Method for producing seamless capsules

Abstract

The invention relates to a method for producing seamless capsules (50) consisting of a small step of small droplets from the distal end (1a) of the nozzle (1) into the cooling liquid (49) in the flow path inside the forming tube (10) to form seamless wet capsules (50w) from droplets. The nozzle (1) consists of an inclined part (25) inclined towards the inside of the nozzle (1) when extended from the middle part towards the distal end (1a). The distance Z between the apex (27) of the void is determined by the virtual surface (26) obtained by extending the outer surface (25a) of the inclined part (25) downwards beyond the distal end (1a) and the upper end (10a) of the forming tube (10) satisfying the condition: -10 mm ≤ Z ≤ 6 mm. When Z < 0, the apex (27) is below the upper end (10a) of the forming tube (10). When Z > 0, the peak (27) is above the top end (10a) of the forming tube (10).

Description

Seamless capsule manufacturing method

[0001] The present invention relates to a method for producing a seamless capsule.

[0002] Patent Document 1 discloses a method for producing spherical seamless capsules in which a fill material is coated with a coating material. In this production method, droplets are discharged downward from the tip of a nozzle into a cooling liquid (hardening liquid) in a flow path of a forming tube. The nozzle tapers midway. The tip of the nozzle is provided with a tip surface having an opening through which droplets are discharged. The tip surface is orthogonal to the central axis of the nozzle and faces horizontally. Furthermore, this production method employs the so-called air nozzle method, in which the tip surface of the nozzle is positioned above the liquid surface of the cooling liquid. When the outer diameter of the seamless capsule to be produced is d, the distance between the tip surface of the nozzle and the liquid surface is set within a range of 0.5d to 3d.

[0003] Japanese Patent Application Laid-Open No. 2002-136576

[0004] However, there is still room for improvement in the method for producing seamless capsules with regard to the stable production of high-quality seamless capsules, such as capsules with no cracks in the shell.

[0005] An object of the present invention is to stably produce high-quality seamless capsules.

[0006] One aspect of the present invention provides a method for producing seamless capsules, comprising a forming step of dropping droplets from a tip of a nozzle into a cooling liquid in a flow path of a forming tube and forming seamless wet capsules from the droplets, wherein the nozzle has an inclined portion that slopes inward from the middle of the nozzle toward the tip, and a distance Z between an apex of a space enclosed by an imaginary plane formed by extending the outer surface of the inclined portion downward from the tip and an upper end of the forming tube is within a range of −10 mm≦Z≦6 mm, and when Z<0, the apex is located below the upper end of the forming tube, and when Z>0, the apex is located above the upper end of the forming tube.

[0007] According to the present invention, high-quality seamless capsules can be stably produced.

[0008] 1 is a schematic diagram of a manufacturing apparatus for carrying out a manufacturing method for a seamless capsule according to an embodiment. 2 is a diagram showing an enlarged view of a nozzle and a forming tube of the manufacturing apparatus of FIG. 1. 3 is a horizontal cross-sectional view of a nozzle taken along line III-III in FIG. 2. 4 is a diagram for explaining the distance between a virtual vertex set in the nozzle and the upper end of the forming tube. 5 is a diagram showing an enlarged view of a nozzle and a forming tube according to a first modified example. 6 is a horizontal cross-sectional view of a nozzle according to a second modified example. 7 is a horizontal cross-sectional view of a nozzle according to a third modified example. 8 is a front view of a nozzle according to a fourth modified example. 9 is a front view of a nozzle according to a fifth modified example. 10 is a front view of a nozzle according to a sixth modified example.

[0009] Hereinafter, embodiments will be described with reference to the drawings. Note that the same or corresponding elements are designated by the same reference numerals throughout the drawings, and detailed descriptions thereof will be omitted.

[0010] 1 uses the manufacturing method according to this embodiment to manufacture seamless capsules 50. The manufacturing apparatus includes a nozzle 1, a content liquid tank 2, a content liquid supply pipe 2a, a coating liquid tank 3, a coating liquid supply pipe 3a, a coolant reservoir 6, a coolant tank 7, a coolant supply pipe 8, a cooling device 9, a forming pipe 10, pumps 11 to 13, a screen 14, and a dryer 15.

[0011] The nozzle 1 is connected to the content liquid tank 2 via a content liquid supply pipe 2a and to the coating liquid tank 3 via a coating liquid supply pipe 3a. The content liquid tank 2 stores a content liquid 41. The content liquid 41 is pressure-fed by a pump 11 from the content liquid tank 2 via the content liquid supply pipe 2a to the nozzle 1. The content liquid 41 is also called a filling liquid, and when filled into the seamless capsule 50, it becomes a content 51, which will be described later. The coating liquid tank 3 stores a coating liquid 42. The coating liquid 42 is pressure-fed by a pump 12 from the coating liquid tank 3 via the coating liquid supply pipe 3a to the nozzle 1.

[0012] 1 and 2 , the coolant reservoir 6 is connected to the coolant tank 7 via a coolant supply pipe 8. The coolant tank 7 stores a coolant 49. The coolant 49 is also called a solidification liquid or a solidifying liquid. The coolant 49 is pumped from the coolant tank 7 via the coolant supply pipe 8 by a pump 13 to the coolant reservoir 6, and is cooled by a cooling device 9 during the pumping process. The coolant 49 is received in the internal space of the coolant reservoir 6. The coolant reservoir 6 stores the coolant 49 flowing into the forming tube 10 in the internal space, with a portion of the nozzle 1 (the inclined portion 25 described below) and the upper end of the forming tube 25 positioned in the internal space of the coolant reservoir 6. The coolant reservoir 6 has a hollow structure, and the inner surface of the coolant reservoir 6 defines the internal space. Specifically, the coolant reservoir 6 has a bottom wall 6a, an upper wall 6b, and a peripheral wall 6c, the inner surfaces of which define an internal space. The bottom wall 6a and the upper wall 6b are generally horizontal and spaced apart vertically. The peripheral wall 6c extends upward from the peripheral edge of the bottom wall 6a. The peripheral edge of the upper wall 6b is located above the peripheral wall 6c, and a spacer 6e is provided between the peripheral edge of the upper wall 6b and the upper end of the peripheral wall 6c. The spacer 6e is a replaceable member that determines the distance between the upper wall 6b and the peripheral wall 6c. The coolant reservoir 6 is provided with a coolant inlet port 6d that allows the coolant 49 to flow into the internal space. The downstream end of the coolant supply pipe 8 is connected to the coolant inlet port 6d. The upper wall 6b is configured to open the space above a liquid level 49L of the coolant 49 to the atmosphere. The coolant 49 is returned from the coolant reservoir 6 to the coolant tank 7 via the forming pipe 10. The forming pipe 10 is open at both ends and forms a flow path for the coolant 49. In the example shown in FIGS. 1 and 2, the coolant 49 flows through the flow path of the forming pipe 10 by hydraulic head pressure. In a modification of this embodiment, the discharge force of the pump 13 can be used to force the coolant 49 through the flow path of the forming pipe 10. In such a modification, a coolant reservoir 6 with a sealed internal space can be used.

[0013] The spacer 6e may be formed of any material and any shape suitable for the purpose of manufacture, provided that it is capable of separating the upper wall 6b from the peripheral wall 6c. Examples of materials for the spacer 6e include resin, metal, natural rubber, and synthetic rubber. The spacer 6e may have a planar shape viewed from the top to bottom, which may cover the entire portion of the periphery of the upper wall 6b that faces the peripheral wall 6c, or may have a shape in which the portion that faces the peripheral wall 6c is partially interrupted.

[0014] The upper end 10a (one end, upstream end) of the forming tube 10 opens into the interior space of the coolant reservoir 6. The central axis of the forming tube 10 is vertical at the upper end of the forming tube 10, and the upper end 10a of the forming tube 10 is horizontal. The cross section of the forming tube 10 is typically circular. The forming tube 10 extends downward from the upper end 10a, penetrates the bottom wall 6a of the coolant reservoir 6, turns upward once, then turns downward again, and terminates. The distance H between the upper end 10a and the inner surface of the bottom wall 6a is variable, and a seal 6f is provided between the forming tube 10 and the bottom wall 6a to prevent the coolant 49 from leaking. The opening at the other end (downstream end) of the forming tube 10 is located above the coolant tank 7 and faces downward. The coolant 49 is discharged from the opening at the other end of the forming tube 10 and received in the coolant tank 7. The upper end of the forming pipe 10 is the portion of the forming pipe 10 that protrudes upward from the inner lower surface of the inner surface of the coolant tank 7 that defines the internal space. The inner lower surface of the coolant tank 7 is the inner surface of the bottom wall 6a.

[0015] The sealing 6f may be made of any material suitable for the purpose of manufacture as long as it can prevent the coolant 49 from leaking out. Examples of the material for the sealing 6f include resin, metal, natural rubber, and synthetic rubber.

[0016] Referring to FIG. 2 , the nozzle 1 is cylindrical as a whole. The central axis A of the nozzle 1 is oriented vertically. A plate-shaped flange 1b protruding radially is provided at an axially intermediate portion of the nozzle 1. The flange 1b is supported on the outer surface (upper surface) of the upper wall 6b of the coolant reservoir 6. The nozzle 1 protrudes upward from the upper wall 6b at a portion axially closer to the base end than the flange 1b. A content liquid inlet port 1c, through which the content liquid 41 flows into the nozzle 1, and a coating liquid inlet port 1d, through which the coating liquid 42 flows into the nozzle 1, are provided at this base end portion. The nozzle 1 passes through the upper wall 6b at a portion axially closer to the tip end than the flange 1b, and enters the internal space of the coolant reservoir 6 from above.

[0017] The flange portion 1b is a replaceable member fixed to the nozzle 1. A fastener such as a screw can be used to fix the flange portion 1b to the nozzle 1. Because the flange portion 1b is supported on the upper surface of the upper wall 6b as described above, the position of the nozzle 1 can be adjusted by adjusting the thickness of the flange portion 1b in the vertical direction. The material of the flange portion 1b can be selected arbitrarily depending on the purpose of manufacturing. Examples of materials for the flange portion 1b include resin, metal, natural rubber, and synthetic rubber. The shape of the flange portion 1b is not particularly limited as long as it allows the nozzle 1 to be installed on the upper wall 6b via the flange portion 1b, but it may be, for example, circular, elliptical, or polygonal in a plan view in the vertical direction.

[0018] In the internal space of the coolant reservoir 6, a liquid level 49L of the coolant 49 is located between the upper end 10a of the forming tube 10 and the inner surface (lower surface) of the upper wall 6b. The position of the liquid level 49L can be controlled in this manner by adjusting the flow rate of the pump 13. The tip 1a of the nozzle 1 is located below the liquid level 49L. In other words, the tip of the nozzle 1 is immersed in the coolant 49 received in the coolant reservoir 6.

[0019] 2 and 3, the nozzle 1 has a central nozzle 21 and an outermost nozzle 22. Both the central nozzle 21 and the outermost nozzle 22 extend axially within the nozzle 1. The central nozzle 21 has a circular cross section centered on the central axis A. The outermost nozzle 22 is concentric with the central nozzle 21, surrounds the central nozzle 21, and has an annular cross section centered on the central axis A. One end (upper end, upstream end) of the central nozzle 21 is connected to the content liquid inlet port 1c. One end (upper end, upstream end) of the outermost nozzle 22 is connected to the coating liquid inlet port 1d. The other end (lower end, downstream end) of the central nozzle 21 and the other end (lower end, downstream end) of the outermost nozzle 22 open at the tip 1a of the nozzle 1. The tip 1a of the nozzle 1 forms a flat tip surface perpendicular to the central axis A. The central nozzle 21 and the outermost nozzle 22 open at this tip surface.

[0020] The nozzle 1 has an inclined portion 25 that slopes inward from the middle of the nozzle 1 toward the tip 1a of the nozzle 1. The inclined portion 25 is provided at a position closer to the tip in the axial direction than the flange portion 1b.

[0021] As can be seen from Figures 2 and 4, in a vertical cross section of the nozzle 1 passing through the central axis A of the nozzle 1, the outer surface 25a of the inclined portion 25 is represented by a pair of straight lines 25b. The pair of straight lines 25b connects an upper end 25c and a lower end 25d of the outer surface 25a of the inclined portion 25. The pair of straight lines 25b are inclined so as to approach each other toward the tip 1a. The pair of straight lines 25b are symmetrical with respect to the central axis A. The lower ends of the pair of straight lines 25b are each connected to a tip surface represented as a horizontal line perpendicular to the central axis A. As can be seen from Figure 3, in this embodiment, in a horizontal cross section of the nozzle 1 passing through the central axis A of the nozzle 1, the outer surface of the inclined portion 25 is circular.

[0022] In this manner, in this embodiment, the inclined portion 25 has a truncated cone shape. The pair of straight lines 25b are the generatrix of the truncated cone.

[0023] 4, an imaginary plane 26 is imagined as an extension of the outer surface 25a of the inclined portion 25 downward from the tip 1a of the nozzle 1. The imaginary plane 26 is represented as a downward extension of a pair of straight lines 25b in a vertical cross section passing through the central axis A of the nozzle 1. The imaginary plane 26 is a point on the central axis A. That is, the downward extensions of the pair of straight lines 25b intersect on the central axis A. This intersection is a vertex 27 of the space enclosed by the imaginary plane 26. In this embodiment, in which the cross section of the outer surface 25a of the inclined portion 25 is circular, this imaginary space is conical, with its base being the tip surface of the nozzle 1 where the central nozzle 21 and the outermost nozzle 22 open.

[0024] The distance Z between the vertex 27 and the upper end 10a of the forming tube 10 is within the range of -10 mm≦Z≦6 mm. The distance Z is the vertical distance between the vertex 27 and the upper end 10a. The vertical direction corresponds to the axial direction of the nozzle 1, the normal direction to the tip surface of the nozzle 1, the axial direction of the forming tube 10, and the perpendicular direction to the opening at the upper end 10a of the forming tube 10. When the vertex 27 coincides with the upper end 10a of the forming tube 10, Z=0. When Z<0, the vertex 27 is located below the upper end 10a of the forming tube 10, i.e., within the flow path of the forming tube 10. When Z>0, the vertex 27 is located above the upper end 10a of the forming tube 10, i.e., outside the forming tube 10. Note that Figure 4 illustrates the case where Z<0, and more specifically, the case where the tip 1a of the nozzle 1 itself is located above the upper end 10a of the forming tube 10 even when Z<0. However, this is merely an example.

[0025] In this embodiment, the distance Z may be within the range of -10 mm≦Z≦6 mm, but the distance Z may be, for example, 5 mm or less, 4 mm or less, 3.5 mm or less, 3.2 mm or less, 3 mm or less, 2 mm or less, 1 mm or less, 0.5 mm or less, or 0 mm or less. Furthermore, the distance Z may be -9.7 mm or more, -9 mm or more, -8 mm or more, -7 mm or more, -6 mm or more, or -5 mm or more.

[0026] In this embodiment, when setting the distance Z between the apex 27 and the upper end 10a of the forming tube 10, the thickness of the spacer 6e, the thickness of the flange portion 1b, and the distance H between the upper end 10a and the inner surface of the bottom wall 6a can be changed, but changing these three is not essential. That is, it is preferable to change at least one of the thickness of the spacer 6e, the thickness of the flange portion 1b, and the distance H between the upper end 10a and the inner surface of the bottom wall 6a. In other words, it is preferable that at least one of the nozzle 1, the upper wall 6b, and the forming tube 10 is configured to be movable up and down along the central axis A of the nozzle 1.

[0027] In addition, in a vertical cross section of the nozzle 1 passing through the central axis A of the nozzle 1, the angle θ formed by a pair of straight lines 25b connecting the upper end 25c and the lower end 25d of the outer surface 25a of the inclined portion 25 is in the range of 20° to 70°.

[0028] 1 and 2, a method for manufacturing seamless capsules 50 using such a manufacturing apparatus includes a forming step of dropping liquid droplets from the tip 1a of the nozzle 1 into the liquid coolant 49 in the flow path of the forming tube 10, and forming seamless wet capsules 50w from the liquid droplets. In this forming step, the tip 1a of the nozzle 1 is positioned below the liquid surface 49L of the liquid coolant 49. In other words, the so-called dripping method is applied to the manufacturing apparatus and method according to this embodiment.

[0029] The droplets dropped from the nozzle 1 include the content liquid 41 supplied from the content liquid tank 2 to the nozzle 1 and ejected from the central nozzle 21, and the coating liquid 42 supplied from the coating liquid tank 3 to the nozzle 1 and ejected from the outermost nozzle 22. The content liquid 41 is ejected downward from the center of the tip surface. The coating liquid 42 is ejected downward from the periphery of the tip surface, covering the content liquid 41 from the outer periphery. In this manner, the nozzle 1 ejects a composite jet 59 containing the content liquid 41 and the coating liquid 42 downward from its tip surface into the cooling liquid 49. The composite jet 59 extends downward from the tip surface in the cooling liquid 49. The composite jet 59 breaks into droplets from its lower end due to surface tension. When the droplets become particles of a predetermined size and the coating liquid 42 completely covers the content liquid 41, the coating liquid 42 solidifies. This produces a seamless capsule 50.

[0030] The seamless capsule 50 has a spherical shape as a whole, and includes a content 51 and a shell layer 52 that encapsulates the content 51. The shell layer 52 is formed by solidification of the shell liquid 42, and is seamless. The content 51 is composed of the content liquid 41, and the content 51 may be in a liquid state, a semi-solid state such as a gel, or a solid state.

[0031] The composite jet 59 is ejected into the flow path of the forming pipe 10, and seamless capsules 50 are formed in the flow path of the forming pipe 10. The formed seamless capsules 50 ride on the flow of the liquid coolant 49 inside the forming pipe 10 and are transported along the forming pipe 10. The upper opening of the liquid coolant tank 7 is covered with a screen 14. The screen 14 allows the liquid coolant 49, which is released from the opening at the other end of the forming pipe 10, to pass through, but prevents the seamless capsules 50 from flowing into the liquid coolant tank 7. The seamless capsules 50 blocked by the screen 14 are recovered as wet capsules 50w.

[0032] The collected wet capsules 50w may be a final product. The manufacturing apparatus may have a dryer 15 for drying the wet capsules 50w. A drying step of drying the wet capsules 50w with the dryer 15 can be performed to obtain dried capsules 50d. In this way, the wet capsules 50w may be an intermediate product for the dried capsules 50d, and the dried capsules 50d may be a final product.

[0033] The content liquid 41 is not particularly limited, and examples thereof include a lipophilic or hydrophilic liquid, a suspension of such a liquid and an insoluble powder therein, or a mixture of such a liquid. The content liquid 41 may contain compounding agents such as excipients, stabilizers, surfactants, adjuvants, or foaming agents, as appropriate.

[0034] The coating liquid 42 contains a natural polymer and water. The natural polymer is a component that solidifies the coating liquid 42 and is often water-soluble. The natural polymer is, for example, at least one selected from the group consisting of gelatin, casein, zein, pectin or a derivative thereof, alginic acid or a salt thereof, agar, gellan gum, carrageenan, furcellaran, chitosan, curdlan, starch, modified starch, pullulan, and mannan. The natural polymer is not limited to the above, and any component can be used as long as it is capable of forming the coating layer 52.

[0035] The coating liquid 42 may further contain a plasticizer. The plasticizer is a component that imparts flexibility to the coating layer 52. The plasticizer can maintain sufficient flexibility and make the dried coating layer 52 less susceptible to cracking, particularly in the dried capsule 50d. Examples of plasticizers include glycerin and sorbitol. The plasticizer is not limited to the above and can be any component that can impart flexibility to the coating layer 52.

[0036] The coating liquid 42 may further contain additives such as coloring matter, flavoring ingredients, preservatives, or fragrances depending on the purpose of the seamless capsule 50.

[0037] The viscosity of the shell liquid 42 is preferably 30 to 350 mPa·s, more preferably 50 to 300 mPa·s, and even more preferably 50 to 250 mPa·s at 60° C. When the viscosity of the shell liquid 42 is within the above range, seamless capsules can be successfully prepared by the dropping method.

[0038] The temperature of the cooling liquid 49 is typically 20° C. or less, and preferably 1 to 18° C. The temperature of each liquid discharged from the nozzle 1 is not particularly limited, and is typically 15 to 70° C., and preferably 20 to 65° C.

[0039] The coolant 49 can include oily components such as medium-chain triglycerides (MCT), vegetable oils (such as palm oil, sunflower oil, safflower oil, sesame oil, rapeseed oil, grapeseed oil, and mixtures thereof), liquid paraffin, and mixtures thereof.

[0040] Referring to FIG. 2 , the coolant 49 flows from the liquid surface 49L in the coolant reservoir 6 toward the opening at the upper end 10a of the forming tube 10. The inclined portion 25 of the nozzle 1 is located near this opening, and the coolant 49 flows along the outer surface of the inclined portion 25 toward the opening of the forming tube 10. The flow along the outer surface moves radially inward of the nozzle 1 as it moves further downward from the tip 1a of the nozzle 1 toward the interior of the forming tube 10. In other words, the coolant 49 flows along an imaginary surface 26 extending downward from the outer surface of the inclined portion 25 and toward a vertex 27 of the space surrounded by the imaginary surface 26. A vortex of the coolant 49 may form near this vertex 27. When such a vortex occurs, the shape of the composite jet 59 flowing out of the nozzle 1 becomes unstable.

[0041] If the apex 27 is too far above the upper end 10a, a disturbance in the flow of the cooling liquid 49 may occur near the opening of the forming tube 10, separate from the apex 27. The composite jet 59 is affected by this disturbance, which inhibits stable formation of the coating layer 52, making the coating layer 52 more susceptible to cracking, and also increasing the variation in particle size of the wet capsules 50w. If the apex 27 is too far inside the forming tube 10, the cooling liquid 49 passes through a narrow space surrounded by the forming tube 10 and the nozzle 1, making it difficult to control the flow rate of the cooling liquid 49. Therefore, when the cooling liquid 49 flows through the flow path of the forming tube 10, the shear force generated by the flow of the cooling liquid 49 becomes unstable, which increases the variation in particle size of the wet capsules 50w.

[0042] In contrast, in this embodiment, the distance Z between the apex 27 and the upper end 10a of the forming tube 10 is within the range of -10 mm≦Z≦6 mm. By adjusting the position of this virtual apex 27 rather than the tip surface of the nozzle 1 in this way, the flow of the liquid coolant 49 flowing into the forming tube 10 can be easily controlled by the inclined portion 25, the shell layer 52 can be stably formed, and the variation in particle size of the wet capsules 50w can be reduced. As a result, high-quality seamless capsules 50 with reduced shell cracking can be manufactured.

[0043] When the angle θ formed by a pair of straight lines 25b connecting the upper end 25c and the lower end 25d of the outer surface 25a of the inclined portion 25 is small, the position of the apex 27 is spaced downward from the tip surface. As a result, the flow of the liquid coolant 49 is likely to become turbulent near the lower end of the composite jet 59, which tends to increase the variation in particle size of the seamless capsules 50 produced. On the other hand, when the angle θ is large, the position of the apex 27 is closer to the tip surface. As a result, the composite jet 59 is easily affected by vortices of the liquid coolant 49 immediately after being discharged. This makes the shape of the composite jet 59 unstable, and the particle size of the seamless capsules 50 produced is unstable. In this embodiment, the angle θ is within the range of 20° to 70°. This stabilizes the particle size of the seamless capsules 50 and reduces the variation in particle size. The lower limit of the angle θ is preferably 30° or more. The upper limit of the angle θ is preferably 60° or less.

[0044] As a result of the above, the coefficient of variation of the particle size of the wet capsules 50w is 0.1 or less. When dry capsules 50d are obtained from such wet capsules 50w, the coefficient of variation of the particle size of the dry capsules 50d is 0.1 or less. In this way, it becomes possible to stably produce high-quality seamless capsules 50. The coefficient of variation is a dimensionless statistical value obtained by dividing the standard deviation of a certain index value of a plurality of samples by its average value.

[0045] Although the embodiment has been described above, the above configuration is merely an example and can be modified as appropriate within the scope of the present invention.

[0046] FIG. 5 shows a first modified example. As shown in FIG. 5, a seamless capsule 50 having a three-layer structure may be produced. In this case, the nozzle 1 further includes an intermediate nozzle 23 formed radially between the central nozzle 21 and the outermost nozzle 22. The intermediate nozzle 23 is concentric with the central nozzle 21 and the outermost nozzle 22, has an annular cross section, and extends axially. The upper end of the intermediate nozzle 23 is connected to an intermediate liquid inlet port 1e into which intermediate liquid 43 supplied from an intermediate liquid tank (not shown) flows. The lower end of the intermediate nozzle 23 opens at the tip surface. The composite jet 59 contains not only the content liquid 41 and the coating liquid 42, but also the intermediate liquid 43 interposed therebetween. A seamless capsule 50 including a content 51, an intermediate layer 53, and a coating layer 52 is produced in the forming tube 10 by dropletization of the composite jet 59.

[0047] Figure 6A shows a second modified example, and Figure 6B shows a third modified example. The horizontal cross section of the outer surface of the inclined portion 25 of the nozzle 1 is not limited to a circular shape. As shown in Figure 6A, the horizontal cross section may be an ellipse. As shown in Figure 6B, the horizontal cross section may be a polygon. In Figure 6B, the polygon is a square as a mere example, but the polygon may be a quadrilateral other than a square. Furthermore, the number of corners or sides of the polygon is not limited to four.

[0048] 7 shows a fourth modified example. The nozzle 1 may be composed of a cylindrical nozzle body 31 and a cap 32 that covers the tip of the nozzle body 31 (see the dashed line). The cap 32 has an inclined portion 25 and a tip 1a, and is detachably attached to the nozzle body 31. A plurality of caps 32 with different angles θ may be prepared for one nozzle body 31, and one cap 32 selected from the plurality of caps 32 may be attached to the nozzle body 31. This makes it possible to select a cap 32 with appropriate specifications depending on the content liquid and coating liquid.

[0049] Figure 8A shows a fifth modified example, and Figure 8B shows a sixth modified example. In the examples shown in Figures 2 and 7, in a vertical cross section of the nozzle 1 passing through the central axis A of the nozzle 1, the outline of the outer surface 25b of the inclined portion 25 is a single straight line, but the outline is not limited to a single straight line. In the fifth modified example of Figure 8A, the outline of the outer surface 25b may be a wavy line or a line similar thereto. When the outline of the outer surface 25b is a wavy line or the like, the intersection point where the downward extensions of the pair of straight lines 25b intersect on the central axis A does not have to coincide with the vertex 27 of the space enclosed by the imaginary surface 26.

[0050] 8B , the outline of outer surface 25b may be a bent line or a curved line. When outer surface 25b has a curved line or the like, the portion of inclined portion 25 that is significantly involved in controlling the flow of the coolant is defined as the main body of inclined portion 25, the straight line connecting the upper end and the lower end of the outer surface of the main body is defined as straight line 25b, and the imaginary surface formed by extending the outer surface of inclined portion 25 downward is defined as imaginary surface 26.

[0051] Although detailed illustrations are omitted, the second or third modified example may be applied to the first modified example, and the fourth modified example may be applied to the first modified example. The second or third modified example and the fourth modified example may be applied simultaneously to the above embodiment or the first modified example. The second or third modified example and the fifth or sixth modified example may be applied simultaneously to the above embodiment or the first modified example.

[0052] The present invention will be described in more detail below with reference to Examples and Comparative Examples (Experimental Classifications 1 to 28), but the present invention is not limited thereto. In the following description, "parts" and "%" are by mass unless otherwise specified.

[0053] (Experimental Group 1) A content solution containing 80 parts of MCT (manufactured by Kao Corporation) was prepared. A coating solution containing 16 parts of gelatin (manufactured by PB Leiner Argentina), 4 parts of sorbitol (manufactured by Roquette China Co. Ltd.), and 300 parts of purified water was prepared. The bloom value of the gelatin was 240, and the viscosity of the coating solution was 50 mPa·s at 60°C. A cooling solution containing 100% MCT (manufactured by Kao Corporation) was prepared. The preparation of these solutions was similar for the other Experimental Groups 2 to 28.

[0054] Using a seamless capsule manufacturing machine (manufactured by Morishita Jintan) having a structure as exemplified in Figure 1, the content liquid was discharged from the center nozzle and the shell liquid from the outermost nozzle simultaneously into a cooling liquid to produce seamless capsules with a two-layer structure. The produced seamless capsules were then air-dried to evaporate the water contained in the shell layer, yielding dried capsules. The mass of the shell layer relative to the total mass of the dried capsule was 30%. The manufacturing method of the dried capsules and the mass ratio of the shell layer described here are the same for other experimental groups 2 to 28.

[0055] As shown in Table 1, a first nozzle (1-60) equipped with an inclined portion was used as a nozzle having a central nozzle and an outermost nozzle. The first nozzle (1-60) was formed to a size expected to produce dried capsules with a particle size of approximately 1 mm, and the angle between the outline of the inclined portion (hereinafter simply referred to as "angle θ") was 60°. In order to obtain the required particle size, the values ​​obtained by dividing the flow rate of the content liquid, the flow rate of the coating liquid, and the flow rate of the cooling liquid by the flow path cross-sectional area of ​​the forming tube were adjusted as shown in Table 1.

[0056] The position of the nozzle relative to the forming pipe was adjusted so that the distance between the apex of the space enclosed by a virtual plane extending the outer surface of the inclined portion and the upper end of the forming pipe (hereinafter simply referred to as "distance Z") was -10.1 mm. The tip of the nozzle was positioned below the liquid surface of the cooling liquid, and the composite jet was discharged into the cooling liquid.

[0057] (Experimental Groups 2 to 4) As shown in Table 1, in Experimental Groups 2 to 4, seamless capsules were produced using the first nozzle in the same manner as in Experimental Group 1, except that the distance Z was changed from that in Experimental Group 1.

[0058] In experimental category 2, the distance Z was adjusted to −1.8 mm. In experimental category 3, the distance Z was adjusted to 3.2 mm. In experimental category 4, the distance Z was adjusted to 13.2 mm.

[0059] (Experimental Groups 5 to 8) As shown in Table 1, in Experimental Groups 5 to 8, a second nozzle (1-30) with an inclined portion was used as the nozzle having a central nozzle and an outermost nozzle. Similar to the first nozzle (1-60), the second nozzle (1-30) was formed to the expected size so that the particle size of the dried capsules to be produced would be around 1 mm, while the angle θ was 30°. The flow rates of the content liquid, coating liquid, and coolant liquid divided by the flow path cross-sectional area of ​​the forming tube were adjusted as shown in Table 1.

[0060] In experimental category 5, the distance Z was adjusted to −14.9 mm. In experimental category 6, the distance Z was adjusted to −4.5 mm. In experimental category 7, the distance Z was adjusted to 0.5 mm. In experimental category 8, the distance Z was adjusted to 10.6 mm.

[0061] (Experimental Groups 9 to 12) As shown in Table 2, in Experimental Groups 9 to 12, a third nozzle (5-60) with an inclined portion was used as the nozzle having a central nozzle and an outermost nozzle. The third nozzle (5-60) was formed to a size expected to produce dried capsules with a particle size of approximately 5 mm, and the angle θ was 60°. The flow rates of the content liquid, coating liquid, and coolant liquid divided by the flow path cross-sectional area of ​​the forming tube were adjusted as shown in Table 2.

[0062] In experimental category 9, the distance Z was adjusted to −19 mm. In experimental category 10, the distance Z was adjusted to −5.7 mm. In experimental category 11, the distance Z was adjusted to −0.7 mm. In experimental category 12, the distance Z was adjusted to 9.3 mm.

[0063] (Experimental Groups 13 to 16) As shown in Table 2, in Experimental Groups 13 to 16, a fourth nozzle (5-40) with an inclined portion was used as the nozzle having a central nozzle and an outermost nozzle. Similar to the third nozzle (5-60), the fourth nozzle (5-40) was formed to the expected size so that the particle size of the dried capsules to be produced would be around 5 mm, while the angle θ was 40°. The flow rates of the content liquid, coating liquid, and coolant liquid divided by the flow path cross-sectional area of ​​the forming tube were adjusted as shown in Table 2.

[0064] In experimental category 13, the distance Z was adjusted to −30 mm. In experimental category 14, the distance Z was adjusted to −5.8 mm. In experimental category 15, the distance Z was adjusted to −0.8 mm. In experimental category 16, the distance Z was adjusted to 9.2 mm.

[0065] (Experimental Groups 17 to 20) As shown in Table 2, in Experimental Groups 17 to 20, a fifth nozzle (5-30) with an inclined portion was used as the nozzle having a central nozzle and an outermost nozzle. Similar to the third nozzle (5-60), the fifth nozzle (5-30) was formed to the expected size so that the particle size of the dried capsules to be produced would be around 5 mm, while the angle θ was 30°. The flow rates of the content liquid, coating liquid, and coolant liquid divided by the flow path cross-sectional area of ​​the forming tube were adjusted as shown in Table 2.

[0066] In experimental category 17, distance Z was adjusted to −36.2 mm. In experimental category 18, distance Z was adjusted to −6 mm. In experimental category 19, distance Z was adjusted to −1 mm. In experimental category 20, distance Z was adjusted to 9 mm.

[0067] (Experimental Groups 21 to 24) As shown in Table 3, in Experimental Groups 21 to 24, a sixth nozzle (8-60) with an inclined portion was used as the nozzle having a central nozzle and an outermost nozzle. The sixth nozzle (8-60) was formed to a size expected to produce dried capsules with a particle size of approximately 8 mm, and the angle θ was 60°. The flow rates of the content liquid, coating liquid, and coolant liquid divided by the flow path cross-sectional area of ​​the forming tube were adjusted as shown in Table 3.

[0068] In experimental category 21, the distance Z was adjusted to −26 mm. In experimental category 22, the distance Z was adjusted to −9.5 mm. In experimental category 23, the distance Z was adjusted to −4.5 mm. In experimental category 24, the distance Z was adjusted to 6.1 mm.

[0069] (Experimental Groups 25 to 28) As shown in Table 3, in Experimental Groups 25 to 28, a seventh nozzle (8-30) equipped with an inclined portion was used as the nozzle having a central nozzle and an outermost nozzle. The seventh nozzle (8-30) was formed to the expected size so that the particle size of the dried capsules to be produced would be approximately 8 mm, in the same manner as the sixth nozzle (8-60), but with an angle θ of 30°. The flow rates of the content liquid, coating liquid, and coolant liquid divided by the flow path cross-sectional area of ​​the forming tube were adjusted as shown in Table 3.

[0070] In experimental category 25, distance Z was adjusted to −51 mm. In experimental category 26, distance Z was adjusted to −9.7 mm. In experimental category 27, distance Z was adjusted to −4.7 mm. In experimental category 28, distance Z was adjusted to 5.3 mm.

[0071] Experimental groups 2, 3, 6, 7, 10, 11, 14, 15, 18, 19, 22, 23, 26, and 27 are examples in which the distance Z is within the range of −10.0 mm≦Z≦6.0 mm. The other experimental groups 1, 4, 5, 8, 9, 12, 13, 16, 17, 20, 21, 24, 25, and 28 are comparative examples in which the distance Z is outside this range.

[0072] (Evaluation) The seamless capsules obtained in each experimental category were evaluated as follows.

[0073] <Mean value of particle size and coefficient of variation> In each experimental group 1 to 28, 20 capsules were randomly selected from the obtained wet capsules, and the particle size (outer diameter) of each wet capsule was measured with a vernier caliper. Based on the particle size data of the 20 capsules, the mean value and standard deviation of the particle size of the wet capsules were calculated. Furthermore, the obtained standard deviation was divided by the mean value to calculate the coefficient of variation of the particle size of the wet capsules. The mean value, standard deviation, and coefficient of variation of the particle size of the dry capsules were calculated in the same manner.

[0074] In the examples, the average particle size of the dry capsules was the same as or close to the expected particle size. Furthermore, in the examples, the coefficient of variation was 0.1 or less for both the wet capsules and the dry capsules, and the particle size variation was suppressed.

[0075] <Wet capsule yield rate> In each of the experimental groups 1 to 28, 100 objects (approximately the same size as the wet capsules) formed from the composite jet discharged from the nozzle and flowing down the forming pipe were visually inspected, and the number of debris pieces whose coatings were broken and not spherical was counted. The yield rate was then calculated by applying the number of objects and the number of debris pieces to the following formula (1): Yield rate (%) = 1 - (number of debris pieces) / (number of objects) x 100 ... formula (1)

[0076] In the examples, a minimum yield rate of 97% was achieved, whereas in the comparative examples, the maximum was 82%, which was experimental category 24, and it was not possible to achieve a high yield rate like that of the examples.

[0077]

[0078]

[0079]

[0080] The present disclosure may include the following aspects. (Aspect 1) A method for producing seamless capsules, comprising a forming step of dropping droplets from a tip of a nozzle into a cooling liquid in a flow path of a forming tube and forming seamless wet capsules from the droplets, wherein the nozzle has an inclined portion that slopes inward from the middle of the nozzle toward the tip, and a distance Z between the apex of a space enclosed by an imaginary plane formed by extending the outer surface of the inclined portion downward from the tip and the upper end of the forming tube is within a range of -10 mm≦Z≦6 mm, and when Z<0, the apex is located below the upper end of the forming tube, and when Z>0, the apex is located above the upper end of the forming tube. (Aspect 2) A method for producing seamless capsules according to Aspect 1, wherein, in a vertical cross section of the nozzle passing through the central axis of the nozzle, an angle formed by a pair of straight lines connecting the upper and lower ends of the outer surface of the inclined portion is within a range of 20° to 70°. (Aspect 3) The method for producing seamless capsules according to Aspect 1 or 2, wherein, in a horizontal cross section of the nozzle perpendicular to the central axis of the nozzle, the outline of the inclined portion is circular, elliptical, or polygonal. (Aspect 4) The method for producing seamless capsules according to any of Aspects 1 to 3, wherein the coefficient of variation of particle size of the wet capsules is 0.1 or less. (Aspect 5) The method for producing seamless capsules according to any of Aspects 1 to 4, wherein the forming step includes a step of positioning the tip of the nozzle below the liquid surface of the cooling liquid. (Aspect 6) The method for producing seamless capsules according to any of Aspects 1 to 5, further including a drying step of drying the wet capsules to obtain dried capsules. (Aspect 7) The method for producing seamless capsules according to Aspect 6, wherein the coefficient of variation of particle size of the dried capsules is 0.1 or less. (Aspect 8) A method for producing a seamless capsule according to any one of Aspects 1 to 7, wherein the cooling liquid flowing into the forming tube is stored in a cooling reservoir, the inclined portion and the upper end of the forming tube are disposed within the cooling reservoir, the cooling liquid reservoir has a bottom wall, an upper wall, and a peripheral wall, and at least one portion of the nozzle, the upper wall, and the forming tube is configured to be movable up and down along the central axis of the nozzle.

[0081] REFERENCE SIGNS LIST 1 nozzle 1a tip 1b flange portion 1c content liquid inlet port 1d coating liquid inlet port 1e intermediate liquid inlet port 2 content liquid tank 2a content liquid supply pipe 3 coating liquid tank 3a coating liquid supply pipe 6 cooling liquid reservoir 6a bottom wall 6b upper wall 6c peripheral wall 6d cooling liquid inlet port 6e spacer 6f sealing 7 cooling liquid tank 8 cooling liquid supply pipe 9 cooling device 10 forming pipe 10a upper end 11-13 pump 14 screen 15 dryer 21 central nozzle 22 outermost nozzle 23 intermediate nozzle 25 inclined portion 25a outer surface 25b straight line 25c upper end 25d lower end 26 imaginary surface 27 vertex 31 nozzle body 32 cap 41 content liquid 42 Coating liquid 43 Intermediate liquid 49 Cooling liquid 49L Liquid surface 50 Seamless capsule 50w Wet capsule 50d Dry capsule 51 Content 52 Coating layer 53 Intermediate layer 59 Compound jet A Central axis Z Distance H Distance θ Angle

Claims

1. A method for producing seamless capsules, comprising a forming step of dropping liquid droplets from a tip of a nozzle into a cooling liquid in a flow path of a forming tube, and forming seamless wet capsules from the liquid droplets, wherein the nozzle has an inclined portion that slopes inward from the middle of the nozzle toward the tip, and a distance Z between the apex of a space enclosed by an imaginary plane formed by extending the outer surface of the inclined portion downward from the tip and the upper end of the forming tube is within the range of -10 mm≦Z≦6 mm, and when Z<0, the apex is located below the upper end of the forming tube, and when Z>0, the apex is located above the upper end of the forming tube.

2. The method for producing a seamless capsule according to claim 1, wherein, in a vertical cross section of the nozzle passing through the central axis of the nozzle, the angle formed by a pair of straight lines connecting the upper and lower ends of the outer surface of the inclined portion is within the range of 20° to 70°.

3. The method for producing a seamless capsule according to claim 1 or 2, wherein in a horizontal cross section of the nozzle perpendicular to the central axis of the nozzle, the outline of the inclined portion is a circle, an ellipse or a polygon.

4. The method for producing seamless capsules according to any one of claims 1 to 3, wherein the coefficient of variation of particle size of the wet capsules is 0.1 or less.

5. The method for producing a seamless capsule according to any one of claims 1 to 4, wherein the forming step includes a step of positioning the tip of the nozzle below the liquid surface of the cooling liquid.

6. The method for producing a seamless capsule according to any one of claims 1 to 5, further comprising a drying step of drying the wet capsule to obtain a dry capsule.

7. The method for producing seamless capsules according to claim 6, wherein the coefficient of variation of particle size of the dried capsules is 0.1 or less.

8. A method for producing a seamless capsule as described in any one of claims 1 to 7, wherein the cooling liquid flowing into the forming tube is stored in a cooling reservoir, the inclined portion and the upper end of the forming tube are disposed within the cooling reservoir, the cooling liquid reservoir has a bottom wall, an upper wall, and a peripheral wall, and at least one portion of the nozzle, the upper wall, and the forming tube is configured to be movable up and down along the central axis of the nozzle.

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