Note: Descriptions are shown in the official language in which they were submitted.
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~~VO 90/12063 PCT/F190/00107
1 Gas-sealed mat~rial
The present invention concerns a gas-sealed material and products
containing gas-sealed material. In particular, ~he invention concerns
a gas-sealed material containing polyolefin, polyvinyl alcohol, and
polyamide, and products containing the same.
Polyolefins are widely used, for ins~ance, in packaging industry in
manufacturing various film products. Ad~antages of polyolefins are
in particular appropriate strength and water resistance properties.
Among the drawbacks may be mentioned permeability to certain gases and
liquids, concerning particularly oxygen and hydrocarbon dissolvents.
Therefore, the usability of polyolefin films is limited to packa~ing
certain substances, such as fcods~uffs, in which minor oxygen perme-
ability is r~-quired.
It is customary to use in packa~ing intus~ry mul~iple layer film
structures in which materials of different layers are selected for a
given purpose. Therefore, s~lch multiple layer structures may contain
layers which form a good barrier against gases, such as oxygen, and
layers which provide other properties for the product, such as
strength properties. In addition, mu}tiple layer structures may
contain other layers which generate, for instance, adhesion between
differeat layers. Products of this kind are, however t expensive to
manufacture.
Polyvinyl alcohol is one of such polymers which has a low oxygen
permeability property. Said property has most often been utilized in
olefin-vinyl alcohol random-mixed polymers and in olefin-vinyl alcohol
segment-mixed polymers. It is also known in the art to ma~ufacture
products containing polyolefin and polyvinyl alcohol in the form of
mixturesj which have a low oxygen permeabllity and which therefore
are exceedingly appropriate for manufacturing e.g. packagln~ films.
In the~Finnish patent application No. 87-5772 is disclosed a mixture
of polyolefin and polyvinyl alcohol, moreover containing optionally
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W O 90/12063 PCT/Fl90/00107
1 plasticizers. When polyoleiln and polyvinyl alcohol are mixed in
molten s~ate, a mixture is obtained which is composed of two phases,
a continuous phase and a dispersed phase. When the diameter of the
par~icles in the dispersed phase is small enough, to~ally transparent
films are obtained. The mixing is usually carried out in a separa~e
compounding phase prior to the extrusion of the end product.
Uhen the PVA in the mixture of polyoleiin and PVA establishes a
continuous phase, a good sealing is provided in the product, for
instance oxygen sealin~, and the product is bright and stable, in
spite of ~wo phases, both in molten and in solid state, and it is
easy to soften by adding plasticizers.
In the EP patent publicizing print No. 280455-A discloses oxygen-
sealed materials containing polyethylene, a polyolefin containing
carboxyl groups, and a third polymer which is incompatible with the
polyethylene. Said third polymer may be, as stated in ~he publication,
a polyamide (PA), e~hylene-vinyl alcohol copoly~er, polyvinyl alcohol
(PVA), polyester, or a mixture thereof, although no exa~ples of
mixtures, for instance mixtures of polyamide and polyvinyl alcohol
is presented. A mixture of polyethylene and PVA is not useful because
of its brittleness, neither is the mixture of polyethylene and poly-
amide useful because o its barrier properties. If, instead, poly-
ethylene is mixed with PVA and polyamide, the product is both sealed
~5 and vi8cous.
Although polyolefin-PVA-PA mixtures are ~enerally speakin~ provided
with good oxygen sealing properties in dry circumstances, in moist
circumstances their oxygen sealing property reduces signifieantly,
3~ so that they are sensitive to moisture. In addition, when mixtures
of polyolefins, PVA, and polyamide are mi~ed in molten state, partial
dissolution of PVA and colouring of the product take place. ~hen
plasticizers are used, their stabili~y in the mixture is not as good
as possible because of which migration o plasticizers take plac~ in
the product. One more drawback in conventional PE/PVA/PA mixtures is
that the melt index of the product is not low enough.
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W O 90/12063 2 0 3 2 ~ 2 2 PCT/F190/0~107
1 The object of the present invention is a material containing
polyole~in, polyvinyl alcohol, and polyamide, in which the moisture
sensitivity of the product regarding oxygen sealing is reduced, the
lightness of the product has increased, and the need for plasticizers
has been eliminated, and, in addition, the stren~th properties of
the films manufactured from the product, such as viscosity, tensile
strength, impact tensile strength, and resistance to rupture, have
improved.
As taught by the invention, it has been surprisingly ound that when
cc~tain internally plasticized polyvinyl alsohol polymers and
amorphous polyamide are mixed in molten state with polyolefins to
which carboxyl acid has been copolymerized or grafted, such products
ar~ obtained which have a lighter colour and th~ oxygen sealing ~ained
in which is considerably less sensitive to mois~ure than in using
conventional polyvinyl alcohol, and in addition, the strength proper-
ties of the films manufac~uret from the product are better than in
using unmodified polyolefin, ordinary polyvinyl alcohol, and poly-
amide.
Therefore, the invention concerns a ~as-sealed material containing
polyoleiin, vinyl alcohol polymer, and polyamide. The gas-~ealed
material of the invention is characterized in that it is produced by
mixing in molten~state 3 to 60 per cent by weight of polyolefin, and
lO to 96 per cent by weight of internally plasticizsd vinyl alcohol
polymer, and l to 50 per cent by weight of an amorphous polyamide.
The term 'internally plasticized vinyl alcohol polymer' refers to a
vinyl alcohol polymer which contains polyglycol groups (polye~her
30 groups) or other groups plasticizing polyvinyl alcohol in the side
chains thereo~. Said plasticizer ~ro~ps are connected into a chain by
copolymerizing, grafting or by means of reactive compoundi~g. One
such internally plasticized polyvinyl alcohol is Vinex polymer (trade
name, Air Products and Chemicals Inc.), in which for comonomer is
~ used an ester of me~hacrylic acid and of polyethylene glycol.
Sa~d internal1y p1asticized vinyl alcohol polymers may be manu-
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W O 90~12063 2 0 3 21~ ~ Pcr/FIgo/Dolo7
1 factured, for instance in th~ manner as disclosed in the US. patent
No. 4,709,999. Said patent presents that the product i5 provided
with ~ood oxygen sealing and that it is appropriate for cast, in-
~ection moulding and extrusion products, and that it is characterized
by good water solubility, and therefore, it is particularly well
appropriate for manufacturing films which are required to possess
water solubility.
The vinyl alcohol polymer used in the polyolefin/polyvinyl alcohol/
polyamide mixture of the invention is advantageously such in which
in the poly(alkyleneoxy)ester derivative for use as a comonomer the
alky].ene of the alcohol component is an ethylene or propylene, and the
acid component is an acrylic acid or methacrylic acid. Said modified
~inyl alcohol polymers may be manufactured, for instance, by poly-
merizing vinyl acetate monomer and poly(alkyleneoxy)acrylate co-
monomsr, and hydrolyzing the copoly~er thus obtained in order to
produce an internally plasticized vinyl alcohol poly~er.
The quantity of the internally plasticized vinyl alcohol polymer in
the polyethylene-polyvinyl alcohol-polyamide mixture of the invention
may be in the range from lO to 96 per cent by wei~ht, preferably in
the range of from 30 to 60 psr cent by weight. In some instances, it
may be preferable to substitute part of the internally plasticized
vinyl alcohol polymer used in the gas-sealed material for unmodified
polyvinyl alcohol if the purpose of the product allows.
The polyolefin in a gas-sealed material of the invention may be
based on homopolymers or copoly~ers of the olefins. Therefore, it
may be low density polyethylene (LDPE), medium density polyethylene
(MDPE) or high density polyethylene (HDPE), polypropylene, or poly-
butene. The polyolefin may also be a copolymer of ethylene together
with other olefins, such as propylene, butene, hexene and octene.
The polyolefin may also be an olefin-ester copolymer, such as
ethylene-vinyl acetate copolymer, ethylene-acrylate-ester copolymer,
or ethylene-methacrylate ester copolymer, or it may be a thermoplastic
olefin-based elastomer, such as EP or EPD rubber.
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1 The polyolefin in the process according to ~he invention may also be
a homopolymer or a copolymer of ~he above-mentioned olefins which
has been modified with the aid of carboxylic acid. To such a modified
olefin polymer is copolymerized or grafted O.l to lO per cent by
weight of carboxylic acid. The carboxylic acid may comprise any
unsaturated carboxylic acid or carboxylic acid anhydride which can
be grafted or copolymeri~ed in polyolefin. Examples of such acids
are, for instance, acrylic acid, methacrylic acid, maleic acid fumaric
acid, itaconic acid, crotonic acid, sorblc acid, and anhydrldes of
the afore-mentioned acids. In grafting or in copolymerizing one or
several above acids may be used. The polyolefin grafted or copolymer-
ized with carboxylic acid may also be a mixture con.aining a poly-
olefin modified in the manner described above, and un unmodified
polyolefin.
Tha quantity of the polyolefin in the gas-sealed material of the
invention may be in the range l to 99 per eent by weight, but
preferably in the range from 30 to 60 per eent by ~eight of the
quantity of the entire mixtur~.
A third component in a gas-sealed material of the invention is
amorphous polyamide. For the polyamide is used a polyamide in whieh
the degree of crystallization varies in the range l to lO per cent,
advantageously in the range l to 5 per cent.
The quantity of amorphous polyamide in a material of the i~vention
may be selected from the range l to 50 per cent by weight.
The amorphous polyamide enhances the viscosi~y and deep-drawing
properties of the mixture of polyolefin and polyvinyl alcohol co-
polymer.
The gas-sealed polyolefin/PVA/PA mixture of the invention can be
manufactured mixing the polyolefin component, vinyl alcohol/copolymer
component, and polyamide component in a melt mixer simultaneously as
a dry mixture, premixed in solid or in molten state, or then various
components are added separately.
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_W O 90/12063 2 0 3 212 2 PCT/F19~/00107
1 From the polyolefin/PVA/PA mixture of the inYention various products
may be prepared by combining the mixture ~ith polyolefins, other
plastics or other materials, such as fibre-based materials. Multiple
layer products may be manufac~ured by coextrusion, (co)extrusion
coating, (co)ex~rusion lamination, adhesion lamination, or using o~her
techniques, and these production procedures may also be combined.
As products containing a gas-sealed material of ~he in~en~ion e.g.
films, moulded-blown bottles and containers, plates, tubes, injection
moulded vessels, deep-drawn films and plates, liquid packaging card-
board, etc. may be mentioned. Sealed multiple-layer products are
generally used for packaging foodstuffs, when oxygen sealing is
desired also in moist circumstances, but the sealing of carbon dioxide
or some other gas may be thought of. In addition, fat, chemical and
odour sealing may be desired both in various foodstuff packages and
technical products.
In the following non-limi~ing ~xampl~s the manufacturing, properties
and application of ~he polyolefin/vinyl alcohol polymer/polyamide
mixture of the inven~ion in sealed one-layer products are described.
The oxygen permeability of the films was measured with an OX-TRAN
lOOO apparatus ~ASTN D 3985). The polyolefins, the vinyl alcohol po-
lymers and polyamides used in the tests of the examples are presented
in the table below.
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Pol~olefins
POl PE (low density polyethylene), melt index (MI)
1.8 g/lO min (190C)
P02 - LLDPE (linear low density polyethylene), grafted
with O.25 per cent by weight of fu~aric acid,
melt index 0.5 g/lO min (l90C)
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W O 90~12063 PC~/FI90/0010'7
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1 PolyvinYl~alcohol
PVAl vinyl alcohol copolymer wherein the comonomer is
an ester of an methacryl acid and an ester of poly-
ethylene ~lycol
(Vinex 4004, Air Products and Chemicals)
PVA2 - polyvinyl alcohol, viscosity 4, hydrolysis degree
88~
Polyamides
PAl ~ amorphous polyamide, degree of crystallization
1-5%
PA2 ; polyamide 6
1~ PA3 polyamide 11
PA4 polyamide 12
Plasticizer
glycerol, degree of purity 99%
Example 1
Polyolefin/PVA/polyamide mixtures of the invention were prepared by
mixing polyolefin, polyvinyl alcohol and polyamide, in molten state,
with the aid of a Berstorff mixer which was provided with a flat
film nozzle. The temperature profile was 130 to 190 to 200 to 210 to
210 to 210 to 220 to 220 to 215 to 215 to 210. The production rate
was 10 kilograms per hour.
The thicknesses of the obtained films wère 150 ~o 200 ~m. The com-
pounds thereof are presented in the accompanying Table 1 A. The
properties of the films are pr~sented in the accompanying Table 1 B.
The oxygen permeability values of the films are calculated for 25 ~m
thickness. The lightness of the films was measured as a so-called
yellowness index conforming to the s~andard ASTM D 1925-70 wlth the
Ultra Scan apparatus of Hunter Lab.
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1 TABLE l A
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Test Polyvinyl_~alcohol Polyolefin ~olvamide
type ~ by weigh~ ~ype ~ by w. type ~ by w
1 PVAl 60 POl 30 PAl 10
2 PVAl 60 POl 10 PAl 9
PA2 21
3 PVAl 60 POl 10 PAl 9
PA3 21
4 PVAl 60 POl 10 PAl 9
PVAl 60 POl 10- PAl 30
6 PVA2 60 POl 40 - -
Note. In test 6, the quantity of polyvinyl alcohol includes 4.5%
glycerol of the PVA quantity.
TABLE 1 E
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Test Oxy~en permeabil. Y~ll9Y5~ Tensile
~ml~m-x24hxbar2 index, thick- strength
0~RH 90~RH ness ~mmach. /trans
(210C) dir. dir.
NPa MPa
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1 0.01 2.5 0.7S 151 15.0 14.5
2 0.09 1.5 0.75 163 44.8 25.0
3 0.12 1.5 0.75 148 4~.0 24.5
4 1.11 l.S 0.75 191 42.5 22.7
2~ 5 0.01 3.0 0.85 190 47.8 29.0
6 0.20 10.0 10.9 172 10.0 7.0
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Polyolefin/PVA/polyamide mixtures of the invention were prepared by
mixing polyolefin, polyvinyl alcohol and polyamide, in molten s~ate,
with the aid of a Berstorff mixer which was provided with a flat
film nozzle. The temperature profile was 130 to 190 to 200 to 210 to
210 to 210 to 220 to 220 to 215 to 210. The production rate was 10
kilograms per hour.
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The thicknesses o~ the obtained films were 140 to 190 ~m. The com-
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1 pounds thereof are presented in ~he accompanying Table 2 A. The
properties of the films are presented in the accompanying Table 2 B.
The oxygen permeability values of the films are calculated for 25 ~m
thickness. The lightness of the films was measured as a so-called
yellowness lndex conforming to the standard ASTM D 1925-70 with the
Ultra Scan apparatus of Hunter Lab.
TABLE 2 A
0 Test Pol w inYl alcohol Polyolefin PolYamide
type ~ by weight type ~ by w. type % by w.
.
l PVAl 80 P02 10 PAl 10
2 PVAl 70 P02 3 PAl 27
3 PVAl 60 PQ2 30 PAl lO
4 PVAl 30 P02 20 PAl S0
15 5 PVAl 10 P02 60 PAl 30
6 PVAl 60 P02 10 PAl 9
PA2 21
7 PVAl 60 P02 10 PAl 9
PA3 21
8 PVAl 60 P02 10 PAl 9
PA4 21
~0 9 PVA2 60 P01 40
10 PVA2 70 P02 30
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Note. In tests 9 and 10, the quantity of polyvin~l alcohol includes
4.5~ glycerol of the PVA quan~ity.
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TABLE 2 B
Test Oxy~en permeabil. Yellowness ~ Q
(ml/m-x24hxbar? index, thick- strength
0%RH 90~RH ness ~m mach./tr~ns
dir. dlr.
MPa ~Pa
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l 0.1 2.9 0.80 142 19.918.5
2 0.051.9 0.70 171 32.225.0
3 0.012.5 0.75 166 16.~~5.0
4 1.5 25 0.85 151 42.539.7
3.6 55 0.85 147 35.031.6
6 0.081.4 0.75 1~6 46.826.0
7 0.101.5 0.75 150 45.227.8
8 0.10i.5 0.75 141 44.525.5
9 0.2010.0 10.9 172 10.07.0
l~ 0.209.6 11.5 162 14.011.0
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