CA2289722A1 - Multi-layer, drawn, heat-sealable, vacuum-plated polypropylene film - Google Patents
Multi-layer, drawn, heat-sealable, vacuum-plated polypropylene film Download PDFInfo
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- CA2289722A1 CA2289722A1 CA002289722A CA2289722A CA2289722A1 CA 2289722 A1 CA2289722 A1 CA 2289722A1 CA 002289722 A CA002289722 A CA 002289722A CA 2289722 A CA2289722 A CA 2289722A CA 2289722 A1 CA2289722 A1 CA 2289722A1
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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
- 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
- B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
-
- 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
- B32B38/00—Ancillary operations in connection with laminating processes
- B32B38/0008—Electrical discharge treatment, e.g. corona, plasma treatment; wave energy or particle radiation
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
- C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
- C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
- C23C14/14—Metallic material, boron or silicon
- C23C14/20—Metallic material, boron or silicon on organic substrates
-
- 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
- B32B2255/00—Coating on the layer surface
- B32B2255/20—Inorganic coating
- B32B2255/205—Metallic coating
-
- 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
- B32B2307/00—Properties of the layers or laminate
- B32B2307/70—Other properties
- B32B2307/746—Slipping, anti-blocking, low friction
-
- 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
- B32B2323/00—Polyalkenes
- B32B2323/10—Polypropylene
-
- 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
- B32B2553/00—Packaging equipment or accessories not otherwise provided for
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L2205/00—Polymer mixtures characterised by other features
- C08L2205/14—Polymer mixtures characterised by other features containing polymeric additives characterised by shape
- C08L2205/18—Spheres
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L2205/00—Polymer mixtures characterised by other features
- C08L2205/22—Mixtures comprising a continuous polymer matrix in which are dispersed crosslinked particles of another polymer
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L31/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an acyloxy radical of a saturated carboxylic acid, of carbonic acid or of a haloformic acid; Compositions of derivatives of such polymers
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- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Health & Medical Sciences (AREA)
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- Mechanical Engineering (AREA)
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Abstract
The invention relates to an orientated, especially biaxially orientated, sealable multilayer film vacuum-plated with aluminium, which is largely free of migrating additives and has the structure ABCD, in which a) C is the core layer, consisting of isotactic polypropylene with an MFI of between 0.5 and 4.5 g/10 minutes; b) is the base layer for vacuum-plating, consists of between 0.1 and 0.5 % of an organic or inorganic antisticking particle with good adhesion to aluminium and between 99.5 and 99.9 % of an olefinic homo-, co-, or terpolymer or a mixture of said olefinic polymers, and is subjected to corona discharge, plasma, flame or fluorine treatment prior to vacuum-plating; c) A is the vacuum-plated aluminium layer, which reduces light transmission by a factor of 1/50 to 1/500; and d) D is the sealable layer consisting of an olefinic homo-, co- or terpolymer and between 0.1 and 0.5 % of an inorganic or organic antisticking particle which is not as adherent to aluminium as the antisticking particle contained in layer B.
Description
WW 5487-foreign ~~~E~ THIS Ate"-1~-TF~-TRANSI~ATI~~ HI/vos/W6/V08.04.1998 A mufti-layer, oriented, thermally sealable. vacuum-metallised ,~olpprop~rlene film This invention relates to a mufti-layer, biaxially oriented, thermally sealable ~ polypropylene film which is vacuum-metallised with aluminium, wherein the aluminium layer exhibits a good adhesive bonding capacity and a reduced number of pinholes and consequently exhibits a good barrier effect in relation to water vapour, oxygen and aromas. The invention also relates to a process for producing said film.
The film to which the present invention relates has, as its characterising features, a core layer of isotactic polypropylene, an outer layer which is subjected to corona discharge, flame or plasma pretreatment or pretreatment with fluorine and which - comprises an olefinic homo-, co- or terpolymer, or a mixture of said polymers, and 0.01 to 0.5 % by weight of anti-seizing particles which exhibit good, strong bonding to aluminium, a second outer layer comprising an olefinic homo-, co- or terpolymer, or a mixture of said polym~°rs, and 0.01 to 0.5 % by weight of anti-seizing particles which exhibit poor bonding; to aluminium, and an aluminium layer which is vapour-deposited under vacuum on the pretreated side.
On account of thein~ good b;~rrier properties in relation to water vapour, oxygen, light ?0 and aromas, polypropylene; films which are vacuum-coated with metals or metal oxides are mostly used for tlhe packaging of sensitive foodstuffs.
The use of biaxially oriented polypropylene films which are vacuum-metallised with aluminium is widely knowm. Metallising improves the barrier effect in relation to ?5 water vapour by a factor of 10 and improves the barrier effect of the film in relation to oxygen by a factor of 100. Further improvements are currently difficult, since the vacuum-deposited metal layer comprises pinholes. These pinholes constitute a large number of very small holes (of diameter about 1 pm) which are distributed on the metal layer in the form of clusters. Considerable amounts of oxygen can diffuse 30 through the pinholes, which has a negative effect on the barrier properties in relation to oxygen.
WW 5487-foreign Thus EP-A 329336 describes a metallisable film which exhibits good barrier properties. However, due to the high content of homopolymer in the layer to be metallised, the bonding of the vapour-deposited layer to the substrate is not ~ satisfactory for current requirements. Moreover, in this vacuum-metallised film there is a large number of pinholes in the vapour-deposited metal layer.
EP-A 395204 describes a rr~etallisable film which exhibits improved adhesion of the metal. No success was achieved in solving the pinhole problem, however. This film therefore has disadvantages with regard to its properties as a barrier layer.
- EP-A 481266 describes a multi-layer, vacuum-metallised film in which, after vacuum-metallising, a protective layer of wax is vapour-deposited on the metal under vacuum.
This film exhibits a. considerably reduced number of pinholes and its barrier properties 1 ~ are improved. However, the; waxes described there result in wetting problems during - the processing step (covering/laminating) which follows vacuum coating, particularly when aqueous adhesive systems are used. Moreover, when composites are produced there is no improvement in barrier properties which corresponds to that achieved in the prior art (see comparative example 3).
It has therefore proved to be; necessary to produce a metallised BOPP film which has a reduced number of pinholes and which thus exhibits improved barrier properties in relation to water vapour ;and oxygen, and which also exhibits good processing properties (bondin~; to water-based adhesives).
This object is achieved by a film according to claim 1. The preferred feature thereof is that the film, which ~is prod.uced by means of a biaxial stretching process, contains a vacuum-metallisable outer layer which is subjected to corona discharge, flame or plasma pretreatment or which is pretreated with fluorine and which comprises an olefinic co- or terpolymer, or a blend of one or more olefinic co- or terpolymers, and anti-seizing particles which exhibit good bonding to vapour-deposited aluminium, a WW 5487-foreign core layer comprising an isotactic polypropylene having an MFI between 0.5 and 4.~
g/10 min, and a sealable oui:er layer, which is situated on the non-metallised side and which comprises an olefinic; co- or terpolymer, or a mixture of one or more olefinic co-or terpolymers, and anti-seizing particles which exhibit poor bonding to alu-~ minium. Surprisingly, the barrier properties, which hitherto could only be definitively influenced by the vacuum-rnetallising step, are considerably improved by the use of anti-seizing particles which exhibit poor bonding to aluminium and which are situated on the opposite side; to that which is metallised.
In order to ensure ;food running properties of biaxially oriented polypropylene films when they are processed on machines, it is necessary to incorporate additives in the - sealing layers or outer layers at least. However, when internal lubricants such as erucic acid amide or polydimethylsiloxane are incorporated in vacuum-metallised films, the latter exhibit poor bonding of the vapour-deposited layer to the base film. In order to impart good machine-running properties to the film despite a lack of internal - lubricants, it is neccasary to incorporate a sufficient amount of anti-seizing particles in the outer layers. Customary anti-seizing particles (average particle diameter:
1 to ~
pm, most preferably: 2 to 4 Vim) which exhibit good bonding to aluminium consist of silica, or of alkali alumin.osilicates, or of alkaline earth aluminosilicates, or of crosslinked polymethyl methacrylates, or of polyamide. Alkaline earth aluminosilicates with an average particle diameter of 2 to 4 pm are particularly preferred. Anti-seizing particles (average particle diameter 1 to 5 pm) which naturally exhibit poor bonding properties comprise crosslinked olefines or crosslinked silicones; particles with an amerage diameter of 2 to 4 pm are particularly preferred.
Of the numerous materials which are used for sealable layers which can be vacuum-metallised, the following arc: preferably used:
- random propylene/ethylene copolymers ;0 - random propylene/olefine (1) copolymers - random propylene/ethylene/olefine terpolymers WW 5487-foreien - random propylene/olefine/ethylene terpolymers - mixtures of two or three of the above polymers.
A material which is particularly preferred is a blend comprising a propylene/ethylene copolymer (90 to 9'9 % by weight) which is characterised in that it contains 1.0, to 10 by weight ethylene (preferably 2 to 6 % by weight) and melts between 110°C and 150°C, preferably ~~etween 120°C and 140°C, and an ethylene/octene copolymer ( 1 to % by weight) wlhich is characterised in that it has a density <0.915 g/cm3, and 0.05 to 0.35 % by weight of a calcium aluminosilicate which is characterised in that its 10 average particle diameter is between 1 and 3 pm.
A mixture which is particularly preferred contains 99.95 to 99.65 % by weight of a random propylene/butene/et:hylene polymer which is characterised in that it has an MFI of 5 to 10 g/10 min and a melting point of 134°C, and contains 0.05 to 0.35 % by I S weight of crosslinked p~olydimethylsiloxane anti-seizing particles which are characterised in th;~t their average particle diameter is between 1 and 5 pm, most preferably 2 to 4 urn.
The films according to th<: invention are most preferably produced by customary processes, such as laminating, coating or melt coextrusion. Extrusion and solidification of the; thick film is followed by biaxial orientation below the crystallite melting point of thf; PP layer. Biaxial orientation can be effected either simultaneously or sequentially. Thc: following process is particularly preferred:
After solidification. of the thick film on the casting roll, the film is stretched in its direction of travel. (longitildinally) at a stretching ratio of 4/1 to 7/1 and at a temperature of 90°C~to 150"C (preferably 110°C to 140°C).
The stretching ratio in the transverse direction is preferably between 8/1 and 12/1 and transverse stretching of the film is effected at a temperature between 130°C and 170°C.
The subsequent thermofixing step is preferably carried out at 100°C to 180°C
(preferably between 150°C and 170°C).. In order to ensure that the substantially nonpolar film surface has WW 5487-foreign an affinity for aluminium, it: is necessary to subject the film to corona discharge (spray discharge) pretreatment. In the course of this procedure, atmospheric oxygen is incorporated in thc: film surface in the form of carbonyl, epoxide, ether or alcohol groups. Other methods of pretreating polypropylene films include flame or plasma treatment and treatment with fluorine.
WW 5487-foreign Example 1 A biaxially oriented film was produced by means of the production process described above (area stretching ratio: 4~/1; longitudinal stretching temperature:
142°C;
transverse stretching temperature: 160°C), and had the following structure:
Total thickness: 20 Vim; layer sequence: ABCD
See above for the definition of layer A.
Outer layer for vacuum-met<illisingJBl:
Thickness: 1 gm Material:
99.75 % by weight propylene/ethylene copolymer 3.5 % by weight ethylene MFI: 5.0 g/10 min density: 0.912 g/cm3 0.25 % by weight calcium aluminosilicate average particle size:
2.5 p m Core la e'~r (Cl:
Thickness: 17 pm Material:
100 % by weight isotactic polypropylene MFI: 3.0 g/10 min Sealing lair (D):
Thickness: 2 pm Material:
99.75 % by weight , propylene/butene/ MFI: 7.0 g/l0 min ethylc°ne copolymer 0.25 % by weight cross Linked polydimethyl-siloxane average particle size:
;0 particles 2.0 ~m WW 5487-foreign _7_ Comparative example 1 A biaxially oriented film w:as produced by means of the production process described above (area stretching ratio: 45/1; longitudinal stretching temperature:
142°C;
~ transverse stretching temperature: 160°C), and had the following structure:
Total thickness: 20 pm; layer sequence: ABCD
See above for the definition of layer A..
Outer layer for vacuum-metallising.jB):
Thickness: 1 pm Material:
- 99.75 % by weight propylene/ethylene copolymer 3.~ % by weight ethylene MFI: 5.0 g/10 min 0.25 % by weight calcium aluminosilicate average particle size:
2.5 p m Core layer lCl:
Thickness: 17 pm Material:
100 % by weight isotac;tic polypropylene MFI: 3.0 g/10 min Sealing layer (D~, Thickness: 2 ~m Material:
99.75 % by weight propylene/ethylene copolymer ethylene content:
3.5 % by weight MFI: 7.0 g/10 min 0.25 % by weight calcium aluminosilicate average particle size:
2.5 pm WW 5487-foreign _g_ Comparative exannple 2 A biaxially oriented film w;~s produced by means of the production process described above (area stretching ratio: 45/1; longitudinal stretching temperature:
I42°C;
transverse stretching temperature: 160°C), and had the following structure:
Total thickness: 20 pm; layer sequence: ABCD
Outer layer for vacuum-metallising (BL
Thickness: 1 pm Material:
99.75 % by weight propylene/ethylene copolymer 3.5 % by weight ethylene MFI: 5.0 g/10 min 0.25 % by weight crosslinked polydimethylsiloxane average particle size:
particles 2.0 ~ m Core la, ey r (Cl-Thickness: 17 ~m Material:
100 % by weight isotactic polypropylene MFI: 3.0 g/10 min Sealing layer (Dl:
Thickness: 2 ~m Material:
99.75 % by weight: prop;ylene/ethylene copolymer ethylene content:
3.5 % by weight MFI: 5.0 g/10 min 0.25 % by weight crosslinked polydimethylsiloxane average particle size:
particles 2.0 p m WW 5487-foreign Comparative example 3 A biaxially oriented film was produced by means of the production process described above (area stretching ratio: 45/1; longitudinal stretching temperature:
142°C;
transverse stretching; temperature: 160°C). During the in-line vacuum-metallising step, this sample was vacuum-coated with a wax layer W (see EP-A 481 266) to protect the aluminium layer (layer A).
Structure:
Total thickness: 20 p.m; layer sequence: WABCD
- Outer lair for vacuum-metallisin~ (Bl:
Thickness: 1 pm Material:
99.75 % by weight propylene/ethylene copolymer 3.5 % by weight ethylene - MFI: 5.0 g/10 min 0.25 % by weight calcium aluminosilicate average particle size:
2.5 p m Core lager (Cl:
Thickness: 17 pm Material:
100 % by weight isota<;tic polypropylene MFI: 3.0 g/10 min ?5 Sealing la er D):
Thickness: 1 pm Material:
99.75 % by weight propylene/ethylene copolymer 3.5 % by weight ethylene MFI: 7.0 g/10 min 0.25 % by weight calcium aluminosilicate average particle size:
2.5 pm WW 5487-foreign The films described in the examples and comparative examples were vacuum-metallised with aluminium to an optical density (OD) of 2.0 (layer A) and were subsequently adhesiuely bonded to a transparent BOPP film by means of an aqueous, polyurethane-based dispersion adhesive.
The OD is understood to be defined by OD = log (Ia/I) where Io is the intensity of the irradiated light is and I is the intensity of the light which is reduced b5~ the film..
The following Table shows that the film according to the invention is considerably superior to films comprising; symmetrical anti-seizing additives and films comprising a protective wax layer.
Nunnber O, perm. O, perm. of compositeAdhesive o (cm3/m'-d (sample/adhesive/20~mbonding pinholesbar) BOPP) capacity xample ew 2 8 ood omparison any 102 6 ood omparison ediuun 83 32 ood 2 mount Comparisonew 0 88 oor Methods of measurement ?0 Determination of th erm abilitX to oxygen (Oz erm.
The permeability to oxygen was determined according to DIN 53380, Part 3, at 23°C
and 0 % relative atmospheric humidity.
WW 5487-foreign Number of pinholes The light from a torch was shone through the film and the number of pinholes was assessed corresponding to the following classification:
none, few, medium amount, many Determination of the bonding of anti-seizing particles to aluminium Films were produced which contained anti-seizing particles in a concentration of 2000 ppm/sealing layer. These films were placed on a BOPP film without anti-seizing - particles, which ha<i been vacuum-metallised with aluminium but which had not been subjected to corona discharge pretreatment, and were loaded at 23°C for a period of 90 minutes with a metal plate and weight such that the total mass of the plate and weight was 1 kg. After removing the metal plate and stripping the film comprising anti-seizing particles from tile BOPP film (which had not been pretreated) which was vacuum-metallised with aluminium, the number of pinholes in the aluminium layer was assessed by means of a torch. The number of pinholes could thus be directly correlated with the bonding of the anti-seizing particles to aluminium. The following ?0 bonding properties were obtained:
ype of anti-seizin;~ umber of pinholesBonding to Al particles alcium aluminosilicate any ood SiO, any ~ood rosslinked polyethylenefew oor rosslinked polydimethylsiloxaneew oor rosslinked PIMA ~ any good WW 5487-foreien Determination of the mel flow index IMFI) The melt flow indea (abbreviated to MFI in the text) was measured according to DIN
53 735 using a loading force of 21.6 N at a temperature of 23°C.
J
Adhesive bonding c:a aci The laminated composite eras held for at least 3 days in a climate of 23°C and a relative humidity of 50 %. Thereafter, the composite was separated by hand.
The composite was classified as follows, based on the area of the aluminium layer which remained on the original side of the film or on the film which was laminated by means - of an adhesive.
Less than 50 % of the aluminium surface bonded to the film surface which was l 5 laminated by mean, of an adhesive: poor.
More than 50 % of the aluminium surface bonded to the film surface which was laminated by means of an adhesive: good.
The film to which the present invention relates has, as its characterising features, a core layer of isotactic polypropylene, an outer layer which is subjected to corona discharge, flame or plasma pretreatment or pretreatment with fluorine and which - comprises an olefinic homo-, co- or terpolymer, or a mixture of said polymers, and 0.01 to 0.5 % by weight of anti-seizing particles which exhibit good, strong bonding to aluminium, a second outer layer comprising an olefinic homo-, co- or terpolymer, or a mixture of said polym~°rs, and 0.01 to 0.5 % by weight of anti-seizing particles which exhibit poor bonding; to aluminium, and an aluminium layer which is vapour-deposited under vacuum on the pretreated side.
On account of thein~ good b;~rrier properties in relation to water vapour, oxygen, light ?0 and aromas, polypropylene; films which are vacuum-coated with metals or metal oxides are mostly used for tlhe packaging of sensitive foodstuffs.
The use of biaxially oriented polypropylene films which are vacuum-metallised with aluminium is widely knowm. Metallising improves the barrier effect in relation to ?5 water vapour by a factor of 10 and improves the barrier effect of the film in relation to oxygen by a factor of 100. Further improvements are currently difficult, since the vacuum-deposited metal layer comprises pinholes. These pinholes constitute a large number of very small holes (of diameter about 1 pm) which are distributed on the metal layer in the form of clusters. Considerable amounts of oxygen can diffuse 30 through the pinholes, which has a negative effect on the barrier properties in relation to oxygen.
WW 5487-foreign Thus EP-A 329336 describes a metallisable film which exhibits good barrier properties. However, due to the high content of homopolymer in the layer to be metallised, the bonding of the vapour-deposited layer to the substrate is not ~ satisfactory for current requirements. Moreover, in this vacuum-metallised film there is a large number of pinholes in the vapour-deposited metal layer.
EP-A 395204 describes a rr~etallisable film which exhibits improved adhesion of the metal. No success was achieved in solving the pinhole problem, however. This film therefore has disadvantages with regard to its properties as a barrier layer.
- EP-A 481266 describes a multi-layer, vacuum-metallised film in which, after vacuum-metallising, a protective layer of wax is vapour-deposited on the metal under vacuum.
This film exhibits a. considerably reduced number of pinholes and its barrier properties 1 ~ are improved. However, the; waxes described there result in wetting problems during - the processing step (covering/laminating) which follows vacuum coating, particularly when aqueous adhesive systems are used. Moreover, when composites are produced there is no improvement in barrier properties which corresponds to that achieved in the prior art (see comparative example 3).
It has therefore proved to be; necessary to produce a metallised BOPP film which has a reduced number of pinholes and which thus exhibits improved barrier properties in relation to water vapour ;and oxygen, and which also exhibits good processing properties (bondin~; to water-based adhesives).
This object is achieved by a film according to claim 1. The preferred feature thereof is that the film, which ~is prod.uced by means of a biaxial stretching process, contains a vacuum-metallisable outer layer which is subjected to corona discharge, flame or plasma pretreatment or which is pretreated with fluorine and which comprises an olefinic co- or terpolymer, or a blend of one or more olefinic co- or terpolymers, and anti-seizing particles which exhibit good bonding to vapour-deposited aluminium, a WW 5487-foreign core layer comprising an isotactic polypropylene having an MFI between 0.5 and 4.~
g/10 min, and a sealable oui:er layer, which is situated on the non-metallised side and which comprises an olefinic; co- or terpolymer, or a mixture of one or more olefinic co-or terpolymers, and anti-seizing particles which exhibit poor bonding to alu-~ minium. Surprisingly, the barrier properties, which hitherto could only be definitively influenced by the vacuum-rnetallising step, are considerably improved by the use of anti-seizing particles which exhibit poor bonding to aluminium and which are situated on the opposite side; to that which is metallised.
In order to ensure ;food running properties of biaxially oriented polypropylene films when they are processed on machines, it is necessary to incorporate additives in the - sealing layers or outer layers at least. However, when internal lubricants such as erucic acid amide or polydimethylsiloxane are incorporated in vacuum-metallised films, the latter exhibit poor bonding of the vapour-deposited layer to the base film. In order to impart good machine-running properties to the film despite a lack of internal - lubricants, it is neccasary to incorporate a sufficient amount of anti-seizing particles in the outer layers. Customary anti-seizing particles (average particle diameter:
1 to ~
pm, most preferably: 2 to 4 Vim) which exhibit good bonding to aluminium consist of silica, or of alkali alumin.osilicates, or of alkaline earth aluminosilicates, or of crosslinked polymethyl methacrylates, or of polyamide. Alkaline earth aluminosilicates with an average particle diameter of 2 to 4 pm are particularly preferred. Anti-seizing particles (average particle diameter 1 to 5 pm) which naturally exhibit poor bonding properties comprise crosslinked olefines or crosslinked silicones; particles with an amerage diameter of 2 to 4 pm are particularly preferred.
Of the numerous materials which are used for sealable layers which can be vacuum-metallised, the following arc: preferably used:
- random propylene/ethylene copolymers ;0 - random propylene/olefine (1) copolymers - random propylene/ethylene/olefine terpolymers WW 5487-foreien - random propylene/olefine/ethylene terpolymers - mixtures of two or three of the above polymers.
A material which is particularly preferred is a blend comprising a propylene/ethylene copolymer (90 to 9'9 % by weight) which is characterised in that it contains 1.0, to 10 by weight ethylene (preferably 2 to 6 % by weight) and melts between 110°C and 150°C, preferably ~~etween 120°C and 140°C, and an ethylene/octene copolymer ( 1 to % by weight) wlhich is characterised in that it has a density <0.915 g/cm3, and 0.05 to 0.35 % by weight of a calcium aluminosilicate which is characterised in that its 10 average particle diameter is between 1 and 3 pm.
A mixture which is particularly preferred contains 99.95 to 99.65 % by weight of a random propylene/butene/et:hylene polymer which is characterised in that it has an MFI of 5 to 10 g/10 min and a melting point of 134°C, and contains 0.05 to 0.35 % by I S weight of crosslinked p~olydimethylsiloxane anti-seizing particles which are characterised in th;~t their average particle diameter is between 1 and 5 pm, most preferably 2 to 4 urn.
The films according to th<: invention are most preferably produced by customary processes, such as laminating, coating or melt coextrusion. Extrusion and solidification of the; thick film is followed by biaxial orientation below the crystallite melting point of thf; PP layer. Biaxial orientation can be effected either simultaneously or sequentially. Thc: following process is particularly preferred:
After solidification. of the thick film on the casting roll, the film is stretched in its direction of travel. (longitildinally) at a stretching ratio of 4/1 to 7/1 and at a temperature of 90°C~to 150"C (preferably 110°C to 140°C).
The stretching ratio in the transverse direction is preferably between 8/1 and 12/1 and transverse stretching of the film is effected at a temperature between 130°C and 170°C.
The subsequent thermofixing step is preferably carried out at 100°C to 180°C
(preferably between 150°C and 170°C).. In order to ensure that the substantially nonpolar film surface has WW 5487-foreign an affinity for aluminium, it: is necessary to subject the film to corona discharge (spray discharge) pretreatment. In the course of this procedure, atmospheric oxygen is incorporated in thc: film surface in the form of carbonyl, epoxide, ether or alcohol groups. Other methods of pretreating polypropylene films include flame or plasma treatment and treatment with fluorine.
WW 5487-foreign Example 1 A biaxially oriented film was produced by means of the production process described above (area stretching ratio: 4~/1; longitudinal stretching temperature:
142°C;
transverse stretching temperature: 160°C), and had the following structure:
Total thickness: 20 Vim; layer sequence: ABCD
See above for the definition of layer A.
Outer layer for vacuum-met<illisingJBl:
Thickness: 1 gm Material:
99.75 % by weight propylene/ethylene copolymer 3.5 % by weight ethylene MFI: 5.0 g/10 min density: 0.912 g/cm3 0.25 % by weight calcium aluminosilicate average particle size:
2.5 p m Core la e'~r (Cl:
Thickness: 17 pm Material:
100 % by weight isotactic polypropylene MFI: 3.0 g/10 min Sealing lair (D):
Thickness: 2 pm Material:
99.75 % by weight , propylene/butene/ MFI: 7.0 g/l0 min ethylc°ne copolymer 0.25 % by weight cross Linked polydimethyl-siloxane average particle size:
;0 particles 2.0 ~m WW 5487-foreign _7_ Comparative example 1 A biaxially oriented film w:as produced by means of the production process described above (area stretching ratio: 45/1; longitudinal stretching temperature:
142°C;
~ transverse stretching temperature: 160°C), and had the following structure:
Total thickness: 20 pm; layer sequence: ABCD
See above for the definition of layer A..
Outer layer for vacuum-metallising.jB):
Thickness: 1 pm Material:
- 99.75 % by weight propylene/ethylene copolymer 3.~ % by weight ethylene MFI: 5.0 g/10 min 0.25 % by weight calcium aluminosilicate average particle size:
2.5 p m Core layer lCl:
Thickness: 17 pm Material:
100 % by weight isotac;tic polypropylene MFI: 3.0 g/10 min Sealing layer (D~, Thickness: 2 ~m Material:
99.75 % by weight propylene/ethylene copolymer ethylene content:
3.5 % by weight MFI: 7.0 g/10 min 0.25 % by weight calcium aluminosilicate average particle size:
2.5 pm WW 5487-foreign _g_ Comparative exannple 2 A biaxially oriented film w;~s produced by means of the production process described above (area stretching ratio: 45/1; longitudinal stretching temperature:
I42°C;
transverse stretching temperature: 160°C), and had the following structure:
Total thickness: 20 pm; layer sequence: ABCD
Outer layer for vacuum-metallising (BL
Thickness: 1 pm Material:
99.75 % by weight propylene/ethylene copolymer 3.5 % by weight ethylene MFI: 5.0 g/10 min 0.25 % by weight crosslinked polydimethylsiloxane average particle size:
particles 2.0 ~ m Core la, ey r (Cl-Thickness: 17 ~m Material:
100 % by weight isotactic polypropylene MFI: 3.0 g/10 min Sealing layer (Dl:
Thickness: 2 ~m Material:
99.75 % by weight: prop;ylene/ethylene copolymer ethylene content:
3.5 % by weight MFI: 5.0 g/10 min 0.25 % by weight crosslinked polydimethylsiloxane average particle size:
particles 2.0 p m WW 5487-foreign Comparative example 3 A biaxially oriented film was produced by means of the production process described above (area stretching ratio: 45/1; longitudinal stretching temperature:
142°C;
transverse stretching; temperature: 160°C). During the in-line vacuum-metallising step, this sample was vacuum-coated with a wax layer W (see EP-A 481 266) to protect the aluminium layer (layer A).
Structure:
Total thickness: 20 p.m; layer sequence: WABCD
- Outer lair for vacuum-metallisin~ (Bl:
Thickness: 1 pm Material:
99.75 % by weight propylene/ethylene copolymer 3.5 % by weight ethylene - MFI: 5.0 g/10 min 0.25 % by weight calcium aluminosilicate average particle size:
2.5 p m Core lager (Cl:
Thickness: 17 pm Material:
100 % by weight isota<;tic polypropylene MFI: 3.0 g/10 min ?5 Sealing la er D):
Thickness: 1 pm Material:
99.75 % by weight propylene/ethylene copolymer 3.5 % by weight ethylene MFI: 7.0 g/10 min 0.25 % by weight calcium aluminosilicate average particle size:
2.5 pm WW 5487-foreign The films described in the examples and comparative examples were vacuum-metallised with aluminium to an optical density (OD) of 2.0 (layer A) and were subsequently adhesiuely bonded to a transparent BOPP film by means of an aqueous, polyurethane-based dispersion adhesive.
The OD is understood to be defined by OD = log (Ia/I) where Io is the intensity of the irradiated light is and I is the intensity of the light which is reduced b5~ the film..
The following Table shows that the film according to the invention is considerably superior to films comprising; symmetrical anti-seizing additives and films comprising a protective wax layer.
Nunnber O, perm. O, perm. of compositeAdhesive o (cm3/m'-d (sample/adhesive/20~mbonding pinholesbar) BOPP) capacity xample ew 2 8 ood omparison any 102 6 ood omparison ediuun 83 32 ood 2 mount Comparisonew 0 88 oor Methods of measurement ?0 Determination of th erm abilitX to oxygen (Oz erm.
The permeability to oxygen was determined according to DIN 53380, Part 3, at 23°C
and 0 % relative atmospheric humidity.
WW 5487-foreign Number of pinholes The light from a torch was shone through the film and the number of pinholes was assessed corresponding to the following classification:
none, few, medium amount, many Determination of the bonding of anti-seizing particles to aluminium Films were produced which contained anti-seizing particles in a concentration of 2000 ppm/sealing layer. These films were placed on a BOPP film without anti-seizing - particles, which ha<i been vacuum-metallised with aluminium but which had not been subjected to corona discharge pretreatment, and were loaded at 23°C for a period of 90 minutes with a metal plate and weight such that the total mass of the plate and weight was 1 kg. After removing the metal plate and stripping the film comprising anti-seizing particles from tile BOPP film (which had not been pretreated) which was vacuum-metallised with aluminium, the number of pinholes in the aluminium layer was assessed by means of a torch. The number of pinholes could thus be directly correlated with the bonding of the anti-seizing particles to aluminium. The following ?0 bonding properties were obtained:
ype of anti-seizin;~ umber of pinholesBonding to Al particles alcium aluminosilicate any ood SiO, any ~ood rosslinked polyethylenefew oor rosslinked polydimethylsiloxaneew oor rosslinked PIMA ~ any good WW 5487-foreien Determination of the mel flow index IMFI) The melt flow indea (abbreviated to MFI in the text) was measured according to DIN
53 735 using a loading force of 21.6 N at a temperature of 23°C.
J
Adhesive bonding c:a aci The laminated composite eras held for at least 3 days in a climate of 23°C and a relative humidity of 50 %. Thereafter, the composite was separated by hand.
The composite was classified as follows, based on the area of the aluminium layer which remained on the original side of the film or on the film which was laminated by means - of an adhesive.
Less than 50 % of the aluminium surface bonded to the film surface which was l 5 laminated by mean, of an adhesive: poor.
More than 50 % of the aluminium surface bonded to the film surface which was laminated by means of an adhesive: good.
Claims (3)
1. An oriented, particularly biaxially oriented, sealable multi-layer film, which is vacuum-metallised with aluminium and which is substantially free from migrating additives, characterised in that it is structured as follows:
ABCD
a) wherein C is the core layer, comprising isotactic polypropylene with an MFT between 0.5 and 4.5 g/10 min, b) B is the base: layer for vacuum-metallising, comprising 0.1 to 0.5 % of organic or inorganic anti-seizing particles which exhibit good bonding to aluminium and 99.5 to 99.9 % of an olefinic homo-, co- or terpolymer or a mixture of said olefinic polymers, and before metallising is subjected to corona-discharge, plasma or flame pretreatment or pretreatment with fluorine, c) A is the vapour-deposited aluminium layer, characterised in that said aluminium layer reduces the transmission of light by a factor of 1/50 to 1 /500, d) and D is the sealable layer, comprising an olefinic homo-, co- or terpolymer and 0.1 to 0.5 of inorganic or organic anti-seizing particles, the bonding of which to aluminium is inferior to that of the anti-seizing particles of layer B.
ABCD
a) wherein C is the core layer, comprising isotactic polypropylene with an MFT between 0.5 and 4.5 g/10 min, b) B is the base: layer for vacuum-metallising, comprising 0.1 to 0.5 % of organic or inorganic anti-seizing particles which exhibit good bonding to aluminium and 99.5 to 99.9 % of an olefinic homo-, co- or terpolymer or a mixture of said olefinic polymers, and before metallising is subjected to corona-discharge, plasma or flame pretreatment or pretreatment with fluorine, c) A is the vapour-deposited aluminium layer, characterised in that said aluminium layer reduces the transmission of light by a factor of 1/50 to 1 /500, d) and D is the sealable layer, comprising an olefinic homo-, co- or terpolymer and 0.1 to 0.5 of inorganic or organic anti-seizing particles, the bonding of which to aluminium is inferior to that of the anti-seizing particles of layer B.
2. A film according to claim 1, characterised in that the anti-seizing particles have an average particle size of 1 to 5 µm.
3. A film according to claims 1 or 2, characterised in that the film is used as a single-component film or as a component of a composite film for packaging purposes.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19720313A DE19720313A1 (en) | 1997-05-15 | 1997-05-15 | Multi-layer, stretched, heat-sealable polypropylene film vacuum-coated |
| DE19720313.2 | 1997-05-15 | ||
| PCT/EP1998/002619 WO1998051494A1 (en) | 1997-05-15 | 1998-05-04 | Multi-layer, drawn, heat-sealable, vacuum-plated polypropylene film |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2289722A1 true CA2289722A1 (en) | 1998-11-19 |
Family
ID=7829496
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002289722A Abandoned CA2289722A1 (en) | 1997-05-15 | 1998-05-04 | Multi-layer, drawn, heat-sealable, vacuum-plated polypropylene film |
Country Status (8)
| Country | Link |
|---|---|
| EP (1) | EP0981440B1 (en) |
| AT (1) | ATE211968T1 (en) |
| AU (1) | AU8015498A (en) |
| BR (1) | BR9808790A (en) |
| CA (1) | CA2289722A1 (en) |
| DE (2) | DE19720313A1 (en) |
| ES (1) | ES2172151T3 (en) |
| WO (1) | WO1998051494A1 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE10025305A1 (en) * | 2000-05-22 | 2001-12-06 | Wolff Walsrode Ag | Foil laminates made from polymer films metallized on both sides and their use as high barrier foils in vacuum insulation panels |
| US20060068183A1 (en) * | 2004-09-29 | 2006-03-30 | Curwood, Inc. | Packaging laminates containing anti-block particles |
| US8048532B2 (en) | 2006-09-15 | 2011-11-01 | Exxonmobil Oil Corporation | Metallized polymeric films |
| EP3656808A1 (en) | 2018-11-23 | 2020-05-27 | Eurocast Sp. z o.o. | The method of coating aluminium oxide sputtered plastic film |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3709252A1 (en) * | 1987-03-20 | 1988-09-29 | Hoechst Ag | METALLIZABLE MULTILAYER FILM, THEIR PRODUCTION AND THEIR USE |
| US4888237A (en) * | 1988-02-16 | 1989-12-19 | Mobil Oil Corporation | Process for manufacturing a metallized polyolefin film and resulting film |
| US5049436A (en) * | 1990-06-11 | 1991-09-17 | Mobil Oil Corporation | Broad sealing multi-layered opp films which yield hermetic seals |
| DE4030669A1 (en) * | 1990-09-28 | 1992-04-02 | Hoechst Ag | BIDDEN SEALABLE, BIAXIALLY ORIENTED POLYOLEFINE MULTILAYER FOIL WITH VERY GOOD OPTICAL PROPERTIES |
| DE4032588A1 (en) * | 1990-10-13 | 1992-04-16 | Hoechst Ag | SINGLE-LOW SEALING BIAXIALLY ORIENTED POLYOLEFIN MULTILAYER FOR METALIZING APPLICATION |
-
1997
- 1997-05-15 DE DE19720313A patent/DE19720313A1/en not_active Withdrawn
-
1998
- 1998-05-04 WO PCT/EP1998/002619 patent/WO1998051494A1/en active IP Right Grant
- 1998-05-04 ES ES98928225T patent/ES2172151T3/en not_active Expired - Lifetime
- 1998-05-04 CA CA002289722A patent/CA2289722A1/en not_active Abandoned
- 1998-05-04 AU AU80154/98A patent/AU8015498A/en not_active Abandoned
- 1998-05-04 DE DE59802636T patent/DE59802636D1/en not_active Expired - Fee Related
- 1998-05-04 AT AT98928225T patent/ATE211968T1/en not_active IP Right Cessation
- 1998-05-04 BR BR9808790-8A patent/BR9808790A/en not_active Application Discontinuation
- 1998-05-04 EP EP98928225A patent/EP0981440B1/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| AU8015498A (en) | 1998-12-08 |
| EP0981440B1 (en) | 2002-01-16 |
| DE59802636D1 (en) | 2002-02-21 |
| BR9808790A (en) | 2000-07-18 |
| ATE211968T1 (en) | 2002-02-15 |
| DE19720313A1 (en) | 1998-11-19 |
| ES2172151T3 (en) | 2002-09-16 |
| WO1998051494A1 (en) | 1998-11-19 |
| EP0981440A1 (en) | 2000-03-01 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued |