An ultraviolet absorber with a triazine ring as a main structure, a preparation method thereof and application thereof in aramid fibers

Abstract

The application discloses a kind of ultraviolet absorber with triazine ring as main structure and its preparation method and its application in aramid fiber, the ultraviolet absorber has the following structural formula: Wherein, R1, R2, R3, R4 It is the group containing phenyl or substituted phenyl, R5 It is piperidyl, piperazyl, pyrrolidinyl and one of the following structures:This ultraviolet absorber has good absorption to UVA-UVB band ultraviolet, especially in 290~320 nm range has good ultraviolet absorption, adding the ultraviolet absorber in aramid fiber can significantly improve its weather resistance and service life, keep mechanical property, delay ultraviolet degradation, reduce the direct damage of fiber.

Description

Technical Field

[0001] This invention belongs to the field of ultraviolet absorbers, and relates to a triazine ultraviolet absorber, its preparation method, and its application in aramid fibers. Background Technology

[0002] Aramid fibers are widely used in aerospace, defense, fiber optic reinforcement, sporting goods, special protective equipment, and automotive industries due to their excellent comprehensive properties, including low density, high strength, high modulus, and high melting point. However, because aramid fibers contain chromophores such as amides and benzene rings, they readily absorb ultraviolet light, leading to molecular chain breakage and affecting the fiber's mechanical properties, resulting in a decrease in impact strength, flexural strength, tensile strength, and elongation. Adding ultraviolet absorbers to aramid fibers can significantly improve their weather resistance and service life, maintain mechanical properties, delay ultraviolet degradation, and reduce direct damage to the fibers.

[0003] Triazine UV absorbers are a relatively broad-spectrum and emerging type of absorber. These absorbers are prepared from cyanuric chloride or its mono- and di-substituted derivatives with phenolic compounds. Triazine UV absorbers possess high efficiency, low colorfastness, high processing temperature, and good compatibility, and are widely used in textiles, plastics, fibers, cosmetics, food, and other fields.

[0004] Traditional UV absorbers have poor adhesion to fibers and are prone to migration and loss. With prolonged use, their UV absorption performance deteriorates. The core characteristic of triazine-based UV absorbers is their reversible UV absorption and release cycle capability. Through reversible changes in their intramolecular structure, they can repeatedly capture UV energy and release it in low-hazard forms such as heat, achieving long-lasting UV protection. Therefore, it is necessary to synthesize a triazine-based UV absorber with good compatibility with aramid fibers. Summary of the Invention

[0005] This invention provides a triazine ring-based ultraviolet absorber for aramid fibers, its preparation method, and its application in aramid fibers. This ultraviolet absorber has good absorption of ultraviolet light in the UVA-UVB band, especially in the 290~320 nm range (the sensitive wavelength of aramid fibers). Adding this ultraviolet absorber to aramid fibers can significantly improve their weather resistance and service life, maintain mechanical properties, delay ultraviolet degradation, and reduce direct damage to the fibers.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A UV absorber with a triazine ring as its main structure has the following structural formula:

[0008]

[0009] Wherein, R1, R2, R3, and R4 are groups containing phenyl or substituted phenyl groups, and R5 is piperidinyl, piperazine, pyrrolidinyl, or one of the following structures:

[0010] .

[0011] A method for preparing the above-mentioned ultraviolet absorber with a triazine ring as the main structure includes the following steps:

[0012] Step 1: Add cyanuric chloride, catalyst A, and m-xylene to organic solvent A, and react at 5-10℃ for 2-4 h. Monitor the reaction progress using thin-layer chromatography (TLC). After the reaction is complete, add resorcinol and heat to 50-90℃ for 4-5 h. After the reaction is complete, pour the mixture into a dilute solution of hydrochloric acid, separate the layers, rotary evaporate, recrystallize from toluene, and perform column chromatography to obtain the intermediate, in which:

[0013] The molar ratio of cyanuric chloride, m-xylene, and resorcinol is 1:2~4:1~5, preferably 1:2:1;

[0014] The weight of the organic solvent A is 10 to 15 times that of cyanuric chloride;

[0015] The organic solvent A can be selected from one of nitrobenzene, dichloromethane, carbon disulfide, o-dichlorobenzene, chlorobenzene, p-dichlorobenzene, dichloroethane, trichloromethane, etc., and is preferably o-dichlorobenzene;

[0016] The catalyst A is one of anhydrous aluminum chloride, anhydrous ferric chloride, anhydrous zinc chloride, etc., preferably anhydrous aluminum chloride, and the amount used is 1 to 3 times the amount of the intermediate.

[0017] Step 2: The intermediate undergoes the Mannich reaction to obtain a novel triazine-based ultraviolet absorber. The specific method is as follows:

[0018] The intermediate obtained in step one, paraformaldehyde, and amine compounds are added to organic solvent B, and the mixture is reacted at 50–100 °C for 2–12 h under a N2 atmosphere to obtain a triazine-based ultraviolet absorber compound, wherein:

[0019] The organic solvent B is one of methanol, ethanol, isopropanol, acetonitrile, N,N-dimethylformamide, dichloromethane, toluene, DMSO, water, etc., preferably ethanol; the amount used is preferably 30 to 50 times the amount of the intermediate.

[0020] The molar ratio of the intermediate, paraformaldehyde, and amine compound is 1:2 to 4:1 to 3, preferably 1:3:2;

[0021] Amine compounds can be selected from one of the following structures:

[0022]

[0023] Specifically, it can be one of the following: secondary amine, 4-Boc aminopiperidine, 4-methoxypiperidine, piperazine-1-carboxylic acid methyl ester, 1-Boc piperazine, 4-hydroxymethylpiperidine, 1-cyclopropylcarbonylpiperidine, 1-acetylpiperidine, piperidine-1-carboxamide, piperazine-1-carboxylic acid methyl ester, N-methylpropyl-2-amine, etc., preferably 4-Boc aminopiperidine.

[0024] Application of three triazine-based ultraviolet absorbers prepared by the above method in aramid fibers.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] (1) The present invention synthesizes a novel triazine ultraviolet absorber through the Mannich reaction, which has a wider absorption range, higher photostability and lower toxicity.

[0027] (2) The novel triazine ultraviolet absorber synthesized in this invention has good solubility in organic solvents and can be used in different environments.

[0028] (3) The novel triazine ultraviolet absorbers synthesized in this invention have light colors and can be applied to the UV-resistant modification of aramid fibers. Attached Figure Description

[0029] Figure 1 The infrared spectrum of the triazine ultraviolet absorber synthesized in Example 2;

[0030] Figure 2 The infrared spectrum of the triazine ultraviolet absorber synthesized in Example 3;

[0031] Figure 3 The infrared spectrum of the triazine ultraviolet absorber synthesized in Example 4;

[0032] Figure 4 The images show the ultraviolet absorption spectra of the triazine ultraviolet absorber synthesized in Example 2 and the commercially available ultraviolet absorber UV-1164 in different organic solvents. Detailed Implementation

[0033] The technical solution of the present invention will be further described below with reference to the embodiments, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0034] Example 1:

[0035] At room temperature and pressure, 500 ml of o-dichlorobenzene, 1 mol of cyanuric chloride, 3 mol of anhydrous aluminum chloride, and 2 mol of m-xylene were added to a 1000 ml three-necked flask equipped with a condenser, thermometer, and stirrer. The mixture was reacted in an ice-water bath for 4 h. Then, 1 mol of resorcinol was added, the ice-water bath was removed, and the temperature was raised to 80 °C for 5 h. After the reaction was completed, the mixture was poured into a dilute solution of hydrochloric acid, separated, rotary evaporated, recrystallized from toluene, and subjected to column chromatography. Petroleum ether:ethyl acetate was used as the eluent, and a gradient elution with a volume ratio of 10:1 to 2:1 was used to obtain the intermediate.

[0036] Example 2:

[0037] At room temperature and pressure, 2 mol of 4-Boc aminopiperidine was added to anhydrous ethanol and stirred until dissolved. Then, 3 mol of paraformaldehyde and 1 mol of the intermediate were added under a nitrogen gas stream, and the mixture was refluxed at 50 °C for 8 h. After the reaction was complete, the solvent was removed by vacuum distillation to obtain crude compound c. Crude compound c was purified by column chromatography using a gradient elution with DCM:MeOH ratios of 100:1 to 10:1. Compound c was then obtained by vacuum distillation.

[0038] Example 3:

[0039] At ambient temperature and pressure, 3 mol of 4-methoxypiperidine was added to anhydrous ethanol and stirred until dissolved. Then, 3 mol of paraformaldehyde and 1 mol of the intermediate were added under a nitrogen gas stream, and the mixture was refluxed at 50 °C for 8 h. After the reaction was complete, the solvent was removed by vacuum distillation to obtain crude compound c1. Crude compound c1 was purified by column chromatography using a gradient elution with DCM:MeOH ratios of 45:1 to 10:1. Compound c1 was then obtained by vacuum distillation.

[0040] Example 4:

[0041] At room temperature and pressure, 3 mol of piperazine-1 carboxylic acid methyl ester was added to anhydrous ethanol and stirred until dissolved. Then, 3 mol of paraformaldehyde and 1 mol of the intermediate were added under a nitrogen gas stream, and the mixture was refluxed at 50 °C for 10 h. After the reaction was complete, the solvent was removed by vacuum distillation to obtain crude compound c2. Crude compound c2 was purified by column chromatography using a gradient elution with DCM:MeOH ratios of 40:1 to 5:1. Compound c2 was then obtained by vacuum distillation.

[0042] Example 5:

[0043] At ambient temperature and pressure, 3 mol of 1-Boc piperazine was added to anhydrous ethanol and stirred until dissolved. Then, 3 mol of paraformaldehyde and 1 mol of the intermediate were added under a nitrogen atmosphere, and the mixture was refluxed at 50 °C for 8 h. After the reaction was complete, the solvent was removed by vacuum distillation to obtain the crude compound c3. The crude compound c3 was purified by column chromatography using a gradient elution with DCM:MeOH ratios of 100:1 to 20:1. The compound c3 was then obtained by vacuum distillation.

[0044] Example 6:

[0045] At ambient temperature and pressure, 3 mol of 4-hydroxymethylpiperidine was added to anhydrous ethanol and stirred until dissolved. Then, 3 mol of paraformaldehyde and 1 mol of the intermediate were added under a nitrogen atmosphere, and the mixture was refluxed at 50 °C for 8 h. After the reaction was complete, the solvent was removed by vacuum distillation to obtain the crude compound c4. The crude compound c4 was purified by column chromatography using a gradient elution with DCM:MeOH ratios of 60:1 to 5:1. The compound c4 was then obtained by vacuum distillation.

[0046] UV absorption performance test

[0047] At 25℃, UV-Vis spectrophotometry was used to perform spectral analysis on intermediate DBDT, commercially available UV absorber UV-1164, and compound c. In the experiment, the above compounds were dissolved in four solvents—DMAC, THF, MeOH, and DCM—to prepare solutions with a concentration of 5 × 10⁻⁶. -5 The test solution was prepared at a concentration of mol / L. Before testing, the sample cell was rinsed multiple times with deionized water and the corresponding solvent and thoroughly dried to eliminate background interference. Based on the Lambert-Beer law A=lg(1 / T)=εbc, the absorbance of each compound at its maximum absorption wavelength was measured. The concentration-absorbance data were linearly fitted using Origin software to establish a standard curve, and finally the experimental maximum molar absorptivity of both compounds was accurately calculated. Figures 1-4 Typical UV absorption spectra of intermediate DBDT, UV-1164, and compound c in different solvent systems are shown.

[0048] Based on preliminary experimental explorations, the application of ultraviolet absorbers in para-aramid fibers adopts a post-finishing method:

[0049] Comparative Example 1:

[0050] Untreated para-aramid fibers were placed in an ultraviolet weathering tester for 7 days, and their mechanical properties were tested.

[0051] Application Example 1:

[0052] Using dichloromethane as a co-solvent and ethanol as the main solvent, a solution containing compound C with a mass fraction of 0.1% was prepared. First, the para-aramid fiber was immersed in the solution containing compound C for 30 seconds, then removed and dried in a 60℃ oven for 30 minutes. Finally, it was placed in an ultraviolet weathering tester for 21 days, and the mechanical properties of the para-aramid fiber were tested.

[0053] Application Example 2:

[0054] Using dichloromethane as a co-solvent and ethanol as the main solvent, a solution containing compound C1 with a mass fraction of 0.1% was prepared. First, the para-aramid fiber was immersed in the solution containing compound C1 for 30 seconds, then removed and dried in a 60℃ oven for 30 minutes. Finally, it was irradiated in an ultraviolet weathering tester for 21 days, and the mechanical properties of the para-aramid fiber were tested.

[0055] Application Example 3:

[0056] Using dichloromethane as a co-solvent and ethanol as the main solvent, a solution containing compound C2 with a mass fraction of 0.1% was prepared. First, the para-aramid fiber was immersed in the solution containing compound C2 for 30 seconds, then removed and dried in a 60℃ oven for 30 minutes. Finally, it was placed in an ultraviolet weathering tester for 21 days, and the mechanical properties of the para-aramid fiber were tested.

[0057] Based on previous experimental explorations, the application of ultraviolet absorbers in meta-aramid fibers is carried out using a blending spinning method:

[0058] Comparative Example 2:

[0059] First, weigh 200-500 g of meta-aramid (PMIA) dope without added UV absorber, then perform wet spinning using a small micro wet spinning machine. After placing the finished meta-aramid fiber in a UV weathering tester for 21 days, test the mechanical properties of the para-aramid fiber.

[0060] According to solubility tests, compounds c, c1, and c2 have excellent solubility in DMAC, making them very suitable for blend spinning. The amount of UV absorber added is 0.5-5% of the solid content of the aramid solution.

[0061] Application Example 4:

[0062] First, weigh 200-500 g of PMIA stock solution, calculate the required mass of compound c, mix the UV absorber and PMIA stock solution evenly, and then use mechanical stirring at 200 rpm for 2 hours to mix them evenly. Then, perform wet spinning using a small micro wet spinning machine. After placing the finished aramid fiber in a UV weathering tester for 21 days, test the mechanical properties of the meta-aramid fiber.

[0063] Application Example 5:

[0064] First, weigh 200-500 g of PMIA stock solution, calculate the required mass of compound c1, mix the UV absorber and PMIA stock solution evenly, and then use mechanical stirring at 200 rpm for 2 hours to mix them evenly. Next, perform wet spinning using a small-scale wet spinning machine. After irradiating the finished aramid fiber in a UV weathering tester for 21 days, test the mechanical properties of the meta-aramid fiber.

[0065] Application Example 6:

[0066] First, weigh 200-500 g of PMIA stock solution, calculate the required mass of compound c2, mix the UV absorber and PMIA stock solution evenly, and then mix them thoroughly using mechanical stirring at 200 rpm for 2 hours. Next, perform wet spinning using a small-scale wet spinning machine. After irradiating the finished aramid fiber in a UV weathering tester for 21 days, test the mechanical properties of the meta-aramid fiber.

[0067] Ultraviolet light (wavelength typically between 290 and 400 nm) carries very high energy, sufficient to break the chemical bonds of many organic polymers (including fibers). Ultraviolet irradiation irreversibly damages the molecular backbone (especially amide bonds) of aramid fibers through photo-oxidative degradation. Impurities or chromophores in the fiber absorb ultraviolet light and react with oxygen, generating highly reactive free radicals. These free radicals "steal" hydrogen atoms from the polymer chains, triggering a chain reaction that leads to further chain breakage. This results in severe degradation of its core mechanical properties—tensile strength and elastic modulus—while also reducing its impact resistance and fatigue resistance. Therefore, in fields with extremely high mechanical performance requirements, aramid fiber products must undergo UV-resistant treatment. Mechanical property tests were performed on the above samples: breaking strength and elongation at break. Each set of data was tested three times and the average value was taken. The test results are shown in Table 1.

[0068]

[0069] As can be seen from Comparative Example 1 and Application Examples 1-4, after 21 days of UV aging, the tensile strength of Comparative Example 1 decreased by 20.17%, while the tensile strength of PPTA fibers in Application Examples 1-3 decreased by 7.26%, 7.28%, and 4.51%, respectively. This indicates that the finishing process with the UV absorber can significantly improve the mechanical properties of PPTA fibers. As can be seen from Comparative Example 2 and Application Examples 4-6, after 21 days of UV aging, the tensile strength of PMIA fibers in Comparative Example 2 decreased by 27.94%, while the tensile strength of PMIA fibers in Application Examples 3-6 decreased by 19.73%, 12.53%, and 12.09%, respectively. The elongation at break of PMIA fibers also showed a slight improvement. This indicates that the novel triazine UV absorber synthesized in this invention has multiple application methods and can effectively improve the mechanical properties of PPTA and PMIA fibers after UV aging.

[0070] The addition of ultraviolet absorbers can slow down the aging of aramid fibers, significantly retain tensile strength and breaking strength, inhibit the generation of surface defects, maintain structural integrity, and ultimately greatly extend the service life and safety and reliability of aramid products in outdoor or ultraviolet environments. This is a key and effective technical means to improve the durability of aramid materials.

Claims

1. An ultraviolet absorber having a triazine ring as a main structure, characterized by The ultraviolet absorber has the following structural formula: Wherein, R1, R2, R3, and R4 are groups containing phenyl or substituted phenyl groups, and R5 is piperidinyl, piperazine, pyrrolidinyl, or one of the following structures: 。 2. A method for producing an ultraviolet absorber having a triazine ring as a main structure, characterized by The method includes the following steps: Step 1: Add cyanuric chloride, catalyst A, and m-xylene to organic solvent A, and react at 5-10℃ for 2-4 h. After the reaction is complete, add resorcinol and heat to 50-90℃ for 4-5 h. After the reaction is complete, pour into a dilute solution of hydrochloric acid, separate the liquid, evaporate by rotary evaporation, recrystallize from toluene, and perform column chromatography to obtain an intermediate. The molar ratio of cyanuric chloride, m-xylene, and resorcinol is 1:2-4:1-5. Step 2: Add the intermediate obtained in Step 1, paraformaldehyde, and amine compound to organic solvent B, and react at 50-100℃ for 2-12 h under N2 atmosphere to obtain a triazine ultraviolet absorber compound, wherein the molar ratio of the intermediate, paraformaldehyde, and amine compound is 1:2-4:1-3, and the amine compound is selected from one of the following structures: 。 3. The method for producing a triazine ring-based ultraviolet absorber according to claim 2, characterized by The organic solvent A is one of nitrobenzene, dichloromethane, carbon disulfide, o-dichlorobenzene, chlorobenzene, p-dichlorobenzene, dichloroethane, and chloroform, and its weight is 10 to 15 times that of cyanuric chloride.

4. The method for producing a triazine ring-based ultraviolet absorber according to claim 2, characterized by The catalyst A is one of anhydrous aluminum chloride, anhydrous ferric chloride, and anhydrous zinc chloride, and its amount is 1 to 3 times that of the intermediate.

5. The method for preparing an ultraviolet absorber with a triazine ring as the main structure according to claim 2, characterized in that... The organic solvent D is one of methanol, ethanol, isopropanol, acetonitrile, N,N-dimethylformamide, dichloromethane, toluene, DMSO, and water, and its amount is 30 to 50 times that of the intermediate.

6. The method for preparing an ultraviolet absorber with a triazine ring as the main structure according to claim 2, characterized in that... The amine compound is one of the following: secondary amine, 4-Boc aminopiperidine, 4-methoxypiperidine, piperazine-1-carboxylic acid methyl ester, 1-Boc piperazine, 4-hydroxymethylpiperidine, 1-cyclopropylcarbonylpiperazine, 1-acetylpiperazine, piperidine-1-carboxamide, piperazine-1-carboxylic acid methyl ester, and N-methylpropyl-2-amine.

7. The application of the ultraviolet absorber with a triazine ring as the main structure as described in claim 1 in aramid fibers.

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