WO2010004504A2

WO2010004504A2 - Polymer sheet

Info

Publication number: WO2010004504A2
Application number: PCT/IB2009/052937
Authority: WO
Inventors: Amnon Slutski; Sagi Slutski; Haim Weiss
Original assignee: Plastart Ltd.; Resht-O-Plast Ltd
Priority date: 2008-07-10
Filing date: 2009-07-06
Publication date: 2010-01-14
Also published as: WO2010004504A3

Abstract

A polymer sheet for producing a heat-sealed peelable product lid, flow-pack or bag; and a method of producing same. The polymer sheet comprises a lower heat-sealing layer comprising polyolefins and additives, a middle layer comprising a polymer support layer and an upper heat resistant layer comprising a polyamide. The polymer sheet is produced in a single extrusion process, extruding simultaneously at least one polymeric heat-sealing layer and at least one polyamide.

Description

Description Title of Invention: POLYMER SHEET

[ 1 ] FIELD OF THE INVENTION

[2] The present invention generally relates to the field of polymer sheets, particularly such sheets applicable for producing peelable container lids, flow-packs, bags and the like.

[3] BACKGROUND OF THE INVENTION

[4] US 5,318,818 (to Sjostrom), which is incorporated herein by reference in its entirety, discloses a strip of material for the manufacture of packaging containers which have an opening device including a pull tab. The strip of material comprises: a first side surface and a second side surface and a longitudinal edge. The edge has one or more cut-outs formed therein and the cut-outs are in the form of a cut extending inwardly from a line defined by the edge of the strip of material. A pull tab is attached to the strip of material, the pull tab extending mainly transversely over a part of the first side surface of the strip of material, around the edge of the strip of material in one of the cut-outs, and mainly transversely over a part of the second side surface of the strip of material. A fold area of the pull tab is formed where the pull tab extends around the edge of the strip of material in one of the cut-outs, wherein the cut-outs are of sufficient depth that the fold area of the pull tab is disposed completely on one side of the line defined by the edge of the strip of material.

[5] WO2006/097927 (to Blajwis, et al), which is incorporated herein by reference in its entirety, discloses a method for manufacturing substantially moisture resistant closures for flexible packages. The method comprises providing a roll of material, printing a design on the roll, heating the roll, forming a three-dimensional shape in the roll substantially proximate to the design and cutting the roll substantially proximate to the three-dimensional shape and the design.

[6] SUMMARY OF THE INVENTION

[7] The present invention relates to a polymer sheet for use as a barrier for the protection of a food item or other suitable application. The polymer sheet is particularly applicable for use as a heat-sealable peelable container lid, a flow-pack or a bag. The present invention also relates to a method of producing such a polymer sheet.

[8] According to one aspect of the invention there is provided a polymer sheet comprising a lower heat-sealing layer; a middle layer comprising a polymer support and binding layer; and an upper heat resistant layer comprising at least one polyamide. The polymer sheet is produced in a single extrusion process.

[9] According to another aspect of the invention there is provided a polymer sheet for producing heat-sealable peelable product lid, flow -pack or bag, the polymer sheet prepared by a process comprising extruding simultaneously at least one heat-sealing polymer layer; a middle support layer; and an upper layer comprising at least one polyamide.

[10] According to yet another aspect of the invention there is provided a method of producing a heat-sealable peelable product lid, flow-pack or bag, the method comprising extruding simultaneously at least one polymer for heat- sealing and at least one polyamide.

[11] According to still another aspect of the invention there is provided a food package comprising a heat-sealable peelable lid, wherein the lid comprises an upper layer comprising at least one polyamide.

[12] BRIEF DESCRIPTION OF THE DRAWINGS

[13] The invention may be understood upon reading of the following detailed description of non-limiting exemplary embodiments thereof, with reference to the following drawings, in which:

[14] Fig. 1 is a perspective view illustration of a container with a lid, according to some embodiments of the present invention;

[15] Fig. 2 is a cross section illustration of a container with a lid, according to some embodiments of the invention;

[16] Fig. 3 is an illustration of a polymer sheet for producing heat-sealed peelable product lids, according to some embodiments of the invention;

[17] Fig. 4 is a cross section illustration of an edge of a food product storage package having a heat-sealed peelable lid, according to some embodiments of the invention;

[18] Fig. 5 is an cross section illustration of a die of a cast extruder for extruding a polymer sheet for producing heat-sealed peelable product lids, according to some embodiments of the invention; and

[19] Fig. 6 is flowchart of a method for producing a polymer sheet, according to some embodiments of the invention.

[20] The following detailed description of the invention refers to the accompanying drawings referred to above. Dimensions of components and features shown in the figures are chosen for convenience or clarity of presentation and are not necessarily shown to scale. Wherever possible, the same reference numbers will be used throughout the drawings and the following description to refer to the same and like parts.

[21 ] DETAILED DESCRIPTION OF SOME EMBODIMENTS OF THE

INVENTION

[22] The present invention discloses a multilayer thermoplastic sheet produced in a single step cast (or blowing) co-extrusion process wherein the upper layer of the multilayer sheet comprises a polyamide. [23] Figures 1 and 2 illustrate a container 130 with a lid 150, according to some embodiments of the invention. The container 130 may be a food container, and may be made e.g. of polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), polyvinyl chloride (PVC), as well as aluminum, paper, and the like. The lid 150 seals the container 130 and may be air tight or arranged to selectively allow gas passage therethrough. The lid 150 may seal the container 130 such as to allow vacuum packaging.

[24] Fig. 3 is an illustration of a polymer sheet 140 for producing heat-sealed peelable product lids, according to some embodiments of the invention. The polymer sheet 140 comprises a lower heat-sealing layer 120, a polymer support layer 110, and an upper heat resistant layer 100 comprising a polyamide. The polymer sheet 140 is produced in a single extrusion process.

[25] According to some embodiments of the invention, lower heat-sealing layer 120 allows heat sealing to a variety of container materials such as plastics, e.g. polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), polyvinyl chloride (PVC), polystyrene (PS), as well as aluminum, paper etc. Lower heat-sealing layer 120 typically comprises one or more polyolefins and additives, and may comprise at least one of: LDPE, a polypropylene random copolymer, an anti-block master-batch, a polyolefin elastomer, a terpolymer, a copolymer of olefins or a combination thereof.

[26] According to some embodiments of the invention, polymer support layer 110 comprises polypropylene and additives for strengthening the sheet 140 and binding lower heat-sealing layer 120 to upper heat resistant layer 100. For example, middle layer 110 may comprise polypropylene such as Adstif HA612M, a crystallizer such as NU 2753HP, and an adhesive such as Admer QF551E.

[27] According to some embodiments of the invention, upper heat resistant layer 100 comprises one or more polyamides (e.g. Ultramid B36LN) and allows handling with current production machines and processes. Using a polyamide(s) as an upper layer results in a sheet that may be cut and processed, is heat resistant, does not melt or stick during processing, yet is easily stretchable and printable, and obviates lamination.

[28] According to some embodiments of the invention upper heat resistant layer 100, comprising one or more polyamides, is as heat resistant as presently used upper layers, yet obviates the use of presently used solvents, is printable and has superior gas barrier properties.

[29] Fig. 4 is a cross sectional illustration of the edge of a storage package for food products with a heat-sealed peelable lid 150, according to some embodiments of the invention. The storage package comprises a container 130 for food products and a heat-sealed peelable lid 150. The lid 150 comprises a lower heat-sealing layer 120, a middle layer comprising a polymer support layer 110, and an upper heat resistant layer 100 comprising polyamides such as Nylon. The container 130 may comprise a sheet made of polymer sheet 140. Polymer support layer 110 may comprise polymeric glue for attaching lower heat-sealing layer 120 to upper heat resistant layer 100. Polymer support layer 110 may further comprise compositions for improving the processing of the polymer materials and the production process.

[30] Fig. 5 is a cross sectional illustration of a die of a cast extruder for extruding a polymer sheet 160 for producing heat-sealed peelable product lids, according to some embodiments of the invention. The die comprises an injector 250 and blades 260 enabling the connection of a feed pipe for each polymer resin that is fed into the die. Polymer resins 200, 210, 220 are fed in a molten state into the die. Upon passing the blades 260 they are combined in a front cavity 240 and then extruded as a three layered sheet 160. The three layers correspond to the polymer resins fed into the die, i.e. the upper layer 100 to the upper polymer resin 200, the middle layer 110 to the middle polymer resin 210, and the lower layer 120 to the lower polymer resin 220. The upper polymer resin 200 may be or comprise a heat resistant resin, while the lower polymer resin 220 may be heat sealing. The middle polymer resin 210 may enable connecting the upper polymer resin 200 to the lower polymer resin 220.

[31] Fig. 6 is flowchart of an embodiment of a method for producing a polymer sheet, according to some embodiments of the invention. The method comprises the steps of: mixing a polymer support composition (step 300); extruding simultaneously: a lower heat-sealing layer, a middle layer comprising at least one polymer support layer , and an upper layer comprising at least one polyamide, e.g. nylon (step 310). For producing a heat-sealable food (or other) package lid, the method typically further comprises: creating and storing the polymer sheet (step 320); and cutting and using lids from the polymer sheet (step 330).

[32] According to some embodiments of the invention, the present polymer sheet enables a more efficient production as it is produced in one step. In addition, avoiding the lamination stage commonly used in the present technologies solves the traditional problems of delamination and curling. The present polymer sheet has a high mechanical strength, withstands high temperatures, is printable (externally) and has superior gas barrier characteristics than typically used polyethylene or polypropylene sheets.

[33] According to some embodiments of the invention, the method avoids using solvents and gluing materials to attach sheets or layers that are produced in different (separate) processes, and thus reduces health risks and environmental damage.

[34] In the above description, an embodiment is an example or implementation of the inventions. The various appearances of 'one embodiment,' 'an embodiment' or 'some em- bodiments' do not necessarily all refer to the same embodiments. Although various features of the invention may be included in a single embodiment, the features may also be provided separately or in any suitable combination. Conversely, although the invention may be described herein in the context of separate embodiments for clarity, the invention may also be implemented in a single embodiment. Reference in the specification to 'some embodiments', 'an embodiment', 'one embodiment' or 'other embodiments' means that a particular feature, structure, or characteristic described in connection with the embodiments is included in at least some embodiments, but not necessarily all embodiments, of the inventions.

[35] It is understood that the phraseology and terminology employed herein is not to be construed as limiting and are for descriptive purpose only. It is to be understood that the details set forth herein do not construe a limitation to an application of the invention. Furthermore, it is to be understood that the invention can be carried out or practiced in various ways and that the invention can be implemented in embodiments other than the ones outlined in the description above. It is to be understood that where the claims or specification refer to 'a' or 'an' element, such reference is not be construed that there is only one of that element. It is to be understood that where the specification states that a component, feature, structure, or characteristic 'may', 'might', 'can' or 'could' be included, that particular component, feature, structure, or characteristic is not required to be included.

[36] Where applicable, although state diagrams, flow diagrams or both may be used to help describe embodiments, the invention is not limited to those diagrams or to the corresponding descriptions. For example, flow or steps need not move through each illustrated box or state, or in exactly the same order as illustrated and described. Methods of the present invention may be implemented by performing or completing manually, automatically, or a combination thereof, selected steps or tasks. The term 'method' may refer to manners, means, techniques and procedures for accomplishing a given task including, but not limited to, those manners, means, techniques and procedures either known to, or readily developed from known manners, means, techniques and procedures by practitioners of the art to which the invention belongs.

[37] The descriptions, examples, methods and materials presented in the claims and the specification are not to be construed as limiting but rather as illustrative only. Meanings of technical and scientific terms used herein are to be commonly understood as by one of ordinary skill in the art to which the invention belongs, unless otherwise defined. The present invention can be implemented in the testing or practice with methods and materials equivalent or similar to those described herein.

[38] While the invention has been described with respect to a limited number of embodiments, these should not be construed as limitations on the scope of the invention, but rather as exemplifications of some of the preferred embodiments. Those skilled in the art will envision other possible variations, modifications, and applications that are also within the scope of the invention. Accordingly, the scope of the invention should not be limited by what has thus far been described, but by the appended claims and their legal equivalents.

Claims

[Claim 1] A polymer sheet for producing a heat-sealable peelable product lid, flow-pack or bag, said polymer sheet comprising: a lower heat-sealing layer; a middle layer comprising a polymer support and binding layer; and an upper heat resistant layer comprising at least one polyamide, said polymer sheet being produced in a single extrusion process.

[Claim 2] A polymer sheet according to claim 1, wherein the lower heat sealing layer comprises at least one polyolefin.

[Claim 3] A polymer sheet according to claim 1, wherein the middle support and binding layer comprises polypropylene.

[Claim 4] A polymer sheet according to claim 1, wherein the middle layer comprises a crystallizer.

[Claim 5] A polymer sheet according to claim 1, wherein the middle layer comprises an adhesive.

[Claim 6] A polymer sheet for producing heat-sealable peelable product lid, flow- pack or bag, said polymer sheet prepared by a process comprising extruding simultaneously at least one heat-sealing polymer layer; a middle support layer; and an upper layer comprising at least one polyamide.

[Claim 7] A method for producing a polymer sheet for a heat-sealable peelable product lid, flow-pack or bag, said method comprising extruding simultaneously at least one polymer for heat-sealing and at least one polyamide.

[Claim 8] A food package comprising a heat-sealable peelable lid, wherein said lid comprises an upper layer comprising at least one polyamide.