Fadable multifunctional monofilament with skin-core structure

Abstract

The invention relates to a multifunctional monofilament capable of fading. More specifically, the present invention relates to a fadable multifunctional monofilament having a skin-core structure comprising an active substance or a functional filler. The invention further relates to a preparation method of the monofilament material and application of the monofilament material to brush materials such as toothbrushes.

Description

TECHNICAL FIELD

[0001] The present invention relates to a discolurable multifunctional monofilament. More particularly, the present invention relates to a discolurable multifunctional monofilament with a core-sheath structure comprising an active substance and / or a functional filler. The present invention further relates to a method for preparing the monofilament material, and the use of the monofilament material for a brush material such as a toothbrush. BACKGROUND

[0002] In daily life, toothbrushes with discolurable brush filaments can remind people to replace toothbrushes in time, which is conducive to improving oral health. However, the brush filaments with only a single discoloration function cannot meet the use requirements of consumers. Multifunctional brush filaments with a discoloration function by introducing functional fillers (such as aluminum Al flakes) or active substances (such as NaF) into the toothbrush filaments are increasingly favored by consumers.

[0003] One of the common techniques for preparing a discolurable monofilament at present is achieved by a dyeing process, which can cause the monofilament with a functional filler or an active substance to lose part of the functional filler or the active substance, and it is difficult to obtain a discolurable multifunctional monofilament with excellent comprehensive performance.

[0004] The inventors unexpectedly found that by providing a discolurable multifunctional monofilament with a core-sheath structure comprising a functional filler or an active substance, the functional filler or the active substance is added only in the core layer, and the thickness parameter of the sheath layer is particularly limited, so that the monofilament with a core-sheath structure can significantly reduce the loss of the functional filler or the active substance in the dyeing process, thereby enabling the multifunctional monofilament to exhibit excellent comprehensive multifunctional characteristics during use. SUMMARY

[0005] The present invention provides a discolurable multifunctional monofilament with a core-sheath structure, wherein the core layer of the multifunctional monofilament comprises an active substance or a functional filler, and the multifunctional monofilament as a whole comprises a dye, and a discoloration effect is generated by means of the gradual release of the dye during use of the multifunctional monofilament, characterized in that the sheath layer of the multifunctional monofilament has a thickness of ≥ 10 μm.

[0006] The present invention further provides a method for preparing a monofilament of a high molecular material as described above, comprising the following steps:

[0007] 1) adding a base resin and an active substance or a functional filler and optionally other auxiliaries to an extruder A to provide a core layer melt of a monofilament with a core-sheath structure; and adding the same or different base resin and optionally other auxiliaries to an extruder B to provide a sheath layer melt of a monofilament with a core-sheath structure;

[0008] 2) the two melts are combined in a co-extrusion spinning pack, the composite melt of the sheath melt and the core melt is extruded from a spinneret, and then the composite melt is cooled and solidified, followed by heat drawing and heat setting to obtain the multifunctional monofilament with a sheath-core structure containing the active substance or functional filler;

[0009] 3) the multifunctional monofilament with a sheath-core structure is subjected to dyeing treatment by a dyeing process;

[0010] 4) optionally, post-treatment is performed after the dyeing treatment to obtain the final fadeable multifunctional monofilament with a sheath-core structure. DETAILED DESCRIPTION

[0012] Except in the examples, or where otherwise explicitly indicated, all numbers in this description indicating amounts of material or conditions of reaction, physical properties of materials and / or use are to be understood as modified in all instances by the term "about".

[0013] All amounts are by weight of the composition, unless otherwise specified.

[0014] It should be noted that when any numerical range is recited herein, any particular upper limit can be associated with any particular lower limit.

[0015] For the avoidance of doubt, the word "comprising" is intended to mean "including" but not necessarily "consisting of" or "composed of." In other words, the listed steps or options need not be exhaustive.

[0016] The disclosure of the application found herein is believed to be applicable to all embodiments found in the claims that are multiple dependent on each other, regardless of the fact that the claims can be found to be multiple independent or redundant.

[0017] Where a feature is disclosed with respect to a particular aspect of the application, e.g., a composition of the application, such disclosure is also believed to apply to any other aspect of the application, e.g., a method of the application, mutatis mutandis.

[0018] Preparation of multifunctional monofilament with a sheath-core structure

[0019] The multifunctional monofilament with a sheath-core structure can be prepared using techniques well known in the art.

[0020] According to one embodiment of the application, the multifunctional monofilament with a sheath-core structure can be prepared by a conventional melt co-extrusion process. Specifically:

[0021] 1) adding base resin and active substance or functional filler and optional other auxiliaries into extruder A to provide a core layer melt of monofilament with a sheath-core structure; and adding same or different base resin and optional other auxiliaries into extruder B to provide a sheath layer melt of monofilament with a sheath-core structure;

[0022] 2) combining the above two melts in a co-extrusion spinning assembly, extruding from the spinning orifice, and then cooling and solidifying the composite melt of sheath and core layer through water bath or air, followed by thermal drawing and heat setting through heating to obtain monofilament with a sheath-core structure containing active substance or functional filler;

[0023] According to the present application, the sheath layer of the multifunctional monofilament with a sheath-core structure has a thickness of at least > 10 μm. In a preferred embodiment of the present application, the sheath layer of the multifunctional monofilament with a sheath-core structure has a thickness of > 20 μm; the upper limit of the sheath layer thickness of the monofilament is only limited by the conditions of the preparation process. In a more preferred embodiment of the present application, the sheath layer of the multifunctional monofilament with a sheath-core structure has a thickness of 20 μm to 100 μm, most preferably 20 to 40 μm.

[0024] Dyeing of multifunctional monofilament with a sheath-core structure:

[0025] After obtaining the multifunctional monofilament with a sheath-core structure, it can be subjected to dyeing treatment by dyeing processes known in the art.

[0026] According to one embodiment of the present application, the obtained multifunctional monofilament with a sheath-core structure is subjected to dyeing treatment by dyeing process: the multifunctional monofilament with a sheath-core structure is immersed in a dyeing solution, the pH of the dyeing solution is adjusted to the range of 1 to 7, and then the solution is heated to a temperature of, for example, 80 to 100 °C and kept for 10 to 60 min for dyeing; after the dyeing is completed, the temperature is lowered and the monofilament is washed with water to obtain dyed monofilament. Finally, the dyed monofilament is subjected to post-treatment such as drying to obtain the finished multifunctional monofilament with a sheath-core structure which is light-degradable.

[0027] As far as the dyes that can be used in the dyeing process of the present application are concerned, the basic requirement is that the dyes used are food-grade dyes.

[0028] According to a preferred embodiment of the present application, the food-grade dyes include acid water-soluble / dispersible dyes.

[0029] According to a further preferred embodiment of the present application, the acid water-soluble / dispersible dyes include those selected from the following types: methylene blue dyes; indigoid dyes including, but not limited to, indigo dyes, indigo violet dyes, indigo red dyes, indigo orange dyes; disperse dyes including, but not limited to, disperse orange, disperse blue, disperse yellow, disperse red, or disperse black, disperse green, disperse violet obtained from any proportion combination thereof, also including anthraquinone dyes; plant-based natural dyes including, but not limited to, curcumin, anthocyanin, curcumin, shikonin, alizarin red, and betalain, and environmentally friendly C.I. Acid Red 249, C.I. Acid Violet 54, C.I. Acid Blue 324 dyes, and the like.

[0030] According to a particularly preferred embodiment of the present application, the indigo dyes that can be used in the present application include, but are not limited to, indigo and its aluminum lake, sodium indigo disulfonate. According to a particularly preferred embodiment of the present application, the plant-based natural dyes that can be used in the present application include, but are not limited to: curcumin, anthocyanin, shikonin, alizarin red, and betalain, and the like.

[0031] Base resin

[0032] In principle, there is no particular limitation on the material used to make the multifunctional filaments of the present application, and the materials commonly used in the art to make the filaments can be used in the preparation of the filaments of the present application.

[0033] According to an embodiment of the present application, the base resin that can be used in the multifunctional filaments of the present application includes polyamide (nylon), polyester, and the like.

[0034] Polyamide PA (Nylon)

[0035] One type of exemplary base resin that can be used in the present application is polyamide or commonly known as nylon.

[0036] The polyamides that can be used in the present application have a linear backbone and can be produced by reacting a dicarboxylic acid with a diamine to form a linear condensation polyamide. Non-limiting examples of dicarboxylic acids include C6 to C12 aliphatic dicarboxylic acids such as adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, and aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, and 2,6-naphthalene dicarboxylic acid, and non-limiting examples of diamines include linear aliphatic or alicyclic diamines, such as ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, isophorone diamine, and 1,4-cyclohexane bis(methylamine), decanediamine, and non-limiting examples of diamines can also include linear aromatic diamines, such as phenylenediamine and diphenylamine. The polyamides used in the present application can also be produced by reacting an amino group-containing carboxylic acid compound or its lactam. Non-limiting examples of amino group-containing carboxylic acid compounds include C6 to C12 aliphatic amino-terminated carboxylic acid compounds such as 6-aminohexanoic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid.

[0037] Exemplary base resin polyamides include PA612, PA610, PA512, PA510, PA6, PA66, PA46, PA1010, PA11, PA12 or mixtures thereof, according to the well-known nomenclature rules for polyamide materials in the art.

[0038] In a particularly preferred embodiment, the base resin employed is PA612, such as Nylon PA612 available from Celanese Corporation 151NC010.

[0039] Polyesters

[0040] Another class of exemplary base resins that can be used in the present application are polyesters.

[0041] Non-limiting examples of polyesters include the reaction product of terephthalic acid and ethylene glycol, i.e. polyethylene terephthalate (PET), and similarly polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT). In addition, various modified polyesters can also be used in the present application, non-limiting examples of which include polybutylene succinate (PBS), polylactic acid (PLA), polyepsilon-caprolactone (PCL), poly-3-hydroxybutyrate (PHB), polyhydroxyvalerate (PHV), and the like. Copolyesters include, for example, polybutylene adipate / terephthalate (PBAT), polybutylene sebacate / adipate (PBSA), copolyhydroxyalkanoate, and the like.

[0042] Exemplary typical representatives of polyesters that can be used in the present application include PET, PBT, PTT, and the like.

[0043] Active substances

[0044] Exemplary active substances that can be used in the present application include sodium fluoride, tea polyphenols, Melia azedarach, clove oil, and the like.

[0045] Sodium fluoride

[0046] Sodium fluoride is a well-known anticariogenic compound that has long been used in toothpaste formulations to provide the corresponding technical effect.

[0047] According to embodiments of the present application, sodium fluoride NaF is added as an active substance used in the present application to the core layer structure of the multifunctional monofilament having a core-sheath structure.

[0048] Commercially available sodium fluoride products can all be used in the present application. The size of the sodium fluoride particles does not exceed the diameter of the monofilament.

[0049] Other active substances

[0050] According to embodiments according to the present application, exemplary other common active substances that can be used in the present application include tea polyphenols, meliatoxins, clove oil, etc. Among them:

[0051] Tea polyphenols: Tea polyphenols are an extract from tea leaves. Tea polyphenols have a high content of free hydroxyl groups, which can bind to salivary proteases, improve the bacterial reproduction caused by protein precipitation in the oral cavity; at the same time, tea polyphenols also have obvious plant antibiotic effects, which can improve oral inflammation.

[0052] Commercially available tea polyphenol products can be used in the present application, for example, the tea polyphenol products can be purchased from KOEI, Dayang, Wuhan Fortuna, Parchem, etc.

[0053] Meliatoxins: Meliatoxins can eliminate free radicals and have antioxidant effects; they have inhibitory effects on various fungi and bacteria, and are antibacterial agents, anti-inflammatory agents, and tooth antifouling agents.

[0054] Commercially available meliatoxins can be used in the present application, for example, the meliatoxins can be purchased from Chengdu Pusai Biotechnology, Hubei Guangao Biotechnology Co., Ltd., Shanghai Yian Biotechnology Co., Ltd., etc.

[0055] Clove oil: Clove oil is an oil extracted from clove leaves, has certain medicinal value, has analgesic, antibacterial, and anti-inflammatory effects, and can be used for oral analgesia, anti-inflammation, and dental caries prevention, etc.

[0056] Commercially available clove oils can be used in the present application, for example, the clove oils can be purchased from Shanghai Yuan Ye Biotechnology Co., Ltd., Nanjing Chemical Reagent Co., Ltd., etc.

[0057] Functional fillers

[0058] Functional fillers can be used in the core layer of the multifunctional monofilament with a core-sheath structure according to the present application to bring special functional technical effects; for example, to give the monofilament a shiny effect.

[0059] Exemplary functional fillers that can be used in the present application include aluminum flakes, mica flakes, etc.

[0060] Aluminum flakes: Small-sized aluminum flakes can be used in toothbrush bristles to give the bristles a shiny aesthetic effect.

[0061] In principle, there is no particular limitation on the use of the aluminum flakes, as long as they can be appropriately incorporated into the monofilament according to the present application.

[0062] According to one embodiment of the present application, the size of the aluminum flake suitable for use in the present application is, for example, 10 to 30 μm in thickness and 20 to 140 μm in length / width (i.e., either length or width). Commercially available aluminum flakes can be used in the present application. For example, the aluminum flakes are commercially available from Hefei Kejing, Zhongti New Material, Avient, and the like.

[0063] According to another embodiment of the present application, mica flakes can also be used to prepare a monofilament material having a similar sparkling aesthetic effect.

[0064] In principle, there is no particular limitation to the use of the mica as long as it can be suitably incorporated into the toothbrush bristles.

[0065] Commercially available mica flakes can be used in the present application. For example, the mica flakes are commercially available from Imerys Minerals, The Earth Pigments Company, Reade International, MATSUO SANGYO, Yamaguchi, and the like.

[0066] In the present application, the amount of the active substance or functional filler added is in the range of 0.2 to 10 wt%, preferably 0.5 to 6 wt%, and more preferably 0.8 to 4 wt%, based on the total weight of the multifunctional monofilament.

[0067] Other additives

[0068] In the polymeric monofilament of the present application, other additives can also be added as needed, including but not limited to antioxidants, light stabilizers, antistatic agents, lubricants, plasticizers, conventional fillers, antibacterial agents, and the like.

[0069] In the present application, the antioxidant can be any antioxidant commonly used in the art. In a preferred embodiment of the present application, the antioxidant is selected from the group consisting of dibutylhydroxytoluene (BHT), phenyl-β-naphthylamine, alkyl-p-quinone, thioether, phenyl salicylate, mercapto thioether, thio-propionic acid ester, hindered phenol, and the like.

[0070] In the present application, the antistatic agent can be any antistatic agent commonly used in the art. In a preferred embodiment of the present application, the antistatic agent is selected from the group consisting of quaternary ammonium salts, ethoxylated amines, aliphatic esters, and sulfonated waxes, and combinations thereof.

[0071] In the present application, the lubricant can be any lubricant commonly used in the art. In a preferred embodiment of the present application, the lubricant is selected from the group consisting of aliphatic esters (e.g., monoglycerides of fatty acids), and combinations thereof.

[0072] In the present application, the plasticizer can be any plasticizer commonly used in the art, in a preferred embodiment of the present application, the plasticizer is selected from the group consisting of terephthalate, phthalate, aliphatic dibasic acid ester, phosphate, chlorinated paraffin, and combinations thereof.

[0073] In the present application, the conventional filler can be any filler commonly used in the art, including but not limited to calcium carbonate, glass fiber, glass flake, glass bead, carbon fiber, talc, wollastonite, calcined clay, kaolin, diatomite, sodium fluoride, magnesium sulfate, magnesium silicate, barium sulfate, titanium dioxide, sodium aluminum carbonate, potassium titanate, and mixtures thereof.

[0074] The present application will be described in more detail with reference to the following examples, which are merely illustrative of the present application and are not intended to limit the scope of the present application. Those skilled in the art can make improvements and adjustments to the technical solutions described without departing from the spirit of the present application, and the specific protection scope of the present application will be defined by the appended claims. DETAILED DESCRIPTION

[0075] The raw materials used in the examples are as follows:

[0076] Nylon 612: Nylon 612 was purchased from Celanese 151NC010.

[0077] Sodium fluoride NaF: Sodium fluoride was purchased from Qiaoli Chemical Co., Ltd., with an average particle size of less than 45 μm.

[0078] Aluminum flake: Aluminum flake was purchased from Avient, with a thickness of about 20 μm and a maximum length or width of < 120 μm.

[0079] Dye: Dye was purchased from SENSIENT methylene blue, and indigo violet from ANGUS.

[0080] The specific dyeing process is as follows: prepare a dyeing solution containing the target color of the dye, and adjust the dyeing solution concentration and pH. Immersing more than 10 Kg of multifunctional monofilament with a skin-core structure in 110 Kg of the dyeing solution under heating to a set dyeing temperature and for a set dyeing holding time. After dyeing, reduce the temperature of the dyeing solution, take out the dyed monofilament, and wash the monofilament to obtain the dyed monofilament.

[0081] Example 1 : Examples of the addition of active substances

[0082] Sodium fluoride NaF was used as the active substance.

[0083] A blank sample of non-sheath core structure (i.e. the sheath thickness is 0) with a filament diameter of 0.152 mm (i.e. 152 pm) and a core layer with 1 wt.% (based on the weight of the filament) of NaF active substance, and a nylon 612 filament sample with the same initial NaF active substance addition amount and a sheath core structure (the sheath thickness is 20 pm, 25 pm, and 30 pm, respectively) were prepared by a melt co-extrusion spinning process.

[0084] The prepared nylon 612 filaments containing sodium fluoride were subjected to dyeing treatment by a dyeing process to obtain dyed multifunctional filaments. Among them, 10 g of multifunctional filaments with a sheath core structure were immersed in 110 g of the dyeing solution according to the filament / dyeing solution ratio described above. The dyeing temperature was 90°C, the dyeing holding time was 10 min, the dyeing solution concentration was ~1 wt.%, and the pH of the dyeing solution was set to ~2. The dye in the dyeing solution was methylene blue.

[0085] The retention rate of the added active substance NaF of the non-sheath core structure and the nylon 612 filaments with a sheath core structure after dyeing was tested by ion chromatography, respectively, relative to the blank sample described above.

[0086] Measurement of NaF retention rate:

[0087] 1 g of filaments before and after dyeing, respectively, with the same length of 30 mm, were weighed and immersed in 30 ml of water at room temperature for 2 h. Then the filament samples were taken out, and the content of F element in the leaching solution after 2 h immersion of the filaments before and after dyeing was measured by inductively coupled plasma atomic emission spectrometry (ICP). The retention rate of NaF was calculated as follows.

[0088]

[0089] The greater the ratio of NaF retention rate, the higher the retention rate of NaF.

[0090] The data are shown in Table 1 below:

[0091] Table 1

[0092]

[0093] The results show that the greater the sheath thickness, the higher the retention rate of the active substance NaF of the discolable filaments with a sheath core structure after the dyeing process, and in particular, when the sheath thickness reaches 20 pm and above, the retention rate of the active substance NaF can be increased to 30.7%; while the retention rate of the active substance of the NaF-containing filaments with a non-sheath core structure is 21.4%.

[0094] Example 2

[0095] Examples of adding functional fillers: aluminum flake as the functional filler.

[0096] By melt co-extrusion spinning process, respectively, the blank sample of non-sheath core structure (i.e. the skin thickness is 0) with 1 wt% aluminum flake (based on the weight of the monofilament), monofilament diameter of 0.152 mm (i.e. 152 μm) and nylon 612 monofilament with sheath core structure (skin layer thickness of 10 μm, 15 μm, 20 μm respectively) with the same aluminum flake addition were prepared.

[0097] The obtained nylon 612 monofilament containing aluminum flake was subjected to dyeing process to obtain dyed multifunctional monofilament. Among them, 10 g of monofilament containing the functional filler with sheath core structure was immersed in 110 g of the dyeing solution. The dyeing temperature was 90 °C, the dyeing holding time was 10 min, the dyeing solution concentration was ~ 1%, and the dyeing solution pH was set to ~ 5. The dye in the dyeing solution was indigo violet.

[0098] The retention rate of the functional filler aluminum flake of the monofilament after the dyeing process was measured.

[0099] Test of aluminum flake retention rate: 3-5 g of monofilament with sheath core structure with the same weight, ~ 30 cm of the same length and 1% aluminum flake content was weighed, and the monofilament without sheath core structure and 1% aluminum flake content was dyed in a dyeing solution containing 1% dye. Among them, the monofilament should be completely immersed in the dyeing solution. After the dyeing was completed, the dyeing solution was filtered through filter paper, and the weight of the filter paper was weighed after the filter paper was dried. The weight of the aluminum flake remaining on the filter paper was calculated by subtracting the dry weight of the filter paper before use, which was recorded as the weight of the aluminum flake falling off.

[0100] Among them, the retention rate of the aluminum flake was calculated according to the following formula:

[0101]

[0102] The results are summarized in Table 2 below.

[0103] The results show that when the skin layer thickness is 0, i.e. without sheath core structure, the nylon monofilament loses a large amount of aluminum flake in the dyeing process, and the aluminum flake retention rate is as low as 72%; when the skin layer thickness is 10 μm, the retention rate of the functional filler aluminum flake of the nylon 612 monofilament can be as high as 100%.

[0104] Table 2

[0105]

[0106] From the experimental results in Table 2 above, it can be seen that for the multifunctional monofilament with sheath core structure adding aluminum flake, slightly different from the monofilament with sheath core structure adding NaF, a satisfactory aluminum flake retention rate is actually obtained when the skin layer thickness is 10 μm or more.

Claims

1. A multi-functional single yarn having a core-sheath structure, wherein the core layer of the multi-functional single yarn contains an active substance or a functional filler, and the multi-functional single yarn contains a dye throughout, and a fading effect is produced by means of gradual release of the dye during use of the multi-functional single yarn, characterized in that, The skin layer of the multifunctional monofilament has a thickness of greater than or equal to 10 μm, preferably greater than or equal to 20 μm. ​ 2. The multifunctional monofilament according to claim 1, wherein the diameter of the multifunctional monofilament is in the range of 100-254 μm, preferably 120-204 μm; and the thickness of the skin layer is in the range of 20-100 μm, preferably 20-40 μm.

3. The multifunctional monofilament according to claim 1 or 2, wherein the active substance contained in the multifunctional monofilament comprises one or more of the following: NaF, tea polyphenol, toosendanin, clove oil.

4. The multifunctional monofilament according to claim 1 or 2, wherein the functional filler contained in the multifunctional monofilament comprises one or more of the following: aluminum flake, mica flake.

5. The multifunctional monofilament according to claim 1 or 2, wherein the active substance or functional filler contained in the multifunctional monofilament is added in a proportion in the range of 0.2-10% by weight, based on the total weight of the multifunctional monofilament, preferably 0.5-6% by weight; more preferably 0.8-4% by weight.

6. The multifunctional monofilament according to claim 1 or 2, wherein the skin layer and the core layer of the multifunctional monofilament are made of a material selected from the group consisting of nylon, polyester, or a combination thereof.

7. The multifunctional monofilament according to claim 1 or 2, wherein the dye is a food-grade dye.

8. The multifunctional monofilament of claim 7, wherein the food grade dye comprises an acid water-soluble / dispersible dye, and the water-soluble / dispersible dye comprises: indigo dye, plant-based natural dye, methylene blue, anthraquinone dye.

9. The multifunctional monofilament according to claim 8, wherein the indigo dye comprises indigo blue, indigo red, indigo purple, or a combination of any proportion thereof.

10. The multifunctional monofilament according to claim 8, wherein the disperse dye comprises disperse orange, disperse blue, disperse yellow, disperse red, or disperse black, disperse green, disperse purple obtained by a combination of any proportion thereof.

11. The multifunctional monofilament according to claim 8, wherein the plant-based natural dye comprises curcumin, anthocyanin, shikonin, alizarin red, and betalain, etc.

12. The multifunctional monofilament according to claim 1 or 2, wherein the skin layer and / or the core layer of the multifunctional monofilament further comprises an additive selected from the group consisting of antioxidant, light stabilizer, antistatic agent, lubricant, plasticizer, conventional filler, antibacterial agent.

13. A method for preparing the multifunctional monofilament as claimed in any one of the preceding claims, comprising the following steps: 1) adding a base resin and an active substance or a functional filler and optionally other auxiliary agents into an extruder A to provide a core layer melt of the monofilament having a sheath-core structure; and adding the same or different base resin and optionally other auxiliary agents into an extruder B to provide a skin layer melt of the monofilament having a sheath-core structure; 2) combining the above two melts in a co-extrusion spinning pack, extruding from a spinneret, and then cooling and solidifying the composite melt of the skin layer melt and the core layer melt, followed by hot drawing and heat setting to obtain the multifunctional monofilament having a sheath-core structure containing an active substance or a functional filler; 3) dyeing the multifunctional monofilament having a sheath-core structure by a dyeing process. 4) optionally, post-treatment after the dyeing treatment to obtain the final multifunctional monofilament with a core-sheath structure.

14. A brush made of the multifunctional monofilament as claimed in one of the preceding claims 1 to 12 or made of the multifunctional monofilament prepared by the method as claimed in claim 13.

15. The brush of claim 14, wherein, The brush is a toothbrush.

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