JP2012179291A - Bristle material for brush and brush - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bristle material for a brush which has excellent dimension stability due to low water permeability, has small change in bristle elasticity and touch, is capable of maintaining excellent cleaning performance, and has high flexible abrasion resistance, and to provide a brush.SOLUTION: The bristle material for a brush formed of cut bristles of a monofilament 1 obtained by melt-spinning a polyamide resin containing a 9-12C aliphatic diamine and a 6-14C aliphatic dicarboxylic acid as a constituent unit.

Description

  The present invention is excellent in dimensional stability because of its low water absorption, has small changes in hair and tactile sensation, can maintain excellent cleaning performance, and has high bending wear resistance, It relates to brushes.

  Conventionally, a synthetic resin monofilament has been used as a bristle material for a brush because it is inexpensive and can be easily processed. As a synthetic resin, a polyamide resin or a polyester resin has been mainly used.

  In particular, polyamide-based resins are excellent in physical properties such as tensile strength and elongation and wear resistance, and chemical properties such as chemical resistance, so toothbrushes, hair brushes, body brushes, cleaning brushes, makeup brushes, paint brushes, rolls It has been widely used in various industrial brushes such as brushes, wheel brushes, cup brushes, and niblet brushes.

  However, in general, polyamide resins have higher water absorption than polyester resins, and there are problems such as dimensional stability changes due to water absorption and physical properties deteriorate. Especially, water such as toothbrushes is used. In the brush application, not only water absorption and tactile sensation changes due to water absorption, which also affects the cleaning performance, but also has problems in terms of hygiene such that bacteria in the oral cavity are easy to propagate.

  Therefore, among polyamide-based resins, polyamide 6 · 10, polyamide 6 · 12, polyamide 11 and polyamide 12 have lower water absorption and better dimensional stability than polyamide 6 and polyamide 6 · 6. It is said that it is suitable as a constituent material of the material. However, since these polyamide-based resins are expensive in raw materials, production costs are likely to be affected. Also, polyamides 11 and 12 have a melting point of 185 to 195 ° C., which is lower than other polyamide-based resins, and thus have poor heat resistance and crystallinity. Since the properties are generally low, it is difficult to say that the constituent material of the brush bristle material exhibits special characteristics superior to those of other polyamide resins.

  Therefore, by performing heat treatment at a temperature of 30 to 150 ° C., X-ray diffraction shows a peak showing crystallinity at 2θ of about 20 ° and about 23 °, respectively, and the intensity ratio I20 / I23 is 1.38-1. There is known a toothbrush in which a polyamide fiber in the range of 42 is implanted (see, for example, Patent Document 1). According to this, a heat treatment in a thermostatic bath at 50 ° C. for 2 weeks gives a toothbrush with a good feeling of use and a long maintenance of plaque removal ability, but at 50 ° C. for 2 weeks or more. Performing heat treatment is a method that has a low practicality because it causes a reduction in production capacity and work efficiency in an actual manufacturing process, and also affects the manufacturing cost.

Further, a polyamide obtained by polycondensation from a diamine component containing 70 mol% or more of xylylenediamine and a dicarboxylic acid component containing 50 mol% or more of an α, ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms (A ) Brushes using stretched polyamide fibers containing 75 to 100% by weight and 25 to 0% by weight of other polyamides (B) are known (for example, see Patent Document 2). This stretched polyamide fiber has a characteristic that the Young's modulus when wet is 400 kgf / mm ² or more, and has a characteristic that a decrease in physical properties is small even when water is absorbed, but a xylylenediamine polyamide resin generally has a slow crystallization rate. Therefore, for example, when it is used for a brush application that repeatedly undergoes bending and wear, such as a toothbrush, a roll brush, a wheel brush, a cup brush, and a niblet brush, breakage is likely to occur. For this reason, there is a method of blending a polyamide-based resin such as polyamide 6 that has a high crystallization speed, but it is difficult to say that it is a sufficient method for preventing breakage of the hair. Means such as raising were necessary.

Japanese Patent Laid-Open No. 10-201538 JP-A-11-81041

  The object of the present invention is that the hair for brushes has excellent dimensional stability due to low water absorption, small change in hair and tactile sensation, can maintain excellent cleaning performance, and has high bending wear resistance. To provide materials and brushes.

  In order to achieve the above object, according to the present invention, a monofilament cut bristle obtained by melt-spinning a polyamide-based resin composed of an aliphatic diamine having 9 to 12 carbon atoms and an aliphatic dicarboxylic acid having 6 to 12 carbon atoms is used. A bristle material for brushes is provided.

In the present invention,
The aliphatic diamine is 1,10-decanediamine, 1,11-undecanediamine, or 1,12-dodecanediamine;
The dicarboxylic acid is sebacic acid or dodecanedioic acid,
The polyamide-based resin is polyamide 10 · 10 having 1,10-decanediamine and sebacic acid as structural units;
In the bending wear characteristic test measured according to JIS L-1095-9.10.2B, the number of bending wear times when the monofilament breaks is 50000 times or more;
About the monofilament, the wetness of the monofilament (B) immersed in water at 20 ° C for 16 hours or more divided by the bending hardness of the monofilament (A) left at 20 ° C under a relative humidity of 65HR% for 24 hours. The bending hardness ratio is 0.8 or more,
A tapered shape is formed at least at one end of the cut bristle;
Is a more preferable condition.

  The bending hardness is set so that the monofilament is cut into a length of about 4 cm and is contacted under a stainless steel bar having a diameter of 2 mm that is installed in a horizontal direction at intervals of 10 mm. 1mm diameter stainless steel hook is hung on the monofilament at the position of, and the maximum generated when the stainless steel hook is pulled up at a take-up speed of 50 mm / min using the Menekea TCM-200 universal tensile / compression tester. It is stress.

  The brush of the present invention is characterized in that any one of the above bristle materials for brush is used as at least a part of the bristle material.

  According to the present invention, since the water absorption is low, the hair for brushes has excellent dimensional stability, small changes in hair and tactile sensation, can maintain excellent cleaning performance, and has high bending wear resistance. You can get materials and brushes.

It is a figure explaining the measuring method of the bending hardness of a monofilament.

  Hereinafter, the bristle material for brushes and the brush of the present invention will be specifically described.

  The bristle material for a brush according to the present invention comprises a monofilament cut bristle obtained by melt spinning a polyamide-based resin having a structural unit of an aliphatic diamine having 9 to 12 carbon atoms and an aliphatic dicarboxylic acid having 6 to 12 carbon atoms. It is what.

  In general, polyamide resins include polyamide 4 · 6 having tetramethylenediamine and adipic acid as constituent units, polyamide 6 having ε-caprolactam as constituent units, and polyamide 6 · 6 having hexamethylenediamine and adipic acid as constituent units. 6, polyamide 6 · 10 having hexamethylenediamine and sebacic acid as constituent units, polyamide 6 · 12 having hexamethylenediamine and dodecanoic acid as constituent units, polyamide 11 having ω-aminoundecanoic acid as constituent units, and ω- Polyamide 12 having laurolactam as a structural unit is well known.

  Among these polyamide-based resins, polyamide 6 and polyamide 6 · 6 are already used in many fields as materials for brush hair because they can be processed easily and inexpensively as general-purpose synthetic resins. Since the characteristics such as dimensional stability, bristle waist, tactile sensation, and bending wear resistance are not high, it has been possible to use only for an inexpensive brush such as a disposable toothbrush.

  This is largely due to the water-absorbing characteristics of the polyamide-based resin, and the polyamide-based resin has a decrease in strength and elastic modulus and a dimensional change due to water absorption. In particular, polyamide 6 has a high water absorption rate, and when the moisture content reaches about 3.5%, it is said that the tensile strength decreases by about 25% and the bending hardness decreases by about 70%. Therefore, when it is used as a constituent material of the brush bristle material, it is easy to cause problems such as the opening of the hair and the tactile sensation are easily lost while continuing to use, and the cleaning property is deteriorated.

  Polyamide resins such as polyamide 6 · 10, polyamide 6 · 12, polyamide 11 and polyamide 12 have lower water absorption and better dimensional stability than polyamide 6 and polyamide 6 · 6. Since it is expensive, it easily affects the production cost. In particular, polyamides 11 and 12 have a melting point of 185 to 195 ° C., which is lower than that of other polyamide resins, so that they are inferior in heat resistance and generally low in crystallinity. In addition, it is difficult to say that the constituent material of the brush bristle material exhibits special characteristics superior to those of other polyamide resins.

  Therefore, as a result of earnestly examining the constituent material of the brush hair material that has low water absorption, excellent dimensional stability, and stable physical properties, the inventor of the present invention has found that the aliphatic diamine and carbon having 9 to 12 carbon atoms. It was found that a cut bristle of a monofilament obtained by melt spinning a polyamide-based resin having an aliphatic dicarboxylic acid of several 6 to 12 as a structural unit is optimal.

  If the number of carbon atoms of the aliphatic diamine, which is a structural unit of the polyamide-based resin, falls below the above range, the water absorption becomes high and dimensional changes are likely to occur, and when used as a constituent material of a brush hair material, The tactile sensation is easily lost and the cleaning property is also easily affected.

  Water absorption is a phenomenon in which water molecules coordinate to an amorphous amide group in a polyamide-based resin, but the smaller the number of carbon atoms in the aliphatic diamine, the higher the amide group concentration in the molecule and the water molecules coordinate. This is thought to be easier.

  Conversely, if the number of carbon atoms of the aliphatic diamine exceeds the above range, the molecular weight of the polyamide is increased, the melting point is lowered, and a brush bristle material having poor heat resistance is easily obtained. This is considered to be due to the general characteristic of the polyamide-based resin that the melting point decreases as the number of methylene groups in the molecule increases.

  On the other hand, when the carbon number of the aliphatic dicarboxylic acid, which is a structural unit of the polyamide resin, is below the above range, the amide group concentration becomes high even if the carbon number of the aliphatic diamine is within the above range. , The dimensional change is likely to occur, and when used as a constituent material of the bristle material for a brush, the fur and the tactile sensation are liable to change and the cleaning property is also easily affected.

  Conversely, if the carbon number of the aliphatic dicarboxylic acid exceeds the above range, even if the carbon number of the aliphatic diamine is within the proper range, the molecular weight of the polyamide is increased, the melting point is lowered, and the heat resistance is poor. It is easy to obtain a hair material.

  From this fact, as a combination of an aliphatic diamine and an aliphatic dicarboxylic acid having excellent physical properties such as dimensional stability and heat resistance, the aliphatic diamine is 1,10-decanediamine, 1,11-undecanediamine, , 12-dodecanediamine, and the aliphatic dicarboxylic acid is preferably sebacic acid or dodecanedioic acid. Specifically, polyamide 9 · 10, polyamide 9 · 12, polyamide 10 · 10, polyamide 10 · 12, polyamide 11 · 6, polyamide 11 · 10, polyamide 11 · 11, polyamide 11 · 12, polyamide 12 · 6, polyamide 12 · 10, polyamide 12 · 12, etc.

  In particular, 1,11-undecanediamine obtained by decomposing castor oil mainly composed of glycerin ester of ricinoleic acid with methanol, and sebacic acid obtained by saponifying castor oil with caustic soda are derived from naturally derived castor oil. Therefore, there is a high possibility that polyamide-based resins having these as structural units will attract attention in the future as materials that are naturally friendly.

  In the present invention, these polyamide resins may be used not only alone but also in combination. Further, polyamide 6, polyamide 6 · 6, polyamide may be composed of these polyamide resins as a main component. 6,10, polyamide 6,12, polyamide 4,6, polyamide 4,10, polyamide 5,6, polyamide MXD6, polyamide 11, polyamide 12, polyamide 6/66 copolymer and polyamide 6/12 copolymer A conventional general-purpose polyamide-based resin may be mixed as a subcomponent, and may further be used as a copolymerization component.

  Further, in the present invention, as long as the effects of the invention are not inhibited, particles such as various inorganic particles, various metal particles, and crosslinked polymer particles, as well as known antioxidants and light resistance are used depending on the purpose. It is also possible to appropriately add agents, anti-mold agents, ion exchangers, anti-coloring agents, anti-static agents, various colorants, waxes, silicone oils, various surfactants and various reinforcing fibers.

  Furthermore, the bristle material for brushes of the present invention has the number of bending wears at the time of breakage of the polyamide-based resin monofilament which is a constituent material in the bending wear characteristic test measured according to the provisions of JIS L-1095-9.10.2B. Is preferably 50000 times or more.

  This is because the brush bristle material is repeatedly bent while being in contact with the object to be cleaned, and the brush bristle material is also required to have durability. For this reason, if the number of bending wear is less than the above range, wear and breakage are likely to occur, and it is difficult to obtain a highly durable brush.

  Polyamide resins, when absorbed, cause a decrease in tensile strength and bending hardness, but on the other hand, the structure is stabilized and toughness is obtained. For this reason, especially when using a polyamide resin with high water absorption in the bristle material of brushes with water, such as toothbrushes, body brushes, paint brushes, and cleaning brushes, a brush with high toughness and bending wear resistance can be obtained. However, as described above, the polyamide-based resin having a high water absorption easily changes in dimensions and loses the fur and the tactile sensation and easily affects the cleanability.

  Further, one of the factors of superiority or inferior wear resistance is the crystallinity of the polyamide resin, and the higher the crystallinity of the polyamide resin, the higher the bending wear resistance. The molecular weight of the polyamide-based resin is a factor of the crystallinity of the polyamide-based resin, and the higher the molecular weight, the lower the crystallinity. Therefore, it is necessary to consider the balance between water absorption and crystallinity when improving the wear resistance of the brush bristle material. Among them, polyamides 10 and 10, and polyamide 10 whose aliphatic diamine has 10 carbon atoms as a structural unit are necessary. -12 is particularly preferable as a constituent material of the bristle material for brushes of the present invention because high wear resistance is obtained.

  Furthermore, in the present invention, for the monofilament used for the brush hair material, the bending hardness of the monofilament (B) immersed in water at 20 ° C. for 16 hours or more is 20 hours at 20 ° C. and a relative humidity of 65 HR% for 24 hours. It is even more preferable that the wet and dry bending hardness ratio divided by the bending hardness of the monofilament (A) that is left is 0.8 or more. The bending hardness is a value obtained by the following method.

[Bending hardness]
Cut the monofilament into a length of about 4 cm and set it in contact with the bottom of a 2 mm diameter stainless steel rod installed in two horizontal intervals at 10 mm intervals. The monofilament has a diameter of 1 mm at the center of the stainless steel rod. A stainless steel hook was hung and the stainless steel hook was pulled up at a take-up speed of 50 mm / min using a Menekea Co., Ltd. TCM-200 universal tension / compression tester, and the maximum stress generated at this time was defined as bending hardness.

  If the dry / wet bending hardness ratio is below the above range, when the obtained monofilament cut bristle is used as a hair bristle for brushes, the fur and the tactile sensation tend to change, and the cleaning performance is also easily affected. When used for brushes with water, such as body brushes, paint brushes, washing brushes, etc., the hair for brushes is particularly susceptible to water, but polyamides 10 and 10 have a particularly high wet-dry bending hardness ratio and are not easily affected by water. It is easy to obtain materials.

  Furthermore, in the present invention, it is particularly preferable that a taper shape is formed on at least one end of the monofilament cut bristle since not only the tactile sensation but also the cleaning effect can be further enhanced. Generally, when a tapered shape is formed at one end of the cut bristle, the tapered portion is easy to bend because the thread diameter is thin. Then, it becomes easy to change a dimension, and it becomes easy to bend a wrinkle in a taper part.

  However, the bristle material for brushes of the present invention uses a polyamide-based resin with low water absorption as its constituent material, so that the taper portion is unlikely to bend and become less susceptible to loss of touch and cleaning. is there.

  The method for producing the brush hair material of the present invention is not particularly limited. As a general method, a polyamide resin monofilament is spun using a known melt spinning machine, and the monofilament is cut to form a cut bristle. The method of doing is mentioned.

  For example, in the case of producing a monofilament, the polyamide resin pellets are first vacuum dried until the moisture content is 0.2% or less, more preferably 0.1%, and the polyamide resin pellets are removed from the melting point of the polyamide resin. Melt spinning at a temperature higher by 30 ° C to 80 ° C. Then, after the synthetic resin melt extruded from the die is cooled and solidified, it is heated and stretched 4.0 to 7.0 times at a temperature of 60 to 200 ° C., and further 100 ° C. or higher and below the melting point of the polyamide resin. A monofilament having sufficient physical properties can be obtained by performing relaxation or constant length heat treatment at a temperature.

  In particular, it is important to dry the raw material before melt spinning. If the moisture content is high, operational problems such as ejection failure and stretch breakage are likely to occur, and the resulting monofilament also has high tensile strength, bending hardness, and bending resistance. It tends to cause a decrease in wear.

  The cross-sectional shape of the bristle material for the brush may be an irregular cross-section such as a circle, a flat shape, a square shape, a half moon shape, a triangle shape, a polygon shape with 5 or more corners, or a core-sheath composite. It may be a structure or a sea-island composite structure.

  Further, when a tapered shape is formed at one end of the cut bristle, it can be easily processed by a mechanical polishing process or a chemical solution dissolving process.

  And when planting this cut bristle as a brush, it can be used for all the hair materials, or can be used for a part according to the use and purpose of the brush.

  Examples of the brush type include a toothbrush, a hair brush, a body brush, a cleaning brush, a makeup brush, a paint brush, a roll brush, a wheel brush, a cup brush, and a niblet brush.

  Hereinafter, although the hair material for brushes of the present invention will be described in detail with reference to examples, the present invention is not limited to the following examples unless it exceeds the gist.

In addition, the toothbrush of the following specification was used for evaluation of bristle and tactile sensation change, cleaning property evaluation, and bending abrasion property evaluation.
Base: Made of ABS (9mm × 22mm)
Number of flocked holes: 34 Number of flocked hairs: 20 per one hole Length: 10mm

[Evaluation of fur and tactile feel]
Regarding the tactile sensation of toothbrushes, 20 people per toothbrush actually used the toothbrush as a monitor for 35 days (5 weeks), twice daily in the morning and evening, once for 3 minutes, and the fur waist and tactile sensation changed. The number of days felt was interviewed, and the average number of days was calculated by dividing the number of days by 20 people. It shows that it is a toothbrush which is excellent in dimensional stability, and there are few changes in hairiness and touch feeling, so that this average number of days is large.

[Cleanability]
A pseudo tooth model is prepared by arranging 9 grooves of 1 mm width x 1 mm depth on a 30 mm square acrylic plate in parallel at intervals of 2 mm. The surface of this pseudo tooth model is 3 minutes and 180 minutes (3 minutes x 2 times / Brushed toothbrush was prepared. The brushing was performed under conditions of a load of 350 g, an amplitude length of 30 mm, and an amplitude speed of 180 reciprocations / minute while applying water at 37 ° C.

Next, prepare a pseudo tooth model that was uniformly adhered with plaque staining solution (plaque check solution) and then dried for 1 day. Using a toothbrush brushed for 3 minutes and 180 minutes, the surface of the pseudo tooth model While applying a load of 350 g, brushing was performed for 3 minutes under the conditions of an amplitude length of 30 mm and an amplitude speed of 180 reciprocations / minute to determine the amount of plaque staining solution removed, and the amount of plaque removal ( %).
Dental plaque removal rate (%) = 100 × (W−w) / W (I)

  In the formula (I), W represents the total mass (g) of the pseudo tooth model and the plaque staining solution before brushing, and w represents the total mass (g) of the pseudo tooth model and the plaque staining solution after brushing. The plaque removal rates of the toothbrushes brushed for 3 minutes and 180 minutes are compared, and the smaller the difference, the better the toothbrush that can last for a long time.

[Bend abrasion resistance evaluation]
Using a bending wear characteristic tester according to JIS L-1095-9.10.2B method, contact with a friction element (hard steel wire (SWP-A)) having a diameter of 1.0 mm fixed to the tester. The monofilament is hung under two free rollers (distance 100 mm between the two rollers) provided so that the monofilament bends at an angle of 55 ° to the left and right of the friction element. Set the monofilament at one end with a load of 0.196 cN / dtex through the top, bring the monofilament into reciprocating contact with the friction element at a speed of 120 reciprocations / min and a reciprocating stroke of 25 mm, and the number of times until the monofilament breaks is the same. Ten were measured for each and the average value was calculated.

[Dry and wet bending hardness ratio]
A monofilament (A) that was allowed to stand for 24 hours at 20 ° C. under a relative humidity of 65 HR% and a monofilament (B) that was immersed in water at 20 ° C. for 16 hours or more were prepared. Then, the monofilaments (A) and (B) are cut into lengths of about 4 cm, respectively, and as shown in FIG. 1, two monofilaments 1 are horizontally placed under the stainless steel rods 2a and 2b having a diameter of 2 mm arranged at 10 mm intervals. 1 mm diameter stainless steel hook 3 is hung on monofilament 1 at the center position of stainless steel rods 2a and 2b, and a TCM-200 type universal tension / compression tester manufactured by Menebea is used. Then, the stainless steel hook 3 was pulled up at a take-up speed of 50 mm / min, and the maximum stress generated at this time was defined as bending hardness. And the value which divided the bending hardness of the monofilament (B) by the bending hardness of the monofilament (A) was made into the dry-wet bending hardness ratio. It shows that it is a monofilament with a small change of the bending hardness by water absorption, so that this value is large.

[Example 1]
Polyamide 10 · 10 having a structural unit of an aliphatic diamine having 10 carbon atoms and an aliphatic dicarboxylic acid having 10 carbon atoms was used as a raw material. Preliminarily dried polyamide 10 · 10 pellets having a moisture content of 0.08% were supplied to a melt spinning machine, melt-kneaded at 245 ° C. in the melt spinning machine, and then the synthetic resin melt was extruded from the die.

  Subsequently, the extruded synthetic resin melt was cooled and solidified in a cooling bath, and then stretched 4.6 times in a hot water bath at 80 ° C. and a dry heat bath at 140 ° C. A 95-fold heat set was applied to obtain a monofilament having a diameter of 0.2 mm.

  Next, the obtained monofilament was cut, and this cut bristle was used for evaluation as a brush hair material.

[Examples 2-6, Comparative Examples 1-4]
A brush hair material was obtained in the same manner as in Example 1 except that the raw material was changed to the polyamide resin shown in Table 1.

[Examples 7 to 8]
A bristle material for a brush was obtained in the same manner as in Example 1 except that the moisture content of the raw material used was adjusted to 0.17% and 0.23%.

[Example 9, Comparative Example 5]
One end of the cut bristle obtained in Example 1 and Comparative Example 3 was polished to form a tapered shape, and this was used for evaluation as a brush hair material.

  As is clear from the results shown in Table 1, the brush hair material of the present invention (Examples 1 to 9) is in comparison with the brush hair material made of a conventional polyamide resin (Comparative Examples 1 to 5). Even when used for a long time, the hair, tactile sensation, and cleanability are not easily lost, and the bending wear resistance is also excellent.

  The bristle material for brushes of the present invention has excellent dimensional stability due to its low water absorption, has little change in fur and tactile sensation, can maintain excellent cleaning performance, and has high bending wear resistance. Is. Therefore, the bristle material for brushes of the present invention is not limited to various brushes such as toothbrushes, hair brushes, body brushes, cleaning brushes, makeup brushes, paint brushes, and various industrial products such as roll brushes, wheel brushes, cup brushes, and niblet brushes. It can be used as a brush, and is particularly practical when used for toothbrushes that require not only cleanability but also massage performance to the gums.

1 Monofilament 2a, 2b Stainless steel bar 3 Stainless steel hook

Claims (8)

A bristle material for a brush comprising a monofilament cut bristle obtained by melt-spinning a polyamide-based resin composed of an aliphatic diamine having 9 to 12 carbon atoms and an aliphatic dicarboxylic acid having 6 to 12 carbon atoms. The brush hair material according to claim 1, wherein the aliphatic diamine is any one of 1,10-decanediamine, 1,11-undecanediamine, and 1,12-dodecanediamine. The brush hair material according to claim 1 or 2, wherein the dicarboxylic acid is sebacic acid or dodecanedioic acid. The brush hair material according to claim 3, wherein the polyamide-based resin is polyamide 10 · 10 having 1,10-decanediamine and sebacic acid as structural units. 5. The brush according to claim 4, wherein, in a bending wear characteristic test measured according to JIS L-1095-9.10.2B, the number of bending wears when the monofilament breaks is 50000 times or more. Hair for hair. About the monofilament, the wetness of the monofilament (B) immersed in water at 20 ° C for 16 hours or more divided by the bending hardness of the monofilament (A) left at 20 ° C under a relative humidity of 65HR% for 24 hours. The bristle material for brush according to claim 4 or 5, wherein the bending hardness ratio is 0.8 or more. The bending hardness is a value obtained by the following method.
[Bending hardness]
Cut the monofilament into a length of about 4 cm and set it in contact with the bottom of a 2 mm diameter stainless steel rod installed in two horizontal intervals at 10 mm intervals. The monofilament has a diameter of 1 mm at the center of the stainless steel rod. A stainless steel hook was hung and the stainless steel hook was pulled up at a take-up speed of 50 mm / min using a Menekea Co., Ltd. TCM-200 universal tension / compression tester, and the maximum stress generated at this time was defined as bending hardness. The brush bristle material according to any one of claims 1 to 6, wherein a taper shape is formed at least at one end of the cut bristle. A brush comprising the brush bristle material according to any one of claims 1 to 7 as at least a part of the bristle material.

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