Note: Descriptions are shown in the official language in which they were submitted.
CA 02276541 1999-06-28
Ticona GmbH DrLv Tic 98/G 009
Extrusion-coated film
The present invention relates to an extrusion-coated film, a process for
producing an extrusion-coated film and the use of the film as a packaging
material.
To produce high-performance packaging, flexible films are molded to the
shape of a tray or capsule using the action of heat and pressure and a
mechanical ram at super- and/or subatmospheric pressures. The film
serves firstly to protect the contents. It has to protect the contents from
the
effects of the environment and must therefore have a high level of barrier
properties with respect to water-vapor, gases and UV. It must have
mechanical stability to protect the contents from physical effects, and so
that it does not itself become damaged by the contents. The quality of the
contents must not be impaired by constituents released from within the film.
Blister packs are increasingly frequently chosen as packaging for a wide
variety of articles, since this type of pack is available in a wide variety of
forms and meets the requirements of mechanized packaging processes.
The starting materials used for blister packs are thermoformable films.
These are plastic films which when heated can be shaped relatively readily
by applying super- or subatmospheric pressure pneumatically, or using a
ram. Appropriate selection of the molds can thus introduce depressions
(blisters) into the film (base film) and these can be matched to the shape of
the article to be packed. After this shaping step the article to be packed is
introduced into the resulting blister. Once the blister has been filled, a
backing film is applied to the base film and encloses the article to be
packed within its blister.
If all of the requirements cannot be covered by a single material, the
properties required in a film are achieved by combining more than one film
to give a composite. Films produced from cycloolefin copolymers have very
good impermeability to water vapor. However, these films have poor
resistance to fats. Environmental-stress-cracking corrosion occurs on
exposure to unsaturated fatty acids.
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The film most frequently used in blister packs is polyvinyl chloride (PVC).
To increase its barrier properties with respect to gases, in particular water
vapor, the PVC base film is frequently coated with PVDC. Films made from
unoriented polypropylene (uPP) give better water-vapor barrier properties
than PVC films and are less questionable from an environmental point of
view. However, the disadvantage is that this material has poorer
thermoformability and higher shrinkage.
The COC mono- or multilayer films described in EP-A-570 188 and
EP-A-631 864 when used as base films give good processing and good
barrier properties.
Relatively new developments in the area of blister packs for
pharmaceuticals describe the use of amorphous polyolefins with good
processing performance and high levels of water-vapor barrier properties.
For example, EP-A-570 188 and EP-A-631 864 describe the use of
polyolefins with cyclic olefins as polymeric building block. These
applications describe the use of these polyolefins (cycloolefin copolymers,
abbreviated to COC) as mono- or multilayer films for blister packs.
Alongside automated packing and the presentation of the product protected
within the blister, for example pharmaceuticals in the form of tablets,
capsules or the like, the blister pack can markedly reduce exposure to
atmospheric moisture and oxygen and thus increase shelf life.
The object of the present invention is to provide a film having a high level
of
barrier properties, very good thermoformability and good resistance to fats,
together with a cost-effective and environmentally friendly process for its
production, and the use of the film for producing blister packs.
The object of the present invention is achieved by means of an extrusion-
coated film comprising at least one film which comprises cycloolefin
copolymer and comprising, on at least one side of this film, a layer of
extrusion-coated thermoplastic material.
Extrusion-coating technology comprises the production of films having
more than one layer by using extrusion from the melt to apply a
thermoplastic to a previously produced film web.
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The film web used for the extrusion-coating may be a monofilm, composed
of one single layer, or else may itself be a composite film.
The thermoplastics used are mostly readily extrudable products, especially
polyethylenes, ionomers or ethylene-vinyl acetate copolymers. Preference
is given to the use of polyethylene and particularly LDPE. These materials
have good bond strength which prevents subsequent delamination.
At a relative humidity of about 85% and at a temperature of about 23 C the
film has water-vapor permeability of < 0.05 g/mzd, puncture resistance of
< 20 N and a thickness < 100 pm.
The films suitable for the purposes of the invention comprise at least one
cycloolefin polymer selected from the class consisting of polymers
containing from 0.1 to 100% by weight, preferably from 10 to 90% by
weight, based on the total weight of the cycloolefin copolymer, of
polymerized units of at least one cyclic olefin of the formulae I, II, II',
III, IV,
V or VI
R~
IHC -CH-~~ CH
R3 C R4 41~'
HC CH
CH
CH.
H C C H 3 d \ (~
R C R -H (I I),
H C C H
C CH2
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4
HC
R3 c RA. ~ch2
Hc CH j
cH CH,
Hc CHcw--- cH~
c~
R3 c q4 c p6
HC CH CH
Cb'
HC I H CH C h9 R
I cH~ cw /
R C Ra R5 - C- Rs R7
HC I CH CH C H CH
H C H
R
p 2
R
HC CH CH
R3 c 4
HC CH ' CH
C H
R9
2
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R2
HC _CH~_~ CH~~CH~ / CH R'
CH CH
R3 C R4 R 7 C (VI),
H C
CHCH CH~'CH CH_CH~\Ri
'
where R1, R2, R3, R4, R5, R6, R7 and R8 are identical or different and are
5 a hydrogen atom or a C1-C20-hydrocarbon radical, such as a linear or
branched C1-C8-alkyl radical or C6-C18-aryl radical or C7-C20-alkylenearyl
radical, or a cyclic or acyclic C2-C20-alkenyl radical, or form a saturated,
unsaturated or aromatic ring, where the same radicals R1 to R 8 in the
different formulae I to VI may have different meanings, and
n may be from 0 to 5, and
from 0 to 99.9 mol%, based on the total composition of the cycloolefin
copolymer, of polymerized units which derive from one or more acyclic
olefins of the formula VII
R9 R10
C C
(VII),
R11 R12
where R9, R10, R11 and R12 are identical or different and are a hydrogen
atom, a linear or branched, saturated or unsaturated C1-C20-hydrocarbon
radical, such as a C1-C8-alkyl radical, or a C6-C18-aryl radical.
The cycloolefin copolymers may also be obtained by ring-opening
polymerization of at least one of the monomers with the formulae I to VI,
followed by hydrogenation of the products obtained.
The novel elastomeric cycloolefin copolymer may also contain from 0 to
45 mol%, based on the total composition of the cycloolefin copolymer, of
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6
polymerized units which derive from one or more monocyclic olefins of the
formula VIII
HC CH
(VIII),
(CI"'12)m
where m is a number from 2 to 10.
The proportion of the polymerized units which derive from cyclic, in
particular polycyclic, olefins, is preferably from 3 to 75 mol%, based on the
total composition of the cycloolefin copolymer. The proportion of the
polymerized units which derive from acyclic olefins is preferably from 5 to
80 mol%, based on the total composition of the cycloolefin copolymer.
The cycloolefin copolymers are preferably composed of polymerized units
which derive from one or more polycyclic olefins, in particular from
polycyclic olefins of the formulae I or III, and polymerized units which
derive
from one or more acyclic olefins of the formula VII, in particular a-olefins
having from 2 to 20 carbon atoms. Particular preference is given to
cycloolefin copolymers which are composed of polymerized units which
derive from a polycyclic olefin of the formula I or III and from an acyclic
olefin of the formula VII. Preference is also given to terpolymers which are
composed of polymerized units which derive from a polycyclic monoolefin
of the formula I or III, from an acyclic monoolefin of the formula VII and
from a cyclic or acyclic olefin which contains at least two double bonds
(polyene), in particular cyclic, preferably polycyclic, dienes, such as
norbornadiene, or cyclic, particularly preferably polycyclic, alkenes with a
C2-C20-alkenyl radical, such as vinylnorbornene.
The novel elastomeric cycloolefin copolymers preferably comprise olefins
with a fundamental norbornene structure, particularly preferably
norbornene, tetracyclododecene and, if desired, vinylnorbornene or
norbornadiene. Preference is also given to cycloolefin copolymers which
contain polymerized units which derive from acyclic olefins with terminal
double bonds, such as a-olefins having from 2 to 20 carbon atoms,
particularly preferably ethylene or propylene. Particular preference is given
to norbornene-ethylene and tetracyclododecene-ethylene copolymers.
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Among the terpolymers, particular preference is given to norbornene-
vinylnorbornene-ethylene, norbornene-norbornadiene-ethylene,
tetracyclododecene-vinylnorbornene-ethylene and tetracyclododecene-
vinyltetracyclododecene-ethylene terpolymers. The proportion of the
polymerized units which derive from a polyene, preferably vinylnorbornene
or norbornadiene, is from 0.1 to 50 mol%, preferably from 0.1 to 20 mol%,
and the proportion of the acyclic monoolefin of the formula VII is from 0 to
99.9 mol%, preferably from 5 to 80 mol%, based on the total composition of
the cycloolefin copolymer. In the terpolymers described, the proportion of
the polycyclic monoolefin is from 0.1 to 99.9 mol%, preferably from 3 to
75%, based on the total composition of the cycloolefin copolymer.
The cycloolefin copolymer according to the invention preferably comprises
at least one cycloolefin copolymer containing polymerized units which
derive from polycyclic olefins of the formula I and containing polymerized
units which derive from acyclic olefins of the formula VII.
The cycloolefin copolymers according to the invention may be prepared at
temperatures of from -78 to 200 C and at a pressure of from 0.01
to 200 bar, in the presence of one or more catalyst systems which
comprise at least one transition metal compound and, if desired, a
cocatalyst and, if desired, a support. Suitable transition metal compounds
are metallocenes, in particular stereorigid metallocenes. Examples of
catalyst systems suitable for preparing the elastomeric cycloolefin
copolymers according to the invention are described in EP-A-407 870,
EP-A-485 893 and EP-A-503 422. These publications are expressly
incorporated herein by way of reference.
Examples of transition metal compounds used are:
rac-dimethylsilylbis(1-indenyl)zirconium dichloride,
rac-dimethylgermylbis(1-indenyl)zirconium dichloride,
rac-phenylmethylsilylbis(1-indenyl)zirconium dichloride,
rac-phenylvinylsilylbis(1-indenyl)zirconium dichloride,
1-silacyclobutylbis(1-indenyl)zirconium dichloride,
rac-diphenylsilylbis(1-indenyl)hafnium dichloride,
rac-phenylmethylsilylbis(1-indenyl)hafnium dichloride,
rac-diphenylsilylbis(1-indenyl)zirconium dichloride,
rac-ethylene-1,2-bis(1-indenyl)zirconium dichloride,
dimethylsilyl(9-fluorenyl)(cyclopentadienyl)zirconium dichloride,
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diphenylsilyl(9-fluorenyl)(cyclopentadienyl)zirconium dichloride,
bis(1-indenyl)zirconium dichloride,
diphenylmethylene(9-fluorenyl)cyclopentadienylzirconium dichloride,
isopropylene(9-fluorenyl)cyclopentadienylzirconium dichloride,
rac-isopropylidenebis(1-indenyl)zirconium dichloride,
phenylmethylmethylene(9-fluorenyl)cyclopentadienylzironium dichloride,
isopropylene(9-fluorenyl)(1-(3-isopropyl)cyclopentadienyl)zirconium
dichloride,
isopropylene(9-fluorenyl)(1-(3-methyl)cyclopentadienyl)zirconium
dichloride,
diphenylmethylene(9-fluorenyl)(1-(3-methyl)cyclopentadienyl)-zirconium
dichloride,
methylphenylmethylene(9-fluorenyl)(1-(3-methyl)cyclopentadienyl)-
zirconium dichloride,
dimethylsilyl(9-fluorenyl)(1-(3-methyl)cyclopentadienyl)zirconium dichloride,
diphenylsilyl(9-fluorenyl)(1-(3-methyl)cyclopentadienyl)zirconium dichloride,
diphenylmethylene(9-fluorenyl)(1-(3-tert-butyl)cyclopentadienyl)-zirconium
dichloride,
isopropylene(9-fluorenyl)(1-(3-tert-butyl)cyclopentadienyl)zirconium
dichloride,
isopropylene(cyclopentadienyl)(1-indenyl)zirconium dichloride,
diphenylcarbonyl(cyclopentadienyl)(1-indenyl)zirconium dichloride,
dimethylsilyl(cyclopentadienyl)(1-indenyl)zirconium dichloride,
isopropylene(methylcyclopentadienyl)(1-indenyl)zirconium dichloride,
4-( Tj 5-cyclopentadienyl)-4,7,7-trimethyl(r,5-4,5,6,7-tetrahydroindenyl-
zirconium dichloride,
[4-( ri5-cyclopentadienyl)-4,7,7-triphenyl( r15-4,5,6,7-tetrahydroindenyl)]-
zirconium dichloride,
[4-( rl 5-cyclopentadienyl)-4,7-dimethyl-7-phenyl( Tj 5-4,5,6,7-tetrahydro-
indenyl)]zirconium dichloride,
[4-( r1-3'-tert-butylcyclopentadienyl)-4,7,7-triphenyl( Tj 5-4,5,6,7-
tetrahydro-
indenyl)]zirconium dichloride,
[4-( rl-3'-tert-butylcyclopentadienyl)-4,7-dimethyl-7-phenyl( ri5-
4,5,6,5 -tetrahydroindenyl)]zirconium dichloride, 5
[4-( rI -3'-methylcyclopentadienyl)-4,7,7-trimethyl( Tj -4,5,6,7-tetrahydro-
indenyl)]zirconium dichloride,
[4-( rj-3'-methylcyclopentadienyl)-4,7,7-triphenyl( r1 5-4,5,6,7-tetrahydro-
indenyl)]zirconium dichloride,
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[4-( 115-3'-methylcyclopentadienyl)-4,7-dimethyl-7-phenyl( 71 5-4,5,6,7-tetra-
hydroindenyl)]zirconium dichloride,
[4-(r1 5-3'-isopropylcyclopentadienyl)-4,7,7-trimethyl( Tj 5-4,5,6,7-
tetrahydro-
indenyl)]zirconium dichloride,
[4-( r~5-3'-isoproplycyclopentadienyi)-4,7,7-triphenyl( r15-4,5,6,7-tetrahydro-
indenyl)]zirconium dichloride,
[4-( r15-3'-isopropylcyclopentadienyl)-4,7-dimethyl-7-phenyl( 1
5-
4,5,6,7-tetrahydroindenyl)]zirconium dichloride,
[4-( rl5-cyclopentadienyl)( r15-4,5-tetrahydropentalene)]zirconium dichloride,
[4-( 115-cyclopentadienyl)-4-methyl( r1 5 -4,5-tetrahyd rope nta le ne)]zi
rcon i u m
dichloride,
[4-( rl5-cyclopentadienyl)-4-phenyl( r15-4,5-tetrahydropentalene)]zirconium
dichloride,
[4-( Tj 5-3'-methylcyclopentadienyl)( Tj 5-4,5-tetrahydropentalene)]zirconium
dichloride,
[4-( Tj 5-3'-isopropytcyclopentadienyl)( Tj 5-4,5-tetrahydropentalene)]-
zirconium dichloride,
[4-( Tj 5-3'-benzylcyctopentadienyl)( r15-4,5-tetrahydropentalene)]zirconium
dichloride,
[2,2,4-trimethyl-4-( rl 5-cyclopentadienyl)( r15-4,5-tetrahydropentalene)]-
zirconium dichloride,
[2,2,4-trimethyl-4-( rl5-(3,4-diisopropyl)cyclopentadienyl)( Tj 5-4,5-
tetrahydro-
pentalene)]zirconium dichloride.
The COC films used according to the invention have specific mechanical
properties. The films can be processed on the machinery used and also
have low puncture resistance and a high level of barrier properties,
especially to water vapor. Suitable COC films of this type are unoriented.
They may be monolayer films or have more than one layer. The films may
comprise organic or inorganic fillers in order to reduce light transmission so
as to render the contents invisible (childproof packaging) or in order to
improve printability or sealing properties.
The cycloolefin copolymers are prepared by heterogeneous or
homogeneous catalysis with organometallic compounds as described in
many patents. Catalyst systems based on mixed catalysts made from
titanium salts and organoylaluminum compounds are described in
DD-A-109 224 and DD-A-237 070. EP-A-156 464 describes the preparation
CA 02276541 2007-07-24
using catalysts based on vanadium. EP-A-283 164, EP-A-407 870,
EP-A-485 893 and EP-A-503 422 describe the preparation of cycloolefin
polymers using catalysts based on soluble metallocene complexes.
5
Unoriented extruded COC films are brittle, making it difficult to find
appropriate processing conditions, and their processing performance is
poor (cf. DE-A-4304309). They readily split or break during winding-up
10 and/or unwinding under tension. Their mechanical strength therefore has to
be increased. This may be achieved by orientation (mono- or biaxial
stretching) of the films. Films oriented in this way are significantly easier
to
handle and do not have the disadvantages described in DE-A-4304309.
The puncture resistance of oriented films was studied in accordance with
DIN 53373. One measure of puncture resistance is penetration energy. It
has now been established that orientation increases the puncture
resistance of the films. Without exception, the values found were larger
than those for unoriented films of comparable thickness. DE-A-4414669
states that 450 N/mm is too high for a film useful as a backing film for
blister packs. Significantly lower values are desirable on blister packing
machinery for fragile pharmaceuticals. The puncture resistances of
aluminum foils can be taken as a preliminary guide: that of a (16 pm)
aluminum foil is 90 N/mm. When oriented COC films are used, therefore, it
is not possible to ensure easy removal of the pharmaceutical from the
blister pack.
Alongside ideal, but not excessively low, puncture resistance, the blister
film must have relatively high toughness. Careful balancing of mechanical
strength (hardness), flexibility and the force required to compress the
compartment is required to enable the contents, such as a tablet, capsule,
suppository or dragee to be capable of release from the pack without
damage and without unreasonable expenditure of effort. Low expenditure
of effort is a particular requirement when elderly people use the product,
and also in the clinical sector where medical personnel are continually
using pressure to remove tablets and can suffer from fatigue or muscular
aching in the fingers.
The water-vapor barrier effectiveness of the films is comparable with that of
unoriented COC films, i.e. the orientation has no marked effect on the
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barrier effectiveness of the films. The thicknesses of the extrusion-coated
layered material with COC films as a base should therefore be within the
range of the thicknesses of the films in the blister after it has been formed.
The resultant thicknesses for the layers of material applied by extrusion are
from 1 to 150 pm, preferably from 5 to 30 pm.
The water-vapor barrier effectiveness is not significantly affected by organic
or inorganic additives. It is from 0.2 to 0.4 g/mz-d for a film thickness of
100 pm. The polarity of the surface can be increased by corona-treating the
film.
The additives may be organic polymers, such as polypropylene or
polyethylene in the form of homo- or copolymers, polyesters, polyamides,
polycarbonate, polyacetals, or acrylate or methacrylate polymers. Inorganic
pigments which may be used are titanium dioxide, barium sulfate, calcium
sulfate, calcium carbonate and barium carbonate.
One or both sides of the COC film may be extrusion-coated with materials
which comprise polymers such as polyethylene, polypropylene or polyvinyl
chloride. The thickness of the layer of material extrusion-coated onto the
COC film is from 1 to 150 pm, preferably from 5 to 30 pm, particularly
preferably from 8 to 12 pm.
The thickness of the layer of PE material is from 1 to 150 pm, preferably
from 5 to 30 pm, particularly preferably from 8 to 12 pm. The thickness of
the COC film is from 50 to 400 pm, preferably from 150 to 350 pm,
particularly preferably from 200 to 300 pm.
The novel extrusion-coated film is used for producing blister packs. Blister
packs or PTP (push-through packaging) produced therefrom have very
good water-vapor barrier properties, thus increasing the value of the
packaged item. They can be used to pack contents such as
pharmaceuticals and foodstuffs, in particular pelletized or encapsuleated
pharmaceuticals, foods containing rice, cookies, snacks, and also
hygroscopic items, such as cigarettes and teabags.
The layer of polymer extrusion-coated here onto at least one side protects
the COC base film from fats, thus increasing the stability and the value of
the composite film.
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The invention is described in more detail using a drawing and examples.
Drawing
The drawing comprises Figures 1 and 2.
Fig 1: shows the construction of an extrusion-coating plant for producing a
2-layer composite film, and
Fig 2: shows the construction of an extrusion-coating plant for producing a
3-layer composite film.
The extrusion-coating plant of Fig. 1 comprises a backing film web (1), an
infeed roller (2), a die (3), a roll (4) and the finished 2-layer composite
film
(5). A web of paper or textile may replace the backing film web. The
product is a two-layer composite. This process permits one side of the
backing film web to be coated with a polymer melt in each pass through the
machine. A second pass through the machine therefore permits coating of
the side of the backing film which was not coated in the first step.
The extrusion-coating plant of Fig. 2 comprises a backing film web (1), a
lay-on roller (2), a die (3), a deflecting roller (6), a chill roller (7), a
roller (8),
a two-layer film web (9), a die (10), the finished 3-layer composite film (11)
and a wind-up (12). This process has to two coating steps in sequence to
apply the polymer melt to both sides of the backing film web, forming a
3-layer film in one pass through the machine.
Example
A 300 m roll of a COC film (Topas type 8007) of thickness 250 pm was
firstly extrusion-coated on one side at a thickness of 12 pm (11g/m2) with
LDPE (density 0.92 g/cm3), using a die. This involved extrusion-coating the
COC film with an application rate of 12 g/m2 at a temperature of 310 C and
a speed of 90 m/min. The process was carried out as in Fig. 1. The single-
side-extrusion-coated COC film was extrusion-coated on its uncoated side
in a second pass through the machine using the application system used
for the first pass and the same LDPE, at a speed of 80 m/min and a
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13
temperature of 320 C. The thickness of the extrusion-coated film was
274 pm.
Its high bond strength meant that measurement of the bond strength
caused the LDPE film to tear. The bond strength between a film made from
pure COC and LDPE is therefore high.
Comparative Example
The procedure of the example was followed except that each side of the
COC film was extrusion-coated with polypropylene at a thickness of 12 pm.
The thickness of the extrusion-coated film was 274 pm. The polypropylene
film could be pulled away from the COC film without tearing. The bond
strength between a film made from pure COC and polypropylene is
therefore low.
