Toothbrush

Abstract

To provide a toothbrush that has a sufficient effect of removing dental plaque using a filament made of synthetic resin containing polytrimethylene terephthalate as a primary component.SOLUTION: A toothbrush 1 includes a filament 10 made of a synthetic resin containing polytrimethylene terephthalate as a primary component, the synthetic resin that composes the filament 10 containing calcium carbonate. With this configuration, by chemically processing the calcium carbonate contained in the synthetic resin that composes the filament 10, fine pores are formed on the filament surface. This leads to a high friction efficiency when the filament 10 makes contact with a tooth surface and thus a high plaque removing effect.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a toothbrush using filaments made of a synthetic resin whose main component is polytrimethylene terephthalate. [Background technology]

[0002] Conventionally, toothbrush bristles are made of filaments made of synthetic resins. Examples of synthetic resins that are widely used to make filaments include polyamide resins (such as 6-10 nylon and 10-10 nylon) and polyester resins (such as butylene terephthalate (PBT)).

[0003] The polyamide resins 6-10 nylon and 10-10 nylon are known as environmentally friendly materials that use plant-derived ingredients, since the sebacic acid used in amide synthesis is a monomer obtained by chemically processing industrial castor oil extracted from castor beans. In recent years, companies have been required to manufacture products that take into account the Sustainable Development Goals (SDGs), and the use of environmentally friendly materials contributes to increasing the added value of products.

[0004] However, when attempting to form a tapered portion in the filament whose cross-sectional area decreases toward the tip, 6-10 nylon and 10-10 nylon are highly alkali-resistant and difficult to hydrolyze, so it was difficult to form the tapered portion by chemical treatment (chemical taper treatment) in which the filament is immersed in a chemical solution containing an alkaline agent. The tapered portion can also be formed by a mechanical processing process (mechanical taper treatment) in which the bristles are mechanically polished, but mechanical taper treatment may increase manufacturing costs due to the workload of ensuring the safety of burrs on the bristles and the need to install equipment to collect the polishing powder.

[0005] On the other hand, the polyester resin PBT can be chemically treated by hydrolysis of polyester to form a tapered filament. However, since PBT is not made from plant-derived ingredients, it cannot be said that the product uses environmentally friendly materials.

[0006] In contrast, the polyester resin polytrimethylene terephthalate (PTT) is produced from 1,3-propanediol (1,3-POD) and terephthalic acid (or dimethyl terephthalate), and since 1,3-POD can be produced in high yields from corn, it is an environmentally friendly material that uses some plant-derived ingredients. In addition, since PTT is a polyester resin, it is possible to form a tapered portion by chemical processing. For this reason, PTT has attracted attention as a raw material for synthetic resins that make up toothbrush filaments (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2017-118939 A [Patent Document 2] JP 2017-140131 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, PTT has a unique crystal structure derived from an odd number of methylene groups (C3), and because PTT molecules are arranged in a gentle spiral shape within the crystal, fibers made of PTT are highly flexible and have a low elastic modulus. Therefore, if filaments are made of a synthetic resin containing PTT as the main component, the bristles of the toothbrush may be soft and the plaque removal power may be reduced. Moreover, if a tapered portion is formed in the filament, the bristles become even softer and the plaque removal power decreases.

[0009] The present invention is devised to solve the above-mentioned problems, and has an object to provide a toothbrush that uses filaments made of a synthetic resin whose main component is polytrimethylene terephthalate and that provides sufficient plaque removal power. [Means for solving the problem]

[0010] In order to solve the above problems, the present invention provides a toothbrush having a head portion with a plurality of bristle implantation holes on the bristle implantation surface, in which bundles of bristle filaments made of synthetic resin primarily composed of polytrimethylene terephthalate are implanted, the toothbrush being characterized in that the synthetic resin constituting the filaments contains calcium carbonate.

[0011] In the toothbrush, it is preferable that the calcium carbonate be added at a concentration of 0.2 to 0.5% relative to the synthetic resin constituting the filaments.

[0012] In the toothbrush described above, the filaments preferably have irregularities formed by a chemical treatment in which the filaments are immersed in a chemical solution containing an alkaline agent.

[0013] In the above toothbrush, the filament preferably has a tapered portion whose cross-sectional area decreases toward the tip.

[0014] In the toothbrush, it is preferable that the tapered portion has an arithmetic mean surface roughness Ra of 0.4 to 0.6 μm. Effect of the Invention

[0015] According to the toothbrush of the present invention, calcium carbonate is added to the synthetic resin that constitutes the filament, and then chemically treated to form micropores on the surface of the filament, which results in a high coefficient of friction when the filament comes into contact with the tooth surface, and a large surface area in contact with the tooth surface, resulting in a high plaque removal effect. [Brief description of the drawings]

[0016] [Figure 1] FIG. 2A is a front view of a toothbrush according to one embodiment of the present invention, and FIG. 2B is a schematic side view showing an enlarged view of a head portion of the toothbrush. [Diagram 2] 1A is an enlarged view of the tip portion of a filament used in the toothbrush, showing a single taper configuration, and FIG. 1B is a view showing a double taper configuration. [Diagram 3] FIG. 1(a) is an electron microscope photograph of the surface of a filament (Example) in which calcium carbonate has been added to a synthetic resin, and FIG. 1(b) is an electron microscope photograph of the surface of a filament (Comparative Example) in which calcium carbonate has not been added to a synthetic resin. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] A toothbrush according to one embodiment of the present invention will be described with reference to the drawings. As shown in Fig. 1(a) and (b), the toothbrush 1 of this embodiment includes a head portion 2, a grip portion 3, and a neck portion 4 connecting the head portion 2 and the grip portion 3. The head portion 2 has a plurality of bristle bundles 5 each formed by bundling a large number of bristles, which are implanted in a predetermined arrangement. The bristles of this embodiment are made of filaments 10 made of a synthetic resin whose main component is polytrimethylene terephthalate (PTT).

[0018] The filament 10 of this embodiment has a tapered portion 11 whose cross-sectional area decreases toward its tip. The head portion 2 is provided with a plurality of bristle implantation holes in a predetermined arrangement, and the filament 10 is bundled and folded in half, and a flat wire 6 (see FIG. 1(b)) is sandwiched between the folded-back portions, and the bristle bundle 5 is driven into the bristle implantation holes together with the flat wire 6, thereby implanting the bristle bundle 5 in the head portion 2. In addition to the above-mentioned driving method, the method of implanting the bristle bundle 5 includes welding and other methods, which can be appropriately selected depending on the specifications of the toothbrush.

[0019] When the filament 10 is tapered only on one end before being folded in half, and the filament 10 is bundled, folded in half, and planted, a so-called single-tapered toothbrush 1 is obtained in which half of the bristles have tapered portions 11, as shown in Figure 2(a). On the other hand, when the filament 10 is tapered on both ends before being folded in half, and planted in the same manner as above, a so-called double-tapered toothbrush 1 is obtained in which all of the bristles have tapered portions 11, as shown in Figure 2(b).

[0020] The synthetic resin constituting the filament 10 of this embodiment is a resin containing 70% by mass or more of PTT, and preferably 90% by mass. As described above, PTT is produced from 1,3-propanediol (1,3-POD) and terephthalic acid as raw materials, and 1,3-POD is a plant-derived component. In a bioplastic product, the ratio of the mass of the plant-derived component to the total mass is called the "bio content," and is expressed in monomer units as 1,3-POD (C3H6O2: molecular weight 74) / PTT (C 11 H 10 O4: molecular weight 206), the bio-content of PTT is calculated to be 35.9%. In order to claim to use environmentally friendly materials, it is desirable for the bio-content to be high, and it is also desirable for the PTT content in the synthetic resin that constitutes the filament 10 to be high.

[0021] In this embodiment, calcium carbonate is contained in the synthetic resin mainly composed of PTT. Calcium carbonate is preferably added at a concentration of 0.2 to 0.5% relative to the synthetic resin constituting the filament 10. If the amount of calcium carbonate added is 0.5% or less, the filament 10 can be stably produced, but if it exceeds 0.5%, the viscosity of the synthetic resin increases and the material properties become non-uniform, so that the filament 10 may easily break during stretching, and there is a risk of unstable productivity, and there is also a concern about adverse effects such as wear on the manufacturing equipment. In addition, if the amount of calcium carbonate added is less than 0.2%, significant unevenness or porosity cannot be formed on the surface of the filament 10, and the surface roughness required for improving the plaque removal power cannot be obtained.

[0022] In a general method for producing a filament, a thermoplastic resin is thermally melted, spinned with a spinneret, and then cooled and stretched to obtain a filament. The filament is coated with an oil to prevent static electricity, and is stretched to adjust the diameter and at the same time to impart strength. In the filament 10 of this embodiment, calcium carbonate is added and mixed before the thermoplastic resin is thermally melted, and then a general filament production process is performed to produce a filament 10 to which calcium carbonate has been added. Although a general process is shown for the spinning method, an optimal process can be selected as appropriate depending on the specifications of the filament, limitations of the production equipment, and the like.

[0023] The tapered portion 11 of the filament 10 is formed by a chemical treatment (chemical taper treatment) in which the filament 10 is immersed in a chemical solution containing an alkaline agent. Specifically, when one end of the bundled filament 10 is partially immersed in a chemical solution (treatment solution) containing an alkaline agent in a treatment bath, the treatment solution is pulled up between the filaments by capillary action. At this time, if the temperature of the treatment solution is made higher than room temperature, a temperature gradient is generated due to the temperature difference between the treatment solution and room temperature, and the temperature gradient of the chemical solution held between the filaments is formed so that it approaches room temperature as it moves away from the treatment bath. The higher the temperature of the treatment solution, the higher the decomposition rate of the resin. Therefore, by providing the above-mentioned temperature gradient, the degree of decomposition of the tip portion immersed in the treatment bath increases, and the degree of decomposition decreases as it moves away from the treatment bath. In this way, the chemical taper treatment of the filament 10 is performed. Incidentally, sodium hydroxide is generally used as the alkaline agent, but other agents may also be used. The above-mentioned chemical treatment may also be performed using, for example, an acidic chemical solution, and the agent is appropriately selected and adjusted taking into consideration the specifications of the tapered shape, the reproducibility of the treatment process, and the like.

[0024] Moreover, by tapering only one end of the filament, a filament for a single taper as shown in Fig. 2(a) is obtained, and by tapering both ends of the filament, a filament for a double taper as shown in Fig. 2(b) is obtained. Note that the taper shape is not limited to these two, and the filament end may be a so-called fork shape in which the filament end is split depending on the filament shape before the chemical taper treatment. Furthermore, the cross-sectional shape of the filament before the chemical taper treatment is not limited to a normal circular shape, and may be a so-called irregular cross-sectional shape.

[0025] In the tapered portion 11 treated as described above, many fine irregularities are formed on the filament surface due to the calcium carbonate exposed on the filament surface, as shown in Fig. 3(a). The irregularities do not depend on the spinning direction. On the other hand, when calcium carbonate was not added to the synthetic resin constituting the filament 10, no fine irregularities were formed, as shown in Fig. 3(b).

[0026] The arithmetic mean surface roughness Ra of the tapered portion 11 (Example) of the filament 10 in which 0.5% calcium carbonate was added to a synthetic resin mainly composed of PTT was 0.49 μm. The arithmetic mean surface roughness Ra of the tapered portion 11 is preferably 0.4 to 0.6 μm. If the arithmetic mean surface roughness Ra is less than 0.4 μm, sufficient plaque removal power cannot be expected. On the other hand, if the arithmetic mean surface roughness Ra exceeds 1 μm, the filament 10 itself becomes structurally fragile, and there is a risk of reduced durability as a toothbrush.

[0027] Here, a plaque removal test was carried out using a toothbrush of the embodiment using a filament 10 containing calcium carbonate and a toothbrush of the comparative example using a filament not containing calcium carbonate. Various test methods for the plaque removal test are described in papers such as "Study on efficient toothbrush head speed and brushing width when removing artificial plaque with a wide bristle toothbrush" Japanese Journal of Conservative Dentistry, Vol. 66, No. 2, p. 124 (Showa University paper), and in this embodiment, a plaque simulant was attached to models of the first molar and second premolar, which are considered to have a large amount of plaque left behind after brushing, and the toothbrushes of the above embodiment and comparative example were slid under the following sliding conditions to clean the plaque simulant, and the plaque removal rate was calculated from the area of ​​the plaque removed part after 5 and 10 sliding times, and the average value of three specimens was obtained. The sliding conditions were a pressure load of the toothbrush against the tooth surface of 200 g, a rotation speed of 180 rpm, and a sliding width (stroke) of 20 mm. The results are shown in Table 1 below.

[0028] [Table 1]

[0029] As shown in Table 1 above, when the number of strokes was 5, the average plaque removal rate in the comparative example was 39.7%, while that in the example was 59%, confirming a significant effect in the example. Also, when the number of strokes was 10, the plaque removal rate in the comparative example was 63.9%, while that in the example was 78.8%, indicating that the example showed better results, although not as good as when the number of strokes was 5.

[0030] From the above results, in the toothbrush 1 of this embodiment, calcium carbonate is contained in the synthetic resin constituting the filament 10, and this is treated with a chemical to form fine irregularities on the surface of the filament 10. As a result, it was shown that a high plaque removal power can be obtained by increasing the friction coefficient when the filament 10 contacts the tooth surface and increasing the surface area. In other words, a filament whose main component is polytrimethylene terephthalate, an environmentally friendly material, has a soft bristles, but by containing calcium carbonate in the synthetic resin and increasing the surface roughness, the plaque removal power can be improved.

[0031] Next, we tested the functionality of toothbrushes when the concentration of calcium carbonate added to the synthetic resin that makes up the filaments was changed. The calcium carbonate concentration was changed to 0%, 0.25%, 0.5%, and 1%. The filaments with each concentration were evaluated and measured for elasticity, elongation, tensile strength, arithmetic mean surface roughness, and ability of the bristles to retain toothpaste solution.

[0032] Using a tensile tester, the elastic modulus, elongation, and tensile strength of a single 30 mm long monofilament before tapering were measured between 0.2-0.5 mm strokes. The arithmetic mean surface roughness Ra was measured using a laser microscope at an evaluation length of 300 μm, 5 mm from the tip of the taper. Three filaments of each concentration were measured, and the average surface roughness for each concentration was calculated. These results are shown in Table 2 below.

[0033] [Table 2]

[0034] As shown in Table 2 above, the modulus of elasticity affects the hardness of toothbrush bristles after implantation, but no significant difference was observed when the amount of calcium carbonate added was less than 1%. In addition, the elongation and tensile strength affect the durability of the bristles, but are not dependent on the concentration of calcium carbonate added, and it was shown that adding a small amount does not affect the physical properties. In contrast, it was confirmed that the arithmetic mean surface roughness Ra increases as the concentration of calcium carbonate increases, and the optimal arithmetic mean surface roughness Ra was 0.49 μm when the concentration of calcium carbonate was 0.5%. In addition to the plaque removal performance shown in the examples, the performance required of the filament includes the ability to remove pigments attached to the teeth, so-called stain, and the ability to clean dirt between teeth or in periodontal pockets, and the arithmetic mean surface roughness of the filament is appropriately adjusted depending on the specifications of the toothbrush.

[0035] The toothbrush according to the present invention is not limited to the above embodiment and can be modified in various ways. For example, the above embodiment shows a toothbrush using a filament containing PTT as the main component and calcium carbonate added thereto, but, for example, all filaments used in one toothbrush do not need to be filaments containing calcium carbonate added thereto, and filaments containing calcium carbonate added thereto may be partially used. In addition, as long as filaments containing PTT as the main component and calcium carbonate added thereto are partially used, filaments containing 6-10 nylon or 10-10 nylon as the main component and not containing calcium carbonate may be partially used. In addition, the toothbrush according to the present invention is not limited to the toothbrush 1 having the grip portion 3 as shown in FIG. 1, and may be configured without a grip portion, such as a replacement brush used for an electric toothbrush. [Explanation of symbols]

[0036] 1 Toothbrush 2 Head section 5 Hair bundle 6. Flat Line 10 Filaments 11 Tapered section

Claims

1. A toothbrush having a head part with a plurality of bristle implantation holes on a bristle implantation surface, and bristle bundles of filaments made of a synthetic resin mainly composed of polytrimethylene terephthalate implanted in the bristle implantation holes, The toothbrush is characterized in that the synthetic resin constituting the filaments contains calcium carbonate.

2. 2. The toothbrush according to claim 1, wherein the calcium carbonate is added at a concentration of 0.2 to 0.5% relative to the synthetic resin constituting the filaments.

3. 3. The toothbrush according to claim 1, wherein the filaments have irregularities formed by a chemical treatment in which the filaments are immersed in a chemical solution containing an alkaline agent.

4. 4. The toothbrush according to claim 3, wherein the filament has a tapered portion whose cross-sectional area decreases toward a tip.

5. 5. The toothbrush according to claim 4, wherein the tapered portion has an arithmetic mean surface roughness Ra of 0.4 to 0.6 μm.

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