Note: Descriptions are shown in the official language in which they were submitted.
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=
SPECIFICATION
POLYPROPYLENE-BASED WRAP FILM
FIELD OF THE INVENTION
The present invention relates to a film used for
packaging of articles such as a food packaging film. In
particular, the invention pertains to a polypropylene-based
wrap film that can hold the quality of causing no change in
both clinging property and pulling-out ease-with the
passage of a certain time.
BACKGROUND ART
Thin thermoplastic resin films have been used at
restaurants, food shops or home when food is stored or
heated in a microwave oven. Among them, a wrap film made
of a vinylidene-chloride-based copolymer resin is used
frequently as a food packaging wrap film, because it is
equipped with excellent properties including moisture
resistance, oxygen gas barrier properties, heat resistance,
clinging property to a container and transparency.
In recent years, various food packaging wrap films
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composed mainly of a polyolefin-based resin have been
proposed. Examples of such films include polyethylene-
based resins, polypropylene-based resins, and poly-4-
methylpentene-1 resins. The surface of these films hardly
has a clinging property so that when they are used, for
example, as a food packaging film, they do not cling to a
container sufficiently, which is a fatal defect for them.
A number of polyolefin-based films mixed with various
additives or another resin, or laminated with another resin
have been proposed in order to satisfy such a desired
performance. They are however inferior in practical
usability, because not only the clinging property to a
container but also a film-to-film clinging property is
heightened, which deteriorates pulling-out ease from a
dispenser box.
With a view to overcoming the above-described various
problems, various proposals have been made as to the
clinging property of a wrap film. JP-A-10-202806 proposes
a self-cohesive wrap film comprising a core layer of a
polypropylene-based resin and a surface layer containing a
surfactant as an adhesive. However, it is difficult to
attain a high clinging property by this technique.
Moreover, when a food material having a high water content
is wrapped with the wrap film and heated in a microwave
oven, it raises a problem of bubbling of the surfactant on
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the wrap film surface by the action of water.
Heightening of the clinging property leads to
necessity of a high pulling-out force, while lowering of
the pulling-out force leads to a deterioration in the
clinging property. An increase in a modulus of elasticity,
which is an index of stiffness, worsens stretching property.
Thus, characteristics necessary for a wrap film tend to
contradict each other. It is therefore a very difficult to
problem to maintain the balance between these
characteristics.
For example, JP-A-2002-46238 proposes a multilayer
film which comprises a core layer comprising a resin having
a barrier property, and a surface layer comprising a resin
composition containing an additive having a clinging
property. However, since additives to attain the clinging
property have a low molecular weight or a low glass
transition point, they show a phenomenon called "bleed in"
and transfer in the film. As a result, in spite that the
film exhibits good balance of clinging property and
pulling-out ease just after film formation, the clinging
property and pulling-out ease happen to be deteriorated
with the passage of time owing to the transfer of the
additive inwards from the surface layer.
A wrap film using a poly(4-methylpentene-1) resin has
been proposed frequently, for example, in JP-A-2001-121660,
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because the resin has excellent heat resistance. Since the
poly(4-methylpentene-1) resin is a material of high
rigidity, a large amount of a plasticizer must be added to
satisfy the level of flexibility which a wrap film is
required to have. If it is added, however, the heat
resistance or low tensile elongation at break which the
resin essentially has is impaired.
An object of the present invention is to provide a
wrap film which, in spite of containing a polypropylene-
based resin, is excellent in a clinging property, does not
require so much force to pull it out from a dispenser box
and undergoes a less change in these characteristics
depending on a lapse of time or storage temperature.
SUMMARY OF THE INVENTION
The present inventors have carried out an extensive
investigation with a view to attaining the above-described
object and completed the present invention. The present
invention mainly relates to the followings:
A polypropylene-based multilayer wrap film having:
(A) a surface layer containing a first composition
comprising 50 to 80 wt.% of (Si) a crystalline
polypropylene-based resin and 20 to 50 wt.% of (S2) at
least one softener selected from amorphous or low-
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crystalline propylene-a-olefin copolymers and butene-1
polymers, and, based on 100 parts by weight of the first
composition, 5 to 15 parts by weight of (S3) a hydrogenated
terpene resin and 10 to 20 parts by weight of (S4) an
aliphatic hydrocarbon which is in liquid at normal
temperature; and
(B) a core layer containing 80 to 98 wt.% of (Cl) a
crystalline polypropylene-based resin and 2 to 20 wt.% of
(C2) an aliphatic hydrocarbon which is liquid at normal
temperature;
The above-described polypropylene-based multilayer
wrap film, wherein between before and after the wrap film
wound around a paper tube is allowed to stand for 3 weeks
at 40 C and RH of 20%, a change in a cling energy falls
within a range of from -20 to +50% and a change in a
pulling-out force falls within a range of from -50 to +20%;
and
The above-described polypropylene-based multilayer
wrap film which has a structure formed of a fibril network
and a matrix existing therebetween when the film surface is
observed as a phase image of an atomic force microscope at
40,000 magnifications, and the fibril has an average width
of 1 nm or greater but not greater than 100 nm and has an
average pore size of 3 nm or greater but not greater than 1
m.
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By specifying the wrap film of the present invention
as described above, it exhibits the following advantages.
Described specifically, use, for the surface layer of the
wrap film, of a resin composition containing predetermined
amounts of a specific softener, a hydrogenated terpene
resin and an aliphatic hydrocarbon which is liquid at
normal temperature makes it possible to plasticize the
resin appropriately, thereby attaining both clinging
property and pulling-out ease.
Addition of an aliphatic hydrocarbon which is liquid
at normal temperature to a core layer (B) which is
contiguous to the surface layer (A) makes it possible to
suppress a reduction in the time-dependent deterioration of
both clinging property and pulling-out ease.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a photograph of the wrap film of the
present invention observed as a phase image of an atomic
force microscope at 40,000 magnifications.
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention will hereinafter be described
specifically.
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The polypropylene-based resin to be used in the
present invention may be a homopolymer having, in the
molecular chain thereof, only a polypropylene unit or a
binary or tertiary copolymer having, in addition, ethylene
or butene-1. Of the copolymers, those obtained by random
copolymerization are preferred from the viewpoint of
transparency. With regards to stereoregularity, either one
of an isotactic or syndiotactic structure, or a mixture
thereof may be used. Although no other particular
limitation is imposed, it has preferably comes up to the
food package standards in consideration that it is safely
used for wrapping food. In addition, it has preferably a
melt flow rate ranging from 1 to 20 g/10 minutes as
measured at 230 C under a load of 2.16 kg by the method in
accordance with ASTM D1238.
The component to be used as a softener contained in
the surface layer (A) is selected from amorphous or low-
crystalline propylene-a-olefin copolymers and butene-1
polymers. From the viewpoint of safety, it preferably has
come up to the food package standards.
The term "amorphous or low-crystalline propylene-a-
olefin copolymer" as used herein means a copolymer of
propylene and an a-olefin having at least 4 carbon atoms
such as butene-1 or pentene-l. Its propylene percentage
preferably ranges from 65 wt.% to 85 wt.%. Its melt flow
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rate preferably rancles from 1 tu 10 g/ln miiiute:_ ~Is
measured at under a load of ~~.1G kg by the method in
a(-'Cordance ,ll t}1 ~:.T1=i D1238. Its densltv in accOI-dance v'J1Lh
ASTM D1505 prefer.ablv ranges fr_-om 0.6'5 to 0.89 c/cm'. It
is rich in flexibilitv by itself and when incorporated in a
crystalline polypropylene-based resin, it does not lose its
transparency and can bring about softening effects.
Examples of the amorphous or low-crystalline polypropylene-
TM
a-olefin copolymer include "TAFMER XR" (trade name; product
of Mitsui Chemicals, Inc.).
The term "butene-i polymer" means a homopolymer
obtained by catalytic pol,,~nerization of a liquici butene-1
monomer. Its melt flow rate preferably falls within a
range of from 0.1 to 5 g/10 minutes as measured at 190 C
under a load of 2.16 kg by the method in accordance with
ASTM D1238. Its density preferably falls within a range of
0.904 to 0.920 g/cm3 in accordance with ASTM D1505.
The above-described softener has good compatibility
with the crystalline polypropylene-based resin. Addition
of it in an appropriate amount is effective for reducing a
modulus in tension or flexural modulus, in other words, for
imparting flexibility without greatly impairing
transparency, humidity resistance and heat resistance which
the crystalline polypropylene-based resin essentially has.
Supposing that the total amount of the crystalline
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polypropylene-based resin and softener is 100 wt.%, the
softener is added in an amount of 20 wt.% or greater from
the viewpoints of the flexibility, hand feeling, and an
ability to follow the contour of an article to be wrapped,
each of the resulting film, and in an amount not greater
than 50 wt.% from the viewpoints of stable film forming
property, processability, appearance or quality of the film
as a product, stiff feeling and handling ease as a
packaging film. The amount is more preferably from 20 to
40 wt.%, still more preferably from 20 to 30 wt.%.
The hydrogenated terpene resin serving another
component of the surface layer (A) has been employed as an
adhesive.
The hydrogenated terpene resin is obtained by
hydrogenation of a homopolymer using, as a raw material, a-
pinene, R-pinene, limonene or dipentene available from the
bark of pine or peel of oranges, or hydrogenation of a
copolymer thereof. The softening point of the hydrogenated
terpene resin is preferably 120 C or greater from the
viewpoint of the stickiness of the resulting film and is
preferably 135 C or less from the viewpoints of flexibility
and clinging property of a portion of the surface layer (A)
containing it. Supposing that the amount of the resin
composition comprising the crystalline polypropylene-based
resin and softener is 100 parts by weight, the hydrogenated
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terpene resin is added in an amount of 5 parts by weight or
greater from the viewpoint of a clinging performance and in
an amount of 15 parts by weight or less from the viewpoint
of suppressing the film-to-film blocking, thereby lowering
a pulling-out force. The amount preferably ranges from 5
to 10 parts by weight, more preferably from 5 to 8 parts by
weight.
The aliphatic hydrocarbon, which is liquid at normal
temperature, and which is contained in the surface layer
(A), is used as an adhesion assistant. As the adhesion
assistant, added is at least one of saturated hydrocarbons
obtained by purification of a crude oil, such as liquid
paraffin, mineral oil, and white mineral oil,
polyisobutylene obtained by homopolymerization of isobutene
and polybutene obtained by copolymerization of isobutene
and n-butene. Of these, mineral oil is most preferred.
Supposing that the amount of the composition comprising the
crystalline polypropylene-based resin and softener is 100
parts by weight, the adhesion assistant is added in an
amount of 10 parts by weight or greater but not greater
than 20 parts by weight from the viewpoints of hand feeling
and stable clinging property. Amounts of 15 parts by
weight or greater are more preferred.
The wrap film of the present invention has a high
clinging property and is excellent in pulling-out ease by
CA 02496926 2005-02-23
using, in combination, the hydrogenated terpene resin
serving as an adhesive and the aliphatic hydrocarbon which
is liquid at normal temperature and serves as an adhesion
assistant. When the wrap film contains an excess
hydrogenated terpene resin as the conventional one does, it
can have a clinging property by strongly pressing films
each other, but the film is inferior in clinging property
and pulling-out ease when pressed under a low load. When
the film contains an excess aliphatic hydrocarbon, which is
liquid at normal temperature, on the other hand, the film
has an excessively plasticized surface and cannot attain
desired high clinging property.
When the hydrogenated terpene resin and the aliphatic
hydrocarbon, which is liquid at normal temperature, each
being a component of the surface layer (A), are added in
amounts of c parts by weight and d parts by weight,
respectively, and if they satisfy the following equation:
d > 0.75 x c + 3.8,
better clinging property and pulling-out ease can be
attained. In other words, by mixing the hydrogenated
terpene resin (S3) with the aliphatic hydrocarbon (S4),
which is liquid at normal temperature, at a specific ratio,
the resulting film is able to have an appropriately
plasticized surface, and exhibit better clinging property
and pulling-out ease.
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To the surface layer (A) comprising the
polypropylene-based resin composition, a known additive
such as antioxidant can be added in an amount not departing
from the object of the present invention. It is however
preferred that the additive does not contain an aliphatic
ester of an aliphatic polyhydric alcohol such as glycerin
fatty acid ester. The additive is used for an antifogging,
plasticizing, processability improving or antistatic
purpose. As described above, when a wet food material is
wrapped with a film containing such an aliphatic ester and
heated in a microwave oven, foams happen to appear on the
wrap surface and cause discomfort to users.
The film of the present invention has a core layer
(B) adjacent to the surface layer (A) . Such a structure
makes it possible to prevent formation of a density
gradient, which will otherwise occur by the transfer, to
the core layer (B), of the aliphatic hydrocarbon of the,
surface layer (A) being liquid at normal temperature by a
bleeding phenomenon, thereby keeping only a sufficient
amount of the aliphatic hydrocarbon in the.surface layer.
The crystalline polypropylene-based resin forming the core
layer (B) may be similar to that employed in the surface
layer (A). It preferably comes up to the standards for
food package.
The aliphatic hydrocarbon (C2) which is liquid at
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normal temperature and which is to be used for the core
layer (B) of the present invention, is a saturated
hydrocarbon such as liquid paraffin, mineral oil or white
mineral oil. Although no particular limitation is imposed
on the physical properties of it, it is usually preferred
that the aliphatic hydrocarbon has a dynamic viscosity at
40 C of from 10 to 80 cSt, more preferably, from 10 to 40
cSt.
Supposing that the total amount of the crystalline
polypropylene-based resin (Cl) and the aliphatic
hydrocarbon (C2) which is liquid at normal temperature is
100 wt.%, the latter is added in an amount of 2 wt.% or
greater in order to suppress a bleeding-in phenomenon and
maintain clinging property = pulling-out ease even after
the passage of time and in an amount of 20 wt.% or less
from the viewpoint of the stiffness and stable film forming
property. It is added preferably in an amount of from 2 to
15 wt.%, more preferably from 2 to 12 wt.%.
Owing to the bleeding-in phenomenon, the aliphatic
hydrocarbon of the surface layer (A), which is liquid at
normal temperature, transfers from the surface layer (A) to
the core layer (B), leading to a decline in the percentage
of the aliphatic hydrocarbon relative to the hydrogenated
terpene resin in the surface layer (A) This causes a
change in the clinging property and pulling-out ease which
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have been obtained in the initial stage. A rise in the
constitution ratio of the surface layer (A) can be
considered easily as a countermeasure against the bleeding-
in phenomenon, but the surface layer (A) has a softness
attaining composition in order to exhibit high clinging
property. Such a countermeasure therefore lowers the
modulus of elasticity of the whole film, thereby causing a
drastic deterioration in the stiffness. In the present
invention, therefore, clinging property and pulling-out
ease can be maintained without causing a drastic
deterioration in the modulus of elasticity of the whole
film by adding a specific amount of a low-viscosity
aliphatic hydrocarbon to the core layer (B) adjacent to the
surface layer (A) to prevent the bleeding-in phenomenon.
The bleeding-in phenomenon of the aliphatic
hydrocarbon of the surface layer (A) can be controlled well
in the following manner. Supposing that the amount of the
aliphatic hydrocarbon of the surface layer (A), which is
liquid at normal temperature, is d parts by weight, the
amount of the aliphatic hydrocarbon of the core layer (B)
which is liquid at normal temperature is e wt.% and a
volumetric percentage of the surface layer (A) (total, if
the surface layer is provided on both sides of the core
layer (B)) to the core layer (B) is f, when the amounts
satisfy the following equation:
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0.13 x d/(34f) < e < 0.66 x d,
the film has satisfactory stiffness while maintaining good
clinging property and pulling-out ease.
The core layer (B) is preferably free of a resin
having a melt peak temperature of 200 C or greater.
Addition of a resin having a high melt peak temperature
such as a poly(4-methylpentene-1) resin actualizes heat
resistance as high as 170 C or greater, but it
simultaneously raises a modulus of elasticity of the
resulting film. As a result, not only the desired clinging
property cannot be attained but also handling ease
including stiffness becomes inferior.
In order to maintain moldability or formability, a
known additive such as antioxidant may be added to the
composition of the core layer (B) within an extent not
departing from the object of the present invention.
With regards to a layer constitution ratio, supposing
that the volumetric ratio of the surface layer (A) to the
core layer (B) is f, the f preferably ranges from 0.2 to
2.7. When the volumetric ratio of the surface layer (A) is
less than 0.2, the clinging property is not exhibited over
the whole film. When it exceeds 2.7, on the other hand,
the film becomes inferior in handling ease, because it
becomes soft and has lowered stiffness.
Although no particular limitation is imposed on a
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ratio of the surface layer (A) when it lies on both sides
of the core layer, almost an equal ratio is preferred,
because it is not necessary to distinguish which side is
which.
A multilayer film may have, in addition to the
surface layer (A) and the core layer (B), another layer
such as a rework layer comprising, for example, a trim edge
formed upon preparation, within an extent not inhibiting
the object of the present invention. In consideration of
the balance between the clinging property and pulling-out
ease, the other layer is preferably 5 wt.% or less of the
whole layer and at the same time, 5% or less of the whole
volumetric ratio. The other layer must be stacked so as
not to disturb the contiguous state of the surface layer
(A) and core layer (B).
As an index relating to the clinging property of the
wrap film of the present invention, the term "cling energy"
is employed. The term "cling energy" is an index for
evaluating film-to-film or film-to-container clinging
property when a container or food is covered with a wrap
film. This clinging property is, as well as pulling-out
ease, an important property of the wrap film as described
above. The above-described cling energy is determined from
an energy required for separating adhered films each
another. A detailed measurement method will be described
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later. This cling energy is preferably from 1.0 to 3.0 mJ,
more preferably from 1.5 to 2.5 mJ from the viewpoint of
sufficient clinging property.
The "pulling-out force" of the wrap film used in the
present invention is a property as important as the
clinging property and by it, pulling-out ease of a film
from a film roll in a dispenser box is evaluated. The
pulling-out force is measured in a manner described later.
This pulling-out force is preferably from 200 to 1000 mN,
more preferably from 200 to 800 mN, still more preferably
from 200 to 600 mN from the viewpoint of good pulling-out
ease.
Wrap films are sometimes stored under high
temperature and high humidity conditions, for example,
kitchen at home or cooking place for business use. It is
preferred that they do not undergo a large change in the
cling energy and pulling-out force during storage. As an
index of the change, employed is a rate of change in the
cling energy or pulling-out force of the wrap film wound
around a paper tube between before and after it is allowed
to stand at 40 C under relative humidity of 20% for 3 weeks.
The rate of change in the cling energy preferably ranges
from -20 to +50%, while that in the pulling-out force
preferably ranges from -50 to + 20%. Within these ranges,
the good balance between the clinging property and pulling-
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out ease will not be lost during the term until the wrap
film is delivered and consumed as a product.
The surface of the film of the present invention
preferably has a predetermined structure when the
information of the phase caused by the stimulation of an
atomic force microscope (AFM) cantilever is imaged. When
the information of the phase caused by the stimulation of
an cantilever is observed at 40,000-fold magnification, a
portion with small delay, in other words, a hard portion is
indicated by a light phase image, while a portion of large
delay, that is, a soft portion is indicated by a dark phase
image. When the desired surface of the wrap film of the
present invention is observed by the above-described method,
there exist a fibrous network structure and a matrix
existing therebetween. The image thus observed is
illustrated in FIG. 1. The "network structure" is a
continuous portion of the image which seems light, while
the "matrix" is a discontinuous portion which is
encompassed by this network structure and seems dark. The
fibrous light portion which can be observed continuously is
called "fibril network structure", while the discontinuous
dark portion is called "matrix". From a region of 10 mm x
mm, 50 images having a size of 2 micron x 2 micron are
selected at random. From these images, a portion which is
most uniform in fibril width and fibril-to-fibril distance
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is extracted. From thus extracted image, 100 fibril widths
and 100 fibril-to-fibril distances are selected and
averages of them except the top 10 and bottom 10 are
calculated and regarded respectively as the fibril width
and size of matrix which will be described later.
The average fibril width preferably ranges from 1 nm
or greater but not greater than 100 nm. Within this range,
the smoothness of the film surface can be maintained,
leading to a further improvement in the clinging property.
The average width more preferably ranges from 10 nm or
greater but not greater than 50 nm.
The size of the matrix (that is, average of the
fibril-to-fibril distance) preferably ranges from 3 nm or
greater but not greater than 1 m. Within this range, the
adhesion component constituting the matrix is retained in
the network structure on the film surface, does not appear
on the surface more than necessary, and a balance between
clinging property and pulling-out ease can be kept. The
matrix size more preferably ranges from 10 nm or greater
but not greater than 50 nm.
In the network structure of the present invention,
the crystalline portion of the propylene-based resin mainly
forms fibril, while the amorphous portion of the propylene-
based resin, softener, hydrogenated terpene resin and
aliphatic hydrocarbon being liquid at normal temperature
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mainly form the matrix. As described above, since the
fibril has a network structure of a predetermined size, a
softened component of the matrix portion having a large
influence on the clinging property is retained by the
fibril, and its amount existing on the surface is only the
minimum amount necessary for the exhibition of the clinging
property, making it possible to exhibit both good clinging
property and pulling-out ease.
When a softened component exists locally on a film
surface free of a network structure, or when a softened
portion exists, as an sea-island structure, in the form
larger in size than the pore of the network structure
specified by the present invention, clinging-property-
imparting components do not exist uniformly on the surface,
leading to a deterioration in the balance between the
clinging property and pulling-out ease.
The film of the present invention preferably has
predetermined flexibility. More specifically, it has
preferably a modulus in tension of 200 to 1000 MPa. The
modulus in tension is determined by measuring, in
accordance with the method described in ASTM-D-882, an
average of modulus in tension at 2% strain of the film in a
machine direction (MD direction) and transverse direction
(TD direction which is perpendicular to the MD direction)
by using a tensile tester (universal tensile compression
CA 02496926 2005-02-23
tester of Shinko Tsushin Kogyosha) The modulus in tension
is preferably 200 MPa or greater from the viewpoints of
flexibility, stiffness and handling ease of the film and
not greater than 1000 MPa from the viewpoints of
flexibility, clinging property and handling ease. It is
more preferably 400 MPa or greater but less than 700 MPa.
The thickness of the film of the present invention is
preferably 3 pm or greater from the viewpoints of strength
and stiffness as a packaging film and handling ease upon
packaging but not greater than 25 m from the viewpoints of
clinging property to articles to be packaged, handling ease
of the film, weight and roll diameter of it as a wrap film
for home use and handling ease upon use. In particular, a
food wrap film for home use which is required to be
convenient, having clinging property and pulling-out ease
has preferably a thickness of from 6 m to 15 m.
For the preparation of the present film, a known film
formation process can be employed. The polypropylene-based
resin composition of the surface layer (A) is prepared by
melting and kneading in an extruder. The softener and
hydrogenated terpene resin which are in the solid form at
normal temperature are charged in a predetermined amount in
a blender, together with commercially-available
polypropylene-based resin pellets. After sufficient and
uniform mixing, the mixture thus obtained is then charged
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in the extruder for the surface layer. The aliphatic
hydrocarbons of the surface layer (A) and core layer (B)
are liquids at normal temperature so that on the halfway of
the screw of each of the surface-layer and core-layer
extruders, liquid injectors are installed to add them to
the molten and plasticized resins. The compositions are
made uniform by kneading under appropriate extruding
conditions and they are extruded from a multilayer die or
the like into a multilayer film having a surface layer and
a core layer, and optionally a rework layer. It is also
possible to sufficiently melt and knead respective
compositions for the surface layer (A) and core layer (B)
in a known apparatus such as twin-screw extruder permitting
midway addition, pelletize the resulting masses and then
pour them in the respective extruders for the surface layer
and core layer.
A film having a multilayer structure, for example, a
three-layer structure can be prepared in the following
manner. In the above-described extruders for the surface
layer and core layer arranged in parallel, predetermined
resins are charged, respectively, followed by sufficient
melting and kneading. Downstream of them, the resins from
these extruders are merged to have three layers, followed
by extrusion in the form of a sheet by using a cyclic dye
or a T die having a slit-like discharge port. The resin
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thus extruded is solidified by cooling in a known manner
such as passing it through a cooling water tank or bringing
it in contact with a cold wind or a cooling roll. The
cooling temperature of the extruded sheet surface is
preferably 10 C or greater from the viewpoints of surface
smoothness and appearance but not greater than 50 C from
the viewpoints of prevention of the bleeding phenomenon on
the surface due to the adhesive incorporated in the surface
layer (A) or clinging property.
It is preferred to stretch the film by an ordinarily
employed known method such as monoaxial or biaxial
stretching by a roll method or tenter method, or a
multiaxial stretching by a tubular method at a stretching
ratio of at least 2 in the machine direction and/or
transverse direction in consideration of the strength as a
film and cutting ease of the film used as a food packaging
wrap film. The stretching ratio is not necessarily same
between the machine and transverse directions. More
preferred is stretching at a stretching ratio of at least 2
in the machine and transverse directions by multiaxial
stretching by the tubular method. After completion of the
stretching, the film is formed into an intended shape by
trimming the end of the film, cutting the film into a
desired size, or winding it around a paper tube.
The film obtained by multiaxial stretching by the
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tubular method may be heat set in a known manner in order
to adjust a thermal shrinkage ratio of the film. Examples
of the method usable for this purpose include indirect
heating by contact heating from a roll or by infrared rays
while restraining the movement of the film in the MD
direction; heating with a hot wind or radiation heat while
restraining the movement of the film in the transverse
direction by a tenter; and heating with a hot wind or
radiation heat while forming bubbles again.
The film according to the present invention is
excellent in, not only the balance between the clinging
property and pulling-out ease which a wrap film is required
to have, but also transparency, heat resistance,
appropriate flexibility, good hand feeling, cutting ease
and safety so that it is used suitably as a food wrap film
for home use.
EXAMPLES
The embodiments for carrying out the present
invention will hereinafter be described. They are each a
embodiment according to the present invention and the
invention is not limited by these Examples. The
performances of the films available by the present
invention and comparative examples will be evaluated in the
24
CA 02496926 2005-02-23
following manner.
(Cling energy)
Film-to-film clinging property when a container such
as dish or food was covered with a wrap film was evaluated
and measurement was conducted in the following manner.
Two Columns having a bottom area of 25 cm2 and a
weight of 400 g were prepared. To their bottom surfaces,
filter papers having the same area were adhered
respectively in advance. At each of the bottom surfaces to
which the filter paper had been adhered, a wrap film was
fixed under tension so as to avoid wrinkles from appearing
in the film. After these two columns were fitted closely
with their film surfaces inside and contact bonded under a
load of 500 g for 1 minute under the conditions of 23 C and
RH of 50%. Then, the films overlapped were separated in a
direction vertical to the surface at a rate of 5 mm/min by
a tensile tester (universal tensile compression tester of
Shinko Tsushin Kogyosha) and the energy (mJ) generated at
this time was designated as cling energy.
(Change in cling energy)
Stability of the cling energy with the passage of
time was evaluated. The cling energy of a wrap film which
had passed 24 hours at 23 C and RH of 50% after formation
CA 02496926 2005-02-23
and the cling energy of this wrap film which had been
stored for 21 days under an atmosphere of 40 C and RH of
20% were measured by the above-described method.
The cling energy before storage was evaluated in
accordance with the following criteria:
@: 1.5 mJ or greater but less than 2.5 mJ
0: 0.5 mJ or greater but less than 1.5 mJ, or
2.5 mJ or greater but less than 3.5 mJ
A: 3.5 mJ or greater but less than 4.0 mJ
x: less than 0.5 mJ, or 4.0 mJ or greater
A change of the wrap film in cling energy between
before and after storage for 21 days under an atmosphere of
40 C and RH 20% was evaluated in the following criteria:
@: -20% < (change) < +50%
0: -50% < (change) < -20%, or
+50% < (change) < + 75%
A: (change) < -50%, or +75% < (change)
X: unmeasurable because the film could not be pulled
out
(Pulling-out force)
Pulling-out ease of a wrap film from a film roll was
evaluated in the following manner.
A film slit to have a width of 300 mm was wound
around a paper tube having an outer diameter of 41 mm, an
26
CA 02496926 2005-02-23
inner diameter of 38 mm and width of 308 mm under tension
of 20N at a rate of 100 m/min and a film roll having a film
length of 20 m was prepared.
Both ends of the paper tube of the above-described
film roll were sandwiched and fixed by an exclusively used
jig having a rotary portion which turns under a light load
and this jig was fixed at the lower part of a tensile
tester (universal tensile compression tester of Shinko
Tsushin Kogyosha). The end portion of the film was adhered
to and fixed at an upper fixing tool of 330 mm wide and a
force available upon unwinding the film at a rate of 1000
mm/min was measured. The maximum load at this time was
designated as a pulling-out power.
In order to find a time-dependent change of the
pulling-out force, the pulling-out force of the sample 24
hours after formation and that of the sample 21 days after
storage under an atmosphere of 40 C and RH of 20% were
measured.
The pulling-out force before storage was evaluated in
accordance with the following criteria:
@: 50 mN or greater but less than 600 mN
0: 600 mN or greater but less than 1200 mN
0: 1200 mN or greater but less than 1500 mN
x: less than 50 mN, or 1500 mN or greater
The pulling-out force of the sample after storage for
27
CA 02496926 2005-02-23
21 days under an atmosphere of 40 C and RH of 20% compared
with that before storage was evaluated in accordance with
the following criteria:
@: -50% < (change) < +20%
0: -80% < (change) < -50%, or
+20% < (change) < + 50%
A: (change) < -80%, or +50% < (change)
x: unmeasurable because the film could not be pulled
out
(Transparency)
The cloudiness of a film was measured using "NDH-
300A" (Nippon Denshoku Industries, Ltd.) in accordance with
the method described in ASTM-D-103 and transparency was
evaluated based on the following criteria.
@: less than 1.0
0: 1.0 or greater but less than 2.0
A: 2.0 or greater but less than 3.0
x: 3.0 or greater
(Heat resistance)
For evaluation of heat resistance, heat resistant
temperature was measured based on Tokyo Consumer Life
Ordinance, Article 11. A film having a heat resistant
temperature of 140 C or greater was ranked @, that having
28
CA 02496926 2005-02-23
a heat resistant temperature of 130 C or 135 C was ranked 0
and that having a heat resistant temperature of 125 C or
less was ranked A.
(Flexibility)
For evaluation of flexibility, moduluses of tension
of a film in the machine direction (MD) and transverse
direction (TD) upon 2% strain were measured using a tensile
tester (universal tensile compression tester of Shinko
Tsushin Kogyosh) in accordance with the method described in
ASTM D882. It was evaluated based on the following
criteria:
In the average of the moduluses in tension of the
film in the MD and TD directions,
@: 400 MPa or greater but less than 700 MPa
0: 200 MPa or greater but less than 400 MPa, or
700 MPa or greater but less than 1000 MPa
A: 100 MPa or greater but less than 200 MPa
x: less than 100 MPa, or 1000 MPa or greater
(Hand feeling)
For evaluation of hand feeling, 50 homemakers
selected at random were asked to carry out organoleptic
evaluation of the hand feeling of a film and evaluation was
made based on the following criteria:
29
CA 02496926 2007-10-16
at least 45 homemakers judged that the film had
good hand feeiing.
0: 40 or qreater but less than 45 homemakers =iudaed
that the film had good hand feeling.
0: 30 or qreater but less than 40 homemakers judged
that the film had good hand feeling.
x: less than 30 homemakers judged that the film had
good hand feeling.
(Cutting property)
A film was wound around a paper tube to have a width
of 300 mm and roll length of 20 m and the resulting film
TM
roll was put in a dispenser box of "Saran Wrap" (trade
name; product of Asahi Kasei Corporation). The film was
cut by a blade attached to the box. The cutting property
of the film was evaluated from how the film was cut based
on the following criteria.
@: The film can be cut sharply with a light force.
0: Some force is necessary for cutting but the film
can be cut sharply.
0: The film can be cut but not easily.
x: The film cannot be cut smoothly. Sometimes it is
not cut but stretched or broken transversely, or the
dispenser box is broken owing to an excessive load applied
upon film cutting.
CA 02496926 2007-10-16
(Observation of the film surface)
The filrn surface was observed as a phase imaqe
obtained by an atomic force microscope. The film was
adhered and fixed to a glass and the surfac.e was observed
TM
as a phase image in a Tapping mode by "Nano Scope IIIa"
(trade name; product of Digital Instrument) Measurement
was conducted using a cantilever (spring constant: 0.07 to
0.58 N/m) of Si single crystal under the conditions of a
scan rate of 0.5 to 1 Hz, scan size of 2 m, Z limit of
440V and sampling points of 512512. When the contact
pressure of the cantilever was controlled, dependina on tne
film, set point ranged from 0.8 to 1.4V at a target
amplitude of 2V and set point ranged from 2.0 to 3.5V at a
target amplitude of 4V. From a 10 mm x 10 mm region of the
sample, 50 images of 2 m x 2 m were selected at random
and observed. Out of these images, a portion which was
most uniform in fibril width and fibril-to-fibril distance
was extracted. The 2 m x 2 m field thus extracted was
enlarged by 40,000 times and from the resulting 80 mm x 80
mm image, 100 fibril widths and 100 fibril-to-fibril
distances were selected. Average of 80 widths or 80
distances after the top 10 and the bottom 10 were omitted
was adopted. The surface structure was evaluated in terms
of average fibril width based on the following criteria:
31
CA 02496926 2007-10-16
1 nm or crreater but less than 50 nrn
0: 50 nm or cIreater but less than 100 nm
x: 1i_10 nm or qreater.
The averaqe fibril-to-fibril distance was evaliiated hased
on the followinq criteria:
@: 10 nm or greater but less than 50 nm
0: 3 nm or greater but less than 10 nm, or
50 nm or greater but less than 1000 nm
x: less than 3 nm, or 1000 nm or greater
The film was evaluated synthetically based on the
above-described results. The film ranked oQ in each item
was judged exceilent, that ranked only @ or 0 was judged
practically usable, and that having a ranking of A or x
was not suited for practical use.
[Example 1]
A crystalline polypropylene-based resin ("Grand
TM
Polypro F327", trade name; product of Grand Polymer Co.,
Ltd., a tertiary copolymer of propylene, ethylene and
butene-1) and, as a softener, a low-crystalline propylene-
a-olefin copolymer resin ("TAFMER XR11OT", trade name;
product of Mitsui Chemicals, Inc.) were mixed at a weight
ratio of 75:25. To 100 parts by weight of the resulting
mixture, 5 parts by weight of a hydrogenated terpene resin
TM
("Clearon P125", trade name; product of Yasuhara Chemical
32
CA 02496926 2007-10-16
Co., Ltd. ) was charged in a blender, followed by thorough
mixing for minutes at normal teinperature. The resulting
mixture was kneaded under a molten state in a co-rotating
twin screw extriider ("TEH-35BS", trade name; product of
Toshiba Machine) having a screw diameter of 37 mm and LIn
of 42, whereby pellets were prepared. As the aliphatic
hydrocarbon, which is liquid at normal temperature, a
TM
mineral oil ("MORESCO white P70", trade name; product of
Matsumura Oil Research /(dynamic viscosity at 40 C of 9.6
cSt)) was added through an injection pump from the midway
of a barrel. It was added in an amount of 15 parts by
weight based on 100 parts by weight in total of the
crystalline polypropylene-based resin and softener. The
resulting mixture was a resin for surface layer.
The same crystalline polypropylene-based resin as
employed above was molten in a co-rotating twin screw
extruder ("TEM-35BS", trade name; product of Toshiba
Machine) having a screw diameter of 37 mm and L/D of 30 and
from the midway of the extruder, 20 parts by weight of a
TM
mineral oil ("MORESCO white P70", trade name; product of
Matsumura Oil Research) was added through an injection pump.
Their amounts were adjusted so that the weight ratio of the
crystalline polypropylene-based resin to the mineral oil
would be 90:10. The resulting composition was mixed
uniformly and the pellets thus obtained were prepared as a
33
CA 02496926 2005-02-23
core layer resin. The volumetric ratio of each layer and
the like are shown in Table 1.
A multilayer stretched film was formed using the
resins thus obtained. First, the resin mixtures were
charged, respectively, in a surface-layer extruding unit
and a core-layer extruding unit of a multilayer extruder
capable of extruding three layers of two kinds into a
symmetric resin layer constitution. After sufficient
molding in each extruding unit, a raw film was extruded
through a multilayer cyclic dye at 220 C, followed by
cooling by water.
The resulting raw film was stretched at 120 C by a
tubular orientation machine at a stretching rate of
in the machine direction and 4 in the transverse
direction. Then, the end portion of the cylindrical film
was trimmed and the film was taken up one by one. By a
tenter whose clip for restraining the film in the machine
direction was set at a predetermined width, the film was
heat set at a hot air temperature of 130 C for a residence
time of 20 seconds. As a result, an almost uniform film of
m thick having a surface layer of 0.25 m thick, a core
layer of 0.5 m thick and another surface layer of 0.25 pm
thick was obtained. As a result of measuring physical
properties of this film, it exhibits good performances as
shown in Table 2. When the film thus obtained was observed
34
CA 02496926 2005-02-23
at 40,000 magnifications as a phase image of an atomic
force microscope, a structure formed of a network fibril
and a matrix existing therebetween was observed.
[Example 2]
In the same manner as in Example 1 except that the
crystalline polypropylene-based resin and the low-
crystalline propylene-a-olefin copolymer resin mixed at a
weight ratio of 65:35 was used as a surface resin, the
mineral oil of the core layer was added in an amount of 7
wt.%, and the thickness ratio of the surface layer, core
layer and another surface layer was changed to
0.20:0.60:0.20, a film having a thickness of 10 m was
formed. As a result of measurement of the physical
properties of the resulting film, it exhibited good
performances as shown in Table 2.
[Example 3]
In the same manner as in Example 1 except that the
crystalline polypropylene-based resin and a low-crystalline
propylene-a-olefin copolymer resin mixed at a weight ratio
of 55:45 was used as a surface resin composition and the
thickness ratio of the surface layer, core layer and
another surface layer was changed to 0.15:0.70:0.15, a film
having a thickness of 10 m was obtained. As a result of
CA 02496926 2005-02-23
measurement of the physical properties of the resulting
film, it exhibited good performances as shown in Table 2.
[Example 4]
In the same manner as in Example 1 except that used
as the surface resin was a resin obtained by adding the
hydrogenated terpene resin and the mineral oil in amounts
of 15 parts by weight and 10 parts by weight, respectively
based on 100 parts by weight of the resin composition of
the surface layer formed of the crystalline polypropylene-
based resin and low-crystalline propylene-a-olefin
copolymer resin, a film having a thickness of 10 m was
obtained. As a result of measurement of the physical
properties of the resulting film, it exhibited good
performances as shown in Table 2.
[Example 5]
In the same manner as in Example 1 except that the
crystalline polypropylene-based resin and low crystalline
propylene-a-olefin copolymer resin were mixed at a weight
ratio of 55:45; the hydrogenated terpene resin and mineral
resin were added in amounts of 10 parts by weight and 20
parts by weight respectively, based on 100 parts by weight
in total of the crystalline polypropylene-based resin and
low crystalline propylene-a-olefin copolymer resin; a
36
CA 02496926 2007-10-16
composition ratio of the core layer polyprcpvlene resin and
mineral oil %-,,as chanaed to arid a thickness ratio of
the stirface la;-er, core laver and another surface layer vvas
changed to a filin having a thickness of 10
~tm was obtained. As a result of measurement of the
physical properties of the resulting film, it exhibited
good performances as shown in Table 2.
[Example 6]
In the same manner as in Example 1 except that as the
mineral oil in the resin composition of the surface layer,
TN
"MORESCO White P40" (trade name; product of Matsumura Oil
Research Corp., kinetic viscosity at 40 C: 4.4 cSt) was
used in an amount of 15 parts by weight, and as the mineral
oil in the resin composition of the core layer, also
TM
"MORESCO White P40" (trade name; product of Matsumura Oil
Research Corp.) was used, a film having a thickness of 10
m was obtained. As a result of measurement of the
physical properties of the resulting film, it exhibited
good performances as shown in Table 2.
[Example 7]
In the same manner as in Example 1 except that as the
aliphatic hydrocarbon being liquid at normal temperature,
~
15 parts by weight of polybutene ("Nissan Polybutene 06SH"
37
CA 02496926 2005-02-23
(having a dynamic viscosity at 40 C of 95 cSt), trade name;
product of NOF CORPORATION) was added, instead of the
mineral oil, to the resin composition of the surface layer,
a film having a thickness of 10 m was obtained. As a
result of measurement of the physical properties of the
resulting film, it exhibited good performances as shown in
Table 2.
[Example 8]
In the same manner as in Example 1 except for the use
of 30 wt.% of a butene-1 polymer ("TAFMER BL4000", product
of Mitsui Chemicals, Inc) as a softener for the resin
composition of the surface layer, a film having a thickness
of 10 m was obtained. As a result of measurement of the
physical properties of the resulting film, it exhibited
good performances as shown in Table 2.
[Example 9)
In the same manner as in Example 1 except for the use
of 70 wt.% of an ethylene propylene random copolymer
("PC630A", trade name; product of Sun Allomer) as the
crystalline polypropylene-based resin for the resin
composition of the surface layer, a film having a thickness
of 10 m was obtained. As a result of measurement of the
physical properties of the resulting film, it exhibited
38
CA 02496926 2005-02-23
good performances as shown in Table 2.
[Example 10]
In the same manner as in Example 1 except for the use
of 75 wt.% of an ethylene propylene block copolymer ("Grand
Polypro J705", trade name; product of Grand Polymer Co.,
Ltd.) as the crystalline polypropylene-based resin for the
resin composition of the surface layer, a film having a
thickness of 10 m was obtained. As a result of
measurement of the physical properties of the resulting
film, it exhibited good performances as shown in Table 2.
[Example 11]
In the same manner as in Example 1 except that the
raw film obtained by extrusion was stretched at a
stretching ratio of 2.5 in the machine direction and 2.5 in
the transverse direction, a film having a thickness of 10
m was obtained. As a result of measurement of the
physical properties of the resulting film, it exhibited
good performances as shown in Table 2.
[Example 12]
In the same manner as in Example 1 except that the
raw film was stretched at 60 C and at a stretching ratio of
4 in the machine direction and 3 in the transverse
39
CA 02496926 2005-02-23
direction, and heat setting treatment after stretching was
not conducted, a film having a thickness of 10 m was
obtained. As a result of measurement of the physical
properties of the resulting film, it exhibited good
performances as shown in Table 2.
[Comparative Example 1]
In the same manner as in Example 1 except that a
resin composition obtained by mixing a crystalline
polypropylene-based resin and a low-crystalline
polypropylene-a-olefin copolymer resin at a weight ratio of
40:60 was used as the surface layer resin and a thickness
ratio of the surface layer, core layer and another surface
layer was changed to 0.15:0.70:0.15, a film having a
thickness of 10 m was obtained. A volumetric ratio of
three layers and the like are shown in Table 3. As a
result of measurement of the physical properties of the
resulting film, it exhibited excessive initial clinging
property and pulling-out force as shown in Table 4.
[Comparative Example 21
In the same manner as in Example 1 except that a
resin composition obtained by mixing the crystalline
polypropylene-based resin and low-crystalline propylene-a-
olefin copolymer resin at a weight ratio of 85:15 was used
CA 02496926 2005-02-23
for the surface layer, a film having a thickness of 10 m
was obtained. As a result of measurement of the physical
properties of the resulting film, its clinging property in
the initial stage was low as shown in Table 4.
[Comparative Example 3]
In the same manner as in Example 1 except that a
resin composition obtained by adding the hydrogenated
terpene resin in an amount of 20 parts by weight based on
100 parts by weight, in total, of the crystalline
polypropylene-based resin and low-crystalline propylene-a-
olefin copolymer resin was used for the surface layer, a
film having a thickness of 10 pm was obtained. As a result
of measurement of the physical properties of the resulting
film, its clinging power in the initial stage was low as
shown in Table 4.
[Comparative Example 4]
In the same manner as in Example 1 except that a
resin composition obtained by adding'the hydrogenated
terpene resin in an amount of 2 parts by weight based on
100 parts by weight, in total, of the crystalline
polypropylene-based resin and low-crystalline propylene-a-
olefin copolymer resin was used for the surface layer, a
film having a thickness of 10 m was obtained. As a result
41
CA 02496926 2005-02-23
of measurement of the physical properties of the resulting
film, its initial clinging power in the initial stage was
low as shown in Table 4.
[Comparative Example 5]
In the same manner as in Example 1 except that a
resin composition obtained by adding 10 parts by weight of
the hydrogenated terpene resin and 5 parts by weight of the
mineral oil to 100 parts by weight, in total, of the
crystalline polypropylene-based resin and low crystalline
propylene-a-olefin copolymer resin was used for the surface
layer, a film having a thickness of 10 m was obtained. As
a result of measurement of the physical properties of the
resulting film, it exhibited low clinging power and high
pulling-out force as shown in Table 4.
[Comparative Example 6]
In the same manner as in Example 1 except that a
resin composition obtained by adding 10 parts by weight of
the hydrogenated terpene resin and 25 parts by weight of
the mineral oil to 100 parts by weight, in total, of the
crystalline polypropylene-based resin and low crystalline
propylene-a-olefin copolymer resin was used for the surface
layer, a film having a thickness of 10 m was obtained. As
a result of measurement of the physical properties of the
42
CA 02496926 2005-02-23
resulting film, it exhibited poor performances such as
inferior stiffness and inferior hand feeling, as shown in
Table 4, because of excessive flexibility.
[Comparative Example 7]
In the same manner as in Example 1 except that the
weight ratio of the crystalline polypropylene-based resin
and mineral oil constituting the core layer was changed to
99:1, a film of 10 m thick was obtained. As a result of
measurement of the physical properties of the resulting
film, it exhibited good clinging property and pulling-out
force in the initial stage as shown in Table 4, which
however increased when it was allowed to stand at 40 C for
21 days.
[Comparative Example 8]
In the same manner as in Example 1 except that the
weight ratio of the crystalline polypropylene-based resin
and mineral oil ("MORESCO WHITE P70", trade name; product
of Matsumura Oil Research Corp.) serving as the aliphatic
hydrocarbon being liquid at normal temperature was changed
to 60:40, a film was tried to be formed. Owing to poor
film forming property, however, the film was not formed.
[Comparative Example 9]
43
CA 02496926 2005-02-23
In the same manner as in Example 1 except that the
resin composition of the core layer was changed to a 75:25
(weight ratio) resin composition of the crystalline
polypropylene-based resin and low-crystalline propylene-a-
olefin copolymer resin (''TAFMER XR11OT", trade name;
product of Mitsui Chemicals, Inc.), a film of 10 m thick
was obtained. As a result of measurement of the physical
properties of the resulting film, its flexibility, and
clinging property and pulling-out force in the initial
stage were on the same level with those of the film
obtained in Example 1 as shown in Table 4, but the clinging
property and pulling-out force increased when it was
allowed to stand at 40 C for 21 days.
[Comparative Example 10]
A monolayer film of 10 m thick was formed in the
same manner as in Example 1 except that the film was
changed to a single layer film having the surface-layer
composition of Example 1. As a result of measurement of
the physical properties of this film, it was stable in
clinging property and pulling-out ease as shown in Table 4,
but inferior in stiffness because of excessive flexibility.
44
CA 02496926 2005-02-23
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CA 02496926 2005-02-23
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CA 02496926 2005-02-23
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L.ML p L.ML ~ lM1 p L.ML p I.ML p LL ~ L.ML p LML p L.Mt_ f -
O
n- d w
C O
O U
t
~ ~3~r~~~='~~~~'~dN~a~~~a~
L C
N ~ U OD
lD
LO ln LO lf) LO LO ln ll=) LO LO
N O N T N Ln N LO N p N_ N_ O_N pN LON LO LON LO
a
O t'N o I- F F ! I F F H F
O>, O~ O t!=) O N O N p N p N p N p N p N p N
N
O O
(D N cu
fl- O N O N l1') N ln N LO N lf) N LO N U') N ln N LO N LO
2 ~ M V' M 00 M f- CM I~. c~"M I- M I- f") f- P- M 1- M 1-
9 y L.L LL L.L l.L LL LL. L.L LL LL
(7 O =
CL
a)
a aN aM a..qr dln atD Cl.l- 0- aD a6" n.
E E E E E E l E E E~
O O x O x O O X O X O O X O x O
UwU~'''='-''~~'-'U"-'U'LULULLJ 0 W
CA 02496926 2005-02-23
rn o x
E x
C O O O O U O O0
N N ~
~E
p~ _
~m E O O O O O O O O O
~
o
U t ~ /) N ~ N 0 0 a) u ~ a)
)
z 2 2 ~) T 2 N 2 _ '
a a n a Ll ci n a n
~ O O O O OO O O O
m ' a 4 O O O x O O x
x x OO OO 00 x OO OO x
~
LL
O O @ @ @ @ @ @ @
Q o
a55 R -.0 LL
= ~ E
a ~
L = ~ p 'O
U _ ~ p ct
a ~O
m
_ E
U Z5 ~ o N
'~ -- U
m ro o2~ 4 4 x 4 x O 4 4 OO
rn>- m
C
N
L(O 2) N
U m ~
N E
o ~ o
0=
cu 4 O 4 O x O O O O
a.
T
~E C
G2)
- ,~
~~~ ' d 4 4 4 x O O O O
C - '
U
L r-L Q~ CL Q~ ci
E E E E ~ ~~ ~~ ~~ E a) E
3 = N M ~
H ~ U w U w U 0 w U w U w U w U w U w U w U w
CA 02496926 2007-10-16
Abbreviations in the table have the following
meaninas:
Ex. = Example, Comp. Ex. = Comparative Example F3~~?: vstalline polypropylene-
based resin ("Grand
Polypro F327", trade name; product of Grand Polymer Co.,
Ltd., MFR = 7.0 g/10 min.)
PC630: Homopolypropylene resin ("PC630A", trade name;
product of Sun Allomer Co., Ltd., MFR = 7.5 g/10 min.)
J705 = Crystalline block polypropylene resin ("Grand
Polypro J705", trade name; product of Grand Polymer Co.,
Ltd., MFR = 10 g/l0 min)
110T = Low-crystalline propylene-a-olefin copolymer resin
("TAFMER XR110T", trade name; product of Mitsui Chemicals,
Inc., MFI = 6.0 g/10 min. (230 C), density: 0.890 g/cc)
TM
BL4000 = butene-l copolymer ("TAFMER BL4000", trade name;
product of Mitsui Chemicals, Inc., MFR = 1.8 g/10 min,
density: 0.915 g/cc)
TM
P125 = Hydrogenated terpene resin ("Clearon P125", trade
name; product of Yasuhara Chemical Co., Ltd.)
TM
P70 = Mineral oil ("Smoil P70", trade name; product of
Mtsumura Oil Research, kinetic viscosity: 12.35 (40 C cSt)
TM
P40 = Mineral oil ("MORESCO WHITE P-40", trade name;
product of Matsumura Oil Research, kinetic viscosity: 4.3
(40 C, cSt)
06SH = Aliphatic hydrocarbon being liquid at normal
49
CA 02496926 2007-10-16
temperature ("Nissan Polvbutene OrSH", trade name; product
of NOF CORPORTION, kinetic viscosity: 95 (40 C cSt)) While the present
invention has been described in
detail and with reference to specific embodiments thereof,
it will be apparent to one skilled in the art that various
changes and modifications cari be made therein without
departing the spirit and scope thereof.
INDUSTRIAL APPLICABILITY
According to the present invention, a polypropylene-
based multilayer film excellent in the balance of clinging
property and pulling-out ease, undergoes a less time-
dependent change in these performances, and is excellent in
transparency, heat resistance, flexibility, hand feeling,
and cutting ease can be provided. The film is usable
suitably as a food packaging wrap film.
