Chemically sharpened co-extruded polyester monofilament with function of preventing toothbrush hair from falling and warping

Abstract

A sharpened filament coated with silicone oil on the surface and having a skin layer-core layer structure wherein the core layer comprises polybutylene terephthalate (PBT) and an optional additive, the skin layer comprises polytrimethylene terephthalate (PTT) and an optional additive, and at least one end of the filament is sharpened by chemical treatment; the co-extrusion sharpened monofilament with the skin layer-core layer structure is characterized in that the ratio of the skin layer thickness to the monofilament diameter of the co-extrusion sharpened monofilament with the skin layer-core layer structure is 3-20%, preferably 5-15%.

Description

TECHNICAL FIELD

[0001] The present invention relates generally to toothbrush bristles. More particularly, the present invention relates to chemically tapered monofilaments of co-extruded polyester for use as toothbrush bristles having the function of preventing toothbrush bristle shedding and bristle splaying. BACKGROUND

[0002] Toothbrushes are an essential part of daily life for people.

[0003] Extruded monofilaments for toothbrush bristles can be produced by conventional extrusion processes. The most common extruded monofilaments are uniform diameter monofilaments. The ends of the monofilaments are tapered to produce tapered monofilaments, also referred to herein as "tapered monofilaments" or "tapered bristles".

[0004] Tapered bristles are an important segment of the toothbrush bristle market because such tapered bristles allow easy access of the toothbrush to the teeth, gums and sulcus. The production of tapered bristles typically involves mechanical tapering and chemical tapering of conventional extruded monofilaments. Currently, the share of chemically tapered polyester monofilaments is increasing.

[0005] US Patent No. 6,090,488 discloses a tapered bristle made of polybutylene terephthalate or polyethylene terephthalate. In the method disclosed in this patent, in the production of the tapered bristle, a length of polybutylene terephthalate (PBT) or polyethylene terephthalate (PET) bristle is first cut, then the bristle is vertically immersed in a strong alkali or strong acid solution to a depth of 10 mm, a tapered end portion having a diameter of 0.10 mm to 0.15 mm is formed by etching, then the bristle is washed with water and dried, then the bristle is loaded into a toothbrush head, and then the bristle end portion is optionally trimmed and rounded. This patent requires that the bristle end portion be rounded by a mechanical method after the bristle is mounted on the brush head.

[0006] JP-2001-169829 discloses a toothbrush bristle having different cross-sectional shapes and predetermined lengths made of polyester monofilaments. In the method of producing the bristle of this patent, the cut bristle is first packed by the paper wrapping method, then the axial direction of the fiber is made perpendicular to the bottom of a stainless steel container, then the end of the packed bristle bundle is immersed in a 40 wt% sodium hydroxide solution at 110°C for a certain period of time, then the other end of the bristle bundle is also treated with the alkali by the same method, then the bristle bundle is washed with water and dried, thereby obtaining a toothbrush bristle having a tapered end portion.

[0007] Polyesters can generally be used to produce the tapered bristles, or monofilaments having tapered end portions. The polyesters include, but are not limited to, polyethylene terephthalate (PET), polybutylene terephthalate (PBT) and polytrimethylene terephthalate (PTT).

[0008] In the production of toothbrushes using PBT tipped bristles, in order to make the process of tufting more smooth, people often increase the lubricity of the surface coating of the tipped bristles, mainly by increasing the amount of coating. But this adjustment will reduce the pull-out force of the bristles on the toothbrush, making the toothbrush prone to shedding, especially for bamboo handle brushes and toothbrushes with special hole patterns. The increased lubricity of the PBT tipped bristles not only makes it easy to move in the desired direction, i.e. along the feeding direction in the filament box of the tufting machine, but also makes it easy to move in the undesired direction, i.e. perpendicular to the feeding direction. This movement perpendicular to the feeding direction will cause the bristles to be bent out of the filament bundle, resulting in uneven bristle height and bent bristles after tufting. Such toothbrushes will be judged as defective and need to be repaired before they can be put on the market, otherwise they can only be scrapped. Because of the characteristics of natural materials, the size of the tufting holes on the bamboo handle is difficult to avoid, so ordinary PBT tipped bristles are prone to damage when applied to bamboo handle brushes in tufting holes with excessive stress. Broken or severely damaged bristles are trapped in the tufting holes and cannot be detected by blowing, until they fall off under stress during use, affecting the user experience of the end consumer.

[0009] JP2003169718A discloses a monofilament and a toothbrush using the same, wherein it is specifically disclosed that the monofilament is provided with a double core structure composed of a first resin layer and a second resin layer, and a taper can be formed at the front end portion of the monofilament of the double core structure. No further details of the structure of the monofilament with the double core structure are disclosed, nor is it disclosed how to improve the yield of the finished product in the toothbrush tufting process.

[0010] There is still a continuing need in the market for chemically tipped polyester monofilaments with the function of preventing toothbrush shedding and bent bristles.

[0011] Surprisingly, the inventors have found that in the chemically tipped co-extruded polyester tipped bristles prepared in the present application, by specifically controlling the ratio of the skin layer thickness to the monofilament diameter of the co-extruded polyester monofilament within a certain range, the co-extruded polyester tipped bristles can significantly improve the pull-out force of the bristles when applied to the tufting process of special hole toothbrushes, solve the problem of toothbrush shedding, and at the same time significantly improve the bent bristle situation during the tufting process. The inventors have also unexpectedly found that when trying to use this co-extruded co-extruded polyester tipped bristles with a specific ratio of skin layer thickness to monofilament diameter on bamboo handle toothbrushes, it can also provide a much lower shedding rate than ordinary PBT tipped bristles on bamboo handle toothbrushes. SUMMARY

[0012] The present invention provides a tipped filament coated with silicone oil having a skin-core structure, wherein the core comprises polybutylene terephthalate (PBT) and optional additives, the skin comprises polytrimethylene terephthalate (PTT) and optional additives, and at least one end of the monofilament is chemically treated to be tipped, characterized in that the ratio of the skin thickness of the co-extruded monofilament having a skin-core structure to the diameter of the monofilament is in the range of 3-20%, preferably 5-15%. The diameter of the monofilament of the co-extruded tipped filament having a skin-core structure is in the range of 0.1-0.5 mm, preferably 0.1-0.25 mm.

[0013] The present invention also provides a method for preparing the chemically tipped co-extruded polyester monofilament. First, a monofilament having a skin-core structure with PBT as the core and PTT as the skin is prepared by a co-extrusion spinning process. By adjusting the pump speed, the thickness of the skin can be precisely adjusted. Then the monofilament having a skin-core structure prepared in the previous step is cut into a cake, immersed in a solution of strong acid and / or strong base with a certain concentration to a certain depth for a certain length of time, so that at least one end is tipped. Finally, the chemically tipped co-extruded polyester monofilament is subjected to the operation of surface coating with silicone oil.

[0014] The present invention also provides a bristle made of the monofilament described above, a toothbrush filament made of the bristle, and a toothbrush comprising the toothbrush filament. DETAILED DESCRIPTION

[0016] 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 by the word "about".

[0017] All amounts are by weight of the composition, unless otherwise specified.

[0018] It should be noted that when any numerical range is recited herein, any particular upper value can be associated with any particular lower value.

[0019] 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.

[0020] The disclosure of the present invention found herein is believed to be applicable to all embodiments found in the claims that are multiplicity dependent on each other regardless of the fact that the claims can be found to be not multiplicity dependent or redundant.

[0021] Where a feature is said herein to be encompassed by a particular aspect of the invention (e.g. a composition of the invention), such disclosure is also believed to apply mutatis mutandis to any other aspect of the invention (e.g. a method of the invention).

[0022] Base resin of monofilament

[0023] The base resin of the monofilament applicable in the present invention is a polyester resin.

[0024] The polyester applicable in the present invention can be generally obtained by condensation polymerization of a dicarboxylic acid and a dihydric alcohol to form.

[0025] Core layer resin

[0026] In the chemical tapered monofilament of co-extruded polyester applicable in the present invention with the function of preventing the bristle shedding and bristle lifting of toothbrush, the polyester resin used as the core layer is a polybutylene terephthalate resin.

[0027] The polybutylene terephthalate resin is abbreviated as PBT resin, which can be generally obtained by condensation polymerization of terephthalic acid and 1,4-butanediol. Specifically, the PBT is generally obtained by direct esterification reaction or ester exchange reaction.

[0028] The PBT resin can be generally used as engineering plastic, spinning material, etc.

[0029] In the embodiment according to the present invention, exemplary representatives of the PBT resin used include PBT B2520 purchased from BASF, PBT L2100 purchased from Sinopec Yizheng Chemical Fibre, PBT 1200 211D / 211M purchased from Changchun Chemical, spinning grade PBT purchased from Hengli Chemical Fibre, etc.

[0030] Most preferably, in the embodiment according to the present invention, the PBT resin used is PBT L2100 purchased from Sinopec Yizheng Chemical Fibre.

[0031] Skin layer resin

[0032] In the chemical tapered monofilament of co-extruded polyester applicable in the present invention with the function of preventing the bristle shedding and bristle lifting of toothbrush, the polyester resin applicable as the skin layer is a polytrimethylene terephthalate resin.

[0033] The polytrimethylene terephthalate resin is abbreviated as PTT resin, which is a relatively new polyester material, and is obtained by condensation polymerization of terephthalic acid (PTA) and 1,3-propanediol (PDO).

[0034] Industrialized PTT is one of the latest industrialized varieties in polyester products, which is developed mainly after the industrialized production of raw material 1,3-propanediol obtains high efficient output.

[0035] Polytrimethylene terephthalate (PTT) resin material combines the performance advantages of various materials, and is one of the latest popular new polymer materials developed internationally, which can be widely used in various fields of fiber materials, engineering plastics and the like.

[0036] In embodiments according to the present application, exemplary representatives of the PTT resin employed include PTT resin commercially available from DuPont China Group Co., Ltd., such as PTT resin available under the trademark K1141 PTT resin obtained.

[0037] Silicone oil

[0038] In embodiments of the present application, the surface of the chemically sharpened co-extruded polyester monofilament needs to be coated with silicone oil.

[0039] In embodiments of the present application, in view of the desired toothbrush bristle application field of the target product, the applicable silicone oil mainly includes food-grade silicone oil.

[0040] Silicone oil generally refers to a linear polysiloxane product that remains in a liquid state at room temperature, and generally has a structural formula as shown below:

[0041]

[0042] wherein R is an alkyl group, an aryl group, R' is an alkyl group, an aryl group, hydrogen, a carbon functional group, an amino-containing alkyl group, and a polyether chain, etc.; X is an alkyl group, an aryl group, an alkenyl group, hydrogen, a hydroxyl group, an alkoxy group, an acetoxy group, chlorine, a carbon functional group, and a polyether chain, etc.; n, m = 0, 1, 2, 3, etc.

[0043] According to the present application, in the above-mentioned structure, when all the organic groups are all methyl groups, the silicone oil is referred to as methyl silicone oil. The organic groups can also be replaced by other organic groups instead of part of the methyl groups to improve certain properties of the silicone oil and adapt to various different uses. Common other groups include hydrogen, ethyl, phenyl, chlorophenyl, trifluoropropyl, etc.

[0044] In embodiments of the present application, the silicone oil can generally be used in the form of an emulsion, i.e., silicone oil emulsion can be used in the present application. In preferred embodiments of the present application, the silicone oil emulsion is generally coated on the surface of the monofilament after being diluted with water.

[0045] In embodiments of the present application, exemplary examples of silicone oils that can be used in the present application are: DOWSIL™ SH 7024, DOWSIL™ 8024, DOWSIL™ MEM 0024 from Dow Inc.; Elkem SILCOLAPSE™ 7140 from Elkem Silicones; Momentive SM2128 from Momentive Performance Materials Inc; KF-56®, KF-52®, KF-52® from Wacker International Group, Germany; and the like. FC 228E, and the like.

[0046] Other additives

[0047] In the polyester filaments of the present application, other additives can also be added as desired, including but not limited to, antioxidants, light stabilizers, antistatic agents, lubricants, plasticizers, fillers, antibacterial agents, and the like.

[0048] 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-beta-naphthylamine, alkyl-p-quinone, thioether, phenyl salicylate, mercapto thioether, thio-propionate, hindered phenol, and the like.

[0049] 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, sulfonated waxes, and combinations thereof.

[0050] 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.

[0051] 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 esters, phthalate esters, aliphatic dibasic acid esters, phosphate esters, chlorinated waxes, and combinations thereof.

[0052] In the present application, the filler can be any filler commonly used in the art, including but not limited to, calcium carbonate, glass fibers, glass flakes, aluminum flakes, glass beads, carbon fibers, talc, mica, wollastonite, calcined clay, kaolin, diatomaceous earth, sodium fluoride, magnesium sulfate, magnesium silicate, barium sulfate, titanium dioxide, sodium aluminum carbonate, potassium titanate, and mixtures thereof.

[0053] Method of making a co-extruded filament having a skin-core structure

[0054] In the present invention, the core-sheath structured monofilament can be prepared by using a method conventional in the art. For example, but not limited to, a melt co-extrusion method. Specifically, in one embodiment of the present invention, a method for preparing the co-extruded monofilament is provided, comprising the following steps:

[0055] 1) The core layer composition B comprising resin PBT is fed into extruder B, and the sheath layer composition A comprising resin PTT is fed into extruder A, and the sheath layer composition A and the core layer composition B are melted respectively.

[0056] 2) The melt of the sheath layer composition A is fed into the sheath material channel in the extrusion spinneret assembly, and the melt of the core layer composition B is fed into the core material channel in the extrusion spinneret assembly, and the two melts are combined in the extrusion spinneret assembly, and the combined melt of the sheath layer composition and the core layer composition is drawn into cold water for quenching and solidification, and then is drawn several times in hot water.

[0057] 3) The sheath layer thickness is adjusted by adjusting the pump speed of the extruder A and the extruder B.

[0058] 4) The sheath layer thickness is adjusted by adjusting the pump speed of the extruder A and the extruder B.

[0059] Thus, the co-extruded monofilament with PBT core layer / PTT sheath layer having a core-sheath structure with different sheath layer thicknesses is obtained.

[0060] Chemical tipping

[0061] The chemical tipping method comprises cutting the monofilament rod of the monofilament with the core-sheath structure having a specific sheath layer thickness and a specific ratio of the sheath layer thickness to the diameter of the monofilament prepared in the previous step into a cake, and then immersing the cake into a strong acid and / or strong base solution with a certain concentration to a certain depth for a certain length of time, so that at least one end of the monofilament is chemically tipped.

[0062] Specifically, the end face of the monofilament cake with the core-sheath structure according to the present invention is immersed into a strong base solution with a certain concentration to a certain depth for a certain length of time with the end face downward, and / or the end face of the monofilament cake with the core-sheath structure according to the present invention is placed in a horizontal direction so as to be completely immersed in the lye for a certain time.

[0063] In one aspect of the present invention, the strong base solution can be a sodium hydroxide solution, a potassium hydroxide solution or a combination thereof.

[0064] In another aspect of the present invention, the time for immersing the monofilament with the core-sheath structure prepared according to the present invention into the strong base solution can be 30 min to 300 min; for example, 60 min to 240 min, or most preferably 120 min to 210 min.

[0065] Silicone oil coating of the surface of chemically sharpened monofilaments

[0066] In the specific embodiment according to the present application, after the chemical sharpening of the monofilaments is completed, the cake of monofilaments is thoroughly washed and dried, and then a silicone oil coating liquid is sprayed. Specifically, a thin film of the silicone oil emulsion is uniformly coated on the surface of the sharpened monofilaments, so that the silicone oil emulsion can penetrate into the sharpened monofilament fibers, but most of the silicone oil emulsion still remains on the surface of the sharpened monofilament fibers, which can make the sharpened monofilaments easy to arrange and obtain a neatly arranged cake. The amount of silicone oil coated on the sharpened monofilament fibers should be appropriate. If the amount of silicone oil coated is too much, it will cause the adhesion between the sharpened monofilaments and the failure of the sharpened monofilaments to be normally transmitted on the planting device in the subsequent planting process. If the amount of oil is too small, it will cause the tow to be dry and difficult to arrange, and the cake cannot be normally transmitted on the planting device, resulting in the defects of the brush.

[0067] The present application will be described in more detail below with reference to the examples, which are only used to illustrate the technical solutions of the present application and are not used to limit the scope of the present application. Those skilled in the art can make improvements and adjustments to the technical solutions 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

[0068] Base stock description

[0069] Polybutylene terephthalate PBT: commercially available polybutylene terephthalate: PBT L2100 purchased from Sinopec Yizheng Chemical Fibre;

[0070] Polytrimethylene terephthalate PTT: using the K1141.

[0071] Silicone oil: using food-grade polydimethylsiloxane aqueous emulsion: specifically using DOWSILTMSH 7024 purchased from Dow Inc.

[0072] Test method description

[0073] 1. Test method for the ratio of the skin layer thickness to the monofilament diameter

[0074] 1.1 Using a laser diameter measuring instrument with a precision of 0.01 mm, measure the diameter of the monofilament at the middle part of the monofilament. Measure the diameter of 150 monofilaments to obtain the average monofilament diameter.

[0075] 1.2 Using a slicer, cut a flat end face at the middle part of the monofilament, and then observe under a microscope. Using the measurement function of the microscope, measure the skin layer thickness of at least 15 monofilaments, and take the average value to obtain the average skin layer thickness of the monofilament.

[0076] 1.3. Calculate the ratio of the skin thickness to the filament diameter (%) according to the following formula.

[0077]

[0078] 2. Test method for the diameter at the top end of the ground filament

[0079] At a distance of 0.5 mm from the top end of the filament, measure the diameter of the filament at a distance of 0.5 mm from the top end of the filament using a microscope with a magnification of 30x or more, and a minimum scale division of 0.001 mm. Randomly select 30 filaments from each sample and repeat the above test. Calculate the percentage of filaments with a diameter of 0.08 mm or less at a distance of 0.5 mm from the top end of the filament among the 30 measured filaments.

[0080] 3. Test method for the height of the tip cone of a filament resulting from chemical grinding

[0081] Using a microscope with a magnification of 30x or more, and a minimum scale division of 0.001 mm.

[0082] 3.1. Measure the diameter of the filament sample at a distance of 4 mm, 5 mm, 6 mm, 7 mm, and 8 mm from the end of the filament, respectively and calculate the average values Ф4, Ф5, Ф6, Ф7, and Ф8, respectively.

[0083] 3.2. Calculate the value Ф90% of 90% of the average value Фm of the diameter of the filament.

[0084] 3.3. Determine the height of the cone:

[0085] From Ф4, compare each value sequentially to Ф90%. When Фx is greater than Ф90% and Фx -1 is less than Ф90% among Ф4, Ф5, Ф6, Ф7, and Ф8, set x-0.5 as the height of the cone for this batch of products, in mm. If Фx is equal to Ф90%, set x as the height of the cone for this batch of products, in mm.

[0086] When Ф4> Ф90%, determine the height of the cone to be ≤3.5 mm.

[0087] When Ф8< Ф90%, determine the height of the cone to be >8 mm.

[0088] 4. Test method for the rate of shedding (%), the rate of bent bristles (%), and the pass rate (%)

[0089] 4.1. Plant the filament sample on the same planting machine at the same speed, and collect 100 toothbrush samples.

[0090] 4.2. Remove the loose bristles on the surface of the toothbrush, and then carefully inspect and divide them into three categories according to the following standards: shedding, bent bristles, and pass.​

[0091] Fallen hair: Wearing gloves, pull the bristles 5 down with force, and find the fallen hair during the process.

[0092] Kinked hair: No hair loss, but the kinked hair is serious, and must be trimmed before leaving the factory.

[0093] Qualified: No hair loss, and the bristles are neat, without the need for trimming.

[0094] 4.3 Count the number of each group, calculate the hair loss rate, kinked hair rate and qualified rate.

[0095] 5 Test method of bristle pull-out force

[0096] The bristle pull-out force test includes the test of the pull-out force of the special-shaped hole bristles and the pull-out force of the bamboo handle brush bristles.

[0097] 5.1 Hang the clamp on the force gauge, zero the force gauge, then remove the clamp to remove the weight of the clamp itself.

[0098] 5.2 Take a toothbrush, pick out 5 bristles in the designated position of the implanted hole, confirm that the bristles are on the same side of the copper sheet, and then use the clamp to clamp the bristles.

[0099] 5.3 Use the force gauge to hang the clamp again, pull out the fixed bristles, and after confirming that the 5 bristles are pulled out, check the maximum force displayed by the force gauge. The force is the effective pull-out force data.

[0100] 5.4 Replace a toothbrush that has not been tested, select the same position of the implanted hole, repeat steps 5.2 and 5.3, collect 6 effective data, and calculate the average value of the pull-out force.

[0101] Preparation of examples

[0102] Description of co-extruded monofilament production

[0103] 1) Add core layer composition B containing resin PBT to extruder B, and add skin layer composition A containing resin PTT to extruder A, and melt skin layer composition A and core layer composition B respectively.

[0104] 2) Make the melt of skin layer composition A enter the skin layer material channel in the extrusion spinning assembly, and make the melt of core layer composition B enter the core layer material channel in the extrusion spinning assembly, and make the two melts above converge in the extrusion spinning assembly; after extruding from the spinning holes on the spinning plate, pull the composite melt of the skin layer composition and the core layer composition into cold water for quenching and solidification, and then stretch several times in hot water. Adjust the skin layer thickness by adjusting the pump speed of extruder A and extruder B.

[0105] 3) Further pass through the shaping treatment of the dry heat oven, and finally wind and package.

[0106] Thus, a monofilament rod having a skin-core structure of PBT core layer and PTT skin layer is obtained.

[0107] Chemical sharpening treatment

[0108] The chemical sharpening method comprises cutting the monofilament rod having a skin-core structure prepared in advance into a cake and immersing it in a 40 wt.% sodium hydroxide aqueous solution heated to 110°C for 180 min, and the tip morphology is controlled by adjusting the concentration and temperature of the lye and the soaking time.

[0109] Silicone oil coating

[0110] After the chemical sharpening of the monofilament is completed, the cake is thoroughly washed, then sprayed with a silicon oil coating liquid, and then dehydrated and dried. Finally, the cake is trimmed and repackaged.

[0111] Examples 1-6

[0112] According to the above preparation examples, under the fixed condition of a monofilament diameter of 0.178 mm, monofilaments having different skin layer thicknesses are prepared respectively:

[0113] Example 1 (not the present application): PBT sharpened filament with a skin layer thickness of 0, which corresponds to sample 1;

[0114] Example 2 (the present application): PTT / PBT co-extrusion sharpened filament with a ratio of skin layer thickness to monofilament diameter of 6%, which corresponds to sample 2;

[0115] Example 3 (the present application): PTT / PBT co-extrusion sharpened filament with a ratio of skin layer thickness to monofilament diameter of 12%, which corresponds to sample 3;

[0116] Example 4 (the present application): PTT / PBT co-extrusion sharpened filament with a ratio of skin layer thickness to monofilament diameter of 16%, which corresponds to sample 4;

[0117] Example 5 (control): PTT / PBT co-extrusion sharpened filament with a ratio of skin layer thickness to monofilament diameter of 22%, which corresponds to sample 5.

[0118] Table 1

[0119]

[0120] As can be seen from the test results of the pull-out force listed in Table 1, when applied to special-shaped hole toothbrushes and bamboo handle toothbrushes, the PTT / PBT co-extrusion sharpened filament prepared according to the method of the present application has a significantly higher pull-out force than ordinary PBT sharpened filaments.

[0121] The following Table 2 shows the comprehensive test results of the shedding rate, the bent hair rate and the qualified rate of the sample No. 1-5 corresponding to the above-mentioned Examples 1-5 when applied to the bamboo handle brush.

[0122] Table 2

[0123]

[0124]

[0125] Please refer to the description of the determination of the taper height of the tapered filament in Section 3.3 of the Test method description ” section

[0126] As for the sample No. 1 of the pure PBT tapered filament, i.e. the tapered filament without the sheath-core structure, the shedding rate and the bent hair rate are high, and the qualified rate of the toothbrush is the lowest.

[0127] According to the present application, the proportion of the filament diameter ≤0.08mm at the end 0.5mm of the PTT / PBT co-extruded tapered filament (sample No. 2, 3, 4) with the ratio of the sheath thickness to the filament diameter in the range of 3% to 20% is 100%, and the end taper height obtained by chemical tapering is ≥4mm. Generally, the greater the taper height of the tapered filament, the thinner the end of the taper, and the softer the feeling of the consumer when using it; and the tapered filament with a taper height ≥4mm is generally considered to be satisfactory. And when applied to the bamboo handle brush, compared with the PBT tapered filament of sample No. 1, the shedding rate and the bent hair rate of sample No. 2, 3, 4 are reduced, and the overall qualified rate is significantly improved.

[0128] As a control group, the sample No. 5 of the PTT / PBT co-extruded tapered filament has a sheath thickness ratio of more than 20% to the filament diameter, there are filaments with a filament diameter >0.08mm at the end 0.5mm, and the end taper height obtained by chemical tapering is <4mm (i.e. determined to be ≤3.5mm). The taper height is small, the end of the taper is relatively thick, and the consumer is easy to feel uncomfortable when using it. And when applied to the bamboo handle brush, the shedding rate and the bent hair rate are increased, resulting in a decrease in the qualified rate compared with sample No. 2, 3, 4.

[0129] It should be understood that the above-mentioned is only a preferred embodiment of the present application, and those of ordinary skill in the art can make several improvements and modifications without departing from the principles of the present application, and these improvements and modifications are also within the scope of the present application.

Claims

1. A co-extruded tipped filament having a skin-core structure coated with silicone oil on the surface, wherein the core layer comprises polybutylene terephthalate (PBT) and optionally additives, the skin layer comprises polytrimethylene terephthalate (PTT) and optionally additives, and at least one end of the monofilament is chemically treated to be tipped, characterized in that, The ratio of the sheath layer thickness to the filament diameter of the co-extruded abrasive filament having a sheath-core structure is in the range of 3-20%, preferably in the range of 5-15%.

2. The co-extruded abrasive filament according to claim 1, wherein the filament diameter of the co-extruded abrasive filament having a sheath-core structure is in the range of 0.1-0.5 mm, preferably 0.1-0.25 mm.

3. The co-extruded abrasive filament according to any one of claims 1 or 2, wherein the co-extruded filament having a sheath-core structure is obtained by melt co-extrusion of the produced core layer and the produced sheath layer.

4. The co-extruded abrasive filament according to any one of claims 1 or 2, wherein the silicone oil coated on the surface of the abrasive filament having a sheath-core structure is a food grade silicone oil; the food grade silicone oil includes methyl silicone oil, amino silicone oil, phenyl silicone oil, etc.

5. The co-extruded abrasive filament according to any one of claims 1 or 2, wherein the additives in the sheath layer and / or the core layer include antioxidants, light stabilizers, lubricants, fillers.

6. A method for preparing the co-extruded abrasive filament having a sheath-core structure according to any one of claims 1-5, comprising the following steps: a. melt co-extruding a co-extruded filament having a sheath-core structure with a PBT core layer and a PTT sheath layer; b. chemically abrading the co-extruded filament having a sheath-core structure produced in step a; c. cleaning and drying the obtained abrasive filament; d. surface coating the chemically abraded filament with silicone oil; e. optionally performing further post-treatment to obtain the final product.

7. The method of claim 6, wherein the chemical sharpening process comprises the steps of: The end face of the coiled filament having a sheath-core structure produced according to the method of claim 6 is immersed in a strong alkali solution with the end face downward, and / or the end face of the coiled filament having a sheath-core structure produced according to the method of claim 6 is placed horizontally so as to be completely immersed in the strong alkali solution.

8. The method according to claim 7, wherein the strong alkali solution is a sodium hydroxide or potassium hydroxide solution, preferably a sodium hydroxide solution.

9. A brush obtained from the co-extruded abrasive filament according to any one of the preceding claims 1 to 5, or obtained from the co-extruded abrasive filament prepared by the method according to any one of claims 6 to 8.

10. The brush of claim 9, wherein, The brush is a toothbrush.

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