Porous polymer fiber as well as preparation method and application thereof

Abstract

The invention discloses a porous polymer fiber as well as a preparation method and application thereof, and relates to the technical field of foaming materials. According to the preparation method of the porous polymer fiber provided by the invention, the polymer matrix containing the foaming agent is foamed by adopting an extrusion foaming process, controllable foaming of the polymer is realized by controlling parameters in the extrusion process, and the obtained porous polymer fiber has the density of 0.7 g / cm < 3 > or below, has high porosity and can be used for preparing the porous polymer fiber. The foam holes are uniform in distribution and size, the range of the size of the foam holes in the fiber is kept within 20 microns, the foam holes are uniformly distributed from the center to the outer layer, and meanwhile, the diameter of the fiber can reach 0.3-0.4 mm while high uniformity is still kept.

Description

Technical Field

[0001] The invention relates to the technical field of foaming materials, and in particular to a porous polymer fiber and a preparation method and application thereof. Background Art

[0002] Polymer porous fibers contain porous structures and have the advantages of being lightweight, heat-insulating, breathable, and highly flexible. They have broad application prospects and have therefore received extensive attention from researchers in recent years. Existing reports have drawn inspiration from porous fibers in nature, such as the porous hair of polar bears and camels, and have used ice crystal templates and phase separation methods to prepare polymer porous fibers. However, existing porous fiber processing methods use a large amount of solvents, have low processing efficiency, and produce fibers with a diameter that is too large, making it difficult to meet actual application needs.

[0003] The continuous extrusion foaming technology using supercritical fluid as a foaming agent can prepare polymer foaming filaments with diameters of millimeters and micrometers. For example, the prior art (Polymer Engineering Sciences, 2013, 53: 2360) has carried out an exploratory study on preparing polymer foaming fibers by continuous extrusion foaming. However, the TPU foaming fibers prepared by the prior art have large diameters, very low porosity, and uneven thickness, which is difficult to meet the application requirements of the industry. How to prepare polymer porous fibers with high porosity and uniform thickness and pores has become a major problem restricting the application of porous fibers. Summary of the invention

[0004] In order to address the deficiencies of the prior art, the present invention provides a method for preparing porous polymer fibers, in which an extrusion foaming process is used to foam a polymer matrix containing a foaming agent, and controllable foaming of the polymer is achieved by controlling the parameters in the extrusion process. The obtained polymer porous fibers have high porosity, and excellent uniformity in pore distribution and wire 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 purpose of the present invention is achieved through the following technical solutions:

[0008] A method for preparing a porous polymer fiber comprises the following steps:

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

[0010] S2. The foamed melt obtained in step S1 is stretched and shaped to obtain porous polymer fibers; the stretching and shaping includes the steps of traction and stretching, the traction temperature is 100-180°C, the stretching temperature is 20-80°C, 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 the first heating section to at least one of a water cooling system and a cold air system.

[0012] In the method for preparing porous polymer fibers provided by the present invention, polymer particles containing a foaming agent can be quantitatively and regularly extruded from a single screw extruder and achieve controllable foaming. Specifically, after the polymer particles containing a foaming agent are conveyed into the first-stage screw structure, the particle temperature is relatively low, which can reduce the loss of the foaming agent and the stable conveying of the material. The particles containing a foaming agent melt in the second-stage screw and are compacted by the screw structure, thereby achieving densification between the particle structures and preventing the escape of the foaming agent; the particles containing a foaming agent continue to melt and foam in the third-stage screw, and the stable conveying of the foaming melt to the die of the extruder is achieved through the metering properties of the screw structure. While controlling the extrusion temperature, the present invention also controls the foaming agent content in the raw material and the rotation speed of the screw. By controlling the above parameters, the present invention can achieve controllable foaming of polymer particles containing a foaming agent, and then in step S2, controllable stretching molding is achieved by controlling the stretching ratio and temperature, thereby improving the fineness of the foaming melt, and obtaining a polymer porous fiber with excellent uniformity in thickness and pore distribution and high porosity.

[0013] It should be noted that the traction in step S2 of the present invention is to drive the foaming melt to move by a traction roller; the drafting is to pull and stretch the foaming melt by a drafting roller so that the fibers gradually reach a predetermined thickness.

[0014] In a specific embodiment of the present invention, the drafting ratio of the draft setting is kept consistent during the drafting and pulling processes.

[0015] In a specific embodiment of the present invention, the method for preparing the porous polymer fiber provided by the present invention is carried out in a micro-extrusion device, wherein the micro-extrusion device comprises 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 comprises a traction roller, a heating channel and a drawing roller, wherein one heating channel and a drawing roller form a group, and preferably the drawing unit comprises a traction roller and one or more sets of heating channels and drawing rollers.

[0016] In a specific embodiment of the present invention, the polymer particles containing the foaming agent 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 0.5-5°C, preferably 1-3°C.

[0018] In a specific embodiment of the present invention, the residence time of the polymer particles containing a 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. Under the premise of controlling the screw speed of the extruder, the residence time of the polymer particles in different heating sections of the extruder can be controlled, thereby controlling the growth degree of nucleation of the polymer particle pores and the pore size.

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

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

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

[0022] In a specific embodiment of the present invention, the shape of the polymer particles containing a foaming agent in step S1 is at least one of round, oval, and knife-cut particle shapes, 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 blowing agent in the polymer particles containing the blowing agent in step S1 in the first heating section 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 blowing agent includes at least one of CO2, N2, alkanes, and hydrogenated chlorofluorocarbon blowing agents (HCFC).

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

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

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

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

[0033] In a specific embodiment of the present invention, the linear speed of the drafting roller in step S2 is 20-40 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 to 0.3 mm and a density of 0.6 to 0.95 g / cm 3 .

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

[0037] The present invention also protects the application of the porous polymer fiber in the field of clothing and wearable devices.

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

[0039] The porous polymer fiber prepared by the present invention has a high porosity and a density of 0.7 g / cm 3 Below, the range of the cell size in the fiber is kept within 20μm, distributed from the center to the outer layer, and the fiber diameter can reach 0.3-0.4mm while still maintaining high uniformity. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of the micro-extrusion device used in the present invention. DETAILED DESCRIPTION

[0041] The present invention is further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents. Among them, the raw material information in each embodiment and comparative example is as follows (the part involving hardness refers to Shore hardness):

[0042] Amorphous polymer A

[0043] A1, polystyrene PS, brand GPPS158K, BASF-Yangzi;

[0044] A2, polyetherimide PEI, grade 1000, SABIC;

[0045] Crystalline polymer B

[0046] B1, low-density polyethylene LDPE, brand 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 to 14

[0051] This embodiment provides a series of preparation methods for porous polymer fibers with different raw materials and process parameters, wherein the preparation methods are carried out in a micro-extrusion device, wherein the micro-extrusion device comprises 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 comprises a traction roller, a heating tunnel and a drawing roller, wherein only one set of the heating tunnel and the drawing roller is included;

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

[0053] S1. Extrusion foaming of polymer particles containing a foaming agent to obtain a foamed melt; the extrusion foaming is performed using a single-screw extruder, the single-screw extruder sequentially comprising a first heating section, a second heating section, and a third heating section, the temperature of the first heating section is 0 to 30°C, the temperature of the second heating section is 160 to 330°C, the temperature of the third heating section is 190 to 380°C, and the real-time temperature of the third heating section is higher than the temperature of the second heating section; the length of the first heating section in the single-screw extruder 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 content of the foaming agent 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 obtain 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 for the preparation in this embodiment are shown in Table 1 below:

[0056] Table 1. Preparation materials and process parameters in Examples 1 to 14

[0057]

[0058]

[0059] Comparative Example 1

[0060] A method for preparing a porous polymer fiber, which differs from Example 5 only in that:

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

[0062] Comparative Example 2

[0063] A method for preparing a porous polymer fiber, which differs from Example 5 only in that:

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

[0065] Comparative Example 3

[0066] A method for preparing a porous polymer fiber, which differs from Example 5 only in that:

[0067] In step S1, the temperature of the first heating section of the single screw extruder is 100°C.

[0068] Comparative Example 4

[0069] A method for preparing a porous polymer fiber, which differs from Example 5 only in that:

[0070] In step S1, the temperature of the first heating section of the single screw extruder is -10°C.

[0071] Comparative Example 5

[0072] A method for preparing a porous polymer fiber, which differs from Example 5 only in that:

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

[0074] Comparative Example 6

[0075] A method for preparing a porous polymer fiber, which differs from Example 5 only in that:

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

[0077] Comparative Example 7

[0078] A method for preparing a porous polymer fiber, which differs from Example 5 only in that:

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

[0080] Performance Testing

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

[0082] Cell size and distribution test: obtained by observation through scanning electron microscope (SEM).

[0083] Fiber diameter test: measured by 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 the fibers obtained in the examples and comparative examples

[0087]

[0088]

[0089]

[0090]

[0091] According to the data in Table 2 above, it can be seen that the porous polymer fiber prepared by the preparation method provided by the present invention has a density of 0.7 g / cm 3 The following is an explanation of the high porosity, uniform pore distribution and size, the range of pore size in the fiber is kept within 20 μm, 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.

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

[0093] According to the data of Examples 5, 11-12, when the raw material contains a foaming agent in the polymer particles with a foaming agent content within the preferred range of 0.5-5wt% of the present invention (Example 5), the foaming of the fiber is more controllable, the extrusion is smooth, the wire diameter is uniform, and the pores are smaller.

[0094] According to the data of Examples 5 and 13 to 14 in Table 2, when the drawing temperature during the stretching and shaping process is within the preferred range of 100 to 150°C of the present invention and the stretching temperature is within the preferred range of 20 to 40°C (Example 5) of the present invention, the pores in the obtained porous polymer fiber are evenly distributed and not easy to break, and the thickness of the obtained fiber is also uniform.

[0095] According to Comparative Example 1, it can be seen that 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 excessively high content of foaming agent, the polymer melt over-expands at the die during extrusion, the pores coalesce and the pore walls rupture severely, and the surface rupture is uneven.

[0096] According to the data of Comparative Examples 2 and 7, it can be seen that too high or too low screw speed during extrusion will also lead to uncontrollable foaming degree. When the screw speed is too high (Comparative Example 7), the raw material is difficult to fully foam, and 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, and the gas completely escapes before extrusion from the die, and the foamed fiber cannot be prepared.

[0097] According to the data of Comparative Examples 3 to 6, it can be seen that the temperature of each extrusion section in step S1 of the present invention should be within a certain range to obtain a controllable foaming filament. Among them, the data of Comparative Examples 3 to 4 show that the temperature of the feed section is too high (Comparative Example 3), the foaming agent will start to escape too early, and a solid fiber is obtained; the temperature of the feed section is too low (Comparative Example 4), the plasticization effect of the raw material is not good, the extrusion is not stable, it is easy to shut down due to excessive screw pressure, and the diameter of the foamed filament is uneven. The data of Comparative Examples 5 to 6 show that the temperature of the plasticization section is too high (Comparative Example 5), the raw material containing the foaming agent enters the melt state too early, the gas escapes too fast and the cell growth time is too long, resulting in serious cell aggregation, and there are almost no cells inside the filament; the temperature of the plasticization section is too low (Comparative Example 6), the polymer particles containing the foaming agent are poorly plasticized, resulting in unstable extrusion, uneven diameter of the foamed filament and more insoluble matter.

[0098] According to the data of Comparative Example 7, the screw speed of the single-screw extruder will also affect the structure of the foamed filament. Too high a speed can easily cause the extruded melt to form turbulence and instability, resulting in unstable extrusion and uneven diameter, and ultimately causing the product to have a spiral shape.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing a porous polymer fiber, characterized in that: The steps include: S1. Extrusion foaming is performed on polymer particles containing a foaming agent to obtain a foamed melt; the extrusion foaming is performed using a single-screw extruder, and the single-screw extruder includes a first heating section, a second heating section, and a third heating section in sequence, the temperature of the first heating section is 0 to 30°C, the temperature of the second heating section is 160 to 330°C, and the temperature of the third heating section is 190 to 380°C, wherein the real-time temperature of the third heating section is higher than the temperature of the second heating section; the screw speed of the single-screw extruder is 20 to 40 rpm, and the content of the foaming agent in the polymer particles containing the foaming agent is 0.1 to 10%; the polymer includes at least one of a crystalline polymer, an amorphous polymer, a semi-crystalline polymer, and a thermoplastic elastomer; S2. The foamed melt obtained in step S1 is stretched and shaped to obtain porous polymer fibers; the stretching and shaping includes the steps of traction and stretching, the traction temperature is 100-180°C, the stretching temperature is 20-80°C, and the stretching ratio during the stretching and shaping process is 1.5-5.

2. The method for preparing the porous polymer fiber according to claim 1, characterized in that: In step S1, the length of the first heating section of the single screw extruder accounts for 25-35% of the length of the screw, and the length of the second heating section accounts for 35-45% of the length of the screw.

3. The method for preparing the porous polymer fiber according to claim 1, characterized in that: The content of the foaming agent in the polymer particles containing the foaming agent in step S1 is 0.5-5%.

4. The method for preparing the porous polymer fiber according to claim 1, characterized in that: In step S1, the foaming agent in the polymer particles containing the foaming agent comprises at least one of a solid foaming agent and a fluid foaming agent.

5. The method for preparing the porous polymer fiber according to claim 4, characterized in that: Including at least one of the following (a) to (f): (a) the amorphous polymer comprises at least one of PS, PMMA, PEI, PI and PSF; (b) the semi-crystalline polymer comprises at least one of PET, PLA and PEEK; (c) the crystalline polymer comprises at least one of PE, PP and PA; (d) the thermoplastic elastomer comprises at least one of TPU, TPEE and PEBA; (e) the fluid foaming agent comprises at least one of CO2, N2, alkanes, and hydrogenated chlorofluorocarbon foaming agents; (f) The solid foaming agent comprises at least one of expandable microspheres, carbonates, azodicarbonamide, and N,N-dinitrosopentamethylenetetramine.

6. The method for preparing the porous polymer fiber according to claim 1, characterized in that: The temperature of the traction is 100-150°C, and the temperature of the drawing is 20-40°C.

7. The method for preparing the porous polymer fiber according to claim 6, characterized in that: The drafting ratio of the drafting in step S2 is 2 to 3.

8. The porous polymer fiber prepared by the preparation method according to any one of claims 1 to 7.

9. The porous polymer fiber according to claim 8, characterized in that The porous polymer fiber has a diameter of 0.05 to 0.3 mm and a density of 0.6 to 0.95 g / cm 3 .

10. Use of the porous polymer fiber according to claim 8 or 9 in the field of clothing and wearable devices.

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