Bio-based aramid fibrids, methods of making, and applications thereof

Abstract

The present application relates to the technical field of fibrid, in particular to a bio-based aramid fibrid, a preparation method and application, the preparation method is: S1, after the polymerization reaction of m-phenylenediamine and isophthaloyl chloride in a polar solvent is completed, furan dicarboxylic chloride is added for reaction, and neutralization treatment is carried out to obtain a polymer; S2, the polymer is added to a fibrid agent for fibrid treatment to obtain the bio-based aramid fibrid; the fibrid agent comprises DMAC, water and dichloromethane. In the preparation method of the bio-based aramid fibrid, through the change of chemical modification and fibrid process, the size of the prepared fibrid is concentrated in the range of 0.05-0.1 mm, the beating degree is stable at 80-90 °SR, the prepared fibrid has better combination capacity than short cut fibers, and the index of aramid paper is improved.

Description

Technical Field

[0001] This invention relates to a bio-based aramid precipitated fiber, its preparation method, and its application, belonging to the field of precipitated fiber technology. Background Technology

[0002] Precipitated fibers, as one of the main raw materials for aramid paper, play an important role in its preparation. In the field of high-end materials technology, precipitated fibers, as a unique morphological fiber material, have been widely used in high-performance paper-based composite materials, sealing materials, and thermal insulation materials due to their huge specific surface area and three-dimensional network structure.

[0003] Conventional methods for preparing precipitated fibers typically involve introducing a polymer solution into a precipitant and applying mechanical shearing to precipitate and fibrillate the polymer, thereby forming a network of micron-sized fibers. For example, these methods are disclosed in patent applications with publication numbers CN119121421A, CN115110171A, and CN119145077A.

[0004] However, the raw materials for conventional meta-aramid precipitated fibers are all petroleum-based and non-renewable. Currently, research on bio-based aramid precipitated fibers is relatively limited, and fully commercialized bio-based aramid precipitated fibers have not yet appeared on a large scale. Bio-based aramid precipitated fibers are more attractive in fields with mandatory or leading environmental requirements, such as green high-end electrical insulation, lightweight green transportation, and environmental protection equipment.

[0005] However, after introducing bio-based polymers, it is difficult to form precipitated fibers. The properties of bio-based polymers cannot meet the conventional processing performance of precipitated fibers. In experiments, it was found that ordinary bio-based aramid precipitated fibers have problems such as low beating degree and many fine fibers. The fibers do not form ribbon-like shapes, which affects their use and cannot meet the application requirements. Therefore, the preparation of a bio-based aramid precipitated fiber can meet the needs of high-end applications and has important value. Summary of the Invention

[0006] This invention addresses the shortcomings of existing technologies by providing a bio-based aramid precipitated fiber, its preparation method, and its application. Through chemical modification and changes in the precipitation process, the prepared precipitated fiber has a size concentrated in the range of 0.05-0.1 mm, and its freeness is stable at 80-90°SR. The prepared precipitated fiber has better bonding ability with chopped fibers, thereby improving the properties of aramid paper.

[0007] The technical solution of this invention to solve the above-mentioned technical problems is as follows: A method for preparing bio-based aramid precipitated fibers, wherein the preparation method is as follows:

[0008] S1. After the polymerization reaction of m-phenylenediamine and isophthaloyl chloride is completed in a polar solvent, furanyl chloride is added to carry out the reaction and then neutralized to obtain the polymer.

[0009] S2. The polymer is added to a precipitation agent for precipitation treatment to obtain the bio-based aramid precipitated fiber;

[0010] The precipitant comprises DMAC, water, and dichloromethane.

[0011] Furthermore, in step S1, the polar solvent is selected from at least one of NMP, DMF, DMSO, and DMAC.

[0012] Furthermore, in step S1, the molar ratio of m-phenylenediamine to isophthaloyl chloride is 1:(0.6-0.65); the molar ratio of m-phenylenediamine to furanyl chloride is 1:(0.4-0.5).

[0013] Furthermore, in step S1, the polymerization reaction of m-phenylenediamine and isophthaloyl chloride is carried out at a temperature of -10 to 0°C.

[0014] Furthermore, in step S1, the reaction temperature for adding furanyl chloride is 30-50℃.

[0015] Furthermore, in step S1, the alkaline substance used for neutralization is at least one of sodium hydroxide, calcium hydroxide, and ammonia.

[0016] Furthermore, the polymer has a polymer solids content of 18-20 wt%, a viscosity of 50-60 Po, and a pH of 6-7.

[0017] Furthermore, in the precipitant, the mass content of DMAC is 60-65%, the mass content of water is 20-30%, and the mass content of dichloromethane is 10-15%.

[0018] The present invention also discloses a bio-based aramid precipitation fiber, wherein the bio-based aramid precipitation fiber is prepared according to the preparation method described in the present invention.

[0019] The present invention also discloses the application of a bio-based aramid precipitation fiber, which is used in the preparation of aramid paper.

[0020] The beneficial effects of this invention are:

[0021] In the preparation method of bio-based aramid precipitated fibers described in this invention, m-phenylenediamine reacts with isophthaloyl chloride, followed by the use of furanyl chloride to increase viscosity, thereby obtaining a bio-based aramid solution. The furanyl chloride added to the reaction system reduces molecular chain rigidity, decreases the forming speed during fiber forming, and improves the fiber's forming ability.

[0022] The conventional preparation process of precipitated fibers uses DMAC aqueous solution as a precipitant. However, due to the rapid molding process of bio-based aramid, a large number of fine fibers are generated. Therefore, in the preparation method of bio-based aramid precipitated fibers described in this invention, a ternary coagulation molding agent (DMAC / water / dichloromethane) is used. Due to the encapsulation of dichloromethane during the molding process, the molding speed of the polymer is slow, making it easier to form ribbon-like precipitated fibers.

[0023] In the preparation method of bio-based aramid precipitated fiber described in this invention, through chemical modification and changes in the precipitation process, the size of the prepared bio-based aramid precipitated fiber is concentrated in the range of 0.05-0.1 mm, and the freeness is stable at 80-90°SR. The prepared bio-based aramid precipitated fiber has better bonding ability with chopped fibers, thereby improving the performance of aramid paper. Attached Figure Description

[0024] Figure 1 Schematic diagram of the bio-based aramid precipitated fiber prepared in Example 1. Detailed Implementation

[0025] The specific embodiments of the present invention will be described in detail below. The present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used is for describing particular embodiments only and is not intended to limit the invention.

[0027] A method for preparing bio-based aramid precipitated fibers, wherein the preparation method comprises:

[0028] S1. After the polymerization reaction of m-phenylenediamine and isophthaloyl chloride is completed in a polar solvent, furanyl chloride is added to carry out the reaction and then neutralized to obtain the polymer.

[0029] S2. The polymer is added to a precipitation agent for precipitation treatment to obtain the bio-based aramid precipitated fiber;

[0030] The precipitant comprises DMAC, water, and dichloromethane.

[0031] Specifically, in step S1, the polar solvent is selected from at least one of NMP, DMF, DMSO, and DMAC.

[0032] Specifically, in step S1, the molar ratio of m-phenylenediamine to isophthaloyl chloride is 1:(0.6-0.65); the molar ratio of m-phenylenediamine to furanyl chloride is 1:(0.4-0.5).

[0033] Specifically, in step S1, the polymerization reaction of m-phenylenediamine and isophthaloyl chloride is carried out at a temperature of -10 to 0°C.

[0034] More specifically, in step S1, after dissolving m-phenylenediamine in a polar solvent, isophthaloyl chloride is slowly added to carry out the polymerization reaction. The reaction temperature in the system is controlled at -10~0℃, the reaction time of the polymerization reaction of m-phenylenediamine and isophthaloyl chloride is 8-10h, and the viscosity of the system after the reaction is completed is 5-20 Po.

[0035] Specifically, in step S1, the reaction temperature for adding furanyl chloride is 30-50℃, the reaction time for adding furanyl chloride is 0.5-2.0h, and the viscosity of the system after the reaction is completed is 50-60 Po.

[0036] Specifically, in step S1, the alkaline substance used in the neutralization process is at least one of sodium hydroxide, calcium hydroxide, and ammonia.

[0037] Specifically, the polymer has a polymer solids content of 18-20 wt% (mass content), a viscosity of 50-60 Po (at 25°C), and a pH of 6-7.

[0038] Specifically, in the precipitant, the mass content of DMAC is 60-65%, the mass content of water is 20-30%, and the mass content of dichloromethane is 10-15%.

[0039] More specifically, the mass ratio of the polymer to the precipitant is 1:(100-150).

[0040] More specifically, the polymer is added to a precipitating agent and subjected to high-speed shearing to obtain the bio-based aramid precipitated fiber, wherein the high-speed shearing rate is 3000-5000 rpm.

[0041] More specifically, after high-speed shearing, the bio-based aramid precipitated fiber product is obtained after solid-liquid separation and drying.

[0042] A bio-based aramid precipitated fiber is disclosed, wherein the bio-based aramid precipitated fiber is prepared according to the preparation method described in this invention. The bio-based aramid precipitated fiber is ribbon-like, with a size concentrated in the range of 0.05-0.1 mm, and a freeness stable at 80-90°SR.

[0043] An application of a bio-based aramid precipitating fiber, wherein the bio-based aramid precipitating fiber is used in the preparation of aramid paper.

[0044] Example 1

[0045] A method for preparing bio-based aramid precipitated fibers, wherein the preparation method comprises:

[0046] S1. After the polymerization reaction of m-phenylenediamine and isophthaloyl chloride is completed in a polar solvent, furanyl chloride is added to carry out the reaction and then neutralized to obtain the polymer.

[0047] The polar solvent is DMAC, the molar ratio of m-phenylenediamine to isophthaloyl chloride is 1:0.6, the polymerization temperature of m-phenylenediamine and isophthaloyl chloride is -4℃, and the polymerization time is 8 hours; the molar ratio of m-phenylenediamine to furanyl chloride is 1:0.4, the reaction temperature after adding furanyl chloride is 30℃, and the reaction time is 1 hour; after the reaction is completed, sodium hydroxide is added to adjust the pH. The polymer has a viscosity of 50 Po, a solid content of 18%, and a pH of 6.

[0048] S2. The polymer is added to a precipitation agent for precipitation treatment to obtain the bio-based aramid precipitated fiber;

[0049] The precipitant comprises DMAC, water and dichloromethane, wherein the mass content of DMAC is 60%, the mass content of water is 30%, and the mass content of dichloromethane is 10%.

[0050] The mass ratio of the polymer to the precipitant is 1:120, and the high-speed shear rate during precipitation is 4000 rpm.

[0051] Example 2

[0052] A method for preparing bio-based aramid precipitated fibers, wherein the preparation method comprises:

[0053] S1. After the polymerization reaction of m-phenylenediamine and isophthaloyl chloride is completed in a polar solvent, furanyl chloride is added to carry out the reaction and then neutralized to obtain the polymer.

[0054] The polar solvent is DMF, the molar ratio of m-phenylenediamine to isophthaloyl chloride is 1:0.62, the polymerization temperature of m-phenylenediamine and isophthaloyl chloride is -8℃, and the polymerization time is 10 h; the molar ratio of m-phenylenediamine to furanyl chloride is 1:0.43, the reaction temperature after adding furanyl chloride is 40℃, and the reaction time is 1.5 h; after the reaction is completed, sodium hydroxide is added to adjust the pH. The viscosity of the polymer is 55 Po, the solid content is 18.5%, and the pH is 6.2.

[0055] S2. The polymer is added to a precipitation agent for precipitation treatment to obtain the bio-based aramid precipitated fiber;

[0056] The precipitant comprises DMAC, water, and dichloromethane, wherein the mass content of DMAC is 62%, the mass content of water is 25%, and the mass content of dichloromethane is 13%.

[0057] The mass ratio of the polymer to the precipitant is 1:100, and the high-speed shear rate during precipitation is 5000 rpm.

[0058] Example 3

[0059] A method for preparing bio-based aramid precipitated fibers, wherein the preparation method comprises:

[0060] S1. After the polymerization reaction of m-phenylenediamine and isophthaloyl chloride is completed in a polar solvent, furanyl chloride is added to carry out the reaction and then neutralized to obtain the polymer.

[0061] The polar solvent is DMSO. The molar ratio of m-phenylenediamine to isophthaloyl chloride is 1:0.63. The polymerization temperature of m-phenylenediamine and isophthaloyl chloride is -1℃, and the polymerization time is 8 hours. Alternatively, the molar ratio of m-phenylenediamine to furanyl chloride is 1:0.47. The reaction temperature after adding furanyl chloride is 43℃, and the reaction time is 2 hours. After the reaction, sodium hydroxide is added to adjust the pH. The polymer has a viscosity of 57 Po, a solid content of 19%, and a pH of 6.7.

[0062] S2. The polymer is added to a precipitation agent for precipitation treatment to obtain the bio-based aramid precipitated fiber;

[0063] The precipitant comprises DMAC, water and dichloromethane, wherein the mass content of DMAC is 63%, the mass content of water is 22%, and the mass content of dichloromethane is 15%.

[0064] The mass ratio of the polymer to the precipitant is 1:140, and the high-speed shear rate during precipitation is 3000 rpm.

[0065] Example 4

[0066] A method for preparing bio-based aramid precipitated fibers, wherein the preparation method comprises:

[0067] S1. After the polymerization reaction of m-phenylenediamine and isophthaloyl chloride is completed in a polar solvent, furanyl chloride is added to carry out the reaction and then neutralized to obtain the polymer.

[0068] The polar solvent is NMP, the molar ratio of m-phenylenediamine to isophthaloyl chloride is 1:0.65, the polymerization temperature of m-phenylenediamine and isophthaloyl chloride is -10℃, and the polymerization time is 8 h; the molar ratio of m-phenylenediamine to furanyl chloride is 1:0.5, the reaction temperature after adding furanyl chloride is 50℃, and the reaction time is 0.5 h; after the reaction is completed, calcium hydroxide is added to adjust the pH. The viscosity of the polymer is 60 Po, the solid content is 20%, and the pH is 7.

[0069] S2. The polymer is added to a precipitation agent for precipitation treatment to obtain the bio-based aramid precipitated fiber;

[0070] The precipitant comprises DMAC, water, and dichloromethane, wherein the mass content of DMAC is 65%, the mass content of water is 20%, and the mass content of dichloromethane is 15%.

[0071] The mass ratio of the polymer to the precipitant is 1:150, and the high-speed shear rate during precipitation is 5000 rpm.

[0072] Comparative Example 1

[0073] Bio-based aramid precipitated fibers were prepared using the same method as in Example 4, except that in step S1 of Comparative Example 1, furanyl chloride was replaced with an equimolar amount of isophthaloyl chloride. The specific preparation process is as follows:

[0074] S1. After the polymerization reaction of m-phenylenediamine and isophthaloyl chloride is completed in a polar solvent, furanyl chloride is added to carry out the reaction and then neutralized to obtain the polymer.

[0075] The polar solvent is NMP, the molar ratio of m-phenylenediamine to isophthaloyl chloride is 1:1.15, the polymerization temperature of m-phenylenediamine and isophthaloyl chloride is -10℃, and the polymerization time is 8 hours. After the reaction, calcium hydroxide is added to adjust the pH. The viscosity of the polymer is 2Po, the solid content is 20%, and the pH is 7.

[0076] S2. The polymer is added to a precipitation agent for precipitation treatment to obtain the bio-based aramid precipitated fiber;

[0077] The precipitant comprises DMAC, water, and dichloromethane, wherein the mass content of DMAC is 65%, the mass content of water is 20%, and the mass content of dichloromethane is 15%.

[0078] The mass ratio of the polymer to the precipitant is 1:150, and the high-speed shear rate during precipitation is 5000 rpm.

[0079] Comparative Example 2

[0080] Bio-based aramid precipitated fibers were prepared using the same method as in Example 1, except that in Comparative Example 2, step S1 increased the solid content, thereby increasing the viscosity and obtaining a high-viscosity polymer. The specific preparation process is as follows:

[0081] S1. After the polymerization reaction of m-phenylenediamine and isophthaloyl chloride is completed in a polar solvent, furanyl chloride is added to carry out the reaction and then neutralized to obtain the polymer.

[0082] The polar solvent is DMAC, the molar ratio of m-phenylenediamine to isophthaloyl chloride is 1:0.6, the polymerization temperature of m-phenylenediamine and isophthaloyl chloride is -4℃, and the polymerization time is 8 hours; the molar ratio of m-phenylenediamine to furanyl chloride is 1:0.4, the reaction temperature after adding furanyl chloride is 30℃, and the reaction time is 1 hour; after the reaction, sodium hydroxide is added to adjust the pH. The polymer has a viscosity of 600 Po, a solid content of 22%, and a pH of 6.

[0083] S2. The polymer is added to a precipitation agent for precipitation treatment to obtain the bio-based aramid precipitated fiber;

[0084] The precipitant comprises DMAC, water and dichloromethane, wherein the mass content of DMAC is 60%, the mass content of water is 30%, and the mass content of dichloromethane is 10%.

[0085] The mass ratio of the polymer to the precipitant is 1:120, and the high-speed shear rate during precipitation is 4000 rpm.

[0086] Comparative Example 3

[0087] Bio-based aramid precipitated fibers were prepared using the same method as in Example 1, except that in Comparative Example 3, step S1 reduced the solid content, thereby lowering the viscosity and obtaining a low-viscosity polymer. The specific preparation process is as follows:

[0088] S1. After the polymerization reaction of m-phenylenediamine and isophthaloyl chloride is completed in a polar solvent, furanyl chloride is added to carry out the reaction and then neutralized to obtain the polymer.

[0089] The polar solvent is DMAC, the molar ratio of m-phenylenediamine to isophthaloyl chloride is 1:0.6, the polymerization temperature of m-phenylenediamine and isophthaloyl chloride is -4℃, and the polymerization time is 8 hours; the molar ratio of m-phenylenediamine to furanyl chloride is 1:0.4, the reaction temperature after adding furanyl chloride is 30℃, and the reaction time is 1 hour; after the reaction is completed, sodium hydroxide is added to adjust the pH. The viscosity of the polymer is 10 Po, the solid content is 17%, and the pH is 6.

[0090] S2. The polymer is added to a precipitation agent for precipitation treatment to obtain the bio-based aramid precipitated fiber;

[0091] The precipitant comprises DMAC, water and dichloromethane, wherein the mass content of DMAC is 60%, the mass content of water is 30%, and the mass content of dichloromethane is 10%.

[0092] The mass ratio of the polymer to the precipitant is 1:120, and the high-speed shear rate during precipitation is 4000 rpm.

[0093] Comparative Example 4

[0094] Bio-based aramid precipitated fibers were prepared using the same method as in Example 1, except that the precipitant in step S2 of Comparative Example 4 did not include water. The specific preparation process is as follows:

[0095] S1. After the polymerization reaction of m-phenylenediamine and isophthaloyl chloride is completed in a polar solvent, furanyl chloride is added to carry out the reaction and then neutralized to obtain the polymer.

[0096] The polar solvent is DMAC, the molar ratio of m-phenylenediamine to isophthaloyl chloride is 1:0.6, the polymerization temperature of m-phenylenediamine and isophthaloyl chloride is -4℃, and the polymerization time is 8 hours; the molar ratio of m-phenylenediamine to furanyl chloride is 1:0.4, the reaction temperature after adding furanyl chloride is 30℃, and the reaction time is 1 hour; after the reaction is completed, sodium hydroxide is added to adjust the pH. The polymer has a viscosity of 50 Po, a solid content of 18%, and a pH of 6.

[0097] S2. The polymer is added to a precipitation agent for precipitation treatment to obtain the bio-based aramid precipitated fiber;

[0098] The precipitant comprises DMAC and dichloromethane, wherein the mass content of DMAC is 90% and the mass content of dichloromethane is 10%.

[0099] The mass ratio of the polymer to the precipitant is 1:120, and the high-speed shear rate during precipitation is 4000 rpm.

[0100] Comparative Example 5

[0101] Bio-based aramid precipitated fibers were prepared using the same method as in Example 1, except that the precipitant in step S2 of Comparative Example 5 did not include DMAC. The specific preparation process is as follows:

[0102] S1. After the polymerization reaction of m-phenylenediamine and isophthaloyl chloride is completed in a polar solvent, furanyl chloride is added to carry out the reaction and then neutralized to obtain the polymer.

[0103] The polar solvent is DMAC, the molar ratio of m-phenylenediamine to isophthaloyl chloride is 1:0.6, the polymerization temperature of m-phenylenediamine and isophthaloyl chloride is -4℃, and the polymerization time is 8 h; the molar ratio of m-phenylenediamine to furanyl chloride is 1:0.4, the reaction temperature after adding furanyl chloride is 30℃, and the reaction time is 1 h; after the reaction is completed, sodium hydroxide is added to adjust the pH. The polymer has a viscosity of 50 Po, a solid content of 18%, and a pH of 6.

[0104] S2. The polymer is added to a precipitation agent for precipitation treatment to obtain the bio-based aramid precipitated fiber;

[0105] The precipitant comprises water and dichloromethane, wherein the water content is 90% by mass and the dichloromethane content is 10% by mass.

[0106] The mass ratio of the polymer to the precipitant is 1:120, and the high-speed shear rate during precipitation is 4000 rpm.

[0107] Comparative Example 6

[0108] Bio-based aramid precipitated fibers were prepared using the same method as in Example 1, except that the precipitant in step S2 of Comparative Example 6 did not include dichloromethane. The specific preparation process is as follows:

[0109] S1. After the polymerization reaction of m-phenylenediamine and isophthaloyl chloride is completed in a polar solvent, furanyl chloride is added to carry out the reaction and then neutralized to obtain the polymer.

[0110] The polar solvent is DMAC, the molar ratio of m-phenylenediamine to isophthaloyl chloride is 1:0.6, the polymerization temperature of m-phenylenediamine and isophthaloyl chloride is -4℃, and the polymerization time is 8 hours; the molar ratio of m-phenylenediamine to furanyl chloride is 1:0.4, the reaction temperature after adding furanyl chloride is 30℃, and the reaction time is 1 hour; after the reaction is completed, sodium hydroxide is added to adjust the pH. The polymer has a viscosity of 50 Po, a solid content of 18%, and a pH of 6.

[0111] S2. The polymer is added to a precipitation agent for precipitation treatment to obtain the bio-based aramid precipitated fiber;

[0112] The precipitant comprises DMAC and water, wherein the mass content of DMAC is 70% and the mass content of water is 30%.

[0113] The mass ratio of the polymer to the precipitant is 1:120, and the high-speed shear rate during precipitation is 4000 rpm.

[0114] Comparative Example 7

[0115] Bio-based aramid precipitated fibers were prepared using the same method as in Example 4, except that the proportion of dichloromethane in the precipitant in step S2 of Comparative Example 7 was increased. The specific preparation process is as follows:

[0116] S1. After the polymerization reaction of m-phenylenediamine and isophthaloyl chloride is completed in a polar solvent, furanyl chloride is added to carry out the reaction and then neutralized to obtain the polymer.

[0117] The polar solvent is NMP, the molar ratio of m-phenylenediamine to isophthaloyl chloride is 1:0.65, the polymerization temperature of m-phenylenediamine and isophthaloyl chloride is -10℃, and the polymerization time is 8 h; the molar ratio of m-phenylenediamine to furanyl chloride is 1:0.5, the reaction temperature after adding furanyl chloride is 50℃, and the reaction time is 0.5 h; after the reaction is completed, calcium hydroxide is added to adjust the pH. The viscosity of the polymer is 60 Po, the solid content is 20%, and the pH is 7.

[0118] S2. The polymer is added to a precipitation agent for precipitation treatment to obtain the bio-based aramid precipitated fiber;

[0119] The precipitant comprises DMAC, water, and dichloromethane, wherein the mass content of DMAC is 55%, the mass content of water is 20%, and the mass content of dichloromethane is 25%.

[0120] The mass ratio of the polymer to the precipitant is 1:150, and the high-speed shear rate during precipitation is 5000 rpm.

[0121] The process conditions for preparing bio-based aramid precipitated fibers and the results of beating degree and average size measurement of the precipitated fibers in the above embodiments and comparative examples are shown in Tables 1 and 2 below.

[0122] The methods for determining the freeness and average fiber size are GB / T 3332-2004 "Determination of pulp freeness (Schober-Regler method)" and GB / T 10336-2002 "Determination of papermaking fiber length (polarized light method)".

[0123] Table 1. Process conditions and test results for Examples 1-4

[0124]

[0125] Table 2. Process conditions and test results of Comparative Examples 1-7

[0126]

[0127] As can be seen from the experimental data in Tables 1 and 2 above, the bio-based aramid precipitated fibers prepared by the preparation method described in this invention in Examples 1-4 have a stable freeness of 80-90°SR and a size concentrated in the range of 0.05-0.1mm. The prepared precipitated fibers and chopped fibers have better bonding ability, which improves the performance of aramid paper. Figure 1 The bio-based aramid precipitated fiber obtained in Example 1, from Figure 1 It can be seen that the bio-based aramid precipitated fibers prepared by the method described in this invention have uniform size and no excessive fine fibers.

[0128] A comparison of the experimental results of Comparative Example 1 and Example 4 shows that if furanyl chloride is not added during the preparation process, the freeness of the precipitated fibers increases significantly and the average fiber size decreases. This is because the addition of furanyl chloride alters the molecular weight, molecular chain rigidity, and other properties of the polymer, affecting the fiber-forming behavior during precipitation, thus resulting in significant differences in freeness and average fiber size.

[0129] A comparison of the experimental results from Comparative Examples 2, 3, and 1 shows that: if the viscosity of the polymer is too high, the average size of the precipitated fibers increases significantly because high viscosity leads to severe molecular chain entanglement, making it difficult to uniformly disperse into fine fibers during precipitation; conversely, if the viscosity of the polymer is too low, the average size of the precipitated fibers decreases significantly, and the freeness increases significantly because low viscosity results in overly dispersed molecular chains, which also affects fiber formation. Therefore, selecting the viscosity of the polymer described in this invention is more conducive to obtaining high-performance bio-based aramid precipitated fibers.

[0130] A comparison of the experimental results of Comparative Example 4 and Example 1 shows that: if water is not added to the precipitant, the fibers will not form; a comparison of the experimental results of Comparative Example 5 and Example 1 shows that if DMAC is not added to the precipitant, the fibers will be coarse and the freeness will be low; a comparison of the experimental results of Comparative Example 6 and Example 1 shows that if dichloromethane is not added to the precipitant, there will be more fine fibers and the freeness will be higher. This is because the presence of dichloromethane can regulate the phase separation behavior of the precipitation process, promoting the formation of a more uniform fiber structure. If dichloromethane is lacking, the phase separation process will be out of control, resulting in a large number of fine fibers, which in turn leads to a higher freeness. Therefore, only when the precipitant includes DMAC, water, and dichloromethane can qualified bio-based aramid precipitated fibers be obtained.

[0131] The comparison of the experimental results of Comparative Example 1 and Example 5 shows that if the proportion of dichloromethane added to the precipitant is too high, it will lead to an increase in fine fibers and a higher degree of beating in the precipitated fibers. An excessively high proportion of dichloromethane will disrupt the dissolution balance between the precipitant and the polymer, slow down the phase separation rate, and destroy the fiber aggregation structure.

[0132] The bio-based aramid precipitated fiber described in this invention has excellent application effects in aramid paper. To further demonstrate this effect, the following aramid paper preparation experiments were conducted:

[0133] Meta-aramid precipitated fibers (prepared using the precipitated fibers of Examples 1-4 and Comparative Examples 1-7 of this invention, respectively) and 7mm meta-aramid chopped fibers were mixed at a mass ratio of 3:7. Aramid paper was prepared by pulping, papermaking, and hot pressing at 250℃. The thickness of the aramid paper was 0.05mm. The tensile strength, tear strength, and temperature resistance of the aramid paper were tested, and the results are summarized below.

[0134] Table 3 Test Results of Aramid Paper

[0135]

[0136] As can be seen from the data in the table above, the aramid paper made using the bio-based aramid precipitated fiber described in this invention as a raw material exhibits excellent tensile strength and tear strength. The size of the bio-based aramid precipitated fiber described in this invention is concentrated in the range of 0.05-0.1 mm, and the freeness is stable at 80-90°SR. It has better bonding ability with chopped fibers, thus improving the performance of aramid paper.

[0137] As can be seen from the results of the aramid paper in Comparative Example 1, the performance indicators are all lower than those of the aramid paper in Examples 1-4. The precipitated fiber in Comparative Example 1 has a freeness of 150°SR and an average fiber size of 0.007mm. The fibers are too fine and the freeness is too high, which makes them prone to agglomeration during papermaking and unable to form an effective stress transfer network structure. At the same time, the molecular chains have poor regularity due to process defects, resulting in extremely low tensile and tear strength and insufficient temperature resistance.

[0138] The results of the aramid paper in Comparative Example 2 show that its performance indicators are all lower than those of the aramid paper in Examples 1-4. The average size of the precipitated fiber in Comparative Example 2 is 0.24 mm, which is too coarse. The interfacial bonding force with the meta-aramid short chopped fiber is poor, the stress transmission is hindered, the network toughness is insufficient, and the regularity of the molecular chain is poor.

[0139] The results of the aramid paper in Comparative Example 3 show that its performance indicators are all lower than those of the aramid paper in Examples 1-4. The average size of the precipitated fibers in Comparative Example 3 is 0.01 mm, which is relatively small. The network density is insufficient, the inter-fiber bonding force is average, and the molecular chain regularity is not as good as that in Examples 1-4.

[0140] Because the precipitated fibers in Comparative Example 4 cannot be formed, the precipitated fibers in Comparative Example 4 cannot be used to prepare aramid paper.

[0141] The results of the aramid paper in Comparative Example 5 show that the performance indicators are extremely poor. This is because the Chengxi fiber prepared in Comparative Example 5 is very coarse and has a low degree of beating, resulting in poor interfacial bonding with the meta-aramid short-cut fiber, which ultimately leads to a significant decline in the performance of the aramid paper.

[0142] The results of the aramid paper in Comparative Example 6 show that the performance indicators are all lower than those of the aramid paper in Examples 1-4. When preparing the precipitated fiber in Comparative Example 6, the amount of DMAC in the precipitant was 70% and the water content was 30%. The composition of the precipitant was unreasonable. The fiber was small and had high freeness. The network bonding was average and the molecular chain regularity was insufficient.

[0143] As can be seen from the results of the aramid paper in Comparative Example 7, the performance indicators are all lower than those of the aramid paper in Examples 1-4. The reason may be that the precipitation process is different from that in the examples, the fiber network density and bonding force are weaker than in the examples, and the molecular chain regularity and thermal stability are reduced.

[0144] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are exhaustively listed. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0145] For those skilled in the art, various modifications and improvements can be made without departing from the concept of the present invention, and these modifications and improvements are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A method for preparing bio-based aramid precipitated fibers, characterized in that, The preparation method is as follows: S1. After the polymerization reaction of m-phenylenediamine and isophthaloyl chloride is completed in a polar solvent, furanyl chloride is added to react and then neutralized to obtain a polymer; the polymer has a polymer solid content of 18-20 wt% and a viscosity of 50-60 Po; S2. The polymer is added to a precipitation agent for precipitation treatment to obtain the bio-based aramid precipitated fiber; The precipitant contains 60-65% DMAC by mass, 20-30% water by mass, and 10-15% dichloromethane by mass.

2. The method for preparing a bio-based aramid precipitated fiber according to claim 1, characterized in that, In step S1, the polar solvent is selected from at least one of NMP, DMF, DMSO, and DMAC.

3. The method for preparing a bio-based aramid precipitated fiber according to claim 1, characterized in that, In step S1, the molar ratio of m-phenylenediamine to isophthaloyl chloride is 1:(0.6-0.65); the molar ratio of m-phenylenediamine to furanyl chloride is 1:(0.4-0.5).

4. The method for preparing a bio-based aramid precipitated fiber according to claim 1, characterized in that, In step S1, the polymerization reaction of m-phenylenediamine and isophthaloyl chloride is carried out at a temperature of -10 to 0°C.

5. The method for preparing a bio-based aramid precipitated fiber according to claim 1, characterized in that, In step S1, the reaction temperature for adding furanyl chloride is 30-50℃.

6. The method for preparing a bio-based aramid precipitated fiber according to claim 1, characterized in that, In step S1, the alkaline substance used for neutralization is at least one of sodium hydroxide, calcium hydroxide, and ammonia.

7. The method for preparing a bio-based aramid precipitated fiber according to claim 1, characterized in that, The polymer has a pH of 6-7.

8. A bio-based aramid precipitated fiber, characterized in that, The bio-based aramid precipitated fiber is prepared according to the preparation method described in any one of claims 1-7.

9. An application of the bio-based aramid precipitated fiber according to claim 8, characterized in that, The bio-based aramid precipitated fiber is used in the preparation of aramid paper.

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