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)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (1)

Family

ID=8146553

Family Applications (1)

Country Status (6)

Cited By (4)

Citations (4)

• 1988
  • 1988-10-27 DK DK597588A patent/DK160036C/da not_active IP Right Cessation
• 1989
  • 1989-09-29 EP EP89912230A patent/EP0440713A1/en not_active Withdrawn
  • 1989-09-29 CH CH2208/90A patent/CH677752A5/de not_active IP Right Cessation
  • 1989-09-29 WO PCT/DK1989/000228 patent/WO1990004517A1/en not_active Ceased
  • 1989-10-06 CA CA002000239A patent/CA2000239A1/en not_active Abandoned
  • 1989-10-19 ES ES8903516A patent/ES2017563A6/es not_active Expired - Lifetime

Patent Citations (4)

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