Brush molded body and toothbrush

Abstract

The objective of the present invention is to provide a brush molded body which has a gentle touch feeling, and with which it is possible to improve the feel during use and the external appearance of a toothbrush. This brush molded body includes a head base portion formed from a soft resin, and a plurality of filaments which project from a supporting surface positioned on the front side in the thickness direction of the head base portion. The head base portion has an engaging hole which extends in a length direction perpendicular to the thickness direction and which opens on one side in the length direction. The brush molded body is provided with: a premolded body, at least a portion of which is molded using a first resin composition, and which comprises a filament group including at least a portion of the plurality of filaments, and a supporting base portion that supports a base portion of the filament group and that is positioned on the front side of the engaging hole to form a portion of the head base portion; and a base main body molded body which includes part of the head base portion and the plurality of filaments other than the premolded body, and which is molded using a second resin composition different from the first resin composition. The premolded body and the base main body molded body are molded bodies that are molded integrally.

Description

[Technical Field]

[0001] The present invention relates to a brush mold and a toothbrush. This application claims priority based on Japanese Patent Application No. 2020-214798, filed on December 24, 2020, the contents of which are incorporated herein by reference. [Background technology]

[0002] One-piece molded toothbrushes have been proposed, which are manufactured using only an injection molding machine (for example, Patent Document 1). One-piece molded toothbrushes have the advantage of being cheaper to manufacture than bristle-implanted toothbrushes, as the filament and head base (or head) are molded as a single unit, eliminating the need to procure filament material or use a bristle implanting machine.

[0003] One proposed integrally molded toothbrush for cleaning is one in which a head portion (brush molded body) having a filament and an insertion hole and a handle portion having an insertion portion at one end are molded separately and then fitted together to provide an integrally molded toothbrush (for example, Patent Documents 2 and 3).The toothbrushes described in Patent Documents 2 and 3 have replaceable head portions that can be disposed of by the user, and are therefore expected to conserve resources by allowing the handle to be reused while only the head portion is discarded.

[0004] The head portion is molded from a single resin material, and therefore there are limitations to improving the usability and appearance (design) of the toothbrush. Patent Document 4 discloses a technique for insert-molding filaments made of a plurality of different resin compositions using a mold in which a separately molded handle portion is arranged. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Utility Model Application Publication No. 61-207233 [Patent Document 2] Chinese Utility Model No. 204561298 [Patent Document 3] Chinese Patent Application Publication No. 107041792 [Patent Document 4] Chinese Utility Model No. 205214577 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the toothbrush described in Patent Document 4 has walls that separate the multicolored filaments, which creates spaces where the filaments cannot be arranged, making it difficult to arrange the filaments in a regular, continuous profile, which causes a problem of impairing the gentle feel of the head portion when inserted into the oral cavity.

[0007] The present invention has been made in consideration of the above points, and an object of the present invention is to provide a brush molded body and a toothbrush that have a gentle feel and can improve the usability and appearance of the toothbrush. [Means for solving the problem]

[0008] According to a first aspect of the present invention, there is provided a brush molded body comprising: a head base portion formed of a soft resin; and a plurality of filaments protruding from a support surface located on the front side of the head base portion in the thickness direction, the head base portion extending in a longitudinal direction perpendicular to the thickness direction and having a fitting hole opening to one side in the longitudinal direction; a filament group including at least a portion of the plurality of filaments; and a support base portion supporting the base of the filament group and located on the front side of the fitting hole and forming a portion of the head base portion; and a pre-molded body at least a portion of which is molded from a first resin composition; and a base body molded body having the head base portion and portions of the plurality of filaments other than the pre-molded body and molded from a second resin composition different from the first resin composition, wherein the pre-molded body and the base body molded body are integrally molded.

[0009] Furthermore, in the brush molding according to one aspect of the present invention, a portion of the plurality of filaments constitute the filament group molded from the first resin composition, and the filaments of the plurality of filaments other than the filament group constitute the base body molding molded integrally with the head base portion from the second resin composition.

[0010] Furthermore, in the brush molding according to one embodiment of the present invention, when the cross-sectional area of ​​the support base portion in a cross section perpendicular to the longitudinal direction of the head base portion is S1 and the cross-sectional area of ​​the region located between the front surface and the support surface inside the fitting hole is S, the value expressed by S1 / S is 0.6 or less in all regions where the fitting hole is provided.

[0011] Furthermore, in the brush molding according to one embodiment of the present invention, in a cross section perpendicular to the longitudinal direction, when the cross-sectional area of ​​the fitting hole is SV and the cross-sectional area of ​​the head base portion is SW, the value expressed by SV / (SW-S1) is 0.5 or less in all areas where the fitting hole is provided.

[0012] Furthermore, in the brush molding according to one embodiment of the present invention, when the area of ​​the head base portion as viewed from the front side in the thickness direction is P and the area of ​​the support base portion as viewed from the front side in the thickness direction is P1, the value expressed by P1 / P is greater than or equal to 0.1 and less than or equal to 0.5.

[0013] Furthermore, in the brush molding according to one embodiment of the present invention, the maximum distance from the base end of the filament to the back surface of the head base portion on the opposite side to the front side in the thickness direction is 2.0 mm or more and 4.5 mm or less.

[0014] Furthermore, in the brush molding according to one embodiment of the present invention, when the maximum distance from the base end of the filament to the back surface of the head base is T and the thickness of the support base in the thickness direction is t1, the value expressed by t1 / T is 0.5 or less.

[0015] Furthermore, in the brush molding according to one embodiment of the present invention, when the distance between the rear surface of the support base and the front surface inside the fitting hole is t2, the value expressed by t1 / (t1+t2) is greater than or equal to 0.2 and less than or equal to 0.8.

[0016] In the brush molded body according to one aspect of the present invention, the number of the filaments in the filament group is defined as FM, and the area where the support base portion is bonded to the base body molded body is defined as Q1 (mm 2 ), the value expressed as FM / Q1 is 1.0 (lines / mm 2 ) or less.

[0017] In addition, the brush molded body according to one aspect of the present invention is characterized in that an uneven structure is provided at the adhesive interface between the support stand portion and the base body molded body.

[0018] Furthermore, in the brush molding according to one embodiment of the present invention, when the maximum length of the head base portion in the longitudinal direction is L1 and the maximum length of the fitting hole in the longitudinal direction is L2, the value expressed by L2 / L1 is greater than or equal to 0.30 and less than or equal to 0.70.

[0019] In the brush molded body according to one aspect of the present invention, the preformed body includes all of the plurality of filaments.

[0020] Furthermore, in the brush molding according to one embodiment of the present invention, the pre-molded body is characterized in having the filament group and the support base molded from the first resin composition, and a second filament group and a second support base supporting the base of the second filament group molded from a third resin composition different from the first resin composition and the second resin composition.

[0021] In the brush molded body according to one aspect of the present invention, the soft resin is polyurethane.

[0022] According to a second aspect of the present invention, there is provided a toothbrush comprising the brush molding of the first aspect of the present invention and a handle body formed of hard resin and having an engaging protrusion that can be attached and detached to the engaging hole of the brush molding.

[0023] According to a third aspect of the present invention, there is provided a toothbrush comprising the brush molding of the first aspect of the present invention and a handle body having a fitting protrusion that fits into the fitting hole of the brush molding, wherein the brush molding and the handle body are integrally molded. [Effects of the Invention]

[0024] The present invention can provide a brush molded body and a toothbrush that have a gentle feel and can improve the usability and appearance of the toothbrush. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a front view of a brush molded body 20 and a toothbrush 1 according to an embodiment of the present invention. [Figure 2] FIG. 2 is a side view of the brush molded body 20 and the toothbrush 1. [Figure 3] FIG. 2 is a front view of the brush molding 20. [Figure 4] 4 is a cross-sectional view taken along the line AA in FIG. 3. [Figure 5] FIG. 2 is a view of the brush molding 20 as seen from the rear end side. [Figure 6] 2 is a cross-sectional view of a plane parallel to a support surface 21a including a fitting hole 22. FIG. [Figure 7] FIG. 2 is a front view of the handle body 10. [Figure 8] FIG. 2 is an enlarged front view of a fitting protrusion 12. [Figure 9] FIG. 2 is an enlarged side view of a fitting protrusion 12. [Figure 10] 1 is a cross-sectional view in the width direction showing a simplified example of a mold MD for molding a preform 40 of the brush molded body 20. FIG. [Figure 11] 1 is a cross-sectional view in the width direction showing a simplified example of a mold MD for molding a base body molded body 50 of the brush molded body 20. FIG. [Figure 12] FIG. 2 is a longitudinal cross-sectional view showing a simplified example of a mold MD for secondary molding. [Figure 13] FIG. 6 is a cross-sectional view in the width direction of the brush molded body 20 according to the second embodiment. [Figure 14] FIG. 10 is a front view of a brush molded body 20 according to a third embodiment. [Figure 15] FIG. 10 is a cross-sectional view in the width direction of the brush molded body 20 according to the third embodiment. [Figure 16] FIG. 10 is a front view showing a modified example of the brush molded body 20 according to the third embodiment. [Figure 17] 10 is a longitudinal cross-sectional view showing a modified example of the brush molded body 20 according to the third embodiment. FIG. [Figure 18] FIG. 10 is a cross-sectional view in the width direction of the brush molded body 20 according to the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, embodiments of the brush molded body and toothbrush of the present invention will be described with reference to Figures 1 to 18. In this embodiment, the description will be given using an example of a toothbrush in which the brush molded body is detachably attached to the handle body.

[0027] The following embodiment shows one aspect of the present invention, does not limit the present invention, and can be modified as desired within the scope of the technical concept of the present invention. In addition, in the following drawings, the scale and number of each structure are different from the actual structure to make each configuration easier to understand.

[0028] FIG. 1 is a front view of a brush molded body 20 and toothbrush 1 according to this embodiment. FIG. 2 is a side view of the brush molded body 20 and toothbrush 1. The toothbrush 1 comprises a rod-shaped handle body 10 and the brush molded body 20. The handle body 10 and the brush molded body 20 are separate components. The brush molded body 20 can be detachably attached (inserted) to the handle body 10. The brush molded body 20 is made of a soft resin. The handle body 10 is made of a hard resin.

[0029] In this embodiment, the front side refers to the side from which the filaments 23 (described later) protrude (the upper side in FIG. 2 ) in the thickness direction (hereinafter simply referred to as the thickness direction), which is the normal direction to the support surface 21a (described in detail later) of the brush body 20. In the thickness direction of the brush body 20, the side opposite the front side will be referred to as the back side as appropriate. Furthermore, the length direction of the handle body 10, which is the direction in which the handle body 10 is inserted into the brush body 20 (hereinafter simply referred to as the insertion direction), is perpendicular to the normal direction. In the length direction, the side in which the handle body 10 is attached to the brush body 20 is referred to as the rear end side, and the side opposite the rear end side will be referred to as the front end side as appropriate. Furthermore, the direction perpendicular to the normal direction and the insertion direction is the width direction of the brush body 20 (hereinafter simply referred to as the width direction).

[0030] [First embodiment of brush molded body 20] Fig. 3 is a front view of the brush molded body 20. Fig. 4 is a cross-sectional view taken along line AA in Fig. 3. As shown in Figs. 3 and 4, the brush molded body 20 includes a head base 21 having a substantially rectangular shape when viewed from the front, and a plurality of filaments 23 provided on the front surface of the head base 21.

[0031] As the soft resin constituting the brush molded body 20, various elastomers can be used, but polyurethane is preferable. Polyurethane tends to have higher tensile strength than other elastomers such as styrene-based or polyester-based elastomers, so by using polyurethane as a soft resin, mechanical strength can be ensured even when the material is thin, and breakage can be reduced when the handle body 10 is fitted into the fitting hole 22 and when the toothbrush 1 is in use.

[0032] Polyurethane contains 0.01 to 1.0 wt% (mass%) of saturated / unsaturated hydrocarbons of C10 or higher, higher alcohols, fatty acid amides, fatty acid esters, low-molecular-weight polyethylene, polyethylene glycol (PEG), fatty acid metal salts, long-chain fatty acids, fatty acid glycerin, liquid paraffin, and silicone, or a combination thereof, which function as lubricants and mold release agents.

[0033] Furthermore, compared to the other elastomers mentioned above, polyurethane has a wider range of hardness options, allowing for selection of resin hardness taking into consideration usability (for example, bending of the tip of the brush molded body) according to the thickness of the brush molded body 20. The hardness of polyurethane is preferably Shore 90A or more and 70D or less. If the polyurethane has a hardness softer than Shore 90A, it will be more likely to deform when formed thinly, resulting in a weaker fit and making the brush molded body 20 more likely to fall off when the toothbrush 1 is in use. If the polyurethane has a hardness harder than Shore 70D, there is a risk of pain when the tip of the head base 21 hits oral tissue if the back surface of the head base 21 is tilted. By setting the polyurethane hardness to be at least Shore 90A and no more than 70D, it is possible to prevent the brush molded body 20 from falling off when the toothbrush 1 is in use, or to prevent pain when the tip of the head base 21 hits oral tissue.

[0034] As the polyurethane, it is preferable to use an ether-based polyurethane from the viewpoint of ensuring water resistance and antibacterial properties.

[0035] The filament 23 has a generally columnar shape that protrudes forward from a support surface 21a located on the front side in the thickness direction of the head base 21. The support surface 21a of the head base 21 is a flat surface parallel to the width direction and the insertion direction. The support surface 21a is located at the base end position of the filament 23 in the thickness direction. The base end side of the filament 23 has a generally triangular prism shape with a generally triangular cross section, and the tip end side has a triangular pyramid shape that extends from the generally triangular prism and tapers. The cross-sectional shape of the filament 23 can be selected from a generally triangular shape, a generally polygonal shape such as a generally square shape, a generally circular shape, a generally star shape, a generally spatula shape, etc. In addition to a tapered shape that tapers to a tip, the filament 23 may have a straight configuration or a tapered shape that tapers from the base end.

[0036] The filaments 23 are arranged in a plurality of rows along the width direction of the brush molding 20 so that adjacent rows in the insertion direction are shifted by half a pitch. In other words, the filaments 23 are arranged in a staggered pattern.

[0037] FIG. 5 is a view of the brush molded body 20 as seen from the rear end side. 5, the plurality of filaments 23 includes a filament group (first filament group) F1 located at the center in the width direction and filament groups F2 located on both sides of the filament group F1 in the width direction. As an example, the filament group F1 is taller than the filament group F2. The maximum length of the filament 23 is preferably 7 mm or more, and more preferably 9 mm or more. The maximum length of the filament 23 is preferably 15 mm or less, and more preferably 13 mm or less. The maximum length of the filament 23 is preferably 7 mm or more and 15 mm or less, and more preferably 9 mm or more and 13 mm or less. If the maximum length of the filament 23 is less than 7 mm, the ability to clean the oral cavity may be reduced. If the maximum length of the filament 23 exceeds 15 mm, the releasability when the brush molded body 20 is molded by injection molding will be reduced. By setting the maximum length of the filament 23 to be 7 mm or more and 15 mm or less, the ability to clean the oral cavity and the releasability during molding can be ensured.

[0038] The cross-sectional area of ​​the base end of the filament 23 is 0.8 mm 2 Preferably, it is less than 0.6 mm 2 It is more preferable that the cross-sectional area of ​​the base end of the filament 23 is 0.8 mm or less. 2 If the cross-sectional area of ​​the base end of the filament 23 is more than 0.8 mm, the filament 23 may become difficult to bend, and the cleaning performance of the gaps between the teeth and the cervical area of ​​the teeth may be reduced. 2 By setting the following, it is possible to ensure the ability to clean gaps between teeth, the cervical area, etc.

[0039] The ratio of the total cross-sectional area of ​​the base ends of the multiple filaments 23 to the area of ​​the support surface 21a of the head base portion 21 is preferably 10% or more and 50% or less. If the ratio of the total cross-sectional area of ​​the base ends of the filaments 23 is less than 10%, the ability to clean the oral cavity may be reduced. If the ratio of the total cross-sectional area of ​​the base ends of the filaments 23 exceeds 50%, the releasability when molding the brush molded body 20 by injection molding will be reduced. By setting the ratio of the total cross-sectional area of ​​the base ends of the filaments 23 to 10% or more and 50% or less, it is possible to ensure the ability to clean the oral cavity and the releasability during molding.

[0040] The filament group F1 constitutes a part of the plurality of filaments 23 and is formed of a first resin composition. The filament group F2 is composed of the filaments 23 other than the filament group F1 among the plurality of filaments 23 and is formed of a second resin composition different from the first resin composition. The first resin composition and the second resin composition can be selected from the soft resins described above, taking into consideration the feel when using the toothbrush 1 and the appearance (design) of the toothbrush 1. For example, when considering the feel when using the toothbrush 1 and achieving both massaging properties and a good brushing feel, the soft resins described above with different hardnesses can be used. Furthermore, when considering appearance, it is also possible to use the soft resin described above as a base material and add a colorant such as a masterbatch to give the filament group F1 and the filament group F2 different colors.

[0041] The head base 21 has a support base 30 and a fitting hole 22 . The support base 30 supports the base ends of the filament group F1 from below. As shown in FIG. 3, the support base 30 has a rectangular parallelepiped shape in a front view and is large enough to include the filament group F1. As shown in FIG. 4, the upper surface of the support base 30 is flush with the support surface 21a. In other words, the upper surface of the support base 30 constitutes a part of the support surface 21a. Hereinafter, the upper surface of the support base 30 will also be referred to as the support surface 21a, as appropriate.

[0042] The support base 30 is located closer to the front than the fitting hole 22. It forms part of the head base 21. The support base 30 is made of a first resin composition. The support base 30 and the filament group F1 constitute a preformed body 40 integrally molded from the first resin composition.

[0043] The fitting hole 22 extends in the insertion direction and opens to the end face 21b on the rear end side (one side). Fig. 6 is a cross-sectional view of the fitting hole 22 taken along a plane parallel to the support surface 21a. As shown in Fig. 6, the fitting hole 22 has a first portion 33 that opens to the end face 21b, and a second portion 34 that is located further back than the first portion 33. As shown in Fig. 4, the first portion 33 and the second portion 34 are disposed spaced apart from the back surface 21c of the head base 21 and the back surface of the support base 30, respectively.

[0044] The head base portion 21 has a protrusion 35 located approximately in the center of the fitting hole 22 in the insertion direction, between the first portion 33 and the second portion 34. The protrusions 35 are provided on both sides of the fitting hole 22 in the width direction. The protrusions 35 are each provided at a position where they will fit into a recess 15 (described below) when a fitting protrusion 12 (see FIG. 7 ; described below) of the handle body 10 is inserted into the fitting hole 22. The protrusion 35 has an arc shape that has an arc center on the outside in the width direction and is convex inward.

[0045] The shortest distance L35 between the protrusions 35 is shorter than the width L33 of the first portion 33 and the width L34 of the second portion 34. The amount by which the protrusions 35 protrude inward in the width direction relative to the second portion 34 is, for example, 1 mm. The amount by which the protrusions 35 protrude relative to the second portion 34 is the amount of undercut that occurs when the mold (slide core) that forms the fitting hole 22 is pulled toward the rear end during injection molding of the brush molded body 20.

[0046] Of the brush molded body 20, the head base portion 21 other than the support base portion 30 is formed from a second resin composition. Of the brush molded body 20, the head base portion 21 other than the support base portion 30 and the filament group F2 constitute a base main body molded body 50 integrally molded from the second resin composition. The brush molded body 20 is a molded body in which a pre-molded body 40 and a base main body molded body 50 are integrally molded. In this case, the pre-molded body 40, which has been primarily molded from the first resin composition, is placed in a cavity in a mold, and the cavity is filled with the second resin composition for secondary molding (insert molding), thereby forming the molded body.

[0047] Returning to FIG. 5 , in a cross section perpendicular to the longitudinal direction of the head base 21, the thickness t1 of the support base 30 is selected from the range of 0.5 mm to 2.5 mm. The thickness t2 between the back surface of the support base 30 and the front surface inside the fitting hole 22 is selected from the range of 0 mm to 2.5 mm. When the back surface of the support base 30 and the front surface inside the fitting hole 22 are flush with each other, the thickness t2 between the back surface of the support base 30 and the front surface inside the fitting hole 22 is 0 mm. In other words, a configuration can be selected in which the back surface of the support base 30 is exposed and faces the fitting hole 22. In this case, the side surfaces in the width direction of the support base 30 are adhered and fixed to the base body molded body 50.

[0048] The thickness t1+t2 between the front surface inside the fitting hole 22 and the support surface 21a is selected from the range of 0.5 mm to 3.5 mm. The length t3 in the thickness direction of the fitting hole 22 is selected from the range of 1.0 mm to 3.0 mm. The thickness t4 between the rear surface inside the fitting hole 22 and the rear surface 21c of the head base portion 21 is selected from the range of 0.3 mm to 2.0 mm.

[0049] In a cross section perpendicular to the longitudinal direction of the head base portion 21, if the cross-sectional area of ​​the support base portion 30 is S1 and the cross-sectional area of ​​the region of thickness t1+t2 located between the front surface inside the fitting hole 22 and the support surface 21a is S, it is preferable that the value represented by S1 / S be 0.1 or more in all regions where the fitting hole 22 is provided. The value represented by S1 / S is preferably 0.6 or less, more preferably 0.5 or less, and even more preferably 0.4 or less. The value represented by S1 / S is preferably 0.1 or more and 0.6 or less, more preferably 0.1 or more and 0.5 or less, and even more preferably 0.1 or more and 0.4 or less.

[0050] In the brush molded body 20 having the fitting hole 22, the cross-sectional area S of the region defined by the thickness t1+t2 between the front surface inside the fitting hole 22 and the support surface 21a, and the cross-sectional area S1 of the support base 30, significantly affect the moldability of the filament 23. In multi-color molding, the primary side is molded, and then the movable side (or fixed side) of the mold is switched to mold the secondary side and subsequent sides. Therefore, molding proceeds while the primary molded body remains in the cavity. This further reduces the flowable region of the secondary side and subsequent sides. Therefore, unlike mono-color molding, multi-color molding tends to result in insufficient resin fluidity in the secondary side and subsequent sides, making filament molding difficult. In this case, sufficient filling speed and holding pressure cannot be ensured, making molding defects such as shorts and sink marks more likely to occur. Specifically, molding defects of the filament 23 are more likely to occur when the value expressed by the above S1 / S exceeds 0.6. In this embodiment, molding defects of the filament 23 can be suppressed by setting the value expressed by S1 / S to 0.6 or less. From the viewpoint of ensuring the formability of the primary side support base 30 and the filament group F1, it is preferable to set the value expressed by S1 / S to 0.1 or more.

[0051] In a cross section perpendicular to the longitudinal direction of the head base portion 21, if the cross-sectional area of ​​the fitting hole 22 is SV and the cross-sectional area of ​​the head base portion 21 including the cross-sectional area SV of the fitting hole 22 is SW, the value expressed by SV / (SW-S1) is preferably 0.1 or more in the entire region where the fitting hole 22 is provided. The value expressed by SV / (SW-S1) is preferably 0.5 or less, more preferably 0.4 or less, and even more preferably 0.3 or less. The value expressed by SV / (SW-S1) is preferably 0.1 or more and 0.5 or less, more preferably 0.1 or more and 0.4 or less, and even more preferably 0.1 or more and 0.3 or less.

[0052] In molding other than the primary side, i.e., molding the base body molded body 50, the presence of the slide core for forming the fitting hole 22, in addition to the presence of the previously molded primary side preform 40, significantly affects resin flow. A smaller slide core occupancy facilitates resin flow within the cavity, improving moldability of the filament 23. Conversely, if the value expressed as SV / (SW-S1), which indicates the slide core occupancy rate, exceeds 0.5, resin flow is restricted during molding of the base body molded body 50, potentially resulting in molding defects of the filament 23 (filament group F2) on the secondary side and beyond. In this embodiment, by setting the value expressed as SV / (SW-S1) to 0.5 or less, molding defects of the filament 23 can be suppressed. Note that, from the perspective of ensuring the strength of the slide core, it is preferable to set the value expressed as SV / (SW-S1) to 0.1 or more.

[0053] If the area (projected area) of the head base 21 as viewed from the front side in the thickness direction is P and the area of ​​the support base 30 as viewed from the front is P1, the value expressed by P1 / P is preferably 0.1 or more, and more preferably 0.2 or more. The value expressed by P1 / P is preferably 0.5 or less, and more preferably 0.4 or less. Furthermore, the value expressed by P1 / P is preferably 0.1 or more and 0.5 or less, more preferably 0.1 or more and 0.4 or less, and even more preferably 0.2 or more and 0.4 or less.

[0054] Resin flow parallel to the support surface 21a is also important as a means of improving the formability of the filaments 23 (filament group F2) other than the primary side. This contributes significantly, particularly when the gate is located at the longitudinal end of the brush molded body 20, such as a side gate. Therefore, if the value expressed by P1 / P exceeds 0.5, the resin flow is hindered due to the occupancy of the cavity region by the primary preform 40, which may result in poor molding of the filaments 23 during molding of the base body molded body 50 on the secondary side and beyond. On the other hand, if the value expressed by P1 / P is less than 0.1, the occupancy rate of the filament group F1 is low, which may result in insufficient functionality (e.g., cleanability). In this embodiment, by setting the value expressed by P1 / P to be 0.1 or more and 0.5 or less, poor molding of the filaments 23 can be suppressed while ensuring the functionality of the filament group F1.

[0055] The maximum distance (maximum thickness) between the support surface 21a and the back surface 21c of the head base 21, i.e., the maximum distance T from the base end of the filament 23 to the back surface 21c, is preferably 2.0 mm or more and 4.5 mm or less. If the maximum distance T is less than 2.0 mm, the gap between the support surface 21a and the surface of the fitting hole 22 facing the support surface 21a, or the gap between the back surface 21c and the surface of the fitting hole 22 facing the back surface 21c, becomes small, reducing the fluidity of the molten resin during molding of the base body molded body 50, which may result in incomplete filling of the resin. Furthermore, if the maximum distance T is less than 2.0 mm, the gap between the surface of the fitting hole 22 facing the support surface 21a and the support base 30 must be reduced, reducing the fluidity of the molten resin during molding of the base body molded body 50. If the maximum distance T exceeds 4.5 mm, the operability of the brush molded body 20 when inserted into the oral cavity may be reduced. In this embodiment, by setting the maximum distance T to be 2.0 mm or more and 4.5 mm or less, it is possible to ensure the filling property of the resin and the operability when the brush molded body 20 is inserted into the oral cavity.

[0056] If the maximum distance from the base end of the filament 23 to the back surface 21c of the head base 21 is T and the thickness of the support base 30 in the thickness direction is t1, the value expressed by t1 / T is preferably 0.5 or less, and more preferably 0.4 or less. If the value expressed by t1 / T exceeds 0.5, the entire brush molded body 20 becomes thicker in order to ensure resin flow when molding the base body molded body 50 other than the primary side, leading to reduced intraoral maneuverability. In this embodiment, setting the value expressed by t1 / T to 0.5 or less is advantageous for achieving both moldability and usability when molding the base body molded body 50 on the secondary side and subsequent sides. Note that, from the viewpoint of ensuring primary side moldability and adhesion of the side of the primary side support base 30 to the head base 21, the value expressed by t1 / T is preferably 0.1 or more.

[0057] Furthermore, the value of the distance between the thickness t1 and the front surface of the fitting hole 22, expressed as t1 / (t1+t2), is preferably 0.2 or greater, more preferably 0.3 or greater. The value of t1 / (t1+t2) is preferably 0.8 or less, more preferably 0.7 or less. The value of t1 / (t1+t2) is preferably 0.2 or greater but 0.8 or less, more preferably 0.3 or greater but 0.7 or less. If the value of t1 / (t1+t2) exceeds 0.8, sufficient space for resin flow cannot be secured between the rear surface of the primary side (the rear surface of the support base 30) and the slide core. This results in reliance on resin flow on the side surface of the support base 30, potentially reducing moldability on the side other than the primary side (the base body molded body 50). Furthermore, resin adhesion between the primary-side support base 30 and the secondary-side base body molded body 50 may be unstable. If the value expressed by t1 / (t1+t2) is less than 0.2, it may be impossible to ensure the formability of the primary-side support base 30. In this embodiment, by setting the value expressed by t1 / (t1+t2) to be 0.2 or more and 0.8 or less, it is possible to ensure the formability of the primary-side support base 30 and the secondary-side base body molded body 50, and to stabilize the resin adhesion between the support base 30 and the base body molded body 50.

[0058] Furthermore, if the thickness t2 is 0.3 mm or more, problems with formability are unlikely to occur even in the case of a wide head specification. The thickness t2 is preferably 0.5 mm or more, and more preferably 0.8 mm or more.

[0059] The number of filaments in the filament group F1 is FM, and the area where the support base part 30 is bonded to the base body molded body 50 is Q1 (mm 2 ), the value expressed as FM / Q1 is 1.0 (lines / mm 2 ) or less, and 0.8 (lines / mm 2 ) or less. When the filaments 23 are released from the mold after molding, they are pulled out by the mold release resistance on the cavity surface. The value expressed by FM / Q1 is 1.0 (fibers / mm 2 ), in multi-color molding, when the preform 40 and the base body molded body 50 are released from the mold after secondary molding, the preform 40 may peel off from the base body molded body 50 due to the release resistance of the filament group F1. In this embodiment, the value expressed by FM / Q1 is 1.0 (filaments / mm 2 ) or less, peeling of the preform 40 from the base body molded body 50 after secondary molding can be suppressed. Note that if the number of filaments F1 cannot be secured sufficiently for the area occupied by the support base 30, the value expressed by FM / Q1 should be set to 0.2 (filaments / mm 2 ) or more.

[0060] To prevent the preform 40 from peeling off from the base body molded body 50 after the secondary molding, it is preferable to provide one or more uneven structures at the adhesive interface between the support 30 and the base body molded body 50. By providing an uneven structure rather than a smooth adhesive interface between the support 30 and the base body molded body 50, the adhesive area can be increased while ensuring moldability, thereby improving the adhesion of the primary preform 40. The uneven structure may be located on either the back or side of the support 30. However, locating the uneven structure on the back is effective for increasing the adhesive area because it is easier to increase the height and width of the unevenness compared to the side. When locating an uneven structure on the side of the support 30, it is only necessary to consider the thickness of the support 30 and the undercuts that occur when molding the preform 40. The height (maximum to minimum) of the uneven structure can be, for example, approximately 0.1 to 0.5 mm, and the pitch of the uneven structure can be approximately 0.5 to 3.0 mm.

[0061] As shown in Figure 4, if the maximum length of the head base portion 21 in the longitudinal direction is L1 and the maximum length of the fitting hole 22 is L2, the value expressed by L2 / L1 is preferably 0.30 or more, more preferably 0.40 or more, and even more preferably 0.45 or more. The value expressed by L2 / L1 is preferably 0.70 or less, more preferably 0.60 or less, and even more preferably 0.55 or less. Furthermore, the value expressed by L2 / L1 is preferably 0.30 or more and 0.70 or less, more preferably 0.40 or more and 0.60 or less, and even more preferably 0.45 or more and 0.55 or less.

[0062] If the value expressed by L2 / L1 is less than 0.30, the area of ​​the handle body 10 made of hard resin where the fitting protrusion 12 is not present becomes large, which may make the front of the brush molded body 20 more likely to bend and reduce the usability of the toothbrush 1. If L2 / L1 exceeds 0.70, the volume occupied by the mold (slide core) that forms the fitting hole 22 during molding becomes large, restricting resin flow and reducing the moldability of the filament 23. By setting the value expressed by L2 / L1 to be 0.30 or more and 0.70 or less, it is possible to prevent a decrease in the moldability of the filament 23 while also preventing a decrease in the usability of the toothbrush 1.

[0063] [Handle body 10] FIG. 7 is a front view of the handle body 10. FIG. As shown in Figure 7, the handle body 10 includes a rod-shaped handle portion 11 and a fitting protrusion 12 provided at the tip of the handle portion 11 and protruding toward the tip end in the longitudinal direction of the handle portion 11. The fitting protrusion 12 is detachably fitted into a fitting hole 22 in the brush molding 20. In the toothbrush 1, the fitting protrusion 12 of the handle body 10 is inserted into the fitting hole 22 in the brush molding 20, whereby the brush molding 20 is attached by covering the fitting protrusion 12.

[0064] In this embodiment, the handle portion 11 has a shape in a front view that gradually narrows from the front end to the rear end, then extends at a constant width, then gradually widens, and then narrows again in a curved manner. The rear end of the handle portion 11 has a substantially semicircular shape in a front view.

[0065] As shown in Figure 2, the handle portion 11 has a side view shape that extends from the tip end toward the rear end with a constant width, and then gradually widens until it reaches its maximum thickness, which is the finger rest portion. The side view shape of the handle portion 11 curves so that the width gradually narrows from the finger rest portion, which is the maximum thickness, toward the rear end. The side view shape of the handle portion 11 has a roughly semicircular rear end.

[0066] In the present invention, the shape of the handle portion is not limited to the shape of this example and can be appropriately set in consideration of strength, operability, design, etc. The dimensions of the handle portion 11 are not particularly limited and can be appropriately set. For example, the length of the handle portion 11 can be 100 to 200 mm.

[0067] The fitting projection 12 is a portion covered by the brush molded body 20 when the brush molded body 20 is attached to the handle body 10. The rear end of the fitting projection 12 is the rear end position of the brush molded body 20 when the brush molded body 20 is attached to the handle body 10.

[0068] FIG. 8 is an enlarged front view of the fitting projection 12. FIG. 9 is an enlarged side view of the fitting projection 12. As shown in FIG. 8, the fitting projection 12 has a base portion 13 provided on the tip side of the handle portion 11 and a tip portion 14 provided at the tip of the base portion 13. As shown in FIG. 9, the base portion 13 and the tip portion 14 have steps with respect to the handle portion 11 on both the front side and the back side and are formed with the same thickness that is thinner than the handle portion 11.

[0069] The base portion 13 is substantially rectangular in plan view. The base portion 13 has steps with respect to the handle portion 11 on both sides in the width direction and is formed with a width L13 that is narrower than the maximum width L11 on the tip side of the handle portion 11 (L13 < L11). The tip portion 14 is substantially elliptical in plan view with the width direction as the major axis direction. The tip portion 14 has a shape in which the side edges are cut out by a straight line parallel to the insertion direction of the fitting projection 12 on both sides in the width direction of the substantially elliptical shape. The tip portion 14 has steps with respect to the base portion 13 on both sides in the width direction and is formed with a width L14 that is narrower than the width L13 of the base portion 13.

[0070] The fitting protrusion 12 has a recess 15 between the base 13 and the tip 14, approximately in the center in the insertion direction. The recess 15 is provided on both sides in the width direction. The recess 15 has an arc shape with the arc center on the outside in the width direction and concave inward. The shortest distance L15 between the recesses 15 is shorter than the width L13 of the base 13 and the width L14 of the tip 14. The recess amount of the recess 15 relative to the edge that defines the width L14 at the tip 14 is, for example, 1 mm.

[0071] The handle body 10 is made of hard resin. An example of a hard resin is a resin having a flexural modulus (JIS K7171) of 1500 MPa or more and 3000 MPa or less. Specific examples include polypropylene resin (PP), polyacetal resin (POM), polyester resin (PCTA), polyethylene terephthalate copolymer (PETG), and high-density polyethylene (HDPE). Among these, PP, a general-purpose resin, is preferred in terms of cost.

[0072] The maximum width L21 of the rear end side (end face 21b) of the head base portion 21 is approximately the same as the maximum width of the handle portion 11 on the tip side. The shape of the fitting hole 22 in a front view is substantially the same as the shape of the fitting protrusion 12 in a front view. The width L33 of the first portion 33 is a length that allows the base 13 of the fitting protrusion 12 to be inserted, and is substantially the same as the maximum width L13 of the base 13. The width L34 of the second portion 34 is a length that allows the tip 14 of the fitting protrusion 12 to be inserted, and is substantially the same as the maximum width L14 of the tip 14. The shortest distance L35 between the protrusions 35 is a length that allows the tip 14 and the recess 15 of the fitting protrusion 12 to be inserted, and is substantially the same as the shortest distance L15 between the recesses 15.

[0073] Next, the procedure for molding the brush molded body 20 will be described with reference to Figures 10 to 12. Figure 10 is a cross-sectional view in the width direction that simply shows an example of a mold MD for molding the preform 40 of the brush molded body 20.

[0074] The mold MD comprises a first mold MD1 and a second mold MD2 for primary molding, which move relatively in the opening / closing direction (up and down direction in FIG. 10). The first mold MD1 and the second mold MD2 are clamped together with a parting surface PL, which is flush with the support surface 21a, as a joining surface. As an example, the first mold MD1 is a fixed mold, and the second mold MD2 is a movable mold.

[0075] The first mold MD1 is attached to, for example, the fixed side of an injection molding machine, and is filled with molten resin from the injection molding machine. The second mold MD2 is attached to, for example, the movable side of the injection molding machine, and moves in the opening and closing direction relative to the first mold MD1, thereby opening and closing the mold MD.

[0076] The first mold MD1 has a molding surface 21aM where the support surface 21a is molded when the first mold MD1 is clamped and joined to the second mold MD2, a cavity F1M where the filament group F1 is molded, and a cavity F2M where the filament group F2 is molded. The cavity F1M and the cavity F2M are open to the parting surface PL of the first mold MD1.

[0077] The second mold MD2 has a cavity 30M in which the support base portion 30 is molded when the second mold MD2 is clamped and joined to the first mold MD1. The cavity 30M opens to the cavity F1M. The cavity 30M does not open to the cavity F2M. The opening of the cavity F2M is closed by the parting surface PL of the second mold MD2. A gate portion (not shown) is provided in the cavity 30M. For example, a side gate type is used as the gate portion, but a pinpoint gate type or a tunnel gate type may also be used.

[0078] In the above-described mold MD, the molten first resin composition is introduced into the cavity 30M from the gate G while the first mold MD1 and the second mold MD2 are clamped together, and fills the cavity 30M and the cavity F1M. Meanwhile, the cavity 30M does not open to the cavity F2M, and the opening of the cavity F2M is blocked by the parting surface PL of the second mold MD2, so the first resin composition is not filled in. Thereafter, the first mold MD1 and the second mold MD2 are cooled while clamped together, thereby forming a preformed body 40 made of the first resin composition and having the filament group F1 and the support base 30.

[0079] Fig. 11 is a widthwise cross-sectional view showing, in a simplified manner, an example of a secondary molding die MD for molding the base body molded body 50 of the brush molded body 20. Fig. 12 is a lengthwise cross-sectional view showing, in a simplified manner, an example of a secondary molding die MD.

[0080] The mold MD comprises a first mold MD1 and a second mold MD12 that move relative to each other in the opening and closing direction. The first mold MD1 is the above-mentioned first mold MD1 that holds the molded preform 40 without releasing it. Note that a portion of the first mold MD1 for primary molding, including cavities F1M and F2M, may be detached and attached to the first mold MD1 for secondary molding.

[0081] The second mold MD12 has a cavity 21M in which the head base 21 is molded when the second mold MD12 is clamped and joined to the first mold MD1, a gate G that opens to the tip end of the cavity 21M and introduces molten resin into the cavity 21M, and an abutment surface 21eM that is provided at the end face 21b in the insertion direction and is perpendicular to the insertion direction. As shown in FIG. 11, the cavity F2M in which the filament group F2 is molded opens to the cavity 21M. For example, a side gate method is used as the gate G, but a pinpoint gate method or a tunnel gate method may also be used. The abutment surface 21eM extends in the second mold MD2 from a position where the back surface of the head base 21 is molded in a direction away from the PL surface.

[0082] The second mold MD12 is provided with a slide core SL. The slide core SL has a core portion 22M in which the fitting hole 22 is formed, and a molding surface 21bM perpendicular to the direction in which the core portion 22M projects and is inserted. As shown in FIG. 11, before mold clamping, the molding surface 21bM is separated from the abutment surface 21eM. When the first mold MD1 and the second mold MD12 are clamped, as shown in FIG. 11, the slide core SL is positioned at a position where a portion of the molding surface 21bM abuts against the abutment surface 21eM and the core portion 22M is inserted into the cavity 21M. The region of the molding surface 21bM that does not abut against the abutment surface 21eM and faces the cavity 21M is a region where the end face 21b is formed. Furthermore, when the first mold MD1 and the second mold MD12 are opened, the slide core SL moves in a direction in which the core portion 22M moves away from the cavity 21M so that the core portion 22M does not interfere with the release of the molded brush molding body 20. The direction in which the slide core SL moves is preferably horizontal to avoid unexpected movement due to its own weight.

[0083] In the above-described mold MD, with the first mold MD1 and the second mold MD12 clamped together, the molten second resin composition is introduced into the cavity 21M from the gate G, filling the cavity 21M and the cavity F2M. The second resin composition filled into the cavity 21M covers the side and back surfaces of the support base 30 and is adhered to the support base 30. Thereafter, the first mold MD1 and the second mold MD12 are cooled while clamped together and released from the mold MD, thereby obtaining a molded body in which the preformed body 40 and the base main body molded body 50 are integrally molded, the preformed body 40 including the filament group F1 and the support base 30 and formed from the first resin composition, and the base main body molded body 50 including the head base 21 and the portions of the multiple filaments 23 other than the preformed body 40 and molded from the second resin composition are obtained.

[0084] That is, a brush molding 20 is obtained in which a filament 23 having a group of filaments F1 formed from the first resin composition and a group of filaments F2 formed from the second resin composition, and a head base portion 21 including a support base portion 30 formed from the first resin composition and formed from the second resin composition are integrally molded as a molding.

[0085] The molded brush body 20 is fitted by inserting the fitting protrusion 12 of the handle body 10 into the fitting hole 22, thereby obtaining a toothbrush 1 in which the brush body 20 and the handle body 10 are integrated. In addition, by pulling out the fitting protrusion 12 of the handle body 10 from the fitting hole 22, the brush body 20 can be detached from the handle body 10 and replaced.

[0086] As described above, the brush molding 20 of this embodiment has a group of filaments F1 formed from a soft resin of a first resin composition and a group of filaments F2 formed from a soft resin of a second resin composition. Therefore, by appropriately selecting the first resin composition and the second resin composition according to the purpose, a brush molding and toothbrush can be obtained that have a gentle feel and can improve the usability and appearance of the toothbrush 1.

[0087] [Second embodiment of brush molded body 20] Next, a second embodiment of the brush molded body 20 will be described with reference to Fig. 13. In these figures, the same elements as those in the first embodiment shown in Figs. 1 to 12 are designated by the same reference numerals, and their description will be omitted. In the first embodiment, a configuration in which the preform 40 is molded from one type of resin composition is exemplified, but in the second embodiment, a configuration in which the preform 40 is molded from multiple types of resin compositions will be described.

[0088] FIG. 13 is a cross-sectional view in the width direction of the brush molded body 20 according to the second embodiment. As shown in FIG. 13, the preform 40 of this embodiment has a filament group (second filament group) F3 arranged in the center in the width direction, filament groups F1 arranged on both sides of the filament group F3 in the width direction, a second support base 31 that supports the base of the filament group F3, and a support base 30 that supports the base of the filament group F1. The filament group F3 is molded from a third resin composition that is different from the first resin composition and the second resin composition. The filament groups F1 and F3 are formed from a plurality of filaments 23 arranged in the longitudinal direction of the head base 21. The third resin composition is appropriately selected from the soft resins described above.

[0089] The second support base 31 is molded from a third resin composition. The widthwise side and back surfaces of the second support base 31 are bonded to the support base 30. The front surface of the second support base 31 is flush with the support surface 21a. The preformed body 40 of this embodiment is a molded body in which the filament group F3 and the second support base 31 molded from the third resin composition and the filament group F1 and the support base 30 molded from the first resin composition are integrally molded.

[0090] As an example, the preform 40 can be obtained by two-color molding, in which the filament group F3 and the second support base 31 are molded with the third resin composition in the primary molding, and the filament group F1 and the support base 30 are molded with the first resin composition in the secondary molding. Alternatively, the preform 40 can be obtained by insert molding, in which the filament group F1 and the support base 30 are molded with the first resin composition using a mold in which the filament group F3 and the second support base 31 molded with the third resin composition are placed.

[0091] The brush molded body 20 of this embodiment is obtained by three-color molding, in which the filament group F3 and the second support base 31 are molded with the third resin composition in the primary molding, the filament group F1 and the support base 30 are molded with the first resin composition in the secondary molding, and the filament group F2 and the head base 21 are molded with the second resin composition in the tertiary molding. Alternatively, the brush molded body 20 can be obtained by insert molding, in which the filament group F2 and the head base 21 are molded with the second resin composition using a mold in which a previously molded preform 40 is placed.

[0092] The brush molding 20 of the above configuration not only provides the same functions and effects as the brush molding 20 of the first embodiment, but also allows the provision of toothbrushes 1 with diverse added value by using a greater variety of resin compositions according to the specifications of the toothbrush 1.

[0093] [Third embodiment of brush molded body 20] Next, a third embodiment of the brush molded body 20 will be described with reference to Figures 14 and 15. In these figures, the same elements as those of the second embodiment shown in Figure 13 are designated by the same reference numerals, and their description will be omitted. In this embodiment, the filament group is simply shown as a region in which the filament group is arranged.

[0094] Fig. 14 is a front view of the brush molded body 20 according to the third embodiment. Fig. 15 is a cross-sectional view in the width direction of the brush molded body 20 according to the third embodiment. 14, in this embodiment, the filament group F1 is provided on both sides of the filament group F3 in the width direction and on both sides of the filament group F3 in the length direction. The filament group F1 is arranged in an O shape surrounding the periphery of the filament group F3.

[0095] 15, the side surfaces of the second support base 31 are bonded to the support base 30. The second support base 31 penetrates the support base 30 in the thickness direction. The back surface of the second support base 31 is flush with the back surface of the support base 30. The other configurations are the same as those of the second embodiment.

[0096] In this embodiment, in addition to obtaining the same effects and advantages as the second embodiment described above, by arranging the filaments 23 two-dimensionally in addition to linearly, it is possible to provide toothbrushes 1 with a variety of added value using even more types of resin compositions depending on the specifications of the toothbrush 1.

[0097] In addition, as a configuration in which the filaments 23 are arranged two-dimensionally, for example, a configuration in which the filament group F1 and the support base 30 and the filament group F3 and the second support base 31 are arranged side by side in the longitudinal direction, as shown in the front view of Figure 16 and the longitudinal cross-sectional view of Figure 17, may be used.

[0098] [Fourth embodiment of brush molded body 20] Next, a fourth embodiment of the brush molded body 20 will be described with reference to Fig. 18. In this figure, the same elements as those in the first embodiment shown in Figs. 1 to 12 are designated by the same reference numerals, and their description will be omitted.

[0099] FIG. 18 is a cross-sectional view in the width direction of the brush molded body 20 according to the fourth embodiment. As shown in FIG. 18, the filament group F1 in the preform 40 of this embodiment includes all of the plurality of filaments 23. The other configurations are the same as those of the first embodiment.

[0100] In the brush molding 20 of the above configuration, as in the first embodiment, the filament group F1 and the head base portion 21 are molded from different resin compositions, so that a brush molding and toothbrush can be obtained that have a gentle feel and can improve the usability and appearance of the toothbrush 1.

[0101] In the brush molding 20 configured as described above, the preform 40 contains all of the filaments 23, and therefore the preform 40 has a large mold release resistance when the brush molding 20 is released from the mold. Therefore, as described above, it is preferable to adopt at least one of the relationship between the number of filaments FM and the bonding area Q1 of the support base 30 and the base body molding 50, and the uneven structure provided at the bonding interface between the support base 30 and the base body molding 50.

[0102] [Example] The present invention will be described in detail below with reference to examples. However, the present invention is not limited to the following examples and can be practiced with appropriate modifications within the scope of the present invention.

[0103] (Examples 1 to 8, Comparative Example 1) Toothbrushes that differed in at least one of the items shown in Table 1 were used as samples of Examples 1 to 8 and Comparative Example 1. The resin constituting each sample was polyurethane.

[0104] [Evaluation method] Each sample of Examples 1 to 8 and Comparative Example 1 was evaluated in terms of the moldability of the filament, ease of brushing the entire oral cavity, and adhesiveness of the preformed body on the primary molding side.

[0105] (1) Evaluation method for filament formability Five brush moldings molded under the same conditions were evaluated according to the following criteria. 5 points: No defects in appearance were observed. 4 points: The tip of the filament is deformed when released from the mold (it bends due to external force when releasing because the pressure was not sufficient). 3 points: The thickness of the filament tip is thinner than the design value. 2 points: The filament length is shorter than the design value (all filaments are more than half the total length). 1 point: The filament length is shorter than the design value (there is a filament that is less than half the total length). The average of the five evaluation points was then calculated and rated on the following four-point scale. ◎(double circle mark): 4.5 or higher, 5.0 or lower. ○ (circle mark): 3.5 or more, less than 4.5 points. △ (triangle mark): 2.5 or more, less than 3.5 points. × (cross mark): Less than 2.5 points.

[0106] (2) Method for evaluating the ease of brushing the entire oral cavity A sensory evaluation was conducted by 10 expert panelists, who evaluated the ease of brushing the entire oral cavity (with particular emphasis on the ease of brushing the back teeth) using the following criteria. 5 points: Very easy to polish. 4 points: Somewhat easy to polish. 3 points: Neither. 2 points: Somewhat difficult to polish. 1 point: Very difficult to polish. The average of the evaluation scores from the 10 expert panelists was then calculated and the products were rated on the following four-point scale. ◎: 4.5 or higher, 5.0 or lower. ○: 3.5 or more, less than 4.5 points. △: 2.5 or more, less than 3.5 points. ×: Less than 2.5 points.

[0107] (3) Method for evaluating the adhesion of the preformed body on the primary molding side Five brush moldings molded under the same conditions were evaluated according to the following criteria. 5 points: No defects in appearance were observed. 4 points: The primary base part is deformed due to the resistance to demolding (the brush surface is no longer smooth). 3 points: No peeling is visible, but peeling is observed at the resin boundary when external force is applied. 2 points: When demolding, part of the primary base part peeled off, but part remained connected. 1 point: The entire primary side has peeled off and separated from the brush molding (the primary side remains in the mold). The average of the five evaluation points was then calculated and rated on the following four-point scale. ◎: 4.5 or higher, 5.0 or lower. ○: 3.5 or more, less than 4.5 points. △: 2.5 or more, less than 3.5 points. ×: Less than 2.5 points.

[0108] [Table 1]

[0109] As shown in Table 1, for sample Example 1 of Examples 1 to 8, in which the value represented by S1 / S, which is the ratio of the cross-sectional area S1 of the support base portion 30 to the cross-sectional area S of the region located between the front surface inside the fitting hole 22 and the support surface 21a, is 0.6 or less, good results were obtained in all of the moldability of the filament, ease of brushing the entire oral cavity, and adhesion of the preformed body on the primary molding side. In contrast, the sample of Comparative Example 1, in which the value represented by S1 / S exceeded 0.6, did not obtain a good evaluation for the moldability of the filament.

[0110] Under the conditions shown in Example 1, good results were obtained in terms of the formability of the filament, the ease of brushing the entire oral cavity, and the adhesiveness of the primary preform.

[0111] Under the conditions shown in Example 2, the value represented by S1 / S increased as the primary support base was expanded. This resulted in a decrease in resin flow from the secondary side onwards, resulting in filament formability being inferior to that of the sample in Example 1. Furthermore, although the number of filaments in the first filament group FM increased as the primary support base was expanded, the adhesive area Q1 of the support base also increased, resulting in the adhesiveness of the primary preform being equivalent to that of the sample in Example 1.

[0112] Under the conditions shown in Example 3, the value expressed by SV / (SW-S1) increased as the slide core became thicker. As a result, the resin flow during molding of the base body molding decreased, and the moldability of the filaments on the secondary side and beyond was inferior to that of the sample in Example 1.

[0113] In both the samples of Example 4 and Example 5, the head thickness was increased, resulting in ease of brushing the entire oral cavity being inferior to that of the sample of Example 1. In addition, in the sample of Example 5, the support base portion was also thickened at the same time, resulting in a larger value expressed by t1 / T, and the resin flow during molding of the base body molded body was reduced compared to the sample of Example 4, resulting in inferior moldability of the filament to that of the sample of Example 1.

[0114] Under the conditions shown in Examples 6 and 8, the value expressed by t1 / (t1+t2) increased in both cases, and sufficient space for the resin to flow was not secured between the back surface of the primary support base and the slide core, reducing the resin flow and resulting in filament formability that was inferior to the sample of Example 1. However, compared to the sample of Example 6, the back surface of the support base of the sample of Example 8 was not exposed to the front surface inside the fitting hole, so the adhesion of the primary preform did not decrease.

[0115] Under the conditions shown in Example 7, the number of filaments in the first filament group FM increased compared to Example 1, but the adhesive area Q1 of the support base did not change, resulting in an increase in FM / Q1 and an inferior adhesion of the primary preform compared to the sample of Example 1.

[0116] While the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to these examples. The shapes and combinations of the components shown in the above examples are merely examples, and various modifications can be made based on design requirements, etc., without departing from the spirit of the present invention.

[0117] For example, in the above embodiment, the toothbrush 1 is configured by the brush molded body 20 and the handle body 10, which are molded separately, and the brush molded body 20 is attached to the handle body 10 by fitting the fitting protrusion 12 of the handle body 10 into the fitting hole 22 of the brush molded body 20, but the configuration is not limited to this. For example, a configuration may be adopted in which the fitting protrusion 12 of the handle body 10 is placed in a mold in which a pre-molded body is placed, instead of the slide core SL, and then insert-molded with a second resin composition during secondary molding. This insert molding allows the toothbrush 1 to be obtained as a molded body in which the fitting protrusion 12 fits into the fitting hole 22 and the brush molded body 20 and the handle body 10 are integrally molded.

[0118] In the above embodiment, the handle body 10 is formed from a hard resin, but the present invention is not limited to this configuration, and may be configured such that a part of the handle body 10 (such as the handle portion 11) is covered with a soft resin. This configuration can improve decorativeness and gripping properties. [Industrial Applicability]

[0119] The present invention is applicable to brush moldings and toothbrushes. [Explanation of symbols]

[0120] 1...toothbrush, 10...handle body, 12...fitting protrusion, 20...brush molded body, 21...head base portion, 21a...support surface, 21c...back surface, 22...fitting hole, 23...filament, 30...support base portion, 31...second support base portion, 40...preformed body, 50...base main body molded body, F1...filament group (first filament group), F3...filament group (second filament group)

Claims

1. The head base portion is made of a soft resin, and a plurality of filaments protrude from a support surface located on the front side in the thickness direction of the head base portion, the head base portion has a fitting hole extending in a length direction perpendicular to the thickness direction and opening to one side in the length direction, a preform having a filament group including at least a portion of the plurality of filaments and a support base portion that supports a base portion of the filament group and is located on the front side of the fitting hole and forms a portion of the head base portion, the preform being at least partially molded from a soft resin of a first resin composition; a base body molded body having the head base portion and portions of the plurality of filaments other than the preformed body, the base body molded body being molded with a second resin composition different from the first resin composition; Equipped with A brush molded body for toothbrush use, characterized in that the pre-molded body and the base body molded body are integrally molded.

2. a part of the plurality of filaments constitutes the group of filaments molded from the first resin composition; Among the plurality of filaments, the filaments other than the filament group constitute the base body molded body integrally molded with the head base portion using the second resin composition. The brush molded body according to claim 1 .

3. In a cross section perpendicular to the longitudinal direction of the head base portion, The cross-sectional area of ​​the support base is S1, When the cross-sectional area of ​​the region located between the front surface and the support surface inside the fitting hole is S, The value represented by S1 / S is 0.6 or less in the entire region where the fitting hole is provided. The brush molded body according to claim 1 or 2.

4. In a cross section perpendicular to the longitudinal direction, The cross-sectional area of ​​the fitting hole is SV, If the cross-sectional area of ​​the head base portion including the cross-sectional area of ​​the fitting hole is SW, then The value represented by SV / (SW-S1) is 0.5 or less in the entire region where the fitting hole is provided. The brush molded body according to claim 3 .

5. The area of ​​the head base portion as viewed from the front side in the thickness direction is defined as P, If the area of ​​the support base portion as viewed from the front side in the thickness direction is P1, The value represented by P1 / P is 0.1 or more and 0.5 or less. The brush molding according to any one of claims 1 to 4.

6. a maximum distance from the base end of the filament to the back surface of the head base portion opposite to the front surface side in the thickness direction is 2.0 mm or more and 4.5 mm or less; The brush molding according to any one of claims 1 to 5.

7. The maximum distance from the base end of the filament to the back surface of the head base portion is T, When the thickness of the support base portion in the thickness direction is t1, The value represented by t1 / T is 0.5 or less. The brush molded body according to claim 6.

8. If the distance between the rear surface of the support base and the front surface inside the fitting hole is t2, The value represented by t1 / (t1+t2) is 0.2 or more and 0.8 or less. The brush molded body according to claim 7.

9. The number of the filaments in the filament group is defined as F M , The area where the support portion adheres to the base body molded body is defined as Q1 (mm ２ ) then, The value expressed by FM / Q1 is 1.0 (lines / mm ２ ) is less than or equal to The brush molding according to any one of claims 1 to 8.

10. an uneven structure is provided at the adhesive interface between the support base portion and the base body molded body; The brush molding according to any one of claims 1 to 9.

11. The maximum length of the head base portion in the longitudinal direction is L1, If the maximum length of the fitting hole in the longitudinal direction is L2, The value represented by L2 / L1 is 0.30 or more and 0.70 or less. The brush molding according to any one of claims 1 to 10.

12. The preform includes all of the plurality of filaments. The brush molding according to any one of claims 1 to 11.

13. The preform is the filament group and the support base portion molded from the first resin composition; a second support base portion that supports a second group of filaments and a base portion of the second group of filaments, the second support base portion being molded from a third resin composition that is different from the first resin composition and the second resin composition; The brush molding according to any one of claims 1 to 11.

14. The soft resin is polyurethane. The brush molding according to any one of claims 1 to 13.

15. A brush molding according to any one of claims 1 to 14; a handle body formed of a hard resin and having a fitting projection that is detachably attached to the fitting hole of the brush molded body.

16. A brush molding according to any one of claims 1 to 14; a handle body having a fitting protrusion that fits into the fitting hole of the brush molded body, The toothbrush is characterized in that the brush body and the handle body are integrally molded.

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