KR100433806B1 - A packaging container intended for the cold storage of liquid foods in ice or water - Google Patents

Abstract

The present invention relates to packaging containers in packaging laminates that retain shape stability and gripping strength even when stored in ice, water or high humidity and their use for the storage of liquid food in refrigerated media containing liquids. The packaging stack 10 is composed of a liquid-absorbing core layer 11 of fiber and an outer plastic film layer 12 selected from the group consisting of polypropylene, HDPE and polyester. In addition, the plastic layer is preferably a biaxially oriented film. Inside the center layer an additional stability-enhancing layer 16 is formed, for example of aluminum foil. Maintaining excellent gripping stability of packaging containers made from the packaging laminates described in accordance with the drawings is that the outer layer of this packaging container has, firstly, improved liquid barrier properties, secondly a thicker thickness, and thirdly the above-described type of packaging It is considered that the elements of high material strength in a conventionally used outer layer in the container are combined. Furthermore, the I-beam effect, which appears as a result of the interaction between the rigid stability-enhancing layer 16 inside the central layer and the plastic film layer 12 with the outer strength, intersects with the intermediate liquid-absorbing central layer 11 ( I-beam effect contributes to maintaining its shape stability and gripping stability even in a humid environment.

Description

PACKAGING CONTAINER INTENDED FOR THE COLD STORAGE OF LIQUID FOODS IN ICE OR WATER}

In the field of packaging, packages with disposable properties (so-called disposable packages) have long been used for the packaging and transportation of liquid foods.

Most packaging materials for such disposable packages consist of a central layer of paper or cardboard and an outer layer, which is a liquid-tight layer of polyethylene, typically low density polyethylene (LDPE).

The composition of the packaging material is to provide the best protection for the packaged product and to facilitate the manufacture and handling of the packaged product. When using a paper or cardboard center layer, the mechanical shape stability of the package is good, allowing the package to be distributed and handled in a simple and reasonable manner. The liquid-tight layer, the outer layer of polyethylene, protects the central layer against moisture and liquids.

Depending on the storage time and the product to be packaged, the packaging material may include various different metal or plastic layers that are barrier to light or gas (eg oxygen gas).

These containers are often manufactured by adhering the longitudinal edges of the web of packaging material to each other in a tubular shape. After manufacturing the tubular shape, the tubing is filled with the desired contents and then narrowly transversely. As a result, the tubes are sealed along a sealing zone with a predetermined distance from each other. Subsequently, the sealing portion of the tube containing the contents is separated from the tube by cutting in the sealing region described above, and then folded into an arbitrary geometric shape according to the set direction of the sealing coupling portion or the seam.

Since the above-mentioned packaging containers are not usually exposed to extremely wet or humid conditions, it is sometimes sufficient to coat the central layer with a single layer of LDPE on each side. However, climatic conditions in countries around the world may require refrigeration during transportation or storage, while at the same time access to refrigerated transportation and refrigeration facilities may be restricted in some areas. Therefore, it is common for food to be cooled with ice in boxes or carriers insulated. Over time, the ice melts, and the refrigerant gradually consists of ice and water, and only water remains. At this time, the packaging container of the above type is absorbed by the water at the exposed cutting edge of the center layer (which imparts shape stability and rigidity to the packaging container) after a certain storage time has elapsed. As a result, it has been found that the shape stability is lost, so-called grip rigidity properties. For example, when stored for a long time in an environment with high relative humidity, such as 80 to 100% RH, the fiber in the center layer absorbs moisture, resulting in poor stability of the packaging container.

The present invention provides excellent storage stability upon storage in a storage medium containing liquid, with a plastic layer attached to the outside of the packaging container and made from a laminated packaging material comprising a core layer of fibrous material. It relates to a packaging container having. Moreover, the present invention relates to the use of this packaging container for the storage of liquid food in frozen storage media containing liquids.

Preferred embodiments of the present invention will be described in more detail below with reference to the accompanying drawings.

1 is a schematic view of a preferred packaging material according to the present invention.

2A and 2B are graphs showing changes in flexural strength and water content over time when the packaging material is stored in water at 5 ° C. in the packaging container made of the packaging material of FIG. 1.

3A and 3C are graphs showing changes in flexural strength and water content, respectively, over time when the packaging material is stored at a high relative humidity, such as 80 to 100% RH, in the packaging container made of the packaging material of FIG. 1;

However, the present invention is described in detail through the embodiments illustrated and illustrated in FIG. 1, but various other changes and modifications may be made without departing from the concept of the invention as defined in the claims. It should be noted that the present will be apparent to those skilled in the art.

Accordingly, it is an object of the present invention to realize a novel packaging container which is free from defects of a packaging container of a type which is closely related to the above-described prior art.

Another object of the present invention is to realize a packaging container of the above-described packaging container having excellent storage stability even when stored in a refrigeration medium containing liquid, for example, maintaining shape stability and grip strength almost completely even after long-term storage. have.

It is still another object of the present invention to provide a packaging container that maintains excellent shape stability and excellent grip strength almost completely even after long-term storage, even when stored in a relative humidity of 80% to 100% RH (relative humidity) in the above-described packaging container. In realizing it.

The above objects of the invention are achieved by a packaging container having the characteristics as specified in the characterizing clause of claim 1 of the claims of the invention. Preferred embodiments of the packaging container according to the present invention have the features specified in the dependent claims of the claims of the present invention.

By coating the core layer with a thicker, more rigid layer of plastic selected from the group consisting of polypropylene, high density polyethylene (HDPE) and polyester instead of LDPE, liquid and moisture do not penetrate into the core layer. This layer of polypropylene, HDPE or polyester described above is excellent in strength and at the same time contributes to this laminated packaging material and imparts improved strength as well.

The plastic layer is preferably made of oriented polypropylene, oriented HDPE or oriented polyester, and in particular according to one preferred embodiment of the invention biaxially oriented polypropylene, biaxially oriented HDPE or biaxially oriented It is preferable that it is made of polyester. The type of polymer is selected to have a suitable layer thickness and to have strength and moisture shielding so that the packaging can be stored in the liquid without losing its shape stability and gripping stability significantly.

Preferably, a film of oriented or biaxially oriented polypropylene, HDPE or polyester is laminated to the central layer via, for example, an interlayer extrudate of thin thickness of polyethylene.

Depending on the storage time and the packaged product, the packaging material often further comprises a layer which is, for example, gas barrier or light barrier to oxygen gas. Typically, this layer is formed on the center layer toward the inner wall of the packaging container, but may be formed on the opposite side. This barrier layer is a metal film such as aluminum foil or silicon oxide (SiOx, where x is 1.5 to 2.2) deposited on a plastic layer of oriented polypropylene, HDPE or oriented polyester, or the like. It may consist of metal oxides, such as these. In addition, the gas barrier layer may be composed of a plastic layer made of a polymer having excellent gas barrier properties such as ethyl vinyl alcohol (EVOH) or polyvinyl alcohol (PVAL).

In order to protect moisture and liquid from penetrating the packaging, cutting edges generated outside the packaging material of the packaging can be protected from exposure to moisture. This protection is possible by applying or impregnating the cutting edge with a mechanical or chemical water-repellent agent by methods known per se. For example, the cut edges may be covered with a plastic strip by laminating or attaching and fixing the plastic strips to the packaging material around each cut edge, or the cut edges may be impregnated with a hydrophobic liquid substance such as oil or fat. The cut edges at the overlapping joints may also be folded under the overlapping packaging so that they are not exposed to ambient moisture or liquid.

1 is a schematic view showing one example of a packaging material according to the present invention indicated by reference numeral 10. This laminated packaging material has a liquid-absorbing central layer 11 of paper or cardboard, for example, of the quality of a conventional packaging material. A plastic film layer 12 made of biaxially oriented polypropylene (BOPP) is disposed in the center layer inwardly toward the inside of the packaging container.

In the packaging material 10 according to the present invention, the plastic film layer 12 may be laminated to the liquid-absorbing center layer 11 via a thin extruded plastic layer 13 made of polyethylene, for example. The plastic film layer 12 made of BOPP is suitably coated on both sides, for example, with thin layers 14 and 15 made of an adhesion promoting polymer or a heat sealable polymer.

In the finished packaging, an additional stability-enhancing layer 16 is introduced on the inner side of the central layer, which has an excellent gas barrier property. The stability-enhancing layer 16 may be made of a metal such as aluminum foil, for example. This stability-enhancing layer 16 of aluminum foil is preferably laminated to the liquid-absorbing central layer 11 via, for example, a thin plastic extrusion layer 17 of polyethylene. In order to ensure that the package does not come into direct contact with the metal (which should be avoided in the case of food packaging), the stability-enhancing layer 16 of aluminum inside the container is suitably provided with a heat-sealing plastic layer 18 of polyethylene, for example. Bonding coating.

2A and 2B and 3A and 3B, respectively, for the storage of the type described with reference to FIG. 1 for storage in water at 5 ° C. and storage under high relative humidity of 5 ° C. and 80-100% RH, respectively. Test was made.

In the packaging material tested in Figs. 2 and 3, the plastic film layer 12 was approximately 18 in thickness by bonding and coating the thin layers 14 and 15 having a thickness of 0.6 to 0.7 mu m of adhesion promoting and heat sealable polymers on both sides. It is made of a BOPP film of μm. The plastic film layer 12 was laminated on the liquid-absorbing center layer 11 via a low density polyethylene (LDPE) extruded film of about 12 mu m, and in the same manner, an aluminum foil of about 25 mu m was formed on the other side of the center layer. Lamination is carried out through an LDPE film. On the other side facing the inside of the packaging container, the stability-enhancing layer 16 made of aluminum foil is bonded and coated with an LDPE layer 18 of about 35 mu m. The liquid-absorbing center layer 11 is, for example, a type of what is known as a paperboard for liquids and is made of packaging quality paper having a strength of 80 mN.

The packaging material 10 used for the test was compared with the conventional packaging material without the plastic film layer 12 as having the same configuration as the packaging material 10. In the conventional packaging material, the center layer was coated with an extruded film of low-density polyethylene (LDPE) of 12 mu m on the side facing the outer side of the packaging container.

Tetra Brik made from packaging A storage test was performed for 12 days on a parallel hexagonal packaging container of 250 ml volume of the type. For each test, measurements were taken after 1, 2, 5 and 12 days for 15 sample packages.

Flexural strength was measured according to SCANP 29:84 using a test instrument (Lorentzon Weltre brand, code 16). The values of the flexural strength GM in the figures are in part the machine direction, ie the machine direction (MD) and in part the geometric mean values of the flexural strengths measured in the cross direction (CD), ie to be.

As apparent from Figs. 2a and 3a, the flexural strength of the packaging material 10 according to the present invention is fully maintained and good when stored for 12 days under water and high humidity, respectively, while the flexural strength of the conventional packaging material corresponding thereto is After storage in water, it decreased about 20% after 1 day and about 30% after 12 days, and decreased about 10% after 12 days when stored under high humidity.

Moreover, as is apparent from FIGS. 2B and 3B, the moisture content of the packaging material in the same storage test is increased in both the packaging material of the present invention and the conventional packaging material, but it can be seen that the packaging material of the present invention has much less moisture content. .

The strength of the paper material in the center layer is much higher than that of the LDPE layer, since the LDPE layer does not contribute significantly to the overall strength of the packaging.

The strength of the packaging material of the core layer decreases with increasing water content, and thus the overall strength of the packaging material also decreases.

On the one hand, in the longitudinal direction (MD) and in the transverse direction (CD), both have strength, and on the other hand, when laminating to the center layer an outer layer of plastic material having a lower moisture permeability than a conventional outer layer of polyethylene, Is much stronger and is much more stable under extreme wet conditions.

Furthermore, in the packaging 10 used for the test, the I-beam effect between the rigid outer plastic film layer 12 and the stability-enhancing layer 16 of the metal foil inside the center layer was obtained. ) The shape of the wet (or wet) core layer is compensated for by the strength of the two layers 12, 16 around it. The reason for this is that the I-beam effect increases as the thickness of the center layer increases because the fiber swells when absorbed by the water and the distance between the two firm layers increases. Thus, this effect contributes to keeping the packaging material in its original strength in water and under high humidity.

Other tests have also shown that the grip rigidity of packaging containers of packaging 10 is maintained after several days of storage in water, whereas conventional packages lose their holding strength and become loose.

The packaging container manufactured by the packaging laminate described with reference to FIG. 1 maintains excellent gripping stability. First, the outer layer of the packaging container has better liquid barrier property, secondly, a thicker thickness, and thirdly, It is believed that this is because these factors, which have a much higher material strength than conventionally used outer layers in a packaging container of the type, act in combination.

Preferably, the outer plastic film layer selected from the group consisting of polypropylene, HDPE and polyester has a thickness of 10 μm or more, and the E-modulus in both the longitudinal and transverse directions is 1000 MPa. It has the above conditions together.

According to one preferred embodiment, the outer plastic film layer has a thickness of 15 μm or more, and the E-modulus in the longitudinal direction and the transverse direction is all 2000 MPa or more.

According to a further preferred embodiment, the E-modulus in the longitudinal and transverse directions of the outer plastic film layer is 3000 MPa or more, respectively.

A significant contribution to the maintenance of good gripping stability is that the outer layer of strength interacts with the layer of strength on the other side of the center layer (in this case, aluminum foil) to produce an I-beam effect with the middle layer located in the middle. To indicate.

As is apparent from the above description, the present invention is suitable for refrigeration in water or ice, like plastic or metal packaging containers, and can be stored under high relative humidity, such as 80-100% RH, even after long-term storage. Packaging containers that do not lose excellent shape stability and gripping strength are realized.

Claims (14)

As a formally stable laminated packaging material 10 for packaging containers having excellent storage stability upon storage in a liquid-containing storage medium, A liquid-absorbing central layer 11 of paper or paperboard; And an oriented plastic film layer (12) in direct contact with a storage medium containing liquid during storage of the packaging, which is present on the first side of this central layer. The oriented plastic film layer so that the packaging made of the packaging material by the I-beam effect can have excellent gripping strength and shape stability even after long term storage in the liquid-containing storage medium. 12) and have a stability-enhancing layer (16) disposed therein and introduced on the second side of the central layer; Said plastic film layer (12) is characterized in that it comprises a layer made of oriented polypropylene, oriented HDPE or oriented polyester, lamination packaging material (10) for packaging containers. delete The laminate packaging according to claim 1, wherein the plastic film layer (12) of polypropylene, HDPE or polyester is biaxially oriented. 2. Laminated packaging according to claim 1, characterized in that the stability-enhancing layer (16) on the second side of the liquid-absorbing central layer (11) consists of a stability-enhancing film of oriented plastic. The laminated packaging material of claim 1, comprising a gas barrier layer. 6. Laminated packaging according to claim 5, characterized in that the gas barrier layer forms a stability-enhancing layer (16) on the second side of the liquid-absorbing central layer (11). The laminated packaging material according to claim 5 or 6, wherein the gas barrier layer is made of a metal layer. The laminated packaging material according to claim 1, wherein the stability-enhancing layer (16) consists of aluminum foil. A packaging container made from the laminated packaging material according to claim 1, 4 or 8 for storage in a liquid-containing storage medium. The packaging container according to claim 9, wherein a cutting edge that can be formed on the outside of the packaging container is protected from being exposed to moisture. The packaging container according to claim 9, wherein the cutting edge is mechanically protected by folding under an overlapping packaging material or coating with a protective plastic strip. The packaging container according to claim 9, wherein the cutting edge is chemically protected by impregnation with a hydrophobic liquid substance. 13. A packaging container according to any one of claims 9 to 12, which is useful for use in the storage of liquid food in liquid-containing refrigeration media. The packaging container according to claim 13, wherein the liquid-containing refrigeration medium is a mixture of ice and water.