for tableware having a ratio of 30/70 or more and 40/60 or less and the surface layer having a surface coating layer containing completely saponified polyvinyl alcohol on the surface.

　By mixing and blending softwood bleached kraft pulp and hardwood bleached kraft pulp, the coated paper for tableware will have an increased paper thickness and improved rigidity and durability. Further, by setting the mass ratio of the bleached softwood kraft pulp to the bleached hardwood kraft pulp in the surface layer to 5/95 or more and 15/85 or less, a large amount of hardwood kraft pulp that is relatively rigid and easily densified is included. The surface layer of can obtain high density and rigid characteristics and is excellent in strength. Furthermore, the surface layer has a high effect of suppressing penetration of moisture or oil components derived from an object such as food into the interior. On the other hand, by adjusting the mass ratio of the bleached softwood kraft pulp to the bleached hardwood kraft pulp in the middle layer to 30/70 or more and 40/60 or less, a large amount of softwood kraft pulp with high flexibility is contained, so that the middle layer is good. Be flexible. The coated paper for tableware has a multilayered laminated structure in which a pair of surface layers having rigidity having the property of being hard but easy to fold and a middle layer having flexibility are combined, so that the surface layer is relatively dense but elastic. It is possible to suppress distortion and breakage while ensuring the. Further, the coated paper for tableware can have good surface strength by having a surface coating layer containing completely saponified polyvinyl alcohol on the surface of the surface layer. Therefore, the coated paper for tableware is excellent in toughness and durability and is suitable for paper tableware that replaces conventional resin disposable tableware.

The coating amount of the surface coating layer is preferably 1 g/m ² or more and 5 g/m ² or less. Thus, when the coating amount of the surface coating layer is in the above range, the coated paper for tableware can further improve toughness and durability.

The ratio of the total basis weight of the pair of surface layers to the total basis weight is preferably 25.0% or more and 35.0% or less. In the coated paper for tableware having a pair of surface layers having rigidity and a middle layer having flexibility, by setting the ratio of the total basis weight of the pair of surface layers to the above range, it is possible to impart a property that is difficult to bend. You can

-It is preferable that the total number of middle layers is 4 or more. When the total number of the middle layers is 4 or more, the toughness and durability of the coated paper for tableware can be further improved.

Another invention made to solve the above problems is a paper tableware made of the coated paper for tableware. Since the paper tableware is composed of the coated paper for tableware, it has excellent toughness and durability.

According to the present invention, it is possible to provide a coated paper for tableware, which has excellent toughness and durability and can be used as a paper tableware that replaces conventional plastic tableware.

Hereinafter, a coated paper for tableware according to an embodiment of the present invention will be described in detail.
<Coated paper for tableware>
The coated paper for tableware includes a pair of surface layers and a plurality of middle layers arranged between the pair of surface layers. The "tableware" in the present invention is a broad concept including not only tableware such as plates, bowls, chopsticks, cups, coasters, trays, muddlers, spoons and forks, but also cooking utensils such as knives and knives. The coated paper for tableware is particularly suitable for knives such as knives and knives.

[Surface]
The coated paper for tableware includes a pair of surface layers. The surface layer is mainly composed of bleached softwood kraft pulp and bleached hardwood kraft pulp. In addition, a "main component" means the component with the largest content on a mass basis.

A mass ratio of the bleached softwood kraft pulp to the bleached hardwood kraft pulp in the surface layer is 5/95 or more and 15/85 or less. By adjusting the mass ratio of the bleached softwood kraft pulp to the bleached hardwood kraft pulp in the above range, since a large amount of relatively hardwood kraft pulp that is relatively rigid and easily densified is contained, the surface layer can obtain high-density and rigid characteristics. And has excellent strength. Furthermore, the surface layer has a high effect of suppressing penetration of moisture or oil components derived from an object such as food into the interior. Further, by combining with a flexible middle layer, it is possible to suppress distortion and bending while ensuring elasticity.

Each layer of the coated paper for tableware may be, for example, ECF (Elemental Chlorine Free) pulp, TCF (Total Chlorine Free) pulp, unbleached kraft pulp (UKP), hardwood unbleached kraft pulp (LUKP), softwood. Non-bleached kraft pulp (NUKP), hardwood semi-bleached kraft pulp (LSBKP), softwood semi-bleached kraft pulp (NSBKP), hardwood sulfite pulp, softwood sulfite pulp and other chemical pulp, or non-wood fibers such as kenaf, hemp and reeds. Various publicly known pulps such as pulps chemically or mechanically produced from can be appropriately combined and used. The coated paper for tableware is used for paper tableware and is brought into direct contact with an object such as food. Therefore, the other pulp used for the coated paper for tableware is preferably chemical pulp, and more preferably ECF pulp, TCF pulp, and unbleached kraft pulp (UKP). The ECF pulp is a chlorine-free bleached chemical pulp produced by bleaching with chlorine dioxide (ClO ₂ ) without using chlorine (Cl ₂ ). TCF pulp is a completely chlorine-free bleached chemical pulp produced by bleaching with oxygen (O), hydrogen peroxide (P), and ozone (Z) without using chlorine (Cl ₂ ). That is, since the ECF pulp and the TCF pulp have a small amount of chlorine ions or no chlorine ions, there is an advantage that there is little risk that organic chlorine compounds such as dioxins are generated even by low temperature incineration, and as a result, environmental load. Can be reduced. In addition, unbleached kraft pulp can be used to imitate the color of wood (ice bar, etc.), and by omitting the bleaching process, it is possible to reduce the environmental load such as energy reduction and CO ₂ reduction. ..

-The lower limit of Canadian Standard Freeness (CSF) of pulp used for the surface of the coated paper for tableware is preferably 410 ml. When the CSF of the pulp used for the surface layer is less than 410 ml, the rigidity of the coated paper for tableware may decrease. On the other hand, the upper limit of the CSF of the pulp used for the surface layer is preferably 470 ml. If the CSF exceeds 470 ml, it becomes difficult to adjust the pulp fiber orientation in the paper machine, and the texture of the coated paper for tableware deteriorates, and the paper strength may decrease when used as a paper container. By mixing and blending the bleached softwood kraft pulp and the bleached hardwood kraft pulp with high freeness, the coated paper for tableware can have a larger paper thickness and improved rigidity. Here, Canadian Standard Freeness (CSF) is disaggregated pulp by disaggregating according to the disaggregation method of pulp of JIS-P8220-1 (2012), and this disaggregated pulp is Canadian of JIS-P8121-2 (2012). It is a value measured according to the standard freeness test method.

[Middle layer]
A plurality of middle layers are provided between the pair of surface layers. The middle layer is mainly composed of bleached softwood kraft pulp and bleached hardwood kraft pulp. The mass ratio of the bleached softwood kraft pulp to the bleached hardwood kraft pulp in the middle layer is 30/70 or more and 40/60 or less. When the mass ratio of the bleached softwood kraft pulp to the bleached hardwood kraft pulp in the middle layer is within the above range, a large amount of softwood kraft pulp with high flexibility is contained, and thus the middle layer has good flexibility. Therefore, since the soft middle layer is combined with the pair of surface layers that are rigid and hard but tend to be easily broken as described above, the coated paper for tableware is excellent in toughness and durability.

-The lower limit of Canadian Standard Freeness (CSF) of pulp used for the middle layer of the coated paper for tableware is preferably 375 ml. If the CSF is less than 375 ml, the dewatering property on the paper machine may be poor, and it may be difficult to adjust the pulp fiber orientation. On the other hand, the upper limit of CSF of the pulp used for the middle layer is preferably 465 ml. If the CSF exceeds 465 ml, fibrillation is less likely to occur and the interlayer strength may be reduced. Further, it is preferable that the Canadian standard freeness of the pulp used for the middle layer is smaller than the Canadian standard freeness of the pulp used for the pair of surface layers from the viewpoint of maintaining the Z-axis strength of the middle layer and ensuring the elastic force.

-The total number of middle layers is preferably 4 or more. When the total number of the middle layers is 4 or more, the toughness and durability of the coated paper for tableware can be further improved. The upper limit of the total number of intermediate layers is preferably 8 or less from the viewpoint of maintaining the interlayer strength.

[Additive]
The coated paper for tableware preferably contains a sizing agent and a paper strength enhancer as a papermaking additive in the surface layer and the middle layer.

(Size agent)
In the coated paper for tableware, a sizing agent can be added to each layer in order to further suppress the permeation of water or oil components derived from an object such as food into the interior. Examples of the sizing agent include styrene-based sizing agents, alkyl ketene dimers (AKD), alkenyl succinic anhydride (ASA), neutral rosin sizing agents, rosin sizing agents, and modified rosin emulsion sizing agents. Among these, rosin sizing agents and modified rosin emulsion sizing agents are preferable.

The above rosin sizing agent is conventionally known in the papermaking field and is not particularly limited. Examples of the rosin-based substance include reinforced rosins obtained by modifying rosins such as gum rosin, wood rosin, tall oil rosin and the like with α,β-unsaturated carboxylic acids such as fumaric acid, maleic acid and acrylic acid, or anhydrides thereof. Examples thereof include rosin esters obtained by reacting rosins with polyhydric alcohols such as glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, and diglycerin. Further, in the present invention, the rosin-based sizing agent includes those obtained by emulsifying these alone or a mixture thereof, and those obtained by individually emulsifying and then mixing. Further, the above emulsified product also includes those added with various polymers in order to further improve the size expression.

The content of the sizing agent in the surface layer is preferably 0.5 kg/t or more and 5.0 kg/t or less in terms of solid content. The content of the sizing agent in the middle layer is preferably 2.0 kg/t or more and 5.0 kg/t or less in terms of solid content. In addition, "kg/t" shows the mass (kg) per ton of pulp. By setting the content of the sizing agent within the above range, the water resistance can be improved.

(Paper strength enhancer)
In the coated paper for tableware, a paper strengthening agent sizing agent can be added to each layer. By adding a paper strength enhancer, various strengths suitable for use as paper tableware can be imparted to each layer.

As the paper-strengthening agent, various known ones such as polyacrylamide resin, polyamide resin, polyamine resin, acrylic resin, melamine resin, urea resin, polyamide epichlorohydrin resin can be used. Among these, it is preferable to use the amphoteric strength enhancer. Examples of the amphoteric polyacrylamides include copolymers of acrylamide with the above anionic monomers and cationic monomers, Mannich modified products of the copolymers of acrylamide with the above anionic monomers, and Hoffmann degradation products. According to the findings of the present inventors, amphoteric polyacrylamide is particularly preferable, and since amphoteric polyacrylamide has a self-fixing function, even if added to improve the inter-paper strength, it does not cause excess cation. The modified rosin emulsion sizing agent can be stably fixed.

The content of the paper strengthening agent in each layer is preferably 12 kg/t or more and 20 kg/t or less in terms of solid content. By setting the content of the paper strength enhancer in the above range, various paper strengths such as the interlayer strength of the coated paper for tableware can be imparted. If the content of the paper strength enhancer is less than the above range, the interlayer strength may be insufficient. On the other hand, when the content of the paper strengthening agent exceeds the above range, the improvement of the interlayer strength is almost leveled off, and further, the yield of the added paper strengthening agent is reduced, so that the stains and foaming in the paper machine system may occur. May occur and the operability may be reduced.

(Other additives)
In addition, the coated paper for tableware may contain various other papermaking additives within a range that does not impair the intended effect of the present invention. Examples of other additives that can be added to the coated paper for tableware include known paper-making agents.

[Surface coating layer]
The coated paper for tableware has a surface coating layer containing completely saponified polyvinyl alcohol on the surface of the surface layer. In order to suppress the penetration of water or oil components derived from the object such as food into the interior and maintain the surface strength, it is necessary to form a relatively strong film on the surface layer that comes into contact with the object such as food. Since the coated paper for tableware has the above-mentioned surface coating layer, the coated paper for tableware has a good surface strength and has a high effect of suppressing penetration of moisture or oil components into the interior.

The coating amount of the completely saponified polyvinyl alcohol is preferably 0.5 g/m ² or more and 5.0 g/m ² or less from the viewpoint of imparting good surface strength.

The surface coating layer preferably contains a wax sizing agent. As the wax-based sizing agent, it is possible to use paraffin wax-based sizing agent, microcrystalline wax-based sizing agent, carnauba wax (carnauba wax)-based sizing agent, and the like. Since it is possible to impart water resistance and water resistance, it is preferable to include a paraffin wax sizing agent.

The coating amount of the wax-based sizing agent is preferably 0.1 g/m ² or more and 0.5 g/m ² or less from the viewpoint of improving water repellency and water resistance.

The surface coating layer preferably contains a surface sizing agent. Examples of the surface sizing agent include styrene-acrylic sizing agent, alkyl ketene dimer (AKD), alkenyl succinic anhydride (ASA), neutral rosin sizing agent and rosin sizing agent. In addition to these sizing agents, acrylic sizing agents are preferably used.

The coating amount of the surface sizing agent is preferably 0.2 g/m ² or more and 1.0 g/m ² or less from the viewpoint of suppressing insufficient strength due to moisture when used for tableware applications.

The above surface coating layer may contain starch, polyacrylic amide, etc. in addition to polyvinyl alcohol, paraffin wax and surface sizing agent. Further, the surface coating layer may further contain, for example, a known additive for papermaking.

As the surface coating layer, (1) a mode in which fibers on the surface of the surface layer are impregnated with an aqueous composition, (2) a mode in which a resin layer of the aqueous composition is formed on the surface of the surface layer, (3) surface layer It is assumed that the surface of the fiber of (1) is covered with the aqueous composition, or (4) a combination of these is included. Further, a part of the composition for surface coating layer may be impregnated.

The lower limit of the application amount of the surface coating layer, from the viewpoint of improving surface strength, is preferably ^{^{1.0g / m 2, 2.0g / m}} 2 is more preferable. The upper limit of the application amount of the surface coating layer, from the viewpoint of suppressing contamination caused by texture reduction and blocking during processing step as paper, preferably ^{5.0g / m 2, 4.0g / m} 2 is More preferable.

[Physical properties of coated paper for tableware]
(Basis weight)
The basis weight is measured according to JIS-P8124 (2011). The basis weight of each layer of the coated paper for tableware does not have to be uniform, and the basis weight of the surface layer and the middle layer is not particularly limited, but the basis weight of one surface layer is 90.0 g/m 2. ^It is preferably ² or more and 300.0 g/m ² or less. The basis weight of the entire middle layer is preferably 450.0 g/m ² or more and 925.0 g/m ² or less.

The lower limit of the dish coated paper overall basis weight, from the viewpoint of obtaining sufficient stiffness, preferably ^{^{700.0g / m 2, 750.0g / m}} 2 is more preferable. As an upper limit of the basis weight of the entire coated paper for tableware, 1000.0 g/m ² is preferable, and 900.0 g/m ² is more preferable. When the grammage exceeds 1000.0 g/m ² , sufficient rigidity is easily obtained, but folding wrinkles are likely to occur by passing through a paper roll during papermaking.

The ratio of the total basis weight of the pair of surface layers to the basis weight of the entire coated paper for tableware is preferably 25.0% or more and 35.0% or less. In the coated paper for tableware having a pair of surface layers having rigidity and a middle layer having flexibility, by setting the ratio of the total basis weight of the pair of surface layers to the above range, it is possible to impart a property that is difficult to bend. You can

(Paper thickness)
The paper thickness is measured in accordance with "Paper and board-Test method for thickness and density" described in JIS-P8118 (2014). The paper thickness of the coated paper for tableware is preferably 950 μm or more and 1300 μm or less. When the paper thickness of the coated paper for tableware is within the above range, peeling of the paper layer of the coated paper for tableware can be suppressed.

(density)
The density of the coated paper for tableware is preferably 0.73 g/cm ³ or more and 0.88 g/cm ³ or less. When the density of the coated paper for tableware is within the above range, rigidity is excellent while enabling low basis weight and weight reduction.

(moisture)
The water content of the coated paper for tableware measured according to JIS-P8127 (2010) is preferably 9.0% or more and 11.0% or less. Since the water content of the coated paper for tableware is within the above range, the flexibility is improved, and therefore workability in a folding machine and tearing of a folded portion when producing tableware using the coated paper for tableware are described. The suppression effect can be improved.

(ash)
Ash content is measured according to JIS-P8251 (2003). The ash content of the coated paper for tableware is preferably 0.1% or more and 10.0% or less. When the ash content of the coated paper for tableware is in the above range, the curl can be adjusted to be flat and the decrease in interlayer strength can be suppressed.

(Surface strength)
The surface strength is as described in JAPAN TAPPI Paper Pulp Test Method No. It is measured according to the "surface strength test method" according to 1 m-72. The lower limit of the surface strength of the coated paper for tableware is preferably 10A. When the surface strength of the coated paper for tableware is within the above range, it is possible to improve the abrasion resistance in the step of dropping the surface layer, conveying and processing.

(Cobb size degree)
The degree of Cobb size is measured using distilled water at 23° C. according to JIS-P8140 (1998). The upper limit of the degree of Cobb size of the coated paper for tableware is preferably 50 g/m ² . When the Cobb size degree of the coated paper for tableware is equal to or more than the above upper limit, the coated paper for tableware may cause wrinkles or wrinkles due to moisture absorption.

(Z-axis strength)
As the Z-axis strength of the water- and oil-resistant paper, the JAPAN TAPPI Paper Pulp Test Method No. The Z-axis strength measured according to 18-1:2000 is preferably 380 kN/m ² or more. By having the above Z-axis strength, it is possible to suppress the occurrence of delamination and wrinkles during tableware molding.

According to the coated paper for tableware, it has excellent toughness and durability and can be used for paper tableware that replaces conventional plastic tableware.

[Method for producing coated paper for tableware]
The method for producing the coated paper for tableware is not particularly limited, but the coated paper can be produced, for example, by the following steps using a known multi-layer paper machine.
(1) If necessary, an additive corresponding to each paper layer is added to and mixed with a slurry obtained by dispersing pulp fibers in water to prepare a stock for each paper layer.

(2) Next, using these raw material slurries, the surface layer, single layer or multiple layers of the middle layer and the surface layer of the coated paper for tableware in a neutral region are adjusted so that the pH of the coated paper for tableware becomes 6 or more and 8 or less. Paper is made by combining.
The papermaking method is not particularly limited, and a known papermaking machine, that is, a paper making machine such as a Fourdrinier, a cylinder, a hybrid former, a gap former, or the like is used to make a paper with three or more layers. In the papermaking step, a coating device such as a size press, a metalling size press, a gate roll coater, or the like can be used to apply the coating liquid on the surface of the surface layer to form a surface coating layer.

(3) Next, it is pressed by a pressure roll to remove water.

(4) Next, it is dried with a dryer cylinder.
After drying, a smoothing treatment may be performed using a calender device such as a nip calender, a super calender, a machine calender, a soft calender and the like. By performing the smoothing treatment, the coated paper for tableware is imparted with high glossiness and can be suitably used for paper tableware having a high-grade feeling.

(5) Finally, it is wound on a reel to obtain coated paper for tableware.

<Paper tableware>
The paper tableware is composed of the coated paper for tableware. Since the paper tableware is composed of the coated paper for tableware, it has excellent toughness and durability.

<Other embodiments>
The present invention is not limited to the above embodiment, and can be carried out in various modified and improved modes other than the above modes.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

The methods for measuring the physical property values of Examples and Comparative Examples are as follows.
[Freeness (mL)]
The obtained coated paper for tableware is disintegrated pulp by disintegrating in accordance with the pulp disintegration method of JIS-P8220-1 (2012), and this disaggregated pulp is a Canadian standard filter of JIS-P8121-2 (2012). The water content was measured according to the method.

[Basis weight (g/m ² )]
It was measured according to "Paper and board-Basis weight measuring method" described in JIS-P8142 (1998).

[Paper thickness (μm)]
It was measured according to "Paper and paperboard-Testing method for thickness and density" described in JIS-P8118 (2014).

[Density (g/cm ³ )]
It was measured according to "Paper and paperboard-Testing method for thickness and density" described in JIS-P8118 (2014).

[moisture]
It was measured according to JIS-P8127 (2010).

[ash]
It was measured according to JIS-P8251 (2003).

[Surface strength]
JAPAN TAPPI No. It was measured according to the surface strength test method using the wax of No. 1.

[Cobb size degree]
It was measured according to JIS-P8140 (1998).

[Z-axis strength]
JAPAN TAPPI Paper Pulp Test Method No. It was measured according to 18-1:2000.

[Bending strength]
The bending strength was measured with a digital force gauge (made by Imada Co., Ltd.), and the test conditions were as follows. The coated food paper was fixed to a 3-point bending jig and the force gage was lowered. The load at that time was defined as the bending strength (N). The test environment was a temperature of 26° C. and a humidity of 70%.

[Example 1]
(1) The formulations of the surface layer and the middle layer are shown below.
(Surface layer)
The following raw materials were added to 100 parts of a pulp slurry having a freeness of 440 mL of NBKP:LBKP of 10:90.
Modified rosin emulsion-based sizing agent (“AL1344” from Starlight PMC):
2.5 kg of solids/t of pulp
Acrylamide-based paper strength enhancer (Harima Chemical Co., Ltd. "Harmide RB-28"):
Solid content 16.0 kg/pulp t
(Middle layer)
The following raw materials were added to 100 parts of pulp slurry having a freeness of 440 mL of NBKP:LBKP of 35:65.
Modified rosin emulsion-based sizing agent (“AL1344” from Starlight PMC):
Solid content 3.5 kg/pulp t
Acrylamide-based paper strength enhancer (Harima Chemical Co., Ltd. "Harmide RB-28"):
Solid content 16.0 kg/pulp t
(2) This pulp slurry was made into a 7-layer structure in which the wire part had a surface layer, a 5-layer intermediate layer and a surface layer using a cylinder multi-layer paper machine. The basis weight of each layer surface 125 g / ^{m 2,} middle 626.5g / ^{m 2,} and a back layer 125 g / ^{m 2,} and a total basis weight 880.0g / ^{m 2.}
(3) On the surface of the surface layer, a coating solution containing polyvinyl alcohol and paraffin wax at 3.5 g/m ² was calender coated to form a surface coating layer in the following coating amounts. The coated paper for tableware of 1 was obtained.
Polyvinyl alcohol ("Gohsenol N300" manufactured by Nippon Synthetic Chemical Industry Co., Ltd.): 2.7 g/m ²
Paraffin wax (“Haricoat RK” manufactured by Harima Chemicals): 0.2 g/m ²
Styrene/methacrylic acid copolymer resin surface sizing agent (mass average molecular weight 9,000, melting point 100° C., "Kaycoat SA20" SP value 10.0, manufactured by Modern Chemical Industry Co., Ltd.): 0.6 g/m ²

[Examples 2 to 2 and Comparative Examples 1 to 6]
For tableware of Examples 2 to 12 and Comparative Examples 1 to 6 in the same manner as in Example 1 except that the types, contents and physical properties of the raw materials were as shown in Tables 1 and 2. I got a coated paper. In Comparative Example 6, a partially saponified 80% polyvinyl alcohol was used. In addition, "-" in the following Table 1 indicates that the corresponding component was not used.

[Evaluation]
Table 3 shows the evaluation results of the obtained coated papers for tableware.

As shown in Table 3 above, in Examples 1 to 12 of the coated paper for tableware, good results were obtained in all of the surface strength, the degree of bump size, the Z-axis strength, and the bending strength.

On the other hand, the mass ratio of the bleached softwood kraft pulp to the hardwood bleached kraft pulp in the surface layer is less than 5/95 or more than 15/85, and the mass ratio of the bleached softwood kraft pulp to the bleached kraft pulp in the middle layer is less than 30/70 or 40/ Any of Comparative Examples 1 to 6 in which the content exceeds 60 or the surface layer contains partially saponified polyvinyl alcohol was inferior in strength.

The coated paper for tableware of the present invention can be suitably used for paper tableware.

Claims

A pair of surface layers and a plurality of middle layers arranged between the pair of surface layers,
The surface layer and the middle layer are mainly composed of bleached softwood kraft pulp and bleached hardwood kraft pulp,
The mass ratio of the bleached softwood kraft pulp to the bleached hardwood kraft pulp in the surface layer is 5/95 or more and 15/85 or less,
The mass ratio of the bleached softwood kraft pulp to the bleached hardwood kraft pulp in the middle layer is 30/70 or more and 40/60 or less,
A coated paper for tableware, the surface of which has a surface coating layer containing completely saponified polyvinyl alcohol.
The coated paper for tableware according to claim 1, wherein the coating amount of the surface coating layer is 1.0 g/m 2 or more and 5.0 g/m 2 or less.
The coated paper for tableware according to claim 1 or 2, wherein the ratio of the total basis weight of the pair of surface layers to the total basis weight is 25.0% or more and 35.0% or less.
The coated paper for tableware according to claim 1, claim 2 or claim 3, wherein the total number of the middle layers is 4 or more.
A paper tableware composed of the coated paper for tableware according to any one of claims 1 to 4.