Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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TITLE OF THE INVENTION
Method for Forming a Band Seal on a Capsule
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to a method for forming a band
seal between a cap and a body of a capsule filled with drugs
for sealing the capsule. More particularly, it relates to a
method.for forming a band seal between a cap and a body of a
capsule in such a manner as to protect the band seal against
defects such as bubbles and voids.
Prior Art
Capsules filled with various drugs are generally sealed
in the prior art by fitting the cap on the body filled with
drugs, and forming a circumferentially extending band seal
axially spanning from the cap edge to the body surface to
secure the cap to the body. The band sealing of capsules
was originally employed for preventing mischief. Since it
became a common practice to fill capsules with liquid drugs,
the purpose of band sealing was diversified into, for
example, purposes of preventing liquid leakage and
preventing permeation of oxygen and water. It is thus
desired to form a positive and accurate band seal on
capsules.
In band sealing of capsules, however, bubbles and voids
often occur in the band seal. Then, after band seals are
formed, all the capsules must be inspected to pick up those
capsules having defects in the band seal. Because the
rejected capsules are discarded, a large number of defective
band seals increases waste and is economically
disadvantageous.
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There is a need for a method for forming a band
seal on a capsule while preventing bubbles and defects from
occurring in the band seal.
SUMMARY OF THE INVENTION
According to the present invention, there is
provided a method for forming a band seal between a body and
a cap of a capsule, comprising the steps of: fitting the
cap on the body, and applying a gelatin-base sealant at
least one time in the form of a band spanning the cap
surface and the body surface across the edge of the cap to
form at least one layer of band seal for securing the cap to
the body, wherein the first application of the gelatin-base
sealant has a viscosity of 0.05 to 0.2 Pa=s at 50 C.
Embodiments of the invention provide a method for
forming a band seal on a capsule in such a manner as to
prevent bubbles and perforations from occurring in the band
seal.
Embodiments of the invention provide a method for
forming a band seal between a body and a cap of a capsule,
comprising the steps of fitting the cap on the body filled
with drugs, and applying a gelatin-base sealant at least one
time in the form of a circumferentially extending band
axially spanning the cap surface and the body surface across
the edge of the cap to form at least one layer of band seal
for securing the cap to the body. We have found that when a
capsule is band sealed one or more times with a sealant by
either one or a combination of at least two of the following
steps (A) to (E) :
the step (A) of applying the sealant at a
temperature of 30 to 40 C at least when the sealant is first
applied,
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the step (B) of applying the sealant having a
viscosity of 50 to 200 centipoises at 50 C at least when the
sealant is first applied,
the step (C) of after the sealant is applied,
blowing cold air at a temperature of lower than 10 C to the
band seal to cool the band seal below 10 C,
the step (D) of reducing the joint distance
between the body and the cap shorter than the standard
capsule length, and
the step (E) of applying the sealant to only an
edge adjacent portion of the cap surface when the sealant is
first applied, it becomes possible to prevent bubbles and
perforations from occurring in the band seal.
Embodiments of the invention provide a method for
forming a band seal as defined just above wherein the step
of applying a gelatin-base sealant is carried out by either
one or a combination of at least two of steps (A) to (E).
Note that the axial direction is the direction of
an axis connecting the closed ends of the cap and the body.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic elevational view of an
apparatus for forming a band seal on capsules.
FIG. 2 is an enlarged transverse cross-sectional
view of a portion of the apparatus where the sealant is
applied to a capsule.
DETAILED DESCRIPTION OF EMBODIMENTS
The band seal forming method according to an
embodiment of the invention is advantageously applied to
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gelatin capsules although the invention is not limited
thereto. No particular limit is imposed on the size of the
capsule and the type of the drug to be filled therein.
When a band seal is formed on a capsule, an
embodiment of the invention employs at least one or a
combination of at least two of the steps (A) to (E):
the step (A) of applying the sealant at a
temperature of 30 to 40 C at least when the sealant is first
applied,
the step (B) of applying the sealant having a
viscosity of 50 to 200 centipoises at 50 C at least when the
sealant is first applied,
the step (C) of after the sealant is applied,
blowing cold air at a temperature of lower than 10 C to the
band seal to cool the band seal below 10 C,
the step (D) of reducing the joint distance
between the body and the cap shorter than the standard
capsule length, and
the step (E) of applying the sealant to only an
edge adjacent portion of the cap surface when the sealant is
first applied.
A prior art method of forming a band seal on a
capsule is by furnishing a sealant in the form of an aqueous
gelatin
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solution having a viscosity of 300 to 400 centipoises at
50 C and applying the sealant to a capsule at a temperature
of 50 to 60 C. The sealant is applied one time or two or
more times. The prior art band sealing method has the
drawback that bubbles and perforations occur in the band
seal as previously mentioned.
We have found the following. The reason why bubbles
generate is that air in the capsule or air at the junction
between the body and the cap expands when a sealant at
elevated temperature is applied to the capsule around its
entire circumference. When band sealing is repeated plural
times, the influence of the temperature of the sealant is
most significant when the sealant is applied for the first
time. Based on this finding, we have succeeded in
restraining the generation of bubbles in the band seal by
the step (A) of carrying out at least the first application
of the sealant in the form of an aqueous gelatin solution at
a low temperature near the limit at which gelatin
coagulates, typically 30 to 40 C, preferably 31 to 33 C.
Where band sealing is carried out two or more times, insofar
as a first shot of the sealant is applied at a low
temperature, the temperature of second and later shots of
the sealant to be applied is not particularly limited.
Preferably second and later shots of the sealant are applied
at a low temperature of 30 to 40 C, especially 30 to 32 C.
In the practice of step (A), the first shot of the sealant
should preferably have a viscosity of 50 to 200 centipoises
at 50 C according to step (B) to be described later.
However, the first shot of the sealant may have a viscosity
as used in the prior art. For example, a sealant having a
viscosity of more than 200 centipoises at 50 C, especially
300 to 400 centipoises at 50 C may be used as the first
shot. Where band sealing is carried out two or more times,
second and later shots of the sealant may have a viscosity
of 50 to 400 centipoises at 50 C.
The second means (B) for effectively preventing bubbles
from generating in the band seal is by using as a first shot
of sealant an aqueous gelatin solution having a viscosity of
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50 to 200 centipoises at 50 C, preferably 50 to 100
centipoises at 50 C so that the first shot may provide a
relatively small buildup of the sealant to reduce the amount
of heat imparted to the capsule. Where band sealing is
carried out two or more times, second and later shots of the
sealant should preferably have a viscosity of 50 to 200
centipoises at 50 C, especially 50 to 100 centipoises at
50 C. In the practice of step (B), the first shot of the
sealant upon application should preferably have a
temperature of 30 to 40 C, especially 30 to 32 C according
to step (A). However, the first shot of the sealant may
have a temperature as used in the prior art, for example, in
the range of 30 to 60 C. Where band sealing is carried out
two or more times, second and later shots of the sealant may
have such a temperature.
The third means (C) for effectively preventing bubbles
from generating in the band seal is by blowing cold air at a
temperature of up to 10 C to the band seal immediately after
the sealant is applied, to thereby cool the band seal below
10 C. This means is to dissipate the amount of heat
imparted to the capsule upon sealing with a cold air blow,
thereby promoting gelation of gelatin to increase the
strength of a seal film before generation of bubbles. Where
band sealing is carried out plural times, cold air is
effectively blown immediately after the first shot of
sealant is applied, but may be blown after the last shot of
sealant is applied. In the practice of step (C), the
sealant upon band sealing may have a temperature and a
viscosity as in the prior art although it is recommended to
combine step (C) with step (A) and/or (B).
The fourth means (D) for mitigating defects in the band
seal is by reducing the joint distance between the body and
the cap shorter than the standard capsule length. More
particularly, there are available capsules of various sizes
including Nos. 0, 1, 2, 3, 4, and 5. According to the
invention, the joint distance between the body and the cap
is made shorter than the standard capsule size. The joint
distance between the body and the cap is the distance
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between the open end of the cap and the open end of the body
when the cap is fitted on the body. The conventional joint
distance of capsules is 21.8 mm for No. 0 capsules, 19.4 to
19.5 mm for No. 1 capsules, 17.8 mm for No. 2 capsules, 15.8
to 15.9 mm for No. 3 capsules, 14.5 mm for No. 4 capsules,
and 11.4 mm for No. 5 capsules. According to the invention,
the joint distance is made shorter than the minimum joint
length of the standard capsule. In the case of No. 2
capsules, for example, the joint distance is made shorter
than 17.8 mm, typically the joint distance is about 17.5 to
17.6 mm. It is preferred that the joint distance be made
shorter than the minimum joint length of the standard
capsule by 0.1 to 0.5 mm, especially 0.2 to 0.5 mm. By
reducing the capsule joint distance, the lock strength is
increased and the leakage of air from within the capsule
upon band sealing is prohibited, thereby preventing bubbles
from generating in the band seal. In the practice of step
(D), the remaining conditions of the band sealing method may
be the same as in the prior art although it is preferred to
combine step-(D) with at least one of steps (A) to (C).
Where band sealing is carried out two or more times,
the step (E) of applying the sealant to only an edge
adjacent portion of the cap surface upon first application
is effective. By applying the sealant to only an edge
adjacent portion of the cap surface rather than applying the
sealant to an area extending from an edge adjacent portion
of the cap to the body surface, only the cap is shrunk to
increase the lock strength of the cap to the body for
thereby preventing the leakage of air from within the
capsule upon application of subsequent shots of sealant.
When the sealant is first applied to only the edge adjacent
portion of the cap, the remaining conditions of the band
sealing method may be the same as in the prior art although
it is preferred that an aqueous gelatin solution having a
viscosity of 50 to 200 centipoises at 50 C, especially 50 to
100 centipoises at 50 C be used as the sealant and applied
at a temperature of 30 to 40 C, especially 30 to 32 C.
After application, cold air or compressed air below 10 C may
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be blown to the sealant film. On second and later shots of
the sealant, it is preferred that an aqueous gelatin
solution having a viscosity of 50 to 200 centipoises at
50 C, especially 50 to 100 centipoises at 50 C be used as
the sealant and applied at a temperature of 30 to 40 C,
especially 30 to 32 C. Step (E) may be combined with step
(D).
The band seal forming method of the invention may be
carried out in a conventional manner insofar as at least one
of steps (A) to (E) is employed. For example, pigments such
as titanium oxide and coloring matters such as Blue No. 1
and Red No. 3 may be added to the aqueous gelatin solution.
The band seal forming method may be carried out by means of
a well-known band sealing apparatus. The axial width of the
band seal may be properly determined in accordance with the
capsule size.
EXAMPLE
Examples of the invention are given below by way of
illustration and not by way of limitation.
In the following Examples, the capsules used were
gelatin capsules of No. 2 size. In order to demonstrate the
bubble restraining effect, the body and the cap were engaged
over a joint distance of 17.80 mm without filling contents
so that bubbles were most likely to generate in the band
seal. The sealant used for band sealing was an aqueous
gelatin solution having a varying concentration or
viscosity.
Band sealing was carried out by means of a fully
automatic capsule sealing machine model S-100*(Japan Elanco
Co., Ltd.) by applying the sealant two times. The sealing
machine is schematically shown in FIGS. 1 and 2. The
machine includes first and second sealing sections 1 and 11,
tanks 2 and 12 containing sealants 3 and 13, respectively,
heaters 4 and 14, sealing rollers 5 and 15, and scrapers 6
and 16. A slat conveyor 21 extends over the tanks 2 and 12
and moves from the first sealing section 1 to the second
sealing section 11 (from the left to the right in FIG. 1).
* Trademark
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A capsule 22 consisting of a body 22a and a cap 22b is
rotatably mounted in a set of slats. As the capsule 22 is
moved forward by the slat conveyor 21, the sealing roller 5
of the first sealing section 1 applies the first sealant 3
to the capsule in a band pattern and the sealing roller 15
of the second sealing section 11 then applies the second
sealant 13 to the capsule in a band pattern again. An
alignment guide 23 is depicted in FIG. 2. Though not shown,
after the second sealant 13 is applied in the second sealing
section 11, the capsule 22 is transferred to a drying
section where the sealant is dried. At the end of drying,
the band seal is fused to the capsule. The band seal has an
axial width of 2.0 mm for both the first and second seals.
The first and second layers of band seal are formed such
that the cap open end is located at the axial center of the
band seal.
In the following Examples, whether or not bubbles were
generated in the band seal was examined by a visual
observation. A percent bubble generation is the number of
bubble generated capsules per 100 capsules.
Example 1
Both the first and second sealants were an aqueous
gelatin solution having a viscosity of 95 centipoises at
50 C. Band sealing was carried out as mentioned above while
the first sealant was at a temperature as reported in Table
1 and the second sealant was at a temperature of 35 C. The
results of bubble generation are shown in Table 1.
Table 1
Example 1
lst sealant temperature ( C) 32 35 40 42
Bubble generation ($) 0 4 15.7 20
Example 2
Both the first and second sealants were an aqueous
gelatin solution having a viscosity at 50 C as reported in
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Table 2. Band sealing was carried out as mentioned above
while the first and second sealants were at a temperature of
40 C. The buildups of the first and second seals and the
results of bubble generation are shown in Table 2.
Table 2
Example 2
lst & 2nd sealant viscosity (cps) 50 125 200 220
Buildup (mg) 2.5 3.0 3.5 4.0
Bubble generation (~) 0 0 0 10
Example 3
Both the first and second sealants were an aqueous
gelatin solution having a viscosity at 50 C as reported in
Table 3. Band sealing was carried out as mentioned above
while the first and second sealants were at a temperature as
reported in Table 3. The results of bubble generation are
shown in Table 3.
Table 3
Example 3 Comparison
lst & 2nd sealant
viscosity (cps) 600 430 220 100 280
lst & 2nd sealant
temperature ( C) 35 35 40 45 45
Bubble generation ($) 20 0 11 0 80
Example 4
Both the first and second sealants were an aqueous
gelatin solution having a viscosity of 95 centipoises at
50 C. The first sealant was at a temperature as reported in
Table 4 and the second sealant was at a temperature of 35 C.
Band sealing was carried out as mentioned above except that
cold air at 10 C was blown to the band seal immediately
after application of the first sealant. The results of
bubble generation are shown in Table 4.
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Table 4
Example 4
lst sealant temperature ( C) 35 35 40 40 45
Cold air blow yes no yes no yes
Bubble generation (~) 0 0 0 4.7 5.3
Example 5
Both the first and second sealants were an aqueous
gelatin solution having a viscosity of 340 centipoises at
50 C. The first sealant was at a temperature as reported in
Table 5 and the second sealant was at a temperature of 35 C.
Band sealing was carried out as mentioned above except that
the size (length) of the cap was changed to give a cap-body
junction distance as reported in Table 5. The results of
bubble generation are shown in Table 5.
Table 5
Example 5 Comparison
Junction distance (mm) 17.45 17.80 17.30 17.90
lst sealant temperature ( C) 35 35 50 50
Bubble generation ($) 0 0 18.6 100
Example 6
Both the first and second sealants were an aqueous
gelatin solution having a viscosity of 95 centipoises at
50 C. The first sealant was at a temperature of 40 C and
the second sealant was at a temperature of 35 C. Band
sealing was carried out as mentioned above except that the
first sealant was applied to only an edge adjacent portion
of the cap and the second sealant was then applied so as to
extend from the edge adjacent portion of the cap to the
body. The bubble generation is shown in Table 6.
For comparison purposes, band sealing was carried out
as above except that the first sealant was applied so as to
extend from the edge adjacent portion of the cap to the
body. The result is also shown in Table 6.
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Table 6
Example 6 Comparison
Bubble generation (~) 0 15.7
It has been demonstrated that the method of the
invention can form a band seal on a capsule while positively
restraining the generation of bubbles and voids during band
sealing.
Although some preferred embodiments have been
described, many modifications and variations may be made
thereto in the light of the above teachings. It is
therefore to be understood that within the scope of the
appended claims, the invention may be practiced otherwise
than as specifically described.
