CA2023507A1 - Sterilizable packaging container of plastic/metal/plastic composite material and process for its production - Google Patents
Sterilizable packaging container of plastic/metal/plastic composite material and process for its productionInfo
- Publication number
- CA2023507A1 CA2023507A1 CA002023507A CA2023507A CA2023507A1 CA 2023507 A1 CA2023507 A1 CA 2023507A1 CA 002023507 A CA002023507 A CA 002023507A CA 2023507 A CA2023507 A CA 2023507A CA 2023507 A1 CA2023507 A1 CA 2023507A1
- Authority
- CA
- Canada
- Prior art keywords
- plastic layer
- thickness
- plastic
- layer
- container according
- 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.)
- Abandoned
Links
Classifications
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- 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
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C51/00—Shaping by thermoforming, i.e. shaping sheets or sheet like preforms after heating, e.g. shaping sheets in matched moulds or by deep-drawing; Apparatus therefor
- B29C51/14—Shaping by thermoforming, i.e. shaping sheets or sheet like preforms after heating, e.g. shaping sheets in matched moulds or by deep-drawing; Apparatus therefor using multilayered preforms or sheets
-
- 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
- B32B15/20—Layered products comprising a layer of metal comprising aluminium or copper
-
- 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
- B32B2307/30—Properties of the layers or laminate having particular thermal properties
- B32B2307/31—Heat sealable
-
- 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
- B32B2307/50—Properties of the layers or laminate having particular mechanical properties
- B32B2307/514—Oriented
- B32B2307/518—Oriented bi-axially
-
- 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
- B32B2311/00—Metals, their alloys or their compounds
- B32B2311/24—Aluminium
-
- 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
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Laminated Bodies (AREA)
- Blow-Moulding Or Thermoforming Of Plastics Or The Like (AREA)
Abstract
Abstract Sterilizable packaging container of plastic/metal/plastic composite material having a proportional thickness of metal of less than 20% of the total thickness of the composite material, produced by forming, of a composite material, containing a first plastic layer of from 0.006 to 0.05 mm in thickness having high extensibility and at the same time having high strength, as well as increasing strengthening during deforming and a second sealable plastic layer of from 0.1 to 0.8 mm in thickness having high extension and high load-bearing capacity during forming and a metal layer located between the plastic layers having a thickness of 0.006 to 0.1 mm of aluminium with an aluminium content of 98% or more or of an alumi-nium alloy, the first plastic layer serving as extension promoter for the metal layer and being quasi-isotropic, and the second plastic layer containing, if appropriate, 10 to 70% by volume, referred to the second plastic layer, of fillers.
Description
Sterilizable packaaina container of Dlastic/metal/plastic composita material and process for its production The invention relates to a sterilizable packaging con-tainer of plastic/metal/plastic composite material, the proportional thickness of the metal layer being lQss than 20%, and process for its production.
Containers known up until now have, however, only a low rigidity, so that they can easily be dented.
For example, a production method for a plastic container is described in the Japanese Patent Publication 61-273929, in which a material composed of three layers i-~ ~uperfi-cially heated and then deep-drawn.
The inventors have therefore set themselves the ob~ect of improving such packaging containers in such a way that they become insensitive to denting or have "spring-back~
properties.
The ob~ect i8 achieved according to the invention with a container which is characterized in that the composite material i8 composed of a first plastic layer having h$gb extension and at the same time high internal stress as well as increasing strengthening during deforming and of a second plastic layer of from 0.1 to 0.8 mm in thickne~s having high extension and high load-bearing capacity during forming, between which there i8 a metal layer having a thickness from 0.006 to 0.1 mm of aluminium with an aluminium content of 98% or more or of an aluminium alloy, the first plastic layer serving as extension promoter for the metal layer and being quasi-isotropic, and the second plastic layer being stiffened during forming due to increasing extension.
The ob~ect is expediently achieved according to the invention with a container which is characterized in that the composite material contains a flrst pla~tic layer of 2023~7 a thickness from 0.008 mm to 0.05 mm having high extensi-bility and at the same time high strength, as well as increasing strengthening during deforming and a second plastic layer of from 0.1 to 0.8 mm in thickness having high extension and high load-bearing capacity during forming, and there is between the plastic layers a met~l layer of a thicknes~ from O.006 to 0.1 mm of aluminium with an aluminium content of 98% or more or of an alumi-nium alloy, the first plastic layer serving as extension promoter for the metal layer and being guasi-isotropic, and the second plastic layer containing 10 to 70% by volume, referred to the second pla~tic layer, of fillers.
The composite material consequently has a first pla~tic layer which is directed outwards on a container produced from the compositQ material, the composite material also has a metal layer, which lies between the first plastic layer and the second plastic layer, and the second plastic layer i~ directed inwards on a container produced from the composite material, i.~. is to be located on the container inner side. The layers can be ~oined to one another in a way known per se. The first and/or the second plastic layer can be laminated, calendered or extrusion-coated to the metal. For ~oining the plastic layers to the metal or pla~tic layerq to one another, solvent-containing or solvent-free laminating adhesives, aqueous dispersion adhesives or thermally activatable adhesive layers are suitable.
The second plastic layer is preferably sealable.
The container~ according to the present invention are ~terilizable and preferably have at least one sealable layer. The advantages of the containers according to the invsntion lie in their rigidlty, i.e. they are insen~i-tive to buckling or have ~spring-back~ properties in their use as packaging for aggre~ive contents, in particular in the ca~e of preserved-food containers.
~02~7 The rigidity proper~ies (insensitivity to denting and "spring-back~ character) make it po~sible to design a package of which the appearance i~ virtually unimpaired by mechanical effect~ during handling, in particular due to careless handling at sales organizations, in com-parison with the containers known today of metal/plastic composites.
The packaging containers according to the invention have a thin metal layer, which acts as a barrier against externally acting, chemical, physical and optical influ-ence~ on the content~.
This metal layer may preferably consist of an aluminium with an aluminium content of 98.6~ or of an aluminium alloy, for example of the type 8101 ~AA 8014), particu-larly preferred is aluminium of a purity of 99.6~.
The thickness of the metal layer i8 expediently less than10~ of the thickness of the composite material.
Metal layers of a thickness from 0.008 to 0.04 mm or from 0.2 to 0.1 mm are preferred, in practice metal layer~ of a thickness from 0.02 to O.OS mm being preferred quite particularly.
The first plastic layer of the composite material, which is generally directed outwards on a packaging container produced therefrom, advantageously consists of a very tough, highly extensible film of a thermopla~tic. Biaxi-ally stretched materials are preferred, such as oriented polye ter (for example oPET), oriented polypropylene (opp)~ oriented polyamide (oPA), oriented low-density or high-density polyethylene (oPE), oriented polymethyl-pentene (oPMP), oriented polystyrene (oPS) polyetherimide(PI), polyether ether ketone (PEEK), polycarbonate (PC) or copolymer~ containing the said thermoplastic~.
These films are to have in particular a high 2û23~7 extensibility and a high strength in machine direction (MD) and in transversal direction (TD) with an increasing strengthening.
For forming reason~, biaxially stretched films having S qua~i-i40tropic propertie~ in MD and TD are preferred.
Such a fil~ serves a~ extension promoter for the metal layer. This layer absorb~ the stresses occurring in the metal layer during forming.
If appropriate, the outwardly and/or inwardly directed plastic layers may be coloured, provided that the exten-sibility is not lmpairPd. The plastic layers may alRo be printed or reverse-printed.
The first, ~enerally outwardly directed plastic layer has the ob~ect of mechanically supporting the metal layer and preventing local constrictions during the forming pro-cess. The fir~t plastic layer expediently has a thickness from 0.01 to 0.04 mm.
The second plastic layer of the compo~ite material, which is generally diracted inward~ on a packaging conta~ner produced from it, may consist of a sealable, highly rigid and highly extensible thermopla~tic matrix.
Preferred as thermoplaRtic matrix are, for example, layers of polypropylene ~PP), polyester (for example polyethylene terephthalate (PET), polystyrene (PS), low-density or high-density polyethylene (P~) polymethyl-pentene (PMP), polycarbonate (PC) and copolymcrs contain-ing these materials. Further examples of the second pla~-tic layer are films of oriented polypropylene (BOPP) or of oriented polyamide ~BOPA) or of oriented polyethylene terephthalate (BOPETP,BOPETG) or of oriented high-density polyethylene (BOHDPE) or of oriented polyc~rbonate (BOPC) or of polyether imide (PEI) or of polyether ether ketone (PEEK) or of oriented polystyrene (BOPS). The second plastic layer contains 10 to 70% by volume of filler~. 20 - 2023~07 to 50% by volume, referred to the second pla~tic layer, of filler~ are preferred.
Copolymers having sterilization properties are preferred.
Examples of filler~ are fibre reinforcing matexials, such as fibres of carbon, glass fibres, ~Revlar~, aramid, natural fillers, such as celluloses, for example ~-cellulose, pine bark, nut husks, sawdust, cotton flock, cork granules, lignin; mineral fillers, such as siliceous earth, aluminium hydrate, kaolin, talc, diatomite, silicates, barite, titanium dioxide, chalk and alXaline earth metal compounds, such a calcium carbonate or mixtures of the said materials; mineral fillers, talc, glass fibre~ and titanium dioxide are proferred.
Furthermore, the second pla~tic layer may contain colour pigments, light-refracting pigments, calcined chalk or glass beads.
The rigidity properties of the container~ according to the invention which are produced from the composite material can be controlled by me~ns of the thickness of the second plastic layer, which may expediently be 0.1 to O.6 mm, and the proportion of fillers.
The second plastic layer preferably ha~ a thickness from 0.2 to 0.5 mm. A proportion of fillers from 20 to 50~ by volume, referred to the second plastic layer is prefer-red.
Particularly preferably, the second plastic layer may befilled with chopped strand~ of glass. The chopped strands of glass may be, for example, 0.1 to 0.8 mm long and O.005 to 0.02 mm thick. An optimum filler content in the second plastic layer i9 30% by volume. The thickness of the second layer containing chopped strands of glass as filler may, in particular, be 0.2 to 0.5 mm.
` 2~23~07 With a particularly preferred R~cond plastic layer of this kind, the modulus of elasticity can be increased at high degrees of forming.
If, for example, the said filler do not conform to the relevant health regulations (Bundesgesundheitsamt, Food and Drug Admini~tration), at least one further, non-toxic plastic layer, which is expediently sealable, may be applied to the second plastic layer.
The thickness of such a layer may be 0.001 to 0.02 mm, preferred materials are polyester, polypropylene, poly-amide or polyethylene.
The second, inwardly directed layer not only performs the role of corrosion protection of the metal layer and of optimizing the friction conditions during the forming lS process but is also of significance for the rigidity properties of the contaLner.
It goes without saying that the material combination described in detail above may also be reversed regarding inside to outqide. ~he requirements and the individual layers are retained. In addition, it is advantageous to provide the inner extension promoter with a sealable layer by surface treatment or by additional application of a sealing coating or by lamination of a sealing f~lm.
In that case, special requirement~ regarding the preven-tion of absorption of flavourings or other volatilesubstances of the contents are no longer imposed on the inwardly directed layer. It is likewise ~necessary to worry about impairment of mechanical properties of the supporting film or of the plastic/adhesive interface by the absorption of water or alcohol.
Both the first and thc second pla~tic layar, as well as the composite laminate, axe pr~ferably sterilizable. A~
a result, these materials are not thermally Lmpaired ~-Q23~
during forming at elevated temperature.
The processing of the composite material described into the sterilizable packaging container~ according to the invention can take place in various way If containers are to be produced from the compositc materials described with low degrees of forming, the forming can be performed by deep drawing by means of a drawing die and female mould.
Low degrees of forming are understood to mean, for example, a ratio of diameter to depth of the container to be produced of 4 or greater than 4 to 1.
The forming may also take place without the supply of heat, since in the~e cases the residual stre~ses are relatively low. The same process can be ussd for con-lS tainers with a greater degree of forming, for whichabsolute dimensional stability is not required. In that case, the composite material is to be formed beyond the required container depth H, that is to say the final geometry is only achieved after relaxation of the resi-dual stre~ses.
For the purpose of better forming, the inwardly directedplastic layer preferably has a smooth, low-~rict$on ~urface and a high forming limit. Fillers ~uch as those mentioned above reduce the recovery after the forming operation and after any sterilization.
Forming in the ~tate below the usual thermoforming temperatures of plastics such as PP, PE, PET in the thickness range from 0.1 to 0.6 mm, usually results in inhomogeneities in the flow behaviour of the pla~tic. The material constricts locally, which results in rapid cracking in the Al layer.
This is the case in particular in the production of containers having a ratio of diameter to height of less than, for example, 4sl.
The inhomogeneous flowing of the filled plastic can be eliminated to the greatest extent by the admixture according to the invention of fillers in the range from 20 - 70% by volume referred to the second plastic layer, to the said plastics. The forming potential of the composite material can thereby be optimally utilized.
The high filler content in the rang~ from 20 to 70~ by volume can al80 accomplish a reduction in the recovery of the thick inner plastic layer after forming.
If the recovery after forming is excessive, the container may be thermally set at the end of the deformation, while still in the loaded state, by the introduction of heat.
The remaining restoring force~ are reduced by the heat, the container remains dimensionally stable.
The inner layer not only performs the role of corrosion protection of the metal layer and optimization of the friction conditions during the forming process, but also contributes to the rigidity properties of the container.
The greater part of the rigidity of the finished con-tainer is advantageously attained by the thickness and the filler content of the second inner plastic layer.
In the case of containers having a ratio of container diameter to container depth of 3 and greater than 3 to 1, the composite material may be formed in one process step at a temperature of, for example, 80C to 130C, the die (male mould andJor female mould) expediently also being heated.
At a ratio of container diameter to container depth of le~ than 3 ~for example down to 1) to 1, it may b0 advantageous, depending on the degree of forming, to work ..... . . ..
~0235~7 g in a plurality of forming steps with drawing dies and hold-down devices, such as are known for metallLc mater-ial~, for example, in which case in particular the final forming step can be performed under thermal effect. In S the final forming step, in a preferred way no greater forming than the elastic recovery is aimed for and the heat has subatantially only the effect of relaxing the residual stresses.
In practice, the process described often requires a plurality of forming steps and 0xpediently alqo a~ least two dies, such as for example one forming die for the cold deformation and one forming die for the stabiliza-tion in the warm state. Another method can first of all use a warm die and subsequently a cold die.
An apparatu~ for carrying out the proces~ is described, for example, in German Patent Specification 2,539,354.
An example of another ~uitable process for the production of a sterilizable packaging container is characterized in that the container i8 made by a combination of stretch forming and deep drawing at elevated temperature balow the thermoforming temperature~ of the plastics us~d.
In order to maximize the forming limit, ideal stretch forming follows deep drawing. In particular by a combina-tion of the two process step~ it i8 possible to creats a high dimensional ~tability and a homogenous thickness distribution of the material. For the case of a thinner plastic layer as inner side of the container - with the consequence of a lesser insenqitivity to denting or reduced "spring-back character" - the process combination of stretch ~orming and deep drawing provides the possibi-lity of shaping the compo~ite material free from fold~.
With an inner plastic layer, for example having a thick-ness less than 0.1 mm, it is advantageously even pO88-lble, depending on fillers, additives and ~dded pigment~, to dispense with the elevated temperature.
A particularly advantageous process for the production of containers of any ratio between container diameter and container depth and expediently for the production of containers having a ratio between container diameter and container depth of 3 or les~ than 3 to 1 and preferably of 2 or less than 2 to 1 is the sub~ect of the present invention. The limits of applicability of thi~ process are generally only reached at a ratio of container diameter to container depth of 1:1.
The process for the production of the sterilizable packaging container described is characterized by a combination of deep drawing, subsequent stretch forming if appropriate, and thermal stabilization of the con-tainer below the thermoforming temperature of the second plastic layer used.
The process i8 based on process step~ which aro known par se, namely deep drawing and, if appropriate, stretch forming, the latter using a female mould, a male mould and a hold-down device. The hold-down device serves the purpose of holding the composite material firmly on the edge of the female mould while the male mould shapes the compo~ite material into the female mould, at the same time stretching it.
The process can be described in more detail by saying that the dsformation of the compo~ite material i~ carried out in an apparatus suitable for deep drawing, the deep drawing step being performed with a hold-down force of the hold-down device such that the material required for the deep drawing step i8 drawn from the re~ion of the female mould and the hold-down device. When the composite material has been formed to the final depth, the com-posite material i8 heated. The heating may be performed both by heating from outside (temperature-controlled dies) or, for example, by heat Lnduced in the aluminium (high-frequency induction heating).
` 2023~Q7 The latter Btep i8 decisive for the ~tabilization of the container geometry by the reduction of residual stresses.
In practice, the process is carried out, for example, in such a way that the deep drawing step i~ carried out at a hold-down force of the hold-down device of 0.8 to 2 kN, which commences at 0% of the container depth (H) and ends at 100% of the container depth (H), which also corres-ponds to the displacement of the male mould. The hold-down force of the hold-down device is to be chosen such that the material can always flow on into the die with increasing H. Depending on the ratio of container dia-meter to container depth, in particular at ratio~ less than 3 ~o 1, a graduation of the hold-down force of the hold-down device is advantageous. With a container depth ~H) of 0% to 60%, the hold-down force may be chosen between 0.6 kN and 1.2 kN and with a container depth of 60% to 100% the hold-down force may be increased to 2.0 kN, in which case the drawing down may also be taken over by a stretching.
In practice, on reaching 100% of the container depth (H), the hold-down force of the hold-down device can b~
increased to 30kN to 60kN, in order that the container rim is smoothed. During or after this last-mentioned operation, a high-frequency heating is performed, for example during 0.3 to l second, at a power of 5 to 18 kW
in a frequency range of 20 to 150 kHZ, the power and frequency of the induction heating having to be adapted to the size and geometry of the container. These optimum data can be determined, for example, by a few specific trials.
For carrying out the processe~ described, the male mould and the female mould are, for example, produced from plastics such as for example polytetrafluoroethylene or polymethylpentene or the surface~ effecti~e in deforma-tion are coated with thess material~. An inductor loop, for example, is placed into the male mould and/or the 21~3~
_ 12 -female mould. A current in then induced through this inductor when the composite material ha~ been formed to the final depth H. The aluminium i8 heated by the induced energy, which reqults in a heat transfer into the plas-tic. As a result, the heat can be supplied in order toreduce the residual stresses remaining in the plastic.
This process is expediently carried out with a high-frequency generator which operates in a power range of 5 - 8 kW and has a high frequency range of 30 - 150 kHz.
The time during which the induced energy acts is expedi-ently between 0.3 and l.0 sec.
The small thickness of the metal layer is not in itself capable of providing adequate rigidity. It serves es~en-tially as a barrier layer.
For inexpensive production of the container, it is advantageous if the second, inwardly directed plastic layer is high-frequency sealable thermally or indirectly via the metal layer with respect to a plastic cover or with respect to a metal layer covered by coating or lamination.
In the choice of a composite laminate having relatively thinner plastic layers which itself still does not have adequate rigidity properties for the intended purpo8e, the container shape produced after the forming process can receive an adequate rigidity in a further process step by in~ection-moulding around it a thermoplastic such as polyethylene, polypropylene, polyester etc. A layer thickness of 0.3 to 0.6 mm is particularly advantageous.
The choice of appropriate mala mould materials or male mould coatings also plays an important role, for example in the case of the fold-free forming of the composite laminates described. Male mould materials such as, inter alia, ~eflon or ~ilicone rubber~ may cause locally different friction and radial compres~ion conditions. The ~3~a7 inwardly directed plastic layer preferably has a low surface friction. A container shape which is free from folds to the greatest extent can be attained by suitable radial compression. Deep drawing at room temperature, with conventional dies, permits a fold-free forming if the container walls are provided with rib~, a~ a result of which the wall surfaces are increased, in order that the folds can be eliminated.
For making smooth-walled container shapes, telescopic male mould~ are preferably used, which have a positive effect on the one hand on the maximum attainable exten-sion forming limit and on the other hand on the fold-free appearance.
For inexpensive production of the container, it i8 advantageous if the inner pla~tic layer i3 high-frequency sealable, for example thermally or indirectly via the metal layer, with respect to a plastic cover or with respect to a metal layer covered by coating or lamina-tion.
On account of their barrier properties, containers according to the present invention find use, for example, as containers for food or for feed stock. The containers are sterilizable in empty and in filled condition.
Containers known up until now have, however, only a low rigidity, so that they can easily be dented.
For example, a production method for a plastic container is described in the Japanese Patent Publication 61-273929, in which a material composed of three layers i-~ ~uperfi-cially heated and then deep-drawn.
The inventors have therefore set themselves the ob~ect of improving such packaging containers in such a way that they become insensitive to denting or have "spring-back~
properties.
The ob~ect i8 achieved according to the invention with a container which is characterized in that the composite material i8 composed of a first plastic layer having h$gb extension and at the same time high internal stress as well as increasing strengthening during deforming and of a second plastic layer of from 0.1 to 0.8 mm in thickne~s having high extension and high load-bearing capacity during forming, between which there i8 a metal layer having a thickness from 0.006 to 0.1 mm of aluminium with an aluminium content of 98% or more or of an aluminium alloy, the first plastic layer serving as extension promoter for the metal layer and being quasi-isotropic, and the second plastic layer being stiffened during forming due to increasing extension.
The ob~ect is expediently achieved according to the invention with a container which is characterized in that the composite material contains a flrst pla~tic layer of 2023~7 a thickness from 0.008 mm to 0.05 mm having high extensi-bility and at the same time high strength, as well as increasing strengthening during deforming and a second plastic layer of from 0.1 to 0.8 mm in thickness having high extension and high load-bearing capacity during forming, and there is between the plastic layers a met~l layer of a thicknes~ from O.006 to 0.1 mm of aluminium with an aluminium content of 98% or more or of an alumi-nium alloy, the first plastic layer serving as extension promoter for the metal layer and being guasi-isotropic, and the second plastic layer containing 10 to 70% by volume, referred to the second pla~tic layer, of fillers.
The composite material consequently has a first pla~tic layer which is directed outwards on a container produced from the compositQ material, the composite material also has a metal layer, which lies between the first plastic layer and the second plastic layer, and the second plastic layer i~ directed inwards on a container produced from the composite material, i.~. is to be located on the container inner side. The layers can be ~oined to one another in a way known per se. The first and/or the second plastic layer can be laminated, calendered or extrusion-coated to the metal. For ~oining the plastic layers to the metal or pla~tic layerq to one another, solvent-containing or solvent-free laminating adhesives, aqueous dispersion adhesives or thermally activatable adhesive layers are suitable.
The second plastic layer is preferably sealable.
The container~ according to the present invention are ~terilizable and preferably have at least one sealable layer. The advantages of the containers according to the invsntion lie in their rigidlty, i.e. they are insen~i-tive to buckling or have ~spring-back~ properties in their use as packaging for aggre~ive contents, in particular in the ca~e of preserved-food containers.
~02~7 The rigidity proper~ies (insensitivity to denting and "spring-back~ character) make it po~sible to design a package of which the appearance i~ virtually unimpaired by mechanical effect~ during handling, in particular due to careless handling at sales organizations, in com-parison with the containers known today of metal/plastic composites.
The packaging containers according to the invention have a thin metal layer, which acts as a barrier against externally acting, chemical, physical and optical influ-ence~ on the content~.
This metal layer may preferably consist of an aluminium with an aluminium content of 98.6~ or of an aluminium alloy, for example of the type 8101 ~AA 8014), particu-larly preferred is aluminium of a purity of 99.6~.
The thickness of the metal layer i8 expediently less than10~ of the thickness of the composite material.
Metal layers of a thickness from 0.008 to 0.04 mm or from 0.2 to 0.1 mm are preferred, in practice metal layer~ of a thickness from 0.02 to O.OS mm being preferred quite particularly.
The first plastic layer of the composite material, which is generally directed outwards on a packaging container produced therefrom, advantageously consists of a very tough, highly extensible film of a thermopla~tic. Biaxi-ally stretched materials are preferred, such as oriented polye ter (for example oPET), oriented polypropylene (opp)~ oriented polyamide (oPA), oriented low-density or high-density polyethylene (oPE), oriented polymethyl-pentene (oPMP), oriented polystyrene (oPS) polyetherimide(PI), polyether ether ketone (PEEK), polycarbonate (PC) or copolymer~ containing the said thermoplastic~.
These films are to have in particular a high 2û23~7 extensibility and a high strength in machine direction (MD) and in transversal direction (TD) with an increasing strengthening.
For forming reason~, biaxially stretched films having S qua~i-i40tropic propertie~ in MD and TD are preferred.
Such a fil~ serves a~ extension promoter for the metal layer. This layer absorb~ the stresses occurring in the metal layer during forming.
If appropriate, the outwardly and/or inwardly directed plastic layers may be coloured, provided that the exten-sibility is not lmpairPd. The plastic layers may alRo be printed or reverse-printed.
The first, ~enerally outwardly directed plastic layer has the ob~ect of mechanically supporting the metal layer and preventing local constrictions during the forming pro-cess. The fir~t plastic layer expediently has a thickness from 0.01 to 0.04 mm.
The second plastic layer of the compo~ite material, which is generally diracted inward~ on a packaging conta~ner produced from it, may consist of a sealable, highly rigid and highly extensible thermopla~tic matrix.
Preferred as thermoplaRtic matrix are, for example, layers of polypropylene ~PP), polyester (for example polyethylene terephthalate (PET), polystyrene (PS), low-density or high-density polyethylene (P~) polymethyl-pentene (PMP), polycarbonate (PC) and copolymcrs contain-ing these materials. Further examples of the second pla~-tic layer are films of oriented polypropylene (BOPP) or of oriented polyamide ~BOPA) or of oriented polyethylene terephthalate (BOPETP,BOPETG) or of oriented high-density polyethylene (BOHDPE) or of oriented polyc~rbonate (BOPC) or of polyether imide (PEI) or of polyether ether ketone (PEEK) or of oriented polystyrene (BOPS). The second plastic layer contains 10 to 70% by volume of filler~. 20 - 2023~07 to 50% by volume, referred to the second pla~tic layer, of filler~ are preferred.
Copolymers having sterilization properties are preferred.
Examples of filler~ are fibre reinforcing matexials, such as fibres of carbon, glass fibres, ~Revlar~, aramid, natural fillers, such as celluloses, for example ~-cellulose, pine bark, nut husks, sawdust, cotton flock, cork granules, lignin; mineral fillers, such as siliceous earth, aluminium hydrate, kaolin, talc, diatomite, silicates, barite, titanium dioxide, chalk and alXaline earth metal compounds, such a calcium carbonate or mixtures of the said materials; mineral fillers, talc, glass fibre~ and titanium dioxide are proferred.
Furthermore, the second pla~tic layer may contain colour pigments, light-refracting pigments, calcined chalk or glass beads.
The rigidity properties of the container~ according to the invention which are produced from the composite material can be controlled by me~ns of the thickness of the second plastic layer, which may expediently be 0.1 to O.6 mm, and the proportion of fillers.
The second plastic layer preferably ha~ a thickness from 0.2 to 0.5 mm. A proportion of fillers from 20 to 50~ by volume, referred to the second plastic layer is prefer-red.
Particularly preferably, the second plastic layer may befilled with chopped strand~ of glass. The chopped strands of glass may be, for example, 0.1 to 0.8 mm long and O.005 to 0.02 mm thick. An optimum filler content in the second plastic layer i9 30% by volume. The thickness of the second layer containing chopped strands of glass as filler may, in particular, be 0.2 to 0.5 mm.
` 2~23~07 With a particularly preferred R~cond plastic layer of this kind, the modulus of elasticity can be increased at high degrees of forming.
If, for example, the said filler do not conform to the relevant health regulations (Bundesgesundheitsamt, Food and Drug Admini~tration), at least one further, non-toxic plastic layer, which is expediently sealable, may be applied to the second plastic layer.
The thickness of such a layer may be 0.001 to 0.02 mm, preferred materials are polyester, polypropylene, poly-amide or polyethylene.
The second, inwardly directed layer not only performs the role of corrosion protection of the metal layer and of optimizing the friction conditions during the forming lS process but is also of significance for the rigidity properties of the contaLner.
It goes without saying that the material combination described in detail above may also be reversed regarding inside to outqide. ~he requirements and the individual layers are retained. In addition, it is advantageous to provide the inner extension promoter with a sealable layer by surface treatment or by additional application of a sealing coating or by lamination of a sealing f~lm.
In that case, special requirement~ regarding the preven-tion of absorption of flavourings or other volatilesubstances of the contents are no longer imposed on the inwardly directed layer. It is likewise ~necessary to worry about impairment of mechanical properties of the supporting film or of the plastic/adhesive interface by the absorption of water or alcohol.
Both the first and thc second pla~tic layar, as well as the composite laminate, axe pr~ferably sterilizable. A~
a result, these materials are not thermally Lmpaired ~-Q23~
during forming at elevated temperature.
The processing of the composite material described into the sterilizable packaging container~ according to the invention can take place in various way If containers are to be produced from the compositc materials described with low degrees of forming, the forming can be performed by deep drawing by means of a drawing die and female mould.
Low degrees of forming are understood to mean, for example, a ratio of diameter to depth of the container to be produced of 4 or greater than 4 to 1.
The forming may also take place without the supply of heat, since in the~e cases the residual stre~ses are relatively low. The same process can be ussd for con-lS tainers with a greater degree of forming, for whichabsolute dimensional stability is not required. In that case, the composite material is to be formed beyond the required container depth H, that is to say the final geometry is only achieved after relaxation of the resi-dual stre~ses.
For the purpose of better forming, the inwardly directedplastic layer preferably has a smooth, low-~rict$on ~urface and a high forming limit. Fillers ~uch as those mentioned above reduce the recovery after the forming operation and after any sterilization.
Forming in the ~tate below the usual thermoforming temperatures of plastics such as PP, PE, PET in the thickness range from 0.1 to 0.6 mm, usually results in inhomogeneities in the flow behaviour of the pla~tic. The material constricts locally, which results in rapid cracking in the Al layer.
This is the case in particular in the production of containers having a ratio of diameter to height of less than, for example, 4sl.
The inhomogeneous flowing of the filled plastic can be eliminated to the greatest extent by the admixture according to the invention of fillers in the range from 20 - 70% by volume referred to the second plastic layer, to the said plastics. The forming potential of the composite material can thereby be optimally utilized.
The high filler content in the rang~ from 20 to 70~ by volume can al80 accomplish a reduction in the recovery of the thick inner plastic layer after forming.
If the recovery after forming is excessive, the container may be thermally set at the end of the deformation, while still in the loaded state, by the introduction of heat.
The remaining restoring force~ are reduced by the heat, the container remains dimensionally stable.
The inner layer not only performs the role of corrosion protection of the metal layer and optimization of the friction conditions during the forming process, but also contributes to the rigidity properties of the container.
The greater part of the rigidity of the finished con-tainer is advantageously attained by the thickness and the filler content of the second inner plastic layer.
In the case of containers having a ratio of container diameter to container depth of 3 and greater than 3 to 1, the composite material may be formed in one process step at a temperature of, for example, 80C to 130C, the die (male mould andJor female mould) expediently also being heated.
At a ratio of container diameter to container depth of le~ than 3 ~for example down to 1) to 1, it may b0 advantageous, depending on the degree of forming, to work ..... . . ..
~0235~7 g in a plurality of forming steps with drawing dies and hold-down devices, such as are known for metallLc mater-ial~, for example, in which case in particular the final forming step can be performed under thermal effect. In S the final forming step, in a preferred way no greater forming than the elastic recovery is aimed for and the heat has subatantially only the effect of relaxing the residual stresses.
In practice, the process described often requires a plurality of forming steps and 0xpediently alqo a~ least two dies, such as for example one forming die for the cold deformation and one forming die for the stabiliza-tion in the warm state. Another method can first of all use a warm die and subsequently a cold die.
An apparatu~ for carrying out the proces~ is described, for example, in German Patent Specification 2,539,354.
An example of another ~uitable process for the production of a sterilizable packaging container is characterized in that the container i8 made by a combination of stretch forming and deep drawing at elevated temperature balow the thermoforming temperature~ of the plastics us~d.
In order to maximize the forming limit, ideal stretch forming follows deep drawing. In particular by a combina-tion of the two process step~ it i8 possible to creats a high dimensional ~tability and a homogenous thickness distribution of the material. For the case of a thinner plastic layer as inner side of the container - with the consequence of a lesser insenqitivity to denting or reduced "spring-back character" - the process combination of stretch ~orming and deep drawing provides the possibi-lity of shaping the compo~ite material free from fold~.
With an inner plastic layer, for example having a thick-ness less than 0.1 mm, it is advantageously even pO88-lble, depending on fillers, additives and ~dded pigment~, to dispense with the elevated temperature.
A particularly advantageous process for the production of containers of any ratio between container diameter and container depth and expediently for the production of containers having a ratio between container diameter and container depth of 3 or les~ than 3 to 1 and preferably of 2 or less than 2 to 1 is the sub~ect of the present invention. The limits of applicability of thi~ process are generally only reached at a ratio of container diameter to container depth of 1:1.
The process for the production of the sterilizable packaging container described is characterized by a combination of deep drawing, subsequent stretch forming if appropriate, and thermal stabilization of the con-tainer below the thermoforming temperature of the second plastic layer used.
The process i8 based on process step~ which aro known par se, namely deep drawing and, if appropriate, stretch forming, the latter using a female mould, a male mould and a hold-down device. The hold-down device serves the purpose of holding the composite material firmly on the edge of the female mould while the male mould shapes the compo~ite material into the female mould, at the same time stretching it.
The process can be described in more detail by saying that the dsformation of the compo~ite material i~ carried out in an apparatus suitable for deep drawing, the deep drawing step being performed with a hold-down force of the hold-down device such that the material required for the deep drawing step i8 drawn from the re~ion of the female mould and the hold-down device. When the composite material has been formed to the final depth, the com-posite material i8 heated. The heating may be performed both by heating from outside (temperature-controlled dies) or, for example, by heat Lnduced in the aluminium (high-frequency induction heating).
` 2023~Q7 The latter Btep i8 decisive for the ~tabilization of the container geometry by the reduction of residual stresses.
In practice, the process is carried out, for example, in such a way that the deep drawing step i~ carried out at a hold-down force of the hold-down device of 0.8 to 2 kN, which commences at 0% of the container depth (H) and ends at 100% of the container depth (H), which also corres-ponds to the displacement of the male mould. The hold-down force of the hold-down device is to be chosen such that the material can always flow on into the die with increasing H. Depending on the ratio of container dia-meter to container depth, in particular at ratio~ less than 3 ~o 1, a graduation of the hold-down force of the hold-down device is advantageous. With a container depth ~H) of 0% to 60%, the hold-down force may be chosen between 0.6 kN and 1.2 kN and with a container depth of 60% to 100% the hold-down force may be increased to 2.0 kN, in which case the drawing down may also be taken over by a stretching.
In practice, on reaching 100% of the container depth (H), the hold-down force of the hold-down device can b~
increased to 30kN to 60kN, in order that the container rim is smoothed. During or after this last-mentioned operation, a high-frequency heating is performed, for example during 0.3 to l second, at a power of 5 to 18 kW
in a frequency range of 20 to 150 kHZ, the power and frequency of the induction heating having to be adapted to the size and geometry of the container. These optimum data can be determined, for example, by a few specific trials.
For carrying out the processe~ described, the male mould and the female mould are, for example, produced from plastics such as for example polytetrafluoroethylene or polymethylpentene or the surface~ effecti~e in deforma-tion are coated with thess material~. An inductor loop, for example, is placed into the male mould and/or the 21~3~
_ 12 -female mould. A current in then induced through this inductor when the composite material ha~ been formed to the final depth H. The aluminium i8 heated by the induced energy, which reqults in a heat transfer into the plas-tic. As a result, the heat can be supplied in order toreduce the residual stresses remaining in the plastic.
This process is expediently carried out with a high-frequency generator which operates in a power range of 5 - 8 kW and has a high frequency range of 30 - 150 kHz.
The time during which the induced energy acts is expedi-ently between 0.3 and l.0 sec.
The small thickness of the metal layer is not in itself capable of providing adequate rigidity. It serves es~en-tially as a barrier layer.
For inexpensive production of the container, it is advantageous if the second, inwardly directed plastic layer is high-frequency sealable thermally or indirectly via the metal layer with respect to a plastic cover or with respect to a metal layer covered by coating or lamination.
In the choice of a composite laminate having relatively thinner plastic layers which itself still does not have adequate rigidity properties for the intended purpo8e, the container shape produced after the forming process can receive an adequate rigidity in a further process step by in~ection-moulding around it a thermoplastic such as polyethylene, polypropylene, polyester etc. A layer thickness of 0.3 to 0.6 mm is particularly advantageous.
The choice of appropriate mala mould materials or male mould coatings also plays an important role, for example in the case of the fold-free forming of the composite laminates described. Male mould materials such as, inter alia, ~eflon or ~ilicone rubber~ may cause locally different friction and radial compres~ion conditions. The ~3~a7 inwardly directed plastic layer preferably has a low surface friction. A container shape which is free from folds to the greatest extent can be attained by suitable radial compression. Deep drawing at room temperature, with conventional dies, permits a fold-free forming if the container walls are provided with rib~, a~ a result of which the wall surfaces are increased, in order that the folds can be eliminated.
For making smooth-walled container shapes, telescopic male mould~ are preferably used, which have a positive effect on the one hand on the maximum attainable exten-sion forming limit and on the other hand on the fold-free appearance.
For inexpensive production of the container, it i8 advantageous if the inner pla~tic layer i3 high-frequency sealable, for example thermally or indirectly via the metal layer, with respect to a plastic cover or with respect to a metal layer covered by coating or lamina-tion.
On account of their barrier properties, containers according to the present invention find use, for example, as containers for food or for feed stock. The containers are sterilizable in empty and in filled condition.
Claims (14)
1. Sterilizable packaging container of plastic/metal/plastic composite material having a proportional thick-ness of metal of less than 20% of the total thickness of the composite material, produced by forming, charac-terized in that the composite material is composed of a first plastic layer having high extension and at the same time high internal stress as well as increasing strength-ening during deforming and of a second plastic layer of from 0.1 to 0.8 mm in thickness having high extension and high load-bearing capacity during forming, between which there is a metal layer having a thickness from 0.006 to 0.01 mm of aluminium with an aluminium content of 98% or more or of an aluminium alloy, the first plastic layer serving as extension promoter for the metal layer and being quasi-isotropic, and the second plastic layer being stiffened during forming due to increasing extension.
2. Sterilizable packaging container according to Claim 1, characterized in that the composite material contains a first plastic layer of from 0.008 to 0.05 mm in thickness having high extensibility and at the same time high strength, as well as increasing strengthening during de-forming and a second plastic layer of from 0.1 to 0.8 mm in thickness with high extension and high load-bearing capacity during forming, and there is between the plastic layers a metal layer of a thickness from 0.006 to 0.1 mm of aluminium with an aluminium content of 98% or more or of an aluminium alloy, the first plastic layer serving as extension promoter for the metal layer and being quasi-isotropic, and the second plastic layer containing 10 to 70% by volume, referred to the second plastic layer, of fillers.
3. Sterilizable packaging container according to Claim 1 or 2, characterized in that the thickness of the metal layer is less than 10% of the thickness of the composite material.
4. Sterilizable packaging container according to Claim 1 or 2, characterized in that the second plastic layer is on the container inner side.
5. Sterilizable packaging container according to Claim 1 or 2, characterized in that the first plastic layer has a thickness from 0.01 to 0.04 mm.
6. Sterilizable packaging container according to Claim 1 or 2, characterized in that the second plastic layer has a thickness from 0.1 to 0.6 mm.
7. Sterilizable packaging container according to Claim 2, characterized in that the second plastic layer contains 20 to 50% by volume, referred to the second plastic layer, of fillers.
8. Sterilizable packaging container according to Claim l, characterized in that the metal layer has a thickness from 0.006 to 0.04 mm.
9. Sterilizable packaging container according to Claim 2, characterized in that the metal layer has a thickness from 0.02 to 0.1 mm.
10. Sterilizable packaging container according to Claim 1 or 2, characterized in that a non-toxic third plastic layer, which is sealable, is applied over the second plastic layer.
11. Process for the production of a sterilizable packag-ing container according to Claim 1 or 2, characterized in that the container is made by a combination of stretch forming and deep drawing at elevated temperature below the thermoforming temperatures of the plastics used.
12. Process for the production of a sterilizable packag-ing container according to Claim 1 or 2, characterized in that the container is made by a combination of deep drawing and thermal stabilization below the thermoforming temperature of the second plastic layer used.
13. Process for the production of a sterilizable packag-ing container according to Claim 1 or 2, characterized in that first of all a container is made which has on the outside a plastic layer which does not have adequate rigidity properties and this container is provided with a thermoplastic layer by injection moulding around it.
14. Process for the production of a sterilizable packag-ing container according to Claim 13, characterized in that the thermoplastic layer has a thickness from 0.3 to 0.6 mm.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CH305789A CH678931A5 (en) | 1989-08-23 | 1989-08-23 | Rigid laminated sterilisable container with spring-back properties |
| CH3057/89 | 1989-08-23 | ||
| CH2077/90 | 1990-06-21 | ||
| CH207790A CH681528A5 (en) | 1990-06-21 | 1990-06-21 | Rigid laminated sterilisable container with spring-back properties |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2023507A1 true CA2023507A1 (en) | 1991-02-24 |
Family
ID=25689445
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002023507A Abandoned CA2023507A1 (en) | 1989-08-23 | 1990-08-17 | Sterilizable packaging container of plastic/metal/plastic composite material and process for its production |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0414636B1 (en) |
| CA (1) | CA2023507A1 (en) |
| DE (1) | DE59003859D1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6888009B2 (en) | 1999-11-01 | 2005-05-03 | H. Lundbeck A/S | Method for the preparation of 5-carboxyphthalide |
Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CH684746A5 (en) * | 1993-02-25 | 1994-12-15 | Alusuisse Lonza Services Ag | Laminate. |
| SE504525C2 (en) * | 1995-07-03 | 1997-02-24 | Tetra Laval Holdings & Finance | Ways to produce from a laminate a packaging container which can be autoclaved or hot-filled |
| CH689799A5 (en) | 1995-11-28 | 1999-11-30 | Alusuisse Lonza Services Ag | Packaging container made of a multilayer composite |
| EP0845350A1 (en) * | 1996-11-29 | 1998-06-03 | Alusuisse Technology & Management AG | Cold formable laminated film |
| US6270869B1 (en) | 1998-12-02 | 2001-08-07 | Alusuisse Technology & Management Ltd. | Cold formable laminate films |
| EP1010519A1 (en) * | 1998-12-16 | 2000-06-21 | Alusuisse Technology & Management AG | Sterilizable laminated sheet |
| DE60031523T2 (en) * | 1999-09-10 | 2007-06-06 | Ishida Co., Ltd. | BAG FOR FOOD, METHOD FOR PACKAGING AND USING A MULTILAYER FILM FOR BAGS |
| DE102005006840B4 (en) * | 2005-02-14 | 2010-01-07 | Küppers, Udo, Dr.-Ing. | Packaging or composite material |
| AT13631U1 (en) * | 2011-03-16 | 2014-05-15 | Constantia Teich Gmbh | Thermoformable, retractable circuit board |
| JP2017507090A (en) * | 2013-12-23 | 2017-03-16 | ソルベイ スペシャルティ ポリマーズ イタリー エス．ピー．エー． | Blister package |
| CN104029437A (en) * | 2014-06-13 | 2014-09-10 | 苏州汉力新材料有限公司 | Porous low-density composite metal material |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2757370A1 (en) * | 1977-12-22 | 1979-07-05 | Bayer Ag | GAS-TIGHT PLASTIC-ALUMINUM COMPOSITE FILMS |
| US4311742A (en) * | 1979-08-17 | 1982-01-19 | Toyo Seikan Kaisha, Ltd. | Retort-sterilizable laminated pouch comprising a flexible gas-barrier substrate and blended crystalline olefin layer |
-
1990
- 1990-08-13 DE DE90810605T patent/DE59003859D1/en not_active Expired - Fee Related
- 1990-08-13 EP EP90810605A patent/EP0414636B1/en not_active Expired - Lifetime
- 1990-08-17 CA CA002023507A patent/CA2023507A1/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6888009B2 (en) | 1999-11-01 | 2005-05-03 | H. Lundbeck A/S | Method for the preparation of 5-carboxyphthalide |
Also Published As
| Publication number | Publication date |
|---|---|
| EP0414636B1 (en) | 1993-12-15 |
| DE59003859D1 (en) | 1994-01-27 |
| EP0414636A1 (en) | 1991-02-27 |
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