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EP0440713A1 - A laminate, in particular for packaging of foodstuffs or stimulants, and a method of manufacturing such laminate - Google Patents

A laminate, in particular for packaging of foodstuffs or stimulants, and a method of manufacturing such laminate

Info

Publication number
EP0440713A1
EP0440713A1 EP89912230A EP89912230A EP0440713A1 EP 0440713 A1 EP0440713 A1 EP 0440713A1 EP 89912230 A EP89912230 A EP 89912230A EP 89912230 A EP89912230 A EP 89912230A EP 0440713 A1 EP0440713 A1 EP 0440713A1
Authority
EP
European Patent Office
Prior art keywords
plastic material
laminate
layer
inner layer
film
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP89912230A
Other languages
German (de)
French (fr)
Inventor
Erik H. Nielsen
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
OTTO NIELSEN EMBALLAGE AS
Original Assignee
OTTO NIELSEN EMBALLAGE AS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by OTTO NIELSEN EMBALLAGE AS filed Critical OTTO NIELSEN EMBALLAGE AS
Publication of EP0440713A1 publication Critical patent/EP0440713A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
    • B32B5/18—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by features of a layer of foamed material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B15/00—Layered products comprising a layer of metal
    • B32B15/04—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B15/08—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B27/065—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of foam
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
    • B32B37/14—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the properties of the layers
    • B32B37/15—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the properties of the layers with at least one layer being manufactured and immediately laminated before reaching its stable state, e.g. in which a layer is extruded and laminated while in semi-molten state
    • B32B37/153—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the properties of the layers with at least one layer being manufactured and immediately laminated before reaching its stable state, e.g. in which a layer is extruded and laminated while in semi-molten state at least one layer is extruded and immediately laminated while in semi-molten state
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2439/00—Containers; Receptacles
    • B32B2439/70—Food packaging

Definitions

  • a laminate in particular for packaging of foodstuffs or stimulants, and a method of manufacturing such laminate.
  • the present invention relates to a laminate, in par ⁇ ticular for packaging of foodstuffs or stimulants, comprising at least two layers, namely an outer layer consisting of a first film of plastic material and an inner layer consisting of a second film of plastic material, optionally with an intermediate layer consisting of a foil or a coating of a metallic material or of a third film of plastic material interposed between the outer and inner layers, said layers being adhesively interconnected to form the laminate.
  • outer layer and inner layer refer to the posi ⁇ tioning of the subject layers and subject surface, respec ⁇ tively, in a finished package made from the laminate, where the exposed surface of the outer layer is the surface of the package facing the ambient, while the exposed surface of the inner layer is the surface of the package facing the packaged article.
  • Laminates of the above type are well-known and widely used within the art of packaging, especially for vacuum packaging of foodstuffs such as meat cuts, pieces of cheese, etc., such articles as dry yeast or stimulants like ground coffee or tea, and by combining various materials in the said two or three layers they may be manufactured for a wide range of applications.
  • the primary function of the outer layer is generally to impart to the laminate mechanical strength as well as resistance to effects of heat to which it is subjected by sealing devices in the packaging machines used for producing the package.
  • the outer layer may typically consist of a biaxially oriented polyester film or a biaxially oriented polyamide film.
  • the primary function of the intermediate layer in laminates comprising such a layer is to form a barrier layer in a package made up from the laminate and especially to prevent transmission of oxygen through the laminate and thereby protecting a packaged article against oxidation from the ambient atmospheric air.
  • the intermediate layer may consist of a metal foil, for example of aluminium or an aluminium alloy, whereby such a metal foil additionally may impart to the laminate some degree of deadfold capability, or the layer may consist of a very thin layer of metal, such as aluminium or an aluminium alloy, applied by vapori ⁇ zation under vacuum to the inwardly facing surface of the outer layer.
  • the intermediate layer may be a polymeric film having barrier properties and consisting of, for example, polyvinylidene chloride, a modified polyvinyle alcohol or polyacrylonitrile in an oriented or non-oriented state.
  • the inner layer is to render the laminate weldable in order hermetically to heat-seal packages made therefrom. At the same time the inner layer often results in reduced transmission of moisture through the laminate, and the "body" imparted to the laminate by the inner layer may cause this to achieve the rigidity ne ⁇ cessary for processing on automatic packaging machines.
  • the inner layer will typically be a film of polyolefine such as low, medium or high density polyethylene and with a melting index, i.e. viscosity in a melted state, adapted to the intended application.
  • the film of the inner layer may also consist of other polymers such as polypropylene, poly- butylene, etc.
  • the adhesive interconnection of the layers is achieved by means of an adhesive, e.g. a polyurethane adhesive, except in the case where the intermediate layer consists of a me ⁇ tallic layer applied by vaporization under vacuum to the inwardly facing surface of the outer layer, and where the adhesive connection thereof to the outer layer is provided during the vaporization process.
  • an adhesive e.g. a polyurethane adhesive
  • One method of reducing the gramweight of the inner layer without diminishing its thickness which has been con ⁇ sidered consists in making the film for the inner layer from foamed plastic material. Admittedly, this makes it possible to reduce the gramweight of this film by up to approx. 50 per cent but the extremely uneven surface of such a film has made it necessary in order to join this with the outer or intermediate layer of the laminate to use highly increased amounts of adhesive for filling the irregularities of the surface, and even so it has proved difficult to achieve an acceptable adhesion of the two lay ⁇ ers.
  • the weight of the additionally required amount of ad ⁇ hesive moreover, reduces the desired effect. This method, therefore, must be deemed unsuitable in practice.
  • Another object of the invention is to provide a la ⁇ minate of the type referred to above, in which the resistance of the laminate to puncture especially from the inside of a package has not been reduced but increased in relation to conventional laminates of comparable kind.
  • Yet another object of the invention is to provide a laminate of the type referred to initially, in which substan ⁇ tially without addition of friction-reducing agents the inside of the inner layer has an acceptable friction coeffi ⁇ cient or "machinability" for processing of the laminate in packaging machines.
  • the second film of plastic material of the inner layer consists of at least two coextruded parts, namely a first part of non-foamed plastic material adhered to the outer layer or intermediate layer and a second part of foamed plastic material forming the inner exposed surface of the laminate.
  • the film of the inner layer may be joined with the outer or intermediate layer by employing the customary amounts of adhesive and achieving the customary acceptable adhesion of the layers.
  • the second foamed part of the inner layer has the effect of substantially reducing the gramweight of the inner layer.
  • the non-foamed part of the inner layer may have a thickness of between 20 and 60 microns, preferably between 30 and 40 microns, while the foamed part of the inner layer may have a thickness of between 35 and 102 microns, preferab ⁇ ly between 51 and 68 microns.
  • non-foamed part and the foamed part of the inner layer substantially consist of the same plastic material.
  • the non-foamed and foamed parts alternatively may consist of different materials, e.g. so that the non-foamed part may consist of one of the polymeric materials having barrier properties mentioned above in connection with the intermediate layer, while the foamed part e.g. may consist of polyethylene or another of the polymeric materials mentioned above in con ⁇ nection with the inner layer.
  • the foamed part e.g. may consist of polyethylene or another of the polymeric materials mentioned above in con ⁇ nection with the inner layer.
  • the invention also relates to a method of manufactu ⁇ ring such a laminate, in which at least two layers, namely an outer layer consisting of a first film of plastic material and an inner layer consisting of a second film of plastic material and optionally an intermediate layer consisting of a foil or coating of a metallic material or of a third film of plastic material are adhered to each other, said method being characterised in that the second film of plastic mate ⁇ rial of the inner layer is obtained by coextrusion of a first plastic material with no foaming agent added and a second plastic material with foaming agent added, where the first plastic material forms that surface of the inner layer which is adhered to the outer layer or to the intermediate layer, respectively, and where the second plastic material forms the inner exposed surface of the laminate.
  • first plastic material and the second plastic material of the inner layer substantial ⁇ ly are identical.
  • first and second materials of the inner layer be different.
  • plastic materials are not immediately coextrudable they may, as it is well known from coextruding solid films, be joined together by a so-called "tie layer" which is coextruded between the materials and may join itself to both of them.
  • the second plastic material of the inner layer is added such an amount of foaming agent that after foaming the plastic material shows an increase in volume of between 50 and 100 per cent, preferably between 70 and 80 per cent.
  • the laminate 1 consists of an outer layer 2, for example in the form of a biaxially oriented polyamide film to the inwardly faced surface of which by so-called vacuum-metallization there is applied an inter ⁇ mediate layer 3 in the form of a very thin coating of a metal such as aluminium, and which in the drawing is shown with relatively exaggerated thickness.
  • an adhesive layer 4 consisting of, for example, a polyurethane adhesive, there is an inner layer, generally designated 5.
  • the inner layer 5 is a plastic film of, for example, low density polyethylene and obtained by coextrusion in a manner known per se, e.g. through a common extrusion orifice of plastic material with no foaming agent added from a first extruder with plastic material containing a foaming agent from a second extruder.
  • the foaming agent used will typically be a chemical reagent which by heating together with the plastic material in the extruder until the extrusion tem ⁇ perature releases a gas which is trapped in a large number of cavities in the extruded plastic material.
  • the inner layer 5 thus consists of two parts, viz.
  • a solid or non- foamed part 6 which by means of the adhesive layer 4 is joined with the intermediate layer or the metal coating 3, and a second part 7 which is foamed and therefore contains a large number of gas-filled cavities or cells 8.
  • the numeral 9 indicates a transitional area or a tie layer between these. Owing to the large number of gas-filled cavities 8 in the part 7 the inside surface 10 of the inner layer 5 is uneven and therefore shows a smaller friction coefficient than would a smooth or even surface of the same plastic material.
  • Gramweight of the laminate (g/m 2 ) as determined by weighing a given area of the laminate.
  • Gramweight of the inner layer (g/m 2 ) determined in the same manner.
  • Friction coefficient Determined according to British Stan ⁇ dard 2782, Method 311 A by means of a Friction Tester made by the firm of Davenport, Herts., England.
  • Ability to resist puncture determined by means of a testing apparatus developed by the applicants, in which a sample of the laminate is stretched tightly so as to leave a free circular area with a diameter of 10 mm. Towards the centre thereof there is advanced a test needle having a diameter of 0.8 mm and a rounded tip with a radius of curvature of 0.4 mm at a speed of 5 mm per minute. The penetrating force is measured in N and the deflection at penetration is mea ⁇ sured in mm. The ability of resistance is determined as the product of the values measured in Nmm.
  • a conventional laminate was made, which laminate comprised an outer layer consisting of a biaxially oriented polyamide film to which an intermediate layer by vacuum metallization was applied in the form of an aluminium coa ⁇ ting.
  • the overall thickness of the outer and intermediate layers was 15 microns.
  • an inner layer consisting of a low density polyethylene film having a thick ⁇ ness of 80 microns.
  • the outer, intermediate and adhesive layers were as specified in Example 1, and the inner layer 1 likewise con ⁇ sisted of a low density polyethylene film, but comprised according to the invention a non-foamed or solid part 6 having a thickness of 30 microns and a foamed part 7 contai ⁇ ning a large number of gas-filled cavities and having a thickness of 50 microns.
  • a foaming agent in the form of a so-called master batch, more specifically 5 per cent "Hydrocel CF 20" from the firm of Boehringer Ingelheim KG, Ingelheim, the German Federal Republic.
  • This master batch is specified to consist of 80 per cent polyethylene and 20 per cent of gas-generating reagent.
  • the results show that by means of the laminate according to the invention it is possible to achieve a reduc ⁇ tion in the gramweight of approx. 20 per cent compared to a similar conventional laminate, while the gramweight of the inner layer was reduced by approx. 25 per cent compared to a conventional inner layer of the same thickness.
  • the lami ⁇ nate according to the invention likewise shows a significant reduction of the friction coefficient, in which connection it should be noted that no friction-reducing agents had been added to the inner layer of the laminate in either of the two examples. While the laminate according to the inven ⁇ tion showed the same resistance to puncture from the outside of the laminate as the conventional laminate, its resistance to puncture from the inside had surprisingly increased by approx. 20 per cent relative to that of the conventional laminate.

Landscapes

  • Laminated Bodies (AREA)
  • Extrusion Moulding Of Plastics Or The Like (AREA)

Abstract

Le stratifié décrit (1) comprend au moins deux couches, soit une couche extérieure (2) composée d'un film plastique et une couche intérieure (5) également composée d'un film plastique, ainsi qu'éventuellement une couche intermédiaire (3) placée entre les couches extérieure et intérieure, une couche adhésive (4) étant utilisée pour joindre la couche intérieure (5) à la couche extérieure (2) ou à la couche intermédiaire (3). La couche intérieure (5) est obtenue par co-extrusion d'un matériau plastique non alvéolaire avec un matériau plastique alvéolaire, de sorte que le film plastique composant la couche intérieure (5) est constitué par une partie non alvéolaire ou solide (6) collée à la couche extérieure (2) ou à la couche intermédiaire (3) et par une partie alvéolaire (7) contenant un grand nombre de cavités ou de cellules repliées de gaz (8) et formant la surface interne (10) du stratifié (1). Les termes "extérieur" et "intérieur" se réfèrent dans ce contexte à la disposition dans un emballage fabriqué à partir du stratifié (1). Un tel stratifié (1) permet une économie de matériau et de poids et présente des avantages du point de vue du traitement et de l'application par rapport à un stratifié similaire classique.The laminate described (1) comprises at least two layers, namely an outer layer (2) composed of a plastic film and an inner layer (5) also composed of a plastic film, as well as possibly an intermediate layer (3) placed between the outer and inner layers, an adhesive layer (4) being used to join the inner layer (5) to the outer layer (2) or to the intermediate layer (3). The inner layer (5) is obtained by co-extrusion of a non-cellular plastic material with a cellular plastic material, so that the plastic film making up the inner layer (5) consists of a non-cellular or solid part (6). glued to the outer layer (2) or to the intermediate layer (3) and by an alveolar part (7) containing a large number of cavities or gas-folded cells (8) and forming the internal surface (10) of the laminate ( 1). The terms "exterior" and "interior" refer in this context to the arrangement in packaging made from the laminate (1). Such a laminate (1) saves material and weight and has advantages from the point of view of processing and application compared to a similar conventional laminate.

Description

A laminate, in particular for packaging of foodstuffs or stimulants, and a method of manufacturing such laminate.
The present invention relates to a laminate, in par¬ ticular for packaging of foodstuffs or stimulants, comprising at least two layers, namely an outer layer consisting of a first film of plastic material and an inner layer consisting of a second film of plastic material, optionally with an intermediate layer consisting of a foil or a coating of a metallic material or of a third film of plastic material interposed between the outer and inner layers, said layers being adhesively interconnected to form the laminate.
In this context the designations "outer layer" and "inner layer" as well as "inner surface" refer to the posi¬ tioning of the subject layers and subject surface, respec¬ tively, in a finished package made from the laminate, where the exposed surface of the outer layer is the surface of the package facing the ambient, while the exposed surface of the inner layer is the surface of the package facing the packaged article.
Laminates of the above type are well-known and widely used within the art of packaging, especially for vacuum packaging of foodstuffs such as meat cuts, pieces of cheese, etc., such articles as dry yeast or stimulants like ground coffee or tea, and by combining various materials in the said two or three layers they may be manufactured for a wide range of applications.
In this connection the primary function of the outer layer is generally to impart to the laminate mechanical strength as well as resistance to effects of heat to which it is subjected by sealing devices in the packaging machines used for producing the package. The outer layer may typically consist of a biaxially oriented polyester film or a biaxially oriented polyamide film.
The primary function of the intermediate layer in laminates comprising such a layer is to form a barrier layer in a package made up from the laminate and especially to prevent transmission of oxygen through the laminate and thereby protecting a packaged article against oxidation from the ambient atmospheric air. The intermediate layer may consist of a metal foil, for example of aluminium or an aluminium alloy, whereby such a metal foil additionally may impart to the laminate some degree of deadfold capability, or the layer may consist of a very thin layer of metal, such as aluminium or an aluminium alloy, applied by vapori¬ zation under vacuum to the inwardly facing surface of the outer layer. Alternatively, the intermediate layer may be a polymeric film having barrier properties and consisting of, for example, polyvinylidene chloride, a modified polyvinyle alcohol or polyacrylonitrile in an oriented or non-oriented state.
The main function of the inner layer is to render the laminate weldable in order hermetically to heat-seal packages made therefrom. At the same time the inner layer often results in reduced transmission of moisture through the laminate, and the "body" imparted to the laminate by the inner layer may cause this to achieve the rigidity ne¬ cessary for processing on automatic packaging machines. The inner layer will typically be a film of polyolefine such as low, medium or high density polyethylene and with a melting index, i.e. viscosity in a melted state, adapted to the intended application. The film of the inner layer may also consist of other polymers such as polypropylene, poly- butylene, etc. To the film material of the inner layer there are in conventional laminates as a rule added certain amounts of additives such as release or slip agents and anti-block agents in order to impart to the inside of the inner layer a suitable low friction coefficient or "machinability" for processing the laminate in packaging machines. These addi¬ tives usually have a tendency to turn "rancid", and in order to avoid problems with unpleasant smells and tastes in the packaged article it may therefore be necessary to add also an antioxidant, which especially in connection with packaging of foodstuffs must be deemed undesirable.
The adhesive interconnection of the layers is achieved by means of an adhesive, e.g. a polyurethane adhesive, except in the case where the intermediate layer consists of a me¬ tallic layer applied by vaporization under vacuum to the inwardly facing surface of the outer layer, and where the adhesive connection thereof to the outer layer is provided during the vaporization process.
For economical and other reasons it will often be desirable to be able to reduce the gramweight (weight in g/m2) of the inner layer, which is normally achieved by reducing the thickness of the film in this layer with a series of undesirable consequences such a reduced rigidity, increased friction coefficient and generally poorer mechani¬ cal properties. One of the latters is less resistance to puncture, which especially applies to vacuum-packaged ar¬ ticles having sharp or pointed particles such as lumps of meat with bone splinters, dry yeast with large amounts of sharp particles, coarsely ground coffee, etc. A puncture of the package in these cases results in a reduced shelf life of the packaged article.
One method of reducing the gramweight of the inner layer without diminishing its thickness which has been con¬ sidered consists in making the film for the inner layer from foamed plastic material. Admittedly, this makes it possible to reduce the gramweight of this film by up to approx. 50 per cent but the extremely uneven surface of such a film has made it necessary in order to join this with the outer or intermediate layer of the laminate to use highly increased amounts of adhesive for filling the irregularities of the surface, and even so it has proved difficult to achieve an acceptable adhesion of the two lay¬ ers. The weight of the additionally required amount of ad¬ hesive, moreover, reduces the desired effect. This method, therefore, must be deemed unsuitable in practice.
It is an object of the invention to provide a laminate of the type referred to initially, in which the gramweight of the inner layer has been reduced without diminishing its thickness, and where there is provided a conventional and acceptable adhesion between the inner layer and the layer joined therewith in the laminate by applying the amounts of adhesive usually employed for this purpose.
Another object of the invention is to provide a la¬ minate of the type referred to above, in which the resistance of the laminate to puncture especially from the inside of a package has not been reduced but increased in relation to conventional laminates of comparable kind.
Yet another object of the invention is to provide a laminate of the type referred to initially, in which substan¬ tially without addition of friction-reducing agents the inside of the inner layer has an acceptable friction coeffi¬ cient or "machinability" for processing of the laminate in packaging machines.
According to the invention, these objects are achieved in that the second film of plastic material of the inner layer consists of at least two coextruded parts, namely a first part of non-foamed plastic material adhered to the outer layer or intermediate layer and a second part of foamed plastic material forming the inner exposed surface of the laminate.
As the first part of the inner layer adhered to the outer or intermediate layer consists of non-foamed plastic material and therefore has an even or smooth surface, the film of the inner layer may be joined with the outer or intermediate layer by employing the customary amounts of adhesive and achieving the customary acceptable adhesion of the layers. At the same time the second foamed part of the inner layer has the effect of substantially reducing the gramweight of the inner layer. It has likewise been found that the laminate according to the invention especially from its inside shows increased resistance to puncture, and that the inner exposed surface of the laminate shows such low friction coefficient that friction-reducing additives to the plastic material in the second part of the inner layer should generally be superfluous.
The non-foamed part of the inner layer may have a thickness of between 20 and 60 microns, preferably between 30 and 40 microns, while the foamed part of the inner layer may have a thickness of between 35 and 102 microns, preferab¬ ly between 51 and 68 microns.
It is preferred that the non-foamed part and the foamed part of the inner layer substantially consist of the same plastic material.
It has, however, been contemplated that the non-foamed and foamed parts alternatively may consist of different materials, e.g. so that the non-foamed part may consist of one of the polymeric materials having barrier properties mentioned above in connection with the intermediate layer, while the foamed part e.g. may consist of polyethylene or another of the polymeric materials mentioned above in con¬ nection with the inner layer. Thereby may be obtained a barrier effect against e.g. oxygen in a laminate consisting of only outer layer and inner layer.
The invention also relates to a method of manufactu¬ ring such a laminate, in which at least two layers, namely an outer layer consisting of a first film of plastic material and an inner layer consisting of a second film of plastic material and optionally an intermediate layer consisting of a foil or coating of a metallic material or of a third film of plastic material are adhered to each other, said method being characterised in that the second film of plastic mate¬ rial of the inner layer is obtained by coextrusion of a first plastic material with no foaming agent added and a second plastic material with foaming agent added, where the first plastic material forms that surface of the inner layer which is adhered to the outer layer or to the intermediate layer, respectively, and where the second plastic material forms the inner exposed surface of the laminate.
It is preferred that the first plastic material and the second plastic material of the inner layer substantial¬ ly are identical.
Alternatively may the first and second materials of the inner layer be different.
In so far such different plastic materials are not immediately coextrudable they may, as it is well known from coextruding solid films, be joined together by a so-called "tie layer" which is coextruded between the materials and may join itself to both of them.
It is furthermore preferred that there to the second plastic material of the inner layer is added such an amount of foaming agent that after foaming the plastic material shows an increase in volume of between 50 and 100 per cent, preferably between 70 and 80 per cent.
The invention will be described in more detail below in that reference is made to the drawing which shows very schematically a greatly enlarged broken section through a laminate according to the invention.
On the drawing is schematically shown a broken section through a laminate according to the invention and which is generally designated 1. The laminate 1 consists of an outer layer 2, for example in the form of a biaxially oriented polyamide film to the inwardly faced surface of which by so-called vacuum-metallization there is applied an inter¬ mediate layer 3 in the form of a very thin coating of a metal such as aluminium, and which in the drawing is shown with relatively exaggerated thickness. Joined with the inter¬ mediate layer 3 by means of an adhesive layer 4, consisting of, for example, a polyurethane adhesive, there is an inner layer, generally designated 5.
The inner layer 5 is a plastic film of, for example, low density polyethylene and obtained by coextrusion in a manner known per se, e.g. through a common extrusion orifice of plastic material with no foaming agent added from a first extruder with plastic material containing a foaming agent from a second extruder. The foaming agent used will typically be a chemical reagent which by heating together with the plastic material in the extruder until the extrusion tem¬ perature releases a gas which is trapped in a large number of cavities in the extruded plastic material. The inner layer 5 thus consists of two parts, viz. a solid or non- foamed part 6 which by means of the adhesive layer 4 is joined with the intermediate layer or the metal coating 3, and a second part 7 which is foamed and therefore contains a large number of gas-filled cavities or cells 8. Between the solid or non-foamed part 6 and the foamed part 7 of the inner layer 5 there is indicated as at 9 an interface, but it will be appreciated that the parts 6 and 7, in so far as they preferably consist of the same plastic material, when coextruded will merge evenly into each other without forming any material interface. In case the parts 6 and 7 consist of different coextruded plastic materials, the numeral 9 indicates a transitional area or a tie layer between these. Owing to the large number of gas-filled cavities 8 in the part 7 the inside surface 10 of the inner layer 5 is uneven and therefore shows a smaller friction coefficient than would a smooth or even surface of the same plastic material.
EXAMPLES In the examples given below a laminate according to the invention has been compared with a corresponding conven¬ tional laminate, the following values having been determined for the two laminates:
Gramweight of the laminate (g/m2) as determined by weighing a given area of the laminate.
Gramweight of the inner layer (g/m2) determined in the same manner.
Friction coefficient. Determined according to British Stan¬ dard 2782, Method 311 A by means of a Friction Tester made by the firm of Davenport, Herts., England. Ability to resist puncture determined by means of a testing apparatus developed by the applicants, in which a sample of the laminate is stretched tightly so as to leave a free circular area with a diameter of 10 mm. Towards the centre thereof there is advanced a test needle having a diameter of 0.8 mm and a rounded tip with a radius of curvature of 0.4 mm at a speed of 5 mm per minute. The penetrating force is measured in N and the deflection at penetration is mea¬ sured in mm. The ability of resistance is determined as the product of the values measured in Nmm.
Example 1 (Comparative example)
A conventional laminate was made, which laminate comprised an outer layer consisting of a biaxially oriented polyamide film to which an intermediate layer by vacuum metallization was applied in the form of an aluminium coa¬ ting. The overall thickness of the outer and intermediate layers was 15 microns. By means of a polyurethane adhesive there was adhered to the intermediate layer an inner layer consisting of a low density polyethylene film having a thick¬ ness of 80 microns.
Example 2
The outer, intermediate and adhesive layers were as specified in Example 1, and the inner layer 1 likewise con¬ sisted of a low density polyethylene film, but comprised according to the invention a non-foamed or solid part 6 having a thickness of 30 microns and a foamed part 7 contai¬ ning a large number of gas-filled cavities and having a thickness of 50 microns. Prior to extrusion there was to the foamed polyethylene added a foaming agent in the form of a so-called master batch, more specifically 5 per cent "Hydrocel CF 20" from the firm of Boehringer Ingelheim KG, Ingelheim, the German Federal Republic. This master batch is specified to consist of 80 per cent polyethylene and 20 per cent of gas-generating reagent.
The values measured appear from Table I below. Table 1 Example 1 Gramweight of laminate g/m2 92.6 Gramweight of inner layer g/m2 73.6 Friction coefficient >1
Resistance to puncture in Nmm from the outside 25.5 from the inside 22.8
Hence, the results show that by means of the laminate according to the invention it is possible to achieve a reduc¬ tion in the gramweight of approx. 20 per cent compared to a similar conventional laminate, while the gramweight of the inner layer was reduced by approx. 25 per cent compared to a conventional inner layer of the same thickness. The lami¬ nate according to the invention likewise shows a significant reduction of the friction coefficient, in which connection it should be noted that no friction-reducing agents had been added to the inner layer of the laminate in either of the two examples. While the laminate according to the inven¬ tion showed the same resistance to puncture from the outside of the laminate as the conventional laminate, its resistance to puncture from the inside had surprisingly increased by approx. 20 per cent relative to that of the conventional laminate.
From the examples given one may therefore conclude in summary that by means of the laminate according to the invention it is possible to achieve a significant saving of material and weight relative to a similar conventional lami¬ nate; that the friction coefficient of the inner surface of the laminate was reduced to the extent that for most applications it will be unnecessary to add to the inner layer any friction-reducing agents, whereby one avoids the drawbacks in connection therewith; while at the same time the resistance of the laminate to puncture from the inside was signifcantly increased in comparison with the resistance showed by a similar conventional laminate, and that the laminate according to the invention thus is better suited for packaging of articles containing pointed or sharp pieces.

Claims

W h a t w e c l a i m i s :
1. A laminate, in particular for packaging foodstuffs or stimulants, comprising at least two layers, namely an outer layer (l) consisting of a first film of plastic mate¬ rial and an inner layer (5) consisting of a second film of plastic material, optionally with an intermediate layer (3) consisting of a foil or coating of a metallic material or of a third film of plastic material interposed between the outer and inner layers, said layers (1,3,5) being adhesively interconnected to form the laminate (1), c h a r a c t e ¬ r i s e d in that the second film of plastic material of the inner layer (5) consists of at least two coextruded parts (6,7), namely a first part (6) of non-foamed plastic material adhered to the outer layer (2) or the intermediate layer (3) and a second part (7) of foamed plastic material forming the inner exposed surface (10) of the laminate.
2. A laminate as defined in claim 1, c h a r a c ¬ t e r i s e d in that the non-foamed part (6) of the inner layer (5) has a thickness of between 20 and 60 microns, preferably between 30 and 40 microns, while its foamed part (7) has a thickness of between 35 and 102 microns, preferably between 51 and 68 microns.
3. A laminate as defined in claim 1 or 2, c h a ¬ r a c t e r i s e d in that the non-foamed part (6) of the inner layer (5) and its foamed part (7) consist of sub¬ stantially the same plastic material.
4. A laminate as defined in claim 1 or 2, c h a ¬ r a c t e r i s e d in that the non-foamed first part (6) of the inner layer (5) and its foamed second part (7) consist of different plastic materials.
5. A method of manufacturing a laminate (1) as defined in any of the previous claims, in which at least two layers, namely an outer layer (2) consisting of a first film of plastic material and an inner layer (5) consisting of a second film of plastic material and optionally an inter¬ mediate layer (3) consisting of a foil or coating of a me- tallic material or of a third film of plastic material are adhered to each other, c h a r a c t e r i s e d in that the second film of plastic material of the inner layer (5) is obtained by coextrusion of a first plastic material with no foaming agent added and a second plastic material with foaming agent added, where the first plastic material forms that surface of the inner layer (5) which is adhered to the outer layer (2) or to the intermediate layer (3) , respec¬ tively, and where the second plastic material forms the inner exposed surface (10) of the laminate (1) .
6. A method as defined in claim 5, c h a r a c t e¬ r i s e d in that the first plastic material of the inner layer (5) and its second plastic material substantially are identical.
7. A method as defined in claim 5, c h a r a c t e¬ r i s e d in that the first plastic material of the inner layer (5) and its second plastic material are different.
8. A method as defined in claim 7, c h a r a c t e¬ r i s e d in that there in between the first and second materials of the inner layer (5) is coextruded a tie layer
(9).
9. A method as defined in any of claims 5 to 8 c h a r a c t e r i s e d in that there to the second plas¬ tic material of the inner layer (5) is added such an amount of foaming agent that after foaming the plastic material shows an increase in volume of between 50 and 100 per cent, preferably between 70 and 80 per cent.
EP89912230A 1988-10-27 1989-09-29 A laminate, in particular for packaging of foodstuffs or stimulants, and a method of manufacturing such laminate Withdrawn EP0440713A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DK5975/88 1988-10-27
DK597588A DK160036C (en) 1988-10-27 1988-10-27 LAMINATE, NECESSARY FOR PACKAGING FOOD OR FOOD, AND PROCEDURE FOR MANUFACTURING THE LAMINATE

Publications (1)

Publication Number Publication Date
EP0440713A1 true EP0440713A1 (en) 1991-08-14

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ID=8146553

Family Applications (1)

Application Number Title Priority Date Filing Date
EP89912230A Withdrawn EP0440713A1 (en) 1988-10-27 1989-09-29 A laminate, in particular for packaging of foodstuffs or stimulants, and a method of manufacturing such laminate

Country Status (6)

Country Link
EP (1) EP0440713A1 (en)
CA (1) CA2000239A1 (en)
CH (1) CH677752A5 (en)
DK (1) DK160036C (en)
ES (1) ES2017563A6 (en)
WO (1) WO1990004517A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0836937A3 (en) * 1996-10-17 2000-04-19 Wihuri Oy Plastic laminate

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA2083004A1 (en) * 1992-05-13 1993-11-14 Thomas Hessen Barrier polyprepylene foam trays
US6132539A (en) * 1995-02-17 2000-10-17 Convenience Food Systems Method for manufacturing packaging materials with a polyolefin foam layer
DE102004019537A1 (en) * 2004-04-22 2005-11-10 All-Plastic Kunststoffwerk Gunzenhausen Gmbh Composite of plastic layers for packaging objects, protective cover, in particular for pieces of furniture, made of at least one such composite, method for producing such a composite and for producing such a protective cover

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Publication number Priority date Publication date Assignee Title
DE2062417A1 (en) * 1970-12-18 1972-06-22 Paul Kiefel GmbH, 6520 Worms Padded thermoplastic sheet laminate - as shrink-on packing material for furniture etc
FI63344C (en) * 1975-04-28 1988-05-03 Wiik & Hoeglund FOER FARING FOR FRAMING OF PLASTIC PLASTICS.
FR2581348B1 (en) * 1985-05-03 1987-06-19 Riedel Paul FLEXIBLE, LIGHTWEIGHT MATTRESS SIMULTANEOUSLY FOR MECHANICAL THERMAL PROTECTION, THERMAL INSULATION, COMFORT
JPH0219225Y2 (en) * 1985-05-21 1990-05-28

Non-Patent Citations (1)

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See references of WO9004517A1 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0836937A3 (en) * 1996-10-17 2000-04-19 Wihuri Oy Plastic laminate

Also Published As

Publication number Publication date
DK160036B (en) 1991-01-21
CA2000239A1 (en) 1990-04-27
DK597588D0 (en) 1988-10-27
DK597588A (en) 1990-04-28
CH677752A5 (en) 1991-06-28
DK160036C (en) 1991-06-10
ES2017563A6 (en) 1991-02-16
WO1990004517A1 (en) 1990-05-03

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