Melt-blown spinning die head, hollow crimped fiber-based flocculus prepared by melt-blown spinning die head and preparation method of hollow crimped fiber-based flocculus

Abstract

The invention belongs to the technical field of non-woven processing, and discloses a melt-blowing spinning die head, a hollow crimped fiber-based flocculus prepared by the melt-blowing spinning die head and a preparation method, the melt-blowing spinning die head comprises a spinneret plate and two gas plates, and the two gas plates are arranged on the two sides of the lower portion of the spinneret plate respectively; the included angles between the planes of the inner sides of the two gas plates and the surfaces of the opposite spinneret plates are respectively recorded as alpha and beta, and the horizontal distances between the outlet ends of the two gas plates and the center of the spinneret orifice are respectively recorded as a and b; alpha ranges from 10 degrees to 45 degrees, beta ranges from 45 degrees to 89 degrees, and alpha is not equal to beta; b is equal to 1.1 a-3a; the preparation method of the hollow crimped fiber-based flocculus comprises the following steps: melt-blowing raw materials are fused and mixed by a screw extruder and then are fed into a melt-blowing metering pump, metered melt is sprayed out by a melt-blowing spinning die head, and the hollow crimped fiber-based flocculus is collected after being stretched by air flow asymmetrically distributed on the two sides and cooled and solidified. The warm keeping performance of the flocculus can be improved while the light and thin characteristics are kept.

Description

Technical Field

[0001] The invention belongs to the technical field of nonwoven processing, and relates to a melt-blown spinning die head and a hollow curly fiber-based flake prepared by the same and a preparation method thereof. Background Art

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

[0003] The prior art cannot effectively construct a multi-layer heat insulation barrier on the fiber surface, resulting in a high heat loss rate through convection and radiation, which seriously restricts the thermal insulation performance of hollow curly fiber products in low temperature environments. For example, the patent application with publication number CN115807271A discloses a spinneret, an asymmetric double hollow curly polyester and a preparation method thereof. The spinneret used in the method to prepare the asymmetric double hollow curly polyester includes a spinneret body and a plurality of spinneret holes formed on the spinneret body, the spinneret holes are of a "9"-like 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 arranged in sequence, the first arc-shaped long hole, the second arc-shaped long hole and the third arc-shaped long hole are all of a "C"-like structure, the spinneret is used and the difference in the hole expansion effect and the shear rate is used to prepare an asymmetric double hollow curly polyester with a bamboo-like shape, that is, a linen-like polyester that integrates the characteristics of special shape, hollowness and curliness. However, although asymmetric structural fibers can improve the fiber entanglement effect, when the shape deviation exceeds 10% due to spinneret hole blockage during the production process, the fiber arrangement orientation degree decreases, causing the thermal conductivity of the flakes to increase by 0.02~0.03 W / (m·K), and the thermal insulation performance is significantly reduced.

[0004] Therefore, it is of great significance to study a melt-blown spinning die head and a hollow curly fiber-based flake prepared therefrom and a preparation method thereof to solve the above-mentioned problems. Summary of the invention

[0005] The purpose of the present invention is to solve the problems existing in the prior art and to provide a melt-blown spinning die head and a hollow curly fiber-based flake prepared by using the same and a preparation method thereof.

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

[0007] A melt-blown spinning die head comprises a spinneret and an air plate, wherein the spinneret is provided with a plurality of spinneret holes, the number of the 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; one air plate is denoted as air plate I, the angle between the plane where the inner side of the air plate I is located and the opposite spinneret surface is α, and the horizontal distance between the outlet end of the 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 the air plate II is located and the opposite spinneret surface is β, and the horizontal distance between the outlet end of the 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 the preferred technical solution:

[0009] In a melt-blown spinning die head as described above, the spinneret holes are C-shaped holes, and the multiple spinneret holes are arranged in a single row; since the outlet expansion effect of the melt is one of the main factors affecting the closed hole-forming ability of the fiber. When using a C-shaped spinneret for melt spinning, the flow and expansion of the melt can be controlled by adjusting the shape and size of the spinneret. Appropriate spinneret design can optimize the flow state of the melt and reduce unnecessary expansion, thereby improving the closed hole-forming ability and overall quality of the fiber.

[0010] The melt-blown spinning die head as described above has a spinneret hole with a diameter of 0.2-0.4 mm, an aspect ratio greater than 10, and a hole pitch of 0.6-1.0 mm.

[0011] The present invention also provides a method for preparing a hollow curly fiber-based flake. 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 uniformly sprayed out through a melt-blown spinning die head, and is stretched by asymmetrically distributed airflows on both sides and collected by a receiving device after being cooled and solidified. After accumulation layer by layer, a hollow curly fiber-based flake is obtained.

[0012] The melt-blown spinning die head is the melt-blown spinning die head as described in any one of the above items;

[0013] a is at least 0.5 mm;

[0014] 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; since the two air ducts are supplied by the same air supply device (hot air blower), when the outlet angle is too small, compression and speed increase will occur, thereby increasing the wind pressure; if the outlet angle is too large, compression and speed will be reduced, thereby reducing the wind pressure;

[0015] Since the wind pressure and air volume are inversely proportional, as the angles α and β decrease, the wind pressure will gradually increase, and the air volume will decrease. On the contrary, as the angle increases, the wind pressure decreases, and the air volume increases. When the wind direction and wind angle of the air duct are controlled at the same time, the wind direction of the air duct on one side is a small angle (10°~45°) and the air volume is small, while the wind direction of the air duct on the other side is a large angle (45°~89°) and the air volume is large. This asymmetric wind direction and air volume configuration is actually creating conditions for the formation of vortices; in the meltblown process, the formation of vortices is mainly caused by the shear and collision of airflow. Figure 4 As shown, the present invention first blows at the melt stream at a relatively small angle and air volume, which plays a guiding role, so that the melt stream begins to deflect and deform slightly, and then blows at the melt stream at a relatively large angle and with a larger air volume. Due to the large angle and sufficient air volume, it will produce strong shear and collision effects on the melt stream. This strong shear force will cause the melt stream to deform and rotate violently, thereby forming a vortex 5. When the two airflows meet at the melt stream, the interaction and collision between them will further enhance the formation of the vortex 5. In addition, under the synergistic effect of the asymmetric vortex and melt blowing, the melt is subjected to a specific mechanical influence during the spraying process, which prompts the fiber to form a unique hollow and curled structure before solidification.

[0016] As the air flow speed and direction in the vortex constantly change, the fiber will also be subjected to alternating stretching and compression, which causes the fiber to deform in different directions and form curls. As the vortex continues to act, the hollow curled shape of the fiber is gradually formed and fixed. At the same time, the molecular chains inside the fiber will also be rearranged to adapt to this hollow curled shape.

[0017] Since the hollow curly fibers finally obtained have a three-dimensional curly structure in three-dimensional space, this structure makes the fibers present three-dimensional characteristics in morphology, rather than a simple two-dimensional plane morphology. When they are stacked on each other, they can form a more fluffy and three-dimensional structure. Fluffy flakes mean that there are larger gaps between the fibers, which provide more storage space for air, allowing the flakes to hold more air. The large amount of air layers in the fluffy flakes form an effective thermal insulation barrier, which improves the warmth retention of the flakes.

[0018] As the preferred technical solution:

[0019] A method for preparing a hollow curly fiber-based flake as described above, wherein the melt-blown raw material includes a polymer, or further includes an auxiliary material;

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

[0021] The polyester polymer is one of PBT (polybutylene terephthalate), PC (polycarbonate), PTT (polytrimethylene terephthalate), TPU (thermoplastic polyurethane), PA6 (polyamide 6), PEA (polyamide polyester), 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] Polyolefin polymers are one of PP (polypropylene), PE (polyethylene) and PS (polystyrene);

[0023] The auxiliary materials are one or more of organic nucleating agents, inorganic nucleating agents, nanometals, metal oxide nanoparticles and ceramic micropowders; these auxiliary materials can improve the thermal insulation performance of the flakes, thereby improving its thermal insulation performance (the reason why improving thermal insulation performance can improve thermal insulation performance is that thermal insulation and warmth retention are essentially the same, both of which are to prevent the transfer of heat. Warmth retention is mainly to prevent internal heat from dissipating to the outside, while thermal insulation prevents external heat from being transmitted into the inside).

[0024] In the method for preparing a hollow curly fiber-based flake as described above, the amount of auxiliary material added relative to the polymer is less than 5wt%.

[0025] In the method for preparing a hollow curly 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 1-20Hz; the asymmetrically distributed airflow is generated by the same hot air blower, and the air temperature of the hot air blower outlet is 130-230°C, and the air pressure is 0.10-0.28MPa; the receiving distance is 50-110cm, and the mesh curtain frequency is 1-8Hz.

[0026] The present invention also provides a hollow curly fiber-based flake prepared by the preparation method as described above, wherein the thickness of the hollow curly fiber-based flake is 2-4 mm, and the thermal resistance is 0.7-2.3 m 2 ·K / W, thermal conductivity is 0.0217~0.02377 W / (m·K), and Crowe value is 4.5~5. The present invention can achieve excellent warmth retention performance (which can be characterized by thermal resistance, thermal conductivity and Crowe value, the greater the thermal resistance and Crowe value, the smaller the thermal conductivity, the better the warmth retention), while keeping the flakes light and thin, which is significantly better than the prior art.

[0027] Beneficial effects:

[0028] (1) The present invention adopts an asymmetric vortex design inside the meltblowing spinning die head. Under the combined effect of the asymmetric vortex and meltblowing, the melt is subjected to specific mechanical effects during the spraying process, so that the fiber forms a hollow and curly structure before solidification. This structure not only improves the fluffiness and warmth retention of the fiber, but also makes the fiber have a wider application prospect in the fields of textiles, fillings, etc.

[0029] (2) The melt-blown spinning die head used in the present invention can realize continuous and automated production of hollow curly fibers, improve production efficiency, reduce production costs, and make hollow curly fibers have a stronger advantage in 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. Appropriate spinneret design can optimize the flow state of the melt and reduce unnecessary expansion, thereby improving the closed hole-forming ability and overall quality of the fiber; in addition, this special hole shape helps the melt flow to pass through the spinneret more evenly, thereby producing hollow curly fibers with stable quality and uniform morphology.

[0031] (4) The present invention adopts the designed melt-blown spinning die head to produce a hollow curly fiber-based flake which has excellent thermal insulation performance while maintaining its light and thin characteristics, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of the melt-blown spinning die head of the present invention;

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

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

[0035] Figure 4 Schematic diagram of the use process of the melt-blown spinning die head of the present invention;

[0036] Among them, 1-spinneret, 2-air duct, 3-air plate, 4-spinneret hole, 5-vortex. DETAILED DESCRIPTION

[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 are not intended 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 fall within the scope limited by the appended claims of the application equally.

[0038] In order to ensure that the properties of the materials used in each embodiment and comparative example are fully disclosed, the manufacturers and brands of the materials are indicated, and products of other manufacturers and brands that meet the requirements of the present invention are also feasible.

[0039] The testing methods of the relevant performance indicators in the following embodiments and comparative examples are as follows:

[0040] Thermal resistance: The hollow curly fiber-based flakes prepared in each embodiment were used as samples, and then the thermal resistance of the samples was tested using GB / T 11048-2018 "Determination of thermal resistance and moisture resistance of textiles under steady-state conditions of physiological comfort (evaporative hot plate method)".

[0041] Thermal conductivity: The hollow curly fiber-based flakes prepared in each embodiment were used as samples, and two samples with a length of 5 cm, a width of 5 cm, and a height of 1 cm were prepared. Then, a Hot Disk sensor (5501 type with a diameter of 15 mm) was clamped between the two samples, and a pressure of 15 N was applied by the clamp to ensure close contact. Then, a thermal constant analyzer (TPS2500, HotDisk Company of Sweden) was started, and the sensor was powered on for heating and the temperature response curve was recorded synchronously. At the same time, the software fitted the temperature data in real time to verify whether it met the theoretical model (the residual should be <1%), and the thermal conductivity was automatically calculated and output. After three parallel tests were performed and the result deviation was <5%, the average value was the thermal conductivity; wherein, the heating power was 20 mW and the heating time was 10 s.

[0042] Crowe value: The hollow curly fiber-based flakes prepared in each embodiment were used as samples, and then the Crowe values ​​of the samples were measured using the ISO11092: "Physiological effects of textiles - Determination of thermal resistance and moisture resistance under steady-state conditions" standard and the Dayong Textile YG(B)606G textile thermal resistance and moisture resistance tester.

[0043] The melt-blown spinning die head used in the embodiment of the present invention is as follows: Figure 1 As shown, it includes a spinneret 1 and an air plate 3;

[0044] like Figure 1~Figure 3 As shown, a plurality of spinneret holes 4 are provided on the spinneret plate 1, and 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 spacing is 0.6-1.0 mm;

[0045] There are two air plates 3, which are respectively arranged on both sides below the spinneret 1. The inner sides of the two air plates 3 form a sandwich groove with the spinneret, i.e., the air duct 2.

[0046] One air plate 3 is denoted as air plate I, the angle between the plane where the inner side of air plate I is located and the opposite surface of spinneret 1 is α, and the horizontal distance between the outlet end of air plate I and the center of spinneret hole 4 is a; another air plate 3 is denoted as air plate II, the angle between the plane where the inner side of air plate II is located and the opposite surface of spinneret 1 is β, and the horizontal distance between the outlet end of air plate 3 and the center of 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 curly fiber-based flake comprises the following steps:

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

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

[0051] Meltblown spinning die: the above-mentioned meltblown spinning die, wherein the number of spinnerets is 2400, the diameter is 0.4 mm, the aspect 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 melt-blown raw materials are melt-mixed by a screw extruder and then fed into a melt-blown metering pump. The metered melt is uniformly 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; wherein, the wind pressure in the air duct formed between the inner side of the air plate I and the spinneret is 0.25 MPa, and the wind pressure in the air duct formed between the inner side of the air plate II and the spinneret is 0.12 MPa;

[0053] The temperatures of zones 1 to 5 of the screw extruder are 240℃, 250℃, 260℃, 270℃, and 280℃ respectively, the die head temperature is 290℃, and the metering pump frequency is 20Hz; the asymmetrically distributed airflow is generated by the same hot air blower, and the air temperature of the hot air blower is 300℃ and the air pressure is 0.28MPa; the receiving distance is 110cm, and the mesh curtain frequency is 8Hz.

[0054] The thickness of the hollow curly fiber-based flakes finally obtained is 4 mm and the thermal resistance is 0.7 m 2 ·K / W, the thermal conductivity is 0.02377W / (m·K), and the Crowe value is 4.5.

[0055] Example 2

[0056] A method for preparing a hollow curly fiber-based flake comprises the following steps:

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

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

[0059] Meltblown spinning die: the above-mentioned meltblown spinning die, wherein the number of spinnerets 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 melt-blown raw materials are melt-mixed by a screw extruder and then fed into a melt-blown metering pump. The metered melt is uniformly 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; wherein, the wind pressure in the air duct formed between the inner side of the air plate I and the spinneret is 0.4 MPa, and the wind pressure in the air duct formed between the inner side of the air plate II and the spinneret is 0.25 MPa;

[0061] The temperatures of zones 1 to 5 of the screw extruder are 130°C, 140°C, 150°C, 160°C, and 170°C respectively, the die head temperature is 180°C, and the metering pump frequency is 1Hz; the asymmetrically distributed airflow is generated by the same hot air blower, and the air temperature of the hot air blower is 190°C and the air pressure is 0.18MPa; the receiving distance is 50cm, and the mesh curtain frequency is 1Hz.

[0062] The thickness of the hollow curly fiber-based flakes finally obtained is 3 mm and the thermal resistance is 0.73 m 2 ·K / W, the thermal conductivity is 0.02267W / (m·K), and the Crowe value is 4.7.

[0063] Example 3

[0064] A method for preparing a hollow curly fiber-based flake comprises the following steps:

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

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

[0067] Meltblown spinning die: the above-mentioned meltblown spinning die, wherein the number of spinnerets is 2000, the diameter is 0.2 mm, the aspect 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 melt-blown raw materials are melt-mixed by a screw extruder and then fed into a melt-blown metering pump. The metered melt is uniformly 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; wherein, the wind pressure in the air duct formed between the inner side of the air plate I and the spinneret is 0.33 MPa, and the wind pressure in the air duct formed between the inner side of the air plate II and the spinneret is 0.05 MPa;

[0069] The temperatures of zones 1 to 5 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 10Hz; the asymmetrically distributed airflow is generated by the same hot air blower, and the air temperature of the hot air blower is 250°C and the air pressure is 0.22MPa; the receiving distance is 80cm, and the mesh curtain frequency is 5Hz.

[0070] The thickness of the hollow curly fiber-based flakes finally obtained is 2 mm and the thermal resistance is 0.76 m 2 ·K / W, thermal conductivity is 0.02201W / (m·K), and Crowe value is 4.9.

[0071] Example 4

[0072] A method for preparing a hollow curly fiber-based flake comprises the following steps:

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

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

[0075] Meltblown spinning die: the above-mentioned meltblown spinning die, wherein the number of spinnerets is 1800, the diameter is 0.25 mm, the aspect 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 melt-blown raw materials are melt-mixed by a screw extruder and then fed into a melt-blown metering pump. The metered melt is uniformly 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; wherein, the wind pressure in the air duct formed between the inner side of the air plate I and the spinneret is 0.35 MPa, and the wind pressure in the air duct formed between the inner side of the air plate II and the spinneret is 0.28 MPa;

[0077] The temperatures of zones 1 to 5 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 8Hz; the asymmetrically distributed airflow is generated by the same hot air blower, and the air temperature of the hot air blower is 240°C and the air pressure is 0.15MPa; the receiving distance is 60cm, and the mesh curtain frequency is 3Hz.

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

[0079] Example 5

[0080] A method for preparing a hollow curly fiber-based flake comprises the following steps:

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

[0082] Meltblown raw materials: composed of PP (manufacturer is China Petrochemical Corporation, brand name H2800) and stearic acid, the amount of stearic acid added relative to PP is 1wt%;

[0083] Meltblown spinning die: the above-mentioned meltblown spinning die, wherein the number of spinnerets 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 melt-blown raw materials are melt-mixed by a screw extruder and then fed into a melt-blown metering pump. The metered melt is uniformly 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; wherein, the wind pressure in the air duct formed between the inner side of the air plate I and the spinneret is 0.3 MPa, and the wind pressure in the air duct formed between the inner side of the air plate II and the spinneret is 0.12 MPa;

[0085] The temperatures of zones 1 to 5 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 12Hz; the asymmetrically distributed airflow is generated by the same hot air blower, and the air temperature of the hot air blower is 230°C and the air pressure is 0.25MPa; the receiving distance is 70cm, and the mesh curtain frequency is 4Hz.

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

[0087] Example 6

[0088] A method for preparing a hollow curly fiber-based flake comprises the following steps:

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

[0090] Meltblown raw materials: PBAT, the manufacturer is Xinjiang Lanshan Tunhe Polyester Co., Ltd., brand number 8801;

[0091] Meltblown spinning die: the above-mentioned meltblown spinning die, wherein the number of spinnerets 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 melt-blown raw materials are melt-mixed by a screw extruder and then fed into a melt-blown metering pump. The metered melt is uniformly 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; wherein, the wind pressure in the air duct formed between the inner side of the air plate I and the spinneret is 0.43 MPa, and the wind pressure in the air duct formed between the inner side of the air plate II and the spinneret is 0.1 MPa;

[0093] The temperatures of zones 1 to 5 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 15Hz; the asymmetrically distributed airflow is generated by the same hot air blower, and the air temperature of the hot air blower is 220°C and the air pressure is 0.28MPa; the receiving distance is 90cm, and the mesh curtain frequency is 2Hz.

[0094] The thickness of the final hollow curly fiber-based flakes is 2.8 mm and the thermal resistance is 0.78 m 2 ·K / W, thermal conductivity is 0.0217W / (m·K), and Crowe value is 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 nano particles and ceramic micro powder.

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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