JP7785019B2 - Brush molded body and toothbrush - Google Patents

Description

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.

Integrated molded toothbrushes have been proposed, which are manufactured using only an injection molding machine (see, for example, Patent Document 1). Because the filament and head base (or head) are molded as a single unit, integrated molded toothbrushes do not require the procurement of filament material or a bristle implantation machine, and have the advantage of being cheaper to manufacture than bristle implanted toothbrushes.

One-piece molded toothbrushes for cleaning have been proposed, in which a head (brush molded body) with a filament and insertion hole and a handle with an insertion hole at one end are molded separately and then fitted together to provide a one-piece molded toothbrush (see, for example, Patent Documents 2 and 3). The toothbrushes described in Patent Documents 2 and 3 have replaceable heads that can be disposed of by the user, allowing the handle to be reused, thereby saving resources.

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.

Japanese Utility Model Application Publication No. 61-207233 Chinese Utility Model No. 204561298 Chinese Patent Application Publication No. 107041792 Chinese Utility Model No. 205214577

However, the toothbrush described in Patent Document 4 has walls that separate the multicolored filaments, which means that the filaments cannot be placed in the wall areas, creating spaces. This makes it difficult to arrange the filaments in a regular, continuous profile, which reduces the gentle feel of the head when inserted into the oral cavity.

The present invention has been made in consideration of the above points, and aims to provide a brush molded body and toothbrush that have a gentle feel and can improve the usability and appearance of the toothbrush.

According to a first aspect of the present invention, there is provided a brush molded body comprising: a head base formed of a soft resin; and a plurality of filaments protruding from a support surface located on the front side of the head base in the thickness direction, the head base 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 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; at least a portion of the preformed body molded from a first resin composition; and a base body molded body molded from a second resin composition different from the first resin composition, the base body molded body including the head base and portions of the plurality of filaments other than those in the preformed body;

Furthermore, in the brush molding according to one aspect of the present invention, a portion of the plurality of filaments constitutes 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.

Furthermore, in the brush molding according to one aspect 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.

Furthermore, in the brush molding according to one aspect 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 as SV/(SW-S1) is 0.5 or less in all areas in which the fitting hole is provided.

Furthermore, in the brush molding according to one aspect 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.

Furthermore, in the brush molding according to one aspect 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.

Furthermore, in the brush molding according to one aspect 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.

Furthermore, in the brush molding according to one aspect 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.

Furthermore, in the brush molding according to one aspect of the present invention, when the number of filaments in the filament group is FM and the area where the support base portion is bonded to the base body molding is Q1 (mm ² ), the value expressed by FM/Q1 is 1.0 (filaments/mm ² ) or less.

Furthermore, in the brush molding according to one aspect of the present invention, an uneven structure is provided at the adhesive interface between the support base portion and the base body molding.

Furthermore, in the brush molding according to one aspect 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 0.30 or more and 0.70 or less.

Furthermore, in the brush molding according to one aspect of the present invention, the pre-molded body is characterized in that it contains all of the plurality of filaments.

Furthermore, in the brush molded body according to one aspect 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.

Furthermore, in the brush molding according to one aspect of the present invention, the soft resin is polyurethane.

In accordance with 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.

In accordance with 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 an engaging protrusion that engages with the engaging hole of the brush molding, wherein the brush molding and the handle body are integrally molded.

The present invention provides a brush molded body and toothbrush that have a gentle feel and can improve the usability and appearance of the toothbrush.

1 is a front view of a brush molded body 20 and a toothbrush 1 according to an embodiment of the present invention. FIG. 2 is a side view of the brush molded body 20 and the toothbrush 1. FIG. 2 is a front view of the brush molding 20. 4 is a cross-sectional view taken along line AA in FIG. 3. FIG. 2 is a view of the brush molding 20 as seen from the rear end side. 2 is a cross-sectional view of a plane parallel to the support surface 21a including the fitting hole 22. FIG. FIG. 2 is a front view of the handle body 10. FIG. 2 is an enlarged front view of a fitting protrusion 12. FIG. 2 is an enlarged side view of a fitting protrusion 12. 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. 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. FIG. 1 is a longitudinal cross-sectional view showing a simplified example of a mold MD for secondary molding. FIG. 10 is a cross-sectional view in the width direction of the brush molded body 20 according to the second embodiment. FIG. 10 is a front view of a brush molded body 20 according to a third embodiment. FIG. 10 is a cross-sectional view in the width direction of the brush molded body 20 according to the third embodiment. FIG. 11 is a front view showing a modified example of the brush molded body 20 according to the third embodiment. FIG. 10 is a longitudinal cross-sectional view showing a modified example of the brush molded body 20 according to the third embodiment. FIG. 10 is a cross-sectional view in the width direction of the brush molded body 20 according to the fourth embodiment.

Embodiments of the brush molded body and toothbrush of the present invention will be described below with reference to Figures 1 to 18. In this embodiment, an example of a toothbrush in which the brush molded body is detachably attached to the handle body will be used.

The following embodiment illustrates 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 components in each structure are different from the actual structure to make each component easier to understand.

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

In this embodiment, the front side refers to the side from which the filament 23 (described later) protrudes (the upper side in Figure 2) in the thickness direction (hereinafter simply referred to as the thickness direction), which is the normal direction of the support surface 21a (described in detail later) of the brush molding 20. In the thickness direction of the brush molding 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 molding 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 molding 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 molding 20 (hereinafter simply referred to as the width direction).

[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 A-A 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 in a front view, and a plurality of filaments 23 provided on the front surface of the head base 21.

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

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 release agents.

Furthermore, compared to the other elastomers mentioned above, polyurethane has a wider range of hardness options, allowing for selection of resin hardness taking into account usability (e.g., 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 with a thin wall, resulting in a weaker fit and making the brush molding 20 more likely to fall off when using the toothbrush 1. If the polyurethane has a hardness harder than Shore 70D, there is a possibility that pain will occur 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 molding 20 from falling off when using the toothbrush 1 and to prevent pain from occurring when the tip of the head base 21 hits oral tissue.

In addition, it is preferable to use ether-based polyurethane as the polyurethane, in order to ensure water resistance and antibacterial properties.

The filament 23 is generally columnar and protrudes forward from the support surface 21a, which is located on the front side of the head base 21 in the thickness direction. 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 of the filament 23 in the thickness direction. The base end of the filament 23 has a generally triangular prism shape with a generally triangular cross section, and the tip end has a triangular pyramid shape that extends from the generally triangular prism and tapers to a narrower point. 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, and the like. In addition to a tapered shape tapering to a narrower point, the filament 23 may be straight or tapered from the base end.

The filaments 23 are arranged in multiple rows along the width direction of the brush molding 20, with adjacent rows offset by half a pitch in the insertion direction. In other words, the filaments 23 are arranged in a staggered pattern.

FIG. 5 is a view of the brush molded body 20 as viewed 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 molding the brush molded body 20 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.

The cross-sectional area of the base end of the filament 23 is preferably 0.8 ^mm2 or less, and more preferably 0.6 ^mm2 or less. If the cross-sectional area of the base end of the filament 23 exceeds 0.8 ^mm2 , the filament 23 will be less flexible, which may reduce its ability to clean gaps between teeth, at the tooth neck, etc. By setting the cross-sectional area of the base end of the filament 23 to 0.8 ^mm2 or less, it is possible to ensure the ability to clean gaps between teeth, at the tooth neck, etc.

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%, oral cavity cleaning performance 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, oral cavity cleaning performance and releasability during molding can be ensured.

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 above-mentioned soft resins as appropriate, taking into consideration the feel in use and the appearance (design) of the toothbrush 1. For example, when considering the feel in use of the toothbrush 1 and achieving both massaging properties and a cleaning feel, the above-mentioned soft resins with different hardnesses can be used. Furthermore, when taking into consideration the appearance, it is also possible to use the above-mentioned soft resin 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.

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.

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

The fitting hole 22 extends in the insertion direction and opens to the end face 21b on the rear end side (one side). Figure 6 is a cross-sectional view of the fitting hole 22 taken along a plane parallel to the support surface 21a. As shown in Figure 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 Figure 4, the first portion 33 and the second portion 34 are positioned at a distance from the back surface 21c of the head base 21 and the back surface of the support base 30, respectively.

The head base 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 that will fit into a recess 15 (described below) when the fitting protrusion 12 (see Figure 7; described below) of the handle body 10 is inserted into the fitting hole 22. The protrusions 35 are arc-shaped with the arc center on the outside in the width direction and convex inward.

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 when the mold (slide core) that forms the mating hole 22 is pulled toward the rear end during injection molding of the brush molded body 20.

Of the brush molded body 20, the head base portion 21 excluding the support base portion 30 is formed from the second resin composition. Of the brush molded body 20, the head base portion 21 excluding the support base portion 30 and the filament group F2 constitute the base body molded body 50, which is integrally molded from the second resin composition. The brush molded body 20 is a molded body in which the pre-molded body 40 and the base body molded body 50 are integrally molded. In this case, the molded body is formed by placing the pre-molded body 40, which has been primarily molded from the first resin composition, in a cavity in a mold, filling the cavity with the second resin composition, and performing secondary molding (insert molding).

Returning to Figure 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 widthwise side of the support base 30 is adhered and fixed to the base body molding 50.

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 of the fitting hole 22 in the thickness direction 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 21 is selected from the range of 0.3 mm to 2.0 mm.

In a cross section perpendicular to the longitudinal direction of the head base 21, if the cross-sectional area of the support base 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.

In a brush molded body 20 having a fitting hole 22, the cross-sectional area S of the region defined by the thickness t1 + t2 between the front surface of 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 (or fixed) side of the mold is switched to mold the secondary side and subsequent sides. This allows molding to proceed 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 from the secondary side onward, 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 ratio 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 that the value expressed by S1/S is 0.1 or more.

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 as SV/(SW-S1) is preferably 0.1 or greater throughout the entire area in which the fitting hole 22 is provided. The value expressed as 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 as SV/(SW-S1) is preferably 0.1 or greater but 0.5 or less, more preferably 0.1 or greater but 0.4 or less, and even more preferably 0.1 or greater but 0.3 or less.

When molding parts other than the primary side, i.e., the base body molded body 50, the presence of the slide core used to form the mating holes 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 the 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 filaments 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 filaments 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 greater.

If the area (projected area) of the head base portion 21 when viewed from the front side in the thickness direction is P, and the area of the support base portion 30 when viewed from the front is P1, the value expressed by P1/P is preferably 0.1 or greater, and more preferably 0.2 or greater. 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 greater and 0.5 or less, more preferably 0.1 or greater and 0.4 or less, and even more preferably 0.2 or greater and 0.4 or less.

Resin flow parallel to the support surface 21a is also important as a means of improving the moldability 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 molding body 20, such as a side gate. Therefore, if the value represented 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 molding body 50 on the secondary side and beyond. On the other hand, if the value represented 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 represented by P1/P to be 0.1 or greater and 0.5 or less, poor molding of the filaments 23 can be suppressed while ensuring the functionality of the filament group F1.

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, will be small, reducing the fluidity of the molten resin during molding of the base body molded body 50 and potentially resulting in resin insufficiency. 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 will have to 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 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 inserting the brush molded body 20 into the oral cavity.

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 represented by t1/T is preferably 0.5 or less, and more preferably 0.4 or less. If the value represented by t1/T exceeds 0.5, the entire brush body 20 becomes thicker in order to ensure resin flow when molding the base body molding 50 other than the primary side, leading to reduced intraoral maneuverability. In this embodiment, setting the value represented by t1/T to 0.5 or less is advantageous for achieving both moldability and usability when molding the base body molding 50 on the secondary side and beyond. Note that, from the perspective of ensuring primary side moldability and adhesion of the side of the primary side support base 30 to the head base 21, it is preferable to set the value represented by t1/T to 0.1 or more.

Furthermore, the value of the distance between the thickness t1 and the front surface inside the fitting hole 22, expressed as t1/(t1 + t2), is preferably 0.2 or greater, and more preferably 0.3 or greater. The value of t1/(t1 + t2) is preferably 0.8 or less, and more preferably 0.7 or less. The value of t1/(t1 + t2) is preferably 0.2 or greater but 0.8 or less, and 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 means that resin flow will depend on the side surface of the support base 30, potentially reducing moldability on the non-primary side (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.

In addition, if the thickness t2 is 0.3 mm or more, there are few problems with formability even with a wide head specification. Thickness t2 is preferably 0.5 mm or more, and more preferably 0.8 mm or more.

If the number of filaments in the filament group F1 is FM and the area of adhesion between the support base 30 and the base body molded body 50 is Q1 (mm ² ), the value represented by FM/Q1 is preferably 1.0 (filaments/mm ² ) or less, and more preferably 0.8 (filaments/mm ² ) or less. When released from the mold after molding, the filaments 23 are pulled out by the release resistance of the cavity surface. If the value represented by FM/Q1 exceeds 1.0 (filaments/mm ² ), in multi-color molding, when the preformed body 40 and the base body molded body 50 are released from the mold after secondary molding, the release resistance of the filament group F1 may cause the preformed body 40 to peel off from the base body molded body 50. In this embodiment, by setting the value represented by FM/Q1 to 1.0 (filaments/mm ² ) or less, peeling of the preformed body 40 from the base body molded body 50 after secondary molding can be suppressed. In addition, if the number of filaments in the group F1 cannot be secured sufficiently relative to the occupied area of the support base 30, it is preferable to set the value expressed by FM/Q1 to 0.2 (filaments/mm ² ) or more, taking into consideration the possibility that the functionality of the primary filament F1 may be reduced.

To prevent the preform 40 from peeling 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 base 30 and the base body molded body 50. By providing an uneven structure rather than a smooth adhesive interface between the support base 30 and the base body molded body 50, the adhesive area is increased while maintaining moldability, improving the adhesion of the primary preform 40. The uneven structure may be located on either the back or side of the support base 30, but locating it 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 base 30, it is only necessary to consider the thickness of the support base 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.

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 represented by L2/L1 is preferably 0.30 or greater, more preferably 0.40 or greater, and even more preferably 0.45 or greater. The value represented 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 represented by L2/L1 is preferably 0.30 or greater but 0.70 or less, more preferably 0.40 or greater but 0.60 or less, and even more preferably 0.45 or greater but 0.55 or less.

If the value represented by L2/L1 is less than 0.30, the area of the handle body 10 made of hard resin where the mating protrusion 12 is not present becomes large, which may make the front of the brush molding 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 mating hole 22 during molding becomes large, restricting resin flow and reducing the moldability of the filament 23. By setting the value represented 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.

[Handle body 10]
FIG. 7 is a front view of the handle body 10. FIG.
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 of 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.

In this embodiment, the handle portion 11 has a front view that gradually narrows from the front end to the rear end, then extends at a constant width, then gradually widens, then narrows again in a curved fashion. The rear end of the handle portion 11 has a roughly semicircular shape when viewed from the front.

As shown in Figure 2, the handle portion 11 in side view extends from the tip end toward the rear end at a constant width, then gradually widens until it reaches its maximum thickness, which forms the finger rest area. The handle portion 11 in side view curves in such a way that its width gradually narrows from the finger rest area at its maximum thickness toward the rear end. The handle portion 11 in side view has an approximately semicircular rear end.

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

The fitting protrusion 12 is the portion that is covered by the brush molding 20 when the brush molding 20 is attached to the handle body 10. The rear end of the fitting protrusion 12 is the rear end position of the brush molding 20 when the brush molding 20 is attached to the handle body 10.

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

The base 13 is generally rectangular in plan view. The base 13 has a step relative to the handle portion 11 on both widthwise sides, and is formed with a width L13 narrower than the maximum width L11 at the tip end of the handle portion 11 (L13<L11). The tip portion 14 is generally elliptical in plan view, with the width direction as the major axis. The tip portion 14 has a shape in which the side edges are cut out on both widthwise sides of the generally elliptical shape in a straight line parallel to the insertion direction of the fitting protrusion 12. The tip portion 14 has a step relative to the base 13 on both widthwise sides, and is formed with a width L14 narrower than the width L13 of the base 13.

The mating 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 is concave on the inside. 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.

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.

The maximum width L21 of the rear end side (end surface 21b) of the head base portion 21 is approximately the same as the maximum width of the front end side of the handle portion 11.
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 into which the base 13 of the fitting protrusion 12 can 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 into which the tip 14 of the fitting protrusion 12 can 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 into which the tip 14 and the recess 15 of the fitting protrusion 12 can be inserted, and is substantially the same as the shortest distance L15 between the recesses 15.

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

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

The first mold MD1 is attached, for example, to the fixed side of the injection molding machine, and is filled with molten resin from the injection molding machine. The second mold MD2 is attached, for example, to the movable side of the injection molding machine, and the mold MD is opened and closed by moving in the opening and closing direction relative to the first mold MD1.

When the first mold MD1 is clamped and joined to the second mold MD2, it has a molding surface 21aM on which the support surface 21a is molded, a cavity F1M on which the filament group F1 is molded, and a cavity F2M on which the filament group F2 is molded. Cavities F1M and F2M open to the parting surface PL of the first mold MD1.

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 is open to the cavity F1M. The cavity 30M is not open to the cavity F2M. The opening of the cavity F2M is closed by the parting surface PL of the second mold MD2. The cavity 30M is provided with a gate portion (not shown). 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.

In the above mold MD, when the first mold MD1 and the second mold MD2 are clamped together, the molten first resin composition is introduced into the cavity 30M through the gate G, filling 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 does not fill the cavity. After this, the first mold MD1 and the second mold MD2 are cooled while clamped together, thereby forming a preform 40 made of the first resin composition and having the filament group F1 and the support base 30.

Figure 11 is a simplified widthwise cross-sectional view of an example of a secondary molding die MD for molding the base body molded body 50 of the brush molded body 20. Figure 12 is a simplified lengthwise cross-sectional view of an example of a secondary molding die MD.

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 first mold MD1 that holds the molded preform 40 without releasing it from the mold. 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.

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 portion G that opens to the tip of the cavity 21M and introduces molten resin into the cavity 21M; and an abutment surface 21eM that is located 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 into the cavity 21M. For example, a side gate method is used as the gate portion 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 the position where the back surface of the head base 21 is molded in a direction away from the PL surface.

A slide core SL is provided in the second mold MD12. The slide core SL has a core portion 22M in which the fitting hole 22 is molded, and a molding surface 21bM perpendicular to the direction in which the core portion 22M is inserted. As shown in Figure 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 Figure 11, a portion of the molding surface 21bM abuts against the abutment surface 21eM, and the slide core SL is positioned at a position where the core portion 22M is inserted into the cavity 21M. The area of the molding surface 21bM that does not abut against the abutment surface 21eM and faces the cavity 21M is the area where the end face 21b is molded. 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.

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 through the gate G, filling the cavity 21M and the cavity F2M. The second resin composition filling the cavity 21M coats the side and back surfaces of the support base 30 and adheres to the support base 30. The first mold MD1 and the second mold MD12 are then cooled while clamped together and released from the mold MD, resulting in a molded body comprising a preformed body 40 formed from the first resin composition and including the filament group F1 and the support base 30, and a base body molded body 50 molded from the second resin composition and including the head base 21 and portions of the multiple filaments 23 other than the preformed body 40, with the preformed body 40 and the base body molded body 50 molded integrally.

In other words, a brush molding 20 is obtained in which a filament 23 having a filament group F1 formed from the first resin composition and a filament group 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.

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. Furthermore, by pulling the fitting protrusion 12 of the handle body 10 out of the fitting hole 22, the brush body 20 can be detached from the handle body 10 and replaced.

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.By appropriately selecting the first resin composition and the second resin composition according to the purpose, it is possible to obtain a brush molding and toothbrush that has a gentle feel and can improve the usability and appearance of the toothbrush 1.

[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.

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 Figure 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 supporting the base of the filament group F3, and a support base 30 supporting the base of the filament group F1. The filament group F3 is molded from a third resin composition 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.

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.

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.

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, it 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.

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 for 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.

[Third embodiment of brush molded body 20]
Next, a third embodiment of the brush molding 20 will be described with reference to Figures 14 and 15. In these figures, the same elements as those in 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.

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.

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.

In this embodiment, in addition to achieving 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 a toothbrush 1 with diverse added value using even more types of resin compositions depending on the specifications of the toothbrush 1.

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.

[Fourth embodiment of brush molded body 20]
Next, a fourth embodiment of the brush molding 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.

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.

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.

In the brush molding 20 configured as described above, the preform 40 contains all of the filaments 23, which increases the mold release resistance of the preform 40 when the brush molding 20 is released from the mold. Therefore, as described above, it is preferable to adopt at least one of the following: the relationship between the number of filaments FM and the adhesive area Q1 of the support base 30 and the base body molding 50; and an uneven structure provided at the adhesive interface between the support base 30 and the base body molding 50.

[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.

(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.

[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.

(1) Evaluation Method of Filament Formability Five brush molded bodies 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 from the mold 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 calculated and evaluated according to the following four levels.
◎(double circle mark): 4.5 or above, 5.0 or below.
○ (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.

(2) Method for evaluating 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: A little difficult to polish.
1 point: Very difficult to polish.
The average of the evaluation scores from the 10 expert panelists was calculated and the evaluation was carried out on the following four-point scale.
◎: 4.5 or more, 5.0 or less points.
○: 3.5 or more and less than 4.5 points.
△: 2.5 or more and less than 3.5 points.
×: Less than 2.5 points.

(3) Method for Evaluating Adhesion of Preformed Body on Primary Molding Side Five brush molded bodies 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 mold release resistance during mold release (the brush surface is no longer smooth).
3 points: No peeling is visible, but peeling is observed at the resin boundary when an external force is applied.
2 points: When demolded, the primary base part was partially peeled off and partially connected.
1 point: The entire primary side peeled off and separated from the brush molding (the primary side remained in the mold).
The average of the five evaluation points was calculated and evaluated according to the following four levels.
◎: 4.5 or more, 5.0 or less points.
○: 3.5 or more and less than 4.5 points.
△: 2.5 or more and less than 3.5 points.
×: Less than 2.5 points.

As shown in Table 1, for Sample Example 1 of Examples 1 to 8, where 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 (S1/S) is 0.6 or less, good results were obtained in terms of filament formability, ease of brushing the entire oral cavity, and adhesion of the preformed body on the primary molding side. In contrast, Sample Example 1 of Comparative Example 1, where the value of S1/S exceeded 0.6, did not receive a good evaluation for filament formability.

When the conditions shown in Example 1 were used, good results were obtained in terms of filament formability, ease of brushing the entire oral cavity, and adhesion of the primary preform.

Under the conditions shown in Example 2, the value represented by S1/S increased as the primary support base was expanded. This reduced resin flow from the secondary side onwards, resulting in filament formability that was inferior to the sample in Example 1. Furthermore, while 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.

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

The thicker heads of the samples in Examples 4 and 5 resulted in the ease of brushing the entire oral cavity being inferior to that of the sample in Example 1. Furthermore, the support base of the sample in Example 5 was also thicker, resulting in a larger value expressed as t1/T, which reduced the resin flow during molding of the base body molded body compared to the sample in Example 4, resulting in inferior filament moldability compared to the sample in Example 1.

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

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 a larger FM/Q1 and an inferior adhesiveness of the primary preform compared to the sample in Example 1.

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.

For example, in the above embodiment, the toothbrush 1 is composed of 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. However, this configuration is not limited to this. For example, the fitting protrusion 12 of the handle body 10 may be 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 fitting protrusion 12 to fit into the fitting hole 22, resulting in the toothbrush 1 being a molded body in which the brush molded body 20 and the handle body 10 are integrally molded.

In addition, while the above embodiment illustrates a configuration in which the handle body 10 is formed from a hard resin, this is not limited to this configuration. For example, a portion of the handle body 10 (such as the handle portion 11) may be coated with a soft resin. This configuration can improve decorativeness and gripping properties.

The present invention is applicable to brush moldings and toothbrushes.

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 (16)

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. 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 . 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. 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 . 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. 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. 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. 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. The number of the filaments in the filament group is defined as F M ,
When the area where the support portion is bonded to the base body molded body is Q1 (mm ² ),
The value represented by FM/Q1 is 1.0 (lines/mm ² ) or less.
The brush molding according to any one of claims 1 to 8. 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. 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. The preform includes all of the plurality of filaments.
The brush molding according to any one of claims 1 to 11. 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. The soft resin is polyurethane.
The brush molding according to any one of claims 1 to 13. 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. 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.