A method for preparing microwave-absorbing fibers with high microwave-absorbing agent content by wet spinning and its products

Abstract

A method for preparing absorbing fibers with a high absorber content by wet spinning and the products thereof, wherein the preparation method comprises the steps of: dissolving a polymer in a solvent, degassing to obtain a sheath spinning solution; dissolving the same polymer in a solvent, adding absorbers to disperse uniformly, degassing to obtain a core spinning solution having a mass fraction ratio of absorbers to polymer of 1:10 to 1:1; selecting a sheath-core spinning assembly for wet spinning, extruding the sheath spinning solution and the core spinning solution from the sheath-core spinning assembly, respectively, and subjecting the fibers to a coagulation bath, stretching, water washing, and drying to obtain a sheath-core structured absorbing fiber. The method for preparing absorbing fibers with a high absorber content by wet spinning employs a coaxial wet spinning process, followed by a coagulation bath, stretching, and heat treatment. The resulting absorbing fibers exhibit excellent absorption performance in the 18 GHz to 2 GHz range and can be widely used in civilian and military applications. They can not only protect some electronic devices from electromagnetic interference but also improve the stealth performance of some military weapons.

Description

Technical Field

[0001] The present invention relates to the fields of wet spinning and absorbing fibers, and in particular to a method for preparing absorbing fibers with high absorbent content by wet spinning and the products thereof. Background Art

[0002] With the development of electronic devices, electromagnetic waves are widely used as a carrier for information generation, transmission, reception, and processing in both civilian and military applications. To protect radar and aircraft equipment from electromagnetic contamination, as well as for radio frequency identification (RFID), the research on electromagnetic wave absorbing materials has gained significant attention in many fields, particularly the military. There are many types of absorbing materials, primarily carbon-based and carbonyl iron inorganic compounds. To achieve military stealth and electromagnetic purification requirements, absorbing materials are often only practical when high in concentration. Therefore, they are typically applied via surface coating, but this has drawbacks such as the permeable layer being easily detached.

[0003] At present, the comprehensive requirements for absorbing materials are thin, wide, light and strong. They not only need to have a wide absorption frequency range and strong absorption performance, but also need to be lightweight. Fiber materials are a good functional carrier with the characteristics of being thin, soft and lightweight. However, in traditional composite fibers, in order to ensure spinnability, the amount of inorganic components added is generally less than 20wt%. Due to this limitation, although such fibers have absorbing performance, it is extremely difficult to achieve the actual use requirements that can be achieved by surface coating. However, polymers with high inorganic component filling (greater than 20wt%) are difficult to have spinning continuity. Therefore, it is of great significance to establish new fiber-forming technologies to construct absorbing fibers filled with high absorbers. Summary of the Invention

[0004] Based on this, the present invention provides a method for preparing absorbing fibers with high absorber content by wet spinning and its products, so as to solve the technical problem that polymer fibers in the prior art are difficult to achieve high inorganic component filling while maintaining spinnability.

[0005] To achieve the above object, the present invention provides a method for preparing an absorbing fiber with a high absorber content by wet spinning, which comprises the following steps:

[0006] (1) a polymer is dissolved in a solvent and degassed to obtain a skin spinning solution having a polymer mass fraction of 8 to 20%; a polymer of the same kind is dissolved in a solvent and an absorber is added to disperse the polymer uniformly, and the polymer is degassed in a degassed kettle for 7 to 10 hours to obtain a core spinning solution having a polymer mass fraction of 10 to 20% and a ratio of the absorber mass fraction to the polymer mass fraction of 1:10 to 1:1; wherein the polymer is polyvinyl alcohol, polyacrylonitrile or cellulose, and the absorber is an inorganic absorber having a particle size of <500 nm, and the inorganic absorber is a carbon absorber (such as graphite, graphene, carbon nanotube or carbon black) or a carbonyl iron absorber, and the carbonyl iron absorber is an absorbing material with carbonyl iron as the main component, and the carbonyl iron is composed of iron and a certain amount of carbon monoxide, and the chemical formula is Fe(CO)5;

[0007] (2) selecting a sheath-core spinning assembly for coaxial wet spinning, wherein the sheath-core spinning assembly has two coaxially arranged needle tubes, and the sheath layer spinning solution and the core layer spinning solution are extruded from the two needle tubes of the sheath-core spinning assembly as the sheath material and the core material, respectively, and passed through a coagulation bath to obtain nascent fibers;

[0008] (3) The spun fiber is stretched, washed, and dried to obtain a sheath-core structured absorbing fiber, wherein the core diameter of the absorbing fiber is not less than 1 / 3 of the total diameter.

[0009] During the specific preparation process, the relative sizes of the sheath and core can be varied by changing the relative apertures of the coaxial needles in the sheath-core spinning assembly. To achieve high absorbency, the absorber content must be as high as possible while ensuring continuous spinnability. The sheath is a pure polymer material with good spinnability. Its purpose is to encase the less spinnable core layer, thereby ensuring that both the sheath and core layers meet the requirements of continuous spinnability. The thickness of the sheath is preferably no less than 1 / 10 of the total diameter.

[0010] As a further preferred technical solution of the present invention, in step (1), the polymer is first washed with water and dehydrated before being dissolved, wherein the washing and dehydration treatment is as follows: the polymer raw material is first washed with distilled water at a temperature not exceeding 30-40°C, and then dehydrated, and this cycle is repeated 1-5 times to remove impurities and small molecular oligomers.

[0011] As a further preferred technical solution of the present invention, when the polymer is polyvinyl alcohol, the coagulation bath used is a saturated sodium sulfate coagulation bath; when the polymer is polyacrylonitrile, the coagulation bath used is dimethylacetamide, dimethyl sulfoxide or sodium bisulfate; when the polymer is cellulose fiber, the coagulation bath used is n-methylmorpholine-n-oxide or sulfuric acid-sulfate solution.

[0012] As a further preferred technical solution of the present invention, the stretching process in step (3) is a sequential wet heat stretching and dry heat stretching, wherein the wet heat stretching temperature is 80-150°C and the dry heat stretching temperature is 120-230°C. The stretching process can orient the fibers in the stretching direction, thereby increasing the fiber strength. The water washing process in step (3) can remove surface impurities and excess solvent.

[0013] As a further preferred technical solution of the present invention, in the core layer spinning solution prepared in step (1), the ratio of the mass fraction of the absorber to the mass fraction of the polymer is 1:2 to 1:1. Under the premise of ensuring spinnability, the absorbing efficiency is increased by increasing the mass fraction of the absorber.

[0014] The present invention also provides an absorbing fiber, which is prepared by any of the above-mentioned methods for preparing absorbing fibers with high absorber content by wet spinning.

[0015] The method for preparing microwave-absorbing fibers with a high microwave-absorbing agent content by wet spinning and the products thereof of the present invention can achieve the following beneficial effects by adopting the above technical solution:

[0016] 1) The ratio of the mass fraction of the absorber in the core layer to the mass fraction of the polymer in the present invention is up to 1:1, which solves the problem of low addition amount of absorbing fiber components. The process can be extended to other high-filling spinning fields.

[0017] 2) The fiber prepared in the present invention has a sheath-core structure, and the sheath and core layers are made of the same type of polymer, which solves the sheath-core interface problem and gives the fiber permanent absorbing properties that will not be lost even if subjected to external friction or washing. At the same time, it also gives it a wider absorbing range and stronger absorbing properties than ordinary absorbing fibers.

[0018] 3) The absorbent component of the absorbing fiber prepared in the present invention is a continuous phase in the core layer, which has a promoting effect on the conductivity loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] Figure 1 This is an optical microscope image of a cross section of the PVA absorbing fiber with a skin-core structure obtained in Example 1;

[0021] Figure 2 This is the reflection loss curve of the PVA absorbing fiber with a skin-core structure prepared in Example 1 in the range of 2 to 4 GHz;

[0022] Figure 3 This is an optical microscope image of a cross section of the PAN absorbing fiber with a skin-core structure obtained in Example 2;

[0023] Figure 4 This is the reflection loss curve of the PAN absorbing fiber with a skin-core structure prepared in Example 2 in the range of 6 to 8 GHz;

[0024] Figure 5 This is an optical microscope image of a cross section of the PVA absorbing fiber with a skin-core structure obtained in Example 3;

[0025] Figure 6 This is the reflection loss curve of the PVA absorbing fiber with a skin-core structure prepared in Example 3 in the range of 12 to 18 GHz.

[0026] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0027] The following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0028] Unless otherwise defined, the technical terms used in the following examples have the same meanings as commonly understood by those skilled in the art to which this invention belongs. The experimental reagents used in the following examples, unless otherwise specified, are conventional biochemical reagents; the experimental methods described, unless otherwise specified, are conventional methods.

[0029] Example 1

[0030] A method for preparing absorbing fibers with high absorber content by wet spinning. The obtained absorbing fibers include a sheath layer and a core layer. The sheath layer is pure polyvinyl alcohol (PVA), and the core layer is a polyvinyl alcohol-based composite filled with carbon-based absorbers.

[0031] The molecular weight of the polyvinyl alcohol in the skin layer and the core layer is 60,000, and the particle size of the carbon-based absorber in the core layer is 10 nm.

[0032] 5 g of polyvinyl alcohol (PVA) was weighed and added to 45 ml of deionized water, heated at 95° C. for 3 h to dissolve, and then degassed at 95° C. for 10 h to obtain the skin spinning solution.

[0033] Weigh 0.5 g of carbon-based absorbers and add them to 44.5 ml of deionized water. Stir the solution under magnetic stirring for 20 minutes, then disperse it by ultrasonication in an ultrasonic machine for 2 hours. Add 5 g of polyvinyl alcohol (PVA) to the obtained solution, heat it at 95 ° C for 3 hours to dissolve it, and then degas at 95 ° C for 10 hours to obtain the core layer spinning solution (the ratio of the mass fraction of the absorber to the mass fraction of polyvinyl alcohol is 1:10).

[0034] Then, a sheath-core spinning assembly with a coaxial needle is selected to spin at a constant speed of 12 m / min, and the spun fibers are coagulated and stretched in sequence. At this time, the temperature of the saturated sodium sulfate coagulation bath is 50°C, the temperature of the wet heat stretching is 130°C, and the temperature of the dry heat stretching is 180°C.

[0035] The stretched fiber was rinsed with distilled water three times and then dried in a vacuum oven at 60°C for 12 hours to finally obtain a PVA absorbing fiber with a skin-core structure and a core diameter accounting for 9 / 10 of the total diameter.

[0036] Figure 1 This is an optical microscope image of the cross-section of the PVA absorbing fiber with a skin-core structure, showing a clear interface of the skin-core structure.

[0037] The electromagnetic parameters of the fiber are measured using a vector network analyzer in the range of 2 to 18 GHz, and the reflection loss (RL) is calculated using the complex dielectric constant and complex magnetic permeability. Figure 2 The prepared PVA absorbing fiber with a skin-core structure has a minimum reflection loss of -18dB in the range of 2 to 4GHz.

[0038] Example 2

[0039] A method for preparing absorbing fibers with high absorber content by wet spinning. The obtained absorbing fibers include a sheath layer and a core layer. The sheath layer is pure polyacrylonitrile (PAN), and the core layer is a polyacrylonitrile-based composite filled with carbonyl iron absorbers.

[0040] The molecular weight of PAN in the skin layer and the core layer is 50,000, and the particle size of the carbonyl iron absorber in the core layer is 200 nm.

[0041] 10 g of PAN was weighed and added to 95 ml of sodium bisulfate solution, heated at 60° C. for 3 h to dissolve, and then degassed at 60° C. for 7 h to obtain the cortex spinning solution.

[0042] Weigh 2.5 g of carbonyl iron absorber and add it to 37.5 ml of deionized water. Stir the solution under magnetic stirring for 20 minutes, then disperse it by ultrasonication in an ultrasonic machine for 2 hours. Add 2.5 g of PAN to the obtained solution, heat it at 60°C for 3 hours to dissolve it, and then degas at 60°C for 7 hours to obtain the core layer spinning solution (the ratio of the absorber mass fraction to the PAN mass fraction is 1:1).

[0043] Then, a sheath-core spinning assembly with a coaxial needle is selected to spin at a constant speed of 8m / min, and the spun fibers are coagulated and stretched in sequence. At this time, the temperature of the sodium bisulfate coagulation bath is 2°C, the temperature of the wet heat stretching is 120°C, and the temperature of the dry heat stretching is 200°C.

[0044] The stretched fiber was rinsed with distilled water three times, and then placed in a vacuum oven and dried at 60° C. for 24 hours, finally obtaining a PAN absorbing fiber with a sheath-core structure and a core diameter of 4 / 5 of the total diameter.

[0045] Figure 3 This is an optical microscope image of the cross-section of the prepared PAN absorbing fiber with a skin-core structure, showing a clear interface of the skin-core structure.

[0046] The electromagnetic parameters of the fiber are measured using a vector network analyzer in the range of 2 to 18 GHz, and the reflection loss (RL) is calculated using the complex dielectric constant and complex magnetic permeability. Figure 4 The prepared PAN absorbing fiber with a skin-core structure has a minimum reflection loss of -12dB in the range of 6 to 8GHz.

[0047] Example 3

[0048] A method for preparing absorbing fibers with high absorber content by wet spinning. The obtained absorbing fibers include a sheath layer and a core layer. The sheath layer is pure polyvinyl alcohol (PVA), and the core layer is a polyvinyl alcohol-based composite filled with carbonyl iron absorbers.

[0049] The molecular weight of PVA in the skin layer and the core layer is 150,000, and the particle size of the carbonyl iron absorber in the core layer is 450 nm.

[0050] 4 g of polyvinyl alcohol (PVA) was weighed and added to 46 ml of deionized water. The solution was heated at 97° C. for 3 h to dissolve, and then degassed at 97° C. for 8 h to obtain the skin spinning solution.

[0051] Weigh 2 g of carbonyl iron absorber and add it to 44 ml of deionized water. Stir the solution under magnetic stirring for 20 minutes, then disperse it by ultrasonication in an ultrasonic machine for 2 hours. Add 4 g of polyvinyl alcohol (PVA) to the obtained solution, heat it at 97 ° C for 3 hours to dissolve it, and then degas at 97 ° C for 8 hours to obtain the core layer spinning solution (the ratio of the absorber mass fraction to the polyvinyl alcohol mass fraction is 1:2).

[0052] Then, a sheath-core spinning assembly with a coaxial needle is selected to spin at a constant speed of 15m / min, and the spun fibers are coagulated and stretched in sequence. At this time, the temperature of the saturated sodium sulfate coagulation bath is 40°C, the temperature of the wet heat stretching is 150°C, and the temperature of the dry heat stretching is 230°C.

[0053] The stretched fiber was rinsed with distilled water three times, and then placed in a vacuum oven and dried at 60°C for 18 hours, finally obtaining a PVA absorbing fiber with a skin-core structure and a core diameter of 1 / 3 of the total diameter.

[0054] Figure 5This is an optical microscope image of the cross-section of the PVA absorbing fiber with a skin-core structure, showing a clear interface of the skin-core structure.

[0055] The electromagnetic parameters of the fiber are measured using a vector network analyzer in the range of 2 to 18 GHz, and the reflection loss (RL) is calculated using the complex dielectric constant and complex magnetic permeability. Figure 6 The prepared PVA absorbing fiber with a skin-core structure has a minimum reflection loss of -25dB in the range of 12 to 18 GHz.

[0056] Example 4

[0057] A method for preparing absorbing fibers with high absorber content by wet spinning. The obtained absorbing fibers include a sheath layer and a core layer. The sheath layer is pure polyvinyl alcohol (PVA), and the core layer is a polyvinyl alcohol-based composite filled with carbonyl iron absorbers.

[0058] The molecular weight of PVA in the skin layer and the core layer is 150,000, and the particle size of the carbonyl iron absorber in the core layer is 450 nm.

[0059] 4 g of polyvinyl alcohol (PVA) was weighed and added to 46 ml of deionized water. The solution was heated at 97° C. for 3 h to dissolve, and then degassed at 97° C. for 8 h to obtain the skin spinning solution.

[0060] Weigh 2 g of carbonyl iron absorber and add it to 44 ml of deionized water. Stir the solution under magnetic stirring for 20 minutes, then disperse it by ultrasonication in an ultrasonic machine for 2 hours. Add 2 g of polyvinyl alcohol (PVA) to the obtained solution, heat it at 97 ° C for 3 hours to dissolve it, and then degas at 97 ° C for 8 hours to obtain the core layer spinning solution (the ratio of the mass fraction of the absorber to the mass fraction of polyvinyl alcohol is 1:1).

[0061] Then, a sheath-core spinning assembly with a coaxial needle is selected to spin at a constant speed of 15m / min, and the spun fibers are coagulated and stretched in sequence. At this time, the temperature of the saturated sodium sulfate coagulation bath is 40°C, the temperature of the wet heat stretching is 150°C, and the temperature of the dry heat stretching is 230°C.

[0062] The stretched fiber was rinsed with distilled water three times, and then placed in a vacuum oven and dried at 60°C for 18 hours, finally obtaining a PVA absorbing fiber with a skin-core structure and a core diameter of 1 / 3 of the total diameter.

[0063] The fiber's electromagnetic parameters were measured using a vector network analyzer over a range of 2 to 18 GHz, and the reflection loss (RL) was calculated from the complex permittivity and complex permeability. The fabricated PVA absorbing fiber with a sheath-core structure exhibited a minimum reflection loss of -31 dB in the 12 to 18 GHz range.

[0064] The present invention also provides an absorbing fiber with a high absorber content prepared by wet spinning, which is prepared by the method for preparing an absorbing fiber with a high absorber content by wet spinning described in any of the above embodiments.

[0065] Although specific embodiments of the present invention are described above, those skilled in the art should understand that these are merely examples and that various changes or modifications may be made to the embodiments without departing from the principles and essence of the present invention. The scope of protection of the present invention is limited only by the appended claims.

Claims

1. A method for preparing microwave-absorbing fibers with high microwave-absorbing agent content by wet spinning, characterized in that: The following steps are involved: (1) A polymer is dissolved in a solvent, and after degassing, a skin spinning solution with a polymer mass fraction of 8 to 20% is obtained; the same polymer is dissolved in a solvent and absorbers are added to disperse uniformly, and after degassing, a core spinning solution with a polymer mass fraction of 10 to 20% and a ratio of the mass fraction of the absorbers to the mass fraction of the polymer of 1:2 to 1:1 is obtained; wherein the polymer is polyvinyl alcohol, polyacrylonitrile or cellulose, and the absorbers are inorganic absorbers with a particle size of 450 nm, and the inorganic absorbers are carbonyl iron absorbers; (2) Selecting a sheath-core spinning assembly for coaxial wet spinning, extruding the sheath spinning solution and the core spinning solution as the sheath material and the core material from the sheath-core spinning assembly respectively, and passing through a coagulation bath to obtain nascent fibers; (3) The spun fibers are stretched, washed, and dried to obtain a sheath-core absorbing fiber, wherein the core diameter of the absorbing fiber is not less than 1 / 3 of the total diameter.

2. The method for preparing microwave-absorbing fibers with high microwave-absorbing agent content by wet spinning according to claim 1, characterized in that: In step (1), the polymer is first washed with water and dehydrated before being dissolved, wherein the washing and dehydration treatments are as follows: the polymer raw material is first washed with distilled water at a temperature not exceeding 30-40° C., and then dehydrated, and this cycle is repeated 1-5 times.

3. The method for preparing microwave-absorbing fibers with high microwave-absorbing agent content by wet spinning according to claim 1, characterized in that: When the polymer is polyvinyl alcohol, the coagulation bath used is a saturated sodium sulfate coagulation bath; when the polymer is polyacrylonitrile, the coagulation bath used is dimethylacetamide, dimethyl sulfoxide or sodium bisulfate; when the polymer is cellulose fiber, the coagulation bath used is n-methylmorpholine-n-oxide or sulfuric acid-sulfate solution.

4. The method for preparing microwave-absorbing fibers with high microwave-absorbing agent content by wet spinning according to claim 1, wherein: The stretching process in step (3) is to perform wet heat stretching and dry heat stretching in sequence. The temperature of wet heat stretching is 80~150℃, and the temperature of dry heat stretching is 120~230℃.

5. A microwave absorbing fiber, characterized in that: The microwave-absorbing fiber is prepared by the method for preparing microwave-absorbing fiber with high microwave-absorbing agent content by wet spinning according to any one of claims 1 to 4.

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