JP6891829B2 - Foam Insulation Paper Container Paper Base Material, Foam Insulation Paper Container Sheet and Foam Insulation Paper Container - Google Patents

Description

The present invention relates to a foamed heat insulating paper container, a foamed heat insulating paper container paper base material used for manufacturing the same, and a sheet for a foamed heat insulating paper container.

In fast food stores, trains, vending machines, etc., heat-insulating containers are widely used as cup-shaped containers for providing hot beverages such as coffee and hot foods such as soup to purchasers.

As an invention relating to a sheet forming a heat insulating container for such an application, for example, there is an invention disclosed in Patent Document 1. This is an invention relating to a foam insulating paper container sheet in which a thermoplastic resin layer such as polyethylene is formed on at least one side of a paper base material, and the surface of the paper base material is treated by a calendar size press.
Compared to the heat insulating container made of expanded polystyrene (EPS), the foamed heat insulating paper container can save petroleum resources and has advantages such as excellent beauty (printability) because the outer surface of the container is smooth. is there.

Effervescent heat insulating paper containers are required to have sufficient strength and ease of handling as well as heat insulating properties. Therefore, in the foamed heat insulating paper container, a portion to be the mouth (hereinafter referred to as a top curl portion) is formed by a top curl process in which the peripheral edge of the upper end opening is wound outward. In addition to increasing the strength of the foamed heat insulating paper container, the top curl portion has a role of acting as a hook when the foamed heat insulating paper container is mechanically supported by an automatic feeding device or the like.

A general automatic feeding device for a cup-shaped container uses the top curl portion of the container to perform automatic feeding. For example, a paper cup automatic supply device in a vending machine stores a large number of paper cups stacked in the vertical direction. The automatic paper cup supply device supports a large number of paper cups by engaging with the top curl part of the lowest paper cup during standby, and at the time of sale, the engagement is released and immediately above. Engage with the top curl of the paper cup. In this way, the automatic paper cup feeding device uses the top curl portion to reliably drop the paper cups one by one and provide them to the user. Such an automatic supply mechanism is also used for automatic supply of foamed heat insulating paper containers.
As described above, since the foam-insulated paper container is often provided with a top curl portion, one of the qualities required for the foam-insulated paper container paper base material is the ease of making the top curl portion. ..

For example, the top curl processing in a paper cup is performed as follows. First, a mold for upper molding and a mold for lower molding of the top curl portion are prepared. Each mold has a predetermined curl shape. Next, the peripheral edge of the upper end opening of the paper cup is curled outward by applying a mold for upper molding from the upper end opening side of the paper cup. Subsequently, by pushing the paper cup downward, the peripheral edge of the upper end opening of the paper cup is wound inward along the curved surface of the lower molding die set downward. In this way, the top curl portion is formed.

Japanese Unexamined Patent Publication No. 2012-21408

In the above-mentioned top curl processing method, when the top curl portion is formed, a tensile force acts on the outside of the top curl portion and a compressive force acts on the inside.
If the tensile force and the compressive force are appropriate, the top curl portion can be formed normally. However, if an excessive tensile force acts on the outside of the top curl portion, breakage or swelling may occur in the top curl portion. On the other hand, if an excessive compressive force acts on the inside of the top curl portion, the top curl portion may be broken or the like. As described above, if an excessive force acts on the top curl portion during the top curl processing, there is a risk of causing a molding defect of the top curl portion.

Further, the foamed heat insulating paper container paper base material requires a certain basis weight and paper thickness in order to secure the moisture for foaming the foamed resin layer. When the basis weight and the paper thickness are increased, the rigidity of the foam-insulated paper container paper base material becomes larger than that of the paper cup base material. Paper with high rigidity is paper that requires a large amount of force to be rolled. Therefore, when the top curl processing is applied to the foamed heat insulating paper container paper base material having a high rigidity, an excessive force is likely to be applied to the top curl portion, so that a defect is likely to occur in the molding of the top curl portion.
Further, if an excessive tensile force acts on the outside of the top curl portion and an excessive compressive force acts on the inside, a large shearing force acts on the paper layer of the foamed heat insulating paper container paper base material. Due to this shearing force, the joint portion (seam portion) on the side surface of the foamed heat insulating paper container of the top curl portion may be peeled off, causing a problem that the seam portion is turned over.

Since the top curl portion plays the role as described above, the foamed heat insulating paper container in which the molding of the top curl portion has a problem cannot be put into practical use.
As one of the methods for suppressing molding defects of the top curl portion, it is conceivable to increase the tensile strength of the foamed heat insulating paper container paper base material. If the tensile strength is large, even if a large tensile force acts during molding, the foamed heat insulating paper container paper base material is less likely to break, so that molding defects of the top curl portion are less likely to occur.

However, increasing the tensile strength of the paper does not solve the problem caused by the difficulty of curling the paper having a large rigidity.
Further, the paper having a high tensile strength is often a paper having a high compressive strength.
Paper having a high compression strength requires a large force to compress and curl the inside of the top curl portion during the top curl processing, so that the top curl portion is likely to be broken or the like. In particular, the seam on the side of the foamed heat insulating paper container has a double foamed heat insulating paper container paper base material, and two sheets of paper are overlapped and rolled up, so top curl processing is more difficult than other parts. become. Therefore, if a foamed heat insulating paper container paper base material having a high compression strength is used, the inside of the top curl portion may not be normally compressed in the seam portion. If the inside of the top curl portion is not compressed normally, a problem that a part of the top curl portion is turned up (turning of the seam part) is likely to occur.
As described above, the foam-insulated paper container paper base material that is difficult to curl has caused a problem that the yield of the foam-insulated paper container is deteriorated.

From the above, there is a demand for a foam-insulated paper container paper base material that is easy to mold the top curl portion and has excellent heat insulating properties and surface beauty.

The present invention has been made in view of such a situation. That is, the subject of the present invention is a foam-insulated paper container paper base material in which the top curl portion can be easily molded by excellent balance between the tensile strength of the paper layer constituting the back surface and the compressive strength of the paper layer constituting the front surface. It is an object of the present invention to provide a sheet for a foam insulation paper container and a foam insulation paper container using the above.

The direction (longitudinal direction) in which the pulp slurry flows out in the process of forming the paper layer in the papermaking of the paper base material in the foamed heat insulating paper container paper base material is hereinafter also referred to as the MD direction.
Foam Insulation Paper Container In a paper base material, the inside is the back surface and the outside is the front surface when the foam insulation paper container is molded. That is, the back surface of the foamed heat insulating paper container paper base material is the outside of the top curl portion, and the front surface is the inside of the top curl portion.
Hereinafter, when the foamed heat insulating paper container paper base material is divided into two parts having an equal thickness in the paper thickness direction, the side including the front surface is referred to as a front layer portion and the side including the back surface is also referred to as a back layer portion.

The present inventors have a foam insulation paper having a tensile strength sufficient to prevent the surface layer portion from breaking due to the tensile force of top curling processing, and a compressive strength sufficiently small to realize the ease of curling of the back layer portion. We proceeded with the study of the container paper base material.
As a result, if there is a predetermined relationship between the tensile strength of the back layer portion and the compressive strength of the surface layer portion, it is possible to realize a foam-insulated paper container paper base material that is easy to curl and does not break the paper base material. I found.
Specifically, if the tensile strength is sufficiently large, the rigidity is sufficiently small, and the ratio of the compressive strength of the surface layer portion to the tensile strength of the back layer portion is sufficiently large, tearing or the like does not occur in the top curl processing, and It is possible to realize a foam-insulated paper container paper base material that is easily curled.
The present invention has been completed based on such findings. That is, the present invention has the following configuration.

(1) A foam-insulated paper container paper base material composed of a paper base material having two or more paper layers and a water-soluble resin layer provided on at least one surface of the paper base material, which is mainly composed of cellulose pulp. The tensile strength in the MD direction is 15.0 kN / m or more, and the taber rigidity in the MD direction measured in accordance with the Taber stiffness testing machine method specified in JIS P8125: 2000 is 17.0 mN · m or less. When the front layer portion including the front surface and the back layer portion including the back surface are divided into two parts having an equal thickness in the paper thickness direction, the specific tensile strength of the back layer portion in the MD direction is T, which is a short span method. A foam-insulated paper container paper base material having a T / C of 3.00 or more, where C is the measured specific compression strength of the surface layer portion in the MD direction.

(2) The NKP compounding number of the outermost paper layer including the back surface is 10 parts by mass or more larger than the NKP compounding number of the outermost paper layer including the front surface. The foam insulation paper container paper base material described.

(3) The foam-insulated paper container paper base according to (1) or (2) above, wherein the fiber orientation ratio of the back layer portion is 0.15 or more larger than the fiber orientation ratio of the surface layer portion. Material.

(4) The item according to any one of (1) to (3) above, wherein the dissociation freeness of the surface layer portion is 430 to 550 ml, and the dissociation freeness of the back layer portion is 450 to 560 ml. Foam insulation paper container paper base material.

(5) The foamed heat insulating paper container paper base material according to any one of (1) to (4) above, wherein the water-soluble resin constituting the water-soluble resin layer is polyvinyl alcohol.

(6) A sheet for a foam-insulated paper container according to any one of (1) to (5) above, wherein thermoplastic resin layers are provided on both sides of the foam-insulated paper container paper base material.

(7) An effervescent heat insulating paper container made of the foam heat insulating paper container sheet according to (6) above.

According to the foamed heat insulating paper container paper base material of the present invention, the balance between the tensile strength of the back layer portion and the compressive strength of the surface layer portion is excellent, the tensile strength is sufficiently large, and the rigidity is sufficiently small. It is suitable for use and can suppress the occurrence of turning over even in the seam part. According to the foamed heat insulating paper container sheet of the present invention, since the foamed heat insulating paper container paper base material is used, the top curl portion can be easily formed. Since the foamed heat insulating paper container uses the foamed heat insulating paper container sheet, it is difficult for the top curl portion to swell or the like.

It is a schematic cross-sectional view of the foam insulation paper container which concerns on this embodiment. It is an enlarged sectional view of the part shown by A of FIG. It is a schematic cross-sectional view of the foam insulation paper container paper base material which concerns on this embodiment. It is a schematic cross-sectional view of the sheet for foam insulation paper container which concerns on this embodiment.

Hereinafter, embodiments of the present invention will be specifically described. The description of the constituent elements described below may be based on typical embodiments or specific examples, but the present invention is not limited to such embodiments. In this specification, the numerical range represented by using "~" means a range including the numerical values before and after "~" as the lower limit value and the upper limit value.

FIG. 1 is a schematic cross-sectional view of the foamed heat insulating paper container 8 according to the present embodiment. Further, FIG. 2 is an enlarged cross-sectional view of the portion shown by A in FIG. As shown in FIG. 1, in the present embodiment, the foamed heat insulating paper container 8 includes a body member 6 and a bottom plate member 7. Both the body member 6 and the bottom plate member 7 are made of foamed heat insulating paper 20. The foamed heat insulating paper 20 may be used for either the body member 6 or the bottom plate member 7.

As shown in FIG. 2, the foamed heat insulating paper 20 has a foamed resin layer 9 made of a thermoplastic resin on at least one side of the paper base material 1. The foamed heat insulating paper 20 has a water-soluble resin layer 2 between the paper base material 1 and the foamed resin layer 9. In FIG. 2, the water-soluble resin layer 2 is formed on both surfaces of the paper base material 1. The foamed heat insulating paper 20 of the present embodiment has a foamed resin layer 9 on the outer wall surface side thereof and a high melting point thermoplastic resin layer 10 on the inner wall surface side thereof.

FIG. 3 is a schematic cross-sectional view of the foam insulating paper container sheet 5 according to the present embodiment. The foam insulation paper container sheet 5 according to the present embodiment is used for manufacturing the foam insulation paper 20 described above. The foam-insulated paper container sheet 5 according to the present embodiment has a thermoplastic resin layer 4 on at least one side of the paper base material 1, and a water-soluble resin layer is provided between the paper base material 1 and the thermoplastic resin layer 4. Has 2. The thermoplastic resin layer 4 is foamed by heat treatment to become a foamed resin layer 9 (see FIG. 2).

FIG. 4 is a schematic cross-sectional view of the foamed heat insulating paper container paper base material 3 according to the present embodiment. The foamed heat insulating paper container paper base material 3 according to the present embodiment is used for manufacturing the foamed heat insulating paper container sheet 5. The foamed heat insulating paper container paper base material 3 according to the present embodiment has a water-soluble resin layer 2 on at least one side of the paper base material 1. When the thermoplastic resin layer 4 is provided on the water-soluble resin layer 2, the foam-insulated paper container sheet 5 is formed.

To manufacture the foamed heat insulating paper container 8, first, a paper container is formed by combining a body member 6 and a bottom plate member 7 made of a foamed heat insulating paper container sheet 5.
When the foam-insulated paper container sheet 5 is heated, the water contained in the paper base material 1 and the water-soluble resin layer 2 is vaporized to become water vapor. The generated water vapor permeates through the water-soluble resin layer 2 and permeates into the heated thermoplastic resin layer 4, and foams the thermoplastic resin. When the thermoplastic resin foams, the thermoplastic resin layer 4 changes to the foamed resin layer 9.
As described above, the paper container becomes an effervescent heat insulating paper container 8 having heat insulating properties by heating.

The foam-insulated paper container paper base material 3 has a paper base material 1 and a water-soluble resin layer 2 on at least one side thereof.
If the water-soluble resin layer 2 is not formed on the surface of the paper base material 1, water vapor is directly released from the paper base material 1 when heated. Due to this release, the amount of water vapor permeated varies from portion to portion of the paper substrate 1, and partial hyperfoaming tends to occur in the thermoplastic resin layer 4. If the over-foamed portion is present, the foamed form becomes non-uniform and the surface becomes uneven, so that both the heat insulating property of the foamed heat insulating paper container 8 and the beauty of the surface are deteriorated.

(Paper base material)
The paper base material 1 has two or more paper layers. The number of layers is not particularly limited, and may be 3 layers, 4 layers, or more layers. That is, the paper base material 1 is a multi-layered paper (laminated paper) made by multi-layer papermaking.

(pulp)
The paper base material 1 contains cellulose pulp as a main component. Cellulose pulp is not particularly limited, but preferably contains chemical pulp from the viewpoint of strength. The chemical pulp is not particularly limited, but preferably contains hardwood kraft pulp (LKP) or softwood kraft pulp (NKP). The pulp may be bleached pulp or unbleached pulp. Further, it is preferable to contain both LKP and NKP. Hereinafter, unless otherwise specified, LKP and NKP include bleached pulp or unbleached pulp, respectively, but hardwood bleached kraft pulp may be referred to as LBKP and softwood bleached kraft pulp may be referred to as NBKP.

Since NKP has a long fiber, the strength of the paper-made product can be increased. Therefore, if the NKP content of the pulp constituting the back layer portion of the paper base material 1 exceeds the NKP content of the pulp constituting the surface layer portion, the tensile strength of the back layer portion is increased and the surface layer portion is compressed. The strength can be reduced.

Hereinafter, the outermost paper layer constituting the surface of the paper base material 1 among the plurality of paper layers of the multi-layer paper is also referred to as a surface layer. Further, the outermost paper layer constituting the back surface of the paper base material 1 is also referred to as a back layer.
The present inventors have proceeded with the study on the difference in the number of NKP compounding portions of the pulp of the back layer and the surface layer in order to increase the tensile strength of the back layer portion and decrease the compressive strength of the surface layer portion.
As a result, it was found that the number of NKP compounding parts of the pulp constituting the back layer is preferably 10 parts by mass or more more than the surface layer, and more preferably 15 parts by mass or more. Here, the difference in the number of blended parts refers to the difference between the content of NKP in 100 parts by mass of total pulp in the back layer (number of parts by mass) and the content of NKP in 100 parts by mass of total pulp in the surface layer.

In order to obtain a back layer portion having a sufficiently large tensile force, the pulp constituting the back layer preferably contains 10 to 30 parts by mass of NKP in 100 parts by mass of the total pulp, and preferably contains 15 to 30 parts by mass. Is more preferable, and it is further preferable to contain 15 to 25 parts by mass. Further, in order to obtain a surface layer portion having a sufficiently small compressive force, the pulp constituting the surface layer of the foamed heat insulating paper container paper base material 3 preferably contains 1 to 15 parts by mass of NKP, and preferably contains 5 to 15 parts by mass. It is more preferable to do so. Within these ranges, the difference in the number of NKP blended parts may be adjusted to a preferable range.

On the other hand, LKP has shorter fibers and is inferior in strength to NKP, but is excellent in the texture and smoothness of the paper made. Since uniform foaming of the thermoplastic resin layer 4 requires good texture and smoothness of the paper base material 1, the pulp of each paper layer in the paper base material 1 is 100 mass of total pulp constituting each paper layer. It is preferable to contain 40 parts by mass or more of LKP, more preferably 60 parts by mass or more, and further preferably 75 parts by mass or more.

The pulp component may contain pulp other than the above-mentioned NKP and LKP (hereinafter, referred to as other pulp). Other pulps include stone ground pulp (SGP), pressurized stone ground pulp (PGW), refiner ground pulp (RGP), thermogrand pulp (TGP), chemigrand pulp (CGP), crushed wood pulp (GP), and thermo. Manufactured from mechanical pulp such as mechanical pulp (TMP), tea waste paper, craft envelope waste paper, magazine waste paper, newspaper waste paper, leaflet waste paper, office waste paper, cardboard waste paper, upper white waste paper, Kent waste paper, imitation waste paper, ground ticket waste paper, etc. Examples thereof include recycled recycled paper pulp (DIP), and pulp chemically or mechanically produced from non-wood fibers such as kenaf, hemp, and reed. The content of the other pulp is preferably less than 3% by mass, more preferably less than 2% by mass, and even more preferably less than 1% by mass with respect to the total mass of the pulp components.

An element that affects the strength of the paper-made product is the degree of beating (freeness) of the pulp component. In general, if the freeness of the pulp component is too low or too high, the strength of the product will decrease, and if the freeness is in the appropriate range, the strength of the product will increase.
Therefore, the present inventors have examined the appropriate range of the dissociation freeness of the back layer and the dissociation freeness of the surface layer. The dissociation freeness refers to the value of the Canadian standard freeness measured using the pulp slurry obtained by dissociating the paper substrate 1. By separating and measuring the paper base material 1 for each paper layer, dissociation freeness of each paper layer of the paper base material 1 can be obtained.

In order to reduce the compressive force while ensuring the strength of the surface layer portion, the dissociation freeness of the pulp constituting the surface layer of the paper substrate 1 is preferably 430 to 550 ml, more preferably 440 to 540 ml. It is more preferably 450 to 530 ml.
On the other hand, in order to secure the tensile strength of the back layer portion, the dissociation freeness of the pulp constituting the back layer of the paper substrate 1 is preferably 450 to 560 ml, more preferably 460 to 550 ml, and 470. It is more preferably ~ 540 ml.

Dissociation freeness can be adjusted by increasing or decreasing the freeness of cellulose pulp before papermaking (referring to Canadian standard freeness; the same shall apply hereinafter).
The freeness of the cellulose pulp constituting the surface layer before papermaking is preferably 380 to 500 ml, more preferably 390 to 490 ml, and further preferably 400 to 480 ml.
The freeness of the cellulose pulp forming the back layer before papermaking is preferably 400 to 510 ml, more preferably 410 to 500 ml, and even more preferably 420 to 490 ml.
The freeness of the pulp before papermaking may be adjusted to the above range by beating at least one of the above-mentioned pulps. When two or more types of pulp are used, the pulps beaten separately may be mixed to bring the pulp into the above range, or the pulp mixed in advance may be beaten to adjust to the above range.

(Filling fee)
The filler to be blended when the paper base material 1 is made into paper can be a filler generally used in the papermaking field, and is not particularly limited. Examples of fillers are clay, calcined kaolin, delaminated kaolin, heavy calcium carbonate, light calcium carbonate, light calcium carbonate-silica composite, magnesium carbonate, barium carbonate, titanium dioxide, zinc oxide, silicon oxide, amorphous. Examples thereof include inorganic fillers such as silica, aluminum hydroxide, calcium hydroxide, magnesium hydroxide and zinc hydroxide, and organic fillers such as urea-formalin resin, polystyrene resin, phenol resin and fine hollow particles. These fillers can be used alone or in combination of two or more. In the case of the above-mentioned acidic papermaking, generally, those obtained by removing acid-soluble ones from these fillers are used.

When papermaking the paper base material 1, it is possible that no filler is added. When the filler of the paper base material 1 is not blended, the foamability is improved when the thermoplastic resin layer 4 is foamed by the moisture contained in the paper base material 1. On the other hand, when the filler is added to the paper base material 1, the opacity of the obtained foam-insulated paper container sheet 5 and the foam-insulated paper container 8 using the same is improved.

(Internal aid)
When papermaking the paper substrate 1, various internal aids can be appropriately selected and used as needed. Examples of internal additives include various internal sizing agents such as rosin, alkyl ketene dimer (AKD) and alkenyl oxalic acid anhydride (ASA), various nonionic, cationic and amphoteric yield improvers, and filtrates. Degree improver, paper strength improver, various starches such as cationized starch, polyacrylamide, urea resin, melamine resin, epoxy resin, polyamide resin, polyamide, polyamine resin, polyamine, polyethyleneimine, vegetable gum, polyvinyl alcohol, latex , Polyethylene oxide, hydrophilic crosslinked polymer particle dispersions and derivatives or modified products thereof, in sulfuric acid bands, aluminum chloride, sodium aluminate, basic aluminum chloride, basic aluminum compounds such as basic polyaluminum hydroxide, in water. Water-soluble aluminum compounds such as easily decomposable alumina sol, polyvalent metal compounds such as ferrous sulfate and ferric sulfate, silica sol, antifoaming agents, coloring dyes, coloring pigments, fluorescent whitening agents, pH adjusters, pitches Examples include control agents and slime control agents.

(Multi-layer structure)
The paper base material 1 is a multilayer material made by papermaking two or more layers of paper. Paper materials having different raw materials and characteristics can be used for each paper layer.
When the paper base material 1 is made of a multilayer material, the texture can be made more uniform. When the formation is uniform, the amount of water vapor that permeates the paper base material 1 when the thermoplastic resin layer 4 is foamed can be made uniform over the entire surface of the paper base material 1. By making the permeation of water vapor uniform, the hyperfoaming of the thermoplastic resin layer 4 is suppressed, and the foaming form of the foamed heat insulating paper container 8 becomes beautiful.

Further, the paper base material 1 may be a multilayer material in which pulp layers and starch layers are alternately laminated. The starch layer does not excessively increase the barrier property and therefore does not interfere with the permeation of water vapor.
In a multilayer material in which pulp layers and starch layers are alternately laminated, the starch layer is provided between the pulp layers to firmly bond the pulp layers to each other. As the starch layer, for example, cationized starch, dicarboxylic acid ester starch, urea phosphate esterified starch, etherified starch, acetylated starch, oxidized starch and the like can be used. In this embodiment, it is preferable to contain cationized starch. By doing so, as described above, since the texture can be made uniform, the amount of water vapor permeated from the paper base material 1 at the time of foaming becomes more uniform, overfoaming is suppressed, and the foaming form becomes uniform. In addition, the starch layer using cationized starch does not excessively interfere with the permeation of water vapor.

The amount of the starch layer formed is preferably ^{0.5 to 2.0 g / m 2.} When the amount of the starch layer formed is 0.5 g / m ² or more, the adhesive force between the pulp layers and the pulp layers is enhanced, and the interlayer strength is improved. Further, when the amount of the starch layer formed is 2.0 g / m ² or less, the starch layer effectively permeates the water vapor from the pulp layer during foaming, and the thermoplastic resin layer 4 can be sufficiently foamed. Therefore, the foaming ratio becomes high and the heat insulating property is improved.

(Water-soluble resin)
The water-soluble resin is applied to the surface of the paper base material 1 to form a film (water-soluble resin layer 2). The water-soluble resin layer 2 has a role of making the foaming of the thermoplastic resin layer 4 uniform and improving the heat insulating property and the beauty of the surface of the foamed heat insulating paper container 8.
The water-soluble resin is a resin that dissolves in water. The water-soluble resin is not particularly limited as long as it is a water-soluble polymer having a film-forming property. Examples of the water-soluble resin include fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, polyvinyl alcohol such as modified polyvinyl alcohol, starches, polyacrylamides, hydroxyethyl cellulose, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, acetyl cellulose and the like. Cellulose ethers and derivatives thereof, and the like. As the water-soluble resin in the present embodiment, these can be used alone or in combination of two or more.

(Polyvinyl alcohol)
The present inventors have investigated a water-soluble resin suitable for the present invention. As a result, it was found that polyvinyl alcohol (PVA) is preferable as the water-soluble resin forming the water-soluble resin layer 2 from the viewpoint of processability.
Polyvinyl alcohol is represented by the chemical formula [-CH ₂ CH (OH)-] _n [-CH ₂ CH (OCOCH ₃ )-] _m , and is called PVOH, PVA, Poval, or the like. Polyvinyl alcohol is generally produced by saponifying a polyvinyl acetate resin obtained by polymerizing a vinyl acetate monomer. In the chemical formula, n indicates a saponified portion and m indicates an unsaponified portion.

As the polyvinyl alcohol, partially saponified polyvinyl alcohol or fully saponified polyvinyl alcohol (in this embodiment, those having a saponification degree of 90 mol% or more) can be used. The degree of polymerization is represented by n + m, and the degree of saponification (mol%) is represented by {n / (n + m)} × 100. The average degree of polymerization can be arbitrarily adjusted depending on how much the vinyl acetate monomer is bonded in the step of polymerizing the vinyl acetate monomer. The degree of saponification can be arbitrarily adjusted depending on how much the vinyl acetate unit is converted into a hydroxyl group in the step of saponifying the polyvinyl acetate resin. The average degree of polymerization and the degree of saponification can be measured according to JIS K6726-1994.

Further, as the polyvinyl alcohol, an unmodified polyvinyl alcohol in which a functional group other than a hydroxyl group (OH group) and an acetic acid group (OCOCH _{3 groups) is not introduced can be used.} Further, as the polyvinyl alcohol, a modified polyvinyl alcohol into which a functional group other than a hydroxyl group or an acetic acid group has been introduced can also be used. Examples of the functional group introduced into the modified polyvinyl alcohol include a carboxyl group, a carbonyl group, a sulfonic acid group, a silanol group, a cationic group, and an alkyl group. That is, examples of the modified polyvinyl alcohol include polyvinyl alcohols such as carboxyl-modified polyvinyl alcohol, silanol-modified polyvinyl alcohol, cationic-modified polyvinyl alcohol, and terminal alkyl-modified polyvinyl alcohol.

Since polyvinyl alcohol has a hydrophilic functional group (hydroxyl group) and a hydrophobic functional group (acetic acid group) coexisting appropriately in the polymer molecule, it forms a film firmly adhered to the paper substrate 1. .. The polyvinyl alcohol layer firmly adhered to the paper base material 1 can appropriately control the amount of water vapor permeated and suppress variations in the amount of water vapor permeated. By forming the polyvinyl alcohol film on the paper base material 1 in this way, the foamed state of the thermoplastic resin layer 4 can be made uniform, and the heat insulating property of the foamed heat insulating paper container 8 can be improved.

The average degree of polymerization of polyvinyl alcohol is preferably 300 to 4000, more preferably 500 to 3000, and even more preferably 1000 to 2000 when measured in accordance with JIS K 6726-1994. By setting the average degree of polymerization to 300 or more, the film forming property is improved. Further, by setting the average degree of polymerization to 4000 or less, the solubility in water is improved, the viscosity of the solution is lowered, and the coating is facilitated.

The saponification degree of polyvinyl alcohol is preferably 80 mol% or more, more preferably 90 mol% or more, and further preferably 95 mol% or more. When the saponification degree is 80 mol% or more, the water solubility is increased and the film forming property is improved. Polyvinyl alcohol can be appropriately selected and used from commercially available ones.

(Starch)
As the water-soluble resin, starches can be used in addition to polyvinyl alcohol.
Examples of starches include unmodified starch, enzyme-modified starch, thermochemically modified starch, oxidized starch, esterified starch, etherified starch (for example, hydroxyethylated starch), cationized starch and the like.

(Polyacrylamides)
As the water-soluble resin, polyacrylamide (PAM) or the like can be used in addition to polyvinyl alcohol.
Examples of polyacrylamides include polyacrylamide, cationic polyacrylamide, anionic polyacrylamide, amphoteric polyacrylamide, nonionic polyacrylamide and the like. Examples of the cationic polyacrylamide include polyacrylamide having a functional group such as an amino group, a quaternary ammonium salt, and an azetidineium ring. Examples of the anionic polyacrylamide include polyacrylamide having a carboxyl group, a sulfone group and the like. Examples of nonionic polyacrylamide include polyacrylamide having a hydroxyl group, an amide group and the like. The amphoteric polyacrylamide is a polyacrylamide having both cationic and anionic functional groups.

(Water-soluble resin layer)
The water-soluble resin layer 2 of the foam-insulated paper container paper base material 3 is provided on at least one side of the paper base material 1. It is also possible to provide it on both sides of the paper base material 1.
Due to the presence of the water-soluble resin layer 2 on the surface of the paper base material 1, the thermoplastic resin laminated on the water-soluble resin layer 2 in the subsequent process is firmly adhered to the paper base material 1. As a result, the amount of water vapor supplied from the paper base material 1 to the thermoplastic resin layer 4 at the time of foaming becomes more uniform, the hyperfoaming of the thermoplastic resin is suppressed, and the foaming form becomes uniform.
The water-soluble resin layer 2 is a layer containing a water-soluble resin as a main component, but if necessary, other resin components may be appropriately contained as long as the effects of the invention are not impaired.

(Amount of water-soluble resin layer formed)
The amount of the water-soluble resin layer 2 formed per one side is preferably ^{0.03 to 6.00 g / m 2 in terms of solid content.} In particular, when using PVA as the water-soluble resin is preferably from 0.05~0.50g / ^{m 2} by solid content, and more preferably 0.06~0.10g / ^{m 2.} When using starch as the water-soluble resin is preferably from 0.80~6.00g / ^{m 2,} and more preferably 1.50~3.00g / ^{m 2.} When using PAM as the water-soluble resin is preferably from 0.03~0.70g / ^{m 2,} and more preferably 0.05~0.60g / ^{m 2.}

When the amount of the water-soluble resin layer 2 formed per one side is within this range, the thermoplastic resin layer 4 can be uniformly foamed, the foamed resin layer can be thickened, and the heat insulating property is improved. Further, when the amount of the water-soluble resin layer 2 formed per one side is within this range, the amount of formation is appropriate, so that when the thermoplastic resin layer 4 is foamed, large irregularities and the like are unlikely to occur on the surface, and the beauty is improved. Can be enhanced. Further, when the amount of the water-soluble resin layer 2 formed is within this range, it is possible to reduce equipment stains in the papermaking process or the drying process when applying the coating liquid, and the stains fall off to cause foreign matter in the foamed heat insulating paper container 8. It is possible to prevent it from being mixed.

If the amount of the water-soluble resin layer 2 formed on one side is less than the lower limit of the above range, uniform foaming may not be obtained and the surface may be uneven, resulting in impaired aesthetics. On the other hand, if the amount of the water-soluble resin layer 2 formed on one side exceeds the upper limit of the above range, the thermoplastic resin cannot be sufficiently foamed, and the heat insulating property may be insufficient.
The amount of the water-soluble resin layer 2 formed can be measured from the amount of weight change before and after the formation.

(Thickness of water-soluble resin permeating into paper substrate)
When the coating liquid containing the water-soluble resin is applied to the paper base material 1, the coating liquid permeates from the surface of the paper base material 1 toward the inside. Then, the coating liquid is dried to solidify, and the water-soluble resin layer 2 is formed. In the present embodiment, the water-soluble resin that has penetrated into the paper substrate 1 and solidified is also regarded as a part of the water-soluble resin layer 2.

The penetration thickness of the water-soluble resin into the paper substrate 1 is preferably 5 to 180 μm. in particular,
When PVA is used as the water-soluble resin, it is preferably 5 to 35 μm, more preferably 10 to 30 μm, and even more preferably 15 to 25 μm. When starch is used as the water-soluble resin, it is preferably 60 to 180 μm, more preferably 65 to 170 μm, and even more preferably 70 to 160 μm. When PAM is used as the water-soluble resin, it is preferably 5 to 70 μm, more preferably 8 to 50 μm, and even more preferably 15 to 30 μm.

When the permeation thickness of the water-soluble resin into the paper base material 1 is within this range, the thermoplastic resin layer 4 can be uniformly foamed, the thickness after foaming can be increased, and the heat insulating property is improved. To do. Further, when the permeation thickness of the water-soluble resin into the paper base material 1 is within this range, the permeation of water vapor generated from the paper base material 1 can be appropriately barriered, so that the variation in the amount of water vapor permeation depending on the location can be reduced. .. As a result, the foam cells can be formed small and homogeneously, and the flatness and beauty of the surface can be improved.

If the permeation thickness of the water-soluble resin into the paper base material 1 is less than the lower limit of the above range, the amount of water vapor permeation may not be uniform, the foaming may be non-uniform, and the beauty may be deteriorated. On the other hand, if the permeation thickness of the water-soluble resin into the paper base material 1 exceeds the upper limit of the above range, the water-soluble resin layer 2 excessively barriers the permeation of water vapor, so that the thermoplastic resin layer 4 is sufficiently used. It cannot be foamed, which may reduce the heat insulating property.
The permeation thickness of the water-soluble resin into the paper substrate 1 can be appropriately adjusted depending on the pressure of the blade or rod, the gap size between the blade or rod and the paper, the angle of the blade, the viscosity of the coating liquid, and the like. The penetration thickness of the water-soluble resin into the paper substrate 1 can be measured from an enlarged photograph of a cross section using an optical microscope, a scanning electron microscope, or the like.

(Air permeability resistance)
The air permeability resistance (air permeability resistance / basis weight) per basis weight of the foamed heat insulating paper container paper base material 3 is preferably ^{1.0 to 6.0 s / g / m 2.} When the air permeation resistance per basis weight is within this range, the foamed heat insulating paper container paper base material 3 is supplied from the paper base material 1 to the thermoplastic resin layer 4 when the foamed heat insulating paper container 8 is foamed, which will be described later. The amount of water vapor is moderately suppressed. By this suppression, the foamed state of the thermoplastic resin layer 4 becomes uniform, so that the balance between the heat insulating property and the beauty of the foamed heat insulating paper container 8 becomes good.
The air permeation resistance per basis weight is more preferably 2.0 to 5.5 s / g / m ² , still more preferably 2.3 to 5.0 s / g / m ² , and particularly preferably 2.7 to 4. It is .5 s / g / m ² . The air permeation resistance is measured according to the Oken type testing machine method described in JIS P8117; 2009.

(Oken type smoothness)
The Oken-type smoothness of the foamed heat insulating paper container paper base material 3 is preferably 30 to 500 seconds. Oken-type smoothness is a unit that is an index for defining the smoothness of the surface of paper. When the Oken type smoothness is 30 seconds or more, the surface property of the foamed heat insulating paper container paper base material 3 is enhanced, and the foamed heat insulating paper container sheet 5 having good surface quality can be obtained. Further, when the Oken type smoothness is 500 seconds or less, it is not necessary to crush the paper base material 1 with a calender or the like in order to obtain high smoothness, and it is possible to prevent the paper thickness from becoming extremely thin. The molding processability of the heat insulating paper container 8 is improved.
Oken-type smoothness is measured according to JIS P8155: 2010.

(Formation index)
The texture index of the foamed heat insulating paper container paper base material 3 is preferably 60 or more, more preferably 80 or more, and further preferably 85 or more. The texture index is an index showing the uniformity of paper (uniformity of microscopic basis weight, smoothness), and the larger the value, the better the texture. By setting the texture index to a predetermined value or more, the water content distribution in the paper substrate 1 becomes uniform. Therefore, the amount of water vapor that permeates the paper base material 1 during foaming becomes uniform over the entire surface of the paper base material 1, superfoaming is suppressed, and the foaming form becomes uniform. The texture index is obtained by measuring the permeation strength of the foamed heat insulating paper container paper base material 3 with a commercially available 3D sheet analyzer and quantifying the variation in thickness. In this embodiment, a 3D sheet analyzer manufactured by M / K System Co., Ltd. is used to measure the formation index with a measurement range of 2 (low sensitivity) and a light source aperture of 1.0 mm.

(amount of water)
The water content of the foam-insulated paper container paper base material 3 is the sum of the water content contained in the paper base material 1 and the water content contained in the partially saponified polyvinyl alcohol layer.
The water content of the paper base material 1 is determined by the basis weight and water content of the paper base material 1. The water content of the foamed heat insulating paper container paper base material 3 is preferably 15 to 32 g / m ² , and more preferably 20 to 23 g / m ² . The water content is measured according to JIS P8127; 2010 after humidity control.

(Basis weight)
The basis weight of the foamed heat insulating paper container paper base material 3 is preferably 100 to 400 g / m ² , more preferably 200 to 400 g / m ² , and even more preferably 220 to 400 g / m ² . If the basis weight is ^{less than 100 g / m 2} , the foaming tends to be insufficient due to the water content, and the heat is easily felt when the obtained foamed heat insulating paper container 8 is gripped by hand. On the other hand, when the basis weight ^{exceeds 400 g / m 2} , the molding processability of the foamed heat insulating paper container 8 is lowered due to the increase in rigidity, and there is a tendency that a problem occurs in molding of the top curl portion.
When the paper base material 1 is composed of multi-layer papermaking as in the present embodiment, the total basis weight of each paper layer is set to be within the above preferable range of the preferred basis weight value, and papermaking is performed.

(Paper thickness)
The paper thickness of the foamed heat insulating paper container paper base material 3 is preferably 130 to 430 μm, more preferably 230 to 430 μm, and further preferably 250 to 430 μm. If the paper thickness is less than 130 μm, the foaming tends to be insufficient due to the amount of water, and the heat is easily felt when the obtained foamed heat insulating paper container 8 is gripped by hand. On the other hand, when the basis weight exceeds 430 μm, the molding processability of the foamed heat insulating paper container 8 is lowered due to the increase in rigidity, and there is a tendency that a problem occurs in molding of the top curl portion.

(density)
The density of the foamed heat insulating paper container paper base material 3 may be appropriately set as desired, and is not particularly limited, but is preferably ^{0.60 to 0.99 g / cm 3.}
When the density of the foam-insulated paper container paper base material 3 is low, water vapor easily passes through the paper base material 1 when the thermoplastic resin layer 4 is foamed, and the foamability tends to be improved. However, if the density of the foamed heat insulating paper container paper base material 3 ^{is less than 0.60 g / cm 3} , the paper strength required for the foamed heat insulating paper container 8 may not be obtained. On the other hand, when the density of the foamed heat insulating paper container paper base material 3 ^{exceeds 0.99 g / cm 3} , it becomes difficult for water vapor to pass through the paper base material 1 when the thermoplastic resin layer 4 is foamed, and the foamability tends to decrease. There is.

(Fiber orientation ratio)
Fiber orientation is a tendency for pulp slurry to flow out onto the wire of a paper machine, dehydrate, and line up in the flow direction (MD direction) in the process of forming a paper layer. The fiber orientation ratio can be adjusted by changing the jet wire ratio (raw material ejection rate ratio).
The jet wire ratio is the ratio of the outflow speed of the pulp slurry to the running speed of the wire, and is represented by the outflow speed of the slurry / the running speed of the wire.

In general, as a method for measuring the fiber orientation of paper or the like, for example, a thermal expansion method, a mechanical breaking strength method, an X-ray diffraction method, an ultrasonic method, a microwave method, an NMR method, a polarized fluorescence method, a dielectric measurement method and the like can be mentioned. Be done. In this embodiment, the ultrasonic method is adopted, the ultrasonic propagation velocity (Vmd) in the vertical direction and the ultrasonic propagation velocity (Vcd) in the horizontal direction are measured, and the ratio (Vmd / Vcd) is used as the fiber orientation ratio to align the fibers. It was used as an index to evaluate the randomness of. When the fiber orientation ratio is 1.0, the fibers are completely randomly oriented.

In the top curl processing, the foamed heat insulating paper container paper base material 3 is wound in the MD direction, so that a tensile force and a compressive force act in the MD direction. Therefore, the tensile strength and the compressive strength that affect the top curl processing are the tensile strength and the compressive strength in the MD direction. One of the methods for adjusting the tensile strength and the compressive strength in the MD direction is the adjustment of the fiber orientation ratio.

For example, when a tensile force in the MD direction acts on the foamed heat insulating paper container paper base material 3 having a large fiber orientation ratio, that is, the fiber orientation is biased in the MD direction, the tensile force acts in the fiber orientation direction. The tensile force tends to work in the direction of stretching the fibers, and it becomes difficult to work in the direction of tearing the bonds between the arranged fibers, and as a result, the paper base material 1 is less likely to break.
Further, when a compressive force in the MD direction acts on the foamed heat insulating paper container paper base material 3 whose fiber orientation is biased in the MD direction, the fibers are compressed along the fiber orientation direction. This compression requires greater force than if the fibers were compressed along the direction of bonding between the fibers.
As described above, the deviation of the fiber orientation in the MD direction increases the tensile strength and the compressive strength in the MD direction.

Therefore, in order to increase the tensile strength of the back layer portion of the foamed heat insulating paper container paper base material 3 and decrease the compressive strength of the surface layer portion, the fibers of the back layer portion should be oriented in the MD direction rather than the fibers of the surface layer portion. Is preferable.
The present inventors examined the fiber orientation ratio between the back layer portion and the surface layer portion, and found the following relationship. That is, the fiber orientation ratio of the back layer portion is preferably 0.15 or more larger than the fiber orientation ratio of the surface layer portion, more preferably 0.20 or more, and further preferably 0.25 or more.
The fiber orientation ratio of the surface layer portion is preferably in the range of 1.10 to 1.55, more preferably in the range of 1.20 to 1.45. On the other hand, the fiber orientation ratio of the back layer portion is preferably in the range of 1.40 to 1.85, more preferably in the range of 1.50 to 1.75. By adjusting the fiber orientation ratio in these ranges, the difference between the fiber orientation ratio of the back layer portion and the fiber orientation ratio of the surface layer portion can be set to a preferable range while setting the compressive strength of the surface layer portion and the tensile strength of the back layer portion to preferable values. Can be.

(Tensile strength)
In order to facilitate the molding of the top curl portion, a foam-insulated paper container paper base material 3 in which the paper base material 1 is not broken by the tensile force during the top curl processing is required.

The present inventors have repeatedly studied the tensile strength of the foamed heat insulating paper container paper base material 3 in order to realize the foamed heat insulating paper container paper base material 3 whose top curl portion can be easily formed.
As a result, it was found that if the tensile strength is 15.0 kN / m or more, it is possible to prevent the paper base material 1 from breaking during the top curl processing. From the viewpoint of effectively suppressing tearing of the top curl portion, the tensile strength is preferably 15.5 kN / m or more, and more preferably 16.0 kN / m or more.

Examples of the method for adjusting the tensile strength include a method of increasing / decreasing the NKP compounding amount with respect to the pulp compounding amount, a method of increasing / decreasing the dissociation freeness, and the like.
The tensile strength was measured according to the method specified in JIS P8113: 2006.

(Taber stiffness)
In order to facilitate the top curl processing, a foamed heat insulating paper container paper base material 3 that is easily curled, that is, has a small rigidity is required.

The present inventors have repeatedly studied the rigidity in order to realize the foamed heat insulating paper container paper base material 3 in which the top curl portion can be easily molded.
As a result, it was found that when the taber rigidity of the foamed heat insulating paper container paper base material 3 is 17.0 kN · m or less, the foamed heat insulating paper container paper base material 3 is sufficiently easy to curl.
If the taber rigidity is larger than 17.0 kN · m, it is not possible to secure sufficient curlability, and a problem occurs remarkably in the molding of the top curl portion. From the viewpoint of effectively suppressing molding defects of the top curl portion, the taber rigidity is preferably 15.5 kN · m or less, and more preferably 14.0 kN · m or less.
On the other hand, when the taber rigidity is smaller than 12.0 kN · m, the foamed heat insulating paper container 8 formed by using the foamed heat insulating paper container paper base material 3 tends to be easily deformed by the grip force. Therefore, the taber rigidity is preferably 12.0 kN · m or more.

The taber rigidity can be adjusted by increasing or decreasing the basis weight, paper thickness, and the like.
The Taber rigidity was measured in accordance with the Taber stiffness tester method specified in JIS P8125: 2000.

(Specific compression strength of the surface layer)
In order to facilitate molding during the top curl processing, a foamed heat insulating paper container paper base material 3 that is easily curled, that is, has a small compression strength of the surface layer portion is required. Therefore, the specific compression strength of the surface layer portion of the foamed heat insulating paper container paper base material 3 is preferably 23.0 N · m / g or less, and more preferably 22.0 N · m / g or less. As a result, it is possible to effectively suppress the turning of the seam portion.
Here, the specific compression strength is a value obtained by dividing the compression strength by the basis weight of the measurement sample. The compressive strength was measured according to the short span method specified in JIS P 8156: 2012.

(Specific tensile strength of the back layer)
In order not to break the top curl portion during the top curl processing, it is necessary to secure the tensile strength of the back layer portion of the foamed heat insulating paper container paper base material 3 in the MD direction.
Therefore, the specific tensile strength in the MD direction of the back layer portion of the paper-made foamed heat insulating paper container paper base material 3 is preferably 60.0 N · m / g or more, and is 65.0 N · m / g or more. Is more preferable.
Here, the specific tensile strength is a value obtained by dividing the tensile strength by the basis weight of the measurement sample.

(Ratio of the specific tensile strength of the back layer and the specific compressive strength of the surface layer)
The present inventors can increase the tensile strength of the back layer portion on which the tensile force acts during top curl processing and reduce the compressive strength of the surface layer portion that is required to be easy to curl. The ratio of the specific compressive strength of was examined. Hereinafter, the specific tensile strength of the back layer portion may be referred to as T, and the specific compression strength of the surface layer portion may be referred to as C. As a result of the examination, if the T / C is 3.00 or more, the foam-insulated paper container paper base material 3 having the property that the paper base material 1 is not broken by the tensile force of the top curl processing and is easily curled is used. It turned out to be obtained.

The T / C is preferably 3.05 or more, more preferably 3.10 or more, and even more preferably 3.20 or more. When the T / C is such a value, it is possible to effectively suppress the turning of the seam portion.
The methods for controlling T / C include a method of making a difference in the NKP content of the pulp constituting the back layer and the surface layer, a method of making a difference in the dissociation freeness of the pulp constituting the back layer and the surface layer, and a method of making a difference between the back layer and the surface layer. There is a method of making a difference in the degree of fiber orientation. Further, the T / C can be controlled by a method of increasing the content of the paper strength agent in the back layer as compared with the surface layer, a method of changing the internal chemicals, and the like.

Since it is the force acting in the MD direction that affects the top curl processing, in principle, the tensile strength, Taber rigidity, specific tensile strength, and specific compressive strength are in the MD direction (flow direction of the paper machine). Measure. However, when it is unclear which direction is the MD direction, the tensile strength is measured at every 22.5 degrees of the angle, and the direction showing the strongest tensile strength is set as the MD direction.

[Manufacturing method of paper base material]
The papermaking method of the paper base material 1 usually includes a step of beating the pulp constituting each layer so as to have a desired freeness, and a step of making a pulp slurry.
Generally, a paper machine is composed of an inlet, a wire part, a press part, a dryer part, a calendar part (smoothing process), and a reel part. The pH at the time of papermaking is not particularly limited, and for example, an acidic papermaking method may be used, or a neutral papermaking method using an alkaline filler such as calcium carbonate may be used.

The form of the inlet and the wire part is not particularly limited. For example, a circular net type paper machine, a short net paper machine, a long net paper machine, a twin wire, a gap former and the like can be mentioned. As a paper machine for making paper base material 1, a paper machine capable of making two or more layers is used. A paper machine capable of combining two or more layers is composed of a plurality of inlets.

In the papermaking method of the paper base material 1, the surface may be subjected to the above smoothing treatment in order to improve the surface strength and the printability. The smoothing treatment is preferably carried out, for example, by pressurizing the paper substrate 1 between reels that can be pressurized. There are no particular restrictions on the various finishing devices for smoothing, but for example, the product is finished by passing it through a machine calendar in front of the winder and / or a super calendar, gloss calendar, soft nip calendar, etc. ..

[Manufacturing method of foam insulation paper container paper base material]
The foam-insulated paper container paper base material 3 is produced by forming a water-soluble resin layer 2 on at least one side of the paper base material 1. The method for forming the water-soluble resin layer 2 is not particularly limited, but a method of applying the water-soluble resin using a blade coater or a rod coater is preferable. By coating with a blade coater or a rod coater, it is possible to uniformly control the coating amount of the water-soluble resin and the penetration thickness into the paper substrate 1. Then, by forming the water-soluble resin layer 2 in which the coating amount of the water-soluble resin and the permeation thickness into the paper base material 1 are within a predetermined range, the heat insulating property and the surface beauty of the foamed heat insulating paper container 8 are improved. Can be improved together.

The blade coater is a device that applies a coating liquid once applied by a roll coater or the like by scraping it with a blade. That is, in the blade coater, a blade (plate blade) having a length that crosses the paper base material 1 is arranged in close proximity to the paper base material 1 at an oblique angle. The blade scrapes off excess coating liquid that cannot pass through the gap between the paper substrate 1 and the blade. The blade coater is a type of coater that adjusts the amount of coating by scraping off the coating liquid with a blade in this way.

A rod coater is a device that applies a coating liquid once applied by a roll coater or the like by scraping it with a smooth rod, a rod wound with a wire, or a rod having a large number of grooves on the surface. Yes, it is also called a bar coater. That is, the rod coater arranges a rod having a length that crosses the paper base material 1 in close proximity to the paper base material 1. The rod scrapes off excess coating liquid that cannot pass through the gap between the paper base material 1 and the rod. The road coater is a type of coater that adjusts the amount of coating by scraping off the coating liquid with a rod in this way.

Both the blade coater and the rod coater can apply the coating liquid at high speed and smoothly, and can apply a high-concentration coating liquid thinly and uniformly. Therefore, a relatively high-concentration coating liquid containing a water-soluble resin can be applied on the paper substrate 1 to a thin and uniform thickness. A high-concentration coating liquid containing a water-soluble resin has a high solution viscosity, so that the coating liquid is suppressed from penetrating into the paper base material 1 after coating on the paper base material 1. Therefore, the penetration thickness of the water-soluble resin into the paper base material 1 can be reduced. Further, when a high-concentration coating liquid is used, the concentration of the water-soluble resin in the water-soluble resin layer 2 can be increased. From the above, even if the amount of the water-soluble resin applied is reduced, the water vapor generated from the paper substrate 1 can be uniformly and effectively barriered.

Of the blade coater and rod coater, the blade coater has a higher linear pressure at the time of scraping than the rod coater, it is possible to precisely adjust the coating amount, and the film thickness is also excellent. preferable.

Conventionally used coaters include calendar size presses and two-roll size presses. In these coaters, in order to form a thin coating film, it was necessary to lower the concentration of the water-soluble resin to lower the solution viscosity. As a result, in the water-soluble resin layer 2 formed by these coaters, the coating liquid penetrates deeper into the paper base material 1, the concentration of the water-soluble resin in the water-soluble resin layer 2 is low, and the coating liquid is generated from the paper base material 1. It was inferior in the ability to barrier water vapor.

Water is usually used as the solvent for the coating liquid. If necessary, an organic solvent such as alcohol, which is soluble in water, may be mixed and used. The coating liquid may contain a surfactant, a defoamer, a dye, a pigment, a sizing agent, a water resistant agent, a paper strength enhancer, a dispersant, a plastic agent, a pH adjuster, a defoaming agent, and a water retention agent, if necessary. Various known auxiliaries such as agents, preservatives, coloring dyes, coloring pigments, and ultraviolet inhibitors may be used in combination.

The method of drying the coating layer after applying the coating liquid is not particularly limited, and may be appropriately selected from known methods used in the papermaking step or the drying step. Further, after the water-soluble resin layer 2 is formed, a smoothing treatment can be performed if necessary. The smoothing process is performed on-machine or off-machine using a smoothing processing device such as a normal super calendar, gloss calendar, or soft calendar.

[Sheet for foam insulation paper container]
As described above, the foam-insulated paper container sheet 5 according to the present embodiment has the thermoplastic resin layer 4 on at least one side of the paper base material 1, and is between the paper base material 1 and the thermoplastic resin layer 4. , Has a water-soluble resin layer 2. The foamed heat insulating paper container sheet 5 is formed by providing the thermoplastic resin layer 4 on the water-soluble resin layer 2 of the foamed heat insulating paper container paper base material 3. Further, by heat-treating the foamed heat insulating paper container sheet 5, the water contained in the paper base material 1 and the water-soluble resin layer 2 is heated and evaporated, and the generated water vapor causes the thermoplastic resin layer 4 to become the foamed resin layer 9. Become. Hereinafter, the foam insulating paper container sheet 5 will be described, but the components already described will be omitted.

(Thermoplastic resin layer)
The thermoplastic resin used for the thermoplastic resin layer 4 is not particularly limited as long as it can be formed on the water-soluble resin layer 2 and can be foamed. As the thermoplastic resin of the thermoplastic resin layer 4, any thermoplastic resin, either a crystalline resin or a non-crystalline resin, can be used.

Examples of the crystalline resin include polyolefin resins such as polyethylene, polypropylene and polymethylpentene, polyester resins, polyamide resins, polyacetal resins, polyphenylene sulfide (PPS) resins and the like.
Examples of non-crystalline resins include polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene (ABS) resin, acrylic resin, modified polyphenylene ether (PPE), polycarbonate, polyurethane, polyvinyl acetate, and non-crystalline polyethylene terephthalate (PET). ) Etc. can be mentioned.
As these thermoplastic resins, a single resin may be used in a single layer, a plurality of resins may be mixed and used, or a plurality of resins may be used.

Among the above-mentioned thermoplastic resins, polyethylene is preferable because it is excellent in extruded laminate property and foamability. Polyethylene is broadly linear low-density polyethylene (density: 910 to 930 kg / m ³ , melting point: 102 ° C to 122 ° C), low density polyethylene (density: 910 to 930 kg / m ³ , melting point: 102 ° C to 122 ° C). ), Medium-density polyethylene (density: 930-942 kg / m ³ , melting point: 110-133 ° C.), high-density polyethylene (density: 942-970 kg / m ³ , melting point: 127-135 ° C.). Among these, low-density polyethylene is preferable because it is particularly excellent in extruded laminate property and foamability.

The thickness of the thermoplastic resin layer 4 is not particularly limited as long as the foamed heat insulating paper container 8 having the desired heat insulating property can be obtained, but from the viewpoint of heat insulating property and processability, the thickness before foaming is 30 to 30 to. It is preferably 80 μm.

(High melting point thermoplastic resin layer, metal layer)
The foam-insulated paper container sheet 5 according to the present embodiment has a high melting point thermoplasticity having a higher melting point than the thermoplastic resin layer 4 on the surface of the paper base material 1 opposite to the surface on which the thermoplastic resin layer 4 is formed. A metal layer such as a resin layer 10 or an aluminum foil may be laminated.
Such a high melting point thermoplastic resin layer 10 and a metal layer formed the thermoplastic resin layer 4 of the paper base material 1 when the foam insulating paper container sheet 5 was heated to foam the thermoplastic resin layer 4. Suppresses the evaporation of water vapor from the surface opposite to the surface. By suppressing this transpiration, sufficient water vapor is supplied to the thermoplastic resin layer 4, and the foamability of the thermoplastic resin layer 4 is improved.

At this time, the melting point of the thermoplastic resin used for the high melting point thermoplastic resin layer 10 does not melt at the heating temperature when the water contained in the paper substrate 1 is heated and evaporated, and it is sufficient that the diffusion of water vapor can be prevented. Therefore, the melting point of the thermoplastic resin is not particularly limited, but is preferably 125 ° C. or higher. Further, in order to form a metal layer on the surface of the paper base material 1, a metal foil may be laminated, or the metal layer may be formed by a vapor phase method such as a vapor deposition method.

Further, when the high melting point thermoplastic resin layer 10 or the metal layer is present on the inner wall surface side of at least one of the body member 6 and the bottom plate member 7 of the foamed heat insulating paper container 8, the liquid or the like filled in the container enters the paper base material 1. It is preferable because it can suppress the penetration.

Further, the refractory thermoplastic resin layer 10 may be laminated on the thermoplastic resin layer 4 of the foam insulating paper container sheet 5. When the high melting point thermoplastic resin layer 10 is laminated on the thermoplastic resin layer 4, when the foam insulating paper container sheet 5 is heated to foam the thermoplastic resin layer 4, the thermoplastic resin layer 4 is penetrated. Evaporation of water vapor is suppressed. By suppressing this transpiration, the foamability of the thermoplastic resin layer 4 is improved.

When the thermoplastic resin layer 4 is present on the outer wall surface side of the body member 6 of the foamed heat insulating paper container 8, the surface thereof is generally not smooth because unevenness due to foaming occurs. When the high melting point thermoplastic resin layer 10 is laminated on the thermoplastic resin layer 4, the surface of the body of the foamed heat insulating paper container 8 can be smoothed, so that a foamed heat insulating paper container 8 having particularly excellent beauty can be obtained. be able to.

The thermoplastic resin used for the high melting point thermoplastic resin layer 10 may be of the same type as the thermoplastic resin used for the thermoplastic resin layer 4, or may be of a different type. For example, consider the case where polyethylene is selected as the thermoplastic resin used for both the thermoplastic resin layer 4 and the refractory thermoplastic resin layer 10. In this case, it is preferable to select low-density polyethylene for the thermoplastic resin layer 4 and medium-density polyethylene or high-density polyethylene for the high-melting point thermoplastic resin layer 10. By selecting in this way, the melting point of the high melting point thermoplastic resin layer 10 can be made higher than that of the thermoplastic resin layer 4.

The difference in melting point between the thermoplastic resin layer 4 and the high melting point thermoplastic resin layer 10, that is, the difference in melting point between the thermoplastic resin used for the thermoplastic resin layer 4 and the high melting point thermoplastic resin layer 10 It is preferably 5 ° C. or higher.
When a plurality of types of resins are laminated and used in the thermoplastic resin layer 4 or the high melting point thermoplastic resin layer 10, it is preferable to set the melting point as follows. That is, it is preferable that the difference in melting point between the resin having the highest melting point in the thermoplastic resin layer 4 and the resin having the lowest melting point in the high melting point thermoplastic resin layer 10 is 5 ° C. or more.

The thickness of the high melting point thermoplastic resin layer 10 suppresses the evaporation of water vapor from the surface opposite to the surface on which the thermoplastic resin layer 4 of the paper substrate 1 is laminated, or penetrates the thermoplastic resin layer 4. It is only necessary to suppress the evaporation of water vapor. Therefore, the thickness of the high melting point thermoplastic resin layer 10 is not particularly limited, but is preferably about 20 to 50 μm.
In particular, when the high melting point thermoplastic resin layer 10 is present on the inner wall surface side of at least one of the body member 6 and the bottom plate member 7 of the foamed heat insulating paper container 8, the thickness of the high melting point thermoplastic resin layer 10 is 20 μm or more. It is preferable to have. When the thickness of the high melting point thermoplastic resin layer 10 is 20 μm or more, it is possible to effectively suppress the permeation of the liquid or the like filled in the container into the paper base material 1.

[Manufacturing method of foam insulation paper container sheet]
The foamed heat insulating paper container sheet 5 can be manufactured by forming the thermoplastic resin layer 4 on the foamed heat insulating paper container paper base material 3 manufactured by the above method.
Hereinafter, the step of forming the sheet for the foamed heat insulating paper container will be described.

The method for forming the thermoplastic resin layer 4 is not particularly limited, and various methods such as an extrusion laminating method, a wet laminating method, and a dry laminating method may be appropriately used for laminating.
The extrusion laminating method is a method in which a thermoplastic resin is extruded from a T-die into a molten resin film on the surface of a foamed heat insulating paper container paper base material 3, and pressed while being cooled between a cooling roll and a nip roll facing the cooling roll. This is a crimping method.
As a method for forming the thermoplastic resin layer 4, an extrusion laminating method is preferable because the adhesion between the water-soluble resin layer 2 and the thermoplastic resin layer 4 and the foamability of the thermoplastic resin layer 4 are improved. The same applies to the method for forming the high melting point thermoplastic resin layer 10.

The operating conditions of the extrusion laminating method, that is, the melting temperature of the thermoplastic resin, the laminating speed, and the like may be appropriately set depending on the type and apparatus of the thermoplastic resin to be used, and are not particularly limited. Generally, the melting temperature is about 200 to 370 ° C., and the laminating speed is about 30 to 200 m / min.

[Manufacturing method of foam insulation paper container]
The foamed heat insulating paper container 8 is formed by molding a foamed heat insulating paper container sheet 5 into a cup shape to manufacture a paper container (paper container molding step) and foaming the obtained container (foamed heat insulating paper container molding step). Can be manufactured.
Hereinafter, the paper container molding process and the foamed heat insulating paper container molding process will be described.

(Paper container molding process)
In the paper container molding step, the paper container is molded using the foam-insulated paper container sheet 5. The method for molding the paper container using the foamed heat insulating paper container sheet 5 is not particularly limited, and the paper container can be produced by a known method. As a specific example, there is a method of molding by a general cup molding machine described below.

First, the foam insulating paper container sheet 5 is printed with necessary printing on the body member blanks such as various patterns and barcodes, and then the body member blanks are punched into a predetermined shape. Positioning of the printed portion can be performed by a conventional method.

Next, a bottom plate member blank is prepared separately from the body member blank. The bottom plate member blank can be manufactured by punching out the foam insulating paper container sheet 5 in the same manner as the body member blank. Further, in order to prevent the liquid or the like filled in the container from permeating into the paper base material 1, the bottom plate member blank may have a structure different from that of the foamed heat insulating paper container sheet 5 of the present embodiment. As the sheet used for the bottom plate member blank, for example, a sheet in which a thermoplastic resin is laminated on a paper base material 1 or a sheet coated with aluminum foil or the like can be used.

The thermoplastic resin used for the bottom plate member blank may be the same type of resin as the thermoplastic resin used for the body member blank, or may be a different resin. If the same type of resin is used as the thermoplastic resin for both, or if both are manufactured from the same foamed heat insulating paper container sheet 5 and used, the body member 6 and the bottom plate member 7 foam at the same time, so that the foamed heat insulating paper container The heat insulating property of 8 becomes even better. In particular, when the foamed heat insulating paper container 8 is used outdoors, in winter, or in a cold region, or when the foamed heat insulating paper container 8 is used for a cup noodle or the like that is left for a while after injecting hot water, the foamed heat insulating paper having the above configuration is used. Container 8 is valid.

Next, the body member blank and the bottom plate member blank are assembled into a container shape by a cup molding machine. When the body member blank and the bottom plate member blank are assembled into a container shape, the thermoplastic resin layer 4 may be present on either the outside or the inside of the body member 6 or both. Whether the thermoplastic resin layer 4 is formed on the outside or the inside of the body member 6 or both may be appropriately determined according to the desired heat insulating property, aesthetics, touch and the like.

(Effervescent heat insulating paper container molding process)
In the foam insulation paper container molding step, the paper container is heat-treated to form the foam insulation paper container 8. In this step, the paper container molded in the paper container molding step is heat-treated. When the heat treatment is performed, the moisture contained in the paper base material 1 of the body member blank and the bottom plate member blank of the paper container is vaporized, and the generated water vapor foams the thermoplastic resin layer 4 to form the foamed heat insulating paper container 8. .. The foamed heat insulating paper container 8 uses foamed heat insulating paper 20 for at least one of the body member 6 and the bottom plate member 7, and the foamed heat insulating paper 20 has a foamed resin layer made of a thermoplastic resin on at least one side of the paper base material 1. Has 9.

The heat treatment conditions (heating temperature, heating time) may be appropriately set according to the type of the paper base material 1 and the thermoplastic resin, and are not particularly limited. The heating temperature is preferably a temperature slightly higher than the melting point of the thermoplastic resin (melting point + 5 ° C. to melting point + 10 ° C.), and more preferably a temperature lower than the melting point of the thermoplastic resin used for the high melting point thermoplastic resin layer 10. Generally, the heating temperature is about 100 to 200 ° C., and the heating time is about 1 to 6 minutes.

Any means such as hot air, electric heat, and electron beam can be used for the heat treatment. The foamed heat insulating paper container 8 can be manufactured at low cost and with high productivity by continuously heat-treating in a tunnel provided with a transport means by a conveyor.

The thickness of the foamed resin layer 9 foamed in this way is not particularly limited, but can be, for example, 800 to 1500 μm. When the thickness of the foamed resin layer 9 is 800 μm or more, sufficient heat insulating properties can be obtained. Further, when the thickness of the foamed resin layer 9 is 1500 μm or less, the surface is less likely to be uneven due to overfoaming, and the beauty is not impaired.

In the foamed heat insulating paper container 8 according to the present embodiment, if necessary, a technique known in the field of paper containers can be applied as long as the desired effect is not impaired. For example, a technique of applying a paint containing 5 to 40% by mass of a synthetic resin component to a part of the outside of the body member 6 to partially suppress foaming (Patent No. 3014629), that is, the outside of the body member 6, that is, , A technique of applying a tuning ink that synchronizes with foaming to form a smooth printing surface on the outer wall surface of the foamed heat insulating paper container 8 (Patent No. 3408156), forcibly processing the upper edge of the opening of the body member 6 into a square cross section. Examples thereof include, but are not limited to, a technique (Japanese Patent Laid-Open No. 2001-354226) in which the upper flange portion is provided and the inner winding end thereof is superposed on the upper portion of the flange portion to form a double structure. Further, in order to enhance the beauty, an ink receiving layer containing a pigment and a binder as main components may be provided on the outermost surface layer of the body member 6 which is the outer wall surface of the foamed heat insulating paper container 8.

As the lid material used for the foamed heat insulating paper container 8, a punched sheet 5 for the foamed heat insulating paper container can be used as in the case of the bottom plate member blank. Further, in order to prevent the liquid or the like filled in the container from permeating into the paper base material 1, the lid material may have a structure different from that of the foam insulating paper container sheet 5 according to the present embodiment. As the sheet used for the lid material, for example, a sheet in which a thermoplastic resin is laminated on a paper base material 1 or a sheet coated with aluminum foil or the like can be used.

The foamed heat insulating paper container 8 according to the present embodiment is a foamed heat insulating paper container for filling hot coffee or the like used in a vending machine or the like, a foamed heat insulating paper container for injecting hot water for instant food, and for cooking with a microwave oven. Can be used as a container, etc.

Examples and comparative examples are shown below. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the examples can be appropriately changed as long as they do not deviate from the gist of the present invention. Therefore, the scope of the present invention should not be construed in a limited manner by the specific examples shown below.
Unless otherwise specified, "parts" and "%" in Examples and Comparative Examples indicate "parts by mass" and "% by mass", respectively.

As described above, among the plurality of paper layers of the paper base material constituting the foam-insulated paper container paper base material, the outermost paper layer constituting the front surface of the paper base material is referred to as a front layer, and constitutes the back surface. The outermost paper layer is called the back layer.
Hereinafter, the five paper layers of the five-layered foam-insulated paper container paper base material will be referred to as a surface layer, a lower surface layer, a middle layer, a lower back layer, and a back layer, respectively, in order from the surface layer.
The three paper layers of the three-layered foam-insulated paper container paper base material are referred to as a surface layer, a middle layer, and a back layer, respectively, in order from the surface layer.
The two paper layers of the two-layer effervescent heat insulating paper container paper base material are referred to as a front layer and a back layer, respectively.

[Example 1]
(Effervescent insulation paper container paper base material)
15 parts of NBKP and 85 parts of LBKP were mixed and beaten to obtain a pulp slurry. 0.5% by mass of cationized starch, 0.1% by mass of polyacrylamide-based paper strength enhancer (PAM-based paper strength enhancer), alkyl keten dimer-based with respect to 100% by mass (solid content equivalent) of the obtained pulp slurry. Add 0.30% by mass of sizing agent and 0.1% by mass of polyamide polyamine epichlorohydrin resin (PAE-based wet paper strength enhancer), and add 5 for surface layer, lower surface layer, middle layer, lower back layer, and back layer. Paper charges for layers were prepared. Using this paper material, the set basis weight of all five layers was set to 60 g / m ² , and paper was made using a twin-wire paper machine for five-layer paper making to obtain a paper base material.

Next, an intermediate saponification type PVA (manufactured by Japan Vam & Poval Co., Ltd., product name: JM17, saponification degree 96.5 mol%) was applied to both sides (front layer and back layer) of the obtained paper substrate by a blade coater. It was coated and dried so that the solid content was 0.06 g / m ² (0.12 g / m ^{2 on} both sides) to obtain the foamed heat insulating paper container paper base material of Example 1.
The foam-insulated paper container paper base material of Example 1 has a basis weight of 302 g / m ² , a paper thickness of 341 μm, a density of 0.89 g / cm ³ , a fiber orientation ratio of 1.29 in the surface layer, and a fiber orientation ratio of 1 in the back layer. The tensile strength was .70, the tensile strength was 18.2 kN / m, the taber rigidity was 14.1 mN ・ m, the specific compression strength of the surface layer was 22.2 N ・ m / g, and the specific tensile strength of the back layer was 69.0 N ・ m / g. ..
The dissociation freeness of the pulp obtained by re-dissociating the surface layer of the foamed heat insulating paper container paper base material of Example 1 and the dissociation freeness of the pulp obtained by re-dissociating the back layer were both 500 ml.

(Sheet for foam insulation paper container)
^{A thermoplastic resin having a high melting point (medium density polyethylene, density 940 kg / m 3} , melting point 133 ° C.) is melted at a melting temperature of 360 ° C. and a laminating speed on one surface of the foamed heat insulating paper container paper base material so as to have a thickness of 40 μm. Extruded at 50 m / min. Then, using a cooling roll and a nip roll (JIS-A hardness: 70), pressure and pressure were applied at a linear pressure of 2 kgf / cm to form a high melting point thermoplastic resin layer.

^{Next, a thermoplastic resin (low density polyethylene, density 918 kg / m 3} , melting point 103 ° C.) was applied to the other surface of the foamed heat insulating paper container paper base material so as to have a thickness of 50 μm, at a melting temperature of 360 ° C. and a laminating speed of 50 m / m. Extruded in minutes. Then, using a cooling roll and a nip roll (JIS-A hardness: 70), the sheets are pressed and crimped at a linear pressure of 2 kgf / cm to form a thermoplastic resin layer to obtain the foam insulating paper container sheet of Example 1. It was.

[Example 2]
In the same manner as in Example 1, three layers of paper materials for the surface layer, the middle layer, and the back layer were prepared. Using this paper material, a twin wire paper machine with three layers is used, with the basis weight of the surface layer being 60 g / m ² , the basis weight of the middle layer being 180 g / m ² , and the basis weight of the back layer being 60 g / m ^2. Paper was made to obtain a paper substrate.

PVA was applied to the obtained paper substrate in the same manner as in Example 1, dried, and the basis weight was 304 g / m ² , the paper thickness was 338 μm, the density was 0.90 g / cm ³ , and the fiber orientation ratio of the surface layer was 1.26. The fiber orientation ratio of the back layer is 1.55, the tensile strength is 18.4 kN / m, the taber rigidity is 14.2 mN ・ m, the specific compressive strength of the surface layer is 21.8 N ・ m / g, and the specific tensile strength of the back layer is 66. A foam insulating paper container paper base material of 8 N · m / g was obtained.
The dissociation freeness of the pulp obtained by re-dissociating the surface layer of the foamed heat insulating paper container paper base material of Example 2 and the dissociation freeness of the pulp obtained by re-dissociating the back layer were both 500 ml.
Then, the high melting point thermoplastic resin layer and the thermoplastic resin layer were formed in the same manner as in Example 1 to obtain a sheet for a foam insulating paper container of Example 2.

[Example 3]
5 parts of NBKP and 95 parts of LBKP were mixed and beaten to obtain a pulp slurry for the surface layer.
15 parts of NBKP and 85 parts of LBKP were mixed and beaten to obtain pulp slurries for the lower surface layer, the middle layer, and the lower back layer.
25 parts of NBKP and 75 parts of LBKP were mixed and beaten to obtain a pulp slurry for the back layer.
With respect to the obtained pulp slurry, a paper strength enhancer or the like was added in the same manner as in Example 1 to prepare five layers of paper materials for the surface layer, the lower surface layer, the middle layer, the lower back layer, and the back layer. .. Using this paper material, the set basis weight of all five layers was set to 60 g / m ² , and paper was made using a twin-wire paper machine for five-layer paper making to obtain a paper base material.

PVA was applied to the obtained paper substrate in the same manner as in Example 1, dried, and the basis weight was 303 ^{g / m 2} , the paper thickness was 335 μm, the density was 0.90 g / cm ³ , and the fiber orientation ratio of the surface layer was 1.24. The fiber orientation ratio of the back layer is 1.69, the tensile strength is 18.3 kN / m, the taber rigidity is 14.0 mN ・ m, the specific compressive strength of the surface layer is 21.5 N ・ m / g, and the specific tensile strength of the back layer is 69. A foam insulating paper container paper base material of 6 N ・ m / g was obtained.
The dissociation freeness of the pulp obtained by re-dissociating the surface layer of the foamed heat insulating paper container paper base material of Example 3 was 490 ml, and the dissociation freeness of the pulp obtained by re-dissociating the back layer was 510 ml.
Then, the high melting point thermoplastic resin layer and the thermoplastic resin layer were formed in the same manner as in Example 1 to obtain a sheet for a foam insulating paper container of Example 3.

[Example 4]
5 parts of NBKP and 95 parts of LBKP were mixed and beaten to obtain a pulp slurry for the surface layer.
15 parts of NBKP and 85 parts of LBKP were mixed and beaten to obtain a pulp slurry for the middle layer.
25 parts of NBKP and 75 parts of LBKP were mixed and beaten to obtain a pulp slurry for the back layer.
With respect to the obtained pulp slurry, a paper strength enhancer and the like were added in the same manner as in Example 1 to prepare paper materials for three layers, one for the surface layer, one for the middle layer, and one for the back layer. Using this paper material, a twin wire paper machine with three layers is used, with the basis weight of the surface layer being 60 g / m ² , the basis weight of the middle layer being 180 g / m ² , and the basis weight of the back layer being 60 g / m ^2. Paper was made to obtain a paper substrate.

PVA was applied to the obtained paper substrate in the same manner as in Example 1, dried, and the basis weight was 300 g / m ² , the paper thickness was 341 μm, the density was 0.88 g / cm ³ , and the fiber orientation ratio of the surface layer was 1.25. The fiber orientation ratio of the back layer is 1.67, the tensile strength is 18.8 kN / m, the taber rigidity is 14.5 mN ・ m, the specific compressive strength of the surface layer is 21.7 N ・ m / g, and the specific tensile strength of the back layer is 68. A 9 N · m / g foam insulating paper container paper base material was obtained.
The dissociation freeness of the pulp obtained by re-dissociating the surface layer of the foamed heat insulating paper container paper base material of Example 4 was 480 ml, and the dissociation freeness of the pulp obtained by re-dissociating the back layer was 510 ml.
Then, the high melting point thermoplastic resin layer and the thermoplastic resin layer were formed in the same manner as in Example 1 to obtain the foam insulating paper container sheet of Example 4.

[Example 5]
A paper material was prepared in the same manner as in Example 1 to obtain a paper base material.
PVA was applied to the obtained paper substrate in the same manner as in Example 1, dried, and the basis weight was 300 g / m ² , the paper thickness was 343 μm, the density was 0.87 g / cm ³ , and the fiber orientation ratio of the surface layer was 1.42. Fiber orientation ratio 1.60 of the back layer, tensile strength 20.5 kN / m, Taber rigidity 16.1 mN ・ m, specific compressive strength of the surface layer 22.0 N ・ m / g, specific tensile strength of the back layer 66. A 3 N · m / g foam insulating paper container paper base material was obtained.
The dissociation freeness of the pulp obtained by re-dissociating the surface layer of the foamed heat insulating paper container paper base material of Example 5 and the dissociation freeness of the pulp obtained by re-dissociating the surface layer were both 500 ml.
Then, the high melting point thermoplastic resin layer and the thermoplastic resin layer were formed in the same manner as in Example 1 to obtain the foam insulating paper container sheet of Example 5.

[Example 6]
5 parts of NBKP and 95 parts of LBKP were mixed and beaten to obtain a pulp slurry for the surface layer.
15 parts of NBKP and 85 parts of LBKP were mixed and beaten to obtain pulp slurries for the lower surface layer, the middle layer, and the lower back layer.
25 parts of NBKP and 75 parts of LBKP were mixed and beaten to obtain a pulp slurry for the back layer.
With respect to the obtained pulp slurry, a paper strength enhancer or the like was added in the same manner as in Example 1 to prepare five layers of paper materials for the surface layer, the lower surface layer, the middle layer, the lower back layer, and the back layer. .. Using this paper material, the set basis weight of all five layers was set to 60 g / m ² , and paper was made using a twin-wire paper machine for five-layer paper making to obtain a paper base material.

Next, starch (manufactured by Oji Cornstarch, product name: Ace A) was applied to both sides (front layer and back layer) of the obtained paper substrate by a blade coater in ^{terms of solid content of 2.00 g / m 2} per side (4 on both sides. It was coated and dried so as to have a concentration of 00 g / m ² ) to obtain a foam-insulated paper container paper base material.
The foam-insulated paper container paper base material of Example 6 has a basis weight of 304 g / m ² , a paper thickness of 342 μm, a density of 0.89 g / cm ³ , a fiber orientation ratio of 1.24 on the surface layer, and a fiber orientation ratio of 1 on the back layer. The tensile strength was .69, the tensile strength was 18.6 kN / m, the taber rigidity was 14.3 mN ・ m, the specific compression strength of the surface layer was 21.5 N ・ m / g, and the specific tensile strength of the back layer was 69.6 N ・ m / g. ..
The dissociation freeness of the pulp obtained by re-dissociating the surface layer of the foamed heat insulating paper container paper base material of Example 6 was 490 ml, and the dissociation freeness of the pulp obtained by re-dissociating the back layer was 510 ml.
Then, the high melting point thermoplastic resin layer and the thermoplastic resin layer were formed in the same manner as in Example 1 to obtain the foam insulating paper container sheet of Example 6.

[Example 7]
In the same manner as in Example 1, two layers of paper materials, one for the front layer and the other for the back layer, were prepared. Using this paper material, the basis weight of the surface layer was set to 150 g / m ² and the basis weight of the back layer was set to 150 g / m ² , and paper was made using a twin-wire paper machine for two-layer paper making to obtain a paper base material. ..
PVA was applied to the obtained paper substrate in the same manner as in Example 1, dried, and the basis weight was ^{303 g / m 2} , the paper thickness was 344 μm, the density was 0.88 g / cm ³ , and the fiber orientation ratio of the surface layer was 1.30. The fiber orientation ratio of the back layer is 1.65, the tensile strength is 19.4 kN / m, the taber rigidity is 15.9 mN ・ m, the specific compressive strength of the surface layer is 22.4 N ・ m / g, and the specific tensile strength of the back layer is 68. A 2 N · m / g foam insulating paper container paper base material was obtained.
The dissociation freeness of the pulp obtained by re-dissociating the surface layer of the foamed heat insulating paper container paper base material of Example 7 and the dissociation freeness of the pulp obtained by re-dissociating the surface layer were both 500 ml.
Then, the high melting point thermoplastic resin layer and the thermoplastic resin layer were formed in the same manner as in Example 1 to obtain the foam insulating paper container sheet of Example 7.

[Comparative Example 1]
20 parts of NBKP and 80 parts of LBKP were mixed and beaten, and the other parts were prepared in the same manner as in Example 1 to obtain a paper base material.
PVA was applied to the obtained paper substrate in the same manner as in Example 1, dried, and the basis weight was 300 g / m ² , the paper thickness was 338 μm, the density was 0.89 g / cm ³ , and the fiber orientation ratio of the surface layer was 1.40. Fiber orientation ratio 1.44 of the back layer, tensile strength 22.8 kN / m, Taber rigidity 16.8 mN ・ m, specific compressive strength of the surface layer 23.6 N ・ m / g, specific tensile strength of the back layer 65. A 1 N · m / g foam insulating paper container paper base material was obtained.
The dissociation freeness of the pulp obtained by re-dissociating the surface layer of the foamed heat insulating paper container paper base material of Comparative Example 1 and the dissociation freeness of the pulp obtained by re-dissociating the surface layer were both 520 ml.
Then, a high melting point thermoplastic resin layer and a thermoplastic resin layer were formed in the same manner as in Example 1 to obtain a sheet for a foam insulating paper container of Comparative Example 1.

[Comparative Example 2]
A paper material was prepared in the same manner as in Example 1 to obtain a paper base material.
PVA was applied to the obtained paper substrate in the same manner as in Example 1, dried, and the basis weight was 301 g / m ² , the paper thickness was 340 μm, the density was 0.89 g / cm ³ , and the fiber orientation ratio of the surface layer was 1.33. The fiber orientation ratio of the back layer is 1.33, the tensile strength is 16.2 kN / m, the taber rigidity is 15.4 mN ・ m, the specific compressive strength of the surface layer is 23.0 N ・ m / g, and the specific tensile strength of the back layer is 54. A foam insulating paper container paper base material of 0 N ・ m / g was obtained.
The dissociation freeness of the pulp obtained by re-dissociating the surface layer of the foamed heat insulating paper container paper base material of Comparative Example 2 and the dissociation freeness of the pulp obtained by re-dissociating the surface layer were both 500 ml.
Then, the high melting point thermoplastic resin layer and the thermoplastic resin layer were formed in the same manner as in Example 1 to obtain the foam insulating paper container sheet of Comparative Example 2.

[Comparative Example 3]
A paper material was prepared in the same manner as in Example 1 to obtain a paper base material.
PVA was applied to the obtained paper substrate in the same manner as in Example 1, dried, and the basis weight was ^{303 g / m 2} , the paper thickness was 339 μm, the density was 0.89 g / cm ³ , and the fiber orientation ratio of the surface layer was 1.70. The fiber orientation ratio of the back layer is 1.29, the tensile strength is 16.5 kN / m, the taber rigidity is 14.2 mN ・ m, the specific compressive strength of the surface layer is 24.4 N ・ m / g, and the specific tensile strength of the back layer is 48. A foam insulating paper container paper base material of 6 N ・ m / g was obtained.
The dissociation freeness of the pulp obtained by re-dissociating the surface layer of the foamed heat insulating paper container paper base material of Comparative Example 3 and the dissociation freeness of the pulp obtained by re-dissociating the surface layer were both 500 ml.
Then, the high melting point thermoplastic resin layer and the thermoplastic resin layer were formed in the same manner as in Example 1 to obtain the foam insulating paper container sheet of Comparative Example 3.

[Comparative Example 4]
A paper material was prepared in the same manner as in Example 1 to obtain a paper base material.
PVA was applied to the obtained paper substrate in the same manner as in Example 1, dried, and the basis weight was 302 g / m ² , the paper thickness was 326 μm, the density was 0.93 g / cm ³ , and the fiber orientation ratio of the surface layer was 1.31. The fiber orientation ratio of the back layer is 1.61, the tensile strength is 17.1 kN / m, the taber rigidity is 14.2 mN ・ m, the specific compressive strength of the surface layer is 23.4 N ・ m / g, and the specific tensile strength of the back layer is 68. A 2 N · m / g foam insulating paper container paper base material was obtained.
The dissociation freeness of the pulp obtained by re-dissociating the surface layer of the foamed heat insulating paper container paper base material of Comparative Example 4 and the dissociation freeness of the pulp obtained by re-dissociating the surface layer were both 400 ml.
Then, the high melting point thermoplastic resin layer and the thermoplastic resin layer were formed in the same manner as in Example 1 to obtain the foam insulating paper container sheet of Comparative Example 4.

[Comparative Example 5]
A paper material was prepared in the same manner as in Example 1 to obtain a paper base material.
PVA was applied to the obtained paper substrate in the same manner as in Example 1, dried, and the basis weight was 302 g / m ² , the paper thickness was 353 μm, the density was 0.86 g / cm ³ , and the fiber orientation ratio of the surface layer was 1.32. The fiber orientation ratio of the back layer is 1.69, the tensile strength is 21.5 kN / m, the taber rigidity is 18.4 mN ・ m, the specific compressive strength of the surface layer is 22.4 N ・ m / g, and the specific tensile strength of the back layer is 69. A foam insulating paper container paper base material of 0 N ・ m / g was obtained.
The dissociation freeness of the pulp obtained by re-dissociating the surface layer of the foamed heat insulating paper container paper base material of Comparative Example 4 and the dissociation freeness of the pulp obtained by re-dissociating the surface layer were both 480 ml.
Then, the high melting point thermoplastic resin layer and the thermoplastic resin layer were formed in the same manner as in Example 1 to obtain the foam insulating paper container sheet of Comparative Example 5.

[Comparative Example 6]
A paper material was prepared in the same manner as in Example 1 to obtain a paper base material.
The obtained paper substrate was not coated with a water-soluble resin, and had a basis weight of 305 g / m ² , a paper thickness of 332 μm, a density of 0.92 g / cm ³ , a fiber orientation ratio of 1.29 on the surface layer, and fibers on the back layer. Orientation ratio 1.70, tensile strength 21.5 kN / m, Taber rigidity 18.4 mN ・ m, Specific compression strength of surface layer 22.4 N ・ m / g, Specific tensile strength of back layer 69.0 N ・ m / g Foam insulation paper container paper base material was obtained.
The dissociation freeness of the pulp obtained by re-dissociating the surface layer of the foamed heat insulating paper container paper base material of Comparative Example 4 and the dissociation freeness of the pulp obtained by re-dissociating the surface layer were both 480 ml.
Then, the high melting point thermoplastic resin layer and the thermoplastic resin layer were formed in the same manner as in Example 1 to obtain the foam insulating paper container sheet of Comparative Example 6.

[Comparative Example 7]
A paper material was prepared in the same manner as in Example 1 to obtain a paper base material.
PVA was applied to the obtained paper substrate in the same manner as in Example 1, dried, and the basis weight was 298 g / m ² , the paper thickness was 320 μm, the density was 0.93 g / cm ³ , and the fiber orientation ratio of the surface layer was 1.18. The fiber orientation ratio of the back layer is 1.55, the tensile strength is 14.2 kN / m, the taber rigidity is 11.1 mN ・ m, the specific compressive strength of the surface layer is 18.0 N ・ m / g, and the specific tensile strength of the back layer is 54. A 3 N · m / g foam insulating paper container paper base material was obtained.
The dissociation freeness of the pulp obtained by re-dissociating the surface layer of the foamed heat insulating paper container paper base material of Comparative Example 7 and the dissociation freeness of the pulp obtained by redissociating the surface layer were both 480 ml.
Then, the high melting point thermoplastic resin layer and the thermoplastic resin layer were formed in the same manner as in Example 1 to obtain the foam insulating paper container sheet of Comparative Example 7.

[Measuring method]
The measurement method carried out on the foam insulation paper container sheet obtained as described above is shown below.

<Basis weight>
Basis weight was measured according to JIS P 8124: 2011. The weight was measured using an electronic balance capable of measuring up to the last 4 digits, and the basis weight was calculated.

<Paper thickness>
The paper thickness was measured using a paper thickness gauge conforming to JIS P 8118: 2014.

<Density>
Density was measured according to JIS P 8118: 1998.

<Dissociation Freeness>
The obtained foamed heat insulating paper container paper base material was impregnated with hot water at 80 ° C. for 4 hours, and the surface layer and the back layer were slowly peeled off with tweezers before the sample dried to obtain a measurement sample. Each of the obtained layers was dissociated according to the method of JIS P 8220: 2012, and the dissociation freeness of the obtained pulp slurry was measured by a method according to JIS P 8121: 2012. As a measuring machine, a Canadian free nester manufactured by Kumagai Riki Kogyo was used.

<Fiber orientation ratio>
The fiber orientation ratio was measured using an apparatus (SST-2500, manufactured by Nomura Shoji Co., Ltd.) for measuring the fiber orientation of the sheet from the angular distribution of the propagation velocity of ultrasonic waves.

<Separation method of surface layer and back layer>
The paper thickness of all layers was measured, and the thickness was removed by grinding using a surface grinding device (manufactured by Sagawa Seisakusho) to half the thickness including the side including the surface to be measured. The grindstone used was a cylindrical grindstone Φ50.8 × 12.7 mm.

<Compression strength>
The compressive strength in the MD direction of the foamed heat insulating paper container paper base material was measured according to the short span method specified in JIS P 8156: 2012.

<Tensile strength>
The tensile strength of the foamed heat insulating paper container paper base material in the MD direction was measured according to the method specified in JIS P 8113: 2006. A horizontal tensile tester (CODE SE-064, manufactured by L & W) was used as the measuring machine.

<Taber Rigidity>
The taber rigidity in the MD direction of the foamed heat insulating paper container paper base material was measured according to the Taber stiffness tester method specified in JIS P8125: 2000.

[Evaluation method]
The foam-insulated paper container sheet obtained as described above was evaluated as follows. The evaluation results of the examples are as shown in Table 1. The evaluation results of the comparative examples are as shown in Table 2.
In addition, ○ and △ are pass, and × is fail.

(Moldability of top curl part)
The top curl portion molded so that the diameter of the curl portion was 3.5 mm was visually evaluated, and a three-stage evaluation was performed.
◯: No shape such as crushing, wrinkles, or swelling is seen in the curl part.
Δ: There are some crushes, wrinkles, and swellings in the curl part, but there is no problem in actual use.
X: Crushes, wrinkles, and swelling are conspicuous in the curl part, which is significantly inferior.

(Turning the seam part)
The top curl portion molded so that the diameter of the curl portion was 3.5 mm was visually evaluated, and a three-stage evaluation was performed.
◯: No curl is seen on the top curl of the seam part.
Δ: The top curl of the seam part is slightly raised and turned up, but there is no problem in actual use.
×: The top curl of the seam part is remarkably inferior due to conspicuous uplift and curling.

(Thermal insulation properties)
An A4 size sample was cut out from the obtained foam insulation paper container sheet. A cylinder was made with the thermoplastic resin layer on the outside. Then, using hot air, the thermoplastic resin layer on the outside of the cylinder was foamed at a heating temperature of 120 ° C. and a heating time of 6 minutes.
The foaming ratio was calculated from the thickness of the obtained foamed heat insulating paper before and after foaming, and evaluated according to the following criteria.
◯: The foaming ratio is 19 times or more, and the heat insulating property is sufficient.
Δ: The foaming ratio is 15 times or more and less than 19 times, and has heat insulating properties.
X: The foaming ratio is less than 15 times, and the heat insulating property is insufficient.

(Beauty)
From the obtained foam insulation paper container sheet, a square test piece having a side of 100 mm was cut out. Then, using hot air, the thermoplastic resin layer was foamed at a heating temperature of 120 ° C. and a heating time of 6 minutes. The surface of the thermoplastic resin layer after foaming was visually observed, and the beauty was evaluated according to the following criteria.
◯: No hyperfoaming was observed, the formed foam cells were small and generally homogeneous, and the surface was also generally flat.
Δ: The formed foam cells are slightly large and the size varies, but the surface irregularities are small and no hyperfoaming is observed.
X: There are large irregularities on the surface such as overfoaming.

As can be seen from Table 1, the foam-insulated paper container sheets of Examples 1 to 7 were excellent in all of the performances of the moldability of the top curl portion, the suppression of curling of the seam portion, the heat insulating property, and the beauty.
Among Examples 1 to 7, the number of NKP blended parts in the back layer is larger than the number of NKP blended parts in the surface layer, the fiber orientation ratio in the back layer portion is larger than the fiber orientation ratio in the surface layer portion, and the paper layer is made together. The foam-insulated paper container sheet having three or more layers was particularly excellent in moldability of the top curl portion. Further, the foam-insulated paper container sheet using PVA as the water-soluble resin and having three or more layers of paper that has been squeezed together is particularly excellent in heat insulating properties and aesthetics.

In the foam insulation paper container sheets of Comparative Examples 1 to 3, the difference between the fiber orientation ratio of the back layer portion and the fiber orientation ratio of the surface layer portion is too small, so that the specific tensile strength of the back layer portion and the specific compression strength of the surface layer portion are The ratio also became smaller, and crushing, wrinkles, and swelling of the top curl part tended to be conspicuous, and especially the floating and curling of the seam part were conspicuous.
The foamed heat insulating paper container sheet of Comparative Example 4 has low desorption freeness in both the surface layer and the back layer, the ratio of the specific tensile strength of the back layer portion to the specific compression strength of the surface layer portion is also small, and the seam portion of the top curl portion is not lifted. The crease was noticeable.
In the foam insulation paper container sheet of Comparative Example 5, since the taber rigidity was too large, crushing, wrinkling, and swelling of the top curl portion were conspicuous, and in particular, lifting and curling of the seam portion were conspicuous.
Since the foam-insulated paper container sheet of Comparative Example 6 was not provided with the water-soluble resin layer, both the heat insulating property and the foaming property were inferior.
Since the tensile strength of the foam insulation paper container sheet of Comparative Example 7 was too small, crushing, wrinkling, and swelling of the top curl portion were conspicuous, and in particular, lifting and curling of the seam portion were conspicuous.

1 Paper base material 2 Water-soluble resin layer 3 Foam insulation paper container Paper base material 4 Thermoplastic resin layer 5 Foam insulation paper container sheet 6 Body member 7 Bottom plate member 8 Foam insulation paper container 9 Foam resin layer 10 High melting point thermoplastic resin Layer 20 foam insulation paper

Claims (7)

A foam-insulated paper container paper base material composed of a paper base material having two or more paper layers and a water-soluble resin layer provided on at least one surface of the paper base material, which contains cellulose pulp as a main component. ,
The tensile strength in the MD direction is 15.0 kN / m or more, and
The Taber rigidity in the MD direction measured in accordance with the Taber stiffness tester method specified in JIS P8125: 2000 is 17.0 mN ・ m or less.
When the front layer portion including the front surface and the back layer portion including the back surface were divided into two parts having an equal thickness in the paper thickness direction, the specific tensile strength of the back layer portion in the MD direction was measured by the T, short span method. A foamed heat insulating paper container paper base material having a T / C of 3.00 or more when the specific compression strength of the surface layer portion in the MD direction is C. The foam insulation according to claim 1, wherein the number of NKP blended parts of the outermost paper layer including the back surface is 10 parts by mass or more larger than the number of NKP blended parts of the outermost paper layer including the front side. Paper container Paper base material. The foamed heat insulating paper container paper base material according to claim 1 or 2, wherein the fiber orientation ratio of the back layer portion is 0.15 or more larger than the fiber orientation ratio of the surface layer portion. The foam-insulated paper container paper according to any one of claims 1 to 3, wherein the dissociation freeness of the surface layer portion is 430 to 550 ml, and the dissociation freeness of the back layer portion is 450 to 560 ml. Base material. The foamed heat insulating paper container paper base material according to any one of claims 1 to 4, wherein the water-soluble resin constituting the water-soluble resin layer is polyvinyl alcohol. A sheet for a foam-insulated paper container according to any one of claims 1 to 5, wherein thermoplastic resin layers are provided on both sides of the foam-insulated paper container paper base material. A foam-insulated paper container comprising the foam-insulated paper container sheet according to claim 6.

Images