A novel heterocyclic azo disperse dye and its preparation method

Abstract

This invention relates to a novel heterocyclic azo disperse dye and its preparation method. The dye has the following structural formula: R1, R2, R3, H, CH3, NHCOCH3; D1 is a substituted benzothiazole or benzoisothiazole. The compound provided by this invention can be used as a dye for dyeing polylactic acid fibers, and has the characteristics of high dyeing rate, bright color, excellent color fastness and strong industrial feasibility.

Description

Technical Field

[0001] This invention belongs to the field of dyes, and specifically relates to a novel heterocyclic azo disperse dye and its preparation method. Background Technology

[0002] Although polyester fiber remains the most widely used material in the textile and apparel industry, the increasing environmental awareness and living standards have led to a shift in market demand towards more diverse, comfortable, and environmentally friendly fiber fabrics. This has prompted more and more researchers to focus on high-performance, green, and environmentally friendly fibers. Polylactic acid (PLA) fiber, as a promising alternative to petroleum-based fibers, is widely used in various fields due to its excellent renewability and biodegradability. Its pollution-free and recyclable characteristics have increased the development potential of PLA in the textile industry. In fact, PLA fiber has a long history of application in the textile industry. Extensive research has yielded significant progress in PLA fiber dyeing processes, achieving optimal dyeing techniques for PLA fibers using existing dyes. However, considerable challenges remain in fabric dyeing. This is because commercially available disperse dyes are primarily developed for dyeing PET fibers. PLA differs significantly from PET in structure and dyeing properties, and only a few commercially available disperse dyes exhibit excellent dyeing results, including high dye adsorption, good uplift properties, and satisfactory colorfastness. This hinders the large-scale commercial production of PLA. Furthermore, in most reports, the dyes studied are mostly screened from existing commercial disperse dyes based on their different energy levels or chemical compositions. However, when existing commercial dyes are applied to dyeing fabrics, problems such as low dye adsorption, low enhancement, and poor color fastness still exist.

[0003] In recent years, heterocyclic disperse dyes have become a major area of ​​research due to their bright colors, high color intensity, good fastness, good dark color effect, high molar extinction coefficient, and good dyeing properties. He Liang and Zhang Shufen et al. [He Liang. Synthesis and application of novel polylactic acid fiber special dyes. Doctoral dissertation of Dalian University of Technology, 2008; He L, Zhang SF, Tang BT, Wang LL, Yang JZ. Dyes with high affinity for polylactide. Chinese Chemical Letters 18(2007)1151-1153; He L, Zhang S, Tang B, Wang L, Yang J. Dyeability of polylactide fabric with hydrophobicanthraquinone dyes. Chinese Journal of Chemical Engineering 17(1)(2009)156-159; He L, Lu L, Zhang S, Freeman HS. Synthesis and application of yellow azo-anthraquinone disperse dyes for polylactide fibers. Coloration Technology 126(2010)92-96; Lu L, He L, Zhang S, Freeman HS. Novel yellow azo-anthraquinone dyes for [polylactide fibers: effects of alkyl chain length. Coloration Technology 128(2012)121-126] To address the problem of low light fastness of traditional disperse dyes on polylactic acid fibers, a series of alkylaminoanthraquinone dyes, 2'-chloro-4'-nitroazobenzene dyes, and 1-(pyrazolinone)azoanthraquinone dyes containing photostable functional groups were designed and synthesized, with dyeing rates of 52-95% (2% owf), over 97% (0.5% owf), and 79-86% (2% owf), respectively. Avinc et al. [Avinc O, Bakan E, A,Gedik G, F. Dyeing of poly(lactic acid) fibers with synthesized novel heterocyclic disazo disperse dyes. Coloration Technology 136(2020)356-369] synthesized novel heterocyclic diazo disperse dyes with methyl, nitro and chloro groups substituted at the ortho, meta and para positions, achieving a dyeing rate of 60-90% (2% owf) on PLA fibers. Choi et al. [Choi JH, Lee HY, Towns AD. Dyeing Properties of Novel Azo Disperse Dyes Derived from Phthalimide and Color Fastness on Poly(lactic acid) Fiber. Fibers and Polymers 11(2)(2010)199-204] synthesized 18 monoazo disperse dyes with phthalimide derivatives as diazo components, achieving a dyeing rate of 7-90% (4% owf) on PLA fibers. Wang Xidong et al. [Wang Xidong. Molecular design and application performance of fine chemicals containing heterocyclic extinction elements. Master's thesis, Zhejiang Sci-Tech University, 2014; Cui Z, Wang X, Chen W, Hu E, Liu K. Synthesis, spectral and dyeing properties of phenylazopyrazolone-containing acylamide disperse dyes designed for poly(lactic acid). Coloration Technology 128(2011)283-289] designed and synthesized a series of amide disperse dyes with high extinction coefficients and pyrazolone heterocyclic structures. These dyes achieved a dyeing rate of 38-97% (0.5% owf) on PLA fibers. Wang Guoyan [Wang Guoyan. Research on the use of lactate-type disperse dyes for dyeing polylactic acid fibers. Master's thesis, Shandong Sci-Tech University, 2019] designed and synthesized eight lactate-type disperse dyes with similar structural units to PLA. They found that five of these dyes achieved a dyeing rate of over 90% (2% owf) on PLA fibers. However, as the above studies show, dye uptake exceeding 95% is rarely reported when the dyeing depth of PLA fibers is 2% owf. Of the 88 dyes included in the current study, only 12 achieved an uptake of 90%. These dyes not only have limited color options but also suffer from poor wash fastness and lightfastness. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the technical problem to be solved by this invention is to provide a novel heterocyclic azo disperse dye and its preparation method. In particular, this invention proposes a novel heterocyclic azo disperse dye for dyeing polylactic acid fibers, which has the characteristics of high dyeing rate, bright color, excellent color fastness and strong industrial feasibility.

[0005] The present invention provides a heterocyclic azo compound as shown below.

[0006]

[0007] Where R1 is At least one of the following, where n satisfies the following conditions: 1≤n≤4, and n is an integer;

[0008] R2 is At least one of the following, where n satisfies the following conditions: 1≤n≤4, and n is an integer;

[0009] R3 is at least one of H, CH3, and NHCOCH3;

[0010] D1 is a substituted benzothiazole or benzoisothiazole.

[0011] Preferably, D1 is At least one of the following: R4 is at least one of -Cl, -NO2, and -Br; R5 is at least one of -Cl, -NO2, and -Br.

[0012] Preferably, the heterocyclic azo structure is as follows:

[0013]

[0014] R1 is At least one of the following, where n satisfies the following condition:

[0015] 1 ≤ n ≤ 4, and n is an integer;

[0016] R2 is At least one of the following, where n satisfies the following conditions: 1≤n≤4, and n is an integer;

[0017] R3 is at least one of H, CH3, and NHCOCH3;

[0018] R4 is at least one of -Cl, -NO2, and -Br;

[0019] R5 is at least one of -Cl, -NO2, and -Br.

[0020] More preferably, the compound is specifically:

[0021]

[0022]

[0023] At least one of the following. A method for preparing a heterocyclic azo compound according to the present invention includes:

[0024] (1) Esterification of N,N-hydroxyethyl m-toluidine;

[0025] (2) Diazotization of aminobenzothiazole;

[0026] (3) The compounds obtained in steps (1) and (2) are coupled to obtain heterocyclic azo compounds.

[0027] Preferably, the compound obtained in step (1) is

[0028] Preferably, the compound obtained in step (2) is Where D1 is At least one of the following: R4 is at least one of -Cl, -NO2, and -Br; R5 is at least one of -Cl, -NO2, and -Br.

[0029] Preferably, the preparation method includes:

[0030] (1) Dissolve N,N-hydroxyethyl m-toluidine in fatty acids, add a catalyst, and heat under reflux to react; purify after the reaction is complete; or dissolve N,N-hydroxyethyl m-toluidine and lactide in toluene, heat and stir to dissolve, add ether solution containing HCl, stir continuously, and remove the solvent after the reaction is complete.

[0031] (2) Dissolve aminobenzothiazole in a concentrated acid solution, and after complete dissolution, cool to 0-5℃; add excess nitrosylsulfuric acid to react, then add aminosulfonic acid to form a solution of the compound; wherein the compound is

[0032] (3) Mix the excess of the compound obtained in step (1) with water, acidify, sonicate to disperse it evenly, cool it to 0-5℃ in an ice-salt bath, add the product of step (2) dropwise, add appropriate amount of crushed ice to maintain the temperature in the reaction bath, after the diazonium salt is added, the reaction ends when the H acid test shows no diazonium salt in the reaction permeation zone.

[0033] The fatty acid in step (1) is one of acetic acid, propionic acid, or butyric acid; the catalyst is concentrated sulfuric acid.

[0034] Further, the preparation includes

[0035]

[0036] The first step is the esterification of N,N-hydroxyethyl m-toluidine.

[0037] N,N-hydroxyethylm-toluidine was dissolved in an appropriate amount of fatty acid, wherein the fatty acid is one of acetic acid, propionic acid, or butyric acid. Concentrated sulfuric acid was added as a catalyst, and the mixture was heated under reflux at 80-160°C for 4-12 hours. After the reaction was completed, the mixture was extracted with ethyl acetate, and the solvent was removed by rotary evaporation to obtain compound 2.

[0038] The molar ratio of N,N-hydroxyethyl m-toluidine to fatty acid is 0.005:(0.02-0.1);

[0039] For every 0.005 mol of N,N-hydroxyethyl m-toluidine, add 1-2 drops of catalyst.

[0040] The second step is the diazotization of aminobenzothiazole.

[0041] Aminobenzothiazole was dissolved in a concentrated acid solution, and after complete dissolution, the temperature was lowered to 0-5℃; nitrosylsulfuric acid was added to react, followed by the addition of aminosulfonic acid, to generate a diazonium salt solution of aminobenzothiazole.

[0042] The ratio of aminobenzothiazole, concentrated acid solution, nitrosylsulfonic acid, and aminosulfonic acid is (0.005-0.006) mol: (3-10) ml: (0.0055-0.0066) mol: (0.0005-0.001) mol.

[0043] The third step is the coupling of compound 2 and compound 3.

[0044] Compound 2 was 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 completely added, the reaction was stopped when no diazonium salt was detected in the reaction zone by H acid testing. The product formed was an aqueous solution of a heterocyclic coupling dye. Ammonia was added to adjust the pH to 5-6, the reaction solution was filtered, washed with water until the filtrate was clear, the filter cake was dried, and recrystallized from ethanol to obtain the desired heterocyclic coupling compound.

[0045] The ratio of compound 2, water, and hydrochloric acid is (0.005mol-0.0055)mol: (20-50)ml: (0.1-1)ml.

[0046] The molar ratio of compound 2 to compound 3 is 0.005 mol - 0.0055 : 0.005 - 0.006.

[0047]

[0048] The first step is the esterification of N,N-hydroxyethyl m-toluidine.

[0049] N,N-hydroxyethyl m-toluidine and lactide were dissolved in toluene, heated and stirred until dissolved, and then an ether solution containing HCl was added. The mixture was stirred continuously, and after the reaction was completed, the solvent was removed by rotary evaporation to obtain compound 2.

[0050] The molar ratio of N,N-hydroxyethyl m-toluidine to lactide is 0.005:(0.02-0.1);

[0051] The ratio of N,N-hydroxyethyl m-toluidine, lactide, toluene, HCl, and diethyl ether is (0.005) mol: (0.02-0.1) mol: (5-10) ml: (0.001-0.005) mol: (0.01-0.05) g.

[0052] The second step is the diazotization of aminobenzothiazole.

[0053] Aminobenzothiazole was dissolved in a concentrated acid solution, and after complete dissolution, the temperature was lowered to 0-5℃; nitrosylsulfuric acid was added to react, followed by the addition of aminosulfonic acid, to generate a diazonium salt solution of aminobenzothiazole.

[0054] The ratio of aminobenzothiazole, concentrated acid solution, nitrosylsulfonic acid, and aminosulfonic acid is (0.005-0.006) mol: (3-10) ml: (0.0055-0.0066) mol: (0.0005-0.001) mol.

[0055] The third step is the coupling of compound 2 and compound 3.

[0056] Compound 2 was dissolved in water, acidified with hydrochloric acid, and sonicated to disperse it evenly. The solution 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 completely added, the reaction was stopped when no diazonium salt was detected in the reaction zone by H acid testing. The product formed was an aqueous solution of compound 4. Ammonia was added to adjust the pH to 5-6, the reaction solution was filtered, washed with water until the filtrate was clear, the filter cake was dried, and recrystallized from ethanol to obtain the desired heterocyclic azo compound.

[0057] The ratio of compound 2, water, and hydrochloric acid is (0.005mol-0.0055)mol: (20-50)ml: (0.1-1)ml.

[0058] The molar ratio of compound 2 to compound 3 is 0.005 mol - 0.0055 : 0.005 - 0.006.

[0059] The present invention provides a heterocyclic azo disperse dye, wherein the dye contains the heterocyclic azo compound.

[0060] Furthermore, the present invention provides a novel heterocyclic azo disperse dye for dyeing polylactic acid fibers, wherein the dye contains the heterocyclic azo compound.

[0061] A dyeing method for a heterocyclic azo disperse dye according to the present invention includes:

[0062] The heterocyclic azo compound, dispersant, zirconium beads, and water are mixed and milled in a sand mill for 2-8 hours. After milling, the dye paste is collected through a sieve.

[0063] The dye paste is mixed with water to obtain a dye solution, which is then added to the fiber or fabric and placed in a high-temperature and high-pressure dyeing instrument for dyeing. The dyed sample is then removed, washed with water and subjected to reduction cleaning, and then dried to obtain the dyed fiber or fabric.

[0064] The process of mixing dye paste with water to obtain dye solution specifically involves adding water to the dye paste according to the bath ratio and then transferring it to a dyeing cup.

[0065] Preferably, the mass ratio of the heterocyclic azo compound, dispersant, and zirconium beads is 1:1 to 2:10 to 30; the mass ratio of the fabric to the heterocyclic azo dye is (25 to 50):1; and the bath ratio of the fabric to the dye liquor is 1:(20 to 40).

[0066] Preferably, the fiber is polylactic acid (PLA) fiber; the fabric is PLA fabric; the zirconium beads have a diameter of 0.3-0.4 mm; and the dispersant is NNO.

[0067] Preferably, the dyeing process involves heating to 50-60°C at a rate of 1-2°C / min, then heating to 100-130°C at a rate of 0.5-1°C / min, holding at that temperature for 20-50 minutes, and then cooling to room temperature.

[0068] This invention provides a dyed fabric prepared by the method described above.

[0069] Beneficial effects

[0070] (1) Compared with existing commercial dyes, the novel heterocyclic azo disperse dye of the present invention, based on the principle of "like dissolves like," introduces a long-chain ester group structure into the dye, which enhances the linearity of the dye and the affinity between the dye and the fiber, resulting in a higher dye uptake rate. At the same time, the presence of the heterocyclic group gives the dye high color intensity, bright color, and excellent fastness properties, thus having broad application prospects in industrial production.

[0071] (2) All intermediates and chemicals required for producing the dyes of this invention are readily available and can be produced using conventional equipment for disperse 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. The dyes produced by this invention all have a high dyeing rate on polylactic acid fibers, reaching up to 99%.

[0072] (3) The compound provided by the present invention can be used as a dye for dyeing polylactic acid fibers. It has the characteristics of high dyeing rate, bright color, excellent color fastness and strong industrial feasibility. Detailed Implementation

[0073] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0074] Example 1

[0075] The first step is the esterification of N,N-hydroxyethyl m-toluidine.

[0076] In a 100 ml round-bottom flask, add 1.86 g (10 mmol) of N,N-hydroxyethylm-toluidine, 1.80 g (30 mmol) of glacial acetic acid, and 1-2 drops of concentrated sulfuric acid sequentially. Shake well and heat under reflux for 4 h with a condenser. After the reaction is complete, add 20 ml of 10% Na₂CO₃ to the flask to adjust the pH to 6.5-7, then add ethyl acetate for extraction. After separating the aqueous phase, add anhydrous magnesium sulfate to the ethyl acetate phase, let stand for 4-6 hours, filter, rotary evaporate, and purify by column chromatography (eluent: ethyl acetate: petroleum ether = 1:10) to obtain compound 1. NMR results show: 1 H NMR (600MHz, Chloroform-d)) δ7.11(t,J=7.8Hz,1H),6.58–6.54(m,3H),4.23(t,J=6.3Hz,4H),3.61(t,J=6.3Hz,4H),2.31(s,3H),2.05(s,6H).

[0077]

[0078] The second step is the diazotization of 2-amino-6-chlorobenzothiazole.

[0079] Add 1 ml (98%) H₂SO₄ and 3 ml (85%) H₃PO₄, along with 0.923 g (5 mmol) of 2-amino-6-chlorobenzothiazole, to a 50 ml three-necked flask. Stir the solution continuously until completely dissolved, then cool to 0-5 °C. Slowly add nitrosylsulfonic acid (0.362 g NaNO₂ + 2 ml H₂SO₄), and react at 0-5 °C for 1 h. Weigh out the aminosulfonic acid to remove excess sodium nitrite, yielding an acidic solution of compound 2.

[0080]

[0081] The third step involves the coupling of 2-amino-6-chlorobenzothiazole diazonium salt with aniline containing an acetate group.

[0082] 5 mmol of compound 1 was dispersed in 20 ml of water and 1 ml of 36% hydrochloric acid. The mixture was cooled to below 5 °C, and crushed ice was added dropwise while adding diazonium solution of compound 2. The mixture was stirred continuously at 0-5 °C for 4 h, and then stirred for another 4 h at room temperature. After the reaction was complete, the pH was adjusted to neutral with sodium carbonate solution, and the mixture was filtered under reduced pressure to obtain a red solid powder.

[0083] The 1H NMR spectrum of the purified dye: 1 ¹H NMR (600MHz, DMSO-d⁶) δ 7.98 (t, J = 8.1Hz, 2H), 7.79 (d, J = 1.8Hz, 1H), 7.42 (dd, J = 8.6, 1.9Hz, 1H), 6.69 (d, J = 9.6Hz, 2H), 4.31 (t, J = 6.1Hz, 4H), 3.76 (t, J = 6.1Hz, 4H), 2.70 (s, 3H), 2.07 (s, 6H). When dyed in an infrared dyeing machine, polylactic acid fabric exhibits a vibrant red color with a dye uptake rate of 95%.

[0084]

[0085] Example 2

[0086] The first step is the esterification of N,N-hydroxyethyl m-toluidine.

[0087] Take a 25 ml round-bottom flask, add 0.93 g (5 mmol) of N-hydroxyethyl m-toluidine, 6.26 g (30 mmol) of butyric acid, and 1-2 drops of concentrated sulfuric acid. Shake well and heat under reflux for 6 h with a condenser attached. After the reaction is complete, add 20 ml of 10% Na2CO3 to adjust the pH to 6.5-7, and then add ethyl acetate for extraction. After separating the aqueous phase, the ethyl acetate phase was added to anhydrous magnesium sulfate and allowed to stand for 4-6 hours. The mixture was then filtered, rotary evaporated, and purified by column chromatography (eluent: ethyl acetate: petroleum ether = 1:10) to obtain compound 1. The NMR results were as follows: 1H NMR (600MHz, Chloroform-d) δ 7.21–7.05 (m, 1H), 6.70–6.48 (m, 3H), 4.28 (t, J = 6.3Hz, 4H), 3.65 (t, J = 6.3Hz, 4H), 2.33 (dd, J = 15.0, 7.6Hz, 7H), 1.67 (dt, J = 14.8, 7.4Hz, 4H), 0.98 (t, J = 7.4Hz, 6H).

[0088]

[0089] The second step is the diazotization of 2-amino-6-nitrobenzothiazole.

[0090] In a 50 ml three-necked flask, add 1 ml (98%) H₂SO₄, 3 ml (99%) acetic acid, 2 ml (85%) H₃PO₄, 1 ml (99%) butyric acid, and 0.976 g (5 mmol) of 2-amino-6-nitrobenzothiazole. Stir the solution continuously until the 2-amino-6-nitrothiazole is completely dissolved, then cool to 0-5 °C. Slowly add nitrosylsulfonic acid (0.362 g NaNO₂ + 2 ml H₂SO₄), and react at 0-5 °C for 1 h. Weigh out the aminosulfonic acid to remove excess sodium nitrite, yielding an acidic solution of compound 2.

[0091]

[0092] The third step involves the coupling of 2-amino-6-nitrobenzothiazole diazonium salt with aniline containing butyrate ester groups.

[0093] 10 mmol of compound 1 was dispersed in 20 mL of water and 1 mL of 36% hydrochloric acid. The mixture was cooled to below 5 °C, and crushed ice was added dropwise while adding diazonium solution of compound 2. The mixture was stirred continuously at 0–5 °C for 4 h, and then stirred for another 4 h at room temperature. After the reaction was complete, the pH was adjusted to neutral with sodium carbonate solution, and the mixture was filtered under reduced pressure to obtain a purplish-black solid powder. The 1H NMR spectrum of the purified dye is as follows: 1¹H NMR (400MHz, Chloroform-d) δ 8.73 (d, J = 2.3Hz, 1H), 8.32 (dd, J = 9.0, 2.3Hz, 1H), 8.12 (d, J = 9.0Hz, 1H), 8.03 (d, J = 9.1Hz, 1H), 6.73 (d, J = 8.6Hz, 2H), 4.34 (t, J = 6.0Hz, 4H), 3.79 (t, J = 6.0Hz, 4H), 2.71 (s, 3H), 2.29 (t, J = 7.4Hz, 4H), 1.64 (q, J = 7.4Hz, 4H), 0.94 (t, J = 7.4Hz, 6H). Under high temperature and high pressure dyeing, polylactic acid fabric exhibits a vibrant purplish-red color with a dye uptake rate of 97%.

[0094]

[0095] Example 3

[0096] The first step is the esterification of N,N-hydroxyethyl m-toluidine.

[0097] Take a 25 ml round-bottom flask, add 0.93 g (5 mmol) of N-hydroxyethyl m-toluidine, 6.26 g (30 mmol) of butyric acid, and 1-2 drops of concentrated sulfuric acid. Shake well and heat under reflux for 6 h with a condenser. After the reaction is complete, add 20 ml of 10% Na2CO3 to the flask to adjust the pH to 6.5-7, then add ethyl acetate for extraction. After separating the aqueous phase, add anhydrous magnesium sulfate to the ethyl acetate phase, let it stand for 4-6 hours, filter, rotary evaporate, and purify by column chromatography (eluent: ethyl acetate: petroleum ether = 1:10) to obtain compound 1. The NMR results are as follows: 1 H NMR(600MHz,Chloroform-d)δ7.21–7.05(m,1H),6.70–6.48(m,3H),4.28(t,J=6.3Hz,4H),3.65(t ,J=6.3Hz,4H),2.33(dd,J=15.0,7.6Hz,7H),1.67(dt,J=14.8,7.4Hz,4H),0.98(t,J=7.4Hz,6H).

[0098]

[0099] The second step is the diazotization of 3-amino-5-nitrobenzisothiazole.

[0100] Add 2 ml (98%) H₂SO₄ and 0.976 g (5 mmol) of 3-amino-5-nitrobenzisothiazol to a 50 ml three-necked flask. Keep the solution stirred continuously until completely dissolved, then cool to 0-5 °C. Slowly add nitrosylsulfonic acid (0.362 g NaNO₂ + 2 ml H₂SO₄), and react at 0-5 °C for 1 h. Weigh out the aminosulfonic acid to remove excess sodium nitrite, resulting in an acidic solution of compound 2.

[0101]

[0102] The third step involves the coupling of 3-amino-5-nitrobenzisothiazole diazonium salt with butyrate-containing aniline.

[0103] 10 mmol of compound 1 was dispersed in 20 mL of water and 1 mL of 36% hydrochloric acid. The mixture was cooled to below 5 °C, and crushed ice was added dropwise while adding diazonium solution of compound 2. The mixture was stirred continuously at 0–5 °C for 4 h, and then stirred for another 4 h at room temperature. After the reaction was complete, the pH was adjusted to neutral with sodium carbonate solution, and the mixture was filtered under reduced pressure to obtain a black solid powder. The 1H NMR spectrum of the purified dye is as follows: 1 ¹H NMR (400MHz, Chloroform-d) δ 9.21 (s, 1H), 8.21 (dd, J = 9.7, 2.2Hz, 1H), 8.06 (d, J = 9.3Hz, 1H), 7.77 (d, J = 9.7Hz, 1H), 6.78 (dd, J = 9.4, 2.8Hz, 1H), 6.71 (d, J = 2.0Hz, 1H), 4.34 (t, J = 6.1Hz, 4H), 3.79 (t, J = 6.1Hz, 4H), 2.69 (s, 3H), 2.31 (t, J = 7.4Hz, 4H), 1.65 (q, J = 7.4Hz, 4H), 0.94 (t, J = 7.4Hz, 6H). When dyed in an infrared dyeing machine, polylactic acid fabric exhibits a vibrant blue color with a dye uptake rate of 96%.

[0104]

[0105] Comparative Example 1

[0106] The commercially available dye (CI Disperse Blue 367, Zhejiang Wanfeng Dyestuff Chemical Co., Ltd.) was used to dye polylactic acid using the same method, achieving a dyeing rate of 29%. The structure of CI Disperse Blue 367 is as follows:

[0107]

[0108] Comparative Example 2

[0109] The commercially available dye (CI Disperse Blue 148, Zhejiang Wanfeng Dyestuff Chemical Co., Ltd.) was used to dye polylactic acid using the same method, achieving a dyeing rate of 83%. The structure of CI Disperse Blue 148 is as follows:

[0110]

[0111] Staining methods

[0112] Take 0.1g of disperse dye, 0.1g of dispersant NNO, 20g of zirconium beads (0.3mm in diameter), and 10mL of water and add them to a sand mill and sand mill for 2 hours. After sand milling, filter the mixture through a sieve, collect the dye dispersion, and dilute it to a 50mL volumetric flask to obtain dye paste. Transfer the disperse dye paste according to the 2% color requirement, add water at a liquor ratio of 1:20, and transfer it to a dyeing cup. Add the moistened PLA fabric and place it in a high-temperature and high-pressure dyeing apparatus. Rapidly raise the temperature to 60℃ at a heating rate of 2℃ / min, and then slowly raise the temperature to 110℃ at a heating rate of 1℃ / min. After holding the temperature for 30 minutes, lower it to room temperature, take out the dyed fabric sample, and wash it to obtain the dyed fabric sample.

[0113] Determination of dye uptake rate:

[0114] Take 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:

[0115] Dyeing rate = (1-A1) / A0 × 100%

[0116] A0 - Absorbance of the dye solution before staining;

[0117] A1 - Absorbance of the residual solution after staining;

[0118] Performance tests were conducted on the PLA fabrics obtained from the examples and comparative examples:

[0119] After the dyed fabric samples were treated and cleaned according to the national standard "Test Method for Color and Intensity of Disperse Dyes" (GB2394-2013), their water fastness, dry rubbing fastness, and wet rubbing fastness were measured. The test results are shown in Table 1.

[0120] Table 1 PLA Fabric Test Data

[0121]

[0122] By comparing the data in Table 1, we can see that:

[0123] Compared with Comparative Examples 1 and 2, Examples 1, 2, and 3 show that the introduction of long-chain ester groups in this invention significantly improves the dyeing rate and color fastness of disperse dyes on polylactic acid (PLA) fabrics. Furthermore, the synthesized dyes exhibit vibrant colors and excellent color fastness, effectively saving dye usage and conserving resources and energy. Therefore, the dyes prepared according to this invention can be applied to the industrial production of PLA fabrics.

Claims

1. A heterocyclic azo compound, characterized by, The compound is specifically: 、 、 、 At least one of the following:

2. A preparation method of the heterocyclic azo compound of claim 1, comprising: (1) esterification of N, N-hydroxyethyl-m-toluidine; (2) diazotization of aminobenzothiazole; (3) coupling of the compounds obtained in step (1) and step (2) to obtain the heterocyclic azo compound.

3. The preparation method according to claim 2, characterized in that, The compound obtained in the step (1) is wherein n = 2; The compound obtained in the step (2) is wherein D1 is , at least one of -Cl, -NO2; R5 is -NO2.

4. The preparation method according to claim 2, characterized in that, Comprise: (1) dissolving N, N-hydroxyethyl-m-toluidine in fatty acid, adding catalyst, heating to reflux reaction; after the reaction is completed, purification; (2) dissolving the aminobenzothiazole in a concentrated acid solution, cooling to 0-5 °C after complete dissolution; adding excess nitrosyl sulfuric acid to react, adding sulfamic acid to form a solution of the compound; wherein the compound is ; (3) mixing excess compound obtained in step (1) and water, acidifying, cooling to 0-5 ℃, adding the product of step (2) dropwise, after the diazonium salt is added dropwise, reacting until there is no diazonium salt in the H acid detection reaction ring, and the reaction is completed; The fatty acid in step (1) is butyric acid; the catalyst is concentrated sulfuric acid.

5. Heterocyclic azo disperse dye, characterized in that The dye contains the heterocyclic azo compound of claim 1.

6. A dyeing method of the heterocyclic azo disperse dye, comprising: Mixing the heterocyclic azo compound of claim 1, dispersant, zirconium beads and water, sand grinding for 2-8 hours, after sand grinding, collecting the dye paste through filtration; Taking the dye paste and mixing with water to obtain a dyeing liquid, adding fibers or fabrics for dyeing, taking out the dyed samples, washing and reducing cleaning, and drying to obtain dyed fibers or fabrics.

7. The dyeing method according to claim 6, characterized in that, The mass ratio of the heterocyclic azo compound, dispersant and zirconium beads is 1:1-2:10-30; the mass ratio of the fabric and the heterocyclic azo disperse dye is (25-50):1; the bath ratio of the fabric and the dyeing liquid is 1:(20-40); The fiber is polylactic acid fiber; the fabric is polylactic acid fabric; the zirconium beads have a diameter of 0.3-0.4 mm; the dispersant is dispersant NNO; The dyeing specifically comprises heating to 50-60 ℃ at a temperature rising speed of 1-2 ℃ / min, then heating to 100-130 ℃ at a temperature rising speed of 0.5-1 ℃ / min, keeping warm for 20-50 min, and then reducing to room temperature.

8. A dyed fiber or fabric prepared by the method of claim 6.

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