Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The invention relates to recycled film based on polyamide
and polyolefin waste occurring e.g. in the production of
laminated filmæ. The invention relates to use of waste
material occurring in the manufacturing proce,s and i8
therefore of high ecological and economic importance. The
deep-drawable film is usable on modern deep-drawing
~ automatic machines for packaging induqtrial medical
;~ equipment, semi-finished product~, and finished parts and
for packaging of food. The film produced according to the
15 invention can be completely recycled. -
In the prior art, there are various known composite film
structures containing scrap material based on polyamide and
polyolefins. The term "scrap material" here means waste - ~-~
20 film occurring e.g. in the production of laminated film, -~
; e.g. edge trimmings, starting rolls or cutting waste, which ~
is subsequently agglomerated and optionally regranulated. ~ ~ -
Most films made from scrap material are single-layer films
(e.g. JE' 04-1119809 or JE 03-237143), and will not be -~
25 further considered here -
~ : --
In the multilayer film sector, incorporation of scrap
material originated from the fact that edge trimmings,
which inevitably occur in the production process, were
returned to the process whenever possible. This is called
"recycling of edge trimmings". The aim is to incorporate
the scrap material substantially without affecting the
properties of the film (e.g. mechanical and optical
properties or transparency). The result is that only small
quantities of scrap material can be incorporated in this
manner. The scrap material is either added in small
quantities to a layer - usually internal - of the fil5m, or
forms a single layer between existing layers. Layers of
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polyamide and polyolefin scrap are morphologically
unhomogeneous and cannot be deep-drawn by themselves in the
prior art. As a result of the incompatibility of the
phases formed, micro-cracks occur even when not under
tension, and result in premature fracture under tensile
loads (Braun, D.: Chemische Prozesse bei der Herstellung
und Verarbeitung von Polymerblends: lD. Braun: "Chemical
processes during the manufacture and proceqqing of polymer
blend"] in "Aufbereiten von Polymerblends, VDI Verlag,
Dusseldorf (1989), pages 129 ff).
AU 88-26-473-A discloses a laminate containing an -
intermediate layer which can comprise scrap material
originating from the same film (e.g. edge trimmings). In
15 this case, obviously, the total composite material can be -
made heat-deformable only if the unhomogeneous, easily-torn
scrap layer is supported on both sides. Machinery for
encapsulating scrap layers i9 described in GB 2075-914.
US-PS 4 668 571 describes a three-layer structure having an -
internal layer which can incorporate scrap material from
the same film. To obtain the desired properties in this
case, pure materia} from the adjacent layers must be mixed
with the scrap layer.
~5 -
US-PS 4 647 509 describes a polystyrene-containing
multilayer structure having a first and a second layer
designed so that scrap material from the two layers can be
recycled by returning to the second layer.
All these films have the disadvantage that only scrap
material originating from the ~ame film can be returned
thereto, and no foreign material can be incorporated in the
scrap. Hitherto there has been no success in obtaining a
composite film comprising a scrap layer with only one
adjacent supporting layer and containing over 50% by weight
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of recycled material relative to the entire film and deep-
drawable.
The problem therefore is to produce a multilayer film which
is deep-drawable and ~ealable and contains large quantities
of recycled material based on polyamide and polyolefins.
To this end, the recycled material can contain any unsorted
polyamide/polyolefin waste film, e.g. produced during the
manufacture of polyamide/polyolefin films. The film
structure according to the invention, therefore, in
addition to being completely recyclable, must therefore
include a scrap layer capable of incorporating waste film
from other polyamide-polyolefin film structures.
The film must be deep-drawable and sealable and -
consequently of use in modern deep-drawing automatic
machines, either as a cover film or a blister film for
packaging. The film therefore must also have good
; 20 lubricating properties.
:.:
The film must have an optically homogeneous appearance, ~ -
both in the deep-drawn state and in the state before
shaping.
~25
Surprisingly this has been achieved by means of a Realable, ~ -
multi-layer recycled film compriæing at least one scrap ~
layer and a sealing layer, characterised in that ~ -
30 - the film is deep-drawable,
- the scrap layer consists of recycled polyamide/
polyolefin and a [primer], the proportion of recycled
material in the scrap layer being 60 to 98% by weight
and the proportion of primer being 2 to 40% by weight,
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- the recycled material has a polyamide content of 3 to
45% by weight and
- the sealing layer has one or more layers and consists
of polyolefinic polymer or copolymer, the layers
optionally being the same or different.
The polyamide/polyolefin recycled material can be
regenerated (granulated with admixtures after remelting),
or regranulated (granulated without admixtures after
remelting) or a~glomerated (without admixtures), prepared
from waste film. The proportion of polyamide in the
recycled material is 3 to 45% by weight. The polyamide is
either an aliphatic polyamide such as PA 6, PA 11, PA 12,
PA 66, PA 6.66, PA 6.8, PA 6.9, PA 6.10, PA 6.11 or
PA 6.12, or a copolymer of the monomer units therein or a
mixture of the aforementioned aliphatic polyamides. The
polyolefinic component consists of polymers such as high-
density, medium-density, low-density or linear low-density
polyethylene, polypropylene or polypropylene copolymers,
e~hylene/vinyl acetate copolymers, ethylene/vinyl alcohol
copolymers, ethylene acrylic acetate copolymers,
ethylene/methylacrylic acetate copolymers, ionomers or
adhesive residues from laminated composite films.
The primer is an anhydride-modified polyolefin or an
anhydride-modified ethylene/vinyl acetate copolymer.
Preferably it is an ethylene, propylene or ethylene/vinyl
acetate based primer grafted with maleic acid anhydride.
The sealing layer is made of conventional sealing material.
This can be a polyethylene, polypropylene, polypropylene
copolymer, ethylene/vinyl acetate copolymer, ethylene
acrylic acid copolymer, ethylene/methylene acrylic acid
copolymer or ionomer, or a blend of the aforementioned
polymers.
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Optionally the invention can contain an intermediate layer
consisting of polyamide or polyolefin or having the
structure polyamide/EVOH-polyamide, or a mixture of
polyamide and polyolefin enriched with primer. Optionally
5 also, a covering layer can be provided on the side remote -
from the sealing layer, using the same material~ as for the
intermediate layer. In both cases, aæ before, the film can
be made by adhesive lamination and/or co-extrusion.
Since both layers are unnecessary for giving deep-drawing
properties to the film, the intermediate and covering layer
can be used to vary the properties of the film (e.g. the
appearance and barrier properties). More particularly, use
can be made of polyamide (to obtain a brilliant appearance
and excellent mechanical strength), polyolefin (to obtain
excellent barriers against water-vapour), a mixture of
polyamide and polyolefin enriched with primer (to obtain
variable adjustable properties) or a polyamide/
EVOH/polyamide structure (excellent oxygen barrier). ~ -
Surprisingly, as a result of the structure of the film
according to the invention, the special requirements
regarding deep-drawing and sealing have been met. It could
not be expected that a mixture of incompatible polymers,
processed in a layer with small quantities of primer and
with only one adjacent support layer, could be deep-drawn
in a multilayer composite structure. It is also surprising
that the scrap layer can contain recycled material based on
polyamide and polyolefins but not originating from the same
film. Unexpectedly, the optical appearance of the film is
homogeneous and comparable in both the original and in the
deep-drawn state.
, .
Advantageously the claimed film is produced by co-
extrusion. If co-extrusion is impossible, the individual
layers are manufactured singly and subsequently joined by
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adhesive lamination. A combination of the processes i8
also possible. Known machinery conventional in the prior
art can be used.
An important feature for evaluating the invention is the
deep-drawing capacity. In order to determine the deep-
drawing capacity, previously-manufactured film samples were
tested on modern automatic deep-drawing machines ~e.g.
Tiromat or Multivac) used in the packaging industry. To
this end, webs of films tensioned in the machine were
heated in portions over a heating plate. The heat can be
applied either from the sealing side or from the side
remote therefrom. After being preheated by plates at
temperatures of 100 - 110C, the films were drawn by
negative pressure into a cavity having the frame dimensions
185 x 115 mm. The depth of the cavity was varied between
20 and 70 mm.
The result of deep drawing was marked as follows:
1. Unsatisfactory - every attempt to form a cavity
results in tears in the film:
Marked "--"
2. Defective - an unacceptable number of attempts to form
a cavity result in cracks in the film:
Marked "-"
3. Good - no cracks occur and the shape of the cavity is
good:
Marked "+"
The elongation at tear to DIN 53 455 was determined at the
same time as the deep-drawing capacity was experimentally
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evaluated. The "elongation at tear" means the alteration
in length of the te~t-piece in mm at the tearing force,
relative to the original measured length in mm (see
definition in DIN 53 455). To this end, tensile tests were
made to the aforementioned DIN. Test-pieces 15 mm wide
were investigated at 23C and 50% relative air humidity.
The test speed was 100 mm/min.
The invention will be illustrated with reference to the
10 following examples: -
A. Exam~le 1: -
Two-layer film having the structure: -
Scrap / ~va
120 / 50 ,um
The film was made by co-extrusion. The scrap layer
contained 20% by weight of primer and 80% by weight of
recycled material. The primer was an LLDPE-based polymer
grafted with maleic acid anhydride. The proportion of
~ 25 polyamide in the recycled material was 33% by weight. EVA
i is an ethylene/vinyl acetate copolymer containing 5% by
weight of vinyl acetate.
B. Exa~elQ Zl
Two-layer film having the structure:
8crap / PE
70 / 70 ,um -
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The film was made by adhesive lamination, the scrap layer
and the PE layer first being extruded in the form of a
single-layer film. The scrap layer contained 15% by weight
of primer and 85% by weight of recycled material. The
primer was an LLDPE-based polymer grafted with maleic acid
anhydride. The proportion of polyamide in the recycled
material was 33% by weight. PE is a commercial low-density
polyethylene.
C. Comparative Example 1:
Single-layer film having the structure:
Scrap
70 ~m
The film was extruded in a single layer. The scrap layer
contained 15% by weight of primer and 85% by weight of - -
recycled material. The primer was an LLDPE-based polymer
grafted with maleic acid anhydride. The content of
po}yamide in the recycled material was 33% by weight.
D. Comparative Examplç_2:
Single-layer film having the structure:
r~p
70 ~m
The film was extruded in a single layer. The scrap layer
contained < 1% by weight of primer and < 99% by weight of
recycled material. The proportion of polyamide in the
recycled material was 33% by weight.
The elongation at tear of the aforementioned filmq A, B, C
and D was measured to DIN 53 455 and the deep-drawing
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properties were evaluated as previously described. The
results are shown in Table 1:
Table 1: Comparison between the film structures A, B, C and
D
Elongation Deep-drawing Proportion of
at tear (%) properties of primer in
the scrap
A.Example 1 485 + 19 + 20%
B.Example 2 436 + 12 + 15%
15 C.Comparison
1 326 + 37 - 15%
D.Comparison
2 36 + 24 -- < 1%
The single-layer film D, which was produced substantially
without a primer, was clearly not deep-drawable. Film C
shows that the primer does not result in adequate deep-
drawing properties when used alone. Films A and B produced
according to the invention were surprisingly deep-drawable.
The measured elongation at tear emphasises the measured
deep-drawing properties. The deep-drawable films A and B
have much higher elongation at tear than films C and D,
which were not deep-drawable.
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