BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a polymeric film according to the preamble of claim 1.

Multiple electronic, automotive, pharmaceutical, diagnostic and food packing applications require very low humidity levels inside the package or encapsulated enclosure to protect moisture sensitive products or components from exposure to environmental humidity.

2. Description of the Related Art

The polymer currently used most frequently in the area of blister packaging is polyvinylchloride (PVC). To increase the water vapor barrier the PVC film is often covered by polyvinylidene chloride (PVdC). From an ecological point of view halogen free materials get more and more important because of their environmental impact during manufacturing and disposal. Consequently halogen free polymers such as cyclic olefin copolymers exhibiting a similar low water vapor transmission rate (WVTR) as PVdC have been developed. Since no pure polymer (including cyclic olefin copolymers) so far was able to block moisture completely, various additives were used to decrease the relative humidity atmosphere within the packaging (physical and chemical desiccants, plate-shaped fillers such as graphite, layered clay, talc and kaolin).

What is therefore needed is a polymeric film with improved barrier properties regarding water vapor and oxygen for pharmaceutical and medical packaging, in particular blister packaging.

BRIEF SUMMARY OF THE INVENTION

It is an object of the invention to provide a deep drawable, halogen free moisture barrier polymeric film with a water vapor transmission rate (WVTR) of below 0.1 g mm m ^"2 day ^"1 at 75 % relative humidity difference at 40 °C.

The invention solves the posed problem with a polymeric film comprising the features of claim 1.

Bestatigungskopie The advantages obtained by the polymeric film according to claim 1 are the following:

- The film has a water vapor transmission rate (WVTR) of less than 0.1 g mm m day ^"1 at 75 % relative humidity difference measured at 40 °C;

- the film is deep drawable;

- the film exhibits a decreased oxygen barrier; and

- the film does not require a compaction step for orienting the glass platelets.

Further advantageous embodiments of the invention can be commented as follows:

In a special embodiment of the invention the alkyl-trimethoxysilane is propyl- trimethoxysilane, butyl-trimethoxysilane or pentyl-trimethoxysilane. In another embodiment the alkyl-trimethoxysilane is hexyl-trimethoxysilane, in particular n- hexyltrimethoxysilane. This selection offers an: optima! combination of that alkyl-group with the polymer of the at least one layer, in particular in the case of a cyclic olefin copolymer as a matrix.

In a further embodiment the alkyl-trimethoxysilane is heptyl-trimethoxysilane, octyl- trimethoxysilane, nonyl-trimethoxysilane or decyl-trimethoxysilane. In a further embodiment the alkyl-trimethoxysilane may be a C13- to C22-alkyl-trimethoxysilane.

The weight ratio of "the polymer" to the "glass platelets" is purposefully in the range of 3 : 1.00 to 3 : 2.25, preferably in the range of 3 : 1.25 to 3 : 1.80.

The volume ratio of "the polymer" to the "glass platelets" is in the purposefully in the range of 4.4 : 1.0 to 7.0 : 1 ,0, preferably in the range of 5.0 : 1.0 to 6.3 : 1.0.

The polymeric film may additionally comprise a carrier layer, preferably comprising polypropylene, placed on the bottom surface of the at least one layer. In a further embodiment the polymeric film additionally comprises a cover layer placed on the top surface of the at least one layer comprising a polymer chosen from the group of: cyclic olefin copolymer, polypropylene and polyethylene which is essentially free of glass platelets. The at least one layer comprising the glass platelets may consist essentially of a cyclic olefin copolymer and the cover layer may consist essentially of a cyclic olefin copolymer, both layers being based on the same type of cycloolefin and the same type of acyclic olefin.

In a special embodiment the polymer of the at least one layer is a cyclic olefin copolymer. The cycloolefin - on which the cyclic olefin copolymer is based - may preferably, be norbornene. The acyclic olefin on which the cyclic olefin copolymer is based may purposefully be selected from the group of ethylene, propylene, butylene or mixtures thereof. The cyclic olefin copolymer is preferably a copolymer of norbornene and ethylene Norbornene may be present in an amount of x = 10 to 90 mole percent and the ethylene may be present in an amount of y = 100 - x mole percent. Norbornene may preferably be present in an amount of x = 15 to 30 mole percent and the ethylene may be preferably present in an amount of y = 100 - x mole percent.

The cyclic olefin copolymer may purposefully have a heat deflection temperature (HDT/B) of at least 50°C, preferably at least 60°C and most preferably of at least 75°C. The cyclic olefin copolymer may purposefully have a heat deflection temperature (HDT/B) of at most 200°C, preferably at most 100°C and most preferably of at most

80°C.

The melt temperature of the cyclic olefin copolymer may purposefully be at least 190°C, preferably at least 230°C. The melt temperature of the cyclic olefin copolymer may purposefully be at most 320°C, preferably at most 250°C.

The glass transition temperature of the cyclic olefin copolymer may be in the range of 30° to 200° C.

The molecular weight of the cyclic olefin copolymer is purposefully higher than 50Ό00, preferably higher than 100Ό00. The molecular weight of the cyclic olefin copolymer is purposefully lower than 180Ό00, preferably lower than 150Ό00.

The cyclic olefin copolymer may have an amorphous structure.

In a special embodiment the polymeric film may be placed between two outer layers of a polymeric material. In case of single layers consisting of different types of polymers they may be connected to each other with suitable commercially available primers or adhesives. The outer layers may be made of cyclic olefin copolymer or polypropylene and have a thickness each in the range of 50 - 100 pm. The outer layers may be made of polyethylene and have a thickness each in the range of 10 - 50 pm.

In a further embodiment the polymeric film is essentially halogen-free.

The cyclic olefin copolymer may purposefully have a water vapor transmission rate WVTR < 0.1 g mm m ^"2 day ^"1 , preferably≤ 0.3 g mm m ^"2 day ^"1 , measured at 75 % relative humidity difference at 40 °C.

In a further embodiment the at least one layer of the polymeric film comprises ethylene vinyl alcohol (EVOH) or polyvinyl alcohol (PVA). Surprisingly the addition of EVOH or PVA confers to the polymeric film an improved property as an oxygen barrier to an extent of < 0.40 cm ³ mm/m ² /bar/d.]

In a special embodiment the average thickness of the polymeric film is more than 40 μηη, preferably more than 00 pm. The average thickness may be less than 1200 pm, preferably less than 800 pm.

In a further embodiment the cyclic olefin copolymer has a water absorption after immersion into water for 24 hours at 23 °C of less than 0.020 %, preferably of less than 0.012 %.

A method of manufacture for attaching the polymeric film according to the invention to a carrier layer is based on the solvent casting technique. Both layers may consist essentially of a cyclic olefin copolymer. In an alternative embodiment the carrier layer is not a cyclic olefin copolymer.

Another method of manufacture for attaching the polymeric film according to the invention to a carrier layer is based on the extrusion technique.

Still another method of manufacture for attaching the polymeric film according to the invention to a carrier layer is based on the calandering technique, wherein the at least one layer consists essentially of polypropylene. The polymeric film according to the invention is useful for pharmaceutical and medical packaging and in particular for blister packaging.

A BRIEF DESCRIPTION OF THE DRAWINGS

Several embodiments of the invention will be described in the following by way of example and with reference to the accompanying drawings in which:

Fig. 1 shows schematically a gas diffusion pathway within composite materials containing aligned platelets; PQ being the : permeability of the continuum, P being the permeability of the composite, μ being the geometric parameter, a being the aspect ratio and , φ being the volume fraction.

Fig. 2 shows SE pictures of cyclic olefin copolymer foils containing glass platelets. The figure at left shows vinyl functionalized glass flakes in cyclic olefin copolymer (according to comparative example C) where the glass platelets appear to be not aligned. The figure at right shows n-hexyltrimethoxysilane functionalized glass platelets in cyclic olefin copolymer (according to example A of the invention).

Fig. 3 shows the comparative measured water vapor transmission rates of a pure cyclic olefin copolymer film of 21 pm (i), a cyclic olefin copolymer film containing commercially available vinyl coated glass flakes with a thickness of 70 pm (ii) and a cyclic olefin copolymer film containing covalent n-hexyltrimethoxysilane surface modified glass flakes with a thickness of 50 pm according to the invention (iii).

DETAILED DESCRIPTION OF THE INVENTION

A low water vapor transmission rate (WVTR) can be achieved by incorporation of horizontally aligned platelet shaped fillers in the film. Their oriented alignment prolongs the diffusion way for gas molecules through the film and thus improves the gas barrier of the film. This is represented more in detail in figure 1 which shows the permeability in composite materials containing platelets; P ₀ being the: permeability of the continuum, P being the permeability of the composite, μ being the geometric parameter, a being the aspect ratio and , φ being the volume fraction.

The correct alignment and the proper embedment of the platelets in the film is crucial and appears to be difficult in reality. A wrong alignment of the platelets (i.e. perpendicular to the film surface) results in an enhancement of gas permeation compared to the film without filler. In prior art the proper alignment of the platelet fillers is usually achieved mechanically, e.g. by a compaction step.

The invention renders such a compaction step unnecessary by ensuring the proper embedment of the platelets in the polymer by surface functionalization. It furthermore simplifies the alignment of the platelets in such a way that the platelets are properly aligned directly after film production without further compaction steps.

The following examples clarify the invention further in more detail.

Raw materials used in the examples

Glass platelets

Chemical composition:

Si0 ₂ = 64 - 70%

K ₂ 0 = 0 - 3%

B ₂ 0 ₃ = 2 - 5%

ZnO = 1 - 5%

Na ₂ 0 = 8 - 13%

MgO = 1 - 4%

CaO = 3 - 7%

Ti0 ₂ = 0 - 3% and

Physical properties:

Apparent Density 0.015 (H ₂ 0=1 )

Real Density 2.60 (H ₂ 0=1 )

Softening Temperature 688°C Melt Temperature 930 - 1020°C

Refractive Index 1.52 and

Particle size distribution:

1000 - 300pm: 10% or less

300 - 50μηη: 65% or more

< 50pm: 25% or less.

Nominal thickness: approx.. 100 nm

Cyclic olefin copolymer

Ethylene norbornene copolymer

Surface functionalization of the glass platelets Example 1

Plain glass platelets (15 g) with a mean thickness of 100 nm were dispersed in ethanol (500 ml_).

NH4OH (25%, 100 ml_) was added and the dispersion was stirred for 30 minutes at 40 °C. N-hexyltrimethoxysilane (15 g) and ethanol (80 mL) was premixed and added. The mixture was stirred over night at 40 °C. The particles were washed with ethanol (2x), toluene/acetone (2x) and acetone (2x) (in the last step the platelets were separated by centrifugation). They were dried for 20 h in the oven (65 °C) and then for 2 h in vacuo at 50 °C.

Example 2:

Plain glass platelets (15 g) with a mean thickness of ca. 100 nm were dispersed in ethanol (500 mL). NH ₄ OH (100 mL) was added and the dispersion was stirred for 30 minutes at 40 °C. N-hexyltrimethoxysilane (15 g) and ethanol (80 mL) was premixed and added. The mixture was stirred over night at 40 °C. The particles were washed with ethanol (2x), xylene (2x) and ethanol (2x) (in the last step the flakes were separated by centrifugation). They were dried for 20 h in the oven (65 °C) and then for 2 h in vacuo at 50°C. Example 3:

Plain glass platelets (15 g) with a mean thickness of ca. 100 nm were dispersed in ethanol (500 mL). NH ₄ OH (100 mL) was added and the dispersion was stirred for 30 minutes at 40 °C. N-hexyltrimethoxysilane (15 g) and ethanol (80 mL) was premixed and added. The mixture was stirred over night at 40 °C. The particles were washed with ethanol (3x) (in the last step the flakes were separated by centrifugation). They were dried for 20 h in the oven (65 °C) and then for 2 h in vacuo at 50°C.

Example 4:

To a dispersion of plain glass platelets (mean thickness ca. 100 nm) in xylene (3.6 wt% glass platelets in xylene, 5 g glass platelets) N-hexyltrimethoxysilane (5 g) was added. The mixture was stirred over night at 80 °C.

Production of polymeric films by solvent casting Example A

3 g of ethylene norbornene copolymer was dissolved in xylene (10 wt%). 3 g of glass platelets (from examples 1 -3) were added to this solution and it was dispersed through standard dispersing techniques such as ultra-sonication. This dispersion was then dissolved with respect to the glass platelet content to the ratio of 2:1 of ethylene norbornene copolymer/glass platelets by weight (33.3 wt% = 14.9 v%), The films were produced by solvent casting on a spiral film applicator. The thickness of the polymer films obtained by this method was in a range of 20 - 200 pm, in particular approximately 70 pm.

Comparative Example B

The same procedure as described in example A was performed but using plain glass platelets, i.e. having no surface functionalization.

Comparative Example C

The same procedure as described in example A was performed but using commercially available vinyl functionalized glass platelets. Example D

To the reaction mixture obtained from the glass platelet surface functionalization of example 4 ethylene norbornene copolymer was added (10 g). The solvent was reduced by a rotary evaporator to yield a final polymer concentration in xylene of around 10 wt%. The films were produced by solvent casting on a spiral film applicator. The thickness of the polymer films obtained by this method was in a range of 20 - 200 μιτι, in particular approximately 70 pm.

Production of polymeric films by extrusion Example E

Production of cyclic olefin copolymer / glass platelet and polypropylen / glass platelet and low density polyethylene / glass platelet composites

Glass platelet powder with an average thickness of 100 nm were compounded into a cyclic olefin copolymer granulate or other olefin polymer with a weight component of 10 to 16 per cent. Because of the increased melt flow index, the mixed compound was extruded with a single-screw extruder and a kneader-system to reach the required homogenization. The result is a film with good barrier properties.

Production of films

The cyclic olefin copolymer (or other olefin polymer) / glass platelet composite was extruded in a multi slit die extrusion line to obtain a film. This film was laminated in a second stage process by a laminator line. For the lamination an adhesive layer is needed by coating or extrusion.

Properties of the polymeric films obtained

The polymeric films were deep drawabie and showed a good transparency.

The water vapor transmission rate (WVTR) of the polymeric film measured with a MOCON device at 40 °C and a relative humidity of 75% was determined to be 0.03 g mm m ^"2 d ^"1 and - as shown in Fig. 3 - remained essentially constant over time. Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the scope of the appended claims.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.