A meltblown spinning die, a hollow crimped fiber-based floc and a preparation method thereof

Abstract

The present invention belongs to the technical field of non-woven processing, and discloses a meltblown spinning die head, a hollow crimped fiber-based floc and a preparation method thereof. The meltblown spinning die head includes a spinneret plate and an air plate. Two air plates are respectively arranged on both sides below the spinneret plate. The angles between the planes where the inner sides of the two air plates are located and the respective opposite spinneret plate surfaces are respectively denoted as α and β, and the horizontal distances between the outlet ends of the two air plates and the center of the spinneret holes are respectively denoted as a and b; α = 10° - 45°, β = 45° - 89°, and α ≠ β; b = 1.1a - 3a. The preparation method of the hollow crimped fiber-based floc is as follows: The meltblown raw material is melted and mixed by a screw extruder and then sent into a meltblown metering pump. The metered melt is ejected from the meltblown spinning die head, and after being stretched and cooled and solidified by the asymmetrically distributed airflows on both sides, the hollow crimped fiber-based floc is collected. The present invention can improve the heat preservation performance of the floc while maintaining the light and thin characteristics.

Description

Technical Field

[0001] The present invention belongs to the technical field of non-woven processing, and relates to a melt-blown spinning die head, a hollow crimped fiber-based floc and a preparation method thereof. Background Art

[0002] As an important thermal insulation material, hollow crimped fibers have been widely used in the thermal insulation field because their internal hollow structure and crimped morphology can effectively lock in air and form a thermal insulation layer, thereby reducing heat loss. However, although certain progress has been made in their preparation process, there are still key problems to be solved in the thermal insulation performance of existing hollow crimped fibers.

[0003] The prior art cannot effectively construct a multi-layer thermal insulation barrier on the fiber surface, resulting in a high heat dissipation rate through convection and radiation, which severely restricts the thermal insulation performance of hollow crimped fiber products in low-temperature environments. For example, the patent application with the publication number CN115807271A discloses a spinneret plate, asymmetric double-hollow crimped polyester and a preparation method thereof. The spinneret plate used in this method to prepare asymmetric double-hollow crimped polyester includes a spinneret plate body and a plurality of spinneret holes formed on the spinneret plate body. The spinneret holes are in a "9"-shaped structure. The spinneret holes include a first arc-shaped long hole, a second arc-shaped long hole and a third arc-shaped long hole that are not connected to each other and are arranged in sequence. The first arc-shaped long hole, the second arc-shaped long hole and the third arc-shaped long hole are all in a "C"-shaped structure. Using this spinneret plate and utilizing the orifice expansion effect and the difference in shear rate, asymmetric double-hollow crimped polyester with a bamboo joint morphology is prepared, that is, imitation linen polyester integrating the characteristics of special shape, hollow and crimp. However, although the asymmetric structure fibers can improve the fiber entanglement effect, when the shape deviation caused by spinneret hole blockage exceeds 10% during the production process, the fiber arrangement orientation degree decreases, resulting in an increase in the thermal conductivity of the floc by 0.02 - 0.03 W / (m·K) and a significant decrease in the thermal insulation performance.

[0004] Therefore, it is of great significance to study a melt-blown spinning die head, a hollow crimped fiber-based floc and a preparation method thereof to solve the above problems. Summary of the Invention

[0005] The object of the present invention is to solve the problems existing in the prior art, and provide a melt-blown spinning die head, a hollow crimped fiber-based floc and a preparation method thereof.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A meltblown spinning die head includes a spinneret plate and an air plate. The spinneret plate is provided with a plurality of spinneret holes. The number of air plates is two, and they are respectively arranged on both sides below the spinneret plate. A slit groove, i.e., an air duct, is formed between the inner sides of the two air plates and the spinneret plate respectively. Denote one air plate as air plate I. The angle between the plane where the inner side of air plate I is located and the opposite spinneret plate surface is α, and the horizontal distance between the outlet end of air plate I and the center of the spinneret hole is a. Denote the other air plate as air plate II. The angle between the plane where the inner side of air plate II is located and the opposite spinneret plate surface is β, and the horizontal distance between the outlet end of air plate II and the center of the spinneret hole is b. α = 10° - 45°, β = 45° - 89°, and α ≠ β; b = 1.1a - 3a.

[0008] As a preferred technical solution:

[0009] For a meltblown spinning die head as described above, the spinneret holes are C-shaped holes, and a plurality of spinneret holes are arranged in a single row. Since the die swell effect of the melt is one of the main factors affecting the ability of the fiber to close and form pores. When using a C-shaped spinneret plate for melt spinning, the flow and swelling of the melt can be controlled by adjusting the shape and size of the spinneret plate. Appropriate spinneret plate design can optimize the flow state of the melt, reduce unnecessary swelling, and thus improve the ability of the fiber to close and form pores and the overall quality.

[0010] For a meltblown spinning die head as described above, the diameter of the spinneret holes is 0.2 - 0.4 mm, the aspect ratio is greater than 10, and the hole pitch is 0.6 - 1.0 mm.

[0011] The present invention also provides a method for preparing a hollow crimped fiber-based flake. The meltblown raw material is melted and mixed by a screw extruder and then fed into a meltblown metering pump. The metered melt is evenly ejected from the meltblown spinning die head, and after being stretched and cooled and solidified by the asymmetrically distributed airflows on both sides, it is collected by a receiving device, and a hollow crimped fiber-based flake is obtained after layer-by-layer accumulation;

[0012] The meltblown spinning die head used is the meltblown spinning die head as described in any one of the above;

[0013] a is at least 0.5 mm;

[0014] The wind pressure in the air duct formed between the inner side of air plate I and the spinneret plate is 0.25 - 0.43 MPa, and the wind pressure in the air duct formed between the inner side of air plate II and the spinneret plate is 0.05 - 0.25 MPa. Since the two air ducts are supplied with air by the same air supply device (hot air blower), when the outlet angle is too small, compression and speed increase will occur, thus increasing the wind pressure; if the outlet angle is too large, compression and speed will decrease, thus reducing the wind pressure;

[0015] Since the wind pressure is inversely proportional to the air volume, as the angles of α and β decrease, the wind pressure will gradually increase, and the air volume will be smaller. Conversely, as the angles increase, the wind pressure decreases, and the air volume increases. When the wind direction and the angle of the wind in the air duct are controlled simultaneously, such that the wind direction of one side of the air duct is at a small angle (10° - 45°) and the air volume is small, while the wind direction of the other side of the air duct is at a large angle (45° - 89°) and the air volume is large, this asymmetric configuration of wind direction and air volume actually creates conditions for the formation of vortices; in the meltblowing process, the formation of vortices is mainly generated by the shear and collision of airflows. As Figure 4 shown, the present invention first blows towards the melt stream at a smaller angle and with a smaller air volume to play a guiding role, causing the melt stream to start to deflect and deform slightly. Subsequently, it blows towards the melt stream at a larger angle and with a larger air volume. Due to the larger angle and sufficient air volume, it will generate a strong shearing and collision effect on the melt stream. This strong shearing force will cause the melt stream to undergo severe deformation and rotation, thereby forming vortex 5. When these two airflows meet at the melt stream, their interaction and collision will further enhance the formation of vortex 5. In addition, under the synergistic effect of the asymmetric vortex and meltblowing, the melt is subjected to specific mechanical effects during the spraying process, prompting the fibers to form a unique structure that is hollow and curled before solidification.

[0016] Since the air velocity and direction in the vortex are constantly changing, it will also produce alternating stretching and compression effects on the fibers. This effect causes the fibers to deform in different directions to form curls. And with the continuous action of the vortex, the hollow and curled morphology of the fibers is gradually formed and fixed. At the same time, the molecular chains inside the fibers will also rearrange to adapt to this hollow and curled morphology.

[0017] Since the finally obtained hollow and curled fibers have a three-dimensional stereoscopic curled structure, this structure makes the fibers exhibit three-dimensional characteristics in terms of morphology, rather than a simple two-dimensional planar morphology. When they are stacked on each other, they can form a more fluffy and three-dimensional structure. The fluffy floc means that there are larger gaps between the fibers, and these gaps provide more storage space for air, enabling the floc to hold more air. A large number of air layers in the fluffy floc form an effective heat insulation barrier, improving the warmth retention of the floc.

[0018] As a preferred technical solution:

[0019] For a method for preparing a hollow and curled fiber-based floc as described above, the meltblown raw material includes a polymer, or further includes auxiliary materials;

[0020] The polymer is one or more of polyester polymers and polyolefin polymers;

[0021] The polyester polymer is one of PBT (polybutylene terephthalate), PC (polycarbonate), PTT (polytrimethylene terephthalate), TPU (thermoplastic polyurethane), PA6 (polyamide 6), PEA (polyamide ester), PCTFE (polychlorotrifluoroethylene), PPS (polyphenylene sulfide), POM (polyoxymethylene), PLA (polylactic acid), PHA (polyhydroxyalkanoate), PCL (polycaprolactone), PET (polyethylene terephthalate), PMMA (polymethyl acrylate), and PBAT (polybutylene adipate terephthalate);

[0022] The polyolefin polymer is one of PP (polypropylene), PE (polyethylene), and PS (polystyrene);

[0023] The auxiliary material is one or more of an organic nucleating agent, an inorganic nucleating agent, a nano metal, a metal oxide nanoparticle, and a ceramic micro powder; these auxiliary materials can improve the heat insulation performance of the flake, thereby improving its warmth retention performance (the reason why improving the heat insulation performance can improve the warmth retention performance is that heat insulation and warmth retention are both essentially to prevent the transfer of heat. Warmth retention is mainly to prevent the internal heat from dissipating to the outside, while heat insulation is to prevent the external heat from entering the inside).

[0024] For the preparation method of a hollow crimped fiber-based flake as described above, the addition amount of the auxiliary material relative to the polymer is less than 5 wt%.

[0025] For the preparation method of a hollow crimped fiber-based flake as described above, the temperatures of the first to fifth zones of the screw extruder are 130 - 240 °C, 140 - 250 °C, 150 - 260 °C, 160 - 270 °C, and 170 - 280 °C respectively, and the die head temperature is 180 - 290 °C; the metering pump frequency is 1 - 20 Hz; the asymmetric distributed air flow is generated by the same hot air blower, the air temperature of the hot air blower outlet is 130 - 230 °C, and the air pressure is 0.10 - 0.28 MPa; the receiving distance is 50 - 110 cm, and the conveying mesh curtain frequency is 1 - 8 Hz.

[0026] The present invention also provides a hollow crimped fiber-based flake prepared by the preparation method described in any one of the above, the thickness of the hollow crimped fiber-based flake is 2 - 4 mm, the thermal resistance is 0.7 - 2.3 m 2 ·K / W, the thermal conductivity is 0.0217 - 0.02377 W / (m·K), and the clo value is 4.5 - 5. While maintaining the lightness and thinness of the flake, the present invention can achieve excellent warmth retention performance (which can be characterized by thermal resistance, thermal conductivity, and clo value. The greater the thermal resistance and clo value, and the smaller the thermal conductivity, the better the warmth retention performance), which is significantly better than the prior art.

[0027] Beneficial effects:

[0028] (1) The present invention adopts an asymmetric eddy current design inside the meltblown spinning die. Under the combined action of the asymmetric eddy current and meltblowing, the melt will be subjected to specific mechanical forces during the spraying process, causing the fibers to form a hollow and curly structure before solidification. This structure not only improves the fluffiness and warmth retention of the fibers, but also makes the fibers have a broader application prospect in the fields of textile, filling, etc.

[0029] (2) The meltblown spinning die adopted by the present invention can realize the continuous and automated production of hollow curly fibers, improve production efficiency, reduce production costs, and enable the hollow curly fibers to have stronger advantages in the market competition.

[0030] (3) The spinneret holes of the present invention are C-shaped holes, and the flow and expansion of the melt can be controlled by adjusting the shape and size of the spinneret plate. Appropriate spinneret plate design can optimize the flow state of the melt, reduce unnecessary expansion, thereby improving the fiber closing and pore-forming ability and overall quality; in addition, this special hole shape helps the melt stream to pass through the spinneret plate more evenly, thus producing hollow curly fibers with stable quality and uniform morphology.

[0031] (4) By adopting the designed meltblown spinning die, the obtained hollow curly fiber-based floc has excellent warmth retention performance while maintaining the light and thin characteristics, and has a broad application prospect. Brief Description of the Drawings

[0032] Figure 1 is a schematic diagram of the meltblown spinning die of the present invention;

[0033] Figure 2 is a right view of the spinneret plate of the present invention;

[0034] Figure 3 is a top view of the spinneret plate of the present invention;

[0035] Figure 4 is a schematic diagram of the use process of the meltblown spinning die of the present invention;

[0036] Among them, 1 - spinneret plate, 2 - air duct, 3 - air plate, 4 - spinneret hole, 5 - eddy current. Detailed Embodiments

[0037] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0038] To ensure that the properties of the substances used in each example and comparative example are fully disclosed, the manufacturers and grades of the substances are specified. Products of other manufacturers and grades that meet the limitations of the present invention are also feasible.

[0039] The test methods for the relevant performance indicators in the following examples and comparative examples are as follows:

[0040] Thermal resistance: The hollow crimped fiber-based batting prepared in each example was used as a specimen, and then the thermal resistance of the specimen was tested using GB / T 11048-2018 "Textiles - Physiological comfort - Determination of thermal and water vapor resistance under steady-state conditions (evaporative hot plate method)".

[0041] Thermal conductivity: The hollow crimped fiber-based batting prepared in each example was used as a specimen respectively, and two specimens with a length of 5 cm, a width of 5 cm, and a height of 1 cm were prepared. Then, the Hot Disk sensor (type 5501 with a diameter of 15 mm) was clamped between the two specimens, and a pressure of 15 N was applied through the fixture to ensure close contact. Then, the thermal constants analyzer (TPS2500, HotDisk Company, Sweden) was started. The sensor would be powered on and heated, and the temperature response curve would be recorded synchronously. At the same time, the software would fit the temperature data in real time to verify whether it conformed to the theoretical model (the residual should be <1%), and the thermal conductivity would be automatically calculated and output. After conducting three parallel tests with a result deviation <5%, the average value was taken as the thermal conductivity; among them, the heating power was 20 mW and the heating time was 10 s.

[0042] Clo value: The hollow crimped fiber-based batting prepared in each example was used as a specimen respectively, and then the Clo value of the specimen was determined using the ISO11092: "Textiles - Physiological effects - Determination of thermal and water vapor resistance under steady-state conditions" standard and the Dairong textile instrument YG(B)606G textile thermal and water vapor resistance tester.

[0043] The meltblown spinning die head used in the examples of the present invention, as Figure 1 shown, includes a spinneret plate 1 and an air plate 3;

[0044] As Figures 1 to 3 shown, a plurality of spinneret holes 4 are provided on the spinneret plate 1. The plurality of spinneret holes 4 are arranged in a single row. The spinneret holes 4 are C-shaped holes. The diameter of the spinneret holes 4 is 0.2 - 0.4 mm, the aspect ratio is greater than 10, and the hole pitch is 0.6 - 1.0 mm;

[0045] The number of air plates 3 is two, and they are respectively arranged on both sides below the spinneret plate 1. A slit groove, i.e., an air duct 2, is formed between the inner sides of the two air plates 3 and the spinneret plate respectively;

[0046] Denote an air plate 3 as air plate I. The angle between the plane where the inner side of air plate I lies and the surface of the opposite spinneret plate 1 is α, and the horizontal distance between the outlet end of air plate I and the center of the spinneret hole 4 is a. Denote the other air plate 3 as air plate II. The angle between the plane where the inner side of air plate II lies and the surface of the opposite spinneret plate 1 is β, and the horizontal distance between the outlet end of this air plate 3 and the center of the spinneret hole 4 is b. α = 10° - 45°, β = 45° - 89°, and α ≠ β; b = 1.1a - 3a.

[0047] Example 1

[0048] A method for preparing a hollow crimped fiber-based flake, the steps are as follows:

[0049] (1) Preparation of raw materials and devices used;

[0050] Meltblown raw materials: composed of PBT (manufacturer is BASF of Germany, grade is B1520), PE (manufacturer is Sinopec Beijing Yanshan Petrochemical Co., Ltd., grade is M1840) and tungsten oxide. The mass ratio of PBT to PE is 10:1. Based on the total amount of PBT and PE, the addition amount of tungsten oxide is 3wt%;

[0051] Meltblown spinning die head: the above-mentioned meltblown spinning die head, where the number of spinneret holes is 2400, the diameter is 0.4 mm, the length-diameter ratio is 13, the hole pitch is 1.0 mm, α = 45°, β = 60°, b = 0.55 mm, and a is 0.5 mm;

[0052] (2) The meltblown raw materials are melted and mixed by a screw extruder and then sent into a meltblown metering pump. The metered melt is evenly ejected through the meltblown spinning die head, and after being stretched and cooled and solidified by the asymmetrically distributed airflows on both sides, a hollow crimped fiber-based flake is collected. Among them, the wind pressure in the air duct formed between the inner side of air plate I and the spinneret plate is 0.25 MPa, and the wind pressure in the air duct formed between the inner side of air plate II and the spinneret plate is 0.12 MPa;

[0053] The temperatures of the first to fifth zones of the screw extruder are 240 °C, 250 °C, 260 °C, 270 °C, 280 °C respectively, the die head temperature is 290 °C, and the metering pump frequency is 20 Hz; the asymmetrically distributed airflows are generated by the same hot air blower. The air temperature at the outlet of the hot air blower is 300 °C, and the wind pressure is 0.28 MPa; the receiving distance is 110 cm, and the frequency of the conveying mesh curtain is 8 Hz.

[0054] The finally obtained hollow crimped fiber-based flake has a thickness of 4 mm, a thermal resistance of 0.7 m 2 ·K / W, a thermal conductivity of 0.02377 W / (m·K), and a Clo value of 4.5.

[0055] Example 2

[0056] A preparation method of a hollow crimped fiber-based flocculent sheet is as follows:

[0057] (1) Preparation of raw materials and equipment used;

[0058] Meltblown raw materials: composed of PC (manufacturer: LG CHEM, South Korea, grade: 1201-22) and PS (manufacturer: Trinseo (Hong Kong) Co., Ltd., grade: 685D), and the mass ratio of PC to PS is 5:1;

[0059] Meltblown spinning die: the above meltblown spinning die, in which the number of spinneret holes is 2200, the diameter is 0.3 mm, the aspect ratio is 11, the hole pitch is 0.8 mm, α = 15°, β = 45°, b = 2.4 mm, and a is 0.8 mm;

[0060] (2) The meltblown raw materials are melted and mixed by a screw extruder and then sent into a meltblown metering pump. The metered melt is evenly ejected through the meltblown spinning die, and after being stretched and cooled and solidified by the asymmetrically distributed airflows on both sides, a hollow crimped fiber-based flocculent sheet is obtained; among them, the wind pressure in the air duct formed between the inner side of air plate Ⅰ and the spinneret plate is 0.4 MPa, and the wind pressure in the air duct formed between the inner side of air plate Ⅱ and the spinneret plate is 0.25 MPa;

[0061] The temperatures of the first to fifth zones of the screw extruder are 130 °C, 140 °C, 150 °C, 160 °C, and 170 °C respectively, the die temperature is 180 °C, and the metering pump frequency is 1 Hz; the asymmetrically distributed airflows are generated by the same hot air blower, the air temperature of the hot air blower outlet is 190 °C, and the wind pressure is 0.18 MPa; the receiving distance is 50 cm, and the frequency of the conveying mesh curtain is 1 Hz.

[0062] The finally prepared hollow crimped fiber-based flocculent sheet has a thickness of 3 mm, a thermal resistance of 0.73 m 2 ·K / W, a thermal conductivity of 0.02267 W / (m·K), and a Clo value of 4.7.

[0063] Example 3

[0064] A preparation method of a hollow crimped fiber-based flocculent sheet is as follows:

[0065] (1) Preparation of raw materials and equipment used;

[0066] Meltblown raw materials: composed of TPU (manufacturer: BASF, Germany, grade: C90A) and silica, and the addition amount of silica relative to TPU is 2 wt%;

[0067] Meltblown spinning die head: The above-mentioned meltblown spinning die head, in which the number of spinneret holes is 2000, the diameter is 0.2 mm, the length-diameter ratio is 12, the hole pitch is 0.6 mm, α = 30°, β = 89°, b = 1.4 mm, and a is 0.7 mm;

[0068] (2) The meltblown raw material is melted and mixed by a screw extruder and then fed into a meltblown metering pump. The metered melt is evenly ejected through the meltblown spinning die head, and after being stretched by the asymmetrically distributed airflows on both sides and cooled and solidified, a hollow crimped fiber-based floc is obtained; among them, the wind pressure in the air duct formed between the inner side of air plate Ⅰ and the spinneret plate is 0.33 MPa, and the wind pressure in the air duct formed between the inner side of air plate Ⅱ and the spinneret plate is 0.05 MPa;

[0069] The temperatures of the first to fifth zones of the screw extruder are 190 °C, 200 °C, 210 °C, 220 °C, and 230 °C respectively, the die head temperature is 240 °C, and the metering pump frequency is 10 Hz; the asymmetrically distributed airflows are generated by the same hot air blower, the air temperature of the hot air blower outlet is 250 °C, and the wind pressure is 0.22 MPa; the receiving distance is 80 cm, and the conveying net curtain frequency is 5 Hz.

[0070] The finally obtained hollow crimped fiber-based floc has a thickness of 2 mm, a thermal resistance of 0.76 m 2 ·K / W, a thermal conductivity of 0.02201 W / (m·K), and a clo value of 4.9.

[0071] Example 4

[0072] A method for preparing a hollow crimped fiber-based floc, the steps are as follows:

[0073] (1) Preparation of raw materials and devices used;

[0074] Meltblown raw material: PLA, the manufacturer is Anhui Fengyuan Fuqinlai Polylactic Acid Co., Ltd., and the grade is FY602;

[0075] Meltblown spinning die head: The above-mentioned meltblown spinning die head, in which the number of spinneret holes is 1800, the diameter is 0.25 mm, the length-diameter ratio is 14, the hole pitch is 0.4 mm, α = 25°, β = 50°, b = 0.8 mm, and a is 0.6 mm;

[0076] (2) The meltblown raw material is melted and mixed by a screw extruder and then fed into a meltblown metering pump. The metered melt is evenly ejected through the meltblown spinning die head, and after being stretched by the asymmetrically distributed airflows on both sides and cooled and solidified, a hollow crimped fiber-based floc is obtained; among them, the wind pressure in the air duct formed between the inner side of air plate Ⅰ and the spinneret plate is 0.35 MPa, and the wind pressure in the air duct formed between the inner side of air plate Ⅱ and the spinneret plate is 0.28 MPa;

[0077] The temperatures of the first to fifth zones of the screw extruder are 180 °C, 190 °C, 200 °C, 210 °C, and 220 °C respectively, the die head temperature is 230 °C, and the metering pump frequency is 8 Hz; the asymmetrically distributed air flow is generated by the same hot air blower, the air temperature of the hot air blower outlet is 240 °C, and the air pressure is 0.15 MPa; the receiving distance is 60 cm, and the conveying mesh curtain frequency is 3 Hz.

[0078] The thickness of the finally obtained hollow crimped fiber-based floc is 2.5 mm, the thermal resistance is 0.71 m 2 ·K / W, the thermal conductivity is 0.02334 W / (m·K), and the clo value is 4.6.

[0079] Example 5

[0080] A method for preparing a hollow crimped fiber-based floc, the steps are as follows:

[0081] (1) Preparation of raw materials and devices used;

[0082] Meltblown raw materials: composed of PP (manufacturer: China National Petroleum and Chemical Corporation, grade: H2800) and stearic acid, and the addition amount of stearic acid relative to PP is 1 wt%;

[0083] Meltblown spinning die head: the above-mentioned meltblown spinning die head, where the number of spinneret holes is 1600, the diameter is 0.35 mm, the aspect ratio is 15, the hole pitch is 0.3 mm, α = 35°, β = 70°, b = 1.8 mm, and a is 0.9 mm;

[0084] (2) The meltblown raw materials are melted and mixed by a screw extruder and then sent into a meltblown metering pump. The metered melt is evenly ejected from the meltblown spinning die head, and after being stretched and cooled and solidified by the asymmetrically distributed air flow on both sides, a hollow crimped fiber-based floc is collected; among them, the air pressure in the air duct formed between the inner side of air plate I and the spinneret plate is 0.3 MPa, and the air pressure in the air duct formed between the inner side of air plate II and the spinneret plate is 0.12 MPa;

[0085] The temperatures of the first to fifth zones of the screw extruder are 170 °C, 180 °C, 190 °C, 200 °C, and 210 °C respectively, the die head temperature is 220 °C, and the metering pump frequency is 12 Hz; the asymmetrically distributed air flow is generated by the same hot air blower, the air temperature of the hot air blower outlet is 230 °C, and the air pressure is 0.25 MPa; the receiving distance is 70 cm, and the conveying mesh curtain frequency is 4 Hz.

[0086] The thickness of the finally obtained hollow crimped fiber-based floc is 3.5 mm, the thermal resistance is 0.75 m 2 ·K / W, the thermal conductivity is 0.02239 W / (m·K), and the clo value is 4.8.

[0087] Example 6

[0088] A preparation method of a hollow crimped fiber-based batting, the steps are as follows:

[0089] (1) Preparation of raw materials and equipment used;

[0090] Meltblown raw material: PBAT, manufactured by Xinjiang Blueshirt Tunhe Polyester Co., Ltd., with the grade of 8801;

[0091] Meltblown spinneret: the above-mentioned meltblown spinneret, in which the number of spinneret holes is 1400, the diameter is 0.15 mm, the aspect ratio is 16, the hole pitch is 0.2 mm, α = 10°, β = 80°, b = 2.2 mm, and a is 1 mm;

[0092] (2) The meltblown raw material is melted and mixed by a screw extruder and then sent into a meltblown metering pump. The metered melt is evenly ejected from the meltblown spinneret, and after being stretched and cooled and solidified by the asymmetrically distributed airflows on both sides, a hollow crimped fiber-based batting is obtained; among them, the wind pressure in the air duct formed between the inner side of air plate I and the spinneret plate is 0.43 MPa, and the wind pressure in the air duct formed between the inner side of air plate II and the spinneret plate is 0.1 MPa;

[0093] The temperatures of the first to fifth zones of the screw extruder are 160 °C, 170 °C, 180 °C, 190 °C, and 200 °C respectively, the die head temperature is 210 °C, and the metering pump frequency is 15 Hz; the asymmetrically distributed airflows are generated by the same hot air blower, the air temperature of the hot air blower outlet is 220 °C, and the wind pressure is 0.28 MPa; the receiving distance is 90 cm, and the conveying net curtain frequency is 2 Hz.

[0094] The finally prepared hollow crimped fiber-based batting has a thickness of 2.8 mm, a thermal resistance of 0.78 m 2 ·K / W, a thermal conductivity of 0.0217 W / (m·K), and a clo value of 5.

Claims

1. A melt-blown spinning die head, comprising a spinneret and an air plate, wherein the spinneret is provided with a plurality of spinneret holes, the number of air plates is two, and the air plates are respectively arranged on both sides below the spinneret, and the inner sides of the two air plates respectively form a sandwich groove with the spinneret, i.e., an air duct, characterized in that: One air plate is denoted as air plate I, the angle between the plane where the inner side of air plate I is located and the opposite spinneret surface is α, and the horizontal distance between the outlet end of air plate I and the center of the spinneret hole is a; the other air plate is denoted as air plate II, the angle between the plane where the inner side of air plate II is located and the opposite spinneret surface is β, and the horizontal distance between the outlet end of air plate II and the center of the spinneret hole is b; α=10°~45°, β=45°~89°, and α≠β; b=1.1a~3a.

2. A melt-blown spinning die head according to claim 1, characterized in that: The spinneret holes are C-shaped holes, and a plurality of spinneret holes are arranged in a single row.

3. A melt-blown spinning die head according to claim 2, characterized in that: The diameter of the spinneret hole is 0.2~0.4mm, the aspect ratio is greater than 10, and the hole spacing is 0.6~1.0mm.

4. A method for preparing a hollow curly fiber-based flake, characterized in that: The melt-blown raw materials are melt-mixed by a screw extruder and then fed into a melt-blown metering pump. The metered melt is evenly ejected through a melt-blown spinning die head, and after being stretched by asymmetrically distributed airflows on both sides and cooled and solidified, a hollow curly fiber-based flake is collected; The melt-blown spinning die head is the melt-blown spinning die head according to any one of claims 1 to 3; a is at least 0.5 mm; The wind pressure in the air duct formed between the inner side of the air plate I and the spinneret is 0.25~0.43MPa, and the wind pressure in the air duct formed between the inner side of the air plate II and the spinneret is 0.05~0.25MPa.

5. The method for preparing a hollow curly fiber-based flake according to claim 4, characterized in that: The melt-blown raw material includes a polymer, or further includes an auxiliary material; The polymer is one or more of a polyester polymer and a polyolefin polymer; The polyester polymer is one of PBT, PC, PTT, TPU, PA6, PEA, PCTFE, PPS, POM, PLA, PHA, PCL, PET, PMMA and PBAT; Polyolefin polymers are one of PP, PE and PS; The auxiliary material is one or more of an organic nucleating agent, an inorganic nucleating agent, nano metal, metal oxide nanoparticles and ceramic micropowder.

6. The method for preparing a hollow curly fiber-based flake according to claim 5, characterized in that: The amount of auxiliary materials added relative to the polymer is less than 5wt%.

7. The method for preparing a hollow curly fiber-based flake according to claim 4, characterized in that: The temperatures of zones 1 to 5 of the screw extruder are 130~240℃, 140~250℃, 150~260℃, 160~270℃, and 170~280℃ respectively, and the die head temperature is 180~290℃; the metering pump frequency is 1~20Hz; the asymmetrically distributed airflow is generated by the same hot air blower, and the air temperature of the hot air blower is 130~230℃, and the air pressure is 0.10~0.28MPa; the receiving distance is 50~110cm, and the mesh curtain frequency is 1~8Hz.

8. A hollow curly fiber-based flake prepared by the preparation method according to any one of claims 4 to 7, characterized in that: The thickness of the hollow curly fiber-based flakes is 2~4mm, and the thermal resistance is 0.7~2.3m 2 ·K / W, thermal conductivity is 0.0217~0.02377 W / (m·K), and Crowe value is 4.5~5.

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