JP2005271972A - Easy-to-open multi-layer container - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an easy-to-open multi-layer container which has a wide range of heat seal processing temperature, has a simple structure, withstands external impact force, and satisfies both the ability to be sealed with stable strength and the ability to easily be opened. <P>SOLUTION: The easy-to-open multi-layer container has a flange along the outer circumference of the opening of the container and is used by peeling a lid heat-sealed to the flange. In the course of peeling the lid, cohesion exfoliation starts within the sealed-face skin layer of the container. The skin layer preferably comprises a polyolefin resin composition containing (A) 50 to 83 wt.% of polypropylenes, (B) 10 to 35 wt.% of high density polyethylenes the density of which is not lower than 0.95 g/cm<SP>3</SP>and the melt flow rate of which is 10 to 100 g/10 min., (C) 5 to 15 wt.% of low density polyethylene, and (D) 2 to 10 wt.% of α-olefin copolymer the density of which is not higher than 0.90 g/cm<SP>3</SP>. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an easily openable multilayer container, and more particularly to an easily openable multilayer container in which peeling starts at a skin layer on a container-side sealing surface when a lid material is peeled off.

  With the diversification of eating habits in recent years, processed foods using various ingredients have come to be handled easily, and easy-open containers with excellent openability that can easily use these processed foods have been widely used. . Such an easy-open container is a seal that closes the lid to the container and seals the food stored in the container in a sealed manner, and at the same time allows the child to easily peel off the lid to ensure safe opening. Containers that are both compatible and easy to open are required.

  For easy-opening sealed containers, use lids made of the same material as the container body to optimize the sealing conditions, or use lids with special sealants on the seals, etc. Easy-opening is given by using the thing of the nature. However, the method based on the optimization of the sealing conditions makes it difficult to achieve both sufficient sealing strength and easy openability, and the optimal conditions are pinpoint, which tends to cause a sealing failure. In addition, when using an easily openable lid material, it requires a special process of co-extrusion to the lid material, so that the cost is high, and in order to fully exhibit the easy openability of the lid material, There are still problems such as the need to pay attention to the sealing conditions.

As another method for providing easy-openability, the container body is a multi-layer container having an easily peelable layer, and special processing such as notching the container instead of peeling at the sealing surface between the lid and the container body. And the method of giving easy-opening property by opening using the delamination of a container main body is also known (for example, refer patent documents 1-4). According to this method, at the time of sealing the lid member, it is only necessary to consider obtaining a sufficient sealing strength to ensure the sealing performance, the adjustment of the sealing conditions is easy, and the sealing failure can be prevented. . However, peeling by this method may complicate the structure between the seal layers and increase the cost.
Japanese Patent Laid-Open No. 62-251363 JP 63-78 JP-A 63-25037 JP 63-44467 A

  In view of the above-mentioned problems, the object of the present invention is to provide a wide range of heat-sealing temperatures, a simple structure, strong shocking external force, and stable strength. It is to provide a multilayer container.

  As a result of intensive studies to solve the above problems, the present inventors have provided a flange on the outer periphery of the container opening and peeled off the heat-sealed lid material to use the easily openable multilayer container. In this case, when the peeling of the lid material is started, the cohesive peeling starts in the sealing surface skin layer of the container, the heat sealing process temperature is wide, the structure is simple, the strength is stable, and both the sealing performance and the easy opening performance are compatible. It can be an easily openable multilayer container, and in particular, the sealing surface skin layer of the container is formed from a composition comprising polypropylene, a specific high density polyethylene, a low density polyethylene and a specific ethylene / α-olefin copolymer. As a result, it was found that the container can be easily obtained, thereby completing the present invention.

  That is, according to the first invention of the present invention, in the easily openable multilayer container in which the flange is provided on the outer periphery of the container opening, and the lid heat-sealed on the flange is used, the lid is peeled off. An easy-open multi-layer container is provided, characterized in that cohesive peeling sometimes starts within the sealing surface skin layer of the container.

According to the second invention of the present invention, in the first invention, the sealing surface skin layer of the container is made of a polyolefin composition containing the following (A) to (D). The easy-open multilayer container described in 1. is provided.
(A) Polypropylene 50 to 83% by weight
(B) High density polyethylene having a density of 0.95 g / cm ³ or more and a melt flow rate of 10 to 100 g / 10 min 10 to 35% by weight
(C) Low density polyethylene 5-15% by weight
(D) Ethylene / α-olefin copolymer having a density of 0.90 g / cm ³ or less 2 to 10% by weight

  According to a third aspect of the present invention, there is provided an easily openable multilayer container according to the first or second aspect, wherein the thickness of the sealing surface skin layer of the container is 10 to 150 μm.

  According to a fourth aspect of the present invention, in the first to third aspects of the invention, the easy-open multilayer container characterized in that the sealant layer of the lid is a polyethylene-based or polypropylene-based single-layer sealant. Is provided.

  According to the fifth invention of the present invention, in any one of the first to fourth inventions, the resin reservoir of the container inner seal edge is the resin of the container outer seal edge during the heat sealing of the lid material at the container flange portion. Provided is an easily openable multilayer container characterized in that heat sealing is performed so as to be larger than the pool.

  The easy-open multi-layer container of the present invention is excellent in pressure strength and peel strength by making a cohesive peeling in the sealing surface skin layer of the container by devising a heat sealing method with the surface resin layer, and easy Can be peeled off.

The easy-open multilayer container of the present invention is an easy-open multilayer container in which a flange is provided on the outer periphery of the container opening and the lid material heat-sealed on the flange is peeled off. One aspect thereof will be described with reference to FIGS. FIG. 1 is a cross-sectional view of an easily openable multi-layer container of the present invention, and FIG. 2 is an enlarged view of the periphery of the flange portion in FIG. 1 when the lid material is peeled off from the container. In the figure, 1 is a container body, 2 is a flange portion, 3 is an opening portion, 4 is a container sealing surface skin layer, 5 is a lid material, 6 is a lid material sealant layer, 7 is a non-seal portion, and 4a is peeling the lid material. It is the part of the container seal surface skin layer that adheres to the lid sealant layer side by cohesive peeling.
When the lid member 5 is peeled from the easily openable multilayer container body 1 of the present invention, the container seal surface skin layer is obtained by peeling the lid member 5 from the non-seal portion 7 previously provided on the flange portion 2 for peeling. Aggregation peeling starts in 4, and the lid 5 is peeled off so that 4 a adheres to the lid sealant layer 6. Such cohesive peeling within the container seal surface skin layer has the characteristics that the strength is stable and can be easily peeled compared to the interface peeling that occurs at the fusion interface between the sealing material of the lid and the container or the lid. .

  The easy-open multi-layer container of the present invention is one in which cohesive peeling occurs within the container seal surface skin layer as described above, and the lid material is easily peeled off. In order for the container seal surface skin layer to contain the following (A) polypropylene, (B) high density polyethylene, (C) low density polyethylene and (D) ethylene / α-olefin copolymer It is preferably formed from a composition.

(A) Polypropylene As the polypropylene (A) used for the container seal surface skin layer, homopolypropylene or a trace amount of ethylene random copolymer is preferable. The MFR of propylene is preferably 0.5 to 20 g / 10 minutes, and more preferably 1.0 to 10 g / 10 minutes. When the MFR is less than 0.5 g / 10 minutes, the seal surface is roughened. When the MFR exceeds 20 g / 10 minutes, the width uniformity of the skin layer is insufficient.
In addition, MFR of a polypropylene is a value measured based on JISK7210.

(B) High-density polyethylene (B) The high-density polyethylene used for the container seal surface skin layer has a density of 0.95 g / cm ³ or more and a melt flow rate (MFR) of 10 to 100 g / 10 minutes, preferably Is a high density polyethylene of 20-60 g / 10 min. If the density of the high-density polyethylene and the MFR are out of the above ranges, the unsealing strength increases, which is not preferable.
In addition, the density of a high density polyethylene is a value measured based on JISK6922-2, and MFR is a value measured based on JISK6922-2.

(C) Low density polyethylene (C) The low density polyethylene used for the container seal surface skin layer is not particularly limited, and is a conventionally known low density polyethylene.

(D) Ethylene / α-olefin copolymer The (D) ethylene / α-olefin copolymer used for the container seal face skin layer has a density of 0.90 g / cm ³ or less, preferably 0.89 to 0.003. This is an ethylene / α-olefin copolymer of 87 g / cm ³ . If the density is out of the above range, it is not preferable in terms of impact resistance.
The density of the ethylene / α-olefin copolymer is a value measured according to ASTM D-1505.

  Examples of the α-olefin of the ethylene / α-olefin copolymer (D) include α-olefins having 3 to 10 carbon atoms, such as propylene, butene-1, hexene-1, and octene-1. Specific examples of the ethylene / α-olefin copolymer include ethylene-propylene copolymer rubber and ethylene-hexene-1 copolymer.

The composition ratio of the components (A) to (D) is 50 to 83% by weight of the component (A), 10 to 35% by weight of the component (B), and 5 to 15% by weight of the component (C). And the component (D) is 2 to 10% by weight.
If each component is out of the above range, the peel strength becomes high, the drop resistance is inferior, and the container rigidity becomes low.

  The thickness of the container seal surface skin layer is not particularly limited, but is usually preferably 10 to 150 μm, more preferably 30 to 120 μm. If the thickness of the skin surface of the container seal surface is less than 10 μm, the peeling strength becomes extremely high due to the influence of the core layer inside the seal skin layer at the time of sealing, resulting in problems such as difficulty in opening. It becomes out of balance.

The resin constituting the container body is not particularly limited as long as it is a thermoplastic resin, but a polyolefin resin such as polypropylene and polyethylene is preferable.
Note that the container body is not limited to a single layer, and may be formed from other materials for the purpose of improving gas barrier properties and reducing deformation when used as a container between the skin layer and the outermost layer. A layer may be provided. Examples of the layer made of other materials include resin layers having excellent gas barrier properties such as transparent ethylene-vinyl alcohol copolymer (EVOH) and polyvinylidene chloride (PVDC). When these other layers are provided, the layers may be bonded with an adhesive layer made of an acid-modified polyolefin, an ethylene-propylene rubber-based transparent adhesive, an ethylene-vinyl acetate copolymer-based transparent adhesive, or the like. In addition, in applications that do not require transparency, a layer such as an aluminum vapor deposition layer, aluminum foil, aluminum, iron, copper, or the like excellent in gas barrier properties may be provided. The layer made of these other materials may be a single layer or a multilayer body composed of two or more layers. In applications where transparency is not required, inorganic fillers 10 to 80 are used. It may be a resin layer containing% by weight.

  The container-side molding of the easy-open multilayer container of the present invention can be obtained by coextrusion or laminating using the container body resin and the skin layer resin. Examples of the co-extrusion molding method include a method in which each material of the container main body layer and the skin layer is melt-extruded using different extruders, and this is laminated by a feed block and formed into a film by a flat die, A method of forming a film in a die using As the laminating process, for example, methods such as extrusion lamination, hot melt lamination, dry lamination, and wet lamination can be used.

  The multilayer laminate obtained as described above is melted by heating and shaped into a shape in which a flange is provided on the outer periphery of the container opening, and can be suitably obtained by ordinary vacuum forming, pressure forming or the like. It can also be obtained by molding by injection molding, injection blow molding, blow molding or the like using the resin material of each layer. The shape of the opening of the container is not particularly limited as long as the shape can accommodate the contents. For example, the shape may be cup-shaped or tray-shaped. Further, the shape of the flange portion at the peripheral edge portion of the opening is not particularly limited, but is usually a circle, a square or the like, and the lid member is heat-sealed on the peripheral edge portion.

  The resin constituting the lid material used for the easy-open multilayer container of the present invention is not particularly limited as long as it is a thermoplastic resin, but is preferably a polyolefin resin such as polypropylene or polyethylene, a polyethylene terephthalate resin, a polyamide resin, or the like. Even if it is a layer, the multilayer which consists of different resin may be sufficient.

  The lid material used for the easily openable multilayer container of the present invention is provided with a sealant layer on the side facing the container seal surface skin layer. As the lid sealant layer, there is no necessity to use a conventional co-pressing type easy peel sealant, and a single layer sealant of the same kind or similar resin excellent in thermal adhesiveness with the container seal surface skin layer is preferable. For example, polyethylene-based sealants such as linear low-density polyethylene containing metallocene and low-density polyethylene (this sealant is made of polypropylene, ethylene-propylene copolymer rubber (EPR) / ethylene-butene copolymer to control peel strength) Polypropylene rubber such as united rubber (EBR), adhesives, etc. may be included) or polypropylene mainly composed of homopolypropylene, block polypropylene, ethylene-propylene random copolymer, ethylene-propylene-butene terpolymer. A single-layer sealant of the type is preferable (in order to control peel strength, linear low density polyethylene or the like may be mixed). Moreover, 20-100 micrometers is preferable and, as for the thickness of a sealant layer, More preferably, it is 20-70 micrometers.

The easy-open multi-layer container of the present invention is such that a cover material having the above sealant layer is adhered to the flange portion of the container having the above skin layer so that the sealant layer side adheres to the skin layer, and a linear heat is applied using a seal bar. Sealed and manufactured.
Line heat sealing is illustrated in FIGS. FIG. 3 is a diagram showing the situation of the first stage of heat sealing, and FIG. 4 is a diagram showing the situation of the second stage of heat sealing. In the heat sealing, the sealant 6 on the lid 5 side melts and is pushed out to both sides by the sealing pressure of the seal bar 10 in the first stage (FIG. 3), and the resin reservoirs 11 and 12 grow on both seal edges. In the stage (FIG. 4), the double structure is formed by being pushed by the biting of the seal bar 10 and also melting the container skin layer 4 so as to sink into the sealants of the resin reservoirs 11 and 12 at both seal edges as 13 and 14. A resin reservoir is formed and fused.
At this time, heat sealing is performed so that the resin reservoirs 11 and 13 at the seal edge inside the container are larger than the resin reservoirs 12 and 14 outside the container, and the thickness (11 + 13) of the resin reservoir inside the container is preferably 30 μm or more. It is preferable to carry out. If the resin pool at the seal edge inside the container is smaller than that at the outside of the container, it will be difficult to open easily.
There is no particular limitation on the method of heat sealing so that the resin pool at the seal edge inside the container is larger than that at the outside of the container as described above. For example, the shape of the seal head of the seal bar is the container inside side of the container. This can be achieved by making the shape longer than the outer side.

  The easy-open multi-layer container of the present invention is excellent in sealing strength and can be easily opened, so that it can be used as a food container such as a dessert cup container, a pudding cup container, and a cooked rice container.

  Hereinafter, the present invention will be described more specifically with reference to examples of the present invention and comparative examples thereof, but the present invention is not limited to these examples. The evaluation methods and resins used in the examples are as follows.

1. Evaluation method (1) Pressure resistance test (puncture): Strength was measured when air was injected into a container at 1 L / min and pressurized and ruptured.
(2) 135 ° peel strength: A tensile test was conducted to peel the lid material from the container in the direction of 135 ° at a speed of 500 mm / min, and the strength when peeled was measured.
(3) Heat seal strength: A tensile test was performed to peel the lid material from the container at a speed of 300 mm / min in the 180 ° direction, and the strength when peeled was measured.
(4) Falling ball impact strength: A 3 kg iron ball was dropped from a height of 40 cm and dropped 3 times, and the sealing performance was maintained as ◯, and the sealing performance was not maintained as x.

2. Resin (1) Polypropylene (PP-1): Density 0.90 g / cm ³ , MFR 0.5 g / 10 min block copolymer (manufactured by Nippon Polychem Co., Ltd.) (for container body)
(2) Polypropylene (PP-2): homopolymer (95% isotactic ratio, density 0.90 g / cm ³ , MFR 2.2 g / 10 min homopolymer (manufactured by Nippon Polychem Co., Ltd.)
(3) Polypropylene (PP-3): Homopolymer with density of 0.91 g / cm ³ and MFR of 2 g / 10 min (manufactured by Nippon Polychem Co., Ltd.)
(4) High density polyethylene (HDPE): density 0.96 g / cm ³ , MFR 20 g / 10 min (manufactured by Nippon Polychem Co., Ltd.)
(5) Low density polyethylene (LDPE): density 0.92 g / cm ³ , MFR 4 g / 10 min (manufactured by Nippon Polychem Co., Ltd.)
(6) Linear low density polyethylene (M-LLDPE) by metallocene catalyst: density 0.88 g / cm ³ , MFR 2 g / 10 min (manufactured by Nippon Polychem Co., Ltd.)
(7) Ethylene-propylene copolymer rubber (EPR): density 0.88 g / cm ³ , MFR 2 g / 10 min (manufactured by JSR)
(8) Linear low density polyethylene (LLDPE-1): density 0.92 g / cm ³ , MFR 2.0 g / 10 min (manufactured by Nippon Polychem Co., Ltd.)
(9) Unstretched polypropylene film (CPP): (Showa Denko Product Co., Ltd.)
(10) Biaxially stretched polyethylene terephthalate film (PET): (Made by Unitika)
(11) Biaxially stretched nylon film (Ny): (Made by Unitika)

(Example 1)
PP-1 was used as the container body resin, the resin composition shown in Table 1 was used as the container skin layer resin, and two types and two layers of 0.8 mm sheets with a skin layer thickness of 80 μm were prepared. A round container having a diameter of 90 mm and a height of 25 mm was formed by vacuum forming using the above sheet.
Next, a laminated film made of polyethylene terephthalate (PET: 12 μm) and nylon (Ny: 15 μm) was used as a lid, and a 30 μm linear low-density polyethylene film was dry-laminated as a sealant on the Ny layer side.
The container was heat sealed using a ring-shaped heat seal bar with a sealing time of 1 second, a pressure of 2 kg / cm ² and a temperature of 170 ° C. to obtain an easily openable multilayer container. Table 1 shows the evaluation results of the obtained easily openable multilayer container.

(Example 2)
As the component (C) of the container skin layer resin composition, an easily openable multilayer container was obtained in the same manner as in Example 1 except that EPR was used instead of M-LLDPE. Table 1 shows the evaluation results of the obtained easily openable multilayer container.

(Example 3)
An easily openable container was obtained in the same manner as in Example 1 except that the ratio of the container skin layer resin composition was changed as shown in Table 1. Table 1 shows the evaluation results of the obtained easily openable multilayer container.

Example 4
An easily openable multilayer container was obtained in the same manner as in Example 1 except that PP-3 having a high crystallinity was used instead of PP-2 as the component (A) of the container skin layer resin composition. Table 1 shows the evaluation results of the obtained easily openable multilayer container.

(Example 5)
An easily openable multilayer container was obtained in the same manner as in Example 1 except that CPP was used instead of linear low density polyethylene (LLDPE) as the sealant layer of the lid. Table 1 shows the evaluation results of the obtained easily openable multilayer container.

(Comparative Example 1)
As the container skin layer, an easily openable multilayer container was obtained in the same manner as in Example 1 except that a resin composition consisting of only two components PP-2 and LDPE was used. Table 1 shows the evaluation results of the obtained easily openable multilayer container.

(Comparative Example 2)
An easy-open multilayer container was obtained in the same manner as in Example 1 except that a resin composition consisting of only two components PP-2 and LLDPE-1 was used as the container skin layer. Table 1 shows the evaluation results of the obtained easily openable multilayer container.

(Comparative Example 3)
As the container skin layer, an easily openable multilayer container was obtained in the same manner as in Example 1 except that a resin composition consisting of only three components PP-2, HDPE and LLDPE-1 was used. Table 1 shows the evaluation results of the obtained easily openable multilayer container.

(Comparative Example 4)
As the container skin layer, an easily openable multilayer container was obtained in the same manner as in Example 1 except that a resin composition consisting of only three components PP-2, HDPE, and LDPE was used. Table 1 shows the evaluation results of the obtained easily openable multilayer container.

  As is clear from Table 1, the easily openable multilayer container of the present invention was a container having excellent pressure strength and peel strength. On the other hand, if HDPE is not used as the container-side skin layer, the sealing strength is excessively low and practical sealability including impact with falling balls cannot be maintained (Comparative Example 1). If HDPE and LDPE are not used, the skin layer The ductility behavior remains and the seal strength becomes high and cannot be easily opened (Comparative Example 2). Even if the amount of HDPE is too small, the brittleness is insufficient and the heat seal strength is low and the practical sealability is not maintained (Comparison) Example 3) If the component (D) was not used, an excessive brittle behavior was exhibited and the container could not withstand a falling ball impact (Comparative Example 4).

  The easy-open multi-layer container of the present invention is excellent in pressure strength and peel strength by making a cohesive peeling in the sealing surface skin layer of the container by devising a heat sealing method with the surface resin layer, and easy And can be used as a food container such as a dessert cup container, a pudding cup container, and a cooked rice container.

It is sectional drawing of the easily openable multilayer container of this invention. It is an enlarged view of the flange part periphery in FIG. 1 at the time of peeling off a cover material from a container. It is a figure explaining the state of the 1st step of the heat seal of this invention. It is a figure explaining the state of the 2nd step of the heat seal of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Container body 2 Flange part 3 Opening part 4 Container skin layer 4a The part of the skin layer adhering to the cover material sealant layer side by cohesive peeling when the cover material is peeled 5 Cover material 6 Cover material sealant layer 7 Non-seal part 10 Seal Bar 11, 12, 13, 14 Resin pool

Claims (5)

  Flange is provided on the outer periphery of the container opening, and in an easily openable multilayer container that peels off and uses the lid material heat-sealed to the flange, peeling starts in the sealing surface skin layer of the container when the lid is peeled off An easily openable multilayer container characterized by that. The easily-openable multilayer container according to claim 1, wherein the seal surface skin layer of the container comprises a polyolefin composition containing the following (A) to (D).
(A) Polypropylene 50 to 83% by weight
(B) High density polyethylene having a density of 0.95 g / cm ³ or more and a melt flow rate of 10 to 100 g / 10 min 10 to 35% by weight
(C) Low density polyethylene 5-15% by weight
(D) Ethylene / α-olefin copolymer having a density of 0.90 g / cm ³ or less 2 to 10% by weight   The easily openable multilayer container according to claim 1 or 2, wherein the seal surface skin layer of the container has a thickness of 10 to 150 µm.   The easily openable multilayer container according to any one of claims 1 to 3, wherein the sealant layer of the lid is a polyethylene-based or polypropylene-based single layer sealant.   The heat sealing is performed so that the resin reservoir at the container inner seal edge is larger than the resin reservoir at the container outer seal edge when the lid member is heat sealed at the container flange portion. The easily openable multilayer container according to any one of the above.

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