JPH1071662A - Paper container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To recycle paper by a method wherein the paper is enabled to be easily peeled off from an Al foil only by dipping a paper container in alkali aqueous solution. SOLUTION: A paper container is made of a laminate wherein a PO resin layer 11/paper paper 12/alkali soluble resin 13/a gas barrier layer 14/a PET film 15/the PO resin layer 11/a PO film 11a (inner surface) are laminated in this order. Since the paper 12 and the gas barrier layer 14 are easily separated from each other by dissolving the alkali soluble resin 13 only by dipping the paper container in alkali aqueous solution, the paper on which the PO resin layer is laminated, comes to be regenerated by a conventional waste paper regenerating process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly aims at reusing a liquid paper container such as a goebel top type paper container or a brick type paper container for the recycling of waste paper, wherein the paper and the gas barrier layer are made of an alkali-soluble thermoplastic resin. By laminating with resin and using the laminate to make a paper container, the paper container can be easily separated from the paper and gas barrier layer with an aqueous alkaline solution, so it can be reused for recycled paper it can.

[0002]

2. Description of the Related Art Conventionally, as paper containers for juice, alcoholic beverages, mineral water, wine, etc., a goebel top type paper container, a brick type paper container, a cup type paper container and the like have been used. In such a paper container, a paper is used as a support, and a thermoplastic resin film is bonded to the surface thereof, and an aluminum foil (hereinafter referred to as an Al foil) and a biaxially stretched polyethylene terephthalate are provided on the other side of the paper container via an adhesive layer. (Hereinafter PE
A gas barrier film obtained by laminating a film (hereinafter referred to as T) is laminated, and a polyolefin film such as polyethylene (hereinafter referred to as PE) is usually laminated on the innermost surface.

[0003] For example, PE / paper / adhesive layer / Al foil / adhesive layer / PET / PE (inner surface), PE / paper / adhesive layer / Al foil / adhesive layer / PE (inner surface), PE / paper / adhesive layer / PET /
Aluminum deposited film / PE (inner surface), PE / paper / adhesive layer / PE
T / silica deposited film / adhesive layer / PE (inner surface).
Then, an ethylene-methacrylic acid copolymer (hereinafter referred to as EMAA) was used as an adhesive layer between the paper and the Al foil, and PE /
Paper / EMAA / Al foil / adhesive layer / PET / PE / PE
(Inner surface) paper containers are often used. Since the beverage paper container is required to have gas barrier properties in order to prevent oxidation of the contents, a gas barrier layer such as an Al foil, an aluminum vapor-deposited film, or a silica vapor-deposited film is laminated.

[0004]

However, in the paper container having the above structure, the paper and the Al foil are firmly adhered to each other and cannot be easily peeled off. is there. Therefore, at present, paper containers having a gas barrier layer such as an Al foil are incinerated without recycling the paper. In addition, since the Al foil is laminated, aluminum remains even after the incineration treatment, and there is a problem in the incineration treatment. In order to solve these problems, the present invention makes it possible to easily separate paper and Al foil by simply immersing a paper container in an alkaline aqueous solution, thereby enabling paper recycling.

[0005]

Means for Solving the Problems In order to solve the above problems, the layer constitution of the paper container is as follows. In the case of a paper container comprising a laminate in which thermoplastic resin layer / paper / thermoplastic resin layer / gas barrier layer / thermoplastic resin layer is laminated in this order, the laminate comprises paper and a gas barrier layer formed from an alkali-soluble thermoplastic resin. A paper container characterized by being a laminate laminated by extrusion lamination. Further, the paper container is characterized in that the alkali-soluble thermoplastic resin is an acrylic resin, and the paper and the gas barrier layer are easily separated by immersing the paper container in an aqueous alkali solution.

That is, paper and Al among the layer constitution of the paper container are described.
By using an alkali-soluble acrylic resin (hereinafter referred to as an alkali-soluble resin) for the adhesive layer of the foil, the paper and the Al foil can be easily peeled off simply by immersing the paper container in an alkaline aqueous solution. After peeling off the laminated part of Al foil and plastic film from paper container, PE
Can be easily recycled into waste paper in the conventional waste paper recycling process. Therefore, the paper container of the present invention can be recycled for recycling used paper, thereby solving the problem of disposal of the container and conserving resources. Further, the alkali-soluble resin used in the present invention is a thermoplastic resin, and can be laminated by an extrusion method with an extruder, so that workability is good and a paper container can be manufactured with the same production efficiency as the conventional one. .

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic sectional view showing an example of the paper container of the present invention. FIG. 2 is a schematic cross-sectional view of the paper container manufactured in Example 3, and FIG. 3 is a schematic cross-sectional view of the paper container manufactured in Example 4. FIG. 4 shows the paper container of the present invention in Example 1.
It is explanatory drawing at the time of manufacturing by. FIG. 5 is an explanatory diagram when a laminate used for the paper container of the present invention is manufactured by an extruder.

FIG. 6 is an explanatory view when a laminate of paper containers is manufactured in the second embodiment. 7 is a schematic sectional view of the paper container manufactured in Comparative Example 1, FIG. 8 is a schematic sectional view of the paper container manufactured in Comparative Example 2, and FIG. 9 is a schematic sectional view of the paper container manufactured in Comparative Example 3. FIG.

The present invention mainly relates to a liquid paper container such as a goebel top type paper container, a brick type paper container and a cup type paper container, and the material composition of the container is basically such that paper is used as a support and paper is used. A gas barrier film (or an Al vapor-deposited film) in which a polyolefin resin film such as PE or polypropylene (hereinafter referred to as PP) is bonded to the surface, and an Al foil is bonded to the inner surface of the paper via an alkali-soluble resin with an adhesive. , A PET film on which a gas barrier layer such as a silica vapor-deposited film is formed, and a polyolefin film such as PE is laminated on the inner surface thereof.

For example, as shown in FIG. 1, milk carton base paper or cup base paper is used as paper for a support, and PE is used as a polyolefin resin layer (hereinafter referred to as a PO resin layer) 11 on the surface of the paper 12. Laminated, and on the back side of the paper, Al foil and P
A gas barrier film obtained by laminating an ET film with an adhesive is laminated, and the PET film 1 of the laminated sheet is further laminated.
On five sides, P sandwiched by PE sandwich lamination
It is obtained by laminating an E film and laminating a PO resin layer 11 and a polyolefin film (hereinafter referred to as a PO film) 11a.

Since the alkali-soluble resin is a thermoplastic resin, it can be extruded from a T-die of an extruder, and the paper and the gas barrier film can be bonded by an extrusion method. Alkali-soluble resins are usually T-
It is extruded in a single layer from the die, but may be extruded in multiple layers to separate the paper and the resin that adheres to the gas barrier layer.

As the paper of the support, milk carton base paper and cup base paper are mainly used, but there is no problem under the Food Sanitation Law, and any paper that can be formed as a container can be used. Paper can also be used. As for the thickness of the paper, those having a basis weight of 100 to 500 g / m ² are used,
For milk carton base paper, the basis weight is usually 113-34.
0 g / m ² paper is used, and also in the case of cup base paper, paper having a basis weight of 113 to 340 g / m ² is used.

[0013] As the alkali-soluble resin used in the present invention, an acrylic resin having an acid value of 100 to 500 mgKOH / g is used. If the acid value is less than 100 mgKOH / g, dissolution in an alkaline aqueous solution becomes slow, and when the paper container is immersed in the alkaline aqueous solution, peeling of the paper from the Al foil becomes difficult. On the other hand, if the acid value exceeds 500 mgKOH / g, the resin may be decomposed during melt processing of the resin, or the processing machine may be corroded, causing problems.

An Al foil is usually used as the gas barrier layer, which is bonded to a PET film using an adhesive, and the gas barrier film is laminated on paper to form a gas barrier paper container. As a gas barrier layer,
In addition to Al foil, PET (hereinafter A)
1) may be used after forming a thin film layer by vacuum evaporation or sputtering. Further, instead of the Al foil, a ceramic such as silica or alumina may be used by forming a thin film layer on a plastic film such as a PET film by vacuum evaporation or sputtering. Other ceramics include indium tin oxide (ITO) or zinc, tin, titanium, zirconium,
Metal oxides such as vanadium, barium, and chromium, silicon nitride, silicon carbide, and the like can be used. The thickness of the ceramic thin film layer can be used in the range of 50 to 3000 °, preferably 1 to
00 to 1000 °.

As the plastic film for forming the ceramic thin film layer, any resin can be used as long as it can be formed into a film with a thermoplastic resin, and is not particularly limited. For example, films such as PET, nylon, polypropylene, polyethylene, polycarbonate, polyvinyl chloride, polyvinylidene chloride, polyacrylonitrile, cellophane, and triacetate can be used. However, in order to strengthen the adhesion between the plastic film and the ceramic thin film layer, a pretreatment such as an anchor coat may be performed. The thickness of the film can be used in the range of 10 to 200 μm, preferably 10 to 80 μm.

An anchor coat layer is provided to improve the adhesion between the Al-deposited surface or the ceramic-deposited surface and the inner PE. As the anchor coat layer, a phenolic resin, a vinyl resin, an acrylic resin, a polycarbonate resin, a polyester resin, a cellulose resin, a urethane resin, an ionomer resin, a polyolefin resin, or a modified resin thereof is used. You.

Hereinafter, the method for producing the paper container of the present invention will be described. First, as shown in FIG. 4A, a milk carton base paper or a cup base paper is used as the paper 12 of the support, and PE is laminated on the base paper 12 by a known extrusion lamination method to produce a laminated paper 3. In addition, as shown in FIG.
Using a foil (having a thickness of 9 to 15 μm), the adhesive 16
The gas barrier film 4 is produced by bonding the PET film 15 with a (two-component curable isocyanate-based adhesive).

Next, as shown in FIG. 5 (a), the alkali-soluble resin 13 is extruded from the extruder 21, and the laminated paper 3 and the gas barrier film 4 are bonded together by a sandwich lamination method. As shown in (1), a laminated sheet 5 is produced. Further, the P of the laminated sheet 5
After applying an isocyanate-based anchor coating agent to the ET film 15 surface, as shown in FIG. 5B, PE11 is extruded from an extruder, and is bonded to a separately produced PE film 11a by a sandwich lamination method.
A laminate 1 as shown in FIG.

[0019]

The present invention will be described below in more detail with reference to examples. Example 1 As shown in FIG. 4 (a), as a support paper 5, a milk carton base paper having a basis weight of 400 g / m ² was used, and low density polyethylene (density: 923 kg / m ² ) was used.
³ , MFR: 3.7 g / 10 min, melting point: 111 ° C.)
20μm thick PE by extrusion method using
11 were laminated to produce a laminated paper 3. Note that M
FR indicates a melt flow rate based on JIS-K-6900, and the same applies hereinafter. Further, as shown in FIG. 4B, a PET film 15 having a thickness of 12 μm and a
The gas barrier film 4 was produced by laminating the Al foil 14a of m with a dry lamination method using a two-component curable isocyanate adhesive 16.

Next, the extruder is used to melt-extrude the laminated paper 3 with the alkali-soluble resin 13 having an acid value of 120 mgKOH / g at a thickness of 30 μm on the paper 12 side. The aluminum foil surface of the gas barrier film 4 is laminated by a sandwich lamination method,
A laminated sheet 5 as shown in FIG. Furthermore, after applying an isocyanate-based anchor coating agent to the PET film 15 surface of the laminated sheet 5, low-density polyethylene (density: 923 kg / m ³ , MFR: 3.7 g / 10
min, melting point: 111 ° C.) by melt extrusion at a thickness of 20 μm, and laminated with a separately prepared PE film 11a having a thickness of 40 μm by a sandwich lamination method,
A laminated body 1 as shown in FIG.

(Embodiment 2) As in Embodiment 1, FIG.
As shown in (a), a laminated paper 3 was produced. Further, an Al vapor-deposited film 14b having a thickness of 400 ° was formed on a PET film 15 having a thickness of 12 μm by a vacuum vapor deposition method.
As shown in (b), a gas barrier film 4 was obtained.

Next, the laminated paper 3 and the barrier film 4 are laminated by the sandwich lamination method using the alkali-soluble resin 13 in the same manner as in Example 1, as shown in FIG. A laminated sheet 5 having an Al deposited film 14b as a barrier layer was produced. Further, in the same manner as in Example 1, a two-component curing type anchor coating agent is applied to the Al vapor-deposited film 14b of the laminated sheet 5 and then PE
Was laminated with a PE film 11a having a thickness of 40 μm by the sandwich lamination method described above to produce a laminate 1 as shown in FIG.

(Embodiment 3) As in Embodiment 2, FIG.
As shown in (a), a laminated paper 3 was produced. Further, a vapor-deposited film 14c of silicon oxide (SiO ₂ ) having a thickness of 500 ° was formed on a PET film 15 having a thickness of 12 μm by a vacuum vapor deposition method to obtain a gas barrier film 4. Next, as in Example 2, using an alkali-soluble resin,
The laminated paper 3 and the gas barrier film 4 are laminated by a sandwich lamination method, and the SiO ₂ vapor-deposited film 1 of the laminated sheet 5 is formed in the same manner as in Example 2.
4c, a two-component curable anchor coat agent is applied, and the laminated sheet 5 and a 40 μm-thick PE film 11a are
A laminate 1 as shown in FIG. 2 was produced by laminating by the sandwich lamination method of E.

(Example 4) In the same manner as in Example 1, a laminated paper 3 and a gas barrier film 4 were produced. next,
In the same manner as in Example 1, the paper side of the laminated paper 3 and the Al foil side of the gas barrier film 4 were laminated by a sandwich lamination method using the following resin to produce a laminated sheet 5. Extruded resin has an acid value of 120mg
A copolymer of an alkali-soluble resin of KOH / g and an unsaturated monomer having ethylene and a carbonyl group, having an acid content of 5% by weight and an MFR of 32 g / 10 min. ,density;
930 kg / m ³ , melting point: 94 ° C.
(Hereinafter referred to as an alkali-soluble copolymer)
Similarly to the above, a two-component curable anchor coating agent is applied to the PET film surface of the laminated sheet 5 and then laminated with a PE film 11a having a thickness of 40 μm by a sandwich lamination method of PE, as shown in FIG. Such a laminate 1
Was prepared.

(Comparative Example 1) In Example 1, an ethylene-methacrylic acid copolymer was used instead of the alkali-soluble resin. Produced.

(Comparative Example 2) In Example 2, an ethylene-methacrylic acid copolymer was used in place of the alkali-soluble resin, and the other conditions were the same as in Example 2 to obtain a laminate 2b as shown in FIG. Produced.

Comparative Example 3 In Example 3, an ethylene-methacrylic acid copolymer was used in place of the alkali-soluble resin, and the other conditions were the same as in Example 3 to obtain a laminate 2c as shown in FIG. Produced.

With respect to the laminates produced in Examples 1 to 4 and Comparative Examples 1 to 3, the state of peeling of the laminates in an aqueous alkaline solution was tested. As a test method, the sample was 1cm x 1c
m-square piece, and the strip was NaOH set at 25 ° C.
The mixture was stirred while being immersed in a 0.5% by weight aqueous solution of the above. As an evaluation method, a sample was peeled after 10 minutes, and a sample that did not peel after 60 minutes was evaluated as x.

Table 1 shows the test results. As can be seen from Table 1, in the laminates produced in Examples 1 to 4, the alkali-soluble resin was dissolved after 10 minutes, and the paper and the barrier layer were completely peeled off. On the other hand, the laminate of Comparative Example not using the alkali-soluble resin did not undergo delamination even after 60 minutes, suggesting that it is difficult to recycle waste paper. Therefore, the paper container of the present invention using the laminates produced in Examples 1 to 4 can easily be peeled off with an aqueous alkaline solution and can be reused for recycling used paper.

[0030]

[Table 1]

[0031]

According to the present invention, since the alkali-soluble acrylic resin is used for the adhesive layer between the paper and the Al foil in the layer structure of the liquid paper container, the paper container is simply immersed in an aqueous alkaline solution. Thus, the paper and the Al foil can be easily separated. Therefore, after peeling off the portion where the Al foil and the plastic film are laminated from the paper container, the paper laminated with PE can be easily recycled into waste paper in the conventional waste paper recycling process. Therefore, the paper container of the present invention can be recycled for recycling used paper, thereby solving the problem of disposal of the container and conserving resources. In addition, the alkali-soluble resin used in the present invention is a thermoplastic resin, and can be laminated by an extrusion method using an extruder, so that workability is good, and a paper container having good gas barrier properties with the same production efficiency as that of the related art. Can be manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a paper container of the present invention.

FIG. 2 is a schematic cross-sectional view of a paper container manufactured in Example 3.

FIG. 3 is a schematic cross-sectional view of a paper container manufactured in Example 4.

FIG. 4 is an explanatory view when the paper container of the present invention is manufactured according to the first embodiment.

FIG. 5 is an explanatory diagram when a laminate of paper containers of the present invention is manufactured by an extruder.

FIG. 6 is an explanatory diagram when a laminate of paper containers is manufactured in Example 2.

FIG. 7 is a schematic cross-sectional view of the paper container laminate manufactured in Comparative Example 1.

FIG. 8 is a schematic sectional view of a paper container laminate manufactured in Comparative Example 2.

FIG. 9 is a schematic cross-sectional view of the paper container laminate manufactured in Comparative Example 3.

[Explanation of symbols]

Reference Signs List 1 laminated body 2a laminated body (laminated body of comparative example 1) 2b laminated body (laminated body of comparative example 2) 2c laminated body (laminated body of comparative example 3) 3 laminated paper 4 gas barrier film 5 laminated sheet 11 PO resin layer (extrusion PE) 11a PO film (PE film) 12 paper 13 alkali-soluble resin 13a alkali-soluble copolymer 14 gas barrier layer 14a Al foil 14b Al evaporated film 14c SiO ₂ deposited film 15 PET film 16 adhesive layer 17 anchor coat layer 18 Ethylene / methacrylic acid copolymer 21 Extruder 22 T die 23 Cooling roll 24 Nip roll

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[Procedure amendment]

[Submission date] October 2, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0005

[Correction method] Change

[Correction contents]

[0005]

Means for Solving the Problems In order to solve the above problems, the layer constitution of the paper container is as follows. In a paper container comprising a thermoplastic resin layer / paper / thermoplastic resin layer / gas barrier layer / thermoplastic resin layer laminate which are laminated in this order, A Le potash soluble thermoplastic laminate is paper and a gas barrier layer A paper container characterized by being a laminate obtained by laminating resin by extrusion lamination. Further, the paper container is characterized in that the alkali-soluble thermoplastic resin is an acrylic resin, and the paper and the gas barrier layer are easily separated by immersing the paper container in an aqueous alkali solution.

Continued on the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location B65D 5/56 B65D 5/56 D

Claims (2)

[Claims] 1. A paper container comprising at least a laminated layer of a thermoplastic resin layer / paper / thermoplastic resin layer / gas barrier layer / thermoplastic resin layer, wherein the laminate comprises paper and a gas barrier layer. A paper container characterized in that the paper container is a laminated body laminated by extrusion lamination using an alkali soluble thermoplastic resin. 2. The method according to claim 1, wherein the alkali soluble thermoplastic resin is an acrylic resin, and the paper and the gas barrier layer are easily separated by immersing the paper container in an alkaline aqueous solution. The paper container as described.