A dyeing method for poly-p-phenylene benzobisoxazole fiber without changing mechanical properties

Abstract

The application belongs to the technical field of high polymer materials, and particularly relates to a dyeing method without changing the mechanical properties of poly-p-phenylene benzobisoxazole (PBO) fiber, which comprises the following steps: adding 4,6-diaminoresorcinol hydrochloride, phosphorus pentoxide, terephthalic acid and pigment phthalocyanine into a reaction device containing polyphosphoric acid, and then performing a reaction under the condition of gradient temperature rising and stirring at a temperature of 45-145 DEG C to obtain a PBO prepolymer solution; and conveying the PBO prepolymer solution into a double-screw extruder to complete a high polymerization, and then conveying the PBO prepolymer solution into a spinning metering pump to prepare a high-performance PBO fiber. The application can dye the PBO fiber without destroying the original structure of the PBO fiber and without reducing the mechanical properties of the PBO fiber.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a dyeing method that does not alter the mechanical properties of poly(p-phenylenebenzodioxazole) (PBO) fibers. Background Technology

[0002] Poly(p-phenylenebenzodioxazole) (PBO) fibers can be produced by solution polycondensation of 4,6-diaminoresorcinol hydrochloride (DAR) and terephthalic acid (TPA) in polyphosphoric acid (PPA), followed by liquid crystal spinning. Through liquid crystal spinning, the rigid rod-like molecules in PBO exhibit almost complete orientation along the fiber axis, forming a highly oriented ordered structure. This gives PBO fibers high strength, high modulus, and high heat resistance, making them widely used in advanced structural composite materials fields such as aerospace and military applications.

[0003] PBO fiber itself is golden yellow or yellowish-brown. Dyeing PBO fiber can meet the needs of various applications, especially in military camouflage. However, PBO fiber lacks active groups in its macromolecular structure, resulting in a very compact fiber structure that is difficult to dye using conventional synthetic fiber dyeing methods. Adding pigments such as titanium dioxide, carbon black, or cobalt green can disrupt the original fiber structure and polymer orientation along the fiber axis, reducing fiber performance. Therefore, a new method for dyeing PBO fiber suitable for industrial production is needed, enabling richer color options without affecting the fiber's mechanical properties. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a dyeing method for poly(p-phenylenebenzodioxazole) (PBO) fibers that does not alter their mechanical properties. By adding phthalocyanine pigments soluble in polyphosphoric acid to the PBO prepolymer system and employing a gradient heating method during the prepolymerization process, the problem of difficult dyeing of PBO fibers in existing technologies can be solved, while simultaneously ensuring the mechanical properties of PBO fibers and greatly expanding the application scenarios of PBO fibers.

[0005] The technical solution of the present invention is as follows:

[0006] A dyeing method that does not alter the mechanical properties of poly(p-phenylenebenzodioxazole) fibers involves adding 4,6-diaminoresorcinol hydrochloride, phosphorus pentoxide, terephthalic acid, and phthalocyanine pigment to a reaction apparatus containing polyphosphoric acid. The reaction is carried out under a gradient temperature increase and stirring at 45-145°C to obtain a PBO prepolymer solution. The PBO prepolymer solution is then fed into a twin-screw extruder, where high-level polymerization is completed. Finally, the solution is fed into a spinning metering pump to produce high-performance PBO fibers.

[0007] Preferably, the phthalocyanine pigment is an unsubstituted phthalocyanine or phthalocyanine derivative that is soluble in polyphosphoric acid. This phthalocyanine pigment exhibits good solubility in polyphosphoric acid, the solvent for PBO polymerization. The phthalocyanine molecule has a planar structure similar to that of the PBO molecule. The structural formula of phthalocyanine is as follows:

[0008]

[0009] M can be iron, cobalt, or copper, etc., and R can be phenyl, pyridyl, or methyl, etc.

[0010] Preferably, the amount of phthalocyanine added is less than or equal to 25‰ of the mass of polyphosphoric acid.

[0011] Preferably, the raw materials used in the dyeing method include 1-5 parts of polyphosphoric acid, 0.2-1 parts of 4,6-diaminoresorcinol hydrochloride, 0.4-2 parts of phosphorus pentoxide, and 0.2-1 parts of terephthalic acid.

[0012] Preferably, the specific process of gradient heating is as follows: first, heat to 45-65℃ and stir for 6-8 hours, then heat to 65-125℃ and stir for 4-6 hours, and then heat to 125-145℃ and stir for 2-4 hours to obtain PBO prepolymer solution.

[0013] Preferably, during the prepolymerization stage, the agitator is switched between forward and reverse rotation every 10-60 minutes, and the agitator speed is 10-100 r / min.

[0014] Preferably, when the speed of the screw extruder is controlled at 10-50 r / min, the temperature is set at 150-200℃.

[0015] Preferably, the PBO prepolymer is prepared as follows: Nitrogen gas is introduced into a reaction apparatus containing polyphosphoric acid, followed by the addition of 4,6-diaminoresorcinol hydrochloride and phosphorus pentoxide. The mixture is then heated in an oil bath to purge hydrogen chloride. After purging the hydrogen chloride, terephthalic acid monomer and phthalocyanine pigment are added. The mixture is then heated gradually at 45-145°C with stirring to prepare the PBO prepolymer. More preferably, the oil bath temperature is raised to 45-65°C and the reaction is stirred for 6-10 hours.

[0016] Preferably, the residence time of the material in the twin-screw extruder is 90 minutes.

[0017] This invention adds phthalocyanine pigments soluble in polyphosphoric acid to a PBO prepolymer system. The polyphosphoric acid-solubilized phthalocyanine molecules have a planar structure similar to PBO, and are tightly bound to the PBO molecular chain through π-π interactions. Furthermore, because phthalocyanine molecules are smaller than PBO molecules along the fiber axis but larger laterally, their planar shape is more easily aligned with the flow direction of polyphosphoric acid. This guides and orients the benzene and oxazole rings of PBO towards the radial direction of the fiber, improving the PBO fiber modulus. By controlling the prepolymerization temperature gradient, the PBO polymerization rate is slowed down in the early stages, resulting in a phthalocyanine / P... BO oligomers provide ample time for self-assembly through conjugation, facilitating the subsequent full utilization of phthalocyanine molecules as templates. In the oligomer stage, phthalocyanine / PBO small molecules are combined through self-assembly before further polymerization to grow PBO molecular chains. This results in more uniform dispersion of phthalocyanine at the molecular level, better guiding the radial size of PBO macromolecules and improving the strength of PBO fibers. If the degree of polymerization of PBO molecules is already high, it is difficult for phthalocyanine molecules to uniformly incorporate into PBO molecular chains at the molecular level. Moreover, if phthalocyanine molecules form aggregates on their own, it is equivalent to introducing impurities into the system, reducing the strength of the prepared fibers.

[0018] This invention provides a dyeing method for poly(p-phenylenebenzodioxazole) (PBO) fibers that does not alter their mechanical properties. This new method can uniformly dye PBO fibers without damaging their original structure or reducing their mechanical properties, thus greatly expanding the application scenarios of PBO fibers. Attached Figure Description

[0019] Figure 1 A schematic diagram of the reaction for preparing PBO homopolymer using the terephthalic acid method is provided. Detailed Implementation

[0020] The present invention will be further illustrated below with reference to embodiments, which will enable those skilled in the art to have a more comprehensive understanding of the present invention, but will not limit the present invention in any way.

[0021] In the following selections of polyphosphoric acid: 85.0% ≤ P2O5 content ≤ 90.0%.

[0022] Example 1: Preparation method of 5‰ unsubstituted nonmetallic phthalocyanine dyed PBO fibers (specifically, phthalocyanine without a central metal and without substituents).

[0023] In a polymerization reactor purged with nitrogen (to remove oxygen), 5.024 kg of polyphosphoric acid solvent, 1.09 kg of 4,6-diaminoresorcinol hydrochloride, and 1.931 kg of phosphorus pentoxide were added. The mixture was then heated in an oil bath to 45°C and stirred for 8 hours to purge hydrogen chloride (the purged hydrogen chloride was passed into a sodium hydroxide solution via a gas venting pipe). After purging the hydrogen chloride, 0.025 kg of unsubstituted nonmetallic phthalocyanine (5‰ of the polyphosphoric acid mass) and 0.850 kg of terephthalic acid monomer were added. The mixture was then gradually heated to 65°C and stirred for 6 hours, then to 125°C and stirred for 4 hours, and finally to 145°C and stirred for 2 hours. The stirring speed was 50 r / min. The stirring paddle was switched between forward and reverse rotation every 20 minutes to obtain a dyed PBO prepolymer solution. The PBO prepolymer solution was then fed into a twin-screw extruder at a speed of 30 r / min and a temperature of 180℃. The material was allowed to remain in the twin-screw extruder for 90 minutes to complete high-level polymerization. The solution was then fed into a spinning metering pump. Due to the high-stretching of the liquid crystal spinning method, the PBO molecules were highly oriented on the fiber axis, resulting in high-performance PBO fibers. The finished product was green, and its tensile modulus was tested to be 162 GPa.

[0024] Example 2: Preparation method of 10‰ unsubstituted nonmetallic phthalocyanine dyed PBO fibers (specifically, phthalocyanine without a central metal and without substituents).

[0025] In a nitrogen-purified polymerization reactor, 5.024 kg of polyphosphoric acid solvent, 1.09 kg of 4,6-diaminoresorcinol hydrochloride, and 1.931 kg of phosphorus pentoxide were added. The mixture was then heated in an oil bath to 45°C and stirred for 8 hours to purge hydrogen chloride (the purged hydrogen chloride was passed into a sodium hydroxide solution through a gas venting pipe). After purging the hydrogen chloride, 0.050 kg of unsubstituted nonmetallic phthalocyanine (10‰ of the polyphosphoric acid mass) and 0.850 kg of terephthalic acid monomer were added. After the addition was complete, the temperature was gradually increased to 65°C and stirred for 6 hours, then increased to 125°C and stirred for 4 hours, and finally increased to 145°C and stirred. The reaction was carried out for 2 hours, with the stirring speed of the agitator at 50 r / min. The agitator was switched between forward and reverse rotation every 20 minutes to obtain a dyed PBO prepolymer solution. The PBO prepolymer solution was then fed into a twin-screw extruder at a speed of 30 r / min and a temperature of 180℃. The material was allowed to remain in the twin-screw extruder for 90 minutes to complete high-level polymerization. The material was then fed into a spinning metering pump. Due to the high-stretching of the liquid crystal spinning method, the PBO molecules were highly oriented on the fiber axis, resulting in high-performance PBO fibers. The finished product was green, and its tensile modulus was tested to be 167 GPa.

[0026] Example 3: Preparation method of 15‰ unsubstituted nonmetallic phthalocyanine dyed PBO fibers (specifically, phthalocyanine without a central metal and without substituents).

[0027] In a nitrogen-purged polymerization reactor, 5.024 kg of polyphosphoric acid solvent, 1.09 kg of 4,6-diaminoresorcinol hydrochloride, and 1.931 kg of phosphorus pentoxide were added. The mixture was then heated in an oil bath to 45°C and stirred for 8 hours to purge hydrogen chloride (the purged hydrogen chloride was passed into a sodium hydroxide solution through a gas venting pipe). After purging the hydrogen chloride, 0.075 kg of unsubstituted nonmetallic phthalocyanine (15‰ of the polyphosphoric acid mass) and 0.850 kg of terephthalic acid monomer were added. After the addition was complete, the temperature was gradually increased to 65°C and stirred for 6 hours, then increased to 125°C and stirred for 4 hours, and finally increased to 145°C and stirred. The reaction was carried out for 2 hours, with the stirring speed of the agitator at 50 r / min. The agitator was switched between forward and reverse rotation every 20 minutes to obtain a dyed PBO prepolymer solution. The PBO prepolymer solution was then fed into a twin-screw extruder at a speed of 30 r / min and a temperature of 180℃. The material was allowed to remain in the twin-screw extruder for 90 minutes to complete high-level polymerization. The material was then fed into a spinning metering pump. Due to the high-ratio stretching of the liquid crystal spinning method, the PBO molecules were highly oriented on the fiber axis, resulting in high-performance PBO fibers. The finished product was green, and its tensile modulus was tested to be 174 GPa.

[0028] Example 4: Preparation method of 20‰ unsubstituted nonmetallic phthalocyanine dyed PBO fibers (specifically, phthalocyanine without a central metal and without substituents).

[0029] In a nitrogen-purified polymerization reactor, 5.024 kg of polyphosphoric acid solvent, 1.09 kg of 4,6-diaminoresorcinol hydrochloride, and 1.931 kg of phosphorus pentoxide were added. The mixture was then heated in an oil bath to 45°C and stirred for 8 hours to purge hydrogen chloride (the purged hydrogen chloride was passed into a sodium hydroxide solution through a gas venting pipe). After purging the hydrogen chloride, 0.100 kg of unsubstituted nonmetallic phthalocyanine (20‰ of the polyphosphoric acid mass) and 0.850 kg of terephthalic acid monomer were added. After the addition was complete, the temperature was gradually increased to 65°C and stirred for 6 hours, then increased to 125°C and stirred for 4 hours, and finally increased to 145°C and stirred. The reaction was carried out for 2 hours, with the stirring speed of the agitator at 50 r / min. The agitator was switched between forward and reverse rotation every 20 minutes to obtain a dyed PBO prepolymer solution. The PBO prepolymer solution was then fed into a twin-screw extruder at a speed of 30 r / min and a temperature of 180℃. The material was allowed to remain in the twin-screw extruder for 90 minutes to complete high-level polymerization. The material was then fed into a spinning metering pump. Due to the high-stretching of the liquid crystal spinning method, the PBO molecules were highly oriented on the fiber axis, resulting in high-performance PBO fibers. The finished product was green, and its tensile modulus was tested to be 166 GPa.

[0030] Example 5: Preparation method of 25‰ unsubstituted nonmetallic phthalocyanine dyed PBO fibers (specifically, phthalocyanine without a central metal and without substituents).

[0031] In a nitrogen-purged polymerization reactor, 5.024 kg of polyphosphoric acid solvent, 1.09 kg of 4,6-diaminoresorcinol hydrochloride, and 1.931 kg of phosphorus pentoxide were added. The mixture was then heated in an oil bath to 45°C and stirred for 8 hours to purge hydrogen chloride (the purged hydrogen chloride was passed into a sodium hydroxide solution through a gas venting pipe). After purging the hydrogen chloride, 0.0125 kg of unsubstituted nonmetallic phthalocyanine (25‰ of the polyphosphoric acid mass) and 0.850 kg of terephthalic acid monomer were added. After the addition was complete, the temperature was gradually increased to 65°C and stirred for 6 hours, then increased to 125°C and stirred for 4 hours, and finally increased to 145°C and stirred. The reaction was carried out for 2 hours, with the stirring speed of the agitator at 50 r / min. The agitator was switched between forward and reverse rotation every 20 minutes to obtain a dyed PBO prepolymer solution. The PBO prepolymer solution was then fed into a twin-screw extruder at a speed of 30 r / min and a temperature of 180℃. The material was allowed to remain in the twin-screw extruder for 90 minutes to complete high-level polymerization. The material was then fed into a spinning metering pump. Due to the high-ratio stretching of the liquid crystal spinning method, the PBO molecules were highly oriented on the fiber axis, resulting in high-performance PBO fibers. The finished product was green, and its tensile modulus was tested to be 146 GPa.

[0032] Example 6: Preparation method of 15‰ unsubstituted copper phthalocyanine dyed PBO fibers (specifically, phthalocyanine with copper as the central metal and no substituents).

[0033] In a nitrogen-purified polymerization reactor, 5.024 kg of polyphosphoric acid solvent, 1.09 kg of 4,6-diaminoresorcinol hydrochloride, and 1.931 kg of phosphorus pentoxide were added. The mixture was then heated in an oil bath to 45°C and stirred for 8 hours to purge hydrogen chloride (the purged hydrogen chloride was passed into a sodium hydroxide solution via a gas venting pipe). After purging the hydrogen chloride, 0.075 kg of unsubstituted copper phthalocyanine (15‰ of the polyphosphoric acid mass) and 0.850 kg of terephthalic acid monomer were added. After the addition was complete, the temperature was gradually increased to 65°C and stirred for 6 hours, then increased to 125°C and stirred for 4 hours, and finally increased to 145°C and stirred for the next 6 hours. The mixture was stirred for 2 hours at a stirring speed of 50 r / min, with the stirring paddle switching between forward and reverse rotation every 20 minutes to obtain a dyed PBO prepolymer solution. The PBO prepolymer solution was then fed into a twin-screw extruder at a speed of 30 r / min and a temperature of 180℃. The material remained in the twin-screw extruder for 90 minutes to complete high-level polymerization. It was then fed to a spinning metering pump. Due to the high-stretching properties of liquid crystal spinning, the PBO molecules were highly oriented on the fiber axis, resulting in high-performance PBO fibers. The finished product was blue, and its tensile modulus was tested to be 172 GPa.

[0034] Comparative Example 1: A method for preparing PBO fibers using terephthalic acid (e.g.) Figure 1 (As shown)

[0035] In a nitrogen-purged polymerization reactor, 5.024 kg of polyphosphoric acid solvent, 1.09 kg of 4,6-diaminoresorcinol hydrochloride, and 1.931 kg of phosphorus pentoxide were added. The mixture was then heated in an oil bath to 45°C and stirred for 8 hours to purge hydrogen chloride (the purged hydrogen chloride was passed into a sodium hydroxide solution via a gas venting pipe). After purging the hydrogen chloride, 0.850 kg of terephthalic acid monomer was added. The temperature was then gradually increased to 65°C and stirred for 6 hours, followed by a further increase to 125°C and stirring for 4 hours, and finally to 145°C and stirring for 2 hours. The stirring speed of the impeller was [missing information]. The PBO prepolymer solution was obtained by switching the agitator forward / reverse rotation every 20 minutes at a speed of 50 r / min. The PBO prepolymer solution was then fed into a twin-screw extruder at a speed of 30 r / min and a temperature of 180℃. The material resided in the twin-screw extruder for 90 minutes, where high polymerization was completed. The resulting material was then fed into a spinning metering pump. Due to the high-ratio stretching of the liquid crystal spinning method, the PBO molecules were highly oriented on the fiber axis, producing high-performance PBO fibers. The finished product was golden yellow, and its tensile modulus was tested to be 161 GPa. Comparative Example 2: Preparation method of 15‰ carbon black-dyed PBO fibers.

[0036] In a nitrogen-filled polymerization reactor, 5.024 kg of polyphosphoric acid solvent, 1.09 kg of 4,6-diaminoresorcinol hydrochloride, and 1.931 kg of phosphorus pentoxide were added. The mixture was then heated in an oil bath to 45°C and stirred for 8 hours to purge hydrogen chloride (the purged hydrogen chloride was passed into a sodium hydroxide solution through a gas inlet pipe). After purging the hydrogen chloride, 0.075 kg of carbon black (15‰ of the mass of polyphosphoric acid) and 0.850 kg of terephthalic acid monomer were added. The mixture was then gradually heated to 65°C and stirred for 6 hours, then heated to 125°C and stirred for 4 hours, and finally heated to 145°C and stirred for 2 hours. The stirring speed of the impeller was 50 r / min, and the impeller was switched between forward and reverse rotation every 20 minutes to obtain a prepolymer solution. The PBO prepolymer solution was then fed into a twin-screw extruder at a speed of 30 r / min and a temperature of 180°C. The material was held in the twin-screw extruder for 90 min to complete high polymerization. The material was then fed into a spinning metering pump. Due to the high stretching of the liquid crystal spinning method, the PBO molecules were highly oriented on the fiber axis, resulting in high-performance PBO fibers. The finished product was black, and its tensile modulus was tested to be 119 GPa.

[0037] Preparation method of unsubstituted nonmetallic phthalocyanine dyed PBO fibers (specifically, phthalocyanine without central metal and without substituents, and without low-temperature self-assembly process in the prepolymerization stage) of Comparative Example 3 (15‰).

[0038] In a nitrogen-purged polymerization reactor, 5.024 kg of polyphosphoric acid solvent, 1.09 kg of 4,6-diaminoresorcinol hydrochloride, and 1.931 kg of phosphorus pentoxide were added. The mixture was then heated to 45°C in an oil bath and stirred for 8 hours to purge hydrogen chloride (the purged hydrogen chloride was passed into a sodium hydroxide solution via a gas venting pipe). After purging the hydrogen chloride, 0.075 kg of unsubstituted nonmetallic phthalocyanine (15‰ of the polyphosphoric acid mass) and 0.850 kg of terephthalic acid monomer were added. The mixture was then heated to 145°C and stirred for 6 hours at a stirring speed of 50 rpm. The stirring paddle is rotated forward / reverse every 20 minutes to obtain a dyed PBO prepolymer solution. The PBO prepolymer solution is then fed into a twin-screw extruder at a speed of 30 r / min and a temperature of 180°C. The material is held in the twin-screw extruder for 90 minutes to complete high polymerization. The material is then fed into a spinning metering pump. Due to the high stretching of the liquid crystal spinning method, the PBO molecules are highly oriented on the fiber axis, resulting in high-performance PBO fibers. The finished product is green, and its tensile modulus is tested to be 137 GPa.

[0039] Comparative Example 1 describes the preparation of PBO fibers using the existing terephthalic acid method. The tensile modulus of the PBO fibers dyed in Examples 1-6 is equal to or even higher than that of the PBO fibers prepared in Comparative Example 1. Comparative Example 2 uses carbon black-dyed PBO fibers, whose tensile modulus is significantly lower than that of Comparative Example 1 and the fibers of Examples 1-6. Comparative Example 2 uses conventional reaction temperature and time in the prepolymerization stage, and its fibers have a significantly lower tensile modulus than those of Comparative Example 1 and the fibers of Examples 1-6. Through Comparative Examples 1-3, it is evident that this invention, by using phthalocyanine pigments in conjunction with a specific gradient temperature increase during prepolymerization, can solve the problem of difficult dyeing of PBO fibers in the prior art, while also ensuring the mechanical properties of PBO fibers, greatly expanding the application scenarios of PBO fibers.

[0040] This invention provides a dyeing method for poly(p-phenylenebenzodioxazole) (PBO) fibers that does not alter their mechanical properties. This new method can uniformly dye PBO fibers without damaging their original structure or reducing their mechanical properties, thus greatly expanding the application scenarios of PBO fibers.

Claims

1. A dyeing method that does not alter the mechanical properties of poly(p-phenylenebenzodioxazole) fibers, characterized in that, Nitrogen gas was introduced into a reaction apparatus containing polyphosphoric acid, followed by the addition of 4,6-diaminoresorcinol hydrochloride and phosphorus pentoxide. The mixture was then heated in an oil bath to remove hydrogen chloride. Terephthalic acid monomer and phthalocyanine pigment were then added, and the mixture was heated gradually from 45 to 145°C with stirring to prepare a PBO prepolymer solution. The PBO prepolymer solution was then fed into a twin-screw extruder, where high-level polymerization was completed. Finally, the solution was fed into a spinning metering pump to produce high-performance PBO fibers. 0 < the amount of phthalocyanine pigment added ≤ 25‰ of the mass of polyphosphoric acid; The specific process of the gradient heating is as follows: first, heat to 45-65℃ and stir for 6-8 hours, then heat to 65-125℃ and stir for 4-6 hours, then heat to 125-145℃ and stir for 2-4 hours to obtain PBO prepolymer solution. During the prepolymerization stage, switch the agitator to rotate forward or backward every 10-60 minutes, with a stirring speed of 10-100 r / min. When the speed of the screw extruder is controlled at 10-50 r / min, the temperature is set at 150-200℃; The residence time of the material in the twin-screw extruder is 30-120 min; The oil bath is heated to 45-65℃ and stirred for 6-10 hours.

2. The dyeing method for poly(p-phenylenebenzodioxazole) fibers without altering their mechanical properties according to claim 1, characterized in that, The phthalocyanine pigment is phthalocyanine and phthalocyanine derivatives that are soluble in polyphosphoric acid.

3. The dyeing method for poly(p-phenylenebenzodioxazole) fibers without altering their mechanical properties according to claim 1, characterized in that, The raw materials used in the dyeing method include 1-5 parts of polyphosphoric acid, 0.2-1 parts of 4,6-diaminoresorcinol hydrochloride, 0.4-2 parts of phosphorus pentoxide, and 0.2-1 parts of terephthalic acid.

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