U.S. patent application number 11/597709 was filed with the patent office on 2007-11-01 for multi-layer structure and method of producing the same.
This patent application is currently assigned to TOYO SEIKAN KAISHA LTD.. Invention is credited to Makoto Etoh, Hiroaki Goto, Atsushi Kikuchi.
Application Number | 20070251945 11/597709 |
Document ID | / |
Family ID | 35450737 |
Filed Date | 2007-11-01 |
United States Patent
Application |
20070251945 |
Kind Code |
A1 |
Etoh; Makoto ; et
al. |
November 1, 2007 |
Multi-Layer Structure and Method of Producing the Same
Abstract
A multi-layer structure comprising a functional resin layer
obtained by covering a core layer of a base body resin or a second
functional resin with a shell layer of a first functional resin,
and a base body resin layer containing the functional resin layer
therein. The layers of the functional resins are formed at
positions where they are allowed to exhibit their functions to a
sufficient degree, a plurality of functions can be imparted, and a
molten resin mass having the above multi-layer structure can be
formed by the compression-forming.
Inventors: |
Etoh; Makoto; (Yokohama-shi,
JP) ; Goto; Hiroaki; (Yokohama-shi, JP) ;
Kikuchi; Atsushi; (Yokohama-shi, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
TOYO SEIKAN KAISHA LTD.
3-1, UCHISAIWAI-CHO, 1-CHOME
CHIYODA-KU, TOKYO, JAPAN
JP
|
Family ID: |
35450737 |
Appl. No.: |
11/597709 |
Filed: |
May 27, 2005 |
PCT Filed: |
May 27, 2005 |
PCT NO: |
PCT/JP05/10205 |
371 Date: |
December 15, 2006 |
Current U.S.
Class: |
220/200 ;
264/349 |
Current CPC
Class: |
B32B 27/325 20130101;
B29C 43/361 20130101; B32B 2307/7242 20130101; B29L 2001/00
20130101; B32B 2307/724 20130101; B32B 2435/02 20130101; B29C
43/203 20130101; B29C 43/146 20130101; B29C 2043/3433 20130101;
B32B 27/08 20130101 |
Class at
Publication: |
220/200 ;
264/349 |
International
Class: |
B65B 7/16 20060101
B65B007/16 |
Foreign Application Data
Date |
Code |
Application Number |
May 31, 2004 |
JP |
2004-161647 |
Claims
1. A multi-layer structure having a base body resin layer of a
thermoplastic resin and a functional resin layer of a functional
resin, wherein said functional resin layer comprises a core layer
of the base body resin or a second functional resin covered with a
shell layer of a first functional resin, and said base body resin
layer wraps the functional resin layer therein.
2. A multi-layer structure according to claim 1, wherein said
multi-layer structure is a container closure comprising a top panel
and a skirt portion hanging down from the peripheral edge of the
top panel, and at least the top panel is formed in said multi-layer
structure.
3. A container closure according to claim 2, wherein a sealing
member is formed on the inner surface of the top panel, the sealing
member having a layer of a functional resin different from the
functional resin used for the container closure.
4. A multi-layer structure according to claim 1, wherein said
multi-layer structure is a preform including a mouth portion, a
body wall and a bottom portion, and at least the body wall and the
bottom portion are formed in the multi-layer structure.
5. A multi-layer structure according to claim 1, wherein said
functional resin is any one of a gas-barrier resin, an
oxygen-absorbing resin, a cyclic olefin resin or a liquid crystal
polymer.
6. A method of producing a multi-layer structure by press-forming a
molten resin mass of a thermoplastic resin and a functional resin,
wherein said molten resin mass is the one that wraps therein a
functional resin mass which comprises a core layer of a base body
resin or a second functional resin covered with a shell layer of a
first functional resin.
7. A method of producing a multi-layer structure according to claim
6, wherein said multi-layer structure is a container closure
comprising a top panel and a skirt portion hanging down from the
peripheral edge of the top panel, and after the container closure
is formed by compression-forming said molten resin mass, a sealing
member is formed on the inner surface of the top panel by feeding
and compressing a molten resin mass containing therein a functional
resin different from the functional resin used for said molten
resin mass.
8. A method of producing a multi-layer structure according to claim
6, wherein said functional resin is any one of a gas-barrier resin,
an oxygen-absorbing resin, a cyclic olefin resin or a liquid
crystal polymer.
Description
TECHNICAL FIELD
[0001] The present invention relates to a multi-layer structure
having a base body resin layer of a thermoplastic resin and a
functional resin layer of a functional resin. More specifically,
the invention relates to a multi-layer structure having a layer
structure in which functional resins such as a barrier resin and an
oxygen-absorbing resin are allowed to efficiently exhibit their
functions, and to a method of producing the same.
BACKGROUND ART
[0002] In the field of packaging containers, there have been used a
variety of resins and resin compositions capable of exhibiting such
functions as heat resistance, barrier property, oxygen-absorbing
property and the like properties. These functional resins are used
in combination with a base body resin which chiefly works to
maintain the formability of the structure.
[0003] As the functional resins, there have been known gas-barrier
resins such as ethylene/vinyl alcohol copolymers, and
oxygen-absorbing resin compositions obtained by blending a resin
base body selected from the group consisting of an ethylene/vinyl
alcohol copolymer, nylon resin and olefin resin with an oxidizing
polymer having-an oxygen-absorbing rate larger than that of the
resin base body and an oxidizing catalyst or an oxidation initiator
(JP-A-2001-39475).
[0004] It has further been known to use the functional resins for
the containers and the container closures. For example,
JP-B-2-60499 discloses a compression-formed article of a
multi-layer structure comprising a first synthetic resin layer and
a second synthetic resin layer formed by using different synthetic
resins, the first synthetic resin layer surrounding substantially
the whole second synthetic resin layer, and a method of its
production, using a gas-barrier resin as the second synthetic resin
layer.
DISCLOSURE OF THE INVENTION
[0005] In the multi-layer structure bodies such as container
closures and containers having a multi-layer structure of
functional resins and other resin such as a base body resin,
however, it is difficult to place the layers of the functional
resins at positions where excellent functions possessed by the
functional resins can be exhibited to a sufficient degree.
[0006] That is, as disclosed in the above-mentioned JP-B-2-60499, a
functional resin is used for the container closures for foods being
positioned in the central portion of the structure wall in order to
avoid the effect of water in the case of a gas-barrier resin such
as an ethylene/vinyl alcohol copolymer or in order to avoid a place
that comes in direct contact with the food when an oxygen-absorbing
agent is contained therein. When the functional resin which is an
oxygen-absorbing resin is covered for its surfaces with a thick
base body resin, however, oxygen that is to be absorbed is
prevented from efficiently arriving at the layer of the
oxygen-absorbing resin, making it difficult to efficiently exhibit
oxygen-absorbing property.
[0007] On the other hand, if the amount of the functional resin is
increased so as to exist up to near the surface of the structure, a
problem arouses concerning the cost and, besides, deteriorating the
mechanical strength and the formability.
[0008] It has also been attempted to combine a plurality of layers
of the functional resins to enhance the effect encountering,
however, the difficulty in efficiently forming the layers by the
compression-forming.
[0009] It is therefore an object of the present invention to
provide a multi-layer structure in which layers of functional
resins are formed at positions where it is allowed to exhibit their
functions to a sufficient degree.
[0010] Another object of the present invention is to provide a
method of efficiently producing a multi-layer structure in which
layers of functional resins are formed at positions where it is
allowed to exhibit their functions to a sufficient degree relying
upon the compression-forming.
[0011] A further object of the present invention is to provide a
method capable of efficiently forming a multi-layer structure
having a plurality of functions relying upon the
compression-forming.
[0012] According to the present invention, there is provided a
multi-layer structure having a base body resin layer of a
thermoplastic resin and a functional resin layer of a functional
resin, wherein the functional resin layer comprises a core layer of
the base body resin or a second functional resin covered with a
shell layer of a first functional resin, and the base body resin
layer wraps the functional resin layer therein.
[0013] In the multi-layer structure of the present invention, it is
desired that: [0014] 1. The multi-layer structure is a container
closure comprising a top panel and a skirt portion hanging down
from the peripheral edge of the top panel, the multi-layer
structure is formed in at least the top panel and, particularly, a
sealing member is formed on the inner surface of the top panel, the
sealing member having a layer of a functional resin different from
the functional resin used for the container closure; [0015] 2. The
multi-layer structure is a preform including a mouth portion, a
body wall and a bottom portion, and at least the body wall and the
bottom portion are formed in the multi-layer structure; and [0016]
3. The functional resin is any one of a gas-barrier resin, an
oxygen-absorbing resin, a cyclic olefin resin or a liquid crystal
polymer.
[0017] According to the present invention, there is provided a
method of producing a multi-layer structure obtained by
press-forming a molten resin mass of a thermoplastic resin and a
functional resin, wherein the molten resin mass is the one that
wraps therein a functional resin mass which comprises a core layer
of a base body resin or a second functional resin covered with a
shell layer of a first functional resin.
[0018] In the method of producing a multi-layer structure of the
present invention, it is desired that: [0019] 1. The multi-layer
structure is a container closure comprising a top panel and a skirt
portion hanging down from the peripheral edge of the top panel, and
after the container closure is formed by compression-forming the
molten resin mass, a sealing member is formed on the inner surface
of the top panel by feeding and compressing a molten resin mass
containing therein a functional resin different from the functional
resin used for the molten resin mass; and [0020] 2. The functional
resin is any one of a gas-barrier resin, an oxygen-absorbing resin,
a cyclic olefin resin or a liquid crystal polymer.
[0021] The present invention is concerned with a multi-layer
structure having a base body resin layer of a thermoplastic resin
and a functional resin layer of a functional resin, wherein the
functional resin layer comprises a core layer of the base body
resin or a second functional resin covered with a shell layer of a
first functional resin, and the base body resin layer wraps the
functional resin layer therein.
[0022] As described above, the functional resin layer comprises the
shell layer of the first functional resin and the core layer of the
base body resin or the second functional resin, the shell layer
covering the core layer, and the base body resin layer wrapping the
functional resin layer therein. Therefore, the functional resin
layer is allowed to exist near the surface of the structure, and
the multi-layer structure permits the functional resin to
effectively exhibit its function.
[0023] According to the present invention, further, the core layer
which is the functional resin layer is formed by using a second
functional resin different from the first functional resin that
constitutes the shell layer to impart a multiplicity of functions
to the multi-layer structure. As will be described later, for
example, an oxygen-absorbing resin is used as the first functional
resin, and a gas-barrier resin is used as the second functional
resin thereby to efficiently absorb oxygen remaining in the
container, to shut off the permeation of oxygen from the exterior
of the container through the container closure and, hence, to
minimize the effect of oxygen upon the content.
[0024] According to the present invention, further, the base body
resin can be used as the core layer which is the functional resin
layer. In this case, a small amount of the functional resin can be
permitted to exist efficiently near the surface of the multi-layer
structure.
[0025] According to the method of producing a multi-layer structure
of the invention, further, there can be efficiently formed by
compression-forming a multi-layer structure permitting the layers
of the functional resins to be formed at positions where they
exhibit their functions to a sufficient degree, and having a
multiplicity of functions.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is a side sectional view schematically illustrating a
container closure which is a conventional multi-layer
structure;
[0027] FIG. 2 is a side sectional view schematically illustrating a
container closure which is a multi-layer structure of the present
invention;
[0028] FIG. 3 is a diagram illustrating a sectional structure of a
molten resin mass used for a method of producing a multi-layer
structure of the present invention;
[0029] FIG. 4 is a view illustrating the steps of producing the
molten resin mass shown in FIG. 3;
[0030] FIG. 5 is a view schematically illustrating the steps of
forming the container closure shown in FIG. 2 by using the molten
resin mass shown in FIG. 3; and
[0031] FIG. 6 is a view schematically illustrating the steps of
forming a sealing member on the inner surface of the top panel of
the container closure formed through the steps illustrated in FIG.
5.
BEST MODE FOR CARRYING OUT THE INVENTION
[0032] FIGS. 1 and 2 are side sectional views schematically
illustrating container closures which are examples of the
multi-layer structures. A container closure 1 includes a top panel
2 and a skirt portion 3. FIG. 1 illustrates a conventional
container closure, and FIG. 2 illustrates a container closure of
the present invention. In the container closures 1 of FIGS. 1 and
2, a layer 4 of a functional resin is existing in almost the whole
region of the top panel 2 and in a portion of the skirt portion 3
in a state of being wrapped in a base body resin 5. In the
conventional container closure comprising the base body resin and
the functional resin shown in FIG. 1, the layer 4 of the functional
resin is positioned in the central portion of the top panel 2. In
the container closure of the present invention shown in FIG. 2, on
the other hand, the functional resin is existing as a shell layer 4
covering the core layer 6 of the base body resin, the shell layer 4
of the functional resin existing being wrapped in the base body
resin layer 5. It will therefore be obvious that the layer 4 of the
functional resin is positioned on the surface side of the body wall
as compared to the conventional container closure shown in FIG.
1.
[0033] It is desired that the above-mentioned multi-layer structure
of the present invention is formed by the compression-forming. It
is, here, important that the molten resin mass that is to be
compression-formed is the one that wraps therein a functional resin
mass which comprises a core layer of a base body resin or a second
functional resin covered with a shell layer of a first functional
resin. Upon compression-forming the molten resin mass having the
above-mentioned structure, it is made possible to efficiently form
a structure maintaining the above multi-layer structure.
[0034] FIG. 3 is a diagram illustrating a sectional structure of a
molten resin mass 10 used for the method of producing a multi-layer
structure of the present invention by compression-forming, wherein
a core layer 12 of a base body resin or a second functional resin
is covered with a shell layer 11 of the first functional resin, and
a functional resin layer comprising the shell layer 11 and the core
layer 12 is wrapped in a base body resin 13.
[0035] In the multi-layer structure of the present invention,
further, an adhesive layer is formed among the shell layer of the
above first functional resin, the core layer of the base body resin
or the second functional resin, and the base body resin layer, or
between any two layers, from the standpoint of suppressing the
peeling between the base body resin layer and the functional resin
layer.
[0036] FIG. 4 is a view illustrating the production of the molten
resin mass shown in FIG. 3. In a molten resin feeder portion 20 in
the compression-forming apparatus, there are formed feed pipes 21
for feeding the base body resin, feed pipes 22 for feeding the
first functional resin, and feed pipes 23 for feeding the second
functional resin. The first functional resin feed pipes 22 and the
second functional resin feed pipes 23 are opened and closed at
their molten resin flow-out ports by using a pin 24.
[0037] As will be understood from FIGS. 4(A) to 4(E), the base body
resin 13 in the molten state is continuously fed through the feed
pipes 21. Next, the pin 24 is raised in the direction of an arrow,
whereby the flow-out ports of the first functional resin feed pipes
22 are opened permitting the first functional resin 11 to flow into
the base body resin 13 (FIG. 4(B)). When the pin 24 is further
raised in the direction of the arrow, the flow-out ports of the
feed pipes 23 for feeding the second functional resin 12 are
opened, whereby the second functional resin 12 flows into the first
functional resin 11 that has been fed already. When the second
functional resin flows out, the first functional resin is
interrupted from flowing out through the feed pipes 22 (FIG.
4(C)).
[0038] Next, when the pin 24 is lowered in the direction of an
arrow, the flow-out ports of the second functional resin feed pipes
23 are closed, and the first functional resin flows in again (FIG.
4(D)). When the pin 24 is further lowered in the direction of the
arrow, the flow-out ports of the first functional resin feed pipes
22 are closed, too, whereby the base body resin only is fed.
Namely, in the base body resin, there is formed a molten resin flow
forming a shell layer of the first functional resin and a core
layer of the second functional resin (FIG. 4(E)). The portion where
there is existing only the base body resin of the molten resin flow
is cut by cutting means such as a cutter to form the molten resin
mass of the structure shown in FIG. 3. The molten resin mass can be
continuously fed into a compression-forming metal mold.
[0039] An adhesive layer may be formed among the shell layer of the
first functional resin, the core layer of the base body resin or
the second functional resin, and the base body resin layer, or
between any two layers. Though not shown, the adhesive feed pipes
for feeding a material that constitutes the adhesive layers are
provided among the resin feed pipes for the shell layer, the core
layer and the base body resin layer or between any two resin feed
pipes for the layers. The flow-in ports of the adhesive material
feed pipes are opened and closed by operating the pin like the
above-mentioned pin 24 to feed the adhesive material.
[0040] FIG. 5 is a view schematically illustrating the steps of
forming the container closure shown in FIG. 2 by using the molten
resin mass shown in FIG. 3. The molten resin mass 10 produced
through the steps shown in FIG. 4 is fed by a molten resin mass
feeding device into a compression-forming metal mold 30 (FIG.
5(A)). Next, a male mold 31 descends, compresses the molten resin
mass 10 into the shape of a container closure in cooperation with
the metal mold 30 (FIG. 5(B)). Thereafter, the male mold 31 is
raised to separate away from the metal mold 30, and a container
closure 33 is formed (FIG. 5(C)).
[0041] In the present invention, a sealing member is integrally
formed on the inner surface of the container closure by feeding a
molten resin mass onto the inner surface of the top panel of the
container closure formed by the above method, the molten resin mass
containing therein a functional resin different from the functional
resin used for the molten resin mass for forming the container
closure, and compression-forming it thereon. By using a functional
resin different from the functional resin used for the container
closure, a multiplicity of functions can be imparted to the
container closure.
[0042] FIG. 6 is a view schematically illustrating the steps of
forming a sealing member on the inner surface of the top panel-of
the container closure formed through the steps shown in FIG. 5. A
molten resin mass 40 produced through the steps shown in FIG. 4 is
fed onto the top panel 41 of the container closure 33 in the
compression-forming metal mold 30 (FIG. 6(A)). A male mold 42 for
forming the sealing member descends, and compresses the molten
resin mass 40 into the shape of a sealing member in cooperation
with the metal mold 30 and the container closure 33 (FIG. 6(B)).
Thereafter, the male mold 42 is raised to separate away from the
metal mold 30 and the container closure 33, and there is formed the
container closure 33 having a sealing member 43 formed thereon
(FIG. 6(C)).
(Layer Constitution)
[0043] In the multi-layer structure of the present invention, an
important feature resides in that the base body resin wraps therein
the functional resin layer which comprises the shell layer of the
first functional resin and the core layer of the second functional
resin or the base body resin.
[0044] Further, an adhesive layer may be formed as described
above.
[0045] Though there is no particular limitation, examples of the
combination of the shell layer and the core layer (shell/core)
include oxygen-absorbing resin/base body resin, oxygen-absorbing
resin/gas-barrier resin, oxygen-absorbing resin/cyclic olefin
resin, oxygen-absorbing resin/liquid crystal polymer, gas-barrier
resin/base body resin, gas-barrier resin/cyclic olefin resin,
gas-barrier resin/liquid crystal polymer, gas-barrier
resin/oxygen-absorbing resin, cyclic olefin resin/base body resin,
and liquid crystal polymer/base body resin.
[0046] In forming the above layer structure, the ratio of the base
body resin, first functional resin and second functional resin
varies depending upon the function to be imparted to the
multi-layer structure and the use of the multi-layer structure, and
cannot be exclusively defined. When the container closure shown in
FIG. 1 is to be formed, however, it is desired that the weight
ratio of the base body resin and the functional resin in the state
of a molten mass is in a range of 99:1 to 70:30.
[0047] In the case of the container closure having the sealing
member formed by the above method, though not limited thereto only,
the functional resin used for the container closure may be any one
of the gas-barrier resin, liquid crystal polymer or cyclic olefin
resin, or a combination thereof, and the sealing member may contain
an oxygen-absorbing resin in the base body resin that constitutes
the sealing member.
[0048] That is, in the container closure, use of the gas-barrier
resin interrupts the permeation of oxygen from the outer side, use
of the liquid crystal polymer improves the mechanical strength and
use of the cyclic olefin resin interrupts the permeation of water
vapor from the outer side. In the sealing member, on the other
hand, use of the oxygen-absorbing resin effectively traps oxygen
remaining in the container, and there is provided the container
closure with the sealing member having excellent properties
stemming from the functions of the container closure and the
sealing member.
[0049] The molten resin mass forming the sealing member may form a
multi-layer structure like the above-mentioned molten resin mass,
or may form a structure in which the functional resin is dispersed
much in the base body resin.
(Base Body Resin)
[0050] The base body resin that can be used for the present
invention may be any thermoplastic resin that has heretofore been
used for the containers, container closures and sealing members
such as liners.
[0051] Concretely, there can be used those resins that can be
melt-formed and crystallized, such as polyolefin resin,
thermoplastic polyester resin, polycarbonate resin, and
polyacrylonitrile resin. When the container closures and the
sealing members are to be formed, in particular, there can be used
a polyolefin resin. When the preforms are to be formed, a
thermoplastic polyester resin can be preferably used.
[0052] Examples of the polyolefin resin include polyethylenes such
as low-density polyethylene (LDPE), medium-density polyethylene
(MDPE), high-density polyethylene (HDPE), linear low-density
polyethylene (LLDPE) and linear very low-density polyethylene
(LVLDPE), as well as polypropylene (PP), ethylene/propylene
copolymer, polybutene-1, ethylene/butene-1 copolymer,
propylene/butene-1 copolymer, ethylene/propylene/butene-1
copolymer, ethylene/vinyl acetate copolymer, ionically crosslinked
olefin copolymer (ionomer) and blends thereof.
[0053] It is desired that the polyolefin resin has a melt flow rate
(MFR) of 0.1 to 25 g/10 min. from the standpoint of extrusion
property.
[0054] Examples of the thermoplastic polyester resin include
thermoplastic polyesters such as polyethylene terephthalate,
polybutylene terephthalate and polyethylene naphthalate, as well as
blends of these polyesters and a polycarbonate or an arylate resin.
In the present invention, it is desired to use a polyethylene
terephthalate (PET) polyester in which a majority proportion
(usually, not less than 80 mol % and, particularly, not less than
80 mol %) of the ester recurring units is an ethylene terephthalate
unit, and having a glass transition point (Tg) of 50 to 90.degree.
C. and, particularly, 55 to 80.degree. C. and a melting point (Tm)
of 200 to 275.degree. C. and, particularly, 220 to 270.degree.
C.
[0055] As the PET polyester, a homopolyethylene terephthalate is
best suited. However, a copolymerized polyester, too, can be used
provided the content of the ethylene terephthalate unit is within
the above range.
[0056] In the above copolymerized polyester, examples of the
dibasic acid other than terephthalic acid include aromatic
dicarboxylic acids such as isophthalic acid, phthalic acid and
naphthalenedicarboxylic acid; alicyclic dicarboxylic acids such as
cyclohexanedicarboxylic acid; aliphatic dicarboxylic acids such as
succinic acid, adipic acid, sebacic acid, and dodecane dioic acid,
which may be used in one kind or in a combination of two or more
kinds. As the diol component other than the ethylene glycol, there
can be exemplified propylene glycol, 1,4-butanediol, diethylene
glycol, 1,6-hexylene glycol, cyclohexane dimethanol, and ethylene
oxide adduct of bisphenol A, which may be used in one kind or in
two more kinds.
(Functional Resins)
[0057] The functional resins are used for imparting some
performance to the multi-layer structure of the present invention,
and stand for the resins different from the above-mentioned base
body resin. Concretely, there can be exemplified resins such as
gas-barrier resin, oxygen-absorbing resin and cyclic olefin resin
having excellent water vapor-barrier property,as well as resins
having excellent rigidity and heat resistance like liquid crystal
polymers.
[Gas-Barrier Resin]
[0058] A representative example of the gas-barrier resin may be an
ethylene/vinyl alcohol copolymer, such as a saponified product of a
copolymer obtained by saponifying an ethylene/vinyl acetate
copolymer having an ethylene content of 20 to 60 mol % and,
particularly, 25 to 50 mol % so as to possess a saponification
degree of not lower than 96% and, particularly, not lower than 99
mol %. The ethylene/vinyl alcohol copolymer (saponified product of
an ethylene/vinyl acetate copolymer) must have a molecular weight
large enough for forming a film and must desirably possess an
inherent viscosity of not smaller than 0.01 dL/g and, particularly,
not smaller than 0.05 dL/g as measured in a mixed solvent of phenol
and water at a weight ratio of 85/15 at 30.degree. C.
[0059] As the gas-barrier resin other than the ethylene/vinyl
alcohol copolymer, further, there can be exemplified polyamides
such as nylon 6, nylon 6.cndot.6, nylon 6/6.cndot.6 copolymer,
metaxylylenediadipamide (MXD6), nylon 6.cndot.10, nylon 11, nylon
12 and nylon 13. Among these polyamides, it is desired to use the
one having amide groups in a number of 5 to 50 and, particularly, 6
to 20 per 100 carbon atoms.
[0060] These polyamides, too, must have molecular weights large
enough for forming a film, and must desirably have a relative
viscosity of not smaller than 1.1 and, particularly, not smaller
than 1.5 as measured in the concentrated sulfuric acid
(concentration of 1.0 g/dL) at 30.degree. C.
[Oxygen-Absorbing Resin]
[0061] As the oxygen-absorbing resin, there can be exemplified a
resin composition blended with an oxygen absorber, and a resin
composition comprising at least an oxidizing organic component and
a transition metal catalyst (oxidizing catalyst).
[0062] As the oxygen absorber-blended resin composition, there can
be exemplified the above base body resin blended with a
conventional oxygen absorber such as an iron-type oxygen
absorber.
[0063] The resin composition containing the oxidizable organic
component and the transition metal catalyst may the oxidizable
organic component and the transition metal catalyst only, but may
further contain resins other than those described above.
[0064] As the resin that can be used in combination with the
oxidizable organic component and the transition metal catalyst,
there can be exemplified the olefin resin and the gas-barrier resin
described above. In particular, it is desired to use the
ethylene/vinyl alcohol copolymer and the polyamide resin. Among
them, it is desired to use a xylylene group-containing polyamide
resin having a terminal amino group concentration of not smaller
than 40 eq/10.sup.6 g since it is not deteriorated by oxidation
even when it has absorbed oxygen.
(i) Oxidizable Organic Component.
[0065] As the oxidizable organic component, there can be
exemplified an ethylenically unsaturated group-containing polymer.
This polymer has a carbon-carbon double bond. The portion of the
double bond and, particularly, .alpha.-methylene neighboring the
double-bonded portion are easily oxidized with oxygen thereby to
trap oxygen.
[0066] The ethylenically unsaturated group-containing polymer is
derived from a monomer of, for example, polyene. There can be used,
as the oxidizable polymer, a random copolymer or a block copolymer
in combination with a homopolymer of polyene, in combination with
two or more kinds of the above polyene, or in combination with
other monomers.
[0067] Among the polymers derived from the polyene, there can be
preferably used polybutadiene (BR), polyisoprene (IR), natural
rubber, nitrile/butadiene rubber (NBR), styrene/butadiene rubber
(SBR), chloroprene rubber, ethylene/propylene/diene rubber (EPDM)
and the like, though the invention is in no way limited thereto
only, as a matter of course.
[0068] In addition to the above ethylenically unsaturated
group-containing polymer, there can be used, as the oxidizable
organic component, a polymer which by itself can be easily
oxidized, such as polypropylene, ethylene/propylene copolymer or
polymetaxylylenediadipamide having a terminal amino group
concentration of smaller than 40 eq/10.sup.6 g.
[0069] From the standpoint of formability, it is desired that the
above oxidizable polymer or the copolymer thereof has a viscosity
at 40.degree. C. over a range of 1 to 200 Pas.
[0070] It is desired that the polyene polymer is an acid-modified
polyene polymer into which a carboxylic acid group, an anhydrous
carboxylic acid group or a hydroxyl group has been introduced.
[0071] It is desired that the oxidizable polymer or the oxidizable
organic component comprising a copolymer thereof is contained in
the oxygen-absorbing resin at a ratio of 0.01 to 10% by weight.
(ii) Transition Metal Catalyst.
[0072] As the transition metal catalyst, there can be preferably
used metals of the group VIII of periodic table, such as iron,
cobalt and nickel. There can be further used metals of the group I,
such as copper and silver, metals of the group IV, such as tin,
titanium and zirconium, metals of the group V, such as vanadium,
metals of the group VI, such as chrome, and metals of the group
VII, such as manganese.
[0073] The transition metal catalyst is used, usually, in the form
of an inorganic salt, an organic salt or a complex of a low valency
of the above transition metal. As the inorganic salt, there can be
exemplified halides such as chlorides, oxy salts of sulfur such as
sulfates, oxyacid salts of nitrigen, such as nitrates, phosphorus
oxy salts such as phosphates, and silicates. As the organic salt,
there can be exemplified carboxylate, sulfonate and phosphonate. As
the complex of a transition metal, further, there can be
exemplified a complex with .beta.-diketone or .beta.-ketoacid
ester.
[0074] It is desired that the transition metal catalyst has a
concentration of transition metal atoms (on the basis of weight
concentration) of in a range of 100 to 3000 ppm in the
oxygen-absorbing resin.
[Other Functional Resins]
[0075] As the functional resins that can be favorably used for the
present invention, there can be exemplified a cyclic olefin resin
and a liquid crystal polymer in addition to the gas-barrier resin
and the oxygen-absorbing resin.
[0076] The cyclic olefin resin usually exhibits various properties
such as heat resistance, moisture resistance and water
vapor-barrier property superior to those of the general-purpose
thermoplastic resins. Use of the cyclic olefin resin makes it
possible to impart excellent properties to the multi-layer
structure.
[0077] As the cyclic olefin, there can be used a known cyclic
olefin that has heretofore been used for the packaging containers.
Usually, there can be used a saturated polymer obtained by
polymerizing an alicyclic hydrocarbon compound having an
ethylenically unsaturated bond and a bicyclic ring, i.e., by
polymerizing a so-called norbornene monomer relying upon a known
ring-opening polymerization method followed by the
hydrogenation.
[0078] As the cyclic olefin resin, further, there can be used a
copolymer of olefin and cyclic olefin in addition to the
homopolymer of a cyclic olefin. Ethylene is a preferred example of
the olefin for deriving an amorphous or low crystalline copolymer
(COC) of olefin and cyclic olefin. Preferably, there can be further
used an .alpha.-olefin having 3 to 20 carbon atoms, such as
propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 3-methyl
1-pentene and 1-decene in one kind or in combination with the
ethylene.
[0079] A preferred cyclic olefin resin is available from Mitsui
Petrochemical Co. in the trade name of APEL.
[0080] Further, the liquid crystal polymer usually exhibits various
properties such as rigidity, heat resistance and barrier property
superior to those of the general-purpose thermoplastic resins. Use
of the liquid crystal polymer makes it possible to impart excellent
properties to the multi-layer structure.
[0081] As the liquid crystal polymer, there can be used a high
molecular liquid crystal polymer that exhibits liquid crystallinity
in a state of solution or in a molten state, such as a known
lyotropic liquid crystal polymer and a thermotropic liquid crystal
polymer.
[0082] Concretely, there can be exemplified (a) the one obtained by
reacting an aromatic dicarboxylic acid, an aromatic diol and an
aromatic hydroxycarboxylic acid, (b) the one by reacting aromatic
hydroxycarboxylic acids of different kinds, (c) the one obtained by
reacting an aromatic dicarboxylic acid with an aromatic diol, and
(d) the one obtained by reacting a polyester such as polyethylene
terephthalate with an aromatic hydroxycarboxylic acid, to which
only, however, the invention is not limited, as a matter of
course.
[Adhesive Layer Resin]
[0083] As the adhesive layer, there can be exemplified
acid-modified polyolefins such as acid-modified polypropylene,
acid-modified high-density polyethylene, acid-modified low-density
polyethylene and acid-modified ethylene/vinyl acetate copolymer, to
which only, however, the invention is in no way limited.
(Multi-Layer Structure)
[0084] The multi-layer structure of the present invention can
assume a variety of forms such as a container, a preform, a sealing
member (liner member), etc. in addition to the container closure
described above.
[0085] Concerning the containers, the above-mentioned molten resin
mass can be directly formed into articles of various shapes such as
a cup, a tray and the like relying upon the compression-forming.
Here, what is important is that the above-mentioned multi-layer
structure is formed at least in the body walls and in the bottom
portions.
[0086] Further, the preform includes the container mouth portion,
body wall and the bottom portion and it is important that the
above-mentioned multi-layer structure is formed in at least the
body wall and the bottom portion. As required, the mouth portion is
thermally crystallized and is, then, subjected to the draw-forming
such as biaxial draw blow-forming to form bottles, cups and the
like.
[0087] Further, the sealing member can be formed in a shape such as
a flat plate that can be applied to a cap shell that is separately
formed.
(Forming Conditions)
[0088] In addition to feeding the molten resin mass having the
above multi-layer structure to the compression-forming machine to
effect the compression-forming, the multi-layer structure of the
present invention can also be formed relying upon a conventional
known compression-forming method.
[0089] The temperature (die head temperature) for extruding the
molten resin may differ depending upon the kind of the resin that
is used but is, usually, desired to be in a range of Tm+20.degree.
C. to Tm+60.degree. C. based on the melting point (Tm) of the base
body resin. When the temperature is lower than the above range, the
shearing rate becomes so great that it becomes difficult to form a
uniformly melt-extruded article. When the temperature is higher
than the above range, on the other hand, the resin is deteriorated
to a large degree and the draw-down becomes very great, which is
not desirable.
[0090] Further, the surface temperature of the compression-forming
mold may be a temperature at which the molten resin is solidified
and is, usually, in a range of 10 to 50.degree. C.
EXAMPLES
[Method of Evaluation]
1. Amount of Oxygen Permeation.
[0091] A cap was fitted in a nitrogen gas atmosphere onto the
mouth-and-neck portion of a glass container of a content of 200 cc,
and an oxygen concentration in the container just after the cap was
fitted was measured by using a gas coulometer [GC-3BT, manufactured
by Shimazu Seisakusho Co.].
[0092] Next, the container to which the cap has been fitted was
left to stand in an atmosphere of a temperature of 30.degree. C.
and a humidity of 80% for 10 days, and an oxygen concentration in
the container was similarly measured. The amount the oxygen has
permeated in 10 days was calculated from the above oxygen
concentration, and an average amount of oxygen permeation per day
(cc/cap/day) was found.
Example 1
[0093] A polypropylene resin (PP) that serves as a base body resin
for forming the cap, an ethylene/vinyl alcohol copolymer (EVOH)
that serves as a first functional resin for forming the shell
layer, and a polypropylene resin that is a base body resin for
forming the core layer, were plasticized by using an extruder, and
were fed to a multi-layer die system shown in FIG. 4 to form 3 g of
a multi-layer molten resin mass of the base body resin and the
functional resin at a weight ratio of 97:3 as shown in a sectional
view of FIG. 3.
[0094] The multi-layer molten resin mass was arranged in a metal
mold cavity shown in FIG. 5, compression-formed by using a male
mold, and was cooled to form a cap shown in FIG. 2 having sizes as
described below, and was evaluated.
[0095] Height: 20 mm
[0096] Mouth diameter: 28 mm
[0097] Average thickness of the top panel: 2 mm
[0098] Average thickness of the shell layer: 0.07 mm
[0099] Average thickness of the core layer: 0.66 mm
Example 2
[0100] A cap was formed and evaluated in the same manner as in
Example 1 but by using a cyclic olefin as a second functional resin
of the core layer.
Comparative Example 1
[0101] A cap was formed and evaluated in the same manner as in
Example 1 but forming a functional resin layer of an ethylene/vinyl
alcohol copolymer (EVOH) of an average thickness of 0.14 mm in the
central portion of the thickness of the top panel to form the cap
of the multi-layer structure shown in FIG. 1 without forming the
core layer.
Comparative Example 2
[0102] A cap was formed and evaluated in the same manner as in
Example 2 but forming a functional resin layer of an ethylene/vinyl
alcohol copolymer (EVOH) having an average thickness of 0.14 mm, an
intermediate base body resin layer having an average thickness of
0.2 mm and a functional resin layer of a cyclic olefin having an
average thickness of 0.3 mm successively from the upper side in the
central portion of the thickness of the top panel to form the cap
of the multi-layer structure shown in FIG. 1. TABLE-US-00001 TABLE
1 Amount of oxygen permeation (cc/cap/day) Example 1 0.001 Example
2 0.001 Comp. Example 1 0.004 Comp. Example 2 0.004
* * * * *