U.S. patent number RE29,340 [Application Number 05/730,464] was granted by the patent office on 1977-08-02 for composite film.
This patent grant is currently assigned to Toyo Boseki Kabushiki Kaisha. Invention is credited to Ikuya Hayashi, Koichi Matsunami.
United States Patent |
RE29,340 |
Matsunami , et al. |
August 2, 1977 |
Composite film
Abstract
A composite film comprising (A) a biaxially drawn film of a
polyamide containing in the molecule not less than 70% (mol) of the
repeating unit consisting of metaxylylenediamine or its mixture
with paraxylylenediamine (of which the content is not more than 30%
(mol) on the basis of the total amount of metaxylylenediamine and
paraxylylenediamine) and an .alpha.,.omega.-aliphatic dicarboxylic
acid having 6 to 10 carbon atoms and (B) a layer of a thermoplastic
resin having a melting point or a softening point at least
50.degree. C. below the melting point or the softening point of the
polyamide provided on at least one surface of the biaxially drawn
film.
Inventors: |
Matsunami; Koichi (Otsu,
JA), Hayashi; Ikuya (Otsu, JA) |
Assignee: |
Toyo Boseki Kabushiki Kaisha
(JA)
|
Family
ID: |
27471365 |
Appl.
No.: |
05/730,464 |
Filed: |
October 7, 1976 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
213811 |
Dec 29, 1971 |
03843479 |
Oct 22, 1974 |
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Foreign Application Priority Data
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Dec 29, 1970 [JA] |
|
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46-128180 |
Dec 29, 1970 [JA] |
|
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46-128181 |
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Current U.S.
Class: |
428/216; 428/334;
428/337; 428/339; 428/476.1; 428/910 |
Current CPC
Class: |
B32B
27/00 (20130101); C08J 7/043 (20200101); C08J
7/052 (20200101); B32B 27/34 (20130101); C08J
7/048 (20200101); C08J 7/0427 (20200101); Y10T
428/263 (20150115); Y10T 428/24975 (20150115); Y10T
428/269 (20150115); Y10T 428/266 (20150115); Y10T
428/31746 (20150401); C08J 2377/00 (20130101) |
Current International
Class: |
B32B
27/00 (20060101); C08J 7/04 (20060101); C08J
7/00 (20060101); B32B 27/34 (20060101); B32B
007/02 () |
Field of
Search: |
;260/78R ;264/289
;428/215,216,474,500,523,910 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lesmes; George F.
Assistant Examiner: Dixon, Jr.; William R.
Attorney, Agent or Firm: Birch, Stewart, Kolasch and
Birch
Claims
What is claimed is:
1. A composite film comprising (A) a biaxially drawn film of a
polyamide containing in the molecule not less than 70% (mol) of the
repeating unit consisting of metaxylylenediamine or its mixture
with paraxylyenediamine, wherein the paraxylylenediamine content is
not more than 30% (mol) on the basis of the total amount of
methaxylylenediamine and paraxylylenediamine, and an
.alpha.,.omega.-aliphatic dicarboxylic acid having 6 to 10 carbon
atoms and (B) a layer of a thermoplastic resin having a melting
point or a softening point at least 50.degree. C. below the melting
point or the softening point of the polyamide provided on at least
one surface of the biaxially drawn film;
the biaxially drawn film having the following physical
constants:
(1) .[.Gas.]. .Iadd.Oxygen .Iaddend.permeability constant (at
30.degree. C.): not more than 9.times.10.sup.-.sup.13 ml.
cm./cm..sup.2 sec. cm. Hg;
(2) Plane orientation index: not less than 0.025;
(3) Degree of balance: not more than 0.045;
(4) Breaking strength: not less than 10 kg./mm..sup.2 in machine
and transverse directions;
(5) Breaking elongation: 30 to 150% in machine and transverse
directions;
(6) Yield strength: not less than 5 kg./mm..sup.2 in machine and
transverse directions; and
(7) Yield elongation: 2 to 6% in machine and transverse
directions;
and the composite film having the following physical constant:
(8) .[.Gas.]. .Iadd.Oxygen .Iaddend.transmission rate (at
30.degree. C.): not more than 50 ml./m..sup.2 24 hr. atm.
2. The composite film according to claim 1, wherein the .[.gas.].
.Iadd.oxygen .Iaddend.transmission rate is not more than 30
ml./m..sup.2 24 hr. atm.
3. The composite film according to claim 1, wherein the thickness
of the biaxially drawn film is 5 to 50.mu..
4. The composite film according to claim 1, wherein the thickness
of the composite film is 6 to 200.mu..
5. The composite film according to claim 1, wherein the melting
point of the thermoplastic resin is 50 to 170.degree. C.
6. The composite film according to claim 1, wherein the
thermoplastic resin is a polyolefin resin.
7. The composite film according to claim 1, which is heat sealable
at a temperature of 70 to 160.degree. C.
8. The composite film according to claim 1, wherein the thickness
of the thermoplastic resin is about 5 to 100.mu..
9. The composite film according to claim 1, wherein the polyamide
has a relative viscosity of about 2.0 to 4.0.
10. The composite film according to claim 1, wherein the polyamide
is a homopolymer selected from the group consisting of
polymetaxylylene adipamide polymetaxylylene sebacamide and
polymetaxylylene suberamide.
11. The composite film of claim 1, wherein the polyamide is
selected from the group consisting of copolymers of
metaxylylene/paraxylylene adipamide, metaxylylene/paraxylylene
pimelamide, metaxylylene/paraxylylene sebacamide and
metaxylylene/paraxylylene azelamide.
Description
The present invention relates to a composite film having an
excellent gas barrier property and a high heat seal strength.
A biaxially drawn film of a metaxylene group-containing polyamide
is provided with a variety of advantageous physical and mechanical
properties such as breaking strength, yield strength, heat
stability and water-proof property. It is particularly excellent in
its gas-barrier property. For instance, the .[.gas-permeability.].
.Iadd.oxygen-permeability .Iaddend.constant of such a film is
normally 9 .times. 10.sup.-.sup.13 ml. cm./cm..sup.2 sec. cm. Hg or
less, which is markedly smaller than that of a biaxially drawn film
of polyethylene terephthalate (i.e., about 3 .times.
10.sup.-.sup.12 ml. cm./cm..sup.2 sec. cm. Hg) and that of a
biaxially drawn film of polycapramide (i.e., about 2 .times.
10.sup.-.sup.12 ml. cm./cm..sup.2 sec. cm. Hg). However, the
melting point of the said film is higher than the temperature
(i.e., around 170 to 180.degree. C.) usually adopted for heat
sealing. In addition, the film tends to shrink on heating. Thus, it
is difficult to heat seal and, even if partly heat sealed, a broad
heat sealing area cannot be achieved and the heat seal strength
resulting therefrom is not sufficient. These drawbacks prevent the
film from being used as a packaging material.
The principal object of the present invention is to embody a
composite film of a metaxylylene group-containing polyamide
provided with favorable physical and mechanical properties,
particularly an excellent gas-barrier property, and film having an
improved heat seal strength.
According to the present invention, there is provided a composite
film comprising (A) a biaxially drawn film of a polyamide
containing in the molecule not less than 70% (mol) of the repeating
unit consisting of metaxylylenediamine or its mixture with
paraxylylenediamine (of which the content is not more than 30%
(mol) on the basis of the total amount of metaxylylenediamine and
paraxylylenediamine) and an .alpha.,.omega.-aliphatic dicarboxylic
acid having 6 to 10 carbon atoms and (B) a layer of a thermoplastic
resin having a melting point or a softening point at least
50.degree. C. below the melting point or the softening point of the
polyamide provided on at least one surface of the biaxially drawn
film.
The biaxially drawn film having the following physical
constants:
(1) .[.Gas.]. .Iadd.Oxygen .Iaddend.permeability constant (at
30.degree. C.): not more than 9 .times. 10.sup.-.sup.13 ml.
cm./cm..sup.2 sec. cm. Hg;
(2) Plan orientation index: not less than 0.025;
(3) Degree of balance: not more than 0.045;
(4) Breaking strength: not less than 10 kg./mm..sup.2 in machine
and transverse directions;
(5) Breaking elongation: 30 to 150% in machine and transverse
directions;
(6) Yield strength: not less than 5 kg./mm..sup.2 in machine and
transverse directions; and
(7) Yield elongation: 2 to 6% in machine and transverse
directions;
And the composite film having the following physical constant:
(8) .[.Gas.]. .Iadd.Oxygen .Iaddend.transmission rate (at
30.degree. C.): not more than 50 ml./m..sup.2 24 hr. atm., when
measured by the procedures as hereinafter described.
In the polyamide used for the formation of a biaxially drawn film
as the base layer, the amount of paraxylylenediamine is to be not
more than 30% (mol), on the basis of the total amount of
metaxylylenediamine and paraxylylenediamine, if the latter is
employed. Further, the repeating unit consisting of the
xylylenediamine and the .alpha.,.omega.-aliphatic dicarboxylic acid
should be included in an amount not less than 70% (mol) in the
molecule chain.
The polyamide may be the one having a relative viscosity of about
2.0 to 4.0, particularly of about 2.2 to 3.0, when determined by
the procedure as hereinafter described.
Examples of the polyamide include homopolymers such as
polymetaxylylene adipamide, polymetaxylylene sebacamide and
polymetaxylylene suberamide, and copolymers such as
metaxylylene/paraxylylene adipamide, metaxylylene/paraxylylene
pimelamide, metaxylylene/paraxylylene sebacamide and
metaxylylene/paraxylylene azelamide.
The copolymers prepared from such monomer components as in the
above exemplified homopolymers and copolymers and aliphatic
diamines (e.g. hexamethylene-diamine), alicyclic diamines (e.g.
piperazine), aromatic diamines (e.g. p-bis-(2-aminoethyl)-benzene),
aromatic dicarboxylic acid (e.g. terephthalic acid), lactams (e.g.
.epsilon.-caprolactam), .omega.-aminocarboxylic acids (e.g.
7-aminoheptanoic acid), aromatic aminocarboxylic acids (e.g.
p-aminomethylbenzoic acid) and the like are also utilizable.
In addition to the said polyamide itself, the biaxially drawn film
may contain any other polymer (e.g. polycapramide,
polyhexamethylene adipamide, polyhexamethylene sebacamide,
polyundecanamide, polyethylene terephthalate, polyethylene,
polypropylene), an antistatic agent, a lubricant, an antiblocking
agent, a stabilizer, a dyestuff, a pigment and the like.
The biaxially drawn film can be manufactured by biaxially drawing
an undrawn film simultaneously or stepwise.
The undrawn film is a substantially unoriented film manufactured by
a per se conventional process such as melt process (e.g. T-die
method, inflation method), wet process or dry process. When, for
instance, the undrawn film is manufactured by the T-die method
according to the melt process, the polyamide incorporated with or
without any additive is heated at a temperature higher than the
melting point, the melted polyamide is extruded through a T-die and
the resulting film is cooled by a roll or a liquid bath maintained
at about 30 to 70.degree. C. to a temperature lower than the
secondary transition point. In the case of the temperature of the
roll or the liquid bath being higher than the secondary transition
point, the resulting film tends not to be flat and tends to have
lines so that even drawing in the subsequent step is effected with
difficulty. The said "secondary transition point" can be determined
by the use of a dilatometer on the temperature dependency of the
specific volume.
Alternatively, the biaxially drawn film may be manufactured by
extruding the polyamide incorporated with or without any additive
according to the inflation method, followed by immediate biaxial
drawing.
The drawing is effectively accomplished at a temperature higher
than the second transition point and lower than the melting point
of the polyamide.
The draw ratio is usually not less than 2, preferably not less than
2.5 in one direction. The draw ratio in the machine direction may
be the same as or different from that in the transverse
direction.
The smultaneous biaxial drawing may be effected by a conventional
procedure such as the tenter method or the inflation method.
In case of the stepwise drawing, the drawing may be ordinarily
carried out between two or more sets of rolls which are arranged in
the advancing direction and have different rotation speeds with
respect to each other. For drawing the film transversely, both
edges of the film are held by tenter clips, and drawing is effected
in a tenter while the film is heated. The order of the drawing in
the machine and transverse directions may be optional. In other
words, the drawing may be effected first in the machine direction
and then in the transverse direction or vice versa.
The drawn film thus obtained by simultaneous or stepwise biaxial
drawing shows, as such, various favorable properties. If necessary,
it may be further subjected to heat treatment at a temperature
between about 5.degree. C. above the drawing temperature in
manufacturer of the drawn film and the melting temperature of the
drawn film for a period of not more than about 5 minutes,
preferably for about 15 to 60 seconds. During the heat treatment,
the film may be kept under a tensioned or relaxed state. As the
result of the heat treatment, the degree of crystallinity of the
film increases and the strain of the film produced in the drawing
process is eliminated so that the mechanical property and the
dimensional stability of the film are considerably improved.
As the base layer for the composite film of the invention, there is
used the biaxially drawn film as above prepared, which has the
following physical constants:
(1) .[.Gas.]. .Iadd.Oxygen .Iaddend.permeability constant: not more
than 9 .times. 10.sup.-.sup.13 ml. cm./cm..sup.2 sec. cm. Hg,
preferably not more than 7 .times. 10.sup.-.sup.13 ml.
cm./cm..sup.2 sec. cm. Hg;
(2) Plane orientation index: not less than 0.025;
(3) Degree of balance: not more than 0.045;
(4) Breaking strength: not less than 10 kg./mm..sup.2, preferably
between 14 and 30 kg./mm..sup.2 in machine and transverse
directions;
(5) Breaking elongation: 30 to 150%, preferably 40 to 120% in
machine and transverse directions;
(6) Yield strength: not less than 5 kg./mm..sup.2, preferably
between 7 and 15 kg./mm..sup.2 in machine and transverse
directions; and
(7) Yield elongation: 2 to 6%, preferably 3 to 5% in machine and
transverse directions.
The thermoplastic resin as the coating layer to be provided on at
least one surface of the drawn film may be one having a melting
point or a softening point at least 50.degree. C. below the melting
point or the softening point of the polyamide constituting the
drawn film. It is favorably provided with such a property that,
when the ultimate composite film is rolled, the coating layer made
thereof does not produce blocking at room temperature. If the
difference between the melting point or the softening point of the
polyamide and the melting point or the softening point of the
thermoplastic resin is less than 50.degree. C., the drawn film will
deteriorate or shrink due to heat when heat sealing is made. The
melting point or the softening point of the thermoplastic resin is
usually not higher than about 170.degree. C., favorably from about
50 to 150.degree. C.
Specific examples of the thermoplastic resin are homopolymers and
copolymers of vinyl compounds (e.g. vinyl chloride, vinyl acetate,
styrene, acrylic acid, methyl acrylate, ethyl acrylate, propyl
acrylate, butyl acrylate, methacrylic acid, methyl methacrylate,
ethyl methacrylate, propyl methacrylate, butyl methacrylate,
acrylonitrile, methacrylonitrile, acrylamide, vinyl ether,
vinylpyrrolidone, vinylidene compounds (e.g. vinylidene chloride,
vinylidene cyanide), .alpha.-olefin compounds (e.g. ethylene,
propylene, butene, pentene, hexene), diene compounds (e.g.
butadiene, isoprene, chloroprene), and their halogenated
derivatives, sulfonated derivatives, sulfochlorinated derivatives
and aminated derivatives. Polyesters, polyamides, polyurethanes,
polyureas and other polycondensation or polyaddition compounds may
be also employed as the thermoplastic resin.
In order to improve the bond strength and/or the heat seal strength
of the coating layer, an appropriate additive such as a plasticizer
may be incorporated into the thermoplastic resin. Any other
additive such as an antiblocking agent, an antistatic agent or a
lubricant may be also incorporated therein.
The thermoplastic resin may be layered on the base layer of the
drawn film by a per se conventional procedure such as laminating,
coating, spraying or the like so as to form a coating layer.
In the case of coating, for instance, a solution or dispersion
containing the thermoplastic resin may be applied partly or wholly
to at least one of the surfaces of the drawn film as the base
layer, and the resulting layered product is dried to give a
composite film. The application may be effected by a per se
conventional procedure such as gravure roll method, reverse roll
method, Mayer bar method or air knife method.
The amount of the thermoplastic resin to be applied depends upon
the use of the resulting composite film. For a packaging sheet to
be used in an automatic packaging machine, the thickness of the
coating layer may be from about 1 to 2.mu.. For a packaging sheet
to be used in the form of a bag for light or middle weight goods,
the thickness may be from about 2 to 10.mu..
In order to increase the bond strength between the base layer and
the coating layer, a conventional adhesive agent may be
incorporated into the thermoplastic resin or precoated on the
surface of the coating layer prior to formation of the coating
layer.
In the case of laminating, for instance, the thermoplastic resin
may be melt extruded on the surface of the drawn film as the base
layer (i.e. extrusion lamination). Alternatively, a conventional
binding agent may be applied on the surface of at least one of the
drawn film as the base layer and a film made of the thermoplastic
resin as the coating layer and, after drying the applied binding
agent, both of the films may be combined each other (i.e. dry
lamination). In the extrusion lamination, the thermoplastic resin
may be melt extruded directly on the surface of the drawn film or,
after application of a conventional anchor coating agent on the
surface of the drawn film followed by drying, melt extruded
thereon. Examples of the anchor coating agent are organic titanium
compounds, polyalkyleneimine, isocyanates, acrylic compounds, etc.
For the extrusion lamination, polyolefins (particularly
polyethylene) are the preferred thermoplastic resin in view of easy
processability, low cost, high heat seal strength and the like.
Unfortunately, however, the composite film obtained by the use of
polyethylene for the coating layer is somewhat inferior in
transparency. For production of the composite film excellent in
transparency, the dry lamination of a drawn or undrawn film of
polypropylene as the coating layer on the drawn film as the base
layer is recommended.
The thus obtained composite film has an excellent gas-barrier
property and shows a heat seal strength.
The .[.gas.]. .Iadd.oxygen .Iaddend.transmission rate of the
composite film of the invention is not more than 50 ml./m..sup.2 24
hr. atm., mostly not more than 30 ml./m..sup. 2 24 hr. atm. For
instance, in case of the composite film of the invention of around
15.mu. thick obtained by coating the thermoplastic resin in a
thickness of 1 to 3.mu. on the surface of the drawn film as the
base layer, the .[.gas.]. .Iadd.oxygen .Iaddend.transmission rate
is ordinarily not more than 15 ml./m..sup.2 24 hr. atm., which is
about 1/2 or less that of a composite film obtained by coating
polyvinylidene chloride in a thickness of 3.mu. on the surface of a
film of polyethylene terephthalate of 20.mu. thick. Further, for
instance, in case of the composite film of the invention obtained
by laminating a film of the thermoplastic resin of 10 to 50.mu.
thick on the surface of the drawn film of around 15.mu. thick as
the base layer the .[.gas.]. .Iadd.oxygen .Iaddend.transmission
rate is normally not more than 15 ml./m..sup.2 24 hr. sec. atm.,
which is so low as not readily realized by any conventional
composite film.
The heat sealing with the composite film of the invention may be
carried out at a temperature of about 70 to 160.degree. C.,
preferably of about 80 to 150.degree. C.
The composite film obtained by coating can afford a heat seal
strength of not less than about 40 g./cm., usually of about 50 to
300 g./cm. The composite film obtained by laminating may give a
heat seal strength of not less than about 300 g./cm., usually of
about 500 to 3000 g./cm.
The thickness of the composite film is substantially of no
limitation and may be usually from about 6 to 200.mu., favorably
from about 6 to 100.mu.. The thickness of the drawn film as the
base layer and the thickness of the thermoplastic resin as the
laminating layer may be each not less than about 5.mu.. Preferred
are about 10 to 50.mu. and about 10 to 100.mu. respectively for the
thickness of the drawn film and the thickness of the laminated
thermoplastic resin.
The composite film of the invention has, as stated above, an
excellent gas-barrier property, a high heat seal strength and
various advantageous mechanical properties. Thus, it is useful as a
packaging material, particularly for such goods as being apt to be
deteriorated, colored, deflavored and so on. Since the mechanical
strength and the heat seal strength are quite excellent, it can be
used for packaging of goods of heavy weights.
Practical and presently preferred embodiments of the present
invention are illustratively shown in the following examples
wherein "MD" and "TD" indicate respectively "machine direction" and
"transverse direction." Measurement of the physical constants is
carried out as follows:
Relative viscosity:
Measured on a solution in 96% sulfuric acid at a concentration of 1
g./100 ml. at 25.degree. C.
Heat seal strength:
The surfaces of the coating layer of the composite film are heat
sealed each other. The strength on peeling in T-letter is measured
by a tensile tester ("Tensiron").
Peel strength:
As the test piece, the composite film of 1 cm. wide is used. The
coating layer is peeled off from the base layer at an angle of
180.degree. with a rate of 200 mm./min. The strength on peeling is
measured by a tensile tester ("Tensiron.")
Breaking strength; breaking elongation:
Measured according to ASTM-D 882.
Yield strength; yield elongation:
Measured according to ASTM-882. D
Haze value:
Determined by the use of a haze tester (manufactured by Toyo Seiki
K.K.) and calculated according to the following equation:
wherein A is a total quantity of transmitted light and A-B is a
quantity of diffused light.
.[.Gas.]. .Iadd.Oxygen .Iaddend.transmission rate; .[.gas.].
.Iadd.oxygen .Iaddend.permeability constant:
Measured by the use of a gas permeability measuring apparatus
(manufactured by Rika Seiki Kogyosha) at 30.degree. C. according
ASTM-ASTM--D 1434-58.
Plane orientation index; degree of balance:
Refractive indexes of a test piece in longitude (x), latitude (y)
and thickness (z) are measured by the use of a refractometer, and
the plane orientation index and the degree of balance are
calculated according to the following equations:
Degree of balance=.vertline.x-y
EXAMPLE 1
A metaxylylene/paraxylylene adipamide copolymer (molar ratio of
metaxylylene/paraxylylene=70/30; relative viscosity, 2.17; melting
point, 255.degree. C.) is melted at 286.degree. C. and extruded
through a flat die onto a cooling roll to give an undrawn film. The
undrawn film is drawn in a machine direction at a draw ratio of 4.2
by the aid of a set of rolls heated at 105.degree. C. and then in a
transverse direction at a draw ratio of 3.75 in a tenter kept at
115.degree. C. The drawn film is subjected to heat treatment at
215.degree. C. for 15 seconds to give a film of 15.mu. thick. The
physical constants of the film are as follows:
(1) .[.Gas.]. .Iadd.Oxygen .Iaddend.permeability constant:
1.6.times.10.sup.-.sup.13 ml. cm./cm..sup.2 sec. cm. Hg.
(2) Plane orientation index: 0.036.
(3) Degree of balance: 0.0011.
(4) Breaking strength: MD, 24.9 kg./mm..sup.2 ; TD, 25.4
kg./mm..sup.2.
(5) Breaking elongation: MD, 65%; TD, 39%.
(6) Yield strength: MD, 11.0 kg./mm..sup.2 ; TD, 11.6
kg./mm..sup.2.
(7) Yield elongation: MD, 2.8%; TD, 3.4%.
A vinyl chloride/vinylidene chloride copolymer (molar ratio, 85/15)
is dissolved in a toluene-methylethylketone mixture (70/30 by
weight) to make a 20% resin solution. The resin solution is applied
on one surface of the above obtained film according to the gravure
roll method, and the resulting film is dried at 110.degree. C. for
10 seconds to give a transparent composite film. The heat seal
strength of the composite film when heat sealed at 150.degree. C.
and the peel strength between the base layer and the coating layer
in the composite film are measured and shown in Table 1.
EXAMPLE 2
A metaxylylene/paraxylylene adipamide copolymer (molar ratio, 99/1;
relative viscosity, 2.28; melting point, 236.degree. C.) is melted
at 275.degree. C. and extruded through a flat die onto a cooling
roll to give an undrawn film. The undrawn film is drawn in one
direction in a machine direction at a draw ratio of 3.75 at
87.degree. C. between two rolls which are rotating at a different
velocity and then in a transverse direction at a draw ratio of 4.3
in a tenter kept at 110.degree. C. The drawn film is subjected to
heat treatment at 210.degree. C. for 20 seconds to give a film of
15.mu. thick. The physical constants of the film are as
follows:
(1) .[.Gas.]. .Iadd.Oxygen .Iaddend.permeability constant:
1.7.times.10.sup.-.sup.13 ml. cm./cm..sup.2 sec. cm. Hg.
(2) Plane orientation index: 0.040.
(3) Degree of balance: 0.024.
(4) Breaking strength: MD, 19.1 kg./mm..sup.2 ; TD, 27.1
kg./mm..sup.2.
(5) Breaking elongation: MD, 91%; TD, 56%.
(6) Yield strength: MD, 9.8 kg./mm..sup.2 ; TD, 9.6
kg./mm..sup.2.
(7) Yield elongation: MD, 3.5%; TD, 3.0%.
A mixture of a vinyl chloride/vinylidene chloride copolymer (molar
ratio, 85/15) and chlorinated paraffin (chlorine content, 40% by
weight) in a ratio of 90/10 by weight is dissolved in a
toluene-methylethylketone mixture (70/30 by weight) to make a 20%
resin solution. The resin solution is applied on one surface of the
above obtained film according to the gravure roll method, and the
resulting film is dried at 110.degree. C. for 10 seconds to give a
transparent composite film. The heat seal strength of the composite
film when heat sealed at 150.degree. C., and the peel strength
between the base layer and the coating layer in the composite film
are measured and shown in Table 1.
EXAMPLE 3
On one surface of a biaxially drawn film of 15.mu. thick produced
as in Example 2, a 15% solution of a vinylidene
chloride/acrylonitrile copolymer (molar ratio, 90/10) in
tetrahydrofuran is applied according to the gravure roll method,
and the films dried at 120.degree. C. for 30 seconds to make a
coating layer of about 2.mu. thick. The heat seal strength of the
composite film when heat sealed and the peel strength between the
base layer and the coating layer in the composite film are measured
and shown in Table 1.
EXAMPLE 4
On one surface of a biaxially drawn film of 15.mu. thick produced
as in Example 2, a 50% aqueous emulsion of a vinylidene
chloride/methyl acrylate copolymer (molar ratio, 90/10) is applied
according to the air knife method, and the film is dried at
120.degree. C. for 30 seconds to make a transparent coating layer
of about 3.mu. thick. The heat seal strength of the composite film
when heat sealed and the peel strength between the base layer and
the coating layer in the composite film are measured and shown in
Table 1.
EXAMPLE 5
A mixture of an ethylene/vinyl acetate copolymer (vinyl acetate
content, 28 mol percent) and a low molecular weight polyethylene
(molecular weight, 1,000 to 4,000) in a ratio of 75/25 by weight is
dissolved in a toluene-methylethylketone mixture (70/30 by weight)
under heating to make a 20% resin solution. The resin solution is
applied on one surface of a biaxially drawn film of 15.mu. thick
produced as in Example 1 according to the gravure roll method, and
the film is dried at 100.degree. C. for 10 seconds. The coated
amount of the resin is 3.5 g./m..sup.2 at dryness. The heat seal
strength of the composite film when heat sealed and the peel
strength between the base layer and the coating layer in the
composite film are measured and shown in Table 1.
EXAMPLE 6
On one surface of a biaxially drawn film of 15.mu. thick produced
as in Example 1, a 10% toluene solution of an ethylene/vinyl
acetate copolymer (vinyl acetate content, 28 mol percent) is
applied, and the film is dried at 100.degree. C. for 10 seconds to
make an undercoat of about 1.mu. thick. A 10% solution of a vinyl
chloride/vinyl acetate copolymer (molar ratio, 85/15) in a
toluene-ethyl acetate mixture (70/30 by weight) is applied on the
undercoat to make a surface coat of about 2.mu. thick. The heat
seal strength of the composite film when heat sealed and the peel
strength between the base layer and the coating layer in the
composite film are measured and shown in Table 1.
REFERENCE EXAMPLE 1
A biaxially drawn film of 15.mu. thick produced as in Example 2 is
subjected to heat adhesion at 130.degree. C. under 1 kg./cm..sup.2
for 1 second, but no heat seal is seen at all. Even at a higher
temperature such as 180.degree. C., heat seal is not caused under 1
kg./cm..sup.2 to 1 second.
REFERENCE EXAMPLE 2
On one surface of a biaxially drawn film of polypropylene of 20.mu.
thick or of a biaxially drawn film of polyethylene terephthalate of
20.mu. thick, a 50% aqueous emulsion of a vinylidene
chloride/methyl acrylate copolymer (molar ratio, 90/10) is applied
to make a transparent coating layer of about 3.mu. thick. The heat
seal strength of the composite film when heat sealed and the peel
strength between the base layer and the coating layer in the
composite film are measured and shown in Table 2 wherein those
measured on the composite film as produced in Example 4 are also
shown.
EXAMPLE 7
A metaxylylene/paraxylylene adipamide copolymer (molar ratio of
metaxylylene/paraxylylene=99/1; relative viscosity, 2.28; melting
point, 236.degree. C.) is melted at 275.degree. C. and extruded
through a flat die onto a cooling to give an undrawn film. The
undrawn film is drawn in a machine direction at a draw ratio of
3.75 by the aid of a roll heated at 87.degree. C. and then in a
transverse direction at a draw ratio of 4.3 in a tenter kept at
110.degree. C. The drawn film is subjected to heat treatment at
210.degree. C. for 15 seconds to give a film of 12.mu. thick. The
physical constants of the film are as follows:
(1) .[.Gas.]. .Iadd.Oxygen .Iaddend.permeability constant:
1.7.times.10.sup.-.sup.13 ml. cm./cm..sup.2 sec. cm. Hg.
(2) Plane orientation index: 0.039.
(3) Degree of balance: 0.021.
(4) Breaking strength: MD, 20.2 kg./mm..sup.2 ; TD, 26.5
kg./mm..sup.2.
(5) Breaking elongation: MD, 86%; TD, 60%.
(6) Yield strength: MD, 9.7 kg./mm..sup.2 ; TD, 10.1
kg./mm..sup.2.
(7) Yield elongation: MD, 3.4%; TD, 2.9%.
An anchor coating agent (concentration, 4%) is applied on one
surface of the above obtained film and, after drying in a dryer of
2 m. in length at 110.degree. C., polyethylene ("Petrosen 205"
manufactured by Mitsui Polychemical Co., Ltd.) is melt extruded at
330.degree. C. with a rate of 60 m./min. on the surface to give a
coating layer of 40.mu.. The heat seal strength of the composite
film when heat sealed at 140.degree. C. under 2 kg./cm..sup.2 for 1
second and the peel strength between the base layer and the coating
layer in the composite film are measured and shown in Table 3.
EXAMPLE 8
A metaxylylene/paraxylylene adipamide copolymer (molar ratio of
metaxylylene/paraxylylene=70/30; relative viscosity, 2.17; melting
point, 255.degree. C.) is melted at 286.degree. C. and extruded
through a flat die onto a cooling roll to give an undrawn film. The
undrawn film is drawn in a machine direction at a draw ratio of 4.2
by the aid of a set of rolls heated at 105.degree. C. and then in a
transverse direction at a draw ratio of 3.75 in a tenter kept at
115.degree. C. The drawn film is subjected to heat treatment at
215.degree. C. for 15 seconds to give a film of 12.mu. thick. The
physical constants of the film are as follows:
(1) .[.Gas.]. .Iadd.Oxygen .Iaddend.permeability constant:
1.6.times.10.sup.-.sup.13 ml. cm./cm..sup.2 sec. cm. Hg.
(2) Plane orientation index: 0.035.
(3) Degree of balance: 0.0012.
(4) Breaking strength: MD, 23.8 kg./mm..sup.2, TD, 25.1
kg./mm..sup.2.
(5) Breaking elongation: MD, 71%; TD, 45%.
(6) Yield strength: MD, 11.5 kg./mm..sup.2, TD, 12.1
kg./mm..sup.2.
(7) Yield elongation: MD, 3.3%; TD, 3.7%.
A binding agent (concentration, 15%) is applied on one surface of
the above obtained film and, after drying by passing through a
dryer of 2 m. in length at a rate of 30 m./min., an undrawn film of
polypropylene of 25.mu. thick is laminated thereon at a temperature
of 60 to 70.degree. C. under a pressure of 5 kg./cm..sup.2. The
heat seal strength of the resulting composite film when heat sealed
at 150.degree. C. under 1 kg./cm..sup.2 for 1 second and the peel
strength between the base layer and the coating layer in the
composite film are measured and shown in Table 4.
The composite film obtained in this Example is quite excellent in
transparency and the haze value is less than 5%.
EXAMPLE 9
Miso (bean paste) is packaged with a composite film consisting of a
biaxially drawn film of polyamide and a polyethylene film prepared
as in Example 7 (film (A)), a composite film consisting of a
biaxially drawn film of polyethylene terephthalate of 12.mu. thick
and a polyethylene film of 50.mu. thick coated with polyvinylidene
chloride of about 3.mu. thick (film (B)), a composite film
consisting of a biaxially drawn film of polypropylene of 20.mu.
thick and a polyethylene film of 50.mu. (film (C)) or a composite
film consisting of a biaxially drawn film of polyamide and a
polypropylene film prepared as in Example 8 (film (D)), and the
packaged product is allowed to stand at 20 to 25.degree. C. The
.[.gas.]. .Iadd.oxygen .Iaddend.transmission rate of each composite
film before packaging and the color change of each composite film
after packaging are measured and shown in Table 5.
From Table 5, is is seen that the composite film of the invention
(i.e., films (A) and (D)) is extremely smaller than the
conventional composite film (i.e., films (B) and (C)) in the
.[.gas.]. .Iadd.oxygen .Iaddend.transmission rate and changes to
brown with much difficulty.
TABLE 1
__________________________________________________________________________
[Gas] Oxygen trans- Heat mission Breaking seal Peel rate strength
strength strength (ml./m..sup.2 (kg./mm..sup.2) Thermoplastic resin
as the coating layer (g./cm.) (g./cm.) 24 hr./atm.) MD TD
__________________________________________________________________________
Example number: 1 Vinyl chloride/vinylidene chloride copolymer 71.0
29.0 7.1 24.8 25.2 2 Vinyl chloride/vinylidene chloride copolymer
plus 120.0i- 42.0 7.9 19.2 27.3 nated paraffin. 3 Vinylidene
chloride/acrylonitrile copolymer 115.0 .sup.(1) 5.2 18.9 27.4 4
Vinylidene chloride/methyl acrylate copolymer 162.5 94.0 5.5 19.4
27.0 5 Ethylene/vinyl acetate copolymer plus polyethylene 297.0
.sup.(1) 6.9 25.0 25.5 6 Ethylene/vinyl acetate copolymer plus
vinyl chloride/vinyl 153.2 .sup.(1) 7.2 24.7 25.3 acetate
copolymer. Reference example 1 None 0 7.4 19.1 27.1
__________________________________________________________________________
.sup.1 Not peeled.
TABLE 2
__________________________________________________________________________
oxygen Heat [Gas] seal Peel transmission strength strength
(ml./m..sup.2 .multidot. Example number Composite film (g./cm.)
(g./cm.) 24
__________________________________________________________________________
hr./atm.) 4 Polyxyleneadipamide/vinylidene chloride-methyl acrylate
162.5 94.0 5.5 polymer (15.mu./3.mu.). Reference example 2
Polypropylene/vinylidene chloride-methyl acrylate 80.0ymer 12.5
45.0 (20.mu./3.mu.). " Polyethylene terephthalate/vinylidene
chloride-methyl acrylate 123.7 45.3 27.2 copolymer (20.mu./3.mu.).
__________________________________________________________________________
TABLE 3
__________________________________________________________________________
[Gas] Oxygen Heat seal strength trans- (kg./15 mm.) mission rate
Peel strength Before After (ml./m..sup.2 .multidot. Anchor coating
agent (g./10 mm.) heated* heated* 24 hr./atm.)
__________________________________________________________________________
Alkyltitanate (i.e., a mixture of tetraisopropyltitanate Not peeled
2.4 1.5 9.0 and tetrabutyltitanate).
Triphenyrolpropane-toluylene-diisocyanate adduct " 2.7 3.4 9.1
Polyester-urethane " 2.6 2.8 9.0 None 80 2.5 1.0
__________________________________________________________________________
*Heating is effected in hot water of 95.degree. C for 30
minutes.
TABLE 4
__________________________________________________________________________
[Gas] Oxygen Heat seal strength trans- Peel (kg./15 mm.) mission
rate strength Before After (ml./m..sup.2 .multidot. Binding agent
(g./10 mm.) heated* heated* 24 hr./atm.)
__________________________________________________________________________
Polyester-urethane Not peeled 1.6 1.5 8.9
Triphenyrolpropane-toluylene-diisocyanate adduct " 1.6 1.6 8.9
Trimethyrolpropane-toluylene-diisocyanate adduct " 1.6 1.5 9.1
RV-300 plus xylene resin triphenyrolpropane- " 1.3 1.1 9.1
toluylene-diisocyanate
__________________________________________________________________________
*Heating is effected in hot water of 95.degree. C. for 30
minutes.
TABLE 5 ______________________________________ [Gas] Oxygen
transmission Days rate up to (ml./m..sup.2 .multidot.24 change
hr..multidot.atm.) to brown ______________________________________
Film number: (A) 8.5 >30 (B) 23.0 7 (C) 38.1 4 (D) 9.1 >30
______________________________________
* * * * *