Note: Descriptions are shown in the official language in which they were submitted.
The invention relates to recycled film ba~ed on polyamide
and polyolefin waste occurring e.g. in the production of
laminated films. The invention relates to use of waste
material occurring in the manufacturing process and is
therefore of high ecological and economic importance. The
deep-drawable film is usable on modern deep-drawing
automatic machines for packaging industrial medical
equipment, semi-finished products and finished parts and
for packaging of food. The 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. JP 04-1119809 or JP 03-237143), and will not be
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 film, or
forms a single layer between existing layers. Layers of
5382- Forei gn countri es
21222~3
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: [D. Braun: "Chemical
processes during the manufacture and processing of polymer
blend"] in "Aufbereiten von Polymerblends, VDI Verlag,
Dusseldorf (1989), pages 129 ff).
AU 88-26-473 discloses a laminate containing an
intermediate layer which can comprise scrap material - -
originating from the same film (e.g. edge trimmings). In
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 scra~ layers is 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 material from the adjacent layers must be mixed
with the scrap layer.
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 same film can be returned
thereto, and no foreign material can be incorporated in the
scrap. There is no existing sealable film comprising a
scrap layer which can contain large quantities of either
WW 5382 2
`~ 21222~3
.
the same or foreign scrap material, based on polyamide and
polyolefins, and which is 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
lubricating properties.
. :
The film must have an optically homogeneous appearance,
both in the deep-drawn state and in the state before
shaping.
Surprisingly, this has been achieved by means of a ~ -
sealable, multi-layer recycled film comprising one scrap
layer, one sealing layer and one accompanying layer
disposed either between the scrap layer and the sealing
layer or externally on the side remote from the sealing
layer, characterised in that
- the film is deep-drawable,
- the scrap layer consists of recycled polyamide/
polyolefin and a primer, the proportion of recycled
-:
~L~2 3 --~
''-
-" 2122 ~J 5 3
material in the scrap layer being 60 to 98% by weight
and the proportion of primer being 2 to 40% by weight,
- the recycled material contains 15 to 45% by weight of
polyamide,
- the sealing layer has one or more layers and consists
of polyolefinic polymer or copolymer, the layers
optionally being the same or different, and
- the accompanying layer is of polyamide, polyolefin
EVOH and/or a primer or primer mixture.
The polyamide/polyolefin recycled material can be
regenerated ~granulated with admixtures after remelting),
or regranulated (granulated without admixtures after
remelting) or agglomerated (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, ethylene/~inyl 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.
WW 5382 4
~ 212~ ,~3
Preferably it is an ethylene, propylene or ethylene/vinyl
acetate based polymer 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.
The accompanying layer, which is disposed between the
sealing and the scrap layer or on the side remote from the
sealing layer, is used for varying the properties of the
film (e.g. the appearance and barrier properties). The
accompanying layer can be of polyamide (disposed externally
to give a brilliant appearance), or polyolefin (to obtain
excellent water-vapour barriers) or a polyamide/polyolefin
mixture enriched with primer (to obtain variable adjustable
properties) or a polyamide/EVOH/polyamide structure -
20 (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 an adjacent accompanying 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
.~ -
WW 5382 5
2 1 % ~ ~J ~ 3
layers are manufactured singly and subsequently joined by
adhesive lamination. A combination of the processes i~
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 "+"
: -
WW 5382 6
21222~3
The elongation at tear to DIN 53 455 was determined at thesame time as the deep-drawing capacity was experimentally
evaluated. The "elongation at tear" means the alteration
in length of the test-piece in mm at the tearing force,
S relative to the original measured length in mm (see
definition in DIN 53 455). To this end, ten~ile 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.
A. Example 1:
Multilayer film having the structure:
PA-PO-HV/~cr~p/EV~
lS / lOS / S0 ~m
The film was produced by co-extrusion. PA-PO-HV is a
polyamide/polyolefin/primer mixture consisting of 35% by
weight of polyamide 6, 10% by weight of primer in the form
of LLDPE-based polymer grafted with maleic acid anhydride,
and 55% by weight of low-density polyethylene (density 923
kg/m3). The scrap layer contained 20% by weight of primer
and 80% by weight of recycled material. The primer was the
same as in the PA-PO-HV layer. The proportion of polyamide
in the recycled material was 33% by weight. EVA is an
ethylene/vinyl acetate copolymer containing 5% by weight of -~
vinyl acetate.
B. Example 2:
:~
Multilayer film having the structure: :~
Scrap / mr / PA / ~ / PE / ~VA
100 / 10 / 20 / - / 20 / 40 ~m
WW 5382 - 7
: ::
2122233
The scrap/HV/PA structure was produced by flat film co-
extrusion and the PE-EVA structure was produced by blown
film co-extrusion. Next, the aforementioned ~tructures
were bonded together by adhesive lamination. 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 content of
polyamide in the recycled material was 33% by weight. HV
is a primer and the same polymer as the primer in the scrap
layer. The polyamide ~PA) was a polyamide 6. The adhesive
system (K) was a solvent-containing aromatic two-component
polyurethane adhesive system. PE is a commercial low-
density polyethylene and EVA is an ethylene/vinyl acetate
copolymer containing 5% by weight of vinyl acetate.
C. Example 3:
Multilayer film having the structure:
PA ~ ~V / Scrap ~ X / PE / EV~
20 / 10 / 100 / - / 20 / 40 ~m
The scrap/HV/PA structure was produced by flat film co-
extrusion and the PE-EVA structure was produced by blown
film co-extrusion. Next, the aforementioned structures
were bonded together by adhesive lamination. The scrap ~ -
layer contained 20% by weight of primer and 80% by weight
of recycled material. The primer was an LLDPE-based
copolymer grafted with maleic acid anhydride. The content
of polyamide in the recycled material was 33% by weight.
HV is a primer and the same polymer as the primer in the
scrap layer. The polyamide (PA) was a polyamide 6. The
adhesive system (K) was a solvent-containing aromatic two-
component polyurethane adhesive system. PE is a commercial
low-density polyethylene and EVA is an ethylene/vinyl
acetate copolymer containing 5% by weight of vinyl acetate.
~.
WW 5382 8
2122283
D. Comparative Example 1:
Single-layer film having the structure:
Scs~p
70 ,um
The film was extruded in a single layer. The scrap layer --
contained 1S% 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
polyamide in the recycled material was 33% by weight.
E. Comparative Example 2.
Single-layer film having the structure:
Scr~p
70 ,um
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
25 polyamide in the recycled material was 33% by weight. ~
The elongation at tear of the aforementioned films A, B, C, - -
D and E was determined to DIN 53 455 and the deep-drawing
properties were evaluated as previously described.
The result is shown in Table 1:
WW 5382 9
21~22~3
Table 1: Comparison between the film structures A, B, C, D
and E
Elongation Deep-drawing Proportion of
at tear t%) properties primer in the
scrap
A. Example 1 485 + 19 ~ 20% by weight
B. Example 2 464 + 9 + 20% by weight
C. Example 3 396 + 26 + 20% by weight
. . _ . . . _
15 D. Comparison
1 336 + 37 - 15% by weight
E. Comparison
2 36 + 24 -- < 1% by weight
The single-layer film E, which was produced substantially
without a primer, was clearly not deep-drawable. Film D
shows that the primer does not result in adequate deep-
drawing properties when used alone. Films A, B and Cproduced according to the invention were surprisingly deep-
drawable. The measured elongation at tear emphasises the
measured deep-drawing properties. The deep-drawable films
A, B and C had much higher elongation at tear than films D
and E, which were not deep-drawable.
-
WW 5382 10
-
.. . .. .. .... . . . .
