EASILY TEARABLE FLEXIBLE PACKAGING SUBSTRATE

Description

FIELD OF THE INVENTION

[0001] This present invention relates to an easy-to-tear polymeric flexible packaging substrate. More particularly, the invention relates to easy-to-tear polymeric film or laminate obtained by surface treatment.BACKGROUND OF THE INVENTION

[0002] Generally, polymeric or thermoplastic flexible packaging materials are difficult to tear because the materials are flexible and are usually comprised of randomly dispersed, long chains of molecules having relatively strong covalent carbon-to-carbon bonds.

[0003] One method of making easy to tear is generally to stretch or orient the thermoplastic materials as they are being cast or blown. Stretching lines up the molecular chains in the stretched direction so that tearing occurs in that direction. This method has limited effectiveness because not all polymers can be readily oriented. Also, only a certain amount of molecules can be aligned, and, despite the stretching, tearing may still not be easy and reliable. Orienting also requires special manufacturing efforts and care. Moreover the tearing may be possible in machine direction but difficult in transverse direction. Apart from that the easy tearing by hand is not that much effective. In case of laminated structures where more than one layers of films are present due to packaging requirements, tearing requires even more efforts or some cutting tools etc. to open the package to access the contents.

[0004] Another method of tearing open the package is forming a tear line, widely used for single layer films, is to employ a star wheel to form a line of intermittent perforations in the films. Perforations are unsuitable for multilayer laminates for many reasons. One such reason is that perforations in the film allow product-environment exchanges which defeat the purpose of using multilayer films, i.e., to protect packaged product by combining gas barrier properties of one material with moisture barrier properties of another.

[0005] Another method of imparting an easy to tear feature to a laminate structure is through the use of laser scoring. Laser scoring, however, requires the use of specialized very expensive equipment, and therefore, leads to increased costs of manufacture.

[0006] An alternative to the above methods of producing an easy-to-tear effect is to produce multiple cuts or scores mechanically in designated area of film to create the easy-to-tear effect in particular direction. Again this method is unsuitable for laminate for many reasons. One such reason is that perforations in the film allow product-environment exchanges which defeat a purpose of using multilayer films, i.e., to protect the packaged product by combining gas barrier properties of one material with moisture barrier properties of another U.S. Pat. No. 4,543,279, to Kai, teaches a film with an easy-opening feature of a plurality of random cuts or scratches formed along the edges of a film.

[0007] As discussed above, the easy to tear flexible polymeric packaging substrate (film / laminate) of the prior arts are not effective i.e. much efforts or cutting tool is required to tear the film / laminate. Therefore there is a need of an improved easy-to-tear flexible polymeric packaging substrate that can easily be torn without much additional efforts or cutting tool, without compromising with the essential features, such as barrier properties. US 2005 / 084636 A1 discloses a multilayer packaging film including a sequentially arranged first layer, second layer, third layer, and fourth layer. The first layer includes a surface-roughened portion, the second layer includes an adhesive, the third layer is a barrier material, and the fourth layer includes a score line. The surface-roughened portion and the score line are in different planes but intersect out of the plan with each other via at least one imaginary axis. Surface roughening in the surface-roughened portion is provided by "dimples, scratches, bores, holes, perforations, and the like. US 5 878 549 A discloses an easy open tear control package and methods of making films such packages. The easy open tear control feature arises from roughening portions of the outer or inner surface of the films, prior to fabricating into the package. The roughened portion is on one face or on each face of the package and is at least a full width of a seal when the film is made into the package. The roughened portion can extend the entire width of the package and can be of any desired length. A preferred film is a continuous extrusion laminated film comprising, a plurality of superimposed layers which comprise from outer surface to inner surface, a first layer of polyester, a second layer comprising a vinylidene chloride copolymer, preferably a vinylidene chloride methyl acrylate copolymer, a third layer of ink, a fourth layer of primer, a fifth layer of low-density polyethylene, a sixth layer of ethylene vinyl acetate, and seventh and eighth layers each of an ionomer resin. US 2016 / 023430 A1 relates to a perforated nonslip non-adhesive surface covering. The perforated grid lines are oriented along the vertical and horizontal axis to provide of the covering sheet. The perforations extend through the profile of the composite material, and are produced with a rotary or flat bed die assembly having a series of perforating rules. The perforating rules consist of a sequence of projecting teeth which are separated at regular intervals by an arrangement of indented gaps. WO 2017 / 142730 A1 provides a polylactic acid polymer-based films comprising a structured surface and articles. The film comprises a semicrystalline polylactic acid polymer; a second polymer such as polyvinyl acetate polymer having a glass transition temperature (Tg) of at least 25°C; and plasticizer. It provides a film / tape with outer surface having structured surface to hold paint for application such as in floor making etc. with adhesive on the other side. US 2014 / 138025 A1 provides a hand-tearable masking tape, comprising a plastic backing with a low adhesion back size on the first major side of the backing and a pressure-sensitive adhesive on the second major side of the backing; Wherein the second major side of the backing comprises a micro-structured hand-tear pattern in straight lines.SUMMARY OF THE INVENTION

[0008] This invention describes easy-to-tear polymeric flexible packaging substrate i.e. polymeric film / laminate as defined in claim 1. Preferred embodiments are described by appended claims 2 to 9.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The advantages and features of the present invention shall be better understood with reference to the following detailed description taken in conjunction with the accompanying drawings, wherein like elements are identified with like symbols and in which: FIG. 1 depicts a top view of a treated surface (102) of an outer layer of a packaging substrate i.e. film / laminate (100) having a plurality of micro-indentations (104), in accordance with an embodiment of the present invention; FIGS. 2A & 2B depict a packaging laminate (200) having two layers (202, 204), in accordance with an embodiment of the present invention; FIG. 3depicts a laminated packaging laminate (300) having three layers (202, 306, 204), in accordance with an embodiment of the present invention; FIGS. 4A & 4B illustrate a two-layer structure of an easy to tear packaging laminate (400), in accordance with another embodiment of the present invention; FIG. 5A depicts another alternate of packaging laminate (300) described in FIG. 3 as packaging laminate (300A), in accordance with an embodiment of the present invention; FIG. 5B depicts another alternate of packaging laminate (400) described in FIG. 4A & 4B as packaging laminate (400A), in accordance with anther embodiment of the present invention. Like reference numerals refer to like parts throughout the description of several views of the drawings.DETAILED DESCRIPTION OF THE INVENTION

[0010] For a thorough understanding of the present disclosure, reference is to be made to the following detailed description in connection with the above-mentioned drawings. Further, reference herein to "one embodiment" or "an embodiment" means that a particular feature, characteristic, or function described in connection with the embodiment is included in at least one embodiment of the disclosure. Furthermore, the appearances of such phrase at various places herein are not necessarily all referring to the same embodiment. The terms "a" and "an" herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.

[0011] The present invention describes an easy-to-tear flexible packaging substrate which can be either polymeric film or laminate thereof. One or both surface of the polymeric film is provided with a plurality of non-through micro-indentations in roll to roll process. However one or both surface of atleast one layer of the packaging laminate is provided with a plurality of non-through micro-indentations by mechanical means in roll to roll process. The micro-indentations with specific depth and density are provided on atleast one surface of the film if the substrate is a polymeric film; and on atleast one surface of each layer / film in case of a laminate, to be used in the packaging based on the specific easy-to-tear requirement. Further, the polymeric film may be single or multilayer polymeric film. The effective easy-to-tear feature refers to ease of opening the packages made using such film / laminate, by hand tearing with little effort without using any cutting tool.

[0012] The easy to tear packaging substrate may be a polymeric film having top surface and a bottom surface. Atleast one surface of the polymeric film is provided with a plurality of non-through micro-indentations of up to a predetermined depth over the entire or partial surface area at a predetermined density. Atleast one surface of the polymeric film may be metallized or coated with high barrier materials to impart barrier to the easy to tear substrate. It should be appreciated that metallization or coating on the corresponding surface of the film is done after treating the surface to provide the micro-indentations.

[0013] The easy to tear packaging substrate may be a laminate which includes an outer polymeric layer having top and bottom surfaces, and at least one inner polymeric layer having top and bottom surfaces. The top surface of the inner layer is laminated with the bottom surface of the outer layer and at least one surface of the outer polymeric layer and atleast one surface of the inner polymeric layer is provided with a plurality of non-through micro-indentations of up to a predetermined depth over the entire or partial surface area at a predetermined density.

[0014] The outer and inner polymeric layers of the easy to tear packaging laminate are laminated using extrusion lamination or adhesive lamination. The adhesive used in the lamination is, solvent based adhesive, water based adhesive, hot melt adhesive or solvent-less adhesive. In other embodiment, atleast one surface of the inner polymeric layer in the easy to tear packaging laminate may be metallized or coated with high barrier material. It should be appreciated that metallization or coating on the corresponding surface of the outer and / or inner film / layer is done after treating the surface to provide the micro-indentations. The easy to tear packaging laminate may be a three layer structure having a metal foil layer as a third layer in between the two polymeric layers. The inner layer is laminated to metal foil layer which in turn is laminated to the outer layer. It should be appreciated that only the polymeric layers of the laminate are provided with the micro-indentations on atleast one surface. The predetermined depth of the micro-indentations is between 1% and 70% of the thickness of the corresponding polymeric layer, more preferably between 5% and 30% of the thickness of the corresponding polymeric layer, whereas the predetermined density of the micro-indentations is between 10 per cm 2< and 10,000 per cm 2< .

[0015] In another embodiment, the easy to tear packaging laminate includes an outer polymeric film layer having top and bottom surfaces laminated with an inner multilayer polymeric film having top and bottom surface. The multilayer film may be a 2, 3, 5, 7, 9 or 11 layer film with a combination of polymeric layer including barrier layer of suitable polymer such as EVOH. The top and / or bottom surfaces of the outer layer and / or inner layer is provided with a plurality of micro-indentations up to a predetermined depth over the entire surface area at a predetermined density according to embodiment of the present invention. However, it is preferred to provide micro-indentations on both surface of each polymeric layer to facilitate easy to tear of the laminate structure.

[0016] Further atleast one surface of the outer and / or atleast one surface of the inner layer may be coated with barrier coating such as PVDC. Atleast one surface of the any polymeric layer may be coated with special coating to reduce OTR values.

[0017] Now hereinafter, various embodiment of the present invention will be described through FIGS. 1-5.

[0018] FIG. 1 depicts a top view of a treated surface (102) of an outer layer of a packaging substrate i.e. film / laminate (100) having a plurality of micro-indentations (104), in accordance with an embodiment of the present invention. The treated surface herein refers to a surface having a plurality of non-through micro-indentations of particular specification provided by embossing means in roll to roll process. The depth of the micro-indentations is between 1 to 70% of the film layer thickness, preferably 5 to 30 % of the film layer thickness. The predetermined density of the micro-indentations is between 10 per cm 2< and 10,000 per cm 2< . Various layers of the packaging substrate (100) may include polymers commonly used in the art of making films and laminates for packaging. The packaging film / laminate web (100) may comprise plurality of polymeric single layer films or multi-layer films or a combination thereof. The laminate may also include, paper, paper board or metal foil or combination thereof along with polymeric layers.

[0019] It should be contemplated that in case of both side surfaces of a film / individual layer of a laminate are provided with the micro-indentations (104), the sum of depth of the micro-indentations from both surface does not exceed the thickness of the polymeric film / layer provided that a substantial thickness of the film / layer is left non-pierced even when the two opposite micro-indentations fall opposite to each other. Examples of single or multilayer polymeric films may include Polyethylene (PE), Biaxially-Oriented Polypropylene (BOPP) film, Polyvinyl Chloride (PVC) film, Poly Carbonate (PC), Cast Polyproylene (CPP) film, Polytetrafluoroethylene, Biaxially-Oriented Polyethylene Terephthalate (BOPET), Polyamide (PA), Acrylic (Polymethyl methacrylate) (PMMA), and Ethylene Vinyl Acetate (EVA), biodegradable polymer or any other suitable polymer or combination thereof. The packaging laminate may include inner and outer layers of one of the above mentioned polymeric film mentioned or combination thereof. In a preferred embodiment, the outer layer in packaging laminate (100) is a Bi-axially oriented polypropylene ("BOPP") or a Bi-axially oriented polyethylene terephthalate ("BOPET") laminated with single layer or multilayer Polyethylene (PE) or other heat sealable polymeric material as inner layer.

[0020] As depicted in FIG. 1, the surface (102) of the packaging substrate (100) includes a plurality of non-through micro-indentations (104) of a predetermined depth and in a predetermined density that are located over the entire surface area (102) to create the easy-to-tear feature of the invention. Although FIG. 1 depicts only a single treated surface (102) having the micro-indentations (104), single or both surfaces of the polymeric film or of each polymeric layer in case of laminate may be treated and provided with the micro-indentations (104) according to the present invention depending on thickness of the laminate and ease of tearing desired.

[0021] The polymeric film (100) may have thicknesses in the range, for example from 5 to 300 microns. The general packaging laminate may have a thickness preferably in the range of 20 to 200 microns.

[0022] The packaging substrate (100) may be printed on untreated surface or treated surfaces. Similarly metallization or barrier coating can be done before or after treatment of surface(s) however it is preferred to perform metallization or barrier coating (e.g., PVdC) after treatment to ensure integrity of metallized surface. Printing can be done by any of the methods known in the art of making flexible packaging. For example, the roll to roll printing can be done by letter press, offset, flexographic, rotogravure, digital, laser or screen printing method.

[0023] FIGS. 2A & 2B, show an easy tear laminate according to the present invention having an outer polymeric layer (202) and the inner polymeric layer (204) laminated together as shown. The bottom surface (202b) of the outer layer (202) and the top surface (204a) of the inner layer (204) are laminated using the suitable lamination process. The layers (202, 204) of the packaging laminate (200) may be laminated using extrusion lamination or adhesive lamination process or other suitable lamination processes. As extrusion or adhesive lamination processes are established processes and also well known to a person skilled in the art hence details of these processes are skipped for brevity. Each layer essentially being a standalone polymeric film, at least one surface of these layers is provided with non-through micro-indentations before lamination, to make it easy to tear.

[0024] FIG. 2B depicts exploded view of laminate of Fig. 2A having treated surfaces (202a, 204a) of the respective layers in a packaging laminate (200) having two layers (202, 204) in accordance with the present invention. As shown, the top surface (202a) of the outer layer (202) and the top surface (204a) of the inner layer (204) are treated mechanically to impart easy to tear feature in the corresponding laminate so as to make the laminate (200) as described in conjunction with FIG. 2A. It should be contemplated that the packaging laminate (200) of the present invention may include multiple layers of suitable polymeric films and atleast one surface of each layer is treated mechanically to impart effective easy-to-tear feature in the laminate. Surface printing or reverse printing may be performed on the outer layer (202) before lamination. Metallization can also be done on either surface (202b) or (204a) or both.

[0025] The bottom surface (202b) of the outer layer (202) and the bottom surface (204b) of the inner laminate (204) may be provided with micro-indentations. The bottom surface (202b) of the outer layer (202) and the top surface (204a) of the inner laminate (204) may be provided with micro-indentations.

[0026] FIG. 3depicts laminated packaging laminate (300) having three layers (202, 306, 204), in accordance with an embodiment of the present invention. The packaging laminate (300) includes an outer polymeric layer (202), an inner polymeric layer (204) and a middle layer (306). The layer (306) may be paper, or paper board, synthetic fibrous substrates. If the middle layer (306) is required to enhance the barrier properties in the packaging laminate (300) essential for the products to be packaged, the layer (306) may be a foil of metal such as, Aluminium, Copper, Silver, any other metal or metal alloy. Optionally layer (306) may be a polymeric layer without or with vacuum metallization using one of or combination of Aluminium, Aluminium Oxide, Zinc Sulphide, Silicon Oxide, Silver, Gold, Copper, Chrome, Silicon Monoxide, Silicon Dioxide, Magnesium Fluoride, Titanium Dioxide, Tin Tungsten Oxide and Indium Tin Oxide or any other suitable metal. It should be appreciated that the micro-indentations, as discussed above, are provided on the polymeric layers (202, 204) and not on the metal foils or paper, or paper board, synthetic fibrous substrates. Surface printing or reverse printing may be performed as described above with reference to FIGS 2A & 2B.

[0027] The bottom surface (202b) of the outer layer (202) and the bottom surface (204b) of the inner laminate (204) may be provided with micro-indentations. The bottom surface (202b) of the outer layer (202) and the top surface (204a) of the inner laminate (204) may be provided with micro-indentations.

[0028] FIGS. 4A & 4B illustrate a two-layer structure of an easy to tear laminate (400), in accordance with another embodiment of the present invention. As shown, the packaging laminate (400) includes an outer layer (402) having top surface (402a) and bottom surface (402b), and an inner layer (404) having top surface (404a) and bottom surface (404b). The top surface (402a) of the outer layer (402) and both surfaces (404a, 404b) of the inner layer (404) are provided with the micro-indentations to impart the easy-to-tear feature in the laminate (400). Alternatively, both surfaces of the outer layer (402) and one surface of inner layer (404) may be treated. The layers (402, 404) of the packaging laminate (400) may be laminated using extrusion lamination or adhesive lamination or any other suitable method known in the art. Surface printing or reverse printing may be performed on the outer layer (402) before lamination. It should be appreciated that layer surfaces (402b) and / or surface (404a) may be metallized which offers barrier properties.

[0029] In alternate embodiment, both surfaces (402a, 402b) of the outer layer (402) and the top surface (404a) of the inner laminate (404) may be provided with micro-indentations.

[0030] FIG. 5A depicts another alternate of laminate (300) described in FIG. 3 as packaging laminate (300A) wherein both surfaces of the outer layer (302) and the inner layer (304) are provided with the micro-indentations (104).

[0031] FIG. 5B depicts another alternate of laminate (400) described in FIGS. 4A & 4B as packaging laminate (400A) wherein both surfaces of the outer layer (402) and the inner layer (404) are provided with the micro-indentations (104).

[0032] The laminate may also be provided with images, barcodes, optical patterns, latent images, Fresnel lenses, holograms, sterling lenses and hot or cold foil stamping for desired information, security, anti-counterfeiting or aesthetics purposes. The adhesive lamination may be carried out using hot melt adhesive, water-based adhesive, solvent less adhesive, UV curable adhesive, E-beam curable adhesive or any other method known in the art.

[0033] The present invention has advantages over the prior art offer easy and smooth tearing in any direction that does not require tear strips or notches in the sachets or pouches made using such laminate, which may lead to problems during opening by tearing by the user.

Claims

1. An easy to tear packaging substrate (100, 200), comprising: (i) a polymeric film having top surface and bottom surface; or (ii) a polymeric film laminate comprising (a) an outer layer (202) having top (202a) and bottom (202b) surfaces; and (b) an inner layer (204) having top (204a) and bottom (204b) surfaces, wherein the top surface of the inner layer is laminated with the bottom surface of the outer layer, wherein at least one surface of the polymeric film or at least one surface of the outer layer (202) and at least one surface of the inner layer (204) of the polymeric film laminate is provided with a plurality of non-through micro-indentations (104) of up to a predetermined depth between 1 % and 70% of the thickness of the corresponding layer of (i) the polymeric film or of (ii) the polymeric film laminate over the entire surface area in a predetermined density between 10 micro-indentations per cm2 and 10000 micro-indentations per cm2.

2. The easy to tear packaging substrate (100, 200) as claimed in claim 1, wherein the polymeric film or the outer (202) and inner (204) layers of the polymeric film laminate are single or multilayer films.

3. The easy to tear packaging substrate (200) as claimed in claim 1, wherein the top surface (204a) of the inner layer (204) of the polymeric film laminate is laminated with the bottom surface (202b) of the outer layer (202) using extrusion lamination or adhesive lamination.

4. The easy to tear packaging substrate (100, 200) as claimed in claim 1, wherein the polymeric film or the outer layer (202) of the polymeric film laminate is one of BOPET, BOPP, PE, PVC, PC, CPP, PA, PMMA, EVA or any suitable polymer film.

5. The easy to tear packaging substrate (200) as claimed in claim 1, wherein the inner layer (204) of the polymeric film laminate is PE or other heat sealable material film.

6. The easy to tear packaging substrate (100, 200) as claimed in claim 1, wherein at least one surface of the polymeric film or at least one layer of the polymeric film laminate is metallized.

7. The easy to tear packaging substrate (200) as claimed in claim 1 further comprising at least one middle layer (306) provided between the outer layer (202) and the inner layer (204) of the polymeric film laminate, wherein said middle layer (306) is at least one from metal foil, paper, paper board or polymeric barrier material.

8. The easy to tear packaging substrate (100, 200) as claimed in claim 1, wherein a polymeric barrier coating is provided on at least one surface the polymeric film or on at least one surface of at least one layer of the polymeric film laminate.

9. The easy to tear packaging substrate (100, 200) as claimed in claim 1, wherein predetermined depth of the micro-indentations (104) is between 5% and 30% of the thickness of the polymeric film or of the corresponding layer of the polymeric film laminate.