Note: Descriptions are shown in the official language in which they were submitted.
2 ~ 3 ~
W O 90/12062 PCT/F190/00l06
1 Gas-sealed ma~erial
The present invention concerns a gas-s2aled material and products
containing gas-sealed material. In particular, th~ in~ention concerns
a gas-sealed material con~aining polyolefin, polyvinyl alcohol, and
polyamide, and products con~aining the sa~e.
1~ Polyolefins are widely used, for instance, in packaging indus~ry in
~anufacturing vario~s fil~ products. Ad~antages of polyolefins are
in particular appropriate strength and water resistance properties.
Among the drawbacks may be mentioned permeabili~y to cer~ain gases and
liquids, concerning particularly oxygen and hydrocarbon dissolven~s.
Therefore, ~he usability of polyolefin films is limited to packaging
certain substances, such as foodstuffs, in which minor oxygen perme-
2bility is required.
It is customary to use in packaging indus~ry multiple layer i`ilm
~0 struc~ures in which materials of dif~erent layers are selected for a
given purpose. Therefore, such multiple layer structures may contain
layers whicn form a good barrier against gases, such as oxygen, and
layers whioh provide o~her properCies for the product, such as
strength properties. In addition, mul~iple layer structures may
contain other layers which generate, for instance, adhesion be~ween
different layers. Products of this kind are, however, expensive to
manufacture. -
.
~ Polyvinyl alcohol is one of such polymers which has a low oxygen
permeability property. Said property has most often been utilized inolefin-vinyl alcohol random-mixed polymers and in olefin-vinyl alcohol
segment-mixed polymers. It is also known in the art to manufacture
prodllcts containing polyolefin and polyvinyl alcohol in ~he form of
mixtures, which have a low oxygen permeability and which ~herei'ore
are exceedingly appropriate for manufacturing e.g. packaging films.
In the Finnish patent application No. 87-5772 is disclosed a mixture
of polyolefln and polyvinyl alcohol, moreover containing optionally
` . ~ '. ' ., ': , ' ' ' '; ' ' ~
W O 90/12062 2 0 3 212 0 PCT/F190/00106
1 plaseici~ers WhPn polyolefin and polyvinyl alcuhol are mixed in
molten state, a mixture is ob~ained which is composed of ~wo phases,
a coneinuous phase and a dispersed phase. ~hen the diameter of the
par~icles in the dispersed phase is small enough, totally transparent
films are obtained. The mixing is usually carried out in a separate
compounding phase prior to the extrusion of the end product.
When the PVA in the mixture of polyolefin and PVA establishes a
continuous phase, a good sealing is provided in the product, for
. 10 instance oxygen sealingj.and the product is bright and stable, in
spite of two 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 discloss oxygen-
sealed materials containing polyethylene, a polyolei'in containing
carboxyl groups, and a third polymer which is incompatible with the
polyethylene. Said third polymer may be, as stated in the publication,
a polyamide (PA), ethylene-vinyl alcohol copolymer, polyvinyl alco-
hol (P~A), palyester, or a mixture thereof, although no examples of
mixtures, for instance mixtures of polyamide and polyvinyl alcohol,
are pres2nted. A mixture of polyethylene and PVA is not useful
because of its brittleness, neither is the mixture of polyethylene
and polyamide useful because of its barrier properties. If, instead,
polyethylene is mixed with PVA and polyamide, the product is both
sealed and viscous.
Although polyolefin-PVA-PA mixtures are generally speaking provided
with good oxygen sealing properties in dry circumstances, in moist
circumsta~ces their oxygen sealing property reduGes significan~ly,
so that they are sensitive to moisture. In addition, when mixtures
oi polyolefins, PVA, and polyamide are mixed in molten state, partial
dissolution of PVA and colouring of the product take place. When
plasticizers are used, their stability in the mixture is no~ as good
as possible because of whlch migration oi plasticizers cake pl.ace in
the product. One more drawback in con~entional PE/PVA/PA mixtures is
that the melt index oiJ the product is not low enough.
~ .
'~
~ .
- ;
W O 90/12062 2 0 3 212 ~ PCT/FIg0/00106
1 The object of the present invention is a material containin~
polyolefin, 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 strength properties of
the films manufactured from the product, such as viscosity, tensile
strength, impact tensile strength, and resistance to rupture, have
improved.
lC As taught by the invention, it h s been surprisingly found that when
certain internally plasticized polyvinyl alcohol copolymers and
polyamide are mixed in moltRn state with polyolefins, such products
are obtained which have a lighter colour and the oxy~en sealing
gained in which is considerably less sensitive to mois~ure than in
using con~entional polyvinyl alcohol, and in addition, the strength
properties of the films manufactured from the product are be~ter
than in using ordinary polyvinyl alcohol and polyamide.
Therefore, the invention conc.erns a gas-sealed material containing
polyolefin, polyvinyl alcohol, and polyamide. The gas~sealed material
of the invention is characterized in that said material is produced
by mixing in molten state 3 to 60 per cent by weight of polyolefin,
10 to 96 per cent by weight of internally plasticized vinyl alcohol
polymer, and 1 to 50 per cent by weight of polyamide.
The term 'internally plasticized vinyl alcohol polymer' refers to a
vinyl alcohol polymer which contains poly~lycol groups (polyzther
groups) or other groups plasticizing polyvinyl alcohol in the side
c~ains thereof. Said plasticizer groups are connected into a chain by
copolymerizin~, grafting or by means of reactive compounding. One
such internally plastizied 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.
3~ Said internally plasticized vinyl alcohol polymers may be manu-
factured, for instance in the manner as disclosed in the US. patent
No. 4,709,999. Sald patent presents that the product is provided
.
.. . .
- : , . ,' ': ' ' ~ " ~ ' ' :
.
. , , ~. .. .
2~32~0
W O 90/12062 PCT/F190/00106
1 with good oxygen sealing and that it is appropriate for cast, ln-
jection moulding and extrusion produces, and that it is characteri7ed
by good water solubiliey, and therefore, it is particularly ~ell
appropriate for manufac~uring films which are required to possess
water solubility.
The vinyl alcohol polymer used in the polyolefin/polyvinyL alcohol/
polyamide mixture of the inven~ion is advaneageously such in which
in the poly(alkyleneoxy)ester derivative for use as a comonomer the
alkylene of the alcohol component is an ethylene or propylene, and the
acid component is an acrylic acid or methacrylic acid. Said modified
vinyl alcohol polyrners may be manufaceured, for instance, by poly-
merizin~, vinyl acetate monomer and poly(alkyleneoxy)acrylate co-
monomer, and hydrolyzin~ the copolymer thus obtained in order to
produce an internally plasticized vinyl alcohol polymer.
The quanticy 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 weighr, preferably in
~0 t-h~ range of from 30 to 60 per 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 copolyrners 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 copolymes 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-vînyl acecate copolyrner, ethylene-acrylate-ester copol~ner,
or ethylene-methacrylate ester copol~ner, or ie may be a ehermoplastic
olefin-based elastomer, such as EP or EPD rubber.
3~ ~
The polyolefin in che process according to the Lnveneion mav also be
a homopoly~er or a copolymer oP the above-mentioned olePins which
.
~ ., . ~, .
.
' ' ' . ' . '' :
,~ .. . .
W O 90/12062 2032~ 2~ PCT/F190/00106
l has been modified with the aid of carboxylic acid. To such a modified
olefin polymer is copolymerized or grafted 0.1 to 10 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 copolymerized in polyolefin. Examples of such acids
are, for instance, acrylic acid, methacrylic acid, maleic acid fumaric
acid, itaconic acid, cro~onic acid, sorbic acid, and anhydrides of
the afore-mentioned acids. In grafting or in copolymerizing one or
several above acids may be used. The polyolefin grafted or copolymer-
lC ized with carboxylic acid ~ay also be a mixture containing a poly-
olefin modified in the manner described above, and un unmodified
polyolefin.
The quantity of the polyolefin in the gas-sealed material of the
invention may be in the range from 1 to 99 per cent by weight, but
preferably in the range from 30 to 60 per cent by weight of the
quantity of the entire mixture.
A third component in a gas-sealed material of the invention is poly-
~0 amide. For the polyamide, for instance the following polyamides may
be used: polyamide 6, polyamide 8, polyamide 10, polyamide 11, polv-
amide 12, polyamide 6.6, polyaMide 6.10, and polyamide 12-elastomers,
or mixtures thereof. The quantity of polymer in the material of the
invention may be selected from the range 1 to 50 per cent by weigh~
The polyamide enhances the viscosity and deep-drawing properties of
the mixture of polyolefin and the poly~inyl alcohol copolymer.
The gas-sealed polyolefin/PVA/PA mixture of the invention can be
3~ manufactured mixing the polyolefin component modified with thz acid,
the vinyl alcohol/copolymer component, and the polyamide component
in a melt mixer simultaneously as a dry mixture, premixed in solid
or Ln molten staee, or then various componenc5 are added separately.
3~ From the polyolefin/PVA/PA mixture of the invention various products
may be prepared by combining the mixture with polyolefins, other
plastics or othsr ma~erials, such as fibre-based materials. Multiple
. . , . ~. - :
~:` ,' ' : ' ' , ~' '', , '
.
. . .- . ~ , : .
`' : , ~' " ' '
W O 90/12062 2 ~ 3 212 ~ p~r/Fl9o/oolo6
1 layer products may be manufactured by coeY.~rUqiO~, (co)extrusion
coaeing, (co)ex~rusion la~ination, adhesion lamination, or using other
techniques, a~d these production procedures may also be combined.
As products containing a gas sealed material of the invention, e.g.
films, moulded-blown bottles and containers, plates, tubes, injection
moulded vessels, deep-drawn fil~s and plates, liquid packaging card-
board, etc. may be mentioned. Sealed multiple-layer products are
~enerally used for packaging foodstuffs, when oxygen sealing is
- 10 desired also in moist circu~stances, 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-limitin~ examples the manufacturing, properties
and application of the polyol~fin/~inyl alcohol polymer/polyamide
~ixture of the inven~ion in sealed on~-layer products are described.
The oxy~en per~eability of the films was measured with an OX-TRAN
1000 apparatus (ASTM D 3985). The polyolefins, the vinyl alcohol po-
lymers and polyamides used in the tests of the e~amples are presentedin the table below.
~olvolefins
~5 POl - LDPE (lo~ density polyethylene), molten index
(MI) 1.8 g/10 min (190C)
PO2 - LLDPE (linear low density polyethylene), grafted
with 0.25 per cent by weight of fumaric acid,
melt index 0.5 g/10 min (190C)
P03 - EAA (ethylene-acrylic acid copolymer), acrylic
acid content 6.5~, melt index 9.5 g/10 min
(190C)
' ' '
": ' ' :' ' ' '
W O 90/12062 2 ~ 3 ~12 ~ pcr/Fl9otoo1o6
PVAl - vinyl aloohol copolymer wherein the comono~er
is an ester of a methacrylic acid and a polyechy-
lene glycol (Vinex 4004, trade name, Air Products
and Chemicals Inc.)
PVA2 - polyvinyl alcohol, viscosi~y 4, degree of hydro-
lysis 88
Pol~amides
PAl - polyamide 6
PA2 - polyamide 11
PA3 - polyamide 12
Plasticizer
glycerol, degree of purity 99
~0 Exam~le 1
Polyolefin/PVA/polyamide mixtures of the i~vention were prepared by
mixing polyolefin, pol~inyl alcohol and polyamide, in molten state,
with the aid of a Berstorff ~ixer which was provided with a fla~
film nozzle. The temperature profile was 130 to 190 ~o 200 to 210 to
210 to 210 to 220 to 215 to 210. The production rate was 10 kilogra~s -
per hour.
The thickn~sses oi the obtained fil~s were 120 to 170 ~m. The com-
pounds thereof are presented in the acco~panying Table 1 A. The
properties of the films are: presented in the acco~panying Table 1 B. :
The oxygen per~eability 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 standard ASTM D 1925-70 with the
Ultra Scan apparatus of Hunter Lab.
.
. :
.
' - - .' :' : ',~ : ' ' .
` ' : ~ " '
'
W O 90/12062 2 0 3 212 0 PCT/F190/00106
1 TABLE 1 A
Test Polw invl alcohol Polvolefin Polvamide
type % by weight type ~ by w. type ~ by w.
_ _ _
1 PVAl 60 POl 30 PAl 10
2 PVAl 60 POl 30 PA2 10
3 PVAl 60 POl 30 PA3 10
4 PVAl 30 POl 40 PA3 30
PVA2 60 POl 40 - -
_
Note. In test 5 the quantity of polyvinyl alcohol includes 4.5
glycerol of the PVA quantity.
ThBL~1 P,
__ _
15 Test Oxygen permeabil. Y~lL4Y;9~ Tensile
(mlL_-x24h~bar) index, thick- s~rength
O~RH 90%RH ness ~m mach./trans
dir. dir.
MPa ~Pa
r 1 0.10 239 0.90 12118.5 15.9
~ 2 0.15 l.S 0.90 14217.8 12.5
3 0.18 2.0 0.95 15017.9 13.5
4 0.20 2.4 0.89 14739.7 32.5
0.20 10.0 10.9 17210.0 7.0
.~
Exam~le 2
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 wi~h a flat
30 film nozzlP. The temperature profile was 130 tO 190 to 200 to 210 ~o
210 to 210 to 220 to 220 to 215 to 210. The production rate was 10
kilograms per hour.
The thicknesses of the obtalned ~ilms were 130 to 210 ~m. The com-
pounds thereof are presented in the accompanying Table 2 A. The
properties of the films are presented in the accompanying Table 2 B.
The oxygen permeabili~y values of the films are calculated for 25 ~m
. ~ ` '~-', ' ',
"
W O 90/12062 ~ ~ 3 ~ ~ ~ PCTtF190/0~106
1 thickness. The lightness of the films was measured as a so-called
yellowness index conforming to the standard ASTM D 1925-70 with the
~ltra Scan appara~us of Hunter Lab.
TABLE 2 A
Test Pol winvl alcohol P_lyolefin ~Qly~mide
type % by weight type ~ by w. type % by w.
.
l PVAl 80 P02 lO PAl lO
10 2 PVAl 70 P02 3 PAl 27
3 PVAl 70 P02 3 PA2 27
4 PVAl 70 P02 3 PA3 27
PVAl 60 P02 30 PAl lO
6 PVAl 30 P02 20 PAl 50
7 PVAl lO P02 60 PAl 30
8 PVAl 60 POl 30 PAl lO
15 9 PVAl 60 P03 30 PAl lO
lO PVAl 60 P02 30 PAl lO
ll PVA2 60 POl 40 - -
12 PVA2 70 P02 30 ~ -
13 PVA2 70 POl 20 PAllO
14 PVA2 70 POl 20 PAllO
PVA2 70 POl 30 - -
~0 ~ - - _ _ , ... . .
Note. In tests ll, 12 and 14, the quantity of polyvinyl alcohol in-
cIudes 4.5% glycerol of the PVA quantity.
~'
ZS
::
3~ : :
- .
: ~ :
...... , ~ .. . .
.
. - ~ ;. : .: ~ :
W O 90/12062 2 0 3 %12 ~ PCT/FI90/00106
1 TABLE 2_P.
Test Oxygen per~eabil. Yellowness
f~l~m--x24hxbar~ index, thick- strength
0%RH90~RH ness ~m mach./trans
dir. dir.
MPa MPa
,, .
1 0.20.8 0.80 140 20.4 19.0
2 l.03.4 0.70 130 33.9 27.5
3 1.13.8 0.70 131 31.2 25.5
4 1.23.5 0.70 145 30.4 23.2
1.11.5 0.53 1.70 22.8 24.8
6 5 20 0.85 172 39.1 27.2
7 3.5S0 O.gO 186 31.5 30.1
8 1.21.6 0.76 192 21.4 20.8
9 0.92.2 0.82 171 20.9 19.7
1.18.8 30.1 164 23.6 21.0
11 0.210.0 10.9 211 10.0 7.0
~5 12 0.29.6 11.5 198 14.0 ll.0
13 0.87.6 11.2 172 17.7 12.3
14 0.88.1 11.0 145 17.8 8.4
0.29.7 11.0 163 10.3 8.7
The results indicate that by using vinyl alcohol copolymer for the
polyvinyl alcohol in the mixture, in which the comonomer is an ester
of methacrylic acid and polyethylene ~,lycol (Vlnex 4004), a product
is obtained ~he low oxygen permeabllity of which chan~es very little
in a moist vicinity. The colour of the product (yellownessj is very
2S low. Polyamide addition increases the t?nsile stren~,th of the product
both in =achine and transversal direction.
:
3;
,
:
:
- : , ~
: . :
