Interdental cleaning tool

Abstract

The present invention describes an interdental cleaning tool comprising: a base portion made of a synthetic resin, the base portion having a handle base and a core base similar to an elongated shaft connected to a front end of the handle base; and a flexible portion made of an elastomer covering at least a portion of the base portion, the flexible portion having at least one flexible cleaning portion covering the core base, the handle base constituting a portion of the handle, and the core base and the flexible cleaning portion constituting an interdental cleaning portion, wherein a plurality of interdental cleaning tools are aligned in parallel, connecting portions for connecting adjacent interdental cleaning tools are provided through adjacent handle bases to be integral with the handle bases, the base portions being made of a synthetic resin material with a fiber material.

Description

Interdental cleaning tool Technical field The present invention relates to a method for manufacturing an interdental cleaning tool, which has a cleaning part covered by an elastomer, and the interdental cleaning tool. Background of the technique An interdental cleaning tool has been marketed, comprising: a base portion made of a synthetic resin, the base portion having a handle base and a core base, similar to an elongated shaft, disposed at a front end of the handle base; and a flexible portion made of an elastomer, the flexible portion having at least one flexible cleaning portion covering the core base, the handle base constituting a handle portion, and the core base and the flexible cleaning portion constituting an interdental cleaning portion (e.g., see Patent Documents 1 to 3). In a widely used method for manufacturing interdental cleaning tools, a synthetic resin material is loaded into a first molding cavity of a first metal mold to produce the base portion. The base portion, molded by the first metal mold, is then placed into a second molding cavity of a second metal mold. An elastomeric material is loaded into the second molding cavity to form a flexible portion, thereby obtaining the interdental cleaning tool. Generally, to obtain a plurality of interdental cleaning tools, a plurality of first molding cavities are arranged in the first metal mold, and the same number of second molding cavities are arranged in the second metal mold.In the manufacture of interdental cleaning tools, synthetic resin material is supplied to the plurality of first molding spaces to simultaneously produce a plurality of base parts connected together by feed channel parts, a primary molded article, formed by the plurality of base parts connected together by the feed channel parts, is inserted into the second molding spaces of the second metal mold, and the elastomer material is loaded into the plurality of second molding spaces, thereby simultaneously molding the plurality of interdental cleaning tools. To simplify the metal mold structure as much as possible, in general, when loading the elastomer material into the second molding spaces, inlets are placed on the front end sides of the interdental cleaning tools in the second molding spaces. The elastomer material is then loaded from the front end sides to the base ends of the core bases of the loaded base parts in the second molding spaces. Furthermore, the elastomer material has a relatively high viscosity. Thus, when molding the flexible cleaning parts in the second molding spaces, if the elastomer material is loaded from the base sides to the front end sides of the core base, loading failures may occur at the front ends of the flexible cleaning parts.Partly due to this, the elastomer material is generally loaded from the front end sides to the base end sides of the core bases to prevent molding failures at the front ends of the flexible cleaning parts. List of citations Patent literature Patent Document 1: Japanese Patent No. 4236571 Patent Document 2: Japanese Patent No. 3002668 Patent Document 3: Publication of Unexamined Japanese Patent Application (Translation of PCT Application) No. 2001-506514 Compendium of the invention Technical problem However, when the elastomer material is loaded into the secondary molding spaces from the leading ends to the base ends of the core bases, as described above, the inlet openings cannot be widened. Consequently, the injection pressure of the elastomer becomes high and prone to variation around the core bases near the inlets. This causes a molding failure problem because the core bases curve toward the side with the lower injection pressure and become exposed. Furthermore, the elastomer material is heated to near the melting temperature of the core bases to improve adhesion. This causes a problem because the core bases soften and are prone to heat deformation from the elastomer material, and thus can deform even with slight variations in injection pressure. An object of the present invention is to provide a method for manufacturing an interdental cleaning tool, which can prevent the deformation of a core base in the molding of a flexible cleaning part using an elastomer material, thereby effectively preventing molding failures of the flexible cleaning part and the interdental cleaning tool. Solution to the problem A method for manufacturing an interdental cleaning tool according to the present invention is a method for manufacturing an interdental cleaning tool comprising: a base portion made of a synthetic resin, the base portion having a handle base and a core base, similar to an elongated shaft, connected to a front end of the handle base;and a flexible part made of an elastomer and covering at least a portion of the base part, the flexible part having at least one flexible cleaning portion covering the core base, the handle base constituting a handle part, and the core base and the flexible cleaning portion constituting an interdental cleaning portion, wherein the method for manufacturing an interdental cleaning tool includes: a base portion molding step of: arranging a metal mold for molding the base portion, with a plurality of first molding spaces aligned in parallel and including core base molding sections and handle base molding sections; arranging the metal mold, with connecting portion molding sections to communicate with the adjacent handle base molding sections;simultaneously supplying a synthetic resin material with a fiber material to the plurality of first molding spaces from open inlets to the first molding spaces at the end base sides of the first molding spaces, opposite the core base molding sections; and simultaneously molding a plurality of base parts such that the base parts are connected to each other in parallel by connecting parts molded in the connecting part molding sections, and a flexible part molding stage of: transferring the plurality of base parts, molded and connected to each other in the base part molding stage, to a metal mold for molding the flexible part; inserting at least portions of the core bases of the base parts into a plurality of second molding spaces in the metal mold;securing the core bases in two or more longitudinal spans, including the front ends and base ends of the core bases, nearly at the centers of the flexible cleaning part molding sections, using at least two pairs of clamping pins, each pair including two pins, which are opposite each other and project into the interior of each flexible cleaning part molding section to be approximately orthogonal to matching surfaces of the metal mold; and loading an elastomer material into the second molding spaces so that the elastomer material is supplied from the front end sides to the base end sides of the flexible cleaning part molding sections. In the manufacturing method, firstly, in the base parts molding stage, the synthetic resin material with the fiber material is simultaneously supplied to the plurality of first molding spaces from the inlets on the end sides of the base of the first molding spaces to mold the plurality of base parts connected to each other by the connecting parts. Then, in the flexible parts molding stage, the plurality of base parts, molded in the base parts molding stage and connected to each other by the connecting parts, are transferred to the metal mold for molding the flexible parts; at least portions of the core bases of the base parts (including at least portions of the core bases covered by the clear flexible parts) are inserted into the second molding spaces;The core base portions are held almost in the centers of the flexible cleaning part molding sections, to be located in the centers of the flexible cleaning part molding sections, by means of a plurality of clamping pins; and the elastomer material is loaded inwards into the flexible cleaning part molding sections from the front end sides to their base end sides, thereby making the interdental cleaning tools, in which the flexible parts are molded integrally with the base parts. As in the previous method, according to the manufacturing process, the synthetic resin material with the fiber material is simultaneously supplied to the multiple first molding spaces through inlets at the base ends of the first molding spaces. Consequently, the fiber material is oriented along the first molding spaces, i.e., along the base portions. This makes it possible to improve the core bases in particular with respect to bending and buckling resistance along the axial direction and effectively prevents folding and buckling of the core bases when using interdental cleaning tools. The fiber material also improves the base portions in terms of dimensional stability and strength stiffness, preventing deformation of the core bases.This makes it possible to prevent at least portions of the core bases in the base parts from being improperly loaded into the secondary molding spaces. The fiber material also raises the thermal distortion temperature of the core bases, thus effectively preventing softening and deformation of the core bases due to the heat generated by the elastomer material during the molding of the flexible cleaning parts. The fiber material also increases the tensile strength of the core bases, preventing deformation of the core bases under the injection pressure of the elastomer material. Consequently, it is possible to prevent the core bases from deforming during the molding of the flexible cleaning parts, thereby more effectively preventing molding defects in the flexible cleaning parts. The addition of the fiber material allows the multiple base parts to be connected by the connecting parts with appropriate strength. This makes it possible to transfer the multiple base parts, molded simultaneously in the base part molding cap, into the secondary molding spaces during the flexible part molding stage, thereby uniformly molding multiple interdental cleaning tools at once. Furthermore, even if the manufactured interdental cleaning tools are packaged while connected by the connecting parts, it is possible to prevent the connected interdental cleaning tools from separating due to vibrations generated during packaging or distribution / sales processes. Additionally, for use, the interdental cleaning tools can be separated relatively easily by hand at the connecting parts.Specifically, if no fiber material is added, the use of polypropylene (PP) as the synthetic resin material, for example, makes it difficult to separate the interdental cleaning tools at the connecting parts due to deformation of those parts. Meanwhile, the use of polybutylene terephthalate (PBT) as the synthetic resin material makes the connecting parts prone to breakage, which causes a problem because the multiple molded base parts cannot be transferred simultaneously to the second molding stage, or the multiple manufactured interdental cleaning tools, connected by the connecting parts, separate unfavorably from each other during packaging or distribution / sales processes.Furthermore, the fiber material added to the synthetic resin is also oriented along the initial molding spaces, specifically along the interdental cleaning tools, around the boundary sections between the handle base molding sections and the connecting portion molding sections. Consequently, the parallel-molded interdental cleaning tools can be properly cut and separated by bending adjacent tools at the connecting portions and breaking the connecting portions apart without significant deformation of the surrounding areas.However, it is necessary to establish the connection strength between the connecting parts and the base parts so that these parts do not easily separate from each other due to vibrations generated when the base parts are transferred from the first molding spaces to the second molding spaces or when the manufactured interdental cleaning tools are in the packaging or distribution / sale processes or similar. The elastomer material is loaded from the front ends to the base ends of the core bases used to mold the flexible cleaning parts. This allows for the simultaneous molding of multiple interdental cleaning tools without complicating the structure of the metal mold used to mold the flexible parts. Furthermore, the core bases are secured in two or more longitudinal sections, including the front ends and base ends, by at least two pairs of locking pins, each pair comprising two opposing locking pins. These opposing pins protrude into the molding sections of the flexible cleaning parts to be approximately orthogonal to matching surfaces of the metal mold used to mold the flexible parts; that is, they protrude in the direction of the opening and closing of the metal mold used to mold the flexible parts.Therefore, compared to conventional methods where core bases are secured by three or more clamping pins at the same positions along a circumferential section, it is possible to simplify the metal mold structure for molding flexible parts and reduce the difficulty of elastomer flow in the cleaning tool molding spaces (hereafter referred to as flow resistance). It is also possible to suppress the influence of the Karman vortex generated near the clamping pins when loading the elastomer. Furthermore, the elastomer is loaded from the front ends of the core bases, where flow is more difficult, thus providing sufficient moldability for the front ends of the cleaning flexible parts. In a preferred embodiment, the connecting part molding sections are elongated along the handle base molding sections and become thinner as they approach a first boundary section of two boundary sections between the connecting part molding section and the handle base molding sections on both sides of the connecting part molding section. According to this configuration, the synthetic resin material supplied to the handle base molding sections can easily enter the connecting part molding sections from the side of the second boundary section.Even if the synthetic resin material simultaneously reaches both boundary sections, the synthetic resin supplied to the adjacent handle base molding sections bonds near the first boundary sections. This allows the molded base parts to be easily cut and separated at positions corresponding to these first boundary sections. Furthermore, the fiber material added to the synthetic resin tends to orient itself along the handle base molding sections around the first boundary sections of the connecting part molding sections. This also allows the base parts to be easily cut and separated at positions corresponding to these first boundary sections. Consequently, multiple interdental cleaning tools molded simultaneously can be easily cut and separated sequentially from the outside. In a preferred embodiment, of the two boundary sections between the connecting part molding section and the handle base molding section on either side of the connecting part molding section, the length of the first boundary section along the handle base molding section is shorter than the length of the second boundary section. According to this configuration, the synthetic resin material supplied to the handle base molding section can enter the connecting part molding sections more uniformly from the side of the second boundary section. This allows the synthetic resin material supplied to the adjacent handle base molding sections to bond more effectively near the first boundary sections. Furthermore, it allows the fiber material to be more appropriately oriented along the handle bases around the first boundary sections.Therefore, interdental cleaning tools can be more easily cut and separated at positions corresponding to the first boundary sections. In a preferred embodiment, two or more connecting part molding sections are arranged at intervals along the handle base molding section. Only one connecting part molding section may be arranged in the center of the handle base molding section along its length. However, if the number of connecting parts molded by the connecting part molding section is one, it is not possible to provide sufficient connection strength to the adjacent base parts. Thus, after molding the interdental cleaning tools, the connecting parts may break, allowing the interdental cleaning tools to fall apart when the molds are opened, or the connecting parts may fold and deform.This easily causes the base parts to misalign within the appropriate positions of the secondary molding spaces, resulting in molding failures of the flexible interdental cleaning parts. Therefore, two or more connecting part molding sections are preferably arranged between a pair of adjacent base parts. Furthermore, if the connecting parts are too long along the base parts, when the interdental cleaning tools are cut and separated, the connecting parts may have sharp corners at both ends of the cut surfaces. Therefore, two or more short connecting part molding sections are preferably arranged at intervals along the handle base molding sections. Preferably, the fiber material uses fiberglass, and the fiberglass-to-synthetic resin ratio is set at 12% by weight or more and 35% by weight or less. Specifically, if the fiberglass-to-fiber material ratio is less than 12% by weight, the cleaning portion is prone to flexing and difficult to insert between adjacent teeth due to the porous structure. If the ratio exceeds 35% by weight, the cleaning portion is prone to breakage and may injure the user's mouth, or the user may accidentally swallow broken pieces. Therefore, the preferred ratio is set between 12% by weight or more and 35% by weight or less. In a preferred embodiment, the synthetic resin material is polypropylene (PP), polybutylene terephthalate (PBT), or polyamide. Preferably, in particular, polypropylene has a low molding temperature and can shorten cycle time and improve productivity, and imposes less thermal load on the molding equipment. If polypropylene (PP) is used as the synthetic resin material, the fiber blending ratio is preferably set at 15% by weight or more and 35% by weight or less. If polybutylene terephthalate (PBT) is used, the blending ratio is preferably set at 12% by weight or more and 35% by weight or less. In a preferred embodiment, a pair of clamping pins, which secure the front end of the core base, have a cross-sectional area, of a portion in contact with the core base, of 0.03 to 0.3 mm², the pair of clamping pins being arranged in positions where the front ends of the pins are in contact with the core base corresponding to an interval of 3 mm from the front end to the base end of the flexible cleaning part molding section, a pair of clamping pins, which secure the base end of the core base, have a cross-sectional area, of a portion in contact with the core base, of 0.1 to 1.1 mm²,The pair of clamping pins is arranged in positions where the front ends of the pins are in contact with the core base, corresponding to a 6 mm interval from the base end to the front end of the flexible cleaning part molding section. In this embodiment, it is possible to stably clamp the core base in the center of the flexible cleaning part molding section, while minimizing flow resistance for the elastomer material and suppressing the influence of the Karman vortex generated during the flexible part molding on the molded body. Consequently, even with certain variations in injection pressure, it is possible to suppress core base deformation and prevent molding defects due to core base deformation. Provided the clamping pins meet the above conditions, it is only required that these clamping pins protrude from the molding sections of the flexible parts to be approximately orthogonal to opposite surfaces, i.e., the mating surfaces of the metal mold for casting the flexible parts. In a more preferred embodiment, the two clamping pins secure the core base at the same positions in a circumferential section and a surrounding section along the core base.In a further preferred embodiment, after the two clamping pins are positioned in the same locations along a circumferential section of the core base, one of the pins is offset at its forward end by a distance shorter than the longitudinal distance of the flexible cleaning part molding section, in the longitudinal direction of the flexible cleaning part molding section. When the two opposing clamping pins are thus offset along the flexible cleaning part molding section, the core base is clamped between the pins over a substantially wider area. Consequently, the core base can be clamped more securely. In a preferred embodiment, the cross-sectional area of ​​the clamping pins increases with increasing proximity to the base side of the flexible cleaning part molding section. The path area of ​​the flexible cleaning part molding section increases with increasing proximity to the end base side. Therefore, when the cross-sectional area of ​​the clamping pins increases with increasing proximity to the base side of the flexible cleaning part molding section, it is possible to minimize flow resistance for the elastomer material at the leading end of the flexible cleaning part molding section and further suppress the influence of the Karman vortex generated near the clamping pins on the molded body and the clamping pins.Therefore, it is possible to more reliably secure the core base and prevent load failure of the elastomer material into the molded section of the flexible cleaning parts. Furthermore, there are no particular limitations on the cross-sectional shape of the clamping pins. For example, the cross-section of the clamping pins can be polygonal, such as circular, oval, triangular, square, or any other shape. Of these shapes, circular, oval, square, and teardrop (drop-shaped) are preferred, as they best suppress the influence of the Karman vortex generated near each clamping pin on the molded body and the clamping pins themselves. The clamping pins may be provided to protrude freely in the flexible part molding section. Alternatively, the clamping pins may be fixed in the metal mold for forming the flexible parts. In this case, however, when the core parts molded by the metal mold for forming the core parts are inserted into the metal mold for forming the flexible parts, the core bases contact the clamping pins, which are prone to causing load failure of the core bases into the metal mold for forming the flexible parts.Thus, preferably as in the present invention, the retaining pins are provided to protrude freely from the flexible cleaning part molding section. The retaining pins are inserted into the metal mold when the core bases are loaded into the flexible cleaning part molding sections in the second molding chambers. The core bases are loaded into the flexible cleaning part molding sections without any protruding retaining pins, and then the mold is closed, causing the retaining pins to protrude. Consequently, it is possible to secure the core bases in the appropriate positions and prevent the core bases from failing to load into the metal mold for molding the flexible parts. In a preferred embodiment, the synthetic resin material used to form the base parts and the elastomer material used to form the flexible parts are compatible with each other. This effectively prevents the flexible parts from separating from the base parts, thus creating durable interdental cleaning tools. In a preferred embodiment, the elastomer material is a styrene-based elastomer that exhibits high flowability, even at low hardness levels, and favorable adhesion to the synthetic resin, compared to other elastomers, such as olefin-based elastomers. More specifically, the elastomer material has a Shore A value of 5 to 70, preferably 10 to 50, more preferably 20 to 50, and most preferably 30 to 40. The interdental cleaning tool according to the present invention includes: a base portion made of a synthetic resin, the base portion having a handle base and a core base, similar to an elongated shaft, connected to a front end of the handle base; and a flexible portion made of an elastomer covering at least a portion of the base portion, the flexible portion having at least one flexible cleaning portion covering the core base, the handle base, and, in some cases, the flexible portion constituting a handle portion, and the core base and the flexible cleaning portion constituting an interdental cleaning portion, wherein a plurality of interdental cleaning tools are aligned in parallel, connecting portions for connecting adjacent interdental cleaning tools are arranged across adjacent handle bases so as to be integral with the handle bases.The base parts are made of a synthetic resin material with a fiber material; the fiber material is oriented along the base part and at least around a first boundary part of two boundary parts between the connecting part and the handle bases on both sides of the connecting part; the fiber material is oriented along the base part so that adjacent interdental cleaning parts can be cut and separated at the first boundary part. In interdental cleaning tools, the fiber material is oriented along the base portions. This improves the core base portions' flexural and buckling strength along the axial direction, effectively preventing folding and buckling of the core bases during use. The fiber material also enhances the base portions' dimensional stability and strength, preventing deformation and allowing for precise molding of the flexible cleaning portions relative to the base portions. This enables the precise production of high-quality interdental cleaning tools. Furthermore, connecting multiple interdental cleaning tools in parallel improves their moldability and ease of packaging.Furthermore, at least around the first boundary portion of the two boundary portions between the connecting part and the handle base, the fiber material is oriented along the handle base. This allows the connecting portions to be separated by breakage without deformation of the surrounding portions. Consequently, interdental cleaning tools connected in parallel can be properly cut and separated at the first boundary portions. In a preferred embodiment, the connecting portions are elongated along the handle bases and become thinner as they approach the first boundary portions. According to the above configuration, as described in detail in the manufacturing method, the synthetic resin material supplied to the adjacent handle base molding sections bonds at the first boundary portions of the connecting portions. Furthermore, the fiber material added to the synthetic resin material tends to orient itself along the handle arms at the first boundary portions. Consequently, when interdental cleaning tools are used, these tools can be easily cut and separated at the first boundary portions without significant deformation of the surrounding areas. In a preferred embodiment, the length of the first limit portion along the handle base is shorter than the length of the second limit portion. According to this configuration, the connection resistance between the connecting portion and the handle base at the first limit portion can be lower than the connection resistance between the connecting portion and the handle base at the second limit portion. This allows the interdental cleaning tools to cut and separate more easily and uniformly at the first limit portion. In a preferred embodiment, two or more connecting parts are arranged at intervals along the handle base. Only one connecting part may be arranged in the center of the handle base along its length. In this case, however, it is not possible to provide sufficient connecting strength between the adjacent base parts. Thus, after molding the interdental cleaning tools, the connecting parts may break, allowing the tools to fall apart when the molds are opened, or the connecting parts may fold and deform, resulting in molding defects. Therefore, two or more connecting parts are preferably provided.Furthermore, if the connecting parts are too long along the base portions, when the interdental cleaning tools are cut and separated, the connecting parts may have sharp corners on both ends of the cut surfaces. Therefore, two or more short connecting parts are preferably arranged at intervals along the handle bases. Preferably, the fiber material uses fiberglass, and the fiberglass-to-synthetic resin ratio is set at 12% by weight or more and 35% by weight or less. Specifically, if the fiberglass-to-fiber material ratio is less than 12% by weight, the cleaning portion is prone to flexing and difficult to insert between adjacent teeth due to the porous structure. If the ratio exceeds 35% by weight, the cleaning portion is prone to breakage and may injure the user's mouth, or the user may accidentally swallow broken pieces. Therefore, the preferred combination ratio is set at 12% by weight or more and 35% by weight or less. In a preferred embodiment, the synthetic resin material is polypropylene (PP), polybutylene terephthalate (PBT), or polyamide. Preferably, in particular, polypropylene has a low molding temperature and can shorten the cycle time of the base part, improve productivity, and impose less thermal load on the molding equipment. If polypropylene (PP) is used as the synthetic resin material, the fiber blending ratio is preferably set at 15% by weight or more and 35% by weight or less. If polybutylene terephthalate (PBT) is used, the blending ratio is preferably set at 12% by weight or more and 35% by weight or less. In a preferred embodiment, the core base is tapered to gradually reduce in diameter at its front end, and the angle formed by the taper with respect to the length of the core base is set from 0.2 to 2.5°, and in a further preferred embodiment, from 0.2 to 1.5°. According to this embodiment, the cleaning portion can be inserted more easily between the teeth, providing an additional advantage: during interdental cleaning, the user can employ an interdental cleaning tool to gently massage the interdental papillae with openings of varying sizes. In a preferred embodiment, the elastomer material is a styrene-based elastomer that exhibits high flowability, even at low hardness levels, and favorable adhesion to the synthetic resin, compared to other elastomers, such as olefin-based elastomers. More specifically, the elastomer material has a Shore A value of 5 to 70, preferably 10 to 50, more preferably 20 to 50, and most preferably 30 to 40. Advantageous effects of the invention According to the method for manufacturing an interdental cleaning tool in the present invention, the synthetic resin material with the fiber material is simultaneously supplied to the plurality of first molding spaces through inlets on the end sides of the base of the first molding spaces. Consequently, the fiber material is oriented along the first molding spaces, i.e., along the base portions. This makes it possible to improve, in particular, the bending and buckling strength of the core bases along the axial direction and effectively prevent folding and buckling of the core bases when using the interdental cleaning tools. The fiber material also improves the dimensional stability and strength of the base portions, preventing deformation of the core bases.This makes it possible to prevent at least portions of the core bases in the base parts from being improperly loaded into the secondary molding spaces. The fiber material also raises the thermal distortion temperature of the core bases, thus effectively preventing softening and deformation of the core bases due to the heat generated by the elastomer material during the molding of the flexible cleaning parts. The fiber material also increases the tensile strength of the core bases, preventing deformation of the core bases under the injection pressure of the elastomer material. Consequently, it is possible to prevent the core bases from deforming during the molding of the flexible cleaning parts, thereby more effectively preventing molding defects in the flexible cleaning parts. The addition of fiber material allows the multiple base parts to be connected by the connecting parts with appropriate strength. Furthermore, even if the manufactured interdental cleaning tools are packaged while connected, it is possible to prevent these connected interdental cleaning tools from separating due to vibrations generated during packaging or distribution / sales processes. Additionally, for use, the interdental cleaning tools can be separated relatively easily by hand at the connecting parts. Moreover, the fiber material added to the synthetic resin is also oriented along the initial molding areas, i.e., along the interdental cleaning tools, around the boundary sections between the handle base molding sections and the connecting part molding sections.Therefore, parallel molded interdental cleaning tools can be cut and separated appropriately by bending adjacent interdental cleaning tools at the connecting parts. The elastomer material is applied from the front ends to the base ends of the core bases to form the flexible cleaning parts. This allows for the simultaneous molding of multiple interdental cleaning tools without complicating the structure of the metal mold used to form the flexible parts. Furthermore, the core bases are secured in two or more longitudinal sections, including the front ends and base ends, by at least two pairs of retaining pins. Each pair of pins includes two pins opposite each other in the vertical direction, for example. When opposing pins are required in addition to the two pairs mentioned above, the same number of pins are ideally placed on both opposite surfaces, but a different number of pins may be placed on each surface.The two opposing pins protrude into the flexible cleaning tool molding sections to be approximately orthogonal to matching surfaces of the metal mold for the flexible parts; that is, they protrude in the direction of the opening and closing of the metal mold. Consequently, compared to conventional cases where the core bases are secured by three or more clamping pins at the same positions in a circumferential section along the core bases, it is possible to simplify the structure of the metal mold for the flexible parts and reduce the flow resistance of the elastomer material in the cleaning tool molding spaces. It is also possible to suppress the influence of the Karman vortex generated near the clamping pins when loading the elastomer.In addition, the elastomer material is loaded from the front end sides of the core bases, where the elastomer material is more difficult to flow, making it possible to provide sufficient moldability of the front ends of the flexible cleaning parts. According to the interdental cleaning tools of the present invention, the fiber material is oriented along the core portions. This improves the bending and buckling resistance of the core portions along the axial direction and effectively prevents folding and buckling of the core portions during use. The fiber material also enhances the dimensional stability and strength of the core portions, preventing deformation and precisely shaping the flexible cleaning portions relative to the core. This enables the precise production of high-quality interdental cleaning tools.Furthermore, connecting multiple interdental cleaning tools in parallel improves their moldability and ease of packaging. Additionally, at least around the first boundary between the connecting portion and the handle base, the fiber material is oriented along the handle base. This allows the connecting portions to be separated by breakage without deforming the surrounding areas. Consequently, interdental cleaning tools connected in parallel can be properly cut and separated at the first boundary. Brief description of the drawings Fig. 1 is a front view of pairs of connected interdental cleaning tools; Fig. 2(a) is a front view of interdental cleaning tools and Fig. 2(b) is a side view of an interdental cleaning tool; Fig. 3 is an enlarged, front view of connecting parts and surrounding parts in interdental cleaning tools; Fig. 4 is a cross-sectional view of Fig. 3 along line IV-IV; Fig. 5 is an enlarged scale view of a cleaning section; Fig. 6 is a cross-sectional view of Fig. 5 along line VI-VI; Fig. 7 is a diagram describing a method for molding a base part using a first metal mold; Fig. 8 is a front view of a mating surface of the first metal mold near molding sections of connecting parts; Fig. 9 is a cross-sectional view of the first metal mold shown in Fig. 8 along line IX-IX; Fig. 10 is a front view of a matching surface of a first metal mold near molding sections of connecting parts in another configuration; Fig. 11 is a diagram describing a method for molding a flexible part by a second metal mold; Fig. 12(a) is an enlarged scale view of a flexible cleaning part molding section and a surrounding section in the second metal mold, before fastening pins protrude, and Fig. 12(b) is an enlarged scale view of the flexible cleaning part molding section and the surrounding section in the second metal mold, after the fastening pins protrude; Fig. 13 is a photograph showing the orientation of a fiber material in the connecting part and the surrounding part; Fig. 14 is a diagram describing a method for performing a horizontal bending test on the interdental cleaning tool; Fig. 15 is a diagram describing a method for performing a separation test on the interdental cleaning tool; Fig. 16(a) is a front view of a mating surface of a metal mold in a metal mold device in another configuration and Fig. 16(b) is a front view of a mating surface of the other metal mold in a metal mold device in another configuration; Fig. 17(a) is a cross-sectional view of Fig. 16(a) along line aa, Fig. 17(b) is a cross-sectional view of Fig. 16(a) in an open mold state along line aa, and Fig. 17(c) is a cross-sectional view of Fig. 16(a) along line cc; Fig. 18(a) is a front view of a mating surface of a metal mold in a metal mold device in another configuration and Fig. 18(b) is a front view of a mating surface of the other metal mold in a metal mold device in another configuration; Fig. 19(a) is a front view of a mating surface of a metal mold for forming base parts in a metal molding device in another configuration, and Fig. 19(b) is a front view of a mating surface of the other metal mold for forming base parts in a metal molding device in another configuration; and Fig. 20(a) is a front view of a mating surface of a metal mold for molding flexible parts in the metal molding device and Fig. 20(b) is a front view of a mating surface of the other metal mold for molding flexible parts in the metal molding device. Description of achievements The embodiments of the present invention will be described below with reference to the drawings. <Herramienta de limpieza interdental> First, a configuration of an interdental cleaning tool 1 will be described. As shown in Figs. 1 to 6, each interdental cleaning tool 1 includes a cleaning part 2 for interdental cleaning and a handle part 3, functionally speaking, and the interdental cleaning tool 1 includes a base part 10 made of a synthetic resin and a flexible part 20 made of an elastomer. The interdental cleaning tools 1 are manufactured in the form of a connected body of interdental cleaning tools 1A, in which a plurality of interdental cleaning tools 1 are connected in parallel so that they can be cut and separated. A user cuts and separates the interdental cleaning tools 1 sequentially at the connecting parts 13 from one side of the connected body of interdental cleaning tools 1A. Fig.Figure 1 shows the connected body of interdental cleaning tools 1A, in which ten interdental cleaning tools 1 are connected in parallel, but the number of connected interdental cleaning tools 1 that constitute the connected body of interdental cleaning tools 1A can be arbitrarily set. (Basic parts) The base 10 parts are made of a synthetic resin with a fiber material. As shown in Figs. 1 to 6, each of the base parts 10 includes a handle base 11, similar to a flat, elongated plate, which constitutes handle part 3, a core base 12, similar to an elongated shaft, connected to a front end of the handle base 11, and connecting parts 13, which connect adjacent handle bases 11 so that they can be cut and separated. The handle base 11 is formed in the form of a flat, elongated plate. Alternatively, the handle base 11 can be formed in the form of a bar with a circular, oval, or polygonal cross-section, for example, provided that the handle base 11 can be easily gripped by hand for cleaning between teeth. The handle base 11 has a narrower front end as it approaches the core base 12 and is uniformly connected to the core base 12. The dimensions of the handle base 11 can be arbitrarily determined, provided that the handle base 11 can be easily gripped by hand for cleaning between teeth. The handle base 11 with the shape shown in Figs. 1 to 6 has a length L1 of 10 to 25 mm, a width W1 of 4 to 10 mm, and a thickness t1 of the gripping portion of 1.0 to 2.0 mm, for example.As before, the handle base 11 is made thin, and thus, in the molding of the base parts 10, it is possible to reduce dimensional variations due to the shrinkage of the handle bases 11 and prevent the appearance of shrinkage marks. This prevents load failures of the base parts 10 into the second metal molds 40 and 41 for molding the flexible parts 20. The core base 12 is formed with an almost straight, elongated shaft configuration. On one gripping side, the core base 12 has an exposed portion 12a, and on its front end, a main core body 12b, which is covered with an elastomer and can be inserted between the teeth. The core base 12 is moderately tapered to reduce the diameter at the front end. The length L2 of the exposed portion 12a, measured from the extreme point of a circle (curve) on a lateral surface of the narrow front end of the handle base 11 to the base end of the covered portion 20a of the flexible part 20, is set, for example, at 10 to 50 mm, preferably 10 to 25 mm, for operational purposes.The flexible cleaning portion 21 has a length L3 that is set from 12 to 22 mm, for example, in terms of interdental cleaning capacity. The core base 12 has an angle 0 formed by the conical shape with respect to the centerline of the core base 12, that is, set from 0.2 to 2.5°, preferably from 0.2 to 1.5° to facilitate insertion between the teeth. The main body of the core 12b has a diameter of the front end portion that is set from 0.4 to 0.6 mm and a diameter of a base end portion that is set from 0.8 to 2.0 mm. The covered portion 21a of the flexible cleaning portion 21 has a diameter D of a front end at the end of a curve that is set from 0.5 to 1.2 mm. Therefore, an extreme front portion of the 12b core main body of at least 5 mm or more from the front end of the 12b core main body can be reliably inserted between the teeth.The angle 0 formed by the tapered shape of the core base 12 is set to be identical along the entire length of the core base 12. Alternatively, the angle 0 can be set to be continuously or gradually smaller at the front end of the core base 12. Furthermore, the exposure portion 12a can be formed with a shaft configuration having an identical diameter along its entire length, and only the main core body 12b can be moderately tapered to reduce the diameter at the front end. Additionally, the exposure portion 12a can be omitted to connect the main core body 12b directly to the handle base 11. As shown in Figs. 2 to 4, the connecting parts 13 are formed between adjacent handle bases 11 to be integrated with the handle bases 11. Each pair of connecting parts 13 is arranged at intervals along the end base side and the front end side of the handle base 11. Boundary parts 13a and 13b between adjacent handle bases 11 and the connecting part 13 between the handle bases 11 have lengths L4 and L5, which are set from 1.5 to 3.0 mm, for example. The length L4 of the first boundary part 13a is set shorter than the length L5 of the second boundary part 13b. The connecting parts 13 are elongated along the handle bases 11 and are formed in the shape of a trapezoid (isosceles trapezoid in Fig. 3) in a front view. The number of connection parts 13 can be arbitrarily set, and thus only one connection part can be arranged.In this case, however, it is not possible to provide sufficient connecting strength between adjacent base parts 10 when manufacturing the interdental cleaning tools 1. Thus, after molding the base parts 10, the connecting parts 13 may break when the molds are opened to allow the base parts 10 to crumble and render the molding of the flexible parts 20 unusable, or the connecting parts 13 may fold and flex, interfering with the loading of the base parts 10 into the appropriate positions of the second molding spaces 42 for molding the flexible parts 20, thereby resulting in molding failures. Consequently, two or more connecting parts 13 are preferably arranged at intervals along the handle bases 11. The connecting part 13 has a projecting length L6 that is set from 0.5 to 1.5 mm, for example. A thickness t2 of the connecting part 13 at the first boundary part 13a is set less than a thickness t3 of the connecting part 13 at the second boundary part 13b. The connecting part 13 is made thinner continuously or gradually from the second boundary part 13b to the first boundary part 13a. The connecting part 13 has a cross-section formed with a configuration of a trapezoid or a triangle (isosceles trapezoid or isosceles triangle in Fig. 4). As shown by a virtual line in Fig.4. When adjacent interdental cleaning tools 1 are bent at the first boundary part 13a to concentrate a bending force on the first boundary part 13a and cause a circular lateral surface 11a on a lateral edge of the handle base 11 to come into contact with an outer surface of the connecting part 13, a large force to separate the interdental cleaning tools 1, based on the lever principle, acts on the first boundary part 13a. Consequently, the interdental cleaning tools 1 can be cut and separated appropriately without significant deformation of the connecting part 13 at the first boundary part 13a. A thickness t2 of the connecting part 13 at the first boundary part 13a is preferably set at 0.10 to 0.25 mm, for example, and most preferably 0.15 mm.A thickness t3 of the connecting portion 13 in the second boundary portion 13b is preferably set at 0.60 to 0.80 mm, for example, and most preferably 0.65 mm. The connecting portion 13 may be formed in any arbitrary configuration, provided that it allows adjacent interdental cleaning tools 1 to be easily and appropriately cut and separated by bending them along the connecting portion 13. Furthermore, the connecting portion 13 may be made thinner in a mid-portion along the projecting length L6. In this case, however, it is unlikely that a large force will act on the first boundary portion 13a in a direction that would cause the interdental cleaning tools 1 to separate based on the lever principle. Therefore, the connecting portion 13 is preferably made thinner at one end along the projecting portion.Furthermore, the connecting part 13 has an inside angle 01 of an oblique side 13c on the end base of the handle base 11 and an inside angle 02 of an oblique side 13d on the end front of the handle base 11. Angles 01 and 02 can be arbitrarily set, but are preferably less than 90°. If inside angles 01 and 02 are set as different angles, inside angle 01 of oblique side 13c on the end base is preferably smaller than inside angle 02 of oblique side 13d on the end front. Consequently, it is possible to orient the fiber material embedded in the synthetic resin material along the handle base 11 near the first boundary part 13a and allow the synthetic resin material supplied to the adjacent handle base 11 to bond near the first boundary part 13a.This further improves the ease of cutting and separating the interdental cleaning tools 1 in the first boundary part 13a. The synthetic resin material for the base 10 parts can be any of the following thermoplastic synthetic resin materials, such as polypropylene (PP), polybutylene terephthalate (PBT), polyethylene, polyethylene terephthalate, polycyclohexylene dimethylene terephthalate, saturated polyester resin, polymethyl methacrylate, cellulose propionate, polyurethane, polyamide, polycarbonate, ABS (acrylonitrile butadiene styrene), and similar materials. Polypropylene (PP) and polybutylene terephthalate (PBT) are particularly preferred because these materials prevent breakage of the base 10 parts. Polypropylene is the most preferred because it has a low molding temperature, can shorten cycle time and improve productivity, and imposes less thermal load on the molding equipment. The fiber material added to the synthetic resin material for the base 10 parts can be glass fibers, carbon fibers, aramid fibers, or similar materials. The fiber material blending ratio depends on the synthetic resin material for the base 10 parts. Generally, if the blending ratio is less than 12% by weight, the synthetic resin material is prone to flexing, and the cleaning part 2 is difficult to insert between the teeth. If the blending ratio exceeds 35% by weight, the cleaning part 2 is prone to breakage. Therefore, the blending ratio is preferably set at 12% by weight or more and 35% by weight or less, more preferably 15% by weight or more and 35% by weight or less, and in particular, preferably 20% by weight or more and 30% by weight or less.Specifically, if polypropylene (PP) is used as the synthetic resin material, the fiber material blending ratio is preferably set at 15% by weight or more and 35% by weight or less. If polybutylene terephthalate (PBT) is used as the synthetic resin material, the fiber material blending ratio is preferably set at 12% by weight or more and 35% by weight or less, and 15% by weight or more and 35% by weight or less. The fiber material is preferably oriented along the base portion 10. This configuration improves the bending and buckling strength of the base portion 10 in the axial direction, effectively preventing the core bases 12 from breaking and buckling when using the interdental cleaning tool 1. Furthermore, when the fiber material is oriented along the base portion 10, it is also oriented along the first boundary portion 13a of the connecting portion 13. Consequently, parallel-molded interdental cleaning tools 1 can be properly cut and separated at the first boundary portion 13a by bending adjacent interdental cleaning tools 1 at the first boundary portion 13a.The addition of the fiber material also improves the dimensional stability and strength stiffness of the core parts 10, preventing their deformation. This prevents the core parts 10 from being improperly loaded into the second molding spaces 42 of the second metal molds 40 and 41. The fiber material also raises the thermal distortion temperature of the core bases 12, effectively preventing softening and deformation of the core bases 12 due to heat generated from the elastomer material during the molding of the flexible cleaning parts 21. Furthermore, the fiber material increases the strength stiffness of the core bases 12, preventing their deformation under the injection pressure of the elastomer material. Consequently, molding defects in the flexible cleaning parts 21 can be effectively prevented. (Flexible part) The flexible part 20 is molded using the elastomer material to be integrated with the base part 10 and includes a flexible cleaning part 21 positioned on the core base 12, as shown in Figs. 1 to 6. Like the flexible part 20, an annular insert adjustment part may be arranged at the base end of the main core body 12b to regulate the insertion between the teeth, or a non-slip part may be arranged on the handle base 11. The insert adjustment part or the non-slip part may be molded independently of the flexible cleaning part 21, but in this case, the structure of the metal mold is complicated. Therefore, the insert adjustment part or the non-slip part is preferably molded to be connected to the base of the flexible cleaning part 21. The flexible cleaning part 21 has a covered portion 21a, covered by the core base 12, and a plurality of projections 21b that are formed at intervals to project outwards at intervals along the covered portion 21a. If the wall thickness of the covered portion 21a is too large, it is necessary to reduce the diameter of the main core body 12b covered by the covered portion 21a. This undesirably reduces the rigidity of the cleaning portion when inserted between the teeth and increases the likelihood of Karman vortex formation during the molding process, subjecting the cleaning portion to a strong influence of the Karman vortex. If the wall thickness of the covered portion 21a is too small, the elastomer material may be undesirably loaded inwards at the base end of the cleaning portion 2. Therefore, the wall thickness of the covered portion 21a is preferably set between 0.1 and 0.2 mm. The protrusions 21b are formed at intervals between them along the covered portion 21a and are located at intervals between them along a circumferential direction of the covered portion 21a.More specifically, to allow the second metal molds 40 and 41, described below, to mold the projections 21b, six kinds of projections 21b are arranged on the covered portion 21a in the circumferential direction: a set of two projections 21b projecting from the covered portion 21a to one side of an opening / closing direction of the metal molds; a set of two projections 21b projecting from the covered portion 21a to the other side of the opening / closing direction of the metal molds; a projection 21b projecting from the covered portion 21a to the side along matching surfaces 40a and 41a; and a projection 21b projecting from the covered portion 21a to the other side along matching surfaces 40a and 41a. A plurality of sets of six classes of projections 21b is formed at intervals between them along the covered portion 21a.Alternatively, the 21b protrusions can be formed in arrangement patterns different from the one above. The cross-sectional area of ​​the base ends of the 21b protrusions, the length of the 21b protrusions, and the spacing and number of the 21b protrusions can be arbitrarily determined. For moldability and cleanability, the cross-sectional area of ​​the base ends of the 21b protrusions is preferably set at approximately 0.03 to 1.5 mm². The length of the 21b protrusions is preferably set at approximately 0.5 to 2.0 mm. The number of 21b protrusions is preferably set at 20 to 100. The spacing of the 21b protrusions is preferably set at 0.5 to 1.5 mm. Furthermore, the 21b protrusions are formed in this document with a circular cone configuration, but they can also be formed with a smooth, conical plate configuration that is flat along the axial direction.Furthermore, the cross-section of the protrusion 21b can not only be formed with the configuration of a circle, but can also be formed with an arbitrary configuration, such as an oval, a polygon, or similar. The elastomer for the flexible parts 20 can be any of the thermoplastic elastomers, such as styrene-based, olefin-based, and polyamide-based elastomers, nylon 6, nylon 6-6, nylon 6-10, and nylon 6-12-based elastomers, and thermoset elastomers, such as silicone rubber, urethane rubber, fluororubber, natural rubber, and synthetic rubber. In particular, the elastomer material is preferably compatible with the synthetic resin material for the base parts 10. For example, if the base parts 10 are to be made of polypropylene, the flexible parts 20 are preferably made of a polyolefin-based or styrene-based elastomer. <Método de fabricación> A method for manufacturing interdental cleaning tool 1 will be described below. As shown in Figs. 7 to 12, the method for manufacturing the interdental cleaning tool 1 includes: a base parts molding step of loading a synthetic resin material into first molding spaces 32 of first metal molds 30 and 31 to produce the base parts 10; and a flexible parts molding step of inserting the base parts 10 molded by the first metal molds 30 and 31 into second molding spaces 42 of second metal molds 40 and 41, and then loading an elastomer material into the second molding spaces 42 to mold the flexible parts 20. (Base parts molding stage) In the base parts molding stage, as shown in Figs. 7 to 9, a synthetic resin material with a fiber material is loaded into the first molding spaces 32 of the first metal molds 30 and 31 to produce the base parts 10.More specifically, the plurality of base parts 10 is produced simultaneously in such a manner as to: arrange in parallel, as the first metal molds 30 and 31, a plurality of first molding spaces 32 that include core base molding sections 32a and handle base molding sections 32b; form pairs of connecting part molding sections 35 between adjacent handle base molding sections 32b in order to communicate with adjacent handle base molding sections 32b; form feed channels 33 at the end base sides of the first molding spaces 32; communicate the feed channels 33 through inlets 34 with the first molding spaces 32; and supply a synthetic resin material with a fiber material to the feed channels 33 to load the synthetic resin material with the fiber material through the inlets 34 into the first molding spaces 32.Accordingly, a primary molded article 10A is produced comprising the plurality of base parts 10, feed channel parts 37, inlet parts 36, and connecting parts 13. The base parts 10 can be molded individually. However, the base parts 10 are preferably molded simultaneously with improved productivity and workability because, in this case, it is possible to transfer the base parts 10 simultaneously while holding the molded feed channel parts 37. The inlets 34 can be formed in arbitrary positions on the end base sides of the first molding spaces 32, opposite the core base molding sections 32a, more preferably closer to an edge than the connecting part molding sections 35 on the end base side of the first molding spaces 32, opposite the core base molding sections 32a.Preferably, side inlets, such as inlets 34, are formed at the base ends of the first molding spaces 32 to reduce the risk that, when the primary molded item 10A is loaded into the second metal molds 40 and 41, the inlets 36 of the primary molded item 10A will become entangled between the second metal molds 40 and 41. Instead of the feed channels 33, which are cold feed channels, hot feed channels may be provided in the first metal molds 30 and 31, but the use of hot feed channels leads to larger first metal molds 30 and 31 and higher manufacturing costs. Therefore, it is preferable to provide the feed channels 33 as cold feed channels.The feed channel parts 37 enable the stable connection of a plurality of base parts 10, allowing the primary molded article 10A to be transferred to the secondary metal molds 40 and 41 with improved handling properties. For the inlets 34, cylindrical pin or spindle-shaped inlets with a diameter of 0.1 to 1.5 mm, for example, can preferably be used to allow the use of cold feed channels and the reduction of spacing between the inlets 34, thereby producing a molded article of a smaller size. As shown in Figs. 7 to 9, the connecting part molding sections 35 are formed to the same size as the connecting parts 13 molded from them. The lengths CL4 and CL5 of the boundary sections 35a and 35b between adjacent handle base molding sections 32b and of the connecting part molding sections 35 between the two handle base molding sections 32b are set from 1.5 to 3.0 mm, for example. The length CL4 of the first boundary sections 35a is set shorter than the length CL5 of the second boundary sections 35b. The connecting part molding sections 35 are elongated along the handle base molding section 32b and are formed with a trapezoidal configuration in a front view (isosceles trapezoid in Fig. 8). The CL6 length of the connecting part molding sections 35 is set from 0.5 to 1.5 mm, for example. The Ct2 thickness of the connecting part molding sections 35 in the first boundary sections 35a is set less than the Ct3 thickness of the connecting part molding sections 35 in the second boundary sections 35b. The connecting part molding sections 35 are configured to be thinner continuously or gradually from the second boundary sections 35b to the first boundary sections 35a. The cross-sections of the connecting part molding sections are formed with the configuration of a trapezoid or a triangle (isosceles trapezoid or isosceles triangle in Fig. 9). The thickness Ct2 of the molding sections of connecting parts 35 in the first boundary sections 35a is preferably set from 0.10 to 0.25 mm, for example, optimally at 0.15 mm. The thickness Ct3 of the molding sections of connecting parts 35 in the second boundary sections 35b is preferably set from 0.60 to 0.80 mm, for example, optimally at 0.65 mm. The number of connecting part molding sections 35 can be arbitrarily determined. There can be only one connecting part molding section 35. In this case, however, it is not possible to provide sufficient connecting strength to the adjacent base parts 10. Thus, after molding the base parts 10, the connecting parts 13 may break, allowing the base parts 10 to collapse upon mold opening, or the connecting parts 13 may fold, interfering with the loading of the base parts 10 into the appropriate positions of the second molding spaces 42, thereby resulting in molding failures. Consequently, two or more connecting part molding sections 35 are preferably arranged at intervals along the handle base molding sections 32b. In the molding stage of the base parts, a synthetic resin material containing a fiber material is simultaneously supplied to the plurality of first molding spaces 32 through inlets 34 at the base ends of the first molding spaces 32, closer to the edges than the molding sections of the connecting parts 35. Consequently, the fiber material is oriented along the first molding spaces 32, i.e., along the base parts 10. This makes it possible to improve the base parts 10 in terms of flexural strength and buckling resistance along the axial direction, and effectively prevents folding and buckling of the core bases 12 when using the interdental cleaning tools 1. The fiber material also improves the dimensional stability and strength stiffness of the base parts 10 to prevent deformation of the base parts 10.This makes it possible to prevent the core parts 10 from being improperly loaded into the second molding spaces 42 of the second metal molds 40 and 41. The fiber material also raises the thermal distortion temperature of the core bases 12, thus effectively preventing softening and deformation of the core bases 12 due to heat from the elastomer material generated during the molding of the flexible cleaning parts 21. The fiber material also increases the tensile strength of the core bases 12, thus preventing deformation of the core bases 12 under the injection pressure of the elastomer material. Therefore, it is possible to prevent the core bases 12 from deforming during the molding of the flexible cleaning parts 21, and thus it is possible to more effectively prevent molding failures of the flexible cleaning parts 21. As shown by arrows in Fig. 8, the synthetic resin material flows from the inlets 34 into the handle base molding sections 32b. The length CL4 of the connecting part molding sections 35 in the second boundary sections 35b is set longer than the length CL1 of the connecting part molding sections 35 in the first boundary sections 35a, and the thickness Ct3 of the connecting part molding sections 35 in the second boundary sections 35b is set greater than the thickness Ct2 of the connecting part molding sections 35 in the first boundary sections 35a.Thus, even if the synthetic resin material simultaneously reaches both boundary sections 35a and 35b, the synthetic resin material is loaded from the second side of boundary section 35b into the connecting part molding sections 35, and thus the synthetic resin material, flowing into the adjacent first molding spaces 32, bonds near the first boundary sections 35a. Consequently, the synthetic resin material supplied to the adjacent handle base molding sections 32b bonds near the first boundary sections 35a, and thus the molded base parts 10 can be easily cut and separated at positions corresponding to the first boundary sections 35a. Furthermore, the synthetic resin material flows into the connecting part molding sections 35, as shown by the arrows in Fig.8, and the fiber material added to the synthetic resin material is thus prone to be oriented along the handle base molding sections 32b in the first boundary sections 35a of the connecting part molding sections 35, as shown in Fig. 13. This also allows the base parts 10 to be easily cut and separated at positions corresponding to the first boundary sections 35a. Accordingly, the interdental cleaning tools 1 can be appropriately cut and separated in order at the first boundary sections 13a from one side of the connected body of interdental cleaning tools 1A molded by bending the adjacent interdental cleaning tools 1 along the first boundary section 13a between them.However, it is necessary to establish the connection resistance between the connecting parts 13 and the base parts 10 so that the parallel-connected base parts 10 do not separate from each other when transferred from the first metal molds 30 and 31 to the second metal molds 40 and 41. In the connecting part molding section 35, an inside angle C01 of an oblique side 35c of the handle base molding section 32b on the base end side and an inside angle C02 of an oblique side 35d of the handle base molding section 32b on the front end side can be set to arbitrary values. Preferably, these angles are set to less than 90°. If the inside angles C01 and C02 are to be set to different values, it is preferred, as shown in Fig. 10, to set the inside angle C01 of the oblique side 35c on the base end side to be less than the inside angle C02 of the oblique side 35d on the front end side.Therefore, it is possible to facilitate the flow of synthetic resin material from the base sides of the second boundary sections 35b into the connecting part molding sections 35 and allow the fiber material near the first boundary sections 35a to be more appropriately oriented along the handle base molding sections 32b. In addition, the synthetic resin material is more likely to bond near the first boundary sections 35a, and thus the interdental cleaning tools 1 can be more easily cut and separated at the first boundary sections 35a. (Flexible parts molding stage) In the flexible parts formation stage, as shown in Figs. 11 and 12, the primary molded article 10A, molded in the first metal molds 30 and 31, is inserted into the second molding spaces 42 of the second metal molds 40 and 41, and then an elastomer material is loaded into the second molding spaces 42 to mold the flexible parts 20, thereby obtaining the connected body of interdental cleaning tools 1A, in which the plurality of interdental cleaning tools 1 are connected in parallel. First, the second metal molds 40 and 41 used in the flexible part molding stage are described below. The second metal molds 40 and 41 are provided with a plurality of second molding spaces 42 in positions corresponding to the plurality of base parts 10 in the primary molded components 10A molded in the first metal molds 30 and 31. The second metal molds 40 and 41 are also provided with adjustment spaces 43, 44, and 45 adapted to the feed channel parts 37, the plurality of inlet parts 36, and the connection parts 13 of the primary molded article 10A. Cleaning flexible part molding sections 46 surrounding the core bases 12, as second molding spaces 42, are formed between the second metal molds 40 and 41 and the base parts 10.At the front ends of the flexible cleaning part molding sections 46, inlets 47 are formed in the mating surfaces 40a and 41a of the second metal molds 40 and 41 and are open at the front ends of the flexible cleaning part molding sections 46. The inlets 47 communicate with common feed channels 48 formed in the second metal molds 40 and 41, so that the elastomer material is supplied from the common feed channels 48 through the inlets 47 to the second molding spaces 42. The diameter of the inlets 47 is preferably set to be equal to or greater than 0.1 mm or equal to or less than 1.0 mm. The second metal molds 40 and 41 are provided with a pair of front end-side clamping pins 50, a pair of middle portion clamping pins 51 (the middle portion clamping pins 51 can be arranged as appropriate or omitted), and a pair of base end-side clamping pins 52, corresponding to the front end-side portion, the middle portion, and the base end-side portion of the flexible cleaning part molding section 46, respectively. The three pairs of clamping pins 50 to 52 are capable of moving in a direction approximately orthogonal to the mating surfaces 40a and 41a of the second metal molds 40 and 41—in other words, in an opening and closing direction of the second metal molds 40 and 41. As shown in Fig.12 (b) , the core bases 12 of the base parts 10 are positioned and held with high precision in the centers of the flexible cleaning part molding sections 46 by projecting the front ends of the three pairs of clamping pins 50 to 52 into the flexible cleaning part molding sections 46 and by inserting the core bases 12 between the front ends of the clamping pins 50 to 52. Of the clamping pins 50 to 52, the front end-side clamping pins 50 have the smallest cross-sectional area, and the mid-portion clamping pins 51 and the base end-side clamping pins 52 have larger cross-sectional areas in the order of mid-portion clamping pins 51, then base end-side clamping pins 52 or in the order of base end-side clamping pins 52, then mid-portion clamping pins 51. That is, the flexible cleaning part molding sections 46 have a smaller path area in the front end-side portions.Therefore, when the cross-sectional area of ​​the front end-side clamping pins 50 is minimized, it is possible to reduce the flow resistance of the elastomer material as much as possible and suppress the influence of the Karman vortex generated during the molding process. This preferably prevents load failure of the elastomer material inward in the molded sections of the flexible cleaning parts 46 and prevents excessive melting of the core base 12. Alternatively, the clamping pins 50 to 52 can be set to have equal cross-sectional area. Furthermore, a plurality of pairs of the mid-portion clamping pins 51 can be arranged at intervals along the axial direction, or the mid-portion clamping pins 51 can be omitted. In this embodiment, the cross-sections of the clamping pins 50 to 52 are circular.Alternatively, to further suppress the influence of the Karman vortex on the molding process, the cross-sections of the clamping pins 50 to 52 can be formed into an elongated oval along the molding sections of flexible cleaning parts 46, a long circle, or an asymmetrical shape with respect to a central axis (e.g., teardrop shape), or similar. The front end-side clamping pins 50 are arranged in positions where the front ends of the pins are in contact with the core base corresponding to a 3 mm interval from the front end portion 46a towards the end base side of the flexible cleaning part molding section 46. The front ends and surrounding front end portions of the front end clamping pins 50 have a cross-sectional area of ​​0.03 to 0.3 mm2.The mid-portion clamping pins 51 are arranged in positions where the front ends of the pins are in contact with the core base corresponding to an interval of ±10% of the length of the cleaning portion 2 along the axial direction, with the center at a midpoint between the front end-side clamping pins 50 and the base end-side clamping pins 52, and the front ends and surrounding portions of the front ends of the mid-portion clamping pins 51 have a cross-sectional area of ​​0.12 to 1.2 mm2.The end-side clamping pins 52 are arranged in positions where the front ends of the pins are in contact with the corresponding core base at a 6 mm interval from the end portion of the base towards the front end of the flexible cleaning part molding section 46, and the front ends and surrounding portions of the front ends of the end-side clamping pins 52 have a cross-sectional area of ​​0.1 to 1.1 mm². Due to the above adjustments, the core bases 12 can be reliably fixed in the molding process, and the influence of the Karman vortex generated in the molding process can be expected to be prevented from being exerted on the molded body. The clamping pins 50 to 52 may have front end surfaces bearing on the core bases 12, which are flat and orthogonal to the axial direction of the clamping pins 50 to 52. Preferably, the front end surfaces are formed as circular surfaces along the outer peripheral surfaces of the core bases 12, thereby improving the clamping property of the core bases 12. The pair of front end-side clamping pins 50 and the pair of middle portion clamping pins 51 are each arranged coaxially. Meanwhile, the pair of base end-side clamping pins 52 is arranged so that its axial line is offset by a length of 0.1 to 1.0 times the diameter of the base end-side clamping pins 52, for example, along the flexible cleaning part molding sections 46. If the pair of clamping pins 52 is offset along the flexible cleaning part molding sections 46, when the core bases 12 are clamped between the clamping pins 52, a substantially wider area for the core bases 12 presses against and engages the clamping pins 52. Consequently, the clamping pins 52 can more securely clamp the core bases 12.The clamping pins to be moved along the molding sections of the flexible cleaning parts 46 can be one, two, or more selected from the clamping pins 50 to 52. The above adjustments make it possible to fix the core bases 12 more firmly in place during the molding process. In addition, it can be expected that the influence of the Karman vortex generated during the molding process will be prevented from affecting the molded body. In the flexible part molding stage, when the primary molded article 10A is inserted into the second molding spaces 42 and the metal molds are closed as shown in Fig. 12(a), the pair of front end-side clamping pins 50, the pair of middle portion clamping pins 51, and the pair of base end-side clamping pins 52 are projected into the cleaning flexible part molding sections 46, thereby clamping the core bases 12 by means of the three pairs of clamping pins 50 to 52. The elastomer material is then injected and supplied to the inlets 47 through the feed channels 48 to load the elastomer material into the cleaning flexible part molding sections 46.Since the cross-sectional areas of the clamping pins 50 to 52 increase with proximity to the base portions of the flexible cleaning part molding sections 46, the core bases 12 can be stably clamped by increasing the contact areas of the clamping pins 50 to 52 and the core bases 12, while preventing, as much as possible, the clamping pins 50 to 52 from interfering with the loading of the elastomer material from the front end portions to the base end of the flexible cleaning part molding sections 46. Consequently, even with certain variations in injection pressure, the flexible cleaning parts 21 can be molded with high precision from the elastomer material, while preventing curvature of the core bases 12. Then, the base parts 10 are covered with the flexible parts 20, the feed channel parts 37 and the inlet parts 36, made of synthetic resin, are removed from the base parts 10 and the flexible parts 20, and the feed channel parts 55 and the inlet parts 56 of the elastomer molded into the feed channels 48 and the inlets 47 are removed from the base parts 10 and the flexible parts 20, thereby obtaining the interdental cleaning tools 1. The following will describe an evaluation trial for interdental cleaning tools 1. Six classes of interdental cleaning tools 1 were manufactured in such a way that: synthetic resin materials were prepared by adding glass fibers as the fiber material to polypropylene (PP), with combination ratios of 0 wt%, 10 wt%, 20 wt%, 30 wt%, 40 wt% and 50 wt%; these synthetic resin materials were used for six classes of base parts 10; and flexible cleaning parts 21, made of a polystyrene-based elastomer, were molded onto the core bases 12 of the six classes of base parts 10. The first metal molds 30 and 31 were provided with the first molding space 32 dimensioned such that the core base body 12b of the base part 10, molded by the first metal molds 30 and 31, had a length of 15 mm, an angle 0 of 2.0°, formed by the tapered configuration along its length, a diameter of 0.45 mm at one front end and a diameter of 1.0 mm at one base. The second metal molds 40 and 41 are configured such that: there is a gap of 0.15 mm between an inner surface of a flexible cleaning part molding section 46 and the outer surface of the main core body 12b; A front end-side clamping pin 50, with a cross-sectional area of ​​0.2 mm2, is arranged at a position 2 mm from the front end to the base end side of the flexible cleaning part molding section 46;A mid-portion clamping pin 51, with a cross-sectional area of ​​0.4 mm2, is arranged at a position 6 mm from the front end to the end base side of the flexible cleaning part molding section 46; and an end-base side clamping pin 52, with a cross-sectional area of ​​0.3 mm2, is arranged at a position 10 mm from the front end to the end base side of the flexible cleaning part molding section 46. The six classes of interdental cleaning tools 1 were then arranged in order, with a vertical orientation, on an autograph (manufactured by Shimadzu Corporation) and subjected to a compression test at a compression rate of 10 mm / min. Table 1 shows the results of the compression test. The six classes of interdental cleaning tools 1 were subjected to a sensory test by ten examiners to determine the presence or absence of flexing of the cleaning parts 2 in use, and to determine the insertion capacity of the cleaning parts 2 between the teeth. Table 1 shows the results of the sensory test. To verify the dimensional stability of the base 10 parts with the addition of an additive, the six classes of base 10 parts were measured for heat strain temperature and mold shrinkage ratio in one direction of flow of the synthetic resin material and in a direction orthogonal to the flow direction in the first molding spaces 32. In addition, one hundred base 10 parts were molded, one of each of the six classes. Of the one hundred base 10 parts, the number of defective base 10 parts, unable to fit into the second molding spaces 42 of the second metal molds 40 and 41, was counted. Table 1 shows the results of the measurements and counts. [Table 1] When the fiberglass blend ratio was equal to or greater than 50% by weight, core bases 12 broke in the compression test, and when the fiberglass blend ratio was equal to or less than 10% by weight, core bases 12 flexed in the use test, resulting in insufficient insertion capacity of the cleaning parts 2. Accordingly, it is understood that the fiberglass blend ratio is preferably set to be equal to or greater than 20% by weight and equal to or less than 40% by weight, in particular, equal to or greater than 30% by weight and equal to or less than 40% by weight, for sufficient insertion capacity of the cleaning parts 2. Furthermore, it is understood that when the amount of fiberglass additive is increased to 10% by weight or more, the core parts 10 are less prone to thermal deformation, and the stability of the molding dimensions is increased.In particular, it is understood that when the amount of glass fiber additive is set at 20% by weight or more, load failures of the base parts 10 into the second metal molds 40 and 41 can be completely prevented. An additional evaluation trial for interdental cleaning tools 1 will be described below. Five classes of interdental cleaning tools 1, with different combination ratios of glass fibers, were manufactured in such a way that: synthetic resin materials were prepared by adding glass fibers as the fiber material to polypropylene (PP), with combination ratios of 0% by weight, 10% by weight, 15% by weight, 20% by weight and 30% by weight; these synthetic resin materials were used for five classes of base parts 10; and the flexible cleaning parts 21, made of a polystyrene-based elastomer, were molded onto the core bases 12 of the five classes of base parts 10. In addition, the interdental cleaning tools 1 were manufactured in the same way as the five classes of interdental cleaning tools 1 except that, instead of glass fibers, 40% by weight of glass beads with a diameter of 0.086 mm (a mean diameter of 0.086 mm and a standard deviation SD of 0.04 mm) was added.Furthermore, interdental cleaning tools 1 were manufactured in the same manner as the five classes of interdental cleaning tools 1, except that 40 wt% talc was added instead of glass fibers. Additionally, two classes of interdental cleaning tools 1, with different glass fiber blending ratios, were manufactured such that: glass fibers were added to polybutylene terephthalate (PBT) in blending ratios of 0 wt% and 15 wt% to form synthetic resin materials; the synthetic resin materials were used to produce two classes of base parts 10; and flexible cleaning parts 21, made of a polystyrene-based elastomer, were molded onto the core bases 12 of the two classes of base parts 10.These interdental cleaning tools 1 were molded from the same first metal molds 30 and 31 and second metal molds 40 and 41 that were used in the previous evaluation trial. The nine classes of interdental cleaning tools were then subjected to a horizontal bending test, a separation test, and a sensory test by ten examiners, in the following procedures. Table 2 shows the test results. (Horizontal bending test) As shown in Fig. 14, each of the interdental cleaning tools 1 was sandwiched in an area of ​​10 mm from the front end, between a pair of fixing members 60 to horizontally support the interdental cleaning tool 1 in a cantilevered state. Then, a force F was applied vertically at a rate of 10 mm / min to the interdental cleaning tool 1 in a position that protruded outwards from the fixing member 60 and separated by 5 mm from the fixing member 60 towards the base end, and the maximum resistance of the flexed cleaning part 2 was measured. (Separation test) As shown in Fig. 15, the two interdental cleaning tools 1, connected in parallel by the connecting part 13, were clamped in the handles 3 by a pair of jaws 61. The jaws 61 were then pulled apart from each other in a direction shown by arrow B at a tension rate of 20 mm / min, and the maximum resistance of the two interdental cleaning tools 1 was measured as they were being pulled apart. (Sensory test) The ten examiners evaluated the interdental cleaning tools 1 to determine the presence or absence of flexing of the cleaning parts 2, the presence or absence of breakage of the cleaning parts 2, and the insertion capacity of the cleaning parts 2 when the incisors were cleaned and when the premolars and molars were cleaned. In Table 2, an index "o" indicates that cleaning part 2 did not flex or break or cleaning part 2 could be inserted between the teeth, and an index "x" indicates that cleaning part 2 flexed or broke or cleaning part 2 could not be inserted between the teeth. [Table 2] The following section describes other embodiments of the present invention in which the configuration of the metal mold device is partially modified. In the following description, the same components as in the preceding embodiment are given the same reference numbers, and detailed descriptions of them are omitted. (1) The metal mold device 70, shown in Figs. 16 and 17, comprises an integration of the metal mold device, including the first metal molds 30 and 31 for producing the base parts 10, and the metal mold device, including the second metal molds 40 and 41 for molding the flexible parts 20 of the prior embodiment. The metal mold device 70 includes a pair of opposing metal molds 71 ​​and 72, and a rotating metal mold 75, wherein the metal mold 71 is fitted into a main metal mold 73 and has an adjustment recess 74 in the center of the main metal mold 73. The main metal mold 73 has a support shaft member 76 in its center extending in a mold opening / closing direction.The support shaft member 76 has a front end connected to the center of the rotating metal mold 75, so that the rotating metal mold 75 is supported in the main metal mold 73 through the support shaft member 76 in order to be able to rotate and protrude from the fitting concavity 74. Two assemblies of core part molding sections 32B, each comprising ten nearly horizontally aligned parallel core part molding sections 32A, are formed with mirror symmetry on the upper portions of the mating surfaces 71a and 72a of the metal molds 71 ​​and 72, with the core base molding sections 32a located on the outside. Two assemblies of flexible part molding sections 42B, each comprising ten nearly horizontally aligned parallel flexible part molding sections 42A, are formed with mirror symmetry on the lower portions of the mating surfaces 71a and 72a of the metal molds 71 ​​and 72, with the cleaning flexible part molding sections 46 located on the outside.The numbers of the assemblies of base part molding sections 32B and flexible part molding section assemblies 42B formed on the matching surfaces 71a and 72a can be arbitrarily set to be identical to each other. The rotary metal mold 75 is square-shaped and configured so that both side edges of the rotary metal mold 75 pass through the longitudinal mid-portion of the core base molding sections 32a. Accordingly, the base part molding sections 32A formed on top of the mating surface 71a of the metal mold 71 include: front end-side base part molding sections 32Aa for molding front end-side portions of the core bases 12 on top of the mating surface 73a of the main metal mold 73; and base end-side base part molding sections 32Ab for molding all handle bases 11 of the base parts 10 and base end-side portions of the core bases 12 on top of the mating surface 75a of the rotary metal mold 75.The flexible part molding sections 42A formed on the underside of the mating surface 71a of the metal mold 71 include: front end-side flexible part molding sections 42Aa, which include the cleaning flexible part molding section 46 for molding the cleaning flexible parts 21 onto the core base 12 on the underside of the mating surface 73a of the main metal mold 73; and base end-side flexible part molding sections 42Ab configured in the same manner as the base end-side flexible part molding sections 32Ab on the underside of a mating surface 75a of the rotary metal mold 75. The base end-side flexible part molding sections 32Ab and the base end-side flexible part molding sections 42Ab are configured in the same manner.In this arrangement, the base end-side molding sections 32Ab are arranged on the top of the mating surface 75a of the rotary metal mold 75 and the base end-side flexible molding sections 42Ab are arranged on the bottom of the mating surface 75a of the rotary metal mold 75. The feed channels 33 are formed vertically on a rear surface of the rotary metal mold 75, corresponding to the base ends of the ten base end-side molding sections 32Ab and the ten base end-side flexible part molding sections 42Ab. The synthetic resin material is supplied through the feed channels 33 to the base end-side molding sections 32Ab from the inlets 34 formed at the base ends of the base part molding section 32A. To manufacture the interdental cleaning tools 1 using the metal mold device 70, first, two sets of primary molded articles 10A, each of which includes the ten base parts 10, are molded by the two upper sets of base part molding section assemblies 32B in the rotating metal mold 75. Then, as shown in Fig. 17(b), the metal molds 71 ​​and 72 are opened to protrude the support shaft member 76 and eject the rotating metal mold 75 from the fitting concavity 74, thereby separating the two sets of primary molded articles 10A from the main metal mold 73. At that moment, each set of primary molded articles 10A is held in the rotating metal mold 75 so that it does not fall off, by means of inlet parts 36A and feed channel parts 37A made of a synthetic resin and molded by inlets 34A and feed channels 33A. Next, the rotating metal mold 75 is rotated 180° and fitted into the fitting recess 74 of the main metal mold 73, as shown in Fig. 17(c). Then, the front end-side portions of the core bases 12 in the two primary molded article assemblies 10A are inserted into the front end-side flexible part molding sections 42Aa. In this state, the metal molds 71 ​​and 72 are closed and the base parts 11 are loaded into the second molding spaces 42. Then, the clamping pins 50 to 52 are protruded to position the core bases 12 in the center of the flexible cleaning part molding section 46. In this state, an elastomer is injected into the flexible cleaning part molding sections 46 from their front end sides, through feed channels 48, to cover the core bases 12 by means of the flexible cleaning parts 21.Therefore, it is possible to obtain two sets of connected bodies of interdental cleaning tools 1A, in each of which ten interdental cleaning tools 1 are connected in parallel. In the molding of the flexible cleaning parts 21 in the lower parts of the metal molds 71 ​​and 72, the base parts 10 are also molded in the upper parts of the metal molds 71 ​​and 72, making it possible to mold the two sets of connected bodies of interdental cleaning tools 1A in order.2. (2) A metal mold device 80, shown in Fig. 18, is provided with a pair of metal molds 81 and 82 opposed to each other. The metal mold 81 is formed by a main metal mold 83 and a sliding metal mold 85 fitted into an adjustment recess 84 in the center of the main metal mold 83. The sliding metal mold 85 is supported to be able to switch its vertical position with respect to the main metal mold 83 and to be able to protrude from the adjustment recess 84. The sliding metal mold 85 is configured in the same way as the rotating metal mold 75 in the prior embodiment, except that the sliding metal mold 85 is vertically movable and able to protrude from the adjustment recess 84, unlike the rotating metal mold 75 of the prior embodiment, which is supported in the main metal mold 73 to be able to rotate and protrude from the adjustment recess 74. Two assemblies of base molding sections 32B, each comprising ten base part molding sections 32A aligned nearly horizontally in parallel, are formed on the upper and lower portions of a mating surface 82a of the other metal mold 82, with the core base molding sections 32a located on the outside. Two assemblies of flexible part molding sections 42B, each comprising ten flexible part molding sections 42A aligned nearly horizontally in parallel, are formed on an intermediate portion atop the mating surface 82a of the other metal mold 82, with the cleaning flexible part molding sections 46 located on the outside. The front end-side base part molding sections 32Aa, which include front end-side portions of the core base molding sections 32a, are formed on the top and bottom portions of a mating surface 83a of the main metal mold 83 on both sides of the fitting concavity 84 of the metal mold 81. The front end-side flexible part molding sections 42Aa, which include the cleaning flexible part molding sections 46, are formed in an intermediate portion along the top of the mating surface 83a of the main metal mold 83 on both sides of the fitting concavity 84. Two sets of base end-side base part molding sections 32Ab, each of which includes ten base end-side base part molding sections 32Ab, are formed with mirror symmetry on a top portion of a mating surface 85a of the sliding metal mold 85.Two sets of base end-side flexible part molding sections 42Ab, each comprising ten base end-side flexible part molding sections 42Ab, are formed with mirror symmetry on a bottom of the mating surface 85a. The base end-side flexible part molding sections 32Ab and the base end-side flexible part molding sections 42Ab are configured in the same manner. When the sliding metal mold 85 is positioned above the fitting concavity 84, the base end-side flexible part molding sections 32Ab are positioned above the mating surface 85a, and the base end-side flexible part molding sections 42Ab are positioned below the mating surface 85a.When the sliding metal mold 85 is positioned below the fitting concavity 84, the base end-side flexible part molding sections 42Ab are positioned above the mating surface 85a and the base end-side base part molding sections 32Ab are positioned below the mating surface 85a. When the sliding metal mold 85 is positioned above the fitting concavity 84, the two sets of flexible part molding section assemblies 42B, each of which includes ten flexible part molding sections 42A aligned in parallel almost horizontally, are formed with mirror symmetry in the middle portion atop the mating surface 81a of the metal mold 81, with the cleaning flexible part molding sections 46 located on the outside, and the two sets of base part molding section assemblies 32B, each of which includes ten base part molding sections 32A aligned in parallel almost horizontally, are formed with mirror symmetry on the top of the mating surface 81a, with the core base molding sections 32a located on the outside.Meanwhile, when the sliding metal mold 85 is positioned under the fitting concavity 84, the two sets of flexible part molding section assemblies 42B are formed with mirror symmetry in the middle portion along the top of the mating surface 81a of the metal mold 81, as described above, and the two sets of base part molding section assemblies 32B are formed with mirror symmetry on the bottom of the mating surface 81a of the metal mold 81, as described above. To manufacture interdental cleaning tools 1 using the metal mold device 80, the sliding metal mold 85 is positioned above the fitting recess 84, for example, and two sets of primary molded items 10A, each comprising ten base parts 10, are molded by the two upper assemblies of base part molding section assemblies 32B. The metal molds 81 and 82 are then opened, and the sliding metal mold 85 is raised out of the fitting recess 84, thereby separating the two sets of primary molded items 10A from the main metal mold 83. At that point, each set of primary molded items 10A is held in the sliding metal mold 85 by the inlet parts 36A and the feed channel parts 37A made of a synthetic resin, as in the rotary metal mold 75. Next, the sliding metal mold 85 is moved to the underside of the fitting recess 84 of the main metal mold 83 and engages in the fitting recess 84. Then, the front end-side portions of the core bases 12 on the primary molded articles 10A are inserted into the front end-side flexible part molding sections 42Aa located in the middle portion at the top of the metal mold 81. In this state, the two metal molds 81 and 82 are closed, and the base parts 11 are loaded into the second molding spaces 42. Then, the set pins 50 to 52 are protruded to position the core bases 12 in the middle portions of the clear flexible part molding sections 46.In this state, an elastomer is injected into the flexible cleaning part molding sections 46, through the feed channels 48 from their front ends, to cover the core bases 12 by means of the flexible cleaning parts 21. Consequently, it is possible to obtain two sets of connected bodies of interdental cleaning tools 1A, each of which includes ten interdental cleaning tools 1 connected in parallel. Furthermore, in the molding of the flexible cleaning parts 21 in the central part of the two metal molds 81 and 82, the base parts are also molded on the top or bottom of the two metal molds 81 and 82, making it possible to mold the two sets of connected bodies of interdental cleaning tools 1A in sequence. (3) In an embodiment shown in Figs. 19 and 20, first metal molds 90 and 91 are provided for producing the base parts 10 and second metal molds 95 and 96 for molding the flexible parts 20. The first metal mold 90 includes: a pair of first split metal molds 90A and 90B that can be moved between a combined state, shown by solid lines, and a separate state, shown by virtual lines in the drawings; and a metal transfer mold 100 fitted into an adjustment concavity 93 in a central part formed by combining the two first split metal molds 90A and 90B.The second metal mold 95 includes: a pair of second split metal molds 95A and 95B that can move between a combined state, shown by solid lines, and a separate state, shown by virtual lines in the drawings; and a transfer metal mold 100 fitted into an adjustment concavity 97 in a central part formed by combining the two second split metal molds 95A and 95B. The transfer metal molds 100 are configured in the same way as the rotating metal mold 75, except that the transfer metal molds 100 are arranged to be able to transfer through the first split metal molds 90A and 90B and the second split metal molds 95A and 95B, unlike the prior embodiment, in which the rotating metal mold 75 is supported in the main metal mold 73 to be able to rotate and protrude from the adjustment concavity 74. Four assemblies of 32B base part molding sections, each comprising ten 32 base part molding sections aligned nearly horizontally in parallel, are formed on the mating surfaces of the first metal molds 90 and 91. Four assemblies of 42B flexible part molding sections, each comprising ten 42A flexible part molding sections aligned nearly horizontally in parallel, are formed on the mating surfaces of the second metal molds 95 and 96. To mold the interdental cleaning tools 1 using the first metal molds 90 and 91 and the second metal molds 95 and 96, first, the first metal molds 90 and 91 are closed to mold four sets of primary molded articles 10A, each of which includes ten base parts 10, by means of the four sets of base part molding section assemblies 32B. Then, the first two metal molds 90 and 91 are opened, and the first split metal molds 90A and 90B are separated to eject the four sets of primary molded articles 10A from the first split metal molds 90A and 90B. At that point, each set of primary molded articles 10A is held in the metal transfer mold 100 by the inlet parts 36A and the feed channel parts 37A made of a synthetic resin, as in the metal rotary mold 75. Next, the metal transfer mold 100 is transferred to an area between the second split metal molds 95A and 95B, and the second split metal molds 95A and 95B are combined to integrate the second split metal molds 95A and 95B with the metal transfer mold 100. After this, the second metal molds 95 and 96 are closed, and the four primary molded article assemblies 10A are inserted into the four flexible part molded section assemblies 42B, and the base parts 11 are loaded into the second molding spaces 42. Then, the clamping pins 50 to 52 are protruded to position the core bases 12 in the central portions of the clear flexible part molding sections 46.In this state, an elastomer is injected into the flexible cleaning part molding sections 46, through the feed channels 48 from their front end sides, to cover the core bases 12 by means of the flexible cleaning parts 21. It is therefore possible to obtain four sets of connected bodies of interdental cleaning tools 1A, each of which includes ten interdental cleaning tools 1 connected in parallel. When the two or more metal transfer molds 100 are arranged and cyclically transferred between the first metal molds 90 and 91 and the second metal molds 95 and 96, it is possible to mold the four sets of connected bodies of interdental cleaning tools 1A in order. The embodiments of the invention have been described above. However, the invention is not limited to the above embodiments. As a matter of routine, the configurations of the embodiments can be modified without departing from the essence of the present invention. List of reference signs 1 Interdental cleaning tool 1A Connected body of interdental cleaning tools Part 2 Cleaning 3. Handle part 10 Base Part 11 Mango base 11a Lateral surface 12 Core Base Part 12 of the exhibition 12b Core body 13 Connection Part 13a First part limit 13b Second part limit 13c Oblique side 13d Oblique side 20 Flexible part 21 Flexible cleaning part Part 21a Covered 21b Outgoing 10A Primary molded article 30 First metal mold 31 First metal mold 32 First molding space 32a Core Base Molding Section 32b Handle Base Molding Section 33 Feed Channel 34 Entry 35 Connection Parts Molding Section 35a First boundary section 35b Second boundary section 32c Oblique side 32d Oblique side 36 Entry section 37 Feed channel part 40 Second metal mold 40a Coincident surface 41 Second metal mold 41a Coincident surface 42 Second molding space 43 Adjustment space 44 Adjustment space 45 Adjustment space 46 Flexible Parts Molding Cleaning Section 46a Front end 47 Entry 48 Feed Channel 50 Front end-side retaining pin 51 Half portion retaining pin 52 Base end-side retaining pin 55 Feed channel part 56 Entry section 60 Fixing member 61 Gag 32A Base Parts Molding Section 32Aa Front end-side base part molding section 32Ab Base end-side base part molding section 32B Base part molding section assembly 33A Power Channel 34A Entrance 36A Entrance section 37A Feed Channel Part 42A Flexible Parts Molding Section 42Aa Front end-side flexible part molding section 42Ab Base end-side flexible part molding section 42B Flexible part molding section assembly 70 Metal mold device 71 Metal mold 71a Coincident surface 72 Metal mold 72a Coincident surface 73 Main metal mold 73a Coincident surface 74 Adjustment concavity 75 Rotating metal mold 75a Coincident surface 76 Support shaft member 80 Metal mold device 81 Metal mold 81a Coincident surface 82 Metal mold 82a Coincident surface 83 Main metal mold 83a Coincident surface 84 Adjustment concavity 85 Metal sliding mold 85a Coincident surface 90 Metal mold 91 Metal mold 90A Divided metal mold 90B Divided metal mold 92 Metal mold 93 Adjustment concavity 95 Metal mold 95A Divided metal mold 95B Divided metal mold 96 Metal mold 97 Adjustment concavity 100 Metal Transfer Mold The following aspects are preferred embodiments of the invention. 1. A method for manufacturing an interdental cleaning tool, the interdental cleaning tool comprising: a base portion made of a synthetic resin, the base portion having a handle base and a core base, similar to an elongated shaft, connected to a front end of the handle base; and a flexible portion made of an elastomer and covering at least a portion of the base portion, the flexible portion having at least one flexible cleaning portion covering the core base, the handle base constituting a handle portion, and the core base and the flexible cleaning portion constituting an interdental cleaning portion, wherein the method comprises: A base part molding step of: arranging a metal mold for molding the base part with a plurality of first molding spaces aligned in parallel, including core base molding sections and handle base molding sections; arranging the metal mold with connecting part molding sections to communicate with the adjacent handle base molding sections; simultaneously supplying a synthetic resin material with a fiber material to the plurality of first molding spaces from inlets open to the first molding spaces at the end bases of the first molding spaces opposite the core base molding sections; and simultaneously forming a plurality of base parts such that the base parts are connected to each other in parallel by connecting parts molded in the connecting part molding sections; and a flexible part molding step of: transferring the plurality of base parts molded and connected together in the base part molding step, to a metal mold for molding the flexible part; inserting at least portions of the core bases of the base parts into a plurality of second molding spaces in the metal mold; securing the core bases in two or more longitudinal spans, including the front ends and base ends of the core bases, nearly at the centers of the flexible part molding sections, by means of at least two pairs of clamping pins, each pair including two pins, which are opposite each other and project into the interior of the flexible part molding sections, to be approximately perpendicular to matching surfaces of the metal mold;and loading an elastomeric material into the second molding spaces so that the elastomeric material is supplied from the front end sides to the base end sides of the flexible cleaning part molding sections.2 2. The method for manufacturing an interdental cleaning tool according to aspect 1, wherein the connecting part molding sections are elongated along the handle base molding sections and are thinner as they approach a first boundary section of two boundary sections between the connecting part molding section and the handle base molding sections on both sides of the connecting part molding section.; 3. The method for manufacturing an interdental cleaning tool according to aspect 1 or 2, wherein, of the two boundary sections between the connecting parts molding section and the handle base molding sections on both sides of the connecting parts molding section, the length of the first boundary section along the handle base molding section is less than the length of the second boundary section. 4. The method for manufacturing an interdental cleaning tool according to any one of aspects 1 to 3, wherein two or more connecting part molding sections are arranged at intervals along the handle base molding section. 5. The method for manufacturing an interdental cleaning tool according to any one of aspects 1 to 4, wherein The fiber material uses fiberglass, and The combination ratio of fiberglass to synthetic resin material is 12% by weight or more and 35% by weight or less. 6. The method for manufacturing an interdental cleaning tool according to any one of aspects 1 to 5, wherein the synthetic resin material is polypropylene (PP), polybutylene terephthalate (PBT) or polyamide. 7. The method for manufacturing an interdental cleaning tool according to any one of aspects 1 to 6, wherein A pair of retaining pins, which hold the front end of the core base, have a cross-sectional area of ​​a portion in contact with the core base set at 0.03 to 0.3 mm2, with the pair of retaining pins arranged in positions where the front ends of the pins are in contact with the core base corresponding to a 3 mm interval from the front end to the base end of the flexible cleaning part molding section, A pair of retaining pins that secure the base end of the core base have a cross-sectional area, of a portion in contact with the core base, set at 0.1 to 1.1 mm², and The pair of clamping pins is arranged in positions where the front ends of the pins are in contact with the core base corresponding to a 6 mm interval from the base end to the front end of the flexible cleaning part molding section. 8. The method for manufacturing an interdental cleaning tool according to any one of aspects 1 to 7, wherein, from the plurality of pairs of retaining pins, at least one pair of two opposing pins is offset along the molded section of flexible cleaning parts. 9. The method for manufacturing an interdental cleaning tool according to any one of aspects 1 to 8, wherein the cross-sectional area of ​​the retaining pins is established as the proximity to the base side of the flexible cleaning molding section increases. 10. The method for manufacturing an interdental cleaning tool according to any one of aspects 1 to 9, wherein the retaining pins are provided to appear freely in the flexible cleaning part molding section. 11. The method for manufacturing an interdental cleaning tool according to any one of aspects 1 to 10, wherein the synthetic resin material for forming the base part and the elastomer material for forming the flexible part are compatible with each other. 12. The method for manufacturing an interdental cleaning tool according to any one of aspects 1 to 11, wherein the elastomer material is a styrene-based elastomer material. 13. An interdental cleaning tool comprising: a base portion made of a synthetic resin, the base portion having a handle base and a core base, similar to an elongated shaft, connected to a front end of the handle base; and a flexible portion made of an elastomer covering at least a portion of the base portion, the flexible portion having at least one flexible cleaning portion covering the core base, the handle base constituting a handle portion, and the core base and the flexible cleaning portion constituting an interdental cleaning portion, wherein A plurality of interdental cleaning tools are aligned in parallel, The connecting parts for connecting adjacent interdental cleaning tools are arranged through the adjacent handle bases in order to be integral with the handle bases. The base parts are made of a synthetic resin material with a fiber material, The fiber material is oriented along the base portion at least a first boundary part of two boundary parts between the connecting part and the handle bases on both sides of the connecting part, the fiber material is oriented along the longitudinal side of the base part so that the adjacent interdental cleaning parts can be cut and separated at the first boundary part. 14. The interdental cleaning tool according to aspect 13, wherein the connecting part is elongated along the handle base and is thinner as the proximity to the first boundary part increases. 15. The interdental cleaning tool according to aspect 13 or 14, wherein the length of the first limit part in the connecting part along the handle base is set shorter than the length of the second limit part. 16. The interdental cleaning tool according to any one of aspects 13 to 15, wherein two or more connecting parts are arranged at intervals along the handle base. 17. The interdental cleaning tool according to any one of aspects 13 to 16, in which The fiber material uses fiberglass, and The combination ratio of fiberglass to synthetic resin material is 12% by weight or more and 35% by weight or less. 18. The interdental cleaning tool according to any one of aspects 13 to 17, wherein the synthetic resin material is polypropylene (PP), polybutylene terephthalate (PBT) or polyamide. 19. The interdental cleaning tool according to any one of aspects 13 to 18, in which The core base is tapered to gradually reduce the diameter at its front end, and The angle formed by the conical shape with respect to the length of the core base is set at 0.2 to 2.5°. 20. The interdental cleaning tool according to any one of aspects 13 to 19, wherein the elastomer material is a styrene-based elastomer material.

Claims

1. A plurality of interdental cleaning tools (1), each interdental cleaning tool (1) comprising: a base portion (10) made of a synthetic resin, the base portion (10) having a handle base (11) and a core base (12), similar to an elongated shaft, connected to a front end of the handle base (11); and a flexible portion (20) made of an elastomer and covering at least a portion of the base portion (10), the flexible portion (20) having at least one flexible cleaning portion (21) covering the core base (12), the handle base (11) constituting a handle portion (3), and the core base (12) and the flexible cleaning portion (21) constituting an interdental cleaning portion, wherein a plurality of interdental cleaning tools (1) are aligned in parallel,Connecting parts (13) for connecting adjacent interdental cleaning tools (1) are arranged through adjacent handle bases (11) to be integral with the handle bases (11); the base parts (10) are made of a synthetic resin material containing a fiber material; the fiber material is oriented along the base part (10) in at least a first boundary part (13a) of two boundary parts (13a, 13b) between the connecting part (13) and the handle bases (11) on both sides of the connecting part (13); the fiber material is oriented along the longitudinal side of the base part (10) so that adjacent interdental cleaning parts can be cut and separated at the first boundary part (13a); the fiber material uses fiberglass.characterized in that the fiberglass-to-synthetic resin material blend ratio is 12% by weight or more and 35% by weight or less.

2. The interdental cleaning tool according to Claim 1, wherein the core base (12) includes a main core body, which is covered by the elastomer, and includes a front end portion with a diameter of 0.4 to 0.6 mm and a base end portion with a diameter of 0.8 to 2.0 mm.

3. The interdental cleaning tool according to Claim 1 or 2, wherein the connecting portion (13) is elongated along the handle base (11) and is thinner as it approaches the first boundary portion (13a).

4. The interdental cleaning tool according to any one of Claims 1 to 3,wherein the length of the first limit portion (13a) on the connecting portion (13) along the handle base is shorter than the length of the second limit portion.

5. The interdental cleaning tool according to any one of Claims 1 to 4, wherein two or more connecting portions (13) are arranged at intervals along the handle base (11).

6. The interdental cleaning tool according to any one of Claims 1 to 5, wherein the synthetic resin material is polypropylene (PP), polybutylene terephthalate (PBT), or polyamide.

7. The interdental cleaning tool according to any one of Claims 1 to 6, wherein the elastomer material is a styrene-based elastomer.

Images