SE527944C2 - Packaging laminate in plastic and with gas barrier, packaging container and method for producing the packaging laminate - Google Patents

Abstract

A gas barrier packaging laminate (10) having durability to stress crack formation and yet a bending stiffness and good integrity between the laminate layers, comprising outer layers of heat-sealable polyolefin (16, 17), two polymer carrier layers (11, 12) each being coated with a SiOx gas barrier layer (13, 14), and an intermediate polymer layer (15) that comprises at least first (15a) and second (15b) part-layers, whereof said first part-layer (15a) has a higher stiffness than said second part-layer (15b) and said second part-layer (15b) has higher elastomeric properties than said first part-layer (15a). A stiff structural sandwich construction is formed by the two stiff carrier layers separated by the intermediate layer that is also shock absorbing to prevent stress-cracking of the SiOx layers. The invention also relates to a packaging container manufactured from the packaging laminate and to a method of manufacturing of the packaging laminate.

Description

The packaging laminate is continuously formed into a tube, filled with contents and sealed into cushion-shaped packaging containers, by a step of simultaneous heat sealing and cutting. Thereafter, the cushion-shaped packaging container is normally folded into a parallelepipedic packaging container. The main advantage of this process concept with continuous forming of a tube, filling and sealing, is that the web can be sterilized continuously, just before the forming of the tube, which allows for an aseptic packaging process, ie. a process in which the liquid content to be filled, as well as the material itself, is depleted of bacteria and the filled packaging container is prepared under clean conditions, so that the filled packaging can be stored for a long time, even at room temperature, without the growth of microorganisms risk in the filled product. An important factor for long-term storage is of course also the gas barrier properties of the filled and sealed packaging container, which in turn is strongly dependent on the gas barrier properties of the packaging laminate itself, but also on the quality of seals and opening device of the finished packaging. Another important advantage of the packaging process of the Tetra Brik® type is, as stated above, the possibility of continuous packaging at high speed, which has a significant impact on cost efficiency. The bag-type beverage packages available on the market today, however, are typically manufactured through other, non-aseptic, more complex and expensive processes of a less continuous nature. In the prior art, it is also known to apply gas barrier coatings of SiOx to a substrate, by means of plasma-enhanced chemical vapor deposition (PECVD).

The advantages of a gas barrier layer of SiOx compared to other gas barrier materials are, firstly, that it has a positive environmental profile and, secondly, that it is not affected, ie. that the barrier properties are kept intact, when it comes in contact with ambient moisture or liquid, it is transparent and because it is applied in very thin layers, it is also flexible and resistant to cracks when it is bent or folded.

It is known from EP-A-385054 to laminate together two gas barrier layers of a silicon compound, such as silica, facing each other, by means of an intermediate adhesive layer. However, this document does not mention resistance to the formation of stress cracks or the integrity of the laminate layers during mechanical action, or the rigidity properties of the laminate, and does not describe an intermediate layer which provides a shock-absorbing but still stiffening effect of the laminate. Furthermore, the layers of silica (SiO 2) described are substantially different from the PECVD coated layers of SiOx contemplated by the present invention.

Thus, there is a need for a thin, gas-tight packaging laminate without metal foil, which has suitable properties for an aseptic, continuous, high-speed packaging process similar to the packaging process for Tetra Brik® Aseptic. Important factors in such a process are the rigidity, elasticity and integrity of the packaging laminate. If the laminate web is too flexible and easy to displace the high speed tube forming process, the process will not be able to run safely and continuously. On the other hand, if the packaging laminate is too thick, in order to obtain the required rigidity and durability, it may be black to handle in the folding operation, and if it is not elastic and has shock-absorbing properties during transport and handling, it will have a tendency to crack and lose their integrity due to mechanical stresses. It is further natural, of course, that the cost-effectiveness of the material itself will be reduced with increasing thickness. Furthermore, the packaging containers which are folded from the packaging laminate must be resistant to the formation of stress cracks to withstand handling during transport, etc., which is a condition which is difficult to combine with the rigidity properties.

The beverage-type beverage packages currently available on the market often have a laminated construction including a single gas barrier layer of e.g. an ethylene vinyl alcohol polymer (EVOH) and does not have the rigidity requirements of the present invention.

It is therefore an object of the present invention to provide a packaging laminate which alleviates the above-discussed disadvantages and problems.

It is an object of the present invention to provide a packaging laminate without foil but with gas barrier properties suitable for aseptic packaging and long-term storage, as well as with sufficient flexural rigidity and integrity and resistance to the formation of stress cracks in mechanical stress, to be suitable for continuous packaging of liquid foodstuffs by means of a continuous tube-forming process and to provide packaging containers which can withstand repeated stresses during transport and handling.

It is a further object of the invention to provide a film for a packaging laminate which has the required rigidity and durability but which is thin enough to fold the package at at least one end thereof.

It is another object of the invention to provide a film for a packaging laminate which has the above-mentioned properties, but which is also transparent to give an attractive appearance to a packaging container made from the laminate.

The invention is also directed to a packaging container filled with beverage or liquid food, which is produced from the packaging laminate according to the invention according to the invention, as well as to a method for manufacturing the laminated packaging material according to the invention.

BRIEF SUMMARY OF THE INVENTION The above objects are achieved by means of an intermediate polymer layer which is laminated between the first and the second gas barrier coated polymeric support layers. The intermediate polymer layer includes at least first and second sublayers, of which said first sublayer has a higher stiffness than said second sublayer, and said second sublayer has higher elastomeric properties than said first sublayer. The overall packaging structure combines the advantages of a structural sandwich construction as well as an elastic shock absorber, as well as a stiffness enhancer, to obtain a film with good flexural stiffness and maintain its integrity under aggressive transport conditions.

The planar layers of a sandwich board, which are here represented by the two polymeric carrier films, function similarly to the flanges of an I-beam, in that they resist bending stresses and increase the bending stiffness of the structure by being separated from each other by an intermediate layer. However, unlike an L-beam structure, the lower density frame layer also provides support all the way to the flanges or planar layers.

It has been observed that the elastomeric property of the second sublayer in the intermediate layer increases the resistance of the packaging container to cracking during cyclic stresses, i.e. exposure to repeated stresses or vibrations that may occur during transport, by absorbing the mechanical stresses with elastic, reversible deformations.

It has also been observed that the rigidity property of the first sublayer of the intermediate layer makes an additional contribution, in addition to the sandwich effect, to the rigidity properties of the packaging laminate as a whole.

As a comparison, it has further been observed that if the intermediate layer consists of a single layer of a high stiffness polymer, such as the polymer in the first sublayer of the present invention, there is an increased risk of the formation of stress cracks in mechanical stresses.

However, it has also been observed, for the sake of comparison, that if the intermediate layer consists of a single layer of a polymer with high elastomeric properties, then the stability of the laminate during sealing may deteriorate because the polymer with high elastomeric properties tends to melt too much and disappear from the seal. the Council, ie that the sealing window is narrowed. Furthermore, the required thickness of such an intermediate layer will increase the cost of the laminate in an undesirable manner.

To overcome these problems, tests have been performed in which the intermediate layer consists of a mixture of a polymer with high stiffness and a polymer with high elastomeric properties (ratios 25/75, 40/60 and 60/40). However, due to the formation of stress cracks, the results showed similar error rates (50 to 90%) in transport test simulations as in the case of an intermediate layer consisting of a single layer of a high stiffness polymer.

The solution to the above problems and needs is thus to offer a thin packaging laminate with good gas barrier properties, by laminating the two polymeric carrier films, coated with the gas barrier layers of SiOx, in a construction with an intermediate spacer layer including at least first and second sublayers, said first sublayers have a higher rigidity than said second sublayer and said second sublayer has higher elastomeric properties than said first sublayer, and the laminate also has outer heat-sealable layers of thermoplastic polymer. In the best embodiment, the intermediate layer is composed of three sublayers, the third sublayer being identical either to the first or to the second sublayer and the three sublayers being arranged symmetrically in the intermediate layer. , i.e. with the two identical sublayers on each outer side of the intermediate layer. Such a symmetrical arrangement reduces the risk of, among other things, cracks in Si0x or curl ("curl"), and ensures good sealing.

When it has been found that it is preferable to have in the intermediate layer more polymer with high elastomeric properties than polymer with high stiffness, the best embodiment of the intermediate layer is that the third sublayer is identical to the second sublayer and that they are arranged on each the side of the first sublayer, all three layers being of substantially the same thickness.

According to one aspect, at least 50% by weight, preferably at least 60% by weight, of said intermediate layer consists of one or more layers with high elastomeric properties.

However, embodiments are conceivable in which the third sublayer is identical to the first sublayer, and arranged so that the second sublayer is positioned between said first sublayer and said third sublayer, all three layers preferably being of substantially the same thickness.

Preferably, each sublayer of the intermediate layer has a thickness of 5-30 μm, preferably 10-25 μm and most preferably 10-20 μm.

The polymeric carrier layers preferably comprise polyester, polyamide or polypropylene materials and therefore have a certain degree of inherent rigidity, although other relatively rigid polymers can also be used for the carrier layers according to the invention. More preferred are the oriented films and thus have a higher degree of crystallinity than non-oriented polymer films have. The structural sandwich construction of two relatively rigid carrier layers laminated to each side of such an intermediate polymer layer comprising a thermoplastic polymer with high elastomeric properties, provides a laminate with good resistance to cracking under repeated mechanical stresses, and surprisingly good flexural stiffness relative to its thickness. In addition, the arrangement of the two PECVD-deposited SiOx layers has been found to result in a much more than doubled gas barrier compared to a laminate or a film containing only one SiOx layer. The construction with a spacer intermediate layer which also acts as a "buffer" for permeation of gas, in particular oxygen, thus provides a surprising improvement in gas barrier properties, which shows that a synergy - effect arises with this special construction. The laminate thus has excellent gas barrier properties and is both economical and easy to handle in continuous high-speed packaging processes.

The total thickness of the intermediate layer is from 30 to 55%, preferably from 35 to 50% of a total thickness of the packaging laminate.

The intermediate layer, which is composed of at least a first and a second sublayer, constitutes the thickest individual layer in the laminate.

The thickness of the carrier layers is preferably from about 5 to about 20, more preferably from about 5 to about 16% of the total packaging laminate. The carrier layers do not only contribute by their thickness to the overall flexural stiffness of the packaging laminate. but also by their interaction with the relatively thicker and spacer intermediate layer.

The oriented polymer carrier film is preferably a prefabricated film of polyester, polyamide (PA) or polypropylene (PP), such as a cast or co-extrusion cast film or more preferably a mono- or biaxially oriented polymer film of polyethylene terephthalate (PET), polyethylene naphthenate (PEN). ), polyamide (PA) or polypropylene (PP), or a multilayer film comprising a substrate surface layer of such a polymer or a multilayer film comprising at least one such mono- or biaxially oriented layer.

By using prefabricated, oriented films as carrier layers, it is ensured that they have the same inherent flexural stiffness relative to other layers in the laminate which are extrusion or co-extrusion laminated, even at lower thicknesses.

A high stiffness polymer for the first sublayer is suitably selected from the group consisting of high density polyethylene (HDPE) and polypropylene (PP).

A thermoplastic polymer with high elastomeric properties for the second sublayer is suitably selected from the group consisting of very low density polyethylene (VLDPE), ultra-low density polyethylene (ULDPE), ethylene-based copolymer or terpolymer and polyolefin-based elastomer or plastomer.

More preferably, the polymer for the second sublayer is a polyethylene copolymer or VLDPE or ULDPE. A particularly well-functioning example of a shock-absorbing polymer is "Attane®" VLDPE from Dow. Other examples are "Exxco012" from Exxon and "Clearflex CLBO" from Polimeri.

The polymer in the second sublayer is thus preferably a thermoplastic polymer with high elastomeric properties, which gives the bag or walls of the packaging laminate sufficient flexibility to absorb and dampen impact energy, without leading to ruptures and leakage along the sealing areas, i.e. the transverse top seal of a wedge-like bag, and the polymer in the carrier layer is an oriented polypropylene or preferably an oriented polyester or polyamide.

According to a most preferred embodiment of the invention, the gas barrier layers of SiOx are positioned in the laminate in such a way that they face each other, with the intermediate polymer layer between them. In this way, optimal gas barrier layers can be obtained and the layers of SiOx will be best protected. However, embodiments are also conceivable in which one or both SiOx layers face outwards in the laminate structure.

The SiOx layer is preferably deposited by PECVD technique, where x = 1.7 to 2.0, with a thickness of from about 50 to about 500 Angstroms (Å), preferably from about 80 to about 300 Å. There are alternative methods to deposit inorganic layers, such as SiOx, on polymer films, which, however, generally result in thicker and less flexible layers of SiOx. This in turn results, due to cracks in the SiOx layer, generally in lower quality laminates with respect to oxygen barrier properties. Thus, it is preferred according to the invention that the gas barrier layers of SiOx be applied by the continuous method of plasma enhanced chemical vapor deposition, PECVD, of SiOx from plasma of an organic silicon compound such as hexadimethylsiloxane (HDMSO).

The thickness of the polymeric carrier layer is preferably from about 7 to about 30 microns, more preferably from about 8 to about 20 microns, most preferably from about 8 to about 15 microns, and in a preferred embodiment, the two carrier layers of polymer have about the same or exactly the same thickness. It is known that the PECVD process works optimally at the above-mentioned thickness of the carrier layer, which is also preferred from an economic point of view.

To ensure a symmetrical and reliable behavior in the filling and packaging process, it is best to use carrier layers, ie. the outer layers of the sandwich structure, which have approximately the same or exactly the same thickness, although it may be possible for certain desired properties to use carrier layers of different thickness or flexural stiffness.

Preferably the total thickness of the intermediate layer is from about 30 to about 90 μm, more preferably from about 35 to about 65 μm, most preferably from about 40 to about 65 μm and this is preferably while the total thickness of the packaging laminate is from about 100 to about 180 pm, most preferably from about 100 to about 150 pm.

For optimal shock-absorbing effect, the thickness of the intermediate layer should be from about 40 to about 65 μm, as the second sublayer comprises a polymer such as e.g. VLDPE or ULDPE. For other alternative polymers in the second sublayer, it may be appropriate to use thicker intermediate layers, such as up to 90 microns, especially if the total thickness of the packaging laminate is desired to be from about more than 150 to about 180 microns.

Thus, the thickness of the intermediate layer (15) is from 35 to 65 μm, the thickness of the polymeric carrier layer (11, 12) is from 8 to 15 μm, the thickness of the outer layers of heat-sealable olefin polymer (16, 17) is from 10 to 25 μm and from 18 to 30 μm, respectively, and the total thickness of the packaging laminate is from 100-150 μm.

Most preferably, the thickness of the intermediate layer (15) is from 40 to 65 μm, the thickness of the polymeric support layer (11, 12) is from 12 to 15 μm, the thickness of the outer layers of heat-sealable olefin polymer (16, 17) is from 10 μm. to 25 μm and from 18 to 30 μm, respectively, and the total thickness of the packaging laminate is from 100 to 150 μm.

According to another preferred embodiment, the thickness of the intermediate layer (15) is from 40 to 65 μm, the thickness of the polymeric carrier layer (11, 12) is from 8 to 12 μm, the thickness of the outer layers of heat-sealable olefin polymer (16, 17) is from 10 to 25 μm and from 18 to 30 μm, respectively, and the total thickness of the packaging laminate is from 100 to 150 μm.

In order to obtain an optimal bending stiffness and elastic properties, preferably the thickness ratio between the intermediate layer and the carrier layer is from 2 to 8.5 and the ratio between the total thickness of the packaging laminate and the thickness of the intermediate layer is from 1.5 to 5, when the total The thickness ratio is from 100 to 150 .mu.m, or the thickness ratio between the intermediate layer and the carrier layer is from 4 to 10 and the ratio between the total thickness of the packaging laminate and the thickness of the intermediate layer is from 1.7 to 3 .mu.m. then the total thickness is from 150 to 180 μm.

A further preferred and important advantage is that such a packaging laminate can be transparent to provide packaging containers with at least a part thereof which is transparent, in order to make the filled contents visible.

According to another aspect of the invention, there is provided a packaging container filled with beverage or liquid food, preferably an aseptic packaging container, made from the packaging laminate according to the invention.

The packaging container according to the invention is a bag or "standing bag" or the like and is durable in handling and distribution and resistant to moisture and oxygen during long-term storage, due to the high-quality packaging laminate, which in turn also provides high quality seals and excellent gas barrier properties. Another important advantage of packaging containers made from the packaging laminate according to the invention is that they can withstand boiling or thawing by means of microwaves, as well as retorting (autoclaving).

According to another aspect of the invention, there is provided a method of making the laminated packaging material of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS Additional advantages and advantageous features of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, in which: Fig. Ta is a cross-sectional view of a first embodiment of a laminated packaging material of the present invention; Fig. 1b is a cross-sectional view of a second, best embodiment of a laminated packaging material according to the present invention; Figs. 2 shows a preferred example of a packaging container made from the packaging laminate according to the invention.

Figs. 3a, 3b and 3c show alternative, preferred embodiments of methods of manufacturing the packaging laminate.

Fig. 4 shows a graph of elongation-stress, relating to four different polymers or polymer blends.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Fig. 1a thus shows a packaging laminate 10, comprising a first and a second carrier layer 11; 12 which are films of a preferably oriented polyester, such as e.g. polyethylene terephthalate (PET, OPET or BOPET), or films of a preferably oriented polyamide (PA), on which coatings of a thin gas barrier layer of SiOx 13; 14 has been applied by plasma-enhanced chemical vapor deposition (PECVD).

The two SiOx layers are preferably facing the interior of the laminate and thus face each other. Between the two carrier layers coated with gas barrier layers, an intermediate layer 15 is laminated including a first sublayer 15a of a thermoplastic, preferably polyolefin-based, polymer with high stiffness, such as e.g. high density polyethylene (HDPE) or polypropylene (PP), and a second sublayer 15b of a thermoplastic, preferably polyolefin-based, polymer with high elastomeric properties, such as e.g. very low density polyethylene (VLDPE), ultra low density polyethylene (ULDPE), polyethylene based copolymers or terpolymers and polyolefin based elastomers or plastomers. The intermediate layer 15 is thicker than any of the surrounding layers in the packaging laminate, and thereby acts as a spacer element between the two carrier layer films of oriented polymer. The two sublayers 15a, 15b are substantially of the same thickness and can in an alternative embodiment exchange places with each other.

Fig. 1b shows a preferred packaging laminate 10 'in which the intermediate layer 15, in addition to said first 15a and second 15b sublayers, includes a third sublayer 15c which is identical to said second sublayer 15b.

The first sublayer 15a is arranged between the second 15b and the third 15c sublayer. Fig. 1c shows yet another embodiment of a packaging laminate 10 'in which the intermediate layer 15, in addition to said first 15a and second 15b sublayers, includes a third sublayer 15d which is identical to said first sublayer 15a. The second sublayer 15b is arranged between the first 15a and the third 15c sublayer. In all the embodiments shown in Figs. 1a, 1b, 1c, the preferred oriented polymeric films have a certain degree of inherent stiffness, since they are oriented, and may therefore have a relatively higher degree of crystallinity than non-oriented polymeric films. The sandwich construction of two relatively rigid carrier layers, which are laminated on each side of a thicker intermediate polymer layer, provides a laminate which has surprisingly good flexural stiffness in relation to its thickness. In addition, the arrangement of the two PECVD-deposited SiOx layers has been found to result in a much more than doubled gas barrier compared to a laminate or a film containing only one SiOx layer.

The arrangement of an intermediate layer which also acts as a "buffer" for the permeation of gas, in particular oxygen, thus gives a surprising improvement in gas barrier properties, which indicates that a synergy effect arises in this particular arrangement. As an example, if two films of SiOx-coated BOPET, each having an OTR value of about 4 cm 3 / m 2 * 24 hours at 23 ° C and 50% RH, are laminated together by a thin polyolefin-based layer, then the total OTR value of the structure will be about 2 cm3 / m2 * 24 hours at 23 ° c and so ° /. RH. Since the same films are laminated together with at least one intermediate layer of polyolefin-based polymer having a thickness of about 55 g / m 2, the OTR value iiii improves about 0.2 om 3 / m2 * 24 hours at 23 ° C and about% RH. Similarly, if two films of SiOx-coated BOPET, each having an OTR value of about 1.6 cm 3 / m 2 * 24 hours at 23 ° C and 50% RH, are laminated to each other by a thin polyolefin-based layer , the total OTR value of the structure will be about 0.8 cm3 / m2 * 24 hours at 23 ° C and 50% RH. When the same films are laminated together with at least one intermediate layer of polyolefin-based polymer having a thickness of about 55 g / m 2, the oTR width is improved by about 0.16 cm The improvement of the gas barrier by the "buffer effect" is thus at least four- or five-fold compared with the improvement which results from using only double gas barrier films which are directly laminated to each other. On the outside of the carrier layer 11, which will form the outside wall of a packaging container made from the packaging laminate, at least one layer 16 of a heat-sealable olefin polymer is applied, preferably a low density polyethylene (LDPE) or a linear low density polyethylene (LLDPE), which also includes so-called metallocene-catalyzed LLDPE (m-LLDPE), ie. LLDPE polymers catalyzed by a single-site catalyst. Other examples of alternative polymers for the outer layer of the packaging wall may be a medium density polyethylene (MDPE) or polypropylene (PP).

On the outside of the carrier layer 12, which will form the inside wall of a packaging container made from the packaging laminate, at least one layer 17 of a heat-sealable olefin polymer is applied, preferably a layer of LDPE or more preferably a layer of LLDPE and most preferably a first sublayer 17a of LDPE and a second, outer sublayer 17b of LLDPE.

The outer layers 16, 17 are each applied in an amount of from about 10 to about 30 microns, in order to obtain optimal heat sealing properties in relation to cost efficiency.

For good adhesion between the different layers in the packaging laminate, adhesive layers of adhesive polymers, tie layers and primers, which are known in the art, are preferably used. Such bonding layers and primers are adapted to the specific choices of polymer in the different layers and can be selected from polyolefins and modified polyolefins, preferably polyethylene-based polymers, such as e.g. LDPE and modified LDPE.

Such examples of bonding layers are homopolymers or copolymers of LDPE or grafted copolymers of polyethylene, grafted with monomers comprising functional groups of the carboxyl or glycyldyl type, such as acrylic monomers or maleic anhydride monomers (MAH), e.g. ethylene (meth) acrylic acid copolymer (E (M) AA), ethylene-glycidyl (meth) acrylate copolymer (EG (M) A)) or MAH-grafted polyethylene (MAH-g-PE).

For optimal adhesion in the bonding layers 18, 19 between the layers of SiOx 13; 14 and the intermediate polyolefin layer 15, a polyethylene base polymer is preferably used which is graft modified by an unsaturated alkoxysilane compound, as described in U.S. Pat. 5,731,092 which is incorporated herein by reference. See especially column 1, row 39 to column 3, row 21 and Examples 1 and 2.

Most preferred is the polyethylene base polymer, which is graft modified by an unsaturated alkoxysilane compound, blended with a non-grafted polyethylene, such as preferably low density polyethylene (LDPE). It has surprisingly been found that the number of adhesion points between the grafted positions in the binder and the silica can be increased enormously if the grafted polyolefin is mixed with a non-grafted polyolefin, i.e. that the number of adhesion points increases despite the fact that there are fewer grafted positions in the binder polymer.

This most preferred embodiment is based on the realization that it is not only the number of grafted positions that affects the degree of adhesion, but also their ability to physically come into contact with the silica. It has been found that the grafting of a polyolefin according to US 5,731,092 results in a crosslinking of the polyolefin, which makes the polyolefin less flexible than the non-grafted polyolefin. Due to the reduced flexibility of the polyolefin, the number of contact points between the bonding layer, which consists of the grafted polyolefin, and the silica, will be smaller than for a bonding layer which consists only of a non-grafted polyolefin of the same type. However, in a bonding layer consisting only of a non-grafted polyolefin, the adhesion in an individual adhesion point of the plurality of adhesion points will not be as good as in an individual adhesion point in a bonding layer consisting only of a grafted polyolefin.

The preferred embodiment further solves the problem related to these conflicting aspects of grafted and non-grafted polyolefin binders, by providing a binder which is a mixture of a grafted polyolefin and a non-grafted polyolefin. In this case, the increased flexibility obtained due to the presence of a non-grafted polyolefin provides an increased number of adhesion points, while the grafted polyolefin provides an increased adhesion at these points, which together results in adhesion properties which are better than the adhesion properties of one grafted polyolefin per se, and one non-grafted polyolefin per se, respectively.

When bonding layers are used between the intermediate layer and the SiOx layers, the thickness referred to as the total thickness of the intermediate layer also includes the thickness of such bonding layers. Any of the polymers discussed above may also be used in any bonding layers 20; 21 between the outer, heat-sealable polyolefin layers 16; 17 and the polymeric carrier layers 11; 12.

Fig. 2 shows a preferred example of a packaging container 20 made from a packaging laminate 10, 10 'or 10 "according to the invention. The packaging container is particularly suitable for small beverage packages for direct use by means of a straw or the like. Such a package typically has a volume of about 330 ml or less, preferably from about 100 to about 250 ml, eg about 125 ml, 200 ml or about 250 ml. wedge-shaped 21, so that it is easy to handle and dimensionally stable when placed on a shelf in the food warehouse or on a table or the like. , are hidden under the triangular corner flaps 23, which are folded and sealed to the bottom of the package.

The packaging container 20 is preferably transparent.

Fig. 3a shows a preferred embodiment 30a of a method of making the packaging laminate 10 ', 10 "according to the invention.

A first web 331 of a polymeric carrier layer 332 coated with a gas barrier layer 333 of SiOx and a second web 334 of a polymeric carrier layer 335 coated with a gas barrier layer 336 of SiOx are advanced toward an extrusion station 337, the two The SiOx layers 333 and 336 are preferably facing each other, and are laminated to each other by co-extrusion of an intermediate three-part polymer layer 338 between them and compression of the two webs 331, 334 and the intermediate layer 338 when passing through a nip after the extrusion station. 337. The intermediate polymer layer 338 may also be coextruded together with adjacent layers of binder polymer 339 for improved bonding to the SiOx layers on the two webs 331 and 334. The resulting laminated web 340 is advanced to an extrusion station 341, where an outer layer of a heat transfer layer sailable polyolefin 342 is extruded on the outside of the polymeric backing layer 335. The resulting web 343 is further advanced to an extrusion station 344, where an outer layer of a heat-sealable polyolefin 345 is extruded on the outside of the polymeric carrier layer 332. The resulting packaging layer is 527 944. the laminate 346 will then be rolled up and stored on a reel, not shown.

Fig. 3b shows another preferred embodiment 30b of a method of producing the packaging laminate 10 ', 10 "according to the invention.

A first web 331 of a polymeric carrier layer 332 coated with a gas barrier layer 333 of SiOx and a second web 334 of a polymeric carrier layer 335 coated with a gas barrier layer 336 of SiOx are advanced toward an extrusion station 337, the two The SiOx layers 333 and 336 preferably face each other, and are laminated to each other by co-extrusion of an intermediate three-part polymer layer 338 between them and compression of the two webs 331, 334 and the intermediate layer 338 when passing through a nip after the extrusion station. 337. The intermediate polymer layer 338 may also be co-extruded together with adjacent layers of binder polymer 339 for improved bonding to the SiOx layers on the two webs 331 and 334. The resulting laminated web 340 is advanced to a hot roll nip 341 ', where a outer layer of a prefabricated film comprising at least one layer of a heat sealable polyolefin 342 'is laminated to the outside of the polymeric carrier layer 335, by applying heat and pressure to the hot roll nip 341 '. The resulting web 343 'is further advanced to a hot roll nip 344', where an outer layer of a heat sealable polyolefin 345 'is laminated to the outside of the polymeric backing layer 332, by applying heat and pressure to the hot roll nip 344'.

The resulting packaging laminate 346 'will then be rolled up and stored on a reel, as shown.

Fig. 3c shows another preferred embodiment 300 of a method of making the packaging laminate 10 ', 10 "according to the invention.

A first web 331 of a polymeric carrier layer 332 coated with a gas barrier layer 333 of SiOx and a second web 334 of a polymeric carrier layer 335 coated with a gas barrier layer 336 of SiOx are advanced against a hot roll nip 337 ', the two SiOx layers 333 and 336 preferably face each other, at the same time as a web of a prefabricated, coextruded film of an intermediate three-part polymer layer 338 'is advanced between the two webs 331, 334 against the nip 337'. The three webs are laminated to each other by application of heat and pressure as they pass through the hot nip 337 '. The intermediate polymer layer 338 'may be a prefabricated film having outer layers of binder polymer 339 for improved bonding to the SiOx layers on webs 331, 334. The resulting laminated web 340' is advanced. to a hot roll nip 341 ', where an outer layer of a prefabricated film comprising at least one layer of a heat sealable polyolefin 342' is laminated to the outside of the polymeric backing layer 335, by applying heat and pressure to the hot roll nip 341 '. The resulting web 343 "is further advanced to a hot roll nip 344 ', where an outer layer of a prefabricated film comprising at least one layer of a heat sealable polyolefin 345' is laminated to the outside of the polymeric backing layer 332, by applying heat and pressure to the hot roll nip 344 '. The resulting packaging laminate 346 "will then be rolled up and stored on a reel, not shown. In the above method 30a, the extrusion stations 341 and 344 may be passed in reverse order according to an alternative, preferred embodiment.

In each of the above methods 30b and 30c, the lamination of the heat-sealable outer polyolefin films can be performed in reverse order, i.e. by first laminating the prefabricated film 345 'to the outside of the polymeric carrier layer 332, in the hot roll nip 344', resulting in a web 347. The web 347 is passed to a hot roll nip 341 ', in which the heat sealable, prefabricated outer film 342 'is then laminated to the outside of the polymeric backing layer 335, resulting in the packaging laminate 346' or 346 ".

Other combinations of hot nip lamination and extrusion lamination are conceivable within the concept of the invention, although not shown in separate figures. For example, a method in which the intermediate three-part polymer layer 338 'is a prefabricated film to be hot nip laminated as described in Fig. 3c can be combined with extrusion lamination of one or both of the outer heat sealable layers 342 and 345, as described in connection with Fig. 3a.

According to other preferred embodiments of methods 30a, 30b and 30c, the surface of the gas barrier layer 333, 336 is treated by SiOx by a surface oxidizing treatment such as Corona treatment, in order to provide improved adhesion to the intermediate polymer layer 338, 338 'or the bonding layers 339, 339'. . According to an alternative embodiment of the method of manufacturing the packaging laminate according to the invention, the various prefabricated webs 331, 334, 338 ', 342 * and 345' are laminated to each other by primer lamination, i.e. lamination by coating and drying a primer or an adhesive on one of the webs, followed by lamination in a nip. The packaging laminate 10, 10 ', 10 "may be provided with a printed decorative layer, in order to make the packaging container more attractive and informative to consumers and to protect its contents from light, which printed decoration may be applied to the SiOx layer 333 or 336 which is directed towards the outside of a package formed from the packaging laminate Alternatively, it may be applied to the other side of the carrier layer 332 or to the outer layer of heat sealable polyolefin 342, 345, 342 ', 345'. be covered by a thin, transparent, protective polymer layer.

Fig. 4 shows a graph of elongation-stress relating to four different polymers or polymer blends, which thus gives a comparative measure of elastomeric properties of the polymers / polymer blends.

Curve 1 represents 100% HDPE, curve 2 represents a mixture of 60% VLDPE and 40% HDPE, curve 3 represents a mixture of 75% VLDPE and 25% HDPE, and finally only 4 represents 100% VLDPE. As can be seen, the elastomeric properties increase with an increasing content of VLDPE, and pure VLDPE has the highest elastomeric properties.

EXAMPLES Comparative, simulated transport tests (tougher than normal, actual transport conditions) were performed on packaging containers made of laminate structures according to the invention and with exactly the same outer sealing layers, two SiOx-coated carrier layers of the same thickness and kind, and an intermediate thick layer in all samples. All the packaging containers had been prepared in the same way. The only difference between the tests of the packaging containers, was the internal composition of the intermediate layer in the laminate structures. 20 packaging containers of the same type were tested for simulated transport, i.e. they were placed on a shaking table and subjected to repeated vibrations for 30 minutes. See the result in Table 1. The reference examples are a laminate with an intermediate layer of 45 g / m 2 of VLDPE alone and a laminate with an intermediate layer of 45 g / m 2 of HDPE alone.

Table 1 Intermediate Stiffness Stiffness Brø fl sföfhåila fl the layers machine direction transverse direction (of 20 (mNm) (mNm) fÖFDaGKIMQQ) VLDPE 45 g / m2 2.0 2.0 1/20 reference HoPE 45 g / mt up: in 4.5 2.0 18/20 reference VLDPE / HDP 3.1 2.0 1/20 LDPE 15/15/15 g / mz VLDPE / HDPE / V 2.0 2.0 3/20 LDPE 10/25/10 g / mz HDPE / VLDPE / H 3.3 2.0 4/20 DPE 15/15/15 g / m2 HDPE / VLDPE / H 1.9 1.9 1/20 DPE 10/25/10 g / mz Leakage often occurred among the packaging containers with intermediate layers of HDPE only, while there was practically no leakage in the packaging containers that had only VLDPE as intermediate layers. . However, the packaging containers that had only VLDPE as an intermediate layer showed an undesirably low rigidity. Laminate according to the invention and with three sublayers of the same thickness, had better stiffness values and the one with the most VLDPE, ie. VLDPE / HDPE / VLDPE and all three sublayers of the same thickness, also had the lowest breaking frequency. In conclusion, it should be noted that the present invention, which has been described above with specific reference to the accompanying figures, is not limited to those embodiments which have only been described and shown as examples, and that modifications and changes obvious to a those skilled in the art are possible without departing from the inventive concept set forth in the appended claims.

Claims (41)

10 15 20 25 30 527 944 Patent claims Gas barrier laminate packaging laminate (10) which is resistant to the formation of stress cracks and yet has a flexural stiffness and good integrity between the laminate layers, comprising: outer layer of heat sealable olefin polymer (16, 17); a first gas carrier layer of SiOx (13), coated on a first polymeric carrier layer (11); a second gas barrier layer of SiOx (14), coated on a second polymeric support layer (12); and an intermediate polymer layer (15) laminated between the first and second gas barrier coated polymeric backing layers, the intermediate polymer layer including at least first (15a) and second (15b) sublayers, said first sublayer (15a) having higher stiffness than said second sublayer. (15b) and said second sublayer (15b) has higher elastomeric properties than said first sublayer (15a), and wherein a stiffness of each of the first and second polymeric backsheets cooperates with a thickness of the intermediate polymer layer, as a shock absorbing spacer layer. in a structural sandwich construction, to provide resistance to stress cracking, flexural stiffness and good integrity between the layers. Gas-barrier packaging laminate according to claim 1, wherein the resistance to stress cracking, the flexural stiffness and the integrity between the layers, make the packaging laminate suitable for packaging liquid foods and beverages, by means of a high-speed, continuous process. Gas barrier laminated packaging laminate according to claim 1, wherein the thickness of the intermediate layer (15) is from 30 to 55%, preferably from 35 to 50% of a total thickness of the packaging laminate (10). Gas barrier laminated packaging laminate according to any one of the preceding claims, wherein each sublayer of said intermediate layer (15) has a thickness of 5-30 μm, preferably 10-25 μm and most preferably 10-20 μm. 10 15 20 25 30 35 527 944 _22. Gas barrier laminated packaging laminate according to any one of the preceding claims, wherein said intermediate layer (15) includes a third sublayer (15c; 15d). A gas barrier packing laminate according to claim 5, wherein said third sublayer (1 Sd) is identical to said first sublayer (15a), and arranged so that said second sublayer (15b) is positioned between said first sublayer and said third sublayer. The gas barrier packing laminate of claim 5, wherein said third sublayer (15c) is identical to said second sublayer (15b), and arranged so that said first sublayer (15a) is positioned between said second sublayer and said third sublayer. Gas barrier laminated packaging laminate according to any one of claims 5-7, wherein said first, second and third sublayers (15a, 15b, 15c; 15d) all have substantially the same thickness. Gas-laminated packaging laminate according to any one of the preceding claims, wherein at least 50% by weight, preferably at least 60% by weight, of said intermediate layers consist of said layers with high elastomeric properties. Gas-barrier packaging laminate according to any one of the preceding claims, wherein a thermoplastic polymer having high elastomeric properties for the second sublayer (15b) is selected from the group consisting of very low density polyethylene, ultra-low density polyethylene, polyethylene based copolymers, polyethylene based terpolymers and polyolefin-based elastomers and plastomers. 11. 1 1. Gas-laminated packaging laminate according to any one of the preceding claims, wherein a high stiffness polymer for the first sublayer (15a) is selected from the group consisting of high density polyethylene (HDPE) and polypropylene (PP). 10 15 20 25 30 35 527 944 _23- A gas barrier packaged laminate according to claim 1, wherein a thickness of the first polymeric backing layer (11) and / or a thickness of the second polymeric backing layer (12) is from 5 to 20% of a total thickness of the packing laminate (10). A gas barrier packaged laminate according to claim 12, wherein the thickness of the first polymeric backing layer (11) and / or the thickness of the second polymeric backing layer (12) is from 5 to 15% of the total thickness of the packing laminate (10). A gas barrier packaging laminate according to claim 1, wherein the first polymeric carrier layer (11) and / or the second polymeric carrier layer (12) is a film of polyester, polyamide or polypropylene, or a multilayer film comprising a substrate surface layer of one of these polymers. The gas barrier packaged laminate of claim 1, wherein the first polymeric backing layer (11) and / or the second polymeric backing layer (12) is a film of a polymer selected from the group consisting of mono- or biaxially oriented polyethylene terephthalate (PET), mono- or biaxially oriented polyethylene naphthenate (PEN), mono- or biaxially oriented polyamide (PA) and mono- or biaxially oriented polypropylene, or a multilayer film comprising at least one oriented layer of one of these polymers. The gas barrier packaged laminate of claim 1, wherein a polymer having high elastomeric properties for the second sublayer includes very low density polyethylene, a high stiffness polymer for the first sublayer includes high density polyethylene and a polymer for the first polymeric backsheet (11). ) and for the second polymeric backing layer (12) includes an oriented polyester or polyamide. The gas barrier packaged laminate of claim 1, wherein the first gas barrier layer of SiOx (13) and the second gas barrier layer of SiOx (14) are positioned in the laminate so that they face each other, seen from their respective carrier layers. 10 15 20 25 30 35 527 944 _24- Gas barrier laminated packaging laminate according to claim 1, wherein the first gas barrier layer of SiOx (13) and the second gas barrier layer of SiOx (14) have been deposited by PECVD technology, at a thickness of from 50 to 500 Å, preferably from 80 to 300 Å. Å, and where x = 1.7-2.0. Gas barrier laminated packaging laminate according to claim 1, wherein a thickness of the first polymeric carrier layer (11) and / or a thickness of the second polymeric carrier layer (12) is from 7 to 30 μm, preferably 8 to 20 μm and most preferably 8 to 15 pm. The gas barrier packaged laminate of claim 1, wherein the first polymeric backing layer (11) and the second polymeric backing layer (12) have the same thickness. The gas barrier packaged laminate of claim 1, wherein the thickness of the intermediate layer (15) is from 30 to 90 μm, more preferably from 35 to 65 μm, most preferably from 40 to 65 μm. Gas barrier laminated packaging laminate according to claim 1, wherein a total thickness of the packaging laminate is from 100 to 180 μm, preferably from 100 to 150 μm. The gas barrier packaged laminate of claim 1, wherein the thickness of the intermediate layer (15) is from 35 to 65 microns, a thickness of the first polymeric carrier layer (11) and / or a thickness of the second polymeric carrier layer (12) is from 8 to 15 μm, a thickness of the outer layers of heat-sealable olefin polymer (16, 17) is from 10 to 25 μm and from 18 to 30 μm, respectively, and a total thickness of the packaging laminate is from 100 to 150 μm. Gas-barrier packaging laminate according to claim 23, wherein the thickness of the intermediate layer (15) is from 40 to 65 μm and the thickness of the first polymeric carrier layer (11) and / or the thickness of the second polymeric carrier layer (12) is from 12 to 15 pm. 10 15 20 25 30 527 944 -25- Gas barrier laminated packaging laminate according to claim 23, wherein the thickness of the intermediate layer (15) is from 40 to 65 μm and the thickness of the first polymeric carrier layer (11) and / or the thickness of the second polymeric carrier layer (12) is from 8 to 12, um. Gas barrier laminated packaging laminate according to claim 1, wherein the intermediate polymer layer (15) is laminated to the adjacent layers (13, 14) of SiOx, by means of a bonding layer (18, 19). The gas barrier packaging laminate of claim 26, wherein the bonding layer (18, 19) comprises a blend of a grafted copolymer of alkoxysilane and polyethylene, with a non-grafted polyethylene. The gas laminate packaging laminate of claim 1, wherein the laminate is transparent. Packaging container made from the packaging laminate according to claim 1. A method of making a packaging laminate including outer layers of heat sealable olefin polymer (16, 17), a first gas barrier layer of SiOx (13) coated on a first polymeric backing layer (11), a second gas barrier layer of SiOx (14) coated on a second polymeric backing layer (12); and an intermediate polymer layer (15) including at least first (15a) and second (15b) sublayers, said first sublayer having a higher stiffness than said second sublayer, and said second sublayer having higher elastomeric properties than said first sublayer, which intermediate layer (15 ) is laminated between the first and second gas barrier coated polymeric backsheets, the method comprising the steps of: advancing a first web (331) and a second web (334) toward each other and toward a first extrusion station (337), the first web ( 331) comprises a first polymeric support layer (332) coated with a first gas barrier layer (333) of SiOx and the second web (334) comprises a second polymeric support layer (335) coated with a second gas barrier layer (336) of SiOx; Lamination of the first web (331) and the second web (334) to each other, by co-extrusion of said sublayers (15a, 15b, 15c; 15d) of the intermediate polymer layer (338), optionally together with a bonding layer (339) on each side of the intermediate polymer layer (338), between the first web and the second web, and compressing the first web and the second web at the first extrusion station (337); extruding a first outer layer (342) comprising a heat sealable polyolefin, on the outside of the first or second polymeric carrier layer (332 or 335), at a second extrusion station (341), and extruding a second, opposite outer layer (345) comprising a heat sealable bar polyolefin, on the outside of the second of the second or first polymeric carrier layer (335 or 332), at a third extrusion station (344). The method of claim 30, wherein the first web (331) and the second web (334) are advanced toward each other so that the gas barrier layers (333, 336) of SiOx face each other. The method of claim 30, wherein the first gas barrier layer (333) of SiOx and the second gas barrier layer (336) of SiOx are treated by a surface activation treatment prior to lamination. The method of claim 32, the van / id surface activation treatment is corona treatment. A method of making a packaging laminate including an outer layer of heat sealable olefin polymer (16, 17), a first gas barrier layer of SiOx (13) coated on a first polymeric backing layer (1 1), a second gas barrier layer of SiOx (14) coated on a second polymeric carrier layer (12); and an intermediate polymer layer (15) including at least first (15a) and second (15b) sublayers, said first sublayer having a higher stiffness than said second sublayer, and said second sublayer having higher elastomeric properties than said first sublayer, which intermediate layer (15) is laminated between the first and second gas barrier coated polymeric backsheets, the method comprising the steps of: advancing a first web (331) and a second web (334) toward each other and toward a first extrusion station (337), the first web (331) comprising a first polymeric carrier layer (332) coated with a first gas barrier layer (333) of SiOx and the second web (334) comprising a second polymeric carrier layer (335) coated with a second gas barrier layer (336) of SiOx; laminating the first web (331) and the second web (334) to each other, by co-extruding said sublayers (15a, 15b, 15c; 15d) of the intermediate polymer layer (338), optionally together with a binder layer (339) on each side of the intermediate polymer layer (338). between the first web and the second web, and compressing them at the first extrusion station (337); heat and pressure lamination in a first hot roll nip (341 '), of a first prefabricated film (342') comprising at least one layer of a heat sealable polyolefin, to the outside of the first or second polymeric backing layer (332 or 335); and heat and pressure lamination in a second hot roll nip (344 '), of a second prefabricated film (345') comprising at least one layer of a heat sealable polyolefin, to the outside of the second of the second or first polymeric backing layer (335 '). or 332). The method of claim 34, wherein the first web (331) and the second web (334) are advanced toward each other so that the gas barrier layers (333, 336) of SiOx face each other. The method of claim 34, wherein the first gas barrier layer (333) of SiOx and the second gas barrier layer (336) of SiOx are treated by a surface activation treatment prior to lamination. The method of claim 36, wherein the surface activation treatment is corona treatment. A method of making a packaging laminate including an outer layer of heat sealable olefin polymer (16, 17), a first gas barrier layer of SiOx (13) coated on a first polymeric carrier layer (11), a second gas barrier layer of SiOx (14) coated on a second polymeric support layer (12): and an intermediate polymer layer (15) including at least first (15a) and second (15b) sublayers, said first sublayer having a higher stiffness than said second sublayer, and said second sublayer has higher elastomeric properties than said first sublayer, said intermediate layer (15) being laminated between the first and second gas barrier coated polymeric backing layers, the method comprising the steps of: advancing a first web (331) and a second web (334) to each other and to a first hot roll nip (337), the first web (331) comprising a first polymeric carrier layer (332) coated with a first gas barrier layer (333) of SiOx and the second web (33 4) comprises a second polymeric support layer (335) coated with a second gas barrier layer (336) of SiOx; laminating the first web (331 'and the second web (334) at a prefabricated web (338'), by advancing the intermediate, dry-made web (338 ') between the first web (331) and the second web (334) and applying heat and pressure to the first hot roll nip (337 '), the intermediate prefabricated film (338') comprising an intermediate polymer layer (338 ') and optionally a bonding layer (339') on each side of the intermediate the polymer layer (338 '); heat and pressure lamination in a second hot roll nip (341 '), of a first prefabricated film (342') comprising at least one layer of a heat sealable polyolefin, to the outside of the first or second polymeric backing layer (332 or 335) ; and heat and pressure lamination in a third hot roll nip (344 '), of a second prefabricated film (345') comprising at least one layer of a heat sealable polyolefin, to the outside of the second of the second or first polymeric carrier layer (335 or 332). ). The method of claim 38, wherein the first web (331) and the second web (334) are advanced toward each other so that the gas barrier layers (333, 336) of SiOx face each other. 527 944 _29- The method of claim 38, wherein the first gas barrier layer (333) of SiOx and the second gas barrier layer (336) of SiOx are treated by a surface activation treatment prior to lamination. » The method of claim 40, wherein the surface activation treatment is corona treatment.