A method for preparing an aminal retanning agent based on chrome-free tanning and high-brightness leather

Abstract

The present invention relates to a preparation method of an aminal retanning agent based on chrome-free tanning, wherein glyoxylic acid and ethylene glycol are added to benzene, heated, stirred, p-toluenesulfonic acid is added, cooled, and the solvent and catalyst are removed by rotary evaporation to obtain an activated glyoxylic acid precursor, and the activated glyoxylic acid precursor is dissolved in thionyl chloride, 3 parts of N, N-dimethylformamide are added, and the activated glyoxylic acid is obtained by rotary evaporation; mellitic acid and pentaerythritol are mixed uniformly, 5-20 parts of concentrated sulfuric acid are added, and the activated glyoxylic acid is added by rotary evaporation, mixed uniformly and heated, concentrated sulfuric acid is added, water is added, and pH is adjusted to obtain an aminal retanning agent based on chrome-free tanning. The aminal retanning agent based on chrome-free tanning of the present application has a relatively suitable particle size and dispersibility, and can promote the adsorption and combination of skin collagen fibers to subsequent retanning, filling, and dyeing materials.

Description

Technical Field

[0001] The invention relates to the technical field of leather making, in particular to an aminal retanning agent based on chrome-free tanning and a preparation method of high-brightness leather. Background Art

[0002] Currently, over 90% of leather on the market is chrome-tanned. Chrome-tanned leather has excellent physical, mechanical, and sensory properties, but it carries the risk of Cr(III) leaching and oxidation to Cr(VI). Therefore, many research institutions and tanneries are currently researching chrome-free tanning, which can be further divided into organic tanning and chrome-free multi-metal tanning. Organic tanning is the most widely studied chrome-free tanning method. Organic tanning does not use metal tanning agents and has excellent ecological and environmental performance. However, organic tanning agents are mostly anionic, as are leather collagen fibers. Traditional leather dyes are also anionic. Due to ion competition, the adsorption and binding ability of organically tanned leather for dyes is relatively weak. Analysis of the structure of leather dyes reveals that leather dyes are anionic synthetic dyes with aromatic ring structures. Therefore, to promote the adsorption and binding of synthetic dyes by organically tanned leather, one approach is to introduce more non-metallic cationic centers or more aromatic ring structure materials to promote absorption. Summary of the Invention

[0003] The invention provides an aminal retanning agent based on chrome-free tanning and a preparation method of high-brightness leather, so as to solve the problem that organic tanned leather has weak adsorption and binding ability to dyes.

[0004] The present invention adopts the following technical solutions:

[0005] A method for preparing an aminal retanning agent based on chrome-free tanning comprises the following steps:

[0006] Step 1: 100 parts of glyoxylic acid and 120 parts of ethylene glycol are added to 500 parts of benzene, the temperature is slowly raised to 60-80°C, and after stirring, 5-10 parts of p-toluenesulfonic acid are added dropwise over 30 minutes. The reaction is then continued at a constant temperature for 3-5 hours, and the temperature is slowly lowered to room temperature. The solvent and catalyst are removed by rotary evaporation to obtain an activated glyoxylic acid precursor. 100 parts of the activated glyoxylic acid precursor are dissolved in 300 parts of thionyl chloride, 3 parts of N,N-dimethylformamide are added, and the reaction is continued at 35-50°C for 2-4 hours. Excess thionyl chloride and N,N-dimethylformamide are removed by rotary evaporation to obtain activated glyoxylic acid.

[0007] Step 2: Take 100 parts of mellitic acid and 650-800 parts of pentaerythritol, mix them evenly, slowly raise the temperature to 60-90°C under nitrogen protection, add 5-20 parts of concentrated sulfuric acid dropwise within 1 hour, then continue to keep warm for 1-5 hours, slowly lower the temperature to room temperature, then remove excess pentaerythritol by rotary evaporation, add 220-300 parts of activated glyoxylic acid, mix evenly, slowly raise the temperature to 70-100°C, add 8-30 parts of concentrated sulfuric acid dropwise within 1 hour, then continue to keep warm for 3-8 hours, slowly lower the temperature to 40-50°C, add 500-650 parts of water, adjust the pH value to 7.0-7.5 with sulfuric acid, keep constant temperature for 1-3 hours, and finally cool to room temperature to prepare a chrome-free tanning based aminal retanning agent.

[0008] A method for preparing high-brightness leather using an aminal retanning agent based on chrome-free tanning, comprising at least a neutralization step and a retanning step;

[0009] Neutralization process: based on the weight of wet white leather, control the drum temperature to 35-40°C, add 2-4% neutralizing tannin and 0.8-1.2% sodium formate, rotate for 20 minutes, add 0-0.5% baking soda and 0.5-1.5% sodium bicarbonate, rotate for 60 minutes, add 1-3% chrome-free tanning aminal retanning agent, rotate for 40 minutes, drain, add 200% water, and rinse;

[0010] Retanning process: Based on the weight of wet white leather, control the drum temperature to 30-35°C, add 75-150% water, add 1-3% chrome-free acetal amine retanning agent, 1-3% lanolin fatliquor, 2-4% acid-resistant acrylic resin retanning agent, rotate for 30-60 minutes, then add 2-4% chrome-free acetal amine retanning agent, 2-4% synthetic tanning agent, 2-4% protein filler, rotate for 60-120 minutes, add 100 -150% water, add 1.2-1.8% formic acid three times, rotate for 10, 10 and 20 minutes respectively, add 3-6% chrome-free acetal amine retanning agent, 1-2% cationic oil, rotate for 20 minutes, add 5-10% organic tanning agent, rotate for 120-180 minutes, then add 2% sodium formate, rotate for 20 minutes, add 2% baking soda, rotate for 60 minutes, add 2% ammonium bicarbonate, rotate for 60 minutes, and drain.

[0011] It can be seen from the above description of the present invention that, compared with the prior art, the present invention has the following advantages:

[0012] 1. The mellitic acid molecule possesses six carboxyl groups, which theoretically can form a primary hyperbranched structure with up to six pentaerythritol molecules. Due to steric hindrance, one mellitic acid molecule can simultaneously graft three to four pentaerythritol molecules. Even primary hyperbranching results in a relatively large molecular structure, but the multiple amino and carboxyl groups form only hydrogen bonds with collagen, resulting in weak reactivity with collagen fibers. Therefore, activating the amino groups can introduce more active sites. Amino groups react with acyl halides to form addition-elimination reactions at room temperature, making them ideal activating functional groups. The carbonyl groups protected with ethylene glycol can be hydrolyzed under acidic conditions during subsequent use and bind to collagen fibers, thereby anchoring the aminal retanning agent to the fibers. The multiple amino groups in the aminal retanning agent provide active cationic centers that promote dye adsorption. Furthermore, the aromatic ring structure forms π-π interactions with the dye, further enhancing dye binding.

[0013] 2. The chrome-free tanning-based aminal retanning agent of the present application has a relatively suitable particle size and dispersion performance, with a particle size of 800-1200 nm and a particle size distribution coefficient of 0.200-0.450. It also has good positive charge and a zeta potential of ≥20 mV.

[0014] 3. The chrome-free tanning-based aminal retanning agent of the present application can effectively promote the adsorption and binding of dyes to leather collagen fibers. Compared with the results without the use of aminal retanning agent, the L value, a value and b value in the Lab value of the dyed leather are significantly improved, and ΔE can be between 2 and 3.

[0015] 4. The acetal amine retanning agent based on chrome-free tanning of the present application can well promote the adsorption and bonding of leather collagen fibers to subsequent retanning, filling and dyeing materials. The shrinkage temperature of the crust leather is ≥75°C, the tearing force is ≥50N, the cracking height is ≥7mm, the bursting strength is ≥100N, and the odor is ≤level 3. DETAILED DESCRIPTION

[0016] Example 1:

[0017] A method for preparing an aminal retanning agent based on chrome-free tanning comprises the following steps:

[0018] Step 1: 100 parts of glyoxylic acid and 120 parts of ethylene glycol are added to 500 parts of benzene. The temperature is slowly raised to 60°C and stirred. 10 parts of p-toluenesulfonic acid are then added dropwise over 30 minutes. The reaction is then continued at a constant temperature for 5 hours. The temperature is then slowly lowered to room temperature and the solvent and catalyst are removed by rotary evaporation to obtain an activated glyoxylic acid precursor. 100 parts of the activated glyoxylic acid precursor are dissolved in 300 parts of thionyl chloride, 3 parts of N,N-dimethylformamide are added, and the reaction is incubated at 50°C for 2 hours. Excess thionyl chloride and N,N-dimethylformamide are removed by rotary evaporation to obtain activated glyoxylic acid.

[0019] Step 2: Take 100 parts of mellitic acid and 800 parts of pentaerythritol, mix them evenly, slowly raise the temperature to 85°C under nitrogen protection, add 18 parts of concentrated sulfuric acid dropwise within 1 hour, then continue to keep warm for 2 hours, slowly lower the temperature to room temperature, then remove excess pentaerythritol by rotary evaporation, add 260 parts of activated glyoxylic acid, mix evenly, slowly raise the temperature to 80°C, add 24 parts of concentrated sulfuric acid dropwise within 1 hour, then continue to keep warm for 4 hours, slowly lower the temperature to 40°C, add 600 parts of water, adjust the pH value to 7.5 with sulfuric acid, keep constant temperature for 2 hours, and finally cool to room temperature to obtain a chrome-free tanning based aminal retanning agent.

[0020] Example 2:

[0021] A method for preparing an aminal retanning agent based on chrome-free tanning comprises the following steps:

[0022] Step 1: 100 parts of glyoxylic acid and 120 parts of glycolic acid were added to 500 parts of benzene. The temperature was slowly raised to 70°C and stirred. 8 parts of p-toluenesulfonic acid were then added dropwise over 30 minutes. The reaction was then continued at a constant temperature for 4 hours. The temperature was then slowly lowered to room temperature and the solvent and catalyst were removed by rotary evaporation to obtain an activated glyoxylic acid precursor. 100 parts of the activated glyoxylic acid precursor was dissolved in 300 parts of thionyl chloride, 3 parts of N,N-dimethylformamide were added, and the reaction was continued at 40°C for 3 hours. Excess thionyl chloride and N,N-dimethylformamide were removed by rotary evaporation to obtain activated glyoxylic acid.

[0023] Step 2: Take 100 parts of mellitic acid and 720 parts of pentaerythritol, mix them evenly, slowly raise the temperature to 75°C under nitrogen protection, add 12 parts of concentrated sulfuric acid dropwise within 1 hour, then continue to keep warm for 3 hours, slowly lower the temperature to room temperature, then remove excess pentaerythritol by rotary evaporation, add 300 parts of activated glyoxylic acid, mix evenly, slowly raise the temperature to 90°C, add 8 parts of concentrated sulfuric acid dropwise within 1 hour, then continue to keep warm for 6 hours, slowly lower the temperature to 45°C, add 500 parts of water, adjust the pH value to 7.2 with sulfuric acid, keep constant temperature for 3 hours, and finally cool to room temperature to obtain a chrome-free tanning based aminal retanning agent.

[0024] Example 3:

[0025] A method for preparing an aminal retanning agent based on chrome-free tanning comprises the following steps:

[0026] Step 1: Preparation of activated glyoxylic acid: 100 parts of glyoxylic acid and 120 parts of ethylene glycol were added to 500 parts of benzene. The temperature was slowly raised to 80°C. After stirring, 6 parts of p-toluenesulfonic acid were added dropwise over 30 minutes. The reaction was then continued at a constant temperature for 3 hours. The temperature was then slowly lowered to room temperature, and the solvent and catalyst were removed by rotary evaporation to obtain an activated glyoxylic acid precursor. 100 parts of the activated glyoxylic acid precursor was dissolved in 300 parts of thionyl chloride. 3 parts of N,N-dimethylformamide were added, and the mixture was reacted at 35°C for 4 hours. Excess thionyl chloride and N,N-dimethylformamide were removed by rotary evaporation to obtain activated glyoxylic acid.

[0027] Step 2: Take 100 parts of mellitic acid and 650 parts of pentaerythritol, mix them evenly, and under nitrogen protection, slowly raise the temperature to 65°C, add 6 parts of concentrated sulfuric acid dropwise within 1 hour, and then continue to keep warm for 4 hours, slowly lower the temperature to room temperature, and then remove excess pentaerythritol by rotary evaporation, add 220 parts of activated glyoxylic acid, mix evenly, slowly raise the temperature to 60°C, add 16 parts of concentrated sulfuric acid dropwise within 1 hour, and then continue to keep warm for 8 hours, slowly lower the temperature to 50°C, add 650 parts of water, adjust the pH value to 7.0 with sulfuric acid, keep constant temperature for 1 hour, and finally cool to room temperature to prepare an acetal amine retanning agent based on chrome-free tanning.

[0028] The chrome-free tanning aminal retanning agents obtained in Examples 1, 2 and 3 were subjected to experimental testing, and the experimental data obtained are shown in Table 1 below:

[0029] Table 1

[0030]

[0031] Example 4:

[0032] A method for preparing high-brightness leather using an aminal retanning agent based on chrome-free tanning, comprising a neutralization step, a retanning step, a filling step, a fatliquor step, and a color overprinting step;

[0033] Neutralization process: based on the weight of wet white leather, control the drum temperature at 36°C, add 3% neutralizing tannin (A, Unitec, Italy) and 1% sodium formate, rotate for 20 minutes, add 0.2% baking soda and 1.3% sodium bicarbonate, rotate for 60 minutes, add 2% chrome-free acetal amine retanning agent, rotate for 40 minutes, drain, add 200% water, and rinse.

[0034] Retanning process: Based on the weight of wet white leather, the drum temperature was controlled at 32°C, 100% water was added, 2% chrome-free aminal retanning agent, 2% lanolin fatliquor (ZLN, Bisuo Chemical), 2% acid-resistant acrylic resin retanning agent (1084, Lanxess Chemical) were added, and the drum was rotated for 60 minutes. Then, 4% chrome-free aminal retanning agent, 4% synthetic tanning agent (FO, BASF), 2% protein filler (FB, Sichuan Desaier) were added, and the drum was rotated for 60 minutes. After 90 minutes, add 100% water, add 1.5% formic acid three times, rotate for 10, 10 and 20 minutes respectively, add 4% chrome-free acetal amine retanning agent, 2% cationic oil (GS, Stahl), rotate for 20 minutes, add 10% organic tanning agent (F90, Stahl), rotate for 120 minutes, then add 2% sodium formate, rotate for 20 minutes, add 2% baking soda, rotate for 60 minutes, add 2% ammonium bicarbonate, rotate for 60 minutes, and drain.

[0035] Filling process: Based on the weight of the wet white leather, the drum temperature was controlled at 32°C, 70% of water was added, 4% of amphoteric acrylic acid (D-37, Shanghai Kaifeng), 6% of anionic acrylic acid (TP340, Zhiqi Trading), and 2% of fatliquor (94S, Sima Chemical) were added, and the mixture was rotated for 20 minutes. Then, 3% of dicyandiamide resin (LH, Li Ning Technology), 3% of melamine resin (DX, Zhejiang Honglin Leather Chemical), 6% of tannin extract (ATO, Jinfeng Leather Chemical), 2% of disperse tannin (TM, BASF Chemical), and 2% of fatliquor (94S, Sima Chemical) were added, and the mixture was rotated for 60 minutes. Then, 6% of tannin extract (ATO, Jinfeng Leather Chemical), 3% of synthetic tanning agent (RL, Derui Chemical), 3% of fatliquor (ZLN, Bisuo Chemical), and 4% of dye (Acid Orange II, Tianjin Hailan Chemical) were added, and the mixture was rotated for 120 minutes.

[0036] Fatliquor process: based on the weight of wet white leather, the drum temperature was controlled at 55°C, 150% of water was added, 3% synthetic fatliquor (505, Kekai Chemical), 3% lanolin (ZLN, Bisuo Chemical), 3% lecithin (LC, Unitec, Italy) were added, and the drum was rotated for 60 minutes. 3% neat's foot oil (OPE, Unitec, Italy), 3% sulfated oil (OB, Temple Chemical), and 3% silicone waterproof oil (S33, Zhejiang Honglin Leather Chemical) were added and the drum was rotated for 180 minutes. Finally, 2.5% formic acid was added in four portions, and the drum was rotated for 10, 10, 10, and 30 minutes respectively, and then drained.

[0037] Color matching process: Based on the weight of the wet white leather, control the drum temperature at 32°C, add 50% water, add 2% dye (Acid Orange II, Tianjin Hailan Chemical), rotate for 30 minutes, add 0.5% formic acid, rotate for 30 minutes; add 2% dye (Acid Orange II, Tianjin Hailan Chemical), rotate for 30 minutes, add 0.2% formic acid and 0.3% aluminum tannin (BN, BASF), rotate for 30 minutes, drain, and the crust leather can be obtained.

[0038] This example uses the chrome-free tanning-based aminal retanning agent prepared in Example 1.

[0039] Example 5:

[0040] The preparation method of the chrome-free aminal retanning agent for high-brightness leather in this embodiment is basically the same as that in Example 4, except that the chrome-free aminal retanning agent prepared in Example 2 is used in this embodiment.

[0041] Example 6:

[0042] The preparation method of the chrome-free aminal retanning agent for high-brightness leather in this embodiment is basically the same as that in Example 4, except that the chrome-free aminal retanning agent prepared in Example 3 is used in this embodiment.

[0043] Comparative Example:

[0044] The method for preparing high-brightness leather based on chrome-free tanning aminal retanning agent in this embodiment is basically the same as that in Example 4, except that chrome-free tanning aminal retanning agent is not added in this embodiment.

[0045] The leathers obtained in the comparative example, embodiment 4, embodiment 5 and embodiment 6 were tested, and the experimental data obtained are shown in Table 2 below:

[0046] Table 2

[0047]

[0048] The above is only a specific implementation of the present invention, but the design concept of the present invention is not limited to this. Any non-substantial changes to the present invention using this concept shall be deemed as an infringement of the protection scope of the present invention.

Claims

1. A method for preparing an aminal retanning agent based on chrome-free tanning, characterized in that: The steps include: Step 1: 100 parts of glyoxylic acid and 120 parts of ethylene glycol are added to 500 parts of benzene, the temperature is slowly raised to 60-80°C, and after stirring, 5-10 parts of p-toluenesulfonic acid are added dropwise over 30 minutes. The reaction is then continued at a constant temperature for 3-5 hours, and the temperature is slowly lowered to room temperature. The solvent and catalyst are removed by rotary evaporation to obtain an activated glyoxylic acid precursor. 100 parts of the activated glyoxylic acid precursor are dissolved in 300 parts of thionyl chloride, 3 parts of N,N-dimethylformamide are added, and the reaction is continued at 35-50°C for 2-4 hours. Excess thionyl chloride and N,N-dimethylformamide are removed by rotary evaporation to obtain activated glyoxylic acid. Step 2: Take 100 parts of mellitic acid and 650-800 parts of pentaerythritol, mix them evenly, slowly raise the temperature to 60-90°C under nitrogen protection, add 5-20 parts of concentrated sulfuric acid dropwise within 1 hour, then continue to keep warm for 1-5 hours, slowly lower the temperature to room temperature, then remove excess pentaerythritol by rotary evaporation, add 220-300 parts of activated glyoxylic acid, mix evenly, slowly raise the temperature to 70-100°C, add 8-30 parts of concentrated sulfuric acid dropwise within 1 hour, then continue to keep warm for 3-8 hours, slowly lower the temperature to 40-50°C, add 500-650 parts of water, adjust the pH value to 7.0-7.5 with sulfuric acid, keep constant temperature for 1-3 hours, and finally cool to room temperature to prepare a chrome-free tanning aminal retanning agent.

2. The method for preparing high-brightness leather using an aminal retanning agent based on chrome-free tanning as claimed in claim 1, characterized in that: At least including neutralization process and retanning process; Neutralization process: based on the weight of wet white leather, control the drum temperature to 35-40°C, add 2-4% neutralizing tannin and 0.8-1.2% sodium formate, rotate for 20 minutes, add 0-0.5% baking soda and 0.5-1.5% sodium bicarbonate, rotate for 60 minutes, add 1-3% chrome-free tanning aminal retanning agent, rotate for 40 minutes, drain, add 200% water, and rinse; Retanning process: Based on the weight of wet white leather, control the drum temperature to 30-35°C, add 75-150% water, add 1-3% chrome-free acetal amine retanning agent, 1-3% lanolin fatliquor, 2-4% acid-resistant acrylic resin retanning agent, rotate for 30-60 minutes, then add 2-4% chrome-free acetal amine retanning agent, 2-4% synthetic tanning agent, 2-4% protein filler, rotate for 60-120 minutes, add 100 -150% water, add 1.2-1.8% formic acid three times, rotate for 10, 10 and 20 minutes respectively, add 3-6% chrome-free acetal amine retanning agent, 1-2% cationic oil, rotate for 20 minutes, add 5-10% organic tanning agent, rotate for 120-180 minutes, then add 2% sodium formate, rotate for 20 minutes, add 2% baking soda, rotate for 60 minutes, add 2% ammonium bicarbonate, rotate for 60 minutes, and drain.

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