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
  • B32B1/00—Layered products having a non-planar shape
• • 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
  • 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
  • B32B27/08—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 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
  • B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
• • 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
  • B32B27/36—Layered products comprising a layer of synthetic resin comprising polyesters
• • 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
  • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
  • B32B7/02—Physical, chemical or physicochemical properties
• • 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
  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/70—Other properties
  • B32B2307/726—Permeability to liquids, absorption
  • B32B2307/7265—Non-permeable
• • 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
  • B32B2398/00—Unspecified macromolecular compounds
  • B32B2398/20—Thermoplastics
• • 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

• This invention concerns a flexible packaging mate ⁇ rial which, by thermoforming or other mechanical process ⁇ ing, is mouldable into dimensionally-stable liquid-tight containers intended especially for food and exhibiting barrier qualities.
• the invention further relates to a method for pro ⁇ ducing this material, as well as a container made there ⁇ of.
• the invention concerns the use of the packaging material for making dimensionally-stable liquid-tight containers exhibiting barrier qualities.
• packaging materials used for making food containers have to exhibit excellent barrier qualities, i.e. the material should have a reduced permeability with respect to, inter alia, oxygen, water/vapour, light or ultraviolet radiation.
• the requirements placed on the barrier qualities of the material may, of course, vary according to the food that the container at issue is to hold.
• Coating the packaging material with an aluminium foil is a highly efficient method of obtaining good bar ⁇ rier qualities.
• the provision of such an alumi ⁇ nium foil makes the packaging material much more expen ⁇ sive, and it is sometimes necessary to cover the alumi- nium foil with special protective layers in order to pre ⁇ vent direct contact between the foil and the food held in the container.
• the aluminium foil When used in trough-shaped table packs for butter, the aluminium foil creates special problems.
• the original sealing used is an aluminium foil which is applied over the trough opening and is sealed against the upper circumferential edge portion of the trough.
• This aluminium foil makes the whole pack more expensive, not only as a result of the cost of material for the foil, but also as a result of the fairly compli ⁇ cated operations required for applying the cut foil to the pack trough and gluing or heat-sealing it onto the pack.
• This known packaging material comprises a fair ⁇ ly thick, stiffening core layer, which on both sides is provided with a thin protective layer or barrier layer.
• the core layer consists of a mixture of plastic and filler, and the plastic preferably is a polyolefin, such as polyethylene or polypropylene.
• filler use is pri ⁇ marily made of chalk, but other possible fillers are talc, mica and clay.
• the amount of filler should be 50-80% of the total weight of the core layer, preferably about 65% by weight.
• the protective layers should consist of a mixture of a plastic of the same type as the plastic used in the core layer and some other plastic.
• this packaging material does not meet the market's requirements on low-weight packages, since the filler in the core layer, if anything, makes the packag ⁇ ing material heavier than comparable prior-art packaging materials, with or without any aluminium foil.
• SE-B-467,772 (corresponds to EP-A-494,595), which discloses a packaging material similar to that discussed above.
• the above US patent therefore suggests a material which comprises a core layer consisting of a foamed ther ⁇ moplastic, which on both sides is provided with a thin skin layer of polyethylene.
• the foamed core layer is meant to have a certain stiffening effect.
• the plastic film composed of these three layers is very thin and is unsuited for the production of dimensionally- stable liquid-tight containers for e.g. edible fat.
• This prior-art three-layer film has a thickness of but about 20-60 ⁇ m, the core layer having a thickness of about 6-38 ⁇ m, and each skin layer having a thickness of about 6-13 ⁇ m.
• One object of the invention is, therefore, to pro ⁇ vide a new packaging material obviating the above-men ⁇ tioned drawbacks and meeting the market's requirements as to low weight and low price.
• a special object of the invention is to provide a packaging material which ensures satisfactory barrier qualities without the need of any metal foil.
• Another object of the invention is to provide a package or container which can be originally sealed with- out the need of any metal foil.
• Yet another object of the invention is to provide a package or container which is made of as few elements and materials as possible and thus is easily recycled.
• a further object of the invention is to provide an efficient method for producing the packaging material, as well as to provide a use of the packaging material for making dimensionally-stable liquid-tight containers exhi ⁇ biting barrier qualities.
• Fig. 1 is a schematic cross-section of a packaging material according to a preferred embodiment of the invention
• Fig. 2 is a partial section of a container according to a preferred embodiment of the invention
• Fig. 3 is a schematic view of a plant for producing the packaging material.
• Fig. 1 is a cross-section of a preferred embodiment of the packaging material according to the invention.
• This material comprises a stiffening, polymeric core layer 1 which on both sides has a barrier layer or pro ⁇ tective layer 2, 3 (skin layer) of polymeric material connected thereto.
• the intermediate core layer 1 comprises a foamed thermoplastic, preferably a thermo ⁇ plastic polyester.
• the density-reducing foaming opera ⁇ tion is carried out by admixing a known foaming agent to the polyester. If based on plastic, the foaming agent includes granulates which, when heated, generate bubbles of gas (e.g. carbon dioxide), which expand the polyester.
• gas e.g. carbon dioxide
• the degree of foaming of the core layer 1 is such that its density is at least 20% lower than that of the protective layers 2, 3, which preferably comprise a non-foamed, thermoplastic polyester.
• the core layer 1 and the protective layers 2, 3 are based on the same thermoplas ⁇ tic, preferably a polyester.
• the packaging material should have a thickness of approximately 125-2500 ⁇ m, depending on the purpose of the container to be produced therefrom.
• the core layer 1, consisting chiefly of foamed polyester, should have a thickness that makes up about 70-95% of the total thick ⁇ ness of the packaging material, and the protective layers 2, 3, consisting chiefly of non-foamed polyester, then make up the remainder of the thickness of the packaging material. Tests meeting these requirements have yielded excellent results.
• a liquid-tight and dimensionally-stable container made of the packaging material according to the invention may be composed of only two elements, namely a trough- shaped element 4 and a lid element 5 sealable therewith (see Fig. 2).
• the trough element 4 has a circumferential flange 6 which, after the container has been filled, is applied against a corresponding circumfe ⁇ rential flange 7 on the lid element 5. At least the one flange is provided with an adhesive, so as to make the original sealing of the container so tight that there is no need of any sealing by means of a metal foil.
• clamping jaws (not shown) are applied against the flanges 6, 7 at a temperature of about 180-200°C and for 0.5-1 s.
• the flanges 6, 7 may on the outside have a thin coating of a protective lacquer (not shown) . Since only one of the circumferential flanges 6, 7 is coated with the adhesive or glue, the glued surface is very restricted, involving a much-reduced consumption of glue. In the case of similar, prior-art original seal- ings, the entire inside of the lid has been provided with a so-called thermolacquer for the adhesion of the trough element to the flange. In the inventive container, only the contact surface between the flanges 6, 7 is glued.
• the container 4, 5 described above further comprises means (not shown) for resealing, e.g. snap-in sealing.
• the trough element 4 has a wall thickness of 300-1200 ⁇ m, preferably 450-1000 ⁇ m and most preferred 550-700 ⁇ m.
• the lid element 5 then has a wall thickness of 125-400 ⁇ m, preferably 150-300 ⁇ m and most preferred 200-240 ⁇ m.
• the trough element 4 may have a wall thickness of up to 2500 ⁇ m, while the lid element 5 may be thinner and have a wall thickness equivalent to that indicated above for the edible-fat container.
• the protective layer 2 will form the inner layer of the trough, while the protective layer 3 will form the outer layer of the trough.
• the inner layer 2 must, of course, be fat-resistant and should in addition form a barrier against oxygen and water/vapour.
• the inner layer 2 is dyed white.
• the core layer 1 is advantageously dyed grey, so as to serve as a light barrier.
• the outer layer 3 may be dyed, for instance for decorative purposes. It should here be observed that the outer layer 3 may, in certain circumstances, be dispensed with, if the inner layer 2 and the core layer 1 provide the barrier qualities required.
• Fig. 3 schematically illustrates a plant in which the inventive method can be applied.
• This plant comprises three silos 8-10 for polyester, three driers 11-13, and four tanks 14-17 for colour granulates and foaming agent, as will be described in more detail below.
• the plant includes three extruders 18-20, one moulding head 21, three cooling rollers 22-24, one thickness gauge 25, one trimming device 26, one mill 27 and one final rolling-up device 28.
• the silo 8 contains virgin material in the form of polyester having a viscosity of about 0.8, i.e. the average intrinsic viscosity is about 0.8.
• the polyester Via the drier 11, the polyester is supplied to the extruder 18, whence the material to form the core layer 1 is supplied to the moulding head 21.
• Foaming agent from the tank 16 and colour granulates, if any, from the tank 17 are supplied to the core-layer extruder 18.
• the silo 10 also contains virgin material in the form of polyester having a lower intrinsic viscosity, namely an average intrinsic visco ⁇ sity of about 0.7. Via the drier 13, this polyester is supplied to the extruder 19 for producing the inner layer 2 and to the extruder 20 for producing the outer layer 3.
• Colour granulates from the tank 14 are used for colouring the outer layer 3, and colour granulates from the tank 15 are used for colouring the inner layer 2, if any such colouring is to be performed.
• the three materials are fed to the moulding head 21, where the materials are laminated at a temperature of about 200-300°C.
• the cooling rollers 22-24 the mate ⁇ rial web is further conveyed to the rolling-up device 28, which serves as intermediate storage means prior to the thermoforming (not shown) of the containers.
• the material web is trim ⁇ med, and the waste material is supplied to the mill 27, whence crushed material is returned to the silo 9 and, via the drier 12, to the extruder 18, where the core- layer material is formed.
• the crushed polyester mate ⁇ rial thus recycled in the process, the molecular chains have been so broken that the intrinsic viscosity is below 0.8, and in some cases even below 0.7.
• Such recycling of crushed polyester enables the process to be controlled in an extremely expedient fashion, as will be described in more detail below.
• the core-layer material leaving the extruder 18 may, by suitable control of the recycling process, be brought to an intrinsic viscosity of approximately
• the polyester to form the protec ⁇ tive layers 2, 3 after the extruders 19 and 20, respec ⁇ tively, is always supplied in the form of virgin material having an intrinsic viscosity of about 0.68-0.72.
• the lamination in the moulding head 21 may be so controlled that the difference in intrinsic viscosity between the core layer and the protective layers at all times exceeds 0.04. This results in excel ⁇ lent lamination.
• the thickness gauge 25 may also be used for controlling the above process.
• Containers having a 50% lower total weight than equivalent prior-art containers and exhibit ⁇ ing perfectly acceptable mechanical properties and bar ⁇ rier qualities have been produced.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Laminated Bodies (AREA)
• Wrappers (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=20391933

Family Applications (1)

Country Status (2)

Cited By (7)

Citations (3)

• 1993
  • 1993-11-30 SE SE9303966A patent/SE502080C2/sv not_active IP Right Cessation
• 1994
  • 1994-11-29 WO PCT/SE1994/001145 patent/WO1995015257A1/en active Application Filing

Patent Citations (5)

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