A synthetic tanning agent containing hexacarbonyl group and its preparation method and application

Abstract

The invention discloses a synthetic tanning agent containing a hexacarbonyl group, a preparation method and an application thereof. The synthetic tanning agent is prepared by using active methylene compounds, acrylates, diols and diol ethers as raw materials; the synthetic tanning agent containing a hexacarbonyl group of the invention has a simple preparation process and a high yield; the synthetic tanning agent contains functional groups such as β-diketones and carboxylates, forms multi-point crosslinking between collagen fibers, produces a tanning effect, and significantly improves the moisture and heat resistance and physical and mechanical properties of collagen; the synthetic tanning agent containing a hexacarbonyl group of the invention can replace chromium powder, reduce environmental pollution in the leather industry, and promote clean production in the leather industry; the invention provides a new idea for the development and research of a novel chrome-free tanning agent.

Description

Technical Field

[0001] The present invention relates to a synthetic tanning agent, a preparation method and an application thereof, and in particular to a synthetic tanning agent containing a hexacarbonyl group, a preparation method and an application thereof. Background Art

[0002] Chrome tanning is the most important and widely used tanning method in leather manufacturing. It gives leather excellent thermal stability, comfortable feel and excellent leather properties. It currently occupies an absolute dominant position in the leather industry. However, in the traditional tanning process, the absorption rate of chrome tanning agent is usually only about 70%. After tanning, high-concentration chromium-containing wastewater will be produced, resulting in a large amount of chrome tanning agent loss. This not only increases the environmental pollution load and wastewater treatment costs, but also causes a huge waste of resources. The chromium-containing wastewater, chromium-containing solid waste, chromium-containing waste leather products, etc. generated by the chrome tanning method may cause ecological and environmental risks, which seriously restricts the sustainable and healthy development of the leather industry. Under the national strategy of sustainable development, people have gradually increased their attention to environmental protection, and it is urgent to solve the problem of chromium pollution in the leather industry. (China, CR, Maguta, MM, Nyandoro, SS, Hilonga, A., Kanth, SV, Njau, KN, Alternative tanning technologies and their suitability in curbing environmental pollution from the leather industry: a comprehensive review. Chemosphere 2020, 254: 126804; J. Kanagaraj, Rames C. Panda, M. Vinodh Kumar. Trends and advancements insustainable leather processing: Future directions and challenges-Areview. Journal of Environmental Chemical Engineering 2020, 8: 104379)

[0003] Therefore, researching green and environmentally friendly chrome-free tanning agents to replace the current chrome tanning method and implementing chrome-free ecological leather manufacturing technology has become a major national need and an inevitable trend for the sustainable development of the leather industry. Chrome-free tanning agents and their tanning technology are the research focus and key areas in the field of clean leather production technology. my country lists chrome-free leather manufacturing technology as a key technology in the field of clean leather production technology (Shen Yiyue, Ouyang Mai, Jiang Qianwen, et al. Research progress on chrome-free ecological leather manufacturing technology and chrome-free tanning agents [J]. Western Leather, 2022, 44(17): 7-12).

[0004] To eliminate the environmental problems of chromium from the source, it is necessary to increase the research and development of chrome-free tanning technology. The key and difficulty of this technology is how to prepare excellent chrome-free tanning agents. In recent years, leather workers have conducted in-depth research on chrome-free tanning agents and introduced some new chrome-free tanning agents, such as non-chrome tanning agents (such as aluminum tanning agents, titanium tanning agents, iron tanning agents, zirconium tanning agents, rare earth metal tanning agents, etc.) (Wei Xiuwei. Research on the application of new zirconium tanning technology in sheepskin tanning [D]. Wenzhou: Wenzhou University, 2019), vegetable tanning agents, aldehyde tanning agents, and chrome-free tanning agents containing triazine rings (Jia Xiqing, Wen Huitao, Niu Ze, et al. Research on tanning process technology combining F-90 with vegetable tanning agents [J]. Leather and Chemical Industry, 2018, 35(6): 1-10; Lidong Yu, Xihuai Qiang, Lu Cui, BoChen, Xinke Wang, Xiaohui Wu. Preparation of a syntan containing active chlorine groups for chrome free tanned leather [J]. Journal of Cleaner Production 2020, 270: 122351; Yu Lidong, Qiang Xihuai, Ma Haofeng, et al. Synthesis of sodium p-(4,6-dichloro-1,3,5-triazine-2-oxy)benzenesulfonate and its tanning performance [J]. Fine Chemicals, 2019, 36(7): 1415-1421; Liu Dou. Preparation of T_Lys / T_Tyr / T_Arg and study on its tanning performance [D]. Xi'an Shaanxi University of Science and Technology, 2019).

[0005] The above-mentioned chrome-free tanning system has problems such as low shrinkage temperature of finished leather, large amount of tanning agent, poor tanning property, and generation of free formaldehyde.

[0006] The invention provides a synthetic tanning agent containing a hexacarbonyl group. The synthetic tanning agent is prepared by using active methylene compounds, acrylates, diols and diol ethers as raw materials. The preparation process of the synthetic tanning agent is simple and the yield is high. The synthetic tanning agent contains functional groups such as β-diketone and carboxylic acid ester, and cyclizes with the guanidine group of arginine and the amino group of lysine in collagen to form a pyrimidine ring, forming multi-point cross-linking to produce a tanning effect, and significantly improves the moisture and heat resistance stability and physical and mechanical properties of collagen. The synthetic tanning agent can replace chromium powder, reduce environmental pollution in the leather industry, and promote clean production in the leather industry. Summary of the invention

[0007] Objectives of the invention: The first objective of the present invention is to provide a synthetic tanning agent containing a hexacarbonyl group. The second objective of the present invention is to provide a method for preparing the synthetic tanning agent. The third objective of the present invention is to provide an application of the synthetic tanning agent in a leather tanning process.

[0008] Technical solution: The synthetic tanning agent containing a hexacarbonyl group of the present invention has a molecular structure as follows:

[0009]

[0010] Where A=C2H4,C3H6,C4H8,C5H 10 , C6H 12 , C8H 16 , diglyceryl ether, triglyceryl ether, tetraglyceryl ether, PEG200, PEG300, PEG400, PEG600, PPG400; R1, R2 are methyl, trifluoromethyl, ethyl, oxymethyl, oxyethyl, isopropyl, tert-butyl, phenyl, methyl carboxylate, ethyl carboxylate, 4,4,4-trifluoro-1-(2-thienyl), 4,4,4-trifluoro-1-phenyl, 4,4,4-trifluoro-1-(2-naphthyl).

[0011] The method for preparing a synthetic tanning agent containing a hexamembered carbonyl group of the present invention comprises the following steps:

[0012] (1) Michael addition reaction

[0013] A series of carboxylate compounds A are prepared by using Michael addition reaction, with active methylene compounds and α, β-unsaturated carboxylic acid ester compounds as raw materials, with organic base or inorganic base as alkaline agent, in a low polarity aprotic organic solvent under the catalytic condition of phase transfer catalyst, at 30-120° C. for 2-12 hours;

[0014] (2) Hydrolysis reaction

[0015] The carboxylate compound A obtained in step (1) is hydrolyzed at 50-120° C. for 4-12 h under alkaline conditions, cooled to room temperature, and the pH is adjusted to 4-5 with an acid to precipitate a solid, which is filtered to obtain a carboxylic acid compound B;

[0016] (3) Esterification reaction

[0017] The carbonyl group of the carboxylic acid compound B is activated by using a carbodiimide compound, and then esterified with a diol or a diol ether to obtain a synthetic tanning agent containing a hexavalent carbonyl group.

[0018] Furthermore, the active methylene compound described in step (1) is 1,3-diphenyl-1,3-propanedione (dibenzoylmethane, CAS registration number 120-46-7), 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione (CAS registration number 326-91-0), 1-phenyl-1,3-butanedione (CAS registration number 93-91-4), 4,4,4-trifluoro-1-phenyl-1,3-butanedione (CAS registration number 326-06-7), 4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedione (CAS registration number 893-33-4), acetylacetone (CAS registration number 123-54-6), hexafluoroacetylacetone (CAS registration number 1522-22 -1), 1,1,1-trifluoro-2,4-pentanedione (CAS accession number 367-57-7), 5,5-dimethylhexane-2,4-dione (CAS accession number 7307-04-2), 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione (CAS accession number 22767-90-4), 2,2,6,6-tetramethyl-3,5-heptanedione (CAS accession number 1118-71-4), 3,5-heptanedione (CAS accession number 7424-54-6), methyl acetylacetonate (CAS accession number 20577-61-1), ethyl acetylacetonate (CAS accession number 615-79-2); the α,β-unsaturated carboxylic acid ester compound is methyl acrylate (CAS 96-33-3), ethyl acrylate (CAS 140-88-5), propyl acrylate (CAS 925-60-0), isopropyl acrylate (CAS 689-12-3), butyl acrylate (CAS 141-32-2), tert-butyl acrylate (CAS 1663-39-4), methyl methacrylate (CAS 80-62-6), ethyl methacrylate (CAS 97-63-2), propyl methacrylate (CAS2210-28-8), isopropyl methacrylate (CAS 4655-34-9), butyl methacrylate (CAS 97-88-1), tert-butyl methacrylate (CAS 585-07-9).

[0019] Furthermore, the organic base described in step (1) is triethylamine, piperidine or pyridine; the inorganic base is anhydrous potassium carbonate or anhydrous sodium carbonate; the phase transfer catalyst is one of tetrabutylammonium bromide, tetrabutylammonium chloride, benzyltriethylammonium chloride (TEBA), tetrabutylammonium hydrogen sulfate (TBAB), trioctylmethylammonium chloride, dodecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride, polyethylene glycol 400-1000 (PEG 400-1000) or polypropylene glycol 400-1000 (PPG 400-1000); the low polar aprotic organic solvent is one of petroleum ether, n-hexane, cyclohexane, ethyl acetate, and 1,4-dioxane.

[0020] Furthermore, the molar ratio of the active methylene-containing compound to the α,β-unsaturated carboxylic acid ester-containing compound in step (1) is 1:(0.9-1.1); the molar ratio of the active methylene-containing compound to the alkali agent and the phase transfer catalyst is 1:(0.6-1.1):(0.01-0.05).

[0021] Furthermore, the alkali solution in step (2) is a sodium hydroxide or potassium hydroxide solution with a mass fraction of 10-30%; the acid is a hydrochloric acid solution, a sulfuric acid solution or a phosphoric acid solution with a mass fraction of 5-20%; and the molar ratio of carboxylate A to sodium hydroxide or potassium hydroxide is 0.2-1.2.

[0022] Further, in step (3), the carbonyl activator is one of N, N'-dicyclohexylcarbodiimide (DCC, CAS 538-75-0), N, N'-diisopropylcarbodiimide (DIC, CAS 693-13-0), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDC, CAS 1892-57-5), and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (CAS 7084-11-9); the diol or diol ether is ethylene glycol (CAS 107-21-1), propylene glycol (CAS 57-55-6), 2,2-dimethyl-1,3-propanediol (CAS 126-30-7), 1,4-butanediol (CAS 110-63-4), 1,5-pentanediol (CAS 111-29-5), 1,4-pentanediol (CAS 626-95-9), 2,4-pentanediol (CAS 625-69-4), 1,5-hexanediol (CAS 928-40-5), 2,5-hexanediol (CAS 2935-44-6) 1,6-hexanediol (CAS 629-11-8), 1,4-cyclohexanediol (CAS 556-48-9), diethylene glycol (CAS 111-46-6), triethylene glycol (CAS 112-27-6), tetraethylene glycol (CAS 112-60-7), polyethylene glycol PEG 200, polyethylene glycol PEG 300, polyethylene glycol PEG 400, polyethylene glycol PEG 600, polypropylene glycol PPG 400.

[0023] Furthermore, in step (3), the mass ratio of the carboxylic acid compound B to the carbonyl activator is 1:(0.8-1.2), and the molar ratio of the carboxylic acid compound B to the diol (diol ether) is 1:(0.4-0.6).

[0024] The invention discloses an application of the synthetic tanning agent containing hexacarbonyl group in the main tanning process of leather.

[0025] The present invention proposes a synthetic tanning agent containing a hexacarbonyl group, which has a simple preparation process and a high yield; the synthetic tanning agent is prepared using active methylene compounds, acrylates, diols and diol ethers as raw materials; the synthetic tanning agent contains functional groups such as β-diketones and carboxylates, which cyclize with the guanidine group of arginine and the amino group of lysine in collagen to form a pyrimidine ring, forming multi-point cross-linking, producing a tanning effect, and significantly improving the moisture and heat resistance stability and physical and mechanical properties of skin collagen. The use of the synthetic tanning agent in the present invention can replace chromium powder, reduce environmental pollution in the leather industry, and promote clean production in the leather industry.

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

[0027] 1) Using active methylene compounds, acrylates, diols and diol ethers as raw materials to prepare a synthetic tanning agent containing a hexavalent carbonyl group, the raw material price is low, the preparation process is simple and the yield is high;

[0028] 2) The β-diketone in the synthetic tanning agent cyclizes with the guanidine group in the collagen protein to form a stable 4,6-dimethylpyrimidine or 6-methylpyrimidin-4-one;

[0029] 3) Carboxylates form intermolecular hydrogen bonds with active functional groups in collagen;

[0030] 4) The synthetic tanning agent contains functional groups such as β-diketone and carboxylic acid, which cyclize with the guanidine group of arginine and the amino group of lysine in collagen to form a pyrimidine ring, forming multi-point cross-linking to produce a tanning effect, significantly improving the moisture and heat stability and physical and mechanical properties of skin collagen. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 General structural formula of synthetic tanning agents containing six-membered carbonyl groups DETAILED DESCRIPTION

[0032] The technical solution of the present invention is further described below in conjunction with embodiments.

[0033] Example 1

[0034] (I) Synthesis of 4-acetyl-5-oxo-hexanoic acid ethyl ester

[0035] In a 250mL four-necked flask equipped with a stirrer, a thermometer, and a reflux condenser, 0.1mol of acetylacetone, ground and dried K2CO3 (0.05mol), 1.5g of polyethylene glycol PEG 600, and 100mL of n-hexane were added, and 0.105mol of ethyl acrylate was added dropwise. The mixture was added for about 10 minutes, and the mixture was reacted at 60°C for 4 hours. Stirring was stopped, and the mixture was filtered with suction. The filter cake was washed with water to obtain 4-acetyl-5-oxo-hexanoic acid ethyl ester (C 10 H 16 O4, CAS 2832-10-2), the structural formula is as follows:

[0036]

[0037] 4-Acetyl-5-oxo-hexanoic acid ethyl ester H NMR (400MHz, CDCl3)

[0038] 4.14ppm (m, 2H, -COOCH2CH3), 3.44ppm (t, 1H, -CHCH2CH2COOC2H5), 2.46ppm (t, 2H, -CH2COOC2H5) , 2.16ppm (s, 6H, -CH(COCH3)2), 2.03ppm (m, 2H, -CH2CH2COOC2H5), 1.26ppm (t, 3H, -COOCH2CH3);

[0039] 4-Acetyl-5-oxo-hexanoic acid ethyl ester NMR carbon spectrum (400MHz, CDCl3)

[0040] 204.48ppm, 172.73ppm, 61.67ppm, 60.68ppm, 32.41ppm, 29.25ppm, 25.39ppm, 14.12ppm;

[0041] Elemental Analysis:

[0042] Theoretical value (%): C, 59.98; H, 8.05; Found value (%): C, 59.96; H, 8.07.

[0043] (II) Hydrolysis of 4-acetyl-5-oxo-hexanoic acid ethyl ester

[0044] In a 250mL four-necked flask equipped with a stirrer, a thermometer, and a reflux condenser, 0.1 mol of 4-acetyl-5-oxo-hexanoic acid ethyl ester was added, and 150mL of a 20% potassium hydroxide solution was added. After stirring at 80°C for 4 hours, the pH was adjusted to 4-5 with dilute hydrochloric acid, and filtered to obtain the product 4-acetyl-5-oxo-hexanoic acid. The product structure is as follows:

[0045]

[0046] 4-Acetyl-5-oxo-hexanoic acid H NMR (400 MHz, DMSO-d6)

[0047] 12.14ppm (s, 1H, -COOH), 3.39ppm (t, 1H, -CHCH2CH2COOH), 2.43ppm (t, 2H, -CH2COOH), 2.15ppm (s, 6H, -CH(COCH3)2), 1.95ppm (m, 2H, -CH2CH2COOH);

[0048] 4-Acetyl-5-oxo-hexanoic acid C NMR (400 MHz, DMSO-d6)

[0049] 204.24ppm, 176.30ppm, 61.56ppm, 32.40ppm, 29.22ppm, 25.64ppm;

[0050] Elemental Analysis:

[0051] Theoretical value (%): C, 55.81; H, 7.03; Found value (%): C, 55.78; H, 7.06.

[0052] (III) Esterification reaction

[0053] In a 250mL four-necked flask equipped with a stirrer, a thermometer, and a reflux condenser, 0.1 mol of 4-acetyl-5-oxohexanoic acid and 0.15 mol of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride were added, and after stirring at 60°C for 4 hours, 0.05 mol of ethylene glycol (CAS 107-21-1) was added, and the reaction was stirred for 5 hours, and filtered to obtain the product ethane-1,2-diylbis(4-acetyl-5-oxohexanoate), and the product structure formula is as follows:

[0054]

[0055] H NMR spectrum of ethane-1,2-diylbis(4-acetyl-5-oxohexanoate) (400MHz, DMSO-d6)

[0056] 4.30ppm(t,4H,-COOCH2CH2COO-), 3.42ppm(t,2H,-CH(COCH3)2), 2.45ppm(t,4H,-CH2COOC H2CH2COOCH2-), 2.11ppm (s, 12H, -COCH3), 1.92ppm (m, 4H, -CH2CH2COOCH2CH2COOCH2CH2-);

[0057] C NMR spectrum of ethane-1,2-diylbis(4-acetyl-5-oxohexanoate)(400MHz, DMSO-d6)

[0058] 204.25ppm, 172.89ppm, 62.31ppm, 61.49ppm, 32.31ppm, 29.19ppm, 25.40ppm;

[0059] Elemental Analysis:

[0060] Theoretical value (%): C, 58.37; H, 7.08; Measured value (%): C, 58.40; H, 7.04.

[0061] Example 2

[0062] (I) Synthesis of 4-propionyl-5-oxo-heptanoic acid ethyl ester

[0063] In a 250mL four-necked flask equipped with a stirrer, a thermometer, and a reflux condenser, 70mL of petroleum ether, 0.05mol of 3,5-heptanedione (CAS 7424-54-6), ground and dried K2CO3 (0.05mol), and 0.5g of dodecyltrimethylammonium chloride were added dropwise, and 0.05mol of ethyl acrylate was added dropwise for about 10 minutes. The mixture was reacted at 75°C for 4 hours, and stirring was stopped. The mixture was filtered with suction, and the filter cake was washed with water to obtain 4-propionyl-5-oxo-heptanoic acid ethyl ester (C 12 H 20 O4), the product structure is as follows;

[0064]

[0065] H NMR spectrum of 4-propionyl-5-oxo-heptanoic acid ethyl ester (400 MHz, DMSO-d6)

[0066] 4.10ppm (m, 2H, -COOCH2CH3), 3.31ppm (t, 1H, -CHCH2CH2COOC2H5), 2.46-2.51ppm (m, 6H, -CH2COOC2H5and-CH(C OCH2CH3)2), 1.98ppm (m, 2H, -CH2CH2COOC2H5), 1.25ppm (t, 3H, -COOCH2CH3), 1.06ppm (s, 6H, -CH(COCH2CH3)2);

[0067] C NMR spectrum of 4-propionyl-5-oxo-heptanoic acid ethyl ester (400MHz, DMSO-d6)

[0068] 208.60ppm, 172.75ppm, 60.67ppm, 58.33ppm, 35.58ppm, 32.25ppm, 25.63ppm, 14.19ppm, 7.55ppm;

[0069] Elemental Analysis:

[0070] Theoretical value (%): C, 63.14; H, 8.83; Found value (%): C, 63.20; H, 8.89.

[0071] (II) Hydrolysis

[0072] In a 250mL four-necked flask equipped with a stirrer, a thermometer, and a reflux condenser, 0.1 mol of 4-propionyl-5-oxo-heptanoic acid ethyl ester was added, and 150mL of a 20% potassium hydroxide solution was added. After stirring at 80°C for 4 hours, the pH was adjusted to 4-5 with dilute hydrochloric acid, and filtered to obtain the product 4-propionyl-5-oxo-heptanoic acid, the structural formula of which is as follows:

[0073]

[0074] H NMR spectrum of 4-propionyl-5-oxo-heptanoic acid (400 MHz, DMSO-d6)

[0075] 12.06ppm (s, 1H, -COOH), 3.34ppm (t, 1H, -CHCH2CH2COOH), 2.50ppm (m, 4H, -COCH2CH3), 2 .36ppm (t, 2H, -CH2COOH), 1.90ppm (m, 2H, -CH2CH2COOH), 1.05ppm (s, 6H, -CH(COCH3)2);

[0076] C NMR spectrum of 4-propionyl-5-oxo-heptanoic acid (400MHz, DMSO-d6)

[0077] 208.64ppm, 176.36ppm, 58.41ppm, 35.59ppm, 32.38ppm, 25.86ppm, 7.53ppm;

[0078] Elemental Analysis:

[0079] Theoretical value (%): C, 59.98; H, 8.05; Measured value (%): C, 60.04; H, 8.08.

[0080] (III) Esterification reaction

[0081] In a 250mL four-necked flask equipped with a stirrer, a thermometer, and a reflux condenser, 0.1 mol of 4-propionyl-5-oxo-heptanoic acid and 0.15 mol of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride were added, and after stirring at 60°C for 4 hours, 0.05 mol of ethylene glycol (CAS 107-21-1) was added, and the reaction was stirred for 5 hours, and filtered to obtain the product ethane-1,2-diylbis(5-oxo-4-propionylheptanoate), and the product structure formula is as follows:

[0082]

[0083] H NMR spectrum of ethane-1,2-diylbis(5-oxo-4-propionylheptanoate) (400 MHz, DMSO-d6)

[0084] 4.38ppm (t, 4H, -COOCH2CH2COO-), 3.31ppm (t, 2H, -CH(COCH2CH3)2), 2.55-2.43ppm (m, 12H, -CH2COOCH2CH2COOCH2-and CH3CH2COCH-), 1.90ppm (m, 4H, -CH2CH2COOCH2CH2COOCH2CH2-), 1.01ppm (t, 12H, -COCH2CH3);

[0085] C NMR spectrum of ethane-1,2-diylbis(5-oxo-4-propionylheptanoate)(400MHz, DMSO-d6)

[0086] 208.66ppm, 172.85ppm, 62.23ppm, 58.30ppm, 35.59ppm, 32.27ppm, 25.58ppm, 7.53ppm;

[0087] Elemental Analysis:

[0088] Theoretical value (%): C, 61.96; H, 8.04; Measured value (%): C, 61.97; H, 8.07.

[0089] Example 3

[0090] (I) Synthesis of 4-benzoyl-5-oxo-hexanoic acid ethyl ester

[0091] In a 250mL four-necked flask equipped with a stirrer, a thermometer, and a reflux condenser, 100mL of n-hexane, 0.1mol of benzoylacetone (CAS 93-91-4), ground and dried K2CO3 (0.05mol), and 1.5g of tetrabutylammonium bromide were added, and 0.105mol of ethyl acrylate was added dropwise. The mixture was added for about 10 minutes, and the mixture was reacted at 60°C for 4 hours. Stirring was stopped, and the mixture was filtered with suction. The filter cake was washed with water to obtain 4-benzoyl-5-oxo-hexanoic acid ethyl ester, the structural formula of which is as follows:

[0092]

[0093] 4-Benzoyl-5-oxo-hexanoic acid ethyl ester H NMR (400MHz, CDCl3)

[0094] 7.99ppm (d, 2H, -CC2H2C2H2CH), 7.49ppm (t, 1H, -CC2H2C2H2CH), 7.40ppm (t, 2H, -CC2H2C2H2CH), 4.16ppm (m, 2H, -COOCH2CH3), 3.83ppm (t , 1H, -CHCH2CH2COOC2H5), 2.51ppm (t, 2H, -CH2COOC2H5), 2.08-2.16ppm (m, 5H, -COCH3and-CH2CH2COOC2H5), 1.22ppm (t, 3H, -COOCH2CH3);

[0095] 4-Benzoyl-5-oxo-hexanoic acid ethyl ester NMR carbon spectrum (400MHz, CDCl3)

[0096] 205.01ppm, 197.89ppm, 172.70ppm, 136.51ppm, 132.69ppm, 128.95ppm, 128.53ppm, 60.59ppm, 58.79ppm, 32.38ppm, 29.18ppm, 26.00ppm, 14.16ppm;

[0097] Elemental Analysis:

[0098] Theoretical value (%): C, 68.69; H, 6.92; Found value (%): C, 68.70; H, 6.92.

[0099] (II) Hydrolysis of 4-benzoyl-5-oxo-hexanoic acid ethyl ester

[0100] In a 250mL four-necked flask equipped with a stirrer, a thermometer, and a reflux condenser, 0.1 mol of 4-benzoyl-5-oxo-hexanoic acid ethyl ester was added, and 150mL of a 20% potassium hydroxide solution was added. After stirring at 80°C for 6 hours, the pH was adjusted to 4-5 with dilute hydrochloric acid, and filtered to obtain the product 4-benzoyl-5-oxo-hexanoic acid. The product structural formula is as follows:

[0101]

[0102] 4-Benzoyl-5-oxo-hexanoic acid H NMR (400 MHz, DMSO-d6)

[0103] 12.11ppm (s, 1H, -COOH), 8.01ppm (d, 2H, -CC2H2C2H2CH), 7.55ppm (t, 1H, -CC2H2C2H2CH), 7.42ppm (t, 2H, -CC2H2C2H2CH) ), 3.78ppm (t, 1H, -CHCH2CH2COOH), 2.36ppm (t, 2H, -CH2COOH), 2.15ppm (s, 3H, -COCH3), 2.00ppm (m, 2H, -CH2CH2COOH);

[0104] 4-Benzoyl-5-oxo-hexanoic acid C NMR (400 MHz, DMSO-d6)

[0105] 204.90ppm, 197.70ppm, 176.22ppm, 136.50ppm, 132.75ppm, 128.93ppm, 128.49ppm, 58.09ppm, 32.34ppm, 29.06ppm, 26.01ppm;

[0106] Elemental Analysis:

[0107] Theoretical value (%): C, 66.66; H, 6.02; Found value (%): C, 66.64; H, 6.02.

[0108] (III) Esterification

[0109] In a 250mL four-necked flask equipped with a stirrer, a thermometer, and a reflux condenser, 0.1 mol of 4-benzoyl-5-oxohexanoic acid and 0.15 mol of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride were added. After stirring at 60°C for 4 hours, 0.05 mol (CAS 107-21-1) was added. The mixture was stirred for 5 hours and filtered to obtain the product ethane-1,2-diylbis(4-benzoyl-5-oxohexanoate). The product structure is as follows:

[0110]

[0111] H NMR spectrum of ethane-1,2-diylbis(4-benzoyl-5-oxohexanoate) (400MHz, DMSO-d6)

[0112] 8.01ppm (d, 4H, -CC2H2C2H2CH), 7.58ppm (t, 2H, -CC2H2C2H2CH), 7.45ppm (t, 4H, -CC2H2C2H2CH), 4.35ppm (t, 4H, -COOCH2CH2COO-), 3.84p pm (t, 2H, -CHCOCH3), 2.50ppm (t, 4H, -CH2COOCH2CH2COOCH2-), 2.17ppm (s, 6H, -COCH3), 2.05ppm (m, 4H, -CH2CH2COOCH2CH2COOCH2CH2-);

[0113] C NMR spectrum of ethane-1,2-diylbis(4-benzoyl-5-oxohexanoate)(400MHz, DMSO-d6)

[0114] 204.93ppm, 197.72ppm, 172.81ppm, 136.52ppm, 132.75ppm, 128.94ppm, 128.49ppm, 62.29ppm, 58.15ppm, 32.24ppm, 29.06ppm, 25.94ppm;

[0115] Elemental Analysis:

[0116] Theoretical value (%): C, 68.00; H, 6.11; Found value (%): C, 68.00; H, 6.12.

[0117] Example 4

[0118] (I) Synthesis of ethyl di(4-benzoyl)-butyrate

[0119] In a 250mL four-necked flask equipped with a stirrer, a thermometer, and a reflux condenser, 100mL of n-hexane, 0.1mol of dibenzoylmethane (CAS 120-46-7), ground and dried K2CO3 (0.05mol), and 1.5g of tetrabutylammonium bromide were added, and 0.105mol of ethyl acrylate was added dropwise. The mixture was added for about 10 minutes, and the mixture was reacted at 60°C for 4 hours. Stirring was stopped, and the mixture was filtered with suction. The filter cake was washed with water to obtain ethyl di(4-benzoyl)-butyrate, the structural formula of which is as follows:

[0120]

[0121] Ethyl di(4-benzoyl)butyrate H NMR (400MHz, CDCl3)

[0122] 8.00ppm (d, 4H, -CC2H2C2H2CH), 7.52ppm (t, 2H, -CC2H2C2H2CH), 7.43ppm (t, 4H, -CC2H2C2H2CH), 4.66ppm (t, 1H, -CHCH2CH2COOC2 H5), 4.14ppm (m, 2H, -COOCH2CH3), 2.50ppm (t, 2H, -CH2COOC2H5), 2.03ppm (m, 2H, -CH2CH2COOC2H5), 1.25ppm (t, 3H, -COOCH2CH3);

[0123] Ethyl di(4-benzoyl)butyrate NMR carbon spectrum (400MHz, CDCl3)

[0124] 197.43ppm, 172.72ppm, 135.98ppm, 132.71ppm, 128.97ppm, 128.53ppm, 60.71ppm, 59.08ppm, 32.16ppm, 26.50ppm, 14.18ppm;

[0125] Elemental Analysis:

[0126] Theoretical value (%): C, 74.06; H, 6.22; Found value (%): C, 74.04; H, 6.24.

[0127] (II) Hydrolysis of ethyl di(4-benzoyl)-butyrate

[0128] In a 250mL four-necked flask equipped with a stirrer, a thermometer, and a reflux condenser, 0.1 mol of ethyl di(4-benzoyl)-butyrate was added, and 150mL of a 20% potassium hydroxide solution was added. After stirring at 80°C for 6 hours, the pH was adjusted to 4-5 with dilute hydrochloric acid, and filtered to obtain the product di(4-benzoyl)-butyric acid. The product structural formula is as follows:

[0129]

[0130] Di(4-benzoyl)-butyric acid H NMR (400 MHz, DMSO-d6)

[0131] 12.12ppm (s, 1H, -COOH), 8.00ppm (d, 4H, -CC2H2C2H2CH), 7.57ppm (t, 2H, -CC2H2C2H2CH), 7.45ppm (t, 4H, - CC2H2C2H2CH), 4.64ppm (t, 1H, -CHCH2CH2COOH), 2.47ppm (t, 2H, -CH2COOH), 2.09ppm (m, 2H, -CH2CH2COOH);

[0132] Di(4-benzoyl)-butyric acid C NMR (400MHz, DMSO-d6)

[0133] 197.18ppm, 176.24ppm, 135.93ppm, 132.73ppm, 128.96ppm, 128.50ppm, 59.11ppm, 32.30ppm, 26.40ppm;

[0134] Elemental Analysis:

[0135] Theoretical value (%): C, 72.96; H, 5.44; Found value (%): C, 72.96; H, 5.44.

[0136] (III) Esterification reaction

[0137] In a 250mL four-necked flask equipped with a stirrer, a thermometer, and a reflux condenser, 0.1 mol of di(4-benzoyl)-butyric acid and 0.15 mol of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride were added, and after stirring at 60°C for 4 hours, 0.05 mol of ethylene glycol (CAS 107-21-1) was added, and the reaction was stirred for 5 hours. The product ethane-1,2-diylbis(di(4-benzoyl)-butyrate) was obtained by filtration. The product structure is as follows:

[0138]

[0139] H NMR spectrum of ethane-1,2-diylbis(di(4-benzoyl)-butyrate) (400MHz, DMSO-d6)

[0140] 8.01ppm (d, 8H, -CC2H2C2H2CH), 7.56ppm (t, 4H, -CC2H2C2H2CH), 7.43ppm (t, 8H, -CC2H2C2H2CH), 4.65ppm (t, 2H, -CHCH2CH2COOCH2CH2COO CH2CH2CH-), 4.37ppm (t, 4H, -COOCH2CH2COO-), 2.52ppm (t, 4H, -CH2COOCH2CH2COOCH2-), 2.06ppm (m, 4H, -CH2CH2COOCH2CH2COOCH2CH2-);

[0141] C NMR spectrum of ethane-1,2-diylbis(di(4-benzoyl)-butyrate) (400MHz, DMSO-d6)

[0142] 197.20ppm, 172.81ppm, 135.95ppm, 132.74ppm, 128.95ppm, 128.50ppm, 62.27ppm, 59.00ppm, 32.13ppm, 26.43ppm;

[0143] Elemental Analysis:

[0144] Theoretical value (%): C, 73.77; H, 5.54; Found value (%): C, 73.75; H, 5.52.

[0145] Example 5

[0146] (I) Synthesis of 4-acetyl-5-oxo-hexanoic acid ethyl ester

[0147] In a 250mL four-necked flask equipped with a stirrer, a thermometer, and a reflux condenser, 100mL of n-hexane, 0.1mol of acetylacetone, ground and dried K2CO3 (0.05mol), and 1.5g of tetrabutylammonium bromide were added, and 0.105mol of ethyl acrylate was added dropwise. The mixture was added over a period of about 10 minutes. The mixture was reacted at 60°C for 4h, and stirring was stopped. The mixture was filtered with suction and the filter cake was washed with water to obtain 4-acetyl-5-oxo-hexanoic acid ethyl ester.

[0148] (II) Hydrolysis of 4-acetyl-5-oxo-hexanoic acid ethyl ester

[0149] In a 250mL four-necked flask equipped with a stirrer, a thermometer, and a reflux condenser, 0.1 mol of 4-acetyl-5-oxo-hexanoic acid ethyl ester was added, and 150mL of a 20% by mass sodium hydroxide solution was added. After stirring at 80°C for 5 hours, the pH was adjusted to 4-5 with dilute hydrochloric acid, and filtered to obtain the product 4-acetyl-5-oxo-hexanoic acid.

[0150] (III) Esterification reaction

[0151] In a 250mL four-necked flask equipped with a stirrer, a thermometer, and a reflux condenser, 0.1 mol of 4-acetyl-5-oxo-hexanoic acid and 0.15 mol of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride were added, and after stirring at 60°C for 4 hours, 0.05 mol of 1,4-butanediol (CAS 110-63-4) was added, and the reaction was stirred for 5 hours to separate the product butane-1,4-diylbis(4-acetyl-5-oxo-hexanoate), and the product structure is as follows:

[0152]

[0153] H NMR spectrum of butane-1,4-diylbis(4-acetyl-5-oxo-hexanoate) (400MHz, DMSO-d6)

[0154] 4.10ppm (t, 4H, -COOCH2CH2CH2CH2COO-), 3.45ppm (t, 2H, -CH(COCH3)2), 2.43ppm (t, 4H, -CH2COOCH2CH2CH2CH2COOCH2-), 2 .12ppm (s, 12H, -COCH3), 1.92ppm (m, 4H, -CH2CH2COOCH2CH2CH2CH2COOCH2CH2-), 1.79ppm (m, 4H, -COOCH2CH2CH2CH2COO-);

[0155] C NMR spectrum of butane-1,4-diyl bis(4-acetyl-5-oxo-hexanoate)(400MHz, DMSO-d6)

[0156] 204.27ppm, 173.06ppm, 64.65ppm, 61.44ppm, 32.32ppm, 29.20ppm, 25.39ppm, 22.48ppm;

[0157] Elemental Analysis:

[0158] Theoretical value (%): C, 60.29; H, 7.59; Measured value (%): C, 60.30; H, 7.56.

[0159] Example 6

[0160] (I) Synthesis of 4-propionyl-5-oxo-heptanoic acid ethyl ester

[0161] In a 250mL four-necked flask equipped with a stirrer, a thermometer, and a reflux condenser, 100mL of n-hexane, 0.1mol of 3,5-heptanedione (CAS 7424-54-6), ground and dried K2CO3 (0.05mol), and 1.5g of tetrabutylammonium bromide were added, and 0.105mol of ethyl acrylate was added dropwise. The mixture was added over a period of about 10 minutes, and the mixture was reacted at 60°C for 4h. Stirring was stopped, and the mixture was filtered with suction. The filter cake was washed with water to obtain 4-propionyl-5-oxo-heptanoic acid ethyl ester.

[0162] (II) Hydrolysis of 4-propionyl-5-oxo-heptanoic acid ethyl ester

[0163] In a 250mL four-necked flask equipped with a stirrer, a thermometer, and a reflux condenser, 0.1 mol of 4-propionyl-5-oxo-heptanoic acid ethyl ester was added, and 150mL of a 20% sodium hydroxide solution was added. After stirring at 80°C for 6 hours, the pH was adjusted to 4-5 with dilute hydrochloric acid, and filtered to obtain the product 4-propionyl-5-oxo-heptanoic acid.

[0164] (III) Esterification reaction

[0165] In a 250mL four-necked flask equipped with a stirrer, a thermometer, and a reflux condenser, 0.1 mol of 4-propionyl-5-oxo-heptanoic acid and 0.15 mol of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride were added, and after stirring at 60°C for 4 hours, 0.05 mol of 1,4-butanediol (CAS 110-63-4) was added, and the reaction was stirred for 5 hours to separate the product butane-1,4-diylbis(4-acetyl-5-oxo-heptanoate), and the product structure is as follows:

[0166]

[0167] H NMR spectrum of butane-1,4-diylbis(4-acetyl-5-oxo-heptanoate) (400MHz, DMSO-d6)

[0168] 4.08ppm (t, 4H, -COOCH2CH2CH2CH2COO-), 3.27ppm (t, 2H, -CH(COCH2CH3)2), 2.51-2.42ppm (m, 12H, -CH2COOCH2CH2CH2CH2COOCH2-and-CH(C OCH2CH3)2), 1.92ppm (m, 4H, -CH2CH2COOCH2CH2CH2CH2COOCH2CH2-), 1.79ppm (m, 4H, -COOCH2CH2CH2CH2COO-), 1.02ppm (t, 12H, -COCH2CH3);

[0169] H NMR spectrum of butane-1,4-diylbis(4-acetyl-5-oxo-heptanoate) (400MHz, DMSO-d6)

[0170] 208.67ppm, 173.00ppm, 64.63ppm, 58.33ppm, 35.62ppm, 32.25ppm, 25.59ppm, 22.48ppm, 7.55ppm;

[0171] Elemental Analysis:

[0172] Theoretical value (%): C, 63.42; H, 8.43; Found value (%): C, 63.40; H, 8.42.

[0173] Example 7

[0174] (I) Synthesis of 4-benzoyl-5-oxo-hexanoic acid ethyl ester

[0175] In a 250mL four-necked flask equipped with a stirrer, a thermometer, and a reflux condenser, 100mL of n-hexane, 0.1mol of benzoylacetone (CAS 93-91-4), ground and dried K2CO3 (0.05mol), and 1.5g of tetrabutylammonium bromide were added, and 0.105mol of ethyl acrylate was added dropwise. The dripping was completed in about 10 minutes, and the reaction was carried out at 60°C for 4 hours. The stirring was stopped, and the mixture was filtered with suction. The filter cake was washed with water to obtain 4-benzoyl-5-oxo-hexanoic acid ethyl ester.

[0176] (II) Hydrolysis of 4-benzoyl-5-oxo-hexanoic acid ethyl ester

[0177] In a 250mL four-necked flask equipped with a stirrer, a thermometer, and a reflux condenser, 0.1 mol of 4-benzoyl-5-oxo-hexanoic acid ethyl ester was added, and 150mL of a 20% potassium hydroxide solution was added. After stirring at 80°C for 4 hours, the pH was adjusted to 4-5 with dilute hydrochloric acid, and filtered to obtain the product 4-benzoyl-5-oxo-hexanoic acid.

[0178] (III) Esterification reaction

[0179] In a 250mL four-necked flask equipped with a stirrer, a thermometer, and a reflux condenser, 0.1 mol of 4-benzoyl-5-oxo-hexanoic acid and 0.15 mol of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride were added, and after stirring at 60°C for 4 hours, 0.05 mol of 1,4-butanediol (CAS 110-63-4) was added, and the reaction was stirred for 5 hours to separate the product butane-1,4-diylbis(4-benzoyl-5-oxo-hexanoate), and the product structure is as follows:

[0180]

[0181] H NMR spectrum of butane-1,4-diylbis(4-benzoyl-5-oxo-hexanoate) (400MHz, DMSO-d6)

[0182] 7.99ppm(d,4H,-CC2H2C2H2CH), 7.56ppm(t,2H,-CC2H2C2H2CH), 7.44ppm(t,4H,-CC 2H2C2H2CH), 4.11ppm (t, 4H, -COOCH2CH2CH2CH2COO-), 3.82ppm (t, 2H, -CHCOCH3), 2. 51ppm (t, 4H, -CH2COOCH2CH2CH2CH2COOCH2-), 2.17ppm (s, 6H, -COCH3), 2.10ppm (m, 4H, -CH2CH2COOCH2CH2CH2CH2COOCH2CH2-), 1.80ppm (m, 4H, -COOCH2CH2CH2CH2COO-);

[0183] H NMR spectrum of butane-1,4-diylbis(4-benzoyl-5-oxo-hexanoate) (400MHz, DMSO-d6)

[0184] 204.92ppm, 197.73ppm, 173.01ppm, 136.50ppm, 132.76ppm, 128.94ppm, 128.50ppm, 64.64ppm, 58.17ppm, 32.26ppm, 29.07ppm, 25.95ppm, 22.47ppm;

[0185] Elemental Analysis:

[0186] Theoretical value (%): C, 68.95; H, 6.56; Found value (%): C, 68.96; H, 6.54.

[0187] Example 8

[0188] (I) Synthesis of ethyl di(4-benzoyl)-butyrate

[0189] In a 250mL four-necked flask equipped with a stirrer, a thermometer, and a reflux condenser, 100mL of n-hexane, 0.1mol of dibenzoylmethane (CAS 120-46-7), ground and dried K2CO3 (0.05mol), and 1.5g of tetrabutylammonium bromide were added, and 0.105mol of ethyl acrylate was added dropwise. The dripping was completed in about 10 minutes, and the reaction was carried out at 60°C for 4 hours. Stirring was stopped, and the mixture was filtered with suction. The filter cake was washed with water to obtain di(4-benzoyl)-butyric acid ethyl ester.

[0190] (II) Hydrolysis of ethyl di(4-benzoyl)-butyrate

[0191] In a 250mL four-necked flask equipped with a stirrer, a thermometer, and a reflux condenser, 0.1 mol of ethyl di(4-benzoyl)-butyrate was added, and 150mL of a 20% potassium hydroxide solution was added. After stirring at 80°C for 6 hours, the pH was adjusted to 4-5 with dilute hydrochloric acid, and the mixture was filtered to obtain the product di(4-benzoyl)-butyric acid.

[0192] (III) Esterification reaction

[0193] In a 250mL four-necked flask equipped with a stirrer, a thermometer, and a reflux condenser, 0.1 mol of di(4-benzoyl)-butyric acid and 0.15 mol of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride were added, and after stirring at 60°C for 4 hours, 0.05 mol of 1,4-butanediol (CAS 110-63-4) was added, and the reaction was stirred for 5 hours to separate the product butane-1,4-diylbis(di(4-benzoyl)-butyrate), and the product structure is as follows:

[0194]

[0195] H NMR spectrum of butane-1,4-diylbis(di(4-benzoyl)-butyrate) (400MHz, DMSO-d6)

[0196] 8.02ppm(d,8H,-CC2H2C2H2CH), 7.58ppm(t,4H,-CC2H2C2H2CH), 7.45ppm(t,8H,-CC2H 2C2H2CH), 4.66ppm (t, 2H, -CHCH2CH2COOCH2CH2CH2CH2COOCH2CH2CH-), 4.1Oppm (t, 4H, -COOCH2CH2CH2CH2COO-), 2.51ppm (t, 4H, -CH2COOCH2CH2CH2CH2COOCH2-), 2.04ppm (m, 4H, -CH2CH2COOCH2CH2CH2CH2COOCH2CH2-), 1.79ppm (m, 4H, -COOCH2CH2CH2CH2COO-);

[0197] H NMR spectrum of butane-1,4-diylbis(di(4-benzoyl)-butyrate) (400MHz, DMSO-d6)

[0198] 197.18ppm, 173.04ppm, 135.92ppm, 132.72ppm, 128.96ppm, 128.50ppm, 64.63ppm, 59.01ppm, 32.20ppm, 26.45ppm, 22.49ppm;

[0199] Elemental Analysis:

[0200] Theoretical value (%): C, 74.29; H, 5.92; Found value (%): C, 74.31; H, 5.95.

[0201] The preparation results of Examples 1-8 for preparing synthetic tanning agents containing hexacarbonyl groups using different raw materials are summarized in Table 1.

[0202] Table 1 Preparation examples of synthetic tanning agents containing six-membered carbonyl groups

[0203] Raw material 1 Raw material 2 Raw material 3 Raw material 4 Yield (%) Example 1 Acetylacetone Ethyl acrylate EDC hydrochloride Ethylene glycol 96 Example 2 3,5-Heptanedione Methyl acrylate EDC hydrochloride Ethylene glycol 95 Example 3 Benzoyl acetone Ethyl acrylate EDC hydrochloride Ethylene glycol 97 Example 4 Dibenzoylmethane Ethyl acrylate EDC hydrochloride Ethylene glycol 96 Example 5 Acetylacetone Ethyl acrylate EDC hydrochloride 1,4-Butanediol 94 Example 6 3,5-Heptanedione Methyl acrylate EDC hydrochloride 1,4-Butanediol 93 Example 7 Benzoyl acetone Ethyl acrylate EDC hydrochloride 1,4-Butanediol 94 Example 8 Dibenzoylmethane Ethyl acrylate EDC hydrochloride 1,4-Butanediol 93

[0204] Table 2 Tanning process

[0205]

[0206] Table 3 Shrinkage temperature and mechanical properties test

[0207]

Claims

1. A method for preparing a synthetic tanning agent containing a hexacarbonyl group, characterized in that: The steps include: (1) Michael addition reaction Using Michael addition reaction, with active methylene-containing compound and α, β-unsaturated carboxylic acid ester compound as raw materials, with organic base or inorganic base as alkaline agent, in the condition of phase transfer catalyst, in low polarity aprotic organic solvent, react at 30-120° C. for 2-12 hours to obtain carboxylic acid ester compound; (2) Hydrolysis reaction The carboxylate compound obtained in step (1) is hydrolyzed under alkaline conditions at 50-98° C. for 4-12 h, cooled to room temperature, and the pH is adjusted to 4-5 with an acid to precipitate a solid, which is filtered to obtain a carboxylic acid compound; (3) Esterification reaction The carbonyl group of the carboxylic acid compound is activated by using a carbodiimide compound, and then esterified with a diol or a diol ether to obtain a synthetic tanning agent containing a hexavalent carbonyl group; The general structural formula of the synthetic tanning agent is: Where A=C2H4,C3H6,C4H8,C5H 10 , C6H 12 , C2H4-O-C2H4, C2H4-O-C2H4-O-C2H4, C2H4-O-C2H4-O-C2H4-O-C2H4; R1, R2 are methyl, trifluoromethyl, ethyl, oxymethyl, oxyethyl, isopropyl, tert-butyl, phenyl, COOCH3, COOC2H5, 4,4,4-trifluoro-1-(2-thienyl), 4,4,4-trifluoro-1-phenyl, 4,4,4-trifluoro-1-(2-naphthyl); In step (1), the active methylene-containing compound is 1,3-diphenyl-1,3-propanedione, 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione, 1-phenyl-1,3-butanedione, 4,4,4-trifluoro-1-phenyl-1,3-butanedione, 4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedione, acetylacetone, hexafluoroacetylacetone, 1,1,1-trifluoro-2,4-pentanedione, 5,5-dimethylhexane-2,4-dione, 1,1,1- One of trifluoro-5,5-dimethyl-2,4-hexanedione, 2,2,6,6-tetramethyl-3,5-heptanedione, 3,5-heptanedione, methyl acetylacetonate, and ethyl acetylacetonate; the α,β-unsaturated carboxylic acid ester compound is one of methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, tert-butyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, and tert-butyl methacrylate; In step (1), the molar ratio of the compound containing active methylene to the compound containing α, β-unsaturated carboxylic acid ester is 1:(0.9-1.1); the molar ratio of the compound containing active methylene to the alkali agent and the phase transfer catalyst is 1:(0.6-1.1):(0.01-0.05); In step (3), the mass ratio of the carboxylic acid compound to the carbodiimide compound is 1:(0.8-1.2), and the molar ratio of the carboxylic acid compound to the diol or diol ether is 1:(0.4-0.6).

2. The method for preparing a synthetic tanning agent containing a hexamembered carbonyl group according to claim 1, characterized in that: In step (1), the organic base is triethylamine, piperidine or pyridine; the inorganic base is anhydrous potassium carbonate or anhydrous sodium carbonate; the phase transfer catalyst is one of tetrabutylammonium bromide, tetrabutylammonium chloride, benzyltriethylammonium chloride, tetrabutylammonium hydrogen sulfate, trioctylmethylammonium chloride, dodecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride, and polyethylene glycol 400-1000; and the low-polarity aprotic organic solvent is one of petroleum ether, n-hexane, cyclohexane, ethyl acetate, and 1,4-dioxane.

3. The method for preparing a synthetic tanning agent containing a hexacarbonyl group according to claim 1, characterized in that: In step (2), the alkaline condition is provided by a sodium hydroxide or potassium hydroxide aqueous solution with a mass fraction of 10-30%; the acid is a hydrochloric acid solution, a sulfuric acid solution or a phosphoric acid solution with a mass fraction of 5-15%; and the molar ratio of the carboxylate to the sodium hydroxide or potassium hydroxide is 0.2-1.

2.

4. The method for preparing a synthetic tanning agent containing a hexamembered carbonyl group according to claim 1, characterized in that: In step (3), the carbodiimide compound is one of N,N'-dicyclohexylcarbodiimide, N,N'-diisopropylcarbodiimide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride; and the diol or diol ether is one of ethylene glycol, propylene glycol, 2,2-dimethyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,4-pentanediol, 2,4-pentanediol, 1,5-hexanediol, 2,5-hexanediol, 1,6-hexanediol, diethylene glycol, triethylene glycol and tetraethylene glycol.

5. Use of the hexacarbonyl-containing synthetic tanning agent according to claim 1 in the main tanning process of leather.

Images