Preparation method and application of dicyandiamide resin grafted keratin tanning and retanning agent for leather

Abstract

The application relates to a preparation method of a dicyandiamide resin grafted keratin tanning agent for leather processing. Waste cattle hair is added with deionized water, alkali, calcium hydroxide, polyaluminum chloride and polyacrylamide flocculation precipitation, filtration, filtration liquid is taken, drying is carried out, the filtration liquid is dissolved in water, pH value is adjusted, 5,5-dihydroxyvaleraldehyde and sulfuric acid are added, pH value is adjusted, benzene carboxylic acid containing is taken, dissolved in thionyl chloride, N,N-dimethylformamide is added, rotary evaporation is carried out to obtain benzene carboxylic acid containing, dicyandiamide, aldehyde group functionalized keratin, glyoxal, glutaraldehyde, ethanol are mixed, pH value is adjusted, then benzene carboxylic acid containing and diethyl ether are added, and pH value is adjusted. Through the flocculation effect of calcium hydroxide, dirt and impurities in the cattle hair are captured, a large amount of water and surfactants are saved, no wastewater is discharged; the reactivity of amino groups and carbonyl groups is utilized to obtain aldehyde group functionalized keratin; the addition reaction of aldehyde group functionalized keratin and dicyandiamide can occur, the molecular weight of the dicyandiamide grafted keratin is increased, and the grafting rate is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of tanning technology, in particular to a preparation method and application of a dicyandiamide resin grafted keratin tanning re-tanning agent. BACKGROUND

[0002] In the tanning process, lime and sulfidized alkali are used for liming and unhairing treatment of rawhide, and a large amount of solid waste, i.e. waste cow hair, is generated after the treatment of rawhide. The waste cow hair treated with lime and sulfidized alkali contains a large amount of dirt and impurities, mainly lime, grease, sand, sulfidized alkali, sodium chloride, and a small amount of meat, blood clots, fascia, etc. The traditional treatment method is to use a large amount of water combined with surfactants and degreasing agents for cleaning, and the water consumption is about 20 times that of waste cow hair, accompanied by a large amount of high-COD and high-SS wastewater, which is a major difficulty in the comprehensive utilization of keratin. Although the keratin obtained by hydrolyzing waste cow hair has carboxyl, amino, sulfhydryl, and hydroxyl groups on its molecular structure, the reactivity is low, and although the molecular structure can be theoretically grafted and modified, the grafting rate is low. Therefore, how to activate the functional groups on the keratin and improve the grafting rate has become another difficulty in the comprehensive utilization of keratin. SUMMARY

[0003] The present application provides a preparation method and application of a dicyandiamide resin grafted keratin tanning re-tanning agent to solve the problems of traditional treatment of waste cow hair accompanied by a large amount of high-COD and high-SS wastewater, and low activity and grafting rate of keratin after treatment.

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

[0005] A preparation method of a dicyandiamide resin grafted keratin tanning re-tanning agent, comprising the following steps:

[0006] Step 1: Take 100 parts of waste cow hair, add 500 parts of deionized water, mix uniformly, then add 8-12 parts of alkali (sodium hydroxide, potassium hydroxide, and must contain calcium hydroxide), react at 60-90°C for 3-6 hours, cool to room temperature, then add 5-10 parts of calcium hydroxide, 1 part of polyaluminum chloride, and 1 part of polyacrylamide flocculation and precipitation, filter the precipitate, take the filtrate, add sulfuric acid to adjust the pH value to 7-8, and vacuum dry to obtain keratin powder;

[0007] Step 2: Dissolve 100 parts of keratin powder in 200 parts of water, adjust the pH value with disodium hydrogen phosphate and sodium dihydrogen phosphate so that it is always controlled at 6.8-7.2, add 280-400 parts of 5,5-dihydroxyvaleraldehyde (CAS: 16776-90-2), stir uniformly, then raise the reaction temperature to 40-60°C, keep constant temperature for 1-3h, then add sulfuric acid to adjust the pH to 2.5-4.5, and aldehyde group keratin is obtained;

[0008] Step 3, take 100 parts of benzene carboxylic acid (terephthalic acid, pyromellitic acid, benzene hexacarboxylic acid) dissolved in 300 parts of thionyl chloride, add 3 parts of N, N-dimethylformamide, react at 35-50°C for 2-4h, rotary evaporation to remove excess thionyl chloride and N, N-dimethylformamide, to obtain activated benzene carboxylic acid;

[0009] Step 4, take 100 parts of dicyandiamide, slowly dispersed in 300 parts of water, add 50-300 parts of aldehyde-based keratin, 50-300 parts of glyoxal, 50-300 parts of glutaraldehyde, wherein the total amount of aldehyde-based keratin, glyoxal, and glutaraldehyde is 300-500 parts, then add 15-25 parts of ethanol, mix well, then use sodium hydroxide to adjust the pH to 8.5-10.0, react at 40-55°C for 30-45 minutes, then add 100-200 parts of activated benzene carboxylic acid, 50-100 parts of diethyl ether, incubate for 10-15 minutes, then slowly reduce to room temperature, adjust the pH to 6.0-7.0 with sulfuric acid, and vacuum dry to obtain a dicyandiamide resin grafted keratin retanning agent.

[0010] Further improvement, the above-mentioned alkali at least contains calcium hydroxide, and can contain sodium hydroxide and potassium hydroxide.

[0011] Further improvement, the above-mentioned benzene carboxylic acid is one or more of terephthalic acid, pyromellitic acid, and benzene hexacarboxylic acid.

[0012] The application of a dicyandiamide resin grafted keratin leather retanning agent at least includes a filling process and a fatliquoring process;

[0013] The specific steps of the filling process are as follows: control the drum temperature at 30-35°C, add 50-100% water, 3-6% small molecule acrylic acid, 1-2% synthetic fatliquoring agent, rotate for 30 minutes, add 3-6% tannin, 1-3% synthetic tanning agent, 1-2% synthetic fatliquoring agent, rotate for 60 minutes, add 6-9% dicyandiamide resin grafted keratin retanning agent, 1-3% melamine retanning agent, 3-6% tannin, 1-2% synthetic fatliquoring agent, rotate for 60 minutes, add 1-3% synthetic tanning agent, 6-9% tannin, 2-3% synthetic fatliquoring agent, rotate for 120 minutes. Finally, add 0.6% formic acid and rotate for 30 minutes;

[0014] The temperature of the rotating drum is increased to 48-52°C, 100-150% of water is added, 3-6% of dicyandiamide resin grafted keratin re-tanning agent, 1-2% of tannin are added, rotating for 20 minutes, 3-6% of synthetic fatliquoring agent, 3-6% of natural fatliquoring agent are added, rotating for 30 minutes, 6-9% of synthetic fatliquoring agent, 3-6% of natural fatliquoring agent are added, rotating for 120 minutes, finally 2.5% of formic acid is added in 4 times, rotating for 10, 10, 10, 30 minutes respectively, and then the crust leather is obtained.

[0015] From the above description of the present application, compared with the prior art, the present application has the following advantages:

[0016] 1. The present application captures the dirt and impurities in the cow hair through the flocculation of calcium hydroxide, saving a large amount of water and surfactant. The sludge produced after flocculation is ordinary comprehensive sludge, which can be directly entrusted to an environmental protection company for disposal at a relatively low cost. The filtrate after pressure filtration is keratin extract, realizing no wastewater discharge. At the same time, in the process of flocculation, the alkalinity of calcium hydroxide can also well hydrolyze the cow hair to extract keratin, and sodium hydroxide and potassium hydroxide can also assist in hydrolysis, thereby improving the hydrolysis rate.

[0017] 2. The present application uses 5,5-dihydroxyvaleraldehyde (CAS: 16776-90-2) or 4,4-dimethoxy-2-butanone (CAS: 5436-21-5) to activate keratin, which utilizes the reactivity of amino and carbonyl groups to graft small-molecule organic compounds containing active carbonyl structures with alcohol protection on the keratin molecules. Then, under weak acid conditions, the protection structure is hydrolyzed to obtain aldehyde functionalized keratin. Aldehyde functionalization can also undergo addition reaction with dicyandiamide. With glyoxal and glutaraldehyde as chain extenders, the molecular weight of dicyandiamide grafted keratin is increased. Finally, a certain amount of activated benzene carboxylic acid is added to further consume the participating amino and hydroxyl groups. A small amount of diethyl ether can block the reactivity of a part of the hydroxymethyl groups and inhibit their self-polymerization in aqueous solution.

[0018] 3. The keratin prepared by the method of the present application has a solid content of ≥90%, an ash content of ≤10%, a water-insoluble content of ≤5%, and a water-soluble content of ≥85%. It has a suitable particle size, particle size distribution coefficient, and zeta potential. The particle size is 200-500 nm, the particle size distribution coefficient is 0.100-0.250, and the zeta potential is ≤-20 mV.

[0019] 4. The dicyandiamide grafted keratin re-tanning agent of the present application has a suitable particle size and particle size distribution coefficient. The particle size is 1000-2000 nm, and the particle size distribution coefficient is 0.200-0.450.

[0020] 5. The dicyandiamide grafted keratin retanning agent of the present application has relatively ideal health and safety performance, with formaldehyde content ≤20 ppm, trichlorophenol content ≤0.5 ppm, tetrachlorophenol content ≤0.5 ppm, pentachlorophenol content ≤0.5 ppm, o-phenylphenol content ≤1 ppm, and dimethyl fumarate content ≤0.1 ppm.

[0021] 6. The dicyandiamide grafted keratin retanning agent of the present application has good tanning and filling properties, and after treatment of the leather with the dicyandiamide grafted keratin, the raw leather shrinkage temperature is ≥90°C, the tear strength is ≥50 N, the burst height is ≥7 mm, and the burst strength is ≥300 N·mm. -1 At the same time, the dicyandiamide grafted keratin retanning agent has good health and safety performance, with formaldehyde content ≤20 ppm, hexavalent chromium content ≤10 ppm, trichlorophenol content ≤0.5 ppm, tetrachlorophenol content ≤0.5 ppm, pentachlorophenol content ≤0.5 ppm, o-phenylphenol content ≤1 ppm, and dimethyl fumarate content ≤0.1 ppm. DETAILED DESCRIPTION

[0022] Example 1

[0023] A preparation method of a dicyandiamide resin grafted keratin tanning agent for leather making, comprising the following steps:

[0024] Step 1, preparation of keratin powder: take 100 parts of waste cattle hair, add 500 parts of deionized water, mix uniformly, then add 10 parts of calcium hydroxide, react at 90°C for 5 hours, cool to room temperature, then add 5 parts of calcium hydroxide, 1 part of polyaluminum chloride, and 1 part of polyacrylamide flocculation and precipitation, filter the precipitate, take the filtrate, add sulfuric acid to adjust the pH value to 7, and vacuum dry to obtain keratin powder.

[0025] Step 2, preparation of aldehyde-keratin: take 100 parts of keratin powder and dissolve in 200 parts of water, adjust the pH value with disodium hydrogen phosphate and sodium dihydrogen phosphate so that it is always controlled at 6.8-7.2, add 280 parts of 5,5-dihydroxyvaleraldehyde (CAS: 16776-90-2), stir uniformly, then raise the reaction temperature to 55°C, keep constant temperature for 2.5 h, then add sulfuric acid to adjust the pH to 4.0, and aldehyde-keratin is obtained.

[0026] Step 3, activation of benzene carboxylic acid: take 50 parts of terephthalic acid and 50 parts of mellitic acid, dissolve in 300 parts of thionyl chloride, add 3 parts of N, N-dimethylformamide, react at 40°C for 2 h, and rotary evaporate to remove excess thionyl chloride and N, N-dimethylformamide, and activated benzene carboxylic acid is obtained.

[0027] Step 4: Preparation of dicyandiamide resin grafted keratin: Take 100 parts of dicyandiamide and slowly disperse it in 300 parts of water, add 100 parts of aldehyde- based keratin, 100 parts of glyoxal, and 100 parts of glutaraldehyde, wherein the total amount of aldehyde-based keratin, glyoxal, and glutaraldehyde is 300 parts, then add 15 parts of ethanol, mix well, adjust the pH to 8.5 with sodium hydroxide, and react at 55°C for 30 minutes, then add 100 parts of activated benzene carboxylic acid-containing and 50 parts of diethyl ether, keep warm for 10 minutes, then slowly reduce to room temperature, adjust the pH to 6.0 with sulfuric acid, and vacuum dry to obtain the dicyandiamide resin grafted keratin retanning agent.

[0028] Example 2:

[0029] A method for preparing a dicyandiamide resin grafted keratin leather retanning agent, comprising the following steps:

[0030] Step 1: Preparation of keratin powder: Take 100 parts of waste cow hair, add 500 parts of deionized water, mix well, then add 4 parts of calcium hydroxide and 4 parts of potassium hydroxide, and react at 80°C for 4 hours. After cooling to room temperature, add 8 parts of calcium hydroxide, 1 part of polyaluminum chloride, and 1 part of polyacrylamide flocculation and precipitation, filter the precipitate, take the filtrate, adjust the pH to 8 with sulfuric acid, and vacuum dry to obtain keratin powder.

[0031] Step 2: Preparation of aldehyde-based keratin: Take 100 parts of keratin powder and dissolve it in 200 parts of water, adjust the pH with disodium hydrogen phosphate and sodium dihydrogen phosphate so that it is always controlled at 6.8-7.2, add 400 parts of 5,5-dihydroxyvaleraldehyde (CAS: 16776-90-2), stir well, then raise the reaction temperature to 40°C, and keep the temperature constant for 1.5 hours, then add sulfuric acid to adjust the pH to 3.5, and obtain the aldehyde-based keratin.

[0032] Step 3: Activation of benzene carboxylic acid-containing: Take 100 parts of pyromellitic acid and dissolve it in 300 parts of thionyl chloride, add 3 parts of N,N-dimethylformamide, and react at 50°C for 4 hours. Rotary evaporation is used to remove excess thionyl chloride and N,N-dimethylformamide, and the activated benzene carboxylic acid-containing is obtained.

[0033] Step 4: Preparation of dicyandiamide resin grafted keratin: Take 100 parts of dicyandiamide and slowly disperse it in 300 parts of water, add 200 parts of aldehyde- based keratin, 100 parts of glyoxal, and 100 parts of glutaraldehyde, wherein the total amount of aldehyde-based keratin, glyoxal, and glutaraldehyde is 40 parts, then add 20 parts of ethanol, mix well, adjust the pH to 9.0 with sodium hydroxide, and react at 50°C for 40 minutes, then add 150 parts of activated benzene carboxylic acid-containing and 50 parts of diethyl ether, keep warm for 10 minutes, then slowly reduce to room temperature, adjust the pH to 6.5 with sulfuric acid, and vacuum dry to obtain the dicyandiamide resin grafted keratin retanning agent.

[0034] Example 3:

[0035] A method for preparing a dicyandiamide resin grafted keratin leather retanning agent, comprising the following steps:

[0036] Step 1: Preparation of keratin powder: Take 100 parts of waste cow hair, add 500 parts of deionized water, mix well, then add 10 parts of calcium hydroxide and 2 parts of sodium hydroxide, and react at 70°C for 3 hours. After cooling to room temperature, add 6 parts of calcium hydroxide, 1 part of polyaluminum chloride, and 1 part of polyacrylamide flocculation and precipitation, filter the precipitate, take the filtrate, adjust the pH to 7.5 with sulfuric acid, and vacuum dry to obtain keratin powder.

[0037] Step 2: Preparation of aldehyde-based keratin: Take 100 parts of keratin powder and dissolve it in 200 parts of water, adjust the pH with disodium hydrogen phosphate and sodium dihydrogen phosphate so that it is always controlled at 6.8-7.2, add 325 parts of 5,5-dihydroxyvaleraldehyde (CAS: 16776-90-2), stir well, then raise the reaction temperature to 45°C, and keep the temperature constant for 2 hours, then add sulfuric acid to adjust the pH to 3.0, and obtain the aldehyde-based keratin.

[0038] Step 3: Activation of benzene carboxylic acid-containing: Take 20 parts of terephthalic acid, 20 parts of pyromellitic acid, and 60 parts of benzene hexacarboxylic acid and dissolve them in 300 parts of thionyl chloride, add 3 parts of N, N-dimethylformamide, and react at 45°C for 3 hours. Rotary evaporation is used to remove excess thionyl chloride and N, N-dimethylformamide, and the activated benzene carboxylic acid-containing is obtained.

[0039] Step 4: Preparation of dicyandiamide resin grafted keratin: Take 100 parts of dicyandiamide, slowly disperse in 300 parts of water, add 250 parts of aldehyde keratin, 100 parts of glyoxal, 100 parts of glutaraldehyde, wherein the total amount of aldehyde keratin, glyoxal, glutaraldehyde is 450 parts, then add 25 parts of ethanol, mix uniformly, then use sodium hydroxide to adjust the pH to 9.5, react at 40°C for 45 minutes, then add 175 parts of activated benzene carboxylic acid containing, 75 parts of diethyl ether, keep warm for 15 minutes, then slowly reduce to room temperature, adjust the pH to 7.0 with sulfuric acid, vacuum drying to obtain dicyandiamide resin grafted keratin retanning agent.

[0040] The keratin obtained from Example 1, Example 2, Example 3, and dicyandiamide grafted keratin were subjected to practical detection, and the experimental data obtained are shown in Table 1 below:

[0041] Table 1:

[0042] Example 4:

[0043] The application of a dicyandiamide resin grafted keratin leather retanning agent includes a retanning process, a neutralization process, a filling process, and a fatliquoring process. In this embodiment, the dicyandiamide resin grafted keratin retanning agent is prepared according to Example 1.

[0044] Retanning process: control the drum temperature at 32°C, add 50% water, add 2% fatty aldehyde (PF, Sima Chemical), 2% protein filler (FB, Sichuan Desai), rotate for 30 minutes, then add 1% acid-resistant fatliquor (B1, Tompa Chemical), 4% chromium tanning agent (Tankrom AB, Şişecam Turkey), rotate for 120 minutes, then set the rotation for 5 minutes, stop for 55 minutes, repeat 8 times.

[0045] Neutralization process: control the drum temperature at 32°C, add 200% water, add 2% neutralizing tannin (A, Italy Unitec), 1% sodium formate, rotate for 20 minutes, add 1% baking soda, 0.5% cyanide carbonate, rotate for 60 minutes, wash with water and drain.

[0046] Filling process: control the temperature of the drum to be 32°C, add 50% water, add 6% small molecule acrylic acid (TP340, Zhiqi Trade), 1% synthetic fatliquoring agent (94S, Sima Chemical), rotate for 30 minutes, add 3% tannin (ATO, Jinfeng Pihua), 3% synthetic tanning agent (RL, Duerui Chemical), 1% synthetic fatliquoring agent (94S, Sima Chemical), rotate for 60 minutes, add 9% dicyandiamide resin grafted keratin retanning agent, 3% melamine retanning agent (MD, Linning Technology), 6% tannin ATO, Jinfeng Pihua), 2% synthetic fatliquoring agent (94S, Sima Chemical), rotate for 60 minutes, add 3% synthetic tanning agent (RL, Duerui Chemical), 9% tannin (LCF, Linning Technology), 3% synthetic fatliquoring agent (94S, Sima Chemical), rotate for 120 minutes. Finally, add 0.6% formic acid, rotate for 30 minutes.

[0047] Fatliquoring process: increase the temperature of the drum to 52°C, add 100% water, add 3% dicyandiamide resin grafted keratin retanning agent, 2% tannin (LCF, Linning Technology), rotate for 20 minutes, add 3% sulfonated synthetic fatliquoring agent (SA, Linning Technology), 3% synthetic phospholipid fatliquoring agent (LLQ, Linning Technology), 3% natural lanolin fatliquoring agent (ZLN, Biso Chemical), rotate for 30 minutes, add 3% synthetic lecithin (PA, Linning Technology), 3% synthetic silicone fatliquoring agent (PF, Linning Technology), 3% natural ox-tallow fatliquoring agent (OPB, Linning Technology), 3% natural sulfited fish oil fatliquoring agent (FA, Linning Technology), rotate for 120 minutes, finally add 2.5% formic acid in 4 times, rotate for 10, 10, 10, 30 minutes respectively, and the crust leather can be obtained.

[0048] Comparative Example:

[0049] The application of the dicyandiamide resin grafted keratin leather-making retanning agent of the comparative example is basically the same as that of Example 4, and the difference lies in that the dicyandiamide resin grafted keratin leather-making retanning agent obtained in Example 1 is not added in the comparative example.

[0050] The crust leather obtained in the comparative example and Example 4 is subjected to experimental detection, and the experimental data is shown in Table 2:

[0051] Table 2

[0052]

[0053] The above is only a specific embodiment of the present application, but the design concept of the present application is not limited thereto, and any non-essential modification of the present application using this concept shall be regarded as an act of infringing the protection scope of the present application.

Claims

1. A method for preparing a dicyandiamide resin-grafted keratin retanning agent for leather tanning, characterized in that, Includes the following steps: Step 1: Take 100 parts of waste cow hair, add 500 parts of deionized water, mix well, add 8-12 parts of alkali, react at 60-90°C for 3-6 hours, cool to room temperature, add 5-10 parts of calcium hydroxide, 1 part of polyaluminum chloride, and 1 part of polyacrylamide for flocculation and precipitation, filter the precipitate, take the filtrate, add sulfuric acid to adjust the pH value to 7-8, and vacuum dry to obtain keratin powder; Step 2: Dissolve 100 parts of keratin powder in 200 parts of water, adjust the pH value with disodium hydrogen phosphate and sodium dihydrogen phosphate to keep it at 6.8-7.2, add 280-400 parts of 5,5-dihydroxypentanal, stir evenly, raise the reaction temperature to 40-60°C, keep the temperature constant for 1-3 hours, then add sulfuric acid to adjust the pH to 2.5-4.5 to obtain aldehyde-modified keratin; Step 3: Dissolve 100 parts of benzyl carboxylic acid in 300 parts of thionyl chloride, add 3 parts of N,N-dimethylformamide, react at 35-50°C for 2-4 hours, and remove excess thionyl chloride and N,N-dimethylformamide by rotary evaporation to obtain activated benzyl carboxylic acid. Step 4: Take 100 parts of dicyandiamide and slowly disperse it in 300 parts of water. Add 50-300 parts of aldehyde-modified keratin, 50-300 parts of glyoxal, and 50-300 parts of glutaraldehyde. The total amount of aldehyde-modified keratin, glyoxal, and glutaraldehyde should be 300-500 parts. Then add 15-25 parts of ethanol and mix well. Adjust the pH to 8.5-10.0 with sodium hydroxide and react at 40-55°C for 30-45 minutes. Then add 100-200 parts of activated phenylcarboxylic acid and 50-100 parts of diethyl ether. Keep warm for 10-15 minutes, then slowly lower to room temperature. Adjust the pH to 6.0-7.0 with sulfuric acid and vacuum dry to obtain the dicyandiamide resin-grafted keratin retanning agent. The alkali contains at least calcium hydroxide, and optionally sodium hydroxide and potassium hydroxide.

2. The preparation method of the dicyandiamide resin grafted keratin tanning agent as described in claim 1, characterized in that: The phenyl carboxylic acid is one or more of terephthalic acid, pyromellitic acid, and benzoic acid.

3. The application of the dicyandiamide resin-grafted keratin retanning agent prepared by the method described in claim 1 or 2, characterized in that, It includes at least the filling process and the fat-adding process; The specific steps of the filling process are as follows: Based on the weight of wet blue leather, control the drum temperature to 30-35°C, add 50-100% water, add 3-6% small molecule acrylic acid, 1-2% synthetic fatliquoring agent, rotate for 30 minutes, add 3-6% tannin, 1-3% synthetic tanning agent, 1-2% synthetic fatliquoring agent, rotate for 60 minutes, add 6-9% dicyandiamide resin grafted keratin retanning agent as described in claim 1, 1-3% melamine retanning agent, 3-6% tannin, 1-2% synthetic fatliquoring agent, rotate for 60 minutes, add 1-3% synthetic tanning agent, 6-9% tannin, 2-3% synthetic fatliquoring agent, rotate for 120 minutes, and finally add 0.6% formic acid, rotate for 30 minutes. Raise the drum temperature to 48-52°C, add 100-150% water, 3-6% of the dicyandiamide resin grafted keratin retanning agent as described in claim 1, and 1-2% of tannin. Rotate for 20 minutes, add 3-6% of synthetic fatliquoring agent and 3-6% of natural fatliquoring agent, rotate for 30 minutes, add 6-9% of synthetic fatliquoring agent and 3-6% of natural fatliquoring agent, rotate for 120 minutes, and finally add 2.5% formic acid in four portions, rotating for 10, 10, 10, and 30 minutes respectively, to obtain the raw leather.

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