CN1070449C - A packaging container intended for the cold storage of liquid foods in ice or water - Google Patents

Abstract

The invention discloses a packaging container made of laminated packaging material, which can be stored under conditions of ice, water or relatively high air humidity, maintain the stability of the container shape and clamping hardness, and be used in Liquid foods are preserved in refrigerated storage media containing liquids. A laminated packaging material (10) comprising a fibrous core layer (11) and an outer layer (12), the outer layer (12) being a plastic layer selected from the group consisting of polypropylene, high density polyethylene and polyester . Preferably, said plastic layer is a biaxial film. An additional stability-increasing layer (16), such as aluminum foil, is provided on the inner side of the core layer. Packaging containers constructed of packaging layers as shown in the drawings maintain good gripping stability, which is due to a combination of factors, among them, compared to the outer layer of packaging containers of the above-mentioned type used in the prior art , The outer layer of the packaging container of the present invention firstly has improved liquid barrier properties, secondly has a larger thickness, and thirdly has higher material hardness. In addition, the rigid layer (12) outside the core layer and the rigid layer (16) inside the core layer cooperate with each other with the core layer (11) in between to create an I-beam effect, which is helpful in high humidity conditions. Maintains shape and gripping stability of packaging containers under ambient conditions.

Description

Packaging containers for freezing and storing liquid food in ice or water and laminated packaging materials therefor

The invention relates to a packaging container which has good storage stability during storage in a storage medium comprising a liquid. The packaging container is made of a laminated packaging material comprising a core layer of fibrous material, on the outer side of which a plastic layer is provided for the packaging container. In particular, the present invention relates to the storage of liquid food in a refrigerated storage medium with a liquid using a packaging container.

In the packaging industry, single-use packaging containers have been used for packaging and delivering liquid food products for a long time.

Packaging materials used in the manufacture of single-use packaging containers in many varieties comprise a core layer of paper or paperboard and an outer, liquid-tight layer of polyethylene, usually low density polyethylene (LDPE).

The structure of this packaging material is required to enable the packaged product to have the best protection performance. At the same time, packaging products are also required to facilitate production and handling. A core layer of paper or cardboard imparts good mechanical stability to the packaging. Thus, the packages can be transported or handled in a simple and rational manner. The outer, polyethylene liquid-tight cover protects the core from absorbing moisture and liquids.

Depending on the storage time and the product to be packaged, the packaging material may comprise a metal layer or a plastic layer with barrier properties, meaning that it is able to isolate light or gases, such as oxygen.

Typically, such packaging containers are made from sheet-like packaging material by interconnecting longitudinal edges of the sheet-like packaging material to form a tubular body. The tubular body is then filled with the desired contents and sealed along narrow, laterally spaced sealing regions. Thus, a tubular body comprising a hermetically closed portion of the contents is formed. The tubular body is then separated by means of a cutting device in the aforementioned sealing area. The packaging container is then shaped by folding the tubular body into a selected geometry, depending on the position of the sealed joint or sealing line.

Usually, the above-mentioned packaging containers are not stored for a long time under conditions of relatively high humidity. Therefore, it is usually sufficient to cover a layer of low-density polyethylene (LDPE) on both sides of the packaging core layer. However, in many countries, climatic reasons require the product to be refrigerated during transport and storage. At the same time, the use of refrigerated conveyors or refrigerated storage is limited in some areas. Thereby, usually put into ice cube cooling food in packing box or the housing that is made by heat-insulating material. Over time, the ice melts, turning the coolant into a mixture of ice and water, eventually becoming water entirely. It has been found that after a certain storage time, packaging containers of the above-mentioned type lose their shape stability and the so-called clamping hardness, because the core layer (which determines the shape stability and rigidity of the packaging container) cuts the edge outwards. Exposed, absorbs moisture, softens the core, and creeps. Under conditions of relatively high humidity, such as 80-100% RH, long-term storage will also cause the fibers in the core layer to absorb moisture, thereby deteriorating the stability of the packaging container.

It is an object of the present invention to provide a packaging laminate of packaging containers which is new relative to the type mentioned in the introduction, so that packaging containers of this type do not have the inherent disadvantages closely associated with packaging containers of the prior art.

Another object of the present invention is to provide a packaging laminate of the above-mentioned type of packaging container, which has good storage stability during storage in refrigerated storage media containing liquids, and which packaging container is completely stable even during long-term storage. Maintain its excellent shape stability and clamping hardness.

Yet another object of the present invention is to provide a packaging container of the above-mentioned type, which is stored under relatively high humidity conditions, such as ambient conditions of the order of 80-100% RH, which almost completely retains its properties even during long-term storage. Excellent shape stability and clamping hardness.

The present invention proposes a laminated packaging material for dimensionally stable packaging containers having good storage stability in storage media containing liquids, said packaging material comprising a liquid-absorbent core of paper or cardboard and an in-core A plastic layer on the first side of the layer for storage media that is in direct contact with liquids during storage in the packaging container is characterized in that the packaging material is a layer applied on the second side of the core layer in order to enhance the gripping hardness, By virtue of the so-called I-beam effect, this layer and the plastic layer are arranged to ensure good gripping stiffness and shape stability in packaging containers produced from the packaging material, even during long-term storage of the packaging containers in storage media containing liquids sex.

The invention also consists in proposing a packaging container for storing storage media containing liquids, characterized in that it is produced from the above-mentioned laminate packaging.

The core layer is covered with a thicker and harder plastic layer selected from the group consisting of polypropylene, high-density polyethylene (HDPE) and polyester, instead of low-density polyethylene (LDPE) to obtain comparative Good performance, that is, preventing liquid and moisture from penetrating the core layer. At the same time, since the above-mentioned polypropylene, high-density polyethylene, and polyester layers have good stiffness, the stiffness properties of the laminated packaging material as a whole are improved.

Preferably, the plastic layer is made of oriented polypropylene, oriented high-density polyethylene or oriented polyester, and according to a preferred embodiment of the present invention, the plastic layer is made of biaxial polypropylene, biaxial high-density polyethylene or Biaxial polyester construction. Combining the hardness and moisture barrier properties of the above-mentioned polymers, the appropriate thickness of the polymer layer is selected so that the packaging container will not lose its shape stability and clamping hardness when it is stored in liquid.

Preferably, an oriented or biaxial film of polypropylene, high density polyethylene or polyester is laminated to the core layer by extruding an intermediate thin laminate, such as polyethylene.

Depending on the storage time and the product to be packaged, the packaging material usually includes additional layers which have light barrier properties or gas barrier properties, eg oxygen barrier. Such a barrier layer is usually arranged on the side of the core layer facing the interior of the packaging container. However, it is also possible to arrange the separation layer on the other side of the core layer. Such an isolation layer may consist of a metal layer, for example aluminum foil or a thin metal layer or metal oxide, such as silicon oxide (SiO _x , where x is 1.5-2.2), arranged on oriented polypropylene, high density Polyethylene or polyester plastic layer. In addition, the gas barrier layer may consist of a plastic layer comprising a polymer with good gas barrier properties, such as ethyl vinyl alcohol (EVOH) or polyvinyl alcohol (PVAL).

To further protect the packaging container from moisture or liquid penetration, the cut edge, if any, on the outside of the packaging material of the packaging container can be prevented from being exposed to water. This protection can be achieved in known ways, namely by mechanical covering or by impregnating the edges of the cut packaging material with a chemical water repellent. For example, covering the cut edges of the packaging material with strips of plastic that are laminated or glued to the packaging material at each cut edge, or a hydrophobic liquid substance such as some type of oil or Grease impregnates the edges of the cut packing material. In addition, the cut edges at the overlapping junctions may be folded below the overlapping packaging material so that they cannot be exposed to surrounding moisture or liquids.

A preferred embodiment of the present invention is described in detail below with particular reference to the accompanying drawings, wherein:

Fig. 1 is the schematic diagram of preferred packaging material of the present invention;

Figures 2a and 2b respectively represent the bending strength and moisture content in the packaging material as the storage time changes for the packaging container made of the packaging material shown in Figure 1 in water at 5°C;

Figures 3a and 3b respectively show that the packaging container made of the packaging material shown in Figure 1 is under a relatively high humidity, that is, 80 to 100% RH conditions, as the storage time changes, the bending strength and bending strength produced in the packaging material moisture content.

However, it can be known that while the specific embodiment of the present invention is described in detail with reference to accompanying drawing 1, those of ordinary skill in the art can draw different modifications or variations without departing from the scope of the present invention. The scope is defined by the claims.

FIG. 1 shows a schematic view of an embodiment of the packaging material of the invention, designated by the reference numeral 10 . This laminated packaging material comprises a core layer 11, such as paper or cardboard, having conventional packaging properties. On one side of the core layer, ie the surface facing the inside of the packaging container, a film consisting of biaxial polypropylene (BOPP) 12 is arranged.

In the packaging material 10 provided by the invention, the layer 12 is laminated to the core layer by means of a thin intermediate layer, ie an extruded plastic layer 13, eg polyethylene. The film 12 of BOPP is suitably covered on both sides with a thin layer 14, 15 consisting of an adhesive-enhancing or heat-sealable polymer.

On the side of the core layer, which in the finished packaging container faces the inner side of the packaging container, an additional layer 16 which increases stability can be provided, and this additional layer 16 can also have good gas barrier properties. This additional stability-increasing layer 16 may consist of metal, such as aluminum foil. Preferably, this aluminum foil 16 is laminated to the core layer 11 via an intermediate layer. The intermediate layer consists of an extruded thin plastic layer, eg polyethylene layer 17 . In order to prevent the packaged product from directly contacting metal (should be prevented according to the requirements of packaged food), the aluminum foil 16 on the inner side of the packaging container is covered with a plastic layer 18, such as polyethylene, which preferably has heat-sealing properties.

In Figures 2a and 2b and 3a and 3b, packaging materials of the type shown in Figure 1 were stored in water and relatively high humidity, eg 80-100% RH, at a temperature of 5°C for testing.

In Figures 2 and 3 the packaging material tested is shown, the layer 12 consists of a BOPP film with a thickness of about 18 microns, covered on both sides with thin layers 14, 15 with a thickness of 0.6-0.7 microns, said thin layers 14, 15 is composed of a tack-increasing and heat-sealable polymer. A film 12 is laminated on the core layer 11 by means of an interlayer of extruded low density polyethylene (LDPE) having a thickness of approximately 12 microns, and an aluminum foil is laminated on the core layer by means of an interlayer in the same manner. On the other hand, the intermediate layer is low density polyethylene with a thickness of about 25 microns. On the other side of the aluminum foil, ie the side facing the inside of the packaging container, the aluminum foil 16 is covered with low density polyethylene 18 having a thickness of approximately 35 microns. The core layer 11 consists of paper having packaging properties, for example of a known type called liquid paperboard, having a hardness of 80 mN.

The packaging material 10 tested was compared with a conventional type of packaging material having the same structure as the packaging material 10 but without the film 12 . In conventional packaging materials, the core layer is covered with an extruded layer of low-density polyethylene having a thickness of 12 micrometers on the side of the core layer facing the outside of the packaging container.

The tests were carried out on storage of 12 days in parallelepiped packaging containers of the TETRA BRIK® type with a volume of 250 m1 made of packaging material. Measurements were taken on 15 packages at 1, 2, 5 and 12 days.

According to SGANP29:84, the flexural strength is measured using the test equipment with the trademark LORENTZON & WELTRE, code 16. The value GM of the flexural strength given in the diagram is expressed as the geometric mean of the measured flexural strength, part of which is measured along the direction of the device (MD) and part along the transverse direction (CD), i.e. GM=√ (MD×CD).

As can be seen from Figures 2a and 3a, according to the flexural strength of the test material 10 of the present invention, under the conditions of relatively high water and air humidity respectively, it is good to store in 12 days, while the corresponding conventional packaging container The flexural strength of the glass drops about 20% after one day of storage, about 30% after 12 days of storage in water, and about 10% after 12 days of storage under high humidity conditions.

It can also be seen from Figures 2b and 3b that, during the same storage test period, the measured moisture content in the packaging material increases in the conventional packaging material and decreases in the material according to the invention.

The stiffness of the paper material in the core layer is significantly higher than that of low density polyethylene, for which reason the low density polyethylene layer does not add significantly to the overall stiffness of the packaging material.

As the moisture content increases, the hardness of the packaging material in the core layer decreases. Therefore, the overall hardness of the packaging material is also reduced.

When the core layer is instead provided with an overlying outer layer of plastic material, on the one hand increases the stiffness in the machine direction (MD) and in the transverse direction (CD), and on the other hand, compared with the conventional polyethylene outer layer Ratio, so that the moisture permeability is reduced, even under relatively high humidity conditions, the hardness and stability of the entire packaging material are increased.

In testing of the packaging material 10, the effect of forming an I-beam between the rigid outer layer 12 of the core and the metal foil 16 on the inwardly facing side was found. The stiffness of the two surrounding layers 12 , 16 compensates for the creep of the core layer upon absorption of moisture or humidity. It is possible that the effect of this I-beam increases as the thickness of the core increases, as the fibers expand after absorbing moisture, and the distance between the stiffer layers increases. Therefore, this effect encourages the packaging material to maintain its original hardness in water and air with high humidity.

It can also be seen from other tests that after being stored in water for several days, the packaging container of the test material 10 still maintains its clamping hardness, while the conventional packaging material loses its clamping hardness and creeps.

The good gripping stability maintained by packaging containers made of the packaging layer shown in Figure 1 is due to a combination of factors, wherein, compared to the outer layers of packaging containers of the type described above used in the prior art , the outer layer of the packaging container of the present invention firstly has relatively good liquid isolation performance, secondly has a relatively large thickness, and thirdly has relatively high material hardness.

Preferably, the outer plastic layer is selected from the group consisting of polypropylene, high density polyethylene and polyester, the plastic layer has a thickness of at least 10 microns and an E-modulus of at least 1000 MPa in the device and transverse directions.

According to a preferred embodiment of the present invention, said outer plastic layer has a thickness of at least 15 micrometers and/or an E-modulus of at least 2000 MPa in the device and transverse directions.

According to another preferred embodiment of the present invention, the above-mentioned outer plastic layer has an E-modulus of at least 3000 MPa in the machine direction and the transverse direction, respectively.

It has also surprisingly been found that the combination of the rigid outer layer and the rigid layer on the other side of the core layer, which is an aluminum foil, results in good gripping stability of the packaging container. In this way, the material with the central core produces the effect of an I-beam.

As can be seen from the above, the packaging containers related to the present invention, such as plastic or metal packaging containers, are suitable for refrigerating items in water or ice, which can be stored under relatively high humidity conditions, i.e. ambient conditions of 80-100%. RH, does not lose its good shape stability and clamping hardness even after long-term storage.

Claims (14)

1. Laminate wrapping material (10) for dimensionally stable packaging containers having good storage stability in storage media containing liquids, said packaging material (10) comprising a liquid-absorbent core of paper or cardboard (11) and the plastic layer (12) on the first face of the core layer (11), used for the storage medium directly in contact with the liquid when the packaging container is stored is characterized in that: in order to strengthen the clamping hardness, the packaging material is an application A layer (16) on the second side of the core layer, through the effect of the so-called I-beam, this layer (16) and the plastic layer (12) are arranged so that in the packaging container produced from the packaging material or even in the packaging container Guarantees good grip hardness and dimensional stability during long-term storage in storage media containing liquids. 2. Laminated packaging material according to claim 1, characterized in that said plastic layer (12) comprises a layer of oriented polypropylene, oriented high density polyethylene or oriented polyester. 3. Laminate packaging material according to claim 2, characterized in that: said plastic layer (12) is biaxial polypropylene, high density polyethylene or polyester. 4. Laminate packaging material according to claim 1, characterized in that: the layer (16) on the second side of the core layer (11) comprises a stability-increasing plastic layer, which layer is in contact with the first side of the core layer The plastic layer can be of the same type or another type. 5. The laminated packaging material of claim 1, including a gas barrier layer. 6. Laminate packaging material according to claim 5, characterized in that the gas barrier layer constitutes the layer (16) on the second side of the core layer (11). 7. Laminate packaging material according to claim 5 or 6, characterized in that the gas barrier layer is formed of a metal layer. 8. 4. Laminate packaging material according to claim 4, characterized in that the stability-increasing layer (16) consists of aluminum foil. 9. The method of using the laminated packaging material according to any one of claims 1-8, characterized in that liquid food is stored in a refrigerated storage medium containing liquid. 10. The method of use according to claim 9, wherein said refrigerated storage medium containing liquid is a mixture of ice and water. 11. A packaging container for storing a storage medium containing liquid, characterized in that it is made from the laminated packaging material described in any one of claims 1-8. 12. 11. Packaging container according to claim 11, characterized in that any cut edges which may appear on the outside of the packaging container are prevented from being exposed to water. 13. The packaging container according to claim 12, characterized in that: the edge of the cut packaging container is mechanically protected by overlapping and folding of the packaging material, or the edge of the cut packaging container is covered with a protective plastic strip. 14. 12. Packaging container according to claim 12, characterized in that the edge of the cut packaging container is chemically protected by impregnation with a hydrophobic liquid substance.

Images