A porous polymer fiber and a method of making and using the same

Abstract

The application discloses a kind of porous polymer fibers and preparation method and application thereof, and relates to the technical field of foamed material.The preparation method of the porous polymer fiber provided by the application foams polymer matrix containing foaming agent by adopting the process of extrusion foaming, and by controlling the parameters in the extrusion process, the controllable foaming of polymer is realized, and the obtained porous polymer fiber, the density reaches 0.7g / cm 3 The following has high porosity, and the cell distribution and size are uniform, the range of cell size in the fiber is kept within 20 μm, and the cells are distributed from the center to the outer layer, and the diameter of the fiber can reach 0.3-0.4 mm while maintaining high uniformity.

Description

Technical Field

[0001] This invention relates to the field of foaming materials technology, specifically to a porous polymer fiber, its preparation method, and its application. Background Technology

[0002] Polymer porous fibers, with their porous structure, possess advantages such as lightweight, thermal insulation, breathability, and high flexibility, and have broad application prospects, thus attracting widespread attention from researchers in recent years. Existing reports draw inspiration from porous fibers found in nature, such as those from polar bears and camels, and employ methods such as ice crystal templates and phase separation to prepare polymer porous fibers. However, existing processing methods for porous fibers use large amounts of solvents, have low processing efficiency, and produce fibers with excessively large diameters, making it difficult to meet practical application requirements.

[0003] Continuous extrusion foaming technology using supercritical fluids as foaming agents can prepare polymer foam filaments with diameters in the millimeter and micrometer ranges. For example, existing technology (Polymer Engineering Sciences, 2013, 53:2360) has explored the preparation of polymer foam fibers through continuous extrusion foaming. However, the TPU foam fibers prepared by this existing technology have large diameters, low porosity, and uneven thickness, making it difficult to meet the application requirements of the industry. How to prepare polymer porous fibers with high porosity, uniform thickness, and uniform cell size has become a major challenge restricting the application of porous fibers. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for preparing porous polymer fibers. The method employs an extrusion foaming process to foam a polymer matrix containing a foaming agent. By controlling the parameters in the extrusion process, controllable foaming of the polymer is achieved, resulting in porous polymer fibers with high porosity and excellent uniformity in cell distribution and filament diameter.

[0005] Another object of the present invention is to provide a porous polymer fiber.

[0006] Another object of the present invention is to provide an application of porous polymer fibers.

[0007] The above-mentioned objective of this invention is achieved through the following technical solution:

[0008] A method for preparing porous polymer fibers includes the following steps:

[0009] S1. Extruding and foaming polymer particles containing a foaming agent to obtain a foamed melt; the extrusion and foaming is performed using a single-screw extruder, which sequentially includes a first heating section, a second heating section, and a third heating section. The temperature of the first heating section is 0–30°C, the temperature of the second heating section is 160–330°C, and the temperature of the third heating section is 190–380°C, wherein the real-time temperature of the third heating section is higher than that of the second heating section; the screw speed of the single-screw extruder is 20–40 rpm, and the content of the foaming agent in the polymer particles containing the foaming agent is 0.1–10%; the polymer includes at least one of crystalline polymers, amorphous polymers, semi-crystalline polymers, and thermoplastic elastomers;

[0010] S2. The foamed melt obtained in step S1 is stretched and shaped to produce porous polymer fibers; the stretching and shaping includes the steps of traction and stretching, the traction temperature is 100-180℃, the stretching temperature is 20-80℃, and the stretching ratio during the stretching and shaping process is 1.5-5.

[0011] In a specific embodiment of the present invention, step S1 controls the temperature of the first heating section by connecting at least one of a water cooling system and a cold air system to the first heating section.

[0012] In the method for preparing porous polymer fibers provided by this invention, polymer particles containing a foaming agent can be quantitatively and timed extruded from a single-screw extruder to achieve controllable foaming. Specifically, after the polymer particles containing the foaming agent are conveyed into the first screw section, the particle temperature is low, which can reduce the loss of the foaming agent and ensure stable material conveying. The particles containing the foaming agent melt in the second screw section and are compacted by the screw structure, achieving densification between particle structures and preventing the escape of the foaming agent. The particles containing the foaming agent continue to melt and foam in the third screw section, and the metering properties of the screw structure ensure stable delivery of the foamed melt to the extruder die. While controlling the extrusion temperature, this invention also controls the foaming agent content in the raw material and the screw speed. By controlling the above parameters, this invention can achieve controllable foaming of polymer particles containing foaming agent. Then, in step S2, controllable stretching and forming are achieved by controlling the stretch ratio and temperature, which improves the fineness of the foamed melt and obtains polymer porous fibers with excellent uniformity in coarseness and cell distribution, as well as high porosity.

[0013] It should be noted that, in step S2 of this invention, the traction is the movement of the foamed melt driven by the traction roller; the stretching is the traction and stretching of the foamed melt by the stretching roller, so that the fibers gradually reach the predetermined thickness.

[0014] In a specific embodiment of the present invention, the draw ratio of the stretching and shaping is kept consistent during the stretching and traction processes.

[0015] In a specific embodiment of the present invention, the method for preparing porous polymer fibers provided by the present invention is carried out in a micro-extrusion device, the micro-extrusion device including a feeding unit, a micro-extrusion unit, a drawing unit, and a winding unit; the micro-extrusion unit is a single-screw extruder; the drawing unit includes a traction roller, a heating duct, and a drawing roller, wherein one heating duct and one drawing roller form a group, preferably the drawing unit includes one traction roller and one or more groups of heating ducts and drawing rollers.

[0016] In a specific embodiment of the present invention, the polymer particles containing a foaming agent described in step S1 are prepared by blending the polymer particles with the foaming agent. When the foaming agent is a fluid, the polymer particles are blended with the foaming agent by impregnation.

[0017] In a specific embodiment of the present invention, the temperature control accuracy of the single screw extruder in step S1 is 0.5 to 5°C, preferably 1 to 3°C.

[0018] In a specific embodiment of the present invention, the residence time of the polymer particles containing the foaming agent in the second heating section and / or the third heating section in step S1 is 0.1 to 1.5 s, preferably 0.2 to 1.0 s, and more preferably 0.3 to 0.8 s. By controlling the extruder screw speed, the residence time of the polymer particles in different heating sections of the extruder can be controlled, thereby controlling the degree of cell nucleation and growth of the polymer particles and the cell size.

[0019] Preferably, the length of the first heating section of the single-screw extruder in step S1 is 25-35% of the screw length, and the length of the second heating section is 35-45% of the screw length.

[0020] In a specific embodiment of the present invention, the total length of the three heating sections of the single-screw extruder described in step S1 accounts for 90% of the screw length.

[0021] Preferably, the content of the foaming agent in the polymer particles containing the foaming agent in step S1 is 0.5% to 5%.

[0022] In a specific embodiment of the present invention, the shape of the polymer particles containing the foaming agent in step S1 is at least one of round, elliptical, and knife-cut granules, the average diameter of the particles is 0.5 to 5.0 mm, the fluctuation range of the average diameter is ±0.5 to 1 mm, and the hardness range of the particles is Shore A10 to Shore D85.

[0023] In a specific embodiment of the present invention, the loss rate of the foaming agent in the polymer particles containing the foaming agent in step S1 is less than 10%, preferably less than 5%.

[0024] Preferably, the amorphous polymer includes at least one of polystyrene (PS), polymethyl methacrylate (PMMA), polyetherimide (PEI), polyimide (PI), and polysulfone (PSF).

[0025] Preferably, the semi-crystalline polymer includes at least one of polyethylene terephthalate (PET), polylactic acid (PLA), and polyetheretherketone (PEEK).

[0026] Preferably, the crystalline polymer includes at least one of polyethylene (PE), polypropylene (PP), and nylon (PA).

[0027] Preferably, the foaming agent includes at least one of a solid foaming agent and a fluid foaming agent.

[0028] More preferably, the fluid foaming agent includes at least one of CO2, N2, alkanes, and HCFCs.

[0029] More preferably, the solid foaming agent includes at least one of expandable microspheres, carbonates, azodicarbonamide, and N,N-dinitrospentamethylenetetramine.

[0030] Preferably, the temperature of the traction is 100-150°C, and the temperature of the stretching is 20-40°C.

[0031] More preferably, the draw ratio of the stretching and shaping in step S2 is 2 to 3.

[0032] In a specific embodiment of the present invention, the linear speed of the traction roller in step S2 is 40 to 60 m / min.

[0033] In a specific embodiment of the present invention, the linear speed of the drawing roller in step S2 is 20 to 40 m / min.

[0034] The present invention also protects a porous polymer fiber prepared by the above preparation method.

[0035] Preferably, the porous polymer fiber has a diameter of 0.05–0.3 mm and a density of 0.6–0.95 g / cm³. 3 .

[0036] More preferably, the diameter of the porous polymer fiber is 0.1 to 0.3 mm.

[0037] This invention also protects the application of the above-mentioned porous polymer fibers in the fields of clothing and wearable devices.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] The porous polymer fibers prepared by this invention have high porosity and a density of 0.7 g / cm³. 3 The difference in pore size in the fiber is kept within 20μm and is distributed from the center to the outer layer. At the same time, the fiber diameter can reach 0.3 to 0.4 mm while still maintaining high uniformity. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the micro-extrusion device used in this invention. Detailed Implementation

[0041] The present invention will be further described below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise stated, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents. The raw material information in each embodiment and comparative example is as follows (the parts involving hardness refer to Shore hardness):

[0042] Amorphous polymer A

[0043] A1, Polystyrene PS, grade GPPS158K, BASF Yangtze;

[0044] A2, Polyetherimide (PEI), Grade 1000, SABIC;

[0045] Crystalline polymer B

[0046] B1, Low-density polyethylene (LDPE), grade 2426H, Maoming Petrochemical;

[0047] B2, PEEK, grade 1000, Mitsubishi Chemical;

[0048] Thermoplastic elastomer C

[0049] Thermoplastic polyurethane (TPU), hardness 60A, BASF, Germany.

[0050] Examples 1-14

[0051] This embodiment provides a series of methods for preparing porous polymer fibers with different raw materials and process parameters. The preparation methods are carried out in a micro-extrusion device, which includes a feeding unit, a micro-extrusion unit, a drawing unit, and a winding unit. The micro-extrusion unit is a single-screw extruder. The drawing unit includes a traction roller, a heating tunnel, and a drawing roller, wherein only one set of heating tunnel and drawing roller is included.

[0052] The preparation method described in this embodiment includes the following steps:

[0053] S1. Extruding and foaming polymer particles containing a foaming agent to obtain a foamed melt; the extrusion and foaming is carried out using a single-screw extruder, which sequentially includes a first heating section, a second heating section, and a third heating section. The temperature of the first heating section is 0–30°C, the temperature of the second heating section is 160–330°C, and the temperature of the third heating section is 190–380°C. The real-time temperature of the third heating section is higher than that of the second heating section. In the single-screw extruder, the length of the first heating section accounts for 30% of the screw length, the length of the second heating section accounts for 40% of the screw length, the screw speed is 30 rpm, the foaming agent content in the polymer particles containing the foaming agent is 5%, and the residence time in the second and third heating sections is 0.5 s.

[0054] S2. The foamed melt obtained in step S1 is stretched and shaped to produce porous polymer fibers; wherein the stretching ratio of the stretching and shaping is 2.5 and the temperature of the stretching roller is 30°C.

[0055] The specific raw materials and process parameters used in this embodiment are shown in Table 1 below:

[0056] Table 1. Raw materials and process parameters used in Examples 1-14

[0057]

[0058]

[0059] Comparative Example 1

[0060] A method for preparing porous polymer fibers, wherein the only difference from Example 5 is:

[0061] The foaming agent content in the polymer particles containing foaming agent described in step S1 is 15%.

[0062] Comparative Example 2

[0063] A method for preparing porous polymer fibers, wherein the only difference from Example 5 is:

[0064] The screw speed of the single-screw extruder described in step S1 is 5 rpm.

[0065] Comparative Example 3

[0066] A method for preparing porous polymer fibers, wherein the only difference from Example 5 is:

[0067] The temperature of the first heating section of the single-screw extruder described in step S1 is 100°C.

[0068] Comparative Example 4

[0069] A method for preparing porous polymer fibers, wherein the only difference from Example 5 is:

[0070] The temperature of the first heating section of the single-screw extruder described in step S1 is -10℃.

[0071] Comparative Example 5

[0072] A method for preparing porous polymer fibers, wherein the only difference from Example 5 is:

[0073] The temperature of the second heating section of the single-screw extruder described in step S1 is 230°C.

[0074] Comparative Example 6

[0075] A method for preparing porous polymer fibers, wherein the only difference from Example 5 is:

[0076] The temperature of the second heating section of the single-screw extruder described in step S1 is 110°C.

[0077] Comparative Example 7

[0078] A method for preparing porous polymer fibers, wherein the only difference from Example 5 is:

[0079] The screw speed of the single-screw extruder described in step S1 is 60 rpm.

[0080] Performance testing

[0081] Foaming behavior test: measured by visual observation.

[0082] The size and distribution of bubbles were measured by scanning electron microscopy (SEM).

[0083] Fiber diameter test: Measured by a laser diameter gauge.

[0084] Fiber density test: Measured by an electronic density balance.

[0085] The specific performance test data is shown in Table 2 below:

[0086] Table 2. Performance test data of fibers obtained in the examples and comparative examples

[0087]

[0088]

[0089]

[0090]

[0091] As can be seen from the data in Table 2 above, the porous polymer fibers prepared using the method provided in this invention have a density of 0.7 g / cm³. 3 The following describes a fiber with high porosity, uniform cell distribution and size, and a cell size range within 20 μm, distributed from the center to the outer layer. The fiber diameter can reach 0.3–0.4 mm while maintaining high uniformity.

[0092] As can be seen from the data in Examples 5, 9-10, when the temperature of the heating section during the extrusion process in step S1 is 5°C (Example 5), the degree of fiber foaming is more controllable, the extrusion is more stable, and the filament diameter is more uniform.

[0093] As can be seen from the data in Examples 5 and 11-12, when the foaming agent content in the polymer particles containing the foaming agent is within the preferred range of 0.5-5 wt% in this invention (Example 5), the foaming of the fiber is more controllable, the extrusion is stable, the filament diameter is uniform, and the pores are smaller.

[0094] According to the data in Examples 5 and 13-14 in Table 2, when the traction temperature during the stretching and setting process is preferably 100-150°C and the stretching temperature is preferably 20-40°C (Example 5), the resulting porous polymer fibers have a uniform distribution of pores and are not easily broken. At the same time, the resulting fibers are also uniform in thickness.

[0095] As can be seen from Comparative Example 1, the preparation method provided by the present invention also has certain requirements on the content of foaming agent in the raw materials. In Comparative Example 1, due to the excessive content of foaming agent, the polymer melt expands excessively at the die during extrusion, resulting in severe cell coalescence and cell wall rupture, and uneven surface rupture.

[0096] As can be seen from the data in Comparative Examples 2 and 7, excessively high or low screw speeds during extrusion can lead to uncontrollable foaming. Specifically, when the screw speed is too high (Comparative Example 7), the raw material is difficult to foam sufficiently, while when the screw speed is too low (Comparative Example 2), the raw material containing the foaming agent stays in the heating section for too long, causing the gas to escape completely before extrusion through the die, making it impossible to prepare foamed fibers.

[0097] As can be seen from the data in Comparative Examples 3-6, the temperature of each extrusion section in step S1 of this invention must be within a certain range to obtain controllable foamed filaments. Specifically, the data from Comparative Examples 3-4 show that if the feed section temperature is too high (Comparative Example 3), the foaming agent will escape prematurely, resulting in solid fibers; if the feed section temperature is too low (Comparative Example 4), the raw material plasticization effect is poor, extrusion is unstable, and the machine is prone to shutdown due to excessive screw pressure, resulting in uneven diameter of the foamed filaments. The data from Comparative Examples 5-6 show that if the plasticizing section temperature is too high (Comparative Example 5), the raw material containing the foaming agent enters the melt state prematurely, and the rapid gas escape, coupled with excessively long cell growth time, leads to severe cell aggregation, resulting in almost no cells inside the filament; if the plasticizing section temperature is too low (Comparative Example 6), the polymer particles containing the foaming agent are poorly plasticized, leading to unstable extrusion, uneven diameter of the foamed filaments, and a large amount of insoluble matter.

[0098] According to the data in Comparative Example 7, the screw speed of a single-screw extruder also affects the structure of the foamed filament. Excessive speed can easily cause the extruded melt to form turbulence and become unstable, resulting in unstable extrusion and uneven diameter, ultimately leading to a spiral shape in the product.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing porous polymer fibers, characterized in that, Includes the following steps: S1. Extruding and foaming polymer particles containing a foaming agent to obtain a foamed melt; the extrusion and foaming is performed using a single-screw extruder, which sequentially includes a first heating section, a second heating section, and a third heating section. The temperature of the first heating section is 0~30℃, the temperature of the second heating section is 160~330℃, and the temperature of the third heating section is 190~380℃, wherein the real-time temperature of the third heating section is higher than that of the second heating section; the screw speed of the single-screw extruder is 20~40 rpm, and the content of the foaming agent in the polymer particles containing the foaming agent is 0.1~10%; the polymer includes at least one of crystalline polymers, amorphous polymers, semi-crystalline polymers, and thermoplastic elastomers. S2. The foamed melt obtained in step S1 is stretched and shaped to produce porous polymer fibers; the stretching and shaping includes the steps of traction and stretching, the traction temperature is 100~180℃, the stretching temperature is 20~80℃, and the stretching ratio during the stretching and shaping process is 1.5~5. In step S1, the length of the first heating section of the single-screw extruder accounts for 25-35% of the screw length, and the length of the second heating section accounts for 35-45% of the screw length. The foaming agent content in the polymer particles containing the foaming agent described in step S1 is 0.5% to 5%; The temperature of the traction is 100~150℃, and the temperature of the stretching is 20~40℃.

2. The method for preparing porous polymer fibers as described in claim 1, characterized in that, In step S1, the foaming agent in the polymer particles containing the foaming agent includes at least one of a solid foaming agent and a fluid foaming agent.

3. The method for preparing porous polymer fibers as described in claim 2, characterized in that, Includes at least one of the following (a) to (f): (a) The amorphous polymer includes at least one of PS, PMMA, PEI, PI, and PSF; (b) The semi-crystalline polymer includes at least one of PET, PLA, and PEEK; (c) The crystalline polymer includes at least one of PE, PP, and PA; (d) The thermoplastic elastomer includes at least one of TPU, TPEE, and PEBA; (e) The fluid foaming agent includes at least one of CO2, N2, alkanes, and hydrochlorofluorocarbons; (f) The solid foaming agent includes at least one of expandable microspheres, carbonates, azodicarbonamide, and N,N-dinitrospentamethylenetetramine.

4. The method for preparing porous polymer fibers as described in claim 1, characterized in that, The draw ratio for the stretching and shaping in step S2 is 2 to 3.

5. Porous polymer fibers prepared by the preparation method according to any one of claims 1 to 4.

6. The porous polymer fiber as described in claim 5, characterized in that, The porous polymer fibers have a diameter of 0.05~0.3 mm and a density of 0.6~0.95 g / cm³. 3 .

7. The application of the porous polymer fiber according to claim 5 or 6 in the fields of clothing and wearable devices.

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