CN1814508B - Thin-package lamina material and package container formed thereby - Google Patents

Abstract

Thin packaging laminate (10) for packaging containers (20) for liquid food, having the following layer structure, in order from the outside to the inside of the laminate: the outside consisting of a thermoplastic material with a white pigment included therein Heat-sealable layer (13); paper layer (12); laminate material layer (15) consisting of thermoplastic material having white pigment included therein; inner heat-sealable layer consisting of thermoplastic material having dark color pigment included therein (14). The invention also relates to a packaging container (20) formed from the packaging laminate (10) for liquid or liquid food contents.

Description

Thin packaging laminate and packaging container formed therefrom

technical field

The present invention relates to thin and heat-sealable paper-based packaging laminates for packaging containers for liquid food products. In particular, the present invention relates to such laminates which are economical, yet still possess sufficient strength and durability, and which can be formed and sealed into packaging containers of simple and flexible shapes. Also, although the laminate has a thin thickness, it should have a sufficient barrier effect for food, such as a light-shielding effect for light-sensitive food, and an appearance acceptable to customers and consumers. The laminate is especially well suited for ultra high temperature (UHT) processed food containers or aseptic food packaging containers.

Background technique

In the market there is a need in the market for hygienic packaging containers for liquid or liquid food that have an acceptable shelf life under ambient conditions. Such containers can be of the aseptic type and/or intended for use in UHT ( UHT) processed food or other types of food. They must also be sufficiently economical for their intended market, therefore, the packaging laminates from which they are formed should advantageously be thin and cost-effective. It does not have to be formed into a self-supporting shape with dimensional and holding stability, but can simply be formed into a simple and flexible shape, such as a pillow. However, one feature it must possess is sufficient light shielding to prevent the photosensitive food within the container from spoiling and/or exhibiting off-flavors.

A problem associated with thin and economical paper-based packaging laminates is that the paper layers are too thin to provide adequate blackout. Therefore, some type of specialized blackout material must be included in the laminate.

In the case of purely plastic-based packaging materials, it is known to introduce carbon black as a light-shielding material.

However, one problem associated with using carbon black as an opacifying material in one layer of the laminate (which is intended to be positioned on the inside of the laminate away from the paper layer) is that its black color passes through a thin, white, but The paper layer that is not fully opaque is partially visible, giving the laminate and container an uneven gray appearance that is not acceptable to consumers. However, it is very uneconomical to use thicker paper to solve this problem.

While it is possible to hide the black color by coating the paper layer with a pigment-containing composition or by printing a colored ink on the paper layer, these solutions are costly and competitive with low cost ideas for desired packaging laminates/containers Inconsistent.

Furthermore, although it is possible to add the white pigment only to the laminate layer of the laminate, that is, in the layer between the paper layer and the inner layer containing carbon black, or only to the outermost layer of the laminate, heat-sealed layers to hide the black color, but this solution leads to certain problems, since a considerable amount of white pigment needs to be introduced in such a separate layer. These problems include Downtime problems due to excessive white pigment deposits on process equipment in the outermost heat-sealable layer of the laminate. Therefore, if the production on the line is temporarily switched to another product, extensive cleaning is necessary and the first few hours of production of the second product in any case obtain a product "contaminated" in its outermost layer with white pigment, giving It has an unacceptable uneven appearance.

Contents of the invention

It is an object of the present invention to provide a thin and heat-sealable paper-based packaging laminate for packaging containers for liquid or liquid food, such as dairy products, which is sufficiently thin and thus inexpensive to compete with force, yet have sufficiently good properties in terms of hygiene, tightness, strength, concealment and appearance of packaging containers formed from the laminate. From a conversion point of view, it should be advantageous to avoid or at least reduce problems in this respect mentioned above.

These and other objects are achieved by a thin packaging laminate for packaging containers for liquid foods, which has the following layer structure, in order from the outside to the inside of the laminate:

- an outer heat-sealable layer consisting of a thermoplastic material having a white pigment included therein,

- thin paper layers,

- a laminate layer consisting of a thermoplastic material with white pigment included therein,

- An inner heat-sealable layer consisting of a thermoplastic material having a dark pigment included therein.

The invention also relates to packaging containers formed from such laminates.

Due to the presence of a dark pigment, preferably a black pigment such as carbon black, in the inner heat-sealable layer, the laminate and the container formed from it obtain sufficient light opacity such that the food contents of the container are not altered by light exposure. Bad. By including a white pigment, such as titanium dioxide (TiO ₂ ), in the thermoplastic laminate layer and the outer heat-sealable layer of thermoplastic material, the laminate and the container formed from it obtain an acceptable white appearance, although Has an inner dark pigment layer.

In a preferred embodiment, the outer heat-sealable layer consisting of the white pigment-containing thermoplastic laminate layer and the white pigment-containing thermoplastic material is bonded directly to the paper layer, ie without any intervening layers.

A particular advantage of including white pigments in the outer heat-sealable layer of thermoplastic material is that the printed design can be located directly on the outer heat-sealable layer of thermoplastic material, where it is optionally protected by lacquer. Also, the finished laminate can be stored in standard form without printed graphics. This also means that the printing takes place on a laminate that is thicker than the paper itself, which is more advantageous than printing directly on thinner paper. Overall, the solution of the invention results in less handling of the thin paper layer itself. An additional advantage is that the more central layers, which require higher strength, need not include large amounts of white pigment filler. Also, less white pigment will be deposited on process equipment than if a large amount of white pigment is contained only in the outer heat-sealable layer, even if a conversion line is temporarily switched to produce a second laminate, residual The white pigment is not a problem because it is positioned in the more central layers of the laminate, below the paper layer, where it is less visible than in the outer layers. Due to reflection phenomena, it is advantageous that the blackout effect of the white pigment is in the Two layers exist in different layers. Also, any streaks formed if white pigment is present in both layers are less visible.

According to one aspect of the invention, said outer heat-sealable layer consists of extruded polyethylene material having a density of 880-970 kg/m ³ , preferably 910-930 kg/m ³ . It may have a density of 8-25 g/m ² , A weight of 10-20 g/m ² is preferred, even more preferably 10-15 g/m ² . It can consist of several preferred coextruded layers, where at least the outermost layer is heat-sealable. The white pigment is included in the layer in a content of at least 1 wt%, preferably at least 2 wt%, still more preferably at least 5 wt%, but at most 30 wt%, preferably at most 20 wt%, still more preferably at most 15 wt%. Suitably, the white pigment is titanium dioxide, although other types of white pigments are conceivable. Because it is difficult to include a greater amount of white pigment in the thermoplastic layer, this layer must be thicker, at the upper end of the range given above, if a large total amount of white pigment is required to hide the dark color in the inner heat sealable layer The words of paint. Also, the laminate layer may consist of several preferably coextruded layers, in which case the white pigment may be contained in one or more or all layers of these part-laryers.

According to another aspect of the present invention, said tissue layer consists of bleached kraft paper having a weight of 30-80 g/m ² , preferably 40-70 g/m ² , still more preferably 40-60 g/m ² . It has the same properties as other Sufficient basis weight and strength of the layers together to obtain sufficient lamination strength. Most preferably, a paper layer of about 50 g/ ^m2 is used, which achieves many advantages over thinner paper layers. For example there are fewer problems related to curling and wrinkling, and since the material is denser, improved opacity is obtained (since shorter fibers and/or fillers can be used due to No need to increase the strength), a wider selection of suitable papers can be obtained, and in some cases the sealing window can be increased, because the increased amount of paper can receive and distribute excess heat, so that local overheating of the plastic sealing layer is avoided, etc. Furthermore, the stiffness of the resulting packaging container will be improved. Of course, other types of flexible paper of similar thickness and properties can be used. It is also conceivable to use multiple layers of paper.

According to yet another aspect of the present invention, said outer heat-sealable layer and laminate layer together comprise at least 1 wt%, preferably at least 2 wt%, still more preferably at least 5 wt%, but at most 30 wt%, preferably at most 20 wt% in the layer %, even more preferably a content of up to 15 wt % of white pigment.

According to yet another aspect of the invention, the thermoplastic material of the laminate layer is a polyethylene material having a density of 880-970 kg/m ³ , preferably 910-930 kg/m ³ . It may have a weight of 8-50 g/m ² , preferably 10-40 g/m ² , still more preferably 15-30 g/m ² . The white pigment is preferably included in the layer in a content of at least 1 wt%, preferably at least 2 wt%, still more preferably at least 5 wt%, but at most 20 wt%, also preferably at most 15 wt%, more preferably at most 12 wt%. Suitably, the white pigment is titanium dioxide, although other types of white pigments are conceivable. Because it is difficult to include a greater amount of white pigment in the thermoplastic layer, this layer must be thicker, at the upper end of the range given above, if a large total amount of white pigment is required to hide the dark color in the inner heat sealable layer The words of paint. Also, the laminate layer may consist of several preferably coextruded layers, in which case the white pigment may be contained in one or more or all of these layers.

The inner heat-sealable layer is suitably composed of a polyethylene material, preferably having a density of 880-970 kg/m ³ , more preferably 910-930 kg/m ³ , polypropylene, ethylene-vinyl acetate and thermoplastic acrylic copolymers (neutralized or unneutralized) in thermoplastic material. It can be composed of several preferably coextruded layers whose innermost layer is at least heat-sealable. Here, it should be noted that the term "most By "inner layer" is meant the outermost layer on the inside of the laminate, ie the layer that is in contact with the contents of the packaging container thus formed. The inner heat-sealable layer may have a total thickness of 10-45 g/m ² , preferably 13-35 g/m ² , still more preferably 20-30 g/m ² , depending on the mass of thermoplastic material. It suitably comprises a content of 0.2-2 g /m ² , preferably 0.2-1 g/m ² , still more preferably 0.3-0.8 g/m ² of the dark pigment. However, because the dark pigment is not very expensive and because it is very easy to incorporate in thermoplastics, it can Conceivably, it could be included in even greater amounts, such as up to 3 or 4 g/m ² . Suitably, the dark pigment is carbon black. Where the inner heat-sealable layer consists of several layers, dark pigments may be contained in one or more or all of these layers.

Preferably, the inner heat-sealable layer is prefabricated prior to its introduction in the packaging laminate, i.e. it constitutes a preformed film, suitable by (co)extrusion blow molding, (co)extrusion casting (extrusioncasting) or (co)extrusion ) to prepare by extruding the glue. Blown or cast film has advantages over extruded layers because it has better strength and less oxidatively degraded material because it is prepared at lower temperatures and it has a more controlled mechanical performance and lateral performance.

The advantage of using a prefabricated film as the inner heat-sealable layer and a prefabricated paper layer as the body layer in the thin laminate according to the invention is that it is easy to change the film and/or paper quality on the converting line if required, e.g. food contact grade , and less stringent requirements for the accuracy of the extruded thickness of the extruded layers (outer heat-sealable layer and laminate layer).

The packaging laminate has a total weight of 60-180 g/m ² , preferably 70-150 g/m ² , still more preferably 75-125 g/m ² .

The invention also relates to the formation of packaging containers with liquid or runny food contents from such packaging laminates. It may for example have the shape of a flexible pillow with one longitudinal seal and two transverse seals at opposite ends of the container.

Description of drawings

The invention is now described in more detail hereinafter with reference to preferred embodiments and drawings. In the attached picture:

Figure 1 shows a cross-section of a laminate according to the invention,

Figure 2 shows a packaging container formed from the laminate of Figure 1,

Detailed ways

A preferred laminate according to the invention is generally indicated at 10 in FIG. 1 . It consists of four layers 12, 13, 14 and 15. The paper layer 12 is made of bleached kraft paper and has a weight of approximately 50 g/ ^m2 . An extruded outer heat-sealable thermoplastic layer 13 constitutes the exterior of the packaging container formed from laminate 10 and is made of low density polyethylene (LDPE) having a weight of approximately 12 g/m ² . Of this weight, 8% is TiO ₂ , which imparts a white and ideal opaque appearance to layer 13, thus hiding the black inner heat-sealable thermoplastic layer 14. Formed packaging containers for food contact. It is a film of extrusion blown linear low density polyethylene (LLDPE) and has a weight of 23 g/m ² . Of this weight, 0.4 g/ ^m2 is carbon black, which imparts a black appearance to layer 14 and acts as an opacifier. When viewed from the outside of the laminate 10 , ie when viewed from the layer 13 , the black color of the layer 14 is concealed by the outer heat-sealable thermoplastic material layer 13 together with the extruded laminate layer 15 . The laminate layer 15 is made of low density polyethylene (LDPE) and has a weight of approximately 17 g/m ² . Of this weight, 6% is _TiO2 , which gives layer 15 a white and desirable opaque appearance, thus hiding the black inner heat-sealable thermoplastic layer 14 .

FIG. 2 shows a packaging container 20 prepared by the laminate form-fill-seal process shown in FIG. 1 . It has the shape of a flexible pillow with one longitudinal seal 22 and two transverse seals 24a, 24b at opposite ends of the container.

From a second roll 42, a film 14a consisting of a heat-sealable thermoplastic material containing dark pigments is unwound. This film constitutes the inner heat-sealable layer 14 of the packaging laminate as shown in Figure 1. It is preferably a film of extrusion blown linear low density polyethylene (LLDPE) comprising the dark pigment.

In conclusion, it should be found that the invention described above with particular reference to the accompanying drawings is not limited to the embodiments described and represented by way of example only, and is not limited to the technical field without departing from the inventive concept as disclosed in the appended claims. Modifications and variations obvious to those skilled in the art are possible.

Claims (22)

1. A thin packaging laminate (10) for a packaging container (20) for liquid food, which has the following layer structure, in order from the outside to the inside of the laminate: - an outer heat-sealable layer (13) consisting of a thermoplastic material with white pigment included therein, - thin paper layers (12), - a laminate layer (15) consisting of a thermoplastic material with white pigment included therein, - An inner heat-sealable layer (14) consisting of a thermoplastic material having a dark pigment included therein. 2. The packaging laminate according to claim 1, wherein said outer heat-sealable layer (13) consists of a polyethylene material having a density of 880-970 kg/ ^m3 . 3. The packaging laminate according to claim 1 or 2, wherein said outer heat-sealable layer (13) has a weight of 8-25 g/ ^m2 . 4. Packaging laminate according to claim 1, wherein said outer heat-sealable layer (13) and said laminate layer (15) together comprise a white pigment in a content of at least 1 wt%, but at most 30 wt%. 5. The packaging laminate according to claim 4, wherein said outer heat-sealable layer (13) comprises a white pigment in a content of at least 2 wt%, but at most 20 wt%. 6. Packaging laminate according to claim 4 or 5, wherein said outer heat-sealable layer (13) consists of two or more layers. 7. The packaging laminate according to claim 1, wherein said outer heat-sealable layer (13) is directly bonded to said tissue layer (12). 8. The packaging laminate according to claim 1, wherein said tissue layer (12) consists of kraft paper having a weight of 30-80 g/ ^m2 . 9. The packaging laminate according to claim 1, having a printed pattern on said outer heat-sealable layer (13). 10. Packaging laminate according to claim 1, wherein the thermoplastic material of said laminate layer (15) is a polyethylene material having a density of 880-970 kg/ ^m3 . 11. Packaging laminate according to claim 1, wherein said laminate layer (15) has a weight of 8-50 g/ ^m2 . 12. Packaging laminate according to claim 11, wherein said laminate layer (15) comprises white pigments in a content of at least 1 wt%, but at most 20 wt%. 13. Packaging laminate according to claim 1, wherein said laminate layer (15) consists of two or more layers. 14. The packaging laminate according to claim 1, wherein said laminate layer (15) is directly bonded to said tissue layer (12). 15. The packaging laminate according to claim 1, wherein said inner heat-sealable layer (14) consists of a thermoplastic material selected from the group consisting of polyethylene material, polypropylene, ethylene vinyl acetate, neutralized Thermoplastic acrylic copolymers and unneutralized thermoplastic acrylic copolymers. 16. The packaging laminate according to claim 15, wherein said inner heat-sealable layer (14) has a weight of 10-45 g/ ^m2 . 17. The packaging laminate according to claim 1, wherein said inner heat-sealable layer (14) comprises dark pigments in an amount of 0.2-2 g/ ^m2 . 18. The packaging laminate according to claim 1, wherein said inner heat-sealable layer (14) consists of two or more layers. 19. The packaging laminate according to claim 17, wherein the dark pigment is carbon black. 20. The packaging laminate according to claim 1, wherein the total weight of the laminate (10) is 60-180 g/ ^m2 . 21. Packaging container (20) with liquid food content, wherein the container is formed by a packaging laminate (10) according to any one of claims 1-20. 22. Packaging container (20) according to claim 21, having the shape of a pillow with one longitudinal seal (22) and two transverse seals (24a, 24b) at opposite ends of the container.

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