Method for forming a band seal on a capsule

Abstract: A method of producing a capsule including forming a band seal between a cap and a body of the filled capsule when the cap has been fitted onto the body, by one or more applications of gelatin-based sealant in the form of a band spanning the cap surface and body surface across the edge of the cap, to form one or more corresponding band seal layers securing between the cap and body; characterised by a preliminary application of gelatin-based sealant around the cap surface alone, adjacent its edge.

Description: 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 reduce or eliminate seal defects such as bubbles and voids. 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. See our EP-A-0 154 966, which describes such a procedure integrated into production apparatus. 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. 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. Therefore, an object of the invention is to provide a method for forming a band seal on a capsule to lessen or eliminate the chance of bubbles and perforations occurring in the band seal. The invention provides a method of producing a capsule including forming a band seal between a cap and a body of the filled capsule when the cap has been fitted onto the body, by applications of gelatin-based sealant, including one or more applications in the form of a band spanning the cap surface and body surface across the edge of the cap, to form one or more corresponding band seal layers securing between the cap and body; characterised in that the first application of gelatin-based sealant is around the cap surface alone, adjacent its edge, to shrink the cap onto the body for increased lock strength. This method may be combined with one or more of the following features (A) to (D): (A): applying the sealant at a temperature of 30 to 40°C at least for the first application; (B): using a sealant having a viscosity of 50 to 200mPa.s (50 to 200 centipoises) at 50°C at least for the first application; (C): after the sealant is applied, blowing cold air at a temperature of lower than 10°C onto the band seal to cool the band seal below 10°C; (D): reducing the joint distance between the body and the cap to shorter than the standard distance. It becomes possible to prevent bubbles and perforations from occurring in the band seal. 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 The band seal forming method according to the invention is advantageously applied to 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. A prior art method of forming a band seal on a capsule is by furnishing a sealant in the form of an aqueous gelatin 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, one preferred measure by which we have succeeded in restraining the generation of bubbles in the band seal is 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 200mPa.s (200 centipoises) at 50°C, especially 300 to 400 mPa.s (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. A second means preferred measure (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 50 to 200 mPa.s (50 to 200 centipoises) at 50°C, preferably 50 to 100 mPa.s (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 mPa.s (50 to 200 centipoises) at 50°C, especially 50 to 100mPa.s (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. A third preferred measure (C) for effectively preventing bubbles from generating in the band seal is by blowing cold air at a temperature of up to 10°C onto 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). A fourth preferred measure (D) for mitigating defects in the band seal is by reducing the joint distance between the body and the cap to shorter than the standard. More particularly, there are available capsules of various sizes including Nos. 0, 1, 2, 3, 4, and 5. According to this measure 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 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 feature (D) 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). According to the present invention, the step of applying the sealant to only an edge- adjacent portion of the cap surface upon first application is used. 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 onto the body surface, only the cap is shrunk, increasing the lock strength of the cap to the body and 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 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 in other respects be carried out in a conventional manner. 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 Reference Examples and an example of the invention are given below by way of illustration. 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 sealants used for band sealing were aqueous gelatin solutions having various concentrations 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). 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. Reference 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. Example 1 1st sealant temperature (°C) 32 35 40 42 Bubble generation (%) 0 4 15.7 20 Reference Example 2 Both the first and second sealants were an aqueous gelatin solution having a viscosity at 50°C as reported in 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. Example 2 1st & 2nd sealant viscosity (cps) 50 125 200 220 Buildup (mg) 2.5 3.0 3.5 4.0 Bubble generation (%) 0 0 0 10 Reference 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. Example 3 Comparison 1st & 2nd sealant viscosity (cps) 600 430 220 100 280 1st & 2nd sealant temperature (°C) 35 35 40 45 45 Bubble generation (%) 20 0 11 0 80 Reference 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. Example 4 1st 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 Reference 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. Example 5 Comparison Junction distance (mm) 17.45 17.80 17.30 17.90 1st sealant temperature (°C) 35 35 50 50 Bubble generation (%) 0 0 18.6 100 Invention Example 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. 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.

Claims: A method of producing a capsule (22) including forming a band seal between a cap (22b) and a body (22a) of the filled capsule when the cap has been fitted onto the body, by applications of gelatin-based sealant, including one or more applications in the form of a band spanning the cap surface and body surface across the edge of the cap (22b), to form one or more corresponding band seal layers securing between the cap (22b) and body (22a); characterised in that the first application of gelatin-based sealant is around the cap surface alone, adjacent its edge, to shrink the cap (22b) onto the body (22a) for increased lock strength. A method according to claim 1 in which for said one or more applications of sealant forming a band seal layer, the gelatin-based sealant is one whose viscosity at 50°C is from 50 to 200 mPa.s (50 to 200 centipoise), applied at from 30 to 40°C. A method according to claim 1 or 2 in which said first application uses a gelatin-based sealant whose viscosity at 50°C is from 50 to 200 mPa.s (50 to 200 centipoise), applied at a temperature from 30 to 40°C. A method according to claim 1 in which air at a temperature below 10°C is blown onto the applied sealant film after said first application of sealant. A method according to any one of the preceding claims in which the joint distance, of axial overlap between the body (22a) and cap (22b), is for No.0 capsules, less than 21.8 mm, for No.1 capsules, less than 19.4 mm, for No.2 capsules, less than 17.8 mm, for No. 3 capsules, less than 15.8 mm, for No. 4 capsules, less than 14.5 mm, for No. 5 capsules, less than 11.4 mm, by from 0.1 to 0.5 mm.

Inventors: ENOMOTO TAKAO, FURUYA YOSHIHIRO, MIZUTA TAIICHI, SATO KOJI, ENOMOTO, TAKAO, FURUYA, YOSHIHIRO, MIZUTA, TAIICHI, SATO, KOJI
Applicants: SHIONOGI & CO, SHIONOGI & CO., LTD.
Application year: 1997
Main classification: A61J3
IPC codes: A61J3