JPH09187900A - Sheet vessel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the adverse influence to taste by forming a sealant layer of a three-layer extruded film made of ethylene-α-olefin copolymer polmerized by using single site catalyst. SOLUTION: Ethylene-α-olefin copolymer (S-PE) polymerized by using single site catalyst is used for a liquid contact layer. The S-PE is formed in a three- layer constitution, and dry laminated with a base material. The S-PE used for an inner surface layer 10 has melt index (MI) of 0.2 to 20 and density of 0.890 to 0.925, the S-PE used for an intermediate layer 9 has MI of 0.2 to 10 and density of 0.925 to 0.965, and the S-PE used for an outer layer 8 has MI of 0.2 to 20 and density of 0.890 to 0925. Thus, a vessel having excellent slipperiness and small odor transfer of resin odor to the content can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper container for packaging mineral water, juice, liquid seasonings or alcoholic beverages such as sake and shochu.

[0002]

2. Description of the Related Art Needless to say, as a paper container in which a liquid is a content, there must be no leakage of liquid from a sealed container. There should be no distribution. That is, airtightness is also required. In this respect, the structure where the paper container is liable to leak or lose airtightness is the joint end of the adhesive plate and the seal part, especially the center seal part of the gobel (roof) in the gobel top type container. is there. In each case,
It can be said that this is a point to be especially noted when reliably sealing the bent step portion of the material forming the container with the molten resin. In order to obtain a reliable sealing property as described above, there is a case where the heating condition is strengthened in the step of heating and press-bonding the inner surface resin, but in that case, the resin of the liquid contact layer is oxidized, Since the oxidative odor is transferred to the contents and the taste is deteriorated, it is difficult to set the sealing conditions and maintain stable operation, and it is necessary to carefully maintain the conditions. Therefore, as a material of the paper container, a material having a wide range of working conditions, particularly a material capable of obtaining hermeticity even at a low sealing temperature has been desired.

Paper containers of the Gobeltop type, brick type, etc. are formed by using various laminated bodies in order to secure the sealing property, storability, rigidity, strength, etc. of the container. General specifications are PE / paper / PE, PE / paper
There are / PE / AL / PET / PE, PE / paper / PE / SiO _x vapor deposition PET / PE, etc. LDPE and MDPE are used as PE for the sealant.
{Abbreviations, PE: polyethylene, LDPE: low-density polyethylene, MDPE: medium density polyethylene, AL: Aluminum foil, PET: polyester, SiO _x: silica}. Polyethylene (hereinafter referred to as PE) is often used as the sealant. High-pressure process low-density polyethylene (hereinafter referred to as LDPE) is most often used because of its advantages such as processability when forming a laminate and good heat-sealing properties when molding a container. is there. But LDPE
Since it contains a large amount of low molecular weight components, the taste is changed by elution of part of the low molecular weight components and conversely by adsorption of the content components. In addition, medium density polyethylene (hereinafter referred to as MDPE) is LDPE
Although the low molecular weight component is not included, it is necessary to raise the sealing temperature during box making. Sealing at high temperatures may oxidize the resin and adversely affect the taste of the contents.

[0004]

[Problems to be Solved by the Invention] Mineral water,
Provided is a paper container for emphasizing the taste of contents such as mugi tea, oolong tea, juice, and sake, which is made of a material capable of obtaining stable workability and sealing property without adversely affecting the taste.

[0005]

For the purpose of the present invention, it was possible to obtain the following paper container having good filling and sealing properties, content resistance and slipperiness. The paper container is as follows. That is, a paper container constituted by a laminate obtained by dry laminating a base material layer containing a paperboard and a sealant layer, wherein the sealant layer is formed from an ethylene-α-olefin copolymer polymerized by using a single-site catalyst. Which is a three-layer coextruded film, wherein the layer structure of the ethylene-α.olefin copolymer constituting the three-layer coextruded film is MI 0.2 to 20, single-site PE layer having a density of 0.890 to 0.925, and MI0. 2-10, single site PE layer with density 0.925-0.965, MI0.2-20, density 0.890-0.925
A single-site PE layer of 1 to 10 μm in the normal direction of the innermost surface of the paper container.
Including unevenness of m.

[0006]

FIG. 1 is a sectional view of an embodiment of a laminate constituting a paper container according to the present invention. Naturally, the material of the sealant layer in contact with the content directly affects the taste of the content, and the present inventors have found that the resin has good sealing suitability and does not contain a low molecular weight component, etc. Focusing on the ethylene-α-olefin copolymer (hereinafter referred to as S-PE) polymerized using a system catalyst, we decided to use it for the liquid contact layer. The S-PE is a good sealant that does not have an offensive odor when evaluated as a liquid contact layer, and has less selective absorption of contents components. , S-PE is laminated, the taste is slightly inferior, and it was not always possible to obtain a stable container in the sealing process. Therefore, the base material and the S-PE
It was found that by interposing a resin layer between the layers, it was easy to obtain the sealing property as a paper container, and an experiment was carried out by laminating various resins. As a result, in order to improve the sealing property, the S-PE has a three-layer structure and is dry-laminated with the base material, so that the sealing property and the taste retention of the contents are very good. Was confirmed.

The three-layer construction of the S-PE has good specifications for hermeticity and retention of the taste of the contents. As the S-PE used for the inner surface layer 10 of the container, the melt index ( (Hereinafter referred to as MI) 0.2 to 20, density 0.890 to 0.9
25 (hereinafter referred to as low density S-PE), S-PE used for the intermediate layer 9
As MI 0.2 to 10 and density 0.925 to 0.965 (hereinafter referred to as medium density S-PE), and the S-PE used for the outer layer 8 is the low density S-PE. By laminating the sealant having such a constitution with the base material, the fluidity of the heated sealant in the paper container molding step shows the suitability for more reliable sealing, and the sealing condition is the oxidation of the resin due to excessive heating. It was also found that the sealing condition was low. The medium-density S-PE used for the mid layer 9 stably exhibits the above-mentioned hermeticity, but if the density is 0.925 or less, it is difficult to obtain a complete hermeticity, and also in terms of maintaining the taste. , Shows a tendency of deterioration. Although S-PE having a density of 0.935 or more is not currently on the market, even if it is put on the market and used in the present invention, S-PE having a density of up to 0.965 does not pose a problem in the practice of the present invention.

The paper container of the present invention is formed by a laminated material obtained by dry-laminating a three-layer co-extruded film of S-PE, but the intermediate layer 9 of the three layers is formed into another layer, that is, an inner layer. 10. By using the copolymer having a density higher than that of the outer layer 8, the fluidity of the sealing resin in the carton molding process can be improved (the sealing resin can be easily moved) and the sealing property can be further improved. There was found. Further, the above-mentioned three layers can be formed into a film by coextrusion, and the film can be formed more stably and at a lower cost than laminating them individually. The method of three-layer coextrusion film formation is T
Either a die-casting method or an inflation method may be used.

As a method for laminating the sealant layer on the substrate, a method of directly coating the sealant layer on the substrate by an extruder, or a method of sandwich laminating or dry laminating a sealant formed by another method with polyethylene Etc. In the method of directly coating the sealant layer on the base material, since the extrusion processing temperature is high, the resin forming the sealant layer is easily oxidized and the taste of the contents is apt to give offensive odor. Even when a sealant film formed by another method is sandwich-laminated with polyethylene, since it is a sandwich laminate by the extrusion method, the extrusion processing temperature at the time of lamination is also high, and the above-mentioned oxidation to the contents due to an oxidative odor indirectly occurs. It tends to cause odor migration problems. In addition, a sufficient laminating strength cannot be obtained, and a peeling phenomenon may occur at the laminating interface. When the polyethylene is laminated by the dry lamination method instead of the sandwich lamination, there is no problem of the oxidative odor due to the resin extrusion processing temperature as in the above method.

As a method for laminating the obtained three-layer coextruded film, an experiment was conducted on the above-mentioned sandwich lamination and dry lamination with polyethylene, but in the former method, PE of the sandwich lamination was coated by the extrusion method. However, there was an indirect transfer of oxidative odor. With the latter method, there was no problem due to an offensive odor and stable sealing was possible. For dry lamination, the density is 0.890-0.
A dying process of 42 dyne (by the Dow method) was applied to the laminated surface of PE of 925, MI 0.2 to 20 by corona discharge.

When the surface treatment of the film by the corona discharge is performed, wrinkles are likely to occur at the time of making the roll when the sealant film (S-PE) is smooth in the wound state of the three-layer coextrusion film. This is because the slippage between the sealant film and the corona discharge treated surface is poor, in the usual film formation, a lubricant is added, but like the contents intended in the present invention, the taste When importance is attached to the above, it is desirable not to use the above-mentioned additive, because the taste may be deteriorated by the additive.
Further, the sealant film and the corona-treated laminated surface may be wound up and may block when stored for a long period of time. If the surface of S-PE has poor slipperiness, it may interfere with the attachment and detachment of the S-PE to and from the mandrel in a filling and packaging machine, even when the carton is formed. Therefore, as a result of various studies, the present inventors formed a fine unevenness on the sealant film (S-PE), and
It has been found that troubles due to blocking and slippage can be prevented at the time of forming a layered film, laminating, and carton molding.

The method of providing the unevenness is not limited to a particular method. For example, in the case of film formation by the T die casting method, a chill roll having an uneven surface may be used. In the case of inflation film formation, unevenness can be formed by mixing an inorganic substance such as shirasu balloon or micro silica into the resin. The measurement of the unevenness was performed by a three-dimensional surface roughness / contour shape measuring machine (manufactured by Nippon Denki Co., Ltd.) including the following examples. In this method, the surface of an object is three-dimensionally measured by a direct contact needle method. As for the unevenness provided by the present invention, when the height difference between the convex portion and the concave portion is 1 to 10 μm, slipping as a film is good and no blocking trouble occurs in the wound state as a film. When the unevenness is 1 μm or less, the effect is not so remarkable, and the unevenness of 10 μm or more may be provided, but the effect is not changed.

[0013]

EXAMPLE An example of material composition according to the present invention and a comparative example were prepared according to the following specifications and various evaluations were made. In the examples and the comparative examples, the substrates had the same specifications, and differences due to the sealant layer and the laminating method were evaluated. That is,
This is a modification of the structure below the mark. The front PE was prepared by the extrusion method. As the resin of the liquid contact layer, the superiority of S-PE to the taste was confirmed, so the same grade S-PE was used for each of the following specifications. Shoulder numbers indicate thickness μm (however, paper is g / m ² ). PE, PE and S-PE, S-PE are laminated by coextrusion, and PE-X is laminated by sandwich lamination. d indicates the density. Base material (common) PE ³⁰ / Paper ³⁵⁰ / EMAA ²⁰ / AL ⁹ / DL / PET ¹² Example 1 PE / Paper / EMAA / AL / DL / PET DL / S-PE ³⁰ / S-PE ³⁰ Example 2 PE / Paper / EMAA / AL / DL / PET DL / S-PE ¹⁵ / S-PE ¹⁵ /
S-PE ³⁰ (Flat) Example 3 PE / paper / EMAA / AL / DL / PET DL / S-PE ¹⁵ / S-PE ¹⁵ /
S-PE ³⁰ (7 μm concavo-convex processing) Comparative example 1 PE / paper / EMAA / AL / DL / PET PE-X ¹⁵ / PE ¹⁵ / S-PE ³⁰ Comparative example 2 PE / paper / EMAA / AL / DL / PET ・ PE-X ¹⁵ / S-PE ¹⁵ / S-PE
³⁰ Comparative Example 3 PE / paper / EMAA / AL / DL / PET · DL / PE- 15 / S-PE 15 / S-
PE ³⁰ Main resin grade used in Examples and Comparative Examples. PE: Mitsubishi Chemical LC500 (MI4.0 d 0.918) PE: Mitsubishi Chemical YK30 (MI4.0 d 0.920) S-PE: Dow Chemical AFFINITY PF1140 (MI1.6, d 0.895) S-PE: Dow Chemical AFFINITY PL1845 (MI3 .5, d 0.910) S-PE: The above PE was used for Dow Chemical AFFINITY HF1030 (MI2.5, d 0.935) PE-X (PE for sandwich laminating).

As a result of laminating the examples and comparative examples, wrinkles at the time of forming a three-layer coextruded film (flat) containing S-PE of the present invention, blocking at winding, and a packaging machine mandrel in a carton forming process. There were no specifications that were particularly problematic, except that the attachment / detachment to / from was a little bad. The matte surface of the inner layer of the example had no problem in desorption to the mandrel. The obtained laminated material was punched out as a blank of a predetermined shape of a 1.8 liter Gobeltop type container, the end portion was skived and hemmed, and a sleeve was prepared by a frame sealer. Taste deterioration test Regarding taste deterioration, a carton with a capacity of 1.8 liters was formed by a packaging machine, filled with mineral water heated to 80 ° C, and stored at room temperature (20 ° C) in a cool and dark place for 3 months.
A sensory test was conducted by 20 panelists. Regarding the filling and packaging machine, the DR-10
(Trade name of DNK Co., Ltd.) ”was used.
As a display of the sensory test results, the deterioration of taste was shown by the number of people in three-level evaluation of large, small, and nothing. The results are shown in Table 1. The results that showed good taste were the lamination method using dry lamination 7 rather than the sandwich lamination using polyethylene, and the specification using S-PE having a high density in the middle layer 9 of the sealant. It was The lamination method by dry lamination showed better results for taste than the sandwich lamination by polyethylene, and the specification using S-PE with a high density in the middle layer of the sealant showed better results for taste.

FIG. 2 is an explanatory view of a method for confirming the level of hermeticity at the top of the Goebel top container. The hermeticity depends on the hermeticity test method using a seal check solution. That is, a carton was formed from a laminate of each specification, mineral water heated to 80 ° C. was filled, and a hermetic seal was made. After 24 hours, the carton is cut horizontally at its body, the filled mineral water is discarded, the top and bottom of the carton are turned upside down, and a seal check solution is put inside to center the degree of leakage or seepage. The seal part SC and the step seal part SD were checked. The level of sealability can be determined by the level of penetration of the seal check liquid. When the seal check liquid permeates to the tip C-3 of the center seal portion SC or the tip B-3 of the step seal, the sealability is incomplete and C
It is a perfect seal if it stops at -1 or B-1 and does not penetrate further. Seal check liquid: “Ageless check liquid (trade name, manufactured by Mitsubishi Gas Chemical Co., Inc.)” The evaluation results of the sealability are shown in Table 2. Judgment level display × ───── Almost sealed, but there is a leak of about a few percent to the extent that the seal check liquid oozes out. △ ───── There is no leak in the static test, that is, seal check, but there is concern about the degree of sealing by checking the cross section of the seal part (there is a risk of leak due to poor transport conditions and impact of strength) Be done). ○ ───── It is a nearly perfect seal and will not leak unless there is an excessive accident. ◎ ───── Completely sealed. There is no leakage. (Below margin) As is clear from the results, S- with a density of 0.925 or more is formed in the intermediate layer.
The carton with PE was able to obtain a reliable hermeticity even when the sealing temperature was about 20 to 30 ° C lower than the specification with bottom density S-PE as the intermediate layer.

Since the sealant films of Experimental Examples 1 and 2 and Comparative Example 3 were flat-finished, slippage was difficult when winding up in the film forming process by the coextrusion method, and wrinkles were observed. In Experimental Example 3, due to the unevenness of the sealing surface, there was no hindrance to the winding at the time of film formation and the attachment / detachment to the mandrel at the time of molding the carton. In Comparative Example 1 and Comparative Example 2, the sandwich lamination method using polyethylene was used, and the film was not subjected to surface treatment, so that blocking during film formation was not observed.
In addition, when the carton was detached from the mandrel at the time of molding, some slippage defects were observed together with other examples in which the carton was not matted.

[0017]

EFFECTS OF THE INVENTION A paper container using a laminate in which a coextruded three-layer film of an ethylene-α-olefin copolymer polymerized using a single-site catalyst is used as a sealant layer and a substrate is dry laminated, and the inner layer surface is By providing irregularities of 1 to 10 μm, the slipperiness is good, the ethylene-α-olefin copolymer has a narrow molecular weight distribution, and the content of low molecular weight substances is small. It was possible to make a container with little odor. Further, the ethylene-α / olefin copolymer has excellent low-temperature sealability, and since sealing work can be performed at low temperatures, resin oxidation odor due to overheating during sealing, which has been a problem in the past, is transferred to the contents. The odor is gone. By making the intermediate layer of the three-layer coextrusion film of the sealant a high-density S-PE, adsorption of content components was reduced, and the container had little change in taste.
Furthermore, by making the PE on the laminate side a low-density S-PE, the filling of the center seal part SC in the sealing step becomes more stable. That is, the low-density S-PE improves the movement of the sealing resin and contributes to the sealing property. Furthermore, the coextrusion 3
By laminating the layer film and the base material by dry laminating 7, taste and contents resistance are improved, and stable laminating strength is obtained. By providing unevenness of 1 to 10 μm on the surface of the ethylene-α-olefin copolymer layer of the three-layer coextruded film, it is possible to prevent blocking during film winding when forming the three-layer film, A wrinkle-free film is obtained, and the slipperiness in a carton is also improved. As described above, the paper container of the present invention is made of a material that does not affect the change in the taste of the contents that value the flavor and has excellent properties in mechanical suitability in laminating and filling and packaging machines. is there. Further, the present invention shows the above-mentioned effects when used not only in the Gobel-top type paper container but also in other forms such as brick type.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an embodiment of a laminated body constituting a paper container according to the present invention.

FIG. 2 is an explanatory diagram of a method for confirming the level of hermeticity.

[Description of sign]

 1 Paper 2 Surface PE 3 Sandwich Lamination Layer 4 Aluminum Foil 5 Dry Lamination Layer 6 Polyester Film 7 Dry Lamination Layer 8 Density 0.890 to 0.925, MI 0.2 to 20 S-PE Layer 9 Density 0.925 or More, MI 0.2 to 10 S-PE layer 10 S-PE layer with a density of 0.890 to 0.925 and MI 0.2 to 20 P printing SC Center seal part SD Step seal part B Pressing mark by press pad C-1 to C-3 Standard of bleeding degree of seal check

Claims (3)

[Claims] 1. A paper container composed of a laminate in which a base material layer containing a paperboard and a sealant layer are dry-laminated, wherein the sealant layer is polymerized by using a single-site catalyst. A paper container characterized by being a three-layer coextruded film made of a polymer. 2. The layer-constituting resin of the ethylene-α.olefin copolymer constituting the three-layer co-extruded film is MI 0.2 to 20, density 0.890 to 0.925, MI 0.2 to 10,
Density 0.925 to 0.965, MI0.2 to 20, Density 0.890 to 0.925
The paper container according to claim 1, wherein the paper container is configured in the order of. 3. The innermost resin is 1 to 10 in the direction normal to the surface of the resin.
The paper container according to claim 1, wherein the paper container is provided with irregularities of μm.