SF-2452 I
1
DESCRIPTION
i
POLYOLEFIN COMPOSITE FILM
5 TECHNICAL FIELD
[0001]
The present invention relates to a polyolefin composite film,
more particularly a polyolefin composite film excellent in
low-temperature heat sealability, heat-sealing strength and
10 transparency.
BACKGROUND ART
[0002]
As a heat-sealable polyolefin composite film conventionally
15 used for packaging and the like, a composite film formed by
laminating a polyolefin resin having a low melting point on a
crystalline polypropylene surface layer is known.
[0003]
For example, the following methods have been specifically
20 proposed. A polypropylene resin composition containing 1 to 50
wt% of a propylene polymer having a melting point of not lower
than 150 °C, 10 to 90 wt% of a propylene copolymer having a melting
point of 100 °C or higher and lower than 150 °C and 1 to 80 wt% of
a propylene or 1-butene copolymer having a melting point of 40 °C
SF-2452
2
or higher and lower than 100 °C is laminated as a heat-fusible layer I
on one side of a biaxially-stretched polypropylene film, to
thereby form a stretched film (Patent Literature 1:
j WO2007/015415). In another example, a coating layer composed of
5 a propylene polymer composition containing a propylene/a-olefin
random copolymer having a melting point of 120 to 140°C, a
propylene/a-olefin random copolymer having a melting point of 80 °C
or higher and lower than 120°C, and a butene-1/a-olefin random
copolymer having a melting point of 40 to 100°C is laminated on
10 both sides of a biaxially-stretched film mainly composed of a
propylene polymer, to thereby form a over-wrap packaging film
(Patent Literature 2: JP-A-2003-170554). As described above, a I
composition containing two or more kinds of propylene copolymers
differing in melting point is used as a surface layer
15 (heat-sealable layer).
[0004]
In addition to the two-layer film, a three-layer film has
also been proposed. For example, an intermediate layer is
provided between a base layer which is a biaxially-stretched
20 polypropylene film and a surface layer composed of a composition
containing two or more kinds of propylene copolymers differing
in melting point, the intermediate layer being composed of a
composition of a propylene homopolymer and a propylene/a-olefin
copolymer, to thereby provide a heat-sealable laminated
i
SF-2452
3
4
polypropylene resin film (Patent Literature 3: JP-A-2005-104151,
Patent Literature 4: JP-A-2005-305998). In another example, a
composition of propylene homopolymer and a propylene/a-olefin
copolymer is used as a base layer; a composition of a propylene
5 homopolymer and a propylene/a-olefin copolymer is used as an
intermediate layer; and a propylene/a-olefin copolymer having a
melting point of not higher than 150 °C or its composition is used
as a surface layer (heat-fusible layer) (Patent Literature 5:
JP-A-2006-305884, Patent Literature 6: JP-A-2006-327183).
10 [0005]
However, the heat-sealable laminated polypropylene resin
film using an intermediate layer specifically proposed in Patent
Literature 3 or Patent Literature 4 is inferior in heat
sealability.
15
Citation List
Patent Literature
[0006]
[Patent Literature 1] WO2007/015415
20 [Patent Literature 2] JP-A-2003-170554
[Patent Literature 3] JP-A-2005-104151
[Patent Literature 4] JP-A-2005-305998
[Patent Literature 5] JP-A-2006-305884
[Patent Literature 6] JP-A-2006-327183
SF-2452
4
t
i
SUMMARY OF THE INVENTION
TECHNICAL PROBLEM
[0007]
5 Such composite films as proposed in Patent Literatures 1
to 6, however, are insufficient in heat-sealing strength at a
relatively low temperature range, and thus are limited in their
applications as a packaging film.
[0008]
10 The present invention provides a polyolefin composite film
excellent in low-temperature heat sealability, heat-sealing
strength and transparency.
TECHNICAL SOLUTION
15 [0009]
That is, a polyolef in composite film according to an aspect
of the present invention has at least one surface layer [i], a
core layer [ii], and an intermediate layer [iii] contacting
directly with both the surface layer [i] and the core layer [ii] ,
20 wherein the surface layer [i] is formed from a propylene
resin composition that comprises:
a propylene/a-olefin random copolymer (A) that comprises
50 to 97 mol% of a unit derived from propylene and 3 to 50 mol%
of a unit derived from C2-10 a-olefins excluding propylene, and/or
SF-2452
5
a 1-butene/a-olefin copolymer (E) that comprises 50 to 95
mol% of a unit derived from 1-butene, 50 to 5 mol% of a unit derived
from C2-10 a-olefins excluding 1-butene and 50 to 5 mol% of a unit
derived from a—olefins excluding 1-butene, the
5 propylene/a-olefin random copolymer (A) and/or the
1-butene/a-olef in copolymer (E) being in an amount of 0 to 50 wt%,
and
a propylene polymer (B) that comprises 50 to 100 mol% of
a unit derived from propylene and 0 to 50 mol% of a unit derived
10 from C2-10 a-olefins excluding propylene and has a melting point
of 120 to 170°C,
the propylene polymer (B) being in an amount of 50 to 100
wt%,
provided that the total amount of (A), (E) and (B) in the
15 surface layer is 100 parts by weight;
wherein the core layer [ii] is formed from a propylene resin
composition that comprises:
a crystalline polypropylene (C) that comprises 97 to 100
mol% of a unit derived from propylene and 0 to 3 mol% of C2-10
20 a-olefins excluding propylene and has a melting point of 150 to
170°C,
the crystalline polypropylene (C) being in an amount of 70
to 100 wt%, and
a propylene/a-olefin random copolymer (A) that comprises
SF-2452
6
*
50 to 97 mol% of a unit derived from propylene and 3 to 50 mol%
of a unit derived from C2-10 a-olefins excluding propylene,
the propylene/a-olefin random copolymer (A) being in an
amount of 0 to 30 wt%,
5 provided that the total amount of (C) and (A) in the core
layer is 100 parts by weight; and
wherein the intermediate layer [iii] is formed from a
propylene resin composition that comprises:
a crystalline polypropylene (C) that comprises 97 to 100
10 mol% of a unit derived from propylene and 0 to 3 mol% of C2-10
a-olefins excluding propylene and has a melting point of 150 to
170°C,
the crystalline polypropylene (C) being in an amount of 50
to 95 wt%, and
15 a propylene polymer (B) that comprises 50 to 100 mol% of
a unit derived from propylene and 0 to 50 mol% of a unit derived
from C2-10 a-olefins excluding propylene and has a melting point
of 120 to 170°C,
a propylene/a-olefin random copolymer (A) that comprises
20 50 to 97 mol% of a unit derived from propylene and 3 to 50 mol%
of a unit derived from C2-10 a—olefins excluding propylene,
and/or
a 1-butene/a-olefin random copolymer (E) that comprises 50
to 95 mol% of a unit derived from 1-butene and 50 to 5 mol% of
SF-2452
7
a unit derived from a—olefins excluding 1-butene,
the propylene polymer (B), the propylene/a-olefin random
copolymer (A) , and/or the 1-butene/a-olefin random copolymer (E)
being in an amount of 50 to 5 wt%,
5 provided that the total amount of (C) , (B) , (A) and (E) in
the intermediate layer is 100 wt%.
[0010]
A polyolefin composite film according to "another aspect"
of the present invention has at least one surface layer [i], a
10 core layer [ii], and an intermediate layer [iii] contacting
directly with both the surface layer [i] and the core layer [ii] ,
wherein the surface layer [i] is formed from a propylene
resin composition that comprises:
a propylene/a-olefin random copolymer (A) that comprises
15 50 to 97 mol% of a unit derived from propylene and 3 to 50 mol%
of a unit derived from C2-10 a—olefins excluding propylene,
the propylene/a-olefin random copolymer (A) being in an
amount of 15 to 100 wt%, and
a propylene polymer (B) that comprises 50 to 100 mol% of
20 a unit derived from propylene and 0 to 50 mol% of a unit derived
from C2-10 a—olefins excluding propylene and has a melting point
of 120 to 170°C,
the propylene polymer (B) being in an amount of 0 to 85 wt%;
wherein the core layer [ii] is formed from a propylene resin
SF-2452
8
t
composition that comprises:
a crystalline polypropylene (C) that comprises 97 to 100
mol% of a unit derived from propylene and 0 to 3 mol% of C2-10
a—olefins excluding propylene and has a melting point of 150 to
5 170°C,
the crystalline polypropylene (C) being in an amount of 70
to 100 wt%, and
a propylene polymer (D) that comprises 50 mol% or more and
less than 97 mol% of a unit derived from propylene, and more than
10 3 mol% and up to 50 mol% of a unit derived from C2-10 a—olefins
excluding propylene, and has a melting point of lower than 140 °C
or a melting point that is not observed as measured by Differential
Scanning Calorimetry,
the propylene polymer (D) being in an amount of 0 to 30 wt%;
15 and
wherein the intermediate layer [iii] is formed from a
propylene resin composition that comprises:
a crystalline polypropylene (C) that comprises 97 to 100
mol% of a unit derived from propylene and 0 to 3 mol% of C2-10
20 a-olefins excluding propylene, and has a melting point of 150 to
170°C,
the crystalline polypropylene (C) being in an amount of 50
to 95 wt%, and
a propylene polymer (D) that comprises 50 mol% or more and
SF-2452
9
»
less than 97 mol% of a unit derived from propylene, and more than
3 mol% and up to 50 mol% of a unit derived from C2-10 a-olefins
excluding propylene, and has a melting point of lower than 140 °C
or a melting point that is not observed as measured by Differential
5 Scanning Calorimetry, and/or
a 1-butene/a-olefin random copolymer (E) that comprises 50
to 95 mol% of a unit derived from 1-butene and 50 to 5 mol% of
a unit derived from a—olefins excluding 1-butene,
the propylene polymer (D) and/or the 1-butene/a-olefin
10 random copolymer (E) being in an amount of 50 to 5 wt%,
provided that the total amount of (C) , (D) and (E) is 100
wt%.
[0011]
The polyolefin composite film according to "another aspect"
15 in the present invention is described above.
[0012]
In a preferable embodiment of the present invention, the
propylene/a-olefin random copolymer (A) has a melting point of
110"C or lower or has a melting point that is not observed. In
20 a preferable embodiment of the present invention, the propylene
polymer (B) has a melting point of 120 to 140 'C, and the
1-butene/a-olefin copolymer (E) has a melting point of 60 to 110 °C.
[0013]
A polyolefin composite film according to a preferable
SF-2452
10
•
embodiment of the present invention comprises a
propylene/a-olefin random copolymer (A) which is a I
| propylene/1-butene random copolymer that satisfies the following
properties:
5 (1) the intrinsic viscosity as measured in decalin at 135 °C
is 0.1 to 5 dl/g,
(2) the molecular weight distribution (Mw/Mn) as determined
by gel permeation chromatography is 1.5 to 3, and
(3) the parameter B value, which shows a randomness of
10 copolymerized monomer chain distribution, is 0.9 to 1.5.
[0014]
In another preferable embodiment of the present invention,
the polyolefin composite film is an unstretched film. I
[0015]
15 In another preferable embodiment of the present invention,
the polyolefin composite film is a biaxially-stretched film.
[0016]
In another preferable embodiment of the present invention,
the percentage of the total thickness of the surface layer relative
20 to the total thickness of the polyolefin composite film is 2 to
10%.
[0017]
In another preferable embodiment of the present invention ,
the percentage of the total thickness of the intermediate layer
SF-2452
11
*
relative to the total thickness of the polyolefin composite film
is 2 to 10%.
[0018]
In another preferable embodiment of the present invention,
5 the polyolefin composite film has a five-layer structure
consisting of surface layer/intermediate layer/core
layer/intermediate layer/surface layer in this order.
[0019]
In another preferable embodiment of the present invention,
10 the total thickness of the polyolefin composite film is 10 to 35
micrometers (urn).
[0020]
In another preferable embodiment of the present invention,
the tensile modulus in the machine stretching direction or in the
15 transverse stretching direction of the polyolefin composite film
is 1.9 to 5.0 GPa.
ADVANTAGEOUS EFFECTS OF THE INVENTION
[0021]
20 The polyolefin composite film of the present invention is
excellent in low-temperature heat sealability, heat-sealing
strength and transparency, and therefore is employable for a wide
range of applications as packaging films for food, industrial
materials and the like.
SF-2452
12
*
DESCRIPTION OF EMBODIMENTS
[0022]

5 The propylene/a-olefin random copolymer (A) , constituting
the surface layer [i] of the polyolefin composite film of the
present invention, is a propylene/a-olefin random copolymer (A)
that comprises:
a unit derived from propylene in an amount of 50 to 97 mol%,
10 preferably 50 to 95 mol%, and
a unit derived from C2-10 a—olefins excluding propylene in
an amount of 3 to 50 mol%, preferably 5 to 50 mol%,
provided that the total amount of the unit derived from
propylene and the unit derived from a-olefins is 100 mol%.
15 Regarding the a-olefins, one kind thereof or two or more kinds
thereof may be used.
[0023]
In a further preferable embodiment, the propylene/a-olefin
random copolymer (A) according to the present invention comprises
20 a unit derived from propylene in an amount of 60 mol% to 80 mol%,
and a unit derived from C2-10 a-olefins, particularly a unit
derived from a-olefins selected from ethylene and 1-butene, in
an amount of 20 mol% to 40 mol%.
[0024]
SF-2452
13
*
The propylene/a-olefin copolymer (A) according to the
present invention preferably has a melting point of 140 °C or lower
or a melting point that is not observed; more preferably a melting
point of 110'C or lower, or a melting point that is not observed.
5 [0025]
The use of a propylene/a-olefin copolymer having a melting
point of higher than 140°C may result in a polyolefin composite
film having inferior low-temperature heat sealability.
[0026]
10 Regarding the propylene/a-olefin copolymer (A) according
to the present invention, one kind of polymer may be used, or two
or more kinds of polymers may be used, as needed.
[0027]
Specific examples of the propylene/a-olefin copolymer (A)
15 according to the present invention include propylene/ethylene
copolymer, propylene/1-butene copolymer and
propylene/ethylene/1-butene copolymer.
[0028]
The propylene/a-olefin random copolymer (A) according to
20 the present invention that is preferred is a propylene/1-butene
random copolymer satisfying the following properties:
(1) the intrinsic viscosity [n] as measured in decalin at
135°C is 0.1 to 5 dl/g;
(2) the molecular weight distribution (Mw/Mn) as determined
i
! SF-2452
| 14
ft
by gel permeation chromatography is 1.5 to 3; and
(3) the parameter B value, which shows a randomness of
copolymerized monomer chain distribution, is 0.9 to 1.5,
preferably 1.0 to 1.4.
5 [0029]
The parameter B value, proposed by Coleman et al. (B. D.
Coleman and T. G. Fox, J. Polym. Sci., Al, 3183(1963)), is defined
as follows:
B = Pi2/(2P1-P2),
10 wherein Pi and P2 are a first monomer content fraction and
a second monomer content fraction, respectively; and Pi2 is the
proportion of (first monomer) - (second monomer) chains in all the
dyad chains.
[0030]
15 When the B value is 1, the copolymer obeys the Bernoulli
statistics. When B<1, the copolymer is a block-like copolymer.
When B>1, the copolymer is an alternating-like copolymer. When
B=2, the copolymer is an alternating copolymer.
[0031]
20 The MFR (melt flow rate; ASTM D-1238, load: 2160 g,
temperature: 230°C) of the propylene/a-olefin random copolymer
(A) according to the present invention is not particularly limited
as long as a film can be formed, but is usually 0.5 to 20 g/10
min, preferably 2 to 10 g/10 min.
SF-2452
15
m
[0032]

The 1-butene/a-olefin copolymer (E) , constituting the
surface layer [i] and the intermediate layer [iii] of the
5 polyolefin composite film of the present invention, is a
1-butene/a-olefin random copolymer (E) that comprises:
a unit derived from 1-butene in an amount of 50 to 95 mol%,
preferably 60 to 95 mol%, particularly preferably 70 to 95 moll,
and
10 a unit derived from a—olefins excluding 1-butene in an
amount of 50 to 5 mol%, preferably 40 to 5 mol%, particularly
preferably 30 to 5 moll,
provided that the total amount of the unit derived from
1-butene and the unit derived from a-olefins is 100 mol%.
15 Regarding the a-olefins, one kind thereof may be used, or two or
more kinds thereof may be used, as needed.
[0033]
The 1-butene/a-olefin random copolymer (E) according to the
present invention preferably has a melting point of 60 to 110°C.
20 [0034]
I The use of a 1-butene/a-olefin copolymer having a melting
I point of higher than 110°C may result in a polyolefin composite
I film having inferior low-temperature heat sealability. On the
j other hand, the use of a 1-butene/a-olefin copolymer having a
i
SF-2452
16
1
melting point of lower than 60 °C may result in a polyolefin
composite film having sticky surface.
[0035]
Regarding the 1-butene/a-olefin random copolymer (E)
5 according to the present invention, one kind of polymer may be
used, or two or more kinds of polymers may be used, as needed.
[0036]
Specific examples of the 1-butene/a-olefin random copolymer
(E) according to the present invention include 1-butene/ethylene
10 copolymer, 1-butene/propylene copolymer and
1-butene/ethylene/propylene copolymer.
[0037]
The 1-butene/a-olefin random copolymer (E) according to the
present invention that is preferred is a 1-butene/a—olefin
15 copolymer satisfying the following properties:
(1") the intrinsic viscosity [n] as measured in decalin at
135°C is 0.1 to 5 dl/g;
(2") the molecular weight distribution (Mw/Mn) as
determined by gel permeation chromatography is 2 to 6; and
20 (3") the parameter B value, which shows a randomness of
copolymerized monomer chain distribution, is 0.9 to 1.5,
preferably 0.9 to 1.4.
[0038]
The MFR (melt flow rate; ASTM D-1238, load: 2160 g,
SF-2452
17
*
temperature: 230°C) of the 1-butene/a-olefin random copolymer (E)
according to the present invention is not particularly limited
as long as a film can be formed, but is usually 1 to 20 g/10 min,
preferably 5 to 15 g/10 min.
5 [0039]

The propylene polymer (B) , constituting the surface layer
[i] and the intermediate layer [ii] of the polyolefin composite
film of the present invention, is a propylene polymer (B) that
10 comprises:
a unit derived from propylene in an amount of 50 to 100 mol%,
preferably 85 to 97 mol%, and
a unit derived from C2-10 a-olefins excluding propylene in
an amount of 0 to 50 mol%, preferably 3 to 15 mol%, and
15 has a melting point of 120 to 170°C, preferably 120 to 140°C,
provided that the total amount of the unit derived from
propylene and the unit derived from a—olefins is 100 mol%.
Regarding the a-olefins, one kind thereof may be used, or two or
more kinds thereof may be used, as needed.
20 [0040]
Regarding the propylene polymer (B) according to the present
invention, one kind of polymer may be used, or two or more kinds
of polymers may be used, as needed.
[0041]
SF-2452
18
9
The use of a propylene copolymer having a melting point of
lower than 120 'C may result in a polyolefin composite film having
insufficient balance between low-temperature heat sealability
and sealing strength.
5 [0042]
Specific examples of the propylene polymer (B) according
to the present invention include block copolymers and random
copolymers including propylene/ethylene copolymer,
propylene/ethylene/1-butene copolymer and propylene/1-butene
10 copolymer.
[0043]
The MFR (melt flow rate; ASTM D-1238, load: 2160 g,
temperature: 230°C) of the propylene polymer (B) according to the
present invention is not particularly limited as long as a film
15 can be formed, but is usually 0.5 to 20 g/10 min, preferably 2
to 10 g/10 min.
[0044]

The crystalline polypropylene (C), constituting the core
20 layer [ii] and the intermediate layer [iii] of the polyolefin
composite film of the present invention, is a crystalline
polypropylene (C) that comprises:
a unit derived from propylene in an amount of 97 to 100 mol%,
preferably 98 to 100 mol%, and
SF-2452
I 19
at least one unit derived from C2-10 a-olefins excluding
propylene in an amount of 0 to 3 mol%, preferably 0 to 2 mol%,
and
has a melting point of 150 to 170°C, preferably 155 to 165°C,
5 provided that the total amount of the unit derived from
propylene and the unit derived from a-olefins is 100 mol%.
When the crystalline polypropylene (C) contains the unit
derived from a-olefins, one kind thereof may be used, or two or
more kinds thereof may be used, as needed.
10 [0045]
The use of a polypropylene having a melting point of lower
than 150 °C in the core layer [ii] tends to result in a polyolefin I
composite film having insufficient rigidity and heat resistance.
[0046]
15 Regarding the crystalline polypropylene (C) according to
the present invention, one kind of polymer may be used, or two
or more kinds of polymers may be used, as needed.
[0047]
Specific examples of the crystalline polypropylene (C)
20 according to the present invention include propylene homopolymer,
propylene/ethylene copolymer and copolymers of propylene and an
a-olefin such as propylene/1-butene copolymer and
propylene/ethylene/1-butene copolymer; propylene homopolymer is
preferred.
SF-2452
20
[0048]
The MFR (melt flow rate; ASTM D-1238, load: 2160 g,
temperature: 230°C) of the crystalline polypropylene (C)
I according to the present invention is not particularly limited
| 5 as long as a film can be formed, but is usually 0.5 to 20 g/10
I
min, preferably 2 to 10 g/10 min.
[0049]

In one aspect of the present invention, the
10 propylene/a-olefin random copolymer (A) constituting the core
layer [ii] and the intermediate layer [iii] of the polyolefin
composite film may be the propylene polymer (D). ,
[0050]
The propylene polymer (D) is a polymer that comprises:
15 a unit derived from propylene in an amount of 50 mol% to
less than 97 mol%, preferably 60 mol% to less than 80 mol%, and
at least one unit derived from C2-10 a-olefins excluding
propylene in an amount of more than 3 mol% and up to 50 mol%,
preferably more than 20 mol% and up to 40 mol%,
20 and has a melting point of lower than 140°C or a melting
point that is not observed as measured by Differential Scanning
Calorimetry, preferably 110°C or lower or a melting point that
is not observed.
Regarding the a-olefins, one kind thereof may be used, or
SF-2452
21
two or more kinds thereof may be used, as needed.
[0051]
Among the propylene polymers (D), a preferred propylene
polymer (D) satisfies the following properties:
5 (1') the intrinsic viscosity [n] as measured in decalin at
135°C is 0.1 to 5 dl/g;
(2' ) the molecular weight distribution (Mw/Mn) as
determined by gel permeation chromatography is 1.5 to 4; and
(3') the parameter B value, which shows a randomness of
10 copolymerized monomer chain distribution, is 0.7 to 1.5.
[0052]
Regarding the propylene polymer (D) according to the present
invention, one kind of polymer may be used, or two or more kinds
of polymers may be used, as needed.
15 [0053]
The use of a propylene polymer having a melting point of
140 °C or higher may result in a polyolefin composite film having
inferior low-temperature heat sealability and/or heat-sealing
strength.
20 [0054]
Specific examples of the propylene polymer (D) according
to the present invention are block copolymers and random
copolymers including propylene/ethylene copolymer,
propylene/1-butene copolymer and propylene/ethylene/1-butene
SF-2452
22
copolymer.
[0055]
The MFR (melt flow rate; ASTM D-1238, load: 2160 g,
temperature: 230°C) of the propylene polymer (D) according to the
5 present invention is not particularly limited as long as a film
can be formed, but is usually 0.5 to 20 g/10 min, preferably 2
to 10 g/10 min.
[0056]

10 The polyolefin composite film of the present invention is
a polyolefin composite film that has at least one surface layer
[i] , a core layer [ii] and an intermediate layer [iii] contacting
directly with both the surface layer [i] and the core layer [ii] .
[0057]
15 In the case where the composite film of the present invention
has a three-layer structure consisting of the surface layer, the
core layer and the intermediate layer, the term "core layer" simply
refers to a layer serving as a core material, not necessarily
meaning a layer that constitutes the center located between the
20 surface layer and the intermediate layer.
[0058]

The surface layer [i] of the polyolefin composite film of
the present invention is formed from an olefin polymer composition
SF-2452
23
•
(X) comprising the propylene/a-olefin random copolymer (A) ,
and/or the 1-butene/a-olefin copolymer (E) in an amount of 0 to
50 wt%, preferably 0 to 30 wt%, more preferably 3 to 30 wt%; and
the propylene polymer (B) in an amount of 50 to 100 wt%, preferably
5 70 to 100 wt%, more preferably 70 to 97 wt%, provided that the
total amount of (A), (E) and (B) in the surface layer is 100 wt%.
[0059]
It is within the scope of the present invention that the
surface layer [i] does not contain the propylene/a-olefin random
10 copolymer (A) and/or the 1-butene/a-olefin copolymer (E) .
However, in a particularly suitable embodiment, the
propylene/a-olefin random copolymer (A) and/or the
1-butene/a-olefin copolymer (E) are included, preferably in an
amount of 3 to 30 wt%.
15 [0060]
The embodiment containing the propylene/a-olefin random
copolymer (A) and/or the 1-butene/a—olefin copolymer (E) is
superior in low-temperature heat sealability compared with
embodiments not containing these components.
20 [0061]

The core layer [ii] of the polyolefin composite film of the
present invention is formed from a propylene polymer
composition (Y) comprising 70 to 100 wt% of the crystalline
SF-2452
24
polypropylene (C) and 0 to 30 wt% of the propylene/a-olefin
copolymer (A), provided that the total amount of (A) and (C) is
100 wt%.
[0062]
5 The use of the crystalline polypropylene (C) alone as a
polymer component of the core layer [ii] leads to further
improvement of increase in the heat-sealing strength, as compared
with when the propylene/a-olefin copolymer (A) and the crystalline
polypropylene (C) are used in combination.
10 [0063]
The use of a composition in which the amount of the
propylene/a-olefin copolymer (A) exceeds 30 wt% may result in a
polyolefin composite film having inferior heat resistance and
rigidity.
15 intermediate layer [iii]>
The intermediate layer [iii] in the polyolefin composite
film of the present invention is formed from a propylene
!
composition that comprises the crystalline polypropylene (C) in
an amount of 50 to 95 wt%, preferably 70 to 95 wt%; and in addition
20 thereto, the propylene polymer (B) , the propylene/a-olefin random
copolymer (A) and/or the 1-butene/a-olef in random copolymer (E) ,
in an amount of 50 to 5 wt%, preferably 30 to 5 wt%, provided that I the total amount of (C) , (B) , (A) and (E) in the intermediate layer
is 100 wt%.
i
i
SF-2452
25
4
[0064]
In the intermediate layer [iii], "and/or" is a term to
indicate that all of the following embodiments are within the
scope of the present invention: the embodiment using one component
5 selected from the propylene polymer (B) , the propylene/a-olefin
random copolymer (A) and the 1-butene/a-olefin random copolymer
(E) ; the embodiment using two components in combination selected
therefrom; and the embodiment using all the three components
selected therefrom.
10 [0065]
The use of a composition in which the amount of the
crystalline polypropylene (C) is less than 50 wt% for the
intermediate layer [iii] of the present invention may result in
a polyolef in composite film having inferior heat-sealing strength.
15 On the other hand, the use of a composition in which the amount
of the crystalline polypropylene (C) exceeds 95 wt% may result
in a polyolefin composite film having inferior heat-sealing
strength.
[0066]
20 The polyolefin composite film according to "another aspect"
of the present invention is described below.
[0067]
That is, in the surface layer [i] , the propylene/a-olef in
random copolymer (A) is used in an amount of 15 to 100 wt% and
!
SF-2452
26
the propylene polymer (B) is used in an amount of 85 to 0 wt%;
preferably, the propylene/a-olefin random copolymer (A) is used
in an amount of 30 to 100 wt% and the propylene polymer (B) is
used in an amount of 70 to 0 wt%; more preferably, the
5 propylene/a-olefin random copolymer (A) is used in an amount of
50 to 100 wt% and the propylene polymer (B) is used in an amount
of 50 to 0 wt% (in each case, the total amount of (A) and (B) is
100 wt%).
[0068]
10 With the configuration described above, a polyolefin
composite film which is excellent in heat-sealing strength at a
relatively low temperature can be obtained.
[0069]
In the present invention, the core layer [ii] comprises 70
15 to 100 wt% of the crystalline polypropylene (C) and 0 to 30 wt%
of the propylene polymer (D).
[0070]
The core layer [ii] may contain recycled materials of the
core layer [ii], recycled materials of polymers that constitute
20 the surface layer [i] and the intermediate layer [iii] and the
like, as long as the range mentioned above is satisfied.
[0071]
The core layer [ii] comprises the crystalline polypropylene
(C) in an amount of 70 to 100 wt%, preferably 80 to 100 wt%,
SF-2452
27
particularly preferably 85 to 100 wt%, and the propylene polymer
(D) in an amount of 0 to 30 wt%, preferably 0 to 20 wt%, particularly
preferably 0 to 15 wt% (in each case, the total amount of (C) and
(D) is 100 wt%).
5 [0072]
In the present invention, the intermediate layer [iii]
comprises, together with 50 to 95 wt% of the crystalline
polypropylene (C) , 50 to 5 wt% of a composition (Z' ) containing
the propylene polymer (D) and/or the 1-butene/a-olefin random
10 copolymer (E) , provided that the total amount of (C) and the
composition (Z') containing (D) and/or (E) is 100 wt%.
[0073] .
The crystalline polypropylene (C) used for the intermediate
layer [iii], as long as being used in the range defined above,
15 may differ from or may be the same as the crystalline polypropylene
J (C) used for the core layer [ii].
[0074]
The propylene polymer (D) that may be used for the
intermediate layer [iii], as long as being used in the range or
20 in the preferred range defined above, may differ from or may be
the same as the propylene polymer (D) used for the core layer [ii] .
[0075]
Similarly, examples of the 1-butene/a-olefin copolymer (E)
that may be used for the intermediate layer [iii] include
SF-2452
28
#
1-butene/ethylene copolymer, 1-butene/propylene copolymer and
1-butene/ethylene/propylene copolymer. Regarding these
polymers, one kind of polymer may be used, or two or more kinds
of polymers may be used, as needed.
5 [0076]
In the present invention, embodiments of the intermediate
layer [iii] include the embodiment where the layer (iii) consists
of the component (C) and the component (D) ; the embodiment where
the layer (iii) consists of the component (C) and the component
10 (E); and the embodiment where the layer (iii) consists of the
component (C) , the component (D) and the component (E) . In these
embodiments, the layer (iii) contains (A) in an amount of 50 to
95 wt%, and (D) and/or (E) in an amount of 50 to 5 wt%, more j
preferably (A) in an amount of 60 to 90 wt%, (D) and/or in an amount
15 of 40 to 10 wt%, provided that the total of (A), and (D) and/or
(E) is 100 wt%.
[0077]
i
I It is desirable that each polymer constituting the
i
intermediate layer contains the polymer defined as the surface
20 layer in the range defined above. Each polymer constituting the
intermediate layer, although not required to necessarily contain
the same polymer as used for the surface layer, may contain the
same polymer as used for the surface layer in view of economy and j
other factors. I
SF-2452
29
«
The above description focuses on the polyolefin composite
film according to another aspect of the present invention.
[0078]
The propylene/a-olefin random copolymer (A) , the
5 1-butene/a-olefin copolymer (E) , the propylene polymer (B) , the
crystalline polypropylene (C), the propylene polymer (D), and
the olefin polymer compositions (X) and (X'), the propylene
polymer composition (Y) , the olefin polymer compositions (Z) and
(Z'), each of which forms the polyolefin composite film of the
10 present invention, may optionally contain antioxidants,
antifogging agents, antistatic agents such as nonionic antistatic
agents and polymer antistatic agents, antiblocking agents, I
lubricants, nucleating agents and the like.
[0079]
15 The polyolefin composite film of the present invention is
formed from the surface layer [i], the core layer [ii] and the
intermediate layer [iii], wherein the intermediate layer [iii]
is configured to directly contract with both the surface layer
[i] and the core layer [ii] . Specific examples of the polyolefin
20 composite film of the present invention include a three-layer film
consisting of [i]//[iii]//[ii] and a five-layer film consisting
of [i]//[iii]//[ii]//[iii]//[i], and are not limited thereto as
long as the polyolefin composite film has [i]//[iii]//[ii]
structure. I
SF-2452
30
[0080]
In the five-layer film consisting of
[i]//[iii]//[ii]//[iii]//[i] , for example, the surface layers
[i] provided on both the sides are not required to be necessarily
5 the same in thickness, but are desirably substantially the same
in thickness. Likewise, the intermediate layers [iii] provided
both the sides are not required to be necessarily the same in
thickness, but are desirably substantially the same in thickness.
[0081]
10 The thickness of each layer of the polyolefin composite film I
of the present invention can be appropriately determined according I
to use. The thickness of the surface layer [i] is usually 0.5 j
to 10 urn, preferably 1 to 5 um; the thickness of the core layer I
[ii] is usually 8 to 60 um, preferably 10 to 50 um, more preferably
15 15 to 45 um; and the thickness of the intermediate layer [iii]
is usually 0.5 to 10 um, preferably 1 to 5 um. As such, the whole
thickness of the polyolefin composite film is usually 9 to 100
um, preferably 10 to 35 jam.
[0082]
20 If the thickness of the intermediate layer is less than 0.5
um, sufficient heat-sealing strength may not be obtained,
depending on use.
[0083]
In a preferred polyolefin composite film of the present
SF-2452
31
*
invention, the surface layer [i] has a thickness of 1 to 20%,
preferably 2 to 10%, more preferably 3 to 8% of the thickness of
the core layer [ii]; and the intermediate layer [iii] has a
thickness of 1 to 20%, preferably 2 to 10%, more preferably 3 to
5 8% of the thickness of the core layer [ii]. When a plurality of
surface layers [i] and intermediate layers [iii] are provided,
the thickness requirements defined above apply to each individual
layer.
[0084]
10 The polyolefin composite film of the present invention is
excellent both in strength and in heat-sealing strength.
[0085]
The polyolefin composite film of the present invention may
be an unstretched film, or a monoaxially-stretched film or a
15 biaxially-stretched film.
[0086]
The polyolefin composite film of the present invention may
have another base material laminated thereon according to use.
The base material is formed from a thermoplastic resin film, an
20 aluminum foil, paper or the like, the thermoplastic resin film j
including films composed of polyesters typified by polyethylene
terephthalate and polyethylene naphthalate; polycarbonate
films; films composed of polyamides such as nylon 6 and nylon 66; j
and films composed of polyolefins such as ethylene/vinyl alcohol I
I
SF-2452 I
32 I
copolymer films, polyvinyl alcohol films, polyvinyl chloride |
films, polyvinylidene chloride films and polypropylene. The
base material formed from such a thermoplastic resin film may be
an unstretched film, or may be a monoaxially or biaxially
5 stretched film. The base material may be of one layer, or of two
or more layers. The thermoplastic resin films may be films
obtained by depositing inorganic substances such as aluminum,
zinc and silica or oxides thereof.
[0087]
10 The polyolefin composite film of the present invention may
be produced by a known method. An exemplary method is
co-extrusion molding by T-die method or inflation method that uses
extruders of the number of which corresponds to the number of types
of the resin composition of layers to be laminated, to thereby
15 produce a composite film. After co-extrusion, the film may be
stretched in at least one direction to form a stretched film.
Examples of the stretching method include monoaxial stretch
molding, successive biaxial stretching and simultaneous biaxial
stretching. In biaxial stretching, the stretch ratio is usually
20 about 3 to 12 times in machine direction, and usually about 3 to
12 times in transverse direction.
[0088]
The polyolefin composite film of the present invention, when
being a biaxially-stretched film, exhibits excellent
SF-2452
33
f
low-temperature heat sealability performance while maintaining
the strength of the polyolefin composite film. For example, the
biaxially-stretched polyolefin composite film of the present
invention exhibits excellent strength and excellent
5 low-temperature heat sealability, not only when having a tensile
modulus (MD, TD) of less than 3GPa but also when having a tensile
i
modulus (MD, TD) of not less than 3GPa.
[0089]
Thus, the polyolefin composite film of the present invention
; 10 desirably has a tensile modulus of 1.9 to 5.0 GPa, more desirably
1.9 to 4.5 GPa, in the machine direction (MD) or in the transverse
direction (TD) of stretching. Still more desirably, the I
i i i
polyolefin composite film of the present invention has a tensile
I modulus falling within the above-mentioned range, both in the
15 machine direction (MD) and in the transverse direction (TD) of
j stretching.
! [0090]
When the composite films according to the present invention
are superposed on each other in such a manner that their surface
20 layers are superposed on each other and are heat-sealed in a method i
described later, it is preferable that the heat-sealing strength
based on 180° peeling strength (temperature at the upper heat seal
bar: 140 °C) is 7.5 N/15 mm or more, more preferably 7.5 N/15 mm
to 75 N/15 mm, particularly preferably 9 N/15 mm to 75 N/15 mm. f
i
i
I SF-2452
34
1
9
[0091]
As required, the polyolefin composite film of the present
invention is surface-treated by e.g., corona treatment, plasma
treatment, flame treatment or and like, in a range that is not
5 detrimental to the object of the present invention.
EXAMPLES
[0092]
Hereinafter, the present invention is described with
10 greater detail with reference to Examples, but the present
invention is not limited to these Examples.
[0093]
Properties indicated in the Examples were measured by the
following methods.
15 [0094]
[Heat-sealing strength]
Polyolefin composite films to be measured were superposed
on each other in such a manner that their surface layers were
superposed on each other. Both sides of the composite films j
20 superposed were sandwiched by a fluororesin sheet having a
thickness of 50 urn (sheet composed of a fluororesin (manufactured I
by DuPont, product name: Teflon (trade mark)), to prepare a test
piece. Subsequently, heat seal bars of a heat seal tester I
(TB-701B manufactured by TESTER SANGYO CO., LTD.) were set so as
i
t I
!
SF-2452
35
IT
to be 5 mm in width x 300 mm in length, and the lower seal bar
was set at 70°C, and the temperature of the upper seal bar was
varied. Then, the test piece (fluororesin sheet/composite
film/composite film/fluororesin sheet), which was held by the
5 heat seal bars, was heat-sealed at a pressure of 0.2 MPa for 1.0
sec. After the fluororesin sheet was detached, the heat-sealed
part of the composite films was allowed to stand under a room
temperature of about 23 "C for 2 days. The composite films
including their heat-sealed parts were slit, the slit part
10 measuring 15 mm in width, while their non-sealed parts were
chucked to a tensile tester ("IM-20ST" manufactured by "INTESCO") .
Then, at a rate of 300 mm/min, the 180° peeling strength between
the composite films was measured. The above operation was
performed five times, and an average value thereof was defined
15 as a heat-sealing strength.
[0095]
[Melting point]
A press sheet having a thickness of 3 mm was prepared by
preheating for 5 min and then pressurizing for 2 min with a
20 hydraulic heat-pressing molding machine set at 190°C, and
immediately thereafter cooling for 4 min with a cooling tank set
at 20°C. This sheet was kept at 23'C ± 2°C for 10 days prior to
testing. Then, the press sheet was cooled to -40°C with a
differential scanning calorimeter (DSC) and then heated to 200 °C
i
i
i
I
j
SF-2452
36
*
at a heating rate of 10°C/min, to determine an exothermic and
endothermic curve. A temperature at the maximum endothermic peak
was defined as a melting point.
[0096]
5 [Heat-sealing initiation temperature]
The heat-sealing initiation temperature was defined as a
temperature (°C) of the upper seal bar at which the heat-sealing
strength as measured by the above method was 2 N/15 mm.
[0097]
10 [Tensile modulus]
By the method in accordance with JIS K7127, the tensile
modulus of the film was measured five times in its machine
direction (MD) and in its transverse direction (TD) , and an average I
value thereof was defined as modulus.
15 [0098]
The following polymers were used for Examples and
Comparative Examples.
[0099]
(1) Propylene/a-olefin random copolymer (A)
20 (1-1)PBR
A propylene/1-butene random copolymer (PBR) (propylene
content: 75 mol%, 1-butene content: 25 mol%, melting point: 77°C,
MFR (230 *C) : 7 g/10 min, intrinsic viscosity [n.] : 1. 8 dl/g, Mw/Mn:
2.0, B value: 1.0) was used.
SF-2452 I
37 I
[0100] I
(1-2) PER
A propylene/ethylene random copolymer (PER) (propylene
| content: 69 mol%, ethylene content: 31 mol%, melting point: 96°C,
| 5 MFR (230°C) : 8 g/10 min, intrinsic viscosity [n] : 1.7 dl/g, Mw/Mn:
2.7, B value: 0.7) was used.
[0101]
j
i
(1-3) PBER (this is also the propylene polymer (D))
A propylene/1-butene/ethylene random copolymer (PBER)
10 (1-butene content: 20 mol%, ethylene content: 14 mol%, melting
i point: not observed, intrinsic viscosity [n] : 1.8 dl/g, MFR
(230°C): 7 g/10 min, Mw/Mn: 2.0, B value: 1.0) was used.
[0102]
(2) Propylene polymer (B)
15 (2-1) r-PP I
A propylene/ethylene/1-butene random copolymer (r-PP) I
(ethylene content: 2.2 mol%, 1-butene content: 1.5 mol%, melting
point: 138°C, MFR (230°C): 7 g/10 min) was used.
[0103] I
20 (2-2) Ter-PP
A propylene/ethylene/1-butene random copolymer (Ter-PP) !
i
t
(ethylene content: 9.5mol%, 1-butene content: 3.9mol%, melting 1
point: 131°C, MFR (230°C): 6 g/10 min) was used. '
[0104]
;
i
1 SF-2452
38
•
(3) Crystalline polypropylene (C)
(3-1) h-PP
A propylene homopolymer (h-PP) (melting point: 160°C, MFR
(230°C): 3 g/10 min) was used.
5 [0105]
(4) 1-butene/a—olefin copolymer (E)
(4-1) BER
A 1-butene/ethylene random copolymer (BER) (1-butene
content: 95 mol%, ethylene content: 5 mol% , melting point: 100 'C,
10 MFR (230 *C) : 9 g/10 min, intrinsic viscosity [n] : 1. 8 dl/g, Mw/Mn:
3.4, B value: 1.0) was used.
[0106] I
i
(4-2) BPR |
!
A 1-butene/propylene random copolymer (BPR) (1-butene
15 content: 75mol%, propylene content: 25mol%, melting point: 77 °C,
MFR (230°C):9 g/10 min, intrinsic viscosity [n] : 1.7 dl/g, Mw/Mn:
i
4.9, B value: 0.9) was used.
j
[0107] [
[Examples 1 to 11 and Comparative Examples 1 to 3] •
20 [Molding of polyolefin composite film]
As shown in Table 1, each polymer mentioned above was used
to form a three-kind five-layer composite film having surface
layers, a core layer and intermediate layers (surface
>
layer//intermediate layer//core layer//intermediate
ir
SF-2452
39
•
layer//surface layer) in a manner as described below.
[0108]
Three extruders equipped with a T-die were used to produce
a three-kind five-layer configuration. Polymers were fed to
5 respective extruders at proportions that are shown in Table 1 for
the surface layer, the core layer and the intermediate layer. The
temperatures of the die and of the resin were set at 230°C, and
the extrusion amounts from the respective extruders were set so
as to achieve that the thickness proportion of surface
10 layer//intermediate layer//core layer//intermediate 1
layer//surface layer would become 1/1/21/1/1. Then, 1
co-extrusion molding was performed to obtain an unstretched film I
having a thickness of 1000 urn. j
[0109]
15 The unstretched film was stretched with the use of a
batch-type biaxial-stretching machine at a stretching
temperature of 158°C at a stretching ratio of 5 times in machine
direction and 8 times in transverse direction, to obtain a
biaxially-stretched polyolefin composite film.
20 [0110] ;
Regarding this polyolefin composite film, "heat-sealing
strength" and "heat-sealing initiation temperature" were
measured. Results thereof are shown in Table 1.
[0111]
SF-2452
40
f
Regarding the polyolefin composite film, the "heat-sealing
strength" and "heat-sealing initiation temperature" were
measured. Results thereof are set forth in Table 1.
I
i
I
>
:.'
:
(
:
r
I
i
u
I | n o o £ £ o
• ^£
u
E EN o oo o §
u w*,
J)
5 § oo ~ o o
z^
"S,
g >—' OlO
a ^H oo .— oo ^- o o ^ -
_£
I s § s £ §
1 u 1 "& o 1
a 0 © ' - ' ' * ^ 2 1
_£
g °° oo ^H oo »-< 5~ J
"P- e->
g ^ —i o\ i—i ~
5 m "> m m >n g
3 oo ~* oo ^ 2
jS
(!)
a °° "-1 °° " 2
_£
u
"& o
g _ n n in m g
J3 OO '—i OO i—i ^^
CM 1
5 W H fc fc OS 1
CNJ r H X ! cu^^04aScd^o«, i O i a i o i e s W & < e J r
Py 0 £ ihO.CQfflo-j: ihfl £ a si > u J2 ?
m w M g w w
u
S S ~> _ — ci cs o z> t- o
O TO O O >—'OS ,—< CS •*}• + ^
S C 00 O oo .— t - r- •* _ —. ^o
S ° CN «n vo ve> «o t>-" °° M M
jd _ _
i JK
5 ON I f l O O " " H "" CS CO
J)
6 o o o t - ~ > 3 - v o r - ^ - „ o o
6 r ^ o « N ' < t v o o o ^ H v o > o go == o
g o t s ' i o r ^ o d o d o d cs m
W
r i o o o d ^ H C S r r > i
w !
;
,-. S cs o <^ <^ ^ ""> °° °° «-i • •
3
1 ) 2 * M •* 00 M ^ n _ _, U-.
• £ E . - i © r ' 3 0 0 f ~ ~ - © m ^ n "!
C g o ' 6 ^ i n o v o \ ^ N ^
O Jf
I X! I I I I I I I I
S g> 6 g « 2 g -S3 3 Q -B 3 Q
w> E >o "i.S e M c o s fiflu
8 £ z §.SEi t H E hE
X ^ X B
SF-2452
43
•
[0113]
The polyolefin composite film of the present invention has |
high heat-sealing strength. I
5 INDUSTRIAL APPLICABILITY
[0114]
The polyolefin composite film of the present invention
provides excellent performance of a heat-sealing strength of 7.5 j
N/15 mm or more at a temperature of 140°C, as well as excellent
10 transparency, and therefore is widely employable for various
packaging materials for food, industrial materials and the like.
i.
i
I
:

SF-2452
44
CLAIMS
1. A polyolefin composite film having at least one surface
15 layer [i], a core layer [ii], and an intermediate layer [iii]
contacting directly with both the surface layer [i] and the core
layer [ii],
wherein the surface layer [i] is formed from a propylene
resin composition that comprises:
20 a propylene/a-olefin random copolymer (A) that comprises
50 to 97 mol% of a unit derived from propylene and 3 to 50 mol%
of a unit derived from C2-10 a-olefins excluding propylene, and/or
a 1-butene/a-olefin copolymer (E) that comprises 50 to 95
mol% of a unit derived from 1-butene and 50 to 5 mol% of a unit
25 derived from C2-10 a-olefins excluding 1-butene, the
propylene/a-olefin random copolymer (A) and/or the
1-butene/a-olefin copolymer (E) being in an amount of 0 to 50 wt%,
and
a propylene polymer (B) that comprises 50 to 100 mol% of
30 a unit derived from propylene and 0 to 50 mol% of a unit derived
from C2-10 a-olefins excluding propylene and has a melting point
of 120 to 170°C,
the propylene polymer (B) being in an amount of 50 to 100
wt%,
35 provided that the total amount of (A), (E) and (B) in the
surface layer is 100 parts by weight; f
SF-2452
45
W
wherein the core layer [ii] is formed from a propylene resin
composition that comprises:
a crystalline polypropylene (C) that comprises 97 to 100
40 mol% of a unit derived from propylene and 0 to 3 mol% of C2-10
a-olefins excluding propylene and has a melting point of 150 to
170°C,
the crystalline polypropylene (C) being in an amount of 70
to 100 wt%, and
45 a propylene/a-olefin random copolymer (A) that comprises
50 to 97 mol% of a unit derived from propylene and 3 to 50 mol%
of a unit derived from C2-10 a-olefins excluding propylene,
I
the propylene/a-olefin random copolymer (A) being in an
amount of 0 to 30 wt%,
50 provided that the total amount of (C) and (A) in the core
layer is 100 parts by weight; and
wherein the intermediate layer [iii] is formed from a
propylene resin composition that comprises:
a crystalline polypropylene (C) that comprises 97 to 100
55 mol% of a unit derived from propylene and 0 to 3 mol% of C2-10
a-olefins excluding propylene and has a melting point of 150 to I
170°C,
the crystalline polypropylene (C) being in an amount of 50
to 95 wt%, and j
i
60 a propylene polymer (B) that comprises 50 to 100 mol% of
I
SF-2452
46
a unit derived from propylene and 0 to 50 mol% of a unit derived
from C2-10 a-olefins excluding propylene and has a melting point I
of 120 to 170°C,
a propylene/a-olefin random copolymer (A) that comprises
65 50 to 97 mol% of a unit derived from propylene and 3 to 50 mol%
of a unit derived from C2-10 a-olefins excluding propylene,
and/or
a 1-butene/a-olefin random copolymer (E) that comprises 50
to 95 mol% of a unit derived from 1-butene and 50 to 5 mol% of
70 a unit derived from a—olefins excluding 1-butene,
the propylene polymer (B), the propylene/a-olefin random
copolymer (A) , and/or the 1-butene/a-olefin random copolymer (E)
being in an amount of 50 to 5 wt%,
provided that the total amount of (C) , (B) , (A) and (E) in
75 the intermediate layer is 100 wt%.
2. A polyolefin composite film having at least one
surface layer [i], a core layer [ii], and an intermediate layer
[iii] contacting directly with both the surface layer [i] and the
80 core layer [ii] ,
wherein the surface layer [i] is formed from a propylene
I resin composition that comprises:
a propylene/a-olefin random copolymer (A) that comprises 1
50 to 97 mol% of a unit derived from propylene and 3 to 50 mol%
i ,
|
i
SF-2452
47
85 of a unit derived from C2-10 a-olefins excluding propylene,
the propylene/a-olefin random copolymer (A) being in an
amount of 15 to 100 wt%, and
a propylene polymer (B) that comprises 50 to 100 mol% of
a unit derived from propylene and 0 to 50 mol% of a unit derived
90 from C2-10 a—olefins excluding propylene and has a melting point
of 120 to 170°C,
the propylene polymer (B) being in an amount of 0 to 85 wt%;
wherein the core layer [ii] is formed from a propylene resin
composition that comprises:
95 a crystalline polypropylene (C) that comprises 97 to 100
mol% of a unit derived from propylene and 0 to 3 mol% of C2-10 I
a-olefins excluding propylene and has a melting point of 150 to
170°C,
the crystalline polypropylene (C) being in an amount of 70
100 to 100 wt%, and
a propylene polymer (D) that comprises 50 mol% or more and
less than 97 mol% of a unit derived from propylene, and more than
3 mol% and up to 50 mol% of a unit derived from C2-10 a—olefins
excluding propylene, and has a melting point of lower than 140 "C
105 or a melting point that is not observed as measured by Differential I
Scanning Calorimetry,
i !
I the propylene polymer (D) being in an amount of 0 to 30 wt%; |
and
j i
|
i :
• i
; j
SF-2452
48
wherein the intermediate layer [iii] is formed from a
110 propylene resin composition that comprises:
a crystalline polypropylene (C) that comprises 97 to 100
mol% of a unit derived from propylene and 0 to 3 mol% of C2-10
a-olefins excluding propylene, and has a melting point of 150 to
170°C,
115 the crystalline polypropylene (C) being in an amount of 50
to 95 wt%, and
a propylene polymer (D) that comprises 50 mol% or more and
less than 97 mol% of a unit derived from propylene, and more than
3 mol% and up to 50 mol% of a unit derived from C2-10 a-olefins
120 excluding propylene, and has a melting point of lower than 140 °C
or a melting point that is not observed as measured by Differential
Scanning Calorimetry, and/or
a 1-butene/a-olefin random copolymer (E) that comprises 50
to 95 mol% of a unit derived from 1-butene and 50 to 5 mol% of
125 a unit derived from a—olefins excluding 1-butene,
the propylene polymer (D) and/or the 1-butene/a-olefin
random copolymer (E) being in an amount of 50 to 5 wt%,
!
i
provided that the total amount of (C) , (D) and (E) is 100 5
j
wt%.
130
3. The polyolefin composite film according to Claim 1
or 2, wherein the propylene/a-olefin random copolymer (A) has a 1
I >
i
SF-2452
49
IT
melting point of 110°C or lower or has a melting point that is
not observed.
135
4. The polyolefin composite film according to any one
of Claims 1 to 3, wherein the propylene polymer (B) has a melting
| point of 120 to 140°C, and the 1-butene/a—olefin copolymer (E)
has a melting point of 60 to 110°C.
140
5. The polyolefin composite film according to any one
of Claims 1 to 4, wherein the propylene/a-olefin random copolymer
(A) is a propylene/1-butene random copolymer that satisfies the
following properties:
145 (1) the intrinsic viscosity as measured in decalin at 135 'C
is 0.1 to 5 dl/g, I
i I
| (2) the molecular weight distribution (Mw/Mn) as determined
by gel permeation chromatography is 1.5 to 3, and
(3) the parameter B value, which shows a randomness of
I 150 copolymerized monomer chain distribution, is 0.9 to 1.5.
I
|
6. The polyolefin composite film according to any one I
| of Claims 1 to 5, wherein the polyolefin composite film is an
unstretched film.
155 j
I
7. The polyolefin composite film according to any one
SF-2452
50
of Claims 1 to 5, wherein the polyolefin composite film is a
biaxially-stretched film.
160 8. The polyolefin composite film according to any one
of Claims 1 to 7, wherein the percentage of the total thickness
of the surface layer relative to the total thickness of the
polyolefin composite film is 2 to 10%.
i
165 9. The polyolefin composite film according to any one
of Claims 1 to 8, wherein the percentage of the total thickness
of the intermediate layer relative to the total thickness of the
polyolefin composite film is 2 to 10%.
I
i •:
170 10. The polyolefin composite film according to any one j
i
i
of Claims 1 to 9, wherein the polyolefin composite film has a
five-layer structure consisting of surface layer/intermediate
layer/core layer/intermediate layer/surface layer in this order.
175 11. The polyolefin composite film according to any one
of Claims 1 to 10, wherein the total thickness of the polyolefin
composite film is 10 to 35 micrometers (urn). i
i
12. The polyolefin composite film according to any one 180 of Claims 1 to 11, wherein the tensile modulus in the machine
::
I &
SF-2452
51
stretching direction or in the transverse stretching direction
of the polyolefin composite film is 1.9 to 5.0 GPa.