RU2445247C2 - Packing laminate and method of its fabrication - Google Patents

Abstract

FIELD: transport, package.

SUBSTANCE: invention relates to packing laminate including paper or cardboard layer and outer waterproof polyolefin coatings. Invention aims at fabricating packing laminate with improved protection against harmful ultraviolet radiation. Laminate 10 comprises paper or cardboard layer 11 and outer waterproof layers 12, 13 one of which 12 includes light absorbing carbon particles. Note here that paper or cardboard layer 11 comprises light reflecting particles embedded and distributed over entire layer 11. Invention covers also method of producing above described laminate and flexible packing pad-shaped container for liquid milk products made by packing laminate bending and thermal soldering.

EFFECT: invention aims at fabricating packing laminate with improved protection against harmful ultraviolet radiation.

17 cl, 2 dwg

Description

FIELD OF THE INVENTION

The present invention relates to a packaging laminate comprising a layer of paper or cardboard and external waterproof polyolefin coatings, one of the polyolefin coatings containing light-absorbing carbon particles. In particular, the present invention relates to such a packaging laminate, as for packaging containers for liquid food products, such as milk or yogurt.

The present invention also relates to a method for producing such a packaging laminate.

State of the art

Dairy products, in particular milk and yogurt, are extremely sensitive to light and quickly break down or become unusable when exposed to visible light. A packaging laminate comprising a layer of paper or paperboard, of course, in itself has the inherent ability to retain light, which is sufficient to eliminate or prevent the penetration of such destructive light, however, provided that this layer is made of unbleached pulp. A problem associated with a packaging laminate having one or more layers of such unbleached pulp or paperboard or a combination of layers of both bleached and unbleached pulp, i.e. bilayer paper, however, is that it does not always meet the processing requirements, established by the competent authorities. For example, in some countries the use of unbleached fiber itself or in combination with bleached fiber is completely prohibited, since in the markets of these countries paper or cardboard must be completely free from unbleached fibers in order to meet the relevant requirements of the government. On the other hand, a packaging laminate containing one or more layers of bleached paper or paperboard has insufficient light-shielding properties to prevent the penetration of harmful visible light, unless another layer is added to compensate for the insufficient light tightness in the first case. To this end, it is known in the prior art to apply at least one outer layer of polyethylene to a packaging laminate, usually on the side that should be directed inside the package, with enough light-absorbing carbon particles to enhance and maintain the required protective properties of the package against visible light.

A packaging laminate with additional impermeability to visible light is described, for example, in WO 2006/073341. The packaging laminate has a layer of paper or cardboard, which, on the one hand, has a first outer coating of polyolefin and, on the other hand, has a second outer coating of polyolefin, which contains light-absorbing carbon particles in order to enhance the light-tightness properties. A coating of particle-containing polyolefin is laminated onto a layer of paper or cardboard by means of an extruded laminating layer. In order to hide the blackened particle-containing polyolefin coating, when converting the packaging laminate into a packaging container by folding and heat-sealing, the packaging laminate is folded so that the black coating is on the inside of the package.

If for some reason the particle-containing polyolefin coating contains such light-absorbing particles in excess, it may be necessary to supplement the packaging laminate with at least one additional layer and / or to provide at least one of the layers of material already present in the packaging laminate with optical properties to hide the black polyolefin coating so that it cannot be seen or even seen outside the package. According to WO 2006/073341, an extruded laminating layer is provided between layers of paper or cardboard and a black polyolefin coating endowed with similar additional optical properties by the addition of reflective white particles of titanium dioxide. By adding reflective white particles to the laminated layer, the packaging is endowed with both a “cleaner” and a whiter appearance, and as a result of the increased contrast, the print sensitivity of the packaging with decorative images or the like is improved.

WO 2006/073344 describes yet another example of a prior art packaging laminate in accordance with the foregoing. This prior art packaging laminate has a relatively thin layer of paper or cardboard, which, on the one hand, has a first outer coating of polyolefin and, on the other hand, has a second outer coating of polyolefin, which includes light-absorbing in order to increase barrier properties against light carbon particles. A black polyolefin coating containing particles is laminated to a layer of paper or paperboard using an extruded laminate. According to WO 2006/073344, the black polyolefin coating is concealed by adding titanium dioxide reflective particles to the first polyolefin coating.

Another packaging laminate of the type described above is known from WO 2006/073343. This prior art packaging laminate includes a relatively thin layer of paper or paperboard, which, on the one hand, has a first outer coating of polyolefin and, on the other hand, has a second outer coating of polyolefin, which, in order to improve the properties of light protection, contains light-absorbing carbon particles. The particle-containing polyolefin coating is laminated to paper or paperboard by means of an extruded lamination layer. In accordance with WO 2006/073343, both titanium dioxide particles having reflective properties are added to the first mentioned outer coating of polyolefins and to the extruded lamination layer to obscure the black polyolefin coating.

The packaging laminates described above are made by a lamination process in which a preformed particle-containing polyolefin film is laminated to one side of a paper or cardboard tape by a lamination layer of a polyolefin that is extruded between the film and the sheet and in which the opposite side is ultimately It turns out to be coated with a polyolefin coating as a result of extrusion.

An inherent disadvantage in the production of these prior art packaging laminates is that the particle-containing polyolefin mixture requires careful control of the thorough mixing process and sophisticated extrusion equipment to ensure uniform distribution of particles throughout the laminate and polyolefin layer, respectively. Such a uniform distribution of particles, among other things, requires a thoroughly mixed mixture of polyolefin and particles, which, not without significant difficulties, can be achieved without using a complex extruder screw. Further thorough mixing requires particle control and melt viscosity correction of the polyolefin to create a uniform melt flow through the extruder. Moreover, the admixture of particles, as well as other solids in the molten polymer increases the risk of excessive wear and damage to parts of the process equipment that are sensitive to the presence of particles, at the same time, at least one separate preliminary preparation or inter-mixing of particles is usually required to mix them with the corresponding polyolefins.

Therefore, in the prior art there is a need for a packaging laminate for food products, in particular liquid dairy products, which provides the necessary protection against harmful UV radiation, but which at the same time can be obtained by a simple lamination process and not requiring overly careful control process or complex technological equipment.

OBJECTS OF THE INVENTION

Thus, one aim of the present invention is to satisfy the aforementioned need in the art.

Another objective of the present invention is the creation of a packaging laminate of the aforementioned type, from which it is possible to obtain cost-effective packaging containers for food products, in particular for liquid dairy products, with the required protective properties.

Another objective of the present invention is to provide a packaging laminate for flexible packaging containers in the form of pillows or bags for liquid dairy products, such as milk or yogurt, which have excellent protection against harmful UV radiation.

Another objective of the present invention is the implementation of a simple method for producing a packaging laminate for flexible and cost-effective packaging containers with the required protective properties for food products, in particular for dairy products.

These and other objectives and advantages will be achieved by the present invention using the packaging laminate according to independent claim 1 and using the method described in independent claim 11, respectively.

Suitable and preferred embodiments of the packaging laminate and the method of the present invention are given in the distinguishing features given in the recorded paragraphs 2-10 and 12-15, respectively.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a packaging laminate is provided comprising a layer of paper or cardboard and external moisture-proof polyolefin coatings, of which one of the polyolefin coatings contains light-absorbing carbon particles. A packaging laminate is characterized in that the layer of paper or paperboard includes reflective particles that are incorporated and distributed throughout the paper or paperboard layer.

As a result of the presence of reflective white particles in the paper or cardboard layer, the fiber layer is “given” the role of hiding the black polyolefin coating, but with the advantage that both the laminated layer and the outer polyolefin coating can be applied by extrusion of “pure” polyolefins, that is, polyolefins without particulate matter. As a result of this role, it is possible to easily produce a packaging laminate according to the present invention, without the requirements for high opaque properties and “clean” and having a white appearance safe packaging laminate.

The amount of reflective white particles in a layer of paper or paperboard can vary over a wide range, but in each individual case it must be large enough so that the black carbon particles in the polyolefin coating containing carbon particles are completely invisible through the paper or paperboard layer. Preferably, the amount is large enough to give the packaging laminate a white background that improves contrast, and thereby improved print sensitivity, which is applied to the packaging laminate for decorative or informational purposes.

In practice, it turned out to be an advantage if the amount of reflective particles is at least 7 wt.% Based on the total weight of the fiber layer in order to give the packaging laminate both the required light-tightness properties and the required white appearance and printability with good contrast. On the other hand, the amount of reflective particles should not be more than about 20 wt.% Based on the total weight of the fiber layer, since the fiber layer will constantly become more brittle and gradually lose its mechanical strength. Thus, the preferred amount of reflective particles in the fiber layer is 7-20 wt.% In terms of the total weight of the fiber layer.

Preferred examples of reflective particles for use in the packaging laminate of the present invention are titanium dioxide particles.

Examples of polyolefins that can be used as an external coating for a packaging laminate of the present invention are polyethylene and polypropylene. Preferably, the polyolefins are selected from the group consisting mainly of low density polyethylene (LDPE), linear low density polyethylene (LLDPE) and metallocene polyethylene (mPE).

Examples of polyolefins that can be used for the applied layer in the packaging laminate of the present invention are polyethylene and polypropylene. Preferably, the polyolefins are selected from the group consisting mainly of low density polyethylene (LDPE), linear low density polyethylene (LLDPE) and metallocene polyethylene (mPE).

In yet another aspect of the present invention, there is provided a method for producing a packaging laminate comprising a layer of paper or cardboard and external moisture-proof polyolefin coatings, one of which contains light-absorbing carbon particles. This method is characterized in that a prefabricated polyolefin film containing light-absorbing carbon particles is laminated to one side of the paper or paperboard web through a lamination layer of the polyolefin that is extruded between the film and the web so that the uncoated side of the web is coated with a polyolefin coating by extrusion.

The method according to this invention takes advantage of the fact that it can be performed without the need for careful control of the process or complex extrusion equipment and that it can be easily performed using simple processing equipment.

Other objectives, advantages and details of the present invention will become apparent from the following description of the invention with reference to the drawings.

Brief Description of the Drawings

Figure 1 schematically shows a cross section of a packaging laminate according to the present invention; and

figure 2 shows the production of the packaging laminate shown in figure 1 by the method of the present invention.

Detailed Description of the Preferred Embodiment and Drawings

Although the invention will be described in accordance with the drawings, it is not limited solely to the illustrated embodiments. It will be apparent to those skilled in the art that the specific details of the illustrated and described embodiments may be modified as described without departing from the concept of the invention described herein. Therefore, the concept of the invention is defined only in the attached claims.

1 schematically shows a cross-section of a packaging laminate according to this invention, generally indicated by reference numeral 10. The packaging laminate 10 has a thin layer 11 of paper or cardboard and external moisture-proof coatings 12 and 13 of polyolefins, of which one coating 12 contains light-absorbing carbon particles in an amount sufficient to give the packaging laminate 10 the required impermeability with respect to visible light, in particular UV radiation. A coating 12 containing particles is laminated to a layer 11 of paper or paperboard using a lamination layer 14 of polyolefins.

The paper or paperboard layer 11 preferably has a density or mass of the carrier of about 50-70 g / m ² and may consist of kraft paper.

Particle containing coating 12 may include polyethylene or propylene polyolefins, and is preferably a polyethylene selected from the group consisting mainly of low density polyethylene (LDPE), linear low density polyethylene (LLDPE), very low density polyethylene (LDPE ), ultra low density polyethylene (ULDPE) and metallocene polyethylene (mPE). Preferably, the particle-containing coating 12 has a coating weight (surface layer weight) of about 15-30 g / m ² . The amount of light-absorbing carbon particles in the coating 12 should be in the range of 0.2-3 g / m ² .

The extruded laminated layer 14 may include polyolefins — polyethylene or polypropylene, and is preferably a polyethylene selected from the group consisting mainly of low density polyethylene (LDPE), linear low density polyethylene (LLDPE), very low density polyethylene (VLDPE), polyethylene ultra low density (ULDPE) and metallocene polyethylene (mPE). The laminated layer 14 preferably has a coating weight (surface layer weight) of 10-30 g / m ² .

The particle-free coating layer 13, like coating 12, comprises polyolefins — polyethylene or propylene, and is preferably a polyethylene selected from the group consisting mainly of low density polyethylene (LDPE), linear low density polyethylene (LLDPE), polyethylene very low density (VLDPE), ultra low density polyethylene (VLDPE) and metallocene polyethylene (mPE). Preferably, the coating 13 has a coating weight (surface layer weight) of about 10-20 g / m ² .

In order to hide the coating 12 having a black color due to carbon particles and to make it invisible through a layer of paper or cardboard 11, the layer of paper or cardboard 11 contains light-absorbing white particles, preferably titanium dioxide particles, which penetrate and distribute throughout the fiber layer eleven.

The number of reflective white particles in the paper or paperboard layer 11 can vary over a wide range, but in each case it should be large enough so that the black carbon particles in the polyolefin coating containing the particles are practically invisible through the paper or paperboard 11. Preferably, their number should also be large enough to give the packaging laminate 10 a white background that improves the contrast of the paint applied for decorative and / or informational purposes on the packaging laminate 10.

In practice, it has proven to be advantageous if the amount of reflective white particles is at least 7% by weight, based on the total weight of the fiber layer, to give the packaging laminate 10 both the required light tightness and the desired white appearance and print sensitivity with good contrast. On the other hand, the number of reflective white particles should not exceed 20 wt.% In terms of the total weight of the fiber layer 11, since the fiber layer 11 will constantly become more brittle and gradually lose its mechanical strength. Therefore, the preferred amount of reflective white particles in the fiber layer 11 is in the range of 7 to 20% by weight, based on the total weight of the fiber layer 11.

The packaging laminate 10 shown in FIG. 1 is obtained by the method schematically illustrated in FIG. 2. On the left in the drawing, a sheet of paper 20 containing light-reflecting particles is unwound from a bobbin (not shown), while a sheet of film 21 of a polyolefin containing light-absorbing carbon particles is unwound from a bobbin (not shown) on the right side of the drawing. The sheets 20 and 21 converge and are passed through the contact zone between the two rotating cooling shafts 22 and 23 at the same time that the polyolefin laminating film 24 is extruded between the sheets 20 and 21 by means of an extruder 25 so as to laminate them. After passing through the contact zone, between two rotating cooling shafts 22 and 23, the laminated webs 20 and 21 are launched through the kink roller 26 to the coating station A, where the uncoated side of the paper web 20 is coated with a film of polyolefins 27, which is applied to the web using an extruder 28 for the formation of the packaging laminate for the purpose of further movement and processing.

In practice, the reflective particles in the paper web 20 may be titanium dioxide, while these titanium dioxide particles should be at least 7 wt.% Based on the total weight of the paper web 20. However, the number of titanium dioxide particles should not exceed 20 wt.% in terms of the total weight of the paper web 20, since the web 20 gradually loses its mechanical strength with increasing number of particles. Thus, in practice, the range of the number of reflective particles should be from 7 to 20 wt.%, In which the paper web 20 effectively hides the black color of the carbon particles in the polyolefin film 21 underneath, while the reflective particles give the packaging laminate a white appearance and good print sensitivity.

Both the particle-containing polyolefin film 21 and the particle-free laminating film 24 as well as the particle-free polyolefin film 27 may include polyethylene or propylene, but preferably include polyethylene selected from the group consisting mainly of low density polyethylene (LDPE ), linear low density polyethylene (LLDPE), and metallocene polyethylene (mPE). The most preferred polyolefin is low density polyethylene (LDPE).

Preferred amounts in the coating layer (weight in the surface layer) of the layers of materials included in the packaging laminate are apparent from the following table:

Material layer The amount in the coating layer (g / m ² ) Particle-Free Polyolefin Coating 10-20 Particle layer 30-100 Laminated layer 10-30 Particulate Coating 15-30

As already mentioned, from the packaging laminate of the present invention, flexible, thin-walled packaging containers for transporting and storing liquid dairy products, for example, such as milk or yogurt, are produced by folding and heat sealing the packaging laminate in a manner known per se.

For example, from the packaging laminate web, such packages in the form of pillows or bags are made so that first the tubular shape is obtained from the web by heat sealing along the longitudinal edges of the pipe. The pipe is filled with the appropriate product and divided into filled pillow-shaped packaging by repeated heat sealing perpendicular to the pipe axis. Then, pillow-shaped packages are sealed from each other by notches or slots in the areas of the pipe where perpendicular welding was performed.

One well-known example of such flexible pillow-shaped packaging is the previously mentioned Tetra Fino® packaging, in which liquid dairy products, such as milk or yogurt, can be safely transported or stored without the risk of harmful UV radiation.

Although the present invention has been described in detail in accordance with the attached drawings, it is not limited solely to the illustrated and described embodiments. For a person skilled in the art, in accordance with the above instructions, it will be obvious that a large number of modifications and changes are possible without deviating from the concept of the invention. Thus, all such modifications and changes are covered by the concept of the invention, as described in the attached claims.

Industrial application

The packaging laminate of the present invention is particularly applicable to flexible, thin-walled packaging containers for liquid dairy products, such as, for example, milk and yogurt, but can naturally be used to package and transport other types of liquid food products, for example juice, wine, cooking oils, etc.

Claims (17)

1. A packaging laminate comprising a layer (11) of paper or paperboard and external moisture-proof coatings (12, 13), one of which (12) contains light-absorbing carbon particles, characterized in that the layer (11) of paper or paperboard contains light-reflecting particles, which embedded and distributed throughout the layer (11) of paper or paperboard. 2. The packaging laminate according to claim 1, characterized in that the amount of reflective particles in the layer (11) of paper or paperboard is large enough so that the coating (12) blackened due to carbon particles becomes invisible through the layer (11) of paper or paperboard . 3. The packaging laminate according to claim 1 or 2, characterized in that the number of reflective particles in the layer (11) of paper or paperboard is large enough to give the packaging laminate a bright appearance. 4. The packaging laminate according to claim 1, characterized in that the reflective particles in the layer (11) of paper or cardboard are composed of particles of titanium dioxide. 5. A packaging laminate according to claim 4, characterized in that the amount of reflecting particles of titanium dioxide in the layer (11) of paper or cardboard is at least 7%, based on the total weight of the layer (11). 6. A packaging laminate according to claim 5, characterized in that the amount of reflective particles of titanium dioxide in the layer (11) of paper or cardboard is less than 20%, calculated on the total weight of the layer (11). 7. A packaging laminate according to claim 1, characterized in that the particle-containing coating (12) is laminated onto a layer (11) of paper or cardboard using a laminating layer (14). 8. A packaging laminate according to claim 7, characterized in that both coatings (12 and 13) and the lamination layer (14) contain a polyolefin. 9. The packaging laminate of claim 8, wherein said polyolefin is selected from the group consisting mainly of low density polyethylene (LDPE), linear low density polyethylene (LLDPE), very low density polyethylene (VLDPE), ultra low density polyethylene (VLDPE) and metallocene polyethylene (mPE). 10. A packaging laminate according to claim 1, characterized in that the particle-containing coating (12) is a blown film. 11. A method of producing a packaging laminate according to any one of claims 1 to 10, characterized in that the pre-fabricated polyolefin film sheet (21) containing light-absorbing carbon particles is laminated to a paper or cardboard sheet (20) containing light-reflecting particles by means of a lamination layer (24) a polyolefin that is extruded between said webs (20 and 21), while the uncoated side of the paper or paperboard web (20) is coated with a polyolefin film (27). 12. The method according to claim 11, characterized in that the film (27) of the polyolefin is obtained by extrusion. 13. The method according to claim 11 or 12, characterized in that the reflective particles in the canvas (20) of paper or cardboard are composed of particles of titanium dioxide. 14. The method according to item 13, wherein the amount of particles of titanium dioxide in the tape (20) of paper or cardboard is at least 7 wt.%. 15. The method according to claim 11, characterized in that the polyolefin in both films (21 and 27) of the polyolefin, as well as in the laminating layer (24) is selected from the group consisting mainly of low density polyethylene (LDPE), linear low density polyethylene density (LLDPE) and metallocene polyethylene (mPE). 16. The method according to claim 11, characterized in that the particle-containing film (21) is a film obtained by blown extrusion. 17. A flexible packaging container in the form of a pillow for liquid dairy products, characterized in that it is made by folding and heat sealing the packaging laminate according to any one of claims 1 to 10.

Images