U.S. patent application number 11/577534 was filed with the patent office on 2008-03-20 for hinge cap having biodegradability.
This patent application is currently assigned to MIKASA INDUSTRY CO., LTD.. Invention is credited to Kunio Murakami, Manabu Sakamoto.
Application Number | 20080067141 11/577534 |
Document ID | / |
Family ID | 36227823 |
Filed Date | 2008-03-20 |
United States Patent
Application |
20080067141 |
Kind Code |
A1 |
Murakami; Kunio ; et
al. |
March 20, 2008 |
Hinge Cap Having Biodegradability
Abstract
A hinge cap comprising a cap body composed of a top wall, an
ejection port provided in the top wall and a sidewall suspending
from the circumferential edge of the top wall, and an upper lid
hinged to the cap body and closing the ejection port, characterized
in that the cap is composed of polyalkylene alkanoate resin having
a flexural elastic modulus of 200-900 MPa, more preferably 300-800
MPa.
Inventors: |
Murakami; Kunio; (Nara,
JP) ; Sakamoto; Manabu; (Nara, JP) |
Correspondence
Address: |
PRICE HENEVELD COOPER DEWITT & LITTON, LLP
695 KENMOOR, S.E.
P O BOX 2567
GRAND RAPIDS
MI
49501
US
|
Assignee: |
MIKASA INDUSTRY CO., LTD.
53, OAZA TERADO, KORYO-CHO
KITAKATSURAGI-GUN, NARA
JP
635-0817
|
Family ID: |
36227823 |
Appl. No.: |
11/577534 |
Filed: |
October 19, 2005 |
PCT Filed: |
October 19, 2005 |
PCT NO: |
PCT/JP05/19646 |
371 Date: |
April 19, 2007 |
Current U.S.
Class: |
215/235 |
Current CPC
Class: |
C08G 63/16 20130101;
C08K 5/20 20130101; B65D 47/0809 20130101; Y02W 90/10 20150501;
B65D 65/466 20130101; Y02W 90/13 20150501; C08K 5/20 20130101; C08L
67/00 20130101 |
Class at
Publication: |
215/235 |
International
Class: |
B65D 47/08 20060101
B65D047/08 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 29, 2004 |
JP |
2004-316187 |
Nov 12, 2004 |
JP |
2004-329454 |
Claims
1-12. (canceled)
13. A hinge cap comprising: a cap body comprising a top wall, an
ejection port formed in the top wall and a side wall suspending
from a circumferential edge of the top wall; and an upper lid
connected with the cap body via a hinge for closing the ejection
port; wherein the cap body and the upper lid are biodegradable and
the cap is made of a polyalkylene alkanoate resin having a flexural
elastic modulus of from 200 to 900 MPa.
14. The hinge cap according to claim 13, wherein the cap is made of
a polyalkylene alkanoate resin and the flexural elastic modulus is
from 300 to 800 MPa.
15. The hinge cap according to claim 13, wherein the polyalkylene
alkanoate resin is polybutylene succinate, its copolymer or a
mixture thereof.
16. The hinge cap according to claim 14, wherein the polyalkylene
alkanoate resin is polybutylene succinate, its copolymer or a
mixture thereof.
17. The hinge cap according to claim 15, wherein the copolymer of
the polybutylene succinate is polybutylene succinate adipate.
18. The hinge cap according to claim 16, wherein the copolymer of
the polybutylene succinate is polybutylene succinate adipate.
19. The hinge cap according to claim 13, wherein the polyalkylene
alkanoate resin contains from 0.01 to 5 parts by weight of a fatty
acid, a fatty acid amide or a mixture of a fatty acid and a fatty
acid amide, per 100 parts by weight of the polyalkylene
alkanoate.
20. The hinge cap according to claim 14, wherein the polyalkylene
alkanoate resin contains from 0.01 to 5 parts by weight of a fatty
acid, a fatty acid amide or a mixture of a fatty acid and a fatty
acid amide, per 100 parts by weight of the polyalkylene
alkanoate.
21. The hinge cap according to claim 15, wherein the polyalkylene
alkanoate resin contains from 0.01 to 5 parts by weight of a fatty
acid, a fatty acid amide or a mixture of a fatty acid and a fatty
acid amide, per 100 parts by weight of the polyalkylene
alkanoate.
22. The hinge cap according to claim 13, wherein the polyalkylene
alkanoate resin contains from 1 to 10 parts by weight of an
antiblocking agent, per 100 parts by weight of the polyalkylene
alkanoate.
23. The hinge cap according to claim 14, wherein the polyalkylene
alkanoate resin contains from 1 to 10 parts by weight of an
antiblocking agent, per 100 parts by weight of the polyalkylene
alkanoate.
24. The hinge cap according to claim 15, wherein the polyalkylene
alkanoate resin contains from 1 to 10 parts by weight of an
antiblocking agent, per 100 parts by weight of the polyalkylene
alkanoate.
25. The hinge cap according to claim 13, wherein the polyalkylene
alkanoate resin contains from 0.1 to 10 parts by weight of a
hydrolysis inhibitor, per 100 parts by weight of the polyalkylene
alkanoate.
26. The hinge cap according to claim 14, wherein the polyalkylene
alkanoate resin contains from 0.1 to 10 parts by weight of a
hydrolysis inhibitor, per 100 parts by weight of the polyalkylene
alkanoate.
27. The hinge cap according to claim 15, wherein the polyalkylene
alkanoate resin contains from 0.1 to 10 parts by weight of a
hydrolysis inhibitor, per 100 parts by weight of the polyalkylene
alkanoate.
28. The hinge cap according to claim 13, wherein the hinge includes
a snap function in turning the upper lid relative to the cap
body.
29. The hinge cap according to claim 28, wherein the hinge
comprises a thin hinge connecting the side wall of the cap body and
the side wall of the upper lid, and a pair of elastic connection
plates connecting the side wall of the cap body and the side wall
of the upper lid on both sides of the thin hinge.
30. The hinge cap according to claim 29, wherein the thin hinge and
the elastic connection plates are integrally formed via a thin
film.
31. The hinge cap according to claim 13, wherein a retention ratio
of a tensile breaking stress of the hinge after opening and closing
the upper lid 3,000 times is 30% or more.
32. The hinge cap according to claim 13, wherein a retention ratio
of a tensile breaking stress of the hinge after opening and closing
the upper lid 3,000 times is 50% or more.
Description
TECHNICAL FIELD
[0001] The present invention relates to a cap made of a synthetic
resin having a biodegradability. More specifically, it relates to a
hinge cap having a biodegradability.
BACKGROUND ART
[0002] Examples of this type of the cap which has been so far used
include a hinge cap in which a cap body and an upper lid are
connected with a hinge having a thin portion (refer to, for
example, Patent Document 1), and a snap hinge cap having a snap
function in which a cap body and an upper lid are connected with a
pair of elastic connection plates on both sides of a hinge having
the thin portion (refer to, for example, Patent Document 2).
[0003] Patent Document 1: JP-Utility Model publication
S49-26863
[0004] Patent Document 2: JP-Patent Appln. publication
H08-301329
[0005] Since the upper lid is connected with the cap body in these
hinge caps, there is no fear of losing the upper lid, and
opening/closing operation by one hand is possible, which is very
convenient in use. Further, in the snap hinge cap, there is no need
to open or close the lid with force because of the snap function (a
biasing force) of the elastic connection plates.
[0006] By the way, these hinge caps have been so far formed of a
synthetic resin such as polyethylene or polypropylene. However,
such polyolefinic polymers have little degradability in natural
environment. These polymers have been problematic in view of
environmental conservation because they remain semipermanently in
the ground after having been discarded and buried.
[0007] A cap formed of polylactic acid having a biodegradability is
disclosed in JP-patent appln. publication H06-105887. However, when
a polylactic acid resin is used in a hinge cap, there is a problem
that a hinge strength is decreased while repeating opening/closing
operation of an upper lid so that the hinge is liable to break.
DISCLOSURE OF THE PRESENT INVENTION
[0008] The present invention aims to provide a hinge cap having a
biodegradability in which when opening/closing operation of an
upper lid is repeated, a hinge strength is retained and the hinge
is hardly broken similarly to the hinge cap made of polyethylene or
polypropylene which has been so far used. Further, it aims to
provide a hinge cap having a biodegradability with a snap function
imparted.
[0009] The present inventors have assiduously conducted
investigations to solve the foregoing problems, and have
consequently found that a hinge cap retaining a hinge strength even
in repeating opening/closing operation of an upper lid and
excellent in snap function can be provided by forming the hinge cap
with a polyalkylene alkanoate resin having a specific flexural
elastic modulus. This finding has led to the completion of the
present invention.
[0010] The present invention provides a hinge cap having a
biodegradability, which comprises a cap body comprising a top wall,
an ejection port formed in the top wall and a side wall suspending
from a circumferential edge of the top wall, and an upper lid
connected with the cap body via a hinge for closing the ejection
port, characterized in that the cap is made of a polyalkylene
alkanoate resin having a flexural elastic modulus of from 200 to
900 MPa. From the standpoint of retaining the hinge strength after
the opening/closing operation of the upper lid, it is preferable
that the flexural elastic modulus of the polyalkylene alkanoate
resin used in the hinge cap of the present invention is from 300 to
800 MPa. It is especially preferable that the polyalkylene
alkanoate resin used in the hinge cap of the present invention has
the flexural elastic modulus of from 300 to 600 MPa. The present
invention is characterized in that the polyalkylene alkanoate resin
is polybutylene succinate, its copolymer or a mixture thereof. As
an example of the copolymer of polybutylene succinate, polybutylene
succinate adipate is mentioned. Other copolymers are of course
available. The polyalkylene alkanoate resin used in the hinge cap
of the present invention may contain from 0.01 to 5 parts by weight
of a fatty acid, a fatty acid amide or a mixture of a fatty acid
and a fatty acid amide, per 100 parts by weight of the polyalkylene
alkanoate. The polyalkylene alkanoate resin used in the hinge cap
of the present invention may contain from 1 to 10 parts by weight
of an antiblocking agent, per 100 parts by weight of the
polyalkylene alkanoate. It is advisable that the polyalkylene
alkanoate resin used in the hinge cap of the present invention may
contain from 0.1 to 10 parts by weight of a hydrolysis inhibitor,
per 100 parts by weight of the polyalkylene alkanoate. The hinge of
the hinge cap of the present invention may be adapted to have a
snap function in turning the upper lid relative to the cap body.
The hinge of the hinge cap of the present invention comprises a
thin hinge by which to connect a side wall of the cap body and a
side wall of the upper lid and a pair of elastic connection plates
by which to connect the side wall of the cap body and the side wall
of the upper lid on both sides of the thin hinge, and it may be
adapted such that the elastic connection plates have a snap
function in turning the upper lid relative to the cap body. The
hinge of the hinge cap of the present invention also includes one
in which the thin hinge and the elastic connection plates are
integrally formed via a thin film. The hinge cap of the present
invention is characterized in that a retention ratio of a tensile
breaking stress of the hinge after opening and closing the upper
lid 3,000 times is 30% or more. In the hinge cap of the present
invention, it is advisable that the retention ratio of the tensile
breaking stress of the hinge after opening and closing the upper
lid 3,000 times is 50% or more.
[0011] The hinge cap comprising the polyalkylene alkanoate resin
having the flexural elastic modulus of from 200 to 900 MPa in the
present invention still retains a prescribed hinge strength in
opening and closing the upper lid repeatedly. Further, a sealing
retention is secured between a port of a container and the cap, so
that the cap excellent in basic performance as a packaging
container can be provided. Moreover, since it has an excellent
biodegradability under conditions of forming a compost or the like
in natural environment, it can be an eco-friendly packaging
material.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a plan view of a hinge cap used in Example of the
present invention.
[0013] FIG. 2 is a side view of a hinge cap shown in FIG. 1 of the
present invention.
[0014] FIG. 3 is a plan view of a hinge cap used in another Example
of the present invention.
[0015] FIG. 4 is a sectional side view of the hinge cap shown in
FIG. 3 of the present invention.
BEST MODE FOR CARRYING OUT THE PRESENT INVENTION
[0016] The present invention is described in detail below.
[0017] The present invention is characterized in that the hinge cap
in which the cap body and the upper lid are connected via the hinge
is formed of the polyalkylene alkanoate resin having the flexural
elastic modulus of from 200 to 900 MPa, whereby the
biodegradability is imparted to the cap and the hinge strength is
retained in repeatedly conducting the opening/closing operation of
the upper lid which is most required for the hinge cap.
[0018] The polyalkylene alkanoate resin used in the present
invention is characterized in that the flexural elastic modulus
according to JIS K7171 is from 200 to 900 MPa. When the flexural
elastic modulus is more than 900 MPa, the hinge might be broken in
repeatedly opening and closing the upper lid. When it is less than
200 MPa, deformation of the cap due to external stress is
increased. Accordingly, these are undesirable. Moreover, in the
snap hinge cap, the snap function is decreased. The flexural
elastic modulus of the polyalkylene alkanoate resin is preferably
from 300 to 800 MPa, especially preferably from 300 to 600 MPa.
[0019] Regarding the polyalkylene alkanoate resin used in the
composition of the present invention, a resin obtained by
condensing one or more of the following aliphatic polyhydric
alcohols and one or more of the following aliphatic polybasic acids
(or derivatives thereof) can optionally be used.
[0020] Examples of the aliphatic polyhydric alcohols as one of the
materials of the polyalkylene alkanoate resin used in the present
invention include ethylene glycol, 1,4-butanediol, 1,6-hexanediol,
1,8-octylene glycol, 1,10-decamethylene glycol, 1,4-cyclohexane
dimethanol and the like. Of these, ethylene glycol, 1,4-butanediol
and 1,4-cyclohexane dimethanol are preferable in consideration of
properties of the resulting polyalkylene alkanoate resin.
[0021] Examples of the aliphatic polybasic acids (or derivatives
thereof) as another material of the polyalkylene alkanoate resin
used in the present invention include succinic acid, succinic
anhydride, adipic acid, sebacic acid, dodecanedicarboxylic acid,
1,4-cyclohexanedicarboxylic acid and the like. Of these, succinic
acid and adipic acid are preferable in consideration of properties
of the resulting biodegradable aliphatic polyester resin. Further,
as a copolymerizable component, aromatic polybasic acids such as
terephthalic acid may be used in combination.
[0022] Examples of the polyalkylene alkanoate resin which is
advantageous in the present invention include polybutylene
succinate which is a dehydrative condensation product of
1,4-butanediol and succinic acid, polybutylene succinate adipate
which is a dehydrative condensation product of 1,4-butanediol,
succinic acid and adipic acid, and the like. Incidentally, as these
polyalkylene alkanoate resins, it is advisable to use
high-molecular compounds obtained by using a chain extender such as
lactic acid, a polyvalent isocyanate or an acid anhydride. Further,
a mixture of polybutylene adipate terephthalate obtained by
dehydrative condensation of 1,4-butanediol, adipic acid and
terephthalic acid with the polybutylene succinate and the
polybutylene succinate adipate is mentioned. The foregoing
polyalkylene alkanoate resins or the mixtures thereof which are
mixed with other biodegradable resins such as starch are also
available. In this case, the components are mixed such that the
final flexural elastic modulus of the mixture is from 200 to 900
MPa, preferably from 300 to 800 MPa, more preferably from 300 to
600 MPa. As a mixing method of the mixture, known methods such as
dry blending of pellets and melt kneading with an extruder can be
employed.
[0023] In the hinge cap of the present invention, it is advisable
to incorporate a lubricant in an amount of from 0.01 to 5 parts by
weight per 100 parts by weight of the polyalkylene alkanoate for
improving a mold releasability of the resin at the time of molding.
In case of the molding by injection molding, it is required to
consider a releasability from a mold for forming a molded article.
For this reason, the specific amount of the lubricant is
incorporated in the cap of the present invention, whereby the mold
releasability in the molding can be improved to increase a
moldability.
[0024] As a merit of containing the lubricant, a property of biting
the resin into a screw at the time of the molding can be
improved.
[0025] When the specific amount of the lubricant is incorporated in
charging the resin into a molding machine, the resin smoothly flows
within the screw. However, when charging the lubricant in an amount
of more than the specific range, the biting property rather worsens
to cause poor molding.
[0026] As the lubricant, a so-called internal lubricant for
imparting an internal lubricity and an external lubricant for
imparting an external lubricity can both be used, and a combination
of these is also available. As the lubricant used in the present
invention, all of lubricants which are generally used in molding a
resin can be applied. Especially when the resin of the present
invention is used in food packages, it is advisable to use resins
which are approved as food additives.
[0027] Specifically, it is possible to use fatty acids such as
stearic acid proposed in JP-patent appln. publication H08-27363,
fatty acid amides such as erucic acid amide, methylenebisstearic
acid amide, ethylenebisstearic acid amide, ethylenebispalmitic acid
amide and ethylenebisoleic acid amide or mixtures of the foregoing
fatty acids and fatty acid amides.
[0028] It is advisable to incorporate, in addition to the foregoing
lubricant, from 1 to 10 parts by weight of an antiblocking agent
for roughening the surface of the molded product of the cap, per
100 parts by weight of the polyalkylene alkanoate, to increase the
surface roughness and improve the mold releasability and for
adjusting the biting property of the resin to improve the
moldability. As the antiblocking agent, known antiblocking agents
are available, and talc particles can advantageously be used.
[0029] The addition of the lubricant and the antiblocking agent may
be either internal addition in which a master batch containing
these components at relatively high concentrations is prepared and
incorporated or external addition in which the lubricant and the
antiblocking agent are directly added to pellets.
[0030] In the present invention, it is further advisable to
incorporate from 0.1 to 10 parts by weight of a hydrolysis
inhibitor for inhibiting the hydrolysis, per 100 parts by weight of
the polyalkylene alkanoate. Since the hinge cap is often used for
packaging a food seasoning solution containing water, a resistance
to hydrolysis is required. In the present invention, the resistance
to hydrolysis can be improved without impairing the
biodegradability inherent in the biodegradable aliphatic polyester
resin by incorporating the specific amount of the hydrolysis
inhibitor. As the hydrolysis inhibitor, its type is not
particularly limited so long as the hydrolysis can be
inhibited.
[0031] As the hydrolysis inhibitor, for example, at least one of
the groups consisting of carbodiimide compounds, surface-treated
inorganic fillers, laminar silicic acid salts, hydrophobic waxes,
hydrophobic plasticizers and olefinic resins proposed in JP-Patent
No. 3514736 and JP-pat-appln. pub. 2003-165917 is selected.
[0032] An example of the hinge cap of the present invention is
described in detail below by referring to the attached
drawings.
[0033] The hinge cap of the present invention comprises, as shown
in, for example, FIGS. 1 and 2, a cap body 1 comprising a top wall
3, an ejection port 5 formed in the top wall and a cylindrical side
wall 4 suspending from a circumferential edge of the top wall, and
an upper lid 2 having a cylindrical side wall with the same
diameter as that of the side wall of the cap body. The side walls
of the cap body and the upper lid are integrally connected via a
thin hinge 6 and a pair of elastic connection plates 8, 8.
[0034] The thin hinge 6 is radially connected with the respective
side walls of the cylindrical cap body 1 and the upper lid 2, and
the pair of the elastic connection plates 8 is formed on the right
and left of the thin hinge 6. Further, a thin film 9 is provided
between the thin hinge 6 and the elastic connection plates 8, and
both are integrally formed.
[0035] When the upper lid 2 is open as shown in FIGS. 1 and 2, the
upper surface of the thin hinge 6 is formed nearly flat, and a thin
portion 7 is formed on its upper surface in a direction crossing
the middle position between the cap body 1 and the upper lid 2. The
thin portion 7 is bent when the upper lid 2 is opened or
closed.
[0036] The pair of the elastic connection plates 8, 8 is connected
with the respective side walls of the cap body 1 and the upper lid
2 via a bending portion 10 adjacent to the right and left of the
thin hinge 6. While the upper lid 2 is open, the plates are
extended horizontally or slightly curved upward. The elastic
connection plate 8 is a thin plate having a nearly uniform
thickness and an elasticity, and imparts a snap function in opening
or closing the upper lid.
[0037] The thin film 9 has, like the elastic connection plate 8, a
snap function. The structure of the hinge is not limited to the
foregoing mode. A structure in which an elastic connection plate 8a
is located in the middle of a pair of right and left thin hinges
6a, 6a as shown in FIGS. 3 and 4 is also available. Further, a
structure in which the thin hinge 6 is separated from the pair of
the elastic connection plates 8, 8 in FIGS. 1 and 2 is also
available. A known hinge mode can properly be employed. A hinge cap
comprising a thin hinge alone without having a snap function is
also included in the present invention.
[0038] A hinge cap A' of the present invention shown in FIGS. 3 and
4 comprises a cap body 1a comprising a top wall 3a, an ejection
port 5a provided in the top wall and a cylindrical side wall 4a
suspending from a circumferential edge of the top wall, and an
upper lid 2a with a cylindrical side wall having the same diameter
as that of the side wall of the cap body. The side walls of the cap
body and the upper lid are integrally connected via the pair of
right and left thin hinges 6a, 6a and the elastic connection plate
8a.
[0039] The upper surfaces of the pair of the right and left thin
hinges 6a, 6a are formed nearly flat, as shown in FIGS. 3 and 4,
when the upper lid 2a is open. A thin portion 7a is formed on the
upper surfaces thereof in a direction crossing a middle position
between the cap body 1a and the upper lid 2a. The thin portion 7a
is bent when the upper lid 2a is opened or closed. The elastic
connection plate 8a is located in the middle of the pair of the
right and left thin hinges 6a, 6a, and connected with the
respective side walls of the cap body 1a and the upper lid 2a via a
bending portion 10a. The elastic connection plate 8a is a thin
plate with a nearly uniform thickness having an elasticity, and
imparts a snap function when opening or closing the upper lid.
[0040] The hinge cap is installed on a container by, for example,
thread engagement between a male thread formed on an outer
periphery of a mouth portion of the container not shown and a
female thread formed in an inner peripheral surface of the side
wall of the cap body. The installation of the cap on the container
is not limited to the foregoing method. So-called capping
installation is also available in which an engagement protrusion
which is engaged with an annular projection formed on the outer
periphery of the mouth portion of the container is formed on an
inner surface of the side wall of the cap body and installed on the
mouth portion by capping.
[0041] The hinge cap of the present invention is characterized in
that in the measurement of a hinge strength (tensile breaking
stress) to be described later, a retention ratio of a hinge
strength after opening and closing the upper lid 3,000 times is 30%
or more. When the retention ratio of the hinge strength is less
than 30%, the thin hinge portion or the bending portion is liable
to break when repeatedly opening and closing the upper lid, which
is undesirable. Preferably, the retention ratio of the hinge
strength is 50% or more.
EXAMPLES
[0042] The present invention is illustrated more specifically below
by referring to Examples and Comparative Example. However, the
present invention is not limited to these Examples. The flexural
elastic modulus of the polyalkylene alkanoate resin used in
Examples was measured according to JIS K7171 using test pieces
formed by injection molding.
[0043] (Cap)
[0044] A hinge cap A shown in FIG. 1 was molded with an injection
molding machine (FE120, manufactured by Nissei Jushi Kogyo K.K.)
under conditions of a cylinder temperature of 175.degree. C., an
injection pressure of 110 MPa and a molding cycle of 18
seconds.
[0045] (Measurement of a Hinge Strength)
[0046] Operation of opening and closing an upper lid of the hinge
cap obtained by injection molding was repeated 3,000 times at an
angle of from 0 to 180.degree.. Subsequently, the cap body was
fixed on a stand of a tensile tester such that the upper lid and
the cap body were arranged at an angle of 180.degree., and the
upper lid was pulled vertically upward at a pulling rate of 300
mm/min to measure the hinge strength. This hinge strength was then
compared with the hinge strength of the hinge cap which was not
subjected to the opening/closing operation of the upper lid.
Example 1
[0047] A hinge cap A shown in FIG. 1 was injection-molded using a
resin comprising 100 parts by weight of polybutylene succinate, 2
parts by weight of erucic acid amide and 1.5 parts by weight of bis
(dipropylphenyl) carbodiimide and having a flexural elastic modulus
of 550 MPa. After the molding, the cap was stored at room
temperature for 3 days, and the hinge strength was then measured,
and found to be 96.5N. The snap function of the hinge was still
good after opening and closing the upper lid. Subsequently, a hinge
strength of a hinge cap without opening and closing the upper lid
was measured, and found to be 182N. Upon comparing both the hinge
strengths, the retention ratio of the hinge strength was 53%.
Further, in order to evaluate the resistance to hydrolysis of the
cap, the cap was stored at room temperature for 3 days after the
molding, and then dipped in warm water of 45.degree. C. for 2
months. After the dipping, the appearance of the cap and the snap
function of the hinge were confirmed. A change in appearance was
not observed, and the snap function was also maintained.
Example 2
[0048] A hinge cap A' shown in FIG. 3 was injection-molded using a
resin comprising 100 parts by weight of polybutylene succinate
adipate and 2 parts by weight of erucic acid amide and having a
flexural elastic modulus of 350 MPa. After the molding, the cap was
stored at room temperature for 3 days, and the hinge strength was
then measured, and found to be 85.1N. Subsequently, a hinge
strength of a hinge cap without opening and closing the upper lid
was measured, and found to be 127N. Upon comparing both the hinge
strengths, the retention ratio of the hinge strength was 67%.
Comparative Example 1
[0049] A hinge cap shown in FIG. 1 was molded using a resin
comprising 100 parts by weight of polylactic acid and 0.2 part by
weight of erucic acid amide and having a flexural elastic modulus
of 4,300 MPa. After the molding, the cap was stored at room
temperature for 3 days. Subsequently, for measuring the hinge
strength thereof, opening/closing operation of the upper lid was
conducted. When the operation was conducted 20 times, the hinge was
broken, and the measurement of the hinge strength was therefore
stopped.
[0050] In the hinge cap of the present invention, it is found that
the hinge strength and the good snap function can be maintained
after opening and closing the upper lid 3,000 times, as is apparent
from Examples 1 and 2. Meanwhile, when the cap is formed of the
biodegradable resin (polylactic acid) which is outside the scope of
the present invention, the hinge is broken at the initial stage of
the opening/closing operation and cannot satisfy the performance as
the hinge cap.
INDUSTRIAL APPLICABILITY
[0051] As has been thus far stated, the hinge cap having the
biodegradability in the present invention is a cap which is
excellent in hinge strength even when repeating the opening/closing
operation of the upper lid, secures a sealing retention between the
mouth portion of the container and the cap and is excellent in
basic performance as a packaging container. It is available as a
cap of a container for drugs, foods, drinks, seasonings or the
like, and useful as an eco-friendly packaging material.
* * * * *