A polymeric porous foamed fiber and a method of making and using the same

Abstract

The application discloses a kind of polymer porous foamed fiber and its preparation method and application, it is related to foamed material technical field.The method provided by the application, first, the polymer particles containing foaming agent are treated at low temperature, and then extruded by using specific process, the escape of foaming agent in low hardness raw material and foaming rate are delayed, so that the polymer raw material with hardness as low as 25A of Shore can be controllably foamed, and then porous polymer foamed fiber is obtained, the foaming behavior of the obtained fiber is good, the extrusion is stable, the foaming filament diameter is uniform, the cell size is 12-26 μm, distributed from center to outer layer, and the diameter of the obtained fiber is less than 0.54 mm, and the density is as low as 0.71 g / cm 3 Within, and the fiber prepared in the application has a closed-cell porous structure, good thermal insulation performance, and is suitable for preparation in the fields of clothing, etc., and has good application prospect.

Description

Technical Field

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

[0002] The porous structure of polymer porous fibers endows these materials with lightweight characteristics and excellent elasticity, thermal insulation, and radiative cooling properties. Fabrics woven from polymer porous fibers exhibit excellent breathability and moisture permeability, making them promising applications in wearable devices, smart clothing, multifunctional sportswear, and shoe uppers. However, existing porous fibers mostly have open-pore structures, which lead to problems such as easy water absorption, increased density after water absorption, and decreased thermal insulation.

[0003] Current reports disclose the use of supercritical fluids as foaming agents to impregnate polymer filaments, followed by micro-extrusion foaming to prepare porous polymer fibers. The porous fibers prepared using this impregnation-micro-extrusion method have a predominantly closed-cell structure, resulting in stable thermal insulation properties in various application environments. However, polymer materials impregnated with supercritical fluids are affected by the plasticizing effect of the supercritical fluid, leading to a decrease in filament hardness. Furthermore, micro-extrusion foaming systems are not suitable for processing polymer materials with a hardness below Shore A of 80A. As the demand for comfort in wearable devices and clothing increases, how to micro-extrude foam low-hardness polymer filaments and improve the comfort of the resulting porous fibers has become a pressing problem to be solved. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for preparing polymer porous foamed fibers. First, polymer particles containing a foaming agent are subjected to low-temperature treatment, and then extrusion foaming is performed using a specific process. This slows down the escape rate of the foaming agent in the raw materials and the foaming rate, enabling controllable foaming of polymer particles with lower hardness. As a result, the foamed fibers obtained better meet the comfort requirements of wearable and other fields.

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

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

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

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

[0009] S1. The polymer particles containing a foaming agent are subjected to low-temperature treatment for ≥30 minutes at a temperature ≤-15℃ and a humidity ≤30% to obtain low-temperature treated masterbatch; the concentration of the foaming agent in the polymer particles containing the foaming agent is 0.5~8wt%;

[0010] S2. The low-temperature treated masterbatch obtained in step S1 is extruded and foamed to obtain a foamed melt; the extrusion and foaming is carried out using a single-screw extruder, which includes a first heating section, a second heating section, and a third heating section in sequence. The temperature of the first heating section is 10-30℃, the temperature of the second heating section is 100-260℃, and the temperature of the third heating section is 270-430℃, wherein the real-time temperature of the third heating section is higher than that of the second heating section;

[0011] S3. The foamed melt obtained in step S1 is stretched and shaped to obtain polymer porous foamed fibers.

[0012] Polymers with lower hardness are more prone to foaming agent escape and loss during storage and transfer. Furthermore, achieving controllable foaming via micro-extrusion foaming is more challenging. Therefore, the preparation method provided by this invention first subjectes the polymer particles containing the foaming agent to low-temperature treatment in step S1. This reduces foaming agent loss and slows down the foaming rate during the heating process, preventing uncontrollable foaming rate and extent in low-hardness raw materials. After low-temperature treatment, the polymer particles containing the foaming agent are fed into a single-screw extruder for controllable foaming, followed by stretching and shaping to obtain polymer foamed fibers. Step S2, by controlling the temperature of different heating sections, allows the polymer system to gradually transition from a glassy state to a highly elastic state and then a viscous flow state, resulting in cell nucleation and rapid cell growth. In this invention, the temperature of the first heating section is controlled to be only 10–30°C, ensuring a sufficiently low loss rate of the foaming agent in the polymer particles, allowing for sufficient phase change and foaming of the polymer. The porous foamed fiber prepared using this method is rich in uniformly distributed pores with a closed-cell structure, exhibiting excellent thermal insulation properties. Furthermore, the reduced hardness of the raw material also lowers the fiber's hardness, better meeting the comfort requirements of clothing and other industries. It should be noted that to achieve controllable foaming, especially for low-hardness raw materials, the content of the foaming agent in the polymer particles in step S1 needs to be limited. If the foaming agent content is too low, it will still be lost during the micro-extrusion process in step S2, despite the low-temperature treatment; if the foaming agent content is too high, the low-hardness polymer raw material is prone to over-foaming during micro-extrusion.

[0013] In a specific embodiment of the present invention, the method for preparing polymer porous foamed fibers provided by the present invention is carried out in a micro-extrusion device, which includes a feeding unit, a micro-extrusion unit, a shaping unit, and a drawing unit; the micro-extrusion unit is a single-screw extruder; the shaping unit includes a shaping channel; and the drawing unit includes one or more hot drawing sections, wherein one set of hot drawing sections includes two hot rollers and a hot plate. More specifically, the speed of the hot rollers is 0–600 m / min, the temperature is 30–200°C, the temperature of the hot plate is 30–200°C, and the hot drawing ratio is 1–5 times, preferably 2–3 times. The drawing unit of the present invention mainly adopts a post-drawing process. Through the action of the hot rollers and the hot plate, the drawing ratio can be controlled by controlling the heating temperature and processing speed without sacrificing the cell structure, thereby obtaining polymer porous fibers of different diameters.

[0014] 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 and then melt-extruding. When the foaming agent is a fluid foaming agent, the polymer particles are blended with the foaming agent by impregnation. More specifically, the melt extrusion is performed using a twin-screw extruder. More specifically, the melt extrusion is followed by a cutting step, which is performed using a pelletizer.

[0015] In a specific embodiment of the present invention, the temperature control accuracy of the low-temperature treatment in step S1 is ±1℃, and the loss rate of the foaming agent in the polymer particles containing the foaming agent during the low-temperature treatment is <5%.

[0016] In a specific embodiment of the present invention, step S2 controls the temperature of the first heating section to be 10-30°C by connecting at least one of a water cooling system and a cold air system to the first heating section.

[0017] Preferably, the temperature of the low-temperature treatment in step S1 is -40 to -15°C, and the humidity is 1 to 5%.

[0018] Preferably, the concentration of the foaming agent in the polymer particles containing the foaming agent in step S1 is 2.5 to 7.5 wt%.

[0019] 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, and the average diameter of the particles is 0.5 to 5.0 mm, with a fluctuation range of ±0.5 to 1 mm.

[0020] More preferably, the polymer particles containing the foaming agent in step S1 comprise the following components in parts by mass:

[0021] 80-100 parts polymer, 2-7.5 parts foaming agent, 0-10 parts nucleating agent, 0-1 part chain extender, 0-0.5 parts antioxidant, and 0-2 parts antistatic agent.

[0022] More preferably, the polymer includes at least one of crystalline polymers, amorphous polymers, semi-crystalline polymers, and thermoplastic elastomers. In a specific embodiment of the present invention, the melting point of the polymer is 100–400°C.

[0023] More preferably, the amorphous polymer includes at least one of PS, PMMA, PEI, PI, and PSF.

[0024] More preferably, the semi-crystalline polymer includes at least one of PET, PLA, and PEEK.

[0025] More preferably, the crystalline polymer includes at least one of PE, PP, and PA.

[0026] More preferably, the thermoplastic elastomer includes at least one of EVA, TPE, TPU, TPEE, and PEBA.

[0027] More preferably, the hardness of the thermoplastic elastomer is Shore A20 to Shore A70.

[0028] The hardness of commonly used amorphous polymers, semi-crystalline polymers, and crystalline polymers in this field is generally high and not adjustable. This invention focuses on the foaming of low-hardness raw materials, preferably using thermoplastic elastomers with a hardness of Shore A20 to Shore A70.

[0029] More preferably, the foaming agent includes at least one of a solid foaming agent and a fluid foaming agent.

[0030] More preferably, the fluid foaming agent includes at least one of CO2, N2, n-pentane, isopentane, butane, and Freon.

[0031] More preferably, the solid foaming agent includes at least one of expandable microspheres, carbonates, azodicarbonamide, and N,N-dinitrospentamethylenetetramine.

[0032] More preferably, the nucleating agent includes at least one of calcium carbonate, talc, mica, montmorillonite, nano-silica, carbon black, and carbon nanotubes.

[0033] More preferably, the chain extender includes at least one of a difunctional acid derivative, an isocyanate, an acid anhydride, and an epoxide.

[0034] More preferably, the antioxidant includes at least one of amine antioxidants and phosphorus antioxidants.

[0035] More preferably, the nucleating agent has a particle size of 0.05 to 5 μm.

[0036] More preferably, the antistatic agent includes a hydrophobic antistatic additive.

[0037] More preferably, when the foaming agent in the polymer particles containing the foaming agent in step S1 is a fluid foaming agent, the fluid foaming agent is blended with the polymer particles by high-pressure impregnation to obtain polymer particles containing the foaming agent, and the high-pressure impregnation is carried out at 5 to 30 MPa.

[0038] In a specific embodiment of the present invention, the temperature control accuracy of the single screw extruder in step S2 is 0.5 to 5°C, preferably 1 to 3°C.

[0039] In a specific embodiment of the present invention, the residence time of the low-temperature treated masterbatch in the first heating section in step S2 is 0.1 to 1.5 s, and the loss rate of the foaming agent during the residence of the low-temperature treated masterbatch in the first heating section is <5%.

[0040] In a specific embodiment of the present invention, the rotational speed of the single screw extruder in step S2 is 20 to 40 rpm.

[0041] The present invention also protects the polymer porous foamed fibers prepared by the above preparation method.

[0042] In a specific embodiment of the present invention, the obtained polymer porous foamed fibers have a diameter of 0.15–0.3 mm and a density of 0.4–0.8 g / cm³. 3 The pore size distribution ranges from 13 to 26 μm.

[0043] In a specific embodiment of the present invention, the resulting polymer porous foamed fiber has a closed-cell structure. This is because during the heating process, the cells undergo nucleation, growth, and then rapid cooling, and the cells solidify during the cooling process. In this process, the closer to the fiber skin layer, the faster the gas escapes and the faster the cooling, causing the cells to collapse and form a skin layer. Therefore, the fiber as a whole exhibits a closed-cell structure.

[0044] This invention also protects the application of the above-mentioned polymer porous foamed fibers in outdoor sports footwear and apparel, electronic wearable devices, functional clothing, and catalysis.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] The method provided by this invention enables controllable foaming of polymer raw materials with a Shore hardness as low as 25A, thereby obtaining porous polymer foamed fibers. The resulting fibers exhibit good foaming behavior, stable extrusion, uniform foam filament diameter, and cell size of 12–26 μm, distributed from the center to the outer layer. Furthermore, the diameter of the resulting fibers is less than 0.54 mm, and the density is as low as 0.71 g / cm³. 3 Within this range, it has good application prospects. Attached Figure Description

[0047] Figure 1 This is a SEM image of the polymer porous fiber obtained in Example 5 of the present invention. Detailed Implementation

[0048] 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):

[0049] Amorphous polymer A

[0050] A1, Polystyrene PS, grade GPPS158K, BASF Yangtze;

[0051] A2, Polyetherimide (PEI), Grade 1000, SABIC;

[0052] Crystalline polymer B

[0053] B1, Low-density polyethylene (LDPE), grade 2426H, Maoming Petrochemical;

[0054] B2, PEEK, grade 1000, Mitsubishi Chemical;

[0055] Thermoplastic elastomer C

[0056] C1, thermoplastic polyurethane EVA, hardness 25A, BASF, Germany.

[0057] C2, thermoplastic elastomer (TPE), hardness 70A, DuPont, USA.

[0058] Foaming agent:

[0059] AC foaming agent azodicarbonamide, commercially available.

[0060] CO2 fluid, commercially available.

[0061] Mixed foaming agent: includes AC foaming agent and CO2 fluid in a mass ratio of 1:1.

[0062] Nucleating agent:

[0063] Calcium carbonate, with an average particle size of 1 μm, is commercially available.

[0064] Chain extender:

[0065] Epoxy chain extender, commercially available.

[0066] Antioxidants:

[0067] Hindered phenolic antioxidants, commercially available.

[0068] Antistatic agent:

[0069] Hydrophobic antistatic agent, commercially available.

[0070] Examples 1-10 and Comparative Examples 1-2

[0071] This embodiment and comparative example provide a series of methods for preparing polymer porous foamed fibers with different raw materials and process parameters, including the following steps:

[0072] S1. Polymer particles containing foaming agent are subjected to low-temperature treatment for 30 minutes at a temperature below -15℃ and a humidity of 1 to 30% to obtain low-temperature treated masterbatch.

[0073] S2. The low-temperature treated masterbatch obtained in step S1 is extruded and foamed to obtain a foamed melt; the extrusion and foaming is carried out using a single-screw extruder, which includes a first heating section, a second heating section, and a third heating section in sequence. The temperature of the first heating section is 25°C, the temperature of the second heating section is 140°C, and the temperature of the third heating section is 270°C, wherein the real-time temperature of the third heating section is higher than that of the second heating section;

[0074] S3. The foamed melt obtained in step S1 is stretched and shaped to obtain polymer porous foamed fiber;

[0075] The polymer particles containing the foaming agent described in step S1 comprise the following components in parts by mass:

[0076] 100 parts polymer, 0.1-10 parts foaming agent, 5 parts nucleating agent, 0.5 parts chain extender, 0.25 parts antioxidant, and 1 part antistatic agent;

[0077] When the foaming agent is a CO2 fluid, the foaming agent is blended with polymer particles to obtain polymer particles containing the foaming agent by high-pressure impregnation, and the high-pressure impregnation is carried out at 20 MPa.

[0078] When the foaming agent is a mixed foaming agent, the AC foaming agent is first blended with the polymer particles, and then the CO2 fluid is blended with the polymer particles to obtain polymer particles containing the foaming agent. The high-pressure impregnation is carried out at 20 MPa.

[0079] The specific raw materials and process parameters used in this embodiment and the comparative example are shown in Table 1 below:

[0080] Table 1. Raw materials and process parameters used in Examples 1-10 and Comparative Examples 1-2

[0081]

[0082] Comparative Example 3

[0083] A method for preparing polymer porous foamed fibers, wherein the only difference from Example 5 is:

[0084] The low-temperature treatment temperature in step S1 is -10℃.

[0085] Comparative Example 4

[0086] A method for preparing polymer porous foamed fibers, wherein the only difference from Example 5 is:

[0087] In step S1, the humidity during the low-temperature treatment is 50%.

[0088] Comparative Example 5

[0089] A method for preparing polymer porous foamed fibers, wherein the only difference from Example 5 is:

[0090] Without performing the low-temperature treatment step in step S1, the polymer particles containing the foaming agent are directly extruded and foamed.

[0091] Comparative Example 6

[0092] A method for preparing polymer porous foamed fibers, wherein the only difference from Example 1 is:

[0093] Without performing the low-temperature treatment step in step S1, the polymer particles containing the foaming agent are directly extruded and foamed.

[0094] Comparative Example 7

[0095] A method for preparing polymer porous foamed fibers, wherein the only difference from Example 5 is:

[0096] The temperature of the first heating section of the single-screw extruder described in step S2 is 100°C.

[0097] Performance testing

[0098] Foaming behavior test: SEM was used to observe the cell morphology.

[0099] Test on bubble size and distribution: measured by visual observation.

[0100] Fiber diameter test: Measured using calipers.

[0101] Fiber density test: The water displacement method was used for measurement.

[0102] Fiber hardness test: Measured using a hardness tester.

[0103] The specific performance test data is shown in Table 2 below:

[0104] Table 2. Performance test data of fibers obtained in the examples and comparative examples

[0105]

[0106]

[0107]

[0108]

[0109] As shown in Table 2 above, the method provided by this invention enables controllable foaming of polymer raw materials with a Shore hardness as low as 25A, thereby obtaining porous polymer fibers with good foaming behavior. The resulting fibers are extruded smoothly, the foamed filaments have uniform diameters, and the cell sizes are moderate, ranging from 12 to 26 μm, distributed from the center to the outer layer with minimal variation in cell size. Furthermore, the resulting fibers have small diameters, less than 0.54 mm, and a density as low as 0.71 g / cm³. 3 Within. Meanwhile, according to Figure 1 It is evident that the fiber prepared in this invention has a closed-cell porous structure, excellent heat retention properties, and is suitable for the preparation of clothing and other products.

[0110] As can be seen from the data in Examples 5, 7-8, and Comparative Example 3, when preparing polymer porous foamed fibers using the method of the present invention, the low-temperature treatment temperature in step S1 should be controlled within the range of ≤-15℃. If the low-temperature treatment temperature in step S1 is too high (Comparative Example 3), excessive foaming agent will escape, thus making the degree of foaming uncontrollable. However, further reducing the low-temperature treatment temperature to -40℃ (Example 7) does not significantly improve the foaming structure of the polymer fiber, but instead increases energy consumption. Therefore, the present invention preferably controls the low-temperature treatment temperature within the range of -40 to -15℃.

[0111] As can be seen from the data of Examples 5, 9-10 and Comparative Example 4, the humidity during low-temperature treatment is too high (Comparative Example 4). In an environment with a temperature below zero, water vapor is prone to crystallize on the surface of the polymer raw material, which will affect the effect of heating and foaming during extrusion.

[0112] As can be seen from the data in Example 5 and Comparative Examples 1-2, the preparation method of the present invention can controllably foam polymer porous foamed fibers with a hardness as low as 25A. However, it is necessary to limit the content of the foaming agent in the polymer raw material. If the foaming agent content is too low (Comparative Example 1), the foaming agent will still be lost during the micro-extrusion process despite low-temperature treatment, resulting in difficulty in controlling foaming. The resulting polymer foamed fibers have irregular cell distribution, uneven fiber diameter, and some areas do not foam. If the foaming agent content is too high (Comparative Example 2), low-hardness polymer raw materials are prone to over-foaming during the micro-extrusion process.

[0113] As can be seen from the data in Comparative Examples 5 and 6, if the low-temperature treatment step in step S1 is not performed, the foaming agent in the polymer raw material will easily escape and be lost during the extrusion process, resulting in uncontrollable foaming and almost no or only a few pores inside the polymer foam fiber.

[0114] As can be seen from the data in Comparative Example 7, in addition to the low-temperature treatment step S1, the polymer raw material should also be extruded using the specific extrusion process of this invention in order to obtain controllable foamed polymer fibers.

[0115] 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 polymer porous foamed fibers, characterized in that, Includes the following steps: S1. Polymer particles containing a foaming agent are subjected to low-temperature treatment for ≥30 min at a temperature of -40 to -15℃ and a humidity of 1 to 5% to obtain low-temperature treated masterbatch; the concentration of the foaming agent in the polymer particles containing the foaming agent is 2.5 to 7.5 wt%. S2. The low-temperature treated masterbatch obtained in step S1 is extruded and foamed to obtain a foamed melt; the extrusion and foaming is carried out using a single-screw extruder, which includes a first heating section, a second heating section, and a third heating section in sequence. The temperature of the first heating section is 10~30℃, the temperature of the second heating section is 100~260℃, and the temperature of the third heating section is 270~430℃, wherein the real-time temperature of the third heating section is higher than that of the second heating section; S3. The foamed melt obtained in step S2 is stretched and shaped to obtain polymer porous foamed fiber; The polymer particles containing the foaming agent described in step S1 comprise the following components in parts by mass: The composition includes 80-100 parts of polymer, 2-7.5 parts of foaming agent, 0-10 parts of nucleating agent, 0-1 part of chain extender, 0-0.5 parts of antioxidant, and 0-2 parts of antistatic agent. The polymer includes a thermoplastic elastomer, which includes at least one of EVA, TPE, TPU, TPEE, and PEBA. The hardness of the thermoplastic elastomer is Shore A20 to Shore A70. The resulting polymer porous foamed fibers have a diameter of 0.15~0.3 mm and a density of 0.4~0.8 g / cm³. 3 The pore size distribution ranges from 13 to 26 μm.

2. The method for preparing polymer porous foamed fibers as described in claim 1, characterized in that, Includes at least one of the following (a) to (f): (a) The foaming agent includes at least one of solid foaming agents and fluid foaming agents; (b) The nucleating agent includes at least one of calcium carbonate, talc, mica, montmorillonite, nano-silica, carbon black, and carbon nanotubes; (c) The chain extender includes at least one of a difunctional acid derivative, an isocyanate, an acid anhydride, and an epoxide; (d) The antioxidant includes at least one of amine antioxidants and phosphorus antioxidants; (e) The particle size of the nucleating agent is 0.05~5μm; (f) The antistatic agent includes a hydrophobic antistatic additive.

3. The method for preparing polymer porous foamed fibers as described in claim 2, characterized in that, Includes at least one of the following (g) to (h): (g) The fluid foaming agent includes at least one of CO2, N2, n-pentane, isopentane, butane, and Freon; (h) The solid foaming agent includes at least one of expandable microspheres, carbonates, azodicarbonamide, and N,N-dinitrospentamethylenetetramine.

4. The method for preparing polymer porous foamed fibers as described in claim 3, characterized in that, When the foaming agent in the polymer particles containing the foaming agent in step S1 is a fluid foaming agent, the fluid foaming agent is blended with the polymer particles by high-pressure impregnation to obtain polymer particles containing the foaming agent. The high-pressure impregnation is carried out at 5~30MPa.

5. Polymer porous foamed fiber prepared by any one of claims 1 to 4.

6. The application of the polymer porous foam fiber according to claim 5 in outdoor sports footwear and apparel, electronic wearable devices, functional clothing, and catalysis.

Images