A flexible, lodging-resistant pbt toothbrush filament and method of making same

Abstract

The present application relates to a drawing process of polybutylene terephthalate (PBT) material, and particularly relates to a flexible and lodging-resistant PBT toothbrush filament and a preparation method thereof, which comprises the following steps: heating and melting polybutylene terephthalate material particles after drying treatment and vacuum packaging in a screw extruder to obtain molten polybutylene terephthalate; filtering through a melt filtration system; extruding through a spinneret of the screw extruder to form viscous flow state primary fibers; introducing the primary fibers into a cooling water bath to obtain viscoelastic state primary fiber filaments; and performing a series of high-drawing processing on the primary fiber filaments so that macromolecular chains are fully ordered to become glassy PBT toothbrush filaments. During the process, the production process is designed to control the breaking strength, breaking strength variation coefficient, breaking elongation, breaking elongation variation coefficient, filament bending recovery rate and the like of the filaments, so as to obtain a flexible and lodging-resistant PBT toothbrush filament and a preparation method thereof.

Description

Technical Field

[0001] This invention relates to the field of polybutylene terephthalate (PBT) filament drawing technology, specifically to a flexible, anti-collapse PBT toothbrush bristle and its preparation method. Background Technology

[0002] Toothbrushes are indispensable tools for oral hygiene and dental health in daily life, and can be divided into electric toothbrushes, manual toothbrushes, and children's toothbrushes. Electric toothbrushes primarily use rounded nylon bristles, which are mechanically rounded on the cross-section, resulting in bristles of equal thickness at both ends, emphasizing strong cleaning power. Manual and children's toothbrushes mostly use PBT tapered bristles. Due to their polyester properties, the bristles can be chemically tapered, resulting in a thicker lower section and a conical tip, emphasizing softness and comfort, and effectively cleaning between teeth. The quality of a toothbrush depends heavily on the quality of its bristles. Currently, a prominent problem facing the domestic industry is how to solve the problem of bristle flattening, commonly known as "frizzing" or "bristle collapse." Bristles that are too soft and not firm, or too hard and not resilient, have poor cleaning ability, easily damage gums, affect lifespan, and cause discomfort. Domestic toothbrush manufacturers often encounter customers specifying imported well-known brand bristles, but the price difference is several times, and delivery time cannot be guaranteed. Against this backdrop, the development of a flexible and anti-collapse PBT toothbrush bristle has always been a goal pursued by the domestic industry. Summary of the Invention

[0003] The purpose of this invention is to obtain a flexible and anti-collapse PBT toothbrush bristle and its preparation method by designing and controlling the breaking strength, coefficient of variation of breaking strength, elongation at break, coefficient of variation of elongation at break, and bending recovery rate of the single filament through the design of the entire bristle drawing process. To achieve the above objective, this invention provides the following technical solution:

[0004] A method for preparing flexible, anti-collapse PBT toothbrush bristles includes the following steps:

[0005] S1: The dried and vacuum-packed PBT granules are fed into an extruder and heated to melt, resulting in molten polybutylene terephthalate. The set temperatures of each zone of the screw extruder from front to back are 240±2℃, 250±2℃, 260±2℃, 270±2℃, 275±2℃, 280±2℃, and 280±2℃; the melt pressure is 110±0.1 bar.

[0006] S2: The molten polybutylene terephthalate is filtered through a melt filtration system; the filtered molten polybutylene terephthalate is extruded through a screw extruder and spinneret to form viscous nascent fibers; the nascent fibers are introduced into a cooling water bath for cooling at a temperature of 20±0.1℃.

[0007] S3: The cooled nascent fiber monofilaments are drawn to make the macromolecular chains fully and orderly arranged to become glassy PBT toothbrush filaments; the total drawing ratio is 4.5-5.5 times, the temperature of the feed drawing roller is 50±0.1℃, and the temperature of the output drawing roller is 80±0.1℃.

[0008] S4: After stretching, the following steps are performed in sequence: winding, hardening, and sharpening.

[0009] The industry practice for setting the temperatures of the different zones within a screw extruder is to sequentially set them as follows: 270±2℃, 275±2℃, 280±2℃, 285±2℃, 285±2℃, 275±2℃, and 270±2℃. Products obtained this way typically exhibit high tensile strength, high elongation at break, and high coefficients of variation for both tensile strength and elongation at break, resulting in poor resistance to lodging. In this application, lowering the temperatures of the first three zones of the screw extruder significantly reduces the coefficients of variation for tensile strength and elongation at break of the PBT toothbrush filaments. Whether these tensile strength and elongation at break indicators are reasonable can be determined by lowering or raising the temperatures of the last four zones of the screw extruder. If it is necessary to increase the tensile strength of a single filament and decrease its elongation at break, this can be achieved by gradually lowering the temperatures of the last four zones of the screw extruder.

[0010] The industry practice for setting the melt pressure within a screw extruder is generally to set it to 80±0.5 bar, which typically results in products with high yarn unevenness. In this application, the melt pressure is set to 110±0.1 bar; this setting, which increases the pressure and maintains it at a relatively stable level, can significantly reduce the yarn unevenness of PBT toothbrush filaments.

[0011] The industry practice for cooling bath temperature is generally to set it to 50±1℃, which typically results in products with high elongation at break and low tensile strength. In this application, the cooling temperature is set to 20±0.1℃; this setting of lowering the temperature while maintaining a basically stable temperature is beneficial for the pre-crystallization of PBT toothbrush bristles and the smooth progress of subsequent drawing, which helps to improve tensile strength and reduce elongation at break.

[0012] Regarding drawing temperature, the industry practice is to set the feed drawing roll temperature to 90±0.1℃, the output drawing roll temperature to 130±0.1℃, and the draw ratio to 3.8-4.5. Products obtained this way typically have high elongation at break and low breaking strength. In this application, the feed drawing roll temperature is 50±0.1℃, the output drawing roll temperature is 80±0.1℃, and the draw ratio is 4.5-5.5. Both the feed and output drawing rolls consist of seven rolls. If the temperature is uneven among the seven rolls or uneven within a single drawing roll, it will lead to uneven and discontinuous macromolecular crystallinity between monofilaments, resulting in high coefficients of variation for breaking strength and elongation at break. This application improves the resilience of the monofilament by using low-temperature drawing and reduces the elongation at break with a relatively high draw ratio, thereby improving the breaking strength and toughness of the monofilament.

[0013] Preferably, the temperature of the constant temperature chamber of the stretching machine is 60±0.1℃.

[0014] The industry standard for constant temperature chambers is 120±0.1℃; in this application, the temperature is 60±0.1℃, which is beneficial for improving the resilience and toughness of the monofilaments. The temperature difference between the transverse and longitudinal directions within the constant temperature chamber also leads to uneven and discontinuous molecular crystallinity between monofilaments, resulting in high coefficients of variation in breaking strength and elongation at break.

[0015] Preferably, a drying system is used to dry the PBT particles to achieve a moisture content of 30 ppm.

[0016] Preferably, the screw of the screw extruder has a length-to-diameter ratio of 30:1 and a rotational speed of 150-250 rpm.

[0017] Preferably, the nascent fibers after cooling need to undergo dehumidification treatment before entering the drawing machine.

[0018] Another object of the present invention is to provide a PBT toothbrush bristle prepared by the above-described preparation method.

[0019] Preferably, the diameter of the PBT toothbrush bristles is 0.07-0.80 mm.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: by reducing the temperature of the first three zones of the screw extruder and increasing the draw ratio, the coefficient of variation of the breaking strength and the coefficient of variation of the breaking elongation of PBT toothbrush filaments are reduced; the resilience of the monofilaments is improved by low-temperature drawing; the uniformity and continuity of the crystallinity between monofilament molecules is improved by reducing the drawing temperature; the unevenness of the PBT toothbrush filaments is reduced by increasing the melt pressure; and the crystallinity of the PBT toothbrush filaments and the smoothness of subsequent drawing are improved by reducing the cooling bath temperature. In summary, the anti-collapse performance of PBT toothbrush filaments is improved by comprehensively optimizing the above process parameters. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1

[0023] A method for preparing flexible and anti-collapse PBT toothbrush bristles includes the following steps:

[0024] S1: The dried and vacuum-packed PBT granules are fed into an extruder and heated to melt, resulting in molten polybutylene terephthalate (PET). The set temperatures of each zone of the screw extruder, from front to back, are 240℃, 250℃, 260℃, 270℃, 275℃, 280℃, and 280℃; the melt pressure is 110 bar; the temperature tolerance is ±2℃, and the melt pressure tolerance is ±0.1 bar; a drying system is used to dry the PBT granules to achieve a moisture content of 30 ppm; the screw length-to-diameter ratio of the screw extruder is 30:1, and the rotational speed is 150-250 rpm.

[0025] S2: The molten polybutylene terephthalate is filtered through a melt filtration system; the filtered molten polybutylene terephthalate is extruded through a screw extruder and spinneret to form viscous nascent fibers; the nascent fibers are introduced into a cooling water bath to obtain viscoelastic nascent fiber monofilaments; after the melt is extruded into nascent fibers through a spinneret assembly, it enters a cooling bath system for cooling at a temperature of 20°C with a temperature tolerance of ±0.1°C;

[0026] S3: The nascent polybutylene terephthalate (PBT) fiber monofilaments undergo a series of high-ratio drawing processes to ensure the macromolecular chains are fully and orderly arranged to form glassy PBT toothbrush filaments. This includes: treating the cooled nascent fibers with a dehumidification system, and then processing them into fine filaments with a diameter of 0.08 mm using a drawing machine; wherein the total drawing ratio is 5.0-5.5 times, the temperature of the feed drawing roller is 50℃, the temperature of the output drawing roller is 80℃, and the temperature of the constant temperature chamber is 60℃, with a temperature tolerance of ±0.1℃; both the feed and output drawing rollers consist of seven rollers. If the temperature is uneven among the seven rollers or uneven in different zones of a certain drawing roller, it will lead to uneven and discontinuous macromolecular crystallinity between the monofilaments. If there is a temperature difference in the transverse and longitudinal directions inside the constant temperature chamber, it will also lead to uneven molecular crystallinity between the monofilaments.

[0027] S4: After traction is completed, the winding, hardening and sharpening are carried out in sequence to obtain the product.

[0028] Comparative Example 1

[0029] A method for preparing PBT toothbrush bristles includes the following steps:

[0030] S1: The dried and vacuum-packed PBT granules are fed into an extruder and heated to melt, resulting in molten polybutylene terephthalate (PET). The set temperatures of each zone of the screw extruder, from front to back, are 265℃, 275℃, 280℃, 285℃, 285℃, 275℃, and 270℃; the melt pressure is 110 bar; the temperature tolerance is ±2℃, and the melt pressure tolerance is ±0.1 bar; a drying system is used to dry the PBT granules to achieve a moisture content of 30 ppm; the screw length-to-diameter ratio of the screw extruder is 30:1, and the rotation speed is 150-250 rpm.

[0031] S2: The molten polybutylene terephthalate is filtered through a melt filtration system; the filtered molten polybutylene terephthalate is extruded through a screw extruder and spinneret to form viscous nascent fibers; the nascent fibers are introduced into a cooling water bath to obtain viscoelastic nascent fiber monofilaments; after the melt is extruded into nascent fibers through a spinneret assembly, it enters a cooling bath system for cooling at a temperature of 20°C with a temperature tolerance of ±0.1°C;

[0032] S3: The nascent polybutylene terephthalate (PBT) fiber monofilaments undergo a series of high-ratio drawing processes to ensure the macromolecular chains are fully and orderly arranged to form glassy PBT toothbrush filaments. This includes: treating the cooled nascent fibers with a dehumidification system, and then processing them into fine filaments with a diameter of 0.08 mm using a drawing machine; wherein the total drawing ratio is 5.0-5.5 times, the temperature of the feed drawing roller is 50℃, the temperature of the output drawing roller is 80℃, and the temperature of the constant temperature chamber is 60℃, with a temperature tolerance of ±0.1℃; both the feed and output drawing rollers consist of seven rollers. If the temperature is uneven among the seven rollers or uneven in different zones of a certain drawing roller, it will lead to uneven and discontinuous macromolecular crystallinity between the monofilaments. If there is a temperature difference in the transverse and longitudinal directions inside the constant temperature chamber, it will also lead to uneven molecular crystallinity between the monofilaments.

[0033] S4: After traction is completed, the winding, hardening and sharpening are carried out in sequence to obtain the product.

[0034] Comparative Example 2

[0035] A method for preparing PBT toothbrush bristles includes the following steps:

[0036] S1: The dried and vacuum-packed PBT granules are fed into an extruder and heated to melt, resulting in molten polybutylene terephthalate (PET). The set temperatures of each zone of the screw extruder, from front to back, are 240℃, 250℃, 260℃, 270℃, 275℃, 280℃, and 280℃; the melt pressure is 80 bar; the temperature tolerance is ±2℃, and the melt pressure tolerance is ±0.1 bar; a drying system is used to dry the PBT granules to achieve a moisture content of 30 ppm; the screw length-to-diameter ratio of the screw extruder is 30:1, and the rotational speed is 150-250 rpm.

[0037] S2: The molten polybutylene terephthalate is filtered through a melt filtration system; the filtered molten polybutylene terephthalate is extruded through a screw extruder and spinneret to form viscous nascent fibers; the nascent fibers are introduced into a cooling water bath to obtain viscoelastic nascent fiber monofilaments; after the melt is extruded into nascent fibers through a spinneret assembly, it enters a cooling bath system for cooling at a temperature of 20°C with a temperature tolerance of ±0.1°C;

[0038] S3: The nascent polybutylene terephthalate (PBT) fiber monofilaments undergo a series of high-ratio drawing processes to ensure the macromolecular chains are fully and orderly arranged to form glassy PBT toothbrush filaments. This includes: treating the cooled nascent fibers with a dehumidification system, and then processing them into fine filaments with a diameter of 0.08 mm using a drawing machine; wherein the total drawing ratio is 5.0-5.5 times, the temperature of the feed drawing roller is 50℃, the temperature of the output drawing roller is 80℃, and the temperature of the constant temperature chamber is 60℃, with a temperature tolerance of ±0.1℃; both the feed and output drawing rollers consist of seven rollers. If the temperature is uneven among the seven rollers or uneven in different zones of a certain drawing roller, it will lead to uneven and discontinuous macromolecular crystallinity between the monofilaments. If there is a temperature difference in the transverse and longitudinal directions inside the constant temperature chamber, it will also lead to uneven molecular crystallinity between the monofilaments.

[0039] S4: After traction is completed, the winding, hardening and sharpening are carried out in sequence to obtain the product.

[0040] Comparative Example 3

[0041] A method for preparing PBT toothbrush bristles includes the following steps:

[0042] S1: The dried and vacuum-packed PBT granules are fed into an extruder and heated to melt, resulting in molten polybutylene terephthalate (PET). The set temperatures of each zone of the screw extruder, from front to back, are 240℃, 250℃, 260℃, 270℃, 275℃, 280℃, and 280℃; the melt pressure is 110 bar; the temperature tolerance is ±2℃, and the melt pressure tolerance is ±0.1 bar; a drying system is used to dry the PBT granules to achieve a moisture content of 30 ppm; the screw length-to-diameter ratio of the screw extruder is 30:1, and the rotational speed is 150-250 rpm.

[0043] S2: The molten polybutylene terephthalate is filtered through a melt filtration system; the filtered molten polybutylene terephthalate is extruded through a screw extruder and spinneret to form viscous nascent fibers; the nascent fibers are introduced into a cooling water bath to obtain viscoelastic nascent fiber monofilaments; after the melt is extruded into nascent fibers through a spinneret assembly, it enters a cooling bath system for cooling at a temperature of 50°C with a temperature tolerance of ±0.1°C;

[0044] S3: The nascent polybutylene terephthalate (PBT) fiber monofilaments undergo a series of high-ratio drawing processes to ensure the macromolecular chains are fully and orderly arranged to form glassy PBT toothbrush filaments. This includes: treating the cooled nascent fibers with a dehumidification system, and then processing them into fine filaments with a diameter of 0.08 mm using a drawing machine; wherein the total drawing ratio is 5.0-5.5 times, the temperature of the feed drawing roller is 50℃, the temperature of the output drawing roller is 80℃, and the temperature of the constant temperature chamber is 60℃, with a temperature tolerance of ±0.1℃; both the feed and output drawing rollers consist of seven rollers. If the temperature is uneven among the seven rollers or uneven in different zones of a certain drawing roller, it will lead to uneven and discontinuous macromolecular crystallinity between the monofilaments. If there is a temperature difference in the transverse and longitudinal directions inside the constant temperature chamber, it will also lead to uneven molecular crystallinity between the monofilaments.

[0045] S4: After traction is completed, the winding, hardening and sharpening are carried out in sequence to obtain the product.

[0046] Comparative Example 4

[0047] A method for preparing PBT toothbrush bristles includes the following steps:

[0048] S1: The dried and vacuum-packed PBT granules are fed into an extruder and heated to melt, resulting in molten polybutylene terephthalate (PET). The set temperatures of each zone of the screw extruder, from front to back, are 240℃, 250℃, 260℃, 270℃, 275℃, 280℃, and 280℃; the melt pressure is 110 bar; the temperature tolerance is ±2℃, and the melt pressure tolerance is ±0.1 bar; a drying system is used to dry the PBT granules to achieve a moisture content of 30 ppm; the screw length-to-diameter ratio of the screw extruder is 30:1, and the rotational speed is 150-250 rpm.

[0049] S2: The molten polybutylene terephthalate is filtered through a melt filtration system; the filtered molten polybutylene terephthalate is extruded through a screw extruder and spinneret to form viscous nascent fibers; the nascent fibers are introduced into a cooling water bath to obtain viscoelastic nascent fiber monofilaments; after the melt is extruded into nascent fibers through a spinneret assembly, it enters a cooling bath system for cooling at a temperature of 20°C with a temperature tolerance of ±0.1°C;

[0050] S3: The nascent polybutylene terephthalate (PBT) fiber monofilaments undergo a series of high-ratio drawing processes to ensure the macromolecular chains are fully and orderly arranged, forming glassy PBT toothbrush filaments. This includes: the cooled nascent fibers are treated with a dehumidification system and then processed into fine filaments with a diameter of 0.08 mm using a drawing machine; wherein the total drawing ratio is 3.8-4.0 times, the feed drawing roller temperature is 90℃, the output drawing roller temperature is 130℃, and the constant temperature chamber temperature is 120℃, with a temperature tolerance of ±0.1℃; both the feed and output drawing rollers consist of seven rollers. If the temperature is uneven among the seven rollers or uneven in different zones of a certain drawing roller, it will lead to uneven and discontinuous macromolecular crystallinity between the monofilaments. If there is a temperature difference in the transverse and longitudinal directions inside the constant temperature chamber, it will also lead to uneven molecular crystallinity between the monofilaments.

[0051] S4: After traction is completed, the winding, hardening and sharpening are carried out in sequence to obtain the product.

[0052] Comparative Example 5

[0053] A method for preparing PBT toothbrush bristles includes the following steps:

[0054] S1: The dried and vacuum-packed PBT granules are fed into an extruder and heated to melt, resulting in molten polybutylene terephthalate (PET). The set temperatures of each zone of the screw extruder, from front to back, are 265℃, 275℃, 280℃, 285℃, 285℃, 275℃, and 270℃; the melt pressure is 80 bar; the temperature tolerance is ±2℃, and the melt pressure tolerance is ±0.1 bar; a drying system is used to dry the PBT granules to achieve a moisture content of 30 ppm; the screw length-to-diameter ratio of the screw extruder is 30:1, and the rotation speed is 150-250 rpm.

[0055] S2: The molten polybutylene terephthalate is filtered through a melt filtration system; the filtered molten polybutylene terephthalate is extruded through a screw extruder and spinneret to form viscous nascent fibers; the nascent fibers are introduced into a cooling water bath to obtain viscoelastic nascent fiber monofilaments; after the melt is extruded into nascent fibers through a spinneret assembly, it enters a cooling bath system for cooling at a temperature of 50°C with a temperature tolerance of ±0.1°C;

[0056] S3: The nascent polybutylene terephthalate (PBT) fiber monofilaments undergo a series of high-ratio drawing processes to ensure the macromolecular chains are fully and orderly arranged, forming glassy PBT toothbrush filaments. This includes: the cooled nascent fibers are treated with a dehumidification system and then processed into fine filaments with a diameter of 0.08 mm using a drawing machine; wherein the total drawing ratio is 3.8-4.0 times, the feed drawing roller temperature is 90℃, the output drawing roller temperature is 130℃, and the constant temperature chamber temperature is 120℃, with a temperature tolerance of ±0.1℃; both the feed and output drawing rollers consist of seven rollers. If the temperature is uneven among the seven rollers or uneven in different zones of a certain drawing roller, it will lead to uneven and discontinuous macromolecular crystallinity between the monofilaments. If there is a temperature difference in the transverse and longitudinal directions inside the constant temperature chamber, it will also lead to uneven molecular crystallinity between the monofilaments.

[0057] S4: After traction is completed, the winding, hardening and sharpening are carried out in sequence to obtain the product.

[0058] The difference between Comparative Example 1 and Example 1 is that the set temperature of the first five zones of the screw extruder is increased and the set temperature of the last two zones is decreased.

[0059] The difference between Comparative Example 2 and Example 1 is that the melt pressure inside the screw extruder is reduced.

[0060] The difference between Comparative Example 3 and Example 1 is that the cooling temperature of the nascent fibers in the cooling bath system is increased.

[0061] The difference between Comparative Example 4 and Example 1 is that the temperature of the feed drafting roller is increased, the temperature of the output drafting roller is increased, the temperature of the constant temperature chamber is increased, and the drafting ratio is decreased.

[0062] The difference between Comparative Example 5 and Example 1 is that the set temperature of the first five zones of the screw extruder is increased and the set temperature of the last two zones is decreased, the melt pressure inside the screw extruder is decreased, the cooling temperature of the cooling bath system on the nascent fibers is increased, the temperature of the feed drafting roller is increased, the temperature of the output drafting roller is increased, the temperature of the constant temperature chamber is increased, and the drafting ratio is decreased.

[0063] To characterize the anti-collapse performance of the PBT toothbrush bristles prepared in the above embodiments and comparative examples, the bristles were fabricated into standard toothbrushes and tested with a 335g weight. The testing speed was 13mm / s, and the testing time was 24 hours. The anti-collapse effect of the bristles was determined based on the proportion of collapsed bristles. The evaluation criteria were: no collapse: 0-30%; slight collapse: 30-50%; collapse: 50-70%; significant collapse: 70-90%; complete collapse: 100%. The test results of the anti-collapse performance of the PBT toothbrush bristles prepared in each example are as follows:

[0064] Table 1. Test results of the anti-collapse performance of PBT toothbrush bristles

[0065] Group Lodging resistance Example 1 No lodging Comparative Example 1 lodging Comparative Example 2 Slight lodging Comparative Example 3 Slight lodging Comparative Example 4 lodging Comparative Example 5 Obvious lodging

[0066] To characterize the breaking properties of the PBT toothbrush filaments prepared in the above embodiments and comparative examples, the breaking strength and elongation at break of the PBT toothbrush filaments prepared in each example were tested according to the FZ / T 54064-2012 polyester monofilament industry standard, and the spinning draw properties were evaluated. The following test results were obtained:

[0067] Table 2. Test results of the breaking properties and spinning draw properties of PBT toothbrush bristles.

[0068]

[0069]

[0070] As shown in Tables 1 and 2, the process method of this application for producing PBT toothbrush bristles can not only maintain their breaking strength and elongation at break without significant reduction, but also significantly improve their anti-loosening properties and facilitate spinning and drawing.

[0071] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing flexible, anti-collapse PBT toothbrush bristles, characterized in that... It includes the following steps: S1: The dried and vacuum-packed PBT granules are fed into a screw extruder and heated to melt, resulting in molten polybutylene terephthalate. The set temperatures of each zone of the screw extruder from front to back are 240±2℃, 250±2℃, 260±2℃, 270±2℃, 275±2℃, 280±2℃, and 280±2℃; the melt pressure is 110±0.1 bar. S2: The molten polybutylene terephthalate is filtered through a melt filtration system; the filtered molten polybutylene terephthalate is extruded through a screw extruder and spinneret to form viscous nascent fibers; the nascent fibers are then introduced into a cooling water bath for cooling at a temperature of 20±0.1℃. S3: The cooled nascent fiber monofilaments are drawn to make the macromolecular chains fully and orderly arranged to become glassy PBT toothbrush filaments; the total drawing ratio is 4.5-5.5 times, the temperature of the feed drawing roller is 50±0.1℃, and the temperature of the output drawing roller is 80±0.1℃. S4: After drawing, the product is obtained by winding, hardening, and sharpening in sequence; the temperature of the constant temperature chamber of the drawing machine is 60±0.1℃; the PBT particles are dried by a drying system to achieve a moisture content of 30PPm; the screw length-to-diameter ratio of the screw extruder is 30:1, and the speed is 150-250rpm; the nascent fibers after cooling need to be dehumidified before entering the drawing machine.

2. A flexible and anti-collapse PBT toothbrush bristle, characterized in that, It is prepared by the method described in claim 1.

3. The PBT toothbrush bristles as described in claim 2, characterized in that, The diameter of the PBT toothbrush bristles is 0.08-1.0 mm.

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