Flexible multilayer packaging film with ultra-high barrier properties

Abstract

The present invention is related to a flexible multilayer packaging film with high gas barrier properties comprising: one or more support layer(s) (1,10); one or more barrier layer(s) (6,60), each of the one or more barrier layer(s) (6,60) comprising an organic layer (2,20) and an inorganic layer(3,30); wherein said multilayer film has an oxygen transmission rate of less than 0.1 cm.sup.3/m.sup.2/24 h/atm, preferably less than 0.05 cm.sup.3/m.sup.2/24 h/atm, most preferably less than 0.03 cm.sup.3/m.sup.2/24 h/atm measured at 23 C. and 50% relative humidity.

Claims

1. Flexible multilayer packaging film with high gas barrier properties comprising: one or more support layer(s) (1,10); one or more barrier layer(s) (6,60), each of the one or more barrier layer(s) (6,60) comprising an organic layer (2,20) and an inorganic layer (3,30); wherein the one or more support layer(s) is (are) selected from the group consisting of oriented polypropylene, as well as oriented polypropylene copolymers, oriented polyester, oriented polyamide, oriented polylactic acid, as well as oriented copolymers of polyester, polyaminde, and polylactic acid, paper and carton; the organic layer of the one or more barrier layer(s) is polyvinyl alcohol or ethylene vinyl alcohol copolymer comprising between 25 to 50 mol % alcohol; the inorganic layer of the one or more barrier layer(s) is AlOx or SiOx; wherein the x in SiOx is comprised between 1 and 2, and wherein AlOx has the formula Al.sub.2O.sub.3; wherein the organic layer is applied on the one or more support layer(s), and the AlOx or SiOx is applied on the organic layer; wherein the one or more barrier layer(s) is (are) sandwiched between an additional sealant layer (5) and the one or more support layer(s); wherein a laminate of said multilayer film has an oxygen transmission rate of less than 0.1 cm.sup.3/m.sup.2/24 h/atm, measured at 23 C. and 50% relative humidity.

2. Flexible multilayer packaging film according to claim 1, wherein the oxygen transmission rate of a laminate of said multilayer film does not increase more than 30%, after having been submitted to a Gelbo Flex mechanical constraint test according to ASTM F392-74 standard.

3. Flexible multilayer packaging film according to claim 1, wherein the organic layer of the one or more barrier layer(s) is polyvinyl alcohol or ethylene vinyl alcohol copolymer comprising between 27 to 45 mol % of alcohol.

4. Flexible multilayer packaging film according to claim 1, wherein the sealant layer has a thickness of at least 10 m and is selected from the group consisting of polyethylene, polypropylene, polyethylene and polypropylene copolymers, and amorphous polyester.

5. Flexible multilayer packaging film according to claim 1, wherein the inorganic layer of the one or more barrier layer(s) is SiOx.

6. Flexible multilayer packaging film according to claim 1, wherein the inorganic layer has a thickness between 20 and 120 nm.

7. Flexible multilayer packaging film according to claim 1, wherein the one or more barrier layer(s) further comprise(s) an aluminium layer having a thickness comprised between 5 m and 50 m.

8. Method for the production of the flexible multilayer packaging film according to claim 1 comprising the steps of: providing one or more support layer(s) (1,10); applying the organic layer (2,20) of the one or more barrier layer(s) (6,60) on the one or more support layer(s) (1,10); applying the inorganic layer (3,30) of the one or more barrier layer(s) (6,60) on the surface of the organic layer (2,20) of the one or more barrier layer(s) (6,60); applying an additional sealant layer (5) on the one or more applied barrier layer(s) (6,60).

9. Method according to claim 8, wherein the inorganic layer is applied by electron beam vacuum deposition.

10. Method according to any of claim 8, wherein the inorganic layer is applied by electron beam vacuum deposition at a pressure lower than 10.sup.31 3 mbar with an applied voltage of 5 to 40 kV.

11. Method according to claim 8, wherein the organic layer is a polyvinyl alcohol layer or an ethylene vinyl alcohol copolymer layer comprising between 25 to 50 mol % alcohol.

12. Method according to claim 8, wherein the support layer(s) is (are) submitted to a compatibilisation treatment to enhance the compatibility between said one or more support layer(s) and said organic layer of the one or more barrier layer(s).

13. Method according to claim 12, wherein the compatibilisation treatment is selected from a plasma treatment, a Corona treatment, a flame treatment, or a combination of one or more of these treatments.

14. Packaging comprising a flexible multilayer film according to claim 1.

15. Flexible multilayer packaging according to claim 1 wherein the oxygen transmission rate is less than 0.05 cm.sup.3/m.sup.2/24 h/atm.

16. Flexible multilayer packaging according to claim 1 wherein the oxygen transmission rate is less than 0.03 cm.sup.3/m.sup.2/24 h/atm.

17. Flexible multilayer packaging film according to claim 2, wherein the oxygen transmission rate of a laminate of said multilayer film does not increase more than 20%, after having been submitted to a Gelbo mechanical constraint test according to ASTM F392-74 standard.

18. Flexible multilayer packaging film according to claim 2, wherein the oxygen transmission rate of a laminate of said multilayer film does not increase more than 10%, after having been submitted to a Gelbo mechanical constraint test according to ASTM F392-74 standard.

19. Flexible multilayer packaging film according to claim 1, wherein the x in SiOx is comprised between 1.5 and 1.8.

20. Flexible multilayer packaging film according to claim 6, wherein the thickness is between 30 and 100 nm.

21. Flexible multilayer packaging film according to claim 6, wherein the thickness is between 40 and 80 nm.

22. Flexible multilayer packaging film according to claim 7, wherein the thickness comprised between 5 m and 25 m.

23. Flexible multilayer packaging film according to claim 7, wherein the thickness comprised between 5 m and 15 m.

24. Method according to claim 8, wherein the organic layer is a polyvinyl alcohol layer or an ethylene vinyl alcohol copolymer layer comprising between 27 to 45 mol % alcohol.

Description

SHORT DESCRIPTION OF THE DRAWINGS

(1) FIG. 1A to 1C schematically represent the progressive construction of a multi-layer film according to the invention.

(2) FIG. 2 represents a picture of a Gelbo Flex Tester designed to determine the flex resistance of flexible barrier materials by applying repetitive strain (i.e. twisting and horizontal motion).

(3) FIG. 3A to 3C schematically represent different sequences of the organic and inorganic layer of the barrier layers in flexible multilayer packaging films of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(4) Laminate constructions in the art using barrier webs with transparent oxide coatings such as SiOx and AlOx can convey good oxygen and water barrier properties; typical barrier values of OTR 0.5 and WVTR 0.4 can be achieved, increasing the barrier of the base film by more than 100 times. However, upon flexing the laminate (simulated by Gelbo flexing) the barrier is compromised, resulting in a significantly reduced barrier performance.

(5) Aluminium foils are known to offer exceptional barrier to oxygen and water; without pin-holes, it is generally not possible to measure barrier properties of multilayer structures containing more than 8 m Aluminium foil. However, after flexing, barrier properties are significantly eroded by the generation of pin-holes through the foil resulting in oxygen transmission rates (OTR) of 0.5 cm.sup.3/m.sup.2/24 h/atm and water vapour transmission rates (WVTR) of 0.5 g/m.sup.2/24 h/atm after 100 flexes.

(6) EVOH and PVOH coatings are also known in the art to convey good oxygen barrier properties; these coatings are generally more resistant to flexing than oxide coatings and aluminium foils. However, barrier levels lower than 0.4 OTR cannot be readily achieved with EVOH and PVOH coatings alone. Moreover, the coatings do not enhance water barrier at all, and their water sensitivity diminishes their effectiveness in applications requiring oxygen barrier under humid conditions.

(7) EVOH containing coextrusions such as PP//EVOH//PP with EVOH layers from 2 to 5 m are widely used in packaging applications can offer good oxygen barrier and flex crack resistance. However, no water barrier is offered by the EVOH layer and barrier levels lower than 1 OTR are not readily achievable with this type of substrate unless much thicker EVOH layers are used.

(8) According to an aspect of the invention, there is provided a flexible multilayer packaging film with high gas barrier properties, in particular, extremely, ultra-high barrier properties, as set out in the appended claims.

(9) According to another aspect of the invention, there is provided a method for producing such flexible multilayer packaging film, as set out in the appended claims.

(10) A flexible multilayer packaging film according to the present invention is schematically illustrated in FIGS. 1A to 1C, wherein (1) depicts a flexible substrate (or support layer); (2,20) the organic layer of the barrier layer (6,60); (3,30) the inorganic layer of the barrier layer (6,60); (4,40) an adhesive layer; and (5) a sealant layer.

(11) Advantageously, the flexible multilayer packaging film of the present invention comprises one or more barrier layer(s) (6,60); advantageously one or two barrier layer(s) (6,60).

(12) Advantageously, the thickness of the organic layer(s) (2,20) (of the barrier layer (6,60)) is comprised between 0.5 m and 10 m, advantageously between 0.8 m and 5 m, advantageously between 1 m and 4 m.

(13) The barrier layer of a flexible multi-layer film of the invention always needs a (flexible) substrate (or support layer) which can be chosen among oriented films such as oPP (oriented polypropylene), oPA (oriented polyamide), oPLA (oriented polylactide polymer), oPET (oriented polyethyleneterephtalate), or oPS (oriented polystyrene), regenerated cellulose, Cellulose Diacetate, PVC (polyvinylchloride), PVdC (polyvinylidene chloride), as well as ECTFE (ethylene chlorotrifluoroethylene), ETFE (ethylene tetrafluroethylene), or PEI (polyetherimide).

(14) Advantageously, the flexible multilayer packaging film of the present invention comprises one or more support layer(s) (1,10); advantageously one or two support layers (1,10).

(15) Advantageously, the thickness of the support layer(s) (1,10) is comprised between 6 m and 110 m, advantageously between 8 m and 100 m, advantageously between 10 m and 40 m, advantageously between 12 m and 20 m; advantageously between 15 m and 20 m.

(16) A layer of EVOH (ethylene vinyl alcohol) or PVOH (polyvinylalcohol) containing between (about) 25 to (about) 50 mol % OH, preferably between (about) 27 and (about) 45 mol % OH is applied as a coherent layer onto a flexible substrate.

(17) More particularly, a layer of EVOH or PVOH is applied as a coherent layer onto a flexible substrate from solution, emulsion, or from a molten phase.

(18) The layer of EVOH or PVOH can be applied onto the flexible substrate from an aqueous or solvent based solution, by a flexographic process. Alternatively, a smooth roll coater or direct rotogravure coating of EVOH or PVOH can equally be used.

(19) The use of a primer or tie layer in order to anchor the EVOH or PVOH coating to the flexible substrate may be required depending on the adhesion of the coating onto the substrate.

(20) A suitable primer layer for use in the present invention will be apparent for those skilled in the art.

(21) Preferably, the primer layer is a polyurethane primer or a polyethylene imine primer.

(22) On the layer of EVOH or PVOH, additionally a SiOx or AlOx ceramic layer can be applied.

(23) Advantageously, the deposition of SiOx (or AlOx) onto the surface of the EVOH or PVOH layer is performed by means of electron beam vacuum deposition.

(24) Preferably, the electron beam vacuum deposition is performed at a (reduced) pressure lower than 10.sup.3 mbar with an applied voltage (to the electrons in the electron beam) of (about) 5 to (about) 40 kV.

(25) EP 0 794 266 for example describes a method and device for coating a substrate surface with SiOx or AlOx by electron beam vacuum deposition, whereby the SiOx or AlOx is vaporized and deposited onto the surface of the substrate. The method and device described in EP 0 794 266 are incorporated herein by reference.

(26) Alternatively, the deposition of SiOx (or AlOx) is directly performed on the surface of the flexible substrate layer and subsequently covered by the EVOH or PVOH layer. The EVOH or PVOH layer can be applied on the already deposited SiOx (or AlOx) layer by the use of an adhesive or by extrusion lamination.

(27) In the context of the present invention, oxides of silicon are referred to as SiOx where x is a number from 1 to 2, preferably from 1.5 to 1.8 (i.e. SiOx in which 1x2, preferably in which 1.5x1.8).

(28) In the context of the present invention, AlOx refers to oxides of aluminum having the formula Al.sub.yO.sub.z where the ratio y/z is a number from 0.2 to 1.5. Preferably, y is 2 and z is 3 (i.e. Al.sub.2O.sub.3).

(29) The resulting coating of the present invention is transparent (or optical clear).

(30) The resulting coated barrier film can be further laminated to a (or one) sealant layer (or seal layer) by the use of an adhesive, extrusion lamination, or thermal lamination.

(31) A suitable adhesive for use in the present invention will be apparent for those skilled in the art.

(32) Preferably, the adhesive is a polyurethane (PU) adhesive (such as e.g. Adcote 811/9L10).

(33) A suitable sealant layer (or seal layer) for use in the present invention will be apparent for those skilled in the art. For instance, a sealant layer used in the multilayer film of the present invention can be a pressure tacky adhesive, an adhesive, as well as a heat seal film such as PE or PP.

(34) For example LLDPE (Linear low-density polyethylene) or PP (polypropylene) coextrusions, or PETG (Polyethylene terephthalate glycol-modified) seal webs, from (about) 150 m down to (about) 10 m thick, can be used as a sealant layer (or seal layer).

(35) Multiple layers of the obtained barrier coated film can be added one to another by the use of an adhesive or by extrusion lamination, to further improve the barrier properties of the resulting flexible multilayer packaging film of the invention, as also illustrated in FIGS. 1A to 1C.

(36) Existing barrier film solutions in the art are for example:

(37) PET/SiOx/adh/PE laminates offering OTR of 0.5 to 1 and WVTR 0.3 to 1;

(38) PET-EVOH/Adh/PE laminates offering OTR of 0.5 to 1 and WVTR of 1 to 2.

(39) By applying the inverse rule of mixtures, it may theoretically be expected that the oxygen barrier achieves a value of OTR of 0.25 by combining EVOH and SiOx.

(40) However, by actually applying SiOx onto the surface of the EVOH coating according to the present invention, barrier performances in a laminate of OTR of even less than 0.05 and as low as 0.01 cm.sup.3/m.sup.2/24 h/atm (at 23 C. and 50% R.H.) and WVTR of less than 0.2 and as low as 0.1 g/m.sup.2/24 h/atm (at 38 C. and 90% R.H.) can be achieved.

(41) Moreover, surprisingly, after Gelbo flexing the laminate these oxygen and water vapour barrier properties values are substantially maintained near their initial un-flexed values.

(42) It has thus been found that the barrier properties of the coated barrier films of the present invention are excellent.

(43) Conversely, the barrier properties of the existing PET-SiOx//PE or PET/Alu/PE laminates in the art are significantly degraded following the same level of flexing.

(44) Furthermore, in the present invention it has been found that the adhesion of the SiOx onto the EVOH is excellent. When delaminating a PET-EVOH-SiOx/Adh/PE laminate, the failure mode is at the EVOH-film interface with a bond strength of more than 4N/15 mm (i.e. the EVOH loosens from the substrate), with no failure at the SiOx-EVOH interface (i.e. the EVOH does not loosen from the SiOx).

(45) More particularly, in the present invention the adhesion of the SiOx onto the EVOH is substantially improved when compared to the adhesion between the constituting layers of the coated barrier films obtained by methods described in the art.

(46) In the present invention, one or more additional support layer(s) (or reinforcing layer(s)) can be further added to the coated barrier layers of the film (or to the flexible multilayer packaging film).

(47) Preferably, the one or more additional support layer(s) comprise (or consist of) oriented polypropylene, oriented polyester, oriented polyamide, oriented polylactic acid, as well as copolymers of those polymers, paper and carton.

(48) Advantageously, the thickness of the additional support layer(s) is comprised between 10 m and 110 m, advantageously between 10 m and 100 m, advantageously between 12 m and 40 m, advantageously between 12 m and 20 m; advantageously between 15 m and 20 m.

(49) In the present invention, a thin aluminium layer can be further added to the coated barrier layers of the film. The thickness of the thin aluminium layer is comprised between (about) 5 m and (about) 50 m, preferably between (about) 5 m and (about) 25 m, most preferably between (about) 5 m and (about) 15 m. Including such thin aluminium layer renders the coating of the invention opaque (instead of being transparent or optical clear). Although aluminium is known to be expensive, the barrier films of the invention incorporating such thin aluminium layer are still less expensive compared to the films known in the art including thicker and/or more aluminium layers.

EXAMPLES

(50) In each of the examples described below of flexible multilayer packaging films, the following values are measured: (a) the oxygen gas transmission rates (OTR) of a laminate of the multilayer film according to the ASTM 3985-2005 standard, at 23 C. and 50% relative humidity (i.e. before Gelbo flexing), (b) the water vapour transmission rates (WVTR) of a laminate of the multilayer film according to the ASTM 1249-90 standard, at 38 C. and 90% relative humidity (i.e. before Gelbo flexing), (c) the OTR of a laminate of the multilayer film according to the ASTM 3985-2005 standard, at 23 C. and 50% relative humidity, after 10 times (or 100 times) Gelbo flexing the laminate according to the ASTM F392-74 standard; (d) the WVTR of a laminate of the multilayer film according to the ASTM 1249-90 standard, at 38 C. and 90% relative humidity, after 10 times (or 100 times) Gelbo flexing the laminate according to the ASTM F392-74 standard.

(51) MOCON OX-TRAN Model 2/21 is an example of an OTR testing system for high barrier testing.

(52) The flexing of the laminate of flexible multilayer packaging films is performed using a Gelbo Flex Tester as illustrated in FIG. 2. Using the Gelbo Flex Tester determines the flex resistance of the flexible barrier materials by applying repetitive strain. The flexing action consists of a twisting motion combined with a horizontal motion, repeatedly twisting and crushing the film. Pin hole formation is the criteria for failure and pin holes are determined by use of colored turpentine by allowing it to stain through the pin holes onto a white backing.

(53) An overview of the results of the measurements is given in Table 1.

(54) In examples 1, 2, 4, and 6, commercially available flexible multilayer packaging films were analysed as comparative examples.

(55) Suitable commercially available flexible multilayer packaging films will be apparent for those skilled in the art.

(56) In example 2, for instance, a JBF A400 polyester film is used. In example 4, SiOx is coated onto a standard 20 m OPP.

(57) The test materials in examples 3 and 5 are prepared according to the invention.

(58) The flexible multilayer packaging film PET-EVOH-SiOx//PE of the invention in example 3 is prepared as follows: 12 m PET/2.5 m PU Adhesive/60 m PE is provided; 1.5 m EVOH is applied onto the PET substrate from a flexographic process; 60 nm SiOx is applied onto the surface of the EVOH by electron beam vacuum deposition (EB coating); the used adhesive in the laminate is a 2K solvent based PU adhesive applied from a forward gravure process; PE is an A/B/C LLDPE coextrusion with a Dow AFFINITY PL1880 metallocene seal layer.

(59) The flexible multilayer packaging film OPP-EVOH-SiOx/Adh/PE according to the invention in example 5 is prepared as follows: 20 m OPP/2.5 m PU Adhesive/60 m PE is provided; 1.5 m EVOH is applied onto the OPP substrate from a flexographic process; 60 nm SiOx is applied onto the surface of the EVOH by electron beam vacuum deposition (EB coating); the used adhesive in the laminate is a 2K solvent based PU adhesive applied from a forward gravure process; PE is an A/B/C LLDPE coextrusion with a Dow AFFINITY PL1880 metallocene seal layer.

(60) From the present description and the examples, other flexible multilayer packaging films according to the invention will be apparent for those skilled in the art.

(61) TABLE-US-00001 TABLE 1 measured OTR and WVTR values before and after 10 times/100 times Gelbo flexing OTR WVTR cm.sup.3/m.sup.2/day/atm g/m.sup.2/day OTR WVTR OTR WVTR 23 C. 38 C. 10 10 100 100 Ex. 50% RH 90% RH Gelbo Gelbo Gelbo Gelbo 1 PET-EVOH/adh/PE 0.5 2 0.6 2 2 PET-SiOx/adh/PE 0.5 0.4 4 0.6 3 PET-EVOH-SiOx//PE 0.01 0.12 0.01 0.15 0.1 0.16 4 OPP-SiOx//PE 4 0.2 13.2 0.5 5 OPP-EVOH-SiOx/adh/PE 0.1 0.1 0.19 6 PET/Alu8/70PE <0.01 <0.01 0.01 0.01 0.35 0.03

(62) From the comparative examples 1, 2, 4, and 6, either without EVOH or without SiOx, it can be seen that the deterioration properties after Gelbo flexing are significant, and that the coated barrier film does not show good barrier properties.

(63) The data for the flexible multilayer packaging films prepared according to the invention in examples 3 and 5 show that the barrier properties are good to excellent, even after being subjected to Gelbo flexing.

(64) The barrier properties of the coated barrier films of the present invention are even substantially improved when compared to the barrier properties of the coated barrier films available (or obtained by methods described) in the art.

(65) Without being bound to theory, the excellent barrier properties of the coated barrier film of the present invention could be due to the fact that in the present invention a flat, smooth surface of the laminate is achieved, said surface having substantially no defects (when compared to films obtained by methods described in the art). The EVOH can be considered as a planarization layer for the SiOx, thus reducing defects in the SiOx coating. It is believed that this planarization coating is beneficial for the barrier properties of the flexible multilayer packaging films according to the present invention.

(66) For example, the (arithmetic average of the) three-dimensional surface roughness (denoted as Sa) of the SiOx receptive layer for conventional PET films used for SiOx coating, such as JBF A400 polyester film, Hostaphan RNK (Mitsubishi Polyester Film GmbH) or Mylar 800 (DuPont Teijin Films), has been measured at 0.15 m to 0.2 m, as measured by Laser Scanning Microscopy (LSM) described in ISO 25178. However, EVOH coated films (such as those used in Examples 3 and 5) have an Sa-value of less than 0.1 m, less than 0.05 m, and even less than 0.03 m.

(67) Different sequences of the organic layer and inorganic layer of the barrier layers in flexible multilayer packaging films of the present invention are schematically illustrated in FIGS. 3A to 3C. In these figures, (1,10) depicts a flexible substrate (or support layer); (2,20) the organic layer of the barrier layer (6,60); (3,30) the inorganic layer of the barrier layer (6,60); (4,40) an adhesive layer; and (5) a sealant layer.

(68) From the description and examples above, it follows that the present invention thus provides a flexible multilayer packaging film with high barrier properties, in particular, extremely, ultra-high barrier properties exhibiting oxygen transmission rates lower than 0.05, preferably lower than 0.01 cm.sup.3/m.sup.2/24 h/atm at 23 C. and 50% relative humidity.

(69) The present invention further provides ultra-high barrier films against oxygen transmission, the films being able to maintain their properties even after submission of a laminate of the film to mechanical constraints such as folding or flexing, in particular, after submission to a normalised Gelbo flex test.

(70) The flexible multilayer packaging films of the invention are aluminium-free (or even metal free), or at least comprising only strongly reduced aluminium (or metal) layer thicknesses, when compared to packaging films obtained by methods described in the art.

(71) The present invention provides a method for producing such flexible multilayer packaging films having high barrier properties, in particular extremely, ultra-high barrier properties.

(72) The film of the present invention can be used in flexible multilayer packaging for many food and non-food applications in packaging industry, more particularly, for those applications where high oxygen barrier properties, in particular, extremely ultra-high oxygen barrier properties are required.