U.S. patent application number 10/128287 was filed with the patent office on 2002-10-24 for resin composition and usage thereof.
This patent application is currently assigned to Kuraray Co., Ltd.. Invention is credited to Ishiura, Kazushige, Shachi, Kenji.
Application Number | 20020155238 10/128287 |
Document ID | / |
Family ID | 26350655 |
Filed Date | 2002-10-24 |
United States Patent
Application |
20020155238 |
Kind Code |
A1 |
Shachi, Kenji ; et
al. |
October 24, 2002 |
Resin composition and usage thereof
Abstract
A resin composition comprising (A) a polyolefin resin, (B) a
vinyl alcohol copolymer and (C') a block copolymer composed of a
polymer block of an aromatic vinyl compound and an isobutylenic
polymer block, the weight ratio of (A) to (B) ranging from 100/10
to 100/1000 and the weight ratio of (C') to [(A)+(B)] ranging from
5/100 to 1000/100 is a flexible resin material having high gas
barrier properties, good heat resistance and good moldability or
formability so that it is useful as a material for various molded
or formed articles. In addition, a closure (cap, stopper or the
like) for containers or a sealing element (packing element) for the
closure for containers which is formed of a resin composition
comprising (A) a polyolefin resin, (B) a vinyl alcohol copolymer
and (C) an elastomer, the weight ratio of (A) to (B) ranging from
100/10 to 100/1000 and the weight ratio of (C) to [(A)+(B)] ranging
from 5/100 to 100/100 has good hermetical sealing properties and
good mountability onto (or within) a container and is also
excellent in the long-term shelf stability of contents.
Inventors: |
Shachi, Kenji; (Tsukuba-shi,
JP) ; Ishiura, Kazushige; (Tsukuba-shi, JP) |
Correspondence
Address: |
OBLON SPIVAK MCCLELLAND MAIER & NEUSTADT PC
FOURTH FLOOR
1755 JEFFERSON DAVIS HIGHWAY
ARLINGTON
VA
22202
US
|
Assignee: |
Kuraray Co., Ltd.
Kurashiki-City
JP
|
Family ID: |
26350655 |
Appl. No.: |
10/128287 |
Filed: |
April 24, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10128287 |
Apr 24, 2002 |
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09002081 |
Dec 31, 1997 |
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6410109 |
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Current U.S.
Class: |
428/36.6 ;
525/57; 525/89 |
Current CPC
Class: |
C08L 23/04 20130101;
C09K 2200/062 20130101; C08L 29/04 20130101; C09K 2200/0642
20130101; C08L 23/0815 20130101; C08L 53/00 20130101; C08L 53/02
20130101; C08L 53/025 20130101; Y10T 428/1379 20150115; C08L 53/005
20130101; Y10T 428/1386 20150115; C09K 2200/0632 20130101; C08L
53/00 20130101; C08L 23/04 20130101; C09K 2200/0622 20130101; C08L
2666/04 20130101; C08L 2666/04 20130101; C08L 2666/24 20130101;
C08L 2666/04 20130101; C08L 2666/02 20130101; C08L 2666/04
20130101; C08L 2666/04 20130101; C08L 2666/24 20130101; C08L
2666/04 20130101; C08L 2666/04 20130101; C08L 23/02 20130101; C08L
23/0815 20130101; C08L 23/04 20130101; C09K 3/10 20130101; C08L
23/02 20130101; C08L 23/02 20130101; C08L 53/02 20130101; C08L
29/00 20130101; C09K 2200/0617 20130101; C08L 53/005 20130101; C08L
53/00 20130101; C08L 23/16 20130101; C08L 53/025 20130101; Y10T
428/1352 20150115 |
Class at
Publication: |
428/36.6 ;
525/89; 525/57 |
International
Class: |
F16L 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 10, 1997 |
JP |
14658/1997 |
Jan 10, 1997 |
JP |
14659/1997 |
Claims
What is claimed is:
1. A resin composition, (1) which comprises as principal components
(A) a polyolefin resin, (B) a vinyl alcohol copolymer and (C') a
block copolymer composed of a polymer block of an aromatic vinyl
compound and an isobutylenic polymer block; (2) said component (B)
being contained in an amount of 10 to 1000 parts by weight per 100
parts by weight of the component (A) and said component (C') being
contained in an amount of 5 to 1000 parts by weight per 100 parts
by weight, in total, of the components (A) and (B).
2. A resin composition, (1) which comprises as principal components
(A) a polyolefin resin, (B) a vinyl alcohol copolymer and (C') a
block copolymer composed of a polymer block of an aromatic vinyl
compound and an isobutylenic polymer block; (2) wherein said
component (B) is contained in an amount of 10 to 1000 parts by
weight per 100 parts by weight of the component (A) and the
component (C') is contained in an amount of 5 to 1000 parts by
weight per 100 parts by weight, in total, of the components (A) and
(B); (3) said resin composition being prepared by mixing said
components (A), (B) and (C') under melting conditions; and (4) said
resin composition satisfying the following conditions: [a]>[b]
and [c'] >[b], supposing that the melt viscosities of the
components (A), (B) and (C') are represented by [a], [b] and [c'],
respectively as measured at the same temperature under said melting
conditions and at a shear rate of 100 sec.sup.-1.
3. A molded or formed article composed of a resin composition as
claimed in claim 1 or 2.
4. A closure, (1) which is a closure for a container, and (2)
wherein at least a sealing element thereof is formed of a resin
composition comprising as principal components (A) a polyolefin
resin, (B) a vinyl alcohol copolymer and (C) an elastomer, said
component (B) being contained in an amount of 10 to 1000 parts by
weight per 100 parts by weight of the component (A) and said
component (C) being contained in an amount of 5 to 100 parts by
weight per 100 parts by weight, in total, of the components (A) and
(B).
5. A closure, (1) which is a closure for a container, (2) wherein
at least a sealing element thereof is formed of a resin composition
comprising as principal components (A) a polyolefin resin, (B) a
vinyl alcohol copolymer and (C) an elastomer; said component (B)
being contained in an amount of 10 to 1000 parts by weight per 100
parts by weight of the component (A) and the component (C) being
contained in an amount of 5 to 100 parts by weight per 100 parts by
weight, in total, of the components (A) and (B); said resin
composition being prepared by mixing said components (A), (B) and
(C) under melting conditions; said resin composition satisfying the
following conditions: [a]>[b] and [c]>[b], supposing that the
melt viscosities of the components (A), (B) and (C) are represented
by [a], [b] and [c], respectively as measured at the same
temperature under said melting conditions and at a shear rate of
100 sec.sup.-1.
6. A sealing element, (1) which is a sealing element for a closure
for a container; and (2) is formed of a resin composition
comprising as principal components (A) a polyolefin resin, (B) a
vinyl alcohol copolymer and (C) an elastomer; said component (B)
being contained in an amount of 10 to 1000 parts by weight per 100
parts by weight of the component (A) and said component (C) being
contained in an amount of 5 to 100 parts by weight per 100 parts by
weight, in total, of the components (A) and (B).
7. A sealing element, (1) which is a sealing element for a closure
for a container; and (2) is formed of a resin composition, which
comprises as principal components (A) a polyolefin resin, (B) a
vinyl alcohol copolymer and (C) an elastomer, said component (B)
being contained in an amount of 10 to 1000 parts by weight per 100
parts by weight of the component (A) and said component (C) being
contained in an amount of 5 to 100 parts by weight per 100 parts by
weight, in total, of the components (A) and (B), is prepared by
mixing said components (A), (B) and (C) under melting conditions,
and satisfies the following conditions: [a]>[b] and [c]>[b],
supposing that the melt viscosities of the components (A), (B) and
(C) are represented by [a], [b] and [c], respectively as measured
at the same temperature under said melting conditions and at a
shear rate of 100 sec.sup.-1.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to a flexible resin composition
having high gas-barrier properties and good heat-resistance and
good moldability or formability and also to a molded or formed
article making the best use of the gas barrier properties, heat
resistance and flexibility each derived from the raw material resin
composition. The molded or formed article according to the present
invention has excellent gas barrier properties and heat resistance
and also good flexibility so that it is useful as a sealing
material, packaging film, container or the like. Owing good
moldability or formability (particularly, extrusion formability),
the resin composition of the present invention is useful as a
component of the above-described molded or formed article.
[0003] The present invention also pertains to a closure for
containers and a sealing element for the closure. The closure and
sealing element according to the present invention are each formed
of a material having suitable flexibility and also excellent gas
barrier properties and oil resistance so that they have good
mountability onto (or within) containers and hermetical sealing
properties and also being excellent in long-term shelf stability
and smell retention of the content.
[0004] 2. Related Art of the Invention
[0005] A polyvinyl chloride resin having a plasticizer added
thereto is used as a sealing material, packaging film, container or
the like because of having excellent flexibility and gas barrier
properties. The polyvinyl chloride resin however evolves gases such
as hydrogen chloride upon disposal by incineration and there is a
possibility of its bringing about adverse effects on the
environment. In addition, since the plasticizer is apt to cause the
bleed out, such a plasticizer-added resin used for a packaging film
or container may potentially contaminate the contents. Moreover, it
has not so high heat resistance.
[0006] Since an ethylene-vinyl alcohol copolymer has high barrier
properties against various gases and organic liquids and does not
emit harmful gases upon disposal by incineration different from a
polyvinylidene chloride resin or polyvinyl chloride resin, its
application to various fields such as food packaging has been
developed. For example, the use of it as a food packaging material
making use of high gas barrier properties is now actualized or
under investigation. The ethylene-vinyl alcohol copolymer is
however inferior in flexibility so that it is sometimes used as a
composition with a soft resin such as polyolefin. The
ethylene-vinyl alcohol copolymer, in general, has low affinity and
inferior compatibility with other resins, so the original gas
barrier properties and the like of the ethylene-vinyl alcohol
copolymer tend to be markedly impaired in such a composition.
[0007] It is known that a resin composition composed of a
polyolefin resin, an olefin-vinyl alcohol copolymer and a modified
copolymer, which has been obtained by graft polymerizing an
unsaturated carboxylic acid or derivative thereof to a
hydrogenation product of a block copolymer having a polymer block
of an aromatic vinyl compound and a conjugated diene polymer block,
has excellent gas barrier properties and is therefore useful as a
food packaging material (Japanese Patent Application Laid-Open No.
HEI 1-313552). It is also known that a resin composition composed
of a polyolefin resin, an ethylene-vinyl alcohol copolymer, a
polyolefin modified with an unsaturated carboxylic acid or
derivative thereof and a hydrogenation product of a block copolymer
having a polymer block of an aromatic vinyl compound and a
conjugated diene polymer block has excellent gas barrier properties
and is therefore useful as a material for bottles, cups and the
like (Japanese Patent Application Laid-Open No. HEI 3-277642). In
such resin compositions containing a polyolefin resin and a vinyl
alcohol copolymer, the above-described modified copolymer
introduced from the hydrogenation product of a block copolymer
having a polymer block of an aromatic vinyl compound and a
conjugated diene polymer block; or the above-described modified
polyolefin and the hydrogenation product of a block copolymer
having a polymer block of an aromatic vinyl compound and a
conjugated diene polymer block are considered to have effects for
improving the compatibility between the polyolefin resin and the
vinyl alcohol copolymer. In such resin compositions, however, heat
resistance is not so high. When the molded or formed article
available from such a resin composition is exposed to high
temperature conditions for long hours, deterioration occurs and the
surface of the article sometimes becomes sticky.
[0008] Incidentally, it is described in European Patent Application
Publication No. 572,667 that a resin composition comprising 0.5 to
35 parts by weight of a block copolymer having a polymer block of
an aromatic vinyl monomer and an isobutylenic polymer block and 100
parts by weight of a thermoplastic resin has improved impact
resistance. In it, exemplified as the thermoplastic resin are
polycarbonate, polyphenylene ether, polystyrene, polyolefin,
polyester, polyvinyl chloride, styrene-methacrylate-acrylonitrile
copolymer, methacrylate-styrene copolymer, acrylonitrile-styrene
copolymer, polymethyl methacrylate, polyphenylene sulfide and
polyvinyl acetate. An ethylene-vinyl alcohol copolymer is not
included in the above examples. It is also described in said
European Patent Application Publication that the above-described
resin composition composed of a thermoplastic resin and a block
copolymer has good thermal stability, impact resistance, solvent
resistance and compatibility, but a description about gas barrier
properties is not included. The gas barrier properties of the
above-described resin composition is insufficient in some cases,
depending on the application purpose.
[0009] In Japanese Patent Application Laid-Open No. HEI 7-118492,
described is a thermoplastic resin composition comprising a
polyolefin and a block copolymer which is composed of a polymer
block of an aromatic vinyl monomer and an isobutylenic polymer
block and has a hydroxyl group at least one end of the block
copolymer. In Japanese Patent Application Laid-Open No. HEI
7-188509, described are a polymer composition obtained by adding,
to a thermoplastic resin such as a polyolefin resin, a specific
combination of block copolymers composed of a triblock copolymer
which has a structure of a polymer block of an aromatic vinyl
monomer--an isobutylenic polymer block--a polymer block of an
aromatic vinyl monomer and a diblock copolymer which has a
structure of a polymer block of an aromatic vinyl monomer--an
isobutylenic polymer block (or a triblock copolymer having a
structure of an isobutylenic polymer block--a polymer block of an
aromatic vinyl monomer--an isobutylenic polymer block); and also a
crown liner formed of said polymer composition. In the above
Japanese patent applications, it is described that a composition
having excellent flexibility and moldability or formability can be
prepared, but the gas barrier properties of the resulting
composition are insufficient in some cases, though depending on the
application purpose. In these applications, there is no description
about the incorporation of a vinyl alcohol copolymer.
[0010] As conventional molding materials for producing a closure
(cap, stopper or the like) for containers and a sealing element
(packing element) for the closure, a resin having suitable
flexibility such as polyvinyl chloride resin and low-density
polyethylene has generally be used. Also a resin composition having
flexibility imparted by the addition of an elastomer or softener to
a polyolefin resin such as high-density polyethylene or
polypropylene has been employed as the molding material. However
the closure or sealing element comprising a polyvinyl chloride
resin may potentially contaminate the contents due to the bleed out
of the remaining monomers and plasticizers under some conditions of
the contents and the environment for use. Because the closure or
the like comprising low-density polyethylene has poor gas barrier
properties, it is inferior in the long-term shelf stability of
contents. The closure or the like comprising the above-described
resin composition of a polyolefin blended with a softener may
potentially contaminate the contents due to the bleed out of the
softener under some conditions of the contents, the environment for
use and the like. Furthermore, in the closure or the like
comprising the above-described resin composition obtained by adding
an elastomer to a polyolefin resin, the incorporation of the
elastomer causes a marked deterioration in gas barrier properties,
leading to inferior long-term shelf stability of contents. In such
a case, an amount of the elastomer added to the polyolefin resin is
sometimes controlled to a small amount and the shortage in
flexibility caused by the reduction in the amount of the elastomer
is made up for by the addition of a softener in combination,
involving the contamination problem described above.
[0011] In Japanese Patent Application Laid-Open No. HEI 5-295053,
it is described that a composition for a sealing material, which
comprises 100 parts by weight of a block copolymer containing a
polymer block of an aromatic vinyl monomer and an isobutylenic
polymer block and 0 to 80 parts by weight of other blending agents,
has high gas barrier properties and flexibility derived from said
block copolymer and that the composition is used for example as a
lid member for sealing bottles. Furthermore, in Japanese Patent
Application Laid-Open No. HEI 5-212104, proposed is the production
of a sealing article for medicinal or medical use which is
conventionally made of a rubber material by using such a block
copolymer. Examples of such an article include rubber stopper for
pharmaceutical agents, rubber stopper for blood sampling tubes and
syringe cap working also as a container for filling pharmaceutical
solutions. It is also described in the latter application that the
sealing article for medicinal or medical use formed using said
block copolymer is excellent in flexibility, gas barrier properties
and elution-free properties and that a thermoplastic polymer such
as a block copolymer of ethylene and propylene can be added to said
block copolymer. Sealing materials as described above each of which
is composed mainly of a block copolymer containing a polymer block
of an aromatic vinyl monomer and an isobutylenic polymer block have
excellent gas barrier properties and at the same time have high
flexibility. The present inventors have made attempts to mold the
above sealing material into a closure or a sealing element for the
closure and then to seal a container by using them. However, it has
been found that when a threaded cap integrally molded from the
sealing material is mounted onto a container, the slide of the cap
in contact with the container is so poor because of too high
flexibility of the cap that excess strength is needed for the
mounting thereof. Furthermore, it has been found that when a
threaded cap mounted with a packing element molded from the sealing
material is to be mounted onto a container, the slide of the cap in
contact with the container is so poor because of too high
flexibility of the packing element that the back motion readily
occurs, whereby complete sealing is not readily achieved.
Furthermore, the oil resistance of the sealing material is not so
high. The gas barrier properties of the sealing material are
insufficient in some cases, though depending on the application
purpose. Based on these findings, the inventors have found that the
closure and sealing element each comprising a material composed
mainly of the block copolymer are applicable in a narrow range of
field in practical use and that the closure and sealing element are
only used for specific applications.
SUMMARY OF THE INVENTION
[0012] A first object of the present invention is to provide a
resin material which has high gas barrier properties and heat
resistance, can exhibit good flexibility even without the addition
of a plasticizer, and is equipped with good formability or
moldability.
[0013] A second object of the present invention is to provide a
molded or formed article having high gas barrier properties and
heat resistance and at the same time, having good flexibility even
when a plasticizer is not added.
[0014] A third object of the present invention is to provide a
closure for containers which is equipped with a sealing element and
has good hermetical sealing properties and mountability onto (or
within) a container, said sealing element being formed of a resin
material which has suitable flexibility and excellent gas barrier
properties and oil resistance without any component presumably
causing bleed out.
[0015] A fourth object of the present invention is to provide a
sealing element for a closure for containers which is formed of a
resin material having suitable flexibility and excellent gas
barrier properties and oil resistance without any component
presumably causing bleed out, and has good hermetical sealing
properties and mountability onto (or within) a container.
[0016] According to the present invention, the first object
described above can be achieved by providing a resin composition,
(1) which comprises as principal components (A) a polyolefin resin,
(B) a vinyl alcohol copolymer and (C') a block copolymer composed
of a polymer block of an aromatic vinyl compound and an
isobutylenic polymer block; (2) said component (B) being contained
in an amount of 10 to 1000 parts by weight per 100 parts by weight
of the component (A) and said component (C') being contained in an
amount of 5 to 1000 parts by weight per 100 parts by weight, in
total, of the components (A) and (B).
[0017] According to the present invention, the second object
described above can be achieved by providing a molded or formed
article composed of the above resin composition.
[0018] According to the present invention, the third object
descried above can be achieved by providing a closure, (1) which is
a closure for a container, and (2) wherein at least a sealing
element thereof is formed of a resin composition comprising as
principal components (A) a polyolefin resin, (B) a vinyl alcohol
copolymer and (C) an elastomer; said component (B) being contained
in an amount of 10 to 1000 parts by weight per 100 parts by weight
of the component (A) and said component (C) being contained in an
amount of 5 to 100 parts by weight per 100 parts by weight, in
total, of the components (A) and (B).
[0019] According to the present invention, the fourth object
described above can be achieved by providing a sealing element (1)
which is a sealing element for a closure for a container and (2) is
formed of a resin composition comprising as principal components
(A) a polyolefin resin, (B) a vinyl alcohol copolymer and (C) an
elastomer; said component (B) being contained in an amount of 10 to
1000 parts by weight per 100 parts by weight of the component (A)
and said component (C) being contained in an amount of 5 to 100
parts by weight per 100 parts by weight, in total, of the
components (A) and (B).
DETAILED DESCRIPTION OF THE INVENTION
[0020] A description will next be made of a resin composition of
the present invention comprising as principal components the
above-described components (A), (B) and (C') and a molded or formed
article made of said resin composition.
[0021] Examples of the polyolefin resin to be used as the component
(A) in the present invention include a homopolymer of an olefin
monomer such as high-density polyethylene, low-density polyethylene
and polypropylene; and copolymers of at least two monomers such as
ethylene-propylene random copolymer, ethylene-propylene block
copolymer, ethylene-1-butene copolymer, ethylene-1-hexene random
copolymer and ethylen-1-octene copolymer. Incidentally, the
polyolefin resin (A) is not limited to any single polyolefin resin.
Depending on the application purpose, two or more polyolefin resins
may be used in combination.
[0022] The vinyl alcohol copolymer to be used as the component (B)
in the present invention is a copolymer containing a vinyl alcohol
unit [--CH.sub.2--CH(OH)--], which can be obtained, for example,
but not limited to, by partial or complete saponification of a
corresponding vinyl ester copolymer.
[0023] As the vinyl alcohol copolymer (B), an olefin-vinyl alcohol
copolymer is preferred. As the olefin-vinyl alcohol copolymer, a
saponification product of an olefin-vinyl carboxylate ester
copolymer is preferred. As the saponification product of the
olefin-vinyl carboxylate ester copolymer, preferred are those
obtained by saponification of an olefin-vinyl carboxylate ester
copolymer containing olefin units and vinyl carboxylate ester units
in a molar ratio ranging from 0.5/99.5 to 99.5/0.5, thereby
converting 10 to 100 mole % of the vinyl carboxylate ester units to
vinyl alcohol units. From the viewpoints of the gas barrier
properties and moldability or formability of the resin composition
with the polyolefin resin (A) and the block copolymer (C'), the
content of an olefin unit in the saponification product of an
olefin-vinyl carboxylate ester copolymer is preferably 2 to 70 mole
%, with 5 to 65 mole % being more preferred and with 10 to 60 mole
% being particularly preferred. The saponification degree in the
saponification product of an olefin-vinyl carboxylate ester
copolymer, that is, a conversion ratio of the vinyl carboxylate
ester units to vinyl alcohol units, is preferably at least 90 mole
%, with at least 95 mole % being more preferred and at least 98
mole % being particularly preferred, judging from the gas barrier
properties and heat resistance of the resin composition obtained
from it. The melt flow rate in the vinyl alcohol copolymer (B) as
measured according to the method described in ASTM D1238 under the
conditions of a temperature of 190.degree. C. and a load of 2.16 kg
is preferably 0.1 to 100 g/10 min, with 0.5 to 50 g/10 min being
more preferred and 1 to 40 g/10 min being particularly preferred
from the viewpoints of the moldability or formability of the resin
composition obtained from the copolymer.
[0024] Among the saponification products of an olefin-vinyl
carboxylate ester copolymer, the saponification product of an
ethylene-vinyl carboxylate ester copolymer is particularly
preferred from the viewpoints of moldability or formability and
mechanical properties of the resin composition with a polyolefin
resin (A) and a block copolymer (C'). The saponification product of
an ethylene-vinyl carboxylate ester copolymer may contain another
structural unit in addition to the ethylene unit and vinyl alcohol
unit insofar as its amount is small (preferably, 10 mole % or
smaller based on the total structural units). Examples of another
structural unit include those derived from .alpha.-olefins such as
propylene, isobutylene, 4-methylpentene-1, 1-hexene and 1-octene;
vinyl carboxylate esters such as vinyl acetate, vinyl propionate,
vinyl versatate and vinyl pivalate; unsaturated carboxylic acids or
derivatives thereof (ex. salt, ester, nitrile, amide and anhydride)
such as itaconic acid, acrylic acid and maleic anhydride; vinyl
silane compounds such as vinyl(trimethoxy)silane; unsaturated
sulfonic acids or salts thereof; and N-methylpyrrolidone. The
saponification product of an ethylene-vinyl carboxylate ester
copolymer may have a functional group such as alkylthio at the
terminal of its molecular chain. Among the saponification products
of an ethylene-vinyl carboxylate ester copolymer, that of an
ethylene-vinyl acetate copolymer is particularly preferred.
[0025] The saponification product of an olefin-vinyl carboxylate
ester copolymer can be prepared, for example, in a manner known per
se in the art by preparing an olefin-vinyl carboxylate ester
copolymer and then saponifying the copolymer. The olefin-vinyl
carboxylate ester copolymer can be prepared, for example, by
polymerizing a monomer composed mainly of an olefin and a vinyl
carboxylate ester under pressure in the presence of a radical
polymerization initiator such as benzoyl peroxide or
azobisisobutyronitrile in an organic solvent such as methanol,
t-butyl alcohol or dimethylsulfoxide. Upon the saponification of an
olefin-vinyl carboxylate ester copolymer, an acid catalyst or an
alkali catalyst can be used.
[0026] The vinyl alcohol copolymer (B) is not limited to any single
use of a vinyl alcohol copolymer. Depending on the application
purpose, two or more vinyl alcohol copolymers may be used in
combination.
[0027] The block copolymer used in the present invention as the
component (C') contains a polymer block (a) of an aromatic vinyl
compound and an isobutylenic polymer block (b).
[0028] Here, the block (a) is a polymer block derived from a
monomer composed mainly of an aromatic vinyl compound. As the
aromatic vinyl compound, styrene, p-methylstyrene,
.alpha.-methylstyrene and the like can be used either singly or in
combination. The block (a) preferably has a number-average
molecular weight falling within a range of 3000 to 80000.
[0029] The block (b) is, on the other hand, a polymer block derived
from a monomer composed mainly of isobutylene. The number-average
molecular weight of the block (b) preferably falls within a range
of 10000 to 200000, because such a range improves the melt fluidity
of the block copolymer (C') and facilitates the mixing with the
polyolefin resin (A) and vinyl alcohol copolymer (B) and subsequent
molding or forming. In addition, it is preferred that in the block
copolymer (C'), the whole weight of the block (a) falls within a
range of 10 to 60% based on the total weight of the block (a) and
the block (b).
[0030] The block copolymer (C') is not limited to any single block
copolymer. Depending on the application purpose, two or more block
copolymers may be used in combination.
[0031] No particular limitation is imposed on the process for the
preparation of the block copolymer (C'). For example, it is
possible to employ a method in which polymerization of a monomer
composed mainly of an aromatic vinyl compound and polymerization of
a monomer composed mainly of isobutylene are carried out
successively in an inert solvent such as hexane or methylene
chloride in the presence of an initiator system composed of a Lewis
acid and an organic compound capable of forming a
cationic-polymerizable active species in combination with the Lewis
acid. Here, examples of the Lewis acid include titanium
tetrachloride, boron trichloride, aluminum chloride and tin
tetrachloride. The organic compound capable of forming a
cationic-polymerizable active species means an organic compound
having a functional group such as an alkoxy group, an acyloxy group
or a halogen atom and examples thereof include
bis(2-methoxy-2-propyl)benzene, bis(2-acetoxy-2-propyl)benzene and
bis(2-chloro-2-propyl)benzene. If necessary, pyridine and amides
such as dimethylacetamide and dimethylformamide may be added to the
polymerization reaction system. According to the above
polymerization method, the triblock copolymer having a structure of
block (a)--block (b)--block (a) may be produced for example by
polymerizing a monomer principally composed of isobutylene in the
presence of an initiator system comprising a Lewis acid and an
organic compound having two functional groups, and adding a monomer
principally comprising an aromatic vinyl compound to the
polymerization reaction system when the above polymerization
reaction is substantially completed, whereby the polymerization
reaction can be continued sequentially.
[0032] The resin composition of the present invention contains the
vinyl alcohol copolymer (B) in an amount of 10 to 1000 parts by
weight per 100 parts by weight of the polyolefin resin (A); and
contains the block copolymer (C') in an amount of 5 to 1000 parts
by weight per 100 parts by weight in total of the polyolefin resin
(A) and vinyl alcohol copolymer (B). If the content of the vinyl
alcohol copolymer (B) is less than 10 parts by weight per 100 parts
by weight of the polyolefin resin (A), the resulting resin
composition is limited in the ultimate level of the gas barrier
properties, though depending on the kind of the polyolefin resin
(A) (for example, when the polyolefin resin (A) is a low-density
polyethylene). When the content of the vinyl alcohol copolymer (B),
on the other hand, exceeds 1000 parts by weight per 100 parts by
weight of the polyolefin resin (A), the resulting resin composition
sometimes has insufficient flexibility. If the content of the block
copolymer (C') is less than 5 parts by weight of per 100 parts by
weight in total of the polyolefin resin (A) and vinyl alcohol
copolymer (B), the flexibility of the resulting resin composition
is insufficient. If the content of the block copolymer (C'), on the
other hand, exceeds 1000 parts by weight per 100 parts by weight in
total of the components (A) and (B), the resulting resin
composition has too high flexibility and is therefore not suited as
a material for the molded or formed article which is requested to
have self-shape maintaining properties and the like.
[0033] For attaining both suitable flexibility as molding or
forming materials and markedly high gas barrier properties, it is
preferred that the content of the vinyl alcohol copolymer (B) is 20
to 500 parts by weight per 100 parts by weight of the polyolefin
resin (A) and the content of the block copolymer (C') is 10 to 50
parts by weight per 100 parts by weight in total of the polyolefin
resin (A) and vinyl alcohol copolymer (B).
[0034] In the present invention, another component, in addition to
the polyolefin resin (A), vinyl alcohol copolymer (b) and block
copolymer (C'), may be added to the resin composition as needed
within an extent not impairing the advantages of the present
invention. An inorganic filler such as calcium carbonate, talc,
carbon black, titanium oxide, silica, clay, barium sulfate or
magnesium carbonate can be added for the improvement of the heat
resistance and weather resistance and a weight increase. An
aliphatic hydrocarbon lubricant such as polyolefin wax, higher
aliphatic alcohol, higher fatty acid lubricant, fatty acid amide
lubricant such as an amide or bisamide of a higher fatty acid or
metallic soap base lubricant such as calcium stearate can be added
for the improvement of the surface lubricating properties of the
molded or formed article obtained from the resin composition. In
addition, a thermal stabilizer, antioxidant or light stabilizer can
be added.
[0035] No particular limitation is imposed on the mixing method of
the components for the preparation of a resin composition of the
present invention. A method similar to that ordinarily employed for
the preparation of a polyolefin resin composition can be
employed.
[0036] When a method in which the polyolefin resin (A), vinyl
alcohol copolymer (B) and block copolymer (C') are mixed under the
melting conditions is adopted, the resulting resin composition has
further improved gas barrier properties so that this method is
preferably adopted. When the above mixing method under the melting
conditions is adopted, it is preferred to use the components (A),
(B) and (C') which can satisfy the conditions of [a]>[b] and
[c']>[b] supposing that [a], [b] and [c'] represent the melt
viscosities of the components (A), (B) and (C'), respectively, as
measured at a temperature similar to that in the above melting
conditions and a shear rate of 100 sec.sup.-1, because a resin
composition with particularly high gas barrier properties can be
provided. As a method for mixing the components (A), (B) and (C')
under the melting conditions, usable is a method comprising melt
mixing these components in a predetermined ratio by a melt kneader
such as extruder or kneader. As a heating temperature upon mixing
under the above melting conditions, any temperature permitting the
melt flow of the components and not causing a substantial thermal
deterioration can be used. In general, a temperature ranging from
150 to 300.degree. C., more preferably, 180 to 280.degree. C. can
be adopted.
[0037] The resin composition according to the present invention has
good formability or moldability so that it can be formed or molded
into an article having a desired size or shape by various forming
or molding methods. Examples of the forming or molding method which
can be adopted include injection molding, extrusion, compression
molding, blow molding and vacuum forming in a manner known per se
in the art. Examples of the formed or molded article include
sheets, films, pipes and bottle-shaped articles. The resin
composition of the present invention can exhibit excellent
formability when subjected to melt extrusion, particularly melt
extrusion film forming, which makes it possible to provide an
article having good surface conditions.
[0038] The article molded or formed from the resin composition of
the present invention has a suitable flexibility, good heat
resistance and high gas barrier properties, so that it is useful as
various sealing materials, packaging films and containers.
[0039] A closure for a container and a sealing element for the
closure according to the present invention, each composed mainly of
the above-described components (A), (B) and (C) will hereinafter be
described.
[0040] A detailed description was already made on the components
(A) and (B), but it is preferred that the content of olefin units
in the saponification product of an olefin-vinyl carboxylate ester
copolymer, which is a preferred example of the vinyl alcohol
copolymer (B), is 2 to 70 mole %, more preferably 5 to 65 mole %
and particularly preferably 10 to 60 mole %, from the viewpoints of
the gas barrier properties and moldability or formability of a
material composed of the resin composition with the polyolefin
resin (A) and elastomer (C). Among the saponification products of
an olefin-vinyl carboxylate ester copolymer, that of an
ethylene-vinyl carboxylate ester copolymer is particularly
preferred from the viewpoints of the moldability or formability and
mechanical properties of the material formed from the resin
composition with the polyolefin resin (A) and elastomer (C).
[0041] Examples of the elastomer (C) include the above-described
block copolymer (C') (ex. a styrene-isobutylene-styrene triblock
copolymer or the like); a block copolymer containing a polymer
block of an aromatic vinyl compound and a conjugated diene polymer
block which may be at least partially hydrogenated (ex.
styrene-ethylene butylene-styrene triblock copolymer (SEBS),
styrene-ethylene-propylene-styrene triblock copolymer (SEPS) or the
like), ethylene-vinyl acetate copolymer; ethylene-propylene rubber
(ex. EPR or EPDM), ethylene-l-butene copolymer, ethylen-l-octene
copolymer, styrene-conjugated diene copolymer or hydrogenated
product thereof, carboxyl- or epoxy-modified styrene-conjugated
diene copolymer and butadiene-acrylonitrile copolymers having at an
terminal thereof a carboxyl or epoxy group.
[0042] Among them, thermoplastic elastomers such as the block
copolymer (C') and a block copolymer comprising a polymer block of
an aromatic vinyl compound and a conjugated diene polymer block
which may be at least partially hydrogenated are preferred.
Particularly, the block copolymer (C') is preferred because the
resin composition containing it with the polyolefin resin (A) and
the vinyl alcohol copolymer (B) exhibits good formability on
extrusion and in addition, it exhibits excellent heat resistance so
that when it is molded or formed into a closure or a sealing
element, deterioration such as change on the surface hardly occurs
even after exposed to high-temperature conditions for long time.
Here the block (a) of the block copolymer (C') is a polymer block
derived from a monomer mainly composed of an aromatic vinyl
compound. Examples of the aromatic vinyl compound include styrene,
p-methylstyrene and .alpha.-methylstyrene; and they can be used
singly or in combination. The block (a) is preferred to have a
number-average molecular weight falling within a range of 3000 to
80000. The block (b), on the other hand, is a polymer block derived
from a monomer composed mainly of isobutylene. Number-average
molecular weight of the block (b) falling within a range of 10000
to 200000 is preferred because it improves the melt fluidity and
facilitates the mixing with the polyolefin resin (A) and vinyl
alcohol copolymer (B) and subsequent molding or forming. It is also
preferred that the total weight of the block (a) in the block
copolymer falls within a range of 10 to 60% based on the total
weight of the blocks (a) and (b) in the block copolymer.
[0043] The elastomer (C) is not limited to any single elastomer.
Depending on the application purpose, two or more elastomers may be
used in combination.
[0044] In the resin composition forming a closure or sealing
element according to the present invention, the content of the
vinyl alcohol copolymer (B) is 10 to 1000 parts by weight per 100
parts by weight of the polyolefin resin (A). The content of the
elastomer (C) is 5 to 100 parts by weight per 100 parts by weight
in total of the polyolefin resin (A) and vinyl alcohol copolymer
(B).
[0045] When the content of the vinyl alcohol copolymer (B) is less
than 10 parts by weight per 100 parts by weight of the polyolefin
resin (A), the resulting resin composition reaches only a limited
level of gas barrier properties and a closure or sealing element
formed thereof is insufficient in the long-term shelf stability and
smell retention of the contents. When the content of the vinyl
alcohol copolymer (B) exceeds 1000 parts by weight per 100 parts by
weight of the polyolefin resin (A), on the other hand, the
resulting resin composition has insufficient flexibility and the
closure or sealing element formed thereof is sometimes inferior in
the hermetical sealing properties for containers.
[0046] If the content of the elastomer (C) is less than 5 parts by
weight per 100 parts by weight in total of the polyolefin resin (A)
and vinyl alcohol copolymer (B), the resulting resin composition
has insufficient flexibility and the closure or sealing element
composed of the resin composition is inferior in the hermetical
sealing properties for containers. If the content of the elastomer
(C) exceeds 100 parts by weight per 100 parts by weight in total of
the above components (A) and (B), on the other hand, the resulting
resin composition tends to have too high flexibility. Such a resin
composition containing an excess of the elastomer (C) is molded
into a closure secured by rotation via a screw and the like, the
slide thereof in contact with a container is so deteriorated that
it will be difficult to mount the closure onto the container via
rotation. When a sealing element molded or formed from the resin
composition is mounted within a closure secured by rotation for
use, the back motion occurs when a screw locks into the opening of
a container and complete sealing cannot be attained easily. Because
a resin composition containing an excess of the elastomer (C) has
low oil resistance, a closure or sealing element formed of the
resin composition is applicable only in a limited range of
fields.
[0047] It is preferred that the content of the vinyl alcohol
copolymer (B) is 20 to 500 parts by weight per 100 parts by weight
of the polyolefin resin (A) and the content of the elastomer (C) is
10 to 50 parts by weight per 100 parts by weight in total of the
polyolefin resin (A) and vinyl alcohol copolymer (B), because when
a closure or sealing element is molded or formed from such a
composition, the above-described problems are overcome, it exhibits
suitable flexibility, which brings about improvements in both the
mountability to the container and hermetically sealing properties,
and in addition it has excellent oil resistance.
[0048] In the closure or sealing element according to the present
invention, it is possible to add another component to the raw
material resin composition as needed, in addition to the polyolefin
resin (A), vinyl alcohol copolymer (B) and elastomer (C) within an
extent not impairing the advantages of the present invention. An
inorganic filler such as calcium carbonate, talc, carbon black,
titanium oxide, silica, clay, barium sulfate or magnesium carbonate
can be added for the improvements of heat resistance and weather
resistance and an increase in weight. An aliphatic hydrocarbon
lubricant such as polyolefin wax, higher aliphatic alcohol, higher
fatty acid lubricant, fatty acid amide lubricant such as an amide
or bisamide of a higher fatty acid or metallic soap base lubricant
such as calcium stearate can be added for the further improvement
of lubricating properties of the closure or sealing element molded
or formed from the resin composition. Besides, a thermal
stabilizer, antioxidant or light stabilizer and the like may be
blended as well.
[0049] No particular limitation is imposed on the mixing method of
the components for the preparation of the above-described resin
composition. A method similar to that ordinarily employed for the
preparation of a polyolefin resin composition can be employed.
[0050] When a method in which the polyolefin resin (A), vinyl
alcohol copolymer (B) and elastomer (C) are mixed under the melting
conditions is adopted, the resulting resin composition (also a
closure or sealing element available therefrom) has further
improved gas barrier properties so that this method is preferably
adopted. When the above mixing method under the melting conditions
is adopted, it is preferred to use the components (A), (B) and (C)
which can satisfy the conditions of [a]>[b] and [c]>[b]
supposing that [a], [b] and [c] represent the melt viscosities of
the components (A), (B) and (C), respectively, as measured at a
temperature similar to that in the above melting conditions and a
shear rate of 100 sec.sup.-1, which makes it possible to provide
the resulting resin composition (and also the closure or sealing
element available therefrom) with particularly high gas barrier
properties. As a method of mixing the individual components under
the melting conditions, usable is a method comprising melt mixing
these components in a predetermined ratio by a melt kneader such as
extruder or kneader. As a heating temperature upon mixing under the
above melting conditions, any temperature permitting the melt flow
of the components and not causing a substantial thermal
deterioration is usable. In general, the temperature ranging from
150 to 300.degree. C., more preferably, 180 to 280.degree. C. can
be adopted.
[0051] The resulting resin composition can be molded or formed into
a closure or sealing element of a desired shape or size in a manner
known per se in the art. For example, a closure integral to a
sealing element may be produced by injection molding of the resin
composition into a given shape. A sealing element independent of
the body of a closure may be produced according to a method
comprising punching a sheet or film, which is produced from the
resin composition by a forming method such as extrusion, by means
of a blanking die and the like. The sealing element thus produced
can be mounted onto the body of a closure by a method such as
thermal fusion, for subsequent use. The sealing element of the
present invention may also be produced by melt extruding and
compression molding the resin composition onto the body of a
closure comprising a different type of a material (for example,
metal).
[0052] At least the sealing element of the closure of the present
invention comprises the resin composition; the closure embraces not
only an integrally molded article of the resin composition but also
a closure with a sealing element formed or molded from the resin
composition as a structural member thereof. The closure of the
present invention embraces a variety of shapes such as cap and
stopper. The suitable pliability of the resin composition is
effectively exerted particularly in those secured by rotation via a
screw and the like. The sealing element (packing element) of the
present invention includes a variety of shapes such as disk and
ring.
[0053] The present invention will hereinafter be described more
concretely in examples. It should however be borne in mind that the
present invention is not limited to or by the following
examples.
[0054] The measurement of the melt viscosity of each of the
components of a resin composition and evaluation of the resin
composition were carried out according to the methods described in
(1) to (6).
[0055] (1) Melt viscosity
[0056] The melt viscosity of each component of a resin composition
was measured by a capillary rheometer ("CAPIROGRAPH 1C", trade
name; product of Toyo Seiki Seisaku-sho, Ltd.) at a shear rate of
100 sec.sup.-1 and a temperature equal to that upon melt kneading
for the preparation of the resin composition.
[0057] (2) Flexibility
[0058] A resin composition was compression molded into a sheet
having a thickness of 6 mm at a temperature higher by 20.degree. C.
than the melt temperature. The hardness (Shore D) of the resulting
sheet was measured in accordance with JIS K7215. Concerning the
sheet having the Shore D hardness not higher than 35, hardness (JIS
A) was measured in accordance with JIS K6301 as needed. The
hardnesses so obtained were designated as a flexibility index.
[0059] (3) Heat resistance of a molded product
[0060] A resin composition was compression molded into a test sheet
of 20 cm long, 20 cm wide and 2 mm thick. The test piece was placed
in a gear oven of 150.degree. C. for 24 hours, followed by cooling
to room temperature. Stickiness on the surface of the test piece
was observed by touching it with a finger. When stickiness was not
observed as before heating, the sheet was ranked as "excellent"
(A); when almost no stickiness was observed, "good" (B); when
slight stickiness was observed, "slightly poor" (C); and when
severe stickiness was observed, "poor" (D). Thus, the heat
resistance was evaluated by judging the thermal deterioration in
accordance with the above four-stage system.
[0061] (4) Gas barrier properties
[0062] A resin composition was compression molded into a film
having a thickness of 200 .mu.m at a temperature higher by
20.degree. C. than the melt temperature. The oxygen permeability
coefficient, namely Po.sub.2, of the film was measured under the
conditions of a 2.5 kg/cm.sup.2 oxygen pressure and a temperature
of 35.degree. C. by using a gas permeation measurement system
("Type GTR-10", trade name; product of Yanagimoto Mfg. Co., Ltd.).
The coefficient was designated as an indicator of gas barrier
properties.
[0063] (5) Film formability
[0064] A resin composition was formed into a film by 20 mm.O
slashed. LABOPLASTMILL (manufacture of TOYO SEIKI SEISAKU-SHO,
LTD.) under the conditions of a temperature of 230.degree. C. and a
rotational speed of a screw of 100 rpm. The surface roughness of
the resulting film was visually observed. When the film had a
markedly smooth surface, it was ranked as "excellent" (A); when it
had a slightly rough surface, "good" (B); and when it has a rough
surface as fish skin, "poor" (C). Thus, the film formability was
evaluated by ranking the surface conditions of the film at the
above three grades.
[0065] (6) Oil resistance
[0066] A resin composition was compression molded into a disk test
piece having a thickness of 6 mm and a diameter of 50 mm at a
temperature higher by 20.degree. C. than the melt temperature.
After immersed in a vegetable oil for 7 days, the test piece was
drawn out to judge the appearance. When no change was observed in
the appearance, it was judged as "good" (A); and when appearance of
the surface roughness was observed, it was judged as "poor" (B).
Thus, the oil resistance was evaluated by judging the surface
conditions at the above two stages.
[0067] The polyolefin resins used in the Examples will be
represented by the following abbreviations:
[0068] Polyolefin resin (A-1): low-density polyethylene ("MIRASON
401", trade name; product of MITSUI PETROCHEMICAL INDUSTRIES,
LTD.)
[0069] Polyolefin resin (A-2): propylene-ethylene block copolymer
("Mitsubishi Polypropylene BC3", trade name; product of Mitsubishi
Chemical Corporation)
[0070] Polyolefin resin (A-3): low-density polyethylene ("MIRASON
68", trade name; product of MITSUI PETROCHEMICAL INDUSTRIES,
LTD.)
[0071] Polyolefin resin (A-4): low-density polyethylene ("MIRASON
B319", trade name; product of MITSUI PETROCHEMICAL INDUSTRIES,
LTD.)
[0072] Polyolefin resin (A-5): ethylen-1-octene copolymer ("ENGAGE
EG8200", trade name; product of THE DOW CHEMICAL COMPANY)
[0073] The vinyl alcohol copolymers used in the Examples will be
represented by the following abbreviations.
[0074] Vinyl alcohol copolymer (B-1): ethylene-vinyl alcohol
copolymer ("EVAL EP-E105", trade name; product of KURARAY CO.,
LTD.)
[0075] Vinyl alcohol copolymer (B-2): ethylene-vinyl alcohol
copolymer ("EVAL EP-G110", trade name; product of KURARAY CO.,
LTD.)
[0076] The elastomers used in the Examples will be represented by
the following abbreviations.
[0077] Elastomer (C-1): a triblock copolymer having a structure of
a polystyrene block--a polyisobutylene block--a polystyrene block
(number average molecular weight: 34000, molecular weight
distribution (Mw/Mn): 1.23, polystyrene block content: 30 wt.
%).
[0078] Elastomer (C-2): a triblock copolymer having a structure of
a polystyrene block--a polyisobutylene block--a polystyrene block
(number average molecular weight: 75000, molecular weight
distribution (Mw/Mn): 1.20, polystyrene block content: 20 wt.
%).
[0079] Elastomer (C-3): a triblock copolymer having a structure of
a polystyrene block--a polyisobutylene block--a polystyrene block
(number average molecular weight:
[0080] 76000, molecular weight distribution (Mw/Mn): 1.27,
polystyrene block content: 30 wt. %).
[0081] Elastomer (C-4): a triblock copolymer having a structure of
a polystyrene block--an ethylene-propylene copolymer block--a
polystyrene block ("SEPTON 2007", trade name; product of KURARAY
CO., LTD.)
[0082] Elastomer (C-5): an ethylen-1-octene copolymer ("ENGAGE
EG8200", trade name; product of THE DOW CHEMICAL COMPANY)
[0083] Elastomer (C-6): an ethylene-propylene copolymer rubber
("ESPRENE V01111", trade name; product of SUMITOMO CHEMICAL CO.,
LTD.)
[0084] Examples 1-14 and Comparative Examples 1-8
[0085] In each of Examples 1 to 14 and Comparative Examples 1 to 8,
a polyolefin resin (A), a vinyl alcohol copolymer (B) and an
elastomer (C) were preliminary mixed at a ratio as shown in Table
1, followed by kneading in a twin-screw extruder under the melting
conditions of a temperature of 220.degree. C., whereby a resin
composition was obtained.
[0086] Evaluation results of the resin composition so obtained are
shown in Table 1.
1TABLE 1 Comp. Comp. Ex. 1 Ex. 2 Ex. 1 Ex. 3 Ex. 2 Ex. 4 Ex. 5 Ex.
6 Ex. 7 Ex. 8 Ex. 9 Polyolefin resin (A) A-1 A-1 A-1 A-1 A-1 A-2
A-3 A-4 A-4 A-5 A-1 (parts by weight) 40 40 70 60 65 40 40 40 60 30
20 Vinyl alcohol copolymer B-2 B-1 -- B-1 B-1 B-1 B-1 B-1 B-2 B-2
B-2 (B) (parts by weight) 30 30 0 20 5 30 30 30 20 30 20 Elastomer
(C) (parts by C-1 C-3 C-1 C-3 C-3 C-1 C-1 C-3 C-2 C-1 C-1 weight)
30 30 30 20 30 30 30 30 20 40 60 Melt viscosity a > c > b c
> a > c c > c > a > b c > a > b c > b >
a a > c > b a > c > b a > c > b a > c > b
(order of magnitude) a > b a > b Hardness (Shore D) 42 42 40
44 42 52 44 48 49 35 or less 35 or less (JIS A) -- -- -- -- -- --
-- -- -- 83 75 Oxygen permeability 360 380 12000 2400 12000 180
5800 56 830 800 2100 coefficient (cc .multidot. 20 .mu.m/m.sup.2
.multidot. day .multidot. atm) Heat resistance B B B B B B B B B B
B (stickiness) Film formability A B -- A -- -- -- B A -- --
(surface condition) Comp. Ex. Ex. Comp. Comp. Comp. Comp. Comp. Ex.
3 10 Ex. 11 12 Ex. 4 Ex. 5 Ex. 13 Ex. 6 Ex. 14 Ex. 7 Ex. 8
Polyolefin resin (A) A-1 A-1 A-1 A-1 A-1 A-1 A-2 A-3 A-1 A-1 A-1
(parts by weight) 40 60 40 60 40 40 40 40 20 65 65 Vinyl alcohol
copolymer B-2 B-2 B-2 B-2 B-2 B-2 B-2 B-1 B-2 B-2 B-2 (B) (parts by
weight) 30 20 30 20 30 30 30 30 20 5 5 Elastomer (C) (parts by C-4
C-1 C-3 C-3 C-5 C-6 C-1 C-4 C-3 C-1 C-4 weight) 30 20 30 20 30 30
30 30 60 30 30 Melt viscosity c > a > b a > c > a >
b c > c > a > b c > a > b c > a > b c > b
> a c > a > b a > c > b c > a > b (order of
magnitude) c > b a > b Hardness (Shore D) 48 45 43 46 43 43
52 45 31 42 43 (JIS A) -- -- -- -- -- -- -- -- -- Oxygen
permeability 440 2200 420 1800 560 280 180 5200 2300 12000 14500
coefficient (cc .multidot. 20 .mu.m/m.sup.2 .multidot. day
.multidot. atm) Heat resistance C B B B C C B C B B C (stickiness)
Film formability C -- -- (surface condition)
[0087] Incidentally, in the above table 1, the characters "a", "b"
and "c" in the column of "melt viscosity" mean the melt viscosity
of a polyolefin resin (A), that of a vinyl alcohol polymer (B) and
that of an elastomer (C), respectively.
[0088] From Table 1, it has been found that judging from the oxygen
permeability coefficient not greater than 5800 cc.multidot.20
.mu.m/m.sup.2 .multidot.day.multidot.atm, the invention resin
compositions prepared in Examples 1 to 14 have excellent gas
barrier properties; and from the hardness within a range of 31 to
52 on the Shore D or the hardness both not greater than 35 on the
Shore D and not less than 75 on the JIS A, the resin compositions
have suitable flexibility as various molding or forming materials.
It has also been found that from the results of "B" (good) in the
evaluation of heat resistance and the results of "A" (excellent) or
"B" (good) in the evaluation of film formability, they are
satisfactory both in heat resistance and extrusion formability.
Incidentally, as apparent from Table 1, when the melt viscosity (b)
of a vinyl alcohol copolymer (B) is smaller than both the melt
viscosity (a) of a polyolefin resin (A) and the melt viscosity (c)
of an elastomer (C) (Examples 1 to 4 and Examples 6 to 14 among
Examples 1 to 14), the oxygen permeability coefficient is 2400
cc.multidot.20 .mu.m/m.sup.2.multidot.day.multidot.atm or smaller,
which suggests particularly excellent gas barrier properties.
[0089] In each of the resin compositions described in Comparative
Examples 1, 2, 7 and 8 which do not contain a vinyl alcohol
copolymer (B) or contain it in a too small amount and are therefore
different from the invention compositions, the oxygen permeability
coefficient is not smaller than 12000 cc.multidot.20
.mu.m/m.sup.2.multidot.day.multidot.atm- , which suggests that the
composition has low gas barrier properties. In each of the resin
compositions described in Comparative Examples 3 to 6 and 8 which
contains an elastomer (C) different from the block copolymer (C'),
the heat resistance is evaluated as "C" (poor) and in the resin
composition in Comparative Example 3 the film formability is
evaluated as "C" (poor). From the above, it has been found that the
resin compositions in Comparative Examples 3 to 6 and 8 have
insufficient heat resistance and the resin composition in
Comparative Example 3 is insufficient also in the film
formability.
[0090] Referential Examples 1 to 16
[0091] Oil resistance of some of the resin compositions obtained in
the above Examples and Comparative Examples was evaluated. The
results are shown in Table 2, together with the evaluation results
already shown in Table 1.
2TABLE 2 Referential Example No. 1 2 3 4 5 6 7 8 Corresponding
Example Ex.2 Ex.3 Ex.1 Ex.10 Ex.11 Ex.12 Comp. Comp. or Comp. Ex.
Ex.3 Ex.4 Polyolefin resin (A) A-1 A-1 A-1 A-1 A-1 A-1 A-1 A-1
(parts by weight) 40 60 40 60 40 60 40 40 Vinyl alcohol copolymer
B-1 B-1 B-2 B-2 B-2 B-2 B-2 B-2 (B) (parts by weight) 30 20 30 20
30 20 30 30 Elastomer (C) (parts by C-3 C-3 C-1 C-1 C-3 C-3 C-4 C-5
weight) 30 20 30 20 30 20 30 30 Melt viscosity c > a > b c
> a > b a > c > b a > c > b c > a > b c
> a > b c > a > b c > a > b (order of magnitude)
Hardness (Shore D) 42 44 42 45 43 46 48 43 Oxygen permeability 380
2400 360 2200 420 1800 440 560 coefficient (cc .multidot. 20
.mu.m/m.sup.2 .multidot. day .multidot. atm) Oil resistance (change
A A A A A A A A in appearance) Heat resistance B B B B B B C C
(stickiness) Referential Example No. 9 10 11 12 13 14 15 16
Corresponding Example Comp. Ex. 13 Ex. 5 Comp. Ex. 9 Ex. 14 Comp.
Comp. or Comp.Ex. Ex. 5 Ex. 6 Ex. 7 Ex. 8 Polyolefin resin (A) A-1
A-2 A-3 A-3 A-1 A-1 A-1 A-1 (parts by weight) 40 40 40 40 20 20 65
65 Vinyl alcohol copolymer B-2 B-2 B-1 B-1 B-2 B-2 B-2 B-2 (B)
(parts by weight) 30 30 30 30 20 20 5 5 Elastomer (C) (parts by C-6
C-1 C-1 C-4 C-1 C-3 C-1 C-4 weight) 30 30 30 30 60 60 30 30 Melt
viscosity c > a > b c > a > b c > b > a c > b
> a a > c > b c > a > b a > c > b c > a
> b (order of magnitude) Hardness (Shore D) 43 52 44 45 32 31 42
43 Oxygen permeability 280 180 5800 5200 2100 2300 12000 14500
coefficient (cc .multidot. 20 .mu.m/m.sup.2 .multidot. day
.multidot. atm) Oil resistance (change A A A A B B A A in
appearance) Heat resistance C B B C B B B C (stickiness)
[0092] Incidentally, in the above table 2, the characters "a", "b"
and "c" in the column "melt viscosity" mean the melt viscosity of a
polyolefin resin (A), that of a vinyl alcohol polymer (B) and that
of an elastomer (C), respectively.
[0093] From Table 2, it has been found that each of the resin
compositions of Referential Examples 1 to 12 has suitable
flexibility of about 40 to 55 as the Shore D hardness, excellent
gas barrier properties of an oxygen permeability coefficient not
greater than 5800 cc.multidot.20
.mu.m/m.sup.2.multidot.day.multidot.atm, and oil resistance judged
as "good" in the evaluation of oil resistance, so that it is a
suitable raw material for a closure for containers or a sealing
element for the closure. Among them, the resin compositions wherein
the vinyl alcohol copolymer (B) has a melt viscosity (b) lower than
that of the polyolefin resin (A) and also that of the elastomer (C)
(Referential Examples 1 to 10) have an oxygen permeability
coefficient of 2400 cc.multidot.20
.mu.m/m.sup.2.multidot.day.multidot.atm and are therefore
particularly excellent in the gas barrier properties. When a block
copolymer (C-1 or C-3) having a polymer block of an aromatic vinyl
compound and an isobutylenic polymer block is used as the elastomer
(C) (Referential Examples 1 to 6, 10 and 11), the heat resistance
is evaluated as "good" (B), which indicates that the heat
resistance as well as gas barrier properties is good. on the other
hand, each of the resin compositions of Referential Examples 13 and
14 containing the elastomer (C) in a large amount shows the Shore D
hardness of 30 or so, which suggests too high flexibility. It is
evaluated as "poor" (B) in the oil resistance evaluation, which
suggests insufficient oil resistance. Accordingly, it has been
found that these resin compositions are not suited as raw materials
for a closure for containers or a sealing element for the closure.
Each of the resin compositions of Referential Examples 15 and 16
containing the vinyl alcohol copolymer (B) in a too small amount
shows the oxygen permeability coefficient not smaller than 12000
cc.multidot.20 .mu.m/m.sup.2.multidot.day.multidot.atm, which
indicates insufficient gas barrier properties. Accordingly, it has
been found that these resin compositions are not suited as raw
materials for a closure for containers or a sealing element for the
closure.
[0094] Example 15
[0095] By injection molding the resin compositions of Referential
Examples 1 to 12, threaded caps each having a diameter of 25 mm and
a height of 13 mm were produced, respectively.
[0096] When attempts were made to mount the resulting threaded caps
onto threaded glass containers, the caps could be locked completely
in any of the cases.
[0097] Comparative Example 9
[0098] In a similar manner to Example 15 except for the use of the
resin compositions of Referential Examples 13 and 14, threaded caps
were produced, respectively.
[0099] When attempts were made to mount each of the resulting
threaded caps onto a threaded glass container, no sufficient
mounting could be procured because of the poor slide between the
cap and the container.
[0100] Example 16
[0101] Each of the resin compositions of Referential Examples 1 to
12 was formed into a sheet of 0.5 mm thick by extrusion. The
resulting sheet was punched into a disk shape, whereby a disk-like
sealing element was produced. The sealing element so obtained was
thermally fused onto the inside of the body of an aluminum threaded
cap for adhesion.
[0102] An attempt was made to mount the resulting threaded cap onto
a threaded glass container, complete locking could be procured.
[0103] Comparative Example 10
[0104] In a similar manner to Example 16 except for the use, as a
resin composition, of the resin compositions of Referential
Examples 13 and 14, a sealing element was produced and it was
thermally fused onto the cap body.
[0105] An attempt was made to mount the resulting threaded cap onto
a threaded glass container, but no sufficient locking could be
procured because of the occurrence of the back motion of the cap
during locking.
[0106] Example 17
[0107] Each of the resin compositions of Referential Examples 1 to
12 was subjected to melt extrusion onto the inside of the body of
an aluminum threaded cap, followed by compression molding, whereby
a cap was produced.
[0108] When the resulting cap was mounted onto a threaded glass
container, complete locking could be achieved.
[0109] Comparative Example 11
[0110] In a similar manner to Example 17 except for the use, as a
resin composition, of each of the resin compositions of Referential
Examples 13 and 14, a cap was produced.
[0111] When an attempt was made to mount the resulting cap onto a
threaded glass container, no sufficient locking could be achieved
because of the occurrence of the back motion of the cap during
locking.
[0112] The resin composition according to the present invention
containing a polyolefin resin (A), a vinyl alcohol copolymer (B)
and a specific block copolymer (C') in a defined ratio has suitable
flexibility as a molding or forming material and besides, has high
gas barrier properties, good heat resistance and good moldability
or formability. The molded or formed articles obtained from the
resin composition therefore exhibit the above properties
effectively and can be used effectively as various sealing
materials, packaging films, containers and the like which are used
under high temperature conditions.
[0113] A closure for containers and a sealing element for the
closure, each formed of a molding material containing a polyolefin
resin (A), a vinyl alcohol copolymer (B) and an elastomer (C) in a
defined ratio and having suitable flexibility and besides, having
high gas barrier properties and good oil resistance, exhibit such
excellent properties effectively, have good mountability onto (or
within) a container and good hermetically sealing properties, and
is excellent in long-term shelf stability of the contents.
* * * * *