U.S. patent application number 10/450536 was filed with the patent office on 2004-03-11 for leak stop plug against needle piercing and method of manufacturing the leak stop plug.
Invention is credited to Naritomi, Masanori, Shiraishi, Masao, Takahashi, Masao.
Application Number | 20040045924 10/450536 |
Document ID | / |
Family ID | 19157812 |
Filed Date | 2004-03-11 |
United States Patent
Application |
20040045924 |
Kind Code |
A1 |
Naritomi, Masanori ; et
al. |
March 11, 2004 |
Leak stop plug against needle piercing and method of manufacturing
the leak stop plug
Abstract
A pierceable stopper enhanced in elasticity so that the liquid
in a container will not leak even after a hollow needle inserted
into the container through the pierceable stopper has been removed
therefrom and a method of producing the pierceable stopper are
provided. A pierceable part (11) through which a hollow needle is
inserted into a container (2) is molded from a thermoplastic
synthetic resin elastic material. The pierceable part is
heat-treated with heated air at a temperature of from 80 to
120.degree. C. to remove the internal stress. The heat-treated
pierceable part (11) is inserted into an injection mold (20, 21). A
molten thermoplastic synthetic resin is injected into a cavity (26)
corresponding to a stopper body (10), which is defined by the
injection mold (20, 21) and the pierceable part (11), to form a
pierceable stopper (5).
Inventors: |
Naritomi, Masanori; (Tokyo,
JP) ; Shiraishi, Masao; (Tokyo, JP) ;
Takahashi, Masao; (Tokyo, JP) |
Correspondence
Address: |
WESTERMAN, HATTORI, DANIELS & ADRIAN, LLP
1250 CONNECTICUT AVENUE, NW
SUITE 700
WASHINGTON
DC
20036
US
|
Family ID: |
19157812 |
Appl. No.: |
10/450536 |
Filed: |
June 20, 2003 |
PCT Filed: |
May 22, 2002 |
PCT NO: |
PCT/JP02/04928 |
Current U.S.
Class: |
215/247 |
Current CPC
Class: |
B29C 45/1676 20130101;
B29L 2031/565 20130101; B65D 51/002 20130101; B65D 51/221 20130101;
A61J 1/1406 20130101 |
Class at
Publication: |
215/247 |
International
Class: |
B65D 039/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 9, 2001 |
JP |
2001-344260 |
Claims
What is claimed is:
1. A pierceable stopper comprising: a pierceable part pierceable
with a hollow needle, said pierceable part being formed by using a
thermoplastic synthetic resin elastic material as a base polymer,
said thermoplastic synthetic resin elastic material being a styrene
elastomer consisting essentially of a hydrogenated product of a
styrene-conjugated diene block copolymer having a weight-average
molecular weight not less than 150,000, wherein said conjugated
diene is at least one selected from isoprene and butadiene, said
pierceable part having a hardness in a range of from 20 to 80 in
terms of JIS(A) hardness and a thickness in a range of from 2
millimeters to 8 millimeters; a stopper body formed from a
thermoplastic synthetic resin having a higher rigidity than that of
the material of said pierceable part, said stopper body having an
outer peripheral portion for preventing a stress from propagating
to an outside when said pierceable part is pierced with said hollow
needle and for defining said pierceable part; and a thermowelded
joint at which said pierceable part and said stopper body are
thermowelded together; wherein said pierceable part, which has been
molded, is heated to perform a heat treatment for removing an
internal stress and then inserted into an injection mold, and a
melt of the thermoplastic synthetic resin is injected into a cavity
defined by said injection mold and said pierceable part at an
injection pressure not lower than 59 MPa to mold said stopper body,
and further, said pierceable part and said stopper body are
thermowelded together in said injection mold to form the
thermowelded joint.
2. A pierceable stopper according to claim 1, wherein said heat
treatment is carried out for a period of time in a range of from 30
minutes to 12 hours by using heated air at a temperature of from 80
to 120.degree. C.
3. A pierceable stopper according to claim 1 or 2, wherein said
thermoplastic synthetic resin elastic material is a styrene
elastomer consisting essentially of a hydrogenated product of a
styrene-conjugated diene block copolymer having a weight-average
molecular weight of from 270,000 to 400,000, wherein said
conjugated diene is at least one selected from isoprene and
butadiene.
4. A pierceable stopper according to claim 1 or 2, wherein said
thermoplastic synthetic resin elastic material is a hydrogenated
product of a styrene-isoprene-butadiene-styrene block copolymer
having a weight-average molecular weight of from 270,000 to
400,000.
5. A pierceable stopper according to claim 4, wherein said
pierceable part is formed from a mixture of said hydrogenated
product of a styrene-isoprene-butadiene-styrene block copolymer, a
paraffin oil, and a polyolefin resin.
6. A pierceable stopper according to claim 4, wherein said
thermoplastic synthetic resin is at least one selected from
polypropylenes, polyethylenes, and ABS resins.
7. A method of producing a pierceable stopper, said pierceable
stopper having: a pierceable part pierceable with a hollow needle,
said pierceable part being formed by using a thermoplastic
synthetic resin elastic material as a base polymer, said
thermoplastic synthetic resin elastic material being a styrene
elastomer consisting essentially of a hydrogenated product of a
styrene-conjugated diene block copolymer having a weight-average
molecular weight not less than 150,000, wherein said conjugated
diene is at least one selected from isoprene and butadiene, said
pierceable part having a hardness in a range of from 20 to 80 in
terms of JIS(A) hardness and a thickness in a range of from 2
millimeters to 8 millimeters; a stopper body formed from a
thermoplastic synthetic resin having a higher rigidity than that of
the material of said pierceable part, said stopper body having an
outer peripheral portion for preventing a stress from propagating
to an outside when said pierceable part is pierced with said hollow
needle and for defining said pierceable part; and a thermowelded
joint at which said pierceable part and said stopper body are
thermowelded together; said method comprising the steps of heating
said pierceable part, which has been molded, to perform a heat
treatment for removing an internal stress; inserting said
pierceable part, which has been heat-treated, into an injection
mold; injecting a melt of the thermoplastic synthetic resin into a
cavity defined by said injection mold and said pierceable part at
an injection pressure not lower than 59 MPa to mold said stopper
body; and thermowelding together said pierceable part and said
stopper body in said injection mold to form the thermowelded
joint.
8. A method of producing a pierceable stopper according to claim 7,
wherein said heat treatment is carried out at a temperature of from
80 to 120.degree. C. for a period of time in a range of from 30
minutes to 12 hours.
9. A method of producing a pierceable stopper according to claim 7
or 8, wherein said thermoplastic synthetic resin elastic material
for forming said pierceable part is a styrene elastomer consisting
essentially of a hydrogenated product of a styrene-conjugated diene
block copolymer having a weight-average molecular weight of from
270,000 to 400,000, wherein said conjugated diene is at least one
selected from isoprene and butadiene.
10. A method of producing a pierceable stopper according to claim 7
or 8, wherein said thermoplastic synthetic resin elastic material
for forming said pierceable part is a styrene elastomer consisting
essentially of a hydrogenated product of a
styrene-isoprene-butadiene-styrene block copolymer having a
weight-average molecular weight of from 270,000 to 400,000.
11. A method of producing a pierceable stopper according to claim
10, wherein said thermoplastic synthetic resin for forming said
stopper body is at least one selected from polypropylenes,
polyethylenes, and ABS resins.
12. A pierceable stopper according to claim 10, wherein said
pierceable part is formed from a mixture of said hydrogenated
product of a styrene-isoprene-butadiene-styrene block copolymer, a
paraffin oil, and a polyolefin resin.
Description
TECHNICAL FIELD
[0001] The present invention relates to a pierceable stopper used
for a liquid container into which a hollow needle can be externally
inserted through the pierceable stopper, and also relates to a
method of producing the pierceable stopper. More particularly, the
present invention relates to a pierceable stopper for a medical
liquid bottle, bag or the like filled with a liquid for medical
treatment. The pierceable stopper is made of a thermoplastic
synthetic resin elastic material and a thermoplastic synthetic
resin material and has a pierceable part enhanced in elasticity so
that it is readily pierceable with a hollow needle for injection or
intravenous drip infusion, and yet there is no leakage of medical
liquid. The present invention also relates to a method of producing
the above-described pierceable stopper.
BACKGROUND ART
[0002] Capsules filled with medical liquids for injection and
bottles or bags filled with medical liquids for intravenous drip
infusion are preferably designed so that the medical liquids
therein can be taken out or a liquid can be injected thereinto
without removing the caps or stoppers therefrom. Therefore, the
caps and stoppers are arranged so that even when they are pierced
with a hollow needle for injection or intravenous drip infusion and
the needle is temporarily pulled out, the liquids in the containers
cannot spill out, and, at the same time, foreign matter, e.g. air,
in the hospital cannot enter the containers. Such stoppers are
desirably mass-produced and reduced in cost so as to be used by an
increased number of people.
[0003] Conventionally, vulcanized rubber is used as a material for
such a stopper. However, the stopper using vulcanized rubber
involves such a danger that an additive, a polymerization solvent,
etc. in the vulcanized rubber may flow out into the medical liquid
in the container, or rubber chippings cut by a hollow needle for
injection or the like may get mixed in the medical liquid.
Accordingly, a stopper using a thermoplastic synthetic resin
elastic material ("elastic material" will hereinafter occasionally
be referred to as "elastomer") has been proposed [Japanese Patent
Application Unexamined Publication (KOKAI) No. Hei 9-173417].
[0004] The inventors of the present invention also proposed a
technique in Japanese Patent No. 3142521, Japanese Patent
Application Unexamined Publication (KOKAI) No. 2001-258991, etc.,
wherein the pierceable part of a pierceable stopper is made by
using a thermoplastic synthetic resin elastic material lower in
elasticity than rubber to prevent leakage of liquid from the
container after the removal of the inserted needle. In the
conventional pierceable stoppers, however, the strain during
molding carried out when they are produced remains in the
pierceable parts as residual stress, and this exceeds the elastic
limit. Consequently, elastic recovery force becomes unfavorably
weak. If a material exhibiting high elasticity is used to solve
this problem, the pierceable stopper becomes difficult to use
because the pierceable part is hard and offers a high resistance to
a hollow needle when stuck thereinto.
[0005] There has also been proposed a stopper comprising two layers
of thermoplastic synthetic resin elastomers. However, satisfactory
effect cannot be obtained with this stopper because there may be a
little leakage of medical liquid when the piercing conditions are
severe. Thus, the user is not always satisfied with this stopper.
Accordingly, there has been a demand for a further improved
pierceable stopper.
[0006] The present invention was made to solve the above-described
problems and to improve the above-described technique disclosed in
Japanese Patent No. 3142521 and Japanese Patent Application
Unexamined Publication (KOKAI) No. 2001-258991 by the inventors of
the present invention, thus attaining the following objects.
[0007] An object of the present invention is to provide a
pierceable stopper in which a pierceable part is previously
heat-treated after it has been molded, that is, the residual stress
in the pierceable part is resolved previously, thereby enhancing
elasticity. Thereafter, a thermoplastic synthetic resin material is
injection-molded, thereby allowing the pierceable part to recover
by the elasticity after the removal of the inserted needle, and
thus preventing leakage of liquid from the container. Another
object of the present invention is to provide a method of producing
the above-described pierceable stopper.
[0008] Still another object of the present invention is to provide
a pierceable stopper that can be produced at a reduced cost, and to
provide a method of producing the pierceable stopper.
[0009] The advantage of the pierceable stopper according to the
present invention is as follows. In the pierceable stopper, the
pierceable part, which is pierceable with a hollow needle, is
formed by using a thermoplastic synthetic resin elastic material
treated to resolve the residual stress (internal stress).
Accordingly, there is no leakage of liquid from the container when
the pierceable part is pierced with a hollow needle or after the
needle has been pulled out. Thus, there is no possibility of the
medical liquid splashing over the surroundings.
DISCLOSURE OF THE INVENTION
[0010] To attain the above-described objects, the present invention
provides the following means: A pierceable stopper according to the
present invention has a pierceable part pierceable with a hollow
needle. The pierceable part is formed by using a thermoplastic
synthetic resin elastic material as a base polymer. The
thermoplastic synthetic resin elastic material is a styrene
elastomer consisting essentially of a hydrogenated product of a
styrene-conjugated diene block copolymer having a weight-average
molecular weight not less than 150,000, wherein the conjugated
diene is at least one selected from isoprene and butadiene. The
pierceable part has a hardness in the range of from 20 to 80 in
terms of JIS(A) hardness and a thickness in the range of from 2
millimeters to 8 millimeters.
[0011] The pierceable stopper further has a stopper body formed
from a thermoplastic synthetic resin having a higher rigidity than
that of the material of the pierceable part. The stopper body has
an outer peripheral portion for preventing a stress from
propagating to the outside when the pierceable part is pierced with
the hollow needle and for defining the pierceable part.
[0012] Further, the pierceable stopper has a thermowelded joint at
which the pierceable part and the stopper body are thermowelded
together.
[0013] The pierceable part, which has been molded, is heated to
perform a heat treatment for removing an internal stress. The
heat-treated pierceable part is inserted into an injection mold,
and a melt of the thermoplastic synthetic resin is injected into a
cavity defined by the injection mold and the pierceable part at an
injection pressure not lower than 59 MPa to mold the stopper body.
Further, the pierceable part and the stopper body are thermowelded
together in the injection mold to form the thermowelded joint.
[0014] [Thermoplastic Synthetic Resin Elastic Material for
Pierceable Part]
[0015] The thermoplastic synthetic resin elastic material used as a
base polymer to form the pierceable part is a styrene elastomer
consisting essentially of a hydrogenated product of a
styrene-conjugated diene block copolymer having a weight-average
molecular weight of from 270,000 to 400,000, wherein the conjugated
diene is at least one selected from isoprene and butadiene.
[0016] Judging from the viewpoint of moldability, external
appearance and so forth, however, the thermoplastic synthetic resin
elastic material is a styrene elastomer having a weight-average
molecular weight of from 270,000 to 400,000. The molecular weight
of this elastomer is considerably high in view of the fact that the
molecular weight of styrene elastomers generally used for other use
applications is of the order of from 70,000 to 120,000.
[0017] Styrene polymers applicable to the present invention consist
essentially of a hydrogenated product of a styrene-conjugated diene
block copolymer, wherein the conjugated diene is a polymer block
comprising either butadiene or isoprene alone or a mixture of
isoprene and butadiene.
[0018] Specific examples of hydrogenated styrene-conjugated diene
block copolymers usable in the present invention are hydrogenated
styrene-butadiene-styrene (SEBS) block copolymers, hydrogenated
styrene-isoprene-styrene (SEPS) block copolymers, and hydrogenated
styrene-isoprene-butadiene-styrene (SEEPS) block copolymers. These
polymer blocks may be used alone or in the form of a mixture of two
or more of them. The use of a hydrogenated SEEPS block copolymer
for forming the pierceable part in the present invention is
particularly effective because the molecular weight of the base
polymer can be designed to be large in comparison to hydrogenated
SEBS and SEPS block copolymers.
[0019] When a mixture of isoprene and butadiene is used as the
conjugated diene, the mixing weight ratio (isoprene/butadiene) is
from (99/1) to (1/99), preferably from (90/10) to (65/35). It is
important to use a hydrogenated styrene-conjugated diene block
copolymer having a styrene content of from 5 to 50% by weight,
preferably from 8 to 45% by weight, particularly preferably from 10
to 40% by weight, a 1,2-micro structure of less than 20%,
preferably less than 15%, and a hydrogenation ratio of not less
than 85%, preferably from 97 to 100%.
[0020] The weight-average molecular weight of a thermoplastic
synthetic resin elastic material used in the present invention is
measured by GPC (Gel Permeation Chromatography) and expressed in
terms of polystyrene weight-average molecular weight as measured
under the conditions shown below. Specific measuring conditions are
as follows.
[0021] (Average Molecular Weight Measuring Conditions)
1 Equipment: 150C ALC/GPC (available from MILLIPORE, U.S.A.)
Columns: ADM/S (available from Showa Denko, Japan) 3 columns
Solvent: o-dichlorobenZene Temperature: 140.degree. C. Flow
velocity: 1 ml/min. Injected quantity: 200 .mu.l Concentration: 2
mg/ml [antioxidant 2,6-di-t-butyl-p-phenol was added in an amount
of 0.2% by weight. Concentration was measured at a wavelength of
3.42 .mu.m with an infrared spectrophotometer "MIRAN 1A"
(trademark), available from FOXBORO (U.S.A.)]
[0022] It is desirable that the readily deflectable portion should
be formed by deflecting the pierceable part in the direction of
penetration of the hollow needle during the process of molding the
stopper body. The hardness of the pierceable part should preferably
be selected within the range of from 20 to 70 in terms of JIS(A)
hardness (durometer hardness). It is preferable that the hardness
of the pierceable part should be within the range of from 45 to 65
in terms of JIS(A) hardness of the measured value obtained with a
durometer of the type A defined by JIS K6253.
[0023] It is particularly preferable that the pierceable part
should be formed from a mixture of the above-described SEEPS block
copolymer, a paraffin oil, and a polyolefin resin from the
viewpoint of hardness, compatibility and so forth.
[0024] [Structure of Pierceable Part]
[0025] The pierceable part should preferably be formed from the
above-described styrene elastomer. It is preferable that the
stopper body should be formed from a thermoplastic synthetic resin
and thermowelded to the pierceable part. The thermowelding process
may be ultrasonic welding whereby different kinds of plastic
materials are welded together by ultrasonic vibration. It is
preferable that the stopper body should be welded to the pierceable
part under pressure in an ultrasonic injection mold. The thickness
of the readily deflectable portion is desirably in the range of
from 1 to 10 millimeters, more desirably in the range of from 2 to
5 millimeters. The hardness, thickness and other structural
requirements demanded for the pierceable part are substantially the
same as in the publicly known technique disclosed in Japanese
Patent No. 3142521.
[0026] [Heat Treatment]
[0027] The heat treatment applied to the pierceable part is a
treatment for removing the internal stress. The heat treatment is
characterized by being carried out for a period of time in the
range of from 30 minutes to 12 hours by using heated air at a
temperature of from 80 to 120.degree. C. It is also possible to
obtain favorable effects by carrying out the heat treatment at a
temperature of 100 to 120.degree. C. for 1 to 2 hours. The heat
treatment may be performed in a heated liquid in place of heated
air.
[0028] [Method of Producing Pierceable Stopper]
[0029] In addition, the present invention provides a method of
producing a pierceable stopper having a pierceable part pierceable
with a hollow needle. The pierceable part is formed by using a
thermoplastic synthetic resin elastic material as a base polymer.
The thermoplastic synthetic resin elastic material is a styrene
elastomer consisting essentially of a hydrogenated product of a
styrene-conjugated diene block copolymer having a weight-average
molecular weight not less than 150,000, wherein the conjugated
diene is at least one selected from isoprene and butadiene. The
pierceable part has a hardness in the range of from 20 to 80 in
terms of JIS(A) hardness and a thickness in the range of from 2
millimeters to 8 millimeters. The pierceable stopper further has a
stopper body formed from a thermoplastic synthetic resin having a
higher rigidity than that of the material of the pierceable part.
The stopper body has an outer peripheral portion for preventing a
stress from propagating to the outside when the pierceable part is
pierced with the hollow needle and for defining the pierceable
part. Further, the pierceable stopper has a thermowelded joint at
which the pierceable part and the stopper body are thermowelded
together.
[0030] According to the pierceable stopper producing method, the
pierceable part, which has been molded, is heat-treated. The
heat-treated pierceable part is inserted into an injection mold. A
melt of the thermoplastic synthetic resin is injected into a cavity
defined by the injection mold and the pierceable part at an
injection pressure not lower than 59 MPa to mold the stopper body,
and the pierceable part and the stopper body are thermowelded
together in the injection mold to form the thermowelded joint.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 is a sectional view of the pierceable stopper
according to the present invention when it is applied to a medical
liquid bag for intravenous drip infusion.
[0032] FIG. 2 is a flowchart showing the process of producing the
pierceable stopper, in which the pierceable part is
heat-treated.
[0033] FIG. 3 is a sectional view showing a mold for forming the
pierceable stopper by injection molding process.
[0034] FIG. 4 is a sectional view showing a mold for forming the
pierceable stopper by injection molding process according to
another embodiment.
BEST MODE FOR CARRYING OUT THE INVENTION
[0035] Embodiments of the present invention will be described below
with reference to the accompanying drawings. FIG. 1 shows an
example in which the pierceable stopper according to the present
invention is applied to a medical liquid bag for intravenous drip
infusion. The structure and function of this application example
are publicly known and detailed in Japanese Patent No. 3142521,
Japanese Patent Application Unexamined Publication (KOKAI) No.
2001-258991, and so forth. The application example will be outlined
below with a view to facilitating the understanding of the present
invention. A medical liquid container 1 for intravenous drip
infusion has a container body 2 made of a film-shaped transparent
synthetic resin material, e.g. polyethylene. The container body 2
contains a medical liquid.
[0036] The container body 2 has an opening 3 formed at the top
thereof. One end of an annular connecting pipe is inserted into the
opening 3. The opening 3 and the connecting pipe 4 are thermowelded
together by ultrasonic welding or the like. One end of a pierceable
stopper 5 is inserted into and connected to the upper end of the
connecting pipe 4. The connecting pipe 4 and the pierceable stopper
5 are also thermowelded together by ultrasonic welding or other
similar means.
[0037] The pierceable stopper 5 comprises a stopper body 10, a
pierceable part 11, an external hermetic sealing film 12, and an
internal hermetic sealing film 13. The external hermetic sealing
film 12 is a kind of partition for preventing the pierceable part
11 and the outside air from coming into direct contact with each
other. The internal hermetic sealing film 13 is a partitioning
member provided to prevent the pierceable stopper 5 and the medical
liquid in the container body 2 from coming into direct contact with
each other and to maintain the airtightness of the container body
2. The internal hermetic sealing film 13 and the container body 2
are joined together by using a publicly known technique, e.g.
thermowelding using ultrasonic waves or bonding using an
adhesive.
[0038] The pierceable part 11 and the stopper body 10, which
constitute the pierceable stopper 5, are formed by using different
kinds of synthetic resin materials. The pierceable part 11 is
disposed inside the stopper body 10 and secured thereto. The
pierceable part 11 is positioned in the central portion of the
stopper body 10. The stopper body 10 and the pierceable part 11 are
integrally molded by an insert dissimilar material injection
molding process (described later). The stopper body 10 is made of a
thermoplastic synthetic resin having mechanical strength, e.g.
polypropylene (PP), polyethylene (PE), ABS resin (ABS),
polycarbonate (PC), or polyamide (PA).
[0039] It should be noted that a styrene elastomer is preferably
used as a material for the pierceable part 11 as described later,
and polypropylene (PP), polyethylene (PE) or ABS resin (ABS) is
preferably used as a material for the stopper body 10 to allow the
stopper body 10 to be thermowelded to the material of the
pierceable part 11. As a material for the pierceable part 11,
various thermoplastic synthetic resin elastic materials can be
used. Thermoplastic synthetic resin elastic materials usable in the
present invention include nylon, polyurethane, olefin, polyester
and styrene elastomers having a JIS(A) hardness of 20 to 65
degrees, which is lower than the hardness of thermoplastic
synthetic resins. One or more thermoplastic synthetic resin elastic
materials are optionally selected from those mentioned above and
used alone or in the form of a mixed elastomer.
[0040] If the JIS(A) hardness is less than 20, the material
strength is weak, so that the pierceable part 11 is likely to tear
when a hollow needle is inserted thereinto. If JIS(A) hardness of
the measured value obtained with a durometer of the type A defined
by JIS K6253 is more than 65 degrees, the material is excessively
hard and offers a high resistance to penetration of the needle.
Accordingly, operability is poor.
[0041] Among the thermoplastic synthetic resin elastic materials,
styrene elastomers are particularly preferable. Typical styrene
elastomers are hydrogenated products of SEBS
(styrene-ethylene-butylene-styrene), SEPS
(styrene-ethylene-propylene-styrene) and SEEPS
(styrene-isoprene-butadien- e-styrene) block copolymers. At least
one of these styrene elastomers is used in this embodiment. Among
the above-mentioned styrene elastomers, SEEPS highly-saturated
hydrogenated styrene elastomers are preferable.
[0042] When a styrene elastomer is applied to the present
invention, it is generally used in the form of a compound
containing one or more of the above-mentioned SEBS, SEPS and SEEPS
hydrogenated styrene elastomers as a base polymer. Raw materials to
be compounded are mixed together roughly in the following
compounding ratio:
SEBS, SEPS, SEEPS or a mixture thereof . . . 100 parts by weight
(1)
Paraffin oil . . . 50 to 300 parts by weight (20)
Polyolefin resin . . . 10 to 50 parts by weight (3)
[0043] It should be noted that 50 to 40 parts by weight of an
inorganic filler may be added to the materials (1) to (3) according
to need. Styrene elastomers applicable to the present invention,
i.e. (1) SEPS, SEBS, or a mixture thereof, are commercially
available in the name of "Septon" (trademark) available from
Kuraray Co., Ltd. (Japan), "Cleiton G (trademark) available from
Cleiton Polymer Japan (Japan), and "Rabalon" (trademark) available
from Mitsubishi Petro-Chemical Co., Ltd. (Japan). It is necessary
to select a base polymer having a specific molecular weight from
among these styrene elastomers. Paraffin oil usable as the above
(2) is as follows.
[0044] Oils having a kinematic viscosity of 200 to 800 centistokes
(cSt), preferably 500 to 600 cSt, at 40.degree. C., and an ignition
point (COC) of 200 to 400.degree. C., preferably 250 to 350.degree.
C., are suitably used. Oils are, in general, mixtures of three,
i.e. aromatic ring, naphthene ring, and paraffin chain, and
classified as follows. An oil in which the number of carbon atoms
present in the paraffin chains accounts for not less than 50% by
weight of the total number of carbon atoms is referred. An oil in
which the number of carbon atoms accounts for 30 to 45% by weight
of the total number of carbon atoms is referred to as "naphthene
oil". An oil in which the number of carbon atoms present in the
aromatic rings accounts for not less than 30% by weight of the
total number of carbon atoms is referred to as "aromatic oil".
[0045] If the pierceable part 11 is pierced with a hollow needle,
there will be no leakage from a crack, tear or cut opening which
may be made in a pierced portion thereof. When the pierceable part
11 is pierced with a hollow needle, a tear or an opening is formed
therein by the wedge action of the needle. After the formation of
the tear or opening in the pierceable part 11, the medical liquid
in the container body 2 needs to be prevented from leaking out
through the tear or the opening in a state where the needle is
stuck into the pierceable part 11 or has been pulled out from it.
The main reason for the leakage is presumed as follows. Penetration
of the needle into the pierceable part 11 causes permanent set,
more precisely, permanent compression set, to be formed around the
opening made by the insertion of the needle. Consequently, the
pierceable part 11 cannot elastically recover from the deformation,
or even if it recovers, the pierceable part 11 cannot be ensured a
sufficient elastic recovery force to close the opening.
[0046] That is, if the pierceable part 11 is ensured a sufficient
elastic recovery force to close the tear or the opening, the
leakage can be prevented. In the present invention, the problem of
leakage is solved by subjecting the pierceable part 11 to a heat
treatment, that is, a treatment for removing the internal stress.
The internal stress disorders the dimensional accuracy of the
product and also causes shrinkage, deformation and breakage. In
particular, the internal stress unfavorably limits the elasticity
required for the use application of the present invention.
[0047] The pierceable part 11 is molded from a thermoplastic
synthetic resin elastic material filled in an injection mold.
Because the thermoplastic synthetic resin elastic material is a
material having rubber-like elasticity and forcedly filled into the
injection mold, the pierceable part 11 has an orientation strain
produced in the direction of flow of the material. The strain
cannot be removed simply by removing the applied pressure. More
specifically, because it is immediately cooled to solidify in the
injection mold, the material cannot return to its original shape.
Hence, the orientation strain remains in the form of residual
stress (internal stress). According to the present invention, as
shown in FIG. 2, step B of heat-treating the pierceable part 11 is
added after step A of molding the pierceable part 11. That is, a
heat treatment (annealing) is performed after the molding process
to remove the residual stress.
[0048] The heat treatment exhibits the effect of preventing the
leakage of liquid. More specifically, because the pierceable part
11 is heated again, the internal stress is resolved, and the
orientation strain is relaxed. Consequently, the balance between
the direction of flow of the material from the gate and the
direction perpendicular to the material flow direction is bettered.
Thus, the leakage of liquid is prevented effectively. That is, the
ratio of MD (Machine Direction) to TD (Transverse direction)
becomes close to 1. In the heat treatment, the pierceable part 11
is heated in an atmosphere of heated air at a temperature roughly
in the range of from 80 to 120.degree. C. for a period of time in
the range of from 30 minutes to 12 hours, although the
heat-treating conditions depend on the kind of resin used. The heat
treatment can be performed with a simple, common device, e.g. an
oven.
[0049] Accordingly, the residual stress can be removed at a reduced
cost without requiring costly equipment. By removing the strain,
the elasticity of the material constituting the pierceable part 11
is recovered. As a result, the elastic recovery force of the
pierceable part 11 is increased. Consequently, when the pierceable
part 11 is pierced with a hollow needle or after the needle has
been pulled out from it, the tear or cut opening made in the
pierced portion thereof is closed by the enhanced elasticity of the
material. Accordingly, there will be no leakage of medical liquid
from the tear or the opening. In actual practice, a favorable
result can be obtained by performing the heat treatment at a
temperature in the range of from 100 to 120.degree. C. for a period
of time in the range of from 1 to 2 hours. Subsequently, the
pierceable part 11, which has been subjected to the removal of
strain, is inserted into a mold for injection molding (C in FIG.
2).
[0050] After the pierceable part 11 has been placed in a
predetermined position, a thermoplastic synthetic resin is injected
into the mold to form a stopper body 10 (D in FIG. 2). Thus, a
pierceable stopper 5 is formed (E in FIG. 2). A specific molding
process of this process will be shown below with reference to FIG.
3. It should be noted that a forced moisture absorption treatment
(moisture conditioning treatment) should desirably be carried out
in combination with the heat treatment according to the kind of
resin used. The forced moisture absorption treatment allows the
dimensional stability and toughness to be maintained.
[0051] FIG. 3 shows a section of a mold assembly for injection
mold. The heat-treated pierceable part 11 is inserted into the mold
assembly for injection molding. The mold assembly is adapted to
mold a stopper body 10 by injection molding to form a pierceable
stopper 5. The mold assembly is formed from a stationary mold
element 20 and a movable mold element 21. The stationary mold
element 20 is provided with a gate 22 and a runner 23 communicating
with the gate 22. When the stationary mold element 20 and the
movable mold element 21 are in a closed position, a first cavity 25
is defined therebetween. The pierceable part 11, which has
previously been molded and subjected to strain removal, is inserted
into the first cavity 25.
[0052] Accordingly, a second cavity 26 is defined between the
stationary mold element 20, the movable mold element 21 and the
pierceable part 11. The second cavity 26 is a cylindrical space for
forming the stopper body 10. A molten thermoplastic synthetic resin
for forming the stopper body 10 is injected into the second cavity
26, thereby forming the stopper body 10. The molten thermoplastic
synthetic resin forms the stopper body 10 while applying pressure
to the pierceable part 11 from the outer periphery thereof. In
other words, the pierceable stopper 5 is formed in a state where
the pierceable part 11 is compressed.
[0053] As the injection pressure for the thermoplastic synthetic
resin, such a pressure is applied as causes a larger amount of
volume reduction than the amount of volume reduction caused by the
natural shrinkage of a melt, a semi-melt or a solid due to a
temperature drop. More specifically, the resin melt is injected at
a pressure higher than the normal injection pressure regarded as
the optimum injection condition for the thermoplastic synthetic
resin. When the viscosity of the thermoplastic synthetic resin is
high, the injection molding pressure is set at a slightly higher
level. It is desirable that the thermoplastic synthetic resin melt
should be injected at an injection pressure not lower than 59 MPa
to form the stopper body 10.
[0054] Meanwhile, the stopper body 10 and the pierceable part 11
are thermowelded together in the injection mold by melting the
surface of the thermoplastic synthetic resin elastic material of
the pierceable part 11 with the heat of the molten thermoplastic
synthetic resin for forming the stopper body 10. When the
pierceable part 11 is pierced with a hollow needle, even if the
pierced portion is cut open, the opening is closed by the
elasticity recovered by the strain removal and an elastic recovery
force derived from the compressive internal stress. Therefore,
there is no possibility of leakage of the medical liquid from the
container. In addition, the thermowelded joint prevents the leakage
of liquid even more effectively.
[0055] (Other Embodiments)
[0056] FIG. 4 is a sectional view showing a production process in a
case where the pierceable part is different in shape from the
above. In this example, a pierceable part 30 has a recessed portion
31. The pierceable part 30 is pressurized in such a manner as to be
clamped at the outer periphery thereof by the pressure applied by
the injected molten resin for forming a stopper body 39. Thus, the
pierceable part 30 is compressed by the injection pressure. The
mold structure will be described below. A previously molded
pierceable part 30 has been inserted into a first cavity 32. A
cylindrical slide core 33 has been inserted into the recessed
portion 31 of the pierceable part 30.
[0057] The slide core 33 is movable into the recessed portion 31.
The amount to which the slide core 33 projects into the recessed
portion 31 is adjustable. A second cavity 36 is defined between a
stationary mold element 34, a movable mold element 35 and the
pierceable part 30 to form a space for forming the stopper body 39
in the same way as the above. In addition, a gap S is formed
between the slide core 33 and the recessed portion 31 of the
pierceable part 30 placed in the first cavity 32. A molten
thermoplastic synthetic resin is injected into the second cavity 36
of the above-described mold structure through a runner 37 and a
gate 38 under the same conditions as the above.
[0058] The pierceable part 30 is deformed by the compressive
pressure of the injected resin to fill the gap S provided in the
recessed portion 31 of the pierceable part 30. Therefore, when the
pierceable stopper is removed from the mold after the injection
molding process, the pierceable part 30 is elastically deformed,
although the deformation is only slight. The recessed portion of
the pierceable part 30 forms locally a readily deformable portion.
Accordingly, when the pierceable part 30 is pierced with a hollow
needle for intravenous drip infusion, the recessed portion 31 is
deformed so as to surround the needle and to come in surface
contact with the outer surface of the needle. Accordingly, the
liquid is unlikely to leak. The pierceable part 30 having the
recessed portion 31 should also be heated-treated before the
stopper body 39 is formed by injection molding. By doing so, the
above-described leak preventing effect is further enhanced.
[0059] It should be noted that containers to which the present
invention is applicable are not limited to those of the type
adapted to take out a liquid therefrom. The present invention is
also applicable to containers of the type that a liquid is
externally injected thereinto through a hollow needle.
EXPERIMENTAL EXAMPLES
[0060] An experiment was carried out under the following conditions
to confirm the performance of the pierceable stopper 5 produced
according to the above-described first embodiment. The pierceable
part 11 was formed by using a styrene elastomer as a base polymer,
i.e. "Septon 4077 " (trademark), available from Kuraray Co., Ltd.
(consisting essentially of SEEPS and having a molecular weight of
300,000). The styrene elastomer was used in the form of a compound
formed by kneading Septon 4077, a paraffin oil and polypropylene in
the mixing ratio of 40:50:10 with a twin-screw extruder. The
hardness of the pierceable part was 49 in terms of JIS(A)
hardness.
[0061] The stopper body 10 was molded under the following molding
conditions by using polypropylene (BC03C, available from Nippon
Polychem Corp.) as a thermoplastic synthetic resin.
[0062] The injection molding conditions for the stopper body 10
were as follows. The injection temperature was 210.degree. C., and
the injection pressure was 78 MPa (800 kgf/cm.sup.2). The injection
molding conditions for the pierceable part 11 were as follows. The
injection temperature was 200.degree. C., and the injection
pressure was 49 MPa (500 kgf/cm.sup.2). The wall thickness of the
pierceable part 11 was 4.8 millimeters. The heat-treating
conditions were as follows. The resin temperature was 115.degree.
C., and the heating time was 1 hour or 8 hours.
[0063] Table 1 below shows the results of a liquid leakage test. In
the test, each pierceable stopper was pierced with a plastic needle
for intravenous drip infusion having a diameter of 4 millimeters,
and left to stand for 1 hour or 5 hours under ordinary temperature
conditions. Then, the condition of leakage after the removal of the
needle was visually judged. The test was carried out 5 times for
each of the test conditions concerning the period of time of
piercing with the needle, i.e. 1 hour, and 5 hours.
2TABLE 1 Results of Liquid Leakage Test Period of time of piercing
with Heat-treating Test results needle conditions (N = 5) 1 hour
Not heat-treated .DELTA., .DELTA., .DELTA., .DELTA., .DELTA.
115.degree. C., 1 hour .circleincircle., .DELTA., .circleincircle.,
.circleincircle., .circleincircle. 115.degree. C., 8 hours
.circleincircle., .circleincircle., .circleincircle.,
.circleincircle., .circleincircle. 5 hours Not heat-treated
.DELTA., .DELTA., .DELTA., X, .DELTA. 115.degree. C., 1 hour
.circleincircle., .DELTA., .DELTA., .circleincircle.,
.circleincircle. 115.degree. C., 8 hours .circleincircle.,
.circleincircle., .circleincircle., .circleincircle.,
.circleincircle. Notes: .circleincircle. No leakage of liquid
.DELTA. A little leakage of liquid X Some leakage of liquid
[0064] Table 2 below shows the results of the test carried out on
pierceable stoppers produced under injection pressure and
heat-treating conditions different from those for the pierceable
stoppers in Table 1 under the same testing conditions as in the
case of Table 1.
3TABLE 2 Results of Liquid Leakage Test Period of time of Heat-
piercing treating Injection pressure Test results with needle
conditions for stopper body (n = 5) 1 hour 115.degree. C. 39 MPa
(Comp. Ex.) X, X, .DELTA., .DELTA., .DELTA. 3 hours 59 MPa
(Example) .DELTA., .circleincircle., .circleincircle.,
.circleincircle., .circleincircle. 108 MPa (Example)
.circleincircle., .circleincircle., .circleincircle.,
.circleincircle., .circleincircle. Notes: .circleincircle. No
leakage of liquid .DELTA. A little leakage of liquid X Some leakage
of liquid
* * * * *