Toothbrush

Abstract

[Problem] To provide a toothbrush with which base cracking and appearance defects can be suppressed while the pull-out strength of bristle bundles is maintained, and with which a further reduction in the thickness of a head portion can be achieved. [Solution] This toothbrush is characterized in that a head portion is a thin head having a thickness of 3.0 mm or less formed from polyacetal resin having a weight-average molecular weight at least equal to 130,000, and in that formula (1) is satisfied, where T1 (mm) is a base thickness, which is the thickness of a bristle implanting base, U1 (mm) is the hole depth of bristle implanting holes, H1 (mm) is an anchor wire drive depth, which is the depth from the bristle implanting surface to the upper edge of an anchor wire that has been driven in, and Mw is the weight-average molecular weight of the polyacetal resin.

Description

Technical Field

[0001] The present invention relates to a toothbrush in which tufts are implanted into a plurality of tufting holes in a thin head portion using flat wires.

Background Art

[0002] In a toothbrush, tufts made of tufted bundles are implanted in tufting holes on a tufting base of the head portion. In order to improve the operability in the oral cavity, the head portion and the neck portion of the toothbrush are designed to be thinner by considering the resin material, the tufting specifications, the shape, etc. (see, for example, Patent Document 1). In Patent Document 1, it is proposed to reduce the thickness of the head portion by making an appropriate combination of the length and width of the flat wire, the diameter and depth of the tufting hole, the resin material, etc.

[0003] However, as can be seen from Patent Document 1, when polyacetal resin (POM) is used as the resin material for the head portion, when tufts are implanted using flat wires while maintaining the pull-out strength for the thin head portion, problems such as cracks (base cracking) and whitening occur (see Example 8 in Table 2 of the literature). That is, when POM is used as the material for the head portion, stable production could not be carried out unless the head thickness was set thick.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Therefore, in view of the above situation, the problem to be solved by the present invention is to provide a toothbrush that can maintain the pull-out strength of the tufts, suppress base cracking and poor appearance, and enable further thinning of the head portion.

Means for Solving the Problems

[0006] The present invention includes the following inventions. [1] In a toothbrush having a tufting base with tufting holes in the head portion, and tufts are implanted into each tufting hole of the tufting base by flat wire driving, the head portion is a thin head formed of a polyacetal resin having a weight average molecular weight of 130,000 or more and a thickness of 3.0 mm or less. When the base thickness, which is the thickness of the tufting base, is T1 (mm), the hole depth of the tufting hole is U1 (mm), the flat wire driving depth, which is the depth from the tufting surface to the upper end of the flat wire driven in, is H1 (mm), and the weight average molecular weight of the polyacetal resin is Mw, the toothbrush is characterized by satisfying the following formula (1).

[0007]

Number

[0008] [2] In a toothbrush having a tufting base with tufting holes in the head portion, and tufts are implanted into each tufting hole of the tufting base by flat wire driving, the head portion is a thin head formed of a polyacetal resin having a weight average molecular weight of 130,000 or more and a thickness of 3.0 mm or less. When the base thickness, which is the thickness of the tufting base, is T1 (mm), the hole depth of the tufting hole is U1 (mm), the flat wire driving depth, which is the depth from the tufting surface to the upper end of the flat wire driven in, is H1 (mm), and the weight average molecular weight of the polyacetal resin is Mw, the toothbrush is characterized by satisfying the following formula (2).

[0009]

Number

Advantages of the Invention

[0010] According to the present invention configured as described above, while maintaining the pulling strength of the tuft of bristles, cracking of the base and poor appearance can be suppressed, and further thinning of the head portion becomes possible. Specifically, when the head portion is a thin head with a thickness of 3.0 mm or less, the operability in the oral cavity is improved. Further, when the head portion is molded from a polyacetal resin having a weight average molecular weight of 130,000 or more, the base thickness which is the thickness of the bristle implantation base is T1 (mm), the hole depth of the bristle implantation hole is U1 (mm), and the flat wire driving depth which is the depth from the bristle implantation surface to the upper end of the flat wire driven in is H1 (mm), and when the weight average molecular weight of the polyacetal resin is Mw, by being configured to satisfy the following formula (1), cracking of the base can be suppressed.

[0011]

Number

[0012] Further, when the head portion is molded from a polyacetal resin having a weight average molecular weight of 130,000 or more, the base thickness which is the thickness of the bristle implantation base is T1 (mm), the hole depth of the bristle implantation hole is U1 (mm), the flat wire driving depth which is the depth from the bristle implantation surface to the upper end of the flat wire driven in is H1 (mm), and when the weight average molecular weight of the polyacetal resin is Mw, by being configured to satisfy the following formula (2), in addition to cracking of the base, poor appearance (generation of unevenness) can also be surely suppressed.

[0013]

Number

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Mode for Carrying Out the Invention

[0015] Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0016] As shown in FIG. 1, the toothbrush 1 according to the present invention has a tufting base 5 with a plurality of tufting holes 20 in a thin head portion 2, and tufts 4 are implanted in each tufting hole 20 using flat wire. The toothbrush 1 in this example may be a manual toothbrush in which the head portion, the neck portion, and the handle portion are integrally formed of a synthetic resin, or may be an electric toothbrush in which a toothbrush cleaning body composed of a head portion and a neck portion is connected to the tip side of a main body portion as a gripping portion incorporating a drive mechanism, and of course, other forms are also acceptable.

[0017] The head portion 2 is integrally formed of a polyacetal resin having a weight average molecular weight of 130,000 or more. The polyacetal resin may be a homopolymer or a copolymer as long as it has not only an amorphous portion but also a crystalline portion. Since the crystallinity increases as the weight average molecular weight increases, it is less likely to crack and the appearance is improved. The head portion 2 is configured as a head composed of a thin tufting base 5 having a thickness (base thickness) T1 of 3.0 mm or less. Preferably, it is configured as a thin head of 2.9 mm or less, more preferably 2.6 mm or less, and even more preferably 2.5 mm or less. Regarding the lower limit of the base thickness T1, which is the thickness of the tufting base 5, 2 mm or more is preferable, and 2.2 mm or more is more preferable. If it is less than 2 mm, it becomes difficult to ensure sufficient pull-out strength. The base thickness T1 relates to at least the portion of the tufting surface where the tufts 4 are implanted.

[0018] On the tufting surface 21 on the ventral side of the head portion 2 (tufting base 5) where the tufts 4 project, a plurality of bottomed tufting holes 20 having a substantially circular cross-section are formed. The number, arrangement form, etc. of the tufting holes 20 are not limited in any way in this example, and are selected from an appropriate range according to various conditions such as the opening diameter, depth, longitudinal cross-sectional shape, number of filaments per tuft, and its material. For example, the opening diameter (inner diameter D1) is appropriately determined to be about 1.2 to 2.4 mm. The tufting hole 20 in this example is basically a straight hole with a circular cross-section as shown in FIG. 2, and an inclined surface with a reduced diameter in a frustum of a cone shape is formed on the peripheral wall of the bottom.

[0019] The hole depth U1 of the hair implanting hole 20 is the depth from the opening of the hair implanting surface 21 to the bottom surface 200 of the hair implanting hole 20. The thickness T2 of the bottom, that is, the distance from the bottom surface 200 of the hair implanting hole to the back surface 22 of the head portion (hair implanting base 5), is referred to as "under the hole to under the base" in this specification. Note that the hair implanting hole 20 may have other shapes. It is preferable that the hole depth (U1) be 0.9 mm or more in terms of maintaining good pull-out strength of the hair bundle.

[0020] Under the hole to under the base (T2) is 0.15 mm or more, more preferably 0.2 mm or more, and even more preferably 0.25 mm or more. When under the hole to under the base becomes 0.5 mm or more, the pull-out strength of the hair bundle cannot be maintained in the thin head of the present invention. Therefore, it is preferable to keep under the hole to under the base less than 0.5 mm, more preferably 0.45 mm or less.

[0021] In each hair implanting hole 20, a hair bundle formed by bundling a plurality of filaments and folded in half is implanted using the flat wire 3. The material of the flat wire 3 is not particularly limited, and a known material such as a metal or a hard synthetic resin used in a general toothbrush may be used. The thickness of the flat wire 3 is set to be 0.1 mm or more and 0.2 mm or less, more preferably 0.15 mm or more and 0.185 mm or less. When the thickness is less than 0.1 mm, it deforms during driving and the pull-out strength cannot be maintained. When the thickness is 0.21 mm or more, particularly in the case of a thin head, the head portion may turn white or there may be a risk of base cracking.

[0022] The engagement margin of the flat wire 3 with respect to the hair implanting hole 20 (the difference in the lateral length L orthogonal to the driving direction of the flat wire 3 with respect to the hole diameter D1 of the hair implanting hole 20) is preferably set to be +0.35 mm or more and +0.6 mm or less, more preferably +0.45 mm or more and +0.6 mm or less. If it is less than +0.35 mm, the amount of penetration is small and the pull-out strength cannot be maintained. If it is more than +0.6 mm, it leads to deformation of the flat wire, and as a result, the pull-out strength of the hair bundle and each filament decreases. When driving so that each end portion in the length direction of the flat wire 3 penetrates by the same amount, it preferably penetrates into the peripheral wall of the hair implanting hole 20 by a length of 0.175 mm or more and 0.3 mm or less.

[0023] The cross-sectional area obtained by cutting with a plane perpendicular to the horizontal direction of the flat wire 3 is 0.1 mm 2 or more and 0.3 mm 2 less than, more preferably 0.12 mm 2 or more and 0.3 mm 2 is set to be below. If the cross-sectional area is less than 0.1 mm 2 it is too small, the flat wire will bend, and as a result, the pulling strength of the hair bundle or a single filament will decrease. In this example, this cross-sectional shape is an oval shape, and it has curved surfaces on the proximal end side and the distal end side in the driving direction, and is considered so as not to impose a burden on the hair bundle 4. The thickness t of the flat wire 3 in this example is the thickness of the straight region excluding the curved surface portions at both ends.

[0024] The driving of the flat wire 3 is as shown by the virtual line in FIG. 2. In this specification, the distance H1 from the implanting surface 21 where the implanting hole opens to the upper end of the flat wire 3 driven in is referred to as the "flat wire driving depth". Also, the distance H2 from the implanting surface 21 to the lower end of the flat wire 3 driven in is referred to as the "plus flat wire" as the driving depth including the longitudinal dimension of the flat wire 3. Further, the distance H3 from the lower end of the flat wire to the bottom surface 200 of the implanting hole is referred to as the "flat wire - hole bottom". It is preferable to set the flat wire driving depth (H1) to a value between 0.07 mm and 0.5 mm in that it can prevent base cracking and maintain both excellent appearance and pulling strength. Also, for the flat wire - hole bottom (H3), it is preferable to ensure 0.5 mm or more, more preferably 0.58 mm or more, in terms of preventing base cracking and maintaining a good appearance.

[0025] The material of the filament is not particularly limited, and it may be an artificial hair made of a resin material such as nylon, polyester, polyolefin, etc., or a natural hair such as pig hair. These may also be combined. In addition, known forms such as cross-sectional shape, cross-sectional size, length, and presence or absence of a tapered shape can be widely adopted.

[0026] The head portion 2 of the toothbrush 1 according to the present invention configured as described above is configured such that for the base thickness T1 (mm), the hole depth U1 (mm) of the implanting hole, the flat wire driving depth H1 (mm), and the weight average molecular weight Mw of the polyacetal resin, the value of X1 in the following formula (3) is 2.96 or more. If this X1 is less than 2.96, there is a possibility of base cracking occurring.

[0027] [Number]

[0028] Further, the head portion 2 of the toothbrush 1 according to the present invention is configured such that the value of X2 in the following formula (4) is 3.33 or more with respect to the base thickness T1 (mm), the hole depth U1 (mm) of the bristle implantation hole, the flat wire driving depth H1 (mm), and the weight average molecular weight Mw of the polyacetal resin. If this X2 is less than 3.33, there is a possibility of base cracking or poor appearance (generation of unevenness). If it is 3.33 or more, it is possible to reliably suppress not only base cracking but also poor appearance (generation of unevenness).

[0029] [Number]

[0030] As described above, the embodiments of the present invention have been described. However, the present invention is not limited to such forms at all, and it goes without saying that the present invention can be implemented in various forms without departing from the gist of the present invention. [Examples]

[0031] [Evaluation of base cracking and appearance] Next, samples of thin head portions with a base thickness of 3.0 mm or less formed of polyacetal resin were produced by changing the base thickness T1, the hole depth U1, the flat wire driving depth H1, the distance from the bottom of the hole to the bottom of the base T2, and the weight average molecular weight Mw of the polyacetal resin, and evaluations of base cracking and appearance (unevenness) as shown in Tables 1 to 8 were obtained.

[0032] (Sample) The base thickness T1, the hole depth U1, the flat wire driving depth H1, the distance from the bottom of the hole to the bottom of the base T2, the distance from the flat wire to the bottom of the hole H3, the weight average molecular weight Mw of the polyacetal resin, the value of X1 obtained by the above formula (3), and the types of polyacetal resins "P1" to "P6" were created with the contents shown in Tables 1 to 4. The inner diameter (opening) of the bristle implantation hole was 1.5 mm.

[0033] The polyacetal resin "P1" is a polyacetal copolymer (number average molecular weight (Mn) 24,900, weight average molecular weight (Mw) 122,000, z average molecular weight (Mz) 247,000, MFR 27 g / 10 min, tensile modulus 2800 Mpa, flexural modulus 2550 Mpa).

[0034] Also, the polyacetal resin "P2" is a polyacetal homopolymer (number average molecular weight (Mn) 55,400, weight average molecular weight (Mw) 130,000, z average molecular weight (Mz) 261,000, MFR 25 g / 10 min, tensile modulus 3300 Mpa, flexural modulus 3000 Mpa). Also, the polyacetal resin "P3" is a polyacetal homopolymer (number average molecular weight (Mn) 58,200, weight average molecular weight (Mw) 143,000, z average molecular weight (Mz) 301,000, MFR 15 g / 10 min, tensile modulus 3100 Mpa, flexural modulus 3000 Mpa).

[0035] Also, the polyacetal resin "P4" is a polyacetal homopolymer (number average molecular weight (Mn) 67,100, weight average molecular weight (Mw) 184,000, z average molecular weight (Mz) 471,000, MFR 7 g / 10 min, tensile modulus 3300 Mpa, flexural modulus 3100 Mpa). Also, the polyacetal resin "P5" is a polyacetal homopolymer (number average molecular weight (Mn) 85,000, weight average molecular weight (Mw) 227,000, z average molecular weight (Mz) 549,000, MFR 2.5 g / 10 min, tensile modulus 3200 Mpa, flexural modulus 3000 Mpa). Also, the polyacetal resin "P6" is a polyacetal copolymer (number average molecular weight (Mn) 24,800, weight average molecular weight (Mw) 141,000, z average molecular weight (Mz) 302,000, tensile modulus 2850 Mpa, flexural modulus 2700 Mpa).

[0036] The number of filaments per tuft to be implanted was 21 to 23 (average 22), the diameter was 0.19 mm, the length was 29 mm, and the material was nylon. The length in the longitudinal direction, which is the driving direction of the flat wire used for driving, was 1.2 mm, the length in the transverse direction orthogonal to this was 2.0 to 2.05 mm (average 2.03 mm), and the thickness was 0.185 mm.

[0037] (Evaluation method for base cracking) Base cracking is visually judged according to the following five - level criteria. "5": No crack. "4": There are holes with slightly thin cracks visible. "3": Thin cracks are visible in many holes, but the spaces between the holes are not connected. "2": Thin cracks are observed in many holes and the spaces between the holes are connected. "1": Cracks (with gaps between the cracks) are visible, or there are cracks spanning multiple holes.

[0038]

Table 1

[0039]

Table 2

[0040]

Table 3

[0041]

Table 4

[0042] As shown in Tables 1 to 4, it can be seen that except for the case of P1 where the weight - average molecular weight Mw of the polyacetal resin is less than 130000, if the value of X1 is 2.96 or more, all evaluations of base cracking can be maintained at "3" or more.

[0043] Tables 5 to 8 show the values of X2 obtained by the above formula (4) instead of the values of X1 for the same samples, and also include the results of the appearance (concavity and convexity) evaluation along with the pedestal cracking evaluation.

[0044] (Appearance evaluation method) The appearance is judged based on the following five - level criteria for the appearance of the back of the head part. "5": No concavity or convexity. "4": Slight concavity and convexity can be seen. "3": When touched with a finger, slight concavity and convexity can be felt. "2": When touched with a finger, concavity and convexity can be felt. "1": There is concavity and convexity to the extent that it catches on the finger when touched.

[0045]

Table 5

[0046]

Table 6

[0047]

Table 7

[0048]

Table 8

[0049] As shown in Tables 5 to 8, it can be seen that except for the sample P1 with a weight - average molecular weight Mw of the polyacetal resin less than 130000, if the value of X2 is 3.33 or more, all evaluations of pedestal cracking and appearance (concavity and convexity) can be maintained at "3" or more.

Explanation of symbols

[0050] 1 Toothbrush 2 Head part 3 Horizontal line 4 Bristle bundle 5 Bristle - planting base 20 Bristle - planting holes 21 Bristle - planting surface 22 Back Hole diameter of the hair implanting hole Depth from the hair implanting surface to the upper end of the flat line ("flat line driving depth") Depth from the hair implanting surface to the lower end of the flat line ("plus flat line") Distance from the lower end of the flat line to the bottom surface of the hair implanting hole ("flat line to hole bottom") Thickness of the head part (hair implanting table) ("table thickness") Thickness of the bottom of the hair implanting hole ("below hole to below table") Hole depth of the hair implanting hole Lateral length of the flat line

Claims

1. A toothbrush having a tufting base with tufting holes in the head portion, wherein tufts are tufted into each tufting hole of the tufting base by flat wire driving, the head portion is a thin head formed of a polyacetal resin having a weight average molecular weight of 130,000 or more and 227,000 or less, and having a thickness of 3.0 mm or less, the thickness of the tufting base, i.e., the base thickness, is 3 mm or less, the distance from the bottom surface of the tufting hole, which is the thickness of the bottom of the tufting hole, to the back surface of the head portion is less than 0.5 mm, a toothbrush, characterized in that when the base thickness is T1 (mm), the hole depth of the tufting hole is U1 (mm), the flat wire driving depth, which is the depth from the tufting surface to the upper end of the flat wire driven in, is H1 (mm), and the weight average molecular weight of the polyacetal resin is Mw, the following formula (1) is satisfied. 【Number 1】

2. A toothbrush having a tufting base with tufting holes in the head portion, wherein tufts are tufted into each tufting hole of the tufting base by flat wire driving, the head portion is a thin head formed of a polyacetal resin having a weight average molecular weight of 130,000 or more and 227,000 or less, and having a thickness of 3.0 mm or less, the thickness of the tufting base, i.e., the base thickness, is 3 mm or less, the distance from the bottom surface of the tufting hole, which is the thickness of the bottom of the tufting hole, to the back surface of the head portion is less than 0.5 mm, a toothbrush, characterized in that when the base thickness is T1 (mm), the hole depth of the tufting hole is U1 (mm), the flat wire driving depth, which is the depth from the tufting surface to the upper end of the flat wire driven in, is H1 (mm), and the weight average molecular weight of the polyacetal resin is Mw, the following formula (2) is satisfied. 【Number 2】

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