Continuous preparation method and application of polyvinylidene fluoride porous radiation cooling fiber

Abstract

The invention relates to the technical field of radiation refrigeration, in particular to a continuous preparation method and application of polyvinylidene fluoride porous radiation cooling fibers.The continuous preparation method comprises the following steps that polyvinylidene fluoride, functional filler and a green diluent are blended in proportion and then added into blending extrusion equipment to be blended and melted, and the polyvinylidene fluoride porous radiation cooling fiber is obtained; then continuously extruding through a spinning die head to obtain a homogeneous solution; guiding and stretching the homogeneous solution into a fiber shape, drawing the homogeneous solution into a solidification liquid, and winding by using a winding machine to form a primary gel fiber; carrying out solid-phase stretching on the primary gel fiber to obtain a stretched gel fiber; immersing the stretched gel fibers into the extract liquor, removing the green diluent, and drying to obtain polyvinylidene fluoride porous fibers; and feeding the polyvinylidene fluoride porous fiber into a drying oven, and drying to finally prepare the polyvinylidene fluoride porous radiation cooling fiber. According to the application, the polyvinylidene fluoride porous radiation cooling fibers are used as raw materials to be processed into textile fabrics or applied to cooling of buildings.

Description

Technical Field

[0001] The present invention relates to the technical field of radiative cooling, and particularly relates to a continuous preparation method and application of polyvinylidene fluoride porous radiative cooling fibers. Background Art

[0002] Due to its efficient and passive thermal regulation characteristics, radiative cooling technology has become an important research direction for solving energy and environmental problems in recent years. This technology achieves a cooling effect without external energy input by reflecting solar radiation and emitting infrared radiation, and is widely used in fields such as architecture, textiles, and personal thermal management. Polyvinylidene fluoride (PVDF) is regarded as an ideal material for preparing porous radiative cooling fibers due to its excellent high-temperature resistance, chemical stability, and radiative cooling performance. However, existing preparation technologies still have many limitations, especially in terms of environmental friendliness and production efficiency, which restrict their large-scale application.

[0003] Currently, electrospinning technology is the mainstream method for preparing PVDF porous fibers. For example, a Chinese patent with the patent number CN202011524345.9 discloses an electrospinning method based on solution evaporation-induced phase separation. In this method, PVDF and polyethylene oxide (PEO) are dissolved in a mixed solvent of N,N-dimethylformamide (DMF) and a small amount of water, and after being stirred for a long time (12 hours) to form a homogeneous solution, porous fibers are obtained through electrospinning and post-treatment. However, this method has significant defects: toxic solvents such as N,N-dimethylformamide (DMF), dichloromethane (DCM), chloroform, and acetone will harm the health of industrial workers and impose a burden on the environment.

[0004] In view of the above problems, there is an urgent need to develop an environmentally friendly, efficient, continuous, and large-scale production suitable preparation method for polyvinylidene fluoride porous fibers. Summary of the Invention

[0005] The first object of the present invention is to overcome the defects and deficiencies of the prior art, and provide a continuous preparation method for polyvinylidene fluoride porous radiative cooling fibers, which can efficiently and greenly continuously produce polyvinylidene fluoride porous radiative cooling fibers with the potential for large-scale production and good radiative cooling performance.

[0006] The second object of the present invention is to provide an application of polyvinylidene fluoride porous radiative cooling fibers.

[0007] The object of the present invention can be achieved by the following technical solutions: A continuous preparation method for polyvinylidene fluoride porous radiative cooling fibers, comprising the following steps: Step 1: Blend polyvinylidene fluoride and functional fillers with a green diluent according to a ratio, then add them to a co - blending and extrusion device for co - blending and melting to form a mixture. Then, continuously extrude the mixture through a spinneret die to obtain a homogeneous melt. The total content of polyvinylidene fluoride and functional fillers in the mixture is 10 - 40% by mass percentage, and the content of the green diluent in the mixture is 60 - 90% by mass percentage. The temperature during the blending of polyvinylidene fluoride, functional fillers, and the green diluent is 140 - 300 °C; Step 2: Guide and stretch the homogeneous melt extruded from the nozzle of the spinneret die in Step 1 into fibrous form, draw it into a water bath tank containing a coagulation liquid at a set temperature, and wind it up with a winder to form nascent gel fibers with a set form. The temperature of the coagulation liquid is 5 - 90 °C. The draw ratio of the homogeneous melt is 1 - 15 times, and the drawing speed of the nascent gel film is 1 - 15 times the extrusion speed of the homogeneous melt. Among them, the drawing speed of the nascent gel fibers is much greater than the continuous extrusion speed of the homogeneous melt through the nozzle of the spinneret die, so that the homogeneous melt is subjected to a stretching effect; Step 3: Perform solid - phase stretching on the nascent gel fibers continuously prepared in Step 2 to obtain stretched gel fibers. The draw ratio is 2 - 20 times, and the temperature is 110 - 160 °C; Step 4: Immerse the stretched gel fibers obtained in Step 3 in an extraction liquid, remove the green diluent, and then dry to obtain polyvinylidene fluoride porous fibers; Step 5: Send the polyvinylidene fluoride porous fibers obtained in Step 4 into an oven and conduct a drying treatment at 30 - 180 °C for 2 h to finally prepare polyvinylidene fluoride porous radiation - cooling fibers.

[0008] As a preference, in Step 1, the functional filler is one or more of magnesium oxide, zirconium dioxide, silicon dioxide, aluminum oxide, titanium dioxide, barium titanate, lead titanate, and lithium niobate.

[0009] As a preference, in Step 1, the green diluent is one or more of polyethylene glycol, γ - butyrolactone, tributyl acetylcitrate, triethyl phosphate, glyceryl triacetate, propylene carbonate, triethyl citrate, dioctyl sebacate, and triethylene glycol.

[0010] As a preference, in Step 1, the co - blending and extrusion device is a twin - rotor extruder, a twin - screw extruder, a triple - screw extruder, a row - type screw extruder, or a biaxial eccentric rotor extruder.

[0011] As a preference, in Step 2, the coagulation liquid is pure water or a mixed solution of the green diluent in Step 1 and pure water, where the mass percentage of the green diluent in the mixed solution is 5% - 50%.

[0012] As a preference, in step 4, the porosity of the polyvinylidene fluoride porous fiber is 40 - 70%, and the average pore size distribution is adjustable from 0.1 - 5 μm.

[0013] As a preference, in step 4, the weight percentage of polyvinylidene fluoride is 50 - 100%, and the weight percentage of the functional filler is 0 - 50%.

[0014] An application of the polyvinylidene fluoride porous radiative cooling fiber as described above, using the polyvinylidene fluoride porous radiative cooling fiber as a raw material to process into a textile or apply to the cooling of a building.

[0015] Compared with the prior art, the present invention has the following advantages and beneficial effects: Compared with the prior art, the present invention uses a green diluent combined with melt stretching and drying treatment. The green diluent is a solvent that is environmentally friendly during the polymer processing, which has low toxicity, biodegradability, renewable property and conforms to the principles of green chemistry. It can significantly reduce the harm to the environment and human health while ensuring the process performance, and can continuously prepare polyvinylidene fluoride porous radiative cooling fibers efficiently and greenly. This method has the characteristics of environmental friendliness, high production efficiency, low cost, and simple process. The prepared polyvinylidene fluoride porous radiative cooling fiber has excellent mechanical properties and thermal stability, and can be well applied to the field of radiative cooling. Description of the Drawings

[0016] Figure 1 It is the surface SEM image of the polyvinylidene fluoride porous radiative cooling fiber in Example 1; Figure 2 It is the cross-section SEM image of the polyvinylidene fluoride porous radiative cooling fiber in Example 1. Detailed Embodiments

[0017] The following further describes the present invention in detail with reference to the embodiments and the drawings, but the embodiments of the present invention are not limited thereto.

[0018] Example 1 A continuous preparation method of a polyvinylidene fluoride porous radiative cooling fiber in this example includes the following steps: Step 1: After adding 30 parts of polyvinylidene fluoride (PVDF), 5 parts of silicon dioxide (SiO2) with a particle size of 2 - 3 μm and 65 parts of triethyl citrate (TEC) into a twin-screw extruder for co-blending and melting, set the temperature of the feeding section of the twin-screw extruder to 160 °C, and the temperature of other sections to 175 °C to form a mixture, and then continuously extrude the mixture through a spinneret die to obtain a homogeneous melt; Step 2: Guide and stretch the homogeneous melt extruded from the nozzle of the spinneret die in Step 1 into fibrous form, draw it into a water bath tank of coagulating liquid at a temperature of 25°C, and wind it up with a winder to form filamentous primary gel fibers; the draw ratio of the homogeneous melt is 1 to 15 times, and the drawing speed of the primary gel film is 1 to 15 times the extrusion speed of the homogeneous melt; wherein the drawing speed of the primary gel fibers is much greater than the continuous extrusion speed of the homogeneous melt through the nozzle of the spinneret die, so that the homogeneous melt is subjected to a stretching effect; the extrusion speed of the homogeneous melt is 3 m / min, and the rotation speed of the casting roll is 15 m / min; Step 3: Perform solid-phase stretching on the primary gel fibers continuously prepared in Step 2 to obtain stretched gel fibers; the draw ratio is 10 times, and the stretching temperature is 150°C; Step 4: Immerse the stretched gel fibers obtained in Step 3 in an extraction liquid, remove the green diluent and then dry to obtain polyvinylidene fluoride porous fibers; the extraction liquid is a mixed solution of ethanol and pure water, wherein the mass percentage of ethanol in the mixed solution is 95%, and the temperature of the extraction liquid is 25°C; Step 5: Feed the polyvinylidene fluoride porous fibers obtained in Step 4 into an oven, perform a drying treatment at 60°C, and the drying time is 2 h, finally preparing polyvinylidene fluoride porous radiation cooling fibers.

[0019] The polyvinylidene fluoride porous radiation cooling fibers prepared in this example have a diameter of 40 μm, as Figure 1 and Figure 2 shown, the tensile strength is 24 MPa, the porosity is 60%, the average pore diameter is 0.5 μm, the solar reflectance is 95%, and the mid-infrared emissivity is 94%.

[0020] An application of the polyvinylidene fluoride porous radiation cooling fibers as described above, which is processed into a textile or applied to the cooling of a building with the polyvinylidene fluoride porous radiation cooling fibers as raw materials.

[0021] Example 2 A continuous preparation method of polyvinylidene fluoride porous radiation cooling fibers in this example includes the following steps: Add 20 parts of polyvinylidene difluoride (PVDF) and 15 parts of silicon dioxide (SiO2) with a particle size of 1 - 3 μm into a twin-screw extruder, Step 1: Add 30 parts of polyvinylidene difluoride (PVDF), 5 parts of silicon dioxide (SiO2) with a particle size of 2 - 3 μm and 65 parts of triethyl citrate (TEC) into a twin-screw extruder for co-blending and melting. Set the temperature of the feeding section of the twin-screw extruder to 140°C, and the temperature of other sections to 155°C to form a mixture, and then continuously extrude the mixture through a spinneret die to obtain a homogeneous melt; Step 2: Guide and stretch the homogeneous melt extruded from the nozzle of the spinneret die in Step 1 into fibrous form, draw it into a water bath tank of coagulating liquid at a temperature of 25°C, and wind it up with a winder to form filamentous as-spun gel fibers; the draw ratio of the homogeneous melt is 1 to 15 times, and the drawing speed of the as-spun gel film is 1 to 15 times the extrusion speed of the homogeneous melt; among them, the drawing speed of the as-spun gel fibers is much greater than the continuous extrusion speed of the homogeneous melt through the nozzle of the spinneret die, so that the homogeneous melt is subjected to a stretching effect; the extrusion speed of the homogeneous melt is 3 m / min, and the rotation speed of the casting roll is 15 m / min; Step 3: Perform solid-phase stretching on the as-spun gel fibers continuously prepared in Step 2 to obtain stretched gel fibers; the draw ratio is 8 times, and the stretching temperature is 150°C; Step 4: Immerse the stretched gel fibers obtained in Step 3 in the extraction liquid, remove the green diluent and then dry to obtain polyvinylidene fluoride porous fibers; the extraction liquid is a mixed solution of ethanol and pure water, wherein the mass percentage of ethanol in the mixed solution is 95%, and the temperature of the extraction liquid is 25°C; Step 5: Feed the polyvinylidene fluoride porous fibers obtained in Step 4 into an oven, perform drying treatment at 60°C, and the drying time is 2 h, finally preparing polyvinylidene fluoride porous radiative cooling fibers.

[0022] The polyvinylidene fluoride porous radiative cooling fibers prepared in this example have a diameter of 50 μm, a tensile strength of 12 MPa, a porosity of 50%, an average pore diameter of 0.6 μm, a solar reflectance of 92%, and a mid-infrared emissivity of 93%.

[0023] An application of the polyvinylidene fluoride porous radiative cooling fibers as described above, using the polyvinylidene fluoride porous radiative cooling fibers as raw materials to process into textiles or apply to the cooling of buildings.

[0024] In addition to the methods mentioned in the above embodiments, in Step 1, the functional filler can be one or more of magnesium oxide (MgO), zirconium dioxide (ZrO2), aluminum oxide (Al2O3), titanium dioxide (TiO2), barium titanate (BaTiO3), lead titanate (PbTiO3), lithium niobate (LiNbO3); the green diluent can be one or more of polyethylene glycol (PEG), γ-butyrolactone (γ-BL), tributyl acetyl citrate (ATBC), triethyl phosphate (TEP), triacetin (GTA), propylene carbonate (PC), dioctyl sebacate (DOS), triethylene glycol (TEG); the co-blending extrusion equipment can be a twin-rotor extruder, a twin-screw extruder, a triple-screw extruder, a row-type screw extruder or a twin-shaft eccentric rotor extruder; In step 2, the solidifying liquid is pure water or a mixed solution of the green diluent in step 1 and pure water, wherein the mass percentage of the green diluent in the mixed solution is 5% to 50%.

[0025] In step 4, the porosity of the polyvinylidene fluoride porous fiber can be 40% to 70%, and the average pore size distribution is adjustable from 0.1 to 5 μm; the weight percentage of polyvinylidene fluoride can be 50% to 100%, and the weight percentage of the functional filler can be 0% to 50%. All these transformation methods are within the protection scope of the present invention.

[0026] The above embodiments merely represent several implementation manners of the present invention. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the appended claims.

Claims

1. A continuous preparation method of polyvinylidene fluoride porous radiation cooling fibers, characterized in that, The steps include: Step 1: After polyvinylidene fluoride and a functional filler are blended with a green diluent according to a ratio, the mixture is added into a blending extrusion device for blending and melting to form a mixture, and then the mixture is continuously extruded through a spinneret to obtain a homogeneous solution; the total content of the polyvinylidene fluoride and the functional filler in the mixture is 10-40% by mass, and the content of the green diluent in the mixture is 60-90% by mass; the temperature when the polyvinylidene fluoride, the functional filler and the green diluent are blended is 140-300°C; Step 2: The homogeneous melt extruded through the nozzle of the spinneret in step 1 is guided and stretched into a fiber shape, drawn into a water bath of a coagulation liquid with a set temperature, and wound up with a winder to form a nascent gel fiber with a set form; the temperature of the coagulation liquid is 5 to 90° C.; the stretching ratio of the homogeneous melt is 1 to 15 times, and the pulling speed of the nascent gel film is 1 to 15 times the extrusion speed of the homogeneous melt; wherein the pulling speed of the nascent gel fiber is much greater than the continuous extrusion speed of the homogeneous melt through the nozzle of the spinneret, so that the homogeneous melt is stretched; Step 3: solid phase stretching the primary gel fiber continuously prepared in step 2 to obtain stretched gel fiber; the stretching ratio is 2 to 20 times, and the temperature is 110 to 160°C; Step 4: immersing the stretched gel fiber obtained in step 3 into an extracting solution, removing the green diluent and drying to obtain a polyvinylidene fluoride porous fiber; Step 5: The polyvinylidene fluoride porous fiber obtained in step 4 is sent into an oven and dried at 30-180°C for 2 hours to finally prepare the polyvinylidene fluoride porous radiation cooling fiber.

2. The continuous preparation method of a polyvinylidene fluoride porous radiative cooling fiber according to claim 1, wherein: In step 1, the functional filler is one or more of magnesium oxide, zirconium dioxide, silicon dioxide, aluminum oxide, titanium dioxide, barium titanate, lead titanate, and lithium niobate.

3. A continuous preparation method of a polyvinylidene fluoride porous radiation cooling fiber according to claim 1, characterized in that: In step 1, the green diluent is one or more of polyethylene glycol, γ-butyrolactone, acetyl tributyl citrate, triethyl phosphate, triacetin, propylene carbonate, triethyl citrate, dioctyl sebacate, and triethylene glycol.

4. A continuous preparation method of polyvinylidene fluoride porous radiation cooling fibers according to claim 1, characterized in that: In step 1, the blending extrusion equipment is a twin-rotor extruder, a twin-screw extruder, a three-screw extruder, a row screw extruder or a twin-shaft eccentric rotor extruder.

5. A continuous preparation method of porous polyvinylidene fluoride radiation cooling fibers according to claim 1, characterized in that: In step 2, the coagulation liquid is pure water, or a mixed solution of the green diluent in step 1 and pure water, wherein the mass percentage of the green diluent in the mixed solution is 5% to 50%.

6. A continuous preparation method of polyvinylidene fluoride porous radiation cooling fiber according to claim 1, characterized in that: In step 4, the porosity of the polyvinylidene fluoride porous fiber is 40-70%, and the average pore size distribution is adjustable from 0.1-5 μm.

7. A continuous preparation method of polyvinylidene fluoride porous radiation cooling fibers according to claim 1, characterized in that: In step 4, the weight percentage of polyvinylidene fluoride is 50-100%, and the weight percentage of the functional filler is 0-50%.

8. Use of the polyvinylidene fluoride porous radiative cooling fiber according to any one of claims 1-7, characterized in that: Polyvinylidene fluoride porous radiation cooling fiber is used as raw material to be processed into textiles or used for cooling buildings.

Images