A heterocyclic azo disperse dye for improving the dye uptake of meta-aramid and a dyeing method thereof

Abstract

This invention relates to a heterocyclic azo disperse dye for improving the dyeing rate of meta-aramid fibers and its dyeing method, belonging to the field of textile technology. The invention provides a series of heterocyclic azo disperse dyes based on pyrazolamine and pyrazolone parent structures, synthesized via diazotization-coupling reactions. The dye molecules possess optimized size and planarity, effectively promoting their diffusion and penetration within the fiber. By introducing substituents such as -Cl and -CH3 to regulate the molecular structure, the matching between the dye and the pre-swollen fiber structure is further enhanced, thereby improving the diffusion path and dyeing uniformity. Furthermore, this invention systematically studies the effects of different organic solvent pretreatments on the dyeing performance of meta-aramid fibers, determines the optimal pretreatment solvent, and optimizes the pretreatment conditions and dyeing process parameters accordingly.

Description

Technical Field

[0001] This invention relates to a heterocyclic azo disperse dye for improving the dyeing rate of meta-aramid fibers and its dyeing method, belonging to the field of textile technology. Background Technology

[0002] Dyes have garnered significant attention due to their ability to impart vibrant colors to matrices. With the development of new materials, higher demands are being placed on dye structures and dyeing processes. Heterocyclic azo disperse dyes, a rapidly developing category in recent years, significantly enhance dyeing affinity, dispersibility, and penetration by introducing heteroatoms into the molecule, resulting in bright and saturated colors and effectively reducing color variations. Simultaneously, these dyes exhibit excellent colorfastness in terms of light, perspiration, washing, and rubbing resistance, and are widely used in synthetic fibers and their blends. Meta-aramid, as one of the most produced and widely used high-performance, high-temperature resistant fibers, possesses a highly stable macromolecular structure and exhibits excellent thermal stability, chemical resistance, and inherent flame-retardant properties. Its good mechanical properties, high mechanical strength, and rigidity make it widely used in high-end workwear fields such as fire-fighting suits and military uniforms.

[0003] The highly crystalline microstructure and dense skin layer of meta-aramid fibers severely hinder the diffusion of dye molecules into the fiber interior, resulting in problems such as low dye uptake, light color, and insufficient color fastness in conventional dyeing processes. To improve dyeing efficiency, current research mainly focuses on improving methods, such as 180℃ high-temperature, high-pressure dyeing, ionic liquid or supercritical CO2 fluid dyeing. These technologies promote dye uptake to some extent, but often face significant challenges: high-temperature, high-pressure methods require addressing high energy consumption; while ionic liquid and supercritical CO2 technologies face challenges due to high cost and complex processes. Summary of the Invention

[0004] This invention provides a heterocyclic azo disperse dye and its dyeing method for improving the dyeing rate of meta-aramid fibers, thus solving problems such as low dyeing rate and uneven dyeing. The dye is synthesized via a diazotization-coupling reaction, and its molecules, with pyrazolamine and pyrazolone as parent structures, possess suitable molecular size and planar configuration, which facilitates migration and adsorption into the fiber. Modifying the molecular structure by introducing substituents such as -Cl and -CH3 further improves the compatibility between the dye and the pre-swollen fiber structure, thereby optimizing its diffusion behavior in the fiber and improving dyeing evenness. Furthermore, this invention systematically investigates the effects of different organic solvent pretreatments on the dyeing performance of meta-aramid fibers, screens out the most effective pretreatment solvent, and optimizes the pretreatment and dyeing process conditions accordingly.

[0005] The technical solution adopted in this invention is: a heterocyclic azo compound, the general structural formula of which is:

[0006]

[0007] Among them, R1, R2, and R3 are selected from hydrogen, C1-C5 alkanes, or halogens, respectively;

[0008] D1 is , .

[0009] Furthermore, the compound specifically comprises:

[0010] , , , , , , , At least one of them.

[0011] A method for preparing a heterocyclic azo compound, the method comprising the following steps:

[0012] (1) Diazotization of pyrazolamide;

[0013] (2) The coupling component in step (1) is coupled to obtain a heterocyclic azo compound;

[0014] The coupling components are respectively based on the differences in R1, R2, and R3. , , , .

[0015] The definitions of R1, R2, and R3 are the same as in claim 1.

[0016] Further, step (1) specifically involves: under ice-water bath conditions of 0-5℃, adding 1-methyl-1H-pyrazole-4-amine or 3-chloro-1H-pyrazole-4-amine, concentrated hydrochloric acid and deionized water sequentially to a three-necked flask, stirring until completely dissolved, then slowly adding sodium nitrite, and continuing to stir the reaction at this temperature to obtain a diazonium salt solution.

[0017] The specific steps (2) are as follows: the coupling component is dissolved in hydrochloric acid aqueous solution, and the above diazonium salt solution is slowly added dropwise to the coupling component solution under stirring at 0-5℃; then, the pH of the reaction system is adjusted to 9-10 using sodium carbonate aqueous solution, and the temperature is maintained for the reaction.

[0018] After the reaction was completed, the precipitate was collected by filtration, washed, and dried to obtain a bright yellow crude product. The crude product was further recrystallized and purified to finally obtain the target product in the form of yellow crystals.

[0019] A heterocyclic azo disperse dye composition, wherein the dye contains the aforementioned heterocyclic azo compound.

[0020] A dyeing method for a heterocyclic azo compound further includes the following steps: mixing the above-mentioned heterocyclic azo compound, dispersant, zirconium beads, and water and sand milling for 2-8 hours; after sand milling, collecting the dye paste by filtration, drying the filtrate by rotary evaporation, and grinding the resulting solid into a uniform powder for later use.

[0021] Prepare the dye solution, put it into the fabric, and then dye it. After dyeing, cool it down, take out the fabric, perform a reduction wash, and then dry it.

[0022] Furthermore, the fabric is pretreated before dyeing, specifically by adding a polar solvent to pretreat the fabric at 65°C for 30 minutes, then washing it with hot water at 90°C, rinsing it with room temperature water, and drying it for later use.

[0023] Furthermore, the conditions for the reduction cleaning are: 2 g / L sodium hydrosulfite, 1 g / L NaOH, bath ratio 1:50, 80℃, and 10 min.

[0024] Furthermore, the mass ratio of the heterocyclic azo compound, dispersant, and zirconium beads is 1:1:150; the mass ratio of the fabric to the heterocyclic azo disperse dye is 50:1; and the bath ratio of the fabric to the dye liquor is 1:20.

[0025] The fabric is meta-aramid fiber, plain weave, 160 g / m². 2 The zirconium beads are 2 mm in diameter; the dispersant is NNO.

[0026] The dyeing process involves heating the temperature to 90°C at a rate of 1°C / min, holding it at that temperature for 60 minutes, and then cooling it down to 75°C after dyeing.

[0027] A dyed fabric is obtained by the dyeing method described above.

[0028] The beneficial effects of this invention are as follows: Compared with existing commercial dyes, the novel heterocyclic azo disperse dye of this invention is designed with dye molecules based on the suitable size and planarity of pyrazole and pyrazolinone heterocycles, which effectively promotes its diffusion in the fiber; at the same time, by controlling the substituents (-Cl,-CH3), the molecular characteristics can be finely adjusted to achieve a better match with the pre-swollen fiber structure, thereby optimizing the diffusion path and improving dyeing uniformity. Therefore, it has broad application prospects in industrial production.

[0029] All intermediates and chemicals required for producing the various dyes of this invention are readily available and can be produced using conventional equipment for dispersible dye production; no specific equipment is required. The technical solution of this invention is simple in process and easy to operate, with no special requirements for dyeing equipment; conventional dyeing equipment can be used.

[0030] This invention explores the effects of different organic solvent pretreatments on the dyeing properties of meta-aramid fibers, comparing them with existing methods such as 180℃ high-temperature and high-pressure dyeing, ionic liquid dyeing, or supercritical CO2 fluid dyeing. It offers advantages such as low energy consumption, low cost, simple process, and low equipment requirements. Furthermore, the pretreatment solvents are easy to recover. Attached Figure Description

[0031] Figure 1 Images of fabric samples before and after dyeing meta-aramid fibers.

[0032] Figure 2 The dyeing rate and ΔK / S value of dyed fabrics under different solvent pretreatments are shown.

[0033] Figure 3 SEM images and tensile strength diagrams of fabrics pretreated with different solvents: (a) Untreated; (b) Treated with solvent E; (c) Treated with solvent F.

[0034] Figure 4 This is a graph showing the change in fiber crystallinity before and after pretreatment.

[0035] Figure 5 Pretreatment and dyeing conditions of meta-aramid fibers, and dyeing rate and ∆K / S value of meta-aramid fibers under different sample numbers.

[0036] Figure 6 The dyeing rate corresponds to different pretreatment temperatures and times.

[0037] Figure 7 The dyeing rate of meta-aramid fibers at different dyeing temperatures is shown.

[0038] Figure 8 The dyeing rate of meta-aramid is given by different dyeing times.

[0039] Figure 9 The dyeing rate of meta-aramid is given at different dyeing pH values.

[0040] Figure 10 The color fastness of heterocyclic azo disperse dyes is denoted by various properties. Detailed Implementation

[0041] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the invention, but do not limit the invention in any way.

[0042] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; the reagents and materials described are commercially available unless otherwise specified.

[0043] A heterocyclic azo compound of the present invention is shown below:

[0044]

[0045] The coupling components are further divided according to different R1, R2, and R3. , , , ;

[0046] Preferably, D1 is , At least one of them;

[0047] Preferably, the heterocyclic azo structure is as follows:

[0048] or ;

[0049] The coupling components are divided into different types based on R1, R2, and R3. , , , ;

[0050] More preferably, the compound is specifically:

[0051] , , , , , , , At least one of them.

[0052] A method for preparing a heterocyclic azo compound according to the present invention includes:

[0053] (1) Diazotization of pyrazolamide;

[0054] (2) The diazotization product of step (1) is coupled with the coupling component to obtain a heterocyclic azo compound;

[0055] Preferably, the compound obtained in step (1) is: The D1 is , At least one of them.

[0056] Preferably, the preparation method includes:

[0057] (1) Under ice-water bath conditions of 0-5℃, 1-methyl-1H-pyrazole-4-amine or 3-chloro-1H-pyrazole-4-amine, concentrated hydrochloric acid, and deionized water were added sequentially to a 100 mL three-necked flask. After stirring until completely dissolved, sodium nitrite was slowly added, and the reaction was continued to be stirred at this temperature for 0.5 h to obtain a diazonium salt solution; wherein compound 1 is ;

[0058] (2) Dissolve the coupling component in hydrochloric acid aqueous solution, and slowly add the above diazonium salt solution dropwise to the coupling component solution while stirring at 0-5℃. Then, adjust the pH of the reaction system to 9-10 with 0.5 mol / L sodium carbonate aqueous solution, and maintain the temperature for 4 h.

[0059] (3) After the reaction was completed, the precipitate was collected by filtration, washed three times with deionized water, and dried at 50°C to obtain a bright yellow crude product. The crude product was further purified by recrystallization from an acetone-water system to finally obtain the target product in the form of yellow crystals;

[0060] Preferably, the preparation includes:

[0061] The first step is the diazotization of 1-methyl-1H-pyrazole-4-amine or 3-chloro-1H-pyrazole-4-amine;

[0062] 1-Methyl-1H-pyrazole-4-amine or 3-chloro-1H-pyrazole-4-amine was dissolved in dilute hydrochloric acid solution. After complete dissolution, the solution was cooled to 0-5°C. Sodium nitrite was added to react with the solution, followed by the addition of aminosulfonic acid to generate a diazonium salt solution. Compound 1 is... ;

[0063] The ratio of diazo component, dilute acid solution, sodium nitrite, and aminosulfonic acid is 0.005 mol: 10 ml: 0.0055 mol: 0.0005 mol.

[0064] The second step is the coupling of compound 1 with the coupling component;

[0065] The coupling component was dissolved in water, acidified with hydrochloric acid, and ultrasonically dispersed to ensure uniform dispersion. The mixture was cooled to 0-5°C in an ice-salt bath, and the diazonium salt was slowly added dropwise, with crushed ice added as needed to maintain the temperature in the reaction bath. After the diazonium salt addition was complete, the pH of the reaction system was adjusted to 9-10 using a 0.5 mol / L sodium carbonate aqueous solution, and the temperature was maintained for 4 hours.

[0066] The H-acid test showed no diazonium salt in the osmosis zone, indicating the reaction was complete. The precipitate was collected by filtration and washed three times with deionized water.

[0067] The product was dried at 50°C to obtain a bright yellow crude product. The crude product was further purified by recrystallization from an acetone-water system to finally obtain the target product in the form of yellow crystals.

[0068] The ratio of coupling component, water, and hydrochloric acid is 0.0055 mol: 20 ml: 1 ml.

[0069] The molar ratio of compound 1 to the coupling component is 0.005 mol: 0.0055 mol.

[0070] Preferably, the method for pretreating meta-aramid fibers according to the present invention includes:

[0071] Adding polar solvents to meta-aramid (plain weave, 160 g / m) 2 Pre-treat at 65℃ for 30 min (taking the optimal conditions as an example). After that, wash with 90℃ hot water for 10 min, then rinse with room temperature water for 5 min, and air dry for later use.

[0072] Preferably, the mass ratio of the meta-aramid fabric to the polar solvent is 1:50.

[0073] The present invention provides a heterocyclic azo disperse dye, wherein the dye contains the heterocyclic azo compound.

[0074] Preferably, the present invention provides a novel heterocyclic azo disperse dye for dyeing meta-aramid fibers and a pretreatment method, wherein the dye contains the heterocyclic azo compound.

[0075] Preferably, a dyeing method for a heterocyclic azo disperse dye according to the present invention includes:

[0076] The heterocyclic azo compound, dispersant, zirconium beads and water are mixed and sand-milled for 2-8 g; after sand milling, the mixture is filtered and separated, and the resulting filter cake is collected to obtain the dye paste; the paste is dried at 65°C and the resulting solid is ground into a uniform powder for later use.

[0077] Prepare the dye solution and put it into the fabric, then dye it. After dyeing, cool it to 75℃, take out the fabric, and perform reduction cleaning (2 g / L sodium hydrosulfite, 1 g / L NaOH, liquor ratio 1:50, 80℃, 10 min). Let it dry before testing.

[0078] Preferably, the mass ratio of the heterocyclic azo compound, dispersant, and zirconium beads is 1:1:150; the mass ratio of the fabric to the heterocyclic azo disperse dye is 50:1; and the bath ratio of the fabric to the dye liquor is 1:20.

[0079] The fabric is meta-aramid (plain weave, 160 g / m²). 2 The zirconium beads are 2 mm in diameter; the dispersant is NNO.

[0080] The dyeing process involves heating the temperature to 90°C at a rate of 1°C / min, holding it at that temperature for 60 minutes, and then cooling it down to 75°C after dyeing.

[0081] This invention provides a dyed fabric prepared by the method described above.

[0082] Example 1

[0083] The following compounds were prepared experimentally:

[0084] , , , .

[0085] Step 1, diazotization of 1-methyl-1H-pyrazole-4-amine:

[0086] In a 100 ml three-necked flask, 1-methyl-1H-pyrazole-4-amine (5 mmol) was dissolved in dilute hydrochloric acid. The solution was stirred continuously until completely dissolved, and then cooled to 0-5 °C. Sodium nitrite was added and reacted at 0-5 °C for 1 h. The excess sodium nitrite was removed by weighing out aminosulfonic acid, and a diazonium salt solution was generated.

[0087] The second step is the coupling of the diazonium salt with the coupling component:

[0088] 1-Phenylacet-3-methyl-5-pyrazolone (5 mmol), 1-(2-chlorophenyl)-3-methyl-5-pyrazolone (5 mmol), 1-(4-methylphenyl)-3-methyl-5-pyrazolone (5 mmol), and 3-methyl-1-p-phenylmethyl-5-pyrazolone (5 mmol) were dissolved in water, acidified with hydrochloric acid, and ultrasonically dispersed. The mixture was cooled to 0-5°C in an ice-salt bath, and the diazonium salt was slowly added dropwise, with crushed ice added as needed to maintain the temperature of the reaction bath. After the diazonium salt was added, the pH of the reaction system was adjusted to 9-10 using a 0.5 mol / L sodium carbonate aqueous solution, and the temperature was maintained for 4 h. The reaction was considered complete when no diazonium salt was detected in the permeation zone by H acid detection. The precipitate was collected by filtration, washed three times with deionized water, and dried at 50°C to obtain a bright yellow crude product. The crude product was further purified by recrystallization from an acetone-water system to finally obtain the target product as yellow crystals.

[0089] The 1H NMR and high-resolution mass spectrometry results of the dye after purification of product I are as follows: 1 H NMR (400 MHz, DMSO)δ 8.01 (s, 1H, CH==N), 7.93 (d, J = 8.1 Hz, 2H, NPhCHO), 7.74 (s, 1H, CH==C), 7.44 (t, J = 7.8 Hz, 2H, NPhCHm), 7.19 (t, J = 7.4 Hz, 1H, NPhCHp), 3.85 (s,3H, NCH3), 2.25 (s, 3H, CH3). ESI-MS, m / Z:[MH] - Theoretical value: 281.1156; Test value: 281.1154.

[0090] The 1H NMR and high-resolution mass spectrometry results of the dye after purification of product II are as follows: 1H NMR (400 MHz, DMSO)δ 7.99 (s, 1H, CH==N), 7.72 (s, 1H CH==C), 7.63 (dt, J = 7.5, 3.6 Hz, 1H,NPhCHO), 7.48 (ddd, J = 9.7, 7.4, 4.3 Hz, 3H, NPhCHm / p), 3.84 (s, 3H NCH3), 2.22 (s, 3H CH3). ESI-MS, m / Z:[MH] - Theoretical value: 315.0767; Test value: 315.0764.

[0091] The 1H NMR and high-resolution mass spectrometry results of the dye after purification of product III are as follows: 1 H NMR (400 MHz, DMSO)δ 7.99 (s, 1H, CH==N), 7.71 (d, J = 9.4 Hz, 2H, NPhCH O ), 7.63 (dd, J = 8.2,2.3 Hz, 1H, CH==C), 7.18 (d, J = 8.3 Hz, 1H, NPhCH m ), 3.85 (s, 3H, NCH3), 2.25 (s, 3H, CPhCH3), 2.23 (s, 3H, CPhCH3), 2.22 (s, 3H, CH3). ESI-MS, m / Z:[MH] - Theoretical value: 309.1469; Test value: 309.1466.

[0092] The 1H NMR and high-resolution mass spectrometry results of the dye after purification of product IV are as follows: 1 H NMR (400 MHz, DMSO)δ 8.00 (d, J = 2.0 Hz, 1H, CH==N), 7.80 (dd, J = 8.6, 2.1 Hz, 2H, NPhCH O ),7.73 (d, J = 2.0 Hz, 1H, CH==C), 7.24 (d, J = 8.1 Hz, 2H, NPhCH m ), 3.85 (d, J = 2.1 Hz, 3H, NCH3), 2.31 (s, 3H, CPhCH3), 2.24 (d, J = 2.0 Hz, 3H, CH3). ESI-MS, m / Z:[MH] - Theoretical value: 295.1313; Test value: 195.1309.

[0093] Example 2

[0094] The following compounds were prepared experimentally:

[0095] , , , .

[0096] Step 1, diazotization of 3-chloro-1H-pyrazole-4-amine:

[0097] In a 100 ml three-necked flask, 3-chloro-1H-pyrazole-4-amine (5 mmol) was dissolved in dilute hydrochloric acid. The solution was stirred continuously until completely dissolved, and then cooled to 0-5 °C. Sodium nitrite was added and reacted at 0-5 °C for 1 h. The excess sodium nitrite was removed by weighing out aminosulfonic acid, and a diazonium salt solution was generated.

[0098] The second step is the coupling of the diazonium salt with the coupling component:

[0099] 1-Phenylacet-3-methyl-5-pyrazolone (5 mmol), 1-(2-chlorophenyl)-3-methyl-5-pyrazolone (5 mmol), 1-(4-methylphenyl)-3-methyl-5-pyrazolone (5 mmol), and 3-methyl-1-p-phenylmethyl-5-pyrazolone (5 mmol) were dissolved in water, acidified with hydrochloric acid, and ultrasonically dispersed. The mixture was cooled to 0-5°C in an ice-salt bath, and the diazonium salt was slowly added dropwise, with crushed ice added as needed to maintain the temperature of the reaction bath. After the diazonium salt was added, the pH of the reaction system was adjusted to 9-10 using a 0.5 mol / L sodium carbonate aqueous solution, and the temperature was maintained for 4 h. The reaction was considered complete when no diazonium salt was detected in the permeation zone by H acid detection. The precipitate was collected by filtration, washed three times with deionized water, and dried at 50°C to obtain a bright yellow crude product. The crude product was further purified by recrystallization from an acetone-water system to finally obtain the target product as yellow crystals.

[0100] The 1H NMR and high-resolution mass spectrometry results of the dye after purification of product V are as follows: 1 H NMR (400 MHz, DMSO) δ13.39 (s, 1H, NH), 8.22 - 8.15 (m, 1H, CH==C), 7.91 (d, J = 8.1 Hz, 2H,NPhCHO), 7.46 (t, J = 7.8 Hz, 2H, NPhCHm), 7.22 (t, J = 7.5 Hz, 1H, NPhCHp), 2.26 (s, 3H, CH3). ESI-MS, m / Z:[M+Na] +Theoretical value: 325.0575; Test value: 325.0572.

[0101] The 1H NMR and high-resolution mass spectrometry results of the dye after purification of product VI are as follows: 1 H NMR (400 MHz, DMSO) δ13.37 (s, 1H, NH), 8.20 - 8.15 (m, 1H, CH==C), 7.65 (dd, J = 5.9, 3.3 Hz, 1H,NPhCH O ), 7.51 (dd, J = 15.7, 4.3 Hz, 3H, NPhCH m / p ), 2.23 (d, J = 2.7 Hz, 3H,CH3). ESI-MS, m / Z:[M+Na] + Theoretical value: 359.0185; Test value: 359.0180.

[0102] The 1H NMR and high-resolution mass spectrometry results of the dye after purification of product VII are as follows: 1 H NMR (400 MHz, DMSO) δ13.38 (s, 1H, NH), 8.19 (s, 1H, CH==C), 7.68 (s, 1H, NPhCH O ), 7.65 - 7.58 (m, 1H, NPhCH) O ), 7.20 (d, J = 8.1 Hz, 1H, NPhCH m ), 2.25 (d, J = 2.7 Hz, 3H,CPhCH3), 2.22 (s, 3H, CPhCH3), 2.08 (d, J = 3.0 Hz, 3H, CH3). ESI-MS, m / Z:[M+Na] + Theoretical value: 353.0888; Test value: 353.0886.

[0103] The 1H NMR and high-resolution mass spectrometry results of the dye after purification of product VIII are as follows: 1 H NMR (400 MHz, DMSO) δ13.38 (s, 1H, NH), 8.18 (s, 1H, CH==C), 7.78 (d, J = 8.0 Hz, 2H, NPhCH O ), 7.28 - 7.21 (m, 2H, NPhCH) m), 2.31 (d, J = 3.9 Hz, 3H, CPhCH3), 2.24 (d, J =3.5 Hz, 3H, CH3). ESI-MS, m / Z:[M+Na] + Theoretical value: 339.0731; Test value: 339.0730.

[0104] Preprocessing methods:

[0105] The meta-aramid fabric was pretreated in a polar solvent at a temperature of 65°C for 30 minutes. After pretreatment, it was washed with hot water at 90°C for 10 minutes and rinsed with room temperature water for 5 minutes. The fabric was then dried for subsequent dyeing.

[0106] Staining method:

[0107] Take 0.1 g of disperse dye, 0.1 g of dispersant NNO, 15 g of zirconium beads (2 mm in diameter), and 10 mL of water and add them to a sand mill and sand mill for 2-8 hours. After sand milling, filter the mixture through a sieve, collect the dye dispersion, and dry it to obtain dye powder. Take the disperse dye powder according to the 2% color requirement, add water at a bath ratio of 1:20, transfer it to a dyeing cup, add the treated meta-aramid fabric, and place it in a high-temperature and high-pressure dyeing instrument. Rapidly heat the fabric to 90℃ at a heating rate of 1℃ / min, hold it for 60 min, and then cool it down to 75℃. Take out the dyed fabric sample, reduce and clean it to obtain the dyed fabric sample.

[0108] Determination of dye uptake rate:

[0109] Pipette 0.1 mL of the staining solution before and after staining into 10 mL volumetric flasks, add acetone to the mark, and measure the absorbance at the maximum absorption wavelength (Amax) using a UV-Vis spectrophotometer. Calculate the staining rate using the following formula:

[0110] In the formula: m and n are the dilution factors of the pre-dyeing and post-dyeing solutions using acetone, respectively; A0 and A are the absorbance of the dye solutions at the maximum absorption wavelength of the dye before and after dyeing, respectively.

[0111] The properties of the pretreated and dyed meta-aramid fabrics were tested and characterized:

[0112] Figure 1 The effects of eight dyes (I-VIII) prepared using this invention on the dyeing of meta-aramid fibers are demonstrated. As shown in the figure, all dyed fabric samples were successfully dyed yellow, and due to the different electronic effects or steric hindrance of the substituent groups in each dye molecule, a gradient color depth effect was ultimately exhibited. The dyeing rate and ΔK / S value of the dyed fabrics under different solvent pretreatments were then compared. Figure 2It can be found that fabrics pretreated with dimethyl sulfoxide and N,N-dimethylformamide exhibit superior dyeing performance, with significantly improved dye uptake and ∆K / S values.

[0113] like Figure 3 As shown, after treatment with dimethyl sulfoxide, obvious erosion marks appeared on the fiber surface, and the tensile strength decreased significantly; while the surface morphology of the fiber treated with N,N-dimethylformamide did not change significantly, and the tensile strength remained basically unchanged compared with the untreated sample. This indicates that N,N-dimethylformamide can effectively improve the dyeing performance of fibers while maintaining their structural integrity and mechanical properties. Meanwhile, X-ray diffraction (XRD) patterns... Figure 4 The results showed that the crystal type (crystal form) of meta-aramid remained unchanged after treatment with dimethyl sulfoxide and N,N-dimethylformamide solvents compared to the untreated sample. However, solvent pretreatment effectively swells the fibers, weakens the hydrogen bonds and van der Waals forces between molecular chains, thereby reducing the density of the crystalline region and increasing the proportion of the amorphous region.

[0114] To further clarify the effect of N,N-dimethylformamide pretreatment on improving dye uptake, this study designed a control experiment using the prepared dye VII as an example. The experiment included two groups: pretreated (samples 3 and 4, pretreated with DMF as the solvent: temperature 65℃, time 30 min) and untreated (samples 1 and 2), and dyeing was performed in aqueous phase and 10% N,N-dimethylformamide solution, respectively. All other conditions remained consistent. Figure 5 The results of dye uptake and ΔK / S values ​​show that the untreated meta-aramid fibers (samples 1 and 2) have significantly lower dye uptake and dyeing depth because the dye molecules have difficulty diffusing into the fiber interior; while the dyeing performance is significantly improved after pretreatment with N,N-dimethylformamide solvent (samples 3 and 4).

[0115] To optimize the dyeing process, this study systematically investigated the effects of temperature and time on the dyeing properties of meta-aramid fibers (using dye VII) when N,N-dimethylformamide was used as the pretreatment solvent. The results are as follows: Figure 6As shown, when the pretreatment time was fixed at 15 min, the dye uptake rate increased significantly with increasing temperature, rising sharply from 69.2% at 45℃ to 89.4% at 65℃; thereafter, with further temperature increases, the increase in dye uptake rate tended to level off. On the other hand, when the pretreatment temperature was fixed at 45℃, the dye uptake rate increased with time, rising from 69.2% at 15 min to 74.3% at 30 min; when the time was further extended to 45 min, the dye uptake rate only increased slightly to 75.8%, indicating that the fiber swelling had approached equilibrium at this point. Considering that prolonged high-temperature treatment would lead to a sharp increase in energy consumption, based on a comprehensive consideration of dye uptake rate and energy efficiency, the optimal process conditions for using DMF as the pretreatment solvent were finally determined to be: temperature 65℃, time 30 min.

[0116] To further optimize the dyeing process, the optimal conditions were explored and determined: dyeing temperature 90℃, time 60 min, pH 5 ( Figure 7 , 8 9).

[0117] After the dyed fabric samples were treated and cleaned according to the national standard "Test Methods for Color and Intensity of Disperse Dyes" (GB2394-2013), their water fastness, dry rubbing fastness, wet rubbing fastness, and light fastness were measured. The test results are as follows: Figure 10 The data from the comparison chart shows that the color fastness test results indicate that all dyed aramid fabrics achieve a washing fastness and dry / wet rubbing fastness of grade 4 or above, meeting the requirements for daily applications. However, in terms of light fastness, dyes I-III only reach grades 2-3, only dye IV reaches grade 3-4, while dyes V-VIII all reach grade 4 or above. This difference stems from the 3-chloro-1H-pyrazole-4-amine structure introduced into the V-VIII series dye molecules. The strong electron-withdrawing inductive effect of its chlorine atom (Cl) effectively enhances the photochemical stability of the dye molecule itself, thereby significantly improving the light fastness of the dyed fabrics.

[0118] This invention provides a heterocyclic azo disperse dye and its dyeing method for improving the dyeing rate of meta-aramid fibers. First, a series of pyrazol-based heterocyclic azo disperse dyes were synthesized via a diazotization-coupling reaction. The dye molecules, relying on the suitable size and planarity of the pyrazol and pyrazolone heterocycles, effectively promote diffusion within the fiber. Simultaneously, by controlling the substituents (-Cl, -CH3), the molecular properties can be fine-tuned to achieve better matching with the pre-swollen fiber structure, thereby optimizing the diffusion path and improving dyeing uniformity. The effects of different organic solvent pretreatments on the dyeing properties of meta-aramid fibers were investigated, an optimal pretreatment dyeing process was established, and the best pretreatment effect was explored. This invention solves the problems of limited dye types available for meta-aramid fibers, poor color fastness after dyeing, and dyeing difficulties.

[0119] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A heterocyclic azo compound, characterized in that, The general structural formula of the compound is: ； Among them, R1, R2, and R3 are selected from hydrogen, C1-C5 alkanes, or halogens, respectively; D1 is , .

2. The compound according to claim 1, characterized in that, The compound is specifically: , , , , , , , At least one of them.

3. The method for preparing a heterocyclic azo compound according to claim 1 or 2, characterized in that: The preparation method includes the following steps: (1) Diazotization of pyrazolamide; (2) The coupling component in step (1) is coupled to obtain a heterocyclic azo compound; The coupling components are respectively based on the differences in R1, R2, and R3. , , , ; The definitions of R1, R2, and R3 are the same as in claim 1.

4. The preparation method according to claim 3, characterized in that, The specific steps (1) are as follows: under the conditions of an ice-water bath at 0-5℃, 1-methyl-1H-pyrazole-4-amine or 3-chloro-1H-pyrazole-4-amine, concentrated hydrochloric acid and deionized water are added to a three-necked flask in sequence. After stirring until completely dissolved, sodium nitrite is slowly added and the reaction is continued at the same temperature to obtain a diazonium salt solution. The specific steps (2) are as follows: the coupling component is dissolved in hydrochloric acid aqueous solution, and the above diazonium salt solution is slowly added dropwise to the coupling component solution under stirring at 0-5℃; then, the pH of the reaction system is adjusted to 9-10 using sodium carbonate aqueous solution, and the temperature is maintained for the reaction. After the reaction was completed, the precipitate was collected by filtration, washed, and dried to obtain a bright yellow crude product. The crude product was further recrystallized and purified to finally obtain the target product in the form of yellow crystals.

5. A heterocyclic azo disperse dye composition, characterized in that, The dye contains the heterocyclic azo compound as described in claim 1 or 2.

6. A staining method for heterocyclic azo compounds, characterized in that, The process includes the following steps: mixing the heterocyclic azo compound, dispersant, zirconium beads, and water as described in claim 1 or 2, and milling them for 2-8 hours. After milling, the dye paste is collected by filtration, the filtrate is evaporated, and the resulting solid is ground into a uniform powder for later use. Prepare the dye solution, put it into the fabric, and then dye it. After dyeing, cool it down, take out the fabric, perform a reduction wash, and then dry it.

7. The staining method according to claim 6, characterized in that, The fabric is pretreated before dyeing, specifically by adding a polar solvent to pretreat the fabric at 65°C for 30 minutes. After pretreatment, the fabric is first washed with hot water at 90°C, then rinsed with room temperature water, and then dried for later use.

8. The staining method according to claim 6, characterized in that, The conditions for the reduction cleaning were: 2 g / L sodium hydrosulfite, 1 g / L NaOH, bath ratio 1:50, 80℃, and 10 min.

9. The staining method according to claim 6, characterized in that, The mass ratio of the heterocyclic azo compound, dispersant, and zirconium beads is 1:1:150; the mass ratio of the fabric to the heterocyclic azo disperse dye is 50:1; and the bath ratio of the fabric to the dye liquor is 1:

20. The fabric is meta-aramid fiber, plain weave, 160 g / m². 2 The zirconium beads are 2 mm in diameter; the dispersant is NNO. The dyeing process involves heating the temperature to 90°C at a rate of 1°C / min, holding it at that temperature for 60 minutes, and then cooling it down to 75°C after dyeing.

10. A dyed fabric, characterized in that: It is prepared by the staining method described in any one of claims 6-9.

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