Note: Descriptions are shown in the official language in which they were submitted.
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Film for Tamper-Proof Coverings
For Goods Carriers
S. P E C I F I C A T I O N
The invention relates to a film comprising a polymer matrix
consisting of polypropylene, filled with a particulate filler,
in particular for tamper-proof coverings for goods carriers,
such as those known, for example, from a plurality of so-called
blister packagings.
Such known films for blister coverings have so far consisted of
aluminum films, plastic-coated aluminum films up to pure,
transparent or opaque plastic films. These films form the
counterpart to the goods carrier or the so-called lower part of
the packaging which, again, can be formed from a plurality of
materials, for example from a stable cardboard layer, a plastic
or aluminum tray adapted to the shape of the goods or the like.
The problem so far with using plastic films as blister covering
was the fact that pressure-sensitive goods, in particular,
could not be pressed through the film and thus removed from the
packaging without this leading to damage to the goods, in
particular in the case of tablets.
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For this reason, when using films as cover portion for such
packagings either one resorted to aluminum films, as is, in
particular, the case for the packaging of pharmaceutical
products, such as, ~=or example, tablets, ampoules or capsules,
or a possibility for removal was, however, provided in the
lower part of the packaging.
The object of the present invention is to provide a film for
tamper-proof coverings for goods carriers which may be produced
from plastics and, nevertheless, displays the known push-
through properties of aluminum film coverings and is suitable
for a sufficiently speedy sealing procedure.
This object is accomplished in accordance with the invention,
in the film described at the outset, in that the film is a
push-through film with a puncture resistance, measured on a
film 150 Evm thick, of less than 450 N/mm and that the
polypropylene matrix is formed by a highly crystalline
polypropylene.
This limit applies t=o films approximately 150 Etm in thickness.
Fer considerably thinner or thicker films, the corresponding
limits can be derived from these values. In the case of the
specified limit, it is possible to press goods not sensitive to
pressure through the cover film of the goods carrier, even
through with some expenditure of force. In the case of more
sensitive products, a lower limit will preferably be selected
for the puncture re:>istance, and this value is then preferably
at approximately 100 to approximately 200 N/mm. Lower puncture
resistances may be recommendable in individual cases where
goods very sensitive to pressure are packed. However, it
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should be noted in 'this respect that with the reduction in the
puncture resistance the protective effect of the packaging
against damage to the goods themselves is, of course, also
decreased and so the numerical range specified above of
approximately 100 to approximately 200 N/mm is to be seen as an
optimum in many cases.
Thin layers consisting of polypropylene with a filler content
of 10 to 60 o by weight of an inorganic filler are known per se
from JP-A-61-248793. The purpose described therein relates to
an adhesive material which is suitable for forming masks for
the production of electronic components or also for spraying
motor vehicles. The improved air permeability mentioned in
this publication is disadvantageous for numerous applications
of the inventive film.
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For the handling of the packaging by the consumer, i.e. in
particular when opening the packaging and, therefore, the
goods, a further property comes into play secondarily, the so-
called resistance to further tearing which determines the force
requirements necessary to allow a film which has been
penetrated once to be torn further open and thus release the
product. This property can also be influenced by the selection
of the filler as well as its proportion in the polymer matrix,
a resistance to furt:her tearing of less than 30 N (method of
measurement according to DIN 53363) being preferably aspired to
in this case. This numerical value applies, in particular, for
films approximately 150 dun in thickness but can also be used
essentially for considerably thinner or thicker films. A value
for the resistance t:o further tearing acceptable for the
handling, in particular, of goods sensitive to pressure as well
is between approximately 2 and 12 N, whereby it should again be
noted that, of cour~>e, considerably lower values are possible
but any arbitrary reduction is subject to limits with a view to
the protection of the goods by the film. A preferred range for
the resistance to further tearing is in the range of 3 to 4 N.
The inventive film contains the filler as a homogeneous
addition to a plastic material which is already completely
polymerized. The filler is not therefore - as known in
conjunction with filler-reinforced plastics - dispersed in the
polymerization reaction mixture consisting of monomer and/or
prepolymer and incorporated into the polymer matrix during the
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hardening of the reaction mixture. However, it is, of course,
conceivable to use ouch reinforced plastic material as polymer
matrix in specific applications, also in conjunction with the
present invention.
A broad range of fillers is available for the fillers of the
film. These can be selected from inorganic and/or from organic
substances.
Preferred examples for the organic substances are, e.g.,
halogenated hydrocarbon polymers, in particular PTFE, polyether
sulfones, cellulose fibers, wood pulp or the like, which have,
like the PTFE, a melting point of > 300°C, as well as
duroplastic materials. In the case of the organic substances
which are intended to serve as fillers, it is important that
these do not liquefy during the processing of the polymer
matrix material, during which temperatures of 220°C and more
can occur, and then form a homogeneous solution with the
polymer matrix material but that these remain essentially in
particle form in the polymer matrix during the processing ar_d
thus serve to weaken the continuous polymer matrix layer and,
therefore, to reduce the puncture resistance and, where
applicable, the resistance to further tearing accordingly.
For the inorganic component of the filler, the substance can be
selected from the f<~mily of silicon dioxides, in particular in
the form of glass or quartz, silicates, in particular in the
form of talc, titanates, Ti02, aluminum oxide, kaolin, calcium
carbonates, in particular in the form of chalk, magnesites,
MgO, iron oxides, s_Llicon carbides, silicon nitrides, barium
s a 1 f a t a f e-r--z-k~et,.
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The form of the filler particles will most often be granular
but lamellar, fibrous or rod-shaped filler particles are also
possible not only a:~ an essentially unitary form but also in a
mixture with other forms as filler particles.
The particle size of the filler (measured over the greatest
extension of the particle) is preferably, on average,
approximately 5 to approximately 100 ~.un. The selection of the
particle size is, of: course, also determined to a not
inconsiderable extent by the thickness of the film layer to be
produced. Care will- thus need to be taken that the average
extension of the particles keeps a clear distance in relation
to the thickness of the film to be produced. Average particle
sizes of between 20 ~un~ and 60 ~~.m, in particular with film
thicknesses of 80 dun to 100 ~,un, are preferred.
In order to ensure that the filler does not lead to a
reinforcement of the polymer matrix, care should be taken that
the filler particles adhere as little as possible to the
polymer matrix. However, the adhesion forces between the
particles and the filler matrix should at least be clearly less
than the tensile strength of the matrix itself. Care will
therefore have to beg taken, in particular, in the case of the
inorganic filler particles that these are essentially free from
so-called coupling or adhesive agents. Such adhesive agents
are customarily used for the production of filled plastics,
with which the focus. is, however, on the particular strength of
the material.
On the other hand, the aim is, of course, for the filler
particles to be distributed in the polymer matrix as evenly as
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possible and for this distribution to also be maintained during
the production process and so supplementary agents which
improve the dispersibility of the filler particles in the
matrix are preferably added.
Particularly suitable as dispersing agents are organic
substances which have a low melting point and a large wetting
capability for the filler. Concrete examples are low-molecular
polyolefin waxes. The dispersing agents are preferably applied
to the filler particles before these are mixed, in particular,
kneaded with the granulate of the matrix polymer.
The thickness of the film is preferably selected to be from
20 ~.un to approximately 600 dun which, on the one hand, ensures
an adequate stability of the film for protecting the packaged
goods and, on the other hand, keeps the forces necessary fcr
opening the packaging within the prescribed limit, within which
at least goods insensitive to pressure can still be removed
from the packaging by the average buyer without any problem by
pushing them through the cover film.
When packaging pharmaceuticals, in particular, it is often
desirable for the film to be designed to be essentially
impermeable to water and steam.
Highly crystalline polypropylenes, such as those described in
EP 0 255 693 Bl, hav:ing a high isotactic proportion of
pentadene of between 0.955 and 1.0 are recommendable as
suitable polymer matrix materials. (Method of measurement
described in EP O 255 693 B1).
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The average molecular weight of the polymers in the polymer
matrix is preferably selected in the range of approximately
10,000 to approximately 600,000.
The module of elasticity (measured in accordance with DIN 53457
on films 50 ~m thick) is preferably 1200 - 1400 N/mm' for the
pure polypropylene to be used. In the case of the filled
polypropylene matrix the module of elasticity may increase, for
example, to values (in N/mm2) of 1800 - 2000 with a 5 o by
weight filling of talc, 2200 - 2400 with a 10 % by weight
filling of talc or_ 3000 - 3400 with a 20 o by weight filling ef
talc.
In the films described thus far, solely the addition of the
fillers to the polymer matrix brought about an improved
puncture resistance or resistance to further tearing.
In the case of larger packaging units, in which a plurality of
products are stored separately from one another on a goods
carrier and covered by the cover film, it is often desirable
for the individual goods to be removable from the goods carrier
separately from one another without the packaging of the
individual goods located adjacent thereto being damaged.
Depending on the nature of the lower part of the packaging, the
normal sealing strength can already be adequate to solve the
above-mentioned problem. However, if the sealing strength in a
direct contact of the film with the lower part is too low or
the sealing times required are too long, it may be necessary to
have an additional sealing layer on the film surface.
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However, in order to essentially retain the puncture resistance
and the resistance to further tearing predetermined by the
original film, it is'. provided in such goods packagings for the
sealing layer to comprise a mixture of a (A) polypropylene
copolymer with an ethylene proportion of approximately 4 to 12
mol o and a polymer (B), selected from the family of ethylene
vinyl acetate copolymer with a vinyl acetate proportion of up
to 18 mol o, ionomer5, ethylene ethyl acrylate copolymers,
ethylene methacrylate copolymers, polypropylenes and
polyethylenes, their copolymers as well as ethylene vinyl
acetate copolymers grafted with malefic acid anhydride.
The mixing ratio of the mixture component (A) to the mixture
component (B) may be varied within a broad range of 5:95 to
95:5, wherein the temperature behavior of the mixture can be
controlled via the component (B) and, in particular, allows a
simple adaptation of the sealing layer to suitable sealing
temperatures and sealing cycle times.
Optimum sealing temperatures are in the temperature range of
145 to 155°C.
The inventive sealing layer is suitable not only for the push-
through films described in the above on the basis of a
polypropylene matrix consisting of highly crystalline
polypropylene but also, in general, for any type of push-
through film which contains the specifications stipulated above
for the puncture resistance. In this respect, polymer matrix
materials are to be mentioned, in particular, such as
polyolefins in general, PVC, polyester, polystyrene or styrene
.? t; 1.
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copolymerisates which take the place of the highly crystalline
polypropylene mentioned at the outset.
Additionally preferred mixing ratios of the mixture components
(A) and (B) are at 35:65 to 65:35. Very good sealing results
are obtained with mixing ratios of approximately 50:50.
The component (A) is preferably used with an ethylene
proportion of 6 - IO mol o, mostly preferred with a proportion
of 8 mol o .
The puncture resistance and resistance to further tearing can
be reduced in addition during the production of the film due to
a selective increase in the cooling temperature of the cooling
roller(s). In this respect, the cooling of the film is
preferably carried out on cooling rollers with temperatures of
between 20 and 100°C, more preferred between 50 and 80°C. In
this respect, the additional reduction in the puncture
resistance and resistance to further tearing can be achieved by
the use of the calendering process.
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The izz.ventive sealing layer material is eminently suitable, in
addition, as sealing layer on deep-drawn films, from. which the
goods carriers or lower parts of the blister pacl~agings are
normally manufactu.,red.
It ~.s recomm.ex~,ded that the same sealing layer be applied to the
push.-through, film tc> be combined w~.th the goods caxrier so that
the sealing layer of the push.-through film is bonded to the
sealing layer- of then deep-drawn film during t?-~e sealing
process.
In the particularly preferred embodiment of the in~en.tion, the
film is builfi up of two a.r more layers, wYiereby the two or more.
layers of the film, are preferably produced by being c:oextruded.
The in~rezztion relates, i,n addition, to a packaging with a lower
part as goods carrier adapted where applicab7.e in its shape to
the goods to be pacYed axed an upper part consisting of an
inventive film already described in the abotre.
Tn such a packaging, the lower part arid the upper paxt are
preferab~_y produced u.,ing the same type of plastic so that a
product made of the same type of materials i.s obtained. Such
products made from the same type of zn,ateria~.s can be recycled
particularly easily and
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reused for the same purpose which
represents an optimum packaging cycle.
A particularly preferred use of the inventive packaging
consists irl the packaging of pharmaceuticals which are present,
in particular, in ampoule, r_apsule or tablet form.
The invention will :now be explained in greater detail in the
following on the basis of one example:
In a first step, a polymer granulate is mixed with the filler
amounts and subsequently extruded or ca:~er_dered. The mixing,
in particular_ the homogenization, can take place by means cf
kneading in accordance with known processes, in particular
twin-screw compounding. The individual components can,
however, also be mixed with one another in a dry mixing
process. A better homogeneity, i.e. a more even d.istributier.
of the fillers in tre polymer matrix, is achieved by means of
the preceding production of a so-called compound.
Treatment of the filler particles with dispersing agents should
take place, in any case, prior to the blending with the matrix
polymer.
The compcund is melted in the extruder, namely at melt
temperatures of approximately 220°C and more as well as at a
melt pressure of up to 250 bar. The melt is preferably cooled
over a chill roll at 20°C to approximately 40°C but other
cooling processes, where necessary with a surface treatment
combined with a corona discharge, are also possible.
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The films are then cut and wound.
A highly crystalline polypropylene having a melt-flow index of
approximately ~3 g/10 min in accordance with DIN 53735
(230°C/2.16 kg) and a density (23°C) in accordance with
DIN 53479 of 0.902 g/cm3 may be mentioned as an example. Types
of polypropylene differing from this can, of course, also be
used.
Chalk or talc is suggested as filler for this example with an
average particle size of 5 to 60 ~.un, better still with an
average particle size of 20 to 30 ~.m. The proportion of
fillers in the overall film weight is preferably from 10 to
55 o by weight. Below a filler proportion of 5 o by weight, an
adequate embrittlement of the polymer with the reduction iii the
puncture resistance and the resistance to further tearing
connected thereto is normally no longer attained. With
proportions clearly above 60 o by weight, the production of the
film is difficult and the physical resistance values are often
no longer adequate for the typical uses.
As is customary in t:he production of propylene films, a
rewinding is also carried out with the inventive film on a
polypropylene basis for reasons of postcrystallization. (The
duration of the post:crystallization is typically 4 to 10 days).
With a mixture of
95 o by weight of polypropylene, highly crystalline, of
the Mitsui company with the product identification
name CJ700,
and
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o by weight of talc as filler, average particle size
20 ~.t,m, a film 150 ~.un thick was produced
(density 0.93 g/cm3) ,
A puncture resistance of 360 N/mm and a damage energy in
accordance with DIN 53313 of 0.5 J/mm could be measured on this
film.
From a mixture of
90 o by weight of polyprcpylene, highly crystalline, of
the Mitsui company with the product identification
name CJ700,
and
% by weight of talc as filler, average particle size
~,un, a film 150 ~,un thick was produced
(density 0.965 g/cm').
A puncture resistance of 220 N/mm and a damage energy of
0.2 J/mm could be measured on this film.
If the mixture is adjusted to 80 o by weight of polypropylene
(specification see above) and 20 % by weight of talc
(specification see a:bove), a puncture resistance of
approximately 100 N/tnm as well as a damage energy of 0.05 J/mm
are obtained. The density of the material was determined at
. 0 4 g / cm3 .
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In accordance with another aspect of the invention, the film as described
herein
may have two or more layers. Advantageously the two or more layers may be
coextruded. In some cases the external layer of the film may be a sealing
layer.
In accordance with another aspect of the invention an advantageous blister
pack can be created, the blister pack having a lower part which may be shaped
as applicable to accommodate the shape of the goods to be packaged, the
blister pack also having an upper part made from a film as described herein.
In
an advantageous embodiment both the upper part and the lower part of the
blister pack may be made of the same material. The lower part may be
produced from a deep drawn film which has a sealing layer as described
herein.
