CN116695270A - Meta-aramid fiber and molecular weight regulating and controlling method and application thereof - Google Patents
Meta-aramid fiber and molecular weight regulating and controlling method and application thereof Download PDFInfo
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- CN116695270A CN116695270A CN202310812373.8A CN202310812373A CN116695270A CN 116695270 A CN116695270 A CN 116695270A CN 202310812373 A CN202310812373 A CN 202310812373A CN 116695270 A CN116695270 A CN 116695270A
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- 238000000034 method Methods 0.000 title claims abstract description 67
- 229920006231 aramid fiber Polymers 0.000 title claims abstract description 51
- 230000001276 controlling effect Effects 0.000 title claims abstract description 27
- 230000001105 regulatory effect Effects 0.000 title claims abstract description 19
- 238000006243 chemical reaction Methods 0.000 claims abstract description 54
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 43
- 238000006068 polycondensation reaction Methods 0.000 claims abstract description 38
- 230000008569 process Effects 0.000 claims abstract description 26
- 229920000889 poly(m-phenylene isophthalamide) Polymers 0.000 claims abstract description 25
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 21
- 238000009987 spinning Methods 0.000 claims abstract description 21
- 150000001282 organosilanes Chemical class 0.000 claims abstract description 11
- 238000002360 preparation method Methods 0.000 claims abstract description 7
- YCGKJPVUGMBDDS-UHFFFAOYSA-N 3-(6-azabicyclo[3.1.1]hepta-1(7),2,4-triene-6-carbonyl)benzamide Chemical compound NC(=O)C1=CC=CC(C(=O)N2C=3C=C2C=CC=3)=C1 YCGKJPVUGMBDDS-UHFFFAOYSA-N 0.000 claims abstract description 6
- FDQSRULYDNDXQB-UHFFFAOYSA-N benzene-1,3-dicarbonyl chloride Chemical compound ClC(=O)C1=CC=CC(C(Cl)=O)=C1 FDQSRULYDNDXQB-UHFFFAOYSA-N 0.000 claims description 45
- 239000011347 resin Substances 0.000 claims description 31
- 229920005989 resin Polymers 0.000 claims description 31
- 238000001035 drying Methods 0.000 claims description 29
- WZCQRUWWHSTZEM-UHFFFAOYSA-N 1,3-phenylenediamine Chemical compound NC1=CC=CC(N)=C1 WZCQRUWWHSTZEM-UHFFFAOYSA-N 0.000 claims description 25
- 239000000126 substance Substances 0.000 claims description 21
- 238000003756 stirring Methods 0.000 claims description 20
- 229940018564 m-phenylenediamine Drugs 0.000 claims description 19
- IJOOHPMOJXWVHK-UHFFFAOYSA-N chlorotrimethylsilane Chemical group C[Si](C)(C)Cl IJOOHPMOJXWVHK-UHFFFAOYSA-N 0.000 claims description 17
- 230000001112 coagulating effect Effects 0.000 claims description 16
- 238000005406 washing Methods 0.000 claims description 16
- 238000001914 filtration Methods 0.000 claims description 15
- 239000002253 acid Substances 0.000 claims description 14
- 239000011230 binding agent Substances 0.000 claims description 14
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 claims description 14
- UHOVQNZJYSORNB-UHFFFAOYSA-N monobenzene Natural products C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 claims description 13
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical group CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 12
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 claims description 12
- ZMANZCXQSJIPKH-UHFFFAOYSA-N Triethylamine Chemical group CCN(CC)CC ZMANZCXQSJIPKH-UHFFFAOYSA-N 0.000 claims description 12
- 239000000835 fiber Substances 0.000 claims description 12
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical group CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 11
- 239000000843 powder Substances 0.000 claims description 11
- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical compound CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 claims description 10
- 238000004090 dissolution Methods 0.000 claims description 10
- 239000003960 organic solvent Substances 0.000 claims description 10
- 239000002798 polar solvent Substances 0.000 claims description 10
- 239000006184 cosolvent Substances 0.000 claims description 9
- 239000003223 protective agent Substances 0.000 claims description 9
- VHYFNPMBLIVWCW-UHFFFAOYSA-N 4-Dimethylaminopyridine Chemical compound CN(C)C1=CC=NC=C1 VHYFNPMBLIVWCW-UHFFFAOYSA-N 0.000 claims description 8
- HEDRZPFGACZZDS-UHFFFAOYSA-N Chloroform Chemical compound ClC(Cl)Cl HEDRZPFGACZZDS-UHFFFAOYSA-N 0.000 claims description 8
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 claims description 8
- YNQLUTRBYVCPMQ-UHFFFAOYSA-N Ethylbenzene Chemical compound CCC1=CC=CC=C1 YNQLUTRBYVCPMQ-UHFFFAOYSA-N 0.000 claims description 8
- JGFZNNIVVJXRND-UHFFFAOYSA-N N,N-Diisopropylethylamine (DIPEA) Chemical compound CCN(C(C)C)C(C)C JGFZNNIVVJXRND-UHFFFAOYSA-N 0.000 claims description 8
- JUJWROOIHBZHMG-UHFFFAOYSA-N Pyridine Chemical compound C1=CC=NC=C1 JUJWROOIHBZHMG-UHFFFAOYSA-N 0.000 claims description 8
- 238000001891 gel spinning Methods 0.000 claims description 8
- 238000009998 heat setting Methods 0.000 claims description 8
- 239000005051 trimethylchlorosilane Substances 0.000 claims description 8
- 238000004804 winding Methods 0.000 claims description 8
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 claims description 7
- 239000004760 aramid Substances 0.000 claims description 7
- 229910001628 calcium chloride Inorganic materials 0.000 claims description 7
- 239000001110 calcium chloride Substances 0.000 claims description 7
- CTQNGGLPUBDAKN-UHFFFAOYSA-N O-Xylene Chemical compound CC1=CC=CC=C1C CTQNGGLPUBDAKN-UHFFFAOYSA-N 0.000 claims description 6
- 239000003495 polar organic solvent Substances 0.000 claims description 6
- VZGDMQKNWNREIO-UHFFFAOYSA-N tetrachloromethane Chemical compound ClC(Cl)(Cl)Cl VZGDMQKNWNREIO-UHFFFAOYSA-N 0.000 claims description 6
- 239000000463 material Substances 0.000 claims description 5
- KWYHDKDOAIKMQN-UHFFFAOYSA-N N,N,N',N'-tetramethylethylenediamine Chemical compound CN(C)CCN(C)C KWYHDKDOAIKMQN-UHFFFAOYSA-N 0.000 claims description 4
- 238000004891 communication Methods 0.000 claims description 4
- 230000003137 locomotive effect Effects 0.000 claims description 4
- UMJSCPRVCHMLSP-UHFFFAOYSA-N pyridine Natural products COC1=CC=CN=C1 UMJSCPRVCHMLSP-UHFFFAOYSA-N 0.000 claims description 4
- HPNMFZURTQLUMO-UHFFFAOYSA-N diethylamine Chemical compound CCNCC HPNMFZURTQLUMO-UHFFFAOYSA-N 0.000 claims description 3
- 125000001997 phenyl group Chemical group [H]C1=C([H])C([H])=C(*)C([H])=C1[H] 0.000 claims description 2
- 125000002924 primary amino group Chemical group [H]N([H])* 0.000 abstract description 19
- 239000000178 monomer Substances 0.000 abstract description 11
- 238000001816 cooling Methods 0.000 abstract description 9
- 238000006116 polymerization reaction Methods 0.000 abstract description 5
- 238000007086 side reaction Methods 0.000 abstract description 5
- 239000002904 solvent Substances 0.000 abstract description 3
- 125000004435 hydrogen atom Chemical group [H]* 0.000 abstract description 2
- 238000006386 neutralization reaction Methods 0.000 abstract description 2
- 230000003647 oxidation Effects 0.000 abstract description 2
- 238000007254 oxidation reaction Methods 0.000 abstract description 2
- 239000002994 raw material Substances 0.000 abstract description 2
- 239000000243 solution Substances 0.000 description 36
- 229920000642 polymer Polymers 0.000 description 11
- 239000000047 product Substances 0.000 description 11
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 8
- IXCSERBJSXMMFS-UHFFFAOYSA-N hydrogen chloride Substances Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 description 7
- 229910000041 hydrogen chloride Inorganic materials 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- 230000015572 biosynthetic process Effects 0.000 description 6
- 239000006227 byproduct Substances 0.000 description 6
- 238000004821 distillation Methods 0.000 description 6
- 238000009775 high-speed stirring Methods 0.000 description 6
- 239000011550 stock solution Substances 0.000 description 6
- 238000003786 synthesis reaction Methods 0.000 description 6
- -1 polymetaphenylene isophthalamide Polymers 0.000 description 5
- 229910001220 stainless steel Inorganic materials 0.000 description 5
- 239000010935 stainless steel Substances 0.000 description 5
- 229920003235 aromatic polyamide Polymers 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 238000012696 Interfacial polycondensation Methods 0.000 description 3
- 238000009826 distribution Methods 0.000 description 3
- 150000004985 diamines Chemical class 0.000 description 2
- 239000000839 emulsion Substances 0.000 description 2
- 239000008096 xylene Substances 0.000 description 2
- GEYOCULIXLDCMW-UHFFFAOYSA-N 1,2-phenylenediamine Chemical compound NC1=CC=CC=C1N GEYOCULIXLDCMW-UHFFFAOYSA-N 0.000 description 1
- NGNBDVOYPDDBFK-UHFFFAOYSA-N 2-[2,4-di(pentan-2-yl)phenoxy]acetyl chloride Chemical group CCCC(C)C1=CC=C(OCC(Cl)=O)C(C(C)CCC)=C1 NGNBDVOYPDDBFK-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 150000001263 acyl chlorides Chemical class 0.000 description 1
- 239000012298 atmosphere Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- FFBHFFJDDLITSX-UHFFFAOYSA-N benzyl N-[2-hydroxy-4-(3-oxomorpholin-4-yl)phenyl]carbamate Chemical compound OC1=C(NC(=O)OCC2=CC=CC=C2)C=CC(=C1)N1CCOCC1=O FFBHFFJDDLITSX-UHFFFAOYSA-N 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000010292 electrical insulation Methods 0.000 description 1
- 229920006253 high performance fiber Polymers 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 150000004988 m-phenylenediamines Chemical class 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 229920005594 polymer fiber Polymers 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-N sulfuric acid Substances OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
- 238000010189 synthetic method Methods 0.000 description 1
- 238000002166 wet spinning Methods 0.000 description 1
Classifications
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
- D01F6/58—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products
- D01F6/60—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products from polyamides
- D01F6/605—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products from polyamides from aromatic polyamides
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G69/00—Macromolecular compounds obtained by reactions forming a carboxylic amide link in the main chain of the macromolecule
- C08G69/02—Polyamides derived from amino-carboxylic acids or from polyamines and polycarboxylic acids
- C08G69/26—Polyamides derived from amino-carboxylic acids or from polyamines and polycarboxylic acids derived from polyamines and polycarboxylic acids
- C08G69/28—Preparatory processes
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G69/00—Macromolecular compounds obtained by reactions forming a carboxylic amide link in the main chain of the macromolecule
- C08G69/02—Polyamides derived from amino-carboxylic acids or from polyamines and polycarboxylic acids
- C08G69/26—Polyamides derived from amino-carboxylic acids or from polyamines and polycarboxylic acids derived from polyamines and polycarboxylic acids
- C08G69/32—Polyamides derived from amino-carboxylic acids or from polyamines and polycarboxylic acids derived from polyamines and polycarboxylic acids from aromatic diamines and aromatic dicarboxylic acids with both amino and carboxylic groups aromatically bound
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
- Y02P70/62—Manufacturing or production processes characterised by the final manufactured product related technologies for production or treatment of textile or flexible materials or products thereof, including footwear
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Health & Medical Sciences (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Textile Engineering (AREA)
- Polyamides (AREA)
Abstract
The invention discloses a meta-aramid fiber and a molecular weight regulating and controlling method and application thereof, which belong to the technical field of preparation of poly (m-phenylene isophthalamide). Meta-phenylene isophthalamide) and m-phenylene isophthalamide are used as raw materials, and the meta-aramid fiber with higher molecular weight is prepared through the process steps of amino protection, pre-polycondensation, spinning and the like, and an amino protection strategy is implemented on DMP by adopting organosilane to replace active hydrogen atoms on amino, so that the occurrence of oxidation side reaction is effectively avoided, and the solubility of a protected monomer in a solvent is also increased; the DMP and IPC are polymerized after the protection of the amino, so that the generation of HCl in the polycondensation process of a low-temperature solution is avoided, the stability of a reaction system is greatly improved, the neutralization step after the reaction is omitted, a nitrogen circulating cooling device is introduced into the reaction system, the nitrogen is ensured to be always subjected to reaction protection in a low-temperature state, the temperature of the polymerization reaction system is rapidly reduced, and the severe release of reaction heat is avoided.
Description
Technical Field
The invention belongs to the technical field of preparation of poly (m-phenylene isophthalamide) fibers, and particularly relates to a meta-aramid fiber, a molecular weight regulating method and application thereof.
Background
Meta-aramid fiber, i.e., poly m-phenylene isophthalamide, PMIA) fiber, is a high performance fiber prepared by polycondensation of m-phenylenediamine (DMP) and m-phthaloyl chloride (IPC) monomers to form a polymer, and spinning the polymer in two main steps. Due to the action of a large amount of hydrogen bonds in meta-aramid molecules, the PMIA fiber has excellent performances in the aspects of heat resistance, flame retardance, electrical insulation, chemical stability, mechanical property and the like. Based on the advantages, PMIA fiber becomes an important basic material in various fields of aerospace, high-speed rail locomotives, military fire protection, petrochemical industry, electronic communication and the like. In practical application, there is a certain requirement on the molecular weight of meta-aramid fiber, and various properties of polymer fiber are generally improved along with the increase of the molecular weight, so that in the production practice process, there is a strict requirement on the molecular weight and the molecular weight distribution. The control of the molecular weight of the aramid fiber is needed to be realized in the step of polymer synthesis, and if the molecular weight of a polymer solution is too low, the phenomenon of yarn breakage easily occurs in the spinning process, so that the quality of a fiber finished product is reduced. The molecular weight of the polymer solution can be indirectly characterized by the viscosity of the solution, and the logarithmic viscosity of the polymer solution is required to be 2.2 dL.g in general for the aramid wet spinning process -1 Left and right.
Currently, the preparation method of the polymetaphenylene isophthalamide comprises interfacial polycondensation, emulsion polycondensation and low-temperature solution polycondensation. However, PMIA resin obtained by the interfacial polycondensation method has low molecular weight and high dispersibility; although the molecular weight of the resin produced by the emulsion polycondensation method is higher than that produced by the interfacial polycondensation method, the molecular weight dispersibility is still larger, and the product quality is unstable. The method mainly adopted in the industrial production of meta-aramid fiber at the present stage is a low-temperature solution polycondensation method, which means a homogeneous phase reaction carried out by placing DMP and IPC in a low-temperature anhydrous organic solvent system, and hydrogen chloride is produced in the process. The low-temperature solution polycondensation has the advantages of small molecular weight dispersibility of the obtained resin and stable operation. However, the problem of overhigh temperature still easily occurs in the process of synthesizing PMIA by low-temperature solution polycondensation at present, and the higher temperature can accelerate the side reaction of acyl chloride hydrolysis, increase byproducts and seriously influence the generation of PMIA with more uniform high molecular weight and distribution. In addition, the activity of the two monomers is higher, and the amino end group in the phenylenediamine is easy to oxidize, so that the molar ratio of the monomers is influenced, and the viscosity of the obtained polymer is reduced; in addition, hydrogen chloride generated in the polycondensation process of the IPC and the DMP is extremely easy to generate m-phenylenediamine salt with the DMP, and cannot react with the IPC further, so that the polycondensation process is stopped, the number of small molecular polymers is increased, the molecular weight of PMIA resin is reduced, and the distribution is wider. Acid chloride forms hydrogen chloride (HCl) when it is polycondensed with diamines, which can cause chain termination if not absorbed or timely discharged from the reaction zone. Although chinese patent CN 1265034C, CN 101876092B, CN 102534840B, CN 110983475a et al all provide improvements to the apparatus, no related patent is currently concerned with controlling the reaction system temperature by adjusting the shielding gas temperature. Chinese patent CN 110983475A, CN 101285214B, CN 1162572C et al all provide a synthetic method for preparing aramid resin polymers by a low temperature method, but related patents for controlling the molecular weight of the product by a protection strategy for monomers during the preparation process of meta-aramid resin polymerization are not yet known.
Aiming at the problems that the existing DMP monomer is easy to oxidize, affects the polycondensation process of a low-temperature solution, causes low molecular weight and poor fiber forming quality of final meta-aramid fiber, and the byproduct HCl in the traditional PMIA low-temperature solution polycondensation process is easy to cause chain termination in a system, so that the molecular weight of a polymer is lower, the reaction heat is higher, side reaction is increased, the viscosity of a reaction system and the molecular weight of a product are affected, a novel preparation method of the meta-aramid fiber is needed to be found, the molecular weight of the product is controlled through a protection strategy of the monomer, the reaction temperature is further controlled, and the molecular weight and the fiber forming quality of the meta-aramid fiber are improved.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide meta-aramid fiber, a molecular weight regulating method and application thereof, so as to solve the technical problems that a meta-phenylenediamine monomer in the existing meta-aramid fiber is easy to oxidize, and a byproduct HCl in a system is easy to cause chain termination and has higher reaction heat in the traditional low-temperature solution polycondensation process of the meta-aramid fiber.
In order to achieve the above purpose, the invention is realized by adopting the following technical scheme:
the invention discloses a molecular weight regulating and controlling method of meta-aramid fiber, which comprises the following steps:
1) Adding m-phenylenediamine into an organic solvent for full dissolution; adding an organosilane protective agent and an acid binding agent, stirring for reaction, distilling and collecting distillate, and drying to obtain a substance A;
2) Fully dissolving the substance A obtained in the step 1) in a polar organic solvent to obtain a solution A; introducing cooled nitrogen into the solution A, adding isophthaloyl dichloride under stirring, and filtering after the pre-polycondensation reaction is finished to obtain a prepolymer;
3) Adding isophthaloyl chloride into the prepolymer prepared in the step 2), and filtering, washing and drying after the polycondensation reaction is finished to obtain the poly-m-phenylene isophthalamide resin;
4) Dissolving the poly (m-phenylene isophthalamide) resin prepared in the step 3) in a polar solvent to obtain a solution B, and adding a cosolvent to obtain a spinning solution; and (3) adopting a dry-wet spinning process, passing the spinning solution through a spinneret plate, entering a first coagulating bath to obtain primary fibers, passing through a second coagulating bath after drafting, and then washing, drying, dry-hot stretching, heat setting and winding to obtain meta-aramid fibers.
Preferably, in the step 1), the stirring reaction condition is 150-155 ℃ and the stirring reaction is continuously carried out for 2-2.5 h; the concentration of the solution A is 0.3 to 0.8mol.L -1 The method comprises the steps of carrying out a first treatment on the surface of the The organic solvent is benzene, toluene, ethylbenzene or xylene; by a means ofThe organic solvent: the mass ratio of the m-phenylenediamine is (4.0-4.5): 1.
Preferably, in step 1), the organosilane protecting agent is trimethylchlorosilane; the m-phenylenediamine: the molar ratio of the organosilane protective agent is 1: (2.2-2.6).
Preferably, in the step 1), the acid binding agent is triethylamine, diethylamine, diisopropylethylamine, tetramethyl ethylenediamine, pyridine or 4-dimethylaminopyridine; the acid binding agent comprises the following components: the molar ratio of the m-phenylenediamine is (3.0-3.5): 1.
Preferably, in step 2), the substance a: the molar ratio of isophthaloyl dichloride is 1: (1.01-1.05); the stirring speed is controlled to be 500-1000 rpm in the dissolution process; the temperature of the pre-polycondensation reaction is-25 to-10 ℃; the stirring speed is 2000-3000 rpm; the addition amount of the isophthaloyl dichloride is 60% -80% of the total amount of the isophthaloyl dichloride.
Preferably, in the step 2), the temperature of the cooled nitrogen is-7 to-2 ℃; the polar organic solvent is N-methyl pyrrolidone, N-dimethylacetamide, chloroform or carbon tetrachloride; the isophthaloyl dichloride is fed in a powder feeding mode or a molten state feeding mode.
Preferably, in the step 3), the addition amount of the isophthaloyl dichloride is 20% -40% of the total amount of the isophthaloyl dichloride; the logarithmic viscosity of the poly (m-phenylene isophthalamide) resin is 1.9-2.3 dL.g -1 。
Preferably, in step 4), the polar solvent is N, N-dimethylformamide, N-dimethylacetamide, dimethylsulfoxide or N-methylpyrrolidone; the concentration of the solution B is 16-20 wt.%; the cosolvent is one or more of calcium chloride and lithium chloride; the addition amount of the cosolvent is 3-5 wt.% of the polar solvent.
The invention also discloses meta-aramid fiber prepared by the preparation method.
The invention also discloses application of the meta-aramid fiber in preparing base materials for aerospace, high-speed rail locomotives, military fire protection, petrochemical industry and electronic communication.
Compared with the prior art, the invention has the following beneficial effects:
the invention discloses a molecular weight regulating and controlling method of meta-position aramid fiber, which adopts organosilane to implement an amino protection strategy on DMP, replaces active hydrogen atoms on amino, effectively avoids oxidation side reaction, and can also increase the solubility of protected monomers in solvents; effectively solves the problems that DMP monomer is easy to oxidize, affects the polycondensation process of low-temperature solution, and causes low molecular weight and poor fiber forming quality of final meta-aramid fiber. The DMP and IPC are polymerized after the protection of the amino, so that the generation of HCl in the low-temperature solution polycondensation process is avoided, the stability of a reaction system is greatly improved, the neutralization step after the reaction is omitted, and the problem that the byproduct HCl in the system is easy to cause chain termination in the traditional PMIA low-temperature solution polycondensation process, so that the molecular weight of the polymer is lower is effectively solved. By adopting the strategy of introducing the nitrogen circulating cooling device into the reaction system, nitrogen is controlled to be introduced into the polymerization system in a low-temperature state, and high-temperature nitrogen escaping from the system is collected, so that the gas is introduced into the reaction system again as a protective atmosphere after being rapidly cooled in the device, the recycling of the gas is realized, the nitrogen is ensured to be always subjected to reaction protection in a low-temperature state, the temperature of the polymerization reaction system is rapidly reduced, the severe release of reaction heat is avoided, and the problems that the reaction heat is higher in the polycondensation process of a low-temperature solution, side reaction is increased, and the viscosity of the reaction system and the molecular weight of a product are influenced are effectively solved.
The invention also discloses the meta-aramid fiber prepared by the method, and the monomer for preparing the meta-aramid fiber is well protected, and the reaction heat and byproducts in the polymerization process are well controlled, so that the meta-aramid fiber has the advantages of higher molecular weight, high fiber forming quality and good strength performance.
The invention also discloses application of the meta-aramid fiber in preparing basic materials for aerospace, high-speed rail locomotives, military fire protection, petrochemical industry and electronic communication, and the materials prepared from the meta-aramid fiber show higher strength, insulativity, flame retardance and heat resistance in the application fields.
Detailed Description
In order that those skilled in the art will better understand the present invention, a technical solution in the embodiments of the present invention will be clearly and completely described below, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, shall fall within the scope of the present invention.
It should be noted that the terms "first," "second," and the like in the description and in the claims are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that the embodiments of the invention described herein may be implemented in sequences other than those described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
The invention is described in further detail below with reference to examples:
the invention provides a method for regulating and controlling the molecular weight of meta-aramid fiber, which comprises the steps of taking m-phenylenediamine and isophthaloyl dichloride as raw materials, and preparing the meta-aramid fiber with higher molecular weight through the process steps of amino protection, pre-polycondensation, spinning and the like.
The molecular weight regulating and controlling method of meta-aramid fiber includes the following steps:
1) Amino protection: fully dissolving m-phenylenediamine with purity of more than 99% in a dry organic solvent, wherein the organic solvent is as follows: the mass ratio of the m-phenylenediamine is (4.0-4.5) 1; then adding an organosilane protective agent, wherein the m-phenylenediamine is as follows: the molar ratio of the organosilane protective agent is 1: (2.2-2.6); meanwhile, a certain proportion of acid binding agent is slowly added for timely removing byproduct hydrogen chloride, so that the reaction is complete, and the acid binding agent is: the molar ratio of the m-phenylenediamine is (3.0-3.5): 1; continuously stirring at 150-155 ℃ for 2-2.5 hours, collecting distillate by a distillation device, and drying to obtain a substance A protected by amino;
in step 1), the organic solvent comprises benzene, toluene, ethylbenzene, xylene or the like; the organosilane protecting agent is trimethylchlorosilane (TMSCl); the acid binding agent comprises triethylamine, diethylamine, diisopropylethylamine, tetramethyl ethylenediamine, pyridine or 4-dimethylaminopyridine;
2) Pre-polycondensation: preparing a substance A and isophthaloyl dichloride (IPC) prepared in step 1) according to a certain molar ratio, wherein the substance A: the molar ratio of isophthaloyl dichloride is 1: (1.01-1.05); fully dissolving the substance A prepared in the step 1) in a dry polar organic solvent with the water content less than or equal to 0.2% at room temperature to obtain a solution A with the concentration of 0.3-0.8 mol.L -1 In the range, the stirring speed needs to be controlled between 500 and 1000rpm in the dissolution process; then introducing dry nitrogen passing through a cooling device into the system to control the gas temperature to be between 7 ℃ below zero and 2 ℃ below zero, and simultaneously controlling the temperature of the reaction system to be between 25 ℃ below zero and 10 ℃ below zero through a cooling jacket of the reaction kettle; adding IPC with purity more than 99% under high-speed stirring to dissolve the IPC in a system, wherein the stirring speed is 200-3000 rpm, the adding amount of the IPC is 60-80% of the total amount of the IPC, and the adding mode is powder feeding or molten feeding; filtering to obtain prepolymer;
in the step 2), the polar organic solvent is N-methyl pyrrolidone (NMP), N-Dimethylacetamide (DMAC), chloroform or carbon tetrachloride;
3) Polycondensation: continuously carrying out polycondensation reaction on the residual 20% -40% of IPC and the prepolymer in the step 2) in a reactive double-screw extruder, fully mixing the prepolymer under the protection of dry and cooled nitrogen, wherein the temperature of a reaction system is the same as that in the step 2), and the temperature is still controlled within-5-0 ℃; after the reaction is finished, filtering, washing and drying a reaction product to obtain the poly (m-phenylene isophthalamide) resin, wherein the poly (m-phenylene isophthalamide)The logarithmic viscosity of the resin is 1.9-2.3 dL.g -1 The logarithmic viscosity measurement is carried out by adopting an Ubbelohde viscometer, taking concentrated sulfuric acid as a solvent, preparing 0.5g of solution per 100mL, and measuring at 30 ℃;
4) Spinning: firstly, preparing spinning solution, and dissolving the poly (m-phenylene isophthalamide) resin obtained in the step 3) in a polar solvent, wherein the concentration of the poly (m-phenylene isophthalamide) resin in the polar solvent is 16-20 wt.%, and simultaneously, a cosolvent is added into the system, and the addition amount of the cosolvent is 3-5 wt.% of the polar solvent; adopting a dry-wet spinning process, enabling the spinning solution to enter a first coagulating bath through a spinneret plate to obtain primary fibers, passing through a second coagulating bath after drafting, and then obtaining meta-aramid fibers through water washing, drying, dry-hot stretching, heat setting and winding;
in step 4), the polar solvent comprises N, N-dimethylformamide, N-dimethylacetamide, dimethylsulfoxide or N-methylpyrrolidone; the cosolvent is one or more of calcium chloride and lithium chloride.
Example 1
A molecular weight regulating and controlling method in meta-aramid fiber synthesis comprises the following steps:
1) Amino protection: 400.0kg of dry benzene is added into a 600L jacketed stainless steel reaction kettle, 96.0kg of high-purity m-phenylenediamine is added for full dissolution; 230.4kg of trimethylchlorosilane are then added, while 269.5kg of triethylamine are slowly added as acid-binding agent; continuously stirring at 150 ℃ for reaction for 2 hours, collecting distillate by a distillation device, drying to obtain a substance A protected by amino, and preserving under a drying condition;
2) Pre-polycondensation: dissolving 50.4kg of substance A prepared in step 1) in dry N, N-dimethylacetamide at room temperature and 800rpm to give a solution A with a concentration of 0.5 mol.L -1 The method comprises the steps of carrying out a first treatment on the surface of the Then dry nitrogen with the temperature of-2 ℃ is introduced into the system, and the temperature of the reaction system is controlled at-25 ℃ through a cooling jacket of the reaction kettle; 28.7kg of high-purity isophthaloyl dichloride powder is added under high-speed stirring at 3000rpm to dissolve the isophthaloyl dichloride powder in the system, and then the prepolymer is obtained by filtration;
3) Polycondensation: transferring 12.3kg of high-purity isophthaloyl dichloride powder and the prepolymer in the step 2) into a reactive double-screw extruder, introducing dry nitrogen at the temperature of-2 ℃ for protection, and controlling the temperature of the whole system at-25 ℃; after the reaction is finished, filtering, washing and drying to obtain the poly (m-phenylene isophthalamide) resin; the logarithmic viscosity of the polyisophthaloyl metaphenylene diamine resin was 2.0 dL.g -1 ；
4) Spinning: taking 1 part of the poly m-phenylene isophthalamide resin obtained in the step 3), dissolving in 5 parts of N-methylpyrrolidone, and simultaneously adding 0.25 part of lithium chloride into the system to obtain spinning solution; and (3) adopting a dry-wet spinning process, sequentially passing the prepared stock solution through a spinneret plate, a first coagulating bath, drafting, a second coagulating bath, water washing, drying, dry heat stretching, heat setting and winding to finally obtain the meta-aramid fiber product.
Example 2
A molecular weight regulating and controlling method in meta-aramid fiber synthesis comprises the following steps:
1) Amino protection: 400.0kg of dry benzene is added into a 600L jacketed stainless steel reaction kettle, 96.0kg of high-purity m-phenylenediamine is added for full dissolution; 230.4kg of trimethylchlorosilane were then added, while 345.1kg of diisopropylethylamine as acid-binding agent was slowly added; continuously stirring at 150 ℃ for reaction for 2 hours, collecting distillate by a distillation device, drying to obtain a substance A protected by amino, and preserving under a drying condition;
2) Pre-polycondensation: dissolving 50.4kg of substance A prepared in step 1) in dry N, N-dimethylacetamide at room temperature and 800rpm to give a solution A with a concentration of 0.5 mol.L -1 The method comprises the steps of carrying out a first treatment on the surface of the Then dry nitrogen with the temperature of-2 ℃ is introduced into the system, and the temperature of the reaction system is controlled at-10 ℃ through a cooling jacket of the reaction kettle; adding 25.5kg of high-purity isophthaloyl dichloride powder under high-speed stirring at 3000rpm to dissolve the isophthaloyl dichloride powder in a system, and filtering to obtain a prepolymer;
3) Polycondensation: 17.1kg of high-purity isophthaloyl dichloride powder and the prepolymer in the step 2) are transferred into a reactive twin-screw extruder, and dry nitrogen gas at the temperature of-2 ℃ is introducedProtecting, wherein the temperature of the whole system is controlled at-10 ℃; after the reaction is finished, filtering, washing and drying to obtain the poly (m-phenylene isophthalamide) resin; the logarithmic viscosity of the polyisophthaloyl metaphenylene diamine resin was 2.2 dL.g -1 ；
4) Spinning: taking 1 part of the poly m-phenylene isophthalamide resin obtained in the step 3), dissolving in 5 parts of N-methylpyrrolidone, and simultaneously adding 0.25 part of calcium chloride into the system to obtain spinning solution; and (3) adopting a dry-wet spinning process, sequentially passing the prepared stock solution through a spinneret plate, a first coagulating bath, drafting, a second coagulating bath, water washing, drying, dry heat stretching, heat setting and winding to finally obtain the meta-aramid fiber product.
Example 3
A molecular weight regulating and controlling method in meta-aramid fiber synthesis comprises the following steps:
1) Amino protection: 400.0kg of dry toluene is added into a 600L jacketed stainless steel reaction kettle, and 91.4kg of high-purity m-phenylenediamine is added for full dissolution; subsequently 220.4kg of trimethylchlorosilane was added, while 343.8kg of tetramethylethylenediamine was slowly added as acid binding agent; continuously stirring at 155 ℃ for 2.2 hours, collecting distillate by a distillation device, drying to obtain an amino-protected substance A, and preserving under a drying condition;
2) Pre-polycondensation: dissolving 50.4kg of substance A prepared in step 1) in dry N-methylpyrrolidone at room temperature and 800rpm to give a solution A with a concentration of 0.6mol.L -1 The method comprises the steps of carrying out a first treatment on the surface of the Then dry nitrogen with the temperature of minus 5 ℃ is introduced into the system, and the temperature of the reaction system is controlled at minus 25 ℃ through a cooling jacket of the reaction kettle; 32.8kg of high-purity isophthaloyl dichloride powder was added under high-speed stirring at 2500rpm to dissolve in the system, followed by filtration to obtain a prepolymer;
3) Polycondensation: transferring 8.2kg of high-purity isophthaloyl dichloride powder and the prepolymer in the step 2) into a reactive double-screw extruder, introducing dry nitrogen at the temperature of-5 ℃ for protection, and controlling the temperature of the whole system at-25 ℃; after the reaction is finished, filtering, washing and drying to obtain the poly (m-phenylene isophthalamide) resin; poly (m-phenylene isophthalamide)The logarithmic viscosity of the diamine resin was 2.3 dL.g -1 ；
4) Spinning: 1 part of the resin obtained in the step 3) is dissolved in 6 parts of N, N-dimethylformamide, and simultaneously 0.25 part of a mixture of lithium chloride and calcium chloride (the mass ratio is 1:1) is added into the system to obtain spinning solution; and (3) adopting a dry-wet spinning process, sequentially passing the prepared stock solution through a spinneret plate, a first coagulating bath, drafting, a second coagulating bath, water washing, drying, dry heat stretching, heat setting and winding to finally obtain the meta-aramid fiber product.
Example 4
A molecular weight regulating and controlling method in meta-aramid fiber synthesis comprises the following steps:
1) Amino protection: 400.0kg of dry ethylbenzene is added into a 600L jacketed stainless steel reaction kettle, and 100.0kg of high-purity m-phenylenediamine is added for full dissolution; 221.0kg of trimethylchlorosilane are then added, while 256.0kg of pyridine are slowly added as acid binding agent; reacting for 2.5 hours at 155 ℃ under continuous stirring, collecting distillate by a distillation device, drying to obtain a substance A protected by amino, and preserving under a drying condition;
2) Pre-polycondensation: dissolving 50.4kg of substance A prepared in step 1) in dry chloroform at room temperature and 500rpm to give a solution A with a concentration of 0.3 mol.L -1 The method comprises the steps of carrying out a first treatment on the surface of the Then dry nitrogen with the temperature of-5 ℃ is introduced into the system, and the temperature of the reaction system is controlled at-15 ℃ through a cooling jacket of the reaction kettle; 29.0kg of high-purity molten isophthaloyl dichloride is added under high-speed stirring at 2500rpm to dissolve the isophthaloyl dichloride in a system, and then the mixture is filtered to obtain a prepolymer;
3) Polycondensation: transferring 12.4kg of high-purity molten isophthaloyl dichloride and the prepolymer in the step 2) into a reactive double-screw extruder, introducing dry nitrogen at the temperature of-5 ℃ for protection, and controlling the temperature of the whole system at-15 ℃; after the reaction is finished, filtering, washing and drying to obtain the poly (m-phenylene isophthalamide) resin; the logarithmic viscosity of the polyisophthaloyl metaphenylene diamine resin was 1.9dL.g -1 ；
4) Spinning: 1 part of the resin obtained in the step 3) is dissolved in 6.25 parts of N, N-dimethylacetamide, and simultaneously 0.19 part of a mixture of lithium chloride and calcium chloride (the mass ratio is 1:1) is added into the system to obtain spinning stock solution; and (3) adopting a dry-wet spinning process, sequentially passing the prepared stock solution through a spinneret plate, a first coagulating bath, drafting, a second coagulating bath, water washing, drying, dry heat stretching, heat setting and winding to finally obtain the meta-aramid fiber product.
Example 5
A molecular weight regulating and controlling method in meta-aramid fiber synthesis comprises the following steps:
1) Amino protection: 400.0kg of dried dimethylbenzene is added into a 600L jacketed stainless steel reaction kettle, and 88.9kg of high-purity m-phenylenediamine is added for full dissolution; 232.2kg of trimethylchlorosilane are then added, while 321.4kg of 4-dimethylaminopyridine are slowly added as acid-binding agent; continuously stirring at 152 ℃ for 2.5 hours, collecting distillate by a distillation device, drying to obtain an amino-protected substance A, and preserving under a drying condition;
2) Pre-polycondensation: dissolving 50.4kg of substance A prepared in step 1) in dry N-methylpyrrolidone at room temperature and 1000rpm to give a solution A with a concentration of 0.8 mol.L -1 The method comprises the steps of carrying out a first treatment on the surface of the Then, dry nitrogen with the temperature of-7 ℃ is introduced into the system, and the temperature of the reaction system is controlled at-20 ℃ through a cooling jacket of the reaction kettle; adding 33.1kg of high-purity molten isophthaloyl dichloride under high-speed stirring at 2000rpm to dissolve the isophthaloyl dichloride in the system, and filtering to obtain a prepolymer;
3) Polycondensation: transferring 8.3kg of high-purity molten isophthaloyl dichloride and the prepolymer in the step 2) into a reactive double-screw extruder, introducing dry nitrogen at the temperature of-7 ℃ for protection, and controlling the temperature of the whole system at-20 ℃; after the reaction is finished, filtering, washing and drying to obtain the poly (m-phenylene isophthalamide) resin; the logarithmic viscosity of the polyisophthaloyl metaphenylene diamine resin was 2.1 dL.g -1 ；
4) Spinning: 1 part of the resin obtained in the step 3) is dissolved in 6.25 parts of dimethyl sulfoxide, and simultaneously 0.25 part of a mixture of lithium chloride and calcium chloride (the mass ratio is 1:1) is added into the system to obtain spinning solution; and (3) adopting a dry-wet spinning process, sequentially passing the prepared stock solution through a spinneret plate, a first coagulating bath, drafting, a second coagulating bath, water washing, drying, dry heat stretching, heat setting and winding to finally obtain the meta-aramid fiber product.
The above is only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited by this, and any modification made on the basis of the technical scheme according to the technical idea of the present invention falls within the protection scope of the claims of the present invention.
Claims (10)
1. The method for regulating and controlling the molecular weight of the meta-aramid fiber is characterized by comprising the following steps of:
1) Adding m-phenylenediamine into an organic solvent for full dissolution; adding an organosilane protective agent and an acid binding agent, stirring for reaction, distilling and collecting distillate, and drying to obtain a substance A;
2) Fully dissolving the substance A obtained in the step 1) in a polar organic solvent to obtain a solution A; introducing cooled nitrogen into the solution A, adding isophthaloyl dichloride under stirring, and filtering after the pre-polycondensation reaction is finished to obtain a prepolymer;
3) Adding isophthaloyl chloride into the prepolymer prepared in the step 2), and filtering, washing and drying after the polycondensation reaction is finished to obtain the poly-m-phenylene isophthalamide resin;
4) Dissolving the poly (m-phenylene isophthalamide) resin prepared in the step 3) in a polar solvent to obtain a solution B, and adding a cosolvent to obtain a spinning solution; and (3) adopting a dry-wet spinning process, passing the spinning solution through a spinneret plate, entering a first coagulating bath to obtain primary fibers, passing through a second coagulating bath after drafting, and then washing, drying, dry-hot stretching, heat setting and winding to obtain meta-aramid fibers.
2. The method for regulating and controlling the molecular weight of meta-aramid fiber according to claim 1, wherein in the step 1), the condition of the stirring reaction is 150-155 ℃ for continuous stirring reaction for 2-2.5 h; the concentration of the solution A is 0.3 to 0.8mol.L -1 The method comprises the steps of carrying out a first treatment on the surface of the The organic solvent is benzene, toluene, ethylbenzene or dimethylBenzene; the organic solvent: the mass ratio of the m-phenylenediamine is (4.0-4.5): 1.
3. The method for controlling the molecular weight of meta-aramid fiber according to claim 1, wherein in step 1), the organosilane protecting agent is trimethylchlorosilane; the m-phenylenediamine: the molar ratio of the organosilane protective agent is 1: (2.2-2.6).
4. The method for regulating and controlling the molecular weight of meta-aramid fiber according to claim 1, wherein in the step 1), the acid-binding agent is triethylamine, diethylamine, diisopropylethylamine, tetramethyl ethylenediamine, pyridine or 4-dimethylaminopyridine; the acid binding agent comprises the following components: the molar ratio of the m-phenylenediamine is (3.0-3.5): 1.
5. The method for controlling the molecular weight of meta-aramid fiber according to claim 1, wherein in step 2), the substance a: the molar ratio of isophthaloyl dichloride is 1: (1.01-1.05); the stirring speed is controlled to be 500-1000 rpm in the dissolution process; the temperature of the pre-polycondensation reaction is-25 to-10 ℃; the stirring speed is 2000-3000 rpm; the addition amount of the isophthaloyl dichloride is 60% -80% of the molar total amount of the isophthaloyl dichloride.
6. The method for regulating and controlling the molecular weight of meta-aramid fiber according to claim 1, wherein in the step 2), the temperature of the cooled nitrogen is-7 to-2 ℃; the polar organic solvent is N-methyl pyrrolidone, N-dimethylacetamide, chloroform or carbon tetrachloride; the isophthaloyl dichloride is fed in a powder feeding mode or a molten state feeding mode.
7. The method for regulating and controlling the molecular weight of meta-aramid fiber according to claim 1, wherein in the step 3), the addition amount of the isophthaloyl dichloride is 20% -40% of the molar total amount of the isophthaloyl dichloride; the logarithmic viscosity of the poly (m-phenylene isophthalamide) resin is 1.9-2.3 dL.g -1 。
8. The method for controlling the molecular weight of meta-aramid fiber according to claim 1, wherein in the step 4), the polar solvent is N, N-dimethylformamide, N-dimethylacetamide, dimethylsulfoxide or N-methylpyrrolidone; the concentration of the solution B is 16-20 wt.%; the cosolvent is one or more of calcium chloride and lithium chloride; the addition amount of the cosolvent is 3-5 wt.% of the polar solvent.
9. Meta-aramid fiber produced by the method of any one of claims 1 to 8.
10. Use of the meta-aramid fiber of claim 9 in the preparation of aerospace, high-speed rail locomotives, military fire protection, petrochemical and electronic communications base materials.
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