High-strength high-modulus PBO fiber and preparation method thereof

Abstract

The invention provides a high-strength and high-modulus PBO fiber and a preparation method thereof, and belongs to the field of high-performance fiber preparation. The preparation method of the high-strength and high-modulus PBO fiber comprises the following steps of (1) burdening, (2) prepolymerization, (3) material storage, (4) defoaming, (5) prefiltration, (6) final polymerization, (7) spinning, (8) solidification and (9) aftertreatment. The PBO spinning solution is high in viscosity and is easy to block equipment and pipelines, so that the prepolymerization kettle, the middle kettle, the defoaming kettle, the double-screw extruder and other equipment involved in the invention are all compactly arranged in space arrangement. Meanwhile, the reaction time and the reaction temperature need to be strictly controlled, the intrinsic viscosity of materials in each process is guaranteed, the process stability is guaranteed, and the high-strength and high-modulus fibers can be obtained.

Description

Technical Field

[0001] The invention relates to the field of high-performance fiber preparation, and in particular to a high-strength and high-modulus PBO fiber and a preparation method thereof. Background Art

[0002] Poly(p-phenylene benzobisoxazole) (PBO) fiber has high strength, modulus, high temperature resistance and good flame retardancy. It is the organic fiber with the best comprehensive performance at present. The main monomers for preparing the polymer are terephthalic acid and 4,6-diaminoresorcinol hydrochloride. PBO fiber can be obtained by liquid crystal spinning. Toyobo of Japan is the first company to realize industrialized production, with an annual production capacity of 1,000 tons and the world's first fiber performance index. Its high-end PBO fiber has a strength of 5.8GPa, a modulus of 280GPa, a single-filament linear density of 1.7dtex, a limiting oxygen index of 68%, and a thermal decomposition temperature of 650℃.

[0003] PBO fiber has the characteristics of light weight, high strength and modulus, dimensional stability, insulation, and high temperature resistance. It is an ideal material for solid rocket engines and black box shells. At the same time, PBO composite materials have good wave transmittance and are the best choice for the preparation of stealth components such as radars and antenna covers. PBO fiber has low density, high strength, and good toughness. It is an excellent energy-absorbing material and is suitable for personal protection or tank armor. PBO fiber has good mechanical properties and can be used in various reinforcing materials. PBO fiber has a super high heat resistance temperature and the thermal decomposition temperature is the highest among commercial organic fibers. Therefore, it can be used as protective clothing and heat-resistant materials in special high-temperature fields.

[0004] The preparation of PBO fiber is a systematic project, including the preparation of spinning solution, spinning, post-treatment and other processes. There are several key difficulties in the preparation of PBO fiber: first, the mixing and dispersion of various powder materials and high-viscosity materials, second, the removal of HCl gas, third, the transportation of high-viscosity materials, and fourth, the batch stability caused by the slow growth of PBO molecular weight. The PBO fiber prepared by the present invention has moderate characteristic viscosity, good batch stability, complete removal of HCl gas, stable material transfer and good spinning stability.

[0005] At present, the preparation of PBO fiber in China is mostly intermittent. During the storage process, the molecular weight of PBO polymer material will slowly increase, resulting in batch instability. At the same time, since the raw materials for preparation are a variety of powders and high-viscosity solvents, it is difficult to mix and disperse the materials evenly using traditional stirring equipment. As the viscosity increases, the stirring effect of traditional reaction equipment becomes worse. PBO will release a large amount of HCl gas during the preparation process, and it is difficult to remove the gas completely through ordinary reactors. Due to the high viscosity of PBO, the viscosity of the prepolymer material usually reaches 500Pa·s, and such a high-viscosity material is difficult to transport between the reactor and the pipeline. Since PBO fiber is prepared in a phosphoric acid environment, the phosphoric acid content in the fiber is high and it is not easy to clean it.

[0006] CN110592706A discloses an industrial production method of poly(p-phenylene benzobisoxazole) fiber, wherein 4,6-diaminoresorcinol phosphate and terephthalic acid are polymerized in a mixed medium of polyphosphoric acid and phosphorus pentoxide at 100-200°C under the protection of an inert gas to obtain a poly(p-phenylene benzobisoxazole) prepolymer solution, and the prepolymer solution is extruded and spun to obtain PBO fiber. The invention uses 4,6-diaminoresorcinol phosphate for polymerization, which saves the time for removing hydrogen chloride and reduces the requirements for equipment.

[0007] CN112941657A discloses a spinning method for poly(p-phenylene benzobisoxazole) fiber, wherein a low-viscosity PBO prepolymer is first prepared, then fed into a twin-screw extruder, a third monomer is added to the polymerization system in a side-feeding manner, and a spinning solution is obtained. The obtained PBO fiber has high internal and external uniformity, good mechanical properties, low phosphoric acid residual rate, and good comprehensive performance.

[0008] CN110205698A discloses a preparation process of poly(p-phenylene benzobisoxazole) high modulus fiber, comprising: a dehydrochlorination step: respectively adding polyphosphoric acid, antioxidant 1010, antioxidant 168, and 4,6-diaminoresorcinol hydrochloride into a degassing kettle, stirring, degassing and defoaming for 10 to 20 hours to obtain a 4,6-diaminoresorcinol reaction solution; a polymerization step: respectively adding the 4,6-diaminoresorcinol reaction solution, terephthalic acid, and phosphorus pentoxide into a polymerization kettle in sequence to carry out polymerization reaction to obtain a polymer material; a filtering step: filtering the polymer material once through a hydraulic filter and then conveying it to a screw extruder, and then entering the filter of a spinning box for secondary filtration; a spinning coagulation step: the polymer material after secondary filtration enters the spinning assembly of the spinning box for spinning to obtain primary precursors, and the primary precursors enter a coagulation bath of a gradually varying concentration phosphoric acid aqueous solution for bundling; a drawing and washing step and a heat treatment step.

[0009] At present, the mechanical properties of poly(p-phenylene benzobisoxazole) fibers prepared in the prior art are average, with a single fiber strength of ≤28 cN / dtex and a modulus of ≤850 cN / dtex, and the product application field is still limited to medium and low-end products.

[0010] The present invention proposes a method for preparing high-strength and high-modulus PBO fibers, and belongs to the field of high-performance fiber preparation. The prepolymerization process of the present invention is intermittent, and is used for intermittent preparation of prepolymer materials. The materials are continuously conveyed from the storage kettle, and after degassing and pre-filtration, viscosity-enhancing polymerization and spinning are performed again. The fibers are washed, oiled, dried and densified to obtain high-strength and high-modulus fibers. Since the PBO spinning solution has a high viscosity and is easy to clog equipment and pipelines, the prepolymerization kettle, intermediate kettle, degassing kettle, twin-screw extruder and other equipment involved in the present invention should be compactly arranged in space. At the same time, the reaction time and reaction temperature should be strictly controlled to ensure the characteristic viscosity of the materials in each process, ensure the process stability, and obtain high-strength and high-modulus fibers. Summary of the invention

[0011] The purpose of the present invention is to propose a method for preparing high-strength and high-modulus PBO fibers. The prepolymerization process is intermittent, which is used to prepare prepolymers intermittently, and the materials are continuously transported starting from the storage kettle. Since the PBO spinning solution has a high viscosity and is easy to clog equipment and pipelines, the prepolymerization kettle, intermediate kettle, degassing kettle, twin-screw extruder and other equipment involved in the present invention should be compactly arranged in space, and the inner wall of the reactor and the inner wall of the pipeline involved should be polished to ensure the smoothness of the inner wall and reduce resistance. The spinning, coagulation, washing, oiling and drying steps involved in the invention are indispensable, and the densification process can be used as an optional step to obtain higher modulus fibers. During the reaction process, the reaction time and reaction temperature should be strictly controlled to ensure the characteristic viscosity of the materials in each process, ensure the process stability, and obtain high-strength and high-modulus fibers.

[0012] The technical solution of the present invention is achieved in this way:

[0013] The present invention provides a method for preparing high-strength and high-modulus PBO fiber, comprising the following steps:

[0014] 1) Ingredients: prepare PBO spinning solution;

[0015] 2) Prepolymerization: After the PBO spinning solution is put into the prepolymerization reactor, nitrogen is introduced and emptied, stirring is started, the pressure in the reactor is maintained at <0.3Mpa, the temperature is 50-60°C, stirring is continued for 1-2h, then the temperature is raised to 90-100°C, stirring is continued for 1.5-2.0h, then the temperature is raised to 110-130°C, stirring is continued for 4-6h, and a prepolymer is obtained;

[0016] 3) Material storage: reversely rotate the stirrer of the reactor in step 2), open the discharge valve at the bottom of the reactor, and the prepolymer enters the middle reactor through the twin-screw extruder, and keep the material discharged continuously. When the liquid level of the prepolymer material is about to reach 10%-20%, transfer the prepolymer in the reactor to the middle reactor, and keep the temperature of the middle reactor at 110-130°C;

[0017] 4) Degassing: The prepolymer in the intermediate reactor is pumped into the degassing reactor, the temperature is controlled at 130-140°C, and the pressure is controlled at -0.085 to -0.095MPa to obtain the degassing prepolymer;

[0018] 5) Pre-filtration: the defoamed prepolymer enters the pre-filter to obtain the filtered prepolymer;

[0019] 6) Final polymerization: The filtered prepolymer enters the final polymerization system, under a slight vacuum state, the vacuum pressure is controlled at -0.045 to -0.085 MPa, the reaction temperature is controlled at 150-190°C, the residence time is 30-45 min, and the prepolymer is obtained;

[0020] 7) Spinning: The prepolymer of step 6) is pumped into a spinning assembly equipped with a filter screen, a distribution plate, and a spinneret, the temperature is controlled at 180-200° C., and the nozzle pressure is controlled at 4-10 MPa to obtain PBO fibers;

[0021] 8) Coagulation: The PBO fiber is then cooled in a coagulation bath at a temperature of 15-30°C to obtain cooled PBO fiber;

[0022] 9) Post-treatment: The cooled PBO fiber is first washed with water, then oiled, dried, and then collected to obtain PBO nascent fiber.

[0023] As a further improvement of the present invention, the preparation method further comprises a densification treatment, wherein the densification is: subjecting the PBO as-spun fibers to a densification treatment at ≥350° C. and then winding the fibers.

[0024] As a further improvement of the present invention, the densification treatment is carried out in a nitrogen atmosphere at 350-650°C.

[0025] As a further improvement of the present invention, the PBO spinning solution in step 1) contains: 9.5-9.9wt% terephthalic acid, 11.9-12.3wt% 4,6-diaminoresorcinol hydrochloride, 58-64wt% polyphosphoric acid, 16.5-18.0wt% phosphorus pentoxide, and 0.05-0.06wt% antioxidant, and preferably the antioxidant is SnCl2.

[0026] As a further improvement of the present invention, in step 2), the pressure in the reactor is maintained at less than 0.3 MPa, which means that when the pressure in the reactor rises to 0.3-0.4 MPa, the pressure is released to 0.1-0.3 MPa.

[0027] As a further improvement of the present invention, the intrinsic viscosity of the PBO prepolymer in step 2) is 0.98-2.1 dL / g.

[0028] As a further improvement of the present invention, in step 2), a coaxial ribbon agitator is provided in the prepolymerization reactor, and preferably, a spiral discharge structure is provided at the bottom of the coaxial ribbon agitator.

[0029] As a further improvement of the present invention, a metering pump is provided at the bottom of the intermediate kettle in step 3).

[0030] As a further improvement of the present invention, the intrinsic viscosity of the prepolymer after degassing in step 4) is 8.0-18.0 dL / g.

[0031] As a further improvement of the present invention, the degassing kettle in step 4) is provided with an embedded vertical twin-screw extruder.

[0032] As a further improvement of the present invention, the degassing kettle in step 4) is a horizontal biaxial self-cleaning reactor, and preferably a vacuum pumping device is provided in the degassing kettle.

[0033] As a further improvement of the present invention, the pre-filter in step 5) is a plug-in filter.

[0034] As a further improvement of the present invention, in step 7), the spinneret assembly is provided with a filter screen and a distribution plate, the filter screen has a mesh size of 100-150 meshes, the spinneret has 60-120 holes, and the hole diameter is 0.25-0.30 mm.

[0035] As a further improvement of the present invention, after the PBO fibers are ejected from the spinneret in step 7), the PBO fibers enter a 30-50 cm air gap insulation layer.

[0036] As a further improvement of the present invention, the air gap layer in step 7) is electrically heated and kept warm, and the temperature is controlled at 40-80°C.

[0037] As a further improvement of the present invention, the coagulation bath in step 8) is a phosphoric acid aqueous solution, the phosphoric acid concentration is 10-20wt%, the coagulation bath temperature is 15-30°C, and the length is 1.5-2.0m.

[0038] As a further improvement of the present invention, the water washing in step 9) is carried out by upper spraying and lower immersion, and the temperature is controlled at 30-40°C.

[0039] As a further improvement of the present invention, the oiling in step 9) is performed by using an oil of PBO-001:PBO-002:PBO-003 in a weight ratio of 70:27:3 to 90:7:3 in an oil tank at 30-40°C.

[0040] The present invention also provides a high-strength and high-modulus PBO fiber prepared by any of the above methods.

[0041] As a further improvement of the present invention, the linear density of the high-strength and high-modulus PBO fiber is 1.7-2.6 dtex.

[0042] As a further improvement of the present invention, the strength of the high-strength and high-modulus PBO fiber is ≥29.6 cN / dtex, preferably 29.6-36.0 cN / dtex.

[0043] As a further improvement of the present invention, the modulus of the high-strength and high-modulus PBO fiber is ≥855 cN / dtex, preferably 855-1700 cN / dtex.

[0044] As a further improvement of the present invention, the elongation of the high-strength and high-modulus PBO fiber is ≤3.5%, preferably 2.5-3.5%.

[0045] The present invention has the following beneficial effects: the present invention aims at the conventional preparation process of PBO, solves the pain points and difficulties in the current preparation process of PBO by optimizing the process formula, reasonably setting the process flow, and adopting key equipment.

[0046] The preparation method and the equipment used in the present invention need to cooperate with each other to perfectly realize the stable preparation of high-quality PBO fibers. By controlling the process conditions, the material transfer in each process is smooth, the material viscosity is moderate, and the fiber is thoroughly washed, high-strength and high-modulus PBO fibers can be continuously and stably prepared.

[0047] 1) The present invention innovatively transforms the two steps of prepolymerization and final polymerization of the traditional PBO polymerization process into a semi-continuous process of prepolymerization, degassing and final polymerization through innovative design, and solves the problem of controlling the molecular weight growth of the prepolymer material in the intermittent reaction process through process control, which is beneficial to the unification of material indicators in each process and the stability of the process;

[0048] 2) The present invention adds materials at one time, thus avoiding the operation steps of adding materials in batches and the problem that adding materials in the middle process may lead to oxidation in the air;

[0049] 3) The present invention adopts a pressurized degassing process to avoid the problem of uneven molar ratio caused by the material being sucked into the vacuum system under negative pressure;

[0050] 4) The present invention adopts a process of degassing and polymerizing at the same time, which avoids the disadvantage that the material is easily oxidized in the process of degassing first and then polymerizing;

[0051] 5) The present invention adopts a coaxial ribbon reactor as a prepolymerization reactor, which solves the problem of difficult mixing, dispersion and stirring of high-viscosity materials;

[0052] 6) The present invention provides a spiral material discharge structure at the lower part of the coaxial ribbon reactor, which is beneficial to the transfer of high-viscosity materials.

[0053] 7) The present invention cleverly arranges a twin-screw extruder at the bottom of the prepolymerization kettle, which can solve the problem of difficult transfer of prepolymer materials and ensure that the prepolymerization kettle materials are transferred cleanly and used for the next batch reaction;

[0054] 8) The present invention adopts a horizontal double-shaft devolatilization reactor as a degassing reactor, which solves the problem that HCl gas in PBO high-viscosity materials is difficult to remove;

[0055] 9) The degassing kettle used in the present invention is provided with an embedded vertical twin-screw extruder at the tail, which is conducive to the forced discharge of high-viscosity materials;

[0056] 10) The present invention sets a plug-in filter after the degassing kettle for pre-filtration, which can ensure that the material is fully filtered under low viscosity conditions, avoiding the problem of difficulty in filtering after the viscosity increases in the later stage;

[0057] 11) The present invention adopts a water washing system with upper spraying and lower immersion, which can fully wash the phosphoric acid of the PBO fiber and reduce the phosphorus content of the fiber;

[0058] 12) The oil formulation used in the present invention can significantly improve the fiber gloss, antistatic performance and anti-aging performance;

[0059] 13) The present invention adopts a high-temperature densification furnace to heat the fiber, which can significantly improve the modulus of the PBO fiber.

[0060] Without violating the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0061] The positive progress of the present invention is that: the synthesis method of the present invention is simple, the reaction conditions are mild, the raw materials are cheap and easy to obtain, the yield is high, and the product purity is good; BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 This is the process flow for preparing the high-strength and high-modulus PBO fibers of Examples 1-3. DETAILED DESCRIPTION

[0063] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0064] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as commonly understood by those of ordinary skill in the art to which the invention belongs. Although any methods and materials similar or equivalent to those described herein can be used to implement or test the present invention, preferred methods and materials are described herein. For purposes of the present invention, the following terms are defined below.

[0065] PBO spinning solution

[0066] The PBO spinning solution of the present invention is prepared from the following raw materials by weight: 9.5-9.9% of terephthalic acid, 11.9-12.3% of 4,6-diaminoresorcinol hydrochloride, 58-64% of polyphosphoric acid, 16.5-18.0% of phosphorus pentoxide and 0.05-0.06% of antioxidant.

[0067] Pre-polymerization

[0068] The prepolymerization of the present invention is to feed the PBO spinning solution into the prepolymerization reactor at one time, introduce nitrogen after feeding, and exhaust the reactor, maintain the pressure in the reactor at 0.1-0.3MPa, start the prepolymerization stirrer, control the temperature in the range of 50-60°C, continue stirring for 1-2h, then increase the temperature to 90-100°C, continue stirring for 1.5-2.0h, then increase the temperature to 110-130°C, continue stirring for 4-6h, HCl gas will be generated during stirring, when the pressure in the reactor rises to 0.3-0.4MPa, the pressure is released to 0.1-0.3MPa through the pressure relief device, and the operation will be repeated according to the total amount of feeding until the pressure no longer rises.

[0069] Storage

[0070] The material storage of the present invention is that after the prepolymerization reaction is completed, the stirrer of the reactor is rotated in the opposite direction, and the bottom discharge valve is opened, and the material enters the middle reactor through the twin-screw extruder; the middle reactor keeps discharging the material continuously, and when the material liquid level is about to reach 10%-20%, the material in the prepolymerization reactor is transferred to the middle reactor, and the temperature of the middle reactor is maintained at 110-130°C.

[0071] Defoaming

[0072] The degassing process of the present invention is to pump the prepolymer material into the degassing kettle by a metering pump at the bottom of the middle kettle, the temperature is controlled at 130-140° C., and the reaction pressure is controlled at -0.085 to -0.095 MPa.

[0073] Pre-filtration

[0074] The pre-filtration of the present invention is that the prepolymer material obtained above is pressurized by a gear pump and then enters a pre-filter, which can filter out most of the impurities in the material.

[0075] Final Reunion

[0076] The final polymerization of the present invention is that the filtered material enters a twin-screw extruder, and is further polymerized and a trace amount of HCl is removed under a slight vacuum state, the vacuum pressure is controlled at -0.045 to -0.085 MPa, the reaction temperature is controlled at 150-190° C., and the residence time is 30-45 min.

[0077] Spinning

[0078] The spinning of the present invention is that the spinning liquid is pumped into a spinning assembly provided with a filter screen, a distribution plate, and a spinneret (assembly) through a metering pump. The spinneret assembly is provided with a filter screen and a distribution plate to further filter trace impurities and distribute materials to the spinneret. The filter screen has a mesh number of 100-150 meshes, the spinneret has a hole number of 60-120 holes, and a hole diameter of 0.25-0.30 mm. The assembly temperature is controlled at 180-200° C., and the nozzle pressure is controlled at 4-10 MPa. The PBO fiber ejected from the spinneret enters a 30-50 cm air gap insulation layer, and the temperature is controlled at 40-80° C. to obtain the PBO fiber.

[0079] solidification

[0080] The coagulation of the present invention is that the fiber enters a coagulation bath device, the coagulation bath is a phosphoric acid aqueous solution, the phosphoric acid concentration is 10-20% by mass, the coagulation bath temperature is 15-30°C, the length is 1.5-2.0m, the fiber is fully cooled in the coagulation bath, and the fiber surface defects are improved.

[0081] Post-processing

[0082] The post-treatment of the present invention is that the fiber first enters a water washing device to remove phosphoric acid in the fiber, and then enters an oiling tank after water washing to oil the fiber. After the oiling is completed, the fiber enters a drying device, and then is wound and collected to obtain a golden PBO nascent fiber.

[0083] Densification

[0084] The densification described in the present invention is an optional step. If a higher modulus PBO fiber is required, the golden PBO primary fiber enters a high-temperature densification furnace. After the fiber is heated in the densification furnace, a higher modulus PBO fiber can be obtained, the modulus is increased by 30-40%, and the fiber color is brown.

[0085] As used herein, the term "about" refers to an amount, level, value, dimension, size, or amount that differs by up to 30%, 20%, or 10% compared to the amount, level, value, dimension, size, or amount of a reference product. Percentages used herein, unless otherwise indicated, are by weight.

[0086] Throughout the specification and claims, unless otherwise required, the following words "comprise" and variations "comprising" and "including" will be understood to imply the inclusion of a stated integer or step, or a group of integers or steps, but not the exclusion of any other integer or step, or other group of integers or steps.

[0087] Experimental Materials:

[0088]

[0089]

[0090] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0091] Embodiment 1:

[0092] Ingredients: Weigh 5.45kg PTA, 6.55kg DAR, 32.9kg PPA, 9.65kg P2O5, and 32.5g SnCl2 respectively and set aside.

[0093] Prepolymerization: The weighed materials are put into the prepolymerization kettle at one time. After the feeding is completed, nitrogen is introduced and emptied several times to maintain the pressure in the kettle at 0.3MPa. The prepolymerization agitator is turned on, and the temperature is controlled within the range of 60℃. Stirring is continued for 2h, then the temperature is raised to 100℃, stirring is continued for 1.5h, then the temperature is raised to 120℃, stirring is continued for 5h, during which HCl gas will be generated. When the pressure in the reactor rises to 0.4MPa, the pressure is released to 0.3MPa through the pressure relief device. After the reaction is completed, the characteristic viscosity of the prepolymer material is sampled and analyzed to be 0.98dL / g.

[0094] Material storage: After the prepolymerization reaction is completed, the agitator of the prepolymerization reactor is rotated in the opposite direction, and the bottom discharge valve is opened, and the material enters the intermediate reactor through the twin-screw extruder. The intermediate reactor keeps discharging the material continuously. When the material liquid level reaches 20%, the material in the prepolymerization reactor is transferred to the intermediate reactor, and the temperature of the intermediate reactor is maintained at 120°C.

[0095] Degassing: The prepolymer material is pumped into the degassing kettle by the metering pump at the bottom of the middle kettle. The temperature of the degassing kettle is controlled at 135°C, the reaction pressure is controlled at -0.090MPa, and the material residence time is controlled at 2.5h. After the degassing is completed, the material intrinsic viscosity is measured to be 9.0dL / g.

[0096] Pre-filtration: After degassing, the material is extruded through the twin-screw extruder at the tail of the degassing kettle to the gear pump, and the material is pumped into the pre-filter.

[0097] Final polymerization: the material is sent to the final polymerization system after pre-filtration, the material residence time is controlled to be 45min, the temperature is set according to the gradient of 150℃, 160℃, 170℃, 175℃, 180℃, 185℃, 190℃, and the pressure is controlled at -0.085MPa. After this step, the material characteristic viscosity is tested by sampling and the result is 26.7dL / g.

[0098] Spinning: The material is pumped into a spinning assembly equipped with a filter screen, a distribution plate, and a spinneret (assembly) through a metering pump. The spinneret assembly is equipped with a filter screen and a distribution plate to further filter trace impurities and distribute the material to the spinneret. The filter screen has a mesh size of 100-150, the spinneret has 60 to 120 holes, and the hole diameter is 0.25 to 0.30 mm. The spinning temperature is controlled at 180-200°C, and the nozzle pressure is controlled at 4-10 MPa. The PBO fiber ejected from the spinneret enters a 30-50 cm air gap insulation layer at a temperature of 40°C to obtain PBO fiber.

[0099] Coagulation: The fiber enters a coagulation bath with a concentration of 10%, a temperature of 30°C and a length of 1.5 m for sufficient cooling.

[0100] Post-treatment: The coagulated fiber enters the post-treatment device, the washing water temperature is controlled at 40°C, the oil agent ratio is PBO-001:PBO-002:PBO-003=70:27:3, the oil agent temperature is controlled at 40°C, and the fiber is wound and collected after drying.

[0101] Embodiment 2:

[0102] Ingredients: Weigh 5.45kgPTA, 6.55kgDAR, 33.0kgPPA, 9.55kgP2O5, and 32.5g SnCl2 respectively and set aside.

[0103] Prepolymerization: Add the weighed materials into the prepolymerization kettle at one time. After the feeding is completed, nitrogen is introduced and emptied several times to maintain the pressure in the kettle at 0.2MPa. Turn on the prepolymerization agitator, control the temperature within the range of 50℃, and continue stirring for 2h. Then raise the temperature to 100℃ and continue stirring for 1.5h. Then raise the temperature to 125℃ and continue stirring for 5h. During this period, HCl gas will be generated. When the pressure in the reactor rises to 0.3MPa, the pressure is released to 0.2MPa through the pressure relief device. After the reaction is completed, the characteristic viscosity of the prepolymer material is sampled and analyzed to be 1.02dL / g.

[0104] Material storage: After the prepolymerization reaction is completed, the agitator of the prepolymerization reactor is rotated in the opposite direction, and the bottom discharge valve is opened, and the material enters the intermediate reactor through the twin-screw extruder. The intermediate reactor keeps discharging the material continuously, and when the material liquid level reaches 20%, the material in the prepolymerization reactor is transferred to the intermediate reactor, and the temperature of the intermediate reactor is maintained at 125°C.

[0105] Degassing: The prepolymer material is pumped into the degassing kettle by the metering pump at the bottom of the middle kettle. The temperature of the degassing kettle is controlled at 135°C, the reaction pressure is controlled at -0.090MPa, and the material residence time is controlled at 3.0h. After this step, the material intrinsic viscosity is measured to be 10.0dL / g.

[0106] Pre-filtration: After degassing, the material is extruded through the twin-screw extruder at the tail of the degassing kettle to the gear pump, and the material is pumped into the pre-filter.

[0107] Final polymerization: the material is sent to the final polymerization system after pre-filtration, the material residence time is controlled to be 45min, the temperature is set according to the gradient of 150℃, 160℃, 170℃, 175℃, 180℃, 185℃, 190℃, and the pressure is controlled at -0.085MPa. After this step, the material characteristic viscosity is tested by sampling and the result is 28.4dL / g.

[0108] Spinning: The material is pumped into a spinning assembly equipped with a filter screen, a distribution plate, and a spinneret (assembly) through a metering pump. The spinneret assembly is equipped with a filter screen and a distribution plate to further filter trace impurities and distribute the material to the spinneret. The filter screen has a mesh size of 100-150, the spinneret has 60 to 120 holes, and the hole diameter is 0.25 to 0.30 mm. The spinning temperature is controlled at 180-200°C, and the nozzle pressure is controlled at 4-10 MPa. The PBO fiber ejected from the spinneret enters a 30-50 cm air gap insulation layer at a temperature of 40°C to obtain PBO fiber.

[0109] Coagulation: The fiber enters a coagulation bath with a concentration of 10%, a temperature of 30°C and a length of 1.5 m for sufficient cooling.

[0110] Post-treatment: The coagulated fiber enters the post-treatment device, the washing water temperature is controlled at 40°C, the oil agent ratio is PBO-001:PBO-002:PBO-003=70:27:3, the oil agent temperature is controlled at 40°C, and the fiber is wound and collected after drying.

[0111] Embodiment 3:

[0112] Ingredients: Weigh 5.40kgPTA, 6.66kgDAR, 33.5kgPPA, 9.55kgP2O5, and 30.0g SnCl2 respectively and set aside.

[0113] Prepolymerization: Put the weighed materials into the prepolymerization kettle at one time. After the feeding is completed, nitrogen is introduced and emptied several times to maintain the pressure in the kettle at 0.25MPa. Turn on the prepolymerization agitator, control the temperature within the range of 60℃, and continue stirring for 2h. Then raise the temperature to 100℃ and continue stirring for 1.5h. Then raise the temperature to 120℃ and continue stirring for 5h. Then raise the temperature to 130℃ and continue stirring for 2h. HCl gas will be generated during this period. When the pressure in the reactor rises to 0.35MPa, the pressure is released to 0.25MPa through the pressure relief device. After the reaction is completed, the characteristic viscosity of the prepolymer material is sampled and analyzed to be 1.9dL / g.

[0114] Material storage: After the prepolymerization reaction is completed, the agitator of the prepolymerization reactor is rotated in the opposite direction, and the bottom discharge valve is opened, and the material enters the intermediate reactor through the twin-screw extruder. The intermediate reactor keeps discharging the material continuously. When the material liquid level is about to reach 20%, the material in the prepolymerization reactor is transferred to the intermediate reactor, and the temperature of the intermediate reactor is maintained at 130°C.

[0115] Degassing: The prepolymer material is pumped into the degassing kettle by the metering pump at the bottom of the middle kettle. The temperature of the degassing kettle is controlled at 140°C, the reaction pressure is controlled at -0.090MPa, and the material residence time is controlled at 3.5h. After this step, the material intrinsic viscosity is measured to be 12.5dL / g.

[0116] Pre-filtration: After degassing, the material is extruded through the twin-screw extruder at the tail of the degassing kettle to the gear pump, and the material is pumped into the pre-filter.

[0117] Final polymerization: the material is sent to the final polymerization system after pre-filtration, the material residence time is controlled to be 45min, the temperature is set according to the gradient of 150℃, 160℃, 170℃, 175℃, 180℃, 185℃, 190℃, and the pressure is controlled at -0.085MPa. After this step, the material characteristic viscosity is tested by sampling and the result is 30.2dL / g.

[0118] Spinning: The material is pumped into a spinning assembly equipped with a filter screen, a distribution plate, and a spinneret (assembly) through a metering pump. The spinneret assembly is equipped with a filter screen and a distribution plate to further filter trace impurities and distribute the material to the spinneret. The filter screen has a mesh size of 100-150, the spinneret has 60 to 120 holes, and the hole diameter is 0.25 to 0.30 mm. The spinning temperature is controlled at 180-200°C, and the nozzle pressure is controlled at 4-10 MPa. The PBO fiber ejected from the spinneret enters a 30-50 cm air gap insulation layer at a temperature of 40°C to obtain PBO fiber;

[0119] Coagulation: The fiber enters a coagulation bath with a concentration of 20%, a temperature of 30°C and a length of 1.5 m for sufficient cooling.

[0120] Post-treatment: The coagulated fiber enters the post-treatment device, the washing water temperature is controlled at 40°C, the oil agent ratio is PBO-001:PBO-002:PBO-003=80:17:3, the oil agent temperature is controlled at 40°C, and the fiber is wound and collected after drying.

[0121] Embodiment 4:

[0122] Ingredients: Weigh 5.40kgPTA, 6.66kgDAR, 33.2kgPPA, 9.60kgP2O5, and 30.0g SnCl2 respectively and set aside.

[0123] Prepolymerization: The weighed materials are put into the prepolymerization kettle at one time. After the feeding is completed, nitrogen is introduced and emptied for many times to maintain the pressure in the kettle at 0.30MPa. The prepolymerization agitator is turned on, and the temperature is controlled within the range of 60℃. Stirring is continued for 2h, and then the temperature is raised to 100℃, stirring is continued for 1.5h, and then the temperature is raised to 120℃, stirring is continued for 5h. During this period, HCl gas will be generated. When the pressure in the reactor rises to 0.35MPa, the pressure is released to 0.25MPa through the pressure relief device, and then the temperature is raised to 130℃, stirring is continued for 2h, and the vacuum state is maintained to control the reaction pressure to -0.090MPa. After the reaction is completed, the characteristic viscosity of the prepolymer material is sampled and analyzed to be 2.1dL / g.

[0124] Material storage: After the prepolymerization reaction is completed, the agitator of the prepolymerization reactor is rotated in the opposite direction, and the bottom discharge valve is opened, and the material enters the intermediate reactor through the twin-screw extruder. The intermediate reactor keeps discharging the material continuously. When the material liquid level is about to reach 20%, the material in the prepolymerization reactor is transferred to the intermediate reactor, and the temperature of the intermediate reactor is maintained at 130°C.

[0125] Degassing: The prepolymer material is pumped into the degassing kettle by the metering pump at the bottom of the middle kettle. The temperature of the degassing kettle is controlled at 140°C, the reaction pressure is controlled at -0.090MPa, and the material residence time is controlled at 4.0h. After this step, the material intrinsic viscosity is measured to be 17.8dL / g.

[0126] Pre-filtration: After degassing, the material is extruded through the twin-screw extruder at the tail of the degassing kettle to the gear pump, and the material is pumped into the pre-filter.

[0127] Final polymerization: the material is sent to the final polymerization system after pre-filtration, the material residence time is controlled to be 45min, the temperature is set according to the gradient of 150℃, 160℃, 170℃, 175℃, 180℃, 185℃, 190℃, and the pressure is controlled at -0.085MPa. After this step, the material characteristic viscosity is tested by sampling and the result is 33.4dL / g.

[0128] Spinning: The material is pumped into a spinning assembly equipped with a filter screen, a distribution plate, and a spinneret (assembly) through a metering pump. The spinneret assembly is equipped with a filter screen and a distribution plate to further filter trace impurities and distribute the material to the spinneret. The filter screen has a mesh size of 100-150, the spinneret has 60 to 120 holes, and the hole diameter is 0.25 to 0.30 mm. The spinning temperature is controlled at 180-200°C, and the nozzle pressure is controlled at 4-10 MPa. The PBO fiber ejected from the spinneret enters a 30-50 cm air gap insulation layer at a temperature of 40°C to obtain PBO fiber;

[0129] Coagulation: The fiber enters a coagulation bath with a concentration of 20%, a temperature of 30°C and a length of 1.5 m for sufficient cooling.

[0130] Post-treatment: The coagulated fiber enters the post-treatment device, the washing water temperature is controlled at 40°C, the oil agent ratio is PBO-001:PBO-002:PBO-003=80:17:3, the oil agent temperature is controlled at 40°C, and the fiber is wound and collected after drying.

[0131] Embodiment 5:

[0132] The as-spun fibers of Example 3 were subjected to densification treatment: the as-spun fibers were placed into a high-temperature densification furnace, the temperature of which was controlled at 600° C., and were wound and collected after high-temperature heat treatment.

[0133] Embodiment 6:

[0134] The as-spun fibers of Example 4 were subjected to densification treatment: the as-spun fibers were placed into a high-temperature densification furnace, the temperature of which was controlled at 600° C., and were wound and collected after high-temperature heat treatment.

[0135] Test Example 1:

[0136] Test sample: PBO fiber prepared in Examples 1-6

[0137] The PBO fibers prepared in Examples 1-6 of the present invention were tested for mechanical properties using a tensor-tensor tester. The results are shown in Table 1.

[0138] In this test, the fiber properties are tested by using the XQ-1 fiber strength and elongation tester, which is connected with the XD-1 vibration fineness tester. The instrument is produced by Shanghai Xinxian Instrument Co., Ltd. The fiber linear density is tested by the vibration method, and the breaking strength, modulus, and elongation of a single fiber are automatically calculated during the test. The fixture specifications used in the test are: 0.33cN, clamping distance: 20mm, and tensile speed 10mm / min. During the test, 30 single filament fibers of each group of samples are extracted for testing and the average value is taken.

[0139] Table 1

[0140]

[0141] In Examples 1 and 2, the mechanical properties of the fibers are low and at a medium level; in Examples 3 and 4, the fiber strength and modulus are significantly improved, achieving good performance; if more excellent performance is to be achieved, improvements can be made through Examples 5 and 6. After Examples 5 and 6, the fiber modulus is greatly improved. After comprehensive consideration of Examples 1-6, Example 6 has the best overall performance.

[0142] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing high-strength and high-modulus PBO fiber, comprising the following steps: 1) Ingredients: prepare PBO spinning solution; 2) Prepolymerization: After the PBO spinning solution is put into the prepolymerization reactor, nitrogen is introduced and emptied, stirring is started, the pressure in the reactor is maintained at <0.3Mpa, the temperature is 50-60°C, stirring is continued for 1-2h, then the temperature is raised to 90-100°C, stirring is continued for 1.5-2.0h, then the temperature is raised to 110-130°C, stirring is continued for 4-6h, and a prepolymer is obtained; 3) Material storage: reversely rotate the stirrer of the reactor in step 2), open the discharge valve at the bottom of the reactor, and the prepolymer enters the middle reactor through the twin-screw extruder, and keep the material discharged continuously. When the liquid level of the prepolymer material is about to reach 10%-20%, transfer the prepolymer in the reactor to the middle reactor, and keep the temperature of the middle reactor at 110-130°C; 4) Degassing: The prepolymer in the intermediate reactor is pumped into the degassing reactor, the temperature is controlled at 130-140°C, and the pressure is controlled at -0.085 to -0.095MPa to obtain the degassing prepolymer; 5) Pre-filtration: the defoamed prepolymer enters the pre-filter to obtain the filtered prepolymer; 6) Final polymerization: The filtered prepolymer enters the final polymerization system, under a slight vacuum state, the vacuum pressure is controlled at -0.045 to -0.085 MPa, the reaction temperature is controlled at 150-190°C, the residence time is 30-45 min, and the prepolymer is obtained; 7) Spinning: The prepolymer of step 6) is pumped into a spinning assembly equipped with a filter screen, a distribution plate, and a spinneret, the temperature is controlled at 180-200° C., and the nozzle pressure is controlled at 4-10 MPa to obtain PBO fibers; 8) Coagulation: The PBO fiber is then cooled in a coagulation bath at a temperature of 15-30°C to obtain cooled PBO fiber; 9) Post-treatment: The cooled PBO fiber is first washed with water, then oiled, dried, and then collected to obtain PBO nascent fiber.

2. The preparation method according to claim 1, characterized in that The preparation method further comprises a densification treatment, wherein the densification is: subjecting the PBO nascent fibers to a densification treatment at ≥350° C. and then winding the fibers.

3. The preparation method according to claim 2, characterized in that: The densification treatment is performed in a nitrogen atmosphere at 350-650°C.

4. The preparation method according to claim 1, characterized in that: The PBO spinning solution in step 1) comprises: 9.5-9.9wt% terephthalic acid, 11.9-12.3wt% 4,6-diaminoresorcinol hydrochloride, 58-64wt% polyphosphoric acid, 16.5-18.0wt% phosphorus pentoxide, and 0.05-0.06wt% antioxidant, preferably SnCl2.

5. The preparation method according to claim 1, characterized in that: In step 2), the pressure in the reactor is maintained at less than 0.3 MPa, which means that when the pressure in the reactor rises to 0.3-0.4 MPa, the pressure is released to 0.1-0.3 MPa.

6. The preparation method according to claim 1, characterized in that: The intrinsic viscosity of the PBO prepolymer in step 2) is 0.98-2.1 dL / g.

7. The preparation method according to claim 1, characterized in that: In step 2), a coaxial ribbon agitator is provided in the prepolymerization reactor, and preferably a spiral discharge structure is provided at the bottom of the coaxial ribbon agitator.

8. The preparation method according to claim 1, characterized in that: In step 3), a metering pump is provided at the bottom of the intermediate kettle.

9. The preparation method according to claim 1, characterized in that: The intrinsic viscosity of the prepolymer after degassing in step 4) is 8.0-18.0 dL / g.

10. The preparation method according to claim 1, characterized in that: In step 4), the degassing kettle is provided with an embedded vertical twin-screw extruder.

11. The preparation method according to claim 10, characterized in that: The degassing kettle in step 4) is a horizontal biaxial self-cleaning reactor, and preferably a vacuum pumping device is provided in the degassing kettle.

12. The preparation method according to claim 1, characterized in that: The pre-filter in step 5) is a plug-in filter.

13. The preparation method according to claim 1, characterized in that: In step 7), the spinneret assembly is provided with a filter screen and a distribution plate, wherein the filter screen has a mesh number of 100-150 meshes, the spinneret plate has 60-120 holes, and the hole diameter is 0.25-0.30 mm.

14. The preparation method according to claim 1, characterized in that: After the PBO fibers are ejected from the spinneret in step 7), the PBO fibers enter a 30-50 cm air gap insulation layer.

15. The preparation method according to claim 14, characterized in that: In step 7), the air gap layer is electrically heated and kept warm, and the temperature is controlled at 40-80°C.

16. The preparation method according to claim 1, characterized in that: In step 8), the coagulation bath is a phosphoric acid aqueous solution with a phosphoric acid concentration of 10-20 wt %, a coagulation bath temperature of 15-30° C. and a length of 1.5-2.0 m.

17. The preparation method according to claim 1, characterized in that: The water washing in step 9) is carried out by spraying from above and dipping from below, and the temperature is controlled at 30-40°C.

18. The preparation method according to claim 17, characterized in that: The oiling in step 9) is performed by using an oil of PBO-001:PBO-002:PBO-003 in a weight ratio of 70:27:3 to 90:7:3 in an oil tank at 30-40°C.

19. A high-strength and high-modulus PBO fiber prepared by the method according to any one of claims 1 to 18.

20. The high-strength and high-modulus PBO fiber according to claim 19, characterized in that: The linear density of the high-strength and high-modulus PBO fiber is 1.7-2.6 dtex.

21. The high-strength and high-modulus PBO fiber according to claim 19, characterized in that: The strength of the high-strength and high-modulus PBO fiber is ≥29.6 cN / dtex, preferably 29.6-36.0 cN / dtex.

22. The high-strength and high-modulus PBO fiber according to claim 19, characterized in that: The modulus of the high-strength and high-modulus PBO fiber is ≥855 cN / dtex, preferably 855-1700 cN / dtex.

23. The high-strength and high-modulus PBO fiber according to claim 19, characterized in that: The elongation of the high-strength and high-modulus PBO fiber is ≤3.5%, preferably 2.5-3.5%.

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