Polymer foamed fiber, preparation method therefor and use thereof

Abstract

A polymer foamed fiber, a preparation method therefor and a use thereof. The interior of the polymer foamed fiber is of a uniform dense closed-cell structure, and the average cell size of the closed-cell structure is 1-50 μm; the diameter of the polymer foamed fiber is 0.3-1.0 mm, the average deviation thereof is 0.05 mm, the cortex thickness thereof is 0-0.1 mm, the density thereof is 0.30-0.90 g / cm3, and the elongation at break thereof is 0-600%. The polymer foamed fiber has the advantages of light weight, uniform thickness, porous structure, uniform and dense internal cell size, uniform thickness of the foamed fiber, controllable cortex thickness of the foamed fiber and the like. Moreover, the preparation method is simple to operate, low in cost, safe, green and environment-friendly, and large-scale continuous production can be achieved.

Description

Polymer foam fiber and its preparation method and application Technical Field

[0001] The invention belongs to the technical field of polymer foam fiber processing, and particularly relates to a polymer foam fiber and a preparation method and application thereof. Background Art

[0002] Polymer foam fibers combine the advantages of both fiber and cellular structures, offering unparalleled advantages over fiber materials, such as low density, high elasticity, large specific surface area, and rapid mass transfer. They hold significant potential for application in a wide range of emerging fields, including functional clothing, wearables, consumer electronics, filtration separation, and catalysis. Existing methods for preparing polymer foam fibers, including coagulation bath phase separation and highly inward emulsion templates, involve the use of large amounts of organic solvents and complex processing. These processes are environmentally unfriendly, have limited applicable polymer systems, and exhibit low processing efficiency, limiting their application.

[0003] Supercritical fluids, including supercritical CO2 and supercritical N2, are widely available, residue-free, and environmentally friendly, making them one of the most important and promising physical foaming agents for polymers. The academic paper Industrial & Engineering Chemistry Research, 2002, 41, 1195, reports on the development of semi-continuous solid-state foamed polyetherimide (PEI) fibers. Using supercritical CO2 as the physical foaming agent, this study prepared foamed fibers with micron / submicron porous structures through a two-step process: saturation in a supercritical fluid autoclave and induced foaming in an oil bath at elevated temperatures. However, this process is complex to operate, has high equipment modification costs, and is limited in its applicable material range. Furthermore, the limited residence time of the supercritical fluid within the solid fiber makes it difficult to scale up and meet practical application requirements.

[0004] Summary of the Invention

[0005] The present invention provides a polymer foam fiber, its preparation method, and application. The polymer foam fiber produced by the present invention has the advantages of being lightweight, uniform in thickness, having a porous structure, uniform and dense internal pores, uniform foam fiber thickness, controllable skin thickness, and uniform pore distribution. Furthermore, the preparation method of the present invention is simple to operate, low in cost, safe, and environmentally friendly, enabling large-scale continuous production.

[0006] In order to achieve the above object, the present invention adopts the following technical solution: a polymer foam fiber, the interior of the polymer foam fiber is a uniform and dense closed-cell structure, the average cell size of the closed-cell structure is 1 to 50 μm; the diameter of the polymer foam fiber is 0.3 to 1.0 mm, the average deviation is ±0.05 mm, the skin thickness is 0 to 0.1 mm, and the density is 0.30 to 0.90 g / cm3 , the elongation at break is 0 to 600%.

[0007] Preferably, the polymer foam fiber comprises the following components in parts by weight: 90-100 parts of polymer, 1-10 parts of nucleating agent, 0-1 parts of chain extender, and 0-0.5 parts of antioxidant. More preferably, the polymer foam fiber comprises the following components in parts by weight: 95-97 parts of polymer, 3-5 parts of nucleating agent, 0.2-0.3 parts of chain extender, and 0.2-0.3 parts of antioxidant.

[0008] Preferably, the polymer has a melting point of 100-230° C. and a hardness of 80A-64D.

[0009] Preferably, the polymer includes one or more of thermoplastic elastomer, polylactic acid (PLA), and polypropylene (PP).

[0010] More preferably, the thermoplastic elastomer includes one or more conventional thermoplastic elastomer components in the art, such as polyethylene terephthalate (PET), polyurethane (TPU), polyester elastomer (TPEE), and nylon elastomer (PEBA).

[0011] Preferably, the nucleating agent includes at least one of calcium carbonate, talc, mica, montmorillonite, nano-silica, carbon black, and carbon nanotubes.

[0012] Preferably, the particle size of the nucleating agent is 0.05 to 5 μm.

[0013] Preferably, the chain extender includes at least one of a bisoxazoline chain extender and an epoxy chain extender.

[0014] Preferably, the antioxidant includes at least one of an amine antioxidant and a phosphorus antioxidant.

[0015] The present invention also claims a method for preparing the polymer foam fiber, comprising the following steps:

[0016] S1, premixing all components, drying, melt-extruding, cooling, obtaining polymer fiber filaments, and winding to obtain polymer fiber rolls;

[0017] S2. First, the polymer fiber roll is immersed in a polyvinyl alcohol solution to form a barrier layer, and then, before the barrier layer is completely air-dried, an inorganic filler layer is passed through to form an isolation layer, thereby obtaining a primary polymer foamed fiber product;

[0018] S3. Place the polymer foam fiber primary product into a high-pressure device and immerse it in a supercritical fluid to form an equilibrium state. Rapidly change the pressure and temperature in the autoclave to destroy the equilibrium state, conditionally induce fiber foaming, take it out, pull it, rinse it, dry it, and rewind it to obtain the polymer foam fiber.

[0019] Preferably, the drying in step S1 is hot air drying, and the moisture content of the material after drying is less than 0.05%.

[0020] Preferably, the melt extrusion in step S1 adopts a twin-screw extruder, and the temperature from the feed port to the extrusion head of the extruder is set to 80 / 180 / 190 / 205 / 215 / 180-190°C.

[0021] Preferably, the winding speed in step S1 is 0.5-2 m / s.

[0022] Preferably, the diameter of the polymer fiber filament in step S1 is 0.10-0.80 mm.

[0023] Preferably, the polyvinyl alcohol solution in step S2 comprises the following components in percentage by weight: 5-10% polyvinyl alcohol (PVA), 70-80% deionized water, 3-10% hydrolyzed starch, and 3-10% gypsum.

[0024] Preferably, the molecular weight of the polyvinyl alcohol is 30,000 to 200,000, and the alcoholysis degree is 99%. More preferably, the molecular weight of the polyvinyl alcohol is 50,000 to 150,000.

[0025] Preferably, the polyvinyl alcohol solution is prepared by uniformly mixing all components to obtain the polyvinyl alcohol solution.

[0026] Preferably, the inorganic filler includes at least one of flaky powder, graphene, micro-nano calcium carbonate, and nano-silicon dioxide.

[0027] Preferably, the barrier layer and the isolation layer are applied at an interval of 10 to 20 seconds in step S2. More preferably, the barrier layer and the isolation layer are applied at an interval of 10 to 15 seconds. Controlling the interval between the application of the barrier layer and the isolation layer can ensure that the inorganic filler is effectively adhered to the surface.

[0028] Preferably, the supercritical fluid in step S3 includes one of supercritical CO2 fluid, supercritical N2 fluid, and a mixed fluid of supercritical CO2 fluid and supercritical N2 fluid.

[0029] Preferably, the solubility of the supercritical fluid in the polymer fiber in step S3 is 0.5-5.0 wt.%, more preferably 1.0-3.0 wt.%.

[0030] Preferably, the hardness of the polymer foamed fiber primary product in step S3 is Shore 80A to Shore 64D. Different polymer hardnesses significantly vary the solubility of the supercritical fluid therein, and the foaming effects induced by the conditions are also different.

[0031] Preferably, the conditions for immersing in the supercritical fluid in step S3 are a pressure of 10-20 MPa and a temperature of 70-120°C.

[0032] More preferably, the conditions for immersing in the supercritical fluid in step S3 are a pressure of 15-18 MPa and a temperature of 80-100°C.

[0033] Preferably, the conditions for inducing fiber foaming in step S3 are rapid changes in pressure and temperature conditions, wherein the pressure sudden change rate is 10-15 MPa / s, and the temperature sudden change rate is 0-80°C / s.

[0034] In the induced foaming process of polymer fibers of the present invention, the degree of induction conditions (speed) affects the degree of cell growth. If the induction conditions change too quickly, the cell structure in the fibers will aggregate and form large cells, resulting in an uneven cell structure. If the induction conditions change too slowly, the supercritical fluid dissolved in the fibers will be completely dissipated, resulting in a finished product with poor foaming effect and excessively high density.

[0035] Preferably, the flushing in step S3 is performed with water, the flushing water flow rate is 0-1 m / s, and the flushing time is 0-30 s.

[0036] More preferably, the flushing water flow rate is 0 to 0.5 m / s, and the time is 0 to 20 s.

[0037] The conditionally induced foaming fibers of the present invention rely on a supercritical fluid dissolved within the fibers to induce nucleation and form a porous structure. Therefore, during conditional induction, the rate of loss of the supercritical fluid dissolved within the fibers primarily determines the pore structure of the foamed fibers. The PVA solution forms a barrier layer on the fiber surface, exhibiting excellent gas barrier properties, effectively extending the fluid's residence time within the fibers and significantly improving the fiber's foaming performance. The varying molecular weights of PVA are primarily reflected in the viscosity of the PVA solution and the gas barrier effect of the barrier layer. By limiting the PVA molecular weight, foamed fibers with more pronounced foaming performance and varying pore structures can be obtained. Furthermore, to achieve lower density foamed fibers, conditionally induced foaming at an appropriate temperature is required. Generally speaking, within a specific temperature range, the polymer state gradually approaches a viscous flow state. The volume expansion effect of the foamed fibers can cause them to adhere to each other, impacting subsequent processing and the final product. Applying an isolation layer over the PVA barrier layer effectively prevents inter-fiber adhesion, thereby ensuring the resulting fiber possesses a porous structure. The barrier layer and isolation layer formed during the preparation process will be removed in the subsequent washing process.

[0038] The present invention also seeks to protect the use of the polymer foam fiber in the fields of lightweight, functional clothing, military aerospace, electronic wearable devices, and thermal insulation.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] The present invention prepares lightweight, uniformly thick and fine polymer foam fibers with a porous structure and a multi-material system through the selection of raw materials, innovative processing methods, induced foaming, and rewinding. This method can achieve large-scale continuous production, is low-cost, simple to operate, safe, and environmentally friendly. The present invention innovates the preparation method of polymer foam fibers. By controlling the content of supercritical fluid in the fiber and the degree of cell growth during the conditional induction process, the cell structure of the foamed fibers is uniform, the thickness of the foamed fibers is uniform, and the cortex thickness of the foamed fibers is controllable, thereby improving the production stability of the conditionally induced foamed fibers. The foamed fibers are weavable, have excellent tensile properties, and are wear-resistant. They are suitable for use in a variety of fields, such as lightweight and functional clothing, military and aerospace, electronic wearable devices, and thermal insulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] FIG1 is a schematic cross-sectional view of a polymer fiber coated with a barrier layer and an isolation layer during the preparation process of the present invention.

[0042] FIG2 is an optical photograph of the polymer foam fiber prepared in Example 1 of the present invention.

[0043] FIG3 is a cross-sectional SEM image of the polymer foam fiber prepared in Example 1 of the present invention.

[0044] FIG4 is a cross-sectional SEM image of the polymer foam fiber prepared in Example 5 of the present invention.

[0045] FIG5 is a cross-sectional SEM image of the polymer foam fiber prepared in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0046] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0047] In the Examples and Comparative Examples, the experimental methods used are conventional methods unless otherwise specified, and the materials and reagents used are commercially available unless otherwise specified.

[0048] The materials used in the examples and comparative examples are as follows:

[0049] polymer:

[0050] A1: Thermoplastic polyurethane, melting point 200°C, hardness 98A, Lubrizol Specialty Chemicals, USA;

[0051] A2: Thermoplastic polyurethane, melting point 190°C, hardness 85A, Jinjiang Guosheng Company, China;

[0052] A3: Thermoplastic polyester elastomer, melting point 220°C, hardness 55D, model 5556, DuPont, USA;

[0053] A4: Nylon elastomer, melting point 180°C, hardness 45D, model 4510, Xubang New Material Technology Co., Ltd.

[0054] A5: Polylactic acid, melting point 150°C, hardness 60D, model 3001, NatureWorks, USA;

[0055] A6: Thermoplastic polyester elastomer, melting point 240°C, hardness 72D, model 7269, DuPont, USA;

[0056] Polyvinyl alcohol: China's Aladdin

[0057] B1: Polyvinyl alcohol, type 2699, molecular weight 114,000, alcoholysis degree 99%;

[0058] B2: Polyvinyl alcohol, type 1788, molecular weight 75,000, alcoholysis degree 99%;

[0059] B3: Polyvinyl alcohol, type 0588, molecular weight 22,000, alcoholysis degree 99%;

[0060] Inorganic fillers:

[0061] Flake powder: size 0.2-10 μm, commercially available;

[0062] Nucleating agent:

[0063] Calcium carbonate, average particle size 1 μm, commercially available;

[0064] Talc powder, with an average particle size of 1 μm, commercially available;

[0065] Carbon black, average particle size 1 μm, commercially available;

[0066] Chain extender: Epoxy chain extender, effective component ≥99%, epoxy equivalent 285g / mol, model ADR4300, BASF, Germany;

[0067] Antioxidant: Phenolic antioxidant, effective component ≥98%, BASF, Germany.

[0068] Preparation method of polyvinyl alcohol solution:

[0069] 10% (weight percentage) of polyvinyl alcohol, 70% of deionized water, 10% of hydrolyzed starch and 10% of gypsum are uniformly mixed to prepare the polyvinyl alcohol solution.

[0070] According to the above preparation method, polyvinyl alcohol B1, B2, and B3 are selected to prepare polyvinyl alcohol solution C1, polyvinyl alcohol solution C2, and polyvinyl alcohol solution C3, respectively.

[0071] Examples 1 to 9 and Comparative Examples 1 to 6

[0072] The components, weight parts, and condition parameters of the polymer foamed fibers of Examples 1 to 9 and Comparative Examples 1 to 6 are shown in Table 1, and the performance parameters of the obtained polymer foamed fibers are shown in Table 2.

[0073] The preparation method of the polymer foamed fiber of Examples 1 to 9 and Comparative Examples 1 to 6 comprises the following steps:

[0074] S1. Premixing and drying all components, adding them to a twin-screw extruder, melt-extruding, cooling, obtaining a polymer fiber filament, and winding them to obtain a polymer fiber roll; wherein the drying is performed by hot air drying, and the moisture content after drying is less than 0.05%. The temperature from the feed port to the extruder head is set to 80 / 180 / 190 / 205 / 215 / 180-190° C., the winding speed is 0.5-2 m / s, and the diameter of the polymer fiber filament is 0.10-0.80 mm;

[0075] S2. The polymer fiber roll is loaded onto a self-made coating device. The polymer fiber filaments are pulled through a transmission and rewound at the other end. During this process, the fiber filaments are first immersed in a polyvinyl alcohol solution to form a barrier layer. Before the barrier layer is completely air-dried, an inorganic filler layer is passed through the coating device to form an isolation layer, thereby obtaining a primary polymer foam fiber product. The coating interval between the barrier layer and the isolation layer is 10 to 20 seconds, and the inorganic filler is a flake powder (the inorganic filler may also be a component such as graphene, micro-nano calcium carbonate, or nano-silicon dioxide).

[0076] S3. Place the polymer foam fiber initial product into a high-pressure device and immerse it in a supercritical fluid to form an equilibrium state. The pressure in the high-pressure device is 10-20 MPa and the temperature is 70-120°C. Then quickly change the pressure and temperature in the autoclave. The pressure change rate is 15 MPa / s and the temperature change rate is 0-80°C / s. The equilibrium state is destroyed and the fiber is induced to foam under the conditions. The fiber is taken out, pulled, rinsed with water, dried, and rewound to obtain a polymer foam fiber. The hardness of the polymer foam fiber initial product is 80A-64D Shore A; the supercritical fluid is a supercritical CO2 fluid; the solubility of the supercritical fluid in the polymer fiber is 0.5-5.0wt.%; the flow rate of the water rinse is 0-1 m / s, and the residence time is 0-30s.

[0077] Table 1 Component dosage in Examples and Comparative Examples (parts by weight)

[0078] Table 2 Performance parameters of polymer foam fibers

[0079] From the data in Table 2, it can be seen that the polymer foamed fibers prepared in the embodiments of the present invention have a porous structure, with appropriate pore size and uniform pore structure, the polymer foamed fibers are uniform in thickness, the skin thickness of the foamed fibers is controllable, and the density is low.

[0080] The hardness of the polymer selected in Comparative Example 1 is not appropriate, the density of the obtained polymer foam fiber is high, and it cannot be foamed to form bubbles; the molecular weight of the polyvinyl alcohol in the polyvinyl alcohol solution in Comparative Example 2 is not appropriate, resulting in a reduced foaming effect, sparse bubbles, uneven distribution, and poor foaming effect; the solubility of the polymer in supercritical CO2 in Comparative Example 3 is not appropriate, resulting in a decreased foaming effect; the pressure sudden change rate in Comparative Example 4 is not appropriate, and the temperature sudden change rate in Comparative Example 5 is not appropriate, the cortex thickness and density of the obtained polymer foam fiber are both high, and the fiber of Comparative Example 4 cannot be foamed to form bubbles, and the bubbles of the fiber obtained in Comparative Example 5 are sparse and unevenly distributed; in Comparative Example 6, no nucleating agent is added, and the bubbles of the obtained polymer foam fiber are sparse, unevenly distributed, and the foaming effect is poor.

[0081] As can be seen from Figures 3 and 4, the polymer foamed fiber prepared in Example 5 of the present invention does not have a skin layer, and has a larger and more uniform pore structure than that in Example 1, and the pore distribution is also more uniform.

[0082] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A polymer foam fiber, characterized in that: The interior of the polymer foam fiber is a uniform and dense closed-cell structure, and the average cell size of the closed-cell structure is 1-50 μm; the diameter of the polymer foam fiber is 0.3-1.0 mm, the average deviation is ±0.05 mm, the skin thickness is 0-0.1 mm, and the density is 0.30-0.90 g / cm 3 , the elongation at break is 0 to 600%.

2. The polymer foam fiber according to claim 1, characterized in that: The invention comprises the following components in parts by weight: 90 to 100 parts of a polymer, 1 to 10 parts of a nucleating agent, 0 to 1 part of a chain extender, and 0 to 0.5 part of an antioxidant.

3. The polymer foam fiber according to claim 2, characterized in that: At least one of the following (1) to (5): (1) The melting point of the polymer is 100-230°C and the hardness is 80A-64D; (2) The polymer includes one or more of thermoplastic elastomer, polylactic acid, and polypropylene; (3) The nucleating agent includes at least one of calcium carbonate, talc, mica, montmorillonite, nano-silica, carbon black, and carbon nanotubes; (4) The chain extender includes at least one of a bisoxazoline chain extender and an epoxy chain extender; (5) The antioxidant includes at least one of an amine antioxidant and a phosphorus antioxidant.

4. A method for preparing the polymer foamed fiber according to any one of claims 2 to 3, characterized in that: The following steps are involved: S1, premixing and drying all components, melt-extruding and cooling to obtain polymer fiber filaments, and rolling to obtain polymer fiber rolls; S2, first immersing the polymer fiber roll in a polyvinyl alcohol solution to form a barrier layer, and then passing through an inorganic filler layer to form an isolation layer, to obtain a polymer foamed fiber primary product; S3, immersing the polymer foam fiber initial product in a supercritical fluid to conditionally induce fiber foaming, taking it out, pulling it, washing it, drying it, and rewinding it to obtain the polymer foam fiber.

5. The preparation method according to claim 4, characterized in that: At least one of the following (1) to (5): (1) The drying in step S1 is hot air drying, and the moisture content of the material after drying is less than 0.05%; (2) The melt extrusion in step S1 adopts a twin-screw extruder, and the temperature from the feed port to the extruder head is set to 80 / 180 / 190 / 205 / 215 / 180-190° C.; (3) The winding speed in step S1 is 0.5 to 2 m / s; (4) The diameter of the polymer fiber filament in step S1 is 0.10 to 0.80 mm; (5) The coating interval of the barrier layer and the isolation layer in step S2 is 10 to 20 seconds.

6. The preparation method according to claim 4, characterized in that: The polyvinyl alcohol solution in step S2 includes the following components in percentage by weight: 5-10% polyvinyl alcohol, 70-80% deionized water, 3-10% hydrolyzed starch, and 3-10% gypsum.

7. The preparation method according to claim 6, characterized in that: The molecular weight of the polyvinyl alcohol is 30,000 to 200,000, and the alcoholysis degree is 99%.

8. The preparation method according to claim 4, characterized in that: The inorganic filler in step S2 includes at least one of flaky powder, graphene, micro-nano calcium carbonate, and nano silicon dioxide; the particle size of the inorganic filler is 0.2 to 10 μm.

9. The preparation method according to claim 4, characterized in that: At least one of the following (1) to (6): (1) The supercritical fluid in step S3 includes one of supercritical CO2 fluid, supercritical N2 fluid, and a mixed fluid of supercritical CO2 fluid and supercritical N2 fluid; (2) the solubility of the supercritical fluid in the polymer fiber in step S3 is 0.5 to 5.0 wt.%; (3) The hardness of the polymer foamed fiber primary product in step S3 is Shore 80A-64D; (4) The conditions for immersing in the supercritical fluid in step S3 are a pressure of 10 to 20 MPa and a temperature of 70 to 120° C.; (5) The conditions for inducing fiber foaming in step S3 are to rapidly change the pressure and temperature conditions, wherein the pressure sudden change rate is 10 to 15 MPa / s, and the temperature sudden change rate is 0 to 80°C / s; (6) The flushing in step S3 is performed by using water, and the flushing water flow rate is 0 to 1 m / s and the time is 0 to 30 s.

10. An application of the polymer foam fiber according to any one of claims 1 to 3 in the fields of lightweight, functional clothing, military aerospace, electronic wearable devices, and thermal insulation.

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