JPH0929868A - Paper container - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide a packaging material that has a good sealing property in a Gobel-top type paper container and does not affect the taste of the content. SOLUTION: As a liquid contact layer 8, an ethylene-α-olefin copolymer polymerized using a single site catalyst and a polyethylene 7 having a density of 0.925 or more and 0.965 or less are formed into a film by a coextrusion method, and the ethylene-α -Affix it to the paper container base material so that the olefin copolymer layer is in contact with the liquid.
The layer thickness ratio between the liquid contact layer and the polyethylene layer having a density of 0.925 or more and 0.965 or less is (1-5): 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Gobel top type paper container for packaging juices, liquid seasonings, sake, alcoholic beverages such as shochu, and the like. It is needless to say that liquid should not leak from any part of the sealed container, since liquid is the main content packed in such a paper container. For long-term storability of the product, there must be no air circulation, that is, airtightness is required. In that respect,
Due to the structure of the paper container, the parts that are apt to leak and impair the airtightness are the joint end part of the adhesive plate and the center seal part in the gobel (roof). In any case, it can be said that it should be particularly noted when the folded step seal portion of the material forming the container is reliably sealed with the molten resin.

In order to obtain a reliable sealing property in this way,
In the process of heating and press-bonding the inner surface resin, there are cases where the heating condition is strengthened, but in that case, the resin of the liquid contact layer is oxidized, and the oxidative odor is transferred to the contents to deteriorate the taste. Therefore, 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.

[0003]

2. Description of the Related Art Gobel top type and bricks
A paper container such as a mold is formed by using various laminated bodies in order to secure hermeticity, storability, rigidity, strength, etc. as a container. As a general specification, PE / paper / PE ( *),
There are specifications such as PE / paper / PE / Al / PET / PE (*), and the sealant PE (*) uses LDPE and MDPE (abbreviations are PE: polyethylene, LDPE: low density polyethylene, MD).
PE: Medium density polyethylene, Al: Aluminum foil, PET: Polyester, the same below}. As the PE of the sealant, high-pressure low-density polyethylene (LDPE) is often used because of its advantages such as processability when forming a laminated material and good heat-sealing property when molding a container. But LDPE
Since it contains a large amount of low molecular weight, part of the low molecular weight substance is eluted,
On the contrary, the taste changes due to the adsorption of the content components. Also MD
PE does not contain low molecular weight components such as LDPE, but the sealing temperature must be higher during box making. LDPE,
Since MDPE has a stable sealing property, the sealing temperature may be raised, but if it is sealed at a high temperature, the resin may oxidize and the taste of the contents may be adversely affected.

[0004]

[Problems to be Solved by the Invention] Mineral water,
As the innermost layer of a liquid paper container filled with various beverages such as juice, Japanese tea, black tea, coffee, liquor, shochu, etc., especially in the stable working conditions during box making, especially the step seal part and the center seal part have a tight sealing property. The obtained material composition provides less deterioration of the taste of the content.

[0005]

In view of the object of the present invention, as a result of earnest research, the present inventors have invented the following paper container. That is, a paper container which has no odor to the contents, is sensually good, and has a good filling and sealing property is as follows. That is, the ethylene-α-olefin copolymer polymerized using a single-site catalyst and a density of 0.925 or more, 0.965
It is a paper container which is made of a laminated material in which the following PE is formed by a coextrusion film forming method, and the ethylene-α / olefin copolymer layer is the innermost surface. Further, the ethylene-α / olefin copolymer layer and the density of 0.925 or more, 0.96
A paper container characterized in that a layer thickness ratio with a PE layer of 5 or less is (1 to 5): 1.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Liquor, shochu, etc. to be filled in a paper container are
It is a product that values a delicate flavor, and therefore the material of the container must not change the flavor of the sake, shochu, etc. In a paper container, in general, as described above, high-pressure low-density polyethylene is often used as the innermost layer, but as a characteristic of the high-pressure low-density polyethylene resin, it contains a low molecular weight component, It tends to have a bad influence on the flavor. It may impair the original flavor balance by adding an offensive odor to the contents or by adsorbing a certain component of the contents components.
As a countermeasure, medium- and low-pressure medium-high-density polyethylene may be used as the liquid contact layer, but in the case of the high-pressure process low-density polyethylene, the adverse effect caused by the low-molecular weight component is small. Since the temperature is high, the resin may oxidize, and the oxidized odor may transfer to the contents. Moreover, since the heat-melted resin has poor fluidity, the above-mentioned sealing property of the container step seal portion is apt to cause a problem.

FIG. 1 is a sectional view of a laminated material constituting a paper container which is an embodiment according to the present invention. Therefore, in the present invention, the ethylene-α-olefin copolymer 8 polymerized by using a single-site catalyst for the resin of the innermost liquid contact layer of the paper container 8
(Hereinafter referred to as S-PE), and polyethylene 7 having a density of 0.925 or more is laminated on the inner layer thereof. The S-PE8 of the innermost liquid contact layer according to the present invention has an extremely narrow molecular weight distribution, that is, since it has a small amount of low molecular weight substances, it has no odor transfer to the contents or selective adsorption of the components of the contents. . In addition, heat sealing is possible at low temperatures, and compared with conventional low density polyethylene, the range of heating conditions is wider, so stable work is possible (some heat fluctuations can be tolerated). However, it was found that when the liquid contact layer was composed only of S-PE, the taste was slightly changed, and the film-forming processability was poor and there was a practical problem.

The inventors of the present invention prepared liquid-contacting layers having various configurations and evaluated them from the viewpoints of box-making property and taste retention, and as a result, the liquid-contacting layer of the container was S-PE8, and the inside thereof was That is, it has been confirmed that a very desirable paper container can be obtained when PE (MDPE or HDPE) 7 having a density of 0.925 or more is laminated on the base material side. Further, in the case where the thickness ratio of S-PE8 to PE7 having a density of 0.925 or more is in the range of 1: 1 to 5: 1, S-PE can obtain particularly preferable results in a thick layer ratio. When the layer ratio is such that the thickness of S-PE is 1: 1 or less, the sealing property at low temperature becomes difficult, and the temperature is raised to seal the resin, so that the oxidative odor of the resin is not transferred. I'm worried. Further, if the thickness ratio of S-PE8 becomes thicker than 5: 1, the sealing property such as the center seal will deteriorate.

The sealant according to the present invention uses polyethylene (S-PE) polymerized with a single-site catalyst as a liquid contact layer and has a density of 0.
Laminates 925 or more PE (MDPE or HDPE), for example,
According to the coextrusion film forming method by inflation, a film satisfying the above conditions can be obtained at the same time. An example of actual film formation is shown below. Film-forming machine: MDPE / S-PE layer thickness ratio 1/2 Layer thickness 40 μm Die diameter 300 mmφ, Fold width 800 mm In the state of inflation bubbles, the S-PE layer was formed outside.

The method of manufacturing the paper container of the present invention will be described. PE ³⁰ / paper ^400g / EMAA ²⁰ as typical substrate composition
The liquid contact layer of the present invention is laminated on / Al ⁹ / Dl / PET ¹² , and PE is coated on the paper to a thickness of 30 μm, and a pattern is provided on the PE surface by gravure printing. Separately PET film 12
The above-mentioned printing 9
The paper surface of PE / paper subjected to the above and the aluminum surface 4 subjected to the dry lamination are sandwich-laminated with 30 μm of ethylene-methacrylic acid copolymer 3 (hereinafter referred to as EMAA). The liquid contact layer 8 is a two-layer coextruded film of MDPE 10 μm and S-PE 30 μm by the coextrusion inflation film forming method. Polyurethane-based on the PET side 5 of the laminated base material
The AC agent was applied, and the MDPE surface of the coextruded film was sandwich-laminated with LDPE.

A blank for 1.8 liters is punched out by forming a folding line and a hole for mounting a spout. As the end surface treatment, skive & hemming processing was performed, and a sleeve was made by a frame sealer.

The use of the paper container of the present invention is not particularly limited, but it is particularly suitable for drinks such as alcohol, shochu, wine, juice, milk, and seasonings such as soy sauce, mirin, dressing, and noodle soup. However, it can also be used as a paper container for chemical products such as detergents, oils, waxes, paints and adhesives, and the use of the paper container of the present invention is not limited to liquid.

[0013]

Example The following specifications were used as the constitution of the laminated material constituting the Goebeltop type liquid container, and the sealability and taste were evaluated. The materials are as follows: PE ³⁰ / paper ^400g / EMAA ²⁰ / Al ⁹ / Dl / PET ¹² / PE ²⁰ / PE film ⁴⁰ {Explanation of abbreviation PE: polyethylene EMAA: ethylene-methacrylic acid copolymer Al: aluminum foil PET: Polyester film} Here, the liquid contact layer is the PE film ⁴⁰ described above. The printed surface (front surface) is the opposite PE ³⁰ surface, and the PE film
^The difference of ⁴⁰ materials and compositions was evaluated. (The shoulder numbers of the materials, unless otherwise stated, indicate the thickness of μm.) In the examples and comparative examples, the same materials are used from the surface PE to PE ²⁰ for bonding PET and PE film. [Grade of material used as base material] PE / paper: 400 g / m ² base paper for milk carton, PE laminating product. PE: "Yukaron LK-30 (trade name of Mitsubishi Chemical Co., Ltd.) EMAA:" Nucrel 1180C (trade name of DuPont Mitsui Polychemical Co., Ltd.) "Al:" Toyo Aluminum Co., Ltd. "PET:" Polyester E-5100 " (Made by Toyobo Co., Ltd.
Product name) ”The composition of the liquid contact layer is as follows. (All films are formed by inflation method) LDPE, MDPE, S-PE (single layer) 40 μm LDPE / S-PE (multilayer) 40 μm Layer thickness ratio 1/3 MDPE / S-PE (multilayer) A 40 μm Layer thickness ratio 1/3 MDPE / S-PE (multilayer) B 40 μm Layer thickness ratio 1/4 HDPE / S-PE (multilayer) 40 μm Layer thickness ratio 1/3 [Grade of material used as wetted layer] LDPE: "Sumikasen F200 (manufactured by Sumitomo Chemical Co., Ltd.)" Density 0.923 MDPE: "Yukaron NK90 (manufactured by Mitsubishi Chemical Co., Ltd.) Density 0.931 HDPE:" Yukaron HY331 (manufactured by Mitsubishi Chemical Co., Ltd.) Name 0.951 S-PE: AFFINITY PF1140 (manufactured by Dow Chemical Co., Ltd.)
Product name ”Density 0.895

"Method of evaluating sealing property" (1) Sample preparation Each liquid contact layer is laminated on a base material, and a sleeve is prepared by printing, folding ruled lines, pouring out process, end face processing and frame sealer, and the inner volume is determined. A 1.8 liter Goebel top paper container was prepared and filled with sake using a filling machine. (2) Filling machine and its conditions A paper container size of 1.8 liters was filled with warm water at 65 ° C. The packing machine used was "General-purpose reclose cap-equipped Gobel top filling machine DR-10 (trade name, manufactured by DNK Co., Ltd.)". It was adhered and sealed by roasting with hot air and pressure cooling with a pressure plate embedded in a press pad. The pressurization conditions were constant at each temperature (25 kg / cm ² ), the hot air temperature was changed to make the box, and the sealability of the step seal part and the center seal part was checked by the seal check liquid. It was (3) Check the sealability with a seal check solution. 2A and 2B show the check position of the sealing property of the paper container of the present invention, FIG. 2A is a perspective view of the paper container, and FIG. 2B is a partially enlarged view thereof. Five SD steps for each sealed paper container
In order to check the center seal SC for leaks, the water inside the container was discarded, the seal check liquid was poured into each seal, and after leaving for 24 hours, the presence or absence of leak was confirmed. Seal check liquid: "Ageless check liquid (trade name of Mitsubishi Gas Chemical Co., Inc.)" The display of the judgment result of the level of sealing property is as follows depending on the position where the seal check liquid has reached (Fig. 2). The relationship between this evaluation result and the actual occurrence of leakage as a packaging container is as follows. X: Almost sealed, but there is a leakage of about a few percent at which the seal check liquid oozes out. △: There is no leakage in the static test, that is, the seal check, but there is concern about the degree of sealing in the cross-sectional confirmation of the seal portion (a degree of risk of leakage due to poor transport conditions and impact of strength) ○: It is a nearly perfect seal and will not leak unless it is an accident. A: Completely sealed. There is no leakage. (Result) LDPE specification ───────── High temperature is required for hermeticity. MDPE specification ───────── Seal temperature is stable at LDPE specification + 30 ℃ high temperature. LDPE / S-PE ──────── The sealing temperature is about the same as the LDPE specifications (below that, the stability is poor). MDPE / S-PEA ─────── LDPE specification is stable at -50 ℃. MDPE / S-PEB ─────── LDPE specification is stable at -50 ℃. HDPE / S-PE ──────── LDPE specification -50 ℃, stable.

[Method of taste evaluation] (1) Sample preparation A sleeve was prepared from a material obtained by laminating a liquid contact layer according to each test specification, and a Gabeltop-type paper container having an internal capacity of 1.8 l was prepared and filled with a filling machine at 65 ° C. Filled with sake. Each sample filled with the above sake was stored in a dark place at 20 ° C. for one month and then subjected to taste evaluation. The taste evaluation was performed by 15 trained panels according to the method of Japanese sake, and the deterioration of taste was indicated by the number of people in three grades, large, small, and nothing. (2) Taste evaluation results 15 panelists: Sensory evaluation results LDPE (single layer) ──────────── Great taste change MDPE (single layer) ──────────── Slight taste change S-PE (single layer) ── ────────── Taste changes slightly LDPE / S-PE (multilayer) ───────── Taste changes slightly MDPE / S-PE (multilayer) A ────── ──Good taste MDPE / S-PE (multilayer) B ──────── Good taste HDPE / S-PE (multilayer) ───────── Good taste

[0015]

As described above in detail, the paper container according to the present invention has the ethylene-α polymerized using a single-site catalyst.
-The olefin copolymer is used as the innermost layer, and the ethylene-α-olefin copolymer polymerized by using this single-site catalyst has a narrow molecular weight distribution and has a very low content of low molecular weight substances. In addition, there is almost no odor transfer to the contents, therefore it does not change the taste, and it is an excellent material as a liquid contact layer, and PE with a density of 0.925 or more and 0.965 or less is added to the base material side of the liquid contact layer. 315 ℃ for both center seal and step seal by installing
Stable conditions were obtained at about 20 to 20% compared to the comparative example.
Stable sealing is possible at a low temperature of 50 ° C, and there is no fear of resin oxidative odor due to heating. As described above, the low molecular weight component is small, and the synergistic effect of eliminating the odor of the resin odor to the contents and eliminating the adsorption of the contents components makes it widely available as a container for liquid products in which flavor is valued. It was

[Brief description of drawings]

FIG. 1 is a sectional view of a laminated material according to an embodiment of the present invention.

FIG. 2 is an enlarged schematic view of a center seal portion of the paper container of the present invention.

[Explanation of symbols]

1 Table PE 2 Paper 3 EMAA 4 Aluminum foil 5 PET 6 PE of sandwich laminate 7 PE layer with a density of 0.925 or more 8 Ethylene-α ・ polymerized by a single site catalyst
Olefin copolymer layer 9 Printing ink b Pressing screw SD Step seal part SC Center seal part

Claims (2)

[Claims] 1. An ethylene-α-olefin copolymer polymerized using a single-site catalyst and a density of 0.925 or more,
965 The following PE is used to form a film by a coextrusion film forming method, and a laminate is used in which the ethylene-α / olefin copolymer layer polymerized using the single site catalyst is the innermost surface. A paper container to do. 2. The layer thickness ratio between the ethylene-α-olefin copolymer layer and the PE layer having a density of 0.925 or more and 0.965 or less is (1-5): 1. Paper container.