JP5563113B2 - Beverage paper container and laminate used therefor - Google Patents

Description

  The present invention relates to a paper container used as a beverage container such as a paper cup, a paper pack as a milk or juice packaging container, and relates to a paper container excellent in recovered paper recovery and a laminate used in the container.

  Paper containers are used as beverage containers such as juices and milk containers that are sold and offered at fast food stores. Since these beverage paper containers are extremely weak in strength when water contained in the beverage whose paper is the contents is absorbed, usually a polyolefin layer such as polyethylene or polypropylene having hydrophobicity is laminated on the inner surface side of the container. A laminate is used. Such a laminate is usually formed by extrusion laminating a polyolefin on a paper substrate.

  By the way, with the recent increase in demands for ecology and recycling, there is an increasing tendency to collect paper base materials as resources and use them for recycled and recycled paper. Furthermore, a high recycling rate has been demanded from the relationship with the Containers and Packaging Recycling Law.

  In the past, milk cartons have been collected for recycling. As for the milk pack, the sticking part for assembling the container is peeled to form a flat plate, and the olefin resin layer coated for waterproofing is peeled and removed to recover the paper base material. However, a laminate formed by melt-extrusion of polyolefin on a paper substrate is in a state where a part of the polyolefin enters the surface of the paper substrate like an anchor at the interface between the polyolefin layer and the paper substrate. And the paper base material are firmly attached.

  It is not easy to peel and remove the polyolefin layer from the laminate with the polyolefin firmly adhered to the paper substrate for the purpose of collecting used paper. Will be collected in a safe state. For this reason, the paper base material recovery rate from such a container is limited to the recovery of a part of the paper base material, and efficient recovery is desired.

  Under such circumstances, as a liquid paper container excellent in recyclability, a paper base material and a resin film are attached to Japanese Patent Application Laid-Open No. 2007-62786 with a wax, specifically, a wax having a melting point of 40 to 130 ° C. Packaging laminates have been proposed. The adhesive force between the paper substrate and the resin film by wax is much smaller than the adhesive force between the melt-laminated polyolefin layer and the paper substrate, so that the resin film can be easily peeled and removed. It is excellent in recyclability in that the material can be recovered 100%.

JP 2007-627863 A

  However, sticking with wax tends to peel off the polyolefin film, but the polyolefin layer may be peeled off during the distribution process or use as a beverage container due to insufficient bonding strength of the polyolefin layer to the paper substrate. In particular, in the case of wax, since the viscosity decreases under a high temperature atmosphere, the polyolefin layer may not be maintained at a stable desired bonding strength as a beverage container using hot water such as a midsummer distribution process or hot coffee. .

  The present invention has been made in view of the above circumstances, and its purpose is that a polyolefin layer for preventing liquid permeation is stably laminated on a paper substrate, and after use, the paper substrate It is an object of the present invention to provide a beverage paper container that is easy to collect, and that has a higher recovery rate, and a laminate used therefor.

The beverage paper container of the present invention comprises polyvinyl alcohol containing 1 to 20 mol% of a side chain 1,2-diol structural unit represented by the general formula (1) in an intermediate layer between a paper base and a polyolefin layer. A beverage container provided with a layer as a main component (hereinafter referred to as “side-chain 1,2-diol-containing PVA layer”), wherein the side-chain 1,2-diol-containing PVA layer is the paper substrate It is provided in contact with . In the following formula (1), R ^{1 to} R ⁶ each independently represent a hydrogen atom or an organic group, and X represents a single bond or a linking group.

The side chain 1,2-diol-containing PVA layer preferably does not contain polyethyleneimine.

The laminate for a paper container of the present invention is a laminate used for a paper container in which a polyolefin layer is laminated on a paper base material on a surface in contact with the contents, and the paper base material and the polyolefin layer In between, a layer mainly composed of polyvinyl alcohol containing 1 to 20 mol% of the side chain 1,2-diol structural unit represented by the general formula (1) (hereinafter referred to as “side chain 1,2-diol-containing PVA”). An intermediate layer including a “layer” is interposed , and the side chain 1,2-diol-containing PVA layer is provided in contact with the paper base material .

  Since the water-soluble PVA layer is interposed between the polyolefin layer for preventing liquid penetration and the paper base material, the beverage paper container of the present invention is immersed in water after use. The material and the polyolefin layer can be separated, the paper base material can be easily recovered, and the paper base material can be recovered almost 100%.

The description of the constituent requirements described below is an example (representative example) of an embodiment of the present invention, and is not limited to these contents.
In the beverage paper container of the present invention, a layer mainly composed of polyvinyl alcohol having a specific structure is provided in the intermediate layer between the paper base and the polyolefin layer.

<Paper base material>
The paper substrate used in the container of the present invention is usually a paper substrate used in a container, and has a basis weight of about 30 to 500 g / m ² , preferably about 100 to 400 g / m ² , and particularly preferably 250 to 350 g. Natural paper, synthetic paper, mixed paper, etc. of about / m ² can be used.
The surface of the paper, particularly the surface on which the polyvinyl alcohol layer is laminated, may be subjected to surface treatment such as corona treatment, flame treatment, or primer treatment as necessary.

<Polyolefin layer>
A polyolefin layer is a layer which comprises the inner surface of the drink container of this invention, and is a layer comprised as a main component by an olefin resin with the layer which contacts the drink used as the contents.

  Specific examples of olefin resins include linear low density polyethylene (LLDPE), low density polyethylene (LDPE), very low density polyethylene (VLDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), ethylene- Vinyl acetate copolymer (EVA), ionomer, ethylene-propylene (block and random) copolymer, ethylene-acrylic acid ester copolymer, polypropylene, propylene-α-olefin (α-olefin having 4 to 20 carbon atoms) Polyolefins in a broad sense such as copolymers, polybutenes, polypentenes or other olefins alone or copolymers, or those olefins alone or copolymers grafted with an unsaturated carboxylic acid or ester thereof, or blends thereof. Based resins, Among these, polyolefins such as linear low density polyethylene (LLDPE), low density polyethylene (LDPE), and very low density polyethylene (VLDPE) are preferably used because they are excellent in bending fatigue resistance and vibration fatigue resistance.

The density of the olefin resin is preferably 0.86 to 0.95 g / cm ³ . In addition, the density said here is a value measured by JISK6760 at 20 degreeC.

  In addition to polyolefin as the main component, the polyolefin layer has plasticizers, fillers, antiblocking agents, antioxidants, colorants, and antistatic agents in a range that does not impair the effects of the present invention and does not impair food safety. Known additives such as an agent, an ultraviolet absorber and a lubricant may be appropriately blended.

  The thickness of the polyolefin layer must be in a range that does not have pinholes or the like so as to ensure liquid impermeability. Specifically, it is 10-200 micrometers normally, Preferably it is 20-100 micrometers, More preferably, it is 30-70 micrometers. If it is too thin, the moisture resistance and waterproofness may be insufficient, and the mechanical strength will be insufficient and it will be easily broken.

<Intermediate layer>
The intermediate layer is a resin layer (hereinafter referred to as “a side chain 1,2-diol-containing PVA”) having a side chain 1,2-diol unit represented by the general formula (1) as a main component Side chain 1,2-diol-containing PVA layer ”), and this side chain 1,2-diol-containing PVA layer is provided in contact with the paper substrate.

In the general formula (1), R ^{1 to} R ⁶ each independently represent a hydrogen atom or an organic group. R ^{1 to} R ⁶ are preferably all hydrogen atoms, but may be organic groups as long as the resin properties are not significantly impaired. Although it does not specifically limit as this organic group, For example, C1-C4 alkyl groups, such as a methyl group, an ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, are preferable, You may have substituents, such as a halogen group, a hydroxyl group, an ester group, a carboxylic acid group, and a sulfonic acid group, as needed.

In the general formula (1), X is a single bond or a linking group, and is preferably a single bond from the viewpoint of thermal stability and stability under high temperature or acidic conditions. The linking group is not particularly limited, but other hydrocarbons such as alkylene, alkenylene, alkynylene, phenylene, and naphthylene (these hydrocarbons may be substituted with halogen such as fluorine, chlorine, and bromine). _{, -O -, - (CH 2} O) m -, - (OCH 2) m -, - (CH 2 O) mCH 2 -, - CO -, - COCO -, - CO (CH 2) mCO -, - _{CO (C 6 H 4) CO} -, - S -, - CS -, - SO -, - SO 2 -, - NR -, - CONR -, - NRCO -, - CSNR -, - NRCS -, - NRNR- _{, -HPO 4 -, - Si (} OR) 2 -, - OSi (OR) 2 -, - OSi (OR) 2 O -, - Ti (OR) 2 -, - OTi (OR) 2 -, - OTi ( _{OR) 2 O -, - Al} (OR) -, - OAl (OR) -, - OAl (O ) Although O- and the like (R is an optional substituent each independently, a hydrogen atom, an alkyl group are preferred, and m is a natural number) and the like. Among these, an alkylene group having 6 or less carbon atoms, particularly a methylene group, or —CH ₂ OCH ₂ — is preferable from the viewpoint of stability during production or use.

  The side chain 1,2-diol-containing PVA having the above-described configuration is water-soluble and has a feature that it can be melt-extruded. Therefore, a water-soluble side chain 1,2-diol-containing PVA layer can be formed on a paper substrate by melt extrusion of the side chain 1,2-diol-containing PVA. Furthermore, the resin constituting the polyolefin layer and the side chain 1,2-diol-containing PVA can be coextruded and laminated on a paper substrate.

  By laminating the side chain 1,2-diol-containing PVA layer on the paper substrate by melt extrusion, a part of the side chain 1,2-diol-containing PVA penetrates into the paper substrate. As a result, a high bonding strength between the paper substrate and the intermediate layer can be ensured based on the anchor effect. Furthermore, the co-extrusion of the olefin resin and the side chain 1,2-diol-containing PVA on the paper substrate ensures the bonding strength between the polyolefin layer and the side chain 1,2-diol-containing PVA layer, and thus A stable lamination of the polyolefin layer that prevents liquid penetration to the paper substrate is ensured.

  Then, by providing a water-soluble side chain 1,2-diol-containing PVA layer between the polyolefin layer and the paper substrate, the paper substrate and the polyolefin layer can be easily separated. That is, by simply immersing the laminate in water, the side chain 1,2-diol-containing PVA layer, which is an intermediate layer, is eluted, so that the polyolefin layer laminated with high bonding strength can be easily removed from the paper substrate. Can be peeled off. Moreover, since the penetrating portion of the side chain 1,2-diol-containing PVA that has penetrated into the surface layer portion of the paper base material is also eluted into water like an anchor, it becomes possible to recover 100% of the paper base material as it is. .

  Normal PVA obtained by saponifying polyvinyl acetate (hereinafter referred to as “unmodified PVA”) is also water-soluble. However, since unmodified PVA has a decomposition temperature close to its melting point and cannot be melt-molded, in order to form an unmodified PVA layer on a paper substrate, an aqueous coating solution of unmodified PVA is first prepared. This is coated on a paper substrate, but the coating solution penetrates into the paper substrate, and it is difficult to form a PVA layer having a predetermined thickness. In this regard, in the side chain 1,2-diol-containing PVA, since the molten resin is extrusion laminated onto the paper substrate, a side chain 1,2-diol-containing PVA layer having a predetermined thickness can be easily formed. it can.

  The content of the side chain 1,2-diol unit contained in PVA is usually preferably 1 to 20 mol%, more preferably 2 to 15 mol%, still more preferably 3 to 10 mol%. When the content of the side chain 1,2-diol unit becomes too high, the thermal stability during extrusion molding tends to be lowered. On the other hand, if the content of the side chain 1,2-diol unit is too low, the melting point becomes high and the paper substrate may be damaged during melt extrusion molding, and it is close to the thermal decomposition temperature (230 to 240 ° C.). Then, the allowable range of the molding temperature is narrowed, and the production conditions are tightened due to the relationship with the laminate with the polyolefin layer.

The content of the side chain 1,2-diol unit in PVA can be determined from a ¹ H-NMR spectrum (solvent: DMSO-d6, internal standard: tetramethylsilane) of a completely saponified PVA. Specifically, it may be calculated from a peak area derived from a hydroxyl group proton, a methine proton, a methylene proton in a 1,2-diol unit, a methylene proton in the main chain, a proton in a hydroxyl group linked to the main chain, and the like.

  The degree of polymerization of the side chain 1,2-diol-containing PVA used in the present invention is preferably 200 to 2000, more preferably 250 to 1000, and still more preferably 300 to 600. If the degree of polymerization is too high, the melt viscosity becomes high and stable extrusion tends to be difficult. Moreover, shear heat generation becomes large, and gel and scorch due to thermal decomposition tend to increase, which causes poor appearance of the inner surface of the container. On the other hand, if the degree of polymerization is too low, the strength tends to be insufficient.

  The degree of saponification of the side chain 1,2-diol-containing PVA used in the present invention is usually 70 to 100 mol%, preferably 80 to 99.9 mol%, more preferably 90 to 99 mol%. %. If the degree of saponification is too low, the odor of acetic acid due to decomposition of the acetyl group tends to become intense at the time of molding, and if acetic acid odor adheres to the laminate, the flavor of the beverage that is the content as a beverage container May be damaged.

  The method for producing the side chain 1,2-diol-containing PVA as described above is not particularly limited. (I) A method for saponifying a copolymer of a vinyl ester monomer and a compound represented by the following general formula (2) , (Ii) a method of saponifying and decarboxylating a copolymer of a vinyl ester monomer and a compound represented by the following general formula (3), (iii) a vinyl ester monomer and represented by the following general formula (4) It is preferably produced by a method of saponifying and deketalizing a copolymer with a compound.

(2) In the formulas (3) and (4), R ^{1 to} R ⁶ are the same as those in the formula (1). R ⁷ and R ⁸ are each independently hydrogen or R ⁹ —CO— (wherein R ⁹ is an alkyl group). R ¹⁰ and R ¹¹ are each independently a hydrogen atom or an organic group.

  As the methods (i), (ii) and (iii), for example, the method described in JP-A-2006-95825 can be employed.

Among them, the method in terms of excellent in copolymerization reactivity and industrial handling (i) are preferred, ^R 1 to R ⁶ are hydrogen atoms, X is a single bond, ^{R 7} and ^{R 8} are ^R 9 -CO 3,4-diasiloxy-1-butene in which R ⁹ is an alkyl group is preferred, and among these, 3,4-diacetoxy-1-butene in which R ⁹ is a methyl group is particularly preferred.

  It should be noted that when vinyl acetate is used as the vinyl ester monomer and this is copolymerized with 3,4-diacetoxy-1-butene, the reactivity ratio of each monomer is r (vinyl acetate) = 0.710, r ( 3,4-diacetoxy-1butene) = 0.701, which is r (vinyl acetate) in the case of vinyl ethylene carbonate, which is a compound represented by the general formula (3) used in the method (ii) = Compared to 0.85 and r (vinyl ethylene carbonate) = 5.4, 3,4-diacetoxy-1-butene is excellent in copolymerization reactivity with vinyl acetate.

  Examples of the vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valelate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, versatic. Although vinyl acid acid etc. are mentioned, vinyl acetate is preferably used especially from an economical viewpoint.

  In addition to the above-mentioned monomers (vinyl ester monomers, compounds represented by the general formulas (2), (3) and (4)), as long as the water solubility and melt extrudability are not impaired, ethylene as a copolymerization component And α-olefins such as propylene; hydroxy group-containing α-olefins such as 3-buten-1-ol, 4-penten-1-ol and 5-hexene-1,2-diol; itaconic acid, maleic acid, acrylic acid Unsaturated acids, such as salts thereof, mono- or dialkyl esters, nitriles such as acrylonitrile, amides such as methacrylamide, diacetone acrylamide, olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, and AMPS Alternatively, a compound such as a salt thereof may be copolymerized.

  The side chain 1,2-diol-containing PVA layer may be composed of one type of the above-mentioned side chain 1,2-diol-containing PVA, or a mixture of two or more different types of side chain 1,2-diol-containing PVA. It may be a PVA containing a side chain 1,2-diol, an unmodified PVA having no 1,2-diol unit in the side chain, or other modified PVA (for example, cation-modified PVA, carvone It may be a mixture with other PVA derivatives such as acid-modified PVA, sulfonic acid-modified PVA) and partially saponified ethylene-vinyl acetate copolymers. As long as it melt | dissolves in water and melt extrudability is not impaired, the other water-soluble resin may be contained. Examples of water-soluble or water-dispersible resins that can be used in combination include starch derivatives such as starch, oxidized starch, and cation-modified starch; natural proteins such as gelatin and casein; cellulose derivatives such as methylcellulose, ethylcellulose, hydroxyethylcellulose, and CMC; Natural polymer polysaccharides such as sodium alginate and pectic acid; water-soluble resins such as polyvinylpyrrolidone and poly (meth) acrylate (excluding polyethyleneimine); SBR latex, NBR latex, vinyl acetate resin emulsion, ethylene-acetic acid Examples include vinyl copolymer emulsions, (meth) acrylic ester resin emulsions, vinyl chloride resin emulsions, and urethane resin emulsions.

  When the side chain 1,2-diol-containing PVA layer includes a PVA-based resin other than the side chain 1,2-diol-containing PVA or other water-soluble resin, from the viewpoint of water solubility and melt extrudability, the side chain The content of 1,2-diol-containing PVA is preferably 60% by weight or more, and more preferably 80% or more.

  Moreover, it is preferable to prepare so that a melting temperature may be set to 150-220 degreeC as a side chain 1, 2-diol containing PVA resin composition used for melt extrusion. When the melting temperature is 150 ° C. or higher, it is not necessary to affect the bonding strength between the paper base material and the polyolefin layer even in the midsummer distribution process or as a container for hot drinks such as hot coffee. On the other hand, if the melting temperature is too high, the paper base material may be burnt or damaged.

  The intermediate layer may be composed of only the side chain 1,2-diol-containing PVA layer, or the side in contact with the paper substrate is composed of the side chain 1,2-diol-containing PVA layer and is in contact with the polyolefin layer. May include other thermoplastic resin layers. For example, a thermoplastic resin layer having adhesion to the polyolefin layer and the side chain 1,2-diol-containing PVA layer may be interposed. As such a thermoplastic resin, for example, a modified olefinic polymer containing a carboxyl group that can be obtained by chemically bonding an unsaturated carboxylic acid or an anhydride thereof to an olefinic polymer by an addition reaction, a graft reaction or the like. A coalescence or the like is preferably used.

  The thickness of the intermediate layer is preferably selected from the range of 0.5 to 50 μm (more preferably 1 to 30 μm, particularly 2 to 20 μm, particularly 3 to 10 μm). If the thickness is less than 0.5 μm, pinholes or the like may occur, and there may be a portion where the polyolefin layer and the paper base material are in direct contact. On the other hand, if it exceeds 50 μm, the mechanical strength becomes insufficient and it is not preferable because it is economically disadvantageous.

<Laminated body>
The laminate as the constituent material of the beverage paper container of the present invention comprises, on a paper base material, a resin layer (side chain 1,2-diol-containing PVA layer, adhesive layer) constituting the intermediate layer, and a polyolefin layer sequentially. It may be produced by laminating, and is preferably a method of producing by melting and coextrusion of resins constituting the intermediate layer and the polyolefin layer on a paper base material, more preferably side chain 1, In this method, the resin constituting the 2-diol-containing PVA layer and the polyolefin layer is melt-coextruded. According to the melt coextrusion method, even when the intermediate layer is composed of the side chain 1,2-diol-containing PVA layer alone, a high bonding strength can be ensured for the polyolefin layer. The coextrusion coating speed is not particularly limited, but is preferably 30 m / min or more, more preferably 50 m / min or more, and particularly preferably 80 m / min or more from the viewpoint of productivity.

<Container>
The beverage paper container of the present invention is configured using the laminate having the above-described configuration. Specifically, a paper cup as a container for cold drinks and hot drinks can be mentioned. In the beverage paper container of the present invention, since the side chain 1,2-diol-containing PVA has a gas barrier property, a liquid such as juice or milk is hermetically packaged, and the beverage of the contents is oxygenated for a certain period of time. It can also be used for paper-packed paper containers that need to be cut off.

  The container of the present invention is excellent in terms of recyclability. That is, the used container only needs to be immersed in water. Water penetrates from the outer surface of the paper substrate or from the outer peripheral edge of the laminate, the side chain 1,2-diol-containing PVA layer is eluted, and the polyolefin layer is peeled from the paper substrate. In this respect, it is convenient because the polyolefin layer does not need to be peeled and removed by mechanical force as in the prior art. In particular, in the case of a container having a complicated shape, in the case of a conventional paper container, in order to peel and remove the polyolefin layer, it is necessary to dismantle it into a flat plate once. Although it must be washed, the container of the present invention only needs to be immersed in water, so washing is unnecessary and disassembly is not necessary. Furthermore, in the conventional container, if the container is cut before the polyolefin layer is peeled and removed, it is necessary to first disassemble the container into a flat plate shape from the viewpoint that the removal and removal of the polyolefin layer becomes complicated. . On the other hand, the container of the present invention only needs to be immersed in water. Water penetrates from the side of the paper substrate that is the outside of the container, water penetrates into the side chain 1,2-diol-containing PVA, and the side chain 1,2-diol-containing PVA elutes, The paper substrate is separated. The fact that the container may be immersed in water in a state where it is appropriately cut is preferable because water can permeate directly into the side chain 1,2-diol-containing PVA layer from the cut surface. As described above, the operation of collecting the paper base material from the container becomes much simpler than the conventional paper container.

  Furthermore, in the paper container of the present invention, since the paper base material and the polyolefin layer can be separated by elution of the side chain 1,2-diol-containing PVA layer, nearly 100% of the paper base material can be recovered. . In this regard, conventionally, in a paper container having gas barrier properties, an EVOH layer as a gas barrier layer is interposed between the paper base material and the polyolefin layer. However, since the EVOH layer is not water-soluble, the EVOH layer is peeled off by applying mechanical force in order to recover the paper substrate, as in the case of the container in which the polyolefin layer is directly laminated on the paper substrate. Even when the pulp is collected by alkali treatment or the like, it is difficult to collect nearly 100% of the pulp from the paper base material. Therefore, the paper container of the present invention is a simple recovery operation and has a high efficiency of almost 100% of the paper base material compared with the conventional paper container in which the gas barrier layer is interposed between the polyolefin layer. It can fully meet the recent ecology and demands for collecting used paper as resource waste.

  In the beverage paper container of the present invention, a resin film or the like is further laminated on the surface on the outer side of the container, on the side where the intermediate layer of the paper base is not laminated, for appropriate purposes such as decorative purposes and waterproofing. Also good. In this case, it is preferable that the resin film is easy to peel off so as not to impair the recyclability which is the effect of the present invention, or it is further provided between the resin film and the paper substrate which are appropriately laminated for the purpose. A chain 1,2-diol PVA layer may be interposed.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the description of the examples unless it exceeds the gist.
In the examples, “parts” and “%” mean weight basis unless otherwise specified.

〔Example〕
(1) Production of side chain 1,2-diol-containing PVA film In accordance with the method described in Production Example 1 of JP-A-2006-95285, vinyl acetate and 3,4-diacetoxy-1-butene were copolymerized. To produce a side chain 1,2-diol PVA resin having a side chain 1,2-diol structural unit content of 4.5 mol%, a polymerization degree of 450, and a saponification degree of 98.5 mol%, The PVA film containing a side chain 1,2-diol (thickness 30 μm) was obtained by melt extrusion.

(2) Preparation paper substrate of the laminate, thickness 420 [mu] m, the paperboard of basis weight 335 g / ^{m 2,} laminated side chain 1,2-diol-containing PVA film prepared above, a polyethylene film having a thickness of 27μm in this order The laminate was produced by pressing at 220 ° C. × 4 kg / cm ² × 1 min with a heating and pressing machine.

(3) Evaluation When the produced laminate was cut to about 5 cm square and immersed in water at 23 ° C. for 3 days, the polyethylene film and the paperboard were separated.
Next, after drying the recovered paperboard, the weight was measured, and the paper recovery rate was calculated by the following formula. In the formula, W ₀ is the mass of the paperboard before the laminate is manufactured, and W ₁ is the mass of the paperboard after the recovery process.
Recovery rate (%) = (W ₁ / W ₀ ) × 100
It was confirmed that the paperboard weight after the recovery processing was the same as the original paperboard weight, and the recovery rate was 100%.

[Comparative example]
Instead of the side chain 1,2-diol-containing PVA film, the side chain 1,2-diol structural unit-containing EVOH resin (ethylene content 38 mol%, saponification degree 98.5 mol%, polymerization degree 450, modification degree 1 0.5 mol%) was prepared and melt extruded to obtain an EVOH film having a thickness of 30 μm.
Using this EVOH film, a laminate was produced in the same manner as in the example and evaluated in the same manner.

  Even when immersed in water for 3 days, separation of the paperboard and the polyethylene film was not observed. After peeling off the polyethylene film from the edge and visually confirming that the resin film did not adhere to the paperboard, the paperboard weight was measured, and the recovery rate was calculated based on the above formula. The recovery rate was 84%.

  The beverage paper container of the present invention can separate the paper base material used as a constituent material and the polyolefin layer for preventing liquid penetration just by immersing in water, and recovers the paper base material almost as it is. be able to. Therefore, when the laminate of the present invention is used as a beverage paper container, the paper base can be recovered with high efficiency simply by immersing the used container in water, which is useful for recycling paper containers and popularizing used paper recovery systems.

Claims (3)

A layer mainly composed of polyvinyl alcohol containing 1 to 20 mol% of the side chain 1,2-diol structural unit represented by the general formula (1) in the intermediate layer between the paper substrate and the polyolefin layer (hereinafter referred to as A beverage container provided with a “side-chain 1,2-diol-containing PVA layer”, wherein the side-chain 1,2-diol-containing PVA layer is provided in contact with the paper substrate. Paper container.

(In formula (1), R ^{1 to} R ⁶ each independently represents a hydrogen atom or an organic group, and X represents a single bond or a linking group.) The beverage paper container according to claim 1, wherein the side chain 1,2-diol-containing PVA layer does not contain polyethyleneimine. A laminate used for a paper container in which a polyolefin layer is laminated on a paper base material on a surface in contact with the contents,
A layer mainly composed of polyvinyl alcohol containing 1 to 20 mol% of the side chain 1,2-diol structural unit represented by the general formula (1) between the paper substrate and the polyolefin layer (hereinafter referred to as “ An intermediate layer including a side chain 1,2-diol-containing PVA layer), and the side chain 1,2-diol-containing PVA layer is provided in contact with the paper substrate. A laminate for paper containers.

(In formula (1), R ^{1 to} R ⁶ each independently represents a hydrogen atom or an organic group, and X represents a single bond or a linking group.)