Polypropylene monofilament with low boiling water shrinkage and method for producing the same

Abstract

This invention provides a polypropylene monofilament with low boiling water shrinkage and its preparation method, relating to the field of polypropylene monofilament technology. Based on a polypropylene monofilament with low boiling water shrinkage, the polypropylene monofilament comprises the following percentage raw materials: 89%–95% polypropylene resin, 4%–10% cyclic olefin copolymer, and 1%–2% inorganic powder; the preparation method of the polypropylene monofilament includes the following steps: S1. preparing a polypropylene monofilament melt, S2. spinning, S3. water bath cooling and crystallization, S4. oven heating and stretching, S5. heat setting and winding. A lower-temperature polypropylene spinning melt is obtained by connecting a first extruder and a second extruder in series. The nascent polypropylene filament is directly cooled and crystallized in a water bath, greatly shortening the stretching process and improving product quality stability. The polypropylene monofilament undergoes a high degree of crystallization in the water bath, exhibiting good temperature resistance and resistance to deformation, improving the spinning stability of subsequent stretching processes, and resulting in a monofilament with high roundness.

Description

Technical Field

[0001] This invention relates to the field of polypropylene monofilament technology, specifically to a polypropylene monofilament with low boiling water shrinkage and its preparation method. Background Technology

[0002] Polypropylene monofilament has advantages such as light weight, resistance to acid and alkali corrosion, and high strength. Its application in fields such as filter cloth for liquid-solid separation, trampoline cloth, geotextile, and civil grid is becoming increasingly widespread. In addition, polypropylene has advantages such as good hydrophobicity and long-lasting charge, making it an important fiber for masks and air purification filters. With the continuous expansion of my country's polyolefin production capacity, the development of functional polypropylene products is of great significance. Monofilament is a relatively coarse synthetic fiber with a diameter of generally 0.05-1mm. Currently, polypropylene monofilament, nylon monofilament, and PTFE monofilament are the main types.

[0003] The invention patent application CN02810061.1 proposes a method to improve the boiling water shrinkage rate of polypropylene fibers by adding a nucleating agent to polypropylene resin, and gives dibenzylidene sorbitol-based compounds as preferred nucleating agents. This provides a new approach to improve the strength of polypropylene fibers and reduce the boiling water shrinkage rate by adding nucleating agents. However, the application of this nucleating agent in the production of polypropylene monofilaments is not widespread at present.

[0004] To improve the strength and dimensional stability of polypropylene monofilament, a method for preparing polypropylene monofilament (patent application number CN201910232558.5) proposes a process technology of blending polypropylene resin with titanium dioxide masterbatch and then spinning it. The melt is extruded from the spinneret and then sequentially enters a water tank and an oven for cooling and stretching. The resulting polypropylene monofilament has a strength of 5.8-6.3 cN / dtex and an elongation at break of 6%-9%, which is suitable for roadbed construction. However, this invention does not address the issue of dimensional stability of polypropylene monofilament shrinkage in hot water.

[0005] This master's thesis, titled "Study on the Structure and Properties of Polypropylene / Nano-Montmorillonite Blended Monofilaments," systematically investigated the role of montmorillonite nucleating agents and the influence of spinning processes such as spinning temperature, water bath temperature, primary stretching hot water temperature, and secondary hot air stretching temperature on the structure and properties of the resulting polypropylene fibers. The study found that water bath and hot water temperatures are key processes affecting the properties and spinning stability of the resulting fibers, and parameter optimization was performed. The optimal process parameters were identified as 25℃ for the water bath and 93℃ for the primary hot water. This implies that the nascent polypropylene filament needs to be cooled before heating. For most manufacturers, maintaining a water bath temperature of 25℃ year-round is difficult, resulting in significant fluctuations in monofilament quality.

[0006] Currently, most of the equipment used in my country for spinning polypropylene monofilament is the two-step water bath method, namely: chip mixing → melt extrusion → metering spinneret → water bath cooling → steam heating and stretching → oven heating and stretching → heat setting → winding. This equipment occupies a large area, the monofilament quality fluctuates greatly, and the boiling water shrinkage rate is high. When used as filter cloth for hot water solid-liquid separation, it is prone to deformation and frequent replacement, which increases the cost for downstream users. Summary of the Invention

[0007] (a) Technical problems to be solved

[0008] To address the shortcomings of existing technologies, this invention provides a polypropylene monofilament with low boiling water shrinkage and its preparation method, which solves the problems of large equipment footprint, large fluctuations in monofilament quality, high boiling water shrinkage, easy deformation and frequent replacement when used as a filter cloth for hot water solid-liquid separation, thus increasing the cost for downstream users.

[0009] (II) Technical Solution

[0010] To achieve the above objectives, the present invention is implemented through the following technical solution: a polypropylene monofilament with low boiling water shrinkage rate, wherein the polypropylene monofilament comprises the following percentage raw materials: 89% to 95% polypropylene resin, 4% to 10% cyclic olefin copolymer and 1% to 2% inorganic powder;

[0011] The method for preparing the polypropylene monofilament includes the following steps:

[0012] S1. Melt for preparing polypropylene monofilament

[0013] First, the first extruder and the second extruder are connected in series. Then, inorganic powder, cyclic olefin copolymer and polypropylene resin are fed into the first extruder through a hopper at a mass ratio of (1.0-2.0):(4-10):(89.0-95.0) and heated until the materials reach a molten state. The polymer melt then enters the second extruder through a melt filter. The polymer melt extruded from the first extruder enters the second extruder at a lower temperature, resulting in a spinning melt with a lower spinning temperature than conventional polypropylene monofilament spinning.

[0014] S2. Made into spinning yarn

[0015] After cooling, the spinning melt passes through a static mixer and a melt metering pump and enters the spinneret assembly for spinning. The spinning melt is extruded from the spinneret assembly's spinneret holes to obtain nascent fiber filaments.

[0016] S3. Water bath cooling crystallization

[0017] The nascent fibers obtained above first pass through an air gap of a certain distance before entering a water bath for cooling.

[0018] S4. Oven heating and stretching

[0019] After cooling, the nascent fiber filaments are drawn into the drying oven by the first and second traction roller groups for heating and stretching. The nascent fiber filaments undergo crystallization and orientation at the same time to obtain polypropylene monofilament semi-finished products.

[0020] S5. Heat setting and winding

[0021] The semi-finished polypropylene monofilament, after being heated in the oven, is fed into the heat-setting zone by the third traction roller for heat-setting treatment, thereby obtaining polypropylene monofilament. The heat-set polypropylene monofilament is then fed into the winding zone for winding.

[0022] In step S1, the first extruder is a single-screw extruder, the second extruder is a counter-rotating twin-screw extruder, and a melt filter is configured between the first extruder and the second extruder.

[0023] The inorganic powder is any one or a combination of several of the following: tourmaline, perlite, barium titanate ceramic powder, and perovskite structural materials.

[0024] The cyclic olefin copolymer is a copolymer formed by the addition polymerization of cyclic olefin monomers with a glass transition temperature of 120-160°C and ethylene monomers.

[0025] In step S1, the first extruder is divided into five temperature zones: the first zone temperature is 150℃~160℃, the second zone temperature is 170℃~180℃, the third zone temperature is 190℃~200℃, the fourth zone temperature is 230℃~240℃, and the fifth zone temperature is 230℃~240℃, with the temperature increasing in increments.

[0026] The second extruder is divided into five temperature zones: the first zone is 220℃~230℃, the second zone is 210℃~220℃, the third zone is 200℃~210℃, the fourth zone is 190℃~200℃, and the fifth zone is 185℃~190℃, with the temperature decreasing in that order.

[0027] In step S2, the temperature of the spinneret assembly is 185℃~190℃, and a static mixer and a melt metering pump are configured in front of it.

[0028] In step S3, the air gap length is 8–15 cm and the water bath temperature is 65°C–90°C.

[0029] In step S4, there are a total of three sets of traction rollers. The first set of traction rollers runs at a speed of 20m / min to 35m / min, the second set of traction rollers runs at a speed of 30m / min to 55m / min, and the third set of traction rollers runs at a speed of 60m / min to 110m / min.

[0030] In step S4, the oven temperature is 135℃~140℃.

[0031] (III) Beneficial Effects

[0032] This invention provides a polypropylene monofilament with low boiling water shrinkage and its preparation method. It has the following beneficial effects:

[0033] 1. This invention solves the shortcomings of the conventional polypropylene monofilament spinning process, which involves two stages of water bath cooling followed by hot water heating. By connecting the first and second extruders in series, a lower temperature polypropylene spinning melt is obtained. The single-stage water bath allows the nascent polypropylene filament to be directly cooled and crystallized in the water bath, greatly shortening the drawing process and improving the stability of product quality.

[0034] 2. Polypropylene monofilaments have undergone a high degree of crystallization in the water bath, and the cyclic olefin copolymer with a high glass transition temperature has been cooled and solidified. Therefore, the monofilaments cannot be deformed when they are drawn out of the water bath, which improves the spinning stability of the subsequent drawing process and results in monofilaments with high roundness.

[0035] 3. This invention improves the crystallinity and temperature resistance of polypropylene monofilament by adding inorganic powder and a high glass transition temperature cyclic olefin copolymer to polypropylene resin, significantly reducing the boiling water shrinkage rate of polypropylene monofilament. Polypropylene monofilament filter cloth is less prone to deformation and has a long service life when used for hot water solid-liquid separation.

[0036] 4. This invention uses dielectric and piezoelectric powder materials as inorganic powders. While improving the high-temperature dimensional stability of polypropylene monofilament (i.e., low boiling water shrinkage rate), it can also make the surface of polypropylene monofilament carry static charge. When used as a filter medium, it can play an electrostatic adsorption function, improve filtration efficiency, and reduce filtration resistance. Attached Figure Description

[0037] Figure 1 A schematic diagram of a polypropylene monofilament with low boiling water shrinkage rate according to the present invention;

[0038] Figure 2 This is a flowchart illustrating a polypropylene monofilament with low boiling water shrinkage rate according to the present invention. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] The testing methods for the relevant performance indicators in the following embodiments are as follows:

[0041] Boiling water shrinkage rate: GB / T 6505 Test method for heat shrinkage rate of chemical fiber filaments

[0042] Charge density: Polypropylene monofilaments were woven into plain weave filter cloths with warp and weft densities of 250 threads / 10cm and 150 threads / 10cm, respectively, and then their surface charge density was tested according to GB / T 12703.2—2021 Test Methods for Electrostatic Properties of Textiles Part 2: Manual Friction Method.

[0043] Average diameter and roundness: Using a flat-head thickness gauge with an accuracy of 0.001 mm, 10 polypropylene monofilaments of 1 m in length were randomly cut. The monofilaments were placed into the thickness gauge one by one, and the readings were taken while twisting the monofilaments. Five diameter values ​​were recorded at any position. Then, the average diameter Φ and the coefficient of variation (C) were calculated. V (Value); Averaging the average diameter and Cv value of 10 monofilaments yields the average diameter and average value of the monofilaments. Cv The value (in %) is rounded to 0.1. The formula for calculating the roundness D of a single filament is as follows:

[0044] D = 100 - Cv

[0045] The method for preparing polypropylene monofilament with low boiling water shrinkage provided by this invention uses, as follows: Figure 2 The equipment shown is constructed by first connecting a hopper to the feed inlet of the first extruder, connecting a melt filter to the discharge outlet of the first extruder, and connecting the discharge outlet of the melt filter to the feed inlet of the second extruder. The discharge outlet of the second extruder is sequentially connected to a static mixer, a melt metering pump, and a spinneret assembly. The monofilaments extruded through the spinneret assembly enter a water bath. The monofilaments are pulled by the first and second traction roller groups before entering the drying oven, and then pulled out of the drying oven by the third traction roller group. The monofilaments are then shaped by the heat-setting roller group and finally wound up by the take-up roller group.

[0046] Example 1:

[0047] like Figure 1-2 As shown, this embodiment of the invention provides a polypropylene monofilament based on a low boiling water shrinkage rate. The polypropylene monofilament comprises the following percentage raw materials: 89% polypropylene resin, 10% cyclic olefin copolymer and 1% perlite, and the perlite is screened using a 1250-mesh sieve.

[0048] The preparation method of polypropylene monofilament includes the following steps:

[0049] S1. Melt for preparing polypropylene monofilament

[0050] First, the first extruder and the second extruder are connected in series. Then, inorganic powder, cyclic olefin copolymer (glass transition temperature 160℃) and polypropylene resin are fed into the first extruder through a hopper at a mass ratio of (1.0%):(10%):(89.0%) and heated until the materials reach a molten state. The polymer melt then enters the second extruder through a melt filter. The polymer melt extruded from the first extruder enters the second extruder at a lower temperature, resulting in a spinning melt with a lower spinning temperature than conventional polypropylene monofilament spinning.

[0051] S2. Made into spinning yarn

[0052] After cooling, the spinning melt passes through a static mixer and a melt metering pump and enters the spinneret assembly for spinning. The spinning melt is extruded from the spinneret assembly's spinneret holes to obtain nascent fiber filaments.

[0053] S3. Water bath cooling crystallization

[0054] The nascent fibers obtained above first pass through an air gap of 8 cm in length and then enter a water bath at a temperature of 90°C for cooling.

[0055] S4. Oven heating and stretching

[0056] After cooling, the nascent fiber filaments are drawn into the drying oven by the first and second traction roller groups for heating and stretching. The nascent fiber filaments undergo crystallization and orientation at the same time to obtain polypropylene monofilament semi-finished products.

[0057] S5. Heat setting and winding

[0058] The semi-finished polypropylene monofilament, after being heated in the oven, is fed into the heat-setting zone by the third traction roller for heat-setting treatment, thereby obtaining polypropylene monofilament. The heat-set polypropylene monofilament is then fed into the winding zone for winding.

[0059] The melt filter has two layers of screens with mesh sizes of 150 mesh and 200 mesh, respectively. The static mixer is a high-temperature melt static mixer. The melt metering pump is a pulsation-free melt pump. The 6-hole circular spinneret assembly is self-made. The oven is 3.5m long.

[0060] In step S1, the first extruder is a single-screw extruder, the second extruder is a counter-rotating twin-screw extruder, and a melt filter is installed between the first extruder and the second extruder.

[0061] In step S1, the first extruder is divided into five temperature zones: the first zone temperature is 160℃, the second zone temperature is 180℃, the third zone temperature is 200℃, the fourth zone temperature is 240℃, and the fifth zone temperature is 240℃, with the temperature increasing in increments.

[0062] The second extruder is divided into five temperature zones: the first zone is 230℃, the second zone is 220℃, the third zone is 210℃, the fourth zone is 200℃, and the fifth zone is 190℃, with the temperature decreasing in that order.

[0063] like Figure 2 As shown, in step S4, the first traction roller group runs at a speed of 35 m / min, and the second traction roller group runs at a speed of 55 m / min.

[0064] In step S5, the third traction roller group runs at a speed of 110 m / min.

[0065] like Figure 2 As shown, the polypropylene monofilaments that have been heated in the oven are fed into the heat setting zone via the third traction roller group; the heat setting zone is a three-roller traction machine with temperatures of 150℃, 155℃ and 150℃ respectively, and speeds of 110m / min, 130m / min and 170m / min respectively.

[0066] like Figure 2 As shown, the oven temperature in step S4 is 135℃.

[0067] Finally, a polypropylene monofilament with low boiling water shrinkage and electrostatic charge was obtained, with a fineness of 0.2 mm, a roundness of 99%, a boiling water shrinkage of 1.0%, and a triboelectric charge surface density of 15.6 μC / m. 2 .

[0068] Example 2:

[0069] like Figure 1-2 As shown, embodiments of the present invention provide a polypropylene monofilament based on a low boiling water shrinkage rate. The polypropylene monofilament comprises the following percentage raw materials: 94.0% polypropylene resin, 4.0% cyclic olefin copolymer (glass transition temperature 120°C), and 2.0% tourmaline, and the tourmaline is screened using an 800-mesh sieve.

[0070] like Figure 1 As shown, the method for preparing polypropylene monofilament includes the following steps:

[0071] S1. Melt for preparing polypropylene monofilament

[0072] First, the first extruder and the second extruder are connected in series. Then, inorganic powder, cyclic olefin copolymer and polypropylene resin are fed into the first extruder through a hopper at a mass ratio of (2.0%):(4.0%):(94.0%) and heated until the materials reach a molten state. The polymer melt then enters the second extruder through a melt filter. The polymer melt extruded from the first extruder enters the second extruder at a lower temperature, resulting in a spinning melt with a lower spinning temperature than conventional polypropylene monofilament spinning.

[0073] S2. Made into spinning yarn

[0074] After cooling, the spinning melt passes through a static mixer and a melt metering pump and enters the spinneret assembly for spinning. The spinning melt is extruded from the spinneret assembly's spinneret holes to obtain nascent fiber filaments.

[0075] S3. Water bath cooling crystallization

[0076] The nascent fibers obtained above first pass through an air gap of 15 cm in length and then enter a water bath at a temperature of 65°C for cooling.

[0077] S4. Oven heating and stretching

[0078] After cooling, the nascent fiber filaments are drawn into the drying oven by the first and second traction roller groups for heating and stretching. At the same time, the nascent fiber filaments undergo heating, crystallization and orientation to obtain polypropylene monofilament semi-finished products.

[0079] S5. Heat setting and winding

[0080] The semi-finished polypropylene monofilament, after being heated in the oven, is fed into the heat-setting zone by the third traction roller for heat-setting treatment, thereby obtaining polypropylene monofilament. The heat-set polypropylene monofilament is then fed into the winding zone for winding.

[0081] The first extruder and the second extruder, specifically according to S1, are as follows:

[0082] a. First extruder: The first extruder is a single-screw extruder;

[0083] b. Second extruder: The second extruder is a counter-rotating twin-screw extruder.

[0084] like Figure 2 As shown, in step S1, the first extruder is a single-screw extruder, and the second extruder is a counter-rotating twin-screw extruder.

[0085] like Figure 2 As shown, in step S1, the first extruder is divided into five temperature zones: the first zone temperature is 150℃, the second zone temperature is 170℃, the third zone temperature is 190℃, the fourth zone temperature is 230℃, and the fifth zone temperature is 230℃, with the temperature increasing in increments.

[0086] The second extruder is divided into five temperature zones: the first zone is 220℃, the second zone is 210℃, the third zone is 200℃, the fourth zone is 190℃, and the fifth zone is 185℃, with the temperature decreasing in that order.

[0087] like Figure 2As shown, in step S4, there are a total of three sets of traction rollers. The first set of traction rollers runs at a speed of 30 m / min, and the second set of traction rollers runs at a speed of 55 m / min.

[0088] In step S5, the third traction roller group runs at a speed of 100 m / min.

[0089] like Figure 2 As shown, the polypropylene monofilaments that have undergone oven heating are fed into the heat setting zone via the third traction roller group; the heat setting zone is a three-roller traction machine with temperatures of 145℃, 150℃ and 150℃ respectively, and speeds of 120m / min, 130m / min and 150m / min respectively.

[0090] The oven temperature in step S4 is 135℃.

[0091] Finally, a polypropylene monofilament with low boiling water shrinkage and electrostatic charge was obtained, with a fineness of 0.4 mm, a roundness of 97%, a boiling water shrinkage of 1.7%, and a triboelectric charge surface density of 24.2 μC / m. 2 .

[0092] Example 3:

[0093] like Figure 1-2 As shown, embodiments of the present invention provide a polypropylene monofilament based on a low boiling water shrinkage rate. The polypropylene monofilament comprises the following percentage raw materials: 91.8% polypropylene resin, 7.0% cyclic olefin copolymer (glass transition temperature 160°C) and 1.2% barium titanate ceramic powder, which are then pulverized into nanoparticles.

[0094] like Figure 1 As shown, the method for preparing polypropylene monofilament includes the following steps:

[0095] S1. Melt for preparing polypropylene monofilament

[0096] First, the first extruder and the second extruder are connected in series. Then, inorganic powder, cyclic olefin copolymer and polypropylene resin are fed into the first extruder through a hopper at a mass ratio of (1.2%):(7.0%):(91.8%) and heated until the materials reach a molten state. The polymer melt then enters the second extruder through a melt filter. The polymer melt extruded from the first extruder enters the second extruder at a lower temperature, resulting in a spinning melt with a lower spinning temperature than conventional polypropylene monofilament spinning.

[0097] S2. Made into spinning yarn

[0098] After cooling, the spinning melt passes through a static mixer and a melt metering pump and enters the spinneret assembly for spinning. The spinning melt is extruded from the spinneret assembly's spinneret holes to obtain nascent fiber filaments.

[0099] S3. Water bath cooling crystallization

[0100] The nascent fibers obtained above first pass through an air gap of 10 cm in length and then enter a water bath at a temperature of 80°C for cooling.

[0101] S4. Oven heating and stretching

[0102] After cooling, the nascent fiber filaments are drawn into the drying oven by the first and second traction roller groups for heating and stretching. At the same time, the nascent fiber filaments undergo heating, crystallization and orientation to obtain polypropylene monofilament semi-finished products.

[0103] S5. Heat setting and winding

[0104] The semi-finished polypropylene monofilament, after being heated in the oven, is fed into the heat-setting zone by the third traction roller for heat-setting treatment, thereby obtaining polypropylene monofilament. The heat-set polypropylene monofilament is then fed into the winding zone for winding.

[0105] like Figure 2 As shown, in step S1, the first extruder is a single-screw extruder, and the second extruder is a counter-rotating twin-screw extruder.

[0106] like Figure 2 As shown, in step S1, the first extruder is divided into five temperature zones: the first zone temperature is 160℃, the second zone temperature is 180℃, the third zone temperature is 200℃, the fourth zone temperature is 230℃, and the fifth zone temperature is 230℃, with the temperature increasing in increments.

[0107] The second extruder is divided into five temperature zones: the first zone is 225℃, the second zone is 215℃, the third zone is 205℃, the fourth zone is 195℃, and the fifth zone is 190℃, with the temperature decreasing in that order.

[0108] like Figure 2 As shown, in step S4, there are a total of three sets of traction rollers. The first set of traction rollers runs at a speed of 20 m / min, and the second set of traction rollers runs at a speed of 30 m / min.

[0109] In step S5, the third traction roller group runs at a speed of 60 m / min.

[0110] like Figure 2 As shown, the polypropylene monofilaments that have been heated in the oven are fed into the heat setting zone by the third traction roller group; the heat setting zone is a three-roller traction machine with temperatures of 145℃, 150℃ and 150℃ respectively, and speeds of 75m / min, 95m / min and 130m / min respectively.

[0111] The oven temperature in step S4 is 140℃.

[0112] Finally, a polypropylene monofilament with low boiling water shrinkage and electrostatic charge was obtained, with a fineness of 0.5 mm, a roundness of 98%, a boiling water shrinkage of 1.2%, and a triboelectric charge surface density of 22.7 μC / m. 2 .

[0113] Example 4:

[0114] like Figure 1-2 As shown, this embodiment of the invention provides a polypropylene monofilament based on a low boiling water shrinkage rate. The polypropylene monofilament comprises the following percentage raw materials: 94% polypropylene resin, 5% cyclic olefin copolymer (glass transition temperature 120°C) and 1% perovskite structure powder material, which is then pulverized into nanoparticles.

[0115] like Figure 1 As shown, the method for preparing polypropylene monofilament includes the following steps:

[0116] S1. Melt for preparing polypropylene monofilament

[0117] First, the first extruder and the second extruder are connected in series. Then, inorganic powder, cyclic olefin copolymer and polypropylene resin are fed into the first extruder through a hopper at a mass ratio of (1.0%):(5.0%):(99.0%) and heated until the materials reach a molten state. The polymer melt then enters the second extruder through a melt filter. The polymer melt extruded from the first extruder enters the second extruder at a lower temperature, resulting in a spinning melt with a lower spinning temperature than conventional polypropylene monofilament spinning.

[0118] S2. Made into spinning yarn

[0119] After cooling, the spinning melt passes through a static mixer and a melt metering pump and enters the spinneret assembly for spinning. The spinning melt is extruded from the spinneret assembly's spinneret holes to obtain nascent fiber filaments.

[0120] S3. Water bath cooling crystallization

[0121] The nascent fibers obtained above first pass through an air gap of 12 cm in length and then enter a water bath at a temperature of 70°C for cooling.

[0122] S4. Oven heating and stretching

[0123] After cooling, the nascent fiber filaments are drawn into the drying oven by the first and second traction roller groups for heating and stretching. At the same time, the nascent fiber filaments undergo heating, crystallization and orientation to obtain polypropylene monofilament semi-finished products.

[0124] S5. Heat setting and winding

[0125] The semi-finished polypropylene monofilament, after being heated in the oven, is fed into the heat-setting zone by the third traction roller for heat-setting treatment, thereby obtaining polypropylene monofilament. The heat-set polypropylene monofilament is then fed into the winding zone for winding.

[0126] like Figure 2 As shown, in step S1, the first extruder is a single-screw extruder, and the second extruder is a counter-rotating twin-screw extruder.

[0127] like Figure 2 As shown, in step S1, the first extruder is divided into five temperature zones: the first zone temperature is 155℃, the second zone temperature is 175℃, the third zone temperature is 195℃, the fourth zone temperature is 235℃, and the fifth zone temperature is 230℃, with the temperature increasing in increments.

[0128] The second extruder is divided into five temperature zones: the first zone is 220℃, the second zone is 210℃, the third zone is 200℃, the fourth zone is 190℃, and the fifth zone is 185℃, with the temperature decreasing in that order.

[0129] like Figure 2 As shown, in step S4, there are a total of three sets of traction rollers. The first set of traction rollers runs at a speed of 30 m / min, and the second set of traction rollers runs at a speed of 55 m / min.

[0130] In step S5, the third traction roller group runs at a speed of 110 m / min.

[0131] like Figure 2 As shown, the polypropylene monofilaments that have been heated in the oven are fed into the heat setting zone via the third traction roller group; the heat setting zone is a three-roller traction machine with temperatures of 145℃, 150℃ and 150℃ respectively, and speeds of 130m / min, 150m / min and 170m / min respectively.

[0132] The oven temperature in step S4 is 135℃.

[0133] Finally, a polypropylene monofilament with low boiling water shrinkage and electrostatic charge was obtained, with a fineness of 0.3 mm, a roundness of 98%, a boiling water shrinkage of 1.7%, and a triboelectric charge surface density of 18.7 μC / m. 2 .

[0134] Example 5:

[0135] like Figure 1-2 As shown, embodiments of the present invention provide a polypropylene monofilament based on a low boiling water shrinkage rate. The polypropylene monofilament comprises the following percentage raw materials: 93% polypropylene resin, 6.0% cyclic olefin copolymer (glass transition temperature 150°C), 0.5% perovskite structure powder material, and 0.5% barium titanate ceramic powder.

[0136] like Figure 1 As shown, the method for preparing polypropylene monofilament includes the following steps:

[0137] S1. Melt for preparing polypropylene monofilament

[0138] First, the first extruder and the second extruder are connected in series. Then, perovskite structure powder, barium titanate ceramic powder, cyclic olefin copolymer (glass transition temperature 150℃) and polypropylene resin are fed into the first extruder through a hopper at a mass ratio of (0.5%):(0.5%):(6.0%):(93.0%). The materials are heated until they reach a molten state. The polymer melt is then passed through a melt filter into the second extruder. The polymer melt extruded from the first extruder enters the second extruder at a lower temperature, resulting in a spinning melt with a lower spinning temperature than conventional polypropylene monofilament spinning.

[0139] S2. Made into spinning yarn

[0140] After cooling, the spinning melt passes through a static mixer and a melt metering pump and enters the spinneret assembly for spinning. The spinning melt is extruded from the spinneret assembly's spinneret holes to obtain nascent fiber filaments.

[0141] S3. Water bath cooling crystallization

[0142] The nascent fibers obtained above first pass through an air gap of 13 cm in length and then enter a water bath at a temperature of 75°C for cooling.

[0143] S4. Oven heating and stretching

[0144] After cooling, the nascent fiber filaments are drawn into the drying oven by the first and second traction roller groups for heating and stretching. At the same time, the nascent fiber filaments undergo heating, crystallization and orientation to obtain polypropylene monofilament semi-finished products.

[0145] S5. Heat setting and winding

[0146] The semi-finished polypropylene monofilament, after being heated in the oven, is fed into the heat-setting zone by the third traction roller for heat-setting treatment, thereby obtaining polypropylene monofilament. The heat-set polypropylene monofilament is then fed into the winding zone for winding.

[0147] like Figure 2 As shown, in step S1, the first extruder is a single-screw extruder, and the second extruder is a counter-rotating twin-screw extruder.

[0148] like Figure 2 As shown, the inorganic powder is any one or a combination of several of the following: tourmaline, perlite, barium titanate ceramic powder, and perovskite structural materials.

[0149] like Figure 2As shown, in step S1, the first extruder is divided into five temperature zones: the first zone temperature is 160℃, the second zone temperature is 180℃, the third zone temperature is 190℃, the fourth zone temperature is 230℃, and the fifth zone temperature is 235℃, with the temperature increasing in that order.

[0150] The second extruder is divided into five temperature zones: the first zone is 230℃, the second zone is 220℃, the third zone is 210℃, the fourth zone is 200℃, and the fifth zone is 190℃, with the temperature decreasing in that order.

[0151] like Figure 2 As shown, in step S4, there are a total of three sets of traction rollers. The first set of traction rollers runs at a speed of 30 m / min, and the second set of traction rollers runs at a speed of 55 m / min.

[0152] In step S5, the third traction roller group runs at a speed of 110 m / min.

[0153] like Figure 2 As shown, the polypropylene monofilaments that have been heated in the oven are fed into the heat setting zone via the third traction roller group; the heat setting zone is a three-roller traction machine with temperatures of 150℃, 155℃ and 150℃ respectively, and speeds of 120m / min, 140m / min and 160m / min respectively.

[0154] The oven temperature in step S4 is 135℃.

[0155] Finally, a polypropylene monofilament with low boiling water shrinkage and electrostatic charge was obtained, with a fineness of 0.3 mm, a roundness of 99%, a boiling water shrinkage of 0.7%, and a triboelectric charge surface density of 25.1 μC / m. 2 .

[0156] In summary, by using the first and second extruders in series, a polypropylene spinning melt with uniform melt mixing and lower temperature is obtained. This reduces the requirement for the heat transfer rate of the cooling water bath and raises the temperature of the only water bath, allowing the low-temperature polypropylene nascent filament to be directly cooled and crystallized. This improves its temperature resistance and makes it less prone to deformation. Therefore, it can be directly drawn out of the water bath via the traction roller and enter the subsequent oven heating and drawing process. This invention eliminates the hot water drawing process, resulting in monofilaments with high roundness and low boiling water shrinkage, which can be used at higher temperatures.

[0157] As the melt temperature decreases, its fluidity deteriorates. However, the counter-rotating twin-screw extruder, which provides forward conveying, can force the melt forward to enter the subsequent spinning process.

[0158] A static mixer is installed after the second extruder to further improve melt uniformity and spinnability.

[0159] To improve the crystallinity and reduce the boiling water shrinkage rate of polypropylene monofilament, polypropylene resin is mixed with inorganic powder and a high glass transition temperature cyclic olefin copolymer in a certain proportion and then fed into the first extruder. After being spun into nascent fiber filaments, the filaments are cooled and crystallized in a water bath. This can greatly improve the crystallization rate and cooling and setting rate of the polypropylene monofilament, so that the polypropylene monofilament remains round and undeformed when pulled out of the water bath by the traction roller, thereby improving the roundness of the polypropylene monofilament. By optimizing the oven hot air temperature, heat setting temperature and the speed ratio of the front and rear traction rollers, polypropylene monofilament with a lower boiling water shrinkage rate is obtained.

[0160] The glass transition temperature of the cyclic olefin copolymer is 120–160℃. Rapid cooling and shaping in a water bath allows the monofilament to maintain its roundness and prevent deformation when interacting with the traction roller in the water bath, thus improving the roundness of the monofilament. The inorganic powders, including tourmaline, perlite, barium titanate ceramic powder, and perovskite structural materials, are blended with polypropylene resin and then spun. On the one hand, they act as nucleating agents, giving the polypropylene monofilament a lower boiling water shrinkage rate. On the other hand, these dielectric and piezoelectric powders can impart thermoelectric and piezoelectric properties to the polypropylene monofilament, giving the surface of the polypropylene monofilament a static charge. When used as a filter medium, the electrostatic adsorption function of the polypropylene monofilament can be utilized, thereby improving the filtration efficiency of the medium and reducing the filtration resistance.

[0161] 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 polypropylene monofilament with low boiling water shrinkage, characterized in that, The polypropylene monofilament comprises the following raw materials by weight percentage: 89%–95% polypropylene resin, 4%–10% cyclic olefin copolymer and 1%–2% inorganic powder; the cyclic olefin copolymer is a copolymer formed by the addition polymerization of cyclic olefin monomers with a glass transition temperature of 120–160°C and ethylene monomers. The preparation method includes the following steps: S1. Preparation of melt for polypropylene monofilament: A first extruder and a second extruder connected in series are heated. Inorganic powder, cyclic olefin copolymer and polypropylene resin are fed into the first extruder and heated to melt. The polymer melt is filtered and then enters the second extruder. The heating temperature of the first extruder increases, while the heating temperature of the second extruder decreases, so that the temperature of the melt entering the second extruder is lower than the temperature of the melt extruded from the first extruder, thus obtaining a low-temperature spinning melt. S2. Spinning: The spinning melt is metered and extruded from the spinneret to obtain nascent fiber filaments; S3. Water bath cooling crystallization: The nascent fiber filaments enter a water bath for cooling after passing through an air gap of a certain distance. The water bath temperature is 65℃~90℃. S4. Oven heating and stretching: The cooled nascent fiber filaments are drawn into an oven for heating and stretching to obtain a semi-finished polypropylene monofilament. S5. Heat setting and winding: Heat setting and winding of the semi-finished polypropylene monofilament.

2. The method of claim 1, wherein: In step S1, the first extruder is a single-screw extruder, the second extruder is a counter-rotating twin-screw extruder, and a melt filter is configured between the first extruder and the second extruder.

3. The method of claim 1, wherein: The inorganic powder is any one or a combination of several of the following: tourmaline, perlite, barium titanate ceramic powder, and perovskite structural materials.

4. The method of claim 1, wherein: In step S1, the first extruder is divided into five temperature zones: the first zone temperature is 150℃~160℃, the second zone temperature is 170℃~180℃, the third zone temperature is 190℃~200℃, the fourth zone temperature is 230℃~240℃, and the fifth zone temperature is 230℃~240℃. The second extruder is divided into five temperature zones: the first zone is 220℃~230℃, the second zone is 210℃~220℃, the third zone is 200℃~210℃, the fourth zone is 190℃~200℃, and the fifth zone is 185℃~190℃.

5. The preparation method according to claim 1, characterized in that: In step S2, the temperature of the spinneret assembly is 185℃~190℃; In step S3, the air gap length is 8–15 cm; In step S4, the first traction roller group runs at a speed of 20m / min to 35m / min, and the second traction roller group runs at a speed of 30m / min to 55m / min. In step S5, the operating speed of the third traction roller group is 60m / min to 110m / min.

6. The method of claim 1, wherein: In step S4, the oven temperature is 135℃~140℃.

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