Note: Descriptions are shown in the official language in which they were submitted.
1
METHOD FOR THE PRODUCTION OF POLYAMIDE NANOCOMPOSITES,
CORRESPONDING PACKAGING MATERIALS AND MOULDED BODIES.
Field of the invention
The present invention relates to a method for the production of polyamide
nanocomposites made from polyamides and phyllosilicates. Polyamide
nanocomposites
produced according to the present method in accordance with the invention can
be used
for producing transparent packaging means, especially packaging means with
high UV
absorption, as well as improved gas and aroma barrier effect. Moreover, the
polyamide
nanocomposites produced in accordance with the invention further offer the
possibility of
producing moulded bodies, hollow bodies, semi-finished products, plates,
tubes, etc.,
even such of larger thickness or wall thickness.
Related technical background
In the field of plastic, nanocomposites materials are understood as polymer
formulations which comprise finely dispersed phyllosilicates such as clay
minerals
within the polymer matrix. The relevant aspect is that the phyllosilicates are
exfoliated
up to the individual layers, i.e. they are split up and then dispersed. The
properties of
such nanocomposites have already been published in numerous patent
specifications and specialised publications. It is known that finely dispersed
clay
minerals or phyllosilicates provide the composite with improved properties
such as
increased mechanical strength, improved barrier properties against oxygen and
carbon dioxide, among other things. The improvement of the properties of a
polymer
matrix by means of finely dispersed clay materials has already been described
in
closer detail in the patents US 4,739,007 and US 4,810,734 for example.
Nanocomposites have also already entered the packaging sector. The exfoliated
clay
minerals ensure in packaging films an inhibited diffusion of gas molecules
such as
oxygen, carbon dioxide or aromatics through the packaging material.
Problems observed in prior art
Polyamides have been established for many years as preferred thermoplastic
polymeric
materials in the packaging field. One of the main reasons is the property
profile of this
class of materials such as favourable barrier effect against oxygen and carbon
dioxide
as well as the outstanding mechanical properties of the packaging foils made
of
polyamide. When using aliphatic polyamides as a matrix for nanocomposite
materials, a
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W003/064503 2
reduction in the transparency can be observed because these nanocomposite
filling
materials are capable of increasing the crystallisation of the aliphatic
polyamides, which
on the other hand can strongly impair the transparency of such products.
A desirable goal in the packaging field is the polyamide nanocomposite as a
part of
multiple-layer films in combination with other polymers such as polyolefines.
Multiple-
layer films which are composed of different types of polymers with mutual
adverse
adhesion can be rigidly connected with each other by suitable bonding layers.
Such
multiple-layer films can be used to produce a large variety of packaging
products such
as containers, bottles, bags, thermomouldable products, tubes, etc. The
products can
be provided with a dyed, light-permeable or transparent configuration. In
order to enable
the successful marketing of a large variety of products, the presentation of
these
products towards the customer plays an increasingly important role. To allow
the
customers to see what is contained in a packaging, the transparency is of
decisive
importance. Numerous suitable barrier materials consist of aliphatic polymers.
Such
compounds usually crystallise during the cooling process and lead to packaging
materials with reduced transparency. The reduction of the transparency by the
crystallisation process can be remedied by using amorphous, partially aromatic
polyamides.
The durability of packaged perishable foodstuffs and other products is defined
predominantly by the oxygen barrier of a packaging. The UV barrier also plays
a
decisive role in numerous other packaging applications because UV rays are
able to
damage sensitive foodstuffs (like oxygen). When storing sensitive foodstuffs
such as
meat in the cold shelves of major distributors, they are often subjected to
damaging UV
radiation because many of the employed light sources also radiate light in the
UV
spectrum.
Special expensive UV absorbers such as Tinuvin 234, a hydroxyl phenyl
benzotriazole
UV absorber produced by Ciba Specialty Chemicals Inc., Basel, Switzerland, can
be
introduced into the materials which represent components of said multiple-
layer
composites. Since these UV absorbers can migrate under application conditions,
the
use of these compounds often requires an additional layer to the multiple-
layer
composite in order to prevent the migration of the UV absorbers into the
packaged
product or into the atmosphere. The addition of an additional layer to the
multiple-layer
CA 02474604 2011-01-14
3
film is not possible in all cases because the number of producible layers is
defined
by the configuration of the film extrusion systems.
The packaging of especially perishable foodstuffs with a further extended
durability
cannot easily be solved by the packaging systems and additives currently
available
on the market. Especially the enabling of a combination of all of the
following listed
properties in a single packaging requires further improvements. Such
properties are:
= Highly transparent packaging
High mechanical strengths
= Extremely high gas barrier effect against oxygen and carbon dioxide
= High aroma barrier effect
= High UV protection
= Additionally extended durability in cold shelves
= Official approval as foodstuff packaging
Summary of the invention
The invention is therefore based on the object of providing a method for
producing
polyamide nanocomposites with which, among other things, it is possible to
produce
transparent and clear packaging materials or packaging means with high
mechanical properties, a high barrier effect against oxygen and carbon dioxide
and
which simultaneously also offer an increased protection against UV radiation.
With respect to a method for the production of polyamide nanocomposites, this
object is achieved with a method for the production of a polyamide
nanocomposite
made from at least one polyamide base polymer and an organically-modified
phyllosilicate in a double-screw extruder with a front-feeder and a side-
feeder,
CA 02474604 2009-11-26
4
wherein a portion (A) of from 8 to 15 wt. % of a granulate of the base
polymer,
based on 100 wt. % of the nanocomposite, is introduced in a dosed manner in
the front-feeder of the double-screw extruder;
and a main portion (B) of the granulate of the base polymer is introduced
through the side-feeder of the double-screw extruder;
wherein 2 to 8 wt. %, based on a total of 100 wt. % of the nanocomposite, of
the organically-modified phyllosilicate is introduced in a dosed manner by
gravity and without the use of a side-feeder into the melt of the granulate
portion (A) of the base polymer;
wherein the melt of the polyamide nanocomposite is subjected to a pressure of
less than 200 mbar within the double-screw extruder;
and wherein a film made of this polyamide nanocomposite has a film note (FN)
of less than 10.
With respect to a packaging means with high UV absorption as well as improved
gas and aroma barrier effect, this object is achieved with a packaging
material with
high UV absorption and improved gas and aroma barrier effect which is produced
with a method that comprises the production of polyamide nanocomposites made
of
base polymers containing aromatic components and of organically-modified
phyllosilicates in a double-screw extruder with a front-feeder and a side-
feeder,
characterized in that for the production of the polyamide nanocomposite a
portion
(A) from 8 to 15 wt.% of a granulate of a base polymer is introduced in a
dosed
manner in the front-feeder of the double-screw extruder and the main portion
(B) of
the granulate of the base polymer is introduced by means of the side-feeder of
the
double-screw extruder and that 2 to 8 wt.% of the modified phyllosilicate is
introduced into the melt of the granulate portion (A) of the base polymer,
with the
recipe components adding up to a sum total of 100 wt.%,
wherein a film made of this polyamide nanocomposite has a film note (FN) of
less
than 10.
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4a
In accordance with the invention, polyamide nanocomposite materials are
produced
by admixing an organically-modified phyllosilicate in a compounding process by
means of a double-screw extruder (e.g. a "WP ZSK 25" of Werner & Pfleiderer).
For
the tests performed in connection with the present invention, the following
screw
geometries were used by taking the percentage number of screw elements per
screw area into account:
Employed screw geometries (Table 1):
Screw D Screw E Screw F
Screw region Screw region Screw region
Worm elements K L M K L M K L M
Conveyor elements 86 40 85 53 100 72 70 50 70
Left conveyor elements - 20 4 7 - - - - -
(retarding)
Kneading blocks 14 20 7 20 - 8 24 - 9
Kneading blocks (not - - - 20 - - - - -
conveying)
Kneading blocks (left - 20 4 - - 3 6 - 3
conveying)
Mixing elements (left - - - - - 6 - 17 6
conveying)
Spacing disks 1 mm - - - - 11 - 23 12
Legend on Table 1:
Screw regions: K Front-feeder up to dosing of modified layer mineral
L Dosing of modified layer mineral up to side feeder
M Side feeder up to die
In the case of screw D, the dosing of the modified layer mineral into the melt
is not
possible.
In order to determine the film note (FN), a flat film is extruded from the
granulate,
e.g. with a "Plasti-Corder" of Brabender Co. For a period of 20 minutes the
film is
CA 02474604 2009-11-26
4b
moved past an optical system which detects the impurities in the film, counts
them
(stated in m2) and determines their size. Such an optical system with an
evaluation
program is sold by OCS GmbH Witten under the name of "Folientest FT4" (Film
Test FT4).
The impurities are subdivided into 10 size classes (cf. Table 2). These
classes are
weighted with different weighting factors.
Table 2:
Size class Weight factor Size class Weight factor
CA 02474604 2009-11-26
[pm] (fi) [pm] (fi)
< 100 0.1 500 - 600 40
100 - 200 1 600 - 700 55
200 - 300 10 700 - 800 100
300 - 400 20 800 - 900 200
400 - 500 30 > 900 350
The film note is calculated according to the following formula by adding the
sum
totals of the weighted impurities per size class and by division by 1000.
xi =fi
I=1 (1)
10 FN =
1000
The following applies: xi = Impurities / m2 / size class
fi = Weight factors
Phyllosilicates within the terms of the invention are understood as 1:1 as
well as 2:1
phyllosilicates. In such systems, layers of SiO4 tetrahedrons are regularly
linked with
such made of M(O,OH)6 octahedrons. M stands for metal ions such as Al, Mg, Fe.
In 1:1
phyllosilicates one tetrahedron layer and an octahedron layer are linked with
each other.
Examples are kaolin and serpentine minerals.
In the case of 2:1 three-layer silicates, two tetrahedron layers are each
combined with
one octahedron layer. If not all octahedron places are occupied with cations
of the
required charge for compensating the negative charge of the Si04 tetrahedrons
and the
hydroxide ions, charged layers will occur. This negative charge is compensated
by the
insertion of monovalent cations such as potassium, sodium or lithium or
bivalent cations
such as calcium in the space between the layers. Examples for 2:1
phyllosilicates are
French chalk, mica, vermiculite, illites and bentonites, with the bentonites,
which include
montmorillonite and hectorite among others, being easily swellable with water
as a
result of their layer charge. Moreover, cations are easily accessible for
exchange
processes.
6
The layer thicknesses of the phyllosilicates are usually 0.5 nm to 2.0 nm
prior to
swelling, especially preferably 0.8 nm to 1.5 nm (distance of the upper edge
of the
layer to the next following upper edge of the layer). It is possible to
further increase
the layer distance, such that the phyllosilicate is converted with polyamide
monomers (swelling), e.g. at temperatures of 25 C to 300 C, preferably 80 C to
280 C and especially 80 C to 160 C over a dwell time of usually 5 to 120
minutes,
preferably 10 to 60 minutes. Depending on the dwell time and the type of the
chosen monomer, the layer distance will additionally increase by 1 nm to 15
nm,
preferably 1 nm to 5 nm. The length of the platelets is usually up to 800 nm,
preferably up to 400 nm. Any existing or constituting pre-polymers usually
also
contribute to the swelling of the phyllosilicates.
The swellable phyllosilicates are characterized by their ion exchange capacity
CEC
(meq/g) and their layer distance dL. Typical values for CEC are at 0.7 to 0.8
meq/g.
The layer distance in a dry, untreated montmorillonite is at 1 nm and
increases by
swelling with water or application with organic compounds to values up to 5
nm.
Examples for cations which can be used for exchange reactions are ammonium
salts of primary amines with at least six carbon atoms such as hexanamine,
decanamine, dodecanamine, stearylamine, hydrogenated fatty acid amines or even
quarternary ammonium compounds such as ammonium salts of a-,w- amino acids
with at least six carbon atoms.
Suitable anions are chlorides, sulphates or even phosphates. In addition to
ammonium salts, it is also possible to use sulphonium or phosphonium salts
such as
tetraphenyl or tetrabutyl phosphonium halogenides.
Since polymers and minerals usually have very different surface tensions,
bonding
agents can also be used in accordance with the invention for treating the
minerals in
addition to the cation exchange. Titanates or even hydrosilicons such as y-
aminopropyl triethoxysilane.
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7
The invention will now be explained in closer detail by reference to the
following
examples and results:
As examples in accordance with the invention, two polyamide nanocomposite
formulations were produced with additions of organically-modified
phyllosilicates of
wt. % and 8 wt. %. An amorphous, partly aromatic copolyamide 61/6T
(isophthalic
acid/terephthalic acid = 2/1) was used as a polyamide matrix which is
obtainable on
the market under the name Grivory G21 of EMS-CHEMIE AG.
As a comparative example a PA 6 which is obtainable on the market under the
name "Grilon F 40 NL" of EMS-CHEMIE AG was produced with 5 wt. % of modified
phyllosilicate. The production of the polyamide nanocomposites was made by the
addition of specially modified phyllosilicate.
In accordance with the invention, it is now possible, as already described
above, to
use phyllosilicates which were modified with onium ions. Such modified
phyllosilicates can be obtained on the market from several firms such as
Sudchemie
(D), Southern Clay Products (USA), Nanocor (USA), CO-OP (J). The modified
phyllosilicates used for the comparative examples and examples in accordance
with
the invention concern montmorillonite treated with quarternary ammonium ions.
The
ligands of the nitrogen are methyl, hydroxyethyl and hydrogenated tallow or
non-
hydrogenated tallow.
The compounded materials was thereafter granulated and dried for 24 hours in
vacuum at 90 C. The compounded polyamide phyllosilicate materials were
processed on a casting film unit of Dr. Collin GmbH, extruder type "3300
D30x25D",
take-off type "136/350" into films in the following manner. The granulates
were
molten in a conventional single-screw, three-heat-zone extruder with a
temperature
profile of 250 C to 260 C. The melt was drawn off through a sheet die with a
die gap
of 0.5 mm directly onto a cooling roller with a take-off speed of 8 m per
minute and
with a set temperature of 130 C.
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7a
Films with a thickness of approximately 50 pm have been produced with the
above
setup:
No phyllosilicates were added in the comparative examples I (aliphatic
polyamide)
and III (partly aromatic polyamide). Examples IV and V represent a combination
in
accordance with the invention of partly aromatic polyamide and
phyllosilicates.
Comparative example I PA 6 "Grilon F40 NL"
Comparative example II PA 6 + 5 wt. % of phyllosilicate
Comparative example III PA 61/6T "Grivory G21"
l
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'WO03/064503 8
Inventive example IV PA 61/6T + 5 wt. % of phyllosilicate
Inventive example V PA 61/6T + 8 wt. % of phyllosilicate
The following measurements were performed on the materials of the comparative
examples and the films produced according to the inventive examples:
The oxygen transmission rate (OTR) was measured by means of the Mocon
measuring
instrument of type "Oxtrans 100" at 23 C and at 0% relative humidity and at
85%
relative humidity ("r.h."; cf. Table 3).
The UV absorption values were determined by means of a Perkin-Elmer Lambda "15
UVNIS" spectrophotometer. The measurements were performed in a wavelength
region
of 200 nm to 400 nm. The recording of the light transmission occurred in the
measured
wavelength region on a scale between 0% and 100%. The evaluation in the
improvement of the UV barrier was made by comparing the surfaces under the
absorption curves of different films, with comparative example III, which only
contained
Grivory G21 without phyllosilicate addition, being set as 100.
In addition, the light transmission was also determined in the visible
wavelength region
of 550 nm, leading to an indication of the transparency of the film. The
established
values are compiled in Table 3 below.
Table 3:
Oxygen permeability % transmission of
cm3/m2 day bar cm3/m2 day bar UV in comparison tight at 550 nm
23 C/0% r.h. 23 C/85% r.h. with Grivory G21 at
200 to 400 nm
Comparative example 25 70 63 70
1
Comparative example 12 30 55 65
11
Comparative example 30 10 100 92
Ill
Example IV 14 5 79 85
Example V 13 4 63 82
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'WO03/064503 9
As is shown by the measurement results of the two examples IV and V in
accordance
with the invention, these films show strongly improved values relating to
oxygen
diffusion and UV absorption as compared with the comparative examples. The
relatively
good values as shown in Table 3 under the comparative examples I and II for UV
absorptions of PA 6 film samples can be explained with a reduced transparency
relative
to the 6116T variants. The measurement of the light transmission values at 550
nm
clearly show this reduced light transmitting capacity.
The employed polyamides containing aromatic groups also come with a favourable
UV
barrier effect, although these polyamides also have a high transparency. The
addition of
a phyllosilicate to these special polyamides further increases the favourable
UV barrier
without substantially impairing the excellent transparency of these products.
The following tables compare exemplary parameters of the method in accordance
with
the invention with parameters of the comparative examples:
Base polymer A (Table 4):
Test No. Dosing point for Modified phyllosilicate Throughput Vacuum Screw Film
base polymer A Type Quantity Dosing point [kg/h] [mbar] grade
[Wt.%]
Comp.ex.1 Front feeder G 5 Front-feeder 10 150 D
Comp.ex.2 Front-feeder G 5 SF 15 150 D *
Comp.ex.3 Front-feeder G 5 MB 20 150 D
Comp.ex.4 Front-feeder + G 5 Front-feeder 20 150 D *
SF
Comp.ex.5 Front-feeder + G 5 Front-feeder 20 150 E 9.19
SF
Example 1 Front-feeder + G 5 Melt 20 150 E 0.67
SF
Example 2 Front-feeder + H 4.5 Melt 20 150 E 0.21
SF
Example 3 Front-feeder + G 5 Melt 20 50 F 1.80
SF
Example 4 Front-feeder + H 4.5 Melt 20 50 F 0.80
SF
PA 61/6T was used each time as base polymer. The change to another screw
improved
the film quality in comparative example 5 to such an extent that a film degree
can be
CA 02474604 2004-07-27
WO03/064503 10
determined. A film degree of around 10 is insufficient however. A strong
improvement in
the film degree is achieved only by a combination of all measures in
accordance with
the invention (cf. examples 1 to 4).
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WO031064503 11
Base polymer B (Table 5):
Test No. Dosing point for Modified phyllosilicate Throughput Vacuum Screw Film
base polymer B Type Quantity Dosing point [kg/h] [mbar] grade
[Wt.%]
Comp.ex.6 Front-feeder G 5 SF 15 150 D *
Comp.ex.7 Front-feeder + G 5 Front-feeder 20 150 D
SF
Comp.ex.8 Front-feeder + G 5 Front-feeder 20 150 E 11.62
SF
Example 5 Front-feeder + G 5 Melt 20 150 E 0.37
SF
Example 6 Front-feeder + H 4.5 Melt 20 150 E 0.62
SF
Example 7 Front-feeder + G 5 Melt 20 50 F 1.43
SF
PA 6 / PA 61/6T Blend was used in each case as base polymer B. In the
comparative
example 7, the split-up of the base polymer B into two parts and the dosing of
the same
at different places already leads to an improvement in the film quality. The
determination of a film degree is only enabled when also the screw geometry is
changed. A very strong improvement in the film degree is achieved only by the
combination of all measures in accordance with the invention (cf. examples 5
to 7).
Base polymer C (Table 6):
Test No. Dosing point for Modified phyllosilicate Throughput Vacuum Screw Film
base polymer C Type Quantity Dosing point [kg/h] [mbar] grade
[Wt. %]
Comp.ex.9 Front-feeder G 5 Front-feeder 10 150 D
Comp.ex.10 Front-feeder G 5 SF 15 150 D *
Comp.ex.11 Front-feeder + G 5 Front-feeder 20 150 D **
SF
Comp.ex.12 Front-feeder + G 5 Front-feeder 20 150 E 21.02
SF
Example 8 Front-feeder + H 4.5 Melt 20 150 E 3.40
SF
Example 9 Front-feeder + G 5 Melt 20 50 F 4.40
SF
Example 10 Front-feeder + G 3.2 Melt 20 50 F 5.61
12
1SF
PA MXD6/MXDI was used in each case as base polymer C. As a result of the split-
up of
the base polymer into two parts and the dosing of the same at different
locations of the
extruder, an improvement in the film quality is achieved in comparative
example 11 as
well. The determination of a film degree is also only enabled when the screw
geometry is
changed. Depending on the employed phyllosilicate, a strong improvement in the
film
degree is achieved only through a renewed change in the screw geometry and the
combination of all measures in accordance with the invention (cf. examples 8
to 10).
Legend in connection with Tables 4 to 6:
SF: Side-feeder
MB: Masterbatch: 1St extrusion: Production of MB (ratio granulate : mod.
phyllosilicate is approx. 70/30). Both in front-feeder.
2nd extrusion: Incorporation of MB in residual granulate.
Both in front-feeder.
Mod. Phyllosilicate: G Montmorillonite, modification;
Quarternary ammonium compound with methyl,
bis-hydroxyethyl, hydrogenated tallow;
H Montmorillonite, modification;
Quarternary ammonium compound with methyl,
bis-hydroxyethyl, tallow;
Screws: D Dosing of the modified phyllosilicate in the melt
not possible;
E No favourable mixing effect between phyllosilicate
Addition and side-feeder;
F Favourable mixing effect between phyllosilicate addition
and side feeder;
Film degree: Very bad film quality: Determination of the film degree not
possible.
** Bad film quality: Determination of the film degree not
possible.
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13
It was surprisingly noticed that the base film quality was obtained when a
small part A
(preferably 8 to 15 wt. %, especially preferably 10 to 12 wt. %) of the
granulate of the
base polymer is dosed in the front-feeder, but that the main part B is added
at a later time
via a side-feeder. The modified phyllosilicate (preferably 2 to 8 wt. %, more
preferably 2
to 5 wt. %, especially preferably 2.5 to 5 wt. %) is dosed into the melt of
the granulate
portion A, preferably without using a side-feeder, simply by gravity. All data
in wt. % relate
to the sum total of the recipe components of 100 wt. %.
The extrusion parameters (low temperature profile, high speed, high
throughput) and the
screw geometry are preferably chosen in such a way that a high shearing is
achieved.
The speed of the screw is preferably more than 200 revolutions per minute
(rpm). More
preferably the speed is 300 rpm, and especially preferably the speed is 400
rpm.
The screw geometry is also relevant. It is necessary to ensure a favourable
melting of the
granulate portion A, e.g. by kneading blocks, before the phyllosilicate is
added. After its
addition and before the side-feeder it is necessary to provide a favourable
mixing effect
again. After the side-feeder it is necessary to provide a sufficient kneading
and mixing
effect. Measures which increase the dwell time also have a positive effect on
the result,
but should not lead to an excessive degradation of the base polymers. The
employed
screw geometries are summarized in Table 1. Moreover, the screw should
preferably be
configured in such a manner that for the purpose of degassing the application
of vacuum
before the die is enabled. A pressure or vacuum of less than 200 mbars is
preferable; a
pressure or vacuum of less than 50 mbars is especially preferable.
A high throughput is also preferable. A throughput of 20 kg/h in combination
with these
recipes constitutes the maximum amount possible for the employed double-screw
extruder (WP ZSK 25). Generally, operations should be conducted in the upper
quarter
of the throughput and speed range of the employed extruder, preferably at the
upper
throughput and speed limit. The throughput limit is determined by the maximum
possible
torque at the desired low temperatures.
The temperatures set on the extruder must be chosen rather low relating to the
melting
point and the melt viscosity of the polymer. Temperatures are preferable which
are 10 C
CA 02474604 2007-11-21
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' W003/064503 14
to 20 C lower than in the incorporation of other filling materials. In the
case of
amorphous base polymers, 10 C to 40 C are mostly suitable, preferably
temperatures
which are 20 C to 40 C lower (relating to the entire T-profile on the
extruder) than usual.
The following temperature profile was set for the processing of PA 61/6T, PA 6
/ PA
61/6T - Blends and PA MXD6/MXDI: Front-feeder 10 C, rising temperatures from
220 C
to 240 C, die temperature 240 C. Operations were conducted at a screw speed of
400
rpm.
The polyamide nanocomposites produced in accordance with the invention can be
processed with conventional plastic processing methods into different
articles, e.g. films,
tubes, bags, bottles and containers. They can be produced either by
monoextrusion or
coextrusion methods. Suitable plastic processing methods are blow or cast film
methods, extrusion blow moulding methods, transfer stretch-blow moulding,
injection
blow moulding, pipe extrusion methods and laminate methods.
Moreover, the use of the method in accordance with the invention for producing
polyamide nanocomposites offers the possibility of producing moulded bodies,
hollow
bodies, semi-finished products, plates, pipes, etc. even with larger wall
thicknesses.
Preferred processing methods which are generally known comprise injection
moulding,
internal gas pressure, and profile extrusion methods as well as blow moulding
by means
of standard extrusion, 3D extrusion and vacuum blow moulding methods. Moulded
bodies include for example radiator tubes, cooling water containers,
compensating
reservoirs and tubes and containers guiding other media (especially media with
higher
temperatures) as are used in the production of means of transport such as
cars,
airplanes, ships, etc.
The packaging articles can be arranged as a single-layer or multiple-layer
packaging. In
the case of multi-layer packaging, the polyamide nanocomposite material can be
used
as outside layer, intermediate layer or also as innermost layer in direct
contact with the
product.
A further embodiment of the invention also relates to the combination of said
polyamide
nanocomposites in combination with a multi-layer composite. The barrier effect
of this
layer is further improved by using phyllosilicates in a barrier layer. This
allows reducing
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' WO03/064503 15
the layer thickness of the barrier layer for achieving a certain required
barrier effect.
Since the barrier material in multi-layer composites mostly represents the
most
expensive component of the packaging, the entire packaging system can thus be
made
cheaper. A further possibility for reducing the costs for the packaging is the
outstanding
UV barrier effect of the partly aromatic polyamide nanocomposites. The use of
the
expensive, special organic UV absorbers can be reduced or entirely eliminated
by using
these polymer formulations, thus avoiding further costs for the required
packaging
system. Organic UV absorbers are also subject to a certain migration, which
may lead
to problems concerning the foodstuff suitability of packaging materials.
Examples for possible applications of the present invention in the packaging
field,
without any limiting effect for the scope of validity of the invention, are
packagings for
semi-finished products and products such as foodstuffs, meat products, cheese
and
milk products, toothpastes, cosmetic products, beverages, paint, varnishes or
detergents. Such packagings include toothpaste tubes, tubes for cosmetic
products and
foodstuffs, packagings for cosmetic products, body care, detergents,
beverages,
foodstuffs, etc.
Surprisingly, it was found that complex packaging problems can be solved by
choosing
special polyamides which are used as matrix polyamides and by special
compounding
methods. Potential polyamides are such which contain aromatic components.
Suitable
polyamides of this type can contain PA 61/6T, PA 6 / PA 61/6T blends or co-
polyamides
produced from HMDA and/or MXDA and aliphatic and/or aromatic dicarboxylic
acids.
Moreover, the processing in accordance with the invention of polyamides based
on
lactams (lactam-6, -11, -12) or other polymers is possible.
Packaging produced by using the method in accordance with the invention offer
extended durability to especially to perishable packaged goods which are
sensitive to
the permeability of packaging covers towards gases, especially oxygen and
carbon
dioxide. Such packaging also shows an improved barrier effect against spices
and
flavours such as distilled oils. The packaging also show an unexpected
reduction in the
transmission of UV light.
