JP2021176784A - Paper base material for foamed heat-insulation paper container, sheet for foamed heat-insulation paper container, and foamed heat-insulation paper container - Google Patents

Abstract

To provide a foamed heat-insulation paper container, a paper base material for a foamed heat-insulation paper container, and a sheet for a foamed heat-insulation paper container which has excellent heat insulating properties and a beautiful surface appearance.SOLUTION: A paper base material 3 for a foamed heat-insulation paper container includes polyvinyl alcohol layers 2 having a formation amount of 0.05 to 0.5 g/m2 per one surface on both surfaces of a paper base material 1 having an air permeability resistance of 2.0 to 6.0 s/g/m2 per basis weight; the sheet 5 for a foamed heat-insulation paper container includes a thermoplastic resin layer 4 at least on one surface of the paper base material 1 having an air permeability resistance falling in the range described above per basis weight and includes the polyvinyl alcohol layer 2 having the formation amount described above between the paper base material 1 and the thermoplastic resin layer 4; foamed heat-insulation paper is used for at least one of a barrel member 6 and a bottom plate member 7 in the foamed heat-insulation paper container 8; the foamed heat-insulation paper includes a foamed resin layer 9 comprising a thermoplastic resin at least on one surface of the paper base material 1 having the air permeability resistance falling in the range described above per basis weight and includes the polyvinyl alcohol layer 2 having the formation amount described above between the paper base material 1 and the foamed resin layer 9.SELECTED DRAWING: Figure 3

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 containers for providing hot drinks such as coffee and hot foods such as soup to purchasers, or as containers for instant noodles in cups. in use.

Conventionally, a expanded polystyrene container is known as a heat insulating container used for such an application. A expanded polystyrene container is manufactured by injecting a raw material in which a foaming agent is added to polystyrene into a mold, applying heat and pressure to the raw material to foam the raw material, and molding the container. The expanded polystyrene container thus obtained is bulky because the entire container is foamed, and is very excellent in terms of heat insulation, but there is a problem that the amount of dust after use increases. be. Further, since the expanded polystyrene container generates high heat when it is incinerated, there is a concern that it may affect the incinerator. Furthermore, from the viewpoint of saving petroleum resources, it is required to review its use.

Further, since there are many minute irregularities on the outer surface of the expanded polystyrene container, there is a problem that it is difficult to clearly express even if a pattern, characters, symbols, etc. are printed on the outer surface of the container. Further, since the strength is weaker than that of a heat-insulating container made of paper, there is a problem that a relatively large container such as for instant noodles in a cup may be cracked during transportation.

The following prior arts are disclosed for these problems. For example, in Patent Document 1, in a foam-insulated paper container sheet in which a thermoplastic resin layer such as polyethylene is laminated on at least one side of a paper base material, the surface of the paper base material is treated by a calendar size press. A sheet for a heat insulating paper container is disclosed.
Further, this Patent Document 1 is characterized in that the foam-insulated paper container sheet is used as a body member and / or a bottom plate member, and the paper base material of the foam-insulated paper container sheet is contained. There is disclosed a foamed heat insulating paper container obtained by heating and evaporating the water content to be formed and foaming the thermoplastic resin layer.

Japanese Unexamined Patent Publication No. 2012-21408

In the foamed heat insulating paper container described in Patent Document 1, since the main base material is paper, the amount of petroleum used is smaller and the environmental load is smaller than that of the container made entirely of expanded polystyrene. However, in the foamed heat insulating paper container described in Patent Document 1, since the permeation amount of water vapor generated from the paper base material during heat foaming is not uniform depending on the location, the foaming of the thermoplastic resin layer becomes non-uniform, and the surface is beautiful. There was room for improvement in sex.
Further, the foamed heat insulating paper container is required to have heat insulating properties.

The present invention has been made in view of the above circumstances. That is, it is an object of the present invention to provide a foamed heat insulating paper container having excellent heat insulating properties and surface beauty. Another object of the present invention is to provide a foam-insulated paper container paper base material and a foam-insulated paper container sheet used for manufacturing the foam-insulated paper container.

The present inventors have studied a method for surface treatment of a paper base material before laminating a thermoplastic resin layer to be a foamed resin layer. As a result, when a predetermined polyvinyl alcohol layer is provided in advance on the surface of the paper base material, the permeation of water vapor generated from the paper base material is appropriately barriered, the water vapor is suppressed from being ejected from a specific place, and the water vapor It was found that the variation in the amount of permeation depending on the location can be reduced. Then, the present inventors have found that the heat insulating property and the beauty of the foamed heat insulating paper container can be improved by this, and have completed the present invention.
The present invention has the following configuration.

(1) Foamed heat insulating paper having a polyvinyl alcohol layer having a formation amount of 0.05 to 0.5 g / m ² and a penetration thickness into the paper base material of 5 to 35 μm on at least one side of the paper base material. Container paper base material.

(2) The foam-insulated paper container paper base material according to (1), wherein the paper base material is a multilayer material in which pulp layers and starch layers are alternately laminated.

(3) The foamed heat insulating paper container paper base material according to (2), wherein the outermost layers on both sides of the multilayer material are the pulp layers.

(4) The foamed heat insulating paper container paper base material according to (2) or (3), wherein the pulp layer contains cationized starch.

(5) A sheet for a foam-insulated paper container having a thermoplastic resin layer on at least one side of a paper base material, and an amount of 0.05 to 0.5 g formed between the paper base material and the thermoplastic resin layer. A sheet for a foam-insulated paper container, characterized by having a polyvinyl alcohol layer having a permeation thickness of / m ^{2 and a penetration thickness into the paper substrate of 5 to 35 μm.}

(6) The foam insulating paper container sheet according to (5), wherein the thermoplastic resin layer has a thickness of 30 to 80 μm.

(7) The foam insulating paper container sheet according to (5) or (6), wherein the thermoplastic resin layer is a polyethylene layer.

(8) A foamed heat insulating paper container using foamed heat insulating paper for at least one of a body member and a bottom plate member, wherein the foamed heat insulating paper has a foamed resin layer made of a thermoplastic resin on at least one side of a paper base material. ^{A polyvinyl alcohol layer having a forming amount of 0.05 to 0.5 g / m 2} and a penetration thickness into the paper base material of 5 to 35 μm is provided between the paper base material and the foamed resin layer. A featured foam insulation paper container.

In the foamed heat insulating paper container according to the present invention, since the amount of water vapor permeated from the paper base material varies little depending on the location, the thermoplastic resin layer is uniformly foamed, and the heat insulating property and the surface beauty are excellent. Further, in the foamed heat insulating paper container paper base material and the foamed heat insulating paper container sheet according to the present invention, the amount of water vapor generated from the paper base material varies little depending on the location, so that the thermoplastic resin layer foams uniformly. It is possible to manufacture a foamed heat insulating paper container having excellent heat insulating properties and surface beauty.

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

Embodiments of the present invention will be described below. However, the embodiments of the present invention are not limited to the following embodiments.

FIG. 1 is a schematic cross-sectional view of the foamed heat insulating paper container 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, in the foamed heat insulating paper container 8, foamed heat insulating paper is used for at least one of the body member 6 and the bottom plate member 7. As shown in FIG. 2, the foamed heat insulating paper 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 container 8 according to the present embodiment has a predetermined polyvinyl alcohol layer 2 between the paper base material 1 and the foamed resin layer 9. In FIG. 2, the predetermined polyvinyl alcohol layer 2 is formed on both surfaces of the paper base material 1. Further, the foamed heat insulating paper container 8 has the foamed resin layer 9 described above on the outer wall surface side thereof, and has a melting point thermoplastic resin layer 10 described later on the inner wall surface side thereof.

FIG. 3 is a schematic cross-sectional view of the foam insulating paper container sheet 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 container 8 described above. The foam insulating 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 predetermined value is provided between the paper base material 1 and the thermoplastic resin layer 4. It has a polyvinyl alcohol layer 2. The thermoplastic resin layer 4 is foamed by heat treatment to become a foamed resin layer 9.

FIG. 4 is a schematic cross-sectional view of the foamed heat insulating paper container paper base material 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 predetermined polyvinyl alcohol layer 2 on at least one side of the paper base material 1. By providing the thermoplastic resin layer 4 on the predetermined polyvinyl alcohol layer 2, the foam insulating paper container sheet 5 is formed.

The foam-insulated paper container sheet 5 is used as the body member 6 and the bottom plate member 7 to form a paper container. After that, by heating the paper container, the water contained in the paper base material 1 and the predetermined polyvinyl alcohol layer 2 is vaporized to become water vapor. The generated water vapor permeates through the predetermined polyvinyl alcohol layer 2 and permeates into the heated thermoplastic resin layer 4, foams the thermoplastic resin, and the thermoplastic resin layer 4 changes to the foamed resin layer 9. .. As a result, the paper container becomes a foam-insulated paper container 8 having heat insulating properties.

According to the study by the present inventors, if a film (layer) made of resin or the like 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, so that the water vapor The amount of permeation becomes non-uniform depending on the location of the paper base material 1, and the foaming of the thermoplastic resin layer 4 tends to cause partial overfoaming. If the over-foamed portion is present, the foaming form becomes non-uniform and the surface becomes uneven, so that both the heat insulating property and the beauty of the surface are deteriorated.

As a result of repeated studies on the material of the film formed on the surface of the paper base material 1, the present inventors set a predetermined amount of formation and a penetration thickness into the paper base material 1 within a predetermined range by using polyvinyl alcohol. It was found that by forming a layer, both heat insulation and surface beauty can be satisfied.
Hereinafter, each member constituting the present embodiment will be described.

(Polyvinyl alcohol)
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.
In this embodiment, 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 K 6726-1994.

Further, in the present embodiment, as the polyvinyl alcohol, an unmodified polyvinyl alcohol into which no functional group other than a _{hydroxyl group (OH group) or an acetic acid group (3 OCOCH groups) has been introduced can be used.} Further, in the present embodiment, 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, and a sulfonic acid group. The reason why polyvinyl alcohol is excellent as a material for a film to be formed on a paper substrate is considered as follows.

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 at the same time. , Water vapor can be appropriately barriered. Therefore, when the polyvinyl alcohol layer that is firmly adhered to the paper base material is formed, the amount of water vapor permeation can be appropriately controlled, and the amount of water vapor permeation can be suppressed from varying depending on the location. As a result, the foamed state of the thermoplastic resin layer can be made uniform, and the heat insulating property can be improved.

Polyvinyl alcohol can be appropriately selected and used from commercially available ones.
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 does not increase, and the coating becomes easy.

The saponification degree of polyvinyl alcohol is preferably 80 mol% or more, more preferably 90 mol% or more, still more 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.

[Predetermined polyvinyl alcohol layer]
When a predetermined polyvinyl alcohol layer that is firmly adhered to the paper base material is formed, the amount of water vapor permeation can be appropriately controlled and the variation in the amount of water vapor permeation depending on the location can be reduced. As a result, the foamed state of the thermoplastic resin layer can be made uniform, and the heat insulating property can be improved.

Further, as will be described later, polyethylene is often used as the thermoplastic resin to be the foamed resin layer. The presence of a predetermined polyvinyl alcohol layer on the surface of the paper base material allows the polyethylene laminated in the subsequent process to adhere firmly to the paper base material. As a result, the amount of water vapor permeated from the paper substrate during foaming becomes more uniform, hyperfoaming is suppressed, and the foaming form becomes uniform.

The predetermined polyvinyl alcohol layer is a layer containing polyvinyl alcohol 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.

(Method of forming a predetermined polyvinyl alcohol layer)
The method for forming a predetermined polyvinyl alcohol layer is not particularly limited. Various known methods such as a coating method, a transfer method, an impregnation method, and an injection method can be used. The predetermined polyvinyl alcohol layer can be formed, for example, by applying or impregnating a coating liquid containing polyvinyl alcohol on at least one surface of a paper substrate and drying it. As the coating liquid, for example, water can be used as a medium and polyvinyl alcohol can be used as an aqueous solution.

The device for applying or impregnating the coating liquid onto the paper substrate is not particularly limited, and a generally known device can be used. Devices for applying or impregnating include, for example, rod coaters, bar coaters, blade coaters, air knife coaters, roll coaters, reverse roll coaters, curtain coaters, slot die coaters, gravure coaters, champlex coaters, brush coaters, slide bead coaters. , Calendar size press, gate roll size press, two-roll or metering blade type size press coater, bill blade coater, short dwell coater, gate roll coater, nip coater by calender and the like.

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 forming a predetermined polyvinyl alcohol layer, 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.

(Amount of polyvinyl alcohol layer formed and thickness permeated into paper substrate)
The predetermined polyvinyl alcohol layer in the present embodiment has a specific range of the amount formed and the thickness of penetration into the paper substrate. In order to make it within a specific range, it may be adjusted by, for example, the pushing pressure, nip pressure, etc. of a coater head of a device for applying or impregnating a coating liquid containing polyvinyl alcohol, and the solid content concentration of the coating liquid or The viscosity may be adjusted.

The amount of the predetermined polyvinyl alcohol layer according to the present embodiment is in ^{the range of 0.05 to 0.5 g / m 2} in terms of solid content per one side of the paper substrate.
When the amount of the polyvinyl alcohol layer formed is in this range, the thermoplastic resin layer can be uniformly foamed, and the thickness after foaming can be increased. Therefore, the heat insulating property is improved. Further, when the amount of the polyvinyl alcohol layer formed is in this range, the amount of formation is appropriate, so that when the thermoplastic resin layer is foamed, large irregularities and the like are less likely to occur on the surface, and the beauty can be improved. Further, when the amount of the polyvinyl alcohol layer 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 and are mixed into the foamed heat insulating paper container as foreign matter. You can prevent it from happening.

If the amount of the polyvinyl alcohol layer formed is ^{less than 0.05 g / m 2} , the film forming property (barrier property) is insufficient, and the amount of water vapor permeated from the paper substrate becomes non-uniform. Therefore, when the thermoplastic resin layer is foamed, large irregularities and the like are generated on the surface, and the beauty of the surface is impaired. Further, if the amount of the polyvinyl alcohol layer formed exceeds 0.5 g / m ² , equipment stains are generated in the papermaking process or the drying process when the coating liquid is applied, and the stains are removed and foreign substances are removed from the foamed heat insulating paper container. There is a risk of mixing. Further, in this case, the permeation amount of water vapor generated from the paper base material is excessively barriered, and the thermoplastic resin layer cannot be sufficiently foamed. Therefore, the foaming ratio becomes low, and the heat insulating property becomes insufficient.
The amount of the polyvinyl alcohol layer formed is preferably ^{0.06 g / m 2} or more from the viewpoint of further enhancing the heat insulating property and the beauty of the surface. From the same viewpoint, the amount of the polyvinyl alcohol layer formed ^{is preferably 0.1 g / m 2} or less.
The amount of the polyvinyl alcohol layer formed can be confirmed by a weight change before and after drying, an optical microscope, a scanning electron microscope, or the like.

When polyvinyl alcohol is applied to the paper base material, the polyvinyl alcohol permeates from the surface of the paper base material toward the inside. Then, the polyvinyl alcohol is dried to solidify, and a polyvinyl alcohol layer is formed. In the present embodiment, polyvinyl alcohol that has penetrated into the paper substrate and solidified is also regarded as a part of the polyvinyl alcohol layer.
In the present embodiment, the penetration thickness of the polyvinyl alcohol layer into the paper substrate is in the range of 5 to 35 μm for the predetermined polyvinyl alcohol layer.
When the penetration thickness of the polyvinyl alcohol layer into the paper substrate is within this range, the thermoplastic resin layer can be uniformly foamed, and the thickness after foaming can be increased. Therefore, the heat insulating property is improved. Further, when the permeation thickness of the predetermined polyvinyl alcohol layer into the paper base material is within this range, the permeation of water vapor generated from the paper base material 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 are improved.

If the penetration thickness of the polyvinyl alcohol layer into the paper substrate is less than 5 μm, the penetration thickness into the paper substrate is too thin, so that the polyvinyl alcohol layer becomes dense and the water vapor generated from the paper substrate is permeated. It will be an excessive barrier. Therefore, the thermoplastic resin layer cannot be sufficiently foamed. Therefore, not only the thermoplastic resin layer does not foam uniformly, but also the thickness after foaming becomes thin, and the heat insulating property is inferior.
Further, if the penetration thickness of the polyvinyl alcohol layer into the paper substrate exceeds 35 μm, the penetration thickness into the paper substrate is too thick, so that the film-forming property (barrier property) of the polyvinyl alcohol layer becomes insufficient. Therefore, the amount of water vapor permeated from the paper base material varies greatly depending on the location, and hyperfoaming occurs, resulting in large irregularities on the surface. Therefore, the beauty of the surface is impaired.
The penetration thickness of the polyvinyl alcohol layer into the paper substrate is preferably 10 μm or more, and more preferably 15 μm or more, from the viewpoint of further enhancing the heat insulating property and the beauty of the surface. From the same viewpoint, the penetration thickness of the polyvinyl alcohol layer into the paper substrate is preferably 30 μm or less, and more preferably 25 μm or less.

The predetermined polyvinyl alcohol layer described above can be provided on at least one side of the paper substrate. That is, the predetermined polyvinyl alcohol layer can be provided on both sides of the paper base material.
The amount of the polyvinyl alcohol layer formed and the thickness of penetration into the paper substrate represent the average amount of formation and the average penetration thickness, and can be confirmed by a weight change before and after drying, an optical microscope, a scanning electron microscope, or the like.

[Paper base material]
(pulp)
In the present embodiment, the type of pulp constituting the paper base material is not particularly limited. Examples of pulp types include coniferous bleached kraft pulp (NBKP), coniferous kraft pulp (NKP), broadleaf bleached kraft pulp (LBKP), broadleaf kraft pulp (LKP), crushed wood pulp (GP), and thermomechanical. Examples thereof include wood-based pulp such as pulp (TMP), chemithermomechanical pulp (CTMP) and deinked pulp (DIP), and natural pulp such as non-wood pulp such as bast pulp, linter pulp and hemp pulp. These pulps can be used alone or in combination of two or more. Above all, it is preferable to use wood pulp from the viewpoint of quality and cost.

The freeness (Canadian standard freeness, CSF) measured according to JIS P 8121-2012 of the pulp constituting the paper base material is preferably adjusted to 300 to 600 ml. The freshness of the pulp 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. When the freeness of the pulp is 300 ml or more, there is no possibility that dehydration in the papermaking process will be delayed, and the operability will be improved. Further, when the filtrate degree of the pulp is 600 ml or less, there is no possibility that the paper strength is lowered. The freeness of the pulp is more preferably 300 to 450 ml.

(Multi-layer material)
Here, FIG. 5 is a schematic cross-sectional view showing a preferable aspect of the foamed heat insulating paper container paper base material according to the present embodiment. Note that FIG. 5 illustrates a state in which a predetermined polyvinyl alcohol layer 2 is provided on one surface of the paper base material 1 which is the multilayer material 13. Further, a predetermined polyvinyl alcohol layer (not shown in FIG. 5) can be provided on the other surface of the paper base material 1 which is the multilayer material 13. The thickness of the paper base material 1 which is the multilayer material 13 is not particularly limited, but can be, for example, 100 to 650 μm.

As shown in FIG. 5, the paper base material 1 in the present embodiment is preferably a multilayer material 13 in which pulp layers 11 and starch layers 12 are alternately laminated. When the paper base material 1 is made of the multilayer material 13, the texture (the degree of proportioning of the fibrous structure constituting the paper) can be made uniform, so that the amount of water vapor permeated from the paper base material 1 at the time of foaming becomes even more uniform. , Overfoaming is suppressed and the foaming form becomes uniform. In addition, the starch layer 12 does not excessively increase the barrier property and does not interfere with the permeation of water vapor.

(Starch layer)
The starch layer 12 is provided between the pulp layer 11 and the pulp layer 11 to firmly bond the pulp layer 11 and the pulp layer 11. As the starch layer 12, 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 at the time of foaming becomes more uniform, overfoaming is suppressed, and the foaming form becomes uniform. Further, the starch layer 12 using the cationized starch does not excessively increase the barrier property and does not further hinder the permeation of water vapor.

The amount of the starch layer 12 formed is preferably ^{0.5 to 2.0 g / m 2.} When the amount of the starch layer 12 formed is 0.5 g / m ² or more, the adhesive strength between the pulp layer 11 and the pulp layer 11 is increased, and the interlayer strength is improved. Further, when the amount of the starch layer 12 formed is 2.0 g / m ² or less, the starch layer 12 effectively permeates the water vapor from the pulp layer 11 during foaming, and the thermoplastic resin layer can be sufficiently foamed. can. Therefore, the foaming ratio becomes high and the heat insulating property is improved.

Note that FIG. 5 illustrates a multilayer material 13 in which the pulp layer 11 is 5 layers and 4 layers of starch layers 12 are interposed between the adjacent pulp layers 11 and the pulp layers 11. It's not a thing. In the multilayer material 13, for example, the pulp layer 11 can be two layers, three layers, four layers, six layers or more, and the starch layer 12 is interposed between the adjacent pulp layers 11 and the pulp layers 11. Can be done. In the present embodiment, when the paper base material 1 is the multilayer material 13, it is preferable that the outermost layers on both sides of the multilayer material 13 are the pulp layers 11. In this way, since the pulp layer 11 is arranged on the outside of the multilayer material 13, the thermoplastic resin layer 4 described later partially penetrates into the pulp layer 11, and the adhesion between the thermoplastic resin layer 4 and the pulp layer 11 is improved. Increase. Further, since the pulp layer 11 is arranged on the outside of the multilayer material 13, problems such as the starch layer 12 peeling off are eliminated, and the handleability and productivity are improved.

(Method of forming starch layer)
The method for forming the starch layer is not particularly limited. Various known methods such as a coating method, a transfer method, an impregnation method, and an injection method can be used. The starch layer can be formed, for example, by applying or impregnating a coating liquid containing starch that functions as an adhesive on at least one surface of a paper substrate and drying it.

The device for forming the starch layer is not particularly limited, and a generally known device can be used. Devices for forming the starch layer include, for example, a rod coater, a bar coater, a blade coater, an air knife coater, a roll coater, a reverse roll coater, a curtain coater, a slot die coater, a gravure coater, a champlex coater, a brush coater, and a slide. Examples include bead coaters, calendar size presses, gate roll size presses, two-roll or metering blade type size press coaters, bill blade coaters, short dwell coaters, gate roll coaters, and calender nip coaters.

(Paper machine)
The paper making method of the paper base material (pulp layer) and the type of the paper machine are not particularly limited, and are a long net paper machine, a twin wire paper machine, a circular net paper machine, a gap former, and a hybrid former (on-top). A known papermaking method such as a former) and a papermaking machine can be selected.
The pH at the time of papermaking may be any of an acidic region (acidic papermaking), a pseudo-neutral region (pseudo-neutral papermaking), a neutral region (neutral papermaking), and an alkaline region (alkaline papermaking). Later, an alkaline agent may be applied to the surface of the paper substrate.

(Filling fee)
The filler to be blended when the paper base material (pulp layer) is made 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 (pulp layer), it is possible to add no filler. When the filler of the paper base material is not blended, the foamability is improved when the thermoplastic resin layer is foamed by the moisture contained in the paper base material. On the other hand, when a filler is added to the paper base material, the opacity of the obtained heat insulating paper container sheet and the foamed heat insulating paper container using the same is improved.

(Internal aid)
When making a paper base material (pulp layer), 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), alkenyl oxalic 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 agent, coloring dye, coloring pigment, fluorescent whitening agent, pH adjuster, pitch Examples include a control agent and a slime control agent. In the present embodiment, the paper base material (pulp layer) preferably contains the above-mentioned cationized starch. In this way, in the case of the multilayer material 13 shown in FIG. 5, the cationized starch and the starch layer 12 in the pulp layer 11 are firmly adhered to each other, so that the adhesive force between the pulp layer 11 and the starch layer 12 is enhanced. .. In particular, it is more preferable to form the starch layer 12 with cationized starch because this effect is enhanced. In addition, the cationized starch does not excessively increase the barrier property and does not interfere with the permeation of water vapor.

The basis weight of the pulp layer is not particularly limited, but can be ^{, for example, 30 to 200 g / m 2.}

[Preferable Embodiment of Foam Insulated Paper Container Paper Base Material]
As described above, the foamed heat insulating paper container paper base material according to the present embodiment has a predetermined polyvinyl alcohol layer on at least one side of the paper base material, and will be described below in addition to these components. It is preferable to have characteristics.

(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 is preferably ^{1.5 to 6.0 s / g / m 2.} When the air permeation resistance per basis weight is in this range, the permeation amount of water vapor is appropriately suppressed in the obtained foam insulation paper container sheet and the foam insulation paper container using the same, and the thermoplastic resin layer is formed. Since the foamed state becomes uniform, the balance between heat insulation and beauty is good. The air permeation resistance per basis weight is more preferably 2.0 to 5.5 s / g / m ² , still more preferably 2.7 to 5.0 s / g / m ² , and particularly preferably 3.0 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 P 8117; 2009.

(Oken type smoothness)
Oken-type smoothness is a unit that is an index for defining the smoothness of the surface of paper. The Oken-type smoothness is preferably 30 to 500 seconds. When the Oken type smoothness is 30 seconds or more, the surface property of the paper base material is enhanced, and a sheet for a foamed heat insulating paper container having a good surface quality can be obtained. Further, when the Oken type smoothness is 500 seconds or less, the paper base material is crushed with a calender or the like in order to obtain high smoothness, so that the thickness of the paper base material is suppressed from becoming too thin, and the foamed heat insulating paper is prevented. The molding process suitability of the container is improved.
Oken-type smoothness is measured according to JIS P 8155: 2010.

(Formation index)
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. The formation index is preferably 60 or more, more preferably 80 or more, and even more preferably 85 or more. By setting the texture index to a predetermined value or more, the water content distribution in the paper substrate becomes uniform. Therefore, the amount of water vapor permeated from the paper substrate during foaming becomes more uniform, hyperfoaming is suppressed, and the foaming form becomes uniform.
The texture index is obtained by measuring the permeation strength of a paper substrate with a commercially available 3D sheet analyzer and quantifying the variation in thickness. As the 3D sheet analyzer, for example, one manufactured by M / K System Co., Ltd. can be used.

(amount of water)
The water content of the foam-insulated paper container paper base material is the sum of the water content of the paper base material and the water content of the predetermined polyvinyl alcohol layer. The water content of the paper base material is determined by the basis weight and water content of the paper base material. The water content of the foamed heat insulating paper container paper base material 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 P 8127; 2010 after humidity control.

(Basis weight)
The basis weight of the foamed heat insulating paper container paper base material is preferably 100 to 400 g / m ² , more preferably 200 to 400 g / m ² , still more preferably 220 to 400 g / m ² , and particularly preferably. It is 260 to 350 g / m ² . When the basis weight is 100 g / m ² or more, foaming is sufficiently formed due to the water content, and it is difficult to feel the heat when the obtained foamed heat insulating paper container is grasped by hand. Further, when the basis weight is 400 g / m ² or less, the molding processability of the foamed heat insulating paper container tends to be improved.

(density)
The density of the foamed heat insulating paper container paper base material may be appropriately set as desired, and is not particularly limited, but is preferably ^{0.60 to 0.99 g / cm 3.} The lower the density of the foamed heat insulating paper container paper base material, the easier it is for water vapor to pass through the paper base material when foaming the thermoplastic resin layer, and the foamability tends to be improved. Foamed Insulated Paper Container When the density of the paper base material is 0.60 g / cm ³ or more, it is easy to obtain the paper strength required for the foamed insulated paper container. Further, when the density of the foamed heat insulating paper container paper base material is 0.99 g / cm ³ or less, water vapor easily passes through the paper base material when the thermoplastic resin layer is foamed, and the foamability tends to be improved. ..

[Sheet for foam insulation paper container]
As described above, the foam insulating paper container sheet according to the present embodiment has a thermoplastic resin layer on at least one side of the paper base material, and a predetermined polyvinyl alcohol is provided between the paper base material and the thermoplastic resin layer. It has a layer. The foamed heat insulating paper container sheet is formed by providing a thermoplastic resin layer on the surface on which the predetermined polyvinyl alcohol layer of the foamed heat insulating paper container paper base material is formed. Further, by heat-treating the foamed heat insulating paper container sheet, the water contained in the paper base material and the predetermined polyvinyl alcohol layer is heated and evaporated, and the generated water vapor causes the thermoplastic resin layer to become a foamed resin layer. Hereinafter, the sheet for the foamed heat insulating paper container will be described, but the description of the components already described will be omitted.

(Thermoplastic resin layer)
The thermoplastic resin used for the thermoplastic resin layer is not particularly limited as long as it can be formed on a predetermined polyvinyl alcohol layer and can be foamed, and the heat of either the crystalline resin or the non-crystalline resin is not particularly limited. Plastic resins can also 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 to 942 kg / m ³ , melting point: 110 to 133 ° C.), high density polyethylene (density: 942 to 970 kg / m ³ , melting point: 127 to 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 is not particularly limited as long as a foamed heat insulating paper container having a desired heat insulating property can be obtained, but from the viewpoint of heat insulating property and processability, the thickness before foaming is 30 to 80 μm. Is preferable.

(High melting point thermoplastic resin layer, metal layer)
The foam insulating paper container sheet according to the present embodiment has a high melting point thermoplastic resin layer or aluminum having a higher melting point than the thermoplastic resin layer on the surface opposite to the surface on which the thermoplastic resin layer of the paper base material is formed. A metal layer such as foil may be laminated. Having such a high melting point thermoplastic resin layer or metal layer is opposite to the surface of the paper base material on which the thermoplastic resin layer is formed when the foam insulating paper container sheet is heated to foam the thermoplastic resin layer. Evaporation of water vapor from the side surface is suppressed, and the foamability of the thermoplastic resin layer is improved.

At this time, the melting point of the thermoplastic resin used for the high melting point thermoplastic resin layer is particularly limited as long as it does not melt at the heating temperature when the water contained in the paper substrate is heated and evaporated and the diffusion of water vapor can be prevented. However, it is preferably 125 ° C. or higher. Further, in order to form a metal layer on the surface of a paper base material, 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 or the metal layer is present on the inner wall surface side of at least one of the body member and the bottom plate member of the foamed heat insulating paper container, it is possible to prevent the liquid or the like filled in the container from permeating into the paper base material. It is preferable because it can be done.

Further, the high melting point thermoplastic resin layer may be laminated on the thermoplastic resin layer of the foam insulating paper container sheet. When the high melting point thermoplastic resin layer is laminated on the thermoplastic resin layer, steam evaporates through the thermoplastic resin layer when the foam insulating paper container sheet is heated to foam the thermoplastic resin layer. Is suppressed, so that the foamability is improved.

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

The thermoplastic resin used for the high melting point thermoplastic resin layer may be of the same type as the thermoplastic resin used for the thermoplastic resin layer, or may be of a different type. For example, when polyethylene is selected for both the thermoplastic resin used for the thermoplastic resin layer and the thermoplastic resin used for the high melting point thermoplastic resin layer, the thermoplastic resin layer is low density polyethylene and the high melting point thermoplastic resin layer. By selecting medium-density polyethylene or high-density polyethylene, the melting point of the high-melting-melting thermoplastic resin layer can be made higher than that of the thermoplastic resin layer.

The difference in melting point between the thermoplastic resin layer and the high melting point thermoplastic resin layer, that is, the difference in melting point between the thermoplastic resin used for the thermoplastic resin layer and the high melting point thermoplastic resin layer is 5 ° C. or more. Is preferable. When a plurality of types of resins are laminated and used in the thermoplastic resin layer or the high melting point thermoplastic resin layer, the resin having the highest melting point among the resins used for the thermoplastic resin layer and the high melting point thermoplastic resin layer It is preferable that the difference in melting point is 5 ° C. or more for the resin having the lowest melting point among the resins used in.

The thickness of the high melting point thermoplastic resin layer suppresses the evaporation of water vapor from the surface opposite to the surface on which the thermoplastic resin layer of the paper substrate is laminated, or the water vapor evaporates through the thermoplastic resin layer. It suffices if it can be suppressed, and it is not particularly limited, but it is about 20 to 50 μm. In particular, when the high melting point thermoplastic resin layer is present on the inner wall surface side of at least one of the body member and the bottom plate member of the foamed heat insulating paper container, if the thickness of the high melting point thermoplastic resin layer is 20 μm or more, the container is filled. It is possible to effectively suppress the permeation of the liquid or the like into the paper substrate.

(Multi-layer material)
Here, FIG. 6 is a schematic cross-sectional view showing a preferable aspect of the foam insulating paper container sheet according to the present embodiment. Note that FIG. 6 illustrates a state in which a predetermined polyvinyl alcohol layer 2 and a thermoplastic resin layer 4 are provided on one surface of the paper base material 1 which is the multilayer material 13. Further, a predetermined polyvinyl alcohol layer and a thermoplastic resin layer (both of which are not shown in FIG. 6) can be provided on the other surface of the paper base material 1 which is the multilayer material 13. In this aspect, since the paper base material 1 is the multilayer material 13, the texture becomes uniform. Therefore, the amount of water vapor permeated from the paper substrate during foaming becomes more uniform, hyperfoaming is suppressed, and the foaming form becomes uniform.

[Method of forming a thermoplastic resin layer]
The method for forming the thermoplastic resin layer and the high melting point thermoplastic resin layer 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 to laminate the thermoplastic resin layer on the paper substrate. The extruded 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 paper base material, and pressed and crimped while being cooled between a cooling roll and a nip roll facing the cooling roll. .. The extrusion laminating method is preferable because the adhesion between the paper base material and the thermoplastic resin layer and the foamability of the thermoplastic resin layer are good.

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.

When the high melting point thermoplastic resin layer is laminated on the thermoplastic resin layer, or when the thermoplastic resin layer is formed of a plurality of thermoplastic resin layers, the plurality of thermoplastic resin layers are laminated. When laminating a plurality of thermoplastic resin layers, the so-called coextrusion laminating method is preferable from the viewpoint of adhesion between the thermoplastic resin layers and production efficiency. The co-extrusion laminating method is a method in which each thermoplastic resin is guided to each T-die in a molten state using a plurality of extruders, and each thermoplastic resin is simultaneously extruded from each T-die and laminated.

Further, in order to improve the adhesiveness between the thermoplastic resin layers, the adhesive resin layer may be sandwiched between the thermoplastic resin layers. Further, in order to improve the adhesiveness between the paper base material and the thermoplastic resin layer, the paper base material may be subjected to corona discharge treatment, ozone treatment or the like in advance.

[Molding of foam insulation paper container]
The method for molding the foamed heat insulating paper container using the foamed heat insulating paper container sheet is not particularly limited, and can be produced by using a known method. As a specific example, there is a method of molding by a general cup molding machine described below.

First, after printing the necessary printing on the body member blank such as various patterns and barcodes at a predetermined position on the foam insulation paper container sheet, the body member blank is 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 a foam insulating paper container sheet 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, the bottom plate member blank may have a structure different from that of the foamed heat insulating paper container sheet 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, 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 and used, the body member and the bottom plate member foam at the same time, so that the heat insulating property of the foamed heat insulating paper container Becomes even better. In particular, when the foamed heat insulating paper container is used outdoors, in winter, in cold regions, or when the foamed heat insulating paper container is used for something such as cup noodles that is left for a while after injecting hot water, the foamed heat insulating paper container having the above configuration is used. It 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 by a cup molding machine, the thermoplastic resin layer may be present on either the outside or the inside of the body member, or both, and the desired heat insulating property is obtained. , Beauty, texture, etc. may be appropriately determined.

[Foam by heat treatment]
In the present embodiment, the body member blank and the bottom plate member blank are assembled into a container shape, and then heat treatment is performed. When the heat treatment is performed, the moisture contained in the paper base material of the body member blank or the bottom plate member blank is vaporized, and the generated water vapor foams the thermoplastic resin layer to form a foamed heat insulating paper container. The foamed heat insulating paper container uses foamed heat insulating paper for at least one of the body member and the bottom plate member, and the foamed heat insulating paper has a foamed resin layer made of a thermoplastic resin on at least one side of the paper base material.

The heat treatment conditions (heating temperature, heating time) may be appropriately set according to the type of the paper substrate 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. 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. By continuously heat-treating in a tunnel provided with a transport means by a conveyor, a foamed heat insulating paper container can be manufactured at low cost and with high productivity.

The thickness of the foamed resin layer 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 is 800 μm or more, sufficient heat insulating properties can be obtained. Further, when the thickness of the foamed resin layer 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 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 to partially suppress foaming (Patent No. 3014629), the outside of the body member, that is, foaming. A technique for applying tuning ink to the outer wall surface of a heat insulating paper container to form a smooth printing surface in synchronization with foaming (Patent No. 3408156), an upper flange portion forcibly processed into a square cross section on the upper edge of the opening of the body member. (Japanese Patent Laid-Open No. 2001-354226) and the like (Japanese Patent Laid-Open No. 2001-354226), in which the inner winding end is superposed on the upper part of the flange portion to form a double structure, and the like, but the present invention is not limited thereto. 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 which is the outer wall surface of the foamed heat insulating paper container.

As the lid material used for the foamed heat insulating paper container, a punched sheet 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, the lid material may have a structure different from that of the foamed heat insulating paper container sheet 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, a sheet coated with aluminum foil, or the like can be used.

The foamed heat insulating paper container 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 instant foods in which boiling water is injected, and a microwaved heat insulating paper container for cooking with a microwave oven. It can be used as a container or the like.

Hereinafter, the effects of the present invention will be described in detail with reference to Examples.
The freshness of the pulp was measured according to JIS P 8121: 2012.
The basis weight of the foamed heat insulating paper container paper base material was measured according to JIS P 8124: 2011.
The density of the foamed heat insulating paper container paper base material was measured according to JIS P 8118: 1998.
The Oken-type smoothness of the foamed heat insulating paper container paper base material was measured according to JIS P 8155: 2010.
The texture index of the foam-insulated paper container paper base material is obtained by measuring the permeation strength of the paper base material with a 3D sheet analyzer (manufactured by M / K System Co., Ltd.) and quantifying the variation in thickness. The higher the formation index, the more preferable.
The water content of the foamed heat insulating paper container paper base material was measured according to JIS P 8127: 2010.
The air permeation resistance per basis weight of the foamed heat insulating paper container paper base material was measured according to the Oken type testing machine method described in JIS P 8117: 2009.

[Example 1]
(Foam insulation paper container paper base material)
Using broad-leaved bleached kraft pulp LBKP (filter water content 430 ml) as pulp, cationized starch 0.5% by mass and polyacrylamide-based paper strength enhancer (PAM-based paper strength) with respect to 100% by mass of pulp raw material in terms of solid content. A paper material slurry to which 0.1% by mass of an enhancer), 0.30% by mass of an alkyl ketene dimer-based sizing agent, and 0.1% by mass of a polyamide polyamine epichlorohydrin-based resin (PAE-based wet paper strength enhancer) is added. Paper was made by machine. Using five pulp layers obtained by papermaking, cationized starch was applied between each layer at a coating rate of 1.0 g / m ² to obtain a paper base material (base paper) having five pulp layers. ..
Next, polyvinyl alcohol (PVA) (manufactured by Japan Vam & Poval Co., Ltd., product name: JM17, saponification degree 96.5 mol%) was applied to both sides (outermost layers on both sides) of the obtained paper substrate by a rod coater. A solid content of 0.08 g / m ² per side (0.16 g / m ^{2 on} both sides) was applied and dried to obtain a foam-insulated paper container paper base material of Example 1. The penetration thickness of PVA into the paper substrate was 18.5 μm.
The foamed heat insulating paper container paper base material of Example 1 has a basis weight of 300 g / m ² , a density of 0.89 g / cm ³ , a Wangken-type smoothness of 89 seconds, a texture index of 90, a water content of 21.0 g / m ² , and a tsubo. The air permeation resistance per amount was 3.66 s / g / m ² .

(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. rice field.

[Example 2]
In the foamed heat insulating paper container paper base material of Example 2, PVA coating (surface treatment method) was performed with a blade coater. The penetration thickness of PVA into the paper substrate was 5.0 μm. Other than that, it is the same as that of the first embodiment.
The foamed heat insulating paper container paper base material of Example 2 has a basis weight of 300 g / m ² , a density of 0.87 g / cm ³ , a Wangken-type smoothness of 81 seconds, a texture index of 92, a water content of 21.5 g / m ² , and a tsubo. The air permeation resistance per amount was 5.33 s / g / m ² .
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 foam insulating paper container sheet of Example 2.

[Example 3]
In the foamed heat insulating paper container paper base material of Example 3, the penetration thickness of PVA into the paper base material was 10.0 μm. Other than that, it is the same as that of the first embodiment.
The foamed heat insulating paper container paper base material of Example 3 has a basis weight of 300 g / m ² , a density of 0.87 g / cm ³ , a Wangken-type smoothness of 81 seconds, a texture index of 92, a water content of 22.1 g / m ² , and a tsubo. The air permeation resistance per amount was 4.65 s / g / m ² .
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 foam insulating paper container sheet of Example 3.

[Example 4]
In the foamed heat insulating paper container paper base material of Example 4, PVA coating (surface treatment method) was performed with a blade coater. The penetration thickness of PVA into the paper substrate was 15.0 μm. Other than that, it is the same as that of the first embodiment.
The foamed heat insulating paper container paper base material of Example 4 has a basis weight of 300 g / m ² , a density of 0.89 g / cm ³ , a Wangken-type smoothness of 89 seconds, a texture index of 92, a water content of 20.5 g / m ² , and a tsubo. The air permeation resistance per amount was 4.03 s / g / m ² .
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 foam insulating paper container sheet of Example 4.

[Example 5]
In the foamed heat insulating paper container paper base material of Example 5, PVA coating (surface treatment method) was performed with a blade coater. The penetration thickness of PVA into the paper substrate was 25.0 μm. Other than that, it is the same as that of the first embodiment.
The foamed heat insulating paper container paper base material of Example 5 has a basis weight of 300 g / m ² , a density of 0.87 g / cm ³ , a Wangken-type smoothness of 81 seconds, a texture index of 92, a water content of 20.8 g / m ² , and a tsubo. The air permeation resistance per amount was 3.01 s / g / m ² .
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 foam insulating paper container sheet of Example 5.

[Example 6]
In the foamed heat insulating paper container paper base material of Example 6, PVA coating (surface treatment method) was performed by a gate roll size press. The penetration thickness of PVA into the paper substrate was 30.0 μm. Other than that, it is the same as that of the first embodiment.
The foamed heat insulating paper container paper base material of Example 6 has a basis weight of 300 g / m ² , a density of 0.87 g / cm ³ , a Wangken-type smoothness of 81 seconds, a texture index of 92, a water content of 21.0 g / m ² , and a tsubo. The air permeation resistance per amount was 2.83 s / g / m ² .
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 foam insulating paper container sheet of Example 6.

[Example 7]
In the foamed heat insulating paper container paper base material of Example 7, the penetration thickness of PVA into the paper base material was 35.0 μm. Other than that, it is the same as that of the first embodiment.
The foamed heat insulating paper container paper base material of Example 7 has a basis weight of 300 g / m ² , a density of 0.87 g / cm ³ , a Wangken-type smoothness of 81 seconds, a texture index of 92, a water content of 21.1 g / m ² , and a tsubo. The air permeation resistance per amount was 2.51 s / g / m ² .
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 foam insulating paper container sheet of Example 7.

[Comparative Example 1]
For the foamed heat insulating paper container paper base material of Comparative Example 1, PVA coating (surface treatment method) was performed by a 2-roll size press. The penetration thickness of PVA into the paper substrate was 40.0 μm. Other than that, it is the same as that of the first embodiment.
The foam-insulated paper container paper base material of Comparative Example 1 has a basis weight of 300 g / m ² , a density of ^{0.88 g / cm 3} , a Wangken-type smoothness of 88 seconds, a texture index of 90, a water content of 20.3 g / m ² , and a tsubo. The air permeation resistance per amount was 1.32 s / g / m ² .
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 foam insulating paper container sheet of Comparative Example 1.

[Comparative Example 2]
In the foamed heat insulating paper container paper base material of Comparative Example 2, PVA coating (surface treatment method) was performed with a blade coater. The penetration thickness of PVA into the paper substrate was 3.0 μm. Other than that, it is the same as that of the first embodiment.
The foamed heat insulating paper container paper base material of Comparative Example 2 has a basis weight of 300 g / m ² , a density of 0.89 g / cm ³ , a Wangken-type smoothness of 103 seconds, a texture index of 80, a water content of 21.0 g / m ² , and a tsubo. The air permeation resistance per amount was 6.32 s / g / m ² .
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 foam insulating paper container sheet of Comparative Example 2.

[Comparative Example 3]
For the foamed heat insulating paper container paper base material of Comparative Example 3, PVA coating (surface treatment method) was performed by a calendar size press, and PVA was applied in a solid content of 0.30 g / m ² per side (0.60 g / m on both sides). ^It was coated and dried so as to be 2). The penetration thickness of PVA into the paper substrate was 50.0 μm. Other than that, it is the same as that of the first embodiment.
The foam-insulated paper container paper base material of Comparative Example 3 has a basis weight of 300 g / m ² , a density of 0.89 g / cm ³ , a Wangken-type smoothness of 103 seconds, a texture index of 75, a water content of 21.0 g / m ² , and a tsubo. The air permeation resistance per amount was 1.31 s / g / m ² .
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 foam insulating paper container sheet of Comparative Example 3.

[Comparative Example 4]
In the foamed heat insulating paper container paper base material of Comparative Example 4, PVA coating (surface treatment method) was performed with a blade coater, and PVA was applied with a solid content of 0.03 g / m ² per side (0.06 g / m ^{2 on both sides).} ), And dried. The penetration thickness of PVA into the paper substrate was 15.0 μm. Other than that, it is the same as that of the first embodiment.
The foam-insulated paper container paper base material of Comparative Example 4 has a basis weight of 300 g / m ² , a density of ^{0.88 g / cm 3} , a Wangken-type smoothness of 88 seconds, a texture index of 90, a water content of 22.5 g / m ² , and a tsubo. The air permeation resistance per amount was 1.28 s / g / m ² .
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 foam insulating paper container sheet of Comparative Example 4.

[Comparative Example 5]
The foam insulation paper containers paper substrate of Comparative Example 5 was a coated, dried as PVA becomes a 0.60 g / ^{m 2} in terms of solid per side content (both in terms 1.20g / ^{m 2).} The penetration thickness of PVA into the paper substrate was 25.0 μm. Other than that, it is the same as that of the first embodiment.
The foam-insulated paper container paper base material of Comparative Example 5 has a basis weight of 300 g / m ² , a density of 0.89 g / cm ³ , a Wangken-type smoothness of 103 seconds, a texture index of 85, a water content of 21.0 g / m ² , and a tsubo. The air permeation resistance per amount was 7.00 s / g / m ² .
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 foam insulating paper container sheet of Comparative Example 5.

The foam-insulated paper container sheet obtained as described above was evaluated as follows. The evaluation results are as shown in Table 1.

(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. Note that ⊚, ○, and △ are acceptable, and × is unacceptable.
⊚: The foaming magnification is 21 times or more, and the heat insulating property is sufficient.
◯: The foaming magnification is 19 times or more and less than 21 times, and the heat insulating property is sufficient.
Δ: The foaming magnification 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. Note that ⊚, ○, and △ are acceptable, and × is unacceptable.
⊚: No hyperfoaming was observed, the formed foam cells were small and homogeneous, and the surface was generally flat.
◯: No hyperfoaming was observed, and the formed foam cells were small and the surface was generally flat, but the size of the foam cells varied.
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 both heat insulating properties and aesthetic performance. It was found that when the penetration thickness of PVA into the paper substrate was 15.0 to 25.0 μm, the heat insulating property and the beauty were particularly excellent.
In the foamed heat insulating paper container sheets of Comparative Examples 1 and 3, since the penetration thickness of PVA into the paper base material was too thick, the amount of water vapor permeated greatly varied depending on the location, and hyperfoaming occurred on the surface. Large irregularities occurred. Therefore, the foam-insulated paper container sheets of Comparative Examples 1 and 3 were inferior in surface beauty.
The foamed heat insulating paper container sheet of Comparative Example 2 had a thin thickness after foaming because the penetration thickness of PVA into the paper substrate was too thin. Therefore, the foam-insulated paper container sheet of Comparative Example 2 was inferior in heat insulating properties.
In the foam-insulated paper container sheet of Comparative Example 4, since the amount of PVA formed was too small, uniform foaming could not be obtained, and large irregularities were generated on the surface. Therefore, the foam-insulated paper container sheet of Comparative Example 4 was inferior in surface beauty.
In the foamed heat insulating paper container sheet of Comparative Example 5, the amount of PVA formed was too large, so that the thermoplastic resin layer could not be sufficiently foamed. Therefore, the foam-insulated paper container sheet of Comparative Example 5 was inferior in heat insulating properties.

1 Paper base material 2 Polyvinyl alcohol 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 11 Pulp layer 12 Staple layer 13 Multilayer material

Claims (8)

On both sides of the paper substrate air resistance per basis weight is 2.0~6.0s / g / ^{m 2,} per side, a polyvinyl alcohol layer is a forming amount 0.05 to 0.5 g / ^{m 2} Foam insulation paper container paper base material with. The foam-insulated paper container paper base material according to claim 1, wherein the paper base material is a multilayer material in which pulp layers and starch layers are alternately laminated. The foamed heat insulating paper container paper base material according to claim 2, wherein the outermost layers on both sides of the multilayer material are the pulp layers. The foamed heat insulating paper container paper base material according to claim 2 or 3, wherein the pulp layer contains cationized starch. A sheet for a foam-insulated paper container having a thermoplastic resin layer on at least one side of a paper substrate having an air permeation resistance per basis weight of 2.0 to 6.0 s / g / m ^2.
A polyvinyl alcohol layer having ^{a forming amount of 0.05 to 0.5 g / m 2} is provided between the paper base material and the thermoplastic resin layer, and the vinyl alcohol layer is formed.
A sheet for a foam-insulated paper container, wherein the polyvinyl alcohol layer is also formed on the other surface of the paper base material. The sheet for a foam-insulated paper container according to claim 5, wherein the thickness of the thermoplastic resin layer is 30 to 80 μm. The sheet for a foam insulating paper container according to claim 5 or 6, wherein the thermoplastic resin layer is a polyethylene layer. A foam insulation paper container using foam insulation paper for at least one of the body member and the bottom plate member.
The foamed heat insulating paper has a foamed resin layer made of a thermoplastic resin on at least one side of a paper base material having an air permeation resistance per basis weight of 2.0 to 6.0 s / g / m ^2.
A polyvinyl alcohol layer having ^{a forming amount of 0.05 to 0.5 g / m 2} is provided between the paper base material and the foamed resin layer, and the vinyl alcohol layer is formed.
A foam-insulated paper container characterized in that the polyvinyl alcohol layer is also formed on the other surface of the paper base material.

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