CN111534882A - A kind of preparation method of functionalized multi-wall carbon nanotube reinforced polyester fiber - Google Patents

Abstract

The invention discloses a preparation method of FMWNT reinforced polyester fiber. into composite pellets; pre-crystallize and dry the compound pellets at 160-180°C; S2, melt-spin the pellets to make molten filaments; S3, melt the filaments at 20-90°C, 50-80% The air with relative humidity and wind speed of 10-20m/min is cooled and then wound into a tube to obtain polyester/MWNT fibers; S4, polyester/MWNT fibers are stored at 25°C and relative humidity of 65% for 20-28h; S5, The polyester/MWNT fiber enters the ethylene glycol, 1,3-propylene glycol or 1,2-propylene glycol bath at 80～140℃ for the first drawing, and the second drawing is performed on the hot roller at 180～200℃, The third drawing is carried out on a hot roll at 200-230°C, and then it is wound into a cylinder after setting, air blowing and cooling, removing surface residues and air blowing and drying. The polyester fiber prepared by the method has good physical and mechanical properties, low price and easy industrialization.

Description

A kind of preparation method of functionalized multi-wall carbon nanotube reinforced polyester fiber

technical field

The invention relates to the field of high-performance fiber preparation, in particular to a preparation method of a functionalized multi-wall carbon nanotube reinforced polyester fiber.

Background technique

High-performance fibers, especially fibers with excellent physical and mechanical properties, are necessary materials for national defense, sports, and industrial equipment. Polyethylene terephthalate (PET), polytrimethylene terephthalate (PPT) and polyethylene naphthalate (PEN) are common raw materials for the preparation of industrial yarns, which are prepared by conventional polycondensation reactions. After further solid phase viscosifying or liquid phase viscosifying polyester, high molecular weight polyester can be obtained. Indirect or direct melt spinning can prepare high-strength industrial yarn, which can be used in liquid conveying hoses, tire cords, ropes, wires, etc. Cable jackets, conveyor belts and inflatable tents have a wide range of applications. "Industrial & Engineering Chemistry Research, 2015 Vol. 54, p. 9150" discloses the research results of PET industrial yarn, and the tensile breaking strength reaches 8.29cN/dtex. Although the strength of industrial yarn is twice that of conventional fibers, and the preparation process requires the use of high-molecular-weight polyesters, the physical and mechanical properties still cannot meet the requirements for use in special places. Continuing to increase the spinning temperature is likely to cause the polymer molecular chain to break, and to continue to increase the molecular weight is likely to cause the molecular chain entanglement density to increase, making it impossible to carry out high-rate drafting. Ultra-high-strength fibers that have been developed at present, or rigid molecular chain structures formed by conjugated double bonds, such as poly(p-phenylene terephthalamide), poly(2-hydroxy-6-naphthoic acid-p-hydroxybenzoic acid) ) copolymer, poly[2,5-dihydroxy-1,4-phenylene pyridodiimidazole], etc., or with ultra-high molecular weight, such as ultra-high molecular weight polyethylene fiber (UHMWPE). The intermolecular force in the polymer with the rigid molecular chain structure of conjugated double bonds is very large, and it is difficult to be drawn. Molecular Structure.

Polyester is an inexpensive and widely available polymer material, and various attempts to improve the strength of polyester fibers have been carried out in the industry. Masato Masada et al. (Fiber Industry (SEN'I GAKKAISHI, Vol. 60, No. 11, p. 338, 2004)) announced a technology for preparing ultra-high-strength PET fibers supplemented by carbon dioxide laser heating in the polyester spinning process, specifically The surface of the melt stream extruded from a single spinneret hole with a diameter of 1.0mm is irradiated with a laser, and the laser intensity is 0-240W/cm ² , which can increase the melt temperature by about 70°C, so that the melt stream can be well drawn. It stretches and forms polyester fibers with high orientation and high crystallinity, and its tensile breaking strength can reach 10cN/dtex. High-intensity laser irradiation reduces the molecular weight of PET, which cannot further improve the breaking strength of fibers. M. Masuda et al. (International Polymer Processing (International Polymer Processing, 2010 XXV Vol. 2, p. 159)) reported the use of spinneret holes with a diameter of 0.3 mm supplemented by laser heating to prepare ultra-high-strength polyester fibers. The tensile strength at break reaches 12.1cN/dtex, the Young's modulus is 1.68GPa, and the elongation at break is 9.1%.

Multi-walled carbon nanotubes (MWNTs) are one-dimensional carbon nanomaterials formed by the curling of multi-layer graphite sheets (six ^- membered rings) composed of sp hybridized carbon atoms. 950GPa, thermal conductivity of 2000-6000W/(mK), is a nanomaterial with excellent performance, but due to its high cost, it is rarely used directly as a fiber material, used as an additive modifier, and has a good performance in the field of mixture preparation. application prospects. However, how to realize the uniform dispersion of MWNTs in polyester is a difficult problem that has plagued the industry for a long time. GXChen et al. (Polymer, Vol. 47, 2006, p. 760) prepared aminated MWNTs, and melt-blended the aminated MWNTs with polyamide 6 and spun them to prepare composite fibers loaded with different aminated MWNTs. , it was measured that the strength of the composite fiber increased by 42% and the modulus increased by 35% when the loading of aminated MWNT was 0.5 wt%. Chinese Invention Patent Application Publication No. CN104357941A discloses a styrene-maleic anhydride copolymer grafted on the surface of graphene and MWNT to improve the affinity between it and polyamide 6 molecular chains, and then adjust the graphene/carbon The ratio of nanotubes exerts the synergistic reinforcement effect of one-dimensional and two-dimensional nanomaterials. In situ polymerization, a polyamide 6/graphene/carbon nanotube mixture is prepared, and high-strength polymer fibers are obtained by melt spinning and post-processing.

Although the physical and mechanical properties of the polymer/MWNT fibers prepared in the prior art are significantly improved compared with the comparative fibers, due to the lack of innovation in controlling the miscibility between MWNT and the polymer and the performance degradation due to the decrease in the molecular weight of the polymer, the obtained The physical and mechanical properties of polymer/MWNT fibers still cannot surpass those of PET industrial yarns.

SUMMARY OF THE INVENTION

In view of the deficiencies of the prior art, the present invention provides a method for industrially preparing functionalized multi-walled carbon nanotube (FMWNT) reinforced polyester fibers, and the prepared fibers have good physical and mechanical properties.

For this reason, the technical scheme of the present invention is as follows:

A preparation method of FMWNT reinforced polyester fiber, comprising the following steps:

S1, 0.05-2 mass parts of functionalized MWNT and 98-99.5 mass parts of high-viscosity PET or PEN are mixed uniformly in a high-speed mixer; ,

Or mix the functionalized MWNT with terephthalic acid or naphthalenedicarboxylic acid and ethylene glycol of corresponding quality, add catalyst and antioxidant, esterify at 150～210℃ for 1～4h, and conduct vacuum polycondensation at 270～300℃ After 8-10 hours, it is made into composite pellets;

When the intrinsic viscosity of the composite pellets is lower than 0.95dL/g, it is necessary to carry out thickening treatment to increase the intrinsic viscosity to 0.95-1.10dL/g. In the present invention, the method for increasing the viscosity is as follows: the pellets are subjected to a viscosity increasing treatment in a rotating drum at 180-200° C. and 1.5-10 Pa for 8-12 hours.

The composite pellets are pre-crystallized and dried at 160-180° C. for 10-20 min;

Wherein, the functionalized MWNTs are hydroxylated, aminated or carboxylated MWNTs with a diameter of 30-50 nm, a length of 0.5-2.0 μm, and a water content of less than 60 ppm, and the proportion of functionalized carbon atoms is the surface of the multi-walled carbon nanotubes. 2 to 5% of the total number of carbon atoms.

S2, the pellets obtained in S1 are melt-spun into melt-spun strands, wherein the spinneret hole diameter of the melt-spinning equipment is 0.15-0.25 mm, and the aspect ratio is 3:1. The use of small diameter spinnerets is beneficial to the preparation of fibers with excellent physical and mechanical properties.

S3, the molten strands are cooled by air at 20-90° C., 50-80% relative humidity, and wind speed 10-20 m/min, and then wound into a tube to obtain polyester/MWNT fibers. In the present invention, the spinning shaft temperature is set at 20-90° C., and the purpose of increasing the shaft temperature is to slow down the solidification rate of the melt stream, so as to increase the drafting ratio. Heterogeneous nucleation of MWNTs helps to increase the solidification rate of molten streamlets, and the use of the same tunnel temperature as in conventional polyester spinning is not conducive to the preparation of ultra-high-strength polyester fibers.

S4, the polyester/MWNT fibers are stored in an environment of 25° C. and a relative humidity of 65% for 20-28 hours.

S5, in order to improve the heating uniformity and the drawing ratio, the polyester/MWNT fiber is firstly drawn into the ethylene glycol, 1,3-propanediol or 1,2-propanediol bath at 80-140°C for the first drawing. 2.0 to 3.0 times, then the second draft on the 180-200°C hot roller, 1.5 to 2.0 times, and then the third draft on the 200-230°C hot roller, the draft is 1.5 to 2.0 Finally, it was shaped on a hot roller at 210-230 °C, cooled by air blowing at room temperature, and then washed in a deionized water bath and an oil bath containing detergent at room temperature to remove residual ethylene glycol, 1,3 - Propanediol or 1,2-propanediol, oiling agent, again air blown and dried, and then wound into a drum, and the winding speed is 200-400m/min. Using a bath of ethylene glycol, 1,3-propanediol or 1,2-propanediol between the first drafting rolls not only helps the fiber bundles to be heated, but also can infiltrate and plasticize the polyester, which is more conducive to drawing Increased elongation.

Preferably, before step S2 is performed, the intrinsic viscosity value of the pellets needs to be measured, according to whether the intrinsic viscosity of the pelletized mixture in phenol/1,1,2,2-tetrachloroethane (mass ratio 3:2) is When the intrinsic viscosity is greater than 0.95dL/g, it determines whether to carry out solid phase tackification, that is to say, when the intrinsic viscosity is 0.95-1.10dL/g, no tackification is required; when the intrinsic viscosity is less than 0.95dL/g, it indicates that the molecular weight of polyester is The low chain length requires solid phase tackifying under vacuum. The method of increasing the viscosity is to carry out the viscosity increasing treatment of the pellets in a rotating drum at 180-200° C. and 1.5-10 Pa, and the treatment time is 8-12 hours.

Preferably, when melt spinning is performed in step S2, the temperatures of the fourth zone of the screw, the elbow and the pump seat are respectively 180-200, 190-250, 240-270, 270-310, 270-310, and 270-310°C.

Preferably, in step S3, the winding speed is 2000-5000 m/min. A high winding rate is not only beneficial to increase the productivity, but also to improve the degree of orientation of the polyester molecular chain.

Preferably, in step S1, the temperatures of the fourth screw zone and the die head of the twin-screw mixer or twin-rotor high-speed mixer are 180-200, 190-250, 240-270, 270-280, 270- 280℃, the extrusion rate is 10～30kg/h.

Preferably, in step S5, the total draft ratio of the three drafts is controlled to be 5.0 to 7.5 times.

The intrinsic viscosity of the high-viscosity PET or PEN is 0.95-1.10 dL/g, and the preferred intrinsic viscosity is 1.05-1.10 dL/g.

The core of the present invention is to add 0.05-2wt% of MWNTs with a diameter of 30-50nm and a length of 0.5-2.0μm MWNT dry powder of hydroxyl, amino or carboxylation in the polyester pelletizing or polyester polymerization process. The material is uniformly dispersed in the polyester resin, which can weaken the π-π conjugation force between the benzene rings or naphthalene rings on the polyester molecular chain, form hydrogen bonds with the carbonyl group, and reduce the interaction force and entanglement between the polyester molecular chains. Density, induces the polyester molecular chain to form a regular crystalline structure on its surface, improves the crystallinity of the fiber, and transfers its high physical and mechanical properties to the polyester matrix. 12cN/dtex, Young's modulus of 250cN/dtex and above, and easy to realize industrialization. At the same time, the rate of heat transfer from the screw sleeve to the polyester molecular chain during processing is increased, the time required to achieve crystal-free melting is reduced, and the stability during melting and conveying is improved.

If the mass fraction of the functionalized MWNT is less than 0.05%, it is difficult to play a modification role, and if the mass fraction exceeds 2%, it is easy to cause uneven dispersion and spinning difficulties, so that the tensile strength and Young's modulus of the fiber cannot meet the requirements. .

The diameter of the functionalized MWNT is 30-50 nm. If the diameter is too small, the flexibility is too large, and the aspect ratio is too large, it is easy to form entanglement in the polyester resin, making dispersion difficult; The uniformity of the dispersion is limited, and at the same time, the number of MWNTs decreases, and the efficiency of heterogeneous nucleation decreases.

The length of the functionalized MWNT is 0.5-2.0 μm, and the length is too small. Although it is easy to be uniformly dispersed in the polyester resin, the van der Waals force between the functionalized MWNT and the polyester molecular chain is low, and it is not easy to play a reinforcing role; the length is too large. , large aspect ratios are easy to form entanglements, making dispersion difficult and unable to play a strengthening role.

The functionalized MWNTs are preferably MWNTs containing hydroxyl, amino or carboxyl functional groups, all of which can form hydrogen bonds with carbonyl groups, the bond strength of O—H ^… :O is 21kJ/mol, and the bond of N—H ^… :O The strength is 8kJ/mol, which further weakens the interaction between polyester molecular chains, which is beneficial to improve the thermal stability time and processability of polyester, and the hydrogen bonding after fiber formation helps to improve the physical and mechanical properties of fibers.

The reinforcing effect is that the one-dimensional nanostructure of MWNT is oriented along the fiber axis during the drawing process after the mixture melt is extruded from the spinneret hole, and is distributed in the fiber, inducing the polyester molecular chain to form regular growth on its surface. When the fiber is subjected to external force and the molecular chain slips, this regular shish restricts the sliding of the molecular chain, transmits the stress to a wider range, and mechanically locks The combined force achieves the purpose of greatly improving the tensile breaking strength of the composite fiber.

The present invention adopts functionalized MWNT with specific diameter and length as reinforcement, and realizes the π-π conjugation effect on the benzene ring or naphthalene ring in the polyester molecular chain by changing the diameter, length, functional group type, addition amount, etc. of the MWNT. The regulation of hydrogen bonding, further solid-phase viscosification of the polymer/MWNT, the use of melt spinning, oil bath heating of the formed fibers, and graded drafting methods improve the crystallinity and orientation of polyester fibers. The tensile strength of the prepared fiber is above 12cN/dtex, the Young's modulus is above 200cN/dtex, and the elongation at break is 6-15%. The production process of the invention is easier to realize industrialization, and the product price is lower.

Detailed ways

The preparation method of the present invention will be described in detail below in conjunction with specific embodiments.

Unless otherwise specified, the raw materials used in the following examples were dried to a moisture content of less than 60 ppm. The composition, structure and properties of the prepared polyester/MWNT fibers were characterized by the following instruments unless otherwise specified:

The surface morphology of MWNT and composite fibers was observed by Hitachi S4800 scanning electron microscope; the mechanical properties of pure polyester fibers and composite fibers were tested by LLY-06 electronic single fiber strength tester. Each fiber was stretched at a constant speed, the clamping distance was 10 mm, and the stretching speed was 10 mm/min, and the average value of each group of fibers was measured 10 times. Young's modulus is the ratio of stress to strain at 1% deformation.

Example 1

A preparation method of aminated MWNT reinforced polyester fiber, comprising the following steps:

S1, take 0.5 parts by mass of aminated MWNT with an average diameter of 50 nm and a length of 0.5 μm (the number of aminated carbon atoms accounts for 2% of the carbon atoms on the surface of the MWNT), and 99.5 parts by mass of PEN with an intrinsic viscosity of 1.08 dL/g is cut into pellets After mixing, it was treated in a high-speed mixer at 1800 rpm for 20 minutes, and then taken out after standing for 30 minutes. Then it was added to a twin-screw extruder with a diameter of 25mm and melted and extruded once. The temperature of the four zones of the extruder and the die head were 200, 250, 270, 280, and 280°C, respectively, and the intrinsic viscosity of the obtained pellets was 0.96dL/g. . The pellets were pre-crystallized at 170 °C and dried for 20 min, and then directly used for melt spinning.

S2, melt spinning: wherein, the temperatures of the first to fourth zones of the single-screw extruder screw, the elbow and the pump seat are respectively 200, 250, 270, 300, 300, and 300 °C; the spinneret holes of the melt spinning equipment The aperture is 0.20mm, the aspect ratio is 3:1, and the number of holes is 96.

S3, the thread is wound into a tube after being cooled by an air duct at 90° C., 65% relative humidity, and a wind speed of 20 m/min, and the winding speed is 4000 m/min.

S4, the polyester/aminated MWNT fibers obtained in step S3 are stored for 24 hours in an environment of 25° C. and a relative humidity of 65%.

S5, the polyester/aminated MWNT fiber obtained in step S4 is firstly drawn into a 1,3-propanediol bath at 140°C for the first drawing, the drawing is 2.5 times, and then the second drawing is performed on a 200°C hot roller 2.0 times of drafting, and then a third drafting on a hot roller at 230 °C, 1.5 times of drafting, the total drafting ratio is 7.5 times, and finally set on a hot roller at 230 °C, and cooled by air blowing at room temperature , and then washed in a deionized water bath and an oil bath containing detergent at room temperature to remove the 1,3-propanediol and oiling agent on the surface, and then air-blown and dried, and then rolled into a tube at a winding speed of 350m/min , to get the finished product.

No agglomeration of MWNTs was observed on the fiber cross section. The tensile breaking strength of the composite fiber was 15cN/dtex, the Young's modulus was 300cN/dtex, and the elongation at break was 8%.

Example 2

A preparation method of carboxylated MWNT reinforced polyester fiber, comprising the following steps:

S1, carboxylated MWNT with an average diameter of 40 nm and a length of 1.5 μm (the number of carboxylated carbon atoms accounts for 5% of the carbon atoms on the surface of the MWNT), 2,6-naphthalenedicarboxylic acid (NDC) and ethylene glycol in a stainless steel reactor Mixing, the molar ratio of ethylene glycol/NDC is 2.8:1; adding n-butyl titanate as a catalyst, the dosage is ^8x10-4 mol of NDC, sterically hindered phenol 1010 is an antioxidant, and the dosage is ^1x10-4 mol of NDC , After purging the reaction kettle with nitrogen for 3 times, the esterification reaction temperature was 210 ° C, the temperature of the reaction kettle was gradually increased to 295 ° C after 4 hours, the pressure was reduced to 1.8 Pa, and after 6 hours, it was extruded into strips, cooled, pelletized, and pelletized. The intrinsic viscosity was 1.06 dL/g. The mass fraction of carboxylated MWNT was determined to be 0.5% by dissolution, filtration and weighing. The pellets were pre-crystallized at 190°C, dried for 10 min, and directly used for melt spinning.

S2, after drying, cut into pellets and add them to a single-screw extruder with a diameter of 25mm. The temperatures of the first to fourth zones of the screw and the elbows are set to 180, 220, 250, 280, 310, and 310°C, respectively, and the temperature of the pump seat is 310°C. The spinneret diameter of the melt spinning equipment is 0.25 mm, and the aspect ratio is 3:1.

S3, the obtained filaments are wound at a speed of 5000 m/min after being cooled by an air duct at 20° C., 65% relative humidity, and a wind speed of 12 m/min.

S4, the polyester/carboxylated MWNT fibers obtained in step S3 are stored for 24 hours in an environment of 25° C. and a relative humidity of 65%.

S5, the fibers obtained in step S4 are firstly drawn into a 1,3-propanediol bath at 110°C for the first drawing, and the drawing is 2.5 times, and then the second drawing is performed on a hot roller at 200°C, and the drawing is 2.0 times. , and then carry out the third drawing on the hot roller at 230 ° C, the draft is 1.5 times, and the total drafting ratio is 7.5 times. Wash in a deionized water bath and an oil bath containing detergent to remove 1,3-propanediol and oiling agent on the surface, blow and dry it again with air and wind it into a tube at a winding speed of 280m/min to obtain a finished product.

No agglomeration of MWNT was found by observing the fiber cross section. The tensile breaking strength of the composite fiber was measured to be 13.2 cN/dtex, the Young's modulus was 225 cN/dtex, and the elongation at break was 12%.

Example 3

A preparation method of hydroxylated MWNT reinforced polyester fiber, comprising the following steps:

S1, take 1.0 mass parts of hydroxylated MWNT with an average diameter of 30 nm and a length of 1.0 μm (the number of hydroxylated carbon atoms accounts for 3% of the surface carbon atoms of the MWNT), and 99.0 mass parts of PET pellets (intrinsic viscosity 1.05dL/g) After mixing, it was treated in a high-speed mixer at 2000 rpm for 10 minutes, and then taken out after standing for 20 minutes. It was added into a double-rotor high-speed mixing extruder with a diameter of 25mm and melted and extruded once. The temperature of the four zones of the extruder and the die head were respectively 200, 250, 265, 270, and 270 ° C, and the intrinsic viscosity of the obtained pellets was 0.86 dL/g. The pellets were thickened for 8 hours in a rotating drum at 200°C and 1.5Pa to make the intrinsic viscosity reach 1.10dL/g, then the pellets were pre-crystallized at 180°C and dried for 20min before being used for melt spinning.

S2, melt spinning: wherein, the temperatures of the first to fourth zones of the single-screw extruder screw, the elbow and the pump seat are respectively 200, 250, 270, 295, 295, and 295°C; the spinneret holes of the melt spinning equipment The aperture is 0.18mm, the aspect ratio is 3:1, and the number of holes is 96.

S3, the thread is wound into a tube after being cooled by an air shaft at 70° C., 65% relative humidity, and a wind speed of 16 m/min, and the winding speed is 3500 m/min.

S4, the polyester/hydroxylated MWNT fibers obtained in step S3 are stored in an environment of 25° C. and a relative humidity of 65% for 22 hours.

S5, the polyester/hydroxylated MWNT fibers obtained in step S4 are firstly drawn into a 1,3-propanediol bath at 100 °C for the first drawing, the drawing is 3 times, and then the second drawing is performed on a 200 °C hot roller stretched, 1.5 times, and then carried out a third draft of 1.5 times on a hot roller at 220 ° C, the total drafting ratio was 6.75 times, and finally set on a hot roller at 220 ° C, and was cooled by air blowing at room temperature, and then separately Wash in deionized water bath and oil bath containing detergent at room temperature to remove oil stains and oiling agent on the surface, air blow and dry again, and then wind up into a tube at a winding speed of 300 m/min.

No agglomeration of MWNTs was observed on the fiber cross section. The tensile breaking strength of the composite fiber was measured to be 12.5cN/dtex, the Young's modulus was 210cN/dtex, and the elongation at break was 13%.

Example 4

A preparation method of hydroxylated MWNT reinforced polyester fiber, comprising the following steps:

S1, hydroxylated MWNTs with an average diameter of 40 nm and a length of 1.2 μm (the number of hydroxylated carbon atoms accounts for 5% of the surface carbon atoms of the MWNT), 1,4-terephthalic acid (PTA) and ethylene glycol in a stainless steel reactor Mixed in medium, the molar ratio of ethylene glycol/PTA was 2.6, zinc acetate was added as a catalyst, and the dosage was ^4x10-4 mol of PTA; sterically hindered phenol 1010 was an antioxidant, and the dosage was ^1x10-4 mol of PTA, and nitrogen purged After 3 times of the reaction kettle, the esterification reaction was carried out at 200 °C. After 4 hours, the temperature of the reaction kettle was gradually increased to 295 °C, and the pressure was 1.5Pa. After 5 hours, it was extruded into strips, cooled and cut into pellets. The mass fraction of hydroxylated MWNT was determined to be 2.0% by dissolving, filtering and weighing. The pellets were pre-crystallized at 180°C, dried for 15 min, and directly used for melt spinning.

S2, melt spinning: wherein, the temperatures of the first to fourth zones of the single-screw extruder screw, the elbow and the pump seat are respectively 200, 250, 270, 295, 295, and 295°C; the spinneret holes of the melt spinning equipment The aperture is 0.25mm, the aspect ratio is 3:1, and the number of holes is 192.

S3, the thread is wound into a tube after cooling through an air shaft at 90° C., 65% relative humidity, and a wind speed of 16 m/min, and the winding speed is 5000 m/min.

S4, the fibers obtained in step S3 are stored for 26 hours in an environment of 25° C. and a relative humidity of 65%.

S5, the fiber obtained in step S4 is firstly drawn into the ethylene glycol bath at 100°C for the first time, and the draw is 2.5 times. The third drafting was carried out on a hot roller at 230 °C, the drafting was 1.5 times, and the total drafting ratio was 7.5 times. Finally, it was finalized on a hot roller at 230 °C, cooled by air blowing at room temperature, and then washed separately at room temperature. The product was washed in a deionized water bath and an oil bath to remove oil stains on the surface, oiled, and then air-blown and dried again, and then rolled into a tube at a winding speed of 350 m/min to obtain a finished product.

No agglomeration of hydroxylated MWNTs was observed on the fiber cross section. The tensile breaking strength of the composite fiber was 12.1cN/dtex, the Young's modulus was 223cN/dtex, and the elongation at break was 11%.

Example 5

Using 1.0 mass parts of hydroxylated MWNTs with an average diameter of 50 nm and a length of 1.5 μm (the number of hydroxylated carbon atoms accounts for 3% of the carbon atoms on the surface of the MWNT), and mixed with 99.0 mass parts of PPT pellets (intrinsic viscosity: 0.70 dL/g) , processed in a high-speed mixer at 2000rpm for 10min, and taken out after standing for 20min. It was added to a double-rotor high-speed mixing extruder with a diameter of 25mm and melted and extruded once. The temperature of the four zones and the die head were 250, 270, 290, 290, and 290°C, respectively. The intrinsic viscosity of the pellets was 0.55dL/g. The viscosity was increased for 10h under 2Pa in the vacuum drum, and the intrinsic viscosity was increased to 0.96dL/g. Pre-crystallization, drying, spinning and post-drawing were carried out using the process conditions of Example 2 to obtain a finished product.

No agglomeration of MWNTs was observed on the fiber cross section. The tensile breaking strength of the composite fiber was measured to be 12.1 cN/dtex, the Young's modulus was 220 cN/dtex, and the elongation at break was 15%.

Example 6

A preparation method of carboxylated MWNT reinforced polyester fiber, comprising the following steps:

S1, take 1.0 mass parts of carboxylated MWNTs with an average diameter of 40 nm and a length of 1.5 μm (the number of carboxylated carbon atoms accounts for 3% of the surface carbon atoms of the MWNT), and 99.0 mass parts of PET pellets (intrinsic viscosity 1.05dL/g) After mixing, it was treated in a high-speed mixer at 2000 rpm for 10 minutes, and then taken out after standing for 20 minutes. It was added into a double-rotor high-speed mixing extruder with a diameter of 25mm and melted and extruded once. The temperature of the four zones of the extruder and the die head were respectively 200, 250, 265, 270, and 270 ° C, and the intrinsic viscosity of the obtained pellets was 0.82. dL/g. The pellets were thickened in a drum at 180°C and 10Pa for 12h to make the intrinsic viscosity reach 1.06dL/g, then the pellets were pre-crystallized at 190°C and dried for 10min before being used for melt spinning.

S2, melt spinning: wherein, the temperatures of the first to fourth zones of the single-screw extruder screw, the elbow and the pump seat are respectively 200, 250, 270, 295, 295, and 295°C; the spinneret holes of the melt spinning equipment The aperture is 0.18mm, the aspect ratio is 3:1, and the number of holes is 96.

S3, the thread is wound into a tube after cooling in an air shaft at 60° C., 65% relative humidity, and a wind speed of 16 m/min, and the winding speed is 4000 m/min.

S4, the polyester/carboxylated MWNT fibers obtained in step S3 are stored for 28 hours in an environment of 25° C. and a relative humidity of 65%.

S5, the polyester/carboxylated MWNT fibers obtained in step S4 are firstly drawn into a 1,3-propanediol bath at 100°C for the first drawing, the drawing is 3 times, and then the second drawing is performed on a 200°C hot roller stretched, 1.5 times, and then carried out a third draft of 1.5 times on a hot roller at 220 ° C, the total drafting ratio was 6.75 times, and finally set on a hot roller at 220 ° C, and was cooled by air blowing at room temperature, and then separately Washed in a deionized water bath and an oil bath containing detergent at room temperature to remove oil stains on the surface, oiling agent, and then air-blown and dried again, and then rolled into a tube at a winding speed of 300 m/min.

No agglomeration of FMWNT was observed in the fiber cross section. The tensile breaking strength of the composite fiber was measured to be 12.1 cN/dtex, the Young's modulus was 202 cN/dtex, and the elongation at break was 14%.

Comparative Example 1

A preparation method of MWNT reinforced PET fiber, comprising the following steps:

0.5 parts by mass of MWNTs with an average diameter of 50 nm and a length of 0.5 μm were used to replace 0.5 parts by mass of aminated MWNTs with an average diameter of 50 nm and a length of 0.5 μm (the number of aminated carbon atoms accounted for 2% of the total carbon atoms) in Example 1, and the rest The composition, process and process parameters are the same as in Example 1, and PEN/MWNT fibers are prepared.

Observation of the fiber cross section showed that the MWNT was partially agglomerated. The tensile breaking strength of the composite fiber was measured to be 6.2 cN/dtex, the Young's modulus was 180 cN/dtex, and the elongation at break was 14%.

Comparative Example 2

A preparation method of carboxylated MWNT reinforced PEN fiber, comprising the following steps:

Adopt the same raw material composition, technological process and technological parameters as in Example 2, the difference is that the obtained silk thread is wound at a speed of 5000m/min after being cooled by an air tunnel at 18°C, 65% relative humidity, and a wind speed of 16m/min.

During the spinning process, there are many filaments, resulting in frequent stoppages. Observation of the fiber cross section shows that the MWNT is partially agglomerated. The tensile breaking strength of the composite fiber is 5.8cN/dtex, the Young's modulus is 190cN/dtex, and the elongation at break is 23%.

It can be seen from the test results of the above two comparative examples that ultra-high-strength fibers cannot be prepared by using conventional MWNT and conventional spinning shaft process parameters.

Claims (10)

1. a preparation method of functionalized multi-walled carbon nanotube reinforced polyester fiber, comprising the following steps: S1, 0.05-2 mass parts of functionalized multi-walled carbon nanotubes and 98-99.5 mass parts of high-viscosity PET or PEN are uniformly mixed in a high-speed mixer; into composite pellets, Alternatively, the functionalized multi-walled carbon nanotubes are mixed with terephthalic acid or naphthalenedicarboxylic acid and ethylene glycol of corresponding quality, catalysts and antioxidants are added, and esterification is carried out at 150-210° C. for 1-4 hours, and at 270° C. for 1-4 hours. ～300℃ vacuum polycondensation for 8～10h to make composite pellets; The composite pellets are pre-crystallized and dried at 170-190° C. for 10-20 minutes; Wherein, the functionalized multi-walled carbon nanotubes are hydroxylated, aminated or carboxylated dry powder of multi-walled carbon nanotubes with a diameter of 30 to 50 nm, a length of 0.5 to 2.0 μm and a moisture content of less than 60 ppm, and wherein functionalized carbon atoms It accounts for 2-5% of the total number of carbon atoms on the surface of multi-walled carbon nanotubes; S2, the pellets obtained in S1 are melt-spun into melt-spun strands, wherein the spinneret hole diameter of the melt-spinning equipment is 0.15-0.25 mm, and the aspect ratio is 3:1; S3, the molten filaments are cooled by air at 20-90° C., 50-80% relative humidity, and wind speed of 10-20 m/min, and then wound into a tube to obtain polyester/multi-wall carbon nanotube fibers; S4, the polyester/multi-walled carbon nanotube fibers are stored in an environment of 25° C. and a relative humidity of 65% for 20-28 hours; S5, the polyester/multi-walled carbon nanotube fibers are firstly drawn into a bath of ethylene glycol, 1,3-propanediol or 1,2-propanediol at 80-140°C for the first drawing, and the drawing is 2.0-3.0 times, and then Carry out the second drafting on a hot roller at 180-200°C for 1.5-2.0 times, and then perform a third draft on a hot roller at 200-230°C for 1.5-2.0 times, and finally at 210- Set on a hot roller at 230°C, cool down by air blowing at room temperature, and then wash in a deionized water bath and an oil bath containing detergent at room temperature to remove residual ethylene glycol, 1,3-propanediol or 1,2 - Propylene glycol, oiling agent, air purging and drying again, and then winding into a drum, and the winding speed is 200-400 m/min. 2. method according to claim 1, is characterized in that: in step S1, also need to measure the intrinsic viscosity value of described composite granulation before carrying out pre-crystallization, drying, when its intrinsic viscosity is less than 0.95dL/g, It was thickened to an intrinsic viscosity of 0.95 to 1.10 dL/g. 3 . The method according to claim 2 , wherein the method for increasing the viscosity is as follows: the pelletizing is subjected to a viscosity increasing treatment in a rotating drum at 180-200° C. and 1.5-10 Pa, and the treatment time is 8. 3 . ~12h. 4. The method according to claim 1, characterized in that: when melt spinning is performed in step S2, the temperatures of the fourth zone of the screw, the elbow and the pump seat are respectively 180-200, 190-250, 240-270, 270- 310, 270～310, 270～310℃. 5. The method according to claim 1, wherein in step S3, the winding speed is 2000-5000 m/min. 6. The method according to claim 1, characterized in that: in step S1, the temperature of the fourth screw zone of the twin-screw kneader or twin-rotor high-speed kneader and the temperature of the die head are respectively 180-200, 190-250 , 240～270, 270～280, 270～280℃, the extrusion rate is 10～30kg/h. 7 . The method according to claim 1 , wherein in step S5 , the total drafting multiple of the three drafting is 5.0 to 7.5 times. 8 . 8 . The method according to claim 1 , wherein the intrinsic viscosity of the high-viscosity PET or PEN is 1.05-1.10 dL/g. 9 . 9. The method according to claim 1, wherein in step S5, the winding speed is 220-350 m/min. 10. A functionalized multi-walled carbon nanotube reinforced polyester fiber, characterized in that: it is prepared by the method according to any one of claims 1-9.