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Films or hollow articles containin~ a Polvamide laver
This invention relates to single or multi-layer films or hollow articles cont~ining at
5 least one polyamide layer which contains nano-disperse fluorine mica, to packages
produced therefrom and to the uses of polyamide filled with nano-disperse fluorine
mica for the production of films or hollow articles.
Films and hollow articles which contain a polyamide layer exhibit many advanta-
geous properties. Good optical properties may in particular be mentioned, such as
10 elevated transparency in uncoloured films or hollow articles and elevated gloss.
Good mechanical properties, such as elevated toughness, elevated puncture
resistance, elevated tear propagation strength and others, are also significant.Moreover, production and further processing are, of course, simple.
Low permeability to oxygen, water vapour, carbon dioxide, fats, flavour sub-
15 stances and other essential components of the packaged goods or to substanceswhich should be kept away from the packaged goods is of particular significance
for many applications for films and hollow articles, in particular for use in the
p~rk~ging sector.
In many cases, the stated requirements placed upon films or hollow articles are
20 achieved by combining various materials in a multi-layer composite. In such acomposite, the stated low permeability to oxygen is either achieved in part by the
polyamide layer or layers of so-called high barrier materials are additionally used,
such as for example polyvinylidene chloride or ethylene/vinyl alcohol copolymers(generally known by the abbreviation EVAL).
25 The use of high barrier layers has many disadvantages. Thus, the halogen content
in the polyvinylidene chloride is frequently unwallted. Moreover, the high barrier
m~teri~l~ are often expensive, difficult to obtain and exhibit disadvantages with
regard to processability, such as for example low heat resistance.
When high barrier layers are dispensed with due to the stated disadvantages, low30 oxygen permeability of a multi-layer composite film or a multi-layer composite
hollow article may, to a certain extent, be ensured by a polyamide layer. However,
the oxygen barrier action of polyamide is frequently too low when it is used in a
layer thickness such as is required to ensure adequate mechanical properties of a
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multi-layer composite film or of a multi-layer composite hollow article. Using the
polyamide in greater thicknesses solely to achieve an adequate oxygen barrier isgenerally prohibitively expensive.
EP-A 358 415 describes films made from polyamides which contain phyllosilicates
5 and, by virtue of the phyllosilicate, have an increased oxygen barrier. However, it
is only possible to incorporate the montmorillonite described in the Examples inEP-A 358 415 into the polyamide by means of a very elaborate process
(montmorillonite must first be reacted with a swelling agent, such as for example
an amino acid, before it can be incorporated into the polyamide).
EP-A 605 005 describes a composition prepared from polyamide and fluorine
mica. Films of this moulding composition are not described. It is not usual to
produce film from polyamides cont~ining a mineral filler such as, for example,
fluorine mica, because these films are generally not transparent, have low glossand poor mechanical properties, such as for example low toughness.
15 The object thus arose of increasing the described excessively low oxygen barrier
action of the polyamide by suitably modifying the polyamide, without impairing
the other desired properties of the polyamide, in particular transparency, gloss or
toughness. Moreover, it must be possible simply and cheaply to produce and
process the modified polyamide.
20 It has surprisingly now been found that polyamides to which fluorine mica hasbeen added as an additive achieve the stated object if the fluorine mica particles
have a sufficiently small particle size. Polyamides provided with fluorine mica of
a sufficiently small particle size exhibit reduced oxygen permeability, wherein the
remaining advantageous properties of the polyamides, such as for example
25 transparency, gloss and toughness, are adequately retained.
The present invention provides single or multi-layer films or hollow articles
cont~ining at least one polyamide layer, wherein the polyamide layer contains
finely dispersed fluorine mica.
The present invention moreover provides the use of polyamide filled with nano-
30 disperse fluorine mica for the production of single or multi-layer films or hollow
articles.
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The present invention furthermore provides packages made from a film according
to the invention or from a hollow article according to the invention.
The finely dispersed fluorine mica in the polyamide layer is a fluorine mica of the
formula (I)
x(MF) - y(aMgF2 - bMgO) - zSiO2
wherein
M denotes an alkali metal and the coefficients x, y, z, a and b have the
following meaning:
0.1<x<2;2~y<3.5;3<z~4;0<a<1;0<b<1anda+b=1.
10 Preferably used fluorine micas of the above-stated formula are those in which M
denotes sodium, lithium or potassium, wherein potassium is not used alone, but
only in addition to lithium or sodium in a proportion by weight of up to a
maximum of one third.
The average particle size of the fluorine mica present in the polyamide layer is15 less than 1 micrometre. The average particle size of the fluorine mica is preferably
less than 100 nanometres. The average particle size of the fluorine mica is
particularly preferably less than 50 nanometres. The particles generally have a size
of at least 0.5 nm.
Average particle size is determined by visual inspection of transmitting electron
20 micrographs of ultra-thin sections of the corresponding moulding compositions. In
the event that the particles are highly anisotropic, particle size is taken to mean
the dimension of the smallest axis (for example in the case of a lamellar particle,
particle size is taken to mean the thickness of a lamella).
The fluorine micas are used in a concentration of 0.1 to 10 wt.%, relative to the
25 total mass of the polyamide layer. The total mass of the polyamide layer is taken
to mean the sum of the mass of the polyamide present in this layer and the mass
of the fluorine mica present in this layer, together with the mass of further
additives optionally present in this layer. The fluorine mica is preferably used in a
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- 4 -
concentration of 0.5 to 5 wt.%. The fluorine mica is particularly preferably used in
a concentration of 1 to 3 wt.%.
The polyamide present in the polyamide layer of the films or hollow articles
according to the invention is a known aliphatic or aromatic or partially aromatic
5 homopolyamide or copolyamide or a blend of two or more polyamides. Preferably
used polyamides are polyamide 6 or polyamide 11 or polyamide 12 or polyamide
6,6 or polyamide 4,6 or polyamide 6,10 or a copolyamide prepared from units of
the stated homopolyamides or a copolyamide prepared from caprolactam units and
units derived from hexamethylenediamine and isophthalic acid or a copolyamide
10 prepared from caprolactam units and units derived from isophorone~ mine and
isophthalic acid. Polyamide 6 or polyamide 6,6 or a copolyamide prepared from
caprolactam units and units derived from hexamethylenediamine and adipic acid
are particularly preferably used.
The fluorine mica used as a filler in the films or hollow articles according to the
15 invention may be produced, for example, using the method described in US-P
5 204 078. The proportion of lithium hexafluorosilicate or sodium hexafluorosili-
cate, which is used together with talc in the production of the fluorine mica, is
preferably 10 to 35 wt.% relative to the mixture of lithium hexafluorosilicate or
sodium hexafluorosilicate and talc.
20 The films or hollow articles according to the invention may contain conventional
quantities of further known auxiliary substances or additives. These further
auxiliary substances or additives may be present in the polyamide layer which
contains the stated fillers or also in other layers of the film.
The following may be mentioned by way of example of further auxiliary
25 substances and additives: processing auxiliaries, such as for example lubricants,
nucleating agents, stabilisers, anti-blocking agents, further fillers, fibrous or
particulate reinforcing materials, such as for example glass fibres, glass beads or
mineral fillers, impact modifiers, such as for example rubbers or polyolefins, flame
retardants, dyes or pigments.
30 The films or hollow articles according to the invention may consist of only one
polyamide layer or have a multi-layer structure. In the case of a multi-layer
structure, the further layers may consist, for example, of polyolefins, such as for
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example polyethylene or polyethylene copolymers, such as for example
copolymers prepared from ethylene and acrylic acid or methacrylic acid or barrier
polymers, such as for example polyvinylidene chloride or copolymers prepared
from ethylene and vinyl alcohol (known as EVAL or EVOH).
5 The films or hollow articles according to the invention are produced in a known
manner, for example by extrusion, coextrusion, coating, l~min~tion or blow
moulding. In the case of the films, extrusion or coextrusion may be performed, for
example, using the so-called chill roll process or using the blown film extrusion
process or blown film coextrusion process. In the case of multi-layer films or
10 hollow articles, conventional commercial coupling agents may be used.
The raw material for the polyamide layers of the films or hollow articles according
to the invention may be produced in a known manner using a continuous or
discontinuous process. A discontinuous process may, for example, involve
polymerisation in an autoclave. A continuous process may, for example, involve
15 polymerisation in a so-called VK tube. Production is preferably performed using a
continuous process. In order to achieve elevated molecular weights, as are
frequently required for use as a film m~teri~l, melt polymerisation may be
followed by solid phase post-condensation. The fluorine mica may be added to thepolyamide before, during or after polymerisation of the monomers to yield the
20 polyamide. If the fluorine mica is added after polymerisation, it is preferably
added to the polyamide melt in an extruder. If the fillers according to the
invention are added before or during polymerisation, the polymerisation may
include a temporally limited stage, during which polymerisation is performed in
the presence of 1 to 50 wt.% of water. Introduction by polymerisation in the
25 presence of such elevated quantities of water is the preferred production process.
The films or hollow articles according to the invention may be further worked orshaped before their ultimate intended use. The films according to the invention
may thus, for example, be thermoformed.
In comparison with other films or hollow articles not containing the fillers
30 according to the invention, the films or hollow articles according to the invention
are distinguished by particularly low permeation values for oxygen and other gases
and flavour substances. The other properties specific to polyamides, such as gloss,
transparency and toughness are not impaired or only insignificantly so. The films
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or hollow articles according to the invention may be produced and processed
simply and at low cost using known processes.
The films or hollow articles according to the invention may be used, for example,
for park~ging purposes. Films or hollow articles according to the invention may
5 be used, for example, for pac~ging foodstuffs, such as meat and meat products,sausage, cheese, beverages and the like The films or hollow articles according to
the invention may also be used, for example, for paçlr~ging cosmetics, such as sun
protection creams or chemicals, such as plant protection products The hollow
articles according to the invention may moreover be used as pipes or tanks These10 may be, for example, pipes or tanks for fuels or oils in motor vehicles
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Examples
Production of the filled polyamide used for film production:
7425 g of caprolactam, 1500 g of water and the quantity and type of filler stated
in the particular Example are heated to 240~C for 2 hours in an autoclave under
5 inherent pressure. The water is then vaporised at this tempel~ule by reducing the
pressure to atmospheric pressure. The resultant composition is then polymerised
for 4 hours at 270~C. The resultant polyamide is extracted with water and dried.
Production of the films:
A 50 micrometre thick flat film is produced using the chill roll process (melt
temperature: 260~C, casting roll temperature: 90~C) from the polyamide produced
using the process described above.
Determination of filler particle size in the films examined:
The particle size of the fluorine mica in the polyamide film is determined by
visual inspection of transmitting electron micrographs. In the event that the
15 particles are highly anisotropic, particle size is taken to mean the dimension of the
smallest axis (for example in the case of a lamellar particle, particle size is taken
to mean the thickness of a lamella).
Example Type of filler Quantity of Average Relative solution
filler in g particle viscosity of
(wt.%) size in extracted polymer
nm (1% in m-cresol,
25~C)
1 (Comparison) no filler - - 4.3
2 fluorine mica 75 (1 wt.%) 9 4.3
3 fluorine mica 150 (2 wt.%) 9 4.3
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Example Oxygen permeation in Tensile Elongation Gloss to Haze to
(cm3 x 25.4 llm) / (m2 x modulus at break to DIN ASTM
24 h x bar) at a relative to DIN 53 455 in 67 530 D
humidity ofthe measuring 53 457 % in scale1003-61
gas of: in MPa divisionsin %
25% 50% 75%
1 (Com- 40 46 69 948 357 97 6.4
~ parison)
2 27 30 46 1370 200 67 2.5
3 20 23 33 1183 318 35 6.3
