CN117248289A - Method for preparing polycaprolactam fibers by melt direct spinning - Google Patents
Method for preparing polycaprolactam fibers by melt direct spinning Download PDFInfo
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- CN117248289A CN117248289A CN202210657740.7A CN202210657740A CN117248289A CN 117248289 A CN117248289 A CN 117248289A CN 202210657740 A CN202210657740 A CN 202210657740A CN 117248289 A CN117248289 A CN 117248289A
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- 229920002292 Nylon 6 Polymers 0.000 title claims abstract description 128
- 238000000034 method Methods 0.000 title claims abstract description 47
- 239000000835 fiber Substances 0.000 title claims abstract description 32
- 238000010036 direct spinning Methods 0.000 title claims abstract description 14
- JBKVHLHDHHXQEQ-UHFFFAOYSA-N epsilon-caprolactam Chemical compound O=C1CCCCCN1 JBKVHLHDHHXQEQ-UHFFFAOYSA-N 0.000 claims abstract description 113
- 239000011552 falling film Substances 0.000 claims abstract description 113
- 238000006116 polymerization reaction Methods 0.000 claims abstract description 79
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 67
- 238000009987 spinning Methods 0.000 claims abstract description 46
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- WPYMKLBDIGXBTP-UHFFFAOYSA-N benzoic acid Chemical compound OC(=O)C1=CC=CC=C1 WPYMKLBDIGXBTP-UHFFFAOYSA-N 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- QQVIHTHCMHWDBS-UHFFFAOYSA-N isophthalic acid Chemical compound OC(=O)C1=CC=CC(C(O)=O)=C1 QQVIHTHCMHWDBS-UHFFFAOYSA-N 0.000 description 2
- 238000002074 melt spinning Methods 0.000 description 2
- 125000000896 monocarboxylic acid group Chemical group 0.000 description 2
- 239000000178 monomer Substances 0.000 description 2
- XNGIFLGASWRNHJ-UHFFFAOYSA-N phthalic acid Chemical compound OC(=O)C1=CC=CC=C1C(O)=O XNGIFLGASWRNHJ-UHFFFAOYSA-N 0.000 description 2
- 238000004064 recycling Methods 0.000 description 2
- YGSDEFSMJLZEOE-UHFFFAOYSA-N salicylic acid Chemical compound OC(=O)C1=CC=CC=C1O YGSDEFSMJLZEOE-UHFFFAOYSA-N 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
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- XBTRYWRVOBZSGM-UHFFFAOYSA-N (4-methylphenyl)methanediamine Chemical compound CC1=CC=C(C(N)N)C=C1 XBTRYWRVOBZSGM-UHFFFAOYSA-N 0.000 description 1
- GEYOCULIXLDCMW-UHFFFAOYSA-N 1,2-phenylenediamine Chemical compound NC1=CC=CC=C1N GEYOCULIXLDCMW-UHFFFAOYSA-N 0.000 description 1
- WZCQRUWWHSTZEM-UHFFFAOYSA-N 1,3-phenylenediamine Chemical compound NC1=CC=CC(N)=C1 WZCQRUWWHSTZEM-UHFFFAOYSA-N 0.000 description 1
- NZTGGRGGJFCKGG-UHFFFAOYSA-N 1,4-diamino-2,3-diphenoxyanthracene-9,10-dione Chemical compound C=1C=CC=CC=1OC1=C(N)C=2C(=O)C3=CC=CC=C3C(=O)C=2C(N)=C1OC1=CC=CC=C1 NZTGGRGGJFCKGG-UHFFFAOYSA-N 0.000 description 1
- CBCKQZAAMUWICA-UHFFFAOYSA-N 1,4-phenylenediamine Chemical compound NC1=CC=C(N)C=C1 CBCKQZAAMUWICA-UHFFFAOYSA-N 0.000 description 1
- LNETULKMXZVUST-UHFFFAOYSA-N 1-naphthoic acid Chemical compound C1=CC=C2C(C(=O)O)=CC=CC2=C1 LNETULKMXZVUST-UHFFFAOYSA-N 0.000 description 1
- VEORPZCZECFIRK-UHFFFAOYSA-N 3,3',5,5'-tetrabromobisphenol A Chemical compound C=1C(Br)=C(O)C(Br)=CC=1C(C)(C)C1=CC(Br)=C(O)C(Br)=C1 VEORPZCZECFIRK-UHFFFAOYSA-N 0.000 description 1
- CGLVZFOCZLHKOH-UHFFFAOYSA-N 8,18-dichloro-5,15-diethyl-5,15-dihydrodiindolo(3,2-b:3',2'-m)triphenodioxazine Chemical compound CCN1C2=CC=CC=C2C2=C1C=C1OC3=C(Cl)C4=NC(C=C5C6=CC=CC=C6N(C5=C5)CC)=C5OC4=C(Cl)C3=NC1=C2 CGLVZFOCZLHKOH-UHFFFAOYSA-N 0.000 description 1
- 239000004114 Ammonium polyphosphate Substances 0.000 description 1
- 239000005711 Benzoic acid Substances 0.000 description 1
- 229920006052 Chinlon® Polymers 0.000 description 1
- VRAHPESAMYMDQI-UHFFFAOYSA-N Nicomol Chemical compound C1CCC(COC(=O)C=2C=NC=CC=2)(COC(=O)C=2C=NC=CC=2)C(O)C1(COC(=O)C=1C=NC=CC=1)COC(=O)C1=CC=CN=C1 VRAHPESAMYMDQI-UHFFFAOYSA-N 0.000 description 1
- 229920002302 Nylon 6,6 Polymers 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- JKIJEFPNVSHHEI-UHFFFAOYSA-N Phenol, 2,4-bis(1,1-dimethylethyl)-, phosphite (3:1) Chemical compound CC(C)(C)C1=CC(C(C)(C)C)=CC=C1OP(OC=1C(=CC(=CC=1)C(C)(C)C)C(C)(C)C)OC1=CC=C(C(C)(C)C)C=C1C(C)(C)C JKIJEFPNVSHHEI-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- BGYHLZZASRKEJE-UHFFFAOYSA-N [3-[3-(3,5-ditert-butyl-4-hydroxyphenyl)propanoyloxy]-2,2-bis[3-(3,5-ditert-butyl-4-hydroxyphenyl)propanoyloxymethyl]propyl] 3-(3,5-ditert-butyl-4-hydroxyphenyl)propanoate Chemical compound CC(C)(C)C1=C(O)C(C(C)(C)C)=CC(CCC(=O)OCC(COC(=O)CCC=2C=C(C(O)=C(C=2)C(C)(C)C)C(C)(C)C)(COC(=O)CCC=2C=C(C(O)=C(C=2)C(C)(C)C)C(C)(C)C)COC(=O)CCC=2C=C(C(O)=C(C=2)C(C)(C)C)C(C)(C)C)=C1 BGYHLZZASRKEJE-UHFFFAOYSA-N 0.000 description 1
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- 235000019826 ammonium polyphosphate Nutrition 0.000 description 1
- 229920001276 ammonium polyphosphate Polymers 0.000 description 1
- 238000010539 anionic addition polymerization reaction Methods 0.000 description 1
- 125000000751 azo group Chemical group [*]N=N[*] 0.000 description 1
- QFFVPLLCYGOFPU-UHFFFAOYSA-N barium chromate Chemical compound [Ba+2].[O-][Cr]([O-])(=O)=O QFFVPLLCYGOFPU-UHFFFAOYSA-N 0.000 description 1
- 235000010233 benzoic acid Nutrition 0.000 description 1
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- XCJYREBRNVKWGJ-UHFFFAOYSA-N copper(II) phthalocyanine Chemical compound [Cu+2].C12=CC=CC=C2C(N=C2[N-]C(C3=CC=CC=C32)=N2)=NC1=NC([C]1C=CC=CC1=1)=NC=1N=C1[C]3C=CC=CC3=C2[N-]1 XCJYREBRNVKWGJ-UHFFFAOYSA-N 0.000 description 1
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- 125000004122 cyclic group Chemical group 0.000 description 1
- LYMBWJDBLCMHBO-UHFFFAOYSA-N cyclooctane;1,2,3,4,5,5-hexachlorocyclopenta-1,3-diene Chemical compound C1CCCCCCC1.ClC1=C(Cl)C(Cl)(Cl)C(Cl)=C1Cl.ClC1=C(Cl)C(Cl)(Cl)C(Cl)=C1Cl LYMBWJDBLCMHBO-UHFFFAOYSA-N 0.000 description 1
- WHHGLZMJPXIBIX-UHFFFAOYSA-N decabromodiphenyl ether Chemical compound BrC1=C(Br)C(Br)=C(Br)C(Br)=C1OC1=C(Br)C(Br)=C(Br)C(Br)=C1Br WHHGLZMJPXIBIX-UHFFFAOYSA-N 0.000 description 1
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- NAQMVNRVTILPCV-UHFFFAOYSA-N hexane-1,6-diamine Chemical class NCCCCCCN NAQMVNRVTILPCV-UHFFFAOYSA-N 0.000 description 1
- 230000008676 import Effects 0.000 description 1
- 235000019239 indanthrene blue RS Nutrition 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
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- 150000003951 lactams Chemical class 0.000 description 1
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- NTNWKDHZTDQSST-UHFFFAOYSA-N naphthalene-1,2-diamine Chemical compound C1=CC=CC2=C(N)C(N)=CC=C21 NTNWKDHZTDQSST-UHFFFAOYSA-N 0.000 description 1
- KYTZHLUVELPASH-UHFFFAOYSA-N naphthalene-1,2-dicarboxylic acid Chemical compound C1=CC=CC2=C(C(O)=O)C(C(=O)O)=CC=C21 KYTZHLUVELPASH-UHFFFAOYSA-N 0.000 description 1
- 150000007524 organic acids Chemical class 0.000 description 1
- FJKROLUGYXJWQN-UHFFFAOYSA-N papa-hydroxy-benzoic acid Natural products OC(=O)C1=CC=C(O)C=C1 FJKROLUGYXJWQN-UHFFFAOYSA-N 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- IEQIEDJGQAUEQZ-UHFFFAOYSA-N phthalocyanine Chemical compound N1C(N=C2C3=CC=CC=C3C(N=C3C4=CC=CC=C4C(=N4)N3)=N2)=C(C=CC=C2)C2=C1N=C1C2=CC=CC=C2C4=N1 IEQIEDJGQAUEQZ-UHFFFAOYSA-N 0.000 description 1
- 229920000768 polyamine Polymers 0.000 description 1
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- 229960004889 salicylic acid Drugs 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
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- 238000005728 strengthening Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 229920002994 synthetic fiber Polymers 0.000 description 1
- 239000012209 synthetic fiber Substances 0.000 description 1
- 230000008719 thickening Effects 0.000 description 1
- 239000004408 titanium dioxide Substances 0.000 description 1
- 239000001038 titanium pigment Substances 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- NFMWFGXCDDYTEG-UHFFFAOYSA-N trimagnesium;diborate Chemical compound [Mg+2].[Mg+2].[Mg+2].[O-]B([O-])[O-].[O-]B([O-])[O-] NFMWFGXCDDYTEG-UHFFFAOYSA-N 0.000 description 1
- XZZNDPSIHUTMOC-UHFFFAOYSA-N triphenyl phosphate Chemical compound C=1C=CC=CC=1OP(OC=1C=CC=CC=1)(=O)OC1=CC=CC=C1 XZZNDPSIHUTMOC-UHFFFAOYSA-N 0.000 description 1
- 238000004383 yellowing Methods 0.000 description 1
- 239000011787 zinc oxide Substances 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
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
- D01D5/00—Formation of filaments, threads, or the like
- D01D5/08—Melt spinning methods
Landscapes
- Engineering & Computer Science (AREA)
- Textile Engineering (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Mechanical Engineering (AREA)
- Polyamides (AREA)
- Polyesters Or Polycarbonates (AREA)
Abstract
The invention discloses a method for preparing polycaprolactam fibers by hydrolytic polymerization, melt adhesion and melt direct spinning, which comprises the steps of firstly, carrying out polymerization reaction on a mixture of caprolactam, water and a molecular weight regulator in a VK tube to prepare polycaprolactam base melt, carrying out melt polycondensation adhesion and devolatilization through an outside-tube falling film devolatilization reactor, and finally spinning the prepared high-viscosity melt. The invention innovatively designs the falling film devolatilization reactor outside the pipe, so that polycaprolactam melt can be subjected to controllable film forming flow, the heat and mass transfer efficiency is enhanced, and the melt tackifying and devolatilization are realized by coupling the polycondensation reaction dynamics and the molecular thermodynamic rules. The relative viscosity of the prepared polycaprolactam melt is 3.20-3.80, the content of hot water extractables is less than or equal to 1.5wt%, and the average breaking strength of the obtained fiber is more than or equal to 8.5cN/dtex. Compared with the slice spinning method, the method omits the production processes of hot water extraction, solid phase polycondensation, screw melting and the like, has the advantages of high efficiency, low energy consumption and the like, and has obvious advantages in the aspects of economy and environmental protection.
Description
Technical Field
The invention belongs to the technical field of synthetic fiber preparation, and relates to a method for preparing polycaprolactam fibers by hydrolytic polymerization, melt polycondensation and adhesion promotion and melt direct spinning.
Technical Field
The polycaprolactam fiber (chinlon 6) is widely applied to the industrial engineering fields of automobiles, buildings, earthwork, aerospace and the like due to the excellent physical and chemical properties of high strength, wear resistance, corrosion resistance, fatigue resistance and the like, and is an important basic raw material in national economy. In recent years, the production technology of domestic polycaprolactam fiber materials is continuously improved, especially the domestic self-supply rate of main raw materials is greatly improved, the import dependence is continuously reduced, the product cost is greatly reduced, and the application field of the polycaprolactam fiber materials is widened. Although polycaprolactam fibers are rapidly developed in recent years, slice spinning is still adopted in industrial production, and the problems of long process flow, high production energy consumption, large equipment investment and the like exist, so that development of efficient low-carbon preparation technology is urgently needed.
In order to obtain the industrial polycaprolactam fiber with excellent performance, the key point is to prepare high-quality and high-viscosity polycaprolactam melt. The polycaprolactam melt preparation process routes can be classified into hydrolysis polymerization, anion polymerization and solid phase polymerization according to polymerization mechanism. The hydrolysis polymerization of polycaprolactam takes water as an initiator, and raw material caprolactam is subjected to ring opening reaction, polyaddition and polycondensation reaction in a hydrolysis polymerization reactor to generate polycaprolactam, so that the reaction is controllable, the technology is mature, and the method is the most common method for preparing middle-low viscosity polycaprolactam materials in industry at present. However, when preparing high-viscosity polycaprolactam melt with relative viscosity up to 3.00 and above, the small molecular substances in the melt at the later stage of the polymerization reaction cannot be timely removed due to the structural limitation of the hydrolysis polymerization reactor, so that the polycondensation and viscosity increasing reaction is limited. At present, the industrial polycaprolactam fiber is prepared by a solid-phase tackifying-slice spinning method generally in industry, namely, a middle-low-viscosity polycaprolactam melt is prepared by a hydrolytic polymerization reactor, then the polycaprolactam melt is subjected to cold zone granulation, hot water extraction, drying and solid-phase tackifying, and finally the polycaprolactam fiber is prepared by melt spinning. Therefore, development of a novel polymerization method is urgently needed, heat and mass transfer efficiency of a high-viscosity system is enhanced, the requirement of polycondensation and tackifying reaction is met, and melt polycondensation is realized to directly prepare high-viscosity polycaprolactam melt.
Furthermore, polycaprolactam fibers have not been melt spun in large scale for technical reasons. The polycaprolactam fiber melt direct spinning has obvious advantages from the aspects of economy and environmental protection, and is an important direction for the preparation of polycaprolactam fiber materials to develop to low energy consumption and high efficiency. To achieve polycaprolactam fiber melt direct spinning, it is critical to prepare polycaprolactam melt that can be used for spinning. Polycaprolactam also solves the problems of vaporization extraction and condensation separation of high boiling point and multiphase substances in a high viscosity complex system to realize melt direct spinning. In the hydrolysis polymerization of polycaprolactam, the ring opening, polyaddition and polycondensation reactions of caprolactam are all reversible equilibrium reactions, and when the reaction reaches equilibrium, the conversion rate of caprolactam is generally about 90%, which means that about 10% of low molecular substances remain in the polymer melt (wherein caprolactam monomer accounts for about 85% and oligomer accounts for about 15%). Therefore, development of a novel polymerization device and a polymerization process method are urgently needed, the difficult problems of melt adhesion promotion of high-viscosity polycaprolactam melt and gas phase extraction of low-molecular substances are overcome, and small-molecular substances such as monomers, oligomers and the like are directly removed in the melt adhesion promotion process of polycaprolactam, so that the requirement of melt spinning is met.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a method for preparing polycaprolactam fibers by hydrolytic polymerization, melt polycondensation and melt direct spinning, which is characterized in that a falling film devolatilization reactor outside a pipe is designed to be matched with the rheological property of melt materials, so that polycaprolactam melt flows along the outer wall of the falling film pipe under the driving of gravity, and the polymerization reaction dynamics and the molecular thermodynamic movement law are coupled, the heat and mass transfer efficiency is enhanced, the requirements of the polycondensation and the adhesion reaction of a high-viscosity system are met, and meanwhile, the effective extraction of high-boiling-point multiphase complex components is completed, and the liquid-phase adhesion-melt direct spinning is realized to prepare the high-performance polycaprolactam fibers.
The technical scheme of the invention is as follows: a method for preparing polycaprolactam fibers by hydrolytic polymerization, melt polycondensation and melt direct spinning comprises the following steps:
(1) Mixing basic components caprolactam, water and a molecular weight regulator in proportion, preheating, continuously injecting into a hydrolysis polymerization reactor, carrying out caprolactam hydrolysis ring opening, addition and polycondensation reaction, and discharging to obtain polycaprolactam basic melt with the relative viscosity of 2.30-3.00;
(2) Conveying the polycaprolactam base melt prepared by hydrolytic polymerization to the upper part of a falling film devolatilization reactor outside a pipe, and performing falling film reaction outside the falling film pipe after being distributed by a film distributor; the outside-tube falling film devolatilization reactor is connected with a vacuum extraction system, so that the purpose of efficiently removing small molecular substances such as caprolactam, oligomers and the like in polymer melt is achieved; the lower part of the falling film devolatilization reactor outside the pipe is provided with a stirrer for uniform material, and then the polycaprolactam melt with the relative viscosity of 3.20-3.80 and the hot water extractables content of less than or equal to 1.5wt% is prepared by discharging;
(3) And conveying the polycaprolactam melt to a spinning box body by a pipeline for spinning to obtain the polycaprolactam fiber.
The method comprises the following specific processes: firstly, adding caprolactam, water and a molecular weight regulator serving as basic components into a batching kettle in proportion, heating and stirring, preheating uniformly mixed raw materials by a preheater, continuously injecting the raw materials into a hydrolysis polymerization reactor, and performing plug flow on the raw materials from top to bottom in the tubular reactor to generate caprolactam hydrolysis polymerization reaction; in the process, caprolactam is subjected to ring opening under the action of ring opening agent water to generate aminocaproic acid, the aminocaproic acid is subjected to addition reaction to open caprolactam, short-chain polymers are formed, and finally polycondensation reaction is carried out between the short-chain polymers to generate long-chain polymers; according to the hydrolysis polymerization mechanism of polycaprolactam, ring opening and addition reaction mainly occur at the upper section of the polymerizer, and polycondensation reaction mainly occurs at the lower end of the polymerizer; the ring-opening rate of caprolactam is improved by controlling the water ratio, the reaction temperature and the pressure of the ring-opening agent, and the base melt viscosity of polycaprolactam obtained by hydrolytic polymerization is cooperatively controlled by controlling the residence time of materials at the lower end of a polymerizer and a molecular weight regulator; finally, polycaprolactam base melt with relative viscosity of 2.30-3.00 is prepared.
The relative viscosity of the prepared polycaprolactam base melt is 2.30-3.00, and the content of hot water extractables is less than or equal to 12wt%.
Conveying polycaprolactam base melt obtained by hydrolytic polymerization to the upper part of a falling film devolatilization reactor outside a pipe by using a pipeline, distributing the melt material by using a film distributor, making the melt material into film flow along the outer wall surface of the falling film pipe under the driving of gravity, and simultaneously carrying out devolatilization and polycondensation reaction; regulating and controlling the falling film flow structure to ensure that polycaprolactam base melt always meets the combination of larger film forming area and faster surface update in the falling film process, strengthens the heat and mass transfer efficiency in the high-viscosity melt, and meets the requirements of polycondensation reaction and devolatilization; the polycaprolactam melt after tackifying and devolatilizing is uniformly stirred by a stirrer at the bottom of a devolatilization reactor, and then discharged to prepare the high-viscosity polycaprolactam melt capable of being directly processed.
The relative viscosity of the prepared polycaprolactam melt is 3.20-3.80, and the content of hot water extractables is less than or equal to 1.5wt%.
And conveying the high-viscosity polycaprolactam melt subjected to film-falling tackifying and devolatilization to different spinning positions by using a pipeline, and carrying out spinning forming after filtering to obtain the high-performance polycaprolactam fiber.
The average breaking strength of the obtained polycaprolactam fiber is more than or equal to 8.5cN/dtex, and the spinning stability is good.
On the basis of adopting the technical scheme, the invention can also adopt the following further technical scheme:
the hydrolysis polymerization reactor in the step (1) is a one-stage reactor, the reaction temperature is 240-275 ℃, the pressure is 0.05-0.3 MPa, and the reaction time is 15-30 hours.
The hydrolysis polymerization reactor in the step (1) is a two-stage reactor, the reaction temperature of the pre-polymerization reactor is 240-275 ℃, the pressure is 0.05-0.3 MPa, and the reaction time is 2-10 hours; the reaction temperature of the post-polymerizer is 240-260 ℃, the pressure is-0.1-0.2 MPa, and the reaction time is 8-20 hours.
The reaction temperature of the falling film devolatilization reactor outside the pipe in the step (2) is 250-285 ℃ and the vacuum degree is 20-400 Pa.
The falling film tube in the step (2) is a round tube, a corrugated tube or a special tube, the diameter or the diameter of the circumscribing circle is 5-100 mm, and the tube length is 5-20 m.
The spinning forming condition in the step (3) is that the spinning temperature is 250-295 ℃, and the spinning speed is 2500-5000 m/min.
In the step (1), the addition amount of the water is 0.5-5 wt% of caprolactam; the molecular weight regulator is one or a combination of more of organic monoacid, organic dibasic acid, monoamine and diamine, and the addition amount is 0-0.6wt% of caprolactam.
The organic acid is aliphatic H (CH) 2 ) n COOH, wherein n=1 to 10; or aromatic, benzoic acid or naphthoic acid.
The monoamine is aliphatic H (CH) 2 ) m NH 2 Wherein m=1 to 10; or aromatic, aniline.
The organic dibasic acid is aliphatic dibasic acid HOOC (CH) 2 ) X COOH, wherein x=1 to 20; or aromatic dibasic acid, which is terephthalic acid, phthalic acid, isophthalic acid or naphthalene dicarboxylic acid.
The polyamine is aliphatic diamine H 2 N(CH 2 ) X NH 2 Wherein x=1 to 10; or aromatic diamine, which is p-phenylenediamine, naphthalene diamine, m-phenylenediamine, o-phenylenediamine or xylene diamine.
In the step (1), besides the basic components, caprolactam and oligomer regrind obtained by vacuum extraction system pumping and condensing in the step (2) or regrind after depolymerization treatment can be added.
After condensing the extracted gas mixture, the obtained caprolactam and the oligomer can be used as the basic raw materials in the step (1) together for recycling, or the oligomer is depolymerized into caprolactam monomers and then used as the basic raw materials in the step (1) for recycling.
In the step (1), one or more of comonomer, catalyst, delustrant, antioxidant, anti-ultraviolet agent, colorant and flame retardant can be added according to the product requirement besides the basic component.
The comonomer is: one or more of aliphatic diamine, aliphatic diacid, aromatic diamine, aromatic diacid, hexamethylenediamine salt, linear amino acid, lactam, and lactone; the catalyst is NH 2 (CH 2 ) One or more of xCOOH and nylon 66 salt, wherein X is 2-8; the delustrant is titanium dioxide; the antioxidant is one or more of antioxidant 1010, antioxidant 168 or antioxidant 616; the anti-ultraviolet agent is one or more of salicylic acid, zinc oxide, calcium carbonate and SEED; the colorant is one or more of phthalocyanine blue, phthalocyanine green, macromolecular red, macromolecular yellow, permanent violet, permanent yellow, azo red, titanium pigment, carbon black, pigment red 179, pigment blue 60, pigment green 36, pigment yellow 214, pigment orange 43, pigment brown 41, solvent violet 59, solvent violet 37, solvent red 143, solvent red 181, solvent blue 94, solvent green 29 and solvent yellow 135; the flame retardant comprises the following components: one or more of tetrabromobisphenol A, zinc borate, magnesium borate, bis (hexachlorocyclopentadiene) cyclooctane, triphenyl phosphate, red phosphorus, organic phosphate, ammonium polyphosphate, zinc borate and decabromodiphenyl ether.
In the step (2), the external falling film devolatilization reactor comprises a vertical kettle body, a film distributor, a falling film pipe, a stirrer and a heating medium system, wherein the bottom of the external falling film devolatilization reactor is a cone, and the stirrer is arranged in the cone and used for uniformly feeding materials and cleaning the wall surface of the cone.
The polycaprolactam melt high temperature high vacuum falling film flow process involves complex endothermic and exothermic processes such as chemical reaction, material phase transition, etc., so that the whole and partial temperature of the film melt needs to be precisely controlled. The jacket type falling film kettle and the sleeve type falling film pipe structure are designed, so that a heating medium circulation mode is optimized, the heat of the melt at each stage of falling film devolatilization is supplemented or released, and the heat requirements of polycondensation reaction and devolatilization are met.
On the basis of fully knowing the polymerization process characteristics of polycaprolactam and the rheological characteristics of a polymer system, the invention uses the design thought of controlling the falling film speed and strengthening the dispersion and mixing of the melt according to the viscosity characteristics of the melt at different stages as a technical solution to improve the film forming efficiency, improve the surface updating frequency of the melt, control the residence time of the melt process and finally realize the liquid phase tackifying and the liquid phase extraction at the same time so as to obtain the directly processable high-viscosity polycaprolactam melt.
In the step (2), the vacuum extraction system comprises a condensation system and a vacuum system; the condensing system comprises one or more volatile component condensing towers connected in series or in parallel, a gas mixture composed of caprolactam, oligomers and other volatile matters extracted from melt is collected after condensation in the process of moving from bottom to top through an air inlet of the condensing tower, and the residual gas is discharged after condensation treatment; the vacuum system comprises a vacuum buffer tank and a vacuum pump; the vacuum pump comprises one or more of a rotary vane vacuum pump, a molecular vacuum pump, an ejector vacuum pump, a diffusion ejector pump, a water ring vacuum pump, a Roots vacuum pump, a screw vacuum pump and a reciprocating vacuum pump.
The complex components of high boiling and heterogeneous composition in polycaprolactam melts are particularly challenging to vapor extract and condense. Firstly, the falling film devolatilization reactor designed by the invention comprises a high-efficiency vacuum extraction system and a multi-stage condensation system, so that the high and stable vacuum degree of polycaprolactam melt in the falling film implementation process is ensured, and the aim of continuously removing a large amount of small molecular substances in the continuous falling film process is fulfilled. In addition, in the presence of low-boiling-point azeotropic substances such as water, caprolactam and the like, the oligomer in the melt is easy to vaporize, and the low-boiling-point substances in the melt are promoted to vaporize and nucleate by regulating and controlling a falling film flow field, so that the synergistic vaporization of the oligomer is enhanced.
Compared with the prior art, the invention has the beneficial effects that:
1. the invention adopts melt polycondensation to directly prepare high-viscosity polycaprolactam melt, prepares high-performance polycaprolactam fiber through melt direct spinning, omits the production processes of granulating, hot water extraction, drying, solid phase polycondensation, remelting and the like compared with the solid phase polycondensation-slice spinning process, has the characteristics of short flow, high efficiency, low energy consumption and the like, and has obvious advantages in the aspects of economy and environmental protection.
2. On the basis of fully researching and knowing the falling film flow characteristic, polymerization reaction characteristic, heat mass transfer characteristic and coupling mechanism of the high-viscosity polycaprolactam melt, the method innovatively designs the falling film devolatilization reactor outside the pipe, so that the high-viscosity polycaprolactam melt flows along the outer wall of the falling film pipe under the action of gravity, the combination of larger film forming area and faster surface updating is always realized in the falling film flow of melt materials from top to bottom, the heat mass transfer efficiency is enhanced, the polycondensation reaction dynamics and the molecular thermal kinematics law are coupled, the melt polycondensation and the adhesion of the high-viscosity polycaprolactam are realized, and meanwhile, the high-efficiency removal of small molecular substances such as caprolactam, oligomers and the like in the high-viscosity melt is completed.
3. The falling film devolatilization reactor designed by the method has high-efficiency devolatilization function, and complex components consisting of high boiling point and multiphase substances in polycaprolactam melt are extracted by gas phase and condensed and separated to the greatest extent. The invention solves the problem that the oligomer with extremely strong processing stability and continuity destructiveness is difficult to remove by using the following rules: in the presence of water, caprolactam and other low boiling point azeotropic substances, the falling film flow field is regulated to promote the low boiling point substances in the melt to be easily vaporized and nucleated, so as to promote the high boiling point oligomers in the melt to be co-vaporized.
Description of the drawings:
fig. 1 and fig. 2 are schematic diagrams of a production flow of polycaprolactam fibers prepared by melt direct spinning, wherein fig. 1 is a production flow of a one-stage VK tube polymerization superposition falling film devolatilization reaction, and fig. 2 is a production flow of a two-stage VK tube polymerization superposition falling film devolatilization reaction.
In fig. 1, 1 is a material meter, 2 is a mixer, 3 is a transfer pump, 4 is a preheater, 5 is a one-stage VK tube polymerization reactor, 6 and 10 are melt transfer pumps, 7 is a falling film devolatilization reactor, 8 is a condensing system, 9 is a vacuum system, 11 is a melt filter, 12 is a spinning box, 13 is a drawing device, and 14 is a winding device.
Wherein, falling film devolatilization reactor includes: 7-1 of a vertical kettle body of a falling film devolatilization reactor, 7-2 of a melt cavity, 7-3 of a film distributor, 7-4 of a falling film pipe, 7-5 of a melt material stirrer, 7-6 of a heat medium inlet and 7-7 of a heat medium outlet; 8-1, 8-2 and 8-3 are condensation systems which can be designed into one stage, two stages or multiple stages (three to six stages) according to production requirements, and high vacuum degree in the falling film devolatilization reactor is maintained.
In fig. 2, 1 is a material meter, 2 is a mixer, 3 is a transfer pump, 4 is a preheater, 5 is a first stage VK tube polymerization reactor, 6, 10 and 16 are melt transfer pumps, 15 is a second stage VK tube polymerization reactor, 7 is a falling film devolatilization reactor, 8 is a condensing system, 9 is a vacuum system, 11 is a melt filter, 12 is a spinning manifold, 13 is a drawing device, and 14 is a winding device.
Wherein 5 and 15 are combined into a two-section type VK tube polymerization reactor, wherein the second section of the VK tube polymerization reactor of 15-1 comprises a kettle body, a 15-2 heat exchanger, a 15-3 collecting tank, a 15-4 buffer tank and a 15-5 vacuum pump; the falling film devolatilization reactor comprises: 7-1 of a vertical kettle body of a falling film devolatilization reactor, 7-2 of a melt cavity, 7-3 of a film distributor, 7-4 of a falling film pipe, 7-5 of a melt material stirrer, 7-6 of a heat medium inlet and 7-7 of a heat medium outlet; 8-1, 8-2 and 8-3 are condensation systems which can be designed into one stage, two stages or multiple stages (three to six stages) according to production requirements, and high vacuum degree in the falling film devolatilization reactor is maintained.
The specific embodiment is as follows:
the invention provides a method for preparing polycaprolactam fibers by hydrolytic polymerization, melt polycondensation and melt direct spinning, which comprises the following steps:
(1) Mixing basic components caprolactam, water and a molecular weight regulator in proportion, preheating, continuously injecting into a hydrolysis polymerization reactor, carrying out caprolactam hydrolysis ring opening, addition and polycondensation reaction, and discharging to obtain polycaprolactam basic melt with the relative viscosity of 2.30-3.00;
(2) Conveying the polycaprolactam base melt prepared by hydrolytic polymerization to the upper part of a falling film devolatilization reactor outside a pipe, and performing falling film reaction outside the falling film pipe after being distributed by a film distributor; the outside-tube falling film devolatilization reactor is connected with a vacuum extraction system to efficiently remove small molecular substances such as caprolactam, oligomers and the like in the polycaprolactam melt; the lower part of the falling film devolatilization reactor outside the pipe is provided with a stirrer for uniform material, and then the polycaprolactam melt with the relative viscosity of 3.20-3.80 and the hot water extractables content of less than or equal to 1.5wt% is prepared by discharging;
(3) And conveying the polycaprolactam melt to a spinning box body by a pipeline for spinning to obtain the polycaprolactam fiber.
Preferably, in step (1): the addition amount of the water is 0.5-5 wt% of caprolactam; the molecular weight regulator is one or a combination of more of organic monoacid, organic dibasic acid, monoamine and diamine, and the addition amount is 0-0.6wt% of caprolactam; stirring at a rotating speed of 50-200 r/min for 10-60 min at the mixing temperature of 80-150 ℃; besides the basic components, one or more of a delustrant, an antioxidant, an anti-ultraviolet agent, a colorant, a flame retardant and a comonomer can be added according to the requirements of the product;
in the step (1), when the hydrolysis polymerization reactor is a one-stage reactor, the reaction temperature is 240-275 ℃, the pressure is 0.05-0.3 MPa, and the reaction time is 15-30 hours; when the hydrolysis polymerization reactor is a two-stage reactor, the reaction temperature of the pre-polymerization reactor is 240-275 ℃, the pressure is 0.05-0.3 MPa, the reaction time is 2-10 hours, the reaction temperature of the post-polymerization reactor is 240-260 ℃, the pressure is-0.1-0.2 MPa, and the reaction time is 8-20 hours.
The polycaprolactam base melt prepared in the step (1) has the relative viscosity of 2.30-3.00 and the hot water extractables content of less than or equal to 12wt%.
Preferably, in step (2): the reaction temperature of the falling film devolatilization reactor outside the pipe is 250-285 ℃ and the vacuum degree is 20-400 Pa;
the relative viscosity of the prepared polycaprolactam melt is 3.20-3.80, and the content of hot water extractables is less than or equal to 1.5wt%.
Preferably, in step (3): the spinning forming condition is that the temperature is 250-295 ℃ and the speed is 2500-5000 m/min.
The average breaking strength of the obtained polycaprolactam fiber is more than or equal to 8.5cN/dtex, and the spinning stability is good.
The properties of the product obtained by implementing the method are measured according to the following standard method: the relative viscosity of polycaprolactam melt and the hot water extractables content value are measured according to national standard GB/T38138-2019; the average breaking strength value of the polycaprolactam fiber is measured according to national standard GB/T14344-2008.
The method is realized by a device shown in the attached figure 1 or the attached figure 2, and the device mainly comprises a metering tank, a batching kettle, a one-section or two-section VK tube polymerization reactor, a falling film devolatilization reactor, a spinning device, a drafting device and a winding device.
The hydrolysis polymerization reactor is a one-stage type VK tube reactor or a two-stage type VK tube reactor which is mature in the industry at present; the viscosity of the basic melt, the composition of the oligomer and the content of the oligomer are regulated and controlled by controlling the caprolactam hydrolysis polymerization implementation process.
The external falling film devolatilization reactor comprises a vertical kettle body, a film distributor, a falling film pipe, a stirrer and a heating medium system; the jacket of the vertical kettle body is internally provided with a heating medium, so that the vertical kettle has a heat preservation function, and the film distributor and the film dropping pipe are internally provided with the heating medium, so that the temperature of a melt can be maintained stable; the falling film pipe is a circular pipe, a corrugated pipe or a special pipe, the diameter or the diameter of an external circle is 5-100 mm, the pipe length is 5-20 m, the shape and the size of the falling film pipe can be optimized to adapt to the rheological property of a hydrolysis polymerization discharging base melt, the falling film flow of the base melt is regulated and controlled to always realize the combination of a larger film forming area and a faster surface updating time, and the requirements of polycondensation reaction and micromolecule removal in a high-viscosity melt on heat and mass transfer are met; the stirrer can homogenize the high-viscosity materials after falling film devolatilization, and simultaneously continuously shear the high-viscosity materials on the inner wall surface of the bottom of the falling film kettle to prevent the materials from adhering to the wall and coking.
To accomplish the purposes of efficient devolatilization and polycondensation and adhesion promotion in high-viscosity melt, an external falling film devolatilizer must be designed with a high-efficiency vacuum extraction system to maintain high vacuum degree in the falling film process, so as to realize continuous extraction and timely condensation separation of a large amount of volatile matters in the melt; the high-efficiency vacuum extraction system comprises a condensation system and a vacuum system; the condensing system comprises one or more volatile component condensing towers which are connected in series or in parallel, and a gas mixture composed of extracted water, caprolactam, oligomers and other volatile matters in the melt is converted into liquid after sufficient heat exchange in the process of moving from bottom to top through an air inlet of the condensing tower and is collected; the vacuum system comprises a vacuum buffer tank and a vacuum pump; the vacuum pump comprises one or more of a rotary vane vacuum pump, a molecular vacuum pump, an ejector vacuum pump, a diffusion ejector pump, a water ring vacuum pump, a Roots vacuum pump, a screw vacuum pump and a reciprocating vacuum pump.
The following examples are given as preferred embodiments of the present invention and are not intended to limit the scope of the invention; in addition, after reading the content of the invention, the person skilled in the art makes various modifications, alterations and equivalent substitutions to the invention, and the invention still belongs to the protection scope of the technical scheme of the invention.
Example 1
The first step: mixing caprolactam, water and terephthalic acid in a mixing kettle according to a proportion, wherein the mixing temperature is 85 ℃, the stirring time is 60min, and filtering, preheating and conveying the mixture to a feed inlet of a hydrolysis polymerization reaction kettle after uniform mixing; wherein, the addition amount of water is 2wt% relative to caprolactam, and the addition amount of terephthalic acid is 0.2wt%; adopting a one-stage VK tube reactor, wherein the hydrolysis ring-opening reaction temperature is 253 ℃, the polymerization reaction temperature is 265 ℃, the reaction pressure is 0.2MPa, and the reaction time is 23 hours; the relative viscosity of the prepared polycaprolactam base melt is 2.45, and the hot water extractable content is less than or equal to 12wt%.
And a second step of: conveying the polycaprolactam base melt prepared in the first step to an out-pipe falling film devolatilization reactor for falling film adhesion and devolatilization, wherein the devolatilization temperature is 258 ℃, and the vacuum degree is 120Pa; the diameter of the circumscribed circle of the adopted falling film pipe is 80mm, and the length is 10m; the adopted condensation system is three-stage series connection; the polycaprolactam melt prepared had a relative viscosity of 3.47 and a hot water extractable content of 0.92 wt.%.
Example 2
The first step: mixing caprolactam, water and terephthalic acid in a mixing kettle according to a proportion, wherein the mixing temperature is 85 ℃, the stirring time is 60min, and filtering, preheating and conveying the mixture to a feed inlet of a hydrolysis polymerization reaction kettle after uniform mixing; wherein, the addition amount of water is 2wt% relative to caprolactam, and the addition amount of terephthalic acid is 0.2wt%; adopting a one-stage VK tube reactor, wherein the hydrolysis ring-opening reaction temperature is 253 ℃, the polymerization reaction temperature is 265 ℃, the reaction pressure is 0.2MPa, and the reaction time is 23 hours; the relative viscosity of the prepared polycaprolactam base melt is 2.45, and the hot water extractable content is less than or equal to 12wt%.
And a second step of: conveying the polycaprolactam base melt prepared in the first step to an out-pipe falling film devolatilization reactor for falling film adhesion and devolatilization, wherein the devolatilization temperature is 258 ℃, and the vacuum degree is 120Pa; the diameter of the circumscribed circle of the adopted falling film pipe is 60mm, and the length is 8m; the adopted condensation system is three-stage series connection; the polycaprolactam melt prepared had a relative viscosity of 3.43 and a hot water extractable content of 1.15 wt.%.
Comparative example 1
The first step: mixing caprolactam, water and terephthalic acid in a mixing kettle according to a proportion, wherein the mixing temperature is 85 ℃, the stirring time is 60min, and filtering, preheating and conveying the mixture to a feed inlet of a hydrolysis polymerization reaction kettle after uniform mixing; wherein, the addition amount of water is 2wt% relative to caprolactam, and the addition amount of terephthalic acid is 0.2wt%; adopting a one-stage VK tube reactor, wherein the hydrolysis ring-opening reaction temperature is 253 ℃, the polymerization reaction temperature is 265 ℃, the reaction pressure is 0.2MPa, and the reaction time is 23 hours; the relative viscosity of the prepared polycaprolactam base melt is 2.45, and the hot water extractable content is less than or equal to 12wt%.
And a second step of: conveying the polycaprolactam base melt prepared in the first step to an out-pipe falling film devolatilization reactor for falling film adhesion and devolatilization, wherein the devolatilization temperature is 258 ℃, and the vacuum degree is 120Pa; the diameter of the circumscribed circle of the adopted falling film tube is 80mm, and the length is 4m; the adopted condensation system is three-stage series connection; the polycaprolactam melt prepared has a relative viscosity of 2.95 and a hot water extractable content of 1.95 wt.%.
Comparing the experimental results of examples 1 and 2 with the experimental result of comparative example 1, the technology of the invention has the advantages that the effective film forming area of the polycaprolactam melt in the film falling process is large, the flow form is controllable, the material retention time in the film falling process meets the plug flow, and the thickening and efficient devolatilization of the polycaprolactam melt can be realized; when the length of the falling film pipe is less than 5m, the average residence time of polycaprolactam melt materials in the falling film reactor is short, the total heat and mass transfer amount in the process is low, and the tackifying and devolatilizing effects are poor.
Example 3
The first step: mixing caprolactam, water and terephthalic acid in a mixing kettle according to a proportion, wherein the mixing temperature is 85 ℃, the stirring time is 60min, and filtering, preheating and conveying the mixture to a feed inlet of a hydrolysis polymerization reaction kettle after uniform mixing; wherein, the addition amount of water is 2wt% relative to caprolactam, and the addition amount of terephthalic acid is 0.2wt%; adopting a one-stage VK tube reactor, wherein the hydrolysis ring-opening reaction temperature is 268 ℃, the polymerization reaction temperature is 265 ℃, the reaction pressure is 0.2MPa, and the reaction time is 18 hours; the relative viscosity of the prepared polycaprolactam base melt is 2.45, and the hot water extractable content is less than or equal to 12wt%.
And a second step of: conveying the polycaprolactam base melt prepared in the first step to an out-pipe falling film devolatilization reactor for falling film adhesion and devolatilization, wherein the devolatilization temperature is 258 ℃, and the vacuum degree is 120Pa; the diameter of the circumscribed circle of the adopted falling film pipe is 80mm, and the length is 10m; the adopted condensation system is three-stage series connection; the polycaprolactam melt prepared had a relative viscosity of 3.40 and a hot water extractable content of 1.49 wt.%.
Example 4
The first step: mixing caprolactam, water and terephthalic acid in a mixing kettle according to a proportion, wherein the mixing temperature is 85 ℃, the stirring time is 60min, and filtering, preheating and conveying the mixture to a feed inlet of a hydrolysis polymerization reaction kettle after uniform mixing; wherein, the addition amount of water is 2wt% relative to caprolactam, and the addition amount of terephthalic acid is 0.1wt%; adopting a two-stage type VK tube hydrolysis polymerization reaction device, wherein the hydrolysis ring-opening reaction temperature of a pre-polymerizer is 253 ℃, the polymerization temperature is 265 ℃, the reaction pressure is 0.2MPa, and the reaction time is 9 hours; the reaction temperature of the post-polymerizer is 260 ℃, the reaction pressure is 0MPa, and the reaction time is 10 hours; the relative viscosity of the prepared polycaprolactam base melt is 2.74, and the hot water extractable content is less than or equal to 12wt%.
And a second step of: conveying the polycaprolactam base melt prepared in the first step to an out-pipe falling film devolatilization reactor for falling film adhesion and devolatilization, wherein the devolatilization temperature is 258 ℃, and the vacuum degree is 120Pa; the diameter of the circumscribed circle of the adopted falling film pipe is 80mm, and the length is 10m; the adopted condensation system is three-stage series connection; the polycaprolactam melt prepared had a relative viscosity of 3.69 and a hot water extractable content of 1.23 wt.%.
Example 5
The first step: mixing caprolactam, water and terephthalic acid in a mixing kettle according to a proportion, wherein the mixing temperature is 85 ℃, the stirring time is 60min, and filtering, preheating and conveying the mixture to a feed inlet of a hydrolysis polymerization reaction kettle after uniform mixing; wherein, the addition amount of water is 2wt% relative to caprolactam, and the addition amount of terephthalic acid is 0wt%; adopting a two-stage type VK tube hydrolysis polymerization reaction device, wherein the hydrolysis ring-opening reaction temperature of a pre-polymerizer is 253 ℃, the polymerization reaction temperature is 265 ℃, the reaction pressure is 0.2MPa, and the reaction time is 8 hours; the reaction temperature of the post-polymerizer is 260 ℃, the reaction pressure is 0MPa, and the reaction time is 10 hours; the relative viscosity of the prepared polycaprolactam base melt is 2.93, and the hot water extractable content is less than or equal to 12wt%.
And a second step of: conveying the polycaprolactam base melt prepared in the first step to an out-pipe falling film devolatilization reactor for falling film adhesion and devolatilization, wherein the devolatilization temperature is 258 ℃, and the vacuum degree is 120Pa; the diameter of the circumscribed circle of the adopted falling film pipe is 80mm, and the length is 10m; the adopted condensation system is three-stage series connection; the polycaprolactam melt prepared had a relative viscosity of 3.86 and a hot water extractable content of 1.34 wt.%.
Comparative example 2
The first step: mixing caprolactam, water and terephthalic acid in a mixing kettle according to a proportion, wherein the mixing temperature is 85 ℃, the stirring time is 60min, and filtering, preheating and conveying the mixture to a feed inlet of a hydrolysis polymerization reaction kettle after uniform mixing; wherein, the addition amount of water is 2wt% relative to caprolactam, and the addition amount of terephthalic acid is 0.8wt%; adopting a two-stage type VK tube hydrolysis polymerization reaction device, wherein the hydrolysis ring-opening reaction temperature of a pre-polymerizer is 253 ℃, the polymerization reaction temperature is 265 ℃, the reaction pressure is 0.2MPa, and the reaction time is 9 hours; the reaction temperature of the post-polymerizer is 260 ℃, the reaction pressure is 0MPa, and the reaction time is 10 hours; the relative viscosity of the prepared polycaprolactam base melt is 2.10, and the hot water extractable content is less than or equal to 12wt%.
And a second step of: conveying the polycaprolactam base melt prepared in the first step to an out-pipe falling film devolatilization reactor for falling film adhesion and devolatilization, wherein the devolatilization temperature is 258 ℃, and the vacuum degree is 120Pa; the diameter of the circumscribed circle of the adopted falling film pipe is 80mm, and the length is 10m; the adopted condensation system is three-stage series connection; the polycaprolactam melt prepared had a relative viscosity of 2.46 and a hot water extractable content of 1.75 wt.%.
Comparing the experimental results of examples 1, 3-5 and comparative example 2, it is known that when the molecular weight regulator terephthalic acid addition is greater than 0.8wt%, the melt polycondensation reaction is inhibited significantly, the viscosity increasing amplitude of the falling film is reduced significantly, and the content of linear oligomer in the basic melt is increased so that the hot water extractable content in the melt is also increased after the falling film devolatilization; when the hydrolysis polymerization temperature in the VK pipe is higher, caprolactam is easy to cyclize into cyclic oligomers, so that the content and the composition of the oligomers in the polycaprolactam base melt are increased, and the falling film devolatilization effect is further affected. The quality of the polycaprolactam base melt obviously influences the viscosity-increasing and devolatilizing effects of the falling film, and the hydrolytic polymerization process of caprolactam in a VK pipe needs to be optimized, so that the obtaining of the base melt favorable for the viscosity-increasing and devolatilizing of the falling film is important.
Example 6
The first step: mixing caprolactam, water and terephthalic acid in a mixing kettle according to a proportion, wherein the mixing temperature is 85 ℃, the stirring time is 60min, and filtering, preheating and conveying the mixture to a feed inlet of a hydrolysis polymerization reaction kettle after uniform mixing; wherein, the addition amount of water is 2wt% relative to caprolactam, and the addition amount of terephthalic acid is 0.2wt%; adopting a one-stage VK tube reactor, wherein the hydrolysis ring-opening reaction temperature is 253 ℃, the polymerization reaction temperature is 265 ℃, the reaction pressure is 0.2MPa, and the reaction time is 23 hours; the relative viscosity of the prepared polycaprolactam base melt is 2.45, and the hot water extractable content is less than or equal to 12wt%.
And a second step of: conveying the polycaprolactam base melt prepared in the first step to an out-pipe falling film devolatilization reactor for falling film adhesion and devolatilization, wherein the devolatilization temperature is 285 ℃ and the vacuum degree is 120Pa; the diameter of the circumscribed circle of the adopted falling film pipe is 80mm, and the length is 10m; the adopted condensation system is three-stage series connection; the polycaprolactam melt prepared had a relative viscosity of 3.39 and a hot water extractable content of 1.18 wt.%.
Example 7
The first step: mixing caprolactam, water and terephthalic acid in a mixing kettle according to a proportion, wherein the mixing temperature is 85 ℃, the stirring time is 60min, and filtering, preheating and conveying the mixture to a feed inlet of a hydrolysis polymerization reaction kettle after uniform mixing; wherein, the addition amount of water is 2wt% relative to caprolactam, and the addition amount of terephthalic acid is 0.2wt%; adopting a one-stage VK tube reactor, wherein the hydrolysis ring-opening reaction temperature is 253 ℃, the polymerization reaction temperature is 265 ℃, the reaction pressure is 0.2MPa, and the reaction time is 23 hours; the relative viscosity of the prepared polycaprolactam base melt is 2.45, and the hot water extractable content is less than or equal to 12wt%.
And a second step of: conveying the polycaprolactam base melt prepared in the first step to an out-pipe falling film devolatilization reactor for falling film adhesion and devolatilization, wherein the devolatilization temperature is 258 ℃, and the vacuum degree is 50Pa; the diameter of the circumscribed circle of the adopted falling film pipe is 80mm, and the length is 10m; the adopted condensation system is four stages connected in series; the polycaprolactam melt prepared had a relative viscosity of 3.58 and a hot water extractable content of 0.81wt%.
Comparative example 3
The first step: mixing caprolactam, water and terephthalic acid in a mixing kettle according to a proportion, wherein the mixing temperature is 85 ℃, the stirring time is 60min, and filtering, preheating and conveying the mixture to a feed inlet of a hydrolysis polymerization reaction kettle after uniform mixing; wherein, the addition amount of water is 2wt% relative to caprolactam, and the addition amount of terephthalic acid is 0.2wt%; adopting a one-stage VK tube reactor, wherein the hydrolysis ring-opening reaction temperature is 253 ℃, the polymerization reaction temperature is 265 ℃, the reaction pressure is 0.2MPa, and the reaction time is 23 hours; the relative viscosity of the prepared polycaprolactam base melt is 2.45, and the hot water extractable content is less than or equal to 12wt%.
And a second step of: conveying the polycaprolactam base melt prepared in the first step to an out-pipe falling film devolatilization reactor for falling film adhesion and devolatilization, wherein the devolatilization temperature is 245 ℃ and the vacuum degree is 600Pa; the diameter of the circumscribed circle of the adopted falling film pipe is 80mm, and the length is 10m; the adopted condensation system is two-stage series connection; the polycaprolactam melt prepared had a relative viscosity of 2.71 and a hot water extractable content of 2.54wt%.
As is clear from the comparison of the experimental results of examples 1, 6 and 7 with comparative examples 2 and 3, when the falling film devolatilization temperature is low, the melt film forming fluidity becomes poor and vaporization of volatile matters is unfavorable, so that the devolatilization effect is poor; conversely, when the temperature is too high, side reactions such as thermal degradation, branching and the like are easy to cause, and when serious, the melt yellowing is caused, so that the quality of the melt after the falling film devolatilization and the subsequent spinning forming are obviously affected. In addition, the high vacuum degree is beneficial to the devolatilization and adhesion enhancement effects of the falling film, but the difficulty of implementing the high vacuum degree is considered, so that the proper vacuum degree range is important. It is noted that in the previous VK tube polymerization process, the implementation conditions such as the content of the molecular weight additive and the reaction temperature determine the quality of the basic melt, so as to influence the viscosity increasing and devolatilizing effects of the falling film. Therefore, the high-efficiency devolatilization and adhesion promotion of the high-viscosity polycaprolactam melt can be realized only by effectively coupling the properties of the falling film flow field, the implementation process conditions and the material properties of the basic melt.
Example 8
Conveying the high-viscosity polycaprolactam melt prepared in the example 5 to a spinning box body by using a pipeline for spinning, wherein the spinning temperature is 280 ℃, and the spinning speed is 3500m/min; the prepared polycaprolactam fiber has the linear density of 1400dtex, the average breaking strength of 9.52cN/dtex and better spinning condition.
Example 9
Conveying the high-viscosity polycaprolactam melt prepared in the embodiment 1 to a spinning box body by using a pipeline for spinning, wherein the spinning temperature is 280 ℃, and the spinning speed is 3500m/min; the prepared polycaprolactam fiber has the linear density of 1400dtex, the average breaking strength of 8.84cN/dtex and better spinning condition.
Comparative example 4
Conveying the high-viscosity polycaprolactam melt prepared in the comparative example 1 to a spinning box body by using a pipeline for spinning, wherein the spinning temperature is 280 ℃, and the spinning speed is 3500m/min; the polycaprolactam fiber prepared has a linear density of 1400dtex, an average breaking strength of 6.25cN/dtex and poor spinning condition.
As can be seen from the comparison of the experimental results of examples 8 and 9 and comparative example 4, the high-performance polycaprolactam fiber with the average breaking strength of more than or equal to 8.5cN/dtex can be obtained by spinning the high-viscosity polycaprolactam melt after the film is reduced and the viscosity is increased, and the spinning stability is better; when the total removal amount of small molecular substances in the high-viscosity polycaprolactam melt is insufficient, high-strength fibers still cannot be obtained after the spinning process is optimized, and the spinning stability is poor.
Claims (10)
1. A method for preparing polycaprolactam fibers by hydrolytic polymerization, melt polycondensation and melt direct spinning is characterized by comprising the following steps:
(1) Mixing basic components caprolactam, water and a molecular weight regulator in proportion, preheating, continuously injecting into a hydrolysis polymerization reactor, carrying out caprolactam hydrolysis ring opening, addition and polycondensation reaction, and discharging to obtain polycaprolactam basic melt with the relative viscosity of 2.30-3.0;
(2) Conveying the polycaprolactam base melt prepared by hydrolytic polymerization to the upper part of a falling film devolatilization reactor outside a pipe, and performing falling film reaction outside the falling film pipe after being distributed by a film distributor; the outside-tube falling film devolatilization reactor is connected with a vacuum extraction system to efficiently remove caprolactam and oligomers in the polymer melt; the lower part of the falling film devolatilization reactor outside the pipe is provided with a stirrer for uniform material, and then the polycaprolactam melt with the relative viscosity of 3.20-3.80 and the hot water extractables content of less than or equal to 1.5wt% is prepared by discharging;
(3) And conveying the polycaprolactam melt to a spinning box body by a pipeline for spinning to obtain the polycaprolactam fiber.
2. The method of claim 1, wherein: the hydrolysis polymerization reactor in the step (1) is a one-stage reactor, the reaction temperature is 240-275 ℃, the pressure is 0.05-0.3 MPa, and the reaction time is 15-30 hours.
3. The method of claim 1, wherein: the hydrolysis ring-opening polymerization reactor in the step (1) is a two-stage reactor, the reaction temperature of the pre-polymerization reactor is 240-275 ℃, the pressure is 0.05-0.3 MPa, and the reaction time is 2-10 hours; the reaction temperature of the post-polymerizer is 240-265 ℃, the pressure is-0.1-0.2 MPa, and the reaction time is 8-20 hours.
4. The method of claim 1, wherein: the reaction temperature of the falling film devolatilization reactor outside the pipe in the step (2) is 250-285 ℃ and the vacuum degree is 20-400 Pa.
5. The method of claim 1, wherein: the falling film tube in the step (2) is a round tube, a corrugated tube or a special tube, the diameter or the diameter of the circumscribing circle is 5-120 mm, and the tube length is 5-20 m.
6. The method of claim 1, wherein: the spinning forming condition in the step (3) is that the spinning temperature is 250-295 ℃, and the spinning speed is 2500-5000 m/min.
7. The method of claim 1, wherein: in the step (1), the addition amount of the water is 0.5-5 wt% of caprolactam; the molecular weight regulator is one or a combination of more of organic monoacid, organic dibasic acid, monoamine and diamine, and the addition amount is 0-0.6wt% of caprolactam.
8. The method of claim 1, wherein: in the step (1), besides the basic components, caprolactam and oligomer regrind obtained by vacuum extraction system pumping and condensing in the step (2) or regrind after depolymerization treatment can be added.
9. The method of claim 1, wherein: in the step (1), one or more of comonomer, catalyst, delustrant, antioxidant, anti-ultraviolet agent, colorant and flame retardant can be added according to the product requirement besides the basic component.
10. The method of claim 1, wherein: in the step (2), the external falling film devolatilization reactor comprises a vertical kettle body, a film distributor, a falling film pipe, a stirrer and a heating medium system, wherein the bottom of the external falling film devolatilization reactor is a cone, and the stirrer is arranged in the cone and is used for uniformly feeding materials and cleaning the wall surface of the cone; in the step (2), the vacuum extraction system comprises a condensation system and a vacuum system; the condensing system comprises one or more volatile component condensing towers which are connected in series or in parallel; the vacuum system comprises a vacuum buffer tank and a vacuum pump; the vacuum pump comprises one or more of a rotary vane vacuum pump, a molecular vacuum pump, an ejector vacuum pump, a diffusion ejector pump, a water ring vacuum pump, a Roots vacuum pump, a screw vacuum pump and a reciprocating vacuum pump.
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