Abstract:
The present invention is related to easy-to-open packaging ( 1 ) comprising an easy tearable multilayer laminate ( 2 ), said laminate comprising at least two polymer layer wherein at least one of said polymer layer comprises a scratched surface ( 6, 6′ ) forming a scratched polymer layer ( 11 ), said scratched surface comprising a multitude of scratched lines parallel to the extrusion direction ( 2 ) of said scratched polymer layer, the scratched lines creating a predetermined tear direction of the packaging.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention is related to an easy to open packaging comprising a weakened and easy tearable laminate with at least two polymer layer as well as possibly barrier layer and a production method for said laminate. 
       TECHNICAL BACKGROUND OF THE INVENTION AND PRIOR ART 
       [0002]    There is currently a growing trend where consumers have less time for cooking. Processed food as “table ready meals” and an increased demand for convenience is becoming more and more important. 
         [0003]    These developments are heavily influencing the packaging industry. Packaging now needs to be multifunctional, and properties like easy openability, recloseability, cookability in the package (trays, pouches, etc.) or use of the package as a serving dish, are only some examples being demanded by consumers. 
         [0004]    One of the major issues related to convenience is the openability of a package. For many applications with flexible or even rigid packs, like trays with a flexible lid, peelable sealing polymer layers are typical, as they allow an easy reopening of the heat-sealed pack. It is common as well to apply a tear notch to a pouch in the side seal which allows opening of the pouch by tearing off the upper part of the pack. However, one disadvantage of using a simple tear notch is that the tearing of the films is heavily influenced by the film/laminate properties and it becomes difficult to control the direction of the tear propagation because the front and back laminate of the pouch tear in different directions and not in a straight line as desired. 
         [0005]    In addition to using specially designed films with low tear propagation force, several methods are known to improve the tear performance (straight lines) further. One option is to use laser perforation as described in EP 0 540 184 or EP 0 357 841. With this method, the laminate can be partially cut (in most cases one layer of a laminate), whereby the tearing will follow the cut line. 
         [0006]    In addition to using a laser, other methods to mechanically create “guide lines” are described in DE 10320429, whereby the sealing layer is notched by mechanical means or as in US 2005/0123724, at least one outer layer is grooved and quite similar in JP 42 67750. It is common to all these types of solutions, that at least one layer of a laminate is once or several times nearly fully cut through. 
         [0007]    Although the outlined easy tear solutions work quite effectively in relation to openability of a package, depending on the laminate construction and application, the treatment can heavily affect the barrier properties (oxygen transmission rate) and therefore diminish the shelf-life of the packaged product. Additionally, when, for example, a stand-up pouch is heated in a microwave oven, the tear performance in the treated area of the still hot laminate can diminish dramatically. 
       AIMS OF THE INVENTION 
       [0008]    The objective of the present invention is to overcome the drawbacks of the described prior art and to offer an easy to open flexible pack as well as a production method thereof, which can be realised at a low cost, while maintaining the barrier properties of the pack, even after additional heat sterilisation of a packaged product, thus yielding optimal tearing properties of the heated packaging laminate. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention discloses an easy-to-open packaging comprising an easy tearable multilayer laminate, said laminate comprising at least two polymer layer wherein at least one of said polymer layer comprises a scratched surface forming a scratched polymer layer, said scratched surface comprising a multitude of scratched lines parallel to the extrusion direction of said scratched polymer layer, the scratched lines creating a predetermined tear direction of the packaging. The scratched lines being a slight weakening a polymer layer and not a cut through the layer. 
         [0010]    According to various preferred embodiments of the present invention, one or several of the following additional features are disclosed:
       the depth of the scratched lines represents less than 50% of the thickness said scratched polymer layer;   the depth of said scratched lines represents less than 20% of the thickness said scratched polymer layer;   the laminate further comprises barrier layer;   the barrier layer are selected from the group consisting of metals, metal oxides, metallised polymer films, SiOx, organic barrier layer coated polyester, polypropylene or polyamide, EVOH, PVOH, polyamide, polyvinylidenchloride, polyvinylidenfluoride, polyacrylnitrile;   the polymer layer are selected from the group consisting of polyolefins, polyesters, polyamides, polyvinylidenchloride, polyvinylidenfluoride, polyvinylchloride, polyacrylate, polymethacrylate and their co-polymers or blends;   the scratched polymer layer is the outside layer of the laminate;   the scratched polymer layer is embedded inside the laminate;   the adhesive layer is directly applied on the scratched surface of the scratched polymer layer;   the multitude of scratching lines is obtained by mechanical scratching means;   the scratching means is sandpaper;   the packaging is a flow pack, a standing pouch or a three/four side sealed pouch;   the scratched lines from the front and back of the packaging are placed on top of each other and in parallel;   the packaging comprises at least one tear notch in the zone of the scratched surface;   the scratched lines have no influence on the oxygen transmission rate of the packaging;   the unidirectional tear properties of the packaging are the same before and after sterilisation of said packaging.       
 
         [0026]    The present invention further discloses a method for the production of the laminate of claim  1  comprising the steps of:
   a) treating a pre-laminate with scratching means for scratching a part of the surface of at least one of his constitutive polymer layer;   b) applying an adhesive directly on the scratched surface;   c) lamination of an additional layer on the adhesived scratched surface.   
 
         [0030]    In preferred embodiments of the production method of the present invention, one or several of the additional features are that:
       the additional layer is a polymer layer selected from the group consisting of polyolefins, polyamides, polyesters, polyacrylates, polymethacrylates, polyacrylnitrile and co-polymers or blends.   the steps b) and c) are replaced by the application of a cold seal or a hot seal consisting of a polymer dispersion/emulsion.   the adhesive ( 10 , 10 ′) is applied by extrusion lamination or extrusion coating.       
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0034]      FIG. 1  represents an easy to open pouch comprising a sand paper treated layer. 
           [0035]      FIG. 2  represents a laminate with scratches on each side. 
           [0036]      FIG. 3  represents the cross-section of the laminate structure including one layer with scratches. 
           [0037]      FIG. 4  represents a schematic overview of the laminate production method with sand paper treatment. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0038]    It was discovered, that “scratching” the surface of a laminate (e.g. PETP/PE, OPA/PE, PETP/ALU/PP, PETP/ALU/OPA/PP or PETP/OPA/PP . . . ) with sandpaper in machine direction (extrusion direction) results in a perfect straight line tearing along the parallel lines resulting from the “scratches”. This was surprising, as the scratches just slightly penetrate the surface of the layer without “cutting” into the layer while all former presented solutions were based on deeper cuts or a multitude of deep cuts in at least one layer. 
         [0039]    The scratches function like guiding lines or rails when tearing the laminate in the same direction. The high number of lines guarantees that, even if the straight tearing stops in one of the starting lines, the adjoining scratches function again as guiding lines. 
         [0040]    However, it is not attractive to have the “scratches” on the surface, which are quite visible. To solve this problem, it was tested to determine if the “scratches” could be placed inside of a laminate. 
         [0041]    The polyamide side of an aluminium oxide coated polyester/polyamide pre-laminate were first treated in the same way (scratched with sandpaper). The treatment did not result in improved tearing along the scratches as expected. The pre-laminate did tear easily in all directions without any preference. A solvent-based adhesive was then applied to the treated polyamide side of the pre-laminate and after evaporation of the solvent in a drying tunnel, a polypropylene film was laminated to the same side. It was quite surprising to discover, that after curing of the adhesive, the laminate then exhibited the same positive tearing characteristics as described above with the outside treated laminates. It was found to be favourable to put the adhesive on the scratched surface directly, as by putting it on the other film, air will be entrapped. 
         [0042]    Pouches were produced from the laminate described above in a way, such that the treatment lines from the front and back of the pouch were placed exactly on top of each other and in parallel. Tear notches were applied to the left and right seal of the pouch in the treated laminate area.  FIG. 1  shows such a pouch (treated zone  6 ; tear notches  7 ,  7 ′). The laminate with two parallel treatment areas  6 ,  6 ′ to produce the pouch is outlined in  FIG. 2 .  FIG. 3  shows the cross-section of the laminate (AlOx-coated polyester  9 , adhesive layers  10  and  10 ′, polyamide  11 , polyproylene  12  and treated polyamide surface  6 ). 
         [0043]    The pouches were filled with water and steam sterilised in an autoclave at 121° C. for 30 minutes. After heating the filled pouches in a microwave oven, the openability of the hot pouch was tested. The pouches opened at low tear force and the tear propagation of both front and back side were exactly in a straight parallel line. 
         [0044]    A comparison of the oxygen permeation of the sterilised pouches with and without treatment did prove that the barrier properties were not influenced. 
         [0045]      FIG. 4  shows a preferred method to produce the laminate as described above. The inner surface of the pre-laminate  13  is treated with sandpaper in station  14  (two treatment zones in parallel). A sandpaper band is slowly rewound from unwind station  15  to winding station  16 . The sandpaper is pressed with reel  17  against the film transport roller  18 . The adhesive is applied on the treated surface in station  19  and the solvent removed from the pre-laminate  20  in the drying channel  21 . The pre-laminate is combined with the polypropylene layer  12  in the lamination station  23  and the final laminate wound up in the winder  24 . 
         [0046]    The adhesive layer  10 , 10 ′ can be applied by extrusion lamination or extrusion coating, in the case of extrusion lamination, no solvent and therefore drying step is necessary 
       DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION 
       [0047]    The following examples are representative embodiments of the present invention but are not intended to limit the possible polymer or barrier layer to those recited in the examples. 
       Example 1 
       [0048]    The polyester side of a laminate PETP-AlOx 12 μm/OPA 15 μm/PP 70 μm produced from Aluminium oxide coated 12 μm polyester (Camclear® 800) adhesive laminated (Liofol® UR 3640 with UR 6055) to a 15 μm bi-axially oriented polyamide (Biaxis® 15), again adhesive laminated (Liofol® UR 3640 with UR 6055) to a 70 μm polypropylene film (Vistalux® PP 210.60) is scratched to create a predetermined tear line. To do this, two stripes of sandpaper (gradation 320) in an appropriate distance to each other are pressed against the bypassing laminate as shown in  FIG. 4  treating station  14 . 
         [0049]    Pouches as outlined in  FIG. 1  are produced from this laminate on a bag making machine. 
         [0050]    Even when heated in a microwave oven, the pouches open in a straight line at low force. 
         [0051]    The oxygen transmission rate of a pouch with and without scratch treatment is &lt;3 cm 3 /m 2  d bar at 23° C./50 r.h. 
       Example 2 
       [0052]    The same laminate structure PETP-AlOx 12 μm/OPA 15 μm/PP μm as in Example 1 is produced, but the sandpaper treatment is performed in-line on the polyamide side of a pre-laminate (PETP-AlOx 12 μm/OPA 15 μm) during lamination as shown in  FIG. 4 . 
         [0053]    The final laminate is again converted to pouches as in  FIG. 1 . 
         [0054]    The results of the opening and the barrier testing are similar to Example 1, but as the treatment is embedded in the laminate, the scratches are not visible and the pouches therefore look favourable. 
       Example 3 
       [0055]    The polyamide side of a pre-laminate PETP 12 μm/ALU 9 μm/OPA 15 μm (polyester 12 μm Mylar® 800, 9 μm Aluminium 8079, 15 μm bi-axially oriented polyamide Biaxis®, adhesive laminated with Liofol® UR 3640/UR 6055) is scratched with sandpaper (gradation 220) and adhesive laminated (Liofol®UR 3640 with UR 6055) to PP (Vistalux® PP 210.60) as shown in  FIG. 4 . 
         [0056]    The final laminate is again converted to pouches as in  FIG. 1 . 
         [0057]    The results of the opening and the barrier testing are similar to Example 1. Very important, as the treatment is embedded in the laminate, the scratches are not visible. 
         [0058]    The oxygen transmission rate of the pouches is not measurable (&lt;0.1 cm 3 /m 2  d bar at 23° C./50 r.h.), as the barrier is too high for conventional measurement equipment. 
       Example 4 
       [0059]    The polyamide side of a pre-laminate PETP 12 μm/ALU 8 μm/OPA 15 μm (polyester 12 μm Mylar® 800, 9 μm Aluminium 8079, 15 μm bi-axially oriented polyamide Biaxis®, adhesive laminated with Liofol® UR 3640/UR 6055) is scratched with sandpaper (gradation 220) and adhesive laminated (Liofol® UR 3640 with UR 6055) to PE (Groflex® K 0040.010) as shown in  FIG. 4 . 
         [0060]    The final laminate is converted to pouches as in  FIG. 1  on a form fill and seal equipment. 
         [0061]    The results of the opening and the barrier testing are similar to Example 1. Very important, as the treatment is embedded in the laminate, the scratches are not visible. 
         [0062]    The oxygen transmission rate of the pouches is not measurable (&lt;0.1 cm 3 /m 2  d bar at 23° C./50 r.h.), as the barrier is too high for conventional measurement equipment. 
       Example 5 
       [0063]    The PETP-met. side of a pre-laminate PETP 12 μm/met.-PETP 12 μm (printed polyester side 12 μm Mylar® 800 adhesive laminated with Liofol® UR 3640/UR 6055 to the metallised side of 12 my metallised polyester Mylar® 800) is scratched with sandpaper (gradation 220) and adhesive laminated (Liofol® UR 3640 with UR 6055) to PE (Groflex® K 0040.010) as shown in  FIG. 4 . 
         [0064]    The final laminate is converted to pouches as in  FIG. 1  on a form fill and seal equipment. 
         [0065]    The results of the opening are similar to Example 1. Very important, as the treatment is embedded in the laminate, the scratches are not visible. 
         [0066]    The oxygen transmission rate of the pouches is &lt;1 cm 3 /m 2  d bar at 23° C./50 r.h. as for the non-treated pouch. 
       Example 6 
       [0067]    The white OPP side of a pre-laminate OPP 20 μm/OPP white 30 μm (30 μm white Trespaphane® RND adhesive laminated with Trespaphane® GND UK 2615/UR 5020 to the printed side of 20 my Trespaphane® GND) is scratched with sandpaper (gradation 220) and coated with 3 g/m2 cold seal swale IP4180 as shown in  FIG. 4 , whereby the cold seal is applied in the adhesive application station  19 , dried in the drying tunnel  21  and directly winded up without adding any further layer. The final laminate is converted to flow-packs on a form-fill-seal equipment. 
         [0068]    The packs can be opened very easily and the opening is in a straight line. 
         [0069]    The invention as outlined herein allows production of an easy-to-open package with a straight opening line on both the front and back side of the package. The opening is functional, even when the package is still hot immediately when taken out of a microwave oven. The barrier properties are unaffected. 
       LEGEND 
       [0000]    
       
           1  stand up pouch 
           2  extrusion direction of the polymer film 
           3  front side of the pouch 
           3 ′ back side of the pouch 
           4 ;  4 ′ left and right side seals 
           5  gusset seal 
           6 ;  6 ′ scratched surface (multitude of scratching lines) 
           7 , 7 ′ tear notches 
           8  laminate 
           9  outside layer 
           10 ;  10 ′ adhesive layer 
           11  middle layer 
           12  sealing layer 
           13  pre laminate 
           14  treatment station 
           15  unwind for sand paper 
           16  upwind for sand paper 
           17  sandpaper 
           18  pressure reel 
           19  adhesive application station 
           20  treated pre laminate with adhesive 
           21  drying tunnel 
           22  unwind unit for sealing layer 
           23  lamination station 
           24  laminate reel for pouch making