Method for manufacturing sealing strips for laminated packaging materials for liquid foods

Abstract

The present disclosure relates to a method of manufacturing a strip (22) for sealing a laminated packaging material (16) for a liquid food product (12), in which a pre-manufactured strip (44) is provided that includes a plurality of layers (34) that include a polymeric material, the plurality of layers (34) including at least an inner surface layer (36), an outer surface layer (38) and a central layer (40). In the method, at least one of the inner surface layer and the outer surface layer (36; 38) is subjected to a heat treatment such that the transparency (46) of the manufactured strip (22) is increased relative to the transparency (48) of the pre-manufactured strip (44). The present disclosure further relates to the strip (22) manufactured by the method, the laminated packaging material (16) and the packaging container (10) that include the strip (22). The present disclosure also relates to an apparatus (42) for carrying out the method.

Description

[Technical field]

[0001] The present invention relates to a method for producing a strip for sealing laminated packaging materials for liquid foods. Furthermore, the present invention relates to the strip obtained from this method. The present invention also relates to a laminated packaging material sealed with the strip and folded and to a packaging container produced therefrom. The present invention also relates to an apparatus suitable for carrying out said method. [Background technology]

[0002] Disposable packaging containers for liquid foods are often manufactured from packaging laminates based on paperboard or carton. Such packaging containers are often used for packaging liquid foods such as milk or fruit juices that are sold for long-term shelf life. The packaging material of such known packaging containers is typically a laminate comprising a bulk or core layer of paper, paperboard or other cellulosic material and an outer liquid-tight layer of thermoplastic plastic. To make the packaging container gas-tight, in particular oxygen-tight for aseptic packaging purposes, the laminates of these packaging containers usually comprise an additional barrier layer, for example aluminum foil.

[0003] Packaging containers are generally produced by modern high-speed packaging machines of the type that form, fill and seal packages from webs or from prefabricated blanks of packaging material. Thus, packaging containers can be produced by joining the longitudinal edges of a web of laminate packaging material together with overlapping joints made by welding heat-sealable inner and outer thermoplastic polymer layers to convert the web into a tube. The tube is then filled with the desired liquid food product and then divided into individual packages by repeating transverse sealing of the tube at a predetermined distance from each other below the level of the contents in the tube. The packaging material is separated from the tube by scoring along the transverse seals and given the desired geometric shape by folding along creases made in the packaging material.

[0004] Packaging containers for sensitive liquid foods, such as milk and juice, can be produced from sheet or prefabricated blanks of laminate packaging material. From tubular blanks of the packaging laminate folded flat, the packaging container is produced by stacking the blanks to form an open tubular container capsule, which is closed at one of its open ends by folding and heat sealing an integral end panel. The container capsule thus closed is filled from its open end with the food product in question, for example juice, and is then closed by further folding and heat sealing the corresponding integral end panel. Such tubular blanks produced from sheet or prefabricated blanks of laminate packaging material can have overlap joints of the type described above. Examples of packaging containers produced from sheet and tubular blanks are conventional so-called gable top packages. Packages of this type can also have a molded top and / or a screw cap made of plastic.

[0005] When any desired structure is formed from a prefabricated blank or web of packaging material by joining the longitudinal ends of the laminate packaging material at overlap joints, cross sections of the laminate packaging material become free at each end of the blank or web to reveal the different layers contained within the laminate packaging material.

[0006] However, when filling the packaging container with liquid food, the liquid food may come into contact with these layers in the laminate packaging material and may adversely affect these layers if they are not waterproof, as is the case for paper materials, for example. This may lead to durability issues for the laminate packaging material due to deterioration of the laminate, and may also affect food hygiene.

[0007] It is therefore known to apply a strip of a sealant, particularly a polymeric material, to the edges exposed to the liquid food in order to prevent the liquid food from affecting the inner layers of the laminate packaging material.

[0008] Such strips are often manufactured as laminates themselves and may comprise an inner surface layer, an outer surface layer and a central layer. The different layers may be laminated together by their own material adhesive properties, for example by extrusion lamination, or by applying an additional adhesive, for example by wet lamination.

[0009] Since the sealing strip must follow the contour of each edge to be sealed in order to achieve a proper sealing function, good flexibility is required, and therefore each strip tends to be quite thin. However, the deformation of the material when applied to the contour of the edge subjects the strip to mechanical stresses. If the bonds between the different layers of the strip are not strong enough, the necessary deformations can cause the layers of the strip to delaminate, at least partially separating the layers.

[0010] Thus, problems arise with respect to sealing function and an improved sealing strip is needed. Summary of the Invention [Problem to be solved by the invention]

[0011] It is now an object of the present invention to at least partially overcome one or more of the above identified limitations of the prior art. In particular, the present invention aims to provide an improved sealing strip that is resistant to delamination and can be manufactured with low technical effort.

[0012] To achieve these objects, a first aspect of the invention relates to a method for manufacturing a strip for sealing a laminate packaging material for liquid food products.

[0013] In the method of the present invention, a pre-manufactured strip is provided that includes multiple layers of polymeric material, the layers including at least an inner surface layer, an outer surface layer, and a central layer.

[0014] In accordance with the present invention, at least one of the inner and outer surface layers is subjected to a heat treatment which increases the transparency of the manufactured strip relative to the transparency of the pre-manufactured strip.

[0015] This is based on the findings of the applicant, according to which the transparency of pre-manufactured strips is rather low due to the non-uniformity of the bonding material present at the bonding interface of the different layers. As known in the art, transparency indicates the amount of light passing through the strip and can therefore range from 0 (no light reaches) to 1 (all light reaches), but transparency is rather a theoretical case. The non-uniformity of the adhesive material of the pre-manufactured strips is the result, for example, of air entrapment or non-uniform distribution of the strip material or adhesive during the lamination process for producing the strip. Therefore, the pre-manufactured strips usually appear opaque.

[0016] In the heat treatment, the strip is subjected to an annealing treatment. This reduces the inhomogeneity of the joining material, since air entrapment is eliminated and uneven material distribution is smoothed. It should be noted that in this specification, the strip is referred to as pre-manufactured strip when it has not yet been heat treated. It is therefore referred to as manufactured strip or simply strip, at least after the heat treatment has begun. The heat treatment results in an increase in transparency and a higher homogeneity of the joining material. This allows visual inspection to confirm that the desired technical effect has been achieved. It should be noted that even a small increase in transparency achieves some improvement according to the described mechanism. This means that the method of the invention is successfully carried out if it is possible to measure a higher transparency in the manufactured strip relative to the transparency of the pre-manufactured strip, within the measurement accuracy achievable by known measurement methods for detecting transparency. Such measurement methods are well known in the art. It is not necessary to quantify the increase in transparency achieved, although it is of course possible. However, it is sufficient for the method of the invention to make a qualitative assessment in terms of whether the transparency can be increased (a "yes" or "no" decision). On that basis, the required evaluation can be carried out by human visual inspection or with the aid of respective measuring devices.

[0017] The main influencing factors for the success of the heat treatment are the material of the pre-manufactured strip, the different layers may comprise different polymeric materials and may comprise additional adhesives in between, as well as the strip surface temperature during the heat treatment and the heat treatment time.

[0018] Based on the present disclosure, one skilled in the art can experiment with different pre-manufactured strips, strip surface temperatures, and heat treatment times to identify in detail the preferred combination of strip and heat treatment parameters that best achieves the above-mentioned transparency enhancing effects.

[0019] This is a validation set of heat treatment parameters to achieve the desired technical effect of the present invention for pre-manufactured strips having inner and outer surface layers of polyethylene (PE) and a center layer of (polyethylene terephthalate) PET or ethylene vinyl alcohol (EVOH) with adhesive applied between each of the surface layers and the center layer in the form of a polyester polyol adhesive.

[0020] From this starting point, other specific heat treatment parameters can be experimentally explored and preferred variations can be specified in detail without further technical problems, where a higher temperature and / or time of heat treatment in principle improves the desired effect, and a lower temperature and / or time of heat treatment in principle reduces the desired effect. The skilled person will be well aware that thermal material stresses of the strip due to the heat treatment limit the available process window in the direction of higher temperature / time values, while a reduction in the desired effect on transparency limits the available process window in the direction of lower temperature / time values. Different strip materials may explore different temperature / time values.

[0021] The main advantage of the increased homogeneity of the bonded material in the strip after heat treatment is that the bonding of the different layers is significantly improved, and therefore the resistance of the strip to delamination is significantly increased.

[0022] This can be checked with a peel test, also called a peel test, where a sample strip is provided and immersed in oleic acid (130 ppm) at 40°C for 4 weeks, simulating a liquid food environment. A tensile force is then applied along the length of the strip. This stretches the material of the strip and, as the different layers of the strip do not have exactly the same mechanical properties, the different mechanical stress levels in the different layers will result in a separation force acting at the interface between the layers.

[0023] As an example, the above-mentioned reference strips (made of PE and PET / EVOH) were previously manufactured according to the prior art. The reference strips were subjected to a peel test. Then, the same reference strips, which were heat-treated according to the method of the present invention, were subjected to the peel test.

[0024] For the reference strip according to the prior art, the peel force caused the layers to at least partially separate / peel off. Delamination was detected at a tensile force of around 250 N / m, where "m" refers to the width of the sample strip. The width is measured perpendicular to the longitudinal direction of the strip, the longitudinal direction being defined by the direction of the tensile force in the peel test. If the pre-manufactured strip is produced in a flow manufacturing process, the longitudinal direction usually coincides with the machine direction of the manufacturing process. In the above example, the sample strip has a width of 7.5 mm. For the sample strip according to the invention, no delamination of the layers is detected before the strip is completely torn off.

[0025] One skilled in the art, based on this disclosure, can perform further experiments using different sample strips and the test methods described above to identify the necessary transparency that exhibits sufficient resistance to peeling.

[0026] Thus, the method of the present invention provides a simple method for producing sealing strips whose peel resistance is tailored to the requirements of a particular product.

[0027] The pre-manufactured strip can generally be achieved by any lamination or extrusion process, in which an inner surface layer and an outer surface layer are applied to a central layer. This is preferably done in a step in which a web of these layers is manufactured, preferably by lamination. The web may be characterized by relatively large dimensions, for example 2.5 m x 3.8 m. In principle, the web may be considered as a pre-manufactured large strip, and the heat treatment according to the invention can be carried out on the web. However, in order to achieve a more even and balanced distribution of the heat on the web surface and to reduce the technical complexity of the heat treatment, the dimensions of the pre-manufactured strip are preferably reduced.

[0028] Therefore, the large web is preferably slit into lanes. This may be done repeatedly to further reduce the dimension of the lanes to the desired final width of the pre-manufactured strip, preferably 7.5 mm. As the applicant has found, a width of 7.5 mm provides excellent heat distribution during heat treatment. The repeated reduction in dimension is beneficial with regard to handling of the flexible material of the strip and the various tools that may be used.

[0029] In one embodiment of the method of the invention, the material of the central layer is different from the material of the inner surface layer and / or the material of the outer surface layer. This typically leads to a higher inhomogeneity in the bonding material at the interface between the central layer and the inner surface layer and / or the outer surface layer of the pre-manufactured strip. As a result, the beneficial effects of the method of the invention described above lead to a particularly significant improvement in the bond between different materials. However, it is emphasized that these beneficial effects also occur when all layers are of the same material. This is due to the fact that inhomogeneity of the bonding material at the bonding interface is technically unavoidable at least to some extent. Now, even if in the case of the same material the bonding is generally good, the method of the invention allows to further reduce the remaining inhomogeneity of the bonding material.

[0030] Concerning the materials of the different layers, some preferred examples are given below. Preferably, the central layer may be made of polyesters such as polyethylene terephthalate (PET), high density polyolefins such as polyamide (PA), polypropylene (PP), or ethylene vinyl alcohol copolymer (EVOH). The inner and / or outer surface layers may be made of ethylene-based polyolefins such as LLDPE or LDPE. In a particularly preferred combination, the central layer is made of PET and the inner and / or outer surface layers are made of LDPE and / or LLDPE. It is also preferred that the central layer is made of PA and the inner and / or outer surface layers are made of LDPE and / or LLDPE. It is also preferred that the central layer is made of EVOH and the inner and / or outer surface layers are made of LDPE and / or LLDPE. It is preferred that the inner and outer surface layers are made of the same material, since this results in the same bonding system between the central layer and the inner and outer surface layers, respectively. The heat treatment therefore improves the homogeneity of the material at the bonding interface on both sides of the central layer of the produced strip as well.

[0031] In one embodiment of the method of the present invention, the transparency of the pre-manufactured strip is detected by a measurement device before the heat treatment, and based on the material of the pre-manufactured strip and the detected transparency, a parameter or set of heat treatment parameters is selected from a plurality of reference heat treatment parameters, the selected parameters resulting in a predetermined increase in the transparency of the pre-manufactured strip during the heat treatment.

[0032] On this basis, the required transparency and peel resistance, respectively, can be achieved with low technical effort.

[0033] Various measuring devices and methods are known that are suitable for detecting transparency. For example, a colorimeter may be used. Another simple example is to place a light source on one side of the strip and a photocell on the other side of the strip, the photocell detecting the light reaching through the strip.

[0034] In one embodiment of the method of the present invention, a plurality of reference heat treatment parameters are stored in a database, and the control unit receives the transparency detected by the measuring device, compares it with the contents of the database, selects the heat treatment parameters that lead to a predefined increase in transparency, and controls the manufacturing process accordingly.

[0035] In this way, the process quality is significantly improved and high efficiency is achieved. The material of the strip can be provided to the control device manually, for example by selecting a specific program during the setup of the control device. In principle, the material can also be determined by a material analysis unit, as known in the relevant art.

[0036] In one embodiment of the method of the present invention, the transparency of the strip is detected by a measuring device during the heat treatment, and the heat treatment is stopped by a control device when the transparency of the strip reaches a preset degree.

[0037] This allows the transparency of the strip to be quantitatively specified with a high level of process stability.

[0038] Detection of the transparency of the pre-manufactured strip during and before heat treatment can also be combined, leading to further improvements in the process quality.

[0039] In one embodiment of the method of the present invention, the reference heat treatment parameters comprise at least a reference strip surface temperature value and a reference heat treatment time value.

[0040] That is, the equipment used to carry out the method of the present invention is adapted and configured to achieve these heat treatment parameters.

[0041] Further exemplary heat treatment parameters that need to be adjusted or configured accordingly may include the heating power of the heat source used in the heat treatment, the relative speed of the heat source and the strip, and the distance between the heat source and the strip, although it should be noted that these are secondary parameters that influence the strip surface temperature achieved and the time over which this is achieved.

[0042] In one embodiment of the method of the present invention, strip surface temperature values ​​are detected on the inner surface layer and / or the outer surface layer by a measuring device and controlled by a control device to coincide with a reference strip surface temperature value selected as a heat treatment parameter during the heat treatment.

[0043] This can be achieved, for example, by means of a thermal camera, further improving the process quality.

[0044] Preferably, both the inner surface layer and the outer surface layer are exposed to the heat treatment.

[0045] In one embodiment of the method of the invention, the strip surface temperature value is selected from the range interval 100°C to 200°C, preferably 140°C to 150°C, and the heat treatment time value is selected so as to achieve a transparency after heat treatment of at least 0.5. Preferably, the transparency after heat treatment is at least 0.6, more preferably at least 0.7, more preferably at least 0.8, more preferably at least 0.9.

[0046] More preferably, the strip surface temperature value is selected from the range of 110°C to 180°C, even more preferably from the range of 120°C to 160°C, most preferably from the range of 130°C to 150°C. It should be noted that any temperature value included in the range from 100°C to 200°C or any transparency from 0.5 to 1 that is achievable by the use of available technical equipment is also disclosed for the method of the present invention. The same applies for any sub-range that can be defined in the range from 100°C to 200°C or in the range of transparency from 0.5 to 1.

[0047] In one embodiment of the method of the present invention, the strip is moved during the heat treatment to bring the measurement device in contact with the heat source used in the heat treatment.

[0048] In this way, a flow manufacturing process can be achieved that allows efficient production of the strip.

[0049] In that case, the process parameters preferably include a speed value of this relative movement, which may be replaced by a duration value of the heat treatment, since a duration value is preferably implied by the speed value, which determines the time for which the heat from the heat source affects the surface of the strip.

[0050] Preferably, one or more measuring devices and / or heat sources used to establish and measure the temperature of the surface of the strip are moved relative to the strip.

[0051] In most cases, the strip is moving and the heat source and heat measuring device are stationary.

[0052] Preferably, the velocity values ​​of the movement are in the range [0.01 m / s; 0.04 m / s]. It should be noted that any velocity value included in that interval that is achievable with the available technical equipment is also disclosed for the method of the present invention, as well as any sub-interval that can be defined in the range from 0.01 m / s to 0.04 m / s.

[0053] In one embodiment of the method of the present invention, the strip is moved in a flow manufacturing process at a speed selected from the range of 0.01 m / s to 0.04 m / s.

[0054] In one embodiment of the method of the present invention, the inner and outer surface layers of the pre-manufactured strip are made of PE and the central layer is made of PET or EVOH.

[0055] A second aspect of the invention relates to a strip for sealing laminate packaging materials for liquid food products, said strip being manufactured by the inventive method according to the present disclosure.

[0056] A third aspect of the present invention relates to a laminated packaging material for liquid food, from which a packaging container for packaging liquid food can be manufactured, the laminated packaging material being folded to form at least two overlapping portions which are joined to each other, the ends of the overlapping portions exposing cross sections of the laminated packaging material, at least one of which is exposed to the liquid food when filled into the packaging container and is sealed by the inventive strip according to the present disclosure.

[0057] A fourth aspect of the present invention relates to a packaging container for packaging liquid food products comprising the inventive laminated packaging material according to the present disclosure, wherein a strip of said laminated packaging material is placed inside the packaging container.

[0058] A fifth aspect of the present invention relates to an apparatus adapted and configured to carry out the inventive method according to the present disclosure, on this basis all apparatus-related features disclosed herein with respect to the inventive method are also disclosed as features of corresponding embodiments of the inventive apparatus, and vice versa.

[0059] Further objects, features, aspects and advantages of the present invention will become apparent from the following detailed description and drawings. [Means for solving the problem]

[0060] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: FIG. [Brief description of the drawings]

[0061] [Figure 1] FIG. 1 shows an embodiment of a packaging container for packaging liquid food products. [Diagram 2] FIG. 1 illustrates one embodiment of a laminate packaging material sealed with a strip. [Diagram 3] FIG. 2 is a cross-sectional view of one embodiment of a strip for sealing a laminate packaging material. [Figure 4] FIG. 1 illustrates an embodiment of a method for producing a strip for sealing a laminate packaging material with reference to an apparatus for carrying out the method. [Diagram 5] FIG. 1 illustrates the difference in appearance between pre-manufactured and heat treated strips. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0062] With reference to Figure 1, one embodiment of a packaging container 10 for a liquid food product 12 is shown. For example, a packaging container making machine 14 (not mentioned further) may provide a laminate packaging material 16 for producing the packaging container 10. The packaging container 10 may be produced, for example, by forming the laminate packaging material 16 into a tubular structure according to the invention, characterized by overlapping portions 24 (see Figure 2) covered and sealed by strips 22 (see Figures 2-5), welded together and presenting at least one exposed edge 26 (see Figure 2).

[0063] The liquid food 12 is filled into the laminated packaging material 16 thus formed, and the packaging container 10 is closed by sealing and cutting with the respective sealing and cutting means 18.

[0064] For purposes of further illustrating the present invention, a machine direction 20 is defined in Figure 1 and will be referenced in the following figures. By machine direction 20, it is meant that the laminate packaging material 16 is typically produced in a flow process having a material feed direction, or in other words, machine direction 20.

[0065] Figure 2 shows a laminate packaging material 16 that can form, for example, a packaging container 10 as shown in Figure 1. The laminate packaging material 16 is folded (folded portions not shown) to form an overlap 24 where the laminate packaging material 16 overlaps two edges 26. The overlap 24 are joined together, for example by welding. At the edge 26 of the overlap 24, a cross section 28 of the laminate packaging material 16 is exposed, exposing different layers 30 of the laminate packaging material 16 to the environment (shown in a cutaway in Figure 2). These layers are well known for this type of laminate packaging material 16 and can comprise, for example, a main layer made of paperboard, at least one barrier layer and a seal layer made of a polymeric material, and a surface coating.

[0066] One of the cross sections 28 is located on the inside 32 of the laminate packaging material 16, the location of which is merely exemplary and shows the side of the laminate packaging material 16 that is intended to form the inside 32 of the packaging container 10 that is exposed to the liquid food 12.

[0067] To protect the layer 30 of the laminate packaging material 16 at a cross section 28 on the inside 32, the cross section 28 is sealed by a strip 22 of the present invention. The location of the respective strips 22 on the laminate packaging material 16 and within the packaging container 10 is exemplarily and diagrammatically shown in Figure 1. By way of example only and for reference to Figure 1, the machine direction 20 is also shown in Figure 2, thus showing how the view of Figure 2 corresponds to the view of Figure 1.

[0068] 3 illustrates in cross-section one embodiment of the strip 22 of the present invention. The strip 22 comprises multiple layers 34 comprising polymeric materials. The multiple layers 34 include at least an inner surface layer 36, an outer surface layer 38, and a central layer 40. By way of example only, the inner surface layer 36 is intended to face the liquid food product 12 on the inside 32 of the laminate packaging material 16 and the packaging container 10, respectively, as shown in FIG.

[0069] In this example, the inner and outer surface layers 36, 38 of the strip 22 are made of PE, and the central layer 40 is made of PET or EVOH. There may be an adhesive between the layers 34, not shown.

[0070] Referring now to FIG. 4, one embodiment of the inventive method of producing a strip 22 for sealing a laminate packaging material 16 is shown with reference to an inventive apparatus 42 adapted and configured to carry out the method.

[0071] In a first step of the method, a pre-manufactured strip 44 is provided, which comprises a plurality of layers 34, made of a polymeric material, comprising at least an inner surface layer 36, an outer surface layer 38 and a central layer 40. According to the invention, at least one of the inner surface layer 36 and the outer surface layer 38 is subjected to a heat treatment such that the transparency 46 (see FIG. 5) of the manufactured strip 22 is increased relative to the transparency 48 of the pre-manufactured strip 44. As shown by the reference line 50, the pre-manufactured strip 44 before the heat treatment and the manufactured strip 22 after the heat treatment has begun. That is to say, the pre-manufactured strip 44 and the manufactured strip 22 are the same part, but are characterized by different material properties before and after the heat treatment has begun.

[0072] The device 42 comprises a heat source 52 which provides thermal energy for the heat treatment. Preferably, both the inner surface layer 36 and the outer surface layer 38 are exposed to the heat treatment. To that end, the device 42 may be designed such that the heat source 52 heats both surface layers 36 and 38 of the strip 22, but may also comprise a second heat source 54. For example, the heat source 52 may be designed as a heat chamber which locally covers the entire strip 22.

[0073] Preferably, the transparency 48 of the pre-manufactured strip 44 is detected by a measuring device 56 prior to heat treatment. A heat treatment parameter 58 is then selected from a plurality of reference heat treatment parameters 60 based on the known material of the pre-manufactured strip 44 and the detected transparency 48, to result in an increase in the transparency 48 of the pre-manufactured strip 44 to a predetermined value during heat treatment. The manufactured strip 22 is then characterized by its increased transparency 46. The reference heat treatment parameters 60 preferably comprise at least a reference strip surface temperature value and a reference heat treatment time value.

[0074] Preferably, a plurality of reference heat treatment parameters 60 are stored in a database 62, and a control unit 64 receives the transparency 48 detected by the measurement device 56, compares it with the contents of the database 62, selects the heat treatment parameters 58 that result in a predefined increase in transparency 48, and controls the manufacturing process accordingly.

[0075] Preferably, the transparency 46 of the produced strip 22 is detected by a measuring device 56 during the heat treatment, and once a predefined transparency 46 of the strip 22 is reached, the heat treatment is stopped by a control unit 64. Preferably, the same measuring device 56 and control unit 64 as described above are used for this purpose.

[0076] During the heat treatment, it is advantageous to detect strip surface temperature values ​​on the inner surface layer 36 and / or the outer surface layer 38 by means of the measuring device 56 and control them by means of the control device 64 so that they correspond to reference strip surface temperature values ​​selected as heat treatment parameters 58 during the heat treatment. Preferably, for this purpose the same measuring device 56 and control unit 64 are used as described above. For multiple measurement purposes the measuring device 56 may comprise respective measuring modules, for example for transparency measurement and temperature measurement.

[0077] During the heat treatment, the strip 22 may be moved relative to the heat sources 52, 54 and / or measuring devices 56 used in the heat treatment, thereby allowing the heat treatment to be integrated into a flow manufacturing process. For purposes of providing an example, a machine direction 20 corresponding to the previous figures is shown in Figure 4, as the method of the present invention may be combined with the manufacture of packaging containers 10.

[0078] Finally, turning to Fig. 5, an example is provided in which the transparency 46 of the produced strip 22 is increased compared to the initial transparency 48 of the pre-manufactured strip 44. The illustrated sample pre-manufactured strip 44 and the sample produced strip 22 are exemplarily identical to the pre-manufactured strip 44 / produced strip 22 described above and are moved relative to the heat source 52 in a flow production process at a speed selected from the range [0.01 m / s; 0.04 m / s]. At the same time, the strip surface temperature is selected from the range [140 ° C; 150 ° C]. All possible combinations of values ​​covered by these ranges, feasible by known technical means, achieve an increase in the transparency 46 of the produced strip 22 with respect to the transparency 48 of the pre-manufactured strip 44.

[0079] FIG. 5 shows two particularly good test results based on the following set of heat treatment parameters 58, both of which produced similar increases in transparency 46:

[0080] In the first test, a set of heat treatment parameters 58 was selected as (speed, strip surface temperature) = (0.0136 m / s, 135°C).

[0081] In the second test, a set of heat treatment parameters 58 was selected as (speed, strip surface temperature) = (0.036 m / s, 150°C).

[0082] The heat affected area of ​​the heat source 52 on the inner surface layer 36 was chosen as a circle with a diameter of 25 mm.

[0083] 5, it can be seen that the pre-manufactured strip 44 appears opaque because the black colored background does not shine through the pre-manufactured strip 44 significantly. Additionally, it can be seen that the heat treated strip 22 appears transparent because the black background shines through the strip 22 significantly.

[0084] The transparency of each 46, 48 was measured using a colorimeter, a measuring device well known in the art. The colorimeter measures three values ​​by placing a sample portion in front of a black background. The measurements are as follows: · "L index" which represents brightness from 0 (black) to 100 (white); "a index" from red (positive values) to green (negative values); and the "b index" ranging from yellow (positive) to blue (negative); It is.

[0085] In both of the above tests, the (L, a, b) values ​​were measured as about (29.87, 3.3, 2.42) in front of a black background for the pre-manufactured strip 44. For the heat treated strip 22, the same values ​​were measured as about (34.58, 3.11, 2.72) in front of a black background. Thus, a significant increase in brightness was demonstrated indicating an increase in the transparency 46 of the manufactured strip 22.

[0086] From the foregoing description, while various embodiments of the present invention have been described and illustrated, the invention is not limited thereto and may be embodied in other ways within the scope of the subject matter defined in the following claims.

[0087] (Reference sign) 10 Packaging containers 12 Liquid food 14 Packaging container manufacturing machine 16 Laminated packaging materials 18 Sealing and cutting means 20 Machine direction 22 Strip 24 Overlap section 26 Edge 28 Section 30 Layers of Laminated Packaging Material 32 Inside 34 Multiple layers of strips 36 Inner surface layer 38 Outer surface layer 40 middle layer 42 Equipment 44 Pre-fabricated strips 46 Transparency of the produced strip 48 Transparency of pre-manufactured strips 50 Reference line 52 Heat source 54 Heat source 56 Measuring Equipment 58 Heat Treatment Parameters 60 Reference Heat Treatment Parameters 62 Database 64 Control device

Claims

1. A method for manufacturing a strip (22) for sealing a laminated packaging material (16) for a liquid food product (12), comprising the steps of: A pre-manufactured strip (44) is provided that includes multiple layers (34) that include a polymeric material; The multiple layers (34) comprise at least an inner surface layer (36), an outer surface layer (38), and a central layer (40); The inner surface layer (36) and the outer surface layer (38) are subjected to a heat treatment such that the transparency (46) of the manufactured strip (22) is increased relative to the transparency (48) of the pre-manufactured strip (44). method.

2. the material of the central layer (40) is different from the material of the inner surface layer (36) and / or the material of the outer surface layer (38); The method of claim 1.

3. Prior to heat treatment, the transparency (48) of the pre-manufactured strip (44) is detected by a measuring device (56), and a parameter or set of heat treatment parameters (58) is selected from a plurality of reference heat treatment parameters (60) based on the material of the pre-manufactured strip (44) and the detected transparency (48), the selected parameter resulting in a predetermined increase in the transparency (48) of the pre-manufactured strip (44) during heat treatment. The method of claim 1.

4. The plurality of reference heat treatment parameters (60) are stored in a database (62); a control device (64) receiving the transparency (48) detected by the measuring device (56), comparing it with the contents of the database (62), selecting heat treatment parameters (58) that result in a predetermined increase in the transparency (48), and controlling the manufacturing process accordingly; The method of claim 3.

5. the transparency (46) of the produced strip (22) is detected by the measuring device (56) during the heat treatment, and the heat treatment is stopped by a control device (64) when a predetermined transparency (46) of the produced strip (22) is achieved. The method of claim 3.

6. the reference heat treatment parameters (60) comprise at least a reference strip surface temperature value and a reference heat treatment time value; The method of claim 3.

7. a strip surface temperature value detected by the measuring device (56) on the inner surface layer and / or the outer surface layer (36; 38) and controlled by the control device (64) during the heat treatment so as to coincide with a reference strip surface temperature value selected as a heat treatment parameter (58); The method of claim 3.

8. Both the inner surface layer (36) and the outer surface layer (38) are subjected to a heat treatment. The method of claim 1.

9. The strip surface temperature value is selected from the range of 100°C to 200°C, and the heat treatment time value is selected to achieve a transparency (46) of at least 0.5 after the heat treatment. The method of claim 1.

10. During the heat treatment, the strip (22; 44) is moved relative to the heat source (52; 54) and the measuring device (56) used in the heat treatment. The method of claim 1.

11. The method, wherein the strip (22; 44) is moved in a flow manufacturing process at a speed selected from the range of 0.01 m / s to 0.04 m / s.

10. The method of claim 9.

12. the inner surface layer (36) and the outer surface layer (38) of the pre-manufactured strip (44) are made of PE, and the central layer (40) is made of PET or EVOH; The method of claim 1.

13. A strip (22) for sealing a laminated packaging material (16) for a liquid food product (12), comprising: The strip (22) is manufactured by the method of claim 1. strip.

14. A packaging container (10) for packaging a liquid food (12) can be manufactured, and a laminated packaging material (16) for the liquid food (12) is provided, The laminate packaging material (16) is folded to form at least two overlapping portions (24) that are joined to each other, and edges of the overlapping portions (24) expose cross sections (28) of the laminate packaging material (16), at least one of the cross sections (28) being exposed to the liquid food (12) when the packaging container (10) is filled and sealed by the strip (22) of claim 13. Laminated packaging materials.

15. A packaging container (10) for packaging the liquid food (12), A manufactured strip (22) comprising a laminate packaging material (16) according to claim 14 and comprising a plurality of layers (34) comprising a polymer material is placed on the inside (32) of the packaging container (10), Packaging container (10).

16. An apparatus (42) adapted and configured to perform the method of claim 1.

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