Colored poly(p-phenylene benzobisoxazole) fiber and method and system for making same

Abstract

The application discloses a kind of colored poly-p-phenylene benzobisoxazole fibers and its preparation method and system, belong to high-performance fiber material preparation field, by deconstructing PBO polymerization process, PBO primary polymer, colored PBO primary polymer, colored PBO prepolymer and colored PBO polymer are prepared in stages, and based on temperature precision control and online viscosity monitoring technology, the viscosity of each stage material is optimized and controlled, by dispersing pigment in low-viscosity PBO primary polymer system, and the viscosity change of each stage in polymerization process is synergistically controlled, effectively extend the mixing window period of PBO polymer and pigment, to realize the efficient uniform dispersion and stable dyeing of pigment.

Description

Technical Field

[0001] This invention relates to a colored poly(p-phenylenebenzodioxazole) fiber and its preparation method and system. Specifically, it relates to a highly efficient dyeing PBO fiber preparation method and supporting system based on in-situ polymerization and precise control of colorant technology, as well as the PBO fiber prepared by it with uniform coloring and excellent performance, which belongs to the field of high-performance fiber material preparation. Background Technology

[0002] Poly(p-phenylenebenzodioxazole) (PBO) fiber is a high-performance organic fiber, widely used in aerospace, special protection, and high-end composite materials due to its excellent high-temperature resistance, high strength, and high modulus. However, the high orientation and dense crystalline structure of PBO macromolecules lead to inherent dyeing defects. In traditional post-dyeing processes, dyes have difficulty penetrating the fiber interior, and the high-temperature and high-pressure environment easily damages the fiber's mechanical properties. Furthermore, the blending method of adding masterbatch before melt spinning results in uneven pigment dispersion and increased agglomerates due to the sharp increase in the dynamic viscosity of PBO resin after the mid-polymerization stage (often reaching thousands of Pa·s), ultimately affecting the fiber's color uniformity and mechanical consistency. To improve the application potential of PBO fibers in special scenarios, the preparation of PBO fibers in different colors has been a key research focus for professionals in the field.

[0003] In existing technologies, the dyeing process of PBO fibers still faces many challenges. For example, Chinese patent CN117867686A reports a dyeing method that does not change the mechanical properties of poly(p-phenylenebenzodioxazole) fibers. This method attempts to introduce pigments at the feeding stage, when the system exhibits Newtonian fluid characteristics, low initial viscosity, and good flowability. However, adding pigments too early can lead to pigment sedimentation and agglomeration due to the solvation of unpolymerized monomers, hindering pigment migration in the subsequent high-viscosity stage and affecting dyeing uniformity. In addition, Chinese patents CN115323507A and CN109778342A report coloring PBO in the post-polymerization stage through blending or in-situ doping, but neither of these methods precisely controls the viscosity of the system at the time of feeding. Once the system viscosity exceeds 200 Pa·s, the diffusion rate of pigment particles decreases by more than 90%, severely affecting dispersion uniformity. At the same time, mixing energy consumption increases sharply at high viscosity, and forced mixing can easily cause local shear overheating, leading to polymer degradation or pigment structure damage.

[0004] In the field of polyester fibers, Chinese patent CN105442078A reports a method for preparing colored polyester fibers through solution dyeing. This method involves adding organic pigments to a liquid dispersion medium (water or ethylene glycol) containing a stabilizer to obtain a colored slurry, which is then added to the system before polymerization. While this provides an efficient solution for preparing colored polyester fibers, its direct application to the dyeing of PBO (poly(p-phenylenebenzodioxazole)) fibers faces fundamental technical barriers, as it is difficult to adapt to the unique polymerization system and product characteristics of PBO. Specifically, the liquid dispersion medium, including water or ethylene glycol, can react upon introduction into the system, severely disrupting the polymerization equilibrium or causing uncontrollable side reactions, thus affecting the final quality of the PBO polymer product.

[0005] In summary, existing dyeing technologies for both PBO and polyester fibers have fundamental limitations in achieving efficient and stable dyeing of PBO fibers. During the dyeing process of PBO fibers, pigments tend to settle at low viscosity levels, while migration is hindered and dispersion is difficult at high viscosity levels, and precise control over the critical viscosity window is lacking. Furthermore, the solution dyeing method for polyester fibers, due to the use of reactive media, is not compatible with the PBO polymerization system. Therefore, from a technical perspective, existing methods struggle to achieve efficient, uniform, and stable dispersion of colorants while maintaining the intrinsic properties of PBO fibers. Summary of the Invention

[0006] The purpose of this invention is to provide a colored poly(p-phenylenebenzodioxazole) fiber and its preparation method and system. This method deconstructs the PBO polymerization process to obtain PBO primary polymer, colored PBO primary polymer, colored PBO prepolymer and colored PBO polymer in stages. Based on precise temperature control and online viscosity monitoring technology, the viscosity of materials at each stage is optimized and controlled. By dispersing the pigment in a low-viscosity PBO primary polymer system and synergistically controlling the viscosity changes at each stage of the polymerization process, the mixing window period of PBO polymer and pigment is effectively extended, thereby achieving efficient and uniform dispersion of pigment and stable dyeing.

[0007] This invention is achieved through the following technical solution: a method for preparing colored poly(p-phenylenebenzodioxazole) fibers, comprising the following steps:

[0008] S1. Using 4,6-diaminoresorcinol hydrochloride and terephthalic acid as raw materials, and polyphosphoric acid and phosphorus pentoxide as solvents, PBO primary polymers were obtained by degassing and activation. The reaction temperature was controlled at 60-120℃, and the dynamic viscosity of the PBO primary polymers was 100-200 Pa•s.

[0009] S2. Pigment and polyphosphoric acid were added to the PBO primary polymer, and the colored PBO primary polymer was obtained by vacuum degassing. The reaction temperature was controlled at 60-130℃, and the dynamic viscosity of the colored PBO primary polymer was 100-300 Pa•s.

[0010] S3. A colored PBO prepolymer is prepared by prepolymerization reaction of colored PBO primary polymer in a single-stage screw mill, with the reaction temperature controlled at 120-150℃ and the dynamic viscosity of the colored PBO prepolymer being 300-800 Pa•s.

[0011] S4. A colored PBO prepolymer and residual terephthalic acid are subjected to a post-polymerization reaction in a two-stage screw compressor to obtain a colored PBO polymer. The reaction temperature is controlled at 150-200℃, and the dynamic viscosity of the colored PBO polymer is above 1000 Pa•s.

[0012] S5. Colored PBO fibers are obtained by spinning colored PBO polymer.

[0013] In steps S1 to S4, the stirring speed during degassing and activation is controlled to be 30–80 r / min, and the stirring speed during vacuum degassing is controlled to be 10–30 r / min.

[0014] In steps S1 to S4, the ratio of the total molar amount of terephthalic acid added to the molar amount of 4,6-diaminoresorcinol hydrochloride added is 0.97 to 1.05:1.

[0015] In step S2, the pigment and polyphosphoric acid are mixed, dissolved and dispersed at 60–130°C, and then mixed with the PBO primary polymer. The mixture is then degassed at 60–130°C and -0.08–0 MPa for 2–6 hours.

[0016] In step S2, the mass concentration of the pigment is 1.0–10.0%, and the amount of pigment added is 1.5–6% of the PBO primary polymer.

[0017] The pigments include organic pigments, inorganic pigments, or combinations thereof.

[0018] In step S3, the intrinsic viscosity of the colored PBO prepolymer is 5–15 dl / g.

[0019] In step S4, the intrinsic viscosity of the colored PBO polymer is 18–32 dl / g, and the solid content is 10–14%.

[0020] Furthermore, the present invention also includes a system for preparing colored poly(p-phenylenebenzodioxazole) fibers using the above-described preparation method, comprising a polymerization reactor, a primary screw extruder, a secondary screw extruder, and a spinning assembly.

[0021] The polymerization reactor performs steps S1 and S2, and uses the stirring system of the polymerization reactor to control the temperature of the material system, and uses an online monitoring system to monitor the dynamic viscosity of the material.

[0022] The primary screw compressor performs the S3 step operation and uses an online monitoring system to monitor the reaction temperature and material dynamic viscosity.

[0023] The secondary screw compressor performs the S4 step operation and uses an online monitoring system to monitor the reaction temperature and material dynamic viscosity;

[0024] The spinning assembly performs step S5.

[0025] A colored poly(p-phenylenebenzodioxazole) fiber is prepared by the above-described preparation method or by the above-described system. The colored fiber obtained satisfies the following requirements: breaking strength of 25-36 CN / dtex; tensile modulus of 145-200 GPa; and color fastness of 4-5.

[0026] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0027] (1) This invention relies on an equipment system and employs a polymerization reactor with controllable stirring speed. By synergistically regulating temperature, speed, and system viscosity, it precisely controls the entire process from monomer mixing, degassing and activation, vacuum degassing, to the introduction of pigments and the achievement of high-speed and efficient mixing within a specific low-viscosity window. After this, the system can smoothly transport the colored primary polymer with significantly increased viscosity, allowing it to pass through a primary screw compressor and a secondary screw compressor in sequence: the primary polymer is further mixed and reacted in the primary screw compressor to generate a colored prepolymer; the polymerization is finally completed in the secondary screw compressor to obtain a high-quality colored PBO polymer.

[0028] (2) By precisely intervening in the prepolymer reaction stage, this invention selects specific process nodes to add pigments and mix them, simultaneously achieving uniform dyeing of materials and effective control of system viscosity. This process ensures that pigment particles are fully encapsulated within the polymer body, rather than merely physically adhering to the surface, thereby endowing the resulting colored fibers with excellent color fastness, including resistance to soap washing, perspiration, and abrasion. At the same time, the product has uniform coloring with no color difference between batches, making it particularly suitable for continuous and large-scale industrial production.

[0029] (3) The present invention integrates the coloring process into the polymerization reaction, and constructs an integrated continuous production process of "polymerization-coloring-spinning". Compared with the traditional fiber dyeing technology, the production process of the present invention significantly shortens the overall process flow, reduces production energy consumption, and fundamentally avoids the generation of dyeing wastewater, which has outstanding environmental and economic benefits.

[0030] (4) This invention innovatively utilizes polyphosphoric acid (PPA) from the PBO polymerization system itself as a solvent to pre-prepare a pigment / polyphosphoric acid solution. Through precise temperature control, the viscosity of the colorant solution can be matched with the viscosity of the PBO primary polymer during the addition window, thereby greatly improving the compatibility between the two and achieving efficient and uniform mixing and dispersion of the colorant.

[0031] (5) The process of this invention can maintain the inherent ultra-high performance of PBO fibers to the maximum extent, specifically including the coordinated use of the following control measures:

[0032] a. Strictly control the proportion of pigments in the polymer;

[0033] b. Select fiber-grade pigments to ensure they can be fully dissolved or uniformly dispersed in the system at the nanoscale;

[0034] c. Achieve stability screening of pigment components, ensuring that the selected pigment components are insoluble in coagulation baths and water systems, and that their temperature resistance is higher than 200℃;

[0035] d. Ensure uniform dispersion of pigments after addition by controlling the viscosity window period appropriately;

[0036] e. Use low-solids polymer formulations to ensure that colored polymer materials have good spinnability.

[0037] (6) In this invention, dyeing is completed in the prepolymerization stage, and the pigment is uniformly dissolved and dispersed in the polymer system. This solution avoids problems such as uneven dispersion, pigment precipitation, and component blockage that may be caused by adding pigment in the postpolymerization stage, thereby effectively preventing phenomena such as fiber breakage and fiber drift during the spinning process, and significantly improving spinning stability and production efficiency.

[0038] (7) This invention supports the flexible combination of organic and inorganic pigments, which can produce PBO fibers in a variety of colors. This feature greatly enriches the product portfolio and can meet the diverse needs of downstream fields such as high-end fire suits, military camouflage, special ropes, and outdoor tents for high-performance colored fibers. Attached Figure Description

[0039] Figure 1 This is a sample photo of the high-performance colored PBO fiber 1# prepared in Example 1 of the present invention.

[0040] Figure 2 These are comparative photos of the high-performance colored PBO fiber 1# of Embodiment 1 of the present invention before and after the color fastness test. Detailed Implementation

[0041] The invention's objective, technical solution, and beneficial effects will be further explained in detail below.

[0042] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the claimed invention. Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0043] Efficient control of the PBO polymerization process is a highly challenging task. Throughout the polymerization process, the system viscosity exhibits a typical three-stage variation (initiation stage, prepolymerization stage, and postpolymerization stage). In the initiation stage, premature addition of pigments can lead to pigment sedimentation and agglomeration due to the solvation of unpolymerized monomers, hindering pigment migration in the subsequent high-viscosity stage. Furthermore, the degassing process can carry pigment particles out of the polymerization system, causing imbalances in the proportions and polluting the exhaust gas treatment system. In the postpolymerization stage, with the formation of the liquid crystal phase, the system viscosity rises sharply to over 1000 Pa·s, resulting in a drastic drop in mixing efficiency and a significant decrease in pigment particle diffusion rate, severely affecting color uniformity. In contrast, the prepolymerization stage constitutes a "window" for pigment addition. With the completion of degassing and activation, the viscosity of the PBO polymer gradually rises to approximately 800 Pa·s. At this point, through reasonable process and formulation design, the shear force provided by the medium-viscosity fluid can be utilized to achieve efficient and uniform mixing of the pigment and polymer.

[0044] Regarding the definition of the "polymer window": This window is not a single point in time, but rather a specific time interval after degassing and activation, during which a low-viscosity primary polymer with a viscosity between 100 and 200 Pa·s is formed. By controlling the temperature to slow down the polymerization process, the time the system remains within this viscosity range can be extended. Furthermore, the addition of pigment solution further reduces the monomer concentration, thereby extending the process window available for mixing. Adding pigment earlier than this window will result in the various problems associated with the aforementioned initiation stage; adding it later will lead to challenges such as decreased dyeing effectiveness due to extremely high viscosity in the later polymerization stages.

[0045] Existing technologies generally do not control viscosity as a core process parameter, causing the timing of pigment addition to deviate from optimal hydrodynamic conditions. Therefore, based on years of engineering research experience in the PBO polymerization process, this invention systematically breaks down the characteristics of each stage of polymerization, clarifies the suitable viscosity window for pigment addition, and aims to provide an efficient and reliable method for preparing colored PBO fibers.

[0046] Specifically, this invention constructs a low-solids content reaction system (polymer content 10-14%, pigment content 1.0-6.0% in the polymer) through a specific formulation design. After degassing and activation in the prepolymerization stage, the viscosity of the system is monitored online. When the material viscosity is in the range of 100-200 Pa·s, the reaction process is controlled by a temperature-controlled stirred tank (temperature 60-130℃) to ensure that the pigment solution is added under low viscosity conditions and temperature control, achieving efficient mixing in a short time. The introduction of the pigment solution not only completes the dyeing but also further extends the mixing window by reducing the concentration of the reactants. After uniform dyeing and vacuum degassing, colored PBO primary polymer is obtained. Subsequently, using the special feeding design of the stirred tank, the material is controllably extruded into the subsequent primary and secondary twin-screw extruders under low temperature and low speed conditions to complete the polymerization reaction. Finally, the material is spun, washed, dried, and wound to obtain colored PBO fibers with excellent color fastness.

[0047] The technical solution of the present invention is further summarized below:

[0048] Step 1: Degassing and Activation

[0049] In a polymerization reactor, polyphosphoric acid, phosphorus pentoxide, terephthalic acid (TPA), and 4,6-diaminoresorcinol hydrochloride (DAR) are added sequentially according to the raw material ratio. Nitrogen is used to replace the air in the reactor, and the temperature of the system inside the reactor is heated to 60-120°C. At the same time, the stirring speed is increased to 30-80 r / min. The temperature and stirring speed of the system inside the reactor are maintained, and the degassing reaction is carried out for 1-6 hours to obtain PBO primary polymer. The dynamic viscosity of the PBO primary polymer is fed back in real time through an online monitoring system.

[0050] In this step, both polyphosphoric acid and phosphorus pentoxide are used as solvents, and their mass ratio with DAR is typically 2.0–5.0:1.0–2.0:1.0. Terephthalic acid (TPA) and 4,6-diaminoresorcinol hydrochloride (DAR) are the polymerization monomers. Terephthalic acid (TPA) is added in two separate steps during degassing activation and post-polymerization. The ratio of the total molar amount of terephthalic acid added to the molar amount of 4,6-diaminoresorcinol hydrochloride added should be controlled within 0.97–1.05:1.

[0051] Step 2: Prepolymerization

[0052] Continue to maintain the stirring speed and heating temperature of the polymerization reactor. When the dynamic viscosity of the PBO primary polymer in the reactor is 100-200 Pa·s, add pigment and polyphosphoric acid solution, and control the temperature of the system in the reactor at 60-130℃. Stir at high speed (30-80 r / min) for 1-5 hours, then adjust the material temperature and stir at low speed (10-30 r / min). Degas at -0.08-0 MPa for 2-6 hours to obtain colored PBO primary polymer. The dynamic viscosity of the colored PBO primary polymer is fed back in real time through an online monitoring system. At this time, the dynamic viscosity of the colored PBO primary polymer is in the range of 100-300 Pa·s. The colored PBO primary polymer was fed into a single-stage twin-screw extruder for further polymerization and mixing. The reaction temperature of the single-stage twin-screw extruder was controlled at 120–150°C, and the rotation speed was 10–40 r / min. The material was kept in the single-stage twin-screw extruder for 1.0–2.0 h. After the prepolymerization reaction was completed, the colored PBO prepolymer was obtained. At this time, the dynamic viscosity of the colored PBO primary polymer was in the range of 300–800 Pa·s, and the intrinsic viscosity was in the range of 5–15 dl / g.

[0053] The pigment and polyphosphoric acid solution added in this step can be prepared beforehand. For example, in a mixing vessel, polyphosphoric acid and pigment are added sequentially, and they are mixed, dissolved, and dispersed at 60–130°C to form a pigment solution with a concentration of 1.0–10.0%. Then, a vacuum is applied, and the mixture is stirred at low speed until ready for use. The amount of pigment added is 1.5–6% of the PBO primary polymer, and it can be added after measurement.

[0054] Optionally, the pigments may be organic pigments, inorganic pigments, or a combination of both. Among them, organic pigments include, but are not limited to: phthalocyanine, anthraquinone, quinacridone, azo, dioxazine, and isoindolineone pigments; inorganic pigments include, but are not limited to: carbon black, cadmium-based pigments, chromate pigments, and iron oxide-based pigments.

[0055] Step 3: Post-polymerization

[0056] The colored PBO prepolymer prepared in the above steps and the remaining terephthalic acid are fed into a two-stage twin-screw extruder. The reaction temperature of the two-stage twin-screw extruder is controlled at 150-200℃, the rotation speed is 10-30 r / min, and the material is held in the two-stage twin-screw extruder for 1.0-3.0 h. After the polymerization reaction is completed, the colored PBO polymer is obtained. At this time, the dynamic viscosity of the colored PBO polymer is greater than 1000 Pa·s, the intrinsic viscosity is 18-32 dl / g, and the solid content is 10-14%.

[0057] Step 4: Spinning

[0058] The colored PBO polymer prepared in the above steps is fed into a spinning assembly for spinning to obtain high-performance PBO fibers with the following properties: breaking strength of 25-36 CN / dtex; tensile modulus of 145-200 GPa; and color fastness of 4-5.

[0059] In this invention, the polymerization reactor is responsible for performing steps one and two, and uses its stirring system to control the temperature of the material system. Simultaneously, an online monitoring system monitors the dynamic viscosity of the material in real time. Specifically, this online monitoring system can employ a stirring device as described in ZL2021104821464, which, under the same process temperature and stirring speed conditions, indirectly reflects the dynamic viscosity range of the polymer based on the current range corresponding to the stirring load. Steps three and four are performed by a primary screw compressor and a secondary screw compressor, respectively. Both are also equipped with online monitoring systems to monitor the reaction temperature and the dynamic viscosity of the material. Specifically, this online monitoring system can employ a temperature and pressure sensor as described in ZL2022105855725, which records the temperature and pressure of the polymer in real time, thereby monitoring changes in its dynamic viscosity. It should be noted that, under the same conveying temperature conditions, differences in the dynamic viscosity of the polymer will be directly reflected in changes in the pressure data measured by the temperature and pressure sensor.

[0060] The specific implementation of the present invention will be described below with reference to the embodiments. Of course, the scope of protection of the present invention is not limited to the following embodiments.

[0061] The equipment and testing methods used in this embodiment are as follows:

[0062] The polymerization reaction was carried out using the stirred tank described in patent ZL202521636284.3; both the primary and secondary screw extruders were twin-screw extruders. The spinning process employed existing wet spinning or dry-jet wet spinning equipment. The dynamic viscosity and intrinsic viscosity of the materials were measured using a rotational viscometer and an Ubbelohde viscometer, respectively.

[0063] Fiber performance testing is conducted in accordance with the following national standards:

[0064] The tests for breaking strength and tensile modulus shall be conducted in accordance with GB / T 19975-2005; the tests for color fastness to washing with soap shall be conducted in accordance with GB / T3921-2008; the tests for color fastness to perspiration shall be conducted in accordance with GB / T 3922-2008; and the tests for color fastness to dry / wet rubbing shall be conducted in accordance with GB / T3920-2008.

[0065] Example 1:

[0066] In a 50L mixing vessel, add 58.000 kg of polyphosphoric acid (PPA), 1.500 kg of phthalocyanine blue pigment, and 0.5 kg of purple pigment. Stir at 60–120°C for 4 hours to prepare a pigment solution with a concentration of 3.33%. Then, evacuate the vessel and stir at low speed until ready for use.

[0067] In a 600L stirred tank, 143.000 kg of polyphosphoric acid (PPA), 56.300 kg of phosphorus pentoxide (P2O5), 25.900 kg of terephthalic acid (TPA), and 35.000 kg of 4,6-diaminoresorcinol hydrochloride (DAR) were added sequentially. The air inside the tank was purged with nitrogen. The system temperature was then gradually increased to 70°C, and the stirring speed was increased to 60 rpm. The polymerization system temperature was maintained at 70℃ for degassing reaction for 5 hours. Then, the temperature was raised to 80℃ and the dynamic viscosity range of the polymer material was fed back online by stirring current. It was confirmed that the viscosity of the polymer system material was in the range of 100-200 Pa·s. Then, 60.000 kg of 3.33% pigment solution was fed into the stirred tank through a metering pump. The stirred tank was mixed at high speed (60 r / min) for 2 hours under the temperature control of 80℃. Then, the stirring speed was reduced (20 r / min) and degassing was performed under vacuum (-0.05 MPa) for 2 hours to obtain colored PBO primary polymer. At this time, the dynamic viscosity of the colored PBO primary polymer was fed back online by stirring current in the range of 100-300 Pa·s.

[0068] The colored PBO prepolymer is fed into a first-stage twin-screw extruder for further polymerization and mixing via a single screw extruder and a precision metering pump at the bottom of the stirred tank. The reaction temperature is 120–150°C, the material residence time in the first-stage twin-screw extruder is 1.5 hours, and the rotation speed is 30 r / min. After the prepolymerization reaction is completed, the dynamic viscosity of the colored PBO prepolymer is within the range of 300–800 Pa·s, as measured online by temperature and pressure sensors.

[0069] The colored PBO prepolymer and residual terephthalic acid are fed into a two-stage twin-screw extruder using a precision metering pump. The polymerization reaction temperature is controlled within the range of 150–200°C. The residence time of the material in the two-stage twin-screw extruder is 1.5 hours, and the rotation speed is 20 r / min. After the polymerization reaction is completed, the dynamic viscosity of the colored PBO polymer is greater than 1000 Pa·s. Then, it is conveyed to the spinning assembly for spinning to obtain high-performance colored PBO fiber #1.

[0070] Comparative Example 1:

[0071] This comparative example serves as a control experiment for Example 1, and its preparation process is as follows:

[0072] In a 600L stirred tank, 143.000 kg of polyphosphoric acid (PPA), 56.300 kg of phosphorus pentoxide (P2O5), 25.900 kg of terephthalic acid (TPA), and 35.000 kg of 4,6-diaminoresorcinol hydrochloride (DAR) were added sequentially. Then, 60.000 kg of a pre-prepared 3.33% pigment solution was pumped into the stirred tank. Nitrogen was used to purge the air from the tank, and the system temperature was gradually increased to 70°C while increasing the stirring speed to 60 r / min. The polymerization system was maintained at 70°C for 5 hours for degassing. The mixture was then heated to 80°C and stirred at 60 r / min for 2 hours. Finally, the stirring speed was reduced to 20 r / min and degassed under vacuum (-0.05 MPa) for 2 hours to obtain the colored PBO primary polymer.

[0073] The colored PBO prepolymer is then fed into a first-stage twin-screw extruder for further polymerization and mixing via a single screw extruder and a precision metering pump at the bottom of the stirred tank. The reaction temperature is 120–150°C, the material residence time in the first-stage twin-screw extruder is 1.5 h, and the rotation speed is 30 r / min. After the prepolymerization reaction is completed, the colored PBO prepolymer is obtained.

[0074] The colored PBO prepolymer and residual terephthalic acid are fed into a two-stage twin-screw extruder using a precision metering pump. The polymerization reaction temperature is controlled within the range of 150–200°C. The material residence time in the two-stage twin-screw extruder is 1.5 hours, and the rotation speed is 20 r / min. After the polymerization reaction is completed, the colored PBO polymer is obtained. It is then conveyed to the spinning assembly for spinning to produce colored PBO fiber #1.

[0075] The high-performance colored PBO fiber 1# prepared in Example 1 was compared with the colored PBO fiber 1# in Comparative Document 1, including the finished fiber color (visual inspection), fiber intrinsic viscosity, breaking strength, tensile modulus, and color fastness. The test results are shown in Table 1 below. Figure 1 and Figure 2 As shown.

[0076] Table 1. Comparison of fibers between Example 1 and Comparative Document 1

[0077]

[0078] As shown in Table 1, Example 1 of this invention achieves efficient mixing and coloring in a short time by adding the pigment solution during a specific window period (i.e., after degassing and activation are completed, and a low-viscosity primary polymer with a viscosity between 100 and 200 Pa•s). Both phthalocyanine blue and purple pigments effectively play their roles, successfully producing deep blue PBO fibers (see Table 1). Figure 1 The batch exhibits uniform coloring, minimal color difference, good polymer spinnability, high fiber strength, and excellent color fastness (see...). Figure 2Because pigment solution was added during the feeding stage in Comparative Example 1, the viscosity of the pigment solution and the unmixed material system did not match. After the pigment solution and the unpolymerized monomer powder were mixed, sedimentation and agglomeration were observed. A large number of agglomerated large particles were found in the filter. Due to the uneven mixing of pigments, the system pressure fluctuated frequently, the spinning stability was poor, the fineness of the prepared fibers was uneven, the color difference was large, and the fiber performance indicators were low.

[0079] Example 2:

[0080] In a 50L mixing vessel, add 58.000 kg of polyphosphoric acid (PPA), 1.500 kg of phthalocyanine blue pigment, 0.5 kg of purple pigment, and 0.1 kg of nano carbon black. Stir at 60~120℃ for 4 hours to prepare a pigment solution with a concentration of 3.5%. Then, vacuum the solution and stir at low speed until ready for use.

[0081] In a 600L stirred tank, 143.000 kg of polyphosphoric acid (PPA), 56.300 kg of phosphorus pentoxide (P2O5), 25.900 kg of terephthalic acid (TPA), and 35.000 kg of 4,6-diaminoresorcinol hydrochloride (DAR) were added sequentially. The air inside the tank was purged with nitrogen. The system temperature was then gradually increased to 70°C, and the stirring speed was increased to 60 rpm. The polymerization system temperature was maintained at 70℃ for degassing reaction for 5 hours. Then, the temperature was raised to 80℃ and the dynamic viscosity range of the polymer material was fed back online by stirring current to confirm that the viscosity of the polymer system material was in the range of 100-200 Pa·s. Then, 60-100 kg of the pre-prepared 3.50% pigment solution was sent into the stirred tank by metering pump. The stirred tank was mixed at high speed (60 r / min) for 2 hours under the condition of 80℃ controlled temperature. Then, the stirring speed was reduced (20 r / min) and degassing was performed under vacuum (-0.05 MPa) for 2 hours to obtain colored PBO primary polymer. At this time, the dynamic viscosity of the colored PBO primary polymer was fed back online by stirring current to the range of 100-300 Pa·s.

[0082] The colored PBO prepolymer is fed into a first-stage twin-screw extruder for further polymerization and mixing via a single screw extruder and a precision metering pump at the bottom of the stirred tank. The reaction temperature is 120–150°C, the material residence time in the first-stage twin-screw extruder is 1.5 hours, and the rotation speed is 30 r / min. After the prepolymerization reaction is completed, the dynamic viscosity of the colored PBO prepolymer is within the range of 300–800 Pa·s, as measured online by temperature and pressure sensors.

[0083] The colored PBO prepolymer and residual terephthalic acid are fed into a two-stage twin-screw extruder using a precision metering pump. The polymerization reaction temperature is controlled within the range of 150~200℃, the material residence time in the two-stage twin-screw extruder is 1.5h, and the rotation speed is 20r / min. After the polymerization reaction is completed, the dynamic viscosity of the colored PBO polymer is greater than 1000 Pa·s. Then it is fed to the spinning assembly for spinning to obtain high-performance colored PBO fiber #2.

[0084] Comparative Example 2:

[0085] This comparative example serves as a control experiment for Example 2, and its preparation process is as follows:

[0086] In a 600L stirred tank, 143.000 kg of polyphosphoric acid (PPA), 56.300 kg of phosphorus pentoxide (P2O5), 25.900 kg of terephthalic acid (TPA) (accounting for 95% of the total TPA feed), and 35.000 kg of 4,6-diaminoresorcinol hydrochloride (DAR) were added sequentially. The air in the tank was replaced with nitrogen, and then the system temperature was gradually increased to 70℃ and the stirring speed was increased to 60 r / min. The polymerization system temperature was maintained at 70℃ for degassing reaction for 5 h. Then, the temperature was raised to 80℃ and the mixture was mixed at high speed (60 r / min) for 2 h under controlled temperature conditions. Then, the stirring speed was reduced (20 r / min) and the mixture was degassed under vacuum (-0.05 MPa) for 2 h to obtain the PBO primary polymer.

[0087] The PBO prepolymer is fed into a first-stage twin-screw extruder for further polymerization and mixing via a single screw extruder and a precision metering pump at the bottom of the stirred tank. The reaction temperature is 120–150°C, the material residence time in the first-stage twin-screw extruder is 1.5 h, and the rotation speed is 30 r / min. After the prepolymerization reaction is completed, the PBO prepolymer is obtained.

[0088] The PBO prepolymer and residual terephthalic acid are fed into a secondary twin-screw extruder using a precision metering pump. Then, 60-100 kg of a pre-prepared 3.50% pigment solution is added to the secondary twin-screw extruder using another metering pump. The polymerization reaction temperature is controlled within the range of 150-200°C, the material residence time in the secondary twin-screw extruder is 1.5 hours, and the rotation speed is 20 r / min. After the polymerization reaction is complete, a colored PBO polymer is obtained. This polymer is then fed to a spinning assembly for spinning to produce colored PBO fiber #2.

[0089] The high-performance colored PBO fiber 2# prepared in Example 2 was compared with the colored PBO fiber 2# in Comparative Document 2. The comparison included the finished fiber color (visual inspection), fiber intrinsic viscosity, breaking strength, tensile modulus and color fastness. The test results are shown in Table 2 below.

[0090] Table 2. Fiber comparison between Example 2 and Comparative Document 2

[0091]

[0092] As shown in Table 2, Example 2 of this invention uses three pigments added during the designed viscosity window for in-situ polymerization and dyeing, fully utilizing the pigment synergy effect to produce navy blue PBO fibers. The polymer has good spinnability, small color difference within batches, and high fiber performance indicators. In contrast, Comparative Example 2 uses the same pigments added during the post-polymerization stage for dyeing. Analysis of the finished fiber color shows that only a portion of the phthalocyanine blue pigment exerted its dyeing effect, resulting in blue-green PBO fibers. During the twin-screw mixing process of the high-viscosity polymer and the low-viscosity pigment solution, the purple pigment, which has relatively low solubility, precipitated due to uneven mixing, and the carbon black pigment easily agglomerated due to insufficient mixing efficiency. This resulted in poor spinnability, such as fiber breakage and filament drift, during the spinning process, further verifying the limitations of adding pigment solution for dyeing during the post-polymerization process.

[0093] Example 3:

[0094] In a 50L mixing vessel, add 57.800 kg of polyphosphoric acid (PPA) and 2.200 kg of phthalocyanine blue pigment. Stir at 60~120℃ for 2 hours to prepare a phthalocyanine blue pigment solution with a concentration of 3.67%. Then, evacuate the vessel and stir at low speed until ready for use.

[0095] In a 600L stirred tank, 143.000 kg of polyphosphoric acid (PPA), 56.300 kg of phosphorus pentoxide (P2O5), 25.900 kg of terephthalic acid (TPA), and 35.000 kg of 4,6-diaminoresorcinol hydrochloride (DAR) were added sequentially. The air in the tank was purged with nitrogen, and then the system temperature was gradually increased to 70℃ while the stirring speed was increased to 60 r / min. The polymerization system temperature was maintained at 70℃ for 5 hours for degassing reaction. Then, the temperature was raised to 80℃ and the dynamic viscosity range of the polymer material was fed back online by the stirring current to confirm that the viscosity of the polymer system material was in the range of 100-200 Pa·s. Then, 60,000 kg of a pre-prepared 3.67% phthalocyanine blue pigment solution was fed into a stirred tank using a metering pump. The mixture was stirred at high speed (60 r / min) for 2 hours under controlled temperature of 80℃. Then, the stirring speed was reduced (20 r / min) and the mixture was degassed under vacuum (-0.05 MPa) for 2 hours to obtain the colored PBO primary polymer. At this time, the dynamic viscosity of the colored PBO primary polymer was found to be in the range of 100 to 300 Pa·s, as indicated by the online feedback of the stirring current.

[0096] The colored PBO prepolymer is fed into a first-stage twin-screw extruder for further polymerization and mixing via a single screw extruder and a precision metering pump at the bottom of the stirred tank. The reaction temperature is 120–150°C, the residence time of the material in the first-stage twin-screw extruder is 1.5 hours, and the rotation speed is 30 r / min. After the prepolymerization reaction is completed, the dynamic viscosity of the colored PBO prepolymer is in the range of 300–800 Pa·s, as measured online by temperature and pressure sensors.

[0097] The colored PBO prepolymer and residual terephthalic acid are fed into a two-stage twin-screw extruder using a precision metering pump. The polymerization reaction temperature is controlled within the range of 150–200°C. The material residence time in the two-stage twin-screw extruder is 1.5 hours, and the rotation speed is 20 r / min. After the polymerization reaction is completed, the dynamic viscosity of the colored PBO polymer is greater than 1000 Pa·s. Then, it is conveyed to the spinning assembly for spinning to obtain high-performance colored PBO fiber #3.

[0098] Example 4:

[0099] In a 50L mixing vessel, add 59.000 kg of polyphosphoric acid (PPA) and 1.000 kg of phthalocyanine blue pigment. Stir at 60~120℃ for 2 hours to prepare a 1.67% phthalocyanine blue pigment solution. Then, evacuate the vessel and stir at low speed until ready for use.

[0100] In a 600L stirred tank, 143.000 kg of polyphosphoric acid (PPA), 56.300 kg of phosphorus pentoxide (P2O5), 25.900 kg of terephthalic acid (TPA) (accounting for 95% of the total TPA feed), and 35.000 kg of 4,6-diaminoresorcinol hydrochloride (DAR) were added sequentially. The air inside the tank was purged with nitrogen. The system temperature was then gradually increased to 70℃, and the stirring speed was increased to 60 r / min. The polymerization system was maintained at 70℃ for 5 hours for degassing. The temperature was then raised to 80℃, and the viscosity of the polymer was confirmed to be within the range of 100–200 Pa·s by online feedback of the stirring current. Then, 60.000 kg of a pre-prepared 1.67% phthalocyanine blue pigment solution was pumped into the stirred tank. The mixture was mixed at high speed (60 r / min) for 2 hours under controlled temperature (80℃). The stirring speed was then reduced to 20 r / min. The colored PBO primary polymer was obtained by degassing under vacuum (-0.05 MPa) for 2 hours at a speed of r / min. The dynamic viscosity of the colored PBO primary polymer was found to be in the range of 100 to 300 Pa·s by online feedback of the stirring current.

[0101] The colored PBO prepolymer is fed into a first-stage twin-screw extruder for further polymerization and mixing via a single screw extruder and a precision metering pump at the bottom of the stirred tank. The reaction temperature is 120–150°C, the residence time of the material in the first-stage twin-screw extruder is 1.5 hours, and the rotation speed is 30 r / min. After the prepolymerization reaction is completed, the dynamic viscosity of the colored PBO prepolymer is in the range of 300–800 Pa·s, as fed back online by temperature and pressure sensors.

[0102] The colored PBO prepolymer and residual terephthalic acid are fed into a two-stage twin-screw extruder using a precision metering pump. The polymerization reaction temperature is controlled within the range of 150–200°C. The material residence time in the two-stage twin-screw extruder is 1.5 hours, and the rotation speed is 20 r / min. After the polymerization reaction is completed, the dynamic viscosity of the colored PBO polymer is greater than 1000 Pa·s. It is then conveyed to the spinning assembly for spinning to obtain high-performance colored PBO fiber #4.

[0103] Comparative Example 3:

[0104] This comparative example serves as a control experiment for Example 3, and its preparation process is as follows:

[0105] In a 600L stirred tank, 143.000 kg of polyphosphoric acid (PPA), 56.300 kg of phosphorus pentoxide (P2O5), 25.900 kg of terephthalic acid (TPA) (accounting for 95% of the total TPA feed), and 35.000 kg of 4,6-diaminoresorcinol hydrochloride (DAR) were added sequentially. The air in the tank was replaced with nitrogen, and then the system temperature was gradually increased to 70℃ while the stirring speed was increased to 60 r / min. The polymerization system temperature was maintained at 70℃ for degassing reaction for 5 hours. Then the temperature was raised to 80℃, and the mixture was mixed at high speed (60 r / min) for 2 hours under the temperature control of 80℃ in the stirred tank. Then the stirring speed was reduced to 20 r / min and degassing was performed under vacuum (-0.05 MPa) for 2 hours to obtain a colored PBO primary polymer, thus obtaining the polymer system.

[0106] The colored PBO prepolymer was then fed into a first-stage twin-screw extruder for further polymerization and mixing via a single screw extruder and a precision metering pump at the bottom of the stirred tank. Simultaneously, 60,000 kg of a pre-prepared 1.67% phthalocyanine blue pigment solution was added to the first-stage twin-screw extruder via a metering pump. The reaction temperature was 120–150°C, the material residence time in the first-stage twin-screw extruder was 1.5 h, and the rotation speed was r / min. After the prepolymerization reaction was completed, the colored PBO prepolymer was obtained.

[0107] The PBO prepolymer and residual terephthalic acid are fed into a two-stage twin-screw extruder using a precision metering pump. The polymerization reaction temperature is controlled within the range of 150–200°C. The material residence time in the two-stage twin-screw extruder is 1.5 hours, and the rotation speed is 20 r / min. After the polymerization reaction is completed, a colored PBO polymer is obtained. It is then fed to the spinning assembly for spinning to produce colored PBO fiber #3.

[0108] The high-performance colored PBO fibers 3# and 4# prepared in Examples 3 and 4 were compared with the colored PBO fiber 3# in Comparative Document 3. The comparison included the finished fiber color (visual inspection), fiber intrinsic viscosity, breaking strength, tensile modulus and color fastness. The test results are shown in Table 3 below.

[0109] Table 3. Fiber comparison between Examples 3 and 4 and Comparative Document 3

[0110]

[0111] As shown in Table 3, Example 3 of this invention uses a relatively large amount of phthalocyanine blue pigment for dyeing, resulting in blue PBO fibers with good polymer spinnability, small color difference within batches, and high fiber performance indicators. Example 4 of this invention uses a relatively small amount of phthalocyanine blue pigment for dyeing, resulting in dark green PBO fibers with good polymer spinnability, small color difference within batches, and high fiber performance indicators. Both examples demonstrate the effectiveness of successfully preparing PBO fibers of the desired color by rationally adding pigment during a specific window period. In contrast, Comparative Example 3 uses pigment added to the first-stage screw. The results show that, compared to Examples 3 and 4, its spinnability is generally lower, its color difference within batches is larger, and its fiber performance is also correspondingly reduced.

[0112] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for preparing colored poly(p-phenylenebenzodioxazole) fibers, characterized in that: Includes the following steps: S1. Using 4,6-diaminoresorcinol hydrochloride and terephthalic acid as raw materials, and polyphosphoric acid and phosphorus pentoxide as solvents, PBO primary polymers were obtained by degassing and activation. The reaction temperature was controlled at 60-120℃, and the dynamic viscosity of the PBO primary polymers was 100-200 Pa•s. S2. Pigment and polyphosphoric acid were added to the PBO primary polymer, and the colored PBO primary polymer was obtained by vacuum degassing. The reaction temperature was controlled at 60-130℃, and the dynamic viscosity of the colored PBO primary polymer was 100-300 Pa•s. S3. A colored PBO prepolymer is prepared by prepolymerization reaction of colored PBO primary polymer in a single-stage screw mill, with the reaction temperature controlled at 120-150℃ and the dynamic viscosity of the colored PBO prepolymer being 300-800 Pa•s. S4. A colored PBO prepolymer and residual terephthalic acid are subjected to a post-polymerization reaction in a two-stage screw compressor to obtain a colored PBO polymer. The reaction temperature is controlled at 150-200℃, and the dynamic viscosity of the colored PBO polymer is above 1000 Pa•s. S5. Colored PBO fibers are obtained by spinning colored PBO polymer.

2. The preparation method according to claim 1, characterized in that: In steps S1 to S4, the stirring speed during degassing and activation is controlled to be 30–80 r / min, and the stirring speed during vacuum degassing is controlled to be 10–30 r / min.

3. The preparation method according to claim 1, characterized in that: In steps S1 to S4, the ratio of the total molar amount of terephthalic acid added to the molar amount of 4,6-diaminoresorcinol hydrochloride added is 0.97 to 1.05:

1.

4. The preparation method according to claim 1, characterized in that: In step S2, the pigment and polyphosphoric acid are mixed, dissolved and dispersed at 60–130°C to form a pigment solution, which is then mixed with the PBO primary polymer and degassed at 60–130°C and -0.08–0 MPa for 2–6 hours.

5. The preparation method according to claim 4, characterized in that: The pigment concentration in the pigment solution is 1.0–10.0%, and the amount of pigment added is 1.5–6% of the PBO primary polymer.

6. The preparation method according to claim 5, characterized in that: The pigments include organic pigments, inorganic pigments, or combinations thereof.

7. The preparation method according to claim 1, characterized in that: In step S3, the intrinsic viscosity of the colored PBO prepolymer is 5–15 dl / g.

8. The preparation method according to claim 1, characterized in that: In step S4, the intrinsic viscosity of the colored PBO polymer is 18–32 dl / g, and the solid content is 10–14%.

9. A system for preparing colored poly(p-phenylenebenzodioxazole) fibers using the preparation method according to any one of claims 1 to 8, characterized in that: Includes polymerization reactor, primary screw compressor, secondary screw compressor and spinning assembly. The polymerization reactor performs steps S1 and S2, and uses the stirring system of the polymerization reactor to control the temperature of the material system, and uses an online monitoring system to monitor the dynamic viscosity of the material. The primary screw compressor performs the S3 step operation and uses an online monitoring system to monitor the reaction temperature and material dynamic viscosity. The secondary screw compressor performs the S4 step operation and uses an online monitoring system to monitor the reaction temperature and material dynamic viscosity; The spinning assembly performs step S5.

10. A colored poly(p-phenylenebenzodioxazole) fiber, characterized in that: The colored fibers prepared by the preparation method described in any one of claims 1 to 8, or by the system described in claim 9, satisfy the following requirements: breaking strength of 25 to 36 CN / dtex; tensile modulus of 145 to 200 GPa; color fastness to soaping of grade 4-5; color fastness to perspiration of grade 4; and color fastness to rubbing of grade 4.

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