U.S. patent application number 15/580726 was filed with the patent office on 2018-06-14 for heat-shrinkable polyester film and package.
This patent application is currently assigned to TOYOBO CO., LTD.. The applicant listed for this patent is TOYOBO CO., LTD.. Invention is credited to Masayuki HARUTA, Masafumi INOUE.
Application Number | 20180162616 15/580726 |
Document ID | / |
Family ID | 57503850 |
Filed Date | 2018-06-14 |
United States Patent
Application |
20180162616 |
Kind Code |
A1 |
INOUE; Masafumi ; et
al. |
June 14, 2018 |
HEAT-SHRINKABLE POLYESTER FILM AND PACKAGE
Abstract
The invention provides a heat-shrinkable polyester film which
has sufficient heat shrinkage properties in a main shrinkage
direction that is in the longitudinal direction, has low heat
shrinkage in the width direction orthogonal to the main shrinkage
direction, does not have excessively high shrinkage stress in the
main shrinkage direction, and has small attenuation of the
shrinkage stress, whereby the followability to a container which is
an object to be packaged is high, and slack is less likely to be
generated.
Inventors: |
INOUE; Masafumi;
(Tsuruga-shi, Fukui, JP) ; HARUTA; Masayuki;
(Tsuruga-shi, Fukui, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TOYOBO CO., LTD. |
Osaka-shi, Osaka |
|
JP |
|
|
Assignee: |
TOYOBO CO., LTD.
Osaka-shi, Osaka
JP
|
Family ID: |
57503850 |
Appl. No.: |
15/580726 |
Filed: |
June 8, 2016 |
PCT Filed: |
June 8, 2016 |
PCT NO: |
PCT/JP2016/067049 |
371 Date: |
December 8, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B32B 2264/102 20130101;
B32B 2439/62 20130101; B32B 2264/10 20130101; C08J 2367/02
20130101; B32B 2264/104 20130101; B32B 27/28 20130101; B32B
2307/418 20130101; C08J 5/18 20130101; B32B 7/022 20190101; B32B
2250/03 20130101; B32B 27/10 20130101; B32B 2264/0214 20130101;
B32B 2270/00 20130101; B32B 2307/30 20130101; B32B 3/02 20130101;
B65D 75/002 20130101; B32B 2307/746 20130101; B32B 2439/60
20130101; B32B 2439/66 20130101; B32B 2250/02 20130101; B32B
2264/0235 20130101; B32B 27/08 20130101; B32B 2519/00 20130101;
B32B 7/04 20130101; B32B 27/36 20130101; B32B 2307/732 20130101;
B32B 27/20 20130101; B32B 2264/025 20130101 |
International
Class: |
B65D 75/00 20060101
B65D075/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 11, 2015 |
JP |
2015-118277 |
Claims
1. A heat-shrinkable polyester film which has a main shrinkage
direction in a longitudinal direction of the film and satisfies the
following requirements (1) to (4): (1) the film has a hot-water
shrinkage in the main shrinkage direction of the film of 40% or
more and 80% or less when treated for 10 seconds in hot water of
98.degree. C.; (2) the film has a hot-water shrinkage in a
direction orthogonal to the main shrinkage direction of the film of
-5% or more and 15% or less when treated for 10 seconds in hot
water of 98.degree. C.; (3) with regard to a shrinkage stress in
the main shrinkage direction of the film measured under hot air of
90.degree. C., the film has a shrinkage stress ratio of 0.6 or more
and 1.0 or less, the shrinkage stress ratio being represented by
the following equation: shrinkage stress ratio=(shrinkage stress
after 30 seconds)/(maximum shrinkage stress); and (4) the film has
a refractive index in the main shrinkage direction of the film of
1.600 or more.
2. The heat-shrinkable polyester film according to claim 1, wherein
a maximum shrinkage stress in the main shrinkage direction of the
film measured under hot air of 90.degree. C. is 15 MPa or less.
3. The heat-shrinkable polyester film according to claim 2, wherein
the film comprises ethylene terephthalate as a main constituent
component and 2 mol % or more of at least one monomer component
that can form an amorphous component in a whole polyester resin
component.
4. The heat-shrinkable polyester film according to claim 3, wherein
neopentyl glycol is used as at least one monomer component that can
form an amorphous component.
5. A package obtained by covering at least a part of an outer
periphery of an object to be packaged with the heat-shrinkable
polyester film according to claim 4 and then shrinking the film on
the covered object by heat.
6. The heat-shrinkable polyester film according to claim 2, wherein
neopentyl glycol is used as at least one monomer component that can
form an amorphous component.
7. The heat-shrinkable polyester film according to claim 1, wherein
the film comprises ethylene terephthalate as a main constituent
component and 2 mol % or more of at least one monomer component
that can form an amorphous component in a whole polyester resin
component.
8. The heat-shrinkable polyester film according to claim 7, wherein
neopentyl glycol is used as at least one monomer component that can
form an amorphous component.
9. The heat-shrinkable polyester film according to claim 1, wherein
neopentyl glycol is used as at least one monomer component that can
form an amorphous component.
10. A package obtained by covering at least a part of an outer
periphery of an object to be packaged with the heat-shrinkable
polyester film according to claim 1 and then shrinking the film on
the covered object by heat.
Description
TECHNICAL FIELD
[0001] The present invention relates to a heat-shrinkable polyester
film and a package. More particularly, the present invention
relates to a heat-shrinkable polyester film which is suitable for a
label application and a banding application to bind a box lunch
container or the like and which enables finishing with less slack
to an object to be packaged since the attenuation of shrinkage
stress of the film at the time of shrinking by heating is
small.
BACKGROUND ART
[0002] Recently, in applications such as label package doubling as
a protection of a glass bottle and a PET bottle etc. and display of
articles, cap sealing, and accumulation package, there have been
widely used drawn films (so-called heat-shrinkable films) composed
of a polyvinyl chloride resin, a polystyrene resin, a polyester
resin or the like. Of these heat-shrinkable films, a polyvinyl
chloride film has problems that heat resistance is low, and it
generates hydrogen chloride gas in incineration and causes dioxin.
A polystyrene film has problems that it is inferior in solvent
resistance, as well as an ink with a special composition needs to
be used in printing, it requires high temperature incineration and
generates a lot of black smoke accompanied by an abnormal odor.
Therefore, as a shrink label, there has been widely used a
polyester-based heat-shrinkable film which is high in heat
resistance, easy to incinerate, and excellent in solvent
resistance, and the use amount tends to increase being accompanied
by an increase in distribution volume of PET containers.
[0003] As an ordinary heat-shrinkable polyester film, one which is
allowed to shrink greatly in the width direction has been widely
utilized. When the film is used as a label film for a bottle or a
banding film for binding a box lunch container or the like, the
film should be made into an annular form, mounted to the bottle or
the box lunch container or the like, and then allowed to
heat-shrink in the circumferential direction. Therefore, when a
heat-shrinkable film that heat-shrinks in the width direction is
mounted as a banding film, after forming an annular-shaped member
such that the width direction of the film is in the circumferential
direction, the annular-shaped member should be cut into segments
having a predetermined length, and each segment should be mounted
to the bottle or the box lunch container, for example, by placing
it by hand over the bottle or the box lunch container. Therefore,
it is difficult to mount a label or a banding film made of the
heat-shrinkable film that heat-shrinks in the width direction to a
bottle or a box lunch container at high speed. For that reason,
recently, there is a need for a longitudinally heat-shrinkable film
which can be wound around a bottle or a box lunch container
directly from a film roll to mount the bottle or the box lunch
container. With such a heat-shrinkable film, a center sealing step
in which an annular-shaped member is formed and sealed or
processing such as cutting, placing by hand, or the like can be
eliminated, and thus mounting at high speed is also possible.
[0004] As a demand for a shrinkable film, it is desired to follow
the shape of an object to be packaged at the time of shrinking and
to have a tight feeling after shrinking. In the case of a label of
a beverage bottle, if the label does not follow the shape of the
bottle and has no tightness, there is a problem that when a
consumer holds the body of the bottle and opens the cap of the
bottle, the cap cannot be opened easily since the label rotates.
Furthermore, in the case of a banding application of a box lunch
container, the shrinkable film is required to be tightly finished
to prevent spilling of the contents in the box lunch container and
to prevent foreign matter contamination.
[0005] As a method for giving tightness after finishing shrinkage
to a shrinkable film, it is conceivable to increase shrinkage
stress. However, if the shrinkage stress is too high, there is a
problem that when a thin soft beverage bottle or box lunch
container is packaged with the film, the bottle or container may
deform. In addition, there is a problem that the bonded portion of
a cylindrical label or a banding film may be separated due to high
shrinkage stress.
[0006] For example, in Patent Document 1, it is described that a
heat-shrinkable film is subjected to intermediate heat treatment
after drawing in the longitudinal direction, and then drawn in the
width direction, whereby the maximum shrinkage stress in the width
shrinkage direction of the film when measured in hot air at
90.degree. C. is large, and the shrinkage stress does not attenuate
much after 30 seconds, and it is described that such a
heat-shrinkable film is satisfactory in followability to a
container in a label application, the slack of the label after
finishing is less likely to be generated, and a satisfactory
appearance can be attained.
[0007] However, in the method described in Patent Document 1, a
large-scale facility for biaxially drawing is necessary, which
causes a problem of increased cost. Furthermore, it is difficult to
mount a film that shrinks in the width direction as described above
to a bottle or a box lunch container at high speed.
PRIOR ART DOCUMENT
Patent Documents
[0008] Patent Document 1: Japanese Patent Publication No. 5240387
(B1)
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0009] An object of the present invention is to provide a
heat-shrinkable polyester film which has sufficient heat shrinkage
properties in a main shrinkage direction that is in the
longitudinal direction, has low heat shrinkage in the width
direction orthogonal to the main shrinkage direction, does not have
excessively high shrinkage stress in the main shrinkage direction,
and has small attenuation of the shrinkage stress, whereby the
followability to a container which is an object to be packaged is
high, and slack is less likely to be generated.
Means for Solving the Problem
[0010] That is, the present invention has the following
constitution.
[0011] 1. A heat-shrinkable polyester film which has a main
shrinkage direction in a longitudinal direction of the film and
satisfies the following requirements (1) to (4):
[0012] (1) the film has a hot-water shrinkage in the main shrinkage
direction of the film of 40% or more and 80% or less when treated
for 10 seconds in hot water of 98.degree. C.;
[0013] (2) the film has a hot-water shrinkage in a direction
orthogonal to the main shrinkage direction of the film of -5% or
more and 15% or less when treated for 10 seconds in hot water of
98.degree. C.;
[0014] (3) with regard to a shrinkage stress in the main shrinkage
direction of the film measured under hot air of 90.degree. C., the
film has a shrinkage stress ratio of 0.6 or more and 1.0 or less,
the shrinkage stress ratio being represented by the following
equation:
shrinkage stress ratio=(shrinkage stress after 30 seconds)/(maximum
shrinkage stress); and
[0015] (4) the film has a refractive index in the main shrinkage
direction of the film of 1.600 or more.
[0016] 2. The heat-shrinkable polyester film according to the above
1, wherein a maximum shrinkage stress in the main shrinkage
direction of the film measured under hot air of 90.degree. C. is 15
MPa or less.
[0017] 3. The heat-shrinkable polyester film according to the above
1 or 2, wherein the film comprises ethylene terephthalate as a main
constituent component and 2 mol % or more of at least one monomer
component that can form an amorphous component in a whole polyester
resin component.
[0018] 4. The heat-shrinkable polyester film according to any of
the above 1 to 3, wherein neopentyl glycol is used as at least one
monomer component that can form an amorphous component.
[0019] 5. A package obtained by covering at least a part of an
outer periphery of an object to be packaged with the
heat-shrinkable polyester film according to any of the above 1 to 4
and then shrinking the film on the covered object by heat.
Effects of the Invention
[0020] The present inventors made intensive studies, and as a
result, have found that in a single layer film made of a single
resin or a laminated film in which different types of resins are
laminated, using at least one layer made of a polyester resin
having a specific composition allows the shrinkage stress in the
main shrinkage direction to be not too high and allows the
attenuation of the shrinkage stress to be small, and thus the film
has high followability to a container which is an object to be
packaged at the time of shrinking and is less likely to slacken.
The present invention has been completed based on this finding.
[0021] That is, according to the present invention, it is possible
to provide a heat-shrinkable polyester film which has sufficient
heat shrinkage properties in a main shrinkage direction that is in
the longitudinal direction, has low heat shrinkage in the width
direction orthogonal to the main shrinkage direction, does not have
excessively high shrinkage stress in the main shrinkage direction,
and has small attenuation of the shrinkage stress, whereby the
followability to a container which is an object to be packaged is
high at the time of shrinking, and slack is less likely to be
generated. The heat-shrinkable polyester film of the present
invention can be suitably used as a film label for a bottle or a
banding film to bind a container such as a box lunch and can be
very efficiently mounted to the bottle or the container within a
short time since the main shrinkage direction is in the
longitudinal direction. In addition, when the heat-shrinkable
polyester film of the present invention is subjected to heat
shrinkage after mounting, shrinkage shortage, lengthwise sink-marks
and container deformation are extremely reduced, and the
followability to the container is sufficient and slack is less
likely to be generated due to small attenuation of the shrinkage
stress, whereby good finishing can be achieved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 shows a box lunch container evaluating wrinkles of
film after shrinking.
[0023] FIG. 2 shows a box lunch container evaluating sink marks of
film after shrinking.
EXPLANATION OF LETTERS OR NUMERALS
[0024] 1: box lunch container [0025] 2: film [0026] 3: wrinkle
[0027] 4: box lunch container [0028] 5: film
MODE FOR CARRYING OUT THE INVENTION
[0029] Hereinafter, the structure of the heat-shrinkable polyester
film according to the present invention will be described.
[0030] The heat-shrinkable polyester film according to the present
invention has at least one layer containing 50 mol % or more of an
ethylene terephthalate unit in 100 mol % of the constituent units
of polyester. The details will be described later, but as a result
of studies made by the present inventors, it has been found that as
for a film having at least one layer containing 50 mol % or more of
an ethylene terephthalate unit in 100 mol % of the constituent
units of polyester, if the draw ratio is increased more than 3
times, the crystallization is promoted, and consequently the
attenuation rate of the shrinkage stress is small and the shrinkage
stress after 30 seconds from the initiation of shrinking becomes
high.
[Case of Single Layer Film]
[0031] In the case of a single layer film, for the reason mentioned
above, the polyester used in the heat-shrinkable polyester film is
a polyester containing an ethylene terephthalate unit as a main
constituent. The content of the ethylene terephthalate unit is 50
mol % or more in 100 mol % of the constituent units of the
polyester. In order to promote crystallization at the time of
drawing in the longitudinal direction as described later, the
content of the ethylene terephthalate unit is preferably 55 mol %
or more, and more preferably 60 mol % or more in 100 mol % of the
constituent units of the polyester. However, if the content of the
ethylene terephthalate unit is too high, it is difficult to obtain
necessary high shrinkage because shrinkage property is inhibited by
crystallization, and therefore the upper limit of the content of
the ethylene terephthalate unit is preferably 70% or less.
[0032] Other dicarboxylic acid components constituting the
polyester of the present invention can include aromatic
dicarboxylic acids such as isophthalic acid,
naphthalenedicarboxylic acid, and ortho-phthalic acid, and;
aliphatic dicarboxylic acids such as adipic acid, azelaic acid,
sebacic acid and decanedicarboxylic acid; and alicyclic
dicarboxylic acid; or the like.
[0033] When an aliphatic dicarboxylic acid (for example, adipic
acid, sebacic acid, decanedicarboxylic acid or the like) is
contained in the polyester, the content is preferably less than 3
mol % (in 100 mol % of the dicarboxylic acid component).
[0034] Further, it is preferable not to contain polybasic
carboxylic acids of tribasic or more (for example, trimellitic
acid, pyromellitic acid and anhydride thereof etc.) in the
polyester. A heat-shrinkable polyester film obtained by using a
polyester containing these polybasic carboxylic acids is hard to
achieve a necessary high shrinkage.
[0035] Diol components constituting the polyester include aliphatic
diols such as ethylene glycol, 1,3-propanediol, 1,4-butanediol,
neopentyl glycol and hexanediol; alicyclic diols such as
1,4-cyclohexanedimethanol; and aromatic diols such as bisphenol
A.
[0036] Further, the polyester has 2% or more of the sum of at least
one monomer component that can form an amorphous component in 100
mol % of a polyhydric alcohol component or in 100 mol % of a
polybasic carboxylic acid component in the whole polyester resin,
preferably 3% or more, more preferably 4% or more, and particularly
preferably 5% or more. If the amount of monomer component that can
form an amorphous component increases, crystallization at the time
of drawing in the longitudinal direction does not sufficiently
proceed, and therefore the upper limit is preferably 20 mol %.
[0037] Examples of the monomer that can form an amorphous component
may include neopentyl glycol, 1,4-cyclohexanedimethanol,
isophthalic acid, 1,4-cyclohexanedicarboxylic acid,
2,6-naphthalenedicarboxylic acid, 2,2-diethyl-1,3-propanediol,
2-n-butyl-2-ethyl-1,3-propanediol, 2,2-isopropyl-1,3-propanediol,
2,2-di-n-butyl-1,3-propanediol, and hexanediol. Among these,
neopentyl glycol, 1,4-cyclohexanedimethanol, or isophthalic acid is
preferably used. In addition, .epsilon.-caprolactone is also
preferably used.
[0038] To a resin for forming the heat-shrinkable polyester film of
the present invention, according to needs, there can be added
various additives, such as waxes, an antioxidant, an antistatic
agent, a crystal-nucleation agent, a viscosity reducing agent, a
heat stabilizer, a pigment for coloring, a color protection agent,
and an ultraviolet absorber.
[0039] By adding fine particles as lubricant to a resin for forming
the heat-shrinkable polyester film of the present invention, it is
preferable to make workability (slipperiness) of the film better.
The fine particles can be arbitrarily selected, for example, as
inorganic fine particles, silica, alumina, titanium dioxide,
calcium carbonate, kaolin, barium sulfate and the like can be
listed. As organic fine particles, for example, an acrylic resin
particle, a melamine resin particle, a silicone resin particle, a
crosslinked polystyrene particle and the like can be listed. The
average particle diameter of the fine particles is in a range of
0.05 to 3.0 .mu.m (when measured by coulter counter), and it can be
suitably selected according to need.
[0040] As a method for compounding the above-described particles in
a resin for forming the heat-shrinkable polyester film, for
example, they can be added in an arbitrary step in production of
the polyester resin, but they are preferably added in a step of
esterification, or in a step after completion of ester exchange
reaction and before start of polycondensation reaction as slurry
dispersed in ethylene glycol etc., followed by carrying out
polycondensation reaction. Further, it is also preferably carried
out by a method in which slurry of particles dispersed in ethylene
glycol, water or the like and raw materials of polyester resin are
mixed using a kneading extruder with a vent, or a method in which
dried particles and raw materials of polyester resin are mixed
using a kneading extruder.
[0041] It is also possible to conduct corona treatment, coating
treatment, frame treatment etc. on the heat-shrinkable polyester
film of the present invention in order to enhance adhesiveness of
film surface.
[Case of Laminated Film]
[0042] In the case of a laminated film in which resin layers having
different resin compositions are laminated, it is necessary to use
at least one polyester layer containing 50 mol % or more of an
ethylene terephthalate unit in 100 mol % of the constituent units
of the polyester in the film laminate structure. For the same
reason as in the case of the single layer film, that is, for the
reason that by providing at least one layer containing 50 mol % or
more of the ethylene terephthalate unit in the film structure of
the laminated film, the laminated film has characteristics that if
the draw ratio is increased more than 3 times, the crystallization
is promoted, and consequently the attenuation rate of the shrinkage
stress is small and the shrinkage stress after 30 seconds from the
initiation of shrinking becomes high.
[0043] In the present invention, when the film is made into a
three-layer structure, it is preferable that an outermost layer
(skin layer) be a layer containing 50 mol % or more of an ethylene
terephthalate unit. The reason for this is to promote the
crystallization of the outermost layer by drawing and reduce the
attenuation rate of the shrinkage stress.
[0044] The composition of a resin for forming a core layer is not
particularly limited. However, from the viewpoint of mechanical
strength and the like, a resin containing an ethylene terephthalate
unit as a main constituent component is preferable, and the content
of the ethylene terephthalate unit is preferably 85 mol % or less
in 100 mol % of the constituent units of the polyester. If the
content of the ethylene terephthalate unit is too large, the
crystallization is excessively promoted, and hence a high shrinkage
cannot be obtained.
[0045] Diol components constituting the polyester in the core layer
include aliphatic diols such as ethylene glycol, 1,3-propanediol,
1,4-butanediol, neopentyl glycol and hexanediol; alicyclic diols
such as 1,4-cyclohexanedimethanol; and aromatic diols such as
bisphenol A.
[0046] Further, the polyester has 2% or more of the sum of at least
one monomer component that can form an amorphous component in 100
mol % of a polyhydric alcohol component or in 100 mol % of a
polybasic carboxylic acid component in the whole polyester resin,
preferably 3% or more, more preferably 4% or more, and particularly
preferably 5% or more.
[0047] Here, the interpretation of the term "can form an amorphous
component" is described in detail.
[0048] In the present invention, the "amorphous polymer"
specifically refers to the case where no endothermic peak due to
fusion is shown in measurement with a differential scanning
calorimeter (DSC). Since the crystallization of the amorphous
polymer does not substantially proceed, the amorphous polymer
cannot be in a crystalline state or has an extremely low degree of
crystallinity even when crystallized.
[0049] Furthermore, in the present invention, the "crystalline
polymer" refers to a polymer other than the above-mentioned
"amorphous polymer", that is, the case where an endothermic peak
due to fusion is shown in measurement with a differential scanning
calorimeter (DSC). The crystalline polymer means a polymer that can
be crystallized when heated, has a crystallizable property, or has
been already crystallized.
[0050] In general, as for a polymer being in a state where a
plurality of monomer units are bonded, when the polymer has various
conditions such as low stereoregularity of a polymer, poor symmetry
of a polymer, a large side chain of a polymer, a large number of
branches of a polymer, and low intermolecular cohesion between
polymers, the polymer becomes amorphous. However, depending on the
existence state, the crystallization sufficiently proceeds, and the
polymer may become crystalline. For example, even for a polymer
having a large side chain, when the polymer is composed of a single
monomer unit, the crystallization of the polymer may sufficiently
proceed, and the polymer may become crystalline. For this reason,
even if the polymer is composed of the same monomer unit, the
polymer can become crystalline or can become amorphous, and
therefore in the present invention, the expression "unit derived
from a monomer that can form an amorphous component" is used.
[0051] The monomer unit in the present invention means a repeating
unit constituting a polymer induced from one polyhydric alcohol
molecule and one polybasic carboxylic acid molecule, and in the
case of .epsilon.-caprolactone, means a constituent unit obtained
by opening the lactone ring.
[0052] When a monomer unit composed of terephthalic acid and
ethylene glycol is a main monomer unit constituting a polymer,
examples of the above unit derived from a monomer that can form an
amorphous component include a monomer unit composed of isophthalic
acid and ethylene glycol, a monomer unit composed of terephthalic
acid and neopentyl glycol, a monomer unit composed of terephthalic
acid and 1,4-cyclohexanedimethanol, and a monomer unit composed of
isophthalic acid and butanediol, or the like.
[0053] Examples of the monomer that can form an amorphous component
of a resin for forming a core layer may include neopentyl glycol,
1,4-cyclohexanedimethanol, isophthalic acid,
1,4-cyclohexanedicarboxylic acid, 2,6-naphthalenedicarboxylic acid,
2,2-diethyl-1,3-propanediol, 2-n-butyl-2-ethyl-1,3-propanediol,
2,2-isopropyl-1,3-propanediol, 2,2-di-n-butyl-1,3-propanediol, and
hexanediol. Among these, neopentyl glycol,
1,4-cyclohexanedimethanol, or isophthalic acid is preferably
used.
[0054] It is desirable that the value obtained by dividing the sum
of the thicknesses of the skin layers by the thickness of the core
layer be 0.1 to 0.5. If the value obtained by dividing the sum of
the thicknesses of the skin layers by the thickness of the core
layer is less than 0.1, the amount of the layer containing 50 mol %
or more of a polyethylene terephthalate unit in the film structure
of the laminated film is small, and this is unfavorable since the
effect of reducing the attenuation rate of the shrinkage stress
cannot be sufficiently obtained. On the other hand, if the value
obtained by dividing the sum of the thicknesses of the skin layers
by the thickness of the core layer exceeds 0.5, the amount of the
core layer which mainly performs a heat shrinkage behavior is
relatively too small, and hence this is unfavorable since the
necessary heat shrinkage cannot be achieved.
[0055] In the heat-shrinkable polyester film of the present
invention, each of the core layer and the skin layers preferably
has a thickness of 1 .mu.m or more. It is not preferred that the
thickness of any of the core layer and the skin layers be less than
1 .mu.m since the necessary shrinkage properties cannot be
obtained.
[0056] To a resin for forming any of the skin layers and the core
layer, according to needs, there can be added various additives
such as waxes, an antioxidant, an antistatic agent, a
crystal-nucleation agent, a viscosity reducing agent, a heat
stabilizer, a pigment for coloring, a color protection agent, and
an ultraviolet absorber.
[0057] The laminated film can be produced by a known method used
for producing a laminated film, and a feed block method, a
multi-manifold method, and the like can be given. For example, in
the case of the co-extrusion method, various resin mixtures for
forming layers are separately melted using an extruder, merged in a
T-die mold equipped with a multi-manifold and extruded, and drawn
by a drawing apparatus, whereby a laminated film can be
obtained.
[0058] Although the form of the laminated film is not particularly
limited, for example, a two-type two-layer structure of A/B, a
two-type three-layer structure of B/A/B, and a three-type
three-layer structure of C/A/B can be exemplified.
[Properties of Heat-Shrinkable Polyester Film of the Present
Invention]
[0059] When the heat-shrinkable polyester film of the present
invention is treated for 10 seconds in no load state in hot water
of 98.degree. C., a heat shrinkage in the longitudinal direction
which is the main shrinkage direction of the film calculated from
the lengths before and after shrinkage according to the following
Equation 1 (namely, hot-water heat shrinkage at 98.degree. C.) is
40% or more and 80% or less.
Heat shrinkage={(length before shrinkage-length after
shrinkage)/length before shrinkage}.times.100(%) Equation 1
[0060] If the hot-water heat shrinkage in the longitudinal
direction at 98.degree. C. is less than 40%, the shrinkage amount
is small in the case of using the film as a banding film, so that
wrinkles and slack are generated on a label after heat shrinkage,
and therefore this is not-unfavorable. On the other hand, if the
hot-water heat shrinkage in the longitudinal direction at
98.degree. C. is more than 80%, when a thin soft beverage bottle or
box lunch container is packaged with the film, a problem of
deformation of the bottle or container arises. In addition, there
is a problem that the bonded portion of a cylindrical label or a
banding film is separated due to high shrinkage stress. The
hot-water heat shrinkage in the longitudinal direction is more
preferably 75% or less, and further preferably 70% or less.
Incidentally, the lower limit of the hot-water heat shrinkage in
the longitudinal direction at 90.degree. C. is more preferably 45%
or more, and further preferably 50% or more.
[0061] Furthermore, when the heat-shrinkable polyester film of the
present invention is treated for 10 seconds in no load state in hot
water of 98.degree. C., a hot-water heat shrinkage in the width
direction which is a direction orthogonal to the main shrinkage
direction of the film calculated from the lengths before and after
shrinkage according to the above Equation 1 is -5% or more and 15%
or less. If the hot-water heat shrinkage in the width direction at
98.degree. C. exceeds 15%, when the film is used as a banding film,
the length of the film in the direction orthogonal to the shrinkage
direction decreases at the time of heat shrinking (occurrence of a
sink mark), thereby causing such problems that the contents of a
box lunch spill out and foreign matters are mixed into the box
lunch due to a decrease in banding force, and therefore this is not
unfavorable. On the other hand, if the hot-water heat shrinkage in
the width direction at 98.degree. C. is less than -5%, the length
of the label in the direction orthogonal to the main shrinkage
direction increases at the time of heat shrinking, the label is
slackened and likely to wrinkle, and therefore this is not
unfavorable. Incidentally, the hot-water heat shrinkage in the
width direction at 98.degree. C. is preferably -4% or more and 9%
or less, more preferably -3% or more and 8% or less, and further
more preferably from -2% or more and 7% or less.
[0062] In the heat-shrinkable polyester film of the present
invention, with regard to the shrinkage stress in the main
shrinkage direction of the film measured under hot air of
90.degree. C., the shrinkage stress ratio represented by the
following equation is 0.6 or more and 1.0 or less.
Shrinkage stress ratio=(shrinkage stress after 30 seconds)/(maximum
shrinkage stress)
[0063] That is, the heat-shrinkable polyester film of the present
invention features specific heat shrinkage properties such that the
shrinkage stress almost comparable to the maximum heat shrinkage
stress is developed even after 30 seconds from the initiation of
shrinking by heat. If the shrinkage stress after 30 seconds/maximum
shrinkage stress (hereinafter, stress ratio) of the film is less
than 0.6, in the case of a label of a beverage bottle, the label
does not follow the shape and has no tightness, thereby causing a
problem that when a consumer holds the body of the bottle and opens
the cap of the bottle, the cap cannot be opened easily since the
label rotates, and therefore this is not unfavorable. Furthermore,
in the case of a banding application of a box lunch container, the
shrinkable film is not tightly finished, thereby causing such
problems that the contents of the box lunch spill out and foreign
matters are mixed into the box lunch. The above-mentioned stress
ratio is more preferably 0.75 or more, and further preferably 0.8
or more. Although a higher stress ratio is preferred because the
followability is more improved, it is improbable that the shrinkage
stress after 30 seconds exceeds the maximum shrinkage stress, and
therefore the maximum value of the above-mentioned stress ratio is
1.
[0064] The heat-shrinkable polyester film of the present invention
has a refractive index of 1.600 or more in the longitudinal
direction which is the main shrinkage direction of the film. It is
not preferable that the refractive index in the longitudinal
direction be less than 1.600 because the film has no rigidity
(stiffness feeling) and is likely to wrinkle when formed into a
label. The lower limit of the refractive index in the longitudinal
direction is preferably 1.625 or more, and more preferably 1.650 or
more. On the other hand, it is not preferable that the refractive
index in the longitudinal direction exceed 1.700 because the
solvent adhesiveness deteriorates when forming a label.
[0065] In the heat-shrinkable polyester film of the present
invention, when a heat shrinkage stress in the longitudinal
direction which is the main shrinkage direction of the film is
measured under the conditions of a test piece width of 20 mm and a
distance between chucks of 100 mm in hot air of 90.degree. C. at
the blowing speed of 5 m/sec, the maximum heat shrinkage stress is
preferably 15 MPa or less. If the maximum heat shrinkage stress is
15 MPa or less, the shrinkage stress is not too high, and when a
thin soft beverage bottle or box lunch container is packaged with
the film, a problem of deformation of the bottle or container does
not occur. This is also preferred because a problem such that the
bonded portion of a cylindrical label or a banding film is
separated due to high shrinkage stress does not arise. The maximum
heat shrinkage stress is more preferably 14 MPa or less, and
further preferably 12 MPa or less. On the other hand, if the
above-mentioned shrinkage stress is too small, when a beverage
bottle or a box lunch container is packaged, the tightness after
finishing shrinkage is insufficient, thereby causing a problem that
when a consumer holds the body of the bottle and opens the cap of
the bottle, the cap cannot be opened easily because the label
rotates. Furthermore, in the case of a banding application of a box
lunch container, problems such that the contents of the box lunch
spill out and foreign matters are mixed into the box lunch arise.
Therefore, the maximum heat shrinkage stress measured by the above
method is preferably 5 MPa or more, and more preferably 6 MPa or
more.
[0066] The thickness of the heat-shrinkable polyester film of the
present invention is not particularly limited, but as a
heat-shrinkable film for a label application and a banding
application, the thickness is preferably 5 to 100 .mu.m, and more
preferably 10 to 95 .mu.m.
[0067] The heat-shrinkable polyester film of the present invention
is not particularly limited in its production method, but the film
can be obtained, for example, by melt-extruding the above-mentioned
polyester raw material with an extruder to form an undrawn film and
by drawing the undrawn film with a method as shown below.
[0068] When a raw material resin is melt-extruded, it is preferable
to dry the polyester raw material using a dryer such as a hopper
dryer or a paddle dryer, or a vacuum dryer. After the polyester raw
material is dried in such a manner, it is melted at a temperature
of 200 to 300.degree. C. and extruded into a film form utilizing an
extruder. In such an extrusion, an arbitrary conventional method
such as a T-die method and a tubular method can be adopted.
[0069] Then, the sheet-like molten resin after extrusion is
quenched so that an undrawn film can be obtained. As a method for
quenching the molten resin, a method in which a molten resin is
cast on a rotary drum from a spinneret and solidified by quenching
to obtain a substantially unoriented resin sheet can be suitably
adopted.
[0070] Further, the obtained undrawn film is drawn in the
longitudinal direction under a predetermined condition as described
below so that the heat-shrinkable polyester film of the present
invention can be obtained. Hereinafter, a preferable drawing to
obtain the heat-shrinkable polyester film of the present invention
will be described in detail while taking into consideration the
difference from a method for drawing a conventional heat-shrinkable
polyester film.
[Preferable Drawing Method of Heat-Shrinkable Polyester Film]
[0071] An ordinary heat-shrinkable polyester film is produced by
drawing an undrawn film in a direction to be shrunk.
Conventionally, there has been a high demand for a heat-shrinkable
polyester film shrinkable in the longitudinal direction which has
followability to the shape of an object to be packaged at the time
of shrinking and a tight feeling after shrinking. However, it is
impossible to obtain a polyester film having a low attenuation rate
of shrinkage stress and having a high shrinkage stress after 30
seconds from the initiation of shrinking merely by drawing the
undrawn film in the longitudinal direction.
[0072] Here, a preferable drawing method of the heat-shrinkable
film of the present invention is described.
[0073] As a result of studies, the inventors have found that as for
a film having at least one layer containing 50 mol % or more of an
ethylene terephthalate unit in 100 mol % of the constituent units
of polyester, if the draw ratio is increased more than 3 times, the
crystallization is promoted, and consequently the attenuation rate
of the shrinkage stress is small and the shrinkage stress after 30
seconds from the initiation of shrinking becomes high.
[0074] In a conventional heat-shrinkable polyester film containing
an amorphous component in a large amount, if the film is subjected
to an only uniaxial drawing, the attenuation rate of the shrinkage
stress is large, and the shrinkage stress after 30 seconds from the
initiation of shrinking reduces. On the other hand, in the present
invention, the heat-shrinkable polyester film has at least one
layer containing 50 mol % or more of an ethylene terephthalate
unit, and the attenuation rate of the shrinkage stress is reduced
by drawing at a high ratio of 3 times or more. It is considered
that such an attenuation of the shrinkage stress is associated with
crystallization due to drawing. In the polyester film of the
present invention which has at least one layer containing 50 mol %
or more of the ethylene terephthalate unit and is drawn at a high
ratio of 3 times or more, molecules are easily crystallized. It is
considered that this crystal of the molecules is low in mobility at
the time of heating compared with amorphous molecules and
suppresses sudden relaxation of molecular orientation when the film
shrinks by heat, and therefore slow relaxation of molecular
orientation occurs. In other words, it is considered that since the
relaxation of orientation occurs for a long time, the attenuation
rate of the shrinkage stress lower, and the shrinkage stress after
30 seconds becomes high. When the film contains a large amount of
amorphous components, or when the draw ratio in the longitudinal
direction is less than 3 times, crystallization does not relatively
proceed, and hence it is assumed that the attenuation rate of the
shrinkage stress in the longitudinal direction becomes high and the
shrinkage stress after 30 seconds reduces.
[0075] Based on the results of studies as described above, the draw
ratio in the longitudinal direction is preferably 3 times or more
and 7 times or less. It is not preferable that the draw ratio in
the longitudinal direction be less than 3 times because the
crystallization of the film is insufficient, the shrinkage stress
does not persist, and as a result, the film does not adequately
follow the shape of an object to be packaged, leading to the
occurrence of defects such as wrinkles when the film is shrunk as a
label or a banding film. This is also not preferable because the
irregularity of thickness in the lengthwise direction of the film
increases. The upper limit of the lengthwise draw ratio is not
particularly limited, but the draw ratio of more than 7 times is
not preferable because it becomes difficult to draw the film in the
longitudinal direction (so-called breakage tends to occur). The
draw ratio is more preferably 3.2 times or more and 6.5 times or
less, and further preferably 3.5 times or more and 6 times or
less.
[0076] The package of the present invention is a package in which a
banding film (and a label) obtained by using the heat-shrinkable
polyester film of the present invention is covered at least on a
part of the outer periphery of an object to be packaged and then to
shrink by heat. The object to be packaged can be exemplified by PET
bottles for beverage, various kinds of bottles, cans, plastic
containers for confectionary, a box lunch and the like, paper-made
boxes, and the like. In general, in the case where a label obtained
by using a heat-shrinkable polyester film is covered on the
packaging object and heat-shrunk, the banding film (and a label) is
heat-shrunk by about 5 to 70% and closely attached on the package.
Additionally, a banding film (and a label) covered on a packaging
object may be printed or may not be printed.
[0077] A method for producing a banding film (and a label) is as
follows; a rectangular film is rounded in the longitudinal
direction to stack the end parts and bonded into a label-form, or a
film wound as a roll is rounded to stack the end parts and bonded
into a tube-form, which is cut into a label. As a method for
bonding the films together, a known method such as fusion sealing,
solvent bonding, bonding with hot-melt adhesive, and bonding with
an energy ray-curable adhesive can be used.
EXAMPLES
[0078] Hereinafter, the present invention is described in more
detail by Examples, but the present invention is by no means
limited to aspects of the Examples, and it can be suitably modified
in the range not departing from the scope of the present invention.
The composition of the raw materials used in Examples and
Comparative Examples is shown in Table 1. The ratio of the mixed
raw material used in each layer is shown in Table 2. The production
condition and the result of the evaluation for the films of
Examples and Comparative Examples is shown in Table 3.
TABLE-US-00001 TABLE 1 composition of polyester raw material (mol
%) polyester acid polyhydric alcohol addition raw component
component amount of material TPA EG BD NPG DEG lubricant 1 100 99
-- -- 1 2 100 99 -- -- 1 7200 3 100 68 -- 30 2 4 100 -- 100 --
--
TABLE-US-00002 TABLE 2 ratio of polyester raw material (wt %) mixed
raw material 1 2 3 4 A 45 5 50 0 B 70 5 25 0 C 25 5 60 10 D 5 5 66
24
[0079] Evaluation methods for films are as follows.
[Tg (Glass Transition Point)]
[0080] Using a differential scanning calorimeter (manufactured by
Seiko Instruments Inc., DSC220), 5 mg of an undrawn film was put in
a sample pan, the lid of the pan was closed, and the temperature
was raised at a temperature rising speed of 10.degree. C./minute
from -40.degree. C. to 120.degree. C. in a nitrogen gas atmosphere
to conduct measurement. Tg (.degree. C.) was obtained based on
JIS-K 7121-1987.
[Intrinsic Viscosity (IV)]
[0081] 0.2 g of a polyester was dissolved in 50 ml of a solvent
mixture of phenol/1,1,2,2-tetrachloroethane (60/40 (weight ratio)),
and the intrinsic viscosity was measured at 30.degree. C. using an
Ostwald viscometer. The unit is dl/g.
[Heat Shrinkage (Hot-Water Heat Shrinkage)]
[0082] A film was cut into a square of 10 cm.times.10 cm, dipped in
hot water of a predetermined temperature .+-.0.5.degree. C. in no
load state for 10 seconds to be heat-shrunk, then dipped in water
of 25.degree. C..+-.0.5.degree. C. for 10 seconds, and taken from
water. Then, the dimensions of the film in the lengthwise and
transverse directions were measured, and heat shrinkage each was
obtained according to the following Equation 1. The direction with
the large heat shrinkage was defined as a main shrinkage
direction.
Heat shrinkage={(length before shrinkage-length after
shrinkage)/length before shrinkage}.times.100(%) Equation 1
[Shrinkage Stress]
[0083] A rectangular film sample of 150 mm in length in the main
shrinkage direction and 20 mm in width was cut out of a
heat-shrinkable film and measured for the shrinkage stress using a
strength and elongation measuring machine with a heating furnace
(TENSILON (registered trade mark of Orientec Co., Ltd) universal
testing instrument PTM-250) manufactured by Toyo Baldwin Co.
(current company name: Orientec Co., Ltd). The heating furnace of
the strength and elongation measuring machine was previously heated
to 90.degree. C., and the distance between chucks for holding the
film sample was set to 100 mm. When the sample was fitted to the
chucks of the strength and elongation measuring machine, the air
blast blown into the heating furnace was once stopped, the door of
the heating furnace was opened, 25 mm of both edges of the sample
of 150 mm in the longitudinal direction were clipped with the
respective chucks, the distance between the chucks was set to 100
mm, and the sample was fixed without looseness such that the
longitudinal direction of the sample was conformed to the direction
between the chucks and the sample became horizontal. After fixing
the sample to the chucks, the door of the heating furnace was
quickly closed, and the air blast was restarted. The point of time
when the door of the heating furnace was closed and the air blast
was restarted was taken as a measurement start point of shrinkage
stress, and the shrinkage stress (MPa) after 30 seconds was
obtained. The maximum value of the shrinkage stress measurement
values from the measurement start point of shrinkage stress to 30
seconds after the start of measurement was taken as a maximum value
of shrinkage stress (maximum shrinkage stress (MPa)). Note that
when the shrinkage stress was measured, the distance between the
chucks was fixed to 100 mm and the transition of shrinkage stress
from the start of measurement to 30 seconds after the start of
measurement was measured. The ratio of a shrinkage stress after 30
seconds from the measurement start point relative to the maximum
shrinkage stress was defined as a shrinkage stress ratio
(represented by the following equation).
Shrinkage stress ratio=(shrinkage stress after 30 seconds)/(maximum
shrinkage stress)
[Refractive Index]
[0084] Using "Abbe refractometer 4T type" manufactured by Atago Co.
Ltd., the measurement was carried out after each sample film was
left in an atmosphere of 23.degree. C. and 65% RH for 2 hours or
longer.
[Shrinkage Finishing Property (Wrap Round)]
[0085] A film of 50 mm in width was wrapped around a plastic
container (side: 150.times.150 mm, height: 100 mm) of a box lunch
so as to bundle the body part and the lid part of the container
such that the circumferential direction of the container
corresponds to the shrinkage direction of the film. After
fusion-sealing at 220.degree. C., the film was heat-shrunk to the
plastic container of a box lunch in a shrink tunnel of a preset
temperature of 90.degree. C. For shrinkage finishing property,
evaluation was made on four points of wrinkles, sink marks,
shrinkage shortage and slack. As to the evaluation of wrinkles, as
shown in FIG. 1, the judgement was made based on the number of
wrinkles of 5 cm or more in length formed in the side direction of
the box lunch container. The criteria were as follows.
Good: 0 to 4 wrinkles Fair: 5 to 14 wrinkles Poor: 15 or more
wrinkles
[0086] With regard to sink marks, FIG. 2 shows a top view of a box
lunch container with a banding film after shrinking, and "L"
indicates a length from the edge of one side of the film to the
edge of the other side of the film. When the length "L" was
measured at 5 mm pitch in the circumferential direction of the box
lunch container, the difference between the maximum value Lmax and
the minimum value Lmin of the lengths was taken as "R". One having
a large "R" was judged as having a large sink mark. The criteria
were as follows.
Good: 0 mm.ltoreq.R<10 mm Fair: 10 mm.ltoreq.R<15 mm Poor: 15
mm.ltoreq.R
[0087] As to shrinkage shortage, the judgement was made based on
whether shrinkage shortage occurred after shrinkage finishing. The
criteria were as follows.
Good: No shrinkage shortage occurred. Poor: Shrinkage shortage
occurred.
[0088] As to slack, the case where the banding film was not
completely brought into intimate contact with the box lunch
container, had no tightness when touched with hands, and was
floating was judged as having slack. The criteria were as
follows.
Good: The film was tightly fitted and not floating. Poor: The film
was loosely finished and floating.
Preparation of Polyester Raw Material
Synthetic Example 1
[0089] 100 mol % of dimethyl terephthalate (DMT) as a dicarboxylic
acid component and 100 mol % of ethylene glycol (EG) as a
polyhydric alcohol component were placed in a stainless steel
autoclave equipped with a stirrer, a thermometer and a partially
circulating cooler such that the amount of ethylene glycol was 2.2
times the amount of dimethyl terephthalate in terms of the molar
ratio, 0.05 mol % (based on the acid component) of zinc acetate was
added as an ester exchange catalyst, 0.225 mol % (based on the acid
component) of antimony trioxide was added as a polycondensation
catalyst, and an ester exchange reaction was carried out while
distilling away generated methanol to outside the system.
Thereafter, a polycondensation reaction was carried out at
280.degree. C. under a reduced pressure of 26.7 Pa to obtain
polyester 1 having an intrinsic viscosity of 0.75 dl/g. The
composition is shown in Table 1.
Synthetic Examples 2 to 7
[0090] Polyesters 2 to 4 shown in Table 1 were prepared in the same
manner as in Synthetic Example 1. In the production of polyester 2,
SiO2 (Silysia 266, manufactured by FUJI SILYSIA CHEMICAL LTD.;
average particle diameter: 1.5 .mu.m) was added as a lubricant at a
proportion of 7,200 ppm relative to the polyester. In the Table,
NPG is neopentyl glycol, BD is 1,4-butanediol, and DEG is
diethylene glycol, which is a side product. The intrinsic
viscosities of polyesters 2, 3 and 4 were 2: 0.75 dl/g, 3: 1.20
dl/g and 4: 1.20 dl/g, respectively. Each polyester was
appropriately formed into a chip.
Example 1
[0091] Polyester 1, polyester 2 and polyester 3 as described above
were mixed in the mass ratio of 45:5:50 and the mixed resin was
introduced into an extruder. The mixed resin was molten at
280.degree. C. and extruded from a T-die and then quenched by
winding it around a rotating metal roll set at a surface
temperature of 30.degree. C. to obtain an undrawn film with a
thickness of 42 .mu.m. Tg of the undrawn film was 75.degree. C. The
obtained undrawn film was introduced to a lengthwise drawing
machine in which a plurality of rolls were continuously disposed,
heated till the film temperature reached 80.degree. C. on a
preheating roll, and then lengthwise drawn by a roll drawing method
at the draw ratio in the longitudinal direction of 3.5 times so as
to allow the thickness of the film after drawing to be 12 .mu.m.
After lengthwise drawing, the film was cooled by a cooling roll
whose surface temperature was set to 25.degree. C., and then wound
as a roll. The resulting film was evaluated for various properties
in the above-mentioned manner. The evaluation results are shown in
Table 3. As a result of the evaluation, the film had adequate
shrinkage property and good shrinkage finishing property.
TABLE-US-00003 TABLE 3 Example Example Example Example Example
Example 1 2 3 4 5 6 layer layer stracture single single single
single two-type two-type stracture layer layer layer layer
two-layer two-layer core layer A A A A C C skin layer A A ratio of
-- -- -- -- 2/8 2/8 skin/core MD ratio 3.5 4.5 5.5 6 3.5 4.5 film
thickness (.mu.m) 12 12 12 12 12 12 Heat longitudinal 50 60 67 70
55 64 Shrinkage direction in hot water width direction 6 8 8.2 9 7
8.1 of 98.degree. C. (%) Shrinkage maximum 9.5 10.2 11.2 12 8 8.5
Stress (MPa) under hot after 30 seconds 7 9.2 10.7 11.5 6.1 8.1 air
of 90.degree. C. (MPa) stress ratio 0.74 0.90 0.96 0.96 0.76 0.95
Refractive longitudinal 1.6176 1.6501 1.6698 1.6823 1.6055 1.6233
Index direction Shrinkage wrinkle Good Good Good Good Good Good
Finising sink mark Good Good Good Good Good Good Property shrinkage
Good Good Good Good Good Good shortage slack Good Good Good Good
Good Good Example Example Example Example Example Example 7 8 9 10
11 12 layer layer stracture two-type two-type two-type two-type
two-type two-type stracture two-layer two-layer two-layer two-layer
two-layer two-layer core layer C C C C C C skin layer A A B B B B
ratio of 2/8 2/8 2/8 2/8 2/8 2/8 skin/core MD ratio 5.5 6 3.5 4.5
5.5 6 film thickness (.mu.m) 12 12 12 12 12 12 Heat longitudinal 69
71 49 58 62 68 Shrinkage direction in hot water width direction 8.5
9 5.8 7.5 7.9 8.2 of 98.degree. C. (%) Shrinkage maximum 9 9.4 9.4
9.7 10.5 12.2 Stress (MPa) under hot after 30 seconds 8.8 9.2 8.2 9
10.1 11.9 air of 90.degree. C. (MPa) stress ratio 0.98 0.98 0.87
0.93 0.96 0.98 Refractive longitudinal 1.6452 1.6700 1.6104 1.6305
1.6511 1.6724 Index direction Shrinkage wrinkle Good Good Good Good
Good Good Finising sink mark Good Good Good Good Good Good Property
shrinkage Good Good Good Good Good Good shortage slack Good Good
Good Good Good Good
Example 2
[0092] A film was produced in the same manner as that in Example 1
except that the draw ratio in the longitudinal direction was set to
4.5 times, and the amount of the molten mixed resin extruded from a
T-die was adjusted so as to allow the thickness of the film after
drawing in the longitudinal direction to be 12 .mu.m. As a result
of the evaluation, the film had adequate shrinkage property and
good shrinkage finishing property.
Example 3
[0093] A film was produced in the same manner as that in Example 1
except that the draw ratio in the longitudinal direction was set to
5.5 times, and the amount of the molten mixed resin extruded from a
T-die was adjusted so as to allow the thickness of the film after
drawing in the longitudinal direction to be 12 .mu.m. As a result
of the evaluation, the film had adequate shrinkage property and
good shrinkage finishing property.
Example 4
[0094] A film was produced in the same manner as that in Example 1
except that the draw ratio in the longitudinal direction was set to
6 times, and the amount of the molten mixed resin extruded from a
T-die was adjusted so as to allow the thickness of the film after
drawing in the longitudinal direction to be 12 .mu.m. As a result
of the evaluation, the film had adequate shrinkage property and
good shrinkage finishing property.
Example 5
[0095] Polyester 1, polyester 2, and polyester 3 as described above
were mixed in the mass ratio of 45:5:50 to prepare a mixed resin
for a skin layer. Polyester 1, polyester 2, polyester 3 and
polyester 4 as described above were mixed in the mass ratio of
25:5:60:10 to prepare a mixed resin for a core layer. The mixed
resin for a skin layer and the mixed resin for a core layer were
co-extruded at a temperature of 280.degree. C. using a T-die mold
equipped with a two-layer multi-manifold using two biaxial
extruders, and quenched with a cooling roll to produce a
two-layered sheet of a skin layer/a core layer. At this time, the
mixed resins were co-extruded such that the thickness ratio of the
skin layer and the core layer was the skin layer: the core
layer=2:8. Next, the obtained sheet was heated to 80.degree. C.,
and then lengthwise drawn by a roll drawing method at the draw
ratio in the longitudinal direction of 3.5 times so as to allow the
entire thickness of the film after drawing to be 12 .mu.m. The film
after lengthwise drawing was cooled by a cooling roll, and then
wound as a roll. The resulting film was evaluated for various
properties in the above-mentioned manner. The evaluation results
are shown in Table 3. As a result of the evaluation, the film had
adequate shrinkage property and good shrinkage finishing
property.
Example 6
[0096] A film was produced in the same manner as that in Example 5
except that the draw ratio in the longitudinal direction was set to
4.5 times, and the amount of the molten mixed resin extruded from a
T-die was adjusted so as to allow the thickness of the film after
drawing in the longitudinal direction to be 12 .mu.m. As a result
of the evaluation, the film had adequate shrinkage property and
good shrinkage finishing property.
Example 7
[0097] A film was produced in the same manner as that in Example 5
except that the draw ratio in the longitudinal direction was set to
5.5 times, and the amount of the molten mixed resin extruded from a
T-die was adjusted so as to allow the thickness of the film after
drawing in the longitudinal direction to be 12 .mu.m. As a result
of the evaluation, the film had adequate shrinkage property and
good shrinkage finishing property.
Example 8
[0098] A film was produced in the same manner as that in Example 5
except that the draw ratio in the longitudinal direction was set to
6 times, and the amount of the molten mixed resin extruded from a
T-die was adjusted so as to allow the thickness of the film after
drawing in the longitudinal direction to be 12 .mu.m. As a result
of the evaluation, the film had adequate shrinkage property and
good shrinkage finishing property.
Example 9
[0099] A film was produced in the same manner as that in Example 5
except that polyester 1, polyester 2, and polyester 3 as described
above were mixed in the mass ratio of 70:5:25 to prepare a mixed
resin for a skin layer. As a result of the evaluation, the film had
adequate shrinkage property and good shrinkage finishing
property.
Example 10
[0100] A film was produced in the same manner as that in Example 9
except that the draw ratio in the longitudinal direction was set to
4.5 times, and the amount of the molten mixed resin extruded from a
T-die was adjusted so as to allow the thickness of the film after
drawing in the longitudinal direction to be 12 .mu.m. As a result
of the evaluation, the film had adequate shrinkage property and
good shrinkage finishing property.
Example 11
[0101] A film was produced in the same manner as that in Example 9
except that the draw ratio in the longitudinal direction was set to
5.5 times, and the amount of the molten mixed resin extruded from a
T-die was adjusted so as to allow the thickness of the film after
drawing in the longitudinal direction to be 12 .mu.m. As a result
of the evaluation, the film had adequate shrinkage property and
good shrinkage finishing property.
Example 12
[0102] A film was produced in the same manner as that in Example 9
except that the draw ratio in the longitudinal direction was set to
6 times, and the amount of the molten mixed resin extruded from a
T-die was adjusted so as to allow the thickness of the film after
drawing in the longitudinal direction to be 12 .mu.m. As a result
of the evaluation, the film had adequate shrinkage property and
good shrinkage finishing property.
Example 13
[0103] A film was produced in the same manner as that in Example 9
except that polyester 1, polyester 2, polyester 3, and polyester 4
as described above were mixed in the mass ratio of 5:5:66:24 to
prepare a mixed resin for a core layer. As a result of the
evaluation, the film had adequate shrinkage property and good
shrinkage finishing property. The evaluation results are show in
Table 4.
Example 14
[0104] A film was produced in the same manner as that in Example 13
except that the draw ratio in the longitudinal direction was set to
4.5 times, and the amount of the molten mixed resin extruded from a
T-die was adjusted so as to allow the thickness of the film after
drawing in the longitudinal direction to be 12 .mu.m. As a result
of the evaluation, the film had adequate shrinkage property and
good shrinkage finishing property.
Example 15
[0105] A film was produced in the same manner as that in Example 13
except that the draw ratio in the longitudinal direction was set to
5.5 times, and the amount of the molten mixed resin extruded from a
T-die was adjusted so as to allow the thickness of the film after
drawing in the longitudinal direction to be 12 .mu.m. As a result
of the evaluation, the film had adequate shrinkage property and
good shrinkage finishing property.
Example 16
[0106] A film was produced in the same manner as that in Example 13
except that the draw ratio in the longitudinal direction was set to
6 times, and the amount of the molten mixed resin extruded from a
T-die was adjusted so as to allow the thickness of the film after
drawing in the longitudinal direction to be 12 .mu.m. As a result
of the evaluation, the film had adequate shrinkage property and
good shrinkage finishing property.
Example 17
[0107] Polyester 1, polyester 2, and polyester 3 as described above
were mixed in the mass ratio of 45:5:50 to prepare a mixed resin
for a skin layer. Polyester 1, polyester 2, polyester 3 and
polyester 4 as described above were mixed in the mass ratio of
25:5:60:10 to prepare a mixed resin for a core layer. The mixed
resin for a skin layer and the mixed resin for a core layer were
co-extruded at a temperature of 280.degree. C. using a T-die mold
equipped with a three-layer multi-manifold using two biaxial
extruders, and quenched with a cooling roll to produce a
three-layered sheet of a skin layer/a core layer/a skin layer. At
this time, the mixed resins were co-extruded such that the
thickness ratio of the skin layer and the core layer was the skin
layer:the core layer:the skin layer=1:8:1. Next, the obtained sheet
was heated to 80.degree. C., and then lengthwise drawn by a roll
drawing method at the draw ratio in the longitudinal direction of
4.5 times so as to allow the entire thickness of the film after
drawing to be 12 .mu.m. The film after lengthwise drawing was
cooled by a cooling roll, and then wound as a roll. The resulting
film was evaluated for various properties in the above-mentioned
manner. The evaluation results are shown in Table 4. As a result of
the evaluation, the film had adequate shrinkage property and good
shrinkage finishing property.
Example 18
[0108] A film was produced in the same manner as that in Example 17
except that polyester 1, polyester 2, and polyester 3 as described
above were mixed in the mass ratio of 70:5:25 to prepare a mixed
resin for a skin layer. As a result of the evaluation, the film had
adequate shrinkage property and good shrinkage finishing
property.
Example 19
[0109] A film was produced in the same manner as that in Example 18
except that polyester 1, polyester 2, polyester 3, and polyester 4
as described above were mixed in the mass ratio of 5:5:66:24 to
prepare a mixed resin for a core layer. As a result of the
evaluation, the film had adequate shrinkage property and good
shrinkage finishing property.
Comparative Example 1
[0110] A film was produced in the same manner as that in Example 1
except that the draw ratio in the longitudinal direction was set to
2 times, and the amount of the molten mixed resin extruded from a
T-die was adjusted so as to allow the thickness of the film after
drawing in the longitudinal direction to be 12 .mu.m. As a result
of the evaluation, the banding film after shrinkage slackened, and
thus the film had poor shrinkage finishing property.
Comparative Example 2
[0111] A film was produced in the same manner as that in Example 1
except that polyester 1, polyester 2 and polyester 3 as described
above were mixed in the mass ratio of 70:5:25 and the mixed resin
was introduced into an extruder, the draw ratio in the longitudinal
direction was set to 2.5 times, and the amount of the molten mixed
resin extruded from a T-die was adjusted so as to allow the
thickness of the film after drawing in the longitudinal direction
to be 12 .mu.m. As a result of the evaluation, the banding film
after shrinkage did not have enough amount of shrinkage, and thus
the film had poor shrinkage finishing property.
Comparative Example 3
[0112] A film was produced in the same manner as that in Example 2
except that polyester 1, polyester 2, polyester 3 and polyester 4
as described above were mixed in the mass ratio of 25:5:60:10 and
the mixed resin was introduced into an extruder. As a result of the
evaluation, the label after shrinkage slackened, and thus the film
had poor shrinkage finishing property.
Comparative Example 4
[0113] A film was produced in the same manner as that in Example 2
except that polyester 1, polyester 2, polyester 3 and polyester 4
as described above were mixed in the mass ratio of 5:5:66:24 and
the mixed resin was introduced into an extruder. As a result of the
evaluation, the banding film after shrinkage slackened, and thus
the film had poor shrinkage finishing property.
Comparative Example 5
[0114] A film was produced in the same manner as that in
Comparative Example 4 except that the draw ratio in the
longitudinal direction was set to 3 times, and the amount of the
molten mixed resin extruded from a T-die was adjusted so as to
allow the thickness of the film after drawing in the longitudinal
direction to be 12 .mu.m. As a result of the evaluation, the
banding film after shrinkage slackened, and thus the film had poor
shrinkage finishing property
TABLE-US-00004 TABLE 4 Comparative Example Example Example Example
Example Example Example 13 14 15 16 17 18 19 layer layer stracture
two-type two-type two-type two-type two-type two-type two-type
stracture two-layer two-layer two-layer two-layer three-layer
three-layer three-layer core layer D D D D C C D skin layer B B B B
A B B ratio of 2/8 2/8 2/8 2/8 1/8/1 1/8/1 1/8/1 skin/core MD ratio
3.5 4.5 5.5 6 4.5 4.5 4.5 film thickness (.mu.m) 12 12 12 12 12 12
12 Heat longitudinal 54 65 70 71 64 58 65 Shrinkage direction in
hot water width direction 7 8.2 8.5 8.5 8.1 7.5 8.2 of 98.degree.
C. (%) Shrinkage maximum 8.46 8.73 9.45 10.98 8.5 9.7 9.9 Stress
(MPa) under hot after 30 seconds 7.38 8.1 9.09 10.71 8 7.6 7.9 air
of 90.degree. C. (MPa) stress ratio 0.87 0.93 0.96 0.98 0.94 0.78
0.80 Refractive longitudinal 1.6092 1.6301 1.6521 1.6712 1.6233
1.6305 1.6301 Index direction Shrinkage wrinkle Good Good Good Good
Good Good Good Finising sink mark Good Good Good Good Good Good
Good Property shrinkage Good Good Good Good Good Good Good shortage
slack Good Good Good Good Good Good Good Comparative Comparative
Comparative Comparative Comparative Example Example Example Example
Example 1 2 3 4 5 layer layer stracture single single single single
single stracture layer layer layer layer layer core layer A B C D D
skin layer ratio of -- -- -- -- -- skin/core MD ratio 2 2.5 4.5 4.5
3 film thickness (.mu.m) 12 12 12 12 12 Heat longitudinal 43 35 70
75 55 Shrinkage direction in hot water width direction 4 3 5 10 3
of 98.degree. C. (%) Shrinkage maximum 6 9 5.5 4.7 3.5 Stress (MPa)
under hot after 30 seconds 3.1 7.5 3.2 1.8 1.2 air of 90.degree. C.
(MPa) stress ratio 0.52 0.83 0.58 0.38 0.34 Refractive longitudinal
1.5880 1.5860 1.6481 1.6462 1.5860 Index direction Shrinkage
wrinkle Good -- Good Good Good Finising sink mark Good -- Good Good
Good Property shrinkage Good Poor Good Good Good shortage slack
Poor -- Poor Poor Poor
INDUSTRIAL APPLICABILITY
[0115] The heat-shrinkable polyester film of the present invention
has excellent properties as describe above and thus can be used
suitably as a label application and a banding application to bind a
box lunch container or the like. A package such as a bottle
obtained by using the heat-shrinkable polyester film of the present
invention as a label or a box lunch container obtained by using the
heat-shrinkable polyester film of the present invention as a
banding film shows a good appearance.
* * * * *