Method of manufacturing seamless capsule

Disclosed is a method of manufacturing a spherical seamless capsule formed by encapsulating a filler material such as a medicine with a capsule shell material such as gelatin. A concentric multiple nozzle is positioned above the liquid surface of a curing liquid such that the tip of the nozzle faces down. A concentric columnar composite flow which is discharged from this concentric multiple nozzle and which is composed of a filler material and a capsule shell material outside the filler material is immersed in the curing liquid, and cut in the curing liquid to form a droplet. The capsule shell material of the droplet is cured by the curing liquid, and thereby a seamless capsule is formed. Since, the droplet is not dropped into the curing liquid, no deformation of the droplet caused by collision against the liquid surface occurs. The tip of the multiple nozzle is positioned above the liquid surface of the curing liquid. This prevents water contained in the curing liquid from adhering to the surface of the nozzle and penetrating into the composite flow.

TECHNICAL FIELD

The present invention relates to a method of manufacturing a spherical seamless capsule formed by encapsulating a filler material such as a medicine, a flavor, a spice, or a fragrance with a capsule shell material such as gelatin.

BACKGROUND ART

Conventionally, a seamless capsule of the above-mentioned type is manufactured by a so-called air nozzle method, as disclosed in, e.g., Japanese Patent Laid-Open No. HEI4-338230, which uses a concentric multiple nozzle comprising a center nozzle and an annular nozzle which concentrically surrounds the center nozzle. That is, a liquid filler material is discharged from the center nozzle of the concentric multiple nozzle, and at the same time a liquid capsule shell material is discharged from the annular nozzle surrounding the center nozzle, thereby forming a composite flow having a concentric columnar form in which the capsule shell material flows so as to cover the outside of the filler material flow. A vibration is applied to the composite flow to cut the composite flow from its lower end in the air, thereby forming a droplet. This droplet is dropped onto the liquid surface of a curing liquid and brought into contact with the curing liquid to cure the capsule shell material. In this way, a spherical seamless capsule is manufactured by encapsulating the filler material with the capsule shell material.

The air nozzle method has the problem that the droplets cut in the air deform when they drop onto and collide against the liquid surface of the curing liquid, and this produces irregularity in the sphericity of manufactured seamless capsules.

It is, therefore, a main object of the present invention to provide a seamless capsule manufacturing method for obtaining high-quality seamless capsules without irregularity.

DISCLOSURE OF INVENTION

To achieve the above object, a method has been proposed in which the lower end portion of the concentric multiple nozzle is immersed in the curing liquid and the concentric columnar composite flow is discharged from the opening in the lower end of the nozzle into the curing liquid. In this submerged nozzle method, however, an S-shaped mark is formed on the surface of a seamless capsule. Therefore, the present inventors made extensive studies and have found that this S-shaped mark is occurred by water mixed and dispersed in the curing liquid. More specifically, water in the curing liquid adheres to and condenses on the outer surface of the lower end portion of the high-temperature concentric multiple nozzle immersed in the curing liquid. When this condensed water gradually grows to form a large droplet, this droplet falls along the outer surface and penetrates into the composite flow immediately after it is discharged from the tip or lower end of the nozzle, forming a longitudinal stripe in the direction of length on the circumferential surface of the composite flow. When a droplet formed by cutting the composite flow rotates in the curing liquid, an S-shaped mark is formed. The present inventors have found the above-mentioned fact.

The present invention made on the basis of this finding is a method of manufacturing a seamless capsule formed by encapsulating a filler material with a capsule shell material, characterized by comprising: a step of positioning a concentric multiple nozzle having a center nozzle and an annular nozzle concentrically surrounding the center nozzle, such that the tip of the concentric multiple nozzle is disposed above the liquid surface of a curing liquid and faces down; a step of supplying a liquid filler material to the center nozzle of the concentric multiple nozzle, and supplying a liquid capsule shell material to the annular nozzle of the concentric multiple nozzle; a step of immersing a concentric columnar composite flow, which includes the flow of the liquid filler material discharged from the center nozzle and the flow of the liquid capsule shell material discharged from the annular nozzle and flowing around said flow of the filler material, in the curing liquid; a step of cutting the composite flow immersed in the curing liquid from the end of the immersed composite flow, thereby forming a droplet; and a step of curing the capsule shell material of the droplet by coming into contact with the curing liquid.

Since in this method the droplet is not dropped into the curing liquid, no deformation of the droplet caused by collision against the liquid surface occurs. Also, the tip of the concentric multiple nozzle is positioned above the liquid surface of the curing liquid. This prevents water contained in the curing liquid from adhering to the nozzle surface and penetrating into the composite flow. Accordingly, S-shaped marks can also be prevented.

As the droplet forming means, a means which applies a vibration to the composite flow is preferred.

When the curing liquid is stored in a capsule forming tube, the position of immersion of the composite flow is preferably misaligned relative to the center of this capsule forming tube. In this case, a difference in curing liquid flow velocity is produced between the outside and inside of the capsule forming tube. This rotates the droplet and improves the shape of the droplet.

Furthermore, lettingdbe the outer diameter of the seamless capsule, it is effective to set the distance between the tip of the concentric multiple nozzle and the liquid surface of the curing liquid to 0.5 d to 3 d.

BEST MODES OF CARRYING OUT THE INVENTION

Now, a preferred embodiment of the present invention will be described below with reference to the accompanying drawings.FIG. 1schematically shows a system for carrying out a seamless capsule manufacturing method according to the present invention.FIG. 2shows a concentric multiple nozzle used in this system and the peripheral construction of the nozzle in an enlarged scale.

InFIG. 1, reference numeral1indicates a filler tank which stores a liquid filler material (hereinafter referred to as a filler liquid) containing, e.g., a medicine, a flavor, a spice or a fragrance. This filler liquid within the filler tank1is extracted through tube33and supplied to a concentric multiple nozzle4through tube23by a variable discharge type filler pump3. Since it is desirable for the flow of the filler liquid to the concentric multiple nozzle4to be as stable as possible, the filler pump3is preferably of a type which imparts no pulsation to the filler liquid flow.

InFIG. 1, reference numeral5indicates a gelatin tank (first tank) for storing a liquid capsule shell material (hereinafter referred to as a gelatin solution) containing a substance having a property of gelling from a sol state, e.g., gelatin, agar, carrageenan, or alginic acid, or a substance such as a gum like guar gum or xanthan gum.

While being stored in the gelatin tank5, the gelatin solution is heated by hot water circulating within a hot-water jacket9provided around the tank5, so as to be maintained at a predetermined temperature, e.g., 50° C.

The hot water which has decreased its temperature in the process of circulating within the hot-water jacket9is supplied to a first constant-temperature bath7through a tube36. In the bath7, a heater8heats the hot water to raise its temperature, and the heated hot water again circulates in the host-water jacket9through a tube37, first hot-water pump10, and tube38.

The gelatin solution within the gelatin tank5is extracted trough an inner tube14aof a double tube14by a variable discharge type gelatin pump15which forms no pulsation in the flow, and is supplied to the concentric multiple nozzle4after passing through an inner tube16aof a double tube16, a spiral tube6aof an intermediate heater6, an inner tube17aof a double tube17, and tube19in this order.

Hot water as a heating fluid is supplied into ane annular space between the inner tube14aand an outer tube14bof the double tube14from a flow inlet provided at the end portion of the tube14on the side of the gelatin tank5. This hot water is maintained at a predetermined temperature by a heater13in a second constant-temperature tank12and supplied to the double tube14through tubes39and40by a second hot-water pump18. The gelatin solution flowing in the inner tube14aof the double tube14is heated by the hot water flowing between the inner tube14aand outer tube14b.

The hot water having flown into the annular space between the inner and outer tubes14aand14bflows into a hot-water jacket15aof the gelatin pump15through a tube41, and then flows into an annular space between the inner tube16aand an outer tube16bof the double tube16through a tube45. In this process, the gelatin solution flowing through the inner tube16ais heated by the hot water flowing between the inner and outer tubes16aand16b.

Subsequently, the hot water within the double tube16enters the intermediate heater6through a tube42and heats, while flowing about the spiral tube6a, the gelatin solution flowing through the spiral tube6a.

The hot water flowing out of the intermediate heater6enters an annular space between the inner tube17aand an outer tube17bof the double tube17through a tube43and heats, in the process of flowing through this space, heat the gelatin solution flowing through the inner tube17a. Thereafter, the hot water flows out of the double tube17, returns to the second constant-temperature bath12through a tube44, and is again heated.

Hence, while flowing through the tubes14a,16a,6a, and17afrom the gelatin tank5to the concentric multiple nozzle4, the gelatin solution is heated by the hot water to gradually raise its temperature from 50° C. to a predetermined temperature, e.g., 80° C. This hot gelatin solution flows into the concentric multiple nozzle4.

As shown inFIG. 2, the concentric multiple nozzle4has a center nozzle4awhich opens downward, and an annular nozzle4bwhich concentrically surrounds the center nozzle4a. The tips or lower ends of the center nozzle4aand the annular nozzle4bare positioned above the liquid surface of a curing liquid in a capsule forming tube20. The curing liquid is a liquid for curing the gelatin solution by coming into contact therewith, and can be suitably selected from, e.g., medium-chain triglyceride, water, liquid paraffin, calcium solution, and vegetable oil such as soybean oil and olive oil.

In the upper portion of a chamber4cin the concentric multiple nozzle4into which the filler liquid is introduced through the tube23, a movable wall4dis provided. The movable wall4dis made of a flexible film or the like and defines a part of the wall portion of the chamber4c. The movable wall4dcan be vertically moved by a vibrator11and can thereby apply vibrations having a predetermined period and amplitude to the filler liquid in the chamber4c. This movement of the movable wall4dgenerates a downward propagating ripple in the filler liquid.

The filler liquid supplied to the concentric multiple nozzle4flows out downward from the center nozzle4a. At the same time, the gelatin solution supplied to the concentric multiple nozzle4flows out downward, in a form which surrounds the filler liquid, from the annular nozzle4b.

Consequently, a concentric columnar composite flow comprising the filler liquid and the gelatin solution covering the circumferential surface of the filler liquid continuously flows out of the concentric multiple nozzle4. The lower end of the composite flow is immersed in the curing liquid in the capsule forming tube20. This immersion position is misalighned relative to the center of the capsule forming tube20. More specifically, the capsule forming tube20is a tubular member having a vertical portion which extends vertically and has an open upper end. The vertical portion of the capsule forming tube20and the concentric multiple nozzle4are arranged such that their central axes are parallel to each other at a predetermined spacing between them. As will be described later, a reserve tank32is formed around the capsule forming tube20, and the curing liquid is supplied to the reserve tank32. Therefore, the curing liquid in the reserve tank32flows into the capsule forming tube20from the open upper end thereof, and flows down in the tube20.

Then, vibrations of the movable wall4dare transmitted to the composite flow via the filler liquid to sequentially cut the composite flow from its end in the curing liquid, thereby forming droplets in which the filler liquid is encupsulated with the gelatin solution.

Each droplet falls by gravity acting on it, together with the curing liquid flowing downward in the capsule forming tube20. The flow velocity of the curing liquid flowing in the center of the capsule forming tube20is higher than the velocity of the curing liquid flow near the tube wall. Therefore, the droplet immersed and cut in the position misaligned relative to the center of the capsule forming tube20rotates by the flow velocity difference between the curing liquid flowing on the outside (tube wall side) of this droplet and the curing liquid flowing on the inside (the side of the center of the capsule forming tube20) of this droplet.

While thus rotationally falling, the droplet gradually becomes spherical because of its surface tension and acquires a good outer appearance. Also, the gelatin solution on the surface of the droplet comes in contact with the curing liquid and cools and/or reacts with the curing liquid and gradually cures.

The effect of improving the outer appearance quality of the seamless capsule by rotation of the droplet inside the capsule forming tube20is obtained not only when the droplet is formed below the liquid surface of the curing liquid, but also when the droplet is formed above the liquid surface and then dropped into the curing liquid.

As shown inFIG. 1, the lower portion of the capsule forming tube20is horizontally curved. An opening20aat the end (lower end) of the curved portion of the tube20is immersed in the curing liquid stored within a curing bath21.

The capsule forming tube20is supported so as to be rotatable about its vertical axis, and is rotated by a motor (not shown). When the capsule forming tube20moderately rotates about its vertical axis, the curing liquid in the capsule forming tube20and its accompanying droplets horizontally flow out of the opening20a. Consequently, in the curing liquid stored in the curing bath21, the droplets are dispersed onto the circumference of a circle having a diameter slightly larger than that of the locus of rotation of the opening20a. Then, while the droplets, moderately fall in the curing liquid, the gelatin solution sufficiently cures to form seamless capsules.

The seamless capsules which have fallen to the bottom of the curing bath21enter, together with the curing liquid, a transfer tube22connected to the opening in the bottom of the curing bath21, and are fed to a separator23through the transfer tube22. In the upper portion within the separator23, a sieve plate24made of a porous plate, net or the like is obliquely disposed. The mesh of the sieve plate24is smaller than the outer diameter of the seamless capsule. Therefore, when the curing liquid and seamless capsules flow into the separator23, the curing liquid passes through the sieve plate24and flows in the bottom of the separator23to be stored there. On the other hand, the seamless capsules roll on the sieve plate24, drop into a collecting container26through a chute25to be stored there.

A cooler27is immersed in the curing liquid stored in the bottom portion of the separator23. A coolant cooled by a refrigerator28circulates through a heat transfer tube27aof the cooler27. Accordingly, the curing liquid stored in the bottom of the separator23is cooled by exchanging heat with the coolant circulating in the heat transfer tube27aof the cooler27.

The curing liquid stored in the separator23is extracted from the bottom of the separator23through a filter29made of silica gel or the like, and enters the reserve tank32around the capsule forming tube20through a curing liquid tube30and a curing liquid pump31provided in the tube30, and then flows over the upper edge of the reserve tank32into the capsule forming tube20.

A portion of the transfer tube22attaining the highest position, i.e., an inverted U-shaped portion22ais lower than the level of the curing liquid in the reserve tank32. The difference between the inverted U-shaped portion22aand the level of the curing liquid in the reserve tank32can be controlled by vertically moving the inverted U-shaped portion22aby means of a vertical moving unit34. In this way, it is possible to adjust the flow velocity of the curing liquid which flows through the transfer tube22from the capsule forming tube20by way of the curing bath21.

Note that inFIG. 1, reference numeral35denotes a temperature sensor.

FIG. 3shows the results of observation of the concentric columnar composite flow which flows out of the concentric multiple nozzle4with vibrations applied. That is,FIG. 3shows the state in which, lettingdbe the outside diameter of the seamless capsule, the upper end of the capsule forming tube20is positioned below the concentric multiple nozzle4with a distance 7.3d, and the composite flow flows down to this position of 7.3dwithout contacting the curing liquid. Note that the outer diameterdof the seamless capsule is substantially determined by the flow velocity of the composite flow from the nozzle and the timing of vibration. Note also that the viscosity of the composite flow and the nozzle diameter have almost no influence on the outer diameterdof the seamless capsule.

The composite flow expands into a large diameter by the Barus effect at the tip of the concentric multiple nozzle4, owing to the viscosity of this composite flow or the normal-stress effect. Hence, the composite flow gradually thins to a distance of about 2 d from the nozzle tip, gradually thickens from that position to a distance of about 3.3 d, gradually thins from that position to a distance of about 4.6 d, gradually thickens from that position to a distance of about 6 d, gradually thins from that position to a distance of about 7.3 d, and then is immersed in the curing liquid. Thereafter, the end portion of the composite flow is cut.

FIGS. 4,5, and6show the results of measurements of the sphericity, eye-diameter, and eccentricity of the seamless capsule while a distance D (seeFIG. 2) between the lower end of the concentric multiple nozzle4and the surface of the curing liquid in the capsule forming tube20is changed, respectively.

When the difference between a long diameter L1and a short diameter L2of the seamless capsule is the smaller, the sphericity of the seamless capsule is the higher. When this difference is large as shown inFIG. 7, the sphericity is judged “low”. As seen fromFIG. 4, the difference between the long diameter L1and the short diameter L2of the seamless capsule abruptly increases, i.e., the sphericity worsens, when the distance D exceeds 3 d.

Also, as seen fromFIG. 5, the eye-diameter, i.e., a diameter Id of debris (so-called eye) S of the filler liquid formed in the film of the seamless capsule shown inFIG. 8increases in the form of a steep curve from an inflection point at which the distance D is 3 d. Fortunately, the debris S called eyes is hardly formed.

Furthermore, the eccentricity, i.e., the ratio (W1/W2) of a thickness W1of a thin portion to a thickness W2of a thick portion of the film of the seamless capsule, as shown inFIG. 9, gradually increases until the distance D becomes 2 d, is substantially constant when the distance D is 2 d to 3 d, and gradually decreases after the distance D becomes larger than 3 d.

It is seen from the above results that when the distance D is 0.5 d or less, the eccentricity of the seamless capsule is large, and this may result in a leak (liquid leak) of the liquid filler material, so this distance D is unsuitable. Also, when the distance D is 3 d or more, the sphericity is low, and this is undesirable in view of the product quality of the seamless capsule. In addition, when the distance D is 3 d or more, the eye diameter and eccentricity increased, thereby leading to a leak (liquid leak) of the liquid filler material, and air bubbles accompanied by the composite flow may be formed in the curing liquid.

On the other hand, it is seen that when the distance D is 0.5 d to 3 d, seamless capsules superior in all of the sphericity, eye-diameter, and eccentricity can be obtained. That is, it is possible to manufacture seamless capsules having an eye-diameter of 500 μm or less, an eccentricity of 0.5 or more, a sphericity of 150 μm or less, and a weight deviation RSD of 0.35% or less. Furthermore, it is possible to manufacture seamless capsules with which the appearance frequency of egg-shaped deformed capsules and capsules having S-shaped marks is 1 or 0 capsule per 2,400 capsules when visual inspection is performed.

Note that when the distance D is 2 d, i.e., in the first narrowed portion or small-diameter portion from above of the composite flow, this narrowed portion collides against the liquid surface to prevent the progress of the formation of spheres from this narrowed portion. As a consequence, the molding properties worsen to increase variations in the film weight. Therefore, the distance D is desirably 0.5 d to 1.5 d.

EXAMPLES

The results of tests 1, 2, and 3 conducted by operating the apparatus shown inFIGS. 1 and 2under the conditions shown in Table 2 by using a filler liquid and gelatin solution having the formulas shown in Table 1 will be described below. Note that test 1 is an example of the present invention, and tests 2 and 3 are comparative examples.

In Table 2, the eccentric distance of the nozzle is the horizontal distance between the central axis of the concentric multiple nozzle and the central axis of the vertical portion of the capsule forming tube.

Under the conditions, in test 1, the distance between the tip of the concentric multiple nozzle and the liquid surface of the curing liquid was set to 1 d.

In test 2, the tip of the concentric multiple nozzle was immersed in the curing liquid.

In test 3, the distance between the tip of the concentric multiple nozzle and the liquid surface of the curing liquid was set to 5 d.

Tables 3 and 4 show the results of the physical property evaluation and visual inspection, respectively, of the seamless capsules obtained by tests 1, 2, and 3 as described above.

In the physical property evaluation, the eye-diameter, the eccentricity, the sphericity, and the weight deviation RSD of the total weight of the capsules immediately after filling (before drying) were calculated (n=10).

In the visual inspection, 2,400 capsules were extracted from the dried capsules and visually inspected to check the number of deformed capsules and the number of capsules having S-shaped marks.

Good results were obtained for all the physical property values in test 1 in which the distance between the nozzle tip and the liquid surface of the curing liquid was set to 1d, compared to test 2 in which the nozzle tip was immersed in the curing liquid as the conventional method. In particular, the eye-diameter, eccentricity, and sphericity improved.

Also, egg-shaped deformed capsules and capsules having S-shaped marks found in test 2 were not found in test 1, i.e., excellent results were obtained in test 1.

On the other hand, in test 3 in which the distance between the nozzle tip and the liquid surface of the curing liquid was set to 5 d, all the physical property values were inferior to those in test 1, and egg-shaped deformed capsules were also found.

In the present invention as has been explained above, since the tip of the concentric multiple nozzle is positioned above the liquid surface of the curing liquid, unlike in the conventional submerged nozzle method, it is possible to reliably prevent a water droplet, which condenses and grows on the outer surface of the lower end portion of the concentric multiple nozzle, from penetrating into the composite flow and forming an S-shaped mark on the surface of a seamless capsule.

Also, since the tip of the concentric multiple nozzle faces downward and the lower end of the concentric columnar composite flow continuously discharged from the concentric multiple nozzle is immersed in the curing liquid and cut there, unlike in the conventional air nozzle method, it is possible to prevent deformation which may occur when a droplet cut in the air falls and collides against the liquid surface of the curing liquid, i.e., to prevent deterioration of the sphericity and eccentricity of a seamless capsule.

Additionally, in the case where, lettingdbe the outer diameter of a seamless capsule, the distance between the tip of the concentric multiple nozzle and the liquid surface of the curing liquid is set to 0.5 d to 3 d, it is possible to obtain a seamless capsule which well satisfies all the production standards such as the sphericity, eye-diameter, and eccentricity.

Furthermore, when the lower end of the concentric columnar composite flow is immersed into the curing liquid which flows down in the capsule forming tube such that the composite flow is misaligned relative to the center of the capsule forming tube, a droplet cut in the curing liquid can be well rotated in the curing liquid. This further improves the sphericity and eccentricity of a seamless capsule.

INDUSTRIAL APPLICABILITY

The present invention can efficiently manufacture seamless capsules having no defects. Accordingly, the present invention can be well utilized in the manufacturing industries of, e.g., medicines, sweets, and foods.