JP2009286488A - Paper container - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paper container which hardly raises malfunctions such as foaming on a sealing section and a liquid leak caused by the foaming by relieving and preventing a foaming phenomenon generated between a paper layer and a barrier film layer caused by evaporation of water contained in the paper layer when laminated materials are melted and joined at the time of hot forming. <P>SOLUTION: In the paper container formed by laminating the paper layer and the barrier film layer via a melting extrusion resin layer, the paper layer at a sealant layer side of the laminated material is embossed at an uneven state in advance before laminating, and the surface at the sealant layer side of the paper layer becomes a clay coated layer. Further, a resin at least at a paper layer side of the melting extrusion resin layer is high-density polyethylene. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a paper container formed by molding a laminated material mainly composed of a paper base material having a barrier film layer and containing beverages, alcohols and the like.

  In recent years, environmental issues have been emphasized, and the easy disposal of containers and packaging materials is required, and the demand for easy incineration, recyclability, or recycled materials is increasing. Liquid paper containers are replaced with conventional glass containers and metal containers, chilled-type liquid foods such as milk, lactic acid drinks, and liquid soups, and room temperature type liquids that require long-term storage such as sake, mentsuyu, and fruit juice drinks. It has come to be used in a wide range of foods. In particular, the need for a paper container made from pulp such as thinned wood that is ecologically compatible with retort sterilization is greatly increasing.

  For this reason, cup-shaped, cylindrical-shaped, or roof-shaped paper containers that are formed by bending from a ruled line that has been formed in advance are proposed as food containers. in use. These paper containers generally use a laminated material having a layer structure such as [outer container] polyethylene / paper / barrier layer / sealant layer [inner container], and the paper and barrier layer are melt extruded. A laminated material laminated through a low density polyethylene resin has been used. However, a paper container suitable for filling and storing liquid contents or solid contents requiring barrier properties against oxygen and water vapor is included in the paper layer, particularly when heat-molded by heat sealing or the like. A technique that suppresses the bubbling (foaming) phenomenon that occurs in the laminated material due to water vapor generated by heating moisture and prevents the occurrence of delamination and pinholes that occur between the layers of the laminated material has been an essential and problematic issue.

  On the other hand, in Patent Document 1, a laminated material in which a thermoplastic resin layer is provided on both surfaces of a base material in which a paper layer and a barrier layer are laminated via a dry laminate layer is thermoformed. No paper liquid container is disclosed. In this case, the heat resistance is improved, but the processing speed is slow, it takes time to cure the adhesive, and there are problems such as residual solvent when the adhesive is not sufficiently dried.

  In Patent Document 2, an outer resin layer is laminated on one surface of a cardboard layer, and an inner surface sealant resin layer is laminated on the other surface of the cardboard layer via an adhesive layer such as a plastic resin layer or a barrier layer. Paper container materials are described. And by providing the outer layer resin layer with a water vapor permeable minute hole that reaches the cardboard layer, when melt-bonding, it is placed between the cardboard layer and the adhesive layer or barrier layer due to evaporation of moisture contained in the cardboard layer. A technique for preventing the foaming phenomenon that occurs is disclosed. In this case, a special processing device is required, and a special paper that can withstand penetration of moisture and the like from the outside needs to be used for the cardboard layer.

  In Patent Document 3, a laminated material in which polyethylene resin, paper, an intermediate resin layer, a barrier film, and a sealant layer are sequentially laminated from the outer surface side, and a high-melting polyethylene resin is used for the intermediate resin layer. A cup-shaped container without the occurrence of is disclosed. In this case, there is a problem that the processing temperature for laminating becomes high, and when the smoothness of the paper is high, the adhesive strength is difficult to be obtained.

Furthermore, in Patent Document 4, a paper container formed by molding a laminated material mainly composed of a paper base material in which a paper layer and a barrier film layer are laminated via a melt-extruded resin layer, and a paper having a sizing degree of 400 seconds or more. A two-part curable adhesive layer having a urethane bond is formed on the substrate at a coating amount of 0.5 g / m ² or more and 4 g / m ² or less, and the adhesive layer is interposed between the paper layer and the melt-extruded resin layer. Thus, a paper container for forming a laminated material in which a paper layer and a barrier film layer are laminated is disclosed. Although this structure improves the adhesion stability of the laminate, there is a problem that the number of steps increases.
Japanese Patent Laid-Open No. 10-138370 JP 2000-2035565 A Japanese Patent Laid-Open No. 2003-221024 JP 2006-168775 A

  The present invention has been made in view of such technical problems, and is a paper container formed by molding a laminated material in which a paper layer and a barrier film layer are laminated via a melt-extruded resin layer, and is laminated at the time of heat molding. Paper that does not cause defects such as foaming of the seal part or liquid leakage due to the foaming phenomenon between the paper layer and the barrier layer due to evaporation of moisture contained in the paper layer when the materials are melt-bonded. The purpose is to provide a container.

  The invention according to claim 1 of the present invention is formed by molding a laminated material mainly composed of a paper base material obtained by laminating at least a paper layer and a sealant layer having a barrier film layer via a melt-extruded resin layer. In the paper container, the paper layer on the sealant layer side of the laminated material is embossed in an uneven shape in advance before lamination.

  The invention according to claim 2 of the present invention is the paper container according to claim 1, wherein the surface of the paper layer of the laminated material on the sealant layer side is a clay coat layer.

  In the invention according to claim 3 of the present invention, at least the paper layer side resin of the melt-extruded resin layer of the laminated material is high-density polyethylene. Paper container.

  According to the paper container of the present invention, when laminating the paper layer and the barrier film layer via the melt-extruded resin layer, the paper layer and the barrier film layer that have been embossed in an uneven shape before the lamination are extruded and sand lamination. Since it is a paper container formed by molding a laminated material laminated by the method, the theoretically clear elucidation has not been made, but the water vapor generated by heating the moisture contained in the paper layer is the paper layer and the molten extruded resin As the foam phenomenon is suppressed by momentarily escaping to the minute gap formed between the layers and the pressure is relaxed, the non-adhered part of the point-adhesive melt-extruded resin layer expands and contracts, It is assumed that the occurrence of pin poles due to bubble breakage is suppressed, delamination and bubbling phenomenon occurring between layers of the laminated material is suppressed, and a paper container free from defects such as liquid leakage can be provided.

  Further, according to the paper container of the present invention, paper having a low density and a high porosity is desirable, but it is difficult to stably make paper and the cost is high. When a paper layer having a rough surface is simply used, the adhesive strength of the lamination of the paper layer and the barrier film layer via the melt-extruded resin layer may vary and become unstable. In that case, a clay coat layer is provided on the surface of the sealant layer of the paper layer and embossed in an uneven shape before lamination, so that fine voids enter the clay coat layer and the interlayer adhesion strength of the laminated material is controlled appropriately And the bubbling phenomenon can be suppressed.

  Furthermore, according to the paper container of the present invention, the resin on at least the paper layer side of the melt-extruded resin layer of the laminated material is a high-density polyethylene, so that the heat resistance at the time of heat molding and the low-density polyethylene are compared. Since the melt viscosity at the time of heating and melting is low and it is easy to adhere to a paper layer embossed in a concavo-convex shape, the interlayer adhesive strength is stabilized, and delamination and bubbling are suppressed.

  Hereinafter, a paper container of the present invention is explained based on one embodiment with reference to drawings. FIG. 1 is a schematic external view showing a cylindrical paper container as an example of the paper container of the present invention. (A) is the schematic diagram seen from the upper part (lid part), (b) is the external appearance schematic diagram which looked at the cross section of the paper container from the side surface. FIG. 2 is an enlarged schematic cross-sectional view illustrating an example of a laminated material constituting the paper container of the present invention.

  As shown in FIG. 1, a cylindrical paper container 10 as an example of the present invention is a paper base material in which at least a paper layer and a sealant layer having a barrier film layer are laminated via a melt-extruded resin layer. A cylindrical body member (side material) 30 and a circular outer peripheral edge standing on the outer surface side (upper) lid material (top material) 40 and a bottom material (bottom material) 50 having a circular outer peripheral edge standing on the outer surface side (lower part). These are such that the inner surface of the outer peripheral edge of the lid member 40 is joined to the upper inner surface of the body member 30, the inner surface of the outer peripheral edge of the bottom member 50 is joined to the lower inner surface of the body member 30, and the outer peripheral edge of the lid member 40. The upper end edge of the body member 30 is folded inward so as to cover the part, and similarly, the lower end edge of the body member 30 is folded inward so as to cover the outer peripheral edge of the bottom member 50, It has a cylindrical structure.

  As shown in FIG. 2, the top material 40, the side material 30, and the bottom material 50 of the cylindrical paper container 10 are basically formed from the outermost layer from the thermoplastic resin layer 21 / paper layer 22 / melt extruded resin layer 25. / Barrier film layer 26 / sealant layer 27 are laminated in order, and the paper layer on the sealant layer side is embossed 29 in advance in a concavo-convex shape before lamination, and the paper layer surface embossed in this concavo-convex shape It consists of the laminated material 20 which laminated | stacked the barrier film layer through the melt extrusion resin layer. In addition, the thickness of each layer of a top material, a side material, and a bottom material can be changed according to a use.

The paper base material constituting the paper layer 22 used in the laminated material 20 constituting the paper container of the present invention is excellent in suitability to bend or squeeze when formed into a cylindrical shape paper container, and has a basis weight. A cup base paper made of virgin pulp of about 200 to 400 g / m ² can be preferably used.

  The paper substrate is embossed in a concavo-convex shape in advance before lamination. Embossing can be performed using known techniques. As a method suitable for the paper container of the present invention, specifically, in a process of laminating a paper layer and a barrier film layer by an extrusion sand lamination method, a metal having a rubber roll and fine protrusions formed in front of the laminating portion The method of pinching the paper substrate which runs with a characteristic embossing roll is preferable. As the embossing roll, a needle-like, conical or pyramidal projection having a height of 3 to 100 μm and an interval of 10 to 300 μm and disposed on the entire surface can be used. The pressure for sandwiching the paper substrate is preferably about 0.5 MPa to 400 MPa. In addition, it does not matter whether it is heated or not.

In addition, paper with a low density and a high porosity is desirable for the paper base material, but such paper is difficult to produce stably and is expensive, so a paper layer with a rough surface is used. By providing the clay coat layer 23 on the surface of the sealant layer side of the layer and embossing in an uneven shape in advance before lamination, a fine void enters the clay coat layer, and the interlayer adhesion strength of the laminated material can be controlled appropriately. In addition, the bubbling phenomenon can be suppressed. It is not necessary to thicken for clay coat layer 23 of the inner surface side is not the purpose of obtaining a proper printing, about 20 g / m ² is preferred. If necessary, the clay coat layer 24 and the print layer 28 can be provided on the surface of the paper base that contacts the thermoplastic resin layer.

  The thermoplastic resin layer 21 can be selected according to the purpose and is not particularly limited. For example, polyethylene resin, polypropylene resin, polyester resin, ethylene-based copolymer resin, polyamide resin (nylon 6, nylon 66, etc.), polyvinyl chloride, and the like can be given.

  Examples of the melt-extruded resin constituting the melt-extruded resin layer 25 used in the laminated material constituting the paper container of the present invention include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), polypropylene (PP), Single unit or blend of ethylene-vinyl acetate copolymer (EVA), ethylene-acrylic acid copolymer (EAA), ethylene-methyl methacrylate copolymer (EMAA), ethylene-ethyl acrylate copolymer (EEA), etc. Can be used.

  Furthermore, in the present invention, medium density or high density polyethylene having a softening point of 110 ° C. or higher can be used as the resin on the paper layer side of the melt-extruded resin layer while using the above resin as a main material. Specifically, medium density or high density polyethylene can be extruded by coextrusion with the above-described resin having a low softening point, which is excellent in extrusion processability at high speed, as the core or barrier film side. The thickness of the melt-extruded resin layer is preferably about 15 to 60 μm.

  The barrier film layer 26 used in the laminated material constituting the paper container of the present invention is a layer that imparts gas barrier properties and water vapor barrier properties, and includes aluminum foil, aluminum vapor deposited film, metal oxide vapor deposited film, and ethylene vinyl alcohol. Polymer resins, vinylidene chloride films, polyvinyl alcohol films and the like can be preferably used. In addition, you may laminate | stack a PET film, a polyamide film, etc. on the said film as needed.

  Next, as the sealant layer 27 used in the laminated material constituting the paper container of the present invention, the sealant layer 27 is exposed on the inner surface of the container and comes into contact with food, and the heat sealability between the sealant layers, or the sealant layer 27 and the heat. The heat-bonding property or thermal adhesiveness with the plastic resin layer 21 is required. Low density polyethylene, medium density polyethylene, high density polyethylene, linear (linear) low density polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ionomer resin, ethylene-acrylic acid copolymer (EAA), ethylene-methyl A polyolefin-based resin such as a methacrylate copolymer (EMAA), an ethylene-ethyl acrylate copolymer (EEA), an ethylene-propylene copolymer, a methylpentene polymer, polyethylene, or polypropylene is mixed with acrylic acid, methacrylic acid, maleic acid, An acid-modified polyolefin resin modified with an unsaturated carboxylic acid such as maleic anhydride, fumaric acid or itaconic acid can be used. A thickness of about 30 to 100 μm can be suitably used.

  Lamination of each layer of the thermoplastic resin layer 21, the paper layer 22, the melt extrusion resin layer 25, the barrier film layer 26, and the sealant layer 27 can be performed using a known method such as a melt extrusion lamination method or a dry lamination method. it can. Moreover, in bonding each layer, an adhesion improving process such as a corona discharge process or an anchor coat process can be performed as necessary.

  Using the laminate material 20 produced in this manner, a known (for example, Toppan Printing Co., Ltd. trademark “Kartkan”) cylindrical paper container molding machine is used, for example, a paper container 10 as shown in FIG. Can be molded.

  Examples of the present invention and comparative examples will be described below. In addition, this invention is not limited to the Example mentioned later.

In the following examples and comparative examples, low density polyethylene (LDPE) has a melting point of 116 ° C., softening point of 104 ° C. and density of 0.918 g / cm ³ , and high density polyethylene has a melting point of 130 ° C. The softening point was 122 ° C. and the density was 0.941 g / cm ³ , all of which were manufactured by Mitsui Chemicals. As the barrier film layer, a barrier film in which aluminum oxide is provided to a thickness of 40 nm by reactive physical vapor deposition on a biaxially stretched polyethylene terephthalate (PET) film having a thickness of 12 μm, and aluminum oxide is sandwiched inside. In such a form, another PET film having a thickness of 12 μm bonded to each other via a two-component reactive polyester adhesive was used.

  A laminated material for a top material, a bottom material and a side material for a cylindrical paper container was produced. Further, the edge protection tape 33 for joining the barrel portion in a cylindrical shape without exposing the paper end face of the side material inside the container was used with both sides of the barrier film layer receiving 20 μm of LDPE. In addition, the tab material 44 for drinking mouth which blocks the opening for injecting contents provided in the lid portion was not used.

<Laminated materials for lid materials (top materials)>
[Outside of container] Lid material composed of LDPE (40 μm) / Cup base paper (250 g / m ² ) / LDPE (55 μm) / PET (12 μm) / Aluminum oxide deposited PET (12 μm) / LDPE (60 μm) [Inner side of container] A laminated material for (top material) was produced.

<Laminated material for bottom material>
[Outside of container] Bottom material comprising LDPE (20 μm) / Cup base paper (200 g / m ² ) / LDPE (35 μm) / PET (12 μm) / Aluminum oxide deposited PET (12 μm) / LDPE (60 μm) [Inner side of container] A laminated material for (bottom material) was produced.

<Laminated material for body member (side material) (I)>
[Outside of container] LDPE (20 μm) // Cup base paper (300 g / m ² ) / Clay coat layer (20 g / m ² ) / Embossed // HDPE (30 μm) // LDPE (15 μm) // PET (12 μm) // A laminated material (i) for a body member (bottom material) composed of aluminum oxide vapor-deposited PET (12 μm) // LDPE (60 μm) [inner side of container] was prepared.

<Laminated material for body member (side material) (b)>
[Outside of container] LDPE (20 μm) // Clay coat layer (20 g / m ² ) / Cup base paper (280 g / m ² ) / Clay coat layer (20 g / m ² ) / Embossed // HDPE (30 μm) // A laminated material (b) for a body member (bottom material) composed of LDPE (15 μm) // PET (12 μm) // aluminum oxide vapor-deposited PET (12 μm) // LDPE (60 μm) [inside the container] was prepared.

<Laminated material for body member (side material) (C)>
[Outside of container] LDPE (20 μm) // Clay coat layer (20 g / m ² ) / Cup base paper (280 g / m ² ) / Clay coat layer (20 g / m ² ) No embossing // HDPE (30 μm) // A laminated material (c) for a trunk member (bottom material) composed of LDPE (15 μm) // PET (12 μm) // aluminum oxide-deposited PET (12 μm) // LDPE (60 μm) [inside the container] was prepared.

  Next, using the above-described laminated material, examples and comparative examples of the paper container of the present invention were produced using the above-described cylindrical paper container molding machine. In the following description, only the points of molding are schematically described.

<Example 1>
The above-mentioned laminated material for body members (A) is formed into a body by using an edge protection tape to form a body, and a circular outer peripheral edge obtained by punching an opening on a cylindrical side material is the outer surface side. And a bottom material (bottom material) having a circular outer peripheral edge standing on the outer surface side is disposed below. Next, while applying heat and pressure, the inner surface of the outer peripheral edge portion of the lid member is joined to the upper inner surface of the trunk member, and the inner surface of the outer peripheral edge portion of the bottom member is joined to the lower inner surface of the trunk member. The upper edge of the body member is folded inward to cover the outer peripheral edge of the material, and the lower edge of the body member is folded inward to cover the outer peripheral edge of the bottom material. A paper container having a diameter of 53 mm and a capacity of 195 g was prepared. A red dye penetrant flaw detection agent liquid (R-1ANT, manufactured by Eiji Shin Chemical Co., Ltd.) is put into 100 paper containers from the opening provided in the lid, and the liquid is left at room temperature for 12 hours with the lid facing up. To see if there is a leak. Also, discharge the dye penetrant flaw detection agent solution, disassemble the container, observe from the inner surface side, visually check whether there is bubbling, ○ if there is no bubbling, × It was. Further, the adhesion between the paper layer and the melt-extruded resin layer at the location adjacent to the joint portion of the body member was confirmed by checking whether or not the paper was peeled off. The case where there was paper peeling was marked with ○, and the case where there was no paper peeling was marked with ×. The evaluation results are shown in Table 1.

<Example 2>
A paper container was created by the same material and the same method as in Example 1 except that (B) was used as the body member laminate material, and the same evaluation and confirmation as in Example 1 were performed. The evaluation results are shown in Table 1.

<Comparative Example 1>
A paper container was prepared using the same material and the same method as in Example 1 except that (C) was used as the laminate material for the trunk member, and the same evaluation and confirmation as in Example 1 were performed. The evaluation results are shown in Table 1.

＜比較結果＞
実施例１及び実施例２の紙容器では、紙層の容器内面の接液側及び両面にクレーコート層を有し、且つ、バリアフィルム層を有したシーラント層側すなわち溶融押し出し樹脂層側がエンボス加工されているため、加熱成形時の熱で紙中の水分蒸発によるバブリングの発生がなく、紙層と溶融押し出し樹脂層との接着が良好であり、液漏れの発生は認められなかった。それに対して、比較例１では、液漏れの発生は無かったが、バブリング現象が発生しており、紙層と溶融押し出し樹脂層との接着も紙剥けがなく、本比較例での１２時間の室温放置では液漏れは発生しなかったが、経時でバブリング破泡部から内容液が徐々に浸透することが予想された。

<Comparison result>
In the paper containers of Example 1 and Example 2, the paper layer has a clay coat layer on the liquid contact side and both sides of the container inner surface, and the sealant layer side having the barrier film layer, that is, the melt-extruded resin layer side is embossed. Therefore, there was no bubbling due to evaporation of moisture in the paper due to heat at the time of thermoforming, adhesion between the paper layer and the melt-extruded resin layer was good, and no occurrence of liquid leakage was observed. On the other hand, in Comparative Example 1, there was no occurrence of liquid leakage, but a bubbling phenomenon occurred, the paper layer and the melt-extruded resin layer did not peel off, and 12 hours in this comparative example. Although liquid leakage did not occur when left at room temperature, it was expected that the liquid content gradually permeated from the bubble-breaking portion over time.

It is an external appearance schematic diagram which shows the cylindrical paper container of an example of the paper container of this invention. It is an expanded sectional schematic diagram explaining an example of the laminated material which comprises the paper container of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Paper container 20 ... Laminate material 21 ... Thermoplastic resin layer 22 ... Paper layer 23, 24 ... Clay coat layer (inner surface) (outer surface)
25 ... Melt extruded resin layer 26 ... Barrier film layer 27 ... Sealant layer 28 ... Printing layer 29 ... Embossed part 30 ... Body member (side material) 33 ... Edge protection Tape 40 ... Lid material (top material) 44 ... Tab material 50 ... Bottom material (bottom material)

Claims (3)

At least in a paper container formed by molding a laminated material mainly comprising a paper base material obtained by laminating a paper layer and a sealant layer having a barrier film layer via a melt-extruded resin layer,
A paper container, wherein the paper layer on the sealant layer side of the laminated material is embossed in an uneven shape before lamination.   The paper container according to claim 1, wherein the surface of the paper layer of the laminated material on the sealant layer side is a clay coat layer.   The paper container according to claim 1 or 2, wherein at least the paper layer side resin of the melt-extruded resin layer of the laminated material is high-density polyethylene.

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