JP6833008B2 - Laminated sheet - Google Patents

Description

The present invention relates to agricultural sheets and laminated sheets.

In the agricultural field, various sheets such as mulch sheets, weed-proof sheets, and greenhouse sheets are used. For example, by covering the surface of soil such as a field with a mulch sheet, the growth of agricultural products can be promoted and weeds can be controlled. Mulch sheets are also used for fumigation of soil. One of the performances required for such a mulch sheet is gas barrier property for suppressing water evaporation from soil and preventing chemicals from scattering during fumigation. Agricultural sheets such as mulch sheets are usually formed into a film using synthetic resin in order to have such gas barrier properties. On the other hand, mulch sheets need to be collected and disposed of after harvesting of agricultural products, but this collection work requires labor and also causes disposal costs, which is a factor in increasing the cost of agricultural products.

Therefore, a biodegradable agricultural sheet has been developed (see JP-A-2000-191930). When a biodegradable agricultural sheet is used as a mulch sheet, it is not necessary to collect and dispose of the mulch sheet because it will be decomposed if the mulch sheet is plowed into the soil after use. However, the conventional biodegradable sheet is not widely used because the production itself is expensive and the biodegradability is not sufficient.

Japanese Unexamined Patent Publication No. 2000-19930

The present invention has been made based on the above circumstances, and an object of the present invention is to provide an agricultural sheet and a laminated sheet which are made of a material having good biodegradability and have sufficient gas barrier properties.

The invention made to solve the above problems includes a paper base material containing pulp as a main component and a coating layer laminated on one surface side of the paper base material, and the coating layer is the main component. It is an agricultural sheet having a layer containing cellulose nanofibers as a main component and a layer containing polyvinyl alcohol as a main component.

According to the agricultural sheet, at least two coating layers are provided on the paper base material, and the coating layers include a cellulose nanofiber layer and a polyvinyl alcohol layer, both of which have good gas barrier properties. Therefore, good gas barrier properties can be exhibited. Further, for example, by forming a plurality of layers having separate layers instead of forming a layer in which cellulose nanofibers and polyvinyl alcohol are mixed, for example, permeation of gas from the generated cracks can be suppressed. Therefore, the gas barrier property can be enhanced. Furthermore, according to the agricultural sheet, all of pulp, cellulose nanofibers and polyvinyl alcohol have biodegradability, and in particular, pulp and cellulose nanofibers are made from natural materials and have good biodegradation. Can exert sex.

The layer containing polyvinyl alcohol as the main component is preferably the outermost layer of the coating layer. By arranging the polyvinyl alcohol layer on the outside and the cellulose nanofiber layer on the inside in this way, higher gas barrier properties can be exhibited.

It is preferable that the outermost surface of the coating layer is subjected to calendar treatment. By applying the calender treatment, the minute voids in the coating layer that may be generated by drying after coating are closed by heating and pressurizing, and the gas barrier property can be further enhanced.

The oxygen permeability of the agricultural ^{sheeting, 8,000cc / m 2 · 24hr ·} atm or less. When the oxygen permeability is less than ^{8,000cc / m 2 · 24hr · atm} , as agricultural sheeting can exhibit particularly good gas barrier properties.

Another invention made to solve the above problems includes a paper base material and a coating layer laminated on one surface side of the paper base material, wherein the coating layer is a cellulose nanofiber as a main component. It is a laminated sheet having a layer containing the above and a layer containing polyvinyl alcohol as a main component. The laminated sheet is formed of a biodegradable material and has sufficient gas barrier properties.

Here, the "main component" means a component having the highest content, preferably a component having a content of 50% by mass or more, and more preferably 80% by mass or more. The "cellulose nanofiber" refers to a cellulose fiber containing cellulose fine fibers having a fiber width of nano size. "Oxygen permeability" means a value measured at 25 ° C. in accordance with JIS-K-7126-1: 2006 "Plastic-film and sheet-gas permeability test method-1 part: differential pressure method". ..

As described above, the agricultural sheet and the laminated sheet of the present invention are made of a biodegradable material and have a sufficient gas barrier property. Therefore, the agricultural sheet and the laminated sheet of the present invention can be suitably used as a mulch sheet, a soil fumigation sheet and the like.

It is a schematic sectional view of the agricultural sheet which concerns on one Embodiment of this invention.

Hereinafter, the agricultural sheet and the laminated sheet according to the embodiment of the present invention will be described in detail with reference to the drawings as appropriate.

<Agricultural sheet>
The agricultural sheet 10 of FIG. 1 is an embodiment of the laminated sheet of the present invention, and is a paper base material 11 containing pulp as a main component and a coating layer laminated on one surface side of the paper base material 11. 12 is provided. The coating layer 12 has a layer containing cellulose nanofibers (CNF) as a main component (CNF layer 13) and a layer containing polyvinyl alcohol (PVA) as a main component (PVA layer 14). According to the agricultural sheet 10, since the paper base material 11 has the CNF layer 13 and the PVA layer 14 having good gas barrier properties, it is possible to exhibit good gas barrier properties. Further, for example, by forming a multi-layer structure in which CNF and PVA are mixed instead of a mixed layer, it is possible to suppress the permeation of gas from the generated cracks, for example, so that the gas barrier You can improve your sex. Further, according to the agricultural sheet 10, all of pulp, CNF and PVA have biodegradability, and in particular, pulp and CNF are made from natural materials and exhibit good biodegradability. be able to.

As the paper base material 11, known paper obtained by papermaking pulp can be used. Examples of the paper base material 11 include filter paper, high-quality paper, medium-quality paper, copy paper, art paper, coated paper, finely coated paper, kraft paper, and the like, and copy paper is preferable.

As the lower limit of the basis weight of the paper base material 11, 40 g / m ² is preferable, 50 g / m ² is more preferable, and 60 g / m ² is further preferable. By setting the basis weight of the paper base material 11 to the above lower limit or more, good gas barrier properties can be exhibited. On the other hand, as the upper limit, 100 g / m ² is preferable, 90 g / m ² is more preferable, and 80 g / m ² is further preferable. If the basis weight of the paper base material 11 exceeds the above upper limit, flexibility, handleability, and the like may decrease, and the cost may increase.

The CNF layer 13 is laminated on one surface side of the paper base material 11. The CNF layer 13 is formed by coating with a CNF coating liquid containing cellulose nanofibers as a main component.

Cellulose nanofibers refer to fine cellulose fibers obtained by defibrating pulp (pulp fibers), and generally refer to cellulose fibers containing cellulose fine fibers having a fiber width of nano size (1 nm or more and 1000 nm or less). Cellulose nanofibers can usually be obtained by defibrating pulp (pulp fiber) by a known method.

Examples of pulp used as a raw material for cellulose nanofibers include broadleaf kraft pulp (LKP) such as broadleaf bleached kraft pulp (LBKP) and broadleaf bleached kraft pulp (LUKP), coniferous bleached kraft pulp (NBKP), and conifer unbleached kraft pulp. (NUKP) and other coniferous kraft pulp (NKP) and other chemical pulp;
Stone Grand Pulp (SGP), Pressurized Stone Grand Pulp (PGW), Refiner Grand Pulp (RGP), Chemi Grand Pulp (CGP), Thermo Grand Pulp (TGP), Grand Pulp (GP), Thermo Mechanical Pulp (TMP), Mechanical pulp such as Chemi-Thermo Mechanical Pulp (CTMP), Bleached Thermo-Mechanical Pulp (BTMP);
Waste paper pulp manufactured from used tea paper, used kraft envelopes, used magazines, used newspapers, used leaflets, used office paper, used corrugated cardboard, used white paper, Kent used paper, imitation used paper, ground ticket used paper, used paper, etc.;
Examples thereof include deinked pulp (DIP) obtained by deinking used paper pulp. These may be used alone or in combination of a plurality of types as long as the effects of the present invention are not impaired.

Among these, as the pulp, chemical pulp is preferable, and hardwood kraft pulp (LKP) is more preferable, from the viewpoint of facilitating the drying of the coating liquid. Such pulp also has the advantage of being low in impurities.

The method for producing cellulose nanofibers is not particularly limited as long as the effects of the present invention are not impaired, and known methods can be used. For example, pulp may be subjected to defibration by mechanical treatment, or may be subjected to defibration by chemical treatment such as enzyme treatment or acid treatment. From the viewpoint that cellulose nanofibers can be obtained more easily and surely, it is preferable to subject the pulp to defibration by mechanical treatment.

Examples of the defibration method by mechanical treatment include a grinding method in which pulp is ground between rotating grindstones, a grinding method using a homogenizer, a ball mill, a roll mill, a cutter mill, and the like.

As a defibration method by mechanical treatment, a grinder method in which pulp is ground between rotating grindstones is preferable from the viewpoint that cellulose nanofibers can be obtained more easily and surely.

As a grinding method for grinding between rotating grindstones, for example, a grinding treatment method using a millstone type grindstone can be used. Specifically, by passing the pulp through the rubbing part of the stone mill type grinder, the pulp is gradually ground by the impact, centrifugal force, shearing force, etc. at the time of passing, and the pulp is not chemically altered. Uniform cellulose nanofibers can be obtained. Therefore, by using the cellulose nanofibers, a gas barrier layer having a dense structure can be formed.

The pulp may be subjected to preliminary beating before defibration. The pre-beating (mechanical pretreatment) is not particularly limited, and a known method can be used. As an example of a specific method, it is preferable to proceed with defibration step by step. In particular, a grinding method in which unbeaten raw material pulp is pre-beaten to 30% or less of the starting raw material in advance using a so-called viscous beating facility such as a niagar beater, and then ground between rotating grindstones. It is preferable to carry out the defibration treatment until cellulose nanofibers are obtained. This method is efficient in the nanocellulose treatment, and good cellulose nanofibers capable of imparting gas barrier properties can be obtained.

The pulp may also be chemically pretreated prior to defibration. Examples of this chemical pretreatment include a hydrolysis treatment using an acid such as sulfuric acid and an oxidation treatment using an oxidizing agent such as ozone. By applying the chemical pretreatment in this way, nanofibers can be efficiently obtained by mechanical or chemical defibration treatment. Depending on the application (for example, food-related application), it may be better not to perform chemical pretreatment.

Cellulose nanofibers preferably have a water retention rate of 300% or less. By using cellulose nanofibers having such a water retention degree, aggregation in the drying process is suppressed, and good drying properties are exhibited. The lower limit of the water retention rate is, for example, 150%. The water retention rate (%) of the cellulose nanofibers is determined by Japan TAPPI No. Measured according to 26.

Cellulose nanofibers preferably have a single peak in the pseudo-particle size distribution curve measured by laser diffraction in an aqueous dispersion. As described above, the cellulose nanofiber having one peak has been sufficiently miniaturized and can exhibit good gas barrier properties. Further, the particle size (mode) of the cellulose nanofibers having this peak is preferably 5 μm or more and 25 μm or less. When the cellulose nanofibers have the above size, better gas barrier properties can be exhibited. The "pseudo particle size distribution curve" means a curve showing a volume-based particle size distribution measured using a particle size distribution measuring device (for example, a laser diffraction / scattering type particle size distribution measuring device manufactured by Seishin Enterprise Co., Ltd.).

The B-type viscosity of the aqueous dispersion having a concentration of 2% by mass of cellulose nanofibers is preferably 1,000 cps or less. With such a viscosity, the coatability is excellent, and the occurrence of coating unevenness can be sufficiently suppressed. As the lower limit of the B-type viscosity, for example, 100 cps is preferable. "B-type viscosity" means a value measured in accordance with JIS-K-7117-1: 1999.

The crystallinity of the cellulose nanofibers is preferably 70% or less. By setting the crystallinity to the above upper limit or less, it is considered that the chemical modification of the cellulose nanofibers becomes easy. The crystallinity can be, for example, 30% or more. "Crystallinity" refers to a value measured by an X-ray analysis method in accordance with JIS-K-0131: 1996.

The CNF coating liquid is an aqueous dispersion of cellulose nanofibers. The lower limit of the cellulose nanofiber concentration of the CNF coating liquid is preferably 0.5% by mass, more preferably 1.0% by mass. If the content of the cellulose nanofibers is less than the above lower limit, the coating amount may increase and the drying efficiency may decrease in order to exhibit sufficient gas barrier properties. On the other hand, the upper limit of the concentration of the cellulose nanofibers in the CNF coating liquid is preferably 3.0% by mass, more preferably 2.5% by mass. If the content of the cellulose nanofibers exceeds the above upper limit, the viscosity of the coating liquid at the time of coating may increase.

In addition to water and cellulose nanofibers, the CNF coating liquid may contain other components as long as the effects of the present invention are not impaired. Examples of other components include inorganic particles, viscosity regulators, pH regulators, surfactants, plasticizers, waxes, water-soluble resins and the like. As the inorganic particles, flat-plate inorganic particles such as clay are preferable. Examples of the surfactant include anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants and the like. As the plasticizer, a polyhydric alcohol such as ethylene glycol is preferable. However, the content of the cellulose nanofibers in the solid content in the CNF coating liquid is preferably 80% by mass or more, more preferably 95% by mass or more.

The CNF coating liquid can be applied by a known method. The coating can be performed by, for example, blade coating, curtain coating, spray coating or the like. The coating amount of the lower limit of the CNF coating liquid, as a solid (CNF) amount is preferably 0.1 g / ^{m 2,} more preferably 0.5 g / ^{m 2,} more preferably 1g / ^{m 2,} 1. 5 g / m ² is particularly preferred. Sufficient gas barrier properties can be exhibited by setting the coating amount to the above lower limit or more. On the other hand, the upper limit of the coating amount, for example, be a ^{5g / m 2, 3g / m} 2 is preferred. If the amount of coating exceeds the above upper limit, the drying property may be lowered and the cost may be increased.

The PVA layer 14 is laminated on the surface of the CNF layer 13 opposite to the paper base material 11. That is, the PVA layer 14 is the outermost layer of the coating layer 12. The PVA layer 14 is formed by applying a PVA coating liquid containing PVA as a main component onto the CNF layer 13.

Polyvinyl alcohol is a polymer obtained by saponifying a polyvinyl ester obtained by polymerizing a vinyl ester compound such as vinyl acetate. Polyvinyl alcohol may be a saponified product of a copolymer of a vinyl ester compound and another monomer or other modified product as long as the effect of the present invention is not impaired.

As the lower limit of the saponification degree of polyvinyl alcohol, 70 mol% is preferable, and 80 mol% is more preferable. On the other hand, as the upper limit, 100 mol% is preferable, and 99.8 mol% is more preferable. The lower limit of the degree of polymerization of polyvinyl alcohol is preferably 500, more preferably 1,000. On the other hand, as the upper limit, 8,000 is preferable, and 4,000 is more preferable. By using polyvinyl alcohol having a saponification degree and a degree of polymerization in the above range, good coatability, gas barrier property and the like can be exhibited. The degree of saponification refers to a value measured in accordance with the JIS-K-6726: 1994 test method. The degree of polymerization (Po) is a value measured according to the JIS-K-6726: 1994 test method, and is the ultimate viscosity [η] measured in water at 30 ° C. after reseminating polyvinyl alcohol and purifying it. It means a value obtained from (dl / g) by the following equation.
Po = ([η] × 103 / 8.29) (1 / 0.62)

As the polyvinyl alcohol, commercially available ones can be used. As the commercially available polyvinyl alcohol, Kuraray's Excelval (registered trademark), Nippon Synthetic Chemistry's Nichigo G-polymer (registered trademark), and the like can be used.

The PVA coating liquid is an aqueous solution of polyvinyl alcohol. The concentration of polyvinyl alcohol in the PVA coating liquid can be, for example, 1% by mass or more and 30% by mass or less. By setting the concentration of the PVA coating liquid in the above range, the drying property, the coating property and the like can be improved.

In addition to water and polyvinyl alcohol, the PVA coating liquid may contain other components as long as the effects of the present invention are not impaired. Examples of other components include inorganic particles, viscosity regulators, pH regulators, surfactants, plasticizers, waxes, water-soluble resins and the like. As the inorganic particles, flat-plate inorganic particles such as clay are preferable. Examples of the surfactant include anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants and the like. As the plasticizer, a polyhydric alcohol such as ethylene glycol is preferable. As the lower limit of the content of the plasticizer, 1 part by mass is preferable and 2 parts by mass is more preferable with respect to 100 parts by mass of polyvinyl alcohol. On the other hand, as the upper limit, 30 parts by mass is preferable, and 25 parts by mass is more preferable. However, the content of polyvinyl alcohol in the solid content of the PVA coating liquid is preferably 80% by mass or more, more preferably 95% by mass or more.

The coating of the PVA coating liquid can be performed by a known method. The coating can be performed by, for example, blade coating, curtain coating, spray coating or the like. The coating amount of the lower limit of PVA coating solution, solid content (PVA) amount, preferably 1 g / ^{m 2,} more preferably ^{2g / m 2, 3g / m} 2 is more preferred. Sufficient gas barrier properties can be exhibited by setting the coating amount to the above lower limit or more. On the other hand, the upper limit of the coating amount, for example 10 g / ^{m 2} and it is possible to, 5 g / ^{m 2} is preferred. If the amount of coating exceeds the above upper limit, the drying property may be lowered and the cost may be increased.

After coating the CNF coating liquid and the PVA coating liquid, the CNF coating layer 13 and the PVA coating layer 14 are formed by drying the coated coating liquid. Drying may be performed each time each coating liquid is applied, or the two coating liquids may be collectively applied after coating. Drying can be performed by a known method.

The lower limit of the coating amount (solid content) of the coating layer 12, that is, the total coating amount (solid content) ^{is preferably 2 g / m 2 and} more preferably 4 g / m 2. On the other hand, as the upper limit, 10 g / m ² is preferable, and 8 g / m ² is more preferable. By setting the coating amount within the above range, it is possible to improve the gas barrier property, the drying property, etc. while suppressing the high cost.

It is preferable that the outermost surface of the coating layer 12 (the surface of the PVA layer 14) is subjected to a calendar treatment (flattening treatment). By applying the calender treatment, the minute voids in the coating layer that may be generated by drying after coating are closed by heating and pressurizing, and the gas barrier property can be further enhanced. The above calendar processing can be performed by a known method. For example, various calendars composed of a combination of a metal roll and an elastic roll such as a super calendar, a gloss calendar, and a soft compact calendar shall be appropriately used with on-machine or off-machine specifications. Can be done.

As the lower limit of the heating temperature during the calendering process, 60 ° C. is preferable, 75 ° C. is more preferable, and 80 ° C. is more preferable. On the other hand, the upper limit can be, for example, 100 ° C. Since the glass transition temperature of polyvinyl alcohol is about 55 to 75 ° C., the polyvinyl alcohol is melted by setting the heating temperature, and minute voids can be effectively closed by calendar treatment.

The pressurization in the calendering process can be, for example, 10 kgf / cm ² or more and 100 kgf / cm ² or less. By performing the calendar processing with the pressurization in the above range, minute voids can be effectively closed.

The agricultural sheet 10 has a good gas barrier property, and can be suitably used as a mulch sheet, a fumigation sheet, a weed-proof sheet, a house sheet, and the like. The oxygen permeability of the agricultural sheeting 10 is preferably not more than ^{8,000cc / m 2 · 24hr · atm} , more preferably not more than ^{6,000cc / m 2 · 24hr · atm} . As the lower limit of the oxygen permeability, for example, be a ^{100cc / m 2 · 24hr · atm} , may be ^{1,000cc / m 2 · 24hr · atm} . When it has such a low oxygen permeability, it can be particularly preferably used as an agricultural sheet.

<Laminated sheet>
The laminated sheet of the present invention includes a paper base material and a coating layer laminated on one surface side of the paper base material, and the coating layer includes a layer containing cellulose nanofibers as a main component and a main component. It is a laminated sheet having a layer containing polyvinyl alcohol as. The laminated sheet is formed of a biodegradable material and has sufficient gas barrier properties. As one embodiment of the laminated sheet, the above-mentioned agricultural sheet 10 can be mentioned. The laminated sheet can be suitably used as various packaging materials, bag-making materials, etc. in addition to agricultural sheets.

<Other embodiments>
The agricultural sheet and laminated sheet of the present invention are not limited to the above embodiments. For example, the CNF layer and the PVA layer in the coating layer may be laminated in the opposite direction to the agricultural sheet shown in FIG. That is, it may be an agricultural sheet (laminated sheet) in which a paper base material, a PVA layer, and a CNF layer are laminated in this order. Even in such an agricultural sheet or a laminated sheet, good gas barrier properties can be exhibited by having two coating layers, a PVA layer and a CNF layer.

Further, in the agricultural sheet and the laminated sheet of the present invention, at least one of the CNF layer and the PVA layer may be laminated in two or more layers. In this case, the coating layer may be formed by alternately laminating CNF layers and PVA layers. Further, coating layers may be provided on both sides of the paper base material, and each coating layer may have a CNF layer and a PVA layer. In the coating layer, a coating layer other than the CNF layer and the PVA layer may be laminated.

Further, the agricultural sheet and the laminated sheet of the present invention may be provided with a layer other than the paper base material and the coating layer, or may have a plurality of paper base materials. Examples of such a structure include a structure in which a coating layer is laminated on the surface of the first paper base material and a second paper base material is laminated on the surface of the coating layer. it can.

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

<Evaluation method>
Various physical properties in Examples and Comparative Examples were measured according to the following evaluation methods.
(Oxygen permeability and nitrogen permeability ^{(cc / m 2 · day ·} atm))
2 hours at 25 ° C using GTR's "GTR-11AET" in accordance with JIS-K-7126-1: 2006 "Plastic-Film and Sheet-Gas Permeability Test Method-Part 1: Differential Pressure Method" It was measured.

The CNF and PVA used in Examples and Comparative Examples are as follows.
・ CNF: Cellulose nanofibers obtained by beating BTMP (bleached thermomechanical pulp bleached product), which is mechanical pulp, with a Naiyagara beater for 2 hours and then defibrating it with a grinder (“Mascoroider” from Masuko Sangyo Co., Ltd.). PVA: Kuraray's Excelval (registered trademark) "RS-2117"

[Example 1]
^{2 g / m 2} (solid content) of CNF aqueous dispersion (CNF concentration 1.5% by mass) as a CNF coating solution is applied to one surface of PPC base paper (68 g / m ^{2) as a paper base material.} did. ^{Next, 3.8 g / m 2} (solid content) of a PVA aqueous solution (PVA concentration 5.0% by mass) as a PVA coating solution was applied onto the surface coated with the CNF coating solution, and dried. The laminated sheet of Example 1 was obtained.

[Comparative Example 1]
Using a coating liquid in which a PVA and CNF were mixed at a mass ratio of 85:15, PPC sheet of this as paper base (68g / ^{m 2)} 7.3g to one surface of the / ^{m 2} (solid content) The laminated sheet of Comparative Example 1 was obtained by coating and drying.

[Comparative Example 2]
Using a coating liquid in which a PVA and CNF were mixed at a mass ratio of 70:30, PPC sheet of this as paper base (68g / ^{m 2)} 5.3g to one surface of the / ^{m 2} (solid content) The laminated sheet of Comparative Example 2 was obtained by coating and drying.

[Comparative Example 3]
Using PVA solution as a coating liquid, which was 2 Kainuriko on one surface of PPC sheet (68 g / ^{m 2)} as a paper substrate (total coating amount 6.5 g / ^{m 2} (solid content)) , A laminated sheet of Comparative Example 3 was obtained.

[Evaluation]
Oxygen permeability and nitrogen permeability were measured for each of the obtained laminated sheets. The oxygen permeability and nitrogen permeability of each laminated sheet were measured for those subjected to calendar treatment at 80 ° C. and 30 kgf / cm ^{2 and those without calendar treatment, respectively.}

As shown in Table 1, it can be seen that the laminated sheet of Example 1 is superior in gas barrier property as compared with the laminated sheet of Comparative Examples 1 to 3. In particular, it can be seen that the laminated sheet of Example 1 has a significantly improved gas barrier property by being subjected to calendar processing.

Since the agricultural sheet and the laminated sheet of the present invention use a material having good biodegradability and have excellent gas barrier properties, they are suitably used as a mulch sheet, a fumigation sheet, a weed-proof sheet, a house sheet and the like. can do.

10 Agricultural sheet 11 Paper base material 12 Coating layer 13 CNF layer 14 PVA layer

Claims (2)

It is provided with a paper base material and a coating layer laminated on one side of the paper base material.
The coating layer has a layer containing cellulose nanofibers as a main component and a layer containing polyvinyl alcohol as a main component.
The content of polyvinyl alcohol in the solid content of the layer containing polyvinyl alcohol as the main component is 80% by mass or more.
A laminated sheet ^{having a total coating amount of 4 g / m 2} or more and 10 g / m ² or less as a solid content of a layer containing polyvinyl alcohol as the main component. Laminated sheet according to claim 1 oxygen permeability is not more than ^{8,000cc / m 2 · 24hr · atm} .

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