A high-strength core-shell structure fluorescent solar concentrator fiber and its preparation method and application

Abstract

A high-strength skin-core structure fluorescent solar light-collecting fiber and its preparation method and application. The present invention belongs to the field of solar light-collecting fibers and their preparation. The purpose of the present invention is to solve the technical problem that the existing fluorescent solar light-collecting fibers cannot take into account both excellent light-collecting performance and mechanical properties. The core layer of the high-strength skin-core structure fluorescent solar light-collecting fiber of the present invention is made of polylactic acid and fluorescent material, and the skin layer is a copolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride. Preparation method: firstly, polylactic acid and fluorescent material are melt-blended and granulated; then melt-spun, and after spinning, different drawing processes are performed, and then heat-set to obtain a high-strength skin-core structure fluorescent solar light-collecting fiber. The present invention obtains a transparent PLA fluorescent solar light-collecting fiber with a certain degree of crystallinity and orientation, excellent mechanical properties and heat resistance through process adjustment.

Description

Technical Field

[0001] The present invention belongs to the field of solar light - collecting fibers and their preparation, and particularly relates to a high - strength skin - core structure fluorescent solar light - collecting fiber, its preparation method and application. Background Art

[0002] With the development of human society, it has become a social consensus to use new, clean and renewable energy as a substitute for traditional energy. Among them, converting solar energy into electrical energy can effectively alleviate the consumption of fossil energy and environmental pollution, that is, photovoltaic power generation. Currently, most of the devices for photovoltaic power generation are solar cells, and their use relies on a sunlight tracking system and weather conditions, which greatly limits their utilization of solar energy. In order to improve the utilization efficiency of solar cells for sunlight and reduce costs, fluorescent solar collectors have become a research hotspot.

[0003] A fluorescent solar collector is composed of a fluorescent material, a transparent optical waveguide material, and a solar cell. Compared with traditional solar cells, a fluorescent solar collector does not require an expensive sunlight tracking system, a complex cooling system, and does not need to rely on weather conditions. Currently, the transparent optical waveguide material in a fluorescent solar collector is mostly in a flat - plate shape. However, the main defects of ordinary flat - plate fluorescent solar collectors are the difficulty in coupling the fluorescent layer and the photovoltaic cell, and the difficulty in light transmission and wiring. To overcome these problems, the new concept of fluorescent solar concentrating fiber (LSCF) has been proposed. LSCF is easy to couple with solar cells and passive fibers. Since LSCF is lightweight and flexible, it can be processed into wearable fabrics with different structures and combined with photovoltaic cells as a mobile power source, having strong flexibility. So far, most of the research on LSCF has been based on high - refractive - index polymers such as polymethyl methacrylate (PMMA), cycloolefin polymer (COP), polycarbonate (PC), and polystyrene (PS) as the matrix, and introducing fluorescent substances to prepare LSCF. However, PMMA, COP, PC, and PS are all amorphous polymers, and their glass transition temperature is their highest service temperature, which is relatively low. In addition, fibers made of amorphous polymers are difficult to be effectively drawn, with low orientation degree and a crystallinity of 0, making it difficult to prepare LSC fibers with good mechanical properties. Crystalline polymers are generally in a mixed state of crystalline and amorphous regions, and there is light refraction at the interface between the crystalline and amorphous regions, making it difficult to prepare transparent materials. Therefore, preparing transparent fibers with a certain degree of crystallinity and orientation, excellent mechanical properties and heat resistance is the key problem to be solved in this field. Summary of the Invention

[0004] To solve the above - mentioned technical problems, the present invention provides the following technical solutions: a high - strength skin - core structure fluorescent solar light - collecting fiber, its preparation method and application.

[0005] One of the objectives of the present invention is to provide a high-strength skin-core structured fluorescent solar light collecting fiber, wherein the core layer is prepared from polylactic acid and a fluorescent substance, and the skin layer is a copolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride.

[0006] As a preferred embodiment of the high-strength skin-core structured fluorescent solar light collecting fiber of the present invention, wherein: the mass ratio of polylactic acid to the fluorescent substance in the core layer is 99.9:0.01 to 95:5.

[0007] As a preferred embodiment of the high-strength skin-core structured fluorescent solar light collecting fiber of the present invention, wherein: the mass ratio of the skin layer to the core layer is 5:95 to 95:5.

[0008] As a preferred embodiment of the high-strength skin-core structured fluorescent solar light collecting fiber of the present invention, wherein: the viscosity-average molecular weight of polylactic acid is 1.0×10 4 ~2.0×10 6 .

[0009] As a preferred embodiment of the high-strength skin-core structured fluorescent solar light collecting fiber of the present invention, wherein: the fluorescent substance is a fluorescent dye, a transition metal ion complex fluorescent material, a rare earth fluorescent material and a quantum dot fluorescent material.

[0010] Another objective of the present invention is to provide a method for preparing a high-strength skin-core structured fluorescent solar light collecting fiber, and the preparation method comprises the following steps:

[0011] Step 1: Melting and blending polylactic acid and the fluorescent substance for pelletizing, and drying in vacuum to obtain polylactic acid / fluorescent substance chips;

[0012] Step 2: Melting and spinning a copolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride and the polylactic acid / fluorescent substance chips, performing drawing first after spinning, and then heat setting to obtain a high-strength skin-core structured fluorescent solar light collecting fiber.

[0013] As a preferred embodiment of the method for preparing a high-strength skin-core structured fluorescent solar light collecting fiber of the present invention, wherein: premixing for 3 to 15 minutes before pelletizing in Step 1.

[0014] As a preferred embodiment of the method for preparing a high-strength skin-core structured fluorescent solar light collecting fiber of the present invention, wherein: the pelletizing temperature in Step 1 is 130 to 250°C, and the rotation speed is 50 to 500 rpm.

[0015] As a preferred embodiment of the method for preparing a high-strength skin-core structured fluorescent solar light collecting fiber of the present invention, wherein: the vacuum drying temperature in Step 1 is 65 to 120°C, and the time is 8 to 48 hours.

[0016] As a preferred embodiment of the method for preparing the high-strength skin-core structured fluorescent solar light collecting fiber of the present invention, in step 2, the spinning temperature is 150 to 250 °C, and the spinning speed is 500 to 5000 m / min.

[0017] As a preferred embodiment of the method for preparing the high-strength skin-core structured fluorescent solar light collecting fiber of the present invention, in step 2, the parameters of the drawing are as follows: the drawing temperature is 65 to 120 °C, and the drawing ratio is 1.5 to 10.0.

[0018] As a preferred embodiment of the method for preparing the high-strength skin-core structured fluorescent solar light collecting fiber of the present invention, in step 2, the heat setting temperature is 90 to 135 °C.

[0019] A third object of the present invention is to provide a method for preparing a high-strength skin-core structured fluorescent solar light collecting fiber, the preparation method comprising the following steps:

[0020] Step 1: Melting and blending polylactic acid and a fluorescent substance for pelletizing, and drying in vacuum to obtain polylactic acid / fluorescent substance chips;

[0021] Step 2: Melting and spinning a copolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride and the polylactic acid / fluorescent substance chips, cooling in water bath after spinning, then performing one-step hot steam drawing, followed by two-step hot air drawing, and finally heat setting to obtain the high-strength skin-core structured fluorescent solar light collecting fiber.

[0022] As a preferred embodiment of the method for preparing the high-strength skin-core structured fluorescent solar light collecting fiber of the present invention, in step 1, premixing is performed for 3 to 15 min before pelletizing.

[0023] As a preferred embodiment of the method for preparing the high-strength skin-core structured fluorescent solar light collecting fiber of the present invention, in step 1, the pelletizing temperature is 130 to 250 °C, and the rotation speed is 50 to 500 rpm.

[0024] As a preferred embodiment of the method for preparing the high-strength skin-core structured fluorescent solar light collecting fiber of the present invention, in step 1, the vacuum drying temperature is 65 to 120 °C, and the time is 8 to 48 h.

[0025] As a preferred embodiment of the method for preparing the high-strength skin-core structured fluorescent solar light collecting fiber of the present invention, in step 2, the spinning temperature is 130 to 250 °C, and the winding speed of the first roller is 1 to 50 m / min.

[0026] As a preferred embodiment of the method for preparing the high-strength skin-core structured fluorescent solar light collecting fiber of the present invention, in step 2, the water bath temperature is 0 to 75 °C.

[0027] As a preferred embodiment of the preparation method of the high-strength skin-core structure fluorescent solar concentrating fiber of the present invention, wherein: in step 2, the temperature of the first hot steam drawing is 20-95 °C, and the drawing ratio is 2-15.

[0028] As a preferred embodiment of the preparation method of the high-strength skin-core structure fluorescent solar concentrating fiber of the present invention, wherein: in step 2, the temperature of the second hot air drawing is 65-140 °C, and the drawing ratio is 1-10.

[0029] As a preferred embodiment of the preparation method of the high-strength skin-core structure fluorescent solar concentrating fiber of the present invention, wherein: in step 2, the heat setting temperature is 90-150 °C.

[0030] The fourth object of the present invention is to provide an application of a high-strength skin-core structure fluorescent solar concentrating fiber, and the high-strength skin-core structure fluorescent solar concentrating fiber is used for preparing a fluorescent solar concentrator.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The present invention obtains a transparent PLA fluorescent solar concentrating fiber with a certain degree of crystallinity and orientation, excellent mechanical properties and heat resistance through process control. The specific advantages are as follows:

[0033] 1) The preparation process of the high-strength skin-core structure fluorescent solar concentrating fiber of the present invention is simple and low-cost. By using the melt spinning method, it has little environmental pollution and belongs to the category of clean production.

[0034] 2) The core layer of the high-strength skin-core structure fluorescent solar concentrating fiber of the present invention is polylactic acid which is resource-renewable and biodegradable, solving the problems of resource shortage and environmental pollution existing in the existing petroleum-based solar concentrating fibers.

[0035] 3) The skin layer of the high-strength skin-core structure fluorescent solar concentrating fiber of the present invention is a crystalline copolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride with high transparency. By regulating the spinning external field, that is, the combination of water bath cooling and low-temperature drawing process, the grain size of polylactic acid is reduced under this process so that visible light can pass through, realizing high crystallinity and high transparency of the core layer, and making the monofilament have both good light collection effect and good mechanical properties.

[0036] 4) The fluorine-based skin layer of the high-strength skin-core structure fluorescent solar concentrating fiber of the present invention can resist the damage of chemical reagents and solvents, has good weather resistance and heat resistance, has a good protective effect on the core layer, and can extend the service life of the core layer. At the same time, the interfacial combination between the fluorine-based skin layer and polylactic acid is good, and there will be no large amount of light scattering loss at the interfacial combination. Specific embodiments

[0037] To make the above objects, features, and advantages of the present invention more apparent and understandable, the following provides a detailed description of the specific implementation manners of the present invention in conjunction with the embodiments of the specification.

[0038] In the following description, many specific details are set forth to facilitate a thorough understanding of the present invention. However, the present invention can also be implemented in other ways different from those described herein. Those skilled in the art can make similar generalizations without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0039] Secondly, the so-called "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that can be included in at least one implementation manner of the present invention. The appearances of "in one embodiment" in different places in this specification do not all refer to the same embodiment, nor are they separate or alternative embodiments that exclude each other with other embodiments.

[0040] Test method for breaking strength and elongation at break: According to the national standard "GB / T 14344-2022 Test Method for Tensile Properties of Chemical Fiber Filaments", the tensile mechanical properties of the high-strength large-diameter core-sheath structured fluorescent solar light collecting monofilaments are tested.

[0041] Fiber average diameter measurement method: For samples prepared with the same experimental parameters, randomly select 5 monofilaments and take pictures under an optical fiber microscope. For each optical microscope image, randomly select 3 positions on the monofilament using ImageJ software to measure the diameter, and take the average value as the average diameter of the monofilament under this parameter.

[0042] Optical property test method: Arrange the high-strength large-diameter core-sheath structured fluorescent solar light collecting monofilaments tightly into a sheet, and use a UV-visible spectrophotometer to test its absorbance and a fluorescence spectrophotometer to test its fluorescence emission intensity.

[0043] Light collection performance test method: Combine the head ends of the tightly arranged 4-cm-wide high-strength large-diameter core-sheath structured fluorescent solar light collecting monofilaments with a solar cell panel, and record the current value output by the solar cell under a solar irradiance of 1000 W / m 2 solar irradiance.

[0044] Crystallinity test method: Weigh 5 mg of the sample, put it into a crucible to obtain the sample to be tested. Test it through DSCQ200 under the conditions of a nitrogen gas flow rate of 50 ml / min and a heating rate of 10 °C / min, and obtain the crystallinity according to the areas of the cold crystallization peak and the melting peak.

[0045] Example 1. The preparation method of a high-strength core-sheath structured fluorescent solar light collecting fiber in this example is carried out according to the following steps:

[0046] Step 1:

[0047] First, a polylactic acid with a D-lactic acid (D-LA) structural unit content of 2 mol% and a viscosity-average molecular weight of 2.0×10 5 , a fluorescent dye Lumogen F Yellow 083 (LY083), and a copolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride were dried in a vacuum oven at 105 °C for 24 h for later use;

[0048] Then, raw materials were weighed according to a mass ratio of polylactic acid to LY083 of 98.8:1.2, put into a high-speed mixer for premixing for 5 min, and then melt-blended and pelletized in a twin-screw blender. The pelletizing temperature was 185 °C, and the screw speed was 400 rpm;

[0049] Then, it was vacuum-dried at 105 °C for 24 h to obtain polylactic acid / fluorescent substance chips.

[0050] Step 2:

[0051] First, the copolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride and the polylactic acid / fluorescent substance chips were added to the hopper of a melt compound spinning device according to a mass ratio of the skin layer to the core layer of 10:90 for melt spinning. The spinning temperature was 195 °C, and the spinning speed was 3000 m / min to obtain as-spun core-shell structured fluorescent solar concentrator fibers;

[0052] Then, the as-spun core-shell structured fluorescent solar concentrator fibers were drawn. The drawing temperature was 80 °C, and the draw ratio was 4.0;

[0053] Finally, it was heat-set at 120 °C to obtain high-strength core-shell structured fluorescent solar concentrator fibers.

[0054] Example 2. The preparation method of a high-strength core-shell structured fluorescent solar concentrator fiber in this example is carried out according to the following steps:

[0055] Step 1:

[0056] First, a polylactic acid with a D-lactic acid (D-LA) structural unit content of 2 mol% and a viscosity-average molecular weight of 2.0×10 5 , a fluorescent dye Lumogen Red 305 (LR305), and a copolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride were dried in a vacuum oven at 105 °C for 24 h for later use;

[0057] Then, raw materials were weighed according to a mass ratio of polylactic acid to LR305 of 98.5:1.5, put into a high-speed mixer for premixing for 10 min, and then melt-blended and pelletized in a twin-screw blender. The pelletizing temperature was 185 °C, and the screw speed was 400 rpm;

[0058] Then, it was vacuum dried at 105 °C for 24 h to obtain polylactic acid / fluorescent substance slices.

[0059] Step 2:

[0060] First, a copolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride and the polylactic acid / fluorescent substance slices were added to the hopper of a melt compound spinning device according to a mass ratio of the skin layer to the core layer of 10:90 for melt spinning. The spinning temperature was 195 °C and the spinning speed was 3000 m / min to obtain skin-core structured fluorescent solar light collecting nascent fibers.

[0061] Then, the skin-core structured fluorescent solar light collecting nascent fibers were drawn, the drawing temperature was 75 °C, and the draw ratio was 3.5.

[0062] Finally, it was heat-set at 125 °C to obtain high-strength skin-core structured fluorescent solar light collecting fibers.

[0063] Example 3. A method for preparing high-strength skin-core structured fluorescent solar light collecting fibers in this example was carried out according to the following steps:

[0064] Step 1:

[0065] First, polylactic acid with a D-lactic acid (D-LA) structural unit content of 2.5 mol% and a viscosity-average molecular weight of 2.0×10 5 , fluorescent luminescent dye Lumogen F Violet 570 (LV570), and a copolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride were dried in a vacuum oven at 105 °C for 24 h and reserved.

[0066] Then, raw materials were weighed according to a mass ratio of polylactic acid to LV570 of 98.8:1.2, put into a high-speed mixer for premixing for 8 min, and then melt-blended and pelletized in a twin-screw blender. The pelletizing temperature was 185 °C and the screw speed was 400 rpm.

[0067] Then, it was vacuum dried at 105 °C for 24 h to obtain polylactic acid / fluorescent substance slices.

[0068] Step 2:

[0069] First, a copolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride and the polylactic acid / fluorescent substance slices were added to the hopper of a melt compound spinning device according to a mass ratio of the skin layer to the core layer of 15:85 for melt spinning. The spinning temperature was 190 °C and the spinning speed was 3000 m / min to obtain skin-core structured fluorescent solar light collecting nascent fibers.

[0070] Then, the skin-core structured fluorescent solar light collecting nascent fibers were drawn, the drawing temperature was 85 °C, and the draw ratio was 3.8.

[0071] Finally, it is heat-set at 130 °C to obtain a high-strength skin-core structure fluorescent solar concentrator fiber.

[0072] Example 4. The preparation method of a high-strength skin-core structure fluorescent solar concentrator fiber in this example is carried out according to the following steps:

[0073] Step 1:

[0074] First, polylactic acid with a D-lactic acid (D-LA) structural unit content of 2.5 mol% and a viscosity-average molecular weight of 2.0×10 5 , fluorescent luminescent dye Lumogen Red 305 (LR305), and a copolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride are dried in a vacuum oven at 105 °C for 24 h and reserved;

[0075] Then, the raw materials are weighed according to the mass ratio of polylactic acid to LR305 of 99:1, put into a high-speed mixer for premixing for 8 min, and then melt-blended and granulated in a twin-screw compounding machine. The granulation temperature is 185 °C, and the screw speed is 400 rpm;

[0076] It is then vacuum-dried at 105 °C for 24 h to obtain polylactic acid / fluorescent substance chips.

[0077] Step 2:

[0078] First, the copolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride and the polylactic acid / fluorescent substance chips are added to the hopper of a melt compound spinning device according to the mass ratio of the skin layer to the core layer of 15:85 for melt spinning. The spinning temperature is 190 °C, and the spinning speed is 4500 m / min to obtain a skin-core structure fluorescent solar concentrator nascent fiber;

[0079] Then, the skin-core structure fluorescent solar concentrator nascent fiber is drawn. The drawing temperature is 85 °C, and the drawing ratio is 3.0;

[0080] Finally, it is heat-set at 120 °C to obtain a high-strength skin-core structure fluorescent solar concentrator fiber.

[0081] Example 5. The preparation method of a high-strength skin-core structure fluorescent solar concentrator fiber in this example is carried out according to the following steps:

[0082] Step 1:

[0083] First, polylactic acid with a D-lactic acid (D-LA) structural unit content of 2.5 mol% and a viscosity-average molecular weight of 2.0×10 5The polylactic acid, the fluorescent dye Lumogen Red 305 (LR305), and the copolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride were dried in a vacuum oven at 105 °C for 24 h and reserved for use;

[0084] Then, raw materials were weighed according to the mass ratio of polylactic acid to LR305 being 99.5:0.5, put into a high-speed mixer for premixing for 5 min, and then melt-blended and pelletized in a twin-screw blender. The pelletizing temperature was 190 °C and the screw speed was 400 rpm;

[0085] Then, it was vacuum-dried at 105 °C for 24 h to obtain polylactic acid / fluorescent substance slices.

[0086] Step 2:

[0087] First, the copolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride and the polylactic acid / fluorescent substance slices were added to the hopper of a melt compound spinning device according to the mass ratio of the skin layer to the core layer being 20:80 for melt spinning. The spinning temperature was 190 °C and the spinning speed was 5000 m / min to obtain a core-shell structured fluorescent solar concentrator nascent fiber;

[0088] Then, the core-shell structured fluorescent solar concentrator nascent fiber was drawn. The drawing temperature was 80 °C and the draw ratio was 3.0;

[0089] Finally, it was heat-set at 120 °C to obtain a high-strength core-shell structured fluorescent solar concentrator fiber.

[0090] Control Example 1. The preparation method of a core-shell structured solar concentrator fiber in this comparative example was carried out according to the following steps:

[0091] Step 1:

[0092] The polylactic acid with a D-lactic acid (D-LA) structural unit content of 2 mol% and a viscosity-average molecular weight of 2.0×10 5 and the copolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride were dried in a vacuum oven at 105 °C for 24 h and reserved for use;

[0093] Step 2:

[0094] First, the copolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride and the polylactic acid were added to the hopper of a melt compound spinning device according to the mass ratio of the skin layer to the core layer being 10:90 for melt spinning. The spinning temperature was 195 °C and the spinning speed was 3000 m / min to obtain a core-shell structured solar concentrator nascent fiber;

[0095] Then, the core-shell structured solar concentrator nascent fiber was drawn. The drawing temperature was 80 °C and the draw ratio was 4.0;

[0096] Finally, it is heat-set at 120 °C to obtain a core-shell structured solar light-collecting fiber.

[0097] The preparation method of a core-shell structured fluorescent solar light-collecting fiber in Comparative Example 2 and this comparative example is carried out according to the following steps:

[0098] Step 1:

[0099] First, polylactic acid with a D-lactic acid (D-LA) structural unit content of 2 mol% and a viscosity-average molecular weight of 2.0×10 5 and the fluorescent dye Lumogen F Yellow 083 (LY083) and a copolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride are dried in a vacuum oven at 105 °C for 24 h and reserved;

[0100] Then, raw materials are weighed according to the mass ratio of polylactic acid to LY083 of 98.8:1.2, put into a high-speed mixer for premixing for 5 min, and then melt-blended and pelletized in a twin-screw compounding extruder. The pelletizing temperature is 185 °C and the screw speed is 400 rpm;

[0101] It is then vacuum-dried at 105 °C for 24 h to obtain polylactic acid / fluorescent substance chips.

[0102] Step 2:

[0103] First, the copolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride and the polylactic acid / fluorescent substance chips are added to the hopper of a melt compound spinning device according to the mass ratio of the skin layer to the core layer of 10:90 for melt spinning. The spinning temperature is 195 °C and the spinning speed is 3000 m / min to obtain a core-shell structured fluorescent solar light-collecting fiber.

[0104] Example 6. The preparation method of a high-strength core-shell structured fluorescent solar light-collecting fiber in this example is carried out according to the following steps:

[0105] Step 1:

[0106] First, polylactic acid with a D-lactic acid (D-LA) structural unit content of 2 mol% and a viscosity-average molecular weight of 2.0×10 5 and the fluorescent dye Lumogen F Yellow 083 (LY083) and a copolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride are dried in a vacuum oven at 105 °C for 24 h and reserved;

[0107] Then, raw materials are weighed according to the mass ratio of polylactic acid to LY083 of 99.2:0.8, put into a high-speed mixer for premixing for 5 min, and then melt-blended and pelletized in a twin-screw compounding extruder. The pelletizing temperature is 190 °C and the screw speed is 400 rpm;

[0108] The polylactic acid / fluorescent material slices were then obtained by vacuum drying at 105°C for 24 hours.

[0109] Step 2:

[0110] First, a copolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride and polylactic acid / fluorescent material slices were added into the hopper of a melt composite spinning device according to a mass ratio of the skin layer to the core layer of 15:85 for melt spinning, the spinning temperature was 195°C, and the one-roll winding speed was 10m / min, to obtain a skin-core structure fluorescent solar light-collecting primary fiber, which was cooled in a water bath after spinning, and the water bath temperature was 40°C;

[0111] Then, a hot steam drawing is performed, the temperature of the hot steam drawing is 80°C, and the drawing multiple is 3;

[0112] Then, the second hot air drawing is performed, the temperature of the second hot air drawing is 120°C, and the drawing ratio is 1.2;

[0113] Finally, it is heat-set at a temperature of 125°C to obtain a high-strength skin-core structure fluorescent solar light-collecting fiber.

[0114] Example 7: The preparation method of a high-strength skin-core structure fluorescent solar light-collecting fiber of this example is carried out according to the following steps:

[0115] Step 1:

[0116] First, the content of D-lactic acid (D-LA) structural unit was 2.5 mol% and the viscosity average molecular weight was 2.0×10 5 The polylactic acid, the fluorescent dye Lumogen Red 305 (LR305), and the copolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride were dried in a vacuum oven at 80° C. for 48 h and set aside;

[0117] Then, the raw materials were weighed according to the mass ratio of polylactic acid to LR305 of 99.2:0.8, put into a high-speed mixer for premixing for 5 minutes, and then melt-blended and granulated in a twin-screw blender at a granulation temperature of 185° C. and a screw speed of 400 rpm;

[0118] The mixture was then vacuum dried at 80°C for 48 hours to obtain polylactic acid / fluorescent material slices.

[0119] Step 2:

[0120] First, a copolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride and a poly(lactic acid) / fluorescent substance slice are added to the hopper of a melt compound spinning device in a mass ratio of the skin layer to the core layer of 10:90 for melt spinning. The spinning temperature is 190 °C, and the winding speed of the first roller is 10 m / min to obtain a core-shell structured fluorescent solar light collecting primary fiber. After spinning, it is cooled in a water bath, and the water bath temperature is 25 °C;

[0121] Then, one-step hot steam drawing is carried out. The temperature of the one-step hot steam drawing is 85 °C, and the drawing ratio is 4;

[0122] Next, two-step hot air drawing is carried out. The temperature of the two-step hot air drawing is 120 °C, and the drawing ratio is 1.2;

[0123] Finally, heat setting is carried out at a temperature of 125 °C to obtain a high-strength core-shell structured fluorescent solar light collecting fiber.

[0124] Example 8. A method for preparing a high-strength core-shell structured fluorescent solar light collecting fiber in this example is carried out according to the following steps:

[0125] Step 1:

[0126] First, poly(lactic acid) with a content of 98 mol% of L-lactic acid (L-LA) structural units and a viscosity-average molecular weight of 2.2×10 4 , a fluorescent dye Lumogen Red 305 (LR305), and a copolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride are dried in a vacuum oven at 105 °C for 24 h and reserved;

[0127] Then, raw materials are weighed according to a mass ratio of poly(lactic acid) to LR305 of 99.6:0.4, put into a high-speed mixer for premixing for 5 min, and then melt-blended and pelletized in a twin-screw compounding machine. The pelletizing temperature is 190 °C, and the screw speed is 400 rpm;

[0128] Then, it is vacuum-dried at 105 °C for 24 h to obtain a poly(lactic acid) / fluorescent substance slice.

[0129] Step 2:

[0130] First, a copolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride and a poly(lactic acid) / fluorescent substance slice are added to the hopper of a melt compound spinning device in a mass ratio of the skin layer to the core layer of 10:90 for melt spinning. The spinning temperature is 195 °C, and the winding speed of the first roller is 10 m / min to obtain a core-shell structured fluorescent solar light collecting primary fiber. After spinning, it is cooled in a water bath, and the water bath temperature is 25 °C;

[0131] Then, one-step hot steam drawing is carried out. The temperature of the one-step hot steam drawing is 80 °C, and the drawing ratio is 4;

[0132] Then, perform a second hot air drawing. The temperature of the second hot air drawing is 120 °C, and the drawing ratio is 1.2;

[0133] Finally, perform heat setting on it. The heat setting temperature is 125 °C to obtain a high-strength skin-core structure fluorescent solar concentrator fiber.

[0134] Example 9. The preparation method of a high-strength skin-core structure fluorescent solar concentrator fiber in this example is carried out according to the following steps:

[0135] Step 1:

[0136] First, dry polylactic acid with a D-lactic acid (D-LA) structural unit content of 2 mol% and a viscosity-average molecular weight of 2.0×10 4 in a vacuum oven at 105 °C for 48 h for later use;

[0137] Then, weigh the raw materials according to the mass ratio of polylactic acid to Eu(OAC)3 of 99.2:0.8, put them into a high-speed mixer for premixing for 5 min, and then perform melt blending and pelletizing in a twin-screw compounding machine. The pelletizing temperature is 185 °C, and the screw speed is 400 rpm;

[0138] Then, vacuum dry at 80 °C for 48 h to obtain polylactic acid / fluorescent substance chips.

[0139] Step 2:

[0140] First, add the copolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride and the polylactic acid / fluorescent substance chips to the hopper of the melt compound spinning equipment according to the mass ratio of the skin layer to the core layer of 15:85 for melt spinning. The spinning temperature is 190 °C, and the winding speed of the first roll is 10 m / min to obtain a skin-core structure fluorescent solar concentrator as-spun fiber. After spinning, cool it in a water bath. The water bath temperature is 25 °C;

[0141] Then, perform a first hot steam drawing. The temperature of the first hot steam drawing is 80 °C, and the drawing ratio is 4;

[0142] Then, perform a second hot air drawing. The temperature of the second hot air drawing is 120 °C, and the drawing ratio is 1.2;

[0143] Finally, perform heat setting on it. The heat setting temperature is 125 °C to obtain a high-strength skin-core structure fluorescent solar concentrator fiber.

[0144] Example 10. The preparation method of a high-strength skin-core structure fluorescent solar concentrator fiber in this example is carried out according to the following steps:

[0145] Step 1:

[0146] First, polylactic acid with a D-lactic acid (D-LA) structural unit content of 2 mol% and a viscosity-average molecular weight of 2.0×10 4 , fluorescent dye Lumogen F Violet 570 (LV570), and a copolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride are dried in a vacuum oven at 80 °C for 48 h for later use;

[0147] Then, raw materials are weighed according to a mass ratio of polylactic acid to LV570 of 98.5:1.5, put into a high-speed mixer for premixing for 10 min, and then melt-blended and pelletized in a twin-screw blender. The pelletizing temperature is 185 °C and the screw rotation speed is 400 rpm;

[0148] Then, it is vacuum-dried at 80 °C for 48 h to obtain polylactic acid / fluorescent substance slices.

[0149] Step 2:

[0150] First, the copolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride and the polylactic acid / fluorescent substance slices are added to the hopper of a melt compound spinning device according to a mass ratio of the skin layer to the core layer of 10:90 for melt spinning. The spinning temperature is 190 °C, the winding speed of the first roller is 10 m / min, and as-spun core-shell structured fluorescent solar concentrator fibers are obtained. After spinning, it is cooled in a water bath, and the water bath temperature is 25 °C;

[0151] Then, it is subjected to one-step hot steam drawing. The temperature of the one-step hot steam drawing is 80 °C and the drawing ratio is 4;

[0152] Then, it is subjected to two-step hot air drawing. The temperature of the two-step hot air drawing is 120 °C and the drawing ratio is 1.2;

[0153] Finally, it is heat-set at 125 °C to obtain high-strength core-shell structured fluorescent solar concentrator fibers.

[0154] Comparative Example 3. The preparation method of a core-shell structured fluorescent solar concentrator fiber in this comparative example is carried out according to the following steps:

[0155] Step 1:

[0156] Polylactic acid with a D-lactic acid (D-LA) structural unit content of 2.5 mol% and a viscosity-average molecular weight of 2.0×10 5 , fluorescent dye Lumogen Red 305 (LR305), and a copolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride are dried in a vacuum oven at 105 °C for 48 h for later use;

[0157] Then, weigh the raw materials according to the mass ratio of polylactic acid to LR305 of 99.2:0.8, put them into a high-speed mixer for premixing for 5 min, and then carry out melt blending and granulation in a twin-screw compounding extruder. The granulation temperature is 185 °C and the screw speed is 400 rpm;

[0158] Then, vacuum dry at 80 °C for 48 h to obtain polylactic acid / fluorescent substance slices.

[0159] Step 2:

[0160] First, add the copolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride and the polylactic acid / fluorescent substance slices to the hopper of a melt compound spinning equipment according to the mass ratio of the skin layer to the core layer of 10:90 for melt spinning. The spinning temperature is 195 °C, the winding speed of the first roller is 10 m / min, and water bath cooling is carried out. The water bath temperature is 25 °C to obtain a core-shell structured fluorescent solar light collecting fiber.

[0161] Comparative Example 4. A method for preparing a core-shell structured solar light collecting fiber of this comparative example is carried out according to the following steps:

[0162] Step 1:

[0163] Polylactic acid with a D-lactic acid (D-LA) structural unit content of 2 mol% and a viscosity-average molecular weight of 2.0×10 4 and the copolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride are dried in a vacuum oven at 80 °C for 48 h and reserved for use.

[0164] Step 2:

[0165] First, add the copolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride and polylactic acid to the hopper of a melt compound spinning equipment according to the mass ratio of the skin layer to the core layer of 10:90 for melt spinning. The spinning temperature is 190 °C, the winding speed of the first roller is 10 m / min to obtain a core-shell structured solar light collecting nascent fiber, and it is cooled by water bath after spinning. The water bath temperature is 25 °C;

[0166] Then, carry out one-step hot steam drawing. The temperature of the one-step hot steam drawing is 80 °C and the drawing ratio is 4;

[0167] Then, carry out two-step hot air drawing. The temperature of the two-step hot air drawing is 120 °C and the drawing ratio is 1.2;

[0168] Finally, carry out heat setting on it. The heat setting temperature is 125 °C to obtain a core-shell structured solar light collecting fiber.

[0169] Performance test:

[0170] (1) The core - sheath structured fluorescent solar light - collecting fibers of Examples 1 - 5 and Comparative Examples 1 - 2 were characterized and tested for mechanical properties, optical properties, and light - collecting properties. The specific test results are shown in Table 1 below:

[0171] Table 1 Comparison table of performance test results of core - sheath structured fluorescent solar light - collecting fibers

[0172]

[0173] As can be seen from Table 1 above:

[0174] (1) Compared with Comparative Example 1, for Examples 1 - 5, pure PLA multifilaments have no light - collecting effect, while the core - sheath structured fluorescent solar light - collecting multifilaments have a significant light - collecting effect.

[0175] (2) Compared with Comparative Example 2, for Example 1, the breaking strength of the heat - drawn transparent core - sheath structured multifilaments is 2.38 times that of the as - spun multifilaments, increasing from 1.2 cN / dtex to 2.85 cN / dtex.

[0176] (2) The core - sheath structured fluorescent solar light - collecting monofilaments of Examples 6 - 10 and Comparative Examples 3 - 4 were characterized and tested for diameter, mechanical properties, optical properties, and light - collecting properties. The specific test results are shown in Table 2 below:

[0177] Table 2 Comparison table of performance test results of core - sheath structured fluorescent solar light - collecting monofilaments

[0178]

[0179] As can be seen from Table 2 above:

[0180] (1) Compared with Comparative Example 3, for Example 7, the breaking strength of the drawn large - diameter core - sheath structured fluorescent solar light - collecting monofilaments is 2.09 times that of the undrawn monofilaments, increasing from 150.6 MPa to 400.8 MPa.

[0181] (2) Compared with Comparative Example 4, for Examples 6 - 10, the large - diameter core - sheath structured monofilaments without introduced fluorescent substances have no light - collecting effect, while the high - strength large - diameter core - sheath structured fluorescent solar light - collecting monofilaments of the present invention have a significant light - collecting effect.

[0182] It should be noted that the above examples are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A high-strength core-shell structure fluorescent solar concentrating fiber, characterized in that, The core layer is prepared from polylactic acid and a fluorescent substance, and the skin layer is a copolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride; The mass ratio of polylactic acid to the fluorescent substance in the core layer is 99.2:0.8, 99.6:0.4 or 98.5:1.5, and the mass ratio of the skin layer to the core layer is 15:85 or 10:90; The viscosity-average molecular weight of polylactic acid is 1.0×10 4 ~2.0×10 6 ; The fluorescent substance is one of fluorescent dye Lumogen F Yellow 083, fluorescent dye Lumogen Red 305, fluorescent dye Eu(OAC)3, fluorescent dye Lumogen F Violet 570; The preparation method of the high-strength skin-core structure fluorescent solar concentrator fiber comprises the following steps: Step 1: Melting and blending polylactic acid and the fluorescent substance for granulation, and vacuum drying to obtain polylactic acid / fluorescent substance chips; Step 2: Melting and spinning the copolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride and the polylactic acid / fluorescent substance chips, cooling in a water bath after spinning, then performing first-stage hot steam drawing, second-stage hot air drawing, and finally heat setting to obtain the high-strength skin-core structure fluorescent solar concentrator fiber; The spinning temperature is 130 - 250 °C, the winding speed of the first roller is 1 - 50 m / min, the water bath temperature is 0 - 75 °C, the temperature of the first-stage hot steam drawing is 20 - 95 °C, the drawing ratio is 2 - 15, the temperature of the second-stage hot air drawing is 65 - 140 °C, the drawing ratio is 1 - 10, and the heat setting temperature is 90 - 150 °C.

2. The high-strength skin-core structure fluorescent solar concentrator fiber according to claim 1, characterized in that In Step 1, premixing is carried out for 3 - 15 min before granulation, the granulation temperature is 130 - 250 °C, the rotation speed is 50 - 500 rpm, the vacuum drying temperature is 65 - 120 °C, and the time is 8 - 48 h.

3. The high-strength skin-core structure fluorescent solar concentrator fiber described in Claim 1 is used for preparing a fluorescent solar concentrator.

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